aptian albian palaeogeography of neo tethyan domain abstract the aptian albian interval 124 5 97 0 ma was a critical time both globally and for the tethyan domain in the tethyan domain it was the time when a united neo tethyan subduction zone became established between the future site of the alps and southeast asia and greatly accelerated the rate of north south convergence throughout the tethyan region a consequent widespread transgression on both laurasian and gondwanian margins deposited orbitolina limestones and associated clastics on wide continental shelf areas on the sea floor of the neo tethys ocean organic rich siliceous black shales radiolarites and turbidites with minor amounts of carbonates were deposited siliceous black shales accumulated under euxinic conditions of restricted small ocean basins of the neo tethyan realm and along their margins these areas received large amounts of organic debris from deltaic areas and coastal plains of the neighbouring continental shelves following the establishment of the north dipping subduction zone the laurasian passive margin was largely converted to an active one fringed by a large number of magmatic arcs that greatly influenced the sedimentation on the margin land areas and continental basins were widespread on this margin in northern tibet china and indo china this was a consequence of the late triassic to early jurassic continental collissions and accompanied intracontinental convergence that lasted well into the cretaceous a detailed aptian albian facies map and a crude palinspastic palaeogeographic map of the entire tethyan realm are prepared in order to express the contrasts in sedimentation on laurasian and gondwanian margins and to show the compatibility of the presented data with the most recent and reliable reconstructions of the major tectonic elements in tethysides

constraints from gps measurements on the dynamics of the zone of convergence between arabia and eurasia we investigate the dynamics of deformation in the zone of convergence between the arabian and eurasian plates using a physical model that treats the lithosphere as a thin fluid sheet deforming in response to lateral variations in gravitational potential energy gpe this model has two free material parameters the power law exponent n of the vertically averaged rheology of the lithosphere and the argand number ar which expresses the relative importance of gpe and stresses required to deform the lithosphere with boundary conditions described by three free parameters the model fits the observed deformation as measured by 367 gps velocities with a root mean square residual of 2 4 mm yr we find negligible improvement when variations in material properties are introduced that represent increases or decreases in the lithospheric strength of the central iranian and turkish iranian plateaux and the zagros mountains effective viscosity of the lithosphere ranges from 5 1022 pa s at 10 nanostrain yr to 1022 pa s at 100 nanostrain yr as well as matching the decadal timescale predominantly interseismic strain rates determined from gps the computed distribution of strain rates is also consistent with the distribution and types of earthquake focal mechanism significant historical earthquake activity is seen in regions with strain rates lower than 20 nanostrain yr implying that it is prudent to base assessments of seismic hazard on regional strain rates

ostracod assemblages in late quaternary varved glaciomarine clay of the baltic sea yoldia stage in eastern middle sweden abstract four cored sites in eastern middle sweden have been analysed for their content of calcareous fossils the investigated sediments consist of late quaternary varved clay deposited during the baltic sea yoldia stage four regional palaeoecological units a d have been established unit a reflects ice proximal conditions unit b optimal conditions for the benthic fauna and unit c the termination of a saline phase in unit c oxygen deficiency might have occurred in the fourth unit d no fossils were found the fauna recorded is poor in taxa and indicates a weak marine influence the salinity was higher in the western part of the investigated area due to the proximity to the inlet of marine water the meltwater influx was high and the salinity probably fluctuated considerably the ostracod cytheromorpha macchesneyi brady and crosskey is reported for the first time in quaternary deposits from northwestern europe and indicates that a connection could have existed between the baltic and the white sea in late glacial times

cretaceous nubia formation and correlative deposits eastern egypt major regressive transgressive complex early to mid late cretaceous nubia formation in and around the natash basin in southeastern egypt incorporates a lower regressive nonmarine sandy facies 1 as much as 100 m thick a middle transgressive paralic to marine facies 2 several tens of metres thick and an upper prograding nonmarine to paralic sandy facies 3 about 120 m thick these deposits extend northwestward across the kharga arch into the large dakhla basin in central and southwestern egypt where facies 1 is several hundred metres thick and has an aptian marine tongue the nubia formation also has correlative lithofacies along the gulf of suez lowland in northeastern egypt there facies 1 is of varying thickness and is an important petroleum reservoir early cretaceous to early cenomanian facies 1 was deposited by high energy low sinuosity braided streams during a low stand of sea level that persisted with only minor interruption for about 50 m y sandy fining upward fluvial sequences record intermittent aggradation and repeated development of paleosols deposits in the dakhla basin were dispersed northward from the deeply weathered nubian shield those in southeastern egypt and in the gulf of suez lowland were dispersed southwestward and westward from uplands on the eastern desert and arabian platforms southward thinning late cenomanian turonian marine facies 2 marks the climax of the first major late cretaceous tethyan transgression waning of northward dispersed detritus fostered development of three extensive beds of oolitic ironstone in the vicinity of aswan as well as a few thin lenses of ironstone in central northern and northeastern egypt distinctive tabular planar cross bedded facies 3 reflects renewed uplift of the nubian shield in late turonian coniacian time and essentially continuous influx of quartzose sand for only a few million years facies 3 was spread across a prograding alluvial plain in migrating sand waves and channel bars in closely spaced non sinuous distributary systems the older regressive facies 1 was succeeded rather abruptly by marine facies 2 as a result of waning detrital influx followed by low energy transgression that developed only minor strand line sand bodies prograding nonmarine facies 3 is separated from overlying transgressive late cretaceous marine deposits by a gradational ripple bedded facies probably produced by gradual waning of detrital supply during continuing high stand of sea level the nubia formation and its correlatives in eastern egypt reflect uplands and irregular topography along the red sea suez tract that had been a broad zone of deformation in late precambrian time the pattern of distribution of early cretaceous facies 1 in the gulf of suez lowland suggests that there may have been very little spreading along the suez graben during cenozoic opening of the red sea

late quaternary marine mollusca as palaeoenvironmental proxies a compilation and assessment of basic numerical data for ne atlantic species found in shallow water abstract temperature salinity and depth limits are given for selected molluscs from boreal and arctic regions of the ne atlantic and adjacent shelf seas the significance of the data for palaeoenviromental analysis is briefly discussed

seismic ray path variations in a 3d global velocity model abstract a three dimensional 3d ray tracing technique is used to investigate ray path variations of p pcp pp and pp phases in a global tomographic model with p wave velocity changing in three dimensions and with lateral depth variations of the moho 410 and 660 km discontinuities the results show that ray paths in the 3d velocity model deviate considerably from those in the average 1d model for a pcp wave in western pacific to east asia where the high velocity 1 2 pacific slab is subducting beneath the eurasian continent the ray path change amounts to 27 km for a pcp ray in south pacific where very slow 2 velocity anomalies the pacific superplume exist in the whole mantle the maximum ray path deviation amounts to 77 km ray paths of other phases p pp pp are also displaced by tens of kilometers changes in travel time are as large as 3 9 s these results suggest that although the maximal velocity anomalies of the global tomographic model are only 1 2 rays passing through regions with strong lateral heterogeneity in velocity and or discontinuity topography can have significant deviations from those in a 1d model because rays have very long trajectories in the global case if the blocks or grid nodes adopted for inversion are relatively large 3 5 and only a low resolution 3d model is estimated 1d ray tracing may be feasible but if fine blocks or grid nodes are used to determine a high resolution model 3d ray tracing becomes necessary and important for the global tomography

tectonic framework of the himalaya karakoram and tibet and problems of their evolution the himalaya the karakoram and tibet were assembled by the successive accretion to asia of continental and arc terranes during the mesozoic and early tertiary the jinsha and banggong sutures in tibet join continental terranes separated from gondwana ophiolites were obducted onto the shelf of southern tibet in the jurassic before the formation of the banggong suture the kohistan ladakh terrane contains an island arc that was accreted in the late cretaceous on the shyok suture and consequently evolved into an andean type batholith further east this trans himalayan batholith developed on the southern active margin of tibet without the prior development of an island arc ophiolites were obducted onto the shelf of india in the late cretaceous to lower palaeocene before the closing of tethys and the formation of the indus yarlung zangbo suture at about 50 ma post collisional northward indentation of india at ca 5 cm a 1 since the eocene has redeformed this accreted terrane collage palaeomagnetic evidence suggests this indentation has given rise to some 2000 km of intracontinental shortening expressions of this shortening are the uplift of mid crustal gneisses in the karakoram on a late tertiary breakback thrust folding of palaeogene redbeds in tibet south directed thrust imbrication of the foreland and shelf of the indian plate north directed back thrusts along the indus suture zone post miocene spreading and uplift of thickened tibet giving rise to n s extensional faults and strike slip faults which allowed eastward escape of tibetan fault blocks

p wave velocity tomography from local earthquakes in western mexico in western mexico the subduction of the rivera and cocos plates beneath the north america plate has deformed and fragmented the overriding plate forming several structural rifts and crustal blocks to obtain a reliable subsurface image of the continental crust and uppermost mantle in this complex area we used p wave arrivals of local earthquakes along with the fast marching method tomography technique we followed an inversion scheme consisting of 1 the use of a high quality earthquake catalog and corrected phase picks 2 the selection of earthquakes using a maximum location error threshold 3 the estimation of an improved 1 d reference velocity model and 4 the use of checkerboard testing to determine the optimum configuration of the velocity nodes and inversion parameters surprisingly the tomography results show a very simple vp distribution that can be described as being controlled by geologic structures formed during two stages of the separation of the rivera and cocos plates the earlier period represents the initial stages of the separation of the rivera and cocos plates beneath western mexico the later period represents the more advanced stage of rifting where the rivera and cocos plates had separated sufficiently to allow melt to accumulate below the colima volcanic complex during the earlier period 14 or 10 1 6 ma ne sw oriented structures lineaments such as the southern colima rift were formed as the two plates separated during the second period 1 6 ma to the present the deformation is attributed to magma generated within and above the tear zone between the rivera and cocos plates rising beneath the region of the colima volcanic complex the rising magma fractured the overlying crust forming a classic triple rift junction geometry this triple rift system is confined to the mid to lower crust perhaps indicating that this rifting process is still in an early stage this fracturing along with fluid circulation and associated heat advection within the fractures can easily explain the observed distribution of vp as well as many of the results of previous seismological studies also surprisingly we find no evidence at deep crustal depths to support either a trenchward migration of the volcanic arc or toroidal asthenospheric flow through the slab tears bounding the jalisco block to the nw and se

three dimensional seismic structure of the upper mantle beneath the central part of the eurasian continent summary this work is a study of the upper mantle seismic structure beneath the central part of the eurasian continent including the northern mongolia altai and sayan orogenic areas and the baikal rift zone seismic velocity models are reconstructed using the inverse teleseismic scheme this scheme uses information from earthquakes located within the study area recorded by the worldwide network the seismic anomaly structure is obtained for diverent volumes in the study area that partially overlap one another special attention has been paid to the reliability of the results several noise and resolution comparisons are made the main results are as follows 1 a cell structure of anomalies is observed beneath the altai sayan region positive cold anomalies correspond to regions of recent orogenesis negative anomalies are located beneath the depression of the great lakes in mongolia and hubsugul lake 2 a large negative anomaly is observed beneath the hangai dome in mongolia 3 strong velocity variations are obtained in a zone around baikal lake a large negative anomaly is traced beneath the southern margin of the siberian craton down to a depth of 700 km contrasting positive anomalies 4 5 per cent are observed at a depth of 100 300 km beneath the baikal rift our geodynamical interpretation of the velocity structure obtained beneath central asia involves the existence of two processes in the mantle thermal convection with regular cells and a narrow plume beneath the southern border of the siberian plate

tethys marginal sedimentary basins in western iran five sedimentary basins formed along the iranian margin of the southern tethys ocean during its evolution these basins record the opening and closing of the ocean basin and the collision of what is now arabia and iran the late paleozoic jurassic isfahan basin opened by continental rifting that began in the devonian and contains an early late paleozoic triassic passive margin sequence and a later clastic wedge phase the early cretaceous sanandaj basin is a forearc overlying the tectonized and subsided isfahan basin the latest cretaceous paleocene kermanshah basin is a remnant of the tethys ocean basin it initially lay along tectonic strike from the lengthening arabian iranian collision orogen to the southeast but was later incorporated into the orogenic foldbelt the late cenozoic zagros basin is a suture foreland basin that formed on the arabian plate as it attempted subduction beneath iran the paleogene tectonic setting of the kashan gavkhuni basin is in doubt but by mid tertiary time it was a foreland basin that lay landward of the collisional foldbelt and was nearly surrounded by other orogenic highlands that formed during convergence of other plates within and marginal to iran

ophiolites as indicators of the geodynamic evolution of the tethyan ocean abstract reviewing the ophiolites of the alpine chain from the western mediterranean to the indian ocean we subdivide them into ten groups of outcrops the geological environment through time the internal composition and history are given for each emphasis is put on the variegated and successive geodynamic processes which can be reconstructed for the different ophiolitic belts since their birth as an ocean like crust to their incorporation through accretion to a continent one can distinguish low versus high tholeiitic partial melting fairly or poorly established ridges simple ridge type crust versus complex ridge ensimatic arc and even more complex type long lived versus short lived oceanic crust stages abrupt large scale pure obduction versus progressive collision related obduction or simple progressive juxtaposition to continent the major events through time in the tethyan ophiolitic belts can be listed as follows spreading ridge activity during the jurassic liguria dinaro hellenides lesser caucasus and the cretaceous peri arabic nain sabzewar with a jump of ridge in between repeated change from ridge to ensimatic arc dinaro hellenic lesser caucasus peri arabic west indian during the latest jurassic and cretaceous upper cretaceous tertiary collision related obductions pontic lesser caucasus liguria squeezing out the elevated portions of these basins lack of oceanic magmatism during the cenozoic but progressive accretion along accretionary wedges of the elevated portions of the remaining mesozoic crust van nain sabzewar zahedan mekran

a jurassic cretaceous island arc in the ladakh himalayas abstract the ladakh mesozoic ophiolite belt western himalaya contains a pile of volcanic thrust sheets dras unit which differ significantly in structure and composition from the ophiolitic melange zones the dras unit is composed of pillow lavas doleritic sills very irregular basaltic basaltic andesites and dacitic flows intercalated with pyroclastics volcanoclastic sediments and radiolarian cherts according to fossil evidence this volcanism must have been active between upper jurassic and upper cretaceous the presence of relict primary minerals such as magnesiochromite clinopyroxene hastingsitic hornblende and ti magnetite as well as distinctive bulk chemistries suggests that the volcanics belong to island arc tholeiite and to calc alkaline rock series typical of present island arcs in the caribbean and pacific model calculations incorporating probed phenocryst phases indicate that in addition to olivine clinopyroxene and plagioclase amphibole and titanomagnetite are crucial fractionating phases in the development of the dacites from a primitive tholeiitic melt the latter process must have taken place at about 1000 c and at moderate depth of 5 15 km within or underneath the island arc today hornblende bearing mafic cumulates appear in the vicinity of kargil within and close to the dras volcanics in a sr evolution diagram the dras volcanics have yielded a pseudo isochron with a low initial 87 sr 86 sr ratio of 0 7035 0 0003 which is in the same range as the mean of modern island arc volcanics however a geologically unrealistic age of 263 m y is obtained from the slope of this isochron the upper mantle is regarded as the source material for the island arc tholeiitic magmas enrichment in k ba sr and lree supports the involvement of components derived from dehydration or incipient melting of subducted tethyan oceanic crust in the mantle

atmospheric circulation upwelling and organic rich rocks in the mesozoic and cenozoic eras abstract by using the basic principles of atmospheric circulation and analogies from present circulation patterns it is possible to construct qualitative atmospheric circulation models on paleogeographic maps the wind patterns predicted by these models then serve as the basis for predicting the locations of ancient upwelling zones atmospheric circulation and upwelling models for seven geologic stages in the mesozoic and cenozoic were constructed and the distribution of the upwelling zones compared with the distribution of organic rich rocks for all time periods together the correlation was statistically significant when the individual time periods were analyzed separately the following pattern emerged significant correspondence between upwelling zones and organic rich rocks in the triassic middle early cretaceous to late cretaceous and middle paleogene to neogene no significant correspondence was found for the intervening times upwelling does not account for all organic rich rocks so called anoxic oceanic events and transgressions play an important role in their deposition it is suggested that upwelling contributes significantly to the pattern of organic rich rock distribution and is important in determining organic facies

lead isotopic study of the xigaze ophiolite tibet the problem of the relationship between magmatites gabbros dolerites lavas and tectonites harzburgites abstract the pb isotopic study of the xigaze ophiolite tibet shows that the tectonic harzburgites and magmatic gabbros dolerites lavas units bear different isotopic signatures the harzburgitic rocks show much higher207pb 204pb values than the samples from the magmatic unit analyses of primary magmatic clinopyroxenes separated from the harzburgites confirmed that this difference is real and not due to secondary alteration processes u pb analysis allowed determination of the crystallization age of the magmatites at 120 10 m y this age is compatible with paleontological age determinations and thus demonstrates that u pb behaved more or less as a closed system since formation of the ophiolite if an exchange with seawater has occurred it must necessarily have happened shortly after crystallization of the xigaze oceanic crust dolerite dykes crossing the harzburgites show similar pb isotopic composition as the magmatites indicating that they were emplaced when the ultramafic rocks were already brittle however the time difference of the emplacement was probably not larger than 280 m y this makes it evident that two sources with different isotopic signatures one similar to normal morb the other with much higher207pb 204pb ratios were active in the immediate neighborhood one possible environment which can account for this association is a propagating ridge

a high resolution record of lateglacial and early holocene marine sediments from southwestern sweden with special emphasis on environmental changes close to the pleistocene holocene transition and the influence of fresh water from the baltic basin a high resolution study of a marine depositional record 43 m long dated by accelerator mass spectrometry from goteborg gothenburg southwestern sweden shows biostratigraphical and sedimentological changes of environmental significance during the lateglacial and early holocene high accumulation rates are recorded from the onset of the deglaciation of the area ca 13 500 yr bp until 10 300 yr bp by which time approximately 100 m of marine sediments were deposited the early holocene is represented by 10 m only of sediment the influence on the skagerrak kattegat coastal area of the dramatic final drainage of the baltic ice lake at 10 300 yr bp is re evaluated its impact on the distal swedish west coast was limited and sediments that were previously related to this drainage are reinterpreted here it is suggested they reflect resuspension and redeposition of sediments from the large inland lake vanern basin between ca 9500 and 9000 yr bp at 10 200 yr bp a general climatic change and a sudden incursion of warm and saline atlantic water into the norwegian sea occurred and the skagerrak altered environmental conditions with more temperate bottom water conditions in the investigation area

extracting stable seismic core phases from ambient seismic noise abstract ambient seismic noise correlation is a powerful tool for extracting the seismic core phases that propagate through the interior of the earth in this study we present and refine the root mean square stacking method to extract stable core phases e g pcp scs pcs scp and pkikp from within the central alborz region iran using empirical green s functions our studies on the extracted core phases using empirical green s functions indicated that the ambient seismic noise method is independent from global seismicity m 5 5 we also show that by dividing ambient seismic records into shorter i e 2700 s and overlapping 70 time windows before the cross correlation procedure we can improve the quality and stability of the empirical green s functions generated consequently 73 days equivalent to 22 of the total time period for the dataset of nonconsecutive ambient seismic noise time windows have been used to retrieve core phase empirical green s functions in a 5 10 s period band

volcanic belts as markers of the mesozoic cenozoic active margin of eurasia abstract from the triassic to the present linear belts of calc alkaline volcanism developed along the southern margin of eurasia in the triassic the calc alkaline belt can be traced in turan fore caucasus crimea and dobrogea its development is related to the closure of the paleo tethys when fragments of gondwana iran afghanistan etc were approaching eurasia since the early jurassic calc alkaline volcanism has been related to subduction of the oceanic crust of the mesozoic tethys five stages of calc alkaline volcanic activity can be distinguished early jurassic middle jurassic early cretaceous late cretaceous paleogene and late miocene quaternary the configuration of the volcanic belts the intensity of the volcanism and the chemistry of the erupted products change considerably from stage to stage mesozoic belts were most pronounced in the pontian transcaucasian segment of the margin starting from the late cretaceous and especially in the cenozoic the volcanic belts can be continuously traced from the balkans to afghanistan most of the belts were actually island arcs formed on the fragments of the hercynian of baikalian basement and in this respect similar to the island arc of japan only the incipient island arcs of senonian age formed close to the passive margin of gondwana are the exceptions they were built on oceanic crust and are geochemically close to the mariana arc at certain times early jurassic eocene parallel chains of island arcs existed in general the situation resembled the present day convergent boundary in the western pacific as closure of the tethys proceeded island arcs gave way to marginal continental volcanic belts with wide spread development of high potassium particularly shoshonitic series peaks of volcanic activity in the bajocian late cretaceous eocene and late miocene present alternated with quiet periods and corresponded to the times when the convergence rate between africa and eurasia increased the opening of the back arc basins is reflected in outbursts of basaltic rift type volcanism these outbursts occurred in the toarcian aalenian bathonian late jurassic aptian turonian and early middle eocene

origin and assembly of the tethyside orogenic collage at the expense of gondwana land abstract the tethysides are a superorogenic complex flanking the eurasian continent to the south and consisting of the cimmerides and alpides products of palaeo and neo tethys respectively we here review their evolution mainly on the basis of new maps showing the distribution of sutures magmatic rocks certain palaeobiogeographically and palaeoclimatologically significant taxa and facies and fragments of pan african 900 450 ma orogenic system forming the basement of many tethyside blocks these are supplemented by palaeomagnetic data reported in the literature a fundamental tenet of this paper is that major sutures which contain ophiolite fragments represent tectonic sections between continental blocks where oceanic crust has been subducted palaeo tethys came into existence largely in late carboniferous time coevally it began to be consumed by both internal and peripheral subduction zones which continued into the permian some of these had been inherited from pre tethyan times in the later permian rifting subparallel with the northern margin of gondwana land began between the zagros and malaysia separating a cimmerian continent from n gondwana land and thus heralding the opening of neo tethys and other smaller oceans that were back arc basins of palaeo tethys this rifting possibly also extended farther west into crete and mainland greece however the north china block yangtze block huanan block the eastern moity of the qangtang block north tibet and annamia all originally pieces of the end proterozoic early palaeozoic gondwana land had already separated from it in pre late carboniferous times possibly during the devonian all of these blocks and the cimmerian continent were characterized by cathaysian floral elements in late palaeozoic time palaeomagnetic and palaeontological data showing the original gondwana land affinity of these continental blocks are supplemented by correlating late proterozoic early palaeozoic pan african sutures orogenic belts and sedimentary basin fragments across tethyside sutures late permian foraminiferal provinces are related to this palaeogeographical interpretation by triassic times most cimmeride subduction zones were already in existence the cimmerian continent accelerated its separation from gondwana land and locally in the late permian began disintegrating internally along the waser rushan pshart banggong co nu jiang mandalay ocean by late triassic time all of the chinese blocks except lhasa and annamia had collided with each other and with laurasia the resulting enormous orogenic collage had a soft cushion between itself and laurasia in the form of the enormous accretionary complex of the songpan ganzi this connection enabled laurasian land vertebrates to reach south east asia by late triassic time in late triassic to middle jurassic times most major cimmeride collisions were completed widespread aridity in central asia occurred in late jurassic time probably in the rain shadow of the newly formed cimmeride mountain wall neo tethyan subduction systems formed along the s margin of the cimmerides or within neo tethyan oceanic lithosphere during the jurassic most if not all were north or east dipping they continued the northerly migration of the tethyside blocks evolution of the tethysides influenced the distribution of marine and terrestrial organisms and affected sea level changes and patterns of atmospheric circulation during much of the mesozoic and cainozoic it is likely to have reflected the surface expression of a persistent trend in the large scale convective circulation in the mantle that continuously transported material northward into the tethyan domain

patterns of historical earthquake rupture in the iranian plateau the iranian plateau accommodates the 35 mrn yr convergence rate be tween the eurasian and arabian plates by strike slip and reverse faults with relatively low slip rates in a zone 1000 km across although these faults have only locally been the subject of paleoseismological studies a rich historical and archeological record spans several thousand years long enough to establish recurrence intervals of 1000 to 5000 yr on individual fault segments several clusters of earthquakes provide evidence of interaction among reverse and strike slip faults probably due to adjacent faults being loaded by individual earthquakes the dasht e bayaz sequence of 1936 to 1997 includes earthquakes on left lateral right lateral and reverse faults the neyshabur sequence of four earthquakes between 1209 and 1405 respected the seg ment boundary between the neyshabur and binalud reverse fault systems the two pairs of earthquakes may have ruptured different faults in each segment similar to the 1971 and 1994 san fernando california earthquakes the 1978 tabas reverse fault earthquake was preceded by the 1968 ferdows earthquake part of the dasht e bayaz sequence the north tabriz fault system ruptured from southeast to north west in three earthquakes from 1721 to 1786 a previous cluster may have struck this region in 855 to 958 the mosha fault north of tehran ruptured in three earthquakes in 958 1665 and 1830 five large earthquakes struck the tehran region from 743 to 1177 but only two that large have struck the area since 1177 other earthquakes occurred in pairs in the talesh mountains near the caspian sea 1863 1896 the iran turkey border 1840 1843 and the nayband gowk fault system both 1981 other historical events did not occur as parts of sequences the historic seismic moment release in iran accounts for only a small part of the plate convergence rate which may be due to aseismic slip or to the iranian historical record long as it is being too short to sample long term deformation across the plateau no historic earthquakes of m 8 have struck iran however several long straight strike slip faults doruneh west neh east neh and nayband have not sustained large historical earthquakes raising the possibility that these long faults could produce earthquakes of m 8 thereby removing at least part of the apparent slip deficit an increased understanding of iran s seismic hazard could be obtained by an extensive paleoseismology program and space geodetic arrays supplementing the abundant historical and archaeological record

late miocene deformation kinematics along the nw zagros fold thrust belt kurdistan region of iraq constraints from apatite u th he thermochronometry and balanced cross sections

high resolution image of uppermost mantle beneath ne iran continental collision zone we invert 3775 relative p wave arrival times using the ach damped least square method of aki et al 1977 to study upper mantle structure beneath the ne iran continental collision zone the data for this study were recorded by 17 three component broad band stations operated from august 2006 to february 2008 along a profile from the center of iranian plateau near yazd to the northeastern part of iran on the turan platform just north of the kopeh dagh mountains the results confirm the previously known low velocity upper mantle beneath central iran our tomographic model reveals a deep high velocity anomaly the surficial expressions of this anomaly are between the ashkabad and doruneh faults where the resolution and ray coverage are good a transition zone in uppermost mantle is recognized under the binalud foreland that we interpreted as suture zone between iran and turan platform our results indicate that atrak valley which is the boundary between the binalud and kopeh dagh mountains can be considered as the northeastern suture of the iranian plateau where eurasia and turan platform under thrust beneath the binalud range and central iran

active tectonics of the alpine himalayan belt between western turkey and pakistan summary over 80 new fault plane solutions combined with satellite imagery as well as both modern and historical observations of earthquake faulting are used to investigate the active tectonics of the middle east between western turkey and pakistan the deformation of the western part of this region is dominated by the movement of continental material laterally away from the lake van region in eastern turkey this movement helps to avoid crustal thickening in the van region and allows some of the shortening between arabia and eurasia to be taken up by the thrusting of continental material over oceanic type basement in the southern caspian mediterranean makran and black sea thus central turkey bounded by the north and east anatolian strike slip faults is moving west from the van region and overrides the eastern mediterranean at two intermediate depth seismic zones one extending between antalya bay and southern cyprus and the other further west in the hellenic trench the motion of northern iran eastwards from the van region is achieved mainly by a conjugate system of strike slip faults and leads to the low angle thrusting of iran over the southern caspian sea the seismicity of the caucasus shows predominantly shortening perpendicular to the regional strike but there is also some minor elongation along the strike of the belt as the causcasus overrides the caspian and black seas the deformation of the eastern part of this region is dominated by the shortening of iran against the stable borders of turkmenistan and afghanistan the north east direction of compression seen in zagros is also seen in north east iran and the kopet dag where the shortening is taken up by a combination of strike slip and thrust faulting large structural as well as palaeomagnetic rotations are likely to have occurred in ne iran as a result of this style of deformation north south strike slip faults in southern iran allow some movement of material away from the collision zone in ne iran towards the makran subduction zone where genuinely intermediate depth seismicity is seen within this broad deforming belt large areas such as central turkey nw iran azerbaijan central iran and the southern caspian appear to be almost aseismic and therefore to behave as relatively rigid blocks surrounded by active belts 200 300 km wide the motion of these blocks can usefully be described by poles of rotation the poles presented in this paper predict motions consistent with those observed and also predict the opening of the gulf of iskenderun ne of cyprus the change within the zagros mountains from strike slip faulting in the nw to intense thrusting in the se and the relatively feeble seismicity in se iran baluchistan this description also explains why the north south structures along the iran afghanistan border do not cut the east west ranges of the makran within the active belts surrounding the relatively aseismic blocks a continuum approach is needed for a description of the deformation even though motions at the surface may be concentrated on faults the evolution of fault systems within the active zones is controlled by geometric constraints such as the requirement that simultaneously active faults do not in general intersect many of the active processes discussed in this paper particularly large scale rotations and lateral movement along the regional strike are likely to have caused substantial complexities in older mountain belts and should be accounted for in any reconstructions of them

marine conditions in central sweden during the early preboreal as inferred from a stable oxygen isotope gradient the marine benthic fauna and the 18 oc of foraminifers and ostracods from six sites situated on a west east transect through central sweden have been analysed in order to estimate the palaeosalinity and palaeocirculation in this shallow marine environment the measurements have been undertaken on material from the early preboreal when the baltic basin was in contact with the north sea through straits in central sweden the 18 oc values have a more negative value towards the east indicating decreasing salinity this was the result of limited possibilities for marine water to penetrate into the baltic basin and the mixing with freshwater from the melting fennoscandian ice sheet four water masses existed in the area a surface layer of freshwater marine water from the north sea brackish marine intermediate water on the swedish west coast and brackish yoldia sea water in the baltic basin the chronology is based on radiocarbon dates of marine fossils and at one site on the occurrence of the vedde ash 10 400 10 300 14 c yr bp this is the first record from marine settings in sweden copyright 2001 john wiley sons ltd journal of quaternary science

the tibetan side of the india eurasia collision results are reported from the 1980 joint french chinese field expedition in tibet the area covered was from the high himalaya in the south to the region of nagqu 250 km north of yangbajain ophiolites in the zangbo valley represent remnants of the crust of an ocean basin which lay adjacent to the gangdise granodiorite belt in the late mesozoic the ophiolites were thrust to the south onto the cretaceous melange and triassic flysch but the age of this event is unclear in the tertiary sediments of the indian margin and the xigaze basin were folded with steeply dipping cleavage which indicates some north south shortening of the crust however the tertiary volcanic sequence on the lhasa block and further north shows comparatively little folding and thrusting in the quaternary deformation of tibet was characterized by east west extension

late weichselian early holocene stratigraphy and environmental conditions in southwestern varmland sweden reflected by benthic foraminifera and molluscs abstract the biostratigraphy at two sites lake uppsalstjarnet and lake osten southwestern varmland southwestern sweden has been investigated the main interest is put on glaciomarine and marine sediments deposited shortly after deglaciation foraminifera and molluscs were present at the deglaciation and some hundred years after arctic faunas dominate in the lowermost layers deposited close to the ice front a transition to faunas affected by increased meltwater influence and higher temperature is recorded higher up in the sequences ams datings of bivalves and foraminifera have yielded ages between ca 10 100 and 9750 bp which infers that southwestern varmland was deglaciated during the latest part of the younger dryas to early preboreal the marine sediments are overlain by varved and sulphide stained clay units deposited when a connection with the sea still was open but the ingression of saline water had ceased

closing the gap between regional and global travel time tomography recent global travel time tomography studies by zhou 1996 and van der hilst et al 1997 have been performed with cell parameterizations of the order of those frequently used in regional tomography studies i e with cell sizes of 1 2 these new global models constitute a considerable improvement over previous results that were obtained with rather coarse parameterizations 5 cells the inferred structures are however of larger scale than is usually obtained in regional models and it is not clear where and if individual cells are actually resolved this study aims at resolving lateral heterogeneity on scales as small as 0 6 in the upper mantle and 1 2 3 in the lower mantle this allows for the adequate mapping of expected small scale structures induced by for example lithosphere subduction deep mantle upwellings and mid ocean ridges there are three major contributions that allow for this advancement first we employ an irregular grid of nonoverlapping cells adapted to the heterogeneous sampling of the earth s mantle by seismic waves spakman and bijwaard 1998 second we exploit the global data set of engdahl et al 1998 which is a reprocessed version of the global data set of the international seismological centre their reprocessing included hypocenter redetermination and phase reidentification finally we combine all data used p pp and pwp phases into nearly 5 million ray bundles with a limited spatial extent such that averaging over large mantle volumes is prevented while the signal to noise ratio is improved in the approximate solution of the huge inverse problem we obtain a variance reduction of 57 1 synthetic sensitivity tests indicate horizontal resolution on the scale of the smallest cells 0 6 or 1 2 in the shallow parts of subduction zones decreasing to approximately 2 3 resolution in well sampled regions in the lower mantle vertical resolution can be worse up to several hundreds of kilometers in subduction zones with rays predominantly pointing along dip important features of the solution are as follows 100 200 km thick high velocity slabs beneath all major subduction zones sometimes flattening in the transition zone and sometimes directly penetrating into the lower mantle large high velocity anomalies in the lower mantle that have been attributed to subduction of the tethys ocean and the farallon plate and low velocity anomalies continuing across the 660 km discontinuity to hotspots at the surface under iceland east africa the canary islands yellowstone and the society islands our findings corroborate that the 660 km boundary may resist but not prevent present day large scale mass transfer from upper to lower mantle or vice versa this observation confirms the results of previous global mantle studies that employed coarser parameterizations

the himalayan passive margin from precambrian to cretaceous times abstract the himalaya passive margin should be separated into the indian himalaya and the pakistan himalaya divided by the nanga parbat haramosh basement uplift in the northwestern syntaxes the indian passive margin shows a complex history involving splitting of microcontinents off the northern gondwana margin from early paleozoic times until the jurassic in contrast the pakistan himalaya formed part of the stable indian shelf until separation from africa started in the jurassic each margin has a distinct stratigraphic history until the mid mesozoic after which they show similar histories until the tertiary the himalaya mountains in india consist of three distinct tectonic units juxtaposed during the neogene by southward thrusting of the northern indian precambrian to mesozoic passive margin the lesser himalaya on the south forms a late precambrian passive margin usually directly overlain by late cretaceous to tertiary clastics its stratigraphy is closest to that of the indian shield in contrast the high himalaya has a thin ordovician to carboniferous shelf sequence deposited after early ordovician deformation and granite intrusion above this thick permian and mesozoic shelf sequences mark the separation of continental blocks off the northern indian margin and the opening of the neotethys ocean the north himalaya formed the slope and basin of this ocean and consists of reactivated paleozoic gneiss domes overlain by thick mesozoic sediments which pass in the northeastern himalaya into an enormously thick sedimentary sequence resting on oceanic crust paleomagnetic and structural evidence indicates at least 500 km of southward thrusting along the main central thrust between the lesser and high himalaya this thrusting together with a further 250 km of erosion at the front of the nappes has removed the entire inner shelf of the himalaya passive margin and can explain the startling contrast between the high and lesser himalaya stratigraphic sequences but there are still discrepancies particularly in the eastern himalaya where precambrian basement is juxtaposed with the north himalaya mesozoic slope these discrepancies can be partly resolved by strike slip movements roughly parallel to the himalaya which have removed parts of the northern indian passive margin such faults of the requisite orientation displacement and age occur in southeast asia where their cumulative displacements can add up to several thousand kilometres similar faults of undoubted pre tertiary age occur in the pakistan himalaya here the passive margin shows a much simpler history of jurassic to miocene subsidence

the mesozoic tertiary evolution of the aquitaine basin the aquitaine basin situated in southwest france with an area of about 60 000 km 2 has the form of a triangle which opens towards the atlantic bay of biscay and is limited to the north by the hercynian basement of brittany and the massif central and to the south by the pyrenean tertiary orogenic belt beneath the tertiary sequence 2 km thick and which outcrops over much of the basin a mesozoic series up to 10 km thick rests generally on a tectonized hercynian basement but locally it covers narrow nw se trending post orogenic trenches of stephano permian age the mesozoic history can be subdivided into four major structural sedimentary episodes 1 during a triassic taphrogenic phase a continental evaporitic complex developed with associated basic magmatism 2 throughout the jurassic a vast lagoonal platform developed initially lower lias as a thick evaporitic sequence followed by a uniform shale carbonate unit indicating a relative structural stability 3 the end of the jurassic and the lower cretaceous saw a fragmentation of this platform due to an interplay between the iberian and european tectonic plates resulting in an ensemble of strongly subsident sub basins 4 during the upper cretaceous and until the end of the neogene the evolution of the aquitaine basin was influenced by the pyrenean orogenic phase with the development towards the south of a trench infilled by flysch which from the upper eocene is succeeded by a thick post orogenic molasse complex the main hydrocarbon objectives in the basin are situated in the jurassic platform e g the lacq giant gas field and the cretaceous sub basins e g the cazaux and parentis oil fields to date production has been about 4 times 10 7 m 3 of oil and about 15 times 10 10 m 3 of gas since the first gas discovery st marcet in 1939

further evidence for the development of photic zone euxinic conditions during mesozoic oceanic anoxic events periods in earth history characterized by extensive organic carbon deposition so called oceanic anoxic events oaes are the subject of considerable scrutiny insight into the extent of anoxic conditions in the water column has been provided by the reported occurrence of derivatives of isorenieratene a carotenoid found only in green sulphur bacteria and thus indicative of photic zone euxinia i e a water column containing free h 2 s in north atlantic deep sea sediments deposited during the cenomanian turonian boundary oae2 bonarelli event in this study we have used the distributions of chlorophyll and bacteriochlorophyll degradation products maleimides 1 h pyrrole 2 5 diones and high molecular weight porphyrins to examine further the cenomanian turonian boundary oae2 as well as other oaes of the early toarcian posidonienschiefer event and early aptian selli event in particular methyl isobutyl me i bu maleimide on structural grounds appears to be diagnostic of green sulphur bacteria this compound occurs in five of seven examined marls that record the early toarcian oae marche umbria italy further expanding the geographical range of toarcian sediments where evidence for photic zone euxinic conditions has been found me i bu maleimide occurs in three of six black shales spanning the livello selli marche umbria italy the type locality for the aptian oae1a providing the first evidence for photic zone euxinic conditions during this event with respect to the cenomanian turonian oae maleimide evidence for photic zone euxinic conditions was found in all the north atlantic sites investigated including those characterized by relatively organic lean sediments several tethyan sites and one site off western australia these data indicate that euxinic conditions were common in the water column during mesozoic oceanic anoxic events

paleomagnetic implications on the evolution of the tethys belt from the atlantic ocean to the pamirs since the triassic abstract we first re examined the apparent polar wander curves for stable eurasia and africa since the triassic these curves were then combined together with curves of north and south america according to the kinematics of the atlantic ocean and a synthetic polar wander curve was given then most of the paleomagnetic results from the tethys mobile belt from the atlantic to the pamirs were analysed several groups of plates microplates and blocks can be seen first relatively stable regions like maghreb and sicily which have not moved much then we have a group formed by iberia sardinia italy and to a lesser extent corsica and the western and central alps for these blocks movements are anticlockwise rotations chiefly driven by the anticlockwise rotation of africa but they are sometimes stronger to the east a major change takes place the north of the aegean sea and the ionian zone are clockwise rotated and these rotations are recent oligocene miocene for the first part pliocene to the present for the second part a major problem arises in turkey caucasus and iran paleomagnetic results indicate a position far to the south of eurasia and at the same time geological evidence is in favour of a position close to eurasia we discuss these discrepancies

a review of the history of the baltic sea 13 0 8 0 ka bp abstract the dynamic history of the baltic sea during the millennia following the last deglaciation has been one of the main topics for many generations of quaternary geologists around the baltic sea based on the present state of knowledge and certain hypotheses a model for the development during the baltic ice lake yoldia sea and ancylus lake stages are presented the oresund strait was the threshold of the initial stage of the baltic ice lake and was eroded down to bedrock as a result of the isostatic uplift the emerging threshold forced the baltic ice lake to rise above sea level at ca 12 0 ka bp this gradual up damming ended at ca 11 2 ka bp when the large glacial lake was lowered 5 10m by possible subglacial drainage at mt billingen a glacial readvance during the younger dryas ended a ca 400 year long land bridge between sweden and the continent by blocking the former drainage route once again the baltic ice lake had to rise above sea level to be drained over the oresund strait at ca 10 5 ka bp a gradual ice recession began and 200 years later when the receding ice sheet could not withhold the up dammed water masses the final drainage of the baltic ice lake occurred which rapidly lowered the water level within the baltic basin with ca 25 m and ended the baltic ice lake stage the next stage the yoldia sea was characterized by a complex pattern of relative sea level changes with large differences within the baltic basin a very restricted baltic sea in the south and thus an extensive landbridge at ca 9 9 ka bp a short 100 200 years saline ingression is seen in the baltic sediment records from stockholm in the north to the southernmost parts of the yoldia sea the gradually shallower strait in south central sweden the narke strait ended the saline influence 300 400 years later the two remaining outlets west of lake vanern gota alv and otteid steinselva had become too shallow to swallow the outflowing yoldia sea waters at this stage the baltic lake vanern level could thus not fall in pace with the relative sea level fall outside the outlet areas this was the isolation of lake vanern and the baltic from the sea and the beginning of the ancylus lake since the water depth of the larger gota alv outlet had to be more or less maintained the ancylus lake level had to rise in pace with the uplift of the outlet region this caused a significant and rapid transgression 10 30 m in ca 300 years in the southern baltic which flooded large areas with recently immigrated pine forests since the oresund strait during the yoldia sea stage had been uplifted more than southerly areas the ancylus transgression ended with a new drainage pathway at ca 9 2 ka bp through the darss sill area in the southern baltic and northwards through the store belt strait this so called dana river had cut off the former large land bridge the quaternary deposits of this new threshold were eroded and a fairly rapid regression set in at ca 9 0 ka bp the dana river had eroded down to the sea level which isolated lake vanern from the ancylus lake and created a land bridge between southern sweden and northwards ca 800 years later when the sea level rose above the oresund threshold marine water could enter the baltic and at ca 8 0 ka bp brackish water characterized the southern baltic this marks the end of the ancylus lake

a tomographic image of indian lithosphere break off beneath the pamir hindukush region summary the p and s seismic anomalies in the upper mantle beneath the pamir hindukush collision zone and surrounding areas are investigated using more than 4 10 5 traveltimes from 5775 events located in the study region recorded by the stations of the worldwide seismic network and reported in the isc catalogue all available epicentral distance ranges of seismic rays are considered all sources are relocated using an algorithm which includes the double difference method in addition source parameters are corrected in the main inversion step simultaneously with the velocity models the high reliability of the resulting p velocity images is confirmed by various tests the s model provides much smoother patterns which are however generally consistent with p anomalies our model shows a complex image of lithospheric plate under the study region under sw hindukush the northwards subducting indian plate is imaged throughout the upper mantle and transition zone further to the ne within a 300 km wide zone the upper part of the plate overturns and then the slab breaks off after it narrows at 250 km depth the tomographic model also provides evidence for the southward subduction of the lithosphere beneath the southern tien shan down to at least 250 km depth to the north of tarim we observe a northward dipping of the tarim plate down to 500 km depth at the crustal depth our model shows alternating belts of high and low velocities parallel to the main thrusting faults which indicate complex crustal structure in this region

structure and dynamics of the upper mantle beneath the alpine himalayan orogenic belt from teleseismic tomography abstract the upper mantle structure beneath the alpine himalayan orogenic belt ahb at depths from 100 to 500 km has been studied by its tomographic inversion of p wave travel times from earthquakes that occurred in the region and were recorded by the worldwide seismological network at teleseismic distances from the isc catalogues the resulting maps were obtained as a sum of independent inversions in about 60 overlapping blocks 600 800 km in diameter this approach is similar to high frequency spatial filtration and allows investigation of much subtler structures than in global inversion high velocity linear patterns along the ahb have been interpreted as traces of continental or oceanic lithosphere sinking to the upper mantle under the effect of active regional compression the tomographic maps show well pronounced traces of subduction in the region of cretan arc hindukush and burma also confirmed by independent data as well as other less certain evidence of subduction positive anomalies in the western part of the ahb are attributed to subduction in the area of cyprus and along the caucasus kopet dagh lut plate in the tomographic maps one can see traces of the subducted indian slab under western part of himalayas beneath eastern himalayas the upper mantle is rather hot zones of sinking lithosphere are traceable around the tarim block a strong low velocity anomaly in mongolia is apparently related to the hangai plume whose existence was inferred from geological and geophysical evidence

seismic tomographic imaging of p and s waves velocity perturbations in the upper mantle beneath iran summary the inverse tomography method has been used to study the p and s waves velocity structure of the crust and upper mantle underneath iran the method based on the principle of source receiver reciprocity allows for tomographic studies of regions with sparse distribution of seismic stations if the region has sufficient seismicity the arrival times of body waves from earthquakes in the study area as reported in the isc catalogue 1964 1996 at all available epicentral distances are used for calculation of residual arrival times prior to inversion we have relocated hypocentres based on a 1 d spherical earth s model taking into account variable crustal thickness and surface topography during the inversion seismic sources are further relocated simultaneously with the calculation of velocity perturbations with a series of synthetic tests we demonstrate the power of the algorithm and the data to reconstruct introduced anomalies using the ray paths of the real data set and taking into account the measurement errors and outliers the velocity anomalies show that the crust and upper mantle beneath the iranian plateau comprises a low velocity domain between the arabian plate and the caspian block this is in agreement with global tomographic models and also tectonic models in which active iranian plateau is trapped between the stable turan plate in the north and the arabian shield in the south our results show clear evidence of the mainly aseismic subduction of the oceanic crust of the oman sea underneath the iranian plateau however along the zagros suture zone the subduction pattern is more complex than at makran where the collision of the two plates is highly seismic