Hemipelagic and turbiditic deposits constrain lower Bengal Fan depositional history through Pleistocene climate, monsoon, and sea level transitions

Weber, Michael E; Reilly, Brendan

doi:10.1016/j.quascirev.2018.09.027

Cited by 39 publications

(39 citation statements)

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“…The thickening of the MPHL toward the center of the study area is linked to the intercalation of thin turbidites (Figures and ; France‐Lanord et al, ). This mixed hemipelagic/turbiditic unit has also been discussed by Weber and Reilly (; their Unit 2b) and marks the transition from the dominance of hemipelagic sedimentation to a turbidite‐dominated regime. The onlapping reflectors overlying the MPHL imply that the turbiditic sedimentation first reappeared proximal to Site U1452 and from there spread gradually west and eastwards, underlining the asynchronous character of the upper boundary of the MPHL.…”

Section: Discussionsupporting

confidence: 63%

“…Curray et al () discuss that their Subfan C is restricted to the eastern part of the Bengal Fan and does not reach DSDP Site 218. However, we do observe fan deposition at 8°N directly prior to the deposition of Subfan D. We are confident that this older subfan observed at 8°N and Subfan C are the same but propose an earlier onset of Subfan C (~0.68 Ma, Weber & Reilly, ) than Curray et al () did (0.465 Ma; Figure ). The MPHL is the third oldest depositional unit identified in our data and represents a time during which no fan sediments reached the study area.…”

Section: Discussionsupporting

confidence: 55%

“…The naming of subfans in this study after Curray et al (). Dating of subfans based on Weber et al () and Weber and Reilly (). LPHL = Late Pleistocene Hemipelagic Layer; MPHL = Middle Pleistocene Hemipelagic Layer.…”

Section: Discussionmentioning

confidence: 99%

“…One stratigraphic marker within the LPHL is the Youngest Toba Tephra (~0.075 Ma, Gasparotto et al, ) which has been recovered at the six eastern Exp 354 sites. The LPHL comprises an average sedimentation rate of ~2.3 cm/kyr, and its onset has been dated to ~0.25 Ma (Weber et al, ; Weber & Reilly, ). The stratigraphy of the drilling transect is further constrained by the first occurrence (FO) of Emiliania huxleyi (~0.29 Ma; age after Gradstein et al, ) identified in all seven drill sites between the LPHL and the MPHL (Figure ).…”

Section: Introductionmentioning

confidence: 99%

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Middle to Late Pleistocene Architecture and Stratigraphy of the Lower Bengal Fan—Integrating Multichannel Seismic Data and IODP Expedition 354 Results

Bergmann

Schwenk

Spieß

et al. 2020

Geochem Geophys Geosyst

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Utilizing a novel data set of integrated high-resolution multichannel seismic data with IODP Expedition 354 drilling results, a Middle to Late Pleistocene stratigraphy for the lower Bengal Fan is developed. The study reveals a high lateral and temporal variability of deposition expressed by lateral shifts (often exceeding 100 km) between successive channel-levee systems (CLSs), which occurred on average every~15 kyr independent from sea-level changes. The CLSs are embedded in sheeted sediments deposited out of unchannelized turbidity currents, which represent almost two thirds of the lower Bengal Fan sediments. On 100-kyr timescales, CLSs and sheeted/unchannelized sediments build up subfans, which alternately occupied the western and the eastern Bengal Fan, while the remaining area was draped by~10 to 20 m-thick layers of background/hemipelagic sediments. Three subfans have been reconstructed: Subfan B (1.24-0.68 Ma) formed concurrently with the Middle Pleistocene Hemipelagic Layer, Subfan C (0.68-0.25 Ma) covered the entire study area, and Subfan D (0.25 Ma to recent) deposited concomitant with the Late Pleistocene Hemipelagic Layer. The continuous succession of subfans indicates an uninterrupted fan activity independent from sea-level cycles at least since the Middle Pleistocene. This remarkable independent behavior in terms of sediment supply has not been observed at the Amazon Fan but is in agreement with observations from the Congo Fan. Finally, the analysis of a complete cross section through the lower Bengal Fan reveals that almost half of the sediment represents sands, indicating that the lower Bengal Fan may not generally be classified as "mud rich" (≤30% sand). Plain Language SummaryThe northern Indian Ocean receives large amounts of material eroded by wind and rain onshore. Most of the sediment comes from the Himalayan mountain range and contains important information about the evolution of the Himalaya as well as the past Asian climate. After erosion, it is transported by large rivers, such as the Ganges and Brahmaputra, to the coast. Underwater, the sediment moves even farther southwards within river-like features, the so-called channel-levee systems. Eventually, the material is deposited within the submarine Bengal Fan, a large sediment body covering most parts of the Bay of Bengal. In this study, we combine the results of a large underwater drilling campaign (IODP Expedition 354) with acoustic images of the subsurface from the lower Bengal Fan in order to develop a profound understanding of the timing and location of channel-levee activity and sediment deposition. This knowledge will eventually help scientists to understand the past climate in the Himalaya region. We show that the location of sediment deposition is highly variable and can move more than 100 km laterally. These variations are investigated in detail for the last 1 million years.

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Section: Discussionsupporting

confidence: 63%

Section: Discussionsupporting

confidence: 55%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Middle to Late Pleistocene Architecture and Stratigraphy of the Lower Bengal Fan—Integrating Multichannel Seismic Data and IODP Expedition 354 Results

Bergmann

Schwenk

Spieß

et al. 2020

Geochem Geophys Geosyst

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“…Stratigraphic summary of recovered sediments. Adapted from Weber and Reilly (2018) and France‐Lanord et al (2016). Ages for relevant chronostratigraphic markers are noted for ash layers (Mark et al, 2017), the upper and lower range of calcareous nanofossil datums (Gradstein et al, 2012), and the lower Jaramillo magnetic reversal (Channell et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Middle to Late Pleistocene Evolution of the Bengal Fan: Integrating Core and Seismic Observations for Chronostratigraphic Modeling of the IODP Expedition 354 8° North Transect

Reilly

Bergmann

Weber

et al. 2020

Geochem Geophys Geosyst

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We investigate chronology and age uncertainty for the middle to upper Pleistocene lower Bengal Fan using a novel age-depth modeling approach that factors lithostratigraphic, magnetostratigraphic, biostratigraphic, cyclostratigraphic, and seismic stratigraphic constraints, based on results from the International Ocean Discovery Program Expedition 354 Bengal Fan and analysis of the GeoB97-020/027 seismic line. The initial chronostratigraphic framework is established using regionally extensive hemipelagic sediment units, and only age-depth models of fan deposits that respect the superposition of channel-levee systems between sites are accepted. In doing so, we reconstruct signals of regional sediment accumulation rate and lithogenic sediment input through the perspective of a two-dimensional~320 km transect at 8°N that are consistent with more distal and more ambiguous regional records. This chronology allows us to discuss the depositional history of the middle to upper Pleistocene lower Bengal Fan within the context of sea level, climate, and tectonic controls. We hypothesize, based on the timing of accumulation rate changes, that progradation and intensification of the Bengal Fan's channel-levee system at 8°N was largely driven by increases in sea level amplitude during this time. However, it is also possible this progradation was influenced by changes in Pleistocene climate and increased Himalayan erosion rates, driving greater sediment flux to the fan.Plain Language Summary Deep sea fans are sediment deposits in the ocean that often form near river systems offshore continental margins. The largest of these, the Bengal Fan in the northern Indian Ocean, contains the most complete record of materials eroded from the Himalayan Mountains and can be used to study the climate and tectonic history of the region. Sediments are moved from the river mouth to the fan in a series of ever-changing channels that distribute sediments across the fan surface, making it impossible to obtain a complete and continuous record of Himalayan erosion at any one location. International Ocean Discovery Program Expedition 354 drilled a series of seven locations in a transect across the fan to capture a more complete record of where sediment was deposited over the last 1.25 Myr, a time characterized by major changes in Earth's climate system. Here we discuss statistics of sediment deposition from a computer model constrained by observations from those seven sites. The results indicate that the Bengal Fan grew rapidly during a time when global sea level changes, caused by the growth and decay of continental ice sheets, became more intense.

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Clay minerals of surface sediments from the lower Bengal Fan: Implications for provenance identification and transport processes

et al. 2020

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Based on the clay mineral assemblages of 98 surface sediments from the lower Bengal Fan, we carried out a quantitative provenance identification and discussed the potential transport processes of fine fractions with the support of the hydrodynamic environment. Illite is the dominant clay mineral in the study area, with an average of 51%, followed by kaolinite, with an average of 20%, while chlorite and smectite account for averages of 17 and 11%, respectively. The study area can be divided into two provinces based on the clay mineral assemblages: Province I, located in the western part of the study area, has relatively higher smectite content, while province II, located in the eastern part, shows higher illite content. The Ganges–Brahmaputra (Himalayan) and the Godavari–Krishna (Indian Peninsula) are suggested to be the major provenances, and the average relative contributions of the Himalayan source and the Indian source are 76 and 24%, respectively. Sediments in province II receive more sediment from the Himalayan source, with an average contribution of 84%, while the Indian source mainly contributed to province I, with an average contribution rate of 32%. The Indian Peninsula materials are predominantly conveyed to the study area by the northeast monsoon circulation, and the relative contribution gradually decreases from northwest to southeast in the lower Bengal Fan. However, most of the Himalayan material is transported to the study area by the southwest monsoon. Our research indicates that the seasonal hydrodynamic pattern of the Northeast Indian Ocean plays an important role in controlling modern sediment transport in the Bay of Bengal, causing terrestrial materials from different sources to show significantly different spatial distribution characteristics.

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Hemipelagic and turbiditic deposits constrain lower Bengal Fan depositional history through Pleistocene climate, monsoon, and sea level transitions

Cited by 39 publications

References 50 publications

Middle to Late Pleistocene Architecture and Stratigraphy of the Lower Bengal Fan—Integrating Multichannel Seismic Data and IODP Expedition 354 Results

Middle to Late Pleistocene Architecture and Stratigraphy of the Lower Bengal Fan—Integrating Multichannel Seismic Data and IODP Expedition 354 Results

Middle to Late Pleistocene Evolution of the Bengal Fan: Integrating Core and Seismic Observations for Chronostratigraphic Modeling of the IODP Expedition 354 8° North Transect

Clay minerals of surface sediments from the lower Bengal Fan: Implications for provenance identification and transport processes

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