Road Log

Abstract This road log runs from the southern edge of Ironton-Arcadia, Missouri, east across the southern portion of the st. Francois Mountain igneous terrane to Cottoner Mountain, a few miles east of the village of Cherokee pass on u.s. Highway 67 south of Fredericktown, Missouri (Fig. 1). All stops are either roadcuts or National Forest lands and are fully accessible. The route of the road log emphasizes the diversity of the terrane and includes rhyolitic ash flows and lavas, andesitic (trachyandesite) lavas, and both mafic and granitic dikes. Stratigraphically, the volcanics are older to the east although individual stops are not arranged in exact descending order. With the exception of the Lake Killarney and Grassy Mountain tuffs (Sides, 1978), all rock unit names are informal and reflect our recent remapping of the region. Only the Des Arc NE quadrangle geologic map, stops 1-3, has been published (Brown, 1988). The Rockpile Mountain, Cherokee Pass and Marquand quandrangle maps will be compiled and released through the Geological Survey, Missouri Department of Natural Resources, over the next 2-3 years (see Brown, this volume, fig. 5., p. 104), and others in the more southern portion of the mountains will follow. A formal stratigraphy will be compiled at a later date.