Understanding the Controls on the Variability of Global Passive Margin Erosion Rates

Singh, Navneet (2022) Understanding the Controls on the Variability of Global Passive Margin Erosion Rates. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS dissertation of NavneetSingh (17MS112)) 17MS112_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (3MB)

Abstract

Earth’s topography shows many topographic features,such as plains, plateaus, and mountain ranges. A high elevation mountain range is formed because of collisions between two tectonic plates which finally form topography via crustal shortening and buckling. High elevation mountain ranges are also exhibited in locations with no ongoing tectonics on the Earth’s surface.These include Brazil’s eastern coast, the northeastern coast of the USA, Africa, Madagascar, the western edge of India, and eastern Australia. The topographic evolution of the Earth’s surface results from tectonic and erosional forcesacting in opposite directions, and there may be feedback between these two forces. In the absence of almost any ongoing tectonics, the calculation of erosion rates enables us to address the erosional processes and their influence on the surface topography of the passive border boundaries. Thus, the persistence and formation of high elevation escarpments, lacking any ongoing tectonic activity at these passive margins, make it along debated and an outstanding problem among geomorphologists. High elevation passive continental edges found in western India, eastern Australia, eastern North America, southern Africa and Madagascar, and eastern South America can give more significant insights into our existing knowledge of the climate-erosion couplings. In situ production of ¹⁰Be originates when cosmic rays activate spallation events in mineral formations at Earth’s surface. These concentrations may be used to simulate erosion rates in a range of Earth’s surface materials. ¹⁰Be-derived denudation rates have already been calculated in hundreds of river basins. In this study, I have compiled openly accessible measurements of ¹⁰Be and the corresponding ¹⁰Be based erosional rates based erosional rates (N=690) from river systems draining the high elevationes carpments from across the world, i.e., eastern North America, eastern South America, southern Africa, Madagascar, western India, SriLanka, and eastern Australia. Additionally, compiling in situ produced cosmogenic nuclide data gives us an opportunity to study the erosion rates of global continental passive margin at a much larger scale than previously studied. I have incorporated topographic, precipitation, and vegetation analysis and the recalculated erosion rates to conclude the following: Erosion rates vary largely across the different margins. The highest catchment averaged erosion rates of 16.45 ± 1.33 m/Myr (India) and the lowest average erosion rates of 2.27 ± 0.07 m/Myr from Namibia. Calculated catchment averaged erosion rates are unrelated to absolute latitude, elevation, and catchment area of the basin. Globally, Erosion rates covary and show a moderate correlation with relief, mean channel steepness, and meanannual rainfall.

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