Petrology of Arbuckle Group, Central Kansas: ABSTRACT

Abstract

The Arbuckle Group (Late Cambrian and Early Ordovician) in Kansas is mostly crystalline dolomite with abundant chert in the upper part. The Arbuckle is entirely in the subsurface, and there are only scattered cores, mostly from the upper part. Depositional constituents and textures have been reported only from the chert. Study of thin sections from three cores from the Central Kansas uplift reveals abundant evidence of depositional components, as well as diagenetic features of dolomitization and porosity. Despite virtually complete dolomitization, it is often possible to identify primary grain types, fabrics, and textures, and by comparison with better preserved examples, to interpret less well-preserved features. Identifiable grain types include oolites, pellets, intraclasts (of micrite, pellets, and oolites), and skeletal grains, including gastropods, echinoderms, and bivalves. Crenulate, laminated dolomite, interpreted as stromatolites, recurs. Depositional textures range from mudstone to packstone. The dolomite is microcrystalline to coarsely crystalline, with porosity ranging erratically from 1 to 22%. Pore types are: (1) intercrystal (most common), supplemented and interconnected by (2) solution-enlarged fractures, (3) moldic, from solution of depositional grains, (4) fenestral, and (5) primary interparticle. Partly dissolved dolomite crystals have collapsed, compacted, and probably contributed to fracturing. Small, closely spaced fractures may be open or plugged by crystals mobilized from surrounding dolomite, thereby isolating bodies of dolomite with high intercrystal porosity. Laminae of low-porosity dolomite, presumably controlled by depositional texture, contribute also to porosity variability. Most large pores are reduced by dolomite cement. Other scarce cements are anhy rite and sparry calcite, which fills oomolds and fractures. End_of_Article - Last_Page 960------------