Abstract

The Franklinian miogeosyncline trends east and northeast through the Queen Elizabeth Islands. A particular location for the flexure separating the geosyncline from the Central Stable Region was applicable in the Silurian and in the earliest Devonian. Later it had a different position, having migrated northwestward. At the same time two mildly positive basement features that trended across the flexure, became more pronounced, the Bache Peninsula arch, and the Boothia-Cornwallis belt. These two features, where they crossed the former geosyncline, acted as parts of the Central Stable Region, while the geosyncline subsided markedly beside them. The effect of the simultaneous flexure migration and basement uplift was that the miogeosyncline became restricted in late Early, Middle, and Late Devonian times. Later, it ceased to exist and the entire region was subjected to widespread erosion.

Throughout the area Devonian is widely conformable with Silurian. On the Central Stable Region and the shelfward margin of the geosyncline the systemic boundary is within Read Bay limestones. In central parts of the geosyncline it is within Cape Phillips shales, and in northwestern parts within fine clastics of the Cape Rawson Group. Graptolitic and shelly faunas are inter-bedded at this level.

Through most of Devonian time fine northwesterly-derived clastics of the outer miogeosynclinal margin grade with carbonates of the medial parts and red beds of shelfward parts. The clastics progressively encroached southeastward and covered the limestones. Unconformable syntectonic and post-tectonic clastic formations, including red beds, were deposited upon the southern miogeosynclinal margin and Central Stable Region in late Early and again in early Middle Devonian time, by widespread shallowing and basement uplift. Through Eifelian time widespread carbonate deposition in medial and shelfward parts of the miogeosyncline included reef buildups to 4,000 feet, followed by widespread sandy limestone in Givetian time. Middle Devonian carbonates grade northwestward to fine clastics. In latest Middle and through most of the Late Devonian, thick quartzose clastics were spread southerly, grading into and overlapping limestones. A Frasnian positive pulse of the Boothia uplift interrupted this deposition.