Search

The Eemian (~130 to 115 ka yr BP), also called Marine Isotope Stage (MIS) 5 or the Last Interglacial, was the most recent interglacial period prior to the Holocene. Since temperatures during the Eemian were, on average, ~2 °C warmer than today, studies of this period offer insights into how variables like effective moisture may change under near-future warming scenarios. Such information could improve climate projections for drought-prone regions like the Mediterranean that are particularly vulnerable to future warming. Therefore, a study was initiated to investigate carbonate-rich, Eemian-aged sediments from Padul Wetland (southern Iberia), a site which contains one of the oldest (>200 ka yr) continuous sediment records in the Mediterranean. The resulting proxy record includes stable isotope (δ13C and δ18O) and clumped isotope (Δ47) compositions of aquatic gastropods (e.g., Radix balthica, Anisus spirorbis) and bivalves (e.g., Pisidium sp.). An age-depth model for the entire 200 000-year record was previously established using a mixture of 43 Accelerator Mass Spectrometry (AMS) radiocarbon dates, 10 Amino Acid Racemization (AAR) dates from gastropods (hydrobiid Milesiana schuelei), and two different sediment accumulation rates (SAR) for peat and carbonate/marl lithologies. Variations in δ18O and δ13C closely correspond with the Pollen Climate Index (PCI) for Padul, which is used to discriminate between cold/arid and warm/humid conditions. The close resemblance of these records suggests that variations in δ18O and δ13C at Padul are also sensitive to moisture changes. Variations in δ18O and δ13C of shelly fauna at Padul also resemble shifts in δ18O from the NGRIP ice core(Greenland) and alkenone-based marine sea surface temperature (SST) records of the western Mediterranean region. Similarities among these records underscore the sensitivity of Padul Wetland to regional- and global-scale climatic changes as well as more local moisture variations. One measurement of Δ47 in the aquatic gastropod Radix balthica suggests that average temperatures at Padul during the Eemian were 19.7 ± 2.6 °C, which is consistent with marine records from the Iberian margin. The interpretation of Δ47 in Pisidium sp. is more complicated, perhaps due to vital effects or because Pisidium sp. have highly variable lifespans and individuals that lived only a few months may not reflect average annual conditions. In summary, the stable and clumped isotope records generated in this ongoing study build on previous Eemian-aged reconstructions from southern Iberia by providing higher resolution proxy data constrained by quantitative temperature reconstructions. This research deepens our understanding of how effective moisture in southern Iberia may change in the near future.

The central Apennines are a Cenozoic fold-and-thrust belt that has been affected by post-orogenic extension in its axial region since the end of the early Pliocene (ca. 4 Ma). Post-orogenic extension generated several intermontane basins bounded by high-angle normal faults, striking NW-SE, subparallel to the backbone of the chain. The Monte Pettino and the Monte Marine seismogenic faults (MPF, MMF) are the boundary faults of the western portion of the late Pliocene-Quaternary L’Aquila intermontane basin. Their long-term activity is typified by exhumed fault cores that coexist with active fault strands localised at the fault hanging walls, providing evidence of a polyphase tectonic activity. The fault cores are decorated by diffuse dolomitization, which indicates structurally controlled fluid-flow and metasomatism. To constrain the long-term (space-time) evolution of the MPF-MMF faults, we integrated fieldwork, stable isotope systematics (δ18O, δ13C and Δ47), carbonate thermoluminescence and U-Th dating. Our results highlight two main tectonic phases, with different structural evolution and fluid-rock interaction. The first phase corresponds to the development of a major cataclastic zone, defined by meter-thick, SW-dipping (65-70°), fault cores exposed at the piedmont of the MPF-MMF ridges. The C-O systematics of the cataclasite and of the associated calcite slickenfibers, which are in the range of the carbonate bedrock, indicate a "closed" system behaviour during fault nucleation and development. Preliminary results from Δ47 thermometry of syn-kinematic carbonate structures indicate temperatures of 34 ± 2 °C. Thermoluminescence dating of dolomite clasts in the fault zone indicates age in the range of 3.0 – 3.4 Ma, whilst the cataclastic fault core is younger (< 800 ka). The second phase is mainly recorded in upper Pleistocene sedimentary Breccias (ca. 350 ka) which unconformably cover the bedrock and the exhumed fault cores at the SE termination of the MPF. It consists of anastomosed, high-angle WNW-ESE striking fault strands, spaced meters apart and with cm-m displacements, associated with carbonate veining and travertines. Stable isotopes measured from the fault slickenfibers, carbonate veins and travertines show negative δ13C and δ18O values, suggesting a depositional system dominated by meteoric fluid ("open" system) with an important contribution of organic carbon. Travertines and veins precipitated at colder temperatures (12 ± 4 °C), in the range of the average local air temperatures, thus excluding precipitation from a hydrothermal circuit. Moreover, their U-Th ages range between 182 and 331 ka, compatible with the temporal constraints from stratigraphic data. Structural and isotopic results do not support tectonic reactivation of the cataclastic core of the MPF during the middle-late Pleistocene, confirming the stratigraphic evidence. Our results provide the first absolute age constraint on the post-orogenic extensional faulting in the L’Aquila basin, demonstrating a two-stage fault activity, characterised by a change from localised (from ca. 3 to ca. 0.8 Ma) to delocalised faulting (200-300 ka to present). We infer that this change in the style of extensional faulting was consequence of the evolving rheological structure of the fault zones, primarily regulated by the feedback and interactions involving structurally-controlled fluid flow, rock metasomatism and cataclastic processes in space and time.

Ostracod shells are small aquatic crustaceans (0.3 - 5 mm) capable of recording climatic and environmental changes at high-resolution in sedimentary archives of modern and ancient lakes. Their stable low-Mg calcite shell mineralogy makes them ideally suited for targeted geochemical analyses. Therefore, ostracods represent the best candidate to develop a new carbonate clumped isotope (∆47) lacustrine paleothermometer that disentangles and quantifies the effects of global climate changes at regional scale. To establish the relationship between ∆47 and the temperature for ostracod shells, three different species were collected in monitored environments at 4°C and 12°C and one was cultivated in the lab at 23°C. Our results show a linear regression between ostracod-∆47 and calcification temperature that is in agreement with previous published calibrations. This implies that ostracods are an equally-good recorder of (paleo)temperatures as other carbonaceous micro- or macrofossils from the marine realm. Moreover, we report the absence of a consistent offset between the species Eucypris virens and Bradleystrandesia fuscata coming from the same environment and precipitated at the same temperature. This observation suggests the absence of a vital effect at the genus and species level. Samples from shallow Lake Trasimeno (Italy) cover the last 50000 years and confirm the ability of the ostracod clumped-isotope thermometer as well as the absence of vital effect in the fossil record. The new paleothermometer identifies warmer/colder and humid/dryer conditions during Greenland Interstadial and Greenland Stadial/Heinrich events respectively.These findings show that the ostracod-∆47 thermometer has several advantages that makes it an attractive tool for scientific drilling: (i) It is independent of ostracod species and geography. Hence, one can also use endemic species. (ii) It is applicable throughout geological time, as extinct species can be used. (iii) Temperature reconstructions for all environments where ostracods live are within reach. We emphasize that also high-diversity lacustrine environments are suitable for ∆47 analysis, by mixing shells of different species together. This is of particular importance when working with small samples size from sediment cores.The establishment of this new lacustrine proxy enables precise paleoclimatic reconstructions from different climate belts. It opens the door to new high-resolution continental paleoclimate and paleoenvironmental reconstructions and therefore has the potential to be a key tool in future lacustrine drilling in the ICDP framework.

The Marine Isotope Stage 3 (MIS 3) – a period between 60 and 27 ka ago during the last glacial cycle – experienced several abrupt climatic warming phases known as Dansgaard-Oeschger (DO) events. The DO events are abrupt transitions from cold (stadial) to mild (interstadial) climate conditions.Speleothems are precious continental records and provide important climatic information at high resolution. However, during this time period, the north central Europe is less studied because the MIS 3 is generally not recorded, due to the climatic conditions. Here, we present the first Belgium continuous speleothem (flowstone) record covering the early MIS 3 (from 60 to 40 ka) from the Verviétois Gallery that is part of the Han sur Lesse cave system (southern Belgium). High resolution bulk stable isotope and elemental combined with U-Th dating are used to define the Belgium climatic variability. Additionally, clumped isotope measurements have been performed to reconstruct temperature to better constrain climatic response during the DO 16-12.The multiproxy approach used to investigate the speleothem record shows a regional response to the global climate conditions during MIS3. The d13C and d18O values as well as the elemental analyses (Mg, Ba and Sr as water availability proxies and P and Zn as soil development) mirror the DO 16 and 12 events indicating dry-wet and cold-warm changes. During interstadials events low values of d18O and d13C and Mg, Ba and Sr content suggest wet/warm conditions, while the increase of isotopic and elemental values during the stadials support a climate deterioration with cooling and drier conditions. The clumped-isotope temperatures, performed on the DO 16 and 12, suggest warm interstadials (12OC +/- 2OC) and cold stadials (7OC +/- 2OC) climate.During the DO12, a delay in the climatic amelioration and the vegetation is observed. This delay, also noted in south-west France cave (Villars cave), seems to be linked to a delay between increase of temperature and water availability allowing the soil above the cave to growth. Also, a climatic deterioration occurred after the DO11, with an increase time lag from the north to the south of Europe, showing a progressive cooling to the south Europe. It is interesting to note that this gradual cooling in Europe coincides, withing dating error bars, with the potential progressive north-south decline of the Neanderthals in Europe.

International audience; Assuming that foraminiferal clumped isotope (Δ47) values are independent of seawater salinity and pH, the combination of Mg/Ca, δ18O and Δ47 values, may in theory allow us to disentangle the temperature, salinity/δ18Osw and pH signals. Here, we present a new Mg/Ca-Δ47 dataset for modern planktonic foraminifera, from various oceanographic basins and covering a large range of temperatures (from 0.2 to 25.4 °C). These measurements were performed on the same samples and species as the ones used for the foraminiferal Δ47 calibration of Peral et al. (2018), allowing comparison between both Mg/Ca and Δ47 paleothermometers (excluding the two benthic foraminiferal data points). There is a good agreement between these two paleothermometers when the Mg/Ca-temperature is corrected for seawater salinity and pH, suggesting that foraminiferal Δ47 may not be influenced by salinity or pH. However, our results show that Δ47 temperature uncertainties still limit our ability to reconstruct pH and δ18Osw from the combination of Mg/Ca, δ18O and Δ47 in a useful manner. We also find that disagreements between Mg/Ca and Δ47 values in G. bulloides persist after correction for vital, salinity and pH effects, suggesting that other process(es) may also influence Mg/Ca in this species. This study also provides an updated I-CDES version of the previously published planktonic and benthic foraminiferal Δ47 calibration of Peral et al. (2018), covering a range of temperature from -2 to 25.4 °C.

The Pliocene sedimentary record provides a window into Earth's climate dynamics under warmer-than-present boundary conditions. However, the Pliocene cannot be considered a stable warm climate that constitutes a solid baseline for middle-of-the-road future climate projections. The increasing availability of time-continuous sedimentary archives (e.g., marine sediment cores) reveals complex temporal and spatial patterns of Pliocene ocean and climate variability on astronomical timescales. The Perth Basin is particularly interesting in that respect because it remains unclear if and how the Leeuwin Current sustained the comparably wet Pliocene climate in Western Australia, as well as how it influenced Southern Hemisphere paleoclimate variability. To constrain Leeuwin Current dynamics in time and space, this project obtained eight clumped-isotope Δ47 paleotemperatures and constructed a new orbitally resolved planktonic foraminifera (Trilobatus sacculifer) stable isotope record (δ18O) for the Plio-Pleistocene (4–2 Ma) interval of International Ocean Discovery Program (IODP) Site U1459. These new data complement an existing TEX86 record from the same site and similar planktonic isotope records from the Northern Carnarvon Basin (Ocean Drilling Program (ODP) Site 763 and IODP Site U1463). The comparison of TEX86 and Δ47 paleothermometers reveals that TEX86 likely reflects sea surface temperatures (SSTs) with a seasonal warm bias (23.8–28.9 ∘C), whereas T. sacculifer Δ47 calcification temperatures probably echo mixed-layer temperatures at the studied Site U1459 (18.9–23.2 ∘C). The isotopic δ18O gradient along a 19–29∘ S latitudinal transect, between 3.9 and 2.2 Ma, displays large variability, ranging between 0.5 ‰ and 2.0 ‰. We use the latitudinal δ18O gradient as a proxy for Leeuwin Current strength, with an inverse relationship between both. The new results challenge the interpretation that suggested a tectonic event in the Indonesian Throughflow as the cause for the rapid steepening of the isotopic gradient (0.9 ‰ to 1.5 ‰) around 3.7 Ma. The tectonic interpretation appears obsolete as it is now clear that the 3.7 Ma steepening of the isotopic gradient is intermittent, with flat latitudinal gradients (∼0.5 ‰) restored in the latest Pliocene (2.9–2.6 Ma). Still, the new analysis affirms that a combination of astronomical forcing of wind patterns and eustatic sea level controlled Leeuwin Current intensity. On secular timescales, a period of relatively weak Leeuwin Current is observed between 3.7 and 3.1 Ma. Notably, this interval is marked by cooler conditions throughout the Southern Hemisphere. In conclusion, the intensity of the Leeuwin Current and the latitudinal position of the subtropical front are both long-range effects of the same forcing: heat transport through the Indonesian Throughflow (ITF) valve and its propagation through Indian Ocean poleward heat transport. The common ITF forcing explains the observed coherence of Southern Hemisphere ocean and climate records.

The Pliocene sedimentary record provides a window into Earth’s climate dynamics under warmer-than-present boundary conditions. However, the Pliocene cannot be considered a stable warm climate that constitutes a solid baseline for middle-road future climate projections. Indeed, the increasing availability of time-continuous sedimentary archives (e.g., marine sediment cores) reveals complex temporal and spatial patterns of Pliocene ocean and climate variability on astronomical timescales. The Perth Basin is particularly interesting in that respect because it remains unclear if and how the Leeuwin Current sustained the comparably wet Pliocene climate in West-Australia, as well as how it influenced Southern Hemisphere paleoclimate variability. To constrain Leeuwin Current dynamics in time and space, this project constructed a new orbitally-resolved planktonic foraminifera (Trilobatus sacculifer) stable isotope record (δ18O and clumped isotopes Δ47) for the Plio-Pleistocene (4–2 Ma) interval of International Ocean Discovery Program (IODP) Site U1459. It complements an existing TEX86 record from the same site and similar planktonic isotope records from the Northern Carnarvon Basin (ODP Site 763 and IODP Site U1463). The comparison of TEX86 and Δ47 paleothermometers reveals that TEX86 likely reflects sea surface temperatures (SST, 23.8–28.9 °C), whereas T. sacculifer Δ47 calcification temperatures probably echo the state of the lower mixed layer and upper thermocline at the studied Site U1459 (18.2–20.8 °C). The isotopic δ18O gradient along a 19° S–29° S latitudinal transect, between 3.9–2.2 Ma, displays large variability, ranging between 0.5 and 2.0 ‰, whereby a low latitudinal gradient is indicative of a strong Leeuwin Current and vice versa. These results challenge the interpretation that suggested a tectonic event in the Indonesian Throughflow as the cause for the rapid steepening of the isotopic gradient (0.9 to 1.5 ‰) around 3.7 Ma. The tectonic interpretation appears obsolete as it is now clear that the 3.7 Ma steepening of the isotopic gradient is intermittent, with flat latitudinal gradients (~0.5 ‰) restored in the latest Pliocene (2.9–2.6 Ma). Still, the new analysis affirms that a combination of astronomical forcing of wind patterns and eustatic sea level controlled Leeuwin Current intensity. A period of relatively weak Leeuwin Current between 3.7 and 3.1 Ma is advocated; a time interval also marked by cooler conditions throughout the Southern Hemisphere. In conclusion, the intensity of the Leeuwin Current and the latitudinal position of the subtropical front are rooted in the same forcing: Heat transport through the Indonesian Throughflow (ITF) valve propagated to the temperate zone through Indian Ocean poleward heat transport. The common ITF forcing explains the observed coherence of Southern Hemisphere ocean and climate records.

The Mid-Pleistocene transition (MPT) took place between 1,200 Ma and 800 ka (still debated). During this transition, the Earth’s orbitally paced ice age cycles intensified, lengthened from ∼40 000 (∼40 ky) to ∼100 ky, and became distinctly asymmetrical while Earth’s orbital variations remained unchanged. Although orbital variations constitute the first order forcing on glacial-interglacial oscillations of the late Quaternary, they cannot explain alone the shifts in climatic periodicity and amplitude observed during the MPT. In order to explain the MPT, long-term evolution of internal mechanisms and feedbacks have been called upon, in relation with the global cooling trend initiated during the Cenozoic, the expansion of Antarctic and Greenland Ice Sheet and/or the long-term decline in greenhouse gases (particularly CO2). A key point is therefore to accurately reconstruction of oceanic temperatures to decipher the processes driving climate variations.In the present work, we studied the marine sediment core MD96-2048 taken from south Indian Ocean (26*10’482’’ S, 34*01’148’’ E) in the region of the Agulhas current. We compared 5 paleothermometers: alkenone, TEX86, foraminiferal- transfer function, Mg/Ca and clumped isotope. Among these approaches, carbonate clumped-isotope thermometry (∆47) only depends on crystallization temperature, and the ∆47 relationship with planktonic foraminifer calcification temperature is well defined. Since Mg/Ca is not only controlled by temperature but is also affected by salinity and pH. The classical d18O in planktic is dependent on SST and d18Osw, which is regionally correlated with the salinity in the present-day ocean. Assuming that the present-day d18Osw-salinity relation was the same during the MPT, we are able to separate changes in d18Osw from temperature effects and reconstruct past salinity. Combining d18O, Mg/Ca and ∆47 on planktonic foraminifera allow in theory to reconstruct SST, SSS and pH.Here, we measured d18O, Mg/Ca and ∆47 on the shallow-dwelling planktonic species Globigerinioides ruber ss. at the maximal of glacial and interglacial periods over the last 1.2 Ma. Our set of data makes it possible to estimate the long-term evolution of SST, salinity and pH (and thus have an insight into the atmospheric CO2 concentration) across the MPT. Frist, strong differences are observed between the 5 derived-SST: the alkenone and TEX86 recorded the higher temperatures than the other SST proxies. Alkenone derived-SST do not show glacial-interglacial variations within the MPT. The Mg/Ca and transfer function derived-SST show a good agreement each other, while the clumped-isotope derived-SST are systematically colder than the other derived-SST. Then, our ∆47-SST, salinity and pH results clearly show that amplitude of glacial-interglacial variations was insignificant between 1.2 and 0.8 Ma (within the MPT) and increased after the MPT. Finally, we also discussed the potential to use this unique combination of proxies to reconstruct changes of atmospheric CO2 concentration.

International audience; Taking advantage of the recent clumped-isotope methodological developments, the present study focuses on the reconstruction of temperatures and seawater δ18O in the central Mediterranean Sea across the Mid-Pleistocene section from Montalbano Jonico (south of Italy). Our results suggest that Mg/Ca paleothermometer can be biased over several intervals, making clumped-isotope a promising choice to reconstruct past changes in seawater temperature and isotopic composition in the Mediterranean Sea. Our results provide the first clumped-isotope temperature and δ18OSW reconstruction across several glacial and interglacial Marine Isotope Stages from MIS 36 to MIS 19 in the central Mediterranean Sea.During the climatic optimums of MIS 31 and MIS 19, considered as close analogues to the current interglacial in terms of insolation forcing, reconstructed average sub-surface temperatures from benthic foraminifer analyses (13.8 ± 1.5 °C and 14.8 ± 1.3 °C, respectively) and isotopic composition of seawater (between 1.6 ± 0.4‰ and 2.0 ± 0.3‰) are similar to the ones measured today below the thermocline in the Gulf of Taranto. Our results show that bottom water conditions remained similar in all the studied glacial periods, with cold temperatures around ~ 8 °C in average. The lack of a clear cooling across the Mid-Pleistocene either suggest that glacial oceanographic conditions in the Mediterranean Sea remained relatively stable between the 41 ka-world and the 100 ka-world or that the tectonic uplift that took place during this transition balanced out the MPT cooling trend through the shallowing of the deposition site.

Understanding millennial and sub-millennial climate variability during past low eccentricity interglacials similar to the Holocene is important for forecasting the evolution of climate and natural variability. The Ideale section (Montalbano Jonico, Southern Italy) studied here provides one of the best records of MIS 19c, the closest orbital analog to the Holocene. This exposed marine series covers Termination IX to the inception of MIS 18 with very high sedimentation rates (i.e. 90–200 cm/ka). We present 1) benthic δ18O and δ13C records at 90–200 year time-resolution, 2) a new 40Ar/39Ar age of 774.1 ± 0.9 ka for tephra layer V4 (Matuyama-Brunhes transitional period) and 3) new calcareous plankton, palynological and authigenic 10Be/9Be data. Our new Bayesian depth-age model suggests a 11.5 ± 3.4 ka (95% confidence) duration for the climatic optimum. The δ18O series reveals millennial-scale oscillations (with sharp transitions

International audience; Accurate reconstruction of past ocean temperatures is of critical importance to paleoclimatology. Carbonate clumped isotope thermometry (“Δ47 ”) is a relatively recent technique based on the strong relationship between calcification temperature and the statistical excess of 13C–18O bonds in carbonates. Its application to foraminifera holds great scientific potential, particularly because Δ47 paleotemperature reconstructions do not require assumptions regarding the 18O composition of seawater. However there are still relatively few published observations investigating the potential influence of parameters such as salinity or foraminiferal size and species. We present a new calibration data set based on 234 replicate analyses of 9 planktonic and 2 benthic species of foraminifera collected from recent core-top sediments, with calcification temperatures ranging from −2 to 25 °C. We observe a strong relationship between Δ47 values and independent, oxygen-18 estimates of calcification temperatures:Δ47 = 41.63 × 103/T2 + 0.2056The formal precision of this regression (± 0.7–1.0 °C at 95 % confidence level) is much smaller than typical analytical errors. Our observations confirm the absence of significant species-specific biases or salinity effects. We also investigate potential foraminifer size effects between 200 and > 560 μm in 6 species, and conclude that all size fractions from a given core-top location and species display statistically undistinguishable Δ47 values. These findings provide a robust foundation for future inter-laboratories comparisons and paleoceanographic applications.

This paper documents the evolution over the last 10 kyr of one of the key parameters of climate: sea-surface temperatures (SSTs) in the North Atlantic. We focus on the southern Bay of Biscay, a highly sensitive oceanographic area regarding the dynamics of the North Atlantic subpolar and subtropical gyres (SPG and STG respectively). This site furthermore offers unique sedimentary environments characterized by exceptional accumulation rates, enabling the study of Holocene archives at (infra) centennial scales. Our results mainly derive from planktonic foraminiferal association analysis on two cores from the southern Landes Plateau. These associations are used as the basis of modern analogue technique transfer functions to track past hydrographical changes. SST reconstructions were thus obtained at an exceptional resolution and compared to a compilation of Holocene records from the northeastern North Atlantic. From this regional perspective are shown fundamental timing differences between the gyre dynamics, nuancing classical views of a simple meridional overturning cell. Our study highlights that western Europe underwent significant oscillations of (annual) SST during the last 10 kyr. During well-known intervals of mild boreal climate, warm shifts of more than 3 ffi C per century are accurately concomitant with positive sea-surface temperature anomalies and rise of micropalaeontological indicators of gyre dynamics in the northern North Atlantic, pointing to periods of greater intensity of the North Atlantic Current (SPG cell especially). Conversely, the SST signal records short-term cold anomalies which could be related to weaker SPG dynamics.

Clumped isotope measurements aim to quantify some statistical properties of the isotopologue population in a given sample, which requires prior knowledge of the absolute isotopic abundance ratios in reference materials such as VSMOW or VPDB. In the case of CO2, matters are further complicated by the need to define a mass-dependent fractionation law linking the three stable isotopes of oxygen. Conversion from raw mass spectrometric data to mass-47 anomalies (Δ47) thus relies on four external parameters: the (13C/12C) ratio of VPDB, the (17O/16O) and (18O/16O) ratios of VSMOW (or VPDB-CO2), and the slope of the triple oxygen isotope line (λ). Here we investigate the influence that these isotopic parameters exert on measured Δ47 values, using (a) real-world data corresponding to seven months of measurements; (b) simple simulations based on randomly generated data; (c) precise comparisons between water-equilibrated CO2 samples and between carbonate standards believed to share quasi-identical Δ47 values; and (d) reprocessing of two carbonate calibration data sets with different slopes of Δ47 versus T. We demonstrate that the use of different sets of isotopic parameters generally produces systematic offsets as large as 0.04‰ in measured Δ47 values, even after following the established standardization procedures. What's more, even using a single set of isotopic parameters can produce intra- and inter-laboratory discrepancies in measured Δ47 values, if some of these parameters are inaccurate, and depending on the isotopic compositions of the standards used for conversion to the absolute scale of Dennis et al. (2011), these errors should correlate strongly with either δ13C or δ18O, or more weakly with both. Based on measurements of samples expected to display quasi-identical Δ47 values, such as 25 °C water-equilibrated CO2 with different carbon and oxygen isotope compositions, or high-temperature standards ETH-1 and ETH-2, we conclude that the traditional set of isotopic parameters used in all early clumped isotope studies produces large, systematic errors controlled by the relative bulk isotopic compositions of samples and standards. These errors are likely to be one of the key factors responsible for current inter-laboratory discrepancies, but cannot easily explain the conflicting carbonate calibration slopes obtained by different groups. By contrast, the isotopic parameters of Brand et al. (2010) appear to yield accurate Δ47 values regardless of bulk isotopic composition. Based on these findings, we offer recommendations aiming to minimize errors related to the choice of isotopic parameters.