摘要:

ABSTRACTWater and sediment movement in The Wash embayment has been determined from an extensive set of data, consisting of tidal current readings and suspended sediment concentration measurements. Instantaneous and residual currents in the embayment show a distinct lateral inhomogeneity, whereas vertically the water column is almost homogenous. The central deep water area (30–40 m) of the embayment is dominated by a residual landward water movement, whilst on the margins, the residual movement is seaward. Sediment is supplied predominantly in suspension from the north, through the northern extremity of Boston Deep. Suspended sediment pathways are coincident with the spring tide water movements and the subtidal channels act as the main conduits. Approximately 6·8 × 106tonnes yr−1of suspended sediments are supplied to the embayment from offshore areas. Bedload sediment supply is of lesser importance, ∼ 1·4 × 104tonnes yr−1. Whereas suspended sediment movement appears to be the dominant mode of transport throughout the embayment, bedload transport is important in reforming the sea bed into a variety of bedforms which are particularly well developed on the margins of channels

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1996.tb01465.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTIn the long continental history of the Provence Basin which extended from Santonian to Oligocene times, a major period of palaeosol development occurred in the Danian. Dolocretes developed within floodplain silts, and partly from palustrine limestones. Dolocretes are overlain by pedogenic facies: calcretes and palustrine limestones. Gradational lower and upper limits of profiles, succession of nodular, coalescent and massive horizons, the epigenesis of quartz by dolomite, the unimodal crystal size and the euhedral dolomite fabric, as well as the absence of biogenic structures and vadose cements show that dolocretes formed in the phreatic zone.The exclusive occurrence of dolocretes around the palaeolake or playa suggests that dolocrete formed by the mixing of groundwaters and lake brines, which infiltrated the phreatic zone during periods of strong evaporation and lake level lowering. The term halo dolocrete is proposed to describe this type of dolocrete deposit.Subsequent alteration of the dolocrete includes leaching of the central core of dolomite crystals and calcitization. Calcitization was either fabric‐destructive (type I) or fabric‐preserving (type II) and took place during very early diagenesis, i.e. concomitant with calcrete formation or palustrine limestone deposition. Fabric‐destructive calcitization is attributed to a drop in the lake level, when the upper part of the dolocrete was subjected to vadose zone processes, whereas the fabric‐preserving calcitization resulted from reactions with dilute lake and groundwaters during rise in lak

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1996.tb01466.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1996.tb01467.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1996.tb01468.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Evolution of the Tasman Sea Basin. Edited by G. J. Van der Lingen, K. M. Swanson and R. J. Muir.Panthalassan Margin of Gondwanaland. Permian‐Triassic Pangean Basins and Foldbelts along the Panthalassan Margin of Gondwanaland. Edited by J. J. Veevers and C. McA. PowellThe Magnetic Anisotropy of Rocks, D. H. Tarling and F. Hroud

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1996.tb01469.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1996.tb01470.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY