Evidence for Glaciation in the Mt. San Jacinto Region

SMSU Event Center BC

Glaciation during the Wisconsin glacial episode (the most recent one) has been well documented in California locales such as the Sierra Nevada. Some hundreds of miles to the south less extensive glaciation has been documented on Mt. San Gorgonio, which is the current southernmost recognized extent of alpine glaciation. Mt. San Jacinto, some twenty miles farther south, was theorized to have been glaciated as well. This project surveyed areas most likely to have been glaciated on Mt. San Jacinto, focusing on a valley similar to that of a known glaciated valley on Mt. San Gorgonio. A detailed ground survey coupled with aerial image analysis was undertaken. During the survey, topographic, depositional, and erosional features were located and documented. Potholes in granitic outcrops without any flowing source of water, boulder fields showing possible fabric (alignment of the long axis with possible ice flow direction), crescent-shaped gouges, and a large morainal-like deposit in front of a depression consistent with that of a cirque were discovered; coupled with the valley’s elevation and orientation make it plausible that Mt. San Jacinto was glaciated or at the very least had experienced periglacial conditions during the colder and wetter climate of the Pleistocene, especially during the Wisconsin glaciation. These findings may represent an extension of the southernmost Wisconsin glaciation in California an additional twenty miles to the south.