Reflectance and confocal laser scanning fluorescence spectroscopy of bituminite in Kimmeridge Clay

This work investigates the characterization of bituminite (amorphous sedimentary organic matter) in Kimmeridge Clay source rock via confocal laser canning microscopy (CLSM) and atomic force microscopy (AFM). As part of an International Committee for Coal and Organic Petrology working group, an immature (0.42% vitrinite reflectance), organic-rich (44.1 wt.% total organic carbon content) sample of Kimmeridge Clay (sample KC-1) was distributed to multiple laboratories for CLSM characterization. Findings from AFM include the observation that surface roughening or surface flattening of bituminite are induced by differential broad ion beam (BIB) milling and are dependent on the location and scale of AFM topology measurement. This result highlights our still limited understanding of the effects of BIB milling to sedimentary organic matter and indicates the need for further research before this technique can be advanced as a standard practice in petrographic sample preparation. Collectively, the results of this study illustrate the general applicability and versatility of AFM and CLSM as tools for organic petrology research, specifically for improved understanding of the nature and properties of the bituminite maceral.