Pebbles of silicified gymnospermous wood occur widely in the drift of southeastern Massachusetts. An investigation of the distribution of these pebbles shows the bedrock source of the wood to be tuffaceous beds that apparently overlie older granite in the Middleboro-Plympton area, Massachusetts, and are at the base of the Carboniferous rocks of the Narragansett Basin. A second center of distribution of the wood may lie offshore, north of Cape Cod. It is estimated that many thousands of large logs were broken up and carried away from the outcrop by Pleistocene ice sheets in the production of the boulder train.

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