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A unique complex of multiphased Holocene drift sands and paleosols, with at least two lacustrine phases, was discovered during a major sanitation project in the Laarder Wasmeren area near Hilversum, the Netherlands. The complex could be studied in detail, highly facilitated by the excellent and large-scale exposure of the various deposits and soils. OSL dating was used to establish ages of the phases, where possible differentiating between time of deposition and time of burial by taking into account the potential effects of bioturbation. Pollen analysis served to reconstruct the vegetation during the various phases.A first minor phase of aeolian activity already started before approx. 5,000 BC, followed around 4,000 BC by a second phase and a rather massive third phase around 3,000 BC. After a long phase of soil formation, the latest, massive drift sand phase started around the 14th to 15th century. It clearly represents the classic drift sand phase that started in the Late Middle Ages in the Netherlands. Sand drifting followed on soil forming phases during which the vegetation became increasingly dominated by ericaceous plants and culminated in heathlands. The first three aeolian phases and associated heathlands are much older than generally assumed for heathland and drift sand to occur in the Netherlands. Moreover, podzolisation was found to have started very early, true podzols already occurring before 4,000 BC.Around 3,000 BC groundwater in the area reached a maximum altitude of about 230 cm +NAP, resulting in local open water in the area. This rise is probably linked to the development of the Dutch coastal area, where at that time peat accumulated and drainage was poor, inducing a rise of the groundwater level in ‘het Gooi’. This groundwater level fell later on, to never reach this altitude again. The Groot Wasmeer was formed by local stagnation on a slowly permeable podzol and already reached a level of 320-325 cm +NAP by 400 BC, which more or less equals its 20thcentury level.The results demonstrate that earlier concepts on the occurrence and age of aeolian phases, podzols and heathland vegetations in the Netherlands are far too schematic, and that early, pre-agricultural cultures may already have had an impact on the stability of fragile cover sand landscapes, e.g. through burning. Results are in line with those from several contemporary studies on early prehistoric cultures and their impact in river dune areas in the Central and Eastern Netherlands.

We present a revised relative mean sea-level (MSL) curve for the Rhine-Meuse delta, western Netherlands, for the period 7900-5300 cal yr BP. The revision is based on a series of new and previously unpublished local groundwater-level index data from buried Late Glacial aeolian dunes in the lower Rhine-Meuse delta, and reinterpretation of existing data. The new index data consist of (AMS and conventional) radiocarbon dates of samples, collected from the base of peat formed on dune slopes, near Vlaardingen (21 index points), Hillegersberg (one index point), and Hardinxveld-Giessendam (10 index points). The Vlaardingen data represent the coast-nearest Rhine-Meuse delta local water-level record, which therefore is highly indicative for sea-level change. Pollen and macrofossil analysis, and dating of paired samples was carried out to assess the reliability of the groundwater-level index data. The revision of the MSL curve involves: (1) a significant (0 to >1 m) upward adjustment for the period 7900-7300 cal yr BP; (2) a downward adjustment of =0.25 m for the period 6650-5300 cal yr BP. The new data indirectly support the reliability of the part of the curve for the period 7300-6650 cal yr BP. A longitudinally fairly uniform river gradient of 2.5-3.0 cm/km in the lower Rhine-Meuse delta during the period 6650-5600 cal yr BP can be inferred from the data sets. A significant river gradient extended further towards the coastline than previously thought and it may be that also the revised MSL curve reflects river-gradient effects. An increased floodbasin effect (stronger intra-coastal tidal damping) seems to have developed in the lower Rhine-Meuse delta in de period 7500-6600 cal yr BP, and was probably a complex response to a major avulsion of the Rhine.

As upward seepage of saline groundwater from the upper aquifer is leading to surface water salinization of deep polders in the Netherlands, we monitored the processes involved in the Noordplas Polder, a typical deep polder. Our results show three types of seepage: (1) diffuse seepage through the Holocene confining layer, (2) seepage through paleochannel belts in the Holocene layer, and (3) intense seepage via localized boils. They differ with regard to seepage flux, chloride concentration, and their location in the polder; thus, their contributions to surface water salinization also differ. Permeable, sandy paleochannel belts cut through the lower part of the Holocene layer, resulting in higher seepage fluxes than the diffuse seepage through the Holocene layer where there are no paleochannels. The average chloride concentration of paleochannel seepage is about 600 mg/l, which is sixfold higher than the average concentration of diffuse seepage. The highest seepage fluxes and chloride concentrations are found at boils, which are small vents in the Holocene layer through which groundwater preferentially discharges at high velocities. This results in upconing of deeper and more saline groundwater, which produces an average chloride concentration of 1100 mg/l. Despite the fact that seepage fluxes are difficult to measure, we were able to calculate that boils contribute more than 50% of the total chloride load entering the Noordplas Polder and they therefore form the dominant salinization pathway.

Deze bijdrage geeft een overzicht van de evolutie van de Beneden-Schelde in België en Zuidwest-Nederland tijdens het Laatglaciaal en het Holoceen, met speciale aandacht voor recente ontwikkelingen in het onderzoek. Tijdens het Laatglaciaal loopt de Schelde in Nederland in een diep dal in noordelijke richting. Als gevolg van de Holocene zeespiegelstijging dringt de zee dit dal binnen, waardoor het rivierverhang sterk vermindert. Rond 6000 jaar geleden kent de mariene invloed in Zeeland een eerste maximum en reikt dan tot op Belgisch grondgebied. Hierna neemt de mariene invloed sterk af en ontwikkelt zich achter de kustbarrière een uitgestrekt veengebied. Rond het begin van onze tijdrekening vergroot de mariene invloed weer. De getijden in de Schelde nemen langzaam toe en de veengroei stopt. Sinds ca. 1100 AD is de getijdenamplitude in de Schelde sterk toegenomen door het ontstaan en ontwikkeling van de Westerschelde en door menselijke ingrepen (bedijkingen en 20ste eeuwse baggerwerken). This paper gives an overview of the evolution of the Lower River Schelde in Belgium and the southwestern Netherlands, with special reference to recent research results. During the Lateglacial the Scheldt in The Netherlands occupies a deeply incised palaeovalley which runs in a northerly direction. In the course of the Holocene sea-level rise, the sea gradually invades this valley, resulting in a strong reduction in river gradient. Around 6000 years ago the marine influence in Zeeland reaches a first maximum and is even felt on Belgian territory. Subsequently marine influence wanes and in the area behind the coastal barrier extensive peat growth takes place. Around the beginning of our era marine influence intensifies again, causing a slow increase of the tides in the Scheldt River and the end of the peat growth. Since ca. 1100 AD tidal amplitude has grown considerably as a result of the development of the Westerschelde and human interference (embankments and 20th-century dredging).

De graafwerken van een getijdendok op de linkeroever van de Schelde nabij Doel (België) boden een uitstekende gelegenheid om de stratigrafie en de paleo-ecologie van Holocene afzettingen in de Beneden Scheldepolders te bestuderen. Een complete organische sequentie, gedateerd tussen 6000 en 1400 BP, werd op basis van pollen, sporen en andere microfossielen, macroresten en diatomeeën onderzocht. Naast een volledig goed ontwikkelde representatieve botanische evolutie vanaf het Atlanticum werd ook belangrijke informatie verzameld over twee specifieke gebeurtenissen. Enderzijds kon de uitbreiding en de paleo-ecologische omstandigheden van de late Calais inundatie, tussen 5800 en 5000 BP, worden gereconstrueerd. Anderzijds werd het mogelijk om een beter inzicht te verwerven over de tijdspanne tussen het einde van de veengroei rond de 6de-7de eeuw AD en de grote strategische overstromingen na 1580 AD. Een periode van non-depositie, gevolgd door lokale afzettingen van laatmiddeleeuwse strategische stormvloeden werd namelijk geattesteerd. The excavations of a huge tidal dock on the left bank of the Scheldt river near Doel (Belgium) provided an excellent opportunity for the study of the stratigraphy and palaeoecology of the Holocene deposits in the Lower Scheldt polders. A complete organic sequence from the period between 6000 and 1400 BP was radiocarbon dated and investigated by means of pollen, spores and other microfossils, macroremains and diatoms. Besides a good developed sequence of the botanical evolution since the Atlanticum, interesting information on two specific events was obtained. Firstly the extension and conditions of the late Calais inundation, between 5800 and 5000 BP could be reconstructed. Secondly it became possible to gain more insight in the timespan between the end of the peat growth around the 6th-7th century AD and the large strategic inundation after 1580 AD. A period of non deposition followed by local deposits of late medieval military storm surges could be recognised.

In this study, all available 14C 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 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 C-14 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 C-14 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 C-14 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.

In this study, all available 14C 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 BCThe 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 C-14 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 C-14 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 C-14 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.

Klimaatswijzigingen in het verleden zijn geregistreerd in zowel terrestrische, ijs- als diepzeekernen. De laatste 10 jaar is paleoklimatologisch onderzoek vooral toegespitst op het temporeel correleren van deze verschillende data en het zoeken naar een mechanisme (oorzaken en gevolgen) dat achter de klimatologische wijzigingen, die wereldwijd zijn geregistreerd, schuilt. De Noord-Atlantische regio is de best gekende regio enkel en alleen door de aanwezigheid van een groot aantal data in de drie domeinen. De klimaatscurves van het zuidelijk halfrond zijn vooral afkomstig van de Antarctische ijskap. Diepzee en terrestrisch paleoklimatologisch onderzoek is hier “ondervertegenwoordigd” en het belang in de paleoklimaatsdiscussie van sub-Antarctische eilanden werd in het verleden eerder “verwaarloosd”. Echter, het beperkte aantal gepubliceerde studies en onze eigen gegevens geven aan dat op deze eilanden een groot potentieel aan bruikbare terrestrische archieven aanwezig is, bovendien de enige terrestrische archieven in de circum-Antarctische oceaan. Past climate change is studied in terrestrial, deep ocean and ice cores. For the last ten years, climatological research has been focused on climatic connections between data from different sources and environments on earth and on the driving mechanism behind these climatic connections. The North Atlantic region is the best known region only because of the many palaeoclimatological data present in this area. Past climate change in the Southern Hemisphere has been attained especially by research of Antarctic ice cores. The number of studies of terrestrial and oceanic cores in the Southern Hemisphere is lower than in the north. The significance of the sub-Antarctic region for the palaeoclimatological discussion has been rather ‘neglected’ in the past. However, the restricted published data and our own research show that sub-Antarctic islands have a great potential for high resolution terrestrial palaeoclimatological research. Moreover, these islands represent the only terrestrial archives in the circum-Antarctic ocean.

Dit artikel gaat over landschappelijke veranderingen in Zuidelijk Flevoland in het midden Holoceen

Reactie op het artikel van ED van Riessen en N. Vandenberghe in Geologie en mijnbouw (1996), p 301 ev.

This research looks at landscape dynamics – erosion and deposition – from two different perspectives: long-term landscape evolution over millennial timescales on the one hand and short-term event-based erosion and deposition at the other hand. For the first, landscape evolution models (LEMs) are often used, which describe landscape forming processes by geomorphic transport laws, usually on annual temporal resolutions. LEM LAPSUS is used in this research to evaluate the landscape dynamics in a study area in south-east Spain: the Guadalentín Basin. The model is calibrated on dated river terrace levels, which show an erosion – deposition – erosion sequence that the model could reproduce. Annual precipitation in this dryland area shows large inter-annual variability and erosion is supposed to be mainly the results of low-frequency, high magnitude rainfall events. Therefore, in this research, landscape dynamics are also assessed using the event-based erosion model OpenLISEM. Eventually, the role of extreme events in long-term landscape evolution are explored by comparing the two models and by incorporating annual rainfall variability into LEM LAPSUS. Another issue that is being addressed in this study is the relative influence of humans as compared to erosion as a natural process. A conceptual model, derived on the basis of dated sediment archives, is tentatively correlated to periods of human impact on the land. Using LAPSUS, the potential influence of historical tillage erosion is simulated, showing that the relatively slow process of tillage erosion added to floodplain aggradation over thousands of years.

This research looks at landscape dynamics – erosion and deposition – from two different perspectives: long-term landscape evolution over millennial timescales on the one hand and short-term event-based erosion and deposition at the other hand. For the first, landscape evolution models (LEMs) are often used, which describe landscape forming processes by geomorphic transport laws, usually on annual temporal resolutions. LEM LAPSUS is used in this research to evaluate the landscape dynamics in a study area in south-east Spain: the Guadalentín Basin. The model is calibrated on dated river terrace levels, which show an erosion – deposition – erosion sequence that the model could reproduce. Annual precipitation in this dryland area shows large inter-annual variability and erosion is supposed to be mainly the results of low-frequency, high magnitude rainfall events. Therefore, in this research, landscape dynamics are also assessed using the event-based erosion model OpenLISEM. Eventually, the role of extreme events in long-term landscape evolution are explored by comparing the two models and by incorporating annual rainfall variability into LEM LAPSUS. Another issue that is being addressed in this study is the relative influence of humans as compared to erosion as a natural process. A conceptual model, derived on the basis of dated sediment archives, is tentatively correlated to periods of human impact on the land. Using LAPSUS, the potential influence of historical tillage erosion is simulated, showing that the relatively slow process of tillage erosion added to floodplain aggradation over thousands of years.

We present a revised relative mean sea-level (MSL) curve for the Rhine-Meuse delta, western Netherlands, for the period 7900-5300 cal yr BP. The revision is based on a series of new and previously unpublished local groundwater-level index data from buried Late Glacial aeolian dunes in the lower Rhine-Meuse delta, and reinterpretation of existing data.The new index data consist of (AMS and conventional) radiocarbon dates of samples, collected from the base of peat formed on dune slopes, near Vlaardingen (21 index points), Hillegersberg (one index point), and Hardinxveld-Giessendam (10 index points). The Vlaardingen data represent the coast-nearest Rhine-Meuse delta local water-level record, which therefore is highly indicative for sea-level change. Pollen and macrofossil analysis, and dating of paired samples was carried out to assess the reliability of the groundwater-level index data.The revision of the MSL curve involves: (1) a significant (0 to >1 m) upward adjustment for the period 7900-7300 cal yr BP; (2) a downward adjustment of

In centralGabon(Africa) the distribution ecology of the Caesalpinioideae tree species (Leguminosae) were studied in two separate low rainfall areas which straddled the same geological transition from upland to lowland. The principle environmental force arranging their distribution was regional drought stress during the two dry seasons. These drought sensitive tree species were able to survive in the two forest-savannah mosaics because local compensation was provided by the permanent presence of water along some of the streams and by reduced exposure (shade) in narrow valleys. According to the Pleistocene forest refuge theory the Caesalpinioideae in the two study areas arrived during the last 10,000 years (Holocene) from the closest forest refugium- the Chaillu Massif (80 km further south). This part ofGabondid not become deforested during the Last Glacial Maximum when climate was much drier because cloud forest conditions in this elevated area compensated for the shortage of rainfall. Arrival of the Caesalpinioideae trees by migration from this refuge area by their normal dispersal mechanism of explosively opening pods is excluded as their advance over the Holocene was only 36 km. Also arrival through occasional long-distance dispersal events by water along watercourses is not viable, because species composition along streams does not show a decreasing gradient with distance from the refuge area. Long-distance dispersal events in the past now obscured by an equilibrium situation of species distributions with present-day habitat is also not possible as the similar hills and lowland in the two study sites are inhabited by very different species. The only conclusion is that the Caesalpinioideae survived the Last Glacial Maximum in the study areas themselves. The present-day general presence of these Caesalpinioideae in the African rain forest between the former forest refugia shows that small pockets of forest persisted in the then savannah.

In centralGabon(Africa) the distribution ecology of the Caesalpinioideae tree species (Leguminosae) were studied in two separate low rainfall areas which straddled the same geological transition from upland to lowland. The principle environmental force arranging their distribution was regional drought stress during the two dry seasons. These drought sensitive tree species were able to survive in the two forest-savannah mosaics because local compensation was provided by the permanent presence of water along some of the streams and by reduced exposure (shade) in narrow valleys. According to the Pleistocene forest refuge theory the Caesalpinioideae in the two study areas arrived during the last 10,000 years (Holocene) from the closest forest refugium- the Chaillu Massif (80 km further south). This part ofGabondid not become deforested during the Last Glacial Maximum when climate was much drier because cloud forest conditions in this elevated area compensated for the shortage of rainfall. Arrival of the Caesalpinioideae trees by migration from this refuge area by their normal dispersal mechanism of explosively opening pods is excluded as their advance over the Holocene was only 36 km. Also arrival through occasional long-distance dispersal events by water along watercourses is not viable, because species composition along streams does not show a decreasing gradient with distance from the refuge area. Long-distance dispersal events in the past now obscured by an equilibrium situation of species distributions with present-day habitat is also not possible as the similar hills and lowland in the two study sites are inhabited by very different species. The only conclusion is that the Caesalpinioideae survived the Last Glacial Maximum in the study areas themselves. The present-day general presence of these Caesalpinioideae in the African rain forest between the former forest refugia shows that small pockets of forest persisted in the then savannah.

Dit artikel gaat over landschappelijke veranderingen in Zuidelijk Flevoland in het midden Holoceen

Dit artikel gaat over landschappelijke veranderingen in Zuidelijk Flevoland in het midden Holoceen

Detailed fieldwork and new extensive 14C dating of residual channel infillings provide data for the reconstruction of the Late-glacial channel downcutting and incision history of the Venlo–Boxmeer lower reach of the River Meuse (= Maas) in the southern Netherlands. Within a period of 500–1300 yr after Late-glacial climatic amelioration, the Meuse responded to increased discharges and decreased sediment supply by adjusting the width/depth ratio of its channels. Two main phases of channel downcutting are followed by two main phases of floodplain lowering and narrowing, indicating net floodplain degradation by the fluvial system as a non-linear response to Late-glacial and Early Holocene climate change. Some 1300 yr after initial late-glacial warming, channels downcut rapidly during the Early Bolling (13.3–12.5 kyr BP) and adopted a high-sinuosity meandering style. Channel downcutting paused around 11.9 kyr BP, possibly in response to rising groundwater levels and/or the Older Dryas cooling event. Between 11.9 and 11.3 kyr BP a new floodplain was formed. Then, lateral erosion took place and initiated a first phase of 2.6 m floodplain lowering during the Late Allerod. Gradual climate deterioration during the Allerod progressively broke up soils and vegetation cover, from 11.3 to 10.9 kyr BP. The Meuse gradually adjusted to an increased ratio of sediment supply over transport capacity through higher width/depth ratios. Main channels became shallower and adopted a low-sinuosity pattern, finally culminating in a braided river system during the Younger Dryas. The final Holocene warming resulted, within 500 yr, in renewed rapid channel downcutting by a single low-sinuosity channel during the Early Preboreal, followed by a second phase of 1.8–2.8 m floodplain lowering. Copyright © 1999 John Wiley & Sons, Ltd.

Reactie op het artikel van ED van Riessen en N. Vandenberghe in Geologie en mijnbouw (1996), p 301 ev.

Voor het natuurgebied Fochteloërveen en omliggende landbouwgronden is een bodemfysische schematisering gemaakt om bodemfysische gegevens beschikbaar te krijgen voor modelinvoer. Voor de omliggende landbouwgronden zijn bestaande bodemkaarten op verschillende schalen gebruikt. Voor het natuurgebied is een detailkartering uitgevoerd. Voor de onderscheiden horizonten zijn Staringreeks-bouwstenen geselecteerd. Voor de horizonten waarvoor dit niet mogelijk was, zijn nieuwe bouwstenen samengesteld op basis van metingen uit vergelijkbare gebieden. Door bestaande gegevenssets te gebruik kan een fysische schematisering worden uitgevoerd. Een gevoeligheidsanalyse zal aantonen of de basisgegevens nauwkeurig genoeg zijn en of de gekozen schaal volstaat.

Voor het natuurgebied Fochteloërveen en omliggende landbouwgronden is een bodemfysische schematisering gemaakt om bodemfysische gegevens beschikbaar te krijgen voor modelinvoer. Voor de omliggende landbouwgronden zijn bestaande bodemkaarten op verschillende schalen gebruikt. Voor het natuurgebied is een detailkartering uitgevoerd. Voor de onderscheiden horizonten zijn Staringreeks-bouwstenen geselecteerd. Voor de horizonten waarvoor dit niet mogelijk was, zijn nieuwe bouwstenen samengesteld op basis van metingen uit vergelijkbare gebieden. Door bestaande gegevenssets te gebruik kan een fysische schematisering worden uitgevoerd. Een gevoeligheidsanalyse zal aantonen of de basisgegevens nauwkeurig genoeg zijn en of de gekozen schaal volstaat.

Dutch Late Weichselian braided river deposits and Holocene meandering river deposits of the Rhine have been studied and compared. Cross sections demonstrate the lateral and vertical variations of the Late Weichselian sediments. Soil mapping of these deposits, even on a very detailed scale, proves very difficult. Best results have been obtained with a legend based on hydrology enabling the distinction of topo-hydrosequences of well drained brown soils, imperfectly drained mottled soils and poorly drained grey soils.Advanced soil formation and notably the dramatic processes in the Late Weichselian period (decalcification, clay illuviation, pseudogleying, periglacial formation of a highly reoriented, very dense microstructure) have caused clay mineralogical, chemical and physical changes in the Late Weichselian soils.The well drained and imperfectly drained Late Weichselian soils have an argillic horizon (Alfisols, Luvisols), occasionally with very low base saturation (Ultisols, Acrisols) and with strong subsequent pseudogleying in the imperfectly drained soils. The Holocene soils demonstrate decalcification and biogenic homogenization as well as some gleying according to their drainage position. These soils are classified as Inceptisols (Cambisols), occasionally as Mollisols (Phaeozems).Less favourable physical characteristics and behaviour (soil strength, structure stability and tillage behaviour) of the Late Weichselian soils and soil material is quantitatively documented. Differences with the Holocene soils and soil material are statistically highly significant and are caused by differences in texture, content, quality and distribution of organic matter and the highly reoriented, very dense microstructure.Use as permanent grassland or ley in the crop rotation is recommended to increase levels of biological activity. This seems the only remedy for the imperfectly and poorly drained Late Weichselian soils that are compacted by natural soil forming processes not counteracted by biological activity. Very recently improved drainage of large areas of Late Weichselian imperfectly drained soils has increased the saturated hydraulic conductivity to noncritical levels through increased earthworm activity to some metres depth.

Dutch Late Weichselian braided river deposits and Holocene meandering river deposits of the Rhine have been studied and compared. Cross sections demonstrate the lateral and vertical variations of the Late Weichselian sediments. Soil mapping of these deposits, even on a very detailed scale, proves very difficult. Best results have been obtained with a legend based on hydrology enabling the distinction of topo-hydrosequences of well drained brown soils, imperfectly drained mottled soils and poorly drained grey soils.Advanced soil formation and notably the dramatic processes in the Late Weichselian period (decalcification, clay illuviation, pseudogleying, periglacial formation of a highly reoriented, very dense microstructure) have caused clay mineralogical, chemical and physical changes in the Late Weichselian soils.The well drained and imperfectly drained Late Weichselian soils have an argillic horizon (Alfisols, Luvisols), occasionally with very low base saturation (Ultisols, Acrisols) and with strong subsequent pseudogleying in the imperfectly drained soils. The Holocene soils demonstrate decalcification and biogenic homogenization as well as some gleying according to their drainage position. These soils are classified as Inceptisols (Cambisols), occasionally as Mollisols (Phaeozems).Less favourable physical characteristics and behaviour (soil strength, structure stability and tillage behaviour) of the Late Weichselian soils and soil material is quantitatively documented. Differences with the Holocene soils and soil material are statistically highly significant and are caused by differences in texture, content, quality and distribution of organic matter and the highly reoriented, very dense microstructure.Use as permanent grassland or ley in the crop rotation is recommended to increase levels of biological activity. This seems the only remedy for the imperfectly and poorly drained Late Weichselian soils that are compacted by natural soil forming processes not counteracted by biological activity. Very recently improved drainage of large areas of Late Weichselian imperfectly drained soils has increased the saturated hydraulic conductivity to noncritical levels through increased earthworm activity to some metres depth.

Geologische inventarisatie van een deel van de Hoeksche Waard

Stiboka onderzoek

Stiboka onderzoek

Geologische inventarisatie van een deel van de Hoeksche Waard