Undergraduate Honors Theses

Thesis Defended

Fall 2017

Document Type


Type of Thesis

General Honors


Geological Sciences

First Advisor

Kathryn Snell

Second Advisor

Lon Abbott

Third Advisor

Derek Brown

Fourth Advisor

Charles Stern


Previous studies attempting to determine the elevation of the Central Rocky Mountains after the Laramide Orogeny (~40 Ma) have been inconclusive. Two endmember hypotheses have been formulated, one from leaf physiognomy and the other from taxonomic nearest living relative relationships, for the South Park Basin at the time of the Eocene-Oligocene (E-O) Boundary, one claiming an elevation 2km below modern elevation and the other 1 km above. This study presents the first dataset to use the stable isotope composition of lacustrine carbonates of the Antero Formation to constrain the elevation of the basin at the E-O boundary. The results show that certain samples should be eliminated from further studies, due to alterations, and that the climate in the South Park Basin produced δ18O values of carbonate between -11.3‰ to -8.5‰ relative to Pee Dee Belemnite.