CHARACTERISTICS OF EXPOSURES EXAMINED. 195 



two feet or more in diameter, is entirely embedded in the shaly lime- 

 stone. This bowlder, as shown in plate 6, was evidently deposited on 

 the bed of the sea and the calcareous mud gathered quietly about it- 

 At about the same horizon, in a quarry on the east side of York, a mas- 

 sive bed of limestone conglomerate is beautifully shown. A photograph 

 of it is reproduced as plate 7. 



The quartzites, shales and limestones beneath these beds of conglom- 

 erate are known to carry the Lower Cambrian or Olenellus fauna ; and 

 the same fauna, with the exception of details of variation of species, 

 occurs in the limestones and shales above the congiomerates, thus plac- 

 ing the latter within the definition of intra-formational conglomerates. 



Virginia Localities. — Mr M. R. Campbell^ informs me that in the vicinity 

 of Radford, Virginia, there is a formation that appears to be a true intra- 

 formational conglomerate. He states that it is in the great Cambro- 

 Silurian limestone, and consists of a yellowish white, chalky limestone 

 matrix, in which are embedded rounded fragments of limestone that 

 are similar in composition to the matrix, and that can only be distin- 

 guished from it with difficulty. A few small grains of foreign material 

 were observed. The exact stratigraphic horizon could not be determined, 

 owing to the complexity of the structure and the poor exposures. Two 

 miles below Radford the actual contact was observed between the con- 

 glomerate and the bedded limestone, where the former rests on the cut 

 edges of the folded limestones beneath. Mr Campbell believes this in- 

 dicates shore conditions, contortion of the limestone deposits and their 

 elevation above sealevel, to form cliffs that supplied material for later 

 beds of the same great formation. 



Another case of this kind was observed by Mr Campbell at a horizon 

 northwest of Bristol, Virginia. He found that here the conglomerate 

 occurs in a bed of shaly limestone, but a few feet thick, that belongs in 

 the Nolichucky (Cambrian) shales. This bed appears to have been 

 broken up largely into flat fragments that were quite well worn on their 

 edges, and then redei)osited in the same bed and cemented into a solid 

 mass of limestone. The peculiar feature of this deposit is its extreme 

 thinness and the apparent freedom from all marks of erosion. It is quite 

 l)ersistent and no evidence of an unconformity was observed. 



Tennessee Localities. — The intra-formational conglomerates already de- 

 scribed have been identified as such by the presence of similar fossils in 

 the bowldei-s of the conglomerate and the supeijacent and subjacent 

 bedded limestones. Those about to be described are identified entirely 

 by lithologic characters. These, however, are so clearly defined and are 



♦Paleozoic Overlaps iu Montgomery and Pulaski Counties, Virginia: Bull. Geol. Soc. of Am., 

 vol. 5, pp. 175-176, 



