Quaternary soils and dust deposition in southern Nevada and California

Abstract

Eolian dust constitutes much of the pedogenic material in late Pleistocene and Holocene soils of many arid regions of the world. Comparison of the compositions and influx rates of modern dust with the eolian component of dated soils at 24 sites in southern Nevada and California yields information on (1) the composition and influx rate of dust in late Pleistocene and Holocene soils, (2) paleoclimate and its effects on the genesis of aridic soils, especially with regard to dustfall events, (3) the timing and relative contribution of dust from playa sources versus alluvial sources, and (4) the effects of accumulation of dust in soil horizons. The <2 mm fractions of A and B horizons of soils formed on gravelly alluvial-fan deposits in the study area are similar to modern dust in grain size, content of CaCO 3 and salt, major oxides, and clay mineralogy; thus, they are interpreted to consist largely of dust. The major-oxide compositions of the shallow soil horizons are nearly identical to that of the modern dust, but the compositions of progressively deeper horizons approach that of the parent material. The clay mineralogy of modern dust at a given site is similar to that of the Av horizons of nearby Holocene soils but is commonly different from the mineralogies of deeper soil horizons and of the Av horizons of nearby Pleistocene soils. These results are interpreted to indicate that dust both accumulates and is transformed in Av horizons with time. Changes in soil-accumulation rates provide insights into the interplay of paleoclimate, dust supply, and soil-forming processes. Modern dust-deposition rates are more than large enough to account for middle and late Holocene soil-accumulation rates at nearly all sites. However, the early Holocene soil-accumulation rates in areas near late Pleistocene pluvial lakes are much higher than modern rates and clearly indicate a dust-deflation and-deposition event that caused rapid formation of fine-grained shallow soil horizons on uppermost Pleistocene and lower Holocene deposits. We interpret late Pleistocene soil-accumulation rates to indicate that dust-deposition rates were low during this period but that increased effective moisture during the late Wisconsinan favored translocation of clay and CaCO 3 from near the surface to deeper in the soil profile. Prelate Pleistocene rates are very low in most areas, mainly due to a pedogenic threshold that was crossed when accumulations of silt, clay, and CaCO 3 began to inhibit the downward transport of eolian material, but in part due to erosion.

Impacts of interrelated biotic and abiotic processes during the past 125000 years of landscape evolution in the Northern Mojave Desert, Nevada, USA

“…Modern dust accumulation rates such as measured by Reheis et al (1995) in southern California and Nevada could be sufficient for the development of incipient Av horizons such as at Site 2. In addition, because the NTS was the principal location of nuclear testing (atmospheric and underground) by the US until 1992 (US Department of Energy (DOE), 2000), completely ruling out the addition of small amounts of aeolian deposition from testing is not possible.…”

“…For example, aeolian dust deposition constitutes much of the pedogenic material in Pleistocene and Holocene soils of the Mojave Desert and other arid regions of the world (Reheis et al, 1995). Incorporation of this dust into near surface soil horizons provides much of the water-holding capacity of aridic soils (e.g., McDonald et al, 1996;McFadden et al, 1998).…”

Aeolian dust in Colorado Plateau soils: Nutrient inputs and recent change in source

“…Although many different methods provide clear evidence for aeolian input into soils (4,6,8,9,11,13,17,18), ecosystem studies would benefit from rapid assessment of aeolian components in soils. Here we demonstrate that magnetic methods, which characterize the type and distribution of iron oxide minerals, can be applied to detect the presence of aeolian dust in young surficial sediments and soils over large arid-land areas.…”

“…M any studies have addressed the presence of aeolian dust in soils and surficial deposits in deserts to provide important geologic and ecologic information bearing on landscape dynamics (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16). From this body of work, we have improved understanding about: (i) current and past sources and flux of dust, hence changing conditions of dust emission; (ii) the genesis of desert soils; (iii) the influences of aeolian silt and clay on water-infiltration rates in soil; (iv) the evolution of desert surfaces (such as desert pavement) relevant to surface stability, as well as the distribution of surface and subsurface water; and (v) interrelations among aeolian dust, distribution of plants and soil crust, rain-water runoff, and productivity.…”

Desert pavement dynamics: numerical modeling and field‐based calibration

“…Eolian deposition rates also vary regionally as a function of distance from playa and fluvial sources as well as prevailing wind directions, but 0·2 cm/kyr is a reasonable value for Holocene deposition (Reheis et al, 1995). The S-shaped curve labeled by k represents the relationship between pavement-formation rate and epipedon thickness (Equation (3)) using h c = 5 cm and k max = 0·002 yr −1 .…”