20 SMITHSONIAN INSTITUTION 



riclges are developed along the outcrop of resistant formations and 

 are separated from each other by parallel valleys etched on the lime- 

 stones. In the process of folding, the rocks often cracked, and large 

 plates were shoved long distances from the southeast. These thrusts, 

 as the geologists call them, bring younger rocks over older ones and 

 thus tend to complicate the true relationships of the strata and their 

 contained fossils. In the Southern Appalachians these thrusts have 

 brought into superposition rocks originally deposited in widely sepa- 

 rated parts of the same sea. Full understanding of this region thus 

 depends on the recognition and correct interpretation of the thrust- 

 plates. 



Investigations and collecting were begun about 18 miles southwest 

 of Montevallo, Ala., at Pratts Ferry, where the Paleozoic structures 

 disappear under the flat-lying Cretaceous sediments of the Coastal 

 Plain. From here the party proceeded northeastward to Pelham, Bir- 

 mingham, Odenville, and Leeds, Ala. More specimens were collected 

 in northeastern Georgia on Chickamauga Creek and at Rock Springs 

 south of Chattanooga. 



From Chattanooga the party moved north to the long and narrow 

 Sequatchie Valley, where a fine Ordovician sequence containing many 

 Stones River fossils occurs near Pikesville. East of Athens, Tenn., 

 a great belt of Ordovician rocks runs northeastwardly to Knoxville. 

 The party followed this belt from Riceville through Friendsville, col- 

 lecting fossils and noting the lateral passage of the shales at Rice- 

 ville into limestone at Knoxville. After collecting trilobites at Bulls 

 Gap northeast of Knoxville, the party moved northwestward to Cum- 

 berland Gap for a few days to study the limestones of the upper 

 Blount and Black River groups. 



In southern Virginia fossils were collected from the Blount shale 

 belt running northeast from Gate City. Fast of Saltville, Va., a large 

 quarry exposes a reef or bioherm at the base of the Blount, in which 

 echinoderms and other fossils are especially abundant. Collections 

 were also taken from the Stones River beds at Marion, near Salem 

 and Lexington, where fossils occur loose in residual soil. Xear Har- 

 risonburg fossils were collected east of the city and at places along 

 United States Highway 1 1 as far north as Strasburg. The high Black 

 River beds at Strasburg abound in good fossils. 



The writer was particularly interested in finding silicified fossils ; 

 for these can be freed from their limestone matrix by dissolving the 

 enclosing rock in acid. Many specimens thus preserved were obtained 

 on this trip, and the Southern Appalachians proved to be a rich 

 source of fine fossils. 



