The δ13C profile from an interval of the Martin Point section in western Newfoundland (Canada) spans the upper Furongian (uppermost Cambrian). The interval (~90 m) is a part of the Green Point Formation of the Cow Head Group and consists of the Martin Point (lower) and the Broom Point (upper) members. It is formed of slope marine carbonates alternating with shales (rhythmites) and conglomeratic interbeds. The preservation of the investigated micritic carbonates was meticulously evaluated by multiple petrographic and geochemical screening tools. The δ13C and δ18O values (−0.5 ± 0.8 ‰VPDB and −7.1 ± 0.3 ‰VPDB, respectively) exhibit insignificant correlation (R2 = 0.002) and similarly the correlation of δ13C values with their Sr and Mn counterparts, which supports the preservation of at least near-primary δ13C signatures that can be utilized to construct a reliable high-resolution carbon-isotope profile for global correlations.

The δ13C profile exhibits two main negative excursions, a lower broad excursion (~3 ‰) that reaches its maximum at ~70 m below the Martin Point / Broom Point members boundary and an upper narrow excursion (~2.5 ‰) immediately below the same boundary. The lower excursion can be correlated with the global latest Furongian HERB event (TOCE), which is also recognized in the C-isotope profile of the GSSP boundary section at Green Point whereas the upper excursion matches with that of the Cambrian‒Ordovician boundary in the same section. The peak of the HERB δ13C excursion is correlated with positive shifts on the Th/U and Ni profiles (redox and productivity proxies).

The Harsin–Sahneh serpentinized peridotites are widely exposed along the Zagros suture zone in the western region of Iran and are considered to represent remnants of Neo-Tethys oceanic lithosphere at the junction of the Arabian and Iran Plates. These rocks are characterized by low contents of SiO2 (38.8–43.5 wt%), Al2O3 (0.1–3.8 wt%), CaO (0.2–8.2 wt%) and TiO2 (< 1 wt%) and high MgO contents (31.1–46.0 wt%). Their enrichments of large ion lithophile elements and light rare earth elements, with high 87Sr/86Sr(i) values (0.7036–0.7109) and relatively high variations in their εNd(t) (–7.5 to +7.8) values, indicate that the Harsin–Sahneh peridotites were metasomatized by flux released from the oceanic subducting slab in an active margin. The chemical compositions and isotopic ratios of these rocks suggest that they were formed as residue of mid-oceanic ridge basalt in the lithosphere that was then subsequently re-melted and metasomatized in a supra-subduction zone system. The occurrence of both mid-oceanic ridge and supra-subduction zone-type peridotites suggests that the heterogeneity of the upper mantle may have occurred due to the different ratios of partial melting and melt–rock reaction processes in different tectonic settings within the Neo-Tethys realm. The Harsin–Sahneh peridotites provide a good explanation of multistage melt extraction as well as melt–rock and metasomatic reactions in the mantle sequence of the Zagros ophiolite complex.

Many of the most diverse clades of Late Palaeozoic echinoids (sea urchins) originated in the Devonian period. Our understanding of diversity dynamics of these Late Palaeozoic clades are thus informed by new systematic descriptions of some of their earliest members. The Proterocidaridae are a diverse and morphologically distinct clade of stem group echinoids with flattened tests and enlarged adoral pore pairs, which are first known from the Upper Devonian. We herein report on a new species of Hyattechinus, Hyattechinus anglicus n. sp., from the Upper Devonian of the North Devon Basin, Devon, UK. This is the first Devonian Hyattechinus known from outside of the Appalachian Basin, USA, and provides novel information regarding the palaeogeographic and stratigraphic distribution of proterocidarids in Late Devonian times. We additionally update the stratigraphic distribution of Devonian Hyattechinus from the Appalachian Basin, following recent biostratigraphic resolution of their occurrences. Hyattechinus appears to have been present in the Rheic echinoderm fauna during Late Devonian times, and comparison of the palaeoenvironmental setting of Hyattechinus anglicus with that of other Hyattechinus from the Famennian of the Appalachian Basin suggests that the genus may have preferred siliciclastic settings. Furthermore, this new taxon increases the diversity of echinoids from the Upper Devonian of Devon to three species.

The deformation of the Solonker Belt and nearby regions is helpful for understanding the tectonic evolution of the Central Asian Orogenic Belt. This study carried out structural analysis in the Mandula and Ganqi areas of western Inner Mongolia, including the Solonker Belt, the Southern Orogenic Belt and the northern Yinshan Belt (Langshan range). Our results reveal that the Solonker Belt, the Southern Orogenic Belt and the northern Yinshan Belt underwent two stages (D1 and D2) of deformation during the Mesozoic period. The D1 stage produced the NNE-directed thrusts and asymmetric folds, indicating a NNE–SSW contraction. The northern Yinshan Belt, the Southern Orogenic Belt and the Solonker Belt formed as a series of NNE-verging tectonic nappes. The D2 stage developed the NE-trending folds and the SE- or NW-directed thrusts that cross-cut the D1 structures. The two events of nearly orthogonal or oblique shortening gave rise to the superimposed structures (e.g. fold interference patterns). The quartz veins that filled the fractures of the D1 deformation contain zircons of Middle Triassic U–Pb ages. The new dating data, along with the regional sedimentary hiatus, led us to infer that the D1 stage of deformation occurred in Middle Triassic time and the D2 stage occurred in Late Jurassic time. We consider that the D1 stage of deformation resulted from a convergent event, which might be related to the closure of the Palaeo-Asian Ocean or limited, narrow ocean basins; and the D2 stage of deformation was the far-field result of subduction of the Palaeo-Pacific Ocean and the closure of the Mongol-Okhotsk Ocean.

The Makkovik Province of eastern Labrador represents part of an accretionary orogen active during an early stage in the development of the Palaeoproterozoic southern Laurentian continental margin. New Nd isotope data for the eastern Makkovik Province suggest that accreted juvenile Makkovik crust was generated in the Cape Harrison domain during a single crust-forming event at c. 2.0 Ga. Pb isotope data support this model, and show a strong similarity to radiogenic crustal signatures in the juvenile Palaeoproterozoic crust of the Ketilidian mobile belt of southern Greenland. As previously proposed, an arc accretion event at c. 1.9 Ga triggered subduction-zone reversal and the development of an ensialic arc on the composite margin. After the subduction flip, a temporary release of compressive stress at c. 1.87 Ga led to the development of a retro-arc foreland basin on the downloaded Archean continental edge, forming the Aillik Group. Unlike previous models, a second arc is not envisaged. Instead, a compressive regime at c. 1.82 Ga is attributed to continued ensialic arc plutonism on the existing margin. The tectonic model for the Makkovikian orogeny proposed here is similar to that for the Ketilidian orogeny. Major- and trace-element analyses suggest that much of the magmatism in the Makkovik orogen results from post-accretionary ensialic arc activity, and that few vestiges remain of the original accreted volcanic arc. This pattern of arc accretion and intense post-accretion reworking is common to many accretionary orogens, such as the South American Andes and North American Cordillera.

Mass transport deposits (MTDs), created by gravity-driven deformation of unlithified sediments, and tectonic mélanges produced by contractional deformation are characterized by a similar chaotic appearance. It follows that distinguishing structures formed by soft-sediment deformation during mass transport from those produced by contractional tectonics can be problematic. In fact, deformation occurring along detachment levels may completely obliterate the original sedimentary fabric. Although a number of advances have been made during recent decades, field criteria for discriminating structures within MTDs that are overprinted by later regional contraction are not readily applicable to all the exposed examples. We address some of these general issues through a detailed case study of the Monte Facito Formation in Italy. This Triassic unit was formed during the Africa–Europe continental separation and, since the Miocene, has been involved in contractional deformation during the construction of the Apennines. The Monte Facito Formation consists of a series of stratigraphically coherent units, separated by chaotic and often deformed intervals, whose origin has been previously attributed to either tectonic or sedimentary processes. An example is provided by a characteristic pebbly mudstone (or ‘paraconglomerate’) which has been interpreted as either a Triassic gravity-flow deposit, or alternatively, as a product of shearing along regional contractional detachments during the Miocene. This detailed field-based study allows us to recognize structures related to the depositional processes that created these chaotic intervals, and which can therefore be interpreted as MTDs. We also discriminate structures connected to later contractional tectonics that locally produced intense reworking of the MTDs.

High-SiO2 rocks referred to as oceanic plagiogranites are common within the crustal sequences of ophiolites; however, their mode of petrogenesis is controversial with both late-stage fractional crystallization and partial melting models being proposed. Here, we present new whole-rock data from plagiogranitic dyke-like bodies and lenses from the lower and middle sections of the sheeted dyke complex of the Cretaceous Muslim Bagh Ophiolite, northwestern Pakistan. The plagiogranites have similar geochemical signatures that are inconsistent with them being the fractionation products of the mafic units of the Muslim Bagh Ophiolite. However, the plagiogranites all display very low TiO2 contents (<0.4 wt%), implying that they formed by partial melting of mafic rocks. Melt modelling of a crustal gabbro from the Muslim Bagh Ophiolite shows that the trace-element signature of the plagiogranites can be replicated by 5–10% melting of a crustal hornblende gabbro with amphibole as a residual phase, resulting in a concave-up middle rare Earth element pattern. Compositional similarities between the Muslim Bagh Ophiolite plagiogranites and Archaean TTG (trondhjemite–tonalite–granodiorite) has implications for the generation of juvenile Archaean continental crust. As the Muslim Bagh Ophiolite was derived in a supra-subduction zone, it is suggested that some Archaean TTG may have been derived from melting of mafic upper crust in early subduction-like settings. However, due to the small volume of Muslim Bagh Ophiolite plagiogranites, it is inferred that they can be instructive on the petrogenesis of some, but not all, Archaean TTG.

The recently uplifted and exposed Pliocene and Pleistocene sedimentary infill of the neotectonic Polis graben provides an excellent opportunity to understand extensional basin development in a marine setting. Fieldwork, facies analysis and dating using nannofossils and strontium isotopes reveal how the sedimentary conditions evolved during infill of the Polis graben during Pliocene and Pleistocene time, and allow a composite succession for the depocentre to be determined for the first time. Six lithofacies are recognized in the northern Polis graben, allowing evolving palaeoenvironments to be inferred. By the end of Miocene time (Messinian) a major c. N–S-trending graben was established; extensional faulting continued during the Pliocene–Pleistocene until recent time. Post-Messinian salinity crisis deposition began with deposition of hemipelagic muds (c. 5.08–2.76 Ma), equivalent to the Nicosia Formation. This was followed by upwards incoming of repeated normal-graded bioclastic carbonates (couplets) (c. 2.76–1.6 Ma), which are interpreted as age-equivalents of the Athalassa Formation elsewhere in Cyprus. The upwards sudden facies change is explained by tectonically controlled shallowing which enabled neritic carbonate production on the basin margins. The appearance of basement-derived material (e.g. ophiolitic extrusive detritus) in the highest stratigraphic levels of the basin fill in the north (c. 1.7–1.6 Ma) reflects onset of rapid surface uplift focused on the Troodos ophiolitic massif. Overall, the syntectonic basin infill appears to document a two-stage, pulsed uplift related to early-stage collision of the African and Eurasian plates in the easternmost Mediterranean region.

Bedding-parallel fibrous calcite veins in black shales (Cretaceous, southern UK) were investigated using a combined field, stable isotopic geochemistry, petrographic and crystallographic method to examine their formation mechanism. Calcite veins occur in all shale beds and are most abundant in the bituminous shales of the Chief Beef Beds. The calcite fibres in these veins exhibit either an antitaxial fibre growth with curvy stylolites as the median zone, or a predominantly syntaxial, upwards growth. The calcite veins range from –0.49 to 1.78‰ of δ13C values, and –6.53 to –0.03‰ of δ18O values, which are both similar to those of their host shales. Our petrographic observations demonstrate that subhorizontal and interconnecting microstylolite networks commonly occur within the calcite veins. Equant calcite grains in the median zones exhibit indenting, truncating and also interpenetrating grain contacts. It is interpreted that the fibrous calcite veins were sourced by neomorphic calcite from their host shales, with evidence from the δ13C signatures, pressure-solution features (stylolites, microstylolites and grain contact styles) and embedded fossil ghosts within the veins. The diagenetic fluids, from which calcite was precipitated, were a mixing of the original seawaters and 18O-depleted meteoric waters. Development of bedding-parallel calcite veins is considered to have been enhanced by pressure solution as a positive feedback mechanism, which was facilitated by the overburden pressure as the maximum principal stress. Calcite fibres, with a predominant subvertical c-axis orientation, exhibit a displacive growth in porous shales and a replacive growth at vein-limestone contacts. This study highlights the critical role of pressure solution in the formation of bedding-parallel calcite veins during burial and diagenesis of immature black shales.