The tongue-shaped mass of debris and associated ridges on the cirque floor below Craig Cerrig-gleisiad, Brecon Beacons National Park is important and controversial because it has been attributed to more than one glacier advance during the Late Devensian. A new origin is proposed involving landslide development from the collapse of part of the western headwall followed by a single phase of glacier development in the Loch Lomond Stadial (Younger Dryas), which reworked the landslide sediments. Evidence for this landslide, which provides useful criteria for differentiating moraines formed by small glaciers from landslides, lies in tension cracks, backward-tilted blocks and bedrock joints dipping out of the western headwall, together with lateral levées, upstanding termini and angular clasts with only occasional, indistinct striae on the tongue-shaped mass, which is interpreted as a flowslide. Glacier reworking of debris in the upper part of the Cwm Cerrig-gleisiad landslide is indicated by subparallel ridges rising to 20 m above the cirque floor containing abraded clasts (16-32% striated). This interpretation is supported by a comparison with the morphological and sedimentary characteristics of a neighbouring landslide at Fan Dringarth, where no glacier developed in the Loch Lomond Stadial. The existence of paraglacial landsliding has significant palaeoenvironmental implications leading to: (1) erroneously large estimates of equilibrium line depression ($Δ$ELA) in the Loch Lomond Stadial; (2) consequent underestimates of summer palaeotemperatures and/or overestimates of the contribution of wind-drifted snow to glacier accumulation; and (3) larger moraines than usual and overestimation of the efficacy of glacial erosion because of antecedent processes.
Largest lichens (genus Rhizocarpon) were measured on 2800 boulders sampled systematically at 28 sites on a thin triangular talus. Sites with similar lichen-size frequency distributions were grouped...
Wildfire can lead to increased fine-sediment (and associated nutrient) delivery to water bodies downstream of burnt terrain. Burnt soils in the drainage basin of Sydney's principal water supply reservoir show enrichment in nutrient and trace element properties (Ca, Mg, P, K, Zn and Pb) in association with mineralization of organic matter. This work aims to explore the potential for using geochemical tracers to quantify the impact of severe wildfire on downstream sediment dynamics and further, to see if a useful record of changing river basin sediment dynamics is recorded in reservoir sediment. Whilst fire-induced changes in geochemistry appear to offer a useful means for discriminating surface sediment sources with respect to fire severity, comparison with the geochemical stratigraphy of the lake is hampered by variable sedimentation dynamics linked to water level fluctuation and overprinting of source signatures by process-related transformations. Further exploration of the factors affecting catchment source signatures and linkages within the system are required before the sedimentary record can be used to full advantage.
Summary Knowledge of soil water repellency distribution, of factors affecting its occurrence and of its hydrological effects stems primarily from regions with a distinct dry season, whereas comparatively little is known about its occurrence in humid temperate regions such as typified by the UK. To address this research gap, we have examined: (i) water repellency persistence (determined by the water drop penetration time method, WDPT) and degree (determined by the critical surface tension method, CST) for soil samples (0–5, 10–15 and 20–25 cm depth) taken from 41 common soil and land‐use types in the humid temperate climate of the UK; (ii) the supposed relationship of soil moisture, textural composition and organic matter content with sample repellency; and (iii) the bulk wetting behaviour of undisturbed surface core samples (0–5 cm depth) over a period of up to 1 week. Repellency was found in surface samples of all major soil textural types amongst most permanently vegetated sites, whereas tilled sites were virtually unaffected. Repellency levels reached those of the most severely affected areas elsewhere in the world, decreased in persistence and degree with depth and showed no consistent relationship with soil textural characteristics, organic matter or soil moisture contents, except that above a water content of c . 28% by volume, repellency was absent. Wetting rate assessments of 100 cm 3 intact soil cores using continuous water contact (–20 mm pressure head) over a period of up to 7 days showed that across the whole sample range and irrespective of texture, severe to extreme repellency persistence consistently reduced the maximum water content at any given time to well below that of wettable soils. For slightly to moderately repellent soils the results were more variable and thus hydrological effects of such repellency levels are more difficult to predict. The results imply that: (i) repellency is common for many land‐use types with permanent vegetation cover in humid temperate climates irrespective of soil texture; (ii) supposedly influential parameters (texture, organic matter, specific water content) are poor general predictors of water repellency, whereas land use and the moisture content below which repellency can occur seem more reliable; and (iii) infiltration and water storage capacity of very repellent soils are considerably less than for comparable wettable soils.
Abstract A series of end moraines, with a remarkable saw-tooth pattern, is reported from the glacier foreland of Bødalsbreen, a northern outlet of the ice cap Jostedalsbreen. The three-dimensional morphology of the moraines is described and analysed. Historical records and lichenometric measurements indicate that they were deposited after the “Little Ice Age” glacier maximum of the mid-eighteenth century. It is inferred that the local topography of Bødalen was conducive to the formation of a heavily crevassed pecten at the snout of Bødalsbreen, which produced the end moraines by a push mechanism during minor glacier advances. The observations suggest that pushing may be an underestimated mechanism in moraine ridge formation generally.
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