Research topics Paléo2D

  1. Main research topics
  2. 1 - Optimization of the source to sink approach and sedimentary transfer laws
  3. 2- Continental surfaces and intraplate deformations Climate Interaction - Geodynamics - topography in Central Asia
  4. 3- Paleoclimate and eustatic variations
  5. 4 – Secular variation of the Earth's magnetic field
  6. 5 – Dating by archaeomagnetism
  7. 6 - Chronological modeling
  8. Soutien technique

Main research topics

Research Themes
1.Optimization of the source to sink approach and sedimentary transfer laws
2. Continental surfaces and intraplate deformations Climate Interaction - Geodynamics - topography in Central Asia
3. Paleoclimate and eustatic variations
4. Secular variation of the Earth's magnetic field
5. Dating by archaeomagnetism
6. Chronological modeling
7. Technical support

1 - Optimization of the source to sink approach and sedimentary transfer laws

The dynamics of the sedimentary systems is driven by the couplings between erosion in the upstream domain, transfer and sedimentation in the downstream basins. This understanding is essential for a better knowledge of the laws of erosion and sedimentation at the geological time scale (10 Ka to 1 Ma), (2) the relative importance of the deformation, the climate and the eustasis and (3) the prediction of the preservation of sedimentary systems.
These approaches have been successfully applied to the Atlantic margins of Southern Africa (South Africa and Namibia, Guillocheau et al., 2012, Braun et al., 2014; Dauteuil et al., 2016) and are extending across Southern Africa. including for the sedimentary systems of Orange, Limpopo and Zambezi (PAMELA project - IFEEMER-Total). The main objective is to understand, in a given paleoclimatic (paleo-precipitation) framework, the effect of mantle dynamics through the uplift of the South African plateau on (1) the processes of decay (chemical erosion vs physical erosion), (2) the stratigraphic architecture of the margin, and (3) the sedimentary balance between the erosion of the plateau erosion and the sedimentation of margins (to the distal deep-sea fan).

Sedimentary fluxes along the South African Plateau since the Cretaceous - Sedimentary fluxes along the South African Plateau since the Cretaceous. (a) Location of the main sources of sediments (deltas and deep-sea fans) and amount of deposited sediments (103 km3) of Upper Cretaceous to Cenozoic. (b) Evolution of the volume of sediments deposited along the Orange margin since the lower Cretaceous (Braun et al., 2014)  - © Sylvie Bourquin

Another approach concerns basins in a rift context to understand the early syn-rift sedimentation and their control factors, based on the example of the Corinth rift (PhD R. Rubi, ENGIE-CNRS project).
The well-developed Gilbert delta with a sedimentation profile from the sediment source to the deep basin allows characterizing the transfer of sediments from the upstream system to the downstream basin. In its proximal part, the deposits are well constrained in terms of sedimentary model and stratigraphic architecture relative to the geodynamic context (work initiated by the PhD of S. Rohais, 2007, Rohais et al., 2007, 2008).
The main objective is to discuss the lateral and vertical variations of erosion and sedimentation along the sedimentation profile in order to better constrain the nature and architecture of the sediments, especially in the distal part of the gravitational deposits (work in progress in R. Rubi's thesis)

Distal depositional environment of early syn-rift phase (Corinth) - © Sylvie Bourquin

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2- Continental surfaces and intraplate deformations Climate Interaction - Geodynamics - topography in Central Asia

The tectonic deformation and the topographic evolution of Asia during the Tertiary have been widely explored as a key example of continental tectonics and of tectonic interactions between erosion, sedimentation and climate. A widely accepted idea is that crustal and lithospheric inheritance plays a dominant role in the location of tertiary deformation in the whole Asian orogen. In this orogenic context, recent studies on the Mesozoic topography of Central Asia reveal the presence of planation surfaces preserved within these chains. These widely distributed planation surfaces are probably from an immense single surface, from northern Tibet to Siberia, during the Upper Jurassic - Cretaceous period. Our recent work shown that the genesis of this surface is contemporaneous with a strong aridification of Central Asia, changing from a humid climate favorable to vegetation to an arid to semi-arid climate that still persists today. However, the exact impact of climate on this surface remains to be explored. Similarly, the geodynamic context that prevailed during the formation of this major planation surface as that which allowed its conservation for about 150 Ma during several major continental collisions remains to be evaluated in detail. These issues are addressed using an integrated approach based on geomorphology and low temperature thermal history of basement, detrital geochronology and paleoenvironmental analysis from the study of sedimentary basins and isotopic analysis of sedimentary basins. climatic markers such as paleosols.

Planation surfaces in the Kyrgyz Tien Shan  - © Sylvie Bourquin

Meso-Cenozoic Planation Surfaces and Armorican Massif ulift - Towards a characterization Wavelength Deformation of the Western Europe.
 
The nature and age of the relief of the Armorican Massif are much discussed since the classical works of Martonne (1905). An analysis of the planation surfaces (Bessin et al., 2015) and associated sediments provides (1) a map of the nested flat surfaces of Eocene basal-Jurassic etchplain and pediment types and (2) a model with the quantification of the uplift based on a new compilation of changes in sea level over time (Bessin et al., 2017).
As part of the Orogen-s2s project (BRGM_Total), this approach will be applied to the old massifs of Western Europe (French Massif Central, Ardennes-Rhine Massif, Cornwall ...) and the basins in surge (Basin Paris-Wessex, Basin of Franconia ...) along regional transects to restore the palaeo-topographies, to better characterize and to understand the lithospheric deformations at long wavelength (x100 km).

Synthetic map of planantion surfaces of Massif Armoricain (Bessin et al., 2015) - © Paul Bessin

 

3- Paleoclimate and eustatic variations

a - Monsoons of Asia caused Greenhouse to Icehouse Cooling (ERC MAGIC).
Discovering the cause of global climatic cooling of the Cenozoic is one of the most important challenge facing the Earth and Environmental Sciences community today (Raymo and Ruddiman, 1992). The erosion and weathering of the Tibetan plateau and the Himalayas are assumed to be the main causes of the enigmatic lowering of pCO2, which has led to an overall cooling of 50 to 34 Ma from a warm climate without ice at the poles (warm ice-free Greenhouse world) with bipolar ice conditions (bi-polar Icehouse) prevailing today (de Conto and Pollard, 2003). Asian monsoons are genetically linked to a high orography associated with the collision between India and Asia from 50 Ma (Molnar et al., 2010). However, the relationship between the Grennhouse - Icehouse transition and the Asian monsoons remains to be explored as it was thought that they only intensified much later, 25,000 years ago (Guo et al., 2003). Our recent findings on monsoon activity in Asia for at least 45,000 years (Licht et al., 2014) raise the fascinating possibility that Asian monsoons have triggered global cooling from the Grennhouse state to Icehouse. Testing this new hypothesis and exploring its implications for feedback mechanisms between regional environments, Asian monsoons and the global climate is the main goal of MAGIC.
Project in progress: http://www.paleoenvironment.eu/Research/projects/Magic/

Monsoons of Asia caused Greenhouse to Icehouse Cooling - © Sylvie Bourquin

b – Tectonic, topographic and climatic evolution and Palaeobiological Changes in Southeast Asia from the late Permian to Jurassic.
The interactions between global and regional climate change and the topographic evolution of major mountain ranges are not limited to the alpine system or to Cenozoic period. The evolution of the Permian to the Jurassic in Asia has also been characterized by an important development of the mountains (the Permian -Trias Indosinian orogeny in Southeast Asia) and profound changes in paleogeography (Jolivet, 2015). The main objective is to understand the evolution of sedimentary basins from the end of the Permian to the Jurassic, the results will offer new perspectives on topographic, climatic and ecological changes during this critical period in this region. The first results obtained in Southeast Asia, from the Laos basin (Bercovici et al., 21012, Blanchard et al., 2015, Rossignol et al., 2016) and the basins of Vietnam (Roger et al., 2014, Rossignol et al., In progress), make it possible to constrain the geodynamic evolution of the blocks of Indochina and South China.

c – Sea Level Change: New Jersey Passive Margin (IODP-ICDP 313)
Understanding the history, causes and impact of sea level change is a challenge for our societies facing sea level rise on a global scale. In such a context, improving our knowledge of sea level changes and shoreline wanderings at the geologic time scale is essential. The analysis of undistorted sediments along passive margins has been used for a long time to reconstruct the level of the past sea. However, the detailed nature of the basic pattern of progeny clinoforms is still poorly understood. This project aims to describe the sedimentary facies and to interpret depositional environments and sedimentary body architecture of the New Jersey Plateau to describe their origin and controls of the distribution of geological reservoirs.

Transition Miocène moyen de la Marge passive du New Jersey - © Sylvie Bourquin

4 – Secular variation of the Earth's magnetic field

We study past directions and the intensity of the geomagnetic field recorded by volcanic and archaeomagnetic materials. Our study areas are Western Europe and Latin America. The purpose of this work is to provide new constraints for geodynamic models and efficient dating tools for archaeological materials and recent volcanic activity.
We have recently confirmed the exceptional geomagnetic secular variation in Chile over the past three centuries, characterized by an almost linear decay of 20 ° and an intensity of 25 mT, making paleomagnetism the best dating tool in this time interval for which uncertainties in the calibrated ages of 14C are often too great.

Paleomagnetic results aboit lavas in Chile - © Pierrick Roperch

 

In Western Europe, during the first millennium BC, our data suggest an increase in the intensity of the 9th century geomagnetic field at 700 BC. J. - C. when a maximum value of ~ 90 μT is reached (Hervé et al., J. Archaelogical Sc., 7, 2016). During the same period, the declination of the geomagnetic field decreased by about 30 ° (Hervé et al., Phys Earth Planet Int., 218, 1-13, 2013). As a result, archeomagnetism promises to be a powerful dating tool for defining historical processes at the transition between the Bronze and Iron ages.
During the last two millennia, the most significant geomagnetic field strength is observed around 800 AD. We recently proposed an improved description of the steep sharp decay in intensity that occurred during more recent periods. Our results confirm that several rapid intensity changes (with rates greater than 10 μT / century) have occurred in Western Europe during recent Earth history (Gomez-Paccard et al., Earth Planetary Science Letters, 454, 55-64, 2016

Variations of Declination in Western Europe during the first millennium BC (Hervé et al., 2013) - © Gwenael Hervé

 

Past intensity of the field at latitude of Paris New data in red (Gomez-Paccard et al., 2016) - © Miriam Gomez-Paccard

We are currently continuing our study work on sites in Argentina and in Chile.


 

5 – Dating by archaeomagnetism

The goal is the development of archeomagnetism to the dating of archaeological baked clay (pottery and tiled ovens, fireplaces and architectural fired clay: tiles and bricks) within the framework of archaeological problems covering the periods of Protohistory in modern times in Western Europe. This activity is supported by UMR 5060 IRAMAT-CRPAA (INSHS) as a partnership with Géosciences-Rennes. The work focuses on the dating of large antique or medieval pottery workshops in France, as part of the rescue and programmed archeology. This work is done for the purpose of dating and also for the purpose of improving the accuracy of the secular variation curves of the geomagnetic field. For example, in 2016, we studied 62 structures in situ (ovens and fireplaces) from the Gallo-Roman and Medieval periods in France.
 

Archéomagnetism : Research and dating

6 - Chronological modeling

ChronoModel (CM) is a time-based modeling software based on Bayesian statistics. It is dedicated to the interpretation of chronological data from different dating methods (14C, archaeomagnetism, luminescence, etc.) combined with a priori information on stratigraphic relations, durations and hiatuses. The applications extend to archeology, earth sciences and the study of paleo-environments.
The software is free, open-source and multiplatform (Mac, Windows, Linux). It has a user-friendly interface where data is manipulated using intuitive graphical elements. These elements explicitly show the data and all the information a priori introduced into the model.
The software can be downloaded from: http://www.chronomodel.fr/
The pre-compiled binaries of the latest version of the application are:
Chronomodel 1.5 for Mac OS X (March 2016): Supported: 10.7 (Leo), 10.8 (Mountain Lion), 10.9 (Mavericks), 10.10 (Yosemite), 10.11 (El Capitan). Chronomodel 1.5 for 32-bit Windows (March 2016): Support: Windows 7, Windows 8, Windows 10 Chronomodel 1.5 for Linux (March 2016): Supported: Unbuntu v14 (Linux).
The source code can be downloaded and compiled freely. It is built with Qt5 and uses the FFTW library (http://www.fftw.org/). The only prerequisite is to have Qt5 installed on your system. The project is hosted on GitHub.com. You can clone the directory by typing: git clone https://github.com/Chronomodel/chronomodel.git

 

Chronological modeling - © Philippe Lanos

 

Soutien technique

The team leans on the services specialized Geosciences-Rennes: