A primary deposit of tin and tungsten has been discovered in association with granites of the Cambrian (?) sub-volcanic igneous complex at Sabaloka, on the Nile north of Khartoum. Wolfram and cassiterite occur in a stockwork of quartz veins which also contain minor amounts of sulphide minerals. The stockwork centres around a small intrusion of primary greisen lying on the contact of a porphyritic microgranite ring-dyke but the greisen and mineralizing solutions are believed to have originated from a nearby mass of biotite-muscovite granite. The deposit has many features in common with the primary tin veins associated with the Younger Granites of northern Nigeria and other parts of northern Africa.

The distribution of Ba, Mn, Nb, Rb, Sr and Zr has been studied in the granites of the Rosses complex. Their variation is interpreted in terms of a process of magmatic evolution involving the formation of granite magma by progressive partial fusion, and its modification during emplacement by the partial assimilation of displaced country rocks. Several greisens from the Rosses complex have also been analysed, and the changes in concentration of trace elements during greisenization are related to observed changes in mineralogy.

The pre-Carboniferous rocks exposed along the coast of Co. Wexford from Rosslare to Bannow Island have been re-examined. Four distinct units are recognized: the Rosslare Complex, the Cul-lenstown Group, the Tagoat Group and the Bannow Group.

The Rosslare Complex and the Cullenstown Group are suggested to be of Pre-Cambrian age. A correlation is proposed between the Cullenstown Group and part of the Mona Complex of Anglesey; the Rosslare Complex is thought to be much older. It is suggested tentatively that all the Bannow Group may be of Ordovician age.

On the basis of stratigraphic, tectonic, and metamorphic studies in certain critical Pre-Cambrian areas of Nagpur-Bhandara-Drug region and twenty-six K-Ar age data of representative samples, the authors have suggested a new generalized succession and correlation of the dated orogenic cycles and phases, and have drawn the following conclusions:-

(a) Amgaon cycle closed during the period 1444–1730 m.y.

(b) Sakoli cycle (I phase) closed at 1330 m.y., and during Sausar orogeny (864–996 m.y.) the north-western part of Sakoli syn-clinorium was deformed and metamorphosed (862–950 m.y.).

(c) Sausars and Sakolis, both post-Amgaon in age, were deposited in separate basins and had different tectonic histories.

(d) Nandgaon folding phase (< c. 1200 m.y.) affecting Bijli rhyolites is younger than Sakoli (I phase), and Chattisgarh Cuddapahs are younger than Khairagarh phase (< c. 600 m.y.).

(e) In Bastar area Bailadila cycle closed at c. 2100 m.y.

The geosynclines of North America were a subject of study and classification by the writer some twenty years ago. In the succeeding years, field studies have been directed toward solving some of the problems that appeared. The following is written to bring out the reasons why geologists from different regions, having differing experiences, reach conflicting opinions about relationships and terminology, and the history of the origin of some of the terminology has not been published previously.

Based on the study of distribution of assemblages of skeletal organic remains we have established the synchronous appearance of a skeleton in certain fossil groups; this enables us to draw the lower boundary of Cambrian according to the first zone with a certain assemblage of skeletal fossils.

Wide distribution, in sections of various parts of the world, of deposits having no trilobites but containing similar assemblages of other skeletal fossils, has made it possible to distinguish them as an independent Tommotian stage. In Siberian sections this can be subdivided into three zones based on archaeocyathans.

The deposits of the Tommotian stage are underlain by deposits containing no skeletal fossils; in their carbonate composition they are, as a rule, rich in oncolites and catagraphs (algae of uncertain affinities or products of algal activity), and stromatolites of a socalled “Vendian” or “Yudomian” assemblage.

A regular distribution of assemblages of organic remains in the Cambrian-Pre-Cambrian boundary layers point to a leading role for a biostratigraphical method in the solution of the problem of the Cambrian lower boundary.

The new genus, Psigraptus, containing P. arcticus n. sp. and genotype and P. lenzi is proposed for two-branched and three-branched reclined graptolites with isolate autothecae. The genus is known only from the Bryograptus-Clonograptus Zone (Tremadocian), Yukon Territory.

The presence of ignimbrite is described for the first time in Malaya. The field relations and a detailed study of the petrography support the interpretation that the 15-mile ridge outcropping in Central Kelantan, Malaya, is a thick “dyke” of ignimbrite which plugs an old feeding fissure. The Temangan Ignimbrite has a texture which is intermediate between tuff and rhyolite lava. The evidence suggests that the Temangan ignimbrite was emplaced as a tuff flow.

Nodules containing siderite and calcite in the Yorkshire Lias have been studied quantitatively using petrographic, X-ray and chemical methods. Ankerite is recorded from the Lias for the first time. It is shown how the relative abundance of early diagenetic siderite and calcite correlates with sandiness of the sediment and provides an index of environmental change.

A simple theoretical explanation is given for the formation of systematic tension joints in sedimentary rocks. This theory shows that the frequency of occurrence of joints in a bed of rock is dependent upon the physical properties of the rock bed, the physical properties of the surrounding rock beds, the thickness of the rock bed, and the degree of tectonic deformation.

The costellae of a population of brachiopods can be quantitatively described by plotting the total number of costellae on a valve against the length of its margin. The resultant curve describes the continuous change of the average distance between adjacent costellae during growth. When costellae first appear, this distance has the value of about 0·06 mm and it increases during growth to various degrees in different brachiopod species.

If it is assumed that costellae mark the sites of setae, then the magnitude of the distance between adjacent costellae can be discussed in terms of the function of setae.

The magnitude of the parameters of the distribution of setae and punctae are compared to the silt/sand dividing line.

The Juan Fernandez Archipelago, located off the coast of Chile, comprises a group of three small, considerably eroded volcanic islands, probably of late Tertiary age. Traces of old craters or calderas have been recognized on Robinson Crusoe Island which is built mainly of basaltic lava flows, many of them picrite-basalts. Coarse-grained ejected blocks, in which olivine predominates, are fairly common on Robinson Crusoe and there are also a number of exposures of dolerite showing pronounced banding. The only acid rock reported from the group is a soda-trachyte from Alexander Selkirk Island. Pumice washed ashore on the islands during the past year is possibly from a submarine eruption near the South Sandwich Islands in 1962.

The presence of pre- and post-Carboniferous structures in Murrisk is noted. Warping of the sub-Carboniferous surface in the eastern part of the Partry Mountain area is ascribed to NE-trending normal faults.

Brøggerhalvøya is situated on the north-west coast of the island of Vestspitsbergen. It is shown to contain a fold and overthrust complex of Tertiary age. Large northerly movement of Pre-Cambrian rocks, previously metamorphosed in the Caledonian diastrophism, occurred over deformed but unmetamorphosed Permo-Carboniferous and Tertiary rocks on a major curved over-thrust. The structure is complicated by rapid plunge variations and subsidiary faulting. The existence of a large klippe is demonstrated and the formation of curved thrust surfaces is discussed.

A brief summary of the stratigraphy is given and its important relationship to the structure discussed. A new lithostratigraphical scheme of nomenclature is proposed.

Photometric recording of the variation in intensity of light transmission by the analyser of a petrological microscope whilst the polarizer is rotating at a rate sufficient to eliminate the periodic output from the photocell as the polars cross and uncross, and a thin section of a crystal aggregate is slowly rotated upon its stage, is found to yield information on the direction and degree of development of any preferred optical orientation that may be present in the section. The theory of the method is considered and an equation derived for the representation of any preferred optical orientation in terms of a direct percentage of areal extent. The direction of the preferred orientation is found to be parallel to the plane of polarization of the stationary analyser when the section is rotated to a position of minimum intensity of light transmission. It is suggested that the method has potential applications in the study of any fabric which is displayed in terms of an optical orientation.

A late Pre-Cambrian eugeosynclinal stratigraphic sequence in the western part of the Scandinavian mountain chain is established. In the Möre region the succession is about 11 km thick. The wellknown late Pre-Cambrian miogeosynclinal sequence in the eastern part of the chain corresponds to the upper part of the eugeosynclinal sequence.

Observations of partial and complete sedimentary infillings of fossils and rock cavities at two localities on Treak Cliff, Castleton, Derbyshire, lead to the conclusion that at these localities the present dip of the limestones is largely or entirely depositional in origin. This conclusion agrees, more or less, with claims made in previous publications but, so far as the authors are aware, this is the first time that direct evidence of high initial dips at Treak Cliff has been recorded.

Easter Island comprises three major volcanoes, Poike a simple strato-volcano, Rano Kau which is of similar size but with a caldera at its summit, and Terevaka which is the largest and most complex of the three. In addition there are about seventy minor eruptive centres. The lavas constitute an alkali-basalt-trachyte-soda-rhyolite series but the acid members are of very restricted development. There is evidence that the parasitic tuff cone of Rano Raraku has had a more complicated history than previous reports have suggested. Although no volcanic activity has ever been reported, some of the lava flows appear to be of very recent origin.

Hornblende and biotite occur very commonly in the granulite facies rocks of the areas mapped, and both appear to occur as stable phases. Thus, these hornblende- and biotite-bearing rocks find accommodation only in the hornblende-granulite subfacies. It appears that most of the rocks in the areas mapped would fall into this subfacies and the mineral assemblages of these rocks are recorded in this paper under the different chemical classes. Hornblende and biotite are very commonly present in the pelitic, quartzo-felspathic, basic and magnesian rocks; phlogopite and sphene are commonly present in the calcareous rocks. A tentative ACFK tetrahedral phase diagram has been constructed for these rocks.

A sequence of 11 tetracoral and conodont faunas, ranging from early Gedinnian to late Givetian, is recognized in the Lower and Middle Devonian limestones of New South Wales and Victoria. These faunas are not only important stratigraphically in eastern Australia, but also provide a basis for the correlation of the Australian Devonian with overseas stages. A table of correlation is given for the principal Devonian limestone sequences of New South Wales and Victoria.