Sea-Level and Crustal Movements along the New England-Acadian Shore, 4,500-3,000 B.P.

Abstract

Remains of three drowned forests have been investigated at Odiorne Point, New Hampshire, and Fort Lawrence and Grand Pré, west-central Nova Scotia. Carbon-14 ages and altitudes below mean tide levels were determined for four in-place stumps of white pine at each locality. Assuming that each dated stump was killed by rising salt water, and that its $$C^{14}$$ age represented its true age at death, it was possible to construct curves showing the sequence of submergence and emergence at each site. A continuous transgression of the sea, approximating 0.31 foot per century, is indicated for the period 4,500-3,200 B.P. This rate corresponds well with Shepard's (1960) estimate of eustatic sea-level rise along the stable Texas coast for this time interval. Interpretation of the submergence-emergence curves in terms of crustal movements yields the following history: 4,500-3,800 B.P.: crustal stability at all three sites; 3,800-3,400 B.P.: crustal downwarping of west-central Nova Scotia at the approximate rate of 2.6 feet per century; slightly greater downwarping at Grand Pré possible, indicating a hinge for the warping lying to the north of Fort Lawrence; slight crustal depression of the New Hampshire coast may have taken place; 3,400-3,250 B.P.: upwarping of west-central Nova Scotia at the approximate rate of 4 feet per century; crustal stability of New Hampshire shore; 3,250-3,000 B.P.: renewed downwarping in west-central Nova Scotia at the approximate rate of 0.88 foot per century; crustal stability of New Hampshire shore.