Climate warming, euxinia and carbon isotope perturbations during the Carnian (Triassic) Crisis in South China

The Carnian Humid Episode (CHE), also known as the Carnian Pluvial Event, and associated biotic changes are major enigmas of the Mesozoic record in western Tethys. We show that the CHE also occurred in eastern Tethys (South China), suggestive of a much more widespread and probably global climate perturbation. Oxygen isotope records from conodont apatite indicate a double-pulse warming event. The CHE coincided with an initial warming of 4 °C. This was followed by a transient cooling period and then a prolonged ~7 °C warming in the later Carnian (Tuvalian 2). Carbon isotope perturbations associated with the CHE of western Tethys occurred contemporaneously in South China, and mark the start of a prolonged period of carbon cycle instability that persisted until the late Carnian. The dry-wet transition during the CHE coincides with the negative carbon isotope excursion and the temperature rise, pointing to an intensification of hydrologic cycle activities due to climatic warming. While carbonate platform shutdown in western Tethys is associated with an influx of siliciclastic sediment, the eastern Tethyan carbonate platforms are overlain by deep-water anoxic facies. The transition from oxygenated to euxinic facies was via a condensed, manganiferous carbonate (MnO content up to 15.1 wt%), that records an intense Mn shuttle operating in the basin. Significant siliciclastic influx in South China only occurred after the CHE climatic changes and was probably due to foreland basin development at the onset of the Indosinian Orogeny. The mid-Carnian biotic crisis thus coincided with several phenomena associated with major extinction events: a carbonate production crisis, climate warming, δ 13 C oscillations, marine anoxia, biotic turnover and flood basalt eruptions (of the Wrangellia Large Igneous Province)

Insights from a new method providing single-shot, planar measurement of gas-phase temperature in particle-laden flows under high-flux radiation

Published online: 31 March 2021Two-colour laser-induced fluorescence (LIF) of toluene has been demonstrated to provide in situ, spatially resolved, planar measurements of the gas-phase temperature in a particle-laden flow with strong radiative heating at fluxes up to 42.8 MW/m². Toluene was seeded in trace quantities into the gas flow laden with particles of mean diameter 173 μm at a volumetric loading sufficiently high for particle–fluid and particle–particle interactions to be significant. The particle number density was also measured simultaneously using Mie scattering. The two-colour LIF method was found to resolve temperature with a pixelto- pixel standard deviation of 17.8 °C for unheated measurements in this system despite significant attenuation of the probe laser and signal trapping of the fluorescence emissions from the densely loaded particles. Following heating of the particles using high flux radiation, the increase in the gas-phase temperature from convection was found to be spatially non-uniform with highly localised regions of temperature spanning from ambient to 150 °C. This gas-phase heating continued well downstream from the limits of the region with radiative heating, with the time-averaged gas temperature increasing with distance at up to 2,200 °C/m on the jet centreline. The temperature of the flow was non-symmetrical in the direction of the heating beam, because the particles attenuate the radiation through absorption and scattering. The addition of radiation at fluxes up to 42.8 MW/m² did not significantly change the particle number density distribution within the region investigated here.Elliott W. Lewis, Timothy C. W. Lau, Zhiwei Sun, Zeyad T. Alwahabi, Graham J. Natha

Study of Bc --> J/psi pi, etac pi decays with perturbative QCD approach

The Bc --> J/psi pi, etac pi decays are studied with the perturbative QCD approach. It is found that form factors and branching ratios are sensitive to the parameters w, v, f_J/psi and f_etac, where w and v are the parameters of the charmonium wave functions for Coulomb potential and harmonic oscillator potential, respectively, f_J/psi and f_etac are the decay constants of the J/psi and etac mesons, respectively. The large branching ratios and the clear signals of the final states make the Bc --> J/psi pi, etac pi decays to be the prospective channels for measurements at the hadron collidersComment: 21 pages, revtex

Early Carnian conodont fauna at Yongyue, Zhenfeng area and its implication for Ladinian-Carnian subdivision in Guizhou, South China

The subdivision of Ladinian and Carnian strata in Guizhou, South China has been a matter of intense debate because of the paucity of age-diagnostic faunas. Here we have carried out a detailed conodont biostratigraphic investigation on the Yangliujing, Zhuganpo and Wayao formations in the Yongyue section of western Guizhou Province. Conodonts are only prolific in the Zhuganpo and Wayao formations. Three genera and twenty species are identified, including two new species Quadralella wanlanensis n. sp. and Quadralella yongyueensis n. sp. They represent a rather endemic fauna of latest Ladinian to early Carnian age. Four conodont zones are established. They are, in the ascending order, the Paragondolella foliata, Quadralella polygnathiformis, Quadralella tadpole, and Quadralella aff. praelindae zones. Thus in the study area, the Zhuganpo Formation is generally of early Carnian (Julian 1) age whilst the Wayao Formation probably extends from the Julian 2 into the late Carnian (Tuvalian substage). The Ladinian–Carnian boundary (LCB) cannot be precisely defined due to the absence of the ammonoid Daxatina Canadensis and the paucity of conodonts. However, the LCB is unlikely lower than the Yangliujing–Zhuganpo formation contact. The Julian 1–Julian 2 (early Carnian) substages boundary is defined in the uppermost Zhuganpo Formation by the occurrence of basal Julian 2 ammonoid Austrotrachyceras ex gr. A. austriacum and is also evidenced by the disappearance of most short-range Julian 1 conodonts in the overlying Wayao Formation

Periodicities in the Daily Proton Fluxes from 2011 to 2019 Measured by the Alpha Magnetic Spectrometer on the International Space Station from 1 to 100 GV

We present the precision measurement of the daily proton fluxes in cosmic rays from May 20, 2011 to October 29, 2019 (a total of 2824 days or 114 Bartels rotations) in the rigidity interval from 1 to 100 GV based on 5.5×109 protons collected with the Alpha Magnetic Spectrometer aboard the International Space Station. The proton fluxes exhibit variations on multiple timescales. From 2014 to 2018, we observed recurrent flux variations with a period of 27 days. Shorter periods of 9 days and 13.5 days are observed in 2016. The strength of all three periodicities changes with time and rigidity. The rigidity dependence of the 27-day periodicity is different from the rigidity dependences of 9-day and 13.5-day periods. Unexpectedly, the strength of 9-day and 13.5-day periodicities increases with increasing rigidities up to ∼10 GV and ∼20 GV, respectively. Then the strength of the periodicities decreases with increasing rigidity up to 100 GV.</p

Microwave assisted laser-induced breakdown spectroscopy at ambient conditions

Abstract not availableJan Viljanen, Zhiwei Sunb, Zeyad T. Alwahab

Contactless thermal diagnostics of acoustically levitated biomass under uniform high flux radiation

This study reports a contactless optical system developed for investigating the fast-thermal processes of biomass under high-flux radiation, particularly for understanding the synergy of renewable biomass and concentrated solar energy. A biomass tablet was successfully suspended using a home-built acoustic levitator in a well-controlled oxygen-lean atmosphere and was irradiated under uniform radiation with a high flux of approximately 1 MW/m2, i.e., ∼1000 suns. The biomass temperature profile was spatio and temporally recorded using an infrared thermographic camera. Several key thermal parameters of the biomass were determined, including the time-resolved heating rate and the ignition temperature. Three different thermal processes were identified from the temperature profiles. These are an initial fast-heating process, a following slow-heating process, and a final biomass ignition depending on the flux of radiation. At high flux, these three processes are merged, and only a steep linear increase in temperature was observed. The contactless apparatus provides the high-fidelity data of the heating rates of biomass and can benefit the understanding of the fast-thermal process associated with biomass under high flux concentrated solar radiation.Wanxia Zhao, Zhiwei Sun, Zeyad T. Alwahab

Emissivity and absorption function measurements of Al(2)O(3) and SiC particles at elevated temperature for the utilization in concentrated solar receivers

Solar thermal receivers collect and can store concentrated solar radiation using solid particles. Solid ceramic particles have shown to be a practical and efficient heat transfer media in solar-particle receivers, however, their emissivity and absorptivity at high temperatures are scarcely reported. This gap has led to large uncertainties in the assessment of solar thermal receivers’ efficiency. In this work, an experimental method was developed to measure the emissivity and absorption function of solar particles at elevated temperatures up to 1200 K. Two types of solar particles, aluminum oxide (Al₂O₃, ∼95% purity) and silica carbide (SiC, ∼99% purity), were studied, particularly aiming to understand the dependence of emissivity and absorption function on temperature. Using a heat transfer model, the emissivity of particles was evaluated based on the fitting of the cooling rate, while the particle absorption function was obtained by fitting of the heating rate, following a well-controlled heating radiation at 910 nm. It was found that the emissivity values of the two particles are independent of temperature, showing constant values of 0.75 ± 0.015 and 0.92 ± 0.012 for Al2O3 and SiC respectively, in the temperature from 300 to 1200 K. The absorption function was found to be increased nonlinearly with temperature for Al₂O₃, while that of SiC dropped slightly. These absorption functions are specified for 910 nm. Using the evaluated experimental values of emissivity and absorption function, the maximum temperature and the temperature rise time of micro-sized particles (hundreds of micrometers) under different radiation fluxes were simulated taking into account the effect of particle diameter.Wanxia Zhao, Zhiwei Sun, Zeyad T. Alwahab

Soluble salts in a Quaternary loess-soil sequence near Xining and the environmental implications

Dust composition is reflective to environmental conditions of the source areas, the transportation dynamics, and the post-depositional environments. In this study, soil chemical analysis and micromorphological approaches were conducted on a loess-soil sequence of the last 900ka near Xining at the western most part of the Loess Plateau. Thirty representative samples were selected to determine the pH, exchangeable sodium percentage (ESP), cation exchangeable capacity (CEC), and the exchangeable cations. Soil solutions of sixty representative samples were analyzed to determine the composition of soluble salts.All the analyzed samples show alkaline properties with the pH values varing from 8.5 to 10.0. pH values in loess layers (generally >9.0) are higher than in soil layers (generally <9.0). Except the Holocene soil S0 with weak alkaline property, ESP in loess varies from 15 ％ ~25 ％ while it ranges from 20 ％ ~40 ％ in soils. Both loess and soil layers contain a significant amount of soluble salts, including abundant sulfates that are thought to have significant climate impacts. Na+ represents a proportion of more than 70 ％ among cations. Among anions, CO2-3 and HCO-3 are more abundant in loess layers than in soil layers while SO2-4 and Cl- are more abundant in soils. These indicate that loess layers contain more Na2 CO3 and NaHCO3, while soil layers mainly contain NaCl and Na2SO4. Overall, soluble salts are much more abundant in soils than in loess layers.Micromorphological investigations show a weak weathering intensity of the studied soils, characterized by relatively fresh feldspars and biotite grains. All soil samples still contain detrital carbonates, suggesting their weakly developed steppe condition. These do not support a chemical weathering origin of the soluble salts. Because the studied section is located on high-terraces and no hydromorphic features were observed in either loess or soil layers, these soluble salts were unlikely to be originated from groundwater. Consequently, we interpret that these soluble salts were derived from eolian dust during the loess deposition. Salt-bearing dust should have been originated from the surrounding alkaline and saline lakes through eolian erosion.Our results therefore revealed a detrital origin for the abundant soluble salts. These indicate that alkaline/saline lakes have been constantly developed in the surrounding areas over the last 900ka. These lakes were probably seasonal and have experienced wind erosion during dry seasons. A most startling feature is the much higher content of soluble salts in loess layers than in soil layers, indicating that the interglacial dusts contain more soluble salts than glacial dusts. These might be attributable to the more abundant rainfalls associated with the higher temperatures and stronger evaporation during the interglacial times

The effect of particle size and volumetric loading on the gas temperature distributions in a particle-laden flow heated with high-flux radiation

The instantaneous, spatially resolved gas-phase temperature distribution within a particle-laden flow heated using high-flux radiation has been measured for a series of heating fluxes, particle volumetric loadings and particle diameters using two-colour laser induced fluorescence of toluene. The temperature of the gas downstream from the start of the heating region was found to increase with an increase in heat flux, an increase in particle loading and a decrease in particle diameter. Coherent regions of high and low temperature in the instantaneous flow associated with spatial variations in the particle distribution were identified for all particle diameters investigated. The time-averaged gas-phase temperature on the jet axis was found to increase approximately linearly with distance in the region downstream from the heating beam to the edge of the measurement region investigated, indicating near-constant convective heat transfer due to the large temperature difference between the gas and radiatively heated particles throughout this region. The axial gradient of gas-phase temperature with distance was also calculated using a simplified, one-dimensional heat transfer model. The difference between the model and measurements was, on average, less than 20%, with the magnitude of this difference found to increase with a decrease in particle diameter and an increase in particle loading.Elliott W. Lewis, Timothy C.W. Laua, Zhiwei Suna, Zeyad T. Alwahabi, Graham J. Natha