Annual report . escription of them all. After studyingmany specimens and microscopic sections, a careful selection of themost characteristic facies has been made and the descriptions ofthese immediately following will perhaps give the best idea of theGrenville within the quadrangle: i Crystalline limestone. This rock, which is medium to coarsegrained and calcitic, is sometimes pure and white but it is oftenmottled with green serpentinous material (ophicalcite) which is prob-ably derived by the decomposition of pyroxene. It is in thin layers 1900. Prosser. Notes on Stratigraphy of Mohawk Valley
Annual report . escription of them all. After studyingmany specimens and microscopic sections, a careful selection of themost characteristic facies has been made and the descriptions ofthese immediately following will perhaps give the best idea of theGrenville within the quadrangle: i Crystalline limestone. This rock, which is medium to coarsegrained and calcitic, is sometimes pure and white but it is oftenmottled with green serpentinous material (ophicalcite) which is prob-ably derived by the decomposition of pyroxene. It is in thin layers 1900. Prosser. Notes on Stratigraphy of Mohawk Valley and SaratogaCounties. N. Y. State Mus. Bui. 34. 1908. Brigham. Glacial Geologv of Amsterdam. Fonda. Gloversville andBroadalbin quadrangles. N. Y. State Mus. Bui. 121. p. 21-31. tqio. Ulrich & Cushinor. Age and Relation of the Little Falls Dolomiteof the Mohawk Waller. N. Y. State Mus. Bui. 140, p. 97-140. 1911. Miller, W. J. Preglacial Course of the Upper Hudson River. Am. Bui. 22:177-186. Plate i. W. J. Miller, photo Grenville gneiss showing stratification and steep dip. The rockis chiefly quartzite interbedded with thin layers of gray of a mile north-northeast of Batchellerville. GEOLOGY OF THE BROADALBIN QUADRANGLE <) and closely involved with thin-bedded, gray, feldspathic and quartz-itic gneisses. The only outcrop actually observed is in the bed ofCadman creek just below the bridge three-fourths of a mile north-northwest of Barkersville. Although other small occurrences mayhave escaped notice, it is certain that the limestone is present onlyin small amount. 2 Quartzite. The rock from one and one-quarter miles northeastof Batchellerville is perhaps the most typical and is coarse grained,light brown to almost white, and made up of nearly pure quartzwith occasional very thin layers containing small flakes of badlydecomposed mica. The rock is foliated, highly granulated and oftenstained with iron oxid. A thin section shows1 96 per cent quartz
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