Abundant microfossils have recently been discovered in the late Palaeoproterozoic Changzhougou Formation, Changcheng Group, Jixian, north China. The Changzhougou microbiota consists dominantly of sphaeromorph acritarchs and some osillatoriacean cynobacterial filaments. The micro-fossils were recovered from shales and are compressed on bedding surfaces. The sphaeromorph acritarchs, ranging from 8.4 to 237.8 μm in diameter, are morphologically simple. On the basis of their dimensions and morphological considerations, the sphaeromorph acritarchs are interpreted as probably representing the resistant, reproductive cysts of unicellular protists. This assemblage is evidently among the oldest known clastic-facies microbiotas in the geological record and provides evidence of protist eukaryotes being extant at 1848 Ma.

Recent (Quaternary) lava fields, such as those of Citlaltépetl (Pico de Orizaba) volcano in Mexico, are excellent places to obtain precise measurements of flow-field dimensions that can be used to estimate volume, eruption duration and effusion rates. The relationship between these parameters and the influence of some other interrelated features such as lava composition, superficial structures and lava type are important tools that can help to infer conditions when the lavas were active and thus improve understanding of how flow fields grow. The Holocene lavas of Citlaltépetl volcano are homogeneous in composition (dacites) and are generally blocky with well-developed levees. The eruption duration obtained for the Citlaltépetl lavas by a method proposed by C. Kilburn and R. Lopes presents a good correlation with the different lava types morphologically classified here. Results from that method compare favourably with the inferred effusion rates estimated by an empirical cooling method (Graetz). The lavas show different behaviour, mainly controlled by fluctuations in the effusion rate that promote changes from single- to multiple-flow style. The maximum distance achieved by a flow is directly proportional to the effusion rate in Citlaltépetl lavas, but it is always lower for multiple flows, independent of the volume of erupted lava. Observations of Citlaltépetl lavas can be used to understand how lava flow growth occurs on other volcanoes.

This paper expands the K–Ar dating and palynologically controlled stratigraphical data base reported in earlier papers to the north trending Selendi and Uşak-Güre basins located to the north of east–west trending Alaşehir graben in western Turkey. These north trending basins began to form during Early Miocene times and most of their basin fills accumulated before 14 Ma, except for the youngest Asartepe formation. Recent studies of both east–west grabens and north trending basins show that they started to develop simultaneously during Early Miocene times under the north–south extensional regime, and the classification of the structures as ‘replacement’ and ‘revolutionary’ has no meaning for the Alaşehir graben and the basins located to its north.

The lower part of the post-Variscan succession around Exeter, south Devon, England, comprises some 800 m of breccias, with subordinate sandstones and mudstones, which rest upon Devonian and Carboniferous rocks folded during the Variscan Orogeny and are overlain, disconformably, by the Aylesbeare Mudstone Group (Early Triassic?). These deposits comprise the most westerly of the early post-Variscan successions preserved onshore in northwest Europe and lie to the south of the Variscan Deformation Front; they are assigned to the Exeter Group (new term). Geochronological and palaeontological studies, in conjunction with detailed geological mapping, show that the constituent formations comprise a lower (Late Carboniferous(?)–Early Permian) sequence separated from an upper (Late Permian) sequence by an unconformity which represents an hiatus with a duration of at least 20 m.y. The lower sequence contains volcanic rocks dated at between 291 and 282 Ma (Early Permian) and pre-dates intrusion of the nearby Dartmoor Granite (280 Ma). In the overlying, palynologically-dated, Late Permian sequence, older breccias contain clasts of the Dartmoor Granite aureole rocks, and younger ones contain clasts of that granite. The lower sequence occurs mainly within the Crediton Trough, an east–west trending, partly fault-bounded, sedimentary basin that probably formed by extensional reactivation of a Variscan thrust. Breccias in this sequence formed largely on alluvial fans; the common occurrence of debris flows and a down-fan passage from gravity flows into fluvially deposited sediments is typical of deposition on semi-arid fans. The upper (Late Permian) sequence is more widespread but includes similar deposits overlain, at the top of the Exeter Group, by aeolian dune and interdune deposits. Correlation within the laterally variable facies associations which comprise these sequences has been achieved using a combination of sedimentary facies analysis, sedimentary geochemistry, and petrographical and geochemical clast typing. The stratigraphy revealed within the Exeter Group is broadly comparable with that recognized in the early post-Variscan Rotliegend successions elsewhere in Europe. This similarity may, however, be deceptive; the upper part of the Exeter Group may be coeval with the Zechstein, and apparently correlatable major unconformities in the group and the Rotliegend may reflect different events in the Variscan fold-belt and Variscan Foreland areas, respectively.

The Slieve League peninsula in southwest Donegal affords some of the best exposures of the Dalradian Appin/Argyll Group transition available in Ireland. As a result, a refined stratigraphical column is available, allowing resolution of small- (metric-) scale imbrication of parts of the sequence. Large-scale D2 thrust nappes dominate the structure of the region, and the rocks have undergone multiple folding and complex cleavage development. In the Glencolumbkille valley, an imbricate duplex has been mapped in detail. Original intrusive relationships of metadolerite sheets controlled the geometry of subsquent deformation. A major ramp cuts up through the established stratigraphy and is controlled by a pre-D2 metadolerite intrusion. Throughout the region, major and minor ramps are localized by the metadolerite sheets. Within the thrust sheets, analysis of quartz petrofabric and clast fabrics in hangingwall mylonites within the Boulder Bed document kinematics and strain localization within the thrust sheets. Axial ratios in the dolomitic clasts increase up to a maximum of 30 [ratio ] 1 adjacent to the ductile thrusts. However, granite clast axial ratios are less pronounced adjacent to some of the shears, suggesting that strain may have partitioned into the matrix at high strains.

The Dowery Hill Member of metamorphosed basalt, dolerite and siltstone is here recognized as the oldest exposed volcanic unit of the Lower Ordovician Ribband Group, with a minimum age of early Arenig. Peperites and resedimented hydroclastic breccia demonstrate a volcanic origin for the basalts. The igneous rocks are tholeiitic, with a trace element geochemistry indicative of a subduction-modified fertile mantle source, which we interpret as recording an early stage of volcanic arc evolution. The member is therefore the oldest known component of the volcanic arc generated by subduction of Iapetus oceanic lithosphere under southeastern Ireland. Subduction started earlier than predicted by current plate tectonic models, and these should be re-evaluated.

The extent of elemental mobility during lower greenschist to amphibolite facies metamorphism of a uniform turbidite suite (Greenland Group, New Zealand) has been evaluated using data for major elements and 19 trace elements. Simple comparison of average compositions at 2 wt % Al2O3 intervals in the data suites shows little contrast between lower greenschist protolith and upper greenschist and amphibolite facies equivalents, except for enrichment of CaO and Sr, and loss of Ba and Rb, particularly in the sandier end members. Division into psammitic and pelitic suites using TiO2/Al2O3 and Zr/Al2O3 ratios allows delineation of individual residual enrichment models on Ti-reference element plots, and both lithotypes can be used to assess potential elemental mobility. These plots show that a large number of elements (Ti, Al, Fe, Mg, Ce, Cr, Ga, La, Nb, Ni, Sc, Th, V, Zn and Zr) constitute immobile reference species, with abundances equal to their equivalent lithotype in the protolith, and little mass loss or residual enrichment. K and Rb also largely conform to the residual model, but in the amphibolite facies some exchange between pelite and psammite may occur. A number of elements show enrichment (Mn, Cu, Pb, U, Na, P) or depletion (Y) in a small number of samples, but the significance of these contrasts is questionable due to relatively large variation in the protolith. In contrast, Ca and Sr show progressive and marked enrichment with increasing grade, and Ba and As are clearly depleted in amphibolite facies psammites. In the amphibolite facies some Si may have been lost by psammites, and gained by the pelites, although there has been no mass change from the suite as a whole. A large part of the Ca and Sr enrichment in the amphibolite facies can be accounted for by metasomatic homogenization of calcareous concretions which occur in the lower grade protolith. The metamorphism of the Greenland Group is thus considered to be essentially isochemical.

The middle and upper members of the Gavilán Formation near Vélez-Rubio (Almería Province, southeast Spain) are interpreted as carbonate platform deposits. The studied outcrops form geologically part of the External Zones of the Betic Cordillera (South Iberian Palaeomargin). A genetic unit limited by intra-Sinemurian and intra-Upper-Carixian sedimentary breaks is defined. The evolution of the parasequence sets in the area, and the development of deeper sedimentation in its northern outcrops, suggest that this platform was isolated with regard to the South Iberian Margin. Three distinct parasequence sets are proposed: progradational parasequence set (only locally present), retrogradational parasequence set (middle member of the Gavilán Formation) and aggradational parasequence set (basically composed of the upper member of the Gavilán Formation). Sedimentary features (such as neptunian dykes, sharp lithological changes, thickness variations), the presence of palaeofaults and the subsidence history all lead to the conclusion of a significant regional tectonic influence in the genetic unit evolution. Normal extensional faulting has been proposed as a major control on sedimentation on this isolated platform. This regional factor has completely distorted the effect of the eustatic fluctuations for this period of time.

The Llanrwst Pb–Zn veinfield occupies fractures in an Ordovician volcano-sedimentary sequence, with three separate mineralizing events (M1, M2 and M3). The Llanfair Pb–Zn–Cu veinfield consists of sporadic mineralization in Silurian sediments. Fluid inclusion data from both veinfields indicate mineralization took place from CaCl2-bearing brines, up to 26 wt % NaCl equivalent, between 125 and 190 °C with cooler (< 100 °C), more dilute fluids associated with later thrusting at Llanrwst. Sulphur at both veinfields was derived during the main phases of sulphide precipitation from the host rocks, with paragenetically late sulphides and sulphates deriving sulphur from 34S-enriched surface waters. Carbon and oxygen isotopic data on vein carbonates shows that both deposits formed from waters that had undergone extensive water–rock interaction. Carbon was derived from at least two sources: marine carbonate dominated at Llanfair, whereas organic matter in the host rocks was more significant at Llanrwst. These data indicate that the veins formed from evolved brines which migrated along fault systems to the loci of deposition during a phase of extensional tectonics in late Devonian to Tournasian times.

The morphological diversity, considered as a biological signal, of a series of four Upper Callovian (Middle Jurassic) ammonite populations of Côte-d’Or (France) is quantified. These populations fall within two third-order sequences of a second-order transgression. A sampling method that adheres as closely as possible to the morphological characteristics of the populations is established. It is valuable in that it eliminates the subjectivity related to taxonomy to allow more objective comparisons between the biological signal (shell morphology) and the physical signal (eustasy).

A different approach to the naming of trace fossils is advocated. The primary ichnotaxobase should be the form of the burrow actually occupied, and the secondary ichnotaxobase should be the morphology of the structure that reflects the manner in which this burrow has been displaced and/or extended. Only by attempting to name trace fossils in this way will it be possible to eliminate features due to sedimentological factors that took place on termination of the animal’s activities, including passive infill and diagenesis. To discriminate between different preservational states the citation should include both the taxonomic and preservational aspects.