The internal structure of a lobate rock glacier located in the San Juan Mountains of southwest Colorado was investigated using ground penetrating radar (GPR). A 440 m, 25 MHz longitudinal profile oriented along the central axis of the rock glacier shows moderate to strongly coherent reflection horizons or layers that can be recognized clearly to a depth of 30-35 m. The layers are interpreted as representing ice-supersaturated sediments and coarse, blocky rockslide debris that are the result of flow, perhaps generated by seasonal snow pack covered by episodic debris flows or high-magnitude discharges of talus from the cirque headwall. Profiles collected at 50 MHz indicate that, in the upper 20 m thickness of the rock glacier, many of these layers are laterally continuous, The total depth of penetration (-40 m at 25 MHz) was sufficient to detect the rock glacier-cirque-floor contact, which is composed of underlying moraine. Several prominent reflection events that subdivide the profile into broad 10-15 m-thick layers represent contacts between major depositional units. These units are believed to be individual flow lobes that were initiated at various cirque-headwall locations. We interpret this rock glacier to be a composite feature that formed by a process involving the development and subsequent overlap of discrete flow lobes that have over-ridden older glacial moraine and protalus rampart materials. The latter materials have been incorporated into the present flow structure of the rock glacier.
Ground penetrating radar datasets were collected from a variety of sites to provide three-dimensional (3D) images of coastal and eolian geomorphic environments. The images will aid in better understanding tectonically active coastlines and the internal geometry of eolian sandstones. An ancient eolian dune complex, consisting of two bedset packages with distinct truncation surfaces, was imaged at Zion National Park, Utah.The 200 MHz 3D dataset shows the internal stratigraphy with southwest dipping reflections ranging from 13 to 20°. A second dataset was collected along the coastline in the southwest portion ofWashington State. This 225 MHz dataset reveals the 3D structure of an erosional scarp caused by earthquake activity in the area. Results from the surveys indicate that the imaging in 3D is an effective means of analyzing internal stratigraphy of geomorphic features by allowing the user to more easily interpret spatial relationships within a dataset.
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