Santorini volcanic field has had 12 major (1–10 km3 or more of magma), and numerous minor, explosive eruptions over the last ~ 200 ka. Deposits from these eruptions (Thera Pyroclastic Formation) are well exposed in caldera-wall successions up to 200 m thick. Each of the major eruptions began with a pumice-fall phase, and most culminated with emplacement of pyroclastic flows. Pyroclastic flows of at least six eruptions deposited proximal lag deposits exposed widely in the caldera wall. The lag deposits include coarse-grained lithic breccias (andesitic to rhyodacitic eruptions) and spatter agglomerates (andesitic eruptions only). Facies associations between lithic breccia, spatter agglomerate, and ignimbrite from the same eruption can be very complex. For some eruptions, lag deposits provide the only evidence for pyroclastic flows, because most of the ignimbrite is buried on the lower flanks of Santorini or under the sea. At least eight eruptions tapped compositionally heterogeneous magma chambers, producing deposits with a range of zoning patterns and compositional gaps. Three eruptions display a silicic–silicic + mafic–silicic zoning not previously reported. Four eruptions vented large volumes of dacitic or rhyodacitic pumice, and may account for 90% or more of all silicic magma discharged from Santorini. The Thera Pyroclastic Formation and coeval lavas record two major mafic-to-silicic cycles of Santorini volcanism. Each cycle commenced with explosive eruptions of andesite or dacite, accompanied by construction of composite shields and stratocones, and culminated in a pair of major dacitic or rhyodacitic eruptions. Sequences of scoria and ash deposits occur between most of the twelve major members and record repeated stratocone or shield construction following a large explosive eruption.

Volcanism at Santorini has focussed on a deep NE–SW basement fracture, which has acted as a pathway for magma ascent. At least four major explosive eruptions began at a vent complex on this fracture. Composite volcanoes constructed north of the fracture were dissected by at least three caldera-collapse events associated with the pyroclastic eruptions. Southern Santorini consists of pryoclastic ejecta draped over a pre-volcanic island and a ridge of early- to mid-Pleistocene volcanics. The southern half of the present-day caldera basin is a long-lived, essentially non-volcanic, depression, defined by topographic highs to the south and east, but deepened by subsidence associated with the main northern caldera complex, and is probably not a separate caldera.

Two internal discontinuities are described from the Tertiary, Shiant Isles sill (northwest Scotland). The lower discontinuity separates picrite from overlying picrodolerite and the recently discovered upper discontinuity separates picrite from underlying crinanite. The sill is thus divided into an inner, strongly differentiated, picrodolerite–crinanite unit and outer picritic units. The lower discontinuity is slightly transgressive with respect to the picrite. The discontinuities are interpreted as the contacts between an earlier-intruded picritic sill (about 30 m thick) and a slightly later-intruded, much thicker, crinanitic sill. The Shiant Isles main sill is therefore a multiple intrusion.

Selected trace fossils from the type section of the ‘Etcheminian Series’ at Hanford Brook are described and illustrated: Helmithoidichnites tenuis Fitch, Monocraterion sp., Palaeophycus tubularis Hall, Planolites sp., Psammichnites gigas Matthew, Subphyllochordra? sp., Taphrhelminthoida dailyi n. sp., and Taphrhelminthopsis cf. T. circularis Crimes et al. The assemblage has elements comparable to those in other Lower Cambrian sequences. It formed in shallow water settings, is mainly endichnial, and contains systematic, guided meander traces that are generally characteristic of deep-water environments in younger sequences; this may be related to global environmental changes early in the Palaeozoic. The guided meander traces are characterized morphometrically, using an image analyser: the meander systems exhibit a strongly bimodal distribution of morphologic elements, reflecting a well developed taxis (sense for position, direction, and distance) during trace production. The method of morphometric analysis has potential for characterizing trace fossils generally, somewhat like X-ray diffractograms characterize minerals.

Crystal rich (∼ 70–98% phenocrysts) magmatic inclusions in pumices for compositionally heterogeneous ignimbrites from the Central Andes of northern Chile are interpreted as the products of crystal accretion at the sidewalls of the magma chambers. The inclusions are typically andesitic in composition and are found as ‘peppery textured’ lenses and bands, or as discrete ovoid ‘blobs’ within dacitic pumices from the early erupted portions of the ignimbrites. The inclusions have a bimodal gain size with large phenocrysts (> 1 mm), typical of those of the host pumice, set in a dominant finegrained framework (< 0.5 mm) of plagioclase, with lesser amounts of hornblende and biotite in equal proportions, and ubiquitous titanomagnetite in a matrix of vesiculated high-Si rhyolite glass. An igneous microgranular texture is defined by this framework. The mineralogy of the inclusions, as well as the compositions of the phenocrysts and glass, are very similar to those of the host pumices. These characteristics, in addition to available major, trace and REE data, are best reconciled if the inclusions represented samples of fractionated crystals and glass from the same magma as the host pumice. The restricted occurrence of these inclusions in the early erupted portions of the ignimbrites suggests that these crystal accumulations occurred in the upper portions of the magma chambers, at the sidewall; the dominantly fine grain size and crystal rich nature of the inclusions are considered to be the result of the higher thermal gradient in the boundary layer.

These inclusions may be an important link between the experimental and geochemical models for the origin of compositional layering in magma chambers by sidewall crystallization. The presence of similar inclusions in other ignimbrites and volcanics, as well as plutonics, suggest that they may be a common feature of silicic magmas.

The brissid echinoid Amoraster (gen. nov.) is described from Miocene strata in southern Australia on the basis of two species: A. paucituberculata sp. nov., which ranges from the Batesfordian (latest Early Miocene) Bochara Limestone to the Bairnsdalian–Mitchellian (Middle–Late Miocene) Port Campbell Limestone in Victoria; and A. tuberculata sp. nov. from the Longfordian (Early Miocene) Mannum Formation in South Australia. Morphological changes which occurred with the evolution of A. paucituberculata from A. tuberculata are interpreted as being adaptations to the occupation of a finer grained sediment by the descendant species.

The NW–SE Cornubian fault zones (FZs) continue to southwest Wales, where they caused dextral offsets during the late Stephanian. A fault bounded area of Devonian–Carboniferous strata, intruded by the Tertiary Lundy Igneous Complex, forms the Lundy Rhomboid. It originated as the Lundy Rhomb Graben, created by 28–40 km of Tertiary sinistral strike–slip faulting along the left-stepping NW–SE Sticklepath–Lustleigh FZ (SLFZ). Tertiary sedimentation in the graben was accompanied by intrusion of the 2.5–4.0 km thick igneous complex into its basement. Sedimentation later spread beyond the graben to form a ‘steer's horns’ basin, of which the Stanley Bank and West Lundy basins are remnants. The strata of the rhomb graben and the ‘steer's horns’ basin constituted the perhaps 4 km deep Lundy Pull-Apart Basin. Subsequent relatively minor dextral faulting on the left-stepping SLFZ inverted the graben into the Lundy Rhomb Horst; the basement of the graben was uplifted ≮ 1–2 km (net) and exposed by erosion of the Tertiary strata. The pull-apart basin developed at the intersection of reactivated Hercynian NW–SE transform FZs, and E–W subduction zone thrusts. Cenozoic N–S tensional and compressional reactivations of the thrusts were respectively associated with transtensional development of the pull-apart basin, transpressional of the rhomb horst.