The various views put forth prior to 1893 to account for the origin of Indian laterites have been clearly and sufficiently discussed in Oldham's edition of Medlicott & Blanford's Manual of the Geology of India (pp. 369 et seq.). Since that year the only contribution of importance to the literature of lateritic genesis in India is a paper by Mr. Thos. H. Holland, F.R.S., the present Director of the Indian Geological Survey, having for its text the conclusions of Bauer. In it the author suggested that laterite might owe its origin to “some lowly organism,” but no sufficient data were advanced in support of the suggestion. Bauer's specimens indicated a certain amount of dehydration in laterites, and this fact, together with the absence of hydration products from certain peridotites in Southern India, was deemed to indicate a general dehydration for the bauxitic laterites of the Deccan. The gibbsite (Al2 O3, 3 H2O) of laterite was supposed to be dehydrated to diaspore (A2 O3, H2O), and it was assumed that “this irregular loss of water is probably the cause of variation in bauxite.”

PETROGENIC problems concern the processes and effects of adding to magma, or subtracting from it, rock-forming substance in general. Increment or loss of silica alone entails relatively simple mineralogical consequences. The more intricate problems concern the addition of associated material (notably alumina, the Ro-oxides, alkalies, and fluxes) in varying relative proportions, and at any stage in the evolution of rest-magma. These additions tend either to promote, counter, or otherwise modify the prevailing trend of differentiation in magma thus augmented.

The main conclusions of the paper may be briefly stated thus:—

1. The deposits, which are of neritic facies, possess a characteristic and peculiar mechanical and mineralogical composition, differing therein from any other British deposit.

2. They exhibit a general constancy in grade from the Dorset coast to the Cotteswolds. Within this limit they conform to two chief types containing respectively 40 to 50 and 60 to 80 per cent, of the very fine sand grade (greater than 0·05 and less than 0·1 mm.). No variation of mechanical composition with hemeral change can be observed.

3. The sands are blue and glauconitic in depth. At the surface they are decalcified and are yellow and brown as a result of oxidation. Minerals such as pyrite and pyrrhotite occur only in depth.

4. The mineralogical composition indicates an abundance of highly angular brownish-pink to colourless garnets (possibly derived from rocks like those of the Lizard), but few red or purplish-red varieties; also of micas (including a pseudo-uniaxial, pale-green to colourless variety), together with chlorite, chloritoid, kyanite, staurolite, orthoclase, and microcline.

5. Tourmaline is only moderately common and is always the grey-brown variety.

6. The abundance of titanium-minerals is characteristic of the deposits. Red and yellow varieties of rutile and sagenite-webs are exceedingly abundant, and anatase, brookite, and sphene are locally so. A reciprocal relation may exist between the occurrence of sphene, ilmenite, and the oxides of titanium.

7. Epidote and glaucophane are rare.

8. Chlorite, chloritoid, glaucophane, kyanite, and staurolite increase in quantity as the deposits are traced southwards.

9. A change in lithology and mineralogy sets in as the deposits are followed north-eastwards into the Midlands and Yorkshire.

10. The sands differ markedly in petrology from the various Palæozoic rocks of Wales and the West Country, from the Trias, and from the Cretaceous and Eocene of Devon and Dorset.

11. The Ordovician, Domerian, Toarcian, and Aalenian of Normandy and Brittany have been examined petrologically for purposes of comparison, but show little resemblance to the sediments under discussion, having been derived locally from the Palæozoic and pre-Cambrian rocks.

12. It is concluded that the Lias–Inferior Oolite sands have been derived from the south or south-west, notably from rocks like those of western Brittany.

13. The rise of the Mendip axis was not sufficiently complete at this time to cut off the supply of sediment from the south or south-west. The deposits north and south of the ridge have the same general character.

At the suggestion of the British Minister at Athens, Sir Edwin H. Egerton, K.C.B., the Trustees of the British Museum recently undertook a series of excavations in the well-known bone-beds of Pikermi, in Attica, and I was honoured by being entrusted with the supervision of the work. The owner of the estate, Mr. Alexander Skousés, former Minister of War, most cordially assented, and gave every possible facility for the undertaking; while Sir Edwin Egerton's unflagging interest and zeal combined to ensure the greatest success. My wife and I went into residence at the farm of Pikermi early in April, and we continued to occupy the simple but comfortable room which Mr. Skousés had kindly placed at our disposal, until the cessation of digging in the middle of July. During much of the time we were accompanied by Dr. Theodore Skouphos, Conservator of the Geological Museum in the University of Athens, which claims some share of the results of all such excavations made in Greece. We have to thank him for much help in dealing with the workmen, who spoke only a language with which I was at first unfamiliar.

The Yerba Loca Formation (Middle–Upper Ordovician), exposed in the Western Precordillera, San Juan, Argentina, is made up of clastic–carbonate turbidites, and basic–ultrabasic rocks. It is affected by regional Siluro-Devonian very low-grade metamorphism that locally reaches greenschist facies. At Ancaucha creek, 45 conodont samples were taken from two sections that include 30 to 50 m thick sills. In order to analyse the thermal alteration patterns produced by these intrusive bodies, conodont Colour Alteration Index (CAI) is contrasted with optical petrography and X-ray diffraction analyses of clay minerals. The intrusions are dated as post-Darriwilian (Da2), as determined by conodont biostratigraphy of the host rock, which indicates the Paroistodus horridus Subzone of the Lenodus variabilis Zone. The distribution of CAI values defines a thermal aureole of about 2.5 times intrusion thickness that prevailed over the later very low-grade metamorphism. Metasomatism at Ancaucha creek is recorded by CAI values of 4 to 7, particularly restricted to a few layers close to the intrusions, as indicated by conodont textures and rock fabric. One-dimensional thermal computer simulation conforms to empirical data indicating temperatures greater than 600 °C for the contact zone, although it points out slightly narrower thermal aureoles. The clay mineral assemblage of most of the analysed samples (chlorite, illite, smectite and I/S mixed-layers) is complex and probably derives from several superimposed processes, thus representing non-equilibrium assemblages. In turn, KI values (0.27–0.32) indicate anchizone metamorphism, in agreement with regional CAI values of 4; consequently, the occurrence of smectite and I/S probably resulted from retrograde diagenesis processes.

Ceratitic ammonoids from the Greville Formation in the Nelson Regional Syncline, South Island of New Zealand, were described as a new genus and species of the Ophiceratidae, Durvilleoceras woodmani, and dated as ‘late Middle Permian’ (Waterhouse, 1973). In fact, Durvilleoceras differs from all known Permian ammonoids in both conch form and sutural pattern, but closely resembles lower Triassic ceratites. Structural and sedimentologic complexities within the Nelson Syncline are such that stratigraphic interpretations are questionable, and the fauna of both the Greville and adjacent formations is sparse. Consequently, we consider that Durvilleoceras is best interpreted as a middle Scythian ceratite of the family Flemingitidae.

Phlogopite-spinel-bronzite rocks, in which aggregates of bronzite and sapphirine appear to be pseudomorphs of aluminous anthophyllite, occur in a restricted low-granulite terrain in the Strangways Range, central Australia. The form of the postulated reaction is gedrite + ΔH = enstatite + sapphirine + silica + escaping “ water ”.

Reconstructing the provenance of siliciclastic marine sediment is important for understanding sediment pathways and constraining palaeoclimate and erosion records. However, physical fractionation of different size fractions can occur during sediment transport, potentially biasing records derived from bulk sediment. In this study, records of radiogenic Sr and Nd isotopic composition and K/Al ratio of the separated clay fraction, as well as bulk grain size, are presented, measured from deep-sea sediments recovered from International Ocean Discovery Program (IODP) Sites U1456 and U1457 in the Arabian Sea. These new records are compared with published bulk sediment records to investigate the influence of sediment transport on these proxies and to constrain provenance evolution and its relationship to climate variability since middle Miocene time. Correlations between grain size and the bulk sediment isotopic composition confirm that transport processes are influencing the bulk sediment record. This relationship, although present, is not as strong in the clay-fraction isotopic records. Heterogeneity of bulk sediment likely drives differences between bulk and clay records, thought to be largely controlled by sediment transport processes. The isotopic records reveal variations in provenance that correlate with climatic change at 8–7 Ma, as well as an increase in overall provenance variability beginning at c. 3.5 Ma, likely linked to monsoon strength and glacial–interglacial cycles. The clay-fraction records highlight the potential value of measuring proxy records from multiple size fractions to help constrain provenance records as well as investigate sediment transport and/or weathering and erosion processes recorded in deep-sea sediment archives.

A new sea spider (Arthropoda: Pycnogonida) from the Lower Devonian Hunsrück Slate (Germany) is described as Pentapantopus vogteli gen. et sp. nov. This is the fifth pycnogonid species known from this exceptional fossil Lagerstätte. The most conspicuous character of the new species is the presence of five pairs of walking legs. This character, in concert with a reduced abdomen, indicates a phylogenetic position of P. vogteli among the crown group pycnogonids. P. vogteli extends the knowledge of fossil pycnogonid body plans and underlines the significance of the Hunsrück Slate, as this locality shows the highest diversity of sea spiders for the entire fossil record so far.

Many fossils in the older rocks have been distorted by pressure, and if only one specimen is available it is often difficult to be sure of its original proportions. Sometimes, however, there is a specimen which not only furnishes sufficient data for the determination of its original form, but can be made to yield a photograph in which the distortion is corrected. In his paper on “Slaty Cleavage” Harker1 showed how, in such cases, the distortion can be determined, and he referred to an earlier paper by Dufet2 in which the same principle is used, though in a different way. So far as I know the method of correcting the distortion photographically has not previously been employed.

Early petrofabric studies of quartz c axis preferred orientation within the Tarskavaig Nappe, located at the southern end of the Moine thrust zone, have been interpreted as indicating that structures within the nappe have been produced by tectonic movements acting at right angles to those responsible for formation of structures within the overlying, but immediately adjacent, Moine Nappe. Such a dramatic contrast in inferred transport direction has not been recognized within the rest of the thrust zone.

Re-examination of the microstructures and c axis fabrics within mylonitic metasediments from the western part of the Tarskavaig Nappe has revealed that these tectonites are characterized by maximum principal extension axes which trend sub-parallel to the WNW-trending Moine thrust zone transport direction. Later folding has reorientated and modified these structures within the eastern part of the nappe producing fabrics which have erroneously been taken to indicate a transport direction orientated sub-perpendicular to that of the rest of the Moine thrust zone.

WNW-trending maximum principal extension axes and WNW-directed overthrust senses are indicated by microstructures within schists from the adjacent Moine Nappe, suggesting that structures within both the Tarskavaig and Moine nappes may be associated with a common west-northwest transport direction.

Essentially coaxial (pure shear) strain paths (indicated by symmetrical c axis fabrics) dominate the internal parts of the Tarskavaig Nappe. Close to the base of the nappe, non-coaxial strain paths, originally associated with WNW-directed overthrusting, are indicated by asymmetrical c axis fabrics and oblique grain shape alignments. Strain compatibility considerations indicate that the lower kinematic domain (which must either be contemporaneous with, or later than, formation of the upper domain) must be characterized by a combination of pure and simple shear deformation.

The following article includes a description of the larger Foraminifera of the Upper Ranikot Series of Sind in Western India. The specimens examined consist of a collection made by Mr. D. Dale Condit and by myself in the winter of 1923, as well as material kindly loaned by the Indian Geological Survey. I wish to thank the directors of the Whitehall Petroleum Corporation for permitting me to make use of the specimens collected during a geological reconnaissance undertaken on their behalf. Of the specimens figured those loaned by the Survey have been returned to Calcutta, and the remainder placed in the Sedgwick Museum, Cambridge.

Tectonothermal analysis of a mainly carbonate unit located in the external part of the Variscan orogen in NW Spain is dealt with using the conodont colour alteration index (CAI) and the study of textures of these microfossils. The Kübler index of the illite (KI) is used as a complementary method. The area is characterized by a great uniformity in the CAI values, which in most cases are <2, indicating diagenetic conditions. In spite of the low CAI values, textures show great variety and were mainly originated by diagenetic processes of apatite dissolution and precipitation. The conodonts underwent a long period of heating (probably from the Pennsylvanian to the Cenozoic) to low temperatures (<100°C) to reach the low CAI values measured. Assuming a normal geothermal gradient, these temperatures required an overburden <3 km that in part was due to burial and in part to tectonic superimposition. Minor local anomalies in the CAI values and some textural alterations, related to dissolution and precipitation of authigenic minerals, could be due to epithermal activity that gave rise to various ore deposits in the studied area mainly during Permian times.

The information gained by us during the first three Swedish expeditions to Spitzbergen having, either directly through our own experience, or indirectly through conversation with most of the intelligent and bold whalers and walrus-hunters of Northern Norway, fully confirmed the observations of Scoresby, Phipps, Tschitschagoff, Parry, Buchan, Franklin, Clavering and others, respecting the impossibility of penetrating by ship during the summer through the crowded ice-masses to the north of Spitzbergen, far beyond the 80th degree of latitude, an Arctic Expedition was sent out from Sweden in 1868, having for its object, among other things, to renew during the autumn months the attempt to sail towards the pole from the northern coast of Spitzbergen. I have, in a report of the expedition of 1868, given a brief accountable result of that undertaking, which showed that even at that period of the year, when the water is most free from drift-ice, the polar basin, at least to the north of Europe, and doubtless also to the north of America and Asia, is so full of drift-ice that all possibility of passing through it in a ship is out of the question.

A single slab of silicified silty and cross-bedded mudstone from the Katkoyeh Formation, east-central Iran yields Yutagraptus cf. mantuanus Riva which indicates a late Arenig age. The slab also bears Dictyonema ghodsiae sp. nov., regarded as the only unequivocally planktonic dendroid from post-Tremadoc strata. The sicula is surrounded by at least twelve vesicular bodies which constitute a raft of floats. These are the only certain floats yet identified in the Order Dendroidea, and one of very few cases known in the Class Graptolithina.

The Spitsbergen archipelago is situated in the north-westernmost part of the Barents Shelf. The structural position of the archipelago and the variety of its geological complexes make this region very important for understanding the tectonic history of the Atlantic sector of the Arctic.

Southern Israel is traversed by a series of north-easterly trending anticlines, the largest of which is the Raman anticline. Here a deep erosion-cirque exposes a sedimentary succession from the Cenomanian down to the Triassic, including a series of magmatic rocks of highly alkaline affinities. The forms of these magmatic bodies are described in detail and from their field-relationships with the sediments it is shown that they include a stock, a laccolith, sills, dykes, and a basaltic flow. This igneous activity took place between Lower Triassic and Upper Jurassic times and was perhaps restricted only to the Jurassic. Comparison with the surrounding areas leads to the conclusion that the Raman region was the centre of magmatic activity during this period.

In this study, relationships between fracture patterns, lithology, thickness, diagenetic processes and grain size are evaluated within Cretaceous sediments in two sections of Dizlu and Kolah Ghazi of Isfahan. This study area was selected based on its outcrops of different rock units and its well-developed tectonic fractures. The fracture patterns within stratigraphic units of these sections are studied using geometrical and statistical analyses. This study finds that variable fracture spacing and fracture spacing ratios can be affected by lithology, thickness, grain size of sediments and diagenetic processes. A study of fracture stratigraphy based on fracture pattern evaluation within different cropped-out sedimentary rocks can be used to improve understanding of the same types of sedimentary rock units below the surface or throughout other sedimentary basins. Consequently, this could improve information regarding storage and fluid flow pattern throughout sedimentary rocks in different regions, even for subsurface purposes.

The uppermost Famennian – lowermost Tournaisian interval has been analysed in detail using biostratigraphy, sedimentology, magnetic susceptibility and geochemistry in a reference section of the relatively shallow carbonate ramp environment within the Pomeranian Basin. High-resolution biostratigraphic study, based on miospores, allows recognition of the standard western European lepidophyta–nitidus (LN) and verrucosus–incohatus (VI) zones, as well as the Convolutispora major Zone, a local Pomeranian equivalent of the European standard hibernicus–distinctus (HD) Zone. The sedimentary succession and specific phenomena recognized close to the Devonian/Carboniferous boundary, such as fluctuations in water column euxinia, wildfire evidence, relative sea-level changes and perturbations of the carbon cycle reflected by positive carbon excursions, display a pattern partly similar to that observed in many areas in Europe during the Hangenberg Event, although the Hangenberg Black Shale horizon is not developed here. These important microscale environmental perturbations were observed not only within the Famennian LN miospore Zone but in a wide interval between the LN and the lowermost local Convolutispora major miospore zones ( = lower part of HD standard miospore Zone). It is still uncertain whether the recognized event(s) were connected solely with the Hangenberg Event, which was possibly complex and multi-phased as is sometimes suggested, or whether they represent a succession of regionally limited, post-Hangenberg events. This question needs to be further investigated on broader stratigraphic and geographical scales.

Enrichment of the heavy rare earth elements (HREE) in carbonatites is rare as carbonatite petrogenesis favours the light (L)REE. We describe HREE enrichment in fenitized phonolite breccia, focusing on small satellite occurrences 1–2 km from the Songwe Hill carbonatite, Malawi. Within the breccia groundmass, a HREE-bearing mineral assemblage comprises xenotime, zircon, anatase/rutile and minor huttonite/thorite, as well as fluorite and apatite.

A genetic link between HREE mineralization and carbonatite emplacement is indicated by the presence of Sr-bearing carbonate veins, carbonatite xenoliths and extensive fenitization. We propose that the HREE are retained in hydrothermal fluids which are residually derived from a carbonatite after precipitation of LREE minerals. Brecciation provides a focusing conduit for such fluids, enabling HREE transport and xenotime precipitation in the fenite. Continued fluid–rock interaction leads to dissolution of HREE-bearing minerals and further precipitation of xenotime and huttonite/thorite.

At a maximum Y content of 3100 µg g−1, HREE concentrations in the presented example are not sufficient to constitute ore, but the similar composition and texture of these rocks to other cases of carbonatite-related HREE enrichment suggests that all form via a common mechanism linked to fenitization. Precipitation of HREE minerals only occurs where a pre-existing structure provides a focusing conduit for fenitizing fluids, reducing fluid – country-rock interaction. Enrichment of HREE and Th in fenite breccia serves as an indicator of fluid expulsion from a carbonatite, and may indicate the presence of LREE mineralization within the source carbonatite body at depth.