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Mountain glaciers in the Sawtooth Mountains responded strongly to reinvigorated atmospheric moisture transport following the last ice-sheet maximum. The glaciers constructed an extensive moraine belt in the southeastern Sawtooth Mountains, allowing determination of a detailed radiocarbon chronology from lake and marsh cores. Moraine morphometry and soil data indicate construction of seven to nine moraines in each of four valleys during two main late Pleistocene ice advances. A basal radiocarbon date from marsh cores in the Alturas valley documents that the maximum advance during marine oxygen isotope stage 2 occurred shortly before ca. 16,900 calibrated (cal.) yr B.P. Minimum limiting dates on glacial-lacustrine sediment in lake and marsh cores from three valleys, clustered around 13,950 cal. yr B.P., document the maintenance or reestablishment of extensive ice volume during early late-glacial time. The ca. 16,900 cal. yr B.P. advance postdates the last ice-sheet maximum by ~4000 yr and is broadly correlative with maximum advances of the North Yellowstone outlet glacier and the Puget Lobe of the Cordilleran Ice Sheet and a near-maximum advance of Wallowa Mountain glaciers. These synchronous advances indicate response of a variety of ice systems to reinvigorated moisture transport following the ice-sheet maximum, as does the subsequent Sawtooth advance during early late-glacial time. Together, these responses indicate strong sensitivity of certain ice systems to moisture-delivery fluctuations. Keywords: glaciation, late Pleistocene, radiocarbon, Idaho, paleoclimate, precipitation.

Prominent scarps on Pinedale glacial surfaces along the eastern base of the Teton Range confirm latest Pleistocene to Holocene surface-faulting earthquakes on the Teton fault, but the timing of these events is only broadly constrained by a single previous paleoseismic study. We excavated two trenches at the Leigh Lake site near the center of the Teton fault to address open questions about earthquake timing and rupture length. Structural and stratigraphic evidence indicates two surface-faulting earthquakes at the site that postdate deglacial sediments dated by radiocarbon and optically stimulated luminescence to ~10-11 ka. Earthquake LL2 occurred at ~10.0 ka (9.7-10.4 ka; 95% confidence range) and LL1 at ~5.9 ka (4.8-7.1 ka; 95%). LL2 predates an earthquake at ~8 ka identified in the previous paleoseismic investigation at Granite Canyon. LL1 corresponds to the most recent Granite Canyon earthquake at ~4.7-7.9 ka (95% confidence range). Our results are consistent with the previously documented long-elapsed time since the most recent Teton fault rupture and expand the fault's earthquake history into the early Holocene. [ABSTRACT FROM AUTHOR]

Abstract: New Zealand glaciers reached their last glacial maximum position at or before ~25ka, and, as early as 23ka, commenced a slow and continual retreat. New cosmogenic exposure ages and field mapping from the Rakaia Valley in the South Island suggest that extensive ice survived well into the latter half of the Last Glacial–Interglacial Transition (18–11ka), with the post-15ka period inferred to have near Holocene climate conditions based on ecological proxy data. By as late as ~15.5ka, glacier termini had retreated as little as 5–10km from glacial maximum positions. Numerous minor ice still-stand positions and oscillations are recognized, but the record specifically excludes evidence for either a major climatic amelioration at ~15–16ka or a significant glacial re-advance during the Antarctic Cold Reversal (ACR) or the Younger Dryas (YD). We conclude that the currently widespread interpretation of an episodic New Zealand glacial record since the LGM is an artifact of valley-dependent retreat processes. Pro-glacial lake formation and local site conditions combined to give an apparent, but misleading, picture of glacial retreat punctuated by major, climatically driven, re-advances. [ABSTRACT FROM AUTHOR]