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Paleosols occur in the Driftless Area of southwestern Wisconsin because this area escaped direct Pleistocene glaciation, allowing long-term loess and colluvium accumulation in selected settings. The most complete known depositional sequence at Oil City, Wisconsin, contains eight lithologic units with five paleosols, all with normal remanent magnetism (i.e., <780 ka). Previous work characterized the stratigraphy, pedology, micromorphology, and clay mineralogy of the section. We investigate chemical weathering of the 8–63 µm silt fraction using X-ray diffraction (XRD) and elemental geochemistry by portable X-ray fluorescence (pXRF). Elemental ratios TiO2/CaO, Zr/Sr, and Rb/Sr generally align with the pedological evidence of weathering. Mineral ratios plagioclase/quartz and K-feldspar/quartz display greater scatter and less certainty in interpretation. The paleosols with Bt horizons have ratios indicating greater weathering than the modern soil. The most weathered paleosol is formed in the unnamed fourth loess unit stratigraphically below the Loveland Member. The stratigraphic position and higher degree of weathering support correlation of the fourth loess with the Yarmouth Geosol and Crowley’s Ridge Silt of the Middle Mississippi valley. Geochemical indices by pXRF are more consistent with established lithologic breaks than mineralogy by XRD. Our results support the use of pXRF for stratigraphic and weathering studies of Quaternary sediments. [ABSTRACT FROM AUTHOR]

Soil morphology changes dramatically across the former transition from forest to grassland in the Midwestern U.S.A. That vegetation boundary shifted as a result of Holocene climatic change and fire suppression following Euroamerican settlement, but the timescale of soil response to those vegetation changes and the factors that influence it are poorly known. On steep colluvial slopes of southeastern Minnesota, Mollisols with thick, dark A horizons typically associated with grassland are found today under deciduous forest. Soils with much thinner and/or lighter-colored A horizons occur immediately up- and downslope of the forest-covered Mollisols. Most of the soils with thick A horizons are not in topographic settings found to favor organic matter accumulation in other landscapes. Principal component analysis highlights important axes of textural and mineralogical variation among horizons of these soils, often related to parent material properties. Soils with and without thick A horizons are separated along one principal component heavily loaded by high pH, reflecting the presence of dolomite fragments in the hillslope sediment that soils with thick, dark A horizons formed in. Stable C isotope analysis reveals that the Mollisols with thick, dark A horizons under forest had C input from vegetation with abundant C 4 grasses in the past. Public land survey data also indicate replacement of grassland or savanna by forest since 1854 on colluvial slopes where forest-covered Mollisols occur today. We propose that the soils with thick, dark A horizons under forest today reflect a lagged response to vegetation change, from grassland or savanna to closed forest. Their thick A horizons and some C 4 -derived organic matter may be preserved because dolomite weathering releases abundant Ca ++ and Mg ++ that favor aggregation and organic matter stabilization. Soils with thin A horizons just up- or downslope may also have formed partly under grasses, but have responded more quickly and/or more substantially to vegetation change. [ABSTRACT FROM AUTHOR]

Art and others from Berkeley joined the CERN NA49 experiment to prototype STAR technology. Together with Joseph Cerny and Earl Hyde, he used the Bevatron proton beam and novel electronic detectors to discover numerous nuclear isotopes with an extreme imbalance of neutrons and protons, notably lithium-11. , a groundbreaker in exploring extreme states of nuclear matter, died peacefully in his home in Berkeley, California, on 30 June 2021. [Extracted from the article]

Abstract: Loess is an important Quaternary sediment that records evidence of landscape instability in sediment source areas and landscape stability in accumulation areas. In Wisconsin, USA loess mantles glaciogenic deposits dating to the last glaciation, but the landscape distribution and effects of the loess mantle on soil formation have received very little attention. This study investigates the influence of glacial landforms on the spatial pattern of loess thickness and how the presence or absence of a loess mantle overlying glaciogenic sediments has influenced soil profile morphology, namely thickness and nature of horizonation. Loess thickness follows systematic trends along hillslopes, with slope percentage explaining most loess thickness variation between summit and backslope positions. In the presence of a loess mantle, solum and Bt horizon thickness is proportional to the thickness of the loess mantle in well-drained profiles. In the absence of a loess mantle, landscape and sediment characteristics that control permeability and water throughflow appear to be the most important determinants of profile characteristics. The loess mantle modulates soil formation above the lithologic discontinuity with sandy calcareous glacial sediments by controlling soil water behavior and having physical and chemical characteristics conducive to transformation to soil genetic horizons. [Copyright &y& Elsevier]

Abstract: Loess has been recognized on the glacial land surface of the Green Bay Lobe for over 100yr, but no systematic explanation of the source of the loess has been advanced. Intriguingly, the loess on the Green Bay Lobe land surface is thicker than predicted by regional thinning trends from the Mississippi Valley and is geographically separated from much loess of southwest Wisconsin by a sandy region devoid of loess. Mapping based on soil survey interpretation indicates that the loess occurs above an escarpment marking the eastern end of the sandy loess-free region. Particle size fining trends demonstrate that the loess was transported by northwesterly winds. Clay mineralogy of the Green Bay Lobe loess is distinctly different than glaciogenic sediments and matches loess of the Mississippi Valley, indicating a regional source and long distance transport of the loess. We propose the loess was transported from the regional source along a surface of transport produced by migration of eolian sand through low-relief landscapes including the glacial Lake Wisconsin basin. Eolian sand migration caused repeated entrainment of dust leading to east-southeastward transport. The loess accumulated above an escarpment that limited sand mobility and re-entrainment of loess beyond this topographic barrier. [Copyright &y& Elsevier]

Abstract: The Farmdale–Sangamon Geosol pedocomplex consists of the Sangamon Geosol and the overlying Farmdale Geosol, which form the most extensive terrestrial record of the last interglacial to glacial transition in the Midwest United States. The geosol complex formed for upwards of 100 ka, extending from the end of MIS 6 through 4 for the Sangamon Geosol, then the Farmdale Geosol for during a brief episode at the end of MIS 3 following slow accumulation and pedogenic modification of eolian silt deposited on top of the Sangamon Geosol. Our study site consists of a buried paleo-hillslope transect that forms a catena, enabling evaluation of slope effects on interglacial-scale soil formation. The Sangamon Geosol is formed in calcareous and illitic glaciogenic sediment. Along the catena the Sangamon Geosol profiles display some morphological changes, namely in terms of colors that we interpret as indicators of differences in drainage. Most thickness and horizonation characteristics are similar all along the transect, with intact upper sola horizons (AE and E horizons) that overlie clay-enriched Bt horizons. The Bt horizons contain abundant clay that exists as illuvial clay coatings, matrix infills, and as mosaic-speckled domains. The clay originated both by in situ weathering and through illuviation from the clay depleted upper sola. Slope does not appear to affect Bt characteristics beyond redder hues of the matrix and clay coatings in the upper slope position. With depth, effects of carbonate leaching and infilling of clay in the matrix decrease and clay coatings are restricted to walls of voids adjacent to aggregates. Clay mineralogy shows illite depletion, but no interstratified kaolinite-expandable minerals, indicating the degree of weathering is not as great as is typical of Sangamon Geosol profiles formed in loess or in glaciogenic sediment of the central Illinois type area. Clay mineralogy is also stratified with depth, coincident with particle size, which probably indicates sorting of layers of illitic dolomite and shale. Variation of horizon and profile characteristics appears to largely be a function of particle size variability and stratification than topographic position in the catena. The influence of hillslope position on soil redistribution during formation of the Sangamon Geosol appears negligible given the uniformity of upper solum horizon thickness and sandy particle size characteristics, so we conclude that a bioturbation and rainwash origin of the upper solum and the texture contrast in these profiles is not the best process model explanation. We suggest that the base-rich nature of these soils led to ecosystem characteristics that discouraged erosion and encouraged infiltration and a lessivage-type origin of the texture contrast. No convincing evidence of MIS 6 through MIS 4 loess occurs at this site. The Farmdale Geosol formed in the Robein Silt, which is Roxana Silt (MIS 3 loess) that was redistributed downslope. The Robein Silt is thicker and finer in the topographic low and indicates the cooler and forested environmental conditions during MIS 3 were conducive to downslope movement of soil and also produced greater differences in drainage-induced soil morphological changes in the Farmdale Geosol. [Copyright &y& Elsevier]

Abstract: The amount and vertical distribution of soil organic carbon (SOC) storage is primarily a function of vegetation type and climate, with influence from soil and landscape properties and human activities. The influence of dust aggradation on landscapes during the Holocene has largely been ignored as a factor in long-term SOC storage. Dust aggradation is important to soil horizonation and C sequestration since the dust deposit buries the landscape and increases solum thickness. Mollisols on loess-covered upland tables in central Nebraska have aggraded throughout the Holocene as Bignell Loess accumulated above the late Pleistocene Brady Soil. In the loess tablelands, the thickness of mollic colors, A horizon properties, and SOC storage all decrease with distance from the source of Bignell Loess, which is along a gradient of increasing precipitation. For example, along a 140-km transect of decreasing Bignell Loess thickness and increasing rainfall, total thickness of A horizons decreases by 70 cm and the thickness of mollic colors decreases by 93 cm. Total SOC storage decreases from 17.5 to 7.7 kg/m2. A portion of the SOC in subsurface horizons of modern soils was likely inherited from the Brady Soil, which probably formed in a climate different than the present, suggesting that SOC storage is probably not in equilibrium with modern climatic conditions. Dust aggradation on a biologically active surface in a steppe environment has affected horizonation, pigmentation and SOC storage in central Great Plains loess-derived Mollisols. [Copyright &y& Elsevier]

Loess grain size data used to infer transport direction or wind strength are generally derived from vigorously disaggregated samples. However, these data may not adequately represent the effective particle size distribution during loess transport, if the transported dust contained aggregates of fine-grained material. Thin sections of minimally altered C and BC horizons in the late Pleistocene Peoria Loess of Nebraska, USA, indicate the presence of aggregates with diameters of 30–1000 μm. The larger aggregates (>250 μm) are unlikely to have been transported, and are interpreted as the result of soil faunal activity and other pedogenic processes after deposition. Aggregates smaller than 250 μm could have a similar origin, but laser diffraction particle size analysis suggests that many are sedimentary particles. Comparison of minimally and fully dispersed particle size distributions from each sampling site was used to estimate the modal diameter of aggregates. The aggregate modal diameter becomes finer with decreasing loess thickness, representing increasing distance from the source. A similar trend was observed in the modal diameter of fully dispersed particle size distributions, which represents the mode of sand and silt transported as individual grains. We interpret both trends as the result of sorting during transport, supporting the interpretation that many of the aggregates were transported rather than formed in place. Aggregate content appears to increase with distance from the source, explaining a much more rapid downwind increase in clay content than would be expected if clay were transported as particles smaller than 2 μm diameter. Although the Peoria Loess of Nebraska contains sedimentary aggregates, many of the coarse silt and sand grains in this loess were transported as primary particles, were thoroughly exposed to sunlight and are potentially well suited for luminescence dating. [Copyright &y& Elsevier]

This paper reexamines the stratigraphy, sources, and paleoclimatic significance of Holocene Bignell Loess in the central Great Plains. A broadly similar sequence of loess depositional units and paleosols was observed in thick Bignell Loess sections up to 300 km apart, suggesting that these sections record major regional changes in the balance between dust deposition and pedogenesis. New optical ages, together with previously reported radiocarbon ages, indicate Bignell Loess deposition began 9000–11,000 yr ago and continued into the late Holocene; some Bignell Loess is <1000 yr old. There is little evidence that Holocene Loess was derived from flood plain sources, as previously proposed. Instead, thick Bignell Loess occurs mainly near the downwind margins of inactive dune fields, particularly atop escarpments facing the dunes. Thus, the immediate loess source was dust produced when the dunes were active. Previous work indicates that widespread episodes of dune activity are likely to have resulted from drier-than-present climatic conditions. The regionally coherent stratigraphy of Bignell Loess can be interpreted as a near-continuous record of climatically driven variation in dune field activity throughout the Holocene. [Copyright &y& Elsevier]

Presents equations for predicting soil organic carbon using loss-on-ignition for North Central U.S. soils. Differences between predictive equations for individual major land resource areas; Recommendation to develop predictive equations for individual soil-geographic regions.

Investigates the relation between seasonal saturation and redoximorphic features of pedons in Valdosta, Georgia. Findings on pedons experiencing a seasonal high water table; Indication of seasonal saturation by grat matrix; Correlation between iron depletions and saturation.

Investigates elemental mass fluxes associated with soil development in late Wisconsinan loess in Illinois and Minnesota. Study of three forest soils formed in Peoria Silt; Proposed dust influx complicating efforts to quantify weathering process in the soils; Far-traveled dust influx occurring simulteneously with final phase of local loess deposition.

Research on soil genesis often assumes a "top-down" model, in which the soil profile develops downward from a stable land surface. This model is inapplicable to upland landscapes affected by frequent dust deposition, where soils grow upward as they develop. On the central Great Plains, late Quaternary loess sections proximal to immediate source areas contain the Brady Soil, a prominent marker separating late Pleistocene Peoria Loess from Holocene Bignell Loess. Farther from immediate dust source areas, the Brady Soil and Bignell Loess are not recognizable in the field. On loess tablelands in these distal regions, surface soils typically contain a prominent, clay-rich B horizon below a thick silty A horizon. Assuming top-down pedogenesis, this could be interpreted as a postglacial soil profile formed in Peoria Loess, with the B horizon produced by weathering and clay illuviation. We propose a strikingly different interpretation, in which the upper B horizon at distal sites is the Brady Soil A horizon that has been transformed by burial, organic matter loss, and modern subsoil structure formation processes. The overlying modern A horizon represents Bignell Loess. Properties of the Brady Soil at proximal sites (a distinctive burrowed zone, high clay content and TiO2/ZrO2, and low volcanic glass content) can be traced to the B horizon in distal soils. A decrease in smectite abundance above the Brady Soil at proximal sites is identifiable at the top of the clay-rich B horizon in distal soils. The spatial variation of clay content in loess and soil horizons is best explained by eolian sedimentation patterns. The higher clay content in the Brady Soil and distal B horizons defines a fine-grained zone that represents a late phase of Peoria Loess accumulation. Evidence of chemical weathering is minimal, and illuvial clay is rare to absent in the clay-rich B horizons. Illuvial clay does often occur deep in the solum and is related to the depth below the top of the Brady Soil. The depth of occurrence of illuvial clay is not related to modern climate parameters, although depth to secondary carbonate appears to be in equilibrium with modern climate. Upland soils in the central Great Plains are composite soils; their properties are the result of a pedosedimentary history linked to regional climate change that has influenced sedimentation and pedogenesis since the late Pleistocene. [ABSTRACT FROM AUTHOR]

Abstract: Various lines of evidence support conflicting interpretations of the timing, abruptness, and nature of climate change in the Great Plains during the Pleistocene–Holocene transition. Loess deposits and paleosols on both the central and northern Great Plains provide a valuable record that can help address these issues. A synthesis of new and previously reported optical and radiocarbon ages indicates that the Brady Soil, which marks the boundary between late Pleistocene Peoria Loess and Holocene Bignell Loess, began forming after a reduction in the rate of Peoria Loess accumulation that most likely occurred between 13.5 and 15cal ka. Brady Soil formation spanned all or part of the Bølling-Allerød episode (approximately 14.7–12.9cal ka) and all of the Younger Dryas episode (12.9–11.5cal ka) and extended at least 1000 years beyond the end of the Younger Dryas. The Brady Soil was buried by Bignell Loess sedimentation beginning around 10.5–9cal ka, and continuing episodically through the Holocene. Evidence for a brief increase in loess influx during the Younger Dryas is noteworthy but very limited. Most late Quaternary loess accumulation in the central Great Plains was nonglacigenic and was under relatively direct climatic control. Thus, Brady Soil formation records climatic conditions that minimized eolian activity and allowed effective pedogenesis, probably through relatively high effective moisture. Optical dating of loess in North Dakota supports correlation of the Leonard Paleosol on the northern Great Plains with the Brady Soil. Thick loess in North Dakota was primarily derived from the Missouri River floodplain; thus, its stratigraphy may in part reflect glacial influence on the Missouri River. Nonetheless, the persistence of minimal loess accumulation and soil formation until 10cal ka at our North Dakota study site is best explained by a prolonged interval of high effective moisture correlative with the conditions that favored Brady Soil formation. Burial of both the Brady Soil and the Leonard Paleosol by renewed loess influx probably represents eolian system response that occurred when gradual change toward a drier climate eventually crossed the threshold for eolian activity. Overall, the loess–paleosol sequences of the central and northern Great Plains record a broad peak of high effective moisture across the late Pleistocene to Holocene boundary, rather than well-defined climatic episodes corresponding to the Bølling-Allerød and Younger Dryas episodes in the North Atlantic region. [Copyright &y& Elsevier]