Reconnaissance work carried out in north-east Southern Rhodesia has shown that the Umkondo System, previously known in the Mozambique Belt, extends into the Zambesi Belt. It is further demonstrated that the two belts were broadly continuous in structure and metamorphism during the important orogeny c. 500 m·y. The possibility that the mobile belts were active considerably earlier than 500 m·y. is discussed.

Axial-trace-fractures are defined as joint or fracture cleavage surfaces which intersect bedding surfaces parallel to adjacent fold axes, and which meet stratigraphically higher bedding surfaces at acute angles closing towards adjacent anticlinal hinges. In the Upper Palaeozoic rocks of South Pembrokeshire these fractures are developed equally on fold limbs, in regions of low dip, and around fold hinges. Characteristically they are interrupted at bedding surfaces and vary in frequency with lithology. The value of the angle they subtend with bedding surfaces varies with lithology and dip.

Calcareous concretionary rods, thought to have been originally normal to depositional surfaces, are now orientated parallel to axial-trace-fractures and at right angles to fold axes.

The axial-trace-fractures of South Pembrokeshire are considered to have been formed immediately before or at the start of the Armorican folding, and then to have been rotated and sheared during the folding.

Other joints associated with axial-trace-fractures are described and briefly discussed.

The structure of the North Island of New Zealand is dominated by a central volcanic high with girdles of Tertiary sediments concentrically about it.

Banding, recorded by previous workers in hornblende picrite and dolerite intrusions near Rhiw, is found to be rhythmic layering. At least three major units (200 to 250 feet in thickness) have been recognized, and intermediate and minor scale units also occur, predominantly within the basal major unit. The majority of the rocks display cumulate textures, and crystallization appears to have been completed by heteradcumulus or adcumulus growth. Thin coarser-grained sheets, rich in plagioclase, and slightly discordant to the layering, are considered to be contemporaneous segregation veins.

Sediments of late Pre-Cambrian age mapped in the Kimberley Region of Western Australia have all the characteristics of tillite, and their glacial origin is confirmed by: the presence of very large polished and striated erratics, the great diversity of megaclasts, their regional extent, and the presence of striated, grooved, and polished quartzite bedrock directly beneath the tillite.

Faceted and flat-iron-shaped pebbles are rare or absent; most megaclasts tend towards an ellipsoidal shape—an observation in agreement with recent theories of glacial abrasion.

Local magnetic anomalies of large magnitude are found over the marginal ultrabasic rocks of the Loch Ailsh intrusion. An intrepretation of these anomalies based on the measured magnetic properties of the pyroxenites shows that they are not reconcilable with a low-angle structure as required by the hypothesis that the intrusion is a stratified laccolite, and suggests that they form a steeply dipping sheet at the syenite-limestone contact. Similar anomalies occur along the southern margin of the Loch Borralan complex, suggesting steeply dipping marginal ultrabasic rocks.

A structural analysis of the cliffs and one pit section in Pleistocene deposits at Weybourne has shown one major phase of ice movement only. Ice moving from approximately 210 degrees caused the disturbance of the upper part of the Chalk (together with the overlying Weybourne Crag) and the deformation and deposition of a chalky-boulder-clay, thought to be equivalent to the Lowestoft till.

A number of rotational strike-slip faults in the Ludlovian-Downtonian deposits of the Llandeilo region, Carmarthenshire, are described.

The succession of individual coloured bands in two manganese ore specimens has been analysed for eight trace elements, and has revealed some long-term chemical variations of possible regional extent throughout the period of ore deposition. Previous work on the distribution of elements between the three types of coloured ore banding is confirmed, and new data on the equivalent coloured bands of the contemporaneous Newfoundland manganese bed reveal an essential chemical, as well as lithological, identity of the two rocks. The effects of weathering and oxidation on ore geochemistry are discussed.

Petrographic and chemical data are presented and a possible means of derivation from an ultrabasic rock is discussed.

A microscopic study of sandstones of Old Red Sandstone and Carboniferous ages along a part of the North Crop of the South Wales Coalfield reveals that the rocks are extensively fractured. The fractures occur in the quartz grains and are often filled with bubble-like inclusions. These planes of inclusion were studied in specimens over a wide area, and are related to the directions of faulting and jointing. The consistency in trend between the macro and micro-structures suggests a homogeneity of the deforming stresses.

Lower Palaeozoic rocks in the Langkawi Islands have been subject to three generations of deformation. In the slightly dynamo-meta-morph slates in the south-east two generations of cleavage folding have been developed with a N.N.W. trend. The first resulted in a recumbent folding with a subhorizontal slaty cleavage, whereas during the second generation the slaty cleavage was deformed in open folds and a crenulation cleavage developed in the steep limbs. The two deformations were probably not formed at exactly the same time, but seem to be related with each other. Boudinage of granite sills was contemporaneous with the development of the slaty cleavage.

In the unmetamorphosed northern part of the area cross-folding is found. Flexure folds with a N.W. trend are superimposed on folds with a N.N.E. trend. In the Upper Palaeozoic sediments such deformations are missing. The Permian and Carboniferous strata show only a slight warping around the granite batholith which was intruded during Jurassic time (Pacific orogeny). A similar warping is found in the large low-angle overthrust, in which Silurian was thrust over Permo-Carboniferous. Consequently this thrust plane is dated as pre-granitic and post Permo-Carboniferous. Contact metamorphism by the granite intrusion has resulted in hornfelses in the Permo-Carboniferous sequence and in the development of oriented minerals, mainly clinozoisite, in the Ordovician-Silurian slates. Knick zones and intense jointing parallel with the mineral orientation (third generation structures) are also a result of the granite intrusion.

The first two generations of folding, which are not present in the Upper Palaeozoic beds, are products of an erogenic phase, “the Langkawi folding phase,” during late Silurian-Devonian time. The lack of Devonian strata in Thailand and the incompleteness of the Devonian sequence in Malaya (recently a few outcrops of probably Middle-Upper Devonian strata are found along the west coast of Malaya) can be an indication that the Langkawi folding phase is not restricted to the Langkawi Islands.

An interesting occurrence of highly potassic lavas and hypabyssal intrusives of assumed Tertiary age is described from North Johore. The thickest lava flow is gravitatively differentiated showing a basal horizon of potassic ankaramite and basanite grading up into highly potassic bolitized flow tops of leucite-tephrite composition. Evidently the parent magma was close to a biotite pyroxenite in composition and possibly an assimilation product of peridotite by granite.

Intersections may exist between a zone of chemical discontinuity (basalt—feldspathic periodtite or eclogite—garnet peridotite) and a phase transition zone (basalt—eclogite or feldspathic peridotite to garnet peridotite) at about the depth of the continental M-discon-tinuity. Variations in depth to the chemical discontinuity and in the positions of isogeotherms produce flexibility in erogenic models. Intersections between the two zones at depth could be reflected at the surface by major fault zones separating large structural blocks of different elevations. The effects of such intersections on the conventional hypothesis for the development of tectogenes, geosynclines, and mountains are considered. The intersections could provide a beginning and an end to the more vigorous changes in surface level occurring during an orogenic cycle.

An example of the development of axial plane schistosity close to a buckled competent band is described. There is a difference in the degree of development of the schistosity on the convex and the concave sides of the fold arch. This is explained as due to variation in contact strain. A similar pattern has been produced experimentally and it is concluded that the axial plane schistosity in the example under consideration is a mechanical phenomenon and has developed perpendicular to the direction of maximum compressive strain.

A chevron-folded phyllite composed of well contrasted quartzose and micaceous layers was examined. The false cleavage in the mica layers is of fan type and measurements show a correlation between the angle of the fan and the thickness of the layer in which it forms. Such a correlation is to be expected if the folds formed by buckling under lateral compression.

A revised Stratigraphical scheme based on numerous measured sections and extensive mapping is proposed for the Carboniferous and Permian sequences of Spitsbergen and Bjørnøya, the important Arctic archipelago, in order to provide an up-to-date framework for future work there. New data on the fusulinid zones is summarized and the age of the sequence discussed. A brief Stratigraphical interpretation with four maps showing outcrops, thicknesses, active faults, and main lithological boundaries is given and recent published and unpublished work is reviewed.