Trends in Plio-Pleistocene Southwest Pacific stable isotope stratigraphy; implications for orbital forcing of ice sheets and mid-Pliocene sea level estimates

Author(s): Patterson, Molly O'Rourke; McKay, Robert M.; Naish, Tim; Wilson, Gary S.; Ohneiser, Christian; Woodard, Stella C.; Bostock, Helen Clare; Caballero-Gill, Rocio P.
Author Affiliation(s): Primary:
University of Massachusetts Amherst, Amherst, MA, United States
Victoria University of Wellington, New Zealand
University of Otago, New Zealand
Rutgers University New Brunswick, United States
National Institute of Water and Atmospheric Research, New Zealand
Brown University, United States
Volume Title: AGU 2015 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2015; American Geophysical Union 2015 fall meeting, San Francisco, CA, Dec. 14-18, 2015. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: We present a new high resolution Early to mid-Pliocene (4.3 to 3.0 Ma) benthic stable isotope record (δ18O and δ13C), a revised magnetostratigraphy and an orbitally tuned age model extending the early Pliocene to early Pleistocene (4.3 to 1.2 Ma) record for ODP Site 1123. Placing the δ18O and δ13C time series on an orbital-scale age model provides the chronological basis for high-resolution proxy records spanning the early Pliocene to early Pleistocene. By comparison with previous published records (DSDP 607, ODP 1090/704, ODP 849, MV0502-AJC), we examine long-term changes in intra and inter-basinal benthic δ13C records in order to trace the ventilation history of deep-water masses. These comparisons highlight that during the warm early to mid-Pliocene (3.6 to 2.7 Ma) South Atlantic and southwest Pacific gradients where much larger than during the Pleistocene. These findings are not consistent with late Pleistocene and modern reconstructions in which South Atlantic δ13C values are slightly lower than South Pacific values at depths bathed by LCDW. Thus, indicating that while LCDW bathing the South Atlantic may have had an enhanced NADW signature, such a situation in the southwest Pacific did not exist during the warm mid-Pliocene. Furthermore, while the δ18O record from Site 1123 demonstrates an overall agreement with the global benthic δ18O stack LR04 exhibiting 40-kyr oscillations in ice volume/temperature, the mid to late Pliocene interval (∼3.3 to 2.8 Ma) demonstrates low frequency ice volume/temperature variability consistent with 100-kyr eccentricity. Eustatic sea-level estimates from δ18O values are consistent with all higher-end (22±10 m compared to modern) values for peak interglacial highstands between 2.9-3.2 Ma. Thus, inferring 100-kyr Antarctic ice sheet variability from marine based margins of the East Antarctic Ice Sheet (EAIS) during the mid to late Pliocene contributed to sea level, whereas after ∼2.9 Ma (post interglacial G17) ODP Site δ18O values are inline with eustatic sea-level estimates derived from the benthic δ18O stack, LR04.
Year of Publication: 2015
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; Atlantic Ocean; C-13/C-12; Carbon; DSDP Site 607; Deep Sea Drilling Project; East Pacific; Equatorial Pacific; IPOD; Isotope ratios; Isotopes; Leg 114; Leg 138; Leg 177; Leg 94; Mid-Atlantic Ridge; North Atlantic; North Pacific; Northeast Atlantic; Northeast Pacific; ODP Site 1090; ODP Site 704; ODP Site 849; Ocean Drilling Program; Pacific Ocean; South Atlantic; Stable isotopes
Coordinates: N410004 N410005 W0325726 W0325727
S540000 S405600 E0140000 E0050000
S465246 S465245 E0072515 E0072515
Record ID: 2016062601
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