Early and Middle Pleistocene environments, landforms and sediments in Scotland
Permanent lenke
https://hdl.handle.net/10037/14986Dato
2018-10-04Type
Journal articleTidsskriftartikkel
Peer reviewed
Sammendrag
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.
Beskrivelse
Accepted manuscript version. Source at: http://doi.org/10.1017/S1755691018000713