The Oligocene marine microfossil record; age assessments using strontium isotopes

Online Access: Get full text
doi: 10.1029/PA004i006p00655
Author(s): Hess, Jennifer; Stott, Lowell D.; Bender, Michael L.; Kennett, James P.; Schilling, Jean-Guy
Author Affiliation(s): Primary:
Univ. R.I., Grad. Sch. Oceanogr., Narragansett, RI, United States
Univ. South. Calif., United States
Univ. Calif., United States
Volume Title: Paleoceanography
Source: Paleoceanography, 4(6), p.655-679. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0883-8305 CODEN: POCGEP
Note: In English. 100 refs.; illus. incl. 12 tables, sketch map
Summary: A strontium isotope record for the latest Eocene to earliest Miocene has been produced for two well-preserved, deep-sea sequences from the Atlantic, (Deep Sea Drilling Project sites 516F and 563) which have magnetostratigraphic age control and four sequences from the Pacific (sites 77B, 292, and 593) and Atlantic (site 529) which lack magnetostratigraphy. The composite 87Sr/86Sr age record of sites 516F and 563 forms a comprehensive, composite standard for the Oligocene against which other sequences can be correlated. Unlike previously published 87Sr/86Sr Oligocene sea water curves which have suggested that the sea water isotopic composition changed monotonically during the latest Paleogene, we note a distinct change in slope between the early Oligocene (36 to 27 Ma) and the late Oligocene to earliest Miocene (27 to ∼20 Ma). The slope of the early Oligocene segment is less steep than that of the late Oligocene to earliest Miocene. We have fit two linear regression curves to the Oligocene to early Miocene seawater δ87Sr data of sites 516F and 563, which we use to establish Sr isotope-age relationships for the Oligocene. The δ87Sr age equations were used to evaluate the synchroneity of specific planktonic and calcareous nannofossil datum levels used to correlate Oligocene sections. Although some datum levels appear to be synchronous between the Atlantic and Pacific, our results show that others are diachronous along longitudinal gradients. This is most evident in several last appearance datums that occurred earlier in the western equatorial Pacific than in the eastern equatorial Pacific. This diachroneity extends into the Atlantic where last occurrences were later than in the eastern equatorial Pacific. Copyright 1989 by the American Geophysical Union.
Year of Publication: 1989
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
Key Words: 03 Geochronology; Absolute age; Alkaline earth metals; Atlantic Ocean; Biochemistry; Biostratigraphy; Cenozoic; Correlation; DSDP Site 292; DSDP Site 516; DSDP Site 529; DSDP Site 563; DSDP Site 593; DSDP Site 77; Dates; Deep Sea Drilling Project; Diagenesis; Eocene; Foraminifera; Geochronology; IPOD; Invertebrata; Isotopes; Leg 31; Leg 72; Leg 74; Leg 82; Leg 9; Leg 90; Lower Miocene; Magnetostratigraphy; Marine environment; Marine sediments; Metals; Microfossils; Miocene; Neogene; Oligocene; Pacific Ocean; Paleo-oceanography; Paleogene; Paleomagnetism; Planktonic taxa; Protista; SEM data; Sediments; Sr-87/Sr-86; Sr/Sr; Stable isotopes; Strontium; Tertiary; Trace elements; Upper Eocene
Coordinates: N120000 N420000 E1380000 E1240000
S302000 S261000 W0351500 W0381000
S301000 S280000 E0031000 E0014500
N330829 N385623 W0323334 W0434603
S453129 S211153 E1745653 E1611336
Record ID: 1990021858
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute.