摘要:

AbstractSince reference is made from time to time to examples of supposed subaqueous sliding on a large scale in the Silurian rocks (Salopian Series) of Denbighshire, North Wales, for the purpose of supporting inferences about the mode of origin of certain intraformational disturbances, the stratigraphical evidence in Denbighshire is reviewed. On the basis of zoning by means of graptolites (or shelly faunas where available), the boundaries of the alleged sheets of slipped material prove to be transgressive. In particular, the largest ‘contemporaneously‐disturbed’ sheet includes parts of the undisturbed succession ranging in age from thenilssonizone to thetumescenszone. Its supposed base would have to cross its supposed surface, so that it would appear to have a negative thickness—of minus 1,000 feet or more. Acceptance of the hypothesis of large‐scale sliding on the sea‐floor in this area is thus incompatible with a belief in the value of graptolites as zonal indices in the Sal

ISSN:0072-1050    

DOI:10.1002/gj.3350010202

出版商:John Wiley&Sons Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractFollowing a brief review of the previous work in the area, the existence of a small lake in the Sabden Valley, the gradual development of Lake Accrington and its subsequent division into Lakes Altham and Blackburn, are discussed in detail. Evidence is also given for the formation of a large lake (Lake Ribchester) in Ribblesdale. The paper also describes the later history of the Altham‐Ribchester‐Blackburn drainage, the origin of the Feniscowles and Hoghton Gorges, the final unsealing of the Ribble Basin, and the formation and history of Lake Hacking in Ribblesd

ISSN:0072-1050    

DOI:10.1002/gj.3350010203

出版商:John Wiley&Sons Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractThe development of an impersistent band of non‐marine shells immediately underlying theGastrioceras subcrenatummarine band and referred toCarbonicola ? lenisulcata(Trueman) andC. ? aff. bellula(Bolton) is traced over much of the area of outcrop of the Lower Coal Measures in Yorkshire and Lancashire. The fauna of an underlying local leaf in the Sheffield area is referred toCarbonicola aff. proteaWright. The shells of both faunas show allometric growth with respect to their height and length.Differences in the petrology of the main non‐marine shell band in five localities have been investigated optically by Professor K. C. Dunham and Mr. T. Deans, and by chemical analysis. What appear to be regional changes in the nature and range of variation of the shells reveal a correlation with petrological change closely comparable with that found in passage upward through the lower parts of cyclic units of sedimentation in the Soft Bed — Bassy Mine succession (Eagar 1947). Changes in the variation of the faunas, when they are traced horizontally on this single horizon, are however, of considerable smaller magnitude than those of the latter. Thus a fauna of dominantly anthraconaioid elongate shells, occurring in fine‐grained richly carbonaceous shale, shows greater variation and an increasing proportion of relatively shortCarbonicolae?as it is followed into shaly mudstone with larger detrital constituents and less carbonaceous matter. The relative proportions of carbonaceous matter, varying inversely with thickness of the band and amount of shells per unit thickness, suggest that sedimentation caused reduction in size in two localities. The significance of the clay‐mineral content and of pyrite, which is unusually abundant and present with framboidal texture in the band, is brieflly discussed. It is suggested that the water was brackish during the formation of the band and that possibly unusually saline or near‐marine conditions may ha

ISSN:0072-1050    

DOI:10.1002/gj.3350010204

出版商:John Wiley&Sons Ltd    

年代:1952

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350010205

出版商:John Wiley&Sons Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractThe geological section exposed in a deep boring for water in the Millstone Grit near Darwen, Lancashire, is described. Details are given of the lithology and palaeontology throughout a thickness of 700 ft. of rock, extending from the Holcombe Brook Grit well into the Fletcher Bank Grit. In discussion, the rhythmic character of sedimentation is emphasised, and attention is also particularly drawn to the importance of marine bands (withGastriocerasaff.sigma, Reticuloceras reticulatumearly mut. γ and late mut. β) and aLingulaband in determining the Grit

ISSN:0072-1050    

DOI:10.1002/gj.3350010206

出版商:John Wiley&Sons Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractA series of morainic deposits, regarded as due to corrie‐glaciation, is described from the Upper Eden Valley on Mallerstang and Ravenstonedale Commons. They lie between 1,250 and 2,000 O.D., chiefly around 1,500‐1,750 O.D. Well‐marked moraines, both lateral and transverse, are present, as well as typical hummocky morainic topography. Some of the glaciers issued from typical corries, and there are transitions from these to long, slightly recessed scars, likewise developed in the basal Millstone Grits. The corrieglaciation is regarded as later than the main Dales and Edenside glaciation' and may be contemporaneous with a recently‐discovered solifluction deposit on the Lunds to the south, in the Upper Ure Valley, and with outwash fans in Ravenstonedale at the foot of the Howgil

ISSN:0072-1050    

DOI:10.1002/gj.3350010207

出版商:John Wiley&Sons Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractThe Silurian rocks of Cwm Graig Ddu consist mostly of blue and grey shales and mudstones, all of Ludlow age, the succession extending from thenilssoniZone of the Lower Ludlow to theHolopellaGrits and Shales at the top of the Upper Ludlow. They are overlain by the Tilestones of the Lower Downtonian. The rocks are exposed along the side of the Brecon road on the western side of the valley, in the cliffs at its head, and in the roadside quarries beyond its head. The succession, generally, closely resembles that of the Builth district, but differs in detail. The Lower Ludlow rocks contain many slumped bands which vary in thickness from several inches to many feet.

ISSN:0072-1050    

DOI:10.1002/gj.3350010208

出版商:John Wiley&Sons Ltd    

年代:1952

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350010209

出版商:John Wiley&Sons Ltd    

年代:1952

数据来源: WILEY