Santa Fe, NM, United States
Santa Fe, NM, United States

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Hall S.A.,Red Rock Geological Enterprises | Miller M.R.,Geo Marine Inc. | Goble R.J.,University of Nebraska - Lincoln
Bulletin of the Geological Society of America | Year: 2010

The Bolson sand sheet occurs in the Tularosa Valley, New Mexico, and the Hueco Bolson, Texas and consists of two principal eolian sand units. Optically stimulated luminescence (OSL) dating provides a new chronology of the sand sheet that relates as well to the formation, preservation, and visibility of the local archaeological record. The lower sand (unit Q2) (44.8 ± 2.9 ka) and the upper sand (unit Q3) (22.2 ± 1.6-5.2 ± 0.3 ka) have a combined thickness of less than 2 m. The Q2 sand is characterized by a red Bt paleosol, and the Q3 sand has a weak calcic paleosol with stage I carbonate morphology. Elevated amounts of airborne silt were incorporated in the Q3 sand during the period 24-14.5 ka, representing higher amounts of dust in the atmosphere during glacial and lateglacial time. Multiple OSL ages from the Q3 sand indicate a slow net sedimentation rate of 0.06-0.09 mm/yr, similar to other OSL-dated sand sheets in the region; sand deposits in dune fields have higher accumulation rates. The McGregor A horizon soil, radiocarbon-dated to younger than 0.5 ka, occurs at the top of the sand sheet and likely formed with desert grassland vegetation. Thousands of recent mesquite coppice dunes (unit Q4d) mantle the sand sheet, and two are dated to the twentieth century by OSL and 137Cs. Archaeological sites that postdate 3000 B.C. are concentrated, sometimes together, on the surface of the sand sheet, while sites that predate 3000 B.C., although rare, may be buried within the Q3 eolian sand. The Q2 sand is too old to contain archaeological sites, although site features may intrude into the sand. Previous chronologies of the sand sheet are based on radiocarbon dates of charcoal from archaeo logical sites, on radiocarbon dates of soil carbonate, and on soil-geomorphology correlations with Rio Grande Valley alluvium. The optical chronology does not support these various correlations. We recommend that the alluvial names Isaacks' Ranch, Fillmore, and Organ no longer be applied to the Bolson sand sheet. © 2010 Geological Society of America.


Hall S.A.,Red Rock Geological Enterprises | Penner W.L.,Parametrix | Palacios-Fest M.R.,Terra Nostra Earth science Research | Metcalf A.L.,University of Texas at El Paso | Smith S.J.,Northern Arizona University
Quaternary Research | Year: 2012

A thick alluvial sequence in central New Mexico contains the Scholle wet meadow deposit that traces upstream to a paleospring. The wet meadow sediments contain an abundant fauna of twenty-one species of freshwater and terrestrial mollusks and ten species of ostracodes. The mollusks and ostracodes are indicative of a local high alluvial water table with spring-supported perennial flow but without standing water. Pollen analysis documents shrub grassland vegetation with sedges, willow, and alder in a riparian community. Stable carbon isotopes from the wet meadow sediments have δ 13C values ranging from -22.8 to -23.3‰, indicating that 80% of the organic carbon in the sediment is derived from C 3 species. The wet meadow deposit is AMS dated 10,400 to 9700 14CyrBP, corresponding to 12,300 to 11,100calyrBP and overlapping in time with the Younger Dryas event (YD). The wet meadow became active about 500yr after the beginning of the YD and persisted 400yr after the YD ended. The Scholle wet meadow is the only record of perennial flow and high water table conditions in the Abo Arroyo drainage basin during the past 13ka. © 2011 University of Washington.


Hall S.A.,Red Rock Geological Enterprises | Penner W.L.,P3planning
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2013

A thick sequence of fine-textured alluvium in central New Mexico has provided an opportunity to reconstruct vegetation type and climate at the western edge of the Great Plains grassland. The analysis of thirty-eight AMS radiocarbon ages, δ13C values, and modern weather data has produced a 12,800calyr record of changing C3-C4 vegetation, temperature, and precipitation. The record begins with the Younger Dryas that was characterized by C3 plants and was about 2.4°C cooler with over 100mm rainfall than today. After 11,000calyrs BP, the climate became less cool and less wet, reaching present-day conditions by 9000yrs. The middle Holocene was C4, warm, and dry although the δ13C record is incomplete for this interval. From 3300 to 1400calyrs BP, the climate was cool and wet with C3 plants, averaging 0.5°C cooler and 22mm greater rainfall than today, matching other records in the region for a wetter climate. After 1400calyrs BP, the local climate became warm and dry, shifting to C4 vegetation. The severe second century drought, first observed in tree-rings in southern Colorado, is supported by the δ13C data and occurred during the interval A.D. 40 to A.D. 180. Hiatuses in the local alluvial and δ13C record extend from 9000 to 6000calyrs BP and from 1000calyrs BP to present. © 2012 Elsevier B.V.


Hall S.A.,Red Rock Geological Enterprises | Goble R.J.,University of Nebraska - Lincoln
New Mexico Geology | Year: 2011

The Mescalero sand sheet that covers most of the Mescalero Plain is formed by two eolian sand bodies, the Lower and Upper units. New and revised OSL ages indicate that the Lower unit accumulated 90-50 ka and the Upper unit was deposited 18-5 ka. Both eolian units are dominated by massive, well-sorted, fine quartz sand. The Lower sand directly overlies the eroded surface of the calcic Mescalero paleosol. The top of the Lower sand incorporates the Berino paleosol, a red argillic soil that formed on the sand sheet during the comparatively wet and cool environment of the late Wisconsinan. The Lower sand and the Berino paleosol are buried by the Upper eolian sand. An unnamed Bw paleosol at the top of the Upper sand formed during the past 5 ka. Locally, archaeological sites younger than 3,000 B.C. are on the surface, whereas older sites are buried within the Upper sand. During the twentieth century, the shrub grassland vegetation of the Mescalero sand sheet was disturbed, leading to the formation of many coppice and parabolic dunes.


Hall S.A.,Red Rock Geological Enterprises | Goble R.J.,University of Nebraska - Lincoln
Geomorphology | Year: 2015

The Strauss sand sheet occurs in south-central New Mexico, USA, and northern Chihuahua, Mexico, covering an area of about 4740km2. Its chronology is determined by 19 OSL ages. The sand sheet formed primarily during three phases of eolian deflation and deposition, each phase with a separate sand source and under different climatic and environmental circumstances. The first phase of eolian sedimentation occurred 45 to 15ka with the deposition of unit 1. The sand source for the first phase was beach-related features along the eastern shoreline of pluvial Lake Palomas in Mexico. The glacial-age climate was cool, wet, and windy because of the southern path of the jet stream at that time. After 15ka, with the onset of warmer conditions of the Bølling-Allerød, the shutting down of the Palomas sand source, and wet conditions of the Younger Dryas, the sand sheet stabilized with weak soil development in unit 1. By 11ka, the climate shifted to Holocene drying conditions and the second phase of sand accumulation began, forming unit 2; the sand source was the local deflation of the previously deposited unit 1 sand. The sand sheet stabilized again by 1.9ka with slightly wetter late Holocene climate; a weak soil formed in unit 2 sand. About A.D. 1500 and extending to about A.D. 1850 or later, an A horizon formed on the sand sheet, probably in response to a desert grassland vegetation during the period of wet climate of the Little Ice Age. In an anthropogenic third phase of eolian activity, after A.D. 1850, the vegetation was likely disturbed by overgrazing; and the unit 2 and A horizon (unit 3) sands were deflated, resulting in the deposition of a thin layer of massive eolian sand (unit 4) across the sand sheet. By about A.D. 1900 mesquite shrubs had increased in abundance; and deflated sand, largely from unit 2, began to accumulate around the shrubs, forming coppice dunes (unit 5). Mesquite coppice dunes continued to increase in number and volume during the twentieth century and at present dominate most of the sand sheet. This third phase of eolian deflation-deposition is ongoing today. © 2015 Elsevier B.V.


Hall S.A.,Red Rock Geological Enterprises | Peterson J.A.,University of Guam
Quaternary Science Reviews | Year: 2013

The Rio Grande is one of the larger rivers in North America, and the development of its floodplain is related to Holocene climate and climate change. The late Pleistocene through early Holocene channel is characterized by a meander or braided system with lateral cutting and backfilling, resulting in the valley-wide deposition of massive to cross-bedded, fine-to-medium textured sand. The late Pleistocene-early Holocene floodplain is also the sand source for the adjacent Bolson sand sheet. The sand sheet stopped accumulating new sand 5000 yrs ago, an event directly related to the shutting off of the sand supply caused by the deposition of overbank muds that covered and sealed the floodplain surface. During the middle Holocene, the river may have dried intermittently with the floodplain becoming deflated and local sand dunes forming on the floodplain. After 5000 yrs the climate was less arid and the river shifted to a regime of increased flooding and overbank deposition of silt and clay. By 2500 yrs, a late Holocene period of wet climate resulted in further overbank deposition and the formation of a cumulic Mollisol across the floodplain, the Socorro paleosol. The period of wet climate corresponds to the Audubon Neoglacial and active rock glaciers in the southern Rocky Mountains, speleothem growth in nearby caves, and other evidence for wet-cool conditions in the region. After 1000 yrs, the climate became drier, and the deposition and accumulation of overbank muds by the flooding Rio Grande came to a halt. Even though the river has flooded often in historic times, and presumably during late prehistoric times as well, there is little evidence for deposition of overbank sediments on the floodplain since A.D. 1000. Accordingly, the present-day surface of the Lower Valley is ten centuries old. Three channels occur on the US side of the Lower Valley floodplain, and during the past 2500 yrs stream flow has shifted from one to the other by the avulsion process of channel reoccupation, although most flow has been in the Rio Grande channel, the largest of the three. © 2013 Elsevier Ltd.


Hall S.A.,Red Rock Geological Enterprises | Boutton T.W.,Texas A&M University | Lintz C.R.,Texas Parks and Wildlife Department | Baugh T.G.,Oklahoma Historical Society
Holocene | Year: 2012

A late-Holocene alluvial sequence in north-central Texas has a 1 m thick buried cumulic soil with an A-C profile called the West Fork paleosol. It formed 2300 to 1000 yr BP and is a local equivalent of the Copan paleosol that is present throughout the southern US Great Plains. Stable carbon isotopes indicate that the paleosol and underlying gray clay formed under vegetation dominated by C 4 species (mean δ 13C: -18.3 ± 0.3‰). Diverse paleoenvironmental studies indicate that the period of paleosol formation was cool and wet and that alluvial water-tables were high, resulting in broad wet meadows across alluvial valleys, characterized by communities of grasses. Present-day wet meadows and bottomlands with Mollisols with A-C profiles along streams in the Great Plains are dominated by C 4 tallgrass species and may serve as analogues to wet-meadow environments during the late Holocene. A shift in climate to warm-dry conditions about 1000 yr BP was accompanied by deep channel cutting, low alluvial water-tables, and colonization of abandoned floodplains by trees and other C3 species, as indicated by a change in carbon isotopes to lower values (mean δ 13C: -20.8 ± 0.5‰) and correlating with the 'Medieval Warm Period'. Other stable carbon isotope studies from late-Holocene alluvium in Texas have been mistakenly interpreted as evidence for paleoenvironmental conditions opposite to those presented in this investigation. We conclude that interpretations of stable carbon isotopes from alluvium based on broad patterns of upland C4 grasses and climate can be in error, especially in cases where wet-meadow deposits and soils are present. © The Author(s) 2011.


Hall S.A.,Red Rock Geological Enterprises | Goble R.J.,University of Nebraska - Lincoln
Journal of Geology | Year: 2012

The Berino paleosol is the first record of a directly dated Aridisol in the American Southwest where paleoclimatic conditions during the time of pedogenesis can be estimated. The noncalcic, argillic paleosol formed in eolian sand during the cool, wet climate of the mid- and late Wisconsin, marine isotope stages 3 and 2, in presently semiarid southeastern New Mexico. Optically stimulated luminescence dating of the Mescalero sand sheet and the Berino indicates that soil formation occurred during the period 50-18 ka. The paleosol is a red 2.5YR hue Bt horizon, 120 cm thick, with 25% clay, 0.36% Fe, and an absence of visible carbonate. It is buried by younger eolian sand, although at the edges of the sand sheet, it is unburied and a relict soil. Red argillic paleosols in other sand sheets in the region may correlate with the Berino. The Berino paleosol is formally named as a pedostratigraphic unit. © 2012 by The University of Chicago.


Hall S.A.,Red Rock Geological Enterprises
Palynology | Year: 2010

Pollen concentrations containing abundant Zea mays pollen grains are AMS radiocarbon dated 3940±40 to 2450±4014C years BP. The maize pollen is from two prehistoric woodrat (Neotoma) middens that occur in fractures in the south-facing sandstone cliff at Chaco Culture National Historical Park. The diameters of the Archaic-age maize pollen grains are significantly larger than Puebloan and modern maize pollen. The size distributions of the earliest Zea grain populations are not normal, suggesting the possibility that more than one variety of maize is represented by the pollen. The occurrence of large numbers of maize pollen grains as well as pollen from weedy plants indicates the nearby presence of an Archaic cornfield, now buried in alluvial fill adjacent to the cliff. It was also found that the AMS radiocarbon ages of the pollen concentrations differ significantly from the age of twigs from the same woodrat middens. Because of the strong age differences of components of woodrat middens, pollen assemblages should be dated independent of plant macrofossils. © 2010 AASP-The Palynological Society.


Hall S.A.,Red Rock Geological Enterprises | Riskind D.H.,Texas Parks and Wildlife Department
Journal of Arid Environments | Year: 2010

Pollen analysis of two woodrat middens from Hueco Tanks, El Paso County, Texas, dated 10,140 ± 70 and 7170 ± 70 14C years BP, shows late persistence of the regional glacial-age Artemisia steppe vegetation in what is historically desert shrub grassland of the northern Chihuahuan Desert. Local populations of Pinus were gone by the end of the Pleistocene, and creosotebush (Larrea) and mesquite (Prosopis) appeared in the local vegetation by mid-Holocene time. Juniperus can be strongly over-represented in midden pollen assemblages due to harvesting of cone-bearing twigs by woodrats. AMS radiocarbon dates on very small samples of midden matrix used for pollen analysis are 3400 and 2200 14C years younger than dates on plant macrofossils from the same middens. Juniperus over-representation in pollen percentages and age differences between pollen and macrofossil content must be taken into account when interpreting the palynology of woodrat middens. © 2009 Elsevier Ltd. All rights reserved.

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