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Late heavy bombardment definition for Encyclopedia

Speleothems provide paleoclimate information on multimillennial to decadal scales in the Holocene. However, seasonal or even monthly resolved records remain scarce. Such records require fast-growing stalagmites and a good understanding of the proxy system on very short timescales. The Proserpine stalagmite from the Han-sur-Less cave (Belgium) displays well-defined/clearly visible darker and lighter seasonal layers of 0.5 to 2 mm thickness per single layer, which allows a measuring resolution at a monthly scale. Through a regular cave monitoring, we acquired a good understanding of how δ18O and δ13C signals in modern calcite reflect climate variations on the seasonal scale. From December to June, outside temperatures are cold, inducing low cave air and water temperature, and bio-productivity in the soil is limited, leading to lower pCO2 and higher δ13C values of the CO2 in the cave air. From June to December, the measured factors display an opposite behavior. The absence of epikarst water recharge between May and October increases prior calcite precipitation (PCP) in the vadose zone, causing drip water to display increasing pH and δ13C values over the summer months. Water recharge of the epikarst in winter diminishes the effect of PCP and as a result the pH and δ13C of the drip water gradually decrease. The δ18O and δ13C signals of fresh calcite precipitated on glass slabs also vary seasonally and are both reflecting equilibrium conditions. Lowest δ18O values occur during the summer, when the δ13C values are high. The δ18O values of the calcite display seasonal variations due to changes in the cave air and water temperature. The δ13C values reflect the seasonal variation of the δ13CDIC of the drip water, which is affected by the intensity of PCP. This same anticorrelation of the δ18O versus the δ13C signals is seen in the monthly resolved speleothem record that covers the period between 1976 and 1985 AD. Dark layers display lower δ18O and higher δ13C values. The cave system varies seasonally in response to the activity of the vegetation cover and outside air temperature between a "summer mode" lasting from June to December and a "winter mode" from December to June. The low δ18O and high δ13C values of the darker speleothem layers indicate that they are formed during summer, while light layers are formed during winter. The darker the color of a layer, the more compact its calcite structure is, and the more negative its δ18O signal and the more positive its δ13C signal are. Darker layers deposited from summer drip water affected by PCP are suggested to contain lower Ca2+ concentration. If indeed the calcite saturation represents the main factor driving the Proserpine growth rate, the dark layers should grow slower than the white layers.

Dust deposition in southern Belgium is estimated from the geochemical signature of an ombrotrophic peatland. The rare earth elements (REE) and lithogenic elements concentrations, as well as Nd isotopes, were determined by HR-ICP-MS and MC-ICP-MS, respectively, along an ∼6 m peat section covering 5300 yr, from 2000 to 7300 cal BP, dated by the 14C method. Changes in REE concentration in the peat correlate with those of Ti, Al, Sc and Zr that are lithogenic conservative elements, suggesting that REE are immobile in the studied peat bogs and can be used as tracers of dust deposition. Peat humification and testate amoebae were used to evaluate hydroclimatic conditions. The range of dust deposition varied from 0.03 to 4.0 g m-2 yr -1. The highest dust fluxes were observed from 2750 to 2550 cal BP and from 5150 to 4750 cal BP, and correspond to cold periods. The ϵNd values show a large variability from -13 to -5, identifying three major sources of dusts: local soils, distal volcanic and desert particles. © Author(s) 2013. CC Attribution 3.0 License., SCOPUS: ar.j, info:eu-repo/semantics/published

To investigate the early history of olivine from the Main-Group pallasites Brahin and Brenham, we have spatially mapped their trace-element distributions using laser-ablation inductively-coupled-plasma mass spectrometry (LA-ICP-MS). Brahin olivine interiors contain ∼100–200 μm patches enriched in Cr, Al, Ti, V, Sc and Ga, separated by linear enrichments of P; these structures bear no relation to current crystal morphologies. Rather, cross-cutting relationships suggest they predate olivine–metal mixing. Brenham olivine also has internal variations for these elements. By contrast, Ni and Co concentrations in olivine from both meteorites decrease near crystal margins, as expected for freezing-in of profiles formed during diffusive re-equilibration with metal during cooling. Brenham olivine also has decreasing Al, Cr and Ti near the margin. Correlations between concentrations of Cr and Al exist for individual Brahin olivine grains, but do not hold over multiple grains, indicating a heterogeneous precursor. Al and Ti are correlated over multiple grains in Brahin, interpreted as Ti cations decorating pre-existing Al-defects. In Brenham olivine, similar geochemical trends exist, but the Cr–Al relationship probably represents both grain margin effects and pre-existing internal heterogeneity. The preservation of structure for elements which are normally fast diffusers in olivine hinges on coupled substitutions involving Al, which along with P diffuses much more slowly than most other elements under some conditions. Al concentrations in olivine are low and variable (3–33 ppm) which is inconsistent with crystallisation from a normal silicate melt; Al-in-olivine thermometers indicate that pallasite olivine was formed in a low-temperature environment. Following its delivery to the magma ocean/core-mantle boundary, Al–P systematics were not substantially modified. Assuming diffusivities for Al and P that are similar to Si (since they reside in the same crystallographic site) and temperatures of 1600–1650 K (from the melting point of the metal and the absence of orthopyroxene in pallasites) an upper limit on the residence time of pallasite olivine of ∼1 Ma can be inferred by the persistence of trace element detail over scales of 100 μm. Following the olivine–metal mixing event, homogeneous Ni and Co distributions were modified by diffusion; Cr and V were partially modified; Al and P were essentially unchanged.

The study of astronomical climate forcing and the application of cyclostratigraphy have experienced a spectacular growth over the last decades. In the field of cyclostratigraphy a broad range in methodological approaches exist. However, comparative study between the different approaches is lacking. Different cases demand different approaches, but with the growing importance of the field, questions arise about reproducibility, uncertainties and standardization of results. The radioisotopic dating community, in particular, has done far-reaching efforts to improve reproducibility and intercomparison of radioisotopic dates and their errors. To satisfy this need in cyclostratigraphy, we initiate a comparable framework for the community. The aims are to investigate and quantify reproducibility of, and uncertainties related to cyclostratigraphic studies and to provide a platform to discuss the merits and pitfalls of different methodologies, and their applicabilities. With this poster, we ask the feedback from the community on how to further design this comparative framework in a useful, meaningful and productive manner. In parallel, we would like to discuss how reproducibility should be tested and what uncertainties should stand for in cyclostratigraphy. On the other hand, we intend to trigger interest for a cyclostratigraphic intercomparison project. The intercomparison project will be structured around several “test scenarios”, which are signals to be analyzed by participants that feature state-of-the-art challenges in time-series analysis of geologic signals. All participants would be free to determine their method of choice. However, a handful of criterions will be required for an outcome to be comparable. Participants will be solicited to submit and/or present and describe their solutions to one or several of the “test scenarios” at a common event (e.g. workshop). The lessons learned from the comparison could be reported in a review paper. The aim of an intercomparison project is not to rank thedifferent methods according to their merits, but to get insight into which specific methods are most suitable for which specific problems, and obtain more information on different sources of uncertainty. As this intercomparison project should be supported by the broader cyclostratigraphic community, we open the floor for suggestions, ideas and practical remarks.

The evolution of planets is driven by the composition, structure, and thermal state of their internal core, mantle, lithosphere, and crust, and by interactions with a possible ocean and/or atmosphere. A planet’s history is a long chronology of events with possibly a sequence of apocalyptic events in which asteroids, comets and their meteorite offspring play an important role. Large meteorite impacts on the young Earth could have contributed to the conditions for life to appear, and similarly large meteorite impacts could also create the conditions to erase life or drastically decrease biodiversity on the surface of the planet. Meteorites also contain valuable information to understand the evolution of a planet through their gas inclusion, their composition, and their cosmogenic isotopes. This paper addresses the evolution of the terrestrial bodies of our Solar System, in particular through all phenomena related to meteorites and what we can learn from them. This includes our present understanding of planet formation, their interior, their atmosphere, and the effects and relations of meteorites with respect to these reservoirs. It brings further insight into the origin and sustainability of life on planets, including Earth. Particular attention is devoted to Earth and Mars, as well as to planets and satellites possessing an atmosphere (Earth, Mars, Venus, and Titan) or a subsurface ocean (e.g., Europa), because those are the best candidates for hosting life. Though the conditions on the planets Earth, Mars, and Venus were probably similar soon after their formation, their histories have diverged about 4 billion years ago. The search for traces of life on early Earth serves as a case study to refine techniques/environments allowing the detection of potential habitats and possible life on other planets. A strong emphasis is placed on impact processes, an obvious shaper of planetary evolution, and on meteorites that document early Solar System evolution and witness the geological processes taking place on other planetary bodies. & 2012 Elsevier Ltd. All rights reserved.

A Devonian magnetic susceptibility (MS) record obtained on limestones ranging from the Uppermost-Eifelian to the Lower-Givetian and located on the southern border of the Dinant Synclinorium in Belgium was selected for time-series analysis. In these carbonate ramp and platform deposits, spectral analyses highlight persistent, high-frequency cycles in both the MS-signal and the microfacies curve, reflecting environmental and climate changes. These metre-scale variations in the MS-signal are interpreted as changes in the flux of magnetic minerals towards the marine system, most likely controlled by monsoon rainfall-intensity. By combining chrono- and biostratigraphic information with theoretical knowledge of sedimentation rates in different depositional environments, these cycles are interpreted as astronomically driven and dominated by precession. It is hypothesized that during precession minima (longitude of the perihelion ≈270°) the trans-equatorial pressure gradient reaches a maximum and intensifies the northeasterly monsoonal circulation. The consequent increase in moisture transport towards the continent leads to enhanced precipitation and runoff, which, in turn, induces a higher flux of detrital material – including magnetic minerals responsible for the MS-signal – towards the marine system. Moreover, this unique high-resolution climate signal reveals half-precessional cycles. These cycles suggest that during precession maxima (longitude of the perihelion ≈90°) southeasterly monsoonal circulation strengthened due to an increased inter-hemispheric pressure gradient.

This study is concerned with the Late Holocene floodplain history of the Karkheh River in Lower Khuzestan, and in particular with the role of human action upon its channel shifts. The research was conducted in a multidisciplinary way, in which resources and approaches from different research fields were combined: (1) geomorphological mapping based on the interpretation of Landsat and CORONA satellite imagery, (2) analyses of geological sequences, including the identification of sedimentary facies and radiocarbon dating of organic material, (3) an archaeological field survey of ancient settlements, and (4) consultation of historical documents, mainly Arabic texts from the 9th–14th century and European travel literature from the 16th-early 20th century. Three main channel belts of the Karkheh were identified (labelled Kh1, Kh2 and Kh3), corresponding to successive stages in the evolution of the floodplain. Two river shifts are documented in the datasets, both taking place within the last 2000 years. The first avulsion regards a shift from channel belt Kh1, once a tributary of the Karun, to the straight river bed of Kh2, taking place at least after 1240–1310 cal BP/710–640 AD. The second avulsion, from Kh2 to Kh3, is clearly documented in historical sources and happened in a single night event in the year 1837/113 cal BP. Reactivation of the Kh2 river bed and its irrigation canals can be attributed to the recent construction of an artificial canal bypassing the second avulsion point. Both river shifts were strongly influenced by human interference, whereby an artificial irrigation canal took over the entire river flow from the main channel belt. Most likely, a combination of human-induced factors, such as weakening of the river levees, high sedimentation rates and disadvantageous channel gradients, led to a situation prone to avulsion.

Review article: Geochemical analysis is an essential tool for the confirmation and study of impact structures and the characterization of the various rock types involved (target rocks, impact breccias, melt rocks, etc.). Concentrations and interelement ratios of the platinum-group elements, as well as the osmium and chromium isotope systems, allow quantification of extraterrestrial components and the identification of impactor types in impact deposits.In addition, chemolithostratigraphy can reveal the possible role of impacts in environmental change throughout the geologic record. This article deals predominantly with terrestrial impact structures.

Due to the interaction of oceanic crust with seawater, NaCl is a main component dissolved in aqueous fluid in subduction zones. The effect of dissolved NaCl (1.64 mol/l) on the partitioning of REE and Hf between garnet (pyrope) and aqueous fluid (doped with similar to 500 ppm of REE and similar to 250 ppm of Hf) has been investigated experimentally at 3 GPa, 850 degrees C(i.e., eclogitic UHP conditions) using the diamond trap technique. Trace elements in both pyrope and diamond aggregate were analyzed using LA-ICP-MS to derive fluid/pyrope partition coefficients (D). Mass balance calculation indicates that lanthanum is present in an accessory phase, tornebohmite. Europium and aluminium concentrations are too high in the aggregate to comply with mass balance and solubility data from the literature, respectively. Transport of these species from the mineral powder to the aggregate is inferred. D(MREE) (Gd and Tb) equals 0.39 +/- 0.11 and 0.22 +/- 0.07, respectively. D(HREE) (Dy to Lu) ranges from 0.09 +/- 0.02 to 0.02 +/- 0.01 with a regular decrease from Dy to Lu. D(Hf) is 0.33 +/- 0.09. Lanthanum is found to be incompatible (D(La) is 2.10 +/- 0.95) whereas for the other LREE (from Ce to Sm), D is lower than 1 (D(Ce) = 0.65 +/- 0.15, D(Pr) = 0.74 +/- 0.22, D(Nd) = 0.71 +/- 0.29 and D(Sm) = 0.61 +/- 0.23). Contrary to D(HRE)E and D(MREE), D(LREE) do not fit a near-parabolic dependence on LREE effective ionic radius. The Hf fluid/pyrope partition coefficient (D(Hf) = 0.33 +/- 0.09) indicates that this element favourably partition into garnet. Finally, it is shown that, compared to pure water, the addition of NaCl in water has no significant effect on REE and Hf behaviour.

The early Cretaceous Bernissart lake deposits (Mons Basin, Belgium) constitute an important historical site in the field of palaeontology. In this study, we focus on the organic matter (OM) content of the 50 m-long borehole core, "Ber 3", drilled at Bernissart. Organic data (Rock-Eval, palynofacies, C/N ratios) and carbon-isotope measurements on bulk OM and selected, isolated wood fragments were collected. The OM distribution exhibits two total organic carbon (TOC) cycles (12 m and 38 m-thick, respectively) that are stacked in a lower frequency cyclic pattern. A general increase of in situ aquatic production and preservation of OM through time is evidenced within the freshwater masses. A spectral analysis of a high-resolution gamma-ray record demonstrates that the sedimentation was controlled by orbitally-induced climatic changes. Precession, obliquity and short- and long-term eccentricity cycles are recognized. The 12 m-thick and the 38 m-thick TOC cycles fit well with a 100 kyr short-term and a 400 kyr long-term eccentricity cycle, respectively. Long-term organic fluctuations are interpreted as resulting from orbitally-induced fluctuating lake levels through time. Carbon-isotope evolution of bulk OM is thought to reflect firstly two local patterns of sedimentation: (1) the changing contribution of in situ amorphous organic matter versus terrestrial OM, and (2), the possible influence of enhanced productivity. The negative δ13CWOOD trend recorded at Bernissart seems equivalent to published coeval δ13CWOOD and δ13CCARB in the Upper Barremian to Lower Aptian. This trend noted at Bernissart is thus regarded as reflecting changes of the carbon-isotope ratios of atmospheric CO2. Previous presented palynological data suggest a "middle" Barremian to Lowermost Aptian stratigraphic range for the succession at Bernissart. According to this new dataset, we refine the age-assignment for Bernissart: the duration of deposition is now estimated to range between 0.55 and 2.2 myr in the Upper Barremian to Lowermost Aptian.

The Brabantian loess is often seen as a homogeneous sediment package, deposited under cold and dry climatic conditions (Haesaerts et al., 1981). However, in 1981 two small tundra gleysols were discovered in the Brabantian loess (Haesaerts et al., 1981). To unravel other possible changes in the sedimentary system during deposition, a more detailed look at the homogeneous Brabantian loess is carried out. The loess transporting process is reconstructed based on the combination of both grain size and grain shape parameters. These parameters are defined with automated dynamic image analysis and statistically compared with the two-dimensional Kolmogorov–Smirnov test. As suggested by Vandenberghe et al. (1998), our gleysols are generally correlated to a period of reduced grain size. Most likely, the more subtle the gleysols, the weaker the link between their formation and grain size reduction. Mazzullo et al. (1992) already stated that aeolian transport was very selective regarding grain size and sorting capacities. Our research points toward an extremely selective aeolian transport regarding the shape of the grains. Therefore, combining both particle size and particle shape can be very useful when reconstructing aeolian transport processes. This combination can also discriminate samples with a different transport and sedimentation history.

Pere Noel cave climatology (air and water temperature, P CO2), hydrology (drip rate, conductivity) and geochemistry of water and calcite deposits (δ 18O, δ 13C, Mg/Ca and Sr/Ca) where studied to better interpret stable isotopic and trace element variations of speleothems. Results of an automated monitoring station and of manual sampling between 1991 and 1998 have demonstrated the highly seasonal signal of drip rate, its control by water excess and rainfall, and, at a shorter scale to air pressure changes. The modern calcite deposit study suggests a relationship between cave calcite isotopic composition (δ 18O and δ 13C) and drip rate likely due to variations in degree of isotopic equilibrium during calcite precipitation. δ 18O and δ 13C of the calcite are therefore, through drip rate, linked to water recharge. Mg/ Ca and Sr/Ca ratios of Pere Noel cave calcite, depend closely on the residence time of the water, and therefore are also linked to drip rate and therefore to water recharge. This crossed link of δ 18O and δ 13C as of Mg/Ca and Sr/Ca to water recharge may explain the very similar variations of these four parameters along the longitudinal axis of a Holocene stalagmite, but it may also be the consequence of kinetic effects during calcite precipitation as suggested by similar variations of the four parameters along a single layer of the Holocene stalagmite.

The area comprising the NE Nile Delta and adjacent northern Sinai is an important hydrocarbon province in Egypt, but the origin of the hydrocarbons and their migration is not fully understood. In this paper, we evaluate organic source facies and assess the results of basin modelling in order to improve our understanding of the regional petroleum system. Organic-geochemical and petrographic analyses of 800 rock samples ranging in age from Early Jurassic to Pleistocene were used in this study. Most of the samples studied had moderate to high TOC contents, and kerogen was a mixture of Types II and III with a wide range of petroleum generation potentials from very poor to very good. Thermal and burial history models indicate that the source rocks entered the early-mature/mature stage in very recent times (Pleistocene to Recent). The top of the oil window ranges in depth from 1,800 m to 4,500 m, whereas the bottom of the oil window was not reached by most of the studied wells. In combination with numerical modelling results, structure contour maps for key horizons reveal possible migration trends and prospective areas. We tentatively identify prospective targets for hydrocarbon exploration, both in the Tertiary sequence and in the Cretaceous succession, especially where carbonate build-ups are present.

Chicxulub crater definition for Encyclopedia

Pallasite meteorites comprise olivine-metal mixtures and occur in a range of textural types with numerous accessory phases such as chromite, troilite, phosphide, phosphate and phosphoran olivine [e.g. 1]. The petrogenesis of pallasites has undergone considerable revision in recent years [1,2,3], and their importance in planetary differentiation is better understood with the recognition of five separate parent bodies [summarized in 1]. However, their formation environment is still poorly constrained, with recent suggestions including a quiescent core-mantle boundary [1], a violent mixture of core and mantle material [2], as well as a surface impact environment [3]. In this paper, the evolution of the well-sampled Main-Group pallasite parent body (source of ~90-95% of all pallasites) is re-evaluated using metal, phosphate and other accessory phase geochemistry as well as metallographic cooling rates.

The development and behavior of million year- scaled depositional sequences recorded within Palaeozoic carbonate platform has remained poorly examined. There- fore, the understanding of palaeoenvironmental changes that occur in geological past is still limited. We herein undertake a multi-disciplinary approach (sedimentology, conodont biostratigraphy, magnetic susceptibility (MS), and geochemistry) of a long-term succession in the Carnic Alps, which offers new insights into the peculiar evolution of one of the best example of Palaeozoic carbonate platform in Europe. The Freikofel section, located in the central part of the Carnic Alps, represents an outstanding succession in a fore-reef setting, extending from the Latest Givetian (in- det.falsiovalis conodont zones) to the Early Famennian (Lower crepida conodont zone). Sedimentological analysis allowed to propose a sedimentary model dominated by distal slope and fore-reef-slope deposits. The most distal setting is characterized by an autochthonous pelagic sedi- mentation showing local occurrence of thin-bedded turbi- ditic deposits. In the fore-reef slope, in a more proximal setting, there is an accumulation of various autochthonous and allochthonous fine- to coarse-grained sediments origi- nated from the interplay of gravity-flow currents derived from the shallow-water and deepwater area. The temporal evolution of microfacies in the Freikofel section evolves in two main steps corresponding to the Freikofel (Unit 1) and the Pal (Unit 2) limestones. Distal slope to fore-reef lithologies and associate changes are from base to top of the section: (U1) thick bedded litho- and bioclastic breccia beds with local fining upward sequence and fine-grained mud- stone intercalations corresponding, in the fore-reef setting, to the dismantlement of the Eifelian-Frasnian carbonate platform during the Early to Late Frasnian time (falsiovalis to rhenana superzones) with one of the causes being the Late Givetian major rift pulse; (U2) occurrence of thin- bedded red nodular and cephalopod-bearing limestones with local lithoclastic grainstone intercalations corre- sponding to a significant deepening of the area and the progressive withdrawal of sedimentary influxes toward the basin, in relation with Late Frasnian sea-level rise. MS and geochemical analyses were also performed along the Fre- ikofel section and demonstrate the inherent parallel link existing between variation in MS values and proxy for terrestrial input. Interpretation of MS in terms of palaeo- environmental processes reflects that even though distality remains the major parameter influencing MS values, car- bonate production and water agitation also play an impor- tant role.

Dealing with uncertainties is inherent to the scienti? c process. In the process of building geologic time scales, the reported uncer- tainties are at least as important as the estimates of the numerical ages. Currently all time scales for the Devonian are based on conven- tional age-depth models, constructed by linear or cubic interpolation between different dated positions. Unfortunately, such models tend to produce overoptimistic con? dence intervals. In this study we apply Bayesian statistics to the Devonian time scale to better incorporate stratigraphic and radioisotopic uncertainty. This approach yields a Devonian time scale characterized by increasing uncertainty with growing stratigraphic distance from a radioisotopically dated sample. This feature is absent from The Geologic Time Scale 2012; therefore, that time scale is overoptimistic. We further constrain the obtained time scale by incorporating astrochronological duration estimates for the Givetian and Frasnian stages. The combination of radioisotopic dating and astrochronology results in a reduction of the uncertainty on the numerical age of the stage boundaries concerned by several million years. For example, we estimate the age of the Frasnian- Famennian boundary at 373.9 ± 1.4 Ma.

Stable isotopes applied to reconstruct climates of the Holocene using a stalagmite from a stalagmite - Grotte du Père Noël, Han-sur-Lesse, Belgium

Every cave system is unique and every stalagmite has its own behavior. A good understanding of what the measured proxies are reflecting is therefore needed when reconstructing the paleoclimate at high-resolution by the use of stalagmites. Generally such information is obtained by cave monitoring and/or by comparing the measured records with other paleoclimate records in the region. The stalagmite presented in this study displays an extremely high growth rate (1mm/y) and annual lamination over the last 700 years allowing to compare the measured proxy values with the instrumental record leading to a robust understanding of its climate transfer function. The age model is established by layer counting and is in good agreement with 4 U/Th-ages and one 14C-age confirming the seasonal character of the layering. A one-year cave monitoring with a two-week cave visiting frequency is done to follow how the different proxy signals are recorded in the modern calcite and how they are linked to the outside cave conditions. Sub-seasonal ?18O and ?13C measurements (3 samples a layer) were carried out on the upper 50 years. The remaining 650 years were sampled for isotopes on a seasonal scale by drilling one sample a layer. LA-ICP-MS measurements for Mg, Sr, Ba, U and Zn concentrations were line tracked on the upper 50 years and will be compared with the sub-seasonally resolved isotope records. Cave monitoring results show that the ?18O and ?13C values of fresh glass-slab calcite increase from November to April when the cave temperatures decrease and the drip rate increase. Results from the sub-seasonal isotope sampling show that the ?18O and ?13C values increase within the white more porous layers and decrease in the dark more compact layers. Consequently, white layers are formed during wetter and colder periods while dark layers reflect drier and warmer conditions. Further comparison of the sub-seasonal isotope and trace elemental records with instrumental data will provide a good understanding of the transfer functions of theserecords for the last 50 years. In a next step, these transfer functions will be used to interpret the full 700-year seasonal isotope record providing a reliable paleoclimate reconstruction for southern Belgium.

High-Fe enstatite chondrites (EH chondrites) are samples of planetesimals accreted in a region of the solar nebula with very low oxygen fugacity [1]. A consequence of this reduction is that Fe exists as metal rather than as FeO in silicates, with pyroxene rather than olivine being the most common mineral (stabilized by low (FeO+MgO)/SiO2) [1, 2]. Like ordinary chondrites, EH chondrites are divided according to textural and limited geochemical criteria, with petrologic type 3 being unequilibrated nebular rocks and types 4-6 having been increasingly metamorphosed. Suggested mineralogical and geochemical criteria for classifying this process include the presence of disequilibrium mineral assemblages e.g. olivine and silica, which react according to Mg2SiO4 + SiO2 -> Mg2Si2O6 [3], and mineral geochemistry, particularly Cr in olivine [4]. We are attempting to consolidate these classification schemes with an investigation of mineral modal abundances and geochemistry.

This paper presents the lead isotopic composition of potential clay sources for pottery production, collected in the four major geological zones of Cyprus (Troodos Ophiolite, Circum Troodos Sedimentary Succession, Mamonia Terrane, Kyrenia Terrane) and evaluates its usefulness in Cypriote pottery provenance studies. The clay isotopic signatures from the four zones are compared to each other and to the isotopic composition of various utilitarian pottery wares from three Late Bronze Age sites, respectively located in southern Cyprus (Alassa-Pano Mandilaris), east Cyprus (Enkomi), and southeast Cyprus (Hala Sultan Tekke). It also explores the potential of this method to better discriminate between potential raw materials used for the production of Base-ring ware, one of the most characteristic fine pottery of Late Bronze Age Cyprus, which was widely spread in the Eastern Mediterranean (Courtois, 1981; Vaughan, 1991, 1994). Results show that three main lead isotopic fields can be distinguished among the Cypriote clay sources and the comparison of Plain sherds with the clay sources allows discrimination between local products and imports. They also clearly indicate that all the Base-ring sherds analyzed in this study were made of the clays from the Kathikas Formation that crops out in only limited parts of southwest Cyprus.

Granites in circum-pacific igneous provinces can often be divided into 'S-' and 'I'-types on the basis of elemental and isotopic characteristics [e.g. 1]. This division reflects a dominance of sedimentary or igneous source components, and dating of granites allows tracking of the relative contributions to growing batholiths in accretionary orogens. In the Lachlan and New England Orogens of Eastern Australia, a progression from S-type through I-type to A-type granites occurs repeatedly over ~100 Myr periods. S-type intrusion occurs during the first major extensional event following major compression, while later I-type intrusion reflects a diminished sedimentary source and increasing mantle contribution. The timing of S- and I-type granites is therefore related to the tectonic evolution of orogens [2]. The S-type phase of intrusion in the New England accretionary orogen (~300-280 Ma) records an environment switching from compression to extension and back to compression as partof this process. We have undertaken U-Pb dating of zircons extracted from small (~backarc) gabbroic and dioritic bodies (Bakers Creek Supersuite), recalculated the ages of S-type granites (Hillgrove Supersuite), and compiled chronological data for the New England Orogen in order to investigate the establishment of magmatism in this area. We find a progression through: (1) diverse magmatism involving gabbroic, dioritic, S- and I-type during establishment of magmatism (305-295 Ma); (2) a major pulse of S-type magmatism (295-285 Ma), ending with; (3) I-type and HREEdepleted (deep crustal) magmatism around the time of the Hunter-Bowen orogenic event (~285-266 Ma). Magmatism occurs over a ~35 Myr period in the region of most voluminous intrusion, but timing varies along-strike and may reflect assymetric rifting of the orogen. Together, these data time the heating, melting, depletion, and exhaustion of the S-type magma source. [1] Kemp, A. I. S. & Hawkesworth, C. J., 2003. Treatise on Geochemistry 3, 349-410. [2] Collins, W. J. & Richards, S. W., 2008. Geology 36, 559-562.

A 500 year seasonally resolved d18O and d13C record from an Belgian stalagmite. Poster

The geochemical nature of the impactites from International Continental Scientific Drilling Project--El'gygytgyn lake drill core 1C is compared with that of impact melt rock fragments collected near the western rim of the structure and literature data. Concentrations of major and trace elements, with special focus on siderophile metals Cr, Co, Ni, and the platinum group elements, and isotope ratios of osmium (Os), were determined to test the hypothesis of an ureilite impactor at El'gygytgyn. Least squares mixing calculations suggest that the upper volcanic succession of rhyolites, dacites, and andesites were the main contributors to the polymict impact breccias. Additions of 2-13.5 vol% of basaltic inclusions recovered from drill core intervals between 391.6 and 423.0 mblf can almost entirely account for the compositional differences observed for the bottom of a reworked fallout deposit at 318.9 mblf, a polymict impact breccia at 471.4 mblf, and three impact melt rock fragments. However, the measured Os isotope ratios and slightly elevated PGE content (up to 0.262 ng g?1 Ir) of certain impactite samples, for which the CI-normalized logarithmic PGE signature displays a relatively flat (i.e., chondritic) pattern, can only be explained by the incorporation of a small meteoritic contribution. This component is also required to explain the exceptionally high siderophile element contents and corresponding Ni/Cr, Ni/Co, and Cr/Co ratios of impact glass spherules and spherule fragments that were recovered from the reworked fallout deposits and from terrace outcrops of the Enmyvaam River approximately 10 km southeast of the crater center. Mixing calculations support the presence of approximately 0.05 wt% and 0.50-18 wt% of ordinary chondrite (possibly type-LL) in several impactites and in the glassy spherules, respectively. The heterogeneous distribution of the meteoritic component provides clues for emplacement mechanisms of the various impactite units.

Secondary Ion Mass Spectrometry (SIMS) is used to date meteoritic olivine using the 53Mn–53Cr short-lived decay scheme. This involves simultaneously measuring the Cr-isotope composition and Mn/Cr ratio of a sample, but the relative sensitivity of SIMS to Cr and Mn over a compositionally varying olivine matrix is poorly understood. We have synthesized a range of olivine samples in Mg–Fe–Ca space, suitable for investigating Mn–Cr relative sensitivity with particular application to olivine in angrites and secondary fayalite in oxidised carbonaceous chondrites. These were analysed by SIMS (using Sensitive High-mass Resolution Ion Micro Probe Reverse Geometry; SHRIMP-RG) and Laser-Ablation Inductively-Coupled-Plasma Mass-Spectrometry (LA-ICP-MS) to determine the relative sensitivity factors (RSF) necessary to correct SIMS 55Mn+/52Cr+ to atomic 55Mn/52Cr. We have found that RSF changes systematically as a function of the olivine matrix by several tens of percent, apparently being controlled by Fe content. Additionally, the RSF values found in this study are considerably different from most of those previously reported. A review of the literature shows that RSF for the Mg-rich San Carlos olivine differs widely between studies, and is probably controlled by SIMS instrumental settings. Our results show that the 55Mn/52Cr of olivine in some SIMS Mn–Cr studies has been accurately determined (e.g. for pallasites and angrites) but for secondary fayalite in carbonaceous chondrites it has probably been underestimated. If the relationship observed for our SIMS instrument holds true for others, then the initial 53Mn/55Mn of these materials (the abundance of 53Mn with respect to 55Mn at the time of crystallisation/isotopic closure) should be lower by a factor of ∼1.6 and ages should be ∼2.6 Ma younger. This would imply that the initial 53Mn/55Mn for secondary fayalites in carbonaceous chondrites is in the range 0.7–1.7 × 10−6, equating to an age of 4555.2–4559.9 Ma relative to the precisely dated D’Orbigny angrite.

Since the Mid-Holocene, the summer position of the Intertropical Convergence Zone (ITCZ) is gradually moving south due to the diminishing boreal summer insolation (Wanner et al., 2006). Understanding this behavior for the Indian Ocean Monsoon (IOM) and its northeast and southwest subsystems is of major importance, especially since further drying is predicted (Fleitmann et al., 2007). To investigate how precipitation from the northeast IOM subsystem is evolving since the mid Holocene, we sampled four stalagmites on Socotra, an island in the northern Indian Ocean. On Socotra, rain is delivered at the start of the southwest IOM in May-June and at the start of the northeast IOM from September to December. The Haggeher Mountains, reaching up to 3000m altitude in the middle of the island, act as a barrier forcing rain delivered by northeast winds to fall on the eastern side of the island, where the studied caves are located. ?18O and ?13C and Mg/Ca and Sr/Ca signals in the stalagmites are interpreted as indicators of wetter or drier conditions created by the northeast IOM. The stalagmite records suggest a weakening of the northeast precipitation between 6.0 and 3.8 ka. After 3.8 ka precipitation intensities remain constant with two superimposed drier periods, between 0 and 0.6 ka and from 2.2 to 3.8 ka. A similar ?18O record to that of eastern Socotra occurs in Northern Oman stalagmites after 6.2 ka. At this time, the summer ITCZ moved south of Northern Oman making precipitation from northeast winds the only moisture source available. A drying around 6 ka is also seen in sedimentary records from the Arabian Peninsula (Lezine et al., 2010; Parker et al., 2006), which nowadays are located outside the migration pathway of the ITCZ. Records on the Arabian Peninsula that today are still within the ITCZ migration belt, and thus receive rain by both the northeast as the southwest IOM, display a gradual drying after the wet Holocene optimum at 8.0 ka. In contrast to the stable northeast rainy season suggested by the records inthis study, speleothem records from western Socotra indicate a wettening of the southwest rainy season on Socotra after 4.4 ka. The local wettening of western Socotra could related to a more southerly path (more over the Indian Ocean) taken by the southwest winds. This local effect shows that in a generally drying pattern, smaller-scale regional changes towards wetter conditions can occur. Fleitmann et al., 2007, QSR; Lezine et al., 2010, Global Planet Change; Parker et al., 2006, Quaternary Research; Wanner et al., 2006, QSR

We present arguments and evidence against the hypothesis that a large impact or airburst caused a significant abrupt climate change, extinction event, and termination of the Clovis culture at 12.9 ka. It should be noted that there is not one single Younger Dryas (YD) impact hypothesis but several that conflict with one another regarding many significant details. Fragmentation and explosion mechanisms proposed for some of the versions do not conserve energy or momentum, no physics-based model has been presented to support the various concepts, and existing physical models contradict them. In addition, the a priori odds of the impact of a >4 km comet in the prescribed configuration on the Laurentide Ice Sheet during the specified time period are infinitesimal, about one in 10 15 . There are three broad classes of counterarguments. First, evidence for an impact is lacking. No impact craters of the appropriate size and age are known, and no unambiguously shocked material or other features diagnostic of impact have been found in YD sediments. Second, the climatological, paleontological, and archeological events that the YD impact proponents are attempting to explain are not unique, are arguably misinterpreted by the proponents, have large chronological uncertainties, are not necessarily coupled, and do not require an impact. Third, we believe that proponents have misinterpreted some of the evidence used to argue for an impact, and several independent researchers have been unable to reproduce reported results. This is compounded by the observation of contamination in a purported YD sample with modern carbon.

Four stalagmites covering the last 7.0 ka were sampled on Socotra, an island in the northern Indian Ocean to investigate the evolution of the northeast Indian Ocean Monsoon (IOM) since the mid Holocene. On Socotra, rain is delivered at the start of the southwest IOM in May–June and at the start of the northeast IOM from September to December. The Haggeher Mountains act as a barrier forcing precipitation brought by the northeast winds to fall preferentially on the eastern side of the island, where the studied caves are located. d18O and d13C and Mg/Ca and Sr/Ca signals in the stalagmites reflect precipitation amounts brought by the northeast winds. For stalagmite STM6, this amount effect is amplified by kinetic effects during calcite deposition. Combined interpretation of the stalagmites' signals suggest a weakening of the northeast precipitation between 6.0 and 3.8 ka. After 3.8 ka precipitation intensities remain constant with two superimposed drier periods, between 0 and 0.6 ka and from 2.2 to 3.8 ka. No link can be established with Greenland ice cores and with the summer IOM variability.In contrast to the stable northeast rainy season suggested by the records in this study, speleothem records from western Socotra indicate a wettening of the southwest rainy season on Socotra after 4.4 ka. The local wettening of western Socotra could relate to a more southerly path (more over the Indian Ocean) taken by the southwest winds. Stalagmite STM5, sampled at the fringe between both rain areas displays intermediate d18O values. After 6.2 ka, similar precipitation changes are seen between eastern Socotra and northern Oman indicating that both regions are affected similarly by the monsoon. Different palaeoclimatologic records from the Arabian Peninsula currently located outside the ITCZ migration pathway display an abrupt drying around 6 ka due to their disconnection from the southwest rain influence. Records that are nowadays still receiving rain by the southwest winds, suggest a more gradual drying reflecting the weakening of the southwest monsoon.

Stable isotope data (Delta18O, Delta13C) were obtained for magnesite (MgCO3) from Holocene salt lake deposits of the Taoudenni-Agorgott basin, Mali, in which it is the only carbonate mineral present. The deposits have a high glauberite content (Na2Ca(SO4)2), representing a type of continental evaporite formation that is commonly magnesite-bearing. Samples from seven different levels in a 5?m long sequence were analysed. ?18OV-PDB values are between +3.17 and +5.91o/oo, which is lower than might be expected for evaporitic environments, recording reduced 18O enrichment at high salinity. ?13CV-PDB values are between ?1.32o/oo and ?4.79o/oo, showing an influence of carbon derived from the decomposition of organic matter rather than from exchange with atmospheric CO2. Covariance between ?18O and ?13C is strong for the lower part of the sequence, recording coupled 18O and 13C enrichment as commonly observed for closed basins. Covariance is lacking for the upper part of the sequence, with only periodic massive magnesite deposition in a more shallow lake

Feathered theropods were diverse in the Early Cretaceous Jehol Group of western Liaoning Province, China. Recently, anatomically distinct feathered taxa have been discovered in the older Middle-Late Jurassic Tiaojishan Formation in the same region. Phylogenetic hypotheses including these specimens have challenged the pivotal position of Archaeopteryx in bird phylogeny. Here we report a basal troodontid from the Tiaojishan Formation that resembles Anchiornis, also from Jianchang County (regarded as sister-taxa). The feathers of Eosinopteryx are less extensive on the limbs and tail than Anchiornis and other deinonychosaurians. With reduced plumage and short uncurved pedal claws, Eosinopteryx would have been able to run unimpeded (with large foot remiges cursorial locomotion was likely problematic for Anchiornis). Eosinopteryx increases the known diversity of small-bodied dinosaurs in the Jurassic, shows that taxa with similar body plans could occupy different niches in the same ecosystem and suggests a more complex picture for the origin of flight.

Lead isotope analyses were carried out on fragments of White Slip II ware, a Late Bronze Age Cypriote pottery ware, and on raw materials possibly used for their production. Sherds originate from three Late Bronze Age sites (Hala Sultan Tekke and Sanidha in Cyprus and Minet el-Beida in Syria) and clays come from the surroundings of Sanidha, a production site for White Slip ware. X-ray fluorescence (XRF) and a Principal Component Analysis (PCA) are combined with Pb isotope analyses to further investigate the effectiveness of the latter method within a multiproxy approach for pottery provenance study. The pottery sherds from the three sites are compared between themselves and with potential raw material. Additional X-ray diffraction (XRD) and analyses using a scanning electron microscope (SEM) equipped with an energy dispersive X-ray detection (EDX) facility were performed on selected sherds and clays. This work confirms that the clay source used for pottery production in Sanidha derives from local weathered gabbro. It also shows that different origins can be proposed for White Slip II ware sherds from Hala Sultan Tekke and Minet el-Beida and that clays were prepared prior to White Slip II ware production. It finally confirms the effectiveness of Pb isotopes in tracing pottery provenance not only by comparing sherd assemblages but also by comparing sherds to potential raw materials. © 2012 Elsevier Ltd., 0, SCOPUS: ar.j, info:eu-repo/semantics/published

This chapter determines the influence of exposure surfaces with possible influx of meteoric waters on the exposed limestone and its effect on porosity and cementation history. The small scale sequences that belong to the lower part of the transgressive systems tract (TST) show a diagenetic evolution starting with marine cementation with fibrous and pendant radiaxial cements that is best developed near the top of the sequences due to evaporation of marine waters. The third order, type 1 sequence boundary caused the pervasive cementation of almost all initial porosity in the limestone below the boundary due to a prolonged exposure. The chapter demonstrates that short-term exposure seems to be more effective than longer exposure in creating porosity in limestone sequences.

Rhythmical alternations between limestone and shales or marls characterize the famous Kowala section, Holy Cross Mountains, Poland. Two intervals of this section were studied for evidence of orbital cyclostratigraphy. The oldest interval spans the Frasnian–Famennian boundary, deposited under one of the hottest greenhouse climates of the Phanerozoic. The youngest interval encompasses the Devonian– Carboniferous (D–C) boundary, a pivotal moment in Earth’s climatic history that saw a transition from greenhouse to icehouse. For the Frasnian–Famennian sequence, lithological variations are consistent with 405-kyr and 100-kyr eccentricity forcing and a cyclostratigraphic floating time-scale is presented. The interpretation of observed lithological rhythms as eccentricity cycles is confirmed by amplitude modulation patterns in agreement with astronomical theory and by the recognition of precession cycles in high-resolution stable isotope records. The resulting relative time-scale suggests that � 800 kyr separate the Lower and Upper Kellwasser Events (LKE and UKE, respectively), two periods of anoxia that culminated in massive biodiversity loss at the end of the Frasnian. Th/U and pyrite framboid analyses indicate that during the UKE, oxygen levels remained low for 400 kyr and d 13 C org measure

The sedimentology, salt mineralogy and stable oxygen- and carbon-isotope signatures of a mid-lake sediment sequence from hypersaline Lake Bogoria in Kenya reveal marked climate-driven changes in water-column mixing regime and salinity over the past 1700 years. Combined with sedimentological data on short sediment sequences from nearby lakes Nakuru and Elementeita, this results in a preliminary reconstruction of hydroclimatic variability in the central Kenya Rift Valley since ca. 300 AD. Stratigraphic analyses of bulk sediment composition, texture and magnetic susceptibility of all three cores; and smear slide, XRD and stable-isotope analyses on carbonate minerals in the Bogoria sequence allowed to define a succession of sedimentary units, corresponding to distinct phases in lake history. In the lowermost unit, four characteristic trona layers (Na3(HCO3)(CO3)·2H2O) are attributed to predominantly dry conditions during the second half of the first millennium AD and the period equivalent to the Medieval Climate Anomaly, until the first half of the 12th century AD. Lake Bogoria was probably polymictic at that time, its surface level standing significantly lower than today. The second unit displays uniform deposition of nahcolite (NaHCO3), indicative of a strongly stratified lake where a layer of less saline surface water (near-)permanently covers a hypersaline water mass with high pCO2. We propose that this depositional phase reflects the rising lake level related to the transition from dry to more humid climate conditions at the onset of the Little Ice Age, as previously documented for other parts of equatorial East Africa. The third, uppermost Bogoria unit contains only sporadic depositions of magadiite (Na2Si14O29(OH)3·11H2O) and various sodium carbonate minerals. This, together with low magnetic susceptibility, is interpreted to indicate humid Little Ice Age conditions, with highest lake level and reduced salinity around the late-15th to early-16th century AD. From the late-18th to early-19th century and again inthe 1870's, the region experienced two episodes of drought more severe than any recorded in historical time. Tentative evidence for these events in the Bogoria record is not well constrained in time, but dated desiccation surfaces in the Nakuru and Elementeita records confirm their widespread nature across eastern equatorial Africa.

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In the Umbria-Marche basin, the aftermath of Ocean Anoxic Event 2 (OAE2, Bonarelli Level) is represented by the Turonian part of the Scaglia Rossa Formation. The Scaglia Rossa pelagic limestones were studied in the classic Contessa and Bottaccione sections near Gubbio, in the Umbria-Marche region of the northeastern Apennines of Italy. Oscillations between radiolarian cherts interbedded with foram-coccolith pelagic limestones are interpreted to follow the rhythm of precession and show hierarchical bundles, which are suggestive of eccentricity-related grouping. Eccentricity-bundles are correlated amongst the two studied sections. Moreover, the magnetic susceptibility signal of the Bottaccione section and the 18O and 13C record of both sections clearly demonstrate the imprint of precession and eccentricity. Eccentricity minima are associated with relatively warm periods (18O minima), characterized by an increased magnetic susceptibility signal and radiolarian blooms, which are expressed by frequent chert beds. Radiolarian blooms seem to hamper primary productivity, given that they correlate with 13C minima. The delineated astronomical cycles constitute an eccentricity-based cyclostratigraphy for the Turonian part of the Scaglia Rossa. Moreover, the constructed cyclostratigraphy is anchored to numerical time by calibration with the astronomical solution La2010 (Laskar et al., 2011) and with recent radioisotopic ages from the Cenomanian- Turonian boundary interval near the GSSP in Colorado, USA (Meyers et al., 2012). The numerical age (93.9 0.15 Ma; Meyers et al., 2012) of the Cenomanian-Turonian boundary (0.75 m above the top of the Bonarelli Level in the Contessa section; Tsikos et al., 2004; Kennedy et al., 2005) is used as the pinpoint to which our astronomical time-scale is anchored. Using the anchored astronomical time-scale for the Turonian of the Umbria-Marche basin, the top of the Bonarelli Level is placed at 93.97 0.25 Ma, and the boundary between the Whiteinella archaeocretacea and Helvetoglobotruncana helvetica planktonic foraminiferal zones is put at 93.48 0.25 Ma. These ages are consistent with the numerical ages obtained from radioisotopic dating of the near-GSSP USGS #1 Portland core (Meyers et al., 2012). High-resolution XRF geochemical analysis through the 82 cm thick Bonarelli Level in the Bottaccione section at Gubbio, reveals four strong 21 cm thick cycles. Spectral analyses on the SiO2 and Al2O3 concentration and in the Si/Al ratio suggest an eccentricity and precession signature if one assumes an average sedimentation rate of 2.0 m/Myr during the OAE2 in this pelagic basin. These results indicate a duration of 410 kyr for the Bonarelli Level and place the bottom of this anoxic interval at 94.38 0.25 Ma. In the near future, the latter marker-bed could be used to connect the astronomical time-scale presented in this abstract to the Cenomanian astronomical time-scale based on the nearby Furlo section (Batenburg et al., this session), in orderto obtain a considerably long (> 5 Myr) astronomically calibrated time-scale across a an intriguing time interval in Earth history, with unprecedented precision and accuracy. References Kennedy, W. J., Walaszczyk, I., and Cobban, W. A.: The global boundary stratotype section and point for the base of the Turonian stage of the cretaceous: Pueblo, Colorado, USA, Episodes, 28, 93-104, 2005. Laskar, J., Fienga, A., Gastineau, M., and Manche, H.: La2010: a new orbital solution for the long-term motion of the Earth, Astron. Astrophys., 532, doi:10.1051/0004-6361/201116836, 2011. Meyers, S. R., Siewert, S. E., Singer, B. S., Sageman, B. B., Condon, D. J., Obradovich, J. D., Jicha, B. R., and Sawyer, D. A.: Intercalibration of radioisotopic and astrochronologic time scales for the Cenomanian-Turonian boundary interval, Western Interior Basin, USA, Geology, 40, 7-10, doi:10.1130/G32261.1, 2012. Tsikos, H., Jenkyns, H. C.,Walsworth-Bell, B., Petrizzo, M. R., Forster, A., Kolonic, S., Erba, E., Silva, I. P., Baas, M., Wagner, T., and Damste, J. S. S.: Carbon-isotope stratigraphy recorded by the Cenomanian-Turonian Oceanic

Magnetic susceptibility (MS) had been used for decades on sedimentary rocks as a paleoclimatic tool and as a tool for high resolution correlations on the basis of the link between MS and detrital inputs (highly magnetic minerals). MS is a very interesting tool for correlation and paleoenvironmental research because data acquisition is fast and straightforward, providing the high amount of samples needed for such study. Although, mostly in the case of Palaeozoic rocks, the original paleoenvironmental signal can be affected by different syn- or post-depositional processes. In this work, we synthesized 10 years of our research on the application and on the origin of the magnetic susceptibility signal through the Devonian record of Belgium. This record is of peculiar interest, because the biostratigraphy is well known and there is a relatively continuous record over 20 My and through various paleoenvironments (platform, ramp, atoll) with different diagenetic maturity. The first step was to compare MS with facies and to try to correlate the different sections. On the Frasnian platform sections, there is a clear link between MS and facies, with MS increasing towards shallower facies. This increase of MS towards shallower facies seems logical since these facies were deposited closer to the detrital inputs sources. When considering ramp (Eifelian-Givetian) and atoll sections (Frasnian), the MS relationship with facies is opposite and MS increases towards the deepest facies. This was interpreted as related to the water agitation and carbonate production rate being lower in the deeper environments and allowing concentration of magnetic particles. Although, correlations were possible between the different atoll sections, but not with the carbonate platform sections, since the MS signals are opposite in both settings. So the depositional setting can be a key parameter influencing the way the original magnetic susceptibility signal is recorded. In order to identify some of the external parameters influencing the magnetic susceptibility signal; a MS curve from the Eiflian-Givetian ramp was selected for time-series analysis. This spectral analysis highlight persistent high-frequency meter scale cycles which are interpreted as reflecting changes in flux of magnetic minerals, most likely controlled by monsoon rainfall-intensity. By combining chrono- and biostratigraphic information with theoretical knowledge of sedimentation rates in different depositional environments, these cycles are interpreted as astronomically driven (precession-dominated). So this show that Magnetic susceptibility signal in some cases can be affected by astronomical forcing, through detrital inputs. To get a better understanding about the nature and origin of the magnetic susceptibility signal, it is crucial to identify the magnetic minerals which are carrying this MS signal. Geochemistry and magnetic analyses (Hysteresis and acquisition curves of the Isothermal Remanent Magnetic Saturation IRM) were performed on three sections (2 Frasnian platformand one Eifelian givetian platform sections). Magnetic parameters show that the MS signal is mostly influenced by small grains magnetites which were formed through remagnetization event. This remagnetization happened during the Carboniferous and is related to the transformation of smectite into illite (realizing iron available for magnetite formation). On 2 sections (1 Frasnian platform and 1 Eifelian givetian platform), there is a strong link between the MS signal and TiO2, Al2O3 and Zr which are detrital proxies. This shows that despite the remagnetization, the MS signal is still related to detrital inputs, indicating that the newly formed magnetite probably remained associated with the original clay minerals, leading to a globally increased signal still reflecting the primary trends. In one section (Frasnian platform), there is no strong link between MS signal and detrital proxies, indicating that in this case the MS signal was affected by the remagnetization event (probably in relation with fluid circulation). In conclusion, MS appears as a convolved signal, influenced on one hand by primary parameters such as detrital inputs and orbital cyclicities. Although, these paleoenvironmental trends can also be affected by depositional parameters such as water agitation and carbonate production. Furthermore, the diagenesis can also have a strong impact on the final signal. This clearly highlights the need to use magnetic susceptibility under the control of other techniques (comparison with other paleoenvironmental proxies or magnetic or geochemical analysis).

To better constrain the emplacement mechanism of the so-called ''mega-block zone,a structurally complex unit of target rocks within the Chicxulub impact structure, the stratigraphic coherence of this zone is tested using its strontium isotopic composition. Fortyeight samples across the 616 m sequence of deformed Cretaceous rocks in the lower part of the Yaxcopoil-1 core, drilled by ICDP in 2002, were analyzed for their 87Sr ? 86Sr isotope ratio. The oceanic anoxic event 2 (OAE2 event), located near the base of the core forms a stratigraphic anchor point. From this point upward to approximately 1050 m depth, the 87Sr ? 86Sr trend shows small oscillations, between approximately 0.7074 and 0.7073, characteristic of Cenomanian to Santonian values. This is followed by an increase to approximately 0.7075, similar to the one reported in the seawater strontium curve during the Campanian. Scattered Sr isotope ratios are attributed to local diagenetic effects, such as those expected from the possible presence of hot, impact-induced dikes and hydrothermal fluid flow, originating from the thick central melt sheet. The absence of Upper Maastrichtian Sr isotope values may result from the removal of upper target lithologies during the impact cratering process. Based on these results, the displaced Cretaceous sequence in Yax-1 appears to have preserved its stratigraphic coherence. During the modification stage, it probably moved as a whole into the annular basin during collapse of the crater wall, thereby breaking up into discrete units along previously weakened detachment zones. This model is consistent with the emplacement mechanism postulated by Kenkmann et al. (2004).

Glass spherules of probable impact origin occur in the Late Devonian Hony section in Belgium. They are found at the stratigraphic level of the Frasnian-Famennian boundary, which is marked by one of the largest mass extinctions in the Phanerozoic. The Hony glass spherules are chemically identical to those previously described from the stratigraphically equivalent Senzeille section located 90 km to the west-southwest. In contrast to the Senzeille layer, the age of the Hony spherule layer is well constrained by conodont biostratigraphy. The spherules have morphological and chemical characteristics similar to tektites and microtektites. They have a broad range of chemical composition with generally high [K2O/Na2O] and [Al2O3(Na2O/+K2O)]. Their water content is in the range measured for tektites and impact glasses. Small inclusions of lechatelierite may be present in the spherules. These glass spherules are likely to be the product of an impact event that occurred at or very near the Frasnian-Famennian boundary. The target rock was probably a clay-rich pelitic sediment intermixed with carbonates. The 368 ± 1 Ma Siljan Ring crater (Sweden) is the most likely impact-site candidate. The Hony and Senzeille glass spherules represent the first substantial evidence that an impact event may be linked to the Frasnian-Famennian mass extinction.

The chosen subject falls within the domain of archaeometry and focuses on the study of archeological glass from the site of Vergina (Macedonia, Greece) using a combination of analytical techniques. Our goal was to answer certain archaeological queries regarding the provenance of the samples and, additionally, to investigate the necessary steps for organizing a holistic research approach for similar analytical problems and the ways of extracting the maximum amount of information from our results. A total of 18 samples from the excavation of Vergina were examined, including 17 glass fragments and glass paste samples as well as a clay matrix sample. The techniques chosen for the analysis of the samples were micro - X Ray Fluorescence Spectroscopy (microXRF), atomic emission spectroscopy using inductively coupled plasma (ICP-AES) and, finally, atomic absorption spectroscopy (??S). The statistical analysis of the results included a Student t-test for the determination of the correlation between the micro-XRF and ICP-AES/AAS techniques, as well as the application of hierarchical classification algorithms, cluster analysis and principal component analysis (PCA). Finally, regarding the clay matrix sample, we employed a three dimensional laser scanning technique in order to obtain an accurate digital model of its inner surface. One of the most important conclusions we reached was the determination of the site Pikrolimni (Macedonia, Greece) as the source of natron in the glass making process, based on the samples' K2O and MgO ratios. The high concentrations of Al2O3, Fe2O3 and MgO of the glass paste samples suggests they constitute by-products of the glass making process and also support the employment of recycled materials. Furthermore, sample 008, the only one exhibiting intense coloring, was found to owe its blue coloration to the high concentrations of Co (0,080%) and Cu (0,021%), elements known as common coloring agents in glass. Additionally, the statistical analysis of the elemental compositions before and after the cleaning of the glass fragments was keen in classifying the samples according to their prior proximity within the excavation site and also their state of corrosion. Finally, regarding the results of the clay matrix, we reached the conclusion that it was used for the smelting of small glass items, probably decorative elements or jewels. The inner surface of the molds did not exhibit any signs of modulation targeted in engraving certain pictorial elements onto the resulting item's surface.

An extensive complex of interconnected salt lakes, fringing the Mediterranean Sea between the town of Larnaca and Cape Kiti, marks the Larnaca coastal plain in Eastern Cyprus. The archaeological site of Hala Sultan Tekke (HST), identified as a Bronze age harbor town, is situated directly to the west of the main salt lake. Archaeological excavations (Aström et al. 1975-2007) revealed that the town was abandoned in the 11th century BC. The archaeological finds testify diverse (copper, wine, ware...) and long-distance trade relations with Crete, Syria, Palestine and Egypt during the Bronze Age. Recent geological and coring investigations were carried out in the surroundings of the salt lake in order to study the palaeoenvironmental evolution of the coastline and to identify possible passageways for ships between the Mediterranean Sea and the inner harbour of HST during the Bronze Age. At the HST site, the main salt lake is protected from the Mediterranean Sea by a NE-SW trending Pleistocene sandstone barrier. A second Middle to Late Holocene ridge, separates the whole complex of interconnected salt lakes from the present-day Mediterranean sea. Hand-operated augering took place in the main salt lake, close to the HST site, as well as in the southernmost lake (Menoui beach) close to the present-day coastline. The facies of the sediment succession in the cores are identified on the basis of lithology, sedimentary structures and macrofossils. Data from mechanical drilling logs (Geological Surface of Cyprus) are integrated to establish the bedrock topography. The preliminary field results indicate that the sedimentary sequence can be subdivided into Pliocene bedrock (Marl), open marine, lagoon, coastal marsh, salt lake and coastal ridge deposits. The open marine sedimentary unit is made up of horizontal packs of fibres and rhizomes of the marine phanerogam Posidonia Oceanica, alternating with beds of bluish-grey sandy , rich in open-marine shells (Abra tenuis, Venerupis aureus). These Posidonia fibers are notin situ but originate from sub littoral meadows nearby. The latter suggest that the bay of Larnaca was open, but protected; its floor being built up behind a Posidonia meadow, which absorbed swells and trapped fine particles. This open marine Posidonia sedimentary unit is mainly found in the sedimentary succession of boreholes located in the southern lake (near Menoui beach), where it is covered by rather thin layers (up to 0.5 m) of lagoon and salt-lake deposits. Close to the HST site, the sedimentary succession in boreholes reflects a more confined marine embayment because of the presence of a Pleistocene barrier. This more confined marine embayment gradually evolved into lagoon, coastal marsh and finally to an enclosed salt lake as a result of the development of a Middle to Late Holocene coastal ridge along the present-day shoreline. This coastal ridge consists of up-to 10 m thick -packages of accumulated pebbles, overlying Posidonia- rich open marine deposits. Based on the preliminary results, itis suggested that during the early Holocene, an open, but protected, marine embayment developed behind a Posidonia meadow. A coastal spit developed rapidly towards the northeast (pebbles transported by long shore drift from an erosion front at Cape Kiti and from the Tremithos river mouth), progressively isolating a lagoon that became enclosed, silted up and eventually evolved into the present-day salt lake. Historical sources document that from the 16th century onwards, the lake became one of the most important locations for salt extraction in the Mediterranean.

The palaeoenvironmental evolution of the Enshunada coastline, Hamamatsu area, located on the central island of Japan is investigated. More in particular the the impact of atsunami, generated by the 1498 Meio earthquake (M8.2-8.4) along the Nankai Through, on the geomorphological evolution of the Enshunada coastline is investigated. Historical sources document the sudden decline at the end of the 15th century of an important harbour town Hashimoto, located along the river Hamana. This river connected the Pacific Ocean with a coastal embayment closed by a sand barrier (i.e. the present-day called Hamana lake) before the 15th Century. During geological fieldwork (geoslicer and auger) the palaeochannel of the Hamana river was detected along the western side of the present-day Hamana coastal embayment. A detailed facies analysis of the undisturbed sediment cores was carried out. On the basis of the sedimentological data, it is suggested that the Hamana river mouth became abruptly closed by the transport ofhuge volumes of sand by the Meio tsunami. This initiated the development of a marsh environment upstream along the channel. The same process, of sudden river mouth enclosure by tsunami-transported sediments was recently observed in the Northeast Japan during the great 2011 Sendai tsunami (Uda, T., 2011). Moreover, our results show that due to the 1498 Meio tsunami, the Hamana back-barrier sheltered environment became again connected to the Pacific Ocean by breaching of its sand barrier. Both environmental changes (river mouth enclosure and barrier breaching) are synchronous with the sudden decline of the harbour town Hashimoto at the end of the 15th century. This suggests that the breaking-off of the water route connecting the harbour town Hashimoto and Pacific Ocean potentially led to the decline of the town.

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Identifying a periodic time-series model from environmental records, without imposing the positivity of the growth rate, does not necessarily respect the time order of the data observations. Consequently, subsequent observations, sampled in the environmental archive, can be inversed on the time axis, resulting in a non-physical signal model. In this paper an optimization technique with linear constraints on the signal model parameters is proposed that prevents time inversions. The activation conditions for this constrained optimization are based upon the physical constraint of the growth rate, namely, that it cannot take values smaller than zero. The actual constraints are defined for polynomials and first-order splines as basis functions for the nonlinear contribution in the distance-time relationship. The method is compared with an existing method that eliminates the time inversions, and its noise sensitivity is tested by means of Monte Carlo simulations. Finally, the usefulness of the method is demonstrated on the measurements of the vessel density, in a mangrove tree, Rhizophora mucronata, and the measurement of Mg/Ca ratios, in a bivalve, Mytilus trossulus.

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We present arguments against an extraterrestrial impact as the agent for an abrupt climate change at the 12.9 ka Younger Dryas boundary, terminal Pleistocene extinctions of N. American megafauna, and the supposed termination of the Clovis culture. Our rejection of this hypothesis is based on multiple independent lines of reasoning and evidence.