摘要:

AbstractSeismic refraction profiles have been established in Eastnor Park (SO 745375) and in the Storridge area (SO 750486), respectively west and north of the Malvern Hills. The seismic results can be explained by a three‐layered subsurface configuration. Layers 1 and 2 are roughly equivalent to Silurian and Cambrian strata and layer 3 is regarded as Precambrian basement.Under both profiles the Cambrian is much thinner than at the southern end of the Hill range where Groom (1902) estimated a minimum thickness of 2,500 ft (762 m). In Eastnor Park the basement dips westwards at about 10° and is overlain by approximately 1,000 ft (305 m) of Cambrian strata. At the western boundary of the Malvern Hills the Cambrian appears to be cut out locally by a pre‐LIandovery fault.In the Storridge area the seismic results are consistent with a shallow basement overlain by a few hundred feet of Cambrian strata, as suggested in an earlier paper on the basis of gravity and magnetic interpretations (Brooks 1

ISSN:0072-1050    

DOI:10.1002/gj.3350060202

出版商:John Wiley&Sons Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractGravity and seismic surveys over the estuaries of the rivers Dovey, Dysynni, Glaslyn and Mawddach have indicated that the rock floor lies at depths of from 100 to 1,250 ft (30 m to 380 m) below the present surface. The methods of survey and difficulties of interpretation are discussed, and the significance of the results is assessed in conjunction with those already published for the Teifi estuary and with preliminary results obtained by seismic reflection profiling in. Cardigan Bay. It is concluded that all the valleys with the exception of the Glaslyn could have been carved during Pleistocene times, but that the much deeper buried valley of the Glaslyn, extending south of Portmadoc across Morfa Harlech, is probably of earlier origin.

ISSN:0072-1050    

DOI:10.1002/gj.3350060203

出版商:John Wiley&Sons Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractThe Viséan sediments between Rhydymwyn and Erryrys have been mapped and divided into a number of lithologic units. A combined study of field relationships and petrography has been made and conclusions have been drawn about depositional environments

ISSN:0072-1050    

DOI:10.1002/gj.3350060204

出版商:John Wiley&Sons Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractA brief description of the carboniferous succession on Halkyn Mountain, North Wales, together with a map illustrating the areal distribution of upper Viséan carbonate and Namurian non‐carbonate lithologies, is presented. The upper Vistan carbonates have been divided into four major units termed in ascending order: A1 (pelsparites and biopelsparites); A2 (alternating biopelmicsparites, non‐argillaceous biomicrites and micrites); B1 (argillaceous calcite siltstones); B2 (alternating non‐argillaceous and argillaceous biomicrites and micrites). Analysis of the distribution of microfacies within each unit indicates that during upper V i s h times, deposition of shallow water, off‐shore, carbonate sand banks alternated with, and finally gave way to, the deposition of in‐shore, lagoonal carbonate muds. The presence of an erosional surface at the top of Unit B2 suggests that a period of emergence took place prior to the deposition of the succeeding Namurian bedded cherts. The cherts can be differentiated into three major lithologies which exhibit characteristics that are consistent with cyclic deposition in a marginal, restri

ISSN:0072-1050    

DOI:10.1002/gj.3350060205

出版商:John Wiley&Sons Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractAlthough the deformation of foliated rocks by kink and glide mechanisms has been studied in detail in recent years, fundamental differences of opinion have emerged, particularly as a result of experimental work. Most theories concerning the relationship of kink‐bands to stress‐fields are empirically based. Evidence on whether kink‐bands are the result of a shear couple and on limiting factors for external rotation is presented. It is concluded that kink‐bands are zones of externally rotated foliation bounded by kink‐planes which develop parallel to planes of high shearing stress at infinitesim

ISSN:0072-1050    

DOI:10.1002/gj.3350060206

出版商:John Wiley&Sons Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractA study of the chemistry, circulation and sedimentation is followed by an outline account of the living and dead communities (particularly foraminifera) characteristic of the main physiographic subenvironments. On the basis of the relationships established these results are used in an interpretation of the vertical sequence.

ISSN:0072-1050    

DOI:10.1002/gj.3350060207

出版商:John Wiley&Sons Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractEight species of Bryozoa, two of them new, have been noted from limestones and calcareous shales of the Lower Limestone Group from Hessilhead Quarry, Beith.

ISSN:0072-1050    

DOI:10.1002/gj.3350060208

出版商:John Wiley&Sons Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractNamurian cliff sections are described in detail. A minimum thickness of about 76 m is ascribed to Namurian A and 198 m and 104 m respectively to Namurian B and C. Faunal marker bands enable the Chokierian, Marsdenian and Yeadonian Stages to be recognised and the detailed structure to be worked out and this confirms the structural interpretation of Dixon. The succession is correlated and compared with adjacent areas in Pembrokeshire and South Wales. The Marsdenian includes a fauna of highly variableSanguinolites. S. ovalisHind is redescribed and a lectotype chosen.

ISSN:0072-1050    

DOI:10.1002/gj.3350060209

出版商:John Wiley&Sons Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractThe distribution of eleven different patterns of magnetic anomalies over the maps is shown. The individual patterns overlying the land are correlated with the underlying geology, and on the basis of this correlation a geological interpretation of the sea areas of the aeromagnetic survey is proposed. The outcrops of crystalline rocks are largely confined to the present land areas, so that in most places the sea floor is composed of Devonian or younger rocks. The Newer Granites are classified into three types based on their magnetic properties. The Great Glen fault passes through Shetland where it causes a 65 km dextral displacement of the Devonian rocks and an unknown but possibly much larger displacement of the older rocks.

ISSN:0072-1050    

DOI:10.1002/gj.3350060210

出版商:John Wiley&Sons Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractMasirah Island is almost entirely composed of a highly faulted and unmetamorphosed folded ophiolite complex which is unconformably overlain by unfolded Eocene limestone and is correlated with the Upper Cretaceous Semail Complex of the Oman Mainland. The ophiolites include serpentine, basalt, pyroclastics and some radiolarite, and intrusive complexes largely composed of serpentine, peridotite, picrite, anorthosite, gabbro and granite, with transitional varieties. Emplacement structures within the intrusions are extremely complicated, with the gabbros full of blocks mostly of serpentine up to 1 km or more in diameter. There are also late stage veins, lenses and irregular bodies of granite. Ophiolites, probably derived from the mantle, are ultrabasic differentiates with soda metasomatism. Tectonic structures are largely pre‐Eocene. They include fractures, some of which are parallel to the late Tertiary submarine Masirah fault which is related to continental drif

ISSN:0072-1050    

DOI:10.1002/gj.3350060211

出版商:John Wiley&Sons Ltd    

年代:1969

数据来源: WILEY