A specimen of shale containing an echelon of quartz-filled vertical tension fractures which merge “at depth” with a single filled fissure dipping 65 degrees confirms, in general, E. M. Anderson's interpretation of dyke echelons. Also illustrated are a change in manner of stress relief and an upward diminution of strain.

Potassium-argon age measurements made on samples of rock from Charnwood Forest and surrounding districts indicate that the porphyroids and syenites probably date from late pre-Cambrian times. The area was affected by both the Caledonian and Hercynianorogenies. A number of the intrusive rocks of the Forest have been shown to date from Caledonian times. A dolerite from the Leicestershire coalfield gave a Permian age.

The paper deals with disturbances of bedding contemporaneous with deposition in Torridonian rocks of Skye and Raasay. Most of the structures described have the general form of sharp upwardly-directed peaks separated by areas of more or less undisturbed bedding; within the peaks the bedding is often contorted or destroyed. The structures are developed in sandstones and are thought to have been formed more or less in situ by the shifting and rearrangement of quicksands. An origin as a result of slumping is rejected. The appearance of the structures is thought to be connected with the environment of deposition which appears to be that of very shallow water.

In North Jan Mayen agglutinate is recognized as an important and widespread pyroclastic deposit of recent parasitic activity associated with the Beerenberg volcano. Lips of agglutinate along fissures, areas up to one square kilometre composed entirely of agglutinate, and other smaller morphological features are described. It is proposed to term the more widespread areas of agglutinate, “agglutinate fields,”, owing to their superficial resemblance to aa lava fields. Two varieties of agglutinate, one composed mainly of pancakes and bombs and the other of driblets of ankaramitic basaltic material are described, and conclusions given on their significance and formation.

The Pre-Cambrian rocks north of Three Rivers, Quebec, are cut by a major fault in which glassy pseudotachylites have been developed. The glass, which is dark brown in thin section, has a specific gravity of 2.76 and a refractive index of 1.567. It has a similarcomposition to the quartz monzonite in which it occurs. Absolute dating by the potassium-argon method indicates that the glass is 975 million years old. The persistence of thisglass indicates how sluggish devitrification can be when the environment is cool and dry.

Evidence is presented for the geological dating of the granitic gneiss of western Ardgour, the southernmost part of the discontinuous granitic gneiss outcrop which extends from Argyll to Inverness-shire along the Loch Quoich line between the “highly inclined” and “flat” belts of the Moines. The granitic gneiss is shown to have been formed before or early in the second of four main fold movements to which the surrounding metasediments have been subjected, and is thought to occupy the core of a complex anti-formal second major fold.

Granodiorite intrusions in Jamaica were assigned by early workers to various ages from Pre-Cambrian to late Tertiary. Recent surveys have shown that the granodiorite intrudes Maestrichtian sediments and has provided material for pebbles in an Eocene conglomerate. Its age is therefore very late Cretaceous or very early Tertiary. Radio-metric determinations using Potassium/Argon; Rubidium/Strontium and isotopic lead methods suggest an age of 65 ± 5 million years.

The distribution of Tertiary to Recent lavas in part of south-west Kenya is outlined, and attention drawn to the predominance of nepheline-rich Miocene lavas over other types west of the Rift Valley, which contrasts with the Pliocene olivine basalt-trachytecomendite association predominating within the Rift Valley. It is inferred that widespread Miocene phonolites west of the Rift Valley derived from a parent of approximate mela-nephelinitic composition, while within the Rift Valley extensive Pleistocene trachytes differentiated from an olivine basaltic parent. Plots of normative feldspathoid: feldspar versus silica, for analysed lavas from Kenya and Tanganyika, are used to illustrate the trends envisaged. The frequent association of nephelinitic lavas and carbonatite complexes in Kenya is discussed and the possibility mooted that the presence of nephelinite lavas may be indicative of nearby carbonatite complexes.

A study has been made in the laboratory of the strength of a “suite” of coal measure rocks in uniaxial and triaxial compression. From the data obtained it is demonstrated that the compressive strengths are profoundly influenced by the composition, porosity and degree of compaction of the rocks. It is indicated that these factors also influence the tensile and cohesive strengths.

A traverse of a noritic gabbro sill (c. 1,000 feet thick) intruding the Roraima Formation showed no cryptic layering, but small-scale fractionation throughout the sill is indicated by the strongly-zoned plagioclase (An80→40), and orthopyroxene (En79→54) with outer rims of inverted pigeonite. Olivine (Fo80) is only present in the chilled margin.

New evidence on the age of the granites underlying the Roraima Formation is given by the discovery of post-Roraima felsite dykes, with high-quartz phenocrysts.

Borehole cores have been obtained of a basic igneous sill at Landywood, near Cannock, Staffordshire. This intrusion consists mainly of microteschenite with a zone of teschenite in the top half of the sill. Later parts of the parental magma of this intrusion were dryer and crystallized to give crinanite and analcite olivine dolerite. These later parts were not intruded in sufficient quantities to spread through the whole of the sill and were restricted to the vicinity of the feeding pipe. Extensive secondary replacement of plagioclase by chlorite and of pyroxene by carbonate occurs in the teschenitic parts of the sill and is ascribed to the action of water and carbon dioxide derived from the magma.

Dykes with melilite occur in the area peripheral to the Rangwa complex. A flow-lineated alvikite dyke situated in the area just outside the North Ruri complex contains calcitic pseudomorphs of phenocrysts, and it is suggested that the majority of these are after melilite. The significance of the observed restriction of melilitic dykes to the peripheral area of the complexes is considered in the light of the recognition of a gradational progression from kimberlite-alnöite dykes to beforsite and alvikite dykes at Alnö island and its environs in Sweden. The possibility that cauldron subsidence is involved in some of the Kenya complexes is considered.

Five nomenclatural problems in the inarticulate brachiopods are discussed and solutions suggested for them. Two new genera, Eodinobolus, type species Obolellina magnifica Billings, 1872 and Orthisocrania, type species Pseudocrania divaricata M'Coy, 1851 are erected. Clistotrema nom. nov. for Orbicella d'Orbigny, 1847 non Orbicella Dana, 1846 is proposed.

Paradoxides sp. is recorded from South America for the first time, together with an associated faunule which includes Ehmania cf. akanthophora Harrington and Kay, 1951.

Evidence is sought to prove, with reference to five examples, that major cyclic changes in Jurassic sedimentation have been controlled by eustatic rises and falls of sea level. Abrupt variations suggestive of pronounced deepening of the sea in areas of marine sedimentation in Europe are correlated with extensive marine transgressions in widely separated parts of the world. A connection is recognized between eustatic movements and evolution and migration of the invertebrate fauna, and relationships between eustatic and local, epeirogenic movements outlined.

Lava channels flanked by lava levees are described from Tristan da Cunha. These have been formed by the building up of the levees by overflow and solidification of fluid lava from the channels. A distinction is made between the terms “lava levee” and “lava moraine”.

The BP Exploration Company's Colston Bassett (South) No. 1 Borehole, Nottinghamshire, entered Coal Measures at 1,134 feet. These persisted for 901 feet, when massive tuffs were encountered which were 679 feet thick and overlay Millstone Grit. The tuff is composed of amygdaloidal glass, devitrified to a montmorillonite, and is rich in analcime. In a nearby borehole, no tuffs were encountered and the Coal Measures were 1,784 feet thick. It seems that at Colston Bassett (South) the lowest Coal Measures sediments are represented by the tuff, which is non-displacive and was perhaps a cone against which the later sediments were deposited.

A network texture made of graphite with calcite filling the holes is described from an area of staurolite-garnet grade of metamorphism. It is pointed out that this is the earliest texture preserved in the rock, and that it resembles a cellular structure and may therefore be of organic origin, possibly a primitive plant. At present, however, it is not certain that the structure is organic in origin.

Specimens of Pseudoclimacograptus marathonensis sp. nov., preserved in relief, from the Ordovician of Marathon, Texas, are described. An account of a series of sections of the proximal end is also given. The material is compared with the compressed syntypes and other specimens of Amplexograptus Confertus (Lapworth), with which the new species had been confused.