21. Synthesis of the Cretaceous Benthonic Foraminifera Recovered by the Deep Sea Drilling Project in the Indian Ocean
- J.R. Heirtzler,
- H.M. Bolli,
- T.A. Davies,
- J.B. Saunders and
- J.G. Sclater
Published Online: 23 MAR 2013
Copyright © 1977 by the American Geophysical Union.
Indian Ocean Geology and Biostratigraphy
How to Cite
Scheibnerova, V. (1977) Synthesis of the Cretaceous Benthonic Foraminifera Recovered by the Deep Sea Drilling Project in 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/SP009p0585
- Published Online: 23 MAR 2013
- Published Print: 1 JAN 1977
Print ISBN: 9780875902081
Online ISBN: 9781118664919
In 1971 to 1973 eight legs (22–29) comprising 62 sites crossed various parts of the Indian Ocean. Of these, four legs (24, 25, 26 and 27) recovered Cretaceous in 18 sites. Seventeen sites penetrated Late Cretaceous horizons, and 8 sites Early Cretaceous horizons and one also entered the Jurassic. Where the oldest sediments included Jurassic, the lowest Early Cretaceous (Neocomian) was also represented. In other sites, the oldest Cretaceous sediments were of Middle or Late Albian or upper Late Cretaceous age. The Cretaceous profiles recovered include hiatuses before and after the Albian.
Except for one site (249) which is off the East African margin, all Late Cretaceous sites are in the Eastern Indian Ocean, in a rather restricted area (about 29°N to 35°S and 100°E to 120°E) off the western and northwestern Australian continental shelf.
Late Cretaceous sediments were recovered much more widely; from 5 sites in the western Indian Ocean, ranging from about 10°N to 35°S and 12 sites in the Eastern Indian Ocean from the northern part of the Ninetyeast Ridge to the Naturaliste Plateau (about 100N to 350S).
Stratigraphically, the recovered sections are all fragmentary, ranging in extent from fractions of a stage (Site 235, 250) to one to three stages at best. This is in part due to incomplete coring programs and poor recovery, but mainly because over wide areas in the Indian Ocean there are considerable intervals of the Cretaceous missing altogether, such as is the case in the southern Indian Ocean (Legs 26 and 27) where the Early Cretaceous is relatively well developed but most of the Late Cretaceous (and also the Tertiary) is missing.
Due to the distribution pattern of the Cretaceous and incomplete recoveries of what is present the scope of this study is considerably restricted.
The most complete recoveries within the Early Cretaceous have been made in the Albian, and to a lesser degree in the Aptian and older in Legs 26 and 27, where faunas and floras, including the benthonic foraminifera, have been studied in considerable detail.
It can be seen that the Late Cretaceous occurrences in the Indian Ocean are spread over a much wider area, but these records are also still only fragmentary. This general pattern of incomplete vertical distribution holds also for the Cretaceous on adjacent landmasses, in western Australia in particular (see BeIford 1958). The most complete sections come from Site 217 with an apparently continuous Maastrichtian-Campanian-Santonian section and from Site 258 with a Cenomanian to San-tonian section, which continues into the Albian and older Cretaceous.
Cretaceous sediments recovered by the DSDP contain both benthonic and planktonic foraminifera, although the numbers of these vary greatly. Many samples are barren in both pre-Albian, Albian and post-Albian deposits.
Benthonic foraminifera from both Early and Late Cretaceous deposits recovered by DSDP in the Indian Ocean correlate closely with coeval faunas on adjacent landmasses especially in South Africa, the Indian Peninsula and Australia. The more southerly the locality, the closer is the correlation with the Great Australian Basin.
The most important Cretaceous genera of foraminifera recovered by the DSDP in the Indian Ocean are: Lingulogavelinella, Orithostella, Gavelinella, Pseudopatellinella, Discorbis, Pseudolamarckina, Osangular ia, Gubkinella, Eponides, Praebulimina, Neobulimina, Aragonia, Globorotalites, Labrospira, Textularia, Recurvoides, Praetrochamminoides, Plectorecurvoides, Praecystammina und Pseudobolivina. Many represent good stratigraphie markers.
The composition and nature of the microfaunas, and changes of them, proved to be good general indicators of Cretaceous bathymetry in the Indian Ocean.
Data on stratigraphie zonation in S-N and E-W distribution are restricted to the W and NW margin of Australia.
The most thorough palaeontological reports are those of Legs 26 and 27. They present general information, and taxonomic descriptions and illustrations of complete or nearly complete foraminiferal faunas. Both the Early and the Late Cretaceous benthonic foraminifera were described and figured only from Leg 27. In the others only the planktonic taxa received attention.