Fossil Age Research Articles

A Molecular Temporal Evolutionary Framework of Land Plants and the Age of Angiosperms

A series of Bayesian molecular clock analyses with varying model combinations, parameters, and tree topologies were conducted to establish a temporal evolutionary framework of land plants and to estimate the age of angiosperms. The data consisted of five organellar and nuclear genes, 633 taxa, and 23 fossil calibration points (FCPs). The analyses were evaluated using an internal search thoroughness measure, effective sample sizes, and two external criteria: the consensus land plant phylogeny and a newly developed method that used the Hennigian reciprocal illumination principle to compare molecular age estimates of 21 nodes representing major land plant clades and the root split in green plants with those of their fossils in an a posteriori fashion. The results show that an analysis using a general time reversible (GTR) DNA substitution model, log normal branch-rate distribution, and Yule tree prior represented the best model combination, with the Birth-Death tree prior being equally optimal. This analysis estimated the age of the land plant crown group as 496.95 million years (MY), with a 95% highest posterior density (HPD) of 465.66–531.43 MY, and the age of the angiosperm crown group as 219.93 MY, with a 95% HPD of 184.09–256.82 MY. The former agrees with the fossil evidence, but the latter is significantly older than the fossil ages. A thorough examination of fossil evidence of angiosperms, as well as their evolutionary history in light of recent knowledge of morphology, physiology, and atmospheric CO2 concentration in the Mesozoic era, suggests that angiosperm radiation might have been delayed after their origin and that the current fossil record probably reflects only the products of that radiation, not the origin of angiosperms. Overall, the study shows that both molecular clock analyses and fossil studies, while agreeing on some aspects but disagreeing on others, can help develop a complete understanding of the temporal evolutionary history of land plants.

APPLICATION OF AMINO ACID RACEMIZATION TO THE DATING OF FORAMINIFERS AND THE IDENTIFICATION OF REMANIÉ FOSSILS AND REWORKED SEDIMENTS

ABSTRACT The reworking of sediments and fossils is a pervasive element of the stratigraphical record and is frustrated by the fact that the taphonomic nature of fossils may not always reliably indicate the presence of remanié fossils. In this work, the extent of racemization of amino acids, a measure of fossil age based on an increasing ratio of D- to L-amino acids, is used to evaluate the integrity of the sedimentary record in selected case studies, based on the analysis of single foraminifers or samples containing fewer than 10 individuals. The short lifespan of foraminifers (c. 2–24 months), enhances their application for defining the age of sedimentary events, as they more closely relate to the age of the depositional event. The selected case studies range in spatial scale from defining the taphonomically active zone in geologically recent shallow marine sediments, to the application of foraminifers in reef island sediment budgets in Tarawa, to the reworking of foraminifers from Late Pleistocene calcarenites into modern beach sediments. The species Elphidium macelliforme, Amphistegina sp., and Lamellodiscorbis dimidiatus are shown to be particularly suited for amino acid racemization investigations of sediment reworking.

Biomolecules in Pleistocene fossils from tropical cave indicate fossil biofilm

Finding biomolecules in fossils is a challenging task due to their degradation over time from physical, chemical, and biological factors. The primary hypothesis for explaining the presence of biomolecules in fossilized bones tissues suggests their survival in the fossilization process. In contrast, some of these biomolecules could either derive from bacteria biofilm, thus without a direct relationship with the fossil record or could be an artifact from measurement procedures. Raman spectroscopy studies across various fossil ages and environments have detected multiple bands ranging from 1200 to 1800 cm−1 associative of organic compounds. However, the significance of these bands remains elusive. Our research aims to address this issue through a deep Raman spectroscopy investigation on Pleistocene teeth from Tayassu and Smilodon populator. These fossils were obtained from a well-preserved stratigraphic succession in Toca de Cima do Pilão cave, near the National Park of Serra da Capivara in semiarid Brazil. We propose two hypotheses to explain the presence of organic compounds related to 1200 to 1800 cm−1 Raman spectral range in fossil tissues: (i) these bands are biological signatures of preserved fossil biomolecules, or (ii) they are exogenous biological signatures associated with the bacterial biofilm formation during post-depositional processes. Our results align with the latter hypothesis, followed by biofilm degradation. However, the specific mechanisms involved in the natural biofilm degradation in fossil records remain unexplored in this study. In our case, the formation of biofilm on fossil bones is attributed to the oligotrophic conditions of the cave sediment matrix. We present a comprehensive model to elucidate the existence of biofilm on fossilized tissues, emphasizing the pivotal role of post-depositional processes, especially water action, in the cave environment. As the fossils were discovered in a cave setting, post-depositional processes significantly contribute to the formation of the biofilm matrix. Although our study provides insights into biofilm formation, further research is needed to delve into the specific mechanisms driving natural biofilm degradation in fossils.

Constraining the age of the Pleistocene sedimentary infill of Cueva Mayor (Atapuerca, N Spain) through a multi-technique dating approach

Establishing chronologies of archaeological sites by using a single dating method may not always reliably constrain the age of a deposit or a fossil, as potential biases may naturally arise, particularly in complex sedimentary settings such as caves. In this study, we performed a multi-technique dating approach that targets different materials in two caves from the Cueva Mayor-Cueva del Silo karst system, Sierra de Atapuerca, Spain. Two new fossil teeth from lithostratigraphic unit LU4 (GE-I pit) at Galería de las Estatuas have been dated by combined U-series/ESR and Amino Acid Racemisation (AAR) methods. The former provides ages of 117 ± 13 and 87 ± 9 ka that agree with previous dating studies of this Neandertal site, confirming the assignment of level LU4 to Marine Isotope Stage (MIS) 5. In contrast, AAR analyses produce very scattered ages, pointing to significant post-burial chemical modifications in dentine. A first set of ages is presented for the Cata Litario pit at Sala de los Cíclopes, a palaeontological site formed exclusively of cave bear fossils belonging to the Middle Pleistocene species Ursus deningeri. We provide U-series/ESR and AAR ages for two bear teeth from lithostratigraphic unit LU5, and extended-range luminescence ages for the sediment deposits that host, and immediately underlie and overlie, the bear accumulation. Depositional ages of the sediment were obtained using single-grain thermally-transferred optically stimulated luminescence (TT-OSL) dating of individual quartz grains and post-infrared-infrared stimulated luminescence (pIR-IR) dating of K-feldspars. Several speleothems, both in situ and reworked fragments embedded in the different lithostratigraphic units, have additionally been dated by U-series to constrain the timing of the sequence formation. The results indicate that the sediment originally entered the cave between MIS-12 and MIS-10 (444 ± 28 ka to 367 ± 32 ka). Nevertheless, the AAR and U-series/ESR fossil ages, as well as some of the speleothem fragment ages from LUs 5 and 6 are significantly younger. Leaving aside methodologically questionable results for one of the bear tooth samples, the most reliable AAR and U-Series/ESR ages range from 287 ± 23 ka to 256 ± 24, while the speleothem fragments indicate several formation episodes between 444 ± 19 and 284 ± 8 ka. The apparent difference between the U-Series/ESR ages on the fossils and the luminescence ages on the host sediment are not likely to be wholly explained by uncertainties on uranium uptake modelling or gamma dose rate evaluation, and thus is most likely related to taphonomic processes or a complex site formation history.The presence of fossils and eroded speleothem clasts of younger age within these levels is consistent with either an event of prior erosion, transport and resedimentation of LUs 4, 5 and 6, and/or a complex post-depositional mixing history for the stratigraphic sequence at Cata Litario. This study highlights the importance of using different dating methods to reconstruct reliable chronological frameworks, and to understand the geological factors that can affect the dated materials. This includes the accumulation and taphonomic histories of fossils, post-depositional mixing or reworking processes affecting sediments during the residence time within the karst system.

Testing extinction events and temporal shifts in diversification and fossilization rates through the skyline Fossilized Birth-Death (FBD) model: The example of some mid-Permian synapsid extinctions.

In the last decade, the Fossilized Birth-Death (FBD) process has yielded interesting clues about the evolution of biodiversity through time. To facilitate such studies, we extend our method to compute the probability density of phylogenetic trees of extant and extinct taxa in which the only temporal information is provided by the fossil ages (i.e. without the divergence times) in order to deal with the piecewise constant FBD process, known as the "skyline FBD", which allows rates to change between pre-defined time intervals, as well as modelling extinction events at the bounds of these intervals. We develop approaches based on this method to assess hypotheses about the diversification process and to answer questions such as "Does a mass extinction occur at this time?" or "Is there a change in the fossilization rate between two given periods?". Our software can also yield Bayesian and maximum-likelihood estimates of the parameters of the skyline FBD model under various constraints. These approaches are applied to a simulated dataset in order to test their ability to answer the questions above. Finally, we study an updated dataset of Permo-Carboniferous synapsids to get additional insights into the dynamics of biodiversity change in three clades (Ophiacodontidae, Edaphosauridae and Sphenacodontidae) in the Pennsylvanian (Late Carboniferous) and Cisuralian (Early Permian), and to assess support for end-Sakmarian (or Artinskian) and end-Cisuralian mass extinction events discussed in previous studies.

In situ U-Pb dating of Jurassic dinosaur bones from Sichuan Basin, South China

Abstract Direct dating of vertebrate fossils is difficult due to complex postburial diagenetic processes and the often low and heterogeneous concentration of radioisotopes (e.g., U) in fossilized bone material. Here, we demonstrate a novel approach to dating vertebrate fossils via laser ablation–inductively coupled plasma–mass spectrometry U-Pb dating of early diagenetic calcite cements precipitated within bone cavities of a Jurassic sauropod from the Sichuan Basin, South China. Early diagenetic calcite yielded a U-Pb age of 165.3 ± 3.6/5.6 Ma, in agreement with a maximum depositional age of 165.8 ± 1.0 Ma from detrital zircon ages of the surrounding rocks, suggesting that diagenesis occurred shortly after the death of the sauropod. This new age demonstrates that the best-known Jurassic large sauropod faunas in South China are much older than those in North America and Africa, suggesting the geographical isolation of South China. Authigenic apatite U-Pb dating on the fibrolamellar bones from the same sauropod gave a distinctly younger age, indicating more complex U-Pb system behavior, possibly due to U uptake by residual organic matter and recrystallization of apatite after early diagenesis. Our findings demonstrate that U-Pb dating of calcite cements within bone cavities has significant potential for constraining the burial age of vertebrate fossils, which could aid in constructing a more robust temporal framework for the radiation and evolution of vertebrates.

Cretaceous Fore‐Arc Basin and Its Provenance in Sakhalin, Far East Russia: U‐Pb Ages of Detrital Zircons From the Yezo Group

ABSTRACTIn order to reconstruct the pre‐Japan Sea configuration of the Cretaceous arc‐trench system, we measured U‐Pb ages of detrital zircons in the five sandstone samples from the Yezo Group in Sakhalin using LA‐ICP‐MS. A sandstone sample from the lowermost horizon (Ai Formation) contains abundant Early Cretaceous (110–100 Ma) zircons with minor amounts of pre‐Jurassic ones. Four sandstones from the uppermost (Krasnoyarka Formation) are enriched dominantly in Late Cretaceous (100–66 Ma) grains. The YC1σ ages of these samples are generally consistent with the previous fossil ages; nonetheless, a possible age extension of the Ai Fm up possibly into the Cenomanian was newly suggested. The stepwise younging in peak age of zircons according to the stratigraphy suggests the continuous replacement of arc granitoid exposures in the Cretaceous magmatic arc in the provenance likely developed on the continent side. This secular trend in zircon age spectra of the Yezo Group in Sakhalin is properly correlated with that in Hokkaido and also with that of coeval sandstones in southwest Japan, suggesting a monotonous sedimentation in the fore‐arc basin of the Late Cretaceous arc‐trench system developed along the Pacific margin, from Sakhalin to southwest Japan for ca. 2500 km in length. Its spatial dimension corresponds to that of the modern representative fore‐arc basin in the Java‐Sumatra region.

Fast Bayesian Inference of Phylogenies from Multiple Continuous Characters.

Time-scaled phylogenetic trees are an ultimate goal of evolutionary biology and a necessary ingredient in comparative studies. The accumulation of genomic data has resolved the tree of life to a great extent, yet timing evolutionary events remain challenging if not impossible without external information such as fossil ages and morphological characters. Methods for incorporating morphology in tree estimation have lagged behind their molecular counterparts, especially in the case of continuous characters. Despite recent advances, such tools are still direly needed as we approach the limits of what molecules can teach us. Here, we implement a suite of state-of-the-art methods for leveraging continuous morphology in phylogenetics, and by conducting extensive simulation studies we thoroughly validate and explore our methods' properties. While retaining model generality and scalability, we make it possible to estimate absolute and relative divergence times from multiple continuous characters while accounting for uncertainty. We compile and analyze one of the most data-type diverse data sets to date, comprised of contemporaneous and ancient molecular sequences, and discrete and continuous morphological characters from living and extinct Carnivora taxa. We conclude by synthesizing lessons about our method's behavior, and suggest future research venues.

Isotope Applications Exploration and Research Progress

Isotopes, as key concepts in chemistry and physics, are extremely important for understanding elemental properties and behavior. This review aims to provide a comprehensive view of the basic theory of isotopes, including their definition and classification: stable isotopes versus radioactive isotopes. Isotopes not only have a place in theoretical studies, but also play a key role in several practical applications, such as radioisotopes for diagnosis and treatment in medicine, isotopes for determining the age of rocks and fossils in geology, tracking sources of pollution and ecosystem changes in environmental sciences. In addition, this paper will explore recent advances in isotope research, including the discovery of new isotopes, the enhancement of isotope analysis techniques, and new applications of isotopes at the intersection of several disciplines, including biology, environmental science, and forensic science. Through these comprehensive discussions, this review aims to provide researchers and students in related fields with an updated and comprehensive research perspective and reference.

Integrated approaches to track saline intrusion for fresh groundwater resource protection in the Mekong Delta

In many coastal regions, groundwater is the sole freshwater resource for drinking and irrigation. However, coastal aquifers often face saline intrusion due to excessive groundwater extraction, climate change, and sea-level rise. This study integrated approaches in geochemistry, geophysics, statistical analysis, and geographic information system (GIS) to identify groundwater salinization pathways in the Ca Mau Peninsula of the Mekong Delta for sustainable protection of the invaluable freshwater resources. We collected 31 well logging data and groundwater samples from 388 wells in the area. A geochemical analysis demonstrated significant salinization in 9% of investigated wells. Calculated entropy-weighted water quality index (EQWI) indicates that only <3% of samples have excellent water quality and about 35% of medium-to-poor water quality groundwater. High salinity is the leading cause of impaired water quality. We combined geochemical and geophysical methods to validate an approach relating well-logging data (formation resistivity) to salinity to determine high-resolution vertical salinity profiles across the aquifer systems. We demonstrated the occurrence of saline groundwater in the surficial aquifers (Holocene and upper Pleistocene) that overlay above fresh and ancient groundwater aquifers (upper middle and lower Pleistocene, and Pliocene). This fresh groundwater is mostly fossil (age >10,000 years) and cannot be recharged directly from rainfall in the area while being highly susceptible to salinization by the downward movement of saline waters from overlaying aquifers. These findings call for appropriate strategies and directives in groundwater management to protect and sustain the critical water resources in the Mekong Delta.

Pyritization and Preservation Model of Chrysophyte Cyst Fossils in Shales during the Triassic Carnian Pluvial Episode, Ordos Basin, China: Evidence from Cyclostratigraphy, Radiometric Dating and Geochemical Analyses

Chrysophyte cyst fossils were widely pyritized and preserved in black shales from the seventh member (Ch7 Mbr) of the Yanchang Formation in the Ordos Basin. The age, pyritization, and preservation model of these fossils have not been studied previously. In this study, the astronomical orbital cycles of the Ch7 Mbr were determined based on the gamma ray series of the Yan56 and Zhen 421 wells. An astronomical time scale (ATS) analysis revealed that the depositional duration of Ch7 Mbr was approximately 5 Ma. According to the 206Pb/238U radiometric dating of zircons using laser ablation inductively coupled plasma mass spectrometry (La-ICP-MS), the tuffs at the bottom of Ch7 Mbr were crystallized at 234 Ma, which served as a geological anchor. The ages of three submembers in Ch7 Mbr were estimated at 234.0–232.4 Ma, 232.4–230.8 Ma, and 230.8–229.1 Ma based on ATS analysis. In addition, chrysophyte cyst fossils were well preserved by pyritization in the Ch7 Mbr black shales. There were six types of microscopic morphologies with different pores, collars, and surface ornamentation under scanning electron microscopy (SEM). The age of the chrysophyte cyst fossils was at least 233.6 Ma in the Triassic Carnian Pluvial Episode (CPE) based on the 405 kyr tuned ATS. Moreover, the paleoredox conditions in Ch7 Mbr were reconstructed, and a preservation model of chrysophyte cyst fossils was established based on geochemical analyses. Fossil pyritization was caused by bacterial sulfate reduction near the water-sediment interface under suboxic to anoxic environmental conditions. Pyritization was initiated on the walls of the chrysophyte cysts by the formation of microcrystalline pyrite. Because of the gradual pyritization of the chrysophyte cyst wall, the organic matter in the interior of the fossil was well preserved.

Reconstructing the provenance of the hominin fossils from Trinil (Java, Indonesia) through an integrated analysis of the historical and recent excavations

In the early 1890s at Trinil, Eugène Dubois found a hominin skullcap (Trinil 2) and femur (Trinil 3, Femur I), situated at the same level ca. 10–15 m apart. He interpreted them as representing one species, Pithecanthropus erectus (now Homo erectus) which he inferred to be a transitional form between apes and humans. Ever since, this interpretation has been questioned—as the skullcap looked archaic and the femur surprisingly modern. From the 1950s onward, chemical and morphological analyses rekindled the debate. Concurrently, (bio)stratigraphic arguments gained importance, raising the stakes by extrapolating the consequences of potential mixing of hominin remains to the homogeneity of the complete Trinil fossil assemblage. However, conclusive evidence on the provenance and age of the hominin fossils remains absent. New Trinil fieldwork yielded unmanned aerial vehicle imagery, digital elevation models, and stratigraphic observations that have been integrated here with an analysis of the historical excavation documentation. Using a geographic information system and sightline analysis, the position of the historical excavation pits and the hominin fossils therein were reconstructed, and the historical stratigraphy was connected to that of new sections and test pits. This study documents five strata situated at low water level at the excavation site. Cutting into a lahar breccia are two similarly oriented, but asynchronous pre-terrace fluvial channels whose highly fossiliferous infills are identified as the primary targets of the historical excavations (Bone-Bearing Channel 1, 830–773 ka; Bone-Bearing Channel 2, 560–380 ka), providing evidence for a mixed faunal assemblage and yielding most of the hominin fossils. These channels were incised by younger terrace-related fluvial channels (terminal Middle or Late Pleistocene) that directly intersect the historical excavations and the reconstructed discovery location of Femur I, thereby providing an explanation for the relatively modern morphology of this ‘bone of contention’. The paleoanthropological implications are discussed in light of the current framework of human evolution in Southeast Asia.

Estimating the Age of Poorly Dated Fossil Specimens and Deposits Using a Total-Evidence Approach and the Fossilized Birth-Death Process.

Bayesian total-evidence approaches under the fossilized birth-death model enable biologists to combine fossil and extant data while accounting for uncertainty in the ages of fossil specimens, in an integrative phylogenetic analysis. Fossil age uncertainty is a key feature of the fossil record as many empirical data sets may contain a mix of precisely dated and poorly dated fossil specimens or deposits. In this study, we explore whether reliable age estimates for fossil specimens can be obtained from Bayesian total-evidence phylogenetic analyses under the fossilized birth-death model. Through simulations based on the example of the Baltic amber deposit, we show that estimates of fossil ages obtained through such an analysis are accurate, particularly when the proportion of poorly dated specimens remains low and the majority of fossil specimens have precise dates. We confirm our results using an empirical data set of living and fossil penguins by artificially increasing the age uncertainty around some fossil specimens and showing that the resulting age estimates overlap with the recorded age ranges. Our results are applicable to many empirical data sets where classical methods of establishing fossil ages have failed, such as the Baltic amber and the Gobi Desert deposits. [Bayesian phylogenetic inference; fossil age estimates; fossilized birth-death; Lagerstätte; total-evidence.].

New discovery of a late Middle Pleistocene mammalian fauna in Ganxian Cave, Southern China

ABSTRACT This report describes fossils recovered from Ganxian Cave in 2008 and 2018 by the Natural History Museum and Anthropology Museum of Guangxi. The cave sedimentary fill yielded rich mammalian fossils consisting mainly of isolated teeth of medium- to large-sized mammals (Primates, Proboscidea, Perissodactyla, Carnivora, Rodentia, Artiodactyla) of typical ‘Ailuropoda-Stegodon’ fauna, (e.g. Stegodon orientalis, Ailuropoda baconi, Pongo weidenreichi, Tapirus sinensis, Megatapirus augustus, Crocuta ultima), and more numerous extant species belonging to 28 taxa in total. The biochronological age of the fauna agreed with the age estimates obtained using Uranium–series and coupled ESR/U-series dating. Collectively, these results indicate a Ganxian fossil age range of 168.9 ± 2.4 ka to 362 ± 78 ka and establish Ganxian Cave as one of the most precisely dated Middle Pleistocene fossil sites in southern China. Comparison of Ganxian fauna with Pleistocene fossil records of the well-documented faunas of southern China and southeast Asia indicates that the Asian elephant (Elephas maximus) probably first appeared in Ganxian Cave. Paleoenvironmental reconstruction-based analysis of the large mammalian fossil assemblage from Ganxian Cave indicates that during the late Middle Pleistocene, the habitat consisted mainly of forests with some open areas and the climate was warm and humid.

Quantitative dual-energy CT as a nondestructive tool to identify indicators for fossilized bone in vertebrate paleontology

Dual-energy computed tomography (DECT) is an imaging technique that combines nondestructive morphological cross-sectional imaging of objects and the quantification of their chemical composition. However, its potential to assist investigations in paleontology has not yet been explored. This study investigates quantitative DECT for the nondestructive density- and element-based material decomposition of fossilized bones. Specifically, DECT was developed and validated for imaging-based calcium and fluorine quantification in bones of five fossil vertebrates from different geological time periods and of one extant vertebrate. The analysis shows that DECT material maps can differentiate bone from surrounding sediment and reveals fluorine as an imaging marker for fossilized bone and a reliable indicator of the age of terrestrial fossils. Moreover, the jaw bone mass of Tyrannosaurus rex showed areas of particularly high fluorine concentrations on DECT, while conventional CT imaging features supported the diagnosis of chronic osteomyelitis. These findings highlight the relevance of radiological imaging techniques in the natural sciences by introducing quantitative DECT imaging as a nondestructive approach for material decomposition in fossilized objects, thereby potentially adding to the toolbox of paleontological studies.

Relative performance of Bayesian morphological clock and parsimony methods for phylogenetic reconstructions: Insights from the case of Myomiminae and Dryomyinae glirid rodents.

Extinct organisms provide crucial information about the origin and time of origination of extant groups. The importance of morphological phylogenetics for rigorously dating the tree of life is now widely recognized and has been revitalized by methodological developments such as the application of tip-dating Bayesian approaches. Traditionally, molecular clocks have been node calibrated. However, node calibrations are often unsatisfactory because they do not allow the fossil age to inform about phylogenetic hypothesis. The introduction of tip calibrations allow fossil species to be included alongside their living relatives, and the absence of molecular sequence data for these taxa to be remedied by supplementing the sequence alignments for living taxa with phenotype character matrices for both living and fossil taxa. Therefore, only phylogenetic analyses that take into account morphological characters can incorporate both fossil and extant species. Herein we present an unprecedented morphological dataset for a vast group of glirid rodents, to which different phylogenetic methodologies have been applied. We have compared the tree topologies resulting from traditional parsimony and Bayesian phylogenetic approaches and calculate stratigraphic congruence indices for each. Bayesian tip-dated clock methods seem to outperform parsimony with our dataset. The strict consensus tree recovered by tip dating invalidates the classic classification and allows dates to be proposed for the divergence and origin of the different clades.

OCTOPUS database (v.2)

Abstract. OCTOPUS v.2 is an Open Geospatial Consortium (OGC) compliant web-enabled database that allows users to visualise, query, and download cosmogenic radionuclide, luminescence, and radiocarbon ages and denudation rates associated with erosional landscapes, Quaternary depositional landforms, and archaeological records, along with ancillary geospatial (vector and raster) data layers. The database follows the FAIR (Findability, Accessibility, Interoperability, and Reuse) data principles and is based on open-source software deployed on the Google Cloud Platform. Data stored in the database can be accessed via a custom-built web interface and via desktop geographic information system (GIS) applications that support OGC data access protocols. OCTOPUS v.2 hosts five major data collections. CRN Denudation and ExpAge consist of published cosmogenic 10Be and 26Al measurements in modern fluvial sediment and glacial samples respectively. Both collections have a global extent; however, in addition to geospatial vector layers, CRN Denudation also incorporates raster layers, including a digital elevation model, gradient raster, flow direction and flow accumulation rasters, atmospheric pressure raster, and CRN production scaling and topographic shielding factor rasters. SahulSed consists of published optically stimulated luminescence (OSL) and thermoluminescence (TL) ages for fluvial, aeolian, and lacustrine sedimentary records across the Australian mainland and Tasmania. SahulArch consists of published OSL, TL, and radiocarbon ages for archaeological records, and FosSahul consists of published late-Quaternary records of direct and indirect non-human vertebrate (mega)fauna fossil ages that have been systematically quality rated. Supporting data are comprehensive and include bibliographic, contextual, and sample-preparation- and measurement-related information. In the case of cosmogenic radionuclide data, OCTOPUS also includes all necessary information and input files for the recalculation of denudation rates using the open-source program CAIRN. OCTOPUS v.2 and its associated data curation framework allow for valuable legacy data to be harnessed that would otherwise be lost to the research community. The database can be accessed at https://octopusdata.org (last access: 1 July 2022). The individual data collections can also be accessed via their respective digital object identifiers (DOIs) (see Table 1).

New Fossil Xyelidae (Hymenoptera: Symphyta) from the Mesozoic of Northeastern China

Simple SummaryOne new genus and two new species, described from new fossil specimens of northeastern China, enhance our knowledge of the Xyelidae in the mid-Mesozoic. A key to the genera of Angaridyelini and a table of known fossil species of Macroxyelinae are provided. After investigating various angles between Rs+M and 1-Rs for known fossil species of Macroxyelinae, we report that the angle and the length of 1-Rs are correlated. In addition, we believe that the tribe Ceroxyelini may have only one genus of Ceroxyela, and suggest that Isoxyela and Sinoxyela should be transferred to Gigantoxyelini.One new genus and species, Leptoxyela eximia gen. et sp. nov., and one new species, Scleroxyela cephalota sp. nov., are described and illustrated based on two well-preserved compression fossils from the Lower Cretaceous Yixian Formation and the Middle Jurassic Jiulongshan Formation of China, respectively. Leptoxyela eximia gen. et sp. nov. is placed in the tribe Angaridyelini, 1966 and Scleroxyela cephalota sp. nov. in the tribe Xyeleciini Benson, 1945; while both tribes are in the subfamily Macroxyelinae Ashmead, 1898 of Xyelidae. A key to the genera of Angaridyelini is provided. In addition, we investigated various angles between Rs+M and 1-Rs for known fossil species of Macroxyelinae, and we found the angle and the length of 1-Rs are correlated; however, we could not see any correlation between the angles and the fossil ages even within a tribe. Furthermore, based on Sc2 connected to R before Rs, the angle between Rs+M and 1-Rs, and the length of the first flagellomere, we believe that the tribe Ceroxyelini may have only one genus of Ceroxyela, and suggest that Isoxyela and Sinoxyela should be transferred to Gigantoxyelini.

The Fossil Taphonomic Patterns and Age of the Newly Discovered Large Dinosaur Fossil Groups in the Yunyang Area, Northeast Sichuan Basin, China

The Fossil Taphonomic Patterns and Age of the Newly Discovered Large Dinosaur Fossil Groups in the Yunyang Area, Northeast Sichuan Basin, China

Radiocarbon as a Dating Tool and Tracer in Paleoceanography

AbstractRadiocarbon is an extremely useful carbon cycle tracer and radiometric dating tool. Here, we review the main principles and challenges involved in the use of radiocarbon in paleoceanography. First, we present a conceptual framework in which there are three possible uses of a radiocarbon measurement: (a) to obtain a calendar age interval, or a fossil entity's age; (b) to obtain an estimate of a carbon reservoir's past radiocarbon activity; or (c) to compare the relative radiocarbon activities of two contemporary carbon reservoirs. We discuss the analysis of marine fossil material, the generation of an atmospheric reference curve, and the interpretation of marine radiocarbon “ventilation metrics” in relation to this reference curve. It is emphasized that marine radiocarbon integrates the influences of: changing radiocarbon production; air‐sea gas exchange effects at the sea surface; transport times within the ocean interior; and the mixing of water parcels with different transit times from the sea surface, and different sea‐surface sources. These controls are what make radiocarbon such a powerful paleoceanographic tracer, though the difficulty of disentangling them is what makes marine radiocarbon dating and tracer studies so challenging. We discuss the implementation of radiocarbon in numerical models, and explore the theory linking ocean‐atmosphere partitioning of radiocarbon and CO2. Finally, we review existing records of marine radiocarbon variability over the last ∼25,000 years, which highlight the influence of ocean‐atmosphere carbon exchange on past atmospheric CO2 and climate, and point to emerging opportunities for resolving the global radiocarbon‐ and carbon budgets over the last glacial cycle.