Conglomerates from the Lettergesh Formation in the Silurian sequence of N Galway, Ireland, demonstrate palaeocurrents from the NE. Fabric studies demonstrate that the conglomerates were emplaced largely by traction currents and not by down-slope sliding or dispersive currents. Stratigraphic relationships demonstrate that the conglomerates were deposited in an environment which was adjacent to fluviatile, shallow-marine and deeper shelf facies at different times. A fan-delta environment of deposition is suggested, which requires a modification of previous Silurian sea-level curves at, or near, the base of the Wenlock.

Vigorous Carboniferous extensional tectonism and associated igneous activity is a feature of Ireland and the neighbouring areas of Newfoundland and Britain. In West Connacht, Ireland, dolerite dikes of late Carboniferous age are newly recognised and distinguished from Tertiary dolerites. In the N, the 320 Ma-old Logmor dike trends N–S across the Ordovician South Mayo Trough, and has an evolved, mildly alkaline basalt geochemistry. In the S, in Connemara, a diffuse and arcuate swarm of ENE–NE trending, 305 Ma-old dolerite dikes, the Teach Doite swarm, cuts the Galway Granite batholith and its envelope of Dalradian gneisses. These more tholeiitic dolerites reveal the mineralogical and geochemical effects of varying degrees of pervasive hydrothermal alteration, imposed on an original magmatic composition similar to that of mid-ocean ridge basalts. Variscan overprinting on k–Ar ages from West Connacht dolerites clusters at 300, 245 and 205 Ma. Overprinting is also a feature of much of the Galway Granite. Carboniferous diking in West Connacht may have responded to nascent opening of the proximate North Atlantic, its pattern related to domal uplift adjacent to the rifted zone.

A major transcurrent fault in the zone of the Iapetus suture in eastern Ireland separates Ordovician (pre-Ashgill) terranes. The stratigraphy of each terrane belongs to a dismembered volcanic arc system: the northern terrane is characterised by acid plinian eruptions and derivative sediments which are displaced relative to the andesitic southern terrane volcanism. Each was a separate palaeoenvironment with its own lithostratigraphical character and faunal elements which were juxtaposed across the fault. However, the late Ashgill to Silurian sediments in both terranes form part of a regional overstep sequence which links across the suture zone, such that the palaeogeographical contrasts were eliminated by the Silurian. The inference is that the detached terranes were gradually amalgamated by late Ordovician transtensional movements. This occurred when regional scale subduction-related volcanism had ended. Final assembly by early Devonian sinistral transpressive movements juxtaposed a northern terrane, akin to the Lake District/SE Ireland calcalkaline volcanic province, with a southern terrane in the tholeiitic province of eastern Ireland. As distinct from a singular fault trace, the Iapetus suture is regarded as a 100 km wide zone of anastomosing late Caledonian transcurrent faults whose precursors were active during late Ordovician (i.e. Taconic) terrane amalgamation.

On 17 July 1983 heavy rainfall resulted in a flash-flood in the headwaters of the West Grain, a small stream tributary to the River Wear in the northern Pennines. Associated with the flood was a series of three boulder-lobes. The morphology of these lobes and the associated sediment facies are described and used to estimate the hydro-dynamic mode of transport and deposition. Estimates of the shear-strength and viscosity are consistent with the initial conclusion (based on the sedimentology) that the deposits represent low-viscosity debris-flows. The boulder snouts moved as inertial grain-flows with an associated pebbly-core exhibiting a degree of matrix strength imparted by intergranular friction. A degree of reworking of the upper surface of the core by fluidal flow during core motion and immediately upon deposition was also identified. The full sedimentary sequence therefore represents debris-flow core deposits subject to low dispersive pressure evolving into fluidal debris-torrent deposits.

Anthraconaia lived on clay grade sediments. In highly variable life assemblages of the A.prolifera group of the E German Wettin Shales (Stephanian C) organic carbon percentage of the host sediment correlates with wu/m and A/L ratios of the shell (where wu is the maximum width ventral to the line of maximum growth, m, L the maximum length measured parallel to the line of the hinge, and A the length anterior to the umbo). Decrease in the organic carbon of the sediment is associated with decrease in umbonal development, elongation of the shell along the m axis, and straightening and reflection of the ventral margin; the latter becomes subparallel to the dorsum or to the m axis with a concomitant decrease in size. These results confirm and amplify earlier work on Anthraconaia in the Appalachian coalfields. The same morphological trends in relation to organic carbon characterise the Anthraconaia modiolaris group of Britain, both within a single succession in upper Westphalian A sediments in Yorkshire, and also in three shell bands of Lower Westphalian B age in S Wales, Yorkshire and central Scotland. In the last named, above the Musselband Coal, statistical formulae (of Leitch 1940) for the species A.salteri are shown to define neither the type assemblage nor its stratigraphical position. The shell-shape/organic carbon relationship has been broadly confirmed on other horizons of lower Westphalian B age in the Scottish and Pennine coalfields. Far from embarrassing the stratigrapher, the relationship, which reflects ultimately trophic level of deltaic palaeoenvironments, contributes to our understanding of non-marine bivalve faunas, especially of the apparent regional distribution of ‘species’ of Anthraconaia.

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.

In their account of the Orlock Bridge Fault of Northern Ireland and its presumed continuation into the Scottish Southern Uplands (the Kingledores Fault) Anderson and Oliver (1986) provide welcome detail in support of major strike-slip movement. However, their identification of the Kingledores Fault as a line of massive strike-slip movement is based on a number of assumptions which are permissible only because biostratigraphical control is generally sparse. In particular the assertion that the Kingledores Fault is a “giant step in the diachronous southerly ascent of the turbidite base” is founded largely on a misinterpretation of evidence recorded by Peach and Horne (1899), Griffith and Wilson (1982) and others.

We naturally regret our failure to convince the British Geological Survey's Southern Uplands team of the nature and importance of the fault which separates Northern and Central Belts, two of the three fundamental divisions of the Southern Uplands terrane which were so brilliantly recognised and defined by their illustrious predecessors (Peach & Home 1899). We welcome the opportunity to clarify the basis of our argument and correct some quite erroneous impressions.