To further our understanding of the evolution, selectivity and ecological composition of marine communities following the latest Permian mass extinction, new collections from underrepresented regions in the immediate extinction aftermath are required. Here, we provide new systematic data and the first palaeobiological account of the benthic invertebrate community from the Great Bank of Guizhou, South China. We systematically describe three brachiopod species, 26 bivalve species, 11 gastropod species, 1 microconchid and 1 crinoid species. The descriptions include 5 new species; 2 bivalve species (Hoernesia? danisae, Atomodesma? hautmanni) and 3 gastropod species (Donaldina erwini, Cossmannina alfischeri and Vernelia samae). This is the most species-rich benthic community known so far from the extinction aftermath, which is typically characterized by a high proportion of Permian holdover genera and cosmopolitan taxa. Taxonomically, this community is different from coeval faunas with dissimilarity values >60%. Ecologically, however, this fauna is similar to faunas from the Dolomites (Italy) and East Greenland. This new data, therefore, suggests that the lower Griesbachian invertebrate faunas were taxonomically heterogeneous, whereas ecologically they were relatively homogenous. The marine community on the Great Bank of Guizhou records genera that survived the mass extinction event with some, but not all, recording a size reduction, that is, the Lilliput effect. The absence of large body fossils and the preferential survival of small species suggest that the mass extinction event was size-selective.

Continental drainage systems archive complex records of rock uplift, source area relief, precipitation, glaciation, and carbon cyclicity driven largely by tectonics and climate. Significant progress has been made in linking such external environmental forcings to the geomorphic expression of landscapes and the stratigraphic record of depositional basins in coastal and offshore areas. However, there are large uncertainties in the degree to which sediment dispersal processes can modify signals between the erosional sources and the depositional sinks. We investigate a Holocene sediment transfer zone with contrasting fluvial and eolian sediment transport mechanisms to understand how river and wind processes impact the propagation of environmental signals in continentalscale drainage systems. To quantify these processes, we employ sediment fingerprinting methods for unconsolidated sand samples (detrital zircon U-Pb geochronology), incorporate sediment mixing models, and correlate the findings with the regional geologic and geomorphic framework. Three contrasting source regions deliver sediment to the Andean foreland: volcanic rocks of the Frontal Cordillera, sedimentary rocks of the Precordillera, and metamorphic basement of the Sierras Pampeanas. Although all samples of Holocene eolian dunes accurately record sediment input from three fluvial source regions, spatial variations in U-Pb results are consistent with north-directed paleowinds, whereby river sediments from Frontal Cordillera sources are transported northward and progressively mixed with river sediments from Precordillera and Sierras Pampeanas sources. In contrast, samples of modern rivers show progressive southward (downstream) mixing along a large axial fluvial system. Sediment mixing induced by eolian transport and reworking of various sources is likely a critical, climate-modulated process in the propagation of environmental signals, potentially involving the aliasing of tectonic signals, local storage and recycling of synorogenic river sediment, and cyclical patterns of sediment starvation and delivery to distal zones of accumulation.

The role of ocean acidification in the end-Permian mass extinction is highly controversial with conflicting hypotheses relating to its timing and extent. Observations and experiments on living molluscs demonstrate that those inhabiting acidic settings exhibit characteristic morphological deformities and disordered shell ultrastructures. These deformities should be recognisable in the fossil record, and provide a robust palaeo-proxy for severe ocean acidification. Here, we use fossils of originally aragonitic invertebrates to test whether ocean acidification occurred during the Permian–Triassic transition. Our results show that we can reject a hypothesised worldwide basal Triassic ocean acidification event owing to the absence of deformities and repair marks on bivalves and gastropods from the Triassic Hindeodus parvus Conodont Zone. We could not, however, utilise this proxy to test the role of a hypothesised acidification event just prior to and/or during the mass extinction event. If ocean acidification did develop during the mass extinction event, then it most likely only occurred in the latest Permian, and was not severe enough to impact calcification.

No abstract

No abstract