Despite its global impact on ecosystems, the Triassic/Jurassic boundary event had only a modest effect on the carbonate depositional systems of the Southern Alps, whereas a fundamental reorganization of the same palaeogeographic area took place during the Sinemurian Age. This paper investigates whether or not the well-documented demise of Sinemurian carbonate platforms in the Tethyan region was a response to a global event by examination of carbon-isotope anomalies in successions of different facies that record this interval of time. A chemostratigraphic transect from Lake Garda up to the eastern Italian border is illustrated by four stratigraphic sections; high-resolution (20 cm over key intervals) chemostratigraphic sampling allowed detection of a major negative δ13C anomaly of ~ 1.5‰, preceded by a positive excursion, both in shallow- and deep-water successions, over the stratigraphical range of the ammonite genus Arnioceras. A comparison with sections from the UK suggests that the positive excursion belongs to the turneri Zone and the succeeding negative excursion falls within the obtusum Zone. In the deep-water Belluno Basin, the negative anomaly occurs in a biogenic chert-rich unit recording the onset of mesotrophic conditions in the basin. In the platform-carbonate successions, this major negative carbon-isotope excursion is developed within a calcarenitic unit corresponding to the lowest occurrence of the foraminifer Paleomayncina termieri. This evidence for deepening and transgression across the carbonate platform suggests pre-conditioning for drowning. Hence, rather than tectonic subsidence alone, environmental factors may have aided the demise of Tethyan carbonate platforms during the Early Jurassic Sinemurian Age.

Nitrogen is an essential element for biological activity, and nitrogen isotopic compositions of geological samples record information about both marine biological processes and environmental evolution. However, only a few studies of N isotopes in the early Cambrian have been published. In this study, we analysed nitrogen isotopic compositions, as well as trace elements and sulphur isotopic compositions of cherts, black shales, carbonaceous shales and argillaceous carbonates from the Daotuo drill core in Songtao County, NE Guizhou Province, China, to reconstruct the marine redox environment of both deep and surface seawater in the study area of the Yangtze shelf margin in the early Cambrian. The Mo–U covariation pattern of the studied samples indicates that the Yangtze shelf margin area was weakly restricted and connected to the open ocean through shallow water flows. Mo and U concentrations, δ15Nbulk and δ34Spy values of the studied samples from the Yangtze shelf margin area suggest ferruginous but not sulphidic seawater and low marine sulphate concentration (relatively deep chemocline) in the Cambrian Fortunian and early Stage 2; sulphidic conditions (shallow chemocline and anoxic photic zone) in the upper Cambrian Stage 2 and lower Stage 3; and the depression of sulphidic seawater in the middle and upper Cambrian Stage 3. Furthermore, the decreasing δ15N values indicate shrinking of the marine nitrate reservoir during the middle and upper Stage 3, which reflects a falling oxygenation level in this period. The environmental evolution was probably controlled by the changing biological activity through its feedback on the local marine environment.

The small, intramontane San Giorgio Basin in southwestern Sardinia has yielded plant macrofossils dominated by sphenophytes, but with subsidiary pteridosperms, ferns, (?)noeggerathians and cordaitanthaleans. They belong to the upper part of the Crenulopteris acadica Zone or possibly the Odontopteris cantabrica Zone, indicating a late Asturian or Cantabrian (≡ late Moscovian) age. They therefore correlate with the post-Leonian deposits in northern Spain, the Nýřany Member in Western and Central Bohemia, and the Llantwit Beds in South Wales. The presence of post-tectonic deposits of this age is further evidence of the widespread influence of the Leonian Phase of tectonic activity in middle Asturian times, whose effect can be observed across Europe. The San Giorgio Basin is therefore a late Variscan rather than post-Variscan basin.

J. Golonka, M. Krobicki, A. Waśkowska, M. Cieszkowski & A. Ślączka reply: We welcome the comments by our Slovakian colleagues and their critique of our results, particularly as we have discussed and published papers together several times about our ideas, sometimes, more or less, disputable (Aubrecht et al.2003, 2006; Krobicki et al.2003; Krobicki, Aubrecht & Golonka, 2003; Golonka et al.2006; Pieńkowski et al.2008). We are pleased to see such warm reaction to our work/paper, which is focused on one of the rudimentary questions in the Pieniny Klippen Belt (PKB) area. How many/what kind of olistoliths/olistostromes occur within the inner structure of the PKB, and when and why did they originate mostly during the Palaeogene part of the Mesozoic–Cenozoic history of this region? We expected this discussion earlier. The content of our paper was presented at the 6th Meeting of the Central European Tectonic Studies Group (CETeG) in Upohlav, Pieniny Klippen Belt, Slovakia (Cieszkowski et al.2008), and later, at the XIX Congress of the Carpathian–Balkan Geological Association in Thessaloniki, Greece (Cieszkowski et al.2010; Golonka et al.2010). Some ideas were also briefly mentioned in the paper by Cieszkowski et al. (2009) in a journal issue edited by D. Plašienka. We assume that the comments are based on recent investigation, because the authors list the grants received to conduct the research. Therefore, the submitted comments sometimes present a point of view different from that published previously by some of the authors of the comments (RA, JM) (see Aubrecht et al.2003; Krobicki, Aubrecht & Golonka, 2003; Wierzbowski et al.2006; Pieńkowski et al.2008). The statement, ‘Certainly there are many still unresolved problems in the geology of the PKB, and it ought to be said that the co-authors of this discussion also do not fully agree with all interpretations formulated and illustrated by the first author’ perhaps explains this controversy. Of course, we agree that ‘there are many still unresolved problems in the geology of the PKB’. We also agree with the statement ‘olistostromes and olistoliths are quite frequent, but not omnipresent’. We depicted the distribution of the olistoliths and their relationship to the non-olistolith tectonic units of the PKB in Golonka et al. (2015, figs 3, 8).

The tectonized and metamorphosed mudrocks within the Variscan accretionary prism of the Kaczawa Mountains in SW Poland comprise sedimentary mélanges together with more coherent stratigraphic units; some represent large olistoliths deposited in a submarine trench. We infer a trend of progressive near-surface stratal disruption in mud-dominated deposits due to dewatering that forms a continuum with subduction-related tectonic structures imposed on unconsolidated sediment during deeper burial. The assemblage of characters suggests that an accretionary prism environment can influence, and leave characteristic traces of, the total burial history of a trench succession.

The early Cambrian Period was a key interval in Earth history with regard to changes in both ocean chemistry and animal evolution. Although increasing ocean ventilation has been widely assumed to have played a key role in the rapid appearance, diversification and spatial colonization of early animals, this relationship is in fact not firmly established. Here, we report a high-resolution Fe-C-S-Al-Ti geochemical study of the lower Cambrian Wangjiaping section from an outer-shelf setting of the Yangtze Sea of South China. Iron speciation data document a redox transition from dominantly euxinic to ferruginous conditions during Cambrian Age 3 (c. 521–514 Ma). Interpretation of coexisting pyrite sulphur isotope (δ34Spy) records from Wangjiaping reveals relatively high marine sulphate availability at Wangjiaping. Furthermore, Wangjiaping section shows lower δ34Spy (‒2.1±5.3‰) and lower TOC (2.4±1.1%) values but higher positive correlation (R2 = 0.66, p < 0.01) between TOC and Fepy/FeHR relative to deeper sections reported previously, suggesting that euxinia developed at Wangjiaping in response to increasing marine productivity and organic matter-sinking fluxes. Our reconstructed redox conditions and fossils at Wangjiaping in comparison with previously well-studied strata in the inner-shelf Xiaotan and Shatan sections suggest that planktonic and benthic planktonic trilobites with bioturbation appeared in the oxic water columns, whereas only planktonic trilobites without bioturbation occurred within the anoxic (even euxinic) water columns during Cambrian Age 3. This finding indicates that spatial heterogeneity of redox conditions in the shelves had an important effect on early animal distribution in the Yangtze Block.

We integrate previous work on the Hegenshan–Heihe suture with our interpretation of geomagnetic anomaly and seismic reflection data to investigate the role of the Hegenshan–Heihe suture in the evolution of late Mesozoic extensional structures in the Wunite depression of the Erlian Basin. Sags in the Wunite depression present as NE50° trending in the western sector, N0°–NE30° trending in the central sector and NE45° trending in the eastern sector. Our results highlight the importance of the pre-existing Hegenshan–Heihe suture in the evolution of the late Mesozoic rift system and reveal the following details. (1) The NE50° extent sags in the western sector are controlled by the c. NE50°-trending suture. Moreover, the extensional deformation of the reactivated suture during Early Cretaceous time resulted in a further vertical and horizontal extension of major border faults. (2) The N0°–NE30° extent sags in the central sector are influenced by the c. NE75°-trending suture. The sinistral strike-slip component of the reactivated suture during Early Cretaceous time resulted in a strike rotation of major border faults from NEE-trending (following the suture) to NNE-trending. (3) Because of strike-slip deformation, which resulted from the deformation of the reactivated suture accrued in major border faults, light dip-slip deformation led to less vertical offset. (4) The NE45°-trending sags in the eastern sector are controlled by the c. NE45°-trending suture. Moreover, the extensional deformation of the reactivated suture during Early Cretaceous time facilitated a further vertical and horizontal prolongation of major border faults.

The Fulu iron formation (IF) is an iron-rich unit in the Neoproterozoic glacial successions, South China. The major element data suggest that the iron sources of the Fulu IF are derived from binary mixing from hydrothermal and detrital loads. The Fulu IF is characterized by slightly positive Eu anomalies similar to other Neoproterozoic IFs, indicating that a high-temperature hydrothermal input may contribute little to Neoproterozoic IFs. A shift from non-existent to slightly negative Ce anomalies of the Fulu IF indicates that the IF precipitated across an iron chemocline separating a weakly oxic surface ocean from an oxygen-depleted deep ocean.

The Ediacaran Doushantuo Formation at Weng'an, South China hosts well-preserved phosphatized microfossils known as the Weng'an biota. A laser ablation ICP-MS analysis of rare earth element (REE) characteristics of the fossil-bearing black phosphorite unit of the Doushantuo Formation at Weng'an was conducted, with the aim of unravelling the depositional conditions and diagenetic processes during formation of the phosphorites. Spherical phosphatized microfossils and phosphatic clasts were analysed, and the REE data display middle REE (MREE) -enriched shale-normalized REE patterns. The spherical phosphatized microfossils show an increase in total REE contents (∑REE) from core to rim. Negative correlations between ∑REE and the extent of MREE enrichment over the other REE (indicated by LaN/SmN, YbN/SmN) are observed for analysed spots within individual phosphatic grains, which may be due to complex diagenetic history of the phosphatic grains, with fluctuations in REE sources and chemical parameters in a high-energy shallow-water environment being additional factors. The LaN/YbN and LaN/SmN characteristics of the phosphatic grains suggest they were mostly influenced by early diagenetic alteration rather than late extensive recrystallization. The negative Ce anomalies in the samples suggest they formed under oxic-bottom-water conditions. Positive Eu anomalies are present in all samples, and are likely to reflect involvement of hydrothermal fluids rather than changes in redox conditions of porewater. Overall this study has major implications for phosphorites as important archives for the study of geochemical proxies, the Ediacaran period and also evolutionary changes.