ALBERT

Description: Morphology of the pore space in claystones – evidence from BIB/FIB ion beam sectioning and cryo-SEM observations G. Desbois, J. L. Urai, and P. A. Kukla eEarth, 4, 15-22, doi:10.5194/ee-4-15-2009, 2009 The morphology of pore space has a strong effect on mechanical and transport properties of mudrocks and clay-rich fault gouge, but its characterization has been mostly indirect. We report on a study of Boom clay from a proposed disposal site of radioactive waste (Mol site, Belgium) using high resolution SEM at cryogenic temperature, with ion beam cross-sectioning to prepare smooth, damage free surfaces. Pores commonly have crack-like tips, preferred orientation parallel to bedding and power law size distribution. We define a number of pore types depending on shape and location in the microstructure: large jagged pores in strain shadows of clastic grains, high aspect ratio pores between similarly oriented phyllosilicate grains and crescent-shaped pores in saddle reefs of folded phyllosilicates. 3-D reconstruction by serial cross-sectioning shows 3-D connectivity of the pore space. These findings offer a new insight into the morphology of pores down to nano-scale in comparison to traditional pore size distributions calculated from mercury Injection experiments, explain slaking of clays by successive wetting and drying and provide the basis for microstructure-based models of transport in clays.

Description: Holocene evolution and sedimentation rate of Alikes Lagoon, Zakynthos island, Western Greece: preliminary results P. Avramidis and N. Kontopoulos eEarth, 4, 23-29, doi:10.5194/ee-4-23-2009, 2009 In the present study we present preliminary results from Alikes lagoon in Zakynthos island, an area that is one of the most seismically active regions of Greece. In order to estimate – interpret the Holocene evolution of the area and to reconstruct the palaeoenvironmental changes, we based on data derived from a 21 m sediment core. Sediment types, structure, colour, as well as contact depths and bed characteristics were recorded in the field. Standarised sedimentological analysis was carried out, on 46 samples including grain size analysis, calculation of moment measures, and micro- and molluscan fossils of 17 selected samples. Moreover, radiocarbon age determinations have been made on individual Cardium shells from two horizons and whole – core Magnetic Susceptibility (MS) measurements were taken. The interpretation of depositional environments suggests a coastal environment (restricted-shallow) with reduced salinity such as a lagoon margin and in a tidal flat and/or marsh particularly. The maximum age of the studied sediments is about 8500 BP. The rate of sedimentation between 8280 BP while 5590 BP was 5.3 mm/yr and between 5590 BP and modern times is on the order of 1.03 mm/yr. These sedimentation rates results are similar to other coastal areas of western Greece.

Description: Thermogeodynamic manifestations in the Caucasus and their genesis G. E. Gugunava, J. K. Kiria, and T. B. Bochorishvili eEarth Discuss., 4, 77-89, doi:10.5194/eed-4-77-2009, 2009 Publication in eE not foreseen (discussion: closed, 2 comments) In the work two aspects of thermal character are considered: first of all this is the connection of subduction phenomena with thermal life of the Caucasus on the basis of over interpreted data of magnetotelluric sounding, and secondly, origin of thermostressed condition of the Caucasus and its geological aspects which is manifested in the following: 1. in the zones of anomalous thermodisplacements thermofaults should occur (Le Pishon et al., 1977). These thermofaults are in good correlation with deep faults which are distinguished by geological and seismic methods, these thermofaults may be earthquake sources (Spitak, Racha, etc. earthquakes), also may be channels through which magma derivates (giving mineral deposits) may penetrate on surface (Gugunava and Gijeishvili, 1989); 2. in the body of sedimentary complex thermostressed seals and seal failures occur, which are apparently traps for oil-gas fluids. Good correlation of thermodense anomalies with oil deposits of the Caucasus is shown (Alexidze et al., 1985; Gugunava, 1980). Everything above mentioned was carried out within frames of stationary thermal model which did not allow us to reveal time characteristics of interconnection of geological medium and thermal field. Now investigations are being carried out within the frames of stationary thermal model and its interconnection with geological environment.

Description: Plate tectonics conserves angular momentum C. Bowin eEarth, 5, 1-20, doi:10.5194/ee-5-1-2010, 2010 A new combined understanding of plate tectonics, Earth internal structure, and the role of impulse in deformation of the Earth's crust is presented. Plate accelerations and decelerations have been revealed by iterative filtering of the quaternion history for the Euler poles that define absolute plate motion history for the past 68 million years, and provide an unprecedented precision for plate angular rotation variations with time at 2-million year intervals. Stage poles represent the angular rotation of a plate's motion between adjacent Euler poles, and from which the maximum velocity vector for a plate can be determined. The consistent maximum velocity variations, in turn, yield consistent estimates of plate accelerations and decelerations. The fact that the Pacific plate was shown to accelerate and decelerate, implied that conservation of plate tectonic angular momentum must be globally conserved, and that is confirmed by the results shown here (total angular momentum ~1.4 +27 kg m 2 s −1 ). Accordingly, if a plate decelerates, other plates must increase their angular momentums to compensate. In addition, the azimuth of the maximum velocity vectors yields clues as to why the "bend" in the Emperor-Hawaiian seamount trend occurred near 46 Myr. This report summarizes processing results for 12 of the 14 major tectonic plates of the Earth (except for the Juan de Fuca and Philippine plates). Plate accelerations support the contention that plate tectonics is a product of torques that most likely are sustained by the sinking of positive density anomalies revealed by geoid anomalies of the degree 4–10 packet of the Earth's spherical harmonic coefficients. These linear positive geoid anomalies underlie plate subduction zones and are presumed due to phase changes in subducted gabbroic lithosphere at depth in the upper lower mantle (above 1200 km depth). The tectonic plates are pulled along by the sinking of these positive mass anomalies, rather than moving at near constant velocity on the crests of convection cells driven by rising heat. The magnitude of these sinking mass anomalies is inferred also to be sufficient to overcome basal plate and transform fault frictions. These results imply that spreading centers are primarily passive reactive features, and fracture zones (and wedge-shaped sites of seafloor spreading) are adjustment zones that accommodate strains in the lithosphere. Further, the interlocked pattern of the Australian and Pacific plates the past 42 Million years (with their absolute plate motions near 90° to each other) is taken as strong evidence that large thermally driven "roller" convection cells previously inferred as the driving mechanism in earlier interpretations of continental drift and plate tectonics, have not been active in the Earth's mantle the past 42 Million years, if ever. This report also presents estimates of the changes in location and magnitude of the Earth's axis of total plate tectonic angular momentum for the past 62 million years.

Description: Geometry of the Turkey-Arabia and Africa-Arabia plate boundaries in the latest Miocene to Mid-Pliocene: the role of the Malatya-Ovacık Fault Zone in eastern Turkey R. Westaway, T. Demir, and A. Seyrek eEarth, 3, 27-35, doi:10.5194/ee-3-27-2008, 2008 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. The Euler vector is tentatively inferred to have involved relative rotation between the Turkish and Arabian Plates at ~0.85±0.15° Ma −1 about a pole at ~37.75±0.15° N, ~38.8±0.3° E. 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 Kahramanmaraş-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: Use of remote sensing and GIS in mapping the environmental sensitivity areas for desertification of Egyptian territory A. Gad and I. Lotfy eEarth Discuss., 3, 41-85, doi:10.5194/eed-3-41-2008, 2008 Revised manuscript has not been submitted (discussion: closed, 3 comments) Desertification is defined in the first art of the convention to combat desertification as "land degradation in arid, semiarid and dry sub-humid areas resulting from climatic variations and human activities". Its consequence include a set of important processes which are active in arid and semi arid environment, where water is the main limiting factor of land use performance in such ecosystem . Desertification indicators or the groups of associated indicators should be focused on a single process. They should be based on available reliable information sources, including remotely sensed images, topographic data (maps or DEM'S), climate, soils and geological data. The current work aims to map the Environmental Sensitivity Areas (ESA's) to desertification in whole territory of Egypt at a scale of 1:1 000 000. ETM satellite images, geologic and soil maps were used as main sources for calculating the index of Environmental Sensitivity Areas (ESAI) for desertification. The algorism is adopted from MEDALLUS methodology as follows; ESAI = (SQI * CQI * VQI) 1/3 Where SQI is the soil quality index, CQI is the climate quality index and VQI is the vegetation quality index. The SQI is based on rating the parent material, slope, soil texture, and soil depth. The VQI is computed on bases of rating three categories (i.e. erosion protection, drought resistance and plant cover). The CQI is based on the aridity index, derived from values of annual rainfall and potential evapotranspiration. Arc-GIS 9 software was used for the computation and sensitivity maps production. The results show that the soil of the Nile Valley are characterized by a moderate SQI, however the those in the interference zone are low soil quality indexed. The dense vegetation of the valley has raised its VQI to be good, however coastal areas are average and interference zones are low. The maps of ESA's for desertification show that 86.1% of Egyptian territory is classified as very sensitive areas, while 4.3% as Moderately sensitive, and 9.6% as sensitive. It can be concluded that implementing the maps of sensitivity to desertification is rather useful in the arid and semi arid areas as they give more likely quantitative trend for frequency of sensitive areas. The integration of different factors contributing to desertification sensitivity may lead to plan a successful combating. The usage of space data and GIS proved to be suitable tools to rely estimation and to fulfill the needed large computational requirements. They are also useful in visualizing the sensitivity situation of different desertification parameters.

Description: Zoogeography of the bottom Foraminifera of the West-African coast V. Mikhalevich eEarth Discuss., 3, 1-9, doi:10.5194/eed-3-1-2008, 2008 Revised manuscript has not been submitted (discussion: closed, 8 comments) The sediment samples from the continental shelf of West-Equatorial Africa (from the Strait of Gibraltar to the Niger estuary), depths ranging from 0 to 69 m were found to contain 176 bottom foraminiferal species. For the majority of them (126 species), their areas of occurrences were mapped and the peculiar features of the geographical range and distribution were studied. The species natural habitats were established based on the taxonomical revision of the species in study all over the World Ocean based on the collections of the Zoological Institute RAS and wide literary data. The method of perforated cards was used to mark the geographical locations of all of the species studied. In order to establish the species geographic zonal distribution (together with their depth habitat) the five characteristic groups of the species were separated: 1. pan-oceanic (cosmopolitan), 2. widely spread tropical-boreal, 3. tropical-law boreal, 4. tropical-subtropical, 5. tropical. The percent of the species of each group among the species composition was established for the fauna of each station and for the whole region.

Description: Decline of coral reefs during late Paleocene to early Eocene global warming C. Scheibner and R. P. Speijer eEarth, 3, 19-26, doi:10.5194/ee-3-19-2008, 2008 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: Characteristics of chlorites in seismogenic fault zones: the Taiwan Chelungpu Fault Drilling Project (TCDP) core sample Y. Hashimoto, O. Tadai, M. Tanimizu, W. Tanikawa, T. Hirono, W. Lin, T. Mishima, M. Sakaguchi, W. Soh, S. R. Song, K. Aoike, T. Ishikawa, M. Murayama, K. Fujimoto, T. Fukuchi, M. Ikehara, H. Ito, H. Kikuta, M. Kinoshita, K. Masuda, T. Matsubara, O. Matsubayashi, K. Mizoguchi, N. Nakamura, K. Otsuki, T. Shimamoto, H. Sone, and M. Takahashi eEarth, 3, 1-6, doi:10.5194/ee-3-1-2008, 2008 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, borehole B). 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 of chlorite 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, on the basis of chlorite characteristics, the reactions at the seismogenic fault are due not only to the thermal decomposition resulting from the temperature rise and but also to rock-fluid interactions.

Description: Syn- and post-orogenic exhumation of metamorphic rocks in North Aegean R. Lacassin, N. Arnaud, P. H. Leloup, R. Armijo, and B. Meyer eEarth, 2, 51-63, doi:10.5194/ee-2-51-2007, 2007 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. 40 Ar/ 39 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.