COMPRESSIONAL AND EXTENSIONAL FEATURES OF THE IBEX HILLS, EASTERN CA

The Ibex Hills lie in a critical position within the Death Valley extensional terrane and a better understanding of this area has the potential to reveal unique solutions to southern Death Valley tectonics. The primary structure is a low angle normal fault exposed in the northern Ibex Hills and some previous workers have suggested this is the southeastern extent of the northwest-directed Amargosa-Black Mountain fault system. Preliminary mapping raises questions on this hypothesis by revealing a map pattern more consistent with southwest directed extension correlated to a kinematically similar regime seen to the south. This interpretation is supported in map view by the fault cutting up-section to the north in the hanging wall from the Crystal Spring formation up to the Noonday Dolomite and placing these units upon Precambrian basement. Another strand of this low angle normal fault repeats the upper Crystal Springs and Horse Thief Springs formations and rejoins the main fault in the northernmost portion of the mapped area. A number of flat lying faults lie atop the structural stack and place Beck Springs and Noonday dolomite on top of Crystal Springs and Horse Thief Springs, although these likely represent landslide blocks.

Extensional structures overprint complex Mesozoic fold systems that suggest two kinematically distinct fold phases. Structure from Motion photogrammetry allowed for the creation of a 3-D outcrop model of these structures with resolution at the cm level. This technique allows for continued interpretation in the lab while still providing the resolution seen in the field, particularly useful in discerning features on cliff faces and steep slope. The resulting outcrop model provides a tool for superior interpretation of the deformation history as well as producing a product which can be seen and used by the geologic community at large. Remote sensing techniques were also used on ASTER multispectral data through the creation of a classification map of the lithology. This allowed for map scale interpretations to be done on areas difficult to access due to both terrain and access constraints, as well as provide a focus for future field efforts based on the classification map pattern.