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  • 1
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    PANGAEA
    In:  Supplement to: Gupta, Anil K; Sarkar, Sudipta; Mukherjee, Baidehi (2006): Paleoceanographic changes during the past 1.9 Myr at DSDP Site 238, Central Indian Ocean Basin: Benthic foraminiferal proxies. Marine Micropaleontology, 60(2), 157-166, https://doi.org/10.1016/j.marmicro.2006.04.001
    Publication Date: 2023-06-27
    Description: Deep-sea benthic foraminifera have been quantitatively analyzed in samples (〉125 µm size fraction) from Ocean Drilling Program (ODP) Site 238, to understand paleoceanographic changes in the Central Indian Basin over the past 1.9 Myr. Factor and cluster analyses of the 25 highest-ranked species made it possible to identify five biofacies, characterizing distinct deep-sea environmental settings. The environmental interpretation of each biofacies is based on the ecology of recent deep-sea benthic foraminifera. The benthic faunal record indicates fluctuating deep-sea conditions in environmental parameters including oxygenation, surface productivity and organic food supply. These changes appear to be linked to Indian summer monsoon variability, the main climatic feature of the Indian Ocean region. The benthic assemblages show a major shift at ~0.7 to 0.6 Ma, marked by major turnovers in the relative abundances of species, coinciding with an increased amplitude of glacial cycles. These cycles appear to have influenced low latitude monsoonal climate as well as deep-sea conditions in the Central Indian Ocean Basin.
    Keywords: 24-238; AGE; Astrononion umbilicatulum; Bulimina alazanensis; Cassidulina carinata; Cibicidoides wuellerstorfi; Counting 〉125 µm fraction; Deep Sea Drilling Project; DEPTH, sediment/rock; DRILL; Drilling/drill rig; DSDP; DSDP/ODP/IODP sample designation; Eggerella bradyi; Ehrenbergina carinata; Epistominella exigua; Favocassidulina australis; Favocassidulina favus; Globocassidulina pacifica; Globocassidulina subglobosa; Glomar Challenger; Gyroidinoides cibaoensis; Gyroidinoides nitidula; Gyroidinoides polius; Indian Ocean//FRACTURE ZONE; Laticarinina pauperata; Leg24; Nuttallides umbonifera; Oridorsalis umbonatus; Pullenia bulloides; Pullenia osloensis; Pullenia quinqueloba; Pyrgo murrhina; Quinqueloculina weaveri; Sample code/label; Siphotextularia rolshauseni; Uvigerina hispidocostata; Uvigerina proboscidea
    Type: Dataset
    Format: text/tab-separated-values, 2340 data points
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  • 2
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    PANGAEA
    In:  Supplement to: Prasad, Sushma; Anoop, A; Riedel, N; Sarkar, Saswati; Menzel, Philip; Basavaiah, Nathani; Krishnan, R; Fuller, D; Plessen, Birgit; Gaye, Birgit; Röhl, Ursula; Wilkes, Heinz; Sachse, Dirk; Sawant, R; Wiesner, Martin G; Stebich, Martina (2014): Prolonged monsoon droughts and links to Indo-Pacific warm pool: A Holocene record from Lonar Lake, central India. Earth and Planetary Science Letters, 391, 171-182, https://doi.org/10.1016/j.epsl.2014.01.043
    Publication Date: 2023-06-27
    Description: Concerns about the regional impact of global climate change in a warming scenario have highlighted the gaps in our understanding of the Indian Summer Monsoon (ISM, also referred to as the Indian Ocean summer monsoon) and the absence of long term palaeoclimate data from the central Indian core monsoon zone (CMZ). Here we present the first high resolution, well-dated, multiproxy reconstruction of Holocene palaeoclimate from a 10 m long sediment core raised from the Lonar Lake in central India. We show that while the early Holocene onset of intensified monsoon in the CMZ is similar to that reported from other ISM records, the Lonar data shows two prolonged droughts (PD, multidecadal to centennial periods of weaker monsoon) between 4.6–3.9 and 2–0.6 cal ka. A comparison of our record with available data from other ISM influenced sites shows that the impact of these PD was observed in varying degrees throughout the ISM realm and coincides with intervals of higher solar irradiance. We demonstrate that (i) the regional warming in the Indo-Pacific Warm Pool (IPWP) plays an important role in causing ISM PD through changes in meridional overturning circulation and position of the anomalous Walker cell; (ii) the long term influence of conditions like El Niño-Southern Oscillation (ENSO) on the ISM began only ca. 2 cal ka BP and is coincident with the warming of the southern IPWP; (iii) the first settlements in central India coincided with the onset of the first PD and agricultural populations flourished between the two PD, highlighting the significance of natural climate variability and PD as major environmental factors affecting human settlements.
    Keywords: AGE; Carbon, organic, total; Carbon/Nitrogen ratio; DEPTH, sediment/rock; L23; Lonar Crater Lake, central India; Nitrogen, total; δ13C, organic carbon; δ15N
    Type: Dataset
    Format: text/tab-separated-values, 3006 data points
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  • 3
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    PANGAEA
    In:  Supplement to: Dumke, Ines; Burwicz, Ewa; Berndt, Christian; Klaeschen, Dirk; Feseker, Tomas; Geissler, Wolfram H; Sarkar, Sudipta (2016): Gas hydrate distribution and hydrocarbon maturation north of the Knipovich Ridge, western Svalbard margin. Journal of Geophysical Research: Solid Earth, 121(3), 1405-1424, https://doi.org/10.1002/2015JB012083
    Publication Date: 2024-02-16
    Description: The seismic data were acquired north of the Knipovich Ridge on the western Svalbard margin during cruise MSM21/4. They were recorded using a Geometrics GeoEel streamer of either 120 channels (profiles p100-p208) or 88 channels (profiles p300-p805) with a group spacing of 1.56 m and a sampling rate of 2 kHz. A GI-Gun (2×1.7 l) with a main frequency of ~150 Hz was used as a source and operated at a shot interval of 6-8 s. Processing of profiles p100-p208 and p600-p805: Positions for each channel were calculated by backtracking along the profiles from the GI-Gun GPS positions. The shot gathers were analyzed for abnormal amplitudes below the seafloor reflection by comparing neighboring traces in different frequency bands within sliding time windows. To suppress surface-generated water noise, a tau-p filter was applied in the shot gather domain. Common mid-point (CMP) profiles were then generated through crooked-line binning with a CMP spacing of 1.5625 m. A zero-phase band-pass filter with corner frequencies of 60 Hz and 360 Hz was applied to the data. Based on regional velocity information from MCS data [Sarkar, 2012], an interpolated and extrapolated 3D interval velocity model was created below the digitized seafloor reflection of the high-resolution streamer data. This velocity model was used to apply a CMP stack and an amplitude-preserving Kirchhoff post-stack time migration. Processing of profiles p400-p500: Data were sampled at 0.5 ms and sorted into common midpoint (CMP) domain with a bin spacing of 5 m. Normal move out correction was carried out with a velocity of 1500 m s-1 and an Ormsby bandpass filter with corner frequencies at 40, 80, 600 and 1000 Hz was applied. The data were time migrated using the water velocity.
    Keywords: Comment; Date/Time of event; Date/Time of event 2; Event label; File name; File size; Latitude of event; Latitude of event 2; Longitude of event; Longitude of event 2; Maria S. Merian; MSM21/4; MSM21/4_548-1; MSM21/4_562-1; MSM21/4_608-1; MSM21/4_619-1; MSM21/4_646-1; MSM21/4_651-1; North Greenland Sea; Seismic profile P100-P102; Seismic profile P200-P208; Seismic profile P400, P500; Seismic profile P600; Seismic profile P700-P706; Seismic profile P800-P805; Seismic reflection profile; SEISREFL; Uniform resource locator/link to sgy data file
    Type: Dataset
    Format: text/tab-separated-values, 32 data points
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  • 4
    Publication Date: 2016-02-02
    Description: A bottom-simulating reflector (BSR) occurs west of Svalbard in water depths exceeding 600 m, indicating that gas hydrate occurrence in marine sediments is more widespread in this region than anywhere else on the eastern North Atlantic margin. Regional BSR mapping shows the presence of hydrate and free gas in several areas, with the largest area located north of the Knipovich Ridge, a slow-spreading ridge segment of the Mid Atlantic Ridge system. Here, heat flow is high (up to 330 mW m-2), increasing towards the ridge axis. The coinciding maxima in across-margin BSR width and heat flow suggest that the Knipovich Ridge influenced methane generation in this area. This is supported by recent finds of thermogenic methane at cold seeps north of the ridge termination. To evaluate the source rock potential on the western Svalbard margin, we applied 1D petroleum system modeling at three sites. The modeling shows that temperature and burial conditions near the ridge were sufficient to produce hydrocarbons. The bulk petroleum mass produced since the Eocene is at least 5 kt and could be as high as ~0.2 Mt. Most likely, source rocks are Miocene organic-rich sediments and a potential Eocene source rock that may exist in the area if early rifting created sufficiently deep depocenters. Thermogenic methane production could thus explain the more widespread presence of gas hydrates north of the Knipovich Ridge. The presence of microbial methane on the upper continental slope and shelf indicates that the origin of methane on the Svalbard margin varies spatially.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 5
    Publication Date: 2010-08-16
    Description: This study is aimed at understanding past 444 ka record of climate variability in the equatorial Indian Ocean using high resolution records of planktic and benthic foraminifera and pteropods from Ocean Drilling Program Hole 716A, Maldives Ridge, southeastern Arabian Sea. In total, 892 samples of 10 cm3 volume from 444 ka old sequence were analysed at 1 cm intervals to generate census data of the foraminiferal fauna and pteropods. The percent and detrended time series of mixed-layer species Globigerinoides ruber and Globigerinoides sacculifer and thermocline species Neogloboquadrina dutertrei, benthic foraminifera Cymbaloporetta squammosa, Sphaeroidina bulloides and Uvigerina proboscidea, and pteropods from ODP Hole 716A reveal significant changes in wind intensity during the past 444 ka. An abrupt decrease in the Cymbaloporetta squammosa population at c. 300 ka (across MIS 8/9) suggests a weakening of equatorial wind intensity, which could be linked to Indian monsoon and may have driven pronounced changes in the oxygen minimum zone in the Maldivian region. These changes were contemporaneous with the Mid-Brunhes Climatic Event, the beginning of aridity in the Indonesian-Australian region and the onset of a humid phase in equatorial East Africa as observed in several oceanic and continental records. This strengthens a connection between equatorial Indian Ocean wind intensity, the Indian monsoon and Indonesian-Australian-African climates. Supplementary materialPercentages of benthic and planktic foraminifera and pteropods used in the present study are available at http://www.geolsoc.org.uk/SUP18413
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  • 6
    Publication Date: 2015-09-04
    Print ISSN: 1550-7998
    Electronic ISSN: 1550-2368
    Topics: Physics
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  • 7
    Publication Date: 2013-08-08
    Print ISSN: 1550-7998
    Electronic ISSN: 1550-2368
    Topics: Physics
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  • 8
    Publication Date: 2012-07-03
    Print ISSN: 1550-7998
    Electronic ISSN: 1550-2368
    Topics: Physics
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  • 9
    Publication Date: 2019-05-31
    Print ISSN: 2470-0010
    Electronic ISSN: 2470-0029
    Topics: Physics
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  • 10
    Publication Date: 2016-05-24
    Print ISSN: 2470-0010
    Electronic ISSN: 2470-0029
    Topics: Physics
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