Collaborative Research: Time of Transformation: integrating the dynamic geologic, climatic and biotic systems of North America during the Early to Late Cretaceous transition

The transition from the Early to Late Cretaceous time period (~130 to 90 million years ago) was marked by profound changes to terrestrial (land-based) ecosystems. These included the extinction and replacement of many dinosaur groups, rapid increases in flowering-plants and pollinating insects, greater diversity of mammals, and major turnovers in aquatic invertebrates. This dramatic reorganization of terrestrial ecosystems occurred against a backdrop of rapid landscape and climatic changes. This includes the rise of a mountain chain running from Nevada through Montana that caused regional environmental changes and formed physical barriers to animal movement. Massive volcanic eruptions caused temperature and sea-level rises that ushered in a greenhouse global climate and flooding of the North American interior by a north-south trending seaway. These environmental changes are preserved within the sedimentary rocks of the Western Interior Basin, an extensive depositional area east of the mountains. This project will examine the cause-and-effect relationships between these climatic and tectonic changes and the evolution of the Late Cretaceous ecosystems. It will be accomplished by correlating time-calibrated climate data in conjunction with detailed fossil occurrences for several important rock formations that span the target time interval and geographic expanse of the Western Interior Basin. The goal is to determine how rapidly climatic and tectonic changes influenced the evolution, distribution, and extinction of land-based life. Public engagement through outreach programs and museum exhibits are an important component of this project.

The Early to Late Cretaceous transition in North America (mid-Cretaceous) is marked by profound faunal and floral reorganization that dramatically altered continental biotas. Such biotic shifts occurred against a backdrop of geologic events and climatic changes during the Aptian to the Cenomanian time interval that preceded the high diversity flora and fauna of the Campanian-Maastrichtian Ages. The North American Western Interior Basin stands out as an exemplar for studying the mid-Cretaceous due to its latitudinal extent, relatively complete rock sequences, and long history of fossil collection. This project will generate 1) a refined chronologic framework for continental strata of the Western Interior Basin); 2) paleoclimatic proxy data to infer regional and global climate trends; and 3) quantitative analyses to integrate climate data with key geologic events that explore influences on paleo-community restructuring on a regional scale. Results will be integrated using paleoecological niche modeling and canonical correspondence analysis with fossil sampling within target formations to fill persistent gaps in biotic diversity data and to determine their effects on dispersal, speciation, and turnover. This research will generate a large body of data relevant to the broad community of geoscientists investigating the Western Interior Basin and could also help in the analysis of future climate states.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.