Unit Name: Fundy Group
Unit Type: Lithostratigraphic
Rank: Group
Status: Formal
Usage: Currently in use
Age Interval: Early Jurassic - Middle Triassic (199.6 - 228.7 ma)
Age Justification: Dawson (1855a) assigned a Late Triassic (Rhaetian) age on the basis of plant fossils in the Blomidon Formation, which has been followed by Powers (1916) and all subsequent workers. Palynomorphs indicate a Rhaetian age, according to Bujak (1979). Baird (1976) described Late Triassic reptile footprints in sandstones of the Wolfville on the south shore of Minas Basin. A 191 ± 2 Ma K-Ar isochron for five samples of the North Mountain Basalt was determined by Hyatsu (1979), with a refined argon isotope correction factor. His analysis of Carmichael and Palmer's (1968) samples resolved the discordance in their dates, indicating a Jurassic (Hettangian) age for the basalt. The Triassic-Jurassic boundary was fixed at 203 Ma by Armstrong and Stump (1970). Olsen (1981) discovered vertebrate bones and reptile footprints of Anomoepus spp., Otozoum sp. and Eubrontes giganteus which are restricted to the Hettangian (Early Jurassic) in Scots Bay and McCoy Brook sediments at Clarke Head, Gerrish Mountain and on the north shore of the Minas Basin (NTS 21 H/8). Palynologic studies by Bujak (1979) of the post-basalt sediments from the Chinampas N-37 well indicate that the Triassic-Jurassic boundary occurs in the Scots Bay, about 120 m above the North Mountain Basalt. Wade (in Bujak, 1979) described 359 m of Scots Bay, therefore the lower 120 m are Rhaetian and the upper 239 m Hettangian-Sinemurian. This discrepancy in age may indicate that volcanism began earlier (Rhaetian) in the southwest Bay of Fundy area, and became younger east and northwards (Hettangian). Donohoe and Wallace (1978, 1982) and Olsen and Baird (1982) regarded the North Mountain Basalt and the overlying Scots Bay and McCoy Brook formations to be Hettangian (Early Jurassic) in age. Further age indicators were miospores, macroflora, and poorly preserved plants.
Province/Territory: New Brunswick; Nova Scotia
Originator: Klein, 1962.
Type Locality:
Klein (1962) identified the type area as that section exposed along the western shore of Chedabucto Bay (NTS 11 F/6), and along the western shore of Nova Scotia in Digby (NTS 21 B/8, 9; 21 A/12, 13), Annapolis (NTS 21 A/14, 15), Kings (NTS 21 A/15; 21 H/1, 2, 8), Hants (NTS 11 E/4, 5, 6), Colchester (NTS 11 E/5, 6), and Cumberland (NTS 21 H/7, 8) counties. In New Brunswick exposures are found in the Maces Bay area (NTS 21 G/1), St. Martins area (NTS 21 H/5), Waterside (NTS 21 H/10), and Grand Manan Island (NTS 21 B/10, 15).
Distribution:
The lower Fundy Group is widespread throughout the areas of NTS 21 A/12, 14, 15; 21 H/1, 2, 8; and 11 E/4, 5. The upper Fundy Group occurs along the western shore of Scots Bay (NTS 21 H/8). In New Brunswick, the Fundy Group is found in the areas of NTS 21 B/10, 15; 21 G/1; and 21 H/5, 10.
Lithology:
In Nova Scotia, the Fundy Group includes, in ascending order, the Wolfville Formation, which is made up of medium- to coarse-grained arenite, arkose, subarkose and orthoquartzite with minor conglomerate; the Blomidon Formation, which is made up of red shales, claystone and siltstone; the North Mountain Basalt, a predominantly subaerial, tholeiitic basalt; and the Scots Bay Formation, which is made up of interbedded sandstones, limestone and claystone. The Fundy Group is believed to have various depositional environments. Alluvial fan and flood plain-alluvial fan deposits were recognized by their primary structures, such as cut and fill stratification, poorly sorted conglomerates and sandstones, and channel stratification. Possible lacustrine deposits were also identified, due to the presence of oscillation ripple marks, current ripple marks, flute and groove casts, mudcracks and graded bedding. In New Brunswick, in the St. Martins area (NTS 21 H/5), the Fundy Group includes, in ascending order, the Honeycomb Point Formation, which consists of interbedded red conglomerate with well sorted, medium-grained quartzose sandstone, and red, medium-grained sandstone that coarsens upward to pebbly sandstone; the Quaco Formation, which consists of pale red to greyish-red cobble to boulder roundstone conglomerate, that contains abundant banded quartzite clasts and local sandstone and conglomerate lenses; and the Echo Cove Formation, which consists of pale red conglomerates interbedded with pale red and greyish-red sandstone and mudstone, greenish-grey, medium- to coarse-grained sandstone, and pebbly sandstone. In the Maces Bay area (NTS 21 G/1) to the west of Saint John, the group includes the Lepreau Formation. It is made up of conglomerate that interfingers with fine- to medium-grained sandstone and pebbly sandstone; the sandstone becomes finer-grained up-section and is interbedded with mudstone, locally containing calcareous nodules.
Relationship:
The rocks of the Fundy Group overlie with angular unconformity the Cambrian to Ordovician Meguma Group, the Kentville and Torbrook formations, South Mountain Batholith, Lower Carboniferous Horton and Windsor groups and the Upper Carboniferous Canso (Mabou) Group. The base of the Fundy Group coincides with the base of the Wolfville, Chedabucto and Lepreau formations (Klein, 1962). In Annapolis County, the Wolfville Formation disconformably overlies Devonian granite. Between Truro and Economy Mountain (NTS 21 H/8) it is faulted against later Carboniferous sedimentary strata. In the Maces Bay area of New Brunswick, the Lepreau Formation is in fault contact with the nearby older rocks and contains clasts from many of them. In the St. Martins area, the Honeycomb Point Formation unconformably overlies the Proterozoic III Coldbrook Group and Carboniferous rocks of the Windsor Group, Hopewell Group and Tynemouth Creek Formation (Plint and van de Poll, 1984). The upper contact of the Fundy Group is not preserved in New Brunswick. In Nova Scotia the top is nowhere exposed, and younger strata are absent. The Fundy Group is truncated by an erosion surface cutting the top of the Chedabucto, Scots Bay, Echo Cove, and Lepreau formations.
History:
Dawson (1855a) was the first to show that the red beds of the Acadian Trough were post-Carboniferous and inferred that their age was Triassic from plant fossils. Powers (1916) made the first regional stratigraphic study and introduced the term Newark Group which consisted of, in ascending order, a lower Wolfville sandstone member, a Blomidon shale member, the Annapolis Formation, the North Mountain Basalt and the upper Scots Bay Formation. Klein (1960) reviewed the Newark terminological history and found that the term "Newark" was applied to the Maritime Provinces in a time-stratigraphic sense. Klein (1962) replaced the term Newark Group with Fundy Group, and placed it in the Newark supergroup (Hubert et al., 1978). Wade et al. (1996) review the stratigraphy of the Fundy Basin and describe its tectonic evolution.
Other Citations:
Armstrong and Stump, 1970; Bujak, 1979; Carmichael and Palmer, 1968; Dawson, 1855a; Donohoe and Wallace, 1978, 1982; Hubert et al., 1978; Klein, 1960, 1962; Olsen, 1981; Olsen and Baird, 1982; Plint and van de Poll, 1984; Powers, 1916; Wade et al., 1996.
Source: LEXICON_NB
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 07 Nov 2004