UPDATES TO THE TAPHONOMY OF THE AARON SCOTT QUARRY (LATE JURASSIC, MORRISON FORMATION, UTAH)

The Aaron Scott Quarry (Brushy Basin Member, Morrison Formation, Jurassic) was the site of a lake margin with a delta forming along the eastern edge. A large, sustained lake such as this one is unknown from the Morrison Formation, which was deposited when the climate was fairly arid. Aquatic fauna such as crocodiles and turtles are abundant. The quarry consists of four bone layers within a calcite cemented unit approximately one foot thick, which overlies an olive gray shale. Three of the bone layers are rip-up clast conglomerates with disarticulated and broken bones that were deposited by fluvial transport onto a delta. Above the second rip up clast layer, an associated skeleton of a Barosaurus is preserved. The layers dip approximately 8 degrees to the southwest, greater than the regional dip of 5 degrees. The rip of clast layers indicate lowering of the lake level and fluvial transport. The sauropods died near the lake and were not transported, leaving the associated skeletons. The rip up clast layers show incision into the underlying layers. The deposition of these units represents a delta on a lake margin with fluctuating lake levels.