Early and Middle Pleistocene environments, landforms and sediments in Scotland

Abstract

This paper reviews the changing environments, developing landforms and terrestrial stratigraphy during the Early and Middle Pleistocene stages in Scotland. Cold stages after 2.7 Ma brought mountain ice caps and lowland permafrost, but larger ice sheets were short-lived. The late Early and Middle Pleistocene sedimentary record found offshore indicates more than 10 advances of ice sheets from Scotland into the North Sea but only 4–5 advances have been identified from the terrestrial stratigraphy. Two primary modes of glaciation, mountain ice cap and full ice sheet modes, can be recognised. Different zones of glacial erosion in Scotland reflect this bimodal glaciation and the spatially and temporally variable dynamics at glacier beds. Depths of glacial erosion vary from almost zero in Buchan to hundreds of metres in glens in the western Highlands and in basins both onshore and offshore. The presence of tors and blockfields indicates repeated development of patches of cold-based, non-erosive glacier ice on summits and plateaux. In lowlands, chemical weathering continued to operate during interglacials, but gruss-type saprolites are mainly of Pliocene to Early Pleistocene age. The Middle Pleistocene terrestrial stratigraphic record in Scotland, whilst fragmentary and poorly dated, provides important and accessible evidence of changing glacial, periglacial and interglacial environments over at least three stadial–interstadial–interglacial cycles. The distributions of blockfields and tors and the erratic contents of glacial sediments indicate that the configuration, thermal regime and pattern of ice flow during MIS 6 were broadly comparable to those of the last ice sheet. Improved control over the ages of Early and Middle Pleistocene sediments, soils and saprolites and on long-term rates of weathering and erosion, combined with information on palaeoenvironments, ice extent and sea level, will in future allow development and testing of new models of Pleistocene tectonics, isostasy, sea-level change and ice sheet dynamics in Scotland.

Late Pleistocene sediments, landforms and events in Scotland: a review of the terrestrial stratigraphic record

“…2015), now provides a reference climatostratigraphic framework for the correlation of Pleistocene terrestrial sediments and events in Scotland (Hall et al . 2018, fig. 1).…”

“…The same core, and core MD95-2006 from the Barra-Donegal Fan, some 200km W of the Scottish mainland (Hall et al . 2018, fig. 2), demonstrate limited delivery of IRD diagnostic of British Palaeogene Igneous Province sources in Scotland and Northern Ireland to these sites during the early part of MIS 3.…”

“…Shetland, Orkney and Caithness together form a topographic divide between the NE Atlantic and the North Sea (Hall et al . 2018, fig. 2).…”

“…In Caithness, aside from older glacial deposits found at depth (Tait 1912; Hall & Whittington 1989; Hall et al . 2018), the oldest till units attributed to the Late Devensian are the Ballantrath Till around Dunbeath (Gordon 1993b) and the Portskerra Till around Melvich (Hall et al . 2011; Fig.…”

“…The focus of the paper on Late Pleistocene terrestrial stratigraphy complements the accompanying review of the terrestrial record of Early and Middle Pleistocene environments, landforms and sediments in Scotland (Hall et al . 2018), offshore stratigraphy (Stewart et al . 2019) and the geomorphological evidence for the last Scottish Ice Sheet and its deglaciation (Ballantyne & Small 2018).…”