18. Maastrichtian to Eocene Foraminiferal Assemblages in the Northern and Eastern Indian Ocean Region: Correlations and Historical Patterns
- 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
McGowran, B. (1977) Maastrichtian to Eocene Foraminiferal Assemblages in the Northern and Eastern Indian Ocean Region: Correlations and Historical Patterns, 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/SP009p0417
- Published Online: 23 MAR 2013
- Published Print: 1 JAN 1977
Print ISBN: 9780875902081
Online ISBN: 9781118664919
Foraminiferal data are summarized from on and adjacent to the Mascarene Plateau, Chagos-Laccadive Ridge, Ninetyeast Ridge, Naturaliste Plateau. Most of the records are Paleocene and Eocene although Maastrichtian strata were encountered on the Ninetyeast Ridge. The review is extended to the margins of India-Pakistan and Australia where three stratigraphie sequences (sensu Sloss, 1963, on a finer scale) are recognized: Campanian-Maastrichtian, Paleocene - Early Eocene, and Middle-Late Eocene. Correlations are based on the recognition of important (i.e. widespread and consistent) biostratigraphic events plotted against Berggrenfs (1972) time scale.
The distribution of Maastrichtian foraminifera supports the notion of rapid transform movement along the Ninetyeast Ridge at that time, whilst the Ridge was sinking rapidly. Foraminiferal biofacies reflect rapid and concerted sinking interrupted by an isochronous hiatus across the Paleocene/Eocene boundary on the Mascarene Plateau and Chagos-Laccadive and Ninetyeast Ridges; the same hiatus occurs on the Naturaliste Plateau. The resumption of sedimentary accumulation on the topographic highs is coeval with a change from calcareous ooze to brown clay in the Central Indian and Wharton Basins. The timing of the interruption matches suggestively Australia/Antarctica separation and other major geotectonic events, and forshadows the demise of the Ninetyeast Ridge as a transform fault.
The earliest Tertiary sequence on the continental margins ends within the Early Eocene with regression, hiatus, or nonidentification, seemingly regardless of whether in detrital (terrigenous) or carbonate facies, or of whether the margin was a leading edge or a trailing edge. Thus, rapid seafloor spreading and sinking in the ocean (Maastrichtian-Paleocene) was followed after an interruption by rapid sinking (Early Eocene) and this caused marginal regression.
Early in the Middle Eocene there is a terminal oceanic event marked by the cherty “Horizon A” which is isochronous; marginal strata were regressive or absent at that time. Later in the Middle Eocene, when the oceanic record is noteworthy mainly for hiatus, there is a synchronous marginal transgression marking the onset of extensive shelf carbonate accumulation. Whereas a tectonic explanation may come to suffice for the Paleocene-Early Eocene, paleo-oceanographic changes become discernible in the Middle Eocene: Australia/Antarctica separation allowed deflection of southern waters to the south, expansion of the tropical belt on the evidence of planktonic and benthonic foraminifera, and a shelf/basin carbonate fractionation with reduced oceanic accumulation in response to the accumulation of the marginal sequence.