T he area that includes the Coachella and Imperial Valleys of southern California, and the western half of the Mexicali Valley and the Colorado River delta in Mexico, is called the Salton Trough, which is part of the larger “Basin and Range”. This region is an area of intense geological activity. 
The San Andreas Fault system runs from central California to southern California, through the Salton Trough into Mexico, and down the Gulf of California as a part of the East Pacific Rise. Millions of years ago the San Andreas Fault system and East Pacific Rise split the Baja Peninsula from the mainland of Mexico. The waters of the Pacific then poured into the rift valley formed by the fault, creating the Gulf of California. Since then tectonic activity along the fault system has moved the Baja Peninsula 162 miles (260 km) westward from the mainland at the southern end of the gulf. The northern “hinge” point of this fault system is in the Salton Trough.
The Colorado River began filling the Salton Trough with sediments millions of years ago. The river delta rapidly spread southward across the north end of the gulf to its present position by four million years ago. Four million years later, the sediments form a natural dike between the waters of the Gulf of California and what is now the Salton Sea. Had it not been for these sediments the area as far north as Indio would be part of the Gulf of California. Damming of the Colorado over the last 80 years has all but eliminated the flow of sediments to the gulf, radically changing the geologic balance between deposition and erosion in the delta of the Colorado River. The Colorado River delta contains over 10,000 cubic miles of the Colorado River's sediments from the last 2 to 3 million years. The sediments that were deposited by the river more than 2 to 3 million years ago have been shifted northwestward by movement along the San Andreas and related faults.
The basin of the Laguna Salada is an example of what geologists call a graben, which is German for "grave". The Laguna Salada graben is an active graben product of tectonic tension of the Gulf of California. A graben is a depressed block of land bounded on opposite sides by parallel faults. In the case of Laguna Salada it’s the Laguna Salada fault on the east side and the Sierra Juarez fault on the west. Through movement of the faults, the strip of land sinks in a process called subsidence. In the case of the Salton Trough and Laguna Salada, the graben has been filled with sediments as it subsided. Although not restricted to them, grabens are characteristic of rift valleys. The Laguna Salada Fault zone is about 70 km in length and slips at an estimated rate of 4 mm/yr. The most recent surface rupture was a magnitude 7 that occurred on February 23rd, 1892. Presently Laguna Salada is a barren lakebed and up until the filling of the Hoover Dam in 1936 it was a shallow lacustrine environment year round fed by waters originating from the Rocky Mountains.
The posted coordinates will place you at the far northern end of Laguna Salada just off of Mexico Highway 2. This is a good starting point if you anticipate traveling to Guadelupe Canyon.
TO LOG THIS CACHE:
1) Take a close look at the dry lake sediments and please describe the composition of the material in these sediments? What do you see?
2) Where would you expect these sediments to originate?
To log this cache e-mail me the answer HERE.
Sources:
Alles, D.L., 2006. Geology of the Salton Trough. Western Washington University, 32p. http://fire.biol.wwu.edu/trent/alles/GeologySaltonTrough.pdf
Contreras, J., Martín-Barajas, A., Herguera, J.C., 2005. Subsidence of Laguna Salada Basin, Northeastern Baja California, México, inferrred from Milankovitch climatic changes. Geofísica Internacional, v. 144, p. 103-111.
Martín-Barajas, A., Vázquez-Hernández, S., Carreño, A.L., Helenes, J., Suárez-Vidal, F., Alvarez, J., 2001. Late Neogene stratigraphy and tectonic control on facies evolution in the Laguna Salada basin, northern Baja California, Mexico. Sedimentary Geology, v. 144, p. 5-35.
Winker, C. D., and S. M. Kidwell, 1986. Paleocurrent evidence for lateral displacement of the Pliocene Colorado River delta by the San Andreas fault system, southeastern California. Geology 14: 788-791.
"That's me 'graben' the bull by the horns. It's how I handle my business ... It's a metaphor... But that actually happened though." -Dodgeball