Coupling erosion and topographic development in the rainiest place on Earth: Reconstructing the Shillong Plateau uplift history with in-situ cosmogenic 10Be

Rosenkranz, Ruben; Schildgen, Taylor F.; Wittmann, Hella; Spiegel, Cornelia

doi:10.1016/j.epsl.2017.11.047

Cited by 33 publications

(45 citation statements)

References 53 publications

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“…Because of its location relative to the SP, encroachment of the Brahmaputra to the DC section likely occurred due to uplift of the SP. The timing of uplift is consistent with a recent estimate based on incision rates in the SP (Rosenkranz et al, 2018).…”

Section: Discussion Brahmaputra Paleo-drainagesupporting

confidence: 79%

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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Section: Discussion Brahmaputra Paleo-drainagesupporting

confidence: 79%

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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“…This is consistent with initiation of plateau surface uplift in the Pliocene (Biswas et al, 2007;Govin et al, 2018;Rosenkranz et al, 2018) and suggests that the Shillong Plateau attained sufficient elevation (1,500 m, e.g., Roe, 2005) to cause orographic rainout on its southern slope only after 1.2-1.7 Ma. The data from our study thus suggest that the effects of a rain shadow were established at 1.2-1.7 Ma.…”

Section: Time Of Changes In Isotopic Composition Of Foreland Meteoricsupporting

confidence: 75%

“…It has been suggested that surface uplift of the plateau reduced the mean annual precipitation in the downwind direction along the Himalayan front of eastern Bhutan (Biswas et al, 2007;Bookhagen & Burbank, 2010;Grujic et al, 2006). Initial basement rock uplift, starting at least 15-9 Ma ago, did not generate significant surface uplift until the basement became exposed at the Miocene-Pliocene transition, decreasing erosion rates and resulting in plateau surface uplift after 4-3 Ma (Biswas et al, 2007), 3.5-2 Ma (Najman et al, 2016), around 4.5 Ma (Rosenkranz et al, 2018) or at 5.2-4.9 Ma (Govin et al, 2018). Our hypothesis is that once the Shillong Plateau reached a sufficient elevation to cause orographic precipitation on its southern side by stable upslope ascent of warm moisture-bearing air masses (Roe, 2005, and references therein), this decreased the amount of precipitation on the leeward side of the plateau, in the foothills of the eastern Bhutanese Himalayas to the north.…”

Section: The Shillong Plateaumentioning

confidence: 99%

Formation of a Rain Shadow: O and H Stable Isotope Records in Authigenic Clays From the Siwalik Group in Eastern Bhutan

Grujić

Govin

Barrier

et al. 2018

Geochem Geophys Geosyst

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We measure the oxygen and hydrogen stable isotope composition of authigenic clays from Himalayan foreland sediments (Siwalik Group), and from present day small stream waters in eastern Bhutan to explore the impact of uplift of the Shillong Plateau on rain shadow formation over the Himalayan foothills. Stable isotope data from authigenic clay minerals (<2 μm) suggest the presence of three paleoclimatic periods during deposition of the Siwalik Group, between ∼7 and ∼1 Ma. The mean δ18O value in paleometeoric waters, which were in equilibrium with clay minerals, is ∼2.5‰ lower than in modern meteoric and stream waters at the elevation of the foreland basin. We discuss the factors that could have changed the isotopic composition of water over time and we conclude that (a) the most likely and significant cause for the increase in meteoric water δ18O values over time is the “amount effect,” specifically, a decrease in mean annual precipitation. (b) The change in mean annual precipitation over the foreland basin and foothills of the Himalaya is the result of orographic effect caused by the Shillong Plateau's uplift. The critical elevation of the Shillong Plateau required to induce significant orographic precipitation was attained after ∼1.2 Ma. (c) By applying scale analysis, we estimate that the mean annual precipitation over the foreland basin of the eastern Bhutan Himalayas has decreased by a factor of 1.7–2.5 over the last 1–3 million years.

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“…The Bhuri Dihing drains the northern part of the Indo-Burmese ranges and denudes at a lower rate (0.2 mm yr −1 ) compared to the main Himalayan tributaries. Denudation rates of the actively uplifting Shillong Plateau have recently been suggested to be very low on average (Rosenkranz et al, 2016). Overall, according to our TCN data, the TsangpoBrahmaputra receives ca.…”

Section: Downstream Denudation Of the Tsangpo-brahmaputra Catchment Amentioning

confidence: 73%

<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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Coupling erosion and topographic development in the rainiest place on Earth: Reconstructing the Shillong Plateau uplift history with in-situ cosmogenic 10Be

Cited by 33 publications

References 53 publications

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

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

Formation of a Rain Shadow: O and H Stable Isotope Records in Authigenic Clays From the Siwalik Group in Eastern Bhutan

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

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Coupling erosion and topographic development in the rainiest place on Earth: Reconstructing the Shillong Plateau uplift history with in-situ cosmogenic 10Be

Cited by 33 publications

References 53 publications

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

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

Formation of a Rain Shadow: O and H Stable Isotope Records in Authigenic Clays From the Siwalik Group in Eastern Bhutan

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

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