CONSTRAINING DINOSAUR BEHAVIOR FROM PALEOENVIRONMENTAL INTERPRETATIONS: EARLY JURASSIC EAST BERLIN FORMATION, DINOSAUR STATE PARK, ROCKY HILL, CONNECTICUT, USA

Abstract The paleoenvironment of the tracked strata in the Early Jurassic East Berlin Formation at Dinosaur State Park (DSP) in Rocky Hill, Connecticut, USA was traditionally ascribed to the margin of a perennial lake, and dinosaur behavior was interpreted within this context. This contribution interprets the environment as an ephemeral lake system based on detailed sedimentological investigations and correlation to nearby outcrops and cores. Laminated carbonaceous mudstone and structureless to planar-bedded mudstone are grouped into a perennial lake facies association that reflects periods of deposition in large lakes in the Hartford Basin. Rippled mudstone, disrupted mudstone, planar-parallel and trough cross-bedded sandstone, and crinkly laminated mudstone to sandstone facies are grouped into the ephemeral lake facies association deposited when the climate was arid. Microbial communities occasionally colonized the shallow subaqueous or exposed moist sediment surface in these ephemeral lake systems. Over 750 Eubrontes tracks are exposed on three beds interpreted as having been deposited in ephemeral lake sandflats. These track layers correlate directly into ephemeral lake facies in nearby cores and outcrops, with no evidence of a contemporaneous perennial lake. This paleoenvironmental interpretation has implications for understanding theropod dinosaur behavior, particularly as it relates to suspected swimming activity and aquatic feeding strategies. Microbial mats likely increased the time the surfaces were available for track registration and enhanced their preservation. Finally, this new interpretation impacts our understanding of the dinosaurian ecological structure of the Early Jurassic in the Hartford Basin and constrains the possible reasons that the theropod dinosaurs were at DSP.