ALBERT

Description: 〈b〉Paleomagnetic determination of paleolatitude and rotation of Bering Island (Komandorsky Islands) Russia: comparison with rotations in the Aleutian Islands and Kamchatka〈/b〉〈br〉 P. S. Minyuk and D. B. Stone〈br〉 Stephan Mueller Spec. Publ. Ser., 4, 329-348, https://doi.org/10.5194/smsps-4-329-2009, 2009〈br〉 A paleomagnetic study was carried out on Paleogene sedimentary rocks from Bering Island, Komandorsky islands, located at the far western end of the Aleutian Island Arc. The age of these sediments has been debated at length, but the combination of magnetostratigraphy with the fossil record indicates that the base of the section is of early Eocene (approximately 55 Ma) and the top latest Eocene age. Paleomagnetic data were obtained from 260 samples from 60 individual bedding units. The combined data show a clockwise rotation 〈i〉R〈/i〉=26.3°±8.5°, 〈i〉F〈/i〉=8.1°±2.5° with respect to the North American Plate and 〈i〉R〈/i〉=38°±8.8°, 〈i〉F〈/i〉=8.7°±2.7° with respect to the Eurasian Plate. They also show a shallowing of the inclination which yields a paleolatitude of 53°, 12° south of its expected latitude. The shallowing may have a component due to compaction, but the wide variation in sampled lithologies, combined with internal consistency of the data set, would argue against the shallowing being significant. To compare these data with other Aleutian Arc data we compiled a comprehensive survey of all available data sets. Out of these we selected four islands for which the data passed basic reliability criteria, namely Umnak, Amlia, Amchitka and Medny islands. All four showed significant clockwise rotation with respect to both North American and Eurasian polar wander paths. Several mechanisms can generate the observed rotation, ranging from block rotation driven by oblique relative motion of the Pacific plate, through lateral transport along the curve of the arc, to whole-arc rotation about its eastern end. The distribution and age spread of the rotation data are insufficient to discriminate between mechanisms, but it seems likely that different mechanism may have operated at different times and in different locations.

Description: 〈b〉Paleomagnetism of the Cretaceous rocks from Cape Kronotskiy, East Kamchatka and reconstruction of terrane trajectories in the NE Pacific area〈/b〉〈br〉 W. Harbert, N. V. Tsukanov, D. V. Alexeiev, C. Gaedicke, R. Freitag, B. V. Baranov, S. G. Skolotnev, W. Kramer, and W. Seifert〈br〉 Stephan Mueller Spec. Publ. Ser., 4, 313-327, https://doi.org/10.5194/smsps-4-313-2009, 2009〈br〉 The Kamchatka Peninsula of northeastern Russia is located along the northwestern margin of the Bering Sea and consists of zones of complexly deformed accreted terranes. Paleomagnetic samples were collected for study from a Late Cretaceous aged locality at Cape Kronotskiy (λ=54°44.8´ N, φ=162°1.29´ E). Two components of magnetization were observed. During stepwise thermal demagnetization, the B-magnetic component was observed up to 600°C having a direction and associated uncertainty in stratigraphic coordinates of 〈i〉D〈sub〉s〈/sub〉〈/i〉=300.7°, 〈i〉I〈sub〉s〈/sub〉〈/i〉=48.7°, α〈sub〉95〈/sub〉=10.9°, k-value=11.8, n=17. The B component paleolatitude calculated from the Fisher mean in stratigraphic coordinates and associated statistics are λ〈sub〉obs〈/sub〉=30.4° N or S, λ〈sub〉95〈/sub〉=8.9°, n=17 (sites), k-value=11. Our overall study paleolatitude result is similar to a previously reported paleomagnetic study completed within this unit. Terrane trajectories calculated using the finite rotation poles of Engebretson et al. (1985), which are corrected for either Pacific-hotspot drift or True Polar Wander hotspot-spin axis relative motion, show that the sampled unit represents a far traveled tectonostratigraphic terrane and support a model in which accretion (docking) events of this composite or superterrane with the North America plate occur at approximately 40 Ma.

Description: 〈b〉Comparison of Cretaceous granitoids of the Chaun tectonic zone to those of the Taigonos Peninsula, NE Asia: rock chemistry, composition of rock forming minerals, and conditions of formation〈/b〉〈br〉 P. L. Tikhomirov, M. V. Luchitskaya, and I. R. Kravchenko-Berezhnoy〈br〉 Stephan Mueller Spec. Publ. Ser., 4, 289-311, https://doi.org/10.5194/smsps-4-289-2009, 2009〈br〉 The Cretaceous granitoid complexes of the Eastern Taigonos and the Prybrezhny Taigonos belts (southern part of the Taigonos Peninsula), Tanyurer pluton of the Okhotsk-Chukotka volcanic belt, and the Peekiney, Moltykan, and Telekay plutons of the Chaun tectonic zone are discussed in relation to their structural position, petrography, rock and mineral chemistry and physicochemical conditions of melt crystallization. These granitoid plutons were generated through melting of a compositionally heterogeneous crustal source, with direct contribution from mafic melts produced in the mantle wedge above active or extinct Benioff zones. Variations of the trace-element composition of granitoids are controlled to a greater extent by local compositional peculiarities of the source regions than by the geodynamic regime as such. The final crystallization of these plutons occurred at comparatively shallow depths, between 1–2 and 6–7 km, in a temperature interval of 700–770°C. The depth of emplacement of the bodies decreases with increasing distance from the areas with oceanic and transitional type crust, as does the degree of incompatible element enrichment of the mantle and crustal sources of melts. Variations in fo〈sub〉2〈/sub〉 values at the late stages of crystallization of the plutons reach 3–4 orders of magnitude, exceeding the limits of the quartz-fayalite-magnetite (QFM) and nickel-nickel oxide (NNO) buffer equilibria, which likely results from local variations of the source composition.

Description: 〈b〉Thermogeodynamic manifestations in the Caucasus and their genesis〈/b〉〈br〉 G. E. Gugunava, J. K. Kiria, and T. B. Bochorishvili〈br〉 eEarth Discuss., 4, 77-89, doi:10.5194/eed-4-77-2009, 2009〈br〉 〈b〉Publication in eE not foreseen〈/b〉 (discussion: closed, 2 comments)〈br〉 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: 〈br〉〈br〉 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); 〈br〉〈br〉 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). 〈br〉〈br〉 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. 〈br〉〈br〉 Now investigations are being carried out within the frames of stationary thermal model and its interconnection with geological environment.

Description: 〈b〉Thermogeodynamic manifestations in the Caucasus and their genesis〈/b〉〈br〉 G. E. Gugunava, J. K. Kiria, and T. B. Bochorishvili〈br〉 eEarth Discuss., 4, 77-89, doi:10.5194/eed-4-77-2009, 2009〈br〉 〈b〉Publication in eE not foreseen〈/b〉 (discussion: closed, 2 comments)〈br〉 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: 〈br〉〈br〉 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); 〈br〉〈br〉 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). 〈br〉〈br〉 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. 〈br〉〈br〉 Now investigations are being carried out within the frames of stationary thermal model and its interconnection with geological environment.

Description: 〈b〉Holocene evolution and sedimentation rate of Alikes Lagoon, Zakynthos island, Western Greece: preliminary results〈/b〉〈br〉 P. Avramidis and N. Kontopoulos〈br〉 eEarth, 4, 23-29, doi:10.5194/ee-4-23-2009, 2009〈br〉 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 〈i〉Cardium〈/i〉 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: 〈b〉Morphology of the pore space in claystones – evidence from BIB/FIB ion beam sectioning and cryo-SEM observations〈/b〉〈br〉 G. Desbois, J. L. Urai, and P. A. Kukla〈br〉 eEarth, 4, 15-22, doi:10.5194/ee-4-15-2009, 2009〈br〉 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: 〈b〉Foraminiferal response to environmental changes in Kiel Fjord, SW Baltic Sea〈/b〉〈br〉 A. Nikulina, I. Polovodova, and J. Schönfeld〈br〉 eEarth, 3, 37-49, doi:10.5194/ee-3-37-2008, 2008〈br〉 The living benthic foraminiferal assemblages in 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 is 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 potential pollution sources as shipyards, harbours and intensive traffic. The results of our survey show that the dominant environmental forcing of benthic foraminifera is nutrients availability coupled with human impact. A comparison with faunal data from the 1960s reveals apparent changes in species composition and population densities. The stress-tolerant species 〈i〉Ammonia beccarii〈/i〉 invaded Kiel Fjord. 〈i〉Ammotium cassis〈/i〉 had disappeared that reflects apparently the changes in salinity over the last 10 years. These changes in foraminiferal community and a significant increase of test abnormalities indicate an intensified environmental stress since the 1960s.

Description: 〈b〉Holocene evolution and sedimentation rate of Alikes Lagoon, Zakynthos island, Western Greece: preliminary results〈/b〉〈br〉 P. Avramidis and N. Kontopoulos〈br〉 eEarth, 4, 23-29, doi:10.5194/ee-4-23-2009, 2009〈br〉 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 〈i〉Cardium〈/i〉 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: 〈b〉Foraminiferal response to environmental changes in Kiel Fjord, SW Baltic Sea〈/b〉〈br〉 A. Nikulina, I. Polovodova, and J. Schönfeld〈br〉 eEarth, 3, 37-49, doi:10.5194/ee-3-37-2008, 2008〈br〉 The living benthic foraminiferal assemblages in 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 is 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 potential pollution sources as shipyards, harbours and intensive traffic. The results of our survey show that the dominant environmental forcing of benthic foraminifera is nutrients availability coupled with human impact. A comparison with faunal data from the 1960s reveals apparent changes in species composition and population densities. The stress-tolerant species 〈i〉Ammonia beccarii〈/i〉 invaded Kiel Fjord. 〈i〉Ammotium cassis〈/i〉 had disappeared that reflects apparently the changes in salinity over the last 10 years. These changes in foraminiferal community and a significant increase of test abnormalities indicate an intensified environmental stress since the 1960s.