http://khure.ipgp.fr/index.php?feed=atom&target=Emmelyne&title=Special%3AContributions!khure - User contributions [en]2026-05-19T07:53:57ZFrom !khureMediaWiki 1.15.1http://khure.ipgp.fr/index.php/MembersMembers2010-01-29T17:08:02Z<p>Emmelyne: </p>
<hr />
<div><h2>!Khure Africa participants</h2><br />
<br />
<h3><br />
Leader, South Africa:<br />
Professor Maarten de Wit (AEON, RSA)<br />
<br><br />
Leader, France:<br />
Professor Vincent Courtillot (IPGP, Fr)<br />
</h3><br />
<br />
* Professor Julia Lee-Thorp (AEON, RSA and Bradford, UK) <br />
* Professor Geoffrey C. P. King (IPGP, Fr) <br />
* Professor Jean-Louis Le Mouël (IPGP, Fr) <br />
* Dr F. D. P. Woody Cotterill (AEON, RSA)<br />
* Professor Jean-Jacques Jaeger (University of Poitiers, Fr) <br />
* Professor Judith Masters (University of Fort Hare, RSA) <br />
* Professor Jean Besse (IPGP, Fr)<br />
* Dr Arnaud Chulliat (IPGP, Fr) <br />
* Professor Rodger Hart (iThemba Labs, RSA)<br />
* Dr Moctar Doucoure (Debeers, RSA) <br />
* Dr Sue Webb (Wits, RSA) <br />
* Dr Armand Galdeano (IPGP, Fr)<br />
* Professor Pascal Philippot (IPGP, Fr)<br />
* Dr Mark van Zuilen (IPGP, Fr)<br />
* Mr Eugene Grosch (AEON, RSA)<br />
* Professor Claude Jaupart (IPGP, Fr)<br />
* Dr Reginald Domoney (University of the Western Cape, RSA)<br />
* Dr David R. Bell (UCT, RSA)<br />
* Dr Stuart Gilder (Munich, De)<br />
* Professor Steven McCourt (University KwaZulu Natal, RSA)<br />
* Professor Francois Guillocheau (University of Rennes 1, Fr)<br />
* Dr Delphine Rouby (University of Rennes 1, Fr)<br />
* Dr Fabien Genin (University of Fort Hare, RSA)<br />
* Professor Paul Dirks (Wits, RSA)<br />
* Dr Pieter Kotzé (Hermanus Magnetic Observatory, RSA)<br />
* Dr Sally Reynolds (IPGP, fr & Wits, RSA)<br />
* Professor Frédéric Fluteau (IPGP, Fr)<br />
* Professor Marian Tredoux (University of the Free State, RSA)<br />
* Professor J. S. Goonie Marsh (Rhodes University, RSA)<br />
* Dr Pierre Cartigny (IPGP, Fr)<br />
* Dr Jérôme Dyment (IPGP, Fr)<br />
* Professor Laure Meynadier (IPGP, Fr) <br />
* Professor Lee Berger (Wits, RSA)<br />
* Professor Paul Dirks (Wits, RSA)<br />
* Dr Erwan Thebault (IPGP, Fr)</div>Emmelynehttp://khure.ipgp.fr/index.php/File:Moulin.pdfFile:Moulin.pdf2009-09-23T12:26:12Z<p>Emmelyne: </p>
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<div></div>Emmelynehttp://khure.ipgp.fr/index.php/File:Cartigny.pdfFile:Cartigny.pdf2009-09-23T08:11:01Z<p>Emmelyne: </p>
<hr />
<div></div>Emmelynehttp://khure.ipgp.fr/index.php/JulyWorkshopJulyWorkshop2009-09-23T08:06:01Z<p>Emmelyne: </p>
<hr />
<div><accesscontrol>Administrators,,Workshop</accesscontrol><br />
<center><h2>!Khure Workshop presentations</h2></center><br />
<br />
<br />
* [[media:dewit_introduction.pdf|Introduction]]: '''Vincent Courtillot – Maarten De Wit'''<br />
* '''E. Thébault''' : [[media:thebault.pdf|The magnetic field over the Southern African continent: from core to crustal magnetic fields]]<br />
* '''M. Moulin (PhD), V. Courtillot, F. Fluteau, G. Marsh, G. Delpech''' : [[media:Moulin.pdf|Paleomagnetic results and dating from the Karoo traps.]]<br />
* '''L. Carporzen, A. Galdeano, S. Gilder, M. Le Goff, R. Hart, M. Muundjua''': Geomagnetic and Palaeomagnetic studies of the magnetic anomalies associated with the Vredefort impact crater, South Africa: a summary and conclusion.<br />
* '''G. King and the A1 project team''': Landscapes, tectonics and hominins in South Africa<br />
* '''J. Dyment, D. Bissessur, R. Fernandes, N. Villeneuve''': [[media:dyment.pdf|Origin of lemurs in Madagascar: what to expect from marine and GPS investigations?]]<br />
* '''J-J. Jaeger''': [[media:Jaeger.pdf|The origin and early evolution of madagascar mammalian fauna : first results and perspectives.]]<br />
* '''P. Philippot, M. Van Zuilen, Y. Teitler (PhD), V. Noel, M. Ader and M. de Wit''': [[media:philippot.pdf|The Barberton Barite Drilling Project: a window on Archean microbial metabolisms]]<br />
* '''Isabelle Duhamel-Achin (PhD), M. Cuney''': Mineralogy and Geochemistry of the Witwatersrand Basin Reefs, South Africa: detrital vs. hydrothermal origin of uranium mineralization, possible sources and constraints for the atmospheric pO2 level prior 2.2 Ga.<br />
* '''F. Guillocheau, M. de Wit, G. Dubois, F. Eckardt, B. Linol, C. Robin, D. Rouby''': [[media:Guillocheau.pdf|Plateau uplift, epeirogeny and evolution of climate : The Kalahari Plateau, a world class laboratory]]<br />
* '''C. Jaupart''': [[media:Jaupart.pdf|Stability of lithosphere and thermal structure]]<br />
* '''P. Cartigny''': [[media:Cartigny.pdf|Traçing Conflict Diamonds ? Yes we can… sometimes.]] Case studies on diamonds from Central African Craton (RDC and CAR)<br />
* '''S. Gilder, M. de Wit, S. Roud, R. Egli and S. Koch''': [[media:de_Wit.pdf|Magnetic signatures of diamonds]]<br />
* '''J. Besse, S. Satolli, R. Domoney, M. de Wit''': [[media:besse.pdf|Disrupted fun in the Cape Fold Belt: pyrite spoils the paleomagnetic party]]<br />
* '''M. Tredoux, Laure Meynadier, M. De Wit''': [[media:tredoux.pdf|Capacity building]]</div>Emmelynehttp://khure.ipgp.fr/index.php/File:Besse.pdfFile:Besse.pdf2009-09-22T16:06:46Z<p>Emmelyne: </p>
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<div></div>Emmelynehttp://khure.ipgp.fr/index.php/File:De_Wit.pdfFile:De Wit.pdf2009-09-22T16:06:31Z<p>Emmelyne: </p>
<hr />
<div></div>Emmelynehttp://khure.ipgp.fr/index.php/File:Jaupart.pdfFile:Jaupart.pdf2009-09-22T16:05:00Z<p>Emmelyne: </p>
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<div></div>Emmelynehttp://khure.ipgp.fr/index.php/File:Guillocheau.pdfFile:Guillocheau.pdf2009-09-22T16:04:39Z<p>Emmelyne: </p>
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<div></div>Emmelynehttp://khure.ipgp.fr/index.php/File:Jaeger.pdfFile:Jaeger.pdf2009-09-22T16:04:18Z<p>Emmelyne: </p>
<hr />
<div></div>Emmelynehttp://khure.ipgp.fr/index.php/File:Dyment.pdfFile:Dyment.pdf2009-09-22T16:04:03Z<p>Emmelyne: </p>
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<div></div>Emmelynehttp://khure.ipgp.fr/index.php/File:Tredoux.pdfFile:Tredoux.pdf2009-09-22T15:47:26Z<p>Emmelyne: </p>
<hr />
<div></div>Emmelynehttp://khure.ipgp.fr/index.php/File:Philippot.pdfFile:Philippot.pdf2009-09-22T15:47:08Z<p>Emmelyne: </p>
<hr />
<div></div>Emmelynehttp://khure.ipgp.fr/index.php/File:Thebault.pdfFile:Thebault.pdf2009-09-22T15:07:10Z<p>Emmelyne: </p>
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<div></div>Emmelynehttp://khure.ipgp.fr/index.php/File:Dewit_introduction.pdfFile:Dewit introduction.pdf2009-09-22T15:06:45Z<p>Emmelyne: </p>
<hr />
<div></div>Emmelynehttp://khure.ipgp.fr/index.php/JulyWorkshopJulyWorkshop2009-09-22T14:19:41Z<p>Emmelyne: </p>
<hr />
<div><accesscontrol>Administrators,,Workshop</accesscontrol><br />
<br />
<center><h2>!Khure Workshop presentations</h2></center><br />
<br />
<br />
* [[media:dewit_introduction.pdf|Introduction]]: '''Vincent Courtillot – Maarten De Wit'''<br />
* '''E. Thébault''' : [[media:thebault.pdf|The magnetic field over the Southern African continent: from core to crustal magnetic fields]]<br />
* '''M. Moulin (PhD), V. Courtillot, F. Fluteau, G. Marsh, G. Delpech''' : [[media:Moulin.pdf|Paleomagnetic results and dating from the Karoo traps.]]<br />
* '''L. Carporzen, A. Galdeano, S. Gilder, M. Le Goff, R. Hart, M. Muundjua''': Geomagnetic and Palaeomagnetic studies of the magnetic anomalies associated with the Vredefort impact crater, South Africa: a summary and conclusion.<br />
* '''G. King and the A1 project team''': Landscapes, tectonics and hominins in South Africa<br />
* '''J. Dyment, D. Bissessur, R. Fernandes, N. Villeneuve''': [[media:dyment.pdf|Origin of lemurs in Madagascar: what to expect from marine and GPS investigations?]]<br />
* '''J-J. Jaeger''': [[media:Jaeger.pdf|The origin and early evolution of madagascar mammalian fauna : first results and perspectives.]]<br />
* '''P. Philippot, M. Van Zuilen, Y. Teitler (PhD), V. Noel, M. Ader and M. de Wit''': [[media:philippot.pdf|The Barberton Barite Drilling Project: a window on Archean microbial metabolisms]]<br />
* '''Isabelle Duhamel-Achin (PhD), M. Cuney''': Mineralogy and Geochemistry of the Witwatersrand Basin Reefs, South Africa: detrital vs. hydrothermal origin of uranium mineralization, possible sources and constraints for the atmospheric pO2 level prior 2.2 Ga.<br />
* '''F. Guillocheau, M. de Wit, G. Dubois, F. Eckardt, B. Linol, C. Robin, D. Rouby''': [[media:Guillocheau.pdf|Plateau uplift, epeirogeny and evolution of climate : The Kalahari Plateau, a world class laboratory]]<br />
* '''C. Jaupart''': [[media:Jaupart.pdf|Stability of lithosphere and thermal structure]]<br />
* '''P. Cartigny''': [[media:Cartigny.pdf|Traçing Conflict Diamonds ? Yes we can… sometimes.]] Case studies on diamonds from Central African Craton (RDC and CAR)<br />
* '''S. Gilder, M. de Wit, S. Roud, R. Egli and S. Koch''': [[media:de_Wit.pdf|Magnetic signatures of diamonds]]<br />
* '''J. Besse, S. Satolli, R. Domoney, M. de Wit''': [[media:besse.pdf|Disrupted fun in the Cape Fold Belt: pyrite spoils the paleomagnetic party]]<br />
* '''M. Tredoux, Laure Meynadier, M. De Wit''': [[media:tredoux.pdf|Capacity building]]</div>Emmelynehttp://khure.ipgp.fr/index.php/JulyWorkshopJulyWorkshop2009-09-22T14:07:51Z<p>Emmelyne: </p>
<hr />
<div><accesscontrol>Administrators,,Workshop</accesscontrol><br />
<br />
<center><h2>!Khure Workshop presentations</h2></center><br />
<br />
<br />
* [[dewit_introduction.pdf|Introduction]]: '''Vincent Courtillot – Maarten De Wit'''<br />
* '''E. Thébault''' : [[thebault.pdf|The magnetic field over the Southern African continent: from core to crustal magnetic fields]]<br />
* '''M. Moulin (PhD), V. Courtillot, F. Fluteau, G. Marsh, G. Delpech''' : [[Moulin.pdf|Paleomagnetic results and dating from the Karoo traps.]]<br />
* '''L. Carporzen, A. Galdeano, S. Gilder, M. Le Goff, R. Hart, M. Muundjua''': Geomagnetic and Palaeomagnetic studies of the magnetic anomalies associated with the Vredefort impact crater, South Africa: a summary and conclusion.<br />
* '''G. King and the A1 project team''': Landscapes, tectonics and hominins in South Africa<br />
* '''J. Dyment, D. Bissessur, R. Fernandes, N. Villeneuve''': [[dyment.pdf|Origin of lemurs in Madagascar: what to expect from marine and GPS investigations?]]<br />
* '''J-J. Jaeger''': [[Jaeger.pdf|The origin and early evolution of madagascar mammalian fauna : first results and perspectives.]]<br />
* '''P. Philippot, M. Van Zuilen, Y. Teitler (PhD), V. Noel, M. Ader and M. de Wit''': [[philippot.pdf|The Barberton Barite Drilling Project: a window on Archean microbial metabolisms]]<br />
* '''Isabelle Duhamel-Achin (PhD), M. Cuney''': Mineralogy and Geochemistry of the Witwatersrand Basin Reefs, South Africa: detrital vs. hydrothermal origin of uranium mineralization, possible sources and constraints for the atmospheric pO2 level prior 2.2 Ga.<br />
* '''F. Guillocheau, M. de Wit, G. Dubois, F. Eckardt, B. Linol, C. Robin, D. Rouby''': [[Guillocheau.pdf|Plateau uplift, epeirogeny and evolution of climate : The Kalahari Plateau, a world class laboratory]]<br />
* '''C. Jaupart''': [[Jaupart.pdf|Stability of lithosphere and thermal structure]]<br />
* '''P. Cartigny''': [[Cartigny.pdf|Traçing Conflict Diamonds ? Yes we can… sometimes.]] Case studies on diamonds from Central African Craton (RDC and CAR)<br />
* '''S. Gilder, M. de Wit, S. Roud, R. Egli and S. Koch''': [[de_Wit.pdf|Magnetic signatures of diamonds]]<br />
* '''J. Besse, S. Satolli, R. Domoney, M. de Wit''': [[besse.pdf|Disrupted fun in the Cape Fold Belt: pyrite spoils the paleomagnetic party]]<br />
* '''M. Tredoux, Laure Meynadier, M. De Wit''': [[tredoux.pdf|Capacity building]]</div>Emmelynehttp://khure.ipgp.fr/index.php/JulyWorkshopJulyWorkshop2009-09-22T14:05:59Z<p>Emmelyne: </p>
<hr />
<div><accesscontrol>Administrators,,Workshop</accesscontrol><br />
<br />
<center><h2>!Khure Workshop presentations</h2></center><br />
<br />
<br />
* [[dewit_introduction.pdf|Introduction]]: '''Vincent Courtillot – Maarten De Wit'''<br />
* '''E. Thébault''' : [[thebault.pdf|The magnetic field over the Southern African continent: from core to crustal magnetic fields]]<br />
* '''M. Moulin (PhD), V. Courtillot, F. Fluteau, G. Marsh, G. Delpech''' : [[Moulin.pdf|Paleomagnetic results and dating from the Karoo traps.]]<br />
* '''L. Carporzen, A. Galdeano, S. Gilder, M. Le Goff, R. Hart, M. Muundjua''': Geomagnetic and Palaeomagnetic studies of the magnetic anomalies associated with the Vredefort impact crater, South Africa: a summary and conclusion.<br />
* '''G. King and the A1 project team''': Landscapes, tectonics and hominins in South Africa<br />
* '''J. Dyment, D. Bissessur, R. Fernandes, N. Villeneuve''': [[dyment.pdf|Origin of lemurs in Madagascar: what to expect from marine and GPS investigations?]]<br />
* '''J-J. Jaeger''': [[Jaeger.pdf|The origin and early evolution of madagascar mammalian fauna : first results and perspectives.]]<br />
* '''P. Philippot, M. Van Zuilen, Y. Teitler (PhD), V. Noel, M. Ader and M. de Wit''': [[philippot.pdf|The Barberton Barite Drilling Project: a window on Archean microbial metabolisms]]<br />
* '''Isabelle Duhamel-Achin (PhD), M. Cuney''': Mineralogy and Geochemistry of the Witwatersrand Basin Reefs, South Africa: detrital vs. hydrothermal origin of uranium mineralization, possible sources and constraints for the atmospheric pO2 level prior 2.2 Ga.<br />
* '''F. Guillocheau, M. de Wit, G. Dubois, F. Eckardt, B. Linol, C. Robin, D. Rouby''': [[Guillocheau.pdf|Plateau uplift, epeirogeny and evolution of climate : The Kalahari Plateau, a world class laboratory]]<br />
* '''C. Jaupart''': [[Jaupart.pdf|Stability of lithosphere and thermal structure]]<br />
* '''P. Cartigny''': [[Cartigny.pdf|Traçing Conflict Diamonds ?: Yes we can… sometimes.]] Case studies on diamonds from Central African Craton (RDC and CAR)<br />
* '''S. Gilder, M. de Wit, S. Roud, R. Egli and S. Koch''': [[de_Wit.pdf|Magnetic signatures of diamonds]]<br />
* '''J. Besse, S. Satolli, R. Domoney, M. de Wit''': [[besse.pdf|Disrupted fun in the Cape Fold Belt: pyrite spoils the paleomagnetic party]]<br />
* '''M. Tredoux, Laure Meynadier, M. De Wit''': [[tredoux.pdf|Capacity building]]</div>Emmelynehttp://khure.ipgp.fr/index.php/JulyWorkshopJulyWorkshop2009-09-22T14:05:08Z<p>Emmelyne: </p>
<hr />
<div><accesscontrol>Administrators,,Workshop</accesscontrol><br />
<br />
<center><h2>!Khure Workshop presentations</h2></center><br />
<br />
<br />
* [[dewit_introduction.pdf|Introduction]]: '''Vincent Courtillot – Maarten De Wit'''<br />
* '''E. Thébault''' : [[thebault.pdf|The magnetic field over the Southern African continent: from core to crustal magnetic fields]]<br />
* '''M. Moulin (PhD), V. Courtillot, F. Fluteau, G. Marsh, G. Delpech''' : [[Moulin.pdf|Paleomagnetic results and dating from the Karoo traps.]]<br />
* '''L. Carporzen, A. Galdeano, S. Gilder, M. Le Goff, R. Hart, M. Muundjua''' :<br />
Geomagnetic and Palaeomagnetic studies of the magnetic anomalies associated with the Vredefort impact crater, South Africa: a summary and conclusion.<br />
* '''G. King and the A1 project team''': Landscapes, tectonics and hominins in South Africa<br />
* '''J. Dyment, D. Bissessur, R. Fernandes, N. Villeneuve''': [[dyment.pdf|Origin of lemurs in Madagascar: what to expect from marine and GPS investigations?]]<br />
* '''J-J. Jaeger''': [[Jaeger.pdf|The origin and early evolution of madagascar mammalian fauna : first results and perspectives.]]<br />
* '''P. Philippot, M. Van Zuilen, Y. Teitler (PhD), V. Noel, M. Ader and M. de Wit''': [[philippot.pdf|The Barberton Barite Drilling Project: a window on Archean microbial metabolisms]]<br />
* '''Isabelle Duhamel-Achin (PhD), M. Cuney''': Mineralogy and Geochemistry of the Witwatersrand Basin Reefs, South Africa: detrital vs. hydrothermal origin of uranium mineralization, possible sources and constraints for the atmospheric pO2 level prior 2.2 Ga.<br />
* '''F. Guillocheau, M. de Wit, G. Dubois, F. Eckardt, B. Linol, C. Robin, D. Rouby''': [[Guillocheau.pdf|Plateau uplift, epeirogeny and evolution of climate : The Kalahari Plateau, a world class laboratory]]<br />
* '''C. Jaupart''': [[Jaupart.pdf|Stability of lithosphere and thermal structure]]<br />
* '''P. Cartigny''': [[Cartigny.pdf|Traçing Conflict Diamonds ?: Yes we can… sometimes.]] Case studies on diamonds from Central African Craton (RDC and CAR)<br />
* '''S. Gilder, M. de Wit, S. Roud, R. Egli and S. Koch''': [[de_Wit.pdf|Magnetic signatures of diamonds]]<br />
* '''J. Besse, S. Satolli, R. Domoney, M. de Wit''': [[besse.pdf|Disrupted fun in the Cape Fold Belt: pyrite spoils the paleomagnetic party]]<br />
* '''M. Tredoux, Laure Meynadier, M. De Wit''': [[tredoux.pdf|Capacity building]]</div>Emmelynehttp://khure.ipgp.fr/index.php/JulyWorkshopJulyWorkshop2009-09-22T13:54:27Z<p>Emmelyne: </p>
<hr />
<div><accesscontrol>Administrators,,Workshop</accesscontrol><br />
<br />
<center><h2>!Khure Workshop presentations</h2></center><br />
<br />
<br />
* [[dewit_introduction.pdf|Introduction]]: '''Vincent Courtillot – Maarten De Wit'''<br />
* '''E. Thébault''' : [[thebault.pdf|The magnetic field over the Southern African continent: from core to crustal magnetic fields]]<br />
* '''M. Moulin (PhD), V. Courtillot, F. Fluteau, G. Marsh, G. Delpech''' : [[Moulin.pdf|Paleomagnetic results and dating from the Karoo traps.]]<br />
* L. Carporzen, A. Galdeano, S. Gilder, M. Le Goff, R. Hart, M. Muundjua :<br />
[[Geomagnetic and Palaeomagnetic studies of the magnetic anomalies associated with<br />
the Vredefort impact crater, South Africa: a summary and conclusion.<br />
* G. King and the A1 project team: Landscapes, tectonics and hominins in South Africa<br />
* J. Dyment, D. Bissessur, R. Fernandes, N. Villeneuve : Origin of lemurs in<br />
Madagascar: what to expect from marine and GPS investigations?<br />
* J-J. Jaeger : The origin and early evolution of madagascar mammalian fauna : first results and perspectives.<br />
* P. Philippot, M. Van Zuilen, Y. Teitler (PhD), V. Noel, M. Ader and M. de Wit, The Barberton Barite Drilling Project: a window on Archean microbial metabolisms<br />
* Isabelle Duhamel-Achin (PhD), M. Cuney : Mineralogy and Geochemistry of the<br />
Witwatersrand Basin Reefs, South Africa: detrital vs. hydrothermal origin of uranium mineralization, possible sources and constraints for the atmospheric pO2 level prior 2.2 Ga.</div>Emmelynehttp://khure.ipgp.fr/index.php/JulyWorkshopJulyWorkshop2009-09-22T12:37:10Z<p>Emmelyne: </p>
<hr />
<div><accesscontrol>Administrators,,Workshop</accesscontrol><br />
<br />
<center><h2>!Khure Workshop presentations</h2></center><br />
<br />
<br />
* [[dewit_introduction.pdf|Introduction]]: Vincent Courtillot – Maarten De Wit<br />
* E. Thébault : [[thebault.pdf|The magnetic field over the Southern African continent: from core to crustal magnetic fields]]<br />
* M. Moulin (PhD), V. Courtillot, F. Fluteau, G. Marsh, G. Delpech : Paleomagnetic results and dating from the Karoo traps.<br />
* L. Carporzen, A. Galdeano, S. Gilder, M. Le Goff, R. Hart, M. Muundjua :<br />
Geomagnetic and Palaeomagnetic studies of the magnetic anomalies associated with<br />
the Vredefort impact crater, South Africa: a summary and conclusion.<br />
* G. King and the A1 project team: Landscapes, tectonics and hominins in South Africa<br />
* J. Dyment, D. Bissessur, R. Fernandes, N. Villeneuve : Origin of lemurs in<br />
Madagascar: what to expect from marine and GPS investigations?<br />
* J-J. Jaeger : The origin and early evolution of madagascar mammalian fauna : first results and perspectives.<br />
* P. Philippot, M. Van Zuilen, Y. Teitler (PhD), V. Noel, M. Ader and M. de Wit, The Barberton Barite Drilling Project: a window on Archean microbial metabolisms<br />
* Isabelle Duhamel-Achin (PhD), M. Cuney : Mineralogy and Geochemistry of the<br />
Witwatersrand Basin Reefs, South Africa: detrital vs. hydrothermal origin of uranium mineralization, possible sources and constraints for the atmospheric pO2 level prior 2.2 Ga.</div>Emmelynehttp://khure.ipgp.fr/index.php/JulyWorkshopJulyWorkshop2009-09-22T08:32:15Z<p>Emmelyne: </p>
<hr />
<div><accesscontrol>Administrators,,Workshop</accesscontrol><br />
<br />
<center><h2>!Khure Workshop presentations</h2></center><br />
<br />
<br />
* Introduction : Vincent Courtillot – Maarten De Wit<br />
* E. Thébault : [[thebault.pdf|The magnetic field over the Southern African continent: from core to crustal magnetic fields]]<br />
* M. Moulin (PhD), V. Courtillot, F. Fluteau, G. Marsh, G. Delpech : Paleomagnetic results and dating from the Karoo traps.<br />
* L. Carporzen, A. Galdeano, S. Gilder, M. Le Goff, R. Hart, M. Muundjua :<br />
Geomagnetic and Palaeomagnetic studies of the magnetic anomalies associated with<br />
the Vredefort impact crater, South Africa: a summary and conclusion.<br />
* G. King and the A1 project team: Landscapes, tectonics and hominins in South Africa<br />
* J. Dyment, D. Bissessur, R. Fernandes, N. Villeneuve : Origin of lemurs in<br />
Madagascar: what to expect from marine and GPS investigations?<br />
* J-J. Jaeger : The origin and early evolution of madagascar mammalian fauna : first results and perspectives.<br />
* P. Philippot, M. Van Zuilen, Y. Teitler (PhD), V. Noel, M. Ader and M. de Wit, The Barberton Barite Drilling Project: a window on Archean microbial metabolisms<br />
* Isabelle Duhamel-Achin (PhD), M. Cuney : Mineralogy and Geochemistry of the<br />
Witwatersrand Basin Reefs, South Africa: detrital vs. hydrothermal origin of uranium mineralization, possible sources and constraints for the atmospheric pO2 level prior 2.2 Ga.</div>Emmelynehttp://khure.ipgp.fr/index.php/AccueilAccueil2009-09-21T14:24:14Z<p>Emmelyne: </p>
<hr />
<div>== <center>!Khure africa - The story is the African wind (San proverb)</center> ==<br />
<br />
[[image:LogoKhure.jpg|link=Background_history|left|thumb|270px|[[Background_history|"The porcupine story from the San (bushman) peoples of South Africa"]]]]<br />
<br />
<h3><center>A South African - French flagship scientific cooperation program in the Geosciences</center></h3><br />
<br><br />
<p>!Khure Africa explores the dynamic co-evolution of Earth and Life and <br />
their links to tectonics and climate change. It concerns the coupled geo-ecodynamic history of the solid Earth, its fluid envelope and the intervening biosphere, from the early earth to its present state.<br><br />
<br><br />
South-Central Africa, including Madagascar, is the chosen open-air laboratory because it is a natural treasure trove waiting to be explored for its past and present geobio-information that is mostly missing in global-change scale models aimed at future forecasts.<br><br />
<br><br />
!Khure Africa integrates researchers from diverse fields within the Earth and Life sciences. In South Africa, scientists from ten universities/institutions are participating, locally coordinated through the Africa Earth Observation Network (AEON) and the University of Cape Town (UCT); in France, participating scientists from six universities/institutions are coordinated through the Institut de Physique du Globe de Paris (IPGP) and University Paris Diderot.<br><br />
<br><br />
!Khure Africa incorporates a strong Capacity Building program, facilitated through visits and exchanges, especially to enhance analytical skills of South African graduate students in France,and intercollaboration to construct new laboratories in South Africa. Joint supervision of PhD, MSc students, and exchanges of scientists, are ongoing and expanding to fill up to 20 students.<br><br />
<br><br />
The !Khure Africa program was initially financially supported through the ARCUS programme, with equal funds from "Région Ile de France" and the French Ministry of Foreign Affairs, with specific help from Professor Samuel Elmaleh (then attaché for S&T at the Embassy of France, Pretoria, South Africa).<br />
The program has been strongly supported from the start by CNRS and its President, Dr. Catherine Bréchignac. The status of the program is now that of a CNRS GDRI (Groupement de Recherche International). Specific help from Dr. Anne Corval, Head of the CNRS Office for sub-Saharan Africa and Indian Ocean in Johannesburg , is gratefully acknowledged.<br><br />
<br><br />
<em><span style="color:#990099;">Le programme !Khure Africa a été fortement soutenu, dès le départ, par <br />
le CNRS et sa Présidente, Catherine Bréchignac. Le financement a été initié à travers le Programme ARCUS, à parité entre la Région Ile-de-France et le Ministère des Affaires Etrangères, en particulier avec l'aide du Professeur Samuel Elmaleh (attaché scientifique et technique à l'ambassade de France à Prétoria).</span></em><br />
</p><br />
<br />
[[image:BandAllLogo2.jpg|left|870px|]]</div>Emmelynehttp://khure.ipgp.fr/index.php/NewsNews2009-09-17T13:53:21Z<p>Emmelyne: </p>
<hr />
<div><h2>Latest news</h2><br />
<br />
<h3><center>- Progress workshop 7 July, 2009, IPGP, Paris, France -</center></h3><br />
<br />
<center><big>Are we on track?</big></center><br />
<center><em>South Africa-France research and training program<br>in the Geosciences !Khure Africa</em></center><br />
<br />
Report back on the first two years of more than ten !Khure Africa sub-programs.<br />
<br />
* Where : The Institut de Physique du Globe, Paris, France, <br />
* When : July 7th, 09h30- 17h00<br />
* How : Talks & discussions to assess the progress and future of this bilateral program.<br />
* Organisers : Professor Frédéric Fluteau & Mrs. Sylvie Larousse.<br />
<br />
<center><em><strong>[[media:ProgramMeeting.pdf|Download the workshop program]]<br><br />
[[JulyWorkshop|Download the workshop presentations]]</strong></em></center><br />
<br />
<em>For further information contact : [mailto:fluteau@ipgp.fr fluteau@ipgp.fr] and [mailto:larousse@ipgp.fr larousse@ipgp.fr].</em></div>Emmelynehttp://khure.ipgp.fr/index.php/NewsNews2009-09-17T13:52:29Z<p>Emmelyne: </p>
<hr />
<div><h2>Latest news</h2><br />
<br />
<h3><center>- Progress workshop 7 July, 2009, IPGP, Paris, France -</center></h3><br />
<br />
<center><big>Are we on track?</big></center><br />
<center><em>South Africa-France research and training program<br>in the Geosciences !Khure Africa</em></center><br />
<br />
Report back on the first two years of more than ten !Khure Africa sub-programs.<br />
<br />
* Where : The Institut de Physique du Globe, Paris, France, <br />
* When : July 7th, 09h30- 17h00<br />
* How : Talks & discussions to assess the progress and future of this bilateral program.<br />
* Organisers : Professor Frédéric Fluteau & Mrs. Sylvie Larousse.<br />
<br />
<em><strong>[[media:ProgramMeeting.pdf|Download the workshop program]]</strong></em><br><br />
<em><strong>[[JulyWorkshop|Download the workshop presentations]]</strong></em><br />
<br />
<em>For further information contact : [mailto:fluteau@ipgp.fr fluteau@ipgp.fr] and [mailto:larousse@ipgp.fr larousse@ipgp.fr].</em></div>Emmelynehttp://khure.ipgp.fr/index.php/JulyWorkshopJulyWorkshop2009-09-17T13:51:07Z<p>Emmelyne: Created page with '<accesscontrol>Administrators,,Workshop</accesscontrol> <center><h2>!Khure Workshop presentations</h2></center>'</p>
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<div><accesscontrol>Administrators,,Workshop</accesscontrol><br />
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<center><h2>!Khure Workshop presentations</h2></center></div>Emmelynehttp://khure.ipgp.fr/index.php/No_AccessNo Access2009-09-17T13:45:01Z<p>Emmelyne: Created page with '<center><h3>Access to this page is for authorized users only. <br> Please Log in.</h3></center>'</p>
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<div>*Khure Workshop</div>Emmelynehttp://khure.ipgp.fr/index.php/Usergroup:WorkshopUsergroup:Workshop2009-09-17T13:36:39Z<p>Emmelyne: Created page with '•Khure Workshop'</p>
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<div>•Khure Workshop</div>Emmelynehttp://khure.ipgp.fr/index.php/File:ProgramMeeting.pdfFile:ProgramMeeting.pdf2009-07-06T16:14:08Z<p>Emmelyne: </p>
<hr />
<div></div>Emmelynehttp://khure.ipgp.fr/index.php/NewsNews2009-07-06T16:08:20Z<p>Emmelyne: </p>
<hr />
<div><h2>Latest news</h2><br />
<br />
<h3><center>- Progress workshop 7 July, 2009, IPGP, Paris, France -</center></h3><br />
<br />
<center><big>Are we on track?</big></center><br />
<center><em>South Africa-France research and training program<br>in the Geosciences !Khure Africa</em></center><br />
<br />
Report back on the first two years of more than ten !Khure Africa sub-programs.<br />
<br />
* Where : The Institut de Physique du Globe, Paris, France, <br />
* When : July 7th, 09h30- 17h00<br />
* How : Talks & discussions to assess the progress and future of this bilateral program.<br />
* Organisers : Professor Frédéric Fluteau & Mrs. Sylvie Larousse.<br />
<br />
<em><strong>[[media:ProgramMeeting.pdf|Download the workshop program]]</strong></em><br />
<br />
<em>For further information contact : [mailto:fluteau@ipgp.fr fluteau@ipgp.fr] and [mailto:larousse@ipgp.fr larousse@ipgp.fr].</em></div>Emmelynehttp://khure.ipgp.fr/index.php/ProjectB5ProjectB52009-07-06T14:20:31Z<p>Emmelyne: </p>
<hr />
<div><center><h2>Project B5 : The tectonic framework of Southern Africa interpreted from gravity and aeromagnetic data</h2><br />
<h3>French pi: A. Galdeano (with J.L. Le Mouël)<br><br />
South African pi: M. Doucouré</h3><br />
<br />
__TOC__<br />
</center><br />
<br />
<h3>Project Participants</h3><br />
* '''South Africa''': Rodger Hart, Susan Webb, Moctar Doucouré<br />
* '''France''': Armand Galdeano, Luis Gaya-Piqué, Jean-Louis Le Mouël, Erwan Thébault<br />
* '''Other''': Stuart Gilder (Munich), Valentin Mikhailov (Moscow)<br />
<br />
<h3>Aims and objectives</h3><br />
<p><br />
#. To identify the major terrain boundaries (edges) including the limits of effects large impacts in Southern Africa.<br />
#. To identify and understand the relationship between felsic (crustal) and mafic (dominantly mantle) rocks in the Earth‟s crust.<br />
#. To apply magnetic and gravity imaging techniques to coherently map out the major structures in Southern Africa.<br />
#. To Understand the relationship between major sedimentary basins and depth to MOHO<br />
#. To understand the horizontal and vertical distribution of Cretaceous age magmatic/volcanic features.<br />
#. To provide MSc training for at least one black South African student (still to be identified).<br />
</p><br />
<br />
<h3>Introduction</h3><br />
[[image:Fig1_B5.jpg|right|250px|thumb|]]<br />
<p>An understanding of the development of both crustal magnetization and gravity features in the crust is essential in interpreting continental scale terrain boundaries which manifest themselves either as major magnetic or gravity anomalies. In order to determine the major gravity and magnetic features in the upper 30 km of Southern Africa, we intend to apply a number of transformations e.g. block leveling and low pass filtering of the gravity and aeromagnetic data of Southern Africa. These crustal features include kimberlites resulting from magmatic events. The distribution of kimberlites will be analysed through anisotropy associated with magnetization directions.</p><br />
<h3>Aeromagnetic Data Set</h3><br />
<p>Aeromagnetic surveys over Southern Africa were flown by the Geological survey of South Africa during the period from 1966 to 1981 [1]. Total field data were collected along north–south flight lines at a nominal terrain clearance of 150 m, flying at 240 km/h with a sampling interval of two seconds. Flight line spacing was 1 km and perpendicular tie-lines were flown every 10 km. In order to facilitate digital transformation, the data were flight line leveled and block leveled, thus establishing a common datum for all aeromagnetic surveys across South Africa. The interpolation of the aeromagnetic map was done with a grid lattice of 250 x 250 m (fig). It should be noted that the post-acquisition treatment of the data has not been published and is unknown.<br> Because of the way the magnetic data set was collected and leveled, the longest wavelength anomalies do not match up across the subcontinent. We want to develop a procedure to do large scale block corrections in order to obtain unity in the data across the subcontinent. One possible way to achieve unity across the different survey areas is to compare aeromagnetic data with satellite data by upward continuing the aeromagnetic data.<br> Finally once the data is corrected we plan to do a interpretative study that will include structures and geometry definition, source depth clustering and separation of crustal/mantle features.</p><br />
<h3>Bouguer Gravity Data Set</h3><br />
<p>The gravity data were collected from a number of regional and detailed surveys conducted by the University of the Witwatersrand, the Geological Survey of South Africa, the institute of Geological Sciences of Great Britain and various mining and exploration companies. Most of the data were gathered along roads with maximum station intervals of approximately 3 km. The majority of station elevations were determined barometrically and the measurements reduced using the Geodetic reference system 1967 formula. A total of 13500 stations were finally accepted for the compiled data set with an average error of ~1,62 mgal (Wilsher 1987). The data set were gridded at 100m intervals and the UTM projection utilized.</p><br />
<p>The gravity data will be used to identify large (>100 km) crustal anomalies (dense rocks).<br>To do this we have to devise techniques to effectively remove topographic and mantle contributions to the gravity field.</p><br />
<p>One example of the processing we can perform across Southern Africa is to correlate the gravity map and the pseudo-gravimetric map (derived from the magnetic map). This can be computed in a moving window of few kilometers. The resulting map will give us the distribution of the coherence (or the “anti-coherence”) between the 2 anomaly fields (gravity and magnetic) which in turn will provide information about the nature of responsible sources.</p><br />
<br />
<h3>Mode of co-operation between the French and South African research teams</h3><br />
<p>The project will involve bilateral travel between France and South Africa for both research teams, including post-graduate students, for the exchanges of ideas, the interpretation and publication of results. Both South African and French research teams will serve as supervisors of the post-graduate students. Tangible items to be shared between France and South African research teams, to the benefit of both countries, will include digital data (including databases), computer programs and other software, maps, and written works including scientific publications, reports and theses.</p><br />
<br />
<h3>Capitalizing on other geophysical studies</h3><br />
#. Magnetotelluric data have recently been collected in the region that have the potential to image to upper mantle depths.<br />
#. Deep (16 sec) seismic data of the region collected during the Kaapvaal seismic program is also available.<br />
#. Recent basic 3D model of the Wits basin has been developed in gOcad which can be used in modeling programs to test ideas.<br />
<br />
<h3>References</h3><br />
<p><br />
* B. Corner and W.A. Wilsher, Structure of the Witwatersrand basin Derived from interpretation of Aeromagnetic and Gravity Data. In: Exploration ‟87. Geol. Surv. Can. Spec. 3 (1989) 523-546.<br />
* D. Gibert & A. Galdeano, A computer program to perform transformations of gravimetric and aeromagnetic surveys, Comp. & Geosciences, 11, 553-588</p></div>Emmelynehttp://khure.ipgp.fr/index.php/ProjectsBProjectsB2009-07-06T14:20:06Z<p>Emmelyne: </p>
<hr />
<div><h2>Research Projects B: Understanding ancient Africa, Life and Earth</h2><br />
<br />
<p><br />
<ul><br />
<li><big>[[ProjectB1|Sub-project B1: Towards a characterization of “conflict diamonds”]]</big><br><br />
<em>French principal investigator: P. Cartigny (with S. Gilder and C. Aubaud)<br><br />
South African principal investigator: M. de Wit (with S. Richardson and D. Bell)</em><br />
</li><br><br />
<li><big>Sub-project B2: Stabilization and evolution of the first continents</big><br><br />
<em>French principal investigator: C. Jaupart<br><br />
South African principal investigator: S. Mc Court (with D. Bell)</em><br />
</li><br><br />
<li><big>[[ProjectB3|Sub-project B3: Archean life: Early life and ancient life-support systems on the Kaapvaal craton]]</big><br><br />
<em>French principal investigator: P. Philippot South African principal investigator: M. de Wit (with H. Furnes in Norway)</em><br />
</li><br><br />
<li><big>[[ProjectB4|Sub-project B4: Anatomy of an old giant impact crater using magnetic imaging]]</big><br><br />
<em>French principal investigator: A. Galdeano (with S. Gilder)<br><br />
South African principal investigator: R. Hart</em><br />
</li><br><br />
<li><big>[[ProjectB5|Sub-project B5: The tectonic framework of Southern Africa interpreted from gravity and aeromagnetic data]]</big><br><br />
<em>French principal investigator: A. Galdeano (with J.L. Le Mouël)<br><br />
South African principal investigator: M. Doucouré</em><br />
</li><br><br />
<li><big>[[ProjectB6|Sub-project B6: Paleomagnetic study of South African Paleozoic and Precambrian formations: ancient ice ages and geodynamics]]</big><br><br />
<em>French principal investigator: J. Besse<br><br />
South African principal investigator: M. de Wit (with R. Domoney)</em><br />
</li><br><br />
</ul><br />
</p></div>Emmelynehttp://khure.ipgp.fr/index.php/ProjectsAProjectsA2009-07-06T14:18:16Z<p>Emmelyne: </p>
<hr />
<div><h2>Research Projects A: Building relief, climate change and evolution</h2><br />
<br />
<p><br />
<ul><br />
<li><big>[[ProjectA1|Sub-project A1: Tectonic geomorphology and climatic influence on Plio-Pleistocene hominin environments in southern Africa]]</big><br><br />
<em>French principal investigator: G. King<br> <br />
South African principal investigators: Paul Dirks, Lee Berger</em><br />
</li><br><br />
<li><big>[[ProjectA2|Sub-project A2: Evolution of African rift propagation into Southern Africa]]</big><br><br />
<em>French principal investigator: P. Tapponnier (with G. King)<br><br />
South African principal investigator: F. Cotterill</em><br />
</li><br><br />
<li><big>[[ProjectA3|Sub-project A3: Plateau uplift, epeirogeny and evolution of climate and biodiversity]]</big><br><br />
<em>French principal investigator: F. Guillocheau (with P. Tapponnier)<br><br />
South African principal investigator: M. de Wit</em><br />
</li><br><br />
<li><big>[[ProjectA4|Sub-project A4: Large igneous provinces, impacts and climate change]]</big><br><br />
<em><br />
French principal investigator: F. Fluteau (with V. Courtillot)<br><br />
South African principal investigator: G. Marsh</em><br />
</li><br><br />
<li><big>[[ProjectA5|Sub-project A5: A restudy of Madagascar-Africa breakup and evolution of Lemurs]]</big><br><br />
<em>French principal investigator: J.J. Jaeger (with J. Dyment)<br><br />
South African principal investigator: J Masters (with M de Wit)</em><br />
</li><br><br />
<li><big>[[ProjectA6|Sub-project A6: Sun and Earth’s magnetic fields and climate change]]</big><br><br />
<em>French principal investigator: A. Chulliat<br><br />
South African principal investigator: P. Kotzé</em><br />
</li><br><br />
</ul><br />
</p></div>Emmelynehttp://khure.ipgp.fr/index.php/ProjectB6ProjectB62009-07-06T14:16:38Z<p>Emmelyne: </p>
<hr />
<div><center><h2>Project B6: Paleomagnetic study of South African Paleozoic and Precambrian formations : ancient ice ages and geodynamics</h2><br />
<h3>French pi: J. Besse<br><br />
South African pi: M. de Wit (with R. Domoney, UWC)</h3><br />
<br />
__TOC__<br />
</center><br />
<br />
<h3>Project Participants</h3><br />
* '''France''': J. Besse, F. Fluteau, collaboration, Y. Donnadieu (LSCE)<br />
* '''South Africa''': M de Wit, R. Domoney<br />
<br />
<h3>Introduction</h3><br />
<p>The climatic history of the Earth is marked by the alternation of hot periods and glacial eras (Fig1). The causes of climatic variability on long timescales are numerous: paleogeographic changes, evolution of atmospheric chemistry, evolution of the solar constant, etc.... Understanding the causes of these climatic changes is thus an essential stake in the current context of global warming and sustainable development.</p><br />
[[image:Fig1_B6.jpg|right|450px|thumb|Fig 1 Main glacial periods (from Hoffman and Shrag)]]<br />
<p>The purpose of this project is to study the glaciations of Precambrian and EarlyPalaeozoic. South Africa is a good target since most of main glaciations (PermoCarboniferous, Ordovician, Neoproterozoic, 2.2Ga and even a recently discovered 3.3 Ga, de Wit, personal communication) have been recorded. We plan first to focus on the glacial episode at the end of Ordovician, which happens during a greenhouse period.</p><br />
<p>The Ordovician glaciation resulted in the formation of an ice cap over a broad part of Gondwana. Contrary to the other glaciations, which lasted several tens of million years, this one may not have exceeded a few million years, even less. The causes of this glaciation are far from being elucidated. In addition to its volume and its duration, this glaciation occurs during a period known for its high atmospheric CO2 content. This period is also marked by deep upheavals of the carbon cycle which are marked by d13C anomalies, observed on Baltica and Laurentia). The acquisition of new paleomagnetic poles specifying the drift of this continent during this period is essential. For that, we propose to sample the Cape fold belt glaciogenic neighboring sediments in the Pakhuis and Cedarberg formations.</p><br />
<p>These data will constitute an essential basis to tackle the numerical modelling of the Late Ordovician glaciation and its validation. This project will also rely upon several numerical models: a coupled ocean-atmosphere GCM: FOAM, a geochemical model: COMBINE and a model of ice-cap: GRIZZLY.</p><br />
<p>The objectives are to understand the influence of the paleogeographic changes on the climate, the consequences on the carbon cycle and the pCO2, as well as the consequences on the formation of the Gondwanian ice-cap. Finally we propose to compare the glaciations (Precambrian, Late Ordovician, Permo-Carboniferous) occurring within distinct paleogeographic and environmental frameworks in the context of the interactions climate/geodynamic/carbon cycle.</p><br />
<br />
<h3>Paleogeography</h3><br />
[[image:Fig2_B6.jpg|left|400px|thumb|Figure 2: Polar wander path of Gondwana during the Early Paleozoic.]]<br />
<p>Palaeogeography is a key element to better understand the climatic evolution during the Early Paleozoic. The Neoproterozoic glacial events occurred in a paleogeography dominated by the amalgamation and disintegration of a supercontinent, Rodinia, sedimentary glacial deposits being observed at low paleolatitudes (Evans 2003), and in a environmental context in which the biologic activity was restricted with respect to Palaeozoic. The Permo-Carboniferous glacial event occurred during a ice-house period, also related to a supercontinent amalgamation, and followed the development of an abundant continental vegetation. The late Ordovician glacial event probably occurred in a fragmented paleogeography, where continental mass dispersed, in a general greenhouse age. The figure 2 shows the South pole position for Gondwana during the Palaeozoic (McElhinny et al., 2003). Upper Cambrian and lower Ordovician poles are relatively well constrained in Western Africa, whereas the rapid Northward drift of Gondwana (more than 6000km in less than 100Ma) is only constrained by two poorly determined paleopoles between 455 and 405 Ma. Whether this rapid drift represents a continuous, plate-related movement, or a local high shift linked to a true polar wander remains unknown. A better knowledge of the location of Gondwana all along the Early Paleozoic is thus required to improve our understanding of the climate changes during the Ordovician. The uncertainties on pole position preclude any reliable modeling of the climatic evolution, as the surface of continent close to the pole is by itself a critical parameter for the inlandsis location. Moreover, the general plate dynamic may also influence the glacial mechanisms. At last, critical parameters to be modelled are the oceanic temperature gradients, the calculation of which requires a precise knowledge of the paleolatitude of the sampling sites.</p><br />
<p>In the cape Fold belt, Pakhuis and Cedarberg formation describe well the Ordovician glaciations, with the presence of glaciogenic sediments and fossils. Several spots may allow parallel sampling of this important section, already partially sampled by Bachtadse and colleagues (1987), but with an unsufficient number of sites.</p><br />
<h3>Climate Modelling</h3><br />
<p>Numerical tools are required to investigate the influences of forcing factors. As an<br />
example, different causes have been advanced to explain the Hirnantian glaciation: a drawdown of CO2 induced by an enhanced weathering of silicate rocks due to the Taconic orogeny (Kump et al., 1999) or a major change in ocean circulation induced by<br />
paleogeographic changes (Hermann et al., 2004). Climate modelling has already been used to simulate the Ordovician ice age (Crowley and Baum, 1991; Crowley and Baum, 1995; Gibbs et al., 1997, 2000). Poussart et al. (1999) used a coupled atmosphere-ocean-sea ice model to simulate the climate during the Latest stage of Ordovician. Most of the experiments have focused on the pCO2 permitting the inception of an ice cap over Gondwana. Accounting for a lower solar constant at 430 Ma, a 8 to12 x pre-industrial atmospheric level is needed to simulate perennial snow over Gondwana. Despite the fact that the previous studies favoured a better knowledge of the Late Ordovician glaciation, the evolution of the Early Paleozoic climate remains largely unkown.</p><br />
<p>We propose to simulate climate, using a fully coupled ocean-atmosphere GCM FOAM1.5 (Fast Ocean Atmosphere Model). The ocean and atmospheric models are linked by<br />
a coupler, which implements the land and sea ice models and calculates and interpolates the fluxes of heat and momentum between the atmosphere and ocean models (Jacob, 1997).<br />
FOAM successfully simulates many aspects of the present-day and past climate (Donnadieu, 2005; Poulsen et al., 2001). The FOAM GCM will run on a parallel supercomputer at the Institut de Physique du Globe de Paris. We also propose to determine the atmospheric pCO2 using a geochemical COMBINE model (Goddéris and Joachimski, 2004). This is an ocean-atmosphere box-model including the mathematical description of the global biogeochemical cycles of carbon, phosphorus, alkalinity and oxygen. In order to calculate the silicate weathering, the COMBINE model will be forced with simulated climatic variables in a suite of FOAM GCM experiments performed at different pCO2. Fixing the CO2 degassing to a given constant value, COMBINE is run until a steady-state PCO2 is reached. This method has been employed by Donnadieu et al. (2003) to simulate the inception of Sturtian ice age during the Neoproterozoic. An ice-sheet model will be used to estimate the volume of the ice-cap. This model includes the dynamic and thermodynamic of land ice. The FOAM GCM climatic variables will be used to force the ice-sheet model.</p><br />
<h3>References</h3><br />
* Bachtadse, V., R. Van der Voo, and I. Haelbich (1987), Paleozoic paleomagnetism of the western Cape Fold Belt, South Africa, and its bearing on the Paleozoic apparent polar wander path for Gondwana, Earth and Planetary Science Letters, 84, 487-499.<br />
* Crowley, T.J., SK. Baum, KY. Kim 1991. General circulation model sensitivity studies experiments with pole-centered supercontinents. Journ. Geophys. Res. 96, 597-610<br />
* Crowley, T.J. and SK. Baum. 1995. Towards reconciling Late Ordovician (440 Ma) glaciation with very high CO2 levels. Journ. Geophys. Res. 100, 1093-1101.<br />
* Donnadieu, Y., Fluteau, F., Ramstein, G., Ritz, C. et Besse, J., 2003. Is there a conflict between the Neoproterozoic glacial deposits and the snowball earth interpretation : an improved understanding with numerical modeling. Earth Planet. Sci. Let., 208, 101-112.<br />
* Donnadieu, Y., Goddéris, Y., Ramstein, G., Nédelec, A. and Meert, J.G., 2004a. Snowball Earth triggered by continental break-up through changes in runoff. Nature, 428: 303-306.<br />
* Evans, D. A. D. (2003). "A fundamental Precambrian-Phanerozoic shift in earth's glacial style?" Tectonophysics 375: 353-385.<br />
* Gibbs, M.T. et al. 1997. An Atmospheric pCO2 threshold for glaciation in the Late Ordovician. Geology. 25, 447-450.<br />
* Gibbs, MT. et al. 2000. Glaciation in the Early Paleozoic “greenhouse”: the roles of paleogeographies and atmospheric pCO2. in : Huber; B.T. et al. (eds). Warm Climates in Earth history. Cambridge. Univ. Press. 386-422.<br />
* Goddéris, Y. and Joachimski, M.M., 2004. Global change in the late Devonian: modelling the Frasnian-Famennian short-term carbon isotope isotope excursions. Palaeogeography, Palaeoclimatology, Palaeoecology, 202: 309-329.<br />
* Herrmann, A.D., et al. (2004) Response of a Late Ordovician paleoceanography to changes in sea level, continental drift, and atmospheric pCO2: potential causes for long-term cooling and glaciation. Palaeogeography, Palaeoclimatology, Palaeoecology 210, 387-401.<br />
* Hoffman, P., and Shraag, D.P, (2002) The snowball earth Hypothesis: testing the limits of the global change, Terra Nova review article, 51p.<br />
* Jacob, R., 1997. Low frequency variability in a simulated atmosphere ocean system, Univ. Wisconsin-Madison, Madison<br />
* McElhinny, M.W., Powell, C.M., et Pisarevsky, S.A., 2003. Paleozoic terranes of eastern Australia and the drift history of Gondwana. Tectonophys., 362, 41-65.<br />
* Poulsen, C.J., Pierrehumbert, R.T. and Jacob, R.L., 2001. Impact of ocean dynamics on the simulation of the Neoproterozoic "snowball Earth". Geophysical research letters, 28: 1575-1578.<br />
* Poussart, C.J. et al. 1999. Late Ordovician glaciation under high atmospheric CO2: a coupled model analysis. Paleoceanography 14, 542-558.</div>Emmelynehttp://khure.ipgp.fr/index.php/ProjectB6ProjectB62009-07-06T14:16:20Z<p>Emmelyne: </p>
<hr />
<div><center><h2>Project B6: Paleomagnetic study of South African Paleozoic and Precambrian formations : ancient ice ages and geodynamics</h2><br />
<h3>French pi: J. Besse<br><br />
South African pi: M. de Wit (with R. Domoney, UWC)</h3><br />
</center><br />
<br />
<h3>Project Participants</h3><br />
* '''France''': J. Besse, F. Fluteau, collaboration, Y. Donnadieu (LSCE)<br />
* '''South Africa''': M de Wit, R. Domoney<br />
<br />
<h3>Introduction</h3><br />
<p>The climatic history of the Earth is marked by the alternation of hot periods and glacial eras (Fig1). The causes of climatic variability on long timescales are numerous: paleogeographic changes, evolution of atmospheric chemistry, evolution of the solar constant, etc.... Understanding the causes of these climatic changes is thus an essential stake in the current context of global warming and sustainable development.</p><br />
[[image:Fig1_B6.jpg|right|450px|thumb|Fig 1 Main glacial periods (from Hoffman and Shrag)]]<br />
<p>The purpose of this project is to study the glaciations of Precambrian and EarlyPalaeozoic. South Africa is a good target since most of main glaciations (PermoCarboniferous, Ordovician, Neoproterozoic, 2.2Ga and even a recently discovered 3.3 Ga, de Wit, personal communication) have been recorded. We plan first to focus on the glacial episode at the end of Ordovician, which happens during a greenhouse period.</p><br />
<p>The Ordovician glaciation resulted in the formation of an ice cap over a broad part of Gondwana. Contrary to the other glaciations, which lasted several tens of million years, this one may not have exceeded a few million years, even less. The causes of this glaciation are far from being elucidated. In addition to its volume and its duration, this glaciation occurs during a period known for its high atmospheric CO2 content. This period is also marked by deep upheavals of the carbon cycle which are marked by d13C anomalies, observed on Baltica and Laurentia). The acquisition of new paleomagnetic poles specifying the drift of this continent during this period is essential. For that, we propose to sample the Cape fold belt glaciogenic neighboring sediments in the Pakhuis and Cedarberg formations.</p><br />
<p>These data will constitute an essential basis to tackle the numerical modelling of the Late Ordovician glaciation and its validation. This project will also rely upon several numerical models: a coupled ocean-atmosphere GCM: FOAM, a geochemical model: COMBINE and a model of ice-cap: GRIZZLY.</p><br />
<p>The objectives are to understand the influence of the paleogeographic changes on the climate, the consequences on the carbon cycle and the pCO2, as well as the consequences on the formation of the Gondwanian ice-cap. Finally we propose to compare the glaciations (Precambrian, Late Ordovician, Permo-Carboniferous) occurring within distinct paleogeographic and environmental frameworks in the context of the interactions climate/geodynamic/carbon cycle.</p><br />
<br />
<h3>Paleogeography</h3><br />
[[image:Fig2_B6.jpg|left|400px|thumb|Figure 2: Polar wander path of Gondwana during the Early Paleozoic.]]<br />
<p>Palaeogeography is a key element to better understand the climatic evolution during the Early Paleozoic. The Neoproterozoic glacial events occurred in a paleogeography dominated by the amalgamation and disintegration of a supercontinent, Rodinia, sedimentary glacial deposits being observed at low paleolatitudes (Evans 2003), and in a environmental context in which the biologic activity was restricted with respect to Palaeozoic. The Permo-Carboniferous glacial event occurred during a ice-house period, also related to a supercontinent amalgamation, and followed the development of an abundant continental vegetation. The late Ordovician glacial event probably occurred in a fragmented paleogeography, where continental mass dispersed, in a general greenhouse age. The figure 2 shows the South pole position for Gondwana during the Palaeozoic (McElhinny et al., 2003). Upper Cambrian and lower Ordovician poles are relatively well constrained in Western Africa, whereas the rapid Northward drift of Gondwana (more than 6000km in less than 100Ma) is only constrained by two poorly determined paleopoles between 455 and 405 Ma. Whether this rapid drift represents a continuous, plate-related movement, or a local high shift linked to a true polar wander remains unknown. A better knowledge of the location of Gondwana all along the Early Paleozoic is thus required to improve our understanding of the climate changes during the Ordovician. The uncertainties on pole position preclude any reliable modeling of the climatic evolution, as the surface of continent close to the pole is by itself a critical parameter for the inlandsis location. Moreover, the general plate dynamic may also influence the glacial mechanisms. At last, critical parameters to be modelled are the oceanic temperature gradients, the calculation of which requires a precise knowledge of the paleolatitude of the sampling sites.</p><br />
<p>In the cape Fold belt, Pakhuis and Cedarberg formation describe well the Ordovician glaciations, with the presence of glaciogenic sediments and fossils. Several spots may allow parallel sampling of this important section, already partially sampled by Bachtadse and colleagues (1987), but with an unsufficient number of sites.</p><br />
<h3>Climate Modelling</h3><br />
<p>Numerical tools are required to investigate the influences of forcing factors. As an<br />
example, different causes have been advanced to explain the Hirnantian glaciation: a drawdown of CO2 induced by an enhanced weathering of silicate rocks due to the Taconic orogeny (Kump et al., 1999) or a major change in ocean circulation induced by<br />
paleogeographic changes (Hermann et al., 2004). Climate modelling has already been used to simulate the Ordovician ice age (Crowley and Baum, 1991; Crowley and Baum, 1995; Gibbs et al., 1997, 2000). Poussart et al. (1999) used a coupled atmosphere-ocean-sea ice model to simulate the climate during the Latest stage of Ordovician. Most of the experiments have focused on the pCO2 permitting the inception of an ice cap over Gondwana. Accounting for a lower solar constant at 430 Ma, a 8 to12 x pre-industrial atmospheric level is needed to simulate perennial snow over Gondwana. Despite the fact that the previous studies favoured a better knowledge of the Late Ordovician glaciation, the evolution of the Early Paleozoic climate remains largely unkown.</p><br />
<p>We propose to simulate climate, using a fully coupled ocean-atmosphere GCM FOAM1.5 (Fast Ocean Atmosphere Model). The ocean and atmospheric models are linked by<br />
a coupler, which implements the land and sea ice models and calculates and interpolates the fluxes of heat and momentum between the atmosphere and ocean models (Jacob, 1997).<br />
FOAM successfully simulates many aspects of the present-day and past climate (Donnadieu, 2005; Poulsen et al., 2001). The FOAM GCM will run on a parallel supercomputer at the Institut de Physique du Globe de Paris. We also propose to determine the atmospheric pCO2 using a geochemical COMBINE model (Goddéris and Joachimski, 2004). This is an ocean-atmosphere box-model including the mathematical description of the global biogeochemical cycles of carbon, phosphorus, alkalinity and oxygen. In order to calculate the silicate weathering, the COMBINE model will be forced with simulated climatic variables in a suite of FOAM GCM experiments performed at different pCO2. Fixing the CO2 degassing to a given constant value, COMBINE is run until a steady-state PCO2 is reached. This method has been employed by Donnadieu et al. (2003) to simulate the inception of Sturtian ice age during the Neoproterozoic. An ice-sheet model will be used to estimate the volume of the ice-cap. This model includes the dynamic and thermodynamic of land ice. The FOAM GCM climatic variables will be used to force the ice-sheet model.</p><br />
<h3>References</h3><br />
* Bachtadse, V., R. Van der Voo, and I. Haelbich (1987), Paleozoic paleomagnetism of the western Cape Fold Belt, South Africa, and its bearing on the Paleozoic apparent polar wander path for Gondwana, Earth and Planetary Science Letters, 84, 487-499.<br />
* Crowley, T.J., SK. Baum, KY. Kim 1991. General circulation model sensitivity studies experiments with pole-centered supercontinents. Journ. Geophys. Res. 96, 597-610<br />
* Crowley, T.J. and SK. Baum. 1995. Towards reconciling Late Ordovician (440 Ma) glaciation with very high CO2 levels. Journ. Geophys. Res. 100, 1093-1101.<br />
* Donnadieu, Y., Fluteau, F., Ramstein, G., Ritz, C. et Besse, J., 2003. Is there a conflict between the Neoproterozoic glacial deposits and the snowball earth interpretation : an improved understanding with numerical modeling. Earth Planet. Sci. Let., 208, 101-112.<br />
* Donnadieu, Y., Goddéris, Y., Ramstein, G., Nédelec, A. and Meert, J.G., 2004a. Snowball Earth triggered by continental break-up through changes in runoff. Nature, 428: 303-306.<br />
* Evans, D. A. D. (2003). "A fundamental Precambrian-Phanerozoic shift in earth's glacial style?" Tectonophysics 375: 353-385.<br />
* Gibbs, M.T. et al. 1997. An Atmospheric pCO2 threshold for glaciation in the Late Ordovician. Geology. 25, 447-450.<br />
* Gibbs, MT. et al. 2000. Glaciation in the Early Paleozoic “greenhouse”: the roles of paleogeographies and atmospheric pCO2. in : Huber; B.T. et al. (eds). Warm Climates in Earth history. Cambridge. Univ. Press. 386-422.<br />
* Goddéris, Y. and Joachimski, M.M., 2004. Global change in the late Devonian: modelling the Frasnian-Famennian short-term carbon isotope isotope excursions. Palaeogeography, Palaeoclimatology, Palaeoecology, 202: 309-329.<br />
* Herrmann, A.D., et al. (2004) Response of a Late Ordovician paleoceanography to changes in sea level, continental drift, and atmospheric pCO2: potential causes for long-term cooling and glaciation. Palaeogeography, Palaeoclimatology, Palaeoecology 210, 387-401.<br />
* Hoffman, P., and Shraag, D.P, (2002) The snowball earth Hypothesis: testing the limits of the global change, Terra Nova review article, 51p.<br />
* Jacob, R., 1997. Low frequency variability in a simulated atmosphere ocean system, Univ. Wisconsin-Madison, Madison<br />
* McElhinny, M.W., Powell, C.M., et Pisarevsky, S.A., 2003. Paleozoic terranes of eastern Australia and the drift history of Gondwana. Tectonophys., 362, 41-65.<br />
* Poulsen, C.J., Pierrehumbert, R.T. and Jacob, R.L., 2001. Impact of ocean dynamics on the simulation of the Neoproterozoic "snowball Earth". Geophysical research letters, 28: 1575-1578.<br />
* Poussart, C.J. et al. 1999. Late Ordovician glaciation under high atmospheric CO2: a coupled model analysis. Paleoceanography 14, 542-558.</div>Emmelynehttp://khure.ipgp.fr/index.php/ProjectB6ProjectB62009-07-06T14:13:50Z<p>Emmelyne: </p>
<hr />
<div><center><h2>Project B6: Paleomagnetic study of South African Paleozoic and Precambrian formations : ancient ice ages and geodynamics</h2><br />
<h3>French pi: J. Besse<br><br />
South African pi: M. de Wit (with R. Domoney, UWC)</h3><br />
</center><br />
<br />
<h3>Project Participants</h3><br />
* '''France''': J. Besse, F. Fluteau, collaboration, Y. Donnadieu (LSCE)<br />
* '''South Africa''': M de Wit, R. Domoney<br />
<br />
<h3>Introduction</h3><br />
<p>The climatic history of the Earth is marked by the alternation of hot periods and glacial eras (Fig1). The causes of climatic variability on long timescales are numerous: paleogeographic changes, evolution of atmospheric chemistry, evolution of the solar constant, etc.... Understanding the causes of these climatic changes is thus an essential stake in the current context of global warming and sustainable development.</p><br />
[[image:Fig1_B6.jpg|right|450px|thumb|Fig 1 Main glacial periods (from Hoffman and Shrag)]]<br />
<p>The purpose of this project is to study the glaciations of Precambrian and EarlyPalaeozoic. South Africa is a good target since most of main glaciations (PermoCarboniferous, Ordovician, Neoproterozoic, 2.2Ga and even a recently discovered 3.3 Ga, de Wit, personal communication) have been recorded. We plan first to focus on the glacial episode at the end of Ordovician, which happens during a greenhouse period.</p><br />
<p>The Ordovician glaciation resulted in the formation of an ice cap over a broad part of Gondwana. Contrary to the other glaciations, which lasted several tens of million years, this one may not have exceeded a few million years, even less. The causes of this glaciation are far from being elucidated. In addition to its volume and its duration, this glaciation occurs during a period known for its high atmospheric CO2 content. This period is also marked by deep upheavals of the carbon cycle which are marked by d13C anomalies, observed on Baltica and Laurentia). The acquisition of new paleomagnetic poles specifying the drift of this continent during this period is essential. For that, we propose to sample the Cape fold belt glaciogenic neighboring sediments in the Pakhuis and Cedarberg formations.</p><br />
<p>These data will constitute an essential basis to tackle the numerical modelling of the Late Ordovician glaciation and its validation. This project will also rely upon several numerical models: a coupled ocean-atmosphere GCM: FOAM, a geochemical model: COMBINE and a model of ice-cap: GRIZZLY.</p><br />
<p>The objectives are to understand the influence of the paleogeographic changes on the climate, the consequences on the carbon cycle and the pCO2, as well as the consequences on the formation of the Gondwanian ice-cap. Finally we propose to compare the glaciations (Precambrian, Late Ordovician, Permo-Carboniferous) occurring within distinct paleogeographic and environmental frameworks in the context of the interactions climate/geodynamic/carbon cycle.</p><br />
<br />
<h3>Paleogeography</h3><br />
[[image:Fig2_B6.jpg|left|400px|thumb|Figure 2: Polar wander path of Gondwana during the Early Paleozoic.]]<br />
<p>Palaeogeography is a key element to better understand the climatic evolution during the Early Paleozoic. The Neoproterozoic glacial events occurred in a paleogeography dominated by the amalgamation and disintegration of a supercontinent, Rodinia, sedimentary glacial deposits being observed at low paleolatitudes (Evans 2003), and in a environmental context in which the biologic activity was restricted with respect to Palaeozoic. The Permo-Carboniferous glacial event occurred during a ice-house period, also related to a supercontinent amalgamation, and followed the development of an abundant continental vegetation. The late Ordovician glacial event probably occurred in a fragmented paleogeography, where continental mass dispersed, in a general greenhouse age. The figure 2 shows the South pole position for Gondwana during the Palaeozoic (McElhinny et al., 2003). Upper Cambrian and lower Ordovician poles are relatively well constrained in Western Africa, whereas the rapid Northward drift of Gondwana (more than 6000km in less than 100Ma) is only constrained by two poorly determined paleopoles between 455 and 405 Ma. Whether this rapid drift represents a continuous, plate-related movement, or a local high shift linked to a true polar wander remains unknown. A better knowledge of the location of Gondwana all along the Early Paleozoic is thus required to improve our understanding of the climate changes during the Ordovician. The uncertainties on pole position preclude any reliable modeling of the climatic evolution, as the surface of continent close to the pole is by itself a critical parameter for the inlandsis location. Moreover, the general plate dynamic may also influence the glacial mechanisms. At last, critical parameters to be modelled are the oceanic temperature gradients, the calculation of which requires a precise knowledge of the paleolatitude of the sampling sites.</p><br />
<p>In the cape Fold belt, Pakhuis and Cedarberg formation describe well the Ordovician glaciations, with the presence of glaciogenic sediments and fossils. Several spots may allow parallel sampling of this important section, already partially sampled by Bachtadse and colleagues (1987), but with an unsufficient number of sites.</p><br />
<h3>Climate Modelling</h3><br />
<p>Numerical tools are required to investigate the influences of forcing factors. As an<br />
example, different causes have been advanced to explain the Hirnantian glaciation: a drawdown of CO2 induced by an enhanced weathering of silicate rocks due to the Taconic orogeny (Kump et al., 1999) or a major change in ocean circulation induced by<br />
paleogeographic changes (Hermann et al., 2004). Climate modelling has already been used to simulate the Ordovician ice age (Crowley and Baum, 1991; Crowley and Baum, 1995; Gibbs et al., 1997, 2000). Poussart et al. (1999) used a coupled atmosphere-ocean-sea ice model to simulate the climate during the Latest stage of Ordovician. Most of the experiments have focused on the pCO2 permitting the inception of an ice cap over Gondwana. Accounting for a lower solar constant at 430 Ma, a 8 to12 x pre-industrial atmospheric level is needed to simulate perennial snow over Gondwana. Despite the fact that the previous studies favoured a better knowledge of the Late Ordovician glaciation, the evolution of the Early Paleozoic climate remains largely unkown.</p><br />
<p>We propose to simulate climate, using a fully coupled ocean-atmosphere GCM FOAM1.5 (Fast Ocean Atmosphere Model). The ocean and atmospheric models are linked by<br />
a coupler, which implements the land and sea ice models and calculates and interpolates the fluxes of heat and momentum between the atmosphere and ocean models (Jacob, 1997).<br />
FOAM successfully simulates many aspects of the present-day and past climate (Donnadieu, 2005; Poulsen et al., 2001). The FOAM GCM will run on a parallel supercomputer at the Institut de Physique du Globe de Paris. We also propose to determine the atmospheric pCO2 using a geochemical COMBINE model (Goddéris and Joachimski, 2004). This is an ocean-atmosphere box-model including the mathematical description of the global biogeochemical cycles of carbon, phosphorus, alkalinity and oxygen. In order to calculate the silicate weathering, the COMBINE model will be forced with simulated climatic variables in a suite of FOAM GCM experiments performed at different pCO2. Fixing the CO2 degassing to a given constant value, COMBINE is run until a steady-state PCO2 is reached. This method has been employed by Donnadieu et al. (2003) to simulate the inception of Sturtian ice age during the Neoproterozoic. An ice-sheet model will be used to estimate the volume of the ice-cap. This model includes the dynamic and thermodynamic of land ice. The FOAM GCM climatic variables will be used to force the ice-sheet model.</p></div>Emmelynehttp://khure.ipgp.fr/index.php/ProjectB6ProjectB62009-07-06T14:11:49Z<p>Emmelyne: </p>
<hr />
<div><center><h2>Project B6: Paleomagnetic study of South African Paleozoic and Precambrian formations : ancient ice ages and geodynamics</h2><br />
<h3>French pi: J. Besse<br><br />
South African pi: M. de Wit (with R. Domoney, UWC)</h3><br />
</center><br />
<br />
<h3>Project Participants</h3><br />
* '''France''': J. Besse, F. Fluteau, collaboration, Y. Donnadieu (LSCE)<br />
* '''South Africa''': M de Wit, R. Domoney<br />
<br />
<h3>Introduction</h3><br />
<p>The climatic history of the Earth is marked by the alternation of hot periods and glacial eras (Fig1). The causes of climatic variability on long timescales are numerous: paleogeographic changes, evolution of atmospheric chemistry, evolution of the solar constant, etc.... Understanding the causes of these climatic changes is thus an essential stake in the current context of global warming and sustainable development.</p><br />
[[image:Fig1_B6.jpg|right|450px|thumb|Fig 1 Main glacial periods (from Hoffman and Shrag)]]<br />
<p>The purpose of this project is to study the glaciations of Precambrian and EarlyPalaeozoic. South Africa is a good target since most of main glaciations (PermoCarboniferous, Ordovician, Neoproterozoic, 2.2Ga and even a recently discovered 3.3 Ga, de Wit, personal communication) have been recorded. We plan first to focus on the glacial episode at the end of Ordovician, which happens during a greenhouse period.</p><br />
<p>The Ordovician glaciation resulted in the formation of an ice cap over a broad part of Gondwana. Contrary to the other glaciations, which lasted several tens of million years, this one may not have exceeded a few million years, even less. The causes of this glaciation are far from being elucidated. In addition to its volume and its duration, this glaciation occurs during a period known for its high atmospheric CO2 content. This period is also marked by deep upheavals of the carbon cycle which are marked by d13C anomalies, observed on Baltica and Laurentia). The acquisition of new paleomagnetic poles specifying the drift of this continent during this period is essential. For that, we propose to sample the Cape fold belt glaciogenic neighboring sediments in the Pakhuis and Cedarberg formations.</p><br />
<p>These data will constitute an essential basis to tackle the numerical modelling of the Late Ordovician glaciation and its validation. This project will also rely upon several numerical models: a coupled ocean-atmosphere GCM: FOAM, a geochemical model: COMBINE and a model of ice-cap: GRIZZLY.</p><br />
<p>The objectives are to understand the influence of the paleogeographic changes on the climate, the consequences on the carbon cycle and the pCO2, as well as the consequences on the formation of the Gondwanian ice-cap. Finally we propose to compare the glaciations (Precambrian, Late Ordovician, Permo-Carboniferous) occurring within distinct paleogeographic and environmental frameworks in the context of the interactions climate/geodynamic/carbon cycle.</p><br />
<br />
<h3>Paleogeography</h3><br />
[[image:Fig2_B6.jpg|left|400px|thumb|Figure 2: Polar wander path of Gondwana during the Early Paleozoic.]]<br />
<p>Palaeogeography is a key element to better understand the climatic evolution during the Early Paleozoic. The Neoproterozoic glacial events occurred in a paleogeography dominated by the amalgamation and disintegration of a supercontinent, Rodinia, sedimentary glacial deposits being observed at low paleolatitudes (Evans 2003), and in a environmental context in which the biologic activity was restricted with respect to Palaeozoic. The Permo-Carboniferous glacial event occurred during a ice-house period, also related to a supercontinent amalgamation, and followed the development of an abundant continental vegetation. The late Ordovician glacial event probably occurred in a fragmented paleogeography, where continental mass dispersed, in a general greenhouse age. The figure 2 shows the South pole position for Gondwana during the Palaeozoic (McElhinny et al., 2003). Upper Cambrian and lower Ordovician poles are relatively well constrained in Western Africa, whereas the rapid Northward drift of Gondwana (more than 6000km in less than 100Ma) is only constrained by two poorly determined paleopoles between 455 and 405 Ma. Whether this rapid drift represents a continuous, plate-related movement, or a local high shift linked to a true polar wander remains unknown. A better knowledge of the location of Gondwana all along the Early Paleozoic is thus required to improve our understanding of the climate changes during the Ordovician. The uncertainties on pole position preclude any reliable modeling of the climatic evolution, as the surface of continent close to the pole is by itself a critical parameter for the inlandsis location. Moreover, the general plate dynamic may also influence the glacial mechanisms. At last, critical parameters to be modelled are the oceanic temperature gradients, the calculation of which requires a precise knowledge of the paleolatitude of the sampling sites.</p><br />
<p>In the cape Fold belt, Pakhuis and Cedarberg formation describe well the Ordovician glaciations, with the presence of glaciogenic sediments and fossils. Several spots may allow parallel sampling of this important section, already partially sampled by Bachtadse and colleagues (1987), but with an unsufficient number of sites.</p></div>Emmelynehttp://khure.ipgp.fr/index.php/File:Fig2_B6.jpgFile:Fig2 B6.jpg2009-07-06T14:11:27Z<p>Emmelyne: </p>
<hr />
<div></div>Emmelynehttp://khure.ipgp.fr/index.php/File:Fig1_B6.jpgFile:Fig1 B6.jpg2009-07-06T14:11:01Z<p>Emmelyne: </p>
<hr />
<div></div>Emmelynehttp://khure.ipgp.fr/index.php/ProjectB6ProjectB62009-07-06T14:10:48Z<p>Emmelyne: New page: <center><h2>Project B6: Paleomagnetic study of South African Paleozoic and Precambrian formations : ancient ice ages and geodynamics</h2> <h3>French pi: J. Besse<br> South African pi: M. d...</p>
<hr />
<div><center><h2>Project B6: Paleomagnetic study of South African Paleozoic and Precambrian formations : ancient ice ages and geodynamics</h2><br />
<h3>French pi: J. Besse<br><br />
South African pi: M. de Wit (with R. Domoney, UWC)</h3><br />
</center><br />
<br />
<h3>Project Participants</h3><br />
* '''France''': J. Besse, F. Fluteau, collaboration, Y. Donnadieu (LSCE)<br />
* '''South Africa''': M de Wit, R. Domoney<br />
<br />
<h3>Introduction</h3><br />
<p>The climatic history of the Earth is marked by the alternation of hot periods and glacial eras (Fig1). The causes of climatic variability on long timescales are numerous: paleogeographic changes, evolution of atmospheric chemistry, evolution of the solar constant, etc.... Understanding the causes of these climatic changes is thus an essential stake in the current context of global warming and sustainable development.</p><br />
[[image:Fig1_B6.jpg|right|450px|thumb|Fig 1 Main glacial periods (from Hoffman and Shrag)]]<br />
<p>The purpose of this project is to study the glaciations of Precambrian and EarlyPalaeozoic. South Africa is a good target since most of main glaciations (PermoCarboniferous,Ordovician, Neoproterozoic, 2.2Ga and even a recently discovered 3.3 Ga, de Wit, personal communication) have been recorded. We plan first to focus on the glacial episode at the end of Ordovician, which happens during a greenhouse period.</p><br />
<p>The Ordovician glaciation resulted in the formation of an ice cap over a broad part of Gondwana. Contrary to the other glaciations, which lasted several tens of million years, this one may not have exceeded a few million years, even less. The causes of this glaciation are far from being elucidated. In addition to its volume and its duration, this glaciation occurs during a period known for its high atmospheric CO2 content. This period is also marked by deep upheavals of the carbon cycle which are marked by d13C anomalies, observed on Baltica and Laurentia). The acquisition of new paleomagnetic poles specifying the drift of this continent during this period is essential. For that, we propose to sample the Cape fold belt glaciogenic neighboring sediments in the Pakhuis and Cedarberg formations.</p><br />
<p>These data will constitute an essential basis to tackle the numerical modelling of the Late Ordovician glaciation and its validation. This project will also rely upon several numerical models: a coupled ocean-atmosphere GCM: FOAM, a geochemical model: COMBINE and a model of ice-cap: GRIZZLY.</p><br />
<p>The objectives are to understand the influence of the paleogeographic changes on the climate, the consequences on the carbon cycle and the pCO2, as well as the consequences on the formation of the Gondwanian ice-cap. Finally we propose to compare the glaciations (Precambrian, Late Ordovician, Permo-Carboniferous) occurring within distinct paleogeographic and environmental frameworks in the context of the interactions climate/geodynamic/carbon cycle.</p><br />
<br />
<h3>Paleogeography</h3><br />
[[image:Fig2_B6.jpg|left|400px|thumb|Figure 2: Polar wander path of Gondwana during the Early Paleozoic.]]<br />
<p>Palaeogeography is a key element to better understand the climatic evolution during the Early Paleozoic. The Neoproterozoic glacial events occurred in a paleogeography dominated by the amalgamation and disintegration of a supercontinent, Rodinia, sedimentary glacial deposits being observed at low paleolatitudes (Evans 2003), and in a environmental context in which the biologic activity was restricted with respect to Palaeozoic. The Permo-Carboniferous glacial event occurred during a ice-house period, also related to a supercontinent amalgamation, and followed the development of an abundant continental vegetation. The late Ordovician glacial event probably occurred in a fragmented paleogeography, where continental mass dispersed, in a general greenhouse age. The figure 2 shows the South pole position for Gondwana during the Palaeozoic (McElhinny et al., 2003). Upper Cambrian and lower Ordovician poles are relatively well constrained in Western Africa, whereas the rapid Northward drift of Gondwana (more than 6000km in less than 100Ma) is only constrained by two poorly determined paleopoles between 455 and 405 Ma. Whether this rapid drift represents a continuous, plate-related movement, or a local high shift linked to a true polar wander remains unknown. A better knowledge of the location of Gondwana all along the Early Paleozoic is thus required to improve our understanding of the climate changes during the Ordovician. The uncertainties on pole position preclude any reliable modeling of the climatic evolution, as the surface of continent close to the pole is by itself a critical parameter for the inlandsis location. Moreover, the general plate dynamic may also influence the glacial mechanisms. At last, critical parameters to be modelled are the oceanic temperature gradients, the calculation of which requires a precise knowledge of the paleolatitude of the sampling sites.</p><br />
<p>In the cape Fold belt, Pakhuis and Cedarberg formation describe well the Ordovician glaciations, with the presence of glaciogenic sediments and fossils. Several spots may allow parallel sampling of this important section, already partially sampled by Bachtadse and colleagues (1987), but with an unsufficient number of sites.</p></div>Emmelynehttp://khure.ipgp.fr/index.php/ProjectB5ProjectB52009-07-06T13:55:52Z<p>Emmelyne: </p>
<hr />
<div><center><h2>Sub-project n°B5 : The tectonic framework of Southern Africa interpreted from gravity and aeromagnetic data</h2><br />
<h3>French pi: A. Galdeano (with J.L. Le Mouël)<br><br />
South African pi: M. Doucouré</h3><br />
<br />
__TOC__<br />
</center><br />
<br />
<h3>Project Participants</h3><br />
* '''South Africa''': Rodger Hart, Susan Webb, Moctar Doucouré<br />
* '''France''': Armand Galdeano, Luis Gaya-Piqué, Jean-Louis Le Mouël, Erwan Thébault<br />
* '''Other''': Stuart Gilder (Munich), Valentin Mikhailov (Moscow)<br />
<br />
<h3>Aims and objectives</h3><br />
<p><br />
#. To identify the major terrain boundaries (edges) including the limits of effects large impacts in Southern Africa.<br />
#. To identify and understand the relationship between felsic (crustal) and mafic (dominantly mantle) rocks in the Earth‟s crust.<br />
#. To apply magnetic and gravity imaging techniques to coherently map out the major structures in Southern Africa.<br />
#. To Understand the relationship between major sedimentary basins and depth to MOHO<br />
#. To understand the horizontal and vertical distribution of Cretaceous age magmatic/volcanic features.<br />
#. To provide MSc training for at least one black South African student (still to be identified).<br />
</p><br />
<br />
<h3>Introduction</h3><br />
[[image:Fig1_B5.jpg|right|250px|thumb|]]<br />
<p>An understanding of the development of both crustal magnetization and gravity features in the crust is essential in interpreting continental scale terrain boundaries which manifest themselves either as major magnetic or gravity anomalies. In order to determine the major gravity and magnetic features in the upper 30 km of Southern Africa, we intend to apply a number of transformations e.g. block leveling and low pass filtering of the gravity and aeromagnetic data of Southern Africa. These crustal features include kimberlites resulting from magmatic events. The distribution of kimberlites will be analysed through anisotropy associated with magnetization directions.</p><br />
<h3>Aeromagnetic Data Set</h3><br />
<p>Aeromagnetic surveys over Southern Africa were flown by the Geological survey of South Africa during the period from 1966 to 1981 [1]. Total field data were collected along north–south flight lines at a nominal terrain clearance of 150 m, flying at 240 km/h with a sampling interval of two seconds. Flight line spacing was 1 km and perpendicular tie-lines were flown every 10 km. In order to facilitate digital transformation, the data were flight line leveled and block leveled, thus establishing a common datum for all aeromagnetic surveys across South Africa. The interpolation of the aeromagnetic map was done with a grid lattice of 250 x 250 m (fig). It should be noted that the post-acquisition treatment of the data has not been published and is unknown.<br> Because of the way the magnetic data set was collected and leveled, the longest wavelength anomalies do not match up across the subcontinent. We want to develop a procedure to do large scale block corrections in order to obtain unity in the data across the subcontinent. One possible way to achieve unity across the different survey areas is to compare aeromagnetic data with satellite data by upward continuing the aeromagnetic data.<br> Finally once the data is corrected we plan to do a interpretative study that will include structures and geometry definition, source depth clustering and separation of crustal/mantle features.</p><br />
<h3>Bouguer Gravity Data Set</h3><br />
<p>The gravity data were collected from a number of regional and detailed surveys conducted by the University of the Witwatersrand, the Geological Survey of South Africa, the institute of Geological Sciences of Great Britain and various mining and exploration companies. Most of the data were gathered along roads with maximum station intervals of approximately 3 km. The majority of station elevations were determined barometrically and the measurements reduced using the Geodetic reference system 1967 formula. A total of 13500 stations were finally accepted for the compiled data set with an average error of ~1,62 mgal (Wilsher 1987). The data set were gridded at 100m intervals and the UTM projection utilized.</p><br />
<p>The gravity data will be used to identify large (>100 km) crustal anomalies (dense rocks).<br>To do this we have to devise techniques to effectively remove topographic and mantle contributions to the gravity field.</p><br />
<p>One example of the processing we can perform across Southern Africa is to correlate the gravity map and the pseudo-gravimetric map (derived from the magnetic map). This can be computed in a moving window of few kilometers. The resulting map will give us the distribution of the coherence (or the “anti-coherence”) between the 2 anomaly fields (gravity and magnetic) which in turn will provide information about the nature of responsible sources.</p><br />
<br />
<h3>Mode of co-operation between the French and South African research teams</h3><br />
<p>The project will involve bilateral travel between France and South Africa for both research teams, including post-graduate students, for the exchanges of ideas, the interpretation and publication of results. Both South African and French research teams will serve as supervisors of the post-graduate students. Tangible items to be shared between France and South African research teams, to the benefit of both countries, will include digital data (including databases), computer programs and other software, maps, and written works including scientific publications, reports and theses.</p><br />
<br />
<h3>Capitalizing on other geophysical studies</h3><br />
#. Magnetotelluric data have recently been collected in the region that have the potential to image to upper mantle depths.<br />
#. Deep (16 sec) seismic data of the region collected during the Kaapvaal seismic program is also available.<br />
#. Recent basic 3D model of the Wits basin has been developed in gOcad which can be used in modeling programs to test ideas.<br />
<br />
<h3>References</h3><br />
<p><br />
* B. Corner and W.A. Wilsher, Structure of the Witwatersrand basin Derived from interpretation of Aeromagnetic and Gravity Data. In: Exploration ‟87. Geol. Surv. Can. Spec. 3 (1989) 523-546.<br />
* D. Gibert & A. Galdeano, A computer program to perform transformations of gravimetric and aeromagnetic surveys, Comp. & Geosciences, 11, 553-588</p></div>Emmelynehttp://khure.ipgp.fr/index.php/File:Fig1_B5.jpgFile:Fig1 B5.jpg2009-07-06T13:50:56Z<p>Emmelyne: </p>
<hr />
<div></div>Emmelynehttp://khure.ipgp.fr/index.php/ProjectB5ProjectB52009-07-06T13:50:33Z<p>Emmelyne: New page: <center><h2>Sub-project n°B5 : The tectonic framework of Southern Africa interpreted from gravity and aeromagnetic data</h2> <h3>French pi: A. Galdeano (with J.L. Le Mouël)<br> South Afr...</p>
<hr />
<div><center><h2>Sub-project n°B5 : The tectonic framework of Southern Africa interpreted from gravity and aeromagnetic data</h2><br />
<h3>French pi: A. Galdeano (with J.L. Le Mouël)<br><br />
South African pi: M. Doucouré</h3><br />
<br />
__TOC__<br />
</center><br />
<br />
<h3>Project Participants</h3><br />
* '''South Africa''': Rodger Hart, Susan Webb, Moctar Doucouré<br />
* '''France''': Armand Galdeano, Luis Gaya-Piqué, Jean-Louis Le Mouël, Erwan Thébault<br />
* '''Other''': Stuart Gilder (Munich), Valentin Mikhailov (Moscow)<br />
<br />
<h3>Aims and objectives</h3><br />
<p><br />
#. To identify the major terrain boundaries (edges) including the limits of effects large impacts in Southern Africa.<br />
#. To identify and understand the relationship between felsic (crustal) and mafic (dominantly mantle) rocks in the Earth‟s crust.<br />
#. To apply magnetic and gravity imaging techniques to coherently map out the major structures in Southern Africa.<br />
#. To Understand the relationship between major sedimentary basins and depth to MOHO<br />
#. To understand the horizontal and vertical distribution of Cretaceous age magmatic/volcanic features.<br />
#. To provide MSc training for at least one black South African student (still to be identified).<br />
</p><br />
<br />
<h3>Introduction</h3><br />
[[image:Fig1_B5.jpg|right|250px|thumb|]]<br />
<p>An understanding of the development of both crustal magnetization and gravity features in the crust is essential in interpreting continental scale terrain boundaries which manifest themselves either as major magnetic or gravity anomalies. In order to determine the major gravity and magnetic features in the upper 30 km of Southern Africa, we intend to apply a number of transformations e.g. block leveling and low pass filtering of the gravity and aeromagnetic data of Southern Africa. These crustal features include kimberlites resulting from magmatic events. The distribution of kimberlites will be analysed through anisotropy associated with magnetization directions.</p></div>Emmelynehttp://khure.ipgp.fr/index.php/ProjectB4ProjectB42009-07-06T13:40:38Z<p>Emmelyne: </p>
<hr />
<div><center><h2>Project B4: Anatomy of an old giant impact crater using magnetic imaging (from the city of Paris to the town of Parys)</h2><br />
<h3>French pi: A. Galdeano (with S. Gilder)<br><br />
South African pi: R. Hart</h3><br />
<br />
__TOC__<br />
</center><br />
<h3>Project Participants</h3><br />
* <strong>South Africa</strong>: Rodger Hart, Susan Webb<br />
* '''France''': Armand Galdeano, Maxime Legoff<br />
* '''Other''': Stuart Gilder (Munich), Laurent Carpozen<br />
<br />
<h3>Aims and objectives</h3><br />
# To apply magnetic imaging to map out the structure of the Vredefort impact crater in high resolution.<br />
# To heighten the profile of the Vredefort impact crater in the light of its world heritage status, by producing useful images of important faults and subtle structural features that have an important bearing on land use (e.g. bridges, water resources).<br />
# To apply our knowledge of the effects of meteorite impacts, to further our understanding on the relative strength of the magnetic field of Earth and other planets in our solar system.<br />
# To provide MSc training for at least one black South African student. A student for this project has already been identified.<br />
<br />
<h3>Introduction.</h3><br />
[[image:Fig1_B4.jpg|right|350px|thumb|Fig. 1. Aeromagnetic map over the Vredefort crater flown in 1981 by the South African Geological Survey. The inserts show the proposed survey regions.]]<br />
<p>The Vredefort dome is the largest impact crater on Earth, and any new information on Vredefort sets a precedent for understanding meteorite impacts both on Earth and on the other planets in our solar system. However, our understanding of the Vredefort structure is still far from complete, and in particular we have very little knowledge of the structure of the crater core, largely because the central area is covered by younger rocks. The central core is key, as it preserves a history of crustal strength, impact, flexure and relaxation from the time when the impact formed. By combining gravity, magnetics, seismics (both Vibroseis and teleseismic), and MT data we can build up an unprecedented 3D model of the structure at depth.</p><br />
<br />
<h3>Aeromagnetic Surveys</h3><br />
<p>Low resolution aeromagnetic images with 1km line spacing over the structure show strong, well-defined concentric patterns (Fig. 1). In the rim, the patterns reflect the different sedimentary strata of the Witwatersrand basin. A prominent negative magnetic anomaly that extends in a broad semicircular belt ~2 to 4 km wide around most of the basement core (inner 30x 30km insert; Fig.1.) is roughly centered above the amphibolite-granulite facies transition which is recognized as a fundamental boundary within the crust and is commonly considered to designate the transition from middle to lower crustal levels [1]. The Vredefort crater contains the only exposure of the amphibolite-granulite facies transition in Southern Africa.</p><br />
<br />
<h3>Proposed Research Program</h3><br />
<h4>High resolution ground magnetic survey</h4><br />
<p>In order to establish the relationship of the negative anomaly to the amphibolite-granulite facies transition zone we undertook a high-resolution ground magnetic surveys over a well-exposed section of the amphibolite-granulite transition (insert a Fig. 2.) The results of this study shows that the magnetic signatures across this transition correlate closely with the geology [2]. In particular, with the transition zone and the the impact related faults that transect the basement. Thus, the results of our pilot study show that detailed ground magnetic surveys can precisely delineate lithological boundaries as well as the impact related radial and concentric faults that juxtapose the different geological units.</p><br />
<p>In our proposed project we plan to extend our high resolution survey over the entire central part of the crater (inner 30x 30km insert; Fig.1) in order to map out the detailed geological structures of the crater core. We intend to do a ground magnetic survey using a Geometrics cesium vapour magnetometer (G-858) and a newly developed vectorial magnetometer. Geographic positions will be collected simultaneously using a GPS receiver. Data will be recorded at 1-second intervals which will yield spatial separation between 1 to 1.5 m.. The GPS positioning has an accuracy of about 10 meters. The average spacing of survey lines will be ~25 m (Fig. 4a).</p><br />
<h4>Mode of co-operation between the French and South African research teams.</h4><br />
<p><br />
The project will involve bilateral travel between France and South Africa for both research teams, including post-graduate students, for fieldwork, acquisition of analytical data (including training of French and South African students), and interpretation, presentation and publication of results. Both teams will serve as supervisors of the post-graduate students. 2 seasons of fieldwork (duration of about one month each season) are planed for 2007 and 2008.</p><br />
<h4>Capitalizing on other geophysical studies</h4><br />
# Magnetotelluric data have recently been collected in the region that have the potential to image to upper mantle depths.<br />
# Deep (16 sec) seismic data of the region collected during the Kaapvaal seismic program is also available.<br />
<br />
<h3>References</h3><br />
<p><br />
* Hart, R. J., Andreoli, M. A. G., Reimold, W. U. and Tredoux, M. (1991). Aspects of the dynamic and thermal metamorphic history of the Vredefort structure: implications for its origin: Tectonophysics, v. 192, p. 313-331.<br />
* Manfriedt Muundjua, Rodger J. Hart, Stuart A. Gilder, Laurent Carporzen , Armand Galdeano, (2007) Magnetic Imaging of the Vredefort Impact crater, South Africa Earth and Planetary Science Letters (in Press)<br />
</p></div>Emmelynehttp://khure.ipgp.fr/index.php/ProjectB4ProjectB42009-07-06T13:37:22Z<p>Emmelyne: </p>
<hr />
<div><center><h2>Project B4: Anatomy of an old giant impact crater using magnetic imaging (from the city of Paris to the town of Parys)</h2><br />
<h3>French pi: A. Galdeano (with S. Gilder)<br><br />
South African pi: R. Hart</h3><br />
<br />
__TOC__<br />
</center><br />
<h3>Project Participants</h3><br />
* <strong>South Africa</strong>: Rodger Hart, Susan Webb<br />
* '''France''': Armand Galdeano, Maxime Legoff<br />
* '''Other''': Stuart Gilder (Munich), Laurent Carpozen<br />
<br />
<h3>Aims and objectives</h3><br />
# To apply magnetic imaging to map out the structure of the Vredefort impact crater in high resolution.<br />
# To heighten the profile of the Vredefort impact crater in the light of its world heritage status, by producing useful images of important faults and subtle structural features that have an important bearing on land use (e.g. bridges, water resources).<br />
# To apply our knowledge of the effects of meteorite impacts, to further our understanding on the relative strength of the magnetic field of Earth and other planets in our solar system.<br />
# To provide MSc training for at least one black South African student. A student for this project has already been identified.<br />
<br />
<h3>Introduction.</h3><br />
[[image:Fig1_B4.jpg|right|350px|thumb|Fig. 1. Aeromagnetic map over the Vredefort crater flown in 1981 by the South African Geological Survey. The inserts show the proposed survey regions.]]<br />
<p>The Vredefort dome is the largest impact crater on Earth, and any new information on Vredefort sets a precedent for understanding meteorite impacts both on Earth and on the other planets in our solar system. However, our understanding of the Vredefort structure is still far from complete, and in particular we have very little knowledge of the structure of the crater core, largely because the central area is covered by younger rocks. The central core is key, as it preserves a history of crustal strength, impact, flexure and relaxation from the time when the impact formed. By combining gravity, magnetics, seismics (both Vibroseis and teleseismic), and MT data we can build up an unprecedented 3D model of the structure at depth.</p><br />
<br />
<h3>Aeromagnetic Surveys</h3><br />
<p>Low resolution aeromagnetic images with 1km line spacing over the structure show strong, well-defined concentric patterns (Fig. 1). In the rim, the patterns reflect the different sedimentary strata of the Witwatersrand basin. A prominent negative magnetic anomaly that extends in a broad semicircular belt ~2 to 4 km wide around most of the basement core (inner 30x 30km insert; Fig.1.) is roughly centered above the amphibolite-granulite facies transition which is recognized as a fundamental boundary within the crust and is commonly considered to designate the transition from middle to lower crustal levels [1]. The Vredefort crater contains the only exposure of the amphibolite-granulite facies transition in Southern Africa.</p></div>Emmelynehttp://khure.ipgp.fr/index.php/File:Fig1_B4.jpgFile:Fig1 B4.jpg2009-07-06T13:36:48Z<p>Emmelyne: </p>
<hr />
<div></div>Emmelynehttp://khure.ipgp.fr/index.php/ProjectB4ProjectB42009-07-06T13:36:36Z<p>Emmelyne: </p>
<hr />
<div><center><h2>Project B4: Anatomy of an old giant impact crater using magnetic imaging (from the city of Paris to the town of Parys)</h2><br />
<h3>French pi: A. Galdeano (with S. Gilder)<br><br />
South African pi: R. Hart</h3><br />
<br />
__TOC__<br />
</center><br />
<h3>Project Participants</h3><br />
* <strong>South Africa</strong>: Rodger Hart, Susan Webb<br />
* '''France''': Armand Galdeano, Maxime Legoff<br />
* '''Other''': Stuart Gilder (Munich), Laurent Carpozen<br />
<br />
<h3>Aims and objectives</h3><br />
# To apply magnetic imaging to map out the structure of the Vredefort impact crater in high resolution.<br />
# To heighten the profile of the Vredefort impact crater in the light of its world heritage status, by producing useful images of important faults and subtle structural features that have an important bearing on land use (e.g. bridges, water resources).<br />
# To apply our knowledge of the effects of meteorite impacts, to further our understanding on the relative strength of the magnetic field of Earth and other planets in our solar system.<br />
# To provide MSc training for at least one black South African student. A student for this project has already been identified.<br />
<br />
<h3>Introduction.</h3><br />
<p>The Vredefort dome is the largest impact crater on Earth, and any new information on Vredefort sets a precedent for understanding meteorite impacts both on Earth and on the other planets in our solar system. However, our understanding of the Vredefort structure is still far from complete, and in particular we have very little knowledge of the structure of the crater core, largely because the central area is covered by younger rocks. The central core is key, as it preserves a history of crustal strength, impact, flexure and relaxation from the time when the impact formed. By combining gravity, magnetics, seismics (both Vibroseis and teleseismic), and MT data we can build up an unprecedented 3D model of the structure at depth.</p><br />
<br />
<h3>Aeromagnetic Surveys</h3><br />
[[image:Fig1_B4.jpg|right|350px|thumb|Fig. 1. Aeromagnetic map over the Vredefort crater flown in 1981 by the South African Geological Survey. The inserts show the proposed survey regions.]]<br />
<p>Low resolution aeromagnetic images with 1km line spacing over the structure show strong, well-defined concentric patterns (Fig. 1). In the rim, the patterns reflect the different sedimentary strata of the Witwatersrand basin. A prominent negative magnetic anomaly that extends in a broad semicircular belt ~2 to 4 km wide around most of the basement core (inner 30x 30km insert; Fig.1.) is roughly centered above the amphibolite-granulite facies transition which is recognized as a fundamental boundary within the crust and is commonly considered to designate the transition from middle to lower crustal levels [1]. The Vredefort crater contains the only exposure of the amphibolite-granulite facies transition in Southern Africa.</p></div>Emmelynehttp://khure.ipgp.fr/index.php/ProjectB4ProjectB42009-07-06T13:32:25Z<p>Emmelyne: New page: <center><h2>Project B4: Anatomy of an old giant impact crater using magnetic imaging (from the city of Paris to the town of Parys)</h2> <h3>French pi: A. Galdeano (with S. Gilder)<br> Sout...</p>
<hr />
<div><center><h2>Project B4: Anatomy of an old giant impact crater using magnetic imaging (from the city of Paris to the town of Parys)</h2><br />
<h3>French pi: A. Galdeano (with S. Gilder)<br><br />
South African pi: R. Hart</h3><br />
<br />
__TOC__<br />
</center><br />
<h3>Project Participants</h3><br />
* <strong>South Africa</strong>: Rodger Hart, Susan Webb<br />
* '''France''': Armand Galdeano, Maxime Legoff<br />
* '''Other''': Stuart Gilder (Munich), Laurent Carpozen</div>Emmelynehttp://khure.ipgp.fr/index.php/ProjectB3ProjectB32009-07-06T13:03:37Z<p>Emmelyne: </p>
<hr />
<div><center><h2>Project B3: Archean life: Early life and ancient life-support systems on the Kaapvaal craton</h2><br />
<h3>French pi: P. Philippot<br />
<br>South African pi: M. de Wit (with H. Furnes in Norway)</h3><br />
<br />
</center><br />
<h3>Project Participants</h3><br />
* South Africa: Maarten de Wit, Eugene Grosch, AEON, Cape Town<br />
* France: Pascal Philippot, Mark van Zuilen IPG-Paris<br />
* Norway: Harald Furnes, Nicola MacLoughlin, Centre for Geobiology, Bergen <br />
* Canada: Karlis Muelenbachs, Isotope centre, Edmonton.<br />
<br />
<h3>Summary</h3><br />
<p>Since the Archean and Palaeoproterozoic are dominated by volcanosedimentary successions that have experienced different degrees of metamorphism, many ongoing controversies exist regarding life in the Precambrian part of Earth history. It is now recognized that future studies of early life and the associated environmental conditions depends on better description of geological context, identification of hydrothermal and metamorphic processes, and detailed structural, isotopic and chemical description of mineral assemblages, stromatolitic microlaminae, and organic microstructures that are indigenous to and syngenetic with the stratigraphic rock record. The most serious problem for understanding the evolution of organisms and their biogeochemical environments from the ancient rock record has been the difficulty in obtaining important sequences of “fresh” rocks, i.e., rocks that have not been severely altered by post-depositional processes. In 2004, pristine drill core samples were recovered from key localities of the Archaen Pilbara Craton, Western Australia. Here we propose to take the advantage of this expertise to perform a new drilling project aimed at intersecting similar 3.3-3.5 billion year old rock succession in South Africa, from the Barberton greenstone belt. The important issue to be addressed concern: 1) the significance of traces (Ichnofossils) of microbial activity in the glassy (now recrystalised) margins of pillow lavas; 2) the significance of elemental sulfur disproportionation as one of the most primitive, rudimentary microbial metabolism on Early Earth and 3) the composition and temperature of hydrothermal fluids and Archaean seawater that have interacted with these rocks, and the origins of asociated carbonaceous material (biogenic vs inorganic). A wide variety of state-of-the-art bulk and in situ analytical techniques will be used to study biologic and geochemical processes in these pristine drill cores.</p><br />
<h3>Scientific Project</h3><br />
<p>Although several decades have passed since the first description of recognisable early Archaean microfossils (DUNLOP et al., 1978), morphology-focused imaging techniques of fossil-like objects and stable isotope (C, N, S) compositions of putative organisms have repeatedly failed to pose limits on the interpretation of the biogenic origin of the microstructures (BRASIER et al., 2002; MOJZSIS et al., 1996; SCHOPF et al., 2002; VAN ZUILEN et al., 2002). Additionally, several abiologic metamorphic and hydrothermal reactions have been identified that can produce kerogen and graphite (BRASIER et al., 2002; VAN ZUILEN et al., 2002), and specific abiologic processes have been described that can generate complex structures that resemble microfossils (GARCIA-RUIZ et al., 2003). In view of these uncertainties and controversies, it is clear that elucidating how and when life may have originated on Earth requires first to understand the conditions that prevailed early in Earth‟s history and the environments in which life may have appeared and later evolved. The recent findings of the Norwegian-led group of ichnofossils in the rims of the worlds oldest pillow lavas in South Africa and Australia (FURNES et al., 2004; 2007a,b ) has dramatically shown that rocks previously ignored in studies of early life (e.g. basaltic igneous rocks) now offer a new paleo-environment as habitats for early life. This holds great potential to track life back even further in time, and must be considered a profitable focus for such early life studies (FURNES et al., 2007a,b; MCLOUGHLIN ET AL., 2007).</p><br />
<p>Life on early Earth is likely to have gone through one or more hot ocean. It is possible that early life diversified near hydrothermal vents where only hyperthermophiles organisms would have survived. Archaean hydrothermal settings would have been varied, with abundant vent fields like black smokers and hydrothermal deposits rich in Fe, Cu, S (De Witt et al., 1982). Microscopic sulfides with low 34S/32S ratios in marine sulfate deposits from the 3,490 Myr-old Dresser Formation, Warrawoona Group, Australia, have been interpreted as evidence for the presence of early sulfate-reducing organisms on Earth (SHEN et al., 2001). This finding is at odd with the long standing consensual notion that the Archean atmosphere was essentially reduced and that oxygen reached appreciable levels around 2 to 2.4 billion years ago (HOLLAND, 1984). The great oxidation story was strengthened considerably in the recent years by the discovery that minerals in ancient rocks had unusual ratios of sulfur isotopes, a phenomenon known as mass-independent fractionation (MIF-S; FARQUHAR et al., 2000). The only known mechanism that can produce this effect is the breakup of sulfur dioxide by ultraviolet light in a low-oxygen atmosphere. The MIF-S isotopic signature is small or entirely absent in rocks younger than 2.4 billion years, suggesting that Earth‟s atmosphere has been oxygen-rich since that time. Recent results obtained from drill core samples from Australia show that the story may be much more complex then originally envisioned, however (Ohmoto et al., 2006; Ono et al., 2006; Anbar et al., 2007; Kaufman et al;, 2007). Using high resolution in situ isotopic techniques, Philippot et al. (2007) showed that the microscopic sulfides from the 3.5 Ga Dresser Foramtion have a mass independently-fractionated sulfur isotopic anomaly (∆33S) that differs from that of their host sulfate (barite). These microscopic sulfides cannot have been produced by sulfate reducing microbes, nor by abiologic processes that involve reduction of sulfate. Instead, they interpret the combined negative ∂34S and positive ∆33S signature of these microscopic sulfides as evidence for the early existence of organisms that disproportionate elemental sulfur. This finding provides strong support in favor of a reduced environment at about 3.5 Ga.</p><br />
<p>Knowledge of the composition and temperature of hydrothermal fluids and seawater is central to elucidating the conditions pertaining to the development of life on early Earth. Cl/Br ratio in fluids is considered conservative in many geological settings and is therefore widely used to trace the origin of fluids (meteoric, oceanic, crustal, mantellic) in the rock record. Analysis of ancient fluid inclusions from the Kaapvaal Craton, South Africa, suggest that Cl/Br in Archaean 3.2 Gyr-old (DE RONDE et al., 1997) and paleoproterozoic 2.2 Gyr-old (GUTZMER et al., 2003) seawater was below present-day value and resulted from mantle buffering. These studies, however, were based on bulk fluid analyses (i.e., crush-leach) which can result in fluid mixing if several fluid generations occur in a single sample. Alternatively, detailed chemical analysis of individual fluid inclusions can be performed by Synchrotron Radiation X-ray micro-Fluorescence, thus allowing independent analysis of different fluids trapped in the same sample. Using this technique, (FORIEL et al., 2004) showed that fluid infiltrating pillow basalts at the base of the Dresser and Apex hydrothermal systems of the Pilbara Craton consisted of mixing trends of fluids with compositions ranging from typical modern seawater enriched in salt by 2 to 3 times (7 to 8 wt% salt) combined with hydrothermal fluid components enriched in Ba and transition metals (Fe, Cu, Zn). Furthermore, as introduced above, sulfur is a key element in Archaean geochemistry, as seawater sulfate concentration is used to constrain the oxidation state of the early ocean and atmosphere, and S may have been a key element for early metabolic processes and for the evolution of primitive life (SHEN et al., 2001, Philippot et al., 2007). Using in-situ SXRF technique, (FORIEL et al., 2004) estimated that the “North-Pole seawater component” contained low sulfate concentration (0–8 mM) compared to 28 mM in present-day ocean, which further supports the notion that early metabolisms used reduced (elemental S) rather than oxidized (sulfate) species as a source of energy.</p><br />
<br />
<h3>Proposed Research Project</h3><br />
<p>The aim of this project is to explore new frontiers of addressing the problem of primitive life by establishing links between hydrothermal fluids and seawater circulation, mineral crystallisation, sediment deposition and diagenesis/metamorphism, and the development of the earliest ecological niches. Specifically, we aim at constraining the composition, and the redox state of the primitive ocean and atmosphere, and to develop integrated geochemical studies involving structural, isotopic and chemical description of mineral assemblages, fluid inclusions and organic microstructures (microfossils?) that are indigenous to and syngenetic with the stratigraphic/hydrothermal rock record.</p><br />
<p>Subtopics:<br />
* Microfossils in pillow margins - what was the optimum temperature-window for preservation?<br />
* Elemental sulfur disproportionation; a widespread early Archean microbial metabolism?<br />
* Interactions between fluids, rocks and microbes - Can we define chemical fingerprints?<br />
* Archean ocean temperature and composition - hot or cold, strongly or middly saline, buffered by organic activity?</p><br />
<h3>Three Proposed Drilling Targets</h3><br />
<p>We take advantage of the expertise we gained while performing the Pilbara Drilling Project in 2004 (VAN KRANENDONK et al., 2006) to recover “fresh” continuous sections at two or three (depending of technical constraints and financial supports) key geologic formations of the Barberton, greenstone belt:</p><br />
<h4>1- Upper Onverwacht Group</h4><br />
<p><em>from the top of the Hooggenoeg Formation (>3,47Ga) into the base of the Kromberg Formation (>3.46 Ga).<br><br />
This proposed section will penetrate the unconformity between a lower marine section of the pillow lavas and interbedded cherts, and the overlying subaerial conglomerates of the Kromberg Formation. The former is the type section of the biogenic (ichtofossils) structures from its pillow lava margins, and typifies Earth’s 3.4 Ga oceanic environments – including an early hydrothermal ocean-floor-type metamorphic overprint. This part of the section will allow the physio-chemical conditions of the biological communities in the pillow margins, and their preservation window to be better defined. The latter section suggests that, here, the top of the pillow lava pile was exposed to the Archean atmosphere at the unconformity. This will allow a variety of tests to be conducted concerning the composition of Archean atmosphere and biosphere conditions at that time.</em></p><br />
<h4>2- Upper Kromberg Formation</h4><br />
<p><em>This is a section of pillow lavas and sheet flow with interlayered cherts and chert xenoliths that overlies enigmatic early carbonated and silicified oceanic shear zones. Studies of fresh samples will allow better definition of the chemical alteration and microbial activities from an Archean marine bottom-surface into its underlying sub-surface fault zones. transition of sea water change. It will also likely solve the chemical composition and temperature of the associated seawater.</em></p><br />
<h4>3- Lower Fig Tree Group</h4><br />
<p><em>This section will penetrate basal shales interbedded with massive barite and jasper that ovelie altered pillow basalt. Although slightly younger (3.3 Ga), the Fig Tree Formation is lithologically similar to the 3.5 Gyr old chert-barite deposit of the Dresser Formation from which Philippot et al., (2007) described elemental sulfur disproportionation rather than sulfate reduction as a viable metabolism during the Early Archean and were Foriel et al (2004) found a “seawater” composition similar to modern seawater.</em></p><br />
<p>The Onverwacht and Warrawoona Groups in Pilbara represent the two unique remnants of early Archean seafloor settings that have experienced only low grade metamorphism, hence providing a unique opportunity to compare for the first time Archean ecosystems of similar ages from two different localities. The two first holes have obtained secured funding from Norwegian sources. The third hole will be supported by French sources.</p><br />
<h3>Approach and Methodology</h3><br />
<p><em><br />
* Duration of project 3 years: early 2008-end 2010<br />
* Student training: 01 Jan 08<br />
* Drilling July/August 2008<br />
* Laboratory follow-up 2008/2009<br />
* Write up thesis completed end 2010<br />
</em><br />
Technical aspects: drill holes of 200-300 meter depth are planned; technical details will be confirmed when the drilling specifics and a drilling contractor have been finalised.</p><br />
<p><strong>Structural, chemical and isotopic analyses</strong> <br><br />
* SEM, EPMA, TEM – AEON, Bergen, IPGP<br />
* Fluid inclusion analysis - IPGP<br />
* Raman spectroscopy, confocal microscopy – IPGP<br />
* LA-ICP-MS – Bergen, AEON<br />
* Synchrotron (SR-XRF, STXM), IPGP<br />
* C, O isotopes analysis - Edmonton<br />
* S isotopes analysis – CRPG, IPGP<br />
* Sm-Nd isotopes – AEON<br />
* Noble gases – CRPG<br />
* Microbial diversity and sample contamination – IPGP, Orsay<br />
</p><br />
<h3>Personnel</h3><br />
<p>We have identified one black South African PhD student, Eugene Grosch, with suitable qualifications, and plan to advertise for at least one more student position for a three year period, to develop combined mineralogical and petrological approaches to perform an integrated microstructural and analytical study using various quantitative techniques including SEM, X-ray elemental mapping, cathodoluminescence imaging, EPM analysis and trace element analysis and in situ oxygen and S isotope analysis.</p><br />
<p>Eugene Grosch will be based at AEON, South Africa, IPGP, France, the new Centre of biogeological at Bergen University, Norway, and the stable isotope lab at the Univerisity of Edmonton, Canada.</p><br />
<p>In addition to principal participants from AEON, IPGP, Bergen University and University of Edmonton listed above, other participants involved in the Pilbara Drilling Project have notified their interests in participating to the project associated with drill hole 3. These include participants from IPGP (Magali Ader, Karim Benzerara, Jean Besse, Pierre Cartigny, Gaston Godard), CRPG (Bernard Marty, Marc Chaussidon, Béatrice Luais) and University Orsay (Purificacion Lopez-Garcia, David Moreira).</p><br />
<p><strong>Norway, Canada and South Africa</strong>: Whole rock geochemistry and isotope analyses of basalts will be carried out in the new Geobiology Centre of Bergen (coordinators Profs H Furnes and R.D Pederson) and AEON in Cape Town (coordinator M de Wit). In Norway the petrography and electron microscopy and relevant geochemistry on the Ichnofossils will be undertaken by Dr Nicole McLouchlin. Stable isotope analyses (O, C) on minerals and whole rocks will be done in Edmonton, Canada, by Karlis Meulenbachs (no funds requested in this proposal).</p><br />
<h3>Relevant References cited</h3><br />
<p><br />
* Anbar, A.D. et al., 2007. A Whiff of Oxygen Before the Great Oxidation Event? Science, 317: 1903-1907.<br />
* Brasier M., Green O. R., Jephcoat A. P., Kleppe A., Van Kranendonk M. J., Lindsay J. F., Steele A., and Grassineau N. V. (2002) Questioning the evidence for Earth's oldest fossils. Nature 416, 76-81.<br />
* De Ronde E. J., Channer D. M. D., Faure K., Bray C. J., and Spooner E. T. C. (1997) Fluid chemistry of Archean seafloor hydrothermal vents: Implications for the composition of circa 3.2 Ga seawater. Geochimica et Cosmochimica Acta 61, 4025-4042.<br />
* de Wit M. J., Hart R., Martin A., and Abbott P. (1982) Archean abiogenic and probable biogenic structures associated with mineralized hydrothermal vent systems and regional metasomatism, with implications for greenstone belt studies. Economic Geology 77, 1783-1802.<br />
* Dunlop J. S. R., Muir M. D., Milne V. A., and Groves D. I. (1978) A new microfossil assemblage from the Archaean of Western Australia. Nature 274, 676-678.<br />
* Farquhar J., Bao H., and Thiemens M. H. (2000) Atmospheric influence of Earth's earliest sulfur cycle. Science 289, 756-758.<br />
* Foriel J., Philippot P., Rey P., Somogyi A., Banks D., and Ménez B. (2004) Biological control of Cl/Br and low sulfate concentration in a 3.5-Gyr-old seawater from North Pole, Western Australia. Earth Planet.Sci. Lett. 228, 451-463.<br />
* Furnes H, Banerjee NR, Muehlenbachs K, Staudigel H, de Wit MJ (2004) Early life recorded in Archean pillow lavas. Science 304:578-581<br />
* Furnes H, Banerjee NR, Staudigel H, Muehlenbachs K, de Wit M, McLoughlin N, Van Kranendonk M (2007a) Bioalteration textures in recent to mesoarchean pillow lavas: A petrographic signature of subsurface life in oceanic igneous rocks. Precamb Research, 158, 156-176.<br />
* Furnes, H., McLoughlin,N., Muehlenbachs,K., Banerjee, N., Staudigel, H., Dilek, H., de Wit, M., Van Kranendonk, M., Schiffman,P. (2007b). Oceanic pillow lavas and hyaloclastites as habitats for microbial life through time – A review. In: Dilek Y, Furnes H, Muehlenbachs K (eds) Links between geological processes, microbial activities and evolution of life, Springer Verlag. in press.<br />
* Garcia-Ruiz J. M., Hyde S. T., Carnerup A. M., Van Kranendonk M. J., and Welham N. J. (2003) Self-assembled silica-carbonate structures and detection of ancient microfossils. Science 302, 1194-1197.<br />
* Gutzmer J., Banks D. A., Luders V., Hoefs J., Beukes N. J., and Von Bezing K. L. (2003) Ancient sub-seafloor alteration of basaltic andesites of the Ongeluk Formation, South Africa: implications for the chemistry of Ancient sub-seafloor alteration of basaltic andesites of the Ongeluk Formation. Chemical Geology 201, 37-53.<br />
* Holland H. D. (1984) The chemical evolution of the atmosphere and oceans. Princeton University Press. Kaufman, A.J. et al., 2007. Late Archean Biospheric Oxygenation and Atmospheric Evolution. Science, 317: 1900-1903.<br />
* McLoughlin N, Furnes H, Banerjee NR, Staudigel H, Muehlenbachs K, de Wit M, Van Kranendonk M (2007) Micro-Bioerosion in Volcanic Glass: extending the Ichnofossil Record to Archean basaltic crust. In: Wisshak M, Laplina L (eds) Springer Verlag. in Press<br />
* Mojzsis S. J., Arrhenius G., McKeegan K. D., Harrison T. M., Nutman A. P., and Friend C. R. L. (1996) Evidence for life on Earth before 3,800 million years ago. Nature 384, 55-59.<br />
* Ohmoto H., Watanabe Y., Ikemi H., Poulson S. R., and Taylor B. E. (2006) Sulphur isotope evidence for an oxic Archaean atmosphere. Nature 442, 908-911.<br />
* Ono S., Wing B., Johnston D., Farquhar J., and Rumble III D. (2006) Mass-dependent fractionation of quadruple stable sulfur isotope system as a new tracer of sulfur biogeochemical cycles. Geochim. Cosmochim. Acta 70, 2238-2252.<br />
* Philippot, P. et al., 2007. Early Archean microorganisms preferred elemental sulfur, not sulfate. Science, 317: 1534-1537.<br />
* Schopf J. W., Kudryavtsev A., Agresti D. G., Wdowiak T. J., and Czaja A. D. (2002) Laser-Raman imagery of Earth's earliest fossils. Nature 416, 73-76.<br />
* Shen Y., Buick R., and Canfield D. E. (2001) Isotopic evidence for microbial sulphate reduction in the early Archaean era. Nature 410, 77-81.<br />
* Van Kranendonk M. J., Philippot P., and Lepot K. (2006) The Pilbara Drilling project: c. 2.72 Ga Tumbiana Formation and c. 3.49 Ga Dresser Formation, Pilbara Craton, Western Australia. In Western Australia Geological Survey, 2006/14, Vol. 2006/14, pp. 25p.<br />
* van Zuilen M. A., Lepland A., and Arrhenius G. (2002) Reassessing the evidence for the earliest traces of life. Nature 418, 627-630.<br />
</p></div>Emmelynehttp://khure.ipgp.fr/index.php/ProjectB3ProjectB32009-07-06T12:51:12Z<p>Emmelyne: New page: <center><h2>Project B3: Archean life: Early life and ancient life-support systems on the Kaapvaal craton</h2> <h3>French pi: P. Philippot <br>South African pi: M. de Wit (with H. Furnes in...</p>
<hr />
<div><center><h2>Project B3: Archean life: Early life and ancient life-support systems on the Kaapvaal craton</h2><br />
<h3>French pi: P. Philippot<br />
<br>South African pi: M. de Wit (with H. Furnes in Norway)</h3><br />
<br />
</center><br />
<h3>Project Participants</h3><br />
* South Africa: Maarten de Wit, Eugene Grosch, AEON, Cape Town<br />
* France: Pascal Philippot, Mark van Zuilen IPG-Paris<br />
* Norway: Harald Furnes, Nicola MacLoughlin, Centre for Geobiology, Bergen <br />
* Canada: Karlis Muelenbachs, Isotope centre, Edmonton.<br />
<br />
<h3>Summary</h3><br />
<p>Since the Archean and Palaeoproterozoic are dominated by volcanosedimentary successions that have experienced different degrees of metamorphism, many ongoing controversies exist regarding life in the Precambrian part of Earth history. It is now recognized that future studies of early life and the associated environmental conditions depends on better description of geological context, identification of hydrothermal and metamorphic processes, and detailed structural, isotopic and chemical description of mineral assemblages, stromatolitic microlaminae, and organic microstructures that are indigenous to and syngenetic with the stratigraphic rock record. The most serious problem for understanding the evolution of organisms and their biogeochemical environments from the ancient rock record has been the difficulty in obtaining important sequences of “fresh” rocks, i.e., rocks that have not been severely altered by post-depositional processes. In 2004, pristine drill core samples were recovered from key localities of the Archaen Pilbara Craton, Western Australia. Here we propose to take the advantage of this expertise to perform a new drilling project aimed at intersecting similar 3.3-3.5 billion year old rock succession in South Africa, from the Barberton greenstone belt. The important issue to be addressed concern: 1) the significance of traces (Ichnofossils) of microbial activity in the glassy (now recrystalised) margins of pillow lavas; 2) the significance of elemental sulfur disproportionation as one of the most primitive, rudimentary microbial metabolism on Early Earth and 3) the composition and temperature of hydrothermal fluids and Archaean seawater that have interacted with these rocks, and the origins of asociated carbonaceous material (biogenic vs inorganic). A wide variety of state-of-the-art bulk and in situ analytical techniques will be used to study biologic and geochemical processes in these pristine drill cores.</p><br />
<h3>Scientific Project</h3><br />
<p>Although several decades have passed since the first description of recognisable early Archaean microfossils (DUNLOP et al., 1978), morphology-focused imaging techniques of fossil-like objects and stable isotope (C, N, S) compositions of putative organisms have repeatedly failed to pose limits on the interpretation of the biogenic origin of the microstructures (BRASIER et al., 2002; MOJZSIS et al., 1996; SCHOPF et al., 2002; VAN ZUILEN et al., 2002). Additionally, several abiologic metamorphic and hydrothermal reactions have been identified that can produce kerogen and graphite (BRASIER et al., 2002; VAN ZUILEN et al., 2002), and specific abiologic processes have been described that can generate complex structures that resemble microfossils (GARCIA-RUIZ et al., 2003). In view of these uncertainties and controversies, it is clear that elucidating how and when life may have originated on Earth requires first to understand the conditions that prevailed early in Earth‟s history and the environments in which life may have appeared and later evolved. The recent findings of the Norwegian-led group of ichnofossils in the rims of the worlds oldest pillow lavas in South Africa and Australia (FURNES et al., 2004; 2007a,b ) has dramatically shown that rocks previously ignored in studies of early life (e.g. basaltic igneous rocks) now offer a new paleo-environment as habitats for early life. This holds great potential to track life back even further in time, and must be considered a profitable focus for such early life studies (FURNES et al., 2007a,b; MCLOUGHLIN ET AL., 2007).</p><br />
<p>Life on early Earth is likely to have gone through one or more hot ocean. It is possible that early life diversified near hydrothermal vents where only hyperthermophiles organisms would have survived. Archaean hydrothermal settings would have been varied, with abundant vent fields like black smokers and hydrothermal deposits rich in Fe, Cu, S (De Witt et al., 1982). Microscopic sulfides with low 34S/32S ratios in marine sulfate deposits from the 3,490 Myr-old Dresser Formation, Warrawoona Group, Australia, have been interpreted as evidence for the presence of early sulfate-reducing organisms on Earth (SHEN et al., 2001). This finding is at odd with the long standing consensual notion that the Archean atmosphere was essentially reduced and that oxygen reached appreciable levels around 2 to 2.4 billion years ago (HOLLAND, 1984). The great oxidation story was strengthened considerably in the recent years by the discovery that minerals in ancient rocks had unusual ratios of sulfur isotopes, a phenomenon known as mass-independent fractionation (MIF-S; FARQUHAR et al., 2000). The only known mechanism that can produce this effect is the breakup of sulfur dioxide by ultraviolet light in a low-oxygen atmosphere. The MIF-S isotopic signature is small or entirely absent in rocks younger than 2.4 billion years, suggesting that Earth‟s atmosphere has been oxygen-rich since that time. Recent results obtained from drill core samples from Australia show that the story may be much more complex then originally envisioned, however (Ohmoto et al., 2006; Ono et al., 2006; Anbar et al., 2007; Kaufman et al;, 2007). Using high resolution in situ isotopic techniques, Philippot et al. (2007) showed that the microscopic sulfides from the 3.5 Ga Dresser Foramtion have a mass independently-fractionated sulfur isotopic anomaly (∆33S) that differs from that of their host sulfate (barite). These microscopic sulfides cannot have been produced by sulfate reducing microbes, nor by abiologic processes that involve reduction of sulfate. Instead, they interpret the combined negative ∂34S and positive ∆33S signature of these microscopic sulfides as evidence for the early existence of organisms that disproportionate elemental sulfur. This finding provides strong support in favor of a reduced environment at about 3.5 Ga.</p><br />
<p>Knowledge of the composition and temperature of hydrothermal fluids and seawater is central to elucidating the conditions pertaining to the development of life on early Earth. Cl/Br ratio in fluids is considered conservative in many geological settings and is therefore widely used to trace the origin of fluids (meteoric, oceanic, crustal, mantellic) in the rock record. Analysis of ancient fluid inclusions from the Kaapvaal Craton, South Africa, suggest that Cl/Br in Archaean 3.2 Gyr-old (DE RONDE et al., 1997) and paleoproterozoic 2.2 Gyr-old (GUTZMER et al., 2003) seawater was below present-day value and resulted from mantle buffering. These studies, however, were based on bulk fluid analyses (i.e., crush-leach) which can result in fluid mixing if several fluid generations occur in a single sample. Alternatively, detailed chemical analysis of individual fluid inclusions can be performed by Synchrotron Radiation X-ray micro-Fluorescence, thus allowing independent analysis of different fluids trapped in the same sample. Using this technique, (FORIEL et al., 2004) showed that fluid infiltrating pillow basalts at the base of the Dresser and Apex hydrothermal systems of the Pilbara Craton consisted of mixing trends of fluids with compositions ranging from typical modern seawater enriched in salt by 2 to 3 times (7 to 8 wt% salt) combined with hydrothermal fluid components enriched in Ba and transition metals (Fe, Cu, Zn). Furthermore, as introduced above, sulfur is a key element in Archaean geochemistry, as seawater sulfate concentration is used to constrain the oxidation state of the early ocean and atmosphere, and S may have been a key element for early metabolic processes and for the evolution of primitive life (SHEN et al., 2001, Philippot et al., 2007). Using in-situ SXRF technique, (FORIEL et al., 2004) estimated that the “North-Pole seawater component” contained low sulfate concentration (0–8 mM) compared to 28 mM in present-day ocean, which further supports the notion that early metabolisms used reduced (elemental S) rather than oxidized (sulfate) species as a source of energy.</p><br />
<br />
<h3>Proposed Research Project</h3><br />
<p>The aim of this project is to explore new frontiers of addressing the problem of primitive life by establishing links between hydrothermal fluids and seawater circulation, mineral crystallisation, sediment deposition and diagenesis/metamorphism, and the development of the earliest ecological niches. Specifically, we aim at constraining the composition, and the redox state of the primitive ocean and atmosphere, and to develop integrated geochemical studies involving structural, isotopic and chemical description of mineral assemblages, fluid inclusions and organic microstructures (microfossils?) that are indigenous to and syngenetic with the stratigraphic/hydrothermal rock record.</p><br />
<p>Subtopics:<br />
* Microfossils in pillow margins - what was the optimum temperature-window for preservation?<br />
* Elemental sulfur disproportionation; a widespread early Archean microbial metabolism?<br />
* Interactions between fluids, rocks and microbes - Can we define chemical fingerprints?<br />
* Archean ocean temperature and composition - hot or cold, strongly or middly saline, buffered by organic activity?</p><br />
<h3>Three Proposed Drilling Targets</h3><br />
<p>We take advantage of the expertise we gained while performing the Pilbara Drilling Project in 2004 (VAN KRANENDONK et al., 2006) to recover “fresh” continuous sections at two or three (depending of technical constraints and financial supports) key geologic formations of the Barberton, greenstone belt:</p><br />
<h4>1- Upper Onverwacht Group</h4><br />
<p><em>from the top of the Hooggenoeg Formation (>3,47Ga) into the base of the Kromberg Formation (>3.46 Ga).<br><br />
This proposed section will penetrate the unconformity between a lower marine section of the pillow lavas and interbedded cherts, and the overlying subaerial conglomerates of the Kromberg Formation. The former is the type section of the biogenic (ichtofossils) structures from its pillow lava margins, and typifies Earth’s 3.4 Ga oceanic environments – including an early hydrothermal ocean-floor-type metamorphic overprint. This part of the section will allow the physio-chemical conditions of the biological communities in the pillow margins, and their preservation window to be better defined. The latter section suggests that, here, the top of the pillow lava pile was exposed to the Archean atmosphere at the unconformity. This will allow a variety of tests to be conducted concerning the composition of Archean atmosphere and biosphere conditions at that time.</em></p><br />
<h4>2- Upper Kromberg Formation</h4><br />
<p><em>This is a section of pillow lavas and sheet flow with interlayered cherts and chert xenoliths that overlies enigmatic early carbonated and silicified oceanic shear zones. Studies of fresh samples will allow better definition of the chemical alteration and microbial activities from an Archean marine bottom-surface into its underlying sub-surface fault zones. transition of sea water change. It will also likely solve the chemical composition and temperature of the associated seawater.</em></p><br />
<h4>3- Lower Fig Tree Group</h4><br />
<p><em>This section will penetrate basal shales interbedded with massive barite and jasper that ovelie altered pillow basalt. Although slightly younger (3.3 Ga), the Fig Tree Formation is lithologically similar to the 3.5 Gyr old chert-barite deposit of the Dresser Formation from which Philippot et al., (2007) described elemental sulfur disproportionation rather than sulfate reduction as a viable metabolism during the Early Archean and were Foriel et al (2004) found a “seawater” composition similar to modern seawater.</em></p><br />
<p>The Onverwacht and Warrawoona Groups in Pilbara represent the two unique remnants of early Archean seafloor settings that have experienced only low grade metamorphism, hence providing a unique opportunity to compare for the first time Archean ecosystems of similar ages from two different localities. The two first holes have obtained secured funding from Norwegian sources. The third hole will be supported by French sources.</p></div>Emmelyne