Offshore redeposited coralline algae as evidence of Paleocene shallow-water carbonate sedimentation in the Magura Basin (Outer Carpathians)

Abstract

Within the upper Paleocene (Thanetian) flysch conglomeratic sandstones of the Magura Nappe, a bed characterized by dominant coralline red algae, with subordinate benthic foraminifera, corals, bryozoans, and molluscs has been identified. It is the only known site showing evidence of rarely explored Paleocene shallow-water areas in the Magura Basin. Corallines occur as abraded coralline algal debris and rhodoliths. The upper Paleocene coralline algal debris consists of rounded, sand- to pebble-size clasts. Two types of rhodoliths were distinguished: abraded sub-spheroidal boxwork up to 0.5 cm in diameter, and irregular boxwork rhodoliths larger than 1 cm in diameter. In the coralline algal assemblage, the most abundant component is Sporolithon sp., with subordinate Lithothamnion sp. and Mesophyllum sp. Karpathia sphaerocellulosa and Spongites sp. are also present. Bioerosions, such as Entobia isp., Gastrochaenolites isp., Trypanites isp., and microborings are common in the coralline debris. This assemblage documents the shallow-water carbonate biogenic sedimentation in the northern Magura Basin during the Thanetian. These corallines formed above the storm wave base and were redeposited offshore in the inner part of the Magura Basin by sediment gravity flows.