geochronology of early to middle paleozoic tectonic development in the southwest newfoundland gander zone southwest newfoundland s gander zone was once considered part of the collided eastern margin of an early paleozoic iapetus ocean distinguished from the rest of the gander zone by the extensive exposure of a polydeformed amphibolite to greenschist facies sequence considered devonian in age overlying presumed precambrian basement it was later found that truly devonian strata were confined to the cape ray fault system the local northwestern boundary of the zone u pb zircon isotopic ages of 452 13 51 ma and 458 22 29 ma on metavolcanic rocks in the upper part of the sequence southeast of the fault system indicate that ordovician and possibly older rocks underlie the gander zone itself a temporal framework for the three main stages of regional deformation corresponding to pre metamorphic recumbent folding d 1 and transpression d 2 and d 3 is presented using u pb and 40 ar 39 ar dates of granitoid and metamorphic rocks d 1 is bracketed as late o

nature of the recent vertical ground movements inferred from high precision leveling data in an intraplate setting ne ardenne belgium yearly high precision leveling surveys have been performed from 1993 to 1998 along a 48 km long local network centered on gileppe lake at the foot of the ardenne massif belgium institut geographique militaire and institut geographique national igm ign levelings of 1948 and 1974 yielded additional information the data were corrected for collimation and thermal errors other sources of error earth tides atmospheric refraction rod miscalibration were estimated and corrections were made when necessary random errors of individual surveys range from 0 15 to 0 74 mm km the recorded elevation changes indicate the existence of tilted segments some 5 to 10 km in length with yearly tilt values amounting up to 2 rads fault movements of a few mm yr are also demonstrated the segment limits are spatially stable from one year to the next but very frequent sense reversals of the vertical motions are observed this explains why the total movement over a 20 to 30 year period is barely higher than the yearly displacements various nontectonic causes of vertical ground movement e g monument instability varying water loading of the lake sediment compaction etc have been considered yielding little satisfactory explanation of the patterns of observed elevation changes we propose that the recorded motions which we call reversible fault creep and reversible tilt respectively are a true tectonic signal reflecting the tectonic noise which accompanies the long term deformation of uplifting areas in intraplate settings such movements are characteristic of fault segments which may occasionally generate earthquakes

strain trajectories above the main central thrust himalaya in southern tibet as a result of the collision of india with asia1 3 a thick pile of precambrian crystalline rocks the main central sheet was transported southwards over the indian continent a marked linear fabric a mineral stretching lineation within the main central sheet varies only slightly from a north south trend which is interpreted as paralleling the direction of transport of the nappe3 6 our study sought to extend the previous observations to the hitherto poorly known part of the main central sheet in southern tibet china the stretching lineation is dominantly north south in the lower part of the sheet but exhibits continuous and discontinuous variations from north south to east west in the upper part7 these variations of lineation trajectory indicate two shear components one subparallel to and one at a high angle with the himalayan belt the recognition of westward wrench shearing in the main central sheet implies a component of relative displacement parallel to the himalayan belt and not only a radial one as generally assumed in previous models this suggests that the kinematic story of the intracontinental deformation following the continental collision is probably not one of simple north south convergence

deformation resulting from regional extension during pluton ascent and emplacement central sierra nevada california solid state foliation lineation small scale folds and domainal shear zones have developed in preexisting granitic and minor metasedimentary wallrock during a combined deformation involving a regional extensional strain and ascent and emplacement of the mt givens pluton mgp mylonite is common throughout much of the 1 2 km wide 10 km long shear zone with ultramylonite best developed near the contact with the mgp which itself lacks significant solid state deformation migmatization accompanies ultramylonite formation in the northern half of the zone but both these features are poorly developed or absent in its southern half where the shear zone is distributed over a wider area strain estimates across the shear zone using microgranitic enclaves as markers show a positive gradient and an increasing ratio of simple shear pure shear towards the mgp microprobe analyses on hornblende and plagioclase yield pressure and temperature estimates of 3 5 kb and 680 c respectively during shear zone formation at least at its late stages of development zircon pb u and 40 ar 39 ar ages constrain timing of the high temperature movement on the shear zone to 90 ma essentially the age of the mgp although movement immediately prior to that time appears likely we speculate that a regional extensional shear zone was developing prior to the emplacement of the mgp which as it ascended heated the wallrock facilitating both further strain in the zone as well as buoyant rise of the pluton along the zone the mgp was near its critical melt fraction during the last several kilometers of its ascent and could have possessed sufficient viscosity strength to impose a weak shear strain on the shear zone rocks although most of the foliation and extensional features in the zone are probably related to the regional strain field late stage folding of the foliation is attributed to shouldering aside of the wallrock by the mgp during the last increment of its ascent and final emplacement

sourcing ceramics with portable xrf spectrometers a comparison with inaa using mimbres pottery from the american southwest seventy five intact mimbres and jornada pottery sherds from the american southwest were analyzed by portable xrf and instrumental neutron activation analysis inaa examination of the data demonstrates that inaa and portable xrf results for elements common to both analyses can be used to construct similar compositional groups when individual compositional groups are compared to one another it is apparent that unambiguous separation of compositional groups is challenging by portable xrf given 1 the limited number of key discriminating elements that can be measured relative to inaa and 2 the relative analytical precision and accuracy of portable xrf for measurements of intact heterogeneous ceramics we conclude that sourcing intact ceramics by portable xrf is challenging and that bulk analytical measurements such as inaa remain a better approach for sourcing archaeological pottery

using portable energy dispersive x ray fluorescence edxrf analysis for on site study of ceramic sherds at el hibeh egypt as part of its geoarchaeological research program the el hibeh project of the university of california berkeley field tested at the site of el hibeh northern middle egypt the utility of a portable edxrf unit for obtaining geochemical analyses of pottery suitable for provenance and other ceramic classification studies when the geochemical ceramic data from the field test are combined with basic petrographic analysis for the pottery sample set compelling results are generated in particular a triangular scattergram using elemental iron strontium and rubidium data in parts per million provides excellent temporal and spatial separation of ceramic fabrics type origin and date the geochemical behavior of iron strontium and rubidium is discussed in relation to geological source materials utilized for pottery manufacture

non destructive provenance study of cuneiform tablets using portable x ray fluorescence pxrf abstract portable x ray fluorescence pxrf apparatus of the last generation was tested to determine its potential for routine provenance determination of clay cuneiform tablets which cannot be analyzed by classical intrusive methods a group of tablets from hattusa bogazkoy and from el amarna which were previously provenanced using optical mineralogy om and instrumental neutron activation analysis inaa was analyzed by pxrf and the results were used to establish the grouping according to their elemental concentrations these groups were compared with the previous results retrieved by om and inaa in order to confirm their validity the results corroborate the high potential of the pxrf for non destructive study of well defined closed assemblages of clay derived delicate artifacts such as cuneiform tablets bullae and fine ware pottery consequently a group of previously unexamined tablets from hattusa was analyzed by pxrf and the results are discussed with implications on future research

displacement of surface monuments vertical motion several measurements of vertical ground motion at pinon flat observatory california indicate the overall weakness and instability of the earth s weathered surface with respect to the underlying rock cumulative long period motions of order 0 5 mm per year dominate these records though smaller elastic deformations caused by precipitation loading atmospheric loading and tidal strains are evident at higher frequencies all of these help to characterize the near surface material the long period records suggest that near surface weathering is the dominant influence on monument motion at least at this site on crystalline rock in a semi arid environment rainfall loading gives an average vertical modulus of 2 6 gpa for the material in the uppermost 26 m of the ground compared with 88 gpa for granite under moderate confining stress atmospheric loading gives similar results but indicates the ground is permeable to airflow at periods longer than a few hours earth tide records show poisson s ratio to be 0 09 in contrast to the normative range of 0 2 0 25 establishing that horizontal strains couple only weakly into vertical ones so that vertical strains near the surface are a poor measure of areal strain the form of the ground surface displacement power spectrum indicates that analyses of geodetic surveys would be improved with the inclusion of a monument positioning error budget that increases with time because of ground instability and the generally small rate of crustal tectonic motions deeply emplaced monuments will be needed for observational programs designed to detect short term changes in crustal deformation over baselengths of order 10 km and less

structural evolution of a major fault zone the cape ray fault zone southwestern newfoundland canada the cape ray fault zone is a major paleozoic structure in southwestern newfoundland and occurs at or close to the boundary between two major continental blocks laurentia and avalonia a detailed structural analysis demonstrates that the fault records early reverse sinistral thrusting of the grand bay complex at amphibolite grade d2 followed by a protracted event d3 characterized by reverse dextral thrusting of the grand bay complex rocks on top of the supracrustal rocks of the windsor point group and retrogression to greenschist facies as well as a pre 384 ma orogen parallel dextral transcurrent mylonite d4 during the later stages of the collision regional scale strain partitioning induced heterogeneity of strain both along and across the strike of the cape ray fault zone the east west oriented segment of the cape ray fault zone is a tear fault that accommodated differential displacement along the length of the fault later stages of the deformation include post 384 ma sinistral transcurrent r

postglacial land uplift in estonia based on four precise levelings abstract the vertical velocities of the fundamental benchmarks of estonian 1st order leveling network were estimated based on the four precise leveling campaigns from 1933 to 2010 the kinematic least squares adjustment of the network was used where heights and velocities were introduced as unknown parameters for detection of outliers baarda s data snooping method was applied estimation of variance components by the helmert s and the iaue methods provided realistic weights in the network adjustment and revealed also that the observation errors of the first three levelings are up to 3 times larger than was assumed a priori to obtain apparent uplift rates and fix velocity in kinematic adjustment the velocity value 2 1 mm yr of the ristna tide gauge on island hiiumaa was transferred to the nearest stable benchmark by using precise levelings from tide gauge to the national height network average standard deviation of velocities at benchmarks was estimated to be 0 5 mm yr based on apparent vertical velocities of the benchmarks an interpolated land uplift surface was created using kriging and minimum curvature gridding methods although the two methods gave similar surfaces rms of differences was below 0 1 mm yr the kriging solution was used in comparison with the results of the earlier studies the uncertainty of new velocity surface was estimated to be 0 5 to 0 7 mm yr the new land uplift model fits well with the fennoscandian land uplift model nkg2005lu the rms of the differences was 0 2 mm yr good agreement was also confirmed with the earlier land uplift maps of estonia rms of differences 0 6 mm yr however clear disagreement was noticed when tide gauge observations from several studies were used in comparison rms of differences up to 1 0 mm yr apparently different velocity solutions of estonian tide gauges are systematically biased the reasons for these biases need further investigation

episodic reactivation of a late precambrian mylonite zone on the gondwanan margin of the appalachians southern newfoundland the grand bruit fault zone of southern newfoundland is a fundamental structure within late precambrian basement on the gondwanan margin of the appalachian orogen within the fault zone a sequence of structures documents changes in the sense of ductile displacement from 1 reverse dip slip to 2 dextral strike slip to 3 sinistral oblique slip and finally to 4 dextral lateral offsets fault movements along this structure were punctuated by emplacement of a variety of plutons and minor intrusions which when precisely dated allow these movements to be bracketed at between 571 ma and 564 ma 497 ma and 427 ma 424 ma and 420 ma and 421 ma and 387 ma respectively the tectonic evolution of the gondwanan inlier of southern newfoundland is mirrored in large part by the record of mylonite development within the grand bruit fault zone these tectonic events are attributable to well constrained regional orogenic events of both the pan african and appalachian cycles newly formed shear zones in the fault zone reactivate parts of much older faults of similar regional orientation and are in some cases kinematically indistinguishable from the ancestral structures integration of precise geochronological data with the sequence of overprinted fault structures demonstrates that although the role of progressive deformation in shear zone development was important the observed disposition of structures and rock units is primarily a function of polyorogenic accretion as a multiple reactivated structural lineament in a gondwanan basement inlier the fault zone exerted fundamental control over the tectonic development of the leading edge of the convergent southeast margin of the orogen

internal structure of the cadillac tectonic zone southeast of val d or abitibi greenstone belt quebec the kirkland lake larder lake cadillac break is a major fault zone of the abitibi greenstone belt well known for its spatially associated gold camps a detailed structural analysis of this fault zone in the val d or area has shown the presence of a 200 750 m wide zone of high strain defined here as the cadillac tectonic zone ctz which includes the narrower schist zone generally regarded as the cadillac break the boundaries of the ctz which coincide with major lithologic contacts strike approximately east west and dip 80 to the north the internal structure of the ctz is best analysed in terms of two increments of the same progressive deformation the d1 strain increment is characterized by an east west striking subvertical s1 foliation at low angle in strike to the bound aries of the ctz and containing subvertical elongation lineation primary lithological contacts have been transposed into s1 and folded by f1a folds f1b intrafolial folds of s1 ranging from noncylindrical subhorizontal f

progressive deformation structures associated with ductile thrusts in the moine nappe sutherland n scotland in the deeper parts of mountain belts polyphase structural sequences observed at outcrop scale can arise due either to overprinting of regionally distinct deformation phases e g reworking changes in orogenic boundary conditions or to localized controls that bring about transient changes in the patterns of ductile flow these are unlikely to be mutually exclusive processes and examples from scotland demonstrate that once regionally separate events are delimited using radiometric evidence it is possible to isolate complex deformation sequences arising due to local controls in the western moine nappe of sutherland the dominant structures were formed during caledonian ductile thrusting towards the wnw whilst earlier precambrian phases are relatively minor in importance two groups of caledonian folds and fabrics are recognized in many exposures main phase d2 structures which are broadly contemporaneous with ductile thrust fabrics and later secondary phase f3 folds the latter can be divided into two geometric groups sheath fold types which formed initially as wnw overturned buckles subsequently modified by ductile shearing and asymmetric types which are commonly open folds apparently formed with axes close or sub parallel to the thrust transport direction secondary structures show a close spatial association with high strain zones along ductile thrusts and can be shown to have formed during the later stages of thrusting in certain critical exposures i propose that they may form due to strain perturbations resulting from variations in the relative rates of ductile flow within the mylonites where differential shearing occurs due to flow normal perturbations wrench related asymmetric fold types may form in contrast secondary sheath fold structures may result from localized compression phases caused by flow parallel perturbations local flow perturbation models may be appropriate in situations where the distribution of later structures is apparently related to spatial variations in strain intensity and or there is a strong geometric and kinematic similarity between sets of folds and fabrics if such features are not observed a regional polyphase sequence is more likely and it is therefore necessary to obtain radiometric dates or some other independent source of data to demonstrate a time separation

origin of kinkbands and shear band cleavage in shear zones an experimental study specimens of artificial kcl mica schist have been deformed in simple shear with different initial orientations 10 intervals between 0 and 170 of the mica schistosity s1 relative to the imposed simple shear plane for most experiments the angular shear strain was 30 the strain rate 4 8 10 4s 1 and the stress normal to the imposed shear plane 20 mpa all experiments were conducted at room temperature deformation of the specimens is achieved largely by slip parallel to the s1 mica foliation however two new types of slip surfaces also develop as either a single orientation set or as a pair of conjugate sets these new slip surfaces are kinkbands and a shear band cleavage the type and number of sets of new slip surfaces which develop depends on the orientation of s1 relative to the shortening and extension fields of the instantaneous strain ellipsoid our experiments indicate that kinkbands or shear band cleavage form in shear zones in which s1 is inclined to the margin of the zone which structure forms and whether it occurs as a single set of structures or as a conjugate pair depends on the initial orientation of s1 in situations where s1 is parallel to the margins of the zone neither structure develops if the deformation is a simple shear the presence of kinkbands or shear band cleavage in such zones where s1 is parallel to the margins is an indication that the zones were transtensional or transpressional respectively we conclude that shear band cleavage is not only an excellent indicator of shear sense but also a qualitative indicator of the ratio of s1 normal shortening to s1 parallel shear conjugate shear bands indicate that s1 normal shortening was relatively strong and single shear band sets indicate that s1 parallel shear was relatively strong

tests of glacial rebound models for fennoscandinavia based on instrumented sea and lake level records summary evidence for changing sea levels in northwestern europe related to glacial rebound is found in both the geological record of the past millennia and in the instrumental records of the past two centuries the latter records are of two types records of sealevel change primarily from the baltic and the gulfs of finland and bothnia and records of the tilting of some of the larger lakes in both finland and sweden the sealevel records are particularly important because of their long duration and high quality their large number and good spatial distribution and the spatially coherent background noise the two instrumental data types are complementary and provide constraints on the upper mantle rheology and on the distribution of ice during the late glacial stage comparisons of the observed rates of change of the water levels with models for glacial rebound yield earth models with a lithospheric thickness of 80 100 km and an uppermantle viscosity of 4 5 1020 pa s evective parameters that are consistent with those obtained from the analysis of the geological evidence for the same region the mareograph results support ice sheet models in which the late weichselian ice thickness over the eastern and southern parts of fennoscandia is relatively thinner than that for the western region also consistent with the interpretation of the geological evidence for sea level change in addition the instrumental records provide constraints on the eustatic sea level change for about the past 100 years a satisfactory separation of the earth rheology parameters from this rate of change can be achieved by estimating the latter only from those records for which the predicted isostatic evects are small a check on these results is possible by using the lake level records to establish constraints on the earth model parameters and the sea level records to constrain also the eustatic change all approaches lead to an average eustatic sea level rise for the past century of about 1 1 0 2 mm yr 1

the geometrical relationship between the stretching lineation and the movement direction of shear zones abstract the geometrical relationship between foliations and lineations in shear zones is considered quantitatively assuming that the internal structures of shear zones have monoclinic symmetry the common practice of directly correlating the pitch or plunge of the stretching lineation with the obliquity of the shear direction is challenged it is the orthogonal projection of the stretching lineation on the shear zone boundary that is parallel to the shear direction a shear zone is parallel to a plane containing both the pole to the symmetry plane and the strike of the shear zone and the shear direction is parallel to the intersection of the symmetry plane and the shear zone boundary the symmetry plane is determined by the stretching lineation and the poles to the s foliation the implications of this study for the interpretation of shear zones are discussed with reference to an actual example

geological interpretation of a high resolution reflection seismic survey at the buchans mine newfoundland sixteen kilometres of high resolution vibroseis reflection seismic data have been acquired in the vicinity of the former buchans mine direct identification of the cause of several reflectors is possible because the geology is tightly constrained by underground workings and drill holes both of which locally exceed 1 km depth many of the mine scale thrust faults are imaged as reflectors but conformable and intrusive contacts generally responded poorly a significant shallow dipping thrust the powerline fault is recognized below the orebodies and traced throughout the buchans area primarily as a result of the seismic survey it truncates ore stratigraphy and forms the floor thrust of a large duplex stack which hosts all the orebodies its presence has negative implications for exploration in the immediate mine area several lines of evidence suggest that this fault has a significant component of out of sequence movement a strong reflector 4 5 km below buchans is correlated with the surface expression

insar monitoring of progressive land subsidence in neyshabour northeast iran summary the area of neyshabour a small historical city located in northeast iran is subject to land subsidence to monitor the temporal evolution of the subsidence the small baseline subset sbas algorithm is used for interferometric synthetic aperture radar sar time series analysis to limit the spatial and temporal decorrelation phenomena the interferograms produced from the raw envisat asar data are characterized by small spatial and temporal baselines accordingly four independent sar acquisition data sets separated by large spatial and temporal baselines are used in the time series analysis to link the separate data sets a smoothing constraint that minimizes the curvature of the subsidence temporal evolution is added to the least squares method the optimum smoothing factor estimated in the smoothed time series analysis reduces the atmospheric noise unwrapping and orbital errors whereas it preserves the non linear seasonal deformation features the time series results show an incremental lowering of the ground surface accompanied by small seasonal effects the mean los deformation velocity map computed from the time series analysis demonstrates a considerable subsidence rate of up to 19 cm yr 1 comparison between the insar time series and continuous gps measurements verifies the accuracy of the obtained results moreover the quantitative integration of the insar derived displacement measurements with observations of the hydraulic head fluctuations causing these displacements yields information about the compressibility and storage properties of the aquifer system

a new lower ordovician arenig faunule from the coy pond complex central newfoundland and a refined understanding of the closure of the iapetus ocean a newly discovered fossiliferous horizon within sediments belonging to the coy pond complex of the exploits subzone in central newfoundland yields the graptolite undulograptus austrodentatus s l and cyclopygid trilobite cyclopyge grandis brevirhachis this late arenig faunule constrains the upper age limit of the ophiolite complex and is the first record of an early ordovician cyclopygid trilobite in north america this is consistent with a paleogeographic affinity for south central newfoundland with the northern oceanic margin of avalonia in a peri gondwanan position during the early ordovician and contrasts with coeval shelly and graptolitic faunas from the notre dame subzone of central newfoundland which show marked laurentian affinities the exploits subzone is generally considered equivalent to the region of scotland lying south of the southern upland fault the newfoundland discovery which is supported by faunal data from elsewhere in newfoundland and in ireland suggests that the region around t

40 ar 39 ar amphibole ages from the kingston complex new brunswick evidence for silurian devonian tectonothermal activity and implications for the accretion of the avalon composite terrane the kingston complex of southern new brunswick canada is a regional ne trending belt of mafic and felsic dikes bordered by dextral ductile shear zones the complex separates two contrasting late precambrian early paleozoic tectonostratigraphic assemblages near the nw margin of the avalon composite terrane rhyolitic dikes within the complex record an early silurian crystallization age dike orientations suggest that emplacement of the complex accompanied sinistral movement interpreted to reflect accretion of the avalon composite terrane to cratonic north america mafic dikes within the complex display greenschist to epidote amphibolite facies metamorphic assemblages that developed during dextral transpression amphibole concentrates from seven metamorphosed mafic dikes record late silurian to early devonian ca 416 390 ma 36 ar 40 ar vs 39 ar 40 ar isotope correlation ages interpreted to date closely the dextral transpressive deformation together with other recent age data the 40 a

granite magma generation ascent and emplacement within a transpressional orogen crustal thickening during transpressive orogenesis may produce anatectic granites which may then localize deformation leading to transcurrent movement granites may be transported from sites of generation through the mid crust in dyke like channelways within relatively narrow strike slip shear zones which link to major fault zones in the upper crust extensional jogs within fault systems provide developing sites for the assembly of plutons from magma arriving from below the model is based upon observations from the cadomian belt of nw france which exposes sections through middle and upper levels of the late precambrian crust within different elements of the orogen the mechanism provides a favourable alternative to diapirism and explains the common collocation of granites and shear zone fault systems within orogenic belts

quantification of vertical movements in the eastern betics spain by comparing levelling data comparison of precision levelling data carried out at diverent times is a technique that allows the quantification of recent vertical movements we used the precision levelling data from the instituto geografico nacional of spain to improve our understanding of the recent tectonic evolution of some areas in the southeastern iberian peninsula eastern betics where significant deformation has occurred during the last century the resulting movements are presented in recent vertical movement profiles profiles with significant movements are discussed taking into account the geologic and seismic features of each zone these profiles are alicante albacete alicante almeria larva near jaen almeria and almeria el palo near malaga the results obtained point to the existence of important tectonic deformation rates near the main tectonic structures crossing the profiles the main tectonic anomalies expressed in constant rates of vertical velocity are a 2 mm year step near the ene wsw trending valldigna jumilla fault zone between alicante and albacete a 0 9 mm year step located in the nne ssw trending cocon terreros fault zone between murcia and almeria a subsidence of about 1 5 mm year of the almeria basin zone that can be related to nw se and e w faults a step of 1 mm year related to the ene wsw trending guadahortuna fault between granada and jaen a 1 mm year step associated with the ene wsw trending cadiz alicante fault zone near the granada area and a 1 4 mm year step related to the tectonic activity of the nw se and ne sw trending system of faults that avect the iberian coast of the alboran sea almeriaa nd granada zone the anomalies related to the ene wsw to e w trending structures are associated with reverse faults whereas the anomalies related to the faults oriented in a ne sw or nw se direction are associated with strike slip faults with a normal component of vertical movement these movements are consistent with the present day betics stress tensor determined with diverent methodologies such as the focal mechanism analysis and microstructural and geomorphological studies that indicate the existence of a maximum horizontal compression in a nnw sse direction together with a perpendicular extension if we consider the rates of vertical deformation to be constant in time and if we consider that all the accumulated stress results in big earthquakes m 6 0 with no ductile deformation an estimate of the minimum return periods for major earthquakes can be made the return periods which range between 500 and 1200 years depending on the zone should be regarded as new information in the assessment of seismic hazard these values are in agreement with those deduced from the seismic catalogues of the areas where there is suycient information 2000 elsevier science b v all rights reserved

extensional and contractional deformation in the blue ridge province virginia basement rocks of the blue ridge anticlinorium in central and northern virginia were involved in two temporally distinct deformation episodes the older event is characterized by a locally pervasive low strain fabric and high strain shear zones a preferred grain shape orientation in recovered quartz feldspar and biotite combined with a poorly developed symmetric quartz c axis pattern defines the low strain fabric kinematic indicators are typically symmetric but where asymmetric they consistently indicate top down to the southeast extensional motion discrete shear zones are within and close to late proterozoic plutons kinematic evidence fron these zones records large noncoaxial strains also with a down to the southeast extensional shear sense feldspar microstructures range from cataclastic fractures to complete recovery suggesting that deformation occurred at greenschist to amphibolite grade both low strain foliations and high strain shear zones are cut by paleozoic thrust related tectonites on the basis of kinematic evidence and spatial association with late proterozoic plutons cross cutting relations with thrust related structures and regional geologic relations we suggest that extensional deformation is related to late proterozoic rifting of the laurentian margin the kinematic histories of the rockfish valley fault zone and related shear zones appear to be relatively simple and consistent with paleozoic west to northwest directed thrusting the rockfish valley fault zone does not separate distinctly different basement terranes and thus its displacement is thought to be small mylonitic rocks from this fault zone display crystal plastic deformation in quartz and cataclastic deformation in feldspars under lower to middle greenschist facies conditions solution transfer processes were an important deformation mechanism in these tectonites thrust related mylonitic rocks are overprinted by related cataclasite and semibrittle shear bands suggestive of a transition toward more brittle deformation as the thrust system cut higher in the crust the rockfish valley fault zone appears to predate the formation of the south mountain cleavage in the valley and ridge province but it may be part of a lengthy progressive thrust related deformation

current vertical movement demonstrated by comparative levelling in brittany northwestern france abstract the current vertical movement of the earth s crust is demonstrated through comparative levelling the two methods presented are complementary first we constructed a profile along traverses in order to highlight localized features such as recurrent faulting or block tilting second we produced a map of relative current vertical movement rates and their error coefficients using a geostatistical kriging method these methods were applied to brittany northwestern france and revealed that 1 the ancient nw se rance and morlaix faults are presently reactivated and 2 the west of the region is tilted with uplift which is interpreted as a lithospheric deformation

promontory promontory collision in the canadian appalachians in cape breton island and southwestern newfoundland the appalachian orogen is extremely narrow the rocks were strongly deformed and underwent high grade barrovian type metamorphism in silurian time and the orogen parallel silurian thrusts are dominantly west vergent antithetic to the westward subduction this area is bounded by two transverse dextral wrench faults the canso fault to the southwest and the gunflap hills fault to the northeast these tectono stratigraphic structural and metamorphic features are explained by silurian collision between the st lawrence promontory on the laurentian margin and the cabot promontory on the avalon margin during the final closure of the iapetus ocean the west vergent antithetic thrusting is interpreted to be related to tectonic wedging while the two transverse wrench faults accommodated differential movement from promontories to reentrants during the collision promontory promontory collision should be a common process and probably played a significant role in shaping the tectonic framework of many orogenic belts

comparative petrology of gneissic rocks in southwestern newfoundland in southwestern newfoundland pelitic migmatites of the meelpaeg subzone of the gander zone are separated by faults and plutons from metasedimentary rocks of the port aux basques gneiss complex pb

tectonic setting and regional significance of the port aux basques gneiss sw newfoundland the port aux basques gneiss of southwest newfoundland comprises three paragneiss and schist assemblages the grand bay and port aux basques complexes and the harbour le cou group they are intruded by large volumes of basic sheets and coeval middle ordovician granitoids the margaree and kelby cove orthogneiss which also cut a tectonic slice of earlier ultrabasic to basic rocks within the grand bay complex the big barachois assemblage the grand bay and port aux basques complexes are juxtaposed by the late silurian isle aux morts fault zone against the harbour le cou group to the east which dominantly comprises sillimanite and garnet bearing pyritiferous metasediments with amphibolitic intrusions and meta pillow basalts in its lower stratigraphic units geochemical studies have shown that metabasites of the grand bay complex port aux basques complex margaree and kelby cove orthogneiss comprise fractionated and crustally contaminated morb like and within plate tholeiites suggestive of an ensialic okinawa type back arc basin these have comparable characteristics to metabasites in the harbour le cou group and suggest that these units comprise remnants of an extensive mid ordovician marginal basin developed within a promontory on the peri gondwanan continental margin in contrast the big barachois assemblage in part comprises a distinct suite of pre mid ordovician island arc tholeiites

assessing the applicability of portable x ray fluorescence spectrometry for obsidian provenance research in the maya lowlands recent innovations in portable energy dispersive x ray fluorescence pxrf spectrometry have increased its utility for the geochemical characterization of obsidian artifacts for archaeological provenance research however concerns over the utility of pxrf instrumental analyses have been raised focused on the validity and reliability of the geochemical data produced here we adopt the framework of richard hughes on reliability validity and scale in obsidian sourcing research 1998 whereby reliability addresses instrument stability and issues of measurement while validity pertains to an instrument s ability to discern geochemical source provenance this is done in order to test the utility of pxrf instruments for archaeological provenance research k means cluster analysis was used to test the accuracy of pxrf through statistical comparison of data acquired via laboratory and portable energy dispersive xrf instruments multivariate analysis was employed to demonstrate obsidian source representation at two classic maya archaeological sites in southern belize uxbenka and ek xux and to test the validity of data obtained from a pxrf instrument in answering archaeological research questions pertaining to regional interactions between lowland maya polities results suggest that portable xrf instruments produce internally consistent results however data acquired from a pxrf instrument are not statistically equivalent to other xrf instruments this is to say that while pxrf is not a reliable technique it is valid for questions pertaining to geochemical source representation

new insights into the appalachian orogen from geology and geochronology along the cape ray fault zone southwest newfoundland reverse oblique overthrusting of high grade port aux basques gneiss over the lower grade supracrustal windsor point group along the cape ray fault zone occurred during late silurian to early devonian time and is attributed to major oblique collision between gondwanan and laurentian continental blocks new u pb zircon 40 ar 39 ar and k ar data limit the timing of this orogenic event the megacrystic granitic phase of the cape ray igneous complex and the cape ray tonalite have been dated at 488 3 ma and 469 2 ma respectively a black rhyolite from the windsor point group yielded an ordovician age 453 5 4 ma a pretectonic gabbro sill within the windsor point group dated at 424 4 3 ma is cut by the windowglass hill granite dated at 424 2 ma synkinematic hornblende and biotite from the grand bay complex mylonites of the port aux basques gneiss have 40 ar 39 ar ages of 407 4 ma and 403 4 ma respectively which is indicative of a late silurian early devonian age for the amphibolite grade deformation these ages are compatible with a previously determined 415 ma monazite age interpreted as the time of peak metamorphism in the port aux basques gneiss and suggests rapid exhumation the east west flexure of the cape ray fault zone represents a tear fault accommodating differential shortening between the cape ray fault zone and the correlative fault system in central newfoundland mid devonian granites 386 3 384 2 ma intervene between the thrusting events and a younger sinistral transcurrent movement this deformation and magmatic history can be correlated throughout the northern appalachians along other major fault boundaries

comparison of xrf and pxrf for analysis of archaeological obsidian from southern peru abstract chemical sourcing is becoming an increasingly important component of archaeological investigation instruments used for elemental analysis generally must be operated in a controlled laboratory environment further many methods require destruction of a small portion of the objects under investigation these facts inhibit the application of chemical sourcing studies in a number of research contexts use of portable non destructive instruments would resolve these issues sixty eight obsidian artifacts from the site of jiskairumoko in southern peru were examined by x ray fluorescence spectrometry xrf and portable x ray fluorescence spectrometry pxrf results were compared for consistency in terms of source determination and individual element concentrations both instruments determined that the same sixty six artifacts derived from the chivay obsidian source and both identified the same two artifacts that could not be assigned to source individual element comparisons showed significant differences but these can be resolved through instrument cross calibration and differences had no bearing on source identification pxrf was found suitable for determining obsidian sources in southern peru and for identifying specimens that require more sensitive analytical methods such as instrumental neutron activation analysis inaa regular use of chivay at jiskairumoko suggests consistent trade relationships developed during the archaic

a consistent map of the postglacial uplift of fennoscandia a consistent map of the recent postglacial rebound of fennoscandia is constructed on the basis of sea level records lake level records and repeated high precision levellings the uplift rates calculated from the sea level series form a consistent framework of the map the sea level stations used are 56 reliable stations in the baltic sea and adjacent waters with series spanning 60 years or more many of them about 100 years using a reference station in the baltic sea and another one outside the baltic all results are reduced to a common time span the 100 year period 1892 1991 in order to eliminate oceanographic changes inland uplift differences are obtained from the repeated national levellings and in four of the large lakes from long water level series in pairs the levellings however yield less accurate land uplift values than the sea level and lake level data the resultant map shows a fairly smooth phenomenon with a maximum apparent uplift in the gulf of bothnia of 9 0 mm yr 1 the standard error is typically 0 2 mm yr i close to the sea level stations larger inland finally the pattern of the present uplift as determined here is observed to be very similar to that of the past uplift as determined from ancient shore lines of the litorina sea however the ratio between the past uplift and the present uplift rate tends to increase somewhat towards the uplift centre this might reflect a non uniform mantle viscosity also the uplift maximum seems to have migrated towards nne

present rate of uplift in fennoscandia from grace and absolute gravimetry abstract fennoscandia is a key region for studying effects of glacial isostatic adjustment the associated mass variations can be detected by the gravity recovery and climate experiment grace satellite mission which observes the earth s gravity field since april 2002 as well as by absolute gravimetry field campaigns since 2003 annual absolute gravity ag measurements have been performed in fennoscandia by the institut fur erdmessung ife institute of geodesy of the leibniz universitat hannover germany within a multi national cooperation this offers a unique opportunity for validation and evaluation of the grace results in this preliminary study the grace results are compared to secular gravity changes based on the surveys from 2004 to 2007 with the fg5 220 gravimeter of the ife the results from grace monthly solutions provided by different analysis centres show temporal gravity variations in fennoscandia the included secular variations are in good agreement with former studies the uplift centre is located west of the bothnian bay the whole uplift area comprises northern europe nevertheless the differences between the grace solutions are larger than expected and the different centre specific processing techniques have a very strong effect on possible interpretations of grace results the comparison of grace to the ag measurements reveals that the determined trends fit well with results from grace at selected stations especially for the solution provided by the gfz variations of land hydrology clearly influence results from grace and the ag measurements

strain refraction in layered systems abstract strain refraction across competence contrasts is presented as a simple model consisting of two components a homogeneous strain and a heterogeneous simple shear for newtonian materials the ratio of the layer parallel simple shear component in adjacent layers is the inverse of their viscosity ratio strong changes in ellipsoid size shape and orientation are predicted across viscosity contrasts the geological implications of strain refraction theory are considered within the context of the cleavage strain debate the particular relationships of relative competence and strain revealed by the refraction model may contribute to the problem of why cleavages of different morphologies in rocks of different lithologies and kinematic histories should appear to be subparallel to the xy planes of measured strain ellipsoids competent rocks should develop dominantly layer orthogonal strain and incompetent layers shear dominated deformation a variety of structural features ranging from cleavage refraction changing lineation orientations folds transected by cleavage changes from coaxial to non coaxial deformation and ramp flat fault geometry may be the result of stress and strain refraction in rocks

portable edxrf analysis of a mud brick necropolis enclosure evidence of work organization el hibeh middle egypt the geochemical and sedimentological compositions of mud brick from a feature called the square enclosure in the eastern desert necropolis of the ancient town site of el hibeh egypt were investigated along with surface sediments from the local nile floodplain for the purpose of establishing possible sources of the mud brick geochemical examination was undertaken with a portable edxrf spectrometer a field portable sedimentological laboratory was used to collect grain size mineralogy and strength analysis data results of the analyses produced evidence of work organization relating to the construction of the square enclosure this discovery is the first archaeological evidence of work organization from the mud brick of ancient egyptian structures and provides a valuable contribution to our knowledge of ancient egyptian work organizational practices

the partitioning of deformation in flowing rock masses abstract most geological structures owe their development to heterogeneous and or non steady flow flow partitioning refers to the division of the instantaneous velocity field into components related to translation strain and rotation flow partitioning during the development of a geological structure usually changes with time and different histories of flow are involved at different points in the developing structure heterogeneity leads to the development of flow domains with different characteristics notably the degree of non coaxiality of deformation and different partitionings of the rotational component of flow into shear induced vorticity and spin during non steady flow there is often continual repartitioning of vorticity between the spin and shear induced components spin is an important aspect of flow leading to the development of structure this paper discusses the partitioning of deformation in a flowing rock mass coaxial flow tends to occur in isotropic materials in regions near weakly constrained boundaries non coaxial flow is favoured by suitably oriented material anisotropy and or the presence of well defined boundary constraints involving parallel relative displacements a developing anisotropy e g a crystallographic fabric in a shear zone can induce a change from coaxial to non coaxial flow other effects are related to the scale of approximation for example bulk shear induced vorticity can be locally converted to spin flow in the crust and mantle of the earth produces geological structures on all scales and involves many different types of rheological response the factors that affect flow partitioning e g spin versus non coaxial deformation are therefore of interest

initial source evaluation of archaeological obsidian from the kuril islands of the russian far east using portable xrf obsidian artifacts recently have been recovered from 18 archaeological sites on eight islands across the kuril island archipelago in the north pacific ocean suggesting a wide ranging distribution of obsidian throughout the island chain over the last 2 500 years although there are no geologic sources of obsidian in the kurils that are known to have been used prehistorically sources exist in hokkaido japan and kamchatka russia the southern and northern geographic regions respectively from which obsidian may have entered the kuril islands this paper reports on the initial sourcing attempt of kuril islands obsidian through the analysis of 131 obsidian artifacts data from this research were generated through the application of portable xrf technology and are used to address research questions concerning prehis toric mobility exchange and social networking in the kuril islands

experimental insights into the partitioning of motion within zones of oblique subduction abstract in zones of oblique convergence the motion is often partitioned into subduction and an associated strike slip component fitch 1972 in this paper we first describe the geodynamic setting of the philippine region as a case study of deformation by strike slip faulting behind parallel subduction zones then we present six small scale laboratory experiments with analogue materials to investigate how partitioning may be controlled by internal boundaries between oceanic lithosphere and continental or island arc lithosphere during the early stages of a typical experiment deformation is taken up on oblique thrusts subduction zones which root into internal boundaries paired strike slip faults develop at later stages thereafter subduction zones and paired strike slip faults operate simultaneously the partitioning occurs without any need for complex constraints on external boundaries

interference between pluton expansion and non coaxial tectonic deformation three dimensional computer model and field implications abstract structures in orogenic belts are greatly controlled by interactions between pluton related and tectonic related strain fields however many aspects of the geometry and evolution of these structures are poorly known for example 1 what is the geometry of these structures if regional deformation is coaxial 2 how does this geometry change with progressive deformation this paper describes a three dimensional simulation of strain shape and magnitude as well as foliation and lineation patterns formed by interactions between pluton expansion and homogeneous coaxial deformation this simulation suggests that interactions between pluton expansion and regional uniaxial shortening generate patterns that are distinct from the patterns produced by regional uniaxial extension or regional non coaxial deformation for example shortening produces doughnut shaped constrictional rings about the pluton whereas extension produces apple shaped flattening regions around the pluton in addition shortening produces one continuous doughnut shaped low strain region around the pluton on the other hand extension creates two separate ellipsoidal low strain regions at the ends of the pluton furthermore shortening forms foliation rings that have triangular two dimensional sections and lineation is concentric around the axis of maximum shortening in contrast extension produces two separate foliation and lineation cones at the ends of the pluton all these structural and strain elements migrate away from the pluton with increasing expansion rates and towards the pluton with increasing tectonic deformation rates although structural studies around plutons should always integrate microstructural radiometric and field measurements simulation generated patterns can be used to evaluate 1 origin geometry and evolution of structures around plutons 2 mechanisms that explain inclusion trails within porphyroblasts 3 contribution of pluton related strains to strains measured in the country rock and 4 type and three dimensional orientation of regional kinematic schemes

the geology and structural history of the cape ray fault zone in southwestern newfoundland structural studies within the cape ray fault zone southwestern newfoundland indicate that three tectonic events d1 to d3 have deformed all regional lithologic units these lithologies are distributed as a tonalitic terrain intrusive into ophiolitic remnants to the northwest a central volcanic sedimentary terrain and a staurolite kyanite gneiss terrain to the southeast d1 produced the dominant northeasterly striking planar fabrics in the host rocks that are axial planar to isoclinal folds the fold axes parallel a synkinematic mineral elongation lineation d2 formed open asymmetrical folds with curvilinear fold axes and local crenulation cleavage the d3 event produced local conjugate kink folds radiometric dates on deformed plutons indicate these deformational events were post 369 12 ma post middle devonian and pre 352 6 ma pre late carboniferous the fault was previously interpreted as a cryptic suture along which opposed margins of the iapetus ocean were juxtaposed supposedly this sut

among polynesia s first pots x ray fluorescence spectroscopy and petrographic thin section microscopy are applied to a sample of anomalous appearing lapita pottery sherds from nukuleka the earliest archaeological site in polynesia both analyses indicate non local origins for the ceramic vessels suggesting they were brought on founding canoes mineral inclusions in ceramic tempers eliminate sources to the west of tonga in eastern melanesia rather the temper source is most probably a dacitic high island from a distant island arc of central melanesia polynesian origins and settlement are issues more complex than currently recognized by the orthodox progressive settlement model for lapita expansion across oceania

pluton emplacement along an active ductile thrust zone piute mountains southeastern california interaction between deformational and solidification processes plutons that are emplaced synchronously with regional deformation offer the opportunity to understand the partitioning of deformation and metamorphism in time and space during orogeny the 85 ma east piute pluton of the eastern mojave desert is an unusually clear example of a syntectonic pluton it was emplaced during thrusting in the southern cordillera combined petrologic and structutal studies lead to empirical models for the dynamic interaction of magmatic and deformational processes during granitoid emplacement and final crystallization trace and major element and isotopic data suggest that closed system differentiation of a single magma batch was responsible for compositional variation granodiorite to leucocratic granite correlation between degree of chemical evolution of compositional units and intrusive sequence suggests that discrete melt segregation events punctuated fractional crystallization modeling of trace element data suggests segregation of monzogranite melts after 50 70 crystallization of the magma and segregation of leucocratic granite after about 80 crystallization deformation promoted segregation of melt fractions at discrete times during crystallization during final ascent and after the magma had crystallized sufficiently 50 70 to attain shear strength monzogranite liquid was incompletely segregated along the active thrust zone at the southern margin of the pluton at essentially the present crustal level and after about 80 crystallization the remaining leucocratic granite melts were more effectively segregated and migrated into thrust related extensional openings including tension gashes undeformed pegmatite and aplite dike arrays indicate that final crystallization coincided with final increments of shear zone movement solid state deformational fabrics and brittle synthetic thrusts that offset the pluton margin record sharp temperature decline during and after crystallization because plutons crystallize rapidly they can be used to estimate strain rates during orogeny thermal modeling suggests that the transition from rheological liquid to solid in the east piute pluton occurred during an interval of about 10 4 yr as final increments of ductile deformation coincided with final crystallization of evolved compositional units total strain recorded by fabric in the pluton apparently accumulated during this interval shear strains estimated from the s c fabric in the granodiorite unit and rotation of pegmatite filled vein arrays are on the order of 1 thus strain rates in the shear zone were on the order of 10 12 sec during crystallization of the pluton this corresponds to displacements of tens of centimeters per year these high strain rates suggest punctuated melt enhanced movement episodes during contractional orogeny

major and trace element analysis of modern egyptian pottery abstract a geochemical survey of modern traditional egyptian pottery using a multi element multi method approach provides a basis for interpreting sedimentary composition and manufacture location of different wares several pottery source compositions were investigated ubiquitous nile silts calcareous silty clays marls mixtures of nile silts with marl clays or carbonates and other sediments each of these source compositions has a distinctive geochemical signature which can be used as a fingerprint this geochemical fingerprint makes it possible to distinguish the following base ceramic compositions from each other nile silts other silts marl clays mixtures of nile silts and marl clays mixtures of nile silts and calcium carbonate when combined with petrographic analysis geochemistry is an especially powerful diagnostic tool such modern fingerprints aid in understanding modern pottery sourcing and composition and provide a potentially powerful tool for providing similar insights into patterns of ancient pottery production

the chaparral shear zone deformation partitioning and heterogeneous bulk crustal shortening during proterozoic orogeny in central arizona the proterozoic chaparral shear zone of central arizona is one of a network of subvertical northeast striking shear zones that divide the proterozoic orogenic belt of arizona into tectonic blocks the zone is several kilometers wide and contains variably developed mylonitic foliation that is subparallel to the regional subvertical foliation stretching lineations plunge shallowly northeast and displacement across the zone was dominantly right lateral several lines of evidence constrain displacement across the zone to be greater than 5 km but probably less than tens of kilometers 1 stratigraphic and plutonic rocks can be correlated across the zone 2 structural and metamorphic histories of tectonic blocks on opposite sides of the zone are similar and 3 integration of shear strain estimated by deflection of earlier fabric suggests greater than 5 km of strike slip more important than scale of movement across the zone structural studies have clarified several aspects of the assembly history of the orogen early north to northwest striking s 1 foliation on both sides of the chaparral shear zone records one or more deformational events that took place between 1 75 and 1 7 ga early fabrics record northeast southwest or east west shortening and west verging thrusting that we interpret to have formed during development of a primitive arc complex in contrast intense deformation in the chaparral shear zone took place during regional northwest southeast shortening d 2 that produced the dominant subvertical northeast striking foliation and the present block architecture of the orogen d 2 is interpreted to have been in part synchronous with emplacement of 1 70 ga granitoids and to record assembly of volcanic belts to north america of general interest is the character of d 2 deformation partitioning in and across the shear zone two types of high strain domains were generated during shortening one type represented by rocks southeast of the shear zone involved extreme shortening and transposition by folding the other type represented by the shear zone involved simple shear deformation in a complicated array of anastomosing and conjugate shear zones overprinting relationships suggest that the second type may have nucleated on the first implying an important component of deformation partitioning in time as well as space mylonitic fabric in the shear zone developed by progressive heterogeneous simple shear followed by brittle fracturing conjugate shear bands suggest a shallow southeast plunging 1 late during strike slip deformation this is consistent with regional d 2 shortening but not with the incremental shortening direction expected during right lateral simple shear this supports a regional kinematic model in which the chaparral shear zone right lateral and a temporally related left lateral shear zone were regional scale conjugate shear zones that accommodated heterogeneous d 2 northwest southeast orogenic shortening via escape block tectonics thus orogen parallel strike slip displacements in the chaparral shear zone were a response to partitioned shortening in the late stages of accretion rather than transpressional accretion during oblique subduction

height and gravity variations by continuous gps gravity and environmental parameter observations in the southern po plain near bologna italy abstract during 1996 a global positioning system gps receiver and a superconducting gravimeter sg were installed at medicina italy in order to monitor ground deformation and signals related to global regional processes and local environmental effects first results provided by this combined observing strategy are presented by focusing on common patterns as well as on the differences observed in the two time series a marked annual signal of increasing amplitude present in both series is becoming quite recognizable towards the end of 1997 seasonal loading effects induced by air pressure the ocean and surficial water table were estimated and modeled for both data sets for the gravity series 12 h data of balloon radio sounding launches have been used to estimate the attraction effect of the seasonal vertical density distribution of the air pressure column above the station mass effects due to the surficial water table and the ocean were also estimated and accounted for the comparison between the observed and modeled series both in the case of gps heights and gravity shows a remarkable agreement and provides a convincing explanation for the observed seasonal fluctuations in the july september 1997 time frame a sudden gravity increase occurred this anomaly is in the order of 3 gal and is present in the data series after accounting for the seasonal fluctuation this step like feature is responsible for most of the estimated positive linear trend present in the data series the anomalous increase in gravity has been interpreted as due to mass density variations likely associated with the uprising of deep seated waters in relation with local stress field changes during the second half of 1997 concurrent seismic activity occurred both in the southern po valley and in central italy umbria seismic crisis