particle dispersal due to interplay of motions in the surface layer of a small reservoir horizontal dispersion mechanisms must be well defined in order to determine the origin and fate of heterogeneous distributions of biogeochemical material here data from an intensive field campaign in valle de bravo reservoir mexico was used to run a three dimensional hydrodynamic model and the simulated flow field was used to characterize the horizontal motions and investigate the dispersal of waterborne particles driven by the dominant circulation patterns the surface layer horizontal motions included an oscillatory component associated with two basin scale internal wave modes and a spatially and temporally complex flow field associated mostly with topographic circulation modeling of particle advection by the horizontal motions led to areal dispersal rates of o 1 to o 10 m2 s 1 comparable with bulk dispersion rates observed in other surface layer studies the aperiodic topographic component of the horizontal flow field not the oscillatory motion or a combination of both sustained most of the particle dispersal in particular local flow features such as stagnation points were shown to be a significant driver for horizontal dispersion and should be taken into consideration when analyzing horizontal distributions of waterborne material

modeling basin scale internal waves in a stratified lake basin scale internal waves provide the driving forces for vertical and horizontal fluxes in a stratified lake below the wind mixed layer thus correct modeling of lake mixing and transport requires accurate modeling of basin scale internal waves examining this capability with a hydrostatic z coordinate three dimensional 3d numerical model at coarse grid resolutions is the focus of this paper it is demonstrated that capturing the correct thermocline forcing with a 3d mixed layer model for surface dynamics results in a good representation of low frequency internal wave dynamics the 3d estuary and lake computer model elcom is applied to modeling lake kinneret israel and is compared with field data under summer stratification conditions to identify and illustrate the spatial structure of the lowest mode basin scale kelvin and poincarewaves that provide the largest two peaks in the internal wave energy spectra the model solves the unsteady reynolds averaged navier stokes equations using a semi implicit method similar to the momentum solution in the trim code with the addition of quadratic euler lagrange dis cretization scalar e g temperature transport using a conservative flux limited approach and elimination of vertical diffusion terms in the governing equations a detailed description is provided of turbulence closure for the vertical reynolds stress terms and vertical turbulent transport using a 3d mixed layer model parameterized on wind and shear energy fluxes instead of the convential eddy viscosity diffusivity assumption this approach gives a good representation of the depth of the mixed layer at coarse vertical grid resolutions that allows the internal waves to be energized correctly at the basin scale wind stresses surface heating and density currents form the driving energy fluxes of a stratified lake the basin scale energy flux from the wind is of particular interest because of its dominant role in setting the thermocline in motion which in the absence of inflows and outflows is the primary energy store for transport and mixing below the wind mixed layer thus modeling the basin scale internal wave behavior is an a priori requirement to modeling and quantifying the flux paths of nutrients in a stratified lake imberger 1994 this paper takes a first step in this direction by analyzing our ability to model basin scale internal waves that are seen in lake kinneret israel energy flux path in a stratified lake energy flux through a stratified lake has a fundamental dependence on forced and free baroclinic motions the wind imparts both momentum and turbulent kinetic energy tke to the water in the sur face layer the tke distributes momentum vertically in the

sedimentologic and stratigraphic properties of early cretaceous neo tethys shelf margin of arabia the qamchuqa formation of the zagros folded zone kurdistan region of iraq abstract the qamchuqa formation is well exposed in the high folded zone hfz of northeast iraq the formation is highly dolomitized and contains thick reservoir units in the subsurface region south of the hfz deposition of the formation took place at the shelf margin of early cretaceous neo tethys ocean it merges south and southeastward to the shallow marine shelf of arabia and to deep basin accumulations farther north in the study area the formation is divided into three members lower member 250m thick of interbedded bioclastic calcimudstone wackestone mw bioclastic packstone bp bioclastic floatstone bf and medium to coarse crystalline dolorudstone dolograinstone cd these strata accumulated in low to medium energy subtidal fore shoal setting the middle member consists of thick succession 325m of massively bedded cd lithofacies interpreted as high energy shoal facies which represents barremian aptian main shelf margin succession the upper member 155m thick consists of three lithofacies of mw cd and fine crystalline dolomudstone fd in ascending order it is interpreted as lagoon mw through subtidal carbonate sand shoal cd to supratidal penecontemporaneous dolomudstone fd the lower two members represent a long term barremian to aptian shallowing upward megacycle capped by late aptian unconformity incurred by relative sea level drop this temporal gap is coeval with an erosional vacuity recognized throughout the arabian peninsula sea level rise in early albian heralded deposition of the upper member which also represents a shallowing upward cycle surmounted by regionally extensive subaerial unconformity recognized in the arabian peninsula correlation and stratigraphic position of the formation under regional context has been discussed

the initial response of a stratified lake to a surface shear stress laboratory experiments are used to study the initial response of a stratified fluid to the action of a wind stress the experiments are described in the context of a parameterization scheme that quantifies the strength of the applied stress relative to the bulk stability of the fluid and also the duration of the wind stress relative to the periods of the waves generated by the stress this study concentrates on the first fundamental internal wave period in experiments where the fluid is considered to have upwelled i e the stratified region of the fluid reaches the surface at the upwind endwall the majority of the experiments use three layer initial density profiles as an approximation to a continuously stratified water column a linear model using normal modes proved successful prior to the commencement of upwelling and this enabled an estimate to be made of the time at which upwelling occurred at this point the wave development ceased and the flows developed via entrainment mechanisms consideration of the energy budget showed that little of the input energy was stored in the system the initial mixing efficiency defined as the ratio of the mean potential energy gained to the energy imparted by the belt never exceeded 30 peak efficiency occurred when the surface stress was just sufficient to bring the interfacial region to the surface

melange genesis and ophiolite emplacement related to subduction of the northern margin of the tauride anatolide continent central and western turkey the tauride anatolide continent stretching for c 900 km across western and central turkey is one of the world s best example of a subducted exhumed passive margin within a collisional orogen twelve widely separated areas were studied and correlated to develop a new plate tectonic model a metamorphosed rifted continental margin of triassic lower cretaceous age tauride anatolide platform is overlain by upper cretaceous cenomanian lower maastrichtian pelagic sediments and then by both tectonic melange subduction complexes and sedimentary melange foredeep gravity complexes the melanges are overthrust by unmetamorphosed ophiolitic rocks commonly peridotites with swarms of diabase gabbro dykes and are underlain by metamorphic soles new geochemical evidence from basaltic blocks in the melange indicates predominantly subduction influenced within plate and mid ocean ridge type settings the dykes cutting the ophiolites were probably intruded during early stage intra oceanic arc genesis the metamorphosed continental margin melanges and ophiolites in the north anatolides are correlated with unmetamorphosed equivalents in the taurides further south e g beysehir and lycian nappes oceanic crust of triassic late cretaceous age formed between the gondwana related tauride anatolide continent in the south and the eurasia related sakarya microcontinent in the north following late triassic early cretaceous passive margin subsidence the continental margin was covered by cenomanian turonian pelagic carbonates c 98 90 ma ophiolites formed in an intra oceanic subduction zone setting in response to northward subduction probably within a two stranded ocean with the inner tauride ocean in the se and the izmir ankara erzincan ocean in the north nw metamorphic soles relate to intra oceanic subduction c 95 90 ma oceanic sedimentary igneous rocks accreted to the advancing supra subduction oceanic slab the tauride anatolide continental margin then underwent diachronous collision with the trench c 85 ma deeply subducted and metamorphosed at hp lt c 80 ma accretionary ophiolitic and exhumed hp lt rocks were gravity reworked into a southward migrating flexural foredeep and progressively overridden c 70 63 ma slices of the upper part of the platform and its margin detached and were thrust southwards as the tauride lycian and beysehir nappes together with regional scale ophiolites the continental margin and melange were simultaneously exhumed during maastrichtian early paleocene 70 63 ma and transgressed by shallow water sediments beginning in the late maastrichtian in the east c 64 ma and the mid late paleocene c 60 ma further west remnant oceanic crust was consumed during early cenozoic time followed by mid eocene 45 40 ma diachronous continental collision and a second phase of regional deformation rather than being progressive there were two stages of collision first upper cretaceous ophiolite emplacement driven by continental margin subduction trench collision and secondly eocene collision of the tauride and sakarya eurasian continents

late cretaceous oceanic crust and early tertiary foreland basin development euboea eastern greece in northern euboea eastern greece late cretaceous platform carbonates of the pelagonian zone pass depositionally upwards into maastrichtian hemipelagic limestones possibly reflecting a rifting event in the adjacent neotethys this is followed by a c 1 km thick unit of siliciclastic turbidites debris flows and detached limestone blocks thrust intercalations of ophiolitic rocks comprise altered pillow basalts and ultramafic rocks with ophicalcite calcite veins in sheared serpentinite contain planktonic foraminifera and the ophicalcite is directly overlain with a depositional contact by globotruncana bearing pelagic limestones and calciturbidites of maastrichtian age the ophiolitic rocks are interpreted as late cretaceous oceanic crust and mantle that formed at a fracture zone or rifted spreading axis within a neotethyan vardar basin to the east during the early tertiary palaeocene eocene the neotethyan basin began to close with development of a subduction accretion complex mainly comprising sheared trench type sandstones associated with ophiolitic slices in response to trench margin collision the pelagonian carbonate platform foundered and limestone debris flows and olistoliths were shed into a siliciclastic foreland basin suturing of the neotethyan ocean basin then resulted in westwards thrusting of oceanic units over the foreland basin thrusting of slices of inferred late cretaceous pelagonian carbonate platform slope and large scale recumbent folding

late stage tectonic evolution of the al hajar mountains oman new constraints from palaeogene sedimentary units and low temperature thermochronometry mountain building in the al hajar mountains ne oman occurred during two major shortening stages related to the convergence between africa arabia and eurasia separated by nearly 30 ma of tectonic quiescence most of the shortening was accommodated during the late cretaceous when northward subduction of the neo tethys ocean was followed by the ophiolites obduction on top of the former mesozoic margin this shortening event lasted until the latest santonian early campanian maastrichtian to eocene carbonates unconformably overlie the eroded nappes and seal the cretaceous foredeep these neo autochthonous post nappe sedimentary rocks were deformed along with the underlying cretaceous tectonic pile during the second shortening event itself including two main exhumation stages in this study we combine remotely sensed structural data seismic interpretation field based structural investigations and apatite u th he ahe cooling ages to obtain new insights into the cenozoic deformation stage seismic interpretation indicates the occurrence of a late eocene flexural basin later deformed by an oligocene thrusting event during which the post nappe succession and the underlying cretaceous nappes of the internal foredeep were uplifted this stage was followed by folding of the post nappe succession during the miocene ahe data from detrital siliciclastic deposits in the frontal area of the mountain chain provide cooling ages spanning from 17 3 to 42 ma consistent with available data for the structural culminations of oman our work points out how renewal of flexural subsidence in the foredeep and uplift of the mountain belt were coeval processes followed by layer parallel shortening preceding final fold amplification

late cretaceous paleocene formation of the proto zagros foreland basin lurestan province sw iran late cretaceous emplacement of ophiolitic radiolaritic thrust sheets over the arabian passive margin was the first manifestation of the protracted closure of the neotethys ocean which ended with the continental collision between arabia and central iran and the formation of the present zagros fold belt this tectonic stacking produced a flexural basin the amiran basin 400 200 km in size in the northwest zagros that was filled with a 1225 m thick shallowing upward detrital succession made up of the amiran taleh zang and kashkan formations this succession sits unconformably above the late cretaceous gurpi formation and is overlain by the oligocene miocene shahbazan asmari carbonate succession dating of the amiran kashkan succession is based on detailed biostratigraphy using large foraminifera and calcareous nannoplankton the cretaceous tertiary k t boundary is located within the uppermost 25 45 m of the gurpi formation the overlying amiran and taleh zang formations have been dated as paleocene in age however the base of the paleocene within the gurpi formation lacks np1 and np2 zones implying a hiatus of 2 m y at ca 65 5 ma which is inferred to correspond to an early folding phase near the cretaceous paleocene boundary the upper part of the kashkan formation is dated to the earliest eocene by palynostratigraphy a large hiatus or very slow deposition lasting about 15 m y occurs between the kashkan and shahbazan formations in the studied region the base of the prograding shahbazan platform deposits is dated by 87sr 86sr stratigraphy at ca 33 9 ma the upper part of the asmari formation is dated as early middle miocene using foraminifera associations reconstruction of the amiran taleh zang kashkan succession of the amiran basin indicates a thickening of the basin fill from the southern pinch out along the se flank of the kabir kuh anticline to sw of the khorramabad anticline where the flexure is at least 900 m in contrast the ne part of the basin underwent coeval contraction and uplift of 1300 m superimposed smaller undulations onto the large scale flexure are interpreted as late cretaceous paleocene folds regional comparisons se zagros oman and turkey indicate that late cretaceous early tertiary deformation affected the entire ne margin of arabia but that compression was not synchronous being younger in lurestan than in the nw persian gulf where inversion tectonics occurred from turonian to mid campanian times the long sedimentary hiatus spanning most of the middle and late eocene must have been related to deep lithospheric processes linked to the initial events of the protracted closure of the neotethys ocean between arabia and central iran the tectono sedimentary history recorded in the zagros basin may help to understand early foreland basin growth in other orogens in which subsequent continental collision has obliterated these early events

oman exotics oceanic carbonate build ups associated with the early stages of continental rifting the so called oman exotic limestones form isolated masses from boulder size to 1 000 m thick of middle to upper permian and upper triassic fossiliferous limestones and crop out within imbricated thrust slices beneath the semail ophiolite in the oman mountains permian exotics are of dominantly reef and forereef facies whereas triassic exotics are more typically of back reef and lagoonal facies they are commonly associated with a substrate of alkalic and transitional tholeiitic basalts and are interpreted as a series of reef associated carbonate buildups deposited in part on oceanic islands or seamounts close to the site of initial rifting of the oman continental margin

cenomanian early turonian carbonate platform of northern oman stratigraphy and palaeo environments abstract the jebel akhdar and adam foothills outcrops in northern oman arabian peninsula offer the opportunity to study in detail the lateral and vertical changes of a cenomanian early turonian carbonate platform formed by the natih formation wasia group eleven sections with less than 5 km offset were logged to express metre scale lithological and biostratigraphical vertical changes the first rudist zonation is established complementing classical benthonic foraminifer and ammonite biozones typical cenomanian rudist association caprinids and radiolitids occur in the natih e c d a lower part whereas lower turonian hippuritid rudists are represented in the upper part of the natih a a sedimentological and palaeoecological approach leads to identification and interpretation the facies and discontinuities of the natih carbonate platform and to a reconstruction of its spatial organization application of the concepts of sequence stratigraphy allows interpretation of the units of the natih in terms of systems tracts an attempt is made to correlate the sequence stratigraphical model to eustatic sea level changes and regional tectonic events three palaeoenvironmental models taking into account bio and lithofacies are proposed

an experimental study of the upwelling response of stratified reservoirs to surface shear stress an experimental study of the dynamic response of non rotating stratified reservoirs to the application of surface shear stresses is presented the experiments were made using two layered and linear stratifications a moving belt was used to supply a shear stress to the fluid detailed measurements of the density field show that upwelling occurs at all values of the wedderburn number w rather than only occurring when w 1 differences between the two layer theory and the present observations are attributed to the fact that the experimental stratifications were continuous rather than layered shearflow dispersion is observed to be an important mechanism for distributing the effects of localized upwelling over the entire length of the mixed layer a model of mixed layer deepening based on upwelling and shearflow dispersion is presented and is compared to the observations of this and other experimental studies

a model for carbonate to terrigenous clastic sequences the development of carbonate sequences that grade toward a source region into terrigenous clastic sediment is poorly understood in both carbonate and terrigenous clastic regimes environments of rapid sedimentation have comparable rates of deposition 102 to 102 5 cm 1 000 yr slowest continuous rates are also comparable 100 5 to 101 cm 1 000 yr because of the inhibiting effect of terrigenous deposition on carbonate skeletal production the slowest rates in a transect tend to occur where mixed lithologies are deposited midway between coarse clastic and pure carbonate sediments this leads to a bimodal distribution of rapid depositional rates and invariably to the development of a basin in the intervening area to develop a model we combine concepts of depositional rate with knowledge of the middle ordovician carbonate to terrigenous clastic sequence of the southern appalachians deposition began on a shallow water ramp sloping gently eastward but everywhere within the photic zone an episode of tectonic subsidence differentiated this ramp into a shallow shelf on the northwest and a deep starved basin on the southeast separated by a linear shelf margin with organic build ups subsequent development of the sequence consisted of the filling of the deep basin first with pelagites then with turbidites during which the carbonate shelf was isolated from terrigenous deposition once the basin filled terrigenous deposition began to affect the shelf inhibition of carbonate deposition near the shelf edge led to formation of successively smaller basins within the old shelf area after the initial pulse of tectonic subsidence deposition of the sequence can be explained by sediment loading subsidence thus the ordovician sequence coupled with the concept of bimodal distribution of sedimentation rates in carbonate to terrigenous clastic facies patterns allows development of a model for basins adjacent to active tectonic lands five model stages are derived by application of calculated deposition rates and sediment loading along a transect away from the terrigenous source these stages are 1 an initial carbonate ramp stage followed by 2 a carbonate shelf starved deep basin stage 3 a carbonate shelf turbidite basin terrigenous shelf stage 4 a carbonate shelf narrowed and shallowed basin broad terrigenous shelf stage and finally 5 a stage in which the initial basin is filled a subsequent starved basin forms on the old carbonate shelf and a new carbonate shelf margin forms a few to tens of kilometres farther from the terrigenous source the model should be useful in predicting depositional facies in analogous basins

zabyat formation semail nappe oman sedimentation on to an emplacing ophiolite the pelagic sediments of the semail ophiolite are depositionally overlain by ophiolite derived sediments of the zabyat formation dominated by matrix supported rudites with subordinate arenites and lutites the detritus was locally derived from the ophiolite in a deep marine environment indicated by both underlying and overlying pelagic carbonates the zabyat rocks are restricted to fault zones in the ophiolite which were active during emplacement they are interpreted as debris shed from the sub vertical fault zones during the initial disruption of the semail ocean floor prior to the final emplacement on to the arabian continental margin this interpretation places constraints on possible mechanisms of ophiolite emplacement

the strongly damped baroclinic response to wind in a multibasin reservoir field data and a forced modal based two layer variable cross section model tlvc were used to examine the baroclinic response to wind in a large multibasin reservoir nechako reservoir british columbia canada the tlvc showed that most of the thermocline deflections at the dam could be accounted for by considering the first two basins upstream of the dam knewstubb and natalkuz lakes and that the thermocline deflections were dominated by the first h1 and second h2 horizontal baroclinic modes of the combined basins calibration of the tlvc against the field data showed that the h1 and h2 modes were strongly damped with effectively no free thermocline oscillations this strong damping had two effects high coherence between the wind and thermocline deflections and phase lags between thermocline deflections at different locations the damping in nechako reservoir is stronger than in many lakes and results from both high velocities within the geometric constriction between knewstubb and natalkuz lakes and drag due to submerged trees which cover 30 of the bed our study provides a picture of overdamped baroclinic response and shows how useful information about the baroclinic response in complex bathymetries can be obtained using relatively simple tools such as the tlvc

influence of climate and dolomite composition on dedolomitization insights from a multi proxy study in the central oman mountains abstract dedolomitization is an important diagenetic process that can yield information on the history of paleo fluids in a given aquifer or outcrop and by extension it offers a window into past hydrologic conditions dedolomitization is also relevant economically as it can alter the porosity and permeability of carbonates thus affecting reservoir quality despite considerable research the process of dedolomitization is still not entirely understood here new findings from the central oman mountains highlight the importance of dolomite chemistry and fluctuating climate on dedolomitization petrographic mineralogical and geochemical data from both altered and pristine dolomite hosted in jurassic carbonate rocks from the sahtan group and outcropping at wadi mistal in the jebel akhdar tectonic window reveal two dolomite bodies with different characteristics stratabound and fault related dolostone the ferroan dolomite crystals are larger in the fault related dolostone whereas the non ferroan dolomite crystals are smaller in the stratabound dolostone petrography reveals a complex suite of alteration textures including pristine dolomite recrystallized dolomite and calcitized dolomite dedolomite iron oxides are present pervasively in the altered rocks and different alteration textures co occur in the same sample relative to unaltered dolomite in this outcrop the recrystallized dolomite is characterized by similar positive carbon isotope values but less negative oxygen isotope values and the calcitized dolomite is characterized by even less negative oxygen isotope values and more negative carbon isotope values based on field data and petrography two phases of alteration are evident an earlier dedolomitization event affecting the stratabound dolomite only and a more pervasive pleistocene holocene alteration phase associated with surface weathering that affected both the fault related dolomite and to a lesser extent the stratabound dolomite stable isotope results further suggest that the more recent subaerial weathering phase happened under two alternating climate regimes dedolomitization was triggered by meteoric fluids that interacted with soil related carbon during humid climatic period s whereas recrystallization of ferroan fault related dolomite happened during more arid climatic period s with less developed soils and lower fluid rock interaction these results suggest that weathering of ferroan fault related dolomite can lead to formation of goethite and recrystallized non stoichiometric dolomite with a reset stable oxygen isotope signature and sometimes to dedolomitization

detection of hydrothermal mineralized zones associated with listwaenites in central oman using aster data abstract listwaenites are highly altered ultramafic rocks that are potentially associated with economic mineralization and research on these is extremely important worldwide in the present study the classification of mineralized listwaenites developed along the serpentinite amphibolite interface of the semail ophiolite its associated lithology and the zones of alteration and mineralization in the fanjah saddle of the central oman mountains region of the sultanate of oman are carried out using advanced spaceborne thermal emission and reflection radiometer aster satellite data the developed band ratioing principal component analysis pca and the spectral angle mapper sam supervised classification and image processing techniques applied on the aster data set have proved their capability for better interpretation and identification of hydrothermally altered rocks and associated mineralization the hyperspectral tools minimum noise fraction mnf pixel purity index ppi and nd visualizer extracted end member spectra and sam classification clearly show the occurrence of minerals and their spatial distributions the promising results are verified and confirmed in the field by identification of alteration and mineralization such as listwaenites silicification serpentinization and talc alteration and are validated further through laboratory analysis the confirmation of the occurrence of base metal mineralization along the serpentinite amphibolite interface in listwaenites suggests that detailed investigation in this and other arid regions which have similar geological conditions may locate mineral deposits the hyperspectral tools applied on aster satellite data show that these can be used as a powerful tool to explore the listwaenites and the potential associated mineralization in other arid geographical regions worldwide

the structure and dynamics of internal waves in baldeggersee1 analysis of long records of temperature depth distribution determined at lo or 20 min intervals at several stations and extending over three stratification seasons provides a detailed picture of the characteristics dynamics and seasonal variation in activity of internal waves in a small lake baldeggersee switzerland wind stress in general was low with occasional bursts of higher energy the ensuing slightly damped internal seiches govern the dynamics of the stratified lake the vertical structure displays a dominant response of the first vertical mode responses in the second vertical mode hitherto rarely recorded are also demonstrated with the help of spectral analysis and models the horizontal structure of the seiches motion displays dominance and persistence of the fundamental basin mode spectral analysis also discloses responses of the second and third basin modes multiplying of the spectra with the local buoyancy frequency leads to a collapse of all spectra into a narrow band pointing toward the possibility of a universal spectrum new light is shed on apparently common examples of waveform asymmetry and on their interpretation it is concluded that in this small basin low energy example internal waves provide motions at all levels but little vertical mixing

k ar ages of metamorphic rocks at the base of the samail ophiolite oman hornblendes from amphiobolities in the sheet of metamorphic rocks beneath the peridotite member of the samail ophiolite and phyllites farther from the peridotite contact have weighted mean sup 40 ar sup 39 ar total fusion ages of 90 0 3 0 m y and 79 5 3 0 m y respectively the amphibolities represent the first tectonic slice welded to the base of the samail ophiolite after it was detached from the tethyan oceanic crust formation of the amphiobolities occurred no more than 3 to 7 m y after crystallization of plagiogranite in the ophiolite the phyllites represent another tectonic slice of ocean floor sediments welded to the ophiolite as it was transported further from the tethyan spreading axis the k ar ages suggest assuming a half spreading rate of 2 to 5 cm yr that detachment of the samail ophiolite and formation of amphibolite facies rocks occurred no more than 60 to 350 km from spreading center using the same spreading rate one can calculate a minimum half width of 300 to 750 km for the tethyan ocean during the late cretaceous

k ar ages of alkaline igneous rocks in the northern oman mountains ne arabia and their relations to rifting passive margin development and destruction of the oman tethys k ar ages of biotites from a variety of alkaline volcanics and minor intrusive rocks in the nothern oman mountains allochthon give a range of ages from triassic 230 ma to mid cretaceous 92 ma and represent igneous activity on the oman continental margin throughout the mesozoic this was a passive margin destroyed by the emplacement across it of a pile of nappes in the late cretaceous including a largely intact thrust sheet of upper cretaceous oceanic lithosphere the semail ophiolite biotite ankaramite dykes cutting compositionally similar volcanics in the thrust complex immediately beneath the ophiolite give triassic ages and are related to the rifting and break up of the northeast arabian margin at the beginning of formation of the oman tethys mid cretaceous cenomanian turonian ages are mostly recorded from the northern part of the mountains where there are alkaline tuffs in a sedimentary melange they are approximately the same age as the ophiolite and may be related to tectonic instability of the oman margin immediately prior to ophiolite emplacement alkaline sills intrusive into a variety of rocks including triassic volcanics give jurassic and cretaceous ages and are interpreted as periodic alkaline activity on the oman margin throughout passive margin development

the internal seiches in gullmar fjord part i dynamics abstract internal seiche motions with period 1 3 days in gullmar fjord are investigated based on mooring data with high vertical and time resolution the period and structure of the internal seiches are well described by a simple analytical three layer model taking into account blocking of the basin water at the sill energy budgets for forcing and damping of the seiches are estimated the internal seiches are forced by direct wind stress on the surface and by internal coastal waves of frequency close to the seiches the latter contribution being a little larger the e folding timescale for the internal seiche damping is approximately equal to the seiche periods which means that the seiches are effectively damped but also that the forcing must be in near resonance in order to maintain the observed seiche motions in the basin water the seiches manifest themselves with large vertical motions and clear upward phase propagation the phase propagation is related with a continuous rather than strictly layer

overview of tectonic settings related to the rifting and opening of mesozoic ocean basins in the eastern tethys oman himalayas and eastern mediterranean regions

caesium from former dartmoor volcanism its incorporation in new red sediments of sw england high concentrations of caesium occur in the new red sandstone of devon england values are most abundant in breccias at the base of the permian and decrease upwards through the sandstones and marls caesium resides in the clay fraction extensive volcanic activity on the south eastern edge of the cornubian massif provided a supply of cs due to its low ionic potential this alkali was concentrated at source under extreme weathering in the hydrolysate fraction of red bed sediments the source area was largely exhausted by late permian reflected by a reduction in cs content of new red sandstone detritus

the cimmerian orogeny in northern iran tectono stratigraphic evidence from the foreland from the permian onwards the gondwana derived iran plate drifted northward to collide with eurasia in the late triassic thereby closing the palaeotethys this eo cimmerian orogeny formed the cimmeride fold and thrust belt the upper triassic middle jurassic shemshak group of northern iran is commonly regarded as the cimmerian foreland molasse however our tectono stratigraphic analysis of the shemshak group resulted in a revised and precisely dated model for the triassic jurassic geodynamic evolution of the iran plate initial cimmerian collision started in the carnian with subsequent late triassic synorogenic peripheral foreland deposition flysch lower shemshak group subduction shifted south in the norian onset of neotethys subduction below iran and slab break off around the triassic jurassic boundary caused rapid uplift of the cimmerides followed by liassic post orogenic molasse middle shemshak group during the toarcian aalenian upper shemshak group neotethys back arc rifting formed a deep marine basin which developed into the oceanic south caspian basin during the late bajocian late jurassic

a longitudinal carbonate fan from the jurassic of the oman mountains the guweyza limestone formation of the hamrat ad duru abstract when sedimentological stratigraphical and structural data are considered the continental rise sediments of oman neo tethys the hamrat duru group can be restored to their original basin configuration prior to their southwest directed emplacement with the semail ophiolite onto the oman continental margin during the late cretaceous the hamrat duru group sediments are preserved in well exposed imbricate fans the largest of which forms the hamrat ad duru range in the south central oman mountains in the south central hamrat ad duru middle and upper jurassic ooid rich carbonate sediment was transported from the adjacent oman carbonate platform during periods of tectonic instability into the oman neo tethys hawasina basin by high and low density turbidity currents to form sediment sheets with a margin parallel axis of deposition palaeocurrents are northwest directed parallel to the oman margin along the southwest of the hamrat ad duru and northeast directed away from the margin in structurally higher more distal imbricates of the northeastern hamrat ad duru this implies sediment input at the southern end of the hamrat ad duru these trends are reflected in the distribution of sedimentary facies with most proximal facies developed in the southern hamrat ad duru passing into progressively more distal facies to the northwest and northeast sediment thinning and fining is more accentuated away from the margin towards the northeast and sedimentation was concentrated parallel to the oman margin the hamrat ad duru represents a longitudinal fan that was at least 120 km long and extended at least 60 km away from the margin

gravity anomalies and flexure of the lithosphere at mountain ranges the bouguer gravity anomaly over the himalayan alpine and appalachian mountains is characterized by a generally asymmetric gravity low which spans the mountains and associated foreland basins the minimum of the gravity low is generally systematically displaced from the region of greatest topographic relief and shows no obvious relationship to surface geology in addition the alps and appalachians are associated with a generally symmetric gravity high that is unrelated to the topographic relief together the gravity low and high form a characteristic positive negative anomaly couple the steep gravity gradient between the positive and negative couple correlates with the insubric line and its equivalents in the alps and the brevard zone in the southern appalachians this gravity anomaly couple is interpreted as evidence for flexure of the continental lithosphere by subsurface buried and surface topographic loading the magnitude of the subsurface load is estimated from the integrated excess mass represented by the positive anomaly and the magnitude of the surface load from the topography by combining these loads the flexure of the lithosphere and the associated bouguer gravity anomaly are calculated for different assumed values of the elastic thickness te of continental lithosphere the best fitting value of te for the himalayas is 80 100 km for the alps 25 50 km and for the appalachians 80 130 km the model calculations suggest that the main contribution to the gravity couple in the alps and appalachians arises not from surface loads such as thrust sheets and nappes but from subsurface loads however in the case of the himalayas the topography appears to be a sufficient load to explain the observed asymmetric gravity low when subsurface loads do exist therefore we would not expect a close correlation between mountain topographic relief and depth to the m discontinuity as required by classical models of isostasy rather the m discontinuity is expected to relate to the center of mass of all the loads acting on the lithosphere the surface and subsurface loads inferred from the gravity anomaly play a major role in the development of mountains and foreland basins the emplacement of large subsurface loads represents the primary event in the alps and appalachians while in the himalayas the emplacement of the surface load is the primary event the emplacement of the subsurface load probably marks the initiation of foreland basin development the regional characteristics of the basin are controlled by the primary load while local variations are controlled by the secondary thrust sheet loads subsequent movement of either load will produce migration of the basin depocenter the origin of the subsurface load is not clear but its association with the insubric line in the alps and the brevard zone in the appalachians suggests that it may be related to the obduction of crustal blocks flakes onto the underlying plate during continental collision or possibly to the preloaded crustal structure of the underlying plate

constraining the onset of flexural subsidence and peripheral bulge extension in the miocene foreland of the southern apennines italy by sr isotope stratigraphy abstract in fold and thrust belts developing at convergent margins the migration of the advancing wedge is accompanied by bulging of the downgoing plate followed by the development of a foredeep basin filled by a thick succession of syn orogenic sediments the transition from forebulge to foredeep marks a key moment in the evolution of the orogenic system in deep water environments the record of this transition is typically complete and progressive conversely in the shallow water continental environment of many collisional systems the uplift of the forebulge area can imply emersion and erosion obliterating the stratigraphic record of key steps of the evolution of the orogenic system the southern apennines constitute one of these collisional fold and thrust belts where the development of the forebulge has implied emersion and erosion with the development of a miocene forebulge erosional unconformity accompanied by extensional deformation associated with the bending of the lithosphere during the forebulge stage in this paper we use strontium isotope stratigraphy to constrain with unprecedented time resolution the age of the forebulge unconformity in areas presently incorporated in the northern sector of the southern apennines fold and thrust belt integration of our results and those of previous studies indicates at the regional scale a younging toward the foreland of the forebulge unconformity across the belt our high resolution ages also reveal a diachronous onset of the flexural subsidence over short distances associated with the occurrence of horst and graben structures possibly resulting from inherited paleotopography along with forebulge extension this work highlights how high resolution dating is critical to unravel the evolution of foreland basin systems at different scales

formation and exhumation of blueschists and eclogites from ne oman new perspectives from rb sr and 40ar 39ar dating seven eclogite facies samples from lithologically different units which structurally underlie the semail ophiolite were dated by the 40 ar 39 ar and rb sr methods despite extensive efforts phengite dated by the 40 ar 39 ar method yielded saddle hump or irregularly shaped spectra with uninterpretable isochrons the total gas ages for the phengite ranged from 136 to 85 ma clinopyroxene phengite epidote phengite and whole rock phengite rb sr isochrons for the same samples yielded ages of 78i2 ma we therefore conclude that the eclogite facies rocks cooled through 500 u ca tc 7 8i2 ma and that the 40 ar 39 ar dates can only constrain maximum ages due to the occurrence of excess ar inhomogeneously distributed in different sites our new results lead us to conclude that high pressure metamorphism of the oman margin took place in the late cretaceous contemporaneous with ophiolite emplacement previously published structural and petrological data lead us to suggest that this metamorphism resulted from intracontinental subduction and crustal thickening along a ne dipping zone choking of this subduction zone followed by ductile thinning of a crustal mass wedged between deeply subducted continental material and overthrust shelf and slope units facilitated the exhumation of the eclogite facies rocks from depths of c 50 km to 10 15 km within c 10 ma and led to their juxtaposition against overlying lower grade rocks final exhumation of all high pressure rocks was driven primarily by erosion and assisted by normal faulting in the upper plate

zagros orogeny a subduction dominated process this paper presents a synthetic view of the geodynamic evolution of the zagros orogen within the frame of the arabia eurasia collision the zagros orogen and the iranian plateau preserve a record of the long standing convergence history between eurasia and arabia across the neo tethys from subduction obduction processes to present day collision from 150 to 0 ma we herein combine the results obtained on several geodynamic issues namely the location of the oceanic suture zone the age of oceanic closure and collision the magmatic and geochemical evolution of the eurasian upper plate during convergence as testified by the successive sanandaj sirjan kermanshah and urumieh dokhtar magmatic arcs the p t t history of the few zagros blueschists the convergence characteristics across the neo tethys kinematic velocities tomographic constraints subduction zones and obduction processes together with a survey of recent results gathered by others we provide lithospheric scale reconstructions of the zagros orogen from 150 to 0 ma across two sw ne transects the evolution of the zagros orogen is also compared to those of the nearby turkish and himalayan orogens in our geotectonic scenario for the zagros convergence we outline three main periods regimes 1 the mid to late cretaceous 115 85 ma corresponds to a distinctive period of perturbation of subduction processes and interplate mechanical coupling marked by blueschist exhumation and upper plate fragmentation 2 the paleocene eocene 60 40 ma witnesses slab break off major shifts in arc magmatism and distributed extension within the upper plate and 3 from the oligocene onwards 30 0 ma collision develops with a progressive sw migration of deformation and topographic build up sanandaj sirjan zone 20 15 ma high zagros 12 8 ma simply folded belt 5 0 ma and with partial slab tear at depths 10 ma to present our reconstructions underline the key role played by subduction throughout the whole convergence history we finally stress that such a long lasting subduction system with changing boundary conditions also makes the zagros orogen an ideal natural laboratory for subduction processes

uranium lead isotopic ages of the samail ophiolite oman with applications to tethyan ocean ridge tectonics plagiogranites are a minor but widespread component of the samail ophiolite plutonic member they crystallized from the most fractionated melts generated by magmatic crystallization and differentiation of a steady state magma chamber beneath the tethyan spreading ocean ridge and their ages are thought to mark the time of ocean crust formation isotopic u pb ages of zircons from 13 plagiogranites collected along a 270 km segment of the samail ophiolite subparallel to the regional trend of the sheeted dike complex the former spreading ridge axis direction define a narrow time interval of 93 5 97 9 m y with a pronounced clustering about 95 m y the zircon ages of the plagiogranites agree remarkably well with the early cenomanian to early turonian biostratigraphic ages of sediments that are intercalated within the ophiolite pillow lavas and that lie just above them tippit et al 1981 the agreement of radiometric and biostratigraphic ages provides strong support for the conclusion that the plagiogranite u pb ages closely date the time span of ocean crust formation no step changes in age patterns are observed along the ridge axis sheeted dike direction suggesting that there are no major internal offsets of the ophiolite by transform or other faults along most of the traverse one possible exception occurs at the southeastern end of the sampled interval ibra area where a 3 m y discontinuity might be caused by an unmapped fault assuming that the regional trend of the sheeted dikes n10 25 w marks the direction of the former spreading ridge axis the present array of sample localities spans a distance of 130 to 195 km normal to that axis i e in the spreading direction the data as a whole do not define a clear cut age trend normal to the spreading axis but by eliminating samples that may be aberrant due to faulting the data array suggests a pattern of increasing ages from east to west this would indicate that the samail ophiolite is derived from the western southwestern side of the tethyan spreading system a conclusion reached independently from geological evidence also the gentle age gradient in the spreading direction i e between 130 and 195 km of ocean crust were formed within an age span of no more than 2 m y suggests a very fast spreading rate this conclusion also is supported by independent geologic evidence

the climatology of internal waves in a deep temperate lake kootenay lake is a long 100 km deep 140 m dimictic lake in southeastern british columbia internal waves were observed over an 18 month period using three thermistor chains moored along the major axis of the lake to characterize their seasonal aspects four types of oscillations are recognized 1 classical seiches with amplitudes of 10 30 m and periods of 1 2 weeks 2 intrabasin waves with periods of 2 4 days 3 large amplitude waves resembling nonlinear surges and 4 high frequency waves associated with both the internal surge and large amplitude internal seiche motions the periods of the major components of the internal wave field are determined mainly by morphometry but vary seasonally with stratification thus the wind which not only forces internal waves but can also modify stratification is important in large lakes like kootenay the thermal structure may vary not only spatially but also temporally at periods comparable to those of the internal waves themselves hence the shape and frequency of these waves may be altered as they pass through the lake

sedimentological and structural evolution of the arabian continental margin in the musandam mountains and dibba zone united arab emirates the northernmost extremity of the oman mountains the musandam peninsula is composed of an allochthonous sequence of permian to middle cretaceous shelf carbonates these are separated from ophiolitic rocks to the south by a northeast southwest trending belt known as the dibba zone this structurally complex belt is composed of allochthonous slope and basin facies sediments haybi volcanic rocks oman exotic limestones sub ophiolitic metamorphic rocks and ultra mafic slices lithofacies correlation confirms that fragmentation and rifting of a vast east facing carbonate platform occurred in middle to late triassic time resulting in the establishment of a shelf edge and small ocean basin this margin was typified from northwest to southeast by ooid skeletal lime sand shoals or small bioherms on the shelf edge a bypass foreslope of well laminated periplatform ooze and basin margin accumulations of carbonate turbidites or debris flows the shelf edge now coincides with the northern boundary of the dibba zone and appears to have remained stationary from middle triassic to late jurassic time periods of arrested carbonate sedimentation on the platform either because of exposure late triassic and middle cretaceous or because of drowning late jurassic are represented in the basin by starved sedimentation and deposition of radiolarian cherts a spectacular platform margin collapse occurred in the middle and late cretaceous as represented by massive conglomerates with clasts as young as albian above an unconformity that progressively removed all of the lower cretaceous the tethyan basinal and ophiolitic rocks of the dibba zone were emplaced from the east southeast during the turonian to lower maastrichtian after emplacement of these allochthonous units compressional deformation in the mid tertiary resulted in large scale open whaleback folds with wavelengths as much as 15 km generally with north south axes in places these folds which affect the complete shelf and allochthonous sequences are overturned toward the west and thrusting has caused previously lower tectonic units of the late cretaceous stacking order to be thrust over previously higher tectonic units thus reversing the late cretaceous tectonostratigraphy the maximum amount of translation on the later thrusts is in excess of 5 km on the hagab thrust where the complete shelf carbonate sequence of the musandam mountains has been thrust west northwest over the previously higher hawasina and haybi thrust sheets the tertiary folding and thrusting can be correlated in time and space with the zagros fold belt of southwestern iran

internal waves of the second vertical mode in a stratified lake a time series of measurements of thermal structure and near bottom currents in a stratified lake revealed both first and second vertical mode internal seiching the transition into second mode seiching occurred after first mode waves usually generated by pulses of strong winds died down we describe the major features of the second mode seiche and discuss its effects on mixing in the lake below the thermocline on the basis of calculations of eddy diffusion coefficients there is only weak mixing in the interior of the hypolimnion scaling arguments suggest that mixing at the lake s edges due to motion of the isotherms is not significant despite the larger amplitudes of the second mode seiche the most important mixing region appears to be a turbulent bottom boundary layer driven by seiche currents however resuspension of bottom sediments did not occur probably due to a combination of sediment nature and low current speeds

structure and sequence of thrusting in deep water sediments during ophiolite emplacement in the south central oman mountains abstract sedimentological and stratigraphical investigations of the deep water passive margin sediments of the oman neo tethys the hawasina ocean when allied with structural relationships between duplexes of these units emplaced on to the oman margin during late cretaceous ophiolite obduction allow the reconstruction of sediment distribution in the hawasina ocean from this starting point and the observed stacking order of duplexes the sequence of thrusting of the oceanic sediments can be deduced imbrication proceeded through foreland propagating thrusts whilst the assembled thrust stack was modified at a late stage of emplacement by out of sequence thrusting related to sequential locking of thrust planes towards the hinterland and gravity sliding off the flanks of a major anticline that developed in the underlying autochthonous shelf and basement two main factors governed duplex and imbricate fan formation and distribution firstly two contrasting sedimentary basins were present along the central oman margin the duru basin distal to the al ayn basin secondly competent sedimentary successions were bulldozed ahead of the semail ophiolite whilst less competent shale and chert units were overridden by the ophiolite or imbricated along its leading edge

petrology of lawsonite pumpellyite and sodic amphibole bearing metabasites from north east oman the assemblages chlorite pumpellyite lawsonite albite quartz chlorite lawsonite quartz epidote and chlorite epidote albite quartz occur in metabasaltic blocks and veins in a metamorphosed tectonic melange in the structurally highest unit of the autochthonous and parautochthonous section underlying the semail ophiolite in saih hatat north east oman the pre permian basement of this section contains mafic units characterized by the assemblage crossite epidote chlorite quartz albite el actinolite these assemblages indicate a down section increase in metamorphic grade from lawsonite albite facies conditions in the melange to epidote blueschist facies conditions in the basement application of empirically and experimentally based thermobarometers as well as petrogenetic grids calculated for a model basaltic system indicates that the p t conditions of metamorphism ranged from 3 to 6 kbar and 250 to 300d c for the melange and p 6 8 kbar t 310d c for the basement units textural relations interpreted in the context of petrogenetic grids indicate that these units followed clockwise p t paths of evolution the estimated p t conditions and down section increase in metamorphic grade in central western and northern saih hatat are consistent with the hypothesis relating metamorphism to the late cretaceous tectonic loading of the continental margin by an ophiolite slab 18 km in thickness these results contrast with field and petrological observations documented for blueschists and eclogites exposed along the eastern coast of saih hatat which may have formed at an earlier stage in response to an early cretaceous collisional event

impact of arc continent collision on the conditions of burial and exhumation of uhp lt rocks experimental and numerical modelling abstract a 2 d physical and finite element numerical modelling of arc continent collision was performed to study the deformation and failure of the overriding lithosphere the experimental technique allowed us to model the whole subduction collision process from oceanic subduction to deep subduction of the continental crust with the numerical approach we have modelled the deformation of the overriding plate only through initial stages of its failure and studied the influence of different parameters on this process the results obtained by both techniques are coherent and mutually complementary they show that the failure of the overriding plate is physically quite plausible or even inevitable during subduction the conditions for such a failure the weakening of this plate are prepared during oceanic subduction the weakening occurs due to the interaction between the subducting lithosphere and the asthenosphere in the mantle corner between the two plates and due to back arc spreading in oceanic subduction zones with a compressional regime no back arc opening thick and strong back arc lithosphere the weakest zone is volcanic arc area when weakening becomes sufficient during subduction the lithosphere fails in this area the failure occurs along a fault dipping under the arc in either of two possible directions and results either in subduction reversal or subduction of the fore arc almost half of the presently active subduction zones are characterised by a tensional subduction regime with back arc spreading in such subduction zones the weakest place is not the volcanic arc but the back arc spreading centre when a subduction regime changes from tensional to compressional failure occurs in the vicinity of the extinct spreading centre this process can occur during oceanic subduction again along either a trench vergent or trenchward dipping fault but the formation of a trench verging fault is most likely in this latter case which is a principal subject of our study the failure is followed by partial subduction of the arc plate complete subduction occurs during arc continent collision subduction of the continental margin when tectonic compression of the lithosphere increases rapidly and becomes sufficient to push the arc plate into the mantle the arc itself can be subducted completely or be partially or completely scraped off and accreted a deeply subducted material including continental margin is preserved at relatively low temperatures between the lithospheric mantle and the cold subducted arc plate to about 150 km depth subduction of the arc plate is a major phenomenon which affects all processes associated with continental subduction from deep burial and hp lt metamorphism to exhumation of subducted material does this process occur in nature future investigations will allow us to answer this question in this paper we analyse the conditions of emplacement of a very young oceanic lithosphere samail ophiolite on the continental crust in oman in the late cretaceous and argue that this lithosphere formed in a back arc basin it reached and overthrust the arabian continent after complete subduction of the arc plate

retrodeforming the arabia eurasia collision zone age of collision versus magnitude of continental subduction the arabia eurasia collision has been linked to global cooling the slowing of africa mediterranean extension the rifting of the red sea an increase in exhumation and sedimentation on the eurasian plate and the slowing and deformation of the arabian plate collision age estimates range from the late cretaceous to pliocene with most estimates between 35 and 20 ma we assess the consequences of these collision ages on the magnitude and location of continental consumption by compiling all documented shortening within the region and integrating this with plate kinematic reconstructions shortening estimates across the orogen allow for 350 km of neogene upper crustal contraction necessitating collision by 20 ma a 35 ma collision requires additional subduction of 400 600 km of arabian continental crust using the oman ophiolite as an analogue ophiolitic fragments preserved along the zagros suture zone permit 180 km of subduction of the arabian continental margin plus overlying ophiolites wholesale subduction of this more dense continental margin plus ophiolites would reconstruct 400 500 km of postcollisional arabia eurasia convergence consistent with a ca 27 ma initial collision age this younger arabia eurasia collision suggests a noncollisional mechanism for the slowing of africa and associated extension

the internal wave field in sau reservoir observation and modeling of a third vertical mode water withdrawal from mediterranean reservoirs in summer is usually very high because of this stratification is often continuous and far from the typical two layered structure favoring the excitation of higher vertical modes the analysis of wind temperature and current data from sau reservoir spain shows that the third vertical mode of the internal seiche baroclinic mode dominated the internal wave field at the beginning of september 2003 we used a continuous stratification two dimensional model to calculate the period and velocity distribution of the various modes of the internal seiche and we calculated that the period of the third vertical mode is 24 h which coincides with the period of the dominating winds as a result of the resonance between the third mode and the wind the other oscillation modes were not excited during this period

modeling circulation in lakes spatial and temporal variations the influence of spatial and temporal variations in wind forcing on the circulation in lakes is investigated using field data and the three dimensional estuary and lake computer model elcom applied to lake kinneret lake kinneret field data from six thermistor chains and eight wind anemometers deployed during july 2001 are presented internal wave motions are well reproduced by the numerical model when forced with a spatially uniform wind taken from a station near the lake center however simulated seiche amplitudes are too large especially vertical mode 2 and lead observations by 3 10 h for a 24 h period wave at different locations around the lake consideration of the spatial variation of the wind field improves simulated wave amplitude and phase error at all stations is reduced to less than 1 5 h this improvement is attributable to a better representation of the horizontally averaged wind stress and can be reproduced with a spatially uniform wind that has the same horizontally averaged wind stress as the spatially varying wind field however a spatially varying wind field is essential for simulating mean surface circulation which is shown to be predominantly directly forced by the surface layer averaged wind stress moment

alkali metals in the permo triassic as geochemical indicators of surficial processes abstract techniques established as most successful in the examination of widely variable but mainly oxidised geological materials require separation and isolation of components prior to analysis these methods reduce the number of variables involved in the production of clastic debris and enable conclusions to be drawn from a practical reversal of rock manufacture alkali metals prove successful as indicators of the surficial processes operative during permo triassic times they demonstrate enrichment by igneous material during early breccia production and subsequent dilution by wider sedimentation in basins to the east of cornubia england alkalis in recent soils river estuarine and beach sediments of southwest england are concentrated in the fine grained m fraction soils developed over permo triassic bedrock modern river estuarine sediments and beach sands all show anomalous enrichment of trace alkali metals they reflect the abundance of li rb and cs in parent material geochemical analyses of clays from deep boreholes in the wessex and central somerset basins enable inter basin comparisons with the high alkali deposits of devon absolute trace alkali levels are broadly similar to those of correlated beds at outcrop concentrations of cs prove higher in the upper permian than in the triassic of the wessex basin whilst values show devonian old red sandstone sediments to be un enriched in li and cs enrichment of li over rb in triassic mercia mudstones of the south devon coast suggests some li capture from sabkha brines by clays during evaporite production

interbasin exchange and mixing in the hypolimnion of a large lake the role of long internal waves we conducted a combined field and numerical study of the effects of episodic internal kelvin type waves on bottom boundary turbulence and the exchange of a passive tracer between the main basin and the side basin of a large lake lake geneva high resolution measurements of the vertical current structure near the entrance of the 25 km long and 70 m deep side basin revealed that hypolimnetic current speeds frequently exceed 0 2 m s 21 leading to a turbulent bottom boundary layer several meters thick with logarithmic current profiles and to a region of strong shear across the thermocline the time series and vertical structure of the currents were reproduced by a threedimensional numerical model of the lake it was demonstrated that after episodes of strong winds from the northeast and southwest exchange flows due to internal kelvin waves were able to temporarily half or double the hypolimnetic volume of the side basin leading to an irreversible exchange of up to 40 of the hypolimnetic water in the side basin of lake geneva within only a few wave cycles with the help of the numerical model it was shown that the key mechanisms of exchange are horizontal dispersion by resolved scales and to a small extent shear dispersion in the bottom boundary layer it is suggested that bottom boundary layer turbulence and the interbasin exchange can explain the structural differences in the oxygen profiles observed in the side basin and the main basin respectively

internal seiche climatology in a small lake where transversal and second vertical modes are usually observed from the analysis of thermistor chain data recorded in a small clongatcd lake compared with the results of numerical simulations second vertical modes of the internal scichcs are shown to be active during more than twothirds of the whole stratifcd period although no rcsonancc with the wind is observed on the other hand due to the wind pattern transversal seiches mainly the first vertical mode are also usually excited and they somctimcs dominate at the end of the stratified period however when the thermocline is very sharp first vertical modeslongitudinal and transversal are the only ones that are excited finally due to the wind a forced oscillation of the whole lake is excited after mortimer 1952 who brought up to date both the earlier descriptions of internal seiches in loch ness watson 1904 and their further interpretations schmidt 1908 wedderburn 1907 wedderburn and young 1915 internal seiches have been recognized as an everyday feature of movement in stratified water systems subject to wind action marmorino and mortimer 1978 hutter 1993 korgen 1995 now the relevance of the internal seiches is widely documented the structure of the horizontal velocities in the water column may determine the regions where the shear is strong enough to create instabilities leading to turbulence that might facilitate the resuspension of bottom sediments wiegand and chamberlain 1987 the periodic vertical displacements of the internal seiches can advect the suspended algal cells forcing them to be exposed to variations in light intensity webster 1990 gaedke and schimmele 1990 and internal scichcs greatly support the flux path of the transference of energy from the wind to the hypolimnion imberger 1994

internal seiche modes and bottom boundary layer dissipation in a temperate lake from acoustic measurements measurements with acoustic doppler current profilers adcps and a thermistor string were used to investigate the seasonal variation of internal seiches in a 5 km long temperate lake and the dissipation induced by the seiches in the bottom boundary layer velocity data from a bottom mounted 1 2 mhz adcp were analyzed by cross spectral analysis to determine the seiche modes the first vertical mode was generally dominant but the second mode made a significant contribution at times and was present throughout the summer season the modal periods which were consistent with normal mode analysis exhibited a marked seasonal change that correlated closely with the evolution of stratification measurements in the bottom boundary layer by another adcp in pulse pulse coherent mode sampling at 4 hz allowed determination of the rate of turbulent kinetic energy dissipation via the structure function method episodes of energy dissipation 1027 wk g21 occurred during peak flow 0 05 m s21 in the seiche motion period 10 h and coincided with times of significant reynolds stress between these episodes dissipation fell below the noise level 5 3 1029 wk g21 the ratio of internal wave energy to the boundary layer dissipation rate implies a decay time of 75 h which is similar to that for energy decay in strong seiches indicating that boundary layer dissipation makes a substantial contribution to energy loss from seiche motions a major mixing event in august caused by near resonant wind forcing brought metalimnion water to the surface and induced substantial mixing the internal motions of stratified lakes have long been observed by measuring the vertical displacement of isotherms it was through such measurements in loch ness by watson 1904 that he and wedderburn 1907 first demonstrated the importance in lakes of internal standing wave seiche motions forced by wind set up subsequent studies notably by mortimer 1974 have investigated the details of the modal structure of the internal seiches in lakes

energetics and damping of basin scale internal waves in a strongly stratified lake energetics and damping of basin scale internal waves and subsequent near bottom transport processes in lake kinneret were investigated using the modal analysis in a layer stratified irregular basin the theory was extended to include small linear damping and energy budgets and damping rates of five dominant internal waves were extracted by fitting numerically calculated internal waves to isotherm displacements measured by six thermistor chains distributed throughout the lake energy contained in the dominant internal waves 3 gj resulted from a balance between energy input from diurnal winds and dissipation within a day both of which were estimated to be 3 4g j d 21 damping was caused primarily by bottom friction and the damping rates e folding time varied from 1 to 3 d depending on the velocity structure currents induced by the internal waves caused considerable spatial variability of the bottom shear stress and near bottom transport processes such as entrainment rate at the top of the benthic boundary layer and mass transfer at the sediment water interface

from rifted margins to foreland basins investigating provenance and sediment dispersal across desert arabia oman u a e arid arabia where chemical weathering and anthropic modifications are negligible is a huge natural laboratory for the study of sediment provenance mafic and ultramafic detritus from ophiolite belts is found along the oman mountains and on masirah island obduction orogen provenance dominant cellular serpentinite grains from residual mantle harzburgites of the sama il ophiolite contrast with gabbroic diabase and basaltic grains from igneous crustal rocks of the masirah ophiolite detritus from autochthonous basement and cover rocks is found along the arabian sea margin rift shoulder provenance transition from carbonate dominated lithic sands undissected stage to hornblende rich plagioclase arkoses dissected stage is best documented at the northern edge of the gulf of aden along the older strike slip owen basin margin only locally are feldspars hornblende and garnet derived from small outcrops of pan african basement modern eolian sands from yemen to the arabian persian gulf display marked enrichment in quartz low plagioclase feldspar ratios and depleted dense mineral assemblages with rounded epidotes hornblende garnet and ultrastables pointing to extensive recycling also fostered by quaternary changes the rub al khali and wahibah sand seas have distinct quartz feldspar ratios reflecting largely separate transport pathways dune fields fed chiefly from rift highlands in the west and south mix with orogenic detritus in the northeast carbonate dominated sands in coastal uae are mostly derived from the zagros mountains blown by northerly shamal winds across the gulf during pleistocene lowstands to reach the backbulge depozone and the foreland beyond contributions from the oman mountains reach only 5 10 of bulk sediment along their southern apron and mostly indirectly through deflation of plio pleistocene fans the sama il ophiolite supplies enstatite and diopside to the eastern uae and wahibah sands the masirah ophiolite supplies amphiboles and clinopyroxenes locally along the batain coast the composition of desert sediments faithfully mirrors tectonic history of source terranes deformation style during orogeny and unroofing level during extension bulk petrography coupled with dense mineral analysis thus represents a powerful tool to investigate not only provenance and sediment transport but also crustal dynamics and geologic evolution at continental scale

late cretaceous chemical sediments related to a carbonate platform foreland basin transition in the oman mountains abstract in the oman mountains ferruginous phosphatic and minor siliceous chemical deposits accumulated in the late cretaceous upper turonian campanian related to the transition from a carbonate platform to a foreland basin this process was synchronous with large scale emplacement of nappes derived from the mesozoic tethys ocean the platform edge was uplifted and later subsided controlled by crustal flexure following initial drowning of the arabian platform turonian flexural uplift produced a regional unconformity the wasia aruma break and the outer shelf area was deeply eroded further inboard ferruginous oolites formed on shoals in shallow protected seas and were later reworked with neritic bioclastic sediment following inferred passage of a flexural bulge subsidence began and ferruginous crusts and nodules precipitated on hardgrounds located along the erosion surface impure lime muds then were deposited on the floor of a subsiding shelf 10s 100 m that was progressively tilted with accumulation of phosphatic deposits in deeper water 100s 1000 m on unstable slopes then the thrust sheets docked with the arabian continent and the platform edge was downflexed to form a foredeep in which deep water clastic sediments accumulated and this was followed by overthrusting of nappes from the tethys ocean

geochemistry and petrogenesis of volcanic clasts in the permian breccias around exeter geochemical comparisons between volcanic clasts from the late permian red beds and various granite plutons and granite porphyries 9elvans9 from sw england show that the clasts have closest affinity with the poorly megacrystic granite of dartmoor and the 9elvan like9 godolphin granite this affinity with the dartmoor granite backs up recently published nd data and age determinations it is concluded that the clasts represent volcanic material derived from an evolving subsurface granitic magma thereby conforming with conclusions ideas of earlier workers for the former presence of a dartmoor volcano

mixed layer deepening in lakes after wind setup laboratory experiments on wind driven mixed layer deepening in a wind flume are described for the situation where the wind shear stress has become balanced by a streamwise pressure gradient so that the mean mixed layer velocity has vanished the results were obtained at two lengths of the flume and include visual observations entrainment rates density profiles velocity profiles and profiles of turbulence intensities an intermediate upwind wedge formed by accumulation of mixed water was observed in all experiments the entrainment law obtained agrees with kraus and turner s relationship and is almost independent of the length of the flume

the structure of basin scale internal waves in a stratified lake in response to lake bathymetry and wind spatial and temporal distribution lake iseo italy field data theoretical analyses and numerical simulations were used to investigate the effects of lake basin bathymetry and spatial and temporal structures of the wind field on the basin scale internal wave spectrum in lake iseo this deep italian basin is characterized by the presence of a large island imparting attributes of an annulus to the lake during the summer of 2010 the internal wave activity was dominated by a basin scale internal wave of vertical and horizontal modes 1 v1h1 superimposed on which were occasional higher vertical modes v2h1 and higher horizontal modes v1h5 trapped by the main island the occurrence of these motions was interpreted as forcing by the wind components with similar horizontal structures and with energies at frequencies near the natural oscillations of the excited modes the modifications of the wind field by the topography in particular controlled the excitation of an anticyclonic wave trapped around the island whose features were investigated on the basis of an extension of the circular model to the case of an annular basin of constant depth

end of the kiaman superchron in the permian of sw england magnetostratigraphy of the aylesbeare mudstone and exeter groups the chronology of permian strata in sw england is fragmentary and largely based on radiometric dating of associated volcanic units magnetostratigraphy from the c 2 km of sediments in the exeter and aylesbeare mudstone groups was undertaken to define a detailed chronology using the end of the kiaman superchron and the overlying reverse and normal polarity in the middle and upper permian as age constraints the palaeomagnetic directions are consistent with other european permian palaeopoles with data passing fold and reversal tests the end of the kiaman superchron in the wordian occurs in the uppermost part of the exeter group the overlying aylesbeare mudstone group is early capitanian to latest wuchiapingian in age the changhsingian and most of the lower triassic sequence is absent magnetostratigraphic comparison with the southern permian basin shows that the exeter and aylesbeare mudstone groups are closely comparable in age with the havel and elbe subgroups of the rotliegend ii succession the altmark unconformities in these successions appear similar in age to the sequence boundaries in sw england indicating that both may be climate controlled clasts in the exeter group from unroofing of the dartmoor granite first occurred at a minimum of c 8 myr after formation of the granite supplementary material additional sampling magnetic fabric and palaeomagnetic data are available at http doi org 10 6084 m9 figshare c 3283400

seasonal evolution of the basin scale internal wave field in a large stratified lake the response of the water column to varying conditions of stratification and wind forcing was investigated in lake kinneret israel using data collected from thermistor chains and acoustic doppler current profilers during 1997 and 1998 the strong daily sea breeze was found to generate a vertical mode 1 internal kelvin wave and basin scale internal poincarewaves of vertical modes 1 2 and 3 the kelvin wave the dominant component of the internal wave field was responsible for alongshore velocities in the nearshore regions in the upwind nearshore regions velocities were dominated by the forced response to the wind and were cross shore in nature in the lake interior the kelvin wave effect on the horizontal velocity field was minor compared to the higher vertical mode poincarewaves the kelvin wave is shown to exist in resonant and nonforced states with the wind whereas the vertical mode 1 poincarewave energy remained relatively constant despite large variability in the forcing condi tions the energy in the higher mode poincarewaves varied greatly both on daily and seasonal timescales the results demonstrate that the wind energy forces multiple basin scale internal wave modes and that prior motion in the water column must be considered when determining the subsequent internal wave response in periodically forced systems lake kinneret israel has long been an important regional resource providing a substantial supply of drinking water as well as supporting a commercial fishery the monomictic lake is forced daily during the summer by a powerful sea breeze with stratification and wind patterns showing little variation from year to year these factors along with a fa vorable bathymetric pattern combine to make lake kinneret an ideal place for the field investigation of large scale inter nal waves and related phenomena such as the benthic bound ary layer horizontal transport and vertical mixing processes in addition to providing substantial insight into the local pro cesses and hence influencing local management study of the lake also provides fundamental knowledge of the dynam ics of enclosed basins on a geophysical scale during summer the internal rossby radius in lake kin neret is typically one half the basin width hence large scale motion in the lake will be affected by the earth s rotation and basin scale internal waves may be of topographic ross by kelvin or poincareform topographic rossby waves are sub inertial frequency oscillations that exist only in rotating fluids with variable bathymetry mysak et al 1985 stocker and hutter 1987 and these waves result from changes in depth affecting the relative vorticity of fluid elements in the absence of vertical boundaries wavelike solutions to the lin ear inviscid equations of motion for a flat bottomed region of homogeneous fluid with a constant rate of rotation are 1

upper cretaceous muti formation transition of a mesozoic nate platform to a foreland basin in the oman mountains the upper cretaceous turonian campanian muti formation sayja member documents the transition from a passive continental margin to a foreland basin related to overthrusting of continental margin and ophiolitic nappes derived from the tethys ocean upper cretaceous northeastward subduction culminated in collision of a trench with the arabian margin as the trench docked with the margin the lithosphere was flexed forming a peripheral bulge that migrated cratonward with time the platform edge was initially uplifted turonian and deeply eroded creating the wasia aruma break after passage of the peripheral bulge subsidence began with accumulation first of ferruginous crusts on hardgrounds lime muds were then deposited on a deepening unstable sea floor along with phosphatic nodules and crusts turonian coniacian passage of the overthrust load over the arabian continental margin edge downflexed the lithosphere santonian campanian resulting in drastic foundering of the old shelf edge to form a foredeep upper platform horizons collapsed as slump sheets and debris flows limestone blocks and lithoclastic debris flows were shed by mass wasting of the already deeply eroded old platform edge mud and silt were derived from the uplifted arabian continent and deposited by mainly gravitational processes in a foredeep below the c c d subsidence of the arabian platform edge allowed the semail ophiolite nappe finally to override the muti basin late campanian with little internal deformation submarine emplacement is suggested by the absence of ophiolitic detritus in the muti formation the stratigraphic evolution of the muti formation is in good general agreement with a model of the transition of an old thermally mature passive continental margin to a foreland basin where the emplaced load is submerged

wind forced motions in stratified lakes and their effect on mixed layer shear the solution for the response of a rectangular n layered stratified lake to an arbitrarily varying in time wind stress is presented the case n 3 is considered in detail for a three layered lake the response is made up of the individual responses of one external and two internal modes when the upper layer is shallow relative to the other two layers the mixed layer shear is due almost entirely to the slower second mode response moreover the upper interface can tilt quite severely while the lower interface remains nearly flat calculations based on the three layer model are compared with measurements made in wellington reservoir western australia

spatial structure of the dominant basin scale internal waves in lake kinneret field data and numerical simulations were used to investigate the effects of basin shape continuous stratification and rotation on the three dimensional structure of the dominant natural basin scale internal wave modes in lake kinneret a stratified lake large enough so that the earth s rotation influences the wave motion the structure of the modes was inferred from power spectral density of measured and simulated isotherm vertical displacements and from rotary power spectral density of isopycnal velocities obtained from numerical simulations the shape of the lake at the level of the thermocline in conjunction with the dispersion relationship determines the horizontal configuration of the natural modes the dominant response to wind forcing was an azimuthal and vertical mode 1 kelvin wave with a natural period of 22 6 h that propagated around the entire basin the second most dominant response was a vertical mode 1 wave with a natural period close to 10 5 h and composed of two counter rotating

geochemistry and palaeo oceanography of metalliferous and pelagic sediments from the late cretaceous oman ophiolite abstract metalliferous and pelagic sediments are exposed within and above the extrusive successions of the upper cretaceous oman ophiolite which on the basis of mostly geochemical evidence is believed to have formed in an incipient marginal basin setting located above a ne dipping subduction zone the ophiolitic extrusives document various volcano tectonic settings which include the axial zones of a spreading ridge fault controlled seamounts and off axis volcanic edifices most of the fe mn and trace metal enriched sediments studied are interpreted as precipitates formed by oxidation of solutions derived from high temperature sulphide precipitating vents the trace element content e g ree and sr was largely scavenged from seawater the sediments are similar to the dispersed metalliferous sediments on the flanks of modern spreading ridges and the basal sediments of dsdp wells and of other ophiolite complexes e g troodos cyprus distinctive mound structures located low in the lavas are attributed to percolation of sulphide rich solutions into already deposited metalliferous oxide sediments the resulting iron silica rock was probably originally precipitated as ferruginous silicates major massive sulphides formed off axis at the base of intermediate basic edifices of volcanic arc affinities fe mn and trace metal enrichment in the sediment cover of a flat topped seamount of axial lavas is interpreted as a dispersion halo around the largest massive sulphide orebody which is situated 5 km away lasail small massive sulphide bodies are common in the axial lavas particularly along major seafloor fault zones the metalliferous sediments locally precipitated near these vents are ferromanganiferous but trace metal depleted the metalliferous and pelagic sediment cover of the extrusive successions generally documents waning hydrothermal input after volcanism ended in the area a model is discussed in which the ophiolite was created at a spreading axis above a subduction zone dipping away from the arabian continental margin with progressive subduction this crust approached the margin initially calcareous sediment accumulated above the calcite compensation depth ccd but then non calcareous radiolarites were deposited as the ophiolitic crust approached the continental margin where the ccd was higher and marginal upwelling possibly enhanced productivity as the edge of the arabian continental margin entered the trench the over riding ophiolite was regionally uplifted allowing short lived chalk accumulation above the ccd this was followed by volcaniclastic deposition related to the tectonic emplacement

sequence of thrusting and origin of culminations in the northern and central oman mountains abstract detailed mapping and structural analysis of three large scale culminations sumeini and asjudi half windows and haybi hawasina window in the oman mountains shows a considerably more complex history of deformation than a simple foreland or downward sequence of thrust development early thrusting processes tended to create a regular stacking order of imbricate slices and major thrust sheets complying with the rules of thrust propagation assembled progressively downwards and forwards in the direction of translation out of sequence thrusts can also be demonstrated in places by truncation of footwall structures folds imbricate slices etc gross strain differences between thrust sheets downward facing structures in footwall units and elimination of thrust sheets beneath late stage thrusts frequently cut up section through the previously assembled stack putting previously younger lower thrust sheets over previously older higher ones many of the culminations in the northern and central oman mountains were formed by ramping associated with this late stage leap frog rethrusting event

cretaceous high pressure metamorphism in ne oman and its relationship to subduction and ophiolite nappe emplacement an occurrence of glaucophane bearing schists is reported from near muscat in ne oman in rocks which underlie the upper cretaceous semail ophiolite nappe these blueschists formed by the metamorphism of quartz sandstones shales and basic igneous rocks belong to a pre permian basement in the area metamorphic micas phengites from these rocks have been dated at between 101 and 80 ma k ar ages indicating a mid to late cretaceous age for the high pressure event a syn to late f 1 assemblage of almandine glaucophane phengite in the pelites shows that the peak of metamorphism reached about 400 450 c and 4 8 kbars pressure this was followed by a greenschist facies overprint with the formation of epidote and albite porphyroblasts in the meta igneous rocks and a widespread retrogression to chlorite the high pressure metamorphism is ascribed to the effects of partial subduction of the ne oman continental margin during the initial stages of ophiolite obduction and the subsequent greenschist facies event to uplift of the area during the later stages of emplacement of the nappes

horizontal structure and excitation of primary motions in a strongly stratified lake a modal analysis in the horizontal plane was extended to a layer stratified basin with irregular bathymetry and the theory was applied to lake biwa to investigate the horizontal structure and excitation of the basin scale internal waves and gyres the horizontal structure of the basin scale internal waves consisted of cyclonic and anticyclonic elliptic cells each of which appeared to follow the dispersion relationship of kelvin and poincare waves in elliptic basins the internal waves were preferentially excited depending on the arrangement of the cells and the wind direction but the spatial distribution of wind stress curl over the lake primarily determined the horizontal structure of the ensuing gyres decoupled evolutionary equations for the individual modes provided a good approximation for excitation of the internal waves and early stages of excitation of the gyres before nonlinear effects and damping become significant the modal decomposition of hydrodynamic simulation results also showed that the primary action of the wind was to excite the internal waves however these internal waves were damped within a few days and the dynamics during calm periods were dominated by the gyres illustrating the importance of internal waves on mixing and gyres on long term horizontal transport

caesium in the up estuary transport of sediments abstract trace elements are used in the teign estuary of southwest england u k to identify the source of sediments barium present in clastic material derived from past mining activity characterises river input whilst strontium from skeletal debris marks the landward transport of marine derived sediments high caesium concentrations occurring in the estuary are traced to estuarine and coastal outcrops of permian sandstones significantly cs values reach a maximum 85 ppm in the middle and upper estuary where river and marine derived sediments mix caesium resides largely in both the clay fraction 40 230 ppm and argillaceous lithic material 60 180 ppm it proves a useful marker for sediment differentiation by indicating the status of up estuary sediment transport

internal seiche dynamics in lake geneva we analyzed season long water level records at 12 stations around the lake of geneva local name leman for evidence of internal seiches modified by coriolis force and compared the results with predictions from a two layer numerical model with real bottom topography for typical wind situations results are also compared with those obtained from current and temperature measurements in the lake agreement was satisfactory in all cases model predictions and measurements both indicated that only three internal seiche modes are excited the 1st mode and the 3rd mode which are kelvin seiche oscillations and the 12th mode which is a poincare seiche the model driven by winds from different directions demonstrates that the wind field constrained by the local topography determines which of the modes is generated

basin scale motion in stratified upper lake constance this paper describes experimental and modeled wind induced oscillations in upper lake constance with an emphasis on a coherent understanding of the basin scale internal dynamics in this example of a large and stratified lake data were collected with eight lake diagnostic systems ldss consisting of thermistor chains and wind anemometers the isotherm displacements as measured by the ldss were interpreted using the three dimensional hydrodynamic estuary and lake computer model elcom three types of basin scale waves were found to dominate the wave motion the vertical mode one kelvin wave that had an observed period around 90 h two vertical mode one poincare waves that had periods near 8 h and 12 h and a vertical mode two poincare wave that had a period near 14 h after strong westerly winds upwelling of cold bottom water was observed east of the sill of mainau where the lake s two subbasins connect the width and length ratios of the subbasins spatial variations of the wind field and rotational effects over the lake are shown to play critical roles in the details of the upwelling structure a sudden fall of the isotherms in lake uberlingen formed a surge the reflection of the surge from the northwestern boundary induced a vertical mode two response leading to an intrusion in the metalimnion that caused a three layer velocity structure in the smaller subbasin

petrochemistry and origin of sub ophiolitic metamorphic and related rocks in the oman mountains the semail ophiolite complex of the northern oman mountains was obducted during cenomanian to campanian upper cretaceous times onto the arabian continental margin during this time span schistose metamorphic rocks of amphibolite and greenschist facies exhibiting polyphase deformation were formed and accreted below the ophiolite slice whole rock and mineral analyses confirm that the amphibolites were originally tholeiitic basalts comparable to present day occurrences at mid ocean ridges a comparison of trace element geochemistries however suggests that the protoliths were not equivalent to the haybi alkaline and transitional tholeiites found in the underlying structural slice or to the semail ophiolite volcanic rocks which lie structurally higher in the sequence it is therefore suggested that the amphibolites may have been derived from jurassic or lower cretaceous oceanic basalts not recognized elsewhere in the oman mountains structurally beneath the amphibolites within the metamorphic sheet greenschist facies metasedimentary rocks including quartzites and marbles are interbanded with metabasite horizons containing actinolite and less commonly blue crossitic amphiboles it is suggested that the sedimentary and volcanic protoliths were metamorphosed in a subduction zone environment during initial ophiolite displacement and were accreted to the base of the ophiolite during progressive underthrusting