256 



STRUCTURAL GEOLOGY OF NORTH AMERICA 



and the Cambrian sediments need not necessarily contain the Kewee- 

 nawan lithologies. 



CRYPTOVOLCANIC OR METEORITE IMPACT STRUCTURES 



Definition 



Eight small circular structures, one of known volcanic origin, and the 

 others supposedly of volcanic origin, have been mapped in the Central 

 Stable Region of the United States, and possibly a ninth one in the 

 Colorado Plateau of Utah. See map of Fig. 16.1. They are described by 

 Bucher (1933) as characterized by a nearly circular outline, a central 

 uplift with intense structural derangement, and a marginal, ring-shaped 



Fig. 16.1. Cryptovolcanic or meteorite impact structures in the United States. 1, Jeptha Knob, 

 Shelby County, Ky.; 2, Serpent Mount structure, Adams and Highland counties, O.; 3, Flynn 

 Creek disturbance, Tenn.; 4, Wells Creek basin, Houston and Stewart counties, Tenn.; 5, 

 Decaturville structure, Camden and Maclede counties, Mo.; 6, Kentland structure, Newton 

 County, Ind.; 7, Magnet Cove, Hot Springs County, Ark.; 8, Upheaval dome, San Juan County, 

 Ut. After Bucher, 1933. 9, Manson, la. 



Fig. 16.2. Geologic map of the Wells Creek basin, Tenn. Reproduced from Bucher, 1933. 1, 

 Wells limestone (L. Ordovician); 2, mid-Ordovician limestone; 3, Hermitage formation (mid- 

 Ordovician); 4, Silurian and Devonian formations; 5, Lower Mississippian formations; 6, War- 

 saw limestone (mid-Mississippian); 7, St. Louis limestone (mid-Mississippian); 8, alluvium. 



