Upper amphibolite facies dolomite and calcite marbles from the Dalradian Connemara Marble Formation of western Ireland display a wide range of textures when viewed in cathodoluminescence that are invisible in transmitted light. Examples observed include growth zones in calcite that appear to represent the infilling of a metamorphic secondary porosity, produced by the large reduction in solid volume accompanying growth of tremolite from dolomite and quartz. Retrograde phenomena are widespread, and include both carbonate pseudomorphs after tremolite and coarse veining, which is in optical continuity with peak metamorphic calcite but otherwise indistinguishable from it. Admixture of such widely differing calcite types may account for scatter in some stable isotope studies of marbles.

The late Carboniferous to Triassic Karoo Supergroup of Madagascar is a sequence of predominantly continental clastic sediments deposited during a long period of regional crustal extension. In the Morondava Basin of western Madagascar the lower two divisions of the Karoo sediments – the Sakoa and the Sakamena – are deposits of fluvial and lacustrine sedimentation systems supplied from the Precambrian metamorphic basement terrain to the east. East–west crustal extension produced a series of graben and half-graben structures after the Sakoa period which were reactivated after the Sakamena. The position and orientation of these half graben, which were marginal to a larger rift system to the west, were partly controlled by the steep NNE–SSW mylonitic fabric in the metamorphic basement. Palaeocurrents in the braided river deposits of the Sakoa and Lower Sakamena indicate flow to the southwest and west in both sequences. The rivers followed a regional palaeoslope to the southwest/west and were apparently not significantly influenced by the local structural trends which were oriented perpendicular to this slope. The absence of local structural control is attributed to extensive erosional events which followed each tectonic episode and preceded the onset of further sedimentation which took place on an essentially peneplained surface. The tectonic episodes brought about changes in base level which caused this part of the basin to fluctuate between erosion and deposition.

Using examples from the Gulf of Suez and southeastern France, the distribution of tension tectonic joints as well as shear tectonic joints in continuous profiles is shown to fit a Gamma distribution. The parameters of this distribution are determined using the maximum likelihood method. Apparent fit with negative exponential distribution in photointerpretation analysis results from lack of resolution. The average joint spacing is directly proportional to bed thickness; it decreases when the degree of rock consolidation increases.

On mainland North Wales basement rocks emerge from beneath a Lower Ordovician cover along the west side of the Llyn peninsula. The basement contains steeply dipping mylonites (Llŷn shear zone) that separate plutonic and gneissic rocks (Sarn Complex) from a melange (Gwna mélange). The western edge of the Ordovician outcrop follows the basement shear zone, and new trenching data confirm that only a faulted relationship exists between cover and basement along this northwestern extremity of the Welsh Basin. Deformation along this margin has propagated into the Arenig cover to produce southeasterly verging thrusts, asymmetric folds and northwesterly dipping cleavage. A prominent steep fault (Daron Fault) cutting the Ordovician succession follows an eastern splay of the Llŷn shear zone and again therefore records brittle reactivation of an underlying mylonite belt. The likelihood of syn-Arenig fault movements is provided by the presence of a prominent late Arenig coarse clastic unit, containing boulders of the basement mylonites, that is found only to the west of the Daron Fault. Steep basement structures such as the Llŷn shear zone, initially generated as major transcurrent faults, are interpreted as having exerted a strong control over the deposition and subsequent deformation of the Ordovician cover sequence.

Compositional variation in Lower Old Red Sandstone (ORS) detrital garnets can be used to evaluate potential source areas and to trace the pattern of early Devonian sediment dispersal. Garnets in northwesterly derived fans along the northern flank of the Midland Valley appear to duplicate spatial variation in the compositions of garnets in the adjacent Dalradian block. Whilst metamorphic clasts ‘resembling’ Dalradian lithologies occur in these fanglomerates, the strike-extent of Dalradian-type crust (c. 1000 km) makes simply matching the clasts a rather imprecise way of constraining source–basin displacement. The garnet data imply that the Ordovician separation inferred for crustal blocks juxtaposed along the Highland Boundary was removed by early Devonian times. Major Silurian displacements are thus invoked along the Highland Boundary with amalgamation largely achieved prior to the ‘Acadian’ transcurrent deformation seen in the slate belts to the south. Vertical changes in the composition of garnets in the thick Lower ORS sequence in the northeast Midland Valley are slight and it is not known to what extent these reflect migration of a differentiated source block or the involvement of recycled additions which become increasingly important towards the base of the ORS succession. The axially dispersed sandstones which interdigitate with the northwesterly derived fans are dominated by spessartine-rich almandines which resemble garnets fed laterally to the basin in the northwest Midland Valley. Although the large scale inferred for the axial fluvial system suggests that its drainage basin extended outside Scotland, almandine-pyropes which might have come from exhumed eclogites in western Norway are absent. Such compositions are widespread in Mesozoic sandstones in the northern North Sea and it is evident that these sediments do not represent the final repository for the 'lost' sediment stripped from Caledonian metamorphic terranes in Scotland. Garnet populations from the Anglo-Welsh Basin do not resemble those in the coeval axial sandstones of the Midland Valley, suggesting that the two basins were not linked at this time. The scale of the Midland Valley axial sandbodies are inconsistent with internal drainage of central Scotland and a route to the early Devonian shoreline must be sought. It may be that 'Acadian' strike-slip motions have displaced the Scottish basins from the coastal alluvial plains they originally fed.

A regional Tertiary basaltic dyke swarm intensifies within a Caledonian granite at Barnesmore, Co. Donegal. Rapid heating along the contact of one (possible feeder) dyke resulted in disequilibrium partial melting of granite wall-rock and the generation of a range in melt composition by the in situ melting of feldspar. The compositional variability of the melt is preserved in a glass containing feldspar spherulites and other quench phases which suggest rapid cooling. During partial melting the trace elements, Rb, Sr, and Ba were mobile and have been concentrated in glassy melted granite close to the contact of one dyke. The textures, mineralogy and geochemistry of dolerite in two dykes indicate localized bulk contamination and mixing with melted granite. This had a particularly marked effect on the crystallization of pyroxene and resulted in a wide range in mineral composition reflecting the degree of contamination. The intensification of a regional dyke swarm in well-jointed granite might control the siting of some major intrusive centres. Granite melted and mixed with basaltic magma may contribute to the evolution of granites in such centres.

Facies analysis suggests that Westphalian (Upper Carboniferous) Coal Measure sequences on the Isle of Arran, Scotland, were deposited in a proximal alluvial plain environment close to the basin margin. Detailed examination of well exposed coastal sections has revealed the existence of six laterally and vertically interrelated sedimentary facies. Facies 1 to 3 are interpreted as fluvial channel deposits. Low sinuosity multistorey (facies 1), low sinuosity vertically accreted (facies 2), and rare high sinuosity laterally accreted channel deposits (facies 3) are developed. Associated overbank sediments comprise the deposits of crevasse splays (facies 4), flood plains (facies 5) and shallow lakes (facies 6). In terms of the spatial distribution of facies, a relatively high proportion of fluvial channel and floodplain deposits (facies 2 and 5) occur in the more proximal sequence at Laggan compared with the more distally located sequence occurring at Corrie. Palaeocurrent measurements from fluvial channel sandstones indicate that sediment source areas and the Westphalian basin margin lay to the north and northwest. Down palaeoslope towards the southeast, normal coal-bearing Westphalian sediments formed penecontemporaneously on the Scottish mainland in Ayrshire.

A sedimentological model is presented for the proximal non-coal-bearing Westphalian sequences of Arran. This model can explain the differences observed between the Arran sediments, and contemporaneous normal coal-bearing Westphalian sediments of the Scottish mainland.

A Lower Cretaceous mixed carbonate-siliciclastic sequence is well exposed in the Zaraya Mountains in Guipuzcoa Province, northern Spain. The sequence begins with interfingering deltaic platform facies and marine patch-reef carbonates. This unit is dominated by mudstones and sandstone with minor interbeds of shallow-water carbonates (calcareous mudstones and sandstones and grainstone-packstones). A thick mixed carbonate-terrigenous unit overlies the siliciclastics and is composed principally of limestones and marls. Periodic influx of terrigenous sediments over a dominantly carbonate sea-floor gave rise to repeated cycles typical of a mixed shallow-water platform. Demise of the southerly derived deltaic input allowed the development of a mainly carbonate third unit. Large (several metres across) bioherms resulted from high in situ organic productivity (mechanical breakage of bioclasts, algal-induced precipitation, trapping and baffling of lime mudstone). The mounds grew making up a coral carbonate mound complex. This prograded to the south, towards a small backreef basin, and slightly retreated in its forereef margin. A period of tectonic instability is thought to have been responsible for the drowning of the shallow-water complex, which was unable to keep pace with relative sea-level rise.

Thin beds and small pods of quartz-spessartine metasediments (coticules) occur in pelites of the Gamlan Formation (Cambrian) of the Harlech Dome. The original microfabric of these sediments has been largely destroyed by recrystallization under low greenschist facies conditions. The quartz-spessartine pods occur throughout the pelites and appear to have formed by the metamorphism of diagenetic Mn-carbonate concretions. The thin beds of quartz-spessartine rock appear to have formed by the metamorphism of a protolith which was deposited rapidly and repeatedly over a wide area. Although there is no direct evidence of the nature of this protolith, the presence of altered Mn-carbonate-rich tuff beds in anchizonal mudstones of similar age in the St Tudwal's Peninsula suggests that the bedded quartz-spessartine rocks are, in fact, metamorphosed Mn-carbonate-rich tuff units. Both the bedded and podiform quartz-spessartine metasediments appear to have formed by reaction between clay minerals and Mn carbonates of earlier diagenetic origin.