132 THE CAMBRIAN. Iuull.SL 



the Primal sandstone. Auroral limestone, andMatinal shales of central 

 Pennsylvania are represented in southeastern Pennsylvania. He criti- 

 cises the correlation upon the evidence of the presence of /Seolithus lin- 

 earis, stating that he has shown it to be very distinct from that found 

 in the Potsdam sandstone. The argument for this is given in his u Azoic 

 Rocks of Pennsylvania." 1 In a later publication Dr. Hunt concludes 

 that — 



There is, in fact, up to this time, no evidence that the typical Potsdam sandstone 

 and Calciferous sandrock of northern New York exist in eastern Pennsylvania; but 

 on the contrary there are many reasons for supposing that in this region, as in east- 

 ern Canada and along the eastern side of the Champlain and Hudson River Valleys, the 

 period of these two subdivisions of the New York system is represented by the First 

 Graywacke of Eaton, the Upper Taconic of Emmons, which, as will be showu farther 

 on, is now recognized as contemporaneous with the typical Potsdam and Calciferous 

 subdivisions. Rocks supposed to represent this Graywacke series are found in the 

 great valley of Pennsylvania, and these, together with the divisions immediately pre- 

 ceding them — namely, the Primitive quartz rock, the Primitive lime rock, and the 

 transition argillite — which constitute the Lower Taconic of Emmons — are, as we shall 

 endeavor to show, represented by the so-called Primal, Auroral, andMatinal of the 

 southeastern area. 3 



He refers the sandstone, limestone, and shale to his pre-Cambrian 

 Taconian system, correlating the formations with the Granular quartzite, 

 Granular limestone, and Transition argillite of the eastern New York 

 section. This correlation, made long before by Prof. Eogers, is sus- 

 tained by the latest observations. The " Granular quartz n of Eaton's 

 section is known to be of Lower Cambrian age ; thelimestoue, of the 

 Trenton-Chazy horizon, and the argillite is referred to the Hudson ter- 

 rane. If the correlation based upon lithologic characters and strati- 

 graphic position by Messrs. Eogers and Hunt be correct, then the quartz- 

 iteof southeastern Pennsylvania is of Cambrian age, and the limestones, 

 with their superjacent shales and schists, are the equivalents of the 

 Trenton and Hudson terranes. 



The statement that the Upper Taconic of Emmons is contemporane- 

 ous with the typical Potsdam and Calciferous subdivisions is no longer 

 sustained, as the Upper Taconic of Emmons is mainly the Lower Cam- 

 brian of the New York section. 



In a discussion on the rocks of Pennsylvania and New York, Mr. T. 

 D. Hand 3 mentions the Cambrian of Cluster Valley, near Philadelphia, 

 and, as undetermined, the hydro mica schist of the South Valley Hill. 

 He states that the Potsdam really exists in between the schist and the 

 limestone, which refers the schist to the Archean. The sandstone is 

 very thin, but it rests upon the Laurentian shore of the ancient ocean, 

 which explains the differences of thickness as compared with the rocks 

 to the northwest. 



'Special report on the trap dikes and Azoic rocks of southeastern Pennsylvania. Second Geol. 

 Surv. Pa., E. 1878, pp. 134-139. 



2 The Taconic Question in Geology. Minora] Physiology and Physiography. A second scries of 

 chemical and geological essays: 1886, p 534. 



3 A discussion on the rocks of Pennsylvania and New York. New York Acad. Sci., Trans., vol. 8, 

 1889, pp. 50, 51. 



