摘要:

AbstractExisting facies models for peritidal carbonates are limited in number and do not reflect the wide spectrum of possible types. The major depositional processes in peritidal carbonate environments are reviewed in order to stress the complex nature of the systems. The tidal channel model is critically discussed and it is suggested that channel deposits may be of minor importance in typical shoaling‐up sequences. The possible causes of multiple asymmetrical sequences are reviewe

ISSN:0072-1050    

DOI:10.1002/gj.3350190402

出版商:John Wiley&Sons Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe fossil plant distribution in the Carboniferous of Saarland indicates that the base of the Westphalian D is in the upper Luisenthal Formation. Two distinctive changes in the middle Westphalian D floras are noted in the Heiligenwald Formation, very similar to those reported in the Upper Pennant Measures of South‐Wales. These changes in the floras, recognizable in two distantly separated coalfields, are made the basis of a threefold biozonation of the Westphalian D. This is the most detailed biostratigraphical resolution presently available for non‐marine strata of this

ISSN:0072-1050    

DOI:10.1002/gj.3350190403

出版商:John Wiley&Sons Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractMt. St. Hilaire occurs as a small funnel‐shaped intrusion in the Monteregian petrographic province of Quebec and consists of alkali gabbros and later nepheline syenites. Based on field relations, petrography, and geochemistry, five types of gabbro are recognized. In order of intrusion these are: leucogabbro, foliated gabbro, kaersutite‐biotite gabbro, kaersutite gabbro, and a gabbro‐melagabbro series. Based on analyses of the early‐forming ilmenite‐titanomagnetite, the gabbros crystallized under high fO2conditions which lead to subsequent crystallization of olivines with high MnO contents. Fractionation of ilmenite and titanomagnetite was a major control on the Ti and A[TV]concentrations in the clinopyroxenes. Plagioclase compositions in the gabbros became richer in Ab contents in the sequence gabbro‐melagabbro to leucogabbro. Whole‐rock analyses suggest that the parental magma of alkali basaltic composition was fairly evolved prior to emplacement. Lack of olivine in the cumulate gabbro‐melagabbros and low Ni and Cr in all gabbros may reflect either extreme olivine fractionation and/or a very low olivine content in the source material for these basalts. Differentiation of the gabbros occurred both pre‐ and post‐emplacement, probably by a process of crystal‐liquid fractionation at depths between 3‐5 and 8 km. This is in accordance with geophysical measurements for other Monteregian intrusions. A model is presented for the m

ISSN:0072-1050    

DOI:10.1002/gj.3350190404

出版商:John Wiley&Sons Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractAn unusual matrix‐supported microbreccia of Caledonian age is described from the Dalradian rocks of Donegal. Field and textural relationships indicate that the breccia formed ‘in situ’ by a non‐dilational mechanism during regional deformation. The presence of breccia veins of low competancy during this deformation caused multi‐décollement folds to be formed adjacent to the breccias. A cyclical mechanism of formation of these breccias is proposed in which fluctuations in the overpressuring of pore fluids escaping from an adjacent crystallizing appinite mass caused periodic excursions from ductile to brittle deformation during the region

ISSN:0072-1050    

DOI:10.1002/gj.3350190405

出版商:John Wiley&Sons Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe Lough Talt and Easky adamellites in the north‐central Ox Mountains inlier were originally regarded as being nearly synchronous in age of emplacement with the more strongly deformed c. 480 Ma Ox Mountains granodiorite. They are now shown by Rb‐Sr whole‐rock dating to be significantly younger at c. 400 Ma. This recognition of the emplacement of late Silurian/early Devonian Newer Caledonian granites in the central Ox Mountains inlier indicates that the thermal overprinting by the adamellites of the regionally metamorphosed Ox Mountains succession is not an early Ordovician event. Earlier interpretations, using deformationai events and igneous intrusions, advanced by others to suggest that the Ox Mountains succession is pre‐Caledonian are now greatly weakened since the deformationai sequence in the Ox Mountains succession is now known to span a longer period of time, ranging from Grampian (late Cambrian to early Ordovician) to Caledoniansensu stricto, and therefore leaves fewer events to have occurred prior to the early Ordovician emplacement of the Ox Mountains grano

ISSN:0072-1050    

DOI:10.1002/gj.3350190406

出版商:John Wiley&Sons Ltd    

年代:1984

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350190408

出版商:John Wiley&Sons Ltd    

年代:1984

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350190409

出版商:John Wiley&Sons Ltd    

年代:1984

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350190401

出版商:John Wiley&Sons Ltd    

年代:1984

数据来源: WILEY