GEOCHEMISTRY OF THREE THIRTY-EIGHTH PARALLEL STRUCTURES IN SOUTHERN MISSOURI: CROOKED CREEK,DECATURVILLE AND WEAUBLEAU IMPACT STRUCTURES

The alignment of seven suspected impact-related geologic structures along the thirty-eighth parallel in Illinois, Missouri and Kansas has intrigued geoscientists for decades. The timing of their formation and whether the structures were related to one meteorite impact event or a series of impacts is unclear. This study focuses on core and outcrop samples from the center and crater rim from three of these complex craters in Missouri, namely Crooked Creek, Decaturville and Weaubleau. Bulk rock geochemical analyses, including major element, trace element, rare earth elements and platinum group elements of breccia and other impactites are being used to provide: (1) chemical characterization of rock types present at impact; (2) trace meteoritic components present (i.e., above average terrestrial crustal abundance); and (3) siderophile element abundances and ratio of elements to differentiate impactor composition and type. These results will enable the comparison of the geochemical signature of the impactors to determine if the impact craters have a common progenitor.

Keywords: impact craters, impactor geochemistry, Crooked Creek, Decaturville, Weaubleau, 38^th parallel