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Sedimentology, stratigraphy and architecture of the Nicobar Fan (Bengal-Nicobar Fan System), Indian Ocean: Results from International Ocean Discovery Program Expedition 362
Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
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Antal upphovsmän: 122020 (Engelska)Ingår i: Sedimentology, ISSN 0037-0746, E-ISSN 1365-3091, Vol. 67, nr 5, s. 2248-2281Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Drill sites in the southern Bay of Bengal at 3 degrees N 91 degrees E (International Ocean Discovery Program Expedition 362) have sampled for the first time a complete section of the Nicobar Fan and below to the oceanic crust. This generally overlooked part of the Bengal-Nicobar Fan System may provide new insights into uplift and denudation rates of the Himalayas and Tibetan Plateau. The Nicobar Fan comprises sediment gravity-flow deposits, mostly turbidites, that alternate with hemipelagite drapes and pelagite intervals of varying thicknesses. The decimetre-thick to metre-thick oldest pre-fan sediments (limestones/chalks) dated at 69 Ma are overlain by volcanic material and slowly accumulated pelagites (0.5 g cm(-2) kyr(-1)). At Expedition 362 Site U1480, terrigenous input began in the early Miocene at ca 22.5 Ma as muds, overlain by very thin-bedded and thin-bedded muddy turbidites at ca 19.5 Ma. From 9.5 Ma, sand content and sediment supply sharply increase (from 1-5 to 10-50 g cm(-2) kyr(-1)). Despite the abundant normal faulting in the Nicobar Fan compared with the Bengal Fan, it offers a better-preserved and more homogeneous sedimentary record with fewer unconformities. The persistent connection between the two fans ceased at 0.28 Ma when the Nicobar Fan became inactive. The Nicobar Fan is a major sink for Himalaya-derived material. This study presents integrated results of International Ocean Discovery Program Expedition 362 with older Deep Sea Drilling Project/Ocean Drilling Program/International Ocean Discovery Program sites that show that the Bengal-Nicobar Fan System experienced successive large-scale avulsion processes that switched sediment supply between the Bengal Fan (middle Miocene and late Pleistocene) and the Nicobar Fan (late Miocene to early Pleistocene). A quantitative analysis of the submarine channels of the Nicobar Fan is also presented, including their stratigraphic frequency, showing that channel size/area and abundance peaked at ca 2 to 3 Ma, but with a distinct low at 3 to 7 Ma: the intervening stratigraphic unit was a time of reduced sediment accumulation rates.

Ort, förlag, år, upplaga, sidor
2020. Vol. 67, nr 5, s. 2248-2281
Nyckelord [en]
Bengal Fan, Indian Ocean, IODP Expedition 362, Nicobar Fan, sediment gravity flow, submarine fan, Sunda Subduction Zone
Nationell ämneskategori
Geovetenskap och relaterad miljövetenskap
Identifikatorer
URN: urn:nbn:se:su:diva-180386DOI: 10.1111/sed.12701ISI: 000515102100001OAI: oai:DiVA.org:su-180386DiVA, id: diva2:1421013
Tillgänglig från: 2020-04-01 Skapad: 2020-04-01 Senast uppdaterad: 2025-02-07Bibliografiskt granskad

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Backman, JanHenstock, Timothy J.Stevens, Duncan E.

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