The congruence between rock quantity and biodiversity through the Phanerozoic has long been acknowledged. Rock record bias and common cause are the most discussed hypotheses: the former emphasizes that the changes in diversity through time fully reflect rock availability; the latter posits that the correlation between rock and fossil records is driven by a common cause, such as sea-level changes. Here, we use the Geobiodiversity Database (GBDB), a large compilation of the rock and fossil records, to test the rock bias hypothesis. In contrast to other databases on fossil occurrences, the section-based GBDB also records unfossiliferous units. Our multiple regression analysis shows that 85% of the variation in sampled diversity can be attributed to the rock record, meaning that major peaks and drops in observed diversity are mainly due to the rock record. Our results support a strong covariation between the number of unfossiliferous units and sampled diversity, indicating a genuine rock bias that arose from sampling effort that is independent of fossil content. This provides a compelling argument that the rock record bias is more prominent than common cause in explaining large-scale variations in sampled diversity. Our study suggests that (1) no single proxy can fully represent rock record bias in predicting biodiversity, (2) rock bias strongly governs sampled diversity in both marine and terrestrial communities, and (3) unfossiliferous strata contain critical information in predicting diversity of marine and terrestrial animals.

The traces left by earthquakes in the unlithified sediments, recorded as soft-sediment deformation structures (SSDS), are well reconstructed as palaeo-seismic signals, while the origin of SSDS, seismic vs. Aseismic, is challenging. The present study discusses the origin of SSDS and its implications on palaeoceanography and sediment architecture. In the Middle Jurassic succession of Spiti Himalayan region in India, the topmost part of the Ferruginous Oolitic Formation (FOF) consists of four layers of SSDS and is underlain by the lower member of the Spiti Formation (SF). The sedimentary facies analysis documents the palaeogeographic shift from the middle shelf (carbonate-shale repository: FOF) to the outer shelf (black shale: lower member of SF). The SSDS layers, exhibiting load casts, ball and pillow structures, indicate gravitational instability, while syn-sedimentary faults and insitu breccia are the results of brittle deformation. The dominance of storms in depositional sites often argues for a possible triggering agent for SSDS. Therefore, it was necessary to distinguish between seismic vs. aseismic triggering agents. The lateral continuity, vertical repetition, confinement of SSDS at the top part of FOF and sharp change of facies assemblage indicate seismicity-induced syn-sediment deformation, i.e. seismite. The transition from middle shelf to outer shelf at the onset of seismite indicates that seismic impact possibly caused the rapid subsidence, resulting in the palaeogeographic shift. The rapid transgression is recorded as carbonate-shale repository to anoxic black shale. This study highlights the importance of sedimentological analysis to distinguish the seismite and its implications on palaeogeographic evolution and sedimentary architecture.

Various magmatisms during the subduction-collision process are crucial to reveal the long-term tectonic evolution of the eastern Central Asian Orogenic Belt. In this paper, we present major and trace elements of whole-rock, zircon U-Pb dating and Hf isotope of the Shanmen pluton. Results imply that the Shanmen pluton consists of quartz diorite and mylonitic granite, with zircon U-Pb ages of 263.7–259.6 Ma. The studied quartz diorite contains high Sr/Y (51.19–90.87) and (La/Yb)N (7.82–13.62) ratios, and belongs to adakitic rocks. Coupled with the positive εHf(t) values of +5.71 to +12.8 with no obvious Eu anomaly, we propose that quartz diorite is the product of the interaction between different degrees of slab melt and the overlying mantle wedge. In contrast, the mylonitic granite has lower MgO (0.28 wt% – 0.47 wt%) contents and positive εHf(t) values of +7.79 to +10.15, indicating an affinity with I-type granite originated by partial melting of the intermediate-basic lower crust. The geochemical characteristics and lithological assemblages, along with the Permian magmatic rocks in the Changchun-Kaiyuan area displaying arc rocks affinity, propose their formation is related to the southward subduction of the Paleo-Asian Ocean (PAO). Based on this study and previous evidence, we lean towards adopting a middle-late Permian slab break-off model, wherein the PAO did not close until the late Permian.

Mafic dykes are typically emplaced through primary hydraulic fracturing of undeformed crust or may make use of pre-existing crustal inhomogeneities, representing the plumbing systems of a large igneous province. The Eastern Dharwar Craton has dense exposures of several generations of Paleoproterozoic mafic dyke swarms ranging from ca. 2.37 Ga to ca. 1.79 Ga. Herein, using anisotropy of magnetic susceptibility fabric data of mafic dykes and associated host granites, the emplacement systematics of the NW- to W-trending ca. 2.21 Ga Anantapur–Kunigal dyke swarm, displaying a radiating geometry, have been studied to understand magma flow dynamics. A low-angle relationship between the silicate and opaque fabrics and good correlation with magnetic lineation, identified via petrographic studies and shape preferred orientation analyses of multiple oriented thin sections, suggest a primary flow-related magnetic anisotropy for the studied dyke samples. The classic subparallel relationship between the trend of the dyke planes and magnetic fabric of the associated host granites suggests that the radiating geometry of the ca. 2.21 Ga dyke swarm was supported by a favourable pre-existing structural grain of the country rock. We interpret the magma for the studied dyke swarm was fed laterally from a distant plume. It was emplaced as laterally propagating primary dyke fractures as well as injected into the pre-existing subparallel crustal inhomogeneities. Corroborating all these inferences, a detailed emplacement model for ca. 2.21 Ga Anantapur–Kunigal dyke swarm is also proposed.

The study presents detailed petrographical, geophysical, structural and geochemical data of the internal nappes zone to establish the deformational history, origin and tectonic setting and constrain the crustal growth and evolution of the active margin of the Dahomeyide belt. Two main lithological units, (i) deformed meta-granitoids (migmatites and gneisses) and (ii) undeformed granitoids, dominate the internal nappes zone. The granitoids are generally I-type, metaluminous to weakly peraluminous, low-K tholeiite to high-K calc-alkaline and of tonalite, granodiorite and granite affinity. The overall trace element patterns of the studied granitoids characterized by the enriched LILE and depleted HFS, with negative peaks of Nb-Ta, Sr, P and Ti, are indications of arc-related magmatism. Structural analysis reveals four deformation phases (D1-D4). D1 represents Northwest-Southeast (NW-SE) Pan African shortening associated with a continent-continent collision, resulting in westward nappe stacking. Progressive NW-SE shortening resulted in D2 and D3 top-to-the-NW dextral and sinistral thrusting events during the Pan-African orogeny. D4 is an extensional event likely associated with the orogenic collapse phase. The gneisses and migmatites, with dominant axial planar foliations, point to their formation in a collisional setting or influence by the Pan-African collisional processes. Continental-arc signatures in these rocks imply continental subduction during their protolith formation. The intrusive granitoid and pegmatite are undeformed, meaning late- to post-orogenic emplacement. These findings suggest that the internal nappes zone archived the subduction-collision and post-collisional phase of the Pan-African orogeny and recorded large-scale migmatization and granitoid emplacement due to partial melting of thickened lower crust between Mid-Cryogenian and late Ediacaran.

The Ediacaran–Cambrian (E-C) transition (∼542–517 Ma) witnessed the rapid evolution of Cambrian animals, which was accompanied by carbon cycling anomalies and a significant increase in the concentration of oxygen in Earth’s atmosphere. The mechanisms stimulating the evolution of complex eukaryotes, however, remain problematic, especially concerning the link between biological evolution and contemporaneous changes in the oceanic environment. In this study, integrated δ13Ccarb–δ13Corg–δ15N compositions were analysed from the YD-4 core samples to understand redox fluctuations and nitrogen cycling of the middle Yangtze Block across the E-C transition. Two negative δ13Ccarb excursions (N1 and N2) and a positive δ13Ccarb excursion (P1) are identified from the studied samples and are supposedly of primary origin. Constrained by of the U-Pb age, biolithology and pattern of isotopic variation, N1, P1 and N2 are comparable to the Basal Cambrian Carbon Isotope Excursion (BACE), Zhujiaqing Carbon Isotope Excursion (ZHUCE) and Shiyantou Carbon Isotope Excursion (SHICE). We interpreted the decreased δ15N values in this study as resulting from intensified atmospheric nitrogen fixation driven by enhanced denitrification associated with expanded marine anoxia, as well as partial ammonium assimilation, while increased δ15N values suggest weakened denitrification associated with an amplified oxic water mass. The temporal coincidence of N1 and N2, with two episodes of negative δ15N excursions, and of P1, with a positive δ15N excursion, suggests that variable oceanic redox conditions and nitrogen bioavailability may have influenced the evolution of the Cambrian eukaryote-dominated community.

The ∼407-myr-old Rhynie chert of Scotland contains exquisite body fossils of land plants, animals and microorganisms, which provide our earliest reasonably complete snapshot of a Phanerozoic terrestrial ecosystem. These fossils have been instrumental to our understanding of the ‘greening of the land’, a major transition in the history of the Earth–life system. Among the primary producers preserved in the chert are cyanobacteria, of which only a fraction have been formally described. Here, we report the occurrence of the colony-forming cyanobacterium Eoentophysalis in the Rhynie chert. To our knowledge, this represents the first bona fide record of Entophysalidaceae from any post-Cambrian fossil assemblage or any non-marine fossil assemblage of any age. The Rhynie Eoentophysalis appears remarkably similar in appearance both to modern marine and freshwater Entophysalis ssp. and to Eoentophysalis belcherensis, a shallow-marine fossil from the ∼2 Ga Belcher Group of Canada that is perhaps the oldest convincing cyanobacterium on record. Darkened cell envelopes in the Rhynie Eoentophysalis correspond well with both E. belcherensis and modern Entophysalis, whose cell envelopes often contain the photoprotective brown pigment scytonemin. The occurrence of Eoentophysalis in the Rhynie chert supports previous claims that the fossilisable traits of entophysalid cyanobacteria are evolutionarily static through geological time. These organisms may be such effective generalists that major changes in their environment – in this case, the transition to a fully non-marine habitat – have not imposed significant selection pressure on these traits.