Origin of the "Cup and Saucer"

Date

1981

Authors

Baumgardner, Jr., Robert W.

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Abstract

The "Cup and Saucer" feature, named due to its resemblance to those utensils (W. J. Brown, 1980, personal communication), is located in southern Mitchell County, Texas. It is situated on private property but can be easily observed about 400 ft (122 m) east of State Highway 163 between Sterling City and Colorado City, 3.4 mi (5.4 km) north of the intersection of that highway with FM2183. The feature lies on the eastern edge of the Hyman NE quadrangle (scale 1:24,000, 7.5-minute series, U.S. Geological Survey, topographic maps), 0.75 mi (1.2 km) south of Beals Mountain. The feature will be described according to the following conventions. The "saucer" portion, which dips concentrically toward the center, will be referred to as the "lower ring." The "cup" portion, located in the center of the saucer, will be called the "core." The outcrops south of the lower ring, also capped by rocks dipping toward the core, will be referred to as the "outer ring."

This feature, long assumed to be a meteorite crater, exhibits characteristics that argue for another explanation. Firstly, the lower ring is capped with massive sandstone rocks that dip only gently (3°30' to 14°10') toward the core, which would not likely result from a violent meteorite impact. Secondly, abundant black stones scattered on the upper surface of the saucer are cemented with iron oxide but are neither fragments of a meteorite nor fused by the heat of an impact. Instead, they appear to be concretions formed in the vadose zone when the ring was still buried by younger sediments and the local water table was higher. Thirdly, if this feature were an ancient impact structure, the core would be composed of breccia created by the meteorite impact. However, the core is composed of friable fine-grained sandstone, volcanic ash, and fluvial gravels, none of which are brecciated.

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