5-1 CD. Walcott — Cambrian Hocks of 



found. In the central portion of the Rome sandstone series 

 of the Cleveland section, 100 to 200 feet above the Olenellus 

 fauna, a few species of the Middle Cambrian fauna were found, 

 and higher up, in the shales and limestones above the sand- 

 stone, an abundant fauna that is now referred to the Middle 

 Cambrian zone. The same succession of faunas was found in 

 the section east from Post Oak Springs, Roane County, Ten 

 nessee. The Middle Cambrian fauna of the sandstone and 

 also of the superjacent shales was found in the section ten 

 miles east of Knoxville at Shook's gap through Bay's Mountain 

 where the section is similar to that west of Cleveland. The 

 same sequence of Middle Cambrian faunas was found in the 

 Knox sandstone and the superjacent shales immediately north 

 of Knoxville. Types of this fauna also occur in the Rome 

 sandstone series at Rome, Georgia, and in the limestones and 

 shales of the Coosa series, in Coosa Valley, north and south of 

 Cedar Bluff, Alabama. 



After returning from the field and when studying the faunas 

 from the Tennessee and. Coosa Valley sections, great doubt 

 arose as to the correctness of placing the Coosa shales beneath 

 the Rome sandstone in the stratigraphic section.* 



Dr. Cooper Curtice who had studied the formations of the 

 Coosa Valley, when collecting for the U. S. Geological Sur- 

 vey in 1885, was instructed to re-examine the sections of the 

 Coosa Valley and those to the south, in Alabama. This expe- 

 dition resulted in the discovery of the Olenellus fauna in the 

 shale in the vicinity of Montevallo, Alabama, and in obtaining 

 evidence showing that the greater portion. of the Coosa shales 

 and limestones of the Coosa Valley we're above the Rome 

 sandstone series. 



The data obtained during the field season enable me to cor- 

 relate and bring into their proper stratigraphic position the 

 collections that have been made by geologists and for the U. S. 

 Geological Survey from the Cambrian rocks of the Southern 

 Appalachians, and to establish the fact that during Middle 

 Cambrian time there was a great deposition of sediments that 

 now form a series of shales and limestones nearly 3,000 feet in 

 thickness. The Lower Cambrian is represented by the lower 

 portions of the Rome sandstone, the limestone immediately 

 subjacent and the series of variegated arenaceous and argilla- 

 ceous shales forming the base of the series. . A study of the 

 fauna shows that the typical Upper Cambrian fauna of the 

 Adirondack region of New York and the upper Mississippi 

 Valley area of Wisconsin and Minnesota, has not yet been 



* The Overthrust Faults of the Southern Appalachians. Bull. Geol. Soc. 

 America, vol. ii. February, 1891, p. 143, pi. 3; also, Bull. -XL S. Geol. Survey, No. 

 81, 1891, p. 304. 



