摘要:

AbstractThe Helgedal Zone is the Caledonian, heterogeneously deformed base of the Jotun Complex, within the Jotun‐Valdres Nappe Complex (Sognefjell, South Norway). It consists of an anastomosing system of shear zones isolating lozengeshaped lenses of less deformed rocks. Structural and geometrical features are described to define the type of deformation and to evaluate the tectonic significance of this zone. Granulitic gabbros and pegmatitic dykes are deformed together in the highly strained mylonitic zones. Microtextural investigations indicate that the quantitative relation between mafic and felsic minerals and the content of quartz determine the different behaviour of the two rock types during deformatio

ISSN:0072-1050    

DOI:10.1002/gj.3350230101

出版商:John Wiley&Sons Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractStudies on surface water characters of the estuarine environment of Iraq, northwestern Arabian Gulf, define three subdivisions of salinity: oligohaline, polyhaline, and euhaline. Textural analysis reveals that surface sediments covering the bottom are composed of six distinct classes: silty clay, clayey silt, sand‐silt‐clays, clayey sand, silty sand and sand. Five physiographic subdivisions are identified and described fluvial‐estuarine, tidal mud flats (subtidal flat, lower intertidal flat, upper intertidal flat, supratidal flat), sand bars, Abdallah‐Shetana channel and submerged estuarine distributary channel and bar systems.The content of organic matter in the sediments ranges from 0.24‐3.69 per cent by weight. High values were recorded from the Abdallah‐Shetana channel while lower values are confined to sand bars and submerged estuarine distributary channel and bar systems.Carbonates, quartz, feldspar, and halite are the main mineral constituents of the non‐clay grade sediments; carbonates are present mainly as low‐magnesium calcite followed by dolomite and high‐magnesium calcite. Aragonite is present only in trace amounts. Both detrital and biogenic sources are suggested for low‐magnesium calcite. A detrital source for dolomite and a biogenic source for high‐magnesium calcite and a

ISSN:0072-1050    

DOI:10.1002/gj.3350230102

出版商:John Wiley&Sons Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractRecent work in the Shelve Ordovician Inlier has produced a variety of evidence for a period of deformation dominated by a braided system of dextral oblique‐slip faults of pre‐upper Llandovery age. Displacement amounts along individual fault strands are generally less than 2 km, but the aggregate displacement across the whole Inlier up to and including the Pontesford‐Linley Fault, must have been much greater. The fault structures found in other parts of Wales are compared to those of the Shelve Inlier, and it is concluded that this style of faulting was of importance in Wales, though it was mostly of pre‐Silurian age. The significance of the fault systems in terms of the late Precambrian to early Caledonian structural framework of Southern Britain is discussed with reference to examples from other parts of th

ISSN:0072-1050    

DOI:10.1002/gj.3350230103

出版商:John Wiley&Sons Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe Mgeni Estuary is situated on the subtropical, mainly microtidal Natal coast. Modern sedimentary environments in the estuary comprise two groups. Barrier‐associated environments include inlet channel, inlet beachface, tidal delta, washover fans, transverse intertidal bars and aeolian dunes. Estuarine environments include subtidal channels, interidal bars, back‐barrier lagoon, tidal creek, tidal creek side‐attached bars, creek mouth bar, mangrove fringe and supratidal mudflats. Each sedimentary facies is described in terms of grain‐size, sedimentary structures, and sedimentary processes. The distinctive flora and fauna play an important role in facies recognition. Vertical sequences produced by infilling of the estuary and subsequent coastal erosion are discussed. The facies are considered sufficiently distinct to warrant recognition in the geological

ISSN:0072-1050    

DOI:10.1002/gj.3350230104

出版商:John Wiley&Sons Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe Rozel Conglomerate Formation, a coarse alluvial fan deposit, overlies the Bouley Rhyolite Formation beneath the headland called La Tete des Hougues, on the north coast of Jersey, Channel Islands. Here the rhyolites form an exhumed palaeotopography which in places is smoothly, but irregularly, eroded. Locally however, there is preservation of a deep Lower Palaeozoic weathering profile. Breccia is preserved spalled from these weathered profiles as a fossil scree deposit, which has subsequently been hydraulically reworked in a palaeotopographic low.Overlying the breccia is a prograding succession of alluvial fan sediments. A 4m thick, upwards‐coarsening sequence of silty sandstones and fine pebble conglomerates is succeeded by the incision of a 3m deep channel. This is overlain by a 28m thick, upwards‐fining sequence of coarse debris flow and streamflood conglomerates. The lower unit is interpreted as a prograding fan sector of reworked fan material, whilst the upper unit is thought to reflect the avulsive initiation and gradual abandonment of a fan lobe sourced from a northern hinterl

ISSN:0072-1050    

DOI:10.1002/gj.3350230105

出版商:John Wiley&Sons Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractA detailed sedimentary study of the Lower Carboniferous (Courceyan) Shipway Limestone Formation at Three Cliffs Bay on the Gower Peninsula (South Wales) has shown that the bioclastic limestones represent a storm‐dominated sequence that contains the storm‐related sedimentary structure hummocky cross‐stratification (HCS). Conformably overlying the Shipway Limestone is a cross‐stratified oolitic sandbody with evidence of subaerial exposure. Six sedimentary lithofacies are identified in these two formations which record a distal to proximal, shallowing‐upward trend that passes from beneath mean wave‐base to above fairweather wave‐base.The shallow marine facies model constructed by Wu (1982) from his study of the Lower Carboniferous limestone sequences of South Wales is re‐evaluated. Modifications proposed for the model include the addition of two distal tempestite facies and a proximal oolite sand body. The Shipway Limestone and Brofiscin Oolite record the first major, basin‐wide, shallowing‐upward phase of the Lower Carbonife

ISSN:0072-1050    

DOI:10.1002/gj.3350230106

出版商:John Wiley&Sons Ltd    

年代:1988

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350230107

出版商:John Wiley&Sons Ltd    

年代:1988

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350230108

出版商:John Wiley&Sons Ltd    

年代:1988

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350230109

出版商:John Wiley&Sons Ltd    

年代:1988

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350230110

出版商:John Wiley&Sons Ltd    

年代:1988

数据来源: WILEY