Till Stratigraphy and Late Wisconsinan Deglaciation of Southern Maine: A Review

• Published in: Géographie physique et Quaternaire
• Main Authors: Thompson, Woodrow B., Borns Jr., Harold W.
• Format: Text
• Language: English
• Published: Les Presses de l'Université de Montréal 1985
• Subjects: Nash; Ice Sheet
• Online Access: http://id.erudit.org/iderudit/032602ar; https://doi.org/10.7202/032602ar

At least two glaciations are recorded by the till stratigraphy of southern Maine. A more deeply weathered lower till is tentatively correlated with the early Wisconsinan (or older) Nash Stream Till in New Hampshire and its inferred equivalents in southern New England and Québec. The Laurentide Ice Sheet flowed south-southeastward across southern Maine in late Wisconsinan time and deposited the upper till. By about 14,000 years ago the ice sheet started to recede from the Maine coast, and the high peaks of the Mahoosuc Range emerged as nunataks in western Maine. Marine transgression accompanied déglaciation of lowland areas of southern Maine, with deposition of end moraines, deltas, and subaqueous outwash along the active ice margin, while thick clay deposits of the Presumpscot Formation accumulated on the ocean floor. The ice margin retreated quickly, reaching the marine limit in central Maine by 13,000 yr BP. The Pineo Ridge moraine system in eastern Maine, formerly thought to represent a major readvance, is reinterpreted as a glacial stillstand near the marine limit. Deglaciation inland from the marine limit in eastern and southwestern Maine occurred by recession of an active ice margin in some areas, and elsewhere by stagnation and downwasting of ice that was separated from the active ice sheet. Southern Maine was ice-free by 12,000 yr BP. but marine submergence persisted until about 11,000 years ago in the southwestern coastal lowland. On a enregistré au moins deux glaciations dans la stratigraphie du till, dans le sud du Maine. Un till inférieur, profond et altéré, est, à titre d'essai, mis en corrélation avec le Nash Stream Till du Wisconsinien inférieur (peut-être même plus ancien), au New Hampshire, et avec ses équivalents probables, dans le sud de la Nouvelle-Angleterre et du Québec. Au Wisconsinien supérieur, la calotte lau-rentidienne s'écoulait en direction SSE dans le sud du Maine où elle déposa le till supérieur. Il y a environ 14 000 ans, le retrait de la calotte glaciaire s'amorça à partir de ...