The Basin and Range province of the western United States is perhaps the best exposed and most accessible example of an intracontinental extensional province on Earth today. Although a variety of lines of geological and geophysical evidence indicate that this region has experienced approximately 200% east-west extension since middle Miocene time, the Basin and Range is underlain today by continental crust of typical (30 km) thickness, but that lies at an average elevation (1-1.5 km) substantially higher than one would expect based on simple geophysical calculations. How the continental crust of the Basin and Range has evolved throughout Cenozoic time to have the characteristics that it has today is an outstanding question that bears directly on the nature of diffuse continental deformation, far away from plate boundaries, and the processes that lead the crust to stretch and thin without rupturing to create new oceanic basins. A variety of tectonic models have been invoked to explain the evolution of the Basin and Range, but the geologic observations that would allow one to discriminate between these models are unresolved. One potential discriminant between these models is the predictions each makes for the paleoelevation history of the western United States. Recent advances in the development of paleo-thermometers, using clumped isotopes in lacustrine carbonates, offers a new approach to determining paleotemperatures from the geologic record, and thus, indirectly the paleoelevations at which the carbonates formed. By applying these new methods to measure the temperature differences between a suite of low-elevation, near sea-level lacustrine carbonates, and coeval lacustrine carbonates in the Basin and Range, this project will develop new constraints on the temporal and spatial evolution of topography across the Basin and Range throughout its Cenozoic evolution, and thus address several key questions about the tectonic evolution of the Basin and Range, including: (1) Was the Basin and Range a high-standing plateau prior to extension?; (2) What was the spatial extent of such a plateau, if it existed?; (3) How did the elevation of the Basin and Range change during late Cenozoic extension?; and (4) What processes accommodated large-magnitude extension in late Cenozoic time?
This research will be incorporated into an education and outreach program directed at early middle-school-aged students in the Greater Detroit area through the development and production of a full-dome planetarium movie on plate tectonics, in collaboration with the Exhibit Museum of Natural History and the 3DLabs at the University of Michigan. Early in middle school is the time when many students begin to lose interest in science. This educational project will incorporate the research data gathered from this project, along with the wealth of geological and geophysical data being collected from other ongoing NSF projects, such as Earthscope, into a fully immersive film on the history of the Earth, the processes that drive plate tectonics, the hazards associated with plate boundaries, and the technology we can apply to study modern plate motions. This movie will be incorporated into outreach days on earth sciences at the Exhibit Museum, which reach 3,000-6,000 students annually, and which are designed to get students to think of science as an active and evolving field of study. By developing new and engaging ways of presenting earth science that demonstrate the elements of excitement of discovery and societal relevance that draw in so many who study the earth, the project aims to increase the participation of students in STEM subjects through middle school and beyond.
