GRAVITY AND MAGNETIC STUDIES OF THE DECATURVILLE IMPACT STRUCTURE, MISSOURI

The lithology of the structure and surrounding area is mainly Cambrian to Ordovician dolomites, limestones, sandstones and shales overlaying a Precambrian crystalline basement approximately 540m deep. The structure makes the surrounding geology interesting by exposing formations otherwise only exposed at the nearby St. Francois mountain range 115 km to the southeast. The impact area is distinguished by complex folding and faulting along with unusual brecciation. In general the region is typically flat lying; however the impact structure is positioned on the apex of a regional upwarp. Most dip angles outside the structure are low with isolated outcrops measuring up to 32°. The dipping beds do not define localized beds and are not structurally traceable because outcrops are scarce. It is more likely that the steeply dipping beds are influenced by the northwest trending Red Arrow fault and not related to the impact structure. Previous gravity studies indicate linear aligning maxima caused by topography within the Precambrian basement trending in a general northwestern direction. More detailed gravity studies indicate numerous elliptically-shaped minima including one in the center of the impact structure. Detailed gravity and magnetic data will be collected to determine the general structure of the crater. Analysis will include the construction of residual anomaly maps and two-dimensional models.