GIS ANALYSIS: A METHOD FOR STRUCTURAL INTERPRETATION AND MINERAL EXPLORATION

GIS mapping and analysis of surface structural features in the Louisville 30 x 60 minute quadrangle suggested the presence of an unmapped northeast-trending fault system in Jefferson County, Ky. Using digital geologic map data, this analysis generated a three-dimensional surface of the mapped structure contours in the Upper Ordovician. A northeast-trending fault system, which flanks a syncline, was delineated and subsequently confirmed by the discovery of a fault in the Rodgers Group’s Jefferson Stone Company Mine at Avoco in Jefferson County, Ky. GIS mapping of the compiled structure contours demonstrate an apparent dip to the west with a predominant north-south-trending strike. A deviation in the structure contours is evident south of the Ballardsville Fault in the Crestwood quadrangle area, southern Oldham County. This anomaly, called the Lyndon Syncline, begins as a pronounced structural depression with over 260 feet of local relief as mapped on the base of the Drakes Formation. Offsets in the strike and the dip direction of the contours in the Louisville East and Jeffersontown quadrangles, Jefferson County, indicate that an unmapped subsurface fault may extend southwest across the area from the Ballardsville Fault to the unnamed fault in Bullitt County. The unnamed fault is in line with a subsurface fault encountered in the mine in eastern Jefferson County, in the southeastern part of the Anchorage quadrangle, near Avoca. This north-trending subsurface fault contains post-mineralization slickensides, suggesting post-Paleozoic fault movement. The fault has 1-2 feet of displacement and is mineralized in the Middle Ordovician Lexington Limestone and brecciated Trenton Black River Group; it includes base metals containing barite, orange and greenish-black sphalerite, galena, and calcite. Vertical stylolites were also noted along the contact between the wall rock and vein deposit. Mineral emplacement along the fault adjacent to a large structural depression near the northern terminus of the Lyndon Syncline further suggests that Mississippi Valley Type ore bodies could exist along the western side of the Cincinnati Arch in deep carbonate rocks.