Middle to Upper Ordovician (Darriwilian to Bolindian) graptolite zones of the northern Canadian Cordillera comprise the following: Glyptograptus euglyphus Zone of late Darriwilian (Llandeilo) age, Nemagraptus gracilis Zone of early Gisbornian (late Llandeilo and earliest Caradoc) age, Climacograptus bicornis and Dicranograptus clingani? zones of early to mid-Gisbornian (early to mid-Caradoc) age, Orthograptus quadrimucronatus Zone of Eastonian (late Caradoc) age, and Dicellograptus ornatus zone of Bolindian (Ashgill) age.A prominent biostratigraphic break equivalent to the spiniferus to hians kirki zones (Eastonian) is shown to exist between the clingani? Zone and the overlying quadrimucronatus Zone.Thirty eight common and (or) important species are illustrated, of which one new species, Orthograptus expansus n. sp., is described and figured.

Summary Lower Ordovician graptolites of the Canadian Cordillera (southeastern British Columbia to northern Yukon) are strongly allied to those of the Victorian sequences of Australia and the nearly identical succession of New Zealand, consequently the Stage classification of Victoria is adopted with only minor modifications. Biostratigraphic zones recognized herein, and their Victorian correlatives, are Tetragraptus approximatus (upper Lancefieldian), T. fruticosus (Bendigonian), Didymograptus protobifidus (Chewtonian), Isograptus victoriae lunatus (very poorly known) and I. v. maximodivergens (lower and upper Castlemanian, respectively), Oncograptus possibly with lower and upper divisions (Yapeenian), Paraglossograptus tentaculatus divisible into a lower unit equivalent to Dariwillian 1 and 2, and an upper unit correlative with about Dariwillian 3 and characterized by the appearance of Sinograptus , and Diplograptus decoratus Dariwillian 4 and higher). Zone by zone diversity studies of Pacific Faunal Province graptolites indicate maximum species’ diversity in the fruticosus and tentaculatus zones and lowest diversity about the lunatus Zone.

The Upper Ordovician graptolite facies of the northern Canadian Cordillera is divided into two biostratigraphic units, the Dicellograptus ornatus Zone and the Pacificograptus pacificus Zone. Interbedded limestone yielded conodont Fauna 12. The uppermost Ordovician equivalents to the graptolite Climacograptus extraordinarius Zone and conodont Fauna 13 are absent, signifying a widespread stratigraphic hiatus probably attributable to the effects of glacially induced regression.The lowest Silurian graptolite fauna, of the Glyptograptus persculptus Zone, is tentatively identified in some sections, although it is absent in others. Conodonts from the zone, although present, are not diagnostic.Thicknesses of the lowest Silurian G. persculptus Zone sediments are anomalously high in comparison with average thicknesses of the zone elsewhere in the world.

The Ogilvie Formation, formerly dated as Eifelian and Givetian, is locally confined to the Early Devonian, Emsian. Regionally the top of the Ogilvie is markedly diachronous ranging in age from Emsian to Givetian. The Ogilvie Formation conformably overlies the Late Silurian to Early Devonian Gossage and/or early Emsian Michelle and Cranswick Formations. The stratigraphic thickness of the Ogilvie varies from 200–3500 ft (61–1068 m) over relatively short geographic distances. The ages of the lower and upper beds of the Ogilvie are based on brachiopods, conodonts, corals, and trilobites. Locally, the lower part of the overlying unnamed shale unit is regarded as a lateral equivalent to parts of the younger Ogilvie carbonate sections. The Eifelian age of the basal beds of the unnamed shale unit is derived from a few strategically located dacryoconarid tentaculite collections. The Ogilvie Formation is a shallow water carbonate shelf deposit, locally reefal, which had its most extensive development in the later part of the Emsian. From the later part of the Emsian through Givetian, the carbonate shelf was gradually inundated by shales until in the late Givetian only a very small area of carbonate deposition remained in the western Yukon (Mount Burgess).The brachiopod affinities lie with the Cordilleran Subprovince of the Old World Province and with forms of similar age described from central Nevada. The conodonts and trilobites are correlative with forms from Arctic Islands, eastern Alaska, and Nevada. The Emsian tetracoral fauna is similar to that of the Emsian of eastern Australia whereas the Eifelian fauna is similar to that of other parts of northwestern Canada.Five informal conodont faunal units, ranging in age from Emsian through Eifelian, are proposed for the Michelle–Ogilvie sequence. In addition, the P. varcus Zone (Givetian) is recognized at the top of the Ogilvie at one section.