The position of the Iapetus Ocean suture can be traced between Ordovician fossil localities in the Southern Uplands and the Lake District which contain, respectively, distinct North American and European faunas. The Southern Uplands contains North American Caradoc faunas in the Northern Belt, and is considered to have been accreted onto the Laurentian (North American) margin between the Llandeilo and the end of the Wenlock. Deep seismic reflection profiling shows that a surface, probably parallel to the suture zone, dips down to the northwest from the Solway Line. In eastern Ireland, the surface trace of the suture coincides with the Navan Fault, which separates the Longford-Down massif from Ordovician sediments containing European faunas. The Navan–Silvermines Fault may represent the surface expression of the suture, but it is masked by Wenlock turbidites, which appear to have crossed over the plate boundary. Northward subduction of continental crust below the margin of Laurentia during the late Silurian may explain the influx of turbidite fans from the north or north west onto depressed crust to the south of the suture. Termination of subduction coincides with the widespread Acadian Orogeny in the Emsian (at 395±5 Ma).

The early Ordovician was a time of maximum continental separation and hence a time when faunal evidence can be used to assess palaeogeography in a critical way. We summarize the known trilobite occurrences (18 genera) from the Arenig–Llanvirn of the Lake District, and record some genera for the first time. Maps of the distribution of some of these forms are given. All genera except Cyclopyge were confined to the Gondwana continent at the time, and some are known from many localities; and two species are widespread in England, Wales, France, Iberia and Bohemia. The fauna is entirely distinct from those of Scandinavia and North America. All the palaeontological evidence points to the Lake District being adjacent to Ordovician Gondwana. In the earlier Ordovician it is not reasonable to suggest that the Iapetus Ocean lay to the south of the Lake District as did Allen (1987).

High concentrations of vanadium, molybdenum, uranium, arsenic, antimony with low concentrations of manganese, iron and cobalt heretofore restricted to Dictyonema flabelliforme-bearing Tremadoc black shales in Balto-Scandia, have been found in coeval black shales in the Saint John, New Brunswick area. Prior palaeogeographic reconstructions place these areas about 400 km. apart in high southern latitudes in the Iapetus Ocean, with New Brunswick in proximity to Avalonia (southeastern Newfoundland). These geochemical similarities are not found in coeval Tremadoc black shales of Bolivia, New York, Quebec, Wales, and Belgium. Palaeo-oceanographic reconstructions of Iapetus support the proximity of Balto-Scandia and the Saint John area during the early Tremadoc and Gee'sx (1981) suggestion that the signature is a feature of eastern Iapetus. Furthermore, first-order modelling of the major surface currents and related primary productivity in the Tremadoc Iapetus Ocean explain the apparent wide latitudinal range of D. flabelliforme (Fortey, 1984) and the anomalous trace metal content of certain black shales of that time. Variations in the elemental content of these black shales is produced by oceanographic and geologic conditions unique to the geographic site. The distinctive Balto-Scandic geochemical signature resulted from the coincidence of anoxic waters transgressing the shelf at latitudes of high organic productivity at the polar Ekman planetary divergence. This produces the conditions for concentrations of V, U, and Mo in the shales. Metal enriched anoxic bottom waters produced by leaching of volcanics or through hydrothermal activity may be the source of the other enhanced signature elements such as As and Sb. The absence of this geochemical signature in younger non-D. flabelliforme Tremadoc and later black shales in Balto-Scandia and other areas suggests that the closing of Iapetus moved the depositional sites into less productive oceanic areas.

Alkaline and ultramafic lamprophyre dykes at Aillik Bay on the coast of central Labrador exhibit features indicative of volatile-rich conditions at the time of emplacement. Aillikites (ultramafic lamprophyres) are flanked by closely spaced fracture systems whose formation was promoted by a carbonate-rich fluid moving ahead of the intruding magma. Sannaites (alkaline lamprophyres) frequently have horned termination structures which are interpreted to be partial reconnections between dyke segments which had separated at an earlier stage of intrusion.

The lamprophyre dykes comprise three sets which are interpreted as cone sheets and radial dykes related to an intrusive centre located beneath the Labrador Sea to the northeast of the coastal exposures. This complex is one of several on the margins of the Labrador Sea, and its position may be influenced by the Archean/Aphebian boundary and by a major oceanic structural feature represented by offsets in seafloor magnetic anomalies.

The earliest of four distinct phases of deformation recognized in the central part of the Proterozoic Mount Isa inlier involved brittle extensional faulting at shallow crustal levels. Extensional faulting produced stacks of imbricate fault slices, listric normal faults and characteristic tourmalinerich breccias. Structures belonging to this phase occur over a large part of the inlier and indicate an important phase of basin-forming crustal or lithospheric extension at 1750–1730 Ma. Late intense ductile deformation and tight folding of the imbricate systems destroyed part of these older structures, and obscures their existence in many parts of the inlier.

The Periadriatic Lineament Zone which forms the boundary between the Eastern and Southern Alps in the Karawanken region of Austria has a complex history spanning the Variscan and Alpine orogenies. Variscan regional metamorphism and polyphase deformation followed by Late to Post Variscan intrusive activity with accompanying contact metamorphism affects a belt of structurally complex rocks referred to as the Eisenkappel Zone to the north of the lineament. Weak Early Alpine deformation in the Southern Alpine rocks can also be recognized in the Eisenkappel Zone. The Young Alpine intrusion of the Karawanken Tonalite was followed by lateral fault displacements associated with the formation of the Periadriatic Lineament. Late Tertiary sediments, caught up in the northward directed thrusting responsible for the uplift of the Karawanken chain, record the youngest deformation in the area.

The Loch Monar Synform folds the Sgurr Beag slide in the central northwest Highlands of Scotland. The east–west trend of the synform is oblique to the regional trend of the slide. However, when late-stage strain effects associated with superimposed folds on the synform are removed using computer techniques, the trace of the synform axial surface becomes perpendicular to the regional trace of the slide. The synform also becomes tighter and recumbent in attitude. The synform axis is parallel to strongly developed lineations. Folds of this generation appear to be localized in the vicinity of the slide. These observations suggest a model of folding associated with movement of the slide, followed by locking up of the slide and internal strain resulting in the superimposed folds and rotation of the synform.

Several phosphatic zones are associated with the oldest remains of shelly fossils on the arctic island of Spitsbergen. The phosphate occurs as reworked nodules and layers associated with a disconformity. A gap in the acritarch biostratigraphic record supports a hiatus associated with the phosphatic zone. Palaeogeographic positions for Svalbard, both (1) as a single unit, and (2) as three isolated parts prior to Caledonian tectonism are consistent with conditions favourable to at least minimal amounts of upwelling. However, upwelling may not have been a prerequisite for development of these phosphate deposits. These phosphates were deposited in a nearshore shelf environmnt which contrasts with the outer shelf setting of many modern and recent phosphate deposits.

Geochemistry of the Lower Cambrian phosphates of Spitsbergen varies with the mode of phosphate occurrence. Concretionary phosphate clasts are chemically zoned such that their centres are enriched in P2O5 and CaO and are depleted in A12O3, SiO2, and K2O. Laminated and thinly bedded phosphate shows no chemical zonation within clasts. Phosphate cements are the most pure with respect to calcium phosphate.

This thin phosphatic zone of Svalbard is minor when compared with thicker and richer Lower Cambrian phosphate deposits, particularly those in the Soviet Union, Southeast Asia, and Australia. Coupled with the near absence of phosphate in some extensive Proterozoic to Lower Palaeozoic successions (e.g. western North America), this emphasizes the fact that widespread Lower Cambrian phosphate deposition was unevenly distributed. Althouth the Upper Proterozoic and Lower Cambrian are characterized by enhanced phosphogenesis, palaeogeographic position was also apparently critical to deposition of phosphatic sediments.