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Glacial and periglacial sediments and landforms record the chronology of glaciation and amount of Pleistocene erosion during colder periods that added substantially to global sediment budgets and contributed to the global CO2 cycle. The now-drained glacial Lake Devlin, dammed in a Front Range tributary valley by a glacier in the North Branch of Boulder Creek (Colorado, USA) preserves an important sedimentary archive of the ca. 32-14 ka Pinedale glaciation, recording both paleoclimate information and an integrated measure of glacial and periglacial erosion rates over a full glacial cycle. Despite rapid erosion of fine-grained deposits after the lake drained, most sediment generated during Pinedale time remains as legacy deposits in the catchment. Geomorphic evidence and dating of glaciolacustrine sediment from surface exposures demonstrate that the ca. 30 ka Pinedale glacial advance was nearly as extensive as the local Late Glacial Maximum at ca. 20 ka. Sedimentary archives dated by 14C, optically stimulated luminescence, and cosmogenic nuclides extend earlier studies (Madole et al., 1973) of pollen and magnetic susceptibility (MS) in cores from the glaciolacustrine deposits of Lake Devlin and of Pinedale climate. Records suggest short-term warming and biotic change at ca. 15 ka after ~14 kyr of cold, dry conditions punctuated by MS peaks at ca. 26.5 ka, 20 ka, and 16.5 ka. Lake Devlin drained catastrophically after ca. 14 ka, millennia after ice had retreated upvalley from the lateral moraine that dammed the lake. Sediment production during the Pinedale was equivalent to a periglacial and glacial erosion rate of ~70 mm kyr1, several times higher than long-term rates in the adjacent Front Range, but much lower than rates measured where modern glaciers are eroding weak bedrock in zones of rapid rock uplift, such as SSE Alaska, USA. Data from the Lake Devlin basin contribute to contemporary discussions of how glacial erosion influences the global CO2 cycle. [ABSTRACT FROM AUTHOR]

Human impacts on earth surface processes and materials are fundamental to understanding the proposed Anthropocene epoch. This study examines the magnitude, distribution, and long-term context of nineteenth- and twentieth-century mining in the Fourmile Creek catchment, Colorado, coupling airborne LiDAR topographic analysis with historical documents and field studies of river banks exposed by 2013 flooding. Mining impacts represent the dominant Anthropocene landscape change for this basin. Mining activity, particularly placer operations, controls floodplain stratigraphy and waste rock piles related to mining cover >5% of hillslopes in the catchment. Total rates of surface disturbance on slopes from mining activities (prospecting, mining, and road building) exceed pre-nineteenth-century rates by at least fifty times. Recent flooding and the overprint of human impacts obscure the record of Holocene floodplain evolution. Stratigraphic relations indicate that the Fourmile valley floor was as much as two meters higher in the past 2,000 years and that placer reworking, lateral erosion, or minor downcutting dominated from the late Holocene to present. Concentrations of As and Au in the fine fraction of hillslope soil, mining-related deposits, and fluvial deposits serve as a geochemical marker of mining activity in the catchment; reducing As and Au values in floodplain sediment will take hundreds of years to millennia. Overall, the Fourmile Creek catchment provides a valuable example of Anthropocene landscape change for mountainous regions of the Western United States, where hillslope and floodplain markers of human activity vary, high rates of geomorphic processes affect mixing and preservation of marker deposits, and long-term impact varies by landscape location. [ABSTRACT FROM AUTHOR]

Infrequent, large magnitude geomorphic events generate quantifiable change on geologically short timescales and are crucial to understanding landscape evolution. Airborne lidar surveys and field measurements were used to investigate floodplain erosion and deposition along a 19.5 km reach of Fourmile Creek, Colorado that was devastated by severe flooding in 2013 that followed a 2010 wildfire. > 350 mm of rain fell on the Fourmile catchment from September 9–15, 2013, generating discharge that exceeded bankfull for > 120 h at the Orodell gage, with local unit stream power > 300 W m − 2 throughout the study reach. Debris flows occurred on steep hillslopes and tributary channels in the most intensely burned areas. Lidar difference measurements and field studies highlight zones of local deposition along the study reach, but demonstrate overall net erosion of ~ 0.25 m for the 19.5 km reach of Fourmile floodplain, mainly by channel widening. Tributary junctions where debris-flow sediment entered the floodplain and local decreases in unit stream power controlled some zones of deposition. Overall, mass balance calculations show that a total sediment loss of ~ 91,000–161,000 m 3 from the Fourmile Creek floodplain and hillslopes, which is broadly consistent with channel sediment flux estimates of 71,000–111,000 m 3 . Measurements from the Fourmile catchment demonstrate that floodplain erosion was a major source of sediment in the 2013 flood and demonstrate that infrequent events marked by long-duration flooding and high total energy expenditure can account for a large fraction of total sediment transport in mountain streams. [ABSTRACT FROM AUTHOR]

Atmospherically-derived cosmogenic nuclides such as meteoric 10 Be offer great potential in Quaternary science because they can be used as landform geochronometers and as sediment tracers. Use of meteoric 10 Be inventories for determining landform age, soil residence time, or erosion rates requires knowing the long-term rate of deposition for this cosmogenic nuclide to the Earth's surface. Here, we present meteoric 10 Be inventories measured at 6 dated sites near the Boulder Creek Critical Zone Observatory, Front Range, Colorado. Each site lies on a relatively stable landform (broad moraine or fluvial terrace) at slopes between <1 and 7° and supports well-developed soil horizons. Time-averaged rates of total meteoric 10 Be deposition (precipitation, dryfall, and dust deposition) calculated from measured inventories at these sites range from 0.4 to 5.0 × 10 6 atoms cm −2 yr −1 ; none of the inventories match expected primary meteoric 10 Be deposition rates that global, latitude-based models or precipitation-specific models predict for this region. Meteoric 10 Be inventories and calculated deposition rates at the three older (>90 ka) sites fall below (0.3–0.7×) model predictions; inventories and rates at the three Pinedale-age sites (LGM; 21–15 ka) are higher (1.5–4×) than model predictions. Previous analysis of soils in the Front Range over the same timeframe as these sites indicate that long-term dust accumulation rates are low and associated secondary meteoric 10 Be deposition is unlikely to account for the deviation from model predictions. At the Pinedale-age sites in particular, long-term dustfall would have to be 1–2 orders of magnitude higher to add the meteoric 10 Be required to account for measured inventories. Low inventories at older sites are consistent with loss of meteoric 10 Be through physical erosion or selective removal of near-surface soil enriched in meteoric 10 Be; time-averaged rates of total meteoric 10 Be deposition for these sites are minima. We speculate that higher inventories at Pinedale-age sites reflect the addition of meteoric 10 Be due to snowdrifts and/or interflow associated with landform location, increasing the effective precipitation-related primary meteoric 10 Be deposition at the sampled sites. Given these constraints, and the spatial variation observed around the Front Range, we suggest that 1.5 ± 0.2 × 10 6 atoms cm −2 yr −1 is an appropriate long-term meteoric 10 Be deposition rate to use across much of the Front Range region that receives 45–55 cm of precipitation a year. This long-term total meteoric 10 Be deposition rate is ∼30–50% higher than that predicted by global or annual precipitation-specific models, emphasizing that local calibration of deposition rates is essential for geomorphic studies around the globe. [ABSTRACT FROM AUTHOR]

We used measurements of cosmogenic 10Be in alluvium to estimate erosion rates on a 103-104 yr time scale for small (0.01-47 km²), unglaciated basins in northern Colorado, southern Wyoming, and adjacent western Nebraska (western United States). Basins formed in Proterozoic cores of Laramide ranges are eroding more slowly (23 ± 7 mm k.y. -1, n = 19) than adjacent basins draining weakly lithified Cenozoic sedimentary rocks (75 ± 36 mm k.y. -1, n = 20). Erosion rates show a relationship to rock resistance and, for granitic rocks, to basin slope, but not to mean annual precipitation. We estimated longer-term (>105 yr time scale) erosion rates for the granitic core of the Front Range by measuring the concentration of 10Be and 26Al produced mainly by muon interactions at depths 1.7-10 m below the surface. Concentrations imply erosion rates of 9-31 mm k.y. -1, similar to shorter-term erosion rates inferred from alluvial sediment. The spatial distribution of erosion rates and stratigraphic evidence imply that relief in the southern Rocky Mountains increased in the late Cenozoic; modern relief probably dates from post-middle Miocene time. [ABSTRACT FROM AUTHOR]

Abstract: In many transport-limited environments, morphology, pedogenic iron and clay content provide a basis for estimating the exposure age of soils and associated landforms. We measured citrate-buffered dithionite (CBD)-extractable Fe (Fed) and clay concentration in fresh rock, saprolite, morainal and colluvial materials, and soil horizons from stable surfaces and hillslopes in the Colorado Front Range. Fresh igneous and high-grade metamorphic rocks contain <1% Fed and 1 to 5% clay. As bedrock and surficial deposits age, Fed and clay accumulate from weathering and dustfall. Late Holocene regolith at warm, dry sites contains small amounts of Fed and clay, but relatively moist soils developed on early Holocene cirque deposits contain as much as 1.5% Fed and 8% clay. Concentrations and total profile accumulation of Fed and clay increase with age in soils developed on stable surfaces of glacial deposits as old as ~130kyr. On stable sites, Fed and clay accumulation from weathering and dust is ~0.02gcm−2 kyr−1 and ~0.2gcm−2 kyr−1, respectively. We used the Fed and clay inventory in soil profiles at dated, stable Front Range surfaces to calculate accumulation functions, which allowed us to estimate soil age at hillslope sites. Heterogeneous parent material, particularly on hillslopes, and climate-related effects add to variability in measured relations. Mobile regolith in Gordon Gulch, one of the Boulder Creek Critical Zone Observatory (CZO) catchments, yields profile ages from about 0.5 to 5×104 yr, comparable to values measured using other techniques. Calculated profile ages are older on a north- vs. south-facing slope and increase from the drainage divide to the footslope. Ages calculated for stabilized colluvium and well-developed buried profiles at nearby hillslope sites (Lefthand, Ward and Rollinsville) suggest that these soils have stabilized over periods >105 yr. In the absence of radiometric ages, the accumulation of Fed and clay in soils on stable sites and hillslopes provides a useful, local chronofunction for 103 to ~3×105 yr. Local footslope thickening of mobile regolith, buried soils, and areas of Fed- and clay-rich stabilized colluvium suggest that steady-state models of hillslope regolith must be modified to account for observed soil properties. [Copyright &y& Elsevier]

Abstract: Granitic regolith, developed in the Boulder Creek catchment and adjacent areas, records a history of deep weathering, some of which may predate Quaternary time. Field and well-log measurements of weathering, chemical denudation and rates of erosion derived from 10Be cosmogenic radionuclide (CRN) data help to quantify rates of landscape change in the post-orogenic Rocky Mountains. The density of oxidized, fractured bedrock ranges from 2.7 to about 2.2 g cm−3, saprolite and grus have densities between ∼2.0 and 1.8 g cm−3, and 30 soil samples averaged 1.6±0.2 g cm−3. Highly weathered regolith in ∼540 wells averages ∼3.3 m thick, mean depth to bedrock in 1661 wells is ∼7 m, and the weathered thickness exceeds 10 m in relatively large local areas east of the late Pleistocene glacial limit. Thickness of regolith shows no simple relationship to rock type or structure, local slope, or distance from channels. Catchments in the vicinity of the Boulder Creek have an average CRN erosion rate of 2.2±0.7 cm kyr−1 for the past 10,000 to 40,000 yr. Annual losses of cations and SiO2 vary from about 2 to 5 g m−2 over a runoff range of 10 to nearly 160 cm. Using measured rates in simple box models shows that if a substantial fraction of void space is created by volume expansion in the weathering rock materials, ∼7 m of weathered rock materials could form in as little as 230 kyr. If density loss results mainly from chemical denudation and some volume expansion, however, the same weathering profile would take >1340 kyr to form. Rates of erosion measured by CRN could be balanced by the rate of soil formation from saprolite if the annual solute loss from soil is 2.0 g m−2 and 70% of the density decrease from saprolite to grus and soil results from strain. Saprolite, however, forms from oxidized bedrock at a far slower rate and rates of saprolite formation cannot balance soil and grus losses to erosion. The zone of thick weathered regolith is likely an eroding relict landscape. The undulating surface marked by relatively low relief and tors is not literally a topographic surface of Eocene, Oligocene or Miocene age unless it was covered with deposits that were removed in Pliocene or Quaternary time. [Copyright &y& Elsevier]

Investigates Pleistocene fluvial incision rates in the western United States using Lava Creek B tephra. Rock uplift and endogenic processes; Climate during and after deposition of the Lava Creek B ash; Length of calculated rates of incision; Middle to late Pleistocene changes in incision rates.

Describes the links between late Pleistocene climate change and mass movements in northern New Mexico. Lacustrine deposits; Effects of glacial melt and pluvial activity; Evidence of landscape response in well-dated lacustrine deposits.

Presents evidence pertaining to the nature, distribution and age of multiple landslide-dammed lakes along the Rio Grande in White Rock Canyon, New Mexico. Lacustrine deposits as evidence for the repeated generation of lakes in White Rock Canyon; Size and duration of late Pleistocene lakes; Outburst flooding; Landslide triggering mechanisms.

Oxbow lakes are important stores for fine-grained sediment, which potentially makes them critical sinks for sediment-associated pollutants. We leverage an exhaustive public archive of coring data, supplemented by our data collection, to provide a quantitative assessment of the role of oxbows as off-channel sinks. We investigated loading trends of sediment-sorbed polychlorinated biphenyls (PCBs) within oxbows of the Housatonic River, an actively meandering river in western Massachusetts, USA. Our results reveal the efficiency of oxbows as sinks, with average PCB concentrations (14.8 ppm) that are nearly twice that of the surrounding floodplain (7.56 ppm). Even though the 5.83 km² floodplain is the largest sink of PCB-laden material, storing as much as 14.1 t of PCBs or 2.42 g m-2, oxbows store more than 20% of all PCBs (3.63 t of PCBs or 11.2 g m-2) while making up just over 5% of the floodplain surface area. Nearly 85% of the oxbow storage of PCBs occurs within the first 50 m of floodplain, making clear the significance of regular oxbow production to the off-channel storage of sediment-associated pollutants. [ABSTRACT FROM AUTHOR]

Abstract The Mg isotope compositions of weathering profiles developed on granite and granodiorite bedrock have been analyzed to investigate Mg isotope behavior during the weathering of felsic rocks in a continental environment. δ26Mg generally exhibits a small increase from the bedrock values, which range from −0.17 ± 0.06‰ to +0.07 ± 0.06‰, until the upper two meters in which a decrease is observed, producing near surface values between −0.14 ± 0.06‰ and +0.09 ± 0.06‰. The small observed increase in isotopic composition below 2 m is likely due to Mg loss to the hydrosphere during biotite weathering and in situ illite production, while the decrease at depths <2 m is likely due to illite weathering near the surface, with a possible minor contribution from downslope deposition of less weathered material. One hydrothermally altered profile shows more extreme fractionation, reaching δ26Mg values as heavy as +0.55 ± 0.06‰ in the near surface component of the section. The fractionation associated with Mg loss during weathering can be modeled by Rayleigh distillation with fractionation factors between the residual rock and fluid ranging from α = 1.00001 to 1.00040. The Mg isotope composition is primarily controlled by the behavior of illite in the weathering profile, as Mg isotope composition is positively correlated with the illite fraction of major Mg-bearing minerals. A thorough understanding of Mg isotope systematics in these complex clay minerals may permit the use of Mg isotopes in paleosols as paleoclimate indicators. Highlights • Mg isotopes are primarily controlled by illite behavior during granite weathering. • Profiles varied from δ26Mg ≅ −0.17‰ in the bedrock up to +0.09‰ in the regolith. • One hydrothermal profile varied from δ26Mg ≅ −0.07‰ in the bedrock up to +0.55‰. • Mg isotopes could help to elucidate Mg cycling in continental environments. [ABSTRACT FROM AUTHOR]

Past interglacial climates with smaller ice sheets offer analogs for ice sheet response to future warming and contributions to sea level rise; however, well-dated geologic records from formerly ice-free areas are rare. Here we report that subglacial sediment from the Camp Century ice core preserves direct evidence that northwestern Greenland was ice free during the Marine Isotope Stage (MIS) 11 interglacial. Luminescence dating shows that sediment just beneath the ice sheet was deposited by flowing water in an ice-free environment 416 ± 38 thousand years ago. Provenance analyses and cosmogenic nuclide data and calculations suggest the sediment was reworked from local materials and exposed at the surface <16 thousand years before deposition. Ice sheet modeling indicates that ice-free conditions at Camp Century require at least 1.4 meters of sea level equivalent contribution from the Greenland Ice Sheet. [ABSTRACT FROM AUTHOR]

Background: Subsurface ice preserved as ice lenses and within rock glaciers as well as glacial and lake ice provides sensitive indicators of climate change and serve as a late-season source of meltwater. Aims: We synthesise the results of geomorphological, geophysical and geochemical studies during the period of 1995–2014, building on a long history of earlier work focused on ice and permafrost studies on Niwot Ridge and the adjacent Green Lakes Valley (GLV), which is part of the Niwot Ridge Long Term Ecological Research Site. Methods: These studies are discussed in the context of how bodies of ice and rock glaciers reflect changing local climate. We review recent results from geophysical investigations (resistivity, seismic refraction and ground-penetrating radar) of the shallow subsurface, ongoing monitoring of the Arikaree Glacier, three rock glaciers and lake ice in the GLV, and interpretations of how subsurface ice melt regulates the flow and chemistry of alpine surface water after seasonal snowfields melt. Results and conclusions: Permafrost conditions reported from Niwot Ridge in the 1970s are generally absent today, but ice lenses form and melt seasonally. Ice is present permanently within the Green Lakes 5 rock glacier and at nearby favourable sites. The Arikaree Glacier has shown a marked decline in cumulative mass balance during the past 12 years after a 30-year period when net mass balance was ca. 0. Duration of seasonal lake ice increases with elevation in GLV, but duration has decreased at all seven lakes that have been monitored during the last three decades. This decrease has been most marked at the lowest elevation where it amounted to a reduction of about 1 d year−1and least at Green Lake 5 where the loss has been at a rate of 0.5 d year−1. Surface temperature measurements from rock glaciers have not shown strong trends during the past 15 years. It has been suggested that almost all of the 2.5-mm year−1increase in stream discharge from the upper GLV in September and October has been derived from melting of subsurface ice. [ABSTRACT FROM PUBLISHER]

Understanding the history of the Greenland Ice Sheet (GrIS) is critical for determining its sensitivity to warming and contribution to sea level; however, that history is poorly known before the last interglacial. Most knowledge comes from interpretation of marine sediment, an indirect record of past ice-sheet extent and behavior. Subglacial sediment and rock, retrieved at the base of ice cores, provide terrestrial evidence for GrIS behavior during the Pleistocene. Here, we use multiple methods to determine GrIS history from subglacial sediment at the base of the Camp Century ice core collected in 1966. This material contains a stratigraphic record of glaciation and vegetation in northwestern Greenland spanning the Pleistocene. Enriched stable isotopes of pore-ice suggest precipitation at lower elevations implying ice-sheet absence. Plant macrofossils and biomarkers in the sediment indicate that paleo-ecosystems from previous interglacial periods are preserved beneath the GrIS. Cosmogenic 26Al/10Be and luminescence data bracket the burial of the lower-most sediment between <3.2 ± 0.4 Ma and >0.7 to 1.4 Ma. In the upper-most sediment, cosmogenic 26Al/10Be data require exposure within the last 1.0 ± 0.1 My. The unique subglacial sedimentary record from Camp Century documents at least two episodes of ice-free, vegetated conditions, each followed by glaciation. The lower sediment derives from an Early Pleistocene GrIS advance. 26Al/10Be ratios in the upper-most sediment match those in subglacial bedrock from central Greenland, suggesting similar ice-cover histories across the GrIS. We conclude that the GrIS persisted through much of the Pleistocene but melted and reformed at least once since 1.1 Ma. [ABSTRACT FROM AUTHOR]

Historic charcoal hearth remains provide a unique archive of the long-term interaction between biochar, soil development, and plant growth. Charcoal as raw material was crucial for production of iron in iron works, and hence numerous charcoal hearths can be found in the forests near historic iron works in Europe and in the eastern united States. Charcoal hearths are round to elliptical forms often around 10 m in diameter and consist of several-decimeter-thick layers that contain charcoal fragments, ash, and burnt soil. We studied the soil chemistry of 24 charcoal hearths and compared them with the surrounding "natural" soils in the northern Appalachians of northwestern Connecticut. The thickness of the topsoils on the charcoal hearths and their carbon content are remarkably higher than in the surrounding topsoils. The presence of residual products from charcoal production classifies the soils as Anthropic Udorthents (US Soil Taxonomy) or Spolic Technosols (Humic) according to the World Reference Base for Soil Resources. The widespread occurrence of charcoal hearth remains, and their high spatial density in different ecosystems underlines their importance for further pedological research. [ABSTRACT FROM AUTHOR]

Relict charcoal hearths are round or elliptical earthen platforms up to 11 m in diameter and a widespread feature of historical industry that supplied charcoal used in the production of iron in furnaces or smelters. The iron industry dominated Litchfield County, Connecticut, and surrounding areas in the northeast United States throughout the 19th century, peaking in ∼1850. The large number of charcoal hearths in this region is a relic of >150 years of widespread iron production. In this study, we describe the architecture and soil stratigraphy of 26 charcoal hearths in Litchfield County. This contribution aims to (1) compare soils that comprise the charcoal hearths with 'natural' adjacent soils, (2) measure the thickness of topsoil developed upon the hearths, and (3) characterize the stratigraphy associated with these features. Results indicate that the black topsoils overlying the charcoal hearths contain residual charcoal and are on average 2.6 times thicker than adjacent Cambisols. Charcoal hearths display two or more black, charcoal-rich strata separated by layers of reddish-brown soil low in charcoal content indicating multiple episodes of use. We also find that many charcoal hearths have been stabilized with boulders on the downslope side during construction and repeated use. Overall, the results presented here provide significant information regarding the construction, use, and associated impacts of earthen platforms for charcoal production in the northeast United States, with further relevance to other areas where historical charcoal production occurred. [ABSTRACT FROM AUTHOR]

Cosmogenic radionuclides (CRNs) are commonly employed to quantify both the production rates and residence times of mobile regolith. Meteoric and in situ CRNs have different accumulation mechanisms and can independently constrain landscape evolution rates. Here we use both in situ and meteoric 10Be to investigate where in the regolith 10Be is stored, and to quantify production rates and residence times of mobile regolith on active hillslopes in Gordon Gulch, within the Boulder Creek Critical Zone Observatory (CZO), Colorado, USA. Our data reveal that two-thirds of in situ 10Be in regolith is produced within saprolite, and at least one-tenth of the meteoric 10Be inventories is stored in saprolite, highlighting the importance of consistent terminology and identification of the mobile regolith-saprolite boundary. We find that mobile-regolith production rates are on average 3.1 cm/k.y., and residence times are between 10 and 20 k.y. A notable exception exists at the depositional north-facing footslope, where residence times likely exceed 40 k.y. Close agreement between the meteoric and in situ results indicates that upperand mid-slope positions are consistent with steady, uniform lowering of the landscape. In addition to comparing the two methods, we develop a one-dimensional analytical model for the 10Be concentration fi elds on an active, steady-state catena with uniform erosion. We then compare model predictions with measurements to evaluate how well our sites adhere to the steady-state assumption underlying the calculations for mobile-regolith residence time and production rates. Such comparisons suggest that calculated residence times and lowering rates are likely no closer than ±25% of the geomorphic reality. [ABSTRACT FROM AUTHOR]

Analyzing meteoric 10 Be in soil profiles along with soil measurements such as pedogenic Fe and clay content permits better understanding of meteoric 10 Be transport in soils, soil formation, and hillslope geomorphology. This study presents meteoric 10 Be depth profiles from saprolite-derived soil catenas sampled in the Gordon Gulch catchment, Colorado Front Range and from nearby c. 130 and 15 ka glacial moraines. We compare meteoric 10 Be data with more classically used soil analyses of clay and extractable iron (Fed) content. Meteoric 10 Be and Fed do not show consistent trends in the hillslope profiles. Meteoric 10 Be and clay concentrations, however, generally decrease with depth and highest concentrations of 10 Be in horizons coincide with highest clay concentrations. Soils at moraine sites are better developed than those on hillslopes, and correlations of 10 Be, Fed, and clay are stronger. In Gordon Gulch, south-facing hillslopes display meteoric 10 Be bulges at depth and lower near-surface concentrations compared to the declining profiles and higher near-surface concentrations of north-facing hillslopes. The aspect differences imply that south-facing hillslopes experience greater vertical mixing than north-facing hillslopes, and that greater lateral transport and erosion has occurred over the last 15–20 ka on south-facing hillslopes relative to north-facing hillslopes. Meteoric 10 Be depth profiles at moraine sites display bulge profiles with highest meteoric 10 Be concentrations in B-horizons, reflecting landform stability and pedogenic processes. Overall, our data demonstrate that signatures of chemical weathering in soils (Fed and clay) may or may not correlate to the meteoric 10 Be added through atmospheric deposition, and that profile shape of meteoric 10 Be can provide insight into the relative contribution of vertical mixing and surface erosion in relation to catena location and aspect during hillslope evolution. [ABSTRACT FROM AUTHOR]

Abstract: Activity and stability phases as well as geomorphic processes within the Critical Zone are well known. Erosion and deposition of sediments represent activity; soils represent geomorphic stability phases. Data are presented from a 4m deep sediment section that was dated by luminescence techniques. Upslope erosion and resulting sedimentation started in the late Pleistocene around 18ka until 12ka. Conditions at the study site then changed, which led to the formation of a well-developed soil. Radiocarbon dating of the organic matter yielded ages between 8552 and 8995cal.BP. From roughly 6.2 to 5.4ka another activity phase accompanied by according sediment deposition buried the soil and a new soil, a Cambisol, was formed at the surface. The buried soil is a strongly developed Luvisol. The black colors in the upper part of the buried soil are not the result of pedogenic accumulation of normal organic matter within an A-horizon. Nuclear magnetic resonance spectroscopy clearly documents the high amount of aromatic components (charcoal), which is responsible for the dark color. This indicates severe burning events at the site and the smaller charcoal dust (black carbon) was transported to deeper parts of the profile during the process of clay translocation. [Copyright &y& Elsevier]

Abstract: At least three sets of moraines mark distinct glacial stands since the last glacial maximum (LGM) in the Three Sisters region of the Oregon Cascade Range. The oldest stand predates 8.1 ka (defined here as post-LGM), followed by a second between ∼2 and 8 ka (Neoglacial) and a third from the Little Ice Age (LIA) advance of the last 300 years. The post-LGM equilibrium line altitudes were 260±100 m lower than that of modern glaciers, requiring 23±9% increased winter snowfall and 1.4±0.5°C cooler summer temperatures than at present. The LIA advance had equilibrium line altitudes 110±40 m lower than at present, implying 10±4% greater winter snowfall and 0.6±0.2°C cooler summer temperatures. [Copyright &y& Elsevier]

Abstract: The post-orogenic evolution of the Laramide landscape of the western U.S. has been characterized by late Cenozoic channel incision of basins and their adjacent ranges. One means of constraining the incision history of basins is dating the remnants of gravel-capped surfaces above modern streams. Here, we focus on an extensive remnant of the Rocky Flats surface between Golden and Boulder, Colorado, and use in situ-produced 10Be and 26Al concentrations in terrace alluvium to constrain the Quaternary history of this surface. Coal and Ralston Creeks, both tributaries of the South Platte River, abandoned the Rocky Flats surface and formed the Verdos and Slocum pediments, which are cut into Cretaceous bedrock between Rocky Flats and the modern stream elevations. Rocky Flats alluvium ranges widely in age, from >2Ma to ∼400ka, with oldest ages to the east and younger ages closer to the mountain front. Numerical modeling of isotope concentration depth profiles suggests that individual sites have experienced multiple resurfacing events. Preliminary results indicate that Verdos and Slocum alluvium along Ralston Creek, which is slightly larger than Coal Creek, is several hundred thousand years old. Fluvial incision into these surfaces appears therefore to progress headward in response to downcutting of the South Platte River. The complex ages of these surfaces call into question any correlation of such surfaces based solely on their elevation above the modern channel. [Copyright &y& Elsevier]

• Soils from 18th–20th century charcoal hearths were analyzed across Connecticut, USA. • Available phosphorus is more than 200% lower in hearths soils than adjacent soils. • Hearth soils are enriched in organic carbon and extractable cations Ca2+, Mg2+, Na+. • Hearths with two charcoal layers indicate multiple episodes of charcoal production. • Charcoal dispersal increases the area of impact for individual hearths by 30×. Relic charcoal hearths (RCHs) have produced distinct legacy effects in forest soils around the world. Recently, LiDAR imagery has revealed thousands of 18th–early 20th century RCHs in Litchfield County, Connecticut, USA; however, the effects of RCHs on a landscape-scale are not well-documented, particularly fine-scale heterogeneity within RCHs and surrounding soils. This study examines the long-term impacts of charcoal production by measuring RCH soil chemical and physical properties from three perspectives: (1) compared to adjacent reference sites (RS adj), (2) laterally at systematic distances away from the RCH center, and (3) vertically within the RCH soil profile. Mean charcoal abundance was greater in RCH sites than RS adj (p < 0.01). Soil organic carbon (SOC), total C, and extractable Ca2+, Mg2+, Na+ were greater in RCH sites as compared to RS adj (p < 0.01), and available phosphorus (p < 0.01), K+, and trace elements (Mo, Ag, Hg, and Se) were lower (p < 0.05). In vertical profiles, many RCHs had 2 charcoal-rich layers within the anthropic epipedon, demonstrating multiple episodes of charcoal production. Peaks in SOC, C:N, Ca2+, Mg2+ corresponded with charcoal-rich layers. Systematic transect sampling across the RCH boundary identified charcoal fragments in soils at distances up to 25 m beyond the RCH boundary, increasing the surface-level (0–15 cm) area of impact for an individual RCH by more than 30×, from a 5-m radius (RCH area = 78.5 m2) to a 30-m radius (total area of impact = 2826 m2). These findings capture fine-scale variations within and among RCH and reference sites and contribute to estimating the total area of forest soils impacted by historical charcoal production. [ABSTRACT FROM AUTHOR]