In a recent letter to this journal, Stewart and Wager (1947) record the occurrence of rhythmic banding in the Cuillin gabbro of Skye. Apparently, before this the only described British example of rhythmic, banding was in the Belhelvie Complex of Aberdeenshire (Stewart, 1946). In view of the interest in these structures aroused by Wager and Deer's vivid and illuminating account of the Skaergaard Complex of East Greenland (Wager and Deer, 1939), a preliminary note on a more accessible occurrence where rhythmic banding is very beautifully displayed, in excellent quarry sections, seems desirable. This occurrence is in the Huntly complex of Aberdeenshire.

The Okenyenya gabbro–syenite complex, one of a number of intrusive igneous complexes of late-Mesozoic age in northwestern Namibia, was emplaced at the time of opening of the South Atlantic Ocean. The 5-km-diameter complex comprises a wide variety of rock types that can be subdivided into two contrasting magmatic suites, one tholeiitic and the other alkaline, which were emplaced in close proximity over a time-span of ~5 Ma. The tholeiitic suite of rocks includes picritic gabbro, olivine gabbro through quartz monzodiorite and syenite, whereas the alkaline suite includes alkaline gabbro, essexite, nepheline syenite and a range of lamprophyric rock types. Detailed petrographic, mineralogical and bulk rock geochemical data show that the earliest, saucer-shaped, intrusion of olivine gabbro–quartz monzodiorite rocks can be subdivided into an Inner Zone and an Outer Zone (each comprising three distinct intrusive units). The individual units can be readily distinguished on the basis of bulk rock geochemical variations, together with cryptic and modal mineralogical variations. An unusual feature of the intrusive body is that bulk rock and mineral compositions become more evolved with apparent depth, within the body as a whole and within each unit. Compositional variation within the individual intrusive units requires a complex interplay between in situ crystallization, variable expulsion of interstitial melt, magma recharge, and re-equilibration of primocrysts with trapped interstitial melt. Cross-cutting dykes of picritic gabbro (MgO = 13–21 %) have compositions consistent with olivine control. Incompatible trace element ratios (e.g. Zr/Nb= 12.5 ± 1.3) suggest that the picritic gabbro magmas were derived from a distinct source region compared to that giving rise to the tholeiitic olivine gabbros (Zr/Nb = 6.8 ± 1.1).

Alkaline gabbro occupies the central region of the complex and, on the basis of major, trace and rare earth element variations, can be subdivided into four distinct intrusive bodies, interpreted as remnant magma chambers, each having experienced variable degrees of crystal accumulation. In places, magma chamber processes have given rise to centimetre-scale rhythmic layering. Incompatible trace element ratios (e.g. Zr/Nb = 4.4 ± 1.2) serve to distinguish the source region of the alkaline gabbro magmas from those giving rise to the tholeiitic suite of magmas. Younger rocks of both the tholeiitic and alkaline suites show strong evidence of the effects of extensive crystal fractionation. The quartz syenite is characterized by a strong negative Eu anomaly indicative of substantial feldspar fractionation and also shows evidence for direct contamination by earlier gabbro, whereas the syenite shows evidence for feldspar accumulation. Both syenites have geochemical characteristics suggesting consanguinity with the Outer Zone rocks of the olivine gabbro–quartz monzodiorite intrusion. In contrast, the essexite and nepheline syenite compositions are qualitatively consistent with derivation from one of the alkaline gabbro magmas by extensive fractionation of plagioclase, clinopyroxene, olivine and amphibole. The final stage of magmatism is represented by a suite of alkaline and ultramafic lamprophyres emplaced as dykes and diatremes, the latter carrying a variety of megacrystic and xenolithic material, including mantle nodules. The alternation between tholeiitic and alkaline magmatism evident within the Okenyenya complex is similar to that characteristic of the evolution of many ocean island volcanoes.

In North-East Scotland the igneous rocks have been divided into two series, whose times of intrusion were separated by the movements responsible for the foliation and disposition of the crystalline schists of that area.2 With the older series, intruded prior to or during those movements, this paper is not concerned. The younger, or non-foliated, series supplies rock types ranging from peridotite to granite. Gabbro is the chief rock in the large independent basic masses formed by the younger igneous rocks; to the more important of these masses may be given the names of the Huntly, Insch, Boganloch, Haddo, Arnage, Maud, and Belhelvie Masses. For the most part they lie within Sheets 76, 77, 86, and 87 of the 1 inch Geological Survey Map of Scotland.

The hot springs that emerge at 46 °C in the centre of Bath Spa, Somerset, are unique in the UK. The four other thermal springs in Britain are also sourced in the Carboniferous Limestone, but they emerge at significantly lower temperatures (20 to 28 °C). Bath is situated in a region of low geothermal gradient (about 20 °C/km depth) in a geological setting that seems an unlikely place for hot springs. Why then are these the only hot springs in Britain, and why are they confined to such a small (20 × 80 m) area? The explanation presented here involves a sequence of geological events involving Triassic dissolution and Pleistocene permafrost that is unique to central Bath.

The brachiopod fauna of the Gorran Quartzites of south Cornwall is described; it comprises five orthid genera. Three taxa are described under open nomenclature, and one new species is assigned to a new genus (Schalidomorthis stubblefieldi). The fauna supports the Llandeilo age suggested by accompanying trilobites. There is no brachiopod evidence to indicate that the quartzite pebbles of the Triassic Budleigh Salterton Pebble Bed are derived directly from the Ordovician of Cornwall.

Clay mineral analysis of shales in the early Liassic Lower Broadford Beds of the Hebrides reveals the presence of abundant quantities of montmorillonite whereas the Upper Broadford Beds contain illite, kaolinite and subordinate mixed layer minerals together with chlorite. Montmorillonite enrichment of the Lower Broadford Beds as a consequence of recent weathering contamination by doleritic sills can effectively be ruled out. It is argued that the montmorillonite may have been derived from the weathering of basic igneous rocks exposed in the sediment source area during Late Triassic times. By Upper Broadford Beds times, the igneous source was either eroded away or transgressed by the early Liassic sea.

Two small outcrops of harzburgite and asbestos-bearing serpentinite, occurring S of Di Zahav in eastern Sinai are the first record of ultramafic rocks from the Sinai Precambrian massif.

It has long been known that the Coniston Limestone Series of the English Lake District and surrounding areas is separable into minor divisions. As a knowledge of these will prove useful in settling the question as to the exact relation between the Couiston Limestone beds and the underlying rocks, no apology seems needed for giving a detailed account of the rocks of this series.

The literature of the subject is extensive, but we fortunately possess an excellent bibliography of works referring to the geology of the Lake District, in the appendix supplied by Mr. Whitaker to the late Mr. Ward's Memoir on the Geology of the Northern Half of the English Lake District.

A new early Cambrian sponge of sphinctozoan organization named Polythalamia americana nov. gen. et sp. is described from Nevada and Alaska, U.S.A. P. americana nov. gen. et sp. shows little resemblance to other Cambrian reported sphinctozoans, but is similar to late Palaeozoic to early Mesozoic forms from Europe and Asia, e.g. Stylothalamia and Amblysiphonella. The polyphyletic origin of sphinctozoans based upon spicule criteria from younger examples is therefore corroborated by the varied morphology and clearly widespread palaeogeographic distribution of Cambrian forms, which were hitherto recognized only from Australia. P. americana nov. gen. et sp. possesses a relatively small, globular multi-chambered calcareous skeleton, with thin but densely perforate walls and a central retrosiphonate, perforate spongocoel. The skeleton is composed of an irregular microstructure of unknown, but probable calcitic, original mineralogy. There are no spicules or primary internal structures, but secondary vesicular filling tissue is present. The pore organization, however, it directly comparable to archaeocyaths, e.g. coscinocyathines, and this character is taken to be the only synapomorphy available for taxonomic and phylogenetic purposes. Indeed, P. americana nov. gen. et sp. is closely associated with a diverse archaeocyath assemblage and draws attention to morphological similarities between some archaeocyaths and sphinctozoans, thus questioning the criteria at present used to distinguish between these groups. Accordingly, a list of nomenclatural synonymies is given to aid comparison. Coscinocyathine archaeocyaths possess chambered juvenile stages and P. americana nov. gen. et sp. is suggested to represent an aspiculate lineage of sphinctozoan grade which may be derived from forms such as Clathricoscinus by neoteny. It appears that at least three clades of sphinctozoan-grade calcified sponges were present by end of early Cambrian time and their occurrence in association with island arcs of the palaeopacific rim is confirmed.

In southeast Rhum, a Mesozoic/Tertiary sequence is preserved as a fault-bounded and rotated wedge. This is juxtaposed between Precambrian rocks (Torridonian sediments and Lewisian gneiss) and caught up in the complex structure of the Tertiary Main Ring Fault (MRF), which shows three distinct phases of movement. The Mesozoic rocks comprise fossiliferous limestone, sandstone and shale, which show differing degrees of thermal metamorphism depending on their relationships to the Layered Complex. On the basis of faunal and lithological evidence the Mesozoic sediments have been correlated with the Lower Liassic Broadford Beds. The Rhum sediments are overlain by sheared Tertiary basalts, the contact between them probably representing the original landscape unconformity. The presence of these younger strata caught up along the MRF provides crucial evidence for a major phase of central subsidence in the early history of the Rhum Tertiary volcanic centre.

A multi-mineral oxygen isotope study sheds light on the origin, cooling and alteration of Late Neoproterozoic A-type granites in the Arabian–Nubian shield of southern Israel. The oxygen isotope ratio of zircon of the Timna monzodiorite, quartz syenite and alkaline granite are within the range of mantle zircon (δ18O(Zrn) = 5.3 ± 0.6‰, 2σ), supporting the co-genetic mantle-derived origin previously suggested based on geochemical data and similar ɛNd(T) values and U–Pb ages (610 Ma). Likewise, olivine norite xenoliths within the monzodiorite (δ18O(Ol) = 5.41 ± 0.07‰) may have formed as cumulate in a parent mantle-derived magma. Within the Timna igneous complex, the latest and most evolved intrusion, an alkaline granite, has the least contaminated isotope ratio (δ18O(Zrn) = 5.50 ± 0.02‰), whereas its inferred parental monzodiorite magma has slightly higher and more variable δ18O(Zrn) values (5.60 to 5.93‰). The small isotope variation may be accounted for either by small differences in the temperature of zircon crystallization or by minor contamination of the parent magma followed by shallow emplacement and intrusion by the Timna alkaline granite. The Timna alkaline granite evolved, however, from a non-contaminated batch of mantle-derived magma. The formation of Yehoshafat granite (605 Ma; δ18O(Zrn) = 6.63 ± 0.10‰), exposed ~30 km to the south of the mineralogically comparable Timna alkaline granite, involved significant contribution from supracrustal rocks. A-type granites in southern Israel thus formed by differentiation of mantle-derived magma and upper crustal melting coevally. Fast grain boundary diffusion modelling and measured quartz-zircon fractionations demonstrate that the Timna and Yehoshafat alkaline granites cooled very rapidly below 600 °C in accordance with being epizonal. One to three orders of magnitude slower cooling is calculated for 30 Ma older calc-alkaline granites of the host batholith, indicating a transition from thick orogenic to extended crust. Significant elevation of the δ18O of feldspars occurred through water–rock interaction at moderate temperatures (100–250 °C), most probably during a thermal event in Early Carboniferous times.

A flora found in a clay lens in the Corton Beds at Lowestoft indicates a late- or full-glacial type of environment during an interval in the deposition of the Corton Beds. The interval may be related to drainage changes associated with the retreat of the North Sea Drift ice and advance of the Lowestoft Till ice.

For the last three summers we have devoted the greater part of our leisure time to the examination of the Silurian Rocks that lie more immediately between the Moorfoot Hills and the English border. Our investigations have been attended with a fair amount of success, and we thought that a short summary of what we have accomplished would not be wholly uninteresting to the Geological Section. As these old Silurian strata of the South of Scotland have only been once alluded to in the papers already read at the Meeting—namely, by the Chairman in his eloquent address—we may be pardoned if we say a few preliminary words concerning them.

Ninella tarimensis from the Lower Cambrian Yurtus Formation of western Xinjiang, China, is shown to be a relative of the halkieriids and siphogonuchitids. These are known principally from dispersed sclerites, presumably secreted by slug-like organisms that were an abundant component of the Cambrian benthos. The sclerites of N. tarimensis are relatively small, strongly recurved and usually possess an upper surface ornamented with transverse sculpture. The lower surface is more or less smooth and is joined to the upper surface via steep faces that may be grooved. The apertural region is quadrate in outline and bears a circular foramen. Ninella is fairly widespread and is known from elsewhere in China (Guizhou and Shaanxi Provinces) and from Kazakhstan. A brief description of the siphogonuchitid scleritome is also presented, based on dispersed sclerites and shells from the Lower Cambrian of Shaanxi Province, China. Formal synonymy of the sciotaxa Siphogonuchites, Dabashanites, Lopochites, and Maikhanella as Siphogonuchites is proposed.

Ignimbrites are useful chronological markers in the geological record at local and regional scales. They also provide information on the dynamics of the eruption that produced them, making their study of great importance in terms of volcanic hazard assessment. However, their study is usually hampered by their lateral variation and discontinuity. When stratigraphic and lithologic criteria are not sufficient for correlation purposes, the use of multiple complementary correlation tools may be necessary to correctly determine their areal extension, volume and facies variations. Whole-rock geochemistry is considered one of the less reliable correlation techniques due to the pyroclastic nature of these deposits and their emplacement dynamics. These may introduce vertical and horizontal geochemical heterogeneity in the final deposit. In addition, the occurrence of zoned ignimbrites due to magma supply of changing composition is common. In this work we show that, if appropriately used, whole-rock geochemistry can be a valid and highly useful tool for ignimbrite correlation. We provide an example from the study of an ignimbrite sequence containing 18 units (sensu lato) in the Sulcis region (SW Sardinia, Italy). A protocol has been developed for unit recognition based on successive simple binary diagrams where the whole-rock composition of a problem sample can be plotted. Immobile trace elements have been preferentially used to minimize effects of element mobilization associated with alteration and weathering. The diagrams provided here are designed for the Sulcis, but the methodology followed to develop them may be applied to other study areas.

The Wudang Complex located in the central part of South Qinling, has been inferred to be a segment of the Yangtze Craton involved in the orogen. In this study, the cooling/exhumation history of the Wudang Complex is revealed through combined published geochronology data and new apatite fission-track results. Three rapid exhumation episodes related to relevant geodynamic events have been identified. Previous 40Ar–39Ar and (U–Th)/He data indicate that the most significant exhumation, induced by the collision between the North and South China Blocks, occurred from c. 237 to 220 Ma after long-term subsidence and sedimentation of the passive continental margin. The second exhumation event, related to the long-distance effect of the Pacific subduction, occurred during the period from c. 126 to 90 Ma. Following the late Cretaceous – Eocene peneplanation stage, the final late Cenozoic exhumation since c. 15 Ma may be attributed to the combined effect of the eastward growth of the Tibetan Plateau uplift and the Asian monsoon.

The sand/matrix ratio technique is described and has been shown to provide a rapid method of correlating till units in the Cumberland lowland which belong to separate glacial phases. Basal tills have a relatively constant sand/silt-matrix ratio compared with flowage tills in the same locality.

The Mesaoria (Mesarya) Basin exemplifies multi-stage basin development within a regional setting of diachronous continental collision. The Plio-Pleistocene represented a period of major sediment accumulation between two topographic highs, the Kyrenia Range in the north and the Troodos Massif in the south. During Pliocene time, open-marine marls and chalks of the Nicosia (Lefkoşa) Formation accumulated in a shelf setting. The Early Pleistocene period was characterized by a relative fall in sea level and a change to shallower-water bioclastic deposition of the Athalassa (Gürpınar) Formation. The northern margin of the basin was approximately delineated by the E–W neotectonic Ovgos (Dar Dere) fault zone. A carbonate ramp system formed directly to the south of this structural feature. During Early Pleistocene time, the basin evolved from an open-marine shelf to semi-enclosed lagoons with deltaic deposits, and finally to a non-marine aeolian setting, flanked by the rising Kyrenia Range to the north. Synthesis of geological evidence from the Mesaoria (Mesarya) Basin as a whole, including outcrop and borehole evidence from the south, adjacent to the Troodos Massif, indicates that the Pliocene – Early Pleistocene represented a relatively quiescent period. This intervened between Late Miocene – earliest Pleistocene southward thrusting–folding of the Kyrenia Range and Pleistocene intense surface uplift of both the Kyrenia Range and the Troodos Massif. The basin development reflects flexurally controlled collapse during Late Miocene – earliest Pliocene time related to southward thrusting, followed by strike-slip during westward tectonic escape of Anatolia, and finally regional uplift controlled by under-thrusting of continental crust from the south, as collision progressed.

A likely example of biochemical evolution in the nautiloids is demonstrated, based on X-ray fluorescence analysis of the Sr content of unaltered shells.

The paper draws attention to the existence in the Tertiary of Australia of three distinctive though not consecutive foraminiferal zones. The lowest zone, found in Victoria and South Australia, is of Upper Eocene age, the upper zone is not younger than Lower Miocene (Burdigalian) and the intermediate zone of Victoriella, corresponding to strata usually referred to the “Janjukian”, probably Upper Oligocene (Chattian) to Aquitanian.