Middle Miocene ocean-climate transition; high-resolution oxygen and carbon isotopic records from Deep Sea Drilling Project Site 588A, Southwest Pacific

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doi: 10.1029/93PA02196
Author(s): Flower, B. P.; Kennett, J. P.
Author Affiliation(s): Primary:
University of California at Santa Barbara, Department of Geological Sciences rine Science Institute, Santa Barbara, CA, United States
Volume Title: Paleoceanography
Source: Paleoceanography, 8(6), p.811-843. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0883-8305 CODEN: POCGEP
Note: In English. 59 refs.; illus., incl. 2 tables
Summary: High-resolution stable isotopic records are presented for the epi-benthic foraminifer Cibicidoides, the inferred shallow-dwelling planktonic Globigerinoides quadrilobatus, and the inferred deep-dwelling planktonic Globoquadrina dehiscens from the middle Miocene (∼16-12 Ma) of Deep Sea Drilling Project site 588A, Lord Howe Rise, southwest Pacific. High-resolution, multiple species oxygen and carbon isotopic data define the timing and character of the well-known middle Miocene climatic-oceanographic transition with a resolution comparable to Quaternary records. The benthic foraminiferal δ18O record is marked by several large fluctuations from ∼16 to 14.8 Ma, followed by a series of rapid (<50 kyr) δ18O increases that suggest a new state of the ocean-climate system after 14.8 Ma. The total middle Miocene benthic oxygen isotopic increase of 1.2 per mil is largely incorporated in two steps, an increase of 0.8 per mil from 14.5 to 14.0 Ma and a second increase of 0.7 per mil from 13.45 to 12.45 Ma. Each step is comprised of a series of marked δ18O increases, indicative of rapid East Antarctic ice sheet growth and contemporaneous deepwater cooling. A strong covariance of 0.7 per mil between the benthic and deep-dwelling planktonic species from 14.5 to 14.0 Ma (including a rapid increase from 14.1 to 14.05 Ma) suggests a 0.7 per mil increase in the δ18O composition of seawater (δ18Osw) because of East Antarctic ice sheet growth. Comparison of the δ18O record of Gs. quadrilobatus suggests that surface waters warmed at this site by ∼3°C from 14.1 to 13.6 Ma. Carbon isotopic time series for each species generally covary throughout the early to middle Miocene interval (∼16-12 Ma), confirming that δ13C variations in this interval largely represent reservoir changes. High-resolution δ13C data allow improved resolution of the latter five of six δ13C maxima within the well-known early to middle Miocene carbon isotopic excursion (the Monterey Carbon Isotopic Excursion from 17.0 to 13.5 Ma). This is useful for global correlation. The last of these maxima ends with a 1 per mil decrease centered from 13.9 to 13.7 Ma, ∼300 kyr after the δ18O increase considered to reflect East Antarctic ice growth. Covariance between benthic δ18O and δ13C from ∼16 to 13.8 Ma suggests a sensitive relation between global carbon cycling and the ocean-climate system prior to 13.8 Ma. Episodic increases in organic carbon burial may have contributed to deep-sea benthic δ13C maxima and synchronous global cooling. The positive relationship ended at ∼13.8 Ma, indicative of changing relations between global carbon cycling and the ocean-climate system brought on by the increased stability of the East Antarctic ice sheet after a major growth phase from 14.5 to 14.0 Ma. Copyright 1993 by the American Geophysical Union.
Year of Publication: 1993
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Anomalinidae; Benthic taxa; Biochemistry; C-13/C-12; Carbon; Cassidulinacea; Cenozoic; Cibicidoides; Cores; Covariance analysis; DSDP Site 588; Deep Sea Drilling Project; Foraminifera; Globigerinacea; Globigerinidae; Globigerinoides; Globigerinoides quadrilobatus; Globoquadrina; Globoquadrina dehiscens; High-resolution methods; IPOD; Invertebrata; Isotope ratios; Isotopes; Leg 90; Marine sediments; Microfossils; Middle Miocene; Miocene; Neogene; O-18/O-16; Oxygen; Pacific Ocean; Paleo-oceanography; Paleoclimatology; Paleotemperature; Planktonic taxa; Protista; Rotaliina; Sediments; South Pacific; Southwest Pacific; Stable isotopes; Statistical analysis; Tertiary; West Pacific
Coordinates: S260642 S260642 E1611336 E1611336
Record ID: 1995004393
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute.