Eolian Dust Accumulation Research Articles

Late Cenozoic Eolian deposition in the North Pacific: Asian drying, Tibetan uplift, and cooling of the northern hemisphere

A newly constructed record of eolian dust accumulation from the central North Pacific shows that dust deposition increased by an order of magnitude quite rapidly at 3.6 Ma. We associate this sudden drying with the uplift of at least the northern portion of the Tibetan Plateau, shutting off the Indian Ocean moisture source to central and western China. This ten‐fold increase in atmospheric dust loading appears to be associated with the 1‐m.y.‐long shift toward heavy δ18O values that occurred at 3.6–2.6 Ma. The dust grain‐size record of wind intensity begins its late Cenozoic coarsening a million years before the drying event, at ∼4.5 Ma. The northern hemisphere cooling that results in intensification of the subpolar westerly winds may have as its ultimate cause the drawdown of atmospheric CO2 in the latest Miocene and the early Pliocene closing of the Panamanian Seaway.

Magnetostratigraphy and paleoclimatic interpretation of a continuous 7.2 Ma Late Cenozoic Eolian sediments from the Chinese Loess Plateau

An almost 300m thick eolian sequence of Late Cenozoic sediments, which includes 162.5m of Quaternary loess‐paleosols and 126m of Late Tertiary eolian Red Clay from the central part of the Chinese Loess Plateau, was investigated to determine the magnetostratigraphy. The results show that eolian dust accumulation, and by inference the related East Asia paleomonsoon, had begun by 7.2Ma. As paleomonsoon are largely controlled by the Tibetan Plateau, this implies that the Plateau had reached some critical elevation by 7.2Ma. The section also documents a rapid increase in eolian dust accumulation in the Late Cenozoic at 3.2Ma that is probably due to the influence of global ice volume on the East Asian monsoon.

Magnetostratigraphy and palaeoclimate of Red Clay sequences from Chinese Loess Plateau

Two Red Clay profiles near Xi’an and Xifeng were investigated in an attempt to determine magnetostratigraphic and palaeoclimatic records. The results show that aeolian dust accumulation and the related East Asia palaeomonsoon system had begun by 6.5 Ma, and it is deduced that the Tibetan Plateau had reached a significant elevation at that time. The late Tertiary palaeoclimatic history of the Red Clay as reflected by magnetic susceptibility is reconstructed during the period of 6.5–2.5 Ma. Stepwise increase in susceptibility of aeolian dust accumulation appears to have a close correlation to the uplift processes of the Tibetan Plateau. The remarkable increase of aeolian dust accumulation at 3.2 Ma appears to be due to the influence of global ice volume on the East Asia monsoon. Palaeomonsoon variation during the late Tertiary as recorded in the Red Clay sequences from the Chinese Loess Plateau can be regarded as the product of a number of interacting factors, such as uplift of the Tibetan Plateau, solar radiation, global ice volume, etc.

Temporal and spatial distributions of dust and its deposition to the China Sea

Atmospheric concentrations of aluminium, an indicator of dust substances, have been determined in a set of high-volume aerosol particle samples collected at different locations over continental China and over the China Sea. High concentrations of dust were observed in northern continental China, and at certain locations such as Beijing dust may include an anthropogenic fraction. The mass particle-size distributions of dust varied depending on its distance from source regions, with the mass median diameter for Al of ~1.6-5.9 μm at Beijing in northern China and ~ 1.9 μm over off-shore areas of the East China Sea. Model-predicted mean dry deposition velocities of dust particles are from 1.4 to 4.8 cm s-1 over northern continental China and from 1.4 to 2.1 cm s-1 over the China Sea. Atmospheric deposition models have been applied to estimate the atmospheric fluxes and deposition of dust at different locations. The estimated atmospheric flux of dust at Xi’an of the Loess Plateau is 25 (4.9 to 44) g m-2 mo-1 which is the highest among the regions we studied. The estimated present-day dust flux is comparable to the late quaternary records of eolian dust accumulation at this site. The total atmospheric deposition of dust to the China Sea is 67 Tg yr-1, accounting for 14% of the total atmospheric deposition of dust to the entire North Pacific. With such a high deposition rate, Asian dust may play an important rôle in biogeochemical cycles of trace substances in the Asia/North Pacific region.

Paleoenvironmental history of post-Toya Ash tephric deposits and paleosols at Iwate Volcano, Japan, using aeolian dust content and phytolith composition

Abstract Physicochemical, mineralogical, and geochemical analyses of post-Toya Ash (90–130 ka) tephric and aeolian deposits at the foot of Iwate volcano, northeastern Japan, revealed the accumulation of deposits of long-range aeolian dust transported from the Asian continent and interstratified with the tephric deposits. Oxygen isotopic ratios of quartz in the 1–10μm fractions from two paleosols formed in the aeolian units (Shibutami cracked layers) are +16.2 and +17.0‰, consistent with this fine-grained quartz being of an aeolian origin. The accumulation of Asian aeolian dust onto tephric deposits in northeastern Japan was dominant in the cold stages of the Last Glacial period (20–34 ka and 50–70 ka). We determined the changes in vegetation and climate by using opal phytolith distribution in the tephra and aeolian deposits and associated paleosols. Similarly, we interpreted the paleoenvironmental history of the tephric deposits by relating the vegetation history to the dust flux and fossil periglacial phenomena (i.e. involution) observed on tephra beds. The paleoclimate sequence obtained coincides closely with the marine oxygen isotope curves, indicating that opal phytolith analysis is useful in determining the Interglacial/Glacial-cycle recorded in aeolian and tephric deposits.

Ice-Volume Forcing of East Asian Winter Monsoon Variations in the Past 800,000 Years

Particle-size measurements of some typical loess-soil samples taken in different localities of the Chinese Loess Plateau demonstrate that the grain size ratio of <2 μm/>10 μm (%) can be used as an indicator of variations in intensity of the East Asian winter monsoon winds. Grain-size curves of the Baoji and Weinan sections show that this proxy indicator is very sensitive to loess-soil alterations. Analytical results also suggest that during soil-forming periods, eolian dust accumulation was still substantial and, hence, loess deposition can be regarded as a nearly continuous process during the Quaternary period. In this study we compared the Baoji grain-size time series with the SPECMAP marine isotope record with the objective of elucidating the dynamic linkage between changes in global ice volume and the winter monsoon circulation. Both records show good agreement at both time and frequency domains. In particular, the winter monsoon variations are also dominated by a 100,000 yr period over the past 800,000 yr. It is thus inferred that direct local insolation forcing could be less important in driving the East Asian winter monsoon variability, and, alternatively, variations in glacial-age boundary conditions may have played a key role in modulating and pacing its strength and timing.

Field experiments of aeolian dust accumulation on rock fragment substrata

ABSTRACTThe effect of rock fragments and rock fragment cover on the accumulation of airborne dust was examined in a long‐term field experiment in the Negev desert of Israel. Four parameters were studied: pebble eccentricity, pebble size, pebble flattening and cover density. The effect of these parameters on the accumulation of dust on the pebbles, on the accumulation of dust between and underneath the pebbles, and on total dust accumulation (pebbles+interpebble space) was measured separately. Accumulation on the pebbles increased as the pebbles became larger, less flattened and more elongated, and as cover density increased. Accumulation between and underneath the pebbles increased as the pebbles became smaller, more flattened and more elongated, and as cover density increased (although the accumulation area available became smaller). Total dust accumulation increased as the pebbles became smaller, more flattened and more elongated, and as cover density increased.Rock fragments act as a dust trap as dust accumulation on pebble‐covered surfaces is several tens of times larger than dust accumulation on similar but pebble‐free surfaces. However, less than 20% of the initially settled dust is protected from further erosion.In the Negev desert, dust erosion by wind is of the order of 10 times larger than dust erosion by water. The rate of long‐term dust accumulation in the Negev is of the order of 15–30 g.m−2.yr−1. This is considerably lower than the rates proposed elsewhere in the literature, which are based upon over optimistic dust retainment percentages.

Preservation and paleoclimatic significance of eolian dust in the Ancestral Rocky Mountains province

Upper Paleozoic (Pennsylvanian-Permian) silty strata of the northern Pedregosa basin (southern Ancestral Rocky Mountains province) exhibit distinctive features that suggest origin of the silt as eolian dust prior to deposition in marine environments. Studies of mechanisms controlling modern eolian dust accumulation imply that combined marginal-marine-epeiric-sea environments constitute an ideal sink for eolian dust. Accordingly, Pedregosa siltstones may reflect the prevalent mode of eolian dust preservation downwind from coeval ergs, and significant volumes of eolian dust may be preserved within analogous epeiric strata. Because eolian dust reflects conditions of aridity and windiness, it bears on paleoclimatic and paleogeographic reconstructions. Recent studies within several basins of the Ancestral Rocky Mountains suggest an eolian derivation for many siltstones and thus corroborate inferences of increasing aridity and concomitant monsoonal conditions for western Pangea. Further regional analysis may provide valuable insights for refining concepts of the zonal to monsoonal transition that accompanied Pangean assembly.

Spatial soil variability in the Cajon Pass chronosequence: implications for the use of soils as a geochronological tool

Spatial variation of soil properties on a single geomorphic surface has a significant influence on surface correlations and age determinations made on the basis of soil properties. Few chronosequence studies have been based on a sufficient number of soils to evaluate the influence of soil variability. We described and evaluate 35 soils on four terrace surfaces which constitute part of a previously described, well-dated soil chronosequence in Cajon Pass in southern California. Soils were described on both bar and swale sites, removed from the influence of deposition adjacent slopes. The influence of eolian silt on the rate of pedogenesis in Cajon Pass indicates that this sequence of soils cannot be considered a chronosequence in the strict sense of the term. Furthermore, the evidence for a pedogenic threshold in these soils indicates that the soils do not develop monotonically with time and that soil development cannot be defined by a continuous univariant chronofunction. The discrete nature of the data from a chronosequence and the complex nature of soil development are better analyzed by multivariate statistical procedures. Systematic variation in soil properties between soils from bar sites and soils from swale sites is Attributed to geomorphic processes which affect either the rate or duration of eolian dust accumulation. Soils from bar sites were less variable and generally less strongly developed that soils from swale sites from the same surface. The degree of variation of soil properties determined for a given landscape position on a surface is sufficient to raise questions concerning the usefulness of chronofunctions for determining the nature of time-dependent pedogenic changes and for providing numerical age determinations. Multivariate statistical methods were used to differentiate among soils developed on three surfaces which differ in age by only 1500 years.

Metal enrichment in bauxites by deposition of chemically mature aeolian dust

Mass-balance equations applied to chemical analyses of a bauxite weathering profile in Western Australia show quantitatively that the ore-grade enrichment of aluminium is due to accumulation of aeolian dust derived elsewhere from chemically mature soils. This finding challenges the prevalent view of bauxite genesis by simple in situ residual enrichment and suggests that regional dust trajectories may serve as a genetic link between laterites, bauxites, heavy mineral beach sands, and clay-enriched marine sediments.

The Influence of Eolian Dust on the Genesis of Alpine Soils in the Front Range, Colorado

AbstractThe chemical and mineralogical properties of the soils in an alpine watershed, Front Range, CO, were studied to assess the sensitivity of the soil environment to acid deposition. Field and laboratory analyses indicated that properties of surface horizons were heavily influenced by eolian dust accumulation whereas the subsurface horizons were mainly derived from local bedrock. Surface and subsurface horizons differed in texture, bulk density, pH, CEC, exchangeable cations, and clay and silt mineralogy. A discriminant analysis based on these parameters proved useful for confirming lithologic differences between the surface (alpine loess) and subsurface horizons (bedrock residua). The alpine environment in the Front Range, which is naturally acidic and therefore very susceptible to acid deposition, has been affected by wind‐blown calcite that has raised the pH of surface horizons. Such natural liming presumably increases the ability of the alpine soils to buffer acid deposition.

Soil chronosequences in Israel

Chronosequences of Israel soils are summarized. Soil development in the coastal plain is related to the time of the dune deposits while those of the inland valley is related to the formation of the sedimentological terraces. Soil development in the mountains is related to the features and stability of the slope. The properties of young soils resemble those of the parent material. With advancing development the soils are affected by various processes, among them also the accretion of aeolian dust. Leaching is significant already at early stages; in some cases like Hamra and Terra-rossa soils the leaching stage is more advanced in earlier stages than in the final stage of soil development. In advanced stages of soil development the effect of the underlying rock on soil properties is reduced. At the final stage soils on moderate relief in the same climatic zone on different bedrocks resemble each other. This is attributed mainly to the effect of the aeolian dust accretion. The final stage of soil development on moderate relief consists of Grumusols in the northern parts of Israel, grumic dark Brown soils in the semi-arid parts of central Israel, loessial light Brown clay loam and loessial Serozems in the arid parts of the northern Negev and Regs in the extremely arid areas of the Southern Negev and Sinai. Petrocalcic horizons are developed on slopes and terraces where the rate of soil erosion equals that of accumulation of aeolian dust. The formation of petrogypsic horizons in the extremely arid zones is restricted to areas where erosion is negligible. The final stages of soil development exhibit a clear climatic zonality. This zonality differs from the soil zonality in the USSR and the USA due to the special features of dust accretion on the soils of Israel.

Soil chronosequences in Israel

Chronosequences of Israel soils are summarized. Soil development in the coastal plain is related to the time of the dune deposits while those of the inland valley is related to the formation of the sedimentological terraces. Soil development in the mountains is related to the features and stability of the slope. The properties of young soils resemble those of the parent material. With advancing development the soils are affected by various processes, among them also the accretion of aeolian dust. Leaching is significant already at early stages; in some cases like Hamra and Terra-rossa soils the leaching stage is more advanced in earlier stages than in the final stage of soil development. In advanced stages of soil development the effect of the underlying rock on soil properties is reduced. At the final stage soils on moderate relief in the same climatic zone on different bedrocks resemble each other. This is attributed mainly to the effect of the aeolian dust accretion. The final stage of soil development on moderate relief consists of Grumusols in the northern parts of Israel, grumic dark Brown soils in the semi-arid parts of central Israel, loessial light Brown clay loam and loessial Serozems in the arid parts of the northern Negev and Regs in the extremely arid areas of the Southern Negev and Sinai. Petrocalcic horizons are developed on slopes and terraces where the rate of soil erosion equals that of accumulation of aeolian dust. The formation of pertrogypsic horizons in the extremely arid zones is restricted to areas where erosion is negligible. The final stages of soil development exhibit a clear climatic zonality. This zonality differs from the soil zonality in the USSR and the USA due to the special features of dust accretion on the soils of Israel.

Mineralogical Analysis of Clays in Soils Developed from Basalts in Australia

AbstractClay mineralogical analyses were made of red soils and black soils developed from southern Victoria, Australia. The clays of the black soils are dominantly montmorillonite (39%) and vermiculite (16%) but have an average siliceous allophane content of 17%. The clays of the red soils are dominantly kaolinite and halloysite (26%) and chlorite (30%) but have an average halloysitic allophane content of 21%. Two to eight per cent of mica and quartz occur in both. A longer period of eolian dust accumulation and concurrent weathering and soil development have occurred in the red soils than in the black soils since the last cycle of geological erosion. A simple chemical method was used for the estimation of allophane (amorphous alumina, silica, and iron oxide with water) and kaolinite plus halloysite. After selective dissolution of allophane, free Al(OH)3, and amorphous SiO2 during 2.5 min of boiling in 0.5N KOH solution, the residue is subjected to heat treatment at 550°C to dehydroxylate the kaolinite and halloysite. This is followed by another 2.5 min dissolution treatment in 0.5N KOH and a further deferration with dithionite. Some iron‐rich montmorillonitesaponite (smectite) and vermiculite are also dehydroxylated on heating and subsequently are partially dissolved in the KOH. The kaolinite and halloysite constituents were then calculated.

Preliminary Report on the Leonard Rockshelter Site Pershing County, Nevada

In september, 1949, while in west central Nevada for the purpose of collecting vegetal materials from the lowermost cultural levels of Lovelock cave (Loud and Harrington, 1929) to be used for radiocarbon dating, the author revisited an open rockshelter site some six miles up the valley from Lovelock cave. The site, since named Leonard rockshelter (site 26- Pe-14) after Zenas Leonard who in 1833 traversed the Humbolt Sink area as a member of the Walker expedition (Leonard, 1904), is not referred to by Loud and Harrington. It is the same site from which, in 1936, Thomas Derby mined bat guano and recovered artifacts described in a brief article (Heizer, 1938). The bat guano formed a layer two to three feet thick lying on ancient gravels of Lake Lahontan and beneath a thick accumulation of aeolian dust and rockfall.