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JulyWorkshop

Emmelyne — Thu, 17 Sep 2009 13:51:07 GMT

Emmelyne:

<accesscontrol>Administrators,,Workshop</accesscontrol>
<center><h2>!Khure Workshop presentations</h2></center>

* [[media:dewit_introduction.pdf|Introduction]]: '''Vincent Courtillot – Maarten De Wit'''
* '''E. Thébault''' : [[media:thebault.pdf|The magnetic field over the Southern African continent: from core to crustal magnetic fields]]
* '''M. Moulin (PhD), V. Courtillot, F. Fluteau, G. Marsh, G. Delpech''' : [[media:Moulin.pdf|Paleomagnetic results and dating from the Karoo traps.]]
* '''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.
* '''G. King and the A1 project team''': Landscapes, tectonics and hominins in South Africa
* '''J. Dyment, D. Bissessur, R. Fernandes, N. Villeneuve''': [[media:dyment.pdf|Origin of lemurs in Madagascar: what to expect from marine and GPS investigations?]]
* '''J-J. Jaeger''': [[media:Jaeger.pdf|The origin and early evolution of madagascar mammalian fauna : first results and perspectives.]]
* '''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]]
* '''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.
* '''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]]
* '''C. Jaupart''': [[media:Jaupart.pdf|Stability of lithosphere and thermal structure]]
* '''P. Cartigny''': [[media:Cartigny.pdf|Traçing Conflict Diamonds ? Yes we can… sometimes.]] Case studies on diamonds from Central African Craton (RDC and CAR)
* '''S. Gilder, M. de Wit, S. Roud, R. Egli and S. Koch''': [[media:de_Wit.pdf|Magnetic signatures of diamonds]]
* '''J. Besse, S. Satolli, R. Domoney, M. de Wit''': [[media:besse.pdf|Disrupted fun in the Cape Fold Belt: pyrite spoils the paleomagnetic party]]
* '''M. Tredoux, Laure Meynadier, M. De Wit''': [[media:tredoux.pdf|Capacity building]]

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Emmelyne — Thu, 17 Sep 2009 13:45:01 GMT

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Usergroup:Workshop

Emmelyne — Thu, 17 Sep 2009 13:36:39 GMT

Emmelyne:

*Khure Workshop

ProjectB6

Emmelyne — Mon, 06 Jul 2009 14:10:48 GMT

Emmelyne:

<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. de Wit (with R. Domoney, UWC)</h3>

__TOC__
</center>

<h3>Project Participants</h3>
* '''France''': J. Besse, F. Fluteau, collaboration, Y. Donnadieu (LSCE)
* '''South Africa''': M de Wit, R. Domoney

<h3>Introduction</h3>
<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>
[[image:Fig1_B6.jpg|right|450px|thumb|Fig 1 Main glacial periods (from Hoffman and Shrag)]]
<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>
<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>
<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>
<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>

<h3>Paleogeography</h3>
[[image:Fig2_B6.jpg|left|400px|thumb|Figure 2: Polar wander path of Gondwana during the Early Paleozoic.]]
<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>
<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>
<h3>Climate Modelling</h3>
<p>Numerical tools are required to investigate the influences of forcing factors. As an
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
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>
<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
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).
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>
<h3>References</h3>
* 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.
* Crowley, T.J., SK. Baum, KY. Kim 1991. General circulation model sensitivity studies experiments with pole-centered supercontinents. Journ. Geophys. Res. 96, 597-610
* 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.
* 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.
* 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.
* Evans, D. A. D. (2003). "A fundamental Precambrian-Phanerozoic shift in earth's glacial style?" Tectonophysics 375: 353-385.
* Gibbs, M.T. et al. 1997. An Atmospheric pCO2 threshold for glaciation in the Late Ordovician. Geology. 25, 447-450.
* 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.
* 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.
* 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.
* Hoffman, P., and Shraag, D.P, (2002) The snowball earth Hypothesis: testing the limits of the global change, Terra Nova review article, 51p.
* Jacob, R., 1997. Low frequency variability in a simulated atmosphere ocean system, Univ. Wisconsin-Madison, Madison
* 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.
* 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.
* Poussart, C.J. et al. 1999. Late Ordovician glaciation under high atmospheric CO2: a coupled model analysis. Paleoceanography 14, 542-558.

ProjectB5

Emmelyne — Mon, 06 Jul 2009 13:50:33 GMT

Emmelyne:

<center><h2>Project 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 African pi: M. Doucouré</h3>

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</center>

<h3>Project Participants</h3>
* '''South Africa''': Rodger Hart, Susan Webb, Moctar Doucouré
* '''France''': Armand Galdeano, Luis Gaya-Piqué, Jean-Louis Le Mouël, Erwan Thébault
* '''Other''': Stuart Gilder (Munich), Valentin Mikhailov (Moscow)

<h3>Aims and objectives</h3>
<p>
#. To identify the major terrain boundaries (edges) including the limits of effects large impacts in Southern Africa.
#. To identify and understand the relationship between felsic (crustal) and mafic (dominantly mantle) rocks in the Earth‟s crust.
#. To apply magnetic and gravity imaging techniques to coherently map out the major structures in Southern Africa.
#. To Understand the relationship between major sedimentary basins and depth to MOHO
#. To understand the horizontal and vertical distribution of Cretaceous age magmatic/volcanic features.
#. To provide MSc training for at least one black South African student (still to be identified).
</p>

<h3>Introduction</h3>
[[image:Fig1_B5.jpg|right|250px|thumb|]]
<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>
<h3>Aeromagnetic Data Set</h3>
<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>
<h3>Bouguer Gravity Data Set</h3>
<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>
<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>
<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>

<h3>Mode of co-operation between the French and South African research teams</h3>
<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>

<h3>Capitalizing on other geophysical studies</h3>
#. Magnetotelluric data have recently been collected in the region that have the potential to image to upper mantle depths.
#. Deep (16 sec) seismic data of the region collected during the Kaapvaal seismic program is also available.
#. Recent basic 3D model of the Wits basin has been developed in gOcad which can be used in modeling programs to test ideas.

<h3>References</h3>
<p>
* 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.
* D. Gibert & A. Galdeano, A computer program to perform transformations of gravimetric and aeromagnetic surveys, Comp. & Geosciences, 11, 553-588</p>

ProjectB4

Emmelyne — Mon, 06 Jul 2009 13:32:25 GMT

Emmelyne:

<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>
South African pi: R. Hart</h3>

__TOC__
</center>
<h3>Project Participants</h3>
* <strong>South Africa</strong>: Rodger Hart, Susan Webb
* '''France''': Armand Galdeano, Maxime Legoff
* '''Other''': Stuart Gilder (Munich), Laurent Carpozen

<h3>Aims and objectives</h3>
# To apply magnetic imaging to map out the structure of the Vredefort impact crater in high resolution.
# 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).
# 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.
# To provide MSc training for at least one black South African student. A student for this project has already been identified.

<h3>Introduction.</h3>
[[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.]]
<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>

<h3>Aeromagnetic Surveys</h3>
<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>

<h3>Proposed Research Program</h3>
<h4>High resolution ground magnetic survey</h4>
<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>
<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>
<h4>Mode of co-operation between the French and South African research teams.</h4>
<p>
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>
<h4>Capitalizing on other geophysical studies</h4>
# Magnetotelluric data have recently been collected in the region that have the potential to image to upper mantle depths.
# Deep (16 sec) seismic data of the region collected during the Kaapvaal seismic program is also available.

<h3>References</h3>
<p>
* 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.
* 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)
</p>

ProjectB3

Emmelyne — Mon, 06 Jul 2009 12:51:12 GMT

Emmelyne:

<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 Norway)</h3>

</center>
<h3>Project Participants</h3>
* South Africa: Maarten de Wit, Eugene Grosch, AEON, Cape Town
* France: Pascal Philippot, Mark van Zuilen IPG-Paris
* Norway: Harald Furnes, Nicola MacLoughlin, Centre for Geobiology, Bergen
* Canada: Karlis Muelenbachs, Isotope centre, Edmonton.

<h3>Summary</h3>
<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>
<h3>Scientific Project</h3>
<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>
<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>
<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>

<h3>Proposed Research Project</h3>
<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>
<p>Subtopics:
* Microfossils in pillow margins - what was the optimum temperature-window for preservation?
* Elemental sulfur disproportionation; a widespread early Archean microbial metabolism?
* Interactions between fluids, rocks and microbes - Can we define chemical fingerprints?
* Archean ocean temperature and composition - hot or cold, strongly or middly saline, buffered by organic activity?</p>
<h3>Three Proposed Drilling Targets</h3>
<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>
<h4>1- Upper Onverwacht Group</h4>
<p><em>from the top of the Hooggenoeg Formation (>3,47Ga) into the base of the Kromberg Formation (>3.46 Ga).<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>
<h4>2- Upper Kromberg Formation</h4>
<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>
<h4>3- Lower Fig Tree Group</h4>
<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>
<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>
<h3>Approach and Methodology</h3>
<p><em>
* Duration of project 3 years: early 2008-end 2010
* Student training: 01 Jan 08
* Drilling July/August 2008
* Laboratory follow-up 2008/2009
* Write up thesis completed end 2010
</em>
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>
<p><strong>Structural, chemical and isotopic analyses</strong> <br>
* SEM, EPMA, TEM – AEON, Bergen, IPGP
* Fluid inclusion analysis - IPGP
* Raman spectroscopy, confocal microscopy – IPGP
* LA-ICP-MS – Bergen, AEON
* Synchrotron (SR-XRF, STXM), IPGP
* C, O isotopes analysis - Edmonton
* S isotopes analysis – CRPG, IPGP
* Sm-Nd isotopes – AEON
* Noble gases – CRPG
* Microbial diversity and sample contamination – IPGP, Orsay
</p>
<h3>Personnel</h3>
<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>
<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>
<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>
<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>
<h3>Relevant References cited</h3>
<p>
* Anbar, A.D. et al., 2007. A Whiff of Oxygen Before the Great Oxidation Event? Science, 317: 1903-1907.
* 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.
* 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.
* 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.
* 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.
* Farquhar J., Bao H., and Thiemens M. H. (2000) Atmospheric influence of Earth's earliest sulfur cycle. Science 289, 756-758.
* 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.
* Furnes H, Banerjee NR, Muehlenbachs K, Staudigel H, de Wit MJ (2004) Early life recorded in Archean pillow lavas. Science 304:578-581
* 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.
* 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.
* 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.
* 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.
* 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.
* 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
* 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.
* 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.
* 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.
* Philippot, P. et al., 2007. Early Archean microorganisms preferred elemental sulfur, not sulfate. Science, 317: 1534-1537.
* 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.
* Shen Y., Buick R., and Canfield D. E. (2001) Isotopic evidence for microbial sulphate reduction in the early Archaean era. Nature 410, 77-81.
* 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.
* van Zuilen M. A., Lepland A., and Arrhenius G. (2002) Reassessing the evidence for the earliest traces of life. Nature 418, 627-630.
</p>

ProjectB1

Emmelyne — Mon, 06 Jul 2009 12:17:39 GMT

Emmelyne:

<center><h2>Project B1: African Diamond Genesis and Craton Evolution: Exploring new ways to characterise conflict diamonds</h2>
<h3>French pi: P. Cartigny (with S. Gilder and C. Aubaud)<br>
South African pi: M. de Wit (with S. Richardson and D. Bell)</h3>

__TOC__

</center>

<h3>Project Participants</h3>
<p>
* France: Pierre Cartigny, IPG-Paris
* South Africa: Maarten de Wit, Steve Richardson, Cape Town
* Germany: Stuart Gilder, Munich; Michael Wiedenbeck, Potsdam
* Exploration Industry: Mike de Wit, Hielke Jelsma, Kinshasa and Johannesburg.
</p>

<h3>Introduction</h3>
<p>
Diamonds known as conflict diamonds, otherwise known as blood diamonds, originate from the war zones of Africa, and specifically from areas controlled by forces or factions opposed to legitimate and internationally recognized governments, and are used to fund military action in opposition to those governments, or in contravention of the decisions of the United Nations Security Council. On December 1, 2000 the UN General Assembly unanimously adopted a resolution defining the role of conflict diamonds with the intent of cutting-off the sources of funding for rebel forces and to help shorten the wars and prevent their recurrence through breaking the link between the illicit transaction of rough diamonds and armed conflict (from: David Cowley, 2007. What Are Conflict Diamonds?).</p>
<p>In May 2000, the diamond producing/trading industry took the first steps to develop a plan that could halt the trade of conflict diamond by establishing a way that diamonds could be certified, and created the Kimberley Process Certification Scheme (KPCS). Yet, governments want the KPCS to be monitored with more transparency and certainty to identify the place of origination of the diamonds. For example, Canada is a major diamond producer, and being member of the Kimberley Process Certification Scheme and (among others) is particularly concerned in regulating the legal diamond industry. Europe is the strongest partner of most African countries because they are a major donor or aiding development in third world countries and is thus concerned in solving conflicts in this part of the world. The fact that the European Commission assumes duties as Chair of the Kimberley Process for 2007 is a further reason why Europe is particularly concerned in monitoring the Kimberley Process Certification Scheme. The benefits to countries that put an end to trading in conflict diamonds are immense and it could mean better economic development and prosperity throughout Africa. Yet, resourceful and unscrupulous groups still manage to elude the legal barriers and still find ways of infiltrating the diamond centers of the world.</p>
<p>Although this list is not exhaustive and will likely change trough time, the main countries concerned so far by this resolution are: Angola, Sierra Leone, Liberia, Ivory Coast, Democratic Republic of Congo, Republic of Congo, Central African Republic. In terms of geology, these diamonds originate largely, but not exclusively, from two regions, namely the West and Central Africa Shields.</p>
<p>The question asked of scientists is either <em>How can a conflict diamond be distinguished from a legitimate diamond</em>; or [and this is not the same question] <em>how can conflict diamonds be distinguished from legitimate diamonds?</em></p>
<p>Nobody can answer any of these two questions yet, as no one ever studied conflict diamonds scientifically in earnest; and in particular no one has yet mastered a non- destructive technique that has the potential to be fast enough to be enable examining bulk samples. Answering these questions require representative suites of conflict diamonds to be made available to scientists. It also require every legitimate mine to have its diamond production well characterised (which is not always the case).</p>
<h3>Method(s)</h3>
<p>Given that some conflict and legitimate diamonds are presently mined within a same region, the method to identify conflict diamonds must be sensitive on the local scale (i.e. the diamond mine) and not to a regional scale only (from one craton or shield to the other).</p>
<p>A large amount of data have been obtained on legitimate diamonds since the last 30 years and one can use these to discuss to potentially recognise diamonds from one legitimate diamond mine from another legitimate diamond mine.</p>
<p>Parameters that can be used to trace the origin of diamonds are:
# the physical characteristics (color, shape, resorption, surface features)
# the types (eclogitic/peridotitic ratios), nature of the inclusions (silicate, sulfide)
# the speciation of nitrogen and its aggregation state (FTIR)
# the stable isotope (C, N) compositions (mass spectrometry or SIMS)
# the radiogenic isotope compositions of diamond inclusions (TIMS)
# the trace element contents of diamond (LA-ICPMS, SIMS)
# the magnetic properties (cryomagnetic characterization)
Because diamond characteristics (size, shape, color, plastic deformation, isotope characteristics) are highly variable within a single diamond mine, distinguishing a conflict diamond be distinguished from a legitimate diamond is unlikely.</p>
<p>Of these other methods, 2-6 characterise chemical signatures, whilst the last (7) reflects a physical property of diamonds that has hitherto not been tested.</p>
<h3>Using established techniques</h3>
<p>Because each mine show some of the parameters 1 to 6 listed above to vary from one mine to the other (a single parameter is not pertinent enough), we can potentially provide a way to chemically identify conflict diamonds using a complete chemical diamond characterisation methodology.</p>
<p>As a first step, we propose to combine parameters 1 to 3 since these are relatively rapid and non-destructive techniques. These techniques will be applied to specimens from a variety of sources with a view of building up a global database of the above characteristics. For this purpose, we have already obtained a pilot sample of diamonds from the Mbuji Mayi in the DRC.</p>
<p>The study of carbon and nitrogen stable isotopes, nitrogen contents (Parameter 4) can be undertaken using (compared to SIMS measurements) well established, rather rapid, accurrate, yet destructive techniques. If successful in tracing the origin of diamonds, this destructive technique would not be an appropriate one anymore because then the sample must be preserved, but SIMS will be. Thus in the first instance, the method will allow to fastly expand the database to conflict and yet unstudied legitimate diamond mines.</p>
<p>The strengh of using parameters 1 to 4 is that these can already use the significant amount of data obtained during the last 30 yeras on legitimate worldwide diamond productions.</p>
<h3>Developing new techniques</h3>
<p>There are potentially several new non-destructive ways to characterize both the physical and chemical properties of diamonds that are briefly summerized below.</p>
<h4>Chemical fingerprinting using trace elements</h4>
<p>Ongoing with this work will be to explore new routes to reliable non-destructive chemical fingerprinting of diamonds of parameters 6. We believe this can be done as briefly described below:</p>
<p>Trace element geochemistry of diamond is relatively well known, and unfortunately to date the bulk or trace element compositions of diamonds are of little value to reveal their origin (Griffith et al., 2006). Moreover the geochemical methods are largely destructive, thus obliterating the diamond sample. Yet the geochemical signatures of individual diamonds, both in the form of trace element and isotopic compositions, have the potential for geographically localizing the origin of a crystal of unknown provenance. Through the use of modern micro analytical techniques it is possible to conduct such measurements in a nearly non-destructive fashion. For this strategy to be applied to the trade in conflict diamonds there are three geochemical questions which must be addressed:
# Are diamonds, in general, homogeneous in their compositions such that a single measurement from any surface is representative of an entire crystal?
# Do diamonds from a common source have one or more geochemical traits which are common to all crystals from that geographic unit (e.g., single diamond pipe or single cratonic region)?
# Do diamonds of different geographic origins differ significantly in one or more such characteristics?
If the answer to each of these three issues is “yes”, then the potential exists to constrain or even localize the source of individual crystals. The first step in this research initiative must therefore be to address all three of these issues.</p>
<p>Due to its high data acquisition rate, ability to measure many elements during a single analysis and its good to excellent limits of detection for many elements, the preferred analytical technique for this initial phase is laser ablation- inductively coupled plasma mass spectrometry (LA-ICPMS) trace element analysis. This approach has, however, two disadvantages: (1) the sensitivity is such that a single analysis will generally consume some 20,000 μm3 of sample during a single analysis and (2) the analytical precision obtained by LA-ICPMS is generally not adequate for isotope ratio measurements. Nonetheless, this analytical method will be able to answer, at least in the case of trace elements, whether geochemical fingerprinting can contribute towards localizing the geographic origin of a single crystal of unknown provenance.</p>
<h4>Strategy, Preliminary Phase at GFZ-Potsdam, Germany</h4>
As a first step, simple test measurements by LA-ICPMS need to be conducted on diamond crystals in order to establish that no unanticipated issues impact the trace element determination in diamond (e.g., adequate optical coupling between laser and sample, stable signal from mass spectrometer, able to focus laser reproducibly on sample surface). If no technical problems are encountered then the next step would be to conduct measurements on a collection of crystals of know origins. (1) Multiple analyses need to be conducted on each crystal to asses whether crystal heterogeneity is a common problem. (2) Two or more crystals from the same pipe need to be analysed to asses if they form a homogeneous population for at least some geochemical properties. (3) Samples from multiple diamond pipes from the same geographic / cratonic region need to be analyzed to assess whether any trace element characteristics are common from across an entire province. (4) Crystals from two or more unrelated geographic sources need to be measured and these data need to be assessed for whether any parameters can distinguish between the different groups. Thus, the minimum study material for this initial phase of research would be approximately:
* 2 random crystals from diamond source “A” of geographic domain “X”
* 2 random crystals from diamond source “B” of geographic domain “X”
* 2 random crystals from diamond source “C” of geographic domain “Y”
* 2 random crystals from diamond source “D” of geographic domain “Y”
Each of the crystals would need to be measured twice by LA-ICPMS for a broad spectrum of trace elements. The data from each duplicate would be used to assess whether trace element zoning is a common or rare feature in diamonds. If intra-crystal variations in concentrations are rare then a principal component analysis of the data would be necessary to asses which element signatures (concentrations or ratios), if any, are characteristic of a given geographic domain and which are also distinctive between domains.</p>
<p>If the results of the LA-ICPMS work indicate that trace elements offer a potential means of constraining the geographic origin of a crystal of unknown provenance then similar work using 13C/12C determinations by secondary ion mass spectrometry (SIMS) should also be undertaken and these data should be assessed along a similar line. In the mean time, conventionnal destructive methods at IPG-Paris will be used to characterise diamonds.</p>
<h4>Strategy, Rough Outline of Advanced Phases at GFZ-Potsdam, Germany</h4>
<p>
Assuming that the preliminary phase of this work is consistent with the use of trace element / isotope signatures for constraining geographic origin then a further work would include:
* Expanding the data base to cover all geographic domains of economic importance and assessing these data to establish which geochemical characteristics are distinctive / unique to which deposits.
* Conducting a set of blind tests to demonstrate the reliability of this approach.
* Developing and certifying a suite of diamond reference materials for the absolute determination of the key characteristics.
* Developing and validating SIMS-based analytical protocols for routine use.
If this approach is to become a standard tool for investigating the trade in conflict diamonds then SIMS will need to become the primary analytical technique. This is because SIMS offers a sensitivity which is a factor of 10 to 50 higher than that of LA-ICPMS, resulting in a concomitant reduction in the amount of sample being consumed. For example, in the case of 13C/12C determinations on diamond the crater produced during SIMS analysis will be on the order of 10μm in diameter and <1μm in depth. In the case of trace element analyses at sub-ppm concentration levels the volume consumed during a SIMS analysis may be of the order of 5 to10 times larger. The disadvantages of SIMS are that it is a significantly slower analytical method and it is not well suited for screening large numbers of elements. SIMS also requires a well polished sample surface on which to conduct the analysis and the crystals, unlike in the case of LA-ICPMS analyses, must be embedded in some form of medium to produce a large (cm-sized), flat surface.</p>
<h3>Physical fingerprinting: Can diamonds be characterized magnetically?</h3>
<p>We propose to test a new method with the intention to characterise diamonds non destructively using their physical properties tied to a magnetic „fingerprint‟, described briefly below. Since this is a new untried method we describe our strategy briefly below. This work will be carried in the Geophysics Department at the Maximillian University, Munich, Germany, under the leadership of Prof S Gilder.</p>
<p><em><strong>A new non-destructive route to test magnetic properties of diamonds</strong></em><br>
Diamond geochemistry is relatively well known, and unfortunately the bulk or trace element compositions of diamonds are of little value to reveal their origin. Geochemical methods are largely destructive, thus obliterating the diamond sample. Moreover, bulk geochemical analyses may be blind to the growth mechanism or strain state acting when the diamonds formed. Such processes are fundamentally important in controlling the way in which inclusions grow and are oriented with respect to the diamond‟s crystallography. Thus, to potentially learn something about the genesis of diamonds, a technique must be sought that is non-destructive and can yield information concerning their strain state and inclusion geometry. Magnetism holds much promise in these respects knowing that a small proportion of the inclusions are magnetic phases such as iron sulfides.</p>
<p>We propose to study the magnetic signatures of individual diamonds in two principal ways: (1) to characterize their low temperature (down to liquid helium, or 4 K) behavior and (2) to measure their magnetic anisotropy. A well-known example of the former is the Verwey transition in magnetite that occurs at around 120 K. The exact temperature and shape of the Verwey transition in magnetic moment vs. temperature space depend on the oxidation state, grain size, composition and internal stress of the magnetite. Oxidation smears out the transition while small additions of aluminum, titanium, etc., will lower the temperature of the transition. When cooled through the Verwey transition in the presence or absence of an external field, large, multi-domain magnetite grains exhibit different responses than small single domain grains. Thus, much can be learned from the response of the magnetic moment at low-temperatures. Even a few nanometer-sized grains produce enough signal to be measurable. Note that the magnetic properties of iron sulfides such as pyrrhotite also undergo important changes at low temperatures.</p>
<p>Solid inclusions are virtually never spherical in diamonds. This means that the solid inclusions inherently have a shape-anisotropy. Moreover, the inclusions may be aligned according to the growth pattern of the diamond, such as along zones or certain crystallographic axes. A quick and non-invasive way to quantify the geometrical alignment of an assemblage of magnetic inclusions is to study the magnetic anisotropy of the diamonds. This can be done in two ways. One is via the anisotropy of magnetic susceptibility. This method yields the eigenvalues of the susceptibility tensor and thus defines the shape of the anisotropy ellipsoid. Another way is via the anisotropy of magnetic remanence. This method is much more time consuming (one and a half hours/sample), but potentially more revealing because the technique can be applied under different imposed field conditions. What this means is that the anisotropies of specific magnetic species and the specific grain size distribution of those species can be analyzed. If a diamond underwent a multiple growth history, with each growth period having a slightly different magnetic composition or characteristic grain size, these differences can be studied individually and thus the generations of growth can be better understood.</p>
<p>The paleomagnetic laboratory at LMU is currently equipped with a Kappabridge to measure the anisotropy of magnetic susceptibility. We have a 2G Inc. three axis superconducting magnetometer together with coil systems that can measure the anisotropy of magnetic remanence. Our proposal also coincides with the arrival of a second 2G Inc. three axis superconducting magnetometer to LMU. This magnetometer will be fit with a low temperature insert and a pulse magnetizer that can measure the full magnetic vector of materials to 4 K.</p>
<p><strong>We have already obtained a pilot sample of 34 diamonds from an operating mine in the Central African Republic (CAR). Work on this set of diamonds is ongoing. Once magnetically tested, this sample will be distributed to the group in IPGP and GFZ-Potsdam for further chemical analyses.</strong></p>
<h3>Capacity Building</h3>
South African PhD candidates will be linked to the projects in Munich and Potsdam at the earliest opportunity in 2008.
<h3>Diamond supplies</h3>
<p>Crucial to all the stated projects is a steady supply of diamonds form different mines and regions. To facilitate this we have established relationships with offices of two diamond exploration companies based in Kinshaha (Dr Mike de Wit) and Johannesburg (Dr Hielke Jelsma). These contacts have assured their interest in the project, and will endeavour to provide a unspecified number of diamonds, and will also help in persuading other active companies into partnership with this !Khure program.</p>

ProjectA6

Emmelyne — Mon, 06 Jul 2009 10:11:03 GMT

Emmelyne:

<center><h2>Project A6: Sun and Earth’s magnetic fields and climate change</h2>
<h3>French pi: A. Chulliat<br>
South African pi: P. Kotzé</h3>
</center>
__NOTOC__
<h3>Project Participants</h3>
<p>
* A. Chulliat (IPGP) – French principal investigator
* P. Kotzé (HMO) – South African principal investigator
* J.-L. Le Mouël (IPGP)
* M. Muundjua (Ph D student)
* E. Thébault (IPGP)
* A. Chambodut (EOST)
</p>

<h3>Background</h3>
[[image:Fig1_A6.jpg|right|250px|thumb|Figure 1: INTERMAGNET magnetic observatories in France and on the African continent. Observatories run by France (alone or in cooperation with other countries) are denoted by blue dots; South African observatories are denoted by red dots. Conjugate points of the Chambon la Forêt (CLF‟) and Hermanus (HER‟) observatories are indicated by small circles.]]
<p>Both South-Africa and France have a long tradition of measuring and studying the Earth‟s magnetic field. The first French magnetic observatory was established in 1883 in Parc Saint-Maur, near Paris, and was later moved to Val-Joyeux in 1900 and then to Chambon-la-Forêt in 1936. The Bureau Central de Magnétisme Terrestre, which is under the responsibility of IPGP, is currently in charge of 16 observatories throughout the world. The first systematic observations in South Africa were performed at Cape Town Observatory (1843 till 1852, and 1932 till 1940). The Hermanus Magnetic Observatory officially commenced operation in 1941. It is now running two other observatories in southern Africa: Hartebeesthoek (in South Africa) and Tsumeb (in Namibia). All French and South African observatories belong to INTERMAGNET, the global network of magnetic observatories transmitting their data in quasi-real time (www.intermagnet.org).</p>
<h3>1- Investigating possible relationships between the magnetic fields of the Sun and the Earth and climate change</h3>
<p>It has become more and more obvious in recent years that solar activity has a deep influence on the Earth‟s climate variability. Yet the relationships between both phenomena are still not well understood. Solar wind, solar magnetic field and solar radiations interact in a complicated manner with the Earth‟s atmosphere. Important elements of this interaction are the Earth‟s magnetic field of internal origin and the rapidly-varying electrical currents in the ionosphere and magnetosphere, which in turn generate magnetic fields detectable on the ground.</p>
<p>The goal of this project is to use the long magnetic data series of Chambon and Hermanus observatories to study relationships between geomagnetic field variations and climate variability. Magnetic data series from observatories are among the longest geophysical data series available. They have all time scales of the magnetic field embedded and thus provide information on both the slowly-varying internal field and the rapidly-varying external field on a long time span. Long temperature series are also available near Paris and Cape Town and will be compared to magnetic series.</p>
<p>We will first focus on the long-term evolution of rapid variations, whose time-scales range from one second to one month. Such variations correspond to various physical processes in the ionosphere and magnetosphere. The Chambon and Hermanus observatories are roughly at the same geomagnetic latitude within their respective hemispheres (about 42°), which could help compensating for seasonal variability. We will try to better characterize the long-term evolution, using appropriate mathematical tools in order to separate the various physical processes involved, and then compare it with temperature.</p>
<p>The study will form part of preparations for the next SWARM satellite mission to be launched in 2010. The project should strengthen historic ties between the two observatories and will investigate scientific questions with increasingly important societal consequences (space weather and global change).</p>
<h3>2- Modelling the secular variation at a regional scale</h3>
<p>The secular variation of the geomagnetic field has considerably accelerated during the last 7 years with an increase in its changing rate especially after the 2003 geomagnetic jerk. As a result of a poor worldwide data distribution, in particular in the Southern hemisphere, determining the geomagnetic acceleration of the changing field at high resolution and at a global scale is not possible. The best model predictions do not represent these changes with a better spatial scale of 3000km (spherical harmonic degree 14) for the secular variation and 6000km (n=7) for the acceleration. It has been observed that geomagnetic jerks could be prominent on a regional scale and, indeed, the most recent dramatic changes occur almost exactly under South Africa, therefore representing the ideal location to perform a high-resolution analysis.</p>
<p>South Africa has a long tradition of repeat station measurements that dates back to the early 1960. The spatial distance between two repeat stations is not more than 300-400 hundred kilometres. In addition, we now have 5 years of continuous satellite measurements of high quality. A joint analysis of satellite and repeat station data over the southern African region with a regional modelling technique (Thébault et al., 2006a, 2006b) should provide an unprecedented spatial view of the secular changes in this region. Collaborating with Hermanus Magnetic Observatory and GFZ, which have performed recent repeat station surveys in Southern Africa, will offer a unique opportunity to achieve this important goal, leading to a better understanding of the Earth‟s core dynamics.</p>
<h3>Objectives and milestones:</h3>
Results will be communicated on a regular basis at workshops, and international conferences. Peer-reviewed articles will be published in international journals.
<h3>Capacity building:</h3>
A PhD student, Mr Manfriedt Muundjua, will be supervised by A. Chulliat and P. Kotzé for his thesis based on a time–series analysis of observatory data.
<h3>Recent bibliography:</h3>
* Chulliat A., Blanter E., Le Mouël J.-L. & Shnirman M., On the seasonal asymmetry of the diurnal and semidiurnal geomagnetic variations, J. Geophys. R., 110, A05301, doi:10.1029/2004JA010551, 2005.
* Le Mouël J.-L., Mayaud P.-N. & Shebalin P., Magnetic activity inside the auroral zones and field-aligned currents, C. R. Geoscience., 335, 935-941, 2003.
* Le Mouël J.-L., Blanter E., Chulliat A. & Shnirman M., On the semiannual and annual variations of geomagnetic activity and components, Ann. Geophys., 22, 3583-3588, 2004.
* Le Mouël J.-L., Kossobokov V. & Courtillot V., Long-term trend of geomagnetic variation, Earth Planet. Sci. Lett., 232, 273-286, 2005.
* Le Mouël J.-L., Shebalin P. & Chulliat A., The field of the equatorial electrojet from CHAMP data, Ann. Geophys., 24, 515-527, 2006.
* Thébault E., Schott J.-J. & Mandea, M., Revised spherical cap harmonic analysis (R-SCHA): Validation and properties, J. Geophys. Res., 111, B01102, doi:10.1029/2005JB003836, 2006.
* Thébault E., Mandea M. & Schott, J.-J., Modelling the lithospheric magnetic field over France by means of revised spherical cap harmonic analysis (R-SCHA), J. Geophys. Res., 111, B05102, doi:10.1029/2005JB004110, 2006.

ProjectA5

Emmelyne — Mon, 06 Jul 2009 09:41:59 GMT

Emmelyne:

<center><h2>Project A5: A restudy of Madagascar-Africa breakup and evolution of Lemurs</h2>
<h3>French pi: J.J. Jaeger (with J. Dyment)<br>
South African pi: J. Masters (with M. de Wit)</h3>
<em>RSA Participants: Phd Student John Decker and students from Univ Fort Hare</em>
__TOC__
</center>

<h3>Background</h3>
<p>
Lemurs are living representative of one of the most primitive strata of primate evolution. They are represented by two distinct groups, the Lemurs and the Loris which split more than 37 Ma ago. Both share many primitive Primates characters but also a uniquely derived character, the tooth comb. This dental speciality is the result of the procumbent inclination of lower incisors and canines which become also peg-like, designing what is commonly called the tooth comb. Their modern geographic distribution is restricted to Madagascar for the Lemurs and to the old world tropics (Tropical Africa & Asia) for the Loris. Their fossil record is very scanty, only fossil Loris being known from the late Eocene to Pleistocene of Africa and from the Miocene of Indo-Pakistan. No fossil of Lemurs older than Holocene is presently known. Thus, the geographic origin of Malagasy Lemurs remains one of the most resistant biogeographic puzzles. Surprisingly, recent discoveries of Eocene Primates in Africa did not contribute to solve that problem. In addition, the peopling of Madagascar is not only restricted to that of Lemurs. Other endemic Madagascar mammals indicate that, according to our knowledge about the history of mammals, 4 or 5 successive waves of peopling occurred during the Tertiary, either from the Indian plate, from Africa or from both places! In order to gain a better understanding of the problem of geographic origin of Lemurs, we propose to address the problem using several distinct methods:
# Reinvestigating marine geophysical and DSDP data in the Mozambique Channel and vicinities, reassessing ancient and recent plate kinematics of this part of the Indian Ocean.
# Prospecting the Paleogene deposits of Madagascar.
# Prospecting the Paleogene deposits of South Africa and Mozambique.
For the first phase of the project, only parts 1 and 2 will be developed here.
</p>
<h3>Part 1: Reinvestigating marine geophysical and DSDP data in the Mozambique Channel and vicinities, reassessing ancient and recent plate kinematics of this part of the Indian Ocean.</h3>
<p>The colonization of Madagascar by lemurs and others mammals from Africa requires either the crossing of land bridge or the transportation on natural rafts. The second hypothesis, also known as the “sweepstakes model” (Simpson, 1952), has been suggested to be very unlikely on the base of statistical calculation (Stankiewicz et al., 2006). Therefore, the “episodic emergence of inter-channel islands along the Davie Fracture Zone during the end of the Mesozoic and early Cenozoic [may have] played a significant role in facilitating this colonization process […]. Alternatively, perhaps Africa was not the source of all of the Malagasy mammals, including the lemurs” (Stankiewicz et al., 2006).</p>
<p>Considering the present-day bathymetry around Madagascar, there are only a few possible candidates for even discontinuous, temporary land bridges: We consider the Davie Ridge, west of Madagascar, and volcanic banks, northeast of Madagascar, to have possibly played such a role during the long and complex history of the western Indian Ocean.</p>
<p>The most likely candidate is the Davie Ridge, a sub meridian structure that separates the Somali Basin, north of Madagascar, from the Mozambique Basin, southwest of Madagascar. The Davie Ridge is initially a major fracture zone which recorded the southward motion of Madagascar separating from north-eastern Africa between 170 and 118 Ma, it is still seismically active and may have been reactivated when the East African Rift initiated, at ~30 Ma (Mougenot et al., 1986a, b). This complex history may translate in two ways: either the Davie Ridge was a prominent, continuous structure that remained at least partly emerged in the Mesozoic and early Cenozoic, then was progressively submerged by the subsidence of an aging crust and possibly dissected by the nascent extensional plate boundary between Somalia and Nubia – the lemur would have crossed the remains of that land bridge shortly before its total submersion; or the Davie Ridge was already a shallow submarine structure during early Cenozoic and was first rejuvenated by the initiation of the new plate boundary, either tectonically (although a significant amount of compression seems unlikely) or, more probably, by some amount of volcanism – in this case the lemur would have crossed the Mozambique Channel passing from volcano to volcano – then eroded, faulted, and affected by subsidence. Both scenarios are plausible in the context of the Somalia-Nubia plate boundary, as suggested on land by the dominantly tectonic Western Branch and the volcanic Eastern Branch of the East African Rift (e.g. Chorowicz, 2006).</p>
<p>We therefore propose to address this problem through a geophysical investigation of the structure of the Davie Ridge and the surrounding basins, first from available seismic data and, if required, through the acquisition of new seismic data, in order to decipher major normal faults, recent volcanism, and possible erosional surface that would mark emersion. Conversely, a detailed characterization of both the initial transform motion along the Davie Ridge at the time of its formation, in the Mesozoic, and the more recent motion of Somalia with respect to Nubia along the East African Rift and its seaward extension are also essential to discriminate among these scenarios.</p>
<p>Another candidate for a discontinuous, temporary land bridge is the set of bathymetric highs that separate Seychelles from Madagascar, including Bulldog Bank, Farquhar Island, Providence Reef, and further north the Amirante Bank. Most of these seamounts are shallower than 200 m and may have emerged during periods of regression in the Cenozoic. The Seychelles micro continent and India have been connected up to magnetic anomaly 27 (62 Ma), the older magnetic anomaly found on the Carlsberg Ridge flanks (Dyment, 1998; Chaubey et al., 2003; Royer et al., 2003). But another land connection, formed by the Deccan-Reunion hotspot track, has probably existed up to 35 Ma, when the Saya de Malha and Nazareth Banks (both parts of the Mascarene plateau) and the Chagos Bank (part of the Chagos-Laccadive Ridge) broke apart and the Central Indian Ridge established in its present configuration.</p>
<p>We propose to investigate this possibility by looking at the sparse geophysical data available on the bathymetric highs between Madagascar and Seychelles on one hand, on the Mascarene Plateau and Chagos-Laccadive Bank on the other hand. Conversely, we plan to refine the paleogeographic reconstructions obtained by the French party in the framework of other projects (CEFIPRA 1999-2003 and 2006-2009) with a special attention to volcanic plateau, seamounts, and other bathymetric highs.</p>
<p>A last possible candidate for a land bridge could be along the Comoros Islands, a chain of volcanic islands which may result from a hotspot plume. The chain is 5-0 Ma old, with traces of volcanic 10 Ma old in northern Madagascar (Emerick and Duncan, 1982) and shallow banks – probably former islands – connecting Madagascar to the Comoros. The most recent and active volcano (Karthala) is located on the westernmost island, Grande Comore. The distance between Grande Comore and the eastern coast of Africa is about 280 km, but this distance can be reduced by a factor of two if the northern end of the Davie Ridge was emerged. The Comoros land bridge is therefore a variation of the Davie Ridge land bridge, which may account only for recent colonization (i.e. Holocene) – before this time, the westernmost islands were not built yet! Again, beyond the work planned to substantiate the Davie Ridge land bridge hypothesis, we plan to revisit the sparse geophysical data available in the southern Somali Basin, around the Comoros Islands.</p>
<p>To summarize, the proposed work is twofold:
* reinvestigating available marine geophysical (mostly seismic and DSDP data) on and in the vicinity of the potential land bridges, in order to find evidences of tectonic and/or volcanic activity and identify possible erosional surfaces which may mark the emersion of these bathymetric high;
* reassessing ancient and recent plate kinematics of this part of the Indian Ocean, through the compilation and re-interpretation of available magnetic anomaly profiles and the use of paleogeographic reconstruction software
providing uncertainty intervals.
</p>
<p>In term of the data required by the project, we will use the so-called “international data” (compiled by and available from the US National Geophysical Data Center - also a World Data Center - in Boulder, Colorado). This general set of single beam bathymetry, magnetics, and gravity data will be complemented by more specific geophysical data collected by the French research vessels in the last 40 years as part of the exploration of the Indian Ocean. Among these data, the magnetics and (single beam) bathymetric data have substantiated the pioneer work of Jacques Ségoufin and Philippe Patriat at Institut de Physique du Globe de Paris in the early eighties (Segoufin and Patriat, 19xx; Patriat and Segoufin, 1988). Although both have retired (Philippe Patriat is still visiting the lab occasionally), their data base remains available to our investigation and has been completed by more recent ship tracks. Conversely, several old seismic profiles (4-6 traces) acquired in the Somali Basin under the guidance of Roland Schlich are available in digital format from the seismic repository at the Institut de Physique du Globe de Strasbourg. As for the denser seismic profiles acquired over the Davie Ridge by French research teams, mostly Geoscience Azur in Nice, the digital tapes are no longer available but the paper sections have been scanned and are available to our investigations. Additional data may also be available in SISMER, the French marine geophysical data repository, in Brest, which will be consulted in this respect. Moreover, data have been acquired by the French hydrographic office in the Mozambique Channel around the “Iles Eparses” (Tromelin, Glorieuses, Juan Nova, Europa and Bassas de India), a French Territory; we have already obtained multibeam bathymetric data from them but should investigate if more is available in this area! The marine data will be completed by the gravity anomaly grids derived from satellite altimetry.</p>
<h3>Part 2: Prospecting the Tertiary deposits of Madagascar in order to find Paleogene mammalian localities.</h3>
<p>The biogeographic puzzle of Madagascar lemurs origins has led to numerous speculations which can hardly been resumed here. The traditional view consider than Lemurs originated in Africa and migrated from Africa to Madagascar sometimes during the Paleocene or the Eocene. This scenario relies on the fact that Lorisidae are the sister group of Lemurs, and are found in Africa since the Late Middle Eocene Fayum Locality (37 Ma; Seiffert et al., 2006) and that the molecular clock indicates a divergence age between Loris and lemurs of between 62 and 58Ma. However, the analysis of the fossil primate record of the lower Eocene of North Africa indicates that no Strepsirrhine with teeth comb did exist at that time in North Africa. The referred Strepsirrhines from Tunisia and Algeria belong to primitive groups of Strepsirrhines which could be ancestral of Lemurs, but in that case tooth comb would have been developed after 50 Ma and before 37 Ma. Another critical point is that the first Loris from Fayum are recorded in the same level as the earliest African anthropoids (Jaeger et al., 1999) which are clearly immigrants from Asia (as are rodents, anthracotheres and other contemporaneous taxa from the same locality). These Loris could therefore as well originated from Asia and enter into Africa at the same time as Anthropoid primates and therefore hold no information relative to the geographic origins of lemurs. A scenario concerning an Indian origin can equally well be supported (Marivaux et al., 2001) because of the absence of fossil remains in Madagascar, older than Holocene.</p>
<p>In order to gain some information about the zoogeographic history of Madagascar, we propose to organize field work to search for Paleogene fossil mammals. We have already a good record of such kind of field work which was successful in many other places as Morocco, India, Pakistan, a.s.o. The main originality of our project is to avoid unfossiliferous terrestrial deposits and to search the marine neritic deposits of the Paleocene and Eocene of Madagascar. Sections provided by ancient geological mapping work (Besairie, 1972.) indicate that some marine layers were deposited under low water depth, allowing the possible occurrence of small channels made by palaeorivers. Microconglomerates from these small channels may contain reworked micromammal remains as in many other world areas. The marine carbonate rich sedimentary environment offers an excellent protection for carbonate apatite (fossil bones and teeth), increasing the chances for fossil preservation. But carbonate matrix may have to be dissolved in diluted acid solution, which is a time consuming process. Paleocene and Eocene marine outcrops are numerous in Madagascar. They occur on the western coast, both in the North (Mahajanga Basin) and in the SouthWest of the continent- island (Morondava Basin). For logistic constraints, a first survey should be organized in the south, near the city of Majunga. Sections of Paleogene marine sediments should be surveyed using gully made by rivers cutting these deposits in an East-West direction.</p>
<h3>References</h3>
<p>
* Besairie,H. Géologie de Madagascar 1 : Les Terrains Sédimentaires Annales Geologiques de Madagascar, 1972, XXXV
* Emerick, C. M. & Duncan, R. A., 1982, Age progressive volcanism in the Comoro Archipelago, western Indian Ocean and implications for Somali plate tectonics.-Earth Planet. Sci. Lett. 60, 415–428.
* Jaeger, J.-J., Thein, T., Benammi, M., Chaimanee, Y., Soe, A. N., Lwin, T., Tun, T., Wai, S., and Ducrocq, S. (1999): A new primate from the middle Eocene of Myanmar and the Asian early origin of the anthropoids. Science, 286, 528-530.
* Marivaux, L., Welcomme, J.-L., Antoine, P.-O., Metais, G., Baloch, I. M., Benammi, M., Chaimanee, Y., Ducrocq, S., and Jaeger, J.-J. (2001). A fossil lemur from the Oligocene of Pakistan. Science 294, 587-591.
* Masters, J.C., Lovegrove, B.G. & M.J. de Wit. 2007. Eyes wide shut: can hypometabolism really explain the primate colonization of Madagascar? J. Biogeogr. 34:21-37.
* Mougenot, D., M. Recq, P. Virlogeux and C. Lepvrier, 1986a, Seaward extension of the East-African Rift, Nature 321 (1986), pp. 599–603.
* Mougenot, D., P. Virlogeux, J.R. Vanney and J. Malod, 1986b, La marge continentale au Nord du Mozambique: résultats préliminaires de la campagne MD40/MACAMO, Bulletin Société géologique France 8 (1986) (II, 3), pp. 419–422.
* Stankiewicz, J., Thiart, C., Masters, J.C. & M.J. de Wit. 2006. Did lemurs have sweepstake tickets? An exploration of Simpson's model for the colonization of Madagascar by mammals. J. Biogeogr. 33: 221-235.
* Yoder, A.D. & M. D. Nowak. 2006. Has vicariance or dispersal been the predominant biogeographical force in Madagascar? Only time will tell. Annu. Rev. Ecol. Syst. 37: 405-31.
</p>

ProjectA4

Emmelyne — Thu, 02 Jul 2009 13:26:45 GMT

Emmelyne:

<center><h2>Project A4: Large igneous provinces, impacts and climate change</h2>
<h3>French pi: F. Fluteau (with V. Courtillot)<br>
South African pi: G. Marsh</h3>

__TOC__
</center>
<h3>Project Participants</h3>
<h4>France:</h4> V. Courtillot, F. Fluteau, J. Besse, X. Quidelleur, G. Delpech, C Jaupart, M. Gérard, H. Bouquerel
<h4>South Africa:</h4> J. Marsh, M. Watkeys, M. Klausen, A. Duncan, plus one or two Msc or PhD students to be determined

<h3>Project Summary</h3>
<p>
The project focuses on detailed flow-by-flow sampling for palaeomagnetic secular variation studies on two well-characterized Karoo volcanic sequences (a) The low-Ti Oxbow sequence of northern Lesotho, and (b) the high-Ti Olifants River sequence of northern Lebombo. Palaeomagnetic measurements will be done at IPGP and will be complemented by K/Ar and 40Ar/39Ar dating (IPGP) and additional geochemical studies (South Africa) where necessary. The project goal is to construct a refined model for the emplacement of the Karoo volcanic sequences with particular emphasis on volumes and duration of eruptive episodes (in particular identification of short large pulses) and their impact on climate modifications with implications for the end-Pliensbachian extinction. This will be compared to the case of the Deccan volcanics and KT mass extinction.
</p>
<h3>Background</h3>
[[image:Fig1_A4.jpg|left|thumb|350px|Figure 1. Correlation of mass extinction events with very large mafic magma eruptions]]
<p>
There is considerable debate on the causes of the biological mass extinction events recognized in the Phanerozoic fossil record. There is consensus that extinctions reflect events of dramatic climate change but the underlying causes of the change remain controversial. Correlations between the mass extinctions and large volume volcanic eruptions (Fig. 1 from Courtillot & Renne, 2003) together with known temperature/climate modification effects of some historical eruptions such as Pinatubo (1991-1992) and Laki (1783-1784) are powerful arguments for a volcanic cause of many of the extinction events. To strengthen and test this hypothesis, large volcanic events have to be investigated in detail to establish (a) the precise timing of the volcanism, (b) volume-duration relationship during the volcanic event and (c) climate change modelling. Detailed results from one such study (Chenet et al, in press) on the Deccan Flood basaltic sequence, which correlates with the large extinction event at the K-T boundary, have shown that flow-by-flow palaeomagnetic sampling of well-characterized stratigraphic sequences allow geomagnetic secular variation data to be recovered from the lava flows. The secular variation can be used as a time proxy which has allowed considerable refinement of the details of the emplacement history of the volcanic sequence, in particular volume-duration relationships. Together with data from red boles intercalated in the lava sequence, results indicate that the Deccan was emplaced as a small number of discrete large-volume short-lived pulses without significant quiescence between them. Gas emissions (largely SO2) of each pulse are of the same order as those proposed for the Chixculub impact, the rival hypothesis for the K-T extinction. These data are strongly suggestive of Deccan volcanism having a significant impact on Earth's climate.</p>
[[image:Fig2_A4.jpg|right|250px|thumb|Figure2:Distribution of Karoo volcanic outcrops, the two main mafic magma systems, and the location of proposed study sections.]]
<p>The coincidental eruption of the Deccan sequence with the occurrence of the Chixculub impact indicates that it is crucial to validate the hypothesis arising from the Deccan results of Chenet et al.(in press) with a similar study in another large continental flood basalt sequence. It is proposed to do so with the Karoo flood basalt sequence of southern Africa (Fig. 2). Outcrop remnants of the Karoo volcanic sequence (largely mafic), as well as intrusions, occur over an area >2.5 * 106 km2 with lava sequences exceeding 1 km in thickness in many places. These eruptions tapped two major mafic magma systems - a low-Ti system in the south and a high-Ti system in the north. Eruptive volumes are of similar magnitude to those of the Deccan (total  2x106 km3). Modern age dating (largely 40Ar/39Ar) indicate that the volcanic sequence was emplaced over a short time at about 180-183 Ma (Duncan et al, 1997; Jourdan et al., 2004) which broadly correlates with the extinction event at the Pliensbachian-Toarcian boundary.
Detailed geochemical studies have established a well-defined geochemical stratigraphy for all major lava remnants and correlations between them (Fig. 3 - Marsh et al., 1997; Sweeney et al, 1994; Klausen et al., 2005 and Duncan & Marsh, unpubl.). A palaeomagnetic reversal stratigraphy has been well-defined for the Lesotho remnant, and tentatively defined in the Lebombo sequence (Hargraves, et al.,1997). As a first step of the prposed program, we have started a detailed flow-by flow sampling for secular variation studies similar to those of Chenet et al.(in press) in the Deccan in the Naude‟s Nek section of southern Lesotho in November 2006 and samples are currently being processed. Thus the Karoo Province has been sufficiently well-characterized for a focussed palaeomagnetic study to yield meaningful results.</p>
<h3>Detailed Research Proposal and Motivation</h3>
<p>To carry out detailed flow-by-flow sampling of two other, complementary sections: (a) the Oxbow section of northern Lesotho and (b) the Olifants River section of the northern Lebombo</p>
<h4>The Oxbow section</h4>
<p>This section lies along the paved road between Butha-Buthe and Mokhotlong in Lesotho. The volcanic sequence is continuously exposed in the Moteng and Mahlasela passes and is some 1500 metres thick. Geochemical and palaeomagnetic data for the lavas has been published by Marsh et al.(1997) and Hargraves et al.(1997). A single palaeomagnetic reversal occurs within this section and has been correlated to the single reversal found in all other sections through the Lesotho volcanic sequence, including Naude‟s Nek. Similar consistent correlations also exist in the lava flow geochemical stratigraphy. This will assist in correlating the detailed geomagnetic secular variation results in the two sections and establish minimum volume/duration relationships for the construction of the low-Ti Lesotho magma system. Precise timing of the eruptions will be addressed through combined K/Ar and 40Ar/39Ar dating</p>
<h4>The Olifants River Section</h4>
[[image:Fig3_A4.jpg|left|200px|thumb|Figure 3: Stratigraphic correlations established with geochemistry of lava flows. Palaeomagnetic reversal stratigraphy from Hargraves et al. (1997)]]
<p>This section comprises an estimated 5 km sequence of the mafic lavas and a further thickness of overlying Jozini Rhyolites of the Lebombo Group as well as numerous cross-cutting dykes. This section is exposed along the banks of the Olifants River in the Kruger National Park and is accessible from a tourist road that follows the river. The mafic rocks in the section include flows of the basal
Mashikiri Formation (nephelinites), the overlying Letaba Formation (picrites) and several basaltic types of the Sabie River Formation. The entire sequence is representative of the high-Ti magma system whose geochemical stratigraphy has been well characterized (Klausen et al.,2005 and unpublished) and correlations established with the volcanic sequence of central and southern Lebombo, with the sequence in the Tuli syncline and northern Botswana, as well as with the low-Ti sequence in Lesotho via an intercalation of flows of one of the high-Ti basaltic chemical types with the low-Ti flows in the Springbok Flats remnant (Fig. 3 modified from Marsh et al., 1997). In addition palaeomagnetic data are available from which a tentative reversal stratigraphy has been constructed. The Olifants River section presents the best locality for a detailed palaeomagnetic and K-Ar and Ar-Ar studies to complement those in the low-Ti Lesotho sections. The results should refine the proposed correlations between the low-Ti and high-Ti volcanic sequences, address the important issue of a time difference in the emplacement of the two systems and hence allow construction of a refined volume-duration model for the whole Karoo province. Such a model is essential to understand the impact of the Karoo volcanism on climate at about 180 Ma.</p>
<h3>References</h3>
<p>
* Chenet, A-L., Fluteau, F., Courtillot, V., Gérard, M. & Subbarao, K.V.(in press, 2007) Reconstructing the eruptive history of the Deccan traps: (I) Constraints from palaeomagnetic secular variation and red bole formation in a 1200m-thick section from the Mahabaleshwar escarpment. J. Geophys. Res.
* Chenet, A.L., Quidelleur, X., Fluteau, F., Courtillot, V., and Bajpai, S., .(in press, 2007) 40K-40Ar Dating of the Main Deccan Large Igneous Province: Further Evidence of KTB Age and Short Duration, Earth Planet. Sci. Lett.
* Courtillot, V.E. & Renne, P.R.(2003) On the age of flood basalt events. C.R. Geosciences, 335, 113-140.
* Duncan, R.A., Hooper, P.R. Rhacek, J., Marsh, J.S. & Duncan, A.R.(1997) The timing and duration of the Karoo igneous event, southern Gondwana. J. Geophys. Res., 102, 18127-18138.
* Hargraves, R.B, Rehacek, J. & Hooper, P.R. (1997) Palaeomagnetism of the Karoo igneous rocks in southern Africa. S.Afr.J.Geol.,100,195-212.
* Jourdan, F., Féraud, G., Bertrand, H., Kampunzu, A.B. Tshoso, G., Watkeys, M.K., & le Gall,B.(2005) The Karoo large igneous province: brevity, origin, and relation with mass extinction questioned by new 40Ar/39Ar age data. Geology, 33, 745-748.
* Klausen, M.B., Marsh, J.S. & Watkeys, M.K.(2005) geochemical variation in the Karoo basalt-rhyolite lava sequence along the northern Lebombo monocline (Olifants River Section). Geol.. Soc. S. Afr. GEO2005 Programme and Abstracts volume.
* Marsh, J.S., Hooper, P.R. Rehacek, J., Duncan, R.A. & Duncan, A.R.(1997) Stratigraphy and age of Karoo basalts of Lesotho and implications for correlation within the Karoo igneous province. American Geophysical Union, Geophysical Monograph 100, 247-272.
* Sweeney, R.J., Duncan, A.R. & Erlank, A.J.(1994) Geochemistry and petrogenesis of Central Lebombo basalts of the Karoo igneous province. J. Petrology, 35, 95-125.
</p>

ProjectA3

Emmelyne — Thu, 02 Jul 2009 11:52:37 GMT

Emmelyne:

<center><h2>Project A3:<br>
Plateau uplift, epeirogeny and evolution of climate and biodiversity</h2>
<h3>French pi: F. Guillocheau<br>
South African pi: M. de Wit</h3></center>

__NOTOC__
<br>
<h3>Project Participants:</h3>
<h4>South Africa</h4>
* Fernando Abdala, University Witwatersrand - I - Therapsid taxonomy
* Marion Bamford, University Witwatersrand - I - Fossil wood taxonomy
* Jennifer Botha-Brink, National Museum - I - Parareptiles, Bone histology, physiology
* Doug Cole, Council for Geoscience - I - Sedimentology, lithostratigraphy
* John Compton, University of Cape Town - V - Marine Sedimentology
* Woody Cotterill, University of Cape Town - I,III - Biodiversity dynamics, palaeo drainage
* Maarten de Wit, University of Cape Town - I,II, III - Tectonics, geochronology,
* Frank Eckardt, University of Cape Town - III - Geomorphology, palaeo-drainage
* Julia Lee-Thorpe, University of Bedford - III - Biology, stable isotopes, hominims
* Johann Neveling, Council for Geoscience - I - Sedimentology, basin modelling
* Merrill Nicolas, University Witwatersrand - I - GIS database
* Rose Prevec, Albany Museum - I - Megaplant taxonomy
* Bruce Rubidge, University Witwatersrand - I - Therapsid taxonomy, biostratigraphy
* Roger Smith, SA Museum - I - Taphonomy, biodiversity changes
* Adam Yates, University Witwatersrand - I - Dinosaur taxonomy

<h4>France</h4>
* Sylvie Bourquin, Rennes 1 University - I - Fluvial sedimentology
* Jean Braun, Rennes 1 University - II - Modelling
* Luc Bulot, Marseille University - II - Biostratigraphy
* Olivier Dauteuil, Rennes 1 University - II - Tectonics
* Francois Guillocheau, Rennes 1 University - I, II, III - Sedimentology, Seismic stratigraphy
* Alain Le Herisse, Brest University - I - Palynology
* Cécile Robin, Rennes 1 University - I, II - Sedimentology, Seismic stratigraphy
* Delphine Rouby, Rennes 1 University - II - Seismic stratigraphy
* Martine Simoes, IPGP - II - Modelling
* Paul Tapponier, IPGP - II - Tectonics
* Jean-Jacques Tiercelin, Rennes 1 University - III - Sedimentology
* Annie Vincens, CEREGE, Marseille - III - Palynology

<h3>Background</h3>
[[image:A3_fig1.jpg|left|thumb|380px|3-D image showing the African surface elevation, and known kimberlites intrusions (vertical yellow lines) that extend down into the underlying lithospheric mantle. Broad arrows, representing the resultant Mesozoic exhumation (green) and erosion (grey-white) of the Kalahari highlands, removing a carapace of 2-6 km of cover, including a substantial volume of Karoo basalts, at a rate in excess of 0.5 km3/yr, with a high rate of CO2 sequestration, resulting in global climate cooling (de Wit, 2007).]]
<p>The Kalahari Plateau is a 1000-1500 m high plateau that stretches ~2500 km from southern to central Africa. It is the world‟s largest subcontinental plateau away from plate margins, and is separated from the Atlantic and Indian Oceans by a narrow transition of steep scarps and mountain ranges. The origin of this plateau and its margins are not understood but can be traced back to peneplanation near sea-level during the continent-wide end-Paleozoic Gondwana glaciation (~300 My), followed by extensional intracontinental tectonics and desertification during the Late Permian-Triassic (Karoo rifts and basins) and continental break-up during the the Late Jurassic - Early Cretaceous (formation of the Atlantic and Indian Oceans). The peneplain was also affected by extensive volcanic activity: three large flood basalt events (the Karroo, 170-180 My; the Etendeka, 132 My; and the Aghulas (100-90 My) and two punctuated episodes of kimberlite emplacement (around 120 My and 90 My). By mid-end Cretaceous, uplift had started and concomittantly the inland region was transformed into a continental desert. Cenzoic evolution of the Kalahari Plateau has strongly controlled geomorphology, biological evolution (including Hominids), climate change and the hydrology of central and southern African.</p>
<p>The goal of this project is to quantify the growth of this major topographic feature of the Earth – the very long wave length Plateau topography, and the associated rates of uplift over the last 300 My, in order to understand the dynamics of Africa‟s surface processes (erosion, transport, sedimentation) climate change, hydrology, and biological evolution in response to landscape evolution.</p>
<p>The growth of the Kalahari Plateau is contemporaneous also with a major climatic change at global scale, as well as changes in both elevation and tenures of large lakes and wetlands (including aquifers) across the Plateau. The question of the climate change over the past few tens of millions years in Africa is of primary importance to predict the climate of the future and to understand the evolution of the Hominids in Africa.</p>
<br>

<h3>Questions:</h3>
<p>
* What was the initial topography, prior to the growth of the Plateau?
* Was the Plateau growth continuous or discontinuous, and at what rate?
* Did the observed uplift drive local/global climate change?
* How did Plateau uplift affect lake and river drainage and biodiverity evolution?
* Is the Plateau currently rising (or subsiding) and deforming?
* How is the East African Rift migrating southwards and merging/dissecting the Kalahari Plateau?<br>
In order to answer these questions, three subprojects have been coordinated.
<br>
* <big>A3.I: Carboniferous to Early Jurassic paleotopography and paleoclimate of South Africa: The Karroo Group</big>
Coordinators: B. Rubidge, University of Witswatersrand (South Africa) & C. Robin, Rennes University (France)
* <big>A3.II: The kinematics of Kalahari Plateau uplift through meso-cenozoic times: a sequence stratigraphic approach</big>
Coordinators: M.de Wit, Cape Town University (South Africa) & F. Guillocheau, Rennes University (France)
* <big>A3.III: The Kalahari “Basin” infilling: age, paleotopography and paleoclimate</big>
Coordinators: W. Cotterill, University of Cape Town (South Africa) & J.J. Tiercelin, Rennes University (France)
</p>

<h3>Capacity Building through Interactive student mentoring and development</h3>
<p>
Exchange between South African and French students.
* 1 South African PhD and 2 French MSc students on the Upper Karroo sedimentology and sequence stratigraphy (Wits/Rennes)
* 1 South African PhD student on the seismic stratigraphy of the Margin (UCT/Rennes)
* 1 French or South African PhD and 2 South African MSc students on the core analysis of drillings (sedimentology and sequence stratigraphy) of the Kalahari deposits (UCT/Rennes)
* 2 South African MSc on palaeoegeomorphology (South African Escarpment evolution)
* 1 South African Post-Doc for compilation and synthesis of palaeo-environmental scenarios in geospatial context, building on AEON databases (UCT/Rennes/IPGP
</p>
<h3>Economic implications and industry collaborations</h3>
<p>We can expect economic implications of our studies on uranium geology (subproject I), on petroleum and gas location and migration (subproject II) and on sedimentary diamonds prospects (subprojects II and III). The following companies have shown interests in participation: South African Petroleum, De Beers, BRC diamond)</p>
<h3>Relevent review reference:</h3>
<p>
* de Wit, M.J. 2007. The Kalahari epeirogeny and climate change: differentiating cause and effect from core to space. South African Journal of Geology, 110, 367-392
</p>

ProjectA2

Emmelyne — Thu, 02 Jul 2009 08:41:33 GMT

Emmelyne:

<center><h2>Project A2:<br>
Evolution of African rift propagation into Southern Africa</h2>
<h3>French pi: P. Tapponnier<br>
South African pi: F. Cotterill</h3>
</center>

<h3>Project Participants</h3>
<p>
* Paul Tapponnier Tectonics, IPGP
* Woody Cotterill University of Cape Town, AEON, and Department of Geological Sciences & Department of Molecular and Cell Biology, South Africa.
* Geoffrey King Tectonics, IPGP
* Laurie Barrier Tectonics, IPGP
</p>
<h3>Project</h3>
<p>One of the key issues with high plateaus is to understand how their flat and high topography is preserved from the attacks of headward erosion. Whatever the origin of the Kalahari plateau, and whether it is presently rising, subsiding, or stable, it seems to have been at an elevation of 1500 m or so for a significant period of time (Mid Cenozoic, Cretaceous or earlier). How could it maintain its flatness at such elevation for such a long time? A significant fraction of the plateau remains internally drained today, and there is evidence that the internally drained surface used to be much larger, with the presence of one or several large lakes.</p>
[[image:A2_fi1.jpg|left|300px|]]
<p>Because mechanisms that preserve local high base levels commonly involve recent and active faulting, we propose to study the relationship between such faulting and the evolution of topography and endorheism. Although South Africa and the Kalahari are not very seismic regions, there is evidence of recent and active tectonics in several areas.</p>
<p>1/ In the Northwest, one branch of the East African rift (EAR) splays off southwestwards towards the Okavango delta, in the very heart of the Kalahari plateau. More should be known about the corresponding normal faults. At what rate do they move? How did they propagate? Do they still do so today? Did they control the sequential capture of Kalahari rivers by the lower Zambezi (Victoria falls?).</p>
<p>2/ In the Northeast and East, one main branch of the EAR has extended into the Mozambique basin. There is also current uplift along the coast south of Durban. Again, little is known about the potential southward propagation or reactivation of recent normal faults along the east side of the plateau. Both questions are related to the mechanics of the southward termination of the EA Rift, a problem that has received less attention than its counterpart to the north.</p>
<p>3/ In the south, at least two fairly large earthquakes (M ≥ 6) have shaken the west part of the Cape Foldbelt (e.g., 1969 Ceres earthquake), but the present day regime of deformation is poorly understood. In general, the foldbelt shows up to ≈ 2 km of local relief, which is more than observed in belts of roughly comparable age (e.g. Urals, Appalachian). It seems unlikely that differential erosion of quartzites or tectonic inversion and normal faulting in the Cretaceous suffice to account for such relief. In fact, some of the roughly EW-striking Cretaceous normal faults appear to be active (e.g., Kango fault). How is such deformation connected with regional plate tectonics?</p>
<p>By using the combination of quantitative geomorphology, surface exposure dating, accurate mapping using DEM and high resolution satellite images that we have successfully applied to other neotectonic problems, we propose to understand and model the recent deformation of South Africa and its bearing on plateau and drainage system evolution. This short-term vision of deformation (1 to x10 million years) will be linked and integrated with the longer time scale documented by sedimentology and other approaches.</p>