Late Weichselian deglaciation and early Holocene development of a cold-water coral reef along the Lopphavet shelf (Northern Norway) recorded by benthic foraminifera and ostracoda

Abstract

Cold-water coral (CWC) settlement in northern Norway is strongly related to the outlet-glaciers of the Fennoscandian Ice-sheet, and dating of known CWC structures show clearly post-glacial ages. Two gravity cores (POS391 559/2,277cm long and POS391 559/3,282cm long) were recovered on a CWC reef in the area of Lopphavet, northern Norway. Detailed investigations on lithology (sediment structures and composition), micropaleontology (foraminifera and ostracoda) and AMS 14C dating on the epibenthic foraminifera Discanomalina coronata were performed on the two cores. Phosphorus analyses were performed only on core POS391 559/3. Results indicate that the whole core POS391 559/2 is representative of a CWC reef environment. The base of the core is dated at 10,600±120cal.yrBP, thus representing one of the oldest ages of a Norwegian coral reef. Core POS391 559/3 documents the passage from a proximal glacier environment characterized by fine silty sediments with intercalation of several dropstone layers to a CWC ecosystem. The transition from the glacial to the interglacial stage is dated as old as 10,725±205cal.yrBP, whereas the base of the core is dated to an age of 15,300±550cal.yrBP. Diversity of benthic foraminifera is higher within the CWC, especially in the intervals containing coral framework. Five clusters are identified based on the Bray–Curtis Similarity Term Analyses and the interpretation of data shows that they are related to different ecological settings, e.g., fluctuations of the sea-ice cover; influence of the warmer and more saline Atlantic water masses; transitional to a fully interglacial environment; well oxygenated, nutrient-rich and high current setting being conducive to CWC.Ostracod assemblages show that these crustaceans may be also used to characterize sedimentary facies on CWC reefs.