New Interpretation of the Permo-Carboniferous Varves at Squantum
Introduction An examination of thick varves in slate in a quarry on Foster Street, Brighton, Massachusetts, in 1925, indicated an interpretation of the seasons which differs materially from that made by the writer in 1915. Inasmuch as the interpretation first given 1 2 was based on varves that stand 50 feet or more above the tillite at Squantum and that were compared directly with Pleistocene varves of the Connecticut Valley, it will be necessary first to describe the structure of Pleistocene varves in order that the different structure recently determined in the Squantum varves may be more thoroughly understood. Sequence of Deposition by Glaciers As a stream comes from a glacier in summer it deposits first coarse gravel, and next, farther away, sand and finer material. 3 The thickest deposit would be near the place where the stream emerged from the glacier, and the deposit of a year might be composed . . .