Also in the other mardels the concentrations of inorganic carbon are high, especially in the Kalefeld sample. It is evident that the 14C dates of the Brasert and Kalefeld mardel deposits are not reliable, due to the reservoir effects. They overestimate the real ages.
A second effect that causes overestimating of 14C ages is the contamination of the organic carbon fraction of the sediments with older redeposited soil organic carbon, present in the colluvial deposit. The δ13C values of the samples of Brasert and Kalefeld (≈ − 27) indicate soil organic PI-3065 originating from eroded forest soils instead of the decomposed organic matter of a local wetland vegetation (Osmond et al., 1981).
Due to these effects, the radiocarbon ages of the samples Brasert and Kalefeld do not correspond with the palynological ages, expressed in the Firbas zoning.
3.2. Pollen record of mardel deposits
3.2.1. Mardel Elteschmuer
Mardel Elteschmuer is situated in Esselbur (490 50′ 28″ N/6° 15′ 82" E; altitude 410 m), 400 m east of the cuesta front. A linear range of wetlands has developed in an elongated subsidence basin parallel to the cuesta front. Considering the vicinity of the cuesta front it is likely that the shape is associated with patterns of tectonic crevasses. Likely, the water infiltration in the crevasses stagnated by sediment jam and wetlands (muers) could develop. The wetland vegetation is now dominated by Betula trees, Molinia and Sphagnum ( Fig. 3).