A TATTERED TAPESTRY: INTERPRETING REMOTE SENSING IMAGERY OF THE OZARK MOUNTAINS

The Ozarks and surrounding borderlands are an ancient landscape that has recorded many geologic events. Remote sensing imagery has been instrumental in the re-discovery of several geologic structures and geomorphic features in the region. Digital elevation models (DEMs) and shuttle radar topography mapping (SRTM) data highlight structural lineaments, regional faults zones, and many other features that have been known for decades, but the advent of imaging tools has made it possible to re-examine and enhance our understanding of the geology, structure, and the resulting landscape evolution.

At least three impact structures are known in southern Missouri: Crooked Creek, Decaturville, and Weaubleau. New and existing geologic maps, together with computer elevation modeling, provide information on the depth of erosion over each structure. Crooked Creek structure has a topographic expression of concentric ridges around a central lowland. The central uplift area, which corresponds with this lowland, is poorly defined over all but the southeastern margin. The central uplift at Decaturville is topographically high with a central depression. The crater moat is generally lower in elevation and deeply incised on its western edge. Both Crooked Creek and Decaturville have shatter cone fields exposed at the surface; these features typically form at depth, suggesting that both structures have been deeply eroded. A few exotic blocks of mid-Mississippian sandstone are present at Crooked Creek, but overlying strata that could bracket the age are missing and presumably were removed by erosion. The central uplift of Weaubleau structure is similar to Decaturville, but thick deposits of breccia blanketed the central uplift and part of the crater moat. Overlying undeformed Mississippian residuum and Pennsylvanian siliciclastics place a upper limit on the age of impact and have protected the structure from extensive erosion.

A large abandoned valley, 40 km long and 2.5 km wide, re-discovered in western Missouri, which is referred to as El Dorado Valley, is enigmatic. The age and origin of this feature are unknown, but it clearly cuts Pennsylvanian strata and pre-date modern stream incision. Flood modeling on the present-day landscape breaches low areas between the Missouri and Arkansas drainage basins very near this feature.