Search

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 (ԑNd) 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 ԑNd 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 ԑNd values resembles that of equatorial Pacific deep waters, though with an offset of about +2 ԑNd 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 ԑNd 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 ԑNd 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.

The historical, zooarchaeological and isotopic data concerning cattle breeding and management in the medieval Middle Nile Valley are considered in this paper in the first such comprehensive research for the region. The main source of data are the nearly 10,300 animal remains. The archaeozoological analyses focused primarily on cattle morphology. Strontium isotope analyses were used to indicate the local/non-local origin of animals encompassing the whole period studied. The empirical data indicate a developed central system of cattle management in medieval Makuria. Textual and iconographic sources additionally reflect an extensive set of values that have been experienced since prehistory in the Middle Nile and correspond to the anthropological definition of the “cattle centred behavior”. Comprehensive analysis of animal remains and the analysis of textual information enabled the formulation of a hypothesis about Makuria’s economic and cultural foundations rooted in the local tradition, constituting an important element of the Nubian identity.

Late antique and medieval cotton and wool textiles found in the middle Nile Valley (Nubia, northern Sudan) were analysed for their technical characteristics and strontium (Sr) isotope composition. All wool textiles exhibit Sr isotope signatures consistent with the isotopic background of the region studied and are considered to be of local origin. However, a medieval wool kilim from Meinarti shows technical and aesthetic features suggesting its foreign Maghreb provenance. As this fabric dates back to the occupation of Meinarti by the Beni Ikrima tribe, it is suggested that the kilim was woven by the Beni Ikrima people from local Nubian raw material. The cotton samples tested come from abroad and document trade with the oases of the Egyptian Western Desert, the west coast of India, and perhaps also with the Arabian Peninsula or Pakistan.

Summary From 19 inhumation graves from the cemetery in Malbork-Wielbark (northern Poland) samples (teeth) were collected for the analysis of strontium (87Sr/86Sr) isotopes in order to try to determine the origin of the subjects. The chronological range of the analyzed statistical sample covers about 300 years of over 600 years of necropolis history, i. e. the period from the end of the early pre-Roman period (phase A3 – the last decades BC) to the C1b phase of the Roman period (more or less the first half of the 3rd century AD). The results of the analysis indicate the local origin of the studied group, and at the same time constitute an interesting contribution to the discussion on the ethnic structure of the Wielbark culture.

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 Nd-143-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 delta C-13 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 work was supported by the National Science Centre, Poland (grant No. 2016/23/D/ST10/00444; to MJ) , and the Eusko Jaurlaritza (Ikerketa Taldeak IT930-16) and the Spanish State Research Agency (project PID2019-105670GB-I00/AEI/10.13039/501100011033; both to LMA)

Archaeological sites at Affad (Sudan) are the only ones in northeastern Africa providing ostological remains of both African aurochs (Bos primigenius), dated to 50 kya, and domestic cattle, dated t...

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

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.

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.

Strontium isotope ratios (87Sr/86Sr) were applied to investigate provenance of the Bronze Age population buried at cemetery in Gogolin-Strzebniów. The study used 12 samples: two human enamel samples from inhumation graves and ten samples of petrous part of temporal bone from cremation burials. Baseline information on the local Sr isotope composition was established on geological data. The human samples of ten individuals yielded a quite narrow range of Sr isotope signatures, from 0.7112 to 0.7121 (Table 1; Fig. 1). The obtained results indicate that these individuals have 87Sr/86Sr values which fits well within the range of Sr isotope signatures established for the local area. Signatures of two individuals are outside this range. The bone remains from grave 59 have a lower value of 87Sr/86Sr (0.7107), and a molar tooth of an individual from grave 63 – has a higher value (0.7128). These two individuals have been recognized as non-local. Moreover, the isotopic composition of neodymium (143Nd/144Nd) was analysed for three casting moulds found in grave 24 (Fig. 2; Table 2). The isotopes of this element are the best indicators of the origin of rocks, sediments and related materials (e.g. ceramics) so they allow not only for estimation of the geographical origin of samples, but also for determining their geological age. Because of these advantages, neodymium isotopes are the most frequently used indicator of provenance in geological research. In this method, we obtain several parameters (ratio 143Nd/144Nd, neodymium epsilon eNd, ratio 147Sm/144Nd, value of the model age TDM) for each analysed sample, which together allow for a very precise identification of the raw material origin. Mould No. 8 is made of clay. This material is characterised by an epsilon value of -12.3 and the value of model age TDM = 1.77 Ga, indicating the possibility of the local origin of the material used for the production of this tool. Mould No. 1 is made of sandstone with a model age value TDM = 2.06 Ga. In Europe, such high TDM values are associated with rocks of the East European Platform, which covers the area of Scandinavia (without Denmark), Russia, Ukraine and north-eastern Poland. During the spread of the Scandinavian ice sheet during the Pleistocene period, erratic “Scandinavian” material was transported to Central Europe. In Poland, post-glacial sediments, often containing various erratics, are common in the area of nearly 90% of the territory. Therefore, it is very likely that the sandstone used to produce mould No. 1 was obtained from local Scandinavian materials. Mould No. 3 was made of sandstone, which has similar values of eNd and a similar 143Nd/144Nd ratio as mould No. 1. It cannot therefore be ruled out that this sandstone is also derived from the Scandinavian materials. However, a fully reliable interpretation of this artefact is impossible, because the rock has an unnaturally low of 147Sm/144Nd ratio and therefore its model age is also low (TDM = 1.25). Although rocks of this model age are known from other areas of the world, in Europe they are found only in Scotland. Therefore, it is very probable that the low ratio of 147Sm/144Nd is the result of the secondary removal of the samarium from this rock, most likely during the interaction with hot metal (bronze).

Exceptionally well-preserved fossil cryptic communities have been discovered in submarine cavities of the Lower and Middle Devonian (Emsian to Givetian) mud mounds in the Hamar Laghdad area (Anti-Atlas, Morocco). The cryptic biota encrusted the roofs of the cavities and grew predominantly oriented upside down. These unique coelobiotic communities were dominated by various solitary rugose corals, which very often displayed a “calice-in-calice” growth pattern. Apart from the rugosans, the cavities were inhabited by other sessile invertebrates: tabulate corals, cladochonids, crinoids and lithistid sponges. Many of the skeletons were encrusted by microbial structures. The high density of organisms overgrowing each other points to intensive competition for space in all studied Devonian submarine crypts. The late Emsian to latest Givetian cavities were colonised by various sets of coelobiotic inhabitants mostly originating from the surrounding deep-water marine environments. It is suggested that the local species pool was a decisive factor in determining the ecological succession and taxonomic structure of cryptic communities. The changes in taxonomic composition and diversity, over time and space, were primarily related to variations in local physical environment. Consequently, the communities in crypts affected by venting of high-temperature fluids or hydrocarbon seepage were of low diversity and included endemic elements and characteristically small specimens.

Significance We sequenced the genomes of 15 skeletons from a 5,000-y-old mass grave in Poland associated with the Globular Amphora culture. All individuals had been brutally killed by blows to the head, but buried with great care. Genome-wide analyses demonstrate that this was a large extended family and that the people who buried them knew them well: mothers are buried with their children, and siblings next to each other. From a population genetic viewpoint, the individuals are clearly distinct from neighboring Corded Ware groups because of their lack of steppe-related ancestry. Although the reason for the massacre is unknown, it is possible that it was connected with the expansion of Corded Ware groups, which may have resulted in violent conflict., The third millennium BCE was a period of major cultural and demographic changes in Europe that signaled the beginning of the Bronze Age. People from the Pontic steppe expanded westward, leading to the formation of the Corded Ware complex and transforming the genetic landscape of Europe. At the time, the Globular Amphora culture (3300–2700 BCE) existed over large parts of Central and Eastern Europe, but little is known about their interaction with neighboring Corded Ware groups and steppe societies. Here we present a detailed study of a Late Neolithic mass grave from southern Poland belonging to the Globular Amphora culture and containing the remains of 15 men, women, and children, all killed by blows to the head. We sequenced their genomes to between 1.1- and 3.9-fold coverage and performed kinship analyses that demonstrate that the individuals belonged to a large extended family. The bodies had been carefully laid out according to kin relationships by someone who evidently knew the deceased. From a population genetic viewpoint, the people from Koszyce are clearly distinct from neighboring Corded Ware groups because of their lack of steppe-related ancestry. Although the reason for the massacre is unknown, it is possible that it was connected with the expansion of Corded Ware groups, which may have resulted in competition for resources and violent conflict. Together with the archaeological evidence, these analyses provide an unprecedented level of insight into the kinship structure and social behavior of a Late Neolithic community.

Middle Devonian (Eifelian/Givetian transition) brachiopod-hosted sclerobiont assemblage from Gondwana (Morocco, eastern Anti-Atlas, Mader Basin) has been studied for the first time. The analysis of hundreds of brachiopod shells revealed at least 26 sclerobiont taxa, making the studied palaeoecommunity one of the most diverse Middle Devonian sclerobiont assemblage reported to date. The palaeocommunity is dominated by encrusting organisms, in particular bryozoans, foraminifers, ascodictyids and microconchids, whereas bioeroders are represented by Clionolithes and Oichnus ichnospecies. As supported by microfacies, fossil preservation and the presence of encrusting Rothpletzella algae, the sclerobionts developed in a calm, euphotic, offshore marine environment situated below normal wave base. Prevalence of articulated shells without signs of either extensive mineral staining, or taphonomic alteration resulting from hydrodynamic processes, as well as preservation of some delicate encrusters (Vinella, Rothpletzella), indicate that the palaeocommunity did not undergo extensive time-averaging. The hosts were colonized syn vivo, as evidenced by the epibiont growth near the commissure margin, the presence of shell malformations and even embedded auloporid corals and cornulitid tubeworms. Competition for space among sclerobionts was apparently limited, as suggested by the very low number of overgrowth interactions, indicating that the shelly substrate available for colonization was abundant. The presence of the same dominant groups of sclerobionts on different host taxa indicates a lack of species-selectivity by these colonizing sclerobionts. It also suggests that the sclerobiont species pool in the environment was generally similar throughout the deposition of the sampled rock interval. As testified by the host brachiopod and bryozoan species, the sclerobiont assemblage from this locality of northern Gondwana had strong affinities with those from the southern margin of Laurussia, most likely reflecting strong connectivity between these regions provided by the South Equatorial – North Gondwana current system during the late Eifelian Kaˇc´ak transgressive episode.

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

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 eNd(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 eNd(t) values is interpreted to document the final closure of the Uralian–Turkestan Ocean. It shows that the subduction along Kazakhstan9s 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

The carbonates forming at deep-sea hydrocarbon seeps provide an archive for the source and migration pathways of the seeping fluids. Interpretation of the archived isotopic and elemental signatures is, however, not straightforward because of mixing between the signals of fluids and ambient seawater, limited understanding of subseafloor fluid circulation, and effects of diagenetic alteration. The Nd isotope system is among the most widely used tracers of circulation patterns in modern and past oceans, but to date Nd isotopes have been rarely used in investigations of fluid migration pathways at hydrocarbon seeps. To test the sensitivity of Nd isotope signals of seep carbonates to record past interactions between the seeping fluids and 143Nd-enriched, volcanic-derived mineral components, we performed Nd, Sr and stable isotope analyses of the Lower Cretaceous (Barremian) seep carbonates found in Baska (Czech Carpathians). These seep deposits are directly underlain by a complex of mafic igneous rocks, which the methane-charged fluids must have passed through on their way to the seafloor. The eNd(t) values measured in the seep carbonates are significantly more radiogenic than the inferred signal of contemporaneous local seawater, and shifted towards the composition typical of the underlying basaltoids. This is in agreement with the 87Sr/86Sr ratios, which are markedly lower that the coeval seawater signature. Consistent co-variance trends are observed among the measured eNd(t), 87Sr/86Sr and δ13C values, attesting increasing role of the volcanic-derived fluid component with increasing contribution of methane-derived carbon. The results of the present approach reveal the potential of Nd isotopes to fingerprint exotic fluid end-members present in plumbing systems of both fossil and modern methane discharges. The method can be of particular use in studies of seeps associated with plate margins, where 143Nd-enriched igneous materials are commonly encountered in the basement or in the sediment column.

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.

International audience; Spectacular Early Devonian carbonate buildups exposed in the eastern Anti-Atlas of southern Morocco and widely known as the Kess-Kess mounds constitute a classical example of deep-water mud mounds interpreted to be related to hydrothermal venting. They developed on the Hamar Laghdad elevation, located near Erfoud, created by a submarine volcanic eruption and composed of peperites and tuffs displaying geochemical characteristics of typical intra-plate basalts. During late Emsian time, reactivation of magmatic processes caused doming of the volcanic complex and the overlying sedimentary strata, and in consequence, a network of radial and tangential faults originated. Most of the mounds developed over the cross-points of these faults. One of the characteristic features of the Kess-Kess mounds is the presence of small caves and rock shelters. They represent fragments of larger fissures, originally open and connected to the seafloor through vent outlets. This system has formed simultaneously with the formation of mounds or immediately after. The irregular and/or pipe-shaped geometry of fissures points to chemical corrosion processes rather than to a tectonic mechanism for their origin. Dissolution of carbonates appears to be in contradiction with enhanced carbonate production, characteristic for the rapid mound growth, but it can easily be explained by mixing of two different carbonate solutions, hydrothermal fluids and seawater. It is suggested that during the formation of the Kess-Kess mounds dissolution took place in zones dominated by hydrothermal fluid-rich mixtures, and precipitation progressed with dilution of the vent fluids by seawater.

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 Sr isotope composition ( 87 Sr/ 86 Sr) and Sr content of waters of the Warta River (central-western Poland) and its tributaries were used to fingerprint water sources and their interactions in space and time. Dissolved Sr in river water of the Warta is characterized by a relatively narrow range of the 87 Sr/ 86 Sr values, from 0.7090 to 0.7105, which contrasts with a strong variation in isotopic signatures of the tributaries, from 0.7080 to 0.7121. With the exception of three streams, which include inputs of mine waters, the waters of tributaries are more enriched in 87 Sr than the master stream. The overall Sr budget of the Warta watershed is determined by the relative contributions of carbonate dissolution and silicate weathering. It can be accounted for by mixing between waters from three reservoirs: 1) groundwater charged with Sr through interaction with Sr-bearing clay minerals, 2) groundwater related to weathering (dissolution) of carbonate rocks, and 3) atmospheric waters charged with Sr from the near-surface weathering and wash-out of Quaternary glaciogenic deposits. Superimposed on the natural Sr isotope systematics is impact of mine waters and fertilizers. The former providing non-radiogenic Sr from the Permian/Mesozoic aquifers constitutes an important anthropogenic element of the Sr budget, whereas the impact of the latter is presumably common but of minor importance. The present-day Sr isotope systematics of the Warta is temporary and different from that of the pre-industrial times.

Neodymium and strontium isotope compositions of clastic material in Lower Paleozoic rocks, in addition to detrital zircon and mica geochronology and faunal data are used to constrain the geotectonic provenance of the Malopolska and Łysogory terranes in southern Poland. Being characterized by markedly different geological histories during Early Paleozoic times, Malopolska and Łysogory were most often interpreted as exotic terranes, but their identity, provenance and accretionary history are still being discussed. This study presents the first systematic Nd and Sr isotope survey of the Lower Paleozoic siliciclastic rocks. Cambrian clastic rocks of Malopolska differ in their Nd and Sr isotope compositions from those of Łysogory. The former are characterized by a wide range of the eNd(505 Ma) values, from − 11.7 to − 5.7, Sr isotope ratios from 0.712 to 0.767, and model ages (T2DM) predominantly younger than 1.9 Ga, whereas the eNd(t) values of the latter vary within a fairly narrow range of the eNd(505 Ma), from − 11.0 to − 8.3, Sr isotope ratios from 0.722 to 0.754, and model ages are older than 1.9 Ga. New Nd data combined with detrital zircon ages provide evidence that Malopolska must have been supplied with clastic material from Amazonian sources during Cambrian times, being also progressively sourced from the Baltic Svecofennian crust in the Middle Cambrian. Detritus recognized in Łysogory has mostly been derived from the Svecofennian basement of Fennoscandia, but it has also a small addition from Cadomian sources. All provenance and biogeographic data suggest that Malopolska was situated close to the Amazonian Craton near the western end of the Cadomian Belt during the Early Cambrian, and it was not until the late Middle Cambrian that Malopolska collided with the Baltica margin. During the Late Cambrian Łysogory occupied a position between Baltica and the Cadomian Belt but it was probably not yet accreted to the Baltic crust at that time.

During the Final Eneolithic the Corded Ware Complex (CWC) emerges, chiefly identified by its specific burial rites. This complex spanned most of central Europe and exhibits demographic and cultural associations to the Yamnaya culture. To study the genetic structure and kin relations in CWC communities, we sequenced the genomes of 19 individuals located in the heartland of the CWC complex region, south-eastern Poland. Whole genome sequence and strontium isotope data allowed us to investigate genetic ancestry, admixture, kinship and mobility. The analysis showed a unique pattern, not detected in other parts of Poland; maternally the individuals are linked to earlier Neolithic lineages, whereas on the paternal side a Steppe ancestry is clearly visible. We identified three cases of kinship. Of these two were between individuals buried in double graves. Interestingly, we identified kinship between a local and a non-local individual thus discovering a novel, previously unknown burial custom.

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 (

Analyses of the Nd isotope composition of conodonts from the Anti-Atlas (Morocco), the Montagne Noire (France) and the Rhenohercynian domain (Germany) provide insight into the temporal and lateral variations in seawater geochemistry in the western part of the Variscan Sea during the Late Devonian. Most of the isotopic excursions accurately record changes in sea level. The eNd values decreased during regression phases when erosion accelerated supply of unradiogenic Nd from old continental sources. A rise in sea level generated a positive shift in eNd values due to input of more radiogenic oceanic water into the seawater reservoir of the shelf areas. The method has great potential for sea-level research, paleoceanography and correlation because sea-level changes can be precisely recognized even in successions with uniform, monotonous lithologies. However, it has a significant limitation being valid only in epeiric seas and shelf areas. We have used the Nd isotope record to reconstruct the eustatic sea-level changes in late Frasnian–early Famennian time. The onset of the organic-rich Kellwasser units coincides with negative trends in eNd values. This accords with oxygen deficiency at the sea bottom being initiated by short-term regressive events, which in turn would be consistent with cooling periods of glacial origin, as previous authors have suggested.

A fauna of bivalve molluscs is described from methane seep carbonates of the Middle Devonian (c. 390 Ma) Hollard Mound in the eastern Anti-Atlas, Morocco. We describe a new modiomorphid genus Ataviaconcha gen. nov. with the type species Ataviaconcha wendti sp. nov. This is a very large, semi-infaunal species occurring in large colonies similar to those formed by Recent chemosymbiotic cold-seep and hydrothermal vent bivalves. It is the second modiomorphid bivalve known from Palaeozoic chemosynthesis-based ecosystems, after the roughly coeval Sibaya ivanovi Little, Maslennikov, Morris & Gubanov, 1999, from the Sibay hydrothermal vent deposit in the Ural Mountains, Russia. The second and much less numerous bivalve species described in this paper is the solemyid Dystactella? eisenmanni sp. nov., belonging to a genus known also from Ordovician to Devonian marine environments distinct from cold seeps and hydrothermal vents. As with other fossil and Recent solemyids, it was an infaunal burrower, most likely livi...

The uppermost Eifelian Kostyukovichi Formation corresponds to a distinct marine transgressive-regressive cycle in predominantly continental to restricted-marine Middle Devonian succession of the intracratonic Belarusian Basin in a near-equatorial area of SE Euramerica. The presence of the conodont ensensis Zone points to the correlation with the global Kacak Episode whose onset coincided with the eustatic If transgression. The comprehensive study of the Kostyukovichi Fm. in 18 boreholes included sedimentological, palaeontological (conodonts, palynoflora, vertebrates) and geochemical analyses (C, O and Nd isotopes in carbonates and bioapatite). The results demonstrate that the sedimentation was characterised by intermittent hypoxic conditions and salinity fluctuations; it was controlled by increasing terrigenous and freshwater influx from the northern Scandinavian Land with carbonate sedimentation limited mostly to the early stage and southern part of the basin. The palynological study and occurrence of phytoclasts document terrestrial plant expansion, while the abundance of diverse fish taxa attests to the proliferation of vertebrates. These bioevents are attributed to transgression, climate humidization, and expansion of aquatic environments in surrounding land areas. Regional review suggests that such attributes of the Belarusian Kacak Episode as the initial If transgression, marine hypoxia, land plants blooms, carbonate decline and terminal regression, are characteristic also for other palaeogeographic settings of the episode worldwide. The Kacak Episode is here explained as a result of complex interrelations of various terrestrial and marine processes and events initiated by a global warming resulting in eustatic transgression and climate humidization. It is proposed that the important component of the terrestrial-marine teleconnections was the late Eifelian plant expansion presumably connected with the proliferation of progymnosperm arborescent plants with deepened root systems. It contributed to transiently increased denudation rates and, indirectly, to the development of marine hypoxia. The episode was terminated by the low-amplitude regression related to the enhanced CO2 sequestration and resulting climatic cooling.

Stratigraphic and structural constraints on the initiation and early evolution of the Cascadia convergent margin, following accretion of the igneous Siletzia terrane at 50–45 Ma, remain elusive. This study applies a novel approach based on the combination of Nd, Sr, C and O isotope analyses of the oldest-known methane-seep carbonates (Humptulips Formation, middle Eocene, 42.5–40.5 Ma) of Cascadia to provide insight into its early hydrogeological regime and incipient subduction history. Both anomalously high eNd and low 87Sr/86Sr signatures of the studied carbonates attest to interactions between the seeping fluids and mafic, igneous components of the forearc basement. Moderately negative δ13Ccarbonate values imply a predominantly thermogenic origin of hydrocarbons at three out of four studied seeps, with likely an important contribution of biogenic methane at a site that was closer to the ancient shoreline. When combined with structural constraints, the recorded signals point to discharge of fluids originating mostly from deep portions of the young subduction wedge underthrust beneath the accreted Siletzia terrane, and their channelled ascent through its thick volcanic succession. These results document the presence of a fluid generation and migration system typical of active convergent margins prior to maturation of typical, calc-alkaline arc magmatism in the Cascades at 40 Ma. The strongly pronounced involvement of the exotic, 143Nd-enriched and 87Sr-depleted fluids reflects the distinctive structural architecture of the newly reorganised subduction zone. Of particular importance was the combination of a relatively thin sedimentary cover of the infant forearc, its extensional tectonics, and the proximity of the young trench to the volcanic backstop that the deep, subducting plate-derived fluids must have interacted with before their seepage at the seafloor.

Nephrites belonging to both the dolomite-related and serpentinite-related genetic types, from the Zloty Stok deposit, and Jordanow Śląski and Naslawice prospects in the Śleza Ophiolite, respectively, were analyzed for Fe and Sr isotope compositions. These deposits in the Central Sudetes (SW Poland), are unusually situated relatively close to each other. This study is a first attempt to perform combined Fe and Sr isotope study of nephrites. Our results show that Fe in the Fe-As-Au-bearing skarn samples from Zloty Stok (2.77-7.00 wt.% Fe, δ56Fe +0.07 to +0.14‰, and δ57Fe +0.12 to +0.21‰), to which the dolomite-related nephrite belongs, is not inherited from the host dolomitic marbles (ca. 0.4 wt.% Fe; δ56Fe -0.08 to -0.07‰, and δ57Fe -0.12 to -0.09‰), but derived from the nearby, ca. 340 Ma granite intrusion (2.64-5.64 wt.% Fe). In contrast, iron in the serpentinite-related nephrites (2.06-3.88 wt.% Fe, δ56Fe +0.41 to +0.45‰, and δ57Fe +0.59 to +0.66‰) was likely inherited from host serpentinites (5.27-4.81 wt.% Fe), rather than metasomatically derived from adjacent granite intrusions (0.13-0.45 wt.% Fe). Moreover, both the marble transformation into a dolomite-related nephrite (and Fe-As-Au-bearing skarn), and the abyssal serpentinite – through ophiolite – towards serpentinite-related nephrite transformation, are accompanied by a progressive increase of δ56Fe and δ57Fe. This increase is regardless of changes in the bulk Fe content, increasing during the dolomite-related nephrite formation, and decreasing during serpentinite-related nephrite formation. This phenomena may be caused by one of the below listed factors, or combinations: a) preferential incorporation of heavy iron by tremolite and diopside; b) preferential incorporation of the heavy iron in the Fe3+-bearing phases, crystallizing during nephrite formation; c) preferential incorporation of the heavy Fe from migrating granite-derived fluids (positive fractionation between aqueous Fe-bearing fluid, and tremolite/diopside); d) positive isotope fractionation between dolomite/antigorite precursor, and newly formed amphibole/clinopyroxene; e) change of the Fe oxidation state. Furthermore, Fe in the rock-forming tremolite from the serpentinite-related nephrites is isotopically heavier than Fe in tremolite from the dolomite-related ones. In contrast to the iron, the isotopic composition of strontium, combined with its content and structural evidence, suggest multiple sources for this element. In the case of the dolomite-related nephrite (ca. 3-4 ppm Sr; initial 87Sr/86Sr = 0.7085), Sr inheritance from the host-dolomitic marble (ca. 90 ppm Sr; initial 87Sr/86Sr = 0.7081), as well as its derivation from intrusions of both the syn- to late-tectonic, ca. 340 Ma granites (ca. 400-440 ppm Sr), and post-tectonic ∼305 Ma granites (86.4 ppm Sr), is suggested. In the case of the serpentinite-related nephrite (6.3-61.7 ppm Sr; initial 87Sr/86Sr 0.7037 to 0.7081), the situation is similar, i.e., Sr in the most primitive samples tends to be sourced from ophiolitic rocks (up to 2.4 ppm Sr in serpentinite), whereas in the more evolved types, it was likely delivered from the adjacent, ca. 340 Ma (8.8-102.6 ppm Sr) partially rodingitized granites, as well as ∼305 Ma granites (ca. 80 ppm Sr). Moreover, these granites caused the fluid-flow, responsible for Sr-bearing clinozoisite vein formation; these veins are likely related with nephrite formation, and with a metallic mineralization.

For the first time, Nd isotope signatures combined with rare earth element (REE) concentrations were used in investigations of ancient seep carbonates. The study was performed on the fossil hydrocarbon seep deposit of the Middle Devonian Hollard Mound (eastern Anti-Atlas, Morocco), where Nd isotopes, REE concentrations, and carbon and oxygen isotope ratios were measured to investigate the origin, former migration pathways and composition of fluids. Relatively high eNd values compared to local Eifelian seawater, as well as consistently appearing positive Eu anomalies in MREE-enriched shale-normalized REE patterns of the seep carbonates provided evidence for interaction between the seeping fluids and the Lower Devonian basaltic volcaniclastics underlying the studied seep deposit. Strongly reducing conditions and increased temperature of methane formation could have constituted an additional factor in the Eu-enrichment of the investigated carbonate phases. The presence of exclusively negative Ce anomalies in these carbonates is in line with observations of other workers that seep limestones may not necessarily display positive Ce anomalies indicative of precipitation under anoxic conditions. The negative Ce anomalies are attributed here to mixing between anoxic pore waters and oxic, Ce-depleted seawater, necessary to enable carbonate precipitation at seeps. The methane-rich fluids ascended most likely from below the volcaniclastic unit and inherited the enriched eNd signatures and positive Eu anomalies due to fluid–rock interactions during their seepage to the seafloor. The carbon isotope data are most consistent with thermogenic origin of methane, although contribution of abiotic and biogenic methane sources cannot be excluded. Our results indicate that neodymium isotope and rare earth element analyses constitute one of the most valuable tools for reconstructing former fluid migration patterns. The study shows also that Nd isotopes and Eu anomalies can serve as sensitive tracers of fluid–rock interactions at submarine springs.

One of the most striking features of modern chemosynthesis-based ecosystems surrounding methane seeps is the presence of abundant chemosymbiotic bivalves. However, such accumulations have rarely been reported from Palaeozoic to mid-Mesozoic seeps, and it is widely thought that general trends in the evolution of chemosynthetic communities paralleled those typifying most marine environments, with the bivalve prevalence starting in the Mesozoic and with Palaeozoic seeps being dominated by brachiopods. Here, we report a discovery of bivalve clusters in the oldest-known methane seep that hosted metazoan fauna, dated to the late Silurian. We identify the bivalves, externally very similar to modern chemosymbiotic forms, as members of the extinct family Modiomorphidae, known previously from a younger, Devonian seep. The bivalves inhabited the seep at a stage of increased fluid flow, when they co-occurred with atrypid brachiopods, and display a set of morphological characteristics suggesting a seep-obligate lifestyle. We conclude that bivalves colonised chemosynthesis-based ecosystems at least as early as brachiopods and apparently first developed specialized lineages able to thrive in seep-related habitats for a prolonged period of time. Rather than being simple ecological successors of brachiopods, rich bivalve communities represent an ancient and recurring theme in the evolution of chemosynthetic assemblages.

An unusual and exceptionally well preserved cryptic community of cnidarians, crinoids, sponges, and microbes developed in a submarine cavity of Middle Devonian age in the Hamar Laghdad area (Morocco). The biota encrusted the cavity roof and grew predominantly in an upside-down position, forming spectacular “hanging gardens.” The investigated assemblage differs strikingly from both its Paleozoic and modern analogues; it constitutes one of a very few known examples of fossil cryptic assemblages developed in relatively deep water settings, and is the first report of a cryptic paleoecosystem dominated by rugose corals. The results support the view that during the middle Paleozoic there was no distinct polarization between open-surface and cryptic faunas in deep-water environments, but keen competition for space already existed in Devonian cryptic assemblages. The regional species pool seems to have been the main determinant of the ecological succession and structure of this cryptic community.

Microbially induced Frutexites microstromatolites developed on corallites of the Givetian rugose coral “Amplexus” in the sedimentary cover of a submarine volcanic intrusion in the eastern Anti-Atlas of southern Morocco. The corals lived in proximity to submarine hydrothermal fluid emissions. Frutexites form irregular shrubs encrusting external walls of corallites. The shrubs, consisting of alternations of calcitic and hematitic laminae, grew predominantly on abandoned corallites. Some Frutexites grew within the sediment, whereas others developed entirely above the seafloor, or started their accretion in water and continued to grow during burial. Three types of Frutexites encrustations have been distinguished. They look similar macroscopically, but differ significantly in their microstructure and mineralogical characteristics, resulting primarily from spatial and temporal variations in redox conditions. Both hematitic and calcitic laminae are primary features of Frutexites. The shrubs accreted as a result of mineralization of microbial biofilms under fluctuating environmental conditions, caused by changes in pH, Fe2+-supply and/or oxygenation, presumably related to discharges of reducing hydrothermal fluids. The calcitic laminae are interpreted to have formed due to activity of heterotrophic (mainly sulphate-reducing) microbes, whereas the hematitic laminae developed as a result of enhanced activity of nitrate-reducers or due to periodical passive mineralization of biofilms with iron. Cathodoluminescence data provide evidence that the nitrate and sulphate reduction preceded the Mn(IV) and Fe(III) reduction, presumably due to increased accumulation of organic matter and a high stability of the iron oxides present.

The rugose coral ‘Amplexus’ occurs frequently in the sedimentary cover of the Devonian submarine volcanic intrusion in the eastern Anti-Atlas, southern Morocco. This study elucidates the palaeoecology of ‘Amplexus’, which forms very rich and mostly monospecific, spot assemblages within the Lower and Middle Devonian carbonates. Geological and isotopic evidences show that these associations developed at hydrothermal vents and at a cold seep site. The assemblages are always spatially associated with micritic carbonate bodies, occurring within bedded, hemipelagic deposits. The ‘Amplexus’ corals preferred locations in the close proximity of submarine hydrothermal fluid seepage, but they generally avoided places with the most elevated temperatures. The corals colonised also a hydrocarbon seep, probably only in its terminal phase of development, when the fluid flow was still at least periodically active. This was only possible as a result of the corals following a calice-in-calice growth, developed due to the environmental toxicity, which facilitated selective survival of larvae that settled in the shelter of empty calices. The ‘Amplexus’ corals appear to have constituted ecological opportunists, thriving in the nutrient-rich, venting- and seepage-affected areas that were hostile for other benthic organisms. It can be suspected that the unusual, extremely simplified morphology of ‘Amplexus’ made it particularly well adapted to living in environments typified by harsh and unstable conditions.

Conodonts collected from sections near the small towns of Thong Pha Phum and Mae Sariang in the westernmost part of Thailand are used to reconstruct the neodymium (Nd) isotopic composition of seawater during the Late Devonian. The study provides the first Devonian seawater signatures recognized within the Australian shelf of northeastern Gondwana and the adjacent Paleotethys Ocean. At Thong Pha Phum site, the seawater was characterized by very low e Nd values (from − 13.1 to − 18.2) and very high Sm/Nd ratios (between 0.36 and 0.66). In contrast, the seawater at the Mae Sariang site was characterized by much more radiogenic signatures (e Nd values from − 8.7 to − 11.1) and uniform, low Sm/Nd ratios (between 0.20 and 0.23). Extremely low e Nd values recognized at Thong Pha Phum attest to a passive margin continental setting and a paleogeographic position very close to a continental area where Paleoproterozoic and Neoarchean rocks were eroded. Thus, the isotopic data provide strong evidence that during Late Devonian time the Sibumasu terrane was situated in the proximity to the Archean cratons of Western Australia, presumably adjacent to the Carnarvon intracratonic basin. Moreover, Sibumasu may not have been situated in an outboard position on the shelf, as previously suggested, but could have been directly attached to the Australian continental crust. By contrast, low and uniform Sm/Nd ratios of seawater at Mae Sariang resemble those of the Variscan and the present-day oceanic seawaters. Therefore, a pelagic setting within the Paleotethys Ocean is postulated for the Mae Sariang succession. This conclusion is also constrained by minor temporal changes in e Nd values and suggests that the Paleozoic of Mae Sariang is not part of the Sibumasu terrane but belongs to the Inthanon Zone.

An 11 m thick condensed sequence of Late Devonian limestones in northwestern Thailand exhibits faunal associations and sedimentological-/microfacies data which are indicative of a pelagic facies setting. The entire long-ranging section is completely free from clastic input. Similar successions are known worldwide in a few sections only. The Mae Sariang section is characterised by low sedimentation rates as recognised by a number of hardgrounds, neptunian dikes and Fe/Mn crusts. The succession comprises a number of pelagic faunal elements e.g. conodonts, cephalopods and pelagic ostracodes. The fauna records rare macrofossils and the faunal diversity is low. The very condensed section ranges from the Late rhenana to praesulcata conodont biozones, but contains some global events as undoubtedly shown by biostratigraphical and carbon-isotope results (including major Kellwasser and Hangenberg biotic crises). In terms of plate tectonics this important succession most probably belongs to the Inthanon Zone comprising remnants of the Paleotethys Ocean.

A monospecific assemblage of myodocopid ostracods has been found in the Middle Devonian of a unique hydrothermal vent system of Hamar Laghdad (eastern Anti-Atlas, southern Morocco), which developed over a submarine eruption of basaltic rocks. This fauna has been recovered from a neptunian dyke representing the sediment infill of an Eifelian venting fissure discovered in the central part of Hamar Laghdad. The assemblage consists of thousands of relatively large shells forming a coquina layer in which the valves are disarticulated, perfectly washed, well sorted and stacked into each other. Their orientation points to transport due to fluids migrating in the vent system. The ostracod specimens, on the base of the general outline, the presence of rostrum and rostral incisure is assigned to the order Myodocopida. The new genus and species Hamaroconcha kornickeri is proposed, most likely representing a new family. Its carapace morphology gives no clear clue to its mode of life; however, a relatively long rostral incisure may suggest that frontal appendages of this species were sufficient for active swimming. Therefore, a nectobenthic lifestyle is postulated for H. kornickeri nov. gen., nov. sp. Isotope data from the sediment infill provide evidence for the activity of hydrothermal fluids.

The Illizi Basin is the easternmost one of a series of cratonic basins of the Algerian Sahara which extend along the northern margins of the Precambrian Reguibat and Hoggar massifs. Devonian rocks crop out along the erosional southern border of the basin and can be roughly divided into three major lithostratigraphic units: (1) Lower Devonian sandstones (upper part of the Tassilis externes), (2) Middle Devonian carbonates (Illizi Formation, introduced in this article) and (3) Upper Devonian shales (Tin Meras Formation). In the present study emphasis was laid on the Middle Devonian carbonates which were dated by conodonts and correlated in 12 sections over a W–E distance of about 350 km. The sequence shows a lateral transition from condensed series in the west, deposited on a submarine high (Amguid Ridge), into a shallow basin (Illizi Basin) which was additionally differentiated into minor ridges and sub-basins. The eastern portion of the basin is characterized by an enhanced clastic input from the Tihemboka Ridge which separates the Illizi Basin from the Murzuq Basin in western Libya. The differential subsidence during the Devonian shows that the Illizi Basin is primarily a depositional structure which subsequently became more accentuated after the Variscan orogenesis at the Carboniferous/Permian transition.

An up to 3,000-m-thick pile of Carboniferous rocks covers the northern fringe of the Precambrian Hoggar Massif (Touareg Shield) in southern Algeria, thus terminating the depositional history of the Palaeozoic in this sector of the North African Craton. The previous Devonian (Eifelian to Frasnian) palaeogeographic configuration of the area, characterized by ridges and shallow basins, is leveled by a widespread Famennian playa and lower Tournaisian delta sedimentation on a largely undifferentiated shelf. Tournaisian to Moscovian strata were deposited under open-marine, deltaic, shallow-subtidal, fluvial, and continental environments. The Carboniferous sequence can be subdivided into 12, largely interfingering, lithostratigraphic formations, which were dated by conodonts, ammonoids, foraminifers, and brachiopods, yielding a modified biostratigraphic framework of the area. The formations are stacked in four transgressive–regressive cycles, which include two major gaps, one during the middle Tournaisian, the other during the middle Visean to Serpukhovian. The oscillations of sea level can be traced into neighboring areas and seem coeval to early pulses of the Late Carboniferous/Early Permian glaciation of Gondwana. To a lesser degree they may reflect more local tectonic effects of the Variscan orogeny.

Large colonies of rugose coral Scruttonia kunthi occurring in the upper Famennian of Sudetes (southern Poland) reveal distinct growth banding in their skeletons. They were investigated for internal structural characteristics and stable isotopic composition. The skeletal tissue consists of alternating light and dark bands which differ in thickness, density and morphology of structural elements, and in occurrence of corallite contraction and rejuvenescense. Darker parts with densely arranged thick skeletal elements are thin in comparison to lighter parts. In addition, they include frequently offsets and contraction of corallites. A couplet of dense and less dense bands is interpreted to represent most probably an annual cycle. The calculated growth rate for Scruttonia kunthi varied from 6 mm/yr to 12 mm/yr. Growth-band formation was influenced environmentally. Oxygen isotopic data provide an evidence that high-density bands were formed in the season of higher environmental stress, with relatively warmer temperatures and higher sedimentation rates. Carbon isotopic signatures are very uniform, and thus enigmatic. They indicate that at least growth rate of the skeleton and seawater temperature had no influence on the coral δ 13 C.