Clay minerals and Sr–Nd isotopes of the sediments along the western margin of India and their implication for sediment provenance

Kessarkar, Pratima M.; Rao, V. Purnachandra; Ahmad, Shoeb; Babu, G. Anil

doi:10.1016/s0025-3227(03)00240-8

Cited by 94 publications

(108 citation statements)

References 46 publications

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“…Consistent with previous studies (e.g. Ramaswamy and Nair, 1989;Rao and Rao, 1995;Kessarkar et al, 2013), there is a narrow nearshore belt of muds (< 25 µm median, > 85 %(Silt+Clay)) at depths shallower than ∼ 50 m, and a belt of coarser sediments extending to ∼ 200-300 m (depending on transect). On the slope, sediments below ∼ 400 m are generally finer (< 61 µm median), with an apparent gradual (slight) decrease with depth, and reaching 9-14 µm median at ∼ 2000 m (Fig.…”

Section: Controls On Om Distributionsupporting

confidence: 91%

Comparative organic geochemistry of Indian margin (Arabian Sea) sediments: estuary to continental slope

et al. 2014

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Abstract. Surface sediments from sites across the Indian margin of the Arabian Sea were analysed for their elemental and stable isotopic organic carbon (C org ) and total nitrogen compositions, grain size distributions and biochemical indices of organic matter (OM) source and/or degradation state. Site locations ranged from the estuaries of the Mandovi and Zuari rivers to depths of ∼ 2000 m on the continental slope, thus spanning nearshore muds and sands on the shelf and both the oxygen minimum zone (OMZ) on the upper slope (∼ 200-1300 m) and the seasonal hypoxic zone that appears on the shelf. Source indices showed mixed marine and terrigenous OM within the estuaries, but consistent predominance (80-100 %) of marine OM on the shelf and slope. Thus, riverine terrigenous OM is diluted or replaced by autochthonous marine OM and/or is efficiently re-mineralised, within or immediately offshore of the estuaries. Organic C contents of surface shelf sediments varied from < 0.5 wt % in relict shelf sands to up to ∼ 4 wt % for nearshore muds, while upper slope sites within the OMZ showed a wide range (∼ 2 to 7 + wt %), progressively decreasing below the OMZ to ≤ 1 wt % at 2000 m. Thus, major variability (∼ 5 wt %) was found at slope sites within the OMZ of similar depth and near-identical bottom-water O 2 concentrations. A strong relationship between %C org and sediment grain size was seen for sediments within the OMZ, but lower relative C org contents were found for sites on the shelf and below the OMZ. Further, C org loadings, when related to estimated sediment surface area, indicated distinct enrichment of C org in the OMZ sediments relative to sites above and below the OMZ and to sediments from normoxic margins. Diagenetic indices confirmed that lower C org content below the OMZ is associated with more extensive OM degradation, but that shelf sediment OM is not consistently more degraded than that found within the OMZ. Together, the results indicate that OM distribution across the margin is controlled by interplay between hydrodynamic processes and varying preservation associated with O 2 availability. This inference is supported by multiple regression analysis. Hydrodynamic processes (expressed as %Silt) followed by O 2 availability, can explain the large majority of %C org variability when the shelf and slope are considered as a whole. However, while O 2 becomes the primary influence on %C org for sediments below the OMZ, %Silt is the primary influence across the OMZ and, apparently, the shelf. Thus, reduced O 2 exposure is responsible for OM enrichment within the OMZ, but hydrodynamic processes are the overriding control on sediment OM distributions across both the shelf and the OMZ.

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Section: Controls On Om Distributionsupporting

confidence: 91%

Comparative organic geochemistry of Indian margin (Arabian Sea) sediments: estuary to continental slope

et al. 2014

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“…These ratios are within the range of isotopic compositions of slope sediments of west coast of India [Kessarkar et al, 2003]. [18] In SS-3101G, from the near equatorial region (Figures 1 and 2 (Figures 5a and 5b).…”

Section: Arabian Sea Sedimentssupporting

confidence: 60%

“…Based on clay mineralogical study, Kessarkar et al [2003] suggest that the penetration of Indus sediments is restricted to the north of Saurashtra (∼20°N), whereas Ramaswamy and Nair [1989] suggest that longshore current helps Indus sediments to be transported to the south of Mangalore. [22] In addition to riverine particulates, another source of sediments to the Arabian Sea is aeolian dust from the deserts of Arabia [Kolla et al, 1976;Sirocko and Sarnthein, 1989].…”

Section: Discussionmentioning

confidence: 99%

Temporal variations in ⁸⁷Sr/⁸⁶Sr and ɛ_Nd in sediments of the southeastern Arabian Sea: Impact of monsoon and surface water circulation

Goswami

Singh

Bhushan

et al. 2012

Geochem Geophys Geosyst

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Sr and Nd isotopic composition of silicate fractions of sediments have been measured in two well dated gravity cores from the eastern Arabian Sea archiving a depositional history of ∼29 and ∼40 ka. The 87Sr/86Sr and ɛNd in the northern core (SS‐3104G; 12.8°N, 71.7°E) ranges from 0.71416 to 0.71840 and −8.8 to −12.8; these variations are limited compared to those in the southeastern core (SS‐3101G; 6.0°N, 74.0°E), in which they vary from 0.71412 to 0.72069 and −9.0 to −15.2 respectively. This suggests that the variation in the relative proportions of sediments supplied from different sources to the core SS‐3104G are limited compared to core SS‐3101G. The 87Sr/86Sr and ɛNd profiles of SS‐3101G exhibit two major excursions, ca. 9 ka and 20 ka, coinciding with periods of Holocene Intensified Monsoon Phase (IMP) and the Last Glacial Maximum (LGM) respectively with more radiogenic 87Sr/86Sr and lower ɛNd during these periods. These excursions have been explained in terms of changes in the erosion patterns in the source regions and surface circulation of the Northern Indian Ocean resulting from monsoon intensity variations. The intensification of North‐East (NE) monsoon and associated strengthening of the East Indian Coastal Current in southwest direction during LGM transported sediments with higher 87Sr/86Sr and lower ɛNd from the western Bay of Bengal to the Arabian Sea. In contrast, enhanced South‐West (SW) monsoon at ∼9 ka facilitated the transport of sediments from the northern Arabian Sea, particularly Indus derived, to the southeastern Arabian Sea. This study thus highlights the impact of monsoon variability on erosion patterns and ocean surface currents on the dispersal of sediments in determining the Sr and Nd isotopic composition of sediments deposited in the eastern Arabian Sea during the last ∼40 ka.

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“…They also could be the particles derived directly from the Indus River, which discharges 100 Mt of sediments annually , and the resuspended sediments that were exported from the wide (up to -500 km) continental shelf and slope of the eastern Arabian Sea. These sediments are composed of organic matter deposited from the overlying water column and detrital materials from the Indus River and the hinterland (Kessarkar et al, 2003;Nath et al, 1997 layer in the Arabian Sea, which is the result of intense respiration and dissolution occurring in the benthic sediments of the continental shelf and slope (Broecker et al, 1980). The Fe and Mn oxidation-reduction cycling involved in these benthic processes has been suggested to produce a sink for particle-reactive elements (boundary scavenging) (Spencer et al, 1981 (Scharer, 1984;Scharer et al, 1986).…”

Section: Pb Isotopes In the Southernmentioning

confidence: 99%

Evolution of anthropogenic Pb and Pb isotopes in the deep North Atlantic Ocean and the Indian Ocean

Lee¹

2013

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, in partial fulfillment of the Requirement for the degree of Doctor of PhilosophyPb and Pb isotopes in the ocean have varied on decadal to centennial time scales due to anthropogenic Pb inputs. Thus, tracing the temporal variation of Pb and Pb isotopes in the ocean provides information on the major sources of Pb and the transport of Pb from sources to the ocean surface and into the ocean interior. In this thesis study, first, a method was developed for the analysis of dissolved Pb and other trace elements in seawater using single batch nitrilotriacetate resin extraction and isotope dilution ICP-MS, which was applied in analyzing seawater Pb concentrations in the rest of the study. A -550 year history of the Pb and Pb isotopes in the deep North Atlantic Ocean is reconstructed using a deep-sea coral, showing the infiltration of anthropogenic Pb to deep sea. Comparing the results to the surface North Atlantic Ocean Pb record using a Transit Time Distribution model, the mean transit time of Pb is estimated to be -64 years. This is longer than the transit time estimate assuming simple advection from a source, showing the importance of advective-diffusive mixing in the transport of Pb to the ocean interior. The later part of the thesis investigates Pb in the Indian Ocean, where no useful Pb data have been previously reported. First, using annually-banded surface growing corals, I reconstruct variations of Pb and isotopes in the surface waters of the central and eastern Indian Oceans during the past half-century. Results of the study show the increase of Pb concentrations from the mid-1970s, and major sources of the Pb are discussed, including leaded gasoline and coal burning, based on their emission histories and Pb isotope signatures. Second, Pb concentration and isotope profiles are presented from the northern and western Indian Oceans. AcknowledgementI would like to thank all the people who made this work possible. First, I owe a big thank to my advisor Ed Boyle. He taught me a lot about trace metal techniques, guided me to find right and important scientific questions whenever I was lost, and supported all my work. Not only that, he was also supportive of me having a family, very understanding and patient, which I cannot be grateful enough.I'd like to thank my committee: Bill Jenkins, Carl Lamborg, Phoebe Lam, and Konrad Hughen. Interests they showed during committee meetings were so inspiring and encouraging. I usually had this magical experience that my work, which looked so boring beforehand, turns into the most interesting one in the world after the committee meeting.I also would like to thank Jess Adkins and Selene Eltgroth, who provided the deep-sea coral and the radiocarbon data used in Chapter 3, and shared their expertise in deep-sea coral analysis with me. My work in Chapter 4 and 5 could not be completed without these people who helped me to collect corals and seawater samples from the Indian Ocean: Miriam Pfeiffer, Aron Meltzner, Kerry Sieh, Bambang Suwargadi, Danny Natawidjaja, Toshitaka Gamo, Hajim...

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Clay minerals and Sr–Nd isotopes of the sediments along the western margin of India and their implication for sediment provenance

Cited by 94 publications

References 46 publications

Comparative organic geochemistry of Indian margin (Arabian Sea) sediments: estuary to continental slope

Comparative organic geochemistry of Indian margin (Arabian Sea) sediments: estuary to continental slope

Temporal variations in ⁸⁷Sr/⁸⁶Sr and ɛ_Nd in sediments of the southeastern Arabian Sea: Impact of monsoon and surface water circulation

Evolution of anthropogenic Pb and Pb isotopes in the deep North Atlantic Ocean and the Indian Ocean

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Clay minerals and Sr–Nd isotopes of the sediments along the western margin of India and their implication for sediment provenance

Cited by 94 publications

References 46 publications

Comparative organic geochemistry of Indian margin (Arabian Sea) sediments: estuary to continental slope

Comparative organic geochemistry of Indian margin (Arabian Sea) sediments: estuary to continental slope

Temporal variations in 87Sr/86Sr and ɛNd in sediments of the southeastern Arabian Sea: Impact of monsoon and surface water circulation

Evolution of anthropogenic Pb and Pb isotopes in the deep North Atlantic Ocean and the Indian Ocean

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Temporal variations in ⁸⁷Sr/⁸⁶Sr and ɛ_Nd in sediments of the southeastern Arabian Sea: Impact of monsoon and surface water circulation