Relative water-level rise in the Flevo lagoon (The Netherlands), 5300-2000 cal. yr BC: an evaluation of new and existing basal peat time-depth data

Abstract

The rise of Holocene (ground)water level as a function of relative sea-level rise has been extensively investigated in the western Netherlands, whereas few studies focused on the Flevo lagoon in the central Netherlands. In this study, all available ,4 C dates from the base of basal peat overlying the top of compaction-free Pleistocene sand in the former Flevo lagoon were evaluated in order to reconstruct water-level rise for the period 5300-2000 cal. yr BC. The present basal peat 14 C data set from Flevoland consists of two subsets: (1) the largely new Almere data (41 dates) representing the southern part of the former Flevo lagoon, with 26 dates especially carried out for this study, and (2) the existing Schokland data (21 dates) representing the eastern part of the lagoon. The Schokland area is located about 50 km from the Almere area. The quality of all basal peat time-depth data was palaeo-ecologically and geologically evaluated, all 14 C dates were calibrated to the same standards, and error margins of age and altitude determination were estimated. After plotting the data as error boxes in time-depth graphs, lower limit curves for water-level rise were constructed for both data sets. Comparison with the mean sea-level curve for The Netherlands ( Van de Plassche, 1982) suggests that water-level rise in the Almere area between 5300 and 2000 cal. yr BC corresponded closely to the rise in mean sea level. The same holds for the Schokland area for the period 5000-4200 cal. yr BC. For the period 4200-2000 cal. yr BC, however, the Schokland data suggest water-level rise to have been slower than mean sea-level rise, leading to local water levels apparently below mean sea level, which is virtually impossible. Hypothetical explanations for this discrepancy include: errors and uncertainties in mean sea-level and local water-level reconstruction, basin subsidence and temporal differences in intra-coastal tidal damping. The presently available data are inconclusive at this point and Holocene water-level rise in the Flevo lagoon awaits further investigations.

New groundwater-level rise data from the Rhine-Meuse delta – implications for the reconstruction of Holocene relative mean sea-level rise and differential land-level movements

“…In a discussion of the available water-level evidence from Flevoland, Makaske et al (2003) proposed three hypothetical explanations for the difference between the Flevoland data and the MSL curve of Van de Plassche (1982): (1) the latter curve erroneously indicates a water level higher than MSL, (2) relative basin subsidence has caused lowering of the Flevoland data relative to the MSL curve, (3) the Schokland data (Roeleveld & Gotjé, 1993) are unreliable. Hypothesis 3 has been ruled out by the research of Van de Plassche et al (2005).…”

“…Instead of summing vertical errors and uncertainties to obtain a maximum vertical range, as has been done in previous palaeowater-level studies (e.g., Törnqvist et al, 1998;Makaske et al, 2003;Van de Plassche et al, 2005), we calculated a total vertical standard deviation based on the various vertical errors and uncertainties mentioned above (except the 'oneway upward corrections' 3b and 4) that are considered as estimates of the 2σ error range (Table 1; a table containing the details of the calculations can be downloaded from: http://www.geo.uu.nl/fg/palaeogeography). Although this total vertical standard deviation necessarily is based on estimates, this statistical approach is more consistent with the way age-error margins (see below) are represented.…”

“…1980; Van de Plassche, 1982Van Dijk et al, 1991;Roeleveld & Gotjé, 1993;Kiden, 1995;Cohen, 2003;Makaske et al, 2003;Van de Plassche et al, 2005). In many cases, basal peats from the slopes of Late Weichselian aeolian dunes were used to reconstruct local curves of groundwater-level rise.…”

Water-level changes in the Flevo area, central Netherlands (5300–1500 BC): implications for relative mean sea-level rise in the Western Netherlands

“…From recently published paleowater-level data we infer that relative average water level in the Flevo area was below the 1982-MSL curve at least as far back as 5300 cal BC. Makaske et al (2002Makaske et al ( , 2003 found that the age-depth position of five new, reliable basal peat samples collected ca. 50 km southwest of Schokland (near the town of Almere; sites d and e in Fig.…”

“…Our objective is to test the hypothesis that the younger part of the Schokland curve runs below the 1982-MSL curve because (1) the radiocarbon ages of the bulk-dated peat samples obtained by RG93 are too ARTICLE IN PRESS (Fig. 1b) where water-level index data were collected, b: Engwierumer polder (Griede, 1978), c: near Rotterdam ( Van de Plassche, 1982), d: and e: near Almere (Makaske et al, 2003); (b) eastern Flevo area, 4: Urk (Roeleveld and Gotje´, 1993), a: Swifterbant (Ente et al, 1986); and (c) former island of Schokland with main study sites (1, 2 and 3) of Roeleveld and Gotje´(1993). For the present paper we revisited site 1.…”