The Grönhögen-2015 core drilling on southern Öland, Sweden, penetrated 50.15 m of Cambrian Series 3, Furongian and Lower–Middle Ordovician strata. The Cambrian succession includes the Äleklinta Member (upper Stage 5) of the Borgholm Formation and the Alum Shale Formation (Guzhangian–Tremadocian). Agnostoids and trilobites allowed subdivision of the succession into eight biozones, in ascending order: the uppermost Cambrian Series 3 (Guzhangian) Agnostus pisiformis Zone and the Furongian Olenus gibbosus, O. truncatus, Parabolina spinulosa, Sphaerophthalmus? flagellifer, Ctenopyge tumida, C. linnarssoni and Parabolina lobata zones. Conspicuous lithologic unconformities and the biostratigraphy show that the succession is incomplete and that there are several substantial gaps of variable magnitudes. Carbon isotope analyses (δ13Corg) through the Alum Shale Formation revealed two globally significant excursions: the Steptoean Positive Carbon Isotope Excursion (SPICE) in the lower–middle Paibian Stage, and the negative Top of Cambrian Excursion (TOCE), previously referred to as the HERB Event, in Stage 10. The δ13Corg chemostratigraphy is tied directly to the biostratigraphy and used for an improved integration of these excursions with the standard agnostoid and trilobite zonation of Scandinavia. Their relations to that of coeval successions in Baltoscandia and elsewhere are discussed. The maximum amplitudes of the SPICE and TOCE in the Grönhögen succession are comparable to those recorded in drill cores retrieved from Scania, southern Sweden. The results of this study will be useful for assessing biostratigraphic relations between shale successions and carbonate facies on a global scale.

The Early Palaeozoic geology of the South China Craton (SCC) is characterized by an Early Palaeozoic intracontinental orogen with folded pre-Devonian strata and migmatites, MP/MT metamorphic rocks and Silurian post-orogenic peraluminous magmatic rocks in both the Yangtze and the Cathaysia blocks. In this contribution, we present new zircon U–Pb ages and Hf isotope data for detrital zircons from the Neoproterozoic to Silurian sedimentary sequences in the southeastern Yangtze Block. Samples from Neoproterozoic rocks generally display a major peak at 900–560 Ma, whereas samples from Lower Palaeozoic rocks are characterized by several broader peaks within the age ranges 600–410 Ma, 1100–780 Ma, 1.6–1.2 Ga and 2.8–2.5 Ga. Provenance analysis indicates that the 900–630 Ma detritus in Cryogenian to Ediacaran samples was derived from the Late Neoproterozoic igneous rocks in South China that acted as an internal source. The occurrence of 620–560 Ma detritus indicates the SE Yangtze was associated with Late Neoproterozoic arc volcanism along the north margin of East Gondwana. The change of provenance resulted in the deposition of 550–520 Ma and 1.1–0.9 Ga detrital zircons in the Cambrian–Ordovician sedimentary rocks. The εHf(t) values of these detrital zircons are similar to those of zircons from NW Australia–Antarctica and South India. This change of provenance in the Cambrian can be attributed to the intracontinental subduction between South China and South Qiangtang, and the convergence of India and Australia when East Gondwana finally amalgamated.

The tonalite–trondhjemite–granodiorite (TTG) Mons Claudianus Batholith (MCB) of Egypt is subsolvus, metaluminous to mildly peraluminous, exhibits wide ranges of SiO2, Al2O3, Sr, Rb, Zr, shows large Ba enrichment, is moderately enriched in rare earth elements (REE) and is depleted in K, Ti, Nb, Y, Hf and heavy REE (HREE), reflecting strong arc geochemical signatures. Moderate fractionation of REE and lack of Eu anomaly characterize the MCB. It is typical of high-Al TTGs of volcanic-arc affinities. U–Pb–zircon dating produced a Pan-African age of 664.12 ± 0.38 Ma. The MCB exhibits 87Sr/86Sr isotopic compositions of 0.70352–0.70626 (initial Sr ratio of 0.70259) and 143Nd/144Nd ratios of 0.51261–0.51276 (εNd; –0.5 to +2.4), suggestive of a mantle source. Anatexis of a basaltic slab under eclogitic conditions leaving garnet in the residue produces high-Al TTG rocks characterized by low Yb values (<1.8 ppm). Values (in ppm) of Yb (0.65–1.8), Y (2.2–19), Nb (1.2–6.4), and ratios of Nb/Ta (7–17), (La/Yb)N of 11.7, Sr/Y and Zr/Sm (58 and 45, respectively) are all consistent with anatexis of a basaltic slab under eclogitic conditions, leaving garnet in the residue to produce this high-Al TTG suite. The data conform to magma generation via partial melting (F = 0.25–0.50) leaving 15–25 % garnet in the residue. Voluminous synorogenic magmatic pulses, resulting from slab melting during the closure of the Mozambique Ocean via convergence of east and west Gondwana, produced the MCB and similar large batholiths forming the core of Pan-African belts. These belts welded together vestiges of fragmented Rodinia, assembling them into a united Gondwana.

Sulphur isotopes can be used as a powerful tool to trace fluid evolution and explore the formation of chimneys. To clarify the in situ S isotopic variations of sulphides at the micro-scale, we analyzed a sulphide chimney collected from the hydrothermal field in the East Pacific Rise 1–2° S using a sensitive high-mass-resolution ion micro-probe for stable isotopes (SHRIMP SI). Three mineral zones can be identified in the chimney: an external outer wall of porous anhydrite and colloform pyrite, an internal middle zone of sub-euhedral pyrite and massive chalcopyrite, and an inner zone of massive pyrite. The δ34SV-CDT values of the sulphides fall within the range 1.83–7.51 ‰ (avg. 4.05 ‰, n = 16), and S isotopic values increase from the core (3.09 ‰, n = 3) to the middle (3.78 ‰, n = 11) to the edge (6.99 ‰, n = 2). These results illustrate mineral crystallization processes and the mixing between seawater-derived S and magmatic–hydrothermal fluids during the growth of the chimney. The zones from the edge to the core are characterized by crystal morphologies of colloform/anhedral pyrite to massive pyrite with decreasing δ34S values, revealing multi-stage mineral deposition and sulphur isotopic fractionation. In contrast to the increase in δ34S values from the core to the edge in one profile (profile A), anomalously low δ34S values in fine-grained pyrite relative to chalcopyrite in another profile (profile B) in the middle zone result from S isotopic exchange between seawater SO42− and fluid H2S due to different fluid–seawater mixing, possibly caused by variations in permeability and porosity across the chimney.

We present a new geological map and new structural, petrographical and geochronological data from the Uppermost Unit of the Cretan nappe pile exposed south of the Dikti Mountains in eastern Crete (Greece). Based on these data, the Uppermost Unit in the study area can be subdivided (from bottom to top) into the Arvi Unit, Theodorii Greenschist and Asterousia Crystalline Complex (ACC)-type rocks. The ACC-type rocks have been affected by polyphase deformation (D1–D3) and metamorphism. Relics of the D1 phase are preserved as internal foliation in garnet porphyroblasts. D2 top-to-the SE shearing under upper amphibolite facies conditions led to the dominant foliation. After post-D2 exhumation, parts of the ACC-type rocks were affected by contact metamorphism of a non-exposed pluton, which intruded at a depth below 10 km during Campanian time (74±2Ma; laser ablation inductively coupled plasma mass spectrometry on zircon). This age, obtained from zircon of chiastolite hornfels, is in line with intrusion ages of ACC-type (meta)granitoids exposed on Crete and on Anafi. The S2-foliation of the ACC-type rocks was reactivated during the late phase of contact metamorphism by D3 top-to-the SE shearing. Latest Cretaceous cross-mica with low silicon content post-dates this shearing event. During middle Paleocene time, the ACC was thrust on top of the Theodorii Greenschist. This thrusting event as well as subsequent brittle thrusting of the greenschists and the ACC-type rocks on top of the prehnite-pumpellyite facies metamorphic Arvi Unit was still accommodated by top-to-the SE kinematics, which is the dominant kinematics of the Uppermost Unit on Crete and on Anafi.

Two hundred and eighty specimens of paradoxidids from two localities in the Holy Cross Mountains (Poland) have been reanalysed using morphometric techniques. Revision of the dataset provided evidence for the presence of two endemic taxa: Acadoparadoxides kozlowskii (Orłowski, 1959) and Acadoparadoxides samsonowiczi (Orłowski, 1959), both belonging to the earliest group of Acadoparadoxides, initially considered to be present only in Gondwanan successions. Thus, this is the first description of the members of this group outside West Gondwana. The taxonomic revision, and the presence of representatives of the earliest acadoparadoxidines coupled with the absence of taxa typical of Scandinavia that were previously described from this locality have resulted in the modification of the biostratigraphic scheme hitherto used in the Holy Cross Mountains. The newly established A. samsonowiczi – A. kozlowskii Assemblage Zone is correlated with the Morocconus notabilis Zone of Morocco, and thus represents the Cambrian Series 2 and 3 boundary interval. Links with West Gondwana challenge the existing palaeogeographic interpretations for the southern part of the Holy Cross Mountains and point to an urgent need to revise the position of the Małopolska Block during the middle Cambrian.

Both the deformation and rupture characteristics of rocks are related to geomechanics. In this paper, we identify the evaluation indexes related to coalbed methane (CBM) accumulation in strongly deformed strike-slip fault zones considering tectonics and fractures. We found that fault scale, the fault combination, the tectonic stress, the preservation conditions and fractures all have important effects on the CBM distribution. Areas near the large-scale opening faults are unfavourable to the preservation of coalbed methane. The distribution of gas wells with different capacities is influenced by tectonic extension and convergence. A 3D geomechanical method was used to analyse the influence of the ‘ribbon effect’ of strike-slip faults on the CBM distribution. Due to the influence of the ‘ribbon effect’, the tectonic stress presents a plane in situ stress heterogeneity, which in turn will affect the gas well productivity. We also calculated the integrated rupture rate (IF) to characterize the degree of tectonic fracture development in the target coal reservoir. The appropriate fracture development degree can improve the petrophysical properties of the coal reservoirs while maintaining good storage conditions, such that the gas wells can achieve a higher production capacity. This study is of great significance for the enrichment of the geomechanical theory of oil and gas exploration.

An Ordovician–Silurian boundary section marked by an uninterrupted, relatively high rate of black shale sedimentation and abundant, diverse graptolites is described from the south-central Pyrenees. The structurally simple Estana section comprises the uppermost part of the quartzite-dominated Bar Formation and overlying black shales of late Hirnantian and early Rhuddanian age, which have been dated by graptolites to the upper Metabolograptus persculptus and lower–middle Akidograptus ascensus–Parakidograptus acuminatus biozones. Due to the absence of M. persculptus, a Metabolograptus parvulus Biozone correlative with the upper part of the persculptus Biozone is recognized below the lowest occurrence of akidograptids, which indicate the base of the Silurian System. The graptolite fauna comprise 27 species including Normalograptus minor, N. lubricus, N. rhizinus, Hirsutograptus, Korenograptus bifurcus, K. bicaudatus, K. lanpherei and Nd. shanchongensis, most of which were formerly considered to be endemic to the low-latitude palaeobiogeographical province of China, Siberia and northern North America. Two new species, N. baridaensis and N. ednae, are described. The succession of graptolite assemblages in the Estana section, and occurrence of several cosmopolitan taxa in its parvulus and lower ascensus–acuminatus biozones that are unknown elsewhere in peri-Gondwanan Europe, suggest that strata immediately surrounding the Ordovician–Silurian boundary may be absent, highly condensed or oxic and barren of graptolites in other sections of northwestern peri-Gondwana. Common graptolite synrhabdosomes and abnormal rhabdosomes may indicate some environmental stress in the parvulus Biozone, although the rather uniform black shale lithology, total organic carbon content and δ13Corg values suggest uninterrupted sedimentation under stable, anoxic conditions.

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.

A prominent large negative δ13Corg excursion and a coeval notable spike in mercury (Hg)/total organic carbon ratio are observed in the middle–upper Permian Gohan Formation in central Korea, located in the eastern Sino-Korean block (SKB), which may represent the Capitanian mass extinction event. The SKB was separated from the South China block by the eastern Palaeo-Tethys Ocean. This finding from the SKB supports the widespread Hg loading to the environment emitted from the Emeishan volcanic eruptions in SW China. This study demonstrates that the Hg cycle was globally perturbed in association with global carbon cycle perturbation that occurred during the Capitanian Extinction.