Abstract: The Basins on the Argentine Continental Margin

Carlos M. Urien

After the stabilization of the central Gondwana Craton, orogenic belts were accreted, as a result of convergence events, and an extensive passive margin developed in southwestern Gondwana. Thermal subsidence in Parana, Karoo-Ventania basins and the Late Paleozoic-Early Mesozoic rifts, were modified by the Gondwana breakup and the South Atlantic opening. Early Paleozoic marine transgressions deposited the Table Mountain Group in Ventania. In southwestern Patagonia foreland clastics were deposited.

Magmatic arcs and marine units indicate a tectonic trough was formed, alternating with continental sequences, over Late Paleozoic metamorphics and intrusives, resulting from plastered terrains along the Gondwana margin.

In Patagonia, Permo-Carboniferous continental and glacio-marine clastics infill the basins, while in Ventania, paralic sequences, grade from neritic to continental to the northeast, extending beneath the continental margin. The Triassic-Jurassic rift basins progressed onto regional widespread acid lavas and were infilled by lagoonal organic-rich sequences. Early drift phase built basins transverse to the margin, with fluvio-lacustrine sequences: Salado, Colorado, Valdes-Rawson, San Julian and North Malvinas intracratonic basins, which underwent transtensional faulting.

Post-Oxfordian to Neocomian brackish sequences, onlapped the conjugate basins during the margin's drift, with petroleum systems, as in Austral and Malvinas.

In the Valanginian, basic extrusions commenced to form on the continental border, heralding the oceanic phase.

Due to thermal subsidence, offlaping sediments prograded onto the remaining half-grabens. Several petroleum systems, proven and hypothetical, are identified in this region.

AAPG Search and Discovery Article #90951©1996 AAPG International Conference and Exhibition, Caracas, Venezuela