Publication Type:

Journal Article

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.

Source:

Geology (Boulder), Geological Society of America (GSA), Boulder, CO, United States, Volume 22, Number 4, p.295-298 (1994)

ISBN:

0091-7613

Keywords:

Anticosti Island, Ashgillian, Baltic region, Brachiopoda, C-13/C-12, Canada, Caradocian, carbon, carbon dioxide, Cincinnati Arch, Cincinnati Ohio, cores, eastern canada, Estonia, Europe, eustasy, geochemical cycle, glacial geology, glaciation, Gondwana, Hamilton County Ohio, Hirnantian, ice caps, ice sheets, Invertebrata, isotope ratios, Isotopes, Kentucky, Latvia, O-18/O-16, Ohio, Ordovician, oxygen, paleo-oceanography, paleobathymetry, paleoclimatology, paleotemperature, Paleozoic, quebec, Scandinavia, Stable isotopes, stratigraphy, Sweden, United States, Upper Ordovician, Western Europe

Abstract:

The end Ordovician glaciation is distinct among Phanerozoic glaciations in that CO (sub 2) 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 p (sub CO2) levels in the oceans and atmosphere and thus promoted glaciation but were unable to sustain icehouse conditions in a greenhouse world.

Notes:

GeoRef, Copyright 2018, American Geological Institute.<br/>1994-025813<br/>central Sweden