Paleocene to Middle Eocene Calcareous Nannofossils of ODP Sites 689 and 690|Maud Rise|Weddell Sea

Pospichal, James J; Wise, Sherwood W.

doi:10.2973/odp.proc.sr.113.205.1990

Cited by 41 publications

(54 citation statements)

References 24 publications

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“…X indicates material reworked. brookina teuriensis and/or Hornibrookina edwardsii have been reported from the southwest Pacific (Edwards, 1973), the South Atlantic , Texas, U.S.A. (Jiang and Gartner, 1986), Argentina (Angelozzi, 1988), the North Sea (Varol, 1989), and the Weddell Sea (Pospichal and Wise, 1990b). These species are never abundant in any of these localities except in the Weddell Sea.…”

Section: Reticu Zygrhimentioning

confidence: 99%

Upper Cretaceous and Cenozoic Calcareous Nannofossils of the Kerguelen Plateau (Southern Indian Ocean) and Prydz Bay (East Antarctica)

Wei¹,

Thierstein²

1991

Proceedings of the Ocean Drilling Program

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Section: Reticu Zygrhimentioning

confidence: 99%

Upper Cretaceous and Cenozoic Calcareous Nannofossils of the Kerguelen Plateau (Southern Indian Ocean) and Prydz Bay (East Antarctica)

Wei¹,

Thierstein²

1991

Proceedings of the Ocean Drilling Program

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“…Nevertheless, the stable isotope record shows a major cooling during the earlymiddle Eocene (Shackleton and Kennett, 1975;Oberhànsli et al, 1984) that may coincide with a major sea-level drop (Vail et al, 1977;Haq et al, 1987). A major canyon-cutting episode has been suggested for this interval along continental margins (Miller et al, 1987(Miller et al, , 1990, which is also a time of cooling and diminished diversity among calcareous microfloras in the high southern latitudes (Pospichal and Wise, 1990;. Of the several Eltanin cores redated by Wei (this volume, Chapter 64), Core 24-10 is the most likely to contain in situ IRD because there is no Neogene material upsection to serve as a possible source of contamination.…”

Section: Eocene Glacial Ice?mentioning

confidence: 99%

Paleogene Glacial History of Antarctica in Light of Leg 120 Drilling Results

Wise¹,

Breza²,

Harwood³

et al. 1992

Proceedings of the Ocean Drilling Program

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The Paleogene glacial history of Antarctica has been inferred largely from indirect evidence of glaciation gathered from the oceans beyond that remote, ice-shrouded, and inhospitable continent. This evidence includes the "proxy" stable isotopic record from the world's oceans; the occurrence of ice-rafted debris (IRD) in the Southern Ocean; inflections in sea-level curves; the presence of hiatuses in the deep-sea record; and changes in clay mineral assemblages, in the diversities of microfossil assemblages, and in the steepness of latitudinal biotic gradients. Ocean Drilling Program Leg 120 has added an important dimension to this growing body of evidence through the discovery of lowest Oligocene IRD at Site 748 on the Southern Kerguelen Plateau at a record distance north of the Antarctic continent (58°S latitude) and within a pelagic biosiliceous-carbonate ooze sequence that has yielded a complementary oxygen isotope record of the cryospheric event. We deduce that an ice sheet reached sea level during the earliest Oligocene (35.8-36.0 Ma) and that the effect was immediate and profound. In addition to the IRD, this event was manifested at Site 748 by a dramatic cooling of the surface waters surrounding the continent as indicated by a sharp increase in the percentage of cold-water calcareous nannoplankton, an increase in planktonic foraminiferal δ 18 θ values, and an increase in the percentage of biosiliceous material in the sediment. The temperature of the bottom waters over the plateau also decreased, and the volume of ice on the continent increased.We have reviewed the accumulated evidence from this and other investigations of the past two decades on and around Antarctica, and have concluded that ice sheets were present on the continent during the Oligocene, including the earliest Oligocene. Not necessarily permanent features, they probably went through many advances and contractions and may have disappeared completely at times. The rapid ice advance during the earliest Oligocene reached sea level at several widely scattered localities around the continent, but only for a brief period of time at some of these localities. Differences of opinion among investigators concern primarily the size and persistence of the Oligocene ice sheet(s).Tantalizing evidence of undated till deposits subjacent to well-dated Oligocene glaciomarine sequences along the Antarctic margin and possible occurrences of IRD beyond suggest the presence of glaciers during the late Eocene and possibly even during the early-middle Eocene. Included among the studies in this Scientific Results volume are new age calibrations from Eltanin piston cores taken at relatively low latitudes (38° to 58°S) in the southeast Pacific from which Eocene IRD has been reported. There is little agreement, however, among investigators as to whether an ice sheet was present at any time during the Eocene, particularly during early-middle Eocene times.

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“…As originally defined, however, the base of Zone CP9 was placed at the F0 of T. contortus, an event that lies clearly above the Paleocene/Eocene boundary in most sequences (e.g., Pospichal and Wise, 1990). For this reason, the base of this zone has sometimes been redefined by the F0 of T. bramlettei, the event that often has been used to define the Paleocene/Eocene boundary (e.g., Pospichal and Wise, 1990). We follow this latter definition here.…”

Section: Cp10 Tribrachiatus Orthostylus Zonementioning

confidence: 99%

Calcareous Nannofossil Biostratigraphy of Site 865, Allison Guyot, Central Pacific Ocean: A Tropical Paleogene Reference Section

Bralower¹,

Mutterlose²

1995

Proceedings of the Ocean Drilling Program, 143 Scientific Results

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A relatively expanded and largely complete upper Paleocene to lower Oligocene sequence was recovered from the pelagic cap overlying Allison Guyot, Mid-Pacific Mountains. The sequence consists of calcareous ooze with a high planktonic foraminifer content. Two separate holes (865B and 865C) were drilled with the advanced piston coring system. Samples from these holes have been the target of intensive calcareous nannofossil biostratigraphic investigations. Calcareous nannofossils are moderately well preserved and diverse throughout the sequence recovered, which extends from nannofossil Zone CP3 to CPI 6. Our data show that unconformities occur in the uppermost lower Eocene and at the Eocene/Oligocene boundary, correlating to part of Zones CPU and CP 12 and Zones CP 15 and CP 16, respectively. Most traditional zonal markers are present; however, the rarity of several of them, particularly discoasters, and the overgrowth of others, including species of Tribrachiatus, in the uppermost Paleocene and lower Eocene makes zonal subdivision of part of this sequence difficult. For this reason, more attention has been paid to establishing the precise ranges of nonzonal taxa. We were able to determine 142 zonal and nonzonal events in the Paleogene section by intensively sampling both holes (1-5 samples in each core section). Sample density increased toward the Paleocene/Eocene boundary. Although the events are spread fairly evenly throughout the section, some of the most dramatic turnover occurs in the boundary and early Eocene interval. Currently unobserved gradational forms in nannofossil lineages indicate that parts of this sequence are more expanded than any other yet recovered. Plate reconstructions show that Site 865 was close to the equator at the time Paleogene sediments were deposited. The near completeness, expansion, paleolocation, and shallow burial depth of this sequence render it an ideal low-latitude Paleogene reference section.

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Paleocene to Middle Eocene Calcareous Nannofossils of ODP Sites 689 and 690|Maud Rise|Weddell Sea

Cited by 41 publications

References 24 publications

Upper Cretaceous and Cenozoic Calcareous Nannofossils of the Kerguelen Plateau (Southern Indian Ocean) and Prydz Bay (East Antarctica)

Upper Cretaceous and Cenozoic Calcareous Nannofossils of the Kerguelen Plateau (Southern Indian Ocean) and Prydz Bay (East Antarctica)

Paleogene Glacial History of Antarctica in Light of Leg 120 Drilling Results

Calcareous Nannofossil Biostratigraphy of Site 865, Allison Guyot, Central Pacific Ocean: A Tropical Paleogene Reference Section

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