Sustained wood burial in the Bengal Fan over the last 19 My

Lee, Hyejung; Galy, Valier; Feng, Xiaojuan; Ponton, C.; Galy, Αlbert; France‐Lanord, Christian; Feakins, Sarah J.

doi:10.1073/pnas.1913714116

Cited by 58 publications

(55 citation statements)

References 57 publications

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“…Current estimates of carbon fluxes in the ocean (Burdige, 2007;Blair and Aller, 2012) posit that sandy fractions are POC free. Yet a recent study (Lee et al, 2019) has found that abundant wood has been buried in sands in the Bengal Fan (Bay of Bengal, Indian Ocean) for the last 19 m.y. Other studies have described organic-rich layers in sandy deep-sea turbidites (Saller et al, 2006;Zavala et al, 2012;Sparkes et al, 2015;Leithold et al, 2016), in some cases even within sands of units Ta and Tb, depending on the density and size of organic debris (McArthur et al, 2016;Schnyder et al, 2017).…”

Section: Sand Mudmentioning

confidence: 99%

“…In contrast, the role of marine sands in global POC burial has long been overlooked (Burdige, 2007). Yet woody debris associated with sands in submarine fans is increasingly being recognized as a major terrestrial POC pool (Leithold et al, 2016;Lee et al, 2019). Submarine fans are formed by turbidity currents, which domi-nate sediment deposition across vast areas of the seabed (Bouma et al, 1985).…”

Section: Introductionmentioning

confidence: 99%

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Efficient preservation of young terrestrial organic carbon in sandy turbidity-current deposits

Hage

Galy

Cartigny

et al. 2020

Geology

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Burial of terrestrial biospheric particulate organic carbon in marine sediments removes CO2 from the atmosphere, regulating climate over geologic time scales. Rivers deliver terrestrial organic carbon to the sea, while turbidity currents transport river sediment further offshore. Previous studies have suggested that most organic carbon resides in muddy marine sediment. However, turbidity currents can carry a significant component of coarser sediment, which is commonly assumed to be organic carbon poor. Here, using data from a Canadian fjord, we show that young woody debris can be rapidly buried in sandy layers of turbidity current deposits (turbidites). These layers have organic carbon contents 10× higher than the overlying mud layer, and overall, woody debris makes up >70% of the organic carbon preserved in the deposits. Burial of woody debris in sands overlain by mud caps reduces their exposure to oxygen, increasing organic carbon burial efficiency. Sandy turbidity current channels are common in fjords and the deep sea; hence we suggest that previous global organic carbon burial budgets may have been underestimated.

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Section: Sand Mudmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Efficient preservation of young terrestrial organic carbon in sandy turbidity-current deposits

Hage

Galy

Cartigny

et al. 2020

Geology

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“…Sediment volumes preserved in the BNFS record the denudation history of the Himalaya Range and have been used to estimate denudation rates over geological timescales (France-Lanord et al, 1993;Einsele et al, 1996;M etivier et al, 1999), whereas variations in the nature and rate of sediment accumulation were related to regional climatic variations (France-Lanord & Derry, 1994;Weber et al, 2003;). Recently, studies have shown the importance of the Bengal Fan in the carbon cycle via uplift and denudation processes in the India-Asia collision zone (carbon dioxide consumption from silicate weathering) and marine sedimentation (burial of organic carbon), which makes the Bengal Fan a net sink of CO 2 at a global scale (France-Lanord & Derry, 1997;Galy et al, 2007;Lee et al, 2019).…”

Section: Bengal Depositional Fanmentioning

confidence: 99%

Sedimentology, stratigraphy and architecture of the Nicobar Fan (Bengal–Nicobar Fan System), Indian Ocean: Results from International Ocean Discovery Program Expedition 362

et al. 2020

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Drill sites in the southern Bay of Bengal at 3°N 91°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 [sub]unit was a time of reduced sediment accumulation rates.

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“…However, perhaps the largest source of uncertainty relates to the dynamics of particulate OC transport versus clastic sediment in relation to its mobility following landslide events. While the general link between the two phases has been demonstrated (Galy et al, 2015;Hilton et al, 2012), there is also evidence that discrete clasts of woody debris can be sorted by flowing water (Hilton et al, 2015;Lee et al, 2019), and its transport behaviour different from the clastic load due to a lower density and different particle shape (Turowski et al, 2016).…”

Section: Limitations Of the Approachmentioning

confidence: 99%

Pulsed carbon export from mountains by earthquake-triggered landslides explored in a reduced-complexity model

Croissant¹,

Hilton²,

Li³

et al. 2020

Preprint

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Abstract. In mountain ranges, earthquakes can trigger widespread landsliding and mobilise large amounts of organic carbon by eroding soil and vegetation from hillslopes. Following a major earthquake, the landslide-mobilised organic carbon can be exported from river catchments by physical sediment transport processes, or stored within the landscape where it may be degraded by heterotrophic respiration. The competition between these physical and biogeochemical processes governs a net transfer of carbon between the atmosphere and sedimentary organic matter, yet their relative importance following a large landslide-triggering earthquake remains poorly constrained. Here, we propose a model framework to quantify the post-seismic redistribution of soil-derived organic carbon. The approach combines predictions based on empirical observations of co-seismic sediment mobilisation, with a description of the physical and biogeochemical processes involved after the earthquake. Earthquake-triggered landslide populations are generated by randomly sampling a landslide area distribution, a proportion of which is initially connected to the fluvial network. Initially disconnected landslide deposits are transported downslope and connected to rivers at a constant velocity in the post-seismic period. Disconnected landslide deposits lose organic carbon by heterotrophic oxidation, while connected deposits lose organic carbon synchronously by both oxidation and river export. The modelling approach is numerically efficient and allows us to explore a large range of parameter values that exert a control on the fate of organic carbon in the upland erosional system. We explore the role of the climatic context (in terms of mean annual runoff and runoff variability) and rates of organic matter degradation using single and multi-pool models. Our results highlight that the redistribution of organic carbon is strongly controlled by the annual runoff and the extent of landslide connection, but less so by the choice of organic matter degradation model. In the context of mountain ranges typical of the southwest Pacific region, we find that model configurations allow for more than 90 % of the landslide-mobilized carbon to be exported from mountain catchments. A simulation of earthquake cycles suggests efficient transfer of organic carbon out of a mountain range during the first decade of the post-seismic period. Pulsed erosion of organic matter by earthquake-triggered landslides therefore offers an effective process to promote carbon sequestration in sedimentary deposits over thousands of years.

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Sustained wood burial in the Bengal Fan over the last 19 My

Cited by 58 publications

References 57 publications

Efficient preservation of young terrestrial organic carbon in sandy turbidity-current deposits

Efficient preservation of young terrestrial organic carbon in sandy turbidity-current deposits

Sedimentology, stratigraphy and architecture of the Nicobar Fan (Bengal–Nicobar Fan System), Indian Ocean: Results from International Ocean Discovery Program Expedition 362

Pulsed carbon export from mountains by earthquake-triggered landslides explored in a reduced-complexity model

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