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Guha, Asit K.
- Paleoceanographic Implications of Planktonic Foraminiferal Abundance at DSDP Sites 219,220 and 241 - An Approach Based on Paleontologic Time Series
Authors
1 Department of Geology and Geophysics, IIT, Kharagpur - 721302, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 41, No 5 (1993), Pagination: 397-416Abstract
Paleontologic Time Series (PTS) analysis in both time and frequency domains on eight series of abundance data of Globorotalia menardii and total planktonic foraminifera from top core sections of DSDP Sites 219, 220 and 241 of Northern Indian Ocean depict cyclic variation presumably due to fluctuations in the Pleistocene paleo-temperature. At these sites, the relative dominance of planktonic foraminifera and G. menardii, uniform effect of post-mortem transport on foraminiferal tests of different sizes and differential sediment accumulation rate are revealed from the nature of energy distribution in the spectra, identical nature of major peaks and varying cycle lengths respectively.Keywords
Paleontologic Time Series (PTS), Deep Sea Drilling Project (DSDP), Pleistocene, Planktonic Foraminifera.- Cretaceous - Paleocene Carbonate Microfacies of Tamil Nadu and Pondicherry
Authors
1 Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur - 721 302, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 47, No 1 (1996), Pagination: 115-127Abstract
Nine types of Standard Microfacies (SMF) are identified in the Cretaceous-Paleocene carbonate sequences of the Ariyalur-Vridhachalam of Tamil Nadu and the Pondicherry areas. Of these four SMFs occur frequently.
The recurrence of SMF types within FZ 7 in successive fonnations of varying thickness indicates multiple transgressive - regressive episodes of unequal areal extent and time interval. A gradual decrease in the number of microfacies types in carbonate lithologies younger than the Turonian suggests progressive stabilization of the shelf. Presence of similar SMF in younger carbonate layers belonging to different areas and ages point to their being time-transgressive lithologic units. The carbonates are of low-Mg calcite variety. Significant depletion of Sr and Na and enrichment of Ba, K and Mn took place due to prolonged diagenetic alteration by meteoric water.
Keywords
Carbonate Rocks, Cretaceous, Paleocene, Ariyalur, Vridhachalam, Pondicherry.- Diversity of Planktonic Foraminiferal Assemblages From Quaternary Sequences at DSDP Sites 219, 220 and 241 in Northern Indian Ocean
Authors
1 Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur-721302, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 49, No 2 (1997), Pagination: 169-178Abstract
The Quaternary planktonic foraminiferal assemblages from DSDP Sites 219,220 and 241 in Northern Indian Ocean have been analysed in terms of diversity changes along the depth of each core. For an understanding of the population dynamics in the region and its relation to the paleoclimatic events (Ericson zones), relative abundance at family and species levels have been studied. Different indices of diversity viz., S, D, Hand E have been worked out and correlated with that of the oscillation in paleoclimatic record, which is based on the fluctuation in abundance of Globorotalia menardii along the depth of the core. It has been noted that during the Quaternary, relative abundance of different species and changes in diversity indices match well with that of the Ericson paleoclimatic zonation, enabling recognition of different stages of glacial and interglacial episodes in Northern Indian Ocean.Keywords
Palaeontology, Foraminifera, Palaeoclimate, Quaternary, Northern Indian Ocean.- New Fossil Steginoporellid and Schizoporellid Species (Bryozoa, Cheilostomata) from the Tertiary Sequences of Western Kachchh, Gujarat and their Significance
Authors
1 Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur - 721 302, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 69, No 4 (2007), Pagination: 803-812Abstract
Five new fossil species, three of the family Steginoporellidae Hincks (Labioporella bassleri, Labioporella hariparensis and Steginoporella bhujensis) and two of the family Schizoporellidae Jullien (Schizoporella sowerbyi and Therenia indica), from the Tertiary sequences of western Kachchh Gujarat are described and illustrated. Significance of the evolutionary, biogeographical and paleoecological aspects of some of these taxa is added.Keywords
Bryozoa, Cheilostomata, Tertiary, Biogeographical Distribution, Kachchh, Gujarat.- Cyclostome Bryozoa from the (eocene) Lutetian of Western Kachchh, Gujarat
Authors
1 Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur 721 302, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 69, No 6 (2007), Pagination: 1271-1278Abstract
Seven bryozoan species belonging to six genera in five families under the Order Cyclostomata are described and illustrated for the first time from the Harudi Formation (Lutetian) of wcstern Kachchh, Gujarat. They are Stornutoporu illiesae n. sp., Voigtopora reticulata n .sp., Discosparsa lakhpatensis n. sp., ldmindronea sp.,Oncousoecia narediensis n.sp.,' proboscina' sp. and Plagioecia taylori n. sp. Of these five are new to science.Keywords
Bryozoa, Cyclostomata, Harudi Formation, Lutetian Epoch, species, Kachchh, Gujarat.- New Calloporid (Bryozoa, Cheilostomata) Species from Tertiary Sequences of Western Kachchh, Gujarat
Authors
1 Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur -721302
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 70, No 1 (2007), Pagination: 121-130Abstract
Eight cheilostomate bryozoan species (Aplousina sp., Copidozourzt feddeni n, sp., Crassimarginatella blanfordi n. sp., C. ukirensis n. sp., Marginaria sengrrptai n. sp., Planicellaria kharaiertsis n. sp., P. naliyaensis n. sp. and Reptoporina chhasraensis n. sp. belonging to the family Calloporidae Norman, 1903 are described and jllustsated for the first time from the Tertiary (Lutetian to Aquitanian) sequences of western Kachchh, Gujarat. In the Tertiary bryozoan assemblages of this area, tRis family has the highest generic diversity.Keywords
Bryozoa, Cheilostomata, Calloporidae, Tertiary, Diversity, Kachchh, Gujarat.- 13th Conference of the International Bryozoology Association at Concepcion, Chile
Authors
1 Department of Geology & Geophysics, Indian Institute of Technology, Kharagpur - 721302, IN