The Cambrian – Lower Ordovician Saint John Group of the Saint John area, southern New Brunswick, has historically been subdivided into 11 formations. The existing scheme is inappropriate, however, as many of the supposed formations, particularly those of Middle Cambrian–Early Ordovician age, were distinguished on a biostratigraphic rather than lithostratigraphic basis. We suggest the sequence can be more appropriately subdivided into seven formations, each of which can be clearly and easily identified by the field geologist. Lower Cambrian formations comprise, from base to top, the Ratcliffe Brook, Glen Falls, and Hanford Brook formations, all of which are retained from the previous nomenclature. Middle Cambrian strata comprise the Forest Hills Formation (to replace the Fossil Brook and Porter Road formations) and Upper Cambrian strata the King Square Formation (to replace the Hastings Cove and Agnostus Cove formations) and Silver Falls Formation (to replace the Black Shale Brook and Narrows formations). Lower Ordovician strata are referred to as the Reversing Falls Formation (to replace the Navy Island and Suspension Bridge formations). Descriptions of each formation are given, major sections of each are included, and stratigraphic correlation of the sequence in different geographic areas is demonstrated.

The northwestern margin of the Mascarene Basin is preserved within a southeasterly dipping homocline in the Oak Bay area of southwestern New Brunswick. The Mascarene Group in this area comprises up to 600 m of massive, resedimented conglomerate of the Oak Bay Formation and approximately 4200 m of volcanic and resedimented volcaniclastic and siliciclastic sandstone and mudstone of the conformably overlying Waweig Formation. The Waweig Formation is formally subdivided into three members: a lower volcaniclastic-and felsic volcanic-dominated Campbell Point Member (~600 m thick), a medial grey to black shale-and mafic volcanic-dominated Sawyer Brook Member (-300 to 600 m thick), and an upper siliciclastic-dominated Simpson Comer Member with minor associated volcanic rocks (-3000 m thick). Five lithofacies recognized in the well-exposed Campbell Point Member include: (i) bedded tuffaceous sandstone facies, (it) chaotic tuffaceous sandstone facies, (iii) waterlain pyroclastic facies, (tv) medium-to thick-bedded sandstone facies, and (v) thin-bedded mudstone facies, all of which are products of sediment gravity flows. The massive conglomerates of the Oak Bay Formation were deposited as debris flows contemporaneous with faulting along the margin of the basin. Strata within the homocline possess a pervasive S, cleavage oriented approximately 35° oblique to bedding and a locally developed S2 cleavage; minor folds are rare and folds related to Sj are absent.Correlation with a more complete Siluro-Devonian sequence in an adjacent fault block in Maine suggests that the Oak Bay and Waweig formations are Late Silurian (Ludlovian-Pridolian). The volcanic centres in Maine were potential sources of much of the epiclastic and pyroclastic detritus in the Waweig Formation. Distinctive stratigraphic sections in more highly deformed fault blocks farther to the southeast attest to the composite architecture of the Mascarene Basin. Existing paleontological evidence may indicate that subsidence of these blocks occurred progressively later to the northwest as a result of sequential downfaulting.Consideration of the regional relationships between the Mascarene Basin with respect to the St. Croix Terrane and Fredericton Trough to the northwest and the New River Terrane to the southeast suggests that the basin developed by backarc rifting from the Silurian to Early Devonian and was flanked by a Late Ordovician to Silurian volcanic arc (Kingston Arc) to the southeast. 35, 59-84(1999) 0843-5561/99/010059-26S4.90/0

An Ordovician flysch trace fossil assemblage from the Aroostook–Matapedia Carbonate Belt, northern New Brunswick, consists of the following identifiable ichnogenera: Alcyonidiopsis, Asteriacites, Asterosoma, Belorhaphe, Bifasciculus, Buthotrephis, Chondrites, Cochlichnus, Cosmorhaphe, Diplichnites, Fucusopsis, Glockeria, Gyrochorte, Helminthoida, Helminthopsis, Neonereites, Paleodictyon, Planolites, Protopaleodictyon, Scalarituba, Spirodesmos, Spirorhaphe, and Taenidium. The stratigraphic range of six ichnogenera, viz. Glockeria, Gyrochorte, Helminthoida, Spirodesmos, Spirorhaphe, and Taenidium, is, therefore, now extended to rocks of Ordovician age.The diversity exhibited by the assemblage is inconsistent with currently proposed models of Phanerozoic flysch trace fossil diversity. It is suggested that existing models suffer from an inadequacy of sampling and systematic effort per period of geological time, as reflected by the limited number of post-Cambrian/pre-Cretaceous, particularly post-Carboniferous/pre-Cretaceous, adequately documented flysch ichnoassemblages. The assemblage described here clearly illustrates a significant radiation of deep-sea behavioural diversity in the Ordovician. This is possibly related to the development during the Ordovician of a sufficient oxygen concentration and supply of organic detritus in the deep sea or colonization of deeper-water habitats concomitant with the significant diversification of Ordovician shelf benthic communities.

The Upper Cambrian? – Arenigian succession of Bell, Little Bell, and Kellys islands, Conception Bay, eastern Newfoundland, consists of at least 1500 m of interbedded micaceous sandstones, siltstones, shales, and ironstones. The succession has previously been formally subdivided into only two groups, namely, a lowermost Bell Island Group and an overlying Wabana Group. The existing lithostratigraphic nomenclature below group level has, to date, only been informally proposed and is therefore herein formally revised. The lowermost Bell Island Group comprises from base to top the Kellys Island, Little Bell Island, Beach, Redmans, Ochre Cove, and Dominion formations. Of these, the Ochre Cove and Dominion formations are newly proposed and the Beach Formation is considerably revised from its historical usage. The Beach Formation contains two newly proposed members, the McGraw and Eastern Head members, both of which in previous nomenclature were informally referred to as "beds." The disconformably overlying Wabana Group comprises from base to top the Powers Steps, Scotia, Grebes Nest Point, Gull Island, and Gravel Head formations. Of these, the Gravel Head Formation is revised from its historical usage and the remainder are newly proposed. The Powers Steps Formation contains a newly proposed member, the Youngsters Gulch Member, previously in part referred to informally as the "pyrite bed."

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