ABSRTRACT BOOK - VUbalr/FLAG/web_data/downloads/FLAG_Budapest2008... · channel of the River Loire, France 11.00-11.20 Cserkész-Nagy, Á.T., Tóth, T., Vajk, Ö ... T.S., Bridgland,

FLAG Biennial Meeting, Budapest, Hungary, September 3–7, 2008 Abstract Book

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FLAG Biennial Meeting

Budapest, Hungary September 3-7, 2008

Advances in river system and environmental change research at the crossroad of Western and Eastern

Europe

ABSRTRACT BOOK


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Scientific programme

WEDNESDAY, SEPTEMBER 3

9.00-9.10 Opening of FLAG Biennial Meeting (Jef Vandenberghe, Chairman of FLAG)

9.10-9.40 Welcome and introduction to Carpathian basin fluvial archives (Annamária Nádor, Gyula Gábris)

9.40-12.00 Session I. CONTROLS ON SEDIMENTARY PROCESSES OF RIVER SYSTEMS Convenor: Jef Vandenberghe 9.40-10.00 Dinis, P., Cunha, P., Dinis, J.: Relevant textural feature of bottom sediments when estimating dynamics and sediment paths in eustarine to fluvial settings. A case study from river Lis eustary (Western Portugal) 10.00-10.20 Herget, J., Carling, P.A., Borodavko, P.S., Parnachov, S.V.: Run-up sediments as (palaeo)hydraulic indicator 10.20-10.40 COFFEE BREAK 10.40-11.00 Rodrigues, S., Breheret, J-G., Macaire, J-J., Juge, P., Bakyono, J-P.: Vegetation controls on sedimentary processes and record in alluvial channels: an ongoing example provided by a side channel of the River Loire, France 11.00-11.20 Cserkész-Nagy, Á.T., Tóth, T., Vajk, Ö., Sztanó, O.: River bed morphology of a regulated meandering river: Middle-Tisza region, Hungary 11.20-11.40 Kiss, T., Sipos, Gy.: Palaeohydrological investigation of Pleistocene and Holocene meanders along the Lower Tisza River, Hungary 11.40-12.00 Stokes, M., Marther, A., Griffiths, J.: Quaternary palaeoflood hydrology of coarse fluvial bar terrace sediments in a high sinuosity transverse drainage (Rio Almanzora, SE Spain) 12.00-14.00 LUNCH BREAK


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14.00-17.40 Session II. TECTONIC , CLIMATIC AND BASE -LEVEL CONTROLS ON RIVER

RESPONSES AND ALLUVIAL ARCHITECTURE Convenor: Annamária Nádor 14.00-14.20 Sinha, R., Tandon, S.K., Gibling, M.R.: Late Quaternary evolution of the Ganga plains, India: myths and misconceptions, new developments and future directions 14.20-14.40 Gibling, M.R., Sinha, R., Tandon, S.K., Jain, M.: Monsoon-generated fluvial sequences: climatic control in the Himalayan Foreland Basin over the past 130,000 years 14.40-15.00 Uhrin, A., Csillag, G., Sztanó, O.: Pliocene rivers in the southeastern foreland of Vértes Hills 15.00-15.20 van Balen, R.T., Kasse, C., Crosato, A.: What controls the sinuosity distribution and meander locations in the Maas, crossing the Roer Valley Rift System? 15.20-15.40 Blanka, V., Kiss, T.: Neotectonic effects on meander development on the River Hernád, Hungary 15.40-16.00 TEA BREAK 16.00-16.20 Cohen, K.M., Erkens, G., Hijma, M.P.: Reading the Rhine-delta Holocene sediment trap 16.20-16.40 Thamó-Bozsó, E., Ó Kovács, L.: Changes in Quaternary fluvial transport directions in the Mid-Hungarian Plain based on statistical analysis of detrital heavy mineral composition of sands 16.40-17.00 Cserkész-Nagy, Á.T., Tóth, T., Sztanó O.: Reconstruction of a Pleistocene meandering river and its climatical background in the NE part of Great Hungarian Plain using UHR seismic images 17.00-17.20 Vandenberghe, J., Kasse, C., Bohncke, S.J.P., Gábris, Gy.: Fluvial pattern changes in a continental lowland setting: the Tisza valley in northeastern Hungary 17.20-17.40 Kasse, C., Vandenberghe, J., Bohncke, S.J.P.: Fluvial changes in the Tisza valley (Hungary) during the last glacial-interglacial transition


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THURSDAY, SEPTEMBER 4 9.00-10.40 SESSION III. ANCIENT AND MODERN HUMAN -RIVER ENVIRONMENT

INTERACTIONS Convenor: David Bridgland 9.00-9.20 Vis, G-J., Kasse, C., Vandenberghe, J., Kroon, D., Jung, S.J.A.: The effect of late Holocene strong human impact on Tagus River terrestrial and marine sedimentation (Portugal) 9.20-9.40 Sipos, Gy., Kiss, T.: Morphological responses to anthropogenic interventions on the Hungarian section of the Maros River 9.40-10.00 Morin, E., Cyprien, A-L., Gay-Ovejero, I., Hinschberger, F., Joly, C., Macaire, J-J., Poirier, N., Visset, L., Zadora-Rio, E.: Spatial variability of anthropogenic impact on Holocene fluvial sedimentation. A case study: the Choisille catchment (Parisian basin, France) 10.00-10.20 Kadlec, J., Diehl, J.F., Beske-Diehl, S., Grygar, T., Svetlik, I.: Natural and human impacts on the magnetic signal from the Late Holocene flood-plain deposits of the Morava River (Czech Republic) 10.20-10.40 White, T.S., Bridgland, D.R., Howard, A.J., White, M.J.: Data from England’s Wash rivers: results from the ALFS-funded Trent Valley and Cambridgeshire Palaeolithic Projects 10.40-11.00 COFFEE BREAK 11.00- 12.20 Session IV. ADVANCES IN DATING AND OTHER ANALYTICAL TOOLS IN FLUVIAL

SEDIMENTS Convenor: Rajiv Sinha 11.00-11.20 Frechen, M., Gabriel, G.: The Heidelberg Drilling project and the Pliocene/Pleistocene sediment succession of the Upper Rhine Graben, Germany 11.20-11.40 Cordier, S., Frechen, M.: Methodological aspects on luminescence dating of fluvial sands from the Moselle basin 11.40-12.00 Lauer, T., Frechen, M., Hoselmann, C., Tsukamoto, S.: Luminescence dating of fluvial sediment core from Viernheim (Heidelberg basin) 12.00-12.20 Grygar, T., Kadlec, J., Svetlik, I.: Chemical analysis of expandable clay minerals as a tool to stratigraphic correlation of flood sediments of the last millennia, Morava Basin, Czech Republic


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12.20-14.00 LUNCH BREAK 14.00- Session V. FLUVIAL ARCHIVES OF TERRACE STAIRCASES Convenor: Gyula Gábris 14.00-14.20 Dinis, J., Cunha, P., Dinis, P.: Fluvial terraces and sequence stratigraphy: upper progradational packages 14.20-14.40 Martins, A.A., Cunha, P.P., Huot, S. Murray, A.S., Buylaert, J.P., Stokes, M.: Geomorphological correlation of the Tejo River terraces in the Gaviao-Chamusca area (Central Portugal) supported by luminescence dating 14.40-15.00 Cunha, P.P., Martins, A.A., Buylaert, J.P., Murray, A.S., Dinis, P., Stokes, P., Hancock, G.: Geomorphology, sedimentology and luminescence dating of the Tejo River Upper Pleistocene in the Carregueira area (Central Portugal, western Iberia) 15.00-15.20 Gomes, A., Araújo, M.A., Albertí, A.P., Cunha, P.P., Chaminé, H.I.: Fluvial archives of the landscape evolution of western Iberia during late Cenozoic: the examples of the terrace staircases of Vouga and Águeda Rivers (Central Portugal) 15.20-15.40 Antoine, P., Limondin-Lozouet, N., Auguste, P., Locht, J-L., Ghaleb, B., Bahain, J-J., Jolly-Saad, M.C.: Interglacial deposits in Northern France terrace systems: new evidences from MIS 11 and 5e calcareous tufa sequences 15.40-16.00 Bridgland, D.R.: The role of glacio-isostasy int he formation of post-deglacial and Holocene river terraces: evidence from northern England 16.00-16.20 TEA BREAK 16.20-17.00 FLAG Business Meeting


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Long-term fluvial archives in Hungary: response of the Danube and Tisza rivers to tectonic movements and climatic changes during the Quaternary: a review

Annamária Nádor1 Gyula Gábris2 1 Geological Institute of Hungary, H-1143 Budapest, Stefánia út 14, [email protected] 2 Eötvös Loránd University, Department of Physical Geography, H-1117 Budapest, Pázmány Péter sétány 1/c, [email protected]

The talk discusses the Quaternary evolution of the Danube and Tisza rivers and their

main tributaries in the context of evolution of the entire Pannonian Basin, which is Europe’s largest intramontane basin, within the Alp-Carpathian orogen. The palaeo-drainage reconstruction of the Pannonian Basin for the pre-Quaternary period is outlined in connection with the gradual regression of Lake Pannon since the Late Miocene. Deltas of rivers that entered the basin from the northwest and northeast were gradually transformed into extended alluvial plains; thus the earliest possible ancestor of the Danube coming southeastwards from the Alps could be as old as Late Miocene. By the Pliocene the whole Lake Pannon was infilled. The former extensional basin formation was replaced by a compresional stress field, which resulted in uplift of the marginal flanks and late-stage subsidence anomalies. The increasing relief led to the formation of the Quaternary drainage pattern. The actively subsiding young basins were filled by fluvial sediments, transported by the Danube and Tisza rivers systems from the uplifting mountains. Between the subsiding regions of the Little- and Great Plains, the Danube has formed an antecedent valley with terrace staircases between the uplifting sections of the Transdanubian Range and the North Midmountains. The formation of the terraces is attributed to periodic climate changes during the Pleistocene combined with differences in the uplift rate. The talk gives a complex overview of the classical chronology of the six terraces based on various data sources: mostly dating of loess/paleosol sequences, travertines, aeolian sand and tephra strata overlying the fluvial sediments, complemented by scattered vertebrate faunal data and archaeological evidence directly from the terrace sediments.

The Quaternary drainage pattern evolution of the Great Plain, with a strong tectonic control, is discussed in detail. Rivers originating from the uplifting marginal areas were drawn towards the subsiding depressions which served as local base level. Changes in subsidence rates in space and time throughout the Quaternary resulted in the evolution of a complex drainage pattern. A special emphasis is placed on the Late Pleistocene–Holocene development of the Middle Tisza region and the Körös basin, where the Berettyó-Körös Rivers form an eastern tributary system of the Tisza River. A comparative evaluation of these two areas is especially relevant, as they provide insights into large-scale Late Pleistocene avulsion of the Tisza River. OSL dating, complemented with inferred transport directions determined from heavy mineral analysis of fluvial sediments in the Körös basin, has revealed an ancient large meandering river system that can be identified with the palaeo-Tisza, which was flowing along a tectonically controlled depression during the Late Pleniglacial. Successions in the Middle Tisza region have allowed differentiation between the older channels of the palaeo-Bodrog river and the Sajó-Hernád alluvial fan and the younger meander belts of the new course of the Tisza. In the Tisza system, changes in river style (braided to various scales of meandering) show correspondence to millennial-scale climate changes of the last 25 ky, while in the Körös basin the effects of tectonics are overprinted onto the regional climatic signals.


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Relevant textural features of bottom sediments when estimating dynamics and sediment paths in estuarine to fluvial settings.

A case study from river Lis estuary (Western Portugal)

Dinis, P.*, Cunha, P. and Dinis, J.

IMAR-Institute of Marine Research, Department of Earth Sciences, University of Coimbra, Portugal * [email protected]

Bottom sediments in river-estuarine environments record prevalent conditions, like dynamics, sediment sources and pathways. In this work we test several textural features that can be used to estimate such environmental conditions. As the data was collected along a straight channel with homogeneous slope, conditions related to local geomorphic particularities are expected to be minimal. The main factors that determined the textural features of the deposits are the source sediments features and the dynamic conditions (primarily fluvial discharge and tidal cycle characteristics). It is demonstrated that mean sediment size, although one of the most common statistical parameter used to characterise a grain-size distribution, may not be a useful parameter in the estimation of hydrodynamic conditions. In estuarine channel sediments the grain-size distribution frequently comprises a mixture of at least two populations, deposited during the ebb and flood periods or spring and neap cycles, being the conditions of reduced hydrodynamics probably responsible for finer populations. As evaluation of the dynamics requires that a single sediment transport unit is analysed, a problem also arises from the sampling procedure. When a dredge is used it is not possible to ensure that just the uppermost sediment level is sampled and the collected sediments may comprise levels from several depositional events. The sediment mixture will be responsible for a bias in the grain-size distribution attributes. To minimize misinterpretations, the possible constituent populations of the grain-size distributions must be discriminated. This can be approximated by simple visual analysis and identification of modes and classification of the grain-size distributions. The discrimination of populations may give valuable information on the prevalent depositional conditions. Sediments in estuarine channel were found to be deposited in contrasting dynamic conditions, involving periods of higher energy than in the fluvial channels upstream. Combined grain-size and particle rounding data may be used to confirm these populations. Differences in roundness of coarser and finer fractions tend to be smaller in sediments that result from mixtures of coastal (beach, spit or dune) and fluvial derived populations. A combination of this set of data may also be used to trace sediment paths.


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Run-up sediments as (palaeo-)hydraulic indicator

Herget, J.1,*, Carling, P.A.2, Borodavko, P.S.3 and Parnachov, S.V.3 1Dept. of Geography, University of Bonn; Meckenheimer Allee 166, D-53115 Bonn, Germany *[email protected] 2School of Geography, University of Southampton, United Kingdom 3Dept. of Geography and Geology, Tomsk State University, Russia

Run-up sediments can be found in river channels and floodplains in front of local obstacles like trees trunks, bridge piers or bedrock cliffs. Upstream of the obstacle, the flow velocity of the current decreases resulting in a locally elevated water surface due to the transfer of energy from kinetic to potential energy. Transported suspension load might be deposited at a higher level in front of the obstacle or mark the higher water level to one side or either side of the obstacle.

Run-up effects as special feature of flood debris lines were first mentioned by Costa in the context of debris flows, but were not investigated in detail. Along the pathway of the Pleistocene ice-dammed lake outburst floods in the Altai-Mountains, Siberia, run-up sediments are located at numerous valley obstructions in front of local bedrock ridges. The clue of the interpretation is not their sedimentological structure or texture, but the configuration of their deposition and especially their elevation in relation to undisturbed flood stage indicators upstream o the obstruction. Typically, they generate a relatively thin layer of deposited suspension load in front of the obstruction.

They indicate the amount of energy transfer and can be used to conclude on the mean flow velocity of the current upstream of the obstruction. According to the energy equation by Bernoulli, energy can only be transferred from kinetic to potential energy as pressure energy is negligible for open channel flow. Hence, once a current is blocked its kinetic is transferred into potential energy indicated by a risen water level. As the amount of the water level differences upstream and in front of the obstruction can be measured in the field – or surveyed of suspension load marks and deposits for palaeofloods – the unknown variable of mean undisturbed flow velocity can be estimated. This principle previously was applied for flow velocity measurements in small channels.


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Vegetation controls on sedimentary processes and record in alluvial channels: an ongoing example provided by a side channel of the River Loire, France

Rodrigues, S.1, *, Bréhéret, J.-G.1, Macaire, J.-J.1, Juge, P.2 and Bakyono, J.-P.1 1Université François Rabelais de Tours, UMR CNRS 6113, ISTO –- TOURS, Laboratoire de Géologie des Environnements Aquatiques Continentaux, UFR Sciences et Techniques, Parc de Grandmont, 37200, Tours, France *[email protected] 2CETU Elmis Ingénieries, Université F. Rabelais, 11 quai Danton, 37500 Chinon, France.

The role of pioneer trees (Populus nigra) on bar formation in secondary channels has been studied in the modern fluvial system of the River Loire (France). On seven plots, subject to various flow and sedimentary conditions, physical features of vegetation, topographical evolution, surface sediments grain-size, and flow velocity were investigated during and after flood events.

Results show that the morphological adaptation of pioneer trees to environmental stresses – such as fast-flowing waters and sediment burying – drive a feedback effect on local sedimentary processes. The dynamics and preservation potential of bedforms, the distribution of sediment grain size and slopes are controlled by i) magnitude, frequency, and duration of the flood, ii) location within the channel (i. e. high- or low-energy zones), iii) morphology of the vegetated bar and iv) biomechanical characteristics of vegetation.

In high-energy zones, bedforms of the vegetated areas are mainly stable obstacle marks subject to sediment reworking during the falling stage of the hydrograph. When water level is high, trees reduce flow velocity and promote sediment deposition; this trapping power decreases as the water level rises because trees bend downstream and reduce their area opposed to the flow. When water level falls, sediment reworking is strongly influenced by morphologically adapted trees and local microtopography.

In the low-energy zones, the slow morphological evolution underlines the effective fixing power of the herbaceous vegetation. These plants also enhance aggradation where the sediment supply is low and composed of suspended material.

The evolution of groves subject to flood events depends on the amalgamation and preservation of obstacle marks. The merging of these bedforms and their fixing by herbs will lead to the formation of ridges and swales and to a rounded cross-sectional morphology. The development of this morphology and the associated accretion of the bed increase the deflexion power of the vegetated bar and exert a feedback on subsequent flow, sedimentary processes (deposition of finer sediments) and vegetation recruitment. These elements show how fluvial archives, specifically mid-channel islands, become stabilized by in situ woody vegetation with intervening bare sandy areas.


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River bed morphology of a regulated meandering river: Middle-Tisza region, Hungary

Cserkész-Nagy, Á.T.1, Tóth, T.2, Vajk, Ö.3 and Sztanó, O.1 1Dept. of Physical and Applied Geology, Eötvös Loránd University, Budapest, Hungary, H–1117, Pázmány P. s. 1/c.; [email protected], [email protected] 2Geomega Ltd., Budapest, Hungary, H–1095, Mester u.4. I/2. 3Directorate for Environmental Protection and Water Management of Middle Tisza District, Szolnok, Ságvári Krt.4.

The Tisza River is the largest meandering river of the Great Hungarian Plain forming its surface since the Pleistocene. Tectonic and climatic influences played an equally important role in channel development until the river regulation works beginning in the middle of the 19th century.

The ultra-high resolution shallow water seismic profiles acquired on Middle Tisza for analysing older subsurface sedimentary structures became a powerful tool in the study of the present river-bed morphology and recent sedimentation. Distribution of erosional and depositional reaches can be mapped comparing the reflexion of the river-bed and the thickness of unconsolidated sediments. Matching up these results to channel cross-sections, detailed topography and channel bathymetric maps revealed the natural morphologic features of a meandering river and some changes of the river-bed due to the anthropogenic effects.

The most spectacular features of the river-bed are large erosional scours, 39 occurring on the nearly 100 km long segment of the Middle Tisza. They can be divided into 4 groups based on their various size, form and location relative to the meander bends. Although most of the scours formed on the erosional, outer part of meander bends, some of them were found on long straight reaches of the river. They can be hardly explained by any natural or anthropogenic effect. These are smaller and shallower than those of the bend. The latter are mostly asymmetrical in longitudinal view and their upstream walls are steeper. A development series can be built up as a function of meander maturing. Symmetrical, narrower scours developing on the outer part of a slightly bended meander shift towards the thalweg and downstream while they become broader and asymmetrical. Downstream shifting is more significant where sinuosity cannot increase due to natural or artificial barrier (non-erosive bank). Double scours form mostly on these places.

Lithological information of the underlying sediments obtained from UHR seismic help to explain the morphological diversity of scours. Deeper ones with steeper walls cut into elder point-bar deposits, while elongated scours with flat base are characteristic on elder horizontal floodplain beds. In special cases pre-regulation river-bend scours now filled-up or post- regulation deepened and shortly afterward slightly infilled ones can be observed.


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Palaeohydrological investigation of Pleistocene and Holocene meanders along the Lower Tisza River, Hungary

Kiss, T.* and Sipos, Gy.

Department of Physical Geography and Geoinformatics, University of Szeged H-6722, Szeged, Egyetem str. 2-6, Hungary *[email protected]

A major aim of palaeohidrological studies is to estimate the mean and maximum discharge, the flood frequency etc. in order to assess the hidrological and climatological conditions of a given period. A number of researches study the deposited sediments in order to determine slope-conveyance, slope-area, step-backwater critical-depth and critical velocity for calculating maximum flood discharge could be calculated (Benito and Thorndycraft, 2005). Another approach is based on morphological measurements, where usually channel width, radius of curvature and channel slope are the most common parameters in determining palaeodischarges (Williams, 1984). In Hungary Gábris (2001, 2008) made such calculations in terms of tributaries of the Tisza River. Certain authors however draw attention to significant, 10-40 % errors in case of palaeohidrological calculations (Sidorchuk and Borisova, 2000).

Considering the Lower Tisza Region palaeomeanders can be identified only in a narrow N-S zone due to active Holocene erosion. Certain palaeomeanders are situated on the higher floodplain, though most of them can be found on the Pleistocene, Early Holocene lower floodplain of the river. Most of these meanders has well developed point-bar systems and fragments of breaches and backswamps are also apparent.

The aim of the present study is to determine the hydrological parameters and age of Lower Tisza palaeomeanders. Planform parameters were determined using aerial photographs, while cross-sectional values and the burial depth of forms were estimated using corings and georadar. The calculation of discharges was based on different formulas introduced by Williams (1984). The errors of these formulas were calculated on present-day morphology and discharge of the Tisza and Danube rivers. Age determination was made with luminescence dating (OSL). Samples were taken from the youngest point-bars of the palaeochannels. The OSL ages are under measurement, thus the study has not been entirely completed by the time of writing the abstract.

Based on their size end morphology the studied palaeochannels can be grouped into three. The largest channels are located on the higher floodplain. Their mean discharge was 3600-7000 m3/s, though maximum discharges could reach 13800-14500 m3/s. These meanders have well-developed point-bar systems, reflecting long and undisturbed meander formation. Fluvial forms are covered by 2-4 m thick loessy sediments.

On the lower floodplain two generations of palaeochannels were identified. The supposedly older set (its members have a size only half of the former ones) reflect a decreasing fluvial activity, with mean and maximum discharges at a range of 1700-2500 m3/s and 7600-10000 m3/s, respectively. The youngest and most intact palaeomeanders are located in the southern part of the study area. These meanders are smaller, thus their discharge data are also the smallest (Qmean = 790-1300 m3/s, Qmax = 4800-6200 m3/s). Their 3-7 member point-bar system is covered by 1-2 m thick floodplain sediments.

Based on morphological data and relative ages of meanders, the studied area can be described by a decreasing fluvial activity from the Pleistocene throughout the Holocene.


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Quaternary palaeoflood hydrology of coarse grained fluvial bar terrace sediments in a high sinuosity transverse drainage

(Río Almanzora, SE Spain)

Stokes, M.1, Mather, A.2 and Griffiths, J.1 1School of Earth, Ocean and Environmental Sciences, University of Plymouth, Drake Circus, Plymouth, Devon, PL4 8AA, UK 2School of Geography, University of Plymouth, Drake Circus, Plymouth, Devon, PL4 8AA, UK

Transverse drainage are discordant river patterns whose flow direction cuts across geological structures such as faults, folds and the regional tectonic fabric (strike) of mountain belts. Such drainage can form spectacular geomorphological features, with reaches often occupying narrow and deeply dissected canyons / gorges that cut through prominent topographic barriers forming important linkages between hydrological and sedimentological basins. Fluvial sedimentation is uncommon or transient in transverse drainage. Deposits are stripped out of channel reaches, with bedrock erosion as the dominant fluvial process. In the rare instances where fluvial deposits are observed, the bedload calibre is typically coarse grained, comprising gravel / conglomeratic sediments that reflect elevated sediment supply from steep valley margins of high relief into high gradient channel reaches.

Studies of the sedimentology and palaeoflood hydrology of transverse drainage are limited. Facies are typically dominated by poorly sorted, low angle cross-stratified gravel-cobble grade conglomerates arranged into a series of diffuse channels that are attributed to braid bar processes (e.g. longitudinal bars). These sedimentation styles appear to correspond to relatively straight or low sinuosity transverse valley reaches. However, transverse drainage can show high sinuosity, meandering forms that develop due to combinations of the fluvial response to bedrock heterogeneities and active tectonics (e.g. tilting / uniclinal shifting).

Within this paper we document the sedimentology and palaeoflood hydrology of a high sinuosity transverse drainage using Quaternary fluvial terraces from the Río Almanzora of SE Spain. Four inset fluvial terrace levels can be mapped along a 7km transverse valley that cuts across an uplifted basement high of metamorphic basement, the Sierra Almagro (≤700 m altitude), linking the Neogene basins of Huercal-Overa and Vera. The transverse reach comprises a sinuous valley with numerous km-scale abandoned meander loops (sinuosity = ≤4.2). River terrace outcrops consistently reveal up to 15m thick units of cobble-boulder conglomerates (Dmax = 0.5-0.7m) that fine up into siltstones. The conglomerates commonly display well developed planar cross-stratification with foresets up to 3m high. Clast imbrication is typically oblique to cross-stratification with a dominant transport direction towards the south. The sediments are interpreted as bank attached bar forms, possibly point bars, with the fining upwards corresponding to cutoff, abandonment and tributary fan infilling of the km scale bedrock valley meanders. Preliminary palaeoflood calculations will be presented and discussed within the context of western Mediterranean climate-related variations in flood regime and flood deposit preservation potential.


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Late Quaternary evolution of the Ganga plains, India: myths and misconceptions, new developments and future directions

Sinha, R.1, Tandon, S.K.2 and Gibling, M.3 1Engineering Geosciences Group, Indian Institute of Technology Kanpur 208018, India 2Department of Geology, University of Delhi, Delhi 3Department of Earth Sciences, Dalhousie University, Halifax, Canada

The river systems of the Indian Subcontinent have fascinated scientists for centuries. The Ganga river, the largest river system in the Himalayan foreland basin, has been the focus of attention for several decades, and some of the most serious difficulties in understanding such large systems reflect the size of the river and its extensive alluvial plains, as well as significant spatial variability from upstream to downstream in climatic parameters and geomorphic diversity. The Ganga plains with its well preserved subsurface alluvial stratigraphic records form an important continental archive for deciphering Quaternary climate change and landscape development. For more than three decades, the Ganga plains has attracted fluvial geomorphologists and sedimentologists seeking to understand landscape diversity and to generate climate proxy data through such archives as sedimentary facies, calcretes, pollens, and clay minerals. The Ganga plains are drained by rivers originating from the Himalaya to the north and the craton to the south, resulting in significant spatial diversity in sedimentation pattern, sediment composition and alluvial architecture. In a recent regional appraisal of the response of the Ganga river system, it has been suggested that climate-related signals show tight coupling between source area, catchment basin, and coastal and marine depocenters. We synthesize here available information from across the Ganga plains and discuss myths and misconceptions about this vitally important region that have persisted in the literature for more than three decades. A large part of the synthesis is based on our work in different windows across the Ganga plains.

The unsubstantiated advocation of base-level changes (sea-level related) in controlling landscape development and alluvial stratigraphy far inland has led to serious misconceptions, including a concept of geomorphic homogeneity across the Ganga plains and regional correlativity of terrace surfaces. Other misconceptions include the Yamuna-Ganga megafan concept, and the Markanda terminal fan model. These views are like ‘urban myths’ that begin to have a life of their own. The concepts of megafans and terminal fans have been used in the wrong context, and the latter now stands negated by the international community. Similarly, the idea of regional geomorphic surfaces correlatable across hundreds of kilometers has been propagated in the literature. Another important issue is the chronological database of the Ganga plains sediments, which is not just fragmentary but also lacks reliability and proper stratigraphic context. This has also resulted in reporting unrealistic sediment accumulation rates in the Ganga plains. Further, the non-reproducibility of poor and inadequately documented field data in key stratigraphic sections has limited the usefulness of the chronological database. Future studies need to be shorn of biased approaches that advocate the predominant role of sea-level and tectonics, underestimate climatic control, and fail to consider geomorphic thresholds. Earlier approaches also failed to recognize the importance of integrating surface and sub-surface data.

Following an integrated approach, we have demonstrated that there is a great variability of alluvial architecture across the Ganga plains. Variable climatic conditions as well as variable hinterland conditions of climate and tectonics have resulted in significant spatial variability in river hydrology, sediment transport characteristics and sedimentation patterns. Incised valleys and wide interfluves in the western plains have formed as a consequence of high stream power and lesser sediment supply, and have generated ‘discontinuity-bounded


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sequences’ in the interfluves and multi-storied sand sheets in valleys. The eastern plains with a higher precipitation regime and higher sediment flux have generated megafan sequences formed by frequently avulsing, wide and shallow channels with abundant sediment supply, which are separated by relatively narrow interfan rivers that have generated thick muddy sequences with sand ribbons through hyperavulsing behaviour. We emphasize that most of the modern landscape and alluvial architecture in this region is climatically controlled and, apart from regional variation in thickness of alluvium, there is little direct evidence of tectonic controls, which have earlier been overemphasized. Our detailed evaluation of stratigraphic development in the southern Ganga plains has shown a strong climatic control and that variations in monsoonal intensity dominated behaviour of the major rivers and interfluves over the past ~100 ka. The interfluve areas near the major rivers aggraded periodically between 27 and 90 ka (MIS 3-5). They subsequently degraded or accumulated sediment only locally, probably reflecting decreased monsoonal precipitation around the LGM (MIS 2). Increased precipitation during the 15 to 5 ka period of monsoon recovery probably increased discharge and promoted incision and widespread badland formation. Although the maximum inland limit of sea-level influence in the Quaternary is debated, the influence of sea-level-induced changes on alluvial architecture of the Ganga plains inland of the Rajmahal hills is not accepted by most workers.


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Monsoon-generated Fluvial Sequences: Climatic Control in the Himalayan Foreland Basin over the past 130,000 years

Gibling, M.R.1, Sinha, R.2, Tandon, S.K.3 and Jain, M.4 1Department of Earth Sciences, Dalhousie University, Halifax, Nova Scotia B3H 3J5, Canada, [email protected] 2Department of Civil Engineering, Indian Institute of Technology, Kanpur 208016, Uttar Pradesh, India, [email protected] 3Department of Geology, University of Delhi, Delhi 110007, India, [email protected] 4Risø National Laboratory, Radiation Research Department, P.O. Box 49, DK–4000 Roskilde, Denmark, [email protected]

Until recently, much of our knowledge of Himalayan foreland-basin dynamics has come from the Neogene Siwalik Group, exposed in the Foothills, with little information available from the modern plains. However, excellent cliffs with floodplain deposits extend along the Ganga and other big rivers in the western and southern plains, some 1200 km inland. The successions date back to ~130 ka, spanning the last glacial cycle.

A remarkable aspect of the cliffs is the presence of discontinuity-bounded sequences a few meters to tens of meters thick, the bounding surfaces of which can be traced for tens of kilometers. Some surfaces are gullied erosional surfaces with local groundwater cements and a mantle of reworked gravel. Others represent large badland gully systems, and include former gullies up to 10 m deep filled with colluvium and reworked carbonate gravel. Still others represent an abrupt change from floodplain to lacustrine and eolian deposits, implying major changes of paleoenvironment.

Fluctuations in monsoonal precipitation – driven by changes in sun’s energy and glacial boundary conditions -- have affected large parts of Asia, as documented from computer-based modeling and regional facies evidence. These fluctuations should have exerted a strong driving force on the alluvial stratigraphy of the Himalayan Foreland Basin. We set out to test this hypothesis.

OSL, ITL, and radiocarbon dates were obtained from cliff and core samples to bracket the age of key surfaces. The resulting age model shows a reasonable first-order correlation between precipitation changes inferred from modeling and periods of incision and accumulation observed in the field. Persistent fluvial activity is recorded through MIS (Marine Isotope Stage) 5 to 3, when models indicate a strong monsoon. Near the onset of the Last Glacial Maximum (LGM) in MIS 2, the Ganga and other rivers experienced reduced discharge, as shown by lacustrine and eolian deposits. As precipitation intensified following the LGM (MIS 2 to 1), incision and valley formation affected rivers across northern India and Nepal, and a large sediment pulse reached the delta and Bengal Fan. Drier periods recorded locally may correspond to the Younger Dryas. Finally, rivers aggraded as precipitation declined after about 6 ka B.P. Modest eolian activity is recorded on the plains after about 30 ka B.P., but no earlier deposits are known.

The big rivers are incised through wide interfluves traversed by small “plains-fed” rivers generated from monsoonal springs. The interfluves appear to have been constructed largely by the plains-fed rivers, which built up substantial sediment accumulations reworked from Himalayan and cratonic sources.

In areas such as Asia where the monsoon exerts an overwhelming effect, changes in fluid and sediment discharge affect sediment transport capacity of rivers, resulting in cycles of floodplain incision and accumulation. Thus, even in tectonically active basins such as the Himalayan Foreland Basin, precipitation (climatic) change may control the architecture of the river deposits. The study area is too far inland for sea-level change to have influenced the alluvial stratigraphy.


16

Pliocene rivers in the southeastern foreland of Vértes Hills

Uhrin, A.1, Csillag, G.2 and Sztanó, O.1 1Department of Physical and Applied Geology, Eötvös Loránd University. Budapest, Hungary, H–1117, Pázmány P. sétány 1/c. 2Geological Institute of Hungary, Budapest, H–1143, Stefánia út 14.

Following the infill of the Late Miocene Lake Pannon, a widespread alluvial plain was formed in the Pannonian Basin during Late Miocene and the Pliocene. Quaternary uplift has inverted the basin fill, hence the Pliocene alluvial deposits are cropping out along the rim of the recent montainous areas, such as in the southeastern foreland of Vértes Hills, where these sediments have been described as Vértesacsa Formation. The aim of our study was to reconstruct the features of the ancient rivers forming the succession, what allows acquiring considerable information about the tectonic evolution of the area. Sedimentary structures were interpreted and palaeocurrent directions were measured in four outcrops; two geoelectric profiles were taken and borehole data available in the area were also examined.

Besides some silt and mud, mainly trough cross-stratified sand appears in the outcrops. In some cases, decreasing thickness of cross-sets and fining upward can be also noticed. The bulk of the sand was probably deposited by vertical accretion in laterally stable channels, however, the development of meanders and point bars has been also recognized in two locations. Unlike the outcrops, geoelectric profiles and borehole data show that narrow sand ribbons interpreted as active channel fills are surrounded by large quantities of floodplain silt and mud, in which sandier crevasse splay deposits are interbedded. Besides, data from the recent mapping of the Vértes Hills suggest the relatively long-term deposition of lacustrine sediments in some parts of the inter-channel area.

Channels flowing across the alluvial plain had generally low sinousity and bankfull depth about 5–7 m, but their vertically aggrading sediments commonly built up sandbodies thicker than this value. Common vertical accretion of channel sediments, together with the prevalence of floodplain deposits throughout the Vértesacsa Formation and the signs of a stable lake and mature calcic soils on the ancient floodplains suggests that mainly anastomosing rivers crossed the area in the Pliocene. Based on palaeocurrent data and the shape of sandbodies, these rivers mainly flew from northwest to southeast, supporting that this part of Pannonian Basin was infilled from the direction of Western Carpathians. Development of an anastomosing system indicates a very gentle gradient of the stream, while the maturity of the palaeosols in floodplain deposits shows quite low rate of floodplain sedimentation (about 1 m during a few 10 000 years), and similarly slow basement subsidence in the area. However, significant variation of palaeocurrent directions between the studied localities suggests that subsidence was not uniform throughout the area, and local Pliocene palaeotopography has also influenced the paths of alluvial channels.


17

What controls the sinuosity distribution and meander locations in the Maas, crossing the Roer Valley Rift System?

van Balen, R.T* ., Kasse, C. and Crosato, A.

Inst. Earth Sciences, VU University Amsterdam, De Boelelaan 1085, The Netherlands *ronald.van.balen @falw.vu.nl

The Maas rises in northwestern France, traverses the Ardennes, and crosses the Roer Valley Rift System before it debouches in to the North Sea. It is generally accepted that the faulting in the rift system affected the paleogeographic- and vertical evolution of the Maas during Quaternary.

After leaving the Ardennes region, the Maas first crosses faults of the Feldbiss fault system. At this location the Maas changes from a braided-meandering to a purely meandering river, with a sinuosity of about 1.5. Within the Roer Valley Graben the sinuosity is fairly constant, despite the presence of some minor faults. After having crossed the Peelboundary Fault zone, the river is straighter, with a more or less constant sinuosity of about 1.2 on the Peel Block. In the Venlo Graben the river changes its course direction from NNE to NNW, parallel to the faults in the subsurface. The sinuosity hardly changes here. At the location where the river leaves the Venlo Graben, the sinuosity increases and the flow direction becomes W. Here the river crosses the Peel Block for the second time, and the sinuosity increases from 1.8 near the Tegelen Fault Zone to 2.6 near the Peelboundary Fault Zone. In this part the meander loops are elongated in the tilt direction.

The elongated meanders and the fact that river stretches with a constant sinuosity are bounded by the important active fault zones are indicators for tectonic control. However, the sinuosity is not directly affected by fault motions, because expected localized sinuosity deviations can not be demonstrated. Instead, the long stretches of constant sinuosity suggest tectonic rotational block motions, influencing river gradient and thereby the sinuosity. However, the inferred motions are in contradiction with the well-known subsidence and uplift patterns. Therefore, the link between tectonics and sinuosity has to be indirect.

Subsurface data show that the fault-bounded blocks consist of important lithological differences. In summary, the high sinuosity stretches are underlain by very coarse sands and gravel (Pleistocene fluvial deposits), whereas the low sinuosity stretch on the Peel Block is underlain by fine glauconitic sands (Tertiary marine sands). The distribution of these lithologies is indeed for a large part caused by tectonic vertical motions, providing the link between sinuosity distribution and faults.

The impact of grainsize of the bedmaterial to the sinuosity of the river can also explain the high-sinuosity Allerød meanders on the Peel Block. In contrast to the Recent meanders, the Allerød meanders developed in coarse-grained fluvial deposits of the preceding (Pleniglacial) Maas terrace.


18

Neotectonic effects on meander development on the River Hernád, Hungary

Blanka, V.* and Kiss, T.

University of Szeged, Department of Physical Geography, H–6722, Szeged, Egyetem str. 2-6, Hungary *[email protected]

Neotectonic movements can affect river systems significantly (Watson et al. 1983, Smith et al. 1997). They can cause changes in watershed drainage pattern, channel pattern and sinuosity, aggradation or degradation of the channel, channel avulsion or diversion. Russ (1982) found that downward from uplifting zones, where gradient increased due to tectonics, rivers incise or sinuosity increase and upward from uplifting zones rivers straighten their course to eliminate the decreased gradient. Watson et al. (1983) suggested that 3 mm/year uplift can cause significant effects in sinuosity. Nevertheless they also drew attention to the fact that alluvial channels are sensitive indicators of any change in hydrology and sediment load, hence it’s difficult to determine the degree of tectonic control (Watson et al. 1983). The consequences of human activities may also disguise neotectonic effects.

The purpose of this research is to identify and evaluate the effects of neotectonic movement on the River Hernád. The „V” shaped fault system between River Hernád and River Sajó developed in the Miocene. Two intensive dislocation zones evolved on the South region of the river. Uplifts within the dislocation zones are still active (1-3.2 mm/year). The rate of movement increases toward the South, as by the narrowing of the „V” shaped fault system higher vertical activity can be experienced (Bendefy 1973).

During the research the lower reach of the river (42 km), between Felsődobsza and Bőcs was surveyed, where tectonic control is the most intense. Human activities, mostly dams (Felsődobsza and Bőcs) raise difficulties in evaluating neotectonic effects, as they artificially affect slope conditions. Sinuosity, meander belt width, gradient of channel and water surface, and bank height was measured to analyse the effects of tectonism on meander development.

Topographic maps (1910 and 1986), survey maps of the Hydrological Directorate (1937, 1957 and 1972), satellite image (2007) and aerial photographs (1953, 1966, 1975, 1988, 1997 and 2002) were used to examine the sinuosity and meander belt width. Images have been geo-corrected using ErdasImagine software, measurements were made under ArcView. The longitudinal section of the river (Hydrological Directorate 1973) was used to analyse the gradient and bank height.

For detailed analysis 8 sub-reaches were identified based on differences in sinuosity. Half of them have higher sinuosity and greater meander belt width. These sections indicate the downstream parts of the uplifting zones, where sinuosity (1.8), meander length, and meander belt width (500-900 m) were increased in order to eliminate the increased gradient. The highest meander belt width was found on the southernmost section of the studied reach, despite of damming, as the result of the highest uplift rate. Damming acts against tectonics, due to reducing the slope of water surface, thus meander development slowed down on this reach. At the same time channel pattern became straighter upward from the intensively uplifting zones (sinuosity 1.2; meander belt width 100-300 m) indicating decreased gradient. The tectonic origin of these pattern changes is indicated by the stabile location of the morphologically different sections on maps (since 1910).


19

Reading the Rhine-delta Holocene sediment trap

Kim M. Cohen*, K.M., Erkens, G. and Hijma, M.P.

*Utrecht University, Fac. of Geosciences, Dept. Phys. Geography, [email protected]

We present the complete budget of Holocene-delivered Rhine sediments in the Netherlands and adjacent parts of Germany. Present amounts of deposits in the Rhine-Meuse delta and upstream trunk valley were quantified using a stratified approach. We broke down the total volume by three sets of criteria.

• Genesis: We utilized architectural element approaches, grouping the heterolithic delta deposits into 5 classes: channel belt bar-sand; clastic channel fills; natural levee deposits; flood basin deposits autochthonous organics.

• Spatial extent: We utilized alluvial architectural and sequence stratigraphical zonations of the study area up to ~150 km upstream of coast line. We segmented our delta budgets for ‘estuary’, ‘lagoon’, ‘lower delta’, ‘central delta’, ‘upper delta’ and ‘delta apex’ sub-regions. In our calculations we account for the diachronic onset of Middle Holocene transgressive and Late Holocene progressive deposition in longitudinal and lateral direction, due to differences in shape and elevation of the sub-regions.

• Age: We used numerous 14C-dates to slice the deltaic deposits in 500-yr intervals from 9 k BP onwards. Valley deposits upstream of the delta and buried by the delta were divided in cruder time slices. The input data for our budget inventory is derived from accumulated borehole data:

100.000’s of archived descriptions from many earlier Rhine-Meuse delta studies (i.e.: (http://www.geo.uu.nl/fg/palaeogeography). These were summarized as valley-wide cross-sections (yielding width-averaged thickness and lithofacies proportions, per segment, per time slice) and GIS maps (area of channel belts vs. floodbasin, per time slice, per segment).

The result is complex set of spreadsheet data, allowing detailed accountancy of sediment import and export, broken down by class, segment and time-slice. Such a set of numbers documents architectural build up and embedded spatial and temporal trends in a quantitative fashion. This opens exciting new ways to read fluvial archives, amongst others to unravel allogenic from autogenic controls. Our focus has initially been on preservation-by-facies; ‘suspended’ fine sediment delivery; ‘bed-load’ coarse sediment delivery; trapping efficiency and residence time. We explicitly address what proportion of sediment must be freshly delivered from upstream of the delta, and what part can be regarded as being locally reworked. This also contributes to questions on effective net rates of sediment transport through lateral migrating alluvial channels at 103-104 time-scales.

The dataset highlights the changing position of the depocentre of the delta during the Holocene. Many competing ideas exist on how to explain the various trends that have emerged from detailed mapping of the Rhine-Meuse delta. For example, continued backfilling of the Rhine delta into Germany in the last 3000 years is evident. Does that indicate continuing impact of downstream sea-level rise? Or does it reflect increased sedimentation due to upstream agricultural revolutions known from numerous Bronze Age archaeological sites? Budget analysis at our level of segregation proves the latter explanation right and the former wrong.


20

Changes in Quaternary fluvial transport directions in the Mid-Hungarian Plain based on statistical analysis of detrital heavy mineral composition of sands

Thamó-Bozsó, E.1 and Ó.Kovács, L.2 1Geological Institute of Hungary, Stefánia út 14, 1143 Budapest, Hungary 2Hungarian Office for Mining and Geology, Columbus utca 17–23, 1145 Budapest, Hungary

Quaternary fluvial sediments in the central part of the Hungarian Plain (Pannonian Basin) have been studied in 10 cored boreholes. The penetrated 40–700 m thick sediment successions consist of sand, silt and clay, and are underlain by Pliocene strata. Heavy mineral data of 590 sand samples from the boreholes complemented by data from modern river sediments have been evaluated using numerical methods.

Both cluster analysis and principal component analysis have identified chlorite and garnet derived from metamorphics as well as volcanogenic hornblende and pyroxene as the dominant minerals of the Quaternary sands. Principal component analysis, in most cases, has provided a clear differentiation between the sediments of the modern Danube and those of the Tisza River and its tributaries, but uncertainties remain with the older sands, probably due to changing, with time, source areas and/or intermixing loads of different palaeo-rivers.

Cluster and principal component analyses have revealed appreciable similarities between the heavy mineral composition of modern river sediments and that of borehole samples, resulting in a more refined reconstruction of the Quaternary fluvial network and sediment provenance. Interpretation relies on the presumption that the Quaternary physiography and geological settings of the source regions were comparable to those of today. Comparative analyses have shown that the modern Tisza River and its tributaries, draining the Hungarian Plain, carry pyroxene, hornblende, chlorite or garnet-rich sediments from the Carpathian Belt, the Apuseni Mountains and the North Hungarian Range, while the River Danube and its tributaries transport garnet-dominated heavy mineral assemblages mainly from the Alps, the western Carpathians and the Bohemian Massif.

Transport directions have also been deduced from the statistical analysis, taking into account sedimentological, palaeontological, palaeomagnetic, and other data as well. During the Quaternary, sediments in the western part of the study area were deposited by the Palaeo-Danube, flowing then from the northwest and partly from the north. In the central part, sediments of the Palaeo-Danube interfinger with deposits of the Palaeo-Tisza and its tributaries, arriving from the northeast or north. Closer to the Apuseni Mountains, direction of the palaeodrainage changed frequently.

A comparison of the heavy mineral composition of modern river sands and those deposited by their ancestors, using principal component analysis, has revealed some differences, interpreted as an impact of tectonic and erosional changes during the Pleistocene. For example, chlorite-rich sands that are abundant in the Early Quaternary become less frequent in the Late Quaternary deposits and are uncommon in the modern rivers, suggesting that their low-grade parent rocks have been progressively eroded.


21

Reconstruction of a Pleiscocene meandering river and its climatical background in the NE part of Great Hungarian Plain by using UHR seismic images

Cserkész-Nagy, Á.T.1, Tóth, T.2 and Sztanó O.1 1Dept. of Physical and Applied Geology, Eötvös Loránd University, Budapest, Hungary, H–1117, Pázmány P. s. 1/c.; [email protected], [email protected] 2Geomega Ltd., Budapest, Hungary, H–1095, Mester u.4. I/2.

The nearly flat surface of the Great Hungarian Plain has been formed mainly by two trunk rivers and several tributaries since the Pliocene onward resulting in a 6–700 m thick alluvial succession. The pre-holocene, upper 20–30 m of the succession in one of the subbasins was investigated by means of 200 km long UHR single channel seismic-section acquired on river Tisza. Its overall bedding is shown by outcrop-scale resolution. Three seismic facies units (boundles of inclined reflections, trough-shaped converging and horizontal, paralell reflections) were indentified on the previously acquired lines, as lateral accretinon of point bars, abandoned channel fills and flood-plain deposits. The series of 5-6 m thick inclined strata sets can be followed consequently at the same level along about the studied area suggesting the presence of an ancient meandering river in the recent valley of the Tisza river during the Pleistocene. Newly measured quasi-3D seismic profiling revealed that each 2–3 km long inclined strata sets – interpreted as lateral accretion – belong to one individual point bars continuously shifting into the same direction. Smaller deviations of shifting direction (up to 35 degree only) are caused by minor steps in natural wandering of the meander bend. Morphometric parameters of point bars and channel cross-sections were used for calculations of ancient channel parameters and thus channel-forming discharge.

Our findigs fit into the tree-axis paleohydrological model of the basin at the Late Pleistocene (Gábris 2002), moreover the existense of the three-axis drainage system can be elongated. The results imlplies that the third river (so called Paleo-Bodrog) revealed by the seismic profiles must have been as large as the second trunk river of the basin (Paleo-Tisza) which was flown on the eastern part of the basin at that time. The drainage area of the recent Tisza was shared equally by the studied river and the Paleo-Tisza. Therefore its discharge coming from a roughly half-sized drainage area indicates a more humid climate of the basin in the Late Pleistocene. Variations of dip angles of inclined reflectors as well as pronounced changes in channel depth can be used for following discharge variations on millennial or centennial scale by exact geochronology obtained from OSL dating of the fluvial sediments.

Reference

Gábris, Gy. 2002: A Tisza helyváltozásai. In: Mészáros, R., Schweitzer, F. & Tóth J. (eds): Jakucs László, a tudós, az ismeretterjesztő és a művész. MTA FKI – PTE SzE kiadása, Pécs, 91–105.


22

Fluvial pattern changes in a continental lowland setting: the Tisza valley in northeastern Hungary.

Vandenberghe, J.*, Kasse, C., Bohncke, S. and Gábris, Gy.

Inst. Earth Sciences, VU University Amsterdam, De Boelelaan 1085, The Netherlands *[email protected]

Due to progressive western shifting as a result of tectonic tilting of the Pannonian basin the successive river patterns of the Tisza were preserved since the Weichselian Middle Pleniglacial. A well-developed system of large meanders, with relatively shallow channels, was typical for the period antedating the last glacial maximum. During the last glacial maximum a low-sinuosity system with parallel branches was formed, possibly joining the extensive alluvial fans of rivers coming from the northern Hungarian mountains. Meanders with very large amplitudes are typical for the Lateglacial period. The channels reached a considerable depth (more than 14 m) and started infilling from the Older Dryas or Alleröd onward according to palynological evidence. These meanders persisted during the Younger Dryas. Subsequent transformation towards a system with smaller meanders is also a common phenomenon in Europe at the beginning of the Holocene. Except for the general meander incision at the beginning of the Lateglacial the Tisza system is characterized by aggradation in the last 35.000 years. This is apparently due to the continuing subsidence of the Pannonian basin in which the Tisza is flowing, in combination with the high sediment load derived from upstream erosion of the Ukrainian and Romanian mountains. This gives the Tisza valley system a characteristic lowland appearance.


23

Fluvial changes in the Tisza valley (Hungary) during the last glacial – interglacial transition

Kasse, C.*, Vandenberghe, J. and Bohncke, S.J.P.

Department of Palaeoclimatology and Geomorphology, Faculty of Earth and Life Sciences, Vrije Universiteit, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands *[email protected]

The Weichselian Late Pleniglacial, Late Glacial and Holocene fluvial development of the Tisza valley in Hungary has been studied and compared with other river systems in western and central Europe. Geomorphological analysis indicated the existence of four Weichselian and Holocene floodplain generations, differing in palaeochannel characteristics and elevation. Coring transects enabled the construction of the channel geometry and fluvial architecture. Pollen analysis of the fine-grained clastic fill of palaeomeanders provided a bio(chrono)stratigraphic framework and vegetation development over time. 14C-dating was undertaken for an absolute chronology, however, the results were problematic due to the partly reworked character of the organic material in the abandoned channel sediments. During the Late Pleniglacial aggradation by a braided (precursor of the) Tisza prevailed and local deflation and dune formation took place. A channel pattern change from braided to meandering and gradual incision occurred during the Late Pleniglacial and start of the Late Glacial, possibly related to more regular discharges and lower sediment supply by vegetation development. The climatic deterioration of the Younger Dryas stadial is not reflected by a fluvial system response and meandering persisted. The Late Glacial to Holocene transition resulted in a floodplain wide incision and terrace scarp development. The Holocene floodplain was formed by laterally migrating smaller meandering channels and intra-Holocene river changes have not been observed.


24

The effect of late Holocene strong human impact on Tagus River terrestrial and marine sedimentation (Portugal)

Vis, G.-J.1,*, Kasse, C.1, Vandenberghe, J.1, Kroon, D.2 and Jung, S.J.A.2 1Department of Palaeoclimatology & Geomorphology, Faculty of Earth and Life Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1085, 1081HV Amsterdam, The Netherlands *[email protected] 2Institute of Earth Science, Grant Institute, University of Edinburgh, West Mains Road, Edinburgh EH9 3JW, United Kingdom

We show the remarkable fact that strong late Holocene human impact in the Tagus catchment is represented in terrestrial sediment records by coarsening and in marine sediment records by fining sediments. To understand this phenomenon, this study answers the question: How is late Holocene human impact translated into the terrestrial and marine sediment records of the Tagus River system? In general, both terrestrial and marine records show an increased magnetic susceptibility since ~2000 cal BP, which is the result of erosion of soil B-horizons from the catchment slopes and the related increased input of ferrimagnetic particles. We found an increased sedimentation rate coeval with an increase in grainsize on land and an unexpected decrease in grainsize off-shore since ~1000 years ago. Review of historical literature revealed an ever increasing impact on the landscape in the Tagus catchment during the last ~3000 years. More and more forests were cleared, culminating in a nearly treeless landscape around the 13th century. Historic topographic maps from the Lower Tagus Valley show rapid silting up of the estuary during the last 500 years, resulting from the increased sediment input. The increased sedimentation rates and grain sizes on land are interpreted as resulting from increased erodibility of the slopes in the catchment combined with intensive Mediterranean precipitation. We interpret the seemingly contradictory sediment fining off-shore combined with an increased sedimentation rate as resulting from preferential deposition, which most likely resulted from an altered composition of the fluvially derived sediment.


25

Morphological responses to anthropogenic interventions on the Hungarian section of the Maros River

Sipos, Gy.* and Kiss, T.

Department of Physical Geography and Geoinformatics, University of Szeged, H–6722, Szeged, Egyetem str. 2-6, Hungary *[email protected]

River Maros is the fourth largest water flow of the Carpathian basin with a catchment of 30 000 km2 and a discharge varying between 31 and 2 420 m3/s. The studied Hungarian section had been severely affected by channelisation and bank stabilisation measures in the 19th and 20th centuries. As a result of anthropogenic interventions the pattern of the river changed, and the artificial form induced the realm of new channel processesin a semi-natural environment.

The main question the research addressed was how present dynamics reflect the response of the morphological system to the great scale human impact experienced approximately one and a half century ago. By answering the above question with the means of cross-sectional analysis, geoinformatics and dendro-geomorphology the stability and equilibrium of the studied river reach could be evaluated, and the prospected morphological changes could be outlined.

Prior to the regulations four morphologically separable sections characterised the studied reach: a (1) meandering–braided and an (2) anastomosing section on the upstream part, while a (3) low sinuosity and a (3) high sinuosity meandering on the downstream part. The first two developed on the elevated alluvial fan surface, while the later ones developed right in front of the fan border. In a close to natural state the morphological parameters (sinuosity, total sinuosity, bend curvature) had shown a great temporal variance (8–10 % in 30–40 years).

A major outcome of regulations was that the pattern of the study reach changed dramatically, braided units appeared on the previously anastomosing and low sinuosity meandering reaches. In the past 50 years morphological values showed insignificant changes compared to pre-regulation processes, however, these slight changes are unidirectional (decrease of total sinuousity, increase of sinuousity). Subsequent to cut offs the channel widened significantly, however, our recent investigations reflected channel narrowing (20 m in average between 1953 and 2000). The greatest changes were recorded in terms of braids located on unmanaged sections.

Assessing the most important morphological changes at different spatial and temporal scales, it was proved that from a morphological point of view dynamic equilibrium processes dominate the studied morphological systems and subsystems. Values are usually oscillating, no accelerating change was detected. In this respect, from the point of view of a physical interpretation (dynamics) the system is in a stable equilibrium, where negative feedback is a key process. Instability can only be observed in short term morphological changes. Steady state was not identified on any of the spatial or temporal scales, the system is in a continuous change in terms of the averages, too.

Considering the regulations we can state that in the short term the river gave a sensitive answer, as new morphological units had appeared. However, based on the present processes a slight trend of restoration can be perceived, which can indicate a robust response on behalf of the system in the long run. Meanwhile, changes identified recently do not threaten morphological stability. Any kind of river metamorphosis at the present equilibrium should take a comforting span of time from the aspect of management strategies.


26

Spatial variability of anthropogenic impact on Holocene fluvial sedimentation. A case study: the Choisille catchment (Parisian basin, France)

Morin, E.1, Cyprien, A-L.2, Gay-Ovejero, I.1, Hinschberger, F.1, Joly, C.2, Macaire, J-J.1, Poirier, N.3, Visset, L.2 and Zadora-Rio, E.3 1Université de Tours, UMR CNRS 6113 ISTO–Tours, Laboratoire de Géologie des Environnements Aquatiques Continentaux, Faculté de Science et Techniques, Parc Grandmont, 37200 Tours, France 2Université de Nantes, UMR CNRS 6566, Laboratoire d’Ecologie et Paléoenvironnements Atlantiques, 2 rue de la Houssinière, BP 92208, 44322 Nantes Cedex 3 France 3Université de Tours, UMR CNRS 6173 CITERES, Laboratoire Archéologie et Territoires, MSH Villes et Territoires, BP 60449, 37204 Tours Cedex 3 France

This work is part of the ECLIPSE program “Impact anthropique sur l'érosion des sols et la sédimentation dans les zones humides associées durant l'Holocène”. It aims to reconstitute the evolution of human impact on soil erosion at various periods via the study of Holocene sedimentary archives. In this framework the Choisille catchment (288 km²; elevation: 50 – 200 m), tributary of the River Loire near Tours (France), has been the subject of an interdisciplinary study (sedimentology, archaeology, palynology). 3 areas are investigated: a downstream stretch, a silicated sub-catchment area and a carbonated sub-catchment area (study in progress).

In the downstream stretch, located near ancient populated areas, drillings were performed along cross sections through valley floor alluviums. They show that a more or less organic clayey silty sedimentation started at the beginning of the Holocene. The sedimentation strongly increased at the beginning of the Subbatlantic (Iron Age), simultaneously with the anthropogenic pressure advent (on set of agriculture), as shown by archaeological and palynological evidences.

In the silicated sub-catchment area, located upstream, drillings have shown that clayey silty sedimentation began at the end of the Roman Period, continued during the Early Middle Ages and increased during the High Middle Ages. Spatial archaeological prospecting has revealed a faint anthropogenic presence at the Roman Period, then a decline of population until the High Middle Ages, characterised by an agricultural revival. Palynological analyses have shown that, in this area, grasslands were dominant since the Early Middle Ages, with an increase in cereal cultures at the beginning of the High Middle Ages.

This difference between a fine, early and regularly increasing sedimentation downstream and the later, intense and non-univocal upstream one does not seem to be strictly resulting from natural factors, which are homogeneous over the whole catchment (lithology, relief, climate and tectonic). This idea and the palaeoenvironnemental dataset show that the fine sedimentation basically results from an anthropogenic impact, notably upstream.

Upstream fluxes, limited before human impact, have provided fine sedimentation downstream since the beginning of the Holocene. The strong increase of sedimentary production since the Antiquity has led to fluxes retention, and thus to a partial valley-floor sediment filling upstream.


27

Natural and human impacts on the magnetic signal from the Late Holocene flood-plain deposits of the Morava River (Czech Republic)

Kadlec, J.1,*, Diehl, J.F.2, Beske-Diehl, S.2, Grygar, T.3 and Svetlik, I.4

1Institute of Geology AS CR, v.v.i., Prague, Czech Republic *[email protected] 2Michigan Technological University, Houghton, USA 3Institute of Inorganic Chemistry AS CR, v.v.i., Prague, Czech Republic 4Nuclear Physics Institute AS CR, v.v.i., Czech Republic

Flood-plain sediments deposited along the lower course of the Morava River draining the eastern part of the Czech Republic, were studied in the Straznicke Pomoravi region to describe the alluvial history of the river over the last millennium. The sediments exposed in up to 5 m high erosional river banks were analyzed using mineral magnetic methods completed with geochemical and mineralogical approaches. The age model of the sedimentary sequences was constructed from radiocarbon dates in association with 206Pb/207Pb and POP (DDT, PCB) analysis and 137Cs activity data. At each key vertical sedimentary section triplicate samples were collected at each stratigraphic level with a vertical separation of less than 0.5 cm. Mineral magnetic parameters such as mass specific susceptibility (χ), ARM, SIRM and their intraparametric ratios (ARM/SIRM, S-ratio) all show similar variations from section to section. The values of magnetic susceptibility are highest in the upper 50 cm of the sections. χ values then show a noticeable decrease downward in the section to 200 cm depth and then stay low throughout the rest of the section. S-ratios near 0.9 in the upper 50 cm suggest the presence of a low coercivity mineral (magnetite) as the cause of the highest susceptibility values. Based on hysteretic data gained at room temperature we knew that paramagnetic or high hysteretic mineral (goethite) dominates especially in the lower portions of the sections.

An interpretation of gained mineral magnetic data allows us to sketch following conclusions:

1. The paramagnetic influence dominates in the flood sediments through all studied sections often masking the ferrimagnetic signal. The paramagnetic iron is most probably carried by clay minerals. Expandable clay minerals smectite and vermiculite were identified in the sediments by the X-ray diffraction.

2. Goethite is a common iron oxyhydroxide presented in the flood sediments. The concentration of goethite increases downward in the sections. The goethite could be a product of dissolution of iron oxides and consequential iron precipitation under redox conditions in the flood-plain environment.

3. The gradual increase of χ and other magnetic parameters in the uppermost 200 cm of each section is the consequence of more intense erosion caused by agriculture activities, which was triggered by medieval colonization in central Europe and dramatically accelerated during the last 60 years during very intensified land use, when the topmost 50 cm of the flood-plain sequences were deposited.

The research is funded by the GA AS CR (projects No. IAA3013505 and IAAX00130801) and the the NSF-NATO (project No. DGE-0411426).


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Data from England’s Wash rivers: results from the ALSF-funded Trent Valley and Cambridgeshire Palaeolithic Projects

White, T.S.1, Bridgland, D.R.2, Howard, A.J.3 and White, M.J.1 1Department of Archaeology, Durham University, South Road, Durham DH1 3LE, UK 2Department of Geography, Durham University, South Road, Durham DH1 3LE, UK 3Institute of Archaeology and Antiquity, University of Birmingham, B15 2TT, UK

The Wash, Britain’s largest estuary, receives the drainage from much of eastern/central England. The main rivers today are the Nene and the Great Ouse, which drain the South Midlands and the Fen basin, but the Wash also receives the Witham and Welland, from south Lincolnshire, and rivers from NW East Anglia. Prior to the Anglian/Elsterian (MIS 12) glaciation, which remodelled the drainage of Midland England and East Anglia, the Wash did not exist and drainage routes have been reconstructed from NW–SE across it, into East Anglia. Another very significant change occurred as recently as the last glacial-to-interglacial transition, before which the Trent, Britain’s third longest river, flowed to the Wash through the Lincoln Gap and along what is now the Witham valley. The Trent is the northernmost British river to preserve an extensive long-timescale terrace record in which both temperate and cold stages are represented. Its catchment lies just beyond the maximum extent of the LGM (MIS 2) ice sheet in Britain, although it was the effects of that glaciation that probably resulted in its diversion from the Wash to the Humber, the next major estuary to the north. In fact there was an even earlier course of the Trent to the Wash, via the more southerly Ancaster Gap, diversion from which might have resulted from glaciation in MIS 12. Provision of a refined age-model for this system, uniquely positioned close to the boundaries of several glaciations, is of considerable value to British Quaternary and Palaeolithic studies. This is particularly the case, since the Trent is the most northerly British river in which Lower and Middle Palaeolithic archaeological material is preserved, perhaps representing the northern limit of Pleistocene human occupation.

Three phases of research funded by the Aggregate Levy Sustainability Fund (administered by English Heritage) have studied geoarchaeological (Lower and Middle Palaeolithic) resources in the rivers targeted here: 1 & 2 looked at the ‘greater Trent’ (including the pre-Devensian courses to the Wash), whereas the 3rd examined rivers in Cambridgeshire (primarily the Great Ouse and the Nene). This has involved recording artefact collections, monitoring active gravel quarries and seeking to enhance knowledge of the geological context of the archaeology by studying the fluvial archives, with a particular emphasis on dating (by means of palaeontology and geochronology) and correlation with the modern global template provided by marine isotope stages. The role of river valleys as hominin occupation zones and/or routeways for migration is well established but possibly overplayed, given the poor sedimentary preservation in other environments. The predominantly west-east drainage of the Wash rivers may in fact have been a hindrance to populations colonizing northern Britain from the Continent and may explain the apparent paucity of occupation in the north Midlands, despite the presence of flint (the main raw material for Palaeolithic tool production) in Lincolnshire and Yorkshire.


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The Heidelberg Drilling Project and the Pliocene/Pleistocene sediment succession of the Upper Rhine Graben, Germany

Frechen, M.* and Gabriel, G.

Leibniz Institute for Applied Geosciences (GGA-Institut), Stilleweg 2, D–30655 Hannover, Germany *[email protected]

During the Pleistocene, the Rhine glacier system acted as a major south – north erosion and transport medium from the Swiss Alps into the Upper Rhine Graben, which has been the main sediment sink forming low angle debris fan. Only some aggradation resulted in the formation of terraces.

The Heidelberg drilling project focuses on the Heidelberg Basin as the thickest and most detailed Quaternary sediment archive of the Northern Upper Rhine Graben. Due to its position in the geosystem Alps – Rhine Graben – North Sea the alpine and the lower Rhine / North Sea depositional patterns interfinger in this area. Therefore, the potential of the Heidelberg Basin sediments for gaining deeper insight into North European and Alpine Pliocene / Pleistocene climate cyclicity and transition in a continental environment was in discussion for many years.

In early 2006 two new scientific core drillings were started with financial support of the Leibniz Institute for Applied Geosciences (GGA-Institute), the Geological Survey of Hessen, and the Geological Survey of Baden-Württemberg. The drilling close to the village of Viernheim represents the typical basin facies, whereas the drilling Heidelberg UniNord is located in the decpocenter. Two more 300 m deep core drillings in the city of Ludwigshafen provided by the geological Survey of Rheinland-Pfalz also contribute to the project, representing the western margin of the basin. All core drillings combined, improved insights are expected into sedimentary development and geochronology, control of the system by neotectonics and past climatic changes, and aspects of applied geology (hydrogeology, geothermal energy, actuotectonics, and seismicity etc.) of the Pleistocene and late Pliocene sediment fill in the Heidelberg Basin.

In order to address all these topics an interdisciplinary geoscientific approach is mandatory within this project. Therefore, a working group was established, that covers different geoscientific disciplines, e.g. geophysics, structural geology, sedimentology, tectonics, palynology, and geochronology. Colleagues from German universities were invited to participate in this project as well as partners from national and international geoscientific organizations.


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Methodological aspects on luminescence dating of fluvial sands from the Moselle basin

Cordier, S.1,2,* and Frechen, M.2 1EA 435 Géonat et UMR 8591, Département de Géographie, Université Paris 12 Val de Marne, 61 avenue du Général de Gaulle F–94010 Créteil Cedex, France 2Section Geochronology and Isotope Hydrology, Leibniz Institute for Applied Geosciences (GGA), Stilleweg 2, D–30655 Hannover, Germany *[email protected]

Fluvial deposits have been recently dated in several fluvial systems in Europe including the Rhine-Maas system. Optical dating of fluvial sands has also been carried out in the basin of the Moselle River, a main left-bank tributary of the Rhine. It was mostly based on IRSL dating of coarse-grain feldspar applying Multiple Aliquot Additive Dose and Single Aliquot Regenerative protocols. The results made it possible to provide a first chronostratigraphical frame for the youngest fluvial deposits, enabling a longitudinal correlation of the middle and lower terraces on a 300 km long valley section, and a correlation between the terrace formation and the glaciations in the Moselle upper basin (Cordier et al., 2005, 2006).

The aim of this contribution is to present the methodological and applied results of IRSL and OSL dating which have been recently made on fluvial sands from outcrops in the valleys of the Moselle and its main tributaries the Saar and the Meurthe.

Methodological aspects include equivalent-dose determination using different SAR protocols for quartz and feldspar specimen, preheat and dose-recovery tests, and a fading correction for the feldspar.

The ultimate applied aim of this study is to set up a more reliable chronological frame for the last and penultimate glacial cycle. This can be compared with the preliminary results derived from the ESR dating on sands from older alluvial terraces, providing a better understanding of the middle and upper Pleistocene evolution of the River Moselle and its tributaries.

References

Cordier, S., Frechen, M., Harmand, D. and Beiner, M. 2005: Middle and Upper Pleistocene fluvial evolution of the Meurthe and Moselle valleys in the Paris basin and the Rhenish Massif. Quaternaire, 16, 203–217.

Cordier S., Harmand D., Frechen M. and Beiner M. 2006: Fluvial system response to Middle and Upper Pleistocene climate change in the Meurthe and Moselle valleys (Eastern Paris basin and Rhenish Massif), Quaternary Science Reviews, 25, 1460–1474.


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Luminescence dating of fluvial sediment core from Viernheim (Heidelberg basin)

Lauer, T.1,*, Frechen, M.1, Hoselmann, C.2 and Tsukamoto, S.1

1Department for Geochronology and Isotope Hydrology, Leibniz Institute for Applied Geosciences, Hannover, Germany *[email protected] 2Hessian Agency for Environment and Geology, Wiesbaden, Germany

Recent developments in optically stimulated luminescene (OSL) dating techniques have enabled to determine depositional ages of fluvial sediments that have only shortly been exposed to sunlight during transportation. In this study, OSL dating was applied to fluvial sands which were derived from a sediment core drilled into the Heidelberg basin infill near to Viernheim. This tectonic basin is situated in the northern part of the Upper Rhine Graben (URG) and hosts up to 400 m thick Quaternary deposits, characterised by thick gravel and sand layers and intercalated fine-grained layers partly with peat, which are correlated to cold and warm periods, respectively. The aim of this study is to deliver the chronological frame of these deposits for a better correlation of the alpine glacial-interglacial-cycles with those in northern Europe, and to investigate the dynamics of aggradation periods that were mainly influenced by neotectonic processes and Upper/Middle Pleistocene climate change. The chronostratigraphy will also be compared with the age model for the fluvial sediment sequences from the southern URG. For the present research, focus is dedicated to sediments that mainly belong to the last glacial/interglacial and are not older than the penultimate glacial.

Ten samples from the core-depth from 1to 71 metres were taken and coarse-grain quartz and potassium rich feldspars were prepared to be used for dating. The single-aliquot regenerative-dose (SAR) protocol was applied for dose estimation. Investigations related to thermal stability of the OSL signals, anomalous fading and the dose distribution due to poor bleaching will be presented.

The ongoing research is part of a PhD study in the frame of the “Leibniz Pakt für Forschung und Inovation” at the GGA-Institute in Hannover. It is focusing on the advancement and application of new OSL techniques and a reconstruction of the paleoenvironmental conditions within the Rhine system.


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Chemical analysis of expandable clay minerals as a tool to stratigraphic correlation of flood sediments of the last millennia,

Morava River, Czech Republic

Grygar, T.1,*, Kadlec, J.2 and Svetlik, I.3 1Institute of Inorganic Chemistry of the AS CR, v.v.i., Rez, Czech Republic *[email protected] 2Institute of Geology of the AS CR, v.v.i., Prague, Czech Republic 3Nuclear Physics Institute of the AS CR v.v.i., Czech Republic

The material deposited in flood plain of an aggrading river can be considered either sediment or soil depending on the rate and continuity of the overbank deposition and general river behaviour. The decision "sediment, or soil?" is necessary to correctly choose tools and terminology already to the material description. The simplest way how to estimate the sedimentology value of the flood sediment is to find any feature permitting stratigraphic correlation in different places in the flood plain; this must subsequently be supported by finding some datable material in the sediment. We perform such work in the Morava River flood plain in Straznicke Pomoravi, south Moravia, Czech Republic. The study area is one of the last non-regulated segments of Morava River, in the region having been affected by landuse changes in the last several millennia. Because of a very weak mineralogical changes within the sediment section, we tried to trace changes in expandable clay minerals, namely in their total content expressed as cation exchange capacity (CEC), and in the composition of the exchangeable cations, Ca(2+) and Mg(2+) (Mg/Ca ratio). For that purpose we use a method with Cu-trien common in analysis of clay mineral specimens, a very efficient and fast lab method. We found that CEC and Mg/Ca variations apparently work as a tool to chemostratigraphic correlation of the sediments from the last millennium, which are currently exposed in erosional banks of meandering loops. The CEC variation indicates either change of the sediments from more clayey to more silty or systematic reorganization of the river style in the 16th century AD. The decrease in the Mg/Ca ratio in the sediments from the last millennium can be explained either by Ca recyclation in A horizons in floodplain, enhanced erosion of top horizons of soils in watershed, or increased relative levels of floodplain above river and consequently decreased ion exchange between river water (Mg/Ca~0.26 at presence) and soil (at top Mg/Ca~0.15 at presence). It is clear that in this interpretation it has been necessary to turn back to beginning and mix the views of the flood sediment being both sediment and soil. We currently try to test our approach by further analyses, including completing radiocarbon dating of selected profiles in Morava River and further fieldwork. The question to be answered is whether the CEC and Mg/Ca correlations work only under the actual settings of Straznicke Pomoravi, or if it could be a more general tool to floodplain profiles.

The work is funded by GA ASCR (project IAAX00130801).


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Fluvial terraces and sequence stratigraphy: upper progradational packages

Dinis, J.1,2, Cunha, P.1,3 and Dinis, P.1,4

1IMAR–Institute of Marine Research, Department of Earth Sciences, University of Coimbra, Portugal [email protected]; [email protected]; [email protected]

Fluvial sequences result from cyclic imbalance between sediment supply and stream power. In most of the conceptual approaches, sequence boundaries are traced using the sedimentary record of episodes of disequilibrium towards more energy (steepening average gradient). These can be produced by upstream uplift, downstream subsidence, base-level drop or climatic-driven changes in loading index (increased upstream erosion and alluvial sediment load).

Strictly, a cycle implies a shift from an initial condition to an opposite extreme and back to the initial condition. In this sense, allogenic controls, and consequently the resulting stratigraphic record, can be considered cyclic: high-low-high, active-quiet-active, wet-dry-wet, cold-hot-cold, etc. Even if reflecting the interplay between those drivers, probably each with a different timing and intensity, the large-scale architecture can be interpreted as a shift between opposite combinations.

After a disequilibrium episode, a clastic wave progrades downstream, followed by a period of retrogradation when the available accommodation is filled in order to reach the graded profile. However, even if the allogenic controls become steady, autogenic behaviour results in downstream aggradation and watershed erosion, while fluvial grade is dynamically adapting to decreasing energy, with gentler and longer profiles. As accommodation declines, progradation increases and aggradation diminish, sometimes to zero (long-term graded profile).

So, whatever driver dominates, a pattern of alluvial depositional architecture emerges: i) lower progradational package (LPP), ii ) aggradational to retrogradational package (ARP), iii ) upper progradational package (UPP). In a sequence stratigraphic model those volumes are separated by conceptual surfaces: i) sequence boundary (SB, where progradation or aggradation changes to degradation), ii ) maximum progradation surface (MPS, separating LPP from ARP) and maximum retrogradation surface (MRS, separating ARP from UPP). Frequently SB is cryptic and MPS and MRS can only be identified as an interval in the depositional record.

The existence of fluvial terraces, in particular staircase complexes, implies a context of long-term incision, with downcutting episodes of successively narrower alluvial valleys separated by minor aggradational episodes. The 3D infill of an incised valley is a combination of upstream migration of the erosion/deposition nickpoint and transversal onlap over valley margins. This probably allows a physical separation between LPP, restricted to the incised valley (buried, or eroded in the long-term evolution), and a wider and probably thinner UPP partially preserved and exposed as part of the terraces staircase.


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Geomorphological correlation of the Tejo river terraces in the Gavião-Chamusca area (central Portugal) supported by luminescence dating

Martins, A.A.1, Cunha, P.P.2, Huot, S.3, Murray, A.S. 3, Buylaert, J.P. 3 and Stokes, M4 1Dept. Geociências Univers. Évora, 7002554 Évora, Portugal; [email protected] 2Dept. Ciências da Terra, IMAR – Instituto do Mar, Univ. Coimbra, Largo Marquês de Pombal, 3000-272 Coimbra, Portugal; [email protected] 3Nordic Laboratory for Luminescence Dating, Department of Earth Sciences, Aarhus University, Risø National Laboratory, DK–4000 Roskilde, Denmark; [email protected], [email protected], [email protected] 4School of Earth, Ocean and Environmental Sciences, University of Plymouth, Drake Circus, Plymouth, Devon, PL4 8AA; [email protected]

The Tejo river is the longest fluvial system (~1000 km) of Iberia, flowing to the Atlantic Ocean. A suite of fluvial terraces along a ~70 km stretch, between Gavião and Chamusca (central Portugal), was studied. The general geomorphological characteristics are defined by an alignment of tectonic depressions, containing soft Tertiary sediments and hard basement blocks, crossed by the river (superimposed). The basement blocks are located at the downstream end of the depressions, acting as local base levels. Luminescence ages are in agreement with geomorphologic data suggesting tectonic vertical displacements of the terraces. It is possible to correlate the terraces along the studied river valley. The T1 and T2 terraces are poorly represented, whereas the T3 terrace constitutes a relatively continuous reference. The lower terraces are only represented in the depressions, in which the river excavated soft Tertiary sediments. Several depositional episodes related to the evolution of this river were identified: the culminant unit (P - sandstones and conglomerates) of the sedimentary basin, deposited just before the beginning of the incision stage of the drainage network; T1 terrace (conglomerates); T2 terrace (conglomerates); T3 terrace (conglomerates); T4 terrace (conglomerates and a sandy top); T5 terrace (gravels and sands); T6 terrace (gravels and a sandy-muddy top); A - Carregueira sands (aeolian); H - Holocene valley infill (gravel base and sandy top). Terrace correlation was based upon: a) aerial photograph analysis, geomorphological mapping and field topographic survey; b) K-feldspar infrared stimulated luminescence (IRSL) dating of the lower terraces levels, as quartz optically stimulated (OSL) signal of the samples from these terraces was too close to saturation for all but two samples. The dating procedure also included a correction for anomalous fading in order to obtain more reliable estimates of the burial ages; the fading rate was found identical for all samples. The ages of the two upper terraces (T1 and T2) are beyond the upper range of the used dating method. The T3 terrace has an age of ~350 (underestimated) to ~290 ka, T4 from ~280 to 126 ka, T5-T6 of ~125 to 51 ka and the Carregueira aeolian sands ages younger than 44 ka. However, in a more upstream reach (Ródão) a younger terrace was dated as 39 to 32 ka. Using the age of the T4 surface, for the last 160 ka a time-averaged incision rate was quantified as ~0.4-0.5 m/ka in the more uplifted block of the valley (according to the geomorphic framework) and ~0.2-0.3 m/ka in the areas adjacent reaches. Long-term fluvial incision appears to have been controlled by regional uplift but the interplay of eustatic and climate controls could have played the main role to the episodes of lateral erosion and aggradation.


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Geomorphology, sedimentology and luminescence dating of the Tejo river upper Pleistocene in the Carregueira area (central Portugal, western Iberia)

Cunha, P.P.1, Martins, A.A.2, Buylaert, J.P.3, Murray, A.S.3, Dinis, P.1, Stokes, P.4 and Hancock, G.5 1Dep. of Earth Sciences, Instituto do Mar, Univ. Coimbra, Portugal; [email protected]

2Centro de Geofísica, Dep. Geociências Univ. Évora, Portugal; 3Nordic Lab. for Luminescence Dating, Dep. of Earth Sciences, Aarhus Univ., Denmark 4School of Earth, Ocean and Environmental Sciences, Univ. Plymouth, UK 5Department of Geology, College of William and Mary, Williamsburg, USA

The Tejo River is one of the major fluvial systems within Western Europe. With a catchment of 86,000km2 and 1007km long, it drains a significant proportion of the continental interior of Iberia into the Atlantic Ocean. Since the middle Pliocene, the Tejo has undergone progressive incision into the Iberian microplate, recorded by a series of inset and regionally correlative river terrace landforms. Along the Lower Tejo (Portugal) eight geomorphic levels can be identified, providing one of the best archives of long term landscape development (ca. 3.4 Ma) and its environmental controlling mechanisms in Iberia. Within the study area of Carregueira (east side of the Middle Portuguese reach of the Tejo), a complete staircase of Tejo River landforms are preserved comprising six fluvial terraces (T1-T6) of 6-20m thick units of gravels and sands that are inset into an extensive high level top basin fill surface of Pliocene age (culminant surface – P).

The purpose of this paper is to focus upon the geomorphology, sedimentology and age of the T6 terrace, that comprises two units. The lower unit, at 15m thick and with the top altitude at 30m, consists of yellowish fluvial gravely sands laterally interbeded with white aeolian sands. The upper unit, up to 15m thick, covers the T6 and older units along the slope of the eastern valley margin. It mainly comprises aeolian sands that are organized into a stacked succession of up to 3.5m high cross-bedded units corresponding to aeolian dune foresets, separated by thin organic soils up to 25cm thick that document wind transport from the NW.

Dating of the T6 at Carregueira was achieved through K-feldspar infrared stimulated luminescence (IRSL), quartz optically stimulated luminescence (OSL) and thermoluminescence (TL) techniques. Results show that the T6 fluvial sediments have an age range from 55 to 24 ka, whilst the upper part of the T6 (aeolian sands) has an age range of 24 to ca. 18 ka. Collectively, these T6 sediments document a prolonged period of cold climate fluvial and aeolian dynamics along the Atlantic margin. More specifically, the aeolian sediments reflect periods of wind reworking of an extensive floodplain area. The occurrence of organic palaeosols within the aeolian succession suggests short periods of climatic amelioration, marked by vegetation growth and hillslope stabilization, during the cold stage.

Project funding: POCI/CTE-GEX/58120/2004, of Fundação para a Ciência e a Tecnologia – POCI 2010 & FEDER


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Fluvial archives of the landscape evolution of western Iberia during late Cenozoic: the examples of the terrace staircases of

Vouga and Águeda rivers (central Portugal)

Gomes, A.1,*, Araújo, M.A.1, Albertí, A.P.2, Cunha, P.P.3, Chaminé, H.I.4 1Dep. of Geography, FLUP, University of Porto, Portugal *[email protected]

2Dep. of Geography, Grupo Investigacións Xeomorfolóxicas e Ambientais, Univ. Santiago Compostela, Spain 3Dep. of Earth Sciences, Instituto do Mar, University of Coimbra, Portugal

4Laboratory of Cartography and Applied Geology, Instituto Superior de Engenharia do Porto; Centro de Minerais Industriais e Argilas, Univ. Aveiro, Portugal

The Vouga River, with a catchment of 3635 km2 and 148 km long, drains the WNW of Iberia into the Atlantic Ocean. The Águeda River is the main tributary. The upper part of the catchment consists of important relieves of metamorphic and igneous rocks but the lower part is developed in a littoral platform, mainly formed by a Mesozoic sedimentary basement.

An important control by tectonics in the hydrographic network pattern is revealed by linear reaches, abrupt direction inflexion of streams and significant nickpoints. Other indicators suggesting recent fault activity include sharply defined mountain fronts with low sinuosity, asymmetric drainage patterns suggesting block tilting, river deflection and capture in the vicinity of the main faults zones, steep valleys with active river incision, and preserved peneplained summits indicating recent uplift of mountain blocks.

The main tectonic lineament systems are: NNE-SSW, NE-SW and N-S. Regional fault movement determined rearrangements of the hydrographical network but also definition of active blocks, witch lead to the establishment of tectonic basins (pull-apart and push-up type structures) associated with a strike-slip regime occurring between the so-called Porto-Coimbra-Tomar and Angeja-Ossela-Santiago de Piães principal displacement zones. This deformation has been particularly significant along a N-S corridor, that segmented the littoral platform into several crustal blocks.

The culminant, up to 30 m thick, unit of the sedimentary basin, consists of gravel and coarse sands probably deposited during the Piacenzian, just before the beginning of the incision stage of the drainage network. The Vouga and Águeda rivers show terrace staircases well developed in the N-S tectonic corridor, particularly in subsident areas, consisting of four depositional terraces and one strata terrace.

The relevance of the late Cenozoic sedimentary and geomorphic records has archives of the interaction between climatic, eustatic and tectonic controls are here discussed.


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Interglacial deposits in Northern France terrace systems: new evidences from MIS 11 and 5e calcareous tufa sequences

Antoine, P.1, Limondin-Lozouet, N.1, Auguste, P.2, Locht, J-L.3, Ghaleb, B.4, Bahain, J-J.5, Jolly-Saad, M.C.6 1”Environnements quaternaires. Dynamiques naturelles et anthropisation", UMR CNRS 8591, Laboratoire de Géographie physique, 1 place A. Briand, F–92195 Meudon Cedex France, e-mail: [email protected], [email protected] 2ESA CNRS 8018, Préhistoire et Quaternaire, Université des Sciences et Technologies de Lille, F–59 655 Villeneuve d'Ascq cedex. e-mail: [email protected] 3Institut National de la Recherche en Archéologie préventive (INRAP), 517 rue Saint-Fuscien 80 000 Amiens 4GEOTOP, Universite du Quebec a Montreal, Case postale 8888, Sta. Centre-Ville, Montreal, PQ.H3C 3P8 Canada. e-mail: [email protected] 5Institut de Paléontologie Humaine, Laboratoire de Préhistoire du Muséum National d'Histoire Naturelle, UMR 6569 du CNRS, 1 rue René Panhard, F–75013 Paris. e-mail: [email protected], [email protected] 6Centre Henri Elhaï, Université Paris–X, 200 Avenue de la République, F–92001 Nanterre

New investigation lead within the CNRS SITEP research Program* on the tufa deposits from the Somme and Seine River basins (Northern France) have allowed the discovery of new interglacial sequences allocated to MIS 5e and 11. The younger one, located at in the Somme basin at Caours is represented by a 4m thick tufa sequence overlying fluvial deposits from the low terrace. The tufa formation itself is mainly composed by paludal (marshy) soil faces showing numerous in situ incrusted vegetal remains and travertine concretions (stromatolithes) rapidly passing through typical fluvial facies (oncolithic sands and cross beddings). The tufa sequence and the upper part of the underlying fluvial silts and marshy soil have provided an abundant malacological fauna that allowed to describe a climatic evolution contemporaneous of the initial phases of the Eemian interglacial, followed by the climatic optimum (up to 70% of forest snails). The organic horizons located at the base of the tufa sequence have provided numerous large mammals (Aurochs, Cervids) and rodent remains (Talpa europaea, Sorex cf. araneus, Clethrionomys glareolus Apodemus sylvaticus, Arvicola cf. terrestris) contemporaneous of the interglacial optimum. Within these organic horizons, 4 Palaeolithic layers have been discovered in situ in association with large mammal remains showing evidences of human operation. Taking into account its relative position within the Somme terraces system, the U/Th ages (average: 123±4 ka BP) and the results of the bioclimatic studies, the Caours sequence represents the first record of the Eemian interglacial in the Somme basin.

The second sequence is located at La Celle in the Seine valley, where the tufa, reaching a total thickness of 8 metres high, edificated downwards the slope and lies on a Middle terrace alluvial formation (gravels and sands overlain by a fine silt unit). The molluscan succession recovered from the upper part of the silt unit and the base of the tufa describes the transition from a Lateglacial open landscape to the open forest environment of an Early Interglacial period. The middle part of the tufa yields assemblages of closed forests corresponding to a climatic optimum. At the top of the calcareous deposit, malacofaunas reflect a dramatic decrease of forest species. Flora described corresponds to interglacial conditions and includes several mediterranean taxa (Ficus, Buxus, Celtis). Mammal remains have been discovered in the middle part of the tufa in association with Acheulean artefacts. Two taxa from this assemblage (Hippopotamus, Macaca) are listed for the first time in Pleistocene deposits from Northern France. Malacological assemblages from the optimum phase belong to the well-known "Lyrodiscus assemblage" which characterizes calcareous tufas of MIS 11 in Northwest Europe. This chronological indication is strengthened by U-series radiometric measures


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undertaken on indurated tufa and on a horse tooth, indicating respectively ages of 387, 505 and 425 ± 46 ka that fit well with an MIS 11 allocation. First results demonstrate that La Celle provides an exceptional long continental record for MIS 11 allowing the reconstruction of detailed palaeoenvironmental evolution of the different Interglacial climatic phases. In the next future new developments are planned on shell amino acid analyses and stable isotopes to improve chronology and high-resolution climatic reconstruction from both sequences.

* Climatic Signature of Pleistocene Interglacials within European tufa, response of the environments and impact on the Palaeolithic occupations.

References:

Antoine, P., Limondin-Lozouet, N., Chaussé, C., Lautridou, J.P., Pastre, J.F., Auguste, P., Bahain, J.J., Falguères, C. & Galehb B. 2007: Pleistocene fluvial terraces from northern France (Seine, Yonne, Somme): synthesis and new results. Quaternary Science Reviews. 26, 2701–2723. Antoine, P., Limondin-Lozouet, N., Auguste, P., Locht, J.L., Galheb, B., Reyss, J.L., Escudé, E., Carbonel, P., Mercier, N., Bahain, J.J., Falgueres, C. & Voinchet P. 2006: Le tuf de Caours (Somme, Nord de la France): mise en évidence d'une séquence de tufs calcaires eemiens et d'un site paléolithique associé. Quaternaire, 17/4, 281–320. Limondin-Lozouet, N., Antoine, P., Auguste, P., Bahain, J.J., Carbonel, P., Chaussé, C., Connet, N., Dupéron, J., Dupéron, M., Falguères, C., Freytet, P., Ghaleb, B., Jolly-Saad, M.C., Lhomme, V., Lozouet, P., Mercier, N., Pastre, J.F. & Voinchet, P. 2006: Le tuf calcaire de La Celle-sur-Seine (Seine et Marne): nouvelles données sur un site clé du stade 11 dans le Nord de la France. Quaternaire, 17/2, 5–29.


39

The role of glacio-isostasy in the formation of post-deglacial and Holocene river terraces: evidence from northern England

David Bridgland

Department of Geography, Durham University, UK

In recent years work related to FLAG Focus 1, in particular in conjunction with the global overview provided by IGCP 449, has demonstrated the fundamental importance of uplift in generating long-timescale river terrace sequences. These are generally found in areas beyond the extent of most if not all of the Middle and Late Pleistocene ice sheets. It has been widely observed, however, that fluvial terraces occur widely in areas glaciated during the LGM. The explanations of these offered by a variety of authors include a similar range to those of longer-timescale sequences, including variations in discharge and sediment load (perhaps related to climate or extreme events), changing base level, and uplift, the latter encompassing glacio-isostatic rebound. This paper looks at data from the very large English drainage system that exits to the North Sea by way of the Humber estuary. This estuary is shared by the largely Pennine-derived drainage of the Yorkshire Ouse, to the north, and Britain's third largest river to the south, the Trent, although the latter only joined the Humber system with post-LGM deglaciation. Separate studies of parts of the Ouse system (Ure and Swale) and of the Middle and Lower Trent have allowed detailed comparison between these northern and southern parts of the Humber drainage. During the LGM the Ure and Swale catchments were completely covered by glacial ice, whereas the Trent was unglaciated, although its lowest reach was probably inundated by proglacial Lake Humber, the eventual drainage of which appears to have coincided with the linking of the Trent and Ouse systems. Thus the Trent has a terrace record going back to the Middle Pleistocene, whereas the Ure and Swale records begin with the melting of the last glacial ice. Importantly, there is considerable difference in the disposition of the post-LGM fluvial deposits in these two subsystems. In the Ure and Swale there are modest terrace staircases, commencing with full glacial deposits that stand up to 35m above the modern floodplain. In the Trent, in contrast, last glacial gravels form the floor of the modern floodplain, with Holocene sediments emplaced directly above them. Thus there is little or no post-LGM incision in the Trent, whereas in the Ure and Swale several incision events are recorded, continuing into the later stages of the Holocene. The various possible explanations of these differences will be discussed, with emphasis placed on glacio-isostatic uplift of the LGM-glaciated Ure and Swale as the main reason for the incision in those valleys.

Documents

ABSRTRACT BOOK - VUbalr/FLAG/web_data/downloads/FLAG_Budapest2008... · channel of the River Loire, France 11.00-11.20 Cserkész-Nagy, Á.T., Tóth, T., Vajk, Ö ... T.S., Bridgland,