Estimating MAT Values of the Hell Creek Formation in eastern Montana and northwestern South Dakota using CLAMP

Author: Michael Nieland, Department of Geology and Geological Engineering

Mentor: Dr. Sarah Keenan, Department of Geology and Geological Engineering

The Hell Creek Formation contains sediments from both the late Cretaceous and early Paleocene with deposition estimates of about 68 to 65 million years ago. Climate studies from this formation could provide additional clues for the causes of the end Cretaceous mass extinction. Among many things, this formation contains well-preserved leaf fossils that could be useful in climate reconstruction through the use of leaf-margin analysis and the Climate Leaf Analysis Multivariate Program (CLAMP). With these analyses, climate factors such as mean annual temperatures (MAT) can be estimated. A prior study on the Hell Creek Formation in eastern Montana estimated a MAT of 11-12 °C + 2 °C using CLAMP and suggested seasonably variable temperatures.

This study intends to further climate research of the Hell Creek Formation by using CLAMP on leaf specimens from both eastern Montana (number of specimens = 20) and northwestern South Dakota (n = 77). Preliminary analysis indicates that MAT values are about 19 °C for Wyoming and 12.5 °C for South Dakota. Some possible explanations for the drastically different value for Wyoming could be due to low sample size, preservation preference in leaves, errors in measurements, and/or seasonal changes in temperature. Furthermore, it aims to determine if a significant difference in MAT values is present between the Montana and South Dakota areas by using a t-test. It is hypothesized that the MAT values of both areas will not be significantly different from one another because they are approximately 300 km from each other and at most are separated by 2.5 million years. Additionally, this study will further the research done on paleoclimates from the Hell Creek Formation through comparisons to previous studies in Montana and providing data from unstudied areas in South Dakota.