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Gupta, Anil K.
- 6th International Conference on Palaeoceanography
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Authors
Affiliations
1 Dept. of Geology and Geophysics, IIT Khragpur-721302, IN
2 National institute of Oceanography, Dona Paula, Goa-403004, IN
3 Naional Geophysical Research Institute, Hyderabad-500007, IN
1 Dept. of Geology and Geophysics, IIT Khragpur-721302, IN
2 National institute of Oceanography, Dona Paula, Goa-403004, IN
3 Naional Geophysical Research Institute, Hyderabad-500007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 53, No 1 (1999), Pagination: 117-118Abstract
No Abstract.- Pleistocene Benthic Foraminifera and DeepM
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Authors
Affiliations
1 Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur 721 302 (W. B.), IN
1 Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur 721 302 (W. B.), IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 37, No 4 (1991), Pagination: 388-406Abstract
The evolution of Pleistocene deep-sea environments at Northern Indian Ocean DSDP Site 219 has been evaluated, using the quantitative analyses of deep-sea benthic foraminiferal fauna. The Pleistocene assemblages are dominated by Uvigerina proboscidea which shows remarkable frequency changes. The relative abundances of characteristic benthic foraminifera, and patterns of Species Diversity and Equitability have enabled identification of four events (C1-C4) of major faunal turnovers. These events have been inferred to represent intervals of fundamental changes in atmospheric oceanic circulation, most likely the cooling and intensification of bottom-waters due to major increase in polar ice volume.Keywords
Pleistocene, Foraminifera, DSDP Site 219, Deep-Sea Environment, Marine Geology.- Benthic foraminifera and Deep-Sea Water Masses in the Tropical Indian Ocean
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Authors
Affiliations
1 Department of Geology and Geophysics, Indian Institutc of Technology, Kharagpur 721 302, W.B., IN
1 Department of Geology and Geophysics, Indian Institutc of Technology, Kharagpur 721 302, W.B., IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 39, No 6 (1992), Pagination: 475-486Abstract
The distribution patterns of important benthic foraminifera from surface sediment samples of 9 DSDP sites from the tropical Indian Ocean were examined. The faunal patterns reveal two major assemblages and one intermediate assemblage. The first assemblage is dominated by Uvigerina proboscidea and Globocassidulina pacifica and confined to a water depth ranging from 1800-2800m. This assemblage is associated with North Indian Deep Water (NIDW). The second assemblage, confined to waters deeper than 3800m, is dominated by Epislomineila umbonifera and is associated with Antarctic Bottom Water (AABW). The third assemblage occurs between 2800 and 3800m and is dominated by Uvigerina hispido-costata, Cibicides wuellerstorfi, Epistominella exigua, Pullenia bulloides, and Oridorsalis umbonatus. This assemblage is associated with a water mass intermediate between NIDW and AABW. A minor assemblage has also been observed at depths shallower than 1800m, dominated by Bulimina aculeata and Astrononion umbilicatulum. This assemblage appears to be associated with a water mass influenced by Antarctic Intermediate Water (AAIW).Keywords
Benthic Foraminifera, Indian Ocean.- Deep-Sea Benthic Foraminiferal Changes and Terminal Miocene Event at Tropical Indian Ocean DSDP Site 214
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Authors
Affiliations
1 Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur 721302, IN
2 Department of Geology, Banaras Hindu University, Varanasi 221005, IN
1 Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur 721302, IN
2 Department of Geology, Banaras Hindu University, Varanasi 221005, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 40, No 3 (1992), Pagination: 262-278Abstract
Quantitative data of Late Miocene deep-sea benthic foraminifera from the tropical Indian Ocean DSDP Site 214 have been combined with oxygen and carbon isotope values to understand the history of deep thermohaline circutation in the Indian Ocean. The important faunal changes include a significant increase in Uvigerina proboscidea percentages at c. 8.S to 7.5 Ma and during 6.2 to 5.2 Mat reaching their maximum values at the Miocene/Pliocene boundary. The increase in U. proboscidea percentages are accompanied by decreasing abundances of Bulimina alazanensis. Obicides kullenbergi, and C. wuellerstorfi. and lower values of H (S) and E'. The δ 180 values are, in general, higher during these intervals While δ13C values show a decreasing trend. The interval between 7.5 and 6.2 Ma is marked by a major increase in B. alazanensis which coincides with slightly higher δl3C and lower δ180 values. C. kullenbergi and C. wuellerstorfi. interestingly, reveal significant variations with higher values before Chroo - 6 Carbon Shift at about 6.2 Ma and a prominent peak immediately preceding the shift, but remain low and less variable following the shift during the remainder of the Late Miocene as do the δ 13C va1ues. The well-known Late Miocene Chron - 6 negative carbon shift is marked by significantly higber U. proboscidea percentages, and lower C. ku/lenbergi, C. wuellerstorfi and B. alazanensis values. Out data support the hypothesis that the shift was caused by excess organic carbon input to the system. and higher rate of upwelling and ocean productivity. The Miocene/ Pliocene boundary marks a warming event and is typified by highest percentages of U. proboscidea and Osanguiaria culter, lighter δ180 and lighterδ13C values, and lowest values of H(S) and E'. The sediment accumulation rates were remarkably higher at the Miocene/Pliocene boundary. These events reflect high rates of surface productivity intensified by strong upwelling.Keywords
Foraminifera, Miocene, Indian Ocean.- Holocene Deep-Sea Benthic Foraminifera and Watermasses in the Indian Ocean and the Red Sea
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Authors
Affiliations
1 Department of Geology & Geophysics, Indian Institute of Technology, Kharagpur - 721302, IN
1 Department of Geology & Geophysics, Indian Institute of Technology, Kharagpur - 721302, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 43, No 6 (1994), Pagination: 691-703Abstract
The distribution of Holocene deep-sea benthic foraminifera in 19 core top samples from the Indian Ocean and the Red Sea is examined to understand the faunal-watermass associations. Relative percentages of significant taxa have enabled to identify distinct assemblages associated wth different watermasses in the Indian Ocean and the Red Sea. The first assemblage in the Indian Ocean is marked by the dominance of Nuttallides umbonifera. This assemblage is found below 4000 m where bottom water is highly carbonate-undersaturated and is influenced by Antarctic Bottom Water (AABW). The second assemblage is characterized by Uvigerina hispido-costata dominance with Cibiddes wuellerstorfi as a subsidiary species. This assemblage is associated with the lower tongue of North Indian Deep Water (NIDW) between 2500 and 4000 m water depths. U. hispido-costata has higher abundances at sites lying below upwelling zone off the Arabian coast in relatively high dissolved oxygen deep water. The third assemblage is dominated by Uvigerina proboscidea between 1500 and 2500 m depth. Globocassidulina pacifica/subglobosa, Pullenia bulloides and C. wuellerstorfi are secondary constituents. This assemblage characterizes high productivity regions (equatorial belt) with relatively low oxygen levels in deep water. The Red Sea Deep Water (RSDW) assemblage is dominated by Bolivina subreticulata and characterizes highly saline, warm, oxygen-poor deep water. Other species of this assemblage are Textularia agglutinans, Astrononion umbilicatulum, Miliolinella subrotunda and Ophthalmidium acutimargo.Keywords
Benthic Foraminifera, Micropaleontology, Holocene, Indian Ocean, Red Sea.- Pliocene - Pleistocene Benthic Foraminifera and Abyssal Circulation Changes at Arabian Sea DSDP Sites 220 and 223
Abstract Views :191 |
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Authors
Affiliations
1 Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur - 721 302, IN
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 45, No 2 (1995), Pagination: 209-216Abstract
Pliocene-Pleistocene benthic foraminifera were analysed from arabian Sea Deep Sea Drilling Project (DSDP) sites 220 and 223. At site 220 the most dominant taxon is Nuttallides umbonifera showing peak abundances in the Early Pliocene, Early and latest Pleistocene possibly representing intervals of highly carbonate-undersaturated bottom waters. The species diversity [H(S)] and equitability (E') trends show inverse relationship with N. umbonifera percentages. At relatively shallower site 223, the benthic assemblage is dominated by Cibicides wuellerstorfi, Oridorsalis umbonatus and Uvigerina hispido-costata through Plio-Pleistocene. N. umbonifera shows peak abundances only in the beginning of the Pliocene. This species shows an abrupt decrease to near extinction near the Plio-Pleistocene boundary and occurs very rarely and sporadically in the Pleistocene at site 223. C. wuellerstorfi and O. umbonatus show increased percentages in the earliest Pliocene, late Early Pliocene, and a short lived peakin the Early Pleistocene (samples 2-5), indicating presenceof relatively warm, oxygenated, and less corrosive bottom water at this site. The peaks of U.hispido-costata at site 223 are inferred to reflect intervals of high surface productivity due to intense upwelling off the Arabian coast.Keywords
Foraminifera, Pliocene-Pleistocene, Arabian Sea.- Occurrence of the Biogenic Bloom in the Oligotrophic Southeastern Indian Ocean: Evidence from Late Neogene Deep-Sea Benthic Foraminifera (ODP Hole 752A)
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Authors
Anil K. Gupta
1,
Moumita Das
1
Affiliations
1 Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur 721302, IN
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 69, No 2 (2007), Pagination: 331-343Abstract
We produced a 12.9 Ma census data of deep-sea benthic foraminifera from subtropical Ocean Drilling Program (ODP) Hole 752A, Broken Ridge, southeastern Indian Ocean to understand paleoceanographic and paleoclimatic changes and their relation to Southern Ocean climate variability as well as latitudinal shifts in the Subtropical Convergence Zone (SCZ). We employed knowledge of the ecology of Recent deep-sea benthic foraminifera from different ocean basins for environmental interpretations at Hole 752A. Benthic faunal data suggest a major transition in deep-sea environments of the southeastern Indian Ocean across 5.5-4.5 Ma roughly coinciding with the end of the Indo-Pacific "biogenic bloom". The benthic biofacies suggest well-oxygenated and nutrient poor deep waters from 12.9 to 10 Ma with variable flux of organic matter. The interval 10-5.5 Mais marked by high and sustainedflux of organic matter at the time when productivity increased many fold throughout the Indian and Pacific Oceans during which time the biogenic bloom peaked and the Indian summer monsoon intensified. Antarctic ice volume significantly increased and southern component deep-water formation enhanced during this time. This southern cooling in the late middle to late Miocene probably pushed the SCZ towards north above Hole 752A. Since 4.5 Ma, the organic flux was low to intermediate and pulsed.Keywords
Paleoceanographic changes, Benthic foraminifera, ODP Site 752, Broken Ridge, SE Indian Ocean.- Mysteries of the Indian Ocean Monsoon System
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Authors
Affiliations
1 Department of Geology & Geophysics, lndian Institute of Technology, Khar agpur - 721 302, IN
2 NOAA Paleoclimatology Program, 325 Bloadway, Bouldct, CO 80305-3328, USA, US
1 Department of Geology & Geophysics, lndian Institute of Technology, Khar agpur - 721 302, IN
2 NOAA Paleoclimatology Program, 325 Bloadway, Bouldct, CO 80305-3328, USA, US
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 65, No 1 (2005), Pagination: 54-60Abstract
South Asian monsoon is an important part of global climate, affecting large areas of the Indian subcontinent Monsoon is life and death to the people of South Asia as good monsoon is a boon to taimers whereas an unusual monsoon can bring misery to the people through widespread floods and droughts Strong differential heating of the Indian landmass and the latent heat released from piccipitation mainly drive the present day summer monsoon circulation During the northeast (winter) monsoon season, winds are dry and biological productivity in the northern Indian Ocean is low providing little food to the deep-sea In opposition, the intense, wet, monsoonal winds of thc southwest (summer) monsoon cause widespread upwelling and high surface productivity, thus a high supply of organic particles to thc sea floor During high surface productivity, distinct fauna and flora flourish in the surface water column in various parts ot the northern Indian Ocean Study of these monsoon proxics accumulating in layers of sediment over hundreds to millions of years help understand the history of monsoons over various time scales Recent study suggests a mechanistic link between the North Atlantic Ocean and the southwest monsoon at century-millennial time scales during the Holocene, suggesting importance of tropics and high latitude teleconnection On short time scales monsoon variability has also been related to the Indian ocean Sea Surface Temperature (SST), Himalayan-Eurasian snow as well as El Nino-Southern Oscillation(ENSO) This study reviews different aspects of past monsoon variability and its future implications.Keywords
lndian Ocean, Summer monsoon, Biological productivity, Holocene, Monsoon proxies.- Middle Pleistocene Transition (MPT) in the Eastern Indian Ocean: A 2000 Kyr Planktic Faunal and Isotope Record from Dsdp Site 214
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Authors
Affiliations
1 Department of Geology & Geophysics, Indian Institute of Technology, Kharagpur - 721 302, IN
1 Department of Geology & 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 63, No 1 (2004), Pagination: 29-38Abstract
Planktic foraminiferal faunal and isotope data from Deep Sea Drilling Project (DSDP) Site 214 reveal a major change in surface water properties in the eastern Indian Ocean, coinciding with the mid-Pleistocene climate transition (MPT). A comparative study of Globigerinoides sacculifer (a surface dwelling, warm water, mixed-layer tropical planktic foraminifer), Globorotalia menardii Complex (a deep dwelling, tropical species group), and Orbulina universa (an intermediate depth warm-water subtropical foraminifer) with the stable isotope record of Globigerinoides ruber suggests a warm, thick mixed layer in the eastern Indian Ocean during,∼2000 Kyr to -900 Kyr. Since -900 Kyr the surface water mass stratification weakened, and the mixed layer as well as thermocline were shallow. A decrease in the population abundance of Gs. sacculifer, together with a decrease in 813C and increase in 5180 values suggest a continuous cool climate and increased surface productivity over the last -900 Kyr. This coincides with an increased variance in the 400-Kyr component of Earth's eccentricity cycle.Keywords
Palaeoclimate, Middle Pleistocene Transition, Planktic Fauna, Oxygen And Carbon Isotopes, Eastern Indian Ocean.- Deep-Sea Paleoceanographic and Surface Productivity Changes in the Northwestern Arabian Sea Driven by the Indian Southwest Monsoon during the last Millennium
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Authors
Affiliations
1 Departrnent of Geology and Geophysics, Indian Institute of Technology, Kharagpur 721 302, IN
2 NOAA Paleoclimatology Program, 325 Broadway, Code E/GC, Boulder, CO 80302, US
1 Departrnent of Geology and Geophysics, Indian Institute of Technology, Kharagpur 721 302, IN
2 NOAA Paleoclimatology Program, 325 Broadway, Code E/GC, Boulder, CO 80302, US