Page:The Journal of geology (IA journalofgeology21894univers).pdf/422

bed of massive quartzite might not be affected by minor folds is recognized, as it is well known to be among the most resistent rocks. The series below, however, possesses quartzites still more massive and flinty, rocks which have been involved in close flexures as sharp as those in fissile associated beds. Through Massachusetts and southern Vermont the quartzite is remarkable for its persistence. The series immediately beneath is extremely variable in character and thickness due to original deposition and to the metamorphism that it has suffered. This series may be wanting, as on Clarksburg Mountain and at North Bennington, Vermont, where the quartzite lies unconformably upon crystalline gneisses.

In Walcott's hypothetical section across this continent, the Cambrian ocean is represented as sending a long arm up the Rutland Valley not covering the Green Mountains or the Adirondacks. Careful search through the Green Mountains proper has not resulted in finding any traces of the quartzite, there is no evidence that it once mantled over the range, although it is not unlikely that the Plymouth Valley was once occupied by Cambrian waters. There are abundant occurrences, however, of the lower series in the heart of the range, where many of the highest peaks are capped by one member or another. There is stratigraphical and microscopical evidence that this series has undergone repeated disturbances; the quartzite exhibits but one. This fact cannot be used legitimately as evidence of disparity in age, as it is probable that the thick bed of quartzite stood like a bulwark among more variable, less-resistant strata, not taking part in and not recording orographic movements unless of extreme intensity. It should not fail to be stated that in many localities the quartzite lies directly upon fissile mica schist, the upper member of the series below in apparent conformity therewith, and the difficulty of referring the schist to the Lower Cambrian or the Algonkian is apparent. I am disposed to believe it of the latter age and to make it the uppermost member of an upper series with the metamorphic conglomerate delimiting the series below. There are many reasons for this view, some of