the thermal and mineral springs of aitoloakarnania prefecture function mechanism and origin of groundwater the study area is located in the northwestern part of greece in aitoloakarnania prefecture in this region where no volcanic activity exists thermal springs such as kremasta and kokkino stefani well known for their healing properties occur the objective of this study was the investigation of these springs as well as the study of the chemical composition and origin of water relationships between these springs were also examined the geological setting of the area comprises sedimentary rocks of the pindos gavrovo tripolis and ionian geotectonic zones deformed by orogenic movements followed by neogene extensional tectonism the thermal and mineral springs were classified into three main groups the first group is characterized by ca hco3 water type and low water temperatures it corresponds to the springs that are hosted in the ionian zone and their possible enrichment in so4 is mainly attributed to the evaporites the other two groups consist of alkaline thermal water mainly hosted in the formations of gavrovo tripolis zone in these two groups the very strong reducing conditions that prevail are expressed by high amounts of nh3 and h2s moreover na f li sr and ba display elevated concentrations the second includes mineral waters of ca na hco3 type that are depleted in calcium their residence time is rather long and they originate from deep water circulation through siliceous rocks the third group includes thermal waters of ca mg na hco3 water type of higher water temperatures that reveal characteristics of deep circulation directly associated with the underlain limestones

effect of organic carbon flux and dissolved oxygen on the benthic foraminiferal oxygen index bfoi variations in oceanic primary productivity flux of organic carbon to the sediments and dissolved oxygen levels in the water column are thought to be important in the control of benthic foraminiferal test size wall thickness morphology and species composition of assemblages by many foraminiferal paleontologists aspects of these processes should be reflected by the benthic foraminiferal oxygen index bfoi based on these foraminiferal characteristics however analyses indicate that the bfoi correlates most strongly with dissolved oxygen levels in overlying water r2 0 81 weakly with oceanic primary productivity r2 0 55 and weakly with organic carbon flux to the sediments r2 0 51 although both dissolved oxygen and organic carbon flux are main controlling factors for benthic foraminiferal assemblages the bfoi is a useful indicator extracted from benthic foraminiferal assemblages for estimating the condition of dissolved oxygen in cretaceous and cenozoic oceans

numerical simulation for groundwater distribution after mining in zhuanlongwan mining area based on visual modflow with large scale coal resources being discovered and mined in mid west china latent environment problems gradually come into view in arid and semi arid region environmental impact assessment of mining on groundwater distribution is a vital mission before mining works in zhuanlongwan mining area zma data of surface elevation were performed by remote sensing information and arcgis the study area was divided into clayey fine sand aeolian loose sand weathered fracture and low permeability zones according to hydrologic conductivities and borehole data by simplifying as a single layer system of phreatic groundwater and optimizing with geological parameters in each unit zone a reasonable model of the groundwater distribution in steady state was then found and calibrated combined with local climate variable groundwater behavior was discussed in relation to different precipitations which reduced the loss of the drain in degrees the study results may give benefit and safety to management in mining as well as being refined in the future

on the hellenic subduction zone and the geodynamic evolution of crete since the late middle miocene abstract in recent syntheses of the geodynamic evolution of the aegean area the hellenic subduction zone and in particular its initiation plays a central role two basic aspects of the recent comprehensive model put forward by le pichon angelier and co workers are a initiation of subduction along the hellenic arc is inferred to have taken place approximately 13 ma ago whereas several others have suggested approximately 5 ma and b migration of the trench system to the south southwest giving rise to an extensional regime in the back arc region which led to general subsidence and formation of the present day aegean sea new data on the structure of the upper mantle underneath the aegean area indicate that the former aspect requires modification the seismic velocity structure indicating a northward dipping slab down to a depth of at least 600 km and the depth distribution of earthquake hypocenters can not be reconciled with straightforward initiation of subduction approximately 13 ma ago estimates of about 5 ma for the time of initiation of the present subduction zone are even more difficult to reconcile assuming 400 km as an upper bound for the effect of stretching of the aegean sea and of other processes contributing to the separation of crete from the eurasian mainland we arrive at an age for the hellenic subduction zone of at least 26 ma as to aspect b geological data of crete lend strong support to the idea that on crete compressional tectonics is of much greater importance than current models imply combining geophysical and geological data we propose a modification of the tectonic evolution for the cretan segment of the hellenic arc whereas the basic process of extension caused by a migrating trench system roll back in a land locked basin remains a very useful and sound concept the tectonics of the margins of a region subject to stretching in this case crete may be more complicated than hitherto thought in our model the documented fragmentation of crete into several basins which started about 12 ma ago is not attributed to initiation of subduction but to inception of the roll back process compressional tectonics on crete is taken to be associated with deformation of the crust resulting from the overall tensional stress regime

u pb single zircon ages and geochemistry of metagranitoid rocks in the cycladic blueschists evia island implications for the triassic tectonic setting of greece abstract u pb zircon geochronology geochemical and microstructural analyses were carried out to a metagranitoid suite exposed in the blueschist unit of the attic cycladic zone on evia island concordant zircons from three metagranitoid samples yielded id tims u pb single grain ages of 234 1 2 ma 232 1 ma and 214 0 7 ma which are interpreted to constrain the intrusion of the igneous protolith in late triassic times these age data in combination with previously published early middle triassic protolith ages of meta igneous rocks from other greek islands support magmatic activity in the cycladic area throughout the triassic major and trace element whole rock analyses reveal that the granitic protolith of the evia metagranitoid suite is of a type affinity implying triassic magmatism in an extensional setting along the northern gondwanan margin rather than back arc extension above a subduction zone subsequent alpine subduction and related high pressure metamorphism led to pervasive non coaxial fabrics of the evia metagranitoid which indicate top to the e se shearing this alpine deformation took place under ductile viscous conditions at temperatures close to 450 500 c and differential stresses of 65 15 10 mpa

global positioning system measurements of present day crustal movements in the arabia africa eurasia plate collision zone we present and interpret global positioning system gps measurements of crustal motions for the period 1988 1994 at 54 sites extending east west from the caucasus mountains of southern russia georgia and armenia to the aegean coast of turkey and north south from the southern edge of the eurasian plate pontus block to the northern edge of the arabian platform viewed from a eurasia fixed reference frame sites on the northern arabian platform move n38 13 w at 20 3 mm yr roughly consistent with the velocity implied by nuvel 1a circuit closure n23 7 w at 24 2 mm yr the motion of arabia appears to be transferred directly to the region of turkey north of the suture however eastern turkey is characterized by distributed deformation while central western turkey is characterized by coherent plate motion involving westward displacement and counterclockwise rotation of the anatolian plate internal deformation within the central part of the anatolian plate is less than 2 mm yr the anatolian plate is decoupled from eurasia along the right lateral strike slip north anatolian fault naf this different response in eastern and western turkey to the collision of arabia may result from the different boundary conditions the hellenic arc forming a free boundary to the west and the asian continent and oceanic lithosphere of the black and caspian seas forming a resistant boundary to the north and east we derive a best fitting euler vector for anatolia eurasia motion of 29 2 0 8 n 32 9 0 4 1 3 0 1 m y the mapped surface trace of the naf corresponds well to a small circle about this pole the new euler vector implies an upper bound for naf slip rate of 30 2 mm yr i e assuming all relative motion is accommodated along the naf using the nuvel 1a euler vector for arabia eurasia and the gps euler vector for anatolia eurasia we determine an arabia anatolia euler vector of 31 2 n 45 2 e 0 9 0 1 m y and an upper bound on the east anatolian fault slip rate of 15 3 mm yr the aegean trough region of western turkey deviates significantly from coherent plate rotation in addition to rotating with anatolia this region shows roughly n s extension at a rate of 14 5 mm yr taken together with satellite laser ranging results along the hellenic arc the contemporary pattern of deformation indicates increasing motions toward the arc suggesting that the westward displacement and counterclockwise rotation of anatolia is driven both by pushing from the arabian plate and by pulling or basal drag associated with the foundering african plate along the hellenic subduction zone

lead and zinc in formation waters alberta basin canada their relation to the pine point ore fluid abstract the source of the ore fluid for the pine point zn pb deposit has been controversial for decades both formation waters from deep in the basin and geothermal fluids from the precambrian basement have been considered as sources of the ore in this carbonate hosted deposit a database of 694 analyses of pb and zn in formation waters from the alberta basin bears on this controversy these waters have a mean content of 4 66 mg l 1 pb and 6 88 mg l 1 zn for each of these metals the maximum content is 360 mg l 1 and the median content is 0 9 mg l 1 in 71 of the samples pb zn with a mean ratio of 2 3 1 this is in contrast to the pb zn ratio of formation waters in other sedimentary basins and geothermal waters but is consistent with that in brines from the canadian shield geochemical modelling using solmineq 88 shows that pb and zn occur mainly as the mecl 4 2 complex it is not possible to produce a sulphide precipitate with zn pb such as the ore at pine point from a formation water with pb zn even when the formation water carries the metals in the absence of h2s and the metals are precipitated by h2s rich brines therefore the present formation waters are a poor candidate for the source of the metals at pine point it is more likely that geothermal fluids rising along the great slave lake shear zone were the source of the metals additional evidence for this alternate source includes 1 the very homogeneous non radiogenic character of the pb isotopes in galena 2 the absence of a thermal anomaly along the great slave lake shear zone 3 a famennian time of deposition based on rb sr dating of sphalerite when overburden was thin and reservoir temperature low and 4 the distribution of sphalerite and galena in the subsurface of the alberta basin in relation to major crustal discontinuities and normal faults cutting the crystalline basement exploration for other zn pb deposits should therefore focus on the location of suitable shear zones and faults up which geothermal fluids might have migrated rather than the flow and composition of formation waters

alpine metamorphism and deformation in phyllites nappes external hellenides southern peloponnesus greece geodynamic implications in the southern peloponnesus allochthonous phyllites sl are juxtaposed on the ionian parautochthonous zone and are overridden in turn by the gavrovo tripolitza or olonos pindus nappes the phyllites sl allochthon consists of three nappes the lower is affected by medium high p low t metamorphism 4 6 5 kb 325 400 c the middle and upper nappes are affected by low p low t metamorphism p 4 kb 250 to 350 c the metamorphosed lower nappe is thrust over ionian unmetamorphosed parautochthonous rocks of the taygete range the explanation of such high p low t metamorphism and of such abnormal superposition is critical for the various models proposed for reconstructing the geodynamic evolution of the hellenides or of other orogenic belts our model a flake tectonic model not a pure subduction one implies a polyphased tectonic evolution with first the ionian zone underthrusting below the gavrovo tripolitza zone and next the phyllites nappes and gavrovo tripolitza nappe overthrusting on the ionian

thermally softened continental extensional zones arcs and rifts as precursors to thickened orogenic belts abstract intra continental deformation of soft zones during continental collision requires weak continental lithosphere which is able to be shortened across considerable width during later convergence this enables significant thickening with formation of an orogenic root we have examined models with a history of lithospheric thinning by pure shear during an earlier phase of intra continental extension with associated heating geologically this situation is appropriate to intra continental rifts and back arc basins if thinning of elevated thermal structure is decoupled from the thinning of lithology then a weak soft lower crust and sub arc rift mantle result this weak structure has a favoured rheology for subsequent convergent thickening while the lithosphere is still hot these regions are associated with formation of granulites and metamorphic assemblages typical of high temperature low pressure ht lp if convergence starts while the heat input is still active then the failed rifts and arcs are shut off by lateral wedging of the hard lower crust and upper mantle of shoulder regions into the softened arc rift domain such sites are ideal for the formation and for the exhumation of metamorphic core complexes subsequent thickening during convergence leads to ht eclogites when the previous arc rift was hot and to medium t eclogites for a thickened standard geotherm these p t paths are counterclockwise and their shapes are strongly dependent on the amount of previous thinning and type of initial geotherm if the compression starts long after cessation of the extensional event and associated thermal anomaly then the geotherm of the extended area relaxes and the whole region hardens in this case no homogeneous thickening occurs and deep continental roots cannot form

cover deformation above a blind duplex an example from west virginia u s a abstract pretectonic cover above blind thrust systems responds to underlying thrusting by combinations of forethrusting backthrusting and coupling the role of these responses was examined in the hanging rock cacapon mountain anticlinorium of the central appalachians this cover fold consists of middle ordovician and younger sedimentary rocks above a blind horse of cambro ordovician carbonates the cover has abundant folding and subsidiary faulting cover cleavage in carbonate and fine grained clastic rocks formed before regional folding in response to layer parallel shortening lps this 15 lps also produced grain suturing and fluid inclusion trails in quartzarenites the lps formed during cover forethrusting accommodating older blind horses in the hinterland with the formation of the underlying horse cover coupling occurred with bending folding additional secondary buckling and cleavage rotation by flexural flow with perhaps minor flattening this cover coupling was insufficient to accommodate horse formation no evidence exists for backthrusting but forelandwards abundant subsurface evidence exists for cover forethrusting with imbricate thrusting this thrusting accommodates horse formation and differs in style from the lps of the older forethrusting event so for this blind system the cover responded with a combination of coupling and forethrusting

rift migration and lateral propagation evolution of normal faults and sediment routing systems of the western corinth rift greece the active corinth rift records hanging wall migration of faulting and slip rate accel eration the rift initiated at approximately 5 4 ma and older parts are well exposed in the northern peloponnese a new correlation of chrono and lithostratigraphy and structure across the onland central to westernmost rift with offshore data reveals westward rift propagation as well as north ward fault migration northward fault migration ended first in the east with the stabilization of major north dipping faults that now bound the gulf the basin then propagated to the wnw in two stages each involving the initiation of a new fault that propagated east to se to link to the sta ble fault system extension rates accelerated in distinct steps as the rift opened to the west the youngest faults in the westernmost rift are associated with high seismicity and highest geodetic extension due to rapid fault growth and linkage at depth the early synrift succession infilled substantial inherited palaeo relief antecedent rivers estab lished vigorous sediment routing systems that controlled facies distribution throughout rifting albeit with drainage reorganization during fault migration events multiple deepening events recorded in the stratigraphy can be due to lateral rift propagation the transition from rift initiation to rift climax is therefore diachronous along the rift axis

the age of the tortonian messinian boundary the tortonian messinian boundary is marked by the first occurrence datum fod of globorotalia conomiozea which is found all over crete in open marine marls with good palaeomagnetic properties within the framework of the miomar project the previously studied sections of langereis et al 1 have been extended and partly resampled here we present new magnetostratigraphic and biostratigraphic results from sections on eastern crete faneromeni central crete kastelli and western crete potamida and skouloudhiana supplemented by cyclostratigraphic data the recently developed geomagnetic polarity time scale ck92 of cande and kent 2 allows an unambiguous correlation of the polarity sequences on crete the fod of g conomiozea occurs in the reversed interval of anomaly c3bn lr this leads to a new age determination of 6 92 ma for the tortonian messinian boundary and a duration of 1 76 myr for the messinian a slightly modified version of ck92 if we use more recent age estimates provides an age of 7 10 ma and a duration of 1 78 myr respectively bipartite sedimentary cycles are distinctly present in the cretan sections studied assuming that these cycles are precession induced and using an average periodicity of 21 7 kyr enables us to independently estimate the duration of the successive individual polarity zones the astronomically derived durations of the cretan polarity zones are in good agreement with ck92 but are approximately 10 shorter

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

nappe stacking resulting from subduction of oceanic and continental lithosphere below greece we quantitatively investigate the relation between nappe stacking and subduction in the aegean region if nappe stacking is the result of the decoupling of upper crustal parts 5 10 km thick from subducting lithosphere then the amount of convergence estimated from balancing the nappe stack provides a lower limit to the amount of convergence accommodated by subduction the balanced nappe stack combined with the estimated amount of completely subducted lithosphere indicates 700 km of jurassic and 2400 km of post jurassic convergence from seismic tomographic images of the underlying mantle we estimate 2100 2500 km of post jurassic convergence we conclude that 1 the imaged slab represents the subducted lithosphere that originally underlay the nappes 2 since the early cretaceous subduction in the aegean has occurred in one single subduction zone and 3 the composition of the original basement of the nappes indicates that at least 900 km of sub upper crust continental lithosphere subducted in the aegean

height of water conducting fractured zone in a coal seam overlain by thin bedrock and thick clay layer a case study from the sanyuan coal mine in north china the accurate determination of the height of the water conducting fractured zone hwcfz in a coal seam covered by thin bedrock and thick clay layer is crucial for aquifer protection mine safety and eco environmental conservation using the sanyuan coal mine in north china as a case study theoretical analysis numerical simulation and field measurements were used to analyze the regularity of the hwcfz in this area per mechanical theory a geometrical model for calculating rock bending and subsidence was established two arcs of equal curvature and lengths and opposite curvature direction were used to fit the curve section of intermediate rock layer after bending the theoretical method for solving the hwcfz was given by calculating the rock layer s tensile ratio in addition rock failure process analysis rfpa software was used to simulate the development of the water conducting fractured zone wcfz during the mining process and the hwcfz was measured by the drilling fluid loss measurement both which verified the feasibility of the theoretical calculation to determine the primary controlling factors affecting the hwcfz the seepage characteristics and plastic properties of the quaternary clay layer were also analyzed using laboratory tests results show that the quaternary clay with a depth greater than 130 m has a permeability coefficient of e 10 m s a liquidity index less than 0 25 and a plasticity index more than 17 indicating the clay layer is impermeable and of great importance to inhibiting the development of wcfz the research can provide significant theoretical insights for effectively preventing water hazards on mine roofs

the importance of the oxygen minimum zone and sediment geochemistry in the distribution of recent benthic foraminifera in the northwest indian ocean abstract the relationship between the distribution of benthic foraminifera and sediment type and depositional environment in the arabian sea is discussed the benthic foraminiferal fauna were sampled in nineteen recent surface sediment samples and geochemical variables of the sediment of the same samples were measured the water depths for the box core samples varies from 440 to 4040 m a total of 103 species and six species complexes were identified the geochemical properties were found to correspond well to the sediment type and depositional environment and six different sediment depositional environment types could be distinguished analysis of the benthic foraminiferal fauna reveals specific faunal assemblages that are closely related to these sediment depositional environment types

seismic coupling and structure of the hellenic subduction zone in the ionian islands region abstract the western hellenic arc has been commonly considered as a largely aseismic subduction zone from the comparison of a small rate of shortening derived from the seismic moment release with a large rate of convergence inferred from geology complete seismic coupling would instead be expected from models that consider a control by plate tectonic forces because of the trenchward velocity of the hellenic aegean upper plate now confirmed with gps measurements in the region of the ionian islands a subduction interplate boundary has been recently imaged and its seismogenic downdip width suggested to be moderate from reflection seismic profiling and local earthquake tomography in the appropriate model for such an earthquake source region which considers a single interplate fault and takes into account these features the moderate seismic moment release is found consistent with complete seismic coupling of this subduction the shallow downdip limit of the seismogenic zone can be interpreted as due to the interplate boundary being overlain there by the ductile deeper crust of the orogenically thickened hellenides

subcrustal microearthquake seismicity and fault plane solutions beneath the hellenic arc subcrustal seismicity recorded in the southern aegean sea during a 7 week microearthquake study was low compared with shallow seismicity most intermediate depth seismicity occurred beneath the western and eastern ends of the hellenic arc this distribution confirms that a slab of lithosphere is being subducted at a very shallow 15 angle for 200 km beneath the western end peloponnese but more steeply beneath the eastern end dodecanese we could locate only one intermediate depth event beneath the central pan of the arc where teleseimically located intermediate depth earthquakes also are infrequent t axes for most of the 22 focal mechanisms of subcrustal earthquakes are roughly parallel to the local dip direction of the seismic zone between depths of 40 and 80 km the mechanisms are more confused than at greater depth perhaps because some of these earthquakes did not occur within the downgoing slab earthquakes deeper than 80 km and within the subducted slab have nearly horizontal p axes that trend nne ssw in the eastern part and nnw sse in the western part of the arc these deeper mechanisms show horizontal p axes along strike perhaps in response to the contortion of the slab or to the westward motion of turkey as well as lengthening downdip probably in response to gravity acting on excess mass in the slab thus the short slab both downdip and along strike subducting beneath the aegean is subjected to a more complex set of forces than the long slabs of the pacific

subduction and the depth of convection in the mediterranean mantle 1 we tie together geological data paleotectonic reconstruction plate motion and tomographic analysis to unravel the history of subduction and back arc extension of the eastern and central mediterranean in these two regions extensional processes started contemporaneously around 30 myr ago but with marked differences in the eastern region the aegean basin opened slowly 1 cm yr behind a shallow dipping slab 40 45 the corresponding high velocity anomaly extends inside the upper mantle and can be also followed in the midmantle down to a depth of at least 1500 km its descent into the midmantle initiated most probably during the late cretaceous and the trench moved northeastward following the path of the eurasian plate and under the persistent push of the african plate conversely in the central mediterranean region subduction initiated later and the motion of the subducting slab is confined to the upper mantle causing punctuated and rapid episodes of back arc extension provencal and tyrrhenian basins behind a slab that dips steeply 75 we explore the causes that control how the slab subducted and interacted with the lower more viscous part of the mantle

recent benthic foraminifera from the continental margin of northwest africa community structure and distribution abstract sediment grab samples were collected at 107 locations along the continental margin of northwest africa these samples form a series of depth transects between the straits of gibraltar and dakar senegal the greater than 250 m size fraction was retained for a census of both the live and dead foraminifera after deleting trace occurrences jaccard and correlation coefficient based cluster analyses were performed to decipher the community structure for this margin the geographic distribution of the four major faunal provinces recognized is conventional in that for both the live and dead assemblages three are related to depth upper slope and shelf middle slope and lower slope and continental rise the biotopes and thanatotopes within these provinces are strongly restricted along vertical or latitudinal boundaries when the data are analysed using jaccard coefficients dendrograms constructed from correlation coefficients emphasize depth related faunal communities dominant species such as cibicides lobatulus trifarina fornasinii planulina ariminensis uvigerina finisterrensis and c wuellerstorfi are generally distributed within a definite depth range along this margin and strongly influence the correlation coefficient based dendrograms other distributions are clearly not depth related but correspond to various environmental variables for example cancris auriculus coarse substrate bolivina subaenariensis oxygen minimum cibicidoides kullenbergi and hoeglundina elegans low organic carbon uvigerina peregrina is also a notable exception to depth dependence in that this dominant species and the province it represents are generally confined to the continental slope south of cape blanc its preference for that region may arise from the high organic carbon and fine grain size of the sediment there from low salinity of the bottom water or from other unknown variables the most important vertical faunal boundary occurs between cape barbas and cape blanc between 22 and 21 n latitude in contrast the canary island ridge intersects the continental margin at a saddle depth of about 1500 m but that physiographic barrier has little effect on provincialism of the deep water benthic foraminifera

kinematics of rock flow in a crustal scale shear zone implication for the orogenic evolution of the southwestern hellenides combined shear sense criteria finite strain data and vorticity analyses were used to study the deformation path in a curved crustal scale shear zone phyllite quartzite series of the southwestern hellenides the results are combined with data on the structural evolution of a cover nappe pindos thrust belt to provide new insights into the orogenic evolution of this region ductile deformation within the phyllite quartzite series was associated with a top to the west southwest shearing and was partitioned into two structural domains a root zone and a frontal domain the root zone is characterized by vertical coaxial stretching high strain and upward movement of the material while the frontal domain comprises simple shear deformation at the base and pure shear at the top this pattern suggests superposition of pure shear on simple shear deformation and implies tectonic extrusion of the material from the root zone the initiation of brittle deformation in the pindos thrust belt was associated with westward translation above the sub horizontal pindos thrust later as the mountain range elevated normal faulting at high altitudes and migration of thrusting to the west occurred while east directed folding and thrusting in the belt started to the east according to the proposed model crustal thickening was taking place throughout the oligocene and early miocene including the subduction of the apulian beneath the pelagonian microcontinent and the intracontinental subduction of the phyllite quartzite series during the lower miocene vertical buoyancy forces led to the successive steepening of the shear zone and the simultaneous duplexing of its basement facilitating tectonic extrusion of the material from its root zone finally an indentation process caused vertical expulsion of the orogenic wedge and gravity collapse in the brittle crust

tethyan vs cordilleran ophiolites a reappraisal of distinctive tectono magmatic features of supra subduction complexes in relation to the subduction mode abstract supra subduction zone ssz ophiolites deserve special attention because they represent fundamental markers of intraoceanic convergence and generation of new lithosphere above subduction zones moreover owing to their structural characteristics and location in the overriding plate these complexes are far better represented and preserved than mid ocean ridge basalt morb ophiolites in orogenic belts in terms of their structure tectonics and magmatic features ssz ophiolites may be classified in two main types 1 tethyan complexes such as those of the albanide hellenide belt which mostly consist of complete and extensive volcanic dyke plutonic and mantle sections with prevalent island arc tholeiitic iat affinity and the significant presence of boninites obducted as relatively intact lithospheric slabs onto collisional continental margins 2 cordilleran complexes including the circum caribbean ophiolites of guatemala cuba and venezuela mostly represented by dismembered sections of arc volcanic plutonic and subordinate mantle sequences with tholeiitic to calc alkaline iac magmatic affinity and acidic differentiates commonly associated with metamorphic subduction complexes and tectonically emplaced onto or juxtaposed against the continental margin within polygenetic terranes these two types appear to be related to significantly different subduction modes and intraoceanic plate dynamics whereby ssz ophiolites were generated the tethyan complexes can best be compared with west pacific type subduction with accentuated steepening and retreat of the subducted slab accompanied by progressive decoupling of the converging plates intense mantle diapirism and tensional events in the upper plate with generation of large iat sheeted dike complexes in open oceanic spreading systems continuous slab sinking and roll back allow increasing asthenospheric diapirism and interarc spreading from the arc axis to the forearc region with generation of boninites and back arc basin basalts babb with intermediate morb iat composition by contrast the genesis of the cordilleran complexes requires a subduction mode characterized by a steady state regime with moderate and constant dip of the subducted slab and limited extension in the backarc region the magmatic evolution of these ophiolites from iat to iac and the significant presence of rhyodacite and tonalite differentiates coherently indicate a more mature stage of arc magmatism as well as the occurrence of efficient differentiation processes developing under nearly closed system conditions in independent magma chambers tethyan complexes are likely to be obducted as large and relatively intact slabs onto the continental margins through the interposition of metamorphic soles which represent relics of the morb lithosphere underplating the ssz ophiolites on the other hand the common emplacement of cordilleran complexes within polygenetic terranes appears to be controlled by prolonged accretionary mechanisms that trap against the continental margin parts of the arc structure subduction complexes melanges and volcanoclastic products

closure of the paleotethys in the external hellenides constraints from u pb ages of magmatic and detrital zircons crete abstract paleotethys was a highly mobile oceanic realm pinching into the supercontinent pangea between gondwana and eurasia in the late paleozoic early mesozoic published paleotethyan reconstructions reveal that the time of paleotethys closure and the position of its suture are highly debated we present new magmatic and detrital zircon ages separated from pre alpine basement and permian to triassic cover rocks exposed in the external hellenides of crete these age data reveal variscan and cimmerian docking of microplates along the southern margin of laurasia and help to constrain the time of paleotethys closure 46 of detrital zircons from quartzite in the variscan basement are pennsylvanian with concordant ages at 321 2 ma 310 3 ma and 300 3 ma the basement is unconformably overlain by arc related volcanics of the tyros unit magmatic zircons of which yielded a concordant u pb zircon age at 285 2 ma thus the metasediments of the basement interpreted as former trench sediments were deposited metamorphosed and exhumed in latest carboniferous to early permian times 302 283 ma magmatic activity during this late variscan phase is also indicated by igneous boulders within olenekian meta conglomerates of the tyros unit which yielded concordant u pb zircon ages at 291 2 and 310 2 ma the late variscan orogenic phase is attributed to the collision of the gondwana derived southern minoan terrane smt with laurasia subsequent to northward subduction of paleotethys lithosphere and visean collision of the northern minoan terrane nmt magmatic activity ceased during the late permian but revived in the lower triassic as is indicated by felsic volcanics 249 2 ma concordant u pb zircon and by detrital zircons 242 3 240 5 ma 237 3 ma concordant u pb zircon of the tyros unit at the same time the variscan chain was exhumed and removed as is shown by the detritus in the lower to middle triassic tyros sediments which includes high grade metamorphic rocks and detrital zircons with u pb ages ranging from 280 to 335 ma a significant change in the detrital components occurred in the ladinian when the variscan basement with its permo triassic cover was thrust on top of clastic sediments today represented by the phyllite quartzite unit s str the phyllite quartzite unit s str shows cadomian and older but no variscan detritus because of its position along the northern margin of the cimmerian ribbon continent thus in the eastern mediterranean paleotethys was closed during the ladinian and the related suture in the external hellenides is situated between the variscan basement active margin in the north and the phyllite quartzite unit s str passive margin in the south carnian crustal extension led to subsidence of the variscan cimmerian chain most parts of which merged below sea level this is the reason why 90 of the detritus of the carnian tyros beds are not related to the variscan but to the cadomian and grenvillian basement of the e gondwana derived cimmerian ribbon continent

a basement interacted fluid in the n81 deposit pine point pb zn district canada sr isotopic analyses of single dolomite crystals the mississippi valley type pb zn deposits of the pine point district northwest territories canada are located close to the eastern edge of the present day western canadian sedimentary basin the deposits are thought to have formed as the result of basin wide fluid flow in the presqu ile barrier the host to the ore deposits a laser ablation multi collector inductively coupled plasma mass spectrometric study of 87sr 86sr ratios of ore related dolomites from the n81 deposit at pine point indicates that at least two sources of sr were present in the mineralizing system one fluid has a range in sr isotopic values from 0 07073 to 0 71200 and is interpreted to be derived from middle devonian seawater that interacted with clastic units in the basin the second fluid has higher sr isotopic values up to 0 71520 similar to those found in some canadian shield brines and is interpreted to represent an evaporated seawater derived brine which has interacted with crystalline basement rocks reactivation of old structures in the basement may have provided a pathway for cross formation fluid flow to the site of mineralization the data suggest that the stratigraphic location of the pine point district near the interface between the western canadian sedimentary basin and its basement may have exerted a fundamental control on the formation of these deposits

tertiary palaeogeography and tectonostratigraphic evolution of the northern and southern peri tethys platforms and the intermediate domains of the african eurasian convergent plate boundary zone abstract the increasing effects of african eurasian convergence during the tertiary resulted in the uplift and emergence of the northern and southern peri tethys platforms palaeogeographic maps covering six selected time slices including the middle eocene late early oligocene late early miocene early middle miocene early late miocene and middle to late pliocene illustrate that environmental and depositional differentiations on the northern platform and along the bordering domains of the convergence zone were more pronounced than on the southern platform and its adjacent areas the tectonic evolution of the northern platform included an overall eastward directed trend in the onset of basin uplift and emergence which started at about the eocene oligocene transition at 34 ma tectonostratigraphic analyses indicate a striking contemporaneity of the events which defined the temporal and spatial development of both the domains of the convergent plate boundary zone and the bordering platforms five episodes of major regional change in palaeogeographic and tectonic setting are distinguished they occurred in the late eocene 37 34 ma early late oligocene 30 27 ma latest early to earliest middle miocene 17 15 ma early late miocene 9 8 ma and late early to early middle pliocene 4 3 ma these episodes encompassed changes which were most probably induced by geodynamic events primarily related to the relative motions of the african arabian and eurasian plates in turn the plate motions are assumed to have triggered discrete steps in the regional kinematics and geodynamics that governed the palaeogeographic evolution of the peri tethys platforms and the intermediate domains of the african eurasian plate boundary zone

the ecology of living stained deep sea benthic foraminifera from the sulu sea the distribution of living rose bengal stained deep sea benthic foraminifera was determined in the upper 20 cm of sediments of eight soutar box cores taken from two depth transects 510 4515 m in the thermospheric 10 c sulu sea despite the uniformity of bottom water temperatures salinities and dissolved oxygen levels below 1000 m significant faunal differences exist at different depths in the low oxygen 1 25 ml l below 1000 m basin the shallowest site 510 m is dominated 10 of the calcareous fauna by cibicidoides uvigerina 150 m and bolivina 63 m while siphonina is codominant with cibicidoides and uvigerina in the 1005 m core the 2000 m cores are dominated by cibicidoides gyroidinoides and oridorsalis while cibicidoides bradyi and oridorsalis umbonatus dominate the 3000 and 4000 m cores infaunal assemblages of valvulineria mexicana are found in the sediments of the 4515 m core relatively low bottom water oxygen values do not necessarily yield typical low oxygen taxa such as bolivina uvigerina chilostomella bulimina and globobulimina changes in the abundances of these taxa in fossil assemblages have been used as indicators of changes in ancient bottom water oxygen levels but may instead reflect organic carbon contents of the sediments an examination of the vertical distributions of foraminiferal assemblages from the 63 m and 150 m fractions reveals that taxa have microhabitat preferences similar to those observed in other regions taxa found in the upper 0 to 1 cm interval epifaunal include cibicidoides wuellerstorfi and hoeglundina elegans while taxa such as chilostomella and globobulimina reach maximum abundances in subsurface sediments and have infaunal microhabitat preferences cibicidoides bradyi and o umbonatus live in sediment depths from 0 to 4 cm and have transitional preferences with both epifaunal and infaunal occurrences intrageneric differences in test morphologies including pore distribution rounded peripheries and variable spire height are observed in cibicidoides and gyroidinoides and are suggested to be related to microhabitat preferences vertical distributions of a number of taxa found in both the 63 to 150 m and 150 m fractions are similar suggesting that juveniles and adults live under similar microhabitat conditions ontogenetic changes in microhabitat preferences of most species are not observed in this study and therefore would not be expected to account for isotopic vital effects reported for some taxa in previous studies

characterization and dispersal of indicator minerals associated with the pine point mississippi valley type mvt district northwest territories canada1 a glacial dispersal study was conducted around a subcropping pb zn deposit o28 in the pine point mississippi valley type mvt district northwest territories canada with the intent of characte

hydrocarbon prospectivity in the hellenic trench system organic geochemistry and source rock potential of upper miocene lower pliocene successions in the eastern crete island greece results of the current and already published studies suggest that the tortonian in age deposits could serve a major source rocks for both oil and gas beneath the messinian evaporites in the hellenic trench system additionally the strong terrestrial input in pliocene deposits could lead to the production of biogenic gas similar to the po basin in adriatic sea italy in the current study fourteen samples from late miocene faneromeni section and twelve samples from the early pliocene makrilia section in eastern crete were collected in order to evaluate their hydrocarbon generation potential for this purpose rock eval analysis and characterization of the organic matter were performed the results document a clear distinction between the two sections faneromeni section contains organic matter of kerogen type iii whereas the makrilia section contains organic matter of kerogen type iv the hi toc plot diagram in both sections indicates poor oil generating potential with the exception of several samples showing fair to good gas and oil potential although thermal maturities of the samples from the two successions are similar according to the t max values samples from faneromeni succession exhibit higher hydrogen index values indicating a better quality of organic matter in terms of hydrocarbon generation very low obtained concentrations of bitumen mg g of rock as well as the predominance of nso compounds compared to the saturates and aromatics indicate low maturation level the n alkanes profiles exhibit a bimodal distribution indicating a mixed origin marine and terrestrial of the organic matter in both areas terrestrial organic matter input is more pronounced in makrilia section the analysis of saturated biomarkers indicates that faneromeni deposits were accumulated under constant organic matter input in an environment influenced by cyclic changes from marine to lagoon origin and vice versa faneromeni section corresponds to a restricted basin during tortonian with quick and often sea level fluctuations just before the messinian crisis while makrilia section represents a very restricted intramontane basin with strong terrestrial influence

contemporary kinematics of the southern aegean and the mediterranean ridge summary this study focuses on the kinematics of the southern aegean and the mediterranean ridge mr a quantification of the deformation of the mr is essential for both evaluating physical models of accretionary wedges in general and for obtaining a self consistent model of the surface deformation over the entire nubia eurasia nu eu plate boundary zone in the eastern mediterranean previous kinematic studies have not properly considered the deformation field south of the hellenic arc although this study focuses on the deformation field of the mr we also discuss the kinematics of the southern aegean because the geometry and movement of the hellenic arc determine to a large extent the kinematic boundary conditions for kinematic studies of the mr we calculate a continuous velocity and strain rate field by interpolating model velocities that are fitted in a least squares sense to published global positioning system gps velocities in the interpolation we use information from a detailed data set of onshore and offshore active faulting to place constraints on the expected style and direction of the model strain rate field in addition we use the orientations of tracks left by seamounts travelling into the wedge to further constrain the offshore deformation pattern our model results highlight the presence of active shear partitioning within the mediterranean ridge high compressional strain rates between the ridge crest and the deformation front accommodate approximately 60 70 per cent of the total motion over the wedge and the outward growth rate of the frontal thrust is 4m m yr 1 strain partitioning within the wedge leads to 19 23 mm yr 1 of dextral motion at the wedge backstop contact of the western mr whereas the pliny and strabo trenches in the eastern mr accommodate 21 23 mm yr 1 of sinistral motion the backstop of the western mr is kinematically part of the southern aegean which moves as a single block the aegean block ae at 33 34 mm yr 1 in the direction of s24 w 1 towards stable nubia nu our model confirms that there is a clear divergence between the western and eastern hellenic arc and we argue for a causal relation between the outward motion of the arc and the gradient in the regional geoid anomaly our results suggest that a significant driving source of the surface velocity field lies south of the hellenic arc and only for the southeastern aegean could there be some effect as a result of gravitational collapse associated with density differences within the overriding plate

benthic foraminifer palaeoecology of the late quaternary continental outer shelf of a landlocked marine basin in central aegean sea greece abstract north evoikos gulf greece constitutes a landlocked epicontinental and semi enclosed basin connected to the central west aegean sea through a strait probably not allowing full exchange of intermediate and deep water masses benthic foraminifer analyses were carried out on a late quaternary core from the outer shelf of the basin with the aim of tracing palaeoceanographic changes the benthic foraminifer species percentage per sample was used to calculate two main biological proxies the benthic foraminifer oxygen index bfoi and benthic foraminifer high productivity bfhp proxy estimated by grouping benthic foraminifer taxa which are known to flourish under high corg flux the estimated values of bfhp and bfoi were controlled mainly by the abundance of bolivinid species which are generally considered as opportunistic and shallow infaunal species tolerant to low oxygen conditions the statistical analysis q mode cluster analysis singled out four time intervals each characterized by certain levels of oxygenation and food availability time interval 1 8513 8300 cal bp is characterized by a mixed fauna of oxyphilic taxa and taxa that live in suboxic environment indicating the existence of a relatively eutrophic system with a well oxygenated sediment water interface time interval 2 8300 8100 cal bp records a deterioration of conditions on sea floor testified by significant oxygen and biotic diversity decrease benthic foraminifer composition in time interval 3 8100 7000 cal bp depicts environmental conditions still highly variable yet with faunal indication of more stable conditions than during the previous interval finally the benthic foraminifer assemblage of time interval 4 7000 3500 cal bp is related to the high food supply and good bottom circulation the data suggest a strong linkage between the quantity and quality of the organic matter supplies and the diversity and composition of the benthic foraminifer faunas moreover this study clearly demonstrates that vertical tectonic movements need to be taken into account when reconstructing the late quaternary palaeoceanography of this region

kinematic vorticity and strain rate patterns associated with ductile extrusion in the chelmos shear zone external hellenides greece abstract kinematic vorticity strain rate finite strain and structural data have been used to describe the heterogeneous nature of ductile deformation in an extruding crustal scale shear zone the chelmos shear zone csz of the external hellenides the csz has a curved shape which is marked by a frontal flat and a steep zone the spatial variation in the kinematic vorticity number is strongly correlated with the geometry and the structural depth of the shear zone the pure shear component of deformation decreases from back to front and from top to bottom the ductile thinning normal to the shear zone s boundaries is higher in the steep zone and decreases westwards quartz grain size and strain rate in the csz is distributed into two approximately homogeneous domains the higher strain rate is recorded in the steep zone and the base of the frontal flat zone with lower rates in the upper parts of the frontal flat zone based on mesoscopic structural data and the spatial distribution of the shear strain rate the existence of a west dipping back flow zone in the boarder zone between these two domains is inferred the overall pattern of deformation in the csz implies that tectonic extrusion from the steep zone occurred at the final stages of ductile deformation and was associated with the formation of the backflow zone in the front of the shear zone ductile deformation of rocks probably started close to simple shear on a planar low angle shear zone progressively became penetrative and more general shear occurred as the csz steepened up this progressive increase in pure shearing may have occurred in a heterogeneous manner and was higher close to both the eastern margin of the steep zone and the top of the frontal flat zone solid state extrusion in the csz was also associated with a heterogeneous and progressive increase in strain rate

guidelines for evaluating petroleum source rock using programmed pyrolysis rock eval pyrolysis is used to rapidly evaluate the petroleum generative potential and thermal maturity of rocks accurate conclusions require programs every 30 60 ft 9 18 m understanding of interpretive pitfalls and supporting data such as visual kerogen vitrinite reflectance and elemental analyses the generative potential of coals is commonly overestimated by pyrolysis and is best determined by elemental analysis and organic petrography most coals show high s2 s3 5 and low hi values 300 mg hc g toc migrated oil and mud additives which alter rock eval data can sometimes be removed by special processing for immature rocks bimodal s2 peaks and pi values over 0 2 indicate contamination pyrolysis downgrades organic poor clay rich rocks which show lower hi and higher tmax values than isolated kerogen because of adsorption of pyrolyzate on the clays tmax values for small s2 peaks 0 2 mg hc g toc are unreliable tmax is affected by maturation organic matter type contamination and the mineral matrix s3 is sensitive to inorganic and adsorbed carbon dioxide and to instrumentation problems acidification of carbonate rich samples and proper maintenance improves s3 measurement constant sample weights 100 mg are recommended below a threshold weight tmax increases by up to 10 c and other parameters decrease organic rich samples which overload the detector can be diluted with carbonate detector linearity is determined by pyrolyzing various weights of an organic rich rock

pb isotope evidence for the role of mesozoic basins in the genesis of mississippi valley type mineralization in somerset uk the mendip bristol veinfield is one of a number of british mississippi valley type deposits the genesis of which has never been fully explained the mendip bristol pb zn ba vein mineralization is hosted in carboniferous permo triassic and jurassic sediments the metal sources involved during mineralization were investigated using pb isotope analysis of vein galenas 206 pb 206 pb values range from 18 311 to 18 594 207 pb 204 pb values from 15 601 to 15 688 and 208 pb 204 pb values from 38 257 to 38 565 the data show three isotopically different mineralizing fluids which it is suggested reflect fluid expulsion from adjacent mesozoic sedimentary basins as a result of overpressuring due to rapid subsidence in the triassic jurassic

early orogenic deformation in the ionian zone of the hellenides effects of slab retreat and arching on syn orogenic stress evolution abstract in this work we report on early orogenic fracture patterns affecting a cretaceous to eocene sedimentary succession exposed in western greece these rocks belong to the cenozoic external hellenides which form the western portion of the aegean orocline the analysis of fracture type orientation and crosscutting relationships provides constraints on the stress and strain patterns during the early stages of orocline formation the fracture patterns in the study area includes early orogenic extensional fractures arranged into two mutually orthogonal sets these developed during progressive burial in the forebulge foredeep system ahead of the advancing compressive front tectonic solution seams at a high angle to bedding postdate these extensional structures solution seams are arranged in different sets oblique to each other and developed in the early stages of thrusting and folding extensional structures and solution seams are oblique to each other their orientation and crosscutting relationships provide evidence for clockwise vertical axis rotation of stress directions with time this is consistent with the progressive arching of the forebulge thrust belt system during progressive slab retreat

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

kinematics of the central hellenides structural analysis along 24 cross sections crosscutting several windows in the central hellenides provides the sense of nappe movements as well as the location of destroyed oceans lying between the apulian and eurasian continents from the mesozoic orogeny took place in two phases the first phase the eo hellenic phase was initiated by convergence of the apulian and pelagonian plates with west directed subduction and closure of the pindos ocean late jurassic obduction of oceanic lithosphere over the western margin of the pelagonian plate was followed by footwall imbrication mylonites and sheath folds during the late cretaceous uplift was associated with ductile normal faulting at depth and tectonic unroofing at shallow crustal levels the second phase the meso hellenic phase comprised the closure of the ambelakia ocean at the eastern margin of the pelagonian plate and continental subduction along the eastern margin of the apulian plate west directed subduction of the ambelakia ocean was associated with eastward directed ductile thrusting folding and blueschist metamorphism blueschist formed within a simple duplex structure at depth and was subsequently overthrusted in the late eocene onto the olympos microcontinent which acted as a major obstacle to the eastward directed nappe movements up to 150 m thick cataclasites kink folds and a spaced cleavage were formed during the late stage of the continental collision a subduction along the eastern margin of the apulian plate caused kink folding and reimbrication of the western parts of the pelagonian basement since the oligocene the overthickened crust collapsed by means of low angle normal faults

organic carbon deposition in the cretaceous of the ionian basin nw greece the paquier event oae 1b revisited we present new stable c o isotopic biostratigraphic and organic geochemical data for the vigla shale member of the ionian zone in nw greece in order to characterize organic carbon rich strata that potentially record the impact of cretaceous oceanic anoxic events oaes in a section exposed near gotzikas nw epirus we sampled a number of decimetre thick organic carbon rich units enclosed within marly locally silicified vigla limestone berriasian turonian all these units are characterized by largely comparable bulk geochemical characteristics indicating a common marine origin and low thermal maturity however the stratigraphically highest of these black shales is further distinguished by its much higher total organic carbon toc content 28 9 wt and hydrogen index hi 529 and much enriched delta 13corg value minus sign 22 1 planktonic foraminiferal and calcareous nannofossil biostratigraphy indicate a lower to middle albian age for the strata immediately above and a lower aptian age for the strata below the uppermost black shale in terms of molecular organic geochemistry the latter black shale is also relatively enriched in specific isoprenoidal compounds especially monocyclic isoprenoids whose isotopic values are as high as minus sign 15 indicating a substantial archaeal contribution to the organic matter the striking similarities between the molecular signatures of the uppermost vigla black shale and coeval organic rich strata from se france and the north atlantic odp site 1049c indicate that this level constitutes a record of the paquier event oae 1b

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

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

decoding sea surface and paleoclimate conditions in the eastern mediterranean over the tortonian messinian transition abstract new sedimentological micropaleontological and geochemical data from the upper miocene pre evaporitic sedimentary sequence of the faneromeni section crete island eastern mediterranean revealed a stepwise restriction of the mediterranean sea preceding the messinian salinity crisis msc which was modulated by a sedimentary cyclicity responding to orbital parameters this cyclicity is manifested by lithological alternations from laminated to indurated homogeneous marls and clayey limestones and covers the tortonian messinian transition tmt 7 6 6 7 ma this time window covers the successive closure of the marine mediterranean atlantic gateways which culminated in the onset of the msc in the present study we present the first evidence for changes in the upper water column reflected by sea surface temperature sst and salinity sss variations that correlate with pronounced paleoclimatic fluctuations planktonic foraminiferal isotopes in combination with paired mixed layer sr ca derived sst data reveal that the very warm late tortonian interval has been followed by a strong long term cooling 10 c and desalination 10 trend during the earliest messinian attributed to the paroxysmal phase of the so called siphon event in particular the climate shift that occurred at the end of a global carbon isotope 13c decrease suggests that changes in the carbon cycle were instrumental in driving late miocene climate dynamics cooling and aridity in the progressively isolated eastern mediterranean sea the observed salinity variability during this time interval also provides further insights about seasonal freshwater inputs and gives new support to the much debated hydrologic regime linear salinity increase vs step function evolution with strong salinity fluctuations preceding the deposition of evaporites the novel methodology of foraminiferal sr ca paleothermometry and results of this study could have numerous potential applications to other regions and relevant extreme geological events therefore in the near future we expect this approach to add important new information to our understanding of neogene climates

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

neotectonic evolution of northwestern continental greece the post miocene sedimentary and structural evolution of nw continental greece changes from west to east

formation of coarsely crystalline hydrothermal dolomite reservoirs in the presqu ile barrier western canada sedimentary basin late stage coarsely crystalline replacement dolomite and associated saddle dolomite cement form a widespread diagenetic facies in the middle devonian presqu ile barrier that extends southwestward from pine point to the subsurface of the foothills in northeastern british columbia these dolomites create hydrocarbon reservoirs in otherwise tight limestones in the subsurface of the northwest territories and northeastern british columbia and host mississippi valley type deposits at pine point the coarsely crystalline replacement dolomite and saddle dolomite cement are interpreted to have formed during burial because they replace blocky sparry calcite cements occur continuously across the sub watt mountain unconformity postdate stylolites and earlier replacement dolomites and overlap sulfide mineralization the dgr18o values of both replacement and saddle dolomites increase eastward updip along the presqu ile barrier from 16 pmil pdb in the deeper subsurface of northeastern british columbia to 7 pmil pdb at pine point whereas the corresponding homogenization temperatures of saddle dolomite fluid inclusions decrease from 178 to 92 c the 87sr 86sr ratios of coarsely crystalline and saddle dolomites decrease eastward along the pres u ile barrier from about 0 7106 in the subsurface of northeastern british columbia to 0 7081 at pine point these geochemical trends suggest a possible basin scale migration of hot radiogenic dolomitizing fluids updip eastward along the presqu ile barrier such large scale fluid movements probably were related to western canada sedimentary basin tectonic compression and sedimentary loading which occurred at least twice during early burial between the late devonian and early carboniferous and during deep burial between the late jurassic and early tertiary

source rock potential of middle cretaceous rocks in southwestern montana the middle cretaceous in southwestern montana is composed of a marine and nonmarine succession of predominantly clastic rocks that were deposited along the western margin of the western interior seaway in places middle cretaceous rocks contain appreciable total organic carbon toc such as 5 59 for the mowry shale and 8 11 for the frontier formation in the madison range most samples however exhibit less than 1 0 toc the genetic or hydrocarbon potential s1 s2 of all the samples analyzed except one yield less than 1 mg hc g rock strongly indicating poor potential for generating commercial amounts of hydrocarbons out of 51 samples analyzed only one a thermopolis shale sample from the snowcrest range showed a moderate petroleum potenti l of 3 1 mg hc g rock most of the middle cretaceous samples are thermally immature to marginally mature with vitrinite reflectance ranging from about 0 4 to 0 6 r0 maturity is high in the pioneer mountains where vitrinite reflectance averages 3 4 r0 and at big sky montana where vitrinite reflectance averages 2 5 r0 at both localities high r0 values are due to local heat sources such as the pioneer batholith in the pioneer mountains

early mesozoic oceanic subduction related volcanic rocks pindos basin greece abstract small outcrops of volcanic rocks of mid triassic to early jurassic age in the deep water mesozoic pindos basin have been systematically sampled and analysed geochemically to interpret the tectonic environment in which these rocks formed associated sediments indicate a rifting environment the volcanic rocks include all the main types found in modern back arc basins shoshonites with clinopyroxenes of calc alkaline affinity occur at the basin margin minor enriched type morb contains clinopyroxene typical of morb minor basalts that resemble oib with some subduction related characteristics contain clinopyroxene typical of alkahne rocks thick andesites and pyroclastic rocks with morb like trace elements except for some lile enrichment are associated with cumulate gabbro and oceanic type plagiogranite these thick andesites and pyroclastic rocks formed at an intra backarc ocean ocean subduction zone the supra subduction zone ophiolites of the eastern margin of the pindos basin which are of similar age are probably related to the same subduction zone the overall volcanic assemblage is related to formation of a back arc basin associated with the subduction of paleo tethys the hypothesis that late triassic eariy jurassic rifting formed only small pull apart basins by transtension is inconsistent with the range of volcanic products and the evidence for significant intra back arc subduction

fluid involvement in the active helike normal fault gulf of corinth greece abstract rock fabric and mineralogical composition from the fault core and the unaffected protolith have been used to define the role of the segmented helike fault to fluid flow sixty samples were investigated by xrd sem observation and sem eds microanalyses detrital smectite calcite and quartz represent the mineral assemblage at the crest of the footwall block in foniskaria sampling site in this site smectite is enriched at the rims of the fault core all other sampling sites located at the base of the fault scarp are characterized by detrital and newly formed minerals detrital minerals include plagioclase quartz calcite and illite in nikolaiika sampling site and smectite illite kaolinite quartz calcite in selinous sampling site in the latter sampling site erionite and cerussite are newly formed minerals with erionite considered as the hydrothermal alteration product of fluids at 80 100 c at the eastern fault segment illite quartz and calcite t13 site corresponds to detrital minerals mineralogy in the fault core reflects its high permeability to down flowing meteoric water and weak hydrothermal alteration the rock fabric suggests mineral alignment parallel to the fault plane mineralogy indicates that the aigion helike and pyrgaki faults in the gulf of corinth host hydrothermal activity at shallow levels

a traverse of the ionian islands front with coincident normal incidence and wide angle seismics abstract marine vertical reflection profiling with a powerful airgun source augmented with a few wide angle seismometer stations on land has been applied along a 180 km line across the presently active deformation front of the subduction of the ionian sea plate beneath the western hellenides east of the ionian islands there is limited evidence for reflectivity down to 23 km interpreted as the base of a rather thin continental type crust under the western slope of the islands a major normal incidence reflector dips eastward first gently to the west of the islands then more steeply under them this reflector may be extrapolated southwestwards beneath a bulge that is thought to represent the modern pre apulian front located over the subduction zone the continuity signature and geometry of this reflector suggest that it may act as the lower limit of the western hellenides where they override the ionian sea quasi oceanic crust rather than just an intracrustal interface of a pre apulian crust the location of the previous deformation front the ionian thrust proposed in previous models can be constrained by the new seismic data the new data raise the possibility of a larger area of evaporite mobility than previously considered insofar as active block motion apparently related to halokinesis is recognized west of the zakynthos anticline diapirism decollement and westward directed over thrusting in the pre apulian crust may have been brought on by late pliocene quaternary reactivation of regional extension associated with the separation of the peloponnesus from northern greece as it was captured by the anatolian aegean rotation and associated also with the fast clockwise rotation of the ionian islands as they were sheared off the apulian domain to the southwest by the initiation of the kefallinia transform

anoxic basins of the eastern mediterranean an overview it is well known that the mediterranean sea underwent several episodes of basin wide stagnation in the plio pleistocene but extant anoxic basins were first discovered between 1983 and 1984 in the strabo trench and in the southwestern slopes of the mediterranean ridge facing the sirte abyssal plain since then several expeditions were carried out to investigate the geology and physiography of the basins as well as the physical and chemical characters of the water column although the geodynamic settings of the tyro and bannock basins are quite different they are very deep closed and filled by dense salty cold brines whose presence is attributed to submarine dissolution of messinian evaporites bannock basin is interpreted as a collapse basin with a complex configuration central domes and several satellite basins most of which are anoxic unlike the tyro basin it is characterized by precipitation of gypsum occurring as euhedral crystals within the sediments and dredged along the steep wall bordering the main basin to the east the interface separating normal seawater from the brines corresponds to a well defined pycnocline with a density contrast of approximately 20 where strong bacterial activity seems to occur and a sudden decrease in transmittance is recorded studies on the water column document drastic changes of all the various parameters measured o2 h2s ca po4 ba across the interface sediments deposited beneath the brines are anoxic this kind of geologically induced anoxia is persistent and diachronous in contrast with the isochronous episodic repetitive and climatically induced anoxia recorded in the same area of the eastern mediterranean

mechanical model for the tectonics of doubly vergent compressional orogens a mechanical model of crustal shortening and deformation driven by the relative convergence of rigid underlying mantle plates explains many features of convergent orogens results based on numerical models and supported by sandbox models show that a coulomb crustal layer subject to basal velocity boundary conditions corresponding to asymmetric detachment and subduction of the underlying mantle passes through three stages of orogenic growth 1 block uplift bounded by step up shear zones 2 development of a low taper wedge over the underthrusting mantle plate and 3 development of a low taperwedge overlying the overthrusting mantle plate and verging in the opposite direction when modified by isostasy basal viscous flow surface erosion and denudation and sedimentation the resultant model orogens exhibit a variety of styles with characteristics in common with small rapidly denuded orogens large orogens with plateaus and extensional characteristics and active subduction margins with doubly vergent accretionary wedges and deformed fore arc basins

the pelagonian zone in greece a polyphase deformed fragment of the cimmerian continent and its role in the geotectonic evolution of the eastern mediterranean data from macedonia greece correlated with those reported from the pontides turkey indicate that the pelagonian zone of the hellenides represents a fragment of the cimmerian continent which separated the paleo tethys and neo tethys oceans a permo triassic age is suggested for separation of the paleozoic continent and initial rifting in the two oceanic basins as the pelagonian zone represented the northwestern european end of the cimmerian continent the paleo tethys and the northern branch of neo tethys would have been very close to each other on either side of this zone thus both oceans at their european end closed within a short time of each other in the late jurassic early cretaceous the sequential development of the two oceans outlines a model for the geotectonic evolution of the internal hellenides in which a correlation of thrusting and folding phases is also given

study of the crustal thickness and the subducting lithosphere in greece from gravity data the area of greece has experienced a complex tectonic history dominated by the subduction of the african plate beneath eurasia in this study the variations of the crustal thickness in the area of greece were obtained by means of the multiple source werner deconvolution mswd method applied to gravity data thicknesses of 40 49 km are estimated beneath the hellenides mountain belt to the west eastward thinning of the crust to thicknesses ranging from 25 km in the north to 30 km in the south is seen in the aegean region these results are in good agreement with recent seismological results demonstrating that the mswd method successfully treated the problem using the crustal model we derived we computed the gravity effect of the crust and extracted it from the bouguer anomaly we also extracted the gravity effect of the subducting lithosphere from the bouguer anomaly producing a residual map where most of the original gravity variation has been successfully removed the remaining anomalies appear related to near surface features and an area of low velocity mantle in the central aegean sea

the pindos fold and thrust belt greece inversion kinematics of a passive continental margin continuous exposure in the pindos mountain chain greece and the detailed stratigraphic measurements in the area enable us to construct eight balanced cross sections across the pindos fold and thrust belt pftb and to approach quantitatively some parameters which controlled foreland evolution the 160 km wide passive continental margin of the apulian continent in greece was progressively shortened from east to west at rates of 6 mm year between the early oligocene and late eocene from the rear to the frontal part of the wedge fault bend folds duplexes and imbricates were formed while strain was partitioned into faulting 34 layer parallel shortening 23 and buckling 9 foreland subsidence and internal deformation of the orogenic wedge are strongly affected by two parameters of equal importance the thrust load of the overthrusted microcontinents and the rigidity of the underthrusted apulian passive margin changes in the thickness of the pre orogenic sediments and reactivated transform faults induced salients during the lower miocene the orogenic wedge in the peloponnese suffered additional uplift and westward gravitational gliding induced by the intracontinental subduction of the palaeozoic rift zone of the phyllite quartzite series which was reactivated and returned to the earth s surface during the hellenic orogeny

geochemistry of upper miocene lower pliocene source rocks in the hellenic fold and thrust belt zakynthos island ionian sea western greece abstract the southwestern margin of the hellenic fold and thrust belt situated along the southern edge of the dinarides albanides hellenides continental convergent zone has been studied in terms of its hydrocarbon generating potential the upper miocene lower pliocene tortonian to zanclean clastic sedimentary succession at zakynthos island provides an excellent opportunity to evaluate the source rock potential of such a system twenty seven mudstone samples were analyzed using organic geochemical techniques such as rock eval pyrolysis bitumen extraction open column chromatography and gas chromatography mass spectrometry the obtained data indicate that the sedimentary sequence contains units with sufficient organic material of good enough quality to be considered as potential source rocks the input of terrestrial organic material and associated gaseous generating potential is indicated by 1 rock eval pyrolytic yields and calculated values of hydrogen and oxygen indices 2 n alkane distribution with dominant long chain components 3 high terrigenous to aquatic organic material ratios 4 odd to even predominance values 5 low sulfur content and 6 occurrence of gammacerane the kerogen is immature as evidenced by 1 t max and production index values 2 odd to even predominance values 3 low diasterane to sterane and pr ph ratios 4 low 20s 20s 20r and sterane ratios and 5 presence of gammacerane

development of concepts concerning the genesis and emplacement of tethyan ophiolites in the eastern mediterranean and oman regions this article uses evidence mainly from the eastern mediterranean and oman to help understand the origin and emplacement of ophiolites field studies in these regions emphasize the diversity of ophiolite related sedimentary and tectonic processes topics to be discussed here include the sedimentary covers of ophiolites their metamorphic soles related melanges and emplaced continental margin slope rise units modes of ophiolite emplacement will also be considered and tectonic reconstructions that have a direct bearing on the origin and emplacement of ophiolites the writer argues that there is compelling evidence that many ophiolites formed by spreading above intraoceanic subduction zones evidence from their intact sedimentary covers however indicates that such subduction was only incipient in most cases as directly associated volcanic arcs or back arc basins are rare metamorphic soles record fragments of oceanic lithosphere derived from settings ranging from open ocean to continental slope rise settings underlying melanges record the subduction of most of the ocean lithosphere formed at spreading ridges continental margin units beneath ophiolites demonstrate that these ophiolites were formed in ocean basins that were mainly initiated by continental rifting in the eastern mediterranean and oman regions ophiolite emplacement was commonly achieved by trench margin collision although strike slip transpression and large scale accretion along subducting margins played a role in some cases taking account of the mesozoic palaeotectonic setting of the eastern mediterranean region it is widely believed that ophiolites of two main ages mid jurassic and late cretaceous were formed in several small oceanic basins separated by rifted microcontinents the history of tethys in pre mesozoic time remains more open to question lastly giant subduction related ophiolites as in oman cyprus or the balkans may not be forming anywhere in the world ocean today but may instead relate to rare events in earth history when regional to global plate boundaries were drastically reorganised

intracontinental wedging and post orogenic collapse in the mesohellenic trough the mesohellenic trough is a 130 km long and about 30 km wide subsiding area which contains a thick sequence of well exposed late cenozoic post orogenic sediments this intermontane basin located at the contact between the apulian and pelagonian collided margins provides a good example of the characteristics needed to study the chronology of late orogenic intracontinental structures

deep sea ecosystem variability of the aegean sea during the past 22 kyr as revealed by benthic foraminifera abstract specific responses of the regional deep sea ecosystems to climatic and oceanographic processes during the last 22 kyr are revealed by benthic foraminiferal faunas from two cores in the northern and southern aegean sea under glacial boundary conditions high diversity benthic foraminiferal faunas and elevated benthic foraminiferal numbers indicate enhanced organic matter availability and well ventilated deep water masses in the whole aegean sea the glacial termination is accompanied by significant fluctuations in productivity and deep water ventilation in the northern aegean sea meltwater inflow from mountain glaciers during the bolling allerod warm period resulted in a restriction of local deep water formation as mirrored by a dominance of bolivinids during the deposition of sapropel s1 drops in benthic foraminiferal number and diversity are more significant in the southern aegean sea when compared to the north this suggests the persistence of local deep water formation in the northern aegean sea during s1 deposition in addition faunal fluctuations within s1 at both sites suggest the repeated influence of short term cooling events on the re ventilation and re colonization of aegean deep sea ecosystems during the middle and late holocene benthic foraminiferal faunas document the establishment of oligotrophic and well ventilated conditions in the southern aegean sea the corresponding faunas from the northern aegean sea reflect generally mesotrophic conditions and variable deep water oxygenation during the entire holocene the deep sea ecosystems of this region responded very sensitively to short term changes in humidity and temperature these abrupt climate changes controlled the inflow of nutrients from rivers and the black sea and the formation of local deep water masses

tectono stratigraphy and evolution of the mesozoic pindos ophiolite and related units northwestern greece the northwest pindos mountains expose mesozoic and tertiary thrust sheets which include the jurassic pindos ophiolite composed of ultramafic and mafic oceanic crustal rocks the tectono stratigraphy of these units is i mainly ultramafic ophiolitic thrust sheet and basal metamorphic sole dramala complex and loumnitsa unit ii late cretaceous platformal limestones orliakas group iii dismembered intrusive and extrusive ophiolitic rocks aspropotamos complex iv tectonic melange and olistostromes dominated by triassic jurassic volcanic and sedimtntary rocks avdella melange v coherent thrust sheets of late jurassic late cretaceous deep water sediments dio dendra group vi early tertiary flysch pindos flysch immobile trace element studies indicate that triassic and jurassic extrusives of the volcanic sedimentary melange formed mainly at within plate and or mid ocean ridge settings by contrast structurally overlying ophiolitic extrusives include boninitic volcanics and island arc tholeiites of supra subduction zone origin initial ophiolite displacement c 165 ma is recorded in metamorphic sole formation including basal peridotite mylonite amphibolites and greenschists the sole rocks have morb and wpb chemical affinities in our favoured model the pindos ophiolite formed above a mid jurassic westerly dipping intra oceanic subduction zone accompanied by accretion to form melange followed by collision and emplacement with the pelagonian margin final suturing of the pindos ocean however did not take place until early tertiary times

on the shape of the subducting slab beneath the peloponnese greece the mediterranean sea floor is subducted beneath the western hellenic arc at a gentle angle for about 200 km and then steepens beneath the gulf of corinth the seismic zone extends to a depth of 150 km but the subducted intact lithosphere could reach 600 km the present relative motion between africa and aegea can be considered as the sum of 2 motions 1 slow 1 cm y relative motion between africa and europe which describes the rate at which the deep slab penetrates the asthenosphere and which started during the upper cretaceous time when africa started to converge toward europe and 2 fast 5 cm y relative motion between the southern aegea and europe manifest by internal deformation within the aegean which may have been active at present rates only since pliocene time i suggest that the increase in the total convergent rates which began about 5 my ago is responsible for the wide flat slab beneath the peloponnese

pine point a case history of lead isotope homogeneity in a mississippi valley type district the lead isotope compositions of 32 galena samples from 20 different deposits in the pine point district are essentially identical within error avg 206 pb 204 pb 18 175 or 0 008 and indicate a remarkable uniformity of isotope composition over a mineralized area of several hundred square kilometers the isotope homogeneity could result from an homogeneous source or from thorough mixing during extraction and subsequent precipitation of lead the homogeneity of the lead isotope data allows an interpretation in terms of a single stage lead evolution model and calculation of a model age of mineralization of about 290 ma late pennsylvanian this age is substantially younger than the middle devonian host rocks 375 ma but much earlier than the post early cretaceous approximately 100 ma tectonic events along the western margin of the mackenzie basin that have been credited with initiating the regional hydrologic regime that resulted in mineralization more complex multistage models are possible but cannot be more precisely defined by present data the homogeneity and nonradiogenic composition of pine point leads is in marked contrast to those reported for devonian carbonate hosted pb zn deposits of the mackenzie platform this discrepancy may be due in part to the different paleogeographic positions of the two groups of deposits the more radiogenic inhomogeneous group is situated on the western edge of the platform adjacent to deep water shales of the selwyn basin pine point in contrast lies more than 500 km to the east within the carbonate platform

thrust sequences in the central part of the external hellenides the model of a foreland propagating sequence already presented for the external hellenides is significantly modified in this paper new data are used including structural maps cross sections stratigraphic determinations and seismic profiles in general thrusts formed a foreland propagating sequence but they acted simultaneously for a long period of time thus during the middle eocene the pindos thrust resulted in the formation of the ionian gavrovo foreland and acted in tandem with the newly formed gavrovo thrust within the basin until the late oligocene the gavrovo thrust consists of segments showing that out of sequence thrusting was important thrust nucleation and propagation history is strongly influenced by normal faults formed in the forebulge region of the ionian gavrovo foreland basin shortening rates within the gavrovo ionian foreland are low about 1 mm year although thrust load played an important role in the formation of this basin the additional load of 3500 m thick clastics in the basin enhanced subsidence and underthrusting

exhumation of high pressure rocks under continuous compression a working hypothesis for the southern hellenides central crete greece combined kinematic structural and palaeostress calcite twinning fault slip data analyses are used to study the exhumation mechanism of the high pressure rocks exposed on the island of crete southern aegean greece our study shows that the evolution of windows in central crete was controlled by two main contractional phases of deformation the first phase d1 was related to the ductile stage of exhumation nnw sse compression during d1 caused layer and transport parallel shortening in the upper thrust sheets resulting in nappe stacking via low angle thrusting synchronously intracontinental subduction led to high pressure metamorphism which however did not affect the most external parts of the southern hellenides subsequent upward ductile extrusion of high pressure rocks was characterized by both down section increase of strain and up section increase of the pure shear component the second phase d2 was associated with the brittle stage of exhumation d2 was governed by nne ssw compression and involved conspicuous thrust related folding considerable tectonic imbrication and formation of a middle miocene basin the major d2 related psiloritis thrust cross cuts the entire nappe pile and its trajectory partially follows and reworks the d1 related contact between upper and lower high pressure tectonic units eduction and doming of the talea window was accompanied by gravity sliding of the upper thrust sheets and by out of the syncline thrusting late orogenic collapse also contributed to the exhumation process therefore it seems that the high pressure rocks of central crete were exhumed under continuous compression and that the role of extension was previously overestimated

pb isotope evidence on the origin of the west shropsh orefield england pb isotope data on ore galenas from the west shropshire orefield show a significant spread of 20 pb 204 pb values with minor variation in 207pb 204 pb and 208pb 204 pb ratios these indicate that lead was derived from multiple sources some of them uranium enriched and incompletely mixed prior to ore deposition four possible mineralizing agents are considered circulating sea water metamorphic waters basinal brines and convecting formation waters pb isotope data exclude a circulating sea water origin for the mineralization and best support a convecting formation water mineralizing agent a model involving a single fluid tapping multiple lead sources is proposed to explain the observed pb isotope variation

tectonics of the hellenic trench a synthesis of sea beam and submersible observations abstract detailed bathymetric investigations were performed in four zones of the hellenic trench system in 1978 using the multi narrow beam echo sounder sea beam on r v jean charcot in 1979 a field study using the 3000 m submersible cyana was conducted in three of the four sites covered by sea beam we summarize here the principal tectonic results of these studies and publish the corresponding sea beam maps it is shown that compressional structures affect the sedimentary cover of the outer wall and trench whereas extensional tectonics is present on the inner wall in addition there is evidence that most of the upper sedimentary cover is not subducted but rather piles up in front of the trench to form the mediterranean ridge we suggest that the surface limit of the zone of mechanical decoupling occurs near the base of the inner wall we show that the gross structure of the trench as well as the strain pattern observed is controlled by the kinematics of subduction and we discuss its evolution since its initiation about 13 m y ago

an exhumation model of the south peloponnesus greece an exhumation model comprising forward and backward thrusting and late orogenic collapse is proposed in order to explain the kinematics of the tectonic windows in the south peloponnesus the model is based on mapping mesoscopic structural data and strain analysis syn compressional thickening took place throughout the oligocene and early miocene which includes the subduction of the pindos ocean at the western margin of the pelagonian microcontinent and the intracontinental subduction of the phyllite quartzite and the plattenkalk series the latter subduction was associated with blueschist metamorphism westward directed ductile thrusting and folding the exhumation history of the deeper parts of the orogen began at the oligocene miocene boundary with the progressive entrance of the low density crust and the plattenkalk carbonates in the subduction zone increased buoyancy caused a the initiation of the phyllite quartzite series extrusion b vertical coaxial stretching and c the evolution of two pop up structures i e the parnon and taygetos anticlines this syn compressional exhumation was taking place in the lower miocene with decreasing rates from 7 to 1 5 mm year the change in the local stress field from compression to extension began in the middle miocene with the formation of hinterland dipping normal faults the exhumation denudation rate caused by the footwall uplift along these faults does not exceed 0 2 mm year

active faulting on the island of crete greece in order to characterize and quantify the middle late quaternary and ongoing deformation within the southern aegean forearc we analyse the major tectonic structures affecting the island of crete and its offshore the normal faults typically consist of 4 30 km long dipslip segments locally organised in more complex fault zones they separate carbonate and or metamorphic massifs in the footwall block from loose to poorly consolidated alluvial and colluvial materials within the hangingwall all these faults show clear evidences of recent re activations and trend parallel to two principal directions wnw ese and nne ssw based on all available data for both onland and offshore structures morphological and structural mapping satellite imagery and airphotographs remote sensing as well as the analysis of seismic profiles and the investigation of marine terraces and holocene raised notches along the island coasts for each fault we estimate and constrain some of the principal seismotectonic parameters and particularly the fault kinematics the cumulative amount of slip and the slip rate following simple assumptions and empirical relationships maximum expected magnitudes and mean recurrence periods are also suggested summing up the contribution to crustal extension provided by the two major fault sets we calculate both arc normal and arcparallel long term strain rates the occurrence of slightly deeper and more external low angle thrust planes associated with the incipient continental collision occurring in western crete is also analysed although these contractional structures can generate stronger seismic events m 7 5 they are probably much rarer and thus providing a minor contribution to the overall morphotectonic evolution of the island and the forearc a comparison of our geologicallybased results with those obtained from gps measurements show a good agreement therefore suggesting that the present day crustal deformation is probably active since middle quaternary and mainly related to the seismic activity of upper crustal normal faults characterized by frequent shallow 20 km moderate to strong seismic events seldom alternating with stronger earthquakes occurring along blind low angle thrust planes probably ramping from a deeper aseismic detachment ca 25 km this apparently contradicting co existence of juxtaposed upper tensional and lower compressional tectonic regimes is in agreement with the geodynamics of the region characterised by continental collision with nubia and the aegean mantle wedging

ionian sea western greece its structural outline deduced from drilling and geophysical data abstract this paper outlines the preliminary structural results obtained by the compilation of geological drilling and geophysical data in western greece most external geotectonic zones of the hellenides are included in the geological setting of the marine and insular domain of western greece ionian pre apulian and apulian zones the gavrovo and pindus zones make a restricted contribution to the marine geological framework continental shelf of southwest peloponesus besides the geographical setting of the geotectonic units their general tectonic characteristics allow the following remarks to be made the main tectonic events younger than eocene are well marked in both ionian and pre apulian zones the detrital sequence shows a fast pinch out towards the apulian platform where the plio quaternary clastic layers overlap what are probably late mesozoic or early tertiary limestones taking into consideration general tectonic features we can distinguish a northern area and a southern one separated by a fault trending 30 n located on the western margin of kephallinia lefkas islands 1 a in the northern area we observe a strong tangential tectonism decreasing towards the apulian platform with transitional characteristics on the pre apulian zone paxos where asymmetrical folding occurs 2 b in the southern area from lefkas kephallinia islands to the s w cape of peloponesus the tangential tectomism is well masked by strong vertical faulting attributed to young plio quaternary deformations the fast subsidence induces huge diapiric structures in the ionian zone salt walls originating from triassic layers intersect a thick pleistocene sequence

deepwater fold and thrust belt classification tectonics structure and hydrocarbon prospectivity a review abstract deepwater fold and thrust belts dwftbs are classified into near field stress driven type 1 systems confined to the sedimentary section and type 2 systems deformed by either far field stresses alone or mixed near and far field stresses dwftbs can occur at all stages of the wilson cycle up to early stage continent continent collision type 1 systems have either weak shale or salt detachments they occur predominantly on passive margins but can also be found in convergent related areas such as the mediterranean and n borneo examples include the niger and nile deltas the west coast of africa and the gulf of mexico type 2 systems are subdivided on a tectonic setting basis into continent convergence zones and active margin dwftbs continent convergence zones cover dwftbs developed during continent arc or continent continent collision and those in a deepwater intracontinental setting e g w sulawesi makassar straits active margins include accretionary prisms and transform margins the greatest variability in dwftb structural style occurs between salt and shale detachments and not between tectonic settings changes in fold amplitude and wavelength appear to be more related to thickness of the sedimentary section than to dwftb type in comparison with shale salt detachment dwftbs display a lower critical wedge taper more detachment folds long and episodic duration of deformation and more variation in vergence structures unique to salt include canopies and nappes accretionary prisms also standout from other dwftbs due to their relatively long continuous duration rapid offshore propagation of the thrust front and large amount of shortening in terms of petroleum systems many similar issues affect all dwftbs these include the oceanward decrease in heat flow offshore increase in age of mature source rock and causes of trap failure e g leaky oblique and frontal thrust faults breach of top seal by fluid pipes one major difference between type 1 and type 2 systems is reservoir rock high quality continent derived quartz rich sandstones are generally prevalent in type 1 systems more diagenetically reactive minerals derived from igneous and ophiolitic sources are commonly present in type 2 systems or many are simply poor in well developed turbidite sandstone units however some type 2 systems particularly those adjacent to active orogenic belts are partially sourced by high quality continent derived sandstones e g nw borneo s caspian sea columbus basin in some cases very high rates of deposition in accretionary prisms adjacent to orogenic belts coupled with uplift due to collision results in accretionary prism related fold belts that pass laterally from sub aerial to deepwater conditions e g s caspian sea indo burma ranges the six major hydrocarbon producing regions of dwftbs worldwide gulf of mexico niger delta nw borneo brazil west africa s caspian sea stand out as differing from most other dwftbs in certain fundamental ways particularly the very large volume of sediment deposited in the basins and or the great thickness and extent of salt or overpressured shale sdetachments

late neogene to quaternary contractional structures in crete greece abstract based on geological and tectonic investigations carried out along an n s coast to coast transect across central crete southern aegean greece new meso and macro structural data mainly collected from neogene quaternary deposits are presented and discussed the occurrence of large scale folds and thrusts together with diffuse minor contractional structures as well as the overall geometry of the fault bounded sedimentary basins document the persistence of a tortonian early pleistocene contractional regime characterized by an nnw sse to nne ssw shortening direction and affecting the upper crust this contractional event s was associated with the ongoing hellenic subduction and caused the development of a southwards migrating out of sequence thrust system consisting of both reactivated inherited structures and new ones the new data emphasize the importance and the extent of this contractional event intervening between the early middle miocene exhumation phase and the still active upper crustal extensional regime that was resumed in the island only during pleistocene when the region was affected by diffuse normal faulting while the contractional event was likely due to a stronger coupling along the overall subduction system the onset of the new extensional stress conditions was probably related to a sudden southwards jump of the basal detachment along the lithospheric african subduction that caused a general stress release in the uppermost crust

coupled simulation optimization model for draining confined aquifer via underground boreholes to prevent water inrush of coal mines in north china groundwater drainage is commonly applied by coal mines to prevent water inrush from confined aquifers underlying coal seams which can also cause environmental problems the previous research has proposed dual factor and triple factor models to manage water resources in coal mines however three features of draining confined water via underground boreholes have not been sufficiently considered the geological heterogeneity workface relocation and draining principle of underground boreholes this paper aims to incorporate the three features into an optimization model for underground borehole draining a novel mathematical model was proposed that included the three features a workflow framework was proposed to conduct the optimization based on gis and a coupled simulation optimization approach an algorithm was designed and a c program was developed to couple feflow with a modified genetic algorithm to search for the optimal solution the application to the liangbei coal mine indicates that the aquifer has been over drained about 69 and 36 of the water could be saved in the first two stages the total draining rate significantly changes with the workface relocation the boreholes located at the headwaters and closer to the workface that are mined now or in the next stage usually have higher rates than other boreholes the distribution of the draining rates is also related to the workface geometry and the aquifer anisotropy the optimization should be repeated as new monitoring data are acquired

mesozoic early tertiary passive margin evolution of the pindos ocean nw peloponnese greece abstract sediment starved deep water slope basin facies of passive margins are of particular interest as they record an interplay of processes including plate tectonic evolution elastic sediment input pelagic deposition and relative sea level change in the past insights have come from deep sea drilling of non emplaced passive margins e g eastern u s a and from preserved sequences within sutured units e g the tethyan and iapetus orogenic belts deep water passive margin successions discussed here represent an excellent example of a relatively sediment starved slope basin setting related to the margin of a microcontinent within the neotethyan ocean in the eastern mediterranean region lithologies are preserved as a series of thrust sheets formed during suturing of the neotethys ocean thrusting resulted in regular in sequence thrusting such that the original slope margin setting can be restored with confidence compared to other tethyan passive continental margin abyssal successions e g oman these sedimentary rocks retain remarkable structural coherence allowing exceptionally detailed three dimensional reconstructions of facies patterns and palaeoceanographic conditions the sedimentary successions belong to the pindos zone of western greece pindos group and comprise deep water carbonate siliciclastic and siliceous rocks ranging in age from late triassic to eocene these rocks accumulated along the western margin of a small neotethyan oceanic basin i e pindos ocean separating the continental blocks of adria apulia and pelagonia the oldest sediments comprise disrupted siliciclastic turbidites largely derived from a metamorphic source to the west and deposited on young oceanic basement from the late triassic to latest maastrichtian variable thicknesses of hemipelagic carbonate and proximal carbonate debris flows accumulated in westerly areas while mainly hemipelagic carbonate and more distal calciturbidite were deposited further east this pattern was interrupted by an extended period of siliceous radiolarian dominated sedimentation during the aalenian to tithonian jurassic from latest maastrichtian onwards progressive closure of the pindos oceanic basin is recorded by a gradual change in sediment composition from dominantly carbonate deposition supplied from the gavrovo tripolitza carbonate platform to the west to siliciclastic sediment derived from the north and east during the eocene oligocene eastward subduction of the pindos ocean resulted in deep sea sedimentary lithologies being detached from their oceanic igneous basement as an accretionary prism and emplaced westwards onto the adjacent carbonate platform ending up as a series of thin skinned thrust sheets

hydrocarbon generation potential of a lower permian sedimentary succession mount agony formation southern sydney basin new south wales southeast australia abstract this research presents a comprehensive approach on the hydrocarbon generation potential applied for the first time on the lower permian mount agony formation that is exposed in the southern sydney basin southeast australia thirty mudstone samples were collected and analyzed using different organic geochemical methods such as rock eval vi toc bitumens extraction and gc ms analysis attributes such as quantity quality and maturity of the organic matter were utilized to estimate the regional source rock potential the obtained data indicate that the examined samples have poor to good dominantly gas prone source rock potential and contain a mixed in origin organic matter the slight predominance of terrestrial organic material is indicated by the low odd to even predominance values slight predominance of higher n alkanes over short chain n alkanes oep25 33 cpi25 33 acl25 33 and tar values some availability of marine organic material is evidenced by the predominance of intermediate chain n alkanes and the low n c19 n c31 and n c24 n c24 ratios the analyzed sediments are thermally mature as suggested by the tmax pi oep 25 33 and cpi25 33 values the pr n c17 ph n c18 c30 moretane c30 hopane ts ts tm and c32s s r ratios as well as by the c30 moretane c30 hopane versus tm ts plot a mudstone rich siliciclastic source rock is implied by the c29 c30 hopane ratios and by the ts ts tm versus 23tricyclic hopane cross plot this research offers original organic geochemical data of a sedimentary succession that was not so far regarded as source rock this study adds to the knowledge available for the types of potential reserves in the southern sydney basin which are mostly focused on coal and coal seam gas resources

application of modflow for simulating groundwater flow in the trifilia karst aquifer greece karst aquifers can have a complex flow as a result of the formation of large conduits from dissolution features as a result a three dimensional finite difference groundwater flow model equivalent porous media may not apply as the dual porosity nature of karst features and the effects of turbulent flow cannot be directly simulated statistical analysis of karst hydrographs of the trifilia aquifer in greece showed the existence of a slightly karstified mass with high primary porosity that regulates the flow an equivalent porous media model was developed to simulate the trifilia karst aquifer using modflow steady state and transient state calibration gave encouraging results for the equivalent porous media approach which does not consider pipe flow or turbulence detailed hydrogeological research conducted in the area helped define the aquifer hydraulic conductivity zones and extent and flux to from the aquifer only hydraulic conductivity and specific yield were adjusted during calibration as the flux to from the system was considered known and applied as boundary conditions small mean absolute and rms piezometric head error of the model under both steady and transient state conditions were achieved

dynamics of sediment subduction accretion at convergent margins short term modes long term deformation and tectonic implications a conceptual model is proposed for the short term operation of subduction accretion systems at convergent margins the operation is described in terms of the mass fluxes among the four system components namely the accretionary or prowedge wedge p an uplifted plug u a retrowedge r and the subduction zone the latter consists of a conduit c of slowly moving and deforming material and an underlying subduction channel where material moves and deforms more rapidly a broad range of convergent margin types can be accommodated within the conceptual model framework with differing short term modes that depend on which of the p u r c components that are active finite element geodynamical model experiments are used to investigate whether these modes are dynamically feasible these experiments determine excitation of modes under controls that include model entry and exit mass fluxes flexural loading by accreted material and slab pull forces boundary velocities corresponding to subduction and subduction zone advance retreat distribution thickness and density of accreted sediment and internal frictional properties of the coulomb sediments that all modes with the exception of p in which only a prowedge is created are seen in the models provides support for the concepts and allows conditions that favor particular modes to be recognized in addition the finite deformation predicted by the models is used to infer the long term tectonic styles associated with both single mode evolutions and those that exhibit mode switching a steady state mass balance can occur for modes 0 pure subduction p c i e where components p and c are active or other modes when the surface mass denudation plus the subduction flux balances accretion plus tectonic underplating the p c mode is favored by subduction zone retreat and or an increasing subduction load and creates an apparent landward dipping backstop p u c is predicted to be the most common mode and it creates an apparent seaward dipping backstop p u r c is an inefficient mode but is favored by easily detached retrocrust or sediment and or a decreasing subduction load