Obliquity and long eccentricity pacing of the middle Miocene climate transition

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doi: 10.1002/ggge.20108
Author(s): Tian Jun; Yang Mei; Lyle, Mitchell W.; Wilkens, Roy; Shackford, Julia K.
Author Affiliation(s): Primary:
Tongji University, Laboratory of Marine Geology, Shanghai, China
Texas A&M University, United States
University of Hawaii at Manoa, United States
Volume Title: Geochemistry, Geophysics, Geosystems - G<sup>3</sup>
Source: Geochemistry, Geophysics, Geosystems - G>3`, 14(6), p.1740-1755. Publisher: American Geophysical Union and The Geochemical Society, United States. ISSN: 1525-2027
Note: In English. 79 refs.; illus.
Summary: The Middle Miocene East Antarctic ice sheet expansion (EAIE), which is indicated by an abrupt ∼1 ppm increase in global benthic foraminiferal δ18O at ∼13.8 Ma, marks the Middle Miocene climate transition (MMCT) and has been related to astronomically modulated changes in the global carbon cycle. Here, we present high resolution (3-4 kyr) benthic foraminiferal δ18O and δ13C records from IODP Site U1337 in the central equatorial Pacific, which spans the period 12.2-15.8 Ma. The isotopic records clearly demonstrate significant imprints from periodic variations in the Earth's orbital parameters, particularly the obliquity (40 kyr) and the long eccentricity (400 kyr) cycles. While the benthic δ18O and δ13C exhibit nearly identical amplitudes for glacial-interglacial cycles from 15.8 to 12.2 Ma, the long-term trends in the benthic δ18O and δ13C had started to reverse after the beginning of the EAIE. Within the 400-kyr band, the benthic -δ18O and δ13C displays a constant phase relationship between 15.8 and 12.2 Ma. At the 41-kyr band, however, a phase reversal reaching >180° between--δ18O and δ13C occurs from 13.8 Ma to 14.0 Ma during the period of the EAIE. A similar phase relationship of benthic foraminiferal--δ18O and δ13C at the 400-kyr band and the 41-kyr band is also observed at ODP Site 1146 from the northern South China Sea. This phase jump occurs when the long-term trends in δ18O and δ13C split, suggesting a decoupling of the global ice volume and ocean carbon reservoir changes during the Middle Miocene. Abstract Copyright (2013), American Geophysical Union. All Rights Reserved.
Year of Publication: 2013
Research Program: IODP Integrated Ocean Drilling Program
ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Antarctic ice sheet; Antarctica; Benthic taxa; C-13/C-12; Carbon; Carbon cycle; Cenozoic; Climate change; Climate forcing; East Antarctic ice sheet; East Pacific; Equatorial Pacific; Expedition 321; Expeditions 320/321; Foraminifera; Geochemical cycle; IODP Site U1337; Ice; Integrated Ocean Drilling Program; Invertebrata; Isotope ratios; Isotopes; Leg 184; Microfossils; Middle Miocene; Miocene; Neogene; North Pacific; Northeast Pacific; Northwest Pacific; O-18/O-16; ODP Site 1146; Ocean Drilling Program; Orbital forcing; Oxygen; Pacific Ocean; Paleoclimatology; Protista; Quaternary; South China Sea; Stable isotopes; Tertiary; West Pacific; World ocean
Coordinates: N192724 N192724 E1161622 E1161622
N035000 N035000 W1231222 W1231222
Record ID: 2014029584
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from John Wiley & Sons, Chichester, United Kingdom, Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union