Substrate and oxygen conditions and their role in the preservation of the first record of articulated ophiuroids for the Mesozoic of South America: preliminary results

FERNÁNDEZ, DIANA ELIZABETH; GIACHETTI, LUCIANA MARÍA; COMERIO, MARCOS; PÉREZ, DAMIÁN E.; GUTIÉRREZ, CAROLINA; PAZOS, PABLO JOSÉ

Congreso; XX Congreso Geológico Argentino; 2017

AGA

Recently, the first articulated ophiuroid remains in the Mesozoic of South America were found in Neuquén basin. Here, their paleoenvironmental setting is interpreted as a low-energy outer ramp setting below the storm wave base, deposited in a period of high carbonate productivity and restricted terrigenous input. Weak storm-derived bottom flows carried bioclasts from more proximal areas. Extracellular polymeric substances and filament-like microstructures are documented. Oxygen-deficient bottom waters and fluctuating oxygen levels at the sediment-water interface are envisaged. The bottom flows might have transported the ophiuroids for a relatively short distance from their life habitat. In the new setting, a drop in the oxygen content might explain their death and preservation of articulated remains. This together with the lack of high energy processes and a cohesive substrate (rich in EPS) could have delayed disarticulation.