Volcanic Initiation of the Eocene Heart Mountain Slide, Wyoming, USA

Abstract

Additional information:Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. A B S T R A C TThe Eocene Heart Mountain slide of northwest Wyoming covers an area of as much as 5000 km 2 and includes allochthonous Paleozoic carbonate and Eocene volcanic rocks with a run-out distance of as much as 85 km. Recent geochronologic data indicated that the emplacement of the slide event occurred at ∼48.9 Ma, using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) extracted from U-Pb zircon ages from basal layer and injectite carbonate ultracataclasite (CUC). We now refine that age with U-Pb results from a lamprophyre diatreme that is temporally and spatially related to the CUC injectites. The ages for the lamprophyre zircons are 48.97 5 0.36 Ma (LA-ICPMS) and 49.19 50.02 Ma (chemical abrasion isotope dilution thermal ionization mass spectrometry). Thus, the lamprophyre and CUC zircons are identical in age, and we interpret that the zircons in the CUC were derived from the lamprophyre during slide emplacement. Moreover, the intrusion of the lamprophyre diatreme provided the trigger mechanism for the Heart Mountain slide. Additional structural data are presented for a variety of calcite twinning strains, results from anisotropy of magnetic susceptibility for the lamprophyre and CUC injectites and alternating-field demagnetization on the lamprophyre, to help constrain slide dynamics. These data indicate that White Mountain experienced a rotation about a vertical axis and minimum of 357 of counterclockwise motion during emplacement.

The concept of tectonic provenance: Case study of the gigantic Markagunt gravity slide basal layer

“…Long run-out landslides are increasingly recognized as ubiquitous features in both subaerial and subaqueous environ- The base of each gravity slide consists of a layer of cataclastic rock, herein referred to non-genetically as the "basal layer" (Biek et al, 2019;Malone et al, 2017;Malone, Craddock, Anders, & Wulff, 2014). The basal layer ranges in thickness from less than a centimetre to several metres and was formed through the frictional wear of upper and lower plate rocks during slide emplacement.…”

Structural Relationships Across the Sevier Gravity Slide of Southwest Utah and Implications for Catastrophic Translation and Emplacement Processes of Long Runout Landslides

“…The continuity and consistency of kinematic indicators, the presence of deformation features including pseudotachylyte, clastic dikes, and localized hydrothermal alteration within the basal deformation zone, all indicate that each collapse structure represents a single high‐velocity emplacement event (Biek et al., 2015, 2019; Hacker et al., 2014). The MGSC structures are of similar volume and runout distance to the Heart Mountain slide of Wyoming (Craddock et al., 2009; Malone et al., 2014, 2017), the only other known mega‐scale terrestrial gravity slide.…”

Emplacement age of the Markagunt gravity slide in southwestern Utah, USA

“…One of the first gravity slides to be recognized was the Heart Mountain gravity slide in Wyoming, USA (>3 400 km 2 ). The low‐angle movement of that slide is attributed to eruptions within the Eocene Absaroka volcanic field (Malone, 1995; Malone et al, 2017). In southwestern Utah, three large‐volume gravity slides have been identified in association with the growth of the Oligocene‐Miocene Marysvale volcanic field (MVF; Figure 1).…”