Pavements and Stone Mantles

Laity, Julie E.

doi:10.1002/9780470710777.ch9

Cited by 13 publications

(7 citation statements)

References 81 publications

(215 reference statements)

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“…There is a spectrum of grain sizes that characterizes the coarse-grained surfaces in arid deserts [Laity, 2011]. In many cases, desert pavements consist of very coarse sediment that are beyond the realm of wind transport [Haff and Werner, 1996].…”

Section: Discussionmentioning

confidence: 99%

Controls on and effects of armoring and vertical sorting in aeolian dune fields: A numerical simulation study

Gao

Narteau

Rozier

2016

Geophysical Research Letters

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Unlike ripples, there are only few numerical studies on grain size segregation at the scale of dunes in aeolian environments. Here we use a cellular automaton model to analyze vertical sorting in granular mixtures under steady unidirectional flow conditions. We investigate the feedbacks between dune growth and the segregation mechanisms by varying the size of coarse grains and their proportion within the bed. We systematically observe the development of a horizontal layer of coarse grains at the top of which sorted bed forms may grow by amalgamation. The formation of such an armor layer controls the overall sediment transport and availability. The emergence of dunes and the transition from barchan to transverse dune fields depend only on the grain size distribution of the initial sediment layer. As confirmed by observation, this result indicates that armor layers should be present in most arid deserts, where they are likely to control dune morphodynamics.

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Section: Discussionmentioning

confidence: 99%

Controls on and effects of armoring and vertical sorting in aeolian dune fields: A numerical simulation study

Gao

Narteau

Rozier

2016

Geophysical Research Letters

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“…At L0106/0130, the quadrants with the highest artifact counts were found on subdued topography covered by fine-grained, artifactbearing sediments allowing the formation of lag deposits through winnowing of fine material by wind and water (as well as sporadic high-energy surface sheet flow during rainstorms), by exposing artifacts and other clasts, but with insufficient energy to move them into areas of net sedimentation where they could be buried. Such deposits sometimes referred to as deflationary desert pavements (Laity, 2011), are familiar to those working in Paleolithic archaeology in the arid zone (e.g., Hill, 2000;Jones et al, 2011;Knight & Zerboni, 2018 (Pedley, 1990) and algae aid removal of carbon dioxide from solution to encourage carbonate precipitation (Ford & Pedley, 1996), whereas flowing water encourages turbulent carbon dioxide degassing, again encouraging carbonate precipitation (Ford & Pedley, 1996). Drivers behind periods of tufa formation in this now semiarid to arid basin were climatic, corresponding to periods of increased rainfall and reduced evapotranspiration as documented elsewhere in Saudi…”

Section: Surface Variability and Artifact Distribution In The Wadi mentioning

confidence: 99%

Paleolithic artifact deposits at Wadi Dabsa, Saudi Arabia: A multiscalar geoarchaeological approach to building an interpretative framework

et al. 2019

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Surface artifacts dominate the archaeological record of arid landscapes, particularly the Saharo‐Arabian belt, a pivotal region in dispersals out of Africa. Discarded by hominins, these artifacts are key to understanding past landscape use and dispersals, yet behavioral interpretation of present‐day artifact distributions cannot be carried out without understanding how geomorphological processes have controlled, and continue to control, artifact preservation, exposure and visibility at multiple scales. We employ a geoarchaeological approach to unraveling the formation of a surface assemblage of 2,970 Palaeolithic and later lithic artifacts at Wadi Dabsa, Saudi Arabia, the richest locality recorded to date in the southwestern Red Sea coastal region. Wadi Dabsa basin, within the volcanic Harrat Al Birk, contains extensive tufa deposits formed during wetter conditions. We employ regional landscape mapping and automatic classification of surface conditions using satellite imagery, field observations, local landform mapping, archaeological survey, excavation, and sedimentological analyses to develop a multiscalar model of landscape evolution and geomorphological controls acting on artifact distributions in the basin. The main artifact assemblage is identified as a palimpsest of activity, actively forming on a deflating surface, a model with significant implications for future study and interpretation of this, and other, surface artifact assemblages.

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“…In a functional sense, the actual parent material for the developing soil is not the basalt bedrock of the flow, but rather, the aeolian sediments added to the surface and incorporated into the vesicular A horizon directly beneath the stone pavement. A considerable amount of additional evidence supporting the accretionary model of pavement development based on investigations of other types of geological surfaces (e.g., cobbly to bouldery alluvial fan deposits) has appeared over the last two decades; Laity [60] and McFadden [61] provide comprehensive summaries of this body of work. Although there are geological settings where selective erosion (aeolian or fluvial) of fine materials may first be required to generate a lag of coarser clasts on the surface (e.g., see later section on Quartz pavements of the Knersvlakte), even in those situations, once such a surface lag is created, the dust-trapping effect of the surface clasts contributes to the accumulation of aeolian sediments and development of an underlying accretionary mantle beneath a stone pavement.…”

Section: Stone Pavementsmentioning

confidence: 99%

“…Behind the knife is the uppermost portion of a sequence of reddened Bt horizons; the colour is 7.5 YR 6/4. Stone pavements and their associated, underlying clast-free vesicular A horizons derived largely from the accretion of aeolian sediments occur on diverse substrates, including fan deposits and terraces of coarse gravelly to stony alluvium and pediments in arid regions throughout the world [60,[68][69][70][71][72]. Soils with the same kinds of clast-free vesicular A horizons beneath pavements have been described for arid regions of South Africa [15,73], and Ellis [74] mapped their overall geographic distribution in western South Africa.…”

Section: Stone Pavementsmentioning

confidence: 99%

Role of Aeolian Dust in Shaping Landscapes and Soils of Arid and Semi-Arid South Africa

2018

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The deposition of fine aeolian sediment profoundly influences the morphology of several different landscapes of the arid and semi-arid western portion of South Africa. Such landscapes and features include: (1) regularly-spaced mounds known as heuweltjies of the succulent Karoo region, (2) barren stone pavements in the more arid regions, and (3) hillslopes with smooth, curvilinear slope profiles that are mantled with coarse, stony colluvium. Investigations of each of these are presented, together with comparisons of similar features found within arid and semi-arid portions of Western North America. Recent findings suggest that the formation of the distinct, regularly-spaced heuweltjies involves a linked set of biological and physical processes. These include nutrient accumulation by termites and the production of dense vegetation patches, which, in turn, serve as a trap for aeolian sediments. Dust deposition is also responsible for the formation of stone pavements as demonstrated by research conducted principally in the Mojave Desert region of the United States. Mineralogical and geochronological studies have demonstrated that the stone clasts remain on the surface as fine aeolian sediments are translocated downward beneath the clasts resulting in a silt-rich soil horizon directly beneath the clasts. Pavements examined in South Africa have the same morphological features that can only be explained by the same process. The formation of soils on hillslopes mantled with stony colluvium are commonly viewed as having formed through the in-situ weathering of the stony colluvium. However, like pavements, mantles of coarse, stony colluvium are effective dust traps that provide the long-term stability required for advanced development of thick, fine-grained soils. This process contributes to the evolution of smooth, vegetated, curvilinear slope profiles. In each of these examples, the accumulation of dust has a profound influence, not only in soil formation, but also on the development of dominant landform characteristics. A greater awareness of these processes will contribute considerably to the growth of knowledge about soils and landscape development in the drylands of South Africa.

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Pavements and Stone Mantles

Cited by 13 publications

References 81 publications

Controls on and effects of armoring and vertical sorting in aeolian dune fields: A numerical simulation study

Controls on and effects of armoring and vertical sorting in aeolian dune fields: A numerical simulation study

Paleolithic artifact deposits at Wadi Dabsa, Saudi Arabia: A multiscalar geoarchaeological approach to building an interpretative framework

Role of Aeolian Dust in Shaping Landscapes and Soils of Arid and Semi-Arid South Africa

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