This study presents a new alkenone-derived Sea Surface Temperature (SST) record and d18O Noelaerhabdaceae data of the 2–5 mm carbonate fractions from the IODP site U1338 located in the Eastern Equatorial Pacific (EEP), over the Miocene–Pliocene. Our data and those available from other sites of the same area show the establishment of a cold tongue during the early Pliocene (4.4–3.6Ma). SST and d18O Noelaerhabdaceae time- series indicate periods of significant salinity variations. Comparison with the d18O benthic curve from sediment cores of the Equatorial Pacific Ocean allows us to distinguish between global changes and local surface salinity variations in the EEP. Ice sheet growth and evaporation–precipitation are then discussed as possible drivers of such changes, along with the role of Central American and the Indonesian sea way restriction. Our data suggest a shallowing of the thermocline in the EEP, between 6.8 and 6 Ma, and its shoaling between 4.8 and 4.0 Ma, suggesting the appearance of the cold tongue (Steph etal.,2010). The Pliocene climate transition would therefore not be primarily driven by Northern hemisphere glaciation.

Changes in seasurface conditions in the Equatorial Pacific during the middle Miocene-Pliocene as inferred from coccolith geochemistry

RAFFI, Isabella;
2013-01-01

Abstract

This study presents a new alkenone-derived Sea Surface Temperature (SST) record and d18O Noelaerhabdaceae data of the 2–5 mm carbonate fractions from the IODP site U1338 located in the Eastern Equatorial Pacific (EEP), over the Miocene–Pliocene. Our data and those available from other sites of the same area show the establishment of a cold tongue during the early Pliocene (4.4–3.6Ma). SST and d18O Noelaerhabdaceae time- series indicate periods of significant salinity variations. Comparison with the d18O benthic curve from sediment cores of the Equatorial Pacific Ocean allows us to distinguish between global changes and local surface salinity variations in the EEP. Ice sheet growth and evaporation–precipitation are then discussed as possible drivers of such changes, along with the role of Central American and the Indonesian sea way restriction. Our data suggest a shallowing of the thermocline in the EEP, between 6.8 and 6 Ma, and its shoaling between 4.8 and 4.0 Ma, suggesting the appearance of the cold tongue (Steph etal.,2010). The Pliocene climate transition would therefore not be primarily driven by Northern hemisphere glaciation.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11564/392683
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