The generic composition of trilobite faunas around the perimeter of North America during the Medial Ordovician is related to the regional palaeogeography deduced from field evidence. Major divisions into shelf, shelf-edge (biohermal mounds) and slope (upper and lower) can be recognized. The Caradoc immersion of the N American plate resulted in landward invasion of pre-adapted slope forms. Some of these genera had European origins and their appearance is due to migration in deeper water facies accompanying closure of the Proto-Atlantic ocean. There is no obvious repeat of Cambrian biomere patterns in the Ordovician although some later Ordovician trilobites, especially shelf inhabitants, had their origins in earlier Ordovician biohermal or slope communities. The origin and composition of the Remopleuridid faunal Province is briefly discussed.

Thrust-bound bodies of trondhjemite, showing variable intensity of deformation, contain micro-structural evidences which suggest that the mylonitic fabric in them had developed in stages. An initial shearing stage was followed by a flattening one when the characteristic mylonitic microstructures and banding developed. These stages were punctuated and overlapped by phases of recovery and recrystallization. Mineral parageneses and microstructures indicate that prograde metamorphism and ductile deformation characterize the flattening stage. The origin of mylonite is explained in a scheme of progressive deformation during which planes of maximum shear strain and flattening became almost parallel, so that brittle microstructures were either modified or obliterated by ductile ones. The sequence of microstructural development and mineral redistribution suggest that in mylonite formation mechanical process is accompanied with chemical mobility.

A technique is described for direct analysis of rock-fabric, utilising hardness differences between various mineral constituents. This renders unnecessary the intermediate step of measuring optical orientations. The direct relation that exists between hardness of the components making up a particular fabric and the start of plastic deformation of each mineral can be measured quantitatively on the basis of polishing hardness differences. If the surface roughness signal is digitalised, then it is possible to automatically construct a microtopography, with contours delineating resistance of individual minerals.

Three sets of kink bands occur in Campanian chalk, near the coast of the Gulf of Elat. The kink bands can be traced by a system of vertical joints, intersecting the chalk and filled with secondary crystalline calcite. The geometry and the development of these structures are described, suggesting a change of the stress regime during the opening of the rift along the studied area.

A method is presented using a nomogram to estimate the size of a random sample from a normal population.

A boulder of plutonic igneous rock, petrologically perhaps best termed a trondhjemite, which occurs as an isolated megaclast in slumped mudstones of the Singa Formation (mainly Carboniferous) at Pulau Tepor off NW Malaya, has been dated by the potassium–argon method. Two feldspar fractions, thought to represent alkali feldspar and plagioclase (though both are highly sodic) yield ages of 1029±15 Ma and 575±10 Ma, respectively, while a whole-rock sample yields an age of 264±4 Ma. The highest age is taken to give a minimum age for the rock, and the lower ages to indicate differential argon loss. This is the first radiometrically proved Precambrian rock from the Malay Peninsula, and tends to reinforce earlier inferences of a Precambrian continent as a source area for Palaeozoic sediments in the region.