Author ORCID Identifier

https://orcid.org/0009-0001-2095-7278

Semester

Fall

Date of Graduation

2023

Document Type

Thesis

Degree Type

MS

College

Eberly College of Arts and Sciences

Department

Geology and Geography

Committee Chair

Dorothy Vesper

Committee Member

Kathleen Benison

Committee Member

Louis McDonald

Abstract

Understanding geochemical and physical properties of cave sediment gives insight to sediment characterization and carbon storage in the cave system. Previous work on clastic sediments largely encompasses physical properties, neglecting the importance of geochemical parameters on sediment deposition.

This study reports physical and chemical properties of sediment cores from three caves: two caves in Puerto Rico and one cave in Virginia. A total of 25 cores were used in this study; 6 of these cores were new and collected in 2022 from Butler Cave (BTC) in Virginia to focus on the effects of water level. Core samples were analyzed for elemental concentrations through Xray fluorescence, grain size, organic carbon, and nitrogen. Select samples were sent for mineralogical analysis. Grain size in the three caves ranged from poorly sorted to extremely poorly sorted. The majority of sediment was composed of sand and silt-sized grains. Sediment samples from Cueva Clara (CAM) and El Tallonal (TAL), the caves from Puerto Rico, had greater organic carbon and nitrogen concentration ranges and higher maximum values than in Butler Cave. Elemental chemistry in samples from all three caves had concentrations of Fe, Al, and Si that were three times to an order-of-magnitude higher than other elemental concentrations in those samples. Organic carbon was positively correlated with S and Fe in Cueva Clara sediment; organic carbon had a negative correlation with S and a positive correlation with Ti in El Tallonal. Organic carbon did not have significant linear correlations with elemental concentrations in Butler Cave sediment. Limited mineralogical analyses of sediment indicated that quartz is the most abundant mineral in the three caves, followed by 2:1-layer silicates. Differences were observed in organic carbon, nitrogen, and their elemental correlations in sediment above or below the water level. Sediment below the water level has a greater range and higher maximums of organic carbon, nitrogen, and C:N ratios than sediment above the water level. Organic carbon had positive correlations with Fe, Al, Ca, and Mn in Butler Cave sediment above the water level; organic carbon had negative correlations with mean grain diameter and Mg in Butler Cave sediment above the water level. C:N ratios in sediment below the water level were, on average, twice as high as C:N ratios in sediment above the water level. The majority of C:N ratios are between the amino acid and humic/fulvic acid range and indicate a possible terrestrial source of carbon.

Results of this study show that there are differences between caves in Puerto Rico and Virginia, indicating possible differences in cave sediment in temperate or tropical regions. Additionally, sample location relative to water level influences the geochemical and physical trends found in sediment.

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