Reports: B8
48187-B8 A Combined Geophysical and Lithostratigraphical Investigation of a Young Pull-Apart Basin: Evaluating the Relationship Between Basin Sedimentation, Late-Quaternary Climate Change, and Tectonics (Lake Elsinore, Southern California)
The following narrative describes the first year of progress for the ACS-PRF grant entitled A Combined Geophysical and Lithostratigraphical Investigation of a Young Pull-Apart Basin: Evaluating the Relationship Between Basin Sedimentation, Late-Quaternary Climate Change, and Tectonics (Lake Elsinore, Southern California).
The goals for the first year were straight forward to acquire a full suite of seismic reflection data from Lake Elsinore. From December 8 to December 10, 2009, we collected over 75km of combined chirp and boomer seismic data with the help of Dr Chris Scholz and Mr. Pete Cattaneo from Syracuse University. Cal-State Fullerton MSc student, Ms. Brittany Pyke, traveled to Syracuse University for one week in spring 2009 to work with Chris and Pete on processing the data.
Our hope was to collect high resolution data for the upper 10 meters of lake sediment for direct comparison to the Lake Elsinore sediment cores and low-to-moderate resolution data for 100 m for comparison to future sediment cores. Unfortunately, the high-resolution chirp system was unable to penetrate the hard sediment-water interface and its gassy under-belly. The boomer was much more successful, but due to signal attenuation in the upper sediments, we imaged only the upper 10-12 meters of the lake. Nonetheless, we consider the seismic portion of this project a success based on our initial results.
Initial results indicate a large lake level regression in the late Holocene coeval to a proposed low stand as inferred from existing sediment core properties. The beauty of seismic data is that, unlike sediment cores that are points of information, the seismic data provide a full picture of basin dynamics that cannot be entirely inferred from individual sediment cores. As a result, the combination of seismic and core data provide a more robust picture of basin dynamics than either of the data by itself. In addition to the early Holocene low stand, there are also other interesting features that are still being interpreted. Brittany will travel back to Syracuse University in Fall 2010 to fine tune the final seismic interpretations and tie the seismic lines to existing sediment core data including radiocarbon dates. Initial results will be presented at the Fall 2009 AGU Meeting.
Finally, the seismic data will guide our planned sediment core efforts this winter during which we plan to extract up to 50 meters of lake sediment from Lake Elsinore.
