163-4 Confirming an impact origin of Weaubleau structure, Missouri, USA

Session: Impact Cratering Processes Across the Solar System: In Memory of Dr. Bevan M. French

Presenting Author:

Authors:

Abstract:

The Weaubleau structure is located in southeastern St. Clair County in west-central Missouri between the towns of Collins and Vista. Two large circular features are associated with the impact: an 8-km ring-like drainage feature and an outer 19-km-diameter drainage feature that is eccentric to the smaller one. We interpret the smaller feature as the impact crater. The larger eccentric ring contains unusual deformational features such as broken folds and thrust faults in the middle Mississippian (Osagean Stage) Burlington-Keokuk Limestone, the uppermost target rock succession. The structure partly is overlain by undeformed lower Pennsylvanian strata that have helped preserve the deformed section below.

Planar deformational features (PDFs) in quartz grains from the uppermost  breccia from the Weaubleau structure occur along rational, low index planes, most commonly {10 1 2 }, {10 1 1}, and {10 1 3}.  We identified 39 grains with a total of 93 PDF planes. This is consistent with interpretation of a meteorite-impact origin. Quartz grains also contain abundant Planar Fractures, consistent with similar features in rounded quartz grains from the Rock Elm impact structure, and interpreted to have formed associated with the impact event. Other investigators (Morrow and Evans, 2007) reported similar results from isolated quartz constituents from the upper breccia from Weaubleau, but sadly Morrow passed away in 2010 before a manuscript was completed.

     Impact breccias are present in road cuts and outcrops around the crater. Several drill cores have been collected from within and around the structure as well, most locations were chosen with a focus on testing hypotheses related to the stratigraphy of the structure. The MoDOT-SMSU Vista 1 core recovered granite clasts in a conglomerate with a mixed limestone and siliciclastic matrix. This indicates that the impact penetrated to basement and that basement in this one core is at least 400 m higher than basement near Osceola on the northern perimeter of the outer ring. Two cores have penetrated impact breccia to a maximum of 320 ft (97.5 m), but the base of the breccia has not been reached.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9507

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