35 Neotectonics Across the Intermountain West from New Data to Classic Concepts

Friday, 17 May 2024
8:00 AM - 12:00 PM
Maple Ballroom

A FRAMEWORK MODEL FOR WESTERN NORTH AMERICAN LANDSCAPES: NEOTECTONICS PUNCTUATED BY GLACIAL AND PERIGLACIAL GEOMORPHOLOGY

Paper number: 35-11
Program: Theme Sessions
Time: 11:00 AM – 11:20 AM

Authors

  • Cal Ruleman Presenting Author
    Geosciences and Environmental Change Science Center, Denver, CO
  • Adam Hudson
    Geosciences and Environmental Change Science Center, Denver, CO
  • William Odom
    U.S. Geological Survey, Reston, VA

Abstract

North American surficial geologic mapping requires a structural, geomorphic, and chronologic foundation for understanding the processes forming the present landscape. A unified model compiling datasets from most geologic disciplines demonstrates western North American Neogene deformation at differing temporospatial rates (0.1-0.3 mm/yr) and styles (transtensional versus transpressional), from the mid-Atlantic spreading ridge to the San Andreas fault system. Terrestrial Quaternary chronologies reveal the following: 1) onset of major glacial-periglacial processes ~1.5-1.0 Ma at rates equal to or greater than 0.5 mm/yr associated with Laurentide and Cordilleran icesheets and ice caps at ; 2) Major incision and topographic development in western North America on the order of ~200-300 meters occurred after the Middle Pleistocene Transition (MPT), following the last major eruption from Yellowstone, ~630 ka; 3) a major erosion/incision interval occurred across North America during marine oxygen isotope stages (MIS) 12-11 (~478-374 ka), the strongest glacial-interglacial signal in the Cenozoic MIS record; 4) MIS 9-7 (~337-191 ka) is primarily an erosional interval, with very weak glacial and strong interglacial frequencies; and 5) reintroduction of strong glacial-interglacial frequencies producing abundant MIS 6-2 (~200-12 ka) deposits at much lower base levels, or inset and within canyons. All of these relationships emanate and diverge from collective and isolated transient Ice Age-generated source regions above 7200 ft/2200 m asl, an elevation defined by contemporary rock glacier footprints and studies coupled with glacial maximum temperature depressions of -6 to -10 °C and associated equilibrium line altitude (ELA) depressions of ~800-1000 meters. Together, these concepts provide a foundation for understanding the climate and tectonic histories forming local and regional landscapes.

Geological Society of America Abstracts with Programs. Vol. 56, No. 4

doi: 10.1130/abs/2024CD-399167

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