ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1994.tb00884.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1994.tb00885.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1994.tb00886.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTCentral and southern Britain was drained by two main river systems during the larger part of the Early and Middle Pleistocene: the Thames and Bytham rivers. Evidence for these rivers and their Quaternary history is represented by their sediments (the Kesgrave and Bytham Sands and Gravels, respectively), the geomorphological position of the sediments, biostratigraphy and amino acid geochronology. Evidence from the earlier parts of the Early Pleistocene (Tiglian C4b and earlier) indicates low‐energy river systems and marine conditions over much of East Anglia. For most of the Early Pleistocene (Tiglian C4c to the Cromerian Complex) the ancestral Thames was the main river with, at its maximal extent, a catchment that extended into Wales, and across East Anglia and what is now the North Sea, to join the ancestral Rhine. During this period, glaciers in the uplands of Wales and periglacial mass movement elsewhere supplied material to the catchment and it was at this time that the bulk of the sorted Quaternary ssediments of lowland Britain were deposited. The Bytham river system has no successor because the landscape now in existence has been fundamentally altered by glacial erosion. This catchment drained most of Midland England and joined the Thames in central East Anglia. Initially, the Bytham river was a tributary of the Thames, but over time it extended its catchment and at the beginning of the ‘Cromerian Complex’it became the main river of southern Britain. With the Anglian Glaciation (01 Stage 121, the Bytham river was destroyed and the Thames was diverted to its present route through L

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1994.tb00887.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTTwo major river systems operated in southern and eastern England throughout the Pleistocene: the river Thames and the Solent river. Both rivers are axial streams of comparable size draining major basinal structures comprising similar Tertiary and Mesozoic rocks. Although the modem Thames flows broadly W‐E in the London Basin, upstream of Reading it flows from the north to drain the south Midlands. It was diverted to its present course through London by glaciation in the Anglian (Elsterian) before which it flowed across East Anglia into the southem North Sea. The Solent river no longer exists since most of its course was drowned by eustatic sea‐level rise during the Flandrian Stage (Holocene). Previously, it flowed eastwards across SE Dorset and S Hampshire as an extension of the modem river Frome in the Hampshire Basin. During periods of low sea‐level (cold stages) it was a tributary of the ‘Channel River’. Fluvial aggradations provide evidence of the former courses of these substantial rivers and their tributaries. The facies and sedimentary structures indicate that the bulk of the deposits in both systems accumulated in braided river environments under periglacial climates. Fossiliferous sediments provide biostratigraphical frameworks. During temperate periods the rivers adopted singlethread courses. Evolution of both rivers reflect their responses to climatic change, local geological structure and long‐term tectonic activity. Both rivers are undoubtedly of considerable antiquity, their records potentially extend from the Early Pleistocene or Late Pliocene, but they may have originated in the ear

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1994.tb00888.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTRecent research on the Somme Valley terrace deposits, that began in 1987, has resulted in an integrated sequence of geological and geomorphological evidence for this area that is of particular significance for prehistoric investigations. This has been achieved using previous evidence and new results from archaeological and geological excavations. These include longitudinal profiles, cartography and detailed synthesis of sections of alluvial deposits, stratigraphy of river deposits and overlying loess sequences. The work, based on a study of the geometry of the terrace system, has resulted in the identification of ninestepped alluvial formations that occur along 70 km of the valley. Detailed study permits the integration of the various alluvial sequences. This suggests that each alluvial sequence results from sedimentation through a single glacial‐interglacial climatic cycle. This hypothesis is confirmed by investigation of soil and loess sequences of the deposits overlying the fluvial sediments. The synthesis presented provides a basis for understanding the deposition of the terrace system and an initial chronostratigraphic interpretation for the deposit

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1994.tb00889.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTThe river Jarama is a medium‐sinuosity meandering river with gravel bedload. Throughout the Quaternary it developed a large number of terraces in a repetitive sequence of aggradation‐stability‐degradation‐stability stages, which are studied in the middle reach of the river, applying geomorphological and sedimentological methods, as well as kadiocarbon dating techniques. The Upper Terrace System of earliest Pleistocene to mid Pleistocene age forms isolated fragments vertically disconnected and colluviated, and their sequential distribution of facies implies lateral shifting of channels and a welldeveloped flood plain. The Middle Terrace System of mid‐to‐late Pleistocene age has differentiated levels in the upstream reaches while downstream they condense giving a thick multi‐episodic series, corresponding to the tectonic tilting of the basin. Classical point bar fining‐upward sequences of a medium‐ to high‐sinuosity river (with gravels and sands as bedload) are clearly differentiated in them. A major degradation stage follows this group of terraces, with an incision of up to 30 m. Then, during a relatively long period of stability, a forest of riparian species developed, prior to the last aggradational stage of the Lower Terrace System. The aggradation resulted in a fining‐upward sequence where lateral accretion is clearly visible in the gravels, due to migration of the medium‐ to low‐sinuosity river. Sedimentation continued and was active up to the 1950s, but since then, intense anthropogenic modifications led to rene

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1994.tb00890.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTHuvial systems from the Dutch and Polish lowlands are compared for their evolution during the Weichselian deglaciation period. In both regions the Pleniglacial braided‐river pattern changed to a meandering pattern in the beginning of the Lateglacial. Several transitional stages between braided and high‐sinuosity meandering systems have been recognized. A difference in fluvial activity is found during the Younger Dryas when the Maas transformed to a braided pattern while the Warta maintained its meandering pattern. Phases of erosion and aggradation are more or less synchronous in the different river basins, but their intensity may differ greatly. The major characteristics of the fluvial systems are obviously a response to the general climatic evolution and related to changes in vegetation. The regional differences are of minor importance and can be explained by site‐specific factors. Threshold values within the latter factors define the changes in river dyn

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1994.tb00891.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTA variety of factors has controlled the evolution of the Vistula river valley. They include climatically induced changes of the river runoff and sediment load, glacial advances and rapid variations of the base level, as well as the influence of the tectonic factor. The first‐order climatic cycles are reflected in separate terrace fills. The second‐order fluctuations may be represented by separate cuts and fills, by the change of the facies or by the change in the granulometric composition. The analysis of the changes in the longitudinal profile helped to discover a great variety of different valley reaches and a general tendency to smooth the long profile during the Quatern

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1994.tb00892.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTThe present‐day drainage system of the Carpathian Basin originates from the gradual regression of the last marine transgression (brackish Pannonian Sea). The flow directions of the rivers including the Danube, are determined by the varying rates and locations of subsidence within the region. The Danube, which forms the main axis of the drainage network, first filled the depression of the Little Plain Lake and then, further southward, the Slavonian Lake. From the end of the Pliocene, the crustal movements which caused the uplift of the Transdanubian Mountains, forced the Danube to flow in an easterly direction, towards the antecedent Visegrid Gorge, and into the subsiding basins of the Great Plain. Climatic changes during the Pleistocene had the effect of forming up to seven fluvial terraces. The uplift of the mountains is demonstrated by the deformation of the terraces, while the subsidence of the Plains is proven by an accumulation of several hundred metres of sediment. The river only occupied its present position south of Budapest in the latest Pleistocen

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1994.tb00893.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY