Author ORCID Identifier

https://orcid.org/0000-0002-1693-8576

Year of Publication

2022

Degree Name

Master of Science (MS)

Document Type

Master's Thesis

College

Arts and Sciences

Department/School/Program

Earth and Environmental Sciences (Geology)

First Advisor

Dr. James Ryan Thigpen

Abstract

Theoretical and numerical geodynamic models of continental collisional systems often involve, either explicitly or implicitly, a necessary yet complicated dependence between tectonics and erosion; however, the exact nature of these relationships remains elusive and controversial. In such models for the Himalayan-Tibetan (H-T) collisional orogen, surface processes are theorized or in some cases required to play an essential role in modulating critical processes active in the evolution of that system. To investigate, at least to first order. these interactions between climate and tectonics, we generate a simplified landscape evolution model of an actively uplifting orogenic wedge acted upon by surface processes. We vary parameters in the equations governing landscape evolution and make observations of the topographic evolution response in the active orogen. We use comparisons with the topography of the modern HT system, along with measured thrust, uplift and erosion rates, to establish erodibility parameter (K) values consistent with observations from the modern Himalayan-Tibetan (HT) orogenic system. These values are then used to assess the viability of uplift and erodibility conditions required in current HT geodynamic models, including crustal channel flow. We find that for uplift rates consistent with convergence rate data from the Himalaya (5 mm yr-1), a reasonable value for the erodibility constant (K) is 1.25 x 10-5 m-1 yr-1, as it yields a maximum elevation similar to those in the modern HT system (~6.7 km). Using this value of K, we find that only uplift rates in the range of 4-7 mm yr-1 can lead to development of maximum topography in the range of that observed in the modern HT system (5-8 km). Because of this, we conclude that uplift rates as high as 13 mm yr-1, which are required in the Miocene crustal channel flow models, would require a pronounced changed in erodibility (> 2.5 x 10-5 m-1 yr-1), likely manifested as a major climate shift that drives substantially increased precipitation. Because observations in the HT system do not currently support such a climatic shift, it is possible that the cessation of channel flow at the HT front may have been driven by a previously unrecognized change in tectonic style or geodynamic mechanism for shortening accommodation.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2022.247

Funding Information

This study was supported by the National Science Foundation Graduate Research Fellowship Program in 2017.

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