A revised chronostratigraphic framework for International Ocean Discovery Program Expedition 355 sites in Laxmi Basin, eastern Arabian Sea

AbstractInternational 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.

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Palaeoredox reconstruction in the eastern Arabian Sea since the late Miocene: Insights from trace element and stable isotopes of molybdenum (δ98/95Mo) and tungsten (δ186/184W) at IODP Site U1457 of Laxmi Basin

Palaeogeography Palaeoclimatology Palaeoecology ◽

10.1016/j.palaeo.2021.110790 ◽

2021 ◽

pp. 110790

Author(s):

M. Alam ◽

M. Tripti ◽

G.P. Gurumurthy ◽

Y. Sohrin ◽

M. Tsujisaka ◽

...

Keyword(s):

Stable Isotopes ◽

Trace Element ◽

Late Miocene ◽

Arabian Sea ◽

Eastern Arabian Sea ◽

And Tungsten

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Inconsistent change in surface hydrography of the eastern Arabian Sea during the last four glacial–interglacial intervals

Geological Magazine ◽

10.1017/s0016756819001122 ◽

2019 ◽

Vol 157 (6) ◽

pp. 989-1000 ◽

Cited By ~ 1

Author(s):

Rajeev Saraswat ◽

S. R. Kurtarkar ◽

R. Yadav ◽

A. Mackensen ◽

D. P. Singh ◽

...

Keyword(s):

Arabian Sea ◽

Isotopic Ratio ◽

Planktonic Foraminifera ◽

Foraminiferal Assemblage ◽

Upwelled Water ◽

Winter Convection ◽

Eastern Arabian Sea ◽

Neogloboquadrina Dutertrei ◽

Stable Isotopic Ratio ◽

International Ocean Discovery Program

AbstractThe 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 (δ18O) 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 δ18Osw-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 δ18Osw-ivc during Termination 4 suggests a lesser change in the monsoon.

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Variations in δ13C values of sedimentary organic matter since late Miocene time in the Indus Fan (IODP Site 1457) of the eastern Arabian Sea

Geological Magazine ◽

10.1017/s0016756818000870 ◽

2019 ◽

Vol 157 (6) ◽

pp. 1012-1021 ◽

Cited By ~ 2

Author(s):

Boo-Keun Khim ◽

Jongmin Lee ◽

Sanbeom Ha ◽

Jingu Park ◽

Dhananjai K. Pandey ◽

...

Keyword(s):

Organic Matter ◽

Late Miocene ◽

Arabian Sea ◽

Sedimentary Organic Matter ◽

Marine Phytoplankton ◽

Land Plants ◽

Terrestrial Organic Matter ◽

Underlying Assumption ◽

Catchment Areas ◽

Eastern Arabian Sea

AbstractA 1108.6 m long core was recovered at Site U1457 located on the Indus Fan in the Laxmi Basin of the eastern Arabian Sea during IODP Expedition 355. Shipboard examinations defined five lithologic units (I to V) of the lower Paleocene to Holocene sedimentary sequence. In this study, δ13C values of sedimentary organic matter (SOM) confirm the differentiation of the lithologic units and further divide units III and IV into two subunits (1 and 2). Based on the underlying assumption that the SOM is decided primarily by a mixture of marine and terrestrial origins, δ13CSOM values at Site U1457 provide information on the terrestrial catchment conditions since late Miocene time. Low δ13CSOM values from late Miocene to late Pleistocene times are similar (c. −22.0 ‰) for the most part, reflecting a consistent contribution of terrestrial organic matter from the catchment areas characterized by dominant C3 land plants. Significantly lower δ13CSOM values (c. −24.0 ‰) in Unit III-2 (∼8 to ∼7 Ma) might be due to a greater input of C3 terrestrial organic matter. The increase in δ13CSOM values at ∼7 Ma and the appearance of high δ13CSOM values (c. −18.0 ‰) within Unit III-1 (∼7 to ∼2 Ma) indicate that C4 biomass overwhelmed the terrestrial catchment environment as a result of enhanced terrestrial aridity in the Himalayan foreland. The three-end-member simple mixing model, estimating the relative contributions of SOM from terrestrial C3 and C4 plants and marine phytoplankton, supports our interpretation of the distribution of C3 and C4 land plants in the terrestrial catchment environment.

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70 kyr record of denitrification and oxygenation changes in the eastern Arabian Sea

GEOCHEMICAL JOURNAL ◽

10.2343/geochemj.2.0472 ◽

2017 ◽

Vol 51 (4) ◽

pp. 329-336

Author(s):

Shital P. Godad ◽

Sushant S. Naik ◽

P. Divakar Naidu

Keyword(s):

Arabian Sea ◽

Eastern Arabian Sea

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Short term response of plankton community to nutrient enrichment in central eastern Arabian Sea: Elucidation through mesocosm experiments

Journal of Environmental Management ◽

10.1016/j.jenvman.2021.112390 ◽

2021 ◽

Vol 288 ◽

pp. 112390

Author(s):

A.C. Anil ◽

D.V. Desai ◽

L. Khandeparker ◽

V. Krishnamurthy ◽

K. Mapari ◽

...

Keyword(s):

Nutrient Enrichment ◽

Arabian Sea ◽

Plankton Community ◽

Short Term ◽

Eastern Arabian Sea ◽

Mesocosm Experiments ◽

Central Eastern ◽

Term Response

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Nutrient retention behind a tropical mega-dam: a case study of the Sardar Sarovar Dam, India

SN Applied Sciences ◽

10.1007/s42452-020-04118-7 ◽

2021 ◽

Vol 3 (1) ◽

Author(s):

Harish Gupta ◽

S. Kiran Kumar Reddy ◽

Mounika Chiluka ◽

Vamshikrishna Gandla

Keyword(s):

Arabian Sea ◽

Inorganic Nitrogen ◽

Nutrient Retention ◽

Significant Loss ◽

N Removal ◽

Narmada River ◽

Sardar Sarovar ◽

The Impact

AbstractIn this study, we demonstrate the impact of the construction of a mega-dam on the nutrient export regime of a large tropical river into the Arabian Sea. Long-term (11 years) fortnight nutrient parameters, upstream and downstream to Sardar Sarovar (SS) Dam, were examined to determine the periodical change in nutrient fluxes from the Narmada River, India. During this 11-year period, the average discharge of the Narmada River upstream to Rajghat (35.3 km3 year−1) was higher than that of downstream at Garudeshwar (33.9 km3 year−1). However, during the same period, the suspended sediment load was reduced by 21 million tons (MT) from 37.9 MT at Rajghat to 16.7 MT at Garudeshwar. Similarly, mean concentrations of dissolved silica (DSi) reduced from 470 (upstream) to 214 µM (downstream), dissolved inorganic phosphate (DIP) from 0.84 to 0.38 µM, and dissolved inorganic nitrogen (DIN) from 43 to 1.5 µM. It means that about 54%, 55%, and 96% flux of DSi, DIP, and DIN retained behind the dam, respectively. The estimated denitrification rate (80,000 kg N km−2 year−1) for the reservoir is significantly higher than N removal by lentic systems, globally. We hypothesize that processes such as biological uptake and denitrification under anoxic conditions could be a key reason for the significant loss of nutrients, particularly of DIN. Finally, we anticipated that a decline in DIN fluxes (by 1.13 × 109 mol year−1) from the Narmada River to the Arabian Sea might reduce the atmospheric CO2 fixation by 7.46 × 109 mol year−1.

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