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Abstract

Sedimentary basins represent geological archives. Accordingly, 3D basin models that integrate geological and geophysical observations can be used to reproduce not only their present-day structural configuration and distribution of physical properties, but also their evolution including the subsidence history. For example, the thickness of deposited sediments reflects the amount of subsidence caused by the sediment load. The corresponding load-dependent vertical movements (called isostatic subsidence) can be sequentially subtracted from the total subsidence in order to reconstruct past depth configurations. Another aspect of basin subsidence is caused by thermal processes that can also be approximated by studying the present-day basin configuration. If the basin formation is related to lithospheric stretching and thinning, it initially involves a thermal disturbance due to which the geothermal gradient is increased by an amount depending on the observed strain. After stretching has ceased, the lithosphere starts cooling down and approaches a thermal equilibrium. This cooling process is accompanied by an increase in rock density and related thermal subsidence, which can also be assessed. By calculating the two subsidence components for certain stratigraphic intervals, the corresponding temporal changes in water depths (paleobathymetries) can be reconstructed for our understanding of subsidence dynamics. This research methodology was applied to the conjugate passive continental margins of Africa and Argentina in order to analyse and compare the evolution of sedimentary basins after the formation of the South Atlantic. This study mainly focussed on the Argentinian Colorado Basin because of its complex evolution and economic resource potential.