"Approximating meteoric 10Be using the concentration of acid-extractable grain coatings: a case study tracing erosion depth on Dominica, Lesser Antilles"

Kira Tomenchok, Honors Thesis 2018

Abstract: Surface process studies on Dominica have emphasized landslide research in order to improve hazard mitigation, but a deficit exists in understanding the general geomorphic processes. The goal of this study is to characterize erosional processes, in addition to landslides, using sediment-fingerprinting techniques. Meteoric 10Be is an accepted fingerprinting tool used to identify sediment sources and infer erosional processes. Due to the analytical cost of 10Bem, we test the validity of the concentration of grain coatings as a proxy for 10Bem in a Caribbean setting. We sampled detrital sediment in two sizes, <63 and 250-850 μm, from the outlets of Dominica's 20 largest watersheds. A strong positive correlation exists between acid-extractable grain coating concentrations from <63 μm sediment and 10Bem, but a weak correlation exists between grain coating concentrations from 250-850 μm sediments and 10Bem . Acid-extractable Fe, Al and Mn, concentrations are selected as the total concentration of grain coatings. With this technique, selected elements are site-dependent; the elements in our study vary with elements selected in Singleton et al. (2017) and Greene (2016). This research affirmed the viability of grain coating concentrations leached from fine-grained sediment as proxy for 10Bem. Transport to the outlet likely affects coating concentrations on coarse-grained sediment more than fine-grained sediment through processes such as abrasion, decreasing the viability of using coarse-sample grain coatings. A strong inverse relationship exists between fine-sample grain coatings and landslide density, affirming that changes of erosional processes are represented in the outlet sediment. Furthermore, watershed characteristics account for varying erosional processes between watersheds. Individual precipitation events and slope show the strongest correlation with landslide activity and land use and geology show weak but positive relationships with landslide activity.

Full thesis available. Contact the Geology Department at 540-458-8800.