Search

We used uranium-lead (U-Pb) dating of zircons from a tephra layer deposited in the La Sal Mountains to assign an age of more than c. 1.3 Ma to underlying loess-mixed slope deposits (cover beds) and paleosols developed therein. For the first time, we show that properties of cover beds and soils before the Mid-Pleistocene Revolution were similar to those formed after the revolution. However, the deepest exposed carbonate-enriched horizon is much farther developed than younger ones, indicating that there was a period of enrichment by far exceeding intensities of younger calcic horizons some time before the revolution, possibly in Neogene times. Remarkable differences between age distributions of detrital zircons (DZ) within the cover beds allow reconstructing the regional provenance of mixed eolian matter with high accuracy: we were able to trace particular cover beds back to areas with outcropping Permian and Upper Cretaceous rocks.

Reconstructing the evolution of arid landscapes is challenged by limited availability of appropriate environmental archives. A widespread surface feature — stone pavement — traps aeolian fines and forms a special accretionary archive. Seven stone pavement-covered sections on basalt flows in the eastern Mojave Desert are condensed into a composite section, comprising five sedimentological units supported by an OSL-based chronology. Three of the units are of accretionary nature and each is covered by a stone pavement. They were deposited > 50.9–36.6 ka, < 36.6–14.2 ka and < 14.2 ka, and they are intimately coupled with the history of nearby Lake Mojave, which advances the current understanding of regional aeolian activity. End-member modeling analysis of grain-size distributions yielded seven sediment transport regimes. The accretionary system operates in two modes: A) episodic formation of a stone pavement by lateral processes once a vesicular horizon has formed on a barren surface; and B) accretion of dust and eventual burial of the clast layer. These findings improve current concepts about stone pavement evolution and their environmental proxy function in arid landscapes. Stone pavement-covered accretionary deposits are a new key archive that allows quantifying the relative importance of dust accretion, slope processes, soil formation and vegetation cover.

Identifying principles of water movement in the shallow subsurface is crucial for adequate process-based hydrological models. Hillslopes are the essential interface for water movement in catchments. The shallow subsurface on slopes typically consist of different layers with varying characteristics. The aim of this study was to draw conclusion about the infiltration behaviour, to identify water flow pathways and derive general validity about the water movement on a hillslope with periglacial slope deposits (cover beds), where the layers differ in their sedimentological and hydrological properties. Especially the described varying influence of the basal layer (LB) as impeding layer on the one hand and as a remarkable pathway for rapid subsurface stormflow on the other. We used a time lapse 3D ERT approach combined with punctual hydrometric data to trace the spreading and the progression of an irrigation plume in layered slope deposits during two irrigation experiments. This multi-technical approach enables us to connect the high spatial resolution of the 3D ERT with the high temporal resolution of the hydrometric devices. Infiltration through the uppermost layer was dominated by preferential flow, whereas the water flow in the deeper layers was mainly matrix flow. Subsurface stormflow due to impeding characteristic of the underlying layer occurs in form of "organic layer interflow" and at the interface to the first basal layer (LB1). However, the main driving factor for subsurface stormflow is the formation of a capillary barrier at the interface to the second basal layer (LB2). The capillary barrier prevents water from entering the deeper layer under unsaturated conditions and diverts the seepage water according to the slope inclination. With higher saturation the capillary barrier breaks down and water reaches the highly conductive deeper layer. This highlights the importance of the capillary barrier effect for the prevention or activation of different flow pathways under variable hydrological conditions.

An essentially pure tephra layer on a steep slope in the La Sal Mountains, Utah, U.S.A., is correlated with the 1.65 Ma old Guaje Tephra derived from the Jemez Mountains, New Mexico, U.S.A. The heavy-mineral contents and glass shards in sediments beneath the La Sal tephra layer indicate that tephra constituents are contained in deposits considerably older than the pure layer. This suggests that tephra material may become reworked while retaining its pure character, possibly due to laminar transport or to dislocation in a frozen condition. This raises the need to handle tephrochronological findings with great care.

The crucial role of stone pavements in arid environments for aeolian or alluvial processes and as numerical dating tools is increasingly acknowledged. This role is based on the assumption that stone pavements are stable landforms, formed gradually over time and predominantly by vertical processes. However, this is challenged by evidence of stone-pavement clast reworking or burial. Bimodal, mostly slope aspect-symmetrical clast orientation is a frequent phenomenon in various study areas. It implies that stone pavements may be influenced by unidirectional lateral processes besides vertical ones. Here, the finding of lateral processes contributing to stone-pavement evolution is supported by numerical modelling and physical experiments. These unequivocally show that unconcentrated overland flow can transport clasts to form a closely packed stone mosaic with characteristics similar to those of natural stone pavements. The commonly observed length-axes orientation angle of 40 ± 14° for natural stone-pavement clasts is consistently reproduced by angle-dependent force equilibrium. Monte Carlo runs confirm the natural scatter and allow characterization of the control parameters of clast orientation. The model explains up to 70% of the natural variance. It is further validated by flume experiments, which confirm model predictions of single object orientation angles. Experiments with multiple objects yield artificial stone pavements with properties similar to those found in the field. The unidirectional lateral process acting on natural stone pavements requires the presence of a vesicular horizon. This underlines the tight genetic coupling of this common epipedon feature and the clast cover. The presented findings highlight the role of stone pavements as process and environment proxies. However, stone pavements represent information since the last surface disturbance only. This has to be considered when using them as age indicators. Copyright © 2013 John Wiley & Sons, Ltd.

The Ore Mountains were one of the important flood source areas for several heavy floods over the last years. Reducing damages caused by floods demands sufficient information on the runoff generation processes in the catchments. The aim of this study is to provide insights into prevailing flow pathways, retention times and threshold behavior of a representative hillslope catchment with layered subsurface in the Ore Mountains. The study site is a forested headwater with gneiss as bedrock. We used hydrometrical methods, soil temperature data and sprinkler experiments. Results indicate that the hydraulic anisotropic structure of the deepest layer in 0.9–1.7 m depth is the major controlling factor for subsurface water flow paths. On one hand, this layer acts as an aquitard for seeping water because of its high bulk density. On the other hand, water within the layer is able to flow laterally because of the sandy texture and coarse clasts oriented parallel to the slope. Moreover, three pre-moisture controlled types of runoff processes were addressed. With low antecedent soil moisture, saturation overland flow dominates in the spring bog. With intermediate or high pre-moisture, interflow is generated. The measured runoff coefficients increase in a nonlinear manner with rising pre-moisture. A soil water tension threshold value near field capacity is the tipping point for nonlinear runoff response. These findings emphasize the impact of the layered structure of the subsurface and of antecedent soil moisture for runoff generation in low mountain ranges and may be useful for establishing flood warning systems.

Vesicular structure is a widespread feature of soils in arid environments. Typically associated with stone pavements, it has a major control function for dust and water fluxes and, hence, for site ecology. Previous models of vesicular structure formation and stability are inconsistent and mostly focused on the investigation of isolated control parameters. To test existing models, to infer plausible mechanisms of vesicular structure formation and to unveil controlling environmental and sedimentological parameters, we present quantitative data of vesicle properties of artificial and natural vesicles. Vesicles are not unstable but their changes in size are non-linear with time. They form due to surface sealing by puddling and by a wetting front, which advances downward, thereby elevating gas pressure within the sediment matrix. Translocation of clay or precipitation of calcium carbonate support vesicle stabilisation. Vesicular structure forms within a wide range of environmental and sedimentological settings: at least 6.3–15.7 mm of water per wetting cycle, 0–70% sand content, 0.8–5.6 mS/cm electric conductivity and 1–28% calcium carbonate content. High sand contents favour larger and rounder vesicles, whereas increasing calcium carbonate content has the opposite effect. The concentration of dissolved ions does not considerably influence vesicle formation. Under an artificial cover stone vesicles could not be created at all, whereas they were concentrated around stone margins. The main limiting factor for vesicle formation in natural environments is root activity. The type and density of surface cover determine fine material fluxes into the aggregates of vesicular horizons. The shape of vesicles may be related to dust influx intensity. Accordingly, horizons with spherical vesicles may indicate constant low dust influx on poorly vegetated surfaces and be, therefore, used as proxies of environmental conditions.

Regolith may be regarded as a continuum, but has a pronounced internal structure (stratification). It is thus a key element controlling processes, properties, and functions of landscapes. However, so far research has focused mainly on regolith genesis and only few investigations explicitly deal with the relationship between regolith structure and site/landscape properties. The need to deal with environmental problems at landscape scale has increased substantially the demand for the investigation of the regolith continuum and its internal structure. Stratification of regolith is a ubiquitous phenomenon not only affecting properties of soils and sites, but also of landscapes. The effects of regolith structure on (i) depth functions of soil properties, (ii) slope hydrology, and (iii) vulnerability against erosion will be shown. The aim of this contribution is to point out the vital position of regolith within landscape ecosystems and to stress the need for an interdisciplinary regolith science emphasizing a geo-hydro-ecological approach.

Many soils in the western U.S.A. contain one or several carbonate-enriched zones (CEZ). Their carbonate admixture is often attributed to steady eolian influx, with intermittent leaching episodes of variable intensity leading to pedogenic enrichment at various depths. This hypothesis would require carbonate contents to decrease and depths to those horizons to increase with elevation. Here I compute correlations for the upper three CEZ of the surface soil and of up to two buried soils between elevation, carbonate content, depth to horizon, and particle-size distribution to test for elevation- dependent trends. Actually, carbonate-content decreases with elevation indicate such trends exist and can be determined with this approach. However, some significant relationship of elevation and depth to CEZ is not supported by the data. Furthermore, influence of local carbonate on CEZ in the surface soils calls for lateral translocation. Gravelly, now-buried sediments collected eolian carbonate better than finer ones, which finding implies these sediments were at the surface once and fossilized later. Altogether, the data indicate cyclical evolution: Several cycles of the formation of colluvial slope deposits with admixed carbonate-bearing loess particles were each followed by pedogenic translocation of the carbonate just to the depth of the next parent-material disconformity. Thus, disconformities are major triggers of soil-carbonate accumulation.

A major gap in the stratigraphic record of underlying rocks of a cuesta landform in southern Franconia causes local absence of resistant cap rock. As a consequence the scarp is atypical, capped by less resistant, mainly pelitic rock. Its dip slope is identified as a planation surface, as it disconformably cuts underlying rock structures. These findings indicate that cuesta landscapes may contain prominent sculptural elements. The formation of the planation surface started during or after the Oligocene at least in the southern part of the study area, but may have started earlier farther north. Evidence of processes acting on this surface is derived from coarse, partially ventifacted gravel, which allow reconstructing two individual river courses. These presumably formed under dry climate. The surface was dissected some 10 Ma after its onset, in Late Miocene times, by deeply cut valleys fostering lacustrine deposits.

Soils of Central European subdued mountain ranges are structured by various layers of relic periglacial slope deposits (Pleistocene cover beds). These have great impact on subsurface substrate properties. Therefore, gaining extensive spatial information on material composition and thickness of slope deposits is essential. Here we present a GIS-supported approach to predict layer properties which goes beyond existing, deterministic procedures. In a section of the Tharandter Wald, Saxony, Germany, we deduced subsurface structures from soil pits and auger cores. Substrates were analysed to clarify stratigraphical setting and relation to parent rock types. We assume cryoturbation, solifluction, slope wash and aeolian sediment admixture to be important processes of periglacial cover bed formation. These processes are mainly controlled by geological and geomorphological factors. Combining assumptions and field data, we determine properties of periglacial cover beds. Based on relief parameters, an integrated data set is generated, which provides information for a geostatistical interpolation of measured layer thicknesses. The composition of solifluidally dislocated substrate is approximated by a modified flow model. Modelling returned thicknesses of loess-bearing layers, i.e. upper layer and intermediate layer. Prediction of the upper layer involved an inverse distance weighted approach and yielded an inaccuracy of

Palaeosols between deposits of the last two deep-lake cycles in the northern Great Basin have multiple carbonate-engulfed horizons, and compound calcic and argillic properties at depth. They are difficult to explain pedogenetically because they bifurcate in places, especially in basin centres where they are separated by sediments of a minor lake expansion of probable early Wisconsinan age. One sequence of processes can account for all phenomena: two cycles of colluviation and synchronous admixture of loess particles were each succeeded by the formation of an argillic over a calcic horizon. Carbonate enrichment resulting from the later period of soil formation affected the buried older soil. This led to welding of the two soils and the formation of a compound horizon carrying the argillic properties of the first and the calcic properties of the second pedogenic phase. Steady aeolian influx to the same soil surface, the commonly invoked mechanism, cannot explain the bifurcated palaeosols and is not needed to explain the welded ones.

Soil profiles developed on moraines of the penultimate glaciation on the Russian Plain have formed from redistributed material, mainly sand, derived from upslope. This material consists of layers, some of which also contain, or may even be dominated by, loess. The lowest layer differs little from the underlying substratum except where it covers deposits other than till; it is mainly inherited from till, but has been altered by solifluction, leading to downslope clast orientation and to a high bulk density. The overlying layers, also solifluction deposits, contain loess, the content of which increases towards the surface. Deeper profiles on flat relief, especially on one particular toeslope, are divided into at least three of these layers, the lowest of which contains a mature truncated paleosol. This buried soil, an Alfisol with clay–humus cutans, is assumed to represent the soil of the last interglacial. Above this, the illuvial horizon of the surface soil is developed. This is overlain by the uppermost layer, which is of loose consistency and rich in loess. It contains the eluvial horizon of the surface soil. On flat relief, modern pedogenesis is dominated by perched water tables resulting from differences in the bulk density of the layers. The maximum loess content in the upper layer and the wide distribution of a paleosol and an intermediate layer make these layers different from similar sequences in Central and Western Europe.

In parts of southern France, the Russian Plain, south central Turkey, the western USA and in Germany, slopes are covered by deposits (cover-beds) formed by geomorphic processes not limited to linear discharges. Often, loess material is mixed into them. Cover-beds usually form sequences of two or more distinct layers, and their distribution depends on the geomorphic, climate-driven processes of their formation. As they influence pedogenesis, they contribute to the understanding of soil properties and soil distribution. Horizon boundaries occur at depths where cover-bed properties change. Where aeolian matter is mixed in, podzolisation is buffered but depletion of clay may occur; loess-rich cover-beds may entirely decouple pedogenesis from bedrock influence. In humid areas, soil-water stagnation is often associated with varying cover-bed bulk densities, particularly upon flat relief. In semiarid areas, deep soil profiles consist of multiple layer sequences often with argillic and calcic properties within the same horizons. They reflect several cycles of cover-bed deposition and incorporation of loess, alternating with decalcification accompanied and followed by clay translocation. This led to the overprinting of buried soils by pedogenic carbonate leached from younger sediments. Synchronous sediment and/or airborne carbonate accretion and pedogenesis, which is usually invoked to explain soil profiles with several calcic horizons, cannot apply to cover-beds.

Numerous case studies carried out in the subdued mountains of Germany during the last decades have revealed that periglacial cover beds play a decisive role in hillslope hydrology. Considering the omnipresence of cover beds in sloped terrain of the mid-latitudes, knowledge of slope-water paths is crucial not only for flood forecast but also for understanding how contaminants pass through ecosystems. Since periglacial cover beds are usually composed of different sedimentary layers, they show a high spatial variability of physical soil parameters, which are, in turn, responsible for small-scale variations of the hydraulic properties. Regardless of bedrock type, the observations reported in this chapter from different regions lead to the conclusion that there is a clear relationship between subsurface layering and runoff-generation processes. The hydraulic anisotropic structure of the deepest (basal) layer is the major factor controlling subsurface water-flow paths. On one hand, this layer acts as an aquitard for seeping water because of its high bulk density. On the other hand, once water has percolated into this layer, it is able to flow in lateral directions because of the coarse clasts oriented parallel to the slope. Therefore, such a cover bed may be treated neither as an aquifer nor as an aquiclude. Besides, as a function of pre-moisture, a nonlinear runoff response to precipitation or snow-melt of the investigated catchments was identified.

Cover beds form a rather uniform veil of most slopes in Central Europe and, most likely, all over the mid-latitudes. Accordingly, their properties are of utmost importance for the formation of soils, for slope hydrology, and for slope dynamics. More research is, however, needed, as there is still insufficient information on the properties of cover-bed successions reaching deeper than 1 m, and there are still many areas where cover beds have not yet been studied at all. The potential use of cover beds for paleoenvironmental reconstructions is also still limited by the unsatisfactory techniques that are currently available for their numerical dating. Furthermore, better techniques for modeling the distribution and the properties of cover beds are required to forecast their influence on flooding events.

Slope deposits, which veil entire slopes or large parts of them in a rather uniform manner (cover beds), are ubiquitous in the subdued mountains of Central Europe. Here we provide an overview of the current state of knowledge on these deposits. The Central European cover beds are divided into (1) the upper layer that is ubiquitously distributed and displays a relatively constant thickness; (2) the intermediate layer the distribution of which is mainly restricted to flat relief, to slope depressions, and to lee-ward facing slopes; and (3) the basal layer, which is rather widespread again. Both the upper and intermediate layer contain intermixed loess, whereas the basal layer is free of loess and typically has a high bulk density. Aside from the loess content, the composition of the layers differs, reflecting varying portions of crushed and chemically weathered rock allocated from up-slope. This causes notable diversity depending on bedrock and, thus, induces remarkable regional differences. Cover beds were mainly formed by periglacial gelifluction. The upper layer formed in the Late Glacial possibly during several short episodes of activity. In contrast, the underlying layers may be diachronous; nevertheless, they display recurring vertical sequences. This is probably due to the fact that loess-free layers usually could not deposit as long as there was loess in the environs, which may have been inherited from older deposits. Thus, the last phase of surface wash, during which older loess was removed, determines the age of the lower layers.

Slope deposits, which veil entire slopes or large parts of them in a rather uniform manner (cover beds), are ubiquitous in the subdued mountains of Central Europe (e.g., Kleber, 1992a ). Here, we show that successions of cover beds are not restricted to this area but occur in many other regions of rather different natural inventories, such as the European Alps, the Russian Plain, south-central Turkey, and the western USA (Great Basin and Rocky Mountains). Cover beds usually form sequences of two or more distinct layers, and their distribution depends on the geomorphic, climate-driven processes of their formation. As they influence pedogenesis, they contribute to the understanding of soil properties and soil distribution: horizon boundaries occur at depths where cover-bed properties change. The properties of the layers and of the soils developed in them are different per region: in humid areas layers free of admixed loess components, thus being solely influenced by weathered local materials, are frequent, whereas in dry regions such layers have not yet been reported. In several areas studied in this chapter, paleosols either occur within cover-bed successions or have been reallocated and incorporated into the cover beds. This provides handles to the ages of layers. The layer successions slowly change with elevation but show a drastic break at around the timberline where Holocene rather than Pleistocene periglacial slope processes gained supremacy.

The genesis of soils has been seen mostly as an autochthonistic process, that is, formation in situ . However, soil geomorphologists have recognized addition and loss of materials, for example, through eolian and colluvial processes, as a major contribution to allochthonistic soil formation. The most important characteristic of these soils is the lithological discontinuity, which separates the lower residual material from the upper allochthonic soil. The chapter deals with (1) developing a model joining the ideas of in situ formation and near-surface processes such as adding or removing material, (2) the pedogenetic processes in soils with lithological discontinuities, and (3) the effect of lithological discontinuities on physical and chemical properties of soils.

Disconformities within soil-parent materials are frequently reported from locations throughout the world, but they are rarely within the goals of systematic research. This article provides an overview of the current state of knowledge on such materials and their pedogenic relevance in Germany. It intends to encourage further discussion on stratified soils in other parts of the world. The slope deposits in Germany are divided into (1) the upper layer that is ubiquitously distributed and displays a relatively constant thickness; (2) the intermediate layer that is restricted to flat relief, to hollows, and to lee-ward facing slopes; and (3) the basal layer that is rather widespread again. Both the upper and intermediate layer contain intermixed loess, while the basal layer is free of loess. These layers were mainly formed by periglacial solifluction. Such deposits are referred to as cover-beds. The upper layer formed during the Younger Dryas within a relatively short episode. In contrast, the lower layers may be diachronous; nevertheless, they display recurring vertical sequences. This is probably due to the fact that loess-free layers usually could not deposit as long as there was loess in the environs. Thus, the last phase of surface wash, during which older loess was removed, determines the age of the lower layers. The composition of the layers differs, reflecting the varying portions of loess and of rock allocated from upslope. In twofold sequences, the cover-beds influence the formation of the soils as they provide weathered material, and as their boundaries, where properties such as texture and bulk density abruptly change, determine the soil-horizon boundaries. Some pedogenic processes are favored (oxidation, depletion of clay), or hindered (podzolization) due to the loess content of the upper layer. Even exceeding this, the dominant loess content of an intercalated intermediate layer in threefold sequences may completely decouple pedogenesis from bedrock influence. In all, soil formation is largely influenced by the constellation of cover-beds at any given site.

El Niño-Southern Oscillation (ENSO) is an important element of earth's ocean-climate system. To further understand its past variability, proxy records from climate archives need to be studied. Ice cores from high alpine glaciers may contain high resolution ENSO proxy information, given the glacier site is climatologically sensitive to ENSO. We investigated signals of ENSO in the climate of the subtropical Andes in the proximity of Cerro Tapado glacier (30°08' S, 69°55' W, 5550 m a.s.l.), where a 36 m long ice core was drilled in 1999 (Ginot, 2001). We used annual and semi-annual precipitation and temperature time series from regional meteorological stations and interpolated grids for correlation analyses with ENSO indices and ice core-derived proxies (net accumulation, stable isotope ratio δ18O, major ion concentrations). The total time period investigated here comprises 1900 to 2000, but varies with data sets. Only in the western, i.e. Mediterranean Andes precipitation is higher (lower) during El Niño (La Niña) events, especially at higher altitudes, due to the latitudinal shift of frontal activity during austral winters. However, the temperature response to ENSO is more stable in space and time, being higher (lower) during El Niño (La Niña) events in most of the subtropical Andes all year long. From a northwest to southeast teleconnection gradient, we suggest a regional water vapour feedback triggers temperature anomalies as a function of ENSO-related changes in regional pressure systems, Pacific sea surface temperature and tropical moisture input. Tapado glacier ice proxies are found to be predominantly connected to eastern Andean summer rain climate, which contradicts previous studies and the modern mean spatial boundary between subtropical summer and winter rain climate derived from the grid data. The only ice core proxy showing a response to ENSO is the major ion concentrations, via local temperature indicating reduced sublimation and mineral dust input during El Niño years.

Quantifying post-depositional alteration of mineral soil material is complicated by the fact that many soils consist of layered parent materials with varying indigenous composition. Part of our study site in the Steigerwald Mountains of northern Bavaria was cultivated during the Middle Ages and later reforested. Soil erosion removed the upper materials, exposing a deposit to contamination from the surface, whereas nearby, the deposit remained protected by overlying layers. We compared heavy metal concentrations within that deposit across this boundary of varying protection. No significant results were obtained for Cd; however, the concentrations of Pb and Cu increase by about 100% or more where the protecting cover thins. The Pb and Cu values provide a measure of the gross post-depositional alteration of that deposit. We expect this procedure can help quantify various pedogenic alterations by comparison with essentially the same, unaltered parent material.