This paper summarizes lithostratigraphic work on Permian rocks in the Sverdrup Basin by Nassichuk and Thorsteinsson; investigation of Permian fusulinaceans by Thorsteinsson; Permian ammonoids by Nassichuk; Permian bachiopods by Waterhouse and Triassic lithostratigraphy and ammonoids by Tozer.

The relationship between Permian and Triassic beds is evident near the north, east and south margins of the Sverdrup Basin, particularly on northern and eastern Axel Heiberg Island; western Ellesmere Island; Cameron Island and Melville Island. The lithostratigraphy of the Permian rocks is rendered particularly complex in that several facies belts are generally in close proximity. A summary account has recently been published by Thorsteinsson (in Douglas et al., 1970). Figure 1 in the text represents a generalized cross-section through the pre-Triassic sequence in the basin and illustrates the salient features of the succession. The overlying Triassic rocks are mainly sandstone with some conglomerate (Bjorne Formation) on the southern and eastern edges of the basin; in the axial part of the basin they are mainly siltstone and sandstone (Blind Fiord Formation). At individual outcrops the Permian and Triassic rocks appear to be concordant, without obvious evidence to indicate either erosion or nondeposition. Viewed regionally there is, however, clearly a substantial unconformity separating the Permian and Triassic rocks. The Bjorne Formation is transgressive on Melville and Ellesmere Islands where, in some sections, it rests directly upon pre-Permian formations.

Fossils are abundant in the Permian formations. Fusulinaceans, ammonoids and brachiopods have been studied in some detail. The study of the fusulinaceans does not contribute to dating the youngest Permian because these fossils do not persist to the top of the section; none younger than Early Artinskian (Aktastinian) occur. The highest Permian beds on the edge of the basin are those of the Trold Fiord Formation. The Trold Fiord beds contain the ammonoid Neogeoceras and a brachiopod fauna (Wyndhamia, etc.), both of which are interpreted as indicating an Early Guadalupian (Wordian) age. It is possible that beds exposed at the top of the Permian sequence in the vicinity of Blind Fiord, western Ellesmere Island are younger than the Trold Fiord Formation at any other

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place; they contain a sparse brachiopod fauna possibly younger than Kazanian (Wordian) but this dating is extremely tentative.

In the Lower Triassic beds fossils are relatively abundant in the Blind Fiord Formation but rare in the Bjorne Formation. Four ammonoid zones have been discriminated within the earliest Triassic (Griesbachian) beds of the Blind Fiord Formation. Otoceras is restricted to the lower two zones (Concavum and Boreale). The earliest zone (Concavum) has been recognized only in the Blind Fiord Formation of northern Axel Heiberg Island. The Boreale Zone is known in the Blind Fiord Formation from many localities on Ellesmere and Axel Heiberg islands. The only fossils known from the lower part of the Bjorne Formation are Otoceras sp. indet., indicating Concavum Zone or Boreale Zone.

The Concavum and Boreale zones are correlated with the beds containing Otoceras woodwardi in the Himalayas. The Lower Triassic sequence in Arctic Canada thus includes equivalents of the beds that define the base of the Triassic System.

Both the physical and paleontological evidence indicate a break in sedimentation between the Permian and Triassic in Arctic Canada. The physical evidence is the regional unconformity beneath the Blind Fiord and Bjorne formations. The paleontological evidence is the absence of faunas unquestionably indicative of latest Permian time (Upper Guadalupian, Dzhulfian and the Paratirolites fauna). Because the basal Triassic beds are correlated with those that define the base of the Triassic System it follows that the period of time unrepresented by sediments lies entirely within the Permian.

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