Although two physically distinct tills of different ages have long been recognized in southern New England, only in the past decade or so has the existence of a similar two-till stratigraphy been recognized in New Hampshire. In southern New England, distinction between the two tills, a lower one and an upper one, initially was based on differences in texture and weathering: the lower compact till has a siltier matrix and an oxidation zone of 10 or more meters; the upper till has a much sandier matrix and an oxidation zone only in the uppermost 1 m. Later, identification of structural features at the contact between the two tills helped to distinguish them. The same stratigraphic relationships are now recognized in all parts of New Hampshire. Excellent exposures at Nash Stream in northern New Hampshire have provided the most complete inland till stratigraphy to date in New England. The tills exposed here are called the Nash Stream (lower) Till and Stratford Mountain (upper) Till; associated deglacial outwash has also been recognized for each of them. The Nash Stream Till is nonoxidized where it is covered by its associated outwash and is oxidized to a depth of 6 to 7 m where it is exposed at the surface. This suggests that a significantly long weathering interval took place before the last ice sheet deposited the Stratford Mountain Till and its associated outwash. The Nash Stream Till, here correlated with the lower till of southern and central New England, may be an early Wisconsinan correlative of the New Sharon Till in Maine and perhaps of the Johnville Till in southeastern Quebec and the Becancour Till in the St. Lawrence Lowland, or it may be even older. The Stratford Mountain Till, of late Wisconsinan Age, is correlated with the surface till throughout New England, and with the Lennoxville Till in Quebec and with at least the upper part of the Gentilly Till in the St. Lawrence Lowland. No middle Wisconsinan units have so far been recognized in New Hampshire and southern New England.

The Laurentide Ice Sheet flowed southeast across the northern White Mountains during the Wisconsinan Stage. In late Wisconsinan time, the regional snowline was probably elevated above the highest peaks. Downwasting ice masses progressively ceased to flow (stagnated) as they became cut off from regional sources to the northwest. Indirect lines of geomorphic evidence and a short radiocarbon chronology indicate that deglaciation proceeded very rapidly once major elements of the regional terrain were exhumed from beneath the ice; there is a distinct downward and locally north-westward progression of deglacial events. North of the city of Berlin, regional ice flow was sustained in the Androscoggin and Dead River valleys. Ice eventually retreated in these valleys and left sequences of stratified drift graded to bedrock at the head of the 70-m knickpoint in the Androscoggin Valley at Berlin Falls. Stratified moraines record temporary positions of these retreating ice fronts. Outwash began to accumulate in the deepest part of the Androscoggin Valley downstream from Berlin after the ice in this area was beheaded at the falls. The local deglaciation was probably complete between 12,100 and 12,600 yr B.P. There is evidence for two separate phases of activity in the relict rock glacier in King Ravine in the Presidential Range. The earliest rock glacier may have formed from a stranded remnant of Laurentide ice. Later activity may have occurred during a period of significant climatic cooling.