Carbonate Facies of the Swope Limestone Formation (Upper Pennsylvanian), Southeast Kansas

Abstract

The Swope Limestone Formation is composed of three members. The basal member, the Middle Creek Limestone, is a thin uniform biomicrite that is known to be present only in the northern part of the Kansas outcrop. The overlying Hushpuckney Shale, composed of black, fissile shale overlain by gray, blocky shale also is known to be present only in the northern part of the outcrop. The Bethany Falls Limestone Member, uppermost member of the Swope, is composed of three facies in the northern part of its Kansas outcrop belt. Here the lower part of this member is composed of (1) biomicrite containing a diverse marine biota, including abundant phylloid algae fragments. This unit interfingers southward with (2) less fossiliferous, color-mottled biomicrite. An oolite-pelletoid facies (3) composed of oosparite, oomicrite, pelsparite, and pelmicrite overlies the biomicrite and mottled biomicrite facies. An algal mound complex composed of phylloid algal biomicrite is present in the southern part of the outcrop belt. South of the mound complex in the extreme southern part of the outcrop belt, a thin dolomitic subfacies of the biomicrite facies, laterally equivalent to the mound complex, wedges out into the detrital sedimentary rocks of overlying and underlying formations.

Ubiquitous distribution of phylloid algae indicates all limestones of the Swope formed in shallow water. The presence of oolitic limestone in the upper part of the Bethany Falls Member overlying biomicrites with a normal marine fauna suggests that shallowing of marine waters took place during deposition of the member. The distribution of subfacies in the oolite-pelletoid facies is analogous to the distribution of facies belts in modern oolitic carbonate sediments on the Bahama Platform west of Andros Island. Oosparites at the southern end of the outcrop belt of the facies resemble tidal bars and marine sand belts along the edge of the Bahama Platform. Oomicrites, pelsparites and pelmicrites in the northern part of the outcrop belt resemble the platform interior sediments of the Bahama Platform. Dolomitic micrites found in Iowa at the extreme northern edge of the Bethany Falls outcrop belt resemble shallow intertidal to supratidal sediments found on the west side of Andros Island.