geochemical insights into provenance of the middle devonian hamilton group of the central appalachian basin u s a abstract in order to better understand the relationship of clastic influx and organic matter accumulation and preservation in the middle devonian acadian foreland basin we conducted a high resolution provenance analysis of a composite section of the hamilton group the hamilton group includes the organic rich marcellus shale one of the most lucrative unconventional shale gas plays in the world and the overlying mahantango formation geochemical analysis of 121 samples from two nearby wells in monongalia county west virginia reveals subtle changes in clay provenance throughout deposition of the marcellus shale and the mahantango formation major element and trace element geochemistry suggest derivation from a felsic igneous granodioritic upper continental crustal source with additional influx from a recycled quartzose sedimentary source all weathering indices indicate increasing chemical weathering intensities throughout deposition of the marcellus shale followed by consistently moderate chemical weathering associated with accumulation of the mahantango formation sm nd isotopic analysis of ten samples throughout the hamilton group yield end values ranging from 7 06 to 11 75 and nd depleted mantle model ages dm ranging from 1 63 to 1 85 ga with ages becoming younger upsection our results suggest that the extrabasinal detritus of the hamilton group originated from a mixed sediment source with clay influx from both rocks associated with the superior craton to the north and northwest dm 2 7 ga and grenville sourced sediments derived from the adjacent acadian fold thrust belt to the east dm 1 4 1 6 ga older sm nd model ages felsic composition and evidence of sediment recycling suggest little to no contribution from the acadian volcanic arc indicating that volcanic tuff of the tioga ash beds represent isolated episodes of volcanic input into the basin model ages end values and trace element geochemistry indicate increased sediment influx from the acadian fold thrust belt throughout deposition of the hamilton group with the highest sediment influx having occurred during mahantango formation deposition increased clay influx from sediment shed off from the acadian fold thrust belt associated with marginal marine regression increased delivery of clastic detritus diluting the flux of organic matter and likely disrupting basin water stratification that aided in preservation of organic matter in the lower marcellus shale the middle devonian acadian basin serves as an example of the influence of detrital influx on organic matter accumulation and preservation in mud dominated depositional systems

high precision microsampling and preparation of zoned garnet porphyroblasts for sm nd geochronology abstract zoned garnet porphyroblasts contain one of the longest continuous records of tectonic processes with growth histories spanning many millions of years well known challenges exist in the physical preparation purification and geochronologic analysis of zoned garnets which have limited the progress and application of this potentially powerful geochronologic tool here we present details of an integrated methodology specifically for the acquisition of high resolution sm nd geochronologic records from zoned garnets that overcome these challenges we develop and demonstrate our methods on large test garnets from a shear zone in the tauern window in western austria chemically contoured microdrilling permits physical sampling of many discrete age annuli each as narrow as 100 m within a single garnet refined hno 3 hf hclo 4 partial dissolution methods cleanse coarse crushed 75 150 m size garnet annuli of detrimental inclusions yielding high 147 sm 144 nd ratios 0 9 to 4 6 and consequently accurate and precise ages experiments on powdered garnet 147 sm 144 nd 143 nd 144 nd with 10 20 ppm 2 rsd precision good enough for 147 sm 144 nd 1 0 in total this integrated sampling and analytical protocol permits the acquisition of 3 11 discrete high precision

inter relationships between deformation partitioning metamorphism and tectonism abstract thrusting from the east loaded the thick pomfret dome stratigraphic sequence in vermont to such an extent that by the time the first schistosity had formed it was 20 km deep this occurred without garnet growth even though rock compositions were ideal for this phase to grow before they reached this depth the rocks remained at this depth until garnet growth ceased 50 million years later after 5 periods of fia development foliation intersection inflection axes preserved within porphyroblasts the first phase of the garnet growth in each sample from the pomfret dome was overstepped in pressure nucleating well above the incoming phase boundary for this phase at 7 kbar for whatever fia set was the first to develop this was not the case 45 km s in the chester dome where a thin stratigraphic sequence overlay a basement high of gneiss lateral ramping against this basement thinned the thrust sheet preventing overstepping frontal ramping to the wnw had the same effect the pressure did not increase in both regions to 7 kbars until fia 2 approximately 50 of the rocks sampled around the pomfret dome did not grow garnet during fia 0 pt pseudosections and overstepped garnet phase boundaries indicate that all would have grown garnet if the bulk composition and pt were the only controlling factors if metastability alone was a factor the other 50 should have grown garnet during the development of fia 1 they did not and this pattern was repeated for fias 2 and 3 why where and when garnet first grew in this pt overstepped environment was recorded by the inclusion trail geometries in each sample all grew at the start of crenulation producing events the variable partitioning of a succession of differently oriented crenulation deformations through the region from fia to fia controlled where garnet growth first occurred successive fias shifted the bulk shortening direction relative to competent rocks deforming sites previously protected and protecting others the nw se trend of fia 0 resulted in most deformation pervasively partitioning ne of the competent gneiss beneath the chester dome and green mountains consequently the bulk of porphyroblast growth within the pomfret dome region occurred at this time the effects of nw se bulk shortening partitioned through similar amounts of gneiss during fia 1 generating the same percentage of new sites for garnet growth in both regions as a result 60 of all garnet growth within the pomfret region had occurred before the n s directed bulk horizontal shortening during fia 2 began resulting in an increase in bulk competency this caused deformation to preferentially partition pervasively through the previously more competent chester region generating 35 of all garnet cores plus loading through crustal thickening to a depth of 7 kbar this increase in pressure prior to fias 3 and 4 enabled other rocks with different bulk compositions to grow garnet for the first time during these later periods of orogeny it also resulted in considerable growth on the rims of garnet porphyroblasts that had grown much earlier during the deformation history

kinematics u pb geochronology and 40ar 39ar thermochronology of the gold hill shear zone north carolina the cherokee orogeny in carolinia southern appalachians the gold hill shear zone is the most prominent pre carboniferous structure in the southern appalachian peri gondwanan tract of carolinia common perception based on indirect evidence holds that it is an acadian dextral strike slip shear zone however our recent structural and geochronologic studies directed at the shear zone indicate that it is a complex structure in both time and space structural studies in central north carolina kinematically link deformation in the shear zone to regional shortening structures in both the hanging wall and footwall and indicate that there was a sinistral component to the deformation collectively these structures constitute a regional sinistral transpressional system we obtained nine new u pb zircon ages ediacaran devonian and 12 new 40 ar 39 ar muscovite ages late ordovician middle mississippian these data in conjunction with the regional geology indicate that the shear zone has 12 km of stratigraphic throw and that the main motion on the zone was late ordovician collectively geologic relations structures and the distribution of 40 ar 39 ar ages indicate that the shear zone was reactivated in the late devonian and the middle mississippian the regional late ordovician silurian sinistral transpressive system of which the gold hill shear zone is part represents the most widespread tectonism documented in carolinia it overlaps in time with the ordovician silurian cherokee unconformity in laurentian strata and late ordovician silurian suprasubduction zone magmatism and metamorphism in peri laurentian rocks and consequently is considered a manifestation of the southern appalachian cherokee orogeny marking the accretion of carolinia to laurentia

effect of ray and speed perturbations on ionospheric tomography by over the horizon radar a new method most recent methods in ionospheric tomography are based on the inversion of the total electron content measured by ground based gps receivers as a consequence of the high frequency of the gps signal and the absence of horizontal raypaths the electron density structure is mainly reconstructed in the f2 region 300 km where the ionosphere reaches the maximum of ionization and is not sensitive to the lower ionospheric structure we propose here a new tomographic method of the lower ionosphere based on the full inversion of over the horizon oth radar data previous studies using oth radar for ionospheric tomography inverted only the leading edge echo curve of backscatter ionograms the major advantage of our methodology is taking into account numerically and jointly the effect that the electron density perturbations induce not only in the speed of electromagnetic waves but also on the raypath geometry this last point is extremely critical for oth radar inversions as the emitted signal propagates through the ionosphere between a fixed starting point the radar and an unknown end point on the earth surface where the signal is backscattered we detail our ionospheric tomography method with the aid of benchmark tests having proved the necessity to take into account both effects simultaneously we apply our method to real data this is the first time that the effect of the raypath deflection has been quantified and that the ionospheric plasma density has been estimated over the entirety of europe with an oth radar

medium scale traveling ionospheric disturbances detected with dense and wide tec maps over north america 1 nighttime and daytime medium scale traveling ionospheric disturbances mstids are detected with dense and wide detrended total electron content tec maps over north america using multiple gps receiver networks the tec maps cover a wide region of 60 130 w and 24 54 n 30 65 n in geomagnetic latitude and have a spatial resolution of 1 05 1 05 in latitude and longitude 0 15 0 15 with 7 7 pixel smoothing and a temporal resolution of 30 seconds the tec maps reveal for the first time that the nighttime mstids propagate southwestward with 200 500 km wavelengths over north america and have wavefronts longer than 2 000 km we also observe that daytime mstids with 300 1 000 km wavelengths propagate southeastward until mid afternoon and southwestward in the late afternoon in the mid to late afternoon these mstids propagating in the different directions are superimposed the tec maps can be a new powerful tool to investigate the mstids

three dimensional estimation of electron density over japan using the geonet gps network combined with sac c data and ionosonde measurements 1 the work presented here proposes a local tomographic approach to obtain a three dimensional description of the ionospheric electron density over japan to do this a combination of gps and ionosonde data is used in order to take advantage of the strong points of each data type the gps data is composed of ground and sac c low earth orbiter observations the ground observations correspond to measurements of 99 receivers out of about 1000 from the dense japanese gps network geonet sac c gps limb sounding observations are processed to obtain vertical profiles of electron density for this purpose an improved approach of abel inversion that considers vertical total electron content data has been used to overcome the assumption of spherical symmetry the resulting profiles have been averaged to build a set of background profiles which are rescaled with the ionospheric nmf2 values sounded by the japanese network of four ionosondes and used by the tomographic algorithm to provide with vertical description of electron density for the validation of this tomographic approach the hourly values of nmf2 given by the four japanese ionosondes and the vertical profiles of electron density measured by the mu radar in shigaraki during the sounding campaign of november 2002 have been used this validation with independent data shows relative discrepancies about 25 and moreover it shows that the use of the profiles obtained from sac c data offers an improvement on the dawn dusk and nighttime bottomside and topside estimations of the electron density with respect to the case of using the iri model

monitoring the daytime variations of equatorial ionospheric anomaly using ionex data and champ gps data a method which can invert the ionospheric electron content above the champ satellite is presented the daytime behavior of the equatorial ionospheric anomaly eia is monitored using the champ global positioning system data and the ionosphere map exchange format data supplied by the center for orbit determination in europe during the period at quiet geomagnetic conditions between november 7 and december 12 2003 results show that the plasma congregates and rises above the geomagnetic equator due to the daytime upward vertical drift during the early variations of eia after being lifted to higher altitudes the topside ionospheric equatorial plasma above the champ orbit over 400 km above the ground controlled mainly by the electromagnetic field starts to diffuse downward to higher latitudes along magnetic field lines and the double humped structure begins to appear in the topside ionosphere above the champ orbit however a single crest is still observed for the entire ionosphere above the ground and this single peak moves slightly to the winter hemisphere as a result of the transequatorial neutral wind with the continuous diffusion of the plasma the two crests also occur for the entire ionosphere at both sides of the geomagnetic equator

young ages from old garnet in the polyphase metamorphic terrane of the limpopo belt south africa abstract the p t t path of high grade metamorphic rocks is significant for understanding vertical motions and heating of the crust in general garnet is used to constrain p t paths and metamorphic zircon is used to obtain t for different metamorphic stages however this approach may be complicated by polyphase tectonothermal events the central zone of the limpopo belt in south africa is a complex precambrian metamorphic terrane that has experienced three distinct high grade metamorphic events at 3 22 ga m1 2 62 ga m2 and 2 02 ga m3 based on zircon dating a previous investigation of a metapelite enclave in the bulai pluton in the central zone showed that metamorphic zircon in the enclave recorded mainly m2 granulite facies metamorphism and was protected by the bulai pluton however titanite and rutile u pb ages of the same sample record the m3 event here we investigated garnet sm nd isotopic systematics of four metapelite samples from the evelyn enclave in the bulai pluton we constructed single mineral sm nd isochrons for garnet using micro samples in order to avoid the risk of isotopic disequilibrium between different minerals or whole rocks metamorphic zircon with sillimanite inclusions has yielded a granulite facies metamorphic age of ca 2 6 ga however the sm nd isotopic data for the garnet record much younger ages of ca 2 03 ga these ages are consistent with the m3 event in this area but were rarely identified in previous zircon dating studies this suggests that the m3 event reached sufficiently high temperatures to totally reset the rutile and titanite u pb and garnet sm nd systems moreover the decoupling of the age of garnet formation and the date it records needs to be carefully considered when reconstructing p t t paths and again highlights the usefulness of garnet in the study of polyphase metamorphic terranes

technogenic soils technosols developed from fly ash and bottom ash from thermal power stations combusting bituminous coal and lignite part i properties classification and indicators of early pedogenesis abstract large amounts of fossil fuel combustion wastes e g fly and bottom ash are discharged on land surface all over the world the uppermost layer of disposal sites is subject to soil forming processes after the development of plant cover due to natural succession or reclamation works the present study presents the analysis of technogenic soils technosols developed from ashes after combustion of bituminous coal and lignite the study involved the determination of their properties their classification and discussion of the indicators of early pedogenesis technosols located on the surface of settling ponds and landfills of selected thermal power stations in poland combusting both bituminous coal and lignite were examined standard pedological methods for the determination of soil morphology and physical chemical properties were applied dithionite and oxalate extractions of fe al si and mn were used in order to determine transformations of soil substrate during pedogenesis moreover optical microscope observations permitted finding microscale effects of soil forming processes in the studied technosols the properties of the analysed technosols are primarily influenced by the properties of the parent material i e ash from thermal power stations which in turn are strongly dependent on 1 the type of ash fly ash vs bottom ash 2 the kind of fuel bituminous coal vs lignite as well as 3 the mode of ash deposition and type of disposal site settling pond vs dry landfill properties of the studied soils are also controlled by the following soil forming factors vegetation input of soil organic matter human acceleration of soil forming processes by reclamation and climatic weather conditions leaching of soluble compounds by water from precipitation the most important morphological and physical chemical indicators of pedogenesis of the studied technosols over several decades of soil formation are as follows 1 the development of soil structure in a horizon related to the accumulation of soil organic matter 2 the decrease in ph a change in reaction from strongly alkaline towards less alkaline or acidic 3 the formation of pedogenic carbonates and their subsequent leaching from the topsoil after several dozen of years of pedogenesis and 4 the release of oxalate extractable al and si during the pedogenesis the studied soils were classified according to wrb as spolic technosols or leptic spolic technosols with various supplementary qualifiers alcalic or eutric arenic and or loamic calcic or protocalcic fluvic hyperartefactic laxic relocatic tephric or vitric certain suggestions to improve the wrb soil system are discussed in the paper

improving the abel inversion by adding ground gps data to leo radio occultations in ionospheric sounding gps radio occultations allow the sounding of the earth s atmosphere i e troposphere and ionosphere the basic observable of this technique is the additional delay due to the refractivity index of a radio signal when passing through the atmosphere this additional delay is proportional to the integrated refractivity in such a way that we can obtain an estimation of the vertical refractivity profiles using observations at different elevation angles by solving an inverse problem traditionally the solution of this inverse problem is obtained by using the abel inversion algorithm assuming a refractivity index that only depends on the altitude in this paper we present a modified abel inversion algorithm for ionospheric sounding that overcomes the spherical symmetry assumption of the traditional abel inversion algorithm processing a set of simulated data and 1 day of real data with this algorithm a clear improvement over the traditional one can be obtained when comparing the derived critical frequencies with the ionosonde measurements it is also shown that this improvement is sufficient to measure critical frequencies associated with the ionospheric e layer

vertical structure of medium scale traveling ionospheric disturbances we develop an algorithm of computerized ionospheric tomography cit to infer information on the vertical and horizontal structuring of electron density during night time medium scale travelling ionospheric disturbances mstids to facilitate digital cit we have adopted total electron contents tec from a dense global positioning system gps receiver network geonet which contains more than 1000 receivers a multiplicative algebraic reconstruction technique mart was utilized with a calibrated iri 2012 model as an initial solution the reconstructed f2 peaklayer varied in altitude with average peak to peak amplitude of 52 km in addition the f2 peak layer anti correlated with tec variations this feature supports a theory in which night time mstid s comprise of oscillating electric fields due to conductivity variations moreover reconstructed tec variations over two stations was reasonably close to variations directly derived from the measured tec dataset our tomographic analysis may thus help understand three dimensional structure of mstids in a quantitative way

monazite age constraints on the tectono thermal evolution of the central appalachian piedmont the central appalachian piedmont lies in the critical juncture between the northern and southern appalachians portions of the orogen with distinct middle to late paleozoic accretionary histories orogen scale compilation maps link the central and southern appalachians but until recently limited geochronological data prevented robust tectonic comparisons between high grade metamorphic rocks in different parts of the orogen we report the results of in situ u th total pb monazite geochronology that date significant deformation and metamorphism as middle silurian 425 ma through middle devonian 385 ma and demonstrate the diachronous nature of orogen development the rosemont shear zone is identified as a major tectonic boundary in southeastern pennsylvania and northern delaware separating the rifted laurentian margin from younger rock units that formed in a magmatic arc setting the laurentian margin rocks occur in a series of nappes in which the metamorphic grade decreases from the structurally highest nappe to the lowest the in situ monazite ages show that maximum temperature in the lowest nappe may have been attained some 15 million years after maximum temperature in the highest nappe we interpret this to be the result of successive nappe emplacement with the warmer overriding sheets contributing heat to lower levels combining geochronologic and thermobarometric results with the geometry of deformation results in a new picture of the tectonic development of the central appalachian piedmont that further links the evolution of the southern and northern appalachians for the laurentian margin rocks tectonism resulted from the approach and collision of peri gondwanan terranes during the silurian to early devonian in a dominantly sinistral transpressive tectonic regime this portion of the pennsylvania delaware piedmont inboard of the rosemont shear zone is contiguous with comparable rocks in the southern appalachians in contrast arc related rock units outboard of the rosemont shear zone experienced primarily thermal metamorphism in the silurian while crustal thickening and associated regional metamorphism is middle devonian in age and likely the result of the accretion of avalonia during the acadian orogeny these arc related and younger rocks probably originated to the north of their present location as part of the northern appalachians they were ultimately emplaced in a right lateral transcurrent regime sometime after the middle devonian thus it is in this portion of the central appalachian piedmont that the northern and southern appalachians are joined

electrical conductivity structure of southeastern north america implications for lithospheric architecture and appalachian topographic rejuvenation abstract we present the first three dimensional view of the lithospheric electrical conductivity structure beneath southeastern north america by inverting earthscope long period magnetotelluric mt data we obtain an electrical conductivity image that provides new insights into both the architecture of the appalachian orogen and the cryptic post rifting geodynamic history of the southeastern united states our inverse solutions reveal several elongate electrically conductive features that we interpret as major terrane sutures within the appalachian orogen most significantly we resolve a highly electrically resistive layer that extends to mantle depths beneath the modern piedmont and coastal plain physiographic provinces as high resistivity values in mantle minerals require cold mantle temperatures the mt data indicate that the sub piedmont thermal lithosphere must extend to greater than 200 km depth this firm bound conflicts with conclusions from seismic results the boundary between the anomalously thick resistive sub piedmont lithosphere and the relatively thin moderately conductive sub appalachian lithosphere corresponds within resolution to the modern appalachian topographic escarpment this newly recognized contrast in lithospheric properties likely has important implications for appalachian topographic rejuvenation

an improved computerized ionospheric tomography model fusing 3 d multisource ionospheric data enabled quantifying the evolution of magnetic storm global navigation satellite system gnss ionospheric tomography is a typical ill posed problem joint inversion with external observation data is one of the effective ways to mitigate the problem in this article by fusing 3 d multisource ionospheric data and improving the stochastic model an improved gnss tomographic algorithm mfcit computerized ionospheric tomography cit using mapping function is presented the accuracy of the algorithm is validated by selected data under different geomagnetic and solar conditions acquired in europe the results show that the estimated statistically significant uncertainty for each of the layers is about 0 50 3 0tecu with the largest absolute error within 6 0tecu the advantage of the mfcit is that it is based on the kalman filter which enables efficient near real time 3 d monitoring of ionosphere the temporal resolution can reach 1 min level here we apply the ionospheric tomography inversion to the magnetic storm on january 7 2015 in the european region and quantified the evolution of the storm the results show that the difference of the core region between the mfcit and code gim is less than 1tecu more importantly during the initial phase of the storm when the ionospheric disturbance is not evident in the single layer code gim model the mfcit shows obvious positive disturbances in the upper ionosphere although there is no disturbance in the f2 layer the mfcit further tracks the evolution of the magnetic storm that the ionospheric disturbance expands from the upper to the lower ionosphere layers and at ut12 00 the disturbance continues to spread to the f2 layer

chronology of paleozoic metamorphism and deformation in the blue ridge thrust complex north carolina and tennessee the blue ridge province in northwestern north carolina and northeastern tennessee records a multiphase collisional and accretionary history from the mesoproterozoic through the paleozoic to constrain the tectonothermal evolution in this region radiometric ages have been determined for 23 regionally metamorphosed amphibolites granitic gneisses and pelitic schists and from mylonites along shear zones that bound thrust sheets and within an internal shear zone the garnet ages from the pumpkin patch a thrust sheet 458 455 and 451 ma are similar to those from the structurally overlying spruce pine thrust sheet 460 456 455 and 450 ma both thrust sheets exhibit similar upper amphibolite facies conditions because of the high closure temperature for garnet the garnet ages are interpreted to date growth at or near the peak of taconic metamorphism devonian metamorphic ages are recognized in the spruce pine thrust sheet where sm nd and rb sr garnet ages of 386 and 393 ma and mineral isochron ages of 397 14 and 375 27 ma are preserved hornblendes record similar sup 40 ar sup 39 ar sm nd and rb sr ages of 398 to 379 ma devonian sup 40 ar sup 39 ar hornblende ages are also recorded in the structurally lower pumpkin patch thrust sheet the devonian mineralmore ages are interpreted to date a discrete tectonothermal event as opposed to uplift and slow cooling from an ordovician metamorphic event the mississippian mylonitization is interpreted to represent thrusting and initial assembly of crystalline sheets associated with the alleghanian orogeny the composite thrust stack of the blue ridge complex was subsequently thrust northwestward along the linville falls fault during middle alleghanian orogeny about 300 ma less

medium scale traveling ionospheric disturbances observed with the superdarn hokkaido radar all sky imager and gps network and their relation to concurrent sporadic e irregularities 1 we present midlatitude medium scale traveling ionospheric disturbances mstids observed with a super dual auroral radar network superdarn hf radar at around 10 mhz in hokkaido japan in combination with a 630 nm all sky imager and a gps network geonet that provides total electron content tec data mstids propagating southward from high latitudes are detected at first with the hf radar and then with the imager and geonet we analyze two mstid events one in winter event 1 and the other in summer event 2 to find that mstids appear simultaneously at least at 55 25 n it is shown that nighttime mstids propagate toward the southwest over a horizontal distance of about 4000 km and daytime mstids do so toward the southeast daytime radar echoes are due to ground sea surface gs scatter while nighttime echoes in event 1 return from 15 m scale f region field aligned irregularities fais and those in event 2 are due to gs scatter doppler velocities of the nighttime f region fai echoes in event 1 are negative motion away from the radar within strong echo regions and are positive motion toward the radar within weak echo regions this fact suggests that the strong weak echoes return from suppressed enhanced airglow tec areas in line with previous observations over central japan the nighttime mstids in events 1 and 2 are often accompanied by concurrent coherent echoes from fais in sporadic e es layers the es echo areas in event 2 rather coincide with suppressed airglow tec areas in the f region that are connected with the echo areas along the geomagnetic field indicating the existence of e and f region coupling at night

the yucatan a laurentian or gondwanan fragment geophysical and palinspastic constraints current reconstructions suggest that the yucatan block has gondwanan provenance and orient the yucatan e w in the ouachita embayment where it overlaps southern laurentia and florida alternatively if the yucatan is oriented ne sw it fits neatly into the ouachita embayment with minimal overlap furthermore many of the v shaped magnetic anomalies in the yucatan that are discordant in the e w reconstruction can be traced across the yucatan laurentian boundary in the ne sw reconstruction a nw trending anomalies continue into southern laurentia where they are associated with cambrian mafic rocks in the southern oklahoma and reelfoot rifts and b ne trending anomalies in the eastern yucatan are parallel to those over grenvillian rocks in the western appalachians furthermore silurian plutons in the maya mountains of belize that have no counterpart in texas may be correlated with the concord salisbury plutons in carolinia a terrane of gondwanan provenance in the southern appalachians nd isotopic data from the chicxulub ejecta in the northern yucatan block are similar to those in the llano grenvillian rocks and differ from those in oaxaquia these correlations suggest that much of the yucatan is of laurentian provenance and implies that the laurentia gondwana suture crosses the yucatan west of the maya mountains in this scenario the ouachita embayment results from the formation of the gulf of mexico during the breakup of pangea rather than the cambrian removal of the argentine cuyania terrane cambrian 515 ma paleomagnetic and faunal data are consistent with cuyania forming either east of the yucatan or off eastern laurentia

seismic velocities and composition of the canadian crust abstract to investigate variations in crustal structure and composition we analyze approximately 80 000 teleseismic p wave seismograms recorded at 343 broadband stations distributed about the canadian landmass these data are binned by horizontal slowness and simultaneously deconvolved into receiver functions we apply stacking methods to retrieve estimates of the bulk crustal velocity ratio vp vs and thickness h from this receiver function dataset under the assumption of locally 1d structure these crustal parameters are analyzed together with a compilation of velocity and thickness estimates from previous active source experiments and global crustal thickness models to investigate competing models of crustal composition and evolution crustal thicknesses vary between 25 km and 48 km with an area weighted average of 37 km for all stations vp vs estimates range from 1 65 to 1 95 and display a systematic increasing trend from nw to se across the churchill superior and grenville provinces analysis of intra crustal conversions indicates little evidence for a well defined widespread conrad discontinuity although the lower crust appears to be more transparent to teleseismic converted waves than the upper crust this observation runs contrary to that of p reflectivity in many active source studies and may be reconciled through a dominant scale length of heterogeneity that is less than 800 m the vp vs observations and vp constraints from active source studies are compared with laboratory measurements for common crustal rocktypes and found to be consistent with bulk compositions falling between granite gneiss and diorite previously reported systematic variations in crustal thickness and vp vs with age in a global data set are not supported by our data set

precise time and conditions of peak taconian granulite facies metamorphism in the southern appalachian orogen u s a with implications for zircon behavior during crustal melting events abstract the time of peak thermal conditions in the granulite facies zone of the southern appalachian orogen corresponds to the time of formation of garnet bearing leucosomes generated by biotite dehydration melting in garnet sillimanite gneisses leucosomes contain unusually abundant zircon occurring as inclusions in euhedral plagioclase phenocrysts and garnet isotope dilution thermal ionization mass spectrometric analysis of 13 elongate euhedral zircon crystals from the leucosome yields a concordant u pb age of 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

quantitative mineralogy for facies definition in the marcellus shale appalachian basin usa using xrd xrf integration abstract determining the mineralogy of mature sedimentary rocks particularly mudrock often defaults to qualitative or semi quantitative methods due to difficulties in correctly quantifying multiple unknown mineral phases constraining mineral abundances is particularly difficult in shale due to preferred mounting orientation of common phyllosilicate phases commonly leading to overestimation of clay minerals and mica we introduce a quantitative approach to constraining mineralogy within mudrock by integrating x ray diffraction xrd and x ray fluorescence xrf data sets collected on splits of the same samples the technique involves partitioning xrf cation concentrations into xrd identified silicate carbonate and sulfide phases then estimating quartz by xrf sio2 balance this method is applied to an example dataset from the economically significant marcellus shale middle devonian appalachian basin usa conventional reference intensity ratio rir interpretation identified nine mineral phases quartz muscovite illite pyrite chlorite albite calcite dolomite and barite their abundances were then re estimated using more highly accurate xrf derived elemental concentrations with stoichiometry from the identified xrd reference phases xrf al2o3 was used to corroborate the calculated xrd xrf results for quality control errors in relevant xrf concentrations can be quantified though not the assumptions in how they are employed nonetheless the resulting xrd xrf mineralogic abundances by this procedure are thought to be more accurate than rir and to remove preferred orientation bias induced that causes overestimation of clay minerals and mica and underestimation of quartz and other phases cluster analysis of the xrd xrf results identified four mineralogical facies that provide insight into potential primary depositional controls on organic matter preservation within the marcellus shale this xrd xrf integration method provides a general framework for estimating mineralogy quantitatively in mudrocks although dataset specific adjustments to the method may be required for different mineralogical suites

mhd nature of night time mstids excited by the solar terminator 1 we have obtained first experimental evidence in favour of the magnetohydrodynamic mhd nature of night time medium scale travelling ionospheric disturbances mstids we used total electron content tec measurement data from the dense gps networks in california and in japan for 2008 2009 it was found that the spectral mstid characteristics are determined by the solar terminator st dynamics in summer mstids are detected 1 5 3 hours before the evening st at 100 km above the point of observations but at the moment of the evening st passage through the magnetoconjugate point at the equinox mstids are registered at once after st appearance in winter mstids are observed 1 5 3 hours after the evening st occurrence at the point of observations but at the moment of the evening st passage in the magnetoconjugate point the mstid occurring synchronously with the st passage through the magnetoconjugate area suggest that the st excited mstids are of mhd nature

hydrochronology of a proposed deep geological repository for low and intermediate level nuclear waste in southern ontario from u pb dating of secondary minerals response to silurian and cretaceous events u pb ages have been measured on secondary dolomite and silica cements in cambrian sandstone at the base of an 840 m thick sub horizontally bedded sedimentary sequence beneath the bruce nuclear site

a two layer model of the ionosphere using global positioning system data we present a new approach to model the ionosphere based on gps data previous authors have used models with an unique shell in this case we have included a second shell to account for the distribution of the electrons in the outer part of the ionosphere we have analyzed the ionospheric electron content of a region above 30 degrees in declination in different conditions of ionospheric activity using the kalman filter the data used has been obtained from the international gps service for geodynamics igs network simultaneously we have studied the receiver and transmitter differential biases showing the effects of neglecting the outer part of the ionosphere in the model it appears a systematic variations for the receivers depending on its latitude not for the satellites

technogenic soils technosols developed from fly ash and bottom ash from thermal power stations combusting bituminous coal and lignite part ii mineral transformations and soil evolution abstract fly ash and bottom ash from thermal power stations are industrial wastes which are susceptible to weathering in the environment first manifestations of transformations occur immediately after deposition of ashes in a disposal site and they continue in technogenic soils technosols developing from the ashes on surfaces of such sites technosols developed from bituminous coal and lignite ashes in poland were studied in order a to identify the most important mineral transformations during the first several decades of soil development and b to discuss the evolution of these soils mineral transformations can serve as good indicators of pedogenesis in the studied technosols quantitative x ray diffraction analyses fourier transform infrared spectroscopy optical microscopy and scanning electron microscope energy dispersive spectroscopy studies showed that the mineral transformations proceeded more dynamically in technosols developed from lignite ashes whereas they were less expressed in soils formed from bituminous coal ashes technosols developed from bituminous coal ashes contained mineral phases inherited from ashes aluminosilicate glass mullite quartz magnetite hematite and traces of maghemite and barite as predominating constituents small contents of pedogenic calcite iron oxyhydroxides and most likely short range order si and al containing phases originated within 60 years of pedogenesis technosols developed from lignite ashes contained aluminosilicate glass quartz hematite inherited from fly ash as well as a variety of secondary minerals vaterite calcite bassanite gypsum ettringite hydrotalcite and brucite which were formed as an effect of rapid mineral transformations after ash deposition after about 40 years pedogenesis accelerated by reclamation and a few years of intense cultivation led to the formation of a new mineral assemblage with the predomination of calcite gypsum and hydrotalcite a concept of evolution of the studied technosols comprising four stages of evolution was proposed i formation of ash during combustion of fuel coal or lignite in a thermal power station ii transport and deposition of ash in a disposal site accompanied by the first weathering alterations iii early pedogenesis and iv further predicted evolution

ionospheric electron concentration imaging using gps over the usa during the storm of july 2000 a new technique for ionospheric imaging is demonstrated during a severe geomagnetic storm of 15th july 2000 the three dimensional time dependent imaging algorithm is applied to multi directional ground based gps data and yields spatial maps of electron concentration this technique is demonstrated by showing a series of images of the mid latitude ionosphere over the usa during the storm of july 2000 a strong uplift in the height of the f layer is observed after 20 ut on 15th july followed by a severe latitudinal electron concentration gradient independent verification of the images is provided by the ionosondes and incoherent scatter radar data the gps images reveal the large scale dynamics of the ionosphere during the disturbed conditions and show the potential of geophysical imaging for storm time ionospheric studies

relationship between the ellisville pluton and chopawamsic fault establishment of significant late ordovician faulting in the appalachian piedmont of virginia

geomagnetic conjugate observations of large scale traveling ionospheric disturbances using gps networks in japan and australia 1 the geomagnetic conjugacy of large scale traveling ionospheric disturbances lstids was studied using total electron content tec data derived from gps networks in japan and australia the number of simultaneous occurrences of lstids within 1 hour in both hemispheres was 5 out of 20 21 events in japan australia when kp 5 and 0 out of 15 10 when kp 4 as for the lstids observed simultaneously in both hemispheres the propagation velocities of equatorward lstid were comparable between the two hemispheres with differences of 10 40 the crossing times at 30 geomagnetic latitude of the simultaneous lstids over japan and australia were also different by several tens of minutes for all five events these observational results indicate that the lstids observed almost simultaneously in both hemispheres are not connected electromagnetically through the geomagnetic field but are generated by atmospheric gravity waves propagating to the equator independently in the two hemispheres

observations of traveling ionospheric disturbances with a satellite beacon radio interferometer seasonal and local time behavior we have operated a very long baseline interferometer array at a northern midlatitude site illuminated by vhf radio beacons from two geosynchronous satellites quasi continuously for over a year the array can detect and measure the trace velocity of traveling ionospheric disturbances tids via their signatures in the line of sight total electron content tec the system noise level is of the order of 1013 m 2 in the tec so that even very weak perturbations can be studied we have used the year long tid detection velocimetry data set to describe local time and seasonal dependences of the wave parameters the most striking finding is that the preferred azimuths of tids in the data set tend to belong to either of two modes the first mode strongest at midday and in the early afternoon particularly around winter equinox propagates southward the second mode strongest in the evening especially during summer solstice through autumn equinox propagates west northwestward the two modes are disposed in local time such as to suggest the agency of clockwise rotation of the tid preferred azimuths versus time as expected by wind filtering in the thermospheric diurnal tide however there is a gap between the two modes azimuth bands moreover the two modes exist in all trace speed quartiles of the data set tids a finding which is at variance with the hypothesis of wind filtering being the primary explanation of these modes

a hafnium isotopic record of magmatic arcs and continental growth in the iapetus ocean the contrasting evolution of ganderia and the peri laurentian margin abstract we test the sensitivity of combined u pb hf isotopic analyses of detrital and magmatic zircon to document complex processes in accretionary orogens using ganderia from the canadian appalachian orogen as an example ganderia hosted a long lived magmatic arc that began at least by 650 ma and continued until 450 ma during which time it drifted northward from the amazonian margin its isotopic record suggests arc activity began earlier possibly at 750 ma proto ganderia within an oceanic domain the u pb hf zircon isotopic array suggests that ganderia formed on a sliver of paleoproterozoic mesoproterozoic basement tdmc 2 2 1 1 ga a transition towards more evolved hf isotopic compositions between 650 and 600 ma is interpreted to coincide with its accretion to the amazonian margin of gondwana consistent with other geological evidence accretion was followed by increasing amounts of juvenile crustal inputs between 550 and 500 ma which is interpreted to reflect subduction roll back and the onset of drift from the gondwanan margin trench retreat culminated in the separation of the ganderia arc and formation of the exclusively oceanic 510 450 ma penobscot popelogan victoria arcs on ganderia accretion of ganderia to the active notre dame subzone along the laurentian margin occurred in the late ordovician and is marked by the abrupt termination of ganderian arc magmatism the notre dame arc evolved along the laurentian margin between 515 and 425 ma and was built on paleoproterozoic archean t dm c 2 9 2 5 ga crust supra subduction zone magmatism occurred at 490 460 ma during the closure of the taconic seaway and was dominated by the recycling of laurentian crust with progressive mixing of evolved and juvenile arc magmas over time the preservation of very evolved notre dame arc zircon in ganderian overstep sequences confirms the arrival of the leading edge of ganderia to laurentia by 450 ma the hafnium isotopic method is proven here to be a powerful tool when used in conjunction with geological constraints and is able to identify the changing nature of magmatism during the evolution of complex accretionary systems

multi tid detection and characterization in a dense global navigation satellite system receiver network the medium scale traveling ionospheric disturbances mstids constitute the most frequent ionospheric wave signatures we propose a method for detecting the number of simultaneous mstids from a time series of high pass filtered vertical total electron content vtec maps and their parameters the method is tested on the vtec map corresponding to a simulated realistic scenario and on actual data from dual frequency global positioning system gps measurements gathered by 1 200 gps receivers of the gps earth observation network geonet in japan the contribution consists of the detection of the number of independent mstids from a nonuniform sampling of the ionospheric pierce points the problem is set as a sparse decomposition on elements of a dictionary of atoms that span a linear space of possible mstids these atoms consist of plane waves characterized by a wavelength direction and phase on a surface defined the part of the ionosphere sounded by the geonet i e 25 n to 50 n of latitude and 125 e to 155 e of longitude the technique is related to the atomic decomposition and least absolute shrinkage and selection operator lasso the geophysical contribution of this paper is showing a the detection of several simultaneous mstids of different characteristics with a continuous change in the velocity b detection of circular mstid waves compatible by time and center with a specific earthquake c simultaneous superposition of two distinct mstids with almost the same azimuth and d the presence at nighttime of mstids with velocities in the range 400 600 m s

exploring laser ablation u pb dating of regional metamorphic garnet the straits schist connecticut usa abstract garnet is a prominent recorder of metamorphic processes and plays a pivotal role in deciphering the pressure temperature evolution of metamorphic rocks however the potential of regional metamorphic garnet for laser ablation u pb dating remains unexplored as variable and low u we applied la icp ms u pb dating to garnet and zircon monazite and xenotime from the straits schist western connecticut usa to constrain the timing of garnet growth within the overall acadian age metamorphic history recorded by this unit we assessed the effects of u rich inclusions on garnet u pb data using high resolution microbeam sampling grain size analysis and calculations assessing how inclusion size and abundance affect u concentrations measured in garnet when analysing garnet our results demonstrate that by scrutinizing the time resolved u signal u rich inclusions can be identified and effectively removed during data evaluation if u rich inclusions are unaccounted for garnet analyses have elevated u contents compared to pure garnet and in a tera wasserburg diagram data points are shifted to the left right or along the garnet regression line for inclusions older younger or of the same age as the garnet respectively garnet from two metapelitic samples yielded lower intercept ages of 409 10 ma and 406 15 ma and a combined u pb age of 406 1 8 3 ma metamorphic zircon yielded age clusters at 446 2 4 2 ma 413 3 3 0 ma and 382 9 2 8 ma monazite ages range between 390 and 355 ma and xenotime yielded 370 1 5 6 ma the 446 ma age peak is attributed to detrital zircon formed during the waning stages of the taconian orogeny early acadian metamorphism is recorded by garnet and 413 ma zircon whereas monazite and zircon ages of 390 to 383 ma coincide with peak metamorphic conditions early carboniferous monazite and xenotime ages could reflect the incursion of fluids into the straits schist during neo acadian metamorphism coeval plutonism in new england or breakdown of garnet during regional exhumation

assessing detrital garnet chemical composition as a quantitative provenance tool a multivariate statistical approach abstract chemical analysis of detrital garnet is a widely utilized quantitative tool for determining the provenance of sediments the goal of this study is to investigate the ability of the compositions of detrital garnet to provide a direct linkage to the specific source rocks from which the garnet was derived to achieve this goal we analyzed detrital garnet isolated from alluvial samples collected from the french broad river and several of its tributaries a watershed that drains portions of the multiply deformed southern appalachian orogen usa to test whether potential linkages between detrital and potential source rock garnet could be achieved garnet crystals were chemically characterized from a wide variety of lithologies that crop out in the french broad watershed and thus are the most likely local sources of detrital garnet mahalanobis distances measured on canonical discriminant functions successfully differentiated garnet compositions among the 18 analyzed source rocks these metrics were then applied to 2 300 detrital garnet compositions to link each grain to its potential source rock approximately 94 of the detrital garnet crystals were linked to their potential source regions thus only 6 of the detrital crystals were treated as unclassified we interpret the unclassified high ca garnets to have been derived from minor sub map scale lenses and boudins of calc silicate or skarns from exposed ocoee or ashe metaclastic units within the french broad river watershed the unclassified high mn detrital garnet grains are interpreted to have been derived from the various felsic granitiods and pegmatites that intrude the region of study

high resolution mapping of tec perturbations with the gsi gps network over japan two dimensional total electron content tec perturbations over japan are mapped with the geographical survey institute gsi gps network geonet gps earth observation network its spatial resolution is 0 15 latitude 0 15 longitude and temporal resolution is 30 seconds two dimensional tec observations with these high resolutions revealed spatial structures and temporal evolutions of traveling ionospheric disturbances tids in the nighttime mid latitude ionosphere on july 03 1997 a preliminary result of the tec perturbation mapping indicates that it would be a strong tool to investigate the ionospheric structures in detail coordinated observations with other ionospheric observation techniques such as incoherent scatter is radars airglow imagers and ionosondes are needed to clarify the vertical structure of the ionosphere

unroofing maine relating pressure of crystallization thermochronological data tectonics and topography abstract we gathered data on the age and depth of crystallization of mid paleozoic igneous and metamorphic rocks from 64 sites in and near maine and also a time series of rock temperatures from the casco bay area of maine by fitting a trend surface to some of our geobarometric data we estimated total erosion at the casco bay site in the last 284 m y and thus the geothermal gradient at that time the temperatures could thus be converted to a time series of erosion assuming airy isostasy we then obtained a time series of the mean height of the land surface above present sea level represented by h of four erosion laws fit to the latter a power law e phu where e is the erosion rate and p and u are fitting parameters provides the best fit without excessive mathematical complexity however the exponent u is unexpectedly 6 km and that it likely began in the late middle paleozoic thus extending earlier estimates of this component of displacement backward in time and upward in magnitude a decrease in denudation rate in the early mesozoic is interpreted as reflecting suturing of gondwana and laurentia to form pangea the denudation rate increased again following mesozoic rifting this latter increase occurs later to the northwest suggesting retreat of a rift flank escarpment at a rate of a few tenths of a millimeter per year using our full geobarometric data set we calculated an average value of u of 1 2 we then generated topographic maps of the state at 380 320 and 200 ma at 380 ma the mountains of western maine were likely somewhat higher than today s rocky mountains drainage then was to the northeast contributing sediment to the maritimes basin the alleghanian collision at 320 ma raised comparable mountains somewhat nearer the present coast in western maine following mesozoic rifting drainage was also to the southeast into rift basins bordering the opening atlantic ocean since the devonian an average of 9 km of rock have been eroded from maine

fast tectonometamorphism and exhumation in the type area of the barrovian and buchan zones the beginning of the grampian episode of tectonometamorphism in scotland is dated by collision and obduction of the ballantrae ophiolite complex at 478 8 ma for the first time we have used zircon and garnet to radiometrically date the peak of the caledonian buchan and barrovian tectonometamorphism in their type areas as contemporaneous at 467 2 5 ma detrital garnet from the neighboring southern uplands flysch terrane has the same radiometric age and occurs in 465 2 5 ma molasse in the midland valley we show that the entire grampian episode lasted 15 2 5 m y and that it took fewer than 7 6 m y to expose high grade rocks following the peak of metamorphism those who study precambrian orogeny should note the brevity of this scottish tectonometamorphic episode and the speed of exhumation

the soapstone ridge complex southern appalachians petrographic mineral compositional and oxygen isotope investigation samples of the soapstone ridge complex ssr in the southern appalachians examined for this study are composed of megacrystic orthopyroxenites amphibole schists and talc chlorite amphibole schists the mineralogy of the ssr samples studied consists of varying proportions of amphibole chlorite talc orthopyroxene and fe ti oxides amphibole is the domi nant mineral in almost all ssr samples studied the amphiboles display zoning whereby cores that are composed of magne siohornblende and edenite consistent with amphibolite facies conditions are rimmed by tremolite actinolite consistent with greenschist facies conditions oxygen isotope compositions of ssr amphiboles investigated show a wide range in 18o values from a low value of 1 8 to a high value of 6 1 such wide ranges in 18oamphibole values occur in ophiolite complexes and oceanic crustal rocks relict orthopyroxene from the ssr has a 18o value of 3 4 a value lower than those from layered intrusions but comparable to some pyroxene 18o values from ophiolites equilibration temperatures calculated for actinolite chlorite yield a temperature of 227 c consistent with greenschist facies conditions it is proposed that the ssr amphibole cores were metamorphosed probably during terrane terrane collision under amphibolite facies conditions with the actinolite rims possibly being formed during thrusting of the ssr rocks onto the continental margin

alteration of secondary minerals along a time series in young alkaline soils derived from carbonatic wastes of soda production abstract industrial activities result in increasing amounts of technical substrates being deposited in landfills these substrates are subject to weathering and pedogenic processes we studied the chemical and mineralogical transformations on naturally weathered waste deposits of soda industry four sites differing in age 15 19 57 and 70 years and derived from carbonatic slurry mainly cao h2o caco3 nacl were selected the formed soils calcareous spolic regosols are weakly to strongly alkaline with ph values ranging from 8 to 12 within 15 years the substrate s initial ph of 12 drops rapidly in the topsoil due to the reaction of dissolved ca either with co2 from the atmosphere or evolved by microbial respiration and finally stabilizes at around 8 1 all soils show high electrical conductivity up to 12 3 ms cm 1 at the youngest site the electrical conductivity strongly decreases within 70 years of weathering due to leaching processes and the formation of less soluble secondary minerals the content of organic c in the studied soils ranges from 2 4 to 70 8 g kg 1 and stocks increase with site age soil structure and soil color change distinctly the binding of co2 results in large amounts of carbonate increasing with time seventy years after deposition calcite caco3 dominates the topsoil 0 30 cm depth comprising about 80 of the soil material the mineral composition was characterized by x ray diffraction besides calcite we found different quantities and different distributions of the less common minerals ettringite ca6 al oh 6 2 so4 3 26h2o thaumasite ca6 si oh 6 2 co3 2 so4 2 24h2o hydrocalumite ca2al oh 7 2h2o and hydrotalcite mg6al2 co3 oh 16 4h2o formation and alteration of these minerals are basically influenced by changes in the soil ph with progressing weathering neither thaumasite nor ettringite are stable due to the non favorable soil reaction ph 8 1 in contrast hydrocalumite and hydrotalcite exist in all investigated soils they are stable also under weakly alkaline conditions and thus may exist in all carbonatic soils results indicate a surprisingly rapid soil development driven by the highly dynamic formation and alteration of minerals in carbonatic substrates under alkaline conditions

stratigraphic context geochemical and isotopic properties of magmatism in the siluro devonian inliers of northern maine implications for the acadian orogeny this paper reports detailed stratigraphic analysis whole rock geochemistry and nd isotopic ratios of basalts from the northern maine inliers these data place constraints on first order controversies about the tectonic conditions leading up to and during the early stages of the acadian orogeny in northern maine late silurian and early devonian stratigraphic sequences indicate a progressive change from shallow water and subaerial exposure ripogenus and the forks formations east branch group to a rapidly subsiding basin prior to the onset of acadian deformation subsidence was accompanied by mafic to intermediate volcanism of the west branch spider lake and fish pond volcanics and that continued with intrusion of the syn deformational greenville plutonic belt including the flagstaff lake igneous complex whose properties we report in this paper trace element geochemistry indicates that magmatism is transdiscriminant showing aspects of within plate volcanic arc and back arc affinities and nd isotopic ratios are moderately positive 2 3 to 3 8 indicating either an uncontaminated and moderately enriched mantle source or a depleted mantle source contaminated by continental crust four possible tectonic models of the acadian orogeny and the siluro devonian sedimentary volcanic sequences of northern maine are evaluated in the context of a subsiding basin associated with this magmatism developed on the amalgamated laurentian plate these include 1 slab detachment during southeast directed subduction of the laurentian continental margin 2 laramide style thrust basins above a shallow northwest dipping subduction zone 3 back arc extension followed by thin skinned shortening above a northwest dipping subduction zone and 4 moluccan style dual dipping subduction zones

application of ionospheric tomography to real time gps carrier phase ambiguities resolution at scales of 400 1000 km and with high geomagnetic activity theinfluenceoftheionospherecanbeoneofthe mainobstacles togpscarrierphaseambiguityresolution in real time particularlyoverlongbaselines thisisimportant toallusersofgpsrequiringsub decimeterpositioning per haps in real time especially with high geomagnetic activity or close to the solar maximum therefore it is desirable to have a precise estimation of the ionospheric delay in real time to correct the data in this paper we asses a real time tomographic model of the ionosphere created using dual frequency phase data simultaneously collected with the re ceiversofanetworkofstationsintheusaandcanada with separationsof400 1000km duringaperiodofhighgeomag netic activity kp 6 when the tomographic ionospheric correctionisincluded theresolutionon the fly otf ofthe widelanedouble dierencedambiguitiesatthereferencesta tions is nearly 100 successful for satellite elevations above 20 degrees while theresolution of thel1 l2ambiguities at the rover is typically more than 80 successful

global observation of the ionospheric electronic response to solar events using ground and leo gps data we present in this work the temporal evolution of the three dimensional electron density at global scale during two ionospheric storms october 18 19 1995 and january 10 1997 computed using only actual global positioning system data the tomographic model is solved by means of a kaiman filtering with a filter updating time of 1 hour in a sun fixed reference frame and with a resolution of 10 10 deg in latitude local time and 100 km in height including also a protonospheric component eight layers the data set contains the data from the international gps service igs with more than 100 ground gps stations worldwide distributed and the gps met low orbiting gps receiver both positive and negative elevation observations are used this means for each storm 1 000 000 of delays 400 occultations and 3000 unknowns per batch the international reference ionosphere and data coming from the ionosonde of the ebre observatory are used to show the reliability of the results

a plate tectonic scenario for the iapetus and rheic oceans abstract the tectonics dynamics and biogeographic landscape of the early paleozoic were dominated by the opening and expansion of one large ocean the rheic and the diminution to terminal closure of another iapetus an understanding of the evolution of these oceans is thus central to an understanding of the early paleozoic but their chronicle also presents a rich temporal profile of the wilson cycle illustrating continental scale rifting microcontinent formation ocean basin development arc accretion and continent continent collision nevertheless contemporary paleogeographic models of the iapetus and rheic oceans remain mostly schematic or spatiotemporally disjointed which limits their utility and hinders their testing moreover many of the important kinematic and dynamic aspects of the evolution of these oceans are impossible to unambiguously resolve from a conceptual perspective and the existing models unsurprisingly present a host of contradictory scenarios with the specific aim to resolve some of the uncertainties in the evolution of this early paleozoic domain and a broader aim to instigate the application of quantitative kinematic models to the early paleozoic i present a new plate tectonic model for the iapetus and rheic oceans the model has realistic tectonic plates which include oceanic lithosphere that are defined by explicit and rigorously managed plate boundaries the nature and kinematics of which are derived from geological evidence and plate tectonic principles accompanying the presentation and discussion of the plate model an extensive review of the underlying geological and paleogeographic data is also presented

statistical analysis of nighttime medium scale traveling ionospheric disturbances using airglow images and gps observations over central china statistical analyses were conducted to investigate the nighttime medium scale traveling ionospheric disturbances mstids for the first time by using airglow images and global positioning system gps data over central china during 2013 2015 our results show that the phase fronts of perturbations are aligned from northwest to southeast direction and propagate toward the southwest direction the characteristics of the nighttime mstids observed by oi 630 0 nm images are consistent with those of the nighttime mstids obtained from the gps data the phase velocity period wavelength and amplitude of nighttime mstids are 50 150 m s 0 5 1 5 h 150 400 km and 2 15 respectively as measured from 630 0 nm images and gps data in addition we utilized the simultaneous observations from oi 630 0 nm and oi 557 7 nm images to explore the relationship between nighttime mstids and gravity waves 100 km in the mesopause it is found that the nighttime mstids frequently occurred in the summer solstice which was not consistent with the occurrence of gravity wave observed in the mesopause our results indicate that the nighttime mstids may be generated by the coupling of electrodynamic processes rather than be trigged by gravity waves from the lower atmosphere

medium scale traveling ionospheric disturbances affecting gps measurements spatial and temporal analysis 1 in this work we present a simple technique to estimate the medium scale traveling ionospheric disturbances mstids characteristics such as occurrence velocity vertical propagation with periods lower than 20 min and its application to a set of gps data both temporally and spatially representative near one solar cycle and four local networks in the northern and southern hemispheres respectively some of the main results presented in this paper are the mstids which occur at daytime in local winter and nighttime in local summer related to the solar terminator and modulated by the solar cycle they present equatorward from 100 to 400 m s and westward 50 to 200 m s horizontal propagation velocities respectively the corresponding periods are compatible higher with the theoretical prediction which is given by the neutral atmosphere

ionospheric response to the geomagnetic storm on august 21 2003 over china using gnss based tomographic technique the impacts of the august 21 2003 geomagnetic storm on the ionosphere over china have been first investigated by using the so called computerized ionospheric tomography cit technique and the observations of the crustal movement observation network of china tomographic results show that the main ionospheric effects of this geomagnetic storm over china are as follows 1 the negative storm phase effect appears in the f region and 2 the positive storm phase effect occurs above the f region meanwhile some key features in the ionospheric structure have been revealed in the ionospheric images during the storm this includes the disturbances and an elongated region of the reduced electron density at the latitude around 32 n statistical comparisons are carried out to confirm the reliability of the global navigation satellite system based cit reconstruction results using the profile obtained from ionosonde observations

shallow mantle velocities beneath the southern appalachians from pn phases to constrain mantle structure that might contribute to the topography of the southern appalachian mountains pn phases from regional earthquakes recorded in northern georgia by earthscope southeastern suture of the appalachian margin experiment and transportable array stations were used to solve for shallow mantle p wave velocities mantle velocities vary laterally with values of 7 6 7 8 km s beneath the higher elevations of the blue ridge terrane and northwestern flank of the inner piedmont terranes and values of 8 3 8 5 km s farther south where elevation is lower the zone of low velocity mantle could represent a source of buoyancy that helps to support the higher elevations in addition to the root of thickened crust that also exists beneath the mountains

lithospheric and asthenospheric contributions to shear wave splitting observations in the southeastern united states we present observations of both null and non null sks splitting from temporary deployments across the southeastern united states in order to evaluate the relative contributions of lithospheric deformation and asthenospheric flow to regional anisotropy data for this study come from four temporary broadband seismic deployments the appalachian seismic transect ast the test experiment for eastern north america teena the south carolina earth physics project scepp and the florida to edmonton array fled in general we find fast directions aligned roughly parallel to absolute plate motion of the north american plate apm within and west of the southern appalachians whereas to the southeast we find a broad area dominated by complex splitting patterns consisting of well constrained null splitting measurements over a range of backazimuths along with a very small number of resolved non null measurements this change in splitting patterns is consistent with a transition from drag induced asthenospheric flow beneath the older sections of the north american continent to vertical or incoherent mantle flow likely in combination with complex lithospheric anisotropy beneath the younger accreted terranes to the southeast in addition to these general patterns we find a number of non null splitting measurements that are not aligned with apm but are instead aligned with prominent magnetic anomalies that may correspond to ancient continental suture zones or faults this would suggest that in these areas a strongly anisotropic but localized lithospheric fabric dominates over any ambient asthenospheric anisotropic signature in areas with generally strong apm parallel splitting this would imply a thick sheared mantle lithosphere whose deformation induced anisotropy is strong enough to overprint the anisotropy induced by apm and is aligned with the shallower crustal structures responsible for generating the observed magnetic anomalies in the southeastern areas dominated by null splitting measurements there may be no strong signature from asthenospheric anisotropy to override but a substantial lithospheric thickness is still required to generate the magnitude of the observed sks splitting 1 s more data are required to verify these results but future datasets including data from usarray may be able to exploit the correlations between null and non null sks splitting measurements and magnetic lineaments to better constrain the provenance of the regional anisotropic signature

detecting magma poor orogens in the detrital record the clastic record is commonly interrogated by analysis of detrital heavy mineral assemblages with the bulk of modern detrital geochronological studies employing u pb dating of detrital zircon however the bias of zircon toward felsic igneous sources and the limited ability of the u pb system in zircon to record low to medium grade metamorphic events means that the u pb detrital zircon record is largely insensitive to magma poor orogens in this study u pb ages were obtained by laser ablation inductively coupled plasma mass spectrometry for apatite and rutile extracted from alluvium of the french broad river fbr in the southern appalachians southeastern united states in contrast to previously published fbr u pb zircon data sets which yield essentially no record of the most recent appalachian metamorphic events ca 320 ma associated with assembly of pangea the u pb detrital rutile and especially the u pb apatite systems together provide a complete record of complex polyphase appalachian orogenesis it is unexpected that the apatite and rutile u pb appalachian age populations differ significantly with probable low temperature breakdown of rutile biasing the rutile data set toward the most recent alleghanian metamorphic event these data make the fbr one of the most intensely studied river systems globally for multiproxy single grain u pb analysis clearly demonstrate dependence of provenance information on mineral proxy choice and emphasize the resolving power of multiproxy provenance studies

improving the real time ionospheric determination from gps sites at very long distances over the equator 1 as the authors have shown in previous work the tomographic approach reduces significantly the mismodeling in the electron content determination using as data the ionosphere crossing radio signals of global navigation satellite systems gnss such as the global positioning system gps we present in this paper the results of a comprehensive study on the performance of an improved tomographic model of the ionosphere this model is obtained from the gps l1 and l2 carrier phase data and it is used to estimate undifferenced and double differenced ionospheric corrections in real time and at very long distances between receivers 500 3000 km the key point of the strategy is the combination of real time geodetic and ionospheric techniques to achieve a significant improvement in the reliability of carrier phase ambiguity resolution this new approach includes also the use of smoothed pseudo ranges to help in ambiguity resolution it has been tested under difficult ionospheric conditions during four consecutive weeks in march april 2001 at solar maximum and at latitudes ranging from 40 to 40 degrees so as to include the equatorial region dual frequency satellite altimetry from topex poseidon has been used to verify the accuracy of the ionospheric model over the oceans in that region

climatology of medium scale traveling ionospheric disturbances observed by a gps network in central china 1 the 15 month climatology of medium scale traveling ionospheric disturbances mstids during a solar minimum period has been constructed from observations of a dense gps receiver array in central china in total 793 mstid events are identified with peaks in occurrence at 1500 lt and 0100 lt the occurrence of mstids decreases following an increase in geomagnetic activity with 46 of the mstids occurring in the daytime daytime mstids are characterized by a major occurrence maximum around the winter solstice and by an equatorward propagation direction the period phase velocity azimuth and amplitude of daytime mstids are 20 60 min 100 400 m s 130 270 and 0 8 1 5 respectively the remaining 54 of the mstids occurred at night and were characterized by a peak in occurrence at the summer solstice and by a southwestward propagation direction the period phase velocity azimuth and amplitude of nighttime mstids are 20 70 min 50 230 m s 170 300 and 2 7 respectively the propagation directions and the seasonal behaviors support the view that daytime mstids are an ionospheric manifestation of atmospheric gravity waves from the lower atmosphere while a possible excitation mechanism of nighttime mstids is the electrodynamics process caused by plasma instability in the f layer

statistical study of nighttime medium scale traveling ionospheric disturbances using midlatitude airglow images 1 we have investigated statistical characteristics of the nighttime medium scale traveling ionospheric disturbances mstids observed in 630 nm airglow images at two stations rikubetsu 43 5 n 34 8 mlat and shigaraki 34 9 n 25 4 mlat in japan for 1998 2000 near the solar maximum period most of the observed mstids propagate southwestward in the images the typical wavelength velocity period and amplitude are 100 300 km 50 100 m s 0 5 1 5 h and 5 15 respectively seasonal variations in these parameters are not clear the occurrence rate has a major peak 50 60 in summer that appears 2 months earlier at lower latitudes and a minor peak in winter similar occurrence characteristics are obtained from midlatitude spread f signatures using multipoint ionosonde data in japan though the coincidence of the spread f and the mstids in airglow images is only 10 15

imaging crustal structure beneath the southern appalachians with wavefield migration to constrain crustal structures in the southern appalachians and the suture zone with the gondwanan affinity suwannee terrane we applied the 2d grt wavefield migration method to the scattered incident p wavefield recorded by the earthscope southeastern suture of the appalachian margin experiment and adjacent transportable array stations we resolve the root of thickened crust beneath the high topography of the blue ridge mountains and estimate its density contrast with the mantle to be only 104 20 kg m3 a weak velocity contrast across the crustal root moho is observed and may be related to an ongoing crustal delamination event possibly contributing to local tectonic rejuvenation beneath the suwannee terrane we confirm prior observations of a gently south southeastward dipping crustal suture indicating the terminal collision of laurentia and gondwana involved several hundred kilometers of overthrusting

a comparison between mid paleozoic new england usa and the modern western usa subduction of an oceanic ridge transform fault system abstract a detailed comparison is made between the mid paleozoic norumbega fault system nfs in maine usa and the san andreas fault system safs of coastal california usa and their tectonic settings the safs formed following subduction of an oceanic ridge transform system and the nfs is interpreted as having formed the same way the parallel evaluation of mid crustal processes associated with the nfs and surface processes associated with the safs gives a unique perspective on modern and inactive crustal scale strike slip fault systems the safs is separated from the cascadia subduction zone by the mendocino triple junction similarly the mid paleozoic nfs is interpreted as having been separated from a convergent zone to the southwest by the interpreted norumbega triple junction the safs cuts a subduction complex the franciscan complex that formed when the margin was still convergent no equivalent subduction complex associated with the nfs has been recognized perhaps because it was eroded away or displaced or because it never formed the safs experienced periods of transpression and transtension whereas the nfs shows transpressive structures only slab window magmatic rocks exist along the safs devonian to earliest carboniferous plutonic rocks along the nfs may in part be slab window magmatic rocks although the effects of the acadian and prior orogenies in the appalachians complicate their identification magmatic rocks along the safs are offset due to the high rate of displacement 20 40 mm yr magmatic rocks along the nfs show little offset consistent with the low rate of displacement 3 mm yr in the model transverse structures are associated with both the safs and nfs other mendocino type triple junctions may have existed in the past but may be difficult to recognize where a past crustal scale intracontinental strike slip fault system terminates on an along strike contemporaneous convergent system such a fault fault trench triple junction may be considered