--> Abstract: Paleo-Environmental Evolution of an Extensional Cretaceous Continental Sequence, Northern Precordillera, Central Argentine Andes; #90063 (2007)

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Paleo-Environmental Evolution of an Extensional Cretaceous Continental Sequence, Northern Precordillera, Central Argentine Andes

 

Reijenstein, Hernan M.1 (1) University of Houston, Houston, TX

 

Sedimentation in extensional basins characterized the early Mesozoic tectono-stratigraphic framework along the central and western margin of South America. Triassic Rift deposits of the Cuyo Basin have been widely studied in contrast to the Cretaceous sequences, which were thought to be missing in the Northern Precordillera. Recent biostratigraphic information helped to define the presence of a new Cretaceous unit, the Cienaga del Rio Huaco Formation (Maastrichtian). This study is based on information gathered from field data, rock sampling, lab work, and sandstone petrographic descriptions. Dickinson's provenance discrimination diagrams were used to investigate sandstone composition and possible source areas. Most of the sampled sandstones showed a combined Magmatic Arc and Recycled Orogen provenance, suggesting a possible source from the widely distributed Permo-Triassic vulcanites and Paleozoic metamorphic rocks of the Central Argentine Andes region. A detailed 180 meters-thick sedimentary section of the Cretaceous Cienaga del Rio Huaco Formation shows the evolving stages of a rift related sedimentation. The first stage is represented by a 25 meters-thick, fining upwards coarse-grained conglomerates and sandstones unit overlaying an unconformity. This succession is overlain by at least a hundred meters of laterally continuous strata composed of sandstones, shale, and gypsum, capped by 30 meters of fine laminated red shale. Different paleo-environments were interpreted along this sequence. The basal unit was deposited in a high-energy braided fluvial system composed of conglomerates and inter-layered coarse-grained sandstones, which gradually evolved into a finer grained meandering system. This event derived into an ephemeral lacustrine-fluvial depositional system with variations in the position of the shoreline.

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California