MAGNETIC FABRICS, PALEOMAGNETISM, AND U-PB ZIRCON AGES OF CLASTIC MARINE SEDIMENTS: IMPLICATIONS FOR PROVENANCE AND TECTONIC HISTORY OF THE GOLD BEACH TERRANE
From the Gold Beach terrane (SW Oregon), paleomagnetic, magnetic fabric, and detrital zircon U/Pb ages can be used to understand the origin and tectonic history of this tectonic unit. Samples collected from the Cape Sebastian, Hunters Cove, and Houstenaden Creek Formations (Liner, 2005) have a paleomagnetic signal that is of variable quality- with only the sediments of the Houstenaden Creek Fm yielding consistent paleomagnetic results. All of the units, however, have well-defined magnetic fabrics. These will be examined using methods of Taira (1989) and Novak et al (2014) to use AMS fabric shape, and the imbrication-angle of the AMS foliation to classify depositional environment. The AMS orientations also yield sediment transport directions for these units. Paleomagnetic results from 7 sites of the Houstenaden Creek Fm pass both fold and reversals tests- but have a streaked distribution of site mean directions indicating local rotations (Liner, 2003). The tilt corrected, inclination-only mean I = 55, yielding a late Cretaceous paleolatitude of 36 N. Correcting for rotation using the site-mean declinations, the AMS results all indicate a consistent SW-directed sediment transport direction. U-Pb ages of 100 detrital zircons from the Houstenaden Creek Fm have two distinct peak in their age distribution- one at 160-170 Ma, and the other at 85-100 Ma. Combined, the paleomagnetic data, sediment transport directions from the AMS, and detrital zircon U-Pb ages would be consistent with detritus sourced from a number of possibilities, including Klamath, Coast Ranges, or Sierra Nevada plutonic sources. Additional data- Hf isotopes, and possible future work including thermochronology of the detritus in the Gold Beach terrane will enable the tectonic interaction with this terrane and the NA margin to be better understood.