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Landscape response to climate forcing: quantifying mechanisms and rates of erosion and weathering along an orographically-enhanced climate gradient.

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Call No.	GB428.C3 D55 2008
Author	Dixon, Jean Louise
Title	Landscape response to climate forcing: quantifying mechanisms and rates of erosion and weathering along an orographically-enhanced climate gradient.
Date	2008
Abstract	Landscapes evolve in response to external forcings such as climate and tectonics that influence the pace and patterns of erosion and weathering processes. Furthermore, internal feedbacks between erosion and weathering regulate the expression of these forcings on upland soil-mantled landscapes. This thesis quantifies links between climate, erosion, weathering and hillslope form along a Sierra Nevada climate gradient. We quantify denudation rates and partition them into physical and chemical components using cosmogenic radionuclide (CRN) 10 Be concentrations in saprolite and stream sediments, and zirconium concentrations in soil, saprolite and rock. Furthermore, we present an adapted set of equations to calculate these rates that specifically accounts for deep saprolite weathering not captured by CRN-derived surface denudation rates. We also quantify dominant soil production and transport processes through field observations and both profiles and inventories of fallout radionuclides 137 Cs and 210 Pb. Our data show clear patterns in erosion and weathering across a climate gradient, and together suggest that climate directly controls chemical weathering by temperature and water-availability control on reaction rates, and that climate influences erosion rates by modulating the efficacy of individual soil transport mechanisms and controlling pace and patterns of chemical weathering processes that reduce rock strength and increase erodability. These results also suggest that saprolite weathering, a process rarely factored into geomorphology studies, plays an important and previously unquantified role in the evolution of upland soil-mantled landscapes. Lastly, we examine morphometric expression of climate and dominant soil transport processes using high resolution laser altimetry data, erosion rates, and calculations of 1D sediment flux. Our tests of predicted functional relationships between hillslope morphology and erosion indicate that current transport laws may have limited applicability at studied Sierran sites and similar landscapes because they do not account for variations in chemical weathering with topography and erosion. Together, our findings are an important contribution to geomorphic understanding of landscape response to climate forcing, and identify previously unquantified controls on the evolution of soil mantled landscapes.
Description	x, 174 leaves : illustrations (some color), color maps
Format	application/pdf
Advisor	Heimsath, Arjun M. ; Dade, Brian ; Magilligan, Francis J. ; Amundson, Ronald
Subject	Climatic geomorphology -- Sierra Nevada (California and Nevada). ; Slopes (Physical geography) -- Sierra Nevada (California and Nevada). ; Weathering -- Sierra Nevada (California and Nevada). ; Chemical denudation -- Sierra Nevada (California and Nevada). ; Erosion -- Sierra Nevada (California and Nevada). ; Saprolites -- Sierra Nevada (California and Nevada). ; Soils -- Sierra Nevada (California and Nevada). ; Beryllium -- Isotopes. ; Zirconium.
College	Dartmouth College -- Department of Earth Sciences.
Issuing Body	Dartmouth Dissertations are made available through the Dartmouth Digital Library.
Degree	Thesis (Ph.D)--Dartmouth College.
Copyright	In Copyright. This material is protected by copyright and/or related rights. You are free to use this material in any way that is permitted by copyright law that applies to your use. For other uses, you need to obtain permission from the rights-holder(s). http://rightsstatements.org/page/InC/1.0/
DOI	https://doi.org/10.1349/ddlp.3524

Title	dixon2008 1
Full Text	LANDSCAPE RESPONSE TO CLIMATE FORCING: Quantifying Mechanisms and Rates of Erosion and Weathering Along an Orographically-Enhanced Climate Gradient A Thesis Submitted to the Faculty In partial fulfillment of the requirements for the degree of Doctor of Philosophy in Earth Science By Jean L. Dixon DARTMOUTH COLLEGE Hanover, New Hampshire August 27, 2008

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Landscape response to climate forcing: quantifying mechanisms and rates of erosion and weathering along an orographically-enhanced climate gradient.

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