Abstract

Lammefjorden is a reclaimed fjord in north-west Sjælland, Denmark. Sediment cores from the area were collected to study its development after the last deglaciation, in particular the sea-level history. Late glacial and Early Holocene lake and bog deposits occur below marine deposits. Sparse late glacial fossil assemblages indicate tree-less environments with dwarf-shrub heaths. Early Holocene deposits contain remains of Betula sec. Albae sp. and Pinus sylvestris, which indicate open forests. The wetland flora comprised the calciphilous reed plant Cladium mariscus and the water plant Najas marina. Marine gyttja from basins is characterised by sparse benthic faunas, probably due to high sedimentation rates. In some areas, shell-rich deposits were found, with large shells of Ostrea edulis, indicative of high summer temperatures, high salinity and strong tidal currents. A marine shell dated to 6.7 cal. ka provides a minimum age for the marine transgression of Lammefjorden.

Highlights

  • In 1873, a large project was initiated to reclaim Lammefjorden in north-west Sjælland (Fig. 1), and today Lammefjorden is one of the largest reclaimed areas in north-west Europe

  • The upper sand unit contained rare remains of, for example, Dryas octopetala, Betula nana and Distichium sp., which indicate an environment with dwarf-shrub heaths of Late Glacial age

  • The Late Glacial sediments are overlaid by marine and brackish-water gyttja with shells of, for example, Mytilus edulis, Cerastoderma sp., Hydrobia sp., Bittium reticulatum, Balanus crenatus and Cyprideis torosa

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Summary

Introduction

In 1873, a large project was initiated to reclaim Lammefjorden in north-west Sjælland (Fig. 1), and today Lammefjorden is one of the largest reclaimed areas in north-west Europe. The geology of the Lammefjorden region was mapped by the Geological Survey of Denmark in the late 1890s (Rørdam & Milthers 1900). Shell samples from Holocene-raised marine deposits were analysed and several of them contained shells of Ostrea and Tapes. These bivalves no longer live in the region and their former presence was taken to indicate stronger tidal currents than at present It was noted that in situ Quercus stumps and peat deposits were found below marine deposits. Both marine and non-marine deposits were referred to as ‘alluvium’ (Holocene), but a more precise age could not be determined

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