ALBERT

Description: 〈b〉Syn- and post-orogenic exhumation of metamorphic rocks in North Aegean〈/b〉〈br〉 R. Lacassin, N. Arnaud, P. H. Leloup, R. Armijo, and B. Meyer〈br〉 eEarth, 2, 51-63, doi:10.5194/ee-2-51-2007, 2007〈br〉 The Olympos-Ossa-Pelion (OOP) ranges, in NW Aegean, encompass Greece highest summit and are located near the extremity of the North Anatolian Fault (NAF). Structural and thermochronological data gathered in the OOP ranges show that the main exhumation of metamorphic nappes occurred in the Eocene, at ca. 43–39 Ma. This early exhumation, associated with ductile, then brittle-ductile normal faulting with northeastward transport, is coeval with orogenic shortening in the close area. Cooling rates, and likely exhumation, have been low between ~40 Ma and ~20 Ma. 〈sup〉40〈/sup〉Ar/〈sup〉39〈/sup〉Ar crystallization ages (between 20 and 15 Ma) appears related to brittle-ductile normal faulting and likely associated with Neogene Aegean back-arc extension. The dating of a diabase dyke, and the geometry of associated brittle jointing, of onshore and offshore active normal faults suggest a shift in extension direction after 4Ma, possibly in relation with the propagation of the NAF in northern Aegean.

Description: 〈b〉Impact vesiculation – a new trigger for volcanic bubble growth and degassing〈/b〉〈br〉 D. A. Rothery, J. M. Sumner, O. Spieler, and D. B. Dingwell〈br〉 eEarth Discuss., 2, 151-167, doi:10.5194/eed-2-151-2007, 2007〈br〉 〈b〉Revised manuscript has not been submitted〈/b〉 (discussion: closed, 3 comments)〈br〉 We highlight a potentially important trigger for bubble growth and degassing in volcanic bombs. We have successfully triggered bubble growth in previously unvesiculated samples of silicate melt during experiments to simulate volcanic bomb impact, by firing pellets at, and dropping weights onto, melt samples. We call this phenomenon "impact vesiculation". Further work is required on real volcanic bombs to establish the extent to which impact vesiculation occurs in nature. However, our experiments are sufficient to demonstrate that impact vesiculation is a viable processes and should be borne in mind in analysis of bubble populations and degassing histories of bombs and spatter-fed lava flows. Degassing caused by impact vesiculation can occur only at ground-level, so any attempt to calculate the amount of erupted gas available for transport high into the atmosphere by convection above the source of a fountain-fed lava flow that is based on subtracting the volatile content of fluid inclusions from the volatile content of the resulting lava flow would be an overestimate if significant impact vesiculation has occurred.

Description: The Eratosthenes Seamount (Eastern Mediterranean) is interpreted as a crustal block in process of break up in response to subduction and incipient collision of the African and Eurasian Plates. Subsidence is considered to be the mechanism triggering the Messinian to Pleistocene water deepening above this unique structure. However, the application of a recently developed transfer equation of depth range distribution of benthic foraminifera indicates that sea-level changes may also have played a role, although it was generally minor. In particular, we suggest that across the Miocene/Pliocene boundary and during the Pliocene-Pleistocene, the eustatic signal is frequently coupled with uplifts and subsidence. The uplift of Cyprus across the Pliocene-Pleistocene transition is clearly recorded in the paleodepth curve. Micropaleontological studies and the use of this transfer equation based on the distribution of benthic foraminifera proves to be useful when studying the paleodepth history of complex sites, where tectonic and eustatic signals combine. We also show that marginal seas record global sea-level changes that can be identified even in tectonically active settings.

Description: The strontium isotope composition of seawater has varied over geological time in response to changes in the rates of continental weathering relative to ocean crust alteration. However, the potential of the seawater 87Sr/86Sr curve to trace globally integrated chemical weathering rates has not been fully realised because ocean 87Sr/86Sr is also strongly influenced by the isotopic evolution of Sr sources to the ocean. A first attempt is made here to normalise the seawater 87Sr/86Srr curve to plausible trends in the 87Sr/86Sr ratios of the three major Sr sources: carbonate dissolution, silicate weathering and submarine hydrothermal exchange. The normalised curve highlights the Neoproterozoic-Cambrian interval as a period of exceptionally high chemical weathering rates, which can be linked to increased nutrient availability, bioproductivity and oxygenation of Earth's surface environment. Use of normalised seawater 87Sr/86Sr curves will, it is hoped, help to improve future geochemical models of Earth System dynamics.

Description: The Lunar cratering record is consistent with the occurrence of a late heavy bombardment (LHB), which marked the end of terrestrial planet accretion 3.8 billion years ago. However, clear evidence of a LHB on Earth has not yet been identified. Here it is shown that the LHB did indeed occur on Earth and that we are breathing its aftermaths. The terrestrial atmosphere and hydrosphere is enriched in noble gases relative to the abundance of volatiles in the mantle. This enrichment is consistent with the mass delivered to Earth during the LHB only if this material consisted of ~0.5% Kuiper-belt objects mixed in with a population of largely chondritic (i.e. asteroidal) impactors. This places strong constraints on dynamical models for early Solar System evolution.

Description: The Olympos-Ossa-Pelion (OOP) ranges, in NW Aegean, encompass Greece highest summit and are located near the extremity of the North Anatolian Fault (NAF). Structural and thermochronological data gathered in the OOP ranges show that the main exhumation of metamorphic nappes occurred in the Eocene, at ca. 43–39 Ma. This early exhumation, associated with ductile, then brittle-ductile normal faulting with northeastward transport, is nearly coeval with orogenic shortening in the close area. Cooling rates, and likely exhumation, have been low between ~40 Ma and ~20 Ma. 40Ar/39Ar crystallization ages (between 20 and 15 Ma) appears related to brittle-ductile normal faulting and likely associated with the onset of Aegean back-arc extension. The dating of a diabase dyke, and the geometry of associated brittle jointing, of onshore and offshore active normal faults imply a shift in extension direction after 4 Ma. Such a shift is probably related the propagation of the NAF in northern Aegean known to have occurred around 5 Ma.

Description: Sediment cores from 13 deep boreholes (1–4.1 km) from Axios zone in Northern Greece have been studied by means of palaeomagnetism. Both low field magnetic susceptibility and intensity of the natural remanent magnetization (NRM) indicate rather weakly magnetised materials. 390 samples have been subjected to demagnetization process (AF and thermal) revealing in most of the cases the presence of magnetite. Isothermal remanent magnetization (IRM) acquisition curves and thermomagnetic analysis suggest the dominance of magnetite. 30 thin sections were studied in order to more precisely characterise the magnetic mineralogy of the samples. This investigation also reveals the presence of magnetite and pyrite in framboidal form. An attempt to re-orient some of the samples was partially successful by using the viscous component and the anisotropy method. Re-orientation techniques were applied in order to correct the palaeomagnetic directions due to the orientation ambiguity of the core samples. The palaeomagnetic results confirm the clockwise Cenozoic rotation, in the study area in agreement with the overall pattern of the onshore results from previous investigations. Finally, the observed inclinations of characteristic remanences in these rocks are much lower than the expected ones but converge with those obtained from formations on land.

Description: Since the 1980s the frequency of warming events has intensified and simultaneously widespread coral bleaching, and enhanced coral mortality have been observed. Yet, it remains unpredictable how tropical coral reef communities will react to prolonged adverse conditions. Possibly, coral reef systems are sufficiently robust to withstand continued environmental pressures. But if coral mortality increases, what will platform communities of the future look like? The co-evolution of early Paleogene carbonate platforms and palaeoclimate may provide insight. Here we document the impact of early Paleogene global warming on shallow-water carbonate platforms in the Tethys. Between 59 and 55 Ma, three discrete stages in platform development can be identified Tethys-wide: during the first stage carbonate platforms mainly consisted of coralgal reefs; during the second – transitional – stage coralgal reefs thrived only at middle latitudes and gave way to larger foraminifera as dominant carbonate producer in low latitudes; finally, during the third stage, newly developing larger foraminifera lineages completely took over the role as main carbonate-producing organisms in low to middle latitudes. We postulate that rising temperatures led to a stepwise demise of Paleocene coral reefs, giving way to an unprecedented expansion of larger foraminifera, dominating Tethyan platforms during the early Eocene.

Description: The iron content and the asymmetry of iron and magnesium ions in chlorites are examined for the Chelungpu Fault in Taiwan, which is a seismogenic fault. The samples are collected from the cores drilled for the Taiwan Chelungpu Fault Drilling Project (TCDP). Three fault zones are recognized as candidates for the source of seismogenic materials. The fault zones are composed of fractured-damaged rocks, breccia, gray gouge, black gouge, and black material. Chlorite from each type of rock was analyzed by using X-ray diffraction (XRD). The iron content and asymmetry of the iron and magnesium ions in the chlorites were estimated from the XRD peak ratios. The hydroxide and silicate layers in the black gouge and black material have low iron contents. Many studies have suggested that a temperature rise occurred at the fault zones. In addition, the temperature rise can result in the production of iron oxides such as magnetite or maghemite, as reported by other studies. However, the temperature rise cannot explain the low value of iron content in the chlorites. Another reason for the low value of iron content is the variation in the pH of the fluid, which can be controlled by radical reactions. Therefore, the reactions at the seismogenic fault are due to not only the thermal decomposition resulting from the temperature rise and but also rock-fluid interactions based on the chlorite characteristics.

Description: We suggest a working hypothesis for the geometry of the strike-slip faults that formed the boundaries between the Turkish, African and Arabian plates in the latest Miocene to Mid-Pliocene (LMMP), between ~7–6 Ma and ~3.5 Ma. This geometry differed significantly from the modern geometry; the northern Dead Sea Fault Zone (DSFZ) was located east of its present line and the TR-AR boundary was formed by the Malatya-Ovacık Fault Zone (MOFZ), located well north of the modern East Anatolian Fault Zone (EAFZ). The MOFZ is potentially the most problematic aspect of such a scheme, given the dramatically different interpretations of it that have been proposed. However, the presently-available evidence, albeit limited, is consistent with our proposed interpretation. Significant differences between the proposed LMMP fault geometry and the modern geometry include, first, the transtensional geometry of the MOFZ, the modern EAFZ being typically a left-lateral transform fault zone but with localized transpression. Second, the MOFZ slip rate was much lower than the ~9–10 mm a−1 EAFZ slip rate; it is estimated as ~2–3 mm a−1, having produced no more than ~8 km of slip during its approximately three million year long activity. Third, unlike at present, there was no throughgoing linkage of left-lateral faulting between the LMMP DSFZ and the MOFZ; instead, the DSFZ terminated northward, and the MOFZ terminated southward, in a zone of localised crustal shortening adjoining the suture of the former Neotethys Ocean in the Kahramanmaraç-Pazarcık region of SE Turkey. The different motion of the Turkish plate relative to Arabia, and, thus, relative to Eurasia, means that senses and rates of crustal deformation can be expected to have been different during the LMMP phase from at present, throughout the eastern Mediterranean region.

Description: We highlight a potentially important trigger for bubble growth and degassing in volcanic bombs. We have successfully triggered bubble growth in previously unvesiculated samples of silicate melt during experiments to simulate volcanic bomb impact, by firing pellets at, and dropping weights onto, melt samples. We call this phenomenon "impact vesiculation". Further work is required on real volcanic bombs to establish the extent to which impact vesiculation occurs in nature. However, our experiments are sufficient to demonstrate that impact vesiculation is a viable processes and should be borne in mind in analysis of bubble populations and degassing histories of bombs and spatter-fed lava flows. Degassing caused by impact vesiculation can occur only at ground-level, so any attempt to calculate the amount of erupted gas available for transport high into the atmosphere by convection above the source of a fountain-fed lava flow that is based on subtracting the volatile content of fluid inclusions from the volatile content of the resulting lava flow would be an overestimate if significant impact vesiculation has occurred.

Description: The living benthic foraminiferal assemblages in the Kiel Fjord (SW Baltic Sea) were investigated in the years 2005 and 2006. The faunal studies were accomplished by geochemical analyses of surface sediments. In general, sediment pollution by copper, zinc, tin and lead was assessed as moderate in comparison with levels reported from other areas of the Baltic Sea. However, the inner Kiel fjord is still exposed to a high load of metals and organic matter due to enhanced accumulation of fine-grained sediments in conjunction with a concentration of pollution sources as shipyards, harbours and intensive traffic. The results of our survey showed that the dominant environmental forcing of benthic foraminifera is nutrients availability coupled with human impact. A comparison with data from the 1960s revealed apparent changes in species composition and population densities over the past decades. The stress-tolerant species Ammonia beccarii invaded Kiel Fjord whereas Ammotium cassis disappeared, possibly due to low salinity that prevailed 10 years ago. These changes in foraminiferal community and a significant increase of test abnormalities indicate enforced environmental stress since the 1960s.

Description: The German Meteorological Service (Deutscher Wetterdienst) is presently developing a European climate information system (EuCLIS) which is presented here. The aim of this system is to distribute climate monitoring information of the area of the WMO (World Meteorological Organisation) Region VI (Europe and the Middle East) via the web. EuCLIS will be the successor of the already existing platform GCMP (Generate Climate Monitoring Products) which emerged from a project of the ECSN (European Climate Support Network). Climate monitoring information can be all kind of maps, diagrams and texts describing the variability of climate variables in space and time. It can be provided by the public national meteorological and hydrological services of all countries of the WMO Region VI. The main advantage is to have one common efficient climate monitoring distribution system for the whole Region, but the individual meteorological and hydrological services have the possibility to administrate their products on their own. EuCLIS considers the WMO metadata standard and modern web portal technology. In an advanced state, EuCLIS is intended to be used as a platform for a function of a Regional Climate Centre for Climate Monitoring which is currently planned at the WMO.

Description: Computer-generated visualizations of geoscientific data, such as those from climate models are in high demand for a wide variety of usages; these include, among others, scientific publications, reports and graphical aides for the general public's improved understanding of complex developments. The paper will focus on the effects of colours in two-dimensional displays. Practical examples are given from which it becomes clear that considerable confusion or even damage can arise from an uninformed use of colour mapping and if results become, e.g., published in an unchecked manner by the media.

Description: The main objective of this work is to determine the parameters of hydrological balance for several basins in the prefecture of Korinthia (SE Greece), using hydrometeorological data and geographic information systems (GIS) technology. Multiple linear regression and GIS were used to estimate the spatial distribution of rainfall. The largest precipitation amounts occur in the SW part of the region and decrease towards the eastern and northern coastal parts. The long term mean annual rainfall is 1.39×109 m3. Based on the Thornthwaite method, infiltration and streamflow were estimated to be 0.29×109 m3/yr and 0.38×109 m3/yr, respectively. The unequal distribution of rainfall results in water surplus in the western part of Korinthia prefecture and water deficit in the eastern. We conclude that he estimation of hydrologic balance is a useful tool in order to establish sustainable water resources management in each hydrological basin.

Description: This paper provides an over view of a new international network of researchers, stakeholders, and end-users of remote sensing tools that will benefit the water resources management community. It discusses the concept of solutions networks focusing on the WaterNet and it invites EGU teams to join the in the initial stages of our WaterNet network. The NASA Water cycle Solutions Network's goal is to improve and optimize the sustained ability of water cycle researchers, stakeholders, organizations and networks to interact, identify, harness, and extend NASA research results to augment decision support tools and meet national and international needs. This paper seeks to invite EU scientific teams and water resource management teams to join our WaterNet Solutions Network.