GEOLOGY OF SARATOGA SPRINGS AND VICINITY 73 



Professor Gushing and the writer collected a number of the 

 species here recorded from the first locality and also on Bald 

 mountain. 



North of Bald mountain the thin-bedded, bluish (50+ feet thick) 

 limestone is seen in sections to grade into more massive light gray 

 limestone beds which, exposed in cliffs at the fault line, are liable 

 to be confounded with the Bald ^Mountain limestone and may have 

 led to the extension of the " Trenton " limestone belt farther north- 

 ward than shown on our map. Georgian brachiopods were found in 

 this massive limestone bed in at least two localities. These lime- 

 stones were seen in several places to rest on black Gambric shales. 

 It is therefore probable that the Schodack beds contain here some 

 thicker limestone beds than observed in the more eastern region. 



The area southeast of Louse hill consists of black shale, a thin- 

 bedded limestone with shale seams and quartzitic bands, with a 

 great number of quartz veins. 



Dark gray shales with brecciated limestone pebbles, the beds 

 reaching 200 feet or more (assuming no repetition) in section given 

 on page 81, are exposed at the west edge of the Bald mountain 

 quarry and in the sections north of it. They are interfolded with 

 the Bald Mountain limestone and Rysedorph Hill conglomerate, but 

 have the appearance of the Schodack beds, and are probably Georg- 

 ian beds forced into the Ordovicic belt near the overthrust plane. 



SCHAGHTICOKE SHALE 



The Schaghticoke shale with its characteristic faunule, consisting 

 of Dictyonema flabelliforme and Staurograptus 

 dichotomus Emmons var. a p e r t u s Ruedemann was dis- 

 covered by us in a cut of the Hudson Valley Railroad, near the 

 mill of the Standard Wall Paper Gompany about a mile north of 

 Schuylerville, and thence traced across the lower part of the rapids 

 of the Hudson below Thomson. The entire belt is probably not 

 more than 1000 feet wide and bounded on both sides by outcrops 

 of Normanskill shale ; its length is unknown since it runs in both 

 directions under the drift. The rock in the exposure is much con- 

 torted and consists for the most part of light greenish gray, glazed 

 argillaceous shale that weathers to a light drab or whitish color 

 with intercalations of coarser light bluish gray more or less sandy 

 mud shale and small streaks of black shale containing the grap- 

 tolites. It also contains 1 3^/2 feet bed of coarse grit with black 

 calcareous and argillaceous pebbles and large, floating, rounded sand 



