摘要:

AbstractThe Carys Mills Formation of NE Maine represents the SW extension of the Matapedia Group and the White Head Formation of southern Gaspé, Quebec. This formation has yielded two main collections, one hitherto considered of Middle Ordovician age (zone 13 of Berry's 1960 Marathon, Texas, zonation) with 7 species referred to 4 genera, and one of the Early Silurian age. A revision of the supposed Middle Ordovician collections reveals that the graptolites are basal Silurian and consist of only one species,Glyptograptus? persculptus.Several hundred specimens, preserved both flattened and in three dimensions, the latter in iron pyrites, allow an analysis of both the rhabdosome changes wrought by diagenetic flattening and those caused by severe tectonic deformation. It is shown that those specimens lying parallel to the bedding plane lineation caused by a high‐angle main cleavage have a silhouette appearance close toGlyptograptus tamariscus(Nicholson), whilst those at right angles to this direction superficially resemble robustAmplexograptusspp., orDiplograptus s.s., orDiplograptus s.l.spp., thus explaining the stratigraphic assignment of earlier workers. An analogue video reshaper confirms the above conclusions.This determination assigns the whole Carys Mills Formation to the Lower Silurian, but the possibility that part of the formation is of Late Ordovician age cannot be excluded. This much is suggested by the Matapedia Group and the White Head Formation which are of Late Ordovician to Early Silurian age, and the Honorat Group, which has yielded graptolites of late Middle Ordovician a

ISSN:0072-1050    

DOI:10.1002/gj.3350160402

出版商:John Wiley&Sons Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThe Monadhliath and Leven Schists are separated north of Glen Roy by some 500m of psammitic rock. Junctions are gradational and conformable, and evidence from sedimentary structures indicates that all three face upwards. The two schists should not be equated, nor should the Monadhliath Schist be included in the Dalradian Supergroup unless the entire Grampian Division is also included.

ISSN:0072-1050    

DOI:10.1002/gj.3350160403

出版商:John Wiley&Sons Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractFluctuation of the carbon isotope composition of marine carbonates has recently been developed as a powerful tool for the identification of ocean‐wide anoxic conditions and changes in the world budget of carbon and oxygen. A change in δ13from the normal marine values (0 to + 2%) to values highly enriched in13C (+3·5 to 4·5%) is recorded at the base of the Zechstein sequence both in central Germany and northeastern England. The change occurred over a relatively short period of time indicating a rapid and pronounced change in the organic carbon/carbonate budget. Evidence from other Permian basins show similar highly enriched δ13C values. This change may correspond to that in carbon balance distinguished by the Garrels and Perry (1975) model and based on the change in sulphur isotopic composition during the Pe

ISSN:0072-1050    

DOI:10.1002/gj.3350160404

出版商:John Wiley&Sons Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractTrace fossils ofBeaconitestype are found abundantly and widely in the Old Red Sandstone magnafacies of the British Isles, particularly in fluviatile deposits, where they occur in or closely associated with channel sandstones. Because of their giant size, however, terminations to the sediment‐filled burrows are almost impossible to detect, and it has hitherto been uncertain whether theBeaconitesorganism dwelt in or near active rivers, or merely colonized the sandy deposits at their abandoned sites. At Llanstephan in southwest WalesB. antarcticusis preserved in a laterally accreted sandstone, a unique example of the trace fossil being truncated by an erosion surface cut during the sideways growth of a presumed point bar. TheBeaconitesorganism is therefore thought to have lived in and near active river channels, where a moist environment was provide

ISSN:0072-1050    

DOI:10.1002/gj.3350160405

出版商:John Wiley&Sons Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractTournaisian miospore assemblages are used to determine the age of some plant‐bearing horizons in the Old Red Sandstone succession of the Slieve Bloom Mountains, Counties Laois and Offaly, Ireland, and the sedimentology and conditions of deposition of the productive lithologies are described. The age of the marine transgression which terminated continental sedimentation is indicated, and the associated depositional environment is discussed. Comparisons are made with other micro‐ and macrofloras from Ireland, Britain, Canada, the U.S.S.R. and Bear Isl

ISSN:0072-1050    

DOI:10.1002/gj.3350160406

出版商:John Wiley&Sons Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractParticle size, pebble shape, pebble fabric, discharge and flow velocity data are used to introduce a model of sandy gravel formation in Welsh gravel‐bed rivers. The development of contact‐imbrication of the typically very bladed and very platy cobbles and larger pebbles subsequently acts to significantly affect the depositional modes and patterns of small pebbles and sand particles. An important distinction is drawn between sand deposition, which can occur at or below the bed surface, and pebble and cobble deposition, which is merely a surface phenome

ISSN:0072-1050    

DOI:10.1002/gj.3350160407

出版商:John Wiley&Sons Ltd    

年代:1981

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350160409

出版商:John Wiley&Sons Ltd    

年代:1981

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350160410

出版商:John Wiley&Sons Ltd    

年代:1981

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350160411

出版商:John Wiley&Sons Ltd    

年代:1981

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350160401

出版商:John Wiley&Sons Ltd    

年代:1981

数据来源: WILEY