COMPILATION MAP OF THE PRECAMBRIAN ROCKS OF THE CENTRAL ST. FRANCOIS MOUNTAINS, MISSOURI

The St. Francois Mountains in southeast Missouri are a Mesoproterozoic terrane composed of granitic intrusives, silicic ash-flow tuffs, lava flows and other rhyolites associated with caldera collapse. The terrane is the center of a large lead mining region and hosts a previously active iron mining district. The Compilation map of the Precambrian rocks of the Central St. Francois Mountains, Missouri is centered on three postulated calderas: Taum Sauk caldera, Butler Hill caldera and Lake Killarney caldera. It is a seamless, spatial representation of twenty-one geologic maps published from 1908-1996 that range from 1:24,000 to 1:125,000 scale. The data is sourced from maps found in Missouri Geological Survey publications, U.S. Geological Survey publications, student theses and dissertations, unpublished maps housed in Missouri Geological Survey archives, and journal publications. The last published geologic map of the St. Francois Mountains was produced in 1979 by the U.S. Geological Survey entitled “Geologic map of exposed Precambrian Rocks, Rolla 1° x 2° Quadrangle, Missouri.” The compilation map presented here includes mapping completed after 1979 as well as details not featured in the 1979 U.S. Geological Survey publication. This compilation map can provide new insight into the complex geology of this Mesoproterzoic terrane of Southeastern Missouri.