GEOLOGY OF SARATOGA SPRINGS AND VICINITY 87 



frequently minute, pale, greenish, slaty particles. Under the miscroscope, it 

 consists of angular grains of quartz, orthoclase, plagioclase. and scales of 

 muscovite, probably clastic. The cement contains not a little carbonaceous 

 matter, secondary calcite, and pyrite. In the more easterly Ordovician area 

 the cement is quite sericitic and the feldspar is partially sericitized, but 

 in other places and along the Hudson, in Rensselaer county, the amount of 

 sericite in the cement is small. The marked features are the heterogeneity 

 of the fragments, their irregular size, angular outline, and usually the absence 

 of any arrangement in them. Chlorite is rarely present. 



A further peculiarity of the Hudson grits is that they contain particles of 

 various fragmental rocks, showing that they were derived from the erosion 

 not only of older granites and gneisses, but of sedimentary rocks of 

 Ordovician or pre-Ordovician age. The particles of clastic rocks were found 

 to consist of shale, micaceous quartzite, calcareous quartzite, limestone or 

 dolomite, slate and flint. The most abundant were found to be quartzite, 

 slate and shale. 



Dale recorded the occurrence of graptolites of the Normanskill 

 horizon from the shales interbedded in the Hudson grits. 



Like the white beds, the grit beds of the Normanskill shale 

 come to the surface on the Schuylerville quadrangle in two well- 

 circumscribed areas. The grit ledges on this map are denoted by 

 the brown symbol and are crowded in the region west and north 

 of Quaker Springs and about Willard mountain. The former 

 region is one of extremely rough topography, owing to the many 

 broken edges of the grit beds in the closed synclines and anticlines. 

 It is for this reason locally known as " The rocky tucks " and was 

 formerly the site of considerable quarrying for sills and building 

 stone. The ledges are especially well seen in the neighborhood 

 of Quaker Springs. The interbedded shale is but rarely seen, 

 since it usually has weathered back too far and is covered by drift. 

 In one place, at least, we found graptolites of Normanskill type in 

 the interbedded shale. The grit itself is barren of fossils, a few 

 joints of crinoid stems being the only traces of fossils observed. 



The belt of grit ledges ends rather abruptly about a mile south 

 of Gates, or 2 miles south of the north bend of Fish creek, not to 

 reappear farther north on the quadrangle. 



The second region of grit outcrops is the Willard mountain 

 ridge. As we noted before, the top of this very prominent ridge 

 is formed by the white-weathering cherty beds ; the flanks con- 

 sist, however, of the Normanskill grit. The grit ledges appear 

 very prominently along the lower road west of the mountain. 

 They form considerable cliffs on the northwest side of the Willarr^ 

 ridge and are observable in outcrops and cliffs along the road 



