22. Neocene Deep Water Benthonic Foraminifera of the Indian Ocean

  1. J.R. Heirtzler,
  2. H.M. Bolli,
  3. T.A. Davies,
  4. J.B. Saunders and
  5. J.G. Sclater
  1. E. Boltovsky

Published Online: 23 MAR 2013

DOI: 10.1029/SP009p0599

Indian Ocean Geology and Biostratigraphy

Indian Ocean Geology and Biostratigraphy

How to Cite

Boltovsky, E. (1977) Neocene Deep Water Benthonic Foraminifera of the Indian Ocean, in Indian Ocean Geology and Biostratigraphy (eds J.R. Heirtzler, H.M. Bolli, T.A. Davies, J.B. Saunders and J.G. Sclater), American Geophysical Union, Washington, D. C.. doi: 10.1029/SP009p0599

Author Information

  1. Museo Argentino de Ciencias Naturales “B. Rivadavia” and Consejo Nacional de Investigaciones Cientificas y Tecnicas, Argentina

Publication History

  1. Published Online: 23 MAR 2013
  2. Published Print: 1 JAN 1977

ISBN Information

Print ISBN: 9780875902081

Online ISBN: 9781118664919

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Summary

Neogene - Recent benthonic foraminifera were studied in 499 samples from 15 sites which were drilled in the Indian Ocean during legs 23, 25, 26 and 27 of the Deep Sea Drilling Project. These sites were located at depths ranging from 1,030 – 5,709m. 306 species were identified, none of them new. Nine species were put in nomenclatura aperta. The unicameral calcareous species belonging to the genera Lagena, Oolina, Fissurina and Parafissurina were not studied. The stratigraphie subdivisions of the sites examined in this study had been previously established by the paleontological staffs of the legs mentioned above by means of planktonic foraminifera and other microfossils. The present study of benthonic foraminifera revealed that the number of cores which contain displaced or/and reworked fauna is much higher than previously thought; only five of the 15 sites have not yielded redeposited specimens. Four of these five sites are located far from the ocean margin. From 10 sites containing redeposited specimens eight should be considered as with heterogeneous material throughout their whole length and two as partially with redeposited specimens. These data cast some doubt on several conclusions made by previous authors who did not realize that sequences at several sites were rather strongly mixed with redeposited material and thus probably are not completely reliable.

On the basis of the data obtained exclusively from the sites which have sediments in situ the following conclusions were drawn: 1) Only Miocene guide fossils (“Bulava indica”*, Bulimina macilenta, B. miolaevis, B. jarvisi, Planulina marialana gigas, and Siphogenerina vesca) could be established. 2) The calcareous: agglutinated species ratio increased with an increase in depth from the 1,000 – 2,000 m range to the 3,500 – 4,000 m range. 3) Qualitative changes in the benthonic foraminiferal faunas as related to the depth changes were insignificant. However, it was observed that Orthomorphina and Osangularia preferred shallower depths and Nonion was found mainly at greater depths. 4) It is believed that the Indian Ocean has not suffered any drastic bathymetric changes since Miocene time.