Using zircons taken from two granite plutons, Strontian (Caledonian, northwestern Scotland) and Kameruka (Bega Batholith, southeastern Australia), this study presents observations that have a bearing on refractory zircons as provenance indicators. Two broad textural types of refractory zircon were identified: (1) those which show simple two-stage growth histories; and (2) those which have apparently undergone repeated periods of growth, resorption, mechanical abrasion, fracturing and fracture-healing. SHRIMP U-Pb ages obtained from the Kameruka zircons indicate that the cores are the textural manifestation of inheritance. The shapes of refractory cores are not unambiguously indicative of their ultimate origin, since they may also be modified by processes that occur before and after incorporation into the magma. The cores within the two populations show a great diversity in types and styles of zoning, and in composition, implying that they have not chemically equilibrated internally, or externally with their host melt.

Evidence is given that many of the Mesozoic, geosynclinal serpentines of Turkey are deep-sea lavas, and that they functioned as efficient fertilizers of surface waters leading to rich crops of radiolaria now preserved in cherts and limestones. Furthermore, in anticlinals at Ankara and Alaca Höyük, Palæozoic, Triassic and Jurassic rocks in the condition of a tectonic mélange are overlain unconformably by Upper Cretaceous and Eocene; while, in associated synclinals at Ayas and Kirsehir, crystalline schists and granites, probably Palæozoic or earlier, emerge from beneath unconformable Oligocene. It is suggested that these crystallines are parts of a Pontic nappe which advanced southwards during Upper Cretaceous times, in part overriding and breaking local rocks to yield the Ankara Mélange, in part bulldozing them forwards to form the Taurus Mountains. The displacement along the Anatolian Thrust at the base of the invading Pontic nappe is reckoned at about 350 km.

A new member of the Tristichopteridae (=Eusthenopteridae), Mandageria fairfaxi gen. et sp. nov., is described from the Late Devonian (Famennian) Mandagery Sandstone outcropping near Canowindra, NSW, Australia. It is represented by several complete or partial heads and bodies, preserved as natural moulds. Mandageria shares derived characters with the Late Famennian tristichopterid Eusthenodon wängsjöi from East Greenland; the pineal plate series is large and kite-shaped and is posterior to the middle of the parietals, the intertemporal does not contact the posterior supraorbital, a posterior process of the premaxilla divides the apical fossa, the anteriormost premaxillary tooth is enlarged, the postorbital is excluded from the orbit by a supraorbital–lacrimal contact, and the coronoids lack marginal teeth except posteriorly. Mandageria fairfaxi differs from Eusthenodon in superficial fusion of the supratemporal, tabular and postparietals, in the lateral extrascapulars being separated by only 2–3 mm in the midline anteriorly, and in having proportionately smaller scales. It also has an elongate supracleithrum, which is probably autapomorphic. The postcranial skeleton is comparable to that of the Frasnian genus Eusthenopteron, but differs in the more posterior position of the median fins, the poorly ossified vertebral column, and the flattened ectepicondyle. Mandageria fairfaxi is the second osteolepiform described from Canowindra (the first, Canowindra grossi) and, other than the now-reinterpreted Marsdenichthys, the first tristichopterid described from Australia.

Diapirism has been discredited as a transport mechanism for magmas partly because diapirs seem to be unable to bring magmas to shallow crustal levels (<10km) and partly because recent developments in the theory of dyke propagation have shown that sufficiently wide dykes are able to efficiently transport felsic magmas through the crust. However, it is still unclear how felsic dykes grow to widths that allow them to propagate faster than they close by magma freezing. Ultimately, it may be the ability of felsic dykes to grow within the source that controls which mechanism dominates ascent.

The ability of dykes to propagate, from the top of rising diapirs depends among other factors on the changing temperature gradient of the wall rocks. The steep gradient around rapidly rising diapirs in the low viscosity lower crust will cause dykes to freeze. As diapirs rise to colder stiffer crust and decelerate, heat diffuses further from the diapir, resulting in shallower temperature gradients that favour dyke propagation. The mechanism may thus swap, during ascent, from diapirism to dyking. Calculations of the thermal evolution of diapirs and their surroundings show that basaltic diapirs may never form because they would be drained by dykes at a very early stage; felsic diapirs may be unable to give rise to successful dykes, whereas diapirs of intermediate magmas may propagate dykes during ascent.

A model for the early Palaeozoic metamorphic history of the Midland Valley and adjacent areas to the S in Scotland, England and Ireland is based on the results of new field mapping, thin section petrography, electron probe microanalysis, X-ray diffractometry, conodont and palynomorph colouration and graptolite reflectance measurement.

The oldest metamorphic rocks of the Midland Valley of Scotland, excluding xenoliths in post-Silurian lavas, are possibly the blueschist occurrences in the melange unit of the Ballantrae complex. These may be tectonised remnants of (?)pre-Arenig ocean-floor subducted during closure of the Iapetus Ocean. In the early Ordovician, the melange terrane was dynamothermally metamorphosed during obduction of newly-formed ocean crust. The obduction process piled up a thick sequence of various ocean-floor types such that burial metamorphism in parts reached pumpellyite-actinolite facies; elsewhere prehnite-pumpellyite and zeolite facies was attained.

Whilst the Midland Valley acted as an inter- or fore-arc basin during the Late Ordovician and Silurian and experienced burial metamorphism, an accretionary prism was formed to the S. Accretion, tectonic burial and metamorphism of ocean-floor and trench sediment was continuous in the Southern Uplands and the Longford-Down massif of Ireland through Late Ordovician to Late Silurian times. Rocks at the present-day surface vary from zeolite facies to prehnitepumpellyite facies. Silurian trench-slope basin sediments can be recognised in part by their lower grade of burial metamorphism. Greenschist facies rocks of the prism probably lie close to the surface.

The Lake District island-arc terrane of Northern England has an early Ordovician history of burial metamorphism up to prehnite-pumpellyite facies. The Late Ordovician and Silurian metamorphic history is one of sedimentary burial complicated by tectonism and intrusion of granite plutons to a relatively high level. The Iapetus suture is marked by a weak contrast in metamorphic grade.

The beginning of dinosaur evolution is currently known based on a handful of highly informative Gondwanan outcrops of Ischigualastian age (late Carnian–early Norian). The richest Triassic dinosaur records of the southern continents are those of South America and South Africa, with taxonomically diverse faunas, whereas faunas from India and central Africa are more poorly known. Here, the known diversity of Gondwanan Triassic dinosaurs is increased with new specimens from central India, which allow a more comprehensive characterisation of these dinosaur assemblages. Five dinosauriform specimens are reported from the probable late Norian–earliest Rhaetian Upper Maleri Formation, including two new sauropodomorph species, the non-plateosaurian Nambalia roychowdhurii and the plateosaurian Jaklapallisaurus asymmetrica, a guaibasaurid and two basal dinosauriforms. The Lower Dharmaram Formation, probably latest Norian–Rhaetian in age, includes basal sauropodomorph and neotheropod remains, providing the second record of a Triassic Gondwanan neotheropod. The currently available evidence suggests that the oldest known Gondwanan dinosaur assemblages (Ischigualastian) were not homogeneous, but more diverse in South America than in India. In addition, the Upper Maleri and Lower Dharmaram dinosaur assemblages resemble purported coeval South American and European beds in the presence of basal sauropodomorphs. Accordingly, the current available evidence of the Triassic beds of the Pranhita–Godavari Basin suggests that dinosaurs increased in diversity and abundance during the late Norian to Rhaetian in this region of Gondwana.

Deposits of windblown sand up to 4 m thick on the Torridon Sandstone massif of An Teallach are shown to be of predominantly niveo-aeolian origin, a form of sedimentation hitherto unrecognised in upland Britain. Sand grains weathered from bedrock and from exposed clasts on plateau areas are blown on to the winter snowpack on surrounding slopes. When the snow melts, the grains are lowered on to the underlying vegetation, which traps the sand and thus allows a stable deposit to accumulate. The deposits formed in this way are massive, poorly sorted and coarser than most aeolian deposits, comprising mainly medium sand (212–600μm) with a substantial proportion of coarse sand and even very small pebbles. The coarseness and poor sorting of the sands reflect the size of grains available for transportation, the strength of the wind, short transport distances and admixture of different grades of sand during deposition. Sand accumulation began in the Early Flandrian before c. 7900 BP, but was eventually much reduced by the establishment of vegetation cover over the plateau source area. Recent disruption of this vegetation cover triggered either by increased storminess or overgrazing resulted in extensive erosion of sand deposits on the plateau and their redeposition on surrounding slopes. Niveo-aeolian deposition continues on lee slopes at present, but is offset by erosion of unvegetated scarps at the margins of the deposits.

This paper provides a comprehensive account of the small spore assemblages of coals in the Limestone Coal Group and Upper Limestone Group (Namurian) of the Lower Carboniferous of Scotland. The coals were obtained from boreholes sunk in the Lothians, Central, and West Fife coalfields. Over ninety species of small spores are figured. Of this number twenty-six are new species. Five new genera—Glomospora, Procoronaspora, Callisporites, Tholisporites and Remysporites—are described. Full descriptions are given of all new genera and species. The assemblages are compared with assemblages of similar age in North America, the U.S.S.R. and elsewhere, and it is shown that the Carboniferous pre-Westphalian microfloras were uniform over wide areas of the earth's surface.

In two papers read before this Society, I have very fully described the Diatomaceæ of the Glenshira Sand, which is very remarkable both for the large number of species found in it, which is certainly more than 320, and for the circumstances in which it must have been deposited. There can be no doubt, from the nature of the locality, which I have lately visited, that this bed was formed in the bottom of the Dhu Loch, a shallow fresh-water lake, at that time extending about two miles farther up the valley than it now does, and being at a higher level. In consequence of a rise in the level of the land, or a fall in that of the sea (from which—that is, from Loch Fine, the lower end of the lake is separated by a narrow and low barrier, through which the waters of the lake pass to Loch Fine), the lake has long ago been drained, till its upper end is nearly two miles from the point it must have reached when the bed of sand was formed. The present level of the lake is considerably lower than it was then; the precise difference I had no means of ascertaining, but I believe it is about 30 feet.

Nearly sixty years ago fossil fishes were first discovered at Glencartholm, since when so much material has been collected from this locality that very few museums in the British Isles are without some representative of this remarkable fauna; remarkable both for the number of specimens collected and for the variety of forms it contains. One of us (J. A. M.-T.) became interested in this fauna while studying some of its more problematical members, and spent a few weeks collecting at Glencartholm during the summers of 1933, 1934, 1935 and 1936. During these visits a large quantity of new material was amassed which, when studied by modern methods with a low-powered binocular microscope under liquids, particularly xylol, revealed far more of the anatomy than it had been possible for earlier workers to describe. Some of these results have already been published and the present paper deals only with the Actinopterygians. The new descriptions in this work are not intended to be exhaustive accounts of all that is known of these fishes, but merely to serve as a supplement and summary to the excellent descriptions of Traquair. In so doing an attempt has been made to re-define all the genera and species, and in some cases it has been necessary to repeat the existing description, but where this has been done care has been taken to be as brief as possible. The definitions of the genera are only intended to apply to the species here described, and are consequently confined to characters which are determinable in these species. In certain cases species have been found to exist on brief and inadequate descriptions, in two species the type specimens being unfigured; in these cases the types have been figured, and new and more complete accounts given. Where the shape or ornament of a bone was indeterminable, it has been omitted without comment, in order to make the text as short as possible.

Most natural systems display non-linear dynamic behaviour. This should be true for magma mingling and mixing processes, which may be chaotic. The equations that most nearly represent how a chaotic natural system behaves are insoluble, so modelling involves linearisation. The difference between the solution of the linearised and ‘true’ equation is assumed to be small because the discarded terms are assumed to be unimportant. This may be very misleading because the importance of such terms is both unknown and unknowable. Linearised equations are generally poor descriptors of nature and are incapable of either predicting or retrodicting the evolution of most natural systems. Viewed in two dimensions, the mixing of two or more visually contrasting fluids produces patterns by folding and stretching. This increases the interfacial area and reduces striation thickness. This provides visual analogues of the deterministic chaos within a dynamic magma system, in which an enclave magma is mingling and mixing with a host magma. Here, two initially adjacent enclave blobs may be driven arbitrarily and exponentially far apart, while undergoing independent (and possibly dissimilar) changes in their composition. Examples are given of the wildly different morphologies, chemical characteristics and Nd isotope systematics of microgranitoid enclaves within individual felsic magmas, and it is concluded that these contrasts represent different stages in the temporal evolution of a complex magma system driven by nonlinear dynamics. If this is true, there are major implications for the interpretation of the parts played by enclaves in the genesis and evolution of granitoid magmas.

Buddington (1959) pointed out that the construction of large crustal magma chambers involves complex internal processes as well as multiple country rock material transfer processes (MTPs), which reflect large horizontal, vertical and temporal gradients in physical conditions. Thus, we have attempted to determine the relative importance of different magmatic and country rock MTPs at various crustal depths, and whether country rock MTPs largely transport material vertically or horizontally, rather than seeking a single model of magma ascent and emplacement.

Partially preserved roofs of nine plutons and in some cases roof–wall transitions with roof emplacement depths of 1·5–11 km were mapped. During emplacement, these roofs were not deformed in a ductile manner, detached or extended by faults, or significantly uplifted. Instead, sharp, irregular, discordant contacts are the rule with stoped blocks often preserved immediately below the roof, even at depths of 10 km. The upper portions of these magma chambers are varied, sometimes preserving the crests of more evolved magmas or local zones of volatile-rich phases and complex zones of dyking and magma mingling. Magmatic structures near roofs display a wide variety of patterns and generally formed after emplacement. Transitions from gently dipping roofs to steep walls are abrupt. At shallow crustal levels, steep wall contacts have sharp, discordant, stepped patterns with locally preserved stoped blocks indicating that the chamber grew sideways in part by stoping. Around deeper plutons, an abrupt transition (sometimes within hundreds of metres) occurs in the country rock from discordant, brittle roofs to moderately concordant, walls deformed in a ductile manner defining narrow structural aureoles. Brittle or ductile faults are not present at roof–wall joins.

Near steep wall contacts at shallow to mid-crustal depths (5–15 km), vertical and horizontal deflections of pre-emplacement markers (e.g. bedding, faults, dykes), and ductile strains in narrow aureoles (0·1–0·3 body radii) give a complete range of bulk strain values that account for 0–100% of the needed space, but average around 30%, or less, particularly for larger batholiths. A lack of far-field deflection of these same markers rules out significant horizontal displacement outside the aureoles and requires that any near-field lateral shortening is accommodated by vertical flow. Lateral variations from ductile (inner aureole) to brittle (outer aureole) MTPs are typically observed. Compositional zoning is widespread within these magma bodies and is thought to represent separately evolved pulses that travelled up the same magma plumbing system. Magmatic foliations and lineations commonly cross-cut contacts between pulses and reflect the strain caused either by the late flow of melt or regional deformation.

Country rocks near the few examined mid- to deep crustal walls (10–30 km) are extensively deformed, with both discordant and concordant contacts present; however, the distinction between regional and emplacement-related deformation is less clear than for shallower plutons. Internal sheeting is more common, although elliptical masses are present. Lateral compositional variations are as large as vertical variations at shallower depths and occur over shorter distances. Magmatic foliations and lineations often reflect regional deformation rather than emplacement processes.

The lack of evidence for horizontal displacement outside the narrow, shallow to mid-crustal aureoles and the lack of lateral or upwards displacement of pluton roofs indicate that during emplacement most country rock is transported downwards in the region now occupied by the magma body and its aureole. The internal sheeting and zoning indicate that during the downwards flow of country rock, multiple pulses of magma travelled up the same magma system. If these relationships are widespread in arcs, magma emplacement is the driving mechanism for a huge crustal-scale exchange process.

Excavations in 1958 for the construction of a dam at Loch Droma, Ross and Cromarty, revealed a deep and extensive section in peat and Late-glacial silts. The section was surveyed, its environs studied, and samples of materials analyzed by the Macaulay Institute, Aberdeen, and the Sub-department of Quaternary Research, University of Cambridge. The watershed location of the site, the early radio-carbon date obtained for the basal silts (12,810 ± 155 B.P.), and the nature of their organic contents, make this a critical site for the elucidation of the deglaciation and vegetational history of the Atlantic seaboard of North-west Scotland. In Part I of this report, W. Kirk describes the site and its setting, and indicates some of the problems it raises for existing glacial chronologies of Northern Scotland, and in Part II, H. Godwin summarizes and comments upon the analyses of organic remains.

Past work on the genus Pitus is reviewed and evidence adduced in favour of the view that it was a genus of arborescent Pteridosperms bearing the sterile bifurcate fronds known as Lyginorachis papilio Kidston. These probably resembled Sphenopteris affinis L. & H. in the compression state. Fertile organs were probably borne on trifurcate fronds in which a stemlike median rachis (Tristichia ovensi Long) bore synangia (Telangium sp.) composed of eight microsporangia, or alternatively seed-cupules of Stamnostoma huttonense Long. Branching in Pitus produced single branches at a wide angle, or pseudo-whorls (close spirals) of about five branches. An anomalous ring of medullary xylem was sometimes associated with branching as in Lyginopteris. This supports the view that Pitus should be classified in the Lyginopteridaceae although it was arborescent and in some respects more advanced than many of the more shrub-like Pteridosperms.

During the “Challenger” Deep-Sea Exploring Expedition a great many peculiar-looking manganese nodules or concretions were dredged from the floor of the ocean at great depths, chiefly in the Red Clay areas of the Pacific, but also in less abundance in the Red Clays of the Atlantic. In the other varieties of Deep-Sea deposits these nodules were much less abundant than in the Red Clays.

In still more recent soundings, both American and British ships have discovered in many regions of the Pacific and Indian Oceans a dark-brown coloured deposit containing a large amount of manganese dioxide, similar in character to the Red Clays from which the “Challenger” procured the largest hauls of manganese nodules. There is then every reason for supposing that manganese deposits and nodules are very widely distributed over the ocean's bed, especially in deep water at great distances from land. It was only occasionally that manganese nodules were present in any abundance in a Globigerina Ooze, and in these exceptional instances there was always much volcanic debris associated with the deposit. In the Blue Muds surrounding continental shores manganese nodules were rarely observed; still, on some rocks and boulders dredged from terrigenous deposits, a coating of manganese dioxide was observed on that portion of the stone which had projected above the surface of the mud.

Devonian rhizodontid fishes from East Gondwana include Gooloogongia loomesi Johanson & Ahlberg 1998 from near Canowindra, New South Wales (NSW), Australia and Aztecia mahalae gen. nov., sp. nov. from southern Victoria Land, Antarctica. Gooloogongia loomesi is known from well-preserved cranial and postcranial material, and as such represents the most complete rhizodont known. Newly discovered elements (braincase, pelvic girdle) are described for the first time. Aztecia mahalae gen. nov., sp. nov. is based on shoulder girdle material formerly assigned to Notorhizodon Young et al. 1992, which, based on skull and lower jaw morphology, is a member of the Tristichopteridae. The presence of several plesiomorphic characters suggests that Gooloogongia occupies a basal phylogenetic position within the Rhizodontida, while Aztecia n. gen. possesses a more derived shoulder girdle. We argue that the Rhizodontida evolved on the Gondwanan landmass. Notorhizodon occupies a relatively derived position within the Tristichopteridae, but is contemporary with the earliest and phylogenetically most basal Laurussian members of the group. This shows that the tristichopterids achieved a worldwide distribution considerably earlier than previously thought.

The Ammonoids described in the present paper were placed first of all, for study, in the hands of Mr J. M. Wordie, whose departure, however, as geologist with Sir E. Shackleton's Antarctic Expedition prevented the completion of the work. A preliminary list of identifications by Mr Wordie included a number of forms of “Schloenbachia” especially “S.” inflata, J. Sowerby sp., this form alone being quoted from ten localities. Professor Gregory, in his “Contributions to the Geology of Benguella,” * referred to these identifications, and in his correlation-table classed the beds with “Schloenbachia inflata” as “Vraconnian,” following the prevailing custom. It may be well, however, to remark here already that A. inflatus, J. Sowerby, will be shown to be an exclusively Albian, and not even uppermost Albian, form, and that there is no evidence of any Cenomanian admixture in the typically Albian fauna of the so-called “zone of A. inflatus” in Angola, so that the term Vraconnian is here rejected. Moreover, Renevier's “Vraconnian” was meant for post-inflata beds, and, in the writer's opinion, Sowerby's species is not represented at all in the Angola collection.

The work described in this paper was carried out in the Department of Zoology of Birkbeck College, University of London, and at the Marine Laboratories at Plymouth and Port Erin. I wish to acknowledge my indebtedness to the University of London for the use of their table at Plymouth, to Birkbeck College for a grant of £5 towards the illustrations, and, in particular, I would express my gratitude to Mr Graham, under whose direction the work was carried out, for his continued kindness and help.

The specimens of Lepidochitona cinereus which were used for the investigation were collected at Bangor, Plymouth and Port Erin, and also obtained from Cullercoats. Most of the material from Plymouth and one specimen from Cullercoats was infected with the Haplosporidian parasite Haplosporidium chitonis (Debaisieux, 1920) and was therefore unreliable for histological and physiological work. Specimens of Acanthochitona crinitus were collected at Plymouth, and showed no sign of infection with Haplosporidium chitonis; a few, however, were slightly parasitised with another Sporozoan. The Californian species Ischnochiton magdalenensis and Cryptochiton stelleri were obtained from Turtox General Biological Supply House, Chicago. Specimens of these species were fixed in formalin, which proved to be a poor fixative for histological work.

Pollen-stratigraphic data, supported by lithological, geochemical and radiocarbon evidence are described from two Late Devensian Lateglacial sites on the Isle of Mull, Inner Hebrides, Scotland. The data suggest that, following the wastage of the Late Devensian ice sheet some time prior to 13,000 BP, an open grass- and sedge-dominated landscape was colonised first by juniper scrub and subsequently by Empetrum heaths. Tree birch development was limited principally, it would seem, by exposure to strong westerly winds, although some scattered birch woodland did become established in more sheltered localities. The thermal maximum of the Lateglacial Interstadial appears to have occurred from c. 13,000 to 12,000 BP after which climate began to deteriorate as the atmospheric Polar Front migrated southwards. The harsh climatic conditions of the Loch Lomond Stadial, the full effects of which were experienced after c. 10,700 BP, led to the break-up of the Interstadial vegetation cover, the development of an ice cap and several smaller cirque and valley glaciers in the hills of south-central Mull, and the establishment of a periglacial regime throughout the island. By c. 10,200 BP, however, climatic amelioration was underway once more, the Loch Lomond Advance glaciers had wasted completely, and a plant succession was initiated which led to the replacement of tundra vegetation communities by Empetrum heath, juniper scrub and eventually hazel-birch woodland within the space of c. 1500 years.

In 1925 Professor A. E. Trueman handed to the writer a copy of Professor Bertrand's paper, “Les Zones Végétales du Terrain Houiller du Nord de la France” (1914, p. 208), with the suggestion that it would be interesting to find out whether the succession of plants in South Wales is similar to that of the North of France, and to determine whether Bertrand's zones can be applied to the Coal Measures of South Wales. Since that time every opportunity has been taken to collect fossil plants from known horizons in South Wales and other coalfields. In addition, specimens have been examined in all the important museums and private collections, and in particular in the collections of the late Dr R. Kidston, which are now preserved in the Museum of Practical Geology.