Cecile Baeteman

Holocene evolution of relative sea-level and local mean high water spring tides in Belgium : a first assessment

Abstract Holocene age-depth data from the Belgian coastal plain, basal peat data particularly, are assessed in terms of local water and tide levels. Basal peat formation was generally induced by sea-level rise; effects of local seepage were limited and significant river-gradient effects were absent. No relation was found between the timing of basal peat inception and substrate permeability. In general, edaphic (moisture) conditions were unfavourable for organic accumulation prior to sea-level related rise of the groundwater table. Error envelopes for the minimum level of local mean high water spring tides and for upper and extreme lower relative mean sea-level limits during the last 9400 solar years (8400 yrs B.P.) are presented. These indicate that the rate of relative sea-level rise showed marked retardations at ca. 7500-7000 yrs cal B.P. (± 6650-6100 yrs B.P.) and ca. 5500-5000 yrs cal B.P. (4400 yrs B.P.). A eustatic explanation appears to be plausible, particularly for the former. Prior to ca. 4000 yrs cal B.P. (ca. 3600 yrs B.P.), the relative sea-level rise in Belgium differs noticeably from that established for the western Netherlands, with both diverging progressively back in time. This implies that considerable differential crustal movement occurred between the two areas in the early Holocene.

Comment to “Relative sea level fluctuations in aegean coastal areas from middle to late holocene by Kosmas Pavlopoulos”

In the light of current and predicted future accelerated sea-level rise it is important to understand the past sea-level history of a particular area and to identify the various factors affecting sea-level changes. A number of models reconstructing past sea-level changes exists. The models, however, require continuous adjustment and confrontation with field data. In a recent paper, Pavlopoulos [1] presents such a comparison of observed rates of sea-level rise with the glacio-hydro-isostatic models of Lambeck [2] and Lambeck & Purcell [3] for six Aegean coastal areas (Lafrouda, Palamari, Marathon Plain, Vravron, Istron, and the areas of Mykonos, Delos and Rhenia). In addition the paper by Pavlopoulos [1] presenting the sea-level curve of the past 6000 years of four Aegean coastal areas collected from literature is also of importance for archaeologists who work in these coastal areas and need to interpret their findings within a context of sea-level and coastal changes. Such a synthesis can be of great use for archaeologists who rely on publications produced by sea-level specialists. However, in contrast to the title, Pavlopoulos [1] does not discuss relative sea-level fluctuations and does not analyze all available information about old sea levels as stated in the objective of the paper. The author only presents a calculation of the rate of sea-level rise in mm/a with very little information about the sea-level index points and without any evaluation of the possible sources of error in the interpretation of the sea-level data. His calculated rate of sea-level rise is then compared with those from the glacio-hydro-isostatic models of Lambeck [2] and Lambeck & Purcell [3]. Depending on a higher or lower rate between the calculated and the modelled rate, the author concludes uplift or subsidence of the coastal area of some of the case studies. We believe that the data presented by Pavlopoulos [1] is equivocal and that the methodology adopted for the calculation of the rate of sea-level rise cannot withstand scrutinity. This discussion reports on our critical evaluation of data and reasoning.

14C Dating and the Reconstruction of the Sedimentary Environment and Occupational History of Saltés (Atlantic coast, Southern Spain)

Abstract The taphonomy and chronological context of shell deposits excavated at the location of the deserted late medieval harbour town of Saltés (Atlantic Coast, Spain) were investigated. An interpretation of the depositional history of the deposits was made on the basis of radiocarbon dating and points to a multiple origin of the assemblages. Although the shell deposits are much older than the medieval site, the investigation showed that they still had an anthropogenic origin.