Loch lomond stadial glacier at Fan Hir,Mynydd Du (Brecon Beacons), South Wales: Critical evidence and palaeoclimatic implications

The c. 1·2 km long, up to c. 25 m high ridge east of the almost north-south aligned Fan Hir scarp, Mynydd Du, South Wales has been regarded as a remarkable protalus rampart formed in the Loch Lomond Stadial (c. 11–10000 years BP ). New data are presented which indicate that it is a moraine. The main points supporting this glacigenic origin are: its curved plan form at the lower, southern end; its scale and the ample depth for snow to glacier ice transformation; the presence of subsidiary ridges interpreted as recessional moraines; the exceptional rate of rockwall retreat required if it were a protalus rampart; and, most importantly, the presence in the ridge of matrix-supported abraded clasts, up to 20% of which are striated. Useful criteria for differentiating moraines and protalus ramparts are thereby proposed and a sound basis is provided for palaeoclimatic reconstruction. Palaeoclimatic inferences imply that the glacier owed its existence to the combined effect of a mean July temperature of c. 8·5°C and topographically enhanced accumulation, nearly half of which was from wind-blown snow.     

Modelling combined open channel flow by artificial neural networks

Combined open channel flow is encountered in many hydraulic engineering structures and processes, such as irrigation ditches and wastewater treatment facilities. Extensive experimental studies have conducted to investigate combined flow characteristics. Nevertheless, there is no simple relationship that can fully describe the velocity profiles in a turbulent flow. The artificial neural network (ANN) has great computational capability for solving various complex problems, such as function approximation. The main objective of this study is to evaluate the applicability of the ANN for simulating velocity profiles, velocity contours and estimating the discharges accordingly. The velocity profiles measured by an acoustic doppler velocimeter in the open channel of the Chihtan purification plant, Taipei, with different discharges at fixed measuring section and different depths are presented. The total number of data sets is 640 and the data sets are split into two subsets, i.e. training and validation sets. The backpropagation algorithm is used to construct the neural network. The results demonstrate that the velocity profiles can be modelled by the ANN, and the ANN constructed can nicely fit the velocity profiles and can precisely predict the discharges for the conditions investigated. Copyright © 2005 John Wiley & Sons, Ltd.     

Ground-Based Observations of the Thermodynamic and Kinematic Properties of Lake-Breeze Fronts in Southern Manitoba,Canada

The effects on the convective boundary layer (CBL) of shading due to shallow cumulus clouds are investigated. The main question is to see whether clouds are able to produce secondary circulations by shading of the surface (dynamic heterogeneities) and how these dynamic heterogeneities interact with static heterogeneities in terms of the production of secondary circulations. Also the effects of cloud shadows on cloud-field characteristics are analyzed. The effects are studied using large-eddy simulations of a cloud-topped CBL with an idealized surface. Over a homogeneous surface, shadows trigger secondary circulations with different strengths depending on the solar zenith angle \(\vartheta \), with large \(\vartheta \) favouring the development of secondary circulations. Over a static heterogeneous surface with a simple striped pattern, the strength of secondary circulations is effectively reduced by dynamic heterogeneities at small \(\vartheta \). At large \(\vartheta \), however, the effect on secondary circulations depends on the orientation of the striped static heterogeneities to the shadow-casting direction of the clouds. The influence of shadows is only small if they are cast perpendicular to the striped heterogeneity, but if stripes and the shadow-casting direction are parallel, secondary circulations are reduced in strength also for large \(\vartheta \). Shadow effects on the cloud-field characteristics vary with \(\vartheta \) as well. The results show that small \(\vartheta \) favours the development of small clouds with a reduced lifetime while large \(\vartheta \) promotes the development of larger clouds with an extended lifetime compared to non-shading clouds.     

Simulation of geomembrane response to settlement in landfills by using the material point method

Because of the multiple layers of dissimilar materials and large deformations involved in the subsidence of a landfill system, large-scale computer simulation of the geomechanical response to subsidence with the use of conventional numerical methods are problematic. The Material Point (MPM), which was recently developed for dynamic problems such as penetration and perforation, is a newly emerging numerical method. The MPM is modified in this paper to simulate the geomechanical response of a landfill cover system that includes a geomembrane under quasi-static loading conditions. Sample problems, for which an analytical solution is available with certain assumptions, are considered to demonstrate the proposed solution procedure. Future work is discussed based on current research results. Copyright © 1999 John Wiley & Sons, Ltd.     

Carbon,hydrogen and nitrogen in carbonaceous chondrites: Abundances and isotopic compositions in bulk samples

Whole-rock samples of 25 carbonaceous chondrites were analysed for contents of C, H and N and δ¹³C, δD and δ¹⁵N. Inhomogeneous distribution of these isotopes within individual meteorites is pronounced in several cases. Few systematic intermeteorite trends were observed; N data are suggestive of isotopic inhomogeneity in the early solar system. Several chondrites revealed unusual compositions which would repay further, more detailed study. The data are also useful for classification of carbonaceous chondrites; N abundance and isotopic compositions can differentiate existing taxonomic groups with close to 100% reliability; Al Rais and Renazzo clearly constitute a discrete “grouplet”; and there are hints that both CI and CM groups may each be divisible into two subgroups.     

Stratigraphic architecture and sedimentology of a Late Pleistocene subaqueous moraine complex,southwest Ireland

Glacigenic sediments exposed in coastal cliffs cut through undulatory terrain fronting the Last Glacial Maximum laterofrontal moraine at Waterville on the Iveragh Peninsula, southwest Ireland, comprise three lithofacies. Lithofacies 1 and 2 consist of interdigitated, offlapping and superimposed ice‐proximal subaqueous outwash and stacked sequences of cohesionless and cohesive subaqueous debris flows, winnowed lag gravels and coarse‐grained suspension deposits. These are indicative of sedimentation in and around small grounding line fans that prograded from an oscillating glacier margin into a proglacial, interlobate lake. Lithofacies 3 comprises braided river deposits that have undergone significant syn‐sedimentary soft‐sediment deformation. Deposition was likely related to proglacial outwash activity and records the reduction of accommodation space for subaqueous sedimentation, either through the lowering of proglacial water levels or due to basin infilling. The stratigraphic architecture and sedimentology of the moraine at Waterville highlight the role of ice‐marginal depositional processes in the construction of morphostratigraphically significant ‘end moraine’ complexes in Great Britain and Ireland. Traditional ‘tills’ in these moraines are often crudely stratified diamictons and gravelly clinoforms deposited in ice‐proximal subaqueous and subaerial fans. Copyright © 2011 John Wiley & Sons, Ltd.     

Occurrence and distribution of shortnose sturgeon,Acipenser brevirostrum,in the upper tidal Delaware River

Sampling in the upper tidal Delaware River between Trenton, New Jersey, and Philadelphia, Pennsylvania, from July 1981 through December 1984 demonstrated the existence of a significant population of shortnose sturgeon. The sturgeon aggregate in the river channel during daylight hours, especially in the area between Trenton and Florence, New Jersey (river km 211.8 to 198.8). Occurrence in the river downstream of Florence appears to be restricted by poor water quality during summer months. Sturgeon were present in the study area throughout the year, but largest numbers were collected from May though November. No spawning was observed during this study, but presence of males with milt suggests that spawning possibly occurs in the Trenton area. Preliminary population estimates (Peterson, Schnabel and Seber-Jolly) indicate an adult population of approximately 6,000–14,000 shortnose sturgeon occupying the upper tidal Delaware River.