Porosity Development in Quartz-Rich, Oolitic Limestones of Upper Arbuckle Group: A Response to Unloading

Deborah A. Ragland, Felicia Matthews

The upper Arbuckle Group of southern Oklahoma is composed of a thick sequence of carbonates deposited in shallow, epicontinental seas. Several concentrations of quartz sandy detritus, two of which are significant markers in outcrop, are found in the Kindblade and Cool Creek Formations. Both units are composed of varying amounts of quartz sand, ooids, peloids, clasts, and micrite matrix cemented by calcite, silica, and minor dolomite. After a complex postdepositional history of burial, tectonism, and uplift, removal of overburden resulted in relaxation of compressive forces and the development of microfractures between and within grains in the mixed mineralogy units. Equidimensional voids formed around the outer edges of syntaxial quartz overgrowths as calcite spar separated from silica spar. Relatively thin cortices pulled away from large nuclei esulting in spherical voids within ooids. Multiple microfractures in the radial cortices connect the inner spherical pores to interparticle porosity. A system of microfractures between crystal boundaries in the calcite cement links the pores. Porosity development varies laterally within the quartz sandy, oolitic units and is, in part, dependent on the original burial depth and the amount of overburden removed. Microfractures in subsurface units, if present, may not be as well developed. Alternatively, microfracturing may be enhanced as a result of subsurface dissolution.

AAPG Search and Discovery Article #91025©1989 AAPG Midcontinent, Sept. 24-26, 1989, Oklahoma City, Oklahoma.