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Testing the Cretaceous greenhouse hypothesis using glassy foraminiferal calcite from the core of the Turonian tropics on Demerara Rise

Paul A. Wilson, Richard D. Norris and Matthew J. Cooper
Testing the Cretaceous greenhouse hypothesis using glassy foraminiferal calcite from the core of the Turonian tropics on Demerara Rise
Geology (Boulder) (July 2002) 30 (7): 607-610

Abstract

Glassy Turonian foraminifera preserved in clay-rich sediments from the western tropical Atlantic yield the warmest equivalent delta (super 18) O sea-surface temperatures (SSTs) yet reported for the entire Cretaceous-Cenozoic. We estimate Turonian SSTs that were at least as warm as (conservative mean approximately 30 degrees C) to significantly warmer (warm mean approximately 33 degrees C) than those in the region today. However, if independent evidence for high middle Cretaceous pCO (sub 2) is reliable and resulted in greater isotopic fractionation between seawater and calcite because of lower sea-surface pH, our conservative and warm SST estimates would be even higher (32 and 36 degrees C, respectively). Our new tropical SSTs help reconcile geologic data with the predictions of general circulation models that incorporate high Cretaceous pCO (sub 2) and lend support to the hypothesis of a Cretaceous greenhouse. Our data also strengthen the case for a Turonian age for the Cretaceous thermal maximum and highlight a 20-40 m.y. mismatch between peak Cretaceous-Cenozoic global warmth and peak inferred tectonic CO (sub 2) production. We infer that this mismatch is either an artifact of a hidden Turonian pulse in global ocean-crust cycling or real evidence of the influence of some other factor on atmospheric CO (sub 2) and/or SSTs. A hidden pulse in crust cycling would explain the timing of peak Cretaceous-Cenozoic sea level (also Turonian), but other factors are needed to explain high-frequency ( approximately 10-100 k.y.) instability in middle Cretaceous SSTs reported elsewhere.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 30
Serial Issue: 7
Title: Testing the Cretaceous greenhouse hypothesis using glassy foraminiferal calcite from the core of the Turonian tropics on Demerara Rise
Affiliation: Southampton Oceanography Centre, School of Ocean and Earth Science, Southampton, United Kingdom
Pages: 607-610
Published: 200207
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 47
Accession Number: 2002-060676
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Annotation: With GSA Data Repository Item 2002064
Illustration Description: illus.
N09°27'14" - N09°27'14", W54°20'31" - W54°20'31"
Secondary Affiliation: Woods Hole Oceanographic Institution, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 200219
Program Name: DSDPDeep Sea Drilling Project
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