Allogenic controls on the fluvial architecture and fossil preservation of the Upper Triassic Ischigualasto Formation, NW Argentina

ALCOBER, O.; LIMARINO, C.O.; COLOMBI, C.

SEDIMENTARY GEOLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2017 vol. 362 p. 1 - 16

0037-0738

The Upper Triassic Ischigualasto Formation in NWArgentina was deposited in a fluvial systemduring the synriftfilling of the extensional Ischigualasto-Villa Unión Basin. The expansive exposures of the fluvial architecture andpaleosols provide a framework to reconstruct the paleoenvironmental evolution of this basin during the UpperTriassic using continental sequence stratigraphy. The Ischigualasto Formation deposition can be divided intoseven sequential sedimentary stages: the 1) Bypass stage; 2) Confined low-accommodation stage; 3) Confinedhigh accommodation stage; 4) Unstable-accommodation stage; 5) Unconfined high-accommodation stage;6) Unconfined low-accommodation stage; and finally, 7) Unconfined high-accommodation stage. The sedimentaryevolution of the Ischigualasto Formation was driven by different allogenic controls such as rises and falls inlake levels, local tectonism, subsidence, volcanism, and climate, which also produced modifications of the equilibriumprofile of the fluvial systems. All of these factors result in different accommodations in central andflank areas of the basin, which led to different architectural configurations of channels and floodplains. Allogenicprocesses affected not only the sequence stratigraphy of the basin but also the vertebrate and plant taphocenosis.Therefore, the sequence stratigraphy can be used not only as a predictive tool related to fossil occurrence but alsoto understand the taphonomic history of the basin at each temporal interval.