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Journal ArticleDOI

Integrated chronostratigraphic calibration of the Oligocene-Miocene boundary at 24.0 ± 0.1 Ma from the CRP-2A drill core, Ross Sea, Antarctica

TL;DR: In this paper, an expanded Oligocene-Miocene boundary interval recovered in the Cape Roberts Project CRP-2A core from beneath the Ross Sea, Antarctica, has yielded a high-resolution integrated chrono stratigraphy that has, in turn, enabled a new, more direct, calibra tion of magnetic polarity and biostratigraphic events.
Abstract: An expanded Oligocene-Miocene boundary interval recovered in the Cape Roberts Project CRP-2A core from beneath the Ross Sea, Antarctica, has yielded a high-resolution integrated chrono stratigraphy that has, in turn, enabled a new, more direct, calibra tion of magnetic polarity and biostratigraphic events. The Oligocene-Miocene boundary interval in the CRP-2A core comprises three ∼60-m-thick, rapidly deposited (>0.5 m/k.y.) sedimentary sequences (sequences 9, 10, and 11). In sequences 10 and 11, single-crystal, laser-fusion 40Ar/39Ar analyses of anorthoclase phenocrysts from two tephra horizons independently calibrate the CRP-2A magnetic-polarity stratigraphy and age model. Sequences 10 and 11 encompass subchron C6Cn.3n, which is dated as 24.3 ± 0.1 to 24.16 ± 0.1 Ma. Sequence 9 is interpreted to encompass subchron C6Cn.2n and the Oligocene-Miocene boundary, which is dated as 24.0 ± 0.1 Ma. These ages are ∼0.2 m.y. older than those of the geomagnetic polarity time scale calibrated from seafloor-spreading ridges and ∼0.9–1.3 m.y. older than the newly proposed astronomically calibrated ages. We contend that the discrepancy with the astronomically calibrated ages arises from a mismatch of three 406 k.y. eccentricity cycles or a 1.2 m.y. modulation of obliquity amplitude in the astronomical calibration of the Oligocene–Miocene time scale.

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Citations
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Journal ArticleDOI
TL;DR: In this paper, Pearson et al. provide an alphanumeric notation for Paleo-Eocene gene zones using the prefix "P" (for Paleocene), "E' (for Eocene) and "0"(for Oligocene) to achieve consistency with recent short-hand notation for other Cenozoic zones (Miocene ['M'], Pliocene [PL] and Pleistocene [PTD]).
Abstract: New biostratigraphic investigations on deep sea cores and outcrop sections have revealed several shortcomings in currently used tropical to subtropical Eocene plank­ tonic foraminiferal zonal schemes in the form of: 1) mod­ ified taxonomic concepts, 2) modifiel:l/different ranges of taxa, and 3) improved calibrations with magnetostratig­ raphy. This new information provides us with an op­ portunity to make some necessary improvements to ex­ isting Eocene biostratigraphic schemes. At the same time, we provide an alphanumeric notation for Paleo­ gene zones using the prefix 'P' (for Paleocene), 'E' (for Eocene) and '0' (for Oligocene) to achieve consistency with recent short-hand notation for other Cenozoic zones (Miocene ['M'], Pliocene [PL] and Pleistocene [PTD. Sixteen Eocene (E) zones are introduced (or nomen­ claturally emended) to replace the 13 zones and subzones of Berggren and others (1995). This new zonation serves as a template for the taxonomic and phylogenetic studies in the forthcoming Atlas of Eocene Planktonic Forami­ nifera (Pearson and others, in press). The 10 zones and subzones of the Paleocene (Berggren and others, 1995) are retained and renamed and/or emended to reflect im­ proved taxonomy and an updated chronologic calibra­ tion to the Global Polarity Time Scale (GPTS) (Berggren and others, 2000).' The PaleocenelEocene boundary is correlated with the lowest occurrence (LO) of Acarinina sibaiyaensis (base of Zone El), at the top of the trun­ cated and redefined (former) Zone P5. The five-fold zonation of the Oligocene (Berggren and others, 1995) is modified to a six-fold zonation with the elevation of (former) Subzones P21a and P21b to zonal status. The Oligocene (0) zomil' components are re­ named and/or nomenclaturally emended.

557 citations

Journal ArticleDOI
TL;DR: In this article, the authors used the newly derived age of the Oligocene/Miocene (O/M) boundary of 23.0 Ma of Shackleton et al. (2000) 447, revised to the new astronomical calculation (La2003) of Laskar et al., to recalculate the spline ages of Cande and Kent (J. Geophys. Res. 100 (1995) 6093), and then tune the Site 1090 y 18 O record to obliquity using La2003.

128 citations

Journal ArticleDOI
TL;DR: In this article, the Oligocene-Miocene proxy records from Ocean Drilling Program (ODP) Leg 154 were used to evaluate how the interaction of long, multi-million year beats in the Earth's eccentricity and obliquity are implicated in the waxing and waning of ice-sheets, presumably on Antarctica.

121 citations


Additional excerpts

  • ...H. Pälike et al. / Quaternary Science Reviews ] (]]]]) ]]]–]]] 3 Wilson et al. (2002)....

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Journal ArticleDOI
TL;DR: In this article, the authors analyzed the Cenozoic sedimentary succession recovered at the CRP-1, CRP 2/2A and CRP 3 drill sites off Cape Roberts on the McMurdo Sound shelf, Antarctica, to reconstruct the palaeoclimate and the glacial history of this part of Antarctica.

101 citations

References
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01 Jan 2000
TL;DR: In this paper, a biostratigraphic zonal framework, consisting of ten diatom zones, is proposed for the Antarctic continental shelf, which correspond well with geochronological data from argon dating of volcanic materials and strontium dating of calcareous macrofossils, as well as nannofossil biochronological data.
Abstract: Marine diatoms are the primary biostratigraphical and palaeoenvironmental tool for interpreting the upper Palaeogene and lower Neogene strata recovered during the second drilling season of the Cape Roberts Project at site CRP-2 in the western Ross Sea, Antarctica. Silicoflagellates, ebridians, and a chrysophyte cyst provide supporting biostratigraphical information. More than 100 dominantly planktic diatom taxa are recognised. Of these, more than 30 are treated informally, pending SEM examination and formal description. Many other taxa are noted only to generic level. Lower Oligocene (c. 31Ma) through lower Miocene (c. 18.5 Ma) diatoms occur from 28 mbsf down to 565 mbsf. Below this level, to the bottom of the hole at 624.15 mbsf, diatom assemblages are poorly-preserved and many samples are barren. A biostratigraphic zonal framework, consisting of ten diatom zones, is proposed for the Antarctic continental shelf. Ages inferred from the diatom biostratigraphy correspond well with geochronological data from argon dating of volcanic materials and strontium dating of calcareous macrofossils, as well as nannofossil biochronological datums. The biochronostratigraphical record from CRP-2/2A provides an important record of diatom events and mid-Cenozoic environmental changes in the Antarctic neritic zone.

51 citations

01 Jan 2000

27 citations


"Integrated chronostratigraphic cali..." refers methods in this paper

  • ...Further testing of our calibration will require high-resolution chronologies based on independent age determinations such as the 40Ar/39Ar data from the CRP2A core (Wilson et al., 2002; McIntosh, 2000)....

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01 Jan 1992
TL;DR: For the Oligocene-Pleistocene sections from high-latitude Ocean Drilling Program Sites 747, 748, and 751 in the southern Indian Ocean, a new subspecies, Coccolithus pelagicus floralis, is described.
Abstract: Detailed calcareous nannofossil range charts for the Oligocene-Pleistocene sections from high-latitude Ocean Drilling Program Sites 747, 748, and 751 in the southern Indian Ocean are presented in this report. Calcareous nannofossils are generally low in abundance in Pliocene-Plei stocene sediments, whereas they are very abundant throughout the Miocene and Oligocene. Species diversity, however, is low compared with assemblages in the lower latitudes. Nannofossil reworking is extensive in the middle Miocene at Site 751, less extensive in the lower Miocene at Site 748, and negligible for the entire Neogene at Site 747. Six nannofossil datums, which have previously been correlated with magnetostratigraphy in the Southern Ocean, were recognized in the upper Oligocene-Pleistocene sequence at Site 747. Three such nannofossil datums are available for the Neogene at Sites 748 and 751. A new subspecies, Coccolithus pelagicus floralis, is described.

26 citations

01 Jan 2000
TL;DR: In this article, an age model for the CRP-2/2A drillhole is presented based on combined microfossil biostratigraphy, 40Ar/39Ar ages on volcanic material, 87Sr/86Sr analyses on mollusc shells, and correlation of a magnetic polarity zonation to the magnetic polity time scale (MPTS).
Abstract: The 624.15 m glaciomarine sedimentary succession recovered in the CRP-2/2A drillcore comprises lower Oligocene (< c. 31 Ma) to lower Miocene (18.5 Ma) strata that are overlain by a thin succession of Pliocene and Pleistocene strata. The age model for the CRP-2/2A drillhole, as presented in this paper, is based on combined microfossil biostratigraphy, 40Ar/39Ar ages on volcanic material, 87Sr/86Sr analyses on mollusc shells, and correlation of a magnetic polarity zonation to the magnetic polarity time scale (MPTS). Between 25.92 and 109.05 metres below sea floor (mbsf), several alternative correlations to the MPTS are possible, all of which suggest that sediment accumulation rates averaged ~180 m/m.y. between unconformities, although actual sedimentation rates may have been higher. Between 109.05 and 306.65 mbsf, the age model is straightforward and average sedimentation rates were much higher (≥1000 m/m.y.). Between 306.65 mbsf and the bottom of the drillcore (624.15 mbsf), fewer datums are available to constrain the age model and unique correlation with the MPTS is not possible, although high average sediment accumulation rates are likely. A significant unconformity is identified at 306.65 mbsf, which may represent as much as 5 m.y. of missing time. Additional unconformities at 25.92 and 130.27 mbsf account for c. 16 and 2.5 m.y. of missing time, respectively. The Oligocene lower Miocene interval documented in the CRP-2/2A drillcore spans about 13 million years, however, it is possible that more time is missing in sequence-bounding unconformities than is represented in the stratigraphic record recovered in the CRP-2/2A drillcore.

23 citations

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