Sedimentary evidence against a local ice-cap on the Shetland Isles at the Last Glacial Maximum S.J. Carr a, *, J.F. Hiemstra b a Centre for Micromorphology, School of Geography, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom b Department of Geography, College of Science, Swansea University, Singleton Park, Swansea SA2 8PP, United Kingdom 1. Introduction The extent, timing and dynamics of the last glaciation of the Shetland Isles have been of considerable interest since the earliest speculations of the glacial theory (Croll, 1870, 1875). As understanding of the configuration of the NW European ice sheets has increased (cf. Ehlers et al., 2011), it has become clear that the Shetland Isles occupy a pivotal position for understanding interactions between the British-Irish and Fennoscandian ice sheets during the last glacial cycle (Sutherland, 1991). Further- more, the islands are located at a critical junction of the North Sea, Norwegian Sea and Atlantic Ocean, and are influenced by fluctuations in the Polar Front and North Atlantic Drift (Gordon et al., 1993), thus making Shetland climatically highly sensitive, especially to the major climatic re-organizations associated with the onset and termination of the Last Glacial Maximum (LGM). During the last glacial cycle, the Shetland Isles occupied a position approximately equidistant between major ice-dispersal areas of the Fennoscandian and British-Irish ice sheets, and there still is controversy about whether the archipelago was inundated by ‘Scandinavian’ ice, by ‘British’ ice, or perhaps ‘only’ experienced a local ice-cap glaciation (see Peach and Horne, 1879; Home, 1881; Chapelhow, 1965; Hoppe, 1974; Mykura, 1976; Flinn, 1978, 1983, 1994; Ross et al., 1993; Ross, 1996). Many of the reconstructions of glaciation on Shetland have been based on data obtained from mapping of striations, lineations and roches-moutonne ´ es, and transport of large erratic boulders (e.g. Finlay, 1926; Hoppe, 1974; Mykura, 1976; Flinn, 1977, 1992, 1994; Sutherland, 1991; Ross et al., 1993), while comparatively little attention has been paid to the available sedimentological evidence (e.g. Ross, 1996), with the notable exceptions of detailed descriptions of a few key sites such as Sel Ayre and Fugla Ness (Chapelhow, 1965; Birnie et al., 1993; Hall et al., 2002). The perceived lack of exposures through glacigenic sequences (cf. Mykura, 1976; Ross, 1996; also note the lack of glacigenic entries on the BRITICE map: Evans et al., 2005) is without question a reason that the nature of the last glaciation on Shetland has yet to Proceedings of the Geologists’ Association 124 (2013) 484–502 A R T I C L E I N F O Article history: Received 28 June 2012 Received in revised form 24 October 2012 Accepted 31 October 2012 Available online 27 November 2012 Keywords: Last Glacial Maximum Sedimentology Lithofacies analysis A B S T R A C T The Shetland Isles occupy a critical position equidistant to major ice-dispersal centres of the British-Irish and Fennoscandian ice sheets during the last glaciation, and have long been the subject of controversy regarding the timing, geometry and style of glaciation on the Shetland Isles. Previous reconstructions of the last glaciation of Shetland, favour development of a local ice-cap, possibly subsequent to early inundation by Fennoscandian ice. However, this model requires complex ice shed migrations and dynamic changes to explain the evidence. Recent studies identify an extensive landform record of NW- flowing ice extending across the region from the North Sea Basin, incompatible with evidence from striae and erratic boulder transport studies. This paper presents glacigenic lithofacies descriptions and structural (clast-fabric, shear-planes) analysis of seventeen sections from around the Shetland archipelago. The sedimentary record of glaciation supports a model of inundation by ice from the North Sea Basin, and includes no sediments representing multiple phases or dynamic local ice-cap glaciation. A preliminary framework which integrates all previous datasets with the results of this study proposes: (1) an early phase of local glaciation that was subsequently overwhelmed by extension of a major ice stream flowing from the North Sea Basin at the LGM; and (2) absence of an extensive local ice- cap formed over Shetland during deglaciation. This study concludes by identifying key areas that require further investigation, most notably more detailed analysis of ice-flow indicators and sediments in the eastern islands of Whalsay, Fetlar and Bressay, and further work to establish the temporal relationships between glacially eroded bedrock and associated subglacial till emplacement. ß 2012 The Geologists’ Association. Published by Elsevier Ltd. All rights reserved. * Corresponding author. E-mail address: s.j.carr@qmul.ac.uk (S.J. Carr). Contents lists available at SciVerse ScienceDirect Proceedings of the Geologists’ Association jo ur n al ho m ep ag e: www .els evier .c om /lo cat e/p g eo la 0016-7878/$ – see front matter ß 2012 The Geologists’ Association. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.pgeola.2012.10.006