Benthic foraminifera of the central Indian Ocean, supplement to: Boersma, Anne (1990): Late Oligocene to late Pliocene benthic foraminifers from depth traverses in the central Indian Ocean. In: Duncan, RA; Backmann, J; Peterson, LC; et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 115, 315-379
Late Oligocene to late Pliocene vertical water-mass stratification along depth traverses in the northern Indian Ocean is depicted in this paper by benthic foraminifer index faunas. During most of this time, benthic faunas indicate well-oxygenated, bottom-water conditions at all depths except under t...
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Language: | English |
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PANGAEA - Data Publisher for Earth & Environmental Science
1990
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Online Access: | https://dx.doi.org/10.1594/pangaea.756728 https://doi.pangaea.de/10.1594/PANGAEA.756728 |
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ftdatacite:10.1594/pangaea.756728 |
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Open Polar |
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DataCite Metadata Store (German National Library of Science and Technology) |
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ftdatacite |
language |
English |
topic |
Drilling/drill rig Leg22 Leg23 Leg24 Leg26 Leg115 Glomar Challenger Joides Resolution Deep Sea Drilling Project DSDP Ocean Drilling Program ODP |
spellingShingle |
Drilling/drill rig Leg22 Leg23 Leg24 Leg26 Leg115 Glomar Challenger Joides Resolution Deep Sea Drilling Project DSDP Ocean Drilling Program ODP Boersma, Anne Benthic foraminifera of the central Indian Ocean, supplement to: Boersma, Anne (1990): Late Oligocene to late Pliocene benthic foraminifers from depth traverses in the central Indian Ocean. In: Duncan, RA; Backmann, J; Peterson, LC; et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 115, 315-379 |
topic_facet |
Drilling/drill rig Leg22 Leg23 Leg24 Leg26 Leg115 Glomar Challenger Joides Resolution Deep Sea Drilling Project DSDP Ocean Drilling Program ODP |
description |
Late Oligocene to late Pliocene vertical water-mass stratification along depth traverses in the northern Indian Ocean is depicted in this paper by benthic foraminifer index faunas. During most of this time, benthic faunas indicate well-oxygenated, bottom-water conditions at all depths except under the southern Indian upwelling and in the Pliocene in the southern Arabian Sea.Faunas suggest the initiation of lower oxygen conditions at intermediate depths in the northern Indian Ocean beginning in Oligocene Zone P21a. Lower oxygen conditions intensified during primary productivity pulses, possibly related to increased upwelling vigor, in the latest Oligocene and throughout most of the late middle through late Miocene. During times of elevated primary production, there may be more oxygen flux into sedimentary pore waters and the shallow infaunal habitat may become more oxygenated.One criterion for locating the source of "new" water masses is vertical homogeneity of benthic foraminifer indexes for well-oxygenated water masses from intermediate through abyssal depths. In the northern Mascarene Basin, this type of faunal homogeneity with depth corroborates the proposal that the northern Indian Ocean was an area of sinking well-oxygenated waters through most of the Miocene before Zone N17.Oxygenated, possibly "new" intermediate-water masses in the low- to middle-latitude Mascarene and Central Indian basins first developed in the late Oligocene. These well-oxygenated waters were probably more fertile than the Antarctic Intermediate Waters (AAIW) that cover intermediate depths in these areas today. Production of intermediate waters more similar to modern AAIW is indicated by the sparse benthic population of epifaunal rotaloid species in the northern Mascarene Basin during middle Miocene Zone N9 and from early through late Pliocene time.Deep-water characteristics are more difficult to interpret because of the extensive redeposition at the deeper sites. Redeposited intermediate, rather than shallow, water fossils and erosion from north to south in the Mascarene Basin are incompatible with the sluggish circulation from south to north through the western Indian Ocean basins today. Such erosion could result from the vigorous sinking of an intermediate-depth water mass of northern origin.Before late Oligocene Zone P22, benthic faunas indicate a twofold subdivision of the troposphere, with the boundary between upper and lower well-oxygenated water masses located from 2500-3000 mbsl. No characteristic bottom-water fauna developed before the end of late Oligocene Zone P22.Deep and abyssal benthic indexes suggest the development of water masses similar to those of the present day in the latest Miocene. Faunas containing deep-water benthic indexes, including the uvigerinids, suggestive of a water mass similar to modern Indian Deep Water (IDW), appeared during the late Miocene in the northern Mascarene and Central Indian basins. In the early Pliocene, this deep-water fauna was found only in the Central Indian Basin, whereas a fauna typical of modern Antarctic Bottom Water (AABW) spread through deep waters at 2800 mbsl in the Mascarene Basin. By late Pliocene Zone N21, however, deep-water faunas similar to their modern analogs were developed in both the eastern and western basins.Abyssal faunas, studied only in the Mascarene Basin, show more or less similarity to those under modern AABW. Bottom-water faunas containing Nuttallides umbonifera or Epistominella exiguua were first differentiated at the end of Zone P22, then appeared episodically during the early Miocene. These AABW-type faunas reappeared and migrated updepth into deep waters during the glacial episodes at the end of the Miocene and at the beginning of the Pliocene. By late Pliocene Zone N21, however, a bottom-water fauna similar to that under eastern Indian Bottom Water (IBW) developed in the Mascarene Basin. Modern bottom-water characteristics of the Mascarene Basin must have developed after ZoneN21. |
format |
Article in Journal/Newspaper |
author |
Boersma, Anne |
author_facet |
Boersma, Anne |
author_sort |
Boersma, Anne |
title |
Benthic foraminifera of the central Indian Ocean, supplement to: Boersma, Anne (1990): Late Oligocene to late Pliocene benthic foraminifers from depth traverses in the central Indian Ocean. In: Duncan, RA; Backmann, J; Peterson, LC; et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 115, 315-379 |
title_short |
Benthic foraminifera of the central Indian Ocean, supplement to: Boersma, Anne (1990): Late Oligocene to late Pliocene benthic foraminifers from depth traverses in the central Indian Ocean. In: Duncan, RA; Backmann, J; Peterson, LC; et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 115, 315-379 |
title_full |
Benthic foraminifera of the central Indian Ocean, supplement to: Boersma, Anne (1990): Late Oligocene to late Pliocene benthic foraminifers from depth traverses in the central Indian Ocean. In: Duncan, RA; Backmann, J; Peterson, LC; et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 115, 315-379 |
title_fullStr |
Benthic foraminifera of the central Indian Ocean, supplement to: Boersma, Anne (1990): Late Oligocene to late Pliocene benthic foraminifers from depth traverses in the central Indian Ocean. In: Duncan, RA; Backmann, J; Peterson, LC; et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 115, 315-379 |
title_full_unstemmed |
Benthic foraminifera of the central Indian Ocean, supplement to: Boersma, Anne (1990): Late Oligocene to late Pliocene benthic foraminifers from depth traverses in the central Indian Ocean. In: Duncan, RA; Backmann, J; Peterson, LC; et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 115, 315-379 |
title_sort |
benthic foraminifera of the central indian ocean, supplement to: boersma, anne (1990): late oligocene to late pliocene benthic foraminifers from depth traverses in the central indian ocean. in: duncan, ra; backmann, j; peterson, lc; et al. (eds.), proceedings of the ocean drilling program, scientific results, college station, tx (ocean drilling program), 115, 315-379 |
publisher |
PANGAEA - Data Publisher for Earth & Environmental Science |
publishDate |
1990 |
url |
https://dx.doi.org/10.1594/pangaea.756728 https://doi.pangaea.de/10.1594/PANGAEA.756728 |
geographic |
Antarctic Indian The Antarctic |
geographic_facet |
Antarctic Indian The Antarctic |
genre |
Antarc* Antarctic |
genre_facet |
Antarc* Antarctic |
op_relation |
https://dx.doi.org/10.2973/odp.proc.sr.115.146.1990 |
op_rights |
Creative Commons Attribution 3.0 Unported https://creativecommons.org/licenses/by/3.0/legalcode cc-by-3.0 |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.1594/pangaea.756728 https://doi.org/10.2973/odp.proc.sr.115.146.1990 |
_version_ |
1766268178887868416 |
spelling |
ftdatacite:10.1594/pangaea.756728 2023-05-15T13:59:34+02:00 Benthic foraminifera of the central Indian Ocean, supplement to: Boersma, Anne (1990): Late Oligocene to late Pliocene benthic foraminifers from depth traverses in the central Indian Ocean. In: Duncan, RA; Backmann, J; Peterson, LC; et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 115, 315-379 Boersma, Anne 1990 application/zip https://dx.doi.org/10.1594/pangaea.756728 https://doi.pangaea.de/10.1594/PANGAEA.756728 en eng PANGAEA - Data Publisher for Earth & Environmental Science https://dx.doi.org/10.2973/odp.proc.sr.115.146.1990 Creative Commons Attribution 3.0 Unported https://creativecommons.org/licenses/by/3.0/legalcode cc-by-3.0 CC-BY Drilling/drill rig Leg22 Leg23 Leg24 Leg26 Leg115 Glomar Challenger Joides Resolution Deep Sea Drilling Project DSDP Ocean Drilling Program ODP article Supplementary Collection of Datasets Collection 1990 ftdatacite https://doi.org/10.1594/pangaea.756728 https://doi.org/10.2973/odp.proc.sr.115.146.1990 2022-02-09T12:04:35Z Late Oligocene to late Pliocene vertical water-mass stratification along depth traverses in the northern Indian Ocean is depicted in this paper by benthic foraminifer index faunas. During most of this time, benthic faunas indicate well-oxygenated, bottom-water conditions at all depths except under the southern Indian upwelling and in the Pliocene in the southern Arabian Sea.Faunas suggest the initiation of lower oxygen conditions at intermediate depths in the northern Indian Ocean beginning in Oligocene Zone P21a. Lower oxygen conditions intensified during primary productivity pulses, possibly related to increased upwelling vigor, in the latest Oligocene and throughout most of the late middle through late Miocene. During times of elevated primary production, there may be more oxygen flux into sedimentary pore waters and the shallow infaunal habitat may become more oxygenated.One criterion for locating the source of "new" water masses is vertical homogeneity of benthic foraminifer indexes for well-oxygenated water masses from intermediate through abyssal depths. In the northern Mascarene Basin, this type of faunal homogeneity with depth corroborates the proposal that the northern Indian Ocean was an area of sinking well-oxygenated waters through most of the Miocene before Zone N17.Oxygenated, possibly "new" intermediate-water masses in the low- to middle-latitude Mascarene and Central Indian basins first developed in the late Oligocene. These well-oxygenated waters were probably more fertile than the Antarctic Intermediate Waters (AAIW) that cover intermediate depths in these areas today. Production of intermediate waters more similar to modern AAIW is indicated by the sparse benthic population of epifaunal rotaloid species in the northern Mascarene Basin during middle Miocene Zone N9 and from early through late Pliocene time.Deep-water characteristics are more difficult to interpret because of the extensive redeposition at the deeper sites. Redeposited intermediate, rather than shallow, water fossils and erosion from north to south in the Mascarene Basin are incompatible with the sluggish circulation from south to north through the western Indian Ocean basins today. Such erosion could result from the vigorous sinking of an intermediate-depth water mass of northern origin.Before late Oligocene Zone P22, benthic faunas indicate a twofold subdivision of the troposphere, with the boundary between upper and lower well-oxygenated water masses located from 2500-3000 mbsl. No characteristic bottom-water fauna developed before the end of late Oligocene Zone P22.Deep and abyssal benthic indexes suggest the development of water masses similar to those of the present day in the latest Miocene. Faunas containing deep-water benthic indexes, including the uvigerinids, suggestive of a water mass similar to modern Indian Deep Water (IDW), appeared during the late Miocene in the northern Mascarene and Central Indian basins. In the early Pliocene, this deep-water fauna was found only in the Central Indian Basin, whereas a fauna typical of modern Antarctic Bottom Water (AABW) spread through deep waters at 2800 mbsl in the Mascarene Basin. By late Pliocene Zone N21, however, deep-water faunas similar to their modern analogs were developed in both the eastern and western basins.Abyssal faunas, studied only in the Mascarene Basin, show more or less similarity to those under modern AABW. Bottom-water faunas containing Nuttallides umbonifera or Epistominella exiguua were first differentiated at the end of Zone P22, then appeared episodically during the early Miocene. These AABW-type faunas reappeared and migrated updepth into deep waters during the glacial episodes at the end of the Miocene and at the beginning of the Pliocene. By late Pliocene Zone N21, however, a bottom-water fauna similar to that under eastern Indian Bottom Water (IBW) developed in the Mascarene Basin. Modern bottom-water characteristics of the Mascarene Basin must have developed after ZoneN21. Article in Journal/Newspaper Antarc* Antarctic DataCite Metadata Store (German National Library of Science and Technology) Antarctic Indian The Antarctic |