a newly recognized type of slickenside striation abstract this note summarizes current views on the origin of slickenside striations and points to the existence of a type of striation not readily explained by established genetic ideas such striations have been seen on fault surfaces in naturally deformed shale and in experimentally deformed paraffin wax they are defined by arrays of shallow slip parallel ridges and grooves of millimetric width and below on any given slip surface the ridges are as common as the grooves and display similar dimensions and profile shapes across any pair of slip surfaces in contact at the end of faulting ridges protruding from one surface fit into or nest with grooves on the other surface the origin of these features is not yet understood

states of paleostress north and south of the periadriatic fault comparison of the drau range and the friuli southalpine wedge this study focuses on the analysis of structures and kinematics of a n s profile along the axis of maximum shortening of the european eastern alps the area includes the southern austroalpine unit in the north and the southalpine unit which is a part of the adriatic indenter the stratigraphically different units are separated by the periadriatic fault the major strike slip fault within the alps in order to assess the kinematics of these units mainly fault slip data from north and south of the periadriatic fault were analyzed we distinguish a succession of five main kinematic groups in both units 1 n s compression 2 nw se compression 3 ne sw compression 3 changes gradually from subvertical to subhorizontal 4 n s compression and 5 nw se compression our study reveals that the deformation sequence on either sides of the paf is similar the mean orientations of the principal stress axes however show small but consistent differences the subhorizontal axes north of the periadriatic fault plunge northward in the south southward a counterclockwise ccw rotation of the southern part in respect to the north is evident and in line with the well known counterclockwise rotation of the adriatic indenter as well as dextral displacement of the n fanning stress field along the periadriatic fault opposing plunge directions are interpreted as a primary feature of the internal stress field within an orogenic wedge further increased during ongoing compression

improving sst reconstructions from coral sr ca records multiple corals from tahiti french polynesia we reconstruct sst from coral sr ca ratios measured at three coral cores taken from the lagoon of tahiti french polynesia two coral cores were drilled from the same coral colony one horizontally and one vertically and a third core was drilled vertically from another coral growing at a different site we evaluate several sr ca records as proxies for regional sst variations 1 the three single core records from tahiti 2 an average sr ca record computed from the two cores drilled from the same coral colony 3 an average sr ca record computed from all three tahiti cores and 4 an average sr ca record computed from the three tahiti cores and a fourth core taken from a different island rarotonga on a monthly scale the average sr ca record including the four coral cores from tahiti and rarotonga shows the best correlation with regional sst the variance of the sst reconstruction is very realistic and the residual sst is low this suggests that reconstructing sst from average proxy records gives a better representation of regional sst variations of the three tahiti cores the one that was drilled horizontally shows the best correlation with grid sst on an annual mean scale all three tahiti corals show much larger interannual sst variations than that indicated by grid sst

introduction to albertosaurus special issue this special issue is being published to mark the passage of a century since barnum brown made a remarkable discovery in the badlands of alberta brown was from the american museum of natural history amnh in new york and he had come to alberta the previous year 1909 to check a report of dinosaur bones near the present day town of drumheller he had been impressed enough to mount an expedition that set off in a flat bottomed scow down the red deer river on august 3 1910 as they floated downstream they frequently stopped and looked for fossils in the badlands on august 11th they found what they thought was much of an albertosaurus skeleton in hard rock they realized by the next day however that they were in fact excavating the well preserved bones of several individuals in his fieldnotes brown s assistant peter kaisen noted that the whole top of a hill is nothing but a mass of bone there are four hind feet in sight vertebrae and a lot of limb bones on september 4th they loaded eight boxes of bones the product of 29 man days spent in the bonebed on the scow and floated the expedition farther downstream the specimens were shipped to new york where they were prepared put on display for a short time and then mostly forgotten although brown occasionally mentioned the 1910 discovery in papers brown 1914 matthew and brown 1923 and

coseismic extension recorded within the damage zone of the vado di ferruccio thrust fault central apennines italy abstract recent high resolution hypocentral localisation along active fault systems in the central apennines illuminates the activation of seismogenic volumes dipping at low angle here we report field and microstructural evidence of seismogenic extensional faults localized within pre existing thrust fault zones the vado di ferruccio thrust fault vftf is a narrow fault zone

geochemistry and skeletal structure of diploria strigosa implications for coral based climate reconstruction abstract geochemical tracers incorporated into the skeleton of reef building corals are ideal proxies for reconstructing environmental parameters of ambient seawater such as temperature and salinity at subseasonal resolution however validation concerns of these environmental proxies due to the complex skeleton of some tropical atlantic corals have hindered such coral based environmental reconstructions in this region compared to the tropical pacific in order to identify complications associated with the complex skeletal architecture of the massive brain coral diploria strigosa we performed microsampling experiments along and across individual skeletal elements we demonstrate that the mesoscale heterogeneity of sr ca 18o and 13c is a systematic feature of d strigosa and is linked to different vital effects between skeletal elements the thecal wall is significantly depleted in sr 18o and 13c compared to the adjacent septa and columella and differences between apparent temperature signatures of several degrees are greater for sr ca suggesting that this temperature proxy is more sensitive to skeletal mixing than 18o parallel subseasonal microsampling experiments performed along individual skeletal elements of a single corallite of a d strigosa coral which grew at a rate of 0 65 cm year allow for investigating potential biases associated with its complex skeletal mesoarchitecture highest correlation between sr ca and 18o from skeletal material retrieved from the centre of the thecal wall suggests that microdrilling the theca provides the best environmental signal compared to adjacent microsampling profiles moreover based on monthly mean climatology the temperature dependence of sr ca for this profile is comparable to previous calibrations published from faster growing d strigosa based on these results we conclude that accurate microsampling along the centre of the thecal wall of d strigosa is a prerequisite for generating robust climate reconstructions from its skeleton

reconstructing twentieth century sea surface temperature variability in the southwest pacific a replication study using multiple coral sr ca records from new caledonia 1 coral based climate reconstructions typically have not used multiple cores from a region to capture and replicate a climate signal largely because of concerns of coral conservation analytical expense and time constraints coral sr ca reproducibility through the twentieth century was investigated using three intracolony and three intercolony coral records from the reefs offshore of amedee island new caledonia different sampling resolutions were examined in coral sr ca fortnightly and monthly and 18o fortnightly monthly and seasonally as well as similar scale subsampling of the daily in situ sea surface temperature sst record the mean coral sr ca 18o and sst values do not change as a function of sampling resolution the coral sr ca signal is highly reproducible the average absolute offset between coeval monthly sr ca determinations between any two coral time series is 0 035 0 026 mmol mol 1 0 65 c which is less than twice the analytical precision of the coral sr ca measurements the stack average of the monthly coral sr ca variations and monthly anomalies are significantly correlated with monthly in situ sst 1967 1992 r 0 96 and 0 64 respectively p 0 05 and n 302 and 1 grid monthly sst data product 1900 1999 r 0 95 and 0 56 respectively p 0 05 and n 1198 the coral sr ca sst reconstruction exhibits interannual and decadal timescale fluctuations that exceed those observed in the gridded sst record which may reflect true differences between sst at a shallow reef site and those averaged over a 1 grid box or inadequacies in the methodology used to create the gridded sst product when few observations are available a warming trend of 0 6 c is observed in the twentieth century coral sr ca sst record

the heterodonty of albertosaurus sarcophagus and tyrannosaurus rex biomechanical implications inferred through 3 d modelsthis article is one of a series of papers published in this special issue on the theme albertosaurus the objective of this study is to analyze how different crown morphologies and different root lengths respond to stresses generated by the bite forces of albertosaurus sarcophagus and tyrannosaurus rex six well preserved teeth of a sarcophagus from the albertosaurus bonebed in dry island park southern alberta were selected to study their biomechanics and t rex teeth were included for comparison the three dimensional 3 d models were obtained through computerized tomography ct scanning and 3 d digitizing finite element analyses were performed in strand7 bite forces for albertosaurus and tyrannosaurus were calculated based on cranial and jaw proportions the results were viewed with the tresca yield criterion the ratios of shear stresses observed along the mesio distal versus labio lingual axes of all models allows the identification of similar stress distribution patterns in the upper and lower jaws of albertosaurus and the upper jaws of tyrannosaurus with a higher amount of shear along the

en echelon fractures in a dextral shear zone tectonic heritage for a hydrothermal cave budapest hungary microtectonic study of brittle structures in the jozsef hill cave budapest highlights the connection between different phases of fracturing and cave formation e w trending dextral faults second order riedels and nw se oriented tension fractures developed in a ene wsw trending dextral shear zone as a result of wnw ese directed compression ascending thermal water dissolved cave galleries and created barite veins along these fractures the first stage of cave formation as inferred from timing of fracturation from the regional stress field was oligocene early miocene between the middle miocene and quaternary new n s to ne sw trending normal faults were formed by ese wnw extension pleistocene differential uplift resulted in the reactivation and enlarging of fault zones dominantly the e w trending older riedels these recent tectonic events enhanced the original en echelon geometry of the older cave corridors

the significance of the theropod collections of the royal tyrrell museum of palaeontology to our understanding of late cretaceous theropod diversity1 significant specimens of theropod dinosaurs were part of the collections that were transferred to the royal tyrrell museum of palaeontology when it split off from the provincial museum of alberta in 1981 collecting activity of the institution increased dramatically in the period leading up to the opening of the building and displays in 1985 and resulted in the recovery and preparation of many fine theropod skeletons new specimens have been added to the collection every year since the museum opened several mostly small taxa are only represented by isolated bones partial skeletons and or teeth theropod specimens also include footprints coprolites eggs and feathers in amber although theropods are relatively rare in comparison with herbivorous dinosaurs the tyrrell has managed to build one of the finest research collections of late cretaceous forms thirty seven species of theropods in the tyrrell are currently accepted as being valid of which 30 are from the upper cretaceous deposits of alberta

comment on a snapshot of climate variability at tahiti at 9 5 ka using a fossil coral from iodp expedition 310 by kristine l delong terrence m quinn chuan chou shen and ke lin 1 the integrated ocean drilling program iodp expedition 310 recovered drill cores from the drowned reefs around the island of tahiti 17 40 s 149 30 w many of which contained samples of massive corals from the genus porites herein we report on one well preserved fossil coral sample a 13 6 cm long porites sp dated by uranium series techniques at 9523 33 years monthly 18o and sr ca determinations reveal nine clear and robust annual cycles coral 18o and sr ca determinations estimate a mean temperature of 24 3 c 3 2 c colder than modern for tahiti at 9 5 ka however this estimate is viewed with caution since potential sources of cold bias in coral geochemistry remain to be resolved the interannual variability in coral 18o is similar between the 9 5 ka coral record and a modern record from nearby moorea the seasonal cycle in coral sr ca is approximately the same or greater in the 9 5 ka coral record than in modern coral records from tahiti paired analysis of coral 18o and sr ca indicates cold wet warm dry interannual anomalies opposite from those observed in the modern instrumental record

diversity and variation of theropod dinosaur teeth from the uppermost santonian milk river formation upper cretaceous alberta a quantitative method supporting identification of the oldest dinosaur tooth assemblage in canada the santonian deadhorse coulee member of the milk river formation preserves the oldest dinosaur body fossils found in alberta however vertebrate remains consist almost exclusively of isolated elements and microvertebrate assemblages here 1572 relatively complete shed non avian theropod teeth from 20 localities in the deadhorse coulee member are measured and analyzed to assess species diversity teeth are referred to or similar to tyrannosaurinae indet cf richardoestesia gilmorei cf richardoestesia isosceles dromaeosauridae indet dromaeosaurinae indet velociraptorinae indet and cf paronychodon lacustris for the taxa identified the large sample size allows for the assessment of their range of variation and accurate identification without the benefit of comparable material of this age multivariate statistics including a principal component analysis and a canonical variate analysis provide reasonable separation of all taxa although better results are achieved by separate analyses based

strontium calcium ratios in modern porites corals from the great barrier reef as a proxy for sea surface temperature calibration of the thermometer and monitoring of enso high precision sr ca ratios are reported for porites corals from davies reef at 19 s on the midshelf of the great barrier reef australia skeletal growth parameters were also determined from coral slabs using x ray photographs and densitometry measurements a calibration of the sr ca thermometer has been obtained using in situ measured sea surface temperatures which gives sr ca 10 10 48 0 01 0 0615 0 0004 t wheret is in c this calibration applies to different species of porites and a large range of annual extension and calcification rates provided sampling follows a major growth axis biases of 1 2 c have been observed in the low density margins where growth is hampered by interfering fans of corallites the analytical and the long term reproducibility of sr ca derived temperatures are both better than 0 3 c 2 coral growth parameters such as the extension rate or density generally appear to respond to environmental changes such as rainfall but do not affect the sr ca partitioning between coralline aragonite and seawater no correlation has been found between calcification rate and sr ca variations consistent with sr ca being mainly controlled by temperature in the great barrier reef the interannual variability in sst is primarily related to the el nino southern oscillation phenomenon and is typically marked by a cold anomaly during the winter preceding the mature warm phase instrumental records show that the surface waters of the coral sea around 19 s have experienced a significant cooling associated with the el ninos of 1965 1972 and 1982 1983 which the porites corals record faithfully the coral derived temperatures for the period from 1965 to 1993 show an increase of 1 3 c which has occurred mainly since 1979 this warming is larger in magnitude but consistent with the trend for the southern hemisphere land and marine temperature records which shows an increase of around 0 4 c

shear fracture patterns and connectivity at geometric complexities along strike slip faults shear fracture patterns and connectivity at geometric complexities such as echelon fault steps and fault bends along strike slip faults are investigated by simulating shear fracture propagation paths using a displacement discontinuity boundary element method together with a maximum distortional strain energy density criterion it is shown that shear fracture patterns and connectivity depend on the specific geometric configurations the applied stress orientations and the coefficient of friction for a given initial configuration of the major faults the subsequent patterns of the associated shear fractures and their linkage can be predicted if the remote state of stress and the coefficient of friction are known the analyses of fault geometries commonly encountered in nature have important implications for evaluating the effect of faults on fluid flow and earthquake hazards associated with the geometric complexities along strike slip faults in the upper crust

radon groundwater monitoring at underground laboratories of gran sasso italy an automatic multiparametric equipment groundwater temperature electrical conductivity ph 222rn has been planned and realized to study the correlations between the variations of radon with the strain processes of the rock and transport properties related to the groundwater geochemistry the monitoring activity at underground laboratories of gran sasso with a groundwater sampling period of twelve hours has been started from may 1996 from geochemical data recorded during the first year a high dynamic behaviour of shallow aquifer has been emphasized due to high permeability of the cretaceous limestones that form part of the gran sasso massif also the residual time series analysis of the geochemical parameters has emphasized pre co seismic anomalies in electrical conductivity and post seismic in radon content in groundwater related to local seismicity

reply to comment by cahyarini et al on a snapshot of climate variability at tahiti at 9 5 ka using a fossil coral from iodp expedition 310

orogen parallel strike slip faults bordering metamorphic core complexes the salzach enns fault zone in the eastern alps austria abstract the approximately ene trending salzach enns fault eastern alps contributed to late stage exhumation of the tauern metamorphic core complex in response to oblique convergence of european and adriatic plates six stages of kinematic evolution with early ductile and later brittle deformational structures were recognized as follows 1 initial ductile deformation is represented by a combination of sinistral shear dominated noncoaxial strain and coaxial strain 2 early brittle sinistral strike slip is combined with a pure shear deformation and represents roughly n s contraction it is followed by 3 sinistral strike slip and 4 ca n s extension due to normal slip striations 5 subsequent n s compression resulted in counterclockwise rotation of the maximum principal stress from ne to nw and led to final dextral strike slip displacements along the salzach enns fault the exhumation of the tauern window was accommodated by dip slip on the fault plane at shallow levels and coaxial flattening at deeper structural levels brittle sinistral faults at shallow structural levels produced a larger amount of strike slip displacement than ductile shear zones at the deeper structural levels which is explained as a scissors like movement and which resulted in the eastward tilting of the tauern window

trace element variations in fossil corals from tahiti collected by iodp expedition 310 reconstruction of marine environments during the last deglaciation 15 to 9 ka abstract climate responses and changes in marine environments during the last deglaciation have been controversial and few paleoceanographic data are available from the tropical south pacific though this region is crucial in the investigations of ocean atmosphere interactions integrated ocean drilling program expedition 310 was conducted to establish the time course of the postglacial sea level rise at tahiti in the south pacific a principal objective of this expedition was to examine the variation of marine environments during the last deglaciation as fossil porites coral is ideal for assessing past marine environments we selected only porites specimens from the many coral specimens retrieved examined them by xrd and dated them by the 14c method in all we obtained 17 pristine porites specimens composed of only aragonite with ages from 15 to 9 ka then we measured mg ca ba ca and u ca ratios and cd contents as proxies for upwelling and sea surface temperature higher ba ca ratios and cd content together with lower reconstructed ssts using u ca ratios in the coral specimens between 12 6 and 9 8 cal ka compared to around 15 cal ka suggest that upwelling and or entrainment of subsurface water into mixed layer was enhanced around tahiti during this period this finding is consistent with previous reports and supports the idea that the south pacific was characterized by la nina like conditions at least from 12 6 to 9 8 cal ka

displacement features associated with fault zones a comparison between observed examples and experimental models abstract fault zones commonly consist of discontinuous surfaces or are composed of different kinds of en echelon fractures tension cracks r or p type fractures which give the brittle shear zone a width translation along these faults and related features can occur by sliding on the elementary planes and or by solution deposition processes with opening of transtension zones and possible dilatation of the shear zone in order to understand how fault planes develop and to investigate the mechanical conditions corresponding to natural configurations displacement along an analogue fault model was examined under conditions of direct shear the experimental fracture patterns were then compared with the natural features the structural elements of certain faults created by testing and showing transpression and transtension zones were found to be similar to natural domino structures bounded by elementary shears and could be compared with computed situations it can be inferred that stresses are reoriented inside the shear zone the angle between elementary fractures depends on their order of development transpression and transtension zones occur systematically and the shear zone undergoes dilatancy under low normal stresses

magnetic fabric in carbonatic rocks from thrust shear zones a study from the northern apennines italy abstract we present the results of an integrated structural and anisotropy of magnetic susceptibility ams investigation in calcareous and marly rocks from thrust shear zones a total of 17 sites from six localities along the frontal and oblique ramp of the olevano antrodoco sibillini thrust and back thrust northern apennines italy were studied to investigate both magnetic fabric and structural characteristics of cretaceous to neogene calcareous and marly rocks in most of the sites ams is controlled by the paramagnetic minerals prevailingly phyllosilicates with minor contribution of ferromagnetic sensu latu ones structural analysis shows the presence of sc and s tectonites associated to predominant simple and pure shear respectively the combination of density diagrams and cluster analysis allowed discriminating the contributions of sedimentary and tectonic processes to the bulk magnetic fabric six different subfabrics were distinguished related to the structural data and associated to deformation stages and regimes a sedimentary fabric b intersection lineation c magnetic foliation parallel to s planes with k1 parallel to the s c intersection d k1 moving toward the slip vector e magnetic foliation parallel either to the s or the c planes with k1 parallel to the slip vector or the transport direction f k1 parallel to extensional planes intersection the magnetic foliation has a double tendency to parallelize to pressure solution cleavage s and shear planes c while the magnetic lineation tends to progressively align with the slip vector except for pure shear dominated sites at less than 15 20 cm from the thrust where it aligns with the transport direction the magnetic fabric is dominated by simple shear deformation the protocol applied for ams analysis shows a great potential to unravel mixed sedimentary and or tectonic features in magnetic fabrics ams can be considered as a useful tool in unravelling the variation of simple pure shear deformation regime in shear zones

analysis of thrust shear zones in curve shaped belts deformation mode and timing of the olevano antrodoco sibillini thrust central northern apennines of italy abstract this work reports the results of our analysis of the brittle ductile shear zone associated with the olevano antrodoco sibillini oas curved shape thrust in the central northern apennines of italy its southern sector is characterized by nnw sse trending footwall anticlines which also affect the oas thrust surface s tectonites in the nne ssw trending sector are crenulated by conjugate extensional surfaces extensional crenulation cleavage the nw se trending segment of the oas thrust is characterized by sc tectonites developed along the thrust related shear zone both the sc and s tectonites are consistent with a top to the n60 70 e direction of tectonic transport the sc tectonites are associated with a simple shear dominated deformation wn 0 86 0 98 on the other hand the s tectonites and their related extensional shear planes document two stages of strain i sub simple shear wn 0 34 0 50 related to oas thrusting contemporaneous to growing incipient footwall anticlines and ii pure shear dominated deformation wn 0 17 0 00 subsequent to the oas thrusting and caused by the definitive growth of footwall anticlines within an in sequence deformation context the present study proposes the analysis of shear zones to i discriminate in sequence against out of sequence evolution and ii use as a tool to constrain the modes and timing of the curved belt s development

oscillations in the southern extent of the indo pacific warm pool during the mid holocene the indo pacific warm pool ipwp is thought to play a key role in the propagation and amplification of climate changes through its influence on the global distribution of heat and water vapour however little is known about past changes in the size and position of the ipwp in this study we use a total of 48 modern and fossil coral records from the mentawai islands sumatra indonesia and muschu koil islands papua new guinea to reconstruct oscillations in the extent of the ipwp since the mid holocene we show that reliable estimates of mean sea surface temperature sst can be obtained from fossil corals by using low resolution sr ca analysis of a suite of corals to overcome the large uncertainties associated with mean sr ca sst estimates from individual coral colonies the coral records indicate that the southeastern and southwestern margins of the ipwp were cooler than at present between similar to 5500 and 4300 years bp similar to 1 2 degrees c 0 3 degrees c and were similarly cool before similar to 6800 years bp this mid holocene cooling was punctuated by an abrupt short lived shift to mean ssts that were warmer than at present between similar to 6600 and 6300 years bp similar to 1 3 degrees c 0 3 degrees c while similarly warm conditions may have also existed after similar to 4300 years bp we suggest that mid holocene cooling at our study sites was related to contractions of the southeastern and southwestern margins of the ipwp associated with the more northerly position of the inter tropical convergence zone itcz that accompanied mid holocene strengthening of the asian summer monsoon conversely intervals of abrupt warming appear to correspond with widespread episodes of monsoon weakening and accompanying southward migrations of the itcz that caused the ipwp to expand beyond our coral sites intervals of a strengthened asian monsoon and cooling in the southwestern ipwp during the mid holocene appear to correspond with a more positive indian ocean dipole iod like mean configuration across the tropical indian ocean suggesting that the asian monsoon iod interaction that exists at interannual time scales also persists over centennial to millennial scales associated mean changes in the pacific enso modes may have also occurred during the mid holocene the dynamic and inter connected behaviour of the ipwp with tropical climate systems during the mid holocene highlights the fundamental importance of the warm pool region for understanding climate change throughout the tropics and beyond c 2009 elsevier ltd all rights reserved

normal faulting transcrustal permeability and seismogenesis in the apennines italy abstract late pliocene pleistocene tectonic evolution of the apennines is driven by progressive eastward migration of extensional downfaulting superposed onto the late miocene early pliocene compressional thrust belt this process has led to distinct structural domains that show decreasing transcrustal permeability from conditions of pervasive mixing between deep and surface fluids in the hinterland west to conditions of restricted fluid circulation and overpressuring in the foreland east at present the highest rates of normal faulting and the strongest seismicity occur in the area bounded by stretched highly permeable crust to the west and thick poorly permeable crust to the east in this area the seismogenic sources of the largest earthquakes 5 m s

empirical assessment of coral sr ca and mg ca ratios as climate proxies using colonies grown at different temperatures 1 coral strontium calcium sr ca and magnesium calcium mg ca ratios might be useful for reconstructing past sea surface temperature sst in tropical oceans where instrumental data are limited however the link between coral skeletal trace elements and sst is disputed and biological factors such as skeletal growth rate may also affect trace elements in a coral we studied the relationships between growth rate and sst and sr ca and mg ca ratios using corals porites spp cultured in thermostated tanks sr ca was controlled primarily by sst while mg ca mainly reflected the growth rate with negligible contribution from species on both the variations these relationships are consistent with modeled results of cation partitioning during aragonite crystal formation

palaeomagnetic and structural evidence of neogene tectonic rotation of the gran sasso range central apennines italy abstract interference between discordant tectonic trends in the central apennines italy was investigated in a palaeomagnetic study of the arc shaped e w to n s oriented overthrust units of the lazio abruzzi carbonate platform gran sasso and the underlying n s oriented imbricates of the marche pelagic domain mt dei fiori samples were taken from 26 sites in the cretaceous palaeogene scaglia formation and in the messinian lower pliocene laga flysch stepwise thermal demagnetization was used to remove secondary components and a stable direction of the characteristic remanent magnetization chrm was determined for 24 sites the palaeomagnetic results point to counter clockwise rotation of the marche domain similar to that of the southern umbria directions in both the scaglia and laga formations of the lazio abruzzi units show counter clockwise rotations up to 90 in the easternmost segment of the gran sasso belt this setting may be framed in a structural context wherein superposition of the e w oriented gran sasso belt onto the n s oriented marche imbricates derives from progressive rotation of the lazio abruzzi platform decoupled by right lateral shearing along the n s oriented rigopiano bussi rivisondoli shear zone

quantifying tooth variation within a single population of albertosaurus sarcophagus theropoda tyrannosauridae and implications for identifying isolated teeth of tyrannosauridsthis article is one of a series of papers published in this special issue on the theme albertosaurus documenting variation in theropod dinosaurs is usually hindered by the lack of a large sample size and specimens representing several ontogenetic stages here variation within 140 disassociated and seven in situ tyrannosaur teeth from the upper cretaceous lower maastrichtian monodominant albertosaurus sarcophagus theropoda tyrannosauridae bonebed is documented this sample represents the largest data set of teeth from one population of a sarcophagus containing both adult and juvenile specimens tooth variation was assessed using multivariate analyses principal component discriminant and canonical variate analyses heterodonty in the teeth of a sarcophagus contributes to the large amount of variation in the data set premaxillary teeth are significantly different from maxillary and dentary teeth but there is no quantifiable difference between a priori identified maxillary and dentary teeth juvenile and adult teeth of a sarcophagus show apparent quantitative differences that are size dependen

the variation of angles between anterior and posterior carinae of tyrannosaurid teeth tyrannosaurid tooth measurements have been shown to be a powerful tool for systematic analyses as well as for studies on function and evolution of theropod dentition in this analysis a variable not previously addressed in depth is added to the tyrannosaurid data set the angle between the anterior and posterior carinae can be difficult to measure consistently and a method is hereby proposed through the use of a digitizer five tyrannosaurid genera were analyzed tyrannosaurus tarbosaurus albertosaurus daspletosaurus and gorgosaurus only in situ data were used and therefore some of the taxa had a limited amount of information available for this analysis the measurements were analyzed through multivariate analyses using paleontological statistics past version 2 06 the analyses included principal component analyses pcas discriminant analyses das and canonical variates analyses cvas the results of these analyses revealed that the angle between carinae contributes significantly to the va

structural deformation pattern within the nw qaidam basin in the cenozoic era and its tectonic implications abstract the qaidam basin is located in the northeastern tibetan plateau and provides an excellent field laboratory in understanding the history and mechanism of the plateau growth it deformed widely over the northwest during the cenozoic but with little thrust loading along the margins where no foreland depression is observed based on satellite images seismic and borehole data we investigated the structural deformation pattern including the structural style and timing of deformation and its formation mechanism within the northwestern qaidam basin during the cenozoic era mapping of surface geology shows that the modern qaidam basin is characterized by five se trending anticlinal belts each belt consists of several right step en echelon anticlines with plenty of normal and strike slip faults crossing the crests those anticlines are generally dominated by double fault systems at different depths an upper thrust fault system controlling the anticlines identified on the surface and a lower dextral transpressional fault system characterized by typical flower structures they are separated by weak layers in the upper xiaganchaigou or the shangganchaigou formations the upper system yields shortening strain 2 5 times larger than that of the lower system and the additional strain is interpreted to be accommodated by hinge parallel elongation in the upper system growth strata indicate that deformation within the qaidam basin initiated in the middle miocene 15 ma and accelerated in the late miocene 8 ma a simple riedel p shear model is used to explain the deformation mechanism within the northwestern qaidam basin

a history of albertosaurus discoveries in alberta canadathis article is one of a series of papers published in this special issue on the theme albertosaurus after many years of taxonomic uncertainty albertosaurus was established as a new genus in 1905 the year alberta became a province of canada gorgosaurus is a closely related tyrannosaurid from the judithian beds of southern alberta that was subsequently synonymized with albertosaurus although most researchers consider the genera as distinct there has been considerable confusion over the temporal and geographic range of albertosaurus albertosaurus sarcophagus is only known from 13 skulls and or skeletons of varying completeness and one possibly two bonebeds all from the horseshoe canyon formation campanian maastrichtian of alberta many of the major albertosaurus specimens are scientifically compromised due to poor collection techniques incomplete locality and stratigraphic information politics vandalism accidents gunplay and landowner issues the background of each specimen is discussed to eliminate some of the sources of confusion and to document how much of each specimen is preserved

sst artifacts in coral proxy records produced by early marine diagenesis in a modern coral from rabaul papua new guinea 1 we investigated the effects of early marine diagenesis on the skeletal geochemistry of a porites coral collected live offshore of rabaul papua new guinea the lowermost 14 cm of the 1 9 m coral core contains physical evidence of alteration which is clearly visible in x radiograph sem and petrography images abrupt and significant increases in coral 18o and sr ca and decreases in coral mg ca occur at the transition from unaltered to altered skeleton all of which imply significant sst cooling if the altered nature of the coral skeleton went unrecognized screening for the effects of early marine diagenesis should become a standard procedure in coral climate studies

concentrated slip zones with subsidiary shears their development on three scales in the cerro brass fault zone appalachian valley and ridge concentrated slip zones bound subsidiary shears at three scales within the cerro brass fault which cuts cambrian dolomites of the n any anticlinorium pennsylvania on the outcrop scale thrust faults along both cerro brass fault zone boundaries acted as concentrated slip zones bounding subsidiary shears developed along original bedding planes the outcrop scale subsidiary shears are zones of concentrated slip bounding hand specimen scale subsidiary shears in turn the hand specimen scale subsidiary shears are concentrated slip zones bounding even smaller scale subsidiary shears subsidiary shears in cerro brass fault zone are analogous to subsidiary shears i e ri and r2 commonly found in laboratory gouge friction experiments the orientations of subsidiary shears at the outcrop and hand specimen scales define a riedel within riedel geometry in which the original bedding played the role of r shears at the outcrop scale and at the same time operated as boundary faults at a smaller scale the presence of subsidiary shears on more than one scale suggests that the coulomb failure theory is not sufficient to explain their origin

co seismic riedel shear structures produced by the 2010 mw 6 9 yushu earthquake central tibetan plateau china abstract riedel shear structures are often developed within strike slip fault zones this study focuses on the riedel shear structures within the co seismic strike slip surface rupture zone produced by the 2010 mw 6 9 yushu earthquake in the central tibetan plateau china field surveys and structural analysis of the surface ruptures reveal that the co seismic riedel shear structures are characterized by i tension cracks t fractures ii compression structures mainly mole tracks p shears and iii discrete shear faults r and y shears developed in unconsolidated alluvial deposits along the pre existing left lateral strike slip ganzi yushu fault zone the t fractures generally show a right stepping en echelon pattern in contrast the p and r shears indicate a left stepping en echelon pattern the riedel shears are inclined to the general trend of the co seismic surface rupture zone at mean counterclockwise angles of 41 t fractures and 21 r shears and a mean clockwise angle of 35 for the p shears the present results show that i the co seismic riedel shear structures indicate a left lateral strike slip sense for the seismogenic fault and ii the t fractures and p and r shears are the primary riedel shear structures formed during the early stages of the evolution of a strike slip fault constrained by pre existing geologic structures

paleoclimate proxy perspective on caribbean climate since the year 1751 evidence of cooler temperatures and multidecadal variability 1 annually resolved coral 18o and sr ca records from southwestern puerto rico are used to investigate caribbean climate variability between 1751 and 2004 c e mean surface ocean temperatures in this region have increased steadily by about 2 c since the year 1751 with sr ca data indicating 2 1 0 8 c and 18o data indicating 2 7 0 5 c coral geochemical records from across the tropics demonstrate that regional variability is important for understanding climate variations at centennial time scales a strong multidecadal salinity signal in the oxygen isotope data correlates with observed multidecadal temperature variations in the northern hemisphere instrumental wind and precipitation data indicate that the most recent coral isotopic variations are caused by expansion and contraction of the steep regional salinity gradient forced by trade wind anomalies through meridional ekman transport the timing of the fluctuations suggests that the multidecadal scale wind and surface circulation anomalies might play a role in atlantic temperature variability and meridional overturning circulation but further work is needed to confirm this suggestion

a snapshot of climate variability at tahiti at 9 5 ka using a fossil coral from iodp expedition 310 1 the integrated ocean drilling program iodp expedition 310 recovered drill cores from the drowned reefs around the island of tahiti 17 40 s 149 30 w many of which contained samples of massive corals from the genus porites herein we report on one well preserved fossil coral sample a 13 6 cm long porites sp dated by uranium series techniques at 9523 33 years monthly 18o and sr ca determinations reveal nine clear and robust annual cycles coral 18o and sr ca determinations estimate a mean temperature of 24 3 c 3 2 c colder than modern for tahiti at 9 5 ka however this estimate is viewed with caution since potential sources of cold bias in coral geochemistry remain to be resolved the interannual variability in coral 18o is similar between the 9 5 ka coral record and a modern record from nearby moorea the seasonal cycle in coral sr ca is approximately the same or greater in the 9 5 ka coral record than in modern coral records from tahiti paired analysis of coral 18o and sr ca indicates cold wet warm dry interannual anomalies opposite from those observed in the modern instrumental record

multivariate analysis of isolated tyrannosaurid teeth from the danek bonebed horseshoe canyon formation alberta canada1 a significant number of fossil remains of the hadrosaurid edmontosaurus have been recovered from the danek bonebed horseshoe canyon formation upper cretaceous alberta bones from theropod dinos

micro and meso scale deformation structures in experimental fault zones abstract kinematic structures of brittle brittle ductile and ductile shear zones were developed in experimental simple shear deformation transparent films of paraffin wax with different initial fabrics were progressively deformed in a manually driven stage mounted shear apparatus producing heterogeneous simple shear 0 36 2 64 at variable strain rates of from 3 3 10 5 to 4 08 10 5 s 1 en echelon fracture arrays compressive and tensile bridges spaced cleavage stylolite like cleavage and sigmoidal cleavage trails were developed in brittle and brittle ductile deformation structures produced in ductile experiments were c s and c s fabrics and type asymmetric tails shear lenses and active folds of pre existing and induced anisotropy planes the experiments offer insight into the microstructural processes involved and demonstrate development of a progression of shear structures in a single non steady deformation

reconstructing seawater δ18o from paired coral δ18o and sr ca ratios methods error analysis and problems with examples from tahiti french polynesia and timor indonesia we compare several statistical routines that may be used to calculate delta o 18 and sss from paired coral sr ca and delta o 18 measurements typically the delta o 18 coral sst relationship is estimated by linear regression of coral delta o 18 vs sst if this method is applied evidence should be given that at a particular site sst and sss do not co vary in the tropical oceans sst and delta o 18 sw sss often co vary and this will bias the estimate of the regression slope of delta o 18 coral sst using a stochastic model we show that covariance leads to a bias in the coefficients of the univariate regression equations as the slope of the delta o 18 coral sst relationship has known we propose to insert this value for gamma 1 in the regression models this requires that the constants of the regression equations are removed to omit the constants we propose to center the regression equations i e to remove the mean values from the variables the statistical error propagation is calculated to assess our ability to resolve past variations in delta o 18 sw sss at tahiti we find that the combined analytical uncertainties of coral delta o 18 and sr ca equal the amplitude of the seasonal cycle of delta o 18 sw sss therefore we cannot resolve the seasonal cycle of sss at tahiti at timor the error of reconstructed delta o 18 sw sss is lower than the magnitude of seasonal variations of delta o 18 sw sss and the seasonal cycle of delta o 18 sw sss can be resolved c 2008 elsevier ltd all rights reserved

nucleation and initial growth of a shear zone network within compositionally and structurally heterogeneous granitoids under amphibolite facies conditions abstract in the neves area the pre alpine intrusive protolith of the zentralgneise unit tauern window eastern alps is well preserved in a kilometric scale low strain domain without pervasive alpine deformation it is compositionally heterogeneous consisting predominantly of granodiorites with lesser leucocratic granites and different generations of lamprophyres and aplites the intrusive rocks are crosscut by fractures that were locally infiltrated by fluids and surrounded by alteration haloes incipient alpine amphibolite facies ductile deformation is strongly localized on these precursor fractures and on lithological planar heterogeneities resulting in the development of several different types of shear zones fractures without alteration haloes initially accommodate slip entirely on the fracture itself with increasing deformation a foliation is progressively developed in the adjacent host rock eventually producing a single heterogeneous ductile shear zone with the typical sigmoidal foliation pattern strong layers aplite dykes and bleached alteration haloes developed to either side of precursor fractures localize shear on their boundaries to produce characteristic paired shear zones shearing is more evenly distributed within weak layers lamprophyres and quartz veins with a marked discontinuity in shear strain against the adjacent little deformed granodiorite shear zone development was accompanied by the formation of new fractures and quartz rich veins in the host rock which in turn also localized shear magmatic contacts fractures and quartz veins are mostly steeply dipping and effectively span the complete range of strike orientations the kinematics of the overprinting strike slip shear zones was determined by the orientation of the initial discontinuities relative to the local principal compressive stress axis 1 here oriented ca 345 discontinuities of almost all orientations show shear reactivation even in the case of very low resolved shear stress indicating an overall viscous response of the system without a specific yield stress the geometry and kinematics of the shear zone network suggest that the overall deformation in low strain domains was close to coaxial during deformation along the shear zone network compatibility was maintained by fracturing with the development of new quartz veins and by distributed ductile deformation of the host rock especially within contractional domains of the shear network and at shear zone intersections deformation never propagates into the undeformed homogeneous granodiorite as discrete ductile shear zones but is limited by the original extent of the precursor discontinuities shear zone development in intact rock is always preceded by fracturing which localizes subsequent shear reactivation

paleomagnetism of the gran sasso range salient central apennines italy pattern of orogenic rotations due to translation of a massive carbonate indenter 1 we report on the paleomagnetism 39 new sites of gran sasso an indenter controlled salient of the external central apennines formed by two orthogonal limbs we find that gran sasso is a complex salient paleomagnetically corresponding to neither a nonrotating nor an oroclinal end member data from the core of the arc show that the indenter itself did not undergo any rotation conversely rotations of variable magnitude and sign are observed along the curve shaped thrust fronts rotations are virtually absent at both end points of the arc moving toward the apex progressively greater counterclockwise ccw and clockwise cw rotations occur along the e w and n s fronts respectively the rotations increase continuously and more than linearly reaching their maximum values 80 ccw and 50 cw around the apex here the more strongly ccw and cw rotated fronts are separated by a domain characterized by local block rotations the inequality between the maximum ccw and cw rotation values is likely a consequence of the asymmetry of the indenter displacement direction n70 e with respect to the preorogenic trends of its margins e w and n s from an oroclinal point of view the fronts close to the end points virtually define a nonrotating arc while the pattern around the apex is similar to that of an orocline we conclude that close to end points nonrotational thrusting normal to the indenter margins occurred while in the vicinity of the apex the peritidal carbonates acted as an ice breaker pushing apart and strongly rotating the weaker multilayer located ahead

taphonomy of the danek bonebed a monodominant edmontosaurus hadrosauridae bonebed from the horseshoe canyon formation alberta the danek bonebed horsethief member horseshoe canyon formation late campanian is dominated by the remains of at least 12 edmontosaurus regalis skeletal remains of a tyrannosaurid and ceratopsid are also known the predominantly disarticulated remains were interred on a periodically inundated floodplain and although the cause of death is unknown a sudden catastrophic death explains the demographic spread faunal diversity rare greenstick fractures and homogeneous weathering abrasion categories of the assemblage the danek bonebed shares a similar taphonomic signature to the liscomb bonebed prince creek formation alaska but it is unique among all other described hadrosaurid bonebeds in the unusually high proportion of bite marked bones 30 suggesting scavenging played a major role in the reworking of the assemblage the highest frequency of bite marks is found on small often unidentifiable and commonly ignored bone fragments underscoring the role that such fragments can play in taphono

reproducibility of geochemical and climatic signals in the atlantic coral montastraea faveolata 1 monthly resolved 41 year long stable isotopic and elemental ratio time series were generated from two separate heads of montastraea faveolata from looe key florida to assess the fidelity of using geochemical variations in montastraea the dominant reef building coral of the atlantic to reconstruct sea surface environmental conditions at this site the stable isotope time series of the two corals replicate well mean values of 18o and 13c are indistinguishable between cores compare 0 70 versus 0 68 for 13c and 3 90 versus 3 94 for 18o mean values from the sr ca time series differ by 0 037 mmol mol which is outside of analytical error and indicates that nonenvironmental factors are influencing the coral sr ca records at looe key we have generated significant 18o sea surface temperature sst r 0 84 and sr ca sst r 0 86 calibration equations at looe key however these equations are different from previously published equations for montastraea variations in growth parameters or kinetic effects are not sufficient to explain either the observed differences in the mean offset between sr ca time series or the disagreement between previous calibrations and our calculated 18o sst and sr ca sst relationships calibration differences are most likely due to variations in seawater chemistry in the continentally influenced waters at looe key additional geochemical replication studies of montastraea are needed and should include multiple coral heads from open ocean localities complemented whenever possible by seawater chemistry determinations

an evaluation of quantitative reconstruction of past precipitation records using coral skeletal sr ca and δ18o data abstract coupled records of 18o and sr ca in porites coral have been used to derive hydrological conditions by removing the sr ca inferred temperature component from the 18o signal nanwan a semi enclosed bay in southern taiwan provides an opportunity to demonstrate the feasibility of quantitatively reconstructing past precipitation history recurrence of seawater 18o offsets between wet and dry seasons in the early 1990s is well correlated with the precipitation record even though the hydrological signal only accounts for 20 of the total annual coral 18o variation of ca 1 offsets can be found in the residual 18o of modern corals after removing the thermal effect which contributes to the other 80 the observed timing and amplitude of the seasonal seawater 18o offsets in nanwan and their correlation with precipitation are reproduced by hydrological models in the mid holocene the seasonal anomaly of residual 18o was twice that of the modern value based on the 9 yr sr ca 18o data recorded in a 6 73 ka porites coral hydrological models suggest an annual rainfall of 1800 3000 mm yr at the window during mid holocene 20 higher than that of the average of 30 yr modern instrumental records of 1500 2500 mm consistent with the qualitative pollen record from lake sediments the seasonal decrease of residual 18o in 5 of 9 yr was earlier than the increase of the coral sr ca inferred temperature which implies that these rainy seasons probably occurred from the early mid spring to mid summer earlier than that from late spring to late summer today the driving force may be related to the changes of solar insolation and the east asian monsoon it is cautioned that the variability of hydrographic conditions imposes restrictions on a precise calculation of the amount of paleo precipitation the dynamic nature of local tectonics monsoons and water circulation should be further addressed to precisely quantify precipitation over the past 10 000 yr from coral geochemical records

evaluation of sampling resolution in coral stable isotope records a case study using records from new caledonia and tarawa we have generated a 40 year long monthly stable isotope record from a porites lutea coral collected offshore of amedee new caledonia 22 s 167 e to investigate the relation between sampling resolution in coral isotope studies and retrieval of sea surface environmental information we interpret the high correlation between our oxygen isotope record and a twenty year long sea surface temperature record at the monthly timescale r 0 88 to indicate that our coral isotope record is an accurate monitor of environmental conditions offshore of amedee the character of the signal and the percent variance explained in the record at the annual band at the quasi biennial oscillation band qbo 2 0 2 4 years and at the el nino southern oscillation band enso 3 8 years changes little in response to a reduction in sampling density from monthly to bimonthly to quarterly similar results have been obtained in a reanalysis of a coral isotope record from tarawa kiribati our results indicate that a significant amount of the information obtained from high density sampling can also be retrieved from lower density sampling in particular bimonthly sampling yields virtually no drop off in variance explained and quarterly sampling is satisfactory for resolving interannual and decadal scale trends in time series the proposed sampling approach may enable a more rapid filling in of numerous spatial holes in coral sampling sites needed for reconstruction of long term decadal scale variations in climate

sea surface temperature and salinity reconstruction from coral geochemical tracers massive scleractinian corals secrete an aragonitic skeleton which incorporates a large array of chemical tracers corals present several advantages for palaeoclimate research they grow continuously and can live up to 1000 years they are easy to date and they can be sampled at high resolution weekly to monthly resolution both live and fossil corals can be collected in the field in the past two decades significant efforts have been made to identify robust tracers of sea surface temperature sst and salinity sss in corals to date sr ca and 18o are considered to be the most reliable sst tracers although changes in seawater 18o can significantly alter sst reconstructed from coralline 18o because these variations in seawater 18o can be linked to sss changes this initial problem can in fact be turned into an advantage and provide us with an sss tracer the sst component in the coral 18o signal can either be evaluated through sr ca measurements or in some case simply filtered out however there is still much uncertainty concerning the exact mode of incorporation of trace elements and stable isotopes into the coral skeleton the effects of growth rate light intensity feeding habits ph and water chemistry are still poorly documented a review of the strength and weaknesses of sr ca and 18o is presented together with some examples of sst and sss reconstructions other potential sst tracers are also reviewed it is expected that the ability to grow corals in aquarium under controlled conditions and that the development of sophisticated analytical techniques at the micrometric level should help us understand better the robustness of each tracers and the factors controlling their incorporation in coral aragonite

fracture initiation growth and effect on stress field a numerical investigation a numerical investigation was made of the relationships between fracture initiation growth stress field and boundary conditions two dimensional plane strain continuum models were used in which fractures appeared as zones of strain localization developed through application of a strain softening mohr coulomb constitutive model r and r fractures developed first followed by y fractures at larger strains the models showed that equal development of conjugate r and r fractures is easily changed to favor one or the other set by minor variations in model initial conditions strength loss in fractures caused stress field rotations in regions bounded by fractures altering the orientation of subsequent fractures the amount and sense of stress field rotation is dependent on the strength loss during displacement on the fractures the orientation of fractures and on the boundary conditions y oriented fractures could be explained on the basis of a mohr coulomb failure criterion provided that stress field rotation is accounted for monitoring of fracture slip activity showed that under conditions of constant boundary velocity slip was discontinuous in time alternating on fractures throughout the model

linkage and evolution of conjugate strike slip fault zones in limestones of somerset and northumbria conjugate strike slip fault zones that cover metre scale areas at beadnell northumbria and kilve somerset were initiated as conjugate vein arrays early conjugate faults are linked by the propagation of one fault that eventually by passes the other fault a model for the development of strike slip faults is presented using fault and vein geometries and the position of damage zones with respect to the master faults as an indication of the propagation direction this model includes the evolution of networks from 1 the initial random development of vein arrays to 2 the isolated development of several unconnected conjugate fault segments that pass into vein arrays through 3 the intersection of a conjugate set of master faults and linkage with minor antithetic faults and the formation of new vein arrays with extensional geometries after a linked network of faults is established to 4 breaching of intersection points by dominant faults and finally 5 the propagation towards oversteps that are breached to form a through going fault the geometry of the active structures simplifies with time as strain is localised along the master fault but the complexities are preserved in the fault walls

atmospheric and oceanic evidences of el nino southern oscillation events in the south central pacific ocean from coral stable isotopic records over the last 137 years we measured 18o and 13c in porites lutea collected in the moorea lagoon where the instrumental records show that an el nino southern oscillation enso event implies both a cloud cover decrease and a weak sea surface temperature sst increase two proxies allow an enso record to be reconstructed at moorea the annual 13c anomaly associated with the south pacific convergence zone motion and an annual 18o anomaly showing increased sst the frequency bands exhibited by the singular spectral analysis ssa and the multitaper method of the annual 18o and 13c records are centered on 2 5 and 5 2 years and 2 4 and 3 2 years respectively which are the main enso modes we used ssa to reconstruct enso events at moorea over the past 137 years results indicate that climate variability at this site is strongly affected by enso events

an assessment of the sr ca ratio in shallow water hermatypic corals as a proxy for sea surface temperature the high precision measurement of the sr ca ratio in corals has the potential for measuring past sea surface temperatures at very high accuracy however the veracity of the technique has been questioned on the basis that there is both a spatial and temporal variation in the sr ca ratio of seawater and that kinetic effects such as the calcification rate can affect the sr ca ratio of corals and produce inaccuracies of the order of 2 4 c in the present study a number of cores of the massive hermatypic scleractinian coral porites from the central great barrier reef have been analyzed for sr ca at weekly to monthly resolution results from a 24 year record from myrmidon reef show an overall variation from 22 7 c to 30 4 c the record shows a warming cooling trend with maximum warming centred on the 1986 1987 summer while some bleaching was reported to have occurred at myrmidon reef in 1982 the sr ca record indicates that subsequent summer temperatures were much higher the 4 5 year record from stanley reef shows a maximum sst of 30 c during the 1997 1998 el nino event the calibrations from myrmidon and stanley reefs are in excellent agreement with previously published calibrations from nearby reefs while corals do not calcify in equilibrium with seawater due to physiological control on the uptake of sr and ca into the lattice of coralline aragonite it can be argued that provided only a single genus such as porites sp is used and that the coral is sampled along a major vertical growth axis then the sr ca ratio should vary uniformly with temperature similarly objections based on the spatial and temporal variability of the sr ca activity ratio of seawater can be countered on the basis that in most areas where coral reefs grow there is a uniformity in the sr ca activity ratio and there does not appear to be a change in this ratio over the growth period of the coral evidence from several corals in this study suggest that stress can be a major cause of the breakdown in the sr ca sst relationship thermal stress resulting from either extremely warm or cool temperatures can produce anomalously low sr ca derived ssts as a result of the breakdown of the biological control on sr ca fractionation it is considered that other stresses such as increased nutrients and changes in light intensity can also lead to a breakdown in the sr ca sst relationship two of the main issues affecting the reliability of the sr ca method are the calibration of the sr ca ratio with measured sst and the estimation of tropical last glacial maximum lgm palaeotemperatures instead of producing a constant calibration just about every one published so far is different from the others what is obvious is that for most calibrations while the slope of the calibration equation is similar the intercepts are not while the cause for this variation is still unknown it would appear that corals from different localities around the world are responding to their own particular environment or that certain types of environments exert a control on the corals physiology sr ca derived sst estimates for the lgm and deglaciation of 5 c 6 c cooler than present are at odds with estimates of 2 c 3 c cooling by other climate proxies the apparent lack of reef growth during the lgm suggests that ssts were too cold in many parts of the tropics for reefs to develop this would lend support to the idea that tropical ssts were much cooler than what the climap data suggests

dental anatomy of the apex predator sinraptor dongi theropoda allosauroidea from the late jurassic of china the dental morphology of the holotype of the theropod sinraptor dongi from the jurassic shishugou formation of china is comprehensively described we highlight a combination of dental features that

slip vectors and fault mechanics in the makran accretionary wedge southwest pakistan the makran is a broadly east west trending arcuate accretionary wedge currently forming where the oceanic floor of the gulf of oman is being subducted north northeastward beneath the south asian margin two traverses across the makran coast ranges extending about 80 km inland from the coastline which lies about 100 km north of the wedge front show that the structure of this region is dominated by large back rotated south directed thrust faults and associated folds related structures include duplexes fault gouge containing reidel shears and melange along fault zones these structures are cut by later north directed backthrusts out of sequence south directed thrusts and apparently conjugate sets of nne trending sinistral and nw trending dextral strike slip faults slip vectors were determined from slickenlines fiber lineations gouge fabrics and riedel shears vectors from early thrusts and bedding parallel slip surfaces corrected for tectonic rotation form a broad south directed concentration lying between the normal to the regional strike varying from 160 to 180 and the present plate convergence vector 200 locally the concentration is bimodal this pattern may represent the interaction between plate forces and body forces in the accretionary wedge the late thrusts have widely variable slip vectors and stair step off the early thrusts they overlap in orientation and slip vector with gently dipping sinistral strike slip faults suggesting that they also stair step in plan off the latter the steep strike slip faults represent the final tectonic stage involving minor n s shortening and longitudinal extension these three stages probably occurred in sequence in any one area but migrated diachronously southward as the wedge grew

a high resolution calibration of sr ca thermometry using the caribbean coral montastraea annularis 1 a relationship has been established between the sr ca ratio in the skeleton of the scleractinian coral montastraea annularis and sea surface water temperature in south florida in order to obtain this correlation specimens of montastraea annularis were transplanted to a site at a local reef where every two to three months throughout a 2 year period the corals were stained with alizarin red s and where water temperature which annually ranges between 20 and 30 c was continually monitored at the end of the experimental period the coral skeleton was sampled at a rate of 50 samples per year each sample corresponding to only around 20 g of calcium carbonate for the 2 5 year period the sr ca ratio exhibited excellent correlation in the first year r2 0 83 sr ca mmol mol 10 11 0 0452 sst c but a rather poorer correlation in the second year r2 0 68 sr ca mmol mol 10 09 0 0406 sst c averaging the data into monthly values for year 1 we determined a relationship of sr ca mmol mol 10 165 0 0471 sst c on the basis of the excellent correlation between temperature and sr ca we feel that this relationship is the most accurate discrepancies in the second year are suggested to arise from slight sampling errors relative to the stain lines

role of shear in development of the helvetic fold thrust belt of switzerland the geometric features of the helvetic nappes of the alps show intense internal deformation set up predominantly by simple shear during nappe transport the nappes are bounded by thrusts that parallel incompetent layers and ramp upward stratigraphically across competent units in the direction of tectonic transport stratal layering is oblique to nappe boundaries thrust surfaces formed after ductile shear zones developed in underlying pre triassic gneissic basement the broad zone of shearing narrowed down as deformation increased to form zones of intense shear and ultimately to form thrust faults contraction along competent layers obliquely inclined to shear surfaces produced buckle folds the geometry of these folds was modified by further shearing as their normal limbs became aligned in the extension field of the strain ellipse for simple shear producing normal faults

fault architecture and deformation mechanisms in exhumed analogues of seismogenic carbonate bearing thrusts abstract faults in carbonates are well known sources of upper crustal seismicity throughout the world in the outer sector of the northern apennines ancient carbonate bearing thrusts are exposed at the surface and represent analogues of structures generating seismicity at depth we describe the geometry internal structure and deformation mechanisms of three large displacement thrusts from the km scale to the microscale fault architecture and deformation mechanisms are all influenced by the lithology of faulted rocks where thrusts cut across bedded or marly limestones fault zones are thick tens of metres and display foliated rocks s cc tectonites and or ypr cataclasites characterized by intense pressure solution deformation in massive limestones faulting occurs in localized narrow zones that exhibit abundant brittle deformation a general model for a heterogeneous carbonate bearing thrust is proposed and discussed fault structure affected by stratigraphic heterogeneity and inherited structures influences the location of geometrical asperities and fault strain rates the presence of clay minerals and the strain rate experienced by fault rocks modulate the shifting from cataclasis dominated towards pressure solution dominated deformation resulting structural heterogeneity of these faults may mirror their mechanical and seismic behaviour we suggest that seismic asperities are located at the boundaries of massive limestones in narrow zones of localized slip whereas weak shear zones constitute slowly slipping portions of the fault reflecting other types of aseismic behaviour

geometry classification and kinematics of s c and s c fabrics in the mushandike area zimbabwe planar fabrics in small dextral shear zones in the mushandike area of the zimbabwe archaean craton consist of a sigmoidal primary foliation s displaced by discrete shears c or c these planar fabrics can be divided into porphyroclastic megacrystic and banded types depending mainly on the values of the angles between s and c or c surfaces the structures that define s surfaces and the spacing of c or c surfaces the values of the angles between the foliations are proposed as the basis for a general classification of planar fabrics in shear zones the values of the angles depend on microstructures and strain microstructural evidence shows that slip did not occur on s surfaces but only on c or c surfaces a model for the development of the fabrics proposes that s surfaces lie parallel to the xy plane of the local finite strain ellipsoid in domains of simple shear between c or c surfaces c surfaces may form in the orientation of a coulomb failure surface the field evidence suggests that an increase in bulk strain is at least partly accommodated by an increase in local strain in domains between c or c surfaces as the s surfaces rotate with the local finite strain ellipsoid

a taxonomic assessment of the type series of albertosaurus sarcophagus and the identity of tyrannosauridae dinosauria coelurosauria in the albertosaurus bonebed from the horseshoe canyon formation campanian maastrichtian late cretaceous the type series of albertosaurus sarcophagus consisting of a type cmn 5600 and a paratype cmn 5601 is inadequately established since it has not been demonstrated that the specimens represent the same taxon this problem has arisen because the original diagnostic characters have a wider distribution among tyrannosauridae or they are in error and both specimens consist of incomplete and damaged skulls the type series was studied to test for the presence of diagnostic characters in the type specimen and if so to provide a rationale for referring the paratype to the taxon of the bones shared between the skulls only five could be compared one character the enlarged posterior pneumatic recess of the palatine is shared between the two specimens this condition differs from the situation seen in other tyrannosaurids this character provided the rationale for assessing the identity of the specimens collected from the albertosaurus bonebed from which one palatine was collected that exhibits the diag

relationships between joint separation and faulting an initial numerical appraisal abstract the relationship between secondary jointing and faulting and major faults was investigated using a regression analysis of average separation of joints and secondary faults versus distance from the closest major fault the analysis was carried out on 95 granite outcrop localities in calabria southern italy the main result of the regression analysis is expressed by s 0 013 d 0 457 where s is the average apparent separation and d is the distance from the closest master fault all values are expressed in meters the correlation coefficient was r 0 95 and the probability of the null hypothesis was 0 00 both data sets range over one order of magnitude thus the result of the analysis is reliable

nucleation and growth of retrograde shear zones an example from the needle mountains colorado u s a abstract brittle and ductile deformation features are heterogeneously developed in late proterozoic retrograde normal slip shear zones that cross cut amphibolites and quartzo feldspathic gneisses in the needle mountains replacement of amphibolite grade minerals by greenschist facies assemblages is spatially related to transgranular fractures that cross cut the older gneissosity steeply dipping chlorite lined slip surfaces are associated with chlorite quartz muscovite filled dilational jogs and narrow breccia zones arrays of slip surfaces are transitional into similarly oriented phyllonite zones within which the foliation locally overprints early cataclastic zones the nucleation of these shear zones under greenschist facies conditions involved fluid infiltration along early transgranular fractures and hydration of fe mg bearing minerals initial displacement occurred by slip along these fractures and local cataclasite development fluids were episodically drawn into dilatant sites along these slip surfaces a transition to plastic deformation resulted directly from the metamorphic breakdown of feldspars and amphiboles to phyllosilicates which allowed strain localization into narrow phyllonite zones thus dilatancy produced by early brittle deformation appears to be the main process by which fluids infiltrate into developing greenschist grade retrograde shear zones reaction softening via hydration reactions causes a brittle to plastic transition and results in strain localization

the temperature relationship in coralline aragonite influence of variability in and skeletal growth parameters this paper provides an evaluation of two of the most likely pitfalls of sr ca thermometry i e the effect of biogenic cycling of sr vs ca in the surface ocean and the effect of variable extension rate on sr incorporation in coralline aragonite the authors also report calibration of the sr ca temperature relationship for three coral species porites lobata pocillopora eydouxi and pavona clavus collected for the hawaiian and galapagos islands analyses of seawater samples show significant spatial and depth variability in the sr ca ratio the uncertainty introduced by this effect is estimated to be 0 2 degrees c for corals located in tropical oligotrophic waters and potentially larger for corals located in upwelling areas sr ca along two different growth axes of a galapagos pavona clavus with annual extension rates of approximately 6 and 12 mm y respectively indicate an offset of 1 2 degrees c with higher sr ca values associated with slower extension rates the offset observed between the two growth axes may be the result of variations in extension and or calcification rate these results are important in determining past sea surface temperatures for reconstruction of paleoclimates

an early pliocene uplift of the central apenninic foredeep and its geodynamic significance van der meulen et al 1998 identified a pattern of lateral shifts of apenninic foredeep depocenters which was interpreted as the regional expression of lateral migration of slab detachment in the sense of wortel and spakman 1992 in addition to being expressed in such a pattern of lateral reorganisations slab detachment is expected to result in rebound this study focuses on plio pleistocene vertical motions of the central apenninic inner forearc here a major late early pliocene phase of uplift is identified by means of 1 micropaleontology based paleobathymetry 2 analysis of the compaction history and 3 numerical modeling of the flexural response of the underlying lithosphere to sediment loading the timing of the uplift event is consistent with that of the regional reorganizations on the basis of this consistency and the fact that it can be demonstrated that the uplift is not related to accretionary processes we interpret this event as rebound after slab detachment

a finite element model of the stress field in strike slip basins implications for the permian tectonics of the southern alps italy abstract a set of finite element models have been used to simulate pull apart basin formation related to a releasing overstep along two right strike slip faults the modelling results have shown the stress field at a releasing fault overstep with respect to strike slip transtensional and transpressional boundary constraints based on the assumption that normal faults strike parallel to the maximum horizontal stress we have predicted the orientation of potential normal faults within the overstep zone linear elastic rheology and plane stress conditions were assumed and four kinds of models with different overlap separation ratios 0 0 5 1 and 2 between the strike slip faults were analysed displacement boundary conditions were applied to the upper left hand and lower right hand corners of the models in order to simulate a right strike slip movement outward and inward displacement components were applied respectively to reproduce transtensional and transpressional conditions all the models mostly show an extensional stress field i e with at least one extensional principal stress axis large zones inside the overstep are affected by general extension both principal axes are extensional and their size increases with both an increase in the overlap separation ratio and with changes from transpressional to transtensional conditions the areas of maximum extension are located near the ends of the fault segments inside the overlap area it is fairly probable that the genesis of the extensional faults that bound the pull apart basins observed throughout the world occurs in these maximum extensional areas and that the extensional faults are parallel to the maximum compression stress axis trajectories the angle between the potential normal faults and the strike slip faults is strongly dependent on the overall boundary conditions i e pure strike slip transtension and transpression of the model in contrast the elastic rock properties and the overlap separation ratio of the faults have a minor control the angle between the normal and strike slip faults can vary from a few degrees in transtensional conditions to 100 120 in transpressional conditions inside the overlap zone an area of subsidence occurs the axis of which is coincident with the junction of the strike slip fault tips where it is also at a maximum i e in the same zones of maximum extension a comparison of the modelling results with the structural setting of the collio and pramollo permo carboniferous pull apart basins southern alps italy indicates that the collio basin developed under strike slip conditions while the pramollo basin was formed under transtensional conditions

shear criteria and structural symmetry abstract during the last decade it has been shown that most relevant shear criteria within ductile rocks are asymmetric structures e g pressure shadows shear bands c s structures fabrics tension gashes folds veins the correspondence between coaxial or non coaxial deformation and symmetric or asymmetric particle velocity fields respectively accounts for the use of structural symmetry as an indicator of strain history the application of this symmetry concept to various field examples emphasizes that i the degree of symmetry of a given structural pattern reflects the bulk strain regime irrespective of the size and the mechanical behaviour of the considered system and ii the strain regime can also be inferred from the order of appearance and dominance of structures which contribute to the total deformation pattern even where the progressive deformation results in a complex pattern which cannot be directly interpreted

thrust belt development in the central apennines italy northward polarity of thrusting and out of sequence deformations in the gran sasso chain the lazio abruzzi carbonate platform overrides the outermost sectors of the foreland fold and thrust belt of the central apennines of italy along an arcuate thrust front which swings from e w to nnw sse orientation the e w striking north verging thrust faults of the gran sasso cut in their footwall the n s oriented east verging imbricates of the marche thrust belt and the adjacent adriatic foredeep our field mapping of the gran sasso imbricate system shows an array of six major thrust faults crosscutting each other in such a way that oblique propagation of higher thrust faults across the preexisting thrust sheets causes rethrusting of earlier imbricated units decapitation of previous folds and superposition of younger on older beds deformation in the gran sasso thrust belt mainly occurred between messinian and middle pliocene times and is partly synchronous with the development of the marche thrust belt thus implying that shortening resulted from a complex combination of northward and eastward propagating thrust systems increasing west to east shortening along the gran sasso thrust front indicates large differential anticlockwise rotation by decoupling along a n s transpressive right lateral shear zone this mechanism could have been induced by the maiella foreland uplift acting as a buttress against which the lazio abruzzi carbonate platform was stacked and forced to rotate anticlockwise with consequent shortening by out of sequence thrust propagation

the control of precursor brittle fracture and fluid rock interaction on the development of single and paired ductile shear zones abstract ductile shear zones can occur as relatively isolated single structures as arrays or as characteristic paired zones in continuous glaciated exposures of metagranodiorites from the tauern window eastern alps the control of initial dilatant brittle fracture and associated fluid rock interaction on the geometry of subsequent ductile shear zones can be unequivocally established shearing occurred under amphibolite facies conditions fractures in weakly deformed metagranodiorites are often less than 1 mm thick but extend for tens of metres many are healed joints without shear offset others show minor mm cm discrete dextral offset such brittle faults commonly display a low angle en echelon arrangement with displacement transferred between discrete fracture segments by ductile compressive bridges the geometry of more strongly reactivated zones depends on the degree and heterogeneity of fluid rock interaction which is related to fluid infiltration and veining along the primary fractures with little fluid rock interaction reactivation produces single heterogeneous ductile shear zones centred on and immediately flanking the pre existing fracture with increased fluid rock interaction a bleached halo is developed symmetrically to either side of a central epidote quartz garnet calcite vein ductile shear zones commonly flank this bleached zone to develop a characteristic paired pattern strain is partitioned localizing in the central fracture vein and the flanking shear zones paired zones may anastomose in accordance with changes in the width of the central bleached zone but are always symmetrically spaced with regard to the central fracture vein with increasing deformation the ductile shear zones broaden into the adjacent metagranodiorite but not into the bleached zone which remains preserved as a low strain region paired shear zones can also develop to either side of aplite dykes examples of characteristic paired shear zones usually with a clear central vein are found in many areas ranging from greenschist to eclogite facies suggesting that the mechanism of their formation is quite general

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

orthorhombically arranged vein arrays abstract it is commonly accepted that arrays of en echelon veins occur either singularly or in conjugate pairs bulk finite plane strain is accompanied by these singular or conjugately arranged arrays when their formation and subsequent displacement occur in the same kinematic framework a new geometric and kinematic model for vein arrays is proposed which takes into account the effects of bulk non plane strain deformations on the evolving arrays in this model four sets of arrays develop during coaxial non plane strain deformations and two non conjugate sets of arrays develop during non coaxial non plane strain deformations the formation of singular and conjugate arrays is restricted to bulk plane strain deformations this model is the natural extension to the brittle ductile realm of models proposed for the geometry and kinematics of brittle faults formed during non plane strain deformations en echelon vein arrays mapped in central australia which cannot be understood as simple conjugate structures are interpreted as having formed during a bulk non coaxial non plane strain deformation

interfering paths of deformation and development of arcs in the fold and thrust belt of the central apennines italy in the foreland fold and thrust belt of the central apennines the major thrust sheets design systems of arcs interfering with noncoaxial trends localization of shortening by thrusting and shearing appears to be controlled by the squeezing of low competence basinal units marche gran sasso monte picca and monte genzana in between the rigid blocks of the lazio abruzzi and adriatic carbonate platforms the geometrical interlocking has been resolved by differential rotations of the superposed thrust sheets as also substantiated by paleomagnetic data the structural analysis and the age of the syntectonic siliciclastic deposits suggest an irregular sequencing of superposed contractional and extensional events during late miocene middle pliocene times interfering kinematic paths characterize the arcuate belts where slip partitioning has adjusted the coeval deformation of the noncoaxially arranged tectonic units in the arcuate gran sasso monte picca thrust belt out of sequence thrusting displacement transfer on high angle strike slip faults and growth of high angle normal faults behind the most rotated blocks have resulted in the back and forth superposition of contractional and extensional structures in adjacent domains our kinematic reconstruction of the central apennines indicates that it is impossible to perform the retrodeformation of tectonic events by assuming a regular outward progression of deformation pulses in such a strongly arcuate belt the irregular trajectories of the displacement field and the complex overprinting relations between different sets of structures reflect the kinematic accommodation of blocks with contrasting rigidity and are not fitted easily within a regionally smoothed stress field

u sr and mg in holocene and pleistocene corals a palmata and m annularis abstract mg sr and u concentrations are reported for living holocene dead and pleistocene montastrea annularis and acropora palmata in an effort to characterize starting materials and identify diagenetic effects in unrecrystallized skeletal aragonite the data indicate that skeletogenesis of minor elements is a taxa specific process yielding different mg sr and u values for each species during diagenesis sr concentrations increase and mg concentrations decrease in both species u diagenesis appears to be affected by skeletal structure establishment of u concentration ranges for modern corals provides a criterion for selecting samples for dating concentration changes in mg and sr during diagenesis limit their usefulness as paleo environmental indicators

initiation and growth of strike slip faults within intact metagranitoid neves area eastern alps italy exhumed strike slip faults exposed in the neves area of the tauern window eastern alps italy formed in the lower brittle crust under hydrous conditions within intact metagranitoids where any precursor fractures were already healed due to earlier amphibolite facies metamorphism faults initiated as newly formed en echelon fractures delineating shear bands with segmentation occurring over scales of 10 3 to 10 2 m due to the initial en echelon pattern stepovers between fault segments were almost invariably contractional during subsequent slip accumulation in initial low slip centimeter to decimeter stages synthetic slip on the segments was associated with the development of a set of antithetic faults in the contractional stepovers oriented at an angle of 30 45 to the bounding faults slip on this antithetic set did not fully compensate for the decrease in slip on the main faults implying an additional deformation mechanism within the stepovers e g block rotation and or out of plane movement in larger faults with slip on the order of a few meters the antithetic faults within the stepover were crosscut by synthetic sigmoidal faults that connected the overstepped fault segments and accommodated most of the subsequent displacement transfer this second stage of evolution involving fault linkage is well documented in the mesule fault which has a current maximum offset of 10 m in the mesule fault the total horizontal slip summed along all secondary faults within the stepover accounts almost entirely for the net slip decrease toward the tips of the overstepping faults however the boundary faults remain nearly straight in spite of the sigmoidal ramp like geometry of the connecting faults since the adjacent blocks are little deformed and there is no evidence for appreciable volume loss or block rotation in the stepover significant out of plane movement is implied although it is difficult to quantify the neves area provides unusually detailed field constraints on fault initiation linkage and displacement accumulation within nonbedded and relatively isotropic granitoid rocks at the base of the brittle crust where neither a free upper surface nor substantial volume change e g by veining and pressure solution was a controlling factor in accommodating fault linkage and displacement transfer

mechanisms of thrust faulting in the gran sasso chain central apennines italy abstract the gran sasso chain in central italy is made up of an imbricate stack of eight thrust sheets which were emplaced over the upper miocene lower pliocene laga flysch the thrust sheets are numbered from 1 to 8 in order of their decreasing elevation in the tectonic stack and their basal thrusts are numbered from t 1 to t 8 accordingly on the basis of their different deformation features the major thrust faults fall into three groups 1 thrust faults marked by thick belts of incoherent gouges and breccia zones t 1 t 2 t 3 2 thrust faults characterized by a sharp plane which truncates folds that had developed in the footwall rocks t 5 t 6 and 3 thrust faults truncating folds developed in both the hangingwall and footwall units and bordered by foliated fault rocks t 7 the deformation features observed for the different faults seem to vary because of two combined factors 1 lithologic changes in the footwall and hangingwall units separated by the thrust faults and 2 increasing amounts of deformation in the deepest portions of the imbricate stack the upper thrust sheets from 1 to 6 are characterized by massive calcareous and dolomitic rocks they maintain a homoclinal setting and are truncated up section by the cataclastic thrust faults the lowermost thrust sheets 7 and 8 are characterized by a multilayer with competence contrasts which undergoes shear induced folding prior to the final emplacement of the thrust sheets bedding and axial planes of folds rotate progressively towards the t 5 t 6 t 7 and t 8 thrust boundaries and are subsequently truncated by propagation of the brittle thrust faults the maximum deformation is observed along the t 7 thrust fault consistent with horizontal displacement that increases progressively from the uppermost to the lowermost thrust sheet in the tectonic stack the axial planes of the folds developed in the hangingwall and footwall units are parallel to the t 7 thrust fault and foliated fault rocks have developed field data and petrographic analysis indicate that cleavage fabrics in the fault rocks form by a combination of cataclasis cataclastic flow and pressure solution slip associated with pervasive shearing along subtly distributed slip zones parallel to the t 7 thrust fault the development of such fabrics at upper crustal levels creates easy slip conditions in progressively thinner domains which are regions of localized flow during the thrust sheet emplacement

allometric growth in tyrannosaurids dinosauria theropoda from the upper cretaceous of north america and asia many tyrannosaurid skeletons have been collected in canada the united states and mongolia these fossils tend to represent mature individuals but juveniles are also known skeletons of five gene

emplacement of pyroclastic dykes in riedel shear fractures an example from the sierra de san miguelito central mexico abstract although magmatic dykes are considered to be emplaced at depth there are very few studies about the emplacement of pyroclastic dykes there are two commonly accepted mechanisms for dike emplacements namely formation of a hydraulic tension fracture and filling of pre existing fractures in the sierra de san miguelito central mexico there is a dike swarm with orientations that do not concur with any of the above two cases instead the dikes have orientations resembling some type of secondary fractures within the fault bounded blocks within a fault bounded block the reverse drag of the normal faults can be explained by simple shear based on the simple shear mechanism we establish a series of equations to calculate the extension and the direction of the simple shear within a fault bounded block as an application of our methodology the value of which is the angle measured from the vertical to the direction of the simple shear is calculated from the domino faults in the sierra de san miguelito mesa central mexico the results demonstrate that the absolute values of for the inclined shear are smaller than 34 the inclined shear can be antithetic 0 synthetic 0 the pyroclastic dykes in the study area have most of the strikes between 300 and 330 and are sub parallel to the major faults the preferred dips of the pyroclastic dykes vary from 80 to 90 the distribution of the pyroclastic dykes in the study area indicates that the dikes were primarily emplaced along the r fractures due to simple shear these results are different from the traditional understanding which assumes that the dykes were mainly emplaced within the tension fractures

stress and fluid control on decollement within competent limestone abstract the larra thrust of the pyrenees is a bedding parallel decollement located within a competent limestone unit it forms the floor of a thrust system of hectometric scale imbrications developed beneath a synorogenic basin the fault rock at the decollement is a dense stack of mainly bedding parallel calcite veins with variable internal deformation by twinning and recrystallization veins developed as extension fractures parallel to a horizontal maximum compressive stress cemented by cavity type crystals conditions during vein formation are interpreted in terms of a compressional model where crack arrays develop at applied stresses approaching the shear strength of the rock and at fluid pressures equal to or less than the overburden pressure the cracks developed in response to high differential stress which was channelled in the strong limestone and high fluid pressure in or below the thrust plane ductile deformation although conspicuous cannot account for the kilometric displacement of the thrust which was mostly accommodated by slip on water sills constituted by open cracks a model of cyclic differential brittle contraction stress reorientation slip and ductile relaxation at a rheological step in the limestone is proposed as a mechanism for episodic decollement movement the model accounts for the peculiar microstructural character of the fault zone for alternating sequences of bedding parallel shortening leading to crack dilation and bedding parallel shear leading to decollement slip and for hanging wall imbrication consequent upon decollement slip

genesis and evolution of a curved mountain front paleomagnetic and geological evidence from the gran sasso range central apennines italy abstract the gran sasso range is a striking salient formed by two roughly rectilinear e w and n s limbs in the past 90 counterclockwise ccw rotations from the eastern gran sasso were reported tectonophysics 215 1992 335 suggesting west east increase of rotation related northward shortening along the e w limb in this paper we report on paleomagnetic data from meso cenozoic sedimentary dykes and strata cropping out at corno grande central part of the e w gran sasso limb the highest summit of the apennine belt predominant northwestward paleomagnetic declinations in the normal polarity state from both sedimentary dykes and strata are observed when compared to the expected declination values for the adriatic foreland our data document no thrusting related rotation at corno grande the overall paleomagnetic data set coupled with the available geological information shows that the gran sasso arc is in fact a composite structure formed by an unrotated low shortening western e w trending limb and a strongly ccw rotated eastern salient late messinian and post early pliocene shortening episodes documented along the gran sasso front indicate that belt building and arc formation occurred during two distinct episodes we suggest that the southern part of a late messinian n s front was reactivated during early middle pliocene time forming a tight range salient due to ccw rotations and differential along front shortening rates the formation of a northward displacing bulge in an overall nw se chain is likely a consequence of the collision between the latium abruzzi and apulian carbonate platforms during northeastward propagation of the apennine wedge inducing lateral northward extrusion of latium abruzzi carbonates towards ductile basinal sediment areas

the effect of colony topography on climate signals in coral skeleton the stable oxygen isotope composition of the aragonitic skeleton of hermatypic corals is a potential archive of paleotemperature and rainfall data biological processes also influence coral 18o although it has been difficult to determine which processes are involved and whether or not they dominate the stable isotope signal we show here that colony topography or surface bumpiness is associated with significant differences in 18o 13c and the timing of high density band formation between same age corallites in the central and fastest growing region of a coral colony these differences reflect changes experienced by individual corallites as they grow from the summit of a bump toward the bottom of a valley corallites on the bump record isotopic temperatures more than 1 c higher and accrete high density skeleton about 2 months earlier than their valley counterparts just 20 mm away we propose that these changes are not caused by corallite aging but rather by changes in the overall rate and timing of light enhanced calcification which is lower and occurs later in shaded valleys than it does on exposed bumps although we conclude that sea temperature is the dominant influence on 18o values in our coral our results show that significant isotopic variations may be expected over a small surface area in a single colony the production of accurate and reproducible coral based climate records thus requires an understanding of the complexities of coral growth processes and incorporation of this knowledge into sampling strategies and interpretation of data