Deforce K. (2011): Middle and Late Holocene vegetation and landscape evolution of the Scheldt estuary. A palynological study of a peat deposit from Doel (N-Belgium). Geologica Belgica 14/3-4: 277-288. (original) (raw)
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Geologica Belgica, 2011
Local and regional environmental conditions for the south-eastern Scheldt estuary during the middle and late Holocene period have been reconstructed based on pollen analysis, loss-on-ignition and radiocarbon dating of a sediment core from Doel (N-Belgium) and the comparison with existing data from other sites from the same region. Postglacial relative sea level rise resulted in the formation of alder carr vegetation in the lower parts of the landscape from c. 7640 cal BP onwards. The vegetation succession was weakly influenced by the deposition of tidal clay deposits between c. 6550 and 5650 a cal BP and eventually culminated in the development of an oligotrophic bog. Peat accumulation seems to have ceased between c. 2030 and 1220 a cal BP, well before it was covered by marine sediments in the late Middle Ages.
Postglacial evolution of vegetation and environment in the Scheldt Basin (northern Belgium)
The infill of abandoned river channels is the main information source on postglacial vegetation and landscape evolution in inland northern Belgium. Palynological studies of these deposits also contribute to a better understanding of the environmental context of the numerous archaeological sites in this area. The results are presented of palynological analyses, including pollen, spores, non-pollen palynomorphs and microcharcoal from the palaeochannel infill at seven sites in the Scheldt and Durme valleys in northern Belgium. Based on the regional vegetation evolution and radiocarbon dating, a biozonation for the Scheldt Basin is constructed encompassing the final Late-glacial and Holocene period. The local taxa show a hydroseral succession from open-water environment, through reed or sedge fen to carr forest. Salix and Viburnum opulus were important elements in the Early Holocene riparian and carr vegetation, but are often underrepresented in pollen diagrams from larger valleys. There are indications for human disturbance and agriculture between 7,000 and 6,400 cal BP. The simultaneous decline of elm and lime in the study area around 4,000 cal BP can be linked to human impact.
Analyses of pollen, plant macrofossils (seeds, fruits, wood and mosses), molluscs, diatoms and vertebrate (mainly fish) remains allowed a detailed reconstruction of a middle-Holocene alluvial forest and its associated hydrological conditions. The use of multiple proxies resulted in a taxonomically more detailed and environmentally more comprehensive understanding of terrestrial as well as aquatic habitats. The results demonstrate possible biases in palaeoecological reconstructions of alluvial and estuarine environments drawn from single proxies. Many locally occurring woody taxa were underrepresented or remained undetected by pollen analyses. Seeds and fruits also proved to be inadequate to detect several locally important taxa, such as Ulmus and Hedera helix. Apparently brackish conditions inferred from diatoms, pollen and other microfossils conflicted strikingly with the evidence from molluscs, fish bones and botanical macroremains which suggest a freshwater environment. Brackish sediment (and the microfossil indicators) is likely to have been deposited during spring tides or storm surges, when estuarine waters penetrated more inland than usual. Despite the reworking and deposition of estuarine and saltmarsh sediment well above the tidal node at such events, local salinity levels largely remained unaffected.
Sedimentology , 2022
In the transformation from tidal systems to freshwater coastal landscapes, plants act as eco-engineering species that reduce hydrodynamics and trap sediment, but nature and timing of the mechanisms of land creation along estuaries remains unclear. This article focuses on the Old Rhine estuary (The Netherlands) to show the importance of vegetation in coastal landscape evolution, predominantly regarding tidal basin filling and overbank morphology. This estuary hosted the main outflow channel of the river Rhine between ca 6500 to 2000 cal BP, and was constrained by peat during most of its existence. This study reconstructs its geological evolution, by correlating newly integrated geological data and new field records to varying conditions. Numerical modelling was performed to test the inferred mechanisms. It was found that floodbasin vegetation and resulting organic accumulation strongly accelerated back-barrier infill, by minimizing tidal influence. After tidal and wave transport had already sufficiently filled the back-barrier basin, reed rapidly expanded from its edges under brackish conditions, as shown by diatom analysis and datings. Reed growth provided a positive infilling feedback by reducing tidal flow and tidal prism, accelerating basin infilling. New radiocarbon dates show that large-scale crevassing along the Old Rhine River – driven by tidal backwater effect – only started as nutrient-rich river water transformed the floodbasin into an Alder carr in a next phase of estuary evolution. Such less dense vegetation promotes crevassing as sediments are more easily transported into the floodbasin. As river discharge increased and estuary mouth infilling progressed, crevasse activity diminished around 3800 to 3000 cal BP, likely due to a reduced tidal backwater effect. The insights from this data-rich Holocene study showcase the dominant role that vegetation may have in the long-term evolution of coastal wetlands. It provides clues for effective use of vegetation in vulnerable wetland landscapes to steer sedimentation patterns to strategically adapt to rising water levels. Keywords: Estuary, Holocene, infilling, peat accumulation, vegetation.
Netherlands Journal of Geosciences, 2016
This paper describes the landscape evolution of the Waasland Scheldt polders in the north of Belgium from the Late Glacial – early Holocene to the present time, and the effects of this changing landscape on the human settlement. The regional landscape evolution has been visualised in a series of palaeogeographical maps for successive time frames. Two different map series were produced: a series of Holocene palaeogeographical reconstructions (11,000–950 cal BP) based on geotechnical, geological and archaeological data, and a series of post-Medieval landscape reconstructions (16th- to 19th-century) based on historical maps, land registers and soil data. Additional palaeoenvironmental information from fossil pollen and plant remains allowed reconstruction of the vegetation and wetland changes, particularly for the middle to late Holocene. Peat growth was the main key to understanding the landscape evolution of the Waasland Scheldt polders. Whereas the landscape evolution during the Hol...
Quaternary Science Reviews, 2020
Interpretation of fossil assemblages in mixed energy environments, such as estuaries, is complex due to the accumulation of material from different sources. In such environments, different proxies may result in contrasting interpretations, as is illustrated by the case of the Scheldt estuary in northern Belgium: during a phase of increased landward tidal ingression between 7000 and 5000 cal BP, mud was deposited, including microfossils that indicate increased salinity, while macrofossil records from the same deposits indicate tidal freshwater environments. By combining multiple proxies, sedimentological analysis and multivariate statistics, it is concluded that considerable landward sediment transport by tidal pumping, possibly enhanced by storms, explains how marine and brackish microfossils are massively present in freshwater tidal deposits. We propose an approach that combines the easily transported microfossils with the more local macrofossils to obtain a coherent reconstruction of the local estuarine environment, and to better understand the sedimentological processes in the wider region.
The Holocene, 2014
Analyses of pollen, plant macrofossils (seeds, fruits, wood and mosses), molluscs, diatoms and vertebrate (mainly fish) remains allowed a detailed reconstruction of a middle-Holocene alluvial forest and its associated hydrological conditions. The use of multiple proxies resulted in a taxonomically more detailed and environmentally more comprehensive understanding of terrestrial as well as aquatic habitats. The results demonstrate possible biases in palaeoecological reconstructions of alluvial and estuarine environments drawn from single proxies. Many locally occurring woody taxa were underrepresented or remained undetected by pollen analyses. Seeds and fruits also proved to be inadequate to detect several locally important taxa, such as Ulmus and Hedera helix. Apparently brackish conditions inferred from diatoms, pollen and other microfossils conflicted strikingly with the evidence from molluscs, fish bones and botanical macroremains which suggest a freshwater environment. Brackish sediment (and the microfossil indicators) is likely to have been deposited during spring tides or storm surges, when estuarine waters penetrated more inland than usual. Despite the reworking and deposition of estuarine and saltmarsh sediment well above the tidal node at such events, local salinity levels largely remained unaffected.
Radiocarbon, 2014
The Mesolithic-Neolithic transition in the wetland margins of the southern North Sea basin occurred well over a millennium after the transition in neighboring loess regions. This article investigates the possible role of hydrological dynamics in the presence of the last hunter-gatherer-fishermen in these wetland regions. A Bayesian modeling approach is used to integrate stratigraphic information and radiocarbon dates both from accurately datable archaeological remains and key horizons in peat sequences in the Scheldt floodplain of northwestern Belgium. This study tests whether the Swifterbant occupation of the study area was contemporaneous with hiatuses in peat growth caused by organic clastic sedimentation due to increased tidal influences and local groundwater rise. The results suggest that the appearance of this culture followed shortly after the emergence of a brackish tidal mudflat landscape replacing a freshwater marsh.