Unit Name: Blomidon Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Formal
Usage: Currently in use
Age Interval: Late Triassic - Early Jurassic (228.7 - 175.6 ma)
Age Justification: A Late Triassic (Rhaetian) age has been assigned, on the basis of several plant fossils. Haycock (1903b, p. 377) reported Estheria ovata (Lea) and Dawson (1868) reported the plant Dadoxylon edvardianun. Powers (1916, p. 121) cited Equisetum rogersii (Schimper) and equated Dawson's Dadoxylon sp. with Voltzia sp. Reptilian fossils from the type area indicated a correlation with the Triassic Brunswick Formation of New Jersey (Baird and Take, 1959, p. 1566; Baird, 1976). According to Bujak (1979), palynomorphs indicate a Rhaetian age for the Blomidon Formation. However, Mertz and Hubert ( 1990), and Fowell and Traverse (1995) show that the Blomidon spans the Norian and Rhaetian stages of the Late Triassic and the lower part of the Hettangian Stage of the Early Jurassic.
Province/Territory: New Brunswick; Nova Scotia
Originator: Powers, 1916; redefined by Klein, 1954.
Type Locality:
Powers (1916) failed to specify a type section, though he implied one along the Minas Basin west shore. Klein (1954) identified the type locality as that section exposed between Cape Blomidon and Paddy Island, on the west shore of the Minas Basin, Kings County, Nova Scotia (NTS 21 H/1).
Distribution:
Klein (1962) reported a thickness varying between 8 and 363 m at the type locality. In the Annapolis Valley, the Blomidon Formation can be traced from St. Mary's Bay near Digby (NTS 21 A/12), northeastwards to the Minas Basin at Cape Blomidon (NTS 21 H/8), a distance of 150 km. On the north shore of the Minas Basin, it is exposed at Economy Mountain near Five Islands, at Clark Head near Parrsboro, Partridge Island, Cape Spencer, and at Cape D'Or (NTS 21 H/8). It is exposed at the base of near vertical cliffs north of Dark Harbour on Grand Manan Island (NTS 21B/15) in New Brunswick ( Powers, 1916; Wade and Jansa, 1994).
Lithology:
Evenly bedded red shales, claystone, and siltstone. Recent workers describe two major facies deposited in an arid environment (Klein, 1962; Mertz, 1980; Perkins, 1981) for both the Blomidon and the underlying sands of the Wolfville Formation.
Relationship:
The Blomidon Formation conformably overlies sandstones of the Upper Triassic Wolfville Formation and paraconformably underlies the Lower Jurassic North Mountain Basalt throughout the region. In the Minas Basin area, the Blomidon and Wolfville formations may locally interfinger. The Blomidon is in fault contact with Lower Carboniferous strata near Parrsboro and Five Islands. The Fundy Group of Nova Scotia includes, in ascending order: the Wolfville and Blomidon formations, the North Mountain Basalt, and Scots Bay Formation. They are included in the Newark supergroup.
History:
Red beds which include rocks of the Blomidon Formation were recognized by Jackson and Alger (1828). Gesner (1836) regarded them as equivalents of the New Red Sandstone of England. Dawson (1855a) confirmed and followed this usage, referring to the red beds as the "New Red Sandstone of Nova Scotia". Dawson (1868, p. 945) believed he was the first to accurately define this group of sediments in Nova Scotia. Powers (1916) introduced the term Annapolis Formation of the Newark Group, which consisted of a lower Wolfville Sandstone Member and an upper Blomidon Shale Member. This usage persisted until the elevation of the two members to formation status within the Fundy Group (Klein, 1962). The terms Annapolis Formation and Newark Group are no longer used, the latter term now being designated a supergroup (Olsen, 1978). Significant studies of Blomidon strata since the work of Powers (1916) include those of Klein (1954, 1962), Mertz (1980), and Perkins (1981). Wade et al. (1996) review the stratigraphy of the Fundy Basin and describe its tectonic evolution.
Other Citations:
Baird, 1976; Baird and Take, 1959; Bujak, 1979; Dawson, 1855a, 1868; Gesner, 1836; Fowell and Traverse, 1995; Haycock, 1903b; Jackson and Alger, 1828; Klein, 1954, 1962; Mertz, 1980; Mertz and Hubert, 1990; Olsen, 1978; Perkins, 1981; Powers, 1916; Wade and Jansa, 1994; Wade et al., 1996.
References:
Baird, Donald M. and Take, William, 1959. Triassic reptiles from Nova Scotia [abstract]; The Geological Society of America (GSA), GSA Bulletin, vol. 70, no .12 (December), Part 2, pp. 1565-1566.
Bujak, J.P., 1979. "Palynological analysis of Mobil-Gulf Chinampas N-37, Bay of Fundy"; Geological Survey of Canada, Eastern Petroleum Geology Subdivision, Unpublished Paleontology Report, EPGS-PAL-3-79JPB, 6 p.
Dawson, J.W., 1855a. Acadian Geology; an account of the geological structure and mineral resources of Nova Scotia, and portions of the neighbouring provinces of British America; Oliver and Boyd, Edinburgh, 388 p.
Dawson, J.W., 1868. Acadian geology (second edition); MacMillan and Company, London, 694 p.
Haycock, E., 1903b. Fossils, possibly Triassic, in glaciated fragments in the Boulder clay of Kings County, Nova Scotia: Proceedings and Transactions of the Nova Scotian Institute of Science, vol. 10 or vol. 3 (Second Series), pp. 376-378.
Jackson, C.T. and Alger, F., 1828. Mineralogy and geology of a part of Nova Scotia; Yale University, American Journal of Science, vol. 14, pp. 305-330.
Klein, George deVries, 1962. Triassic sedimentation, Maritime Provinces, Canada; The Geological Society of America (GSA), GSA Bulletin, vol. 73, no. 9 (September), pp. 1127-1145.
Mertz, K.A., 1980. Sedimentology of the Upper Triassic Blomidon and Wolfville formations, Gerrish Mountain, north shore of Minas Basin, Nova Scotia: Unpublished M.Sc. thesis, University of Massachusetts, Northampton, Massachusetts, 198p.
Perkins, R.E., 1981. Sedinentology of the Upper Triassic redbeds of Kings County, Nova Scotia: Unpublished M.Sc. thesis, University of Massachusetts, North Rhampton, Massachusetts, 196 p.
Powers, S., 1916. The Acadian Triassic; Journal of Geology, vol. 24, pp. 1-26, 105-122 and 254-268.
Source: LEXICON_NB
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 31 Mar 2009