Revised Quaternary glacial succession and post-LGM recession, southern Wind River Range, Wyoming, USA. (15th July 2018)

• Record Type: Journal Article
• Authors: Dahms, Dennis; Egli, Markus; Fabel, Derek; Harbor, Jon; Brandová, Dagmar; de Castro Portes, Raquel; Christl, Marcus
• Is Part Of: Quaternary science reviews. Volume 192(2018)
• Page Start: 167
• Page End: 184
• Publication Date: 2018-07-15
• Subjects: Glacial succession -- Cosmogenic surface-exposure dating -- Wind River Mountains -- Wyoming -- Deglaciation -- Younger Dryas -- Older Dryas -- Temple Lake -- Alice Lake; Geology, Stratigraphic -- Quaternary -- Periodicals; Stratigraphie -- Quaternaire -- Périodiques; 551.79
• DOI: 10.1016/j.quascirev.2018.05.020
• Languages: English
• ISSNs: 0277-3791

Abstract

Abstract: We present here a more complete cosmogenic chronology of Pleistocene glacial deposits for the Wind River Range, Wyoming, USA. Fifty-one new and thirty-nine re-calculated 10 Be and 26 Al exposure ages from Sinks and North Fork canyons, Stough Basin, Cirque of the Towers and the Temple Lake valley allow us to more tightly constrain the timing and sequence of glacial alloformations in the southern portion of the range. Moraines, diamicts and bedrock exposures here have previously been correlated with as many as five Pleistocene and four Holocene glacial events. Exposure ages from Pleistocene alloformations associated with trunk glaciers in Sinks Canyon and North Fork Canyon generally confirm earlier age estimates. Cosmogenic radionuclide (CRN, 10 Be and 26 Al) ages from moraines and striated bedrock surfaces previously mapped as Pinedale correspond to MIS2, while boulder exposure ages from moraines mapped as Bull Lake correspond generally to MIS5-MIS6. Geomorphic data from a moraine previously mapped as Younger pre-Sacagawea Ridge appears to correspond most closely to the Sacagawea Ridge glacial episode (MIS-16), but the uncertainty of a single 10 Be exposure age suggests the unit could be as young as MIS-10 or as old as MIS-18. Boulders from a diamict on Table Mountain previously reported as Older pre-Sacagawea Ridge yield two 10 Be exposure ages that suggest the presence of Early Pleistocene glacial activity here possibly older than 1–2 Ma (>MIS-30). Bedrock exposure ages within Sinks Canyon suggest the Pinedale valley glacier had retreated from the floor of Sinks Canyon to above PopoAgie Falls by ca. 15.3 ka. Cirque glaciers in Stough Basin appear to have retreated behind their riegels by ca. 16 ka, which suggests the cirque glaciers were decoupling across their riegels from the valley glaciers below at this time, prior to their readvance to form Lateglacial moraines. New 10 Be boulder exposure ages from moraines previously correlated to the Temple Lake and Alice Lake allostratigraphic units in the cirques of Stough Basin and Cirque of the Towers show general equivalence to the stadial event just prior to the onset of the Bølling interstadial (17.5–14.7 ka) and to the Intra-Allerød Cold Period-Younger Dryas stadial phase (13.9–11.7 ka), respectively. From this evidence, the Temple Lake Alloformation of the Wind River Mountains now should correspond to the INTIMATE GS-2.1a (Oldest Dryas) stadial event while the Alice Lake Alloformation should correspond to the INTIMATE GS-2 stadial (IACP-Younger Dryas). Thus, we consider that evidence no longer exists for early-to mid-Holocene glacial events in the southern Wind River Range. Highlights: Numeric ages for the Table Mountain diamict and the Pinedale, Bull Lake and Sacagawea Ridge moraines in Sinks Canyon. Estimated recession rates for LGM glaciers in Sinks and North Fork canyons. Revised ages for the Alice Lake and Temple Lake alloformations.