structural geology of the penobsquis salt structure late bashkirian inversion tectonics in the moncton basin new brunswick eastern canada this study uses new information acquired from field mapping mineral exploration boreholes and seismic reflection profiles to constrain the structural geology deformation mechanisms and timing of the penobsquis salt structure this information is used to place the development of the salt structure into the context of the tectonic evolution of the moncton basin the penobsquis salt structure is an elongate salt wall separated from underlying rocks by a mylonitic detachment horizon it may be divided into two segments a southwestern asymmetric southeast verging structure and a northeastern strongly asymmetric to overturned southeast verging structure associated with the penobsquis fault an initial low amplitude salt anticline formed during deposition of the mabou group serpukhovian time the salt anticline was modified into a high amplitude salt wall after deposition of cumberland group sediments early bashkirian or later the sense of asymmetry of the penobsquis salt structure the presence of thrust faults within the structure the spatial association of the structure with a major reverse fault in the salt cover and the temporal association of salt movement and compressional tectonic events suggest that the salt structure developed in response to tectonic contraction during inversion of the moncton basin

the role of advective heat transport in talik development beneath lakes and ponds in discontinuous permafrost 1 regions of warm thin discontinuous permafrost have been observed to be experiencing rapid changes in lake and pond dynamics in recent decades even though surface water and groundwater interactions are thought to play a significant role in heat transport in these regions the effect of these interactions on permafrost remains largely unquantified in order to examine the influence of groundwater flow on permafrost dynamics we modeled the development of a sub lake talik under permafrost conditions similar to those observed in the southern central seward peninsula region of alaska using a numerical solution that couples heat transport and groundwater flow including the effect of water phase changes on soil permeability and latent heat content a comparison of model simulations with and without near surface subpermafrost groundwater flow indicates that stable permafrost thicknesses are 2 to 5 times greater in the absence of groundwater flow simulations examining the thermal influence of lakes on underlying permafrost suggest that a through going talik can develop in a matter of decades and that the incorporation of advective heat transport reduces the time to complete loss of ice beneath the lake by half relative to heat transport by conduction alone this work presents the first quantitative assessment of the rates of sub lake permafrost response to thermal disturbances such as talik development in systems with near surface groundwater flow the results highlight the importance of coupled thermal and hydrologic processes on discontinuous permafrost dynamics

anatomy and evolution of a pull apart basin stellarton nova scotia the stellarton basin is a late paleozoic pull apart basin located close to the meguma avalon terrane boundary in the canadian appalachians at the stepover between the cobequid and hollow strike slip faults the basin contains 3 km of rapidly deposited pennsylvanian clastic sedimentary rocks representing lacustrine and deltaic environments extensively documented through coal related mining and drilling coal seams and oil shales allow stratigraphic correlation within the basin permitting reconstruction of basin subsidence and structural evolution coal seams represent approximately paleo horizontal surfaces thickness variations corrected for tilt and compaction in the most coal rich part of the basin fill show that the south basin margin subsided rapidly during deposition acting as a trap for coarse sediment and allowing coal forming mires to develop in the north abundant soft sediment deformation structures reflect synsedimentary tectonic activity north striking normal faults dissected the basin fill during and soon after deposition early in the diagenetic history contouring of mine plans allows fault heaves to be identified and also shows that both coal seams and faults were folded by east to northeast trending folds consistent with 1 an environment of deformation involving dextral strike slip motion and 2 clockwise rotation of fault blocks during progressive strain later north northeast striking contractional structures within the basin and a positive flower structure at the northwest margin probably represent a transition from transtension to transpression the basin illustrates the role of rotational progressive strain in the reorientation of structures generated during transtension it displays evidence for changes in tectonic style through time from transtension to transpression that may typify basins developed on major strike slip faults

subsidence in late paleozoic basins in the northern appalachians during the interval between continental collision in the devonian and continental breakup in the triassic the northern appalachians became the site of a wide plate boundary zone of dominantly right lateral strike slip as is typical of intracontinental transforms tectonism was both diachronous and rapidly variable along strike through regimes of pure strike slip transpressional deformation and rapid subsidence of extensional basins up to 9 km of mainly nonmarine clastic sediments accumulated in these local depocenters which subsided episodically in two stages 1 an initial phase of stretching and thinning of the lithosphere when subsidence was rapid fault controlled and often accompanied by volcanism and 2 a subsequent phase of gradual thermal subsidence during which the depositional basins expanded to bury the earlier border faults and progressively younger sedimentary units onlapped basement the largest depocenter the magdalen basin opened as a pull apart between strike slip faults in newfoundland and new brunswick from late devonian to early carboniferous subsequent thermal subsidence affected a large area during medial and late carboniferous a phenomenon that is well recorded to the north and west where no later tectonism occurred in areas to the south and east of the basin strike slip on other faults continued into the time of thermal subsidence introducing complications such as localized transpressional deformation and rapid subsidence in smaller pull aparts

devonian carboniferous tectonics and basin deformation in the cabot strait area eastern canada the magdalen basin in the cabot strait bay st george area was a major depocenter for devonian carboniferous sediments in eastern canada structure within the basin is complex and is characterized by northeast and east trending mainly dextral strike slip faults associated with the bend in the appalachian orogenic belt known as the st lawrence promontory under the cabot strait two linear grabens parallel the major fault trends and preserve up to 6 km of devonian carboniferous sedimentary rocks comprising mainly coarse grained terrigenous clastics with a lower carboniferous transgressive episode recorded by marine carbonates evaporites and fine grained clastics several unconformities within the sedimentary succession record deformation associated with movement alo g the regional strike slip faults minor local unconformities are interpreted within the upper horton early visean upper barachois late westphalian and post pennsylvanian successions a major unconformity cuts out most of the namurian and westphalian section in the study area and can be correlated on a regional scale kinematic strain partitioning along the master cabot fault led to the development of doubly vergent compressional structures within a wrench borderland this was complicated by transpressive deformation at a restraining bend in the master fault and by deformation associated with overstepped ends of splays of the regional fault system the magdalen basin probably formed in an early phase of post acadian extension and was later reactivated by regional strike slip faults the presence of thick source and reservoir rocks as well as diverse trapping possibilities and a favorable burial and maturation history indicate that the cabot strait area has good potential for accumulating and preserving petroleum

predrill pore pressure prediction using seismic data 1a predrill estimate of pore pressure can be obtained from seismic velocities using a velocity to pore pressure transform but the seismic velocities need to be derived using methods having sufficient resolution for well planning purposes for a deepwater gulf of mexico example significant differences are found between the velocity field obtained using reflection tomography and that obtained using a conventional method based on the dix equation these lead to significant differences in the predicted pore pressure parameters in the velocity to pore pressure transform are estimated using seismic interval velocities and pressure data from nearby calibration wells the uncertainty in the pore pressure prediction is analyzed by examining the spread in the predicted pore pressure obtained using parameter combinations which sample the region of parameter space consistent with the available well data if calibration wells are not available the ideas proposed in this paper can be used with measurements made whi

degradation of permafrost beneath a road embankment enhanced by heat advected in groundwater for the past few decades northwestern north america has been affected by climate warming leading to permafrost degradation and instability of the ground this is problematic for all infrastructure built on permafrost especially roads and runways thaw settlement and soil consolidation promote embankment subsidence and the development of cracks potholes and depressions in road pavement in this study we investigate highway stability in permafrost terrain at an experimentally built road embankment near beaver creek yukon a network of 25 groundwater monitoring wells was installed along the sides of the road to estimate groundwater flow and its thermal impact on the permafrost beneath the road data on topography water table elevation ground temperature and stratigraphy of the soil were collected at the site the geotechnical properties of each soil layer were determined by laboratory analysis and used to calibrate a two dimensional groundwater flow model field observations showed that water was p

amount of extension on small faults an example from the viking graben extension estimates based on palinspastic restoration of only the largest faults in a deformed terrane may be significantly deficient due to neglect of small faults i e unsampled faults most of which have smaller displacements than do sampled faults small faults individually account for little extension but there may be large numbers of them the cumulative extension on small faults can be calculated from the fractal size distributions of fault displacements independent extension estimates support the inference from fault population statistics that small faults account for significant amounts of extension for example restorations of mesozoic faults interpreted from seismic reflection profiles across the viking graben in the north sea yield extension estimates that are only 40 75 of independent estimates the fractal size distribution of fault displacements in the viking graben is consistent with the hypothesis that the remaining 25 60 of extension resulted from displacements on small faults

crustal thickness under the gulf of st lawrence northern appalachians from gravity and deep seismic data we have determined crustal thickness in the gulf of st lawrence an area that corresponds to an offset of the main northern appalachians units a complete bouguer anomaly was calculated from recent depth to basement compilations and sediment densities from well data the moho surface was obtained by inverting the bouguer anomaly assuming a single density contrast at depth and using an average depth provided by deep reflection seismic data the resulting crustal model shows a moho depth of 42 44 km beneath the grenville craton north of the appalachian deformation front south of this front the depth to moho displays a pronounced thinning of the crust beneath the carboniferous magdalen basin this is in striking contrast to the deep seismic data which give a moho depth of about 43 km the modelling of the bouguer anomaly in the magdalen basin taking into account the seismic reflection and refraction data reconciles these different results and suggests that a 43 km deep moho beneath the basin is as

long term thermal and settlement characteristics of air convection embankments with and without adjacent surface water ponding in permafrost regions abstract surface water is an important local factor in engineering geological conditions in permafrost regions in this paper the impacts of surface water ponding on the long term thermal and settlement characteristics of an air convection embankment ace were investigated based on 13 years of data records from field observations along the qinghai tibet railway qtr the time series of the ground temperatures and the settlement of two aces with and without adjacent surface water ponding were investigated and compared the results indicated that surface water ponding could significantly affect the thermal performance of the ace without surface water ponding the ace showed a satisfactory cooling effect the underlying permafrost table rose and the shallow permafrost layer cooled significantly after construction of the embankment however with surface water ponding the great heat capacity and latent heat of the ponded water and related capillary action impeded the thermal interaction between the ace and the underlying permafrost before the drainage of the ponded water no permafrost cooling occurred beneath the embankment the settlement of the two aces also differed significantly the creep of the ice rich permafrost layer immediately beneath the permafrost table was inferred as the main contribution of the settlement the temperature of the layer was the main factor determining the rate of settlement the results can help the hydro thermal analysis of engineering foundations built over permafrost and provide a reference for embankment construction and maintenance in permafrost regions with rich surface water

in situ monitoring of settlement at different layers under embankments in permafrost regions on the qinghai tibet plateau abstract ground temperature and settlement at different soil layers are monitored at four typical sections of the qinghai tibet highway qth and one section of a newly built test road nbtr in beilu river basin for the purpose of extensive investigation on the rather complicated mechanism of embankment settlement owing to several physical and mechanical processes i e settlement sources taking place in different soil layers in permafrost regions combining the ground temperature with borehole drilling exploration thawing temperatures of the permafrost layers in the five sections are determined and then characteristics of permafrost degradation are analyzed three types of sections are summarized to clarify different settlement sources in different soil layers on these bases characteristics of embankment settlement under different geological conditions are analyzed the influence of the seasonal changes of air temperature on embankment settlement is discussed since the two sections one on qth and the other on nbtr are both located in beilu river basin they are compared with respect to the variation of the main settlement source in the process of permafrost degradation the results help to understand the mechanism of embankment settlement

permafrost warming under the earthen roadbed of the qinghai tibet railway this paper investigates the stability of the earthen roadbed built in the warm and ice rich permafrost region the varying thermal regime of the subgrade and the ongoing settlement of the roadbed were observed at field the temperature data demonstrate that in warm and ice rich permafrost regions adoption of earthen roadbed results in warming of the underlying permafrost it is primarily because the earthen roadbed traps the warm season absorbed heat in the natural ground in addition the carried heat of the earthen roadbed that was constructed in warm season propagates downward to warm the underlying soil the warming permafrost layer promotes the roadbed settlement which was mostly linearly developed in the past five service years a comprehensive analysis for the varying thermal regime and the ongoing settlement shows that the unfrozen water liberated from the warming undrained layer experiences consolidation the deformation of the undrained soils is mainly responsible for settlement of the roadbed in comparison the temperature variation of this warming permafrost layer is found to be less beneath roadbeds protected by thermosyphons or crushed rock revetments the installation of thermosyphons into the earthen roadbed is recommended to prevent the further degradation of the underlying permafrost

role of evaporite withdrawal in the preservation of a unique coal bearing succession pennsylvanian joggins formation nova scotia the pennsylvanian joggins formation in the cumberland group of nova scotia is widely regarded as the world s best exposure of coal bearing carboniferous strata this 1 5 km thick coal bearing unit is famous for upright fossil lycopsid trees and is preferentially preserved in the athol syncline in the western cumberland basin new seismic profiles show that the athol syncline is atop a salt weld and that the joggins formation thins on the flanks of adjacent evaporite cored anticlines these observations indicate that during deposition of the joggins formation at least 1 km of syndepositional subsidence was facilitated by flow of underlying salt into the adjacent anticlines in contrast halo kinesis was mainly active during the mississippian in the eastern cumberland basin tatamagouche syncline minibasins were filled by mabou group sediments whereas the cumberland group is thin and lacks significant coals this basinwide comparison shows that much of the subsidence responsible for the preservation of the coal bearing joggins formation was the result of salt withdrawal at depth

fault development in transtension mccully gas field new brunswick canada abstract in the mississippian moncton sub basin new brunswick canada 3d seismic data reveal structure within the mississippian mccully gas field the asymmetric basin elongated ne sw is bounded to the se and nw by major dextral fault zones curved en echelon extensional faults strike ese wnw gentle folds trend ne sw contractional faults show varied orientations these features are all consistent with deformation of the basin in an environment of dextral transtension analogous faults in outcrops 13 km to the sw constrain sub seismic deformation and show that deformation occurred soon after deposition before complete lithification strike slip basins undergo concurrent extension contraction and rotation producing complex kinematic history which can be unraveled using the heaves and orientations of fault arrays based on measurements from the 3d data set a horizon in the gas field displays an apparent stretch of 1 14 and a perpendicular apparent shortening of 0 976 faults are oriented on average at 40 to the shear zone boundary these values show that the basin was deformed in transtension with overall angle of transtension alpha 47 to 50 however part of this deformation post dated the overlying sussex group removal of this component suggests alpha was in the range 62 65 during deposition of the horton group variations across the shear zone indicate that deformation was heterogeneous in space and time an initial large strike slip component transitioned to more divergent deformation as the deformation zone widened fault curvature likely reflects propagation during development of these heterogeneities overall the deformation reflects an oblique rift environment with n s extension that developed between major dextral strike slip faults these results show that with 3d seismic data sets it is possible to reconstruct details of strain history in transtensional basins that are potentially useful for understanding basin compartmentalization and fluid flow over time

truncation and translation of appalachian promontories mid paleozoic strike slip tectonics and basin initiation accreted terranes of the appalachian iapetan and peri gondwanan realms display structural trends that are mainly concordant with promontories and embayments in the laurentian margin indicating that during accretion the shape of the continental margin acted as a template around which accreted terranes were molded in north carolina and new foundland post accretion transcurrent motion appears to be recorded by displaced outboard portions of promontories no longer concordant with those in laurentia a bend in structural trends confined to the peri gondwanan realm at the north carolina south carolina state line is interpreted to represent the dextrally displaced outboard portion of the virginia promontory in newfoundland the hermitage flexure is interpreted as a dextrally displaced laurentian promontory that originated along strike to the northeast in both places promontories were truncated and dextrally translated for 220 250 km by a devonian mississippian orogen parallel transcurrent system which may well have extended for the length of the eastern laurentian margin south of the nearby st lawrence promontory extreme thinning of appalachian crust beneath the maritimes basin is consistent with extension at a releasing stepover estimates of extension are consistent with those obtained from promontory offsets

low angle faulting in strike slip dominated settings seismic evidence from the maritimes basin canada abstract the maritimes basin is an upper paleozoic sedimentary basin centered in the gulf of st lawrence canada early phases of basin formation included the development of partly connected sub basins bounded by high angle faults in an overall strike slip setting interpretation of reprocessed seismic reflection data indicates that a low angle detachment contributed to the formation of a highly asymmetric sub basin this detachment was rotated toward a lower angle and succeeded by high angle faults that sole into the detachment or cut it this model bears similarities to other highly extended terranes and appears to be applicable to strike slip and or transtensional settings

some effects of velocity variation on avo and its interpretation in recent years interest has increased in the interpretation of the amplitude variation of reflected signals as a function of offset avo a more meaningful relationship for interpreting reflection coefficients at the target horizon is amplitude variation with incident angle ava the challenge is to convert from avo to ava the effects of velocity variation in the overburden on amplitude variation with offset avo and on the final inversion of avo data into velocity density and poisson s ratio can be significant examples are given here for subsurface medium with a vertical velocity gradient range of 0 2s 1 to 0 8s 1 when the medium is treated as homogeneous in the conversion from avo to ava this velocity variation causes significant errors about 10 percent in both the gradient of ava and in the normal incident reflection coefficient such errors produce errors of similar magnitude in the inversion of ava data into the elastic parameters of velocity poisson s ratio and density the errors dep

well constrained seismic estimation of pore pressure with uncertainty the safe drilling of wells for hydrocarbon exploration or production requires that the wellbore pressure be maintained between the formation pore pressure and the maximum pressure the formation can withstand without fracturing this task is made more difficult when drilling in overpressured areas which require a quantitative predrill prediction of pore pressure with uncertainty to be made a predrill estimate of pore pressure can be obtained from seismic velocities using a velocity to pore pressure transform calibrated by offset well data however the uncertainty in velocity is often not quantified this example from the gulf of mexico uses seismic velocities with uncertainty derived by combining seismic velocities with well data den boer et al 2006 parameters in the velocity to pore pressure transform are estimated using seismic velocities density logs pressure information and well velocities derived by inverting time depth pairs from check shots in the area pore pressure and associated uncer

causes of pile foundation failure in permafrost regions the case study of a dry bridge of the qinghai tibet railway abstract pile foundations are widely used to support dry bridges crossing large extents of warm and ice rich permafrost zones along the qinghai tibet railway qtr the performance of these pile foundations are related to permafrost conditions surrounding the piles however the impacts of permafrost degradation on the stability of pile foundations have been rarely investigated in this study permafrost degradation has been assessed around several pile foundations in the tanggula mountain area along the qtr 15 years after the first field investigation in 2001 for the construction of the qtr this assessment is mainly based on drilling geophysical surveys and monitoring of the settlements affecting the pile foundations the permafrost in contact with the piles has significantly thinned after the piles were casted in place and put into service about 8 years ago moreover the thickness of residual permafrost is less than the embedment length for some piles and therefore the adfreeze bond between the piles and permafrost has significantly decreased in addition artesian sub permafrost groundwater has been observed around the middle lower and below the piles due to this sub permafrost aquifer the end bearing capacity of the piles and the friction between the piles and thawed soils have also probably decreased the applied load on the piles is now supported by the residual permafrost resulting in large settlements of the piles the thaw consolidation and settlement of degrading permafrost have also potentially contributed to the total settlement according to the investigation presented herein the occurrence of sub permafrost aquifer which was induced by permafrost degradation is the primary cause of pile settlements the failure mechanisms of the piles as revealed by this assessment are useful for the design and maintenance of piles in warm and ice rich permafrost regions moreover the use of geophysical methods for investigating pile foundation failure due to permafrost degradation has proved effective

assessment of frozen ground conditions for engineering geology along the qinghai tibet highway and railway china abstract the qinghai tibet highway and railway the corridor across the qinghai tibet plateau traverses 670 km of permafrost and seasonally frozen ground in the interior of the plateau which is sensitive to climatic and anthropogenic environmental changes the frozen ground conditions for engineering geology along the corridor is complicated by the variability in the near surface lithology and the mosaic presence of warm permafrost and talik in a periglacial environment differential settlement is the major frost effect problem encountered over permafrost areas the traditional classification of frozen ground based on the areal distribution of permafrost is too generalized for engineering purposes and a more refined classification is necessary for engineering design and construction a proposed classification of 51 zones sub zones and sections of frozen ground has been widely adopted for the design and construction of foundations in the portion of the corridor studied the mean annual ground temperature magt near surface soil types and moisture content and active faults and topography are most commonly the primary controlling factors in this classification however other factors such as local microreliefs drainage conditions and snow and vegetation covers also exert important influences on the features of frozen ground about 60 of the total length of the corridor studied possesses reasonably good frozen ground conditions which do not need special mitigative measures for frost hazards however other sections such as warm and ice rich or saturated permafrost particularly in the sections in wetlands ground improvement measures such as elevated land bridges and passive or proactive cooling techniques need to be applied to ensure the long term stability of thermally unstable thick permafrost subsoils and or refill with non frost susceptible soils due to the long history of the construction and management of the corridor by various government departments adverse impacts of construction and operation on the permafrost environment have been resulted it is recommended that an integrated executable plan for the routing of major construction projects within this transportation corridor be established and long term monitoring networks installed for evaluating and mitigating the impact from anthropogenic and climatic changes in frozen ground conditions

new insight on the geometry and evolution of the moncton sub basin from 3d seismic reflection data in the mccully area new brunswick canada abstract within the maritimes basin of eastern canada the onshore moncton sub basin is one of the ne trending second order depocenters that recorded a complex tectonic history from late devonian to late carboniferous analysis of a 3d seismic volume in the mccully gas field area exemplifies the complex interplay between mainly continental sedimentation and several tectonic episodes that contribute to a net extension or shortening in an overall strike slip setting the new interpretation demonstrates the role of normal faults oblique to the sub basin axis in initial phases of sub basin development and their influence on the deposition of the upper devonian lower mississipian horton group sediments a subsequent episode of transpression is recorded by syn folding growth strata base of the mississipian sussex group preserved on both flanks of an anticline that belongs to a fold system that shows an en echelon geometry relative to sub basin bounding faults deposition of a marine interval middle mississipian windsor group including evaporitic strata is succeeded by an halokinetic growth succession upper mississipian pennsylvanian mabou group found in minibasins that formed through drape folding downbuilding in response to salt walls development this polyphased history illustrates the complexity of strike slip basins that are often controlled by structures with different geometry and kinematics in time and or space

in situ creep of frozen soil fenghuo shan tibet plateau china field measurements of frozen soil creep in the upper 3 0 m of permafrost indicate that creep occurs in both winter and summer between 1992 and 1993 the mean rate of creep ranged from 0 44 cm at 1 6 m depth to 0 16 cm at 2 8 m depth but there was extreme variability creep parameters n and a as defined by the power flow law were calculated from field data parameter n ranged between 1 96 and 2 29 and increased with depth while a decreased with depth comparisons of creep rates for different permafrost environments suggest that ground temperature largely controls the magnitude of permafrost creep key words permafrost creep parameters tibet plateau

creep behaviour of undisturbed clay permafrost an in situ analysis of naturally occurring creep has been carried out at the proposed canadian arctic gas pipeline crossing of great bear river in the northwest territories this is the last of fou

typical embankment settlement heave patterns of the qinghai tibet highway in permafrost regions formation and evolution abstract the qinghai tibet highway qth in china has been experiencing a serious embankment settlement heave for more than half a century the settlement heave is resulted from several mechanical processes taking place in different soil layers in this paper four typical settlement heave patterns of road embankments in permafrost regions namely steady low rate fluctuate down step and steady high rate are proposed based on 3 year monitored data of embankment settlement heave and ground temperature at four road sections as well as previous published data of the qth their formation mechanisms and evolution trend in the process of permafrost degradation are discussed from the viewpoints of engineering geology and mechanical process based on the clarification of the deformation characteristics of different soil layers of a typical road embankment the results show that the four patterns are caused by the negligible settlement heave freeze thaw cycling in an open condition consolidation of the thawed permafrost layers and creep of warm permafrost layers respectively the pattern will change from one to another during the process of permafrost degradation which will become very complex with the occurrence of frost heave the results can help revealing the deformation mechanism of road embankments in permafrost regions and can benefit road construction and maintenance in the future

late paleozoic strike slip faults in maritime canada and their role in the reconfiguration of the northern appalachian orogen major late paleozoic faults many with documented strike slip motion have dissected the ordovician devonian appalachian orogen in the maritime provinces of atlantic canada activity alternated between east west faults minas trend and ne sw faults appalachian trend nw se faults canso trend were probably conjugate to minas trend faults major dextral movement on faults with appalachian trend in total between 200 and 300 km began in the late devonian this movement initiated the maritimes basin in a transtensional environment at a releasing bend formed around a promontory in the laurentian margin and thinned the crust accounting for the major subsidence of the basin appalachian trend strike slip continued in the mississippian but was accompanied by major movement on e w minas trend faults culminating around the mississippian pennsylvanian boundary juxtaposing the meguma and avalon terranes of the appalachians close to their present day configuration however strike slip continued during the pennsylvanian permian interval resulting in transpressional deformation that reactivated and inverted earlier extensional faults a final major episode of transtension mainly sinistral occurred during the mesozoic opening of the atlantic ocean restoration of movements on these faults amounting to several hundred kilometers of slip explains anomalies in the present day distribution of terranes amalgamated during early paleozoic appalachian tectonism in the restored geometry the nashoba and ellsworth terranes of ganderia are adjacent to one another and the meguma terrane lies clearly outboard of avalonia a restored post acadian paleogeography not the present day geometry of the orogen should be used as a basis for reconstructions of its earlier paleozoic history

effect of sunny shady slopes and strike on thermal regime of subgrade along a high speed railway in cold regions china abstract ground temperature and deformation of embankment were monitored at typical sections of the harbin qiqihar high speed railway hsr to investigate complex causes of differential embankment deformation due to sunny shady slopes and route strike in cold regions maximum frozen depth ground temperature frost heave and thaw settlement of the embankment in the sunny and shady sides were analyzed relative to measurement dates and then a numerical model for the embankment temperature filed was also established on these bases the influence of route strike on the embankment thermal regime and its mechanism were then revealed and proper engineering countermeasures were proposed to mitigate the transverse embankment thermal difference the formation mechanism of the differential deformation due to sunny shady slopes was discussed the results showed that both temperature and maximum frozen depth of the sunny side were greater than the shady side whereas the cumulative frost heave of the sunny side was less than the shady side with opposite trends found for the cumulative thaw settlement the temperature difference between the sunny and shady shoulders decreased gradually with increasing strike angle the findings are potentially helpful for better understanding differential embankment deformation in cold regions as well as for improving hsr embankment quality and operational safety

damage and mitigation of railway embankment drainage trench in warm permafrost a case study abstract warm permafrost sites such as those extensively existing on the qinghai tibet plateau present a challenging geological environment for infrastructure engineering a reliable drainage system is crucial for long term stability of railway embankment in such sites this paper presents a case study of the drainage trench along the qinghai tibet railway embankment the damage patterns to the precast u shaped concrete lining originally installed in 2008 is described a coupled thermal hydro mechanical finite element model and its results including temperature and stress distributions during ground freezing are presented parametric study was also conducted to assess the sensitivity of these results to soil water content and the stiffness of the u shaped concrete lining based on the modeling results a new design including a coarse grained transition layer and impermeable geotextile was proposed for field experiment and its field performance six years after its construction is presented the damage to the original trench was characterized by disjointed lining segments and extensive longitudinal cracks mostly located below the mid height of the linings factors contributing to the damage include challenging construction conditions uneven thaw settlement and frost heave stress modeling results show that significant horizontal frost heave stress can develop on the outside surface of the u shaped lining and hence results in large tensile stress at the outside edge of the u shaped lining the tensile stress may exceed the lower bound of the concrete flexural strength and induce longitudinal cracks at depths below the mid height of the lining which agrees well with field observation field performance of the new trench design during a period of six years shows that the improved design performed well and can be adopted for future engineering practice in similar challenging geology conditions

structural variety and tectonic evolution of strike slip basins related to the philippine fault system northern luzon philippines the northern part of the philippine fault zone in luzon corresponds to a complex braided system of left lateral strike slip faults the nw oriented main active branch which emerges from the philippine sea splits into an array of north striking splays responsible for the tectonic evolution of the central cordillera this complex fault pattern has favored local stress field variations strike slip basins have evolved in this framework along or in the vicinity of the main splays of the philippine fault apart from the classical pull apart tectonics on a releasing fault termination overlap or bend we describe other mechanisms such as the strike slip tilting or the warping of a strip limited by two strike slip faults the strike slip basins are good recorders of the evolution of the philippine fault system those located along the north striking cordilleran faults individualized in late early pliocene to pleistocene time when the present day philippine fault initiated but their main control is the fault shape acquired in upper middle miocene time the recent tectonic evolution of the fault system is best recorded in central luzon where the active basins trace an asymmetrical v shape with the longest branch trending ne parallel to the east luzon trough and the shortest one trending nw related to the philippine fault both the fault pattern and the basin distribution demonstrate the influence of the benham rise in the tectonic evolution of luzon the structural setting is interpreted as the result of an early miocene collision event between the benham rise and the eastern margin of luzon and subsequent inception of the nw striking strand of the philippine fault the present locations of the basins result from the interaction between the structural heritage and the present day regional plate motion