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Sediments and Sedimentary Rocks
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
Moraine is a general term for landforms made of till; several different kinds of moraines are labeled in Figure 8.33. End moraines, which form at a glacial terminus as ice melts, leave ridges and piles of glacial debris oriented generally perpendicular to the direction of ice flow. Because ice advances or retreats depending on seasonal and longer-term climate changes, glaciers commonly leave more than one end moraine behind; two are shown in Figure 8.33. The end moraine formed at the farthest point of glacier advance is called the terminal moraine. Ground moraines consist of material deposited from glacial ice beneath a glacier. After glacial ice is gone, ground moraines are characterized by uneven topography, typically with many small ridges and basins. Ground moraines may be small or extensive and may be closely associated with terminal moraines.
Surface Processes
Published in F.G.H. Blyth, M. H. de Freitas, A Geology for Engineers, 2017
F.G.H. Blyth, M. H. de Freitas
Some of the processes which deposit glacial drift differ sufficiently for the shape of their accumulations to be diagnostic of their mode of formation. Distinctive landforms can be identified of which the most common are now described. Debris dropped at the front of a glacier as the ice melts forms a hummocky ridge or terminal moraine, in the British Isles these end-moraines are found for example in north Yorkshire, South Wales, and southern Ireland. Extensive terminal moraines exist in Canada, Scandinavia and Russia. Other mounds of sand and gravel which were derived from the ice along its margins during pauses in its retreat, and lie parallel to the ice-front, are known as kames. Good examples of kames in Britain can be seen near Carstairs, Lanarkshire, and in the Clyde valley, and at places in the north of England.
Three-dimensional hydrostratigraphical modelling of the regional aquifer system of the St. Maurice Delta Complex (St. Lawrence Lowlands, Canada)
Published in Canadian Water Resources Journal / Revue canadienne des ressources hydriques, 2018
Guillaume Légaré-Couture, Yves Leblanc, Michel Parent, Karine Lacasse, Stéphane Campeau
Facies encountered in drilling along the Saint-Narcisse morainic complex vary widely. In general, the upper layer consists of coarse-grained sediments, from sand to cobbles and boulders, and is associated with ice retreat from the terminal moraine. This material generally lies above the groundwater table and is too coarse to form a reservoir, but it contributes to the overall recharge of the surrounding aquifers. Multiple stratigraphic wells drilled in the center of the Saint-Narcisse Moraine showed the presence of a layer of fine-grained sediments or diamicton (till) at the base, confirming that the material was emplaced in a marine environment during a re-advance of the ice sheet. Although the permeability of this unit is lower than that of the overlying coarse-grained material, it cannot be considered an aquitard due to its higher proportion of fine sand. However, a sandy aquifer confined below the marine fine-grained sediments was observed in some borings. For example, an aquifer contained in 20 m of medium sand was discovered when drilling borehole FE-09-11 in the village of Sainte-Angèle-de-Prémont. This deposit should be investigated further, given its positive aquifer characteristics.
Glacial lake changes and outburst flood hazard in Chandra basin, North-Western Indian Himalaya
Published in Geomatics, Natural Hazards and Risk, 2018
Finally, lakes with area greater than 2000 m2 and within 10 km from nearest glacier terminus were catalogued in the glacial lake inventory with following set of attributes assigned to each lake: spatial location of the lake in latitude and longitude and elevation (z) in m, the area of the lake in m2;lake dam type: the lakes were classified into three classes based on dam type namely: (i) ice-dammed which are either impounded by a glacier or embedded on glacier surface as supra glacier pond/lake, (ii) moraine-dammed lakes impounded by either recessional terminal moraine or lateral moraine, (iii) bedrock-dammed lakes impounded by a solid rock mass or lakes without any clear dam structure in the flat terrain of glacier fore-fields (Worni et al. 2013; Emmer et al. 2015);glacier lake distance in m;lake drainage type: divided into (i) surface drainage, and (ii) closed lakes, based on recognizable surface or no surface outflow assessed mainly from Google Earth.
Frontal fault location and most recent earthquake timing for the Alpine Fault at Whataroa, Westland, New Zealand
Published in New Zealand Journal of Geology and Geophysics, 2018
Robert Max Langridge, Jamie D. Howarth, Simon C. Cox, Jonathan G. Palmer, Rupert Sutherland
The Whataroa valley and coastal plain holds a record of the glacial through interglacial climatic cycles that have affected the Southern Alps region during the Late Quaternary (Cox and Barrell 2007; Barrell et al. 2011). Glacial advances are represented by lateral and terminal moraine complexes formed when large glaciers extended to near the current coastline. Geophysical profiles and drilling indicate that the Whataroa valley hosts a deep (>200 m), u-shaped glacial trough, similar to other fiords and lake-filled valleys that extend to the northwest from the Southern Alps, that was formerly filled by a large moraine-bounded, pro-glacial lake (Suggate et al. 1968; Davey 2010; Barrell et al. 2011; Davy et al. 2013; Thomas 2018). Following the retreat of ice, the valley has filled with lacustrine and alluvial deposits. Within the hangingwall block, high alluvial terrace remnants exist around the valley sides (Chinn 1981; Cox and Barrell 2007). In contrast, no latest Pleistocene or early Holocene terraces are known on the northwestern side of the fault due to the relative subsidence on the footwall block and burial by younger fill deposits. The history of Whataroa River alluviation on the footwall block is represented by a suite of late Holocene alluvial aggradation and degradation terraces that have been characterised through geologic and dendrochronologic dating (Cullen et al. 2003; Berryman et al. 2001). In this study, we have qualitatively characterised the evolution of the Whataroa River near the site as a suite of degradation surfaces ranging from the oldest, highest surface (tw4) to the river channels and bars of the current floodplain (tw0) (Figure 4).