03/31/2022
By Erica Gavin

The Kennedy College of Sciences, Department of Environmental, Earth and Atmospheric Sciences invites you to attend a Master’s thesis defense in Environmental Studies by Ericka M. Boudreau on: "Detrital Mineral Constraints Reflecting Northward Translation of the Gold Beach Terrane, SW Oregon."

This will be held in Olney Science Center 212 on Thursday, April 14, 2022 at 4 p.m.

Committee members include:

  • Richard Gaschnig of UMass Lowell
  • Nelson Eby of UMass Lowell
  • Basil Tikoff of the University of Wisconsin Madison

Abstract:
Evolution of the western North American Cordillera during the Mesozoic included the progressive accretion of allochthonous terranes, some of which may have experienced large-scale northward translation as described in the Baja-BC hypothesis. We investigate evidence for northward translation through the analysis of detrital minerals gathered from Late Cretaceous sandstones in the Gold Beach terrane of southwestern Oregon. Detrital zircon, monazite, and titanite U-Pb geochronology, trace element geochemistry, and Hf and Nd isotope analysis, as well as garnet species classification, suggest a northwestern Mexico to southern California provenance. These results offer a comprehensive geochemical record of tectonic and depositional processes in the Gold Beach terrane. While Jurassic ages can be supplied by plutons in the Klamaths, Northern Sierras, or Blue Mountains Province, geochemical characteristics point towards sources in the Mojave-Sonoran Desert. Evolved Late Cretaceous zircon and titanite require derivation from a combination of sources in the Sierra Nevada and Peninsular Ranges Batholith and the younger Idaho Batholith. Peraluminous plutons in the southern Sierras, Peninsular Ranges, and Mojave Desert may also be the source of igneous garnets and mid-Cretaceous monazites. This compilation of data supports moderate northward translation of the Gold Beach terrane.