Upper Devonian strata (Melville Island Group) in the western Arctic Islands are part of a clastic wedge at least 10,000 ft thick. The strata represent the uppermost part of the Lower to Middle Paleozoic sequence of the Franklinian miogeosyncline.

Three major depositional facies are recognized. (1) Marine shelf facies--interbedded green, very fine-grained, argillaceous quartz sandstone, siltstone, and shale with a few marine fossils. Organic limestones are rare. (2) High energy shoreline facies--white, fine to coarse-grained, well-sorted quartz sandstone with plant and fish remains. (3) Low energy shoreline facies--interbedded, very fine-grained, argillaceous quartz sandstone, siltstone, shale, and coal.

On Bathurst and Melville Islands, the Group is divided into the Hecla Bay Formation (early to middle Frasnian) consisting mainly of high-energy shoreline facies, and the overlying Griper Bay Formation consisting of 2 informal members. The lower member (mid to late Frasnian) consists of marine shelf facies, and the upper member (early to middle Famennian) consists of high- and low-energy shoreline facies. On Prince Patrick and Banks Islands only the Griper Bay Formation is developed. Two informal members are recognized, the lower comprising the entire Frasnian stage, and the upper a part of the Famennian.

The source area for the sediments is interpreted to have been a tectonic highland situated along the present western continental margin.

Mississippian (Ellesmerian) deformation resulted in the development of open anticline-syncline couples and normal faults. On Bathurst and Melville Islands these structures trend east-west. In contrast, the structures trend north-south on Banks Island. This sharp bend in the Ellesmerian fold belt may be interpreted to be an orocline superimposed on the Franklinian geosyncline during the Ellesmerian orogeny. Restoration of the orocline clarifies otherwise irreconcilable facies relations in the Upper Devonian strata of the Western Arctic Islands.

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