Paper No. 75-10
Presentation Time: 10:40 AM
NEW INSIGHTS ON THE IMPACT OF YELLOWSTONE HOTSPOT TRACK ON MAJOR DRAINAGE REORGANIZATION OF THE NORTHERN ROCKIES AND PACIFIC NORTHWEST
STAISCH, Lydia1, O'CONNOR, Jim E.2, HOLM-DENOMA, Chris3, WALKUP, Laura C.4, AVERY, Margaret S.4, PIVARUNAS, Anthony F.4 and PRASSACK, Kari5, (1)USGS, 2130 SW 5th Ave, Portland, OR 97201; U.S. Geological Survey, 2130 SW 5th Ave, Portland, OR 97201-4908, (2)U.S. Geological Survey, 2130 SW Fifth Avenue, Portland, OR 97201, (3)U.S. Geological Survey, Geology, Geophysics, and Geochemistry Science Center, Denver Federal Center, Denver, CO 80225, (4)U.S. Geological Survey, Geology, Minerals, Energy, and Geophysics Science Center, 345 Middlefield Road, MS 975, Menlo Park, CA 94025, (5)National Park Service, Glen Canyon National Recreation Area & Rainbow Bridge National Monument, PO Box 1507, 691 Scenic View Drive, Page, AZ 86040
Recent provenance analysis of late Miocene – Pliocene sandstones in the northern Rocky Mountains and Pacific Northwest suggest that major drainage reorganization of the Snake and Columbia Rivers was driven by the interplay of broad uplift produced along the Yellowstone Hotspot track and regional subsidence produced via densification of the eastern Snake River Plain. The evidence for basin isolation and integration between ~10 and ~2 Ma is catalogued in the sedimentary remnants of Lake Idaho, located within the western Snake River Plain, and “Lake Ringold”, located in the Pasco Basin. While the Snake River’s modern course through Hells Canyon links these two basins, previous work on detrital zircon provenance analysis suggests that Lake Idaho was isolated from the Pasco Basin and upper Snake River drainage system prior to ~4.3 Ma. The exact timing on how and when the Snake River changed its course and connected these two basins is still a matter of debate.
In this study, we focus on two primary stratigraphic records: the Glenns Ferry formation within the Hagerman Fossil Beds National Monument, and the Clarkston Heights gravels, located just outside Clarkston, WA and Lewiston, ID. We sampled fluvial and lacustrine strata throughout the Glenns Ferry formation for detrital zircon provenance analysis and clumped isotope analysis. The results of these samples provide further insight into the evolution of sources, climate, and environment of the Glenns Ferry Formation. At the Clarkston Heights gravels, prior work established that the basal units were sourced entirely from the paleo-Salmon and Clearwater River systems, despite this site’s location along the modern Snake River immediately downstream of Hells Canyon. Here, we sampled throughout the exposed aggregational gravel unit for detrital zircon provenance analysis and recorded clast compositions and flow directions to identify changes in source terrane.
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