ionospheric disturbances during the magnetic storm of 15 july 2000 role of the fountain effect and plasma bubbles for the formation of large equatorial plasma density depletions 1 we investigate the role of the fountain effect and plasma bubbles for the formation of the large equatorial plasma depletions during the geomagnetic storm of 15 july 2000 the large equatorial plasma depletions are detected in the atlantic sector on the night of the 15th by the defense meteorological satellite program dmsp f15 and the first republic of china satellite rocsat 1 the observations show discontinuous drop of the plasma density at the walls of the depletions flat plasma density inside the depletions and persistence or growth of the depletions over night these properties are not consistent with the trough morphology induced by the fountain effect the coincident ionospheric observations of dmsp f15 and rocsat 1 demonstrate that the large depletions are created in the longitude regions where plasma bubbles are present the occurrence of the large depletions after sunset elongation in the north south direction formation of steep walls and colocation with plasma bubbles at lower altitudes or earlier times suggest that the large depletions are closely associated with plasma bubbles

detritic tourmalines with complex zonation in the cretaceous exotic flysches of the western carpathians where did they come from abstract the period of the cretaceous marked a time of convergence in the tethyan realm characterized by both collisions and local ophiolitic obduction sedimentary records from this period are full of detritic materials of unknown provenance so called exotics among these exotic rocks and minerals was tourmaline with complex zonation which began to appear in considerable amounts research conducted in albian to senonian exotics of the western carpathians has shown that there are two kinds of complex zoned grains 1 grains with a fabric consisting of several tourmaline phases which are chaotically arranged as laths and 2 grains displaying a fine intergrowth of tourmaline and quartz the first type of tourmaline shows a continuous trend of al and its substitution by fe3 at the y and z sites thus shifting from a schorl dravitic composition to a bosiite one the second type consists of a dominant presence of schorl dravitic tourmaline however with a scarce occurrence of al enriched oxy dravitic foititic and magnesio foititic compositions tourmaline with complex zonation occurs in metamorphics which include hp and uhp facies evaporitic complexes and hydrothermal deposits they also appear locally in granites and pegmatites in most of the rocks saline and boron rich fluids played a substantial role in the high pressure metamorphics there was an influx of fluids during their exhumation because the examined exotics are rich in ophiolitic material including hp to uhp rock pebbles it is substantiated to assume that the also represented the main source of the complex zoned tourmaline they may have also combined with permian lower triassic evaporites where the dismembered ophiolites are often embedded hydrothermal veins and granitoids did not represent a regionally significant and widespread source at that time

longitudinal variability of low latitude total electron content tidal influences 1 recently nighttime ultraviolet uv observations obtained by image fuv and timed guvi instruments have revealed a longitudinal wave number four pattern in the nighttime airglow intensity and in the position of the equatorial anomalies during equinox and high solar flux conditions in the present study we have extended this work and determined the longitudinal variability of the low latitude total electron content tec climatology during different geophysical conditions with a special emphasis on the longitudinal wave number four structure in the low latitude ionosphere we have used more than 5 million low latitude topex tec observations covering the entire 13 years of topex tec data from august 1992 until october 2005 this data set was used to determine the local time seasonal solar cycle and geomagnetic activity dependence of the longitudinal variability of tec at equatorial and low latitudes and in particular to address the existence and evolution of the wave number four longitudinal pattern under these conditions our study shows that the wave number four pattern is created during the daytime hours at equinox and june solstice but is absent or washed out by other processes during december solstice during equinox the wave number four pattern is created around noon with well defined longitudinal enhancements in the low latitude tec these enhancements which are symmetric about the geomagnetic equator during this season last for many hours and can be clearly seen past midnight the longitudinal patterns are found to be nearly identical between the vernal march april and autumnal september october equinoxes and largely independent of the solar cycle conditions the wave number four pattern is also observed during geomagnetically active conditions indicating that the processes that create this pattern are also present during active times the variations between the well defined longitudinal maxima and minima are of the order of 20 during june solstice the wave number four pattern is also observed in the afternoon hours but in contrast to the equinox cases it exhibits a strong hemispheric asymmetry and is not observed during the night the low latitude tec exhibits clear longitudinal variations during december solstice with large daytime enhancements over the east asian and pacific regions and a third enhancement emerging in the afternoon over the atlantic ocean but a clear wave number four pattern is not observed during this season although the equatorial and low latitude tec values exhibit clear longitudinal patterns during all seasons a significant amount of scatter remains in the tec data that is not accounted for by changes in the solar cycle the season or the local time or by the longitudinal variability this remaining scatter is largest near the poleward edges of the anomalies and is of the order of 40

the lomagundi jatuli carbon isotopic event recorded in the marble of the tandilia system basement rio de la plata craton argentina abstract the lomagundi jatuli event corresponds to the most important 13c positive anomaly 5 globally reported in palaeoproterozoic marine carbonates between 2 30 and 2 06 ga in the tandilia system argentina rio de la plata craton this event was recorded in the basement marble of the san miguel area the calcite diopside marble hosted by biotite gneiss and intruded by 2 12 ga garnet leucogranite was metamorphosed in amphibolite facies during the transamazonian cycle paas normalised rare earth elements ree and y for the carbonate rocks are hree enriched and display positive eu and y anomalies typical of primary precipitates from a mixed hydrothermal marine environment carbonate additionally a truly negative ce anomaly for all the samples indicates that the depositional environment was oxidising positive 13c values ranging from 5 90 to 4 30 v pdb and 18o from 17 45 to 13 84 v smow were determined in this marble both gradually decreasing towards the contact with the leucogranites these values indicate that devolatilization reactions took place during the crystallisation of a wollastonite vesuvianite grossular diopside skarn generated by the leucogranite intrusions into the marble 18o values obtained from diopside and calcite crystals in the marble sectors furthest from the contacts with leucogranite allowed a 663 623 c formation temperature to be calculated considering oxygen in a calcite diopside geothermometric pair these temperatures are consistent with the metamorphic degree amphibolite facies reached in this portion of the basement although the san miguel marble shows petrographic and mineralogical evidence of regional and contact metamorphism important geochemical and isotopic characteristics together with its estimated palaeoproterozoic age indicate that the marble protolith was a marine carbonate deposited during the lomagundi jatuli event

storm time signatures of the ionospheric zonal ion drift at middle latitudes 1 using a quantitative identification of convection and particle boundaries at high latitudes the relative extent of auroral convection and auroral precipitation is examined during superstorm events during superstorms the convection reversal boundary normally located near 75 magnetic latitude moves to magnetic latitudes near 60 the edge of the diffuse auroral precipitation that normally terminates near 60 magnetic latitude moves to magnetic latitudes near 40 this limited study shows that during the main phase of the superstorm ion drifts driven by the magnetosphere penetrate to latitudes as low as the dip equator on the dusk side but extend only a few degrees equatorward of the auroral zone on the dawn side evidence for ion drifts driven by a disturbance dynamo may be found during the storm recovery phase when the interplanetary magnetic field is less strongly southward or turns northward but the previously established flows below the auro al region remain

paleomagnetism of middle late jurassic sediments from poland and implications for the polarity of the geomagnetic field abstract paleomagnetic data for the middle late jurassic sediments from nine localities of krakow czestochowa upland belonging to stable europe and from three valleys of the lower subtatric nappe belonging to mobile europe are presented the majority of the rocks investigated comprising limestones stromatolites and radiolarites were found to be normally magnetized natural remanent magnetizations nrm of reversed polarity were found in limestones and stromatolites of middle callovian age from the stable region and in one exposure of oxfordian radiolarites from the mobile region along one of the middle callovian sections studied the nrm direction of the specimens changed from r to n the mean paleomagnetic pole positions obtained for the krakow czestochowa upland lat 72 3 n long 150 4 e 95 7 3 and for the lower subtatric nappe lat 71 7 n long 132 2 e 95 4 3 are consistent with the data for stable europe lat 74 7 n long 147 1 e 95 5 0 the paleomagnetic results presented do not reveal any major relative rotations either within the lower subtatric nappe or between this area and the krakow czestochowa upland the reversed directions of nrm observed indicate the existence of a period of reversed field direction in the middle callovian and perhaps also in the oxfordian

paleomagnetic and magnetic fabric data from lower triassic redbeds of the central western carpathians new constraints on the paleogeographic and tectonic evolution of the carpathian region in the central western carpathians cwc most published paleomagnetic results from permo mesozoic rocks document extensive remagnetizations and come from thin skinned thrust units that have undergone multistage deformation we present results from lower triassic redbeds from the autochthonous cover overlying the basement that carry a primary magnetization petromagnetic results indicate that the dominant ferromagnetic carrier is hematite while magnetic susceptibility and its anisotropy are controlled by both ferromagnetic and paramagnetic minerals magnetic fabrics document weak deformation related to late cretaceous shortening the directions of the high unblocking temperature remanence components pass both reversal and fold tests attesting to their primary nature paleomagnetic inclinations are flatter than expected from reference datasets suggesting small latitudinal separation between the cwc and stable europe paleomagnetic declinations are mostly clustered within individual mountain massifs implying their tectonic coherence they show only minor differences between the massifs indicating a lack of significant vertical axis tectonic rotations within the studied central parts of the cwc the paleomagnetic declinations are therefore representative of the whole of the cwc in terms of regional paleogeographic interpretations and imply moderate counterclockwise rotations c 26 of the region with respect to stable europe since the early triassic

the tandilia system of argentina as a southern extension of the rio de la plata craton an overview the southernmost outcrops of the rio de la plata cratonic region are exposed in the tandilia system in eastern argentina the geological evolution comprises mainly an igneous metamorphic paleoproterozoic basement named buenos aires complex which is covered by neoproterozoic to early paleozoic sedimentary units which display subhorizontal bedding the basement of calc alkaline signature consists mainly of granitic tonalitic gneisses migmatites amphibolites some ultramafic rocks and granitoid plutons subordinate rock types include schists marbles and dykes of acid and mafic composition tandilia was recognized as an important shear belt district with mylonite rocks derived mainly from granitoids the tectonic scenario seems related to juvenile accretion event 2 25 2 12 ga along an active continental margin followed by continental collision 2 1 2 08 ga after u pb zircon data the collisional tectonic setting caused thrusting and transcurrent faulting favouring the anatexis of the crustal rocks the tholeiitic dykes constrain the time of crustal extension associated with the last stages of the belt evolution the basement was preserved from younger orogenies such as those of the brasiliano cycle after a long paleoweathering process the sierras bayas group c 185 m thick represents a record of the first neoproterozoic sedimentary unit siliciclastic dolostones shales limestones superposed by cerro negro formation c 150 400 m thick siliciclastics assigned to upper neoproterozoic age the final sedimentary transgression during early paleozoic was the balcarce formation c 90 450 m thick deposited over all the mentioned precambrian units based on all the geological background a tectonic evolution is offered

effects observed in the ionospheric f region in the east asian sector during the intense geomagnetic disturbances in the early part of november 2004 1 the sun was very active in the early part of november 2004 during the period of 8 10 november 2004 intense geomagnetic disturbances with two superstorms were observed in a companion paper hereinafter referred to as paper 1 the effects observed in the f region during the intense geomagnetic disturbances in the early part of november 2004 in the latin american sector were presented in the present paper we investigate the effects observed in the f region during the intense geomagnetic disturbances in the early part of november 2004 in the east asian sector we have used the ionospheric sounding observations at ho chi minh city vietnam and okinawa yamagawa kokubunji and wakkanai japan in the present investigations also gps observations in the east asian sector several longitude zones have been used to study the effect in the f region during the intense geomagnetic disturbances the ion density versus latitudinal variations obtained by the dmsp f15 satellite orbiting at about 800 km altitude in the east asian sector and the magnetic field data obtained at several stations in the japanese meridian are also presented several important features from these observations in both the sectors during this extended period of intense geomagnetic disturbances are presented the east asian sector showed very pronounced effects during the second superstorm which was preceded by two storm enhancements it should be mentioned that around the beginning of the night on 10 november ionospheric irregularities propagating from higher midlatitude region to low latitude region were observed in the japanese sector the most intense geomagnetic field h component in that sector was observed on 10 november at l 2 8 indicating that the auroral oval and the heating got further to low latitudes and the ionospheric irregularities observed in the japanese sector on this night are midlatitude ionospheric disturbances associated with the second superstorm the absence of ionospheric irregularities in the japanese sector during the 8 november superstorm suggests that the magnetosphere ionosphere system was possibly preconditioned primed when the second interplanetary structure impacted the magnetosphere

late magmatic controls on the origin of schorlitic and foititic tourmalines from late variscan peraluminous granites of the arbus pluton sw sardinia italy crystal chemical study and petrological constraints abstract tourmalines from the late variscan arbus pluton sw sardinia and its metamorphic aureole were structurally and chemically characterized by single crystal x ray diffraction electron and nuclear microprobe analysis mossbauer infrared and optical absorption spectroscopy to elucidate their origin and relationships with the magmatic evolution during the pluton cooling stages the arbus pluton represents a peculiar shallow magmatic system characterized by sekaninaite fe cordierite bearing peraluminous granitoids linked via afc processes to gabbroic mantle derived magmas the fe2 al dominant tourmalines occur in a pegmatitic layers and pods as prismatic crystals b greisenized rocks and spotted granophyric dikes as clots or nests of fine grained crystals in small miaroles locally forming orbicules c pegmatitic veins and pods close to the contacts within the metamorphic aureole structural formulae indicate that tourmaline in pegmatitic layers is schorl whereas in greisenized rocks it ranges from schorl to fluor schorl tourmalines in thermometamorphosed contact aureole are schorl foitite and mg rich oxy schorl the main substitution is na fe2 al which relates schorl to foitite the homovalent substitution oh f at the o1 crystallographic site relates schorl to fluor schorl while the heterovalent substitution fe2 oh f al o relates schorl fluor schorl to oxy schorl tourmaline crystallization in the arbus pluton was promoted by volatile b f and h2o enrichment low oxygen fugacity and fe2 activity the mineralogical evolutive trend is driven by decreasing temperature as follows sekaninaite quartz schorl quartz fluor schorl quartz foitite quartz the schorl foitite evolution represents a distinct trend towards al increase and unit cell volume decrease these trends are typical of granitic magmas and consistent with li poor granitic melts as supported by the absence of elbaite and other li minerals in the arbus pluton tourmaline bearing rocks reflect the petrogenetic significance of contribution from a metapelitic crustal component during the evolution of magmas in the middle upper crust

zircon and whole rock nd pb isotopic provenance of middle and upper ordovician siliciclastic rocks argentine precordillera graptolite bearing middle and upper ordovician siliciclastic facies of the argentine precordillera fold thrust belt record the disintegration of a longlived cambro mid ordovician carbonate platform into a series of tectonically partitioned basins a combination of stratigraphic petrographic u pb detrital zircon and nd pb whole rock isotopic data provide evidence for a variety of clastic sediment sources four upper ordovician quartzo lithic sandstones collected in the eastern and central precordillera yield complex u pb zircon age spectra dominated by 1ae05 1ae10 ga zircons secondary populations of 1ae22 1ae30 and 1ae46 ga rare 2ae2 and 1ae8 ga zircons and a minor population 2 of concordant zircons in the 600 700 ma range archaean age grains comprise 1 of all zircons analysed from these rocks in contrast a feldspathic arenite from the middle ordovician estancia san isidro formation of the central precordillera has two well defined peaks at 1ae41 and 1ae43 ga with no grains in the 600 1200 ma range and none older than 1ae70 ga the zircon age spectrum in this unit is similar to that of a middle cambrian quartz arenite from the la laja formation suggesting that local basement rocks were a regional source of ca 1ae4 ga detrital zircons in the precordillera terrane from the cambrian onwards the lack of grains younger than 600 ma in upper ordovician units reinforces petrographic data indicating that ordovician volcanic arc sources did not supply significant material directly to these sedimentary basins nd isotopic data n 32 for middle and upper ordovician graptolitic shales from six localities define a poorly mixed signal end 450 ma 9ae 6t o 4ae5 that becomes more regionally homogenized in upper ordovician rocks 6ae 2 1 ae0 tdm 1ae51 0ae15 ga n 17 a trend reinforced by the u pb detrital zircon data it is concluded that proximal recycled orogenic sources dominated the siliciclastic sediment supply for these basins consistent with rapid unroofing of the precordillera terrane platform succession and basement starting in mid ordovician time common pb data for middle and upper ordovician shales from the western and eastern precordillera n 15 provide evidence for a minor 30 component that was likely derived from a high l u pb terrane

super medium scale traveling ionospheric disturbance observed at midlatitude during the geomagnetic storm on 10 november 2004 1 medium scale traveling ionospheric disturbances mstids whose peak to peak amplitude was larger than 20 tecu 1016el m2 were observed at midlatitude during the geomagnetic storm on 10 november 2004 this amplitude was more than 10 times larger than that of the average mstid high resolution data of the gps earth observation network geonet clarified the characteristic of the total electron content tec disturbances over japan on 10 november 2004 the disturbances started around 1000 ut in the central part of japan the maximum of tec temporal change was 7 2 tecu in 30 s the disturbances had several wave fronts which extended from northwest to southeast and propagated from northeast to southwest tec data around japan revealed that the disturbances were mainly observed from 18 n s to 34 n s of the geomagnetic latitude in the both hemispheres since those characteristics were similar to those of mstids in spite of the unusual large amplitude the mstids are referred as super mstids in this paper tec variations of the super mstids were also observed at 460 km altitude by the grace satellite the ion density fluctuations of the super mstids were observed in situ by the champ and dmsp f15 satellites which flew at 360 km and 850 km respectively it is found that the plasma density variations of the super mstids occurred mainly above 360 km altitude the characteristics that distinguish the event from plasma bubbles are its successive wave fronts constant northwest southeast direction along which the wave fronts stretched and late local time of the occurrence it is found that the uplift of the ionosphere around sunset excited the super mstids at midlatitudes the uplift was attributed to the strong eastward electric field during the geomagnetic storm

pre neogene evolution of the western carpathians constraints from the bochnia tatra mountains section polish western carpathians on the basis of field studies and subsurface data this first balanced transect crosses most of the carpathian foreland basin and the entire polish western carpathian thrust units outer flysch nappes pieniny klippen belt and inner carpathian tatric thrust sheets it shows that 1 me outer carpathians are made up of several flysch units whose internal structure is strongly controlled by initial thicknesses whereas the thin flysch successions are strongly deformed by tight folds and include several imbricated thrust sheets by contrast the thick flysch successions are less deformed and accreted in slightly imbricated thrust sheets and 2 the inner carpathians are structured in an antiformal stack of basement thrust sheets the unfolding of this cross section shows that the post middle oligocene shortening in the european foreland platform and outer carpathians exceeds 180 km in the substratum most of this shortening seems to be solved by basement consumption vertically beneath the suture zone of the pieniny klippen belt additional basement shortening took place also 1 in the inner carpathians where during the neogene buried basement thrust sheets were piled up to form an antiformal stack and 2 beneath the inner zones of the outer carpathians palinspastic restoration of the cross section reflects two well differentiated zones prior to the late oligocene late miocene compression 1 the present inner carpathians and the pieniny klippen belt characterized by a late cretaceous thrust belt unconformably overlain by an undeformed palaeogene cover and 2 the outer flysch carpathians in which pre upper oligocene configuration comprised a typical foreland basin flexed toward the ssw with a system of nw trending highs and troughs

isotopic studies on detrital zircons of silurian devonian siliciclastic sequences from argentinean north patagonia and sierra de la ventana regions comparative provenance the silurian devonian siliciclastic sedimentary units known as sierra grande formation and the upper part of the ventana group crop out in the eastern area of the north patagonian massif and in the ventania system toward the atlantic border of argentina both sequences show similar stratigraphical characteristics and were deposited in a shallow marine platform paleoenvironment previous contributions have provided evidence of an allochthonous patagonia terrane that amalgamate to gondwana during the permian triassic however other lines of research support a crustal continuity southward where the pampean and famatinian events extend into the northern patagonia in either case the detrital input to the eo mesopaleozoic basins generated along the passive margin tectonic setting should reflect the sedimentary sources in this contribution new age data on the sedimentary provenance of these units is provided by u pb and lu hf isotopic studies on detrital zircons using la icp ms and shrimp methodologies the main sedimentary sources of detrital zircons for both regions are of cambrian ordovician and neoproterozoic age while a secondary mode is mesoproterozoic zircons from older cratonic sources mesoarchean paleoproterozoic ages are scarcely recorded the sample from the upper section of the devonian lolen formation ventana group shows an important change in the sedimentary provenance with a main mode of mesoproterozoic detrital zircons detrital source areas considering the orogenic cycles known for southwest south america famatinian pampean brasiliano mesoproterozoic grenvillian and paleoproterozoic transamazonian are proposed

detrital chromites in metasediments of the east arabian continental margin in the saih hatat area constraints for the palaeogeographic setting of the hawasina and semail basins oman mountains in oman the convergence between arabia and eurasia resulted in the late cretaceous overthrusting of oceanic crust and mantle lithosphere onto the arabian continental margin during this compressional event a part of the continental plate was subducted to a depth of more than 60 km 0 5 gpa 250 350 c to more than 2 0 gpa 550 c resulting in progressive metamorphism of the continental margin sediments well exposed in the saih hatat tectonic window northeastern oman mountains we attempt to constrain the possibility of one continuous history of extension starting along the east arabian continental margin in the permian that was followed by one continuous history of convergence starting at 90 ma near a dead oceanic ridge this compression resulted in the observed progressive metamorphism by ophiolite overthrusting onto the continental margin constraining arguments are the palaeogeographic setting before ophiolite obduction of the as sifah units and the hawasina complex near ghurba detrital chromites in the triassic cretaceous metasediments of the hawasina complex are compared with magmatic semail chromites and the whole rock chemistry of these metasediments and associated metabasites are investigated in contrast to former hypotheses differences in the chemical composition between detrital and magmatic chromites and the probable origin of all detrital chromites in the hawasina basin from permian age oceanic rocks suggest that the high pressure metamorphic sediments of as sifah can be considered as part of the basal deposits of the hawasina basin

effects of chemical weathering and sorting on the petrogenesis of siliciclastic sediments with implications for provenance studies the bulk chemical compositions mineralogy and mineral proportions of sands and muds of the mallacoota basin in southeastern australia reflect the composition of weathering profiles mantling source rocks rather than bedrock muds contain abundant clay minerals that are virtually absent from the source rocks but abundant in the weathering profiles sands are strongly enriched in quartz relative to source rocks even in the headwaters of the fluvial system demonstrating that feldspar destruction occurs by in situ chemical weathering within profiles and before detritus enters the fluvial system k feldspar is proportionally more abundant in fluvial sands than in source rocks because plagioclase is more rapidly destroyed than either quartz or k feldspar in weathering profiles subsequent erosion and sorting produce sands enriched in quartz with high k feldspar plagioclase ratios relative to source rocks the composition of plagioclase incorporated into the fluvial sands is also controlled by chemical weat

characterizing the 10 november 2004 storm time middle latitude plasma bubble event in southeast asia using multi instrument observations 1 the development and dynamics of ionospheric plasma bubble pb irregularity during the super storm of 7 11 november 2004 are investigated using the data from a multi instrument network operated in southeast asia analysis of fluctuations in global positioning system total electron content gps tec ionosonde gps scintillation and in situ satellite density data indicates a series of intense pb associated irregularities at equatorial low and middle latitudes in the japanese longitude on 10 november however in the chinese sector the scintillations and pb irregularities are confined within the range of 20 50 n in geographic latitude and 110 125 e in geographic longitude the absence of equatorial pb irregularities in this sector shows a major difference from that in the close by longitude japanese sector in the southern hemisphere australian sector the irregularities occurrence is present as a symmetrical distribution at conjugate latitudes combined analysis of the data from osan and wuhan ionosondes illustrates that the middle latitude spread f irregularities initially develop at the lower part of the f region and then distribute in the whole f region this initiation of spread f at lower altitudes indicates that the middle latitude pb associated irregularities are locally generated these results together with the irregularities occurrence sequence from higher to lower latitudes and the onset time delay of several hours implies that the presence of pb associated irregularities within a latitude range of 20 50 n in the chinese sector cannot be attributed to the effects of prompt penetration electric fields ppefs although the equatorial pbs in the close by longitude are seen to be associated with ppefs the possible mechanism is the f region plasma instabilities triggered by wave structures which act as an external driving force and seed active plasma dynamics and instability growth at middle latitude

compositional evolution and substitutions in disseminated and nodular tourmaline from leucocratic granites examples from the bohemian massif czech republic two distinct textural types of tourmaline were distinguished in leucocratic granites of the bohemian massif moldanubicum saxothuringicum i commonly euhedral disseminated tourmaline dt crystallized in relatively early stage of the granite consolidation and ii typically interstitial nodular tourmaline nt formed during the stage transitional from late solidus to early subsolidus crystallization very similar chemical composition and similar fractionation trends in both dt and nt tourmaline types indicate crystallization in a quasi closed system from early solidus to early subsolidus stage of granite consolidation the substitutions in tourmaline from nt granites in the moldanubicum are more similar to the substitutions in tourmaline from li poor granitic pegmatites in the same region relative to tourmaline from dt granites plotting of emp analyses of tourmaline in diverse diagrams strongly suggests using combination of ternary diagrams al fe mg and na ca xsite vacancy and simple plots involving single cations elements such as na al f na fe mg rather then more complicated diagrams e g r1 r2 r3 to characterize chemical composition and to derive substitution mechanisms in ca poor tourmaline from granitic rocks the complex diagrams e g r1 r2 versus r3 do not enable to investigate compositional evolution in the xsite and wsite properly and oversimplifies the real substitutions we recommend using specific diagrams for specific tourmaline compositions e g carich lirich

basement evolution of the sierra de la ventana fold belt new evidence for cambrian continental rifting along the southern margin of gondwana u pb sensitive high resolution ion microprobe data together with geochemical and nd isotope analyses obtained in the basement complex of the sierra de la ventana fold belt indicate that the early palaeozoic passive margin history of the basin followed cambrian magmatism related to rifting in a 600 ma neoproterozoic crust the cambrian episode started with intrusion of 531 4 and 524 5 ma a and i type granites derived from a dehydrated infracrustal source e nd 530 3 1 to 5 9 and culminated with eruption of high zr peralkaline spherulitic rhyolites derived from an undepleted lithospheric mantle 509 5 ma e nd 509 0 5 to 1 0 these rift related magmatic rocks were covered by shelf sediments deposited along a once continuous passive margin encompassing the sierra de la ventana fold belt the cape fold belt the falkland malvinas microplate and the ellsworth mountains block in antarctica the cambrian rifting event defined the outline shape of the southern part of gondwana and can be regarded as the initiation of the supercontinent stage which lasted until jurassic break up the conjugate continental fragments separated from gondwana during the cambrian rifting could be the source for microcontinents with c 1000 ma basement rocks that collided with the proto andean margin during ordovician silurian times

kinematic evolution of the romanian carpathians abstract the regional pattern of contraction and extension directions and the evolution of the strain field from paleogene to neogene times enabled a reconstruction of the migration path of the carpathian collision front the carpathian nappes were thrust around the moesian plate during paleogene and early neogene times and protruded into a small oceanic embayment between the moesian and european plates the arc structure of the carpathian fold thrust belt was formed in late neogene times as a result of the eastward escaping tisza dacia block due to n directed convergence of the adriatic plate and the retreating subduction of an oceanic slab brittle deformation structures in the romanian carpathians suggest three tectonic events related to major plate motions 1 paleogene to middle miocene ne to ene contraction caused right lateral curved strike slip faults 2 middle miocene to pliocene fan shaped orientations of contraction directions were caused by right lateral oblique convergence in the southern carpathians frontal convergence in the southern eastern carpathians and left lateral convergence in the northern eastern carpathians 3 pleistocene to holocene general e w extension and n s contraction in the carpathian arc and local ese wnw contraction in the vrancea area is related to the late roll back stage and break off of the subducted slab in the bend area

paleomagnetism of jurassic sediments as evidence for oroclinal bending of the inner west carpathians abstract the jurassic carbonates from the krizna nappe contain a pre tectonic characteristic component of remanence the declinations for individual nappe fragments differ and form a fan like pattern they are close to the tectonic vergencies measured in the field which suggests that the arcuate structure of the inner carpathians results from an oroclinal bending of an originally straight belt

sedimentary evolution of the mesozoic continental redbeds using geochemical and mineralogical tools the case of upper triassic to lowermost jurassic monte di gioiosa mudrocks sicily southern italy the continental redbeds from the internal domains of the central western mediterranean chains have an important role in the palaeogeographic and palaeotectonic reconstructions of the alpine circum mediterranean orogen evolution since these redbeds mark the triassic jurassic rift valley stage of tethyan rifting the composition and the sedimentary evolution of the middle triassic to lowermost jurassic continental redbeds of the san marco d alunzio unit peloritani mountains southern italy based on mineralogical and chemical analyses suggests that the studied mudrock sediments share common features with continental redbeds that constitute the internal domains of the alpine mediterranean chains phyllosilicates are the main components in the mudrocks the 10 a minerals illite and micas the i s mixed layers and kaolinite are the most abundant phyllosilicates the amount of illitic layers in i s mixed layers coupled with the illite crystallinity values ic are typical of high degree of diagenesis corresponding to a lithostatic tectonic loading of about 4 5 km the mineralogical assemblage coupled with the a cn k plot suggest post depositional k enrichments palaeoweathering proxies pia and ciw record intense weathering at the source area further the studied sediments are affected by reworking and recycling processes and as consequence it is likely these proxies monitor cumulative effect of weathering the climate in the early jurassic favoured recycling and weathering occurred under hot episodically humid climate with a prolonged dry season the source area is the low grade paleozoic metasedimentary basement mafic supply is minor but not negligible as suggested by provenance proxies

low latitude oxfordian position of the oravic crustal segment pieniny klippen belt western carpathians palaeogeographic implications abstract the bajocian and the oxfordian kimmeridgian crinoidal limestones of the pieniny klippen belt pkb western carpathians and the bathonian callovian neptunian dykes which cut them were sampled for rock magnetic and palaeomagnetic study the sampled sections were babina mestecko vrsatec bolesovska dolina and szaflary sirm t curves show that the limestone and the dykes from mestecko contain hematite with blocking temperature t b about 650 670 c babina limestone and dykes contain magnetite with t b between 470 and 570 c usually accompanied by small hematite tail sometimes goethite with t b about 80 100 c is seen dykes and limestone from vrsatec contain magnetite with t b of 570 c or hematite with unblocking temperature of 670 c after cleaning of recent soft component by a temperature of 200 c and a field of 10 20 mt the hard component was revealed after tilt correction the locality mean directions found in limestones have scattered declination but similar reversed inclination between 35 and 40 for the bajocian and between 35 and 49 for the oxfordian kimmeridgian an exception was the mean direction for the bajocian limestone from bolesovska dolina which has normal polarity fold test for inclination only showed pre folding inclinations for the bajocian and oxfordian kimmeridgian limestones and scattered inclinations for the in situ and tilt corrected directions for the dykes the mean palaeoinclination calculated for bajocian and oxfordian kimmeridgian by means of inclination only test are 38 5 3 and 42 5 11 2 respectively which corresponds to 21 7 1 5 n and 24 6 5 6 n of palaeolatitude this is about 10 15 lower than the value of inclination expected for that age for the pieniny klippen belt from the jurassic poles for stable europe as positive inclination only fold test proves pre folding age of isolating directions other possibility flattening of inclination should be considered anisotropy of magnetic susceptibility ams and magnetic unhysteretic remanent magnetisation aarm can be used for the evaluation of origin and for the deviation of natural remanent magnetisation nrm the axes of ams are scattered for all localities the degree of anisotropy is low the shape parameter t shows equal distribution of oblate and prolate fabric on the contrary the arm maximum axes are well clustered especially for mestecko and vrsatec the maximum axes are distributed in a vertical plane for mestecko and in horizontal plane for babina and vrsatec this evidences that the aarm fabric is not related to sedimentation and compaction the anisotropy axes are not close to the nrm directions for mestecko they are steeper this excludes an effect of shallowing of nrm on this basis we can assume that more southern palaeolatitude of the pieniny klippen belt than expected is a demonstration of palaeogeography and tectonics and points to a close vicinity of the pkb to the african plate in the jurassic the results from the polish part of pkb which emerged in the latest years showed the same palaeolatitude for the callovian kimmeridgian limestones the low palaeomagnetic inclinations measured in the bajocian crinoidal limestones show that the southward drift may have started earlier than previously expected

palaeomagnetism and palaeogeography of the western carpathians from the permian to the neogene geodynamic models for the western carpathians require evaluation of palaeomagnetic data from the outer carpathian flysch belt from limestones of the klippen belt and from volcanic and sedimentary rocks of the inner carpathians palaeomagnetic data for the permian to the neogene are evaluated the data indicate marked mostly anticlockwise tectonic rotations of larger rock complexes and nappes the distribution of palaeomagnetic poles is characteristic of a collision zone and crosses the apparent polar wandering path for the african plate tectonic rotations are observed in both the inner carpathians and the klippen belt as well as in the outer carpathian flysch belt most drift occurred during the permian to triassic interval with northward movement from initial southern equatorial latitudes drift decelerated from the jurassic to the neogene fig 1 simplified geological map of the western carpathians showing the localities mentioned in the text the carpathian mountains represent a complex alpine fold and thrust belt which is over 1500 km long and has a pronounced arcuate shape figure 1 shows that part of the western carpathians within the territories of slovakia and moravia the system can be subdivided into three main tectonostratigraphic zones namely the outer zone or outer carpathian flysch belt the klippen belt and the inner zone or inner carpathians this paper summarizes palaeomagnetic data obtained in the western carpathians from units of permian to neogene age by various authors these data come from flysch deposits of the outer carpathians limestones of the klippen belt and volcanic and sedimentary rocks of the inner carpathians and mainly come from morris a tarling d h eds 1996 palaeomagnetism and tectonics of the mediterranean region geological society special publication no 105 pp 175 184 175

building and exhumation of the western carpathians new constraints from sequentially restored balanced cross sections integrated with low temperature thermochronometry western carpathian orogeny has been the subject of intense scientific debate due to the occurrence of enigmatic features leading several authors to provide contrasting geological models in this paper a new interpretation for the tectonic evolution of the western carpathians is provided based on i an analysis of the stratigraphy of the mesozoic tertiary successions across the thrust belt domains ii a reappraisal of the stratigraphy and sedimentology of the tectonic melange i e the so called pieniny klippen belt marking the suture between the inner and outer carpathians and iii the construction of a series of balanced and restored cross sections validated by 2d forward modeling our analysis provides a robust correlation of the stratigraphy from the outer to the inner carpathians independently of the occurrence of oceanic lithosphere in the area and allows for the reinterpretation of the tectonic relationships among the inner carpathians the outer carpathians and the pieniny klippen belt and the exhumation mechanisms affecting this orogenic belt in order to constrain the evolution during the last 20 ma our model also integrates previously published and new apatite fission track and apatite u th sm he data these latter indicate a middle late miocene exhumation of the pieniny klippen belt in this study the recent regional uplift of the pieniny klippen belt is described for the first time using a 2d kinematic model for the tectonic evolution of the western carpathians

geochronological constraints on tourmaline formation in the western fold belt of the mount isa inlier australia evidence for large scale metamorphism at 1 57 ga boron metasomatism during two deformational events resulted in tourmaline formation in parts of late palaeoproterozoic eastern creek volcanics of the western fold belt of the mount isa inlier despite low u pb ratios 1 as measured by laser ablation icp ms when the step leaching process was applied to the tourmaline it process extracted pb fractions with 206 pb 204 pb up to 76 illustrating the method s ability to efficiently separate radiogenic and common pb that are hosted in different crystal lattice sites tourmaline from two syn d2 metamorphic hydrothermal veins at anderson s lode and eldorado yield similar pb step leaching ages of 1573 12 and 1577 48 ma respectively tourmaline from a post d2 but pre d3a vein at king was dated at 1528 51 ma although there is evidence to suggest some contribution from u rich inclusions i e zircon and monazite to some leach steps the isochrons are thought to provide robust ages for hydrothermal tourmaline formation during two discrete thermal events this is supported by estimates of pb closure temperatures in tourmaline derived from ionic porosity models the 1575 ma ages for d2 also reflect the main metamorphic event in the western fold belt but are 40 myr older than accepted age estimates for this episode the revised timing for peak metamorphism tectonism in the western fold belt corresponds with the age of metamorphism in the eastern fold belt suggesting broadly coeval tectonic histories across the entire inlier from at least 1600 ma

palaeomagnetic results from the fold and thrust belt of the western carpathians an overview the western carpathians are separated into an outer and inner carpathians both comprising several nappe systems by the extremely narrow and highly deformed pieniny klippen belt the main phase of deformation and thrusting took place during the late cretaceous in the inner carpathians at the end of cretaceous paleocene in the pieniny klippen belt and in the miocene in the outer carpathians in this paper a large amount of palaeomagnetic results of different quality available from several nappe stacks and from overstep sequences were reviewed and interpreted in terms of tectonics the data suggest that all three main units participated in two phases of anticlockwise rotation starting at 18 5 ma that is the outer carpathian nappes in front of the already consolidated alpine carpathian pannonian block became accreted to the block late cretaceous nappe transport neogene uplift of core mountains and possibly oroclinal bending of pre oligocene age can account for important differences in pre cenozoic palaeomagnetic declinations most of them exhibit less or no anticlockwise rotation suggested by the overstep sequences implying pre cenozoic clockwise rotations of variable angles

provenance of the lower paleozoic balcarce formation tandilia system buenos aires province argentina implications for paleogeographic reconstructions of sw gondwana abstract lower paleozoic moderately sorted quartz arenites from the balcarce formation deposited in eastern argentina tandilia system comprise mainly detrital material derived from old upper crustal material the sources were magmatic sedimentary and subordinated felsic metamorphic terranes high concentrations of tourmaline and ti rich heavy minerals including zircon and nearly euhedral chromite are common trace element concentrations nb cr on rutile indicate pelitic and metabasaltic sources respectively major element analyses on chromites indicate a basic volcanic protolith of mid oceanic ridge origin which was exposed close to the depositional basin the delivery of chromite may be associated with convergent tectonics causing the consumption and obduction of oceanic crust during pre upper ordovician times the oblique orthogonal collision of the precordillera terrane with the western border of the rio de la plata craton west of the balcarce basin or source further to the east from a lower palaeozoic extensional basin are possibilities geochemical and petrographic data exclude the underlying precambrian and cambrian sedimentary rocks as dominant sources and favour the basement of the rio de la plata craton including cambrian rift related granites of south africa and the sierras australes eastern argentina as main suppliers of detritus trace element geochemistry of recycled pyroclastic material associated with the quartz arenites also suggests volcanic arc sources the provenance of the pyroclastic material may either be the puna famatina arc located in north and central argentina or a hypothetical active margin further to the south these ash layers are equivalent in age to volcanic zircons found in the devonian bokkeveld group in western south africa the deposition of a glacial diamictite of hirnantian age sierra del volcan diamictite is interpreted as a member of the balcarce formation based on the stratigraphic re location of the glacial diamictite and trace fossils the balcarce formation is considered here to be ordovician to silurian in age the balcarce formation can be correlated with similar rocks in south africa the peninsula formation and the upper table mountain group windhoek and nardouw subgroups including the hirnantian glacial deposit of the pakhuis formation

in situ elemental and boron isotopic variations of tourmaline from the maogongdong deposit in the dahutang w cu ore field of northern jiangxi province south china insights into magmatic hydrothermal evolution abstract in this paper we present a systematic investigation of in situ major trace elements and boron isotopic variations of tourmaline from the maogongdong deposit in the dahutang w cu ore field of northern jiangxi province south china which demonstrates both the magmatic and hydrothermal origin for the formation of the tourmalines the tourmaline occurs mainly in granites pegmatites and quartz veins five types of tourmaline are identified 1 disseminated tourmaline in the pegmatites tur p type 2 isolated and disseminated tourmaline clots in the granites tur r1 type 3 typical anhedral quartz tourmaline nodulars in the granites tur r2 type 4 tourmaline clots in quartz tungsten sulfide veins tur q1 type 5 euhedral needle columnar tourmaline crystals in quartz or quartz sulfide veins tur q2 type these tourmalines mostly fall into the alkali group representing schorl dravite solid solution series petrography and chemical discrimination diagrams suggest that the tur p tur r1 and tur r2 are of magmatic origin and the tur q1 and tur q2 are of hydrothermal origin hydrothermal tourmalines have higher mg mg fe ratios higher li be sn rb co sr v pb zn ni contents and lower na na ca ratios lower nb ta contents than the magmatic tourmalines the tur p show negative eu anomalies and their ree patterns are equivalent to the muscovite granite the eu anomalies in tur r1 and tur r2 change from negative to positive compared with magmatic tourmalines tur q1 and tur q2 exhibit more pronounced positive eu anomalies and a majority of the tur q1 and tur q2 have higher ree contents tourmalines from the maogongdong deposit have a b isotopic composition range from 17 9 to 12 3 the average 11b values of the tur p tur r1 and tur r2 are 13 8 14 8 and 14 5 respectively tourmalines in early hydrothermal veins have similar 11b values average 14 6 while the tourmalines in later hydrothermal veins have slightly lower 11b values average 16 5 boron isotopic variations of tourmaline are controlled by temperature rayleigh fractionation and external fluid

provenance analysis and tectonic setting of the ordovician clastic deposits in the southern puna basin nw argentina provenance studies on early to middle ordovician clastic formations of the southern puna basin in north western argentina indicate that the sedimentary detritus is generally composed of reworked crustal material tremadocquartzrich turbidites tolar chico formation mean composition q t 89 f7 l4 are followed by volcaniclastic rocks and greywackes tolillar formation mean q t 33 f42 l25 these are in turn overlain by volcaniclastic deposits mean qt24 f30 l46 of the diablo formation late arenig early llanvirn that are intercalated by lava flows all units were deformed in the ocloyic orogeny during the middle and late ordovician sandstones of the tolar chico formation are characterized by th sc ratios 1 la sc ratios 10 whereas associated fine grained wackes show slightly lower values for both ratios lree light rare earth elements enrichment of the arenites is 50 chondrite eu eu values are between 0 72 and 0 92 and flat hree heavy rare earth elements patterns indicate a derivation from mostly felsic rocks of typical upper crustal composition the e n d t s e d values scatter around 11 to 9 the calculated nd t d m residence ages vary between 1 8 and 2 0 ga indicating contribution by a palaeoproterozoic crustal component the th sc and la sc ratios of the tolillar formation are lower than those of the tolar chico formation normalized ree rare earth elements patterns display a similar shape to paas post archaean average australian shale but with higher abundances of hrees eu eu values range between 0 44 and 1 17 where the higher values reflect the abundance of plagioclase and feldspar bearing volcanic lithoclasts average e n d t s e d values are less negative at 5 1 and nd t d m are lower at 1 6 ga this is consistent with characteristics of regional rocks of upper continental crust composition which most probably represent the sources of the studied detritus the rocks of the diablo formation have the lowest th sc and la sc ratios lower lree abundances than the average continental crust and are slightly enriched in hrees eu eu values are between 0 63 and 1 17 the nd isotopes e n d t s e d 3 to 1 t d m 1 2 ga indicate that one source component was less fractionated than both the underlying early ordovician and the overlying middle ordovician units synsedimentary vulcanites in the diablo formation show the same isotopic composition our data indicate that the sedimentary detritus is generally composed of reworked crustal material but that the diablo formation appears to contain 80 of a less fractionated component derived from a contemporaneous continental volcanic arc there are no data indicating an exotic detrital source or the accretion of an exotic block at this part of the gondwana margin during the ordovician

equatorial ionospheric electric fields during the november 2004 magnetic storm 1 we use radar measurements from the jicamarca radio observatory magnetometer observations from the pacific sector and ionosonde data from brazil to study equatorial ionospheric electric fields during the november 2004 geomagnetic storm our data show very large eastward and westward daytime electrojet current perturbations with lifetimes of about an hour indicative of undershielding and overshielding prompt penetration electric fields in the pacific equatorial region during the november 7 main phase of the storm when the southward imf the solar wind and reconnection electric fields and the polar cap potential drops had very large and nearly steady values this result is inconsistent with the recent suggestion that solar wind electric fields penetrate without attenuation into the equatorial ionosphere for several hours during storm main phase the largest daytime prompt penetration electric fields about 3 mv m ever observed over jicamarca occurred during the november 9 storm main phase when large equatorial electrojet current and drift perturbations were also present in the pacific and brazilian equatorial regions the rise and decay times of these equatorial electric fields were about 20 min longer than of the corresponding solar wind electric fields the ratios of prompt penetration electric fields and corresponding solar wind electric field changes were highly variable even during the day and had largest values near dawn also the prompt penetration electric fields did not show polar cap potential drop saturation effects our results clearly highlight that the relationships of prompt penetration and solar wind electric fields and polar cap potentials are far more complex than implied by simple proportionality factors

palaeogeographic evolution of the pieniny klippen basin using stratigraphic and palaeomagnetic data from the veliky kamenets section carpathians ukraine abstract a 40 m thick carbonate succession of the bajocian to berriasian age from the veliky kamenets quarry novoselica area pieniny klippen belt ukraine resembles both the czorsztyn and niedzica successions of the pieniny klippen belt traditionally considered ridge slope related deposits a total of 176 individually oriented cores collected from the bottom to the top of the sequence with sampling density dependent on inferred sedimentation rates show multicomponent remanent magnetization with magnetite as a main magnetic carrier thermal demagnetization revealed two main components of natural remanent magnetization nrm a low blocking temperature component s of normal polarity is considered of posttectonic probably thermoviscous origin due to overheating by neogene volcanics a stable high blocking temperature nrm component p shows dual polarity distribution and is considered primary it was possible to recognize 23 polarity zones that have been correlated with a biostratigraphic scale since two significant sedimentary gaps occur at 422 and 860 cm the main hiatus ms from the base the latter comprising the middle callovian early oxfordian time span 6 8 ma an obtained pattern of magnetic reversals presented in this study cannot be considered complete a palaeolatitude of 41 5 is calculated for the mid jurassic part below ms similar to that expected for the european craton at the kamenets locality the mid oxfordian limestone directly overlying the ms has palaeolatitudes around 28 6 this implies a relatively fast opening of the oceanic domain to the north from the kamenets block this conclusion combined with similarity of the kamenets sequence to ridge related sediments of the pieniny klippen belt makes it possible to speculate on the existence of the kamenets ridge a new term a structure of uncertain although possible structural links to the czorsztyn ridge palaeomagnetic declinations suggest 100 counterclockwise rotation of the whole section before the neogene

minor counterclockwise rotation of the tatra mountains central western carpathians as derived from paleomagnetic results achieved in hematite bearing lower triassic sandstones abstract paleomagnetic studies accompanied with tectonic fieldworks have been carried out within hematite bearing lower triassic red beds from the tatra mountains central western carpathians in order to determine tectonic rotations of regional scale the studied rocks contain primary remanent magnetization recorded by hematite and display both polarities the obtained inclination is slightly lower than expected for stable europe which could imply either minor latitudinal separation or come from the inclination error the results from six sampling sites representing rocks situated in autochthonous cover of the crystalline basement and inclined only during the neogene uplift imply 19 counterclockwise rotation considering the tectonic position of the studied rocks this rotation could be attributed to the entire tatra block in turn results from rocks tilted in two tectonic events during late cretaceous compression and further in neogene uplift requires double tectonic correction as normal unfolding procedure results in spurious declination it is suggested that the latter mechanism together with local rotations of allochthonous nappes may explain part of variable rotations reported in previous paleomagnetic studies of mesozoic rocks from the central western carpathians

response of the equatorial ionosphere in the south atlantic region to the great magnetic storm of july 15 2000 the effects of the great magnetic storm of july 15 2000 on the equatorial ionosphere have been studied by ground based and satellite in situ measurements a large westward plasma drift in the evening equatorial ionosphere was observed as a result of the ionospheric disturbance dynamo in that environment the imf bz turned southward and presumably caused penetration of e fields to low latitudes this e field initiated the onset of 250 mhz and l band scintillations at ascension island 15 w and precipitous tec decrease at fortaleza brazil 38 w bounding the narrow longitude region in the south atlantic these impulsive ionospheric effects were extremely well correlated with abrupt decreases of sym h 1 min resolution dst the dmsp in situ measurements showed the presence of severe ion density bite outs extending over 30 latitude in the south atlantic magnetic anomaly region the rocsat 1 satellite measured upward and large southward ion drifts in the same sector

average characteristics and activity dependence of the subauroral polarization stream 1 data from the millstone hill incoherent scatter radar taken over two solar cycles 1979 2000 are examined to determine the average characteristics of the disturbance convection electric field in the midlatitude ionosphere radar azimuth scans provide a regular database of ionospheric plasma convection observations spanning auroral and subauroral latitudes and these scans have been examined for all local times and activity conditions we examine the occurrence and characteristics of a persistent secondary westward convection peak which lies equatorward of the auroral two cell convection individual scans and average patterns of plasma flow identify and characterize this latitudinally broad and persistent subauroral polarization stream saps which spans the nightside from dusk to the early morning sector for all kp greater than 4 premidnight the saps westward convection lies equatorward of l 4 60 invariant latitude spans 3 5 of latitude and has an average peak amplitude of 900 m s in the predawn sector saps is seen as a region of antisunward convection equatorward of l 3 55 spanning 3 of latitude with an average peak amplitude of 400 m s

basement chronology of the antarctic peninsula recurrent magmatism and anatexis in the palaeozoic gondwana margin abstract a revised pre jurassic chronology is presented for the antarctic peninsula on the basis of new u pb zircon dating using both conventional 11 samples and shrimp microprobe data 10 samples the age range for plutonism and high grade metamorphism is from 435 8 ma silurian to c 206 ma approximately the triassic jurassic boundary with peaks of activity in devonian carboniferous permian and mid triassic times although some are represented by rocks with limited outcrops the new data confirm the importance of mid and latest triassic magmatic events previously identified using rb sr geochronology the adie inlet gneiss previously thought to be neoproterozoic is recognized as a permian migmatite derived from paragneiss with a provenance dominated by cambrian granitoids granite gneiss from nw palmer land previously dated as cambrian is shown to be triassic detrital zircons in metasedimentary rocks and inherited zircons in granitoids are dominated by mesoproterozoic to cambrian components with sparse palaeoproterozoic to archaean grains suggesting sources within gondwana at times these sources were nearby as shown by an archaean cobble sized granite clast from a permo triassic conglomerate another clast in the same conglomerate previously thought to be devonian in age has an ordovician crystallization age

provenance signatures for the miocene volcaniclastic succession of the tufiti di tusa formation southern apennines italy the tufiti di tusa formation a siliciclastic turbidite system of lower miocene age in southern italy is mainly composed of volcaniclastic and quartzolithic sandstones interbedded with mudrocks sandstones are subdivided into four distinctive petrofacies evolving from quartzolithic to volcaniclastic lithofeldspathic and feldspatholithic reflecting detrital evolution from growing orogen quartzolithic petrofacies to active volcanism volcaniclastic petrofacies the mineralogical composition of the associated mudrocks is predominantly characterized by phyllosilicates mainly illite smectite mixed layers i s r1 associated with minor amounts of i s r0 in the lower part of the succession and i s r3 in its upper part together with illite detrital micas and chlorite and minor amounts of chlorite smectite mixed layers and kaolinite in addition to quartz calcite and feldspars the most abundant phyllosilicates are i s mixed layers 10 a minerals illite and micas and chlorite while kaolinite and chlorite smectite mixed layers are present as a few per cent or in trace amounts x ray diffraction patterns show the occurrence of the ordered i s r1 mixed layers in most samples but at the top of the succession some samples are characterized by i s r3 mixed layers whilst in the lower part of the succession i s r1 is associated with a lower amount of i s r0 these features suggest that the tufiti di tusa formation experienced a medium diagenetic grade and the occurrence of i s r3 could be explained by k availability in samples in the upper part of the succession the lithic fragments in sandstones are metasedimentary rocks of palaeozoic age and andesite to dacite volcanic rocks of early miocene age the associated mudrocks also contain trace element ratios cr v y ni la sc th sc th co th cr cr th and eu eu consistent with a provenance containing intermediate to silicic sources with scarce or absent basic rocks the chemical index of alteration 63 2 to 71 6 suggests a moderate degree of weathering in the source furthermore the k cs ratios of sediments confirm likely moderate rather than intense weathering the index of compositional variability icv values from 1 2 to 2 5 are high enough to suggest the mudrocks are first cycle sediments with little recycling the al ti zr diagram and the th sc v zr sc plot indicate poor sorting and rapid deposition of the sediments detrital and sedimentary evolution of the tufiti di tusa formation provides constraints in terms of relations between a growing orogenic system and active volcanism in the central mediterranean to contribute to geodynamic and palaeogeographic reconstructions of the earliest collision in the southern apennines region

critical evaluation of six tectonic setting discrimination diagrams using geochemical data of neogene sediments from known tectonic settings abstract an attempt is made to evaluate 6 tectonic setting discrimination diagrams 1 discriminant function and 5 bivariate diagrams frequently used by many researchers for this purpose an extensive database was established for major element geochemistry derived from miocene to recent sand and sandstone medium to fine grained samples collected from a variety of tectonic settings including 1 passive margin pm setting 2 active continental margin acm setting and 3 oceanic island arc oia setting our results suggest that the discrimination fields proposed to infer tectonic settings for six commonly used discrimination diagrams do not work properly for the analyzed miocene to recent sediments the success for these diagrams varies from 0 to about 62 we therefore recommend that these diagrams be used with prudence

first geochronological constraint for the palaeoproterozoic lomagundi jatuli δ13c anomaly in the tandilia belt basement argentina rio de la plata craton abstract geochronological data of palaeoproterozoic carbonates with 13c values between 5 and 16 suggest that the positive carbon isotope excursion of the global lomagundi jatuli event lje occurred mostly between 2220 and 2060 ma in the southern portion of the rio de la plata craton the lje was recorded in calcite diopside marble of the tandilia belt basement the marble was found at the san miguel area as part of a metamorphic rock assemblage mainly composed of gneisses and migmatites formed during the transamazonian orogeny the latter represents the maximum magmatic and metamorphic activity in the tandilia belt basement the marble derived from a calcareous siliciclastic sedimentary marine sequence was intruded by leucogranites that provoked the san miguel skarn formation first u pb la icp ms age of 2206 14 ma obtained from titanites of the skarn also placed the metasomatic processes into the transamazonian orogeny in addition this age corresponds to the minimum age for the marble s protolith deposition which matches with the beginning of the lje worldwide these new data would favor the correlation between the san miguel marble and the montevideo formation marble of the tandilia terrane uruguay within the rio de la plata craton and not with the paso severino formation of the piedra alta terrane which is at least 60 ma younger new 13c determinations in calcite crystals from the marble allowed the lowest and the highest carbon values 3 19 and 6 90 respectively to be obtained the lowest values are within the range of normal marine carbonates between 5 and 5 despite having been altered by contact metamorphism while the highest values are typical of the lje carbonates in this sense the early deposition of the carbonate protolith within the lje together with the effect of post depositional metamorphic processes would justify the wide range of values shown by the isotopic ratios of c

neoproterozoic to early cambrian crustal evolution of the pan african saldania belt south africa abstract the saldania belt forms part of a system of neoproterozoic mobile belts that surround and weld older cratons on the african continent it is a poorly exposed low grade orogenic belt composed of a number of inliers unroofed in mega anticlinal hinges of the permo triassic cape fold belt along the southern tip of africa deformed meta volcanosedimentary units are contained within tectonostratigraphic terranes separated by deep rooted sinistral dextral strike slip fault zones which display evidence of prolonged reactivation sedimentary rocks and volcanics of the boland terrane malmesbury group lower kango group and gamtoos group are considered to be distal facies of rift successions overlying the mid proterozoic crystalline basement on the southwestern edge of the kalahari craton these lithologies have been deposited in semi pull apart basins that formed in response to the breakup of rodinia and progressive opening of the proto atlantic adamaster ocean from 780 750 ma fragments of juvenile pan african crust with wpb morb characteristics occur in the bridgetown formation swartland terrane malmesbury inlier and attest to ocean floor spreading in this belt the thick turbidite successions of the swartland and tygerberg terranes malmesbury group reflect deeper water conditions and were deposited partly on oceanic crust in an evolving ocean continental margin basin marked by increasing sea levels and reduction of continental freeboard reversal of spreading and closing of the adamastor ocean possibly initiated by the opening of iapetus occurred in the period 600 570 ma although this movement vector caused sinistral transpressional reactivation of the gariep and saldanian margins there is no proper collision orogen developed in the saldania belt the bridgetown formation represents the suture between the southern rifted margin succession of the kalahari craton and a poorly developed southern orogenic belt represented in part by the swartland and tygerberg terranes this geosuture is similar to that of the south atlantic which formed in the analogous gariep belt between 575 and 543 ma multiphase s i and a type granites of the cape granite suite intruded the saldania belt in a pervasive transpressive regime between 550 and 510 ma comparing well with the timing of peak metamorphism collision in the gariep belt 545 ma the absence of a proper collisional orogen and the strongly developed northwesterly structural grain in the saldania belt seem to suggest that the cape granite suite was generated in a strike slip regime a discrepancy of approximately 50 ma between the age of the collision granites of the dom feliciano belt and cape granite suite suggests that they are genetically unrelated similarities in structural styles magmatism and dated events between the saldania ross delamarian chain of orogens however indicate a common history the evolution of this chain and that of the gariep damara dom feliciano belts can be accommodated in a single plate tectonic model of simultaneous sinistral transpressive subduction driven by the rifting of laurentia from south america and opening of the iapetus ocean loading and depression of the western and southern kalahari craton margin by thrust stacks of the late neoproterozoic orogens led to the formation of syn to post orogenic peripheral foreland basins such as those represented by the nama and vanrhynsdorp groups lowering of sea level and increased continental freeboard deposition of the unconformity based upper kango group and possibly the molassic franschhoek formation occurred in intra orogen pull apart basins which possibly developed between 530 and 510 ma in the saldania belt

new berriasian palaeopole from the central west carpathians tatra mountains southern poland does it look apulian summary a palaeomagnetic study was carried out in the northern part of the central west carpathians in the tatra mts 20 e 49 n berriasian pelagic carbonates from the krizna nappe fatricum were investigated at three localities 166 samples embracing a 100 m vertical section a mixed polarity pre folding magnetite related component was calculated for 87 samples representing the lower and middle berriasian the palaeopole 152 e 63 n is located close to the coeval eurasian palaeopole implying a net post berriasian 15 20 clockwise tectonic rotation of the krizna nappe in the investigated area relative to stable europe berriasian palaeolatitudes from the tatra mts are similar to those from the pieniny klippen belt and northern calcareous alps but systematically higher than in the transdanubian and italian apulian sections taking into account the fact that palaeomagnetic data from the overlying ter tiary rocks indicate 60 counter clockwise rotation of the central west carpathians after the oligocene the krizna nappe must have rotated clockwise before the eocene probably during the late cretaceous thrusting available palaeomagnetic data point to a palaeotectonic affinity of the central west carpathi ans and northern calcareous alps in the mesozoic the central west carpathians and northern calcareous alps reveal a rotation pattern that is predominantly clockwise whereas areas be longing to the apulian plate e g transdanubian mts southern alps and appenines show mostly counter clockwise rotations

chemical compositions and tectonic significance of chrome rich spinels in the tianba flysch southern tibet abstract turbiditic sandstones from the mid late cretaceous tianba flysch sequence are well exposed near tianba in the north nieru valley southern tibet and contain significant amounts of chrome rich spinels microprobe results show that the spinels have a well developed fe ti trend and have cr documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 normalfont selectfont declaretextfontcommand textcyr cyr pagestyle empty declaremathsizes 10 9 7 6 begin document landscape mathrm cr mathrm al end document 0 4 0 65 mg documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs

elemental and b o h isotopic compositions of tourmaline and associated minerals in biotite muscovite granite of mashhad ne iran constraints on tourmaline genesis and element partitioning abstract abundant tourmaline occurs in late triassic biotite muscovite granites of mashhad ne iran with several distinct morphologies including tourmaline nodules in granite pegmatitic tourmalines aplitic tourmalines and vein related tourmalines quartz tourmaline vein tourmaline rich vein and radial tourmalines pegmatitic and aplitic tourmalines are compositionally fe rich schorl and the nodule radial and vein tourmalines are mg rich schorl the tourmalines have generally low abundances for most trace elements except for sr ga li be sn pb and some transition elements tourmalines have low ree abundances and are enriched in lree and depleted in hree mostly below detection limits with positive eu anomalies the concentration of several trace elements e g pb be sn ga sr pb and ree correlates well with the major element composition of the tourmalines e g mg mg mg fe vacancy x site vacancy na and na na ca trace element data of coexisting minerals with tourmaline indicate that the oligoclase and albite show the most preference in sr pb and eu and lrees biotite readily incorporates rb ba zn li cs and nb k feldspar has high contents of rb ba sr and pb and garnet incorporates hrees and y during magma differentiation the b o h isotopic compositions for all tourmalines are consistent with an s type granite source that was derived from partial melting of the continental crust the pegmatitic and aplitic tourmalines with fe rich schorl composition indicate magmatic conditions and the radial vein and nodule tourmalines with mg rich schorl composition formed during the transition from magmatic to hydrothermal conditions due to the internal evolution of the granitic magma

topside ionospheric irregularities as seen from multisatellite observations we use in situ data from champ and dmsp satellites along with data of gps receiver onboard champ satellite and ground based gps receivers to study the occurrence and global distribution of ionospheric irregularities during the main phase of the geomagnetic storm of 29 31 august 2004 minimum dst excursion of a128 nt using the champ gps measurements we created maps of gps phase fluctuation activity and found two specific zones of the most intense irregularities 1 the region of the auroral oval at high latitudes of both hemispheres and 2 the low latitudes equatorial region between africa and south america at high latitudes the topside ionospheric irregularities appeared to be more intensive in the southern hemisphere which is most likely due to seasonal variations in the interhemispheric field aligned currents system an analysis of multi instrumental observations reveals reinforcement of the equatorial ionization anomaly after sunset in atlantic sector on 30 august and formation of the significant plasma depletions and irregularities over a large longitudinal range equatorial irregularities were also found in the morning sector at the recovery phase of the storm in addition to low earth orbit leo gps measurements we analyze the leo in situ measurements and we show that these two techniques cannot be interchangeable in all cases because of the altitudinal extent of plasma irregularities overall we demonstrate that the leo gps technique can serve a useful tool for detection of the topside ionospheric irregularities during space weather events and may essentially contribute to other methods based on various instruments

strong longitudinal difference in ionospheric responses over fortaleza brazil and jicamarca peru during the january 2005 magnetic storm dominated by northward imf 1 in this study we investigate the response of the equatorial f layer to disturbance zonal electric field associated with imf interplanetary magnetic field variations dominated by a strong northward bz episode during the magnetic storm that occurred on 21 january 2005 we compared the results obtained from digisondes operated at fortaleza brazil geogr 3 9 s 38 45 w dip angle 11 7 and jicamarca peru geogr 12 0 s 76 8 w dip angle 0 64 a large auroral activity ae intensification that occurred at 1715 ut produced a large f layer peak height increase from 300 km to 600 km over jicamarca with no noticeable simultaneous effect over fortaleza then the bz turning northward at 1940 ut with a rapid change in ae that was accompanied by a large decrease of f layer height and total suppression of the pre over fortaleza with no simultaneous effect over jicamarca strong increase in the ae index from 400 to 1000 nt with superimposed oscillations under bz north that soon followed was associated with increases in both the f layer height and the vertical drift velocity over fortaleza at 2130 ut with no corresponding signatures over jicamarca these remarkable contrasting responses to prompt penetration electric field ppef as well as to disturbance wind dynamo electric field ddef and other effects observed at the two locations separated only by 2 h in lt in the south american sector are presented and discussed in this paper effects onspread f development and fof2 behavior during this storm event are also addressed in this work

paleomagnetic implications on the evolution of the tethys belt from the atlantic ocean to the pamirs since the triassic abstract we first re examined the apparent polar wander curves for stable eurasia and africa since the triassic these curves were then combined together with curves of north and south america according to the kinematics of the atlantic ocean and a synthetic polar wander curve was given then most of the paleomagnetic results from the tethys mobile belt from the atlantic to the pamirs were analysed several groups of plates microplates and blocks can be seen first relatively stable regions like maghreb and sicily which have not moved much then we have a group formed by iberia sardinia italy and to a lesser extent corsica and the western and central alps for these blocks movements are anticlockwise rotations chiefly driven by the anticlockwise rotation of africa but they are sometimes stronger to the east a major change takes place the north of the aegean sea and the ionian zone are clockwise rotated and these rotations are recent oligocene miocene for the first part pliocene to the present for the second part a major problem arises in turkey caucasus and iran paleomagnetic results indicate a position far to the south of eurasia and at the same time geological evidence is in favour of a position close to eurasia we discuss these discrepancies

storm time plasma transport at middle and high latitudes associated with the large scale enhancement of the ionospheric convection electric field during disturbed geomagnetic conditions solar produced f region plasma is transported to and through the noontime cleft from a source region at middle and low latitudes in the afternoon sector as a result of the offset between the geomagnetic and geographic poles the afternoon sector region of strong sunward convection is shifted to increasingly lower geographic latitude throughout the interval between 12 ut and 24 ut a snowplow effect occurs in which the convection cell continually encounters fresh corotating ionospheric plasma along its equatorward edge producing a latitudinally narrow region of storm enhanced plasma density sed and increased total electron content which is advected toward higher latitudes in the noon sector the millstone hill incoherent scatter radar regularly observes sed as a spatially continuous large scale feature spanning local times between noon and midnight and at latitudes between the polar cap and its mid or low latitude source region for local times away from noon the latitude of most probable sed occurrence moves equatorward by 6 for an increase of 2 in the kp index during strong disturbances the topside sed is observed to be convecting sunward at 750 m s 1 with a flux of 1014 m 2 s 1 this feature accounts for the pronounced enhancement of ionospheric density near dusk at middle latitudes observed during the early stages of magnetic storms called the dusk effect and constitutes a source for the enhanced f region plasma observed in the polar cap during disturbed conditions

models for relative motion of crustal blocks within the carpathian region based on restorations of the outer carpathian thrust sheets details of the oligocene present day motion of the adriatic block with respect to europe can be determined by palinspastic restorations of the outer carpathians thrust sheets the arcuate nature of the carpathians poses problems for simple restorations of sections because they create converging restoration paths which require large amounts of strike parallel extension 40 50 such large amounts of extension are not seen on maps or in the field a combination of thrust transport directions changing with time between and within thrust sheets and divergent transport directions helps minimise the arc parallel extension necessary 18 25 the pannonian basin can be treated either as an area dominated by strike slip motion rigid block movements or as an area of back arc extension the differences in restoration geometry produced by these two scenarios help to indicate which of the two mechanisms was dominant the consequences of the rigid block restoration indicate the model is inappropriate because it requires approximately 20 clockwise rotation of the adriatic block during the late tertiary it also indicates at least 300 km strike slip motion distributed among the late tertiary faults of the dinaride balkanide and hellenide mountain belts the back arc extension model alleviates the the 20 clockwise rotation of the adriatic block and requires about 200 km distributed strike slip motion in yugoslavia and bulgaria

tectonic environment of the devonian gramscatho basin south cornwall framework mode and geochemical evidence from turbiditic sandstones the portscatho formation within the allochthonous unit of the middle and upper devonian gramscatho group is a thick sequence of deep water sandstones and interbedded slates deposited by southerly derived turbidity currents into the gramscatho basin of south cornwall throughout an approximately 3 5 km thick sequence the portscatho formation is petrographically and chemically coherent except that the upper section shows a higher proportion of metamorphic clasts high but variable cr and low uniform zr abundances complementary framework mode and bulk geochemistry indicate that the sandstones were derived from a dissected continental magmatic arc of predominantly acidic composition similar to average upper continental crust but with an admixture of minor intermediate basic material flysch deposition took place in a fore arc setting the presence of an arc to the south of cornwall during the devonian implies that there was subduction at the margin of the gramscatho basin whose ultimate closure was accommodated by the northward stacking of flysch ophiolite nappes

storm induced plasma stream in the low latitude to midlatitude ionosphere 1 geomagnetic disturbances from 7 to 12 november 2004 were quite intense and the maximum excursion of dst reached 374 nt unusual ionospheric phenomena have been observed around the world that have been associated with successive magnetic storms during this period the ionospheric total electron content tec was increased at the longitudes of japan within a short time after sunset on 8 november from 20 tec units at 1830 jst to 97 tec units at 2015 jst jst ut 9 h where 1 tec unit 1 1016 el m2 the enhanced tec was significant over hokkaido 43 n and the center of the enhanced region was well within the plasmasphere as an l value of approximately 1 5 the drift velocity of the plasma in the density enhanced region measured by the defense meteorological satellite program dmsp satellite was westward with a peak value of 250 m s in the earth s frame demonstrating a positive correlation between density and drift velocity a similar tec event was observed after sunset on 10 november tec was enhanced from 15 tec units at 1830 jst to 45 tec units at 2030 jst during the second event the ionosphere was highly structured and the rate of the tec index roti increased the two dimensional map of a roti enhanced region exhibited the west to northwest transportation of plasma in which density irregularities were entrained a physical mechanism is proposed to explain these disturbances i e storm induced plasma stream which is different from a phenomenon called storm enhanced density at midlatitudes

longitudinal structure of the equatorial anomaly in the nighttime ionosphere observed by image fuv 1 the far ultraviolet imager fuv on board the image satellite provides an instantaneous global view of the oi 135 6 nm nightglow with 2 min time resolution because the oi 135 6 nm emission from the nighttime ionosphere is determined by the line of sight integrated plasma density the nightglow images are useful for studying the nighttime low latitude ionosphere globally with the image fuv 135 6 nm observations from march to june 2002 we have examined the global characteristics of the nighttime equatorial anomaly ea by constructing a constant local time map lt map in which pixels within an assigned local time range are extracted from the image fuv nightglow images obtained over an observation period of 3 days or more and are put together to compose a global distribution map of emission intensities at that local time these lt maps show that the development of the ea has a significant longitudinal structure in which peaks and dips of the crest emission intensity and the crest latitude have about 90 longitudinal separation in the longitude range from 0 to 250 although there is not enough data over the american sector this result suggests that the ea longitudinal structure has a prominent zonal component of the wave number 4 the observed longitudinal structure of the nighttime ea could not be fully explained by factors such as the empirical electric field and neutral wind models the geomagnetic declination angle or the displacement of the geomagnetic equator from the geographic equator to explain the observed longitudinal structure of the ea in particular the wave number 4 feature we may need to consider other forcing for example nonmigrating tide originated from the lower atmosphere

new paleomagnetic results from the upper cretaceous red marls of the pieniny klippen belt western carpathians evidence for general ccw rotation and implications for the origin of the structural arc formation abstract the pieniny klippen belt pkb is a narrow arcuate structure separating the central and outer western carpathians formed during several cenozoic deformational stages the primary aim of this study was to obtain paleomagnetic constraints for the mechanism of formation of the arc we investigate albian santonian red pelagic marls from 14 localities distributed along a strike length of ca 400 km ams measurements reveal a pattern characteristic of weakly deformed sedimentary rocks and magnetic lineations do not correlate with the general strike of the pkb paleomagnetic analysis revealed well defined hematite based ancient magnetization components at 13 localities which are dated using fold and inclination tests a within locality fold test is negative for two localities exhibiting large ccw rotations of similar magnitude situated at the two ends of the pkb remanences of pre folding age were documented for 11 localities with an overall mean paleomagnetic direction of d 311 i 53 and 95 11 the indicated general ccw rotation most probably took place during the miocene together with western central and outer carpathians paleolatitudes for the pkb indicate a considerable separation from the southern margin of stable europe leaving space for coordinated rotation a paleomagnetic oroclinal test involving all localities with primary magnetizations was negative when localities with monoclinal steep dips are omitted due to possible declination bias the overall mean paleomagentic direction does not change significantly but correlation is observed between the general trend of the pkb and the paleomagnetic declinations thus we conclude that the present shape of the arc can be partly due to oroclinal bending this must have happened before oligocene since paleomagnetic declinations for neighboring paleogene basins in the central and outer western carpathians reveal a uniform ccw rotation of ca 50 magnitude irrespective of the position of the localities in relation to the carpathian arc

ionospheric signatures of plasmaspheric tails 1 we make direct comparisons between gps maps of total electron content tec over the north american continent millstone hill radar observations of storm enhanced density and low and high altitude satellite measurements of the perturbation of the outer plasmasphere during the march 31 2001 geomagnetic storm we find that storm enhanced density sed and plumes of greatly elevated tec are associated with the erosion of the outer plasmasphere by strong sub auroral polarization electric fields the sed tec plumes identified at low altitude map closely onto the magnetospheric determination of the boundaries of the plasmapause and plasmaspheric tail determined by euv imaging from the image spacecraft characteristics of the sed tec plumes tails for the march 31 2001 event are tec 100 tecu f region sunward velocity 1000 m s sunward flux 5 1024 ions s 1 total transport to dayside magnetopause merging region 3 hr event 5 1028 ions

dependence of anisotropy of magnetic susceptibility of rocks on temperature abstract the influence of heating on the low field magnetic susceptibility k and its anisotropy ams has been studied in some sedimentary igneous and metamorphic rocks the results show that heating causes a better grouping of the anisotropy ellipsoid axes especially in sediments in all the rocks studied the ams is mainly due to the matrix i e paramagnetic and diamagnetic minerals rather than the ferromagnetic minerals the ams of the diamagnetic components is removed during heating an experiment involving thermal remagnetization of one sediment sample indicates that the processes of thermal magnetization do not influence the directions of anisotropy axes in this rock

kinematics of retreating subduction along the carpathian arc romania kinematic axes and resultant vectors of displacement along the carpathian arc and the apuseni mountains aid in the reconstruction of retreating subduction along the carpathians the recent vertical position of the subducted slab below the vrancea area of the eastern carpathians represents the final rollback stage of a small fragment of oceanic lithosphere formerly situated between the moesian and east european plates the ages and locations of the eruption centers of the andesitic volcanic chain along the carpathian arc in the overriding plate as well as the thrust directions are used as markers to reconstruct the rollback area of the subducted slab between the moesian and east european plates

a provenance study of the paleozoic ventania system argentina transient complex sources from western and eastern gondwana abstract the u pb and lu hf isotopic analyses of the different sedimentary sequences of the ventania system an old paleozoic orogenic belt exposed in the southern region of the rio de la plata craton in the province of buenos aires argentina provide new evidence for the understanding of the tectonic evolution of the western sector of the gondwanides mountain belt these ranges formed as result of the late paleozoic collision of the patagonia terrane against the continental margin of gondwana the provenance analysis together with the sedimentary paleocurrents confirm a dominant source from the tandilia system a paleoproterozoic mountain belt formed during the amalgamation of the rio de la plata craton at about 1800 2200 ma and incorporated to western gondwana during the brasiliano orogeny at 550 530 ma the local dominant source at the base of the early paleozoic changed to more distant supplies toward the top of the sequences when an increasing participation of detritus from first cambrian 560 520 ma zircons from the pampean orogen and later on ordovician 480 460 ma zircons from the famatinian orogen is recorded the detrital zircon patterns and the maximum age of the units shed light on some previous discrepancies in the early paleozoic stratigraphy the balcarce formation an early paleozoic sedimentary cover of the tandilia metamorphic and igneous basement shows striking differences when compared with the new data from the ventania system the two data sets reveal different sources for the two regions the late paleozoic foreland basin deposits mark an abrupt change of 180 in the paleocurrent directions in the petrographic composition of the sediments and in the provenance of detrital zircons these data indicate a southern provenance with the first evidence of carboniferous and permian magmatic zircons the oldest archean zircons together with the finding of clasts with archeocyathids support the provenance from patagonia which was derived from eastern gondwana the u pb ages of the ash fall tuffs in the tunas formation confirm the early permian age of the eurydesma fauna in the ventania system the u pb data together with the lu hf isotopic data enhance the comprehension of the tectonic evolution of the ventania system as part of the larger gondwanides belt that amalgamated to western gondwana during late permian times with some independent pieces derived from eastern gondwana

extreme enhancement in total electron content after sunset on 8 november 2004 and its connection with storm enhanced density 1 after sunset on 8 november 2004 the ionospheric total electron content tec was observed to have anomalously increased following a severe daytime positive tec storm at longitudes of japan the observation was made using a dense gps receiver network and covered a geographic latitudinal range of 27 to 45 n there was a greater increase in tec at higher latitudes in the evening and the tec reached 90 tec units at 45 n 40 n magnetic latitude at 1145 ut 2045 lt the tec enhancement exhibited features significantly different from those of positive tec storms normally observed at japan s longitudes these features are interpreted as low latitude signatures of a storm enhanced density sed previously seds were reported only at longitudes of america and this led to the hypothesis that geomagnetic field configurations at these longitudes play a role in their formation the present observations indicate that seds can be observed at other longitudes

provenance and depositional environment of rhenohercynian synorogenic greywackes from the giessen nappe germany the giessen nappe of the south eastern rhenish massif can be subdivided into a northern group and southern group of frasnian lower carboniferous greywackes that differ slightly in their sedimentology clast petrography heavy mineral assemblages and bulk geochemistry

neoproterozoic to lower palaeozoic successions of the tandilia system in argentina implication for the palaeotectonic framework of southwest gondwana the cryogenian to uppermost ediacaran successions of the tandilia system sierras bayas group and cerro negro formation in central eastern argentina is exceptional because of its unmetamorphosed and nearly undeformed character its sediment provenance trend and the absence of any identified glacial deposit and the deposition of warm water carbonates we decipher a dramatic change in the basin evolution from small scale depositional areas during the neoproterozoic to a larger basin related to an active continental margin throughout the uppermost ediacaran the base of the succession is represented by immature detritus of alkaline composition villa monica formation but towards the top of this formation the material is sorted and reworked nonetheless still reflecting in its detritus the local rocks the clastic deposition is interrupted by diagenetic overprinted dolomites the unconformable overlying quartz arenitic ediacaran cerro largo formation reworked the cryogenian villa monica formation and contains mainly felsic granitic and metamorphic basement material of slightly wider variety while the dominant alkaline geochemical signature in rocks of the villa monica formation disappears based on diagenetic petrographic and sedimentological data we can interpret the unconformity representing a longer time of erosion the cerro largo formation shows a transition to mudstones and the heterolithic facies of the olavarria formation the top of the sierras bayas group is represented by limestones loma negra formation which are discordantly overlain by the uppermost ediacaran cerro negro formation the latter displays detrital material derived from a continental arc mafic and felsic sources several arc related geochemical proxies th sc 20 are recorded in the sediment detritus as are syn depositional pyroclastites the absence of volcanic material in the underlying rocks allows proposing that the cerro negro formation is related to an active continental margin fringing gondwana terra australis orogen as a retro arc or retro arc foreland basin