Kansas Geological Survey, Open File Report 96-50
The Morrowan interval in the Minneola complex varies in thickness from 5 to 120 ft. (2 to 37 m.). It unconformably overlies the Mississippian age Ste. Genevieve Limestone and occurs below the 13-Finger Limestone where present, or the Inola Limestone (Fig. 2). The productive sandstones in the Minneola complex are lenticular and up to 15 ft. (5 m.) thick. These sandstones are interbedded with shales and siltstones that can form both source and seal for the sandstones. In some cases a conglomeratic sandstone up to 20 ft. (6 m.) thick occurs at the base of the Morrowan section. Porosities in the tight sandstones vary from 1-4% while those in the productive sandstones vary from 12-18%.
Figure 2--Idealized stratigraphic section for the Minneola complex (from Clark, 1995). Productive Morrow sandstone is indicated in yellow.
Although the uppermost productive Morrowan sandstones are generally thicker, more porous and better preserved in the fluvial paleochannels, they are not necessarily limited to them (Fig. 3). However, the sandstones are concentrated along northwest-southeast barrier bar trends that intersect the channels. These barrier bar trends represent stillstands in a generally transgressive episode, with shale or other non-productive units deposited between the trends. These sandstones were deposited during a final transgressive phase. Earlier transgressive-regressive cycles resulted in the deposition of conglomeratic basal sandstones, siltstones, marine shales, and sporadically distributed lower and middle nonproductive Morrowan sandstones. Later transgression covered the barrier bar sandstones with marine shale and limestone (Fig. 2).