T48 Oblique Motion on the North American Cordilleran Margin: Jurassic to Paleogene (Posters)

Sunday, 22 September 2024
8:00 AM - 5:30 PM
Hall D

EXPLORING DIFFERENCES IN NORTH AMERICAN APPARENT POLAR WANDER PATHS AND IMPLICATIONS FOR TERRANE RECONSTRUCTION OF THE BLUE MOUNTAINS, OR-ID

Paper number: T48-1
Program: Technical Sessions
Time: 8:00 AM – 5:30 PM

Authors

  • Bernie Housen Presenting Author
    Western Washington University, Bellingham, WA

Abstract

This contribution will focus on the Mesozoic APWP of North America, comparing recent global compilations that use different approaches to data quality, compilation, and path construction, and will focus on some implications for terrane reconstruction using paleomagnetic data from the Blue Mountains (OR-ID). Vaes et al., 2023 present a global APWP model (V23) that (when possible) uses site-level data from a large compilation of paleomagnetic studies. A weighted moving window average set of poles for 5 Ma age ranges are calculated, and this global path is then used to tabulate a reference APWP for most large plates. EKM19 (Enkin 2006, Kent and Irving 2010, Kent et al., 2015, and Muttoni and Kent, 2019) is constructed using data criteria to favor igneous rocks, has the majority of data from North America, and uses selected global data for Cretaceous and for Late Jurassic times. H24 uses only data from North America, includes a reevaluation of Cretaceous igneous rocks using updated geochronology (Housen, 2021, Tikoff et al., 2023), and inclination-corrected results for key Late Jurassic units (Housen and Mirzaei, 2022).

For a comparison, a location in the Blue Mountains (118 W, 45 N) was selected. These paths have some common features- paleolatitudes of ~ 20 N from 240-200 Ma, northward motion between 200-150 Ma, and higher latitude (~57 N) from 150 Ma to as late as 50 Ma. The differences are for Middle to Late Jurassic times. The E-K-M19 path moves the NA margin very rapidly to higher paleolatitudes (60 N) from 160-145 Ma, the V23 path has gradual northward motion to 55 N, and the H24 path has moderate paleolatitudes (40 to 50 N) from 160-135 Ma. The other difference between these paths occurs during mid-late Cretaceous time. Both the V23 and E-K-M19 paths have NA at slightly lower (55 N) latitudes than the H24 path, and have NA remain at these latitudes until 50 Ma, while the H24 path places NA at 50 N between 80 Ma and 65 Ma. For the Blue Mountains terranes, the Wild Sheep Creek volcanics have a paleolatitude of 18 N or 18 S, with large CCW rotation for the N location. The Jurassic-Cretaceous plutons (Bald Mtn, 145 Ma, Wallowa, 125 Ma) have N-S relative motion wrt NA using either the H24 or V23 paths from 145-120 Ma. The younger plutons, remagnetized sediments, and E/I corrected results from the Ochoco Basin place the BM ~600 km south of their present location. Large CW rotations are also present from 145 Ma to present.

Geological Society of America Abstracts with Programs. Vol. 56, No. 5

doi: 10.1130/abs/2024AM-405093

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