Progress in the Gondwanan Carboniferous–Permian palynology and correlation of the Nilawahan Group of the Salt Range,Pakistan: A brief review     

IRFAN U JAN 《Journal of Earth System Science》2014,123(1):21-32

This paper comprises of two sections. The first section describes challenges in the Carboniferous–Permian Gondwanan stratigraphic palynology, and progress in techniques such as presence of the ‘rare-marine intervals’, and ‘radiometric dating’ in some Gondwanan successions, e.g., South Africa, Australia and South America, as tools to confidently calibrate these palynozones. The second section describes developments in the palynological work on the Carboniferous–Permian Nilawahan Group of the Salt Range, Pakistan, and summarises their correlation with the coeval succession of the Gondwana continents and with the Russian/International stages.  相似文献   

Design of a spatial data structure using the relational normal forms     

JAN W. VAN ROESSEL 《International journal of geographical information science》2013,27(1):33-50

Abstract

In previous work, a relational data structure aimed at the exchange of spatial data between systems was developed. As this data structure was relational it was of first normal form, but compliance with the higher normal forms was not investigated. Recently, a new procedural method for composing fully normalized data structures from the basic data fields has been developed by H. C. Smith, as an alternative to the process of non-loss decomposition which is difficult to understand. Smith's method has been applied to data fields required to store points, lines and polygons in a chain-node spatial data model. When geographic domain, coverage layer and map are also considered, the procedure naturally leads to a catalogue model, needed for the exchange of spatial data. Although the method produces a fully normalized data structure, it is not as easy to identify which normal forms are responsible for the ultimate arrangement of the data fields into relations, but the benefits of these criteria for data base development also apply to spatial data structures and related ancillary data.  相似文献   

LAND USE DEVELOPMENT IN GREATER COPENHAGEN     

JAN MAGNUSSEN M.Sc.  CHR. W. MATTHIESSEN Ph.D. 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):65-69

Magnussen, Jan and Wichmann Matthiessen, Chr.: Land Use Development in Greater Copenhagen. Geografisk Tidsskrift 75: 65–69. København, juni 1, 1976.

The paper attempts to elucidate the land use development within Greater Copenhagen during this century. Sequences expressing the intensification of use und the process of urban renewal are the objects of the analysis.  相似文献   

Geochemistry of Holocene salt marsh and tidal flat sediments on a barrier island in the southern North Sea (Langeoog,North‐west Germany)     

KERSTIN KOLDITZ  OLAF DELLWIG  JAN BARKOWSKI  RAINER BAHLO  THOMAS LEIPE  HOLGER FREUND  HANS‐JÜRGEN BRUMSACK 《Sedimentology》2012,59(2):337-355

The barrier islands of the southern North Sea were formed during the Holocene sea‐level rise. These islands form part of a highly dynamic environment whose evolution continues today. Subjected to sea‐level changes, tides and storm events, the sedimentary record reflects processes occurring under varying energy conditions. This article presents geochemical, mineralogical and diatom investigations carried out in the salt marsh of the East Frisian barrier island of Langeoog, which is re‐exposed to a rising sea‐level due to de‐embankment. The major aim of this study is to improve the knowledge of the sedimentological and geochemical development of these deposits under the influence of sea‐level rise, with a special focus on the geochemistry and distribution of heavy mineral‐associated elements. Correlation diagrams between FeO, TiO₂ and MnO, as well as ternary plots (Al₂O₃–SiO₂–Zr or TiO₂), clearly indicate the variable appearance of heavy minerals in different lithological facies, comprising marsh soil, mixed and sand flat, and relocated beach sands. A dominating abundance of ilmenite followed by zircon, garnets and some other heavy minerals is evidenced by Scanning Electron Microscope‐Energy Dispersive X‐ray measurements. The data presented here suggests that these geochemical proxies are useful tools for characterizing depositional energy conditions. Increasing depositional energy is evident for the lithological units in the following order: marsh soil, mixed flat, sand flat and relocated beach sand. The energetic conditions during sediment deposition, as well as the sedimentary history, are confirmed by diatom analyses as an additional independent indicator. Depending on source rock composition, the geochemical parameters used in this study may also help to investigate depositional energy regimes of other siliciclastic sedimentary systems.  相似文献   

Tsunami backwash deposits with Chicxulub impact ejecta and dinosaur remains from the Cretaceous–Palaeogene boundary in the La Popa Basin,Mexico     

PETER SCHULTE  JAN SMIT  ALEXANDER DEUTSCH  TOBIAS SALGE  ANDREA FRIESE  KILIAN BEICHEL 《Sedimentology》2012,59(3):737-765

The La Popa Basin in north‐eastern Mexico features outstanding, continuous three‐dimensional exposures of the Cretaceous–Palaeogene boundary event deposit in shallow shelf environments pierced by salt stocks. In the area to the south‐east of the El Papalote diapir, the Cretaceous–Palaeogene deposit consists of two superimposed sedimentary units and erosively overlies upper Maastrichtian sand‐siltstones with soft‐sediment deformation and liquefaction structures. The basal unit 1 is an up to 8 m thick chaotic, carbonate‐rich bed that discontinuously fills incised gutters and channels. Besides abundant silicic and carbonate ejecta spherules from the Chicxulub impact, unit 1 includes large sandstone boulders and abundant shallow‐water debris (for example, mud clasts, algae, bivalve shells, gastropod shells and vertebrate remains). Unit 1 is conformably overlain by unit 2. Distal to the diapir, unit 2 consists of a centimetre to decimetre‐thick conglomeratic, coarse bioclast and spherule‐bearing sandstone bed. Closer to the diapir, unit 2 becomes a metre‐thick series of four to eight conglomeratic to fine‐grained graded sandstone beds rich in shell debris and ejecta spherules. Unit 2 is conformably overlain by structureless to parallel laminated sandstone beds that may mark the return to the pre‐event depositional regime. The sedimentary characteristics of the Cretaceous–Palaeogene deposit, including its erosive base, its sheet‐like geometry, the presence of multiple, graded beds, evidence for upper flow regime conditions and the absence of bioturbation, support an origin by a short‐term multiphase depositional event. The occurrence of soft‐sediment deformation structures (for example, liquefaction) below the Cretaceous–Palaeogene deposit suggests that earthquakes were the first to occur at La Popa. Then, shelf collapse and strong backflow from the first tsunami waves may have triggered erosion and deposition by violent ejecta‐rich hyperconcentrated density flows (unit 1). Subsequently, a series of concentrated density flows resulting from tsunami backwash surges may have deposited the multiple‐graded bedding structures of unit 2. The specific depositional sequence and the Fe‐Mg‐rich as well as Si‐K‐rich composition of the ejecta spherules both provide a critical link to the well‐known deep marine Cretaceous–Palaeogene boundary sites in the adjacent Burgos basin in north‐eastern Mexico. Moreover, the pulse‐like input of Chicxulub ejecta material at the base of the event deposit allows for correlation with other Cretaceous–Palaeogene boundary sites in the Gulf of Mexico and the Atlantic, as well as in Central and Northern America. The presence of diverse dinosaur and mosasur bones and teeth in the event deposit is the first observation of such remains together with Chicxulub ejecta material. These findings indicate that dinosaurs lived in the area during the latest Maastrichtian and suggest that the tsunami waves not only eroded deltas and estuaries but the coastal plain as well.  相似文献   

“Stratigraphic,sedimentological and palaeoenvironmental constraints on the rise of the Urgonian platform in the western Swiss Jura” by A. Godet et al. (2010) Sedimentology 57, 1088–1125: Discussion     

MARC A. CONRAD  BERNARD CLAVEL  BRUNO GRANIER  JEAN CHAROLLAIS  ROBERT BUSNARDO  ELISABETTA ERBA  SILVIA GARDIN  ROGER JAN DU CHÊNE  DANIELLE DECROUEZ  ANTONIETTA CHERCHI  ROLF SCHROEDER  JACQUES SAUVAGNAT  MARC WEIDMANN 《Sedimentology》2012,59(3):1121-1125

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长江上游蒋家沟泥石流输沙年际变化与降水旋回特征关系   总被引：1，自引：0，他引：1  

王裕宜  詹钱登  田冰  洪勇  邹仁元 《山地学报》2008,26(5)

根据小不流域1956～2002年的降水资料,运用Mann-Kendall(M-K)非参数检验法和自相关函数,发现1990代降水旱现显著增加的趋势,其降水年均值比前期年均值增加96.5 mm(16.2%).并结合37 a气候变化下的蒋家沟高频率暴雨泥石流输沙最时序观测资料,分析了降雨变化与泥石流输沙量的关系,结果显示1990年代泥石流输沙量有显著增加的趋势,1990年代的年均输沙量比前期(1965～1989年)的年均输沙量多91×104m3/a.反映了暴雨泥石流输沙年际变率对降水年际变化的回应关系.本文已经初步揭示暴雨泥石流灾害活动年际变化的基本规律,并且为未来暴雨泥石流中、短期时间尺度的预测研究提供一条新路.  相似文献   

THE EFFECT OF SYNOPTIC SCALE WEATHER SYSTEMS ON SUB‐SURFACE SOIL TEMPERATURES IN A DIURNAL FROST ENVIRONMENT: PRELIMINARY OBSERVATIONS FROM SUB‐ANTARCTIC MARION ISLAND     

WERNER NEL  JAN C. BOELHOUWERS  MPHUMZI B. ZILINDILE 《Geografiska Annaler: Series A, Physical Geography》2009,91(4):313-319

Marion Island in the South Indian Ocean has a maritime climate dominated by diurnal frost processes in the landscape. We test the hypothesis that synoptic time‐scale measurements are essential in understanding the drivers of diurnal frost processes. Preliminary results from automated microclimate measurements in a polar desert habitat show that diurnal soil surface temperatures on Marion Island are influenced by a complex interaction of radiation balance, air mass circulation, cloud cover and snow. The passage of synoptic scale weather systems influences soil thermal characteristics through changes in dominance of the radiation budget. Soil frost on Marion appears to be dependent on clear skies, while synoptic weather systems affect the duration and intensity of soil frost processes and non‐radiative heat fluxes. Air circulation patterns at Marion Island influence diurnal scale temperature fluctuations and its direct and indirect interactions with ecosystem processes. The data suggest that in a maritime sub‐Antarctic environment the climatic drivers of soil frost occur at a finertemporal resolution than for seasonal and permafrost environments and needs to be measured at a diurnal time‐scale to be meaningful.  相似文献   

Links between bulk sediment particle size and magnetic grain‐size: general observations and implications for Chinese loess studies     

FRANK OLDFIELD  QINGZHEN HAO  JAN BLOEMENDAL  ZOË GIBBS‐EGGAR  SHIVA PATIL  ZHENGTANG GUO 《Sedimentology》2009,56(7):2091-2106

Using a combination of particle size analysis, magnetic measurements, scanning electron microscopy and transmission electron microscopy imaging, this study shows that in a wide range of depositional environments, there is a strong link between particle size classes and magnetic response, especially below the upper limit of stable single domain magnetic behaviour. Ferrimagnetic grain assemblages dominated by stable single domain magnetosomes regularly have peak susceptibility and remanence values in coarser grades than do those containing finer‐grained, viscous and superparamagnetic secondary magnetic minerals formed during pedogenesis. This effect is despite the fact that there is a one to two orders of magnitude size difference between the particle size boundaries (at 1 or 2 μm) and key domain state transitions (mostly below 0·05 μm). The implications of these results are explored using samples spanning 22 Myr of loess accumulation on the Chinese Loess Plateau. The results from the loess sections, complemented by data from low‐temperature magnetic experiments, show that there are subtle distinctions in mean ferrimagnetic grain‐size between the Pleistocene and Miocene parts of the record, thus allowing more refined rock magnetic interpretations of the fine‐grained ferrimagnetic mineral assemblages arising from the effects of weathering, pedogenesis and possibly diagenesis in the sections studied.  相似文献   

A Periglacial Palaeoenvionment in the Upper Carboniferous–Lower Permian Tobra Formation of the Salt Range, Pakistan     

Irfan U. JAN  Shahid IQBAL  Sarah J. DAVIES  Jan A. ZALASIEWICZ  Michael H. STEPHENSON  Michael WAGREICH  Muhammad HANEEF  Muhammad HANIF  Sajjad AHMAD 《《地质学报》英文版》2017,91(3):1063-1078

The Upper Carboniferous—Lower Permian(Upper Pennsylvanian-Asselian) Tobra Formation is exposed in the Salt and Trans Indus ranges of Pakistan.The formation exhibits an alluvial plain(alluvial fan-piedmont alluvial plain) facies association in the Salt Range and Khisor Range.In addition,a stream flow facies association is restricted to the eastern Salt Range.The alluvial plain facies association is comprised of clast-supported massive conglomerate(Gmc),diamictite(Dm)facies,and massive sandstone(Sm) Hthofacies whereas the stream flow-dominated alluvial plain facies association includes fine-grained sandstone and siltstone(Fss),fining upwards pebbly sandstone(Sf),and massive mudstone(Fm) Hthofacies.The lack of glacial signatures(particularly glacial grooves and striatums) in the deposits in the Tobra Formation,which are,in contrast,present in their timeequivalent and palaeogeographically nearby strata of the Arabian peninsula,e.g.the AI Khlata Formation of Oman and Unayzah B member of the Saudi Arabia,suggests a pro-to periglacial,i.e.glaciofluvial depositional setting for the Tobra Formation.The sedimentology of the Tobra Formation attests that the Salt Range,Pakistan,occupied a palaeogeographic position just beyond the maximum glacial extent during Upper Pennsylvanian-Asselian time.  相似文献