Changes in coastal zone processes at a high sea‐level stand: a late Holocene example from Belgium

Abstract

This paper presents the results of an investigation of late Holocene deposits on the Belgian coastal plain. The upper clastic deposits overlying the uppermost intercalated peat bed were studied on the basis of lithology, radiocarbon dates and foraminiferal assemblages to determine why silting-up phases or peat beds are lacking, and to establish the evolution of the sedimentary environments as well as the age of the deposits. Two contrasting sites, in quite different locations and showing a different stratigraphy, were studied. It appears that the coastal evolution was not gradual and continuous, but characterised by short periods with high-energy conditions alternating with long periods where low-energy conditions and little sedimentation prevailed. The evolution is determined mainly by tidal channel activity. At about 3400 cal. yr BP, the peat was eroded in narrow zones by the main tidal channels and this until the landward limit of the plain.The peat was only partly flooded and mudflats fringed the channels. With time, new tributaries formed and the channel network progressively enlarged. The channels were rapidly filled, followed by a period of little sedimentation, which lasted at least until 1400-1200 cal. yr BP. The following channel activity is characterised by lateral sedimentation, rather than vertical erosion, together with increased sediment reworking. The mechanisms of coastal change in the late Holocene might be similar over the entire plain, but the timing of the changes is certainly not.

Holocene sedimentary infilling of a tide-dominated estuarine mouth. The example of the macrotidal Seine estuary (NW France)

“…On the other hand, the period 3500-2500 yr B.P. is known all along the coasts of northern Europe as a period of climatic deterioration with severe coastal retreats and barrier destructions [Long et al, 1996;Régnault et al, 1996;Spencer et al, 1998;Clavé et al, 2001;Baeteman et al, 2002;Meurisse et al, 2005;Billeaud et al, 2010]. This hypothesis of a climatic crisis to explain the major environmental change recorded in the sedimentary infilling of the Seine mouth is preferred here, since the impact of this crisis on coastal areas has been widely documented, including already in the outer Seine Estuary [Sorrel et al, 2009].…”

Past landscapes and present-day techniques: reconstructing submerged medieval landscapes in the western part of Sealand Flanders

“…In periods of 'high energy' marine influence, new deposits changed the tidal landscape rapidly. Parts of these deposits were sand flats which were formed in estuaries; often channels silted up with sandy deposits as well Baeteman et al 2002). Some of these sandy soils remained visible in the landscape as slight elevations, allowing inhabitants to settle.…”

The Holocene coastal deposits of Sussex: a re-evaluation

“…As well as peat cutting, activities such as vegetation cutting and grazing, for which there is evidence from the Bronze Age onwards (Waller and Schofield 2007), may have retarded the accumulation of peat and promoted a shift from organic to clastic sedimentation in the East Sussex valleys. Lowering the water table by drainage, would have caused peat compaction, a process which may also have occurred naturally as a result of tidal creek extension following inundation (Baeteman et al 2002). These processes could all have provided accommodation space in the late Holocene, though the absence of thick post-peat deposits in valleys such as the Brede and Combe Haven, in contrast to the some of the levels, suggests that coastal processes (inundation followed by erosion and sediment compaction), were of greater significance in this respect.…”