Twenty-three species of the Family Discoasteraceae Vekshina, 1959 recovered from 18 samples of the Blue Clay at Fort Chambray, Gozo, and 31 samples from Fomm-Ir-Rih Bay, Malta, have been studied under light and scanning electron microscopes. Fourteen Middle Miocene species are reviewed, their stratigraphical ranges and importance as marker species discussed. Nine species are described as new. On the basis of the discoaster species present, a Middle Miocene age (NN.6 Discoaster exilis Zone – NN.7 Discoaster kugleri Zone) for the Blue Clay in Malta and Gozo is suggested.

The Hartshill Formation (c. 270 m) consists largely of shallow-water feldspathic sandstones and greywackes lying unconformably on Precambrian (Vendian?) volcanic rocks and below shales with the first olenellid trilobites. Five members are recognized. The Park Hill Member is conglomeratic and arkosic near the base, passing up into green-grey megarippled quartzites with some thick shale bands. The Tuttle Hill Member is more shaly and glauconitic with conspicuous bioturbation. The Jee's Member is of distinctly cross-laminated glauconitic, feldspathic greywackes and shales with numerous trace fossils. Conglomerates, shales, sandstones, phosphorites and limestones comprise the Home Farm Member, withadiverse Tommotiantype shelly fauna and stromatolites near the top. Massive arkoses and greywackes of the Woodlands Member yield similar shelly fossils in calcareous beds at the base and top while the overlying Purley Shale yields the first Lower Cambrian trilobites.

Schemes of Scottish Caledonian metamorphic zonation involving the Thermal Anticline have traditionally been used for reconstructing movement on the Great Glen Fault. Interpretation of the highland zonal pattern in terms of inverted zones severally parallel to the Moine Thrust and to the Highland Border Fault, representing perturbation of isotherms by under-thrusting, can be fitted to either sinistral or dextral models of transcurrent motion.

Folds of a 12 mm thick calcite-rich vein, embedded in slate and with a primary planar fabric of parallel, thin and plate-like calcite crystals, or laminae, have a vein thickness/arc length ratio near 1. Folds were first entirely dependent for development on intra-laminar strain and inter-laminar sliding. As limb dips increased, however, pressure solution began to thin laminae in limb regions only. As adjacent inter-laminar surfaces met at fold inflexion points, where laminae were first cut through, loss on fabric-cutting surfaces began to replace inter-laminar pressure solution. The resulting stylolites grew across the vein in fold limbs, at the limit eliminating them. In contrast, in folded equigranular calcite rocks stylolites are widely developed in both limbs and hinges, and eventual fold collapse through late stage concentration of pressure solution takes place in fold hinges and not limbs.

An unusual type of mottled area is described from titaniferous augites in the Dippin sill, Isle of Arran. These are characterized by abundant magnetite inclusions, irregular embayed outlines and distinctive chemical compositions. The possibility that these are due to zoning, especially sector zoning, is examined and discarded. They probably represent partly resorbed relics of pyroxene which crystallized at depth prior to the emplacement of the sill. As such they could have considerable petrogenetic implications both with regard to the sill itself and to alkaline basic magmas in general.

Richardson's (1911) detailed correlations of the Upper Rhaetic and Lower Lias strata of W Somerset are in need of revision; he wrongly identified the basal Langport Bed as the Cotham Marble at Blue Anchor and Lilstock. Likewise, his correlations of the Upper Rhaetic and Lower Lias strata between W Somerset and Glamorgan are erroneous; the lower parts of his Glamorgan Langport Beds were equated with the upper part of his W Somerset Cotham Beds. The greater part of the W Somerset Watchet Beds are, in the hand specimen, lithologically similar to Liassic shales and not to the White Lias ‘marly’ beds of Lavernock as he stated. The matter is important because the W Somerset coast is the recommended type area for the base of the Jurassic System, and Richardson&s classification of the strata is taken as the starting point for fixing this horizon.

Lava trees and tree moulds are common in many areas where fluid basaltic lava has moved rapidly over forested terrain. Lava trees are formed only by thin flows, but tree moulds are preserved in both thin and thick flows. Both structures may indicate the direction of flow of the lava in which they are preserved. The usefulness of lava trees in this regard is limited to recent flows; tree moulds, however, have been described in rocks as old as middle Tertiary. Features commonly well preserved on the inner walls of moulds indicate the local flow direction. When found in sufficient number, tree moulds provide information on the palaeoslope and vent location.