The biritual necropolis at Kazimierza Wielka, site 12, represents one of the most significant archaeological discoveries in south-eastern Poland in recent years. The cemetery is dominated by inhumation burials, most of which contain female remains, while cremations are less frequent; both burial types are accompanied by rich grave goods. The burials date to the end of the Younger Pre-Roman Period and the Early Roman Period (1st century BC – 2nd century AD). During the Pre-Roman Period, the region was inhabited by a culturally and ethnically diverse Celtic–Przeworsk communities traditionally associated with the Tyniec group, while in the Roman Period the area experienced intensive settlement by communities of the Przeworsk culture. Nevertheless, the funerary practices and grave inventories at this site are atypical for that cultural tradition. The coexistence of biritual burial practices and imported grave goods suggest that part of the cemetery’s community could be of non-local origin. Strontium isotope analyses (⁸⁷Sr/⁸⁶Sr) of dental enamel and cremated bones from 26 individuals corroborate these interpretations, revealing patterns of mobility and the integration of non-local individuals, particularly females, into the local social and funerary landscape.

The palaeogeographic configuration of the continental fragments and seaways that developed during the Devonian evolution of the Rheic Ocean remains insufficiently understood. One of the elusive elements is the palaeogeography of north-western Gondwana, and most notably the position of the Moroccan Meseta – the central part of the Moroccan Variscides, comprising a collage of blocks once located at the northern periphery of Gondwana. While some reconstructions place the Meseta as a distal, continuous segment of the Gondwana margin, others depict a very different scenario, envisaging that at some point the Meseta became separated from Gondwana by a wide oceanic basin. Here, we aim to better understand the Late Devonian position of the Meseta using a novel approach that combines two palaeoceanographic tracers: neodymium (Nd) and oxygen isotopes. These proxies, applied together on conodont apatite – an established archive of the composition (Nd and O isotopes) and temperature (O isotopes) of past seawater – provide new constraints on the pre-Variscan oceanography of the Gondwana margin. The analysed, uppermost Givetian-lower Famennian sections, which are representative of the Gondwana mainland (eastern Anti-Atlas) and the cratonward part of the Western Meseta (Middle Atlas) show similar, relatively unradiogenic εNd values. These signatures point to dominance of continental weathering-derived Nd sources in the epicontinental seas of northwestern Gondwana. The temporal trends observed in the studied sections also show notable similarities, which are primarily interpreted as reflecting variations in the continental-runoff vs. open-oceanic contributions to the local marine Nd isotope budget. These variations were controlled by changes in sea level, local tectonic movements, and the evolution of vascular plants on land. The distal, outboard margin of the Western Meseta exhibits less variable and more radiogenic εNd values, indicating a greater contribution from open-oceanic seawater. While the observed trends in oxygen isotope signatures are generally consistent with global records, the δ18O values are significantly lower than those reported from other parts of the Rheic realm. The most likely explanation for the observed 18O depletion is the increased role of freshwater input in the relatively high-latitude, semi-restricted epicontinental basins. Overall, the observed εNd–δ18O signatures are consistent with the location of Moroccan Meseta at the northern Gondwana margin. Some local variations in the isotope signals can be attributed to the semi-isolated nature of the studied basins, rather than to a presence of an extensive Late Devonian oceanic seaway between the Anti-Atlas and Meseta domains.This work was supported by the National Science Centre, Poland, grant No. 2022/47/ST10/00205.

Modern sediments from reef facies at Discovery Bay, Jamaica, were analyzed to document changes in biotic sediment composition over the past four decades and to evaluate their relationship to the impacts of hurricanes, rising temperatures, and sea-level rise. Discovery Bay is a classical Caribbean reef research site, where reef community structure has been quantitatively and systematically documented since 1977, providing a robust long-term framework for interpreting sedimentary responses to environmental and climatic stressors. New data reveal that sediments from the backreef/lagoonal zone are dominated by plates of the green alga Halimeda (35.7–54.0%) and coral fragments (29.7–48.7%). Compared to the 1982–1999 period, Halimeda has nearly doubled in relative abundance, while coralline algae, echinoid fragments, and the encrusting foraminifer Homotrema rubrum have decreased by more than 50%. Despite the present scarcity of living corals in the backreef, coral fragments remain abundant in the sediments. They are derived mainly from the adjacent reef crest, where only old, dead coral skeletons are present today. Intensified wave action associated with sea-level rise promotes erosion of the old reef framework and transport of sand-sized material into the backreef. Additional coral skeletal material is supplied by storm-induced reworking of older backreef sediments. In the fore-reef zone (

This study examines a grave of the Z & lstrok;ota culture from the Late Eneolithic period (the first half of the 3rd millennium BC), discovered at a cemetery in Sadowie, southeastern Poland. The deliberately constructed grave chamber contained the remains of six individuals of varying sex and age: five males and one female. Evidence of fatal injuries was observed on the skulls of three individuals, while flint arrowheads were embedded in the postcranial skeletons of two others. Interdisciplinary studies were conducted to investigate the biological characteristics of the buried individuals and the circumstances surrounding their deaths. Genetic analyses indicated kinship ties between some of the individuals. Strontium isotope analyses revealed that most of the individuals were local to the Sadowie area, with the exception of one female who was identified as non-local. Stable carbon and nitrogen isotope ratios in bone collagen revealed that the individuals had similar diets, predominantly based on C3 plants, with notable contributions from animal protein, likely derived from herbivorous meat and/or dairy products. The studied burial provides further evidence of prehistoric violence among Late Eneolithic communities.

Neodymium (Nd) isotopes, tracers of seawater composition and mixing, measured in calcitic bivalve shells and calcitic micrite from the Middle Miocene deposits in Poland and Ukraine, were used to reconstruct the seawater circulation and the evolution of seawater geochemistry in the Fore-Carpathian Basin, the northern peripheral part of the Paratethys. The data revealed a wide variation in epsilon Nd values for the Badenian seawater, ranging from -12.1 to -6.6. This is in contrast to the more radiogenic composition of the Sarmatian seawater, with Nd isotope signatures ranging from -8.7 to -6.4. The shift towards more radiogenic epsilon Nd values during the Sarmatian aligns well with the opening of a wider gateway connecting the Central and Eastern Paratethys, which facilitated an inflow of waters from the Eastern Paratethys. The significant variation in the Nd isotope composition of the Badenian and Sarmatian seawater provides evidence for the mixing of relatively radiogenic open sea water with unradiogenic riverine waters. Results from this study indicate that the largest influx of unradiogenic Nd by riverine waters came from the crystalline basement of the Ukrainian Shield and the Paleozoic substrate of the Holy Cross Mountains in Poland. There is no evidence that riverine waters draining the Carpathian orogen constituted an essential source of radiogenic neodymium. The inflow of radiogenic open sea water from another domain of the Central Paratethys seems more likely. The lateral distribution of Nd isotope signatures of seawater in the basin points to a circulation pattern consisting of a northwest-oriented current associated with mesoscale anticyclonic offshoot eddies.

Densely packed accumulations of scutelluid trilobite sclerites, found in subseafloor vent fissures and cavities within the Devonian Hamar Laghdad elevation (Anti-Atlas, Morocco), were investigated to understand their taphonomic, ecological, and behavioural significance. The assemblages are monospecific and composed of disarticulated exuviae, with a predominance of pygidia and no complete trilobite carapaces. Two Pragian-age lumachelles, deposited in subseafloor cavities within bioclastic packstones, are dominated by Platyscutellum massai, while five Emsian-age lumachelles occurring in fissures within the Kess-Kess mounds contain Cavetia furcifera. This study provides key insights into the moulting behaviour, life habits, and palaeoecological preferences of scutelluid trilobites during the Early Devonian. Morphological features indicates that both trilobite species were adapted to open marine environments, ruling out a permanent cave-dwelling lifestyle. The assemblages are interpreted as the result of mass moulting behaviour within subseafloor fissures and cavities. Size-frequency data suggest synchronised, size-segregated moulting events. Although a reproductive function for these aggregations remains speculative, parallels with modern arthropods suggest that mass moulting may have conferred both protective and reproductive advantages. These findings reinforce the interpretation that the mass gathering of trilobites, particularly during ecdysis, may have been an adaptive strategy in response to ecological pressures in Early Devonian marine environments. The preferred concave-up orientation of sclerites suggests passive gravitational settling within fissures and cavities, rather than transport by horizontal currents, while the breakage of smaller sclerites points to reworking by episodic hydrothermal fluid discharge.

Neodymium (Nd) isotopes constitute a versatile tracer frequently used in oceanography to identify water masses and track their circulation, both in the modern and ancient oceans and seas. In this research, for the first time, primary marine gypsum is being used as a new archive preserving Nd isotope signatures of past seawater and brines in very shallow-water settings. Nd isotope signatures (εNd values) coupled with Sr isotope ratios (87Sr/86Sr) allowed to constrain mixing processes and composition of brines in a marine evaporite basin that developed in the Fore-Carpathian Basin during Badenian (Middle Miocene) time. We measured the Nd and Sr isotope composition of selenite crystals collected from gypsum successions, well-exposed in southern Poland and western Ukraine. The crystals reveal wide temporal variations in εNd(t) values, from −14.4 to −6.1, contrasted by relatively uniform 87Sr/86Sr ratios, from 0.7089 to 0.7093, and provide evidence for the mixing of sea and riverine waters during the brine formation. Gypsum precipitation taking place in very small sub-basins (evaporite pans) was controlled by episodic, significant inflows of riverine waters that triggered the formation of dissolution surfaces and cyclicity within the sabre gypsum successions. Riverine-water inflows into the Fore-Carpathian Basin are postulated from two main directions, from the Ukrainian Shield (western Ukraine) and the Holy Cross Mountains (southern Poland). In conclusion, we show that Nd isotopes are much more sensitive than Sr isotopes in detecting marine vs non-marine contributions in the composition of brines and gypsum deposits.

Over the past decades, neodymium isotopes have received considerable attention in palaeoceanography as a tool for reconstructing past seawater circulation, local weathering inputs, and sea-level changes. In this study, we have investigated the Nd isotope composition of Serpukhovian (Carboniferous) carbonates of a shallow-water succession to test icehouse cyclicity and seawater dynamics on the Karatau carbonate platform in southern Kazakhstan. The cyclic succession formed in response to glacio-eustasy and composed of subtidal and intertidal limestones displays a large variation in the εNd(326 Ma) values from –1.6 to +4.3, corresponding to differences in the isotopic composition of two seawater masses present in the adjacent Uralian–Turkestan Ocean during the Serpukhovian, highly radiogenic deep water and less radiogenic surface water. The Nd isotope excursions within the icehouse cycles are more complex than simple transgressive-regressive cycles. They probably reflect a temporal pattern of the sub-Milankovitch climatic perturbations during the interglacial periods in the Carboniferous. The episodic appearance of rich brachiopod communities was forced by the inflow of highly radiogenic, nutrient-rich waters, presumably driven by upwelling. Nd isotope analyses of cyclic intertidal and subtidal carbonates have great potential to produce high-resolution records of seawater dynamics on shallow-water carbonate platforms. This study was supported by the Polish National Science Centre, grant No. 2013/11/B/ST10/04751.

Over the past decade, the neodymium (Nd) isotope composition of mineral matter from peat cores has seen increasingly common use as a tracer of dust influx associated with major changes in the Holocene atmospheric circulation. However, the incomplete understanding of the local controls on the sources of the sediment supplied to peatlands remains a key difficulty in the interpretation of the archived Nd isotope signals. Here, we used neodymium isotopes to reconstruct environmental disturbances in peatlands. We performed a multi-proxy study of two peatlands that experienced peatland burning and validated the recorded peat Nd signatures using reference surface sampling. Our data show a link between the Nd isotope signals and local environmental disturbances: peat burning, local fire activity and pollution fluxes. Our study illustrates the crucial role of identifying local events that influence the supply of mineral material to peatlands. Insufficient recognition of such local controls may either obscure the large-scale variations in the atmospheric circulation patterns, or introduce artefacts to the Holocene climate record. We also provide recommendations for the use of Nd isotopes in palaeoecological studies of peatlands.

Seepage of methane-rich fluids is common in subduction zones throughout Earth's history. However, the causes and hydrogeological regimes of methane seepage in the geological past are commonly elusive. To provide insights into the hydrogeological regime and structural evolution of the Cretaceous subduction zone of Hokkaido, Japan, this study investigates the timing of discharge and migration pathways of fluids emitted at five ancient methane seeps using U-Pb dating and coupled Sr, Nd, C, and O isotope analyses of the authigenic seep carbonates. The carbonates were collected from forearc-basin sediments of the Yezo Group, which are underlain by a mafic igneous basement (lower Sorachi ophiolite) detached from the subducting plate. The subduction zone is known to have experienced intermittent accretionary and non-accretionary stages, and the U-Pb dates determined for seep carbonates document two fluid discharge events, -100 and -80 Ma, falling within the accretionary periods. The 87Sr/86Sr ratios (0.70682-0.70781) and epsilon Nd values (-5.9 to -0.1) of the carbonates show significant variability, indicating the seeping fluids experienced interactions with the mafic rocks of the lower Sorachi ophiolite and with siliciclastic sediments of the Yezo Group. The delta 13C values of the carbonates, as low as - 49 parts per thousand, suggest a primarily microbial origin of the seeping methane, which makes methane migration from the underplating materials at high temperatures (>100 degrees C) unlikely. These results demonstrate that the episodic expulsion of the methane-rich fluids, originating from within the forearc basin rather than from the underplating materials, occurred during the accretionary stages and played a major role in methane seepage in the Cretaceous subduction system.

The Humboldt Current System along the Pacific coast of South America creates one of the most productive ecosystems on Earth. To trace the origin of the water masses in this area, we measured neodymium isotope compositions (ENd) in tooth enameloid of two genera of coastal sharks from latest Oligocene to early Pleistocene strata in the Pisco and Sacaco basins in southern Peru. Most ENd values range from -4 to -1, with a strong negative excursion in the late Miocene (-8-7 million years ago [Ma]) with values as low as -9.2. The overall trend of the ENd values resembles that of equatorial Pacific deep waters, though with an offset of about +2 ENd units until about 6 Ma. With a major input of hinterland weathering considered unlikely, we interpret this pattern as reflecting a modern-type upwelling regime, though with a lower contribution of Antarctic waters than today. Starting about 6 Ma, the contribution of Antarctic waters to the upwelling waters increased approximately to present-day levels, coincident with, and possibly driven by, increased Antarctic glaciation and the Andes reaching their present-day elevation, both of which likely enhanced the counter-clockwise circulation in the South Pacific Ocean. The negative excursion of ENd values in the Pisco/Sacaco basins -8-7 Ma coincides with a late Miocene biogenic bloom in the Pacific Ocean and elsewhere, and with a strongly increased northward bottom current observed on the Nazca Drift System just offshore our sampling area. Thus, the negative excursion of ENd values in the Pisco/Sacaco basins likely resulted from a southern sourced input of nutrient-rich, unradiogenic water, which could have been an important contributor to the biogenic bloom. (c) 2023 The Author(s). Published by Elsevier B.V. on behalf of International Association for Gondwana Research. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/ 4.0/).

Middle Miocene crystals of sabre gypsum and subcrystal of giant gypsum intergrowth cropping out in southern Poland near Busko have been analysed for their Sr isotope composition. The new isotopic data revealed fluctuations in 87Sr/86Sr values within the primary gypsum crystals providing new insight into paleohydrological conditions during the Badenian salinity crisis in the Polish part of the Carpathian Foredeep Basin. The isotopic composition of a glassy gypsum subcrystal decreased progressively with the subcrystal growth, ranging from 0.70892 to 0.70884 near the crystal apex. The 87Sr/86Sr ratios of the sabre gypsum crystals are in the range of 0.70887–0.70934 and there are significant fluctuations within each gypsum layer tested. Similar intra-layer fluctuation patterns observed in various sections provide a strong argument for the synchronous origin of the investigated portions of the sulphate successions. The studied primary gypsum has a more radiogenic composition than the Badenian seawater. Its isotope signatures reflect spatial and temporal changes in the supply of continental derived radiogenic Sr to the Carpathian Foredeep Basin. Contrary to previous studies, the Palaeozoic clastic rocks of the Holy Cross Mountains are suggested as potential sources of radiogenic strontium. The new Sr isotope data support a salina model for the evaporitic basin of the Carpathian Foredeep.This study was supported by the Polish National Science Centre, grant No. 2017/27/B/ST10/00493.

In recent years, Nd isotopes have seen increasingly common use in studies of hydrocarbon seeps. Given the distinct Nd isotope signature of mafic igneous rocks, particular emphasis in these investigations has been on reconstructing former interactions between the seeping fluids and volcanic materials. The results of our case studies on ancient seeps underlain by mafic volcanic bodies, including Cretaceous seep carbonates of the Outer Carpathians (Czech Republic) and Basque-Cantabrian Basin (Spain), as well as Eocene seeps of the Cascadia convergent margin (Washington) consistently document their significant enrichment in volcanogenic Nd, reflected in their increased Nd isotope ratios (εNd values). The extent of this 143Nd-enrichment varies depending on the geological context of given seeps, most notably the εNd signatures and thickness of the volcanics and overlying sedimentary piles, and the Nd isotope signal of background local pore waters. The highest εNd values are observed in seep carbonates very shallowly underlain by thick mafic volcanics: the Cretaceous seep of the Carpathians and Eocene seeps of Cascadia. For the former, the εNd values are up to 7.5 units higher than the signature of coeval non-seep pore water, whereas for the latter the εNd values are as high as +1.9, close to the highest value ever recorded for seawater. More moderate 143Nd-enrichment typifies the Cretaceous seeps of Spain, for which the volcanic intrusions were emplaced at considerable depths below the seafloor. In such cases, the Nd isotope signature of the fluid-volcanic interactions was partially obscured by subsequent interactions between the fluids and the overlying sediments. Rather than focusing solely on exploring the new geochemical tool, the primary aim of our studies was to address broader questions regarding the tectonic architecture and geological history of the sedimentary basins that host given seep deposits. For the Eocene seeps of Washington, the Nd isotope data served to document interactions between the methane-rich fluids and the volcanic terrane of Siletzia, which underlies the Cascadia forearc; these results placed important stratigraphic and structural constraints on the activation and earliest history of convergence in Cascadia, following Siletzia accretion. For the studied Cretaceous seeps, all hosted by early, sediment-covered rifts, the studies demonstrated that Nd isotopes offer a valuable new tool of deconvolving methane fluxes from different organic matter alteration pathways for the very complex, sedimentary-magmatic systems of incipient rifts. At the same time, these studies emphasized important limitations of Sr isotopes, the system most commonly used to document interactions between the seeping fluids and igneous rocks. Because of the much higher Sr/Nd ratios observed in pore waters than in igneous rocks, the potential of Sr isotopes to record fluid-volcanic interactions is considerably lower than that of Nd isotopes. Thus, broader use of Nd isotopes can assist in identifying potential volcanogenic fluid endmembers for the numerous sedimented rifts for which evidence for magmatic involvement in the fluid expulsion remains equivocal. This work was supported by the National Science Centre, Poland, grant No. 2016/23/D/ST10/00444

Strontium isotopes have seen common use as a tracer of volcanic-influenced fluids at hydrothermal vents and cold seeps hosted by sedimented rifts. However, for some fluid emissions, no apparent contribution of volcanogenic Sr has been observed, despite geological or seismic evidence suggesting magmatic involvement in the fluid expulsion. Here, we explore the behaviour of Sr during fluid-rock interactions in a sedimented rift based on the isotope and elemental composition of Albian hydrocarbon-seep carbonates of the Basque-Cantabrian Basin, Pyrenees. The basin represents a peri-cratonic rift formed during the opening of the Bay of Biscay and infilled with organic-rich siliciclastics affected by subvolcanic intrusions. The intrusions stimulated thermogenic hydrocarbon generation in the sediments and resulted in enrichment of the associated seep carbonates in volcanic-derived, radiogenic Nd. In contrast, none of the 87Sr/86Srcarbonate ratios observed in this study provide evidence for subseafloor interactions between the seeping fluids and igneous materials. Instead, all four studied seep deposits show various degrees of 87Sr-enrichment, bearing the fingerprint of interactions with the rift-filling siliciclastics, rather than a volcanogenic signature. Furthermore, for three deposits, the observed unusual, positive correlation between the Sr and Nd isotope ratios attests to a presence of an evolved, deep-seated fluid end-member enriched in both 87Sr and 143Nd. This isotope decoupling can be explained by the different responses of Nd and Sr to subseafloor fluid-volcanic interactions, with a moderate degree of elemental exchange able to modify the fluid Nd isotope signal, but insufficient to affect the fluid Sr isotope signature. The study shows that for many sedimented seeps and vents, and especially for low-temperature, hydrocarbon-dominated emissions, volcanic-influenced fluids can be more reliably traced using the Nd isotope system, whereas Sr isotopes cannot provide standalone evidence for their absence.

The neodymium isotope composition of micritic limestones from the Devonian–Carboniferous carbonate platform of the Greater Karatau (southern Kazakhstan) was investigated to test the ability of calcite micrite to archive Nd isotope signatures of seawater. The carbonate fraction that displays seawater-like rare earth element (REE + Y) signatures is often more radiogenic than the dispersed terrigenous material in the samples. Hence, its Nd isotope composition is interpreted to correspond to the seawater from which the micrite was precipitated. The seawater on the Karatau platform exhibited an extremely wide range of ε Nd (t) values from –9.3 to +4.3 (the most radiogenic value measured for past seawater to date) and very uniform Sm/Nd ratios, from 0.19 to 0.22, lying within the range characteristic for modern oceanic water. The temporal trend in ε Nd (t) values is interpreted to document the final closure of the Uralian–Turkestan Ocean. It shows that the subduction along Kazakhstan's active margin had already started at the beginning of the Tournaisian ( c . 355 Ma), at least 23 Myr earlier than previously thought. The application of Nd isotope time series on biostratigraphically dated carbonates opens a new direction for geotectonic studies. This approach has the potential to provide useful constraints for the precise dating of the duration of geotectonic and volcanic events. Supplementary material: Nd isotope and REE concentration data, summary of stratigraphic and lithological data, field photographs and additional geochemical plots are available at: https://doi.org/10.6084/m9.figshare.c.5110163

Spatial variation in 87 Sr/ 86 Sr signatures has been investigated in various components of the natural environment of Poland (Central Europe) including rocks and sediments, surface waters, and flora.The geological substrate is characterized by a very wide range of Sr isotope ratios, from 0.7023 to 1.1486.High 87 Sr/ 86 Sr values (above 0.72), related to the Pleistocene glacial

Studies on the involvement of intrusive magmatism in hydrocarbon generation within sedimentary basins have gained momentum owing to increasing appraisal of the role that such processes may play in controlling global carbon cycle perturbations, and the exploration potential of the volcanic sedimentary basins. Nevertheless, for many areas the causal link between the intrusions and surrounding hydrocarbon systems remains disputed, encouraging a search for methods that could aid in identifying different hydrocarbon sources. Here, we have performed a multi-proxy geochemical study of the middle Cretaceous methane-seep deposits of the Basque-Cantabrian Basin, an early-stage, peri-cratonic rift marking the Mesozoic opening of the Bay of Biscay. Infilled by a thick sedimentary succession intruded by shallow-level igneous bodies, the basin shares analogies with modern young, sedimented rifts that sustain hydrocarbon seepage. We have applied a novel approach that uses the Nd isotope composition of the seep deposits to constrain the relationship between hydrocarbon seepage and igneous activity, and to explore the general potential of Nd isotopes to trace magmatic-influenced fluids in volcanic sedimentary basins. The Nd isotope data have been combined with rare earth element analyses and carbon and oxygen isotope measurements, providing broad insight into the former composition of the seeping fluids. For three out of four investigated seeps, the Nd isotope ratios observed in authigenic seep carbonates include signatures markedly more radiogenic than that reconstructed for background seawater-derived pore waters. The level of this 143Nd-enrichment varies both between and within individual deposits, reflecting spatial and temporal differences in fluid composition typical of seep-related environments. The radiogenic Nd isotope signals provide evidence of subseafloor interactions between the seeping fluids and mafic igneous materials, supporting the model of an igneous control on the mid-Cretaceous methane expulsion in the Basque-Cantabrian Basin. The thermogenic origin of the methane is in accord with the moderately negative δ13C values and paragenetic successions observed in the studied seep carbonates. For a single deposit, its relatively unradiogenic Nd isotope composition can be attributed to the smallest size and shallowest emplacement depth of the underlying intrusion, likely resulting in a short-lived character and limited hydrocarbon-generation potential of the associated contact metamorphism. The study demonstrates that Nd isotope analyses of seep carbonates offer a tool in disentangling methane fluxes from different organic matter alteration pathways for the numerous, both fossil and modern sedimented rifts for which the involvement of various methane sources remains insufficiently understood.

This study presents first isoscape maps of strontium isotope signatures and their spatial variation in Poland, based on ~900 samples of rocks, sediments, surface water, and flora. This dataset is supplemented by 87Sr/86Sr ratios predicted for several carbonate rock units. High, radiogenic Sr isotope ratios (>0.72), related to the Pleistocene glacial deposits, are omnipresent throughout the country and are also found in the Sudetes and the Holy Cross Mountains, where igneous and clastic Palaeozoic rocks are widely exposed. The lowest Sr signatures (<0.71) occur predominantly in the Silesian-Małopolska and Lublin uplands and are related to exposures of Palaeozoic, Mesozoic, and Neogene carbonate rocks. The large variation of 87Sr/86Sr ratios in the environment across the country is chiefly driven by the diversity in the geological substrate, and locally, it is also influenced by anthropogenic contamination. Strontium isoscapes for the geological substrate and surface waters differ from each other, in terms of the range of 87Sr/86Sr values and their distributional pattern. The differences result primarily from mixing processes in the geosphere (weathering), hydrosphere, and biosphere that control Sr inputs from various natural sources present in the environment. On the other side, they are also created by anthropogenic contamination of surface water and presumably of soils. This situation has important implications for future archaeological provenance and migration studies, as isoscapes for surface water and vegetation cannot be directly used to estimate the local 87Sr/86Sr baselines for past human populations. Therefore, caution is required when modern Sr data of surface water and plants are used in archaeological research. 87Sr/86Sr values of the geological substrate, which may be affected by anthropogenic contamination to a lesser extent than water, soil, and vegetation, are favoured for the baseline estimation for historical times.

Stratigraphic and structural context of the early evolution of the Cascadia convergent margin, following major subduction reconfiguration associated with accretion of the igneous Siletzia terrane at 50−45 Ma, remains insufficiently understood. Here, we have applied a novel approach that uses combined Nd, Sr and stable isotope analyses of ancient methane-seep carbonates to constrain the early hydrogeological regime of the Cascadia margin. Analyses included the oldest-known seep deposits of Cascadia, formed during mid-Eocene time (42.5−40.5 Ma). A combination of exceptionally high εNd and low 87Sr/86Sr signatures observed in these carbonates consistently point to former interactions between the seeping fluids and mafic, igneous constituents of the forearc basement. Moderately negative δ13Ccarbonate values imply thermogenic origin of hydrocarbons at three out of four studied seeps, with likely contribution of biogenic methane at a single, landward-most site. When combined with structural constraints, the recorded signals point to discharges of fluids originating from deep portions of the young subduction wedge, and their channeled ascent through the Siletzia terrane. The results document the presence of a fluid expulsion system indicative of active convergence prior to maturation of typical arc magmatism in the Cascades at 40 Ma. The exceptionally pronounced role of exotic, 143Nd-enriched, 87Sr- and 18O-depleted fluids recorded for early Cascadia reflects its distinctive structural architecture, including the relatively thin sedimentary cover of the young forearc, its extensional tectonics, and the near-trench position of the volcanic terrane that the descending plate-derived fluids must have migrated through prior to reaching the seafloor.