The Franklinian eugeosyncline, mobile from the late Precambrian or Cambrian to the late Devonian or early Mississippian, is exposed mainly in northernmost Axel Heiberg and Ellesmere Islands. The Silurian and Devonian arenites consists of the following genetic groups:

1) Lower Silurian calcareous lithic arenite: post-tectonic marine shelf deposits produced by Ordovician (?) uplift of metamorphosed limestone off northern Ellesmere Island.

2a) Late Middle and early Upper Silurian lithic and volcanic, partly graded arenites: early syntectonic deposits, related to Caledonian movements, composed of sediments as in (1) with contemporaneous keratophyric pyroclastics.

2b) Upper Silurian and Devonian quartz-chert arenites: marine and nonmarine syntectonic and post-tectonic sediments, produced by Caledonian uplift of quartzose sandstone, chert, etc., with some contemporaneous pyroclastics in the upper part.

3) Devonian graded volcanic arenites: early syntectonic turbidites related to a major late Devonian orogeny derived from Silurian keratophyric rocks, to contemporaneous volcanism, or both.

Most of the inferred source rocks seem to have recognizable equivalents in the pre-Devonian (mainly pre-Ordovician) eugeosynclinal succession. The Silurian and Devonian arenites, then, originated partly by contemporaneous pyroclastic volcanism but mainly by uplift, erosion, and rapid redeposition of strata deposited earlier in the mobile belt itself. Turbidity current deposition seems to be confined to syntectonic phases. Sandstones with more than 10% of clay matrix are relatively sparse.

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