Bivalvia biostratigraphy of Aksütlü region (Hekimhan, NW Malatya, Türkiye) and paleoclimatological interpretations

Oxygen and Carbon Isotope Ratios in Martian Carbon Dioxide: Measurements and Implications for Atmospheric Evolution

Concerning climatic conditions during the Miocene Climate Optimum (MCO), global temperatures were about 3-4°C warmer than modern, and characterized by globally lower ice volume. Indian Ocean Sub-Antarctic Mode Water (SAMW) is primarily formed south of 30°S and is the primary return path for deep waters to the surface, migrating and intermixing northwards at Intermediate Water (IW) depths. Today, the SAMW carries access nutrients into the lower latitudes, strongly impacting latitude productivity. During warmer climates, decreasing sea ice may increase nutrient trapping in the Southern Ocean, reducing the nutrient flux through SAMW into the lower latitudes. Thus, the MCO may indicate future climate, nutrient transport, and SAMW formation by exploring differences between cooler (modern) and warmer (MCO) climates.Ocean Drilling Project (ODP) Site 752, located on Broken Ridge in the southeastern Indian Ocean at a water depth of 1086.3 m, is a key location for investigating changes in IW conditions in the Indian Ocean after the MCO and the Middle Miocene Climatic Transition (MMCT). In particular, the reactions to global warming and the reorganization of oceanic and atmospheric circulation following the MCO and MMCT can be detected. This also includes the analysis of SAMW, Antarctic Intermediate Water (AAIW), and Tasman Leakage (TL).The present study aims to reconstruct paleoenvironmental conditions and bottom-water oxygenation at Site 752 during the Middle to Late Miocene (15-8 Myrs). To achieve this, we apply benthic foraminifera assemblages as proxies for bottom water oxygenation, for example, enhanced Benthic Foraminifera Oxygen Index (eBFOI), paleoproductivity, and stable carbon and oxygen isotopes.Initial results in the Middle to Late Miocene show an occurrence of oxic benthic foraminifera at a relatively constant abundance, especially in the early Late Miocene. In addition, in a relatively high oxic environment, an increase of dysoxic conditions occurred during the early Late Miocene, with peaks of abundance in dysoxic and deep infaunal benthic foraminifera. A co-occurrence of infaunal dysoxic and epifaunal oxygen-rich species is accompanied by enhanced current winnowing and an increase of nutrient flux during the Late Miocene (Lyu et al., 2023; DOI: 10.1029/2023PA004761). These data indicate that during the Late Miocene, since approximately 10 Ma, the strengthening of SAMW and AAIW formation resulted in notable changes in bottom-water conditions at Broken Ridge, such as increased current winnowing. The observed changes in IW are potentially linked to the shift of the southern hemisphere westerlies towards the north and the subsequent northward migration of the frontal system in the southern hemisphere around Antarctica after 12 Ma.

Chemical and isotopic (O, H, C) composition of surface waters in the catchment of Lake Donggi Cona (NW China) and implications for paleoenvironmental reconstructions

Isotopic evidence of saber-tooth development, growth rate, and diet from the adult canine of Smilodon fatalis from Rancho La Brea

Abstract: Predominant Zn‐rich ore bodies were found to a deep part of the Sakonishi area in the Kamioka mining district, Japan. The ore mineralization was recognized at 230 to 300m above sea level in the Sakonishi area. Since crystalline limestone is broadly distributed over the area, and the variation in isotopic composition is easily detected, the isotopic prospecting should be powerful in surveying of the extent of the ore bodies and the related hydrothermal system. Although isotopic anomalies have been extracted two‐dimensionally so far, three‐dimensional information is possibly more powerful.In this paper, Zn‐rich ore bodies in the Sakonishi area are treated as hydrothermal ore deposits, and the importance of the activity of hydrothermal fluids during mineralization is emphasized. Oxygen and carbon isotopic ‘iso–surfaces’ are three‐dimensionally calculated for the Sakonishi area. The δ18O values of crystalline limestone from the surface and from the drill holes range from +8. 1 to +21. 1% and from –2. 7 to +20. 4%, respectively. The δ13C values of crystalline limestone from the surface and from the drill holes range from –1. 0 to +5. 3% and from –7. 7 to +4. 6%, respectively. The oxygen and carbon iso‐topic ratios at the mineralization level are extremely low, but there are exceptions as to carbon isotopes. The oxygen isotopic ratios of crystalline limestone may decrease by isotopic exchange reaction with a hydrothermal fluid, while the carbon isotopic ratios slightly change. Since the precipitated calcite from a hydrothermal fluid has low carbon isotopic ratio and various oxygen isotopic ratio depending on the formation temperature, the bulk sample of crystalline limestone containing the precipitated calcite has oxygen and carbon isotopic ratios of relatively low values accordingly. Thus the decrease mechanism for carbon isotopic ratio of crystalline limestone is different from that for oxygen isotopic ratio. Samples with the carbon isotopic ratio of –4 to –8% are considered to be crystallized from hydrothermal fluids.Since the oxygen and carbon isotopic ratios of crystalline limestone at the ore mineralization level are low, the ore bodies are considered to have formed by a prominent hydrothermal activity. Thus oxygen and carbon isotopic ratios of crystalline limestone can be used as an indicator of the related hydrothermal activity. The alteration such as chloritization is intense near fractures in the Sakonishi area, showing that the hydrothermal system is controlled by a fracture system. It is assumed that the decreased isotopic ratios indicate the high degree of reactivity with hydrothermal fluids, and the depleted zone in oxygen and carbon isotopes may correspond to the conduit of the hydrothermal fluids.

Carbon and hydrogen isotope ratios of cellulose nitrate and oxygen isotope ratios of cellulose from species of greenhouse plants having different photosynthetic modes were determined. When hydrogen isotope ratios are plotted against carbon isotope ratios, four clusters of points are discernible, each representing different photosynthetic modes: C(3) plants, C(4) plants, CAM plants, and C(3) plants that can shift to CAM or show the phenomenon referred to as CAM-cycling. The combination of oxygen and carbon isotope ratios does not distinguish among the different photosynthetic modes. Analysis of the carbon and hydrogen isotope ratios of cellulose nitrate should prove useful for screening different photosynthetic modes in field specimens that grew near one another. This method will be particularly useful for detection of plants which show CAM-cycling.

Stable carbon and oxygen isotope ratios were measured for carbonate in samples of hadrosaurid tooth enamel and dentine, and gar scale ganoine and dentine from five geologically “contemporaneous“ (two-million-year resolution) and geographically distant late Campanian formations (Two Medicine, Dinosaur Park, Judith River, Kaiparowits, and Fruitland) in the Western Interior Basin. In all cases, isotopic offsets were observed between enamel and dentine from the same teeth, with dentine being characterized by higher and more variable carbon and oxygen isotope ratios. Isotopic offsets were also observed between gar ganoine and hadrosaur enamel in all sites analyzed. Both of these observations indicate that diagenetic overprinting of enamel isotope ratios did not entirely obfuscate primary signals. Decreases in carbon and oxygen isotope ratios were observed in hadrosaur enamel from east to west, and overlap in isotope ratios occurred only between two of the sampled sites (Dinosaur Park and Judith River Formations).The lack of isotopic overlap for enamel among localities could be due to diagenetic resetting of isotope ratios such that they reflect local groundwater effects rather than primary biogenic inputs. However, the large range in carbon isotope ratios, the consistent taxonomic offsets for enamel/ganoine data, and comparisons of enamel-dentine data from the same teeth all suggest that diagenesis is not the lone driver of the signal. In the absence of major alteration, the mostly likely explanation for the isotopic patterns observed is that hadrosaurids from the targeted formations were eating plants and drinking waters with distinct isotopic ratios. One implication of this reconstruction is that hadrosaurids in the Late Cretaceous of the Western Interior did not migrate to an extent that would obscure local isotopic signatures.

Carbonate cement is the most abundant cement type in the Fourth Member of the Xujiahe Formation in the Xiaoquan-Fenggu area of the West Sichuan Depression. Here we use a systematic analysis of carbonate cement petrology, mineralogy, carbon and oxygen isotope ratios and enclosure homogenization temperatures to study the precipitation mechanism, pore fluid evolution, and distribution of different types of carbonate cement in reservoir sand in the study area. Crystalline calcite has relatively heavy carbon and oxygen isotope ratios (δ13C = 2.14‰, δ18O = −5.77‰), and was precipitated early. It was precipitated directly from supersaturated alkaline fluid under normal temperature and pressure conditions. At the time of precipitation, the fluid oxygen isotope ratio was very light, mainly showing the characteristics of a mixed meteoric water-seawater fluid (δ18O = −3‰), which shows that the fluid during precipitation was influenced by both meteoric water and seawater. The calcite cement that fills in the secondary pores has relatively lighter carbon and oxygen isotope ratios (δ13C = −2.36‰, δ18O = −15.68‰). This cement was precipitated late, mainly during the Middle and Late Jurassic. An important material source for this carbonate cement was the feldspar corrosion process that involved organic matter. The Ca2+, Fe3+ and Mg2+ ions released by the clay mineral transformation process were also important source materials. Because of water-rock interactions during the burial process, the oxygen isotope ratio of the fluid significantly increased during precipitation, by about 3‰. The dolomite cements in calcarenaceous sandstone that was precipitated during the Middle Jurassic have heavier carbon and oxygen isotope ratios, which are similar to those of carbonate debris in the sandstone (δ13C = 1.93‰, δ18O = −6.11‰), demonstrating that the two are from the same source that had a heavier oxygen isotope ratio (δ18O of about 2.2‰). The differences in fluid oxygen isotope ratios during cement precipitation reflect the influences of different water-rock interaction systems or different water-rock interaction strengths. This is the main reason why the sandstone containing many rigid particles (lithic quartz sandstone) has a relatively negative carbon isotope ratio and why the precipitation fluid in calcarenaceous sandstone has a relatively heavier oxygen isotope ratio.

Breath tests in domestic and foreign medicine are recognized as an effective and safe way to identify pathogens in the gastrointestinal tract, in particular the Helicobacter Pylori bacteria. At the end of the 20th century, a urease breath test was introduced into clinical practice to diagnose diseases of the gastrointestinal tract; it was based on the use of urea labeled with a stable isotope 13C ( 13C-urease breath test). The essence was to measure the delta value of the ratio of carbon and oxygen isotopes in exhaled air.Over decades of clinical practice of using this test, a wealth of experience related to the diagnosis of diseases caused, including by the Helicobacter Pylori bacteria has been accumulated. A significant amount of knowledge has also been accumulated in terms of metrological support of the carbon and oxygen isotope delta in exhaled air.The article describes the procedure and results of developing a development of a measurement standard of carbon and oxygen isotope delta in exhaled air, implemented within the R&D a/c No. «Sistema-2020-М» at the D. I. Mendeleyev Institute for Metrology (VNIIM). The authors presented the theoretical study, test methodology, their sequence and results. The article also contains a report on the international comparisons CCQM-P204 “Isotope ratios of CO2 (δ13VPDB and δ18VPDB) in pure CO2” with the application of the measurement standard developed by VNIIM. The metrological characteristics of the measurement standard obtained during the comparisons correspond to the most accurate measurements of the ratio of carbon and oxygen isotopes, which guarantees the recognition of the measurement results at the international level. Considering the high demand for breath tests in medical practice and obvious prospects of this type of diagnostics, further research will be aimed at creating a State Primary Standard for the delta value unit of the ratio of isotopes of carbon, oxygen, hydrogen based on the created measurement standard and the development of certified reference materials of the ratio of isotopes of carbon, oxygen, hydrogen in liquid, solid, and gaseous media, including for the purpose of replacing foreign-made materials.

Intercolony variability of skeletal oxygen and carbon isotope signatures of cultured Porites corals: Temperature-controlled experiments

Isotopic analysis of archaeobotanicals to reconstruct past climates: Effects of activities associated with food preparation on carbon, hydrogen and oxygen isotope ratios of plant cellulose

Stable isotope analysis of cellulose is an increasingly important aspect of ecological and palaeoenvironmental research. Since these techniques are very costly, any methodological development which can provide simultaneous measurement of stable carbon and oxygen isotope ratios in cellulose deserves further exploration. A large number (3074) of tree-ring α-cellulose samples are used to compare the stable carbon isotope ratios (δ(13)C) produced by high-temperature (1400°C) pyrolysis/gas chromatography (GC)/isotope ratio mass spectrometry (IRMS) with those produced by combustion GC/IRMS. Although the two data sets are very strongly correlated, the pyrolysis results display reduced variance and are strongly biased towards the mean. The low carbon isotope ratios of tree-ring cellulose during the last century, reflecting anthropogenic disturbance of atmospheric carbon dioxide, are thus overestimated. The likely explanation is that a proportion of the oxygen atoms are bonding with residual carbon in the reaction chamber to form carbon monoxide. The 'pyrolysis adjustment', proposed here, is based on combusting a stratified sub-sample of the pyrolysis results, across the full range of carbon isotope ratios, and using the paired results to define a regression equation that can be used to adjust all the pyrolysis measurements. In this study, subsamples of 30 combustion measurements produced adjusted chronologies statistically indistinguishable from those produced by combusting every sample. This methodology allows simultaneous measurement of the stable isotopes of carbon and oxygen using high-temperature pyrolysis, reducing the amount of sample required and the analytical costs of measuring them separately.

Over the late Holocene, a variety of hydroclimate-sensitive proxies have identified substantial, multidecadal changes in Indian summer monsoon (ISM) precipitation, the most prominent of which is the “4.2 ka event”. This interval, dated to ~4.2-3.9 ka, is associated with severe droughts across South Asia that are linked to societal change. Given the absence of the 4.2 ka event in polar records, the 4.2 ka event is generally associated with low latitude forcings, but no clear consensus on its origins has been reached.We investigated the ISM response to the 4.2 ka event through analysis of aragonite stalagmites from Siddha cave, formed in the lower Paleozoic Dhading dolomite in the Pokhara Valley of central Nepal (28.0˚N, 84.1˚E; ~850 m.a.s.l.). The climate of this region is dominated by small monthly variations in air temperature (21±5˚C) but strong precipitation seasonality associated with the ISM: ~80% of the annual 3900 mm of rainfall occurs between June and September. High uranium and low detrital thorium abundances in these stalagmites yield precise U/Th ages that all fall within stratigraphic order. These dates reveal continuous growth from 4.30-2.26 ka, interrupted only by a hiatus from 3.27-3.10 ka. Overlap with coeval aragonite stalagmites reveals generally consistent trends in carbon and oxygen isotope ratios, suggesting that these stalagmites reflect environmental variability and not secondary (e.g., kinetic) effects.Many stalagmite-based paleomonsoon reconstructions rely on oxygen isotope ratios, which track amount effects in regional rainfall. However, our on-going rainwater collection and analysis program, as well as a previous study conducted in Kathmandu, 120 km the east of Siddha cave, reveals that amount effects in precipitation are weak in this region, particularly during the monsoon season, and thus we rely instead on carbon isotope ratios, which have been demonstrated to track site-specific effective precipitation. Siddha cave stalagmite carbon isotopes, in contrast to other South Asian proxy records, indicate that ISM rainfall increased at Siddha cave from 4.13-3.91 ka. As a further test of this result, we analyzed uranium abundances in the section spanning 4.3-3.4 ka. Uranium serves as an indicator of prior aragonite precipitation and thus of hydroclimate, and like carbon isotopes, suggests increased ISM rainfall coincident with the 4.2 ka event.This precipitation anomaly is nearly identical in timing and structure but anti-phased with stalagmites from Mawmluh cave, northeastern India. We investigated the climatic origins of this precipitation dipole using observational data from the Global Precipitation Climatology Centre (GPCC) and Hadley Center Sea Ice and Sea Surface Temperature (HadISST) products. Preliminary spatial composites suggest that large precipitation differences between Mawmluh and Siddha caves are associated with SST anomalies in the equatorial Pacific. Additionally, superposed Epoch Analysis shows relatively rapid eastern Indian Ocean cooling during the summer monsoon season coeval with large precipitation differences between these sites. Our findings lend support to a tropical Indo-Pacific origin of the 4.2 ka event.

Carbon and Oxygen Isotope Ratios in Rona Limestone, Romania. The carbon and oxygen isotopic compositions of limestones provide criteria for the evaluation of the depositional environment. For Jurassic and younger samples, the best discrimination between marine and fresh-water limestones is given by Z parameter, calculated as a linear correlation between δ 13 C and δ 18 O (‰ PDB). Rona Limestone (Upper Paleocene - Lower Eocene), outcropping on a small area in NW Transylvania (Meses area) is a local lacustrine facies. There, it divides Jibou Formation into the Lower Red Member and the Upper Variegated Member, respectively. Recently, a sequence containing a marine nannoplankton assemblage was identified in the base of Rona deposits. The main goal of our study was to characterize, based on the isotopic record, the primary environment of formation of the deposit, as well as that in which some diagenetic processes (the formation of dolomite and of green clay around the siliceous chert nodules) took place. Ten samples representing limestones, dolomitic limestone, marls and the green carbonate-rich clay were studied from petrographical and mineralogical points of view, and the carbon and oxygen isotopic ratios from the carbonate (calcite) component were measured. In conclusion, it was found that the procedure of extraction of CO2 we used enabled the discrimination between the isotopic prints of calcite vs. dolomite. This pleads for considering our results as a primary isotopic pattern in the bulk rock. The oxygen and carbon isotope data indicate a fresh- water depositional environment with Z<120. The δ 13 C mean value (-4.96 ‰ PDB) is, generally, representative for fresh-water carbonates of the Tertiary period. The same environment characterized also the formation of carbonates within the green clay.

Human Impacts on Tree‐Ring Growth Reconstructed from Stable Isotopes