Glacioeustatic changes in the early and middle Eocene (51-42 Ma); shallow-water stratigraphy from ODP Leg 189 Site 1171 (South Tasman Rise) and deep-sea δ18O records

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doi: 10.1130/B25486.1
Author(s): Pekar, Stephen F.; Hucks, Audrey; Fuller, Michael; Li, Shawna
Author Affiliation(s): Primary:
Queens College, School of Earth and Environmental Sciences, Flushing, NY, United States
Pennsylvania State University, United States
University of Hawaii at Manoa, United States
Columbia University, United States
Volume Title: Geological Society of America Bulletin
Source: Geological Society of America Bulletin, 117(7-8), p.1081-1093. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0016-7606 CODEN: BUGMAF
Note: In English. With GSA Data Repository Item 2005108; Lamont-Doherty Earth Obs., Contrib. No. 6724. 51 refs.; illus., incl. 4 tables, sketch map
Summary: Sequence boundary ages determined in shallow-water sediments obtained from ODP (Ocean Drilling Program) Leg 189 Site 1171 (South Tasman Rise) compare well with other stratigraphic records (New Jersey, United States, and northwestern Europe) and δ18O increases from deep-sea records, indicating that significant (>10 m) eustatic changes occurred during the early to middle Eocene (51-42 Ma). Sequence boundaries were identified and dated using lithology, bio- and magnetostratigraphy, water-depth changes, CaCO3 content, and physical properties (e.g., photospectrometry). They are characterized by a sharp bioturbated surface, low CaCO3 content, and an abrupt increase in glauconite above the surface. Foraminiferal biofacies and planktonic/benthic foraminiferal ratios were used to estimate water-depth changes. Ages of six sequence boundaries (50.9, 49.2, 48.5-47.8, 47.1, 44.5, and 42.6 Ma) from Site 1171 correlate well to the timings of δ18O increases and sequence boundaries identified from other Eocene studies. The synchronous nature of sequence boundary development from globally distal sites and δ18O increases indicates a global control and that glacioeustasy was operating in this supposedly ice-free world. This is supported by previous modeling studies and atmospheric CO2 estimates showing that the first time CO2 levels decreased below a threshold that would support the development of an Antarctic ice sheet occurred at ca. 51 Ma. Estimates of sea-level amplitudes range from ∼20 m for the early Eocene (51-49 Ma) and ∼25 m to ∼45 m for the middle Eocene (48-42 Ma) using constraints established for Oligocene δ18O records.
Year of Publication: 2005
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Antarctic ice sheet; Antarctica; Australasia; Australia; Biofacies; Biostratigraphy; Cenozoic; Correlation; Cycles; Deep-sea environment; Eocene; Eustasy; Foraminifera; Glacial geology; Glaciation; Ice sheets; Invertebrata; Isotope ratios; Isotopes; Leg 189; Lower Eocene; Magnetostratigraphy; Marine environment; Marine sediments; Microfossils; Middle Eocene; O-18/O-16; ODP Site 1171; Ocean Drilling Program; Oxygen; Pacific Ocean; Paleogene; Protista; Sea-level changes; Sediments; Sequence stratigraphy; Shallow-water environment; South Pacific; South Tasman Rise; Southwest Pacific; Stable isotopes; Tasman Sea; Tertiary; West Pacific
Coordinates: S483000 S482900 E1490700 E1490600
Record ID: 2005074721
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