Atlas of Taxonomic and bio-chronostratigraphic studies on Paleogene larger benthic foraminifera from Indian Sedimentary Basins
By: SUDHIR SHUKLA
Office: Dy. General Manager (Geology),
ONGC, KDMIPE, Geology Group-II,
Dehradun -248 195 ; INDIA.
Foraminiferal studies related to nummulitids morphometry were initiated by the author in the Institute of Petroleum Exploration, ONGC during late 1980s. The biometric analysis of Paleogene larger foraminifera aimed at standardization of larger benthic foraminiferal species in terms of biometric and qualitative characters and to make them precise and valuable for taxonomy and stratigraphic ranges. The abundance, diversity and high evolutionary rates make larger foraminifera immensely useful biostratigraphic tools for dating the marine sediments world over.
Considering importance of nummulitids in Paleogene biostratigraphy world over, and keeping in mind the limitations with the available Indian publications, which are often with non-adequate descriptions, absence of morphometrics and incomplete stratigraphic ranges (either from one or fewer sedimentary basins), it was difficult to both the industrial as well as academia stratigraphers to fully utilize the biostratigraphic potential of these taxa in biostratigraphic conclusions, besides furthering geological modeling and interpretations.
Larger benthic foraminifera of the Indian Paleogene comprise diversified and complex foraminiferal assemblages belonging to several genera such as Nummulites, Assilina, Miscellanea, Lockhartia, Daviesina, Actinosiphon, Discocyclina, Pellatispira, Operculina etc. Several species amongst these genera have tremendous index value in high impact biostratigraphy and are characterized by their short geological ranges which could be utilized for intra and inter - regional stratigraphic correlations. Precise larger foraminifer biofacies during the Paleocene, Eocene and Oligocene have also been recognized in the sedimentary successions in different petroliferous basins across the Indian Shelf. It is a well accepted fact that the larger benthic foraminifera constitute very important group of microfossils in the Tertiary biostratigraphy and paleoecology of Indian sedimentary basins.
Systematic taxonomic analysis of 89 species from 17 genera of larger benthic foraminifera and comparison of their stratigraphic ranges with the high impact bio-chronostratigraphic zonations will help in future chrono-stratigraphic / sequence stratigraphic analysis. More so ever, with the advent of recent ”Shallow Benthic Zones”, world-over these fossil groups are extensively used in high impact biostratigraphic zonation and paleoenvironmental interpretations besides paleogeographic mapping of sediments in both petroliferous and yet to explore basins. The present monograph is prepared with the objective to compile systematic taxonomic analysis of selected species of larger benthic foraminifera belonging to families such as Rotaliidae, Nummulitidae, Calcarinidae, Discocyclinidae and Orbitolinidae etc. and establish high impact biostratigraphic zonations based on larger foraminifera for future chrono-stratigraphic / sequence stratigraphic analysis of Paleogene sediments. Standard international level references on Indian foraminiferal taxonomy and stratigraphic ranges are created by way of such specialized monographs.
The present study is an attempt in this direction to solve some of the existing problems regarding nummulitid identifications by offering both qualitative and quantitative parameters and subsequent interpretations. Simultaneously, efforts have also been made to create local reference by preparing an atlas of taxonomic and bio-chronostratigraphic studies on Paleogene larger benthic foraminifera from Indian sedimentary basins to help biostratigraphic correlations.
A few copies of this monograph are available (on sale @ US dollar 60) from KDMIPE, ONGC, DehraDun , India on payment.