AAPG Annual Convention and Exhibition

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Crustal Architecture of the Argentinian Atlantic Margin

Abstract

The Atlantic margin of Argentina is relatively under-explored and the nature of the transitional crust remains an area of significant uncertainty. In this presentation, we look at the area between the Agulhas and Florianopolis Fracture Zones, an area which includes the Rawson, Colorado, Salado and Pelotas Basins, to address some of the fundamental questions about the region's crustal architecture and tectonic evolution. Our analyses use the latest, newly derived satellite gravity data, which incorporates multiple cycles of the Cryosat-1 geodetic mission, self-consistent magnetic compilations and independent constraints from seismic data. This enables us to investigate the along strike variability of the Argentinian continental margin and especially the character of the transitional crust. In particular, we discuss insights from the gravity and magnetic data as to the nature of the magmatic additions along the margin and the apparent transition from magma-rich to magma-poor environments. We also investigate the impact of deep crustal architecture on the development of rift basins and source-to-sink relationships in the region and the influence of increased magmatism on the petroleum systems along the passive margin. The resulting interpretations are then further tested using 2D forward modelling and 3D inversion of the gravity and magnetic data for the distribution of crustal types, sediment thickness and crustal thickness. Newly recovered and reprocessed Petroleum Agency of South Africa (PASA) gravity and magnetic data from the conjugate southern Africa margin give remarkable insights into the character and position of the continent-ocean transition zone and we assess the degree to which this is replicated on the Argentinian side of the Atlantic. Specific derivatives of the gravity and magnetic data (e.g. Analytic Signal) highlight similarities in the conjugate margins geometries and we gauge the degree to which this can be considered indicative of a specific rifting mechanism.