Implementing Single Crystal Zircon U-Pb Dating of Smectitic Clays in the Late Jurassic Morrison Formation as a Proxy for Long-Distance Correlation of Terrestrial Strata in the Western United States
Geoscience, University of Wisconsin-Madison, Madison, WI, USA
The Late Jurassic Morrison Formation is well exposed in the Western United States and is renowned for its fossils, including abundant dinosaur remains and uranium deposits. The Morrison consists of channelforms, interfluvial deposits, and lacustrine facies deposited as part of an alluvial system that covered much of the Western United States. These deposits are laterally variable, even across outcrop, complicating correlation from local to regional scales. Additionally, deposition of the Morrison was relatively short lived, requiring high precision dating techniques to make dates meaningful.
Until recently, dating methods did not have the precision or resolution to be useful within the Morrison. As a result, numerical ages are not widely available in most areas of the Morrison. This proposal targets areas with no to sparse numerical calibration dates. Current methods employ CA-TIMS to date single ashfall zircons with great precision and accuracy (0.1%). Here, I propose to use single crystal zircon U-Pb ages to constrain ages in portions of the Morrison of Wyoming, the objective being to correlate sections regionally and improve temporal resolution.
This project will target areas in Wyoming because very few age dates exist for the Morrison Formation in Wyoming. These dates will then be used to tie fossil occurrences to sites on the Colorado Plateau where more dates exist. Results will be used as part of a larger project to understand the controls on fossil preservation in an alluvial setting–a topic that is not well-understood.
AAPG Search and Discovery Article #90199 © 2014 AAPG Foundation 2014 Grants-in-Aid Projects