the present day formation of apatite in mexican continental margin sediments abstract results of pore water and sediment analyses from the western mexican continental margin strongly suggest the present day formation of apatite the interstitial water phosphate and fluoride profiles indicate chemical removal at a depth which corresponds to a large maximum in the phosphorus content of the sediments apatite is identified within this maximum via x ray diffraction but is elsewhere undetectable in the core radioisotopic thorium uranium and radium data support the conclusion that this deposit is modern the present day depositional environment is consistent with those reported by other workers for phosphorite formation with the exception that pore water magnesium is not depleted below its seawater value

carnian norian biomagnetostratigraphy at silicka brezova slovakia correlation to other tethyan sections and to the newark basin correlations of upper triassic magnetic stratigraphies from tethyan sections have been hampered by difficulties with conodont biostratigraphy and taxonomy and discontinuous sedimentation particularly in the hallstatt limestones of turkey and austria the magnetic stratigraphy and conodont biostratigraphy from the upper carnian to upper norian limestones exposed at silickabrezova slovakia can be correlated to other tethyan sections and to the continental succession in the newark basin the resulting correlations help to resolve some of the apparent discrepancies in existing conodont zonations and result in a revised correlation to north american terrestrial vertebrate and palynological zones the correlations imply that the norian rhaetian boundary lies within newark polarity zone e17r at v207 ma the carnian norian boundary lies close to the base of newark polarity zone e7r at v226 ma this implies durations for the norian and rhaetian stages of 19 myr and 7 myr respectively 2002 elsevier science b v all rights reserved

potbellies wasp waists and superparamagnetism in magnetic hysteresis because the response of a magnetic substance to an applied field depends strongly on the physical properties of the material much can be learned by monitoring that response through what is known as a magnetic hysteresis loop the measurements are rapid and quickly becoming part of the standard set of tools supporting paleomagnetic research yet the interpretation of hysteresis loops is not simple it has become apparent that although classic single domain pseudo single domain and multidomain loops described in textbooks occur in natural samples loops are frequently distorted having constricted middles wasp waisted loops or spreading middles and slouching shoulders potbellies such complicated loops are often interpreted in oversimplified ways leading to erroneous conclusions the physics of the problem have been understood for nearly half a century yet numerical simulations appropriate to geological materials are almost unavailable in this paper we discuss results of numerical simulations using the simplest of systems the single domain superparamagnetic sd sp system examination of the synthetic hysteresis loops leads to the following observations 1 wasp waisting and potbellies can easily be generated from populations of sd and sp grains 2 wasp waisting requires an sp contribution that saturates quickly resulting in a steep initial slope and potbellies require low initial slopes the sp contribution approaching saturation at higher fields the approach to saturation is dependent on volume hence the cube of grain diameter therefore there is a very strong dependence of hysteresis loop shape on the assumed threshold size 3 we were unable to generate potbellies using an sp sd threshold size as large as 30 nm and wasp waists cannot be generated using a threshold size as small as 8 nm the occurrence of both potbellies and wasp waists in natural samples is consistent with a room temperature threshold size of some 15 nm 5 4 simulations using a threshold size of 15 20 nm with populations dominated by sp grain sizes that is with a small number of sd grains produce synthetic hysteresis loops consistent with measured hysteresis loops and transmission electron microscopic observations from submarine basaltic glass 5 simulations and measurements using two populations with distinct coercivity spectra can also generate wasp waisted loops a relatively straightforward analysis of the resulting loops can distinguish the latter case from wasp waisting resulting from sp sd behavior

how many oceans meliata vardar and pindos oceans in mesozoic alpine paleogeography the timing of rifting and subduction in the meliata vardar and pindos zones of the hellenic dinaric carpathian region indicates that they cannot be considered remnants of a single ocean basin in contrast to several recently published mesozoic paleogeographies sea floor spreading in the meliata zone culminated in middle triassic ladinian time and ceased in the late triassic and subduction occurred from this time until late jurassic closure in contrast sea floor spreading in the vardar zone began in early jurassic time and culminated in the middle jurassic and subduction occurred from latest jurassic time in the pindos zone sea floor spreading was initiated in the early triassic with late jurassic and early tertiary subduction

the drift history of adria and africa from 280 ma to present jurassic true polar wander and zonal climate control on tethyan sedimentary facies article i nfo the orogenic belts surrounding the undeformed adriatic sea represent the margins of an area known as adria the african promontory we have undertaken a critical appraisal of paleomagnetic data from regions of adria considered parautochthonous relative to africa obtained either from biostratigraphically dated sed imentary rocks corrected for inclination shallowing or from igneous rocks that are regarded as free from any inclination shallowing bias paleomagnetic directions were used to calculate paleomagnetic poles for compar ison with coeval and inclination flattening free paleomagnetic poles from stable africa visual coherence of paleopoles for several time slices from the early permian to the eocene supports the construction of a com posite apparent polar wander path apwp valid for parautochthonous adria and stable africa this compos ite apwp is compared to previous apwps finding good agreement with the global apwp of kent and irving 2010 both apwps show a remarkable and rapid polar shift of 40 in the jurassic that other apwps tend to underestimate we interpret this shift to represent a major episode of true polar wander tpw from 183 ma in the early jurassic to 151 ma in the late jurassic using a simple zonal climate model the drift motion of adria attached to africa appears to be consistent with the distribution of permian cretaceous sed imentary facies on adria

new magnetobiostratigraphic results from the ladinian of the dolomites and implications for the triassic geomagnetic polarity timescale abstract we investigated for magnetostratigraphy the rio nigra and rio frommer stratigraphic sections from alpe di siusi seiser alm dolomites northern italy in order to improve the calibration of the triassic time scale both sections are characterized by ammonoid and conodont associations typical of longobardian late ladinian middle triassic age moreover the rio nigra section is constrained by a u pb zircon date of 237 77 0 05 ma building on the recently verified newark hartford astrochronological polarity timescale for the late carnian rhaetian plus the hettangian and through magnetostratigraphic correlations of an updated inventory of tethyan marine stratigraphic sections from the literature some of which are provided with u pb zircon age constraints we propose a revised geomagnetic polarity time scale for the entire triassic

a middle late triassic ladinian rhaetian carbon and oxygen isotope record from the tethyan ocean abstract we obtained bulk sediment 18o and 13c data from biostratigraphically constrained tethyan marine sections at aghia marina greece guri zi albania and brumano and italcementi quarry italy and revised the published chemostratigraphy of the pizzo mondello section italy we migrated these records from the depth to the time domain using available chronostratigraphic tie points generating ladinian rhaetian 13c and 18o records spanning from 242 to 201 ma the 18o record seems to be affected by diagenesis whereas the 13c record appears to preserve a primary signal and shows values increasing by 1 in the ladinian followed by an 0 6 decrease across the ladinian carnian boundary followed by relatively constant but oscillatory carnian values punctuated by a negative excursion at 233 ma in the early carnian a second negative excursion at 229 5 ma across the early late carnian boundary and a positive excursion at 227 ma across the carnian norian boundary the norian record is characterized by a long term decreasing trend and a negative excursion at 216 ma rapid increases and decreases in 13c have been observed in the rhaetian but these may be at least in part due to mixing of different sources of carbonate carbon with different 13c values our triassic 13c record has been compared to data from the literature and a composite 13c record spanning the last 242 myr of earth s history has been generated this composite record shows a sequence of dated 13c trends and events that can be used for stratigraphic correlation as well as for a better understanding of the global carbon cycle in the mesozoic cenozoic

magnetization carriers and remagnetization of bedded chert abstract article history received 22 october 2010received in revised form 11 january 2011accepted 25 february 2011editor p demenocalkeywords bedded chertremanencebiogenic magnetitehematite bedded chert is the only sediment type representative of the paleozoic to early mesozoic pelagic marineenvironment becauseoftheirassociationwithophiolitesandislandarcrocks presenceofdatablemicrofossilsandpaleohorizontalreferenceprovidedbywell developedbeddingsurfaces beddedchertsequencesareoftentargeted for paleomagnetic tectonic studies however processes of magnetization acquisition in biosiliceoussediments and consequently the signi cance of their magnetic record are not well understood our rockmagnetic study of a triassic jurassic radiolarian chert sequence the mino terrane central japan shows thatthe ferrimagnetic assemblage of the gray chert units is of detrital origin while the red chert s assemblage isdominated by authigenic phases pigmentary hematite and biogenic magnetite which contribute to thenatural remanent magnetization the presence of magnetofossils places red oxic chert in the category ofprospective environmental archives magnetite producing magnetotactic bacteria were apparently able totolerate elevated concentrations of dissolved silica as well as a steep redox gradient in sedimentary pore waters during the deposition of red chert layers a strong uniaxial anisotropy due to chain alignment of thebiogenic magnetite grains likely contributes to the acquisition of anomalously stable partial thermoviscousmagnetization by chert even at low metamorphic temperatures 2011 elsevier b v all rights reserved

first paleomagnetic results from mio pliocene series of the hellenic sedimentary arc abstract paleomagnetic measurements have been conducted on the mio pliocene series along the external sedimentary hellenic arc in order to detect the presence or absence of rotational deformations in different sections of the arc in the central eastern part of the arc crete and rhodes paleomagnetic directions are very closely aligned along the north south direction showing that this portion of the arc has not undergone significant rotation since at least 7 m y for crete and 4 m y for rhodes in the western and northwestern parts results from south peloponnesos zakinthos kephallinia and corfu indicate that this section of the arc has undergone a clockwise rotation detailed analysis of the data from the three ionian islands shows that their rotation began about 5 m y b p and has proceeded since then at roughly 5 m y giving a total amplitude of about 26 it is suggested that the beginning of this rotation is related to the lower pliocene compressive phase which most probably initiated the tectonic activity of the present day ionian margin

paleomagnetism of external southern and central dinarides and northern albanides implications for the cenozoic activity of the scutari pec transverse zone paleomagnetic investigations have been conducted on 43 cretaceous to miocene sites 500 oriented cores from the southern and central external dinarides and from the northern external albanides the 24 reliable sites out of 33 from the dinarides do not document any significant rotation with respect to africa since at least early eocene this result contrasts with the very coherent post eocene 45 clockwise rotation previously observed in the external albano hellenides from peloponesus to the tirana basin these new results suggest that the scutari pec line located between the two orogens and considered as a mesozoic transform fault on the basis of geological observations is the place where the torsion between the dinarides and the albanides recently occurred on a local scale four sites out of 10 from two ridges located in northern albania south of the scutari pec line but with a dinaric trend show that these two structures have undergone a 30 post eocene clockwise rotation this intermediate value of rotation between the north and the south suggests that the scutari pec line is in fact a rather wide transversal zone in which the two ridges are located it acted as a decoupling zone between the dinarides and the albano hellenides during the cenozoic and probably until the pleistocene time the strong seismic activity recorded in this region and the anomalously high positive heat flow documented by other authors are also evidence for the recent activity of the scutari pec transverse zone

delimitation of ground failure zones due to land subsidence using gravity data and finite element modeling in the queretaro valley mexico abstract sedimentary basins of arid and semiarid zones are often subject to regimes of intense ground water withdrawal as it is normally the only source of water for development of communities an associated phenomenon is land subsidence which can develop to ground failures and consequently damage to infrastructure aquifer deformation can be analyzed using a stress strain or a flux force approach depending on the aquifer material compact or loose and on whether the water withdrawal forms a predominant flow direction toward a cone of depression geometry of the aquifer system also plays an important role as uneven thickness induces differential compaction and hence tensional and shear stresses on the ground mass in this work we present a stress strain approach to analyze subsidence for an unconfined aquifer of varying thickness this is done in two steps namely when the aquifer is in equilibrium and when it is totally depleted using this scheme in a region where ground failure is evident a portion of the aquifer system of the queretaro valley is analyzed the geometry of the hydrologic basement is first modeled using gravity measurements properly correlated with wells and field data then a stress analysis is implemented using the finite element method in order to identify probable zones of ground weakness which are calibrated with known ground failures the results indicate that both tensional and shear stress are present which induce ground failure in the form of surface faults

land subsidence and ground failure associated to groundwater exploitation in the aguascalientes valley mexico ground failure associated with land subsidence due to groundwater withdrawal is the main geotechnical hazard in the aguascalientes valley causing enormous economic loss by damage to public and private properties including urban infrastructures the aguascalientes valley forms a tectonic graben flanked by north to south trending normal faults where the hydrologic hydrogeologic and anthropogenic conditions are favorable for ground deformation the intensive withdrawal of groundwater has produced a critical decline in potentiometric levels particularly beneath the aguascalientes city where most of the ground failures have occurred most of the ground failures observed in this valley are directly linked to irregularities of the bedrock and buried paleo channels currently the damage caused by ground failures is variable and considerable even though local government is aware of this problem and has undertaken actions in order to mitigate the ground failure related damages for instance mapping the location of ground failures in the entire valley carrying out resistivity surveys aimed at detecting incipient ground failures and buried cracks and carrying out gravimetric surveys for detecting zones in the subsoil with the geologic conditions for the potential development of ground failures

mesozoic tertiary tectonic evolution of albania in its regional eastern mediterranean context abstract research carried out since the opening of albania to the western geological community in the 1990s allows the geology and tectonics of this small balkan country to be integrated into an overall interpretation of neotethys in the eastern mediterranean region specifically greece and the former yugoslavia region albanian geology is most famous for the occurrence of contrasting ophiolites of jurassic age the country is sub divided into three main geotectonic units those in the west i e sazani ionian kruja krasta cukali and the albanian alps relate to the western margin of apulia effectively part of north africa from early mesozoic time onwards in the east is the korabi zone interpreted as a microcontinent located further northeast within neotethys between the two is the mirdita zone dominated by two contrasting jurassic ophiolites the western type ophiolite and the eastern type ophiolite taking account of evidence from greece and former yugoslavia the following tectonic evolution is proposed from early mesozoic time onwards neotethys in albania existed as a northward continuation of the pindos oceanic basin in greece pindos mirdita ocean a korabi microcontinent was rifted off apulia in the early mid triassic followed by passive margin subsidence until late middle jurassic time a rifted slow spreading mor type ophiolite formed within the western pindos mirdita oceanic basin in late triassic early late jurassic time using present co ordinates the shkoder peje scutari pec lineament in the north of albania is interpreted as an important transform fault zone that influenced the regional tectonic evolution during the entire mesozoic early tertiary rift drift emplacement history of the pindos mirdita ocean taking account of evidence from the greek and former yugoslavia ophiolites the easterly albanian ophiolites formed within the pindos mirdita ocean above a westward dipping intra oceanic subduction zone in the early late jurassic metamorphic soles were formed during initial intra oceanic displacement ca 162 174 m y and underlying melanges originated as subduction accretion complexes the mor western type ophiolite evolved into the iat boninitic eastern type ophiolite after subduction began during tithonian berriasian time trench margin collision emplaced the ophiolites eastwards over the korabi margin coupled with redeposition of ophiolitic and continental margin material as exotic blocks debris flow deposits and turbidites these were emplaced onto the upper surface of the ophiolitic thrust sheet during the latest stages of emplacement onto the korabi microcontinent following collision in the east oceanic crust remained within a small remnant pindos mirdita oceanic basin passive conditions were restored in the mid late cretaceous with shallow water carbonate deposition on microcontinental units and both pelagic and redeposited carbonates in basinal settings from the maastrichtian onwards africa eurasia convergence resulted in large scale westward thrusting deforming the apulian foreland in oligo miocene time the suture zone was re activated in oligo miocene time as the albanie thassalie piggy back type basin in central and southern albania albania as a whole was rotated 45 clockwise as part of the western aegean arc in post eocene time coastal and offshore albania experienced strong subsidence after early miocene time forming the periadriatic basin including the tirana depression interpreted as a foredeep related to continuing regional convergence southern albania experienced extensional tectonics in plio quaternary time related to southward roll back of the aegean active margin

triassic mid ocean ridge basalts from the argolis peninsula greece new constraints for the early oceanization phases of the neo tethyan pindos basin

mesozoic alpine facies deposition as a result of past latitudinal plate motion the fragmentation of pangaea as a consequence of the opening of the atlantic ocean is documented in the alpine mediterranean region by the onset of widespread pelagic sedimentation1 shallow water sediments were replaced by mainly pelagic limestones in the early jurassic period radiolarian cherts in the middle late jurassic period and again pelagic limestones in the late jurassic cretaceous period1 during initial extension basin subsidence below the carbonate compensation depth ccd is thought to have triggered the transition from early jurassic limestones to middle late jurassic radiolarites1 it has been proposed that the transition from radiolarites to limestones in the late jurassic period was due to an increase in calcareous nannoplankton abundance when the ccd was depressed below the ocean floor1 but in modern oceans sediments below the ccd are not necessarily radiolaritic here we present palaeomagnetic samples from the jurassic cretaceous pelagic succession exposed in the lombardian basin italy on the basis of an analysis of our palaeolatitudinal data in a broader palaeogeographic context we propose an alternative explanation for the above facies tripartition we suggest that the lombardian basin drifted initially towards and subsequently away from a near equatorial upwelling zone of high biosiliceous productivity our tectonic model for the genesis of radiolarites adds an essential horizontal plate motion component to explanations involving only vertical variations of ccd relative to the ocean floor it may explain the deposition of radiolarites throughout the mediterranean and middle eastern region during the jurassic period

accretion tectonics of the neotethyan ermioni complex peloponessos greece late cretaceous early tertiary terrigenous and calcareous turbidites exposed in the argolis peninsula of southern greece represent an accretionary complex assembled during the closure of a late cretaceous neotethyan ocean massive sulphide bodies thrust slices of cherts and serpentinized ultramafics are found imbricated within a tectonic stack of approximately 8 km thickness basalts with overlying cenomanian maastrichtian pelagic limestones and metalliferous sediments are found distributed throughout the complex the basalts give trace element chemical signatures consistent with an origin at a mid ocean ridge or back arc basin folding and shearing is locally intense in fault zones 10 20 m across resulting in a block in matrix fabric metamorphism within the complex is of low to high diagenetic grade with grade generally increasing structurally up section palaeo slope indicators suggest that the ocean basin lay to the present se the ssw to nne emplacement is at variance with the sw vergent early tertiary thrusting of the hellenides and may be explicable in terms of transpressional tectonics along the southeastern termination of the pelagonian micro continent the processes which assembled the ermioni complex appear to have operated in a similar fashion to those seen along the margins of major ocean basins although active over much shorter periods of time

jellyfish lake palau regeneration of c n si and p in anoxic marine lake sediments sediment cores from jellyfish lake were processed under an inert atmos phcre and the pore waters extracted and analyzed for the following parameters ph titration alkalinity ta cl h4si04 pod3 nh4 ca2 mg2 sod2 and h2s additionally in one set of pore water samples core lo the 613c of the x0 was also determined the ta h4si04 pod3 nh and h s increased with depth in the pore waters above anoxic bottom water values h s values increased to 3 8 pm in one case both h sio and pod3 concentrations increased to a maximum value and then decreased with depth suggesting removal into solid phases the h sio concentrations are equal to or greater than pore water values observed in sediments underlying upwelling areas pod3 concentrations are in general lower than pore water values from terrigenous nearshore areas but higher than nearshore carbonate pore water values from florida bay or bermuda the ca2 cl and mg2 cl ratios show slight decreases in the top 15 20 cm suggesting that authigenic carbonate may be forming this suggestion is supported by the fact that the pore waters are saturated with respect to caco due to the very high tas the 613c measurements of the pore water x0 are from a shorter core these measurements reach their most negative concentration at 72 cm and tilen become slightly heavier this change is accompanied by a decrease in ta suggesting the onset of methanogenesis at this location in this core

on the mesozoic ionian basin summary new seismic reflection profiles of the italian deep crust project crop provide new insights on the structure of the ionian sea in spite of the apennines and hellenides neogene subduction zones two conjugate passive continental margins are preserved at the margins of the ionian sea along the malta escarpment to the southwest and the apulian escarpment to the northeast the ionian sea is likely to be a remnant of the mesozoic tethys ocean confined by these two conjugate passive continental margins the transition from continental to oceanic crust appears sharper to the northeast than to the southwest the basin between southeast sicily and southwest puglia was about 330 km wide and suggests a low spreading rate the inferred oceanic ridge should have been flattened by thermal cooling and buried by later sediments based on stratigraphic and structural constraints to the north in the apennines belt the ocean continued to the northwest this palaeogeography is supported by the seismicity of the apennines slab underneath the southern tyrrhenian sea which implies downgoing oceanic lithosphere the adjacent absence or paucity of deep seismicity does not imply absence of subduction but rather it can be interpreted as due to the more ductile behaviour of the subducted continental lithosphere surprisingly we note that where the oceanic inherited basin is subducting underneath the apennines in the hangingwall of the subduction hinge there are outcropping slices of continental crystalline basement previously deformed by the alpine orogen

land subsidence in central mexico detected by alos insar time series abstract massive groundwater extraction is common throughout mexico and is well known to result in land subsidence however most land subsidence surveys focus on one single city mainly mexico city and thus fail to reveal the regional extent of the problem here we use 2007 2011 interferometric synthetic aperture radar insar time series analysis of alos data to resolve land subsidence in the entire central mexico region we identify land subsidence in 21 areas including 17 cities linear vertical rates over 30 cm yr are observed in mexico city while in the other locations rates of 5 10 cm yr are detected we define 3 main categories of subsidence using the averaged velocity maps in conjunction with previously published structural surface geology and land use mapping 1 rapid large scale subsidence 2 rapid local scale subsidence and 3 slow patchy subsidence the correlation between subsidence and land use confirms that groundwater extraction mainly for agricultural and urban activities is the main cause of land subsidence we observe that the boundaries of the subsiding areas are typically characterized by high velocity gradients often coinciding with pre existing faults motion on these faults being driven by water extraction rather than by tectonic activity regional surveys of this type are necessary to understand the spatial and temporal evolution of land subsidence to constrain the distribution and connectivity of water bearing units and ultimately to reach better hazard mitigation plans

middle triassic paleomagnetic data from northern bulgaria constraints on tethyan magnetostratigraphy and paleogeography magnetostratigraphic and biostratigraphic data are presented from the anisian middle triassic peri tethyan edivetur section of northwestern bulgaria a dual polarity component of magnetization carried by magnetite delineates a magnetic stratigraphy of mainly reversed polarity magnetozones are dated by means of foraminifer and conodont biostratigraphy data from edivetur are compared with data from middle triassic tethyan limestone sections with the aim of contributing to the completion of the middle triassic magnetic polarity time scale we also propose that paleomagnetic data from edivetur can be used as proxy data for the paleogeographic position of the moesian platform the moesian platform was located at 21 24 n along the southern margin of europe it was probably marginally separated but not detached or rotated away from europe by the north dobrugea transtensional trough which is interpreted as a back arc basin resulting from the northward subduction of the neo tethys vardar or paleo tethys ocean paleomagnetic data from this study and other minor tectonic elements are used to generate a paleogeographic sketch map of the pangea bounded western tethys and peri tethys at middle early late triassic time 2000 elsevier science b v all rights reserved

middle triassic magnetostratigraphy and biostratigraphy from the dolomites and greece abstract magnetostratigrapic and biostratigraphic data across the anisian ladinian middle triassic boundary were obtained from the frotschbach seceda section from the dolomites region of northern italy and the vlichos section from the greek island of hydra where the aghia triada published section was also resampled the frotschbach seceda section includes two radiometrically dated u pb tuff levels and covers two of the three chief candidates for the position of the base of the ladinian namely at the base of the secedensis zone or the subsequent curionii zone the aghia triada section yields biochronological evidence for the base of the secedensis zone whose significance is however critically discussed in the light of the magnetostratigraphic correlation with frotschbach seceda the vlichos section can be correlated with aghia triada and frotschbach seceda by means of magnetic polarity stratigraphy and sparse fossil occurrences the satisfactory correlation of the magnetozones allows us to construct a composite geomagnetic polarity sequence tied to tethyan ammonoid and conodont biostratigraphy for about a 2 4 myr interval across the anisian ladinian boundary

magnetostratigraphy of the kavur tepe section southwestern turkey a magnetic polarity time scale for the norian we present the magnetostratigraphy of the late triassic pelagic kavur tepe section from the taurides southwestern turkey the section investigated is about 30 m thick and consists of fine grained whitish limestones the biostratigraphy based on the conodont zonation gives an age from the lacian 2 zone lower norian to the sevatian 2 zone upper norian the paleomagnetic analyses indicate very favourable behaviour with two magnetic components which can be isolated both by thermal and af demagnetization the magnetization is carried by magnetite and goethite which are clearly evident in irm experiments the first component of normal magnetic polarity has roughly the direction of the present day field the high unblocking temperature component shows directions of both polarities in total fifteen magnetic polarity intervals are observed within the kavur tepe section the characteristic calculated fisherian mean direction is particularly tightly grouped d 220 2 and i 32 1 with k 40 9 95 1 7 and nsamp 179 after bedding correction polarity correlations with two other sections in turkey and in austria northern calcareous alps show that the kavur tepe sediments were deposited in the southern hemisphere by combining the magnetostratigraphic results from the bolucektasi tepe 1 and the kavur tepe sections an almost complete norian magnetic polarity sequence is established showing 30 magnetic intervals that are well calibrated with the conodont and ammonoid zonations a magnetic reversal frequency close to about 2 7 reversals myr is derived for the norian this medium frequency is in agreement with the hypothesis of a long time constant 150 200 myr in the changes of the magnetic reversal frequency since the kiaman reversed superchron

comparison of evolution and tectonic significance of the pindos and vourinos ophiolite suites northern greece abstract the pindos ophiolite located on the western edge of the sub pelagonian othris zone comprises a complex series of westward verging thrust sheets dominantly composed of peridotite tectonite phaneritic mafic and leucocratic rocks and pillow lavas harzburgite tectonites from part of the east central thrust sheet dramala complex show three well developed foliations the oldest compositional layering s 0 has been isoclinally folded and preferred orientations of elongate grains and aggregates of olivine and orthopyroxene parallel to the axial surfaces of the isoclines define the second foliation s 1 spinel lineations parallel fold axes of the isoclinal folds thermometric calculations from mineral compositions and grain sizes of olivines and pyroxenes associated with the oldest preserved foliations compositional layering s 0 s 1 indicate that rocks of the tectonite suite equilibrated at depths of between 45 and 60 km at temperatures between 1210 c and 925 c and at differential stresses from 5 to 10 mpa in general rocks indicative of higher temperatures of equilibration formed at lower values of differential stress the third and youngest foliation is defined by bands of fine grained olivine and pyroxene mylonite that cut across older structural elements mylonites equilibrated at temperatures between 650 c and 710 c presumably indicative of shallower depths 30 20 km than the older foliations accompanied by differential stresses ranging from 200 to 300 mpa and probably formed during obduction of the complex the sense and orientation of shear determined from kinematic indicators within the mylonitic zones indicate an updip displacement vector inclined at an angle of 20 to 40 toward 016 suggesting obduction to the east northeast relative to the present position of the pindos ophiolite there is no direct evidence for the amount of rotation about a vertical axis that may have occurred during obduction or later tectonic transport the composition internal structure environments of equilibration stress history and inferred direction of obduction of the pindos ultramafites are strikingly similar to those of the vourinos complex located 40 km to the northeast on the eastern margin of the sub pelagonian zone it is probable that the two ophiolites shared a common origin and an identical early obduction history during late jurassic times the vourinos and its metamorphic sole were thrust over a thick sequence of shelf carbonates and a thin diamictitic melange both units being metamorphosed to lower greenschist facies comparable units beneath the pindos thrust sheet the loumnitsa unit and the avdella melange are thicker somewhat more lithologically diverse and comprise amphibolite greenschist radiolarite pillow lava garnetite exotic marble flysch and poorly metamorphosed fossiliferous limestone typically occurring in tightly folded thin thrust slices differences in the timing and direction of post emplacement thrust transport of the two complexes are marked and may have begun late in the obduction phase

sr isotope variations in the upper triassic succession at pizzo mondello sicily constraints on the timing of the cimmerian orogeny abstract the late triassic cimmerian orogeny was a result of the final closure of the palaeotethys ocean and the accretion of gondwana derived cimmerian continents to southern eurasia determining the timing of the cimmerian orogeny is crucial to our understanding of the large scale climate changes driven by the uplift of the cimmerian mountains here we present stratigraphic variations in 87sr 86sr values of upper triassic pelagic limestone from the pizzo mondello section sicily italy that constrain the timing of uplift of the cimmerian mountains the 87sr 86sr values remain relatively constant in the lower part of the section decreasing slightly in the tuvalian upper carnian and lacian lower norian however 87sr 86sr ratios rise sharply at the lacian alaunian lower middle norian boundary and continue to rise through to the sevatian upper norian this observation indicates an increased input of radiogenic strontium derived from continental weathering which resulted from the rapid uplift and erosion of the cimmerian mountains at this time the climatic and environmental changes following the uplift of the cimmerian mountains provide an explanation for 1 an intense sea surface temperature warming event in the western tethys ocean and 2 a rapid increase in precipitation on the northern coast of the tethys during the alaunian sevatian

evolution and origin of the ground fissures in xian china large scale extraction of ground water in xian has resulted in significant drawdown of the phreatic surface and in land subsidence across this ancient capital of china it has also triggered the rejuvenation of the normal faults in the upper portions of the quaternary deposits underlying the city leading to surface rupturing and the development of ground fissure zones across the city these ground fissure zones are structurally controlled in the sense that they are directly linked to the normal faults in the quaternary deposits all trending in an east northeasterly direction in essence they are the surface expressions of the deeper faults under current drawdown conditions the ground fissures have resulted in extensive property damage along their paths of propagation this paper describes their occurrence their possible causative mechanism and the resultant damage of necessity xian will still be dependent on ground water supply to a large extent in the years ahead however ground water extraction will have to be managed in an environmentally sustainable manner in order to minimize the geological hazards associated with the ground fissures

evaluation and analysis of surface deformation in west chapala basin central mexico vertical deformation was measured at 14 benchmarks within the urban area of jocotepec mexico using first order leveling methods and then spatially analyzed in relation to land subsidence and soil discontinuity patterns the study area is located within the western portion of the chapala basin middle west mexico observations of vertical surficial deformation were made at each benchmark september and november 2012 relative to a fixed station and compared to an initial survey of each benchmark april 2012 results indicate that a maximum subsidence of 7 16 cm over the 8 month measurement interval occurs near downtown coincident with the largest levels of drawdown and translates to a maximum subsidence rate of 0 89 cm month for the sampling period two benchmarks located northwest and southeast of the urban area exhibited uplift of 2 8 and 0 76 cm respectively suggesting a complex mechanical response between the sedimentary soil units and the factors causing deformation a potential spatial relationship exists between subsidence patterns and soil discontinuities four separate cones of groundwater depression were observed with two being coincident with subsidence bowls downtown and south of the urban area however there is no clear relationship between drawdown and subsidence in the remaining areas hydrogeologic reconstructions reveal alternating sequences of alluvial aquifers and highly deformable lacustrine aquitards an analysis of the soil discontinuities reveals that they are directly aligned with the patterns of vertical deformation

coupled multiphase flow and poromechanics a computational model of pore pressure effects on fault slip and earthquake triggering the coupling between subsurface flow and geomechanical deformation is critical in the assessment of the environmental impacts of groundwater use underground liquid waste disposal geologic storage of carbon dioxide and exploitation of shale gas reserves in particular seismicity induced by fluid injection and withdrawal has emerged as a central element of the scientific discussion around subsurface technologies that tap into water and energy resources here we present a new computational approach to model coupled multiphase flow and geomechanics of faulted reservoirs we represent faults as surfaces embedded in a three dimensional medium by using zero thickness interface elements to accurately model fault slip under dynamically evolving fluid pressure and fault strength we incorporate the effect of fluid pressures from multiphase flow in the mechanical stability of faults and employ a rigorous formulation of nonlinear multiphase geomechanics that is capable of handling strong capillary effects we develop a numerical simulation tool by coupling a multiphase flow simulator with a mechanics simulator using the unconditionally stable fixed stress scheme for the sequential solution of two way coupling between flow and geomechanics we validate our modeling approach using several synthetic but realistic test cases that illustrate the onset and evolution of earthquakes from fluid injection and withdrawal

using major ions and stable isotopes to characterize recharge regime of a fault influenced aquifer in beiyishui river watershed north china plain a thorough understanding of recharge is usually a prerequisite for effective groundwater management the recharge regime remains unrevealed in the piedmont plain of the north china plain where is considered as the main recharge zone of the quaternary aquifer to characterize the recharge regime a case study is presented in the piedmont plain of the beiyishui river watershed the piedmont plain consists of proluvial fan and alluvial fan plain and groundwater quality in the two parts is distinct total dissolved solids and isotopic compositions are higher in the groundwater of proluvial fan than the groundwater of the alluvial fan plain local precipitation only recharges the groundwater in the proluvial fan fracture water ascending along a buried normal fault and lateral inflow from the proluvial fan feed the unconfined aquifer in the alluvial fan plain the runoff of the beiyishui river seeps in the streambed of upper reaches and then overflows seasonally in middle reach the recharge from middle reach to the aquifer is negligible in addition the fracture water originates from precipitation in the mountainous area with an average elevation about 500 m and discharges to the overlaying aquifer the contribution of fracture water to the aquifer was estimated to be 77 9 in the alluvial fan plain area due to the mixture in the aquifer major ions leached from soil of the proluvial fan are diluted and the hydrochemical pattern is changed from ca mg hco3 so4 to ca mg hco3 it is considered that fracture water is the major recharge source of the unconfined aquifer and the variation of precipitation in mountainous area would primarily affect the recharge this paper also shows the hydrological efficiency of buried normal fault as preferential flow

the nature of triassic extension related magmatism in greece evidence from nd and pb isotope geochemistry the widespread triassic volcanic rocks of greece dismembered during the hellenide orogeny are used to interpret the nature of triassic rifting four assemblages of volcanic rocks are distinguished on geochemical criteria 1 a predominant subalkaline basalt andesite dacite series with a high proportion of pyroclastic rocks 2 minor shoshonites 3 alkali basalt and 4 morb the stratigraphic and palaeogeographic distribution of these rock types is synthesized new pb and nd isotopic data are used to discriminate between hypotheses suggesting that either subduction or extension was responsible for the triassic volcanism in the subalkaline basalt assemblage e nd is negative with depleted mantle model ages 1 5 ga pb isotopic compositions are mostly close to the very distinctive compositional field of cenozoic extensional rocks of the aegean area with very high 207 pb 204 pb for relatively low 206 pb 204 pb ratios these isotopic data confirm interpretations based on trace elements that subalkaline basalts were predominantly derived from melt depleted peridotite in the sub continental lithospheric mantle as a result of extension small areas of enriched hydrous mantle partially melted to yield shoshonitic magmas nd and pb isotopic compositions of the alkali basalts are quite different from those in other rock types and suggest a himu mantle source component derived from a small plume which also influenced morb compositions distribution of these various rock types is used to constrain palaeogeographic reconstruction of triassic micro continental blocks

ocean ridge origin and tectonic setting of mesozoic sulphide and oxide deposits of the argolis peninsula of the peloponnesus greece abstract metal oxide and sulphide deposits chemically similar to the hydrothermal deposits of modern and ancient oceanic spreading axes occur in two areas of the argolis peninsula of the peloponnesus greece in the first in northeastern and central argolis manganese ores immediately overlie morb type extrusives of mid jurassic age after triassic rifting this oceanic crust formed during jurassic time and was then tectonically emplaced over the adjacent continental margin in the late jurassic the manganese ores palea epidavros were precipitated from low temperature hydrothermal vent waters on the axis of a relatively unrifted ocean ridge which was possibly slow spreading the deep sea sediment cover comprises pelagic carbonate accumulated on the ridge flanks then ribbon radiolarites deposited on the abyssal plain below the ccd located close enough to a continental margin to allow deposition of shallow water derived calciturbidites in the second area ermioni in the southern argolis peninsula adheres massive sulphides and metalliferous oxide sediments occur with mafic extrusives and terrigenous turbidites although previously regarded as a single stratigraphical succession shale sandstone formation the mafic lavas and metal deposits are interpreted here as ophiolitic slices that were incorporated into the turbidites by thrusting possibly as a trench accretionary complex the massive sulphides were precipitated from high temperature vents sited near the axis of a relatively unrifted spreading ridge which was possibly fast spreading ferruginous ochres and ferromanganiferous umbers oxide sediments were dispersed around these vents whereas strongly fractionated manganese ores precipitated from separate low temperature hydrothermal sites alternative tectonic scenarios are discussed

tectonic history of a segment of the pelagonian zone northeastern greece continental metamorphic rocks and ophiolitic bodies within the pelagonian zone of the hellenides in the livadi area northeastern greece show repeated periods of deformation that accompany thermal events of early cretaceous and possibly late eocene age structures associated with the earlier deformation indicate thrusting towards the northeast accompanying regional metamorphism of upper greenschist to lower amphibolite facies later structures and a retrogression to lower greenschist facies associated with emplacement of the livadi ophiolitic rocks into their present position are likewise attributed to northeast directed thrusting and probably accompanied the allochthonous movement of the pelagonian basement over the mesozoic platform carbonates of mt olympos emplacement vectors of northeast polarity are inconsistent with tectonic models of the hellenides involving large scale southwestward obduction of mesozoic ophiolites from a single ocean located northeast of the pelagonian zone tectonic models inv

artificial recharge of the phreatic aquifer in the upper friuli plain italy by a large infiltration basin to cope with the general reduction of water availability and increase the subsurface storage of high quality surficial waters an artificial recharge project is ongoing in northern italy within the warbo life project funded by eu warbo is aimed at implementing large scale use of artificial recharge in italy where water directives still strongly limit its application in this context the mereto recharge site was selected in the upper fruili plain where the water availability is guaranteed during winter period by the tagliamento and ledra rivers an infiltration basin about 5 5 m deep and 45 7 m2 wide was built at mereto in the early 2000s but the possibility of implementing the recharge has been allowed only very recently the site is characterized by an elevation of 105 m asl and the depth to the groundwater table averages 50 m below a few meter thick organic soil the aquifer is composed by coarse deposits with an estimated thickness of 100 m and an average vertical hydraulic conductivity on the order of 10 4 m s a 0 1 m3 s infiltration flow has been preliminary estimated corresponding to an infiltration rate of 60 cm h geophysical investigations electrical resistivity tomography high resolution seismic surveys together with infiltration and pumping tests have been carried out to characterize the vadose zone and the unconfined aquifer in the study area functional approaches and three dimensional 3d finite element numerical computations have been used to predict the effect of the artificial recharge the results of these investigations will greatly reduce the hydrogeological knowledge gaps and will be used to fine tune the recharge program and to define the monitoring concept this contribution aims to provide a methodology for the implementation of managed aquifer recharge programs using existing structures

evaluation of subsurface infiltration and displacement in a subsidence reactivated normal fault in the aguascalientes valley mexico in this study the main hydromechanical characteristics of a portion of the oriente fault in the valley of aguascalientes mexico are analyzed and discussed this discontinuity corresponds to a normal fault that was originated before the formation of the aguascalientes graben however its recent activity and potential reactivation may be directly linked to the land subsidence currently occurring in the center of the valley a 1 year campaign to monitor deformation in two transects perpendicular to this fault indicates continuous deformation activity with maximum vertical descending values of 43 mm in the hanging wall on the other hand a fieldwork procedure to determine the geologic structure of the fault zone and to establish the infiltration patterns of a selected point in the fault was performed as well this field test consisted of analyzing the resistivity patterns of profiles across and along the fault implemented before during and after pouring groundwater into the fault and monitoring the fluids movement through the fault zone results suggest that the fault contains three perpendicular fault branches in a distance of 80 m portraying a potential domino fault system the high infiltration capacity of the fault opening allowed the rapid intrusion of water into the subsoil and the distinguishable changes in electrical resistivity in the profiles parallel to the fault plane suggest that the infiltrating water goes down into the soil through the fault plane or adjacent to it

geodynamic evolution of ophiolites from albania and greece dinaric hellenic belt one two or more oceanic basins all the geological constraints for an exhaustive reconstruction of the triassic to tertiary tectonic history of the southern dinaric hellenic belt can be found in albania and greece this article aims to schematically reconstruct this long tectonic evolution primarily based on a detailed analysis of the tectonic setting the stratigraphy the geochemistry and the age of the ophiolites in contrast to what was previously reported in the literature we propose a new subdivision on a regional scale of the ophiolite complexes cropping out in albania and greece this new subdivision includes six types of ophiolite occurrences each corresponding to different tectonic units derived from a single obducted sheet these units are represented by 1 sub ophiolite melange 2 triassic ocean floor ophiolites 3 metamorphic soles 4 jurassic fore arc ophiolites 5 jurassic intra oceanic arc ophiolites and 6 jurassic back arc basin ophiolites the overall features of these ophiolites are coherent with the existence of a single though composite oceanic basin located east of the adria pelagonian continental margin this oceanic basin was originated during the middle triassic and was subsequently early jurassic affected by an east dipping intra oceanic subduction this subduction was responsible for the birth of intra oceanic arc and back arc oceanic basins separated by a continental volcanic arc during the early to middle jurassic from the uppermost middle jurassic to the early cretaceous an obduction developed during which the ophiolites were thrust westwards firstly onto the neighboring oceanic lithosphere and then onto the adria margin

earth fissures and localized differential subsidence long linear tension cracks associated with declining groundwater levels at four sites in subsiding areas in south central arizona fremont valley california and las vegas valley nevada occur near points of maximum convex upward curvature in subsidence profiles oriented perpendicular to the cracks profiles are based on repeated precise vertical control surveys of lines of closely spaced bench marks association of these fissures with zones of localized differential subsidence indicates that linear earth fissures are caused by horizontal tensile strains probably resulting from localized differential compaction horizontal tensile strains across the fissures at the point of maximum convex upward curvature ranging from approximately 100 to 700 microstrains 0 01 to 0 07 per year were indicated based on measurements with a tape or electronic distance meter

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

revision of the timing magnitude and distribution of neogene rotations in the western aegean region to evaluate the dimension and the timing of the clockwise rotating domain and the nature of the structures that accommodate the rotating domain in the western aegean region paleomagnetic analyses were carried out in northern western and southwestern greece the results show that the rotating domain covers an area including the external albanides western mainland greece including evia and probably at least partly the peloponnesos smaller clockwise rotations on the order of 30 408 were reported previously from the chalkidiki peninsula and the islands of skyros and limnos previously two phases of approximately 258 of rotation were suggested the last one during the plio pleistocene our analysis shows that the western aegean domain rotated approximately 408 clockwise between 15 13 and 8 ma followed by an additional 108 after 4 ma the rotating domain is accommodated in the north by deformation associated with the scutari pec fault zone and in the west by the ionian thrust and the hellenic subduction zone to the south no rocks older than 10 ma are available so no conclusive data are obtained to the east of the rotating domain extensional detachment systems of the cyclades and rhodope areas were active during the rotation phase and may explain at least part of the differences in finite amounts of rotation between nonrotation or counterclockwise rotations observed in northern and eastern greece and the large clockwise rotations in western greece d 2004 elsevier b v all rights reserved

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

imaging rainfall infiltration processes with the time lapse electrical resistivity imaging method electrical resistivity imaging eri was carried out continuously for 10 days to map the subsurface resistivity distribution along a potentially hazardous hillslope at the jieshou junior high school in taoyuan taiwan the reliability of the inverted resistivity structures down to about 25 m depth was examined with synthetic modeling using the same electrode arrangements installed on land surface as in field surveys together with a doi depth of investigation index calculated from the eri data the subsurface resistivity distribution is consistent with results from well logging these eri recordings were taken daily and provided highly resolved imagery of the resistivity distribution underground and illustrated the dynamical fluid flow behavior due to heavy rainfall infiltration using archie s law the resistivity distribution was transformed into a map of relative water saturation rws which is strongly correlated with the rainfall infiltration process we then found that the averaged rws is significantly correlated with daily precipitation our observations indicate that time lapse eri is effective in monitoring subterraneous rainfall infiltration moreover the preferential flow paths can be delineated according to the changes in averaged rws derived from the eri data

middle late jurassic sedimentary melange formation related to ophiolite obduction in the alpine carpathian dinaridic mountain range abstract the middle late jurassic mountain building process in the western tethyan realm was triggered by west to northwestward directed ophiolite obduction onto the wider adriatic shelf this southeastern to eastern adriatic shelf was the former passive continental margin of the neo tethys which started to open in the middle triassic its western parts closed from around the early middle jurassic boundary with the onset of east dipping intra oceanic subduction ongoing contraction led to ophiolite obduction onto the former continental margin since the bajocian trench like basins formed concomitantly within the evolving thin skinned orogen in a lower plate situation deep water basins formed in sequence with the northwest westward propagating nappe fronts which served as source areas of the basin fills basin deposition was characterized by coarsening upward cycles i e sedimentary melanges as synorogenic sediments the basin fills became sheared successively by ongoing contractional tectonics with features of typical melanges analyses of ancient neo tethys melanges along the eastern mediterranean mountain ranges allow both a facies reconstruction of the outer western passive margin of the neo tethys and conclusions on the processes and timing of jurassic orogenesis comparison of melanges identical in age and component spectrum in different mountain belts figured out one neo tethys ocean in the western tethyan realm instead of multi ocean and multi continent scenarios

the cimmerian evolution of the nakhlak anarak area central iran and its bearing for the reconstruction of the history of the eurasian margin new structural sedimentological petrological and palaeomagnetic data collected in the region of nakhlak anarak provide important constraints on the cimmerian evolution of central iran the olenekian upper ladinian succession of nakhlak was deposited in a forearc setting and records the exhumation and erosion of an orogenic wedge possibly located in the present day anarak region the triassic succession was deformed after ladinian times and shows south vergent folds and thrusts unconformably covered by upper cretaceous limestones following the late jurassic neo cimmerian deformation palaeomagnetic data obtained in the olenekian succession suggest a palaeoposition of the region close to eurasia at a latitude around 208n in addition the palaeopoles do not support large anticlockwise rotations around ver tical axes for central iran with respect to eurasia since the middle triassic as previously suggested the anarak metamorphic complex amc includes blueschist facies metabasites associated with discontinuous slivers of serpentinized ultramafic rocks and carboniferous greenschist facies variscan metamorphic rocks including widespread metacarbonates the amc was formed at least partially in the triassic its erosion is recorded by the middle triassic baqoroq formation at nakhlak which consists of conglomerates and sandstones rich in meta morphic detritus the amc was repeatedly deformed during post triassic times giving origin to a complex structural setting characterized by strong tectonic fragmentation of previously formed tectonic units based on these data we suggest that the nakhlak anarak units represent an arc trench system developed during the eo cimmerian orogenic cycle different tectonic scenarios that can account for the evolution of the region and for the occurrence of this orogenic wedge in its present position within central iran are critically discussed as well as its relationships with a presumed variscan metamorphic event the cimmerian orogeny affecting the southern eurasian margin between turkey and thailand is related to the collision of several microplates most of which detached from northern gondwana in the early permian during the opening of the

magnetostratigraphy of the kavaalani section southwestern turkey consequence for the origin of the antalya calcareous nappes turkey and for the norian late triassic magnetic polarity timescale a magnetostratigraphic study of the kavaalani section of uppermost carnian to upper norian age located in the antalya calcareous nappes southwestern turkey reveals nineteen polarity intervals this pattern correlates very well with two other polarity sequences obtained from the same nappe system bolucektasi tepe and kavur tepe if these sections were deposited in the same northern hemisphere this new interpretation changes our previous conclusions regarding the southern hemisphere origin of the magnetic remanence of the kavur tepe section the paleomagnetic data obtained from the kavur tepe and the kavaalani sections therefore reflect large 180 internal rotations within the antalya nappes these nappes were likely formed close to the northern tip of the arabian promontory we propose a revised yet still preliminary version of the norian magnetic polarity sequence

the drift history of iran from the ordovician to the triassic new late ordovician and triassic palaeomagnetic data from iran are presented these data in conjunction with data from the literature provide insights on the drift history of iran as part of cimmeria during the ordovician triassic a robust agreement of palaeomagnetic poles of iran and west gondwana is observed for the late ordovician earliest carboniferous indicat ing that iran was part of gondwana during that time data for the late permian early early tri assic indicate that iran resided on subequatorial palaeolatitudes clearly disengaged from the parental gondwanan margin in the southern hemisphere since the late early triassic iran has been located in the northern hemisphere close to the eurasian margin this northward drift brought iran to cover much of the palaeotethys in approximately 35 ma at an average plate speed ofc 7 8 cm year 21 and was in part coeval to the transformation of pangaea from an irvin gian b to a wegenerian a type configuration

the end triassic mass extinction a new correlation between extinction events and δ13c fluctuations from a triassic jurassic peritidal succession in western sicily abstract a new 13ccarb curve was obtained from an expanded peritidal succession in western sicily and was used to investigate the relationships between isotopic signatures and biological events on carbonate platforms across the triassic jurassic boundary tjb the resulting curve shows two main negative carbon isotopic excursions cies that fit well with the initial and main cies that are recognized worldwide and linked to the end triassic extinction ete in the studied section the first negative cie marks the disappearance of the large megalodontids which were replaced by small and thin shelled specimens while the main cie corresponds to the last occurrence lo of the megalodontids and approximately 50 m upsection to the total demise of the rhaetian benthic foraminifer community upward the carbon curve shows a positive trend ca 1 and a gradual recovery of the benthic communities after an approximately 10 m thick barren interval populated only by the problematic alga thaumatoporella parvovesiculifera a comparison between the mt sparagio 13ccarb curve and other coeval ccarb and corg curves from carbonate platform ramp and deep basin successions indicates similar isotopic trends however the diverse magnitudes and responses of benthic communities confirm that the carbon cycle perturbations have been globally significant and were influenced by external forces such as camp volcanism the multiphase nature of the extinction pulses could have been caused by local environmental changes related to transgression regression phenomena overall this study adds new data and a new timing to the effect of the acidification process on carbon productivity and benthic communities in different environments across the tjb

peri equatorial paleolatitudes for jurassic radiolarian cherts of greece abstract radiolarian rich sediments dominated pelagic deposition over large portions of the tethys ocean during middle to late jurassic time as shown by extensive bedded chert sequences found in both continental margin and ophiolite units of the mediterranean region which paleoceanographic mechanisms and paleotectonic setting favored radiolarian deposition during the jurassic and the nature of a tethys wide change from biosiliceous to biocalcareous mainly nannofossil deposition at the beginning of cretaceous time have remained open questions previous paleomagnetic analyses of jurassic red radiolarian cherts in the italian apennines indicate that radiolarian deposition occurred at low peri equatorial latitudes similar to modern day deposition of radiolarian rich sediments within equatorial zones of high biologic productivity to test this result for other sectors of the mediterranean region we undertook paleomagnetic study of mesozoic mostly middle to upper jurassic red radiolarian cherts within the aegean region on the peloponnesus and in continental greece sampled units are from the sub pelagonian zone on the argolis peninsula the pindos olonos zone on the koroni peninsula near karpenissi in central greece and the ionian zone in the varathi area of northwestern greece thermal demagnetization of samples from all sections removed low temperature viscous and moderate temperature overprint magnetizations that fail the available fold tests at argolis and koroni however the cherts carry a third high temperature magnetization that generally exhibits a polarity stratigraphy and passes the available fold tests we interpret the high temperature component to be the primary magnetization acquired during chert deposition and early diagenesis at kandhia and koliaky argolis the primary declinations and previous results indicate clockwise vertical axis rotations of 40 relative to stable europe due to ambiguities in hemispheric origin n or s and thus paleomagnetic polarity the observed declinations could indicate either clockwise cw or counterclockwise ccw vertical axis rotations thus at adriani koroni the primary declinations indicate either cw or ccw rotations of 95 or 84 depending on paleomagnetic polarity and age the primary inclinations for all peloponnesus sites indicate peri equatorial paleolatitudes similar to those found for coeval radiolarian cherts exposed in other mediterranean orogenic belts our new paleomagnetic data support the interpretation that mesozoic radiolarites within the tethys ocean were originally deposited along peri equatorial belts of divergence and high biologic productivity

a method to predict the group fissuring and faulting caused by regional groundwater decline ground fissuring is a recurrent problem in many countries where water extraction surpasses the natural recharge of aquifers due to differential settlement the soil layer undergoes deformation and cracks with serious consequences for civil infrastructure here we propose an approximate analysis of the fissuring process that can be used to predict the location of cracks which increasingly affect some middle and large sized cities in the world for that purpose the ground loss theory is applied to sediments overlying a sinusoidal shaped graben this analysis shows the existence of a tensile zone at the border of the graben with maximal values on its shoulder where tension cracks are more likely to appear it also shows that soil deformation under differential settlement may evolve into ground faulting if water withdrawal continues finally when a crack has completely developed the tensile zone shifts towards the center of the graben creating a new area for potential cracking and faulting

environmental isotopes and hydrochemical study applied to surface water and groundwater interaction in the awash river basin an environmental isotope and hydrochemical study was carried out to conceptualize the surface water and groundwater interaction and to explore the groundwater flow pattern in relation to the geological setting more emphasis is given to the afar depression where groundwater is a vital source of water supply conventional field hydrogeological study and river discharge records support the isotope and hydrochemical analysis the region is tectonically active comprising rift volcanic terrain bordered by highlands the result revealed that recent meteoric water is the major source of recharge three distinct groundwater zones were identified associated with the highlands transitional escarpment and the rift towards the rift the ionic concentration and isotopic enrichment 2h and 18dego increases following the groundwater flow paths which is strongly controlled by axial rift faults the groundwater flow converges to the seismically active volcano tectonic depressions with internal drainage and to the awash river within the afar depression at least four groundwater regimen are identified 1 fresh and shallow groundwater associated with alluvial deposits ultimately recharged by isotopically depleted recent highland rainfall and the evaporated awash river 2 cold and relatively younger groundwater within localized fractured volcanics showing mixed origin in axial fault zones 3 old groundwater with very high ionic concentration and low isotopic signature localized in deep volcanic aquifers and 4 old and hot saline groundwaters connected to geothermal systems the study demonstrated that dependable groundwater can only be obtained from the first two aquifer types in aerially restricted zones in flat plains following river courses local wadis and volcano tectonic depressions the conventional hydrogeological survey and discharge records indicate substantial channel losses from the awash river which becomes a more dominant source of recharge in central and lower awash valleys copyright 2007 john wiley sons ltd

paleomagnetic evidence for cenozoic clockwise rotation of the external albanides abstract a paleomagnetic study of 750 samples obtained from 55 late eocene to middle pliocene sedimentary sites demonstrates a clockwise rotation of about 45 of the external zones of albania this rotation occurred either in two phases of roughly equal amplitude during the early middle miocene and plio pleistocene or in a single phase with a clear acceleration of the movement during the plio pleistocene the good agreement of these results with those from southern albania and northwestern greece indicates that a large geographical area is involved in the rotation the active aegean compressive front thus extends much farther north than hitherto believed and the rotational pattern is not significantly distorted by the tectonic discontinuities recorded by geological studies the external zones of the albano hellenic belt appear to have rotated virtually as a single entity from the peloponnesos to northern albania over a deep decollement level probably involving the basement itself

paleolatitudes of late triassic radiolarian cherts from argolis greece insights on the paleogeography of the western tethys the hellenides fold and thrust range comprises two subparallel ophiolite belts of triassic to jurassic age the external ophiolite belt e g mirdita pindos argolis in the west and the internal ophiolite belt in the east broadly separated by the continental crust units of the korabi pelagonian zone it is still a matter of debate whether these ophiolites derived from a single ocean meliata maliac vardar or mark the suture of two distinct oceanic seaways pindos and meliata maliac vardar we contribute to the resolution of this controversy by studying the migdalitsa ophiolitic complex in argolis greece which contains triassic oceanic basalts and pertains to the external western ophiolite belt three key areas were mapped and several sites were targeted for structural biostratigraphic and paleomagnetic analyses radiolarian cherts in primary or tectonic contact with oceanic basalts were dated to the late triassic carnian norian using radiolarians and provided paleomagnetic directions of primary origin carried by magnetite and hematite the derived mean direction was corrected for sedimentary inclination shallowing and yielded a paleolatitude of 22 n that was placed in a broader paleogeographic context by reconstructing pangea at 225 5 ma using a recent apparent polar wander path corrected for sedimentary inclination shallowing the late triassic paleogeography of the tethys ocean was constrained using additional paleolatitude estimates from the literature which we checked and corrected when possible for sedimentary inclination shallowing according to our reconstruction the meliata maliac vardar ocean between adria the promontory of africa and europe represents the locus of origin of the late triassic argolis ophiolitic rocks of the external ophiolite belt presently resting in tectonic contact on the pindos subpelagonian zones which represent a deep water trough with no substantial evidence of in situ oceanization in the triassic

early permian pangea b to late permian pangea a the pre drift wegenerian model of pangea is almost universally accepted but debate exists on its pre jurassic configuration since tedirving introd ucedpangea b by placing gond wana farther to the east by v3000 km with respect to laurasia on the basis of paleomagnetic data new paleomagnetic data from radiometrically dated early permian volcanic rocks from parts of adria that are tectonically coherent with africa gondwana integrated with published coeval data from gondwana and laurasia again only from igneous rocks fully support a pangea b configuration in the early permian the use of paleomagnetic data strictly from igneous rocks excludes artifacts from sedimentary inclination error as a contributing explanation for pangea b the ultimate option to reject pangea b is to abandon the geocentric axial dipole hypothesis by introducing a significant non dipole zonal octupole component in the late paleozoic time averaged geomagnetic field we demonstrate however by using a dataset consisting entirely of paleomagnetic directions with low inclinations from sampling sites confined to one hemisphere from gondwana as well as laurasia that the effects of a zonal octupole field contribution would not explain away the paleomagnetic evidence for pangea b in the early permian we therefore regard the paleomagnetic evidence for an early permian pangea b as robust the transformation from pangea b to pangea a took place during the permian because late permian paleomagnetic data allow a pangea a configuration we therefore review geological evidence from the literature in support of an intra pangea dextral megashear system the transformation occurred after the cooling of the variscan mega suture andlasted v20 myr in this interval the neotethys ocean opened between india arabia and the cimmerian microcontinents in the east while widespread lithospheric wrenching and magmatism took place in the west around the adriatic promontory the general distribution of plate boundaries and resulting driving forces are qualitatively consistent with a right lateral shear couple between gondwana and laurasia during the permian transcurrent plate boundaries associated with the pangea transformation reactivated variscan shear zones andwere subsequently exploitedby the opening of western neotethyan seaways in the jurassic