Environmental change in Danish marine waters during the Roman Warm Period inferred from mollusc data

Modern geological research into the late and postglacial history of the inner Danish waters (i.e. Kattegat, Bælthavet and Øresund, plus the adjoining fjords and estuaries) began at the turn of the last century. Since then most investigations have focused on the timing of the initial marine inundation of the area, the early to mid-Holocene changes in land–sea configuration and sea level changes during the mid-Holocene Littorina period. Research on the late Holocene marine environment has received less emphasis, undoubtedly due to problems in finding continuous marine sediment records, as sedimentation in large areas of the Danish waters seems to have been characterised by complex spatial and temporal patterns of deposition and non-deposition (e.g. Lykke-Andersen et al. 1993). In an ongoing project we aim to explore the continuous development of Danish coastal environments over the last 9000 years using a variety of proxy data, including molluscs, diatoms, foraminifera, algal pigments, plant macrofossils and physical properties of sediments. The project spans both environmental and cultural history, and addresses the important links between them, as the nature of the coastal environment has exerted major influences on cultural and societal expression and activity from Mesolithic to modern times. This paper presents some of the first results from the project concerning environmental changes in the Roman Warm Period (c. 2000–1600 years B.P.) as shown by changes in molluscan faunas at two coring sites in Horsens Fjord and Tempelkrog in southern Isefjord (Fig. 1).