Abstract

The Solund district of western Norway contains a maximum preserved stratigraphic thickness of 5,200 metres of coarse conglomerate with lesser sandstone. This section is thought to be Middle Devonian from its lithostratigraphic similarity to nearby deposits containing plant and fish remains. The sediments are thought to represent post-Caledonian humid alluvial-fan deposits analogous to those in the Triassic Newark basins of the Appalachian Mountains. Devonian block-faulting and graben formation resulted in deposition of alluvial sediments in basins adjacent to contemporaneously uplifting highlands. The present structural basin of the Solund district preserves part of a large, northeast—striking, coalesced fan complex, with the provenance to the southeast composed of Caledonian metamorphic and igneous rocks.

The Devonian rocks consist primarily of thick, irregularly bedded polymict cobble and boulder conglomerates having consistently oriented imbrication and alignment of elongate clasts on bedding surfaces. Dispersed lens-shaped bodies of interstratified sandstone and finer conglomerate are common, with a basal sedimentary breccia derived from the underlying basement locally. The thick conglomerates contain thin lenses of horizontally stratified sandstones, but otherwise lack internal structures. Structures within the sandstone - fine conglomerate areas include horizontal stratification, various types of trough and tabular cross-stratification, straight asymmetrical ripple markings, ripple-drift bedding, primary-current lineation, channel cut-and-fill, linear cobble-boulder trains, and conglomerate-sandstone cycles fining-upward. Rapid deposition in braided-stream channels in midfan areas is postulated, with palaeocurrent data, fabric analysis, and textural and clast distribution patterns suggesting relatively uniform transport from the southeast. Post-depositional faulting and folding during the Svalbardian disturbance have modified the original depositional basin.