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Fast-(semi)quantitative elemental mapping using state-of-the-art laser ablation-inductively coupled plasma-time of flight-mass spectrometry (LA-ICP-TOF-MS) was applied to a set of chondritic meteorite samples.

The Cenomanian–Turonian Oceanic Anoxic Event (OAE 2: 94 Ma) marked one of the most severe episodes of climate and environmental change during the Cretaceous Period. The primary feature of this interval was widespread marine anoxia/euxinia, leading to deposition of organic-rich, thinly-bedded, mudstones across the world’s oceans, which in turn caused a pronounced positive shift in δ13C of seawater that is recorded (and characterizes) OAE 2 strata worldwide. The event was also marked by climate warming (with superimposed cooling pulses), biotic stress, and terrestrial perturbations such as increased continental weathering. However, the majority of studied records of OAE 2 were deposited in deep-marine Atlantic and Tethyan settings or European epicontinental basins. Thus, the record of environmental change in other locations or environments is less clear. The Western Interior Seaway (WIS) represented a marine corridor across North America that connected the Arctic and Atlantic marine realms. Thus, understanding the environmental and oceanographic changes in the WIS during OAE 2 is crucial to resolving the wider impact of the event across the global marine realm. Several previous works have focused on sites towards the southern end of the WIS (e.g., Pueblo, Iona Core). In this study, we present a new multi-proxy geochemical dataset from a site in the central–northern part of the Western Interior Seaway: Pratts Landing (western Alberta, Canada). Previous palynological studies have highlighted a southward migration of boreal dinoflagellates during the Plenus Cold Event midway through OAE 2, as well as increased input of terrestrial organic matter. Here, we correlate these data with information from redox, nutrient, and volcanic proxies, and compare the Pratts Landing record with other deep- and shallow-marine records of OAE 2 to gain a wider perspective over the environmental changes that operated in different settings during that time interval. This viewpoint is key for understanding the differences and complexities in how surface phenomena were disturbed during OAE 2, and interpreting geochemical records of different settings during that time interval.

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 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.

Micrometeorites, tiny extraterrestrial particles, largely produced by collisions of celestial bodies, which survived atmospheric entry, fall on Earth at a rate of 40000 tons annually, and can be retrieved on the Antarctic. Micrometeorites represent a valuable source of information on the chemical evolution of the Solar System. Their microscopic size (50-2000 mm) warrants the use of novel in situ mapping techniques of elemental analysis. Hyphenated with a low-dispersion laser ablation (LA) system, ICP-ToF-MS allows for 2D mapping at several hundred hertz, with each laser shot recorded as a single pixel, and for quasi-simultaneous rapid acquisition of almost the entire periodic table. In this contribution we present approaches for and results of high-resolution multi-element 2D mapping of micrometeorites cross-sections via LA-ICP-ToF-MS. Quantitative data for each pixel was obtained through a combination of multi-point calibration - via a set of natural glass reference materials - and 100% oxide normalization to account for ablation yield. variations. Detection limits down to a few ng/g were attained while only using a 5x5 µm square laser spot. Analysis of the elemental images of micrometeorites allows to recognize and isolate melts of different composition, complimenting petrographic observations.

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.

Iron (Fe) is an essential nutrient for microalgal metabolism. The low solubility of Fe in oxic aquatic environments can be a growth-limiting factor for phytoplankton. Synthetic chelating agents, such as ethylenediaminetetraacetic acid (EDTA), are used widely to maintain Fe in solution for microalgal cultivation. The non-biodegradable nature of EDTA, combined with sub-optimal bioavailability of Fe-EDTA complexes to microalgae, indicates opportunity to improve microalgal cultivation practices that amplify production efficiency and environmental compatibility. In the present study, the effects of four organic chelating ligands known to form readily bioavailable organic complexes with Fe in natural aquatic environments were investigated in relation to growth and biochemical composition of two marine microalgae grown as live feeds in shellfish hatcheries (Chaetoceros calcitrans and Tisochrysis lutea). Three saccharides, alginic acid (ALG), glucuronic acid (GLU), and dextran (DEX), as well as the siderophore desferrioxamine B (DFB), were compared to EDTA. Organic ligands characterized by weaker binding capacity for cationic metals (i.e., ALG, GLU, DEX) significantly improved microalgal growth and yields in laboratory-scale static batch cultures or bubbled photobioreactors. Maximal microalgal growth enhancement relative to the control (e.g., EDTA) was recorded for GLU, followed by ALG, with 20–35% increase in specific growth rate in the early stages of culture development of C. calcitrans and T. lutea. Substitution of EDTA with GLU resulted in a 27% increase in cellular omega 3-polyunsaturetd fatty acid content of C. calcitrans and doubled final cell yields. Enhanced microalgal culture performance is likely associated with increased intracellular Fe uptake efficiency combined with heterotrophic growth stimulated by the organic ligands. Based upon these results, we propose that replacement of EDTA with one of these organic metal-chelating ligands is an effective and easily implementable strategy to enhance the environmental compatibility of microalgal cultivation practices while also maximizing algal growth and enhancing the nutritional quality of marine microalgal species commonly cultured for live-feed applications in aquaculture.

Fractionation effects related to evaporation and condensation had a major impact on the current elemental and isotopic composition of the Solar System. Although isotopic fractionation of moderately volatile elements has been observed in tektites due to impact heating, the exact nature of the processes taking place during hypervelocity impacts remains poorly understood. By studying Fe in microtektites, here we show that impact events do not simply lead to melting, melt expulsion and evaporation, but involve a convoluted sequence of processes including condensation, variable degrees of mixing between isotopically distinct reservoirs and ablative evaporation during atmospheric re-entry. Hypervelocity impacts can as such not only generate isotopically heavy, but also isotopically light ejecta, with δ56/54Fe spanning over nearly 5‰ and likely even larger variations for more volatile elements. The mechanisms demonstrated here for terrestrial impact ejecta modify our understanding of the effects of impact processing on the isotopic evolution of planetary crusts., Fe isotopic composition of the distal ejecta of a terrestrial impact crater records both evaporation and condensation, refining the nature of the isotopic fractionation taking place during hypervelocity impacts in the Solar System.

The end-Triassic extinction event (∼ 201.5 Ma) is one of the five major mass extinction events in Earth's history, however, considerable discussion continues on the exact causes and timing of the event. This is because, whilst certain geochemical data on T-J sections appears to be largely comparable globally, with for example a significant (up to 6‰) negative carbon-isotope (δ13C) excursion at the extinction horizon, more often than not other geochemical variations are neither uniform nor fully consistent between sections. Critical to this discussion is that the majority of the studied sections containing the end-Triassic extinction event are limited to shallow marine or terrestrial sections, which are prone to discontinuities and hiatuses. In this study, we present carbon isotopes (δ13Ccarb), total organic carbon (TOC), major and trace, mercury (Hg) and highly siderophile elements (HSE), osmium-isotope compositions and paleomagnetic data of a relatively less studied deep-marine T-J succession in the Budva Basin, Čanj, Montenegro. At Čanj, deep-marine Triassic limestones are abruptly interrupted by a ∼ 6 cm finely laminated clay layer, before transitioning to more argillaceous Jurassic red beds. The clay layer is interpreted to represent the end-Triassic extinction interval and is characterized by a negative carbon isotope excursion, relative heavy rare earth element (HREE) enrichment, Hg increase, HSE enrichment and a sharp shift to unradiogenic osmium-isotopic ratios. This establishes the Čanj section as a unique and well-preserved outcrop that exquisitely encapsulates the end-Triassic extinction in the Tethyan marine realm. The distinct geochemical markers recorded at Čanj are consistent with the Central Atlantic Magmatic Province as the main driver behind the end-Triassic extinction.

Long-lived radioactive isotope systematics, such as Sm-Nd and Lu-Hf, are useful tools as important chronometers and tracers for chemical differentiation processes. Even though Antarctic meteorites include rare meteorites such as ungrouped meteorites, the effects of Antarctic alteration on the Sm-Nd and Lu-Hf systems in chondrites have not yet been evaluated in detail. Moreover, the heterogeneity of Sm-Nd and Lu-Hf data in bulk chondrites prevents the determination of precise average Sm-Nd and Lu-Hf values (e.g., for individual chondrite groups). To examine the effects of Antarctic alteration and sample heterogeneity on the Sm-Nd and Lu-Hf isotope systematics, ten Antarctic H chondrites (HCs) and three HCs from hot deserts were characterized for their modal abundances, elemental abundances, and Sm-Nd and Lu-Hf isotopic compositions. Regardless of the classical weathering index for Antarctic meteorites and the normalized Rb abundance used as a chemical alteration indicator in this study, the modal and elemental abundances in Antarctic HCs appear to be in good agreement with those in non-Antarctic HCs. The Sm-Nd and Lu-Hf isotopic compositions of the characterized H chondrites fall within the range measured for both HC falls and for falls of other chondrite groups, except in the case of the most heavily altered sample. Consequently, the effects of Antarctic alteration processes on the Sm-Nd and Lu-Hf systematics in HCs appear to be limited, except in the case of Asuka 09516. The latter meteorite exhibits severe mineralogical and chemical alteration, with considerable losses of even the rare earth elements (REEs), which are considered relatively immobile. The 147Sm/144Nd, 143Nd/144Nd, 176Lu/177Hf, and 176Hf/177Hf of bulk HCs correlate with their P/Mg and Y/Mg. Furthermore, the Lu-Hf ratios correlate strongly with their P/Ca and Y/Ca as well as their P/Mg and Y/Mg. Thus, the distribution of the elements between constituent minerals in ordinary chondrites (OCs) may control the heterogeneity observed for the bulk Sm-Nd and Lu-Hf data. In this context, the weight ratio of Ca-phosphates to Ca-pyroxene, or at least that of Ca-phosphates to silicates, may be a key factor leading to the observed elemental and isotopic variations. This observation indicates that the nugget effect of Ca-phosphates in OCs as the result of insufficient homogenization or terrestrial alteration leads to the heterogeneities displayed by the Sm-Nd and Lu-Hf data. Moreover, it also indicates that the use of equilibrated OCs for the determination of Sm-Nd and Lu-Hf data is affected more by sample heterogeneity, especially with respect to Ca-phosphates, than is the case for unequilibrated OCs, based on the re-distribution of REEs during thermal metamorphism on their parent bodies. This study demonstrates that Antarctic meteorites commonly preserve their original Sm-Nd and Lu-Hf isotopic compositions as much as chondrite falls, although exceptions are possible in the case of severe alteration. Similar to previous studies, we recommend the use of unequilibrated chondrites, for which the re-distribution of REEs is less extensive, for the determination of well-constrained average Sm-Nd and Lu-Hf isotopic compositions for individual chondrite groups as well as their robust Chondritic Uniform Reservoir values.

The Chicxulub impact triggered a global impact winter at the Cretaceous-Paleogene (K-Pg) boundary 66 million years ago. Yet, the exact killing mechanisms of the K-Pg mass extinction including the wipe-out of non-avian dinosaurs, remain poorly constrained. Here, we present paleoclimate simulations based on new sedimentological constraints from an expanded K-Pg boundary deposit in North Dakota, to evaluate the relative and combined effects of impact-generated sulfur and silicate dust as well as soot from global wildfires on the post-impact photosynthetic activity. In prior works, the relative contribution of dust was considered peripheral compared to the other types of fine-grained ejecta. However, our results show that a massive plume of micrometer-sized silicate dust was a key factor driving the K-Pg impact winter due to a long atmospheric lifetime at least 20 years. The dust-induced photosynthetic shut-down, together with additional effects of soot and sulfur, led to the catastrophic collapse of primary productivity on land and in the ocean, steering the mass extinction in the direct aftermath of the Chicxulub impact.

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.

Ordinary chondrites (OC) represent the most abundant type of meteorites, representing more than 85% of the total world collection. Yet they remain poorly studied for their stable isotope compositions. Results have been published for a range of elements but generally as part of broader studies (e.g. [1], [2]). Stable isotope variations of moderately volatile elements (MVE) such as Cu and Zn are useful tools to investigate fractionation effects induced by condensation and evaporation. OC may have also experienced shock events on their parent bodies as they exhibit different shock features, resulting in the loss of volatile elements and subsequently leading to possible isotope fractionation of MVE. Therefore, new stable isotope data are required to reconcile literature data with the shock degree of OC and behavior of MVE. In recent years, high precision isotope measurements of MVE gallium have shown promising results regarding isotopic fractionation in volatility-controlled processes such as condensation and evaporation [3]. Here, Ga will thoroughly be investigated together with Cu and Zn and compared to previous studies in order to evaluate the possible shock effects on MVE isotopes in ordinary chondrites. In this study, we have determined the shock stage as well as the degree of weathering of a series of H6 ordinary chondrites according to the classification established by [4] and [5], respectively. Elemental data were collected using two different ICP-MS instruments at ULB and VUB whereas isotope ratios were measured using the Nu II HR-MC-ICP-MS in combination with an Aridus 2 desolvating nebulizer at ULB. We report new data on the MVE isotopes Cu, Zn, and the recently developed Ga as well as more refractory Fe in bulk H6 chondrites and aim to link isotopic variations to the shock degrees recorded in ordinary chondrites.

Achondritic micrometeorites represent one of the rarest (ca. 0.5–2.1%) particle types among Antarctic micrometeorite collections. Here, we present major, trace element and oxygen isotope compositions on five vitreous, achondritic cosmic spherules (341–526 µm in size) recovered from the Widerøefjellet sedimentary trap in the Sør Rondane Mountains (SRMs) of East Antarctica. We also present the first iron isotope data for four of these achondritic cosmic spherules. The particles were initially identified based on the atomic concentrations of Fe-Mg-Mn and their distribution in Fe/Mg versus Fe/Mn space, spanning a relatively wide range in Fe/Mg ratios (ca. 0.48–1.72). The Fe/Mn ratios cover a more restricted range (22.4–31.7), comparable to or slightly below the values measured for howardite-eucrite-diogenite (HED) and martian meteorites. One particle (WF1801-AC3) displays an elevated Fe/Mn ratio of ∼78, comparable to the values determined for lunar rocks. The negative correlation observed between the CaO + Al2O3 contents and the Fe/Si ratios of achondritic spherules reflects both the mineralogy of the precursor materials, as well as the extent of volatilization experienced during atmospheric entry heating. This trend suggests that the primary mineralogy of precursor materials may have been compositionally similar to basaltic achondrites. Based on their distribution in Ca/Si versus Al/Si space, we argue that the majority of achondritic cosmic spherules predominantly sample pyroxene- and/or plagioclase-rich (i.e., basaltic) precursor bodies. Such precursor mineralogy is also inferred from their rare earth element (REE) patterns, which show resemblances to fine-grained basaltic eucrites or Type 1 achondritic spherules (n = 3 – av. REEN = 11.2–15.5, (La/Yb)N = 0.93–1.21), pigeonite-rich equilibrated eucrite precursors or Type 2 achondritic spherules (n = 1 – av. REEN = 27.9, (La/Yb)N = 0.10), and possibly Ca-phosphates from (primitive) achondritic bodies (n = 1 – av. REEN = 58.8, (La/Yb)N = 1.59). This is clearly demonstrated for particle WF1801AC-1, which was likely inherited from a fine-grained eucritic precursor body. The pre-atmospheric oxygen isotope composition was reconstructed through compensation of mass-dependent fractionation processes as well as mixing with atmospheric oxygen, using iron isotope data. Two particles (WF1801AC-2, WF1801-AC4) display corrected oxygen isotope compositions (δ18O = 3.7–4.4‰) largely consistent with HED meteorites and may thus originate from HED-like parent bodies. The corrected oxygen isotope compositions (δ18O = 12.6–12.8‰) of the remaining particles (WF1801-AC3, WF1801-AC5) do not correspond to known meteorite fields and may represent two distinct types of unknown achondritic parent bodies or residual atmospheric entry effects. Finally, the abundance (ca. 0.5%) of achondritic cosmic spherules within the Widerøefjellet sedimentary trap is comparable to that observed in the South Pole Water Well (SPWW – ca. 0.5%), Novaya Zemlya glacier (ca. 0.45%) and Transantarctic Mountain (TAM) (ca. 2.1%) collections, confirming their overall rarity in micrometeorite collections. Unambiguous evidence for micrometeorites from the Moon or Mars remains absent from collections to date.

Meteorites are prone to errestrial weathering not only after their fall on the Earth’s surface but also during storage in museum collections. To study the susceptibility of this material to weathering, weathering experiments were carried out on polished sections of the H5 chondrite Asuka 10177. The experiments consisted of four 100-days cycles during which temperature and humidity varied on a twelve hours basis. The first alteration cycle consisted of changing the temperature from 15 to 25 °C; the second cycle consisted of modifying both humidity and temperature from 35 to 45% and 15 to 25 °C, respectively; the third cycle consisted of varying the humidity level from 40 to 60%; and the fourth cycle maintained a fixed high humidity of 80%. Weathering products resulting from the experiments were identified and characterized using scanning electron microscopy–energy dispersive spectroscopy and Raman spectroscopy. Such products were not observed at the microscopic scale after the first cycle of alteration. Conversely, products typical of the corrosion of meteoritic FeNi metal were observed during scanning electron microscope surveys after all subsequent cycles. Important increases in the distribution of weathering products on the samples were observed after cycles 2 and 4 but not after cycle 3, suggesting that the combination of temperature and humidity fluctuations or high humidity (>60%) alone is most detrimental to chondritic samples. Chemistry of the weathering products revealed a high degree of FeNi metal corrosion with a limited contribution of troilite corrosion. No clear evidence of mafic silicate alteration was observed after all cycles, suggesting that postretrieval alteration remains limited to FeNi metal and to a lesser extent to troilite.

Widespread marine anoxia triggered by the runoff and recycling of nutrients was a key phenomenon associated with the Frasnian–Famennian (FF) mass extinction. However, the relative importance of global-scale processes versus local influences on site-specific environmental change remains poorly understood. Here, nitrogen-isotope (δ15N) trends are combined with organic-biomarker, phosphorus, and Rock-Eval data in FF sites from the USA (H-32 core, Iowa), Poland (Kowala Quarry), and Belgium (Sinsin). Up-to-date cyclostratigraphic age models for all three sites allow the nature and timing of changes to be precisely compared across the globe. Negative δ15N excursions across the FF interval from the H-32 core and Kowala correlate with geochemical evidence for euxinic, phosphorus-rich, water columns, and possible cyanobacterial activity, suggestive of increased diazotrophic N fixation, potentially coupled with ammonium assimilation at the latter site. By contrast, previously studied sites from Western Canada and South China document enhanced water-column denitrification around the onset of the Upper Kellwasser (UKW) Event, re-emphasizing the geographical heterogeneity in environmental perturbations at that time. Moreover, environmental degradation began >100 kyr earlier in Poland, coeval with a major increase in bioavailable phosphorus supply, than in Iowa, where no such influx is recorded. These regional differences in both the timing and nature of marine perturbations during the FF interval likely resulted from the variable influx of terrigenous nutrients to different marine basins at that time, highlighting the importance of local processes such as terrestrial runoff in driving environmental degradation during times of climate cooling such as the UKW Event.

During atmospheric entry, micrometeorites experience variable degrees of (i) evaporation due to gas drag heating and (ii) mixing with atmospheric oxygen. Evaporation affects the physical properties and chemical and isotopic compositions of fully melted cosmic spherules (CSs). Oxygen isotope ratios of pristine micrometeorites are commonly used to relate these particles to their appropriate parent bodies. However, the degree of mixing with atmospheric oxygen and isotope fractionation by evaporation in CSs generally remains unclear, leading to uncertainties in their initial oxygen isotope ratios, which in turn complicates the precursor body identification. Previously, several studies have estimated the degree of evaporation based on contents of major refractory elements Ca and Al in combination with Fe/Si atomic ratios. This now commonly adopted chemical classification system has not yet been assessed with O and Fe isotope variability. As evaporation leads to both isotope and chemical fractionation, it is imperative to verify whether the predicted amounts of evaporation based on isotopic and chemical proxies converge.Here, we measure the major and trace element compositions of 57 chondritic (mostly vitreous) CSs, along with their Fe isotope ratios. The δ56Fe isotope and chemical (K, Zn, Na or CaO and Al2O3 concentrations) fractionation in these particles show no correlation. This can be interpreted in two ways: (i) separate processes govern chemical and isotope fractionation or (ii) the selected proxies for isotope and/or chemical fractionation are inadequate. Because the initial Fe isotope ratios of chondrites display limited variation (0.005 ± 0.008‰ δ56Fe), Fe isotope ratios in CSs are assumed to only have changed through evaporation. At the same time, the chemical compositions of CSs show larger variability, so the CSs are thus often not chemically representative of their precursor bodies.As oxygen isotope ratios are commonly used to identify the precursor bodies of (micro)meteorites, triple oxygen isotope ratios are measured in 37 of the 57 CSs. Based on the relationship between δ57Fe and δ18O, the effect of evaporation on the O isotope ratios can be corrected, which allows for a more precise precursor body reconstruction. Via this method, two 16O-poor spherules with greatly varying degrees of isotope fractionation (~1.0‰ and 29.1‰ δ56Fe, respectively) can be distinguished. Furthermore, it is observed that CSs that likely have an OC-like heritage all underwent the same degree of atmospheric mixing (~8‰ δ18O). These findings highlight the potential of including Fe isotope measurements to the regular methodologies applied to CS studies.

The Valanginian Weissert Event (~134 Ma) represented the first major carbon-cycle disturbance of the Cretaceous Period, characterized in the sedimentary record by a prolonged positive excursion in carbon-isotope ratios. The event has been widely linked with climate cooling, documented in several geographic regions; however, some areas show minimal evidence of temperature change at that time, or even warming and enhanced humidity around the onset of the event. Moreover, although the carbon-isotope excursion has generally been attributed to enhanced burial of organic matter, there is no evidence of widespread marine anoxia that would have promoted such deposition. Consequently, key questions remain regarding the causes of climate and environmental degradation during the early Valanginian. Understanding changes in volcanic activity and silicate weathering rates through late Berriasian to early Valanginian times is crucial for resolving this debate, as both processes influence atmospheric pCO2 levels and global temperatures. In particular, volcanism associated with formation of the Paraná-Etendeka large igneous province (LIP) during the Valanginian has long been proposed as the ultimate trigger of the Weissert Event via carbon emissions and greenhouse warming,but weathering of juvenile LIP basalts could equally have caused climate cooling.In this study, we investigated the osmium-isotope composition (187Os/188Os) of deep-marine organic-rich Berriasian–Valanginian sediments from two proto-Atlantic Ocean archives (DSDP sites 534 and 603). Given the palaeoenvironmental setting of the two sites, the recorded 187Os/188Os seawater compositions of the proto-Atlantic should be representative of the global ocean. We find that seawater 187Os/188Os shifted from ~0.6 to ~0.75 during the latest Berriasian, suggestive of an increased flux of radiogenic osmium to the ocean during that time, likely resulting from enhanced weathering of the continental crust. Interestingly, however, there is no evidence of global climate warming during the late Berriasian that would have caused this weathering. Following the late Berriasian radiogenic shift, seawater osmium gradually changed to a more unradiogenic isotopic composition (~0.45) during the early Valanginian; the lowest 187Os/188Os values correlating with both the peak in the Weissert Event carbon-isotope excursion and evidence for climate cooling. This unradiogenic shift could reflect a decline in weathering of radiogenic crustal material; however, it also stratigraphically correlates with geochronological and geochemical evidence for the time of maximum igneous activity on the western (Paraná) part of the Paraná-Etendeka LIP. Therefore, we conclude that the early Valanginian shift to unradiogenic 187Os/188Os seawater compositions resulted from erosion of juvenile primitive basalts, suggesting that combined weathering of the continental crust and the Paraná-Etendeka LIP played a key role in causing the global cooling associated with the Weissert Event.

This study presents a new classification of a ∼100-m-thick crater suevite sequence in the recent International Ocean Discovery Program (IODP)-International Continental Scientific Drilling Program (ICDP) Expedition 364 Hole M0077A drill core to better understand the formation of suevite on top of the Chicxulub peak ring. We provide an extensive data set for this succession that consists of whole-rock major and trace element compositional data (n = 212) and petrographic data supported by digital image analysis. The suevite sequence is subdivided into three units that are distinct in their petrography, geochemistry, and sedimentology, from base to top: the ∼5.6-m-thick non-graded suevite unit, the ∼89-m-thick graded suevite unit, and the ∼3.5-m-thick bedded suevite unit. All of these suevite units have isolated Cretaceous planktic foraminifera within their clastic groundmass, which suggests that marine processes were responsible for the deposition of the entire M0077A suevite sequence. The most likely scenario describes that the first ocean water that reached the northern peak ring region entered through a N-NE gap in the Chicxulub outer rim. We estimate that this ocean water arrived at Site M0077 within 30 minutes after the impact and was relatively poor in rock debris. This water caused intense quench fragmentation when it interacted with the underlying hot impact melt rock, and this resulted in the emplacement of the ∼5.6-m-thick hyaloclastite-like, non-graded suevite unit. In the following hours, the impact structure was flooded by an ocean resurge rich in rock debris, which caused the phreatomagmatic processes to stop and the ∼89-m-thick graded suevite unit to be deposited. We interpret that after the energy of the resurge slowly dissipated, oscillating seiche waves took over the sedimentary regime and formed the ∼3.5-m-thick bedded suevite unit. The final stages of the formation of the impactite sequence (estimated to be

We report the discovery of a unique, refractory phase-bearing micrometeorite (WF1202A-001) from the Sør Rondane Mountains, East Antarctica. A silicate-rich cosmic spherule (~400 µm) displays a microporphyritic texture containing Ca-Al-rich inclusion (CAI)-derived material (~5–10 area%), including high-Mg forsterite (Fo98-99) and enstatite (En98-99, Wo0-1). The micrometeorite also hosts a spherical inclusion (~209 µm), reminiscent of chondrules, displaying a barred olivine texture. Oxygen isotopic compositions of the micrometeorite groundmass (δ17O = –3.46‰, δ18O = 10.43‰, ∆17O = –1.96‰) are consistent with a carbonaceous chondrite precursor body. Yet, a relict forsterite grain is characterized by δ17O = –45.8‰, δ18O = –43.7‰, ∆17O = –23.1‰, compatible with CAIs. In contrast, a relict low-Ca pyroxene grain (δ17O = –4.96‰, δ18O = –4.32‰, ∆17O = –2.71‰) presumably represents a first-generation silicate grain that accreted 18O-rich gas or dust in a transient melting scenario. The spherical inclusion displays anomalous oxygen isotope ratios (δ17O = –0.98‰, δ18O = –2.16‰, ∆17O = 0.15‰), comparable to anhydrous interplanetary dust particles (IDPs) and fragments from Comet 81P/Wild2. Based on its major element geochemistry, the chondrule size, and oxygen isotope systematics, micrometeorite WF1202A-001 likely sampled a carbonaceous chondrite parent body similar to, but distinct from CM, CO, or CV chondrites. This observation may suggest that some carbonaceous chondrite bodies can be linked to comets. The reconstructed atmospheric entry parameters of micrometeorite WF1202A-001 suggest that the precursor particle originated from a low-inclination, low-eccentricity source region, most likely either the main belt asteroids or Jupiter family comets (JFCs)., SCOPUS: ar.j, info:eu-repo/semantics/published

Fast-growing speleothems allow for the reconstruction of palaeoclimate down to a seasonal scale. Additionally, annual lamination in some of these speleothems yields highly accurate age models for these palaeoclimate records, making these speleothems valuable archives for terrestrial climate. In this study, an annually laminated stalagmite from the Han-sur-Lesse cave (Belgium) is used to study the expression of the seasonal cycle in northwestern Europe during the Little Ice Age. More specifically, two historical 12-year-long growth periods (ca. 1593-1605 CE and 1635-1646 CE) and one modern growth period (1960-2010 CE) are analysed on a sub-annual scale for their stable-isotope ratios (δ13C and δ18O) and trace-element (Mg, Sr, Ba, Zn, Y, Pb, U) contents. Seasonal variability in these proxies is confirmed with frequency analysis. Zn, Y and Pb show distinct annual peaks in all three investigated periods related to annual flushing of the soil during winter. A strong seasonal in-phase relationship between Mg, Sr and Ba in the modern growth period reflects a substantial influence of enhanced prior calcite precipitation (PCP). In particular, PCP occurs during summers when recharge of the epikarst is low. This is also evidenced by earlier observations of increased δ13C values during summer. In the 17th century intervals, there is a distinct antiphase relationship between Mg, Sr and Ba, suggesting that processes other than PCP, i.e. varying degrees of incongruent dissolution of dolomite, eventually related to changes in soil activity and/or land-use change are more dominant. The processes controlling seasonal variations in Mg, Sr and Ba in the speleothem appear to change between the 17th century and 1960-2010 CE. The Zn, Y, Pb, and U concentration profiles; stable-isotope ratios; and morphology of the speleothem laminae all point towards increased seasonal amplitude in cave hydrology. Higher seasonal peaks in soil-derived elements (e.g. Zn and Y) and lower concentrations of host-rock-derived elements (e.g. Mg, Sr, Ba) point towards lower residence times in the epikarst and higher flushing rates during the 17th century. These observations reflect an increase in water excess above the cave and recharge of the epikarst, due to a combination of lower summer temperatures and increased winter precipitation during the 17th century. This study indicates that the transfer function controlling Mg, Sr and Ba seasonal variability varies over time. Which process is dominant - either PCP, soil activity or dolomite dissolution - is clearly climate driven and can itself be used as a palaeoenvironment proxy.

Due to the straightforward and non-invasive sampling, ease of transport and long-term storage and access to time-resolved information, determination of element concentrations and isotope ratios in hair and nails finds increasing use. Multi-isotopic information preserved in keratinous tissues allows one to reveal dietary, physiological and environmental influences, but progress in this area is still limited by complicated and time-consuming analytical procedures and challenges in accuracy assessment. In this study, longitudinal distributions of δ34S, 87Sr/86Sr, 207,208Pb/206Pb, δ66Zn, δ56Fe, δ65Cu, δ26Mg, and δ114Cd were obtained for hair and nails collected from nine subjects with different age, biological sex, diet and/or place of residence. For S and Zn, the distribution along hair strands revealed a trend towards a heavier isotopic signature from the proximal to the distal end, with a maximum difference within the hair of a single subject of 1.2‰ (Δ34S) and 0.4‰ (Δ66Zn). For Fe, Cu, Mg and Cd, a shift towards either a lighter (Cu) or heavier (Fe, Mg and Cd) isotopic composition is accompanied by increasing concentration towards the distal hair end, indicating possible isotope fractionation during deposition or external contamination with a different isotopic composition. Pb and Sr isotope ratios are relatively stable throughout the hair strands despite notable concentration increases towards the distal end, likely reflecting external contamination. The isotopic composition of Sr points to tap water as a probable main source, explaining the relative stability of the ratio for individuals from the same geographical location. For Pb, isotopic compositions suggest tap water and/or indoor dust as possible sources. Similar δ34S, 87Sr/86Sr, 207,208Pb/206Pb, δ66Zn, δ56Fe, and δ65Cu observed for hair, fingernails and toenails sampled from the same individual suggest that keratinous tissues are conservative receivers of internal and external inputs and can be used complementary. Seasonal variation in δ34S, 207,208Pb/206Pb, and δ65Cu was observed for fingernails.

Micrometeorites experience varying degrees of evaporation and mixing with atmospheric oxygen during atmospheric entry. Evaporation due to gas drag heating alters the physicochemical properties of fully melted cosmic spherules (CSs), including the size, chemical and isotopic compositions and is thus expressed in its chemical and isotopic signatures. However, the extent of evaporation and atmospheric mixing in CSs often remains unclear, leading to uncertainties in precursor body identification and statistics. Several studies have previously estimated the extent of evaporation based on the contents of major refractory elements Ca and Al in combination with the determined Fe/Si atomic ratios. Similarly, attempts have been made to design classification schemes based on isotopic variations. However, a full integration of any previously defined chemical classification schemes with the observed isotopic variability has not yet been successful. As evaporation can lead to both chemical and isotope fractionation, it is important to verify whether the estimated degrees of evaporation based on chemical and isotopic proxies converge. Here, we have analysed the major and trace element compositions of 57 chondritic (mostly V-type) CSs, along with their Fe isotope ratios. The chemical (Zn, Na, K or CaO and Al2O3 concentrations) and δ56Fe isotope fractionation measured in these particles show no correlation. The interpretation of these results is twofold: (i) isotopic and chemical fractionation are governed by distinct processes or (ii) the proxies selected for chemical and isotope fractionation are inadequate. While the initial Fe isotopic ratios of chondrites are constrained within a relatively narrow range (0.005 ± 0.008‰ δ56Fe), the chemical compositions of CSs display larger variability. Cosmic spherules are thus often not chemically representative of their precursor bodies, due to their small size. As oxygen isotopes are commonly used to refine the precursor bodies of meteorites, triple oxygen isotope ratios were measured in thirty-seven of the characterized CSs. Based on the relationship between δ18O and δ57Fe, the evaporation effect on the O isotope system can be calculated, which allows for a more accurate parent body determination. Using this correction method, two ‘Group 4’ spherules with strongly variable degrees of isotope fractionation (δ56Fe of ∼1.0‰ and 29.1‰, respectively) could be distinguished. Furthermore, it was observed that all CSs that probably have a OC-like heritage underwent roughly the same degree of atmospheric mixing (∼8‰ δ18O). This highlights the potential of including Fe isotope measurements to the regular methodologies applied to CS studies.

Meteorites provide a unique view into the origin and evolution of the Solar System. Antarctica is the most productive region for recovering meteorites, where these extraterrestrial rocks concentrate at meteorite stranding zones. To date, meteorite-bearing blue ice areas are mostly identified by serendipity and through costly reconnaissance missions. Here, we identify meteorite-rich areas by combining state-of-the-art datasets in a machine learning algorithm and provide continent-wide estimates of the probability to find meteorites at any given location. The resulting set of ca. 600 meteorite stranding zones, with an estimated accuracy of over 80%, reveals the existence of unexplored zones, some of which are located close to research stations. Our analyses suggest that less than 15% of all meteorites at the surface of the Antarctic ice sheet have been recovered to date. The data-driven approach will greatly facilitate the quest to collect the remaining meteorites in a coordinated and cost-effective manner. ispartof: SCIENCE ADVANCES vol:8 issue:4 ispartof: location:United States status: published

Antarctica is the most productive region for collecting meteorites, as the visually contrasting meteorites are easily detectable and tend to concentrate at specific areas exposing blue ice. Blue ice areas act as meteorite stranding zones if the flow of the ice sheet and specific geographical and climatological settings combine favorably. Previously, possible meteorite stranding zones were identified by chance or through visual examination of imagery, which limits the discovery of new locations for future meteorite searching campaigns.

Sulfur isotope ratios are often used as biogeochemical tracers to gain understanding of abiotic and biological processes involved in the sulfur cycle in both modern and ancient environments. There is however a lack of matrix-matched well-characterized isotopic reference materials that are essential for controlling the accuracy and precision. This study therefore focused on expanding and complementing the currently available sulfur isotope ratio data by providing the bulk sulfur isotopic composition, as determined using multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS), for a comprehensive set of commercially and/or readily available biological and geological reference materials. A total 7 isotopic reference materials and 41 elemental reference materials were studied. These reference materials include standards of terrestrial and marine animal origin, terrestrial plant origin, human origin, and geological origin. Different sample preparation protocols, including digestion and subsequent chromatographic isolation of S, were evaluated and the optimum approach selected for each matrix type. For achieving enhanced robustness, the sample preparation and sulfur isotope ratio measurements were done at two different laboratories for selected reference materials, while at one of the laboratories the measurements were additionally performed using two different MC-ICP-MS instruments. Determined δ34SVCDT and δ33SVCDT values compared well between the different laboratories, as well as between the different generation MC-ICP-MS instruments, and for standards that were previously characterized, our data are similar to literature values. The δ34SVCDT ranges determined for the different categories of the reference materials – terrestrial animal origin: +2 to +9‰, marine animal origin: +15 to +20‰, human origin: +6 to +10‰, terrestrial plant origin: −20 to +7‰, and geological origin: −12 to +21‰ – fit the expected values based on previous studies of similar types of matrices well. No significant mass-independent fractionation is observed when considering the expanded uncertainties for Δ33SV-CDT.

A late afternoon in February 1971, a meteorite impacted the rooftop of a house in Tintigny village in southern Belgium. Confirmed as a possible meteorite by the schoolteacher, the meteorite and its fall story did not leave the village. Finally, 46 years after the fall event, we got the opportunity to study and characterize this meteorite. In this work, we give a detailed report on its textural, mineralogical, whole-rock elemental and oxygen isotopic composition. Officially named as Tintigny, we classified it as an achondrite from howardite-eucrite-diogenite (HED) clan and more precisely a polymict eucrite. A brecciated basaltic rock believed to be originated from the surface of V-type asteroids namely the asteroid 4-Vesta. Tintigny has recorded the evidence of the impact metamorphism and metasomatism processes active on its parent body. Tintigny is one of the 39 eucrite falls known to date, and one of the 11 eucrites occurred in Europe. It is the fifth officially recognized meteorite and the first achondrite from Belgium. This report shows the importance of studying and accessing such a meteorite for further cosmochemical and planetary investigations and enriching our knowledge on the formation of HED meteorites and their parent bodi(es). In addition, it brings the attention to its importance as a scientific heritage that has to be properly understood and safeguarded for the generations of scientists, scholar, and amateurs to come., info:eu-repo/semantics/published

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.

Compared with Phanerozoic strata, sulfate minerals are relatively rare in the Precambrian record; this is probably due to the lower concentrations of sulfate in dominantly anoxic oceans. Here, we present a compilation of sulfate minerals that are stratigraphically associated with the Ediacaran Shuram excursion (SE) – the largest negative δ13C excursion in Earth history. We evaluated 15 SE sections, all of which reveal the presence of sulfate minerals and/or enriched carbonate-associated sulfate concentrations, suggesting a rise in the sulfate reservoir. Notably, where data are available, the SE also reveals considerable enrichments in [Ba] relative to pre- and post-SE intervals. We propose that elevated seawater sulfate concentrations during the SE may have facilitated authigenesis of sulfate minerals. At the same time, the rise in Ba concentrations in shelf environments further facilitated barite deposition. A larger sulfate reservoir would stimulate microbial sulfate reduction and anaerobic oxidation of organic matter (including methane), contributing to the genesis of the SE. The existence of sulfate minerals throughout the SE suggests that oxidant pools were not depleted at that time, which challenges previous modelling results. Our study highlights the dynamic interplay of biogeochemical C, S and Ba cycles in response to the Shuram oxygenation event. Supplementary material: SEM and EDS data and figures S1-S4 and tables S1-S3 are available at: https://doi.org/10.6084/m9.figshare.c.5602560 Thematic collection: This article is part of the ‘Sulfur in the Earth system’ collection available at: https://www.lyellcollection.org/cc/sulfur-in-the-earth-system

This newsletter reports the classification of 821 meteorites collected from ice fields near the Yamato and Belgica Mountains by JARE-15, 20, 39, and 41 (Yamato 74, 79, 98, and 00, Belgica 98 meteorites) and from the Balchen and/or Nansen Ice Fields by JARE-29, 31, 51 and JARE-54/BELARE 2012-2013 (Asuka 87, 88, 90, 09, and 12 meteorites). JARE-51 and JARE-54/BELARE 2012-2013 were the Japan-Belgium joint expeditions. The meteorites include forty-nine carbonaceous chondrites (44 CM, 3 CV, 1 CK, 1 CH), thirty-six achondrites (16 eucrites, 15 diogenites, 1 mesosiderite, 4 ureilites), and twenty-one iron meteorites.

This work presents isotopic data for the non-traditional isotope systems Fe, Cu, and Zn on a set of Chicxulub impactites and target lithologies with the aim of better documenting the dynamic processes taking place during hypervelocity impact events, as well as those affecting impact structures during the post-impact phase. The focus lies on material from the recent IODP-ICDP Expedition 364 Hole M0077A drill core obtained from the offshore Chicxulub peak ring. Two ejecta blanket samples from the UNAM 5 and 7 cores were used to compare the crater lithologies with those outside of the impact structure. The datasets of bulk Fe, Cu, and Zn isotope ratios are coupled with petrographic observations and bulk major and trace element compositions to disentangle equilibrium isotope fractionation effects from kinetic processes. The observed Fe and Cu isotopic signatures, with δ56/54Fe ranging from −0.95‰ to 0.58‰ and δ65/63Cu from −0.73‰ to 0.14‰, mostly reflect felsic, mafic, and carbonate target lithology mixing and secondary sulfide mineral formation, the latter associated to the extensive and long-lived (> 105 years) hydrothermal system within Chicxulub structure. On the other hand, the stable Zn isotope ratios provide evidence for volatility-governed isotopic fractionation. The heavier Zn isotopic compositions observed for the uppermost part of the impactite sequence and a metamorphic clast (δ66/64Zn of up to 0.80‰ and 0.87‰, respectively) relative to most basement lithologies and impact melt rock units indicate partial vaporization of Zn, comparable to what has been observed for Cretaceous-Paleogene boundary layer sediments around the world, as well as for tektites from various strewn fields. In contrast to previous work, our data indicate that an isotopically light Zn reservoir (δ66/64Zn down to −0.49‰), of which the existence has previously been suggested based on mass balance considerations, may reside within the upper impact melt rock (UIM) unit. This observation is restricted to a few UIM samples only and cannot be extended to other target or impact melt rock units. Light isotopic signatures of moderately volatile elements in tektites and microtektites have previously been linked to (back-)condensation under distinct kinetic regimes. Although some of the signatures observed may have been partially overprinted during post-impact processes, our bulk data confirm impact volatilization and condensation of Zn, which may be even more pronounced at the microscale, with variable degrees of mixing between isotopically distinct reservoirs, not only at proximal to distal ejecta sites, but also within the lithologies associated with the Chicxulub impact crater.

Quantitative insights into the geochemistry and petrology of proximal impactites are fundamental to understand the complex processes that affected target lithologies during and after hypervelocity impact events. Traditional analytical techniques used to obtain major- and trace-element data sets focus predominantly on either destructive whole-rock analysis or laboratory-intensive phase-specific micro-analysis. Here, we present micro–X-ray fluorescence (µXRF) as a state-of-the-art, time-efficient, and nondestructive alternative for major- and trace-element analysis for both small and large samples (up to 20 cm wide) of proximal impactites. We applied µXRF element mapping on 44 samples from the Chicxulub, Popigai, and Ries impact structures, including impact breccias, impact melt rocks, and shocked target lithologies. The µXRF mapping required limited to no sample preparation and rapidly generated high-resolution major- and trace-element maps (~1 h for 8 cm2, with a spatial resolution of 25 µm). These chemical distribution maps can be used as qualitative multi-element maps, as semiquantitative single-element heat maps, and as a basis for a novel image analysis workflow quantifying the modal abundance, size, shape, and degree of sorting of segmented components. The standardless fundamental parameters method was used to quantify the µXRF maps, and the results were compared with bulk powder techniques. Concentrations of most major elements (Na2O–CaO) were found to be accurate within 10% for thick sections. Overall, we demonstrate that µXRF is more than only a screening tool for heterogeneous impactites, because it rapidly produces bulk and phase-specific geochemical data sets that are suitable for various applications within the earth sciences.

Large bolide impacts in the Phanerozoic produced global change identifiable in the postimpact sediments. Aside from a few isolated examples, however, evidence of postimpact change associated with Precambrian impacts is sparse. This study used the Neoarchean Paraburdoo spherule layer as a case study to search for impact-induced change in the sediments above the spherule layer. We found possible minor sedimentary changes that may have been due to either a disturbance by bottom currents or changing diagenetic conditions. Contrary to the trends found with several post–Great Oxidation Event large bolide impacts, we found no evidence of shifts in tectonic regime, sediment weathering and deposition, or paleoenvironment induced by the Paraburdoo spherule layer impact, for which the impactor is estimated to have been approximately three times larger than the Cretaceous–Paleogene bolide. This lack of a clear signal of climatic shift may be due to one or more mechanisms. Either the Paraburdoo spherule layer’s deposition in several-hundred-meter-deep water within the Hamersley Basin of Western Australia was too deep to accumulate and record observable changes, or the Neoarchean’s high-CO2 atmospheric composition acted as a threshold below which the introduction of more impact-produced gases would not have produced the expected climatic and weathering changes. We also report minor traces of elevated iron and arsenic concentrations in the sediments immediately above the Paraburdoo spherule layer, consistent with trends observed above other distal impact deposits, as well as distinctive layers of hematite nodules bracketing the spherule layer. These geochemical changes may record ocean overturn of the Neoarchean stratified water column, which brought slightly oxygenated waters to depth, consistent with the observation of tsunami deposits in shallower impact deposits and/or heating of the global oceans by tens to hundreds of degrees Celsius in the wake of the Paraburdoo spherule layer impact. Either or both of these mechanisms in addition to impact-induced shallow-water ocean evaporation may also have caused a massive die-off of microbes, which also would have produced a postimpact increase in iron and arsenic concentrations.

The IODP-ICDP Expedition 364 drilling recovered a 829 m core from Hole M0077A, sampling ~600 meters of near continuous crystalline basement within the peak ring of the Chicxulub impact structure. The bulk of the basement consists of pervasively deformed, fractured, and shocked granite. Detailed geochemical investigations of forty-one granitoid samples, i.e., major and trace element contents, and Sr–Nd isotopic ratios, are presented here, providing a broad overview of the composition of the granitic crystalline basement. Mainly in situ granite, but also granite clasts (in impact melt rock), granite breccias, and aplite were analyzed, yielding relatively homogeneous compositions between all samples. The granite is part of the high-K, calc-alkaline metaluminous series. Additionally, they are characterized by high Sr/Y and (La/Yb)N ratios, and low Y and Yb contents, which are typical for adakites. However, other criteria (such as Al2O3 and MgO contents, Mg#, K2O/Na2O ratios, Ni concentrations, etc.) do not match the adakite definition. In addition, initial 87Sr/86Srt=326 Ma is indicative of an hydrothermal fluid metasomatic event occurring shortly after the granite formation, affecting mainly samples crosscut by shear fractures or in contact with aplite,, where the fluid circulation was enhanced, and would have preferentially affected fluid-mobile element concentrations. The initial εNd (t=326 Ma) values range from -4.0 to 3.2 for the samples which were less affected by the hydrothermal overprint and indicate that a minor Grenville basement component may be involved in the granite genesis. Our results are consistent with previous studies, further supporting that the cored granite unit intruded the Maya block during the Carboniferous, in an arc setting with crustal melting related with the closure of the Rheic ocean associated with the assembly of Pangea. Then, an hydrothermal metasomatic event, possibly related to the initial breakup of Pangea, occurred ca. 50 Myr after the granite crystallization. Importantly, the granites sampled in Hole M0077A are unique in composition when compared to granite or gneiss clasts from other drill cores recovered from the Chicxulub impact structure. This marks them as valuable lithologies that provide new insight into the Yucatán basement.