A Combined Rare Earth Element and Sedimentologic Approach to Taphonomic Interpretations of the Early Cretaceous Crystal Geyser Dinosaur Quarry, Utah

Celina Suarez¹, Marina Suarez², Dennis O. Terry¹, D.E. Grandstaff¹, and James I. Kirkland^3
1 Temple University, Philadelphia, PA
² Temple University,
³ Utah Geological Survey, Salt Lake City, UT

The Crystal Geyser Dinosaur Quarry (CGDQ) is one of several new vertebrate fossil localities just above the Morrison-Cedar Mountain Formation contact in east-central Utah. The quarry is located at the base of the Early Cretaceous Cedar Mountain Formation and contains mostly basal therizinosauroid dinosaurs with few ankylosaur, crocodile, and turtle remains. Rare earth element (REE) signatures in fossils were used, along with classical taphonomic and sedimentologic techniques, to determine the sedimentary environment, timing of bone emplacement, and degree of spatial and temporal averaging. Travertine banding, tufa intraclasts, pisolites, and feathery calcite with radial extinction indicate that sediments were deposited in a subaerial spring environment. Differences in REE signatures indicate three different, well separated fossilization events. Bones from the first event, characterized by middle-REE enrichments and positive cerium (Ce) anomalies, indicate fossilization in a near-neutral pH environment. Variations in REE signatures within the unit are consistent with extensive spatial averaging. Bones in this "geochemical interval" are typically dominated by Voorhies Group 2, have scratch marks, and show patchy current orientation. Bones deposited in the second event are more light-REE enriched with smaller positive Ce anomalies. Variations in REE signatures suggest even greater amounts of averaging. These bones show more fracturing with fewer Voorhies Group 2 bone elements. Bones from the last event have greater LREE enrichment, no Ce anomaly, and low signature variance, indicating less taphonomic processing. These bones are near vertical, truncated, and show high degrees of abrasion

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005