Sub-surface erosion is intensely active in weathered granite debris at the scarp foot of Jebel Qasim. Powerful flushes of sub-surface water after heavy rain remove much of the decomposing feldspar partly by solution and partly by mechanical eluviation. The sedentary debris gradually contracts as the feldspar is removed and when removal is nearing completion the debris may become compacted. The compacted debris occupies less than 40 per cent by volume of the granite from which it was derived.

The upper fringing pediment around this hill is mantled by moist incoherent debris holding small local pockets of water which persist throughout the dry season. Annual recharge of this sub-surface water ensures intense weathering in the debris.

The combination of intense weathering and sub-surface erosion with ensuing contraction of the debris occurring just below the piedmont angle may be sufficient to explain the maintenance of this angle during slope retreat.

In South-East Arran there are many Kainozoic composite and multiple intrusions, mostly in the form of sills, composed of basic, intermediate, and acid rocks, xenolithic enclosure of, basic members by less basic ones being common. The pyroxene of all the rock types is a normal augite and not a pigeonite. Contact hybridization has played an important role in the partial or complete digestion of xenoliths. The genesis of the different members of the intrusions is attributed to the complex process of deep-seated hybridization of two types of magmatic material of contrasting basic and acid composition. The order of injection of magma is, invariably, from basic to acid, though in the intrusions, the spatial sequence of the rock types varies much; their complicated structures are ascribed to a series of pulsations of contaminated magma with its composition tending progressively in the acid direction.

The concept of tectonic regimes is developed so as to specify the symmetry and orientation of bulk deformation for use in tectonic analysis. Four symmetry patterns combined with possible arrangements of principal axes in vertical and horizontal directions as in a compression belt give thirteen regimes which are in turn defined and tentatively related to some known tectonic structures. A theoretical orogenic sequence of regimes is developed and the paper concludes with a review of some of the difficulties.

A study of Stephanocerataceae and Perisphinctaceae of the Middle Jurassic demonstrates that the structure of the septa comprises a complex vault and pillar system which is functionally adapted to the dimensions of the tube so as to give maximal stability to the shell. Only through a study of the septum can we interpret the different forms of the suture and discriminate between important and unimportant features. Different septa may have analogous sutures, especially in the external parts. These septal patterns are strikingly consistent within subfamilies or families even where other features suggest overlap between the groups. Some parts of the septum are not adapted, but either retained from earlier ontogeny or inherited, and constitute vestigial (genotypic) characters distributed through taxons.

These empirical results have been applied to the taxonomy of some groups of hitherto doubtful systematic position (Cadomitinae, Normannitinae, Sphaeroceratinae, Parkinsoniidae, Spiroceratidae).

A re-examination of the Moine—Sub-Moine boundary of the Morar dome shows it to be a zone of transition between two metamorphic states. Some notes on the structure accompany a mineralogical description of the changes across the boundary; discussion is made of evidence that the metamorphic boundary transgresses the geological boundaries. The schists of the core are thought to be in a lower metamorphic state than those of the envelope.

From a locality in North Staffordshire. Microspore assemblages are described from the Six Inch Mine coal seam, the immediately overlying carbonaceous shales, and the marine shale bed. Marked differences occur within this thin sequence in the proportions of certain genera present; in particular, the dominance of Florinites in the marine shales is discussed. Whilst the proportionate numbers of genera vary, the actual species present are more or less the same, though a greater variety exists in the shales. Three new genera and seven new species are described.

Seventeen Connemara pelites have been chemically and modally analysed and a garnet, a staurolite, and a biotite from them chemically analysed. The results show that these pelites are rather poor in silica and rich in alumina and total iron. It is believed that this was an original feature of the composition.

The detailed examination of rocks recently collected from a traverse and from isolated points within this intrusion has led to the conclusion that it is a large, layered intrusion showing rhythmic and cryptic variation, and comparable in many respects with the Great Dyke of Southern Rhodesia.

The purpose of this note is to put on record the discovery of Lower Coal Measure strata in the west of Ireland. The succession is approximately 500 feet thick and includes the Gastrioceras subcrenatum and the Gastrioceras listeri marine bands. Of particular interest is the occurrence of a coarse felspathic sandstone in the cycle of sedimentation which includes the G. listeri horizon: the sandstone is very similar in lithology to the distinctive Clay-Gall Sandstone of the Leinster Coalfield.

Karroo sedimentation in the mid-Zambezi area presents an instance of deposition in an intra-cratonic basin during a complete climatic semi-cycle. Mention is made of the tectonic factors which controlled the course of Karroo sedimentation in the area, and the nature of the pre-Karroo surface is commented upon. An account is given of the depositional history of the mid-Zambezi basin during the Karroo period. The structural development of the region since Karroo times is outlined, and it is suggested that the present valley is essentially a downwarped and eroded part of the peneplain which still forms the adjacent plateau to the north-west.

Granites of the main movement-phase of an orogenic zone form an integral part of the tectonic pattern being characteristically located at the intersection of cross- and main-folds. Here, an older granitic core pierces upwards through the anticlinal vault to form a diapir-fold in which migmatization, synchronous with movement, leads to the evolution of granodiorite. At higher structural levels where pressure is lower K-granites occur. Only at sub-volcanic levels has evidence of melting been found.

Recent hydrothermal investigations, by Bowen and Tuttle, show that synthetic haplo-pitchstones which begin to crystallize at minimum temperatures become richer in K as pressure decreases. These results are closely comparable with evidence provided by the sub-volcanic K-microgranites (migmatized Caledonian granodiorite) of Slieve Gullion, but have no application to the granodiorites.

The paper contains eight analyses of primary and recrystallized pyroxenes from the layered ultramafic peridotite at Dawros. The assemblages in which these pyroxenes occur are compared to those from other peridotites and some comments are made on the pyroxene sequence. Consideration is also given to the problems arising as the result of the metamorphism of the primary igneous accumulate at Dawros.

An account is given of the petrography and chemistry of the bostonite of Rudh'a' Chromain, Mull.

Primary shears with oblique-slip displacement can only arise by failure after a rotation of two of the three principal axes of stress from an expected vertical and horizontal position relative to the earth's crust, and are either normal-wrench or thrust-wrench hybrids. As a consequence of a full 90° clockwise or anticlockwise rotation, the changes in pitch of striations on slicken-sided fault planes belonging to both categories are stereographically represented by two small circle courses which are ∠90°–ø apart for the normal-wrench association, and ∠180°–ø apart for the thrust-wrench one: ∠ø being the angle of internal friction. Using these assumptions to analyse the distribution of oblique-slip shears exposed in the south-western part of the Midland Valley of Scotland, it appears probable that two unrelated sets of commonly occurring normal-dextral shears are of primary origin, for the inferred azimuthal orientations of the principal axes of stress are remarkably close to those estimated for other, more orthodox tectonic features found elsewhere in the Midland Valley and appropriately absent in the south-west.

The amphibolite at Durcha passes from a dark, hornblende-rich rock, through every gradation of delicate striping and banding by quartzo-feldspathic material out into psammitic Moine schist, within a few metres. Irregular cross-cutting bands of quartz and feldspar which seem to “ feed ” the delicate stripes can be seen and there are intergrown mixtures of the dark and light components which recall appinites. Chemical and other evidence suggests that the dark rock is a concordant thpleiitic dolerite sill, whilst the macroscopic and microscopic evidence from the pale bands suggests that they are metasomatic in origin and connected with the widespread permeative alkali-injection of the Moine Schists. They seem to have been introduced into the sill along closely-spaced foliation planes parallel with those in the adjacent sediments and with the original contacts of the sill.

The presence of locally abundant pebbles of Middle Devonian Limestone in the New Red Sandstone near North Tawton, Devonshire, is recorded. It is suggested that these were derived in Permian times from a nearby outcrop of Devonian limestones which projected through the Culm Measures of the mid-Devon syncline.

The shell-substance of the non-marine lamellibranchs from a band in the Lower similis-pulchra Zone of Lancashire is shown to be ankerite. The same mineral also forms pockets inside certain of the shells, the pockets being developed most frequently in the stratigraphically uppermost part of the spaces between the valves. It is considered that the ankerite in the pockets has occupied spaces left by shrinkage of the original mud-filling of the shells. Chemical analyses, specific gravity, and optical properties of the ankerite are given; its composition closely approximates to (Mg2Fe)Ca3(CO3)6.

A sequence of eleven faunal units characterized by pelagic foraminifera and embodying thirteen significant events has been recognized in the Tertiary of Victoria. They form a continuous sequence from the Upper Eocene to the Middle Miocene. Some of these events have been recognized in the same order in New Zealand, Europe, North America, the Caribbean region, and Saipan.

Alternation of morphogenetic systems conditioned by wide swinging of climatic belts equatorward and poleward has been used to explain otherwise puzzling relict forms in many regions. A characteristic finely dissected landscape relief prevalent in some middle-latitude regions is in strong contrast with smoothed, coarse-textured, whalebacked, relatively featureless relief in others, notably western Europe, which are now in the humid-temperate zone. This latter is believed to be relict from the periglacial regimes of Pleistocene ice ages. In New Zealand where the former landscape type is typically developed, there has also been quite strong “periglaciation”, and in Europe running-water erosion cannot but have operated to some extent in interglacial ages. It appears that the periglacial smoothing has been pushed to the extreme limit in Europe but that its effects have been neutralized in New Zealand by the vigour of dissection in the alternating warm ages. Periglacial smothering, or “fossilization”, of fine-textured relief, which has been followed by renewed fine dissection, is very common at Wellington, New Zealand. The reasons are not clear why running water should have been (and should still be) more efficient in dissecting the New Zealand landscape than that of Europe, so that the relict periglacial landscape remains intact in the latter region.

This paper gives details of part of the Hecla Hoek Succession already outlined (Harland and Wilson, 1956). Field work in 1956 and 1957 in general confirmed the succession, and this account includes the results of the later work. A large-scale repetition of a sedimentary cycle is demonstrated, and the relationship with equivalent rocks in Nordaustlandet is discussed.