kennetcook thrust system late paleozoic transpression near the southern margin of the maritimes basin nova scotia a major zone of deformation affects early carboniferous rocks in the southern part of the maritimes basin of nova scotia close to the boundary between the avalon and meguma terranes of the appalachians field relationships at cheverie indicate thrusting of tournaisian horton group clastics over visean windsor group carbonates evaporites and clastics a relationship confirmed by the cheverie 01 well mapped relationships to the south indicate that a system of thrusts here termed the kennetcook thrust system climbs upsection to the southeast becoming a decollement within windsor group evaporites industry seismic profiles clearly show deformed windsor group and include fold and fault structures indicative of evaporite flow and solution collapse below the windsor group half grabens filled with horton group are clearly imaged offsets at graben related faults show that these structures were inverted during later shortening above the windsor group less deformed rocks of the pennsylvanian scotch vil

le bassin de tizi n test haut atlas maroc exemple d evolution d un segment oblique au rift de l atlantique central au trias detailed mapping completed by a microtectonic study of the tizi n test triassic basin located along the tizi n test fault zone in the moroccan high atlas has allowed us to improve the knowledge on the geometry of the structures and the activity of faults during the triassic extensional events related to the rifting of the central atlantic the latter are reflected by the development of a rift at present inverted and deformed by the collision of africa and europe comprising kilometric scale grabens and half grabens bounded by major faults trending ene wsw with a dip towards the nnw and a dip slip syndepositional motion inverse analysis of fault slickenside populations shows a heterogeneous triassic state of stress however in the most significant measurement sites the maximum horizontal stress 1 is vertical while the minimum stress 3 is horizontal with a nw se trend the strike slip component appears to be very small during the triassic a noticeable fact because of the obliquity of the basin w

synsedimentary collapse of portions of the lower blomidon formation late triassic fundy rift basin nova scotia a chaotic mudstone unit within the lower blomidon formation late triassic has been traced for 35 km in the mesozoic fundy rift basin of nova scotia this unit is characterized by highly disrupted bedding that is commonly cut by small 0 5 m domino style synsedimentary normal faults downward movement of material geopetal structures variable thickness and an irregular partially faulted contact with the overlying unit the chaotic unit is locally overlain by a fluvial sandstone which is overlain conformably by mudstone although the thickness of the sandstone is highly variable the overlying mudstone unit exhibits only gentle regional dip the sandstone unit exhibits numerous soft sediment deformation features including dewatering structures convoluted bedding kink bands and convergent fault fans the frequency and intensity of these features increase dramatically above low points at the base of the sandstone unit these stratigraphic relations suggest buried interstratal karst the subsurface

minas fault zone late paleozoic history of an intra continental orogenic transform fault in the canadian appalachians abstract the minas fault zone mfz defines the boundary between the avalon and meguma terranes in the canadian appalachians and is exposed in mainland nova scotia and southern new brunswick these terranes originated along the gondwanan margin but had accreted to laurentia by the middle devonian the surface trace of the mfz is adjacent to the southern margin of the latedevonian permian maritimes basin the late devonian late carboniferous evolution of the mfz involves several episodes of oblique dextral shear that resulted in basin formation and inversion and at various times the zone was the focus of magmatism regional fluid flow and mineralization in the late devonian early carboniferous asymmetric rifting accompanied by dextral shear produced two coeval sequences the horton group which is dominated by continental clastic strata and the fountain lake group which consists predominantly of bimodal volcanic rocks that overlie high level plutons emplaced along active shear zones the overall tectonic environment may have been dominated by dextral transtension along the southern margin of laurentia which corresponded with the northern flank of the rheic ocean a major change in the evolution of the minas fault zone occurred in the late mississippian early pennsylvanian and produced the e w chedabucto fault clockwise rotation of pre existing structures local zones of transtension and transpression as well as regional fluid flow and extensive mineralization this major change may reflect the onset of laurentia gondwana oblique collision the effects of which continued into the latest carboniferous with coeval development of flower structures and pull apart basins in zones of local transpression and transtension

large scale alluvial architecture and correlation in a triassic pebbly braided river system lower wolfville formation fundy basin nova scotia canada abstract determining what the controls are on the large scale 10 km horizontal architecture of coarse grained fluvial deposits is important for understanding subsurface fluid distribution and extraction from these important aquifers and hydrocarbon reservoirs this contribution describes the architecture of coarse grained fluvial sediments from an almost continuous lateral profile 27 km long by 115 m high in the upper triassic wolfville formation fundy basin nova scotia the lateral extent and quality of exposure allows development of a high resolution correlation scheme and definition of architectural elements the lower wolfville formation lithofacies composed of breccias conglomerates sandstones mudstones and paleosols comprises alluvial fan fluvial and ephemeral lake margin facies associations alluvial fan deposits form 15 of the studied section and are developed locally between the overlying fluvial facies and the unconformity with carboniferous strata where they infill remnant topography the succession is dominated 80 by pebbly sandstones deposited as part of a gravelly braided fluvial system and ends abruptly with a thin ephemeral lake margin facies association 5 the large scale architecture and sedimentology of the pebbly sandstone succession is documented with particular attention focussed on bounding surfaces and stacking patterns in the fluvial facies association two scales of development of erosion surface and cycles can be recognized the s surfaces can be correlated across the profile 27 km and show evidence of up to 10 m of erosion a significant facies or grain size change onlap and association with mature calcic paleosols the e surfaces can be correlated between 5 and 17 km display erosion of the regional extent of the e and s surfaces indicate that the gravelly fluvial system has a large scale sheet like geometry which comprises a series of stacked erosion dominated multi story bodies high resolution architectural elements are poorly defined in this coarse fluvial system and make it difficult to constrain the scale of the depositional system an individual high resolution cycle records braid plain development and is interpreted as a multi story channel belt the braid plain width is estimated at 19 km but the width of individual active channels is unknown the sediments were deposited in a proximal fluvial setting disconnected from marine influences we interpret the high resolution cycles and bounding e surfaces to record a progressive decrease in runoff and fluvial transport capacity indicative of a drying upward climatically driven signal the origin of the s surface bounded packages is more difficult to determine a variety of mechanisms are considered including changes in discharge driven by climatic fluctuations changes in stream power related to drainage capture within the source area and tectonic tilting an important aspect of the study is that the s surfaces can be identified and correlated for 27 km and provide an example of a robust high resolution correlation framework in coarse grained braided fluvial deposits that could be applied elsewhere in contrast the e surfaces do not display any significant changes in facies or grain size across them such that many of the smaller scale cycles could potentially be miscorrelated

a high resolution simulation of the ocean during the pomme experiment simulation results and comparison with observations 1 a modeling study of physical processes occurring in an area of the northeast atlantic 21 33 15 33 w 38 00 45 00 n that was extensively sampled during the programme ocean multidisciplinaire meso echelle pomme october 2000 september 2001 is carried out the model is a mesoscale version of the ocean general circulation model opa developed at the laboratoire d oceanographie dynamique et de climatologie in paris it is used in a three dimensional limited area domain with a high resolution grid approximately 5 km horizontal spacing 69 vertical levels and realistic boundary conditions initial state air sea fluxes open boundary fluxes and bottom topography the objectives of the study are to properly simulate the upper ocean dynamics particularly mesoscale activity and mixed layer evolution during a key period restratification of the pomme experiment pomme 1 and pomme 2 from february to may 2001 and to compare model results with oceanographic observations collected during the experiment in order to establish confidence in the model some results provided by the high resolution simulation in particular features related to mixed layer depth and vertical velocities are also presented there is no pronounced north south mixed layer depth gradient but strong filament shaped structures associated with stirring at the periphery of eddies are present mixed layer restratification is simulated it is associated with submesoscale mixed layer depth structures and intense vertical velocity filaments in the upper ocean correlated with the relative vorticity gradient field

development and hydrocarbon potential of mesozoic sedimentary basins around margins of north atlantic the late triassic early jurassic rift basins of iberia offshore eastern canada and the continental shelf of western europe are fragments of a formerly coherent northeast trending rift system that probably formed as a result of tensional stress between europe africa and north america the separation of europe north america and iberia was preceded by a late jurassic early cretaceous rifting phase that is clearly distinct from the earlier mesozoic rifting episode and was little influenced by it the two periods of rifting are separated by a middle jurassic relatively tectonically quiet period the distribution of hydrocarbon finds within the rift basin suggests that the best prospects are in areas where the two rifting episodes are superimposed lack of mature source r cks in the later mesozoic rift basins and an unfavorable temporal relationship between hydrocarbon generation and tectonic activity in the early mesozoic basins are proposed as explanations for the apparently poor hydrocarbon prospectivity of large areas of the mesozoic basins

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

basin scale salt tectonic processes of the laurentian basin eastern canada insights from integrated regional 2d seismic interpretation and 4d physical experiments

strike slip duplexes abstract strike slip fault systems often contain zones of steep imbricate faults geometrically similar to imbricate fans and duplexes in dip slip thrust and normal fault systems they are evident in map view rather than in vertical sections examples of duplexes are cited from both active and ancient systems and from theoretical and physical models duplexes may form at bends on strike slip faults by a process kinematically analogous to the sequential imbrication of ramps on dip slip faults however some may form and many may initiate as non sequential riedel fractures at fault offsets or on straight fault segments this process is more marked than in dip slip systems where primary anisotropy such as bedding exerts more control on fault geometry strike slip duplexes may be shunted along the fault system parallel to the regional slip vector however duplexes or individual horses will usually also move up or down perpendicular to the slip vector because of the unconstrained upper surface to the fault system these factors mean that no section through a strike slip system should be expected to area balance the faults of strike slip duplexes and imbricate fans may root in kinematically necessary low dip faults or may converge downwards and appear in vertical sections as flower structures

controls on the architecture of a triassic sandy fluvial system wolfville formation fundy basin nova scotia canada implications for the interpretation and correlation of ancient fluvial successions abstract architectural element analysis was developed to describe and reconstruct fluvial system stacking patterns and understand the controls on fluvial architecture the architecture of braided fluvial systems at the scale of channel belts is still poorly understood and upscaling from outcrop observations to basin scale architecture remains partly speculative nonetheless predictive sedimentary models are necessary to understand the connectivity of sand bodies from small scale outcrop to basin scale this contribution presents a dataset from the late triassic sandy braided fluvial system of the fundy basin nova scotia canada we describe facies associations architectural elements and stacking patterns at different scales and discuss the controls on fluvial architecture and upscaling issues the studied section shows at the base multilateral stacked channel bodies with little preservation of fine grained floodplain facies it changes upwards into multistory stacked channel bodies that form channel belt complexes intercalated with thicker floodplain deposits based on grain size evolution large scale sequences encompass several channel belt complexes controls on channel and channel belt migration or avulsion are considered to be related to autocyclic processes in contrast large scale vertical evolution and grain size variations record allocyclic signals in particular gradual grain size variations suggest a climatic control which influences the bedload transport capacity of the depositing fluvial system architectural evolution including an upward increase in the preservation of floodplain units is considered to be due to an increase in generation of accommodation space we question the existing definition of the order of large scale sixth to seventh order bounding surfaces recognized previously and highlight difficulties associated with reconstructing development of a regional fluvial system using these bounding surfaces

kinematic significance of sediment filled fissures in the north mountain basalt fundy rift basin nova scotia canada abstract numerous sediment filled fissures are present near the upper surface of the north mountain basalt 202 ma of the fundy basin which formed during triassic jurassic rifting the fissures are infilled with the same clastic material comprising the basal parts of the overlying earliest jurassic age sedimentary formations which accumulated less than 200 k y after the cooling of the basalt nearly all of the 1368 fissures measured in this study are planar to sub planar and are sub vertical after correcting the basalt flows to paleo horizontal the fissures typically formed along preexisting columnar joints within the basalt northeast striking fissures generally define a preferred orientation and commonly are wider than other fissures the sediment filled fissures therefore indicate earliest jurassic age nw se extension this extension direction is consistent with that indicated by the ne striking shelburne diabase dike the attitude of mesoscopic faults and the geometry of the fundy rift basin thus sediment filled fissures by themselves can serve as useful kinematic indicators and place tight constraints on the relative timing of extension

does stommel s mixed layer demon work abstract stommel argued that the seasonal cycle leads to a bias in the coupling between the surface mixed layer and the main thermocline of the ocean he suggested that a demon operated that effectively only allowed fluid at the end of winter to pass from the mixed layer into the main thermocline in this study stommel s hypothesis is examined using diagnostics from a time dependent coupled mixed layer primitive equation model of the north atlantic cme the influence of the seasonal cycle on the properties of the main thermocline is investigated using two methods in the first the rate and timing of subduction into the main thermocline is diagnosed using kinematic methods from the 1 resolution cme fields in the second tracer diagnostics of the cme and idealized experiments using a date tracer identifying the timing of subduction are performed over the subtropical gyre both approaches generally support stommel s hypothesis that fluid is only transferred from the mixed layer into the main therm

stratigraphic record of the early mesozoic breakup of pangea in the laurasia gondwana rift system rift basins of the central atlantic margins cam of north america and morocco preserve largely continental sequences of sedimentary strata and less important minor basalt flows spanning much of the early mesozoic the best known is the newark basin of new jersey new york and pennsylvania where an astronomically calibrated magnetic polarity time scale is developed lacustrine cycles of milankovitch origin are commonly present in cam basins with the period changing from 10 ky paleoequator with coals to 20 ky 4 10n to perhaps 40 ky northward with evaporites cycles of100 ky 413 ky and2 my are also important four mostly unconformity bounded tectonostratigraphic sequences are present the anisian ts i is fluvial and eolian ts ii ts iv late triassic to early jurassic consist of tripartite lacustrine sequences caused by extension pulses the newark basin accumulation rate history allows comparison with quantitative rift basin models the north american plate s slow northward drift resulted in a relative shift of climate although the rapid humidification during the latest triassic and early jurassic is associated with a sea level rise the triassic jurassic mass extinction is of independent origin plausibly impact related

inferring the subduction rate and period over the north atlantic abstract the annual rate at which mixed layer fluid is transferred into the permanent thermocline that is the annual subduction rate sann and the effective subduction period x1d4af eff is inferred from climatological data in the north atlantic from its kinematic definition sann is obtained by summing the vertical velocity at the base of the winter mixed layer with the lateral induction of fluid through the sloping base of the winter mixed layer geostrophic velocity fields computed from the levitus climatology assuming a level of no motion at 2 5 km are used the vertical velocity at the base of the mixed layer is deduced from observed surface ekman pumping velocities and linear vorticity balance a plausible pattern of sann is obtained with subduction rates over the subtropical gyre approaching 100 m yr twice the maximum rate of ekman pumping the subduction period x1d4af eff is found by viewing subduction as a transformation process converting mixed layer fluid into stratified thermocline fluid the effective

low angle extensional faulting reactivated mylonites and seismic reflection geometry of the newark basin margin in eastern pennsylvania low angle 25 to 35 dips have been determined for the border fault of the newark basin near riegelsville pennsylvania on the basis of a vibroseis profile and two continuously cored drill holes across faults at the basin margin a group of moderately strong planar reflections in a zone 0 5 km thick in gneiss and carbonate rocks of the footwall block coincides with the updip projection of imbricate fault slices and mylonites associated with the musconetcong thrust system of drake et al 1967 contrasts in acoustic impedance among mylonitic dolostone and mylonitic gneiss and their protoliths determined from measurements on samples from a third cored hole are sufficiently large to account for reflections seen in the footwall block analysis of drill core and surface outcrops supports the conclusion that low angle extensional faulting in the early mesozoic was localized by reactivation of paleozoic imbricate thrust faults in the basement rocks extension in the northwest southeast quadrant was approximately perpendicular to the strike of the ancient thrust faults in eastern pennsylvania the data presented here are the most explicit three dimensional information obtained thus far in the eastern united states in support of the concept of fault reactivation in controlling formation of early mesozoic extensional basins

dating transcurrent terrane accretion an example from the meguma and avalon composite terranes in the northern appalachians the polygenetic minas geofracture separates the meguma and avalon composite terranes of the maritime appalachians dynamically recrystallized muscovite and biotite occur within d3 shear zones which developed during dextral movement along the geofracture these record 40ar 39ar plateau ages between circa 360 and 370 ma comparable plateau ages are recorded by micas within undeformed portions of granitic plutons and their low pressure contact metamorphic aureoles these are similar to u pb ages previously reported for igneous monazite therefore indicating relatively rapid postmagmatic cooling at shallow crustal levels the d3 fabrics were superimposed on earlier s1 structures which formed during initial amalgamation of the meguma and avalon composite terranes whole rock slate phyllite samples collected outside high temperature portions of the plutonic contact aureoles yield 40ar 39ar plateau ages which correspond to groupings of circa 400 395 ma 390 385 ma and 380 375 ma these are interpreted to date diachronous formation of the s1 fabrics and concomitant low grade regional metamorphism in the circa 25 ma between initial amalgamation and granitic plutonism it is inferred that there was a slow rise of isotherms through the crust as a result of overthrust tectonic thickening this led to crustal melting and the production of widespread granitic magmas which were emplaced immediately prior to d3 dextral shearing

introduction to the pomme special section thermocline ventilation and biogeochemical tracer distribution in the northeast atlantic ocean and impact of mesoscale dynamics conducted in the northeast atlantic ocean 15 20 21 20 w 38 n 45 n the programme ocean multidisciplinaire meso echelle pomme is a research project aimed at a better understanding of the biological production and the carbon budget of the region in relation to the formation mechanisms of the 11 12 c mode water of the northeast atlantic with the help of two research vessels several tens of floats and drifters and nine moorings the field experiment was carried out between autumn 2000 and autumn 2001 with a more intensive phase in the winter and early spring of 2001 the field experiment resolved small several kilometers to regional several hundred kilometers scales and daily to seasonal variability a first analysis of the rich data set focused on the large scale and the mesoscale variability it shows that the distribution of water mass characteristics and biological activity is strongly influenced by the mesoscales in this supposedly quiet transition zone between the subtropical and subpolar gyres the seasonal variability however presents an imprint of the large scale structures with a clear north south gradient in properties and budgets this region is found on an annual average to be a sink of atmospheric co2 smaller scales associated with fronts and filaments were clearly observed in many fields temperature but also chlorophyll oxygen biogenic particles etc with modeling studies suggesting that they play a significant role in subduction ventilation and transport of biogeochemical tracers in the pomme region

diachronous rifting drifting and inversion on the passive margin of central eastern north america an analog for other passive margins integration of new data with existing information indicates that the tectonic development of the passive margin of eastern north america between the carolina trough and scotian basin was considerably more complex than the classic two stage rift drift model first the transition from rifting to drifting was diachronous in the southeastern united states the rift drift transition occurred after the late triassic synrift deposition and before eastern north america magmatism in the earliest jurassic 200 ma in maritime canada the rift drift transition occurred after eastern north america magmatic activity and synrift deposition in the early jurassic and before postrift deposition in the early middle jurassic 185 ma second the deformational regime changed substantially after rifting on both the southern and northern segments of the margin generally northwest southeast postrift shortening replaced northwest southeast synrift extension northeast striking reverse faults formed and many of the rift basin boundary faults had reverse displacements in the southeastern united states the change in the deformational regime occurred in the late triassic early jurassic during the rift drift transition simultaneously diabase sills and dikes many striking nearly perpendicular to the trend of the rift basins intruded the continental crust and a massive wedge of volcanic or volcaniclastic rocks developed near the continent ocean boundary in maritime canada the change in the deformational regime occurred during or after the early jurassic and before or during the early cretaceous that is during the rift drift transition or early stages of sea floor spreading

eastern north atlantic mode waters during pomme september 2000 2001 four hydrographic surveys in the northeast atlantic 38 45 n 15 21 w carried out during the programme ocean multidisciplinaire meso echelle pomme experiment september 2000 2001 are used to investigate the water masses in the upper layers corresponding to eastern north atlantic mode waters a large meridional gradient in isopycnal temperature salinity is witnessed which has no counterpart in climatology and is associated with an anomalous eastward current near 41 n waters tend to be warmer more salty somewhat more stratified and less oxygenated on isopycnal surfaces in the southern part of the domain in addition there is an overlying zonal gradient of properties in particular north of the jet consistent with earlier descriptions however these large scale distributions also change significantly through the pomme year in particular between the february and early april surveys which we attribute to 1 the arrival of a 2001 vintage of mode waters in particular in the northeastern part of the domain and to 2 stirring by the mesoscale motions which contribute to down gradient transport equivalent diffusion coefficient of 2000 m 2 s for s 27 10 on a smaller scale there are noticeable changes in properties between surveys some of which can be shown by quasi lagrangian diagnostics to result from advection by the horizontal circulation in particular in the southwest corner of the domain between the surveys p1 february 2001 and p2 april 2001 horizontal isopycnal advection is responsible for a large cooling freshening and oxygen increase or in the northeast corner where new oxygenated and freshly ventilated water in particular for surface s q 27 05 kg m 3 penetrates during that period in other regions or for a longer period water masses are often difficult to track as a result of dispersion or stirring by the eddies and too small of a pomme domain

seismic behaviour of mountain belts controlled by plate convergence rate the relative contribution of tectonic and kinematic processes to seismic behaviour of mountain belts is still controversial to understand the partitioning between these processes we developed a model that simulates both tectonic and seismic processes in a continental collision setting these 2d seismo thermo mechanical stm models obtain a gutenberg richter frequency magnitude distribution due to spontaneous events occurring throughout the orogen our simulations suggest that both the corresponding slope b value and maximum earthquake magnitude mathrm m max correlate linearly with plate convergence rate by analyzing 1d rheological profiles and isotherm depths we demonstrate that plate convergence rate controls the brittle strength through a rheological feedback with temperature and strain rate faster convergence leads to cooler temperatures and also results in more larger seismogenic domains thereby increasing both mathrm m max and the relative number of large earthquakes decreasing b value this mechanism also predicts a more seismogenic lower crust which is confirmed by a transition from uni to bi modal hypocenter depth distributions in our models this transition and a linear relation between convergence rate and b value and mathrm m max is supported by our comparison of earthquakes recorded across the alps apennines zagros and himalaya these results imply that deformation in the alps occurs in a more ductile manner compared to the himalayas thereby reducing its seismic hazard furthermore a second set of experiments with higher temperature and different orogenic architecture shows the same linear relation with convergence rate suggesting that large scale tectonic structure plays a subordinate role we thus propose that plate convergence rate which also controls the average differential stress of the orogen and its linear relation to the b value is the first order parameter controlling seismic hazard of mountain belts

an experimental study of the secondary deformation produced by oblique slip normal faulting we have used scaled clay models to define the secondary deformation produced by oblique slip normal faulting in the models the master fault beneath the clay layer dips 45 degrees and strikes at a 45 degrees angle relative to the heave direction i e the horizontal component of the displacement direction thus the master fault has both normal dip slip and strike slip components of displacement the modeling results show the following 1 the fault patterns produced by oblique slip normal faulting vary significantly with depth secondary faults that strike obliquely to the master fault trend are more abundant near the top of the clay layer whereas secondary faults that are subparallel to the master fault trend are more abundant at depth 2 a single episode of oblique slip normal faulting produces two populations of secondary faults that have different trends and ages secondary faults that strike obliquely to the master fault trend are more abundant during the early stages of the experiments whereas secondary faults that strike subparallel to the master fault trend are more abundant during the later stages of the experiments 3 relay ramps between overlapping secondary synthetic normal faults are wide and temporally persistent in oblique slip models the ramps are cut by numerous small scale normal faults that are subparallel to the ramp bounding faults cross faults are uncommon and begin to develop only during the final stages of the experiments 4 both map and cross section data are necessary to distinguish among the deformation patterns produced by strike slip oblique slip and dip slip faulting the map views of oblique slip models closely resemble those of strike slip models in both models many of the secondary faults strike obliquely to the master fault trend these map views however differ considerably from those of dip slip models in which most of the secondary faults strike subparallel to the master fault trend alternatively the cross sectional views of oblique slip models are similar to those of dip slip models in both models a highly faulted extensional forced fold develops these cross sectional views are dissimilar to those of strike slip models which show no appreciable folding and no change of regional level

response of the atmospheric boundary layer to a mesoscale oceanic eddy in the northeast atlantic fields of air sea turbulent fluxes and bulk variables were derived from satellite sensor data from february to april 2001 over a region of the northeast atlantic where a field experiment programme oce an multidisciplinaire meso echelle pomme was conducted the satellite products are in good agreement with in situ data in terms of heat fluxes sea surface temperature and wind speed the central part of the experimental domain presented a cyclonic eddy in the ocean which corresponded to a cold sea surface temperature sst anomaly winds were weaker within the eddy than outside of it with lower latent and sensible heat loss in order to analyze the relationship between the sst and wind anomalies three numerical experiments were conducted with a regional atmospheric model three 3 month runs of the model were performed using a realistic sst field a smoothed sst field in which the cold sst was not present reference run and an sst field where the cold anomaly was increased by two degrees successively the fields simulated with the realistic sst were consistent with satellite sensor derived observations in particular the weak wind area over the cold sst anomaly was successfully rendered whereas it was not present in the forcing fields taken individually the three runs did not reveal the presence of secondary circulations however anomalous secondary circulations were clearly identified with respect to the reference run the origin of the latter circulations was investigated with the giordani and planton generalization of the sawyer eliassen equations according to our results differential heating induced by the cold sst anomaly mostly altered the vertical wind through the effect of friction and only marginally through pressure gradient forces in the upper part of the boundary layer the wind speed increased decreased over downstream the cold sst we found that stability was the main factor that induced the simulated patterns of the friction term in the diagnostic equations therefore our results show that mesoscale wind patterns were significantly affected by sst gradients through the effect of stability in a region of low oceanic eddy activity

transtensional arm of the early mesozoic fundy rift basin penecontemporaneous faulting and sedimentation formed as a major right lateral fault zone during paleozoic collisional orogenies and reactivated as a left oblique system during the early mesozoic the east striking minas fault zone of atlantic canada controlled adjacent sedimentation in the fundy rift basin producing a series of synsedimentary microbasins northeast striking boundary faults of the fundy basin underwent mostly early mesozoic normal slip and are reactivated paleozoic thrusts the adjacent basin has a much thicker section transverse folds and synthetic rider blocks contrasts in structural and stratigraphic styles are a response to local deformation controlled by reactivated fault zones of differing orientation under consistent northwest southeast early mesozoic extension rather than responses to a sequence of changing stress patterns

paleomagnetism of the moenkopi and chinle formations in central new mexico implications for the north american apparent polar wander path and triassic magnetostratigraphy in central new mexico red sedimentary rocks unconformably overlying permian carbonates of the san andres formation have been correlated with the early middle triassic moenkopi and late triassic chinle formations of the colorado plateau paleomagnetic samples from triassic sections exposed on basement cored uplifts along both the east and west side of the rio grande rift near albuquerque yield upon thermal and chemical demagnetization well defined high unblocking temperature dual polarity magnetizations carried by hematite the characteristic magnetization is interpreted as an early acquired chemical remanent magnetization based on a positive intraformational microconglomerate test and bedding parallel magnetization polarity zonation the moenkopi and lowermost chinle formations produced paleomagnetic poles respectively at 57 6 n 100 3 e n 36 sites k 74 1 a95 2 8 and 60 8 n 88 9 e n 17 sites k 130 3 a95 3 1 these data plus previously published and additional results from the underlying permian strata suggest that portions of central new mexico have experienced a small clockwise rotation i e less than 10 similar to that of the colorado plateau with respect to the north american craton the paleomagnetic directions of the chinle formation and related strata in eastern new mexico document about 12 great circle distance of rapid apparent polar wander during mid carnian to late norian times along a track which contains other cratonic poles of similar age we present a preliminary magnetic polarity time scale for the triassic that incorporates the present new mexico data and previously published data mostly form continental red bed sequences this magnetic polarity scale provides a basic framework which can be tested with future data from triassic sections where additional biostratigraphic control exists

uniquely extensive seismite from the latest triassic of the united kingdom evidence for bolide impact a 2 4 m thick seismite in places overlain by a previously unreported tsunamite can be traced across 250 000 km 2 of the outcrop and subcrop of the latest triassic rhaetian cotham member of the penarth group united kingdom an extent unique for the british phanerozoic its consistent thickness intensity of deformation and preferred orientations of slump fold axes indicate a seismic event of m 10 with an epicenter 600 km w or nw of central britain the magnitude of the event is incompatible with known terrestrial mechanisms fault volcano but is consistent with a major bolide impact a short but unknown interval separates the top of the cotham member seismite from major geochemical and biotic perturbations associated with the end triassic extinction although a direct link between the seismite and these other events remains equivocal the exceptional extent of mega seismites such as this may prove a useful indicator of previously undocumented bolide impacts

mapping subtle structures with light detection and ranging lidar flow units and phreatomagmatic rootless cones in the north mountain basalt nova scotia light detection and ranging lidar is an emerging technology to generate high resolution digital elevation models dems subtle topographical differences among three flow units of the jurassic north mountain basalt eastern canada are visible on a lidar derived dem the boundaries were verified by field mapping and allow a simple projection of the contact planes through the terrain model to provide a three dimensional visualization of the flow units several ring structures in the lower flow unit distinguishable only in the lidar data are interpreted to be the remnants of rootless phreatomagmatic cones glacial erosion has since excavated the highly fractured cone material leaving the more resistant dike and quenched melt to form protruding ring structures the ability to detect subtle variations in topography using lidar may identify previously undetected landscape elements

salt diapir reactivation and normal faulting in an oblique extensional system vulcan sub basin nw australia oblique extension and salt diapirism have their own distinct mechanisms that control the geometry and kinematics of structures in this study we document a geological phenomenon from the vulcan sub basin in nw australia that combines these processes a salt diapir reactivated in an oblique extensional system detailed structural analysis of this natural example with a focus on normal fault systems allows characterization of the oblique extensional system and investigation of how the pre existing structural fabrics and salt diapir control deformation and interact with each other under oblique extension after comparison with forward modelling results and using constraints from geological evidence our fault strike analysis indicates that the neogene flexural extension orientation in the oblique extensional system is around 347 revealing a perpendicular relationship between extension direction and fault strikes from the deformation zone the salt diapir reactivated during neogene extension strongly influences local structure in the oblique extensional system by altering fault strikes stepping patterns deformation zone width and fault density indicative of a stress strain concentration effect of the salt diapir owing to its extremely low strength these results provide valuable insights into the understanding of oblique extensional systems the geomechanical role of salt during extension and the neogene tectonic evolution of nw australia supplementary material dominant seismic frequency analysis uninterpreted seismic profiles additional structural and isochron maps a 3d view of fault systems and original measurements of the fault system are available at http doi org 10 6084 m9 figshare c 3148321

tectonic evolution of the fundy rift basin canada evidence of extension and shortening during passive margin development seismic and field data show that the fundy rift basin of southeastern canada experienced two distinct episodes of deformation during mesozoic time the first episode during middle triassic to early jurassic time was extensional rifting associated with nw se extension reactivated ne trending paleozoic compressional structures as normal faults forming the northwestern boundary faults of the fundy basin displacements on the low angle boundary faults locally exceeded 10 km rifting also reactivated east trending paleozoic compressional structures as oblique slip faults with normal and sinistral strike slip components forming the northern boundary faults of the fundy basin several kilometers of sediments and lava flows filled the basin during rifting the second deformational episode occurred during or after early jurassic time and probably before or during early cretaceous time inversion associated with nw se shortening occurred along all faulted margins of the fundy basin the northwestern boundary faults experienced several kilometers of reverse displacement broad anticlines developed within their hanging walls and the fundy basin acquired its synclinal form the northern boundary faults of the fundy basin became oblique slip faults with reverse and dextral strike slip components gentle synclines tight anticlines and faults with reverse separation deformed the synrift strata near the northern margin of the fundy basin neither collision nor subduction zones existed near the fundy basin during mesozoic time hence we believe that tectonic processes associated with seafloor spreading e g incipient ridge push forces continental resistance to plate motion produced the shortening in the fundy basin shortening occurred during the transition from rifting to drifting as north america separated from northern africa and or during the early stages of drifting as the seafloor spreading centers of the north atlantic propagated northward

a double cycle lake basin formed in extensional to transtensional setting the paleogene nanpu sag bohai bay basin china abstract it has been known that both extensional and transtensional tectonics commonly trigger a one cycle evolution of lake sediments but lake cycle development co controlled by extensional and transtensional tectonics still need identification here we report a double cycle of lake sediments formed in extensional to transtensional phases in the paleogene nanpu sag of the bohai bay basin china the sag successively experienced five phases of lake type evolution characterized by 1 overfilled 2 balanced fill 3 overfilled 4 balanced fill and 5 overfilled extensional tectonics was responsible for the opening of the basin and the initial creation of accommodation 1st through 3rd phase next subsidence increased again through transtensional tectonics resulting in the creation of new accommodation 4th 5th phases investigations show this double cycle lake type evolution is also present in other lake basins with similar tectonic settings e g both extensional and transtensional tectonics a different exploration and exploitation strategy should be devoted to the double cycle evolution of lake basins controlled by extensional to transtensional tectonics in comparison to the single cycle evolution in extensional or transtensional lake basins

depositional facies paleogeography and palaeoclimatology of the lower jurassic mccoy brook formation fundy rift basin nova scotia the mccoy brook formation is a 230 m sequence of redbeds of early jurassic age that accumulated in the subtropical fundy rift basin the basin was asymmetrical bordered on the northern side by the cobequid fault system and adjacent highlands the formation is a mosaic of terrestrial facies a multi and single storey fluvial sandstones were deposited by rivers that collected drainage from the norhern highlands and flowed southwest across the valley floor b graded bed sequences of sandstone mudstone were deposited by flood events on the fluvial floodplains and the margins of playas c interbedded sandstones and finely laminated to disrupted red mudstones represent deposits of interfingering sandflats at the toes of alluvial fans and playas respectively the fabrics of both lithologies are commonly disrupted by desiccation and intrastratal precipitation of calcite and minor gypsum d plane bedded conglomerate and pebbly sandstone record deposition in shallow channels that traversed alluvial fans e non bedded breccias of basalt boulders up to 8 m in size in a sand to mud matrix formed as talus against palaeocliffs of the lower jurassic north mountain basalt the palaeocliffs resulted from synsedimentary faulting within the basin f basalt conglomerate beds with matrix to clast supported fabrics comprise sequences deposited by debris flows probably generated by remobilization of talus g a thin sequence of limestone siltstone and muddy sandstone containing fish scales and bones formed in a shallow lake on a basalt flow h sandstones containing m scale crossbeds and a three fold hierarchy of erosional surfaces accumulated as barchans and barchanoid transverse ridges that moved southwest in the valley all of these facies occur within an area of 18 km2 located south of the fault bounded highlands synsedimentary faulting within the basin during early deposition of the mccoy brook formation created palaeocliffs of north mountain basalt talus and debris flow deposits accumulated adjacent to these cliffs interfingering with eolian fluvial and lacustrine sediments during later deposition of the mccoy brook formation the early fault controlled topography was buried as alluvial fans prograded southward from the highlands broad sandflats extended basinward from the toes of the fans interfingering with playa mudflats on the valley floor the palaeoclimate was semi arid as evidenced by gypsum bearing playa redbeds eolian sandstones and caliche palaeosols

new early jurassic tetrapod assemblages constrain triassic jurassic tetrapod extinction event the discovery of the first definitively correlated earliest jurassic 200 million years before present tetrapod assemblage fundy basin newark supergroup nova scotia allows reevaluation of the duration of the triassic jurassic tetrapod extinction event present are tritheledont and mammal like reptiles prosauropod theropod and ornithischian dinosaurs protosuchian and sphenosuchian crocodylomorphs sphenodontids and hybodont semionotid and palaeonisciform fishes all of the families are known from late triassic and jurassic strata from elsewhere however pollen and spore radiometric and geochemical correlation indicate an early hettangian age for these assemblages because all typical triassic forms are absent from these assemblages most triassic jurassic tetrapod extinctions occurred before this time and without the introduction of new families as was previously suggested by studies of marine invertebrates this pattern is consistent with a global extinction event at the triassic jurassic boundary the manicouagan impact structure of quebec provides dates broadly compatible with the triassic jurassic boundary and following the impact theory of mass extinctions may be implicated in the cause

the shelburne dike an early mesozoic diabase dike in nova scotia mineralogy chemistry and regional significance a diabase dike about 140 km long the shelburne dike cuts in a northeasterly direction across the southwestern part of nova scotia the dike recently dated at 201 ma forms part of a major appala

effects of the mixed layer time variability on kinematic subduction rate diagnostics abstract an eddy resolving primitive equation general circulation model is used to estimate water mass subduction rates in the north atlantic ocean subtropical gyre the diagnostics are based on the instantaneous kinematic approach which allows the calculation of the annual rate of water mass subduction at a given density range following isopycnal outcrop positions over the annual cycle it is shown that water mass subduction is effected rapidly 1 2 months as the mixed layer depth decreases in spring consistent with stommel s hypothesis and occurs mostly over the area of deep late winter mixed layers 150 m across the central north atlantic in the density range 26 27 2 annual subduction rates o 100 200 m yr 1 are found south and east of the gulf stream extension in the density range of subtropical mode waters from roughly 26 2 to 26 6 in the northeastern part of the subtropical gyre annual subduction rates are somewhat larger o 250 m yr 1 from a density of about 26 9 east of the nort

modeling the three dimensional upper ocean heat budget and subduction rate during the subduction experiment a global three dimensional primitive equation general circulation model is used to estimate the upper ocean heat budget and subduction rates in the eastern north atlantic during the period of the subduction experiment june 1991 through july 1993 the seasonal cycle is dominated by one dimensional processes throughout the subtropical gyre i e a local balance between the net heat flux into the ocean through the surface and a vertical redistribution due to vertical mixing however closure of the heat budget on long timescales involves redistribution by ekman transports both horizonal and vertical geostrophic advection and vertical diffusion subgridscale parameterizations of eddy processes weakly restratify the upper ocean the annual rate at which waters are subducted from the mixed layer into the permanent thermocline is estimated using both kinematic and thermodynamic methods these subduction rates and patterns are generally consistent with each other and also with previous estimates of the large scale subduction rate based on climatologies and models consideration of a finite thickness ekman layer is shown to reduce the thermodynamic estimate of the subduction rate at low latitudes by o 50 in much better agreement with the kinematic method the effects of convergent eddy fluxes in the mixed layer and a diabatic thermocline on the subduction rate are also calculated and found to be small but not negligible the seasonal and interannual evolution of the sea surface temperature and mixed layer depth in the model compare well with in situ measurements at five mooring locations taken as part of the subduction experiment these results demonstrate that a global low resolution general circulation model forced with surface fluxes of heat and freshwater can accurately reproduce the evolution of the upper ocean thermal structure and provide a useful tool for the analysis of air sea interaction and climate variability on seasonal to interannual timescales

threshold of erosion of submarine bedrock landscapes by tidal currents since sea level stabilized 7000 yr bp shelf seas experiencing semi diurnal tides will have been affected by streaming four times per day if tidal erosion of bedrock were even only marginally efficient the 10 million streamings since then should have left geomorphological imprints we examine high resolution multibeam sonar data from three areas with extreme tidal currents the minas passage bay of fundy experiencing 8 knot surface tidal currents was surveyed in 2007 with a multibeam sonar in an area near to transverse dunes which are evidence for bedload transport the data show local overhanging surfaces near to the sediment rock contact potentially created by abrasion by saltating particles however they are uncommon in the straits of messina where surface currents reach 10 knots surveying revealed ridges lying oblique to the flow that are not obviously broken into separate outcrops by erosion in the bristol channel uk sonar data collected where currents reach 3 4 knots at 1 5 m above the bed reveal outcrops of limestone with superimposed sand dunes but only minor rounding of blocks holocene tidal currents have apparently been generally ineffective at eroding bedrock we examine this issue further by compiling extreme tidal streams around the uk and from them estimate shear stresses representing a macro tidal environment where peak surface currents reach 9 7 knots those data are compared with shear stresses in mountainous rivers where long term rates of erosion are comparable with tectonic uplift rates and are thus geomorphologically significant whereas river stresses reach 102 103 pa the largest tidal stresses are generally 101 and only rarely approach 102 pa too small for quarrying to operate generally however the vertical faces in the minas passage may represent the onset of abrasion given this limited evidence for abrasion we explore conditions in the geological past for tides that may have locally eroded bedrock

constraints on synrift intrabasinal horst development from alluvial fan and aeolian deposits triassic fundy basin nova scotia the authors would like to acknowledge shell e and p for funding this study rob raeside at the acadia university and liz kosters for their support during the field seasons we also would like to thank brian p j williams for enthusiastic discussions in the field

alternating crustal architecture in west iberia a review of its significance in the context of ne atlantic rifting the crustal architecture of the western iberian margin is investigated so that the relationship between synrift intra plate segmentation magmatic events and subsequent margin convergence can be discussed in the context of the evolution of the central north atlantic ocean the evidence in this paper indicates distinct crustal architectures for nw iberia lower plate and sw iberia upper plate as shown by 1 the different geometries of the rotated tilt blocks across thinned continental crust 2 the distinct dips of deep crustal detachments and 3 the presence of first order strike slip zones bounding different crustal segments we demonstrate that a switch in the dip direction of the crustal detachment is accomplished by accommodating persistent transcurrent deformation along first order transfer zones and associated uplifted hinges both of which accommodated synrift displacement and post rift margin inversion this alternating architecture explains why recurrent magmatism is conspicuously located on the upper plate margin which we consider to have favoured in discrete pulses the emplacement of magma finally the crustal detachment underlying the upper plate is interpreted to have been reactivated since the eocene as the weak zone accommodating ocean continent convergence and the putative onset of margin subduction supplementary material summary of the three main magmatic events on the onshore and offshore west iberia and their associated occurrences location and magmatism type in relation with the syn to post rift evolution of the margin are available at https doi org 10 6084 m9 figshare c 3591209

structural stratigraphic and sedimentological characterisation of a wide rift system the triassic rift system of the central atlantic domain abstract the extension driven break up of the pangean supercontinent in the present day central and north atlantic domains commenced during permo triassic times permian rift processes in this region are generally attributed to crustal collapse during the latter part of the hercynian variscan orogeny but the triassic rifting style is more complex and the presence of a single over riding first order control is equivocal basement terrane structures and boundaries provide pre existing zones of weakness that had significant influences on the location timing orientation and extent of triassic rifting the 201 ma central atlantic magmatic province camp a large igneous province lip increased lithospheric heat flow at the end of rifting produced uplift and doming and also contributed to deformation and subsequent continental breakup analysis of the triassic basin structures in the central atlantic and north atlantic domains respectively georgia to nova scotia and conjugate margin and newfoundland iberia shows that four main basin types are geographically distributed 1 southern basins georgia to virginia small to medium size with limited growth structures 2 basins in the central east domain new jersey nova scotia wide basins with growth structures along long lived inherited bounding faults 3 basins in the central west domain offshore ns and morocco that comprise numerous half graben sub basins in a lower unit and an upper very wide tabular unit and 4 northern basins newfoundland portugal that are tabular and extremely wide basin architectures suggest that subsidence was regional in extent and not necessarily controlled by main faults variations in crustal characteristics are considered to have led to the development of the four main basin types stratigraphic data show that the onset of deposition in the central and southern north atlantic domain was restricted to a central segment between two main structural lineaments overall crustal rheology and inheritance exhibited first order controls on subsidence and basin development triassic basins in the central and north atlantic domain were all filled by continental deposits in various palaeo environments such as alluvial fan mega fluvial systems terminal fluvial systems fan delta fluvial systems permanent oxic and anoxic lakes playa lakes and saline lakes some of them interbedded with aeolian and volcanic deposits most basins were far from any marine domain but marine ingressions from the tethys domain are inferred from dolomite and marine fauna in portugal and from thick salt deposits in morocco and offshore canada during the late rhaetian a series of palaeogeographic maps are presented utilising plate reconstructions based on sahabi et al 2004 in order to summarize continental scale palaeo environment distribution our tectono stratigraphic model suggests that initial strain was accommodated in a central segment by inherited faults during the early and middle triassic during the carnian the rift domain was increasingly extended with the development of half graben basins in the central segment and some in the northern segment in both segments the initial strain re activated inherited faults and later the rift zones evolved towards significantly wider basins marked by the presence of a major erosional truncation surface across the basins and followed by lacustrine sedimentation that eventually overlapped paleo topographic highs subsidence of such regional extent is likely driven by thermal processes following a phase of extreme lithospheric thinning and lower crustal removal associated with mantle uplift the architecture of the triassic rifting has the characteristics of the wide rift mode very large basins with some active faults for which subsidence is driven by lower crustal flow within a high heat flow region nevertheless some faults were active during late triassic sedimentation but accounted for a relatively minor part of the overall subsidence pulses of active subsidence and topographic rejuvenation led to fluvial dominated deposition within basins non rejuvenation of hinterland led to more lacustrine dominated sedimentation and eventual connection of basins across topographic highs due to regional thermal subsidence during the latest rhaetian basins with the lowest elevations were possibly flooded by marine waters resulting in precipitation of thick salt deposits

vorticity and vertical circulation at an ocean front abstract density and velocity data with 4 km horizontal resolution from a survey of a front during fasinex frontal air sea interaction experiment are combined to describe the structure of the top 300 m of the ocean the geostrophic velocity field is derived and is used to examine the relative importance of stratification relative vorticity and twisting terms in ertel s potential vorticity q tenfold isopycnic changes in q are found across a horizontal scale of only 10 km these changes are confined to isopycnals that outcrop from the seasonal thermocline into the mixed layer the ageostrophic velocity field is quantified by solution of the omega equation and vertical velocities of up to 40 m day 1 are found small 40 km surface trapped top 200 m eddies are found to play a crucial role in the transport and effective diffusion of properties across the thermocline out of the mixed layer

crustal deformation and submarine canyon incision in a meso cenozoic first order transfer zone sw iberia north atlantic ocean using a dense grid of high quality 2d seismic profiles dredge and outcrop data the offshore prolongation of a first order transfer zone the messejana plasencia fault zone mpfz is explained within the context of oblique rifting between southwest iberia newfoundland and west tethys the offshore mpfz is shown to comprise a 5 10 km wide region of deformation oblique to the continental margin reactivated in the mesozoic as part of a wider transcurrent domain the sao vicente sub basin here the geometry of faults and strata denotes the generation of a pull apart basin during the jurassic early cretaceous in contrast its late cretaceous to cenozoic evolution favours left lateral transpression during the counter clockwise rotation and eastward migration of iberia towards its present position erosion was subsequently enhanced in the sao vicente sub basin due to the reactivation of syn rift structures by documenting the evolution of the sao vicente sub basin and adjacent mpfz this work demonstrates 1 the temporal and spatial scales in which first order transfer zones accommodate crustal movements during continental rifting and subsequent inversion episodes 2 the generation of an extensive region of strain accommodation in the vicinity of the mpfz an observation with profound implications to future palaeogeographic reconstructions of the north atlantic ocean and 3 that the sao vicente canyon the physiographic expression of the mpfz incised the margin as early as the latest cretaceous paleocene synchronously with the onset of tectonic uplift in southwest iberia in such a setting the sao vicente sub basin and mpfz formed important by pass corridors for sediment sourced from proximal areas of the margin at present the mpfz comprises a complex releasing restraining bend accommodating important vertical and horizontal movements in southwest iberia based on earthquake data from similar transfer zones the mpfz should be able to generate large magnitude earthquakes and potentially destructive tsunamis

on the edge of camp geology and volcanology of the jurassic north mountain basalt nova scotia abstract the north mountain basalt nmb is a sequence of continental tholeiitc basalts that are part of the larger 200 ma central atlantic magmatic province camp the nmb occur within the fundy basin one of several mesozoic extensional basins that formed during the incipient rupture of pangea in addition to the nmb the fundy basin was also filled by fluvial alluvial playa lacustrine and aeolian sediments under arid to semi arid conditions mapping of a 200 km long segment of the nmb along the southern coast of the bay of fundy indicates for the first time the lateral continuity of the three recognized lava units the east ferry margaretsville and brier island members efm mm bim respectively that comprise the nmb the efm 150 m are massive and characterized by pervasive development of columnar jointing both colonnade and entablature in addition whereas the efm contains abundant layers of mafic pegmatite the bim is characterized by abundant mesostasis possibly reflecting widespread quenching of this flow and locally abundant segregation pipes due to mobilization of a late stage felsic liquid these two units represent expansive eruption of low viscoity flows onto a low slope surface which encouraged uniform thickness and their massive nature but the role of faulted basins cannot be ruled out in contrast the mm 170 m consists of numerous 16 inflated pahoehoe sheet flow lobes evidence that these flows formed as pahoehoe flows is represented by exceptional development of the vesicle zonation i e upper crust vesicle sheets vesicle cylinders pipe vesicles as observed in modern hawaiian flows historical icelandic flows and ancient flows of the columbia river basalt group the thickness of upper crust zones indicates that the individual flows formed over months to years whereas inclined basal pipe vesicles indicate the mm and bim flowed to the south the similar age and nature of the nmb to other basalt sequences in camp suggest that similar processes operated throughout this lip thereby having implications for such phenomena as atmospheric contamination and extinction events caused by eruption of these voluminous basaltic lava flows

the subpolar mode water of the north atlantic ocean abstract the warm waters of the subtropical and subpolar basins of the north atlantic have tight regional temperature salinity relationships and are conventionally called the regional central waters a volumetric census of the temperature salinity characteristics of the north atlantic by wright and worthington 1970 shows that waters characterized by certain segments of the t s relationships have large volumes compared to those of other segments volumetric mode waters such mode waters appear as layers with increased vertical separation between isopycnals pycnostads the present study reports on the existence of pycnostads in the central and eastern north atlantic these subpolar mode waters are formed by deep winter convection in the subpolar north atlantic and participate in the upper water circulation of the northern north atlantic the seasonal outcropping of the pycnostads occurs within and adjacent to the north atlantic current the irminger current the east and west greenland currents and

ventilation of the north atlantic and north pacific subduction versus obduction abstract ventilation in the north atlantic and north pacific is examined by analyzing the levitus climatological data and the hellerman and rosenstein wind stress data ventilation between the permanent pycnocline and the overlying seasonal pycnocline and mixed layer consists of two physical processes subduction and obduction subduction takes place mainly in the subtropical basin where surface water is irreversibly transferred into the permanent pycnocline below obduction takes place in the subpolar basin where water from the permanent pycnocline is irreversibly transferred into the mixed layer above veatilation in the north atlantic and north pacific can be clarified into four physically different regions the subductive region the obductive region the ambiductive region where both subduction and obduction take place and the insulated region where neither subduction nor obduction occurs although the total subduction rates in these two oceans are comparable the total obduction rates are considera

eolian sandstones in upper triassic lower jurassic red beds of the fundy basin nova scotia abstract eolian sandstones occur interbedded with alluvial fan and braided river red beds in the upper triassic wolfville formation and at the base of the lower jurassic mccoy brook formation in nova scotia extensive semiaridity and aridity in the subtropical rift valley favored deposition of eolian sandstones caliche paleosols alluvial fan conglomerates braided river alluvium and playa mudstones in postdrift configuration paleowinds blew to the southwest west and northwest down the valley reflecting the direction of trade winds at 25 n paleolatitude a three step hierarchy of surfaces truncates cross beds first order bedding planes of low relief extend for at least hundreds of meters truncating all eolian structures these surfaces were sculptured by desert flash floods and then deflated to ventifact bearing bimodal regs second order surfaces bound cross bed sets and are mostly concave up and dip downwind recording shifts in migration direction of individual dunes or dunes superimposed on larger dune structures third order surfaces within cross bed sets formed on the lee sides of dunes due to fluctuations in wind direction and strength barchans initially developed on the alluvial fan and braided river alluvium later coalescing into barchanoid transverse ridges as evidenced by the internal geometry of the eolian sandstones p

controls on the stratigraphic development of the triassic fundy basin nova scotia implications for the tectonostratigraphic evolution of triassic atlantic rift basins abstract the late triassic synrift succession of the minas sub basin bay of fundy nova scotia includes a fluvio alluvial fan dominated unit lower and middle wolfville formation a transitional fluvio playa unit upper wolfville formation and an upper playa dominated package blomidon formation we describe the facies development in the 240 m thick upper wolfville formation examine vertical facies stacking patterns and develop a depositional model for this succession the unit comprises channelized and unconfined fluvial deposits interbedded with aeolian and playa sediments that grade upward into playa deposits the succession comprises progradational and retrogradational fluvial packages and thin aggradational playa claystones comparison with 11 other atlantic margin continental triassic rift basins allows an assessment of the controls that govern rift basin development the transition from fluvial to playa or lacustrine conditions occurs in all basins at different times the lack of synchronicity indicates that global climate change was not a controlling factor we suggest that the fluvial to lacustrine or playa transition was due to a decrease in source area relief related to a decline in regional tectonic activity and that the basin was hydrologically closed throughout sedimentation this tectonostratigraphic model may be appropriate for other triassic basins developed along the atlantic margin

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

shallow pycnoclines and mode water subduction in the eastern north atlantic abstract a lagrangian one dimensional model is used to study the subduction of subpolar mode water in the eastern north atlantic and to analyze recently observed hydrological features related to this process considering a southward moving column of mode water subduction occurs when the upper part of the column starts gaining buoyancy in an annual budget the seasonal pycnocline on top of the column can no longer be completely eroded in winter and it is shown how its remnant forms a shallow secondary pycnocline at about 200 m depth which isolates the lower part of the fluid column from the atmosphere this mechanism for the subduction of subpolar mode water induces a strong meridional gradient in the winter mixed layer depth the various components of the buoyancy input are thoroughly studied horizontal advection in the shallow ekman layer and vertical advection along the column are shown to modify significantly both the thermal and haline contents of the column with magnitudes comparable to the ai

role of synsedimentary strike slip faults in the formation of moroccan triassic basins upper triassic sandstone and siltstone infilled basins in the massif ancien of the high atlas morocco are distributed along a complex east northeast trough at the boundary between the hercynian orogen and the west african craton the formation of these basins involved a dense pattern of pre existing faults hydroplastic slickensides which affect nonlithified sediments help identify not only dip slip but also strike slip faults together with other tectonic and sedimentary structures the directional distribution of these faults leads to a model in which extension varies from north northwest during lower unit sandstone infilling to northwest during upper unit siltstone infilling the latter direction is compatible with the formation of the lower liassic intrusional doleritic dikes of the anti atlas

influence of preexisting fault fabric on inversion related deformation a case study of the inverted fundy rift basin southeastern canada 1 preexisting zones of weakness significantly influenced the structural development of the fundy basin during rifting and subsequent basin inversion the preexisting fabric consisting of ne striking faults with gentle dips and east striking faults with steeply dipping upper segments and gently dipping lower segments formed during paleozoic and older orogenic activity during mesozoic rifting the preexisting fabric was reactivated creating a border fault system composed of linked ne and east striking extensional fault zones with anomalous dips gentle and steep compared to those of newly formed normal faults during inversion the preexisting fabric was again reactivated as the hanging wall of the composite border fault system moved nne relative to the footwall inversion was highly oblique on the ne striking fault zones producing gentle fault parallel buttress folds and fault perpendicular detachment folds above the low angle fault zones inversion was moderately oblique on the east striking fault zone producing relatively tight fault parallel buttress and detachment folds above the gently dipping lower fault segments and reactivating the steeply dipping upper fault segments as left lateral strike slip faults thus inversion related deformation on the east striking fault zone was partitioned at shallow levels i e partitioned updip our work shows that the geometry of preexisting extensional faults and their obliquity relative to the shortening direction profoundly affect deformation style during basin inversion namely the type of inversion related faults the type and shape of inversion related folds and the distribution of deformation e g updip partitioning depend in part on the geometry of the preexisting extensional faults and the variations in these geometries with depth and along strike

geologic evolution of the gulf of maine region abstract in this study we reconstruct the evolution of the northern new england passive margin whose development has been influenced by pleistocene glaciations the morphology of the northern new england shelf is rather unique consisting of a inner lowland the gulf of maine with an average depth of 150 m and an area of 90 700 km2 and georges bank a high whose crest is less than 40 m deep and has an area of 27 000 km2 the bank s northern slope facing the gulf of maine has a maximum relief of 377 m on the seaward side of georges bank is the 2000 m high continental slope deeply cut by canyons two channels northeast and great south channels east and west of georges bank provide passageways from the gulf of maine to the open sea this morphology was acquired by a combination of tertiary fluvial erosion pleistocene glacial erosion deposition and pleistocene holocene marine processes fluvial glacial erosion in the gulf of maine was so extensive as to expose basement thus making it possible to map the various terranes making up this foundation these terranes include the pre carboniferous avalon and meguma units a carboniferous permian rift basin formed by the oblique continental collision during the closure of the paleozoic proto atlantic and a late triassic early jurassic rift system created during the opening of the present atlantic basement in the gulf of maine remained above sea level from the opening of the atlantic 190 ma early jurassic to the eocene 55 ma that the gulf of maine remained a high for so long may have been due to igneous activity along the northwest trending boston ottawa lineation extending from the vicinity of the st lawrence river canada to gulf of maine from late triassic to early cretaceous the northwest trending new england seamounts south of georges bank may represent a seaward extension of this lineation on georges bank rising hundreds of meters above the gulf of maine the basement exposed in the gulf is mantled by sediments thousands of meters thick included in these sediments are early jurassic to earliest cretaceous reefs along the continental slope and carbonates north of the reefs grading landward into continental sediments cretaceous cenozoic continental marine terrigenous sediments and pleistocene glacial deposits the continental slope on the seaward flank of georges bank has a complex history of early to mid mesozoic carbonate accretion mid to late mesozoic and cenozoic calcareous terrigenous sediments and canyon erosion burial and exhumation going back to early cretaceous