New Mexico Geological Society Annual Spring Meeting — Abstracts

δ¹⁸O values from calcareous foraminifera and routinely used to determine ancient climatic features such as seawater temperature and the rise and fall of sea level is a well do0cumented and effective tool for understanding paleo-climate. Their use in pre-Cenozoic deposits is usually not impossible because calcite is highly susceptible to diagenetic alteration. Conodonts make a good proxy for older rocks (Paleozoic-Mesozoic) because they are made of apatite as opposed to calcite are not prone to alteration by diagenic processes. They Gray Mesa Formation at Mesa Sarca displays well preserved Pennsylvanian (Desmoinesian) age old rock that shows trends of transgression and regression on meter scales (cycles) and 40-80m scales (sequences). In this study, conodonts are used as a proxy to determine whether the transgression and regression sequences (40-80m thick) from the Gray Mesa Formation at Mesa Sarca are due to glacial eustasy. This will be determined by using δ¹⁸O values from the conodonts. Glacial eustasy as a mechanism will leave greater δ¹⁸O values at the base of the unit and smaller δ¹⁸O values at the top of the sequence.