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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 57 (1973)

Issue: 2. (February)

First Page: 429

Last Page: 430

Title: Late Paleogene-Neogene Planktonic Biostratigraphy and Its Geologic Implications, California: ABSTRACT

Author(s): Orville L. Bandy

Article Type: Meeting abstract

Abstract:

Planktonic microfossils indicate that at least in some typical sections, the Narizian Stage (Kreyenhagen Shale) is middle Eocene, spanning part of the range for the P10-P14 zones (about 49-45 m.y. ago). The Refugian Stage is essentially late Eocene, representing Paleogene zones P15-P17 (about 45-37.5 m.y. ago). Oligocene time is represented approximately by the Zemorrian Stage, defined by Paleogene zones P18-P22 (about 37.5-22.5 m.y. ago). Miocene subdivisions are: early Miocene, Saucesian Stage (Neogene zones N4-N8), radiometric age span about 23-15 m.y. ago; middle Miocene, Relizian, and Luisian Stages (Neogene zones N9-N12), radiometric age span about 15-11 m.y. ago; and the late Miocene Mohnian Stage (Neogene zones N13-N18), radiometric age span about 11-3 m.y. ago. T e Pliocene is represented by the Repettian, Venturian, and the lower part of the Wheelerian Stage (Neogene zones N19-N21) with a radiometric age span of about 3-1.79 m.y. ago. The Quaternary is younger than 1.79 m.y., embracing the upper part of the Wheelerian Stage, the Hallian, and younger units, representing Neogene zones N22 and N23. Employing planktonic criteria, boundaries of stages based on benthic species are clearly time-transgressive.

A major structural change occurred in the Zemorrian Stage, the Oligocene, introducing a new set of basin patterns with the destruction of the Farallon plate and the adjacent spreading center, about 29-24 m.y. ago. A second important structural change occurred about 4 m.y. ago, in the late Miocene, with the development of a different pattern of basins and the formation of the Gulf of California. This new tectonic pattern resulted from, or was related to, the development of a westerly motion of the Pacific plate. The major volcanism of the California Tertiary occurred following the destruction of the Farallon plate, during the early and middle Miocene.

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Maximum sedimentation rates for the middle Eocene Narizian Stage (Kreyenhagen Shale) are less than 100 m/m.y., for the late Eocene (Refugian Stage) about 100 m/m.y., for the Oligocene Zemorrian Stage about 166 m/m.y., for the early Miocene about 140 m/m.y., for the middle Miocene about 500 m/m.y., for the late Miocene about 250 m/m.y., and for the Pliocene-Pleistocene they are almost 2,000 m/m.y. The very rapid sedimentation rates, following the second major change in tectonic patterns about 4 m.y. ago, are similar to those today in Santa Barbara basin; they are less than the much higher rates recognized for the late Pleistocene in basins of the continental borderland.

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Copyright 1997 American Association of Petroleum Geologists