Semester

Spring

Date of Graduation

2024

Document Type

Thesis

Degree Type

MS

College

Eberly College of Arts and Sciences

Department

Geology and Geography

Committee Chair

Charles Shobe

Committee Co-Chair

Dorothy Vesper

Committee Member

Jaime Toro

Abstract

Quantifying chemical erosion in the lithologically-heterogenous Appalachian Valley and Ridge

Amelia J. Zanoni

The interplay between physical and chemical erosion is well understood in landscapes underlain by a uniform rock type, but many regions are underlain by a mixture of rock types with varying erosion resistance and solubility. We used measurements of stream-water chemistry to estimate chemical erosion rates in the Appalachian Valley and Ridge, a region where the mechanisms of lithologic control over topography are poorly understood. Newly acquired stream water samples were collected from 51 locations across the research area during the Fall of 2023. The sampled waters were combined with existing USGS data to create a stream water chemistry dataset consisting of ~15,200 samples. We calculated chemical erosion rates for Valley and Ridge watersheds using the chemistry of both our new stream water samples and the existing USGS data. Chemical erosion rates were greater in parts of the research area underlain by carbonate rock. We compared our calculated chemical erosion rates with denudation rates determined from detrital cosmogenic radionuclide measurements. By using published 10Be denudations rates for the Valley and Ridge, physical erosion rates were estimated, and it was found that physical erosion was the dominant process in the portions of the study underlain primarily by siliciclastic rocks. Our results indicate a conceptual model in which the carbonate valleys of the Valley and Ridge experience significant chemical erosion, while the ridges maintain steep topography that enables predominantly physical erosion. Future studies are needed to further constrain chemical erosion rate estimates in the Appalachian Valley and Ridge through improved estimates of runoff, rock density, and other key parameters.

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