Geomorphic Expression of Abrupt Climate Change in Southwestern North America at the Glacial Termination

Abstract

Eolian and subaqueous landforms composed of gypsum sand provide geomorphic evidence for a wet episode at the termination of glacial climate in southwestern North America. Drying of pluvial Lake Estancia, central New Mexico, occurred after ca. 12,000 14C yr B.P. Thereafter, eolian landforms on the old lake floor, constructed of gypsum sand, were overridden by rising lake water, modified by subaqueous processes, and organized into beach ridges along the lake's eastern shore. Preservation of preexisting eolian landforms in the shallow lake suggests abupt changes in lake level and climate. Available radiocarbon ages suggest that the final highstand recorded by beach ridges may have developed during the Younger Dryas (YD) stade. The beach ridges provide information about lake surface area, which was 45% of the lake area reached during the maximum highstands of the late Pleistocene. A similar proportional response has been reported for YD climate changes outside the North Atlantic region.

Definition and origin of the dune-field pattern at White Sands, New Mexico

“…For the Lake Otero shoreline, gypsum would have been the only available clastic grains available for shoreline processes. The most analogous case found is for Late Pleistocene Lake Estancia, located to the north of the Tularosa Basin in central New Mexico (Anderson et al, 2002). Multiple gypsum sand beach ridges, the largest being $3 m high and 20 km long, occur along the eastern lake margin, and consist of aeolian cross-stratified sand.…”

“…and 7000 14 C yrs B.P. (Allen and Anderson, 2000;Anderson et al, 2002, see discussion in Allen et al, 2009), with yet younger periods at $4000, 2000 and 1100 ka (see discussion in Langford et al, 2009). The core taken in Area 3 (see Section 5.1) shows that deflation toward the 1206 m paleo-shoreline and subsequent accumulation in this area (i.e., Fig.…”

Unusual Holocene and late Pleistocene carbonate sedimentation in Bear Lake, Utah and Idaho, USA

“…Pluvial Lakes Manix and Mojave were overflowing into pluvial Lake Manly (Death Valley) as early as 24 cal ka until about 17 cal ka Wells et al, 2003). During the LGI, Lake Estancia in central New Mexico reached its highest and most persistent stand (Allen and Anderson, 1993, 2000: Anderson et al, 2002, and a lake occupied the San Agustin Plains of west-central New Mexico (Markgraf et al, 1984). Also during the LGI, major wetlands occupied the now dry basins in southern Nevada (Quade et al, 2003 and references therein).…”

Using cosmogenic nuclides to contrast rates of erosion and sediment yield in a semi‐arid, arroyo‐dominated landscape, Rio Puerco Basin, New Mexico

“…Rainfall delivery from Pacific frontal systems decreased and the summer monsoon became the dominant source of precipitation (Poore et al, 2005). Pluvial lakes shrank as the climate warmed and dried (Anderson et al, 2002). The Holocene monsoon variability has been recently documented from correlation of packrat midden and tree-ring records from the Rio Puerco Basin with position of the Intertropical Convergence Zone (ITCZ) interpreted from Gulf of Mexico sediments (Poore et al, 2005).…”

“…The late Pleistocene climate of New Mexico was significantly cooler and wetter than during the Holocene or at present. The hydrologic mass balance supported large pluvial lakes in southwestern North America, including Lake Estancia to the east of the Rio Puerco Basin (Anderson et al, 2002). Packrat midden data, which define palaeovegetation communities and thus climate, for New Mexico (Anderson et al, 2000) indicate a significantly lower tree line.…”