BULK SEDIMENTARY ORGANIC CARBON CHEMOSTRATIGRAPHY OF DINOSAUR-BEARING STRATA IN THE YUCCA FORMATION OF WEST TEXAS

The Yucca Formation of West Texas sparse but important dinosaur fossils. The exact age of these Cretaceous dinosaur-bearing units are not well constrained. To that end, two stratigraphic sections were collected to construct C-isotope chemostratigraphic profiles using bulk sedimentary organic carbon. Bulk samples were decarbonated with 0.5M hydrochloric acid, rinsed, dried and weighed into tin capsules. One of the sections included a partial skeleton of a small ornithopod dinosaurs (“Yucca Dino Section”). The other section was collected near the Indio Mountains Field Station (“IMFS section”). Samples were combusted on a Costech 4010 Elemental analyzer attached to a Thermofinnigan MAT 253 isotope ratio mass spectrometer. Of the 10 samples ran from the “Yucca Dino Section”, the average δ¹³C was found to be -25.68‰ vs VPDB. For the “IMFS section”, 8 samples were analyzed averaging -25.18‰ vs VPDB. Overall, the isotopes values at the “Yucca Dino Section” show a gradual increase in isotope values, however it is unclear whether this is a result of changes in the c-cycle or related to depositional environment. The “IMFS section” showed little variation. Results were compared with marine organic C isotope chemostratigraphic records known to be Early Cretaceous and the positive trend may correlate with positive trends that occur in the Aptian and early Albian, but more data is needed . Future work should include analysis of longer stratigraphic sections.