Gale, A., Pälike, H., Hardenbol, J., Huggett, J., Laurie, E. and Skipper, J.
Milankovitch cyclicity and sea-level change in the Late Eocene-Early Oligocene interval: evidence for rapid and extensive Antarctic glaciation at 33.5 Ma? (abstract of paper presented at EUG XI, Strasbourg, France, 8-12 April 2001).
Journal of Conference Abstracts, 6, (1), .
We have studied an expanded succession of coastal marine,
estuarine and lacustrine sediments of Late Eocene-Early
Oligocene age in the Isle of Wight southern England. In this
succession, a strong Milankovitch signal (406, 100, 40 and
weaker 20Ka) is recorded from the relative abundance of
neoformed illite and illite-smectite, which formed in soils
by seasonal wetting and drying. The orbital timescale is
calibrated using magnetostratigraphic, and to a lesser
extent, biostratigraphic data. Combined orbital calibration
and sequence stratigraphic analysis allows us to identify the
major control on sea-level as the 406Ka long eccentricity
cycle, which caused sea-level to fluctuate by 10-15 m.
These values have been determined from the amount of
incision at observed at sequence boundaries on a regional
scale. Minor sea-level changes of 1-3 m were controlled by
obliquity. The position of the Early Oligocene heavy δ18O
event can be inferred in the Isle of Wight from its magnetostratigraphic
proxy (base of chron 13n). We have determined
the sea-level fall at this level to be approximately
12 m, close in magnitude to drops associated with the
preceding 3 Late Eocene 406 Ka sequences. This evidence
does not support recent estimates of a 50-90 m sea-level fall
within the Early Oligocene based on the calculation that a
significant part of the oxygen isotope event was caused by
rapid Antarctic ice buildup. Rather, orbitally driven sealevel
changes throughout the Late Eocene-Early Oligocene,
although probably glacioeustatic in origin, remained of
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