Subduction initiation and the rise of the Shillong Plateau
Discrepancies between geodetically and geologically estimated thrust fault slip rates are generally viewed as a methodological problem. Even when slip rate is steady over geological time, a discrepancy may exist because each method is sensitive to different deformation processes. However, this offer...
| Main Authors: | , , , , , , , |
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| Other Authors: | |
| Format: | Journal Article |
| Language: | English |
| Published: |
2021
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| Online Access: | https://hdl.handle.net/10356/151580 |
| _version_ | 1826119192580980736 |
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| author | Mallick, Rishav Hubbard, Judith Lindsey, Eric Ostrom Bradley, Kyle Moore, James Daniel Paul Ahsan, Aktarul Alam, A. K. M. Khorshed Hill, Emma M. |
| author2 | Asian School of the Environment |
| author_facet | Asian School of the Environment Mallick, Rishav Hubbard, Judith Lindsey, Eric Ostrom Bradley, Kyle Moore, James Daniel Paul Ahsan, Aktarul Alam, A. K. M. Khorshed Hill, Emma M. |
| author_sort | Mallick, Rishav |
| collection | NTU |
| description | Discrepancies between geodetically and geologically estimated thrust fault slip rates are generally viewed as a methodological problem. Even when slip rate is steady over geological time, a discrepancy may exist because each method is sensitive to different deformation processes. However, this offers a tool to estimate the partitioning of convergence between footwall and hanging wall deformation, and therefore a way to discriminate among orogenic styles. Here we investigate one such discrepancy for the Shillong Plateau, a basement-cored contractional orogen within the Himalayan foreland basin. Using a regional block model to explain the modern geodetic velocity field and explicit uncertainty analysis of the geologic rates, we show that this discrepancy cannot be reconciled simply by invoking uncertainties in individual methods. Our results indicate that the Shillong Plateau is not an ongoing forward break of the Bhutan Himalayas, as was believed until recently. Instead, the observed inter-plate convergence and plateau uplift in this region may be driven primarily by an attempt of the negatively buoyant Indian passive margin lithosphere (the Surma Basin), south of the plateau, to initiate subduction. As a result, the uplift history of the plateau, which constrains the geologic rate, is significantly lower than expected given the geodetic convergence rate. We propose that this convergence is largely accommodated by the transport of the footwall into the mantle. This geodynamic scenario has important regional seismotectonic implications: (1) the cold and brittle sinking passive margin may have enabled the deep extent (∼30 km) and therefore large magnitude of the MW 8+ Shillong Earthquake of 1897; (2) the collapse of the Indian lithosphere into the mantle may have created the anomalously deep (∼20 km) Surma Basin; and (3) this subsidence may also drive accelerated post-Miocene westward propagation of the Indo-Burman Wedge. We propose that the Shillong Plateau is the only modern example of passive margin collapse, and can serve as a natural laboratory to study the earliest phase of subduction. |
| first_indexed | 2024-10-01T04:56:08Z |
| format | Journal Article |
| id | ntu-10356/151580 |
| institution | Nanyang Technological University |
| language | English |
| last_indexed | 2024-10-01T04:56:08Z |
| publishDate | 2021 |
| record_format | dspace |
| spelling | ntu-10356/1515802021-07-10T20:11:04Z Subduction initiation and the rise of the Shillong Plateau Mallick, Rishav Hubbard, Judith Lindsey, Eric Ostrom Bradley, Kyle Moore, James Daniel Paul Ahsan, Aktarul Alam, A. K. M. Khorshed Hill, Emma M. Asian School of the Environment Earth Observatory of Singapore Science::Geology::Structural geology Active Tectonics Geodesy Geology Discrepancies between geodetically and geologically estimated thrust fault slip rates are generally viewed as a methodological problem. Even when slip rate is steady over geological time, a discrepancy may exist because each method is sensitive to different deformation processes. However, this offers a tool to estimate the partitioning of convergence between footwall and hanging wall deformation, and therefore a way to discriminate among orogenic styles. Here we investigate one such discrepancy for the Shillong Plateau, a basement-cored contractional orogen within the Himalayan foreland basin. Using a regional block model to explain the modern geodetic velocity field and explicit uncertainty analysis of the geologic rates, we show that this discrepancy cannot be reconciled simply by invoking uncertainties in individual methods. Our results indicate that the Shillong Plateau is not an ongoing forward break of the Bhutan Himalayas, as was believed until recently. Instead, the observed inter-plate convergence and plateau uplift in this region may be driven primarily by an attempt of the negatively buoyant Indian passive margin lithosphere (the Surma Basin), south of the plateau, to initiate subduction. As a result, the uplift history of the plateau, which constrains the geologic rate, is significantly lower than expected given the geodetic convergence rate. We propose that this convergence is largely accommodated by the transport of the footwall into the mantle. This geodynamic scenario has important regional seismotectonic implications: (1) the cold and brittle sinking passive margin may have enabled the deep extent (∼30 km) and therefore large magnitude of the MW 8+ Shillong Earthquake of 1897; (2) the collapse of the Indian lithosphere into the mantle may have created the anomalously deep (∼20 km) Surma Basin; and (3) this subsidence may also drive accelerated post-Miocene westward propagation of the Indo-Burman Wedge. We propose that the Shillong Plateau is the only modern example of passive margin collapse, and can serve as a natural laboratory to study the earliest phase of subduction. Ministry of Education (MOE) Nanyang Technological University National Research Foundation (NRF) Published version This research was supported by the Earth Observatory of Singapore and the National Research Foundation Singapore and the Singapore Ministry of Education under the Research Centres of Excellence initiative, and by a Singapore National Research Foundation Investigatorship awarded to EMH (Proposal ID NRF2018NRF-NRFI001-21). 2021-07-05T06:18:30Z 2021-07-05T06:18:30Z 2020 Journal Article Mallick, R., Hubbard, J., Lindsey, E. O., Bradley, K., Moore, J. D. P., Ahsan, A., Alam, A. K. M. K. & Hill, E. M. (2020). Subduction initiation and the rise of the Shillong Plateau. Earth and Planetary Science Letters, 543, 116351-. https://dx.doi.org/10.1016/j.epsl.2020.116351 0012-821X https://hdl.handle.net/10356/151580 10.1016/j.epsl.2020.116351 2-s2.0-85085240292 543 116351 en NRF2018NRF-NRFI001-21 Earth and Planetary Science Letters https://researchdata.ntu.edu.sg/dataverse/shillongmibb © 2020 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). application/pdf |
| spellingShingle | Science::Geology::Structural geology Active Tectonics Geodesy Geology Mallick, Rishav Hubbard, Judith Lindsey, Eric Ostrom Bradley, Kyle Moore, James Daniel Paul Ahsan, Aktarul Alam, A. K. M. Khorshed Hill, Emma M. Subduction initiation and the rise of the Shillong Plateau |
| title | Subduction initiation and the rise of the Shillong Plateau |
| title_full | Subduction initiation and the rise of the Shillong Plateau |
| title_fullStr | Subduction initiation and the rise of the Shillong Plateau |
| title_full_unstemmed | Subduction initiation and the rise of the Shillong Plateau |
| title_short | Subduction initiation and the rise of the Shillong Plateau |
| title_sort | subduction initiation and the rise of the shillong plateau |
| topic | Science::Geology::Structural geology Active Tectonics Geodesy Geology |
| url | https://hdl.handle.net/10356/151580 |
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