A possible phytosaurian (Archosauria, pseudosuchia) coprolite from the late triassic fleming fjord group of jameson land, central east Greenland

Funding Information: This project is part of a combined sedimentological, palaeontological and magnetostratigraphical investigation of the Late Triassic vertebrate-bearing continental deposits in central East Greenland supported by the Independent Research Fund Denmark. We thank Dennis V. Kent for productive discussions on Late Triassic stratigraphy. We are grateful to Karen Dybkjær, GEUS, for help with palynological examination of the coprolite. We thank Bo Markussen, Department of Mathematical Sciences at the University of Copenhagen, for guidance about statistical analyses. We gratefully acknowledge support from Dronning Margrethes og Prins Henriks Fond, Arbejdsmarkedets Feriefond, Oticon Fonden, Knud Højgaards Fond, Louis Petersens Legat, Det Obelske Familiefond, Ernst og Vibeke Husmans Fond, the Carlsberg Foundation and Geocenter Møns Klint. GEUS provided valuable logistical support. We thank Adrian Hunt and an anonymous referee for constructive reviews.A large, well-preserved vertebrate coprolite was found in a lacustrine sediment in the Malmros Klint Formation of the Late Triassic Fleming Fjord Group in the Jameson Land Basin, central East Greenland. The size and internal and external morphology of the coprolite is consistent with that of crocodilian coprolites and one end of the coprolite exhibits evidence of post-egestion trampling. As the associated vertebrate fauna of the Fleming Fjord Group contains abundant remains of pseudosuchian phytosaurs, the coprolite is interpreted as being from a large phytosaur.publishersversionpublishe

Triassic-Jurassic vegetation response to carbon cycle perturbations and climate change

Disturbances in terrestrial vegetation across the end-Triassic mass-extinction (ETME) and earliest Jurassic (∼201.5–201.3 Ma) have previously been linked to carbon cycle perturbations induced by the Central Atlantic Magmatic Province. Large-scale volcanic degassing has been proposed to have affected the terrestrial realm through various mechanisms. However, the effects of long-term “super greenhouse” climate variability on vegetation dynamics following the mass-extinction remain poorly understood. Based on a 10-million-year long multi-proxy record of northern Germany (Schandelah-1, Germany, paleolatitude of ∼41°N) spanning the late Rhaetian to the Sinemurian (∼201.5–190.8 Ma), we aim to assess mechanistic links between carbon cycle perturbations, climate change, and vegetation dynamics. Based on a high-resolution palynofloral record a two-phased extinction emerges, confirming extinction patterns seen in other studies. The first phase is associated with a decline in arborescent conifers, coinciding with a negative carbon isotope excursion and an influx of aquatic palynomorphs. Following this decline, we find a stepwise rise of ferns at the cost of trees during the latest Rhaetian, culminating with the extinction of tree taxa at the Triassic-Jurassic boundary. The rise in ferns is accompanied by an increase in reworked organic matter and charcoal, suggestive of erosion and wildfires. Furthermore, the Hettangian (201.3–199.3 Ma) vegetation in NW Europe shows evidence of long-term disturbance reflected by the periodic resurgence of fern taxa, similarly accompanied by increases in reworking and charcoal. This periodicity is linked to the 405-kyr eccentricity cycle indicating a biome that responded to astronomically induced variability in hydrology. A transition into an apparently more stable biome starts during the early Sinemurian, where palynofloral assemblages become dominated by bisaccate pollen taxa, mainly derived from conifers. The ETME was clearly forced by the effects of volcanogenic emissions, such as SO2, CO2 and other pollutants, acting on both short (0.1–10 kyrs) and long timescales (10–100 kyrs). In contrast, charcoal and detrital input indicators show that the disturbances during the Hettangian were driven by periodic shifts in the regional hydrological regime. This was forced by the effects of orbital insolation variation and potentially exacerbated by increased atmospheric pCO2. The cyclic progression of ecosystem disturbance was similar to that of the ETME and only recovered during the early Sinemurian. Atmospheric pCO2 remained elevated after CAMP-activity had subsided due to a collapse of terrestrial biomass and carbonate producers. This inability to store carbon on long timescales could therefore have impeded global recovery

A Late Cretaceous amber biota from central Myanmar

International audienceInsect faunas are extremely rare near the latest Cretaceous with a 24-million-year gap spanning from the early Campanian to the early Eocene. Here, we report a unique amber biota from the Upper Cretaceous (uppermost Campanian ~72.1 Ma) of Tilin, central Myan-mar. The chemical composition of Tilin amber suggests a tree source among conifers, indicating that gymnosperms were still abundant in the latest Campanian equatorial forests. Eight orders and 12 families of insects have been found in Tilin amber so far, making it the latest known diverse insect assemblage in the Mesozoic. The presence of ants of the extant sub-families Dolichoderinae and Ponerinae supports that tropical forests were the cradle for the diversification of crown-group ants, and suggests that the turnover from stem groups to crown groups had already begun at ~72.1 Ma. Tilin amber biota fills a critical insect faunal gap and provides a rare insight into the latest Campanian forest ecosystem

Organic pyrolysis data from eastern Baffin Bay, sediment core AMD14-204C

Radiocarbon dating of Arctic marine sediment is often challenging due to the low availability of calcareous fossils. Consequently, bulk organic matter dating has at times been used to establish sediment core chronologies. Yet, radiocarbon dates based on bulk organic matter often appear to deviate vastly from dates based on fossils, mainly caused by input of carbon from other sources, including terrigenous organic matter. In this study, we aim to examine the link between the composition of the bulk organic matter and the age offsets between the bulk radiocarbon dates and those obtained from calcareous foraminiferal tests. All samples are taken from the marine sediment core AMD14-204C from offshore Upernavik (eastern Baffin Bay). The radiocarbon dates for bulk organic matter are on average ~3000 years older than the radiocarbon dates based on foraminifera, but with changing age offsets throughout the record. To investigate the cause of this age offset and its variations over time, we applied X-ray Fluorescence analysis, stable isotopes, organic pyrolysis and microscopic organic petrology to examine the distribution and characterization of the organic matter. The results show that the older organic matter includes clastic input of reworked sedimentary rocks potentially originating from West Greenland and/or the Canadian Arctic Archipelago. Changes in the input of contemporary marine algal produced organic matter versus both terrigenous input and reworked ancient organic matter appear to control the age offsets between the bulk and foraminifera dates. Low Hydrogen Index and low δ13Corg together with high Oxygen Index, indicative of high influence of terrigenous organic matter, seem to correspond to samples with the largest age offsets; 1000-2000 years greater than in other samples. To examine the cause of the variations in the age offsets, a new quantification of the autochthonous organic matter as a fraction of the TOC was calculated. This shows that samples with the largest age offsets contained the lowest fraction (as low as ~12 %) of autochthonous organic matter in the TOC

Characterization of organic matter in marine sediments to estimate age offset of bulk radiocarbon dating

International audienceThis is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain

Magnetic Stress-Driven Metal-Insulator Transition in Strongly Correlated Antiferromagnetic CrN

Traditionally, the Coulomb repulsion or Peierls instability causes the metal-insulator phase transitions instrongly correlated quantum materials. In comparison, magnetic stress is predicted to drive the metalinsulator transition in materials exhibiting strong spin-lattice coupling. However, this mechanism lacksexperimental validation and an in-depth understanding. Here we demonstrate the existence of the magneticstress-driven metal-insulator transition in an archetypal material, chromium nitride. Structural, magnetic,electronic transport characterization, and first-principles modeling analysis show that the phase transitiontemperature in CrN is directly proportional to the strain-controlled anisotropic magnetic stress. Thecompressive strain increases the magnetic stress, leading to the much-coveted room-temperature transition.In contrast, tensile strain and the inclusion of nonmagnetic cations weaken the magnetic stress and reducethe transition temperature. This discovery of a new physical origin of metal-insulator phase transition thatunifies spin, charge, and lattice degrees of freedom in correlated materials marks a new paradigm and couldlead to novel device functionalities