This paper describes the suture zone between the Asian plate and the accreted Kohistan island arc in the Chitral district of NW Pakistan.

The southern part of the Asian plate consists of two tectonic units separated by the N-dipping Reshun fault. The northwestern unit comprises Devonian carbonates and quartzites overlain by Devonian to Permian shales and slates with some limestones (Lun shales). Its structure is complex with S-verging thrusts and isoclinal folds. Along the Reshun fault, the relatively undeformed Reshun Formation may represent molasse. The central unit includes N-dipping Upper Palaeozoic slates and quartzites (Darkot Group), probably faulted against an antiformal tract of slates, schists derived from a volcanic assemblage and Cretaceous limestones (Chitral slate, Koghozi greenschist, Krinj and Gahiret limestones). Asian plate sediments are intruded by granitic and granodioritic plutons, variably deformed and locally porphyritic.

The Northern suture melange of volcanic, sedimentary and serpentinite blocks in a slate matrix separates the Asian plate from the southeastern unit, the Kohistan arc. This comprises Cretaceous volcanic rocks with some sediments (Shamran Volcanic Group, Drosh, Purit and Gawuch Formations) intruded by aphyric diorites, tonalites and granites. These intermediate plutonic rocks pass southwards into a mafic layered complex and amphibolites representing deep levels of the arc. The volcanic rocks and sediments dip to the N and have a horizontal lineation. The structural history of southern Asia and Kohistan is consistent with an originally curved Northern suture: motion of the arc was initially to the NE relative to Asia and subsequently to the NW.

Since the late 1980s an extensive programme of trenching/borehole drilling has been undertaken in order to study the Lower Devonian ‘Lower Old Red Sandstone’ deposits of the Rhynie outlier in the Grampian Highlands of Scotland. The boreholes have provided new information on the stratigraphical succession and geological structure of the Rhynie outlier, both of which were hitherto poorly understood due to the paucity of good surface exposure and the complex geological relationships of the deposits. One hundred and eighteen palynological samples were collected, representing much of the stratigraphical sequence of the inlier, of which 106 were productive. Productive samples yield assemblages of well preserved palynomorphs, dominated by spores and phytodebris, but also containing arthropod cuticle and rare freshwater algal remains. The spore assemblages are systematically described and two new genera and six new species proposed. They are similar throughout the sequence and the spores belong to the polygonalis–emsiensis Spore Assemblage Biozone of Richardson & McGregor (1986) and the PoW Oppel Zone (possibly Su Interval Zone) of Streel et al. (1987), indicating an early (but not earliest) Pragian–?earliest Emsian age range, that may possibly be restricted to latest Pragian–?earliest Emsian. The palynomorph assemblages contain only terrestrial forms, supporting sedimentological interpretation of the deposits as ‘Lower Old Red Sandstone’ fluviatile and lacustrine deposits, with occasional extrusive volcanics and volcaniclastic sediments intercalated. The palynomorphs are of variable thermal maturity (within and between samples), probably reflecting differential heating associated with the complex volcanic/hydrothermal system. The new palynological data provide, for the first time, a reliable biostratigraphical age for the deposits, and suggest that they accumulated relatively rapidly. Spore biostratigraphy and thermal maturity studies facilitate correlation of the tectonically complex deposits, and shed light on other aspects of the geological history of the outlier. The palynomorph assemblages also aid interpretation of the biota of the Rhynie basin, including the exceptionally preserved biotas of the Rhynie and Windyfield cherts.

Plutonic complexes with interlayered mafic and silicic rocks commonly contain layers (1–50 m thick) with a chilled gabbroic base that grades upwards to dioritic or silicic cumulates. Each chilled base records the infusion of new basaltic magma into the chamber. Some layers preserve a record of double-diffusive convection with hotter, denser mafic magma beneath silicic magma. Processes of hybridisation include mechanical mixing of crystals and selective exchange of H2O, alkalis and isotopes. These effects are convected away from the boundary into the interiors of both magmas. Fractional crystallisation aad replenishment of the mafic magma can also generate intermediate magma layers highly enriched in incompatible elements.

Basaltic infusions into silicic magma chambers can significantly affect the thermal and chemical character of resident granitic magmas in shallow level chambers. In one Maine pluton, they converted resident I-type granitic magma into A-type granite and, in another, they produced a low-K (trondhjemitic) magma layer beneath normal granitic magma. If comparable interactions occur at deeper crustal levels, selective thermal, chemical and isotopic exchange should probably be even more effective. Because the mafic magmas crystallise first and relatively rapidly, silicic magmas that rise away from deep composite chambers may show little direct evidence (e.g. enclaves) of their prior involvement with mafic magma.

This study of the mineralogy and metamorphism of the Moine schists approaches the problem through consideration of the chemical composition of the minerals. The principal minerals of the Moine schists are studied individually, thirty-three new analyses of minerals being given, with four of schists. For all but six analyses the trace elements have been determined and are tabulated. Muscovites, biotites and garnets all show variation of composition with increasing metamorphic grade, respectively with decreasing Fe2O3 and SiO2, increasing MgO and Al2O3, and decreasing CaO plus increasing MgO, these being only the principal variations. The crystal chemistry of the muscovites, biotites and garnets is briefly discussed. Some new data are presented for the relationship of plagioclase and epidote, a relationship which can only be used with extreme caution to indicate metamorphic grade. A dependence of the incidence of a sutured quartz aggregate in psammitic schists upon the microcline content is noted, and it is suggested that the incidence of the breakdown of quartz under the combined effect of temperature (the dominant cause), stress and potassio solutions, all active in the core, is responsible for the production of the core-envelope boundary. This boundary transgresses the strike; within it retrogressive changes have converted Garnet-zone schists to Biotite-zone schists, but outside it the only retrogressive change is garnet to chlorite. The retrogressive metamorphism formed a distinct episode separated from the initial regional metamorphism by an unknown time-interval; during the second metamorphism isotherms were concentric with the dome, declining outwards. The evidence of an epidiorite from the west coast of Morar suggests that during the first metamorphism the zonal state there was that of the Dalradian Biotite-zone; “almandine” garnets in the adjacent schists are extremely rich in CaO and are in equilibrium with microcline.

Igneous charnockites are characterised by distinctively high abundances of K2O, TiO2, P2O5 and LIL elements and low CaO at a given SiO2 level compared to metamorphic charnockites, and I-, S- and A-type granites. They form a distinctive type of intrusive igneous rocks, the Charnockite Magma Type (CMT or C-type), which generally lack hornblende and consist of pyroxene, alkali feldspar, plagioclase, quartz, biotite, apatite, ilmenite and titanomagnetite. Although this mineral assemblage superficially resembles that of metamorphic charnockites, magmatic charnockites are characterised by inverted pigeonite, exceptionally calcic alkali feldspar, potassic plagioclase, and coexisting opaque oxides, all with crystallisation temperatures of 950-1050°C. Apatite is a ubiquitous phase which, together with the very high concentrations of Zr and TiO2 over a wide silica range, is consistent with the derivation of the Charnockite Magma Type by very high temperature partial melting and fractionation.

The credibility of intrusive charnockites as a magmatic type has historically foundered because of their apparent restriction to granulite belts and the absence of any reported extrusive equivalents. We report examples of volcanic rocks, of various ages, with the same distinctive major and trace element compositions, mineral assemblages and high temperatures of crystallisation as intrusive chamockites.

The Charnockite Magma Type is considered to be derived by melting of a hornblende-free or poor, LILE-enriched fertile granulite source which had not been geochemically depleted by a previous partial melting event but which was dehydrated in an earlier metamorphism. Whereas H2O-saturated melting produces migmatites or "failed" granites, and vapour-absent melting of an amphibolite can produce I-type granites, according to this model the vapour-absent melting of a hornblende-free or hornblende-poor granulite at even higher temperatures produces charnockites.

Twenty-two years have now elapsed, since Runge first published his remark, able experiments on coal naphtha, and it would, perhaps, be difficult to instance any chemical investigation which has formed the point of departure of a greater number of researches. When we consider the vast quantity of bodies which have, first and last, been obtained from coal-tar, it might appear that little more remained to be done,—that the mine was exhausted,—but so far from this being the case, the discovery of one substance has only served to pave the way for the isolation of others.

Among the bodies examined by Runge, there was one which apparently possessed comparatively few features of interest; indeed its very name (the first syllable derived from λευχός was intended to express its supposed inability to produce coloured reactions, a feature which, in the chemistry of the time, militated greatly against its claims to notice. I have used the expression “supposed inability,” because I shall show further on, that this substance is capable, under certain conditions, of affording extremely brilliant colorations. Eventually, Gerhardt, by acting on quinine, cinchonine, and strychnine, with hydrate of potash, obtained the same body. The first chemist who succeeded in procuring any of its compounds in a state of tolerable purity was Hofmann, whose analysis of the platinum salt is very nearly exact. But, at the time of that analysis, he was of opinion that the products obtained from coal and chinoline were essentially different, an opinion which he subsequently retracted. In the mean time, the alkaloid, as obtained from cinchonine was examined by Bromeis and Laurent, their results, however, not elucidating the composition of the basic fluid obtained in the manner alluded to.

Graphic correlation using graptolites and conodonts provides a high-resolution timescale for correlating from coastal to deep oceanic sections and, thereby, also a detailed record of the sequence of changes during the Mulde Secundo-Secundo Event. That interval includes sedimentary facies otherwise unknown in older Wenlock to early Ludlow strata on Gotland. The identified sequence of changes includes a detailed record of, in order: two extinctions (Datum points 1 and 1·5); widespread deposition of carbon-rich sediments extensive enough to cause a δ13C increase of c. 4.8‰, the onset, maximum and end of a sea-level fall and rise of at least 16 m during 30 kyr; a third extinction (Datum 2); a disaster fauna; and a slow faunal recovery. Thus, a secondary result of the event was a weakened greenhouse effect triggering a glaciation: the Gannarve Glaciation (new term). The order of changes proves that regression did not cause the extinctions. Faunal and sea-level changes, as well as the sedimentary succession, fit well with predictions based on an oceanic model. Extinctions were primarily caused by a severe drop in primary planktonic productivity, causing starvation among planktonic larvae in non-coastal settings. The Grötlingbo Bentonite (new term), the thickest in the Wenlock of Gotland, was deposited across the basin shortly after Datum 2. Temporal resolution is high enough to permit some comparison with Quaternary glaciations.

The Lower Devonian plant- and arthropod-bearing cherts of the Rhynie area of Aberdeenshire, NE Scotland, were deposited from silica-rich waters emanating from the hot-springs of a precious-metal (Au) bearing epithermal system. Cherts were deposited at temperatures up to 100°C. The hot-springs were active in the waning phase of local volcanism and reworked volcanic debris is associated with the hot-spring system. Plant and animal communities inhabited a low energy alluvial plain with small ponds. Hot-springs deposited surficial sinter and silicified standing plants and underlying plant litter in a generally terrestrial setting, but aquatic organisms were present in low temperature pools within areas of sinter deposition. Silicification also affected plants and sediment in the shallow subsurface. The cherts display massive, vuggy, laminated, lenticular, nodular and brecciated textures in laterally impersistent beds. Faunal and floral variation between beds is of local significance, possibly reflecting general water availability. Variations in preservation of plants reflect not only degrees of imperfection in the permineralisation process, but also silicification at different times in the cycle of plant growth and decay.

The Palaeogene volcanic succession of the Faroe Islands in the NE Atlantic Ocean is formalised using a purely lithostratigraphic approach and following international guidelines. The Faroe Islands Basalt Group (FIBG) has a gross stratigraphic thickness of ∼6·6 km, dominated by subaerial basalt lava flows, and is subdivided into seven formations. The Lopra Formation forms the basal ∼1·1 km of the Lopra-1/1A borehole, dominated by hyaloclastites, volcaniclastic sandstones and invasive basaltic lavas/sills. It is overlain by the ∼3·25 km-thick Beinisvørð Formation, dominated by laterally extensive basalt sheet lobes separated by minor volcaniclastic lithologies. The Beinisvørð Formation is overlain by the <15 m-thick, inter-eruption, coal-bearing facies of the Prestfjall Formation and the <50 m-thick, syn-eruption, pyroclastic and sedimentary facies of the Hvannhagi Formation. Lava flow volcanic activity resumed with the <1·4 km-thick Malinstindur Formation, dominated by thinly bedded compound basalt lava flows. The top of this formation is marked by a regional disconformity surface, overlain by sandstone and conglomerate deposits of the maximum 30 m-thick Sneis Formation, a newly recognised stratigraphic unit. The final phase of volcanism recorded on the Faroe Islands consists of the >900 m-thick Enni Formation composed of a mixture of basalt sheet lobes and compound flows with abundant volcaniclastic units, e.g. the Argir Beds, that may require a further subdivision at this stratigraphic level. The new lithostratigraphy allows for more refined biostratigraphical and sequence stratigraphic correlations and prepares for a revised geological map of the Faroe Islands.

The prominent felsic granulites in the southern part of the Bohemian Massif (Gföhl Unit, Moldanubian Zone), with the Variscan (∼340 Ma) high-pressure and high-temperature assemblage garnet+quartz+hypersolvus feldspar ± kyanite, correspond geochemically to slightly peraluminous, fractionated granitic rocks. Compared to the average upper crust and most granites, the U, Th and Cs concentrations are strongly depleted, probably because of the fluid and/or slight melt loss during the high-grade metamorphism (900–1050°C, 1·5–2·0 GPa). However, the rest of the trace-element contents and variation trends, such as decreasing Sr, Ba, Eu, LREE and Zr with increasing SiO2 and Rb, can be explained by fractional crystallisation of a granitic magma. Low Zr and LREE contents yield ∼750°C zircon and monazite saturation temperatures and suggest relatively low-temperature crystallisation. The granulites contain radiogenic Sr (87Sr/86Sr340 = 0·7106–0·7706) and unradiogenic Nd ( = − 4·2 to − 7·5), indicating derivation from an old crustal source. The whole-rock Rb–Sr isotopic system preserves the memory of an earlier, probably Ordovician, isotopic equilibrium.

Contrary to previous studies, the bulk of felsic Moldanubian granulites do not appear to represent separated, syn-metamorphic Variscan HP–HT melts. Instead, they are interpreted as metamorphosed (partly anatectic) equivalents of older, probably high-level granites subducted to continental roots during the Variscan collision. Protolith formation may have occurred within an Early Palaeozoic rift setting, which is documented throughout the Variscan Zone in Europe.

Assemblages of acritarchs are described from the Fucoid Beds of Skiag Bridge, Knockan Cliff and Skye in NW Scotland, and Holmia Shales of the Mjøsen area of Norway, the Bastion Formation of Ella Ø in East Greenland, the Lower Cambrian of the Burin Peninsula in Newfoundland and from the Gog Formation of the Rocky Mountains of Banff National Park, Alberta. These are shown to be correctable on the basis of acritarchs and with the Lower Cambrian successions of the Russian Platform. Twenty-one genera and fifty-three species of acritarchs and one tasmanitid are described. These include the new genera Skiagia and Volkovia, and thirteen new species, Acrum cylindiferum, Micrhystridium coniferum, M. ellaensis, M. ellipticum, M. flexispinosum, M. gogensis, M. minutum, M. ordensis, Multiplicisphaeridium ? waltoni, Skiagia brevispinosa, S. scottica, Revinotesta ordensis and Evittia irregulare. A number of recombinations have also been made.

In the southern part of the Archaean craton of South India, an approximately 3.4–2.9 b.y. old migmatite–gneiss terrane (Peninsular gneiss complex) has been subjected to granulite facies metamorphism about 2.6 b.y. ago. During this event, the extensive charnockite-khondalite zone of southern India developed. A younger metamorphism (Proterozoic?) led to retrogression of the charnockites and khondalites, mainly under the conditions of the amphibolite facies.

The physical conditions of metamorphism have been evaluated by applying methods of geothermobarometry to the widespread charnockitic assemblages with garnet, orthopyroxene, clinopyroxene, plagioclase, and quartz. The interpretation of the P–T estimates includes a critical discussion of potential error sources, e.g. errors of the analytical data and the calibrations of the models, and takes into account the complex metamorphic history of the rocks and the kinetics of the mineral equilibria.

P-T estimates were obtained for seven subareas from the rim compositions of the coexisting minerals: Shevaroy Hills 680±55°C—7·4±1 kb; Kollaimalai area 680±40°C—8·6± 1 kb; Nilgiri Hills 680±90°C—6·6±0.8kb (upland massif) and 705±60°C—9·3±0.8 kb (northern margin); Bhavani Sagar area 650±50°C—7·2± 1 kb; Sargur-Mysore area 690±60°C—7·6 kb; Bangalore-Kunigal-Satnur area 760±50°C—6 kb. Except for the last subarea, the P-T model data reflect the conditions of a late annealing stage probably related to the retrogressive metamorphism. Conditions near the peak of granulite facies metamorphism (730–800°C—6·5–9·5 kb) are recorded by the core compositions of the minerals. Although a rather uniform cooling history of the main part of the charnockite-khondalite terrane is suggested from the temperature data, differential uplift of smaller blocks is indicated by the regional variation of the pressure data.

There are few parts of mechanics in which theory has differed more from experiment than in the theory of elastic solids.

Mathematicians, setting out from very plausible assumptions with respect to the constitution of bodies, and the laws of molecular action, came to conclusions which were shewn to be erroneous by the observations of experimental philosophers. The experiments of Œersted proved to be at variance with the mathematical theories of Navier, Poisson, and Lamé and Clapeyron, and apparently deprived this practically important branch of mechanics of all assistance from mathematics.

Archaeological investigations demonstrate that peoples first settled the Caribbean islands approximately 6000–7000 years ago. At least four major, and multiple minor, migrations took place over the next millennia by peoples from Mesoamerica and South America who practised various subsistence strategies and had different levels of technology. For decades, researchers have been interested in investigating how these groups adapted to and impacted insular environments through time. This paper combines archaeological, palaeoecological, historical, and modern biological data to examine the effects of humans on Caribbean island ecosystems using a historical ecology approach. By synthesising a wide range of data sources, we take a human/nature dialectical perspective to understanding how peoples adapted to and modified their environments. The data suggest that earlier foraging/fishing Archaic groups (ca. 6000–3000 BP), who used a stone tool and shell technology and transported few, if any non-indigenous plants or animals, still impacted island landscapes as evidenced by bird and sloth extinctions. As more advanced ceramic making horticulturalists entered the Antillean chain around 2500 BP, there is an observable change to island environments as a result of forest clearance, overexploitation of both terrestrial and marine resources, and growing populations. Palaeoecological and palaeoenvironmental records also suggest, however, that an increased moisture regime during the late Holocene probably led to a decrease in near-shore salinity and heavier sediment and nutrient loads in rivers. These conditions would have been exacerbated by land clearance for agriculture, leading to coastline progradation, increased turbidity, and mangrove development resulting in changes to the availability of resources for humans on some islands. Although prehistoric peoples in the Caribbean were certainly impacting their environments, it was not until Europeans arrived and population centres grew that intensive and widespread degradation of island landscapes and resources occurred. Modern ecological studies, along with historical and archaeological data, indicate that hundreds of species have been driven to extinction or extirpation – many others have significantly diminished in number, especially within the last two millennia.

The principal descriptions and figures of the Ordovician and Silurian brachiopods of the Girvan district are found in Davidson's Monograph on the British Fossil Brachiopoda, completed about thirty years ago, and issued by the Palæontographical Society. The third volume of this work (published 1866–1870), and the Supplement to the fifth volume (published 1882–1883), dealing with species from Ordovician and Silurian beds, contain descriptions of many Girvan forms, but not apart from those occurring in other British localities. No independent and comprehensive treatise on this group as represented in the Girvan area has been published, though many short papers have dealt with a few species or portions of the fauna. Especially noteworthy are the papers and works by M'Coy and Salter, mentioned in the list at the end of this memoir.

Consideration of six balanced cross-sections through parts of the Finnmark Caledonides, N Norway indicates that shortening varies between 25% and 75%. A restored long cross-section across the width of the orogen, constructed with the aid of a branch line map, demonstrates a foreland propagating thrust system, with earlier formed more internal metamorphic nappes thrust SE 330 km under ductile conditions and then carried piggyback ESE a further 296 km on later brittle thrust sheets. Total shortening is 78·7% with a translation of the most internal thrust sheet of 626 km.

The restored section suggests that: (1) the rate of propagation of deformation from hinterland to foreland is c. 2·27 cm y−1; (2) incorporation of basement into the nappes resulted from inversion of extensional faults formed during Iapetus rifting; (3) during rifting a Finnmark basement ridge separated a 220 km wide southeasterly Gaissa basin from the passive Iapetus continental margin which was at least 423 km wide; (4) the Finnmark Caledonides resulted from a continent-microcontinent collision which obducted continental crust at least 600 km across the Baltic margin; and (5) the Caledonian Baltoscandian margin prior to Iapetus suturing extended at least 400 km W of the Norwegian coast. On a Bullard reconstruction this overlaps with Laurentian rocks in Greenland. The excess continental crust is accounted for by shortening of the Baltoscandian margin during collision.

The tract of country extending across this island, from the sea-coast of Galloway to that of Berwickshire, consists, with little interruption, of that species of rock, which has of late been most generally known by the German name of Grauwacke. But as this rock does not differ essentially from what in Cornwall is called Killas, I am disposed, in concurrence with several members of this Society, in particular with Mr Allan, who has of late been in Cornwall, and has paid particular attention to that subject, to reject the uncouth term Grauwacke, and adopt that of Killas, as being more congenial to our language.

The Newark-APTS established a high-resolution framework for the Late Triassic and Early Jurassic. Palaeomagnetic polarity correlations to marine sections show that stage-level correlations of continental sequences were off by as much as 10 million years. New U–Pb ages show the new correlations and the Newark basin astrochronology to be accurate. Correlation of Newark-APTS to the Chinle Formation/Dockum Group, Glen Canyon Group, Fleming Fjord Formation and Ischigualasto Formation led to the following conclusions: (1) there are no unequivocal Carnian-age dinosaurs; (2) the Norian Age was characterised by a slowly increasing saurischian diversity but no unequivocal ornithischians; (3) there was profound Norian and Rhaetian continental provinciality; (4) the classic Chinle-, Germanic- and Los Colorados-type assemblages may have persisted to the close of the Rhaetian; (5) the distinct genus-level biotic transition traditionally correlated with the marine Carnian–Norian is in fact mid-Norian in age and within published error of the Manicouagan impact; (6) the end-Triassic marine and continental extinctions as seen in eastern North America were contemporaneous; and (7) compared to Triassic communities, Hettangian and Sinemurian age terrestrial communities were nearly globally homogenous and of low diversity. Consequently, the complex emerging picture of dinosaur diversification demands biostratigraphically-independent geochronologies in each of the faunally-important regions.

The behaviour of trace elements during partial melting depends primarily on their mode of occurrence. For elements occurring as trace constituents of major phases (e.g. Li, Rb, Cs, Eu, Sr, Ba, Ga, etc.), slow intracrystalline diffusion (D ≍ 10−16 cm2 s−1) at the temperature range of crustal anatexis causes all effective crystal-melt partition coefficients to have a value close to unity and impedes further melt-restite re-equilibration. Usually, therefore, the trace element composition of crustal melts simply depends on the mass balance between the proportion and composition of phases that melt and the proportion and composition of newly formed phases. The behaviour of trace elements occurring as essential structural components in accessory phases (e.g. P, La-Sm, Gd-Lu, Y, Th, U, Zr, Hf, etc.) depends on the solubility, solution kinetics, grain size and the textural position of accessory phases. In common crustal protoliths a significant mass fraction of monazite, zircon, xenotime, Th-orthosilicates, uraninite; etc.—but not apatite—is included within other major and accessory phases. During low melt fraction anatexis the amount of accessory phases available for the melt is not sufficient for saturation, thus producing leucosomes with concentrations of La-Sm, Gd-Lu, Y, Th, U and Zr lower than expected from solubility equations. Low concentrations of these elements may also occur if the melt is prevented from reaching equilibrium with the accessories due to fast segregation. However, the first mechanism seems more feasible as leucosomes that are undersaturated with respect to monazite and zircon are frequently saturated, even oversaturated, with respect to apatite.

Both textural maturity and structure acquired by gravels on beaches are largely a response to the interaction between beach surface and wave-backwash energy. The turbulent energy driving the processes of particle rejection andselection at the surface of growing gravel sheets is partly controlled by the grain size of the sheet itself, so the process is to a large extent self-regulating. Beach surfaces are seen to comprise many discrete sheets of gravel competing for growth at their boundaries, but each characterised by a uniform or uniformly gradational texture.

There are two main types of gravel sheet: (1) selection pavements which occur on low beach slopes, showing little areal grain-size or grain-shape variation, and (2) turbulence shadows which occur on steeper slopes and produce assemblages of clasts which may show perfect lateral shape and size gradation.

The clasts which make up these various gravel sheets are termed ‘clast assemblages’, and such assemblages are the fundamental units from which beaches are constructed. Clast assemblages are classified in terms of their textural maturity—the degree to which they exhibit uniformity in clast size and shape. In beach sections they are, either singly or in combination, bounded by planes of discontinuity (bedding planes) to form beds.

Repeated combinations of either clast assemblages or beds in a genetic association are regarded as sedimentary structures, many of which are diagnostic of the gravel beach environment. Growth of beaches involves the stacking of sedimentary structures, and four growth patterns have been identified. The beach structure is, therefore, classified in a hierarchy comprising clast assemblage, bed, structures and growth form, and it is the growth pattern which may be related to tidal range. P.ecognition of the processes which generate beach gravels through the structure of the gravels permits an analysis of the internal structure of major gravel bodies such as barrier beaches. It adds another set of criteria which may further lead to an understanding of the processes responsible for the generation and evolution of these large gravelforms.

Three types of gravel lithosomes have been identified. (1) Regressive barrier bars which form a series of gravel ridges separated by lagoonal deposits. Barriers are built initially by swash bars which grow in size and coarsen through time to become wave-resistant forms. They form as a response to times when the sediment, unable to be evenly distributed and sorted on the beach surface, forms a discrete bar seaward of the active beach. This is the result of a punctuated or continuously high sediment supply compared with the wave energy available to disperse the sediment, or a falling sea level which shifts the locus of sediment accretion. (2) In contrast, regressive (prograding) gravel sheets form as a response to a continuous supply of sediment to the beach surface, allowing it to build seaward by the uniform accretion of sediment which is sorted and retained on its surface. (3) Gravel sheets produced in transgression are characterised by an abundance of spherical clasts and are often overlapped by the sand beaches which occur seaward of them.