new caledonia obducted peridotite nappe offshore extent and implications for obduction and postobduction processes one of the largest ophiolitic peridotite masses in the world covers a quarter of the island of grande terre new caledonia the peridotite nappe was obducted during the eocene is weakly deformed and corresponds to the highest of a structurally simple pile of thrust nappes we present new marine seismic data that allows us to track the offshore continuation of the peridotite nappe along strike for a distance of more than 500 km south of new caledonia and to image its pre syn and post obduction sedimentary records offshore the peridotite nappe underlies a c 150 km wide and 2 km deep basin flat topped horsts of peridotite are clearly bounded by major normal faults in contrast faults are obscure onland to the east the peridotite nappe roots along the eastern margin of the felicite ridge new name a c 300 x 25 km dome shaped ridge which we interpret as being the southern extension of the hp lt metamorphic core complex observed in new caledonia two alternative tectonic models address the relative timing and relationships between peridotite nappe emplacement uplift of a metamorphic core complex and extensional tectonics these models provide new ideas for the understanding the formation of the eastern margin of the zealandia continent our results contribute to an understanding of how oceanic mantle is emplaced onto continental margins

unroofing of active metamorphic core complexes in the d entrecasteaux islands papua new guinea metamorphic core complexes in the d9entrecasteaux islands are forming as a result of active extension at the western end of the woodlark basin spreading center high grade metamorphic rocks exist in the cores of gneissic domes including eclogites formed at minimum depths of 45 75 km i e 13 21 kbar high temperatures were maintained during uplift of basement rocks from 13 21 kbar t 730 900 c through 7 11 kbar t 570 730 c to 5 6 kbar t 730 c subsequent rapid cooling 100 c m y of the basement occurred between 1 and 2 ma on the basis of 40 ar 39 ar geochronology the core zone rocks were transected by kilometre scale amphibolite facies ductile shear zones active at depths of 25 35 km extensive intrusion of granodiorite plutons occurred and the age of granodiorite intrusions constrains late stage shear zone activity to 2 ma and younger unroofing was accomplished by faults and shear zones bounding the gneiss domes juxtaposing them against ultramafic rocks and sedimentary deposits surface uplift continues today and has led to topographic elevations of up to 2 5 km

development of p t prograde and p retrograde t prograde isogradic surfaces during blueschist to eclogite regional deformation metamorphism in new caledonia as indicated by progressively developed porphyroblast microstructures the mid tertiary blueschists eclogites and eclogitic gneisses of northern new caledonia are the products of four phases of regional meta morphism and deformation d d4 omphacite lawsonite and mn rich garnet isogradic surfaces were developed during the second deformation d2 under prograde pressure and temperature conditions subsequent deformations d3 d folded these d isogradic surfaces however within the p retrograde t prograde metamor phic environment of the d phase omphacite altered to albite and chlorite as a result a late stage sub horizontal isogradic surface developed for omphacite out where this mineral is preserved as relics within syn d albite porphyroblasts other minerals that crystallized for the first time epidote or had rim additions almandine phengite during d also form nearly horizontal isogradic surfaces porphyroblastic garnet and albite contain inclusion trails which allow their microstructural development and crystallization of the matrix to be traced from d to d late syn d the temperature increased mark edly in association with an extensive exothermic decarbonation even though the rocks were in a state of pressure retrogression this caused considerable neocrystallization recrystallization and growth of matrix and porphyroblasts such that although s foliation crenulated by d and d is readily observable almost all signs of stored strain due to d and d have been removed and the deeper schists and eclogitic gneisses superficially appear to have undergone a drastic annealing recrystallization post dating deformation

synoptic systems interacting with the rocky mountain barrier observations and theories abstractusing a composite analysis for strong sea level pressure perturbations off the west coast of north america the evolution of large amplitude synoptic systems upstream of the rocky mountains is investigated for the winter season corresponding previous analyses are refined by avoiding multiple counting of events and extended by including potential vorticity vertical motion and deformation in the analysis cyclonic and anticyclonic anomalies behave similarly with weak local extrema forming in the lee of the mountain range southeast of the parent systems however neither the geopotential anomaly nor the associated potential vorticity anomaly cross the mountain range nevertheless these anomalies contribute to the sea level pressure anomaly in the lee for both positive and negative anomalies potential vorticity exhibits a bipolar structure with lobes over the reference point and over the cordillera respectively the relevance of several theories describing the interaction between synoptic syste

folding of mylonitic zones in cordilleran metamorphic core complexes evidence from near the mylonitic front metamorphic core complexes of north america are asymmetric when viewed perpendicular to the direction of tectonic transport on one side mylonitic fabrics and the overlying detachment fault dip gently in the direction of upper plate transport and the mylonitic rocks have a down dip sense of shear on the opposite side the mylonitic zone rolls over to a dip opposed to the direction of upper plate transport diverges downward from the detachment fault and dies out upward across a mylonitic front new kinematic data show that the backdipping mylonitic zone in most complexes is a downfolded continuation of the main mylonitic zone folding of the mylonitic zone was accompanied by the formation of antithetic shear zones and occurred during the late stages of mylonitization

numerical modeling of a coastal trapped disturbance part i comparison with observations abstract the coastal trapped disturbance ctd of 15 17 may 1985 represents an example of a strong mesoscale trapped event along the west coast of north america with abrupt transitions in many basic meteorological parameters in this study a comparison between observations and a numerical simulation of this event using the regional atmospheric modeling system rams is presented the model is shown to realistically reproduce ctd characteristics such as the coastal transition from northerly to southerly flow as a mesoscale coastal ridge of higher pressure with associated drops in marine layer temperature propagates northward along the west coast of north america simulated sea level pressure and temperature fields near the surface match well with observations especially at the synoptic scale the model realistically simulates mesoscale sea level pressure and 6 h pressure changes during the event the modeled hourly time evolution of sea level pressure and the southerly transitions at a series of coastal

regional fluid characterisation and modelling of water rock equilibria in the boom clay formation and in the rupelian aquifer at mol belgium abstract interstitial water from the boom clay formation around the hades high activity disposal experimental site an underground research facility belonging to the nuclear research centre sck cen at mol dessel belgium underground research facility at mol belgium and waters sampled at different locations in the rupelian aquifer underlying the clay formation have been studied the boom clay is a tertiary mudrock containing about 55 clay and the rupelian aquifer is located in a silty layer special care was taken to adapt or improve measurement sampling conservation and analysis methods to get a reliable regional and local database for the purpose of testing a general model describing the regulation and acquisition of the composition of these fluids the isotopic and chemical composition of the waters allows them to be assigned to a common origin namely mixing between a marine endmember and the clay interstitial water followed by reequilibration with the host rock through dissolution precipitation reactions involving identified secondary minerals oxidation reduction state and trace element behavior are also discussed and the limits of the model are outlined

overthrust emplacement of new caledonia ophiolite geophysical evidence geophysical studies support inferences from outcrop geology that during the late eocene an ophiolite sheet exposed on new caledonia was thrust southward over a rock complex consisting of sedimentary volcanic and metamorphic rocks that range in age from pre permian to eocene the outcropping ultramafic complex consists of a layered sequence approximately 3000 m thick including harzburgite dunite wehrlite serpentinite and gabbro the absence of pillow basalts and sheeted dikes on land suggests that during or after overthrusting these units were removed either by thrust faulting or by erosion seismic refraction profiles collected over the adjacent loyalty basin show that the lower crust and upper mantle are characterized by velocities of 4 7 5 8 6 8 and 8 1 8 4 km s suggesting the presence of a complete oceanic section that includes sediment basalt gabbro and peridotite the lower crust is probably 6 5 km thick beneath the loyalty basin a seismic reflection profile that extends across the loyalty basin is interpreted to show the oceanic crust rising toward new caledonia we suggest that the ophiolite on new caledonia is continuous with this rising oceanic crust studies of gravity anomalies observed both on land and offshore indicate the presence of a short wavelength high amplitude 180 mgal asymmetrical free air gravity anomaly along the northeastern coast of new caledonia a gravity anomaly profile calculated for a geological model characterized by a 10 km thick slab of oceanic crust and mantle material extending continuously from the ophiolite on new caledonia to the oceanic crust of the loyalty basin successfully matches the observed gravity data we interpret the extension of the high gravity anomaly over the whole length of the eastern lagoon as evidence for the lateral extension of the root zone of the ultramafic complex a tentative geodynamic reconstruction suggests that the proto loyalty basin crust formed a marginal basin along the eastern margin of gondwanaland prior to upper cretaceous time after the opening of the new caledonia basin during upper cretaceous to early paleocene time a subduction zone developed along the western margin of new caledonia while this zone was active the loyalty basin lithosphere overthrust new caledonia in a southeasterly direction and locally rotated clockwise this compressional tectonic event was terminated by upper eocene time

structural analysis of basement tectonites from the aegean metamorphic core complex of ios cyclades greece abstract the island of ios in the cyclades aegean sea greece exposes high pressure metamorphic rocks that were subjected to miocene continental extension subsequent to the alpine collisional orogeny the pre alpine history of the lower plate of this aegean metamorphic core complex involves intrusion of granitoids into metasediments which subsequently underwent hercynian amphibolite facies metamorphism during the alpine orogeny d2 these rocks were overthrust by the cyclades blueschist nappe later the lower plate was tectonically exhumed during oligo miocene continental extension and associated plutonism final exhumation occurred as a result of the operation of a south directed crustal scale shear zone and low angle normal faults this study shows that the ios core complex reflects an intrinsic relationship between early thrusting and later extensional tectonism basement rocks have been exhumed from beneath the nappes that originally overrode them

high pressure veins in eclogite from new caledonia and their significance for fluid migration in subduction zones abstract this paper describes the petrology and geochemistry of high pressure veins and associated metasomatic selvages that are hosted by eclogite in the pouebo eclogite melange of northern new caledonia isotopic and geochemical evidence indicates that the mafic host rock represents seafloor altered fractionated morb that underwent eclogite facies metamorphism in a subduction zone within the host rock are cm thick garnet quartz phengite veins that are enveloped by garnet poor omphacite rich selvages or bleach zones petrography thermometry oxygen isotope characteristics and mass balance calculations are used to show that the veins largely formed by fluid mediated mass transfer from the bleach zones during prograde metamorphism minerals in the veins are free of inclusions but the vein garnets preserve complex chemical zoning features that are not present in the host rock garnets vein garnets have mn and hree zoning patterns that are indicative of progressive garnet growth during prograde metamorphism whereas mg and ca contents reveal prominent sector zoning and fine scale intergrowth features we propose that the veins formed over a prolonged period during subduction by local circulation of fluid that was sourced from prograde dehydration of minerals in the host rock fluid circulation may have been driven by episodic microcracking sealing around garnet porphyroblasts which led to significant mass transfer and progressive vein growth mass balance calculations and phengite trace element compositions also require the additional of pelite derived components to the veins these components were probably introduced into the veins at conditions close to peak metamorphism via a relatively small external fluid flux this model for vein formation is consistent with previous studies that suggest fluid flow in deeply subducted oceanic crust is highly restricted in many cases the delay of fluid migration after hydrous mineral breakdown may provide an important source of water for arc magmas as free fluid is transported to deeper levels in subduction zones

the large scale coastal wind field along the west coast of north america 1981 1982 we study the statistical properties of the coastal wind field along the west coast of north america for two summers 1981 and 1982 coastal ocean dynamics experiments 1 and 2 respectively and the intervening winter using measured winds and geostrophic winds calculated from fleet numerical oceanography center atmospheric pressure analyses summer wind fluctuations are driven primarily by the interaction between two relatively stationary pressure systems the north pacific subtropical high and southwest u s thermal low and by their interactions with propagating atmospheric systems to the north in particular propagating cyclones and associated fronts are often followed by a northeastward intensification of the high producing strong upwelling events along the california coast this summer event sequence occurs more frequently and is displaced farther to the south on average during summer 1981 winter wind fluctuations are primarily driven by propagating cyclones and anticyclones and they tend to have larger variance and space scales than in summer a preference for poleward equatorward propagation exists in summer winter and the largest time scales are observed in summer 1982 coastal atmospheric boundary layer processes substantially modify winds within 100 200 km of the coast consequently measured wind fluctuations are strongly polarized in the alongshore direction and have means and rms amplitudes that can vary considerably between nearby stations along the coast calculated wind fluctuations are less polarized in the alongshore direction and have alongshore correlation scales about 60 larger than those for measured winds they represent fluctuations with alongshore wavelengths of 900 km rather well but represent poorly those with smaller wavelengths and those due to coastal atmospheric boundary layer effects

interaction of a warm season frontal system with the coastal mountains of the western united states part i prefrontal onshore push coastal ridging and alongshore southerlies abstract observational analyses and numerical simulations are used to investigate the interaction between a warm season frontal system trough and the complex terrain of the western united states prior to frontal landfall synoptically driven offshore flow was associated with the northward development of a thermal trough and a coastal pressure ridge and associated southerly winds moved northward along the coasts of northern california oregon washington and southwestern british columbia this coastal pressure ridge coupled with the subsequent weakening of the offshore flow resulted in the onshore push of cool marine air approximately 24 h before frontal passage the onshore surge of cool marine air into warm dry continental air associated with the thermal trough produced a mesofront that moved over the coastal and cascade mountains diagnosis of a realistic simulation of the event shows that both solar heating and adiabatic warming from downslope flow over the rockies and the cascade mountains are i

an observational and numerical study of an intense landfalling cold front along the northwest coast of the united states during coast iop 2 abstract this paper presents an observational and numerical study of an intense wintertime cold front that made landfall along the northwest coast of the united states during iop 2 3 4 dec 1993 of the coastal observation and simulation with topography experiment observations suggest that the offshore frontal zone was associated with two transitions the first characterized by a substantial temperature gradient a nearly vertically oriented wind shift from southwesterly ahead to westerly behind and a convective rainband while the second transition had a slantwise wind shift zone from westerly ahead to northwesterly behind the frontal zone was quite narrow 5 km wide and nearly vertical below 850 mb and its width increased by 1 2 orders of magnitude above 850 mb well before the frontal landfall low level flow to the west of the olympics was associated with geostrophic balance in the cross shore direction and downgradient acceleration in the alongshore direction which contributed to the formation

large scale structure of the eclogite blueschist belt of new caledonia abstract this paper considers the large scale geometry of the northern part of the eclogite blueschist belt of new caledonia based largely on classical style structural analysis but in consideration of modern concepts regarding crustal extension exhumation of high pressure rocks and uplift shear zones played an important role in the evolution of the region early shear zones and high pressure metamorphism appear to be associated with overthrusting of an ultramafic sheet middle stage shear zones are associated with large scale continental extension during which the high pressure rocks were exhumed the extended crust was subsequently folded during renewed compression producing an orogen scale antiform throughout the high pressure belt that folds all previously formed structures late stage shear zones formed when the orogen was once again thrown into extension relatively youthful normal faults caused late block faulting uplifting a regional peneplain and producing the present geomorphology previously published interpretations of the structure and geometry of the belt have suggested that the high pressure rocks are found in the core of a regionally developed antiform interpreted as a metamorphic core complex our structural mapping shows that allochthonous slices of high pressure rocks are draped over a younger unrelated foliation antiform lower grade retrogressed equivalent rocks are found within the core of the antiform thus the metamorphic core complex model is rejected

reaction transport modelling of a freshening aquifer tertiary ledo paniselian aquifer flanders belgium abstract the semi confined ledo paniselian eocene aquifer in flanders belgium is recharged in the areas with higher topography where it is covered by the bartonian clay initial conditions in these sediments were marine hydrogeochemical modelling of the groundwater type distribution in the aquifer with a reaction transport model considers recharge of fresh cahco3 water by downward flow through the overlying clay in the aquifer in an upstream direction progressively more freshened water types are found a typical nahco3 type occurs upstream of the brackish fresh water interface the different stages of cation exchange produce a chromatographic sequence of groundwater types which agrees well with observations cation exchange processes occurring mainly in the percolated clay result in a na increase and peaks of k nh 4 and mg2 in the aquifer which are spatially separated as a result of groundwater flow calcite equilibrium gypsum dissolution in the clay and sulphate reduction in the aquifer have also been included in the modelling

northerly surface winds over the eastern north pacific ocean in spring and summer 1 persistent spring and summer northerly surface winds are the defining climatological feature of the western coast of north america especially south of the oregon coast northerly surface winds are important for upwelling and a vast array of other biological oceanic and atmospheric processes intermittence in northerly coastal surface wind is characterized and wind events are quantitatively defined using coastal buoy data south of cape mendocino on the northern california coast the defined wind events are then used as a basis for composites in order to explain the spatial evolution of various atmospheric and oceanic processes wind events involve large scale changes in the three dimensional atmospheric circulation including the eastern north pacific subtropical anticyclone and southeast trade winds composites of qscat satellite scatterometer wind estimates from 1999 to 2005 based on a single coastal buoy indicate that wind events typically last 72 96 h and result in anomalies in surface wind and ekman pumping that extend over 1000 km from the west coast of north america it may be useful to consider ocean circulation and dependent ecosystem dynamics and the distribution of temperature moisture and aerosols in the atmospheric boundary layer in the context of wind events defined herein

a nonhydrostatic mesoscale simulation of the 10 11 june 1994 coastally trapped wind reversal abstract during the summer months the california coast is under the influence of persistent northwesterly flow several times each summer this regime is disrupted by coastally trapped wind reversals ctwr in which the northwesterly flow is replaced by southerlies in a narrow zone along the coast controversy exists as to the physical mechanisms responsible for initiation and maintenance of ctwrs while it is clear that coastal terrain is important in creating the trapped response the precise role played by terrain is unclear in the present study these issues are investigated using a nonhydrostatic mesoscale model to simulate the 10 11 june 1994 ctwr event the results show that the model successfully reproduces many of the observed features of this event including anomalous vertical structure involving the relatively shallow boundary layer with a warm nearly neutral layer above the northward propagation of southerly flow in advance of a tongue of coastal stratus fog and a substantial reduction i

eocene arc continent collision in new caledonia and implications for regional southwest pacific tectonic evolution new caledonia preserves evidence that constrains models for the tectonic evolution of the southwest pacific region onland geology reflects four main tectonic phases 1 early mesozoic development of subduction related terranes and their accretion to the gondwana margin 2 cretaceous passive margin development and sea floor spreading during the gondwana breakup 3 foundering of an oceanic basin and the eocene arrival of thinned gondwana margin crust at a southwest facing subduction zone resulting in collisional orogenesis and obduction of an ophiolitic nappe from the northeast and 4 detachment faulting during extensional collapse resulting in unroofing of metamorphic core complexes the last phase explains supposedly anomalous metamorphic gradients in the northeast of the island

plutonism and the origin of metamorphic core complexes the formation of metamorphic core complexes may be triggered by plutonic activity during episodes of continental extension pulses of ductile deformation have taken place during short lived thermal events initiated by the heat input from intruded plutons sills or dikes such intrusions may be the underlying cause for differential uplift of the footwall during tectonic denudation of metamorphic core complexes fast cooling inferred from 40 ar 39 ar apparent ages may have taken place after periods of magma arrival and need not be the result of rapid erosional or tectonic denudation heterogeneity of 40 ar 39 ar apparent ages can be explained by rapid cooling of deforming mylonites formed at shallow crustal levels in the thermal aureoles of intruded sills or sill swarms under such circumstances apparently isothermal decompression paths may actually link pressure temperature points set during periods of transient mineral growth during and after periods of igneous activity

eclogites and blueschists of the pam peninsula ne new caledonia a reappraisal high p rocks of the pam peninsula ne new caledonia are divided into three zones 1 an uppermost ferroglaucophane lawsonite zone of cretaceous to eocene metasediments and metavolcanics of the diahot terrane that experienced peak conditions involving p 7 9 kbar and t 400 58 c 2 albite epidote omphacite zone diahot terrane rocks that experienced blueschist facies conditions of p 12 6 1 2 kbar and t 570 36 c 3 lowermost metabasic eclogites of uncertain age that form the pouebo terrane which experienced high p conditions of p 23 9 3 0 kbar and t 600 c eclogite occurs as metre to kilometre scale pods in coarse grained hydrous mineral rich glaucophanite formed during hydration and decompression of the pouebo terrane metamorphism and deformation were consequent to 44 51 ma eocene convergence when sedimentary and ophiolitic nappes were thrust over the eclogites in a sw direction white mica ages constrain metamorphism to have ended by 37 1 ma large steps in metamorphic grade are coincident with sw dipping and ne dipping faults that separate the three zones and were formed during two stages 1 comparatively slow uplift and hydration of the pouebo terrane before it was juxtaposed with the albite epidote omphacite zone at p 14 kbar 2 comparatively rapid uplift of both the pouebo terrane and the albite epidote omphacite zone to form a domal core of eclogite flanked by significantly lower grade rocks to the sw and ne

role of tectonic denudation in warping and uplift of low angle normal faults large displacement on a low angle normal fault results in isostatic uplift of the lower plate in response to tectonic denudation simple models of the denudation process predict warping of the lower plate into a broad antiform or antiform synform pair with axes perpendicular to the direction of extension the amount of warping is strongly influenced by initial fault geometry surface topography the amount of extension and the distribution of extension within the upper plate late stage processes that augment antiform growth include one sided denudation of the antiform reverse faulting due to concave upward flexure and wholesale detachment and reverse drag folding of the antiform antiformal uplifts now exhumed by erosion form mountain ranges in the southwestern united states where conditions were favorable for warping during mid tertiary crustal extension four major structural domains are apparent in transects across these uplifts and adjacent areas 1 unextended area 2 synformal upper plate 3 antiformal uplift and 4 wedge shaped upper plate each domain is separated from adjacent domains by the traces of a master low angle normal fault

tectonic mode switches and the nature of orogenesis abstract the birth and death of many mountain belts occurs in lithosphere that over rides major subduction zones here the tectonic mode shortening versus extension can abruptly switch even during continuous and otherwise smooth convergence if the hinge line of the foundering slab rapidly retreats i e rolls back the foundering slab creates a gravitational potential well into which the orogen collapses this motion coupled with stress guides can pull the orogen apart a slowing of roll back or of hinge retreat means that the subduction flexure may subsequently begin to be pushed back or be pushed over by the advancing orogen the consequence of such changes in relative motion is that orogenic belts are affected by abrupt tectonic mode switches the change from push to pull leads to a sudden change from horizontal extension to horizontal shortening potentially throughout the entire mass of the orogenic lithosphere that over rides the subducting slab the sequencing of these tectonic mode switches affects the thermal evolution of the orogen and thus fundamentally determines the nature of orogenesis this insight led to us to our quite different views as to how orogens work it is evident that orogens affected by abrupt push pull mode switches are characterized by high pressure metamorphism whereas orogens affected by abrupt pull push mode switches are characterized by high temperature metamorphism magmatism and anatexis

an observational and numerical study of a cold front interacting with the olympic mountains during coast iop5 abstract this paper documents the three dimensional flow and precipitation structures associated with a weak cold front interacting with the olympic mountains and the subsequent development of a puget sound convergence zone this study utilizes data collected during coast iop5 the fifth intensive observing period of the coastal observation and simulation with topography field experiment that took place on 11 12 december 1993 one of the most important data sources was a noaa p 3 aircraft which provided flight level data radar reflectivity and doppler winds as it circumnavigated the olympics initially frontal passage along the western foothills of the olympics was accompanied by a 2 3 c temperature drop a rapid wind shift to northwesterlies and an intense line of precipitation 35 45 dbz however the wind shift and associated precipitation structures attenuated when the front began to ascend the windward slopes of the olympics surface and p 3 observations document the deformation of the front

scales of structural heterogeneity within neotectonic normal fault zones in the aegean region abstract structural heterogeneities within neotectonic normal fault zones in the aegean region are important controls on the geomorphic expression of their uplifted footwall blocks contrasting fault rocks and slip plane phenomena corrugations comb fractures slip parallel fractures and pluck holes are responsible for mesoscopic inhomogeneities within fault scarps along strike disruptions in the continuity of fault scarps step over zones step up zones step down zones footwall cross faults and hangingwall cross faults are products of perturbations in slip plane geometry or intersections with transverse faults large scale variations in range front morphology reflect contrasting patterns of deformation within fault zones some major fault zones and many minor fault zones are characterized by a migration of the active slip plane towards the hangingwall resulting in a distributed network of high angle faults and a range front which is stepped in profile the presence of a localized mass of uneroded bedrock hangingwall salients protruding from the hangingwall of some major fault zones results in intense deformation along a principal slip plane and a range front which is ramp like in profile as a consequence of structural heterogeneities within neotectonic normal fault zones fault scarps and range fronts in the aegean region are subject to a temporally and spatially variable pattern of degradation

the west coast thermal trough mesoscale evolution and sensitivity to terrain and surface fluxes abstractdespite the significant impacts of the west coast thermal trough wctt on west coast weather and climate questions remain regarding its mesoscale structure origin and dynamics of particular interest is the relative importance of terrain forcing advection and surface heating on wctt formation and evolution to explore such questions the 13 16 may 2007 wctt event was examined using observations and simulations from the weather research and forecasting wrf model an analysis of the thermodynamic energy equation for these simulations was completed as well as sensitivity experiments in which terrain or surface fluxes were removed or modified for the may 2007 event vertical advection of potential temperature is the primary driver of local warming and wctt formation west of the cascades the downslope flow that drives this warming is forced by easterly flow associated with high pressure over british columbia canada when the terrain is removed from the model the wctt does not form and high

effects of coastal orography on landfalling cold fronts part i dry inviscid dynamics abstract in this study the interaction of cold fronts with idealized coastal terrain typical of the western united states and canada is considered two issues are examined first what are the factors that determine the strength of the coastal winds and second what are the orographic effects on the frontal evolution to address these issues the authors utilize a two dimensional boussinesq terrain following coordinate numerical model in which a uniform prescribed flow is forced to move over a plateau the resultant across mountain velocities are characterized by a zone of strongly decelerated flow upstream of the windward slope and a train of inertia gravity waves downstream a barrier jet oriented parallel to the mountain is produced by the coriolis force the variations of the magnitude of the upstream deceleration and the barrier jet over a wide range of froude numbers and rossby numbers are described steady linear theory applied to flow over a plateau shows that the upstream deceleration is dete

mg fe carpholites from aluminous schists in the diahot region and implications for preservation of high pressure low temperature schists northern new caledonia abstract mg fe carpholite is widespread in the diahot region of new caledonia in highly aluminous schists and as veins in what was originally a clay rich hydrothermal alteration envelope about massive suphide deposits these carpholites have fe fe mg ratios of 0 03 0 65 and no significant mn component mg carpholite quartz occur in assemblages with chlorite or pyrophyllite pyrophyllite kaolinite and pyrophyllite diaspore temperatures of 230 320 c and minimum pressures of 7 kbar are indicated for the mg fe carpholite bearing rocks the regional distribution of aragonite and mg fe carpholite parallel to a major zone of dominantly transcurrent movement and oblique to the trend of the subduction complex indicates the high p low t schists owe their rapid uplift and preservation to the vertical component of the transcurrent faulting

the onshore surge of marine air into the pacific northwest a coastal region of complex terrain abstract many coastal locations around the world experience rapid transitions from warm dry continental air to cool moist marine air these onshore pushes or surges of marine air can be accompanied by strong winds large temperature drops and a substantial increase in low clouds a detailed case study of a typical pacific northwest event as well as a composite of several events are presented it is shown that all major surges are initiated by synoptic scale changes and that the mesoscale topography of the region amplifies the synoptic signal annual monthly and diurnal climatologies are discussed this paper also discusses the origin of associated west coast phenomena such as heat troughs and narrow coastal pressure ridges

tectonics of mid tertiary extension along a transect through west central arizona large magnitude miocene extension in west central arizona occurred primarily along three imbricate northeast dipping normal faults the structurally highest of these faults the gently dipping buckskin rawhide detachment fault accommodated approximately 66 km of crustal extension whereas the two structurally lower faults accommodated a total of about 20 km extension due to this large magnitude extension an area at the earth s surface that was 10 to 20 km wide is now over a 100 km wide and crystalline rocks with mid tertiary mylonitic fabrics uncovered by detachment faulting are exposed over roughly 2000 km in the harcuvar metamorphic core complex most of the upper plate of the buckskin rawhide detachment fault was largely undeformed by internal extension only the thin tapered end of the upper plate was highly extended during extension the lower plate must have flexed to conform to the listric underside of the upper plate and to have flattened to its present subhorizontal form as it was uncovered grooves on the underside of the upper plate were apparently imposed on the pliable lower plate as it was denuded forming extension parallel folds in the lower plate low flexural strength characterized the lower plate during denudation and a highly mobile low viscosity deeper crust must have effectively decoupled the upper crust from the mantle lithosphere

the west coast thermal trough climatology and synoptic evolution abstractalthough the west coast thermal trough wctt is the most important mesoscale feature over the u s west coast during the warm season its initiation evolution and structure are not well understood originating in the southwest united states this inverted trough can extend northward into oregon washington and british columbia with large impacts on temperature wind humidity and air quality using ncep s north american regional reanalysis narr annual and diurnal climatologies of wctts reaching the northwest united states were constructed for the entire year wctts are most frequent along the coast near the california oregon border with weaker maxima west of the cascade and coastal mountains over the coastal region they occur most often during autumn while east of the cascade mountains the highest frequency is during summer there is strong diurnal variability in wctt frequency during the summer with little diurnal variation in winter though compositing revealed important seasonal d

metamorphic core complexes of cordilleran type in the cyclades aegean sea greece the islands of ios and naxos in the cycladic archipelago greece contain elongate domes over which a pervasive north to north northeast stretching lineation is warped these islands may be metamorphic core complexes of cordilleran type involving middle crustal rocks drawn upward and outward from underneath the sedimentary basins now 100 km to the south from ca 25 ma onward during uplift the crystalline rocks now exposed on the islands were deformed noncoaxially in the deeper levels of a major shallow dipping ductile shear zone this shear zone may have connected with low angle normal faults in its upper levels because it is probable that its later history involved the metamorphic complexes being dragged out from under a stretching and fracturing upper plate composed mainly of unmetamorphosed sedimentary and ophiolite suite rocks this model can be extended to explain the exhumation of the high pressure low temperature metamorphic rocks on crete which with the cyclades forms a distended paired metamorphic belt separated by an active sedimentary basin