The lithostratigraphic characteristics of the iconic Blue Lias Formation of southern Britain are influenced by sedimentation rates and stratigraphic gaps. Evidence for regular sedimentary cycles is reassessed using logs of magnetic susceptibility from four sites as an inverse proxy for carbonate content. Standard spectral analysis, including allowing for false discovery rates, demonstrates several scales of regular cyclicity in depth. Bayesian probability spectra provide independent confirmation of at least one scale of regular cyclicity at all sites. The frequency ratios between the different scales of cyclicity are consistent with astronomical forcing of climate at the periods of the short eccentricity, obliquity and precession cycles. Using local tuned time scales, 62 ammonite biohorizons have minimum durations of 0.7 to 276 ka, with 94% of them <41 ka. The duration of the Hettangian Stage is ≥2.9 Ma according to data from the West Somerset and Devon/Dorset coasts individually, increasing to ≥3.7 Ma when combined with data from Glamorgan and Warwickshire. A composite time scale, constructed using the tuned time scales plus correlated biohorizon limits treated as time lines, allows for the integration of local stratigraphic gaps. This approach yields an improved duration for the Hettangian Stage of ≥4.1 Ma, a figure that is about twice that suggested in recent time scales.

Granitoid stocks crop out in the Ghahan and Sarbadan areas near Tafresh city, which is situated in the central part of the Urumieh–Dokhtar Magmatic Arc, Iran. The stocks, consisting of porphyritic and sub-granular diorite and granular granodiorite, intruded into Eocene volcano-sedimentary units. Normalized multi-element diagrams indicate that the analysed rocks are enriched in large-ion lithophile elements and depleted in high field strength elements. These geochemical features are typical of subduction-related calc-alkaline arc magmas. The stocks belong to the ferromagnetic and I-type granitoid series. Anisotropy of magnetic susceptibility provides information about the internal fabric of the granitoids. Susceptibility values range from 5.6 × 10−3 to more than 71.6 × 10−3, averaging 27.9 × 10−3 SI. Relatively low anisotropy values (P%) rarely exceed 10 %. Shape parameters (T) vary between −0.48 and +0.74, averaging + 0.2. Each stock is interpreted to contain a distinct feeder zone in which magnetic lineation plunges steeply (> 60°), suggesting that the magma ascended mainly in a NW–SE conduit and, to a lesser extent, in an E–W direction. Integration of magnetic fabric data, field observations and tectonic setting indicates that the shear zone that was developed between the Indes and Talkhab faults had created an opening into which the Ghahan and Sarbadan stocks were emplaced by way of creating a suitable tensional space for the ascent of magma.

The Hudesheng mafic–ultramafic intrusions are located in the Oulongbuluke Block, north of the Qaidam Block in Qinghai Province, NW China. We carried out a detailed study of the intrusions, including field observations, petrology, zircon U–Pb geochronology, Lu–Hf isotopes, bulk-rock major- and trace-element geochemistry, and mineral compositions, to provide a better understanding of their properties and the regional tectonic evolution. Zircon U–Pb dating on gabbro and pyroxenite samples yielded ages of 465 and 455 Ma, respectively. Geochemical data, in conjunction with the field observations and petrological features, suggest that the complex is Alaskan-type and the magma was derived from a depleted mantle source that was hydrous picritic basalt in composition and influenced by crustal contamination and slab-derived fluid metasomatism. Based on all the chronological, petrological, mineralogical and geochemical and regional geological data, we conclude that the palaeo-ocean closed diachronously from west to east between the Qaidam and Oulongbuluke blocks, and that the ocean in the east of the North Qaidam region closed after ∼455 Ma.

Arcuate fold-and-thrust belts have been extensively studied in the literature. Less attention, however, has been paid to the characteristics of local-scale arcuate structures, meaning 5–10 km long fold or thrust traces that display map-view curvature. Nevertheless, detailed investigation of small arcuate structures hosted in major arcs can contribute to understanding the pervasiveness of deformation mechanisms. We performed a combined geological and palaeomagnetic study on 21 sites from a c. 60 km2 area in the Northern Apennines in order to analyse minor arcs at a kilometric scale. As evidenced by the geological and structural analysis performed on the 21 sites, the fold axial trend changes from N–S to NW–SE in the study area. The comparison with palaeomagnetic results shows the lack of correlation between vertical axis rotations and fold axial trends. As a consequence, the minor arcuate shapes of thrusts and related folds are interpreted as mostly primary features inherited from the geometry of the palaeomargin, represented by pre-orogenic faults, according to a context of inversion tectonics.

The Bengbu area in the southeastern North China Craton (NCC) consists predominantly of Archean–Palaeoproterozoic (gneissic) granitoids with minor supracrustal rocks (the Fengyang and Wuhe groups). This study presents new zircon laser ablation – inductively coupled plasma – mass spectrometry U–Pb and Lu–Hf isotopic data and trace-element contents for these granitoids, which improve understanding the Archean–Palaeoproterozoic crustal evolution of the NCC. Magmatic zircon U–Pb data reveal that zircons in the (gneissic) granitoids were generated by multi-stage events at 2.93, 2.73, 2.53–2.52 and 2.18–2.13 Ga. Metamorphic zircon U–Pb data obtained from these rocks show two distinct metamorphic ages of 2.49–2.52 and 1.84 Ga, suggesting that the Bengbu area experienced a regional metamorphic event at the end of the Neoarchean Era and encountered reworking by a tectonothermal event associated with the formation of the Palaeoproterozoic Jiao-Liao-Ji Belt. Trace-element compositions of magmatic zircons reveal the highest Ti concentrations (8.08±3.38 ppm) and growth temperatures (718±44 °C) for the zircons aged 2.13–2.17 Ga and an increase in zircon U/Yb ratios from 2.93 Ga (0.34±0.12) through 2.73 Ga (0.96±0.42) to 2.53 Ga (1.05±0.46), but an evident decrease at 2.17–2.13 Ga (0.61±0.40 ppm). Similar Palaeoarchean xenocrystic and detrital zircons with negative ɛHf(t) values, late Mesoarchean magmatic zircons with juvenile Hf isotopic features, early Neoarchean magmatic zircons with model ages of 2.9–3.0 Ga, and two regional metamorphic events at 2.52–2.48 and 1.88–1.80 Ga in the Bengbu and Jiaobei areas indicate a Palaeoarchean–Mesoarchean micro-continent entrained in the Jiao-Liao-Ji Belt at the southeastern NCC.

We present updated U–Pb ages and Hf isotopic compositions of detrital zircons and whole-rock geochemical data to investigate the provenance and tectonic setting of late Neoproterozoic and early Cambrian sandstones from the Cathaysia Block, in order to offer new constraints on its tectonic evolution and its palaeo-position within the supercontinent. The source rocks for the studied sandstones were dominated by felsic–intermediate materials with moderate weathering history. U–Pb dating results show major populations at c. 2500 Ma, 1000–900 Ma and 870–716 Ma with subordinate peaks at 655–532 Ma, consistent with the global Neoarchean continental crust growth, assembly and break-up of Rodinia, and Pan-African Event associated with the formation of Gondwana. Zircon U–Pb ages and Hf isotopic data suggest that most derived from exotic terranes once connected to the Cathaysia Block. Using whole-rock geochemical analysis, it was determined that the studied sedimentary rocks were deposited in a passive continental margin and the Cathaysia and Yangtze blocks were part of the same continent; no Cambrian ocean existed between them. Compiling a detrital zircon dataset from Qiangtang, northern India, the Lhasa Terrane and Western Australia, the Cathaysia Block seems to be more similar to the Qiangtang and western part of the northern India margin, instead of having a direct connection with the Lhasa Terrane and Western Australia in the Gondwana reconstruction during the late Neoproterozoic and Cambrian eons.

One of the world’s most notable intraplate volcanic regions lies on the eastern Australian plate and includes two age-progressive trails offshore (Tasmantid and Lord Howe seamount chains) and the world’s longest continental hotspot trail (Cosgrove Track). While most studies agree that these chains formed by the rapid northward motion of the Australian plate over a slowly moving mantle source, the volcanic output along these trails, their plate–mantle interactions and the source of the magmatism remain unconstrained. A geophysical mapping and dredging campaign on the RV Southern Surveyor (ss2012_v06) confirmed the prolongation of the Lord Howe Seamount Chain to the South Rennell Trough, ∼200 km further north than previously sampled. Radiometric dating of these new samples at 27–28 Ma, together with previously published results from the southern part of the chain, indicate straightforward northward motion of the Australian plate over a quasi-stationary hotspot as predicted by Indo-Atlantic and Pacific hotspot models. A peak in Lord Howe Seamount Chain magmatism in late Oligocene time, also seen in the Tasmantid and Cosgrove trails, matches a 27–23 Ma slowdown of Australian plate motion. The average magma flux of the Lord Howe hotspot is estimated at 0.4 m3 s−1, similar to rates of crustal production at the South Rennell Trough prior to cessation of spreading in middle Oligocene time, supporting a potential genetic relationship to this spreading system. In addition, plate tectonic modelling suggests that the seamounts and plateaus in the Coral Sea may host the earliest evidence of plume activity in the area.

A pycnodont premaxilla bearing a large incisiform tooth with an unusual crown morphology is described from the Palaeocene (Thanetian) phosphate deposits of Morocco. This peculiar tooth shows a broad, fan-shaped multicuspid crown with nine cusps, well adapted for benthic macroalgal scraping. This morph, assigned to a new species of Pycnodus (P. multicuspidatus sp. nov.), emphasizes the phenotypic plasticity of the group and documents an additional trophic specialization among Palaeogene pycnodontiform fishes. In the post-K/Pg boundary marine ecosystem of the Ouled Abdoun Basin, P. multicuspidatus sp. nov. may have opportunistically replaced Maastrichtian fish taxa with a similar front dentition and feeding behaviour, such as the putative specialized pycnodontiforms Stephanodus and Hadrodus.

The transition between the seemingly disparate Ediacaran and Cambrian faunas is both enigmatic and body-fossil poor. The Chapel Island Formation on the Burin Peninsula, Newfoundland, Canada, contains a rich diversity of ichnofossils, providing new insight into the nature of the Ediacaran–Cambrian transition and early Fortunian ecosystems. Five ichnoguilds are recognized within the Treptichnus pedum zone. Ichnologic data are analysed from an ecospace perspective, revealing a more protracted transition between Ediacaran and Cambrian ecosystems. Our analysis documents the appearance of limbs, vertical burrows and uncontroversial equilibrium structures, as well as the retention of ‘other’ feeding styles, such as microbial grazing and chemosynthesis.

Jurassic siliceous hot-spring (sinter) deposits from Argentine Patagonia were evaluated to determine the distribution and preservation quality of their entombed microbial fabrics. Detailed study showed that the Claudia palaeo-geothermal field hosts the best-preserved sinter apron in the Deseado Massif geological province, where we also found hot-spring silica–biotic interactions extending into hydrothermally influenced fluvial and lacustrine settings. Carbonaceous material was identified by petrography and Raman spectroscopy mapping; it is inter-laminated with silica across proximal vent to distal marsh facies. The ubiquitous presence of microbial biosignatures has application to studies of hydrothermal settings of early life on Earth and potentially Mars.