Element, carbon and oxygen isotope fractionations have been studied in laminated deposits, manganese nodules and phosphorite lenses in clastic sediments of the Cambrian Timna Formation, southern Israel. Comparisons of element abundances show that only manganese, phosphorus and uranium were mobilized and concentrated during diagenesis: element fractionations among the diagenetic manganese components particularly resemble those observed in present-day suboxic pelagic marine sediments. Epigenetic processes involving reducing solutions reversed the diagenetic geochemical trends, with the redox-sensitive elements manganese and uranium showing considerable depletions in nodules, and iron and lead showing corresponding enrichments. The manganese oxides of nodules have calculated δ18O compositions varying from –1.6 to 3.1 ‰. These compositions are significantly lower than a δ18O value of 7.9 ‰ obtained for the manganese oxides of an ocean floor nodule and are taken to largely represent temperature differences between the ocean floor and the shallow marine Timna conditions. Slight decreases in δ18O accompany the transformation from diagenetic type A to epigenetic type B manganese nodules; corresponding shifts to lower δ18O are also inferred for the structural carbonate of apatites. Such shifts are compatible with re-equilibration accompanying a slight temperature increase and/or low temperature meteoric-water alteration. δ13C values of –7 to –12‰ obtained for the apatites of laminated deposits and phosphorite lenses are consistent with phosphorite diagenesis in suboxic to anoxic pore-waters. Early diagenetic redox conditions are indicated to be major controls governing the development of the assemblages.

Arenig (Ordovician) clastic sediments crop out in the Harlech Dome region (North Wales), and are placed in a single stratigraphic unit: the Allt Lwyd Formation. This unit records a marine transgression onto an erosion surface produced during late Tremadoc arc volcanicity. Four discrete petrofacies are denned, and reflect differing proportions of detritus derived from Tremadoc-type basic-intermediate igneous rocks, and the local sedimentary basement. Initial shallow marine siliciclastic sandstones and conglomerates are overlain by extensive deep water mud-rich units. These generally shallow up into a complex arc-apron deposit, with sediments derived from the eroding Tremadoc arc, as well as from similar, synchronous volcanics. Predominantly epiclastic sandstones and conglomerates were deposited in deltaic and tidal environments in an arc-apron complex, and capped by condensed mudstones and an ironstone, deposited as sea level rose across these systems. Sediments were ponded in north–south orientated troughs and derived from uplifted blocks. Facies and petrofacies distribution were controlled by syn-sedimentary north-south and northeast–southwest faults. The Allt Lwyd Formation was ponded in a fault-controlled basin (the Dolgellau Basin), one of a series of interconnected sub-basins flooded by the Arenig transgression. The sediments preserved reflect deposition during the transgression of a volcanic arc, prior to the extrusion of marginal basin-type volcanics.

Middle Cambrian and Caradoc metabentonites and associated mudrocks are described from the northern part of the Welsh Lower Palaeozoic basin. They occur in areas of slight deformation, distant from thick piles of contemporaneous volcanics. The < 2 μm fraction from anchizonal Middle Cambrian metabentonites consists dominantly of 1Md micas (with up to 5% randomly interstratified smectite) with lesser 1M and 2M1 muscovite, corrensite, quartz, chlorite and kutnohorite. Interbedded mudrocks are similar but contain, additionally, minor paragonite and regular (6:4) paragonite-muscovite. Late diagenetic grade Caradoc bentonite consists of rectorite, pyrophyllite and small amounts of chlorite. Interbedded mudrocks are similar but contain, additionally, 1Md mica with up to 10% smectite interlayers, minor kaolinite and quartz.

Metabentonites contain high concentrations of the trace elements Ce, La, Hf, Nb, Ta, Th, Y and Zr in comparison with associated mudrocks. Discriminant diagrams indicate derivation from trachyandesite–dacite–rhyolite magmas in a within-plate setting. Major element variations in Cambrian metabentonites compare closely with those described in Silurian examples whereas the Caradoc metabentonite is closely similar to rhyolitic tuffs in the Caradoc Llewelyn Volcanic Group.

Both geochemical and field evidence indicate that whereas Middle Cambrian mudrocks were derived from bentonitic material adulterated variably by a terrigenous input. Lower Cambrian mudrocks were derived from a strongly depleted source such as basic Mona Complex rocks. Geochemical and field evidence suggest Caradoc mudrocks southeast of the Aber–Dinlle fault are largely volcanogenic; and the geological setting of Tremadoc, Arenig and Llanvirn mudrocks demands some volcanogenic input.

The Caradoc volcanic succession of Snowdonia is represented by a single bentonite northwest of the Aber–Dinlle fault. The fault system was either a highly effective contemporaneous barrier or, more probably, a site of post-Caradoc transcurrent movement.

The Lower Cambrian Fucoid Beds of northwest Scotland are a 20 m thick mixed clastic-carbonate sequence of thinly bedded storm beds deposited on the western margin of the Iapetus Ocean. Proximal facies display plane beds, current ripple laminations and wave ripple laminations and were deposited under the influence of combined steady andoscillatory currents. The steady component of flow appears to have expanded in an offshore direction and weakened during the final stages of storm deposition with respect to the oscillatory component, producing less asymmetrical ripples with less evidence of a preferred migration direction. Distal facies are represented by thin ‘graded rhythmites’. The palaeocurrent data suggest a wide spread of sediment transport directions, but with a north to northeasterly mode which may reflect a geostrophic component of flow. Following storms these beds were burrowed and echinoderms colonized the sea floor, although the limited extent of these processes and the presence of abundant collophane suggests that the fairweather Fucoid Beds shelf was generally quiescent and possibly dysaerobic.

An analysis of outcrop and borehole information relating to the strata between the Upper Band and Better Bed coals of the central and south Pennines shows that two lithological facies can be recognized within a cyclic sequence of mudstones, siltstones and sandstones. In one facies, sandstones and siltstones contain abundant mica, and argillaceous beds are neutral grey in colour. Petrographically the sandstones are feldspathic but contain little lithic material other than multigrain quartz. In the other facies, mica is much less common, argillaceous beds are greenish grey, and sandstones and siltstones contain a notable proportion of chloritic lithoclasts. The sediments of both facies were deposited in lower delta plain/shallow-water delta environments, and palaeocurrent measurements show that the micaceous facies was supplied from the north or east while the green facies came in from the west.

Three named divisions of the sequence are based on recognition of the two facies types. They correspond roughly with three upward-coarsening transgressive–regressive sedimentary cycles of presumed eustatic origin. In the lowest part of the succession (Shibden division) the main clastic input was of the micaceous type. Sandstones are found only in the north of the basin, where they form a series of superimposed delta-front bodies. Mudstones were deposited elsewhere, in a large body of open water which, although linked to the sea, was generally of lowered salinity. The restriction of the delta-front sandstones to the same geographical area over a long period of time is attributed to differential subsidence of the basin across deep-seated structures.

The sediments of the overlying Brighouse division belong to the green facies, and the source of the elastics lay to the west. After an initial period of mudstone deposition in an extensive, apparently non-marine, body of open water, fluviodeltaic sand and silt spread across the entire area. There is no obvious control of sandstone distribution by basement structures.

The succeeding Bradley Wood division includes sediments of both micaceous and green facies. A lobe of medium-grained micaceous sandstone around Sheffield (Thurlstone Channel) represents a fluvial incursion from the east and a linear body of fine-grained green-facies sandstone south of Chesterfield (Bole Hill Channel) represents a similar incursion from the west. Elsewhere, small units of finer-grained elastics are probably deltaic deposits linked to the same sources. The location of the channel sand-bodies suggests control by deep-seated fractures.

The metaluminous to peraluminous granitoids of the Donegal batholith, northwest Ireland, were emplaced at c. 400 Ma into greenschist-amphibolite facies metasediments of the Dalradian Supergroup. Sm-Nd and Rb-Sr isotopic data are provided for eleven granitoid samples from six of the plutons and one specimen from the northeast granodiorite pluton of the Newry complex, Co. Down; the Donegal results reveal essentially similar initial Sr isotope ratios (0.7051–0.7068) but highly variable initial eNd values, −1.2 to −8.3 (and −0.5 for Newry). Certain granitoids have distinctive Nd isotopic compositions characteristic of the involvement of old, LREE-enriched continental crust in some cases or young crust and/or mantle-derived magmas in others. The Nd and Sr isotopic variations can be explained by a variety of mixing hypotheses.