| Abstract Submission No. | ABS-4.1-0142 |
| Title of Abstract | Constraining the differential tectonic uplift in the eastern Himalayan wedge using the river incision model |
| Authors | BHAGYA S DEV*, NILESH K JAISWARA |
| Organisation | CSIR - NGRI |
| Address | CSIR-NGRI , HYDERABAD Hyderabad, TELANGANA, India Pincode: 500007 E-mail: bhagyaasha2146@gmail.com |
| Country | India |
| Presentation | Poster |
| Abstract | The Himalayan range has evolved as a wedge system due to the underthrusting of the Indian plate into the Eurasian plate. Tectonic and erosional processes have shaped the Himalayan wedge through the evolution of the drainage system. The differential strain partitioning along the Himalayan Arc causes different uplift-erosion regimes, resulting in a transient landscape. A Major knickpoint set (> 3064m) observed on the eastern Himalayan transient basin: Kosi, Teesta, Torsa, Raidak, Sankosh, and Manas, demarcating a significant change in the tectonic-erosion setting in the region. Another set of knickpoints was identified at lower elevations (<2631 m) in the easternmost basins, indicating a second phase of tectonic-erosion change. We have used geomorphic indices like chi profile, Normalised Steepness Index (ksn), paleochannel reconstruction to evaluate erosion and uplift rates, and knickpoints modelling for spatial and temporal constraints. The ksn values of the upper segment of the rivers have < 190 m0.9, termed as the upper relict reach, while the lower segments have >190 m0.9. The two sets of knickpoints are related to the two or multiple phases of tectonic regimes shift, and the relict reach preserves the previous signature of the older uplift-erosion phase. Thus, the reconstructed paleochannel from the relict reach estimates the degree of surface uplift since the drainage perturbation. The upper transient reach gives the estimated surface uplift ranging from 1600 m to ~4000 m, while the lower relict reach gives an uplift of ~800-1700 m. The second phase of uplift was observed only in the basins east of the Dubri/ Jamuna Fault, where, in the Brahmaputra basin, a plateau has grown since 5 Ma, known as the Shillong plateau. We speculate that the second phase of the transient signal must have developed due to differential strain partitioning, possibly coeval with the Shillong plate growth in the south. |
| Keywords | Himalayan wedge, Transient knickpoints, relict reach, Ksn |