Holocene marine diatoms from the Faeroe Islands and their paleoceanographic implications

Abstract

Temporal oceanographic changes based on mid- and late Holocene marine diatom floras from the Faeroe Islands region have been studied. The four studied coring sites are located in the Skalafjord and a more open-ocean environment, the mouth of the Kaldbaksfjord, at water depths ranging between 50 and 70 m. Comparison of the diatom records in the fjord sediments with those from the outer part of the fjord shows that the fjord provides a more optimum potential for paleoceanographic reconstructions. The concentrations of marine taxa and relative abundance of freshwater diatom species in the marine environment were analyzed with the aim of relating them to environmental conditions. Estimated diatom concentrations were very low and ranged from a maximum of 14.4 × 10 6 valves per gram dry sediment in the inner part of the fjord to a minimum of 0.1 × 10 6 outside the fjord. The freshwater diatom flora that occurred between 1200 and 700 cal. yr. BP in the inner part of the fjord suggests much higher precipitation during this time and increased freshwater discharge into the fjord. Presence of Actinocyclus normanii, which is an indicator of increasing trophy, is related to the first human settlement on the Faeroe Islands. Maximum-likelihood factor analysis (MLFA) was used to describe the most essential relationship among the diatom species, and to employ these relationships for inferring Holocene environmental changes in the Faeroe Islands. The first two MLFA factors are related to oceanic influences in the region. Factor 1 is represented by a warmer water diatom assemblage and is suggested to correspond to inflow of the Norwegian–Atlantic Current to the Skalafjord, whereas Factor 2 is an indicator of a colder-water diatom assemblage that corresponds to inflow of Arctic–Norwegian Water Mixing (ANWM) during the 4900–3200 cal. yr. BP time interval.