Dating topography of the sierra nevada dating hints
The Tioga 4 advance coincided with the expansion of nearby pluvial Lake Lahontan to its maximum size. Late Pleistocene and recent palynology in the central Sierra Nevada, California, In: E. The Sierra Nevada advances correlate well with the glacial chronology of the Alps during the same period, and also with the episodes of melting and advance of the European and Laurentide Ice Sheets. These show that the glaciers reached their maximum extent for the last glacial cycle between 21 and 18 ka, i.e., during the global Last Glacial Maximum. A slow retreat began at 18 ka and accelerated rapidly at about 17 ka. After retreating an unknown distance, the glaciers began to readvance at about 16.7 ka, reaching the Tioga 4 limit at 16.2 ka. These Great Valley Group strata crop out in a homocline along the western margin of California’s Central Valley, and are in fault contact with the Franciscan accretionary complex (Dickinson This paper focuses on samples of the Great Valley Group collected in and around Joaquin Ridge near Coalinga (Figure 1).
The spread of the Mesozoic ages and the number of peaks in the grain-age histograms increase with decreasing depositional age.Unfortunately, chronological control is not adequate to determine whether this advance was during the early Younger Dryas or slightly preceded it. The equilibrium-line-altitude reduction during the Tioga 3 was about 1200 m, that during the Tioga 4 about 800 m, and during the Recess Peak 100 to 200 m. Times of glacial advance in the Sierra Nevada may be connected to the melting history of the ice sheets, and to Heinrich events, by expansion and contraction of sea ice in the southern North Atlantic. Geological Society of America Bulletin 110, 1318-1332.