More detailed examination of the material collected by Mr. Beadnell and myself in the Fayûm in 1901 has led to the recognition of two additional species of Mœritherium, and has made it clear that the Sirenian belongs to a distinct genus, which presents some characters of much interest and is nearly related to Prototherium (Halitherium) veronense, described by Zigno from remains found in beds of Upper Eocene age at Monte Zuello in Northern Italy.

In an attempt to obtain information about garnet nucleation a series of eleven apparently homogeneous metamorphic rocks, from a small area near Mallaig, Inverness, Scotland, have been analysed to determine bulk chemical and modal compositions, garnet grain size and number of garnet crystals occurring in unit volume of rock (N). No correlation of N with any function of chemical and modal compositions could be found, and it is therefore concluded that, if the influence of trace components can be neglected, externally imposed factors (for example, time-temperature variation) or internal physical factors (for example, the surface area of the rock just prior to garnet formation) must exert a controlling influence on garnet nucleation. It was found, however, that in each specimen, there was a preferred crystal radius and the relative frequency of occurrence about this preferred value was constant for all samples studied. Preliminary comparison with other systems, investigated by the authors, suggested that the nature of this relationship may provide evidence of the conditions under which these rocks recrystallized.

The Maures Massif forms an important piece of the southernmost part of the Variscan belt of western Europe. This massif exhibits high-grade bimodal felsic–basic volcanic complexes, a distinctive lithological feature documented elsewhere in similar domains of the European Variscides and referred to the Cambro-Ordovician extensional episode. Two major alkalic and tholeiitic compositional groups and subordinate transitional metabasites have been identified, occurring at several distinct horizons or in bimodal complexes. This chemical diversity is interpreted in terms of variable degrees of partial melting of progressively depleted mantle source(s), which experienced melting at different depths, from garnet to spinel stability domains, during a progressive mantle upwelling associated with intracontinental rifting. This setting is reinforced by the presence of metabasites with compositions similar to continental flood basalts, showing slightly humped REE patterns, and interpreted as resulting from the melting of a partially depleted source at a relatively low degree of melting, in the garnet–spinel transition zone. The metafelsites from the tholeiitic bimodal complex exhibit the distinctive major and trace element characteristics of A-type rhyolites. Their elemental variations are consistent with fractional crystallization of major and accessory phases, but some discontinuous REE profiles result from a hydrothermal fractionation mechanism. The modelling of common anhydrous fractionating assemblages suggests that these A-type compositions may be derived from the associated tholeiites by extensive degrees of fractionation (90 %) with some continental crust involvement, or by anhydrous partial melting (∼30 %) of an underplated mafic parent of tholeiitic composition. The bimodal character of the Late Cambrian Maures magmatism, together with the chemistry of the various metabasites and metafelsites, suggests plume-induced intracontinental magmatic activity, resulting in lithospheric thinning prior to the onset of rifting and break-up of the Palaeozoic continental lithosphere, at this northern margin of Gondwana.

Recent investigations indicate that three distinct lithostratigraphical units can be recognized in the Red and Norwich Crag deposits of the area around Aldeburgh and Orford, Suffolk. These effectively represent a refinement of a stratigraphy originally suggested by Prestwich in 1871. A lowermost coarse-grained shelly sand, the Red Crag Formation, rests on an eroded London Clay surface and is banked against the Pliocene Coralline Crag. The Red Crag Formation passes upwards into a fine-grained generally unfossiliferous well-sorted sand, the Chillesford Sand Member, which overlaps the Red Crag Formation to rest directly on the Coralline Crag. The Chillesford Clay Member is regarded as the lateral equivalent of the upper Chillesford Sand Member, the two members together comprising the Norwich Crag Formation in this area. Sections that have been zoned palaeontologically may be integrated into this lithostratigraphical framework. These indicate that the Red Crag Formation correlates with the Pre-Ludhamian Stage, and the Chillesford Sand Member and the Chillesford Clay Member correlate with the Bramertonian Stage. Type sections are established for the three units described.

Palaeomagnetic data from mid to late Palaeozoic rocks are potentially valuable for testing models of the assembly of Spitsbergen and for determining the palaeo-position of parts of Spitsbergen relative to the major tectonic elements that comprised the Old Red Continent. Fine-grained red sandstones from the Tournaisian to Namurian Billefjorden Group, collected by members of Cambridge Spitsbergen expeditions, were subjected to stepwise chemical and thermal demagnetization. The characteristic magnetization is found in normal and reverse polarities and corresponds to a pole position at 23° S, 332 °E, dp = 5.7°, dm = 10.5°, which is near an early Carboniferous pole computed for the Baltic Shield-Russian Platform (Baltica). When compared to Laurentia (North America) in the context of the revised Mauch Chunk palaeomagnetic study, Spitsbergen falls a few degrees south of the Bullard reconstruction but the error of the determination of the palaeolatitude overlaps with this position. Therefore relative motion between any part of Spitsbergen and Laurentia and Baltica during the Carboniferous is not resolved.

We apply fission-track thermochronology to shed new light on the tectonic history of Zealandia during Late Cretaceous continental extension and the onset of Late Tertiary mountain building in the Southern Alps of New Zealand. The Southern Alps are one of the fastest erosionally exhuming mountain belts on Earth. Exhumation of the Bonar Range in Westland just to the northwest of the Alpine Fault is orders of magnitude slower. We report apatite and zircon fission-track ages from samples that were collected along an ENE–WSW profile across the central Bonar Range, parallel to the tectonic transport direction of a prominent ductile fabric in the basement gneiss. Zircon fission-track (ZFT) ages show a large spread from 121.9 ± 12.1 Ma to 74.9 ± 7.2 Ma (1σ errors). The youngest ZFT ages of 78 to 75 Ma occur at low elevations on either side of the Bonar Range and become older towards the top of the range, thereby showing a symmetric pattern parallel to the ENE-trending profile across the range. Age–elevation relationships suggest an exhumation rate of 50–100 m Ma−1. We relate the ZFT ages to slow erosion of a tectonically inactive spot in the Late Cretaceous magmatic arc of Zealandia. Therefore, the first main significance of the paper is that it demonstrates that not all of 110–90 Ma Zealandia was necessarily participating in extreme core complex-related extension but that there were enclaves of lithosphere that underwent slow erosion. The apatite fission-track (AFT) ages range from 11.1 ± 1.9 Ma to 5.3 ± 1.0 Ma and age–elevation relationships suggest an exhumation rate of c. 200 m Ma−1. We relate the AFT ages to the inception of transpressive motion across the Alpine Fault and modest exhumation in its footwall in Late Miocene times. If so, the second significant point of this paper is that transpressive motion across the Alpine Fault was already under way by c. 11 Ma.

The subject matter of the present note is furnished by the abnormal redness of many parts of the Arran Carboniferous. W. Gunn, in his invaluable memoir, records this colouration without particular comment; but, as Scottish geologists are aware, B. N. Peach, under whose supervision Gunn carried out his survey, has long claimed that the Arran Carboniferous is stained by solutions that have percolated down from overlying New Red Sandstone. After a careful consideration of the exposures, I feel convinced that two features of Peach's proposition are secure:—

(1) The red colour of much of the Arran Carboniferous is not original.

(2) It must be in some way connected with the New Red Sandstone.

The Codó Formation exposed in the eastern Grajaú Basin, northeastern Brazil, consists mostly of black shales, limestones and evaporites arranged into several shallowing-upward cycles formed by progradation of lake deposits. Three ranks of cycles are distinguished. The lower-rank cycles correspond to millimetric interbeddings of: bituminous black shales with evaporites, calcimudstones or peloidal wackestone–packstone; grey/green shale with calcimudstone, peloidal wackestone–packstone or ostracodal wackestone/grainstone; and ostracodal wackestone/grainstone and/or calcimudstones with cryptomicrobial mats and ooidal/pisoidal packstones. The intermediate-rank cycles average 1.7 m in thickness and are formed by complete and incomplete cycles. Complete cycles show a transition from central to intermediate and then to marginal facies associations and include two types: C1 cycle with central lake deposits consisting of evaporites and black shales; and C2 cycle with central lake deposits formed by grey/green shale. Complete cycles were produced by the upward gradation from central to marginal environments of the lake or saline pan–sabkha system. Incomplete cycles are those where at least one facies association is lacking, having been formed by successions either with central and intermediate facies associations (I1) or intermediate and marginal facies associations (I2). The higher-rank cycles are, on average, 5.2 m thick and consist of four depositional units that display shallowing-upward successions formed by complete and incomplete intermediate-rank cycles that vary their distribution upward in the section, and are bounded by sharp surfaces. While the lower-rank cycles display characteristics that reveal their seasonal signature, detailed sedimentological characterization and understanding of stratal stacking patterns related to the intermediate and higher-rank cycles support a genesis linked to syn-sedimentary tectonic activity. This is particularly suggested by the high facies variability, limited lateral extension, and frequent and random thickness changes of the intermediate-rank cycles. Additionally, the four higher-rank cycles recognized in the Codó Formation match with stratigraphic zones having different styles of soft-sediment deformation structures attributed to seismic activities. Therefore, the several episodes of lake shallowing recorded in the Codó Formation are linked to seismic pulses that alternated with sediment deposition. This process would have created significant changes in the lake water level and resulted in sharply bounded successions with upward gradation from deeper to relatively shallower facies associations.

In this review of the Downtonian Eurypterida of Perton, Here-fordshire, a new genus Salteropterus and a new family Hugh-milleriidae are proposed, and the family Pterygotidae accordingly emended. Hitherto unknown morphological details of the Perton Eurypterida are described and discussed.

The drift succession in east-central Ireland is the result of a series of ice movements spreading from major centres of dispersion within theIrish Sea Basin and over the north-central Irish plain, and from local mountain sources. These glaciations have produced laterally and vertically complex sequences of deposits. The large-scale events influenced almost the entire area; problems of correlation emerge when considering episodes of relatively restricted extent such as those associated with upland ice-caps in the S and the hitherto unreported readvances which interrupted the withdrawalof ice-sheets across the northern part of the region under examination. Thetask of assigning the older units to particular Quaternary cold stages is frustrated by the absence of interstratified organic horizons. Two possible models of glaciation are considered: one may be regarded as ‘traditional’; the other requires a much shorter period of time by assuming that the stratigraphy records differences in the relative strengths of essentially contemporaneous ice-masses.

The Carboniferous fossil plants from the Severn Coalfield are described for the first time. They indicate a late Westphalian D age for these strata (Lobatopteris vestita Biozone) and are clearly similar to floras reported from the Forest of Dean Coalfield. There is also evidence that they can be correlated with the Grovesend Beds in the eastern part of the South Wales Coalfield. It seems that the start of sedimentation in the Forest of Dean and Severn coalfields is related to Leonian (late Hercynian) earth movements.

Load-cast structures in the Caledonian, synorogenic, Fongen-Hyllingen layered basic complex closely resemble those deformations resulting from reverse density stratification in experimentally studied, water-saturated sediments. The mushroom-shaped structures are apparently restricted to a single horizon within an interlayered, metamorphosed, dunite–troctolite sequence. They generally have a symmetrical form, revealing a polygonal pattern in the plane of the layering. The density contrast between an olivine-rich crystal mush overlying a plagioclase-rich crystal mush, both very close to the igneous sediment–magma interface, is believed to have caused the deformation. Subsequent consolidation occurred by adcumulus growth.

In a paper published in the Geological Magazine last year (LXXIII, 385–112), it was mentioned that in my collection of Scottish Carboniferous crinoids there remained ten or eleven species to be described. In the present paper eleven species are dealt with, but I find this does not complete the list since there are still a few others, including species of Hydreionocrinus, Eupachycrinus, etc., and some very minute forms belonging to unknown genera which require further elucidation. It is my hope later on to describe these along with a revision of the Scottish Carboniferous crinoids as a whole. Meanwhile, on another page is given a list of all the species known to date so that a comparison can be made with the faunas of other regions. Here, I wish to add to the list of species already given from Coplow Knoll, Clitheroe (C1) (Geol. Mag., 1935, LXXII, p. 205), the following species: Platycrinus coronatus Goldfuss, Dichocrinus sp., Symbathocrinus conicus Phillips, and Mespilocrinus forbesianus de Koninck & Le Hon.

Heavy minerals in Ordovician successions in western Ireland record, in the Upper Arenig Sheeffry Formation, the erosion of an ophiolite/island arc complex. The appearance of staurolite and garnet at a basin-wide horizon in the Lower Llanvirn Upper Derrylea Formation signals the unroofing of the Dalradian metamorphic complex. Parts of the Ordovician sequence on Inishturk and in two small inliers are correlated with the standard sequence with unexpected results. The garnet-, sillimanite-, and staurolite-bearing Letter Formation correlates with the Upper Derrylea Formation and, on Inishturk, heavy minerals in south-younging turbidites reveal a sinistral ramp zone, that places the Sheeffry Formation structurally above and to the south of the younger Derrylea Formation.

A preliminary summary of the lower Visean to uppermost Moscovian (Carboniferous) conodont succession and biostratigraphy of the Dianzishang section in Zhenning, Guizhou, South China is presented. Eleven conodont zones, in ascending order, can be recognized: Gnathodus praebilineatus, Gnathodus bilineatus, Lochriea ziegleri, Declinognathodus noduliferus, Neognathodus symmetricus, ‘Streptognathodus’ expansus (primitive form), ‘Streptognathodus’ expansus, Mesogondolella donbassica – Mesogondolella clarki, Idiognathodus podolskensis, Swadelina fauna and Idiognathodus swadei zones. The first occurrences of Lochriea ziegleri at the base of the Serpukhovian Stage, Declinognathodus noduliferus noduliferus at the base of the Bashkirian Stage and ‘Streptognathodus’ expansus at the base of the Moscovian Stage are recognized. The definitions of these stage boundaries, as well as that of the base of the Kasimovian Stage are discussed. Correlations with the Naqing section in South China, Russian and North American sections, as well as other important sections in the world, are considered.

This study focuses on the status of the Makrotantalon Unit (Andros, Greece) within the framework of the Cycladic nappe stack. We document unambiguous evidence that this unit has experienced blueschist-facies metamorphism and identify previously unknown lawsonite ± pumpellyite assemblages in glaucophane-free metasediments. The position of the presumed tectonic contact at the base of this unit is vague, but roughly outlined by serpentinites. Only a single outcrop displays a weak angular unconformity with cohesive cataclasites in the footwall. Rb–Sr geochronology was carried out on 11 samples representing various rock types collected within or close to inferred or visible fault zones. Owing to a lack of initial isotopic equilibration and/or subsequent disturbance of the Rb–Sr isotope systematics, isochron relationships are poorly developed or non-existing. In NW Andros, direct dating of distinct displacement events has not been possible, but a lower age limit of ~ 40 Ma for final thrusting is constrained by the new data. Sporadically preserved Cretaceous ages either indicate regional differences in the P–T–d history or a different duration of metamorphic overprinting, which failed to completely eliminate inherited ages. The detachment on the NE coast records a later stage of the structural evolution and accommodates extension-related deformation. Apparent ages of ~ 29–25 Ma for samples from this location are interpreted to constrain the time of a significant deformation increment. On a regional scale, the Makrotantalon Unit can be correlated with the South Evia Blueschist Belt, but assignment to a specific subunit is as yet unconfirmed.

The colours of conodont elements recovered from Silurian limestones in the Oslo region, Norway, range from brown to grey. Samples from the south of the region contain black and grey conodonts, indicative of high palaeotemperatures. There is a general decrease in thermal metamorphism towards the north, with the lowest palaeotemperatures recorded from Toten, Ringsaker and parts of the Ringerike district. There is a close correlation between thermal metamorphism and the proximity of Permian intrusions.

The Working Group has the responsibility of recommending a specific level within a suitable stratigraphic section to serve as the global stratotype for the Cambrian–Ordovician Boundary. Commencing in 1974, comprehensive studies culminated in a plenary session in Calgary in 1985 resulting in decisions on the ‘golden-spike’ principle of selecting the boundary at a horizon just below the first influx of nematophorous graptolites. Conodonts are to be used as the primary guide for the selection of the specific horizon and the global stratotype section must have potential for studies using paleomagnetism, geochemistry and other non-biological correlation tools. The specific horizon will correspond approximately to the base of the Tremadoc Series of Wales and slightly higher than the base of Canadian Series as used in western North America.

The Calgary meeting considered the Broom Point and Green Point sections in Newfoundland, Canada, and the Xiaoyangqiao section at Dayangcha, China, as prime candidates to serve as the global stratotype. A delegation from the Working Group inspected the Dayangcha sections in 1986. For this visit, comprehensive documentation and description of the sequence were prepared and published and are briefly summarized in the present issue.

Specific uncertainties remain to be resolved for the Dayangcha and Newfoundland stratigraphic sections before the Working Group will be ready to recommend selection of a global stratotype.

The morphology of Cyrtograptus rigidus Tullberg n. subsp. A is described from uncompressed material. Particular attention is directed to the sequence of development of the connecting structure of cladium and main branch, which is demonstrated with the aid of figured growth stages of cleared and uncleared specimens. Also discussed is the intimate relationship of relative rate of growth of characters of cladium to those on the main branch. Cursory study of numerous other uncompressed species of Cyrtograptus in the author's collection reveals that the principles of cladial development outlined here are of general application.

The purpose of this study is to use the mechanisms of deformation band formation to help with interpreting the timing of phases of deformation in an area with a complex geological history. Deformation bands and zones of deformation bands are described from the quartzites of the Lower Devonian Muth Formation in the Pin Valley, NW Himalayas. Thin-section analyses show that the deformation bands in the Muth Formation formed early in the diagenetic history before porosity was lost. Deformation mechanisms involved cataclasis, translation, rotation of quartz grains and effective porosity reduction. The orientations of the deformation bands cannot be reasonably grouped with the orientations of faults related to Himalayan deformation in the Pin Valley. Additionally, the deformation bands are deformed by Eo-Himalayan (Eocene) folds, which in turn are cut by later faults. The later faults that cross-cut the Eo-Himalayan folds developed in the already-cemented Muth Formation at much higher temperature and pressure conditions by crystal plastic deformation mechanisms, indicated by quartz crystals with undulatory extinction, abundant kink bands, dislocation glide, elongated subgrains, slightly curved deformation lamellae and pronounced shape-preferred orientation. These two completely contrasting deformation mechanisms on the microstructural scale characterize two distinct fault sets that formed at different depths in the crust. Based on these differences, a pre-Himalayan origin of the deformation bands is concluded, thus representing a set of rare pre-Himalayan deformation structures. After unfolding to remove Eo-Himalayan crustal shortening, the orientation of the deformation bands and restored relative offsets of sedimentary bedding are most compatible with ∼ E–W-oriented shortening associated with N–S extension. The age of the deformation bands in the Muth Formation is bracketed by an early Devonian sedimentation age of the Muth Formation and a middle Cretaceous age of considerable cementation as deduced from compiled burial histories. Accepting a pre-middle Cretaceous age of the deformation bands, maximum conditions of about 80°C and 60 MPa lithostatic pressure during their formation are estimated from the amount of overburden during the middle Cretaceous. We suggest the deformation bands are a result of either the Neo-Tethys rifting event beginning in the early Carboniferous or the extension related to late Carnian/early Norian rapid subsidence, although a hitherto unknown deformation event cannot be excluded.