Lateglacial ice-cap dynamics in NW Scotland: evidence from the fjords of the Summer Isles region

Martyn S Stoker, Tom Bradwell, John Howe, Ian Wilkinson, Kate McIntyre

Research output: Contribution to journalArticle

39 Citations (Scopus)

Abstract

The seaboard of western Scotland is a classic fjord landscape formed by glaciation over at least the last 0.5 Ma. We examine the glacial geology preserved in the fjords (or sea lochs) of the Summer Isles region of NW Scotland using high-resolution seismic data, multibeam swath bathymetry, seabed sediment cores, digital terrain models, aerial photographs, and field investigations. Detailed analyses include seismic facies and lithofacies interpretations; sedimentological and palaeoenvironmental analyses; and radiocarbon dating of selected microfauna. Our results indicate that the Pleistocene sediments of the Summer Isles region, on- and offshore, can be subdivided into several lithostratigraphic formations on the basis of seismic character, geomorphology and sedimentology. These are: subglacial tills; ice-distal and glacimarine facies; ice-proximal and ice-contact facies; moraine assemblages; and Holocene basin fill. The submarine landscape is also notable for its large-scale mass-movement events - the result of glaciodynamic, paraglacial or seismotectonic processes. Radiocarbon dating of marine shells indicate that deglaciation of this part of NW Scotland was ongoing between 14 and 13 ka BP - during the Lateglacial Interstadial (Greenland Interstadial 1) - consistent with cosmogenic surface-exposure ages from previous studies. A sequence of numerous seafloor moraine ridges charts oscillatory retreat of the last ice sheet from a buoyant calving margin in The Minch to a firmly grounded margin amongst the Summer Isles in the early part of Lateglacial Interstadial (GI-1) (pre-14 ka BP). Subsequent, punctuated, frontal retreat of the ice mass occurred in the following similar to 1000 years, during which time ice-cap outlet glaciers became topographically confined and restricted to the fjords. A late-stage readvance of glaciers into the inner fjords occurred soon after 13 ka BP, which calls into question the accepted limits of ice extent during the Younger Dryas Stadial (Greenland Stadial 1). We examine the wider implications of our chronostratigraphic model, discussing the implications for British Ice Sheet deglaciation, Lateglacial climate change, and the style and rates of fjord sedimentation. (C) 2009 NERC. Published by Elsevier Ltd. All rights reserved.
Original languageEnglish
Pages (from-to)3161-3184
Number of pages24
JournalQUATERNARY SCI REV
Issue number8
DOIs
Publication statusPublished - 2009

    Fingerprint

Keywords

  • Geosciences, Multidisciplinary
  • Geography, Physical
  • EVENT STRATIGRAPHY
  • YOUNGER DRYAS
  • CORE RECORD
  • OVERDEEPENED SEA LOCH
  • INTIMATE GROUP
  • LAST TERMINATION
  • HOLOCENE TRANSITION
  • NORTH-ATLANTIC REGION
  • WESTER ROSS READVANCE
  • GLACIAL-INTERGLACIAL TRANSITION

Cite this