COYOTE FLAT LANDSLIDE
Many of the short faults, especially in the vicinity of Coyote Flat, cut very young Quaternary glacial till and allu- vium, suggesting that slide movement may not be finished. Initial movement is, however, at least pre-last glacial.
Topography
Coyote Flat topography is immature, irregular, and hummocky (Figure 8).
Benches
Besides the main Coyote Flat bench, there are a number of smaller named benches within the overall slide mass.
Warren Bench is an approximately three miles long and half a-mile-wide bench located near the toe of the Coyote Flat landslide. It is located in Sections 11, 14, 23, and 26, of T9S, R33E, SBBM, about three miles west of Big Pine.
Groundwater
The presence of closed depressions or sags (Figure 9) and springs and swampy ground (Figure 10) are also suggestive of geologically recent landsliding. A number of named and unnamed springs discharge where the slide mass meets Owens Valley fill, as well as within the slide mass itself.
Driving Forces
There have been numerous glacial periods and interglacial periods during the past approximately 2.6 million years (Alfred Wegener Institute, 2020). The age of landsliding has not been estab- lished, but it must have been after the Sierras rose, or as they were rising, and as the Owens Valley graben was forming. If during this period of tectonic unrest, glaciers piled great thicknesses of ice on what is now Coyote Flat, then it seems reasonable to suggest that perhaps thick glacial ice might have, more than once, provided driving forces to initiate and perpetuate landslide movement down into Owens Valley.
Summary and Conclusions
The Coyote Warp land mass located on the east side of the Sierra Nevada Mountains, in the vicinity of Bishop and Big Pine, California, has been attributed to structural warping (Bateman, 1965, p. 174). A review of Bateman’s descrip- tion of the Coyote Warp land mass and adjacent areas (1965, p. 174-183), as well as other pertinent literature (see refer- ences), leads to an alternative conclusion that the physical and geologic features observed may well be artifacts of a geologically recent mega-landslide, the Coyote Flat Landslide. Additional field work, including geophysical investiga-
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Figure 6 - Topographic map showing outline of Coyote Flat landslide and location of struc- ture section, A-A’ (Figure 7). B is the approximate location of Figure 2; C is the approxi- mate location of Figure 3; D is the approximate location of Figures 4 and 5. Bishop Creek bounds the slide on the northwest side; Big Pine Creek bounds it on the south. Owens Valley fill and surficial alluvium cover the toe. The landslide appears to have rotated coun- ter-clockwise into Owens Valley. Dashed line approximately locates side and back scarps, dotted line shows guesstimated position of buried toe. Base Map: United States Geological Survey, 1947.
tions, will further our understanding of the Coyote Flat Landslide.
References
Alfred Wegener Institute, 2020, Irregular appearances of glacial and interglacial climate states: phys.
org/news/2020-10- Irregular-glacial-
interglacial-climate-states.html. October 26, 2020.
Axelrod, D. I., and Ting, W. S., 1961, Early Pleistocene floras from the Chagoopa Surface, southern Sierra
Jul.Aug.Sep 2021 • TPG 5
Figure 5 - Two sag-ponds in the middle and far distance (greenery) of the toe area, along the southern flank of the Coyote Flat landslide. Looking northwesterly from Big Pine Creek Road. © W. J. Elliott 9-29-2019.
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