Comparitive Variations in Structural and Magmatic Style along Eastern South America, Trinidad to Argentina, as Revealed by Long Offset 2D Seismic Data

Pindell, James¹; Graham, Rod; and Emmet, Peter A.
¹[email protected]

ION-GXT long-offset 2D SPAN seismic reflection surveys now cover most of eastern South America, including Trinidad, northern and eastern Brazil, Uruguay, and Argentina, allowing full crustal interpretation to the Moho and deeper. This greater margin comprises three primary segments associated with different stages and kinematic styles of Atlantic opening. The oldest is the Trinidad-Demerara NW-SE transform margin (Late Jurassic-Barremian), followed by the southern South Atlantic N-ward propagating rift (Neocomian-Aptian), followed in turn by the "amalgamated pull-apart" Equatorial Atlantic margin (Aptian-Albian). Variations seen in given cross sections range from (1) hyper-extended continental crust to abrupt high-angle marginal offsets, (2) entirely non-magmatic to heavily magmatic, with magmatic sections showing different magmatic styles, and (3) salt-lacking to salt-bearing, with great differences in the amount of apparent mother salt and salt deformation. The differing rift styles, constrained by both basement structure and overlying depositional geometries, produce different basement architectures, which in turn control marginal sedimentary architectures. The crustal mapping allows inferences regarding heat flow history, but equally important are observations regarding water depth for certain depositional sequences, and the timing for downslope slumping of salt-bearing sections. Regarding paleo-continental reconstructions, debate continues over the relative importance of the creation of new terrane (igneous and exhumed crust/mantle) vs hyper-extension and low-angle detachment faulting…and how to fit these aspects into the pre-rift fits. Despite these uncertainties, this margin displays a range of tectonic styles seen at other margins around the world.

AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013