Holocene sea-level rise and its effect on the mass balance of coastal deposits

摘要

A mass balance study of the Holocene accumulation wedge has been carried out in the lowland area between the Ems and Weser rivers on the German North Sea coast. This region, which comprises various sedimentary environments, such as barrier islands, sheltered and open tidal flats, bay flats, and estuaries, is highly suitable for such quantitative studies and can serve as a model for general mass transport and accumulation processes connected with transgressions over coastal lowlands. Data for the study was taken from borehole records, hydrographic soundings and topographic surveying to prepare structure contour maps and sequence maps at a scale of 1:25,000 showing the outlines and the internal make-up of the Holocene accumulation wedge. The irregularly distributed data was interpolated into a regular grid and the volumes of allochthonous clastic sediments and autochthonous peat, which make up 90% and 10%, respectively, of the coastal Holocene, were calculated. A comparison of the amount of clastic material supplied by the Ems, Weser, and Elbe rivers during the last 7500 years with the total volume of the accumulation wedge shows that about 90% is from marine and only 10% from riverine sources. By comparing the results of the quantitative analysis of the Holocene sedimentation with the present-day morphological and hydrodynamic observations, predictions of the future development of the coastal lowland area can be made.