Various ways in which Lower Carboniferous reef limestones have accumulated are described, and terms defining them are introduced. Regional sedimentation, lithology, structure, fauna, and erosion history are kept separate in the discussion. The reef limestones of Northern England are briefly reviewed in the light of this classification.

The Castores and probably the Santa Rosa plutons of north-west Isla Navarino, southern Chile, have been emplaced by in situ diapirism into metasedimentary rocks of the Upper Jurassic (?)–Lower Cretaceous Yaghan Formation. For the former, this model is consistent with the concentric foliation paralleling the margin of the pluton and the foliation and stratification planes in the metamorphic aureole. Only the southern part of the Santa Rosa Pluton is preserved, and it has some structures similar to those of the Castores Pluton, which can also be interpreted as produced by an inflating diapir. The main intrusive rocks of these plutons are quartz-monzodiorites and quartz-diorites with synmagmatic foliation. They were preceded by minor bodies of hornblende gabbros, and followed by dykes and small bodies of non-foliated granodiorites. Non-foliated to weakly foliated granodiorites, forming the centre of the Castores Pluton, probably represent a younger intrusive pulse.

Twelve K–Ar mineral dates from 10 specimens of plutonic rocks, interpreted as near crystallization ages, span the period 80–90 Ma. These dates do not show the sequence of intrusion of the different rock-types, which may suggest that all of them were intruded and cooled in a short period of time. The timing of emplacement of these plutons in relation to tectonism is difficult to determine; however, a post-tectonic emplacement for at least the Castores Pluton, is proposed.

The Ordovician pterygometopid subfamily Chasmopinae is considered to include not only Chasmops McCoy, 1849, and Uralops Ancigin, 1970, but also a number of other genera which encompass species previously referred to Chasmops. These are: Toxochasmops McNamara, 1979; Scopelochasmops gen.nov.; Bolbochasmops gen.nov.; and Rollmops gen.nov. A close correlation is shown to exist between distribution of chasmopines and lithofacies, which indicates habitation in ashallow water environment. A westerly spread of chasmopine species at various times from eastern Baltoscandia is considered to correspond with a similar spread of the shallow water environment. This is shown by the periodic appearance of members of the subfamily in the Oslo region and Britain. Thereis a general reduction in number of chasmopine species and genera away fromthe eastern Baltic.

Of the upper dental series, Probst attempts to give a tolerably complete account, but it is only illustrated by very imperfect woodcuts. Two of the foremost awl-shaped teeth are figured by Lawley (l.c. figs. 2, 3), and the same author ascribes to the upper jaw of this species three other of the Pliocene specimens. Fig. 19 represents an anterior upper tooth from the Middle Eocene of Hampshire, and the original of Fig. 20 is another from the Miocene of Baltringen, Wurtemberg. The former (B. M., p. 4707) exhibits a short thick base with an oblique principal cone, in front of which are a number of minute denticulations; posteriorly there is only one secondary cone, pointing sharply backwards, and about half the size of the principal cone; and this is followed by another small denticle. The second specimen (B. M. 35533) has also a short thick root, and shows a somewhat similar crown; the large principal cone is followed by one small secondary and a terminal denticle, and in front there are a few coarse serrations at its base.

The paper by Dr. Callaway, “On a Cause of River Curves,” in the Geological Magazine for October, 1902, suggests comment for two reasons: first, because the cause that he brings forward seems of doubtful application; second, because the habitual entrance of branch streams at a certain part of the curves of main streams is satisfactorily explained by controls which seem to be of surer and more powerful application than the control which he advocates.

In ascribing to a tributary the power to make a main stream bend in a definite manner towards the tributary, and thus determine the habitual entrance of tributaries on the convex side of the main stream's curves, Dr. Callaway argues that the detritus brought by the tributary will be deposited on the further side of the main stream and somewhat below the tributary's mouth. Various examples known to me of the deposits formed by side streams in the channels of main streams do not bear out this conclusion: the detritus is not deposited on the further side of the main stream, but as a delta at the mouth of the tributary or a little below it; and the main stream does not bend toward, but away from the tributary. The Rhine, the Colorado, and many other rivers that might be instanced, show abundant examples of this kind. Moreover, the assumption of an initially straight main river, as stated by Dr. Callaway, involves an extreme improbability. Rivers cannot be habitually straight in their initial stage, and the bends with which they begin are as a rule spontaneously exaggerated in their later development.

Modern detailed stratigraphical studies have demonstrated very clearly the long and involved tectonic history of the majority of the main structural units of England. It has been proved that, in certain areas, the thickness and the lithology of the sediments were partly determined by repeated pene-contemporaneous folding along definite axes, and thus it has been possible to trace the gradual growth of some of the main fold lines of the country. The Weald is typical of these areas, whose structure, at first sight simple enough, reveals on closer study much complexity of the minor folding and faulting and also gives evidence of long continued movement along certain lines; movement contemporaneous with the deposition of beds which were involved in the final crescendo of tectonic activity.

The Drumian Wheeler Formation preserves one of the most diverse exceptionally preserved faunas of the Cambrian period. Here we describe Messorocaris magna gen. et sp. nov., a new non-biomineralizing arthropod from this formation tentatively assigned to the family Sanctacarididae. The new taxon exhibits a vaulted axial region, and wide pleural regions forming sickle-shaped lateral extensions in the trunk, a character particularly distinctive within the Sanctacarididae. This description provides an opportunity to stress the fact that the ‘Wheeler fauna’ encompasses two distinct assemblages, as confirmed by similarity analysis. These contemporaneous faunas lived at different bathymetries, and should be treated as separate entities.

There are several kinds of acid volcanic rocks in Wales. In the X neighbourhood of Snowdon there are at least five kinds, as follows:

1. There are undoubted lavas, showing lines of viscous flow and sometimes vesicular, and weathering into cubical blocks. Such may be seen on Crib Goch and on Crib Yddysgl, on Cerrig Cochion, and elsewhere. These rocks are rarely cleaved.

2. There are rocks like the last as to fracture and mode of weathering, but which are neither viscous nor vesicular. They are probably masses of felsitic dust or mud. Such may be seen in Cwm Llan.

3. There are also massive felstones, rudely cleaved, such as form Moel Meirch. and Clogwyn Llwyd.

4. There are the so-called ashes of various kinds, usually wellbedded and often highly cleaved.

5. Lastly, there are highly cleaved felsitic rocks, which show no lines of viscous flow, are generally unbedded, and which are in many places fragmentary.

THE origin of chert has of late been discussed with renewed activity, especially in American scientific journals. Difference of opinion centres mainly round the question of the source of the silica; whether it is of direct inorganic origin, or the result of the solution and redeposition of organic silica. Further points at issue relate to the age and formation of the chert; whether it is an original deposit contemporaneous with the country rock, or a metasomatic replacement of the latter and therefore of later age.

The previous literature on the pre-Cambrian rocks of Ireland is considerable in amount. The views of the early workers are briefly referred to in the Handbook of the Geology of Ireland, by G. A. Cole and T. Hallissy, published in 1924. This work doubtless expresses the opinion of Irish geologists of the present day.

Southwestern Europe is one of the best regions for characterizing the dinosaur assemblages that prevailed just before the end-Cretaceous extinction. Aiming to better document this scenario, we provide the first evidence of dinosaur skin impressions in the red-beds of the Tremp Formation (southern Pyrenees). The impressions are assigned to sauropods (probably titanosaurians) on the basis of their scale morphology, arrangement and size. They represent a valuable tool for analysing the last occurrences of the sauropod clade before the K–Pg extinction, as they fall within chron C29r (latest Maastrichtian), thus representing some of the last in situ remains of this clade worldwide.

Ignimbrite steeply intrusive into the basaltic agglomerate of the Kilchrist vent is described. Like the intrusive ignimbrite near Kilchoan, Ardnarnurchan, it shows flow structure parallel to the walls, flow being similarly expressed by the elongation and alignment of the constituent shreds of devitrified glass and pumice lapilli. Fragments of basalt, derived from the vent agglomerate, are sometimes also drawn out in the direction of flow.

The northern, James Ross Island region of the Larsen Basin, on the eastern, back-arc margin of the Antarctic Peninsula magmatic arc, includes one of the thickest and most complete Upper Cretaceous sedimentary successions exposed in the Southern Hemisphere. However, the southern part of the basin remains poorly known, mainly owing to inaccessibility and lack of exposure. Table Nunatak, an isolated, 1-km-long, 400-m-wide outcrop at the tip of Kenyon Peninsula, is the only known exposure of Upper Cretaceous or younger strata in this region. The 62-m-thick succession exposed there is assigned to the newly defined Table Nunatak Formation. It consists mainly of sharp-based, amalgamated beds of fine-grained sandstone up to 2.8 m thick, with subordinate intervals of intensely bioturbated mudstone. Wave ripples are present at some levels, and locally developed swaley cross-stratification provides evidence for storm-generated combined-flow deposition. However, most sandstone beds appear to be internally structureless apart from normal grading, and are interpreted as the direct suspension deposits of highly sediment-charged storm- and/or flood-related flows. The succession represents relatively nearshore deposition, probably at the mouth of a river or deltaic distributary channel. Charcoalified plant debris, abundant at the tops of some sandstone beds, suggests a periodically wildfire-swept hinterland forested largely by coniferous trees. Dinoflagellate cyst assemblages indicate a late Santonian age, and suggest correlation with the basal part of the Lachman Crags Member of the Santa Marta Formation (Marambio Group) on James Ross Island. Palaeocurrents, sandstone petrography and the high sediment supply rate proposed for the Table Nunatak Formation, suggest a relatively high-relief source area to the west, with large-scale erosion of granitoid plutons and metamorphic rocks, possibly related to arc uplift during a mid-Cretaceous compressional episode. The formation is evidence of a major southward extension of the Upper Cretaceous strata exposed in the northern Larsen Basin, and suggests lateral continuity of shallow-marine deposition for at least 500–600 km along the Weddell Sea margin of the Antarctic Peninsula in Santonian times.

Several enigmatic sedimentary structures are present in Upper Silurian and Lower Devonian terrestrial rocks of south Wales. These are millimetre ripples, wrinkle structures, ‘cauliflower’ and ‘molehill’ structures, calcretized matgrounds, ‘pepper-pots’ and ‘fairy rings’. Most of the structures occur on fine-grained sandstone bedding surfaces in both inclined and non-inclined red heterolithic deposits that form a large part of the Lower Old Red Sandstone in south Wales. These deposits consist of conspicuous units up to 3 m thick, comprising millimetre- to centimetre-scale laminasets of alternating mudstone and fine-grained sandstone, interpreted as muddy point bars on ephemeral channel margins, crevasse-splay lobes or distal flood-out deposits from ephemeral flow. They are rich in trace fossils reflecting animal locomotion, burrowing, foraging, ploughing and resting. Millimetre ripples and wrinkle structures are related to rapid growth of cyanobacterial mats on wet sediment surfaces, especially in films of standing water, that may have been a critical constituent of the food chain for terrestrial communities. Pustular ‘cauliflower’ and ‘molehill’ structures are preserved on tuffs and have been linked to algal blooms formed following an increase in nutrients due to ashfall into floodplain ponds. The tuffs are associated with a diverse ichnofauna indicating that opportunist colonizers took advantage of an abundant food source.

A sequence of eleven faunal units characterized by pelagic foraminifera and embodying thirteen significant events has been recognized in the Tertiary of Victoria. They form a continuous sequence from the Upper Eocene to the Middle Miocene. Some of these events have been recognized in the same order in New Zealand, Europe, North America, the Caribbean region, and Saipan.

Within a largely concealed, caldera-related volcaniclastic succession of the Ordovician Borrowdale Volcanic Group in the western Lake District, two thick (100–350 m) ignimbrites within the Fleming Hall Formation exhibit a number of features that in combination make them unusual deposits. They are both homogeneous with comparatively low-SiO2 (63%) bulk composition, contain only a moderate crystal content, are generally poor in lithic clasts, show uniformly very dense welding (yielding parataxitic to massive vitrophyric texture) throughout and lack associated fall-out or surge deposits. Ignimbrites of comparable bulk composition in this geological setting are usually part of zoned sheets and/or frequently very crystal-rich. Large-scale, unzoned densely welded ignimbrites are usually rhyodacitic to rhyolitic. By contrast, ignimbrites of intermediate composition that display dense welding are relatively small deposits that form by agglutination of hot, plastic spatter.

It is postulated that the Fleming Hall ignimbrites were derived from low column height, low explosivity eruptions that conserved heat and minimized entrainment of accidental lithic clasts and the formation of fine ash. The very dense welding and lack of bubble-wall shard vitroclastic textures indicate that pyroclasts were hot and relatively dry, probably occurring as mildly vesicular (scoriaceous) fragments which welded or fused together during aggradational deposition rather than by post-depositional compactional loading. There is little variation in the degree of matrix or melt crystallization throughout the two ignimbrites, despite the fact that high temperatures must have been maintained for many years following deposition. Both display virtually ubiquitous development of micropoikilitic glass devitrification texture, which suggests that the viscosity of the supercooled dacitic melt was sufficiently high, probably due to initial degassing, to inhibit significant melt crystallization after deposition.

The eruption of the Fleming Hall magmas was probably initiated by the rise or injection of hotter, more basic, magma, and not by overpressurization due to volatile exsolution resulting from cooling and crystallization. Foundering of the chamber roof caused forcible and rapid eruption of the magma, probably along a series of volcanotectonic faults rather than a central vent, and probably flooded the resultant caldera depression. It is predicted that this type of eruption will not have produced a widely dispersed deposit, the bulk of which may have been largely contained within its own caldera.

Strata exposed near Tabbowa Tank, Tabbowa Basin, western Sri Lanka have yielded the first representatives of the distinctive Permian Glossopteris flora from that country. The assemblage includes gymnosperm foliage attributable to Glossopteris raniganjensis, roots referable to Vertebraria australis, seeds assigned to Samaropsis sp., sphenophyte axes (Paracalamites australis) and foliage (Sphenophyllum emarginatum), and fern foliage (Dichotomopteris lindleyi). This small macroflora is interpreted to be of probable Lopingian (late Permian) age based on comparisons with the fossil floras of Peninsula India. Several Glossopteris leaves in the assemblage bear evidence of terrestrial arthropod interactions including hole feeding, margin feeding, possible lamina skeletonization, piercing-and-sucking damage and oviposition scarring. The newly identified onshore Permian strata necessitate re-evaluation of current models explaining the evolution of the adjacent offshore Mannar Basin. Previously considered to have begun subsiding and accumulating sediment during Jurassic time, we propose that the Mannar Basin may have initiated as part of a pan-Gondwanan extensional phase during late Palaeozoic – Triassic time. We interpret the basal, as yet unsampled, seismically reflective strata of this basin to be probable organic-rich continental strata of Lopingian age, equivalent to those recorded in the Tabbowa Basin, and similar to the Permian coal-bearing successions in the rift basins of eastern India and Antarctica. Such continental fossiliferous strata are particularly significant as potential source rocks for recently identified natural gas resources in the Mannar Basin.

The Harihada–Chegendalai ophiolitic mélange, which is located between the Bainaimiao arc and the North China Craton, holds significant clues regarding the tectonic setting of the southern margin of the Central Asian Orogenic Belt. The ophiolitic mélange is mainly composed of gabbroic and serpentinized ultramafic rocks. Here, zircon U–Pb dating, in situ zircon Hf isotopic, whole-rock geochemical and in situ mineral chemical data from the ophiolitic mélange are reported. The zircons in the gabbroic rocks yielded concordia U–Pb ages of 450–448 Ma and exhibited slightly positive ϵHf(t) values (0.87–4.34). The geochemical characteristics of the gabbroic rocks indicate that they were generated from a mantle wedge metasomatized by subduction-derived melts from sediments with continental crust contamination, in a fore-arc tectonic setting. These rocks also experienced the accumulation of plagioclase. The geochemical characteristics of the ultramafic rocks and their Cr-spinels indicate that they may constitute part of residual mantle that has experienced a high degree of partial melting and has interacted with fluids/melts released from the subducted slab in the same fore-arc tectonic setting. The ophiolitic mélange may therefore have formed in this fore-arc tectonic setting, resulting from the northward subduction of the South Bainaimiao Ocean beneath the Bainaimiao arc during Late Ordovician time, prior to the collision between the Bainaimiao arc and the North China Craton during the Silurian to Carboniferous periods.