Implications of seawater Mg/Ca variability for Plio-Pleistocene tropical climate reconstruction

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doi: 10.1016/j.epsl.2008.03.014
Author(s): Medina-Elizalde, Martín; Lea, David W.; Fantle, Matthew S.
Author Affiliation(s): Primary:
University of California, Santa Barbara, Santa Barbara, CA, United States
Other:
Pennsylvania State University, United States
Volume Title: Earth and Planetary Science Letters
Source: Earth and Planetary Science Letters, 269(3-4), p.584-594. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0012-821X CODEN: EPSLA2
Note: In English. 77 refs.; illus., incl. sketch map
Summary: Recent reconstructions of Mg and Ca concentrations of seawater indicate that seawater Mg/Ca changed significantly over the last 5 million years (Ma). Tropical sea surface temperature (SST) records for the last 5 Ma based on foraminiferal Mg/Ca paleothermometry assume constant seawater Mg/Ca. These SST records suggest that average equatorial Pacific SSTs remained thermally stable from 5 to 2 Ma, after which significant cooling occurred only in the eastern equatorial Pacific. This study examines the implications of adjusting available equatorial Pacific SST records based on Mg/Ca paleothermometry to account for the inferred past variations of seawater Mg/Ca. The results suggest that both the cold and the warm regions of the equatorial Pacific were much warmer during the early Pliocene (30-31°C), and that both regions experienced a marked cooling from ≈4 Ma to ≈1 Ma. This new interpretation of foraminiferal Mg/Ca creates a discrepancy with alkenone unsaturation-based SST records from the eastern equatorial Pacific, which might be due to either overestimation of changes in past seawater Mg/Ca or to factors affecting the interpretation of the UK'37 index. The adjusted SST records are consistent with the hypothesis that higher levels of greenhouse gases maintained the warmth of the early Pliocene. Abstract Copyright (2008) Elsevier, B.V.
Year of Publication: 2008
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Alkaline earth metals; Alkenones; Calcium; Cenozoic; Chemical ratios; El Nino Southern Oscillation; Equatorial Pacific; Foraminifera; Greenhouse effect; Invertebrata; Ketones; Leg 130; Leg 138; Leg 167; Magnesium; Metals; Mg/Ca; Microfossils; Neogene; ODP Site 1014; ODP Site 806; ODP Site 846; ODP Site 847; Ocean Drilling Program; Organic compounds; Pacific Ocean; Paleo-oceanography; Paleoclimatology; Paleotemperature; Pleistocene; Pliocene; Protista; Quaternary; Reconstruction; Sea water; Sea-surface temperature; Tertiary; Tropical environment
Coordinates: N325002 N325002 W1195853 W1195853
N001906 N001907 E1592142 E1592140
S030549 S030541 W0904904 W0904906
N001134 N001136 W0951911 W0951914
Record ID: 2008103866
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands