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The only known regional dyke swarm in New Zealand is described. Dykes are 1·5–2 feet thick and have been intruded vertically into unconsolidated Cretaceous sediments. The present attitude of dykes is found to be affected by compaction of these sediments and by regional folding and bedding-plane slip. A rough measure of total compaction is obtained.
Lower Carboniferous strata are shown to be absent from the Amazon basin and Ghana, the Bermejo series of Bolivia is Permo-Triassic, the Sekondi series of Ghana does not include glacial deposits and may prove to be Devonian, early Carboniferous glaciation is unknown in Africa and restricted to Argentina in South America. In the light of these interpretations the extent to which late Carboniferous glaciation affected northern South America and Africa is briefly reviewed and shown to conflict with the reconstructions by L. C. King (1958). The non-glaciation of Africa and South America north of at least latitude 25 degrees South during early Carboniferous times is regarded as proving that these areas did not pass through the south polar region at that time. The known distribution of early and late Carboniferous glacial deposits is considered in relation to continental drift and movement can only have been westwards during the Carboniferous period.
A sequence of reversed graded beds occurs in a group of flaggy rocks intercalated within the Upper Dalradian grits of Inishowen. Usually these beds have a thickness between ½ inch and 2 inches, and are characterized by a laminated, argillaceous base which grades up into a fine-grained, arenaceous upper member.
Evidence is presented which shows that nepheline develops a preferred c-axis orientation in response to deformative stresses. It is believed that this is the first record of a stress-induced preferred orientation of nepheline.
Regional variations in modal analyses of the Chandos Lake pluton (Ontario) and the Beinn an Dubhaich granite are compared. Trend surface analysis maps for the latter area show a southwest “grain” parallel to the axis about which King (1960) suggested the sheet of granite is folded. The modal data thus appear to confirm King's hypothesis, and to indicate a more mafic base and increase in quartz content upwards through the sheet. The value to petrogenesis of quantitative variation studies of rock masses is briefly discussed.
An unusual fayalite-bearing quartz-monzonite occurs around Bauchi in Northern Nigeria and is distinguished from the high-level fayalite granites of the Newer Granites ring complexes by the presence of a linear structure conformable with those in the surrounding rocks, the gradational nature of its contacts, the extreme coarseness of its mineral constituents and the abundance of myrmekite. It is similar to them in its distinctive green colour and in the high FeO: Fe2O3 ratio. The rock is believed to be definitely older than the rocks of the ring-dyke complexes.
The distribution of alpha radioactivity in thin sections of Shap granite is discussed and more than 95 per cent of the activity is shown to be concentrated in the accessory minerals. The results of this study are compared with those obtained for the Adamello granodiorite by other workers using similar techniques.
Two adjacent areas of intrusive plutonic rocks, occurring in western Iceland are briefly discussed. These intrusions are of gabbros and granophyres, believed to be of Tertiary age, of types closely comparable to those of S.E. Iceland.
A new genus, Levifenestella, is erected, with L. maeve n.sp. from the Tournaisian of Co. Sligo, Ireland, as type species. A new species of Fenestella, F. polynodosa, from the same horizon and locality, is described. A Russian species, F. rossica Shulga-Nesterenko, is recorded from the Tournaisian of Hook Head, Co. Wexford.
Underground borings through the Lower and Middle Coal Measures beneath the Firth of Forth have proved sequences of rhythmically bedded volcanic detritus and a thin basalt lava. The detritus is believed to have been derived from a contemporaneous cinder cone or cones previously located by an off-shore boring. The new evidence suggests that locally there was an eastward shift of focus of eruption during Coal Measure times. The relationship of volcanism to this type of rhythmic sedimentation is discussed.
Methods of impregnating clays with the cement Lakeside 70C and two resins of the Araldite range are described and some details of the techniques of mounting and grinding specimens are included.
The Skiddaw Group between Buttermere and Troutbeck is approximately 6,000 feet thick and can be subdivided into four formations which in ascending order are: Hope Beck Slates; Loweswater Flags; Mosser-Kirk Stile Slates; Latterbarrow Sandstone. The coarser elastics exhibit most of the characteristics of sediments deposited by turbidity currents. The source of these deposits is thought to lie to the south. The occurrence of contemporaneous vulcanism in the Loweswater Flags on Watch Hill has been confirmed. Tourmaline and andalusite are recorded for the first time from the metamorphic aureole east of Crummock Water.