PhD student Allison Curley publishes her second paper, this time in EPSL.
During the Late Cretaceous, North America was split in two by the Western Interior Seaway. To the west, mountains were rising to become today’s Rocky Mountain range. Major river systems drained from these mountains, across plains and into the seaway, influencing coastal salinity and seaway chemistry.
Previous work analyzing the d18O composition of mollusks living in these freshwater environments has documented two different clusters of data, reflecting high-altitude rivers draining from the mountains vs. low-altitude rivers and ponds. However, how much of this difference in d18O was due to the temperature of the water as opposed to the d18O composition of the water remained unknown. Allison here measures these freshwater mollusks for their clumped isotope composition and separates the influences of temperature and d18Ow.
Temperature estimates from multiple sites document a similar latitudinal temperature gradient as has been found in previous studies. Spatial patterns of d18Ow are consistent with a Campanian Proto-North American Monsoon and the lowest d18Ow values are consistent with a paleoelevation of >3500 m in the Proto-Cordillera.
She also analyzed 87Sr/86Sr in the hopes of using a two-end-member mixing model with d18Ow to estimate the freshwater influence in coastal regions and back out seaway salinity. However, 87Sr/86Sr was too spatially variable to accomplish this.
Link to Paper: https://www.sciencedirect.com/science/article/pii/S0012821X24006125