STRUCTURAL INSIGHT INTO IMPACT TRAJECTORY THROUGH MAPPING THE GEOLOGY OF THE KENTLAND IMPACT STRUCTURE

The Kentland Impact Structure in northwestern Indiana, USA, represents the heavily eroded remains of a complex impact crater approximately 12.5 km in diameter. Regionally the strata are sub-horizontal with a dip of approximately 1º to the southwest. Exposures of the structure are confined to those of the central uplift, accessible in the Newton County Stone Quarry, east of Kentland, Indiana, where mining operations have been occurring since the late 1800s. Continued quarry operations have further exposed the deformed and displaced strata that exhibit unique structural features associated with an impact event.

A geologic map of the previously exposed portion of the central uplift within the quarry was published by Gutschick (1987) and displays a trend of structural features oriented in a manner consistent with bilateral symmetry. Studies of other complex impact structures have suggested this type of symmetry in complex impact structures is the result of low-angle (oblique) impacts. Since the publication of Gutschick’s (1987) map, quarry exposures have approximately doubled, presenting an opportunity to extend the original mapping and further assess the apparent bilateral symmetry and the original trajectory of the impactor.

This research seeks to map more recent exposures and assess the hypothesis that the Kentland Impact Structure represents an oblique impact event, in which the impactor originated from the north-northwest or south-southeast direction (in present-day bearings) as the Gutschick (1987) map suggests. Structural data were collected, and stratigraphic units were identified during targeted field excursions, then compiled and combined with analysis of high-resolution imagery and core data to investigate and map parts of the field area that were either inaccessible or more difficult to access while in the field. The data will be integrated into mapping software such as ArcGIS Pro to create an updated geologic map that incorporates data from this research and a digitized version of Gutschick’s (1987) map. This updated geological map will offer a new view of the Kentland Impact Structure, as well as increase our understanding of complex impact structures.