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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
Ice is formed by compaction of snow in cold regions and at high altitudes, where the supply of snow exceeds the wastage by melting. In an intermediate stage between snow and ice the partly compacted granular mass is called neve. Ice of sufficient thickness on land will begin to move down a slope and such a moving mass is called a glacier. It may occupy a valley, as a valley glacier, of which many examples are found in the Alps, the Rockies, the Himalayas and other mountain regions; they are the relics of larger ice-caps (Fig. 3.37). Where several valley glaciers meet on low ground in front of a mountain range a piedmont glacier is formed, e.g. the Malaspina Glacier of Alaska. The accumulations of thick ice much larger than those of valley glaciers, constitute the ice-sheets, and cover great areas. The Greenland ice-sheet extends over about 1.73 × 106 km2; drill cores have been obtained from the ice at depths up to 1400 metres. The Antarctic ice-sheet is more than six times greater in extent. Rock peaks protruding through an ice cover are called nunataks. When land ice meets the sea it begins to float and break up into icebergs; any land-derived debris held in the ice is carried by the bergs and dropped as they become reduced by melting.
Cover successions on early Paleozoic basement in Marie Byrd Land, West Antarctica – evidence for Cretaceous plant-bearing rocks at South Polar latitudes
Published in New Zealand Journal of Geology and Geophysics, 2023
Christopher J. Adams, John D. Bradshaw
Milan Rock is a small isolated nunatak within the Land Glacier, where sandstones and siltstones are found as erratics amongst glacial debris on its south side. A detailed geological description is given in Grindley and Mildenhall (1980). These rocks are not otherwise seen in situ. Some mudstone erratic blocks have yielded plant fossils, principally the Devonian lycopod Haplostyga (Grindley et al. 1980;). However, the detrital zircon samples used in this study are from small fine-grained siltstone-greywacke that contains only indeterminate plant fragments. The erratics might possibly be derived from a shallow-water sedimentary sequence (Wilkins Formation) nearby which underlies low-grade calcalkaline metavolcanics (Ruppert Coast Volcanics) of uncertain age, possibly late Paleozoic or Mesozoic (Grindley and Mildenhall 1980).
Re-visiting the structural and glacial history of the Shackleton Glacier region of the Transantarctic Mountains, Antarctica
Published in New Zealand Journal of Geology and Geophysics, 2022
The Permian-Triassic boundary at Collinson Ridge (Figure S5), directly east of Kitching Ridge, is located at a REMA-elevation of 1900 m, which gives a similar offset (ca. 350 m, down to the west beneath the Shackleton Glacier) to that determined for displacement (300–400 m) of the Kukri/Maya Erosion Surface across Shackleton Glacier between Mount Wade and Mount Butters. To the south, along the trend of this inferred fault, a reliable estimate of offset is not possible because of the lack of detailed stratigraphic data and/or a key horizon. Fremouw strata are present at Dismal Buttress (Figure S7) up to an elevation of about 2200 m, but there are no overlying massive sandstone cliffs similar to the basal Falla beds at Misery Peak 8 km to the southeast across Shackleton Glacier at an elevation of about 2350 m. However, at Half Century Nunatak about 10 km to the north at a REMA estimated elevation of about 2300 m (c.f. about 2600 m on the Liv Glacier topographic map) a succession of pale-coloured resistant sandstone ledges, which resemble Falla strata cropping out south of Schroeder Hill (Elliot and Collinson 2022), is interpreted to belong to that formation. Falla strata are not present at Mount Black, which has an elevation of 3000 m, and if correctly identified at Half Century Nunatak, the Fremouw-Falla contact will have a low southerly dip (≥3°). This implies a down to the north fault between Half Century Nunatak and Dismal Buttress, which is supported by a sliver of Falla strata, at a REMA estimated elevation of 2200 m, identified along the Shackleton Glacier valley wall north of Dismal Buttress (Figure S7).
Sponge spicule assemblages from the Cambrian (Series 2–3) of North Greenland (Laurentia): systematics and biogeography
Published in GFF, 2019
GGU samples 301338 and 301351 were collected by M.R. Blaker and J.S. Peel on 15th–17 August 1985 from about 15 m above the base of the lower member of the Henson Gletscher Formation (Cambrian Series 2, Stage 4) on a nunatak in southern Freuchen Land (82°09ʹN, 42°25ʹW; Fig. 1B, C, locality 4). GGU sample 301352 was collected by J.S. Peel on 17 August 1985 from the lower member of the Henson Gletscher Formation (Cambrian Series 2, Stage 4) at the southern end of a nunatak at the north-east end of the glacier feeding south-west into Jungersen Gletscher (82°10ʹN, 42°4ʹW; Fig. 1C, locality 5).