Provenance Shifts During Neogene Brahmaputra Delta Progradation Tied to Coupled Climate and Tectonic Change in the Eastern Himalaya

Betka, Paul; Thomson, Stuart N.; Sincavage, R.; Zoramthara, C.; Lalremruatfela, C.; Lang, K. A.; Steckler, Michael S.; Bezbaruah, Devojit; Borgohain, Pradip; Seeber, Leonardo

doi:10.1029/2021gc010026

Cited by 10 publications

(7 citation statements)

References 135 publications

(352 reference statements)

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“…The Eocene‐Oligocene event is recorded by exhumation of the Triassic Pane Chuang Formation that we infer may be explained by uplift of the suture zone units in the hanging wall of the Kabaw Fault (Model B) during the accretion of the Burma Terrane to India (Najman et al., 2022). The later Oligocene‐Miocene event records the collision of the Burma Terrane with the Eastern Himalaya (Najman et al., 2022; Westerweel et al., 2020) and a change in the dynamics of the accretionary prism as more Himalayan sediment is delivered to the Bengal Basin (Betka et al., 2021; Najman et al., 2022). Thus, it is likely that deformation along the Kabaw Fault Zone occurred in episodic tectonic events throughout the Cenozoic (cf.…”

Section: Discussionmentioning

confidence: 99%

New GNSS and Geological Data From the Indo‐Burman Subduction Zone Indicate Active Convergence on Both a Locked Megathrust and the Kabaw Fault

et al. 2023

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The Indo‐Burma subduction zone is a highly oblique subduction system where the Indian plate is converging with the Eurasian plate. How strain is partitioned between the Indo‐Burma interface and upper plate Kabaw Fault, and whether the megathrust is a locked and active zone of convergence that can generate great earthquakes are ongoing debates. Here, we use data from a total of 68 Global Navigation Satellite System (GNSS) stations, including newly installed stations across the Kabaw Fault and compute an updated horizontal and vertical GNSS velocity field. We correct vertical rates for fluctuating seasonal signals by accounting for the elastic response of monsoon water on the crust. We model the geodetic data by inverting for 11,000 planar and non‐planar megathrust fault geometries and two geologically viable structural interpretations of the Kabaw Fault that we construct from field geological data, considering a basin‐scale wedge‐fault and a crustal‐scale reverse fault. We demonstrate that the Indo‐Burma megathrust is locked, converging at a rate of 11.6±5.4 $11.6\pm 5.4$ mm/yr, and capable of hosting >8.2 Mw megathrust events. We also show that the Kabaw Fault is locked and accommodating strike‐slip motion at a rate of 8.4±3.0 $8.4\pm 3.0$ mm/yr and converging at a rate of 5.7±4.1 $5.7\pm 4.1$ mm/yr. Our interpretation of the geological, geophysical, and geodetic datasets indicates the Kabaw Fault is a crustal‐scale structure that actively absorbs a portion of the convergence previously ascribed to the Indo‐Burma megathrust. This reveals a previously unrecognized seismic hazard associated with the Kabaw Fault and slightly reduces the estimated hazard posed by megathrust earthquakes in the region.

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Section: Discussionmentioning

confidence: 99%

New GNSS and Geological Data From the Indo‐Burman Subduction Zone Indicate Active Convergence on Both a Locked Megathrust and the Kabaw Fault

et al. 2023

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“…Therefore, we interpret the zircon crystals to represent roughly syn-depositional volcanic grains which have only experienced enough burial to reset the AFT age of sample MY19-170A (Figure 3g). Alternatively, the ZHe ages could reflect Himalayan-derived detrital material, similar to results from sample 16CMP7, collected 25 km to the NW from the middle Barail Group (Betka et al, 2021); this scenario would require a similar magnitude of burial heating over a shorter interval. The thermal model shows a poorly constrained cooling path close to the deposition age, which is set to 32-30 Ma.…”

Section: Zone T1 (West Of Lemyo West-vergent Thrust)mentioning

confidence: 67%

The Timing of Collision Between Asia and the West Burma Terrane, and the Development of the Indo‐Burman Ranges

Najman

Sobel

Millar³

et al. 2022

Tectonics

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The West Burma Terrane (WBT) is a small terrane bounded to the east by the Asian Sibumasu Block and to the west by the Indo‐Burman Ranges (IBR), the latter being an exhumed accretionary prism that formed during subduction of Indian oceanic lithosphere beneath Asia. Understanding the geological history of the WBT is important for reconstruction of the closure history of the Tethys Ocean and India‐Asia collision. Currently there are major discrepancies in the proposed timings of collision between the WBT with both India and Asia; whether the WBT collided with India or Asia first is debated, and proposed timings of collisions stretch from the Mesozoic to the Cenozoic. We undertook a multi‐technique provenance study involving petrography, detrital zircon U‐Pb and Hf analyses, rutile U‐Pb analyses and Sr‐Nd bulk rock analyses on sediments of the Central Myanmar Basins of the WBT. We determined that the first arrival of Asian material into the basin occurred after the earliest late Eocene and by the early Oligocene, thus placing a minimum constraint on the timing of WBT‐Asia collision. Our low temperature thermochronological study of the IBR records two periods of exhumation, in the early‐middle Eocene, and at the Oligo‐Miocene boundary. The Eocene event may be associated with the collision of the WBT with India. The later event at the Oligo‐Miocene boundary may be associated with changes in wedge dynamics resulting from increased sediment supply to the system; however a number of other possible causes provide equally plausible explanations for both events.

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“…Most of the Miocene and Early Miocene sediments were marine in nature (Betka et al, 2021; Kent & Dasgupta, 2004; Kent et al, 2002; Uddin & Lundberg, 1999). It is observed in the seismic section S1S1′ that the thickness of the marine units increases from the HFT to the NPT boundary.…”

Section: Resultsmentioning

confidence: 99%

Morphotectonic forcing and anthropogenic impact behind a recently emerged relict island of the Brahmaputra River

Gogoi

Chetia

Borgohain

et al. 2022

Earth Surf Processes Landf

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Large rivers can be significantly impacted upon by both tectonics and human activities; yet, there are very few studies where these natural and anthropogenic impacts combine. A new river island called Dibru-Saikhoa has appeared very recently on the Brahmaputra valley map in Assam. More than 200 km 2 in area, it is situated in the extreme upstream reach of the Brahmaputra River and represents the second biggest relict island after Majuli (with a present area of $500 km 2 ). The cause of the formation of this island is generally attributed to river dynamics, with only a minor anthropogenic role. However, our study, considering morphological changes from 1915 to 2019 and subsurface geophysical data, suggests that the anthropogenic factor was an important 'trigger' of island formation, acting on a system made sensitive to change by the combination of local tectonics and rapidly changing sediment influx.Making use of the satellite-borne Bouguer gravity data and ground survey-based seismic sections, we located some of the prominent blind faults. Taking into consideration recent activation and interplay of these faults, the mode of accommodation space generation, and aggradation characteristics due to fluvial processes, we suggest a multi-order mechanism of formation of this relict island. The first-order trigger is due to the unstable river morphology of the Siang, which is responding to tilting of the valley floor as a co-seismic phenomenon, and subsequently influences two other rivers-the Dibang and the Lohit. Second-order forcing comes from intra-plate residual pop-up that comes into play due to uneven sediment loading. The third-order forcing is inter-plate suturing, which causes arching and fracturing of the basement.

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Provenance Shifts During Neogene Brahmaputra Delta Progradation Tied to Coupled Climate and Tectonic Change in the Eastern Himalaya

Cited by 10 publications

References 135 publications

New GNSS and Geological Data From the Indo‐Burman Subduction Zone Indicate Active Convergence on Both a Locked Megathrust and the Kabaw Fault

New GNSS and Geological Data From the Indo‐Burman Subduction Zone Indicate Active Convergence on Both a Locked Megathrust and the Kabaw Fault

The Timing of Collision Between Asia and the West Burma Terrane, and the Development of the Indo‐Burman Ranges

Morphotectonic forcing and anthropogenic impact behind a recently emerged relict island of the Brahmaputra River

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