Institute for Geological and Geochemical Research

The liptinite maceral group has been revised by ICCP in accordance with the ICCP System 1994. After the revision of the classifications of vitrinite (ICCP, 1998), inertinite, (ICCP, 2001) and huminite (Sykorova et al., 2005) this liptinite classification completes the revised ICCP maceral group classifications. These classifications are collectively referred to as the “ICCP System 1994”. In contrast to the previous ICCP Stopes Heerlen (ICCP, 1963, 1971, 1975, 1993) this new classification system is applicable to coal of all ranks and dispersed organic matter. The classification as presented here was accepted in the ICCP Plenary Session on September 11, 2015 at the ICCP Meeting in Potsdam. The decision to publish this classification in the recent form was accepted at the ICCP Plenary Session on September 23, 2016 in Houston.

In stable isotope ratio mass spectrometry (IRMS), the stable isotopic composition of samples is measured relative to the isotopic composition of a working gas. This measured isotopic composition must be converted and reported on the respective international stable isotope reference scale for the accurate interlaboratory comparison of results. This data conversion procedure, commonly called normalization, is the first set of calculations done by the users. In this paper, we present a discussion and mathematical formulation of several existing routinely used normalization procedures. These conversion procedures include: single-point anchoring (versus working gas and certified reference standard), modified single-point normalization, linear shift between the measured and the true isotopic composition of two certified reference standards, two-point and multi-point linear normalization methods. Mathematically, the modified single-point, two-point, and multi-point normalization methods are essentially the same. By utilizing laboratory analytical data, the accuracy of the various normalization methods (given by the difference between the true and the normalized isotopic composition) has been compared. Our computations suggest that single-point anchoring produces normalization errors that exceed the maximum total uncertainties (e.g. 0.1 per thousand for delta(13)C) often reported in the literature, and, therefore, that it must not be used for routinely anchoring stable isotope measurement results to the appropriate international scales. However, any normalization method using two or more certified reference standards produces a smaller normalization error provided that the isotopic composition of the standards brackets the isotopic composition of unknown samples.

Abstract The potential for carbonate clumped isotope thermometry to independently constrain both the formation temperature of carbonate minerals and fluid oxygen isotope composition allows insight into long‐standing questions in the Earth sciences, but remaining discrepancies between calibration schemes hamper interpretation of temperature measurements. To address discrepancies between calibrations, we designed and analyzed a sample suite (41 total samples) with broad applicability across the geosciences, with an exceptionally wide range of formation temperatures, precipitation methods, and mineralogies. We see no statistically significant offset between sample types, although the comparison of calcite and dolomite remains inconclusive. When data are reduced identically, the regression defined by this study is nearly identical to that defined by four previous calibration studies that used carbonate‐based standardization; we combine these data to present a composite carbonate‐standardized regression equation. Agreement across a wide range of temperature and sample types demonstrates a unified, broadly applicable clumped isotope thermometer calibration.

Abstract The structure of the Pannonian basin is the result of distinct modes of Mid-Late Miocene extension exerting a profound effect on the lithospheric configuration, which continues even today. As the first manifestation of extensional collapse, large magnitude, metamorphic core complex style extension took place at the beginning of the Mid-Miocene in certain parts of the basin. Extrapolation of the present-day high heat flow in the basin, corrected for the blanketing effect of the basin fill, indicates a hot and thin lithosphere at the onset of extension. This initial condition, combined with the relatively thick crust inherited from earlier Alpine compressional episodes, appears to be responsible for the core complex type extension at the beginning of the syn-rift period. This type of extension is well documented in the northwestern Pannonian basin. Newly obtained deep reflection seismic and fission-track data integrated with well data from the southeastern part of the basin suggests that it developed in a similar fashion. Shortly after the initial period, the style of syn-rift extension changed to a wide-rift style, covering an area of much larger geographic extent. The associated normal faults revealed by industry reflection seismic data tend to dominate within the upper crust, obscuring pre-existing structures. However, several deep seismic profiles, constrained by gravity and geothermal modeling, image the entire lithosphere beneath the basin. It is the Mid-Miocene synrift extension which is still reflected in the structure of the Pannonian lithosphere, on the scale of the whole basin system. The gradually diminishing extension during the Late Miocene/Pliocene could not advance to the localization of extension into narrow rift zones in the Pannonian region, except some deep subbasins such as the Makó/Békés and Danube basins. These basins are underlain coincidently by anomalously thin crust (22–25 km) and lithosphere (45–60 km). Significant departures (up to 130 mW m −2 ) from the average present-day surface heat flow ( c. 90 mW m −2 ) and intensive Pliocene alkaline magmatism are also regarded as evidence for the initiation of two newly defined narrow rift zones (Tisza and Duna) in the Pannonian basin system. However, both of these narrow rifts failed since the final docking of the Eastern Carpathians onto the European foreland excluded any further extension of the back-arc region.

The Periadriatic Line (PAL) is a remarkable, several hundred kilometer long fault system of the Alpine orogen. Its dextral character was documented by several authors using diverse criteria, but detailed kinematics and timing of movements had not been investigated along its whole length. Structural and paleomagnetic measurements, mapping, and stratigraphic and sedimentological studies have helped to unravel the Miocene‐Pliocene evolution of the Slovenian segment of the PAL. Brittle deformation was characterized by NW‐SE to N‐S compression and perpendicular tension. Deformation has resulted in dextral strike‐slip faulting, folding, and tilting of beds. The first transpressional event corresponds to the first phase of lateral extrusion of the East Alpine‐Western Carpathian‐Northern Pannonian block in the early Miocene (24–17.5 Ma). After a short period of transtension during the Karpatian (17.5–16.5 Ma), dextral transpression reoccurred during the middle Miocene to Pliocene and lasted up to the Quaternary. Middle Miocene dextral slip can be connected to the second phase of extrusion. The highly deformed rocks within the dextral shear zones show variable clockwise, sometimes counterclockwise, rotations. The mechanism of rotation seems to be complex, ranging from regional rotation to local folding due to pure or simple shear (domino‐type rotation).

Abstract The clumped isotopic composition of carbonate‐derived CO 2 (denoted Δ 47 ) is a function of carbonate formation temperature and in natural samples can act as a recorder of paleoclimate, burial, or diagenetic conditions. The absolute abundance of heavy isotopes in the universal standards VPDB and VSMOW (defined by four parameters: R 13 VPDB , R 17 VSMOW , R 18 VSMOW , and λ ) impact calculated Δ 47 values. Here, we investigate whether use of updated and more accurate values for these parameters can remove observed interlaboratory differences in the measured T‐Δ 47 relationship. Using the updated parameters, we reprocess 14 published calibration data sets measured in 11 different laboratories, representing many mineralogies, bulk compositions, sample types, reaction temperatures, and sample preparation and analysis methods. Exploiting this large composite data set ( n = 1,253 sample replicates), we investigate the possibility for a “universal” clumped isotope calibration. We find that applying updated parameters improves the T‐Δ 47 relationship (reduces residuals) within most labs and improves overall agreement but does not eliminate all interlaboratory differences. We reaffirm earlier findings that different mineralogies do not require different calibration equations and that cleaning procedures, method of pressure baseline correction, and mass spectrometer type do not affect interlaboratory agreement. We also present new estimates of the temperature dependence of the acid digestion fractionation for Δ 47 (Δ* 25‐X ), based on combining reprocessed data from four studies, and new theoretical equilibrium values to be used in calculation of the empirical transfer function. Overall, we have ruled out a number of possible causes of interlaboratory disagreement in the T‐Δ 47 relationship, but many more remain to be investigated.

The International Commission on Stratigraphy (ICS) utilises benchmark chronostratigraphies to divide geologic time. The reliability of these records is fundamental to understand past global change. Here we use the most detailed luminescence dating age model yet published to show that the ICS chronology for the Quaternary terrestrial type section at Jingbian, desert marginal Chinese Loess Plateau, is inaccurate. There are large hiatuses and depositional changes expressed across a dynamic gully landform at the site, which demonstrates rapid environmental shifts at the East Asian desert margin. We propose a new independent age model and reconstruct monsoon climate and desert expansion/contraction for the last ~250 ka. Our record demonstrates the dominant influence of ice volume on desert expansion, dust dynamics and sediment preservation, and further shows that East Asian Summer Monsoon (EASM) variation closely matches that of ice volume, but lags insolation by ~5 ka. These observations show that the EASM at the monsoon margin does not respond directly to precessional forcing.

Abstract Two methods for estimating the yield of different crops in Hungary from satellite remote sensing data are presented. The steps of preprocessing the remote sensing data (for geometric, radiometric, atmospheric and cloud scattering correction) are described. In the first method developed for field level estimation, reference crop fields were selected by using Landsat Thematic Mapper (TM) data for classification. A new vegetation index (General Yield Unified Reference Index (GYURI)) was deduced using a fitted double-Gaussian curve to the National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) data during the vegetation period. The correlation between GYURI and the field level yield data for corn for three years was R 2=0.75. The county-average yield data showed higher correlation (R 2=0.93). A significant distortion from the model gave information of the possible stress of the field. The second method presented uses only NOAA AVHRR and officially reported county-level yield data. The county-level yield data and the deduced vegetation index, GYURRI, were investigated for eight different crops for eight years. The obtained correlation was high (R 2=84.6–87.2). The developed robust method proved to be stable and accurate for operational use for county-, region- and country-level yield estimation. The method is simple and inexpensive for application in developing countries, too. Acknowledgments Our dear friend and colleague, Dr György Tarcsai, died during this long research work, in which he was a very effective partner in the first half of this activity. Let this paper be a small memorial to Gy. Tarcsai. The authors sincerely thank the FÖMI Research Center for their cooperation in the starting phase of this R&D. This work was carried out within the long-range R&D funds of the Hungarian Space Office, and from some special aspects in connection with earlier and actual (T034831, T037611 and F037603) OTKA contracts of the Hungarian Academy of Sciences. Notes †Deceased. Additional informationNotes on contributorsGy. TarcsaiFootnote† †Deceased.

In the Denizli Basin (Turkey), located in the western Anatolian extensional province, travertine and tufa deposition has been an ongoing process for at least 600,000 years. Travertine bodies, which are 30 to 75 m thick and each covers areas of 1 to 34 km2, are up to 1 km3 in volume. Today, spring waters in this area have temperatures of 19 to 57 °C, are of the Ca–Mg–HCO3–SO4 type in the Pamukkale, Kelkaya and Pınarbaşı areas and the Ca–Mg–SO4–HCO3 type at Çukurbağ. Thermal waters along the northern margin of the basin are generally hotter than those in the east–southeast and south. The δ18O and δD values of the spring waters indicate a meteoric origin. The average temperatures of the hydrothermal systems in the Denizli Basin appear to have decreased from Pleistocene to Holocene. Travertine, which formed from the hotter water, is more widespread than the tufa that formed in the cooler spring waters. Deposition of the travertine, which formed largely on slopes, in depressions, and along fissure ridges (mostly on northern basin margins), was controlled by the interplay between various intrinsic and extrinsic parameters. The travertines are formed largely of calcite with only minor amounts of aragonite in some of the vertically banded, crystalline crust, raft and pisoid travertines found in some of the northern sites. The aragonitic samples, rich in Sr, are typically found around the spring orifices and along the central axis of the fissure ridges. The stable isotope values of the travertine found in the northwest and southeast parts of the basin are different. The δ13C values of the northern travertine deposits are more positive (3.7 to 11.7‰ VPBD) than those found in the south–southeast areas (− 4 to 5.8‰ VPDB). In contrast, the travertine and tufa in the southeastern areas have higher δ18O values (− 15.2 to − 7.8‰ VPDB) than those of the northern areas (− 16.6 to − 4.8‰ VPDB). Available evidence indicates that spring activity and associated travertine precipitation in the Denizli Basin were controlled largely by tectonic activity rather than by climatic conditions.

Late Tertiary post-orogenic alkaline basalts erupted in the extensional Pannonian Basin following Eocene-Miocene subduction and its related calc-alkaline volcanism. The alkaline volcanic centres, dated between 11⋅7 and 1⋅4 Ma, are concentrated in several regions of the Pannonian Basin. Some are near the western (Graz Basin, Burgenland), northern (Nógrád), and eastern (Transylvania) margins of the basin, but the majority are concentrated near the Central Range (Balaton area and Little Hungarian Plain). Fresh samples from 31 volcanic centres of the extension-related lavas range from slightly hy-normative transitional basalts through alkali basalts and basanites to olivine nephelinites. No highly evolved compositions have been encountered. The presence of peridotite xenoliths, mantle xenocrysts, and high-pressure megacrysts, even in the slightly more evolved rocks, indicates that differentiation took place within the upper mantle. Rare earth elements (REE) and 87Sr/86Sr, 143Nd/144Nd, δ18O, δD, and Pb isotopic ratios have been determined on a subset of samples, and also on clinopyroxene and amphibole megacrysts. Sr and Nd isotope ratios span the range of Neogene alkali basalts from western and central Europe, and suggest that the magmas of the Pannonian Basin were dominantly derived from asthenospheric partial melting, but Pb isotopes indicate that in most cases they were modified by melt components from the enriched lithospheric mantle through which they have ascended. δ18O values indicate that the magmas have not been significantly contaminated with crustal material during ascent, and isotopic and trace-element ratios therefore reflect mantle source characteristics. Incompatible-element patterns show that the basic lavas erupted in the Balaton area and Little Hungarian Plain are relatively homogeneous and are enriched in K, Rb, Ba, Sr, and Pb with respect to average ocean island basalt, and resemble alkali basalts of Gough Island. In addition, 207Pb/204Pb is enriched relative to 2O6Pb/204Pb. In these respects, the lavas of the Balaton area and the Little Hungarian Plain differ from those of other regions of Neogene alkaline magmatism of Europe. This may be due to the introduction of marine sediments into the mantle during the earlier period of subduction and metasomatism of the lithosphere by slab-derived fluids rich in K, Rb, Ba, Pb, and Sr. Lavas erupted in the peripheral areas have incompatible-element patterns and isotopic characteristics different from those of the central areas of the basin, and more closely resemble Neogene alkaline lavas from areas of western Europe where recent subduction has not occurred.

Abstract Ultramafic xenoliths from alkali basalts in the Perjani Mountains in the Eastern Transylvanian Basin (ETB) of Romania are mainly spinel Iherzolites, although spinel harzburgites, websterites, clinopyroxenites and amphibole pyroxenites are also present. Amphibole veins cut some spinel peridotite samples. All are derived from the shallow lithospheric upper mantle. In general, textural variations are restricted to protogranular and porphyroclastic types, compared with the more varied textures found in mantle xenoliths from the alkali basalts of the neighbouring Pannonian Basin. Also, ETB peridotites are richer in amphibole. Thus, the mantle beneath the edge of the ETB is less deformed but more strongly metasomatized than the mantle closer to the centre of the Pannonian Basin. Mineralogical and bulk-rock geochemical variations resemble those of spinel Iherzolites from other sub-continental shallow mantle xenolith suites. There is no apparent correlation between deformation and geochemistry, and much of the major and trace element variation is due to variable extraction of picritic melts. The REE patterns of separated clinopyroxenes from the peridotite xenoliths are mostly LREE depleted, although clinopyroxenes from regions adjacent to amphibole veins have experienced an enrichment in La and Ce and a change in their Sr and Nd isotopic values towards those of the vein, while still retaining an overall LREE depletion. Clinopyroxenes from the websterites and clinopyroxenites are more variable. Amphibole in the hydrous pyroxenites and amphibole veins is strongly LREE enriched and is considered to be metasomatic in origin. 87Sr/86Sr and 143Nd/l44Nd isotopic ratios of the xenoliths vary between 0·7018 and 0·7044, and 0·51355 and 0 51275, respectively. These value are more depleted than those obtained for xenoliths from the Pannonian Basin. The lower l43Nd/l44Nd and higher 87Sr/Sr86 values are found in anhydrous pyroxenites, metasomatic amphiboles in veins and amphibole pyroxenites, and in the only example of an equigranular spinel Iherzolite in the suite. The ETB xenoliths were brought to the surface in alkaline vokanism which post-dated a period of Miocene to Pliocene subduction-related cak-alkaline volcanism. However, the effects of the passage of either slab-derived fluids or cak-alkaline magmas through the ETB lithospheric mantle cannot be discerned in the chemistry of the xenoliths. The metasomatic amphibole has 87Sr/Sr86 and 143Sr/Sr144 ratios similar to the host alkali basalts, but the least evoked cak-alkaline magmas also have similar Sr and Nd isotope compositions. The REE patterns of the amphibole resembk those of amphiboles considered to have crystallized from alkaline melts. No preferential enrichment in elements typically associated with slab-derivedfluids (K, Rb and Sr) relative to elements typically depleted in cak-alkaline magmas (Ti, 2jr and Nb) has been observed in the vein amphiboles, although some interstitial amphibole is depleted in all incompatible trace elements, including LREE. Thus, despite its position close to the calc-alkaline volcanic arc of the Eastern Carpathians, we cannot readily detect any interaction between the lithospheric upper mantle beneath the ETB and subduction-related magmas or fluids. Metasomatism in the lithospheric mantle is instead largely related to the passage of a primitive alkaline magma similar to the host alkali basal

Because coal does not conduct electricity and graphite is costly and inert, little attention has been given to the development of a carbon fuel cell (i.e., a battery that utilizes a consumable carbon anode to generate electrical power). In this work we show that a packed bed of carbonized charcoal particles subject to a compressive pressure (ca. 8 MPa) can be a good electrical conductor (σ < 0.2 Ω·cm). Low electrical resistivities σ are manifest by many different charcoals after carbonization at a heat treatment temperature (HTT) of 950 °C. The 5 orders of magnitude decrease in the electrical resistivity of charcoal with increasing HTT from 650 to 1050 °C is not associated with any dramatic change in the carbons' X-ray diffraction spectrum, its Fourier transform infrared spectrum, or its elemental analysis. Our findings cause us to visualize carbonized charcoal to be a macromolecular, cross-linked, three-dimensional, aromatic structure replete with conjugation and π bonds that facilitate the movement of electrons, as well as nanopores, and micromolecular cracks. Because charcoal powder is competitive in price with fossil fuels and because carbonized charcoal is extremely reactive with a volumetric energy density (in a compacted packed bed) comparable to conventional liquid fuels, compact packed beds of carbonized charcoal hold promise for use as electrodes and consumable anodes in fuel cells. The packed-bed apparatus we describe is a prototype anode for use in a biocarbon fuel cell.

Significance Atmospheric dust is a major component of climate change. However, the relationship between glacial continental dust activity and abrupt centennial–millennial-scale climate changes of the North Atlantic is poorly known. Recent advances in high-precision radiocarbon dating of small gastropods in continental loess deposits provide an opportunity to gain unprecedented insights into dust variations and its major drivers at centennial–millennial scales from a near-source dust archive. Here, we show that Late Quaternary North Atlantic temperature and dustiness in Greenland and Europe were largely synchronous and suggest that this coupling was driven via precipitation changes and large-scale atmospheric circulation.

Abstract. Characterizing the temporal uncertainty in palaeoclimate records is crucial for analysing past climate change, correlating climate events between records, assessing climate periodicities, identifying potential triggers and evaluating climate model simulations. The first global compilation of speleothem isotope records by the SISAL (Speleothem Isotope Synthesis and Analysis) working group showed that age model uncertainties are not systematically reported in the published literature, and these are only available for a limited number of records (ca. 15 %, n=107/691). To improve the usefulness of the SISAL database, we have (i) improved the database's spatio-temporal coverage and (ii) created new chronologies using seven different approaches for age–depth modelling. We have applied these alternative chronologies to the records from the first version of the SISAL database (SISALv1) and to new records compiled since the release of SISALv1. This paper documents the necessary changes in the structure of the SISAL database to accommodate the inclusion of the new age models and their uncertainties as well as the expansion of the database to include new records and the quality-control measures applied. This paper also documents the age–depth model approaches used to calculate the new chronologies. The updated version of the SISAL database (SISALv2) contains isotopic data from 691 speleothem records from 294 cave sites and new age–depth models, including age–depth temporal uncertainties for 512 speleothems. SISALv2 is available at https://doi.org/10.17864/1947.256 (Comas-Bru et al., 2020a).

Abstract. Reconstructions of global hydroclimate during the Common Era (CE; the past ∼2000 years) are important for providing context for current and future global environmental change. Stable isotope ratios in water are quantitative indicators of hydroclimate on regional to global scales, and these signals are encoded in a wide range of natural geologic archives. Here we present the Iso2k database, a global compilation of previously published datasets from a variety of natural archives that record the stable oxygen (δ18O) or hydrogen (δ2H) isotopic compositions of environmental waters, which reflect hydroclimate changes over the CE. The Iso2k database contains 759 isotope records from the terrestrial and marine realms, including glacier and ground ice (210); speleothems (68); corals, sclerosponges, and mollusks (143); wood (81); lake sediments and other terrestrial sediments (e.g., loess) (158); and marine sediments (99). Individual datasets have temporal resolutions ranging from sub-annual to centennial and include chronological data where available. A fundamental feature of the database is its comprehensive metadata, which will assist both experts and nonexperts in the interpretation of each record and in data synthesis. Key metadata fields have standardized vocabularies to facilitate comparisons across diverse archives and with climate-model-simulated fields. This is the first global-scale collection of water isotope proxy records from multiple types of geological and biological archives. It is suitable for evaluating hydroclimate processes through time and space using large-scale synthesis, model–data intercomparison and (paleo)data assimilation. The Iso2k database is available for download at https://doi.org/10.25921/57j8-vs18 (Konecky and McKay, 2020) and is also accessible via the NOAA/WDS Paleo Data landing page: https://www.ncdc.noaa.gov/paleo/study/29593 (last access: 30 July 2020).

Abstract. Stable isotope records from speleothems provide information on past climate changes, most particularly information that can be used to reconstruct past changes in precipitation and atmospheric circulation. These records are increasingly being used to provide “out-of-sample” evaluations of isotope-enabled climate models. SISAL (Speleothem Isotope Synthesis and Analysis) is an international working group of the Past Global Changes (PAGES) project. The working group aims to provide a comprehensive compilation of speleothem isotope records for climate reconstruction and model evaluation. The SISAL database contains data for individual speleothems, grouped by cave system. Stable isotopes of oxygen and carbon (δ18O, δ13C) measurements are referenced by distance from the top or bottom of the speleothem. Additional tables provide information on dating, including information on the dates used to construct the original age model and sufficient information to assess the quality of each data set and to erect a standardized chronology across different speleothems. The metadata table provides location information, information on the full range of measurements carried out on each speleothem and information on the cave system that is relevant to the interpretation of the records, as well as citations for both publications and archived data. The compiled data are available at https://doi.org/10.17864/1947.147.

This study focuses on particle size effect on monomineralic powders recorded using attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy. Six particle size fractions of quartz, feldspar, calcite, and dolomite were prepared (&lt;2, 2–4, 4–8, 8–16, 16–32, and 32–63 µm). It is found that the width, intensity, and area of bands in the ATR FT-IR spectra of minerals have explicit dependence on the particle size. As particle size increases, the intensity and area of IR bands usually decrease while the width of bands increases. The band positions usually shifted to higher wavenumbers with decreasing particle size. Infrared spectra of minerals are the most intensive in the particle size fraction of 2–4 µm. However, if the particle size is very small (&lt;2 µm), due to the wavelength and penetration depth of the IR light, intensity decreases. Therefore, the quantity of very fine-grained minerals may be underestimated compared to the coarser phases. A nonlinear regression analysis of the data indicated that the average coefficients and indices of the power trend line equation imply a very simplistic relationship between median particle diameter and absorbance at a given wavenumber. It is concluded that when powder samples with substantially different particle size are compared, as in regression analysis for modal predictions using ATR FT-IR, it is also important to report the grain size distribution or surface area of samples. The band area of water (3000–3620 cm –1 ) is similar in each mineral fraction, except for the particles below 2 µm. It indicates that the finest particles could have disproportionately more water adsorbed on their larger surface area. Thus, these higher wavenumbers of the ATR FT-IR spectra may be more sensitive to this spectral interference if the number of particles below 2 µm is considerable. It is also concluded that at least a proportion of the moisture could be very adhesive to the particles due to the band shift towards lower wavenumbers in the IR range of 3000–3620 cm –1 .

Abstract Soon after their formation, the terrestrial planets experienced intense impact bombardment by comets, leftover planetesimals from primary accretion, and asteroids. This temporal interval in solar system evolution, termed late accretion , thermally and chemically modified solid planetary surfaces and may have impeded life's emergence on the Hadean (pre-3850 Ma) Earth. The sources and tempo of bombardment, however, remain obscure. Here we present a timeline that relates variably retentive radiometric ages documented from asteroidal meteorites to new dynamical models that invoke an early episode of planetesimal-driven giant planet migration after the dispersal of the protoplanetary disk. Reconciliation of geochronological data with dynamical models shows that such giant planet migration should lead to an intense ∼30 Myr influx of comets to the entire solar system manifested in radiometric age data. The absence of wholesale crustal reset ages after ∼4450 Ma for the most resilient chronometers from Earth, Moon, Mars, 4 Vesta, and various meteorite parent bodies confines the onset of giant planet migration to ca. 4480 Ma. Waning impacts continue to strike the inner planets through a protracted monotonic decline in impactor flux, in agreement with predictions from crater chronology. New global 3D thermal analytical bombardment models derived from our revised impact mass-production functions show also that persistent niches for prebiotic chemistry leading to the emergence of life on the early Hadean Earth could endure late accretion since at least about 4400 million years ago.

The incorporation of water in olivine and pyroxenes interlayered within fertile lherzolite compositions was explored experimentally near the wet solidus of lherzolite at 25 and 4 GPa. The concentrations and activities of water were varied to establish the partitioning of water between nominally anhydrous minerals (NAMs) and the hydrous minerals pargasite and phlogopite. The water content in NAMs was determined by Fourier-transform infrared (FTIR) spectroscopy. The main absorption bands in NAMs from these experiments are very similar to those generally found in natural upper mantle peridotites. Olivine, orthopyroxene and clinopyroxene contain 32-190, 290-320 and 910-980 ppm of water under the studied conditions. The partition coefficients between coexisting clinopyroxene and orthopyroxene (D cpx/opx) are 27 11 and 35 15 at 25 and 4 GPa respectively, whereas values for coexisting orthopyroxene and olivine (D opx/ol) are 67 2 and 47 11, at 25 and 4 GPa respectively. The storage capacity in NAMs in a model mantle composition close to the vapour-saturated solidus (water-rich vapour) is 190 ppm at both 25 and 4 GPa. Pargasite is the most important phase accommodating significant amounts of water in the uppermost mantle. Its breakdown with increasing pressure at 3 GPa at the vapour-saturated solidus (which is at 1025C at 25 GPa) results in a sharp drop in the water storage capacity of peridotite from 1000 ppm to 190 ppm H 2O. At pressures &gt;3 GPa, melting in fertile lherzolite begins at the vapour-saturated solidus if the bulk H 2O concentration exceeds 190 ppm. The Author 2012. Published by Oxford University Press. All rights reserved.

Amorphous calcium carbonate (ACC) is a precursor of crystalline calcium carbonates that plays a key role in biomineralization and polymorph evolution. Here, we show that several bacterial strains isolated from a Hungarian cave produce ACC and their extracellular polymeric substance (EPS) shields ACC from crystallization. The findings demonstrate that bacteria-produced ACC forms in water-rich environment at room temperature and is stable for at least half year, which is in contrast to laboratory-produced ACC that needs to be stored in a desiccator and kept below 10 °C for avoiding crystallization. The ACC-shielding EPS consists of lipids, proteins, carbohydrates and nucleic acids. In particular, we identified large amount of long-chain fatty acid components. We suggest that ACC could be enclosed in a micella-like formula within the EPS that inhibits water infiltration. As the bacterial cells lyse, the covering protective layer disintegrates, water penetrates and the unprotected ACC grains crystallize to calcite. Our study indicates that bacteria are capable of producing ACC, and we estimate its quantity in comparison to calcite presumably varies up to 20% depending on the age of the colony. Since diverse bacterial communities colonize the surface of cave sediments in temperate zone, we presume that ACC is common in these caves and its occurrence is directly linked to bacterial activity and influences the geochemical signals recorded in speleothems.