摘要:

AbstractA suite of Caradocian trace fossils from the Berwyn Hills, Central Wales, are examined. They include forms produced by trilobites (Cruziana, Rusophycus, Trichophycus, Monomorphichnus), pelecypods (Lockeia), ?gastropods (?Imponoglyphus) and traces of debatable affinity probably produced by oligochaete and polychaete annelids, amphipods and crustaceans (Skolithos, Planotites, Teichichnus, Diplocraterion, Arenicolites, ?Gyrochorte, ?Palaeophycus, Vermiforichnus). Representatives of theSkolithosandCruzianacommunities coexist in this assemblage and no subdivision into discrete ichnofacies is therefore possible. The trace fossils are examined in terms of their relationship to the structure and composition of Upper Ordovician communities and it is concluded that substrate and ecological controls were more important limiting environmental parameters than depth.

ISSN:0072-1050    

DOI:10.1002/gj.3350120101

出版商:John Wiley&Sons Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractGravity measurements across the southern margin of the Galway granite, on the Islands of Gorumna and Lettermullen, reveal small positive Bouguer anomalies of amplitudes less than 40 g.u. associated with the denser country rock. These anomalies suggest that the ‘country rock’ is no more than a thin wedge, thickening southwards. Such a structure may form part of a large roof pendant or roof section with the true granite margin lying further south. Magnetic anomaly profiles across the granite contact reveal that the rock groups, making up the country rock, have distinct magnetic character which may provide a means of mapping their southern extent beneath Galway

ISSN:0072-1050    

DOI:10.1002/gj.3350120102

出版商:John Wiley&Sons Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe cuticie of the lobsterHoploparia longimana(Sowerby) from the Cambridge Greensand (Upper Cretaceous), when etched in E.D.T.A. and examined with the scanning electron microscope, reveals detail of ultrastructure not previously described from any fossil arthropod cuticle. The fibre patterns of laminae and inter‐laminae are described and interpreted by comparison with those in modern crustacean cuticles. Horizontal tubules at the laminae may represent a lamina membrane. The pore canals are round with fibrous walls and are surrounded by elliptical voids, possibly originally occupied by vertical fibres. Wider canals, around 15 μm in diameter, are probably setal ducts. The cuticle is now largely composed of an apati

ISSN:0072-1050    

DOI:10.1002/gj.3350120103

出版商:John Wiley&Sons Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractFour phases of deformation (D1‐D4) and a ubiquitous non‐tectonic bedding‐cleavage are described. D1 structures are gravity collapse folds without an associated cleavage, formed before the extrusion of the Borrowdale Volcanics. Pre‐Bala folds recognised in the Volcanics are not readily observable in the Slates on a small scale, but may be present on a wider aspect. D2‐D4 folds and cleavages are end‐Silurian structures, the result of the main closure of the Lake District Geosyncline during the Caledonian Orogeny. D2 is the result of crustal shortening and is closely related in time to the emplacement of the Skiddaw Granite; D3 resulted from vertical shortening in conjunction with the intrusion of the Lake District Batholith; and D4 resulted from post‐granite shortening of the existing fold axes. A correlation of the history of deformation with those of other areas is a

ISSN:0072-1050    

DOI:10.1002/gj.3350120104

出版商:John Wiley&Sons Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractA recently driven sewer tunnel west of Blackburn has shown the presence of a thick turbidite sequence between theR. gracileandR. bilingueGoniatite Bands. Above theR. bilingueBand, turbidites pass up through delta slope deposits into delta top fluviatile sandstones, derived from the northeast. The section provides evidence for the westward limit of advance of the pre‐R. gracileKinderscoutian delta slope and also enables a more accurate R2isopachyte map to bc draw

ISSN:0072-1050    

DOI:10.1002/gj.3350120105

出版商:John Wiley&Sons Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe Rosroe Formation is established as the lowest part of the Llanvirn succession exposed on the southern limb of the Mweelrea‐Partry Syncline. Lithological description is followed by interpretation in terms of two structurally controlled submarine fans, developed at the southern margin of the South Mayo Trough. A review of stratigraphic relations between succeeding parts of the Llanvirn succession leads to reinterpretation of the closing marine phases of the South Mayo Trough: northward slope progradation is inferred to have resulted in graduai northward spread of shallow water and emergent condition

ISSN:0072-1050    

DOI:10.1002/gj.3350120106

出版商:John Wiley&Sons Ltd    

年代:1977

数据来源: WILEY