Well-developed Desert Pavements Research Articles

Origin, structure and geochemistry of a rock glacier near Don Juan Pond, Wright Valley, Antarctica

AbstractThe South Fork of Wright Valley contains one of the largest rock glaciers in the McMurdo Dry Valleys, Antarctica, stretching 7 km from the eastern boundary of the Labyrinth and terminating at Don Juan Pond (DJP). Here, we use results from ground-penetrating radar (GPR), qualitative field observations, soil leaching analyses and X-ray diffraction analyses to investigate rock glacier development. The absence of significant clean ice in GPR data, paired with observations of talus and interstitial ice influx from the valley walls, support rock glacier formation via talus accumulation. A quartz-dominated subsurface composition and discontinuous, well-developed desert pavements suggest initial rock glacier formation occurred before the late Quaternary. Major ion data from soil leaching analyses show higher salt concentrations in the rock glacier and talus samples that are close to hypersaline DJP. These observations suggest that DJP acts as a local salt source to the rock glacier, as well as the surrounding talus slopes that host water track systems that deliver solutes back into the lake, suggesting a local feedback system. Finally, the lack of lacustrine sedimentation on the rock glacier is inconsistent with the advance of a glacially dammed lake into South Fork during the Last Glacial Maximum.

Mapping Changes in Desert Pavement Surfaces of the Lower Colorado Desert of Southern California using Landsat Time Series Analysis

Potential disturbance of desert soils from renewable energy development in southern California is receiving increasing attention due to potential impacts on air quality and greenhouse gas emissions. This study was designed to quantify and map, for the first time, changes in desert pavement surface area using 20 years of Landsat satellite image data across the Lower Colorado Desert. Landsat-derived maps of geomorphic surface classes from 1990 to 2014 for the Lower Colorado Desert area showed that a relatively stable area of around 1920 km 2 was covered by well-developed desert pavements prior to 2014. Based on 2014 Landsat imagery, coverage of well-developed pavements within solar energy development boundaries of the Lower Colorado Desert area totaled to 421 km 2 , the majority of which (>82%) were located in eastern Riverside County. If disturbed as a result of construction activities, these desert pavements could become a source of dust from exposure of the underlying fine particle layer.

Dating desert pavements – First results from a challenging environmental archive

Desert pavements are widespread landforms of arid environments. They consist of a monolayer of clasts at the surface, associated with an underlying unit of eolian fines. In some situations, buried desert pavements can be observed, which is interpreted as a change in the environmental conditions. Therefore, it is believed that desert pavements represent important paleoenvironmental sediment archives, especially for arid environments, where natural archives of past environments are rare. To better understand the formation process of desert pavements and to enable the paleoenvironmental interpretation of these valuable sediment archives, reliable chronologies are of crucial importance. Thus, OSL dating was applied to samples from well-developed desert pavements in two different study areas, the Cima Volcanic Field, eastern Mojave Desert, USA, and the desert of northeastern Badia, Jordan. To test the suitability of the sediments for OSL dating, the luminescence characteristics of the fine- and coarse-grain quartz fraction are described and compared. Finally, first OSL ages are presented.

Desert pavements as indicators of soil erosion on aridic soils in north-east Patagonia (Argentina)

Desert pavements are prominent features of many geomorphic surfaces in arid and semiarid lands. In the semiarid soils of north-eastern Patagonia, gravel cover in the shrub interspace areas of shrub-dominated communities is generally high, and contrast with that of grass-dominated patches where gravel cover is either absent or negligible. In the present study we analyze the relationship between soil erosion and desert pavement formation, in three sites, the upper, middle and lower slope positions of a flank pediment where well-conserved soils served as reference areas. We used the gravel cover and mass, as well as the thickness of the remnant A horizon, as determined by the depth of the Bt horizon of a Xeric Calciargid, as measures of soil erosion. Surface gravel at four cardinal points in respect to mounds associated with shrub-clumps was collected and the depth to the Bt horizon was determined. The mean thickness of the A horizon in the well-conserved soils were 11.3, 10.0 and 13.5 cm for the upper, middle and lower slope positions, respectively. For the same positions, the mean coarse fragment contents (> 2.0 mm) in the 0–10 cm depth of the A horizon in the well-conserved soils were 144, 92 and 119 g kg −1, and the mean surface gravel mass in the eroded patches were 5.3, 3.1 and 4.7 kg m −2. Surface gravel mass and depth of the remnant A horizon gave different estimates of the magnitude of soil erosion in the flank pediment. Thus, the mean/maximum soil loss, as determined by the mean gravel mass on the soil surface for the upper, middle and lower slope positions were, 28.3/68.2, 27.0/63.8 and 31.5/56.4 mm, respectively. These figures increased to a mean of 50.0, 52.5 and 82.0 mm for the same positions when soil loss was determined as the difference between the thickness of the A horizon of the well-conserved soil and that of the remaining A horizon in eroded patches. The loss of the A horizon by wind and water erosion seems to initiate the change from grass steppe to a stable shrub steppe characterized, in the shrub interspaces, by well-developed desert pavements. The strong correlation between surface gravel mass and the thickness of the remaining A horizon indicates that accelerated soil erosion has played an important role in the formation of desert pavements, and that desert pavements are good indicators of the extent and intensity of the erosion process in the Punta Ninfas area.

Desert pavement-coated surfaces in extreme deserts present the longest-lived landforms on Earth

All exposed rocks on Earth’s surface experience erosion; the fastest rates are documented in rapidly uplifted monsoonal mountain ranges, and the slowest occur in extreme cold or warm deserts—millennial submeterscale erosion may be approached only in the latter. The oldest previously reported exposure ages are from boulders and clasts of resistant lithologies lying at the surface, and the slowest reported erosion rates are derived from bedrock outcrops or boulders that erode more slowly than their surroundings; thus, these oldest reported ages and slowest erosion rates relate to outstanding features in the landscape, while the surrounding landscape may erode faster and be younger. We present erosion rate and exposure age data from the Paran Plains, a typical environment in the Near East where vast abandoned alluvial surfaces (10 2 –10 4 km 2 ) are covered by well-developed desert pavements. These surfaces may experience erosion rates that are slower than those documented elsewhere on our planet and can retain their original geometry for more than 2 m.y. Major factors that reduce erosion converge in these regions: extreme hyperaridity, tectonic stability, fl at and horizontal surfaces (i.e., no relief), and effective surface armoring by a clast mosaic of highly resistant lithology. The 10 Be concentrations in amalgamated desert pavement chert clasts collected from abandoned alluvial surfaces in the southern Negev, Israel (representing the Sahara-Arabia Deserts), indicate simple exposure ages of 1.5–1.8 Ma or correspond to maximum erosion rates of 0.25–0.3 m m.y. –1 . The 36

Luminescence ages for alluvial-fan deposits in Southern Death Valley: Implications for climate-driven sedimentation along a tectonically active mountain front

Controversy exists over whether alluvial-fan sedimentation along tectonically active mountain fronts is driven by climatic changes or tectonics. Knowing the age of sedimentation is the key to understanding the relationship between sedimentation and its cause. Alluvial-fan deposits in Death Valley and throughout the arid southwestern United States have long been the subjects of study, but their ages have generally eluded researchers until recently. Most mapping efforts have recognized at least four major relative-age groupings (Q1 (oldest), Q2, Q3, and Q4 (youngest)), using observed changes in surface soils and morphology, relation to the drainage net, and development of desert pavement. Obtaining numerical age determinations for these morphologic stages has proven challenging. We report the first optically stimulated luminescence (OSL) ages for three of these four stages deposited within alluvial-fans along the tectonically active Black Mountains of Death Valley. Deposits showing distinct, remnant bar and swale topography (Q3b) have OSL ages from 7 to 4 ka., whereas those with moderate to poorly developed desert pavement and located farther above the active channel (Q3a) have OSL ages from 17 to 11 ka. Geomorphically older deposits with well-developed desert pavement (Q2d) have OSL ages ∼25 ka. Using this OSL-based chronology, we note that alluvial-fan deposition along this tectonically active mountain front corresponds to both wet-to-dry and dry-to-wet climate changes recorded globally and regionally. These findings underscore the influence of climate change on alluvial fan deposition in arid and semi-arid regions.

THE MICROMORPHOLOGY OF GYPSUM AND HALITE IN REG SOILS—THE NEGEV DESERT, ISRAEL

Gypsum and halite are the most common salts in reg soils developed on alluvial parent material under extremely arid conditions in the Negev Desert, Israel. The aim of this paper is to document the changes in the micromorphology of these salts at different stages of Reg soil development on two alluvial fan chronosequences. The micromorphological analyses included thin section observations and scanning electron microscope and electron microprobe analyses. In this arid soil environment, gypsum and halite possess a variety of crystal forms which may change with depth in a single profile and/or between profiles of different ages. The variety of crystal forms results from changes in the microenvironmental conditions that occur in desert reg soils over time. Poikilitic lenticular gypsum is found in all Reg soils and is distributed throughout the profiles. The conditions needed for such crystals to form are high ionic impurities and deposition in a void system where space is not limiting. Microcrystalline alabastrine gypsum is only found in mature Reg soils and is crystallized when the profile has high amounts of fine material and a well-developed desert pavement. In a well-developed Reg soil, profile indicators, such as a well-developed desert pavement and high amounts of fine earth, limit the leaching depth and cause gypsum deposition from supersaturated soil solutions under high evaporation rates close to the surface. Prismatic and fibrous gypsum are less common. Low amounts of prismatic gypsum are found in young and mature soils while fibrous gypsum is found only in mature soils in re-cemented shattered gravel. The halite crystal form is mainly cubic with low amounts of host material incorporated into the crystal. It occurs predominantly in mature Reg soil profiles through the crystallization from supersaturated soil solutions at the depth of maximum water penetration. Although the alabastrine, prismatic and fibrous gypsum and cubic halite are deposited in a displacive manner, no correlation was found between their occurrence and the distribution of shattered gravel in the soil profile.

Late Cenozoic Antarctic paleoclimate reconstructed from volcanic ashes in the Dry Valleys region of southern Victoria Land

Research Article| February 01, 1996 Late Cenozoic Antarctic paleoclimate reconstructed from volcanic ashes in the Dry Valleys region of southern Victoria Land David R. Marchant; David R. Marchant 1Institute for Quaternary Studies, University of Maine, Orono, Maine 04469 Search for other works by this author on: GSW Google Scholar George H. Denton; George H. Denton 2Department of Geological Sciences and Institute for Quaternary Studies, University of Maine, Orono, Maine 04469 Search for other works by this author on: GSW Google Scholar Carl C. Swisher, III; Carl C. Swisher, III 3Berkeley Geochronology Center, Berkeley, California 94709 Search for other works by this author on: GSW Google Scholar Noel Potter, Jr Noel Potter, Jr 4Department of Geology, Dickinson College, Carlisle, Pennsylvania 17013 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1996) 108 (2): 181–194. https://doi.org/10.1130/0016-7606(1996)108<0181:LCAPRF>2.3.CO;2 Article history first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation David R. Marchant, George H. Denton, Carl C. Swisher, Noel Potter; Late Cenozoic Antarctic paleoclimate reconstructed from volcanic ashes in the Dry Valleys region of southern Victoria Land. GSA Bulletin 1996;; 108 (2): 181–194. doi: https://doi.org/10.1130/0016-7606(1996)108<0181:LCAPRF>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract We report the discovery of numerous in situ Miocene and Pliocene airfall volcanic ashes that occur within the hyperarid Dry Valleys region of the Transantarctic Mountains in southern Victoria Land, Antarctica. Ashes that occur above 1000 m elevation rest at the ground surface, covered only by a thin ventifact pavement 1 to 2 cm thick. The ash deposits are loose and unconsolidated and show no signs of chemical weathering. Laser-fusion 40Ar/39Ar analyses of volcanic crystals and glass shards indicate that the ashes range from 4.33 Ma to 15.15 Ma in age. The Arena Valley ash (4.33 ± 0.07 Ma) rests on the surface of a well-developed desert pavement and ultraxerous soil profile at 1410 m elevation. Lack of geomorphic evidence of liquid water on surficial sediments coeval and older than the Arena Valley ash, together with the pristine condition of volcanic crystals and lack of authigenic clay formation, indicates a cold desert at and since 4.33 Ma. The Beacon Valley ash (10.66 ± 0.29 Ma), the Koenig Valley ash (13.65 ± 0.06 Ma), and the Nibelungen Valley ash (15.15 ± 0.02 Ma) fill the upper half of relict sand-wedge troughs that form only in cold-desert conditions. The lack of authigenic clay-sized minerals in these ash deposits, along with preservation of sharp lateral contacts with surrounding sand-and-gravel deposits, suggests that frozen conditions (without rain or well-developed active layers during summer months) have persisted in Beacon, Koenig, and Nibelungen Valleys since ash deposition. Ash-avalanche deposits that rest on rectilinear slopes contain matrix ash dated to 7.42 ± 0.31 Ma in upper Arena Valley and 11.28 ± 0.05 Ma in lower Arena Valley. Little slope development has occurred since emplacement of these ash-avalanche deposits. Such slope stability is consistent with cold-desert conditions well below 0 °C. Taken together, these ash deposits point to persistent polar conditions similar to the present at elevations above 1000 m in the western Dry Valleys region during at least the last 15.0 m.y. This conclusion contradicts the view that, during part of the Pliocene epoch, East Antarctica was largely free of glacier ice and that scrub vegetation (Nothofagus, Southern Beech) survived along the Transantarctic Mountain front in the Dry Valleys region and to at least lat 86°S (Webb and Harwood, 1993). Instead, it supports marine and geomorphological evidence that calls for a stable Antarctic cryosphere, much the same as today, since middle Miocene time. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Desert Pavement Evolution: An Example of the Role of Sheetflood

Patches of young, well-developed desert pavement were found atop bare rock on the Pisgah basalt flow, California. These particular stone mosaics formed directly atop the flow; no soil is present, or ever has been. Therefore, soil expansion and aeolian processes played no significant role in their creation or maintenance. The unusual setting at Pisgah allows sheetflood to be the sole agent responsible for the lateral movement of surface stones into these mosaics. The Pisgah mosaics thus represent an end-member case of desert pavement types, and they may represent a previously unrecognized initial substage of accretionary mantle formation.

Influences of eolian and pedogenic processes on the origin and evolution of desert pavements

Research Article| June 01, 1987 Influences of eolian and pedogenic processes on the origin and evolution of desert pavements Leslie D. McFadden; Leslie D. McFadden 1Department of Geology, University of New Mexico, Albuquerque, New Mexico 87131 Search for other works by this author on: GSW Google Scholar Stephen G. Wells; Stephen G. Wells 1Department of Geology, University of New Mexico, Albuquerque, New Mexico 87131 Search for other works by this author on: GSW Google Scholar Michael J. Jercinovich Michael J. Jercinovich 1Department of Geology, University of New Mexico, Albuquerque, New Mexico 87131 Search for other works by this author on: GSW Google Scholar Geology (1987) 15 (6): 504–508. https://doi.org/10.1130/0091-7613(1987)15<504:IOEAPP>2.0.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Leslie D. McFadden, Stephen G. Wells, Michael J. Jercinovich; Influences of eolian and pedogenic processes on the origin and evolution of desert pavements. Geology 1987;; 15 (6): 504–508. doi: https://doi.org/10.1130/0091-7613(1987)15<504:IOEAPP>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Well-developed desert pavements are present above eolian deposits that mantle flows of the Cima volcanic field, located in the Mojave Desert, California. Soil-stratigraphic data and geochemical data demonstrate that eolian and pedogenic processes play major roles in the evolution of these pavements. Eolian dust (1) accelerates mechanical fragmentation of flow rock, providing the source material for pavements, and (2) accumulates slowly below basaltic colluvium in flow depressions, eventually promoting development of cumulate soils below the evolving stone pavement. An increase in dust flux during the Holocene has raised ancient Pleistocene pavements as much as 20 cm above the former land surface. The results of our studies demonstrate for the first time that most desert pavements do not form by deflation, by overland flow, or by upward migration of stones through a slowly formed, clayey argillic horizon. Desert pavements are born and maintained at the surface. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Variations in surface roughness within Death Valley, California: Geologic evaluation of 25-cm-wavelength radar images

Images — processed from 25-cm wavelength, side-looking airborne radar — of the salt flats and gravel fans on the floor of Death Valley, California, show distinctive variations in radar backscatter (that is, variations in image gray tones) that can be correlated with systematic changes in the surface roughness of different geologic units. Well-developed desert pavements on the oldest boulder gravel units of late Pleistocene age are clearly delineated as weak backscatterers on the images. A gradation in the size of gravel constituents near the base of the giant gravel fans is associated with an abrupt change in the backscatter energy. The change takes place at gravel radii between 0.08λ and 0.14λ (2.0 and 3.5 cm). A breakpoint observed in the Rayleigh scattering region of the total radar cross section is virtually independent of the antenna depression angle as long as the resolution area does not lie in the first pulse width of the echo (the 90° depression angle). With the longer wavelength radar systems, antenna depression angles of 45° to 90° appear to be well suited for investigations of surface roughness because of the suppression of radar shadows and the increased radar return from the near range.