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Formation of the Fish Creek-Vallecito basin, Salton Trough, California

Catherine Shirvell, UCLA Department of Earth & Space Sciences, Los Angeles, CA, [email protected]


The Fish Creek-Vallecito (FCV) basin is one of the oldest rift-related basins in the Salton Trough.  The Salton Trough is the northern-most portion of the North American-Pacific oblique-rift system.  The purpose of this study is to understand the structural development of the FCV basin by recording the interplay between sedimentation and tectonics.  Documenting the formation of the FCV basin will provide insight into the earliest stages of oblique-continental rifting as well as the structures on which oblique extension is accommodated in the continental crust. 

Understanding the development of the FCV basin will be accomplished by field work, specifically: 1) detailed geologic mapping (1:12,000), especially where the oldest syn-rift sediments are exposed, 2) sedimentological and stratigraphic analysis of these sediments, including description of lithofacies variations, paleocurrent analysis, and correlation based on clast composition, and 3) kinematic analysis of faults.  One 2-month field season (January-February 2005) has already been completed.  Approximately half of the map area was covered during this time.  In addition to geologic mapping, over 100 fault planes and ~50 paleocurrent indicators were measured in this area.  Furthermore, the previously described stratigraphy was altered to reflect new observations.

During the upcoming 2006 field season (January-March 2006) I will finish mapping the remaining northern portion of the FCV basin, gather additional fault and paleocurrent measurements, and continue to revise and add to the existing stratigraphy of the oldest sedimentary deposits in the FCV basin.