Bathymetric and isotopic evidence for a short-lived Late Ordovician glaciation in a greenhouse period

The end Ordovician glaciation is distinct among Phanerozoic glaciations in that CO2 levels were generally high, yet major continental ice sheets accumulated on the Gondwana supercontinent. New oxygen isotopic data indicate substantial changes in sea-water temperatures and ice volume coinciding with...

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Bibliographic Details
Published in:Geology (Boulder) 1994-04, Vol.22 (4), p.295-298
Main Authors: Brenchley, P. J, Marshall, J. D, Carden, G. A. F, Robertson, D. B. R, Long, D. G. F, Meidla, T, Hints, L, Anderson, T. F
Format: Article
Language:English
Subjects:
Anticosti Island
Ashgillian
Baltic region
Brachiopoda
Brackish
C-13/C-12
Canada
Caradocian
carbon
carbon dioxide
central Sweden
Cincinnati Arch
Cincinnati Ohio
cores
Eastern Canada
Estonia
Europe
eustasy
Freshwater
geochemical cycle
Geology
glacial geology
glaciation
Glaciers
Gondwana
Greenhouse effect
Hamilton County Ohio
Hirnantian
ice caps
ice sheets
Invertebrata
isotope ratios
isotopes
Kentucky
Latvia
Marine
O-18/O-16
Ohio
Ordovician
oxygen
paleo-oceanography
paleobathymetry
paleoclimatology
paleotemperature
Paleozoic
Quebec
Scandinavia
Sea level
stable isotopes
stratigraphy
Sweden
United States
Upper Ordovician
Western Europe
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Summary:The end Ordovician glaciation is distinct among Phanerozoic glaciations in that CO2 levels were generally high, yet major continental ice sheets accumulated on the Gondwana supercontinent. New oxygen isotopic data indicate substantial changes in sea-water temperatures and ice volume coinciding with glacio-eustatic changes in sea level reflecting the growth and decay of the Gondwana ice cap. Major glaciation was apparently confined to the Hirnantian and was 0.5-1 m.y. long, rather than the 35 m.y. of earlier estimates. Carbon isotope values indicate significant changes in carbon cycling as the oceans changed from a state with warm saline bottom waters to a state with cold deep-water circulation and then back again. We believe that the changes in the carbon cycle effected a reduction in pCO2 levels in the oceans and atmosphere and thus promoted glaciation but were unable to sustain icehouse conditions in a greenhouse world.
ISSN:0091-7613
1943-2682
DOI:10.1130/0091-7613(1994)022<0295:BAIEFA>2.3.CO;2