strain gradients in zones of ductile thrusting insights from the external hellenides abstract new finite strain data from a thrust sense shear zone which extends for 600 km along strike in the high pressure belt of the external hellenides greece were used to describe the variation of ductile strain with structural distance d from the basal thrust sampling was carried out along four traverses across the central and southeastern parts of the zone the strain ratio in xz sections r xz of 120 samples was obtained using the theta curve the mean object ellipse and the mean radial length methods all methods give very consistent results based on these results four strain profiles were constructed depicting a non linear increase of r xz values with proximity to the basal thrust these profiles in combination with published strain data from the northwestern parts of the zone enabled us to obtain an empirical logarithmic function describing the relationship between r xz and d this function includes only one varying parameter which represents the strain gradient in linear r xz ln d space the value of strain gradient is directly correlated with the strain level in the thrust zone and provides information for strain localization at its base the proposed function may also be used for quantifying the strain profiles of ductile to semi ductile thrust zones in other orogenic belts such as the alps the appalachians and himalaya

simulation of igneous differentiation processes one of the primary goals of igneous petrology is the definition and evaluation of the roles of the processes responsible for chemical differentiation quantitative simulation of these processes not only requires an understanding of the systematics of mineral liquid equilibria in natural systems but also some understanding of how different processes interact the programs presented here consist of empirically calibrated expressions of mineral melt equilibria that are built around a thermodynamic framework the framework of the programs which are designed to model phase equilibria based igneous differentiation have been published in earlier works nielsen and dungan 1983 nielsen 1985 nielsen 1988 a b nielsen et al 1988 this presentation is to show how modeling can be used to gain otherwise unobtainable insights into the mechanics of igneous differentiation in particular for processes that are difficult to simulate in the laboratory in this chapter we will simulate the major differentiation processes that are characteristic of shallow igneous magma chambers these processes include crystallization recharge assimilation and eruption in each example we will examine how observations of natural systems can be converted into the mathematical constraints necessary for the construction of computer based models since our primary goal is to model natural igneous systems the examples show how phase equilibria modeling can be used to help solve problems related to interpretation of the chemical and mineralogic diversity of suites of natural lavas

thermochronology of the high pressure metamorphic rocks of crete greece implications for the speed of tectonic processes new fission track thermochronologic data from the high pressure p low temperature t rocks of crete greece combined with pressure temperature and stratigraphic constraints reveal that their subduction began between 36 and 29 ma metamorphism took place in western crete at peak conditions of 10 2 kbar and 400 50 c between 24 and 19 ma and rapid exhumation to 10 km and 300 c at a minimum rate of 4 km m y was completed before 19 ma constraints from the thermal history of the plate above the inferred extensional detachment reveal that tectonic unroofing contributed 85 to 90 of the overall exhumation of the high p low t rocks of crete we propose that the hellenic subduction zone has acted as a retreating plate boundary since at least the early oligocene and collision and extension during this time were driven by roll back associated with slab pull rather than by gravitational collapse as a consequence of crustal thickening the speed of subduction and exhumation of the high p low t rocks of crete within 10 m y has important implications for other orogenic belts showing that rocks can be subducted metamorphosed at high pressure and exhumed despite slow overall plate convergence within the uncertainties of many paleontologic and isotopic age data

tectonostratigraphic models of the alpine terranes and subduction history of the hellenides abstract the tectonostratigraphy of the hellenic terranes is related to their paleogeodynamic and paleogeographic evolution which comprises three major stages i continental rifting in the northern margin of gondwana characterised by volcanosedimentary complexes of late paleozoic triassic ii continental drifting and contemporaneous oceanic opening of tethyan basins in between the continental terranes during triassic paleogene with shallow water carbonate platforms on the continental terranes and ophiolite suites interlayered with pelagic sediments within the tethyan basins iii accretion of the tectonostratigraphic terranes with docking along the active european margin characterised by flysch melange sedimentation along the trenches from early jurassic to neogene two tectonostratigraphic models can be distinguished one for the continental terranes carbonate platforms and another for the oceanic basins the duration of each geodynamic stage for each terrane is obtained from the chronology of the tectonostratigraphic facies change the general trend is younger ages observed in the southern terranes and older ages towards the northern terranes the two alternative tectonostratigraphic models are applied in the two groups of terranes and the chronology of the geodynamic paleogeographic stages is estimated the hellenic subducted slab as shown in the seismic tomographic images is correlated to the terrane paleogeography using the estimated widths and the average subduction rates the upper 1700 km of the slab correspond to the three southern more external terranes whereas the remainingpart of the slab may represent the other more internal terranes a palinspastic model of the hellenides is presented taking into account the chronology of each stage for every terrane obduction of ophiolites over the southern platforms is observed in all four oceanic basins blueschist exhumation formation of core complexes and tectonic windows through extensional detachments occur after micro collision of continental terranes platforms and their isostatic uplift within the upper plate after their detachment from the subducting slab

nocturnal meso beta basin and katabatic flows on a midlatitude island abstract a mesoscale simulation for the island of majorca spain in the western mediterranean sea is used to study the nocturnal system of winds under weak synoptic pressure gradients a very high vertical resolution is used in the first 500 m above ground level to characterize with large detail the thin circulations close to ground namely basin and katabatic flows it is found that the island the basin and the slope scales interact strongly especially when a quasi steady state is reached in the second part of the night a high mountain range creates a high pressure area upwind where local winds can develop katabatic flows converge to the valleys where they interact with a cold pool which is advected slowly to sea by the land sea night breeze effect combined with a topographic forcing the katabatic flows experience small entrainment at the top and have well defined characteristics the results are partially confirmed by the observations and some satellite images

a ductile extensional shear zone at the contact area between hp lt metamorphic units in the talea ori central crete greece deformation during early stages of exhumation from peak metamorphic conditions we report on an extensional ductile shear zone in central crete at the contact area between the high pressure low temperature hp lt metamorphic phyllite quartzite unit sensu stricto pq s str and the talea ori group plattenkalk unit mapping and microscopic analysis along the 20 km long contact reveal extensional shear bands shear band cleavages c type and associated quartz veins in both units occurring over a width of up to a kilometer the shear offset along the shear bands is systematically perpendicular to the contact with the hanging block pq s str being downfaulted abundant discordant quartz veins are associated to shear band boundaries asymmetric boudinage and foliation boudinage forming m wide vein networks these mesoscopic deformation structures together with related microstructures such as strain shadows growth rims of albite porphyroblasts and stylolites indicate dissolution precipitation creep as main deformation mechanism accompanied by vein formation temperatures during deformation are indicated to be close to peak metamorphic temperatures 300 350 c by the growth rims of albite porphyroblasts and micas present in the shear band cleavages which are consistent with quartz vein microstructures showing subgrains and sutured high angle grain boundaries peak metamorphic temperatures inferred by the degree of graphitization of carbonaceous material are similar in the hanging wall and the footwall of the shear zone which is consistent with fast and nearly adiabatic exhumation our study demonstrates the importance of ductile shear zones with high strain rate dissolution precipitation creep and vein formation in hp lt metamorphic rocks for the early exhumation history

fault structure and deformation rates at the lastros sfaka graben crete abstract the lastros and sfaka faults have an antithetic relationship and form a ca 2 km wide graben within the ierapetra fault zone in eastern crete both faults have impressive bedrock fault scarps many metres in height which form prominent features within the landscape t lidar investigations undertaken on the lastros fault are used to accurately determine vertical displacements along a ca 1 3 km long scanned segment analyses show that previous estimations of post glacial slip rate are too high because there are many areas along strike where the scarp is exhumed by natural erosion and or anthropogenic activity in areas not affected by erosion there is mean scarp height of 9 4 m this leads to a slip rate of 0 69 0 15 mm a using 15 3 ka for scarp exhumation using empirical calculations the expected earthquake magnitudes and displacement per event are discussed based on our observations trenching investigations on the sfaka fault identify different generations of fissure fills retrodeformation analyses and 14c dating of the fill material indicate at least four events dating back to 16 055 215 cal bp with the last event having occurred soon after 6102 113 cal bp the lastros fault is likely the controlling fault in the graben and ruptures on the lastros fault will sympathetically affect the sfaka fault which merges with the lastros fault at a depth of 2 4 km the extracted dates from the sfaka fault fissure fills therefore either represent activity on the lastros fault assuming they formed coseismically or accommodation events cross sections show that the finite throw is limited to around 300 m and the derived slip rate for the lastros fault therefore indicates that both faults are relatively young having initiated 435 120 ka

tectono sedimentary evolution of lower to middle miocene half graben basins related to an extensional detachment fault western crete greece crustal extension in the overriding plate at the aegean subduction zone related to the rollback of the subducting african slab in the miocene resulted in a detachment fault separating high pressure low temperature hp lt metamorphic lower from non metamorphic upper tectonic units on crete in western crete detachment faulting at deeper crustal levels was accompanied by structural disintegration of the hangingwall leading to the formation of half graben type sedimentary basins filled by alluvial fan and fan delta deposits the coarse grained clastic sediments in these half grabens are exclusively derived from the non metamorphic units atop the detachment fault being in direct tectonic contact with hp lt metamorphic rocks of the lower tectonic units today the basins must have formed in the period between c 20 and 15 ma prior to the exposure of the hp lt metamorphic rocks at the surface and juxtaposed with the latter during ongoing deformation

the sedimentary and geomorphological imprint of the ad 365 tsunami on the coasts of southwestern crete greece examples from sougia and palaiochora abstract the southwestern coast of crete one of the most seismically active regions in europe experienced co seismic crust uplift by 9 m during the ms 8 3 mega earthquake that struck the eastern mediterranean world on 21 july ad 365 an associated tsunami event caused thousands of fatalities and destroyed many coastal settlements and infrastructure between the levante in the east and the adriatic sea in the northwest so far coastal sedimentary archives in southwestern crete including distinct palaeotsunami fingerprints are rarely investigated therefore a multi proxy study including sedimentological geochemical geochronological and microfaunal methods was conducted in order to detect onshore coastal sedimentary archives that functioned as fine sediment traps and document palaeotsunami imprint we found adequate archives at the sougia and palaiochora coastal plains that were used to reconstruct the palaeogeographical evolution and the palaeoseismological history of sw crete during the late holocene our studies revealed distinct geomorphological sedimentological geochemical and microfaunal traces of high energy impact from the marine side related to seismic events at the sougia coastal plain a sheet of fine sand with a neat microfossil and geochemical fingerprint was found sandwiched between underlying pre tsunami muds and overlying post tsunami colluvial silt in the palaiochora coastal plain tsunami overflow of a flat neogene bedrock platform led to the accumulation of sand dominated deposits that were subsequently covered by colluvial material from the adjacent hillslopes based on radiocarbon and luminescence dating approaches it is shown that the ad 365 tsunami event is the best fit candidate for the tsunami related sediments deposited at both sougia and palaiochora this study for the first time presents multi proxy evidence of the ad 365 tsunami imprint on fine sedimentary archives along the western and southwestern coast of crete

describing surface fluxes in katabatic flow on breidamerkurjokull iceland summary for very stable boundary layers there is no well accepted theory today in this study an improved prandtl model with varying diffusivity is applied to less than ideal conditions for pure katabatic flow pertaining to very stable boundary layers we find that the improved prandtl model adequately describes the usual and persistent

late cenozoic deformation of the hellenide foreland western greece the late cenozoic structural evolution of western greece involved the shortening of mesozoic passive continental margin and cenozoic foreland basin sequences in a foreland propagating fold and thrust system and superimposed neotectonic deformation related to the development of an active island arc although the pre apulian zone has been regarded as the undeformed western foreland to the thrust belt three dimensional exposures in the ionian islands of kephalonia and zakinthos afford evidence of significant late neogene and quaternary shortening including thrusting on reactivated normal faults time relations and fault kinematics show that these structures are compatible with the westward migration of the locus of hellenide thrusting beyond its previously recognized limit and outer arc compression related to active subduction the presence of the pre apulian zone in the west contrasts with other aegean foreland areas where no such intermediate block lay between the thrust pile and old mesozoic oceanic crust consequently the pre apulian block took up continued hellenide shortening in the late miocene while oceanic crust was being overridden subducted in southern parts of the arc to the east the pre apulian zone subsequently overrode the ocean floored ionian sea during the late neogene the confusion in determining driving mechanisms for late cenozoic deformation in western greece and the apparent conflict between evidence for the age of initial subduction in different parts of the arc are explained by this model which is consistent with regional considerations including structuration in adjacent areas and important paleomagnetic rotations in the arc

thrust faults and extensional detachment faults in cretan tectono stratigraphy implications for middle miocene extension abstract the revised tectono stratigraphy of crete and especially of the phyllites quartzites complex demonstrated the distinction of the probable paleozoic low medium grade metamorphic rocks of the arna unit from the underlying permo triassic phyllites and associated carbonate sediments trypali facies of western crete unit as well as the overlying permo triassic phyllites and associated sediments of the tyros ravdoucha beds at the base of the tripolis unit the pre existing mixture of the above tectono stratigaphic units in a single complex created a number of misinterpretations as far as stratigraphy metamorphism and interpretation of low angle faults as thrusts or detachments especially in cases where the inferred tectonic contact concerns the transition between the tyros beds and the base of the tripolis carbonate platform there is no structural omission and therefore the contact represents a minor disharmonic sliding surface and not a detachment based on the revised tectono stratigraphic analysis the determination of the structural omission for each tectonic contact was possible and several detachments were described for the first time footwall rocks of the detachments comprised several tectonic units usually from the lower nappes and hanging wall rocks comprised several tectonic units usually from the upper nappes the detachment may separate not only metamorphosed units in the footwall mani western crete arna from non metamorphosed units in the hanging wall tripolis pindos and higher nappes but also all other possible combinations from the cretan nappe pile extension in crete started in the middle late miocene with the formation of extensional detachment faults the reported extensional structures of oligocene to early miocene age do not correspond to crustal extension of crete but to localized shear zones related to nappe stacking and the exhumation of metamorphic rocks extensional detachments in crete form a tectonic horst through two oppositely dipping e w trending zones one dipping north related to the opening of the cretan basin and the other dipping south related to the formation of the messara supra detachment basin the deformation history of units within crete can be summarized as i compressional deformation producing arc parallel east west trending south directed thrust faults in oligocene to early miocene time ii extensional deformation along arc parallel east west trending detachment faults in middle miocene time with hanging wall motion to the north and south and iii late miocene quaternary transtensional deformation along high angle normal and oblique normal faults that disrupt the older arc parallel structures

aegean tectonics strain localisation slab tearing and trench retreat abstract we review the geodynamic evolution of the aegean anatolia region and discuss strain localisation there over geological times from late eocene to present crustal deformation in the aegean backarc has localised progressively during slab retreat extension started with the formation of the rhodope metamorphic core complex eocene and migrated to the cyclades and the northern menderes massif oligocene and miocene accommodated by crustal scale detachments and a first series of core complexes mccs extension then localised in western turkey the corinth rift and the external hellenic arc after messinian times while the north anatolian fault penetrated the aegean sea through time the direction and style of extension have not changed significantly except in terms of localisation the contributions of progressive slab retreat and tearing basal drag extrusion tectonics and tectonic inheritance are discussed and we favour a model 1 where slab retreat is the main driving engine 2 successive slab tearing episodes are the main causes of this stepwise strain localisation and 3 the inherited heterogeneity of the crust is a major factor for localising detachments the continental crust has an inherited strong heterogeneity and crustal scale contacts such as major thrust planes act as weak zones or as zones of contrast of resistance and viscosity that can localise later deformation the dynamics of slabs at depth and the asthenospheric flow due to slab retreat also have influence strain localisation in the upper plate successive slab ruptures from the middle miocene to the late miocene have isolated a narrow strip of lithosphere still attached to the african lithosphere below crete the formation of the north anatolian fault is partly a consequence of this evolution the extrusion of anatolia and the aegean extension are partly driven from below asthenospheric flow and from above extrusion of a lid of rigid crust

tertiary extension of continental crust and uplift of psiloritis metamorphic core complex in the central part of the hellenic arc crete greece kinematic analysis of the deformation in central crete suggests that the structural evolution and exhumation of the high pressure low temperature hp lt rocks outcropping at the mount psiloritis metamorphic core complex are associated with a regional miocene north south extension and thinning of the continental crust this tectonic regime developed under bulk coaxial strain conditions with ductile deformation in the lower and brittle deformation in the upper crust and followed on the decompressional path a north south compression associated with a hp lt metamorphism in the lower crust this compressional event took place during oligocene early miocene and led to overthickening of the accretionary wedge in the hellenic arc an east west directed compression accompanied in the final stages the miocene north south extension of the continental crust

the interaction of katabatic flow and mountain waves part i observations and idealized simulations abstract the mutual interaction of katabatic flow in the nocturnal boundary layer nbl and topographically forced gravity waves is investigated due to the nonlinear nature of these phenomena analysis focuses on information obtained from the 1993 atmospheric studies in complex terrain field program held at the mountain canyon plains interface near eldorado canyon colorado and idealized simulations perturbations to katabatic flow by mountain waves relative to their more steady form in quiescent conditions are found to be caused by dynamic pressure effects based on a local froude number climatology case study analysis and the simulations the dynamic pressure effect is theorized to occur as gravity wave pressure perturbations are transmitted through the atmospheric column to the surface and through altered horizontal pressure gradient forcing to the surface based katabatic flows it is proposed that these perturbations are a routine feature in the atmospheric record and represent a significant p

observations of flow and turbulence in the nocturnal boundary layer over a slope measurements were conducted on an eastern slope of the salt lake basin slb as a part of the vertical transport and mixing experiment vtmx conducted in october 2000 of interest was the nocturnal boundary layer on a slope in particular katabatic flows in the absence of significant synoptic influence extensive measurements of mean flow turbulence temperature and solar radiation were made from which circulation patterns on the slope and the nature of stratified turbulence in katabatic winds were inferred the results show that near the surface 25 50 m the nocturnal flow is highly stratified and directed downslope but at higher levels winds strongly vary in magnitude and direction with height and time implying the domination of upper levels by air intrusions these intrusions may peel off from different slopes surrounding the slb have different densities and flow at their equilibrium density levels the turbulence was generally weak and continuous but sudden increases of turbulence levels were detected as the mean gradient richardson number dropped to rig about unity with a short timescale fluctuated on the order of a few tens of seconds while modulating with rig a longer along slope internal waves sloshing timescale of about half an hour the mixing efficiency or the flux richardson number of the flow was found to be a strong function of similar to that found in laboratory rig experiments with inhomogeneous stratified shear flows the eddy diffusivities of momentum and heat were evaluated and they showed a systematic variation with when scaled with the shear length scale and the rms rig vertical velocity of turbulence

including coriolis effects in the prandtl model for katabatic flow katabatic flow down long glaciers in high latitudes experiences deflection due to the coriolis force if the coriolis force is added to the classic prandtl model for katabatic flow the cross slope wind component does not approach a true steady state but rather diffuses upwards in time on the other hand the down slope component and the potential temperature perturbations do reach stationarity on the same time scale as in the classic prandtl model numerical and approximate analytic solutions are presented describing this spatio temporal behaviour both solutions are in accordance with physical intuition the analytic approximate solution can be useful in boundary layer parameterizations and data analysis copyright 2007 royal meteorological society

north south extension within the convergent himalayan region recent work by burg et al 1984 indicates the presence of east west striking gently north dipping normal faults in the higher himalayas and southern tibet that formed during postcollisional convergence of india and tibet these faults extend for at least 800 km along strike we interpret these normal faults as probable late miocene extensional features with perhaps several tens of kilometres of down to the north displacement a simple elastic model suggests that these normal faults may have formed during gravitational collapse of the miocene topographic front between india and tibet in this interpretation gravitational collapse occurred by southward motion relative to india and tibet of a wedge of crustal rocks bounded above by gently north dipping normal faults and below by thrust faults that probably dip north north south extension produced in this way is probably confined to upper crustal levels only and does not reflect regional extension of the entire lithosphere

disruption of the hellenic arc late miocene extensional detachment faults and steep pliocene quaternary normal faults or what happened at corinth 1 extensional faults exposed in the peloponnesus and mainland greece most of which are described here for the first time record a transition from regional extension of the aegean domain to the modern tectonic system the east peloponnesus detachment system trends north northwest from the southern peloponnesus to 30 km north of the gulf of corinth dips gently northeast and is late miocene early pliocene in age it has a minimum displacement of 25 30 km and appears to be the youngest of the regional scale extensional systems with significant displacement that formed parallel to the hellenic arc the partially coeval east sterea extensional system which extends from the gulf of corinth to the aegean sea contains low angle normal faults that both crosscut and trend parallel to older structures of the hellenic arc late miocene to early pliocene displacement within this zone disrupted the arc parallel structures of the hellenides upper pliocene quaternary normal faults which trend approximately east west and generally dip steeply at the surface continue the disruption of the hellenic arc much of the subsidence within the gulf of corinth appears to be unrelated to the younger faults and is instead related to the motion on the east peloponnesus detachment which crosscuts the modern graben

coriolis effects in homogeneous and inhomogeneous katabatic flows katabatic flows along a planar slope in a viscous stably stratified fluid are investigated analytically and numerically with an emphasis on flow features arising from the action of the coriolis force two idealized flow types are considered turbulent flow along a uniformly cooled slope and two dimensional laminar flow induced by a cold strip of finite width running down the slope in the case of turbulent flow along a uniformly cooled slope the downslope velocity exhibits a boundary layer structure but the cross slope velocity and buoyancy fields spread inexorably upward this behaviour is qualitatively similar to that found in laminar flows along a uniformly cooled slope in contrast in the two dimensional strip flow a steady state is reached in which the cross slope wind and buoyancy fields vanish far above the slope but the downslope and slope normal velocity fields do not vanish these latter two flow components comprise two purely horizontal along isentrope counter flowing currents an upslope current entering the top of the boundary layer on one side of the strip and a downslope current flowing out of the boundary layer into the environment on the other side of the strip the slope normal vorticity associated with these currents originates in the stretching of planetary vorticity in a broad zone of convergent flow over the cold strip copyright 2008 royal meteorological society

slip vector analysis with high resolution t lidar scanning abstract a palaeostress analysis of an active bedrock normal fault scarp based on kinematic indicators is reconstructed using terrestrial laser scanning tls for this purpose three key elements are necessary for a defined region i the orientation of the fault plane ii the orientation of the slickenside lineation or other kinematic indicators and iii the sense of motion of the hanging wall the paper specifies a workflow in order to obtain stress data from point cloud data using terrestrial laser scanning tls in an active tectonic environment the entire analysis was performed on a continuous limestone bedrock normal fault scarp on the island of crete greece at four different locations along the wnw ese striking spili fault at each location we collected data with the terrestrial light detection and ranging system t lidar we then validated the calculated three dimensional stress results at three of the locations by comparison with conventional methods using data obtained manually with a compass clinometer numerous kinematic indicators for normal faulting were discovered on the fault plane surface using t lidar data when comparing all reconstructed stress data obtained from t lidar to that obtained through manual compass measurements the degree of fault plane orientation divergence is 005 03 for dip direction and dip the degree of slickenside lineation divergence is 003 03 for dip direction and dip therefore the percentage threshold error of the individual vector angle at each investigation site is lower than 3 for the dip direction and dip for planes and lower than 6 for the strike the maximum mean variation of the complete calculated stress tensors is 005 03

mid holocene tectonic geomorphology of northern crete deduced from a coastal sedimentary archive near rethymnon and a late bronze age santorini tsunamite candidate abstract the late bronze age lba tsunami and the a d 365 tsunami are supposed to have affected the northern coasts of crete however near coast sedimentary archives have been rarely investigated in this area and sedimentary archives including palaeotsunami fingerprints are still unknown the main objective of our research was to search for appropriate tsunami sediment traps in order to gain detailed insights into the holocene palaeotsunami history of northern crete we found an excellent fine sediment archive near pirgos located to the west of rethymnon based on a multi electrode geoelectrical survey and an 11 m deep sediment core we analysed the event geochronostratigraphical record by means of sedimentological geochemical geochronological geomorphological and microfossil investigations the pirgos record revealed a thick unit of homogeneous mud of a lagoonal environment starting 6000 years ago the lagoon was affected by five high energy events leaving layers of allochthonous sand microfossil analyses of these layers revealed a mixed foraminiferal assemblage including species from brackish habitats but also displaced and transported species from open marine and deep water environments considering sedimentary characteristics the local wave climate of the cretan sea and the overall geomorphological setting we interpret these layers as related to extreme wave events ewe based on a local radiocarbon age depth model we identified one ewe layer as a reliable candidate for the lba santorini tsunami another ewe layer is most probably associated with the a d 365 tsunami this ewe ended abruptly the lagoonal conditions at pirgos because of to the 1 64 m coseismic uplift at the site the pirgos lagoon existed between the first half of the 6th mill b c and at least the end of the 2nd mill b c we found that the area around pirgos has continuously subsided over 3000 or so years reflecting constant tectonogeomorphological conditions dominated by the nearby subduction zone between the aegean and african plates

resolving cambrian carboniferous permian and alpine monazite generations in the polymetamorphic basement of eastern crete greece by means of the electron microprobe the electron microprobe based investigation of accessory monazites in polished thin sections is a helpful tool in resolving the geochronology of a polymetamorphic basement the method was applied to variably altered gneisses and micaschists from the retrogressed originally amphibolite facies basement in eastern crete greece the presented data indicate that most monazite formed or recrystallized in response to high fluid activity during alpine low temperature metamorphism this low temperature monazite is characterized by distinctly low yttrium uranium and thorium contents however older grains were able to survive in less retrogressed samples and have been traced with the electron microprobe using microstructural and compositional criteria in situ chemical th u pb dating of these pre alpine monazites provides evidence for an igneous event in the cambrian and two different metamorphic events in the carboniferous and permian

footwall degradation styles and associated sedimentary facies distribution in se crete insights into tilt block extensional basins on continental margins abstract depositional facies resulting from footwall degradation in extensional basins of se crete are studied based on detailed geological maps regional transects lithological columns and outcrop photos during an extensional episode affecting crete in the late miocene early pliocene depocentres trending n20 e and n70 e were filled with fan deltas submarine mass wasting deposits sandy turbidites and fine grained hemipelagites sourced from both nearby and distal sediment sources deposition of proximal continental and shallow marine units and relatively deep marine turbidites and mass transport deposits occurred within a complex mosaic of tectonically controlled depocentres the new geological maps and transects in this work reveal that depositional facies in se crete were controlled by a their relative proximity to active faults and uplifting footwall blocks b the relative position depth and relative height above sea level of hanging wall basins and c the nature of the basement units eroded from adjacent footwall blocks distal sediment sources supplied background siliciclastic sediment hemipelagites which differ markedly from strata sourced from local footwalls in parallel mass transport of sediment was ubiquitous on tectonically active slopes and so was the presence of coarse grained sediment with sizes varying from large blocks 50 m wide to heterolithic mass transport deposits and silty sandy turbidites we expect similar tectono sedimentary settings to have predominated in tectonically active miocene basins of the eastern mediterranean in which hydrocarbon exploration is occurring at present and on rifted continental margins across the world

cambrian granitoids in pre alpine basement of crete greece evidence from u pb dating of zircon the pre alpine basement of eastern crete consists of at least three sub complexes which show differences in age and grade of pre alpine metamorphism u pb analyses of zircons of two orthogneisses yielded upper intercepts in the concordia diagram at 511 16 ma chamezi crystalline complex and 514 14 ma myrsini crystalline complex these values are interpreted as protolith ages of the gneisses suggesting that parts of the basement underwent cadomian pan african imprints at the northern margin of gondwana the lower intercept ages are attributed to alpine subduction which led to high pressure low temperature metamorphism t ca 300 c brittle ductile deformation and hydrothermal fluid activity due to pervasive alpine fluid migration the zircons of the chamezi crystalline complex display disturbed zonation and solution resulting in 87 radiogenic pb loss ca and al gain and zr depletion

postnappe stacking extension and exhumation of high pressure low temperature rocks in the island of crete greece the island of crete consists largely of nappes of contrasting lithologies and metamorphism that were stacked southward during an oligocene early miocene n s compression with the lower nappes undergoing a high pressure low temperature hp lt metamorphism this was followed by a n s miocene crustal extension that caused thinning of the nappes and uplift of the hp lt metamorphic rocks ductile conditions took place in the lower nappes associated with a retrograde greenschist metamorphism while semiductile to brittle conditions took place in the upper nappes a major normal detachment fault separates the lower and the upper nappes the quartz texture analyses and the symmetry of structures indicate bulk coaxial deformation while the results of strain analysis suggest both constrictional and flattening strains a younger ne sw compression affected both the thinned nappe pile and the late miocene pliocene sedimentary basins finally a pliocene ne sw extension led to further uplift and exhumation of the hp lt metamorphic rocks this cyclic tectonometamorphic process of alternate compression and extension took place during the migration of the hellenic orogenic belt toward the most external units including successive tectonic events

miocene high pressure metamorphism in the cyclades and crete aegean sea greece evidence for large magnitude displacement on the cretan detachment the cyclades in the backarc region of the present hellenic subduction zone are known for widespread late cretaceous to eocene high pressure metamorphism in the cycladic blueschist unit we report 40 ar 39 ar and rb sr phengite ages of 24 21 ma for high pressure metamorphism 8 10 kbar 350 400 c in the lowest tectonic unit in the cyclades the basal unit which structurally underlies the cycladic blueschist unit the basal unit is correlated with the tripolitza unit of the external hellenides in the forearc region of the hellenic subduction zone the tripolitza unit is unmetamorphosed on crete where it is separated from the underlying high pressure 8 10 kbar 300 400 c plattenkalk and phyllite quartzite units by the extensional cretan detachment the age for high pressure metamorphism in the latter units is similar to our age for the basal unit in the cyclades because pressure temperature conditions in the plattenkalk and phyllite quartzite units on crete and the basal unit in the cyclades are also similar they must have been in close proximity in the early miocene hellenic subduction zone a palinspastic reconstruction suggests a subsequent displacement of 100 km on the cretan detachment this is one of the greatest displacement magnitudes ever reported from detachment faults because of this large offset the cretan detachment was an efficient agent for exhuming high pressure rocks

the tectonic development of the hellenic arc and the sea of crete a synthesis abstract we use field analyses together with interpretation of aerial photographs orbital imagery and sea beam data to define more accurately the geometry of fault systems in the hellenic arc the tectonics of the area are dominated by extensional processes related to normal faulting we then use sea beam data previous oceanographic studies and extrapolation of field analyses on surrounding islands to describe the fault pattern of the cretan sea basin which is found consistent with the land fault pattern the mechanisms of the late neogene and quaternary deformation of the central and southern aegean region are analysed in terms of stress trajectories as revealed by field studies of fault populations we then examine the subsidence of the sea of crete in terms of a model of uniform stretching of the lithosphere the opening of the sea of crete was cylindrical and did not result in bending of crete this leads us to modify the southern portion of an earlier kinematic reconstruction of aegea in agreement with recent paleomagnetic results the implications of the opening of the sea of crete on the tectonic evolution of the straits to the west and east of crete are discussed finally the uplift of the outer arc is explained by underplating due to subduction

late carboniferous plutonism within the pre alpine basement of the external hellenides kithira greece evidence from u pb zircon dating in memory of theodor doutsos for his invaluable contribution to the understanding of geology of greece u pb zircon dating of three granitic orthogneisses sampled from kithira island sw greece provide the first reliable evidence for carboniferous plutonism within the pre alpine basement of the external hellenides concordant zircons from two samples yielded ages at 324 2 ma and 323 3 ma whereas the third sample yielded a lower intercept age at 320 1 2 ma the concordant ages are interpreted to date the emplacement of the igneous protolith ages of inherited zircons of two orthogneisses range from 2 5 to 2 4 ga indicating late archaean early proterozoic crustal components in combination with published ages for other aegean metagranitoids the new u pb ages provide additional evidence of a temporally restricted period of plutonism in the pre alpine aegean region from 325 to 300 ma comparing the post neoproterozoic evolution of the investigated basement with that of the cycladic and pelagonian basements and of the continental massifs of ne greece and turkey we argue that all these crustal blocks were part of the gondwana derived cimmerian terrane based on the spatial and temporal distribution of late carboniferous aegean plutonism we suggest that this period of magmatic events results from the southward subduction of palaeotethys beneath the marginal fragments of northern gondwana

incipient continental collision and plate boundary curvature late pliocene holocene transtensional hellenic forearc crete greece u ring t c brachert write in their recent paper ten veen kleinspehn 2003 proposed that the western messara graben of central crete underwent transtensional deformation since about 3 4 ma transtension is supposed to be dominantly resolved along 070 striking sinistral faults and that the 070 striking faults have strike slip normal slip ratios of 10 100 1 ten veen kleinspehn 2003 then use their results from the western messara graben to propose that sinistral transtension should represent tectonic escape of central and eastern crete during incipient collision of the libyan passive margin the interpretation of the kinematic data on which ten veen kleinspehn 2003 base their tectonic model is in contrast to earlier studies which have attributed the young i e pliocene to recent kinematics of crete largely to radial extension angelier et al 1982 fassoulas 2001 ring et al 2001 ten veen kleinspehn 2003 p 167 argued that onshore structural assemblages is critical to deciphering forearc kinematics and therefore we present our kinematic data from onshore faults in the western and central messara graben and compare our data together with the fault slip data of fassoulas 2001 from the heraklion graben and microseismicity data hatzfeld et al 1993 delibasis et al 1999 with the fault slip data of ten veen kleinspehn 2003 fig 9 for discussing the kinematics of the young faults we believe that fault slip data directly reflect the kinematics of the faults from which they were collected and therefore allow testing the proposition often veen kleinspehn that sinistral transtension is supposed to be mainly resolved at the 070 striking faults the latter of which are known to be an integral part of the youngest set of faults on crete fassoulas 2001 and are in part seismically active delibasis et al 1999 in general

to be or not to be that is the question the cretan extensional detachment greece we present new structural data from the contact zone between the high pressure phyllite quartzite unit pq and the overlying non high pressure tripolitza unit in east central crete for testing pro

miocene detachment in crete and exhumation p t t paths of high pressure metamorphic rocks a major problem posed by the geology of crete is the horizontal contact of an upper unit without miocene metamorphism onto a metamorphosed lower one with early miocene high pressure low temperature hp lt parageneses this very sharp contact is roughly parallel to the major oligo miocene thrust planes which were reactivated as a large scale detachment which allowed exhumation of high pressure units we describe the extensional deformation and the metamorphic evolution of the lower plate most first order deformation features relate to the retrogression from high pressure to low pressure conditions a n s pervasive stretching is observed everywhere often associated with a top to the north sense of shear the extreme variation of thickness of the phyllite quartzite nappe upper part of the lower plate is probably the result of large scale boudinage similar to the one seen in large outcrops the most important observation is the systematic occurrence of fresh carpholite immediately below the base of the tripolitza nappe except in northwestern crete where a late extensional shear zone is present deeper in the nappe pile carpholite is systematically retrograded this observation reveals a drastically different pt history for the upper part of the phyllite quartzite nappe it also suggests that the late extensional shear zone found along the northern side of crete cuts inside the metamorphic structure and brings the nonmetamorphosed tripolitza nappe directly in contact with the deeper parts of the phyllite quartzite nappe pt t paths suggest a fast temperature decrease in the top of the phyllite quartzite during retrogression and hence during the top to the north shear the deeper part of the phyllite quartzite nappe shows a low temperature regime throughout but its pt path includes an isothermal decompression in the first stage we produce a tentative map of domains having experienced similar pt trajectories during decompression the overall cool regime is related to the continuous underthrusting of cola continental units during exhumation isothermal decompression observed in the core of the phyllite quartzite nappe implies fast exhumation during extension and the faster cooling of the upper part is related to a continuous displacement toward the north of a cooler unit during exhumation single grain 39ar 40ar ages obtained on phengites 15 25 ma in various structural sites are in good agreement with these conclusions and with the geological context suggesting that underthrusting of cold units at the front the accretionnary complex occurred contemporaneously with unroofing below a north dipping detachment near the top of the wedge the age of this detachment is bracketed between the end of the high pressure event 20 ma and the deposition of the breccia early to middle miocene in the neogene basins

temporally constant quaternary uplift rates and their relationship with extensional upper plate faults in south crete greece constrained with 36cl cosmogenic exposure dating in order to investigate how active upper plate faults in crete influence uplift above the hellenic subduction zone we mapped deformed late quaternary marine terraces along 17 profiles across strike of the south central crete fault sccf identified and dated palaeoshorelines using in situ 36cl exposure dating on wave cut platforms correlated them with the quaternary sea level curve and calculated uplift rates we identified 16 distinct palaeoshorelines from field observations and study of digital elevation models dems located along the footwall and hangingwall of the sccf and the footwall of the offshore ptolemy trench fault cosmogenic dating constrains the ages of three palaeoshorelines as 76 100 and 125 ka we use these dates to guide a correlation of other mapped palaeoshorelines with quaternary sea level highstands between 200 and 980 ka with results implying that the uplift rate is constant through time at each of the 17 profile locations elastic half space modelling implies that uplift in both the hangingwall and footwall of the sccf is influenced by uplift related to offshore upper plate faults in addition to background regional uplift perhaps from the subduction interface by correlating palaeoshorelines across the active south central crete fault we derive a throw rate of 0 41 mm yr for this fault which can also be expressed as a slip rate of 0 58 mm yr the fault specific earthquake recurrence interval assuming repetition of 1 1 m slip events is approximately 2700 years for the sccf

the weak and superfast cretan detachment greece exhumation at subduction rates in extruding wedges low angle normal faults detachments are only efficient agents for bringing rocks from 40 100 km depth back to the earth s surface if they operate with extreme slip rates exceeding 20 km ma 1 here we propose a slip rate of 20 30 km ma 1 for the cretan detachment in the aegean greece the cretan detachment and the subjacent subduction thrust bounded an extruding wedge above the miocene hellenic subduction zone during exhumation the high pressure rocks in the wedge were not significantly deformed very low shear coupling at the bounding faults which are therefore weak is needed to prevent significant deformation in the extruding wedge the proposed slip rate of 20 30 km ma 1 is similar to the subduction rate of 35 45 km ma 1 at the hellenic subduction zone we argue that extruding wedges can only slip at rates similar to subduction rates if there is very low shear coupling at the bounding faults which may also explain the paradox of almost non deformed but very rapidly exhumed rocks

eo alpine metamorphism in the uppermost unit of the cretan nappe system petrology and geochronology the uppermost unit of the cretan nappe system consists of ophiolites on the top and an ophiolitic melange at the base

raman spectroscopic carbonaceous material thermometry of low grade metamorphic rocks calibration and application to tectonic exhumation in crete greece we present new raman spectra data of carbonaceous material cm to extend the range of the raman spectra of cm thermometer rscm to temperatures as low as 100 8c previous work has demonstrated that raman spectroscopy is an excellent tool to describe the degree of graphitization of cm a process that is independent of pressure but strongly dependent on metamorphic temperature a linear relationship between temperature and the raman parameter r2 derived from the area of the defect band relative to the ordered graphite band forms the basis of a previous thermometer because r2 shows little variability in low temperature samples 330 8c serves as a lower limit on the existing thermometer herein we present raman spectra from a suite of low temperature 100 to 300 8c samples from the olympics mountains and describe other aspects of the raman spectra of cm that vary over this range in particular the raman parameter r1 the ratio of heights of the disordered peak to ordered peak varies regularly between 100 and 350 8c these data together with published results from higher temperature rocks are used to calibrate a modified rscm thermometer applicable from 100 to 700 8c application to low grade metasediments in the otago region in the south island of new zealand gives temperatures consistent with previous estimates demonstrating the reliability of the modified rscm thermometer we apply the modified rscm thermometer to 53 samples from crete to evaluate the role of the cretan detachment fault in exhuming miocene high pressure low temperature metamorphic rocks exposed there the metamorphic rocks below the detachment the plattenkalk and phyllite quartzite units give metamorphic temperatures that range from 250 to 400 8c consistent with previous petrologic estimates we also demonstrate that the tripolitza unit which lies directly above the detachment gives an average metamorphic temperature of about 260 8c the modest break in metamorphic temperature in central crete indicates that the cretan detachment accounts for only 5 to 7 km of exhumation of the underlying hp lt metamorphic rocks which were initially accreted at 35 km we argue that the bulk of the exhumation 28 km out of 35 km total occurred by pervasive brittle stretching and erosion of structural units above the detachment d 2005 elsevier b v all rights reserved

timing of tectonic emplacement of the ophiolites and terrane paleogeography in the hellenides the timing of tectonic emplacement of the ophiolites is analyzed in the four oceanic terranes of the hellenides h2 h4 h6 h8 the criteria for this analysis are based on a the post emplacement sedimentary cover or intrusive rocks b the syn emplacement tectonostratigraphic formations and c the youngest rocks involved in the structure of the autochthon and the allochthon unit in each case the timing becomes younger towards the more external tectonic units of the hellenides with i late eocene oligocene age in the external ophiolite belt of the pindos cyclades oceanic terrane h2 ii late jurassic early cretaceous age in the internal ophiolite belt of the vardar axios oceanic terrane h4 iii post liassic pre late jurassic age in the ophiolites of lesvos circum rhodope oceanic terrane h6 and iv pre late jurassic age in the ophiolites of volvi eastern rhodope terrane h8 an ophiolite obduction model can be applied with the ophiolitic nappes always emplaced on top of pre alpine continental terranes with mesozoic shallow water carbonate platforms the geometry of the continental terranes drifting during the mesozoic within the tethys ocean controls the number and dimensions of the tethyan oceanic basins where a continental terrane dies out the two adjacent oceanic basins merge into one larger basin this seems to be the case of the pelagonian terrane h3 which is terminated north of skopje where the pindos oceanic basin h2 merges with the vardar axios oceanic basin h4

middle miocene graben development in crete and its possible relation to large scale detachment faults in the southern aegean the linkage between the development of south facing cretan graben and large scale detachment faulting in the southern aegean is unknown widespread serravallian deposits in the ierapetra graben of crete supply constraints to middle miocene graben development in the southern aegean the ierapetra graben and by inference the cretan graben in general were hitherto believed to have formed as a result of sinistral transpression during n s shortening we argue that the formation of the cretan graben is due to n s extension the south dipping n s extending kritsa normal fault served as the master fault controlling graben development in the ierapetra graben the kritsa normal fault is either an antithetic fault related to the top n cretan detachment or a synthetic fault associated with the top s ios detachment the overall geometry and timing relationships lead us to favour a connection with the ios detachment which in turn implies a large scale displacement on the ios detachment

the cretan ophiolite bearing melange greece a remnant of alpine accretionary wedge abstract new data collected in central crete on the ophiolite bearing units result in a better understanding of the role and tectonic significance of these units in the construction of this segment of the hellenides these nappes are composed of three main tectonic units that characterized by different metamorphic facies conditions are represented by an un metamorphosed lower unit a greenschist to hp greenschist facies intermediate unit and a blueschist facies upper unit these chaotic thrust nappes include blocks of oceanic and continental deriving rocks and can be considered as a remnant of an accretionary complex the lower unit represents the toe of the wedge whereas the intermediate and upper units refer to the innermost and deeper subducted portions exhumed and superimposed on top of each other during the early stages of continental collision the structural evolution of the accretionary wedge was controlled by four main contractional deformation events that including distinct groups of structures developed at different crustal levels were driven by sse and ssw directions of tectonic transport our data strongly suggest that the ophiolite bearing tectonic wedge was accreted during the paleogene subduction of a late jurassic cretaceous oceanic realm beneath the continental margin of the pelagonian domain and it was successively involved in the continental collision with the adria block the greenschist to blueschist facies metamorphism and the subsequent exhumation and emplacement of the intermediate and upper units above the frontal portion of the wedge may mainly be due to deep duplexing marking the onset of continental collision we thus suggest that the ophiolite bearing units of crete represent a single suture zone related to the closure of a unique oceanic domain pindos cycladic ocean subducted beneath the internal hellenides platform continental domains thus assuming the significance of a southern oceanic seaway of the largest eastern neotethys developed since the triassic between eurasia and africa

slab segmentation and late cenozoic disruption of the hellenic arc the hellenic subduction zone displays well defined temporal and spatial variations in subduction rate and offers an excellent natural laboratory for studying the interaction among slab buoyancy subduction rate and tectonic deformation in space the active hellenic subduction front is dextrally offset by 100 120 km across the kephalonia transform zone coinciding with the junction of a slowly subducting adriatic continental lithosphere in the north 5 10 mm yr and a rapidly subducting ionian oceanic lithosphere in the south 35 mm yr subduction rates can be shown to have decreased from late eocene time onward reaching 5 12 mm yr by late miocene time before increasing again along the southern portion of the subduction system geodynamic modeling demonstrates that the differing rates of subduction and the resultant trench offset arise naturally from subduction of oceanic pindos lithosphere until late eocene time followed by subduction of a broad tract of continental or transitional lithosphere hellenic external carbonate platform and then by miocene entry of high density oceanic ionian lithosphere into the southern hellenic trench model results yield an initiation age for the kephalonia transform of 6 8 ma in good agreement with observations consistency between geodynamic model results and geologic observations suggest that the middle miocene and younger deformation of the hellenic upper plate including formation of the central hellenic shear zone can be quantitatively understood as the result of spatial variations in the buoyancy of the subducting slab using this assumption we make late eocene middle miocene and pliocene reconstructions of the hellenic system that include quantitative constraints from subduction modeling and geologic constraints on the timing and mode of upper plate deformation

low angle normal faults and seismicity a review although large low angle normal faults in the continental crust are widely recognized doubts persist that they either initiate or slip at shallow dips 30 because 1 global compilations of normal fault focal mechanisms show only a small fraction of events with either nodal plane dipping less than 30 and 2 andersonian fault mechanics predict that normal faults dipping less than 30 cannot slip geological reconstructions thermochronology paleomagnetic studies and seismic reflection profiles mainly published in the last 5 years reinforce the view that active low angle normal faulting in the brittle crust is widespread underscoring the paradox of the seismicity data for dip slip faults large enough to break the entire brittle layer during earthquakes m w 6 5 consideration of their surface area and efficiency in accommodating extension as a function of dip suggests average recurrence intervals of earthquakes r tan assuming stress drop rigidity modulus and thickness of the seismogenic layer do not vary systematically with dip if the global distribution of fault dip normalized to total fault length is uniform the global recurrence of earthquakes as a function of dip is shown to be r tan sin this relationship predicts that the frequency of earthquakes with nodal planes dipping between 30 and 60 will exceed those with planes shallower than 30 by a factor of 10 in good agreement with continental seismicity assuming major normal faults dipping more than 60 are relatively uncommon revision of andersonian fault mechanics to include rotation of the stress axes with depth perhaps as a result of deep crustal shear against the brittle layer would explain both the common occurrence of low angle faults and the lack of large faults dipping more than 60 if correct this resolution of the paradox may indicate significant seismic hazard from large low angle normal faults

a theory for the estimation of surface fluxes in simple katabatic flows the classical prandtl model describes the basic dynamics of katabatic flows but it fails in determining the gradients near the surface because the eddy diffusivity k is independent of height z an improvement is proposed to the prandtl model by using the wkb method to solve the dynamic equation for any prescribed reasonably smooth k z profile the surface fluxes are obtained by extrapolation from the katabatic jet down to the surface thus the fluxes depend primarily on the jet which is well captured by the wkb method the profiles of wind temperature momentum and heat fluxes as well as the surface fluxes calculated using the model are tested against observations from a meteorological field campaign on the pasterze glacier austria in 1994 and their numerical simulations generally there is a good agreement between observations and theory

the low level katabatic jet height versus monin obukhov height in this short note we discuss a long standing problem in modelling the atmospheric boundary layer abl over complex terrain namely an excessive use of the monin obukhov length scale lmo this issue becomes increasingly relevant with the ever increasing resolution of numerical weather prediction and climate models which typically use lmo in one way or another for parametrizing the surface layer or at least for formulating the lower boundary conditions hence inevitably the models under represent a significant part of the mesoscale flow variability we focus here on the stable abl over land in particular sloped cooled flows however a qualitatively similar reasoning applies to the corresponding unstable abl we show that for sufficiently stratified flows over moderately sloped surfaces monin obukhov scaling is inadequate for describing the basic abl dynamics which is often governed by katabatic and drainage flows copyright 2007 royal meteorological society

turbulence in the nocturnal boundary layer with light and variable winds turbulence quantities are analyzed from nine months of data collected on the floor of a valley where nocturnal cold pools are frequent often the speed of the vectoraveraged wind over the night is less than 0 5 m s 1 near calm winds with no preference for wind direction the quantity of such near calm data is sufficiently large to allow new types of analyses as well as the opportunity to examine statistics of the previously ignored near neutral subclass of near calm winds for near calm weak winds and strong stratification the turbulence can be difficult to isolate from wave like motions and more complex small scale structures the smallest scale perturbations on time scales less than 5 s behave most like turbulence larger scale perturbations are characterized by very weak vertical velocity fluctuations and large temperature fluctuations but lead to systematic downward heat flux after extensive averaging for near calm nocturnal conditions significant turbulence is mainly generated by short term minutes accelerations of unknown origin the turbulence between such infrequent mixing events is extremely weak but not zero while the turbulence in the events approximately follows similarity theory the extremely weak turbulence scales neither with stratification nor bulk shear and its inferred vertical length scale is small compared to the distance from the ground even at the 2 m level copyright c

geochemical sedimentary and micropaleontological evidence for a late maastrichtian oceanic seamount within the pindos ocean arvi unit s crete greece abstract we test the model of bonneau 1984 who hypothesised that the arvi unit in southern crete represents upper cretaceous oceanic crust of a pindos oceanic basin the arvi unit is dominated by basaltic lava flows pelagic carbonates and terrigenous sandstone turbidites the enriched within plate type geochemistry of the basaltic lavas is consistent with a seamount setting the subaqueous lava structures and associated pelagic carbonates further justify a seamount origin peperites composed of lava pelagic carbonate mixtures date the arvi unit as late maastrichtian using diagnostic planktic foraminifera the lavas are overlain by pelagic carbonates also of late maastrichtian age that then pass gradationally upwards into sand to pebble grade gravity flows the clastic sediments contain grains derived from several sources namely continental metamorphic and plutonic ophiolite related e g serpentinite gabbro diabase deep sea e g chert pelagic carbonate and shallow marine e g shell fragments the terrigenous detritus is inferred to have come from the pelagonian microcontinent unit asteroussia nappe then to the northeast where ophiolites and deep sea sediments were obducted during late jurassic time the inferred arvi seamount was accreted at the southeasterly subducting active margin of the pelagonian microcontinent after maastrichtian time related to closure of the pindos ocean the new evidence from the arvi unit provides additional evidence for the existence of the pindos ocean between the apulian and pelagonian continental units in the greece albania region

the tectonometamorphic evolution of high pressure low temperature metamorphic rocks of eastern crete greece constraints from microfabrics strain illite crystallinity and paleodifferential stress abstract analysis of strain paleodifferential stress illite crystallinity and microfabrics of quartz and calcite suggest that multiply alternating late oligocene early miocene n s convergence and n s extension caused significant vertical discontinuities in the grade of high pressure low temperature metamorphism of the phyllite quartzite unit pqu of eastern crete constrictional fabrics and parallelism of d2 stretching lineations and fold axes are attributed to enhanced slab pull forces at greater depth of subduction a major d3 extensional detachment is present in the upper part of the pqu where slates with lowest metamorphic grade diagenesis anchizone transition are resting on top of anchimetamorphic rocks the highest metamorphic grade anchi epizone transition has been determined for skythian rocks on top of pre alpine basement revived n s convergence d4 led to e w trending map scale folds and top to the s directed brittle thrusts there is a clear correlation between d2 related metamorphic grade finite strain differential stress and deformation mechanisms at the anchi epizone transition solution precipitation and dislocation creep of quartz and calcite caused maximum finite strains rxz up to 7 at high strain rates and moderate differential stresses 80 200 mpa at the diagenesis anchizone transition deformation was accommodated by cataclasis dislocation glide and solution precipitation creep resulting in relatively low finite strains rxz

the three metamorphic belts of the hellenides a review and a kinematic interpretation summary new results obtained in the three metamorphic belts of the hellenides suggest that each belt has a different structure geotectonic setting and evolution the external metamorphic belt of peloponnesus crete has probably resulted from nappe movement in the vicinity of an evolving island arc system the blueschists occurring within this external belt are allochthonous and have been transported with other nappes over the external carbonate platform of the pre apulian plattenkalk ionian tripolitza almyropotamos units this implies that there was only one true blueschist domain initiated in the cycladic area during early eocene the kinematic interpretation is based on the distinction of a and b structures and on the nature of the shear zones between the different domains especially that between the metamorphic hellenides below and the non metamorphic hellenides above the existence of the probably lower palaeozoic meta sedimentary sequence of kastoria in the northern pelagonian zone indicates that the overlying ophiolite bearing almopias unit has been derived from within the hercynian domain the kastoria sedimentary sequence the ophiolites of vertiskos and the carbonate platform of pangeon are considered to be most likely elements of a probable hercynian orogeny

momentum balance of katabatic flow on steep slopes covered with short vegetation katabatic flows over alpine mountainous terrain differ from their forested or bare slope counterparts due to the presence of well ventilated short vegetation the impact of a grass canopy and larger scale pressure perturbations on the one dimensional mean momentum balance is explored via theory and field measurements the model presented here reproduces the measured velocity jet shape and turbulent flux gradients these two features imply that even when monin obuhkov similarity theory breaks down its use for a stability adjusted mixing length remains effective to first order results reveal that outer layer pressure effects can be significant under low speed wind conditions at the top of the thin katabatic layer when larger variations in the wind direction are observed an analytical expression to estimate the jet height which can be utilized in large scale weather prediction models shows the importance of including canopy effects for the thin katabatic flow region above the vegetation

multiseismic cycle deformation rates from holocene normal fault scarps on crete greece morphotectonic features reveal recent seismic activity on normal faults on crete allowing slip rates palaeoearthquake magnitudes and earthquake recurrence intervals to be inferred the studied faults show major escarpments 100s m high 10s km long separating uplifted mesozoic rocks from quaternary deposits during the holocene slip rates outpaced erosion sedimentation rates and 5 15 m high fresh scarps formed at the base of the major escarpments based on our field observations and following empirical relationships between magnitude surface rupture length and maximum co seismic vertical displacement it is possible to infer some important seismotectonic parameter relative to the investigated faults taking into account the possible sources of error and the corresponding uncertainties our preferred long term slip rates range between 0 5 and 1 3 mm yr 1 the maximum expected magnitudes between 6 3 and 6 6 or 6 5 and 6 8 considering worst case scenarios while the mean recurrence intervals range between 260 and c 840 years these estimates are in good agreement with the shallow seismicity thus allowing to improve our knowledge on the seismic potential in crete horizontal extension rates could be also inferred from our geological data and compared with the few available gps data

map view restoration of aegean west anatolian accretion and extension since the eocene 1 the aegean region greece western turkey is one of the best studied continental extensional provinces here we provide the first detailed kinematic restoration of the aegean region since 35 ma the region consists of stacked upper crustal slices nappes that reflect a complex paleogeography these were decoupled from the subducting african adriatic lithospheric slab especially since 25 ma extensional detachments cut the nappe stack and exhumed its metamorphosed portions in metamorphic core complexes we reconstruct up to 400 km of trench perpendicular ne sw extension in two stages from 25 to 15 ma the aegean forearc rotated clockwise relative to the moesian platform around euler poles in northern greece accommodated by extensional detachments in the north and an inferred transfer fault se of the menderes massif the majority of extension occurred after 15 ma up to 290 km by opposite rotations of the western and eastern parts of the region simultaneously the aegean region underwent up to 650 km of post 25 ma trench parallel extension leading to dramatic crustal thinning on crete we restore a detachment configuration with the mid cycladic lineament representing a detachment that accommodated trench parallel extension in the central aegean region finally we demonstrate that the sakarya zone and cretaceous ophiolites of turkey cannot be traced far into the aegean region and are likely bounded by a pre 35 ma n s fault zone this fault became reactivated since 25 ma as an extensional detachment located west of lesbos island the paleogeographic units south of the izmir ankara sava suture however can be correlated from greece to turkey

the dynamics of idealized katabatic flow over a moderate slope and ice shelf summary a non hydrostatic numerical weather prediction model has been employed to simulate idealized katabatic flows over a moderate slope and adjoining ice shelf the topography of coats land and the adjoining brunt ice shelf antarctica has been used this is typical of much of the antarctic coastline the regional atmospheric modeling system version 4 3 has been adapted for simulations over compacted snow most notably through changes to the multi layer soil model the simulations are initialized using clear sky conditions and at rest on the slope a shallow katabatic flow develops the winds becoming approximately steady on the slope by 12 h the peak downslope winds are about 7 m s 1 at 30 m above the snow surface the katabatic flow depth ranges from 50 to 100 m down the slope over the ice shelf the katabatic flow peters out while a pool of cold air develops primarily through sensible heat loss into the surface and partially balancing the net radiative heat loss to space near surface and sounding data from the model simulations compare well with archetypal and typical katabatic flow observations especially after some tuning of the model s turbulence parametrization an analysis of the downslope flow dynamics shows the buoyancy force is generally balanced by the inertial force except towards the foot of the slope where it is balanced by upslope forces related to gradients in the potential temperature deficit and katabatic layer height caused by the pool of cold air over the ice shelf over time the cooling of the ice shelf boundary layer leads to an apparent retreat of the katabatic flow from the ice shelf and some way up the slope the dynamical analysis explains the surface climatology observed such that the persistent katabatic winds of coats land rarely reach the brunt ice shelf the simulated katabatic flow moves from shooting to tranquil towards the foot of the slope this transition acts to trigger a train of internal gravity waves which propagate energy upwards away from the katabatic flow jump previous studies have also found shooting to tranquil katabatic flow transitions so to generalize these findings would suggest that internal gravitywave generation is ubiquitous around much of coastal antarctica and greenland

tectonic evolution of a crustal scale oblique ramp hellenides thrust belt greece abstract this study investigates the tectonic evolution of the omalos transverse zone which served as a crustal scale oblique ramp in the external hellenides thrust belt on crete island the omalos oblique ramp developed above an inherited mesozoic fault zone that strikes ne sw oblique to the regional ssw directed tectonic transport during the early miocene pleistocene evolution of the thrust belt the oblique ramp was repeatedly reactivated localizing deformation above the inherited structure geological and structural mapping combined with kinematic analysis of ductile and brittle structures suggest that the omalos oblique ramp generated a local kinematic field which deviated significantly from the regional kinematic pattern in the thrust belt the most conspicuous feature in the tectonic evolution of the oblique ramp is a change from a ductile wrench dominated to a brittle primarily reverse faulting regime across the brittle ductile transition followed by brittle wrench deformation after the final exhumation of high pressure hp rocks deflections of transport and compression orientations from the regional pattern are attributed to buttressing against basement cover offsets produced by the pre existing fault zone to oblique ramping and to transfer faulting respectively our findings are potentially applicable to other examples of crustal scale oblique thrust ramps in various tectonic settings

on the turbulence structure of deep katabatic flows on a gentle mesoscale slope a comprehensive analysis of the turbulence structure of relatively deep midlatitude katabatic flows with jet maxima between 20 and 50 m developing over a gentle 1 mesoscale slope with a long fetch upstream of the meteor crater in arizona is presented the turbulence structure of flow below the katabatic jet maximum shows many similarities with the turbulence structure of shallower katabatic flows with decreasing turbulence fluxes with height and almost constant turbulent prandtl number still stark differences occur above the jet maximum where turbulence is suppressed by strong stability is anisotropic and there is a large sub mesoscale contribution to the flux detecting the stable boundary layer top depends on the method used flux vs anisotropy profiles but both methods are highly correlated the top of the stable boundary layer however mostly deviates from the jet maximum height or the top of the near surface inversion the flat terrain formulations for the boundary layer height correlate well with the detected top of the stable boundary layer if the near surface and not the background stratification is used in their formulations however they mostly largely overestimate this boundary layer height the difference from flat terrain boundary layers is also shown through the dependence of size of the dominant eddy with height in katabatic flows the eddy size is semi constant with height throughout the stable boundary layer depth whereas in flat terrain eddy size varies significantly with height flux gradient and flux variance relationships show that turbulence data from different stable boundary layer scaling regimes collapse on top of each other showing that the dominant dependence is not on the scaling regime but on the local stability

an observational and numerical study of a regional scale downslope flow in northern arizona 1 boundary layer observations taken during the metcrax field study in october of 2006 near winslow in northern arizona revealed the frequent presence of a near surface wind maximum on nights with relatively quiescent synoptic conditions data from a sodar a radar wind profiler several surface stations and frequent high resolution rawinsonde soundings were used to characterize this boundary layer wind phenomenon and its relation to synoptic conditions and the ambient environment the data analyses are augmented by high resolution mesoscale numerical modeling it is found that the observed nocturnal low level wind maximum is part of a regional scale downslope flow converging from high terrain of the colorado plateau toward the little colorado river valley the depth of this downslope flow is between 100 and 250 m with a peak speed of 4 6 m s 1occurring usually within the lowest 50 m above ground opposing ambient winds lead to a longer evening transition period shallower slope flows and a smaller horizontal extent as compared to supporting synoptic winds a simple analytical solution based on local equilibrium appears to agree fairly well with the observed layer mean downslope wind speed but the classic prandtl solution for maximum downslope wind speed fails to match the observations the properties of the flow appear to be insensitive to changes in soil moisture land cover and surface roughness length the contribution to the low level wind maximum by inertial oscillation at night is found to be insignificant