Lake Estancia was a lake formed in the Estancia Valley, now in central New Mexico, United States. The lake, which left various coastal landforms in the valley, was mostly fed by creek and groundwater from the Manzano Mountains, and fluctuated between freshwater stages and saltier stages. The lake had a diverse fauna, including cutthroat trout; they may have reached it during a possible past stage where it was overflowing.
Lake Estancia appears to have formed between the Pliocene and Pleistocene, when a previous river system broke up. It reached a maximum water level ("highstand") presumably during the Illinoian glaciation and subsequently fluctuated between fuller stages and a desiccated basin. Around the Last Glacial Maximum (LGM) time interval, several highstands and a low water level state occurred during the "Big Dry" climate interval. Between 16,100 and 14,500 years ago the lake reached its highest stand of the last 30,000 years before drying up again during the Bølling-Allerød climate interval. The lake briefly returned during the Younger Dryas climate interval and eventually desiccated during the Holocene, after about 8,500 years ago. Wind-driven erosion has excavated depressions in the former lakebed that are in part filled with playas (dry lake beds).
The lake was one of several pluvial lakes in southwestern North America that developed during the late Pleistocene. Their formation has been variously attributed to decreased temperatures during the ice age and increased precipitation; a shutdown of the thermohaline circulation and the Laurentide Ice Sheet altered atmospheric circulation patterns and increased precipitation in the region. The lake has yielded a good paleoclimatic record.
History and climatological implications The Estancia Valley became a closed basin at some point during the Pliocene to middle Pleistocene. Previously, the Estancia Valley was occupied by a river that flowed through the Encino Basin into the Pecos River and eventually into the Brazos River. Fault movement was probably responsible for the breakup of this drainage system. Dissolution of the Yeso Formation from the Permian period may have contributed to the subsidence of the basin.
The low thickness of lake sediments in the Estancia Valley suggests that the lake began to form only in the middle Pleistocene. Early Lake Estancia, most likely larger than the LGM lake, existed possibly during the Illinoian glaciation and largely dried up in the warm and dry climate of the Sangamonian interglacial. Climate changes recorded in the cave deposits in the Cavenee Caverns northwest of the Lake Estancia basin have been correlated to fluctuations of Lake Estancia; they suggest that Lake Estancia may have desiccated 134,000–121,000 years ago. Between 69,000 and 19,000 years ago, water levels were higher 41,000–38,000 years ago and lower 57,000–51,000 and 45,000–43,000 years ago, consistent with climate patterns recorded in regional cave deposits. The low water level stages correlate to the timing of maximum summer insolation and warm periods in Greenland; however, problems with dating these fluctuations make any inference about correlations to events elsewhere in North America problematic.
Last Glacial Maximum and later The lake sediment record indicates that shallow lakes re-formed between 45,000 and 40,000 years ago. Water levels began to rise 24,000 years ago, and at least five highstands occurred during the LGM, with two more before and after the LGM. At least ten separate oscillations in water levels took place. Radiocarbon dating has yielded ages of 24,300 years ago for the first freshwater stage and 20,040 for the gap between the second and third freshwater stage. The expansion of lakes during the LGM was triggered by the growth of the Laurentide Ice Sheet, which forced the jet stream southward. A highstand around 23,000 years ago appears to coincide with Heinrich event 2, an episode in the North Atlantic where ice discharge into the ocean was increased and impeded heat transport by ocean currents.
The highstands lasted until 18,100–17,000 years ago when water levels declined, an event christened the "Big Dry" in the Lake Estancia basin. This dry interval separates the LGM highstand from the following highstands, and correlates to an episode of strong East Asian Monsoons. Evidence of the "Big Dry" has also been identified in South America, where the drying of paleolake Sajsi in the Altiplano of Bolivia may correlate to the Lake Estancia event, but not elsewhere in the Great Basin. It appears that during the "Big Dry" climate patterns in New Mexico decoupled from climate variations elsewhere on the world. Both its beginning and its end have been correlated to ice-rafting events in the North Atlantic but it is not clear how ice-rafting events could simultaneously trigger the beginning and the end of a dry episode. Possibly, the southward migration of the Intertropical Convergence Zone during the "Big Dry" cooled the northeastern Pacific, inducing drought despite the occurrence of a more winter-like atmospheric circulation over North America, which would be expected to increase precipitation. Later research has proposed that the end of the "Big Dry" may relate to the ice-rafting events, given chronological uncertainties.
Another highstand took place after the "Big Dry" during the late phase of the so-called Mystery Interval, when Antarctica and the European Alps were already warming despite the cooling that occurred at the time of Heinrich event 1. This highstand was the largest highstand of the last 30,000 years not only of Lake Estancia, but also in other Great Basin lakes. It appears that the end of the "Big Dry" and the transition to the Mystery Interval highstand correlates to a southward movement of the thermal equator and an abrupt weakening of the East Asian Monsoon. These events could have been triggered by an extended shutdown of the thermohaline circulation, which caused Arctic sea ice to expand and Antarctic sea ice to contract, causing a southward migration of the Intertropical Convergence Zone. The forcing by the Laurentide Ice Sheet was important for the Mystery Interval lake level changes as well. The highstand between 16,100 and 14,500 years ago has been christened the "Big Wet".
There were two more highstands 14,000–12,500 years ago, followed by desiccation 12,000 or 14,000 years ago when the lake declined over the course of a millennium. This decline of water levels was a consequence of a drier climate in the Southwestern United States, the so-called "Clovis-age drought", and relates to the Bølling-Allerød period, a time period where climate changed. The exposed lake bed was eroded by wind, producing dunes. "Lake Willard", the final highstand at about elevation, has been linked to the Younger Dryas when a moister climate returned to the Southwestern United States. It took place 11,000–10,000 years ago and was short lived. Ridges on the eastern side of the Estancia Valley formed during this highstand.
Similarities have been noted between the record of Lake Estancia and that of Lake Cochise in Arizona, Lake Mojave in California and San Luis Lake in Colorado. The timing of Lake Estancia highstands is coherent with the timing of highstands in other Great Basin lakes. Water levels at other Great Basin lakes too declined with the Bølling-Allerød period and concomitant abrupt global climate change. Conversely, the water level changes at Lake Estancia are opposite to lake-level fluctuations at low latitudes. Lake level rises probably took only a few decades. Fluctuations in water levels occurred secondarily to changes in the atmospheric moisture transport.
Short term changes Millennial-scale oscillations are documented from lake deposits, which have been explained by streamflow pulses lasting several decades and separated by several centuries. These pulses were intense enough to increase inflow but not so long-lasting to raise water levels to overflow. Some lake level changes may have been too short to leave detectable shoreline deposits. Gypsum concentrations show strong 600 years long and weaker 350 and 250 years long cycles. The slow changes in the continental ice sheets cannot explain short-term changes in the lake, and other causal mechanisms have been sought. Solar cycles such as the Gleissberg solar cycle have been proposed as explanation for these fluctuations.
Holocene Beach terraces and other beach deposits were emplaced early in the Holocene; after about 8,500 years before present Lake Estancia dried up. La Niña conditions during the Holocene reduced water inflow into the lake, which owing to high evaporation rates could not be compensated by summer precipitation. After Lake Estancia dried up, two separate wind deflation events took place, the first dated to either 4,000 or 7,000 years ago and the second to either 4,000 or 2,000 years ago. The deflation removed Quaternary sediments thus exposing their internal structure. The deflation also generated the playa basins and the "Willard soil" during the Altithermal climate phase. Dunes developed during hot and dry conditions of the middle Holocene. After the middle Holocene the climate became wetter again, reducing dune activity. The existence of a "Lake Meinzer" with a depth of and an area of after the Altithermal has been inferred. Presently, dry lakes occur on the bed of Lake Estancia and are fed by groundwater.
Geography and geomorphology Lake Estancia developed within the Estancia Valley, a closed basin in central New Mexico's Torrance County. The settlements of Estancia, Moriarty and Willard lie within the valley, which is about southeast of Albuquerque. Interstate 40 crosses the northernmost parts of the lakebed of Lake Estancia, and New Mexico State Road 41 and U.S. Route 60 pass over the western and southern lakebed, respectively; formerly the tracks of the New Mexico Central Railroad and the Atchison, Topeka and Santa Fe Railway also traversed the lake bed. The lowest units of the Salinas Pueblo Missions National Monument are located close to the shorelines of former Lake Estancia.
Estancia Valley covers an area of and is flanked to the east by the Pedernal Hills, to the northwest by the Sandia Mountains, to the west by the Manzano Mountains, to the south by the Juames Mesa and Chupadera Mesa and to the southeast by the Rattlesnake Hills. The Estancia Basin is near the Rio Grande-Pecos River drainage divide.
The central points of the valley contain over sixty playas, which formed within blowouts; the largest is Laguna del Perro and others include Laguna Chica and Laguna Salina. They hold water only briefly and are not remnants of Lake Estancia. The lowermost point of the valley lies at elevation.
The lake At its greatest extent, the lake was about by wide and covered the present-day locations of Estancia, McIntosh, Progresso and Willard. The lake may have resembled Lake Tahoe in California, although Lake Tahoe is deeper. Lake Estancia was the easternmost pluvial lake in Southwestern North America.
Distinct shoreline landforms in the Estancia Valley occur at various elevations, including bars, beaches, gravel deposits, ridges, scarps, spits, swales, terraces and wave-cut cliffs. A spit protruded northward into a bay on Lake Estancia's eastern shore. On the eastern side of Lake Estancia is a gypsum ridge about high and long, and smaller ridges are found elsewhere. These features are subdivided into an "older", less well developed shoreline at higher elevations and a "younger", better developed shoreline at lower elevations. Most shoreline deposits were formed by the accumulation of material; only in a few places did the lake actively erode pre-existing terrain.