GEOLOGICAL MAPPING, AND KINEMATIC-FAULT-SLIP AND GIGAPAN™ IMAGE ANALYSIS, KENTLAND IMPACT STRUCTURE, INDIANA, USA

The Kentland (Newton County Stone) quarry exposes anomalously steeply dipping, highly brittlely deformed, Ordovician-Silurian sedimentary rocks in the central uplift of a ~13 km diameter, ~<97 Ma complex crater, that is deeply eroded and shallowly buried. We are working to determine the kinematics and relative timing of faults bounding associated megablocks in the central uplift of this impact structure. Rocks in the quarry and subsurface were previously studied and mapped in detail in the 1960s-1980s by Prof. Ray Gutschick (Notre Dame). Quarry expansion has created many new exposures (e.g. pits 7 and 8) that we have recently mapped and are studying. During field mapping we collected fault-slip and bedding orientation data. Preliminary fault-slip analyses in pit 8 indicate that there are three distinct fault groups: 1) ~E-W striking, north-dipping, bedding parallel faults, 2) steeply southward dipping, ~E-W striking, reverse faults, and 3) steep, NE-SW striking, oblique- and strike-slip faults. We also shot and stitched together ~3000 photos into Gigapan^™ photo mosaics to map and study the inaccessible high walls in the quarry, to modify and improve our geological maps, and to better understand fault geometries and chronologies. We will apply forward modeling of general complex crater development to place fault groups into a viable and sensible chronology. We will compile available subsurface data and combine this with our quarry "outcrop" maps and data to better understand the size, shape, and nature of the crater megablocks.