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Introduction
Published in Barry G. Clarke, Engineering of Glacial Deposits, 2017
It is estimated that at some time 30% of the world’s land mass was covered by glaciers or ice sheets (Benn and Evans, 2010); a quarter of North America, one-third of Europe, and 60% of the United Kingdom were covered in glacial materials (Flint, 1971). A glacier is a slow moving mass or ‘river’ of ice formed by accumulation and compaction of snow falling on the upper reaches of a valley glacier or near the centre of ice sheets. About 22% of the Earth’s land surface was covered by glaciers at the last ice age; currently, glaciers and ice sheets cover 9.6% of the terrestrial surface. Glacial ice is an important dynamic element of the earth system; for example, 25.7 × 106 km3 of ice is found in the Antarctic Ice Sheet, equivalent to a rise of 61 m sea level; mountain glaciers are an important water resource. As glacial ice advances, it deforms and erodes the bedrock and underlying soil, including remnants of previous glaciations, and transports, homogenises and deposits glacial soils beneath the glacier, at the ice margins or remote from the ice margins. Most of the terrestrial glacial soils are remnants of the last glacial advance leaving extensive deposits of glacial drift (Table 1.1). Since the last glacial period, the ice has receded leaving ice sheets confined to Greenland and Antarctica and valley glaciers in the Alps, Himalayas, Andes and North Alaska (Table 1.2), with the ice sheets representing 96.6% of the current glaciated area.
Strong tides during Cryogenian glaciations: tidal rhythmites from early and late Cryogenian glacial successions and interglacial beds, South Australia
Published in Australian Journal of Earth Sciences, 2023
High-quality paleomagnetic and rock magnetic data for the red brown Elatina rhythmite at Pichi Richi Pass, including positive fold tests on soft-sediment slumps and rock-magnetic tests (high-field isothermal remanence, thermoremanence, and the elongation–inclination method), plus data for correlative strata elsewhere in the Adelaide Rift Complex, established the early acquisition and minimal inclination-shallowing of remanence directions and the low paleolatitude (≤10°) of the terminal Cryogenian Elatina glaciation (Schmidt et al., 1991, 2009; Schmidt & Williams, 1995, 2013). Paleomagnetic data for red beds from the Angepena Formation of the interglacial succession between the Sturt and Elatina glaciations (Figure 2; Williams & Schmidt, 2015), together with paleomagnetic data for pre-interglacial beds from the Officer Basin (Pisarevsky et al., 2001, 2007), indicated that southern Australia lay in low paleolatitudes (6–10°) during the interglacial interval and the preceding Sturt glaciation.
Miocene-Holocene river drainage evolution in Southland, New Zealand, deduced from fish genetics, detrital gold and geology
Published in New Zealand Journal of Geology and Geophysics, 2022
Dave Craw, Ciaran Campbell, Jonathan M. Waters
The western portion of this mountain barrier between Central Otago and Southland has been breached intermittently since the Miocene, including during various Pleistocene glaciation events right through to the Last Glacial Maximum (Table 1; Turnbull and Allibone 2003; Craw et al. 2007). These various events have added complexity to the determination of paleodrainage patterns in that area and redistribution of alluvial gold and other heavy minerals (Craw et al. 2012; Craw 2013; Craw, Kerr, et al. 2015; Upton and Craw 2016). The drainage configuration around the eastern portion of the mountain barrier has been intimately related to the evolution of the Pomahaka catchment and its relationships to Southland drainages and the Clutha catchment, principally during the Pleistocene (Figures 6A–C, 7A–D, 8A,B). The full significance of these eastern drainage changes for alluvial gold redistribution in Eastern Southland is yet to be determined.
Glaciers and glaciation of North Island, New Zealand
Published in New Zealand Journal of Geology and Geophysics, 2021
Shaun R. Eaves, Martin S. Brook
While moraines offer useful constraints on past downstream glacier limits, their use in isolation offers little information on former ice thickness or lateral ice extent on the upper mountain. Absence of such constraints is challenging for glacier modelling studies that seek to investigate the climate conditions for past glaciation (e.g. Eaves, Mackintosh, Anderson, et al. 2016). Recent identification of lava textures and chemical signatures that result from lava-ice interactions offers the novel potential for three-dimensions glacier reconstruction using the geological record (Conway et al. 2015; Cole et al. 2018, 2019). Further combination of such phenomena with quantitative age information about lava emplacement (e.g. 40Ar/39Ar; Conway et al. 2016) on both Tongariro and Ruapehu offers potential insight into ice extents outside of the former advance events captured by the moraine record. If present, such evidence could also provide rare constraint of past glacial cover on other volcanoes, such as Mt Taranaki, where post-glacial volcanism may have removed or buried glacial landforms.