The 10 to 20 m resolution of SPOT image data, together with their potential for stereoscopic viewing, provides an excellent base for geological mapping inremote and rugged terrain that is akin to high-level aerial photographs. Their large format (60 × 60 km) also gives the advantage of synoptic coverage that ranks with images from the Landsat series of satellites. Use of stereo pairs of single-band SPOT images has enabled some revision of existing geological maps of the southern Aravalli Hills in Rajasthan at a scale of 1:100000, and has added significantly to knowledge of their complex mid-Proterozoic structure. In particular, many possibly early low-angled faults have been discovered, together with the tectonic nature of a major terrain boundary and much detail of intricate structures has been added in the more remote areas. The potentialfor lithological discrimination of multispectral SPOT data is severely limited by its restricted coverage of geologically important spectral features, and it is far surpassed by that of Landsat Thematic Mapper data, which would have been capable of more comprehensive lithofacies reconnaissance, had they been available.

Metabasalts of the Upper Ordovician Solund-Stavfjord Ophiolite Complex of the westernmost Norwegian Caledonides, show N-to E-MORB affinity, with high Th/Ta (or Nb) ratios giving evidence of subduction influence. The Solund–Stavfjord Ophiolite Complex is overlain by a heterogeneous assemblage of sedimentary and volcanic rocks, the Stavenes Group, of which the Heggøy Formation of metasandstones and phyllites conformably overlies the metabasalts of the Solund–Stavfjord Ophiolite Complex. The Heggøy Formation contains, in places, abundant metabasalt pillow lavas and minor intrusions, geochemically similar to those of the Solund–Stavfjord Ophiolite Complex, and basic metavolcaniclastites of island arc tholeiite (IAT) composition. This indicates that the Solund–Stavfjord Ophiolite Complex and Heggøy Formation developed in a marginal basin between a continental margin and an active subduction system, for which the present-day Andaman Sea may provide a realistic model. The other magmatic rocks of the Stavenes Group, showing both calc-alkaline and alkaline affinities, are less well time-constrained, but they are thought to represent an advanced stage of the island arc development, and ocean island build-up, respectively.

Upper Ordovician – lower Silurian sequences of the Bohemian Massif (in the Moldanubian Zone and Barrandian preserved in the Prague Basin; Rožmitál area; metamorphic ‘islets’ in the mantle of Central Bohemian Pluton; and in the Železné hory area), as well as along the northern margin of the Bohemian Massif in the Saxothuringian and Lugian (= West Sudetian) zones, show evidence of regressive–transgressive facies changes which can be related to glacio-eustatic sea-level fluctuations recognized elsewhere. Glacio-marine diamictites of late Ordovician (Hirnantian) age occur in the Prague Basin and Rožmitál area, and in north Bavaria and Thuringia. They provide evidence of temporary cooling of the region. Facies changes caused by synchronous sea-level changes allow stratigraphic correlation of even the faulted, weakly metamorphosed and biostratigraphically poorly dated sections in the Bohemian Massif. Correlation is based on sections in the Prague Basin in which the changes are best recorded and dated.

The proposed correlation of Lower Old Red Sandstone dacitic ignimbrites between the Northern Midland Valley and Grampian terranes of central Scotland has been investigated in a combined palaeomagnetic and geochemical study. Statistically indistinguishable late Silurian palaeolatitudes (Grampian terrane 27.0° S±3.5°; Northern Midland Valley terrane 22.9° S± 1.8°), comparable remagnetization histories, a shared ‘normal’ polarity for the primary magnetization and equivalent gyroremanence acquisition, favour correlation across the Highland Boundary Fault. Similar chemistry for biotite phenocrysts further corroborates correlation which was initially made on the basis of a similar field appearance and petrography.

This correlation, together with evidence from provenance studies, suggests that the separation of the Northern Midland Valley and Grampian terranes inferred for the Ordovician period was largely removed by late Silurian times, with scope for relative displacements of the order of only tens of kilometres after Lower Old Red Sandstone deposition.

Metabentonites occur extensively in the Moffat Shale Group of the Southern Uplands of Scotland. At Dob's Linn 135 metabentonite beds, 1–50 cm thick, occur in Ashgill to Llandovery strata, representing an aggregate thickness of 6 m of compacted ash accumulated over approximately 25 Ma. The metabentonites are characterized by relatively high concentrations of trace elements, including Ba, Cs, Hf, Nb, Rb, Ta, Th, U, Y, Zr and REEs, which were inherited from evolved vitric ash. Immobile trace element data indicate that a spectrum of silicic ash compositions accumulated, ranging from subalkaline to mildly peralkaline. In the late Ordovician N. gracilis to G. persculptus biozones, subalkaline ash falls predominated, whereas peralkaline ash falls predominated in the Llandovery (Silurian) P. acuminatus to M. convolutes biozones, giving way to predominantly subalkaline ash falls during accumulation of the M. sedgwickii to R. maximus biozones. Changeovers in the dominant ash types are marked by increased proportions of ash. The magmas from which the ash types evolved were generated in an ensialic arc transitional to a back-arc setting, and involved attenuated sialic crust and mantle characterized by variable depletion in HFS elements. Lithological, petrological and REE characteristics suggest that the Moffat Shale Group is not exclusively pelagic in origin and probably accumulated in a back-arc basin bordering an ensialic arc terrane.

The use of calcrete horizons as a means of assessing rates of sediment accretion in ancient alluvial sequences is reviewed. Any attempt to use such horizons in quantifying ancient alluvial deposition must appreciate that accurate data on rates of formation of Quaternary calcretes are limited. Such data show considerable variations in the rates and no reliable data exist at all for some calcrete types. The abundance of calcretes in the geological record warrants a new initiative to improve our understanding oftheir origins and rates of formation.