Horton Group

Unit Name: Horton Group
Unit Type: Lithostratigraphic
Rank: Group
Status: Formal
Usage: Currently in use
Age Interval: Middle Devonian - Early Carboniferous (397.5 - 318.1 ma)
Age Justification: Based upon a sparse macroflora, Bell (1960) correlated the Horton Group with the Tournaisian of Europe and the early Mississippian Pocono Formation of the eastern USA. The Horton Bluff and Cheverie formations contain the plant fossils Aneimites acadica, Lepidodendropsis corrugata, Triphyllopteris and Sphenopteris, which indicate a Late Tournaisian age. Palynological studies (e.g. Barss, 1967; Barss and Hacquebard, 1967; Hacquebard, 1972; McGregor, 1971) delineated seven miospore zones (a-g), which indicated an age of Middle Devonian to Early Visean. Utting et al. (1989) and Martel et al. (1993) found Late Devonian (late Fammenian) miospores in the lowermost part of the Horton Group in the type area. These were overlain by miospore assemblages which could be assigned to the Emphanisporites rotatus - Indotriradites explanatus Zone of the Tournaisian. Utting et al. (1989) and Martel and Gibling (1996) considered the youngest age of the Horton Group (Cheverie Formation) in the type section to be late Tournaisian, based on the presence of miospore assemblages assignable to the Spelaeotriletes cabotii Subzone of the Vallatisporites vallatus Zone.
Province/Territory: New Brunswick; Nova Scotia

Originator: Dawson, 1873; redefined by Bell, 1929.

Type Locality:

Not designated; however, inferred to be the Horton Bluff, Kings County, Nova Scotia (NTS 21 H/1). The type area is the southwestern part of the Minas Subbasin, Hants and Kings counties, Nova Scotia.

Distribution:

The Horton Group can be traced eastwards from the type area across mainland Nova Scotia and into New Brunswick and Cape Breton. At the type area the thickness of the group, based upon drill data is about 425 m (Bell gave thicknesses of 1067 m for the Horton Bluff and 190 m for the Cheverie). In the Truro map-area Stevenson (1958) gave a minimum thickness of 1229 m. Along the southwest Mabou River (NTS 11 K/3) in Cape Breton, Murray (1960) gave the following thicknesses: Craignish Formation, 1563.6 m; Strathlorne Member, 320 m; and Ainslie Member, 354.7 m.

Lithology:

Non-marine clastics, red and grey to black, generally coarse-grained near the base and the top with fine clastics between. It is dominantly arkosic to subarkosic, with some lithic and orthoquartzitic units; units coarsen towards source areas that are often older slates and granites; the sediments are fluvial and lacustrine, intermontane. The group is subdivided into two formations in the type area, the Horton Bluff and the Cheverie formations, and two formations Strathlorne-Ainslie and Craignish formations in Cape Breton. The group is subdivided into two formations in the type area, the Horton Bluff and the Cheverie formations, and two formations Strathlorne-Ainslie and Craignish formations in Cape Breton. The Horton Group is also represented in New Brunswick, where it includes the Memramcook, Albert and Moncton formations. The Horton Group represents sediments deposited in lacustrine, fluvial, pro-delta and floodplain environments, with occasional restricted marine conditions. For further details refer to the Horton Bluff and Cheverie formations.

Relationship:

In the type area, an angular unconformity or faulting separate the Horton Group from older basement rocks of the Meguma Terrane, such as the Cambrian to Ordovician Meguma Group and Devonian granite of the South Mountain Batholith; different members of the Horton Bluff Formation or the Cheverie Formation may lie in contact with the older rocks (Martel and Gibling, 1996). According to Moore (1985), the Horton Group is disconformably to unconformably overlain by the Lower Carboniferous Windsor Group. The Horton Group is also represented in New Brunswick where it includes the Memramcook, Albert and Moncton formations (see individual enteries for more information).

History:

The history of nomenclature as applied to sediments now included in the group is reviewed in Bell (1929). Chronologically correlative sediments have been placed in the Red Sandstone Group (Jackson and Alger, 1828), Red Sandstone District (Gesner, 1836) and Old Red Sandstone, Gypsiferous Series (Lyell, 1843) and estuarine or lacustrine plant bearing unit (Dawson, 1847). The term Horton Bluff Series was introduced by Dawson in 1873. The age of the beds was recognized as Early Carboniferous by Logan in 1843 (1845), Lyell (1843), Woodman (1899), Lambe (1910), and Bell (1929). Fletcher, who began geological mapping of the Windsor Group type area in 1890 assigned a Devonian age to the beds, based upon a supposed lithologic and structural correlation with certain rocks in Cape Breton. Bell (1929) shortened the term Horton Bluff Series to Horton Series and divided it into the Horton Bluff and Cheverie formations. The Horton Series was renamed the Horton Group by Bell (1960), who redescribed the three members of the Horton Bluff Formation and subdivided the middle member into a lower sandstone and upper shale unit. Murray (1960) recognized three formations within the group in Cape Breton. Martel and Gibling (1996) formally subdivided the Horton Bluff Formation into four members which are, in ascending order: the Harding Brook Member, the Curry Brook Member, the Blue Beach Member, and the Hurd Creek Member.

Other Citations:

Barss, 1967; Barss and Hacquebard, 1967; Bell, 1929, 1960; Dawson, 1847, 1873; Gesner, 1836; Hacquebard, 1972; Jackson and Alger, 1828; Lambe, 1910; Logan, 1843; Lyell, 1843; Martel and Gibling, 1996; Martel et al., 1993; McGregor, 1971; Moore, 1985; Murray, 1960; Stevenson, 1958; Utting et al., 1989; Woodman, 1899.

References:

Barss, M.S. and Hacquebard, P.A., 1967. Age and the stratigraphy of the Pictou Group in the Mari-time Provinces as revealed by fossil spores, pp. 267-282: in E.R.W. Neale and H. Williams (eds.), Collected Papers on Geology of the Atlantic Region - Hugh Lilly Memorial Volume; Geological Association of Canada, Special Paper 4, 292 p.

Barss, M.S., 1967. Illustrations of Canadian fossils: Carboniferous and Permian spores of Canada (Report, 2 figures and 38 plates); Geological Survey of Canada, Paper 67-11, 17 p. (total 94 p.).

Bell, W.A., 1929. Horton-Windsor district, Nova Scotia; Geological Survey of Canada. Memoir 155, 268 p.

Bell, W.A., 1960. Mississippian Horton Group of type Windsor-Horton District, Nova Scotia; Geological Survey of Canada, Memoir 314, 58 p.

Dawson, J.W., 1847. The Gypsum of Nova Scotia: Academy of Natural Science, Philadelphia, Proceedings, vol. 3, pp. 270-274.

Dawson, J.W., 1873. Report on the fossil plants of the Lower Carboniferous and Millstone Grit formations of Canada; Geological Survey of Canada, Separate Report 430, 47 p.

Gesner, A., 1836. Remarks on the geology and mineralogy of Nova Scotia: Gossip and Coade, Halifax, Nova Scotia.

Hacquebard, P.A., 1972. The Carboniferous of eastern Canada; Septieme Congres International de Stratigraphie et de Geologie du Carbonifere, Krefeld 1971, Compte Rendu, vol. 1, pp. 69-90.

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.

Lambe, L.M., 1910. Palaeoniscid fishes from the Albert shales of New Brunswick: Geological Sur-vey of Canada, Memoir 3, 69 p.

Lyell, C., 1843. On the coat formation of Nova Scotia and the age and relative position of the gyp-sum and accompanying marine limestones: Proceedings, Geological Society of London, vol. 4, pp. 184-186; also American Journal of Science, vol. 45, pp. 356-359.

Martel, A.T. and Gibling, M. 1996. Stratigraphy and tectonic history of the Upper Devonian to Lower Carboniferous Horton Bluff Formation, Nova Scotia; Atlantic Geology, vol. 32, no.1, pp. 13-38.

Martel, A.T., McGregor, D.C. and Utting, J., 1993. Stratigraphic significance of Upper Devonian and Lower Carboniferous miospores from the type area of the Horton Group, Nova Scotia; Canadian Journal of Earth Sciences, vol. 30, pp. 1091-1098.

McGregor, D.C., 1971. Hymonozotriletes lepidophytus Kedo and associated spores from the Devonian of Canada: in Colloque sur la Stratigraphie carbonifere; Congres et Colloques, Universite de Liege, vd. 55, pp. 315-326.

Moore, R.G. 1985: Cheverie Formation. In: Lexicon of Canadian Stratigraphy, Volume VI, Atlantic Region. Edited by G.L. Williams, L.R. Fyffe, R.J. Wardle, S.P Colman-Sadd, and R.C. Boehner. Canadian Society of Petroleum Geologists, Calgary, pp. 74-75.

Murray, B.C. 1960. Stratigraphy of the Horton Group in parts of Nova Scotia; Nova Scotia Research Foundation Publication, pp. 1-123.

Stevenson, I.M., 1958. "Truro map-area, Colchester and Hants counties, Nova Scotia"; Geological Survey of Canada, Memoir 297, 124 p.

Utting, J., Keppie, J.D. and Giles, P.S. 1989. Palynology and stratigraphy of the Lower Carboniferous Horton Group, Nova Scotia; Contributions to Canadian Paleontology, Geological Survey of Canada, Bulletin 396, pp. 117-143.

Woodman, J.E., 1899. Ore bearing schists of middle and northern Cape Breton: Nova Scotia Department of Mines, Report 1898, 39 p.

Source: GEOLOGICAL SURVEY OF CANADA
Contributor: G.L. Williams
Entry Reviewed: No
Name Set: Lithostratigraphic Lexicon
LastChange: 04 Dec 2007