Knowledge and description of sedimentary systems

Sedimentary budgets :  concept, methods and integration in basin analysis on a land-sea continuum (HDR 2022)

In a given sediment compartment¹, the sedimentary budget consists in evaluating sedimentary inputs, transfers and exports, and equating them to the net gain or loss over a specified period of time (figure). 

Sedimentary budgets are very widely used in geosciences:
-    they have been used for many years in the field of oil exploration to predict the occurrence and quality of oil reservoirs or source rocks;
-    and more recently in the environmental field, as a component of risk assessments, in order to anticipate coastal erosion and adjust land-use planning in a context of climate change. 
Often deployed on a sediment compartment scale, these budgets, when integrated on a larger scale, offer the possibility of acquiring a global vision of sedimentary systems. Thus, through the development and implementation of numerical methods and tools, my HDR research was aimed at quantifying these budgets on a sedimentary basin² scale across the land-sea continuum (see figure). The approach adopted helped determine the relevant boundary conditions and gain a better understanding of the interactions between the various compartments, based on global balances. 
 

¹ A sediment compartment is a distinct geological zone characterized by specific deposit conditions
² A sedimentary basin is a depression of the Earth's crust, often very extensive, where sediments accumulate over a long period of time. They may contain several types of sedimentary rocks

 

This research has resulted in direct applications at IFPEN for:
•    basin modeling: in order to characterize the deformation dynamics of sedimentary basins (such as burial or uplift rates, for example), with implications for the determination of thermicity³), the timing of deformation⁴ and/or sand generation periods, all information that is essential in basin and reservoir exploration [1, 2];
•    reservoir modeling: to link the stratigraphic architecture of sedimentary basins to climate forcing, with a view to better constraining the distribution, heterogeneities and quality of a source rock or reservoir [3];
•    impact analysis: to anticipate the response of landscapes and landforms to climate-related, catastrophic and extreme events, with a particular focus on the issue of erosion [4];
•    the environment: to track and trace pollutants, such as plastics and microplastics, with a view to defining environmental monitoring tools and proposing remediation solutions [5, 6].
With respect to the latter aspect, which represents a major challenge for our societies, my research represents an important step forward in terms of identifying and characterizing areas where microplastics accumulate, with a view to applying appropriate solutions. The three PhD theses I have been co-supervising since 2023 all fit squarely with this crucial area of research for the environment. 

³ Time and space evolution of underground temperature
⁴ i.e., a chronological timeline of major events affecting basin structures

References :

1. Crombez V, Rohais S, Baudin F, Euzen T, Zonneveld JP, Power M, 2019. “3D stratigraphic architecture, sedimentary budget, and sources of the Lower and Middle Triassic strata of Western Canada: evidence for a major basin structural reorganization”. Petroleum Geoscience, petgeo2019-024.
   >> https://doi.org/10.1144/petgeo2019-024
      
2. Rohais S, Lovecchio JP, Abreu V, Miguez M, Paulin S, 2021. “High-resolution sedimentary budget quantification – example from the Cenozoic deposits in the Pelotas basin, South Atlantic”. Basin Res. 00:1-29. 
   >> https://doi.org/10.1111/bre.12556
         
3. Rohais S, Hamon Y, Deschamps R, Beaumont V, Gasparrini M, Pillot D, Romero-Sarmiento MF, 2019. “Patterns of organic carbon enrichment in a lacustrine system across the K-T boundary: Insight from a multi-proxy analysis of the Yacoraite Formation, Salta rift basin, Argentina”. International Journal of Coal Geology, Volume 210, ISSN 0166-5162, 
   >> https://doi.org/10.1016/j.coal.2019.05.015
    
4. Chaboureau AC, Donnadieu Y, Sepulchre P, Robin C, Guillocheau F, Rohais S, 2012,"The Aptian evaporites of the South Atlantic: a climatic paradox?", Climate of the past, Volume: 8 Issue: 3 Pages: 1047-1058, 
   >> https://doi.org/10.5194/cp-8-1047-2012
    
5. Romero-Sarmiento M-F, Ravaleojaona H, Pillot D, Rohais S,“Polymer quantification using the Rock-Eval® device for identification of plastics in sediments”, Science of The Total Environment. Vol. 807, Part 3. 
   >> https://doi.org/10.1016/j.scitotenv.2021.151068
    
6. Rohais S, Armitage JJ, Romero-Sarmiento M-F, Pierson, J-L, Teles V, Bauer D, Cassar C, Sebag D, Klopffer M-H, Pelerin M, 2024,“A source-to-sink perspective of an anthropogenic marker: a first assessment of microplastics concentration, pathways, and accumulation across the environment”, Earth Sci. Rev. 254, 104822. 
   >> https://doi.org/10.1016/j.earscirev.2024.104822
       
    

To know more : Sébastien Rohais

>> ISSUE 57 OF SCIENCE@IFPEN