The Basin and Range Province of the western United States is perhaps the premier example of a continental extensional orogen on Earth today. Nonetheless, the amount of extension that has occurred across the Basin and Range, and the mechanisms that accommodate it, remain strongly debated. This is particularly true in the Death Valley region, where up to 400% crustal extension has been proposed in the last ~15 million years. In part, this debate hinges on the interpretation of fluvial sediments located on the eastern side of Death Valley, which contain unique clasts derived from a source ~80 km to the WNW on the western side of Death Valley, with one interpretation positing that most of the transport of the clasts from source to sink was accomplished by tectonic processes, and another that the transport is primarily due to sedimentologic processes. In this paper, Nathan A. Niemi describes a new method to quantitatively assess the transport distance of fluvial sediments using the dilution of distinct detrital zircon U-Pb age populations. Detrital zircon U-Pb age spectra from sedimentary rocks on the east of Death Valley contain a Jurassic age peak that is similar in age and magnitude to unique plutonic source rocks in western Death Valley, supporting an interpretation of large-magnitude extension across Death Valley. The proposed methodology is applicable for discriminating tectonic versus sedimentary transport in any orogenic system in which a unique zircon source population can be identified.
|Contact: Kea Giles|
Geological Society of America