Sedimentary features, occurrence, and cyclicity of microbialite facies in the Roubidoux and Jefferson City Formations of Missouri and Kansas

Outcrop studies of sedimentary and stratigraphic features of microbial buildups are important in developing conceptual models for exploration of potential microbialite reservoirs. This study examines the occurrence and distribution of Lower Ordovician microbial fabrics in central Missouri and Kansas. The units studied include the Roubidoux, Jefferson City, and Cotter Formations of the Arbuckle Group. To determine the depositional environments suitable for microbialite development, micro-, meso-, and macroscale features were examined, and their stratigraphic relationships were established to the surrounding lithofacies. Microscopic-scale analysis reveals heavy dolomitization of strata; however, remnant depositional features provide vital clues about the microbialite development. The occurrence of microbial structures is placed within a cycle stratigraphic framework. The microbialites occurred within cyclical shallow-marine deposits and are grouped into three cycle types. Type 1 deposits include subtidal mudstones to packstones that grade into intertidal stromatolites. Type 2 deposits are composed of subtidal mudstones and packstones with thrombolite fabrics that grade into supratidal facies. Type 3 deposits include intertidal or supratidal facies that grade into supratidal facies.