Vincent, Edith; Killingley, John S (1985): Oxygen and carbon isotope composition of Globoquadrina venezuelana and Oridorsalis umbonatus at DSDP Leg 85 Holes [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.803564, Supplement to: Vincent, E; Killingley, JS (1985): Oxygen and carbon isotope record for the early and middle Miocene in the central equatorial Pacific (Leg 85) and paleoceanographic implications. In: Mayer, L; Theyer, E; et al. (eds.), Initial Reports of the Deep Sea Drilling Project, Washington (U.S. Govt. Printing Office), 85, 749-769, https://doi.org/10.2973/dsdp.proc.85.122.1985
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Abstract:
Oxygen and carbon isotope stratigraphies are given for the planktonic foraminifer Globoquadrina venezuelana (a deep-dwelling species) at three DSDP sites located along a north-south transect at approximately 133°W across the Pacific equatorial high-productivity zone. The records obtained at Sites 573 and 574 encompass the lower Miocene. At Site 575 the record includes the middle Miocene and extends into the lowermost lower Miocene. The time resolution of the planktonic foraminifer isotope record varies from 50,000 to 500,000 yr. The benthic foraminifer Oridorsalis umbonatus was analyzed for isotope composition at a few levels of Site 575. Isotope stratigraphies for all three sites are compared with carbonate, foraminifer preservation, and grain size records. We identified a number of chemostratigraphic signals that appear to be synchronous with previously recognized signals in the western equatorial Pacific and the tropical Indian Ocean, and thus provide useful tools for chronostratigraphic correlations. The sedimentary sequence at Site 573 is incomplete and condensed, whereas the sequences from Sites 574 and 575 together provide a complete lower Miocene record. The expanded nature of this record, which was recovered with minimum disturbance and provides excellent calcareous and siliceous biostratigraphic control, offers a unique opportunity to determine the precise timing of early Miocene events. Paleomagnetic data from the hydraulic piston cores at Site 575 for the first time allow late early Miocene paleoceanographic events to be tied directly to the paleomagnetic time scale.
The multiple-signal stratigraphies provide clues for paleoceanographic reconstruction during the period of preconditioning before the major middle Miocene cooling. In the lowermost lower Miocene there is a pronounced shift toward greater d13C values (by -1%) within magnetic Chron 16 (between approximately 17.5 and 16.5 Ma). The "Chron 16 Carbon Shift" coincides with the cessation of an early Miocene warming trend visible in the d18O signals. Values of d13C remain high until approximately 15 Ma, then decrease toward initial (early Miocene) values near 13.5 Ma. The broad lower to middle Miocene d13C maximum appears to correlate with the deposition of organic-carbon-rich sediments around the margin of the northern Pacific in the Monterey Formation of California and its lateral equivalents. The sediments rimming the Pacific were probably deposited under coastal upwelling conditions that may have resulted from the development of a strong permanent thermocline. Deposition in the upwelling areas occurred partly under anaerobic conditions, which led to the excess extraction of organic carbon from the ocean. The timing of the middle Miocene cooling, which began after the Chron 16 Carbon Shift, suggests that the extraction of organic carbon preconditioned the ocean-atmosphere system for subsequent cooling.
A major carbonate dissolution event in the late early Miocene, starting at approximately 18.7 Ma, is associated with the enrichment in 13C. The maximum dissolution is coeval with the Chron 16 Carbon Shift. It corresponds to a prominent acoustic horizon that can be traced throughout the equatorial Pacific.
Project(s):
Deep Sea Drilling Project (DSDP)
Coverage:
Median Latitude: 4.192691 * Median Longitude: -134.438584 * South-bound Latitude: 0.498500 * West-bound Longitude: -135.036000 * North-bound Latitude: 5.850000 * East-bound Longitude: -133.309500
Date/Time Start: 1982-04-02T00:00:00 * Date/Time End: 1982-04-21T00:00:00
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
3 datasets
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Datasets listed in this publication series
- Vincent, E; Killingley, JS (1985): (Table 4) Oxygen and carbon isotope composition of the benthic species Oridorsalis umbonatus in DSDP Holes 85-575A and 85-575B. https://doi.org/10.1594/PANGAEA.803563
- Vincent, E; Killingley, JS (1985): (Table 3) Oxygen and carbon isotope composition of Globoquadrina venezuelana in DSDP Leg 85 Holes. https://doi.org/10.1594/PANGAEA.803562
- Vincent, E; Killingley, JS (1985): (Table 2) Percentages of the sand fraction in sediments at DSDP Leg 85 Holes. https://doi.org/10.1594/PANGAEA.803561