Paleoflooding reconstruction from Holocene levee deposits in the Lower Meuse valley, the Netherlands

This study investigates the Holocene levee deposits and paleoflooding history of the Lower Meuse in the Netherlands based on archeological investigations and sedimentary analyses (grain size, end-member modelling, magnetic susceptibility and thermogravimetric analyses). The levee on the left bank in the study area near Ooijen contains a continuous sedimentary record in the NW downstream part. The archeological evidence and sedimentary results, including a grain size based flood energy index (LFEI), indicate that the Lower Meuse experienced a quiescent flooding period and low sedimentation rates during the mid-late Mesolithic when the levee was low and human influence was minor. Deposition during the Mesolithic shows a fining-upward trend and a highly-developed soil containing abundant artefacts. During the Neolithic and Bronze Age, the flooding intensity was low but gradually increased to a moderate level probably because of deforestation and increased runoff. Limited Bronze Age findings may reflect decreased human activity because of the increased flooding. Starting from the Iron Age, the Meuse experienced a generally enhanced flooding regime, which is reflected by erosion and coarsened sedimentation in the Iron Age and Roman Period. The high peak discharges during the Iron Age may have re-opened a low-lying paleochannel near to the levee during the intensified floods. This general increasing trend is interrupted by the lower flooding phase in the early Middle Ages (Dark Ages). From the middle to the late Middle Ages, the floods intensified again. The coarsening deposition and higher sedimentation rates since the Iron Age resulted from increased floods and higher sediment supply by deforestation and soil erosion. The findings of this study agree with a recent paleoflood reconstruction for the Lower Meuse by using a floodplain archive, implying that levee sediment records have potential in paleohydrological studies if the completeness of the record and chronological information is guaranteed

Time-integrated 3D approach of late Quaternary sediment-depocenter migration in the Tagus depositional system: From river valley to abyssal plain

Quantification of sediment volumes in continental to deep ocean basins is key to understanding processes of sediment distribution in source-to-sink depositional systems. Using our own and published data we present the first quantification of sediment-volume changes in basins along the course of a major southwest European river during the deglaciation. The salient points of this quantitative record in the Tagus and equivalent North Atlantic basins show crucial roles for sea level, climate and land-use in the distribution of sediments. The bypass of sediments starved the Tagus basins, and subsequently sedimentation mainly occurred on the Tagus Abyssal Plain during the sea-level lowstand of the Last Glacial Maximum. The main sediment depocenter rapidly shifted via the continental shelf to the Lower Tagus Valley during sea-level rise in the deglaciation period. Finally, the main sediment depocenter shifted further landward into the Lower Tagus Valley during sea-level high stand in the Holocene. During the high-stand phase (last 7 ky), sediment flux increased up to 2.5 times, due to climate and land-use changes. The average catchment denudation rate during the last 12 ky (0.04–0.1 mm/y) is in agreement with those of other European catchments. Our study clearly demonstrates the added value of detailed knowledge of 3D depocenter distribution, size and chronology. This allowed us to identify an increased sediment flux during the last 7 ky, which was not identified using local observations from boreholes alone. The uniqueness of the Tagus depositional system lies in the combination of a large accommodation space in the bedrock-confined Lower Tagus Valley, the steep lowstand-surface gradient and the narrow continental shelf with canyons indenting the shelf break

A pleniglacial fluvial deposit from the Combe d'Ain (Jura, France) [Un dépôt fluviatile pléniglaciaire de la Combe d'Ain (Jura, France}]

An olive-green clay, discolouring to orange when exposed to air, was discovered underlying glaciolacustrine deposits in the Combe d'Ain (Jura, France). A core was taken to investigate the age and depositional origin of this deposit. Geochemical analyses (total organic carbon and nitrogen) show that the sediments are very poor in organic material, while gram size analyses provide evidence for the varved nature of the overlying glaciolacustrine sediments. The gram size analyses also suggest a floodplain environment for the olive-green clays. Palynological analyses revealed an assemblage suggesting an open landscape dominated by Poaceae and Cyperaceae and contributions of Chenopodiaceae and Artemisia. Tree pollen is scarce and there is ample evidence for reworking of older material Barren ground near the core location is indicated by the presence of spores of Lycopodiella inundata (Lycopodium inundatum) Combining the gram size evidence and the presence of L. inundata suggests a fluvial (floodplain) environment as most likely origin. Using the lithostratigraphic position, the morphological development of the Combe d'Ain and the severe climatic conditions indicated by the palaeoecological content, the deposits are tentatively dated to ~22 ka BP.Une argile vert olive, décolorée en orange quand exposée à l'air, a été découverte sous des dépôts glacio-lacustres dans la Combe d'Ain (Jura, France), Une carotte a été prise pour déterminer l'âge et l'origine sédimentaire du dépôt. Des analyses géochimiques (carbone organique total et azote) montrent que les sédiments sont très pauvres en matière organique tandis que les distributions granulométriques bimodales prouvent le caractère varvé des sédiments glacio-lacustres susjacents. Les analyses granulométriques suggèrent aussi un environnement alluvial pour les argiles vert olive. Des analyses palynologiques montrent un assemblage indicatif d'un paysage ouvert dominé par des Poacés et des Cypéracés avec des contnbutions de Chénopodiacés et d' Artemisia. Les pollens d'arbres sont rares et le remaniement de matériel ancien a été clairement prouvé. Une surface ouverte près du site de sondage est indiquée par la présence de spores de Lycopodiella inundata (Lycopodium inundatum). La combinaison des arguments granulométnques et la présence de L. inundata suggèrent un milieu fluviatile (alluvial) comme le plus vraisemblable. En utilisant la position lithostratigraphique, le développement morphologique de la Combe d'Ain et les conditions climatiques sévères indiquées par le contenu paléoécologique, nous proposons de situer ces dépôts vers 22 mille ans BP.Aalbersberg Gérard, Kasse Cornelis. A pleniglacial fluvial deposit from the Combe d'Ain (Jura, France) [Un dépôt fluviatile pléniglaciaire de la Combe d'Ain (Jura, France}]. In: Quaternaire, vol. 14, n°2, 2003. pp. 97-103

Sensitivity of floodplain geoecology to human impact: A Holocene perspective for the headwaters of the Dijle catchment, central Belgium

Floodplain deposition rates have increased markedly under influence of human impact throughout the late Holocene in many western and central European catchments. Consequently the geomorphology and ecology of many floodplains changed. In this study we discuss this human impact and its influence on the floodplain geoecology during the middle and late Holocene for the headwaters of the Dijle catchment, located in the Belgian loess belt. The floodplain geoecology and the regional vegetation was reconstructed from sedimentological and palynological analyses. An age–depth model for the studied sequences was obtained using 17 radiocarbon dates. Statistical analyses of the pollen data (cluster analysis and canonical correspondence analysis) were used to detect changes in the pollen record. Our data show that until c. 2500 cal. BP, human impact was nearly absent or localized with no discernible influence on the floodplain geoecology. The floodplain was in a stable phase and consisted of a marshy environment where organic material could accumulate, which is interpreted as the natural state of the floodplain. From c. 2500 cal. BP onwards, human impact gradually increased. However, only when human impact in the catchment crossed a threshold around 500 cal. BP, the floodplain geoecology changed with clearing of the Alder carr forest, the establishment of a single channel river and the dominance of minerogenic overbank sedimentation. Spatial variability in the coupling between increasing human impact and changes in floodplain geoecology can be attributed to differences in hillslope–floodplain connectivity and local differences in human impact

Glacial geology of Saalian relief around Midwolda, eastern Groningen, the Netherlands

Due to canal-digging activities in 2011 and 2014, two small and one large temporary exposure, all ranging from 4 to 5 m in depth, were studied with respect to the sedimentology and structural geology, in the glacial ridge of Midwolda, Groningen, the Netherlands. The lowermost unit consists of clay of Elsterian age and is composed of glaciolacustrine and turbiditic deposits (Peelo Formation). These show synsedimentary deformations due to loading, as well as post-sedimentary Saalian glaciotectonic deformations, consisting of folding, and faulting structures. The overlying Saalian till sequence consists of two main units. The lower unit, with clear features of a subglacial deformation zone (e.g. lateral heterogeneity), has a local origin and strongly resembles the underlying Elsterian clay. Glacial tectonic and morphological observations indicate a primary NE-SW ice-flow direction. The second till layer has a sandy texture and high crystalline gravel content, while glacial-tectonic indicators point to a NW-SE ice-flow direction. The deformation of the till layers has caused a repetition and mixing of till layers, due to the last ice movement. The NW-SE ice movement is supported by the morphology as well as data from erratic gravel counts. Correlation with geological cross-sections strongly suggests regional subsurface control on ice-sheet behaviour

From natural to human-dominated floodplain geoecology – a Holocene perspective for the Dijle catchment

© 2015 Elsevier Ltd. Floodplain systems underwent important changes in many West and Central European catchments through the late Holocene. To better understand the relation between these changes and anthropogenic land cover changes, we evaluated detailed data on floodplain changes against detailed data on human impact for the Dijle catchment (758 km2), Belgium. The results show that during the Neolithic Period, human impact was nearly absent and floodplains consisted of a strongly vegetated marshy environment where organic material accumulated, which is considered as the natural state of the floodplain. The increase in human impact from Bronze Age onwards caused an increase in soil erosion and hillslope-floodplain connectivity. Consequently, sediment input in the floodplain system increased and floodplain geoecology changed towards an open floodplain dominated by clastic overbank deposits, mainly as the indirect result of an intensification of agricultural activities. Based on these data, a generalized model of floodplain development is presented. At the scale of the entire Dijle catchment, the gradual changes in floodplain morphology coincided with the gradually increasing human impact in the catchment, which suggests a linearity between the external forcing (human impact) and geomorphic response (floodplain change). However, at the narrow floodplains in the headwaters, the gradual increase in human impact contrasts with the abrupt change in floodplain geoecology, only triggered when human impact reached a threshold. Observed differences in the process-response model at catchment scale are attributed to differences in hillslope-floodplain connectivity, the location within the catchment and to differences in the timing and intensity of human activities between subcatchments.status: publishe

The meandering Dijle River in the western European loess region: an anthropogenic landscape

Floodplain deposition rates have increased markedly under influence of human impact throughout the Late Holocene in many Western and Central European catchments. These variations in sedimentation rates have changed the geomorphology and ecology of many floodplains. In this study we discuss the human impact and its influence on floodplain geoecology during the Middle and Late Holocene for the Dijle catchment (760 km 2 ), located in the Belgian part of the western European loess belt. Based on sedimentological and palynological data, the geoecology of the floodplain and the regional vegetation was reconstructed at 6 locations. Age-depth models for each of the studied sequences were obtained through 60 radiocarbon dates. Human impact in the catchment was quantified based on statistical analysis of the pollen data (cluster analysis and correspondence analysis). Our data shows that until ca. 2500 cal BP, human impact was either absent or limited to local disturbances yielding no clear influence on the floodplain geoecology. The river environment was in a stable phase and consisted of a marshy environment were organic material could accumulate, which is interpreted as the natural state of the floodplain. From ca. 2500 cal BP onwards, human impact gradually increased. However, only when human impact in the catchment crossed a threshold, the floodplain geoecology changed with clearing of the Alder carr forest, the dominance of minerogenic overbank sedimentation and the emergence of a single channel meandering river. Spatial and temporal variability in the coupling between increasing human impact and changes in floodplain geoecology can be attributed to differ- ences in hillslope-fluvial system connectivity and local differences in human impact. Overall, this study shed new lights on the indirect effect of anthropogenic forces on floodplain geoecology. It also shows that the contemporary morphology of the Dijle River floodplain contrasts widely with that of the Middle Holocene, which was dominated by peat formation in marshes and gyttja deposition in floodplain lakes. These changes in floodplain geoecology are the result of human disturbances in the catchment.status: publishe

Reconstruction and semi-quantification of human impact in the Dijle catchment, central Belgium: a palynological and statistical approach

Reconstructing and quantifying human impact is an important step to understand how, when and to what extent humans have changed the landscape during the Holocene. In this study we present a reconstruction of vegetation changes throughout the Holocene based on palynological data of six study sites in the Dijle catchment, located in the Belgian loess belt. A reconstruction of human impact in the catchment is extracted from the palynological study based on statistical analyses (cluster analysis and non-metric multidimensional scaling (NMDS)). The NMDS analysis on the pollen data do not detect large-scale Mesolithic or Neolithic human activities on the Dijle catchment. In these periods, human impact in the catchment was probably limited to local disturbances and small-scale forest clearances. Only from the Bronze Age onwards (ca 3900 cal a BP) human impact was clearly detected in the pollen records and vegetation gradually changed. Human impact further increased from the Iron Age onwards, except for a temporary halt between ca 1900 and 1600 cal a BP, possibly coupled with the Migration Period in Europe. The general vegetation development and increasing human impact are rather similar at the catchment scale, beside some local variations in timing and intensity of the human impact in the different subcatchments. The applied methodology, cluster analysis and NMDS, proves to be a useful tool to provide semi-quantitative insights in the temporal and spatial vegetation changes related to increasing human impact.publisher: Elsevier articletitle: Reconstruction and semi-quantification of human impact in the Dijle catchment, central Belgium: a palynological and statistical approach journaltitle: Quaternary Science Reviews articlelink: http://dx.doi.org/10.1016/j.quascirev.2014.08.006 content_type: article copyright: Copyright © 2014 Elsevier Ltd. All rights reserved.status: publishe