lithospheric processes and products in the southern canadian cordillera a lithoprobe perspective analyses of lithoprobe and other data from southwestern canada provide new insights on how this portion of the cordillera formed during plate convergence along the western margin of north america crustal rocks are detached from their mantle lithosphere which must have been consumed during subduction detachment occurred at or near the base of the crust beneath the intermontane and or omineca belts probably along the tips of tectonic wedges while the rocks were still outboard of the relatively cool mechanically rigid north american craton during the late cretaceous and early tertiary rotation of detached rocks caught between the north american craton and the oceanic plates accounts for some apparently conflicting results between paleomagnetic data that indicate large northward translation of rocks in the western cordillera and regional geological features that appear to preclude comparable amounts of translation of rocks in the eastern cordillera during the same time interval transpression assoc

tectonic implications of 40ar 39ar muscovite dates from the mt haley stock and lussier river stock near fort steele british columbia the mt haley and lussier river stocks are located northeast of cranbrook b c near the south end of the western main ranges of the southern canadian rocky mountains both are multiphase potassium feldspar porphyritic monzonite plutons that intrude lower paleozoic miogeoclinal strata they crosscut and thermally overprint the lussier river fault and the thrust and fold structures in the east flank of the purcell anticlinorium and the west limb of the porcupine creek anticlinorial fan structure muscovite from the mt haley stock yielded a 40ar 39ar plateau age of 108 2 0 7 ma 2 and a single crystal step heating analysis of muscovite from a skarn in the metamorphic aureole adjacent to the lussier river stock gave a plateau date of 108 7 0 6 ma 2 these dates constrain the timing of thrusting and folding in this portion of the western rocky mountains and of the displacement along the lussier river st mary fault to pre middle albian

transverse folding and superposed deformation mount fisher area southern canadian rocky mountain thrust and fold belt a northeast facing panel of middle proterozoic purcell supergroup strata occurs beneath cambrian and devonian strata along the east side of the rocky mountain trench in the mount fisher area anomalous northeast trending folds faults and cleavage that formed during cretaceous paleocene deformation occur in this panel in the northern part of the area the dominant structure in the southern part is the northwest trending lizard segment of the mesozoic hosmer nappe which folds an older north trending cleavage that probably formed during the east kootenay orogeny 1300 1350 ma thickness and facies variations in purcell strata and changes in the level of erosion beneath the sub devonian unconformity imply that many of the important structural boundaries in the mount fisher area and also the normal faults along the southern rocky mountain trench follow the locus of older structures that were active in the middle proterozoic and the early paleozoic the anomalous northeast trending structures in the moun

structure and evolution of the northern potwar deformed zone pakistan the northern potwar deformed zone npdz is part of the active foreland fold and thrust belt of the salt range and potwar plateau in northern pakistan about 500 km of seismic reflection profiles are integrated with surface geologic and drilling data to examine the deformation style and structure of the npdz with particular emphasis on history of deformation of the dhurnal oil field the seismic lines suggest that the overall structure of the eastern npdz is a duplex structure developed beneath a passive roof thrust the roof thrust is generated from a tipline in the miocene murree formation and the sole thrust is initiated from the same eocambrian evaporite zone that extends 80 km southward beneath the soan syncline and salt range the dhurnal oil field structure is a pop up at the southern margin of the npdz and developed beneath the passive roof thrust the passive roof thrust crops out just north of dhurnal on the steep northern limb of the soan syncline an overstep passive roof thrust sakhwal fault is interpreted west of dhurnal this fault developed due to

ndsr isotopic study of proterozoic to triassic sediments from southeastern british columbia abstract sedimentary rocks from the southeastern canadian cordillera varying in age from mid proterozoic to triassic have been analysed for their nd isotopic composition e nd t values range from 1 5 to 17 2 and nd model ages t dm nd vary from 1 00 to 2 32 ga much in excess over their stratigraphic ages the difference between the two ages ranges from 0 43 to 1 93 ga decreasing as the sediments become stratigraphically older nd isotopic compositions of sediments suggest that there are two distinct continental sources of sediments in the cordilleran miogeocline a an older source e nd 0 from 20 3 to 23 8 with apparent crustal residence ages of 2 26 2 32 ga and b a younger source average e nd 0 14 0 with the crustal residence age of about 1 8 ga the older residence ages are interpreted to be due to mixtures of materials from the archean and proterozoic crusts sediments belonging to the laib formation lower cambrian and lower clastic part of the milford group namurian appear to have derived from an archean continental segment with some admixture of sediments from the early proterozoic source the younger crustal source which seems to be the principal supplier of sediments for most of the stratigraphic units aldridge formation middle proterozoic horsethief creek group upper proterozoic hamill and lardeau groups lower cambrian nelway formation middle cambrian active formation ordovician and part of milford group is not the archean canadian shield immediately to the east recent subsurface mapping of the alberta basement beneath the phanerozoic sedimentary cover using u pb zircon dating of igneous lithologies 1 has established the extensive archean and early proterozoic crustal provinces it is proposed here that the early proterozoic province of west central alberta is the most likely source of the easterly derived sedimentary rocks of the cordilleran miogeocline with t cr ages from 1 94 to 1 50 ga on the basis of sedimentologic tectonic and isotopic evidence we suggest that the younger sediments could be to some extent recycled older sediments for the triassic slocan and ymir groups eastern part of quesnel terrane sedimentologic lithologic tectonic and isotopic evidence suggest the source was a western one with about 1 8 ga crustal residence age comparison of the crustal residence ages with stratigraphic ages shows the best fit nd evolution curve for the cordilleran miogeocline approximately coincides with the continental growth curve deduced for the north atlantic province and similar to the growth curve for gondwana during the phanerozoic this curve also passes through the north american composite the levelling off of crustal residence ages for the mid proterozoic to triassic sediments at about 1 8 ga supports the idea of negligible crustal growth since at least 1 7 ga the average crustal residence age of the modern miogeoclinal and cratonic sediments

the tsunami mode of a flat earth and its excitation by earthquake sources summary tsunami generation by earthquakes in a flat isotropic elastic vertically stratified earth underlying a uniform depth incompressible ocean can be studied in terms of the tsunami normal mode of the combined ocean solid earth system we derive in a way that demonstrates their natural extension from traditional approaches to tsunami theory the equations and boundary conditions governing the tsunami mode displacement and stress eigenfunctions then solve the excitation problem by a variational method this leads to a straightforward expression for the far field tsunami displace ments due to a point moment tensor source in the solid earth numerically computed spectra and waveforms reveal clearly the dependence of the far field tsunami on the source depth duration moment and mechanism

physical and chemical properties of the sulphur mountain thermal springs banff national park and implications for endangered snails nine thermal springs in three groups occur along the flank of sulphur mountain in banff national park the principal recharge zone is suggested to be above 2000 m elevation on mount rundle circulation depths are estimated to be 3 2 0 6 km and discharge is focused along the sulphur mountain thrust springs show constant temperature and total dissolved solids load throughout the winter whereas both drop in association with spring snowmelt the degree and timing of temperature drops are a function of elevation with the highest springs showing the earliest and most significant temperature drop the highest elevation springs also show the greatest seasonal variability in water chemistry unusual seasonal flow stoppages of these springs are related to extreme low precipitation years the biogeochemistry of the thermal springs and population fluctuations of the endemic and endangered banff springs snail physella johnsoni are strongly related to seasonal variability in flow rates changes in redox condi

evolution of the triangle zone in the rocky mountain foothills near coalspur central alberta a triangle zone which commonly occurs along the external margin of a foreland thrust and fold belt with a buried thrust front is underlain by a subhorizontal blind foreland verging thrust that ends against a foreland dipping hinterland verging thrust these contemporaneous thrusts active towards the end of orogenesis enclose an intercutaneous wedge that moved towards the foreland during orogenesis a triangle zone evolves through periodic replacement of faults bounding the active wedge replacements occur in cycles during each of which a lower fault tends to be replaced by one in a lower stratigraphic horizon an upper fault by one farther away from the foreland each cycle ends with the lower fault moving to a younger horizon where it joins a new more external upper fault near coalspur the triangle zone exposes the remnants of several wedges involving upper cretaceous and paleocene molasse most of these wedges developed during the last cycle but one and have a combined displacement of about 5

lateral and vertical changes of deformation style in the osen roa thrust sheet oslo region abstract changes in deformation style and amounts of shortening in the osen roa thrust sheet of the oslo region occur vertically and laterally approaching the thrust front in the south deformation in the cambromiddle ordovician sequence passes laterally from closely spaced imbricates in the north 50 60 shortening through triangle pop up and imbricate zones toward the south 20 37 shortening to widely spaced zones of deformation up to 20 shortening approaching the thrust front changes in deformation style are attributed to changing boundary conditions across the klekken thrust declining end of orogenic forces and an increase in thickness of competent units in the ordovician rocks to the south vertical changes in deformation style are attributed to the increasing percentage of competent units upward in the cambro silurian sedimentary rocks in the north the accompanying decrease in shortening upwards requires a structurally necessary upper detachment horizon to separate folded late middle ordovician silurian sediments from imbricated early cambro middle ordovician sediments below while southward in the oslo area the upper detachment needs to be placed between silurian and cambro ordovician units finally in eiker with less than 20 shortening the whole cambrosilurian sequence appears to have deformed as a single unit in the northern oslo region the upper detachment probably has a backthrust sense of motion above an imbricate stack passive roof duplex further south the upper detachment is probably directed toward the foreland

understanding kinematic data from the moine thrust zone in terms of a kinematics based mathematical model of deforming thrust wedges abstract a salient recess pair along the moine thrust zone exhibits significant lateral kinematic variations specifically the more steeply dipping portion of the thrust surface associated with the recess shows evidence for greater strain magnitudes and more out of the plane motion than the adjoining salient additionally a subset of the grain shape data has grain shape approximations with their long axes oriented perpendicular to the regional transport direction to more fully understand these kinematic features we developed a kinematics based mathematical model of thrust wedge deformation our numerical model predicts an increase in strain magnitude as well as non plane strain flattening in the region of a thrust ramp consistent with the strain patterns observed within the recess along the moine thrust zone furthermore in the absence of a lateral confining boundary condition much of the model thrust wedge experiences transport perpendicular maximum extension except for the region closest to the thrust where simple shear deformation is dominant using our numerical model we predict the amount of lateral confining strain needed to induce plane strain deformation ps as well as the amount of lateral confining strain necessary to make the long axis of the strain ellipsoid parallel with the transport direction parallel we have found that the incremental parallel can be as much as 42 of the incremental strain magnitude thus we consider transport perpendicular lineations like those seen along the moine thrust zone to be the result of lateral confining boundary conditions that are weak enough to allow transport perpendicular maximum extension

middle jurassic exhumation along the western flank of the selkirk fan structure thermobarometric and thermochronometric constraints from the illecillewaet synclinorium southeastern british columbia new thermobarometric and thermochronometric data from the illecillewaet synclinorium a broad regional southwest verging structure in the western flank of the selkirk fan structure indicate that accretion of the intermontane superterrane resulted in deep burial 20 25 km of the outer margin of ancestral north america and that subsequent southwest verging folding and thrusting were accompanied by rapid exhumation southwest verging folding of lower paleozoic rocks in the illecillewaet synclinorium was initiated during regional peak metamorphic conditions at 6 7 kbar crystallization of late synkinematic granitoid plutons that intrude the illecillewaet synclinorium also occurred at pressures of 6 7 kbar however equilibration of the contact aureoles of the plutons occurred at 3 3 5 kbar during the latter stages of the southwest verging deformation evidently a decompression on the order of 3 kbar occurred concurrently with southwest verging folding and thrusting in the illecillewaet synclinorium thermochronometric analyses further indicate that plutonic rocks from the illecillewaet synclinorium cooled rapidly between times of crystallization and times of ar closure in biotite regional relationships indicate that the accretion of the intermontane superterrane to the edge of the north american margin in southeastern british columbia occurred between 187 and 173 ma toarcian bajocian subsequent southwest verging deformation occurred approximately between 173 and 168 ma bajocian bathonian thus the removal of at least 10 km of rocks from above the illecillewaet synclinorium inferred from thermobarometric data occurred approximately between 173 and 168 ma rapid denudation of the selkirk fan structure was probably the result of synorogenic extension or extensional collapse contemporaneous with the development of southwest verging structures at deeper levels of the orogen the data presented here indicate that all significant deformation and most of the exhumation along the western flank of the selkirk fan structure were complete by late middle jurassic time after the middle jurassic the selkirk fan structure must have been transported passively northeastward along the basal decollement of the cordilleran foreland thrust and fold belt together with the intermontane superterrane as the fold and thrust belt tectonically overrode the margin of the north american craton

the irish variscides a fold belt developed within a major surge zone an arcuate fold belt characterizes the irish variscides south of the dingle dungarvan line the folds are cross cut by numerous faults which tend to be sinistral in the west and dextral in the east clockwise transection of major fold axes by minor folds and by cleavage has been recorded in the east while anticlockwise transections are common in the west these and other features suggest that north south dextral and sinistral shearing occurred in the east and west respectively this is considered to be a consequence of the morphology of the munster basin which allowed the development of a surge zone in the centre of the fold belt the variscan sole thrust is believed to lie at the base of or within the old red sandstone however to the east thinning of the upper palaeozoic cover sequence forces the sole thrust to cut down laterally stratigraphic section into lower palaeozoic basement in the depocentre the sole thrust surged ahead by propagating along bedding surfaces or possibly a devonian carboniferous extensional detachment beneath the basin while to the east and offshore to the west its propagation was inhibited by the absence of easy decollement horizons within the basement consequently the tip line became strongly arcuate and the thrust developed into a surge zone the sole thrust propagated northwards by stick slip processes much of the deformation within the cover sequence occurred during sticking events particularly fold tightening and accommodation faulting

variszische duktile tektonik im bohmischen massiv die verformungsanalyse und richtungsverteilung der streckungslineationen in den duktilen bereichen des bohmischen massiv zusammen genommen mit der lage der foliationsflachen deuten darauf hin das die blattverschiebungen wahrend der variszischen deformation die entscheidende rolle gespielt haben die kompatibilitat der deformation im gesamtbereich wurde durch uberschiebungen und transpression in den durch die blattverschiebungen begrenzten blocke erreicht das variszische tektogen wurde als blattverschiebungsorogen auf einer kontinentalen oberproterozoischen kruste angelegt die zonen mit intensiver krustenverkurzung und damit groster krustenmachtigkeit sind durch weitraumige anatexis und granitische intrusionen gekennzeichnet

the possible role of fluids for the structuring of the continental crust abstract some well known seismic reflectivity patterns of continental crusts characterize specific tectonic terranes the role of fluids in enhancing or destroying such structures is studied seismicity is strongly dependent on the different pore pressure of fluids in intraplate settings in strike slip or extensional areas hydrostatic pore pressure seems to be approached in accordance with standard rheological models and standard seismicity depth distributions in suture zones or zones of developing loads possibly also along zones of near horizontal normal faults extremely high pore pressure develops which approaches lithostatic values they are accompanied by a number of weakening processes with enhanced shear and reduced viscosity these values correlate with low seismic velocities v p in accordance with an empirical v p relationship

thrust tectonics thin skinned or thick skinned and the continuation of thrusts to deep in the crust abstract the paper analyses the geometry of thin skinned thrust zones where the thrusts shallow out at depth and of thicker skinned fault zones where much of the crust is involved and where the thrusts are frequently observed to become steeper downwards in the interiors of many orogenic belts the steep dip of faults is not original but due to the folding above lower decoupling zones the energy involved in the internal deformation of hanging wall rocks may prohibit many faults becoming more shallow upwards such shallowing upwards faults may occur in more ductile rocks to maintain compatibility between zones which have experienced different deformation intensities but displacements on the faults are unlikely to be large another mechanism for producing faults which steepen downwards is proposed for the major thrusts which form the southern margin to the himalayas these carry large thicknesses 30 to 100 km of crustal and upper mantle rocks to the south causing flexuring and isostatic depression of the indian plate the steeply dipping thrusts are not footwall ramps these may be some distance behind the steepened zone this thrust induced isostatic bending of the crust has important implications when considering regional seismic interpretations as well as thrust mechanics and kinematics

deformation of stratiform znpb barite deposits in the northern canadian cordillera abstract the major stratiform sediment hosted zn pb barite deposits of the northern canadian cordillera occur in the palaeozoic selwyn basin kechika trough they formed in euxinic fine grained clastic dominated extensional basins that developed within the carbonate platform of the passive margin of ancestral north america during the late jurassic to mid cretaceous these basins and the stratiform ore deposits were subjected to low greenschist facies regional metamorphism and fold and thrust deformation as they were incorporated into the western part of the rocky mountains mackenzie mountains foreland fold and thrust belt this paper summarises the results of detailed field and microscopic studies on four of these deposits the tom deposit the howards pass deposit the cirque deposit and the driftpile creek deposit the dominant mineralogy of these deposits is sphalerite galena pyrite and in some cases significant barite is present low greenschist grade metamorphism and deformation is characterised by cataclastic flow and brecciation in coarse grained massive pyritic sulphides and by folding recrystallisation and cleavage development in fine grained sulphides and barite relict primary depositional diagenetic structures are found within the orebodies deformation is characterised by strong pressure solution fabrics in barite in fine grained laminated pyrite layers and in mixed sulphide carbonate beds marked local transposition is found with significant remobilisation of galena barite and pyrite the deformation mechanics of these sulphide barite deposits are illustrated using schematic deformation mechanism maps

tsunami speed variations in density stratified compressible global oceans 1 tsunami speed variations in the deep ocean caused by seawater density stratification is investigated using a newly developed propagator matrix method that is applicable to seawater with depth variable sound speeds and density gradients for a 4 km deep ocean the total tsunami speed reduction is 0 44 compared with incompressible homogeneous seawater two thirds of the reduction is due to elastic energy stored in the water and one third is due to water density stratification mainly by hydrostatic compression tsunami speeds are computed for global ocean density and sound speed profiles and characteristic structures are discussed tsunami speed reductions are proportional to ocean depth with small variations except in warm mediterranean seas the impacts of seawater compressibility and the elasticity effect of the solid earth on tsunami traveltime should be included for precise modeling of transoceanic tsunamis

mesozoic deformation in the nevada test site and vicinity implications for the structural framework of the cordilleran fold and thrust belt and tertiary extension north of las vegas valley detailed studies in the cp hills and mine mountain area of the nevada test site nts together with analysis of published maps and cross sections and a reconnaissance of regional structural relations indicate that the cp thrust of barnes and poole 1968 actually comprises two separate oppositely verging mesozoic thrust systems 1 the west vergent cp thrust which is well exposed in the cp hills and at mine mountain and 2 the east vergent belted range thrust located northwest of yucca flat regional structural relations indicate that the cp thrust forms part of a narrow sigmoidal belt of west vergent folding and thrusting traceable for over 180 km along strike the belted range thrust represents earlier mesozoic deformation that was probably related to the last chance thrust system in southeastern california as suggested by earlier workers a reconstruction of the pre tertiary geometry of the cordilleran fold and thrust belt in the region between the nts and the las vegas range bears a close resemblance to other regions of the cordillera and suggests that west vergent deformation developed in the hinterland of a part of the sevier fold and thrust belt characterized by substantial structural relief reconstruction of the fold and thrust belt also suggests that previous estimates of upper crustal tertiary extension north of the las vegas valley shear zone e g 80 guth 1981 are 2 or 3 times too large

mesoscale and regional kinematics of the northwestern yalakom fault system major paleogene dextral faulting in british columbia canada the northwestern yalakom fault system yfs lies on the eastern margin of the coast belt in southwestern british columbia the yalakom fault is the most significant structure in the fault system with at least 115 km of dextral slip mostly of early tertiary age the nw yfs is up to 25 km wide and is bounded on the southwest by the tchaikazan fault zone which had 5 km or more of dextral slip kinematic and paleostress analysis of mesofaults and map scale structures shows that secondary faults within the nw yfs had both dextral and sinistral oblique slip three large synclines had increasing amounts of clockwise vertical axis rotation from southeast to northwest block rotation between two synthetic strike slip faults with large offset yalakom and moderate offset tchaikazan is similar to current kinematics between the san andreas and san jacinto faults in southern california the nw yfs was active from latest cretaceous to mainly eocene time and postdates early late cretaceous thrust faulting to the southwest early stage mesofaults are compatible with the thrust belt and suggest that open folds developed in the foreland of the thrust belt before strike slip faulting commenced the abrupt northwest termination of the yfs may be related to extension within the adjacent tatla lake metamorphic complex some dextral slip may have been transferred farther northwest through the coast belt but these structures have not been documented in west central british columbia most of the 120 km of dextral slip on the yfs was transferred to the north via a mosaic of normal and strike slip faults in central british columbia thus the yfs forms the southwestern margin of a broad zone of transtensional structures that extends to the tintina rocky mountain trench fault zone these structures accommodated northwestward displacement of the northwestern cordillera in paleogene time

outcrops as guides to subsurface natural fractures example from the nikanassin formation tight gas sandstone grande cache alberta foothills canada abstract outcrop studies are essential for understanding subsurface fractures because some key attributes such as length and height distribution cannot be measured using wellbores discrepancies between outcrop and subsurface fracture attributes arise because loading paths due to burial exhumation and thermal paths differ consequently even where rock type and structural setting are close matches differences may exist in mechanical properties and fracture growth here we investigate petrologic criteria and disseminated arrays of quartz filled microfractures as tools for comparing and contrasting fractures in outcrop with those as sampled by core for tight gas sandstones fracture cements are key diagnostic criteria for proving correspondence between outcrop and core we offer guidelines on selecting suitable outcrop analogs that differ markedly from current practice our illustration uses outcrops and core samples of late jurassic to early cretaceous nikanassin formation a tight gas sandstone but aspects of the outcrop vetting procedure can be applied to other rock types in some core and outcrops nikanassin formation fractures contain quartz and ankerite cement assemblages crack seal and rind textures and aperture size distributions that show that the outcrop and subsurface localities we examined share the same fracture stratigraphy and similar diagenesis these outcrops can thus be used to measure attributes including those that are unlikely to be captured in core such as fracture height and length distributions relative and absolute fracture intensity with structural position and degree of fill by synkinematic cement in our example absolute fracture intensity and distribution of postkinematic carbonate cements are site specific and differ between outcrop and core but in ways that can be quantified

duplex structures in the lewis thrust sheet crowsnest pass rocky mountains alberta canada abstract the lewis thrust sheet of the southern canadian rocky mountains contains many spectacular examples of small scale duplex structures this paper presents the results of a detailed analysis of such structures found in the mississippian carbonates of the banff formation at crowsnest pass southwestern alberta foreland dipping hinterland dipping and antiformal stacked duplexes are found in the hangingwall of the lewis thrust out of sequence thrusts back thrusts and folds that push out of the plane of the cross section termed lateral lobes give rise to complex internal geometries dominant slip vectors are towards 080 090 but the complex fault geometries have generated significant variations in slip away from this direction the duplex structures occur as discrete thrust fault bounded packages with each package having different slip vectors the panels above and below the duplex structures show consistent slip vectors towards 080 090 whereas the duplexes exhibit a wide scatter of slip vectors from 350 160 the stacking of duplexes with many horses can be likened to the stacking of many inverted soup bowls herein termed turtle back structures and will involve a wide scatter of slip directions particularly if the horses are of limited lateral extent such a stacking mechanism involving out of section movement invalidates the assumption of two dimensional plane strain in the plane of the cross section that contains the regional tectonic transport direction correctly balanced cross sections cannot be constructed through such stacked duplex structures as described in this paper

aspects of the three dimensional structure of the alberta foothills and front ranges ever more detailed subsurface images of the alberta foothills and front ranges obtained from improving seismic techniques coupled with an ever expanding base of information from deep wells and improved structural analysis techniques have produced an understanding of fold thrust deformation that is probably applicable to other fold thrust belts comprehensive subsurface data obtained by the petroleum industry are used to outline and analyze the three dimensional configuration of fold thrust deformation of paleozoic carbonate strata these data indicate that displacement changes smoothly along individual thrusts but displacement changes along strike may be large marked by considerable horizontal rotation 20 30 or more of hanging wall stratigraphic cutoffs relative to the footwalls stacking of thrusts with varying displacements has produced summed horizontal rotations of hanging wall cutoffs of as much as 45 50 the three dimensional trajectories of the thrusts through the stratigraphy are smooth for large distances interrupted by abrupt offsets at lateral and oblique ramps these are more common than previously realized the intersections of these ramps with other thrusts produce complex three dimensional links between thrusts with concomitant abrupt displacement changes some simple examples of these linkages are examined with a three dimensional geometric analysis the predictions of the analysis are consistent with structural geometries observed in two case studies of subsurface structures the links at lateral ramps imply simultaneous displacement on parts of the thrusts connected by the ramps since the ramps extend downdip 20 km or more displacement occurred simultaneously on structures occupying relatively interior and exterior positions in the thrust belt the smooth and long radius of curvature folding of many upper detachments indicated by reflection seismic data also is consistent with simultaneous or overlapping periods of motion on groups of thrusts distributed along regional dip most major alberta foothills thrust sheets terminate southward at lateral ramps at the paleozoic level the abrupt southwest northeast offsets at these features are most clearly apparent on a palinspastic reconstruction these offsets cause the paleozoic deformation front to step out east and northeast around the southern and eastern margins of the main arc of the foothills in contrast northward thrust terminations at the paleozoic level commonly occur at both tip lines and lateral ramps subsurface data reveal that there have been some misconceptions regarding large scale structural relationships for example the mcconnell and livingstone sheets are actually portions of the same thrust sheet as are the bighorn and nikanassin sheets when corrected for these misconceptions the data from the alberta foothills suggest that maximum displacement has a nonlinear relationship to thrust length although a linear relationship cannot be ruled out

strain analysis and fold shape in a limestone layer and implications for layer rheology abstract folds are developed in thin limestone layers within slates of the mckay formation exposed to the east of the rocky mountain trench british columbia canada they possess geometrical characteristics expected of development by buckling strain in the profile plane of a selected fold is similar to that predicted by tangential longitudinal strain except that magnitudes are too low for the observed curvature this is attributed to inhomogeneity of strain on the scale of measurement largely because of pressure solution material removed by pressure solution from the inner arc of the fold appears to form veins perpendicular to the hinge a direction of tectonic stretching bedding parallel stylolites developed diagenetically prior to tectonism layer parallel shortening during the initiation of buckling was less than 20 and probably less than 10 the mean arclength thickness ratio is 6 5 and 7 1 with a dispersion of 0 48 and 0 37 for local and regional populations of 29 and 212 folds respectively application of buckling theory to this data suggests that folding followed a non linear flow law the viscosity contrast between limestone and slate would be higher and the power law exponent lower if initial irregularities in the layers were in the form of a constant amplitude spectrum rather than one of white roughness the data do not allow a choice of initial amplitude spectrum to be made nor do they closely constrain estimates of n the power law exponent and viscosity contrast deformation in the limestone layers was accommodated by intracrystalline flow twin gliding pressure solution and extensional veining the last two linked by diffusive mass transfer the first two dominated deformation in the profile plane of the fold and the last in association with fracturing allowed for extension parallel to the hinge experimental and theoretical considerations suggest that deformation by a combination of these processes should be non linear the non linear flow law deduced from buckling analysis is consistent with expectations based on observations of active deformation mechanisms

zebra dolomitization as a result of focused fluid flow in the rocky mountains fold and thrust belt canada discordant zebra dolomite bodies occur locally in the middle cambrian cathedral and eldon formations of the main ranges of the canadian rocky mountains fold and thrust belt they are characterized by alternating dark grey a and white b bands forming an abba diagenetic cyclicity these bands developed parallel to both bedding and cleavage dark grey a bands consist of fine 300 m non planar crystalline impure dolomite the white b bands are composed of coarse up to several millimetres milky white pure saddle dolomites b1 which are often covered by pore lining zoned dolomite b2 the b phases often possess a saddle shaped morphology in contrast to the replacement origin of the a dolomite the zoned b2 dolomite rims are interpreted as a cement formed in open cavities the b1 dolomite is interpreted as the result of recrystallization with diagenetic leaching of non carbonate components all the zebra dolomites studied are nearly stoichiometric and are characterized by enriched na and depleted sr concentrations fe and mn concentrations in these dolomites differ depending on the sample locality fluid inclusion data indicate that the dolomites formed from relatively hot th 130 200 c saline 20 23 wt cacl2 eq fluids a diagenetic high temperature origin is also supported by depleted 18o values 20 to 14 vpdb a contribution of 87sr enriched fluids is reflected in the 87sr 86sr values 0 7091 0 7123 zebra dolomite development is explained by focused fluid flow which exploited areas of structural weaknesses e g basin platform rim areas faults etc expulsion of hot basinal brines in a tectonically active regime generated overpressures which explains the development of secondary porosity during zebra dolomitization as well as the intra zebra fracturing at decimetre to micrometre scale

middle palaeozoic thrusting in the eastern lachlan fold belt southeastern australia abstract early to middle palaeozoic clastic and volcanic strata in the goulburn bungonia region 150 km southwest of sydney are divided by the n trending yarralaw fault into two domains in the western domain major e w shortening formed folds axial planar cleavage and w dipping contraction faults in all pre upper devonian units this deformation formed an anticlinorium cored by a w dipping thrust system with an overturned e younging limb in the eastern domain upright flattened chevron folds occur in ordovician strata with stratal repetition along steep contraction faults spaced at intervals of 1 km or less zones of tectonic melange occur in the hangingwalls of these faults and have a well developed scaly fabric with a steeply plunging striation overprinting a bedding parallel cleavage in mudstone in interbedded silurian shale and limestone a classical stair step trajectory is recognized for the frome hill fault which duplicates the succession and has undergone back rotation to its present steep dip overall thrusting progressed from east to west with deformation in the eastern domain pre dating intrusion of the early devonian marulan batholith whereas farther west deformation continued into the middle devonian the folds and thrusts in the goulburn bungonia region are part of a major fold thrust zone that extends throughout the eastern lachlan fold belt and which was formed in the middle silurian to middle devonian during a period of plate convergence between gondwana and the palaeo pacific ocean the fold thrust zone is inferred to have an arc frontal arc setting above a w dipping subduction zone and the deformation relates to underthrusting of an allochthonous terrane with major shortening in the hangingwall block

using laterally compatible cross sections to infer fault growth and linkage models in foreland thrust belts abstract we investigate changes in shortening displacement and fold geometry to understand the detailed along strike structural variation within fold thrust belts and infer thrust growth and linkage mechanisms field observations from the vercors in se france are used to characterise deformation style in the region parallel cross sections are constructed analysed and used to create shortening and thrust displacement profiles from the northern to southern vercors sections show changes in structural style and shortening accommodation from thrust dominated in the north to fold dominated in the south the total shortening distance in the vercors does not change significantly along strike 3400 4650 m however displacements along individual thrust zones do vary significantly and displacement profiles show a range in displacement gradients 16 107 m km despite relatively simple shortening patterns in the vercors sections show a more complex 3d internal structure of the fold thrust belt thrust displacements and geometries suggest both large scale thrust zones and small scale thrusts are soft linked transferring displacement along strike through transfer zones short soft linked thrust segments indicate an intermediate stage of thrust growth and linkage well documented for normal fault systems which form prior to the formation of thrust branches and hard linked displacement transfer

deep sea observations and modeling of the 2004 sumatra tsunami in drake passage 1 the 2004 sumatra tsunami was clearly recorded by two uk bottom pressure gauges dpn and dps deployed in drake passage between south america and antarctica these open ocean records were examined to estimate characteristics of the tsunami waves and to compare the results of numerical simulations with the observations maximum wave heights measured at these gauges were 4 9 cm at dpn and 7 4 cm at dps the travel times from the source area were 19 h 46 min and 19 h 39 min respectively consistent with the times obtained from the nearby coastal tide gauges the numerical model described well the frequency content amplitudes and general structure of the observed waves with only small time shifts probably related to wave dispersion effects the shifts were 15 min for dpn and 10 min for dps with the modeled waves leading the observations in each case further inspection of the simulated and observed records revealed that the identified tsunami waves are related to the second main train of waves propagating by the energy conserving route along the mid ocean ridges while the first train of waves travelling by the fastest route across the ocean remained unrecognizable in the observed dps and dpn records and undetectable in the records of coastal tide gauges because of their insignificant amplitudes compared to the background variability

structure and tectonic development of the southern rocky mountain trench the rocky mountain trench is one of the youngest most prominent and most enigmatic structures of the canadian cordillera approximately 650 km of seismic reflection data providing regional three dimensional coverage over an area of 10 000 km include six crossings of the rocky mountain trench between 49 n and 50 15 n prominent reflections from mid proterozoic moyie sills outline thrust and fold structures of a late jurassic to early cretaceous fault system that was cut by the rocky mountain trench fault in the tertiary the near basement reflections outline a 10 km high west facing basement ramp the hinge line of which spatially coincides with the rocky mountain trench in this area this ramp is part of a mid proterozoic margin upon which the belt purcell supergroup was deposited and is preserved beneath the trench during mesozoic contraction the basal detachment of the foreland belt closely followed the craton cover contact across the basement ramp thrusting ceased and extension was initiated when a culmination of thick basinal strata was juxtaposed with the basement ramp in the eocene miocene the basement ramp and the culmination above it focused stress reactivating the basal detachment and causing extensional faulting in the southern rocky mountain trench the rocky mountain trench fault may be linked via the basal detachment to the flathead fault on the east and the eocene extensional faults that flank the omineca belt on the west

dispersive tsunami of the 2010 chile earthquake recorded by the high sampling rate ocean bottom pressure gauges 1 cabled ocean bottom pressure gauges deployed offshore japan recorded the pressure change associated with the 2010 chile earthquake tsunami over a wider frequency range than that of coastal tide gauges or hydrophones although it was difficult to recognize the dispersive features in the original records the spectrograms clearly showed wave dispersion a low frequency tsunami 1 mhz arrived after an elapsed time of 24 hr from the earthquake origin time while a high frequency tsunami 9 mhz arrived after an elapsed time of 48 hr the arrival times can be explained by assuming a constant water depth of 4 km however the calculated waveform does not correctly reproduce the number of wave packets appearing in the observations cabled ocean bottom pressure gauges deployed offshore can record broadband tsunami signals reflecting the wide wavenumber range spatial spectrum for sea bottom deformation caused by the earthquake

influence of a turbidite deposit on the extent of pyritization of iron manganese and trace metals in sediments from the guaymas basin gulf of california mexico abstract a core collected in the guaymas basin contained an organic poor mn oxide rich and relatively fe oxide rich turbidite layer that affected the distribution of fe mn c s and trace metals results indicate that sediments not influenced by the turbidite layer achieved a 100 degree of pyritization and by extension that pyrite production is fe limited in these sediments in contrast the mud slide layer apparently supplied enough reactive fe to transfer essentially 98 of the total s present at the base of the turbidite 17 19 cm to the pyrite reservoir c s ratios showed rapid decreases with depth from a high of 38 close to the sediment water interface to minimum values of 2 8 at the lower limit of the turbidite layer a ratio equal to the average c s value of normal marine modern sediments where concentrations of organic c and pyrite supposedly have attained quasi steady values a significant part of the reactive mn was associated with carbonates 41 12 and to a much lower degree with pyrite 2 7 1 2 the turbidite layer is currently showing a depletion of mn relative to the host sediment it is possible that mn a major metal constituent in these sediments was initially present in high concentrations in the mud slide but was eventually mobilized and transferred either to the water column or to the sediments immediately below the turbidite layer metals associated with this element probably followed the same path affecting their incorporation into pyrite the turbidite layer apparently affected the distribution of most of the trace metals associated with pyrite except maybe cd pb and to a certain extent cr however cu cr zn ni and co were all found to be highly pyritized 80 in the sediments of the guaymas basin

the diagenesis of phosphorus in a nearshore marine sediment abstract chemical analyses have been made for total inorganic phosphorus total organic phosphorus and organic carbon in plankton and in anoxic sediments from long island sound u s a when combined with laboratory experiments the measurements of other studies on the same sediments and mathematical modelling the results indicate that 1 1 a large proportion of dissolved phosphate in the upper 10 cm of sediment zone of bioturbation is provided by the release of adsorbed phosphate during the reduction of ferric oxyhydroxides 2 2 below the zone of bioturbation phosphate is liberated to solution solely via organic matter decomposition and the release is stoichiometrically coupled to bacterial sulfate reduction and ammonia formation 3 3 a steady state diagenetic model can be used to predict the profile of organic phosphorus from that of dissolved phosphate at depths below the zone of bioturbation 4 4 the flux of dissolved phosphate out of the sediment must arise largely from phosphate liberation occurring very close 5 5 there is a large preferential loss of phosphorus relative to carbon from organic matter at the time of or prior to burial whereas after burial phosphorus is not lost preferentially at this location

the structure and tectonic evolution of the aguilon fold nappe sierra alhamilla betic cordilleras se spain abstract detailed structural work in the sierra alhamilla se spain shows that the aguilon nappe comprising triassic and older metasedimentary rocks is a fold nappe the most prominent set of small scale folds changes from dominantly n vergent in the upper right way up limb to s vergent in the greatly thinned lower limb the nappe closes to the north and must have been emplaced in this direction nappe formation was accompanied by small scale folding and extensive solution transfer producing a pronounced differentiated crenulation cleavage these structures overprint an earlier set of folds and cleavage and are overprinted in turn by late n vergent structures the lower limb of the nappe was thinned and disrupted during continued nappe transport pre triassic schist in the core of the nappe was affected by medium grade metamorphism of probable post triassic age the contact with low grade permo triassic sediments above and below the schist coincides with a distinct change in metamorphic grade this contact may be a post metamorphic extensional fault that is now folded around the nappe which suggests that nappe formation was preceded by extensional faulting this is consistent with gravity spreading as the driving process for nappe emplacement

excess area and depth to detachment a plot of the excess area in cross section vs the depth to a reference level for several stratigraphic horizons in a compressional fold produces a curve that gives the depth to detachment the curve is a straight line for detachment folds the slope of the line is the displacement on the lower detachment and the depth intercept where excess area zero is the depth to detachment for a fault bend fold the result is a line that abruptly changes slope at the position corresponding to the upper detachment the difference in slope between the two parts of the line is the displacement on the upper detachment added layer parallel shear produces a curve on the graph tested on detachment folds from the jura mountains the method accurately predicts the depth to detachment he tip top field anticline in the wyoming thrust belt is found to be interpretable as either a detachment anticline with a basal detachment close to the top of the basement or as a fault bend fold with a basal detachment at the base of the triassic the excess area diagram is useful for testing a cross section for balance determining the structural style detachment anticline vs fault bend fold and for examining alternatives in the construction of cross sections

crustal evolution of the eastern canadian cordillera the cordillera is not like the himalayas the himalayas are supported by the indian continent that was thrust under the asian continent the eastern cordillera is supported not by imbricated continents but by imbricated continental margin of the ancient western north america that ancient margin was compressed and imbricated as it was confined between the north american craton and the minicontinent of stikinia in the eastern canadian cordillera tectonic thickening is in the collision zone and not on either side of it as for example in the tibetan plateau where the underthrust indian continent has duplicated the thickness of the crust in the eastern canadian cordillera jurassic and early cretaceous thrusts and faults are directed away from the collision zone toward the converging blocks the oppositely directed thrust faults outline wedge shaped sheets of rock sedimentary and volcanic rocks cover the crystalline rocks on which they were deposited basement and the underlying upper mantle may have been detached from each other during the compression the basement therefore would have imbricated internally between the cover and the mantle as a duplex structure confinement of the ancient margin s basement between the colliding blocks requires that the volume of basement under the margin be the same as that presently between the colliding blocks the possibility of such an equality has been tested and confirmed in cross section the cross section of the ancient western margin from that test has many features comparable to cross sections recently drawn through the eastern continental margin of canada

numerical tsunami simulation including elastic loading and seawater density stratification systemic discrepancies between observed and modeled tsunami wave speeds were previously identified for two recent major tsunamis the 2010 maule and 2011 tohoku events to account for these discrepancies we developed a numerical tsunami propagation code solving the shallow water equation and including the effects of elastic loading of the seafloor by the tsunami as well as a linear density profile in the seawater column we show here that both effects are important to explain the commonly observed difference between observations and simulations we conclude that the density variation in the seawater column affects the wave speed without changing the waveform whereas the loading effect has an effect on the wave speed and the waveform showing a negative phase before the main arrival due to the depression of the seafloor surrounding the tsunami wave the combination of both effects is needed to achieve a better match between observations and simulations

magnetic models of the moyie anticline purcell anticlinorium southeastern canadian cordillera two dimensional magnetic models of the moyie anticline contribute to an independent project targeting development of a regional three dimensional 3d model of much of the purcell anticlinorium by compensating for shortcomings in reflection seismic signatures and distributions of drill holes and surface structural data modelling has focused on prominent anomalies related to relatively strong magnetizations within the creston formation and moyie sills models of the western flank of the anticline indicate the creston formation forms the bulk of a westward thickening wedge shaped sedimentary package whose west dipping layers are truncated by a steeply west dipping moyie fault truncating also moyie sills on the opposite side near surface dips of the fault range from 54 to 87 stratigraphic comparisons across the fault indicate minimum reverse dip displacements ranging from 5 6 to 8 5 km the eastern flank of the moyie anticline is modelled consistently as a monoclinal eastward dipping stratigraphic pa

the calculation of horizontal thrust transport using excess area in cross sections abstract existing balancing methods utilizing excess area in cross sections rely heavily on the presence of a perfectly horizontal decollement surface this is rarely the case in thrust belts and the commonly observed hindward dip of floor thrusts imparts uplift and internal strain to the thrust wedge during transport a modified excess area balancing technique is presented to account for hinterland dipping floor thrusts

traveltime delay and initial phase reversal of distant tsunamis coupled with the self gravitating elastic earth systematic tsunami traveltime delays of up to 15 min relative to the numerically simulated long waves from the 2010 chilean and 2011 tohoku oki earthquakes were widely observed at deep ocean tsunamimeters enigmatic small negative phases appearing before the main peak were commonly found only at the trans oceanic locations the frequency dependence of the measured tsunami phase velocities shows reverse dispersions at long periods i e the tsunami speed becomes slower at periods beyond 1000 s this is consistent with the phase velocities of a tsunami mode coupled with a self gravitating elastic earth suggesting that the effects of compression and dilatation of seawater elastic tsunami loadings on a solid earth and the geopotential variations associated with the motion of mass during tsunami propagation are responsible for the traveltime delays and the initial negative phases simple 1 d tsunami propagation tests confirm that the reverse dispersion creates a small negative phase that precedes the main peak at large distances a new method to simulate tsunami waveforms on real ocean bathymetry that takes into account seawater compressibility the elasticity of the earth and geopotential perturbations has been developed by applying a phase correction to the simulated long waves the simulated waveforms in which phase corrections are applied for the dispersion effects accurately reproduce the observed waveforms including a small initial negative phase that appears at distant locations the traveltime difference between the observed and simulated waveforms has been decreased to less than 5 min and the waveform difference between them remarkably diminishes

ground tilt changes in japan caused by the 2010 maule chile earthquake tsunami 1 oscillating ground tilt perturbations accompanied by the 2010 maule chile earthquake tsunami were observed over a broad inland area facing the pacific ocean coast in japan by a high density tiltmeter network through an analysis of ground tilt data observed at more than 500 stations we were able to obtain a detailed spatiotemporal distribution of the tsunami induced tilt changes and reveal a relationship between the tilt amplitude and the distance from the coast at distances of 1 km or less the peak tilt amplitudes were 5 10 2 rad and were almost constant with respect to the distance at distances greater than 3 km amplitudes were inversely proportional to the distance and reached 5 10 3 rad approximately 50 km away from the coast the dominant ground tilting directions were almost the same as the direction orthogonal to the coastline these observed ground tilt changes and their characteristics were successfully modeled with a loading deformation caused by sea level variations accompanied by the tsunami applying a two dimensional boxcar tsunami model to the observed data we estimated the water volume per unit length of coast for the maule earthquake tsunami to be 2 7 103 m3 m within the distance of 14 20 km seaward of the coastline

the 15 august 2007 peru earthquake and tsunami influence of the source characteristics on the tsunami heights the tsunami caused by the 2007 peru earthquake mw 8 0 provoked less damage than by the seismic shaking itself numerous casualties due to the earthquake in the vicinity of pisco however it propagated across the pacific ocean and small waves were observed on one tide gauge in taiohae bay nuku hiva marquesas french polynesia we invert seismological data to recover the rupture pattern in two steps the first step uses surface waves to find a solution for the moment tensor and the second step uses body waves to compute the slip distribution in the source area we find the slip distribution to consist of two main slip patches in the source area the inversion of surface waves yields a scalar moment of 8 9 1020 nm and body wave inversion gives 1 4 1021 nm the inversion of tsunami data recorded on a single deep ocean sensor also can be used to compute a fault slip pattern yielding a scalar moment of 1 1 1021 nm we then use these different sources to model the tsunami propagation across the pacific ocean especially towards nuku hiva while the source model taken from the body wave inversion yields computed tsunami waves systematically too low with respect to observations on the central pacific ocean dart buoy as on the polynesian tide gauge the source model established from the surface wave inversion is more efficient to fit the observations confirming that the tsunami is sensitive to the low frequency component of the source finally we also discuss the modeling of the late tsunami arrivals in taiohae bay using several friction coefficients for the sea bottom

structural divergence and transpression in the teslin tectonic zone southern yukon territory the structural and tectonic evolution of the teslin tectonic zone a complex belt of ductilely deformed rocks forming the southern extension of the yukon tanana terrane in the northern canadian cordillera is elucidated with new field data and by the reinterpretation of existing data the zone includes greenschist to amphibolite facies metasedimentary and metaplutonic rocks of the nisutlin and anvil assemblages characterized by s and l s tectonite fabrics primary contact relationships and ages show that most rocks in the zone were contiguous by mississippian time mapping identified a number of strain domains which preserve s fabrics dipping northeasterly or southwesterly variable mineral lineation orientations and a variety of shear directions including easterly and westerly vergent thrust shear down to the east and down to the west normal shear and dextral strike slip shear regional constraints and microstructures suggest that latest ductile deformation was late triassic to early jurassic in age structural characteristics are explained most effectively by convergent dominated transpression in combination with tectonic wedging and associated back thrusting above a low angle west dipping detachment oblique eastward and upward movement of the rocks over the detachment which may have coincided with the top of thinned north american continental crust produced easterly vergent shear and localized or widespread tectonic wedging and back thrusting produced westerly vergent shear the transpressive deformation postdates formation of the nisutlin assemblage by mississippian time and subduction of the slide mountain ocean beneath the nisutlin assemblage in permian to early triassic time the western margin of the teslin tectonic zone was truncated by cretaceous strike slip faults and translated northward rocks of the peraluminous orthogneiss assemblage of the yukon tanana terrane in central yukon acted as the tectonic wedge and were overthrust by rocks of the nisutlin and anvil assemblages in early jurassic time before unroofing by local extension in cretaceous time

proterozoic craton to basin crustal transition in western canada and its influence on the evolution of the cordillera deep seismic reflection data have imaged a crustal scale west facing ramp or ramp system in the subsurface of western canada in northwestern canada the ramp is within proterozoic crust east of the cordillera and is unconformably overlain by paleozoic sedimentary rocks indicating that it was formed during the proterozoic in this region similar structures are visible within the cordillera in southern canada and the northwestern united states along a south projection of the ramp observed in the north in the monashee complex of british columbia and in the priest river complex in northern washington reflections are visible that dip westward from the surface to near the base of the crust and are structurally discordant with underlying more horizontal reflections thus outlining footwall ramps we propose that the proterozoic crustal ramp in the north and the footwall ramps in the cordillera probably coincide with a proterozoic crustal transition from thick craton on the east to thin crust on the west thi

real time experimental forecast of the peruvian tsunami of august 2007 for u s coastlines 1 at 23 41 utc on 15 august 2007 an offshore earthquake of magnitude 8 0 severely damaged central peru and generated a tsunami severe shaking by the earthquake collapsed buildings throughout the region and caused 514 fatalities the tsunami resulted in three casualties and a representative maximum runup height of 7 m in the near field the first real time tsunami data available came from a deep ocean tsunami detection buoy within 1 hour of tsunami generation these tsunami data were used to produce initial experimental forecasts within 2 hours of tsunami generation the far field forecasts indicated that the tsunami would not flood any of the 14 u s communities comparison with real time tide gage data showed very accurate forecasts

structural evolution of the argentine precordillera the rio san juan section abstract the argentine precordillera ap represents a high level fold and thrust belt which was formed during the andean tertiary crustal shortening in a w e transect studied mostly e directed imbrications are combined with folding and involve a pile of cambrian to tertiary sediments the thrust belt is detached above a main decollement within the ordovician to lower devonian strata to the east it is bounded by a back thrust zone directed westwards restored sections allow an estimate of crustal shortening and also provide insight into the structural development during pre tertiary times carbonate platform sequences of cambrian to ordovician age grade into a volcani clastic succession with transitional melanges representing deposits along a western continental slope in the western and easternmost parts of the ap cambrian to silurian deposits are affected by a first folding which to the west is combined with a slight metamorphic overprint during carboniferous to permian times intensified mobility along the eastern rim and in the western parts of the ap leads to crustal extension which partly was triggered by the formation of synsedimentary normal faults in the central ap no angular unconformities at the base of carboniferous permian deposits were found there was no field evidence found to postulate a terrane boundary within the ap area and an onset of thrust tectonics during cretaceous to early tertiary times

continental margin tectonics submarine accretionary prisms submarine accretionary prisms are sites of incipient mountain building where sediments and rocks of the deep ocean are uplifted deformed and ultimately transformed to continental crust accretionary prisms develop at sites of lithospheric convergence that is subduction zones commonly accretionary prisms form along continental margins although accretionary prisms may also occur adjacent to island arcs which are ultimately coalesced into continental landmasses here we review the studies of submarine accretionary prisms during the past four years with primary focus on the contributions of geoscientists from the united states

a reappraisal of the structure of the spanish segment of the iberian pyrite belt the major structural features of the iberian pyrite belt are described in terms of geometry deformation mechanisms scale timing kinematics and the mutual relationships among the various architectural elements the result of such an analysis allows this zone to be considered as a s verging thin skinned fold and thrust belt propagating southwards over a mid crustal basal detachment this was the response in the footwall of the suture to the major phase of hercynian oblique collision between the south portuguese plate and the ossa morena zone of the iberian autochthon this thin skinned event inverted a previous extensional structure acquired during the initial stages of the collisional process and intimately linked to the formation of the ore deposits that make this region a world class metallogenic province

diagenetic cycling of trace elements in the bottom sediments of the swan river estuary western australia abstract teflon strips were used in situ in the bottom sediments at two sites in the swan river estuary to collect diagenetic fe mn oxyhydroxides and monitor monthly changes in their morphology and trace element geochemistry this study demonstrates that substantial concentrations of trace elements accumulate at the redox front during the formation of diagenetic fe mn oxyhydroxides it is likely that the fe mn oxyhydroxides initially nucleate and grow on the teflon strips via bacterial activity trace element geochemistry of the diagenetic fe mn oxyhydroxides is influenced by changes in the supply of trace elements from either the bottom sediments and or water column or changes in the physico chemical status of bottom and porewaters if sufficient diagenetic fe mn oxyhydroxides are preserved in the upper layer s of the bottom sediment it is possible that diagenetic secondary trace element enrichment profiles may be produced which modify the historical input of natural or anthropogenic trace element sources alternatively partial or complete dissolution of the diagenetic fe mn oxyhydroxides in response to temporal changes in the redox status of the bottom sediment may lead to a substantial underestimate of trace element fluxes in historical bottom sediment profiles this study highlights that considerable care must be taken when interpreting short to long term geochemical profiles in bottom sediments due to the possible occurrence of rapid seasonally mediated diagenetic processes

estimating the effect of earth elasticity and variable water density on tsunami speeds the speed of tsunami waves is typically calculated using the shallow water approximation over a rigid body earth recent comparisons of tsunami arrival times from the 11 march 2011 tsunami suggest however that the standard formulation has errors around the 1 level and it has been suggested that the elasticity of the earth can explain the discrepancy while previous work has indeed shown that such elastic deformation can modify tsunami speeds the effect has been neglected partly due to the difficulty in understanding how large this elastic effect is here we remedy this by providing a new derivation and expression for how to incorporate the first order effect that solid earth elasticity and ocean water compressibility have on tsunami speeds this result is shown to agree approximately with previous theory and helps to explain observed timing discrepancies from the 11 march 2011 tsunami the dispersive elastic correction and the non dispersive compressibility correction together may account for the majority of the observed discrepancy

lithospheric structure in the southern canadian cordillera from a network of seismic refraction lines lithospheric velocity structure and its relationship to regional tectonics and development of the southern canadian cordillera are derived from a synthesis of interpretations from nine in line seismic refraction wide angle reflection profiles and broadside data recorded during the lithoprobe southern cordillera refraction experiment score and other refraction experiments across southern british columbia and one profile in northwestern washington consistency of the score two dimensional models at their intersection positions is achieved through application of a simultaneous inversion of all relevant traveltime data the cross sectional and map presentations demonstrate the strong degree of three dimensional heterogeneity within the crust and upper mantle a first order characteristic is the continuous increase in crustal velocities westward from the foreland belt to the insular belt the variations do not correlate with the morphogeological belts they do correspond with large scale geological and or

travertine mounds of the cave and basin national historic site banff national park the cave and basin national historic site is a fan shaped travertine deposit associated with four thermal spring outlets tentative age dating of the travertine mound indicates growth initiated with onset of the late holocene shift to more humid and cool climate conditions and suggests that the flow of thermal waters was limited during the hypsithermal which in turn places constraints on the evolutionary biology of endemic species in the spring system two large caves and one collapsed cave structure are developed within the deposit cave development is in response to both physical erosion of till underlying the travertine and acid gas attack of calcite that makes up the deposit this process is buffered by formation of reaction crusts of gypsum on the interior cave walls only minor modern travertine growth occurs due to historic flow control measures understanding the flow of water through the historic site is critical for long term preservation

area length and thickness conservation dogma or reality abstract the basic assumption of quantitative structural geology is the preservation of material during deformation however the hypothesis of volume conservation alone does not help to predict past or future geometries and so this assumption is usually translated into bed length in 2d or area in 3d and thickness conservation when subsurface data are missing geologists may extrapolate surface data to depth using the kink band approach these extrapolations preserving both thicknesses and dips lead to geometries which are restorable but often erroneous due to both disharmonic deformation and internal deformation of layers first the bolivian sub andean zone case is presented to highlight the evolution of the concepts on which balancing is based and the important role played by a decoupling level in enhancing disharmony second analogue models are analyzed to test the validity of the balancing techniques chamberlin s excess area approach is shown to be on average valid however neither the length nor the thicknesses are preserved we propose that in real cases the length preservation hypothesis during shortening could also be a wrong assumption if the data are good enough to image the decollement level the chamberlin excess area method could be used to compute the bed length changes

global tectonics since the breakup of pangea 180 million years ago evolution maps and lithospheric budget abstract pangea the earth s youngest single supercontinent broke up 180 million years ago tectonic plates were subsequently formed by dispersal of the continental fragments and accretion of new oceanic lithosphere the configurations of all the major lithospheric plates at 0 20 65 95 140 180 ma bp are reconstructed on six globes of the earth each with a radius of 10 cm it appears that plate boundaries maintain a remarkably close fit on model globes of constant radii if the reconstructions include the recovery of subducted spreading patterns this is illustrated with maps in equatorial orthographic oblique orthographic and transverse hammer aitoff projections the snug fit of the tectonic plates at every tested time since the breakup of pangea 180 ma bp is consistent with the theory of plate tectonics on a non expanding earth and contradicts rapidly expanding earth models the areas of oceanic lithosphere produced and consumed during the past 180 ma bp are estimated from surface measurements of the globes reconstructed on the basis of particular assumptions these measurements suggest a consistent increase in the production rate of oceanic lithosphere during the past 140 ma it was decided to revise the assumptions and see if alternative reconstructions of the ancient spreading patterns on the floors of the tethys and eo pacific oceans could avoid implying an increase of lithospheric production rates with time this appeared to be possible the revised maps suggest that ophiolites older than 180 ma bp may have been obducted in cenozoic collision zones of the himalayas andes rockies and the western part of the banda arc timor new guinea estimates of the ocean floor production and consumption budget appear to be quite similar for both map series and only the possible ranges are summarized here time averaged for the past 180 ma world wide production and consumption of oceanic lithosphere appears to have varied between 2 6 and 3 5 km2 a 1 at most the mean of world wide spreading velocities ranges between 2 4 and 3 5 cm a 1 and world wide means of subduction velocities lie between 4 2 and 6 3 cm a 1 more accurate estimates are possible on the basis of particular assumptions and have been specified for the various time intervals distinguished i e the neogene 0 20 ma bp palaeogene 20 65 ma bp upper cretaceous 65 95 ma bp lower cretaceous 95 140 ma bp and middle and upper jurassic 140 180 ma bp

analytical solutions for estimating tsunami propagation speeds abstract recent studies suggest that the tsunami speed can be slowed down by around 1 due to earth elasticity water compressibility and density stratification analytical solutions of wave dispersion relationship accounting for such effects were found in previous studies in this paper we investigate the additional effects of water viscosity ocean stratification due to temperature salinity and numerical dispersion theoretical solutions are derived and checked with known solutions all the formulas are then simplified for long tsunamis waves so that the propagation speed can be calculated explicitly the simplified solutions are evaluated using realistic geophysical parameters for a typical tsunami wavelength of 200km the viscous effect is found to be negligible ocean stratification due to temperature salinity causes significant speed reduction because of the high density change rate which has been ignored before we also evaluate the numerical dispersion of tsunami simulations which is shown to be potentially comparable to physical dispersion

development of normal faults during emplacement of a thrust sheet an example from the lewis allochthon glacier national park montana u s a abstract geologic mapping in southern glacier national park montana reveals the presence of widespread e dipping normal faults within the basal portion of the lewis allochthon the displacement along the normal faults increases downward from less than 1 m at the highest exposure 200 300 m above the lewis thrust to a maximum of 200 m near or at the lewis thrust the normal faults are located below discrete bedding parallel shear zones associated with mesoscopic structures characterized by ne or sw trending striations on bedding surfaces and asymmetric e verging folds these shear zones lie directly below the e directed brave dog fault a major bedding subparallel fault within the lewis allochthon the shear zones are interpreted to have formed during the development of the brave dog fault striations on the brave dog fault normal faults and shear surfaces in the shear zones are consistent with the transport direction of the lewis thrust the kinematic compatibility of the normal faults with the lewis thrust the concentration of the normal faults along the basal part of the lewis plate and the increase in displacement along them toward the lewis thrust all suggest that their development was synkinematic with eastward emplacement of the lewis allochthon the normal faults may have formed as riedel shears r that accommodated a bulk simple shear strain within the thrust plate between the simultaneously moving subhorizontal brave dog and lewis faults

detachment levels in the marathon fold and thrust belt west texas surface and subsurface data are integrated to characterize the structural architecture of the marathon fold and thrust belt in west texas multiple detachment levels are present within the thrust belt and result in distinct structural domains in addition to the basal decollement whose stratigraphic position varies along strike we recognize a regionally extensive detachment zone in the late mississippian to early pennsylvanian lower tesnus formation the lower tesnus detachment forms a structural domain boundary that can be observed along strike in the surface data and at depth in the subsurface the stratigraphic intervals above and below this detachment exhibit characteristic patterns of deformation the lower tesnus detachment is folded by imbrication and the formation of duplexes in the early mississippian to ordovician section suggesting that the detachment may have initially formed as a perched decollement in the foreland that was subsequently exploited as a roof thrust in a duplex system as deformation progressed in a break forward sequence and older strata were incorporated into the toe of the allochthonous wedge the structural model presented here for the marathon region may be applicable across much of the ouachita orogenic system

the measurement of phosphorus sulfide and metals in sediment of dianchi lake by dgt diffusive gradients in thin films probes one combined agi chelex 100 dgt probe and the other ferrihydrite dgt probe were arranged back to back at the same location of the sediment water interface swi of trophic dianchi lake for the simultaneous determination of soluble reactive phosphorus srp metals and sulfide with the high spatial resolutions dgt computer imaging densitometry cid technique was used for grayscale analysis of agi gel in sediments the character of dgt profiles of metals indicated the geochemical processes such as the reductive dissolution of fe and mn oxides and the release of trace metals adsorbed on them srp dgt profile and upward diffusive flux across swi indicated the breakdown of alga biomass in the uppermost surface sediment the reductive dissolution of fe p in deeper surface sediment and the distinct internal p loading character of sediment of dianchi lake metal sulfide solubility was assessed by saturation index si based on dgt cid technique the sulfate reduction and microniche character in anoxic sediment were verified and assessed

synthetic tsunami mareograms for realistic oceanic models summary we study how the tsunami mode is generated by a scaled double couple seismic source and how it propagates in realistic oceanic models the method developed and used is the direct extension to tsunami waves propagating in multilayered oceanic media of the well known haskell method the most intensive tsunamis may be expected from sources located within the crust in the deep water parts of the ocean the extension to laterally heterogeneous structures shows that if the thickness of the ocean liquid layer diminishes the maximum amplitude of the tsunami wave train increases

mode wave equivalence and other asymptotic problems in tsunami theory abstract a study is conducted of the asymptotic behavior of the gravity modes of an incompressible spherical oceanic layer surrounding a rigid earth as its radius goes to infinity the flat layered earth dispersion relation c gh for the phase velocity of the tsunami wave is derived and the existence of only one branch of tsunami modes is proved a result fundamental for the use of mode theory in marigram synthesis studied further are the influence of such parameters as finite incompressibility in the ocean and finite rigidity of the ocean floor on the dispersion of tsunami modes both theoretically and numerically for a number of models it is concluded that for all physically acceptable models of both the ocean and its floor tsunami dispersion is not significantly affected by either this includes in particular the case of a sedimentary layer which is found to have no effect on tsunami propagation the maximum and extremely small rigidity allowed in the fluid before the tsunami modes disappear is also derived

convection tectonics some possible effects upon the earth s surface of flow from the deep mantle until a little more than a century ago the land surface not only was the only part of the earth accessible to humans but also was the only part for which geophysical and geochemical methods could then provide any details since then scientists have developed ways to study the ocean floors and some details of the interior of the earth to ever greater depths these discoveries have followed one another more and more rapidly and now results have been obtained from all depths of the earth new methods have not contradicted or greatly disturbed either old methods or old results hence it has been easy to overlook the great importance of these recent findings within about the last 5 years the new techniques have mapped the pattern of convection currents in the mantle and shown that these rise from great depths to the surface even though the results are still incomplete and are the subject of debate enough is known to show that the convection currents take two quite different modes one of these breaks the st

slip distribution and seismic moment of the 2010 and 1960 chilean earthquakes inferred from tsunami waveforms and coastal geodetic data the slip distribution and seismic moment of the 2010 and 1960 chilean earthquakes were estimated from tsunami and coastal geodetic data these two earthquakes generated transoceanic tsunamis and the waveforms were recorded around the pacific ocean in addition coseismic coastal uplift and subsidence were measured around the source areas for the 27 february 2010 maule earthquake inversion of the tsunami waveforms recorded at nearby coastal tide gauge and deep ocean assessment and reporting of tsunamis dart stations combined with coastal geodetic data suggest two asperities a northern one beneath the coast of constitucion and a southern one around the arauco peninsula the total fault length is approximately 400 km with seismic moment of 1 7 1022 nm mw 8 8 the offshore dart tsunami waveforms require fault slips beneath the coasts but the exact locations are better estimated by coastal geodetic data the 22 may 1960 earthquake produced very large 30 m slip off valdivia joint inversion of tsunami waveforms at tide gauge stations in south america with coastal geodetic and leveling data shows total fault length of 800 km and seismic moment of 7 2 1022 nm mw 9 2 the seismic moment estimated from tsunami or joint inversion is similar to previous estimates from geodetic data but much smaller than the results from seismic data analysis

speculations on the petroleum geology of the accretionary body an example from the central aleutians abstract in the 300 km wide adak amlia sector of the central aleutian trench 36 000 km 3 of offscraped trench fill makes up the wedge shaped mass of the aleutian accretionary body within this wedge seismic reflection profiles reveal an abundance of potential hydrocarbon trapping structures these structures include antiforms thrust and normal faults and stratigraphic pinchouts maximum closure on these features is 2 km in addition the silt and possibly sand size sediment within the offscraped turbidite deposits and the porous diatomaceous pelagic deposits interbedded with and at the base of the wedge may define suitable reservoirs for the entrapment of hydrocarbons potential seals for these reservoirs include diagenetically altered and produced siliceous and carbonate sediment the organic carbon input into the central aleutian trench based on carbon analyses of dsdp legs 18 and 19 core samples suggests that the average organic carbon content within the accretionary body is approximately 0 3 0 6 heat flow across the aleutian terrace indicates that at present the oil generation window lies at a depth of 3 6 5 km at depths of 8 km which corresponds to the maximum depth the offscraped sediment has been seismically resolved beneath the lower trench slope the probable high 170 180 c temperatures prohibit all but gas generation the dewatering of trench sediment and subducted oceanic crust should produce an abundance of fluids circulating within the accretionary body these fluids and gases can conduct hydrocarbons to any of the abundant trapping geometries or be lost from the system through sea floor seepage in the aleutian accretionary body all the conditions necessary for the formation of oil and gas deposits exist the size and ultimate preservation of these deposits however are dependent on the deformational history of the prism both during accretion and after the accretion process has been superceded by subsequent tectonic regimes