CAMBRIAN AND LOWER ORDOVICIAN. 113 



It is here called the Shenandoah because it has the same limits and stratigraphic associations 

 as the extensive and well-known limestone of that name. 



That calcareous sedimentation, which began in Cambrian time, continued into Ordovician 

 time is shown by the presence of Lower Ordovician fossils in an upper member of the Shenandoah 

 limestone. 



Further sedimentation in Ordovician time is represented by the Octoraro. This is the 

 best-known Paleozoic deposit in this region and, like the preceding Paleozoic sediments, is 

 dynamically metamorphosed and free from igneous intrusions. 



K 18. NEW JERSEY. 



The Cambrian and Lower Ordovician strata of New Jersey have been described 

 recently by Waller®*"* and Kummel®^^ on the basis of earlier reports and recent field 

 work. From Kummel's paper we take the following general description: 



The Hardyston quartzite is the lowest formation of the Cambrian system, and is probably 

 to be correlated with the Poughquag quartzite of Dutchess County, N. Y., and the Chickies 

 quartzite of Pennsylvania. It is unconformable on the pre-Cambrian complex and is the oldest 

 fossiliferous rock in New Jersey. It varies considerably in composition and thickness. Typi- 

 cally it is a quartzite, at many places conglomeratic and containing pebbles of quartz, feldspar, 

 granite, gneiss, and slate. Locally the formation is a calcareous sandstone. It is usually but 

 not invariably feldspathic. In some localities its arkose character is so marked that it is not 

 readily distinguishable from a coarse granite. Beds of slate occur in its upper portion. 



Its thickness ranges from a few feet to 200 or more, and it passes into the overljdng sand- 

 stone through slaty or shaly layers, several of which are in places interbedded with limestone 

 layers, so that its upper limits are indefinite. Since it contains a species of Olenellus, it is 

 regarded as of Georgian (Lower Cambrian) age. 



The Hardyston quartzite grades upward into the thick magnesian Kittatinny limestone 

 of the Kittatinny Valley. Above, it is limited by an unconformity at the base* of the Jackson- 

 burg (Trenton) limestone. The presence of thin shales and scattered seams of sandstone in 

 the great mass of limestone shows an influx of land sediments at recurrent intervals during 

 its formation. 



The known fauna of the Kittatinny is not extensive and is found at but few localities, but 

 it sufl&ces to establish the Cambrian age of the greater part of the formation. No Middle Cam- 

 brian fossils have been found, but as the Olenellus fauna of the Hardyston quartzite is con- 

 sidered to be of Lower Cambrian age, and as no evidence of a break in sedimentation has been 

 observed, a Middle Cambrian fauna would naturally be expected between the Olenellus fauna 

 below and the Dikelocephalus fauna above. In one locality a fauna of Ordovician (Beekman- 

 town) age has been found in beds near the top of the Kittatinny limestone. This formation, 

 therefore, where complete, represents a period extending from the middle or upper part of 

 the Lower Cambrian to the lower part of the Ordovician, inclusive. 



From a discussion of the fossils found in the Kittatinny limestone, probably 

 mostly from its upper portion, Weller **"* concludes : 



The position of. these various fossiliferous beds of the Kittatinny limestone in the forma- 

 tion as a whole can not be determined with certainty, but it may probably be stated, with a 

 degree of safety, that all of these fossiliferous localities, with the exception of that near Carpen- 

 tersville, are in the upper portion of the formation. The CarpentersviUe locality is probably 

 somewhere in the lower third of the entire series. So far as the fossils afford any definite evi- 

 dence, the age of all is upper Cambrian. No middle Cambrian faunas have been recognized, 

 although the Olenellus fauna of the Hardyston quartzite is usually considered to be of lower 

 Cambrian age, and a middle Cambrian fauna would naturally be expected to occur somewhere 

 in the formation. 



48011°— 32 8 



