PRELIMINARY TAPHONOMIC STUDIES OF TERRESTRIAL VERTEBRATE REMAINS AT ARROYO PILMATUÉ, MULICHINCO FORMATION, LAS LAJAS, NEUQUÉN BASIN

PINO, DIEGO; CORIA, RODOLFO A.; DIAZ MARTINEZ, IGNACIO; TUNIK, MAISA; BELLARDINI, FLAVIO; BAIANO, MATTIA A.; WINDHOLZ, GUILLERMO

Mar Chiquita

Jornada; 31 JORNADAS ARGENTINAS DE PALEONTOLOGÍA DE VERTEBRADOS; 2017

Museo Municipal de Ciencias Naturales Pachamama, APA

Remains of ornithopod, theropod and sauropod dinosaurs found in the lower section of the Mulichinco Formation(Valanginian), 10 km north of Las Lajas, have permitted initial taphonomic and paleoenvironmental studies of this site to beundertaken. Preliminarily, 4 facies are recognized: a) mid-grained sandstones with sabulite interbeddings; b) fine conglomerateswith 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 sandpackage with tabular geometry 1.5?2 m thick, made of mid- to gross-grained sandstones with thin conglomerate interbeddingsand sabulite sandstones with good selection (facies 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). Theassociation of facies allows inference of fluvial channel development, with lateral migration of bars and scarce developmentof flood plains. Larger specimens are considered to be allochthonous 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 thicksabulite sandstones to thin, well-selected conglomerates. Dispersed elements of smaller volume usually behave as roundedclasts, which prevents their association with semi-articulated elements from the main carcass.