Silurian marine communities west of Dingle, Ireland

Abstract

Coastal exposures of the Dunquin Group west of Dingle, Ireland, consist of shallow marine and volcanic deposits of Wenlock age. Stratigraphic sequences show a gradient from offshore silts to nearshore silts and sands, followed by nonmarine, lagoonal sediments and volcanics. Bioturbation decreases from the offshore to lagoonal ends of the gradient, and communities of shelled invertebrates are restricted to marine sediments. These communities are dominated by brachiopods, corals, and crinoids, and show the greatest species diversity and trophic complexity in offshore, slowly deposited silts. Nearshore sediments contain low-diversity, brachiopod-dominated assemblages in storm-deposited shell beds and large, isolated colonies of tabulate corals. The Dingle area was probably located along the eastern margin of the Proto-Atlantic Ocean in Wenlock times as a volcanic island area isolated from major shelves across Britain and Scandinavia. Derivation of Dunquin communities was from this shelf area, and at least one interval of geologically rapid, faunal invasion is apparent.