T250 Geologic Timescale—Current Status, Future Enhancement, and Applications (Posters)

Wednesday, 7 November 2012
9:00 AM - 6:00 PM
Hall B

PALEOGENE-NEOGENE TIME SCALE

Paper number: T250-9
Program: Technical Sessions
Time: 9:00 AM – 6:00 PM

Authors

Abstract

Of the 17 Paleogene and Neogene stages, only 5 remain to be formally defined: the Bartonian and Priabonian stages of upper Eocene, the Chattian (base of upper Oligocene), and the Burdigalian and Langhian stages of lower and middle Miocene. The biostratigraphy of Paleogene-Neogene marine successions is well established, using several microfossil groups. Calcareous nannofossils and planktonic foraminifera are the two most widely used groups for biostratigraphic purposes in open marine deposits, especially in low- and mid-latitude settings. The reversal history of the Earth’s magnetic field has been the backbone of the Cenozoic correlations, especially between marine and terrestrial settings.

The Cenozoic Era has astronomical tuning “downward” relative to the Present of magnetic polarity chrons and major microfossil and nannofossil datums through the beginning of the Priabonian of late Eocene (magnetic polarity chrons C1n through C13n). Astronomical tuning “upward” relative to the base-Cenozoic (66.0 Ma) spans the Paleogene and early Eocene (Chrons C29r through C24n). The current age model for the intervening middle Eocene incorporates a spline-fit to a suite of radioisotope dates within Chrons C15r-C23r, but cyclostratigraphy analysis of new IODP drill sites in the north Atlantic should enable the astronomical tuning of the entire Cenozoic in the near future. Ages for other marine biostratigraphic datums, terrestrial mammal zones, stable isotope events and sea-level trends are mainly derived from correlations to this astronomically tuned bio-magnetostratigraphic scale.