The Silurian strata of northwest Greenland consist of an intricate assemblage of graptolitic rocks and limestones of varied facies deposited at the seaward edge of a carbonate platform that covered most of northern Greenland during Silurian time. Facies changes are abrupt and the formations are in part facies equivalents of each other. The Offley Island Formation consists of biostromal and biohermal limestones and associated calcarenites and limestone conglomerates. The Cape Schuchert Formation is composed primarily of somewhat argillaceous calcisiltites, but includes minor biostromal and biohermal limestones and related calcarenites. The graptolitic rocks are assigned to the Cape Phillips Formation and consist of calcareous shale and mudstone, chert, argillaceous limesto e, and local strings of small bioherms. The term "Cape Tyson Formation" is considered obsolete. All the rocks exposed at the studied localities are of about late Llandovery age, but younger and older Silurian rocks may be present elsewhere in northern Greenland.

Extensive development of biostromal and biohermal rocks may be characteristic of the seaward edge of the Silurian carbonate platform in Greenland and the Canadian Arctic Islands. The position of the edge can be traced from Greenland to east-central Ellesmere Island and Grinnell Peninsula to Cornwallis Island, from there westward south of Bathurst Island and through southern Melville Island.

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