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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 55 (1971)

Issue: 2. (February)

First Page: 330

Last Page: 330

Title: Time-Transgressive Aspects of Some Critical Planktonic Species: ABSTRACT

Author(s): Orville L. Bandy

Article Type: Meeting abstract

Abstract:

The origin of Globigerina bulloides in temperate areas occurs in the middle Miocene in Neogene zones 9 or 10, whereas in tropical sections it appears in the upper Miocene in Neogene zones 16 or 17, a cool-water cycle. In both cases it could be represented as being derived from Globigerina praebulloides. The origin of the temperate Globorotalia (Turborotalia) pachyderma, dextrally coiled, occurs in Neogene zone 13 or just below in temperate areas, whereas it invaded subtropical areas only during the principal cold cycles subsequent to deposition of zone 13.

Forms of Neogloboquadrina lacking umbilical toothlike structures such as N. dutertrei subcretacea appeared in tropical and warm temperate areas in the late Miocene. Neogloboquadrina dutertrei dutertrei with umbilical toothlike structures appeared near the end of Pliocene or at the beginning of Pleistocene time in Neogene zone 22 in tropical areas, whereas the primitive forms continued into the Holocene in temperate areas. Thus, there is an apparent extinction datum plane of the primitive form near the end of Neogene zone 21 deposition in tropical areas but not in temperate areas. Coiling characteristics and form ratios distinguish this group from Globorotalia (Turborotalia) pachyderma.

Praeorbulina spp. appear initially in the lower Miocene Neogene zone 8 in tropical areas; isomorphs of this genus appear initially in temperate areas in Neogene zones 11 or 12. The earlier forms originated from species of Globigerinoides whereas those in temperate areas appear to have originated from Globigerina.

Ecologic-evolutionary relations are responsible for these and many other kinds of time-transgressive aspects of planktonic datum planes.

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