A PRELIMINARY IN SITU AND BASIN-WIDE 10BE TCN STUDY OF THE STE. FRANCOIS AND OZARK MOUNTAINS LANDSCAPE

The Ozark Mountains, Missouri and Arkansas, pose a major geologic and geomorphic anomaly. They form a topographically high, structurally uplifted “block” that exposes buoyant (?) mid-Proterozoic granite-rhyolite basement rocks in the North American mid-continent. The Ste. Genevieve fault bounds the Ozarks on its steepest and structurally highest northeastern side. We are using 14 precisely surveyed in situ terrestrial cosmogenic ¹⁰Be samples of multi-level strath terraces in “shut-ins” (Precambrian bedrock canyons) that span east to west the core of the Ozark dome (i.e. the Ste. Francois Mountains) to determine river incision rates and exposure ages and to test whether uplift is symmetric or asymmetric across the Ozarks. Sample analysis is in progress. We will then perform a basin-wide ¹⁰Be analysis to compare the effects of lithology on erosion, and to gauge overall (basin-wide) versus local (shut-ins) erosion rates. We incorporate additional tectonic geomorphic data, obtained from DGPS surveys, high resolution DEMS, created using GIS, and detailed geomorphic maps, to identifying active knick-point migration, zones of anomalous stream steepness, etc. and to place the exposure ages, erosion/incision rates, and exhumation rates in the context of this unique landscape.