a semi analytical estimation of the effect of second order ionospheric correction on the gps positioning summary we developed a semi analytical method to evaluate the effect of the second order ionospheric correction on gps positioning this method is based on the semi analytical positioning error simulation method developed by geiger and santerre in which assuming the continuous distribution of the satellites a normal equation is formed to estimate the positioning error taking all the contributions of the ranging error by the visible satellites into account our method successfully reproduced the averaged time series of three igs sites which is comparable to the rigorous simulation we then evaluated the effect of the ionospheric error on the determination of the reference frame we evaluated the additional helmert parameters that are required for the ionospheric effect we found that the ionospheric effect can lead to annual scale changes of 0 1 ppb with an offset of 1 8 mm and a semi annual oscillation of 1 mm in the z direction however these values are too small to explain the current deviations between the gps derived reference frame and the itrf reference frame next we estimated the apparent scale changes due to the ionospheric error in the geonet coordinate time series in japan we could qualitatively reproduce the observed semi annual scale changes peaking at the equinoxes and having asymmetrical amplitudes between the vernal and autumnal equinoxes

apparent geocenter oscillations in global navigation satellite systems solutions caused by the ionospheric effect of second order 1 the international reference ionosphere iri2007 and international geomagnetic reference field igrf2005 models are used to create a worldwide model of apparent global navigation satellite systems gnss site displacements due to unmodeled higher order ionospheric delays for different time seasons and phases of the solar activity cycle it is shown that diurnal and seasonal variability of the higher order ionospheric delays causes apparent oscillations of the geometric center of the earth s figure as determined by gnss the amplitude of the oscillations in the z direction reaches 2 5 mm for the semiannual and 3 5 mm for 11 year components when satellite orbits are considered fixed and degree 1 parameterization is used failure to account for the higher order ionospheric delay when performing precise orbit determination for space borne receivers flying above while the ground based fiducial network is located below the ionosphere will result in biases between the ground and the space segment such biases changing with time and location can cause difficulties in interpretation of results from satellite altimetry and satellite gravity missions as systematic biases in orbital parameters can be interpreted as manifestations of geophysical processes on the basis of the results presented it is recommended to introduce the modeling of the second order ionospheric delay in routine gnss processing for global geodetic networks especially in view of the forthcoming solar activity maximum

the ordovician brachiopods of cornwall the brachiopod fauna of the gorran quartzites of south cornwall is described it comprises five orthid genera three taxa are described under open nomenclature and one new species is assigned to a new genus schalidomorthis stubblefieldi the fauna supports the llandeilo age suggested by accompanying trilobites there is no brachiopod evidence to indicate that the quartzite pebbles of the triassic budleigh salterton pebble bed are derived directly from the ordovician of cornwall

early palaeozoic palaeobiogeography of the variscan regions abstract the palaeobiogeographic method appears to be an attractive alternative for reconstruction of the palaeogeography of the variscan regions during the palaeozoic the evolution of faunal assemblages and climatic characteristics from the cambrian up to the end of the devonian demonstrates that baltica and north gondwana represent two major and independent palaeogeographic entities separated by a mid european rheic ocean which opened as early as the cambrian and closed progressively from the devonian the south armorican ocean whose closure generated the so called ligerian orogen is regarded as a branch of the rheic ocean both a tornquist s sea separating baltica from its western extension avalonia during the ordovician and a proto tethys ocean extending between southwestern europe and north africa during the devonian are excluded from our reconstructions

magnetic overprinting in southeastern australia and the thermal history of its rifted margin the magnetizations of many rock units in southeastern australia have been severely overprinted interpretation of early work was hindered by this and one of the aims of the current research is to ascertain the nature of the overprint mechanism its geological significance and its regional extent results from three igneous bodies from the sydney basin which have been studied previously in a reconnaissance fashion have provided a new insight into the reason for such widespread magnetic overprinting the hornsby breccia hb and milton monzonite mm yield similar magnetic signatures both containing discrete high and low temperature magnetizations with directions of dec 72 inc 83 95 4 and dec 13 inc 76 95 2 respectively for hb and dec 60 inc 78 95 4 and dec 348 inc 79 95 6 respectively for mm the corresponding pole positions are 29 s 166 e a95 7 and 59 s 139 e a95 4 for hb and 22 s 171 e a95 7 and 55 s 158 e a95 11 for mm the paleomagnetic direction and pole from the third body studied the mogo hill basalt mh are dec 241 inc 81 95 5 and 41 s 130 e a95 9 this pole position and the two low temperature overprint pole positions from hb and mm are consistent with ages ranging from 100 m y to approximately 70 m y when compared to the late mesozoic apparent polar wander path we relate the overprinting to uplift erosion and rapid supracrustal cooling of the southeastern margin of australia associated with initial phases of marginal rift development prior to seafloor spreading in the tasman sea the temperatures of rocks now exposed may have reached 200 c or higher before the rapid cooling blocked and stabilized the overprint magnetizations

groundwater induced vertical movements observed in tsukuba japan 1 the anomalous vertical movements observed in tsukuba and their relevance to groundwater level changes are investigated first we investigated the vertical coordinate time series of an igs station tskb w r t a nearby stable site and found that the time series has a strong correlation with the groundwater level changes of the deep wells next we investigated those of the gps antenna attached at the tip of the antenna of tsukuba vlbi station w r t tskb we found that the time series is decomposed into components that have 1 high correlation with the groundwater level changes of the shallow wells and 2 high correlation with the air temperature poroelastic movements of aquifers due to groundwater level changes and thermal expansion of the vlbi antenna are likely for the mechanisms of these high correlations

marginal faunal belts and their structural implications with examples from the lower palaeozoic fossils provide an independent criterion for testing structural hypotheses generated from field evidence or geochemistry as well as functioning in their traditional role in the dating of rocks or determining biogeographic realms on a global scale the identification of exterior oceanic biofacies may be of use in discriminating the course of former continental margins the isograptid graptolite biofacies early to middle ordovician can be distinguished from contemporary epicratonic graptolite biofacies its worldwide occurrence corresponds with continent margins reconstructed from other criteria hence a new isograptid record from irian jaya e new guinea although based on a small sample suggests that there may have been an ordovician oceanic site there on a continental scale the tectonic juxtaposition of different biofacies or of different stratigraphical packages contributes to an understanding of tectonics and can serve to quantify displacement the accretionary prism hypothesis for the southern uplands of scotland is supported and contrasted with the rearrangement of biofacies in the cambro ordovician cow head group of western newfoundland which reveals not only the original shelf margin slope topography now vanished but also provides an estimate of the movement involved in the emplacement of one taconic allochthon on a more local scale faunal evidence is used in assessing the original position of 9suspect9 marginal areas using the simplest possible model this shows for example that anglesey was not greatly separated from gondwana in the early ordovician but strike slip movement cannot be disproved local changes in relative sea level are determinable from sediments and faunas in marginal belts these may differ from the global eustatic curve and when this happens it is a measure of local tectonic activity particular sea level curves may serve to define structurally coherent units within mobile belts new sea level curves are contrasted for a segment of n wales north of the bala fault with that for central sw wales arenig llandovery the s welsh area mostly responded passively to the eustatic curve which can adequately account for shifts in facies and faunas while n wales had a curve often at odds with eustasy and reflecting its structural history

comments on cretaceous climatic equability in polar regions recently we examined the apparent contradiction of the former occurrence of extensive biota at very high palaeolatitudes as evidenced principally by the cretaceous flora and fauna of the gippsland and otway basins of victoria douglas and williams 1982 our study was prompted by new palaeomagnetic data which indicated near polar palaeolatitudes for southeastern australia during the cretaceous supplementary evidence of floras and faunas at high northern palaeolatitudes supported the conclusion that in view of the apparent respiration requirements of the flora reasonable equability of light day night cycle throughout the year is indicated for polar regions during the late mesozoic and earliest cenozoic we further suggested that a reduced obliquity of the ecliptic may have been the cause of such equability it should be pointed out that we offered no explanation of the relatively temperate climate of polar regions during the cretaceous compared with polar regions today a reduction in obliquity would increase equability of light and insolation at high latitudes but cannot account for overall polar warming axelrod 1984 reviewed alleged palaeopolar biota including our cretaceous forms and explained them by the nature of the thermal environments in polar regions and by the physiological responses of plants and animals allied to those that lived there he questioned the necessity for equability of light and the idea of a reduced obliquity we find his thesis unconvincing however and emphasize the following points 1 it is clearly established that in southeastern australia during the early cretaceous forests comprising a diverse partly evergreen flora ranging from cryptogams to large trees were extant these forests afforded habitats for a wide range of animal life including dinosaurs 2 the mesozoic apw path for australia schmidt and embleton 1981 ndicates that this biotic community existed at very high to polar palaeolatitudes ca 70 85 s the australian palaeomagnetic data are supported by apw paths for other gondwana continents after reconstruction or

a precise worldwide correlation of early ordovician graptolite sequences fourteen early ordovician tremadoc llandeilo graptolite sequences from around the world are precisely infrazonally correlated based on the stratigraphic ranges of 130 species and species groups the composite standard sequence css of graptolites has been determined from the six best regional sequences by a nonparametric graphic correlation two data sets were selected one comprised first appearance events of 103 taxa the other first and last appearance events of 45 taxa the results of the two runs accord well and reveal respectively 66 and 73 successive bioevents in early ordovician time event spacing averages 0 7 0 8 ma and enables fine subdivision correlation and homotaxial testing for diachroneity the strong correlation between each of the six regional sequences and the css indicates the high level of accordance among graptolite successions around the world

an interpretation of cretaceous and tertiary biota in polar regions abstract rich fossil floras and vertebrate faunas lived within the arctic and atarctic circles during the cretaceous and paleogene these occurrences seem explicable by the nature of the thermal environments in polar regions and by the physiological responses of plants and animals allied to those that lived there there seems no need to invoke a lower tilt to the earth s axis to provide greater warmth and light in polar regions to account for these fossil records

a revision of ordovician series and stages from the historical type area this paper is a revision of the standard chronostratigraphy of the ordovician of the historical type area in england and wales the revision is a response to the need for more precise definitions of series and stages especially for practical international correlation in some cases this has entailed moving horizons for series bases away from those in the classical sections the scheme will be used as the standard for a forthcoming revision of the correlation chart of the british ordovician system the ordovician is divided into five series tremadoc arenig llanvirn caradoc and ashgill the llanvirn is extended to include part of the classical llandeilo series which is included within it as a stage where stage subdivisions of standard series have not yet been defined as in the tremadoc they are proposed in this paper however bancroft s fine stadial divisions of the caradoc which have been criticized for their brevity and local utility are combined into four new stages which will have wider application the former caradoc subdivisions are retained as substages for the purposes of regional correlation

a terrestrial scenario for the cretaceous tertiary boundary collapse of the marine pelagic ecosystem in this paper we present an expansion of the model for marine ecosystem collapse at the cretaceous tertiary boundary presented by brinkhuis and zachariasse 1988 a long term sea level drop at the end of the cretaceous culminated in a short term regressive pulse at k t time deep water production was curtailed minimizing the vertical advection of nutrients and oxygen in the oceans consequently a productivity crisis developed which could only be survived by cosmopolitan shallow dwellers and the oxygen minimum zone omz expanded no sustained oceanic anoxic event followed the k t boundary event since productivity had dropped to extremely low values at k t time however the short term expansion of the omz invoked by the combination of minimized oxygen advection and abrupt mass mortality caused dysoxic conditions even to reach up to the shelves as can be deduced from sedimentological chemical and faunistic observations

palaeomagnetism of volcanic rocks of the kodiak islands indicates northward latitudinal displacement in the past decade it has become widely accepted that southern alaska is composed of allochthonous terranes1 4 but the times of amalgamation and their accretion to north america remain controversial palaeomagnetists and geologists generally agree that the talkeetna superterrane consisting of the wrangellia and peninsular terranes fig 1 was far to the south of its present position with respect to north america in triassic and jurassic time1 4 this consensus is lost when it comes to the question of the relative position of these terranes in the tertiary previously limited palaeomagnetic evidence suggested that the peninsular terrane may have lain substantially south of its present position4 but the timing of deformational and thermal events and the apparent absence of a tertiary suture zone argue for a cretaceous docking of wrangellia and the peninsular terrane5 6 here we present new palaeomagnetic results demonstrating that the kodiak islands were indeed at a more southerly latitude 62 myr ago around 43 n and discuss the implications of this conclusion

space time distribution of afterslip following the 2003 tokachi oki earthquake implications for variations in fault zone frictional properties 1 gps time series following the september 25 2003 ut tokachi oki earthquake m w 8 0 reveal significant deformation we use the network inversion filter to invert for the spatial and temporal evolution of afterslip in the 30 days following the earthquake afterslip is concentrated adjacent to the coseismic rupture zone between the 2003 rupture and the inferred source regions of the 1968 tokachi oki and the 1973 nemuro oki earthquakes the inversion shows a rapid decay of slip rate in the 2003 rupture zone with slower deceleration in the surrounding regions the stress velocity paths for the afterslip regions approximately follow d d in v 0 6 mpa suggestive of steady state velocity strengthening friction the complementary spatial pattern of coseismic rupture and afterslip may indicate along strike spatial variations of frictional properties although other interpretations can not be ruled out

a reassessment of facies and faunas in the type llandeilo ordovician wales abstract detailed analysis of the lithological and faunal successions of the type llandeilo forms the basis of an evaluation of the sequence of depositional environments and a quantitative description of the entombed faunas comprising mainly brachiopods trilobites and ostracods recorded distribution patterns confirm the validity of the existing trilobite trinucleid biostratigraphic zones but emphasize the importance of benthic bivalved taxa which are particularly abundant in the lower llandeilo groups of assemblages comprising localized faunules or associations despite exhibiting evidence of transportation are readily identified as representative of more widespread contemporary palaeocommunities recently described from wales and the welsh borderland the relationship between these palaeocommunities and the transgressive llandeilo sequence indicates a shoreface to open shelf zonation of ecosystems controlled primarily by substrate conditions rather than depth

spurious annual vertical deformations over japan due to mismodelling of tropospheric delays summary we quantitatively estimate the spurious annual vertical deformations due to the mismodelling of tropospheric delays over japan through a numerical simulation for this purpose we simulate the gps data for present day satellite distributions using realistic cumulative tropospheric delays that are calculated using ray tracing and numerical weather models to obtain the spurious deformations the simulated gps data are then analysed by using the same gps processing software and the same analysis strategies as those used in the analysis of the observed gps data in the estimated spurious annual vertical deformations it is found that the amplitudes of the deformations increase toward the north reaching up to 3 mm at around 45 n whereas the phase lags are uniform throughout japan and vary by around 220 indicating spurious subsidence in the middle of february in the western part of japan the observed annual vertical deformations are less affected by spurious annual vertical deformations and more likely caused by the atmospheric and oceanic loading in the northern part of japan we observe large up to 8 mm annual vertical deformations with phase lags corresponding to subsidence in winter subsidence in winter is interpreted to be the effect of snow loading however some part of the observed subsidence is found to be spurious due to the mismodelling of the tropospheric delays these spurious signals may be mitigated by using mapping functions that are constructed by using direct ray tracing and numerical weather models in the gps analysis

definition of the tremadoc series and the series of the ordovician system in britain the tremadoc series and series of the ordovician system are widely used in international correlations and this review explains and summarizes how the base of each of these series is recognized in britain no type section in which the base of any one of them is displayed has ever been selected and formally designated hence the basal horizon of each series is a matter of general understanding rather than precise definition this general understanding is of particular biozones or of assemblages of fossils and their relative ages the geographical separation between type sections of series and differences in facies complicate the understanding of relative ages of biozones brachiopod and trilobite faunas of the llandeilo caradoc and ashgill series have been studied in detail in recent years and biozones proposed these biozones have proved difficult or impossible to recognize outside their type areas in britain and brachiopod trilobite faunas of the tremadoc arenig and llanvirn series are likewise highly provincial thus for correlation within and outside britain attention has been focused on the standard graptolite biozones particularly since such conodont faunas as have been found have not proved useful yet there are problems associated with these standard biozones for example the tetragraptus approximatus biozone is unknown in wales or england the relationship between the base of the glyptograptus teretiusculus biozone and the earliest llandeilo shelly faunas requires clarification and at what level the base of the caradoc series may lie in the nemagraptus gracilis biozone is unknown thus to bring precision to definitions of ordovician series in britain the identification of continuous fossiliferous sequences that will serve as stratotypes is required such a section for the basal portion of the tremadoc series has recently been proposed systematic studies related to particular biozones are needed for example early caradoc and early ashgill brachiopods and graptolites of the didymograptus bifidus and glyptograptus teretiusculus biozones the stratigraphical ranges and abundances of species in particular sections require documentation so that the type of biozone assemblage acme concurrent range etc may be recognized such work could lead towards chronostratigraphy the provision of a standard stratigraphical scale in britain for the tremadoc series and ordovician series

palaeo oceanography and biogeography in the tremadoc ordovician iapetus ocean and the origin of the chemostratigraphy of dictyonema flabelliforme black shales high concentrations of vanadium molybdenum uranium arsenic antimony with low concentrations of manganese iron and cobalt heretofore restricted to dictyonema flabelliforme bearing tremadoc black shales in balto scandia have been found in coeval black shales in the saint john new brunswick area prior palaeogeographic reconstructions place these areas about 400 km apart in high southern latitudes in the iapetus ocean with new brunswick in proximity to avalonia southeastern newfoundland these geochemical similarities are not found in coeval tremadoc black shales of bolivia new york quebec wales and belgium palaeo oceanographic reconstructions of iapetus support the proximity of balto scandia and the saint john area during the early tremadoc and gee sx 1981 suggestion that the signature is a feature of eastern iapetus furthermore first order modelling of the major surface currents and related primary productivity in the tremadoc iapetus ocean explain the apparent wide latitudinal range of d flabelliforme fortey 1984 and the anomalous trace metal content of certain black shales of that time variations in the elemental content of these black shales is produced by oceanographic and geologic conditions unique to the geographic site the distinctive balto scandic geochemical signature resulted from the coincidence of anoxic waters transgressing the shelf at latitudes of high organic productivity at the polar ekman planetary divergence this produces the conditions for concentrations of v u and mo in the shales metal enriched anoxic bottom waters produced by leaching of volcanics or through hydrothermal activity may be the source of the other enhanced signature elements such as as and sb the absence of this geochemical signature in younger non d flabelliforme tremadoc and later black shales in balto scandia and other areas suggests that the closing of iapetus moved the depositional sites into less productive oceanic areas

nontidal ocean mass loading detected by gps observations in the tropical pacific region 1 the effect of nontidal ocean mass loading is investigated as a possible cause for the seasonal variability observed in the vertical components of the gps derived site coordinates of tropical pacific islands the nontidal ocean mass origin sea level changes moslcs are estimated by subtracting the steric height changes observed at buoys from the net sea level changes measured by satellite altimetry assuming a linear relationship between the moslcs at the closest buoys and the gps vertical movements the coherences and the admittances are estimated we found evidence that the vertical movements are caused by the loading effect at three out of four sites the occasional deviations between the vertical movements and predicted loading deformations are presumably due to the invalidity of the assumption of a linear relationship between the moslcs and the loading deformation and or of the mean temperature salinity relationship used in estimating steric heights in the corresponding periods

high resolution correlation of anglo welsh middle to upper ordovician sequences and its relevance to international chronostratigraphy abstract continuously fossiliferous sections in south wales and shropshire spanning the base of the upper ordovician permit precise correlation of the nemagraptus gracilis biozone a horizon currently under scrutiny for the selection of a global stratotype section and point gssp using graphic correlation we have compiled a new composite global standard for the middle upper ordovician which shows that the first occurrence of the key graptolite n gracilis is not everywhere of the same age appearing earlier in north american successions than it does in britain species of dicellograptus by contrast appear to be almost synchronous in their first appearance the status and correlation of standard british biozones through the llandeilian caradoc interval based on graptolites and trilobites are revised suitable sections for the definition of bases of biozones are proposed if the base of the n gracilis biozone is accepted internationally as the base of the upper ordovician this biozone being coincident with the base of the caradoc series there are sections suitable for its precise definition in the british succession

ocean mass variations from grace and tsunami gauges 1 we compared the mass variations from gravity recovery and climate experiment grace with those measured by bottom pressure recorders bprs deployed as tsunami gauges prior to the comparison we estimated the degree 1 stokes coefficients by the degree 1 loading method using both the gps and grace data we successfully recovered the degree 1 stokes coefficients that are consistent with those from the satellite laser ranging analysis and from the loading model we found that the use of the grace data in the degree 1 loading method significantly mitigates the aliasing effect from the unmodeled higher degree loading deformations then we compared the mass variations from grace with those from the five bprs that have been deployed as part of the deep ocean assessment and reporting of tsunamis dart system we observed a fairly good over 0 4 correlation except for one station that is close to the u s mainland however we found that the grace derived mass variations underestimate those from bprs by nearly a factor of 2 through numerical simulation we found that the artificial leakage from the landmass is responsible for the low correlation observed at the station and the spatial averaging in the grace processing may be responsible for the underestimation of the mass variations from bprs by grace these results illustrate the importance of performing a simulation for these effects with numerical models before comparing the grace derived mass variations with those from pointwise measurements

southern polar forests the early cretaceous floras of victoria and their palaeoclimatic significance abstract a diverse fossil flora including cryptogams pteridosperms cycadales bennettitales ginkgoales coniferales and angiosperms occurs in early cretaceous fluvial and lacustrine strata in the otway and gippsland basins in southern victoria both evergreens e g araucarians cycads ferns and deciduous or semi deciduous forms e g certain pteridosperms and ginkgoales seem to have been represented certain ferns ginkgos and conifers grew to a large size overall the assemblages are typical of early cretaceous floras the associated fauna includes dinosaurs hypsilophodontids allosaurs lepidosaurs chelonians birds fish including the lungfish ceratodus and insects the evidence of the biota as a whole suggests a warm to cool temperate relatively equable climate of moderate seasonality with no widespread winter freezing the complex mesozoic apparent polar wander path apw indicated for australia places victoria in high to polar palaeolatitudes ca 70 85 s during the early cretaceous this apw path is supported by paths for other gondwana continents the existence of the victorian early cretaceous forest and biotic communities through polar nights of about two to five months duration is difficult to accept evergreen species would have required relative equability of light whatever the temperature the dinosaurs foliage throughout the year and the lungfish warm to temperate conditions without freezing in view of the consistency of mesozoic palaeomagnetic results for gondwanaland and the enigmatic presence of mesozoic and early cenozoic fossil floras and faunas in very high northern palaeolatitudes the possibility of a reduced obliquity of the ecliptic in mesozoic early cenozoic time should be considered

a lancefieldian graptolite from the lake district large dictyonema species including d pulchellum t s hall have been collected from beds in the uldale fells northern lake district below strata yielding didymograptus protobalticus monsen they suggest the presence there of graptolitic beds transitional from lancefieldian to bendigonian in age approximately tremadoc arenig and suggest that the area may yet provide an internationally correlatable base to the arenig series in britain