Gravity and aeromagnetic data sets provide systematic coverage over the whole of the Welsh Basin. Physical property information shows considerable overlap in densities within the Lower Palaeozoic and Precambrian formations, with relatively few units of the exposed succession being strongly magnetic. While the geophysical anomalies cannot be interpreted unambiguously in terms of these sources, the data can still be used to test different geological models and to indicate the range of possible solutions. The major fault zones are seen to influence the anomaly patterns in a variety of ways, reflecting a combination of differing near-surface contrasts and effects within the underlying basement. The general increase in gravity values towards Cardigan Bay may originate from the lower crust, and the large amplitude aeromagnetic low seen over Cardigan Bay indicates that a distinctive change in the character of the crust occurs here. Two-dimensional modelling in central Wales shows that a westward thickening of the Welsh Basin, to a maximum of about 10 km, may also be significant. It is necessary to postulate a separation of the base of denser, Lower Palaeozoic rocks from the underlying, more magnetic basement in order to account for offsets in anomaly source locations. This implies the presence of less dense Cambrian sediments and/or non-magnetic components of the Precambrian basement.

Cumulate apatite crystals with infilled tube-like cavities parallel to the c-axis are described from a layered gabbro intrusion in Northern Norway. These are considered to be skeletal crystals produced by rapid growth in the supercooled roof zone of the magma chamber. At least two stages of growth are suggested on the basis of the morphology of the apatites. The interiors of the crystals contain phases representing the trapped magma or the cumulus mineral phase within which they are enclosed. Recirculation of the apatite primocrysts by convection currents is indicated by the interrupted form of some of the tubes.

The Foraminifera of the Chalk were treated of in Nos. 89 and 90 of the Geol. Mag., November and December, 1871, with the view of aiding collectors and authors in their arrangement of these numerous and puzzling microzoa in their catalogues and cabinets. We shall be rendering further service to students, if we refer them to the Rev. Henry Eley's clear and useful, though somewhat hard, drawings of the Foraminifera usually found in the English Chalk and Flint. These were published ia his “Geology in the Garden; or, the Fossils in. the Flint Pebbles.” 8vo. London, 1859.

During an expedition to the Lake District, led by Miss Elles, the contact of the Threlkeld microgranite with the rocks into which it has been intruded was examined. The lower contact of the microgranite with the Skiddaw Slates is now well exposed at the eastern end of the main quarry south of Threlkeld railway station; and also in the light-railway cutting connecting this quarry with the newer quarries to the S.W. This contact is transgressive to the bedding of the slates, and at the first-named exposure the two rocks are dove-tailed into each other. The slate can be seen to be but slightly hardened and so little alteration has been effected that well-preserved graptolites were found within 18 inches of the contact.

Shumardiid trilobites had a small, unique morphology, and formed a key constituent in trilobite faunas during the Cambrian–Ordovician. Because of their unusual morphology, they have been the subject of research s, into various aspects such as their life habit, functional morphology, evolutionary origin and ontogeny. Originally, a flat, adult-like protaspid morphology was suggested for shumardiids, but subsequently a bulbous protaspid morphology interpreted to be associated with metamorphosis was also suggested for this unique trilobite group. This article documents the ontogeny of the two co-occurring shumardiid trilobites, Akoldinioidia latus Park and Kihm and Koldinioidia choii Park and Kihm, from the middle Furongian Hwajeol Formation, Taebaeksan Basin, Korea. Interestingly, protaspides of the two shumardiids have a bulbous morphology. Given the stratigraphic occurrences of the two shumardiids, it can be inferred that commutavi protaspis appeared quite early in the shumardiid evolution. The co-occurrence of the two closely related trilobites is reminiscent of sexual dimorphism, although further evidence is required to prove it. The appearance of metamorphosis-undergoing protaspides in the Furongian shumardiids may have been due to the onset of increasing ecological pressure in the early phase of the Great Ordovician Biodiversification Event.

White marble in Glen Dessarry, West Highlands of Scotland, occurs as three lenses associated with schists and calc-silicate rocks. The minerals identified in all these rocks are apatite, biotite, calcite, chondrodite, clinochlore, clinozoisite, diopsidic-pyroxene, dolomite, epidote, forsterite, garnet, hornblende, magnetite, phlogopite, plagioclase, potash-feldspar, pyrites, quartz, scapolite, sillimanite, sphene, vesuvianite, zoisite.

Two parageneses may be distinguished. One, due to high-grade regional metamorphism, apparently with little or no introduction of material, is a diopsidic-pyroxene, forsterite, phlogopite, calcite, dolomite association forming white marble. The other association occurs as veinlets and small irregular bodies in the white marble. It appears to be due to circulating solutions in which pyroxene and forsterite were unstable. Minerals of this paragenesis include potash-feldspar, plagioclase, scapolite, hornblende, minerals of the epidote group, calcite, and quartz. In certain localities scapolite formed at the expense of plagioclase and was succeeded by crystallization of epidote.

Within the Tethyan Zone of Central West Nepal, the Nilgiri Limestone is the dominant unit. The significance of the separation of the Larjung Formation is questioned in the light of new outcrops examined, and the Nilgiri Sandstone is described. Recumbent fold structures are correlated between Annapurna, Nilgiri and Dhaulagiri. Between these mountains the Thakkhola graben faults are continued southwards, and estimates are made of the magnitude of their throws.

The relationship between silicate rock density and composition has been investigated and empirical formulae have been obtained that give a factor equivalent to a ‘normative’ density. Comparison between this factor and measured density may provide useful diagrams assisting the interpretation of metamorphic petrogenesis. The factor itself is a viable differentiation index aiding comparison between the compositions and liquidus temperatures of volcanic suites.

The purpose of this note is to place on record two rare crinoids and a blastoid recently found at Coplow Knoll, Clitheroe. One of the crinoids belongs to a new species of Camerata now named Steganocrinus westheadi in honour of its finder, Mr. Stanley Westhead, of Clitheroe. The genus Steganocrinus has not hitherto been recorded from English Carboniferous rocks so that its occurrence at Coplow is noteworthy. The other crinoid, here temporarily assigned to “Pachylocrinus” conicus (Phillips), shows a considerable portion of the arms and was found by the author on a visit to Coplow last year. No other specimen of this species so complete has yet been recorded. On a later visit in the autumn of the same year a single finely preserved specimen of a blastoid was found. In its general characters this specimen does not appear to differ from Orophocrinus pentangularis (Miller), and in ordinary circumstances would call for no special comment here. Blastoids, however, are so rare at Coplow that the occurrence of this specimen, the only one ever found by the author at, or known to him from, this locality, is deemed worthy of record.

Robert Etheridge, Jnr. (1874a, p. 310), records that the same species of Spirorbis as that in the Lesmahgow Silurian occurs in the North Esk section. The D. J. Brown collection with the specimens referred to is missing at the Royal Scottish Museum; but it would be interesting to know how closely these specimens compare with S. lewisii J. de C. Sowerby from the English Wenlock and Ludlow.

Petrofabric analysis has been carried out on Carboniferous rocks involved in thrust masses of the Benton system in Pembrokeshire. Evidence is contributed, which indicates stages of fracturing and crystallographic control in the deformation of individual quarts grains.

“In a trough from 2 to 10 kilometres wide and 100 to 300 metres deep lies the Nile, meandering through a flood plain formed by yearly deposits of silt brought down from the Abyssinian table-land by the Blue Nile and the Atbara. This trough was determined in the first instance by fractures of the crust which caused a strip of country from about Edfu (lat. 25° N.) to Cairo to be depressed, leaving the plateau standing high above it, just as the Red Sea and the gulfs of Suez and Akaba were formed, probably about the same epoch. This interference with the drainage of the country doubtless produced a series of lakes in the low-lying area, while the drainage of the eastern plateau commenced to excavate the valleys which now exist as dry desert wadies, their development being in many cases far from complete, as shown by the cliffs which interrupt the slope of the valley when a harder bed of rock than usual is met with.

Anyone who studies the relation of the rocks of the Lizard Peninsula to those immediately to the north must realize that Porthallow, the little village in a sheltered cove near St. Keverne, is a critical locality in the problem, and one indeed that may hold the key to the solution of the relative ages of the rocks on either side of the sinuous line called the Lizard Boundary. Porthallow is at the eastern extremity of that line. The western extremity is on Polurrian Beach, near Mullion, where a very clear fault with a breccia about 22 feet thick separates two totally distinct formations, sandy and argillaceous killas on the north from hornblendegneiss on the south. At Porthallow, however, although there are cliffs on either side of the cove washed by the sea, the geology is far from having the textbook clearness of Polurrian Beach and there is room for much difference of opinion. Text-fig. 1 is a sketch-map of the locality based on the Ordnance Survey 25 in. to the mile map, and first the main features of the geology will be described. For the neighbouring country the reader is referred to the Survey 1 in. map (Sheet 359) and to the 6 in., Sheet lxxxi N.E.

Through the kind intervention of Dr. R. Rutsch, of Basle, who himself is interested chiefly in the Tertiary mollusca of Trinidad, I have recently been able to study some tolerably well-preserved ammonites from beds in the Northern Range which have long been the subject of discussion. The ammonites had been already recognized by the Trinidad geologists as Upper Jurassic and bore the provisional identification: “Idoceras sp.,” which would have indicated a Lower Kimmeridgian age; but since confirmation of this seemed desirable, I was asked to see whether the ammonites were determinable, and if so to publish a note on the results of my investigation.

It was noted by the Rev. C. Noury in 1886 that sedimentary rocks were found in a small coastal area to the south of Fort Pezerie, on the south-western extremity of Guernsey. Professor T. G. Bonney observed the same area independently in September, 1910, after describing it in field notes in 1888 as a closejointed and rather schistose diabase. The Rev. E. Hill in 1884 had also regarded the rock in this area as constituting a dyke-formed diabase.

Wood-grained chert is an unusual type of banded nodular chert that is characterized by alternating thin dark-coloured bands and thicker light-coloured bands, which give the chert a texture reminiscent of the growth rings of wood. The wood-grained texture found in some chert nodules in the Portland Limestone Formation of southern England is the result of variations in the concentration of calcite inclusions within the chert. Light-coloured bands contain more abundant calcite inclusions than adjoining darker coloured chert bands. The Portland Limestone wood-grained cherts formed by the late diagenetic replacement of a highly compacted carbonate sand, in which abundant siliceous sponge spicules were the silica source. Oxygen and hydrogen isotope data (δ18O=27.0 to 29.3‰; δ18O=−71 to −91‰ V-SMOW), indicate that either chert formation or, more likely, the opal-CT to quartz transformation, occurred in meteoric or mixed marine and meteoric pore waters at temperatures in the range of 20–60°C. The wood-grained texture likely formed by a self-organization process. A feedback mechanism is proposed for the origin of the texture in which calcium and carbonate ions released during the replacement of the host limestone resulted in calcite supersaturation along the boundaries of growing chert nodule. Calcite inclusion-rich chert bands formed within the calcite supersaturated zone and inclusion-poor bands formed outside of the calcite-supersaturated zone. Wood-grained chert provides another example of how the coupling of reaction and transport can produce repetitive patterns in otherwise unordered sediments or rock.