NH41A-1795
Emplacement Mechanisms and Evolution of the Long-runout Quaternary Eureka Valley Landslide in Eastern California
Thursday, 17 December 2015
Poster Hall (Moscone South)
Jessica A Watkins1,2, Jennifer E. C. Scully2,3, Michael J Lawson2, Edward J Rhodes2,4 and An Yin2, (1)California Institute of Technology, Pasadena, CA, United States, (2)University of California Los Angeles, Earth, Planetary, and Space Sciences, Los Angeles, CA, United States, (3)NASA Jet Propulsion Laboratory, Pasadena, CA, United States, (4)University of Sheffield, Geography, Sheffield, United Kingdom
Abstract:
Debate over characterization of the transport mechanism(s) of long-runout landslide deposits, specifically the role of water or fluids in their initiation and transport, has occurred over the past several decades. Using the Elm, Blackhawk, Sherman, and Martian landslides as examples, turbulent grain flow, air-layer lubrication, mechanical fluidization, basal lubrication, and acoustic fluidization have been proposed as emplacement mechanisms. A key component missing from this body of work is an in-depth geological analysis of a well-preserved and well-exposed long-runout landslide deposit. Here, we analyze in detail the geomorphology and structure of a long-runout landslide in southeastern Eureka Valley, California in order to constrain the previously proposed hypotheses for mechanisms of long-runout landslide emplacement. Based on integrated field, photogeologic, spectral, and luminescence dating investigations of the extremely well-preserved Eureka Valley landslide deposit, we interpret its initiation to be the result of normal-fault-generated fracture in the Upper Cambrian strata of the bounding Last Chance Range western margin. The long-distance transport of the Eureka Valley landslide is proposed to be translational and likely due to lubrication of the fluidized landslide mass through the presence of basal clays, which resulted in 3D simple shear internal deformation within the landslide sheet. Post-emplacement, the landslide deposit is interpreted to have undergone fluvial modification and rotation. We determine the minimum landslide emplacement age and the maximum age of post-emplacement rotation to be early to mid Holocene (8275 +/- 300 yr BP to 9465 +/- 380 yr BP). Our analysis of features related to long-distance transport may be applied to other long-runout landslides with similar morphologies, including those on other planetary surfaces, providing continued insight into these prominent yet enigmatic natural hazards.
