GEOLOGY OF THE POUGHKEEPSIE QUADRANGLE 



45 



Fig. 14 Worm borings in 

 Cambric quartzite 



of 1906 (see figure 14), fossils had not been discovered in this 

 formation up to tlie summer of 1909. 



In August of that year the writer 

 discovered in the yard of Ward Ladue 

 at the West Hook a fossiHferous slab 

 of compact quartzite, about three 

 feet square, and plainly derived from 

 a bed about five inches thick. Both 

 surfaces were covered with fossils, 

 chiefly brachiopods and the cephalic 

 borders and spines of trilobites. Some 

 of the latter were from one and one- 

 half to two inches long. 



This slab was from a fine-grained, 

 gray quartzite bed and was very compact 

 and resistant. The fresh surface showed numerous rusty markings. 



This discovery led to persistent search for the fossiliferous rock 

 in place. 



Directly south from Ward Ladue's house a gorge in the quartz- 

 ite apparently marks the beginning of the normal fault displacement 

 that extends southward just to the west of the public road. The 

 western wall of this gorge is composed of thickly bedded compact 

 quartzite. The eastern wall shows thinner rusty layers interbedded 

 with the compact rock. The fact that only a hundred feet or so to the 

 eastward the quartzite is overlain by the limestone, together with the 

 evidence of faulting, were taken to indicate that the rocks in the 

 eastern wall are younger than those on the western or upthrow side. 

 With this assumption as a basis, and in the belief that the rusty 

 layers interbedded in the superficial portion of the quartzite should 

 yield fossils, if such were present, the eastern wall was given a very 

 careful examination. No fossils could be found between Ladue's 

 and the point where the gorge intersects the road. Although the 

 dip of the quartzite is very gentle along here, the thickness crossed 

 is considerable. 



The gorge was then traced southward from the road. A rich 

 assemblage of fossils M^as discovered in the eastern wall about 250 

 yards southeast of Herman Adam's house. The ledge occurs just 

 beneath an old stone wall that separates the gull)^ from an old 

 orchard. The fossil traces were first discovered in the compact 

 rock similar to that seen in the slab in Ladue's yard, and showing 

 the same rusty markings on the fresh surface. This rock overlies 



