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Retentiveness of rare earth elements in garnet with implications for garnet Lu‐Hf chronology
No full textIncorporation of rare earth elements (REE) in garnet enables garnet chronology (Sm-Nd, Lu-Hf), and imparts a garnet-stable signature on cogenetic phases, which allows petrochronology and general petrogenetic tracing of garnet stability in minerals and melts. Constraints on the uptake and redistribution mechanisms, as well as on the diffusive behaviour of REE in garnet are required for allowing accurate interpretation of REE signatures and ages. Garnet REE profiles are often measured to gain insight into the nature and cause of REE zoning. Interpretation of such profiles is nevertheless complicated by poor constraints on the extent of diffusive relaxation. This is especially relevant for Lu, which, according to experiments, has a relatively high diffusivity and thus may re-equilibrate with possible consequences for Lu-Hf chronology. To provide new insight into the REE systematics of garnet, we applied quantitative trace-element mapping of garnet grains from metamorphic rocks that record peak temperatures above 750°C and cooling rates as low as 1.5°C Ma−1. Garnet in all samples preserves Rayleigh-type or oscillatory growth zoning with sharply defined interfacial angles that match the garnet habit. Re-equilibration of REE compositions appears restricted to domains with nebulous and patchy zoning, which likely form by interface-coupled dissolution and re-precipitation reactions mediated by fluids or melts, rather than REE volume diffusion. The possible effect of Lu diffusion in the analysed grains was investigated by comparing the observations to the results from 2D numerical modelling using Lu diffusivities from recent diffusion experiments. This test indicates that Lu diffuses significantly slower in natural garnet than experiments predict. The retentiveness of REE in garnet demonstrates the reliability of REE signatures in magmatic tracing and petrochronology and establishes Lu-Hf chronology as a robust means of dating garnet growth and recrystallization in metamorphic rocks, including those that underwent high- or ultrahigh-temperature conditions
Phylogenomics and topological conflicts in the tribe Anthospermeae (Rubiaceae)
No full textGenome skimming (shallow whole-genome sequencing) offers time-and cost-efficient production of large amounts of DNA data that can be used to address unsolved evolutionary questions. Here we address phylogenetic relationships and topological incongruence in the tribe Anthospermeae (Rubiaceae), using phylogenomic data from the mitochondrion, the nuclear ribosomal cistron, and the plastome. All three genomic compartments resolve relationships in the Anthospermeae; the tribe is monophyletic and consists of three major subclades. Carpacoce Sond. is sister to the remaining clade, which comprises an African subclade and a Pacific subclade. Most results, from all three genomic compartments, are statistically well supported; however, not fully consistent. Intergenomic topological incongruence is most notable in the Pacific subclade but present also in the African subclade. Hybridization and introgression followed by organelle capture may explain these conflicts but other processes, such as incomplete lineage sorting (ILS), can yield similar patterns and cannot be ruled out based on the results. Whereas the null hypothesis of congruence among all sequenced loci in the individual genomes could not be rejected for nuclear and mitochondrial data, it was rejected for plastid data. Phylogenetic analyses of three subsets of plastid loci identified using the hierarchical likelihood ratio test demonstrated statistically supported intragenomic topological incongruence. Given that plastid genes are thought to be fully linked, this result is surprising and may suggest modeling or sampling error. However, biological processes such as biparental inheritance and inter-plastome recombination have been reported and may be responsible for the observed intragenomic incongruence. Mitochondrial insertions into the plastome are rarely documented in angiosperms. Our results indicate that a mitochondrial insertion event in the plastid trnSGGA – rps4 IGS region occurred in the common ancestor of the Pacific clade of Anthospermeae. Exclusion/inclusion of this locus in phylogenetic analyses had a strong impact on topological results in the Pacific clade
Calcitic shells in the aragonite sea of the earliest Cambrian
No full textThe initial acquisition of calcium carbonate polymorphs (aragonite and calcite) at the onset of skeletal biomineralization by disparate metazoans across the Ediacaran-Cambrian transition is thought to be directly influenced by Earth’s seawater chemistry. It has been presumed that animal clades that first acquired mineralized skeletons during the so-called “aragonite sea” of the latest Ediacaran and earliest Cambrian (Terreneuvian) possessed aragonite or high-Mg calcite skeletons, while clades that arose in the subsequent “calcite sea” of Cambrian Series 2 acquired low-Mg calcite skeletons. Here, contrary to previous expectations, we document shells of one of the earliest helcionelloid molluscs from the basal Cambrian of southwestern Mongolia that are composed entirely of low-Mg calcite and formed during the Terreneuvian aragonite sea. The extraordinarily well-preserved Postacanthellashells have a simple prismatic microstructure identical to that of their modern low-Mg calcite molluscan relatives. High-resolution scanning electron microscope observations show that calcitic crystallites were originally encased within an intra- and interprismatic organic matrix scaffold preserved by aggregates of apatite during early diagenesis. This indicates that not all molluscan taxa during the early Cambrian produced aragonitic shells, weakening the direct link between carbonate skeletal mineralogy and ambient seawater chemistry during the early evolution of the phylum. Rather, our study suggests that skeletal mineralogy in Postacanthella was biologically controlled, possibly exerted by the associated prismatic organic matrix. The presence of calcite or aragonite mineralogy in different early Cambrian molluscan taxa indicates that the construction of calcium carbonate polymorphs at the time when skeletons first emerged may have been species dependentThis study was funded by the National Natural ScienceFoundation of China (grants 41930319, 42121005, 41890844, and 42072003); the State Administration of Foreign Experts Affair China Postdoctoral Science Foundation (grant 2022M712987); the Swedish Research Council (grants VR2016-04610 and VR2017-05183); and the Young Thousand Talents Plan of China program (grant 41720104002)</p
Ctenodactylid rodents (Rodentia, Ctenodactylidae) from the early Oligocene Nanpoping fauna of Lanzhou Basin, Northwest China
No full textCtenodactylid rodents prospered during the Paleogene in East and Central Asia, and due to their high diversification, they are important for biostratigraphic correlations. Here, we present new and diverse material from the late early Oligocene Nanpoping mammal fauna of the Lower Member of the Xianshuihe Formation from the Lanzhou Basin, Central China. Nine species – Tataromysplicidens, Tataromys sigmodon, Tataromys minor, Yindirtemys ulantatalensis, Yindirtemys shevyrevae, Alashania tengkoliensis, Karakoromys decessus, ?Euryodontomys ampliatus and Helanshania deserta – were recognized and described here in detail, the latter five species for the first time from early Oligocene Nanpoping fauna of the Lanzhou Basin. For the Lanzhou Basin, ctenodactylids show the maximum richness in the early Oligocene and have a comparatively high diversity compared with other contemporaneous faunas until the abrupt decline at the late Oligocene, with only Yindirtemys left. Ctenodactylid diversification in the early Oligocene may be related to the semi-arid climate with episodes of higher precipitation, and the following niche partitioning.The research was financially supported by the National Natural Science Foundation of China (NSFC 42172010). ZY L sincerely appreciates the China Scholarship Council (no. 202106970018) for one year of research as a visiting Ph.D. student with TM at the Swedish Museum of Natural History</p
Integration of Ukrainian paleobotanists and palynologists into the international community of scientists
No full textIntroduction. The European Palaeobotany and Palynology Conference is held every 4 years. At meetings and seminars of the conference, a wide range of scientific problems related to taxonomy of ancient plants, morphology, nomenclature, as well as the latest results of paleobotanical and palynological research are represented, ways of using them for stratigraphic constructions, paleogeographic, including paleoclimatic reconstructions, and the study of archaeological monuments are discussed.Formulation of the problem. A necessary aspect of today’s scientific research in Ukraine is the integration of the research results of Ukrainian scientists into the world scientific space. An important component in the implementation of this direction is the active participation of scientists in international projects and the presentation of research results at international professional conferences. The presented publication is devoted to an overview of one of these forums.Formulation of the purpose of the article. The main purpose of the article is to highlight the latest directions of the modern stage of paleobotanical and palynological research of the world scientific community, which were represented at the 11th European paleobotanical – palynological conference, as well as the characteristics of the scientific results of Ukrainian scientists, which was presented at this forum.Presenting main material. The 11th European Conference on Paleobotany and Palynology was held in Stockholm on June 19-22, 2022. The conference was jointly organized by the Swedish Museum of Natural History and Stockholm University. The head of the organizing committee and event coordinator was Professor Vivi Vaida.The conference gathered more than 240 delegates from 44 countries of the world, which proves the authority of the conference and the exit of EPPC beyond Europe to the international level. More than 180 oral scientific presentations and about 70 poster presentations were presented during the plenary and sectional meetings.The organizers of the conference condemned Russia’s invasion of Ukraine, and the support of the Ukrainian scientific community and the people of Ukraine was felt at all stages of the conference preparation.Main scientific directions of symposia work. Work during the conference took place in 35 scientific symposia of various topics, covering almost all modern aspects of paleobotany and palynology. The article provides a general description of the latest research that was discussed at the conference.Achievements of Ukrainian scientists represented at the conference. In total, scientists from Ukraine presented 2 oral reports – O. A. Shevchuk (The first Cretaceous megaspores from Ukraine) and D. O. Pustovoitova (History of palynological research of Mesozoic deposits in Ukraine) and 6 posters – O. A. Shevchuk (Paleobotanical research in Ukraine); O. A. Sirenko (Changes in the vegetation of Ukraine in the Gelasian time (by palynological data)); A. B. Ivanina, A. О. Myronova (Standardized characteristics of the Geminospora extensa Zone from the Givetian of western Ukraine); V. Р. Grytsenko and O. A. Shevchuk (On the collections of fossil plant and algae in the geological department of the National Museum of Natural History at the National Academy of Sciences of Ukraine); A. I. Martyshyn, O. A. Shevchuk (Taphonomy of tubular fossils (algae) from the deposits of the Late Ediacaran of Ukraine); N. I. Boyarina (The collection of the late Carboniferous plant fossils of the Donets Bassin in the Institute of Geological Sciences of NAS of Ukraine: general review). The scientific reports presented concerned various aspects of paleobotanical and palynological research: historical, taphonomic, stratigraphic, paleogeographic and paleoclimatic reconstructions, review of paleobotanical collections and problems of their storage in modern military conditions. The presented materials covered the results of the study of micro- and macro-plant remains from rocks of all subdivisions of the Phanerozoic (Paleozoic, Mesozoic, Cenozoic), as well as the Neoproterozoic (Ediacaran).Conclusions. At the conference, during the plenary and sectional meetings, considerable attention was paid to the results of research devoted to climate changes and their impact on the biota of high latitudes in the past, as well as reconstructions of the paleogeographic conditions of the formation of deposits of different ages, especially Holocene. Attention is focused on the need to develop new research methods, in particular 3D modeling of paleontological objects, popularization of paleobotany and palynology achievements, preservation of paleontological monuments, interaction of amateur paleontologists with professional paleontologists and scientific institutions and organizationsFellowship of O. Shevchuk funded by the Swedish Strategic Research Fund</p
Determination of a correction factor for C-POD data comparability : Accounting for irregular settings between C-POD deployments
No full textSwedish National Monitoring program on harbour porpoise