ICE-PROXIMAL GLACIOMARINE SEDIMENTATION AND SEA-LEVEL CHANGE IN THE INVERNESS AREA, SCOTLAND - A REVIEW OF THE DEGLACIATION OF A MAJOR ICE STREAM OF THE BRITISH LATE DEVENSIAN ICE-SHEET
Jw. Merritt et al., ICE-PROXIMAL GLACIOMARINE SEDIMENTATION AND SEA-LEVEL CHANGE IN THE INVERNESS AREA, SCOTLAND - A REVIEW OF THE DEGLACIATION OF A MAJOR ICE STREAM OF THE BRITISH LATE DEVENSIAN ICE-SHEET, Quaternary science reviews, 14(3), 1995, pp. 289-329
Evidence of both rising and falling relative sea levels and glacitecto
nic movements is preserved in two formations of raised glaciomarine de
posits that were laid down in front of an oscillating 'grounded' tidew
ater glacier in the Inverness Firth. These changes occurred during the
latter stages of the disintegration of the Moray Firth ice-stream, on
e of the major ice streams that drained the British main Late Devensia
n ice sheet. Most of the glaciomarine deposits antedate a sequence of
glacio-isostatically tilted Late Devensian marine shorelines and assoc
iated littoral and estuarine deposits. The shorelines began forming at
about 13,000 BP and record a progressive fall in relative sea level.
A new model for the deglaciation of the Moray Firth region is proposed
after a critical appraisal of published accounts of both onshore and
offshore Quaternary sequences. The disintegration of the Moray Firth i
ce stream involved several rapid phases of retreat to pinning points,
caused by iceberg calving and triggered by rising global sea level. Ea
ch retreat was followed by minor readvances or stillstands, possibly c
aused by short-lived accelerated periods of glacio-isostatic rebound a
nd concomitant temporary falls in relative sea level. Two such events
occurred in the Inverness Firth: the Ardersier Oscillation and the Alt
urlie Stillstand. Substantial differences (lower relative sea levels,
later deglaciation) are apparent between the pattern of ice-retreat in
the Moray Firth region and published accounts of the deglaciation of
the Irish Sea basin. These differences require a reassessment of some
current hypotheses concerning the disintegration of major ice streams
associated with high relative sea levels. Furthermore, geological and
geomorphological evidence suggesting both rising and falling sea level
s in the Inverness area, prior to ca. 13,500 BP, is not fully compatib
le with recently published computer simulations of the dissolution of
the British main Late Devensian ice sheet.