摘要:

AbstractThe Abu Dom complex is one of a cluster of Younger Granite ring‐complexes piercing the Proterozoic gneisses of the Bayuda Desert of Sudan. Intrusive rocks predominate and range from early metaluminous syenites to later peralkaline syenites and granites. They are disposed as ring‐dykes, nested intrusions, and cone‐sheet swarms. Field evidence and geochemical variation indicate that the peralkaline rocks evolved from a metaluminous syenitic parent magma as a result of high‐level fractionation. The suite carries a clear within‐plate signature exemplified by marked enrichments in HFS elements such as

ISSN:0072-1050    

DOI:10.1002/gj.3350200402

出版商:John Wiley&Sons Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThe glacigenic succession along the border of northeast Wales records the advance, coalescence and subsequent uncoupling of Welsh and Irish Sea ice‐sheets during the Late Devensian cold stage. During coalescence, extensive basal tills were deposited and considerable diversion of pre‐existing drainage was accomplished by subglacial meltwater. Analysis of borehole data and quarry exposure indicates that a complex assemblage of ice‐contact, proglacial fluviatile and lacustrine environments was developed during uncoupling and subsequent retreat. Neither of the previously proposed models for the formation of the so‐called Wrexham ‘delta‐terrace’ are adequate to explain the wide variety of sedimentary successions observed and the feature is a complex, diachronous structure that reflects rapidly changing depositionai conditions, including ice‐frontalluvial fans, sandar and proglacial and ice‐contact lakes, formed at the margin of a ret

ISSN:0072-1050    

DOI:10.1002/gj.3350200403

出版商:John Wiley&Sons Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractPre‐Caledonian basement is exposed in three areas within the Irish orthotectonic Caledonides: 1. In northwest County Mayo the Erris Complex comprises the Annagh Division, which is largely Grenvillian but includes older gneisses, and the Inishkea Division, which is probably equivalent to the older Moines of Scotland. 2. In the northeast Ox Mountains, Rosses Point and Lough Derg inliers there is a granulite fades, dominantly metasedimentary basement which is probably late Grenville in age. 3. Laxfordian and probably older gneisses are seen in the Inishtrahull Platform northeast of Malin Head, County Donegal.In addition, some gneisses within the belt of ‘Connemara migmatites’ in south Connemara may be fragments of allochthonous basement and some high grade metamorphic rocks in the Tyrone Central inlier have been referred to as pre‐Caledonian basement, but there is at present no conclusive support for these suggestions. The Ox Mountains succession seen in the Clew Bay region and the southwest and central Ox Mountains is probably not pre‐Caledonian basement.Basement in the paratectonic Caledonides is confined to the Cadomian and possibly pre‐Cadomian Rosslare Complex (older than 625 Ma) and the nearby late Precambrian (to early Cambrian ?) Cuilenstown Formation in southeast County Wexford. In addition, an unseen block of basement defined by magnetics immediately to the north of the Dingle peninsula of County Kerry is probably of Rosslare Complex affinity. Granulite facies xenoiiths recovered from volcanic rocks of Carboniferous age about 70 km to the west of Dublin, indicate the character of basement there, though its age is not proven.All contacts between basement and Lower Palaeozoic Caledonian cover in the orthotectonic Caledonides are synmetamorphic slide zones and faults and in the paratectonic Caledonides the contacts are either faults, which are often rooted in older mylonites, or are unexposed and presumed to be major struct

ISSN:0072-1050    

DOI:10.1002/gj.3350200404

出版商:John Wiley&Sons Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractINTAL is an expert system which will identify igneous rocks in the hand specimen on the basis of a description given to the computer by an inexperienced geologist. It assumes only that the user can identify the common rock‐forming minerals and has a rudimentary knowledge of the jargon of an igneous petrographer. The computer has no control over the user's initial description, which is freely written in English, and only partial control over any subsequent interactive dialogue. INTAL is programmed in BASIC and may be used on a small microcomputer. The program works by repetitively scanning all user input for significant keywords until the attributes of a production rule are assembled and the rock is identifie

ISSN:0072-1050    

DOI:10.1002/gj.3350200405

出版商:John Wiley&Sons Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThe Pallaskenry Borehole, Co. Limerick, Ireland provides an almost complete Courceyan (Dinantian) succession from Old Red Sandstone facies up to Waulsortian limestones. A revised lithostratigraphic‐al nomenclature for this succession is presented. Examination of the conodont and coral faunas in the borehole has enabled biozones to be defined which can be recognized throughout the Limerick Province. Biostratigraphical correlations are made with Courceyan successions at Hook Head, Co. Wexford, in the Mendip Hills and in Knap Farm Borehole in the Southwestern Province of Britain. Conodont taxa show a clear distinction betweeen the shelf faunas of the Limerick Province, Hook Head and eastern Mendip, and distal shelf faunas from south Cork, Knap Farm and Dinant, Belgium, which probably reflect their different palaeogeographical positions.Acknowledgements.The authors wish to express their thanks to Professor G. D. Sevastopulo, Drs. R. L. Austin, J. R. Nudds and P. Strogen and Mr. M. Mitchell for constructive criticism of the manuscript. We would also like to thank Dr. T. R. Reilly, Mr. C. McDermot and Dr. A. Sleeman of the Geological Survey of Ireland, and Dr. M. E. Philcox for fruitful discussion on the Iithostratig‐raphical nomenclature. G. LI. Jones was a Research Fellow at Trinity College, Dublin during the period of this work. He was funded through the Upper Palaeozoic Atlas of Ireland (UPAIR) Project, financed by the Department of Energy and administered through the Geological Survey of Ireland and Trinity College. He gratefully acknowledges the organization and supervision provided by Professors C. H. Holland and G. D. Sevastopulo and Dr. D. Naylor; and the assistance with conodont processing given by Ms. B. Thornbury. Thanks are also extended to Mr. J. Kennedy and Mr. P. Moffat for assistance with the diagr

ISSN:0072-1050    

DOI:10.1002/gj.3350200406

出版商:John Wiley&Sons Ltd    

年代:1985

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350200407

出版商:John Wiley&Sons Ltd    

年代:1985

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350200409

出版商:John Wiley&Sons Ltd    

年代:1985

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350200410

出版商:John Wiley&Sons Ltd    

年代:1985

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350200411

出版商:John Wiley&Sons Ltd    

年代:1985

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350200412

出版商:John Wiley&Sons Ltd    

年代:1985

数据来源: WILEY