Structural and depositional evidence for repeated ice-marginal oscillation along the eastern margin of the Late Devensian Irish Sea Ice Stream |
| |
| Institution: | 1. British Geological Survey, Keyworth, Nottingham, NG12 5GG, UK;2. British Geological Survey, West Mains Road, Edinburgh, EH9 3LA, UK;1. College of Life and Environmental Sciences, University of Exeter, Penryn Campus Penryn TR10 9EZ, United Kingdom;2. College of Life and Environmental Sciences, ESI, University of Exeter, Penryn Campus Penryn TR10 9EZ, United Kingdom;3. GeneCology Research Centre, University of Sunshine Coast, 90 Sippy Downs Drive, Sippy Downs QLD 4556, Australia;1. Department of Life Sciences, University of Siena, Via P.A. Mattioli 4, 53100 Siena, Italy;2. Department of Botany and Zoology, Masaryk University, Kotlá?ská 2, 611 37 Brno, Czech Republic;3. Czech Union for Nature Conservation, Local Chapter “Bílé Karpaty”, Bartolomějské náměstí 47, 698 01 Veselí nad Moravou, Czech Republic;4. Nature Conservation Agency of the Czech Republic, Regional Office Protected Landscape Area Authority Bílé Karpaty, Nádra?ní 318, 763 26 Luha?ovice, Czech Republic;5. Institute of Ecology and Evolutionary Biology, National Taiwan University, Roosevelt Rd. 1, 10617 Taipei, Taiwan;6. Department of Forest Protection and Entomology, Czech University of Life Sciences, Kamýcká 129, 165 00 Praha, Czech Republic;7. Department of Biology and Ecology, University of Ostrava, Chittussiho 10, 710 00 Ostrava, Czech Republic;8. Institute of Entomology, Biology Centre, Czech Academy of Sciences, Brani?ovská 31, 370 05 ?eské Budějovice, Czech Republic;1. OGS (Istituto Nazionale di Oceanografia e di Geofisica Sperimentale), Borgo Grotta Gigante 42C, Trieste, 34010, Italy;2. Maynooth University Department of Geography, Maynooth, Co. Kildare, Ireland;3. British Geological Survey, Murchison House, West Mains Road, Edinburgh, Scotland, EH9 3LA, UK;4. Department of Geography, Durham University, Durham, DH1 3LE, UK;5. Geological Survey of Ireland, Beggars Bush, Haddington Road, Dublin, Ireland;6. Department of Geography, Trinity College Dublin, Ireland |
| |
| Abstract: | Late Devensian glacigenic sediments and landforms along the north-west coast of Wales document the advance and subsequent retreat of the eastern margin of an Irish Sea Ice Stream that met, coalesced and ultimately uncoupled from ice radiating outwards from the adjacent Welsh Ice Cap centred over Snowdonia. Across the boundary between the two former ice masses is a set of sediment–landform assemblages that reflect rapidly changing erosional and depositional conditions during ice interaction. From the inner part of the ice-stream the assemblages range outwards, from a subglacial depositional assemblage, characterised by drumlin swarms; through a subglacial erosional assemblage, marked by prominent bedrock scours and large subglacial rock channels; through an ice-marginal assemblage, identified by closely spaced, glaciotectonised push moraines and intervening marginal sandur troughs; into a freely expanding proglacial sandur and lacustrine delta assemblage. The ice-marginal assemblage provides evidence for numerous oscillatory episodes during retreat and at least 20 ice-marginal limits can be identified. At least 11 of these display multiple criteria for identifying readvance and, in the ideal case, is characterised by a moraine form built by localised tectonic stacking of diamict to the rear, fronted by a clastic wedge of ice-front alluvial fan gravel and intercalated flow till. The distribution of sediment–landform assemblages suggests a highly dynamic, convergent ice-stream flow pattern, with high ice velocity, a sharply delineated lateral shear margin, pervasive ice-marginal glaciotectonic deformation and a tightly focused ice-marginal sediment delivery system; all signature characteristics of contemporary ice streams. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
