GEOLOGIC MAPPING AND FRAMEWORK STUDIES APPLIED TO FEDERAL LAND-MANAGEMENT ISSUES IN THE OZARKS OF MISSOURI

When federal land managers are required to make decisions that will affect the future domestic supply of base-metal raw materials and the potential integrity of world-class natural resources, they MUST have the most accurate, unbiased scientific data upon which to base their decisions. As part of a USGS multi-discipline scientific team, the main objective of the Ozark Geologic Mapping Project has been to provide such data in an area of southern Missouri, where there is a desire to develop known extensions of the Viburnum Trend (largest lead-mining district in the world) on National Forest Land. This is a karst region and is within the recharge area for some of the world’s largest and most scenic spring systems, many of which are under the jurisdiction of the National Park Service and the U.S. Forest Service. This project is producing detailed geologic maps for fifteen 7.5’ quadrangles, reconnaissance geologic maps for two 100,000-scale sheets, and a 3-D geologic framework that is based upon the mapping and integration of subsurface data. This information will contribute significantly to the understanding of the natural hydrogeologic system, as well as karst processes active in the area, and will allow for a better assessment of potential effects of exploration and mining on the environment. Noteworthy results of the geologic mapping-framework study to date include: the identification of a very important control on ground-water flow, spring locations, and loci of mineral deposition that is exerted by the relatively impermeable protrusions of igneous basement rock into regional carbonate aquifers; the identification of sedimentary facies and stratigraphic controls on the formation of major cave systems, which are conduits for the large springs; and the delineation of many previously unknown faults, one of which influences a recharge divide between the two biggest springs in the area.