Since limestone pebbles are virtually absent because of great age of the drift, and soil profiles are not diagnostic because slope wash on rolling country has cut off the upper horizons, the amount of weathering which the gneissic pebbles have suffered is used as a criterion of age. The pebbles, dug from undisturbed till 4 feet below the surface, were classified with respect to the amount of weathering each one exhibits. To give a starting point for post-Jerseyan weathering a similar analysis was made of the gneissic pebbles in fresh Wisconsin till a few miles to the north. By comparing the curves plotted from these data it appears that there are two and possibly three divisions within the drift sheet. In a northern belt of drift stones are approximately 20 percent more weathered than those in the Wisconsin, whereas in a southern belt they are 30 percent more weathered. The possible third type, 12 percent more weathered, occurs near Budd Lake.

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