摘要:

AbstractOver much of its outcrop in south Central Wales, the earliest facies of the Ludlovian, comprising grey shaly mudstones, is overlain by an important turbidite facies. In the present paper these two facies are described and the boundary between them is fixed at the first appearance in the succession of numerous thick turbidite beds. While its horizon cannot be precisely defined with reference to the faunal sequence, there are grounds for believing that this boundary is not significantly diachronous in the area considered. Finally, some suggestions are made as to the possible significance of the facies boundary.

ISSN:0072-1050    

DOI:10.1002/gj.3350040101

出版商:John Wiley&Sons Ltd    

年代:1964

数据来源: WILEY

摘要:

AbstractThe microfauna and microflora of the Lower Miocene limestones of the Darai Complex of Papua have been found to recrystallize in a constant order related to the biological affinities of the fossil genera. This recrystallization is independent of the sparry or micritic nature of the interstitial material.Dolomitisation also destroys the fossil skeletons in a comparable order except that the coralline algae appear to be relatively more resistant to replacement by dolomite.Only when the skeletons of the most resistant fossil groups have been recrystallized can the occurrence of interstitial sparry calcite be suspected to have originated from recrystallization of an original micritic matrix. Obliteration of fossil remains by recrystallization presents an additional hazard in the interpretation of biofacies in limestones of this type.

ISSN:0072-1050    

DOI:10.1002/gj.3350040102

出版商:John Wiley&Sons Ltd    

年代:1964

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350040103

出版商:John Wiley&Sons Ltd    

年代:1964

数据来源: WILEY

摘要:

AbstractTwo ignimbrite horizons are recognised in a Caradoc marine sequence. The uppermost, the Pandy Ash forms a single mappable unit, but is shown to consist of at least three separate flows, including both welded and non‐welded tuffs. Locally lahars occu

ISSN:0072-1050    

DOI:10.1002/gj.3350040104

出版商:John Wiley&Sons Ltd    

年代:1964

数据来源: WILEY

摘要:

AbstractThe composition of the feldspar phenocrysts, and the enclosing glassy or finely crystalline ground‐masses, of three phonolites suggests that the addition of calcium or the addition of excess sodium (molecular ratio Na2O + Ka2O>Al2O3) to compositions in the feldspar field of the system NaAlSiO4‐KAlSiO4‐SiO2will change the composition of the minimum on the nepheline‐feldspar boundary when this is projected into this

ISSN:0072-1050    

DOI:10.1002/gj.3350040105

出版商:John Wiley&Sons Ltd    

年代:1964

数据来源: WILEY

摘要:

AbstractSilurian strata of Upper Llandoverian and Wenlockian age, lying in a complex synclinorium south of the Highland Boundary Fault Zone in Co. Mayo, are affected by two main structural episodes. A tight, curving, E–W synclinorium, verging to the south, was developed during the first episode of deformation (F1). Large‐scale cross‐buckling, followed by variable flattening in the axial‐planar schistosity, was responsible for a considerable plunge variation of F1folds. A mechanism is described whereby primary downward‐facing minor folds may be produced in an upward‐facing major structure. Three slides, of considerable magnitude, are co‐planar with the schistosity. During the second episode of deformation (F2) a slip‐cleavage, dipping steeply to the NNE, was superimposed upon the F1synclinorium. It is deduced, partly from an analysis of the geometry of F2minor structures, that the arcuate curvature of the F1synclinorium is pre‐F2and was developed during the F1deformation as a response to the presence of an early or pre‐F1granite pluton. F2folds show a great variability in plunge and facing direction, depending upon their position in th

ISSN:0072-1050    

DOI:10.1002/gj.3350040106

出版商:John Wiley&Sons Ltd    

年代:1964

数据来源: WILEY

摘要:

AbstractThe present coastal configurations of these estuaries are contrasted with known fluvial drowned estuaries and attention is drawn to their non‐fluvial characteristics. Two other sub‐parallel depressions in Wirral and southwest Lancashire are described, together with the sub‐glacial surfaces of all four. Their floors are found to contain irregular rock‐bound hollows, and other features reminiscent of glaciated areas. It is suggested that they are escape routes taken by Irish Sea ice hemmed in by the mountains of Wales and the outliers of the Pennines. The term “iceways” is suggested for such ice‐gouged features. A rock shelf in the University area of Liverpool is also tentatively attributed to the sam

ISSN:0072-1050    

DOI:10.1002/gj.3350040107

出版商:John Wiley&Sons Ltd    

年代:1964

数据来源: WILEY

摘要:

AbstractKimberlites are discussed in the light of knowledge obtained from their occurrence in the Siberian platform. Their relation to tectonic pattern, the basement and its cover are considered together with their petrographic and chemical composition and their association with basaltic rocks. It is concluded that kimberlites originated from a deep‐seated kimberlite magma which was injected periodically. The chemical resemblance to peridotes is noted and the peculiarities of kimberlite are put down to periodic enrichment of peridotitic magma with volatiles. It is suggested that diamonds owe their origin to both primary and assimilated carbo

ISSN:0072-1050    

DOI:10.1002/gj.3350040108

出版商:John Wiley&Sons Ltd    

年代:1964

数据来源: WILEY

摘要:

AbstractNew isotopic age determinations on all the granites of southwest England are presented and discussed in relation to the data of previous workers on the Dartmoor and Land's End granites, and with particular reference to the dating of the Hercynian orogeny in that region and to the more precise fixing of the Carboniferous‐Permian boundary. The possibility of a measurable non‐contemporaneity of the individual granites is shown, and their ages compared with those of Armorica and central Europe.The different granite phases within the composite plutons and the various associated late magmatic processes of pegmatitic injection, pegmatoid metasomatism, greisenisation, tourmalinisation and hydro‐thermal mineralisation, are shown to be pene‐contemporaneous.Some data on basic igneous rocks relative to the history of the Variscan fold‐belt in southwest England, and particularly to the Hercynian orogeny, are discussed.Age data on the Wolf Rock and Epsom Shoal phonolites are presented; their Mesozoic extrusion raises problems not yet r

ISSN:0072-1050    

DOI:10.1002/gj.3350040109

出版商:John Wiley&Sons Ltd    

年代:1964

数据来源: WILEY

摘要:

AbstractThe succession consists of Skiddaw Slates followed by Borrowdale Volcanic rocks (Ordovician) and is very similar to that previously described southeast of Ullswater (Moseley 1960). The Ullswater Group, more than 4000 ft thick forms the lowest part of the volcanic succession and consists of tuffs, basalts, basic andesites, and andesites. Above this about 1000 ft of the rocks of the Birk Fell Group, which are dominantly felsitic, are exposed.Important structural elements are the Ullswater Anticline, the Ullswater Thrust and the high angle faults. The anticlinal axis follows Ullswater as far as Glencoynedale and can be demonstrated only in the Borrowdale Volcanic rocks. The anticline does not appear to continue downwards into the Skiddaw Slates which are not only of different tectonic facies to the volcanics, but are separated from them by the southeasterly dipping Ullswater Thrust. This thrust was induced by the disharmony between the competent volcanics and the incompetent Skiddaw Slates, and is thought to be an imbricate thrust complex rather than a single dislocation.The high angle faults, the third important structural element, have northwest, northerly and westerly trends. It is probable that the northwesterly faults, at least, are wrench faults, although a strike slip component can be demonstrated in one instance only. The nature of the movement of the northerly and westerly faults cannot be ascertained.

ISSN:0072-1050    

DOI:10.1002/gj.3350040110

出版商:John Wiley&Sons Ltd    

年代:1964

数据来源: WILEY