. Bulletin of the Geological Society of America. Geology. 268 SxMYTH—ROCKS OF NORTHWESTERN ADIRONDACK REGION. is in small tongues or veins there is a marked tendency for them to follow the lamination of the gneiss, producing structures precisely like those described and figured by Lehmann * in the case of similar intrusions occurring in Saxony (see figure 2). At many of the exposures abundant inclusions of gneiss in granite give further evidence of intrusion. While these relations are most extensively shown in Pitcairn, indications of the same sort may be found in Diana, particularly just nort
. Bulletin of the Geological Society of America. Geology. 268 SxMYTH—ROCKS OF NORTHWESTERN ADIRONDACK REGION. is in small tongues or veins there is a marked tendency for them to follow the lamination of the gneiss, producing structures precisely like those described and figured by Lehmann * in the case of similar intrusions occurring in Saxony (see figure 2). At many of the exposures abundant inclusions of gneiss in granite give further evidence of intrusion. While these relations are most extensively shown in Pitcairn, indications of the same sort may be found in Diana, particularly just north of Harrisville, north of Indian lake, and two miles east of Natural Bridge, on the Bonaparte road. Thus it is evident that the limestone belts of Antwerp-Gouverneur and of Diana-Pitcairn are separated by a gneissic area whose southern border is made up largely of intrusive rocks. How much of this area is but a continuation of the intrusions can be determined only by very close and careful study, and perhaps not even then; but the facts at hand are certainly suggestive and seem to point out a fruitful line of Figure 2.—Granite Veins paral- lel to Lamination of Gneiss. The drawing is from field sketch made one mile north of Pitcairn Forks. Gabbros. FIRST VARIETY. Area of Occurrence.—Of gabbros there are three varieties, the most im- portant being of somewhat exceptional character, which renders its affinities rather uncertain. The most typical gabbro oc- cupies an area of hardly more than a square mile, just east of the village of Pitcairn, or, as it is called more com- monly by the inhabitants, Geers. The southern edge of this area is marked by a steep cliff, like that formed by the granite and gneiss just described. The two cliffs are almost in line, though not continuous, and the structural relations of both are very * J. Lehmann : Untersuchungen iiber die Entstehung der schiefer Gesteine, p. Please note that these images are extract
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