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Letter to Nature. Warm tropical ocean surface and global anoxia during the mid-Cretaceous period

Letter to Nature. Warm tropical ocean surface and global anoxia during the mid-Cretaceous period
Letter to Nature. Warm tropical ocean surface and global anoxia during the mid-Cretaceous period
The middle of the Cretaceous period (about 120 to 80 Myr ago) was a time of unusually warm polar temperatures, repeated reef-drowning in the tropics and a series of oceanic anoxic events (OAEs) that promoted both the widespread deposition of organic-carbon-rich marine sediments and high biological turnover. The cause of the warm temperatures is unproven but widely attributed to high levels of atmospheric greenhouse gases such as carbon dioxide. In contrast, there is no consensus on the climatic causes and effects of the OAEs, with both high biological productivity and ocean 'stagnation' being invoked as the cause of ocean anoxia. Here we show, using stable isotope records from multiple species of well-preserved foraminifera, that the thermal structure of surface waters in the western tropical Atlantic Ocean underwent pronounced variability about 100 Myr ago, with maximum sea surface temperatures 3–5 °C warmer than today. This variability culminated in a collapse of upper-ocean stratification during OAE-1d (the 'Breistroffer' event), a globally significant period of organic-carbon burial that we show to have fundamental, stratigraphically valuable, geochemical similarities to the main OAEs of the Mesozoic era. Our records are consistent with greenhouse forcing being responsible for the warm temperatures, but are inconsistent both with explanations for OAEs based on ocean stagnation, and with the traditional view (reviewed in ref. 12) that past warm periods were more stable than today's climate.
surface layer, cretaceous, anoxia, anoxic conditions, sea surface temperatures, paleoceanography, geology
0028-0836
425-429
Wilson, P.A.
f940a9f0-fa5a-4a64-9061-f0794bfbf7c6
Norris, R.D.
81ac4a17-2a84-4c7c-9c02-c9f14bb2695e
Wilson, P.A.
f940a9f0-fa5a-4a64-9061-f0794bfbf7c6
Norris, R.D.
81ac4a17-2a84-4c7c-9c02-c9f14bb2695e

Wilson, P.A. and Norris, R.D. (2001) Letter to Nature. Warm tropical ocean surface and global anoxia during the mid-Cretaceous period. Nature, 412 (6845), 425-429. (doi:10.1038/35086553).

Record type: Article

Abstract

The middle of the Cretaceous period (about 120 to 80 Myr ago) was a time of unusually warm polar temperatures, repeated reef-drowning in the tropics and a series of oceanic anoxic events (OAEs) that promoted both the widespread deposition of organic-carbon-rich marine sediments and high biological turnover. The cause of the warm temperatures is unproven but widely attributed to high levels of atmospheric greenhouse gases such as carbon dioxide. In contrast, there is no consensus on the climatic causes and effects of the OAEs, with both high biological productivity and ocean 'stagnation' being invoked as the cause of ocean anoxia. Here we show, using stable isotope records from multiple species of well-preserved foraminifera, that the thermal structure of surface waters in the western tropical Atlantic Ocean underwent pronounced variability about 100 Myr ago, with maximum sea surface temperatures 3–5 °C warmer than today. This variability culminated in a collapse of upper-ocean stratification during OAE-1d (the 'Breistroffer' event), a globally significant period of organic-carbon burial that we show to have fundamental, stratigraphically valuable, geochemical similarities to the main OAEs of the Mesozoic era. Our records are consistent with greenhouse forcing being responsible for the warm temperatures, but are inconsistent both with explanations for OAEs based on ocean stagnation, and with the traditional view (reviewed in ref. 12) that past warm periods were more stable than today's climate.

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More information

Published date: 2001
Keywords: surface layer, cretaceous, anoxia, anoxic conditions, sea surface temperatures, paleoceanography, geology

Identifiers

Local EPrints ID: 8033
URI: http://eprints.soton.ac.uk/id/eprint/8033
ISSN: 0028-0836
PURE UUID: c36b4d92-d3a7-4029-a371-1dcc3875c79b
ORCID for P.A. Wilson: ORCID iD orcid.org/0000-0001-6425-8906

Catalogue record

Date deposited: 11 Aug 2004
Last modified: 16 Mar 2024 03:13

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Contributors

Author: P.A. Wilson ORCID iD
Author: R.D. Norris

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