First dinosaur tracks found in the Mulichinco Formation (Lower Cretaceous), Neuquen Basin, Argentina: Paleoenvironmental implications

Abstract

This study focuses on the analysis of the first dinosaur tracks discovered in the Mulichinco Formation, Neuquen Basin, Argentina. The deposition of this unit occurred during the early Valanginian, Early Cretaceous, making it the oldest known record of dinosaur tracks for that period in the basin. The aim of this study is to provide a paleoenvironmental interpretation of the area and potential trackmakers based on the morphology of the tracks and the facies analysis of the depositional system. The depositional system evolved from a moderately sinuous fluvial system in the lower interval to a braid distal plain system with the development of bodies of water without marine influence, culminating in an estuary with marine influence in the upper interval. The paleoenvironmental conditions during the deposition of the unit were favourable for the presence and interaction of diversity large continental vertebrates. The track-bearing surfaces in the lower interval suggest that the organisms exploited the temporary gaps created between channel migration and floodplain formation as areas for transit or water sources. In the middle interval, the abundant presence of traces fossils of invertebrates and symmetrical ripples suggest a more stable depositional system where fluctuations in the water column were common. The co-occurrence of various track-makers and remains of large vertebrates described in the Mulichinco Formation is unusual among track sites at the basin. Overall, this study provides new insights into the Early Cretaceous paleoenvironmental conditions of the Neuquen Basin and the diversity of large verte- brates that inhabited the region during this time.