EVIDENCE FOR GLACIATION IN THE MT. SAN JACINTO REGION

Glaciation during the Wisconsin glacial episode has been well documented in California locales such as the Sierra Nevada. 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 during the Wisconsin glaciation. Mt. San Jacinto, some twenty miles farther south, is 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. Analysis of satellite imagery of this valley led to a detailed ground survey during which topographic, depositional, and erosional features were located and documented. Boulder fields showing possible fabric (alignment of the long axis with possible ice flow direction), crescent-shaped gouges and potholes in granitic outcrops and a large moraine-like deposit in down slope from a feature with the morphology consistent with that of a cirque were discovered. These features 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.