Upper Carboniferous–Lower Permian Palaeoaplysina build-ups on Svalbard: the influence of climate, salinity and sea-level

Abstract

AbstractUpper Carboniferous–Lower Permian Palaeoaplysina build-ups on Svalbard developed on a partly restricted marine warm-water carbonate platform at low palaeo-latitudes. The Palaeoaplysina build-ups mostly have a flat-topped tabular geometry, representing the mature stage of build-up growth. With decreasing accommodation space, continued vertical growth was hampered and lateral growth became dominant. The tabular growth form of the build-ups is probably a result of lateral amalgamation of several minor mounds. In central Spitsbergen many of the tabular build-ups form parts of continuous ridges or ring-shaped to polygonal build-up complexes encircling a lagoon. Lateral interfingering between bedded fusulinid dolostones along the build-up margins and barren dolostones further out in the lagoon may indicate increasing salinity from the lagoon margin to the central part. These lateral facies changes are often associated with evaporites (gypsum) and low biodiversity, especially abundant euryhaline fusulinids or even barren beds. On the sea side of the Palaeoaplysina build-ups, the frequent renewal of normal saline seawater allowed the highest biodiversity (e.g. stenohaline crinoids). The uppermost part of some build-ups contain Microcodium, indicating intermittent subaerial exposure and vegetation cover during lowstand, probably caused by eustatic sea-level changes and/or local tectonics. The biota of the build-ups and their lateral sediments is typical for a shallow marine chloroforam association, indicating a tropical climate during deposition.