Carbon in watershed bedrock and its importance in global carbon cycling

Over geologic timescales, weathering of silicate rocks plays a significant role in the regulation of atmospheric carbon dioxide and thereby global climate. The Sierra de las Minas of Guatemala, my study area, has high physical erosion, frequently occurring from landslides. This erosion increases water throughflow and water contact with fresh mineral surfaces, which in turn may increase chemical weathering in the region. Carbonation, the mode of chemical weathering of particular interest to this study, involves dissolution of atmospheric carbon dioxide by rain water, forming soluble carbonates. My study aims to describe components of an important process in the carbon cycle, and to contribute to a better understanding of the functions and interactions of Earth systems. Shale samples which had undergone various degrees of weathering, collected from streambeds and outcrops of watersheds in the region, have been analyzed for total inorganic and organic carbon (TOC) to quantify and distinguish carbon derived from decomposition of living organisms and the carbonation weathering process. Samples were also analyzed for major, minor and trace elements by X-Ray Fluorescence Spectrometry to determine the elemental composition of the rocks, indicating the lithology of the weatherable rocks in the region. TOC levels range 1.8-5% and 1-4% for TIC.Shell Exploration and Production CompanyNo embarg