Expedition 354 summary

France‐Lanord, Christian; Spieß, V.; Klaus, A.; Adhikari, R.R.; Adhikari, S.K.; Bahk, Jang-Jun; Baxter, A.T.; Cruz, J.W.; Das, S.K.; Dekens, P. S.; Duleba, Wânia; Fox, L.R.; Galy, Αlbert; Ge, Jun; Gleason, James D.; Gyawali, B.R.; Huyghe, Pascale; Jia, Guodong; Lantzsch, Hendrik; Manoj, M.C.; Martin, Y. Martos; Meynadier, L.; Najman, Yani; Nakajima, A.; Ponton, C.; Reilly, Brendan; Rogers, K.G.; Savian, J.F.; Schwenk, T.; Selkin, P.A.; Weber, Michael E; Williams, T.; Yoshida, Kohki

doi:10.14379/iodp/proc.354.101.2016

Cited by 9 publications

(14 citation statements)

References 92 publications

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“…Rapid erosion and transport continuing for several tens of million years ended up in the colossal accumulation of 12.5 × 10 6 km 3 of orogen-derived sediments in the Bengal Fan [44]. In the long term, only~10% of Himalayan detritus remained stored in the Ganga foreland basin [45] without reaching the sea.…”

Section: The Bengal Sediment Systemmentioning

confidence: 99%

Provenance of Bengal Shelf Sediments: 1. Mineralogy and Geochemistry of Silt

et al. 2019

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This article illustrates a multi-technique frontier approach for the provenance study of silt-size sediments. The mineralogical composition of low-density and heavy-mineral fractions of four samples of fine to very coarse silt deposited on the Bengal shelf was analyzed separately for six different grain-size classes by combining grain counting under an optical microscope, Raman spectroscopy, and X-ray diffraction. The geochemical composition was determined on both bulk-sediment samples and on their <5-μm classes. Such a “multiple-window” approach allowed capturing the full mineralogical information contained in each sample, as well as the size-dependent intra-sample variability of all compositional parameters. The comparison between grain-size distributions obtained by different methods highlighted a notable fallacy of laser granulometry, which markedly overestimated the size of the finest mode represented by fine silt and clay. As a test case, we chose to investigate sediments of the Bengal shelf, where detritus is fed from the Meghna estuary, formed by the joint Ganga and Brahmaputra Rivers and representing the largest single entry point of sediment in the world’s oceans. The studied samples show the typical fingerprint of orogenic detritus produced by focused erosion of collision orogens. Bengal shelf silt is characterized by a feldspatho-quartzose (F-Q) composition with a Q/F ratio decreasing from 3.0 to 1.7 with increasing grain size, plagioclase prevailing over K-feldspar, and rich transparent-heavy-mineral assemblages including mainly amphibole with epidote, and minor garnet and pyroxene. Such a detrital signature compares very closely with Brahmaputra suspended load, but mineralogical and geochemical parameters, including the anomalous decrease of the Q/F ratio with increasing grain size, consistently indicate more significant Ganga contribution for cohesive fine silt. The accurate quantitative characterization of different size fractions of Bengal shelf sediments represents an essential step to allow comparison of compositional signatures characterizing different segments of this huge source-to-sink system, from fluvial and deltaic sediments of the Himalayan foreland basin and Bengal shelf to the Bengal Fan.

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Section: The Bengal Sediment Systemmentioning

confidence: 99%

Provenance of Bengal Shelf Sediments: 1. Mineralogy and Geochemistry of Silt

et al. 2019

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“…The hemipelagic units proved useful for shipboard stratigraphy because they often contained abundant biomarkers, magnetic reversals, and tephra layers, and these hemipelagic sediments could often be identified as continuous reflectors in the seismic lines. One hemipelagic unit, deposited at ~1-2 cm/ky in the middle Pleistocene and recording the Matuyama/Brunhes boundary, Jaramillo Subchron, and/or Cobb Mountain Subchron, was observed at all sites across the transect, providing a framework for correlation between corederived chronologies and seismic imaging for the last 1.25 My (see the Expedition 354 summary chapter [France-Lanord et al, 2016b]). The physical properties of these middle and late Pleistocene calcareous sediments, particularly magnetic susceptibility and sediment lightness (L*), could be correlated between all seven sites where magnetostratigraphy or tephra layers provide initial tie…”

Section: Introductionmentioning

confidence: 94%

“…International Ocean Discovery Program (IODP) Expedition 354 cored seven sites along a ~320 km transect of the Bengal Fan at 8°N to investigate fan development and depocenter migration ( Figure F1) (see the Expedition 354 summary chapter [France-Lanord et al, 2016b]). Because any one site includes local variations in depositional processes, the transect approach and accurate stratigraphic correlation of sites are essential for understanding sediment fluxes and the climate and tectonic history of the region.…”

Section: Introductionmentioning

confidence: 99%

“…Pliocene and Pleistocene sediments recovered during Expedition 354 can broadly be categorized as high-accumulation rate sands and turbidites deposited by downslope processes and lower accumulation rate hemipelagic calcareous clays deposited when fan processes move the depocenter away from the site (see the Expedition 354 summary chapter [France-Lanord et al, 2016b]). The hemipelagic units proved useful for shipboard stratigraphy because they often contained abundant biomarkers, magnetic reversals, and tephra layers, and these hemipelagic sediments could often be identified as continuous reflectors in the seismic lines.…”

Section: Introductionmentioning

confidence: 99%

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Data report: paleomagnetic directions from IODP Expedition 354, Hole U1451A, Cores 23H and 24H

Reilly¹,

Stoner²,

Selkin³

et al. 2018

Proceedings of the International Ocean Discovery Program

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“…Site U1453 (see Figures F3, F4, and F8 in the Expedition 354 summary chapter [France-Lanord et al, 2016d]) is located along the seven-site transect of ~200 m penetration drilled during Expedition 354 to study the evolution of the Middle Bengal Fan at 8°N. In combination, these sites will provide a complete inventory of Pleistocene fan architecture and evolution in the 300 km long central segment of the Bengal Fan.…”

Section: Background and Objectivesmentioning

confidence: 99%

Site U1453

France‐Lanord¹,

Spieß²,

Klauss³

et al. 2016

Proceedings of the International Ocean Discovery Program

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Contents 1 Site summary 3 Background and objectives 4 Operations 6 Lithostratigraphy 10 Biostratigraphy 11 Paleomagnetism 14 Geochemistry and microbiology 17 Physical properties 21 Downhole measurements 26 Stratigraphic synthesis 30 References Site summarySite U1453 (proposed Site MBF-4A) is in the center of our seven-site transect of shallow-penetration holes. It is located at 8°0.42′N, 86°47.90′E in a water depth of 3690.5 m. Combined with the other transect sites, Site U1453 will document depocenter migration and quantify overall sediment delivery to 8°N since the Pleistocene.Site U1453 is located ~1 km south and ~5 km east of a prominent surficial channel. The channel exhibits pronounced meandering point bars and internal terraces. Sediment transported by this channel has therefore significantly influenced deposition at this site during the channel's lifetime. A prominent buried point bar is located <1 km west of the site. The overall seismic reflectivity at the drill site is relatively high, indicating coarse material throughout most of the drilled section, except for the lower portion of the drill hole. Distinct and variable local spillover deposits were expected at the site in response to the channel and meander evolution. Toward the base of the hole, lower seismic reflectivity and distinct layering is inferred to reflect hemipelagic or distal levee deposition.In addition to coring, downhole logging was introduced as an important objective of Site U1453 after attempts to log at Sites U1450 and U1451 were unsuccessful. Logging data are essential for determining the inventory of lithofacies and structures in the fan given the limitations in completely recovering unconsolidated coarse material and the importance of measuring in situ physical properties and imaging fine-scale sedimentary structures. Therefore, we decided to log Hole U1453A despite its shallow ~215 m penetration to increase chances that we could acquire this critical in situ log data. This was particularly important for characterizing the in situ properties of thick sandy intervals that half-length advanced piston corer (HLAPC) cores returned as loose and liquefied sand. Principal resultsSite U1453 contributes to the overall seven-site transect drilled during Expedition 354. When integrated with the seismic profile and refined chronostratigraphic data from the remaining part of the transect, this site will document fan construction processes and the depocenter migration time frame. Specifically, Site U1453 provides an almost completely recovered succession of silt-and/or sanddominated sheeted units related to the formation and evolution of a large meandering channel system lacking a distinct levee unit. Intercalation of these sheets with thinner levee units either from the large channel or from nearby smaller channels may help us understand why the channel has been apparently maintained in this position for a relatively long time period. This type of configuration is part of the different processes that influence interlevee deposition. A few th...

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Expedition 354 summary

Cited by 9 publications

References 92 publications

Provenance of Bengal Shelf Sediments: 1. Mineralogy and Geochemistry of Silt

Provenance of Bengal Shelf Sediments: 1. Mineralogy and Geochemistry of Silt

Data report: paleomagnetic directions from IODP Expedition 354, Hole U1451A, Cores 23H and 24H

Site U1453

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