Using Lead Isotopes to Determine Pottery Provenance in Cyprus: Clay Source Signatures and Comparison with Late Bronze Age Cypriote Pottery

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.     

The politics and policy of carbon capture and storage: Framing an emergent technology

Over the past decade carbon capture and storage (CCS) has attracted increasing international attention as a climate change mitigation option and moved into the center of climate policy debates and negotiations. This special issue of Global Environmental Change brings together leading scholars to analyze the politics, policy and regulation of CCS in cross-country comparisons as well as in a global context. The aim is to contribute on two fronts: first, by applying concepts, theories and methodologies from the social and policy sciences, to elucidate how societies are engaging with CCS as a mitigation option; and secondly, to point toward a future research agenda which, while exploring basic aspects of technology development as situated in a social context, would also be aligned with the needs of the climate and environmental policy community. The contributions address at least one of three inter-related research areas; CCS and the emergence of long-term climate and energy strategies; regulation, policy instruments and public acceptance; and international politics and CCS in developing countries.     

A Unifying Phase Diagram for the Dynamics of Sheared Solids and Granular Materials

We present a simple unifying model that can be used to analyze, within a single framework, different dynamic regimes of shear deformation of brittle, plastic, and granular materials. The basic dynamic regimes seen in the response of both solids and granular materials to slowly increasing loading are scale-invariant behavior with power law statistics, quasi-periodicity of system size events, and persisting long term mode switching between the former two types of response. The model provides universal analytical mean field results on the statistics of failure events in the different regimes and distributed versus localized spatial responses. The results are summarized in a phase diagram spanned by three tuning parameters: dynamic strength change (weakening, neutral or strengthening) during slip events, dissipation of stress transfer (related to the void fraction in granular materials and damaged solids), and the ratio of shear rate over healing rate controlling the regaining of cohesion following failures in brittle solids. The mean field scaling predictions agree with experimental, numerical, and observational data on deformation avalanches of solids, granular materials, and earthquake faults. The model provides additional predictions that should be tested with future observation and simulation data.     

Environmental changes in an alpine lake (Gossenköllesee, austria) over the last two centuries – the influence of air temperature on biological parameters

Changes in microfossils (diatoms, chrysophytes, chironomids and cladocera remains), geochemistry and deposition of atmospheric pollutants have been investigated in the sediment records of the alpine lake Gossenköllesee (Tyrol, Austria) spanning the last two centuries. The sediment records were compared with seasonal and annual air temperature trends calculated for the elevation (2417 m a.s.l.) and the geographical position (47° 1346N, 11° 0051E) of the lake, and with precipitation records available since 1866 from Innsbruck. Temperature trends followed a 20–30 year oscillation between cold and warm periods. Regarding long-term changes, temperature trends showed a U-shaped trend between 1780 and 1950, followed by a steep increase since 1975.Physical, geochemical, and organic parameters were not controlled by air temperature. Among the biological records only diatoms and chrysophytes reacted to air temperature changes: the relative abundance of planktonic diatoms increased during warm periods and changes in mean annual alpine air temperature explained 36.5% of their variation. The relation between abundance of seasonal stomatocyst types and air temperature varied on two different time scales: while summer stomatocysts were influenced by short term temperature fluctuations, the autumn stomatocysts were affected only by the long term changes. Other biological parameters exhibited a constant species composition (chironomids, pigments) or changes were small and independent of temperature (cladocera). Spheroidal carbonaceous fly-ash particles, and trends in Pb and Cr indicated increasing deposition of atmospheric pollutants but had no detectable effects on the biological parameters either. In respect to temperature variations over the last 200 years, this alpine lake is much less sensitive than expected and has thus to be regarded as a well buffered site. However, temperature alone is not sufficient to understand changes in species composition and other biogeochemical processes with unknown historical patterns might have affected species composition more strongly.     

Preservation of high‐P rocks coupled to rock composition and the absence of metamorphic fluids

Eclogites, blueschists and greenschists are found in close proximity to one another along a 1‐km coastal section where the Cyclades Blueschist Unit (CBU) is exposed on SE Syros, Greece. Here, we show that the eclogites and blueschists experienced the same metamorphic history: prograde lawsonite blueschist facies metamorphism at 1.2–1.9 GPa and 410–530°C followed, at 43–38 Ma, by peak blueschist/eclogite facies metamorphism at 1.5–2.1 GPa and 520–580°C. We explain co‐existence of eclogites and blueschists by compositional variation probably reflecting original compositional layering. It is also shown that the greenschists record retrogression at 0.34 ± 0.21 GPa and T = 456 ± 68°C. This was spatially associated with a shear zone on a scales of 10–100‐m and veins on a scale of 1–10‐cm. Greenschist facies metamorphism ended at (or shortly after) 27 Ma. We thus infer a period of metamorphic quiescence after eclogite/blueschist facies metamorphism and before greenschist facies retrogression which lasted up to 11–16 million years. We suggest that this reflects an absence of metamorphic fluid flow at that time and conclude that greenschist facies retrogression only occurred when and where metamorphic fluids were present. From a tectonic perspective, our findings are consistent with studies showing that the CBU is (a) a high‐P nappe stack consisting of belts in which high‐P metamorphism and exhumation occurred at different times and (b) affected by greenschist facies metamorphism during the Oligocene, prior to the onset of regional tectonic extension.     

Sedimentary patterns and geometries of the Bahamian outer carbonate ramp (Miocene–Lower Pliocene, Great Bahama Bank)

Core, logging and high-resolution seismic data from ODP Leg 166 were used to analyse deposits of the Neogene (Miocene–Lower Pliocene) Bahamian outer carbonate ramp. Ramp sediments are cyclic alternations of light- and dark-grey wackestones/packstones with interbedded calciturbidite packages and minor slumps. Cyclicity was driven by high-frequency sea-level changes. Light-grey layers containing shallow-water bioclasts were formed when the ramp exported material, whereas the dark-grey layers are dominantly pelagic. Calciturbidites are arranged into mounded lobes with feeder channels. Internal bedding of the lobes shows a north-directed shingling as a result of the asymmetrical growth of these bodies. Calciturbidite packages occur below and above sequence boundaries, indicating that turbidite shedding occurred during third-order sea-level highstands and lowstands. Highstand turbidites contain shallow-water components, such as green algal debris and epiphytic foraminifera, whereas lowstand turbidites are dominated by abraded bioclastic detritus. Gravity flow depocentres shifted from an outer ramp position during the early Miocene to a basin floor setting during the late Miocene to early Pliocene. This change was triggered by an intensification of the strength of bottom currents during the Tortonian, which was also responsible for shaping the convex morphology of the outer ramp. The Miocene and Lower Pliocene of the leeward flank of Great Bahama Bank provides an example of the poorly known depositional setting of the outer part of distally steepened carbonate ramps. The contrast between its sedimentary patterns and the well-known Upper Pliocene–Quaternary slope facies associations of the flat-topped Great Bahama Bank shows the strong control that the morphology of a carbonate platform exerts on the depositional architecture of the adjacent slope and base-of-slope successions.     

Community structure in boreal lakes with recurring blooms of the nuisance flagellate Gonyostomum semen

Blooms of the nontoxic raphidophyte Gonyostomum semen have shown a recent increase in frequency and distribution in the Fennoscandian region. Due to large cell size and several grazer-avoidance strategies, G. semen is hypothesized to be inedible for most zooplankton species and therefore may constitute a bottleneck for the transfer of energy and nutrients in pelagic food webs. Repression of other phytoplankton through increased competition and induced mortality could further exacerbate this effect. In a field study of four lakes with recurring blooms of G. semen and four lakes without blooms, we found significant differences in community structure between the two lake groups during the bloom period. Bloom-lakes had lower biovolumes of small chrysophytes and chlorophytes and zooplankton assemblages were predominated by small, potentially bacterivorous cladocerans, suggesting a limited availability of edible phytoplankton and an increased importance of microbial pathways during G. semen blooms. Low biovolumes of large cladocerans in bloom-lakes may be due to interference of G. semen with filter feeding. Moreover, high abundances of the phantom midge Chaoborus flavicans in bloom-lakes suggest that the flow of energy and nutrients is directed more towards this invertebrate predator than fish. This could have negative impacts on fish populations, especially if bloom periods are prolonged.     

Warming at 18,000 yr B.P. in the Tropical Andes

Palynological, paleopedological, and glacial geomorphological evidence from the area of the high plain of Bogotá in the Colombian Eastern Cordillera indicates a significant climatic warming around 18,000¹⁴C yr B.P. Comparison of dated vegetation changes, pedogenic episodes, and glacier fluctuations provides the basis for defining the so-called “La Laguna Interstadial” that lasted from 19,500 to 17,000 yr B.P. During this interstadial period, mean annual temperatures in the tropical Andes were up to 4°C higher than during the preceding and following stadial periods, when full-glacial conditions prevailed and temperatures were up to 8°C colder than at present.     

Faroe Shelf Water

Faroe Shelf Water (FSW) is the water mass that occupies the shallow parts of the Faroe Shelf, surrounding the Faroe Islands (62°N, 7°W). Intensive tidal mixing induces a high degree of homogeneity and the circulation system allows a partial isolation from surrounding waters. This water mass, therefore, supports a unique ecosystem of great importance for commercial fish stocks and studies have shown a clear dependence of the ecosystem on the physical processes that maintain this system and control the exchange between the FSW and the off-shelf waters. In order to identify and quantify these processes, a large observational dataset has been analysed and related to alternative theories. From this analysis, the extent and properties of the FSW have been quantified and the degree of stratification explained in terms of the Simpson–Hunter theory. The residual clockwise circulation system, which is responsible for the partial isolation from off-shelf waters, is shown to be mainly generated by tidal rectification. The typical exchange rate of water between the FSW and the off-shelf regimes has been determined by the use of simple models based on the heat and the salt budgets but the actual exchange rate is found to vary considerably in time and space. These results support earlier suggestions that this exchange is the main limiting factor for the phytoplankton spring bloom on the Faroe Shelf and that variations in exchange rate are responsible for the large inter-annual variation in spring bloom timing and intensity. The observations indicate that the on-shelf/off-shelf exchange intensity is not symmetrically distributed around the shelf, but rather concentrated around the narrow southern tip of the Faroe Shelf, where off-shelf waters during intensive exchange events may be imported all the way to the shore.