Based on calibrated radiocarbon ages of terrestrial gastropod shells (Succineidae, Discus, Stenotrema, Webbhelix), the chronology of Peoria Silt (loess) deposition in the Central Lowlands is updated. These taxa provide reliable ages (within ~0.2 ka), based on historical shell dating, shell-organic age comparisons, and stratigraphic consistency. A compilation of 53 new and 36 published Peoria Silt shell ages (calibrated), from 12 localities, date from 30.0 to 17.4 ka. Proximal (fossiliferous) loess from 10 sections had mean loess accumulation rates of 0.6–2.2 mm/yr. Study sites along the upper Mississippi, Illinois, to mid-Mississippi, and Ohio-Wabash Valleys suggest Peoria loess accumulated from ~27 to 15 ka, ~29 to 18 ka, and ~30 to 18 ka, respectively. The cessation age for Peoria Silt, based on surface extrapolations, is ~1–6 ka earlier than some prior Illinois estimates, even assuming slower loess accumulation in the modern solum. Younger loess in northwestern Illinois likely reflects, in part, Superior and Des Moines Lobe glacial-meltwater sediment, and Iowan Erosion Surface inputs to the upper Mississippi Valley, after the Lake Michigan Lobe receded. Furthermore, stronger winds, drier conditions, and reduced vegetation cover in valley deflation areas may have favored higher accumulation rates and later loess deposition in northwestern relative to southeastern areas.

Lynchets, often the defining component of historic agricultural landscapes in northern Europe, are generally associated with soft-limestone geologies and are particularly well developed on loess-mantled landscapes. To understand their formation and chronology, the authors present their geoarchaeological analyses of lynchet soils and loess deposits at Blick Mead and Charlton Forest in southern England, and Sint Martens-Voeren in Belgium. The lynchets date from the late prehistoric to the medieval periods and were constructed by plough action at the English sites, and by both cut-and-fill and ploughing in Belgium. This has resulted in the preservation of highly fertile loessic soils across chalk slopes, lost elsewhere. Although each example is associated with local/regional agricultural histories, the lynchets’ effective soil-retention capacities allowed them to survive as important heritage features with environmental benefits over millennia.

The literature reports that freezing of aqueous aluminosilicate clay suspensions can produce clay aggregates that disperse with agitation. Our experiments indicate that colloidal suspensions extracted from north Idaho loess soils (Boralfs), when frozen, form silt- and sand-sized agglomerates that resist dispersion with agitation. XRD and TEM analyses showed that colloids are dominantly halloysite between 0.10 to 0.30 μm in diameter. The colloidal halloysite has anomalously high mole ratios of Si/Al and a high Fe content. Freeze-produced agglomerates are light yellow to yellowish-brown in color, occur in the form of plates, wedges, cuspates, or laths, and often exhibit uniform optical properties, suggesting a crystalline product. Selected area electron diffraction, however, indicates that the agglomerates are polycrystalline. With proper orientation, agglomerates produce acute bisectrix interference figures that are optically negative with variable 2V, generally <30°. XRD analyses and IR spectra imply that the agglomerates are halloysite. Measured optical properties, however, are difFerent than those reported for halloysite and may be affected by the high Fe content and polycrystalline nature of the agglomerates. Grains, exhibiting similar optical properties as laboratory-produced agglomerates, are a minor proportion of the very-fine sand fraction in some horizons of the soils studied. Freeze-aided agglomeration of colloidal material may be an important process in temperate climates. It may be overlooked because of particle destruction by soil pretreatments or morphological order and/or optical similarity to some micaceous minerals.

Situated at the southernmost limits of the late Pleistocene Eurasian permafrost zone, the loess–paleosol sequences of the Lower Volga region contain numerous traces of cryogenesis. Cryogenic features are represented by thin vertical wedges in loess and paleosols, and involutions and wedges in alluvial deposits. Here we describe and interpret four stages of cryogenesis during the late Pleistocene, based on analysis of cryogenic structure morphology, morphoscopy of quartz grains, and micromorphology of subaerial sediments, in addition to calculation of the Cryogenic Weathering Index and a new luminescence chronology derived from published ages. These stages differ in type and distribution of cryostructures and formed in different paleogeographic conditions. Stage I, dated 95–90 ka (Marine Isotope Stage [MIS] 5b), is characterized by the existence of continuous permafrost in northern part of the Lower Volga valley. Stage II (75–70 ka, MIS 5a/MIS 4) is characterized by dry and cold conditions and widespread permafrost. During stage III (52–45 ka, MIS 3b/c), the permafrost was thin and of sporadic distribution. Stage IV (37–35 ka, MIS 3a) is characterized by thin and rare sporadic permafrost. The processes of cryogenic transformation of sediments in the region during these stages took place under both permafrost and seasonal frost conditions. The results obtained significantly improve current understanding of the extent of the permafrost in the south of the East European Plain during the late Pleistocene.

The Holocene is a critical period for understanding the East Asian monsoon system (EAM) over long timescales, but high-precision dating and high-resolution records from the Holocene epoch at monsoonal margins of East Asia are lacking. Here, on the basis of closely spaced radiocarbon and optically stimulated luminescence dating results obtained from a typical loess–paleosol sequence on the northern Chinese Loess Plateau (CLP), we provide an independent age-based, high-resolution depositional record of East Asian summer (EASM) and winter monsoons (EAWM) variations over the past ~14 ka. We find that both the EASM and EAWM simultaneously strengthened sometime during the Holocene optimum (~7–5 ka BP), with greater seasonality, and weakened during the Late Holocene. These findings are counterintuitive to our understanding of the EAM variations based on loess records at suborbital scales during interglacial periods, providing an alternative scenario of the monsoon system evolution. We postulate that high-latitude forcing and surface feedbacks, such as vegetation change, have modulated the EAM variations during the Holocene warmth.

Fe-reducing micro-organisms can change the oxidation state of structural Fe in clay minerals. The interactions with complex clays and clay minerals in natural materials remain poorly understood, however. The objective of this study was to determine if Fe(III) in loess was available as an electron acceptor and to study subsequent mineralogical changes. The loess samples were collected from St. Louis (Peoria), Missouri, USA, and Huanxia (HX) and Yanchang (YCH), in the Shanxi Province of China. The total Fe concentrations for the three samples was 1.69, 2.76, and 3.29 wt.%, respectively, and Fe(III) content was 0.48, 0.69, and 1.27 wt.%, respectively. All unreduced loess sediments contained Fe (oxyhydr)oxides and phyllosilicates. Bioreduction experiments were performed using Shewanella putrefaciens CN32 with lactate as the sole electron donor and Fe(III) in loess as the sole electron acceptor with and without anthraquinone-2, 6-disulfonate (AQDS) as an electron shuttle. Experiments were performed in non-growth (bicarbonate buffer) and growth (M1) media. The unreduced and bioreduced solids were analyzed by X-ray diffraction, Mössbauer spectroscopy, diffuse reflectance spectroscopy, and scanning electron microscopy/energy dispersive spectroscopy. Despite many similarities among the three loess samples, the extent and rate of Fe(III) reduction varied significantly. In the presence of AQDS the extent of reduction in the non-growth experiment was 25% of total Fe(III) in HX, 34% in Peoria, and 38% in YCH. The extent of reduction in the growth experiment was 72% in HX, 94% in Peoria, and 65% in YCH. The extent of bioreduction was less in the absence of AQDS. Overall, AQDS and the M1 growth medium significantly enhanced the rate and extent of bioreduction. Fe(III) in (oxyhydr)oxides and phyllosilicates was bioreduced. Siderite was absent in control samples, but was identified in bioreduced samples. The present research suggests that Fe(III) in loess sediments is an important potential source of electron acceptors that could support microbial activity under favorable conditions.

Chlorite is one of the most common Fe-bearing minerals and is susceptible to weathering in loess and soils. The conventional method for analyzing chlorite, based on XRD with the Rietveld technique, is quantitative, but very time consuming and expensive. In this paper we develop a new methodology based on diffuse reflectance spectroscopy (DRS) and selective chemical extractions to identify chlorite qualitatively in the Chinese loess sequence and present evidence suggesting that DRS may be used to quantify chlorite content. The spectral signature of chlorite in loess is obscured by Fe oxides, but becomes obvious when they are removed. Changes in the ferrous absorption band near 1140 nm vary consistently with changing chlorite content. Using this spectral feature, DRS can distinguish chlorite contents as small as 1 wt.% in loess sediments. Future possibilities for this method in other soil and sediment types need to be explored.

The long, continuous deposition of dust in the Chinese loess plateau offers a unique opportunity to study the nature of Fe oxide formation in a wide range of climatic conditions. A technique to obtain quantitative estimates of the concentration of hematite and goethite in loess and paleosol samples is reported. Experiments using diffuse reflectance spectroscopy on sets of laboratory mixed and natural loess and paleosol samples show that it is possible to obtain rapid and quantitative estimates of the absolute concentration of hematite and goethite in the Chinese loess sediments. Typical loess and paleosol samples were deferrated using the CBD procedure to produce a natural matrix material to which hematite and goethite in known weight percentages were added to produce a set of calibration standards. Spectral violet, blue, green, yellow, orange, red and brightness of standards were calculated from the reflectance data and served as independent variables for a multiple linear regression analysis. The effect of changing matrix from loess to paleosol was overcome by including a variety of different loess and paleosol samples in the regression equations. The resulting calibration equations provide estimates of wt.% hematite and goethite and have correlation coefficients >0.93. The total measured hematite and goethite concentrations exhibited consistent variations with CBD extractable iron. Tests of the equations for buffering changes in matrix composition were run with samples of varying mineralogical composition (calcite, illite, etc.) and demonstrated that the equations are well buffered for changes in matrix composition from loess to paleosol.

Loess is a collapsible soil; when it collapses, it can cause significant damage to structures built on it. Improvement in the stability and strength performance of loess is necessary to meet engineering needs. In the present study, the effects on the physical-chemical and rheological characteristics of Ghardaïa loess of adding bentonite and lime (southern Algeria) were examined. Rheological characterization of suspensions was implemented to assess the mechanical sensitivity of the bonds and the structural inter-particle resistance to both the chemical effect and mechanical impact. By analyzing the viscosity results and the evolution of the rheological parameters, the improvements needed in terms of the resistance characteristics of the loess-bentonite and loess-lime mixtures were evaluated and confirmed. The loess physical sensitivity was examined through grain-size distribution and plasticity properties. The pH and electrical conductivity of the mixtures were also used to explore structural modifications. Physical test results showed that introduction of the additives changed the loess texture and improved the plasticity of mixtures. Chemical examination (via change in pH and electrical conductivity) revealed the structural changes in the mixtures studied. Rheological test results showed that increasing concentrations of bentonite and lime improves the mechanical strength and increased the yield stress, consistency, and viscosity of the suspensions. The creation of cement interactions between mixture particles explained the increase in those parameters. Hydration, agglomeration, and inter-particle flocculation induced by the additives promoted these interactions. The experimental results led to the conclusion that bentonite and lime may represent an effective means to improve the performance in terms of preventing loess collapse and to increase its resistance to mechanical impact. The results presented in the present study may provide a geotechnical and rheological working database for the control and treatment of loess collapse and landslides in the region under study. Technical data related to loess may, therefore, be beneficial in terms of civil engineering, public works, hydraulics, and the manufacture of construction materials.

The concept of a loess transportation surface portends that saltating sands deflate silt/dust and send them into suspension. This process continues until a topographic barrier stops the saltating sand, allowing loess deposits to accumulate downwind. This paper reports on loess transportation surfaces in west-central Wisconsin, USA. During the postglacial period, cold, dry conditions coincided with strong northwesterly winds to initiate widespread saltation of freely available sands, deflating any preexisting loess deposits. Large parts of the study area are transportation surfaces, and lack loess. Loess deposits were only able to accumulate at “protected” sites—downwind from (east of) topographic barriers, such as isolated bedrock uplands and the north-to-south flowing Black River. Loess in locations from these barriers is thicker (sometimes >5 m) than would be expected, and in places has even accumulated above preexisting loess deposits. For example, downwind (east) of the Black River, most of the low-relief landscape is covered with ≈40–70 cm of silty loess, even though it is many tens of kilometers from the initial loess source. Upwind of the river, on the transportation surface, the low-relief landscape is only intermittently mantled with thin, scattered deposits of silty-sandy eolian sediment, and generally lacks loess.

Although black soil in northeast China undergoes severe erosion, the contribution of parent materials, mainly Quaternary loess and non-loess sediments, to soil erodibility remains unclear. Considering the inheritance of ferromagnetic materials by parent materials, changes in magnetic parameters can successfully determine soil erodibility on a regional scale with a close climatic background. Here, we analysed the magnetic indicators of 142 samples from the black soil horizon formed on loess and non-loess sediments, covering areas of severe and slight erosion in the region to determine the effects of parent materials on the erodibility of black soil in northeast China. Both low-frequency magnetic susceptibility and frequency magnetic susceptibility (χfd) were proportional to the decrease in erosion rate due to erosion-induced leaching of ferromagnetic materials, and the change in χfd was narrow for black soil with loess parent materials, corresponding to relatively low soil erodibility. Compared with loess, the addition of soil organic matter could stabilise soils against erosion, thereby inducing a decrease in the erodibility of black soil formed on loess. Additionally, sustainable soil management policies to protect black soil from further erosion are necessary and urgent under the pressure of maintaining high grain yields and preventing erosion in northeast China.

We examine the Holocene loess record in the Heye Catchment on the margins of the Tibetan Plateau (TP) and China Loess Plateau (CLP) to determine: the region to which the Heye Catchment climate is more similar; temporal change in wind strength; and modification of the loess record by mass wasting and human activity. Luminescence and radiocarbon dating demonstrate loess deposited in two periods: >11–8.6 ka and <5.1 ka. The 8.6–5.1 ka depositional hiatus, which coincides with the Mid-Holocene Climatic Optimum, is more similar to the loess deposition cessation in the TP than to the loess deposition deceleration in the CLP. Grain-size analysis suggests the Heye loess is a mixture of at least three different grain-size distributions and that it may derive from multiple sources. A greater proportion of coarse sediments in the older loess may indicate stronger winds compared with the more recent depositional period. Gravel incorporated into younger loess most likely comes from bedrock exposed in slump scarps. Human occupation of the catchment, for which the earliest evidence is 3.4 ka, postdates the onset of slumping; thus the slumps may have created a livable environment for humans.

We conducted the first detailed mineral magnetic investigation of more than nine loess–paleosol couplets of the composite Titel-Stari Slankamen loess section in Serbia, which provides one of the longest and most complete terrestrial record of paleoclimatic changes in Europe since ~1.0 Ma. The results show that the ferrimagnetic mineral assemblage of the loess units is dominated by partially oxidized multidomain (MD) and pseudo-single domain (PSD) magnetite; however, with an increasing degree of pedogenesis, the eolian contribution is gradually masked by pedogenic superparamagnetic(SP) and single-domain (SD) ferrimagnets (mainly maghemite). The overall consistency of ferrimagnetic grain-size parameters indicates an absence of dissolution of the fine-grained ferrimagnetic fraction despite changes in climate regime over the past 1.0 Ma. The variations of normalized dJ/dT@120K and normalized χheating@530°C reflect a long-term stepwise increase in aridity during glacials with a major step at ~0.6–0.5 Ma, over the last 1.0 Ma. Overall, the results provide an improved basis for the future use of the magnetic properties of Serbian loess deposits for paleoclimatic reconstruction.

The aeolian loess-paleosol sequences in the Chinese Loess Plateau (CLP) are an excellent archive of variations in atmospheric circulation in the geological past. However, there is no consensus regarding the roles of the East Asian winter monsoon and westerly winds in transporting the dust responsible for loess deposition during glacial and interstadial periods. We conducted detailed measurements of the anisotropy of magnetic susceptibility (AMS) on two parallel loess profiles covering the most recent 130 ka in the western CLP to determine paleowind directions. Results show that the magnetic lineations of the loess and paleosol units in both sections are significantly clustered along the northwest to southeast direction. These observations demonstrate that the prevailing wind system responsible for dust transport in the western CLP was the northwesterly winter monsoon, rather than the westerly winds. The AMS-derived dust-bearing wind direction was relatively stable during the last glacial and interglacial cycle in the western CLP, consistent with sedimentary and AMS evidence from the eastern CLP. Accordingly, it is reasonable to conclude that large areas of deserts and Gobi deserts areas located in the upwind direction were the dominant sources for the aeolian deposits of the Loess Plateau.

Paleoenvironmental reconstructions are commonly based on isotopic signatures of a variety of carbonate types, including rhizoliths and land-snail shells, present in paleosol-loess sequences. However, various carbonate types are formed through distinct biotic and abiotic processes over various periods, and therefore may record diverging environmental information in the same sedimentological layer. Here, we investigate the effects of carbonate type on δ13C, δ18O, and clumped isotope-derived paleotemperature [T(Δ47)] from the Quaternary Nussloch paleosol-loess sequence (Rhine Valley, SW Germany). δ13C, δ18O, and T(Δ47) values of co-occurring rhizoliths (-8.2‰ to -5.8‰, -6.1‰ to -5.9‰, 12–32°C, respectively), loess dolls (-7.0‰, -5.6‰, 23°C), land-snail shells (-8.1‰ to -3.2‰, -4.0‰ to -2.2‰, 12–38°C), earthworm biospheroliths (-11‰, -4.7‰, 8°C), and “bulk” carbonates (-1.9‰ to -0.5‰, -5.6‰ to -5.3‰, 78–120°C) from three sediment layers depend systematically on the carbonate type, admixture from geogenic carbonate, and the duration of formation periods. Based on these findings, we provide a comprehensive summary for the application of the three isotopic proxies of δ13C, δ18O, and Δ47 in biogenic and pedogenic carbonates present in the same sediment layer to reconstruct paleoenvironments (e.g., local vegetation, evaporative conditions, and temperature). We conclude that bulk carbonates in Nussloch loess should be excluded from paleoenvironmental reconstructions. Instead, pedogenic and biogenic carbonates should be used to provide context for interpreting the isotopic signature for detailed site- and time-specific paleoenvironmental information.

The loess deposits in Shandong Province in eastern China potentially provide valuable insights into past environmental changes. However, their precise provenance and paleoclimatic implications are unclear. We studied three loess sections located in the piedmont of the Central Shandong Mountains (PCSM) and in an offshore island in Bohai Gulf. Both the glacial loess and interglacial paleosol units are characterized by a coarse grain size, indicating a proximal sediment source. Using the “grain size–transport distance” model established for the Chinese Loess Plateau (CLP), the estimated source-sink distance is ~200–300 km for the PCSM loess and ~100–200 km for the coastal loess. This suggests that fluvial deposits of the Yellow River system in the North China Plain and sediments on the adjacent continental shelf are the major provenance for the Shandong loess. In contrast to the CLP, the Shandong loess does not show a consistent pattern of coarse grain size and low magnetic susceptibility values in glacial loess compared with interglacial paleosols, likely due to frequent changes in dust sources caused by diversions of the Yellow River and local hydroclimatic conditions. Nevertheless, the loess-paleosol alternations in the Shandong loess are a product of global glacial–interglacial cycles.

Calcareous loess in North Canterbury, eastern South Island, New Zealand (NZ), preserves subfossil bird bone, terrestrial gastropods, and eggshell, whose abundances and radiocarbon ages allowed us to reconstruct aspects of palaeoenvironment at high resolution through 25 to 21 cal ka BP. This interval includes millennial-scale climatic variability during the extended last glacial maximum (30–18 ka) of Australasia. Our loess palaeoclimatic record shows good correspondence with stadial and interstadial climate events of the NZ Climate Event Stratigraphy, which were defined from a pollen record on the western side of South Island. An interstade from 25.4 to 24 cal ka BP was warm but also relatively humid on eastern South Island, and loess grain size may indicate reduced vigour of the Southern Hemisphere westerly winds. The subsequent stade (24–22.6 cal ka BP) was drier, colder, and probably windier. The next interstade remained relatively dry on eastern South Island, and westerly winds remained vigorous. The 25.4–24 ka interstade is synchronous with Heinrich stade 2, which may have driven a southward migration of the subtropical front, leading to warming and wetting of northern and central South Island and retreat of Southern Alps glaciers at ca. 26.5 ka.

Two phases of archaeological investigation were performed in the Novi Sad City Museum at Petrovaradin Fortress. In this study, we summarize the results of geo-archaeological investigations of the second period of excavation inside the Novi Sad City Museum building. The fortress is situated on a Danube terrace with the top of the bedrock at ca.123 m asl. The investigated section consists of undisturbed fine-sandy silt. The grain-size distribution of the sediments indicates clearly its alluvial reworking but shows also a general similarity with typical primary loess in the region. All analyzed proxies indicate slightly stronger weathering in the upper part of the profile. Luminescence ages suggest that the investigated sequence covers the last glacial period and the terrace presumably formed during MIS 4. Subsequently, the Danube started its incision at the start of the next warmer period (MIS 3) onward. This terrace age and elevation enable us to derive an uplift rate of the terrace of ca. 0.73 mm/a for the last 60 ka, which seems to increase towards the present. Basal loessic material, in which artifacts occur, likely in the reworked position, indicate that the area close to today's Petrovaradin Fortress was already inhabited in MIS 5.

The Channeled Scabland–Palouse region of the Pacific Northwest (PNW) of the United States preserves geomorphic and pedosedimentary records that inform understanding of late Pleistocene–Holocene paleoclimate change in a region proximal to the last glacial period Cordilleran Ice Sheet. We present a clumped (Δ47) and conventional (δ18O, δ13C) isotopic study of Palouse loess–paleosol carbonates in combination with carbonate radiocarbon (14C) dating to provide new measures of regional late–last glacial (~31–20 cal ka BP) and Holocene soil conditions. Average clumped isotope temperatures (T(Δ47)) for last glacial Palouse loess–paleosol carbonates (9±4°C) are significantly lower than those for Holocene-aged carbonates (T(Δ47)=18±2°C) in study sections. Calculated soil water δ18OVSMOW values (−16±2‰) for last glacial carbonates are also offset relative to those for Holocene-aged samples (−11±1‰), whereas calculated soil CO2 δ13CVPDB values are similar for the Holocene (−16.9±0.2‰) and late–last glacial (−16.7±1.1‰) periods. Together, these paleoclimate metrics indicate late–last glacial conditions of pedogenic carbonate formation in the C3 grassland soils of the Palouse were measurably colder (9±5°C) than during the Holocene and potentially reflect a more arid last glacial paleoclimate across the Palouse, findings in agreement with previous proxy studies and climate model simulations for the region.