Abstract

The Middle to Upper Devonian Bird Fiord Formation, a constituent formation of the Franklinian Geosyncline, Canadian Arctic Islands, displays considerable vertical and lateral facies variation. On southwest Ellesmere Island, five informally defined members represent 1. a basal sabkha setting, 2. a carbonate-dominated shelf, 3. a clastic-dominated shelf, 4. deltaic/clastic shelf interdigitation, and 5. fluvial-deltaic environments. The change from carbonate to clastic lithology is associated with the onset of deltaic sedimentation, however, shelf processes redistributed distal deltaic sediments into sheet-like layers. Extensive cliff exposures permit examination of shelf lithofacies and their sequences. Broad (?tidal) channels, low-amplitude bar forms, small-scale scour surfaces and abundant rippling attest to distribution of sediment by active currents.

Delta encroachment is indicated by the introduction of extensive noncalcareous, cross-bedded, proximal mouth-bar sandstones interbedded with bioclastic shelf sequences. These mouth-bar deposits are lensoid in cliff section; their tops commonly display evidence of reworking by shelf processes. Further advance of the delta is indicated by an upward increase in non-calcareous, cross-bedded sandstones and the occurrence of well defined distributary channels. The uppermost member of the formation consists of stacked channel sequences, which probably represent a braided stream environment.

The lower carbonate members are absent on Grinnell Peninsula (Devon Island), Comwallis and Bathurst Islands. In these areas, a spectrum of shallow clastic shelf and interface environments (barrier island, tidal channel, lagoon, distributary channel and interdistributary bay) occur in the Bird Fiord Formation transition from carbonates of the underlying Blue Fiord Formation to the deltaic environments of the overlying Okse Bay Group.