摘要:

AbstractFining‐upwards cycles on a scale of thickness from a few metres to a few tens of metres, and consisting of a coarse grade member (erosive base) overlain by a fine grade member, are the hall‐mark of a distinct non‐marine sedimentary facies widely distributed in space and time. Using data on modern alluvial sediments, it is shown that the interpretation of the cycles in terms of an alluvial environment is probably correct. The cyclicity itself cannot yet be accounted for, although three principal factors are likely to have been inv

ISSN:0072-1050    

DOI:10.1002/gj.3350040201

出版商:John Wiley&Sons Ltd    

年代:1965

数据来源: WILEY

摘要:

AbstractCertain flow‐banded and fragmental rocks amongst the Moelwyn Volcanic Series are shown to be of intrusive origin, although at one time they were believed to be extrusive lavas, ashes and agglomerates. Thus the thickness and extent of the volcanic rocks are greatly reduced. New palaeontological evidence shows that part of the Moelwyn Volcanic Series is Caradocia

ISSN:0072-1050    

DOI:10.1002/gj.3350040202

出版商:John Wiley&Sons Ltd    

年代:1965

数据来源: WILEY

摘要:

AbstractThe law of growth of the left valve inGryphaea arcuatais investigated, and it is shown that it is possible to define a growth‐invariant measure of tightness of coiling.Recent papers by A. Hallam and G. M. Philip are discussed. The latter author's conclusions are shown to be based upon premises which are untenable. It is here concluded that there is a change in tightness of coiling from theangulatato thegmuendense‐bucklandihorizons at the Glamorgan, Yorkshire, and S. England localities from which Hallam collected his samples ofGryphaeashells. The trend is towards less tightly coiled shells in the higher beds, amounting to an average reduction of a few millimetres in peripheral length at an arbitrary constant radius of 20 mm. There are differences between localities of the same order of magnitude, and it is therefore proper to adopt a cautious attitude towards this result. It is however clear that the pronouncedapparentincrease in shell coiling originally reported by Trueman in 1922 is simply the direct concomitant of increased s

ISSN:0072-1050    

DOI:10.1002/gj.3350040203

出版商:John Wiley&Sons Ltd    

年代:1965

数据来源: WILEY

摘要:

AbstractTwenty feet to thirty feet of black shale, phosphorite and limestone exposed near Welshpool, Montgomeryshire, exhibit a facies which enables a correlation to be made between the Welsh graptolitic Nod Glas shales of Caradoc age and the shellyOnniaBeds of south Shropshire.Graptolitic evidence suggests that the visible thickness of the Nod Glas near Welshpool belongs to the top of theDicranograptus clinganizone, and the shelly fauna indicates the zone ofOnnia gracilis.At the base of the Nod Glas throughout Montgomeryshire is a phosphatic horizon of variable development.

ISSN:0072-1050    

DOI:10.1002/gj.3350040204

出版商:John Wiley&Sons Ltd    

年代:1965

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350040205

出版商:John Wiley&Sons Ltd    

年代:1965

数据来源: WILEY

摘要:

AbstractTrilobites and brachiopods are described and figured from the Caradoc Series of the Twll Ddu district, northeast of Snowdon. They indicate a Longvillian age for the Banded Pumice Tuffs of the Bedded Pyroclastic Series, and exhibit affinities with corresponding faunas in South Shropshire as well as other parts of North Wales and Northern England.

ISSN:0072-1050    

DOI:10.1002/gj.3350040206

出版商:John Wiley&Sons Ltd    

年代:1965

数据来源: WILEY

摘要:

AbstractStructures in an Ordovician inlier are described and regional conclusions are reached from the evidence at this critical locality.

ISSN:0072-1050    

DOI:10.1002/gj.3350040207

出版商:John Wiley&Sons Ltd    

年代:1965

数据来源: WILEY

摘要:

AbstractThe Los Ajaches area, Lanzarote, Canary Islands consists of a Tertiary volcanic series overlain by Quaternary lava areas. A trachyte outcrop, the only acid volcanic rock on the island, was relocated and mapped during a survey in 1963. Erosion stages at heights of 460, 400, 300, 190 and 100 m, occur in the eastern highlands. The coastal plain has a remarkable raised beach succession at heights of 55,35,25,15,6. and 1 m. This chronological sequence enables a new dating of the Quaternary vulcanism. Certain observations are also made on landform development and correlation with other areas.

ISSN:0072-1050    

DOI:10.1002/gj.3350040208

出版商:John Wiley&Sons Ltd    

年代:1965

数据来源: WILEY

摘要:

AbstractBouguer gravity anomalies in Wales are shown on a quarter‐inch to the mile scale and are described. Regional and residual anomalies are presented on maps, and the origin of the main residual anomalies is discusse

ISSN:0072-1050    

DOI:10.1002/gj.3350040209

出版商:John Wiley&Sons Ltd    

年代:1965

数据来源: WILEY

摘要:

AbstractThe late Pre‐Cambrian Portaskaig Boulder Bed Series shows a very uniform sequence for some 600 km along the Caledonian strike, from Connemara on the west coast of Ireland to Aberdeenshire in Scotland. The Series, which is divided into four groups of beds, comprises numerous individual boulder beds separated by stratified sediments. The lower boulder beds are carbonate‐bearing and contain abundant intrabasinal fragments of dolomite and few extrabasinal crystalline rocks while the higher beds are psammitic and contain mainly extrabasinal crystalline rocks. Varve‐like banding, involutions and sandstone polygons suggest periglacial conditions. It is concluded that the boulder beds represent subaqueous tills deposited on unconsolidated sediments. Contemporaneous deformation of some of these sediments is attributed to the movement of ice, although the possibility that sliding of the unconsolidated sediments occurred locally is consi

ISSN:0072-1050    

DOI:10.1002/gj.3350040210

出版商:John Wiley&Sons Ltd    

年代:1965

数据来源: WILEY