Rocks at Waterside, New Brunswick

Waterside beach in New Brunswick is a UNESCO Fundy Biosphere Reserve Amazing Place. The red rocks here are Triassic in age, like the ones at St. Martins further to the south along the western shore of the Bay of Fundy. The Bay of Fundy occupies the Fundy Basin which lies between the Provinces of Nova Scotia and New Brunswick in Canada. The Fundy Basin contains scattered outcrops of Mesozoic Period conglomerate, sandstone, shale. mudstone and basalt flows. Remnants of Middle to Late Triassic sedimentary rocks form small crescent shaped outcrops 2.5 km long and 2.3 km wide, along the New Brunswick shore at Maces Bay, Saint John, St Martins, Martins Head, and Waterside at Chignecto Bay. These deposits lie unconformably over Carboniferous rocks in a broad synclinal structure that has an axis gently dipping southwestwards towards the Gulf of Maine (Ballard & Uchupi 1945).

The rocks at Waterside belong to the Fundy Group which is part of the Newark Supergroup. The broad rock bands seen in the vertical cross-sections of the cliff are amazingly different in colour, composition and texture; and include coarser conglomerates as well as finer-grained sandstones. The layers were originally formed when rivers flowing into a major water body slowed down, and deposited their heavy load of sediment in an alluvial fan that gradually grew further out (prograded) into the water. Over time the sediments built up to considerable depths and became consolidated into rock. This rock was eventually raised above water level  by earth movements. Some of the consolidated rock layers in the cliffs at Waterside have minor stratifications showing cross-bedding, which indicates to a geologist the type and direction of the current flow that deposited them. There is also a series of large overlapping biconvex lenses of a paler, more calcareous material, the meaning of which presently eludes me.

REFERENCES

Powers, Sidney (1916) The Acadian Triassic, The Journal of Geology, Volume XXIV, Number 1.

Ballard, R.D., and Uchupi, Elazar, 1972, Carboniferous and Triassic rifting: A preliminary outline of the tectonic history of the Gulf of Maine: Geological
Society of America Bulletin, v. 83, no. 8, p. 2285-2302.

Luttrell, Gwendoline W. (1989) Stratigraphic Nomenclature of the Newark Supergroup of Eastern North America – A lexicon and correlation chart of Newark Supergroup stratigraphic nomenclature, including a review of the origin and characteristics of the early Mesozoic basins of eastern North America,  U.S. Geological Survey Bulletin 1572, United States Government Printing Office, Washington.

Nadon, G. C. and Middleton G. V. (2011) The stratigraphy and sedimentology of the Fundy Group (Triassic) of the St Martins area, New Brunswick, Canadian Journal of Earth Sciences 02/2011, 22 (8), 1183-1203.