Plio-Pleistocene exhumation of the eastern Himalayan syntaxis and its domal ‘pop-up’

Bracciali, Laura; Parrish, Randall R.; Najman, Yani; Smye, Andrew J.; Carter, Andrew; Wijbrans, J. R.

doi:10.1016/j.earscirev.2016.07.010

Cited by 86 publications

(96 citation statements)

References 165 publications

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“…Studies suggest that most of the sediment is produced within the NBGPm in both the long and short term. Thermochronological data (Finnegan et al, 2008;Stewart et al, 2008;Bracciali et al, 2016;Salvi et al, 2017) display minimum closure ages for various thermochronometers in a reduced area centered at the confluence between the Po-Tsangpo and the Yarlung Tsangpo, even though this area with high denudation rates has been suggested to extend farther southwards than earlier recognized (Enkelmann et al, 2011). The recent erosional activity displays a similar pattern, with a maximum landslide density in the NBGPm around the abovementioned confluence, and which significantly decreases further downstream along the upper Siang (Larsen and Montgomery, 2012).…”

Section: True Denudation Rates or Possible Biases In The Tcn Signal?mentioning

confidence: 69%

“…The eastern Himalayan syntaxis has been proposed as a typical example of how active tectonic deformation, thermal weakening of the crust, and steep topography could be selfsustained by intense erosion and rapid exhumation of crustal material within the framework of the tectonic aneurysm model (Zeitler et al, 2001). Although the extent and nature of this coupling has recently been challenged (Bendick and Ehlers, 2014;Wang et al, 2014;King et al, 2016), there is ample evidence for superimposed rapid exhumation (Burg et al, 1998;Seward and Burg, 2008;Zeitler et al, 2014;Bracciali et al, 2016) and active erosion (Finlayson et al, 2002;Finnegan et al, 2008;Stewart et al, 2008;Enkelmann et al, 2011;Larsen and Montgomery, 2012;Lang et al, 2013) in a focused area around the Namche Barwa-Gyala Peri massif (NBGPm), where the course of the Tsangpo-Brahmaputra is marked by a sharp bend to the south-west (Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

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<sup>10</sup>Be systematics in the Tsangpo-Brahmaputra catchment: the cosmogenic nuclide legacy of the eastern Himalayan syntaxis

Lupker¹,

Lavé²,

France‐Lanord

et al. 2017

Earth Surf. Dynam.

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Abstract. The Tsangpo-Brahmaputra River drains the eastern part of the Himalayan range and flows from the Tibetan Plateau through the eastern Himalayan syntaxis downstream to the Indo-Gangetic floodplain and the Bay of Bengal. As such, it is a unique natural laboratory to study how denudation and sediment production processes are transferred to river detrital signals. In this study, we present a new 10 Be data set to constrain denudation rates across the catchment and to quantify the impact of rapid erosion within the syntaxis region on cosmogenic nuclide budgets and signals. The measured 10 Be denudation rates span around 2 orders of magnitude across individual catchments (ranging from 0.03 to > 4 mm yr −1 ) and sharply increase as the Tsangpo-Brahmaputra flows across the eastern Himalaya. The increase in denudation rates, however, occurs ∼ 150 km downstream of the Namche Barwa-Gyala Peri massif (NBGPm), an area which has been previously characterized by extremely high erosion and exhumation rates. We suggest that this downstream lag is mainly due to the physical abrasion of coarse-grained, low 10 Be concentration, landslide material produced within the syntaxis that dilutes the upstream high-concentration 10 Be flux from the Tibetan Plateau only after abrasion has transferred sediment to the studied sand fraction. A simple abrasion model produces typical lag distances of 50 to 150 km compatible with our observations. Abrasion effects reduce the spatial resolution over which denudation can be constrained in the eastern Himalayan syntaxis. In addition, we also highlight that denudation rate estimates are dependent on the sediment connectivity, storage, and quartz content of the upstream Tibetan Plateau part of the catchment, which tends to lead to an overestimation of downstream denudation rates. While no direct 10 Be denudation measurements were made in the syntaxis, the dilution of the upstream 10 Be signal, measured in Tsangpo-Brahmaputra sediments, provides constraints on the denudation rates in that region. These denudation estimates range from ca. 2 to 5 mm yr −1 for the entire syntaxis and ca. 4 to 28 mm yr −1 for the NBGPm, which is significantly higher than other large catchments. Overall, 10 Be concentrations measured at the outlet of the Tsangpo-Brahmaputra in Bangladesh suggest a sediment flux between 780 and 1430 Mt yr −1 equivalent to a denudation rate between 0.7 and 1.2 mm yr −1 for the entire catchment.

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Section: True Denudation Rates or Possible Biases In The Tcn Signal?mentioning

confidence: 69%

Section: Introductionmentioning

confidence: 99%

<sup>10</sup>Be systematics in the Tsangpo-Brahmaputra catchment: the cosmogenic nuclide legacy of the eastern Himalayan syntaxis

Lupker¹,

Lavé²,

France‐Lanord

et al. 2017

Earth Surf. Dynam.

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“…We can identify paleo-Brahmaputra input to the sediments because Transhimalayan zircons are typically of Cretaceous-Eocene age. In contrast, zircons derived from Indian-plate Himalayan drainages are dominated by >400 Ma and Miocene ages (e.g., Bracciali et al, 2016;Cina et al, 2009;Gehrels et al, 2011;Lang and Huntington, 2014;Fig. 2).…”

Section: Results: Provenance Analysismentioning

confidence: 99%

“…These data therefore show a shift to Brahmaputra-type values at 5.2-4.9 Ma. Rutile U-Pb dating of sample SJ8 (depositional age 4.9 Ma) returned 25 out of 92 ages unique to the syntaxis (U-Pb ages <9 Ma; Bracciali et al, 2016; Data Repository sections 2 and 7), also demonstrating that these deposits are sourced from the Siang River.…”

Section: Results: Provenance Analysismentioning

confidence: 99%

Timing and mechanism of the rise of the Shillong Plateau in the Himalayan foreland

Govin

Najman

Copley

et al. 2018

Geology

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The Shillong Plateau (northeastern India) constitutes the only significant topography in the Himalayan foreland. Knowledge of its surface uplift history is key to understanding topographic development and unraveling tectonic-climate-topographic coupling in the eastern Himalaya. We use the sedimentary record of the Himalayan foreland basin north of the Shillong Plateau to show that the paleoBrahmaputra river was redirected north and west by the rising plateau at 5.2-4.9 Ma. We suggest that onset of plateau uplift is a result of increased fault-slip rates in response to stresses caused by the Indian lithosphere bending beneath the Himalaya.

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“…6), using age bins given in Table 1. Samples A, B, C (composite sample), X and Y are from Lang et al (2016) and samples Z, T-40a and T-41a are from Bracciali et al (2016). The complete age datasets are given in the data repository, Table S1 in the Supplement.…”

Section: Applications To a Detrital Age Datasetmentioning

confidence: 99%

Extracting information on the spatial variability in erosion rate stored in detrital cooling age distributions in river sands

2018

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Abstract.One of the main purposes of detrital thermochronology is to provide constraints on the regional-scale exhumation rate and its spatial variability in actively eroding mountain ranges. Procedures that use cooling age distributions coupled with hypsometry and thermal models have been developed in order to extract quantitative estimates of erosion rate and its spatial distribution, assuming steady state between tectonic uplift and erosion. This hypothesis precludes the use of these procedures to assess the likely transient response of mountain belts to changes in tectonic or climatic forcing. Other methods are based on an a priori knowledge of the in situ distribution of ages to interpret the detrital age distributions. In this paper, we describe a simple method that, using the observed detrital mineral age distributions collected along a river, allows us to extract information about the relative distribution of erosion rates in an eroding catchment without relying on a steady-state assumption, the value of thermal parameters or an a priori knowledge of in situ age distributions. The model is based on a relatively low number of parameters describing lithological variability among the various sub-catchments and their sizes and only uses the raw ages. The method we propose is tested against synthetic age distributions to demonstrate its accuracy and the optimum conditions for it use. In order to illustrate the method, we invert age distributions collected along the main trunk of the Tsangpo-Siang-Brahmaputra river system in the eastern Himalaya. From the inversion of the cooling age distributions we predict present-day erosion rates of the catchments along the Tsangpo-Siang-Brahmaputra river system, as well as some of its tributaries. We show that detrital age distributions contain dual information about present-day erosion rate, i.e., from the predicted distribution of surface ages within each catchment and from the relative contribution of any given catchment to the river distribution. The method additionally allows comparing modern erosion rates to long-term exhumation rates. We provide a simple implementation of the method in Python code within a Jupyter Notebook that includes the data used in this paper for illustration purposes.

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Plio-Pleistocene exhumation of the eastern Himalayan syntaxis and its domal ‘pop-up’

Cited by 86 publications

References 165 publications

<sup>10</sup>Be systematics in the Tsangpo-Brahmaputra catchment: the cosmogenic nuclide legacy of the eastern Himalayan syntaxis

<sup>10</sup>Be systematics in the Tsangpo-Brahmaputra catchment: the cosmogenic nuclide legacy of the eastern Himalayan syntaxis

Timing and mechanism of the rise of the Shillong Plateau in the Himalayan foreland

Extracting information on the spatial variability in erosion rate stored in detrital cooling age distributions in river sands

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Plio-Pleistocene exhumation of the eastern Himalayan syntaxis and its domal ‘pop-up’

Cited by 86 publications

References 165 publications

&lt;sup&gt;10&lt;/sup&gt;Be systematics in the Tsangpo-Brahmaputra catchment: the cosmogenic nuclide legacy of the eastern Himalayan syntaxis

&lt;sup&gt;10&lt;/sup&gt;Be systematics in the Tsangpo-Brahmaputra catchment: the cosmogenic nuclide legacy of the eastern Himalayan syntaxis

Timing and mechanism of the rise of the Shillong Plateau in the Himalayan foreland

Extracting information on the spatial variability in erosion rate stored in detrital cooling age distributions in river sands

Contact Info

Product

Resources

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<sup>10</sup>Be systematics in the Tsangpo-Brahmaputra catchment: the cosmogenic nuclide legacy of the eastern Himalayan syntaxis

<sup>10</sup>Be systematics in the Tsangpo-Brahmaputra catchment: the cosmogenic nuclide legacy of the eastern Himalayan syntaxis