File:Breakdown detachment surface (Ohio Caverns, western Ohio, USA) 3 (30863440846).jpg

Ohio Caverns is the largest cave system in Ohio. It is located in a bedrock knob called Mt. Tabor on the southern side of the Bellefontaine Outlier (= Ohio's elevationally highest area). The cave is hosted in the Middle Devonian Columbus Limestone, which is part of a widespread shallow marine carbonate succession in eastern and midwestern America.

The cave ceiling shown above is a breakdown detachment surface. Small to large blocks of rock that fall down from ceilings or upper walls in caves are called breakdown. Such rocks sometimes form large piles that can block entire cave passages. The surface in the photo is not an ordinary bedding plane - it's a stylolite. Stylolites are pressure dissolution surfaces. They represent surfaces where some limestone was dissolved away. Stylolites can be present in limestone, marble, and dolostone. In cross-section view, stylolites make a jagged up-and-down pattern, somewhat like a seismographic recording of an earthquake. In bedding plane view, they are non-planar and rough. Crusts of insoluble material are frequently present at stylolite surfaces. Dissolution occurs in the first place due to pressure from the weight of overlying rocks.

At Ohio Caverns, breakdown detachment principally occurs along stylolites, but non-stylolite bedding planes are also breakdown surfaces.

Locality: Ohio Caverns, Mt. Tabor, east of the town of West Liberty, northern margin of Champaign County, western Ohio, USA

For a recent technical article on the geology of Ohio Caverns, see: