The TMSA hypothesis: Do clay-mineral interlayer surfaces provide an unrecognized sink for organic carbon in the geological record?

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This research will test the hypothesis that the adsorption of organic carbon onto the interlayer surfaces of smectitic clay minerals comprises a significant mode of carbon sequestration and preservation in the geologic record. This model provides a unifying theory for organic carbon burial and the formation of some black shale deposits in which dissolved organic carbon present in natural waters and pore fluids is attracted to charged mineral surfaces of detrital clay minerals, and preserved from microbial degradation by physical sheltering. Upon burial, mineral surfaces may act to coordinate polymerization of complex organic substances such as kerogen and catalyze cracking during catagenesis. The proposed research will: 1) determine the geological extent of the relationship between interlayer mineral surface area and total organic carbon in a range of black shale deposits, economically important source rocks, and modern sediments, 2) establish or dismiss the presence of organic matter within the smectite interlayer sites of these deposits using X-ray diffraction (XRD) techniques and high resolution transmission electron microscopy (HRTEM) imaging of crystal edges and determine whether there is amorphous kerogen that is mineral associated, and 3) measure the compositional differences of OM associated with mineral surfaces versus the total bulk TOC and particulate fraction separated using density and centrifugation techniques.