EES Virtual Seminar: The sediment routing systems of the Guyana Shield: from the Atlantic Rifting to the Andean Rise

Dr. Delphine Rouby
Université de Toulouse, France

Abstract: Sediment routing systems of cratonic domains have not been studied extensively because their relief and erosion rates are very low although their vast dimensions make them contribute significantly to global sediment export to oceans. To investigate the export capacity of a peri-Atlantic cratonic domain, we study sediment routing systems of the Atlantic margin of the Guiana Shield through the stratigraphic architecture of its basins (i.e., the Guiana-Suriname and Foz do Amazonas basin) with an emphasis on clastic sediments accumulation rates, depositional environments and grain size distribution histories.

The accumulation history of the margin shows periods of low siliciclastic supply reflecting subdued shield relief and denudation, in the Early Cretaceous for the Guiana-Suriname basin, as well as during the Paleogene and Miocene for the entire margin, enhanced by intense continental lateritic weathering. Periods of higher siliciclastic supply reflected preferential mechanical erosion of rifting-related topography (e.g., for Early Cretaceous Equatorial Atlantic rifting) and/or changes in drainage organization at continental scale (e.g., establishment of the modern Orinoco and Amazon Rivers in the Late Miocene). In the Late Cretaceous, the drainage area feeding the Guiana-Suriname basin decreased due to seaward migration of its watershed while the drainage area feeding the Foz do Amazonas basin increased due to landward migration of its watershed. Finally, the rift-related topography of the Early Cretaceous Equatorial Atlantic was steeper than that of the Late Jurassic Central Atlantic and sustained coarser and higher siliciclastic supply to the margin.



Online via Zoom
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Isabelle Coutand