Abstract

On the Borden Peninsula of northern Baffin Island, N.W.T., approximately 19,000 feet (5,800 m) of unmetamorphosed and nearly undeformed sedimentary rocks of Helikian age with basal volcanics have been downfaulted into the basement gneisses along a broad, northwesterly trending graben.

Following the Hudsonian Orogeny during which the basement complex was metamorphosed, a stable shelf environment developed. Despite pronounced regional subsidence, shallow-marine and non-marine conditions that existed during the Helikian depositional episode suggest an overall balance between the rate of subsidence and the rate of deposition. Deposition was interrupted four times by broad regional upwarps. The corresponding unconformities indicate a considerable lateral variation in the amount of erosion that took place during the preceding hiatal episodes. The locus of maximum uplift shifted progressively westward, whereas facies changes in the preserved rock record show that subsidence was persistently more pronounced to the east.

The Helikian depositional episode was initiated by basic volcanics of the Nauyat Formation. An easterly-derived clastic blanket of orthoquartzites (Adams Sound Formation) and black shales (Arctic Bay Formation) characterizes the remainder of the early depositional stages. An algal-dominated carbonate environment prevailed during the middle stages (Society Cliffs and Victor Bay Formation), and a westerly-derived clastic wedge (Strathcona Sound, Athole Point and Elwin Formations) closed the depositional episode.

Pronounced unconformities above and below the succession and the progression from basal well-sorted clastics through carbonates into molasse-type red beds at the top are typical attributes of major depositional cycles which appear to be particularly well-developed during Proterozoic time.