Abstract
Recognized meteorite impact features are relatively rare in the U.S. Midcontinent region, but recently with increased interest and research, the number has increased dramatically. We add another possibility to the growing list, the Edgerton structure in northwestern Miami County, Kansas. The feature is elliptical (∼5.5 × 6.5 km, slightly elongated east-west) with radial surface drainage. The feature was first observed on hillshade maps of digitized topography of 7.5 minute quadrangles. Subsequent magnetic profiles show a higher magnetic value in the center of the ellipse with higher values around the edges; this shape is characteristic of an impact feature. Depth to the anomalous body is estimated to be about 1 km, which puts it in the Precambrian crystalline basement under a cover of Paleozoic sediments. There are no deep boreholes in the vicinity and no seismic profiles are available. If it is an impact structure, it will be the second such feature documented in Kansas, the first being the Brenham meteorite crater at Haviland in Kiowa County in southwestern Kansas. It would be older than the other impact structures identified in the Midcontinent—Manson in Iowa, Ames in Oklahoma, Haswell Hole in Colorado, and possibly Belton in Missouri and Merna in Nebraska. There are at least two other prospective impact features in Kansas: the Goddard ring west of Wichita and Garden City ellipse north-west of Garden City.
Highlights
Circular, oval, or elliptical features, observed on airphotos, remote-sensed images, topographic quadrangle maps, hillshade maps, or on the ground in the field, may be the result of several independent or combination of factors
There are at least five causes of physiographic circular features: (1) erosion widens a valley and closes the open end giving an illusion of a circular feature, for example, Cheyenne Bottoms in Barton County, (2) solution of material and collapse of overlying material to form a sinkhole, for example, Old Maids Pool in Wallace County, (3) meteorite impact feature, for example, Haviland crater in Kiowa County, (4) buffalo wallows—formed by animals and enlarged by wind, with many examples on the High Plains [1], (5) dish-shaped structure with compaction of overlying sediments
A followup magnetic profile is highly suggestive of a circular feature with a rim and central high, which could indicate that it is an impact feature
Summary
Oval, or elliptical features, observed on airphotos, remote-sensed images, topographic quadrangle maps, hillshade maps, or on the ground in the field, may be the result of several independent or combination of factors. (3) meteorite impact feature, for example, Haviland crater (the term crater is used here in the sense of a meteorite impact feature and does not necessarily imply a surface depression) in Kiowa County,. Many meteorites have been found and catalogued in the state, only one meteorite feature has been identified and recorded, the Brenham crater near Haviland in Kiowa County in southwestern Kansas [10]. Circular and radial drainage patterns on the surface may reflect circular features in the subsurface in Kansas [12]. We suggest that there are several intriguing such features in Kansas recognizable on topographic, hillshaded, and other maps that with detailed study may prove to be impact features (Figure 1; [13]). A followup magnetic profile is highly suggestive of a circular feature with a rim and central high, which could indicate that it is an impact feature. No subsurface data or seismic profiles are located close enough to confirm our preliminary identification
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