Glacial geology of Grand Manan Island, New Brunswick

Grand Manan is the largest of an archipelago of 20 islands at the mouth of the Bay of Fundy. Twenty-four kilometres long and 11 km wide, its western part consists of Triassic basalt with cliffs up to 120 m high. The eastern section consists of older rocks, is low lying, and is the site of the main settlements. Early scientific visitors thought that the island had escaped glaciation but there is abundant evidence to show that it did not, although the age of the last glaciation has not yet been established. Outwash and raised beach deposits are found throughout the island. Glacial striae show directions of ice movement ranging over 120°. Examples of multidirectional striae on the same rock surface have been observed. Isolated glacial erratics, some from the New Brunswick mainland, are found in the eastern part of the island, with one unusual assemblage on the south coast. A few exposures of till are described, one exhibiting two superposed tills of differing lithology, as known elsewhere in the Maritime Provinces. Carbon-14 dating of organic matter exposed at about half tide level and about 4 m above high tide level appears to agree with estimates of the changes of sea level during the last 16 000 years for other parts of the Maritime Provinces.