KWRRI Research Reports


Factors controlling the porosity and permeability of the Curdsville Limestone Member of the Lexington Limestone of Middle Ordovician Age in the Blue Grass Region of Kentucky are geological.

Microstratigraphic analysis had led to the division of the lower Lexington Limestone, consisting principally of the Curdsville Member into three beds which may be subdivided into "zones" made up of several lithologic types and sub-types. Lower, middle, and upper bed characteristics are helpful in determining the regional depositional history in the progressively transgressing Curdsville sea. Paleogeography of Curdsville time has been determined by delineation of two local facies: (1) a carbonate bank--shoal area facies, and (2) a shelf--channel area facies.

Permeable carbonate bank--shoal facies are best developed on the structurally high Jessamine Dome Shoal Area where the Curdsville Limestone is found at shallow depth. Ground waters of meteoric origin have created sink holes, solution valleys, and caverns through solution enlargement of fractures comprising an extensive intersecting joint system.

Detailed examination of the Bryantsville Quadrangle on the Jessamine Dome Shoal Area indicates that "fracture traces" such as sink hole, solution valley, and stream channel alignments are controlled mainly by nearly vertical joints in the Curdsville and underlying Tyrone Limestones. High frequency and intersection of joint fractures may indicate the presence of permeable limestone aquifers at shallow depth, The hypothesis can be tested by drilling several wells in prospective areas.

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The work upon which this report is based was supported in part by funds provided by the United States Department of the Interior, Office of Water Resources Research, as authorized under the Water Resources Research Act of 1964.