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Abstract: Well-preserved shorelines in Estancia basin and a relatively simple hydrologic setting have prompted several inquiries into the basin''s hydrologic balance for the purpose of estimating regional precipitation during the late Pleistocene. Estimates have ranged from 86% to 150% of modern, the disparity largely the result of assumptions about past temperatures. In this study, we use an array of models for surface-water runoff, groundwater flow, and lake energy balance to examine previously proposed scenarios for late Pleistocene climate. Constraints imposed by geologic evidence of past lake levels indicate that precipitation for the Last Glacial Maximum (LGM) may have doubled relative to modern values during brief episodes of colder and wetter climate and that annual runoff was as much as 15% of annual precipitation during these episodes. [Copyright &y& Elsevier]

Eolian landforms in Estancia basin, central New Mexico, record two episodes of extreme drought and low groundwater levels during the middle Holocene (7000-5400 [sup 14]C yr B.P.), followed by a rise in the water table through the late Holocene. Blowouts and associated lunettes formed when water levels fell below the desiccated floor of pluvial Lake Estancia, allowing widespread deflation. Elevation of the water table in the basin is regulated by a balance between evaporation from playas that occupy the blowouts and recharge of aquifers in the adjacent Manzano Mountains. Isotopic analyses of modern precipitation and groundwater reveal that recharge originates primarily as winter moisture, which is amplified during El Niños and diminished during La Ni˜as. Thus, changes in the elevation of a reconstructed Holocene water table may reflect systematic changes in El Niño-Southern Oscillation (ENSO) circulation. [ABSTRACT FROM AUTHOR]

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. [Copyright &y& Elsevier]

Examines the paleoclimatic information from Estancia basin, New Mexico. Indications of submillennial Pleistocene climatic oscillations provided by lake sediments in the basin; Reconstruction of changes in salinity and inferred episodes of wet and dry climate; Correlation of ostracode zones and carbon dating; Changes in hydrology and climate.

Reports on evidence gathered from the Estancia basin in the southwestern United States supporting rapid shifts in climate during the last ice age. Pulsations in the supply of moisture; Recoding of pulses during stream discharges; Spreading of water laden with quartz over the saline lake; Pulses organized into cycles; Role of stream discharges in freshening of the lake.

Abstract Newly acquired U Th dates on gypsum sands contained within Pleistocene lake sediments allow us to extend the record of climatic change in the Estancia Basin of central New Mexico back to ∼69 ka from a previous limit of ∼29 ka. Using a hydrologic balance index (HBI) that reflects variations in sediment mineralogy and bedding characteristics, we find strong similarities to speleothem oxygen isotopic records for the southwestern United States as well as to isotopic variations in Greenland ice cores. Intervals of wetter climate in the Estancia Basin generally appear to correlate to colder conditions in the North Atlantic and conversely. The existence of a pronounced dry period from 18.1 to 17 ka matches in timing the Extrapolar Climate Reversal of Asmerom et al. (2017) at Fort Stanton cave in southern New Mexico and confirms a different origin for this stadial-like event. Furthermore, the new U Th dates support the existing Estancia Basin interpretation of a dry Bølling/Allerød followed by a wet Younger Dryas, a result consistent with speleothem and wet meadow evidence from New Mexico and Arizona (Asmerom et al., 2010, 2017; Polyak et al., 2004; Hall et al., 2012; Wagner et al., 2010) but in conflict with an interpretation of speleothem evidence from central Texas (Feng et al., 2014). Highlights • U Th dates extend the record of climatic change in the Estancia Basin of New Mexico to ∼69 ka. • The dates were acquired from gypsum sands produced during lowstands of pluvial Lake Estancia. • A new U Th date provides support for a wet Younger Dryas interval in central New Mexico. • A dry period from 18.1 to 17 ka matches in timing the Extrapolar Climate Reversal at Stanton Cave. • An Estancia Basin hydrologic balance index shows similarities to the Greenland ice sheet record. [ABSTRACT FROM AUTHOR]

Abstract: Sediment cores from Lakes Minnewaska and Mohonk in the Shawangunk Mountains of southeastern New York were analyzed for pollen, plant macrofossils, macroscopic charcoal, organic carbon content, carbon isotopic composition, carbon/nitrogen ratio, and lithologic changes to determine the vegetation and landscape history of the greater Catskill Mountain region since deglaciation. Pollen stratigraphy generally matches the New England pollen zones identified by Deevey (1939) and Davis (1969), with boreal genera (Picea, Abies) present during the late Pleistocene yielding to a mixed Pinus, Quercus and Tsuga forest in the early Holocene. Lake Minnewaska sediments record the Younger Dryas and possibly the 8.2calkyrBP climatic events in pollen and sediment chemistry along with an ~1400calyr interval of wet conditions (increasing Tsuga and declining Quercus) centered about 6400calyrBP. Both Minnewaska and Mohonk reveal a protracted drought interval in the middle Holocene, ~5700–4100calyrBP, during which Pinus rigida colonized the watershed, lake levels fell, and frequent fires led to enhanced hillslope erosion. Together, the records show at least three wet–dry cycles throughout the Holocene and both similarities and differences to climate records in New England and central New York. Drought intervals raise concerns for water resources in the New York City metropolitan area and may reflect a combination of enhanced La Niña, negative phase NAO, and positive phase PNA climatic patterns and/or northward shifts of storm tracks. [Copyright &y& Elsevier]

Bear River, the largest river in the Great Basin, had some of its flow diverted into Bear Lake through a series of canals constructed between 1911 and 1918, turning Bear Lake into a reservoir. The prediversion lake had an unusually high Mg2+:Ca2+ ratio (38 by weight), which resulted in precipitation of CaCO3 as aragonite. The amount and mineralogy of the carbonate did not change immediately after the diversion, but during the middle of the 20th century, high-Mg calcite began to precipitate. In contrast, at the time of diversion there were very distinct changes in the isotopic composition of the carbonate that clearly define the time of diversion within the sediments. Sedimenttrap studies show that the CaCO3 polymorph that precipitates in the epilimnion of the lake today is high-Mg calcite. Samples in sediment traps placed 2 m above the bottom of the lake in 45 m of water (bottom traps) contain predominantly aragonite and quartz, with lesser amounts of high-Mg and low-Mg calcite and dolomite. Isotopic evidence from the sediments shows that the aragonite that accumulated in the bottom sediment traps and that constitutes the bulk of postdiversion sediments is reworked and redistributed from shallow sites to deep sites. [ABSTRACT FROM AUTHOR]