The significance of crypto- and macrobioturbation in the New Albany Shale for the interpretation of depositional histories: An integrated approach using core descriptions, CT scans, neoichnology experiments, and geochemistry

An integrated method of core descriptions, neoichnology experimentation, X-ray computed tomography (CT), and geochemistry was used to observe and evaluate macro- and cryptobioturbation in the Selmier and Camp Run members of the New Albany Shale. The purpose of this dissertation project is to examine relative sedimentation rates, substrate consistency, and interpret relative bottom-water oxygenation from observations of lithology, redox and clastic proxies, burrow morphologies and abundances, ichnodiversity, and three dimensional arrangement of bioturbation in several transects across the Illinois Basin. The redox proxy Mn and the clastic proxies Si/Al and Ti/Al were used to evaluate relative bottom-water oxygenation, relative proximity to the shoreline, and reworking of sediments. Ichnogenera and other biogenic structures identified include Chondrites, Palaeophycus, Planolites, Scolicia, Teichichnus, Thalassinoides, Zoophycos, graphoglyptids, cryptobioturbation and biodeformational structures. CT scans aided in identifying burrows associated with diagenetic pyrite such as Palaeophycus, Planolites, and graphoglyptids. Cryptobioturbation was identified as a fabric of subtle, blurry sediment contacts. The Selmier Member has a large ichnodiversity (8 ichnogenera), large abundance of total burrows in all cores (152 burrows observed), large abundance of biodeformational structures, contains calcite shell material (brachiopods), and smaller proportions of black vs gray beds. These observations suggest low sedimentation rates (<1 cm ky-1), water-rich substrates (~90% water by volume), and high relative bottom-water oxygen concentrations (~1.0 mL O2 l-1 H2O) for extended time periods. The Camp Run Member has a lower ichnodiversity (7 ichnogenera), lower abundance of total burrows in all cores (99 burrows observed), lower abundance of biodeformational structures, a greater abundance of graphoglyptids and cryptobioturbation, and higher proportions of black vs gray beds when compared to the Selmier Member. These observations suggest intermittently higher relative sedimentation rates, a generally firmer substrate, and lower bottom-water oxygenation with shorter durations of dysoxic conditions. On proximal (shallower) to distal (deeper) basin transects in both the Selmier and Camp Run members, the thickness of bioturbated beds, the abundance and diversity of burrows, decrease due to lower bottom-water oxygenation.