T256 Oceans and Climates through Earth History: From Proxy Reconstructions to Model Assessments (Posters)

Wednesday, 7 November 2018
9:00 AM - 6:30 PM
Halls J-K

MIOCENE PLANKTONIC FORAMINIFERAL STABLE ISOTOPES AND SEA SURFACE TEMPERATURES AT NORTH ATLANTIC SITE 608

Paper number: T256-11
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Abstract

The Miocene (22.8-5.3 Ma) was an epoch of general global cooling, punctuated by the Miocene Climatic Optimum (MCO), a warming that occurred at 17-14.7 Ma. We measured δ18O and δ13C values of two species of planktonic: Globoquadrina venezuelana (a thermocline dweller) and Globigerinoides quadrilobatus (a surface dweller) from the 250-300 μm and 212-250 μm size fractions, respectively. Ages were calibrated to the Geomagnetic Polarity Time Scale (Gradstein et al., 2012) using magnetochronology. Both species showed >1‰ increase in δ18O values in the Early Middle Miocene (ca. 14.8-12.8 Ma), with surface dwelling G. quadrilobatus showing a further 0.5 ‰ increase in the Late Miocene (ca. 8-7 Ma). These δ18O changes are larger than global d18Oseawater estimates of ~0.5 ‰ at this time (Cramer et al., 2011), suggesting surface and thermocline cooling of 1-2°C at this site. Benthic foraminiferal δ18O data (Miller et al,. 1991;Wright et al., 1992) and the Tex86 paleotemperature proxy from Site 608 (Super et al., 2018) support this interpretation. We interpret there was a further surface-water cooling of ~1-2°C at 8 Ma, which is consistent with the data from UK’37 at higher latitudes Site 982. Our work emphasizes the complex development of the meridional thermal gradient in the North Atlantic following the MCO.

Geological Society of America Abstracts with Programs. Vol. 50, No. 6

doi: 10.1130/abs/2018AM-316779

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