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〉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〉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〉Map – geographic locations related to the manuscript sequence〈/b〉〈br〉 〈br〉 Stephan Mueller Spec. Publ. Ser., 4, 3-3, https://doi.org/10.5194/smsps-4-3-2009, 2009〈br〉

Description: 〈b〉Age and paleomagnetism of the Okhotsk-Chukotka Volcanic Belt (OCVB) near Lake El'gygytgyn, Chukotka, Russia〈/b〉〈br〉 D. B. Stone, P. W. Layer, and M. I. Raikevich〈br〉 Stephan Mueller Spec. Publ. Ser., 4, 243-260, https://doi.org/10.5194/smsps-4-243-2009, 2009〈br〉 Paleomagnetic results from the upper two thirds of the whole section of the Okhotsk-Chukotka Volcanic Belt (OCVB) volcanics exposed in the area around Lake El'gygytgyn, Chukotka yield stable, consistent magnetic vectors and well-preserved reversed directions. The magnetostratigraphy and 〈sup〉40〈/sup〉Ar/〈sup〉39〈/sup〉Ar geochronologic data reported here indicate that the sampled OCVB volcanics were erupted between about 90 and 67 Ma, and show no significant change in the apparent pole position over that time. The OCVB extends from northeast China, across Northeast Russia to the Bering Straight. This belt is made up of both extrusive and intrusive rocks, with the extrusive rocks and their associated sediments being dominant. The whole belt important in interpreting the paleogeography of the region because it overlies many of the accreted terranes of Northeast Russia. Most importantly, it overlies parts of the Chukotka-Alaska block which is thought to have moved out of the Arctic Ocean region, as well as terranes accreted from the south. These latter terranes have been rafted northwards on the paleo-plates of the Pacific, implying that the present relative paleogeography of all of the terranes overlain by the OCVB were essentially in place by 67 Ma, and possibly as early as 90 Ma. However, comparing our paleomagnetic pole position for the OCVB with those for North America and Eurasia (a proxy for Siberia) shows a statistically significant displacement of the OCVB pole to the south west. This implies that not only the OCVB, but the underlying terranes of northeast Russia, experienced southerly displacement with respect to the Siberian and North American platforms since the Late Cretaceous.

Description: 〈b〉Tectonic reconstruction of Uda-Murgal arc and the Late Jurassic and Early Cretaceous convergent margin of Northeast Asia–Northwest Pacific〈/b〉〈br〉 S. D. Sokolov, G. Ye. Bondarenko, A. K. Khudoley, O. L. Morozov, M. V. Luchitskaya, M. I. Tuchkova, and P. W. Layer〈br〉 Stephan Mueller Spec. Publ. Ser., 4, 273-288, https://doi.org/10.5194/smsps-4-273-2009, 2009〈br〉 A long tectonic zone composed of Upper Jurassic to Lower Cretaceous volcanic and sedimentary rocks is recognized along the Asian continent margin from the Mongol-Okhotsk fold and thrust belt on the south to the Chukotka Peninsula on the north. This belt represents the Uda-Murgal arc, which was developed along the convergent margin between Northeast Asia and Northwest Meso-Pacific. Several segments are identified in this arc based upon the volcanic and sedimentary rock assemblages, their respective compositions and basement structures. The southern and central parts of the Uda-Murgal arc were a continental margin belt with heterogeneous basement represented by metamorphic rocks of the Siberian craton, the Verkhoyansk terrigenous complex of Siberian passive margin and the Koni-Taigonos Late Paleozoic to Early Mesozoic island arc with accreted oceanic terranes. At the present day latitude of the Pekulney and Chukotka segments there was an ensimatic island arc with relicts of the South Anyui oceanic basin in a backarc basin. Accretionary prisms of the Uda-Murgal arc and accreted terranes contain fragments of Permian, Triassic to Jurassic and Jurassic to Cretaceous (Tithonian–Valanginian) oceanic crust and Jurassic ensimatic island arcs. Paleomagnetic and faunal data show significant displacement of these oceanic complexes and the terranes of the Taigonos Peninsula were originally parts of the Izanagi oceanic plate.

Description: 〈b〉Provenance analysis and tectonic setting of the Triassic clastic deposits in Western Chukotka, Northeast Russia〈/b〉〈br〉 M. I. Tuchkova, S. Sokolov, and I. R. Kravchenko-Berezhnoy〈br〉 Stephan Mueller Spec. Publ. Ser., 4, 177-200, https://doi.org/10.5194/smsps-4-177-2009, 2009〈br〉 The study area is part of the Anyui subterrane of the Chukotka microplate, a key element in the evolution of the Amerasia Basin, located in Western Chukotka, Northeast Russia. The subterrane contains variably deformed, folded and cleaved rhythmic Triassic terrigenous deposits which represent the youngest stage of widespread marine deposition which form three different complexes: Lower-Middle Triassic, Upper Triassic (Carnian) and Upper Triassic (Norian). All of the complexes are represented by rhythmic interbeds of sandstone, siltstone and mudstone. Macrofaunas are not numerous, and in some cases deposits are dated by analogy to, or by their relationship with, other units dated with macrofaunas. The deposits are composed of pelagic sediments, low-density flows, high-density flows, and shelf facies associations suggesting that sedimentation was controlled by deltaic progradation on a continental shelf and subsequent submarine fan sedimentation at the base of the continental slope. Petrographic study of the mineral composition indicates that the sandstones are lithic arenites. Although the Triassic sandstones appear similar in outcrop and by classification, the constituent rock fragments are of diverse lithologies, and change in composition from lower grade metamorphic rocks in the Lower-Middle Triassic to higher grade metamorphic rocks in the Upper Triassic. This change suggests that the Triassic deposits represent an unroofing sequence as the source of the clastic material came from more deeply buried rocks with time.

Description: 〈b〉Multi-phase tectonic structures in the collision zone of the Kolyma-Omolon microcontinent and the eastern margin of the North Asian craton, Northeastern Russia〈/b〉〈br〉 A. V. Prokopiev and V. S. Oxman〈br〉 Stephan Mueller Spec. Publ. Ser., 4, 65-70, https://doi.org/10.5194/smsps-4-65-2009, 2009〈br〉 The sequence of formation of structures is established in the zone of junction of the eastern margin of the North Asian craton and the northeastern flank of the Kolyma-Omolon microcontinent, in the area of bend of the Kolyma structural loop. Detailed structural studies revealed two phases in the formation of Mesozoic structures – an early thrust phase and a late strike-slip phase. Structures formed during each of the phases are described. Thrust structures are represented by the Setakchan nappe on which the minimum amount of horizontal displacement is estimated at 13–15 km. Later superposed left-lateral strike-slip faults have a north strike. Formation of these latter structures occurred during the second phase of collision between the Kolyma-Omolon microcontinent and the eastern margin of the North Asian craton.

Description: 〈b〉Geology of the Shelves surrounding the New Siberian Islands, Russian Arctic〈/b〉〈br〉 D. Franke and K. Hinz〈br〉 Stephan Mueller Spec. Publ. Ser., 4, 35-44, https://doi.org/10.5194/smsps-4-35-2009, 2009〈br〉 A total of 11 700 km of multichannel seismic reflection data were acquired during recent reconnaissance surveys of the wide, shallow shelves of the Laptev and western East Siberian Seas around the New Siberian Islands. To the north of the Laptev Sea, the Gakkel Ridge, an active mid-ocean ridge which separates the North American and Eurasian Plates, meets abruptly the steep slope of the continental shelf. Extension has affected the Laptev Shelf since at least the Early Tertiary and has resulted in the formation of three major, generally north-south trending rift basins: the Ust' Lena Rift, the Anisin Basin, and the New Siberian Basin. Our data indicate that the rift basins on the Laptev Shelf are not continuous with those on the East Siberian Shelf. The latter shelf can best be described as an epicontinental platform which has undergone continuous subsidence since the Late Cretaceous. The greatest subsidence occurred in the NE, manifested by a major depocentre filled with inferred (?)Late Cretaceous to Tertiary sediments up to 5 s (twt) thick. On the basis of deep reflection data we revise and adjust Mesozoic domain boundaries around the New Siberian Islands.

Description: 〈b〉A seismic swarm near Neshkan, Chukotka, northeastern Russia, and implications for the boundary of the Bering plate〈/b〉〈br〉 K. G. Mackey, K. Fujita, B. M. Sedov, L. V. Gounbina, and S. Kurtkin〈br〉 Stephan Mueller Spec. Publ. Ser., 4, 261-271, https://doi.org/10.5194/smsps-4-261-2009, 2009〈br〉 A seismic swarm lasting over two years occurred near the village of Neshkan, Chukotka, far northeastern Russia, beginning with a 〈i〉M〈sub〉L〈/sub〉〈/i〉, 4.2 (4.1 〈i〉m〈sub〉b〈/sub〉〈/i〉) earthquake on 9 December 2002. The swarm generated considerable anxiety among the local populace and authorities. Two temporary seismic stations were deployed during the latter part of September 2003, and recorded over 150 events with magnitudes up to 3.0. Eighteen locatable events appear to form a northeast striking linear trend, parallel to other seismicity trends in Chukotka, extending 20 km to the southwest from the village. We interpret this trend as a previously unknown fault. A small pond located ~1 km west of the village drained and some apparent surface deformation was observed over the course of the earthquake sequence. Relocation of historic seismicity in the region shows that a magnitude 6.0 in 1996 may have ruptured an adjacent fault segment. Other, less well located but larger, teleseismic events earlier in the 20th century may also have occurred on or near this fault. The seismicity is consistent a proposed region of transtension along the northern boundary of a Bering plate.

Description: 〈b〉South Anyui suture: tectono-stratigraphy, deformations, and principal tectonic events〈/b〉〈br〉 S. D. Sokolov, G. Ye. Bondarenko, P. W. Layer, and I. R. Kravchenko-Berezhnoy〈br〉 Stephan Mueller Spec. Publ. Ser., 4, 201-221, https://doi.org/10.5194/smsps-4-201-2009, 2009〈br〉 Geochronologic and structural data from the terranes of the South Anyui suture zone record a protracted deformational history before, during and after an Early Cretaceous collision of the passive margin of the Chukotka-Arctic Alaska continental block with the active continental margin of the North Asian continent. Preceding this collision, the island arc complexes of the Yarakvaam terrane on the northern margin of the North Asian craton record Early Carboniferous to Neocomian ages in ophiolite, sedimentary, and volcanic rocks. Triassic to Jurassic amphibolites constrain the timing of subduction and intraoceanic deformation along this margin. The protracted (Neocomian to Aptian) collision of the Chukotka passive margin with the North Asian continent is preserved in a range of structural styles including first north verging folding, then south verging folding, and finally late collisional dextral strike slip motions which likely record a change from orthogonal collision to oblique collision. Due to this collision, the southern passive margin of Chukotka was overthrust by tectonic nappes composed of tectono-stratigraphic complexes of the South Anyui terrane. Greenschists with ages of 115–119 Ma are related to the last stages of this collision. The postcollisional orogenic stage (Albian to Cenomanian) is characterized by sinistral strike slip faults and an extensional environment.

Description: 〈b〉Deformation of the Northwestern Okhotsk Plate: How is it happening?〈/b〉〈br〉 D. Hindle, K. Fujita, and K. Mackey〈br〉 Stephan Mueller Spec. Publ. Ser., 4, 147-156, https://doi.org/10.5194/smsps-4-147-2009, 2009〈br〉 The Eurasia (EU) – North America (NA) plate boundary zone across Northeast Asia still presents many open questions within the plate tectonic paradigm. Constraining the geometry and number of plates or microplates present in the plate boundary zone is especially difficult because of the location of the EU-NA euler pole close to or even upon the EU-NA boundary. One of the major challenges remains the geometry of the Okhotsk plate (OK). whose northwestern portion terminates on the EU-OK-NA triple junction and is thus caught and compressed between converging EU and NA. We suggest that this leads to a coherent and understandable large scale deformation pattern of mostly northwest-southeast trending strike-slip faults which split Northwest OK into several extruding slivers. When the fault geometry is analysed together with space geodetic and focal mechanism data it suggests a central block which is extruding faster bordered east and west by progressively slower extruding blocks until the OK plate boundary faults are encountered. Taking into account elastic loading from both the intra-OK faults and the OK-Pacific (PA) boundary reconciles geodetic motions with geologic slip rates on at least the OK-NA boundary which corresponds to the Ulakhan fault.

Description: 〈b〉The Tommot pluton: a Middle Paleozoic rift-related alkaline gabbro and syenite complex, Yakutia, northeast Russia〈/b〉〈br〉 V. A. Trunilina, P. W. Layer, L. M. Parfenov, A. I. Zaitsev, and Y. S. Orlov〈br〉 Stephan Mueller Spec. Publ. Ser., 4, 97-109, https://doi.org/10.5194/smsps-4-97-2009, 2009〈br〉 The Tommot pluton is located within the continental Omulevka terrane of the inner zone of the Verkhoyansk-Kolyma Mesozoic orogen. It is a small complex (~12 km〈sup〉2〈/sup〉) composed of alkaline-ultramafic rocks, alkaline and subalkaline gabbroids, and alkaline and quartz syenites. The pluton is unique both in the composition and age of its constituent rocks. Mineralogical-petrographical and geochemical studies of the rocks indicate that the alkaline rocks resulted from the melting of depleted mantle horizons. K-Ar, Rb-Sr, and 〈sup〉40〈/sup〉Ar/〈sup〉39〈/sup〉Ar age determinations confirm a Paleozoic age of the rocks. Formation of the alkaline rocks is related to Middle Paleozoic rifting which occurred as two discrete events: a Late Devonian event, which affected the marginal part of the Siberian continent, and a Late Carboniferous event that reflects internal deformation of the Omulevka terrane or late-stage extension. A spatially associated alkali granite, the Somnitel'nyy pluton, is Late Jurassic–Early Cretaceous in age and is synchronous with accretion of the Kolyma-Omolon Superterrane to Siberia in the Mesozoic.

Description: 〈b〉Biography – Leonid M. Parfenov (1937–2002)〈/b〉〈br〉 K. Fujita, A. V. Prokopiev, and D. B. Stone〈br〉 Stephan Mueller Spec. Publ. Ser., 4, 5-9, https://doi.org/10.5194/smsps-4-5-2009, 2009〈br〉

Description: 〈b〉Geochronology and thermochronology of Cretaceous plutons and metamorphic country rocks, Anyui-Chukotka fold belt, North East Arctic Russia〈/b〉〈br〉 E. L. Miller, S. M. Katkov, A. Strickland, J. Toro, V. V. Akinin, and T. A. Dumitru〈br〉 Stephan Mueller Spec. Publ. Ser., 4, 157-175, https://doi.org/10.5194/smsps-4-157-2009, 2009〈br〉 U-Pb isotopic dating of seven granitoid plutons and associated intrusions from the Bilibino region (Arctic Chukotka, Russia) was carried out using the SHRIMP-RG. The crystallization ages of these granitoids, which range from approximately 116.9±2.5 to 108.5±2.7 Ma, bracket two regionally significant deformational events. The plutons cut folds, steep foliations and thrust-related structures related to sub-horizontal shortening at lower greenschist facies conditions (〈i〉D〈/i〉〈sub〉1〈/sub〉), believed to be the result of the collision of the Arctic Alaska-Chukotka microplate with Eurasia along the South Anyui Zone (SAZ). Deformation began in the Late Jurassic, based on fossil ages of syn-orogenic clastic strata, and involves strata as young as early Cretaceous (Valanginian) north of Bilibino and as young as Hauterivian-Barremian, in the SAZ. The second phase of deformation (〈i〉D〈/i〉〈sub〉2〈/sub〉) is developed across a broad region around and to the east of the Lupveem batholith of the Alarmaut massif and is interpreted to be coeval with magmatism. 〈i〉D〈/i〉〈sub〉2〈/sub〉 formed gently-dipping, high-strain foliations (〈i〉S〈/i〉〈sub〉2〈/sub〉). Growth of biotite, muscovite and actinolite define 〈i〉S〈/i〉〈sub〉2〈/sub〉 adjacent to the batholith, while chlorite and white mica define 〈i〉S〈/i〉〈sub〉2〈/sub〉 away from the batholith. Sillimanite (± andalusite) at the southeastern edge the Lupveem batholith represent the highest grade metamorphic minerals associated with 〈i〉D〈/i〉〈sub〉2〈/sub〉. 〈i〉D〈/i〉〈sub〉2〈/sub〉 is interpreted to have developed during regional extension and crustal thinning. Extension directions as measured by stretching lineations, quartz veins, boudinaged quartz veins is NE-SW to NW-SE. Mapped dikes associated with the plutons trend mostly NW-SE and indicate NE-SW directed extension. 〈sup〉40〈/sup〉Ar/〈sup〉39〈/sup〉Ar ages from 〈i〉S〈/i〉〈sub〉2〈/sub〉 micas range from 109.3±1.2 to 103.0±1.8 Ma and are interpreted as post-crystallization cooling ages following a protracted period of magmatism and high heat flow. Regional uplift and erosion of many kilometers of cover produced a subdued erosional surface prior to the eruption of volcanic rocks of the Okhotsk-Chukotka volcanic belt (OCVB) whose basal units (~87 Ma) overlie this profound regional unconformity. A single fission track age on apatite from granite in the Alarmaut massif yielded an age of 90±11 Ma, in good agreement with this inference.

Description: 〈b〉Summary of Northeast Asia geodynamics and tectonics*〈/b〉〈br〉 L. M. Parfenov, G. Badarch, N. A. Berzin, A. I. Khanchuk, M. I. Kuzmin, W. J. Nokleberg, A. V. Prokopiev, M. Ogasawara, and H. Yan〈br〉 Stephan Mueller Spec. Publ. Ser., 4, 11-33, https://doi.org/10.5194/smsps-4-11-2009, 2009〈br〉 The compilation, synthesis, description, and interpretation of regional geology and tectonics of major regions, such as Northeast Asia (Eastern Russia, Mongolia, Northern China, South Korea, and Japan) and the Circum-North Pacific (the Russian Far East, Alaska, and Canadian Cordillera), requires a complex methodology that includes: (1) definitions of key terms; (2) compilation of a regional geodynamics map that can be constructed according to modern tectonic concepts and definitions; and (3) formulation of a comprehensive tectonic model. This article presents a summary of the regional dynamics and tectonics of Northeast Asia as developed for a new summary geodynamics map of the region. This article also describes how a high-quality summary geodynamics map and companion tectonic analysis substantially aids in the understanding of the origin of major rock units, major structures, and contained mineral and fuel resources, and provides important guidelines for new research. 〈br〉〈br〉 * Prepared in memory of Leonid M. Parfenov, the leader of the geodynamics map team for the International collaborative project on NE Asia tectonics and metallogenesis.

Description: 〈b〉Detrital zircon geochronologic tests of the SE Siberia-SW Laurentia paleocontinental connection〈/b〉〈br〉 J. S. MacLean, J. W. Sears, K. R. Chamberlain, A. K. Khudoley, A. V. Prokopiev, A. P. Kropachev, and G. G. Serkina〈br〉 Stephan Mueller Spec. Publ. Ser., 4, 111-116, https://doi.org/10.5194/smsps-4-111-2009, 2009〈br〉 Strikingly similar Late Mesoproterozoic stratigraphic sequences and correlative U-Pb detrital-zircon ages may indicate that the Sette Daban region of southeastern Siberia and the Death Valley region of southwestern North America were formerly contiguous parts of a Grenville foreland basin. The Siberian section contains large numbers of detrital zircons that correlate with Grenville, Granite-Rhyolite, and Yavapai basement provinces of North America. The sections in both Siberia and Death Valley exhibit west-directed thrust faults that may represent remnants of a Grenville foreland thrust belt. North American detrital-zircon components do not occur in Siberian samples above a ~600 Ma breakup unconformity, suggesting that rifting and continental separation blocked transfer of clastic sediment between the cratons by 600 Ma. Faunal similarities suggest, however, that the two cratons remained within the breeding ranges of Early Cambrian trilobites and archeocyathans.

Description: 〈b〉Seismotectonics of the Chersky Seismic Belt, eastern Sakha Republic (Yakutia) and Magadan District, Russia〈/b〉〈br〉 K. Fujita, B. M. Koz'min, K. G. Mackey, S. A. Riegel, M. S. McLean, and V. S. Imaev〈br〉 Stephan Mueller Spec. Publ. Ser., 4, 117-145, https://doi.org/10.5194/smsps-4-117-2009, 2009〈br〉 The Chersky seismic belt represents a zone of deformation between the North American and Eurasian plates in northeast Russia. The belt extends from the Laptev Sea into the Chersky Range where it splits into two branches. One branch extends to Kamchatka and the Aleutian-Kurile Junction, while the other branch extends south towards Sakhalin Island. Focal mechanisms indicate a change from extension to transpression in the northern Verkhoyansk Range and generally left-lateral transpression in the Chersky Range extending to northern Kamchatka. The few focal mechanisms on the second branch suggest right-lateral transpression. A large number of faults, sub-parallel to the seismicity and presumed to be strike-slip, are visible in satellite imagery and topographic maps and are also associated with seismically generated landslides. 〈br〉〈br〉 These data support a model in which the Sea of Okhotsk forms the core of a separate Okhotsk microplate surrounded by diffuse boundaries on the north and west. Microseismicity in continental northeast Russia is most heavily concentrated within and between the fault systems along the northern boundary of the proposed Okhotsk plate and indicates a high level of deformation. The sense of slip on the faults (both from focal mechanisms and geology) are also generally consistent with the extrusion of the Okhotsk plate to the southeast as it is compressed between its larger neighbors. The northernmost part of the Okhotsk plate may be decoupled to some degree from the more stable central Sea of Okhotsk.

Description: 〈b〉Review of geology of the New Siberian Islands between the Laptev and the East Siberian Seas, North East Russia〈/b〉〈br〉 M. Kos'ko and E. Korago〈br〉 Stephan Mueller Spec. Publ. Ser., 4, 45-64, https://doi.org/10.5194/smsps-4-45-2009, 2009〈br〉 The New Siberian Islands comprise De Long Islands, Anjou Islands, and Lyakhov Islands. Early Paleozoic, Mesozoic and Cenozoic sediments and igneous rocks are known on the De Long Islands. Cambrian slate, siltstone, mudstone and silicified limestone occur on Bennett Island. Ordovician volcanogenic turbidites, lavas, and small intrusions of andesite-basalt, basalt, dolerite, and porphyritic diorite were mapped on Henrietta Island. The igneous rocks are of calc-alkaline island arc series. The Ordovician age of the sequence was defined radiometrically. Early Paleozoic strata were faulted and folded presumably in the Caledonian time. Early Cretaceous sandstone and mudstone are known on Bennett Island. They are overlain by a 106–124 Ma basalt unit. Cenozoic volcanics are widespread on the De Long Islands. Zhokhov Island is an eroded stratovolcano. The volcanics are mostly of picrite-olivine type and limburgite. Radiometric dating indicates Miocene to Recent ages for Cenozoic volcanism. 〈br〉〈br〉 On the Anjou islands Lower-Middle Paleozoic strata consist of carbonates, siliciclastics, and clay. A Northwest-southeast syn-sedimentary facies zonation has been reconstructed. Upper Paleozoic strata are marine carbonate, clay and siliciclastic facies. Mudstone and clay predominate in the Triassic to Upper Jurassic section. Aptian-Albian coal bearing deposits uconformably overlap lower strata indicating Early Cretaceous tectonism. Upper Cretaceous units are mostly clay and siltstone with brown coal strata resting on Early Cretaceous weathered rhyolite. Cenozoic marine and nonmarine silisiclastics and clay rest upon the older units with a transgressive unconformity including a weathering profile in the older rocks. 〈br〉〈br〉 Manifestations of Paleozoic and Triassic mafic and Cretaceous acidic magmatism are also found on these islands. The pre-Cretaceous structure of the Anjou islands is of a block and fold type Late Cimmerian in age followed by faulting in Cenozoic time. 〈br〉〈br〉 The Lyakhov islands are located at the western end of the Late Cimmerian South Anyui suture. Sequences of variable age, composition, and structural styles are known on the Lyakhov Islands. These include an ancient metamorphic sequence, Late Paleozoic ophiolitic sequence, Late Mesozoic turbidite sequence, Cretaceous granites, and Cenozoic sediments. Fold and thrust imbricate structures have been mapped on southern Bol'shoi Lyakhov Island. North-northwestern vergent thrusts transect the Island and project offshore. Open folds of Jurassic–Early Cretaceous strata are characteristic of Stolbovoi and Malyi Lyakhov islands. 〈br〉〈br〉 Geology of the New Siberian Islands supports the concept of a circum Arctic Phanerozoic fold belt. The belt is comprised of Caledonian, Ellesmerian, Early Cimmerian and Late Cimmerian fold systems, manifested in many places on the mainland and on islands around the Arctic Ocean. Knowledge of the geology of the New Siberian Islands has been used to interpret anomalous gravity and magnetic field maps and Multi Channel Seismic (MCS) lines. Two distinguishing structural stages are universally recognized within the offshore sedimentary cover which correlate with the onshore geology of the New Siberian Islands. Dating of the upper structural stage and constituent seismic units is based on structural and stratigraphic relationships between Late Mesozoic and Cenozoic units in the archipelago. The Laptev Sea–western East Siberian Sea seismostratigraphic model for the upper structural stage has much in common with the seismostratigraphic model in the American Chukchi Sea.

Description: 〈b〉Editors and Acknowledgement〈/b〉〈br〉 〈br〉 Stephan Mueller Spec. Publ. Ser., 4, 1-1, https://doi.org/10.5194/smsps-4-1-2009, 2009〈br〉

Description: 〈b〉Late Pleistocene palaeoproductivity patterns during the last climatic cycle in the Guyana Basin as revealed by calcareous nannoplankton〈/b〉〈br〉 G.-E. López-Otálvaro, J. A. Flores, F. J. Sierro, I. Cacho, J.-O. Grimalt, E. Michel, E. Cortijo, and L. Labeyrie〈br〉 eEarth, 4, 1-13, doi:10.5194/ee-4-1-2009, 2009〈br〉 Variations in the assemblage and abundance of coccoliths reveal changes in oceanic and atmospheric dynamics in the Guyana Basin over the last climatic cycle, mainly linked to latitudinal variations in the ITCZ (Intertropical Convergence Zone). Records of the N ratio (a palaeoproductivity index of coccolithophores) allowed us to monitor nutri-thermocline fluctuations. Nannofossil accumulation rates (NAR) vary closely with the N ratio, indicating a strong correlation between these two palaeoproductivity proxies. Decreases in the N ratio and NAR values suggest lower palaeoproductivity during glacial substages, indicating a deep nutri-thermocline (deep stratification of the mixed layer) as a consequence of the piling up of warm water dragged by the NEC. This setting was favoured by the southern shift of the ITCZ and Trade winds which blew perpendicular to the Guyana coast. By contrast, increases in the N ratio and NAR values revealed higher palaeoproductivity during interglacial substages, suggesting a shoaling of the nutri-thermocline. This scenario is favoured by a northward displacement of the ITCZ with the southeast Trade winds blowing alongshore. Additionally, palaeoproductivity changes during substages of Marine Isotope Stage (MIS) 6-5 are of much higher amplitude than those recorded in substages of MIS 4-2 and the early Holocene. Similarities between the palaeoproductivity and the 65° N summer insolation records, suggest a link between the depth of nutri-thermocline, the latitudinal migration of the ITCZ and ice-sheet changes in the Northern Hemisphere.

Description: 〈b〉Geotectonic setting of the Tertiary Uyandina and Indigirka-Zyryanka basins, Republic Sakha (Yakutia), Northeast Russia, using coal rank data〈/b〉〈br〉 H.-J. Paech〈br〉 Stephan Mueller Spec. Publ. Ser., 4, 85-96, https://doi.org/10.5194/smsps-4-85-2009, 2009〈br〉 Outcrops along the Inach River in the Uyandina basin and those along the Myatis' River in the Indigirka-Zyryanka basin were studied in detail and sampled for coal rank determinations. The Uyandina basin is an intramontane pull-apart basin characterized by extensional structures within the Moma rift system. The coal rank is below 0.3% vitrinite reflectance (〈i〉R〈sub〉r〈/sub〉〈/i〉), which indicates shallow, immature conditions of basin formation and very low subsidence. The Myatis' River coal-bearing outcrops in the Indigirka-Zyryanka basin reveal compression induced by continent collision. The compressive deformation includes also lowermost Pliocene strata. Due to the position in the Verkhoyansk-Chersky fold belt adjacent to the Kolyma-Omolon microcontinent the Indigirka-Zyryanka basin has much in common with a foredeep, i.e. the asymmetry in thickness and tectonic structure. The vitrinite reflectance data (〈i〉R〈sub〉r〈/sub〉〈/i〉) which range from 0.25% to more than 5% reinforce the accepted models that describe basin subsidence and geothermal history and the tectonic deformation.

Description: 〈b〉Structural studies near Pevek, Russia: implications for formation of the East Siberian Shelf and Makarov Basin of the Arctic Ocean〈/b〉〈br〉 E. L. Miller and V. E. Verzhbitsky〈br〉 Stephan Mueller Spec. Publ. Ser., 4, 223-241, https://doi.org/10.5194/smsps-4-223-2009, 2009〈br〉 The Pevek region of Arctic Russia provides excellent beach cliff exposure of sedimentary and igneous rocks that yield detailed information on the nature, progression and timing of structural events in this region. Regional folding and thrust faulting, with the development of a south-dipping axial plane cleavage/foliation developed during N-S to NE-SW directed shortening and formation of the Chukotka-Anyui fold belt. This deformation involves strata as young as Valanginian (136–140 Ma, Gradstein et al., 2004). Fold-related structures are cut by intermediate to silicic batholiths, plutons and dikes of Cretaceous age. Reported K-Ar whole rock and mineral ages on the granitoids range from 144 to 85 Ma, but to the south, more reliable U-Pb zircon ages on compositionally similar plutons yield a much narrower age range of ~120–105 Ma (Miller et al., this volume) and a pluton in Pevek yields a U-Pb age on zircon of 108.1±1.1 Ma with evidence for inheritance of slightly older 115 Ma zircons. Magmas were intruded during an episode of E-W to ENE-WSW directed regional extension based on the consistent N-S to NNW-SSE orientation of over 800 mapped dikes and quartz veins. Analysis of small-offset faults and slickensides yield results compatible with those inferred from the dikes. Younger tectonic activity across this region is minor and the locus of magmatic activity moved southward towards the Pacific margin as represented by the 〈90 Ma Okhotsk-Chukotsk volcanic belt (OCVB). A lengthy period of uplift and erosion occurred after emplacement of Cretaceous plutons and produced the peneplain beneath the younger OCVB. 〈br〉〈br〉 Based on our studies, we speculate that ~120–105 Ma magmatism, which heralds a change in tectonic regime from compression to extension, could represent one of the consequences of the inception of rifting in the Amerasian Basin of the Arctic, forming the Makarov Basin north of the Siberian shelf at this longitude. A synthesis of available seismic reflection, gravity and magnetic data for the offshore Siberian Shelf reveals a widespread, seismically mappable basement-sedimentary cover contact that deepens northward towards the edge of the shelf with few other significant basins. Various ages have been assigned to the oldest strata above the unconformity, ranging from Cretaceous (Albian – 112–100 Ma) to Tertiary (Paleocene–Eocene – ~60–50 Ma). The period of uplift and erosion documented along the Arctic coast of Russia at this longitude could represent the landward equivalent of the (yet undrilled) offshore basement-sedimentary cover contact, thus overlying sedimentary sequences could be as old as early Late Cretaceous. Although quite speculative, these conclusions suggest that land-based geologic, structural, petrologic and geochronologic studies could provide useful constraints to help resolve the plate tectonic history of the Arctic Ocean.

Description: 〈b〉Middle Paleozoic-Mesozoic boundary of the North Asian craton and the Okhotsk terrane: new geochemical and geochronological data and their geodynamic interpretation〈/b〉〈br〉 A. V. Prokopiev, J. Toro, J. K. Hourigan, A. G. Bakharev, and E. L. Miller〈br〉 Stephan Mueller Spec. Publ. Ser., 4, 71-84, https://doi.org/10.5194/smsps-4-71-2009, 2009〈br〉 The Okhotsk terrane, located east of the South Verkhoyansk sector of the Verkhoyansk fold-and-thrust belt, has Archean crystalline basement and Riphean to Early Paleozoic sedimentary cover similar to that of the adjacent the North Asian craton. However, 2.6 Ga biotite orthogneisses of the Upper Maya uplift of the Okhotsk terrane yielded Early Devonian 〈sup〉40〈/sup〉Ar/〈sup〉39〈/sup〉Ar cooling ages, evidence of a Mid-Paleozoic metamorphic event not previously known. These gneisses are also intruded by 375±2 Ma (Late Devonian) calc-alkaline granodiorite plutons that we interpret as part of a continental margin volcanic arc. Therefore, Late Devonian rifting, which affected the entire eastern margin of North Asia separating the Okhotsk terrane from the North Asian craton, was probably a back-arc event. 〈br〉〈br〉 Our limited 〈sup〉40〈/sup〉Ar/〈sup〉39〈/sup〉Ar data from the South Verkhoyansk metamorphic belt suggests that low grade metamorphism and deformation started in the Late Jurassic due to accretion of the Okhotsk terrane to the North Asia margin along the Bilyakchan fault. Shortening and ductile strain continued in the core of the South Verkhoyansk metamorphic belt until about 120 Ma due to paleo-Pacific subduction along the Uda-Murgal continental margin arc.

Description: 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 cutting 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 sectioning shows 3-D connectivity of the pore space. These findings call for reinterpretation of 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: 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 E+27 kgm2s−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 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. 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: 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: In the present study we present preliminary results of Zakynthos Alikes lagoon, which 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 palaeonvironmental changes, we based on the data of 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 were 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 study sediments is about 8500 BP. The rate of sedimentation between 8280 BP and 5590 BP was 5.3 mm/yr and between 5590 BP and modern times 1.03 mm/yr. The rate of sedimentation was higher until mid-Holocene while decrease after to 1.03 mm/yr, results which are similar to other coastal areas of western Greece.

Description: The New Siberian Islands comprise De Long Islands, Anjou Islands, and Lyakhov Islands. Early Paleozoic, Mesozoic and Cenozoic sediments and igneous rocks are known on the De Long Islands. Cambrian slate, siltstone, mudstone and silicified limestone occur on Bennett Island. Ordovician volcanogenic turbidites, lavas, and small intrusions of andesite-basalt, basalt, dolerite, and porphyritic diorite were mapped on Henrietta Island. The igneous rocks are of calc-alkaline island arc series. The Ordovician age of the sequence was defined radiometrically. Early Paleozoic strata were faulted and folded presumably in the Caledonian time. Early Cretaceous sandstone and mudstone are known on Bennett Island. They are overlain by a 106–124 Ma basalt unit. Cenozoic volcanics are widespread on the De Long Islands. Zhokhov Island is an eroded stratovolcano. The volcanics are mostly of picrite-olivine type and limburgite. Radiometric dating indicates Miocene to Recent ages for Cenozoic volcanism. On the Anjou islands Lower-Middle Paleozoic strata consist of carbonates, siliciclastics, and clay. A Northwest-southeast syn-sedimentary facies zonation has been reconstructed. Upper Paleozoic strata are marine carbonate, clay and siliciclastic facies. Mudstone and clay predominate in the Triassic to Upper Jurassic section. Aptian-Albian coal bearing deposits uconformably overlap lower strata indicating Early Cretaceous tectonism. Upper Cretaceous units are mostly clay and siltstone with brown coal strata resting on Early Cretaceous weathered rhyolite. Cenozoic marine and nonmarine silisiclastics and clay rest upon the older units with a transgressive unconformity including a weathering profile in the older rocks. Manifestations of Paleozoic and Triassic mafic and Cretaceous acidic magmatism are also found on these islands. The pre-Cretaceous structure of the Anjou islands is of a block and fold type Late Cimmerian in age followed by faulting in Cenozoic time. The Lyakhov islands are located at the western end of the Late Cimmerian South Anyui suture. Sequences of variable age, composition, and structural styles are known on the Lyakhov Islands. These include an ancient metamorphic sequence, Late Paleozoic ophiolitic sequence, Late Mesozoic turbidite sequence, Cretaceous granites, and Cenozoic sediments. Fold and thrust imbricate structures have been mapped on southern Bol'shoi Lyakhov Island. North-northwestern vergent thrusts transect the Island and project offshore. Open folds of Jurassic–Early Cretaceous strata are characteristic of Stolbovoi and Malyi Lyakhov islands. Geology of the New Siberian Islands supports the concept of a circum Arctic Phanerozoic fold belt. The belt is comprised of Caledonian, Ellesmerian, Early Cimmerian and Late Cimmerian fold systems, manifested in many places on the mainland and on islands around the Arctic Ocean. Knowledge of the geology of the New Siberian Islands has been used to interpret anomalous gravity and magnetic field maps and Multi Channel Seismic (MCS) lines. Two distinguishing structural stages are universally recognized within the offshore sedimentary cover which correlate with the onshore geology of the New Siberian Islands. Dating of the upper structural stage and constituent seismic units is based on structural and stratigraphic relationships between Late Mesozoic and Cenozoic units in the archipelago. The Laptev Sea–western East Siberian Sea seismostratigraphic model for the upper structural stage has much in common with the seismostratigraphic model in the American Chukchi Sea.

Description: Strikingly similar Late Mesoproterozoic stratigraphic sequences and correlative U-Pb detrital-zircon ages may indicate that the Sette Daban region of southeastern Siberia and the Death Valley region of southwestern North America were formerly contiguous parts of a Grenville foreland basin. The Siberian section contains large numbers of detrital zircons that correlate with Grenville, Granite-Rhyolite, and Yavapai basement provinces of North America. The sections in both Siberia and Death Valley exhibit west-directed thrust faults that may represent remnants of a Grenville foreland thrust belt. North American detrital-zircon components do not occur in Siberian samples above a ~600 Ma breakup unconformity, suggesting that rifting and continental separation blocked transfer of clastic sediment between the cratons by 600 Ma. Faunal similarities suggest, however, that the two cratons remained within the breeding ranges of Early Cambrian trilobites and archeocyathans.

Description: The Pevek region of Arctic Russia provides excellent beach cliff exposure of sedimentary and igneous rocks that yield detailed information on the nature, progression and timing of structural events in this region. Regional folding and thrust faulting, with the development of a south-dipping axial plane cleavage/foliation developed during N-S to NE-SW directed shortening and formation of the Chukotka-Anyui fold belt. This deformation involves strata as young as Valanginian (136–140 Ma, Gradstein et al., 2004). Fold-related structures are cut by intermediate to silicic batholiths, plutons and dikes of Cretaceous age. Reported K-Ar whole rock and mineral ages on the granitoids range from 144 to 85 Ma, but to the south, more reliable U-Pb zircon ages on compositionally similar plutons yield a much narrower age range of ~120–105 Ma (Miller et al., this volume) and a pluton in Pevek yields a U-Pb age on zircon of 108.1±1.1 Ma with evidence for inheritance of slightly older 115 Ma zircons. Magmas were intruded during an episode of E-W to ENE-WSW directed regional extension based on the consistent N-S to NNW-SSE orientation of over 800 mapped dikes and quartz veins. Analysis of small-offset faults and slickensides yield results compatible with those inferred from the dikes. Younger tectonic activity across this region is minor and the locus of magmatic activity moved southward towards the Pacific margin as represented by the

Description: 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 R=26.3°±8.5°, F=8.1°±2.5° with respect to the North American Plate and R=38°±8.8°, F=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: 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 fo2 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: The study area is part of the Anyui subterrane of the Chukotka microplate, a key element in the evolution of the Amerasia Basin, located in Western Chukotka, Northeast Russia. The subterrane contains variably deformed, folded and cleaved rhythmic Triassic terrigenous deposits which represent the youngest stage of widespread marine deposition which form three different complexes: Lower-Middle Triassic, Upper Triassic (Carnian) and Upper Triassic (Norian). All of the complexes are represented by rhythmic interbeds of sandstone, siltstone and mudstone. Macrofaunas are not numerous, and in some cases deposits are dated by analogy to, or by their relationship with, other units dated with macrofaunas. The deposits are composed of pelagic sediments, low-density flows, high-density flows, and shelf facies associations suggesting that sedimentation was controlled by deltaic progradation on a continental shelf and subsequent submarine fan sedimentation at the base of the continental slope. Petrographic study of the mineral composition indicates that the sandstones are lithic arenites. Although the Triassic sandstones appear similar in outcrop and by classification, the constituent rock fragments are of diverse lithologies, and change in composition from lower grade metamorphic rocks in the Lower-Middle Triassic to higher grade metamorphic rocks in the Upper Triassic. This change suggests that the Triassic deposits represent an unroofing sequence as the source of the clastic material came from more deeply buried rocks with time.

Description: A seismic swarm lasting over two years occurred near the village of Neshkan, Chukotka, far northeastern Russia, beginning with a ML, 4.2 (4.1 mb) earthquake on 9 December 2002. The swarm generated considerable anxiety among the local populace and authorities. Two temporary seismic stations were deployed during the latter part of September 2003, and recorded over 150 events with magnitudes up to 3.0. Eighteen locatable events appear to form a northeast striking linear trend, parallel to other seismicity trends in Chukotka, extending 20 km to the southwest from the village. We interpret this trend as a previously unknown fault. A small pond located ~1 km west of the village drained and some apparent surface deformation was observed over the course of the earthquake sequence. Relocation of historic seismicity in the region shows that a magnitude 6.0 in 1996 may have ruptured an adjacent fault segment. Other, less well located but larger, teleseismic events earlier in the 20th century may also have occurred on or near this fault. The seismicity is consistent a proposed region of transtension along the northern boundary of a Bering plate.

Description: U-Pb isotopic dating of seven granitoid plutons and associated intrusions from the Bilibino region (Arctic Chukotka, Russia) was carried out using the SHRIMP-RG. The crystallization ages of these granitoids, which range from approximately 116.9±2.5 to 108.5±2.7 Ma, bracket two regionally significant deformational events. The plutons cut folds, steep foliations and thrust-related structures related to sub-horizontal shortening at lower greenschist facies conditions (D1), believed to be the result of the collision of the Arctic Alaska-Chukotka microplate with Eurasia along the South Anyui Zone (SAZ). Deformation began in the Late Jurassic, based on fossil ages of syn-orogenic clastic strata, and involves strata as young as early Cretaceous (Valanginian) north of Bilibino and as young as Hauterivian-Barremian, in the SAZ. The second phase of deformation (D2) is developed across a broad region around and to the east of the Lupveem batholith of the Alarmaut massif and is interpreted to be coeval with magmatism. D2 formed gently-dipping, high-strain foliations (S2). Growth of biotite, muscovite and actinolite define S2 adjacent to the batholith, while chlorite and white mica define S2 away from the batholith. Sillimanite (± andalusite) at the southeastern edge the Lupveem batholith represent the highest grade metamorphic minerals associated with D2. D2 is interpreted to have developed during regional extension and crustal thinning. Extension directions as measured by stretching lineations, quartz veins, boudinaged quartz veins is NE-SW to NW-SE. Mapped dikes associated with the plutons trend mostly NW-SE and indicate NE-SW directed extension. 40Ar/39Ar ages from S2 micas range from 109.3±1.2 to 103.0±1.8 Ma and are interpreted as post-crystallization cooling ages following a protracted period of magmatism and high heat flow. Regional uplift and erosion of many kilometers of cover produced a subdued erosional surface prior to the eruption of volcanic rocks of the Okhotsk-Chukotka volcanic belt (OCVB) whose basal units (~87 Ma) overlie this profound regional unconformity. A single fission track age on apatite from granite in the Alarmaut massif yielded an age of 90±11 Ma, in good agreement with this inference.

Description: Geochronologic and structural data from the terranes of the South Anyui suture zone record a protracted deformational history before, during and after an Early Cretaceous collision of the passive margin of the Chukotka-Arctic Alaska continental block with the active continental margin of the North Asian continent. Preceding this collision, the island arc complexes of the Yarakvaam terrane on the northern margin of the North Asian craton record Early Carboniferous to Neocomian ages in ophiolite, sedimentary, and volcanic rocks. Triassic to Jurassic amphibolites constrain the timing of subduction and intraoceanic deformation along this margin. The protracted (Neocomian to Aptian) collision of the Chukotka passive margin with the North Asian continent is preserved in a range of structural styles including first north verging folding, then south verging folding, and finally late collisional dextral strike slip motions which likely record a change from orthogonal collision to oblique collision. Due to this collision, the southern passive margin of Chukotka was overthrust by tectonic nappes composed of tectono-stratigraphic complexes of the South Anyui terrane. Greenschists with ages of 115–119 Ma are related to the last stages of this collision. The postcollisional orogenic stage (Albian to Cenomanian) is characterized by sinistral strike slip faults and an extensional environment.

Description: The Eurasia (EU) – North America (NA) plate boundary zone across Northeast Asia still presents many open questions within the plate tectonic paradigm. Constraining the geometry and number of plates or microplates present in the plate boundary zone is especially difficult because of the location of the EU-NA euler pole close to or even upon the EU-NA boundary. One of the major challenges remains the geometry of the Okhotsk plate (OK). whose northwestern portion terminates on the EU-OK-NA triple junction and is thus caught and compressed between converging EU and NA. We suggest that this leads to a coherent and understandable large scale deformation pattern of mostly northwest-southeast trending strike-slip faults which split Northwest OK into several extruding slivers. When the fault geometry is analysed together with space geodetic and focal mechanism data it suggests a central block which is extruding faster bordered east and west by progressively slower extruding blocks until the OK plate boundary faults are encountered. Taking into account elastic loading from both the intra-OK faults and the OK-Pacific (PA) boundary reconciles geodetic motions with geologic slip rates on at least the OK-NA boundary which corresponds to the Ulakhan fault.

Description: 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 Ds=300.7°, Is=48.7°, α95=10.9°, k-value=11.8, n=17. The B component paleolatitude calculated from the Fisher mean in stratigraphic coordinates and associated statistics are λobs=30.4° N or S, λ95=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: The Okhotsk terrane, located east of the South Verkhoyansk sector of the Verkhoyansk fold-and-thrust belt, has Archean crystalline basement and Riphean to Early Paleozoic sedimentary cover similar to that of the adjacent the North Asian craton. However, 2.6 Ga biotite orthogneisses of the Upper Maya uplift of the Okhotsk terrane yielded Early Devonian 40Ar/39Ar cooling ages, evidence of a Mid-Paleozoic metamorphic event not previously known. These gneisses are also intruded by 375±2 Ma (Late Devonian) calc-alkaline granodiorite plutons that we interpret as part of a continental margin volcanic arc. Therefore, Late Devonian rifting, which affected the entire eastern margin of North Asia separating the Okhotsk terrane from the North Asian craton, was probably a back-arc event. Our limited 40Ar/39Ar data from the South Verkhoyansk metamorphic belt suggests that low grade metamorphism and deformation started in the Late Jurassic due to accretion of the Okhotsk terrane to the North Asia margin along the Bilyakchan fault. Shortening and ductile strain continued in the core of the South Verkhoyansk metamorphic belt until about 120 Ma due to paleo-Pacific subduction along the Uda-Murgal continental margin arc.

Description: A long tectonic zone composed of Upper Jurassic to Lower Cretaceous volcanic and sedimentary rocks is recognized along the Asian continent margin from the Mongol-Okhotsk fold and thrust belt on the south to the Chukotka Peninsula on the north. This belt represents the Uda-Murgal arc, which was developed along the convergent margin between Northeast Asia and Northwest Meso-Pacific. Several segments are identified in this arc based upon the volcanic and sedimentary rock assemblages, their respective compositions and basement structures. The southern and central parts of the Uda-Murgal arc were a continental margin belt with heterogeneous basement represented by metamorphic rocks of the Siberian craton, the Verkhoyansk terrigenous complex of Siberian passive margin and the Koni-Taigonos Late Paleozoic to Early Mesozoic island arc with accreted oceanic terranes. At the present day latitude of the Pekulney and Chukotka segments there was an ensimatic island arc with relicts of the South Anyui oceanic basin in a backarc basin. Accretionary prisms of the Uda-Murgal arc and accreted terranes contain fragments of Permian, Triassic to Jurassic and Jurassic to Cretaceous (Tithonian–Valanginian) oceanic crust and Jurassic ensimatic island arcs. Paleomagnetic and faunal data show significant displacement of these oceanic complexes and the terranes of the Taigonos Peninsula were originally parts of the Izanagi oceanic plate.

Description: The sequence of formation of structures is established in the zone of junction of the eastern margin of the North Asian craton and the northeastern flank of the Kolyma-Omolon microcontinent, in the area of bend of the Kolyma structural loop. Detailed structural studies revealed two phases in the formation of Mesozoic structures – an early thrust phase and a late strike-slip phase. Structures formed during each of the phases are described. Thrust structures are represented by the Setakchan nappe on which the minimum amount of horizontal displacement is estimated at 13–15 km. Later superposed left-lateral strike-slip faults have a north strike. Formation of these latter structures occurred during the second phase of collision between the Kolyma-Omolon microcontinent and the eastern margin of the North Asian craton.

Description: The Tommot pluton is located within the continental Omulevka terrane of the inner zone of the Verkhoyansk-Kolyma Mesozoic orogen. It is a small complex (~12 km2) composed of alkaline-ultramafic rocks, alkaline and subalkaline gabbroids, and alkaline and quartz syenites. The pluton is unique both in the composition and age of its constituent rocks. Mineralogical-petrographical and geochemical studies of the rocks indicate that the alkaline rocks resulted from the melting of depleted mantle horizons. K-Ar, Rb-Sr, and 40Ar/39Ar age determinations confirm a Paleozoic age of the rocks. Formation of the alkaline rocks is related to Middle Paleozoic rifting which occurred as two discrete events: a Late Devonian event, which affected the marginal part of the Siberian continent, and a Late Carboniferous event that reflects internal deformation of the Omulevka terrane or late-stage extension. A spatially associated alkali granite, the Somnitel'nyy pluton, is Late Jurassic–Early Cretaceous in age and is synchronous with accretion of the Kolyma-Omolon Superterrane to Siberia in the Mesozoic.

Description: Paleomagnetic results from the upper two thirds of the whole section of the Okhotsk-Chukotka Volcanic Belt (OCVB) volcanics exposed in the area around Lake El'gygytgyn, Chukotka yield stable, consistent magnetic vectors and well-preserved reversed directions. The magnetostratigraphy and 40Ar/39Ar geochronologic data reported here indicate that the sampled OCVB volcanics were erupted between about 90 and 67 Ma, and show no significant change in the apparent pole position over that time. The OCVB extends from northeast China, across Northeast Russia to the Bering Straight. This belt is made up of both extrusive and intrusive rocks, with the extrusive rocks and their associated sediments being dominant. The whole belt important in interpreting the paleogeography of the region because it overlies many of the accreted terranes of Northeast Russia. Most importantly, it overlies parts of the Chukotka-Alaska block which is thought to have moved out of the Arctic Ocean region, as well as terranes accreted from the south. These latter terranes have been rafted northwards on the paleo-plates of the Pacific, implying that the present relative paleogeography of all of the terranes overlain by the OCVB were essentially in place by 67 Ma, and possibly as early as 90 Ma. However, comparing our paleomagnetic pole position for the OCVB with those for North America and Eurasia (a proxy for Siberia) shows a statistically significant displacement of the OCVB pole to the south west. This implies that not only the OCVB, but the underlying terranes of northeast Russia, experienced southerly displacement with respect to the Siberian and North American platforms since the Late Cretaceous.

Description: Outcrops along the Inach River in the Uyandina basin and those along the Myatis' River in the Indigirka-Zyryanka basin were studied in detail and sampled for coal rank determinations. The Uyandina basin is an intramontane pull-apart basin characterized by extensional structures within the Moma rift system. The coal rank is below 0.3% vitrinite reflectance (Rr), which indicates shallow, immature conditions of basin formation and very low subsidence. The Myatis' River coal-bearing outcrops in the Indigirka-Zyryanka basin reveal compression induced by continent collision. The compressive deformation includes also lowermost Pliocene strata. Due to the position in the Verkhoyansk-Chersky fold belt adjacent to the Kolyma-Omolon microcontinent the Indigirka-Zyryanka basin has much in common with a foredeep, i.e. the asymmetry in thickness and tectonic structure. The vitrinite reflectance data (Rr) which range from 0.25% to more than 5% reinforce the accepted models that describe basin subsidence and geothermal history and the tectonic deformation.

Description: A total of 11 700 km of multichannel seismic reflection data were acquired during recent reconnaissance surveys of the wide, shallow shelves of the Laptev and western East Siberian Seas around the New Siberian Islands. To the north of the Laptev Sea, the Gakkel Ridge, an active mid-ocean ridge which separates the North American and Eurasian Plates, meets abruptly the steep slope of the continental shelf. Extension has affected the Laptev Shelf since at least the Early Tertiary and has resulted in the formation of three major, generally north-south trending rift basins: the Ust' Lena Rift, the Anisin Basin, and the New Siberian Basin. Our data indicate that the rift basins on the Laptev Shelf are not continuous with those on the East Siberian Shelf. The latter shelf can best be described as an epicontinental platform which has undergone continuous subsidence since the Late Cretaceous. The greatest subsidence occurred in the NE, manifested by a major depocentre filled with inferred (?)Late Cretaceous to Tertiary sediments up to 5 s (twt) thick. On the basis of deep reflection data we revise and adjust Mesozoic domain boundaries around the New Siberian Islands.

Description: The Chersky seismic belt represents a zone of deformation between the North American and Eurasian plates in northeast Russia. The belt extends from the Laptev Sea into the Chersky Range where it splits into two branches. One branch extends to Kamchatka and the Aleutian-Kurile Junction, while the other branch extends south towards Sakhalin Island. Focal mechanisms indicate a change from extension to transpression in the northern Verkhoyansk Range and generally left-lateral transpression in the Chersky Range extending to northern Kamchatka. The few focal mechanisms on the second branch suggest right-lateral transpression. A large number of faults, sub-parallel to the seismicity and presumed to be strike-slip, are visible in satellite imagery and topographic maps and are also associated with seismically generated landslides. These data support a model in which the Sea of Okhotsk forms the core of a separate Okhotsk microplate surrounded by diffuse boundaries on the north and west. Microseismicity in continental northeast Russia is most heavily concentrated within and between the fault systems along the northern boundary of the proposed Okhotsk plate and indicates a high level of deformation. The sense of slip on the faults (both from focal mechanisms and geology) are also generally consistent with the extrusion of the Okhotsk plate to the southeast as it is compressed between its larger neighbors. The northernmost part of the Okhotsk plate may be decoupled to some degree from the more stable central Sea of Okhotsk.

Description: The compilation, synthesis, description, and interpretation of regional geology and tectonics of major regions, such as Northeast Asia (Eastern Russia, Mongolia, Northern China, South Korea, and Japan) and the Circum-North Pacific (the Russian Far East, Alaska, and Canadian Cordillera), requires a complex methodology that includes: (1) definitions of key terms; (2) compilation of a regional geodynamics map that can be constructed according to modern tectonic concepts and definitions; and (3) formulation of a comprehensive tectonic model. This article presents a summary of the regional dynamics and tectonics of Northeast Asia as developed for a new summary geodynamics map of the region. This article also describes how a high-quality summary geodynamics map and companion tectonic analysis substantially aids in the understanding of the origin of major rock units, major structures, and contained mineral and fuel resources, and provides important guidelines for new research. * Prepared in memory of Leonid M. Parfenov, the leader of the geodynamics map team for the International collaborative project on NE Asia tectonics and metallogenesis.

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〉Palaeomagnetic investigations of sediments cores from Axios zone (N. Greece): implications of low inclinations in the Aegean〈/b〉〈br〉 E. Aidona, D. Kondopoulou, R. Scholger, A. Georgakopoulos, and A. Vafeidis〈br〉 eEarth, 3, 7-18, doi:10.5194/ee-3-7-2008, 2008〈br〉 Sediment cores from 13 deep boreholes (1–4.1 km) distributed within 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. A set of 390 samples have been subjected to thermal and alternative field demagnetization. Isothermal remanent magnetization (IRM) acquisition curves and thermomagnetic analysis suggest the dominance of magnetite. Thin sections from 30 selected samples were studied in order to more precisely characterise their magnetic mineralogy. 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. These techniques were applied in order to correct the palaeomagnetic directions due to the orientation ambiguity of the core samples. The corrected mean direction converges towards an eastward value, in agreement with the overall pattern of the onshore results from previous investigations in the study area. 〈br〉〈br〉 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: 〈b〉Zoogeography of the bottom Foraminifera of the West-African coast〈/b〉〈br〉 V. Mikhalevich〈br〉 eEarth Discuss., 3, 1-9, doi:10.5194/eed-3-1-2008, 2008〈br〉 〈b〉Revised manuscript has not been submitted〈/b〉 (discussion: closed, 8 comments)〈br〉 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: 〈b〉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〈/b〉〈br〉 R. Westaway, T. Demir, and A. Seyrek〈br〉 eEarth, 3, 27-35, doi:10.5194/ee-3-27-2008, 2008〈br〉 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〈sup〉−1〈/sup〉 EAFZ slip rate; it is estimated as ~2–3 mm a〈sup〉−1〈/sup〉, 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〈sup〉−1〈/sup〉 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: 〈b〉Decline of coral reefs during late Paleocene to early Eocene global warming〈/b〉〈br〉 C. Scheibner and R. P. Speijer〈br〉 eEarth, 3, 19-26, doi:10.5194/ee-3-19-2008, 2008〈br〉 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: 〈b〉Characteristics of chlorites in seismogenic fault zones: the Taiwan Chelungpu Fault Drilling Project (TCDP) core sample〈/b〉〈br〉 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〈br〉 eEarth, 3, 1-6, doi:10.5194/ee-3-1-2008, 2008〈br〉 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: 〈b〉Use of remote sensing and GIS in mapping the environmental sensitivity areas for desertification of Egyptian territory〈/b〉〈br〉 A. Gad and I. Lotfy〈br〉 eEarth Discuss., 3, 41-85, doi:10.5194/eed-3-41-2008, 2008〈br〉 〈b〉Revised manuscript has not been submitted〈/b〉 (discussion: closed, 3 comments)〈br〉 Desertification is defined in the first art of the convention to combat desertification as 〈i〉"land degradation in arid, semiarid and dry sub-humid areas resulting from climatic variations and human activities".〈/i〉 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. 〈br〉〈br〉 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; 〈br〉〈br〉 ESAI = (SQI * CQI * VQI)〈sup〉1/3〈/sup〉 〈br〉〈br〉 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. 〈br〉〈br〉 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. 〈br〉〈br〉 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: 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: 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: Variations in the assemblages and abundances of calcareous nannoplankton have allowed us to interpret changes in oceanic and atmospheric dynamics in the Guyana Basin, mainly linked to the southeast trades over the last climatic cycle. Records of the paleoproductivity index of coccolithophores (N ratio) allowed us to monitor the nutri-thermocline fluctuations. Additionally, nannofossil accumulation rates vary closely with the N ratio, indicating a strong correlation between these two paleoproductivity proxies. The dominance of upper (small Noelaerhabdaceae, Emiliania huxleyi and Gephyrocapsa oceanica), over lower photic zone dwellers (Florisphaera profunda) during Termination II and interglacial substages 5.1 and 5.3 is related to eutrophic conditions due to a shoaling of the nutri-thermocline as a consequence of enhanced southeast Trade Winds. This activated an upwelling at the continental margin of the Guyana Basin. Low N ratio values and the dominance of F. profunda over the glacial substages of MIS 5 and glacial MIS 2-4 are linked to a deep nutri-thermocline (deep stratification of the mixed layer), at times of low influence of the southeast Trade Winds, and a weak upwelling. However, the N ratio during MIS 2-4 was slightly higher than those seen for the MIS 4/5 boundary and glacial substages 5.2 and 5.4. These micropaleontological proxies follow the insolation at high northern latitude (65° N): the high N ratio and NAR data from the Guyana Basin during Termination II and interglacials 5.1. and 5.3 are correlated with high insolation values, and low values of the N ratio and NAR during the MIS 4/5 boundary, glacials 5.2, 5.4 and MIS 2-4 are correlated with low insolation at the same latitudes. This situation suggests a link between the ITCZ, the southeast Trade Wind dynamics and the Northern Hemisphere climate changes during the last climatic cycle.

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: For more than three years, the GRACE pair of satellites have been orbiting the Earth, monitoring the time variable mass distribution for scales ranging from regional to global. The GRACE data have been released for a broad scientific community and sets of gravity fields are available. This paper shows that there are evidences at interrannual time scales for the presence of ENSO signal in the data, strongly correlated with the hydrological mass distribution, and also similar to the expected hydrological signature associated with the ENSO cycle. This signal dominates, at global scale, the one associated with geodynamic sources.

Description: Exceptional preservation of aragonite secreted by ammonites offers an opportunity to determine the seasonal temperature variations of Mesozoic surface waters. Ontogenetic profiles of carbon and oxygen isotope compositions have been obtained from the nacreous layer of a well-preserved Late Jurassic (Oxfordian) ammonite (Perisphinctes) from Madagascar. A similar range of oxygen isotope compositions was also obtained from an associated benthic bivalve (Astarte) which suggests the absence of sampling bias. Late Jurassic seasonal variations in the southern Hemisphere were close to 2.5°C and relatively weak when compared to the 2.5–6.5°C temperature range prevailing in the present-day Indian ocean at a paleolatitude of 40±1° S. According to the hypothesis of an ice cap-free Late Jurassic Earth, average sea surface temperatures may have been up to 7°C higher than now.

Description: We review both present and past motions at major plate boundaries, which have the horizontal component in average 10 to 100 times faster (10–100 mm/yr) than the vertical component (0.01–1 mm/yr) in all geodynamic settings. The steady faster horizontal velocity of the lithosphere with respect to the upward or downward velocities at plate boundaries supports dominating tangential forces acting on plates. This suggests a passive role of plate boundaries with respect to far field forces determining the velocity of plates. The forces acting on the lithosphere can be subdivided in coupled and uncoupled, as a function of the shear at the lithosphere base. Higher the asthenosphere viscosity, more significant should be the coupled forces, i.e., the mantle drag and the trench suction. Lower the asthenosphere viscosity, more the effects of uncoupled forces might result determinant, i.e., the ridge push, the slab pull and the tidal drag. Although a combination of all forces acting on the lithosphere is likely, the decoupling between lithosphere and mantle suggests that a torque acts on the lithosphere independently of the mantle drag. Slab pull and ridge push are candidates for generating this torque, but, unlike these boundary forces, the advantage of the tidal drag is to be a volume force, acting simultaneously on the whole plates, and being the decoupling at the lithosphere base controlled by lateral variations in viscosity of the low-velocity layer.

Description: We have performed fall-experiments with basaltic andesite rock samples from Merapi volcano, using an apparatus designed to analyze samples heated up to 850°C. Relative pressure changes during impact and fragmentation of the samples were measured by a pressure transducer. From 200°C, dynamic pressure waves were formed on impact and fragmentation. Peak and duration of the pressure signal, and degree of fragmentation were found to strongly increase with increasing temperature of rock samples. The pressure waves are most likely generated by sudden heating of air forcing it to expand. We propose that the observed pressure changes are analogues to pyroclastic surges that may be generated on impact and fragmentation of large blocks during passage of a pyroclastic flow over a steep cliff. We infer that rock temperatures of ca. 400°C are sufficient for this process to occur, a temperature common in pyroclastic flows even in distal reaches.

Description: A pseudotachylyte bounded by a carbonate-matrix implosion breccia was found at a fossilized out-of-sequence thrust in the Shimanto accretionary complex, Japan. This occurrence resulted from the following events: first implosion of host rock due to interstitial fluid pressure increase and asymmetric fracturing; second, Ca-Fe-Mg carbonate precipitation; and third, frictional melting. The rock-record suggests that these events took place in a single seismogenic slip event. Resulting from abrupt drop in fluid pressure after implosion, hydro-fracturing and fluid escape, recovered high effective friction promoted melting during fault movement. Coexistence of fluid implosion breccia and pseudotachylyte has never been reported from continental pseudotachylyte, but might be characteristic from hydrous seismogenic faults in subduction zone.

Description: We report here the results of a petrographic and geochemical study of remarkably well-preserved kimberlites from the Kangamiut region in Greenland. The samples contain between 5 and 45% of olivine in the form of rounded "nodules", each 1 to 5 mm in diameter. Most originally were single crystals but many consist of polycrystalline, monomineralic aggregates. Olivine compositions vary widely from nodule to nodule (from Fo 81-93) but are constant within individual nodules. A thin rim of high-Ca olivine of intermediate composition (Fo 87-88) surrounds many nodules. Deformation structures in olivine in the nodules and in the matrix demonstrate a xenocrystic origin for the olivine: only olivine in the thin rims is thought to have crystallized from the kimberlite magma. Using major and trace element data we show that the kimberlite compositions are controlled by the addition of xenocrystic olivine into a parental magma that contained only about 16–18% MgO. The monomineralic character of the olivine nodules is problematic because dunite is a rare rock in the lithospheric mantle. The source of the xenocrystic olivine lacked pyroxene and an aluminous phase, which make up about half of most mantle-derived rocks. It appears that these minerals were removed from the material that was to become the nodules, perhaps by fluids that immediately preceded the passage of the kimberlites. We speculate that this mantle "defertilization" process was linked to interaction between CO2-rich fluid and mantle and that this interaction controlled the geochemical and isotopic composition of kimberlites.

Description: Nine ERS-1 and ERS-2 descending orbit data acquired over the Aira Caldera between June 1995 and November 1998 were used to create 31 differential interferograms. Although the interferograms exhibit a relatively low level of coherence, even for couples sampling short time intervals (6 months), Differential Interferometric Synthetic Aperture Radar (DinSAR) reveals a pattern of range change signal during the observation period in the urban area of Kokubu city. The analysis of the ground deformation time series relative to the earliest ERS images evidenced a maximum uplift of 23 mm between the north and the south of the city during the studied period. Taking the reduced surface of the coherent area into account, we performed a simple modelling of the deformation field assuming a spherical inflating source within an elastic half-space medium. This simple model predicts a source located beneath the centre of Aira Caldera with a maximum volume increase of 30 106 m3 between 1995 and 1997, which would produced an inflation of about 7 cm of the centre of Aira Caldera and 4 cm of the south of Kokubu city. These results are in good agreement with other geophysical observations carried out on Aira caldera during this unrest period. Despite the limited spatial extent of the coherent areas around Aira Caldera, this study shows that DinSAR method using ERS data can be successfully used to detect subtle ground displacement changes of the volcanic complex and thus provides complementary information to ground-based geodetic monitoring of dynamic processes at Aira Caldera and Sakurajima volcano.

Description: Researchers at the Center for Climatic Research (CCR) at the University of Wisconsin-Madison have revised and calibrated a global volcanic database compiled from more than 2000 radiocarbon-dated eruptions from the late Pleistocene and Holocene. The updated database is available online as an appendix to this correspondence (http://www.electronic-earth-discuss.net/1/123/2006/eed-1-123-2006-supplement.zip). We briefly describe the database, suggest some potential applications, and invite other researchers in the geologic and atmospheric sciences to both use and help refine the archive by incorporating additional data as it becomes available.

Description: We report gravel of the River Euphrates, capped by basalt that is Ar-Ar dated to ~9 Ma, at Shireen in northern Syria. This gravel, preserved by the erosion-resistant basalt, allows us for the first time to reconstruct the history of this major river during the Late Miocene. In response to progressive regional surface uplift, the Euphrates extended SE by ~800 km between the early Middle Miocene, when the coast was near Kahramanmarac{s} in southern Turkey, and the Pliocene, when it lay in western Iraq, east of the Arabian Platform uplands.

Description: To study the effect of stress-activated positive hole (p-hole) charge carriers on the infrared (IR) emission from rocks, we subjected a portion (~10 vol.%) of a large (60×30×7.5 cm3) block of anorthosite, a nearly monomineralic (Ca-rich feldspar) igneous rock, to uniaxial deviatory stress up to failure. We measured the IR emission from a flat surface ≈40 cm from the stressed rock volume over the 800–1300 cm−1 (7.7–12.5 μm) range. Upon loading, the intensity and spectrum of the IR emission change. Narrow bands near instantly appear at 930 cm−1 (10.75 μm), 880 cm−1 (11.36 μm), 820 cm−1 (12.4 μm) plus additional bands in the 1000–1300 cm−1 (10.0–7.7 μm) range. Upon further loading the bands broaden and shift. Their intensities increase but also fluctuate. Near the emission maxima at 300 K, at 1150 cm−1 and 1030 cm−1 (8.7 and 9 μm), barely any intensity increase occurs suggesting that the temperature of the surface does not actually increase. We propose that the observed narrow IR emission bands arise from vibrationally excited O-O stretching modes which form when p-hole charge carriers (activated in the stressed rock) spread into the unstressed portion of the rock to the surface, where they recombine and radiatively decay. The effect, stimulated IR emission due to hole-hole recombination, may help explain the enhanced IR emission seen in night-time satellite images of the land surface before major earthquakes known as "thermal anomalies''.

Description: A linear model is developed to study the effect of variations in composition upon extensive physical properties of continuously deposited sediment sequences. By applying this model to natural and synthetic remanence acquisition, an optimal method of relative paleointensity determination is derived. The sediment is regarded as a mixture of independent components, each of which behaves uniformly in depth with respect to its physical properties. The concentration of each sediment component is assumed to independently vary linearly with an external "environmental" signal. Remanence acquisition in each sediment component is linear in external field and concentration of the component. It is demonstrated that in this case the ideal normalization procedure for relative paleointensity determination is to divide the natural remanent magnetization by a biased normalizer. Common magnetic cleaning techniques improve the relative paleointensity record by removing nonlinear behavior and by reducing the bias to the normalizer. The proposed linear sediment model for any extensive physical property clearly separates the influences of concentration of sediment components from those of environmental signals. It thus opens many possibilities for extensions to nonlinear models.