The Upper Jurassic Vaca Muerta basal deposits in the Picún Leufú area, Neuquén Basin: Evidence of a rapid transgression

PAZ, M.; PONCE, J.J.; CARMONA, N.B.; MÁNGANO, M.G.; BUATOIS, L.A.

General Roca

Congreso; XVI Reunión Argentina de Sedimentología; 2018

Asociación Argentina de Sedimentología

The Vaca Muerta Formation basal deposits constitute an example of a marinetransgression over the continental Tordillo Formation in the Neuquén Basin, Argentinaduring the Tithonian. We have integrated the sedimentological and ichnological datasetsof the basal transgressive deposits in order to better understand the sedimentaryevolution of this interval. Analysis of six stratigraphic sections (20 m each) of theTordillo-Vaca Muerta formation transition was coupled with petrographic description ofseven thin sections in the Picún Leufú area (Southern Neuquén Basin). Thesedimentary evolution can be summarized as follows: (1) a deformational phasegenerated a topographic high in the Picún Leufú anticline, (2) an early phase of highwater table triggered liquefaction, early stabilization and coastal eolian dune reworking,(3) an embayment phase with deposition of mud flat, bay margin and distal bay faciesshowing the Glossifungites Ichnofacies delineating transgressive surfaces, and (4) alate stage of siliciclastic basinal condensation recording hemipelagic deposition andoxygen-deficient conditions, which ended with a Maximum Flooding Surface on top.Sedimentologic and ichnologic evidence indicates that the transgression did notconstitute a catastrophic flooding over the eolian deposits, and rather records a lowenergyand rapid flooding event that promoted preservation of a reworked eolian reliefand the analyzed marginal marine transitional deposits.