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Testing climate models for future and past climate change critically depend on our ability to quantitatively reconstruct past climate. This requires the proper deconvolution of temperature and salinity effects on proxy incorporation. Paleosalinity is the single most important oceanographic parameter which currently can still not be quantified from sedimentary records. During the PaleoSalt project focus was on the development of proxy-tools allowing past salinity reconstructions from carbonate archives. Our research team selected a marine bivalve which is tolerant to a wide range of salinities and is available also from archaeological collections. The fast growing and relatively short-lived blue mussel also offers the potential to investigate seasonal variability and amplitudes. Our objectives were to refine existing proxy tools such as d18Oc (calibration and signal treatment) and to develop new proxies (dD, isotopes of Mg and trace elements; i.e. a multi-proxy approach) as well as mathematical tools to improve the robustness and sensitivity of reconstructions of environmental conditions. To that purpose we have used two parallel approaches: an in situ study along the salinity gradient of the Scheldt estuary and an ex situ growth experiment under controlled laboratory conditions. Though the d18O results for shells grown under controlled conditions of temperature, salinity and food supply validate the existing equations for temperature reconstruction based on d18O water (e.g. Wanamaker et al., 2006), the carbonate system of the growth medium stands up as an important additional control factor that needs to be taken into account. Other methodologies are being developed for the identification of lipid compounds and their dD signature in shell organic matter and for the assessment of dMg in shell and tissue material, as potential salinity proxies. We recently acquired a new Fast Excimer (193 nm) Laser - ICP-MS system to investigate trace element records in the mussel shells from the controlled growth experiments andSchelde sites and first results will possibly be schown. We also developed mathematical tools to correct for bias in proxy records due to variable growth rate induced time base distortion and to correct the averaging effect that can be induced when sampling the shell. Finally a multi-proxy model was developed for temperature and salinity reconstruction .

Speleothem fluid inclusions are a potential paleo-precipitation proxy to reconstruct past rainwater isotopic composition ( δ 18 O, δ D). To get a better insight in the extraction of inclusion water from heated speleothem calcite, we monitored the water released from crushed and uncrushed speleothem calcite, heated to 900 °C at a rate of 300 °C/h, with a quadrupole mass spectrometer. Crushed calcite released water in three not well individualised peaks between 25 and 360 °C, 360 and 650 °C and between 650 and 800 °C while uncrushed calcite released water in two distinct temperature intervals: between 25 and 550 °C and between 550 and 900 °C. Water from two speleothems from the Han-sur-Lesse cave was recovered using three different techniques: i) the crushing and heating to 360 °C technique, ii) the decrepitation by heating to 550 °C and iii) the decomposition by heating to 900 °C technique. Measurements of the δ D of water recovered by the decomposition of Han-sur-Lesse calcite heated to 900 °C did not show a 20 to 30‰ offset as found by previous authors. However a difference of 7‰ was observed between water released before and after decomposition of the calcite. Water recovery from the Han-sur-Lesse samples suggests that a simple heating technique (up to 550 °C) without crushing could both (a) recover water with δ D representative of that of the drip water and (b) double the water yield as compared to the crushing and heating method. Our study warns for possible contamination of the recovered inclusion water with hydration water of lime, responsible for the recovery of water with very negative δ D values.

Laudatio

Siderophile elements have been used to constrain projectile compositions in terrestrial and lunar impact melt rocks. To obtain a better knowledge of compositional differences between potential chondritic projectile types, meteorite analyses of the elements Ru, Rh, Pd, Os, Ir, Pt, Cr, Co, Ni, and Au were gathered into a database. The presented compilation comprises 806 analyses of 278 chondrites including new ICP-MS analyses of Allende and two ordinary chondrites. Each data set was evaluated by comparing element ratios of meteorites from the same chondrite group. Characteristic element abundances and ratios were determined for each group. Features observed in the element abundance patterns can be linked directly to the presence of certain components, such as the abundance of refractory elements Os, Ir, and Ru correlating with the occurrence of refractory inclusions in CV, CO, CK, and CM chondrites. The refined characteristic element ratios appear to be representative not only for meteorites, but also for related asteroidal bodies. Chondrite element ratios were compared to previously published values from impact melt rocks of the Popigai and Morokweng impact structures confirming that an identification of the specific type of projectile (L and LL chondrite, respectively) is possible. The assessment for Morokweng is supported by the recent discovery of an LL chondrite fragment in the impact melt rocks. Ultimately, the database provides valuable information for understanding processes in the solar nebula as they are recorded in chondrites. A new type of complementarity between element patterns of CK and EH chondrites is suggested to be the result of condensation, redox, and transportation processes in the solar nebula.

In September 2007, thirty-three scientists attended an international workshop in Longyearbyen (Svalbard, Norway) to discuss impacts of extraterrestrial bodies into marine environment and to prepare for the drilling of the 142-Ma-old Mjølnir impact structure in the Barents Sea (Fig. 1; Gudlaugsson, 1993; Dypvik et al., 1996, Tsikalas et al., 1998). A field trip visited the ejecta layer in the Janusfjellet Mountain in Isfjorden, just outside Longyearbyen (Fig. 2). The workshop focused on two topics: 1) mechanisms of marine impact cratering including ejecta formation and distribution, geothermal reactions, and the formation of tsunami, and 2) environmental effects of marine impacts. Both topics are highly relevant to the Mjølnir event and the geological evolution of the Arctic, as well as to the biological changes at the Jurassic-Cretaceous boundary. Against thisbackground were a) concrete drilling targets formulated, b) plans outlined for compiling data from existing geological and geophysical surveys as the basis for Integrated Ocean Drilling Program (IODP) and International Continental Scientific Drilling Program (ICDP) drilling proposals, and c) a steering group and science teams established for compiling old and new material as a foundation for the developmentof drilling proposal.

Dated oxygen and carbon isotopic profiles from a Holocene stalagmite (11.9-1.1 ka) from the Jeita cave, Lebanon, are compared to variations in crystallographic habit, stalagmite diameter and growth rate. The profiles show generally high ?18O and ?13C values during the late-glacial period, low values during the early Holocene, and again high values after 5.8 ka. On the basis of the good correlation between the morphological and crystallographic aspect of the stalagmite and its isotopic records, as well as the isotopic response of speleothems from central and northern Israel, we relate high ?18O and ?13C values to drier conditions. Between 6.5 and 5.8 ka an increase in isotopic values, a decrease in growth rate and stalagmite diameter suggest a transition from wet conditions in the early Holocene towards drier conditions in the mid-Holocene. The transition occurred in two steps, first a progressive change to drier conditions started at 6.5 ka but was interrupted by a short (? 100 years) return to wetter conditions, followed by an equally rapid (

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Knowledge of the geology is essential to evaluate the possible occurrences of raw materials in a given area. It also forms the base for geomorphological and soil-engineering studies. The mineralogical and geochemical characterisation of the immediate subsurface constitutes the background for environmental investigations such as the reconstruction of the palaeoclimate and to determine anthropogenic influences based on geochemistry. Since 1989, prof. Willy Viaene and his team carried out a systematic study of the geology in the area of the archaeological site of Sagalassos. The present work is a tribute to prof. Willy Viaene and summarizes the work performed by his group and colleagues to fully characterize and understand the rocks, exploited and used in ancient times.

Geoarchaeological research was performed to reconstruct the floodplain history in the surroundings of two ancient Mesopotamian cities: Tell ed-D?r and Sippar. The mapping of the floodplain is based on facies analyses of the sedimentary succession of 225 hand operated boreholes. The archaeological sites Tell ed Dar and Sippar are closely linked to a palaeochannelbelt of the Euphrates, located in the western part of the study area. Channel activity started at least in ca 3100 BC 5050 cal BP, until ca 1400 1000 BC 3350 2950 cal BP. The channel belt was part of an avulsion driven multiple Euphrates channel network that gradually became abandoned from the second half of the 2nd millennium BC. A second mapped Euphrates, Tigris or Joint Euphrates Tigris palaeochannel belt became abandoned well before 3100 BC.

Stable isotope signatures in biogenic carbonates and tissues represent a common proxy for reconstructing environmental conditions. Today, salinity reconstruction has been recognized as a major goal. This study focuses on the isotopic signatures of the organic matrix of bivalve shells collected along estuarine salinity gradients. Two systems are compared: the Scheldt Estuary (in the Netherlands) using Mytilus edulis and the Auray River (Gulf of Morbihan, France) with Ruditapes philippinarum. The carbonate phase of the shell is removed by acid treatment leaving behind the organic shell matrix that faithfully preserves the original tri-dimensional shell structure, possibly allowing for subsampling of different time windows of the animals life. This bulk organic matter is analyzed by EA-IRMS. As observed for soft tissues, the shell organic matrix yields an isotopic composition close to that of suspended organic matter. Furthermore, the isotopic composition of the suspended organic matter along the strong biogeochemical gradient of the estuary is correlated with the salinity. Therefore, the d13C and d15N values of shell organic matter can be related to the average salinity of each location where the shells were collected. Moreover, shell organic matrix offers advantages over soft tissue: first, it provides a signature integrated over the animal’s life time, thus smoothing out seasonal variations; second, it makes it possible to work with fossil organic matter to reconstruct past environmental conditions. It is protected from degradation after the death of the organism by the shell’s mineral phase. However, when using different specimens, possible physiological effects (the avoidance of which requires that similar ages, sizes or weights be selected), food availability (importance of location, season) or species (Mytilus vs. Ruditapes) must be considered.

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Calcitized Jurassic dolostones from central Mount Lebanon (Kesrouane Formation) are discussed utilizing petrographic, mineralogical and geochemical data. In particular, two sequential extraction methods for both major/trace elements and stable isotope analyses provide results that support and refine conventional bulk analyses data. The new data demonstrate that the major dedolomitization phase of the investigated Jurassic carbonates occurred as a result of the migration of karst-related meteoric waters (characterized by soil-derived carbon, and estimated d18OV-SMOW composition between -7.2 per mill and -3.4 per mill into previously dolomitized horizons within the limestone rock, during the final uplift and emergence of Mount Lebanon, after Palaeogene time. The study demonstrates that, in this case, the mechanisms of dedolomitization and their resulting fabrics are controlled primarily by the texture of the original dolomite rock. Pervasively dolomitized rocks, where the micritic matrix is entirely dolomitized, show calcitization mainly through dissolution/precipitation. By contrast, the rock textures that still include a considerable amount of limey micritic matrix - spared from dolomitization - are more prone to mole per mole and mimic replacement of the dolomite crystals by calcite.

A key region to study high resolution climate changes of the Southern Hemisphere is undoubtedly the southern part of Chile because it has the advantage to be far removed from the Northern Hemisphere ice sheets and thermohaline circulation influences. In order to reconstruct the regional climate evolution since the Last Glacial Maximum, we investigated the sedimentary infilling of Lago Puyehue (40°S, 164 km2, elevation 185 m) by a multi-proxy analyse of a 11 m long core. Sediments from this core are transported by interflow currents and are made of finely laminated silts, with only small disturbances due to volcanic and seismic activities. Several proxies were measured: grain-size, mineralogy, magnetic susceptibility, major elements geochemistry and biogenic silica concentration. These are used to reconstruct paleo-precipitation and paleo-productivity changes around 40°S. Results evidence that sediment grainsize is highly correlated with the biogenic sediment content and can be used as a proxy for lake paleoproductivity. On the other hand, the magnetic susceptibility signal is highly correlated with the aluminium and titanium concentrations and can be used as a proxy for the terrigenous supply. Temporal variations of sediment composition demonstrate that, since the Last Glacial Maximum, the Chilean Lake District was characterized by 3 abrupt climate changes superimposed on a long term climate evolution. These rapid climate changes are: (1) the end of the Last Glacial Maximum at 17,300 cal. yr. BP; (2) a 13,100-12,300 cal. yr. BP cold event, ending rapidly and interpreted as the local counter part of the European Younger Dryas event, and (3) a 3400-2900 cal. yr. BP climatic instability related to low solar activity. The timing of the 13,100-12,300 cold event is compared with similar records in both hemispheres and demonstrates that this Southern Hemisphere climate change lags behind the Northern Hemisphere Younger Dryas cold period by 500 to 1000 years.

International audience; The ability of inorganic geochemistry to record environmental change and especially human impact has been evidenced by several studies across Europe, especially in peat, where it is possible to record the impact of agriculture, mining and other industries. However, despite the numerous investigations on the impact of ancient human activities such as ore mining and smelting, little attention has been paid to geochemistry as a tool to solve problems of palaeopollution in the surroundings of archaeological sites. This paper presents geochemical evidence of the impact of a possible early Roman road built in SE Belgian peatland. Increased Zn and Pb concentrations suggest that Pb-Zn ores were transported on the road. Lead isotope analyses suggest that these ores are locally derived, being compatible with those found in the nearby Pb-Zn ore deposits from East Belgium. Present results provide direct evidence that East Belgian Pb-Zn ores were already being mined during Roman times, i.e. earlier than previously suspected (i.e. 14th century) and that Zn appears to be relatively immobile here. On a broader scale, it also demonstrates that such an early road already had an impact on the environment in terms of metal pollution. This paper enlarges on the range of possibilities offered by geochemistry in the field of geoarchaeology.

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Article on the impact of islam on daily life of Aramaic-speaking christian women in Iraq.

Very little was known in the West on the Christian minorities of Iraq until world mass media began to report on violent attacks on their churches and on repressions against their community members. This contribution analyzes the minority's life conditions and the causes and results of the repeated persecution by the Muslim majority, to which Aramaic Christians as well as the Iraqi Jews as Dhimmis were subjected for centuries in their countries of origin. It also comments on the temporary social emancipation installed after the introduction of the civil rights law in 1959, which continued through the seventies of the 20th century, and on the strategies of marginalization and humiliation imposed by state authorities on the members of the Christian community at schools and in daily life. Especially the Aramaic Christian women were exposed to strong pressure, because of the internal patriarchal code of behaviour based on Christian tradition. The pressure of the repressive Muslim environment enhanced their deplorable situation. This constant repression applied by partially contradictious instances produced a traumatized and phobic personality that is living with a permanent fear of persecution. In the years following the American invasion (2003), the menaces threatening the existence of the religious minorities in Iraq were radically intensified. The goal aiming at the uprooting of the Christians in Iraq is carried out in an even more radical way than the persecution and expulsion of the Iraqi Jews in the period from 1941 to 1951.

In this paper, we investigate the potential use of oxygen and strontium isotope ratios (d18Op and 87Sr/86Sr) measured in archaeological fish enamel as provenance indicators. d18Op and 87Sr/86Sr were measured in a suite of archaeological carp remains recovered from the Anatolian townsite of Sagalassos dated to the Early Byzantine period (AD 450e650) and compared to that of modern fish, river and lake waters from the Anatolian region. We used sequential leaches in weak acetic acid to remove diagenetic Sr from fossil tooth enamel, monitoring the effectiveness of this approach by measuring the Sr/Ca ratios of the leachates via an isotope dilution thermal ionization mass spectrometry method (ID TIMS). d18Op values mostly excluded a riverine origin. 87Sr/86Sr ratios of one fish overlapped with the 87Sr/86Sr signatures of two lakes in the Anatolian region, and atleast one lake (Golcuk) could be removed as a candidate owing to a very distinctive 87Sr/86Sr signature not found in any of the fish remains. Most of the tooth samples analyzed could not be assigned a precise geographical origin since the 87Sr/86Sr ratios measured in enamel did not match that of any of the local lakes selected as potential origin. This result suggests that carp may have originated from lakes that have not yet been sampled, although this conclusion is not supported by other archaeological evidence. Alternatively, the lack of correspondence between lakes and fish Sr isotope ratios highlights several possible sources of uncertainties including spatial heterogeneity in 87Sr/86Sr ratio within a lake, the contribution of dietary strontium to the 87Sr/86Sr ratio of fish tooth enamel, and post-mortem alteration of the tooth Sr isotope signal during fossilization. In spite of the high precision of the strontium isotope analyses and the wide range of variation in the surface waters of the Anatolian lakes and rivers, this method may remain limited to distinguishing between lakes situated in regions of bedrock of very distinct age and geology until these sources of uncertainty are more fully investigated.

Recently, an interdisciplinary geoarchaeological project has been launched to investigate the interaction between men and the palaeoenvironments in the Larnaca region (Cyprus) during the Late Bronze Age. A part of this project concerns the identification of the provenance of the raw material utilized in production of pottery and potential source changes during this period. It tests the use of lead isotopic signatures (206Pb/204Pb vs 207Pb/204Pb) as a tracer of the pottery source. Therefore, eighteen sherds of the most common pottery types, excavated at the Late Bronze Age site near the Hala Sultan Tekke mosque, were selected and compared with a first set of thirteen outcrops, located in the vicinity of the archaeological site. The chosen outcrops were sampled during a preliminary geological survey based on the lithologies: holocene deposits (sand, silt, clay), pleistocene terrace deposits (calcarenites, sands) and palaeogene marls, which possibly could have been used as primary raw material for the pottery. Both sets of samples were analyzed for lead isotopes using the MC-ICP-MS (ULB, DSTE). In parallel, the mineralogy of the sherds and of the different outcrops was defined using X-ray diffraction (ULg, URAP). Thin sections were also realized on the eighteen sherds and examined under the microscope to better characterize their composition. First results show that most of the lead isotopic composition of sherds correlates with some outcrop samples.

The projectile that killed the dinosaurs 65 million years ago came from the asteroid belt

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Here we present the results of a geochemical study of the projectile component in impactmelt rocks from the Lappajärvi impact structure, Finland. Main and trace-element analyses, including platinum group elements (PGEs), were carried out on twenty impact-melt rock samples from different locations and on two shocked granite fragments. The results clearly illustrate that all the impact melt rocks are contaminated with an extraterrestrial component. An identification of the projectile type was performed by determining the projectile elemental ratios and comparing the corresponding element ratios in chondrites. The projectile elemental ratios suggest an H chondrite as the most likely projectile type for the Lappajärvi impact structure. The PGE composition of the highly diluted projectile component (~0.05 and 0.7 wt% in the impact-melt rocks) is similar to the recent meteorite population of H chondrites reaching Earth. The relative abundance of ordinary chondrites, including H, L, and LL chondrites, as projectiles at terrestrial impact structures is most likely related to the position of their parent bodies relative to the main resonance positions. This relative abundance of ordinary chondrites suggests a strong bias of the impactor population toward inner Main Belt objects.

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In an attempt to identify the type of projectile, 14 samples from the Bosumtwi crater in Ghana were analyzed for platinum group element (PGE) concentrations by nickel sulfide fire assay inductively coupled plasma mass spectrometry (ICPMS). The majority of the samples come from the impactite material recovered by cores LB07A and LB08A, which were drilled by the International Continental Scientific Drilling program (ICDP). One sample originates from the fallback material found at the contact between the impactite and the overlying lake sediment in core LB05B. No clear signature of a meteoritic contamination was identified in the 13 impactite samples. The target rock apparently dominates the PGE contribution in the impactites. These results agree with the PGE concentrations reported for the suevites collected at the crater rim and in other parts of the Bosumtwi ICDP cores. However, based on Cr and Os isotopic signatures, a meteoritic component could be present in the sample of fallback material, supporting the reports of the existence of meteoritic material in the Ivory Coast tektites. Further analyses of the fallback material from the Bosumtwi drill cores should confirm (or not) this first result.

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[1] Carbonate substrates (dolomites and limestones) are susceptible to fungal attack that results in significant microbial diagenesis of these substrates. In a 15-day experimental study, fungi growing in Petri dishes from airborne spores attacked petrographic thin sections and chips prepared from the dolomites of Terwagne Formation (Visean, Bocahut quarry at Avesnes-sur-Helpe, northern France) and limestones of the Morrone di Pacentro Formation (Lower Cretaceous, Italy). The analyses of the fungal material (samples of mycelia), thin sections and chips under optical microscopy, scanning electron microscope (SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), Raman spectroscopy and stable isotopes (C and O) revealed an extensive fungally induced diagenesis. The results indicate strong diagenesis and biomineral neomorphism: neo-dolomite, glushinskite, weddellite, whewellite and possibly struvite, as well as intense substrate “de-micritization” and “micritization” with oxalates, grain bridging and cementation, open space filling, formation of intergranular and intragranular porosity, and permeability enhancement. Advanced stages of diagenesis were characterized by dissolution and replacement of original minerals by new substrates produced by fungal biomineralization. The formation of new substrates on the original attacked surfaces produced microscale stratification. Stable isotope analysis of fungal biomineralized material and of attacked and unattacked chip surfaces revealed marked differences in their isotopic signatures. The C and O isotopes of biomineralized material within the fungal mass were fractionated differently as compared to the signature measured in the original and unattacked surfaces. In sedimentary cycles, such microbially modified isotopic signature of carbonate substrates may be used to define microbial events, and consequently whether certain types of diagenesis were produced by microbial interaction. The finding of neo-dolomite formed during fungi-dolomite substrate interaction suggests the possibility of sedimentary dolomite recycling in a fungal microenvironment. The results of this experimental study confirm the significant role of fungi in reshaping carbonate substrates and forming new biominerals in the natural environment.

Impact events and evolution of the Earth

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A late Eocene asteroid shower to the Earth Moon system resulted in an increased flux of impact ejected 3He-rich lunar matter to Earth, which is recorded by a 2 Ma enduring 3He-anomaly in marine sediments.

The three major geochemical methods for impactor identification are evaluated with respect to their potential and limitations with regards to the precise detection and identification of meteoritic material in impactites. The identification of a projectile component in impactites can be achieved by determining certain isotopic and elemental ratios in contaminated impactites. The isotopic methods are based on Os and Cr isotopic ratios. Osmium isotopes are highly sensitive for the detection of minute amounts of extraterrestrial components of even 0.05 wt% in impactites. However, this only holds true for target lithologies with almost no chemical signature of mantle material or young mantle-derived mafic rocks. Furthermore, this method is not currently suitable for the precise identification of the projectile type. The Cr-isotopic method requires the relatively highest projectile contamination (several wt%) in order to detect an extraterrestrial component, but may allow the identification of three different groups of extraterrestrial materials, ordinary chondrites, anenstatite chondrites, and differentiated achondrites. A significant advantage of this method is its independence of the target lithology and post-impact alteration. The use of elemental ratios, including platinum group elements (PGE: Os, Ir, Ru, Pt, Rh, Pd), in combination with Ni and Cr represents a very powerful method for the detection and identification of projectiles in terrestrial and lunar impactites. For most projectile types, this method is almost independent of the target composition, especially if PGE ratios are considered. This holds true even in cases of terrestrial target lithologies with a high component of upper mantle material. The identification of the projectile is achieved by comparison of the "projectile elemental ratio" derived from the slope of the mixing line (target-projectile) with the elemental ratio in the different types of possible projectiles (e.g., chondrites). However, this requires a set of impactite samples of various degree of projectile contamination.

On Earth, the Archaean aeon lasted from 4.0 to 2.5 Ga; it corresponds to a relatively stable period. Compared with today, internal Earth heat production was several times greater resulting in high geothermal flux that induced the genesis of rocks such as komatiites and TTG suites, which are no more generated on Earth since 2.5 Ga. Similarly, the details of plate tectonic modalities (plate size, plate motion rate, plate thickness, tectonic style, irregular crustal growth, etc...) were different of modern plate tectonics. Both atmosphere and ocean compositions have been progressively modified and the greater heat production favoured the development of hydrothermalism and therefore created niches potentially favourable for the development of some forms of life. Catastrophic events such as giant meteorite falls or world-sized glaciations drastically and suddenly changed the environment of Earth surface, thus being able to strongly affect development of life. Even if specialists still debate about the age of the oldest indubitable fossil trace of life, Archaean can be considered as having been extremely favourable for life development and diversification.

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Stalagmite from Belgium are studied

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Except the old Jack Hills zircon crystals, it does not exit direct record of the first 500 Ma of the Earth history. Consequently, the succession of events that took place during this period is only indirectly known through geochemistry, comparison with other telluric planets, and numerical modelling. Just after planetary accretion several episodes were necessary in order to make life apparition and development possible and to make the Earth surface habitable. Among these stages are: the core differentiation, the formation of a magma ocean, the apparition of the first atmosphere, oceans and continents as well as the development of magnetic field and of plate tectonics. In the same time, Earth has been subject to extraterrestrial events such as the Late Heavy Bombardment (LHB) between 3.95 and 3.8 Ga. Since 4.4 to 4.3 Ga, the conditions for pre-biotic chemistry and appearance of life were already met (liquid water, continental crust, no strong meteoritic bombardment, etc...). This does not mean that life existed as early, but this demonstrates that all necessary conditions assumed for life development were already present on Earth.

Based on material delivered at several summer schools, this book is the first comprehensive textbook at the graduate level encompassing all aspects associated with the emerging field of astrobiology. Volume II gathers another set of extensive lectures covering topics so diverse as the formation and the distribution of elements in the universe, the concept of habitability from both the planetologists' and the biologists' point of view and artificial life. The contributions are held together by the common goal to understand better the origin of life, its evolution and possible existence outside the Earth's realm. The volume ends with 120 pages of a very useful appendix comprising "Some Astrophysical Reminders", "Useful Astrobiological Data" and "An Astrobiological Glossary".

This book emerged from several interdisciplinary meetings and schools gathering a group of astronomers, geologists, biologists, and chemists, attempting to share their specialized knowledge around a common question: how did life emerge on Earth? Their ultimate goal was to provide some kind of answer as a prerequisite to an even more demanding question: is life universal? The resulting state-of-the-art articles were written by twenty-five scientists telling a not-so linear story, but on the contrary, highlighting problems, gaps, and controversies. Needless to say, this approach yielded no definitive answers to both questions. However, by adopting a chronological approach to the question of the emergence of life on Earth, the only place where we know for sure that life exists; it was possible to break down this question into several sub-topics that can be addressed by the different disciplines.

Numerous Variscan syntectonic calcite veins cross-cut Palaeozoic rocks in the Moravian Karst. A structural, petrographic and stable isotopic analysis of the calcite veins and a microthermometric study of fluid inclusions in these vein cements have been carried out to determine the origin of the Variscan fluids and their migration during burial and deformation. The isotopic parameters of white (older, more deformed) and rose (younger) calcites are: 87Sr/86Sr is between 0.7078 and 0.7082 (white) and 0.7086 (rose), δ18O is between +17.7 and +26.1 (white) and between +14.8 and +20.7 ‰ SMOW (rose), δ13C ranges from +0.1 to +2.5 (white) and from −0.3 to +1.6 ‰ V-PDB (rose). The isotopic signatures point to precipitation in an older fluid system buffered by the host rock (white calcites) and to an open, younger fluid-dominated system (rose calcites). Parent fluids (H2O–NaCl system) had salinities between 0.35 and 17.25 eq. wt % NaCl. The pressure-corrected and confined homogenization temperatures suggest formation of the calcite veins from a fluid with a temperature between 120 and 170 °C, a pressure of 300–880 bar at a depth between 2.1 and 3.2 km. The fluids were most likely confined to a particular sedimentary bed as a bed-scale fluid migration (white older calcite veins) or, later, to a pile of Palaeozoic sediments as a stratigraphically restricted fluid flow (rose younger calcite veins). The low temperatures and pressures during precipitation of calcites, which took place close to a peak of burial/deformation, confirm the distal position of the Moravian Karst region within the Variscan orogen.

International audience; This concluding chapter is divided into two main parts. The first part is a summary of the main facts and events which constitute the present body of knowledge of the chronology of life in the solar system, in the form of ‘‘highlights'' in astronomy, geology, chemistry and biology. The second part raises the interrogation ‘‘Is life universal?'', and tries to provide answers based on these facts and events. These answers turn out to differ widely among the various disciplines, depending on how far they feel able to extrapolate their current knowledge.

Once life appeared, it evolved and diversified. From primitive living entities, an evolutionary path of unknown duration, likely paralleled by the extinction of unsuccessful attempts, led to a last common ancestor that was endowed with the basic properties of all cells. From it, cellular organisms derived in a relative order, chronology and manner that are not yet completely settled. Early life evolution was accompanied by metabolic diversification, i.e. by the development of carbon and energy metabolic pathways that differed from the first, not yet clearly identified, metabolic strategies used. When did the different evolutionary transitions take place? The answer is difficult, since hot controversies have been raised in recent years concerning the reliability of the oldest life traces, regardless of their morphological, isotopic or organic nature, and there are also many competing hypotheses for the evolution of the eukaryotic cell. As a result, there is a need to delimit hypotheses from solid facts and to apply a critical analysis of contrasting data. Hopefully, methodological improvement and the increase of data, including fossil signatures and genomic information, will help reconstructing a better picture of life evolution in early times as well as to, perhaps, date some of the major evolutionary transitions. There are already some certitudes. Modern eukaryotes evolved after bacteria, since their mitochondria derived from ancient bacterial endosymbionts. Once prokaryotes and unicellular eukaryotes had colonized terrestrial ecosystems for millions of years, the first pluricellular animals appeared and radiated, thus inaugurating the Cambrian. The following sections constitute a collection of independent articles providing a general overview of these aspects.

Standard secular variation curves of the geomagnetic field direction for the last few millennia for different countries in Europe, based mainly on baked materials discovered in archaeological sites, are reaching sufficient accuracy and reliability that archaeomagnetic dating within this timespan in these areas is becoming feasible now. Orientation errors during sampling and sample preparation can be kept to a minimum and measurement errors of baked materials are in general very small. Nevertheless, even when the secular variation in the site to be dated is similar to that in the reference site, systematic or regular deviations between the remanence vector and geomagnetic field direction in kilns, due to internal and external factors, may result in biased average magnetisation directions and consequently in diverging archaeomagnetic dates. In more or less circular kilns, important non-random deviations of the remanence direction in the walls, in function of the relative azimuth as seen from the centre of the kilns, have been noticed in spite of precise and highly reliable average kiln magnetisation directions. The effect was revealed in the walls of the combustion chambers of roman pottery kilns and of mediaeval brass melting and working kilns, of different shape, lined with refractory bricks. Several hypotheses for the origin of these deviations were examined and anisotropy and/or magnetic refraction are unlikely to be the principal causes. The regular component of these deviations may be responsible for a strongly biased average magnetisation direction when only part of the kiln wall is preserved or when sampling is limited to certain parts of it and consequently result in unreliable dates when applying the archaeomagnetic dating method.

Volumes presenting the results of the ICDP Chicxulub drilling project