the leka opholite complex central norwegian caledonides field characteristics and geotectonic significance the leka ophiolite complex loc of lower ordovician age u pb zircon age of 497 2 ma contains the following components 1 a lower strongly deformed harzburgite unit representing the depleted upper mantle this unit becomes progressively richer in dunite towards 2 a sequence of ultramafic cumulates unconformably overlying the harzburgite tectonite the crystallization sequence in the ultramafic cumulates is olivine chromite clinopyroxene orthopyroxene in the south western part of the ultramafic cumulate sequence layers of metagabbro appear interlayered with banded dunite wehrlite the above mentioned rock sequences may be in tectonic contact with 3 layered metagabbros which give way upwards to laminated and vari textured metagabbro within the laminated vari textured metagabbro is the first appearance of 4 metabasalt dykes which increase upwards in abundance from scattered single dykes to a 100 sheeted dyke swarm associated with the vari textured metagabbro and metabasalt dykes are minor acid intrusions within the upper part of the dyke swarm is the first appearance of 5 pillow lavas which are associated with thick volcaniclastic metasediments at apparently higher stratigraphic levels geochemically the metabasalt dykes and associated pillow lavas range from predominant island arc tholeiite iat to morb character and typical metaboninites are also present this range of geochemical composition as well as the crystallization sequence of the cumulates strongly suggests that the first stages in the formation of the loc was by spreading above a subduction zone the pillow lavas associated with volcaniclastic rocks are of morb or wpb type and these probably represent the later spreading stages of the loc in a back arc basin but at sufficient distance to be unaffected by the geochemical fingerprints of the subduction process

textural variation in the pyrite rich ore deposits of the roros district trondheim region norway implications for pyrite deformation mechanisms the roros district is a pyrite rich polymetallic sulfide orefield in the southeastern part of the trondheim region central norwegian caledonides all of the ore deposits at roros are hosted within a cambrian to silurian succession that was deformed and metamorphosed at lower greenschist to lower amphibolite facies conditions during the caledonian orogeny samples from five individual deposits across the orefield have been analyzed using a combination of reflected light petrographic observation orientation contrast imaging and electron backscatter diffraction results indicate that whereas samples from each ore deposit have a variety of different textures all of them preserve plastic deformation in pyrite grains that occurred at peak metamorphic conditions characterized by the development of internal lattice misorientation within pyrite grains and low angle 2 dislocation walls these observations indicate that the principal deformation mechanisms at peak metamorphic conditions were dislocation glide and creep the preservation of brittle fracturing represents later overprinting events

paleozoic laurentia gondwana interaction and the origin of the appalachian andean mountain system laurentia the rift bounded precambrian nucleus of north america may have broken out from a neoproterozoic supercontinent between east and west gondwana several lines of evidence suggest that the appalachian margin of laurentia subsequently collided with the proto andean margin of the amalgamated gondwana supercontinent in different relative positions during early and mid paleozoic time in route to final docking against northwest africa to complete the assembly of pangea hence the appalachian and andean orogens may have originated as a single mountain system the overall hypothesis retains the same paleomagnetic and paleobiogeographic controls as previous global reconstructions for the paleozoic era laurentia gondwana collisions may help to explain contemporaneous unconformities in the paleozoic sedimentary cover of the laurentian gondwanan and baltic cratons

geochemistry of caledonian metabasalts from some norwegian ophiolite fragments major and trace element analyses of metabasalts from five of the lower palaeozoic caledonian ophiolite fragments along a strike distance of some 800 km of the west norwegian coast are presented characteristically the ree patterns show depletion of both lree and hree relative to intermediate ree giving an upward convex shape but nearly flat lree depleted or enriched patterns occur the ree patterns of the metabasalts from three of these sequences i e the lykling solund and stavfjorden ophiolite fragments show little within sequence but large between sequence variation the ree patterns of the metabasalts from the gullfjellet major bergen arc and skalvaer ophiolite fragments however show significant within sequence variations indicative of local source heterogeneties

interseismic strain accumulation across the central north anatolian fault from iteratively unwrapped insar measurements the north anatolian fault naf is a major tectonic feature in the middle east and is the most active fault in turkey the central portion of the naf is a region of global navigation satellite systems gnss scarcity previous studies of interseismic deformation have focused on the aseismic creep near the town of ismetpasa using radar data acquired in a single line of sight direction requiring several modeling assumptions we have measured interseismic deformation across the naf using both ascending and descending data from the envisat satellite mission acquired between 2003 and 2010 rather than rejecting incorrectly unwrapped areas in the interferograms we develop a new iterative unwrapping procedure for small baseline interferometric synthetic aperture radar insar processing that expands the spatial coverage our method corrects unwrapping errors iteratively and increases the robustness of the unwrapping procedure we remove long wavelength trends from the insar data using gnss observations and deconvolve the insar velocities into fault parallel motion profiles of fault parallel velocity reveal a systematic eastward decrease in fault slip rate from 30 mm yr 25 34 95 confidence interval ci to 21 mm yr 14 27 95 ci over a distance of 200 km direct offset measurements across the fault reveal fault creep along a 130 km section of the central naf with an average creep rate of 8 2 mm yr and a maximum creep rate of 14 2 mm yr located 30 km east of ismetpasa as fault creep is releasing only 30 40 of the long term strain in the shallow crust the fault is still capable of producing large damaging earthquakes in this region

a small baseline approach for investigating deformations on full resolution differential sar interferograms this paper presents a differential synthetic aperture radar sar interferometry difsar approach for investigating deformation phenomena on full resolution difsar interferograms in particular our algorithm extends the capability of the small baseline subset sbas technique that relies on small baseline difsar interferograms only and is mainly focused on investigating large scale deformations with spatial resolutions of about 100 spl times 100 m the proposed technique is implemented by using two different sets of data generated at low multilook data and full single look data spatial resolution respectively the former is used to identify and estimate via the conventional sbas technique large spatial scale deformation patterns topographic errors in the available digital elevation model and possible atmospheric phase artifacts the latter allows us to detect on the full resolution residual phase components structures highly coherent over time buildings rocks lava structures etc as well as their height and displacements in particular the estimation of the temporal evolution of these local deformations is easily implemented by applying the singular value decomposition technique the proposed algorithm has been tested with data acquired by the european remote sensing satellites relative to the campania area italy and validated by using geodetic measurements

recent advances in sar interferometry time series analysis for measuring crustal deformation abstract synthetic aperture radar sar interferometry is a technique that permits remote detection of deformation at the earth s surface and has been used extensively to measure displacements associated with earthquakes volcanic activity and many other crustal deformation phenomena analysis of a time series of sar images extends the area where interferometry can be successfully applied and also allows detection of smaller displacements through the reduction of error sources here we review recent advances in time series sar interferometry methods that further improve accuracy this is particularly important when constraining displacements due to processes with low strain rates such as interseismic deformation we include examples of improved algorithms applied to image deformation associated with the 2010 eruption of eyjafjallajokull volcano in iceland slow slip on the guerrero subduction zone in mexico and tectonic deformation in western anatolia turkey

lower cambrian burgess shale type fossil associations of south china abstract burgess shale type preservation has been reported from numerous qiongzhusian and canglangpuian sections of southern china during the last few decades the early cambrian chengjiang type faunas of east yunnan were of particular interest due to their excellent preservation and taxonomic diversity a new definition and revision of the chengjiang type faunas is given which indicates that distinct ecological variations occurred between the chengjiang and haikou faunas on a smaller scale and between the arthropod dominated faunas of shallow shelf and the sponge dominated faunas of deeper shelf e g hunan on a larger scale recent finds from the yuanshan formation of deze east yunnan and the niutitang formation of zhongnan zunyi county guizhou indicate a much wider distribution of burgess shale type fauna during this period than was previously known the present investigations of the latter fauna revealed the presence of tsunyidiscus niutitangensis naraoia spinosa n cf longicaudata isoxys curvirostratus i paradoxus skioldia aldna amplectobelua trispinata cf tsunyiella diandongensis scenella sp cambrorhytium elongatum hyalosinica archaica and choiaella radiata the occurrence of burgess shale type preservation on the yangtze platform is not restricted to a small area as in the burgess shale but known from a ca 80 km wide geographic stripe extending for more than 500 km along the rim of proterozoic platform core this wide distribution of burgess shale type preservation is interpreted to be triggered by the coincidence of specific palaeoecological conditions including the rapid sedimentation of finest siliciclastic particles and the partial influence of suboxic water masses

estimating spatiotemporal ground deformation with improved persistent scatterer radar interferometry ast synthetic aperture radar interferometry has been applied widely in recent years to ground deformation monitoring although difficulties are often encountered when applying the technology among which the spatial and temporal decorrelation and atmospheric artifacts are the most prominent the persistent scatterer interferometric synthetic aperture radar ps insar technique has overcome some of the difficulties by focusing only on the temporally coherent radar targets in a time series of synthetic aperture radar sar images this paper presents an improved ps insar technique by introducing ps neighborhood networking and empirical mode decomposition emd approaches in the ps insar solution linear deformation rates and topographic errors are estimated based on a least squares method while the nonlinear deformation and atmospheric signals are computed by singular value decomposition and the emd method an area in phoenix az is used as a test site to determine its historical subsidence with 39 c band sar images acquired by european remote sensing 1 and 2 satellites from 1992 to 2000

the annieopsquotch ophiolite belt of southwest newfoundland geology and tectonic significance the annieopsquotch ophiolite belt consists of ophiolite fragments exposed from buchans in central newfoundland to the southwest tip of the island the largest remnants belong to the annieopsquotch complex in the northeast and the long range mafic ultramafic complex in the southwest the arenigian annieopsquotch complex exposes an ophiolite stratigraphy from layered cumulate gabbro moho sequence through high level gabbro sheeted dikes pillow lava and chert the long range mafic ultramafic complex consists largely of cumulate and high level metagabbro with subordinate ultramafic rock and metabasalt all engulfed as massif to xenolith size fragments in ordovician tonalitic and younger mafic to felsic granitoid intrusions the latter rocks are intersected by a wide locally gently inclined high temperature ductile thrust zone which also encompasses amphibolite semipelitic schist and marble between buchans and the southwest tip of newfoundland the tonalite terrane encloses many smaller ophiolitic fragments the ophiolite fragments of the northern half of the belt have similar dike trends have n type morb chemistry and likely formed one major allochthon of iapetus oceanic crust this was disrupted by the intrusion of tonalite and other magmas in an arc or arc trench environment and by subsequent faulting an attempt is made to assess the significance of the annieopsquotch belt in relation to ether newfoundland ophiolites

a baseline combination method for precise estimation of ice motion in antarctica differential synthetic aperture radar interferometry d insar is a powerful method for measuring surface deformation such as in studies of the earthquake cycle volcano deformation monitoring land subsidence monitoring and glaciological studies however its application to glaciological studies is limited by the lack of accurate digital elevation models dems particularly over the antarctic ice sheet previous studies on ice motion using d insar are mostly based on short baseline interferograms because these data sets are insensitive to dem errors unfortunately short baseline interferograms are often unavailable in this paper we refine the insar technique by using a combination of two interferograms to make accurate ice flow velocity measurements the refined technique is tested in the grove mountains area east antarctica ice flow velocities from the baseline combination method are in good agreement with those measured by short baseline interferograms this method is also capable of reducing phase errors by combining the appropriate data sets the reliability of the data sets is assessed by defining a baseline combination parameter and ensuring that it is less than or equal to 1 0 with this method we are able to extend the usefulness of d insar for glaciological studies

ordovician faunas island arcs and ophiolites in the scandinavian caledonides ordovician faunal data from the scandinavian caledonides is tested with new geochemical information from zircons to give u pb ages and source origins of volcanic arc and ophiolite sequences early ordovician arenig llanvirn low latitude toquima table head faunas from the upper upper allochthon are associated with an island arc system formed adjacent to laurentia contemporaneous mafic magmas were contaminated by crustal material during subduction and associated granites contain inherited zircons of archaean age the nearest source for such rocks is on the laurentian rather than the baltic side higher latitude celtic province faunas from the upper upper allochthon are from one insular site accessible to forms from both laurentia and baltica the late ordovician low latitude holorhynchus and subtropical hirnantia faunas occur in overstep sequences above deeply eroded early ordovician arc complexes the transgression appears to be coeval with a second generation of spreading related complexes single detrital zircons from sediments show sources from archaean proterozoic and early ordovician terranes this suggests that deposition was in a basin situated along the same continental margin laurentia to which the early ordovician ophiolite arc sequences had already become accreted the late ordovician faunas link both laurentia and baltica at a time of narrowing of lapetus the new geochemical data together with the faunal information is supported by recent palaeomagnetic studies

a new hypothesis for organic preservation of burgess shale taxa in the middle cambrian wheeler formation house range utah cambrian konservat lagerstatten are the most significant fossil deposits for our understanding of the initiation of phanerozoic life although many modes of preservation may occur these deposits most frequently contain nonmineralized fossils preserved in the form of kerogenized carbon films a rare yet important taphonomic pathway that has not previously been explained for any unit by a comprehensive model the middle cambrian wheeler formation of utah one of these lagerstatten contains abundant kerogenized preservation of nonmineralized tissues which occurs within a distinctive taphofacies that accumulated under the following conditions 1 domination of the siliciclastic fraction by clay sized particles 2 close proximity to a carbonate platform which resulted in mixed carbonate clay sediments 3 a well developed oxygen minimum precluding benthic colonization and burrowing and 4 relative proximity to oxic bottom waters facilitating transport of organisms from a habitable environment to one that favored their preservation we propose that preservation of nonmineralized tissues in the wheeler formation may have resulted from a combination of influences that reduced permeability and thus lowered oxidant flux which in turn may have restricted microbial decomposition of some nonmineralized tissues those influences include near bottom anoxia preventing sediment irrigation by restriction of bioturbation reducing conditions near the sediment water interface that may have acted to deflocculate aggregations of clay minerals resulting in low permeability face to face contacts early diagenetic pore occluding carbonate cements and an absence of coarse grains such as silt skeletonized microfossils fecal pellets or bioclasts this model may be applicable to kerogenized preservation of macrofossils in other fossil lagerstatten

complete remagnetization of some permian dykes from western norway induced during burial uplift abstract stable paleomagnetic directions in four basaltic dykes and in some associated caledonian metamorphic rocks define high latitude mesozoic paleomagnetic pole positions which are not compatible with the k ar age of 250 my determined for the dykes a monotonic increase of 40 occurs in the potassium content of samples taken across a dyke 32 cm wide this is accompanied by only a 1 2 variation in the k ar age of the samples suggesting the absence of any significant level of initial argon titanomagnetite grains having bulk compositions around x 0 6 have suffered extensive low temperature alteration forming assemblages of ferri rutile granules in a matrix of pure magnetite the complete remagnetisation of both the dykes and the associated country rocks is probably an expression of a vrm acquired at elevated temperatures 150 500 c at the emplacement depth of the dykes a stable remanent magnetisation was locked in during uplift of the area probably related to the kimmerian basin development in the adjacent north sea and the epeirogenic uplift of western fennoscandia

nonlinear subsidence rate estimation using permanent scatterers in differential sar interferometry discrete and temporarily stable natural reflectors or permanent scatterers ps can be identified from long temporal series of interferometric sar images even with baselines larger than the so called critical baseline this subset of image pixels can be exploited successfully for high accuracy differential measurements the authors discuss the use of ps in urban areas like pomona ca showing subsidence and absidence effects a new approach to the estimation of the atmospheric phase contributions and the local displacement field is proposed based on simple statistical assumptions new solutions are presented in order to cope with nonlinear motion of the targets

geochronology of the buchans roberts arm and victoria lake groups and mansfield cove complex newfoundland volcanic groups of the central mobile belt of the newfoundland appalachians have previously been subdivided into early and late arc sequences separated in time by a quiescent caradocian stage defined in some areas by fossil bearing black shales new u pb zircon ages of and 473 2 ma for rhyolites of the buchans and roberts arm groups respectively show them to be correlative early ordovician sequences these ages serve to refute both the previous rb sr whole rock isochron ages of 447 ma and the idea that these groups were late arc sequences these new ages corroborate evidence from late arenig early llanvirn conodonts in the buchans group and calibrate this fossil occurrence a new u pb zircon age of 479 3 ma from plagiogranite of the mansfield cove complex immediately west of the roberts arm group shows that this plutonic body is only slightly older than the adjacent volcanic rocks and not hadrynian as previously supposed local field relationships suggest this body may represent part of a dis

cambrian palaeomagnetic data from baltica implications for true polar wander and cambrian palaeogeography a reliable early cambrian c 535 ma and a preliminary late cambrian c 500 ma palaeomagnetic pole from baltica sweden overlap within uncertainty and they are also broadly compatible with vendian c 583 ma palaeomagnetic data apparent polar wander for baltica amounts to less than 25 between 583 and 500 ma and therefore negates recent speculations that the earth tipped 90 during the early cambrian true polar wander throughout vendian and cambrian times baltica lay at southerly latitudes c 30 60 s baltica was geographically inverted and present day northern baltica faced the nw margin of gondwana which covered the south pole laurentia eastern baltica and laurentia west gondwana were separated by the iapetus ocean while the aegir sea separated western baltica from the taimyr region of siberia during the cambrian baltica probably moved eastward along the gondwana margin and by c 515 520 ma subduction in the aegir sea was initiated a major event is recognized in late cambrian or early ordovician times c 500 478 ma when baltica must have undergone a 55 counter clockwise rotation in c 22 million years 3 ma we relate this to the early caledonian finnmarkian orogeny which involved arc continent collision following subduction

u pb ages of ophiolites and arc related plutons of the norwegian caledonides implications for the development of iapetus u pb zircon ages are reported for four ophiolites and three crosscutting arc related plutons from the norwegian caledonides plagiogranite differentiated from gabbro of the karmoy ophiolite is dated at 493 7 4 ma whereas arc related trondhjemite cutting this ophiolite crystallized at 485 2 ma a crosscutting clinopyroxene phyric gabbro intrusion is dated at 470 9 5 ma by near concordant magmatic titanite sphene and discordant u rich 2903 6677 ppm zircon lower intercepts of 247 68 and 191 70 ma defined by the plagiogranite and clinopyroxene phyric gabbro best fit lines may reflect a real low t alteration rift related event

strain discontinuities within the seve koli nappe complex scandinavian caledonides this paper utilizes the results of a regional survey of the state of finite strain carried out in an area built up of stacked thrust sheets to draw conclusions about the relative timing of penetrative deformation and thrust motion and to place constraints on the deformation models devised to explain the geometry of the individual thrust sheets a strain survey within the seve koli nappe complex reveals abrupt changes which represent discontinuities in the strain pattern one of these discontinuities coincides with the boundary between the seve and koli nappes and separates intense transversal stretching strain within the seve nappe from the longitudinal strains of lower intensity within the koli nappe the weight of geological evidence favours the interpretation of this strain discontinuity as a unconformity with significant deformation of the seve nappe occurring before rocks of the overlying koli nappe were deposited middle ordovician a second discontinuity marks the junction between the krutfjell nappe and the underlying lower grade koli rocks the strain distribution is incompatible with a previous interpretation of the discontinuous krutfjell nappe as a string of mega boudins an interpretation which implies considerable post thrust flattening of the nappe pile the strain results and other evidence favour earlier deformation of the krutfjell nappe before these rocks were thrust over the underlying tectonic units the lens shaped outcrop configuration of the krutfjell nappe is explicable in some cases if the geometry of this nappe is a westerly thinning wedge within the low grade koli nappe rocks north of the grong culmination the longitudinal stretching is difficult to explain in terms of easterly directed nappe movements whereas the clear transverse strains in other tectonic units appear to predate the main silurian thrusting event

a new baseline linear combination algorithm for generating urban digital elevation models with multitemporal insar observations the lack of high resolution digital elevation model dem data presents one major limitation for deformation mapping using synthetic aperture radar interferometry insar techniques with high spatial resolution radar imagery e g terrasar x this article presents a baseline linear combination blc approach to generate interferograms with nearly zero baselines so as to minimize the effects of the uncertainties in the dem used it incorporates the baseline combination bc method with adjacent gradient networking to successfully unwrap the interferograms even in abruptly discontinuous areas which in turn can be used to estimate a high resolution dem the blc approach does not require any deformation model instead it utilizes nearly zero baseline interferograms to assist with 3 d phase unwrapping application of the blc approach to the terrasar x data set in shenzhen china shows that the blc derived dem agrees with the digital surface model dsm obtained from light detection and ranging lidar with a correlation coefficient of 0 998 and a root mean square error rmse of 2 05 m demonstrating the effectiveness of the blc approach note that the blc approach is not only able to be employed in urban areas with high buildings but also in mountain areas with steep slopes

sm nd dating of seve eclogites norrbotten sweden evidence for early caledonian 505 ma subduction the seve nappes consist of long transported thrust sheets belonging to the upper allochthon within the scandinavian caledonides eclogites from two different megalenses within the seve nappe complex in norrbotten northern sweden have been dated with the sm nd method the two eclogite bearing megalenses have been subjected to different pressure and temperature conditions during the high pressure metamorphism garnet omphacite whole rock from ts2 within the tsakkok lens give an age of 505 18 ma 2 i 0 512231 0 000024 mswd 0 10 garnet and whole rock from ts5 and whole rock ts3 also fall on the above isochron the composite isochron gives an age of 503 18 ma 2 these results are interpreted to date the peak of the high pressure metamorphism 500 630 c and 12 15 kbars for the tsakkok lens the eclogites in the vaimok lens at grapesvarre were subjected to higher pressure and temperature conditions and more extensive reequilibration during the early cooling stages retrograde breakdown reactions accompanied by retrograde zoning of relict garnet seems to be associated with disturbance of the sm nd isotopic systems in contrast a sample with unzoned garnet and well preserved high pressure mineralogy from grapesvarre gives a sm nd garnet omphacite age of 503 14 ma 2 i 0 512010 0 000038 2 the ages for the seve eclogites are significantly older than the sm nd eclogite dates from the western gneiss region of norway wgr suggesting the existence of at least two eclogite forming events in the caledonide orogen the younger event has been related to the main continent continent collision stage of the caledonian orogeny while the older event that led to the production of the norrbotten eclogites must have taken place several hundred kilometres to the north and in a different tectonic setting more oceanward to the wgr it appears that the older event ca 505 ma was restricted to the subduction of dyke intruded sedimentary cover rocks which are thought to represent the rifted edge of the baltic continent

the origin of oceanic plagiogranites from the karmoy ophiolite western norway both field relationships and geochemical characteristics indicate two suites of plagiogranitic and related rocks coexisting in the higher parts of the karmoy ophiolite of western norway the plutonic zone of this ophiolite can be subdivided into three complexes the east karmoy igneous complex the visnes high level complex and the veavagen igneous complex and plagiogranitic rocks are well developed in the first two of these within the east karmoy igneous complex plagiogranites are associated with high temperature pre basic dyke shear zones rare earth element modelling indicates that these plagiogranites were derived by anatexis of amphibolite hydrated diabase assuming a starting material consisting of 40 hornblende and 60 plagioclase and that batch melting occurred within the stability field of hornblende in comparison plagiogranite occurs in a number of bodies in the upper part of the visnes high level complex and forms a sandwich horizon together with biotite diorites and epidosites between a roof assemblage of dykes microgabbros and magnetite gabbros and a floor assemblage of layered and non layered gabbros the r e e modelling of the petrogenesis of this series of plagiogranites indicates that they were derived by filter pressing of a differentiated interstitial liquid to the vari textured gabbros although the distribution of highly hygromagmatophile elements such as k rb ba etc cannot be explained satisfactorily by this model alone depletion in these elements appears to be an autometasomatic effect

the spence shale lagerstatte an important window into cambrian biodiversity the spence shale member of the langston formation is a cambrian miaolingian wuliuan lagerstatte in northeastern utah and southeastern idaho it is older than the more well known wheeler and marjum lagerstatten from western utah and the burgess shale from canada the spence shale shares several species with these younger deposits yet it also contains a remarkable number of unique species because of its relatively broad geographical distribution and the variety of palaeoenvironments and taphonomy the fossil composition and likelihood of recovering weakly skeletonized or soft bodied taxa varies across localities the spence shale is widely acknowledged not only for its soft bodied taxa but also for its abundant trilobites and hyoliths recent discoveries from the spence shale include problematic taxa and provide insights about the nature of palaeoenvironmental and taphonomic variation between different localities supplementary material a generic presence absence matrix of the spence shale fauna and a list of the spence shale localities are available at https doi org 10 6084 m9 figshare c 4423145

shear deformation and eclogite formation within granulite facies anorthosites of the bergen arcs western norway the anorthosites of the bergen arcs contain two distinct metamorphic mineral assemblages which are stable under different p t conditions a granulite facies assemblage which equilibrated at t 800 900 c p 10 kbar is defined by the minerals plagioclase al rich diopside cpx i garnet gnt i scapolite orthopyroxene dark brown hornblende this assemblage is linked by corona structures to a primary magmatic mineralogy where coexistence of olivine and plagioclase limits the maximum crystallization pressure of the anorthosites to 8 kbar at 1200 c the anorthosites are transected by a series of fine grained shear zones in which the granulite facies assemblage is replaced by an eclogite mineralogy defined by omphacite cpx ii jd40 50 garnet kyanite epidote clinozoisite phengite quartz amphibole with plagioclase sometimes remaining in the marginal parts mineral compositions indicate equilibration conditions for the eclogite paragenesis of t 700 800 c p 16 19 kbar a series of textural and mineralogical changes which can be observed as the strain increases into the shear zones demonstrates that the eclogite mineralogy is formed at the expense of the granulite facies minerals during the early stages of shear zone development the eclogite mineralogy defines a strong mylonitic fabric which again is truncated by centimetres thick secondary shear zones containing clasts of both granulite and eclogite minerals these latter fine grained ultramylonites may be connected to uplift of this deep seated complex the eclogite shear zones are highly oblique to the granulite structures indicating that the eclogite shear zones formed under a new stress regime rb sr dating shows that the granulite facies assemblage formed in sveconorwegian time or earlier while minerals from shear zones define ages around 400 ma indicating a caledonian formation of the eclogites this work demonstrates the critical role of deformation in triggering metamorphic reactions whether the shear stress also was important in stabilizing the eclogite assemblages is not clear from the available data

a burgess shale like fauna from the lower cambrian of north greenland the cambrian explosion refers to the major adaptive radiation of the metazoans during the earliest phanerozoic an event that is best known by the abrupt appearance of hard parts near to the precambrian cambrian boundary 550 myr bp 1 deciphering this important evolutionary episode depends largely on the study of these skeletal remains2 3 together with trace fossils that include burrows and trackways4 5 many of these latter fossils evidently represent the activities of soft bodied organisms such as worms and lightly sclerotized arthropods whose exact identity is seldom known not least because they can be fossilized only in exceptional circumstances6 however documenting the soft bodied representatives of early metazoan communities cannot be neglected if they accounted for a substantial fraction of these early biotas7 here we report a new soft bodied fauna from the lower cambrian of north greenland this assemblage has highly significant similarities with the younger burgess shale and provides additional evidence for the geological longevity of this faunal type and its widespread distribution in deeper waters of cambrian oceans

using gis to study palaeobiogeographic and macroevolutionary patterns in soft bodied cambrian arthropods abstract soft bodied cambrian arthropods from burgess shale type deposits are some of the most famous and extensively studied fossil invertebrates but global species level assessments of their biogeographic patterns have not previously been explored quantitatively here we use a newly developed occurrence database in conjunction with geographic information systems gis analysis and paleogis which allows fossil locality positions to be viewed in the context of cambrian palaeogeography to quantitatively reconstruct geographic distribution patterns of primarily soft bodied arthropod species further we compare these patterns with those of co occurring trilobite taxa soft bodied cambrian arthropods show both statistically larger geographic ranges and greater stratigraphic longevities than co occurring trilobites many of the most widely distributed soft bodied arthropods were likely capable of swimming and this may in part explain their extensive distributions

the palaeogeography of early ordovician iapetus terranes an integration of faunal and palaeomagnetic constraints abstract new and existing fossil data from ireland britain newfoundland and scandinavia emphasize a significant degree of latitudinal variation in biogeographic patterns across the ordovician iapetus ocean platform provinces together with marginal belts and island complexes can be recognised with increasing clarity on the basis of palaeontological information statistical analysis of the distribution patterns of about 70 early ordovician brachiopod genera across some 25 sites using both cladistic and phenetic methods together with a critical analysis of their geological settings combined with current palaeogeographic and palaeomagnetic data reaffirm the existence of the celtic brachiopod province during the early ordovician the majority of sites assigned to the celtic province define a high latitude peri gondwanan belt shadowing the distribution of the low latitude circum laurentian toquima table head faunas rapidly changing ordovician faunal signals across the baltic province and exploits zone of central newfoundland track the cross latitude movement of these terranes from high temperate to near tropical belts during the period new fossil information together with continuing statistical appraisal of an expanding database are providing more accurate and sophisticated models for the dynamics of the iapetus ocean system

paleoecology of benthic metazoans in the early cambrian maotianshan shale biota and the middle cambrian burgess shale biota evidence for the cambrian substrate revolution abstract as the depth and intensity of bioturbation increased through the proterozoic phanerozoic transition the substrates on which marine benthos lived changed from being relatively firm with a sharp sediment water interface to having a high water content and blurry sediment water interface microbial mats once dominant on normal marine proterozoic seafloors were relegated to stressed settings lacking intense metazoan activity this change in substrates has been termed the agronomic revolution seilacher a pfluger f 1994 from biomats to benthic agriculture a biohistoric revolution in krumbein w e ed biostabilization of sediments bibliotheks and informationsystem del carl von ossietzky universitat oldenburg 97 105 and the impact of the subsequent development of the mixed layer on benthic metazoans has been termed the cambrian substrate revolution bottjer d j hagadorn j w dornbos s q 2000 the cambrian substrate revolution gsa today 10 9 1 7 because the early cambrian was a transitional time in this substrate revolution it is hypothesized that benthic metazoans adapted to typical proterozoic style soft substrates co existed with benthic metazoans adapted to more typical phanerozoic style soft substrates paleoecological examination of the benthic metazoans of the early cambrian maotianshan shale chengjiang biota and middle cambrian burgess shale biota combined with examination of core samples from the rocks in which the maotianshan shale biota is preserved was performed in order to test this hypothesis results of the core analysis reveal that the rocks in which the maotianshan shale biota was preserved and therefore the substrate on which it lived contains almost no evidence for bioturbation of any kind while the immediately underlying rocks of similar lithology are dominated by intermediate levels of horizontal bioturbation and contain some evidence for the beginning of mixed layer development these results suggest that benthic metazoans of the maotianshan shale biota lived on a typical proterozoic style soft substrate and that environmental conditions associated with the exceptional preservation of the maotianshan shale biota may have also suppressed bioturbation levels results of the paleoecological analysis indicate that the maotianshan shale and burgess shale biotas contain mobile and sessile benthic metazoans adapted to typical proterozoic style soft substrates and others adapted to typical phanerozoic style soft substrates in addition the maotianshan shale biota is dominated by benthic suspension feeding genera adapted to typical proterozoic style soft substrates indicating that this biota lived during the early stages of the cambrian substrate revolution the burgess shale biota however contains more benthic suspension feeding genera adapted to typical phanerozoic style soft substrates than the maotianshan shale biota which suggests that the soft substrate on which they lived had more advanced levels of mixed layer development this research suggests that the adaptive radiation of benthic metazoans during the cambrian explosion was driven in part by the cambrian substrate revolution as benthic metazoans were forced to adapt to the development of the mixed layer in subtidal siliciclastic soft substrate environments during the cambrian

lead isotope systematics of strata bound sulfide deposits in the caledonides of norway a lead isotope investigation has been carried out on approximately 40 strata bound sulfide deposits in the caledonides of norway the deposits occur in a wide range of palcotectonic enviromnents and lithostratigraphie units a plot of their lead isotope data 206 pb 204 pb vs 207 pb 204 pb displays a linear trend with volcanogenie deposits in an ocean floor environment at the least radiogenic end and sediment hosted deposits in an intraplate continental environment at the radiogenic end this trend is probably a result of mixing mantle derived lead with lead derived from an older radiogenic basement within the upper allochthon there is a general decrease in radiogenicity of the lead with higher teetono stratigraphic position this is paralleled by an increase in the proportion of volcanic rocks and is interpreted to reflect the diminished input of radiogenic lead from continentally derived sediments the uniform character of the radiogenic end member indicates that lead in sediments derived from a continental domain was the immediate source and that the lead was homogenized during sedimentary transport this is in agreement with the observed lithologies in the footwall sequences of the sampled deposits early obduetion of ophiolites and island ares onto laurentia has been proposed as a model for the scandinavian caledonides although not ruled out by the lead isotope data from norway these data give no reason for invoking derivation of continental lead from the laurentian side of the iapetus ocean a compilation of similar lead isotope data from the whole caledonian appalachian orogen shows regional differences in the slopes of the mixing lines reflecting different basement continental sources of lead the lead isotope compositions of massive sulfide deposits may therefore become a useful tool in interpreting the origin of exotic terranes

geochronology of caledonian metamorphic allochthons in the otta heidal region south norway tectonostratigraphic and palaeogeographical implications the caledonian appalachian belt formed in the early paleozoic by the assembly and dispersal of continental and oceanic crustal fragments of diverse provenance the characterization of these terranes and information on their origins are essential in reconstructing the course of the orogeny the region of northern gudbrandsdalen in norway is important for elaborating these questions as it represents a geological transition in architectural style and composition of the caledonian nappes and the meeting point of tectonic elements with diverse geological histories of both baltic and exotic origins in the past century this complexity has generated conflicting interpretations which we have tested with new mapping and isotope dilution thermal ionization mass spectrometry u pb dating the new data show the following 1 a metagabbro low in the tectonostratigraphy has an age of 1497 5 ma correlating with the espedalen complex of telemarkian 1550 1480 ma affinity 2 the structurally higher crystalline rudihoe mukampen suite was metamorphosed at high grade during the sveconorwegian orogeny mainly between 980 and 900 ma with older components pointing to a gothian 1700 1600 ma affinity 3 these ages and mapping indicate that the rudihoe mukampen suite is a lateral equivalent of the upper jotun nappe 4 the overlying dominantly metasedimentary steinho complex was metamorphosed in the ordovician at about 473 3 ma 5 both the rudihoe mukampen suite and steinho complex were intruded by trondhjemite dykes at 430 427 ma these units are structurally overlain by the lowest elements of the trondheim nappe complex which includes serpentinite lenses and conglomerates the products of hyperextension locally with ordovician fossils the new results dispel some of the problematic interpretations proposed earlier and represent new firm elements that will anchor future tectonic reconstructions of the caledonides in this region

early ordovician terne linkages between oceanic and continental ternes in the central scandinavian caledonides the presence of a first order unconformity in the central part of the scandinavian caledonides linking together early ordovician late cambrian outboard oceanic ternes and the continental margin of baltic is of considerable importance for interpreting the geodynamic framework of the orogen this and other criteria for terne linkage are described together with implications for the regional tectonostratigraphic development in this segment of the caledonides

suspect terranes and accretionary history of the appalachian orogen the north american connection or the grenvillian continental crust that separated from eastern north america during the initiation of the appalachian orogenic cycle is poorly defined within the present orogen a variety of terranes occur outboard of the north american miogeocline all structurally uncoupled and therefore suspect stratigraphic analysis indicates that appalachian accretion progressed from the miogeocline outward the boundaries of the earliest accreted western terranes are marked by melange and ophiolite complexes later boundaries between eastern terranes are steep mylonitic zones and brittle faults accretionary events defined by stratigraphic analysis correspond to times of major deformation plutonism and metamorphism in the history of the orogen

a novel method for deformation estimation based on multibaseline insar phase unwrapping the three pass differential synthetic aperture radar interferometry dinsar is one of the approaches in radar interferometry applications for measuring the deformation of the earth surface the conventional three pass dinsar needs a successful single baseline sb phase unwrapping pu procedure on each interferogram to ensure accurate deformation monitoring because of the limitation of the phase continuity assumption the sb pu becomes a challenging processing step when the study area has strong phase variation in this paper the multibaseline mb insar pu methodology which can eliminate the phase continuity assumption by means of the baseline diversity is transplanted into the conventional three pass dinsar domain based on mb pu a novel terrain deformation estimation approach is developed both theoretical analysis and experimental results demonstrate that the proposed method is an effective surface deformation estimation method

ordovician volcanism in the welsh borderland basaltic andesitic and rhyodacitic rhyolitic volcanism was widespread during ordovician time in the welsh basin new chemical data are presented for llanvirn to caradoc lavas and tuffs from the welsh borderland which during ordovician time formed the southeastern margin of the welsh basin in view of the observed chemical alteration immobile elements are used in the interpretation of the original geochemical character the data indicate that the llanvirn stapeley volcanic group of the shelve inlier was a bimodal basalt basaltic andesite rhyodacite rhyolite association the basalts have trace element contents of tholeiitic associations with a subduction related character the caradoc whittery and hagley volcanic groups of the shelve inlier comprise lavas and tuffs of calc alkaline andesite blocks sampled from the breidden hills show that these were also derived from a calc alkaline volcano associated caradoc pumice and ash flow deposits from the breidden hills are probably of altered calc alkaline rhyodacite rhyolite composition the sibdon carwood basalt flow the only known example of ordovician volcanism east of the pontesford linley and church stretton lineaments has transitional tholeiitic to alkaline character with trace element contents influenced by subduction related processes the overall tholeiitic to calc alkaline nature of the magmatism is consistent with the view that during llanvirn to caradoc time the welsh basin was an ensialic marginal basin

taphonomy and depositional circumstances of exceptionally preserved fossils from the kinzers formation cambrian southeastern pennsylvania abstract the emigsville member of the kinzers formation cambrian southeastern pennsylvania is a deposit of exceptional preservation containing three main lithofacies that were part of a mixed siliciclastic carbonate debris fan developed seaward of a carbonate shelf along the appalachian margin of laurentia fossils were exceptionally preserved in a shelf environment subject to tempestite deposition most remains are fragmentary which emphasizes the importance of predation as a taphonomic process where emigsville sediments were deposited remains are preserved mostly as organic carbon films pyrite crusts and aluminosilicate films these preservation styles apparently depended upon the development of microbial consortia in isolated microenvironments and some of the microbes were autolithified sedimentary and biological evidence suggests that anoxia salinity fluctuations and sedimentary obrution played relatively minor roles in the emigsville member of the kinzers formation the abundance of exceptionally preserved remains suggests that exceptional sedimentary conditions were not necessary in the cambrian in order for exceptional preservation to occur the abundance of predation evidence in a deposit of exceptional preservation reinforces the concept that predation was the primary taphonomic filter during cambrian time

using gis to unlock the interactions between biogeography environment and evolution in middle and late devonian brachiopods and bivalves abstract the late devonian was a time of profound evolutionary and environmental change associated with the frasnian famennian biodiversity crisis one way to unravel the faunal dynamics of this complex crisis is to document the spatial and temporal patterns associated with biodiversity decline this analysis investigates the relationship between biogeography relative sea level and environmental changes in laurentian brachiopod and bivalve species during the givetian through famennian stages upper middle to terminal devonian representatives from all major brachiopod and bivalve clades and paleocommunities were examined to provide a cross faunal comparison species ranges were reconstructed both spatially and temporally at the level of conodont zones using gis to understand the timing and extent of species invasions and the importance of geographic range during the crisis interval species geographic ranges were linked closely with both relative sea level change and depositional environment and expanded as relative sea level rose in addition times of interbasinal species invasions corresponded closely with sea level rises that breached tectonic barriers species with larger geographic ranges were more resistant to extinction during the late devonian this relationship is reflected partly in a general trend towards increased extinction resistance in taxa that are found farther offshore in environments that potentially included more area for example there is an increased survival advantage for species that inhabited the middle and outer platform environments though not for species inhabiting the open shelf additionally species whose givetian to frasnian history includes at least one interbasinal invasion event were more likely to survive the late devonian biodiversity crisis than noninvasive species this may have relevance for our understanding of the current biodiversity crisis given the role that invasive species are playing in mediating modern extinctions

tectonic framework and phanerozoic evolution of sundaland abstract sundaland comprises a heterogeneous collage of continental blocks derived from the india australian margin of eastern gondwana and assembled by the closure of multiple tethyan and back arc ocean basins now represented by suture zones the continental core of sundaland comprises a western sibumasu block and an eastern indochina east malaya block with an island arc terrane the sukhothai island arc system comprising the linchang sukhothai and chanthaburi blocks sandwiched between this island arc formed on the margin of indochina east malaya and then separated by back arc spreading in the permian the jinghong nan uttaradit and sra kaeo sutures represent this closed back arc basin the palaeo tethys is represented to the west by the changning menglian chiang mai inthanon and bentong raub suture zones the west sumatra block and possibly the west burma block rifted and separated from gondwana along with indochina and east malaya in the devonian and were accreted to the sundaland core in the triassic west burma is now considered to be probably cathaysian in nature and similar to west sumatra from which it was separated by opening of the andaman sea basin south west borneo and or east java west sulawesi are now tentatively identified as the missing argoland which must have separated from nw australia in the jurassic and these were accreted to se sundaland in the cretaceous revised palaeogeographic reconstructions illustrating the tectonic and palaeogeographic evolution of sundaland and adjacent regions are presented

u pb geochronology of the coney head complex newfoundland the coney head complex white bay newfoundland comprises allochthonous plutonic rocks and deformed equivalents emplaced over the continental margin during the ordovician taconic orogeny a u pb zircon age of 474 2 ma for tonalite considered as having formed by partial melting in an island arc indicates that it crystallized in arenig time a microgranite dated by u pb zircon titanite at 432 2 ma cuts the tonalite inherited proterozoic zircon in the microgranite indicates that the rock formed from magma generated in part by melting of continental crust or sediments derived from such crust these relationships indicate that the microgranite was emplaced in silurian time after ordovician transport of the tonalite above a continental substrate

uranium lead zircon and titanite ages from the northern portion of the western gneiss region south central norway abstract the geochronologic history of the northern portion of the western gneiss region south central norway has been investigated by u pb analyses of zircon and titanite from various basement units and one supracrustal gneiss a six point four zircon and two titanite discordia line from a migmatite melt pod and its host gneiss astfjord migmatite gneiss defines upper and lower intercept ages of 1659 1 1 8 ma and 393 6 3 6 ma respectively the upper intercept age is interpreted as a time of tonalite emplacement and migmatite formation in the region a seven point three zircon and four titanite discordia line from the ingdal granite gneiss has similar upper and lower intercept ages 1652 9 1 7 ma and 396 1 4 9 ma respectively and the upper intercept age is interpreted as the time of granite crystallization the lower intercept age from both theastfjord migmatite gneiss and the ingdal granite gneiss is interpreted as the time of regional metamorphic resetting and is evidence for caledonian influence in the region titanite from these two gneiss units as well as from other tonalite granite and supracrustal gneisses throughout the western gneiss region displays a remarkably uniform pattern of discordance titanite discordance is variable from 6 to 100 and in general the degree of discordance is proportional to the caledonian metamorphic grade of nearby supracrustal schists episodic diffusional lead loss from titanite during caledonian metamorphism probably caused the discordance pattern but a combined mechanism of mixing and diffusional lead loss cannot be ruled out in any case the seventeen point titanite and zircon discordia line clearly indicates that 1 the bulk of the granitoid terrane in this portion of the western gneiss region was emplaced migmatized and cooled in a short time interval about 1657 ma ago 2 a second short lived thermal event that exceeded the blocking temperature of titanite occurred about 395 ma ago and 3 titanite and zircon in the region were not isotopically disturbed by comparable geologic events in the period from 1657 to 395 ma or at any time after 395 ma

geology and paleobiology of islands in the ordovician iapetus ocean review and implications a history of islands in the iapetus ocean and their destruction is recorded by widespread occurrences of lower to upper ordovician volcanic and epiclastic rocks and some limestone through the axial parts of the appalachian caledonide orogen in north america and northwestern europe assemblages of arenigian and llanvirnian benthic shelly fossils chiefly brachiopods from these rocks constitute the celtic biogeographic province that is distinguished by its endemic genera and by some that are older than in other biogeographic provinces some that are younger than elsewhere and others that have not hitherto been found together evidence from these fossils and from the geology of the rocks pertaining to them suggests that north american terranes that included islands of arenigian llanvirnian age lay at middle to high latitudes both in mid ocean and within the armorican continental margin whereas coeval rocks in west central ireland and norway that have toquima table head shelly fossils were originally part of the laurentian continental margin eradication of the celtic assemblage and the reduction of ordovician faunal provinciality in the appalachian caledonide region coincide with llanvirnian obduction subduction of hundreds of kilometres of iapetus ocean crust late llanvirnian and younger ordovician rocks in the remnant basin including some of peri insular origin have brachiopods of scoto appalachian affinities no discrete islands of ashgillian age have been recognized although fossiliferous volcaniclastic and polymictic conglomerates indicate intermontane basins in some places shelly fossils in these rocks and those in the siltstones and limestones from the gaspe peninsula are like those of ashgillian age elsewhere

the influence of external digital elevation models on ps insar and sbas results implications for the analysis of deformation signals caused by slow moving landslides in the northern apennines italy advanced interferometric synthetic aperture radar insar postprocessing like persistent scatterer insar ps insar offers the possibility to investigate slow moving landslides where standard interferometry is problematic these advanced algorithms involve the analysis of a series of sar acquisitions in both time and space one input that requires particular attention for landslide applications is the external digital elevation model dem that is used to correct the interferograms for the topographic phase term when multiple elevation data sets are available for a given study area it is difficult to decide which one should be used in this paper we test the sensitivity of ps insar small baseline subset sbas results to different dems the study area is located in the northern apennines of italy where chaotic clay shales and fine grained flysch host slow moving earth flows and ancient rock slides c band envisat and x band cosmo skymed data are processed with different dems we describe a simple framework to statistically analyze the influence of these models on the final ps insar sbas results we find that individual interferograms do not vary much depending on the dem while the results from ps insar and sbas analysis do vary this is likely caused by the way the dem error is estimated we find also that the quality of the dem is more important than the resolution and that x band insar data are more sensitive to the choice of the dem than c band the significance of the results is discussed with reference to two landslide areas

the great appendage arthropod tanglangia biogeographic connections between early cambrian biotas of australia and south china abstract the cambrian great appendage arthropod tanglangia luo and hu in luo et al 1999 has until now been known from a single species from the chengjiang biota of southwest china cambrian series 2 stage 3 a new species from the emu bay shale konservat lagerstatte on kangaroo island south australia cambrian series 2 stage 4 tanglangia rangatanga sp nov extends the geographic and stratigraphic ranges of this genus and amplifies the biogeographic links between non biomineralised faunas from the early cambrian of australian east gondwana and the south china plate

sar monitoring of progressive and seasonal ground deformation using the permanent scatterers technique spaceborne differential radar interferometry has proven a remarkable potential for mapping ground deformation phenomena e g urban subsidence volcano dynamics coseismic and postseismic displacements along faults as well as slope instability however a full operational capability has not been achieved yet due to atmospheric disturbances and phase decorrelation phenomena these drawbacks can often be at least partially overcome by carrying out measurements on a subset of image pixels corresponding to natural or artificial stable reflectors permanent scatterers ps and exploiting long temporal series of interferometric data this approach allows one to push the measurement precision very close to its theoretical limit in the order of spl sim 1 mm for c band european remote sensing ers like sensors in this paper the detection of both time uniform and seasonal deformation phenomena is addressed and a first assessment of the precision achievable by means of the ps technique is discussed results highlighting deformation phenomena occurring in two test sites in california are reported fremont in the southern bay area and san jose in the santa clara valley