Tens of thousands of rock exposures in New Hampshire show only slight superficial alteration of glacier-worn surfaces. Long search has yielded only 46 examples of rotted rock, and these are believed to record more prolonged weathering during preglacial or interglacial time.
At three localities, in particular, deeply rotted rock, of types usually fresh and sound, is covered by fresh till, and injected by long narrow dikes of the till matrix, as if already weak when the till was emplaced. Petrographic study of materials supports this view.
Among other relics of weathering before the last glaciation are boulders of oddly irregular shape in the till, which are neither “meteors” nor products of postglacial decay.
Other facts and considerations indicate that there is much old residual material in the till.