The interesting relation between the Porphyrite of Whitberry Point, at the mouth of the Tyne near Dunbar, and the adjacent sedimentary rocks, was first noticed, we believe, by Professor Geikie, who speaks of it in the Memoirs of the Geological Survey of East Lothian, pages 40 and 41, and again in the new edition of Jukes's Geology, pp. 269. The volcanic mass which forms the point, consists of a dark felspathic base with numerous crystals of augite: it is circular in form, and is exposed for two-thirds of its circumference in a vertical precipice facing the sea, about twenty feet in height.

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.

Zoœcia generally elongated, but very variable in shape and dimensions; length of area ·68 to ·48 mm., breadth of area ·36 to ·2 mm.; no fornt wall, side walls very low, with a further depression at the head of the zoœcium, and furnished all round with slender buttresses, which are much more easily distinguished in the upper part of the zoœcium, owing to their greater size and Projection there, than in the lower Part.

The Magnesian Limestone of England forms a comparatively narrow outcrop stretching southwards for about 150 miles from South Shields to Nottingham. At either end the formation is fairly well known from the many quarries and sections opened up in the industrial areas of East Durham on the one hand and South Yorkshire and Nottinghamshire on the other. Away from these regions, however, our knowledge is scanty, and particularly so in the North Riding of Yorkshire, in the tract of country between the rivers Tees and Swale. Information is lacking mainly because the district is so thickly covered with Glacial and Recent deposits that, except at the extreme ends of this Tees-Swale stretch, rock is nowhere exposed. All the way from the Darlington country down to Catterick and beyond, for sheer lack of evidence the Trias—Magnesian Limestone boundary was assumed to be of normal, unfaulted character, but all was so uncertain that any borings in the area were likely to prove invaluable. How invaluable will be gathered from the following account of two recent bores, which throws an entirely new light, not only on the geological structure but also on the stratigraphy of this obscure region.

The pith-casts of Calamites are common Coal-measure fossils, sometimes of use in helping to fix the horizon of certain coals. They are, however, notoriously difficult taxonomically, and in several cases there is difference of opinion among authorities both as to the essential characters of a particular type of pith-cast, and also as to what is the most nearly correct name to apply to it. Immense space is still taken up by arguments as to what, exactly, some ancient and often manifestly rough drawing, supposed to represent a type, really depicts—with a view to maintaining a strict priority as regards nomenclature. If the original specimen is now lost, as is not infrequently the case, the guessing still continues. Some workers are not content to start their synonymies chronologically with the next oldest figure, the original of which still survives and the nature of which is agreed to on all hands.

The Raibl period was the natural sequel of the variable and unequal movements which prevailed over Alpine areasinPermian and pre-Raibl Triassic time. Many basins formerly open were then enclosed; rauchwackes and beds of dolomite and gypsum were interbedded with fossiliferous deposits. Whereas,insome places, the dolomitic nature of the deposit is confined to special horizons, in the South Tyrol “Dolomites” it may almost be said to reign throughout. This makes it all but impossible to say when Schlern dolomite ends and Raibl beds begin. in the present incomplete state of our knowledge with regard to the heteropism of the Raibl series throughout the whole Alps, I have judged it best to begin the Raibl horizon at any particular place with the first appearance of a distinctly Raibl fauna, even although that fauna may not have been proved to correspond to the acknowledged lowest fauna of Raibl age in distant parts of the Alps.

To return for a moment to the succession of Schlern dolomite upon the Cassian beds of Enneberg, I found that, where Schlern dolomite rests on Cipit limestones, it has at its base a conglomeratic appearance, as if Cipit blocks had been imbedded in a beautifully fine white or reddish dolomitic mud, instead of the dingy brown and black tufaceous sediments. This is the case in several places, e.g. upon Pordoi and Sella Jochs, where there is no evidence of unconformity. Again, where the dolomite succeeds the thin-bedded marls and limestones of Cassian age, it does so conformably; but one and the same bed is at some parts calcareous and fossiliferous, at other parts dolomitic and unfossiliferous. Seeing that this holds good at various horizons in Lower as well as Middle Trias over the whole area of South Tyrol, we need f in d nothing remarkable in it from the point of view of the stratigraphical succession. Indeed, I have only mentioned these observations as an indication of the particular mode of transition from conditions of deposition favourable for the Cassian fauna to those in which the Raibl fauna was enabled to make an occasional appearance in the South Tyrol dolomites. At a very little distance above the base of Schlern dolomite all signs of Coral life disappear, and the deposit looks a homogeneous rock, although always retaining local variation in the degree of its dolomitism. At this stage the rock often shows typical Oolite structure. As regards the presence or want of stratification, it has as little to do with the question of the Coral Keef origin of the dolomite as the amount of magnesic salts in the rock—stratification is present and absent in one and the same “Keef.”

In 1928 Dr. P. Tesch published a note on the occurrence of an igneous rock in Dutch Coal-measures (1).1 As this is the first occurrence of an igneous rock in Holland, the present authors have decided to publish a more detailed petrographical description of the rock, together with an attempt to correlate it with similar rocks in Great Britain and Germany.

But while it is difficult to collect fossils in situ in the upper part of the Lower Lias, a very good knowledge of the fauna is obtained from the material which may be collected on the tunnel heaps between Old Dalbyand Saxelby. I have been permitted to study the large collection of specimens from these heaps which are preserved at University College, Nottingham, and the Engineer of the Midland Railway Company gave me leave to make small excavations. The following lists give some idea of the fauna, which contains abundant Ammonites, especially of the genera Tragophylloceras, Polymorphites, and Platypleuroceras. The Foraminifera likewise are unusually interesting; a list of genera identified by Wilson has already been given by Quilter; according to the list given by H. B. Woodward no Textularia-like form is known from the Lias of any other British locality.

In working out, at the request of Sir Archibald Geikie, the petrography of the Lower Carboniferous Volcanic rocks in Haddingtonshire (the results of which I propose shortly to publish), I have been led to examine the igneous material that builds up the isolated hills (necks), situated on the margin of the volcanic area of the Garlton Hills. Among these, the rock of Traprain Law especially attracted my attention. It is a close-grained, dark brown to grey rock. Some varieties have a glistening or greasy surface, and are speckled over with dark spots, while others show glancing cleavage surfaces of a clear glassy felspar (sanidine).

Sedimentary rocks exposed at Dob’s Linn, Scotland, have significantly influenced our understanding of how life evolved over the Ordovician to Early Silurian. The current interpreted chronostratigraphic boundary between the Ordovician and Silurian periods is a Global Boundary Stratotype Section and Point (GSSP), calibrated to 443.8 ± 1.5 Ma (Hirnatian–Rhuddanian age), based on biostratigraphic markers, radioisotopic dates and statistical modelling. However, challenges arise due to tectonic disturbances, complex correlation issues and the lack of systematic dating in Ordovician–Silurian stratigraphic sections. Here, hundreds of zircon grains from three metabentonite ash horizons were dated using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). A subset of the grains were re-analyzed using Chemical Abrasion Isotope Dilution Thermal Ionization Mass Spectrometry (CA-ID-TIMS). We present a high-precision CA-ID-TIMS 238U-206Pb weighted mean date of 440.44 ± 0.55/0.56/0.72 Ma (±analytical/with tracer/with U-decay constant) for the Coronagraptus cyphus biozone. However, the study reports younger, and in certain cases, older LA-ICP-MS zircon dates within the Coronagraptus cyphus, Akidograptus ascensus and Dicellograptus anceps zones, suspected as being influenced by Pb loss and LA-ICP-MS matrix mismatch. The study reports concerns about the suitability of Dob’s Linn as a GSSP section and examines various LA-ICP-MS maximum depositional age (MDA) approaches, suggesting the use of the TuffZirc date and the youngest mode weighted mean (YMWM) as suitable MDA calculations consistent with CA-ID-TIMS results.

The Diwani hills are located SE of Balaram–Abu Road in the Banaskantha district of north Gujarat. The crystalline rocks of the Diwani hill area are a diverse assemblage of Precambrian metamorphic and igneous rocks. These rocks are petrologically more complex and date back to the Aravallis or earlier. The mineralogical assemblages such as grt–sp–opx–qz of these rocks indicate their origin in anhydrous or dry conditions, implying metamorphism under pyroxene granulite facies. These granulitic rocks were subjected to Delhi orogenic deformation and were later intruded by the Erinpura granite. Textural and microstructural relationships, mineral chemistry, P–T–X pseudosection modelling and the oxidation state of pelitic granulites from the Diwani hill area of north Gujarat are all part of the current approach. The winTWQ program and pseudosection modelling in the NCKFMASHTO model system utilizing Perple_X software were used to restrict the P–T evolution of these pelitic granulites. The unification of these estimates shows that the pelitic granulites reached their pressure and temperature maxima at 8.6 kbar and 770 °C, respectively. The oxygen fugacity (log fO2) versus temperature computations at 6.2 kbar revealed log fO2–T values of −13.0 and 765 °C, respectively. The electron microprobe dating of monazite grains separated from the granulites of the Diwani hills yields ages ranging from 769 Ma to 855 Ma. The electron microprobe dating presented here from the Diwani hills provides evidence for a Neoproterozoic (Tonian) metamorphic event in the Aravalli–Delhi Mobile Belt.

Encrinurids are common in Ordovician and Silurian strata but whether they survived into the Early Devonian is still controversial. This paper documents the encrinurid Batocara sp. near the Silurian–Devonian boundary in western Junggar, Xinjiang. The highest horizon of Batocara sp. is located above the first appearance datum of the Devonian conodont Caudicriodus, confirming that encrinurids may cross the Silurian–Devonian boundary. The presence of Caudicriodus angustoides bidentatus, Zieglerodina planilingu and plate-type loboliths of scyphocrinoids above the highest horizon of Batocara sp. indicates that encrinurids here extend only into the lower part of the first conodont zone of the Lochkovian (i.e., Caudicriodus hesperius Biozone). Encrinurids are widely distributed and easily recognized, and unlike graptolites and conodonts are not controlled by lithofacies. Therefore, it might be possible to use the highest horizon of encrinurids as indicator fossils to identify the approximate position of the Silurian–Devonian boundary in areas or sections where graptolites and conodonts are not present, and at least in northwest China.

Previous hydrocarbon explorations in the middle of the Tarim Basin indicate that strike-slip faults play an important role in the development of Ordovician carbonate reservoirs and hydrocarbon accumulation. The SB5 fault in the Tarim Basin was the target of this investigation. An evaluation of the stress in situ was carried out and provided boundary conditions to build a 3D geomechanical model. The distribution and application of present in situ stress in the strike-slip fault were studied. The results show good agreement between the absolute measured stress in situ and the modelled stresses, revealing a different stress regime along the strike-slip fault. The uplift segment belongs to a strike-slip stress state, and other areas belong to a normal fault stress state. The strike-slip fault has a significant influence on the present in situ stress distribution. The direction of the maximum horizontal stress deflects near the fault and tends to be parallel to the fault strike. This work introduces a comprehensive evaluation of the present in situ stress of the fractured carbonate reservoirs controlled by the strike-slip fault system. The present in situ stress direction can clarify the propagation direction of hydraulic fracturing and serve to evaluate the effectiveness of natural fractures.