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  • 1
    Online Resource
    Online Resource
    Timing, cause and consequences of mid-Holocene climate transition in the Arabian Sea
    Cambridge University Press (CUP) ; 2016
    In:  Quaternary Research Vol. 86, No. 2 ( 2016-09), p. 162-169
    Details
    In: Quaternary Research, Cambridge University Press (CUP), Vol. 86, No. 2 ( 2016-09), p. 162-169
    Abstract: We reconstruct centennial scale quantitative changes in surface seawater temperature (SST), evaporation-precipitation (from Mg/Ca and δ 18 O of surface dwelling planktic foraminifera), productivity (from relative abundance of Globigerina bulloides ), carbon burial (from %CaCO 3 and organic carbon [%C org ]) and dissolved oxygen at sediment-water interface, covering the entire Holocene, from a core collected from the eastern Arabian Sea. From the multi-proxy record, we define the timing, consequences and possible causes of the mid-Holocene climate transition (MHCT). A distinct shift in evaporation-precipitation (E-P) is observed at 6.4 ka, accompanied by a net cooling of SST. The shift in SST and E-P is synchronous with a change in surface productivity. A concurrent decrease is also noted in both the planktic foraminiferal abundance and coarse sediment fraction. A shift in carbon burial, as inferred from both the %CaCO 3 and %C org , coincides with a change in surface productivity. A simultaneous decrease in dissolved oxygen at the sediment-water interface, suggests that changes affected both the surface and subsurface water. A similar concomitant change is also observed in other cores from the Arabian Sea as well as terrestrial records, suggesting a widespread regional MHCT. The MHCT coincides with decreasing low-latitude summer insolation, perturbations in total solar intensity and an increase in atmospheric CO 2 .
    Type of Medium: Online Resource
    ISSN: 0033-5894 , 1096-0287
    URL: Article
    DOI: 10.1016/j.yqres.2016.06.001
    RVK:
    RA 1000
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2016
    detail.hit.zdb_id: 1471589-2
    detail.hit.zdb_id: 205711-6
    SSG: 13
    SSG: 14
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  • 2
    Online Resource
    Online Resource
    Inconsistent change in surface hydrography of the eastern Arabian Sea during the last four glacial–interglacial intervals
    Cambridge University Press (CUP) ; 2020
    In:  Geological Magazine Vol. 157, No. 6 ( 2020-06), p. 989-1000
    Details
    In: Geological Magazine, Cambridge University Press (CUP), Vol. 157, No. 6 ( 2020-06), p. 989-1000
    Abstract: The eastern Arabian Sea is influenced by both the advection of upwelled water from the western Arabian Sea and winter convective mixing. Therefore, sediments collected from the eastern Arabian Sea can help to understand the long-term seasonal hydrographic changes. We used the planktonic foraminifera census and stable isotopic ratio (δ 18 O) from sediments drilled during the International Ocean Discovery Program Expedition 355 to reconstruct surface hydrographic changes in the eastern Arabian Sea during the last 350 kyr. The increased abundance of Globigerina bulloides suggests enhanced advection of upwelled water during the latter half of MIS7 and the beginning of MIS6, as a result of a strengthened summer monsoon. A large drop in upwelling and/or advection of upwelled water from the western Arabian Sea is inferred during the subsequent interval of MIS6, based on the rare presence of G. bulloides . The comparable relative abundance of Neogloboquadrina dutertrei , G. bulloides and Globigerinoides ruber suggests that during the early part of MIS5, hydrographic conditions were similar to today. The upwelling decreased and winter convection increased with the progress of the glacial interval. A good coherence between planktonic foraminiferal assemblage-based monsoon stacks from both the eastern and western Arabian Sea suggests a coeval response of the entire northern Arabian Sea to the glacial–interglacial changes. The glacial–interglacial difference in δ 18 O sw-ivc was at a maximum with 4–5 psu change in salinity during Termination 2 and 3, and a minimum during Termination 4. The significantly reduced regional contribution to the glacial–interglacial change in δ 18 O sw-ivc during Termination 4 suggests a lesser change in the monsoon.
    Type of Medium: Online Resource
    ISSN: 0016-7568 , 1469-5081
    URL: Article
    DOI: 10.1017/S0016756819001122
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2020
    detail.hit.zdb_id: 956405-6
    detail.hit.zdb_id: 1479206-0
    SSG: 13
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  • 3
    Online Resource
    Online Resource
    A late Pleistocene sedimentation in the Indus Fan, Arabian Sea, IODP Site U1457
    Cambridge University Press (CUP) ; 2020
    In:  Geological Magazine Vol. 157, No. 6 ( 2020-06), p. 920-928
    Details
    In: Geological Magazine, Cambridge University Press (CUP), Vol. 157, No. 6 ( 2020-06), p. 920-928
    Abstract: The intensity of turbidite sedimentation over long timescales is driven by sea-level change, tectonically driven rock uplift and climatically modulated sediment delivery rates. This study focuses on understanding the effect of sea-level fluctuations and climatic variability on grain-size variations. The grain size and environmental magnetic parameters of Arabian Sea sediments have been documented using 203 samples, spanning the last 200 ka, obtained from International Ocean Discovery Program (IODP) Site U1457. Grain-size end-member modelling suggests that between ~200 and 130 ka there was an increase in the coarse silt fraction caused by sediment transport following reworking of the Indus Fan and development of deep-sea canyons. The sediment size and enhanced magnetic susceptibility indicate a dominant flux of terrestrial sediments. Sedimentation in the distal Indus Fan at c . 200–130 ka was driven by a drop in sea level that lowered the base level in the Indus and Narmada river systems. The low sea-stand caused incision in the Indus delta, canyons and fan area, which resulted in the transportation of coarser sediment at the drilling site. Magnetic susceptibility and other associated magnetic parameters suggest a large fraction of the sediment was supplied by the Narmada River during ~200–130 ka. Since ~130 ka, clay-dominated sedimentation is attributed to the rise in sea level due to warm and wet climate.
    Type of Medium: Online Resource
    ISSN: 0016-7568 , 1469-5081
    URL: Article
    DOI: 10.1017/S0016756819000396
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2020
    detail.hit.zdb_id: 956405-6
    detail.hit.zdb_id: 1479206-0
    SSG: 13
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  • 4
    Online Resource
    Online Resource
    A revised chronostratigraphic framework for International Ocean Discovery Program Expedition 355 sites in Laxmi Basin, eastern Arabian Sea
    Cambridge University Press (CUP) ; 2020
    In:  Geological Magazine Vol. 157, No. 6 ( 2020-06), p. 961-978
    Details
    In: Geological Magazine, Cambridge University Press (CUP), Vol. 157, No. 6 ( 2020-06), p. 961-978
    Abstract: International Ocean Discovery Program Expedition 355 drilled Sites U1456 and U1457 in Laxmi Basin (eastern Arabian Sea) to document the impact of the South Asian monsoon on weathering and erosion of the Himalaya. We revised the chronostratigraphic framework for these sites using a combination of biostratigraphy, magnetostratigraphy and strontium isotope stratigraphy. The sedimentary section at the two sites is similar and we divided it into six units bounded by unconformities or emplaced as a mass-transport deposit (MTD). Unit 1 underlies the MTD, and is of early–middle Miocene age at Site U1456 and early Paleocene age at Site U1457. An unconformity (U1) created by emplacement of the MTD (unit 2) during the late Miocene Epoch (at c. 9.83–9.69 Ma) separates units 1 and 2 and is identified by a marked change in lithology. Unit 3 consists of hemipelagic sediment with thin interbeds of graded sandstone of late Miocene age, separated from unit 4 by a second unconformity (U2) of 0.5–0.9 Myr duration. Unit 4 consists of upper Miocene interbedded mudstone and sandstone and hemipelagic chalk deposited between c. 8 and 6 Ma. A c. 1.4–1.6 Myr hiatus (U3) encompasses the Miocene–Pliocene boundary and separates unit 4 from unit 5. Unit 5 includes upper Pliocene – lower Pleistocene siliciclastic sediment that is separated from unit 6 by a c. 0.45 Myr hiatus (U4) in the lower Pleistocene sediments. Unit 6 includes a thick package of rapidly deposited Pleistocene sand and mud overlain by predominantly hemipelagic sediment deposited since c. 1.2 Ma.
    Type of Medium: Online Resource
    ISSN: 0016-7568 , 1469-5081
    URL: Article
    DOI: 10.1017/S0016756819000104
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2020
    detail.hit.zdb_id: 956405-6
    detail.hit.zdb_id: 1479206-0
    SSG: 13
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  • 5
    Online Resource
    Online Resource
    Persistent increase in carbon burial in the Gulf of Mannar, during the Meghalayan Age: Influence of primary productivity and better preservation
    Cambridge University Press (CUP) ; 2023
    In:  Geological Magazine Vol. 160, No. 3 ( 2023-03), p. 561-578
    Details
    In: Geological Magazine, Cambridge University Press (CUP), Vol. 160, No. 3 ( 2023-03), p. 561-578
    Abstract: The oceans store a substantial fraction of carbon as calcium carbonate (CaCO 3 ) and organic carbon (C org ) and constitute a significant component of the global carbon cycle. The C org and CaCO 3 flux depends on productivity and is strongly modulated by the Asian monsoon in the tropics. Anthropogenic activities are likely to influence the monsoon and thus it is imperative to understand its implications on carbon burial in the oceans. We have reconstructed multi-decadal CaCO 3 and C org burial changes and associated processes during the last 4.9 ky, including the Meghalayan Age, from the Gulf of Mannar. The influence of monsoon on carbon burial is reconstructed from the absolute abundance of planktic foraminifera and relative abundance of Globigerina bulloides . Both C org and CaCO 3 increased throughout the Meghalayan Age, except between 3.0–3.5 ka and the last millennium. The increase in C org burial during the Meghalayan Age was observed throughout the eastern Arabian Sea. The concomitant decrease in the C org to nitrogen ratio suggests increased contribution of marine organic matter. Although the upwelling was intense until 1.5 ka, the lack of a definite increasing trend suggests that the persistent increase in C org and CaCO 3 during the early Meghalayan Age was mainly driven by higher productivity during the winter season coupled with better preservation in the sediments. Both the intervals (3.0–3.5 ka and the last millennium) of nearly constant carbon burial coincide with a steady sea-level. The low carbon burial during the last millennium is attributed to the weaker-upwelling-induced lower productivity.
    Type of Medium: Online Resource
    ISSN: 0016-7568 , 1469-5081
    URL: Article
    DOI: 10.1017/S001675682200111X
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2023
    detail.hit.zdb_id: 956405-6
    detail.hit.zdb_id: 1479206-0
    SSG: 13
    Location Call Number Limitation Availability
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