Petrographic, mineralogical and geochemical characterization of finegrained rocks of the Pilmatué Member (Upper Valanginian-lower hauterivian) of the Neuquén Basin (Argentina): Implications for siliciclastic input, carbonate productivity and redox conditi

REMIREZ M.; SPALLETTI L.A.; ISLA M.

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2020

0895-9811

Petrographic, mineralogical and geochemical analyses of mixed siliciclastic-carbonate offshore deposits of thePilmatué Member (Neuquén Basin) were carried out to define two scenarios for deposition: a confined rampsetting (CRS) and an open ramp setting (ORS). The CRS involves marly to carbonate-rich fine-grained mudstones, mostly laminated and non-bioturbated, enriched in redox proxies and depleted in rare earth elements(REE). The ORS comprises abundant siliciclastic-rich mudstones, mostly coarser-mudstones, depleted in redoxproxies and with REE pattern similar to the PAAS. These variations are explained through fluctuations in carbonate productivity/terrigenous input, and changes in the circulation pattern of the basin. Within the CRS, highcarbonate productivity would be favored due to the general greenhouse condition for the Early Cretaceous andthe scarcity of terrigenous supply, related to the landward migration of the shoreline and low effectiveness ofsediment distribution by marine currents. Furthermore, high organic matter productivity should lead to anoxygen-depletion close to the sediment-water interface. Instead, increasing sediment supply and dissolvedoxygen in the ORS is related to shoreline progradation in the south and the consequent installation of across shelfflows that allowed vertical water circulation and the oxygen replenishment in benthic environment.