SCK'CEN

0096098 CK C W/C()92()36/IVK/P-1S

STUDIECENTRUM VOOR KERNENERGIE CENTRE D'ÉTUDE DE L'ÉNERGIE NUCLÉAIRE Late Pliocène to Holocene évolution of the palaeogeography and the hydrographie net of the Campine (N-Belgium)

An overview from literature

Use Van Keer Waste and Disposai SCK'CEN, Mol, Bel.sium

BLG-840

May 2000 DISTRIBUTION LIST

H. von Maravic, EC (5) H. Pitsch, CEA (2) M. Hassanizadeh, TUD (2) J.L. Michelot, UPS (2)

SCK'CEN

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PHYMOI. PmiCLi

Late Pliocène to Holocene évolution of the palaeogeography and the hydrographie net of the Campine (N-Belgium)

An overview from literature

Ilse Van Keer

BLG-840

EC Contract No FI4W-CT96-0026

Waste and Disposai SCK-CEN, Mol, Belgium

May 2000 TABLE OF CONTENTS

1 Introduction. 3

2 Late Pliocène to Middle Pleistocene évolution of tidal and fluvial environments in the Belgium - Dutch border région 3 2.1 Late Pliocène and Praetiglian (2.55 - 2.20 Ma BP) 3 2.1.1 Late Pliocène '. .'. 3 2.1.2 Late Pliocène - Praetiglian transition 3 2.2 - Waalian - Menapian (1.70 - 0.77 Ma BP) 6 2.2.1 Eburonian 6 2.2.2 Waalian 7 2.2.3 Menapian 7 2.3 Bavelian - Cromerian (0.77 - 0.30 Ma years BP) 7 2.4 Elsterian .....7 2.5 Holsteinian 7 3 Palaeogeographical évolution of the Belgium - Dutch border région over the last 150 000 years 8 3.1 Saalian (200 000 -126 000 years BP) 8 3.2 (126 000 -116 000 years BP) 8 3.3 Weichselian glacial (116 000 -10 000 years BP).. 11 3.4 Holocene interglacial 11 4 Palàeoclimate estimâtes over the last 150 000 years 11 4.1 Température and précipitation 11 4.2 Végétation 13 4.3 Sea-level fluctuations 13 4.4 Permafrost conditions 15 4.5 Relief and évolution of the hydrographie net 17 5 Summary 22

REFERENCES 23

ABBREVIATIONS •• 26 ABSTRACT A literature study has been carried out to describe the palaeogeographical and palaeohydrological évolution of the Belgium-Dutch border région during the Late Pliocène to Holocene time period. Palaeogeographic maps given by Zagwijn (1974) and Kasse (1988) are enclosed.

KEYWORDS Belgium - Dutch border région, literature study, palaeoclimatology, palaeogeography, Quatemary 1 Introduction

A literature study on the palaeogeographical and palaeohydrographical évolution of the Belgium-Dutch border région during Late Pliocène to Holocene has been carried out in the framework of the EC project: "A palaeohydrogeological study of the Mol site, Belgium". The main objective of the PHYMOL project is to develop a methodology that can be applied in performance assessments of an argillaceous repository System to simulate the ground-water flow and transport of radionuclides for the present conditions as well as for conditions corresponding to the expected long term climatological évolution. The results of the geochemical and isotopic analyses performed on ground-water samples from aquifers surrounding the Boom Clay, suggest that the deep groundwaters resuit from a mixing between a large fraction of meteoric water and a small fraction of marine water (Marivoet et al, 1998). To reconstruct the composition of the ground waters, it is essential to know when the infiltration of meteoric water to the ground water has started. Therefore, a comprehensive literature study has been carried out to illustrate the palaeo• geographical évolution of the Belgium-Dutch border région during the Late-Pliocene and Holocene periods. Hereby spécifie attention is paid to the évolution of tidal and fluvatile environments. Figure 1 shows the chronostratigraphy of the mentioned time period. From palaeogeographic maps information on 1) the timing of meteoric water infiltration; 2) the extent of the mixing zone; 3) évidence for perturbation of the water rock system (glaciations, sea-level change, river network and permafrost); 4) the extent of these perturbations, can be deduced. In this report a compilation of palaeogeographic maps from Zagwijn (1974) and Kasse (1988), who described and illustrated the palaeogeographical évolution of the mentioned area thoroughly, is given.

2 Late Pliocène to Middle Pleistocene évolution of tidal and fluvial environments in the Belgium - Dutch border région

2.1 Late Pliocène and Praetiglian (2.55 - 2.20 Ma BP)

2.LI Late Pliocène During the Late Pliocène a sédimentation basin of fluviatile and marine deposits existed in the southem part of the Netherlands and in northem Belgium (Zagwijn, 1974; Kasse, 1988). The coast line, the shape of which is determined by the tectonic activity of the Roer Valley Graben and the Lower Rhine Embayement, went through Zeeuwsch-Vlaanderen and the Northem Campine. The River Rhine had its course towards the northwest and was building a delta in the Roer Valley Graben.

2.L2 Late Pliocène - Praetiglian transition This time period is characterised by marine and fluvial sédimentation followed by a period of non-deposition (Kasse, 1988; Fig. 2A). The occurrence of the Meuse fluvial system is thought to be Late Pliocène to Praetiglian in age. The ancient Meuse followed a northeastem course and discharged into the Rhine east of Heerlen-Sittard. From this point, the Rhine and Meuse flowed in a northwest-westerly direction through northem Belgium, where they deposited thick beds of the Mol and the Merksplas sands. Because of the eastwest-northeast palaeocoastline configuration, it is possible that the Merksplas sands are the estuarine or nearshore equivalent of the fluviatile Mol sands. To the north the Mol and Merksplas sands change into marine deposits.

mean température in July(°C) T paleo- martne magnetism influence T T lOVars O 20 HOLOCENE Weichselian Eemian Saalian Holsteinianl tlstenan MIDOLE PLEISTOCENE Cromerian

Bavelian

Menapian

Waaüan

EARLY Eburonian PLEISTOCENE

Tiglian

Praetiglian

LATE Reuverian PLIOCENE

SCK-CEN/IVK/flg99022

Figure 1 Chronostratigraphy and température curve of the Late Pliocène to Holocene (firom Zagwijn, 1989).

2.2 Tigiian (2.20 - 1.70 Ma BP) Afler the Praetiglian the Rhine-Meuse sédimentation ceased in western Noord Brabant (the Netherlands) and adjacent northem Belgium. It seems that this period of non-deposition, which corresponds to the cool B, lasted until the Middle Tiglian (Tiglian C3). Subsequenly, the climate ameliorated and a sea-level rise resulted in a transgression in the mentioned area (Kasse, 1988). Hereby, large parts of the Belgium-Dutch border région were Ti-rn NnTi-nzRi.ANi)^ THE NLI HERLANDSs

Mcrkspl

Legend EO Rh.ne ^ Meuse landward tidal ^ seaward tidal ® tidal litter zone marine jOKni BELGIUM O 10 20 sok BELGIUM

SCK-CEN/IVK/llcWdOl SC'K-n;N71VK/|-n:'J')l)ll2

THE NETHERLANDS,- ^iii rrîtrtîl riî: THE NETHERLANDS ;ïyS;

iiinho

Legend ]3 Rliine SU Meuse Legend § landward tidal ^ seaward tidal Ç3 Rhine H tidal litter zone E Meuse . marine 113 Scheldt r' J O » 20 301 O » 20 30wn BELGIUM ' BELGIUM

SCK-CEN/IVK/ng99(X)4 SCK-CEN/IVK/lis'jy(X)5

NETHERLANDS

Legend ED Rhme Ei Meuse El Scheldt § landward ^ seaward

O X) 20 30km BELGIUM

SCK-CEN71VK/lis')')IKlf,

Figure 2 Palaeogeography of the Belgium - Dutch border région (from Kasse. 1988) during the A) Late Pliocène; B) Tiglian C3; C) Tiglian C5; D) Eburonian and E) Waalian. Référence cities: A: Antwerp; B: Breda; Br: Brussels; E: Eindhoven; M: Maastricht. affected by tidal processes. The tidal sédiments are found north of the line Putte, Westmalle and Turnhout. The Rhine still occupied a north-western course through the Roer Valley Graben. In the neighbourhoód of Eindhoven the fluviatile environment of the Rhine probably merged into tidal environments. Outside the estuaries the flooding of the Tertiary plain is reflected by the déposition of the Rijkevorsel Member (Fig. 2B), which fprms the lower part of the Campine Clays. These, probably lagoonal clays were deposited in an inshore landward tidal environment characterised by a fairly low salinity. Simultaniously with the déposition of the Rijkevorsel Clay, the Hoogerheide Member was formed in a seaward inshore tidal environment, where salinity could have been somewhat higher. The period between the Tiglian C3 and C5 is characterised by régression of the sea and déposition of eolian and fluviatile sédiments (Beerse Member) in periglacial environments. The sédiments from the Beerse Member were probably supplied by rivers from the Scheldt Basin in central Belgium. After the Tiglian C4 the cümate ameliorated duHng the Tiglian C5. This climatic improvement caused a transgression of thé sea in Noord-Brabant, northem Belgium and the southwestem Netherlands. During the Tiglian C5 the Belgium-Dutch border région was completely covered by tidal deposits (Kasse, 1988; Fig. 2C). The Turnhout member, which forms the upper part of the Campine Clays, consists of rather clayey sédiments, which were deposited in a landward tidal environment. Salinity was low although locally periodic fluxes of sait or brackish water occurred. To the south of the Turnhout member, a tidal litter zone developed. In the west, salinity was somewhat more brackish than in the east. The courses of the Rhine and Meuse Rivers were probably comparable to former Tiglian periods. Towards the end of the Tiglian C5 the sea-level rise decreased and the depositional environments silted up completely. The area was covered by a continuous clay layer. Brackish environments were succeeded by tidal, fresh water, eutrophic environments, fed by large rivers. The sea inundated Noord^Brabant once more after this régression period. This transgression marks the last phase of tidal sédimentation during the Tiglian C5, before the sea finally withdrew from Noord-Brabant and northem Belgium during the Tiglian C6. The coastline had shifted to the west and the sea did not occupy the present territory of the Netherlands anymore. The régression at the end of the Tiglian was probably caused by silting of the tidal environments and by a climatic détérioration resulting in an eustatic sea-level drop because of the approaching Eburonian glacial.

2.2 Eburonian - WaaUan - Menapian (1.70 - 0.77 Ma BP) These three time periods are characterised by fluviatile déposition in Noord-Brabant and the Campine Basin by rivers from the Scheldt basin (central Belgium) and by the Meuse (Kasse, 1988).

2.2.1 Eburonian During the onsèt of the Eburonian the climate became colder with a mean annual température below -5°C. During this time large ice-sheets covered North America (Nebraskan inland-ice). A sea-level drop was the result of considérable amounts of frozen ocean water. Permafrost conditions, pointing to mean annual températures < 5°C, existed during spécifie phases. The Rhine had changed course from southeast-northwest in a more or less east-west direction. Riveirs from the Scheldt basin transported sédiments from the south, which they deposited in northem Belgium and the southem part of the Netherlands (Kasse, 1988; Fig. 2D). 2.2.2 Waalian At the beginning of the Waalian an amélioration of the climate is recorded, which resulted in a sea-level rise. The corresponding marine transgression, however, did not result in a flooding of the Belgium-Dutch borderzone. This transgression is only recognised in the western Netherlands. Rhine occupied its east-west course. The Meuse had probably left its northeastem course through Limburg and flowed more west (Kasse, 1988; Fig. 2E).

2.2.3 Menapian After the Waalian the climate deteriorated during the Menapian. According to Vandenberghe & Kasse (1988), permafrost conditions were occasionally present, which points to a mean annual température of around -5°C. The most characteristic feature of the Menapian is the shift of the Meuse river to the Northwest over the Campine Plateau. The Rhine stiU occupied the same course which was foUowed during the Eburonian and Waalian.

2.3 Bavelian - Cromerian (0.77 - 0.30 Ma years BP) This time period is characterised by increased faulting and fluviatile déposition by the Rhine and Meuse Rivers (Kasse, 1988). During the Bavelian the Rhine River, which was probably characterised by a meandering river regime, foUowed a southeast-northwest course through Germany, the Roer Valley Graben and the Central Graben. In Belgium, the course of the Rhine over the Campine Plateau is unknown. During the Cromerian the tectonic activity of the western boundary faults of the Central Graben increased. Rhine and Meuse migrated laterally over large distances.

2.4 Elsterian During this glacial the northerri part of the Netherlands was completely covered by the Scandian ice sheet, which was in contact with the ice sheet covering Great Britain (Berendsen, 1998; Fig. 3A). Because pf the huge amount of frozenocea n water, a sea-level drop between 80 to 100 m is recorded. The rivers (Meuse, Scheldt and Rhine) were forced in southwesterly direction through the Street of Dover. This drainage system existed from the Elsterian until the Weichselian (Berendsen, 1998). Furthermore, this time periöd is characterised by the formation of deep erosional incisions. In the northem part of the Netherlands, gullies up to 100 m, locally up to 300 m, below sea sevel are recognised. These long and narrow gullies are most likely the result of melting under the ice sheet.

2.5 Holsteinian The cold Elsterian is succeeded by a period düring which a temperate oceanic climate prevailed. Early in the Holsteinian interglacial period, the sea level increased as a result of melting of the inland ice. According to Cameron et al. (1993) the shorelines lay partly landward of those of the present North Sea. At this time, there was probably no marine coimection between the North Sea and the English Channel through the Dover Street (Zagwijn, 1979; Hinsch, 1985). The coastline ran more or less parallel to the present northem coastline of the Netherlands (Zagwijn, 1974). The River Rhine was flovwng from the Lower Rhine district, where its course was similar to the present, to the northwest where it was building Ml alluvial fan. SCK-CEN/IVK/fig99027

sea continent [;y' '"' | inland ice "v^. river course

Figure 3 Propagation of inland ice sheet in Northwestern Europe at three time periods during the Pleistocene; A) Elsterian; B) Saalian and C) Weichselian (From Berendsen, 1998).

3 Palaeogeographical évolution of the Belgium - Dutch border région over the last 150 000 years

3.1 Saalian (200 000 - 126 000 years BP) During the Saalian glacial, probably about 150 000 years ago, a large sheet of inland-ice spread across Denmark, northem Germany and the northem Netherlands, from which it covered about half of the territory (Fig. 3B). According to Berendsen (1998), the southem North Sea Basin was ice free. Probably there was no contact between the Scandinavian and British ice sheets. As a conséquence the sea level decreased to a level of 120 to 140 m below Amsterdam Water Mark (A.W.M). The Rivers Rhine and Meuse were forced in a westerly course parallel to the southem limit of the inland-ice (Zagwijn, 1974; Fig. 4A). South of the glaciated area, toundra- like conditions resulting in permafrost formation, existed.

3,2 Eemian (126 000- 116 000 years BP) During this warm-temperate climate approximately 100 000 years ago, melting of the inland ice resulted once more in a sea-level rise, which led to the establishment of a shallow sea once more during the Eemian Stage. The river Rhine continued its northem course which it had at the end of the Saalian and which was probably similar to the present one. The river Meuse probably had the same course as it has at present. In the southwest, a valley system of the River Scheldt and its tributaries came into existence. Here estuarine déposition prevailed (Zagwijn, 1974; Fig. 4B).

According to Zagwijn (1983) and StreifiF (1991) the Eemian was characterised by a sea-level rise of ca. 20 m/yr, Along the North Sea coast, the Eemian Sea flooded only main river valleys. Saalian during maximal extension of the inland ice

SCK-CEN/IVK/fig99014 SCK-CEN/IVK/fig99016

Holocene Late WeichseHan about 4300 years before present about 10.500 years before present (Subboreal-Calais IVa)

SCK-CEN/IVK/ag99017 SCK-CEN/IVK/eg99019

Figure 4aPalaeogeography of the Netherlands and northem Belgiiun. A) the Saalian; B) the Eemian; C) the Late Weichselian; and D) the Holocene (From Zagwijn, 1974). Legend see page 10. 10

General legend Additional legend

I I • Fault; active during the Pleistocene Figure 4A: Saalian

i Pre-Tertiary naar the surface Inland-ice

Depositional area of the River Rhine Inland-ice on Pre-Tertiary

Direction of main flow of the lïiver Plhine CSacial Outwash

Depositional area of the rivers Meuse. Scheldt, a.o. Figure 4C: Weichselian

Direction of main flow of the nvers Meuse, Scheldt, a.o. Ice-pushed ridge

NAP Depositional area of rivers from North-Germany (Elbe, We s er, Ems, a.o. -lOm Top of Pleistocene deposits Direction of main flow of North-Gcrman rivers 20 m

Depositional area of the North Sea, mcl mlets and estuaries

Figure 4D: Holocene

Intertidal and brackish depositional area Beach banier

Area of peat deposils Beach harrier, assumed

Scale 1 : 2.500.000 organic mud in initial lake Flevo

Geological Survey of the Netheriands

AuthorZagw^nW.H. (1974)

SCK-CEN/IVK/fig99020b

Figure 4bLegend Figure 4a 11

3.3 Weichselian glacial (116 000 - 10 000 years BP) After the Eemian the story repeats itself once more. The climate deteriorated late in the Eemian and early in the Weichselian, glaciers accumulated and the sea-level dropped. According to Jansen et al. (1979), at the height of the Late the sea level feil to at least 110 m below the present-day sea level. This time the extent of inland ice (Fig. 3C) was more restricted than in the preceeding glacial and the Netherlands remained completely in the permafrost zone. Although the area covered by major ice sheets in Western and northem America is well known, it is not clear whether the Scandinavian and British ice sheets were in contact with each other or not. Figure 5 shows two models of the extent of the Scandinavian ice sheet at the last glacial cycle (Holmlund & Fastook, 1995; Kleman et al., 1997). The major discrepancy between the two models occur for the Early Weichselian. According to Kleman et al. (1997), inland ice covered Norway , north-westem S weden and northem Finland at 110 000 years BP. Holmlund & Fastook (1995) however, suggest the formation of local mountain ice caps. Lauritzen (1995) support the model of Holmlund & Fastook (1995). Based on the formation of Norwegian speleothems at about 110 000 years BP, it is assumed that an ice sheet could not have extended over Westem Norway at that time. The North Sea Basin was almost ice free (Berendsen, 1998). At the end of the Weichselian glaciation, about 10 500 years ago (Fig. 4C), the sea-level was still low and the greater part of the North Sea was a land surface. During the Weichselian interval of ice invasion, the Rhine and its tributaries continued to flow down the English channel (Cameron et al, 1989).

3.4 Holocene intergiacial During the most recent climatic amélioration the sea level rose again as a result of ice melting. The sea flooded the present North Sea and may have reached the present costal area (Zagwijn, 1974; Fig. 4D). During this sea-level rise one can recognise three zones of sédimentation. © a littoral sandy zone of beach ridges and dunes, 0 a clayey zone of tidal flats, salt-marshed and brackish lagoons and G) at greatest distance from the sea a zone of peat formation in a fresh water environment. Behind the banier zone freshwater flowed in from the Meuse, Rhine, Scheldt and others. In that zone, sait water was replaced by freshwater.

4 Palaeodimate estimâtes over the last 150 000 years Ages based on '^C indicates that the fluids in the main part of the hydrogeological system in Belgian Campine are mostly younger than 45 000 00 years (Beaufays et al., 1994; Philippot, 1999). Therefore, in the PHYMOL project it was decided to mn simulations covering approximately the last 100 000 years. SCK«CEN proposed to model the hydrogeologicd system from Eemian times (126 000 years BP) to present, in order to simulate a complete Racial cycle. In the following paragraphs estimâtes are given for température, précipitation, dominant végétation type, relative sea level and permafrost conditions for the mentioned time period. Table 1 summarises the results.

4.1 Température and précipitation Unfortunately no Late Pleistocene climate curve is available for Belgium. Therefore we have to rely on data provided by Zagwijn & van Staalduinen (1975) who constmcted a climate curve for the Netherlands of the Late Pleistocene. This curve is based on pollen analyses, C-14 12 datings and relies of permafrost (e g. frost wedges and cryoturbations) and gives the estimated July température together with a relative subdivision in cold and warm stages.

10 kà

105 000 BP

'fl [100 ica

90 000 BP

65 kà^

ST

1, 61 000 BP

^1 1 /"^ 1 TT».'' 1

20 000 BP SCK<:EN/IVK/fig99022 Figures Left: Glacier expansion during the last glaciation modelled by Holmlund & Fastook (1995). The shaded ares correspond to régions covered by ice. Right: Glacier expansion modelled by Kleman et al. (1997). D: Ice di\'ide. (From Holmgren & Karlén, 1998). 13

Furthermore, data given by local studies carried out in the Belgium - Dutch border région (Vandenberghe & Van den Broek, 1982; Vandenberghe et al., 1984; Vandenberghe, 1993) are added to Table 1. For the Netheriands, van Gijssel (1995) distinguished five difièrent climate States (Table 2) based on température and botanical data. Relies of permafrost indicate mean annual air (and ground) températures below 0 °C. Indications of the minimum température of the warmest month (July) and in some times of the coldest month (January) can be derived from marine and organic palynological data.

Changes in précipitation during the Pleistocene are not well known (Holmgren & Karlén, 1998). In gênerai, a température decrease during glacial times resulted in reduced evaporation and thus précipitation is likely to have been smaller than at present. Température and precipitaion values (broad range) can be estimated from pollen assemblages and individual species for longer and discontinuous time periods. The European pollen records (Guiot et al., 1989) indicate a great variability in précipitation with mostly lower values than the present for the last 140 000 years. A detailed reconstmction of variations in Late Quateraary mean annual températures and précipitation together with the proposed climatic stages for the Netherlands is shown in Figure 6.

Table 2: Climate states for the Netherlands as defined by van Gijssel (1995)

climate State T annuali mean T Julv. mean (°C) glacial, ice sheet margin or cover g tundra, continuous oermafrost co <-8 tundra. discontinuous permafrost do <-2 boreal b >0 > 10 temoerate t >5 > 15

4.2 Végétation The dominant végétation types (Table 1) are reflected in the pollen diagrams from peat accumulations of Late Pleistocene to Holocene deposits in the northem Campine (De Ploey, 1961) and in the Netherlands (Zagwijn & van Staalduinen, 1975). During the last few thousand years the Campme landscape was changed drastically by human activity such as deforeistation, cultivation of land and artificial drainage. All these activities have important effects on the végétation and ground-water regime. As a conséquence the present hydrological situation can not be regarded as représentative for fiiture climatic changes.

4.3 Sea-level fluctuations Sea-level fluctuationsdétermin e the large-scale ground-water table gradients and are a result of climatic changes. The formation of large ice sheets in continental areas during glaciations resulted in a considérable lowering of the sea level. The Saalian is characterised by a major sea level drop between 120 and 140 m. At the sea's maximum extent during the Eemian, the shorelines extended partly beyond those of the present North Sea (Cameron et al., 1993). The location of Eemian "schorre" dépositions in the Belgian coastal plain suggest that the Eemian sea level is comparable to the present-day sea level (De Moor & Pissart, 1992). The sea level probably decreased to more than 50 m below Amsterdams Water Mark (AWM) during the early Weichselian Bramp /Amersfoort and Odderade interstadials. From a fluvial pattem at the bottom of the southem North Sea and in the Channel, a decrease of more than 100 m in sea level during the Weichselian glacial periods can be deduced (De Moor & Pissart, 1992). Köhn (1989) recpnstmcted the Holocene transgression of the Belgian coastline (Fig. 7). The Table 1. Paleoenviromnental estimâtes of northem Belgium and southem Netherlands (after De Ploey, 1961; Zagwdjn, 1975; Jelgersma, 1979; Vandenberghe, 1984: Haeiô 1985; Zagwijn, 1986; Zagwijn, 1989; De Moor & Pissart, 1992, Vandenberghe, 1993; van Gijssel; 1993; de Gans & van Gijssel, 1996; Van Andel & Tzedakis, 1996; Isarin^ 1997). B.P.: Before Present, i.e. before 1950; OWM: Ostend Water Mark; t: teimperate; b: boréal; dp: tundra, discontinuous permafrost; cp: continuous permafrost: a: according to biostiatigraphical data; b: according to permafrost data; c: according to glacial data, d: according to pollen data; pl.: present level.

CHRONOSTRATIGRAPHY TIME. CLIMATE MEAN AIR TEMPÉRATURE MEAN ANNUAL DOMINANT RELATIVE STATE PRÉCIPITATION VEGETATION TYPE SEA LEVEL. JULY JANUARY ANNUAL B.P °c mm -mOWM Subatianticami 3 000- Present t 16-18 lto2 10 moor & park 1-2 Subboreal 5 000- 3 000 b-t 10 en e deciduous forest PI Âtlanticum 8 000- 5 000 b 17-19 Oto3 10 700 - 800 deciduous forest 0 - 20 Boréal 9 000- 8 000 b 10 park landscape 20-40 Preboreal 10 000 - 9 000 b 10 park landscape 40-50 Younger Dryas 10 550 - 10 000 dp 14-15 -18 -2 parktwidra -65 11000- 10 550 dp >13 ai u -18 -2 Allered 11 800- 11000 dp park tundra Lat ( Older Diyas 12 000 - 11 800 dp 400-600 (a, b) 50 - 100 Weichs ( BoUing 13 000 - 12 000 dp 8-15 -1.5 park tundra

Late Pleniglacial 25 000 - 13 000 cp 6-10 -22 <-8 200-250(a,b) arctic steppe >100 ~ '§ 60 000- 25 000 dp-b 10-13 -9 -4.5 to-1.5 200-400(a,b) J Middle Pleniglacial shrub tundra 50 - 100 ^ Pc ^ Early Pleniglacial 75 000 - 60 000 cp 10 max. <-18 <-8 200 - 250 (a, b) polar desert 50 - 100

Odderade interstadial 82 000 - 75 000 b 10-15 <-2 >0 400 - 800? (a ,b) coniferous forest 0-50 § Rehderstall stadial 94 000 - 82 000 dp <10 <-5 -4to0 50 - 100 • PM Brorup interstadial 99 000 - 94 000 b 10-15 <-2 >0 deciduous forest 0-50 tl Intra-Brerup stadial 103 000 - 99 000 dp <10 <-5 -4to0 0-50 Amersfoort interstadial 105 000 - 103 000 b 10 -15 <-2 >0 0-50 Heming stadial 116 000- 105 000 dp <10 <-5 -4to0 50 - 100 min. > 0.2 to 126 000- 116 000 t 16-18 10-12 600 - 900 (a) deciduous forest <8 3 Eemia n

Late Saalian 135 000- 126 000 dp <10 ? <0 200 - 600? (a, b) 50 -100

Middle Saalian > 135 000 cp <0 ? ? <200 (c) Saalia n polar desert 120 - 140 Tem po rature Prccipilotion PalaaotBrnpetaiuro ariumaiios nnoma(ies((rfn| L'stiniatesl C) PincipitBlion Infürrcd agc of Dtiith Hfithorlaiids ;C|, GrandoPjle4 (meanJanuery Imean Janusry. osiimates (mm) lostratigraphv IGuiot et al., 1992) annital and July) onnual and July) Imoan annua)) chfonostrat, imiTs (kal 6 -4 O -400 -200 O 100 -20 -10 O 10 20 U 200 4ÜU

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EEMIAN V) Eemian

LATE VI

MIÜDLEIVIII

.SCK-CEN/IVK/llgyjD.K)

Presentannual meantemperatureand Pollen flHHI Estimation from pollen data precipitatian lor Grande Pile: data 9.5'C and 1080 mm(Guiot et al., 19921 t^^^ Estimation from sedlmentological Error bars are not indicsted. data

Figure 6 Detailed reconstruction of variations in Late Quaternary mean annual températures and précipitation as derived from the Grand Pile pollen record (Vosges, Guiot et al., 1992) and trom pollen analytical and sedimentological data of the northern Netherlands (from van Gijssel, 1995) end of the Weichselian glaciation and the Early Holocene is characterised by a fast increase in sea level because of melting of the inland ice and remnants of the ice sheets, respectively (Holmgren & Karlén, 1998). The sea-level rise was reduced in the Mid Holocene (4 000 - 6 000 years BP). Around 18 000 years BP, 15 000 years BP and 10 000 years BP the sea occurred at a level of -100 m Ostend Water Mark (OWM), -80 m OWM and -40 à -50 m OWM., respectively. From the Atlanticum onwards, an asymptotic stabilisation occurred. Around 8 000 years BP, 6 000 BP and 5 000 years BP the sea level reached a height of -20 m OWM, -2.5 m OWM, and present level, respectively. The Subatlanticum is characterised by small sea-level fluctuations of 1 or 2 m. Figure 8 shows the extent of the sea at different time intervals during the Holocene.

4.4 Permafrost conditions The présence of continuous permafrost during the Saalian is most likely, although évidence is lacking. Ice-wedge casts, polygons and pingo's are indications of continuous permafrost (Vandenberghe, 1993; Berendsen, 1998). The occurrence of cryoturbations and thermokarst are characteristic for severe winter conditions and may point to discontinuous as well as continuous permafrost (van Gijssel., 1993). The présence of a permafrost in the northern Campine during the Weichselian glacial had already been deduced by De Ploey (1961). 16

10O0O 5000 1000 O

SCK-CEN/IVKyfig99023 Figure 7 The Holocene transgressions of the Belgian coastline (from Köhn, 1989). T: age in 14-C years BP; MSL: present-day mean sea level; •: position of the samples; Dm: depth in m below the present-day MSL.

sea level:-30 m sea level: -20 m

c

SCK-CEN/IVK/fig99024 land sea

Figure 8 Palaeogeography of the southem North Sea at 9 OOOBP, 8 300 BP and 7 800 BP (after Jelgersma, 1979).

According to Haest (1985) and Vandenberghe (1993) two periods of continuous permafrost formation can be recognised in the southem part of the Netherlands and in northem Belgium. Ice-wedge casts are indications of continuous permafrost in the middle part of the Early

Pleniglacial. Towards the end of this time period, large cryoturbations developed by the disappearance of the permafrost (Vandenberghe, 1993). The Late Pleniglacial was, like the

Early Pleniglacial, characterised by the occurrence of ice-wedge casts and scars of closed- system pingo's (Vandenberghe & Krook, 1981) which point to the development of a continuous permafrost zone. The présence of discontinuous permafrost during the Younger Dryas has been reported by Isarin (1997).

Based on the depth of pingoruines, de Gans (1981) suggests a permafrost thickness of 12 to 20 metres during the Middle Weichselian. Observations from Eastem Germany indicate 17 thicknesses of more than 50 m (Eismann, 1981). According to simulations caried out by Boulton and Caban (1997), permafrost thickness beyond the ice sheet may be about 100 m. In Figure 9, the présence or absence of continuous and discontinuous permafrost in relation to glacier évolution during several glacial periods is shown (Boulton & Caban, 1997).

Permafrost installation and extension (Figure 10) in Western Europe is related to low insolation rates in spring and summer, low précipitation (< 200 mm/y) prostrated tundra végétation (van Vliet-Lanoë, 1996).

4.5 Relief and évolution of the hydrographie net Information on the types of hydrological conditions prevailing during the geological past can be deduced from palaeogeographical information on relief, surficial geology and sédimentation or érosion pattems (van Gijssel, 1993). The most important characteristics of the relief in northem Belgium are the présence of asymmetrie, subséquent valleys. These valleys are the result of differential fluvial incisions in altemating sandy and clayey sédiments of tiie Tertiary and Early Pleistocene (De Moor & Pissart, 1992). The formation of a hydrographie net in a certain area is the resuit of a régression. The maximum extent of marine deposits indicates the lower boundaries of a river network. The withdrawal of the Tertiary seas in Belgium occurred in northem direction and resulted in the formation of a consequent river network with a dewatering in northem direction. At present, the main part of the hydrographie net in the Campine belongs to the Scheldt basin and is drained in an east-west direction (Figure 10). The central part of the basin is drained by the river sytem of the Nete and Rupel. The Dijle and Demer river System drains the southem part of the Scheldt basin. The eastem part of the Campine is drained by tributaries of the river Meuse (e.g. streams Mark, Distel and Molenbeek). These streams foUow a northem course.

During the Early Pleistocene the Belgian - Dutch border région belonged to the southem North Sea Basin in which the Rhine, Meuse and Scheldt deposited their sédiments (Kasse, 1988). The E-W trending coastline was preserved until the end of the Tiglian (Zagwijn, 1974; Kasse, 1988). After the Tiglian the sea finally withdrew from the Dutch-Belgian border. At the start of the Early Pleistocene Rhine and Meuse sédiments were deposited in the northem and northeastem part of Belgium. During the Tiglian C4 déposition of the Beerse Member took place in northem Belgium. Sédiments from the Beerse member were probably supplied by northward flowing rivers from the Scheldt basin (Kasse, 1988). Sediment supply from rivers from the Scheldt basin has been very important during the Early Pleistocene (Kasse, 1990). Déposition of Scheldt material was favoured by low sea level during glacial phases and uplift of the central Belgian border. The SW-ÎŒ direction of the eastem Scheldt basin remained preserved until the Middle Pleistocene (Vandenberghe & De Smedt, 1979; Kasse, 1988). The Middle and Late Pleistocene is characterised by érosion. Because of uplift west of the Central Graben, the base leyel of the rivers in Middle-and Lower Belgium decreased (Vandenberghe & De Smedt, 1979; Kasse, 1988), resulting in érosion of their lower courses. During periods of low sea level, the denudation was more intense. As a result of this process, the stmctural characteristics of the Tertiary substrate came into existence (Vandenberghe & De Smedt, 1979). The SW-NE elongated Diestian sandstone ridges are the most striking relief in the southem Campine. The E-W striking Boom and Asse Clay formed the résistant éléments in the west. Further lowering of the relief resulted in the érosion of the Miocène sands and outcropping of the Boom Clay in the Demer - Dijle 18

20 WEICHSELIAN ICE SHEET

40 H

continuous discontinuous permafrost pemnafrost

100 H

Ice sheet margin

140 -\ SAALIAN ICE SHEET

160 -

180 H

SCK-CEN/IVK/fig99029

200 km Central Netherlands South Sweden Nonvay

Figure 9 Simidated surface profiles of continuous-discontinuous permafrost and ice sheet from the Saalian maximum in the Netherlands through positions equivalent to those of the Late Saalian, Weichselian inaxitniim and the Younger Dryas stage (from Boulton & Caban, 1997) 19

18 000B.P

active

SCK-CEN/IVKyfigPTOS j ice sheet discontinuous permafrost

1,11,114 continuous permafrost '•'•'( seasonal frost

[^"•"'J southem boundary of active ice wedge polygons

Figure 10 Permafrost extension at 18 000 BP (from van Vliet-Lanoë, 1996) confluence area (Vandenberghe & De Smedt, 1979). Because of these résistant Diestian ridges and clay beds the rivers from central Belgium diverged to the northwest (Vandenberghe & De Smedt, 1979). Subséquent érosion in the Nete basin led to the genesis of the Campine microcuesta (De Ploey, 1961). The westward flowing rivers induced increased érosion in the Flemisch valley of northwestem Belgium (Tavemier & De Moor, 1974; Vandenberghe & De Smedt, 1979). This érosion could have been resposible for the genesis of the Scheldt escarpement in the Northem Campine (Kasse, 1988; Figure 11). According to Vandenberghe & De Smedt (1979), the eastem Scheldt basin was incised in dififerent phases by relatively narrow and deep gullies from the end of the Saalian to the start of the Weichselian. Filling of these deep guUies took place during the last glacial. During the Late Weichselian the meandering rivers incised again a few meters. Déviations of the Demer and Dijle Rivers at the end of the Younger Dryas and at the end of the Boreal was caused by abundant aggradation. The actual fiavial system came into existence afler the Early Holocene flandrian trangression (Vandenberghe, 1977). The présence of the Meuse in the Belgium-Dutch border région is restricted to the late Early Pleistocene (Kasse, 1988). Figure 12 illustrâtes that during the Late Menapian the southem part of the Netherlands and northem Belgium were situated in the confluence area of the Meuse and the rivers fromth e Scheldt basin. m

"•'I- '

• i

•' > '

\ • '•v.-., .. . . 4- '•"•:'î

^•^î-.-.,Ja3,»-..t:,i

S. sfH- Bcigiiini { j

France li-^^ K S' "

SCK-CEN/IVK/liïï99l)31 Figure 11 Actual hydrographie net in the Campine Basin (N-Belgium). 21

THE NETHERLANDS

Scheldt Escarpement

Catnpine ' Microcuesta

\ Flemish Valley

O Km BELGIUM

SCK-CEN/IVK/fig99025 Figure 12 The Scheldt escarpment as a resuit of érosion processes in the southem part of the Netherlands and northem Belgium (from Kasse, 1988). : country border, A: Antwerp; B: Bmssels; Br: Breda; E: Eindhoven; M: Maastricht.

NETHERLANDS

. • » • .

Scheldt

Legend 3 Rhine Meuse Scheldt 30 Km BELGIUM

SCK-CEN/lVK/fig99026 Figure 13 Palaeogeography of the Late Menapian (from Kasse, 1988). 22

5 Summary During the Early Pleistocene the Belgium - Dutch border zone belonged to the southem part of the North Sea Basin where tidal sédimentation took place. At that time an east-west trending cöastline existed which was preserved until the Late Tiglian. The last marine incursion afFecting the Northern Campine dates back from the Tiglian C5, about 1.9 Ma years BP. The Middle Pleistocene to Holocene is characterised by periods of climate détérioration which lead to glaciations. The Elsterian time period reflects the first of three (Elsterian, Saalian and Weichselian) widespread invasions of ice across the North Sea Basin. The progradation of the ice sheet characterising these periods never reached Belgium. A température increase corresponding to climatic améliorations, followed each of the glaciations and resulted in the development of tidal and marine envirormients similar to those of the present. 23

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ABBREVIATIONS

AWM Amsterdams Water Mark BP Before Present, i.e. before 1950 ka thousand years Ma Million years OWM Ostend Water Mark PHYMOL a PalaeoHYdrological study of the MOL site, Belgium