THE UPPER JURASSIC VACA MUERTA BASAL DEPOSITS IN THE PICÚN LEUFÚ AREA, NEUQUÉN BASIN: EVIDENCE OF A RAPID TRANSGRESSION

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

General Roca

Congreso; Reunion Argentina de Sedimentología 2018; 2018

Asociación Argentina de Sedimentología

The Vaca Muerta Formation basal deposits constitute an example of amarine transgression over the continental Tordillo Formation in the NeuquénBasin, Argentina during the Tithonian. We have integrated the sedimentologicaland ichnological datasets of the basal transgressive deposits in order to betterunderstand the sedimentary evolution of this interval. Analysis of sixstratigraphic sections (20 m each) of the Tordillo-Vaca Muerta formationtransition was coupled with petrographic description of seven thin sections inthe Picún Leufú area (Southern Neuquén Basin). The sedimentary evolutioncan be summarized as follows: (1) a deformational phase generated atopographic high in the Picún Leufú anticline, (2) an early phase of high watertable triggered liquefaction, early stabilization and coastal eolian dunereworking, (3) an embayment phase with deposition of mud flat, bay margin anddistal bay facies showing the Glossifungites Ichnofacies delineatingtransgressive surfaces, and (4) a late stage of siliciclastic basinal condensation recording hemipelagic deposition and oxygen-deficient conditions, which ended with a Maximum Flooding Surface on top. Sedimentologic and ichnologic evidence indicates that the transgression did not constitute a catastrophic flooding over the eolian deposits, and rather records a low-energy and rapid flooding event that promoted preservation of a reworked eolian relief and the analyzed marginal marine transitional deposits.