Latest Pleistocene history of pluvial Lake Franklin, northeastern Nevada, USA

摘要

At its maximum extent during the last glacial cycle, Lake Franklin covered 1100 km2 of the Ruby Valley of northeastern Nevada, making it one of the largest pluvial lakes between Lakes Bonneville and Lahontan. Mapping of shorelines, surveying of topographic profiles, and radiocarbon dating of gastropod shells were employed to reconstruct the latest Pleistocene history of the lake. During the first half of the Last Glacial Maximum (LGM), Lake Franklin covered ~42% of its maximum area. This extent increased to -60% during the second half of the LGM. Some radiocarbon ages suggest that the lake briefly rose to near its highstand between 20 and 18 ka, but the best constrained rise occurred ca. 17 ka, when the lake rapidly transgressed to its highstand elevation of 1850 m. This rise was synchronous with highstands of nearby pluvial lakes, implicating a regional shift in the balance between precipitation and potential evaporation. The lake dropped to 1843 m, before rising once more to 1850 m ca. 16.0 ka. After falling and stabilizing at 1843 m again ca. 15.4 ka, the lake rapidly regressed to <1818 m (a loss in area of >70%) by 14.8 ka. This regression was synchronous with the fall of Lake Bonneville from the Provo shoreline and the regression of Lake Lahontan from the Sehoo shoreline. Radiocarbon ages and stratigraphic evidence document a final transgression in the latest Pleistocene that reached 1820 m (34% of maximum area) ca. 13.0 ka, synchronous with the Recess Peak Glaciation in the Sierra Nevada, and overlapping with the start of the Younger Dryas and minor transgressions of Lakes Bonneville, Lahontan, and Owens. The correspondence of this Lake Franklin history with other cli- mate archives from this region underscores the value of pluvial lake deposits as sources of paleoclimate information and indicates synchronous forcing of climate changes during the last glacial-interglacial transition.