10 CD. Walcott — Cambrian Rocks of Pennsylvania. 



discovered by the Pennsylvania survey that indicate the Tren- 

 ton horizon. I think it is only a matter of detailed search and 

 patience to discover localities of fossils, both in quartzites and 

 limestones throughout this belt, from where it enters the state 

 from Maryland and crosses the Delaware into New Jersey. 



If we follow on the line of the strike of the limestones 

 across the Delaware into New Jersey, the same type of section 

 is found to extend northeasterly across the state and into Orange 

 county, N. Y. At Hardistonville, Sussex county, New Jersey, 

 Dr. Beecher discovered the Olenellus fauna in the blue lime- 

 stones resting on the basal quartzite.* The fossils are found 

 on the southeastern side of the limestone belt ; and on the 

 northwestern side the limestones dip beneath the shales as in 

 the Pennsylvania section. In the geological report of New 

 Jersey for 1868, pp. 131, 132, numerous localities of the fos- 

 siliferous Trenton limestone are described, and a section given 

 showing the limestone passing beneath the shales to the west- 

 ward. 



The discovery of the Olenellus or lower Cambrian fauna in 

 the Reading sandstone practically completes the correlation of 

 the South mountain, Chickis and Reading quartzites of Penn- 

 sylvania and establishes the correctness of the early correla- 

 tions of McClure, Eaton, Emmons, and Rogers. They all con- 

 sidered the basal quartzite as the same formation from Vermont 

 to Tennessee ; and the discoveries of recent years have proven 

 that the basal sandstone of Alabama, Tennessee, and Virginia 

 (Chilhowee quartzite) ; Maryland, Pennsylvania and New 

 Jersey (the Reading quartzite) ; New York and Vermont (Ben- 

 nington quartzite) ; were all deposited in lower Cumbrian time, 

 and that they contain the characteristic Olenellus fauna through- 

 out their geographic distribution. The superjacent limestones 

 carry the Olenellus fauna in their lower portions, in northern 

 and southern Vermont, eastern New York, New Jersey and 

 Pennsylvania. To the south of Pennsylvania the lower por- 

 tions of the limestones appear to be represented by shales, and 

 the upper and middle Cambrian faunas are found in the lower 

 half of the Knox dolomite series of Tennessee, and they will 

 probably be discovered in the same series in Virginia and 

 Maryland, when a thorough search is made for them. The 

 same may be predicted, but with less assurance, for the North- 

 ern belt of limestone crossing Pennsylvania and into New 

 Jersey, as the limestones between the Olenellus zone and the 

 Trenton zone represent the intervals of the middle and upper 

 Cambrian and *the lower Ordovician, or the Calciferous and 

 Chazy zones, of the New York section. The working out of 



*Geol. Surv. New Jersey; Ann. Rep. State Geologist, 1890, pp. 31, 43, 49. 



