Preliminar taphonomic studies of terrestrial vertebrate remains at arroyo Pilmatué, Mulichinco Formation, Las Lajas, Neuquén Basin.

PINO, D.; CORIA, R.A.; DIAZ-MARTINEZ I.; TUNIK, M.; BELLARDINI, F.; BAIANO, M.A.; WINDHOLZ, G.J.

San Luis

Congreso; Reunión de comunicaciones de la Asociación Paleontológica Argentina (RCAPA, 2017).; 2017

Universidad Nacional de San Luis

Remains of ornithopod, theropod and sauropod dinosaurs found in the lower section of the Mulichinco Fm (Valanginian), 10 km north of Las Lajas, have permitted initial taphonomic and paleoenvironmental studies of this site to be undertaken. Preliminarily, 4 facies are recognized: a) mid-grained sandstones with sabulite interbeddings; b) fine conglomerates with a good selection of pebble size inner clasts and dominance of quartz and subordinate volcanic lithics; c) sandstones with parallel or massive lamination; and d) mudstones with parallel lamination. The fossils are buried in a sand package with tabular geometry 1.5-2 meters thick, made of mid- to gross-grained sandstones with thin conglomerate interbedding sand sabulite sandstones with good selection (facie a). These remains are semi-articulated, disarticulated, both associated and non-associated, with long bones that are principally NE-SW oriented, being broken to very broken (weathering grade 1 to 2, slight to moderate abrasion and with fragile deformation recognized in 60% of the specimens). The association of facies allows inference of fluvial channel development, with lateral migration of bars and scarce development of flood plains. Larger specimens are considered to be aloctonous in origin, although with no significant carcass transportation. Disarticulation of remains would be due to intermittent energy pulses, which are inferred from a gradation of thick sabulite sandstones to thin, well-selected conglomerates. Dispersed elements of smaller volume usually behave as rounded clasts, which prevents their association with semi-articulated elements from the main carcass.