Anatomy of a phylloid algal buildup, Raytown Limestone, Iola Formation, Pennsylvanian, Southeast Kansas, U.S.A.

Abstract

Quantitative petrography and temporal-spatial relationships of microfacies were used to interpret the depositional history of Iola carbonates. The Paola Limestone, consisting of four microfacies, was deposited on a carbonate ramp and appears to record the maximum transgression within the Iola cycle of deposition. The overlying Raytown Limestone was composed of nineteen microfacies arranged in three vertically successive depositional models of similar general configuration. These models revealed an initial bioclastic bar evolving upward into a complex bioaccumulated-bioconstructed phylloid algal buildup. The latter was replaced landward by a siliciclastic distal deltaic environment and graded basinward into upper ramp and lower ramp carbonates. Locally, restricted circulation caused the development of hypersaline conditions. The shallowing-upward depositional evolution of the phylloid algal buildup consisted of four distinct stages: bioclastic (hydrodynamic buildup), bioaccumulation, bioconstruction, and bioclastic (destruction in storm-dominated conditions and intermittent emergence). Diagenesis of Iola microfacies was complex and included: marine phreatic 1 (bioturbation, syneresis, micritization, micrite lithification, and hardground genesis; freshwater vadose—phreatic undersaturated 1 (dissolution of evaporites, moldic dissolution, collapse brecciation, and vadose silt infiltration); marine phreatic 2 (isopachous rim and botryoidal cementation); freshwater phreatic saturated 2 (sparite cementation, and extensive neomorphism); deep burial (anhydritization, dolomitization, stylolitization, and silicification); and late uplift (fracturation and cementation). Most of the diagenesis was microfacies specific.