the flank margin model for dissolution cave development in carbonate platforms the bahama islands contain many abandoned dissolution caves at elevations between two and seven metres above current sea level the development of dissolution caves in tropical carbonate islands is dependent on the position and nature of the freshwater lens lens position is controlled by sea level which in stable carbonate platforms like the bahamas is a function of glacioeustatic sea level still stands caves in the bahamas that are currently subaerial must have developed during past higher sea levels during the late quaternary sea levels higher than present have been relatively short lived and that limits the amount of time that a freshwater lens could be situated at the elevation required for the cave formation the bahama islands are low lying landforms where only aeolian ridges extend to elevations higher than six metres above current sea level past high sea level events greatly reduced the exposed land area of the bahama islands thus also limiting both the catchment for and size of freshwater lenses caves must be younger than the rock in which they are developed most subaerial bahamian caves are found in limestones that are less than 150000 years old development of large dissolution caves under these limitations of time and lens size requires a powerful dissolutional mechanism the mixing of discharging freshwater with tide pulsed incoming marine water under the flanks of emergent dune ridges may have produced the conditions necessary bahamian caves formed by this process are phreatic chambers with complex interconnections and blind tubes their presence demonstrates that significant dissolution can occur rapidly as a result of the mixing of fresh and marine waters beneath small carbonate islands

the fold test in palaeomagnetism summary the fold test suggested by mcelhinny is shown to be inappropriate more correctly one should determine whether the mean direction of a group of sites from one limb of a fold may be distinguished statistically from the mean direction of a group of sites from another limb details of the application of this test are given with examples it is shown that the test indicates significance under far less severe folding than does the test suggested by mcelhinny

spreading evolution of the troodos ophiolite cyprus some recent developments particularly the recognition of transform tectonized and nontransform tectonized fabrics close to the southern troodos transform fault provide a framework for a new evolutionary model of the troodos ophiolite this model proposes that most of the ophiolite formed at the solea axis against a dextrally slipping southern troodos transform spreading was largely accommodated by magmatic accretion the ridge then jumped to the east a last phase of amagmatic stretching driving normal faulting above a detachment horizon in the solea graben a ridge jump boundary separates the old crust formed at the solea axis from the new crust generated at the outside corner of the new ridge with a dextrally slipping continuation of the southern troodos transform the final episode involved extension of the crust generated at the new ridge to form the larnaca graben in the eastern part of the ophiolite

multiple tectonic rotations and transform tectonism in an intraoceanic suture zone sw cyprus abstract new palaeomagnetic data from the late cretaceous neotethyan troodos ophiolite and related units in sw cyprus provide compelling evidence that transform tectonism is recorded outside the main outcrop of the fossil southern troodos transform fault zone sttfz high level intrusive and extrusive sequences were sampled along the sw margin of the troodos massif and in ophiolitic slivers preserved along arcuate fault lineaments further to the south and west these units show cross cutting relationships with corresponding differences in remanent magnetisation directions characteristic of syn magmatic rotation in an active transform setting net tectonic rotation analyses allow decomposition of the total rotation at these sites into early and late components early transform related rotations are consistently clockwise in agreement with all other studies of rotations associated with the sttfz further to the east late rotations and the net rotations derived at localities where cross cutting relationships were not present are regarded as composite in origin the composite rotation axes closely relate to the orientation of observed regional structures in these circumstances additional constraints are used to attempt geologically viable interpretations the overall distribution of transform related rotations steeply and shallowly plunging rotation axes and spreading axis related rotations sub horizontal rotation axes is comparable with that along the sttfz and adjacent parts of the troodos massif this is most readily explained by simple along strike extension of the primary spreading axis and transform fabrics into sw cyprus with minor late disruption by high angle dextral shear zones and neotectonic graben systems

spreading structure of the troodos ophiolite cyprus some paleomagnetic constraints it has been suggested that grabens on the northern flank of the troodos ophiolite formed by listric faulting in an oceanic environment and represent axial valleys fossilized by ridge jumping this paleomagnetic survey of the solea graben was carried out to constrain the structural interpretation an analysis was devised which restores both the dikes sampled to vertical and the primary remanent magnetizations to a previously derived structurally corrected remanent magnetization direction typically two solutions for the original dike orientation and the pole and angle of net rotation are obtained for each dike sampled these solutions can be separated if a locally consistent original dike strike is assumed reasons are discussed for the selection of the solution that gives an original northwesterly dike strike results are consistent with a graben rotations are up to 78 at the sites studied rotation vectors are subhorizontal and subparallel to the original dike strike suggestive of an axial process for the development of the structure however on the basis of field observations an alternative mode of origin is proposed invoking ephemeral extreme upper crustal extension by listric faulting on the west flank of an intermediate to fast spreading axis the grabens being formed by antithetic faulting

foraminifera in elevated bermudian caves provide further evidence for 21 m eustatic sea level during marine isotope stage 11 abstract two hypotheses have been proposed to explain the origin of marine isotope stage mis 11 deposits in small bermudian caves at 21 m above modern sea level 1 a 21 m mis 11 eustatic sea level highstand and 2 a mis 11 mega tsunami event importantly the foraminifera reported in these caves have yet to be critically evaluated within a framework of coastal cave environments after statistically comparing foraminifera in modern bermudian littoral caves and the mis 11 calonectris pocket a 21 m cave to the largest available database of bermudian coastal foraminifera the assemblages found in modern littoral caves and calonectris pocket a cannot be statistically differentiated from lagoons this observation is expected considering littoral caves are simply sheltered extensions of a lagoon environment in the littoral zone where typical coastal processes waves storms homogenize and rework lagoonal reefal and occasional planktic taxa fossil protoconchs of the bermudian cave stygobite caecum caverna were also associated with the foraminifera these results indicate that the mis 11 bermudian caves are fossil littoral caves breached flank margin caves where the total mis 11 microfossil assemblage is preserving a signature of coeval sea level at 21 m brackish foraminifera polysaccammina pseudothurammina and anchialine gastropods 95 300 individuals indicate a brackish anchialine habitat developed in the elevated caves after the prolonged littoral environmental phase the onset of sea level regression following the 21 m highstand would first lower the ancient brackish ghyben herzberg lens

distortions rotations and crustal thinning at ridge transform intersections when an oceanic ridge intersects a transform fault the newly formed oceanic crust may be severely distorted frequently exhibiting major rotations of fault blocks1 4 such effects typically extend over a 10 km wide strip parallel to the transform by contrast studies of contemporary oceanic transforms suggest that deformation is restricted to a single fault trace within the transform domain5 9 this apparent inconsistency can be reconciled if the rotations occurred at the ridge transform intersection during accretion of the crust here i develop a kinematic model that considers the effect of an ephemeral period of stretching on a region that broadens as the transform is approached along the ridge the strains calculated from this model indicate extension at the ridge simple shear at the transform and composite strains in the region of distributed deformation the model predicts very rapid rotation rates 100 in 104 105 yr the implications for the topography and structure of ridge transform intersections are considered and the alternating periods of extension by stretching and by intrusion are illustrated by reference to contemporary transforms on the mid atlantic ridge the model may also explain the common occurrence of cross cutting dykes near transform faults in ophiolites

spreading structure of the troodos ophiolite cyprus orientations of dikes within the sheeted dike complex of the troodos ophiolite reveal primary spreading structure produced at a complex ridge transform intersection three structural grabens are defined by listric and planar normal faults and rotated dikes that dip symmetrically toward graben axes faults flatten at depth into a detachment within the upper parts of the plutonic complex large exhalative massive sulfide deposits occur within the pillow sections of two of the grabens and appear to be associated with underlying altered and mineralized normal fault zones that channeled hydrothermal fluids we suggest that the grabens are fossil axial valleys produced by successive eastward jumps of an approximately north trending present coordinates slow spreading ridge crest a simple model for ridge migration indicates eastward jumps of 8 13 km changes in ridge orientation are suggested by changes in trends of dikes and graben axes comparison of the pattern of dikes near the arakapas fault zone with the structure of active ridge transform intersections suggests that the fault is a right offset sinistral transform in contrast to earlier models in which a ridge to the west of the exposed troodos complex was proposed

the tectonic history of the nigde kirsehir massif and the taurides since the late mesozoic paleomagnetic evidence for two phase orogenic curvature in central anatolia the nigde kirsehir massif known also as the central anatolian block is bordered by the sutures of the neotethys ocean the massif suffered several deformation phases during and after the consumption of the surrounding oceans and the post collisional events of the continental pieces of anatolia in latest cretaceous to miocene previous paleomagnetic studies on the nigde kirsehir massif and its surroundings displayed either insufficient data or have claimed large rotations and or remagnetization in order to understand the tectonic history of the nigde kirsehir massif and its adjacent blocks we have sampled 147 different sites in the age range of upper jurassic to miocene from the nigde kirsehir massif throughout its w sw and e se boundaries and the central southeastern taurides the results display that except the limestones in central taurides all rocks examined carry a primary magnetization among these an important finding is that rotations between the massif and the central eastern taurides indicate an oroclinal bending with counterclockwise rotation of r 41 1 7 6 in the se and clockwise rotation of r 45 9 9 3 in the central taurides from upper cretaceous rocks with respect to the african reference direction paleomagnetic rotations in the se taurides are compatible with the vergent direction of the thrusts generated from consumption of the intra tauride ocean prior to post collisional convergence between taurides and the massif in the central taurides it has been shown that the clockwise rotation of 45 9 9 3 started in middle eocene because of a remagnetization in upper creataceous limestones the deformation was linked to the final closure of the southern neotethys and the collision between the african and eurasian plates in the nigde kirsehir massif counterclockwise rotation up to 25 5 7 3 is recognised during middle eocene and interpreted in terms of block rotation together with the taurides after the miocene a counterclockwise rotation of 16 8 3 9 along the eastern taurides shows that this area was mostly affected by the westward movement of anatolia despite the nigde kirsehir massif and its sw w area the central taurides which is recognised as stable with counterclockwise rotation less than 10

is the troodos ophiolite cyprus a complete transform fault bounded neotethyan ridge segment we report new paleomagnetic data from the sheeted dike complex of the troodos ophiolite cyprus that indicate that its northern limit is marked by a hitherto unrecognized oceanic transform fault system the style magnitude and scale of upper crustal fault block rotations in the northwestern troodos region mirror those observed adjacent to the well known southern troodos transform fault zone along the southern edge of the ophiolite a pattern of increasing clockwise rotation toward the north coupled with consistent original dike strikes and inclined net rotation axes across this region is compatible with distributed deformation adjacent to a dextrally slipping transform system with a principal displacement zone just to the north of the exposed ophiolite combined with existing constraints on the spreading fabric this implies segmentation of the troodos ridge system on length scales of 40 km and suggests that a coherent strip of neotethyan lithosphere representing a complete ridge segment bounded by transforms has been uplifted to form the currently exposed troodos ophiolite moreover the inferred length scale of the ridge segment is consistent with formation at a slow spreading rate during tethyan seafloor spreading and with a supra subduction zone environment as indicated by geochemical constraints

miocene remagnetisation of carbonate platform and antalya complex units within the isparta angle sw turkey abstract a palaeomagnetic study has been carried out within the mesozoic and tertiary units of the relatively autochthonous carbonate platforms and the allochthonous deep sea volcanics and sediments of the antalya complex exposed around the isparta angle sw turkey the antalya complex is interpreted as a mosaic of carbonate platforms basinal sediments volcanic and ophiolitic rocks which formed within a southerly strand of the neotethyan ocean adjacent to gondwana the results indicate a widespread remagnetisation event negative fold tests show that the remanence at most sites is of secondary origin e g within the cirali lavas the magnetisation is carried by magnetite of presumed authigenic origin the remagnetisation event is believed to have occurred in the early middle miocene burdigalian langhian it was possibly triggered by the migration of orogenic fluids ahead of the advancing lycian nappes during their emplacement onto the carbonate platforms subsequent to remagnetisation a large segment of the isparta angle underwent an anticlockwise rotation of 30 this rotation is attributed to the overall convergence and bending of the hellenic arc and the final stages of emplacement of the lycian nappes during the late miocene in agreement with previous studies previously southerly palaeolatitudes were inferred from late triassic extrusives of the godene zone calbali dag unit the post folding magnetisation identified here within the cirali lavas of the godene zone to the south implies that these low palaeolatitudes result from the inappropriate application of structural tilt corrections the available data cannot be used to substantiate an origin for the antalya units south of the equator in the early mesozoic instead a position close to the northern margin of gondwana is indicated

vertical distribution and alteration of dikes in a profile through the troodos ophiolite in situ oceanic crust at intermediate depths of from one to five km is presently largely inaccessible to continuous examination and sampling except in the possibly special circumstances of major transform faults the study of ophiolites over this interval where thin sub vertical dikes are usually important may provide guidance to the nature of in situ oceanic crust at these depths the likelihood that similarities exist between in situ and ophiolitic oceanic crust has recently been strengthened by the possible identification of a dike complex below 0 8 km depth in dsdp hole 504b1 sub vertical basic dikes occur over a 4 6 km depth interval from 0 2 to 4 8 km crustal depth in a profile through the troodos cyprus ophiolite exponential growth and arctangent decay in dike density occur over 2 3 km and 1 0 km intervals respectively secondary magnetite is the dominant dike magnetic material of the dikes and associated screens these results have implications for the construction alteration history and magnetization of in situ oceanic crust at intermediate depths

paleomagnetic arguments for block rotations along the arakapas fault cyprus paleomagnetic data from the sheeted dike complex north of the arakapas fault reveal significant internal rotations the north south trending dikes have remanent magnetization directions close to the well known westerly paleomagnetic direction of the troodos massif whereas the east west trending dikes near the arakapas fault have northerly remanent magnetization directions the paleomagnetic data are in agreement with the apparent clockwise rotation of the dikes contrary to recent geological analyses which postulate that the pattern of dike trends is due to dike injection into a sigmoidal stress field along a sinistral transform fault the paleomagnetic results indicate clockwise rotations about vertical axes in response to a dextral shear in addition to the rotations around vertical axes small rotations around subhorizontal axes are inferred from the paleomagnetic data for tilted dikes thus these data reinforce the vertical intrusion hypothesis

a 20 m middle pleistocene sea level highstand bermuda and the bahamas due to partial collapse of antarctic ice marine deposits at 20 3 m on the tectonically stable coastlines of bermuda and the bahamas support the hypothesis of a partial collapse of the antarctic ice sheet during the middle pleistocene beach sediments fill a sea cave at 22 m in bermuda and horizontal fenestrae filled beds crop out on platforms at two sites as high as 21 m in eleuthera bahamas carbonate beach sands are bound by an early generation of isopachous fibrous cement that is characteristic of a phreatic marine environment amino acid racemization and tims thermal ionization mass spectrometry dates constrain the age of the deposits to between 390 and 550 ka while proxy evidence supports a correlation with oxygen isotope stage 11 this direct geologic evidence of a 20 decrease in polar ice during the middle pleistocene has important implications for the stability of ice sheets during warm interglaciations

the late cretaceous palaeolatitude of the neotethyan spreading axis in the eastern mediterranean region abstract a compilation of available palaeomagnetic data from the troodos cyprus and baer bassit syria ophiolitic terranes of the eastern mediterranean tethyan orogenic belt is presented the ophiolites represent fragments of oceanic lithosphere generated at a neotethyan spreading axis in the late cretaceous although debate continues over the tectonic setting of this spreading axis and its position within the eastern mediterranean palaeogeography two types of model reconstructions have been proposed type 1 the ophiolites formed in a southerly neotethyan basin by spreading above an oceanic subduction zone the baer bassit ophiolite was then emplaced a relatively short distance tens of kilometers southwards on to the arabian continental margin leaving the troodos ophiolite isolated in an intra oceanic setting to the west and type 2 the ophiolites formed in a northerly neotethyan basin by spreading at a normal oceanic ridge with subsequent large scale thrusting hundreds of kilometers to the south of emplaced ophiolites over microcontinental fragments to reach their present positions palaeomagnetic determination of the palaeolatitude of the neotethyan spreading axis is therefore of considerable interest previous palaeomagnetic analyses have demonstrated the presence of significant and in some cases extreme relative tectonic rotations of a variety of origins in both ophiolites to allow palaeomagnetic data from these rotated units to be combined an inclination only formulation of the palaeomagnetic tilt test is employed this provides unequivocal evidence that both ophiolites retain pre deformational remanent magnetizations which are interpreted as original ocean floor magnetizations acquired close to the time of crustal formation in the late cretaceous the mean inclinations of 37 0 2 6 for the troodos terrane and 41 1 3 4 for the baer bassit terrane indicate respective palaeolatitudes for the spreading axes of 20 6 n 1 8 and 23 6 n 2 5 consistent with a late cretaceous position between the arabian and eurasian margins these data together with a well defined palaeolatitude of 25 5 n 4 5 for the eastern pontides previously reported in the literature provide constraints which must be incorporated in any successful tectonic reconstruction of the eastern mediterranean tethys the implications of these constraints for type 1 and 2 models are discussed using a series of plate tectonic cross sections constructed along a line extending northwards from the arabian continental margin in the absence of palaeomagnetic data from late cretaceous rocks of the eastern taurides however it is presently impossible to use these palaeolatitudinal constraints to resolve the root zone debate on a purely palaeomagnetic basis solutions which satisfy the constraints may be found for both types of model reconstruction additional published field based geological considerations however strongly support models in which the troodos and baer bassit and other southerly ophiolites were generated in a southern neotethyan basin rather than those involving generation in a northerly basin and subsequent large scale thrust displacement to the south

paleomagnetic constraints on the formation of the solea graben troodos ophiolite cyprus abstract the solea graben on the northern flank of the troodos ophiolite cyprus is a 15 20 km wide asymmetric structure primarily defined by dike attitudes in the sheeted dike complex the wider western portion of the graben consists mainly of gently dipping dikes while the eastern portion is narrow and consists of blocks of dikes with widely varying attitudes using a method which restores the sampled dikes to vertical and the primary remanent magnetizations to a previously known stable remanent magnetization direction for the troodos complex we have calculated rotation axes and amounts of rotation for the dikes the rotation axes for dikes in the western portion of the solea graben are subhorizontal and subparallel to the original strikes of the dikes in the eastern portion the rotation axes have varying attitudes including some which are very steep our results are consistent with field observations that suggest that the western solea graben formed by listric normal faulting near the axis of a spreading center with rotation of the dikes above a detachment surface across the graben axis on the eastern portion more intense intrusive activity and minor normal faulting resulted in less rotation about subhorizontal axes and some rotations about vertical axes

late palaeozoic marginal basin and subduction accretion the palaeotethyan kure complex central pontides northern turkey the kure complex located in the central pontides of northern turkey is a c 20 km thick pile of thrust imbricated deep sea sediments intercalated with a dismembered ophiolite the ophiolitic rocks include serpentinized harzburgite massive gabbro cumulate and isotropic sheeted dykes and basic volcanic rocks the extrusive rocks are mainly pillow lavas sheet flows and lava breccias geochemical evidence of immobile major and trace elements and pyroxene chemistry indicate mid ocean ridge mor and volcanic arc basalt vab compositions and suggest that the kure ophiolite was generated above a subduction zone chrome spine1 analysis also supports this interpretation in some thrust sheets the extrusives are depositionally overlain by hemi pelagic shales passing up into terrigenous turbidites and shales which are up to several hundred metres thick in intact successions cyprus type massive sulphides interpreted as precipitates from black smokers are located along the lava sediment contact individual intact sediment units up to several kilometres thick within the kure complex are separated by narrow up to 10 m wide zones of intense shearing layer parallel extension and melange formation asymmetrical folds reverse faults thrusts and duplex structures throughout the kure complex indicate mainly northwards emplacement the kure complex is thought to have opened in the late palaeozoic as a marginal basin above a northward dipping palaeotethyan subduction zone located along the southern margin of eurasia the kure marginal basin later closed in response to inferred southward subduction leading to development of an accretionary prism prior to late jurassic time the kure complex is unlikely to represent the main palaeotethyan suture as has been suggested in some earlier tectonic reconstructions regional comparisons with dobrogea crimea and caucasus suggest the kure basin opened then closed along a south eurasia active margin

palaeomagnetic evidence for clockwise rotations related to dextral shear along the southern troodos transform fault cyprus abstract the southern troodos arakapas fault represents a late cretaceous oceanic fracture zone which was locally disrupted during late cretaceous eocene palaeorotation of the troodos microplate opinions are divided as to the sense of displacement along the transform fault and the exact timing of initiation of palaeorotation palaeomagnetic studies of turonian zeolite facies lavas and sediments exposed within the transform domain have revealed considerable variations in the declination of remanent magnetisation between sites along the arakapas fault belt the western margin of the limassol forest complex and the eastern flank of the troodos ophiolite at seven sites clockwise rotation of fault blocks has occurred about steeply inclined axes one fault block at the western end of the arakapas fault belt has experienced a net anticlockwise rotation while at six other sites only simple tilting about sub horizontal axes is indicated the overall clockwise sense of block rotation and initial dyke strikes calculated at three sites are consistent with right lateral slip along the transform cross cutting relationships revealed by the analysis of one site demonstrate that these rotations took place during crustal genesis and are not a product of post spreading disruption of the fracture zone sites located further south in the eastern limassol forest complex show no relative rotation with respect to the main troodos ophiolite to the north and have experienced only simple tilting however if our results are considered in conjunction with existing palaeomagnetic data from the area it appears that the entire area lay within a complicated zone of localised and predominantly clockwise block rotations produced by dextral slip along the transform some areas were rotated by over 100 about steeply inclined axes whereas others experienced only simple tilting the whole area was later subjected to a bulk 90 anticlockwise rotation along with the troodos microplate data obtained from the umbers and radiolarites perapedhi fm exposed on the eastern flank of the limassol forest block indicate that at least 30 and possibly up to 45 of this 90 rotation took place over a maximum of 15 ma

origin and emplacement of the late cretaceous baer bassit ophiolite and its metamorphic sole in nw syria abstract the baer bassit ophiolite of inferred late cretaceous age was emplaced from the south tethys ocean onto the leading edge of the arabian continental margin in latest cretaceous maastrichtian time dismembered sequences in different thrust sheets can be correlated to produce a complete ophiolite sequence with a metamorphic sole at the base overlain in turn by upper mantle tectonite rare cumulates massive and layered gabbros localized high level plagiogranites sheeted dykes basic extrusives and minor fe mn sediments umbers the restored ophiolite sequence is similar to that of the more intact troodos and hatay ophiolites but dissimilar to oman the baer bassit extrusives are magnesian and strongly depleted comparable to primitive island arc tholeiites and some boninitic lavas which favours a subduction related origin a well developed metamorphic sole is divisible into high grade amphibolite facies assemblages in the north and lower grade greenschist facies assemblages in the centre of the region but no complete inverted metamorphic gradient is preserved in any one local area the protoliths of both the high grade amphibolites and lower grade rocks greenschists are interpreted as alkali basalts and pelagic sediments including chert similar to the volcanic rocks in an underlying unmetamorphosed melange the metamorphic fabrics progressively evolved from ductile to brittle during tectonic transport towards the southeast most of the metamorphic fabrics evolved during intense shearing but some of the alkaline metabasites apparently were metamorphosed under relatively static strain conditions the apparent absence of preserved inverted metamorphic gradients in baer bassit may reflect a complex deformation history during emplacement alternatively differing p t conditions may be recorded at different depths at the base of the over riding mantle wedge during emplacement the front of the ophiolite was tectonically imbricated and overthrust by the main ultramafic slab bassit massif the thickest massif baer is underlain by a high grade metamorphic sole and was internally shortened but without thrust duplication of the entire ophiolite sequence following covering by late maastrichtian palaeogene marine calcareous sediments the area was subjected to mid tertiary regional folding this was followed by neogene dominantly left lateral strike slip deformation along the african eurasian plate boundary extending from south of cyprus to the dead sea transform fault as a result the originally emplaced thrust sheets were dissected into three main composite units baer bassit and the southeastern units separated by strongly faulted and sheared ophiolitic blocks and unmetamorphosed volcanic sedimentary melange

volcanic glass compositions of the troodos ophiolite cyprus fresh volcanic glass is preserved throughout the extrusive section of the troodos ophiolite which indicates that the lavas have not been pervasively metamorphosed glass compositions reveal the existence of two major magma suites apparently corresponding to distinct stratigraphic intervals the basal 400 500 m of the sequence consists of an andesite dacite rhyolite assemblage containing abundant hyaloclastites the remainder of the section comprises a basalt basaltic andesite assemblage with high mgo and low tio 2 and total iron the lower sequence is interpreted as an evolved arc tholeiite suite the upper has some similarities to boninitic lavas the close association in time and space of these two suites is similar to that observed in the mariana and bonin arcs and suggests that all of the troodos lavas were erupted in a subduction zone environment most probably in an incipient arc or fore arc

paleomagnetic results along the bitlis zagros suture zone in se anatolia turkey implications for the activation of the dead sea fault zone abstract the tectonic evolution of se anatolia is associated with the collision between the taurides and the arabian platform in the early cenozoic after the final closure of the southern branch of the neotethys ocean during late cretaceous to early eocene times the ongoing deformation was characterized by northward movement of arabia followed by westward extrusion of anatolia having been displaced along the northern and eastern anatolian transform faults the neotectonic deformation history between the anatolian plate and the arabian platform since the closure of the southern neotethyan oceanic basin from late cretaceous to present has not been studied in detail paleomagnetically therefore we carried out a paleomagnetic study of mesozoic and cenozoic rocks at 34 localities along the bitlis zagros suture zone in se anatolia located in the boundary region between the taurides and the arabian platform and delimited by the dead sea fault paleomagnetic results from the area show clockwise rotations of 35 6 14 1 and 26 7 8 0 with respect to the african plate from upper jurassic lower cretaceous and upper cretaceous limestones respectively the paleomagnetic results indicate also an earlier deformation opening due to the dead sea fault zone dsfz farther north on the tauride block counterclockwise rotation of 34 5 12 5 is recorded by upper cretaceous limestones in the se of the study area on the northern margin of arabia however smaller counterclockwise rotations of 12 3 8 3 and 2 5 10 0 in late cretaceous and 12 7 13 6 in middle eocene rocks show relative tectonic stability middle miocene rocks close to the suture zone show counterclockwise rotation by about 39 4 10 9 while farther away from the suture zone counterclockwise rotations of 21 9 9 9 and 7 5 5 8 are observed paleolatitudinal motion from south to north from the late jurassic to the present is in concordance with the apparent polar wander path of eurasia and africa

reply to mega highstand or megatsunami discussion of mcmurtry et al elevated marine deposits in bermuda record a late quaternary megatsunami sed geol 200 2007 155 165 by paul j hearty and storrs l olson our recent paper mcmurtry g m tappin d r sedwick p n wilkinson i fietzke j and sellwood b 2007a elevated marine deposits in bermuda record a late quaternary megatsunami sedimentary geol 200 155 165 critically re examined elevated marine deposits in bermuda and concluded that their geological setting sedimentary relations micropetrography and microfaunal assemblages were inconsistent with sustained intertidal deposition instead we hypothesized that these deposits were the result of a large tsunami that impacted the bermuda island platform during the mid pleistocene hearty and olson hearty p j and olson s l in press mega highstand or megatsunami discussion of mcmurtry et al elevated marine deposits in bermuda record a late quaternary megatsunami sedimentary geology 200 155 165 2007 aug 07 sedimentary geol 200 155 165 in their response attempt to refute our conclusions and claim the deposits to be the result of a 21 m eustatic sea level highstand during marine isotope stage mis 11 in our reply we answer the issues raised by hearty and olson hearty p j and olson s l in press mega highstand or megatsunami discussion of mcmurtry et al elevated marine deposits in bermuda record a late quaternary megatsunami sedimentary geology 200 155 165 2007 aug 07 sedimentary geol 200 155 165 and conclude that the bermuda deposits do not provide unequivocal evidence of a prolonged 21 m eustatic sea level highstand rather the sediments are more likely the result of a past megatsunami in the north atlantic basin

new evidence and model on the evolution of the southeast anatolian orogen this paper describes the orogenic evolution of the southeast anatolian orogenic belt based mostly on new geologic data collected from its constituent tectonic units in the course of new mapping programs of the past decade the southeast anatolian orogenic segment of the alpides may be divided into three approximately east west trending zones from south to north they are the arabian platform followed by a zone of imbrication and then a zone of nappes the arabian platform includes a mostly marine sedimentary succession deposited from early cambrian to middle miocene time the zone of imbrication is a narrow belt sandwiched between the arabian platform and the zone of nappes it consists of imbricated thrust slices emplaced onto a late cretaceous to early miocene sequence the zone of nappes is the highest tectonic unit consisting of two stacks of nappes simply designated the lower and upper nappes the lower nappe is represented by the slices of a polyphase metamorpbic ophiolitic assemblage and the maden group the upper nappe rests on the lower nappe and is represented by the bitlis and poturge metamorphic massifs southeastern anatolia underwent two major episodes of alpide deformation the first occurred during the late cretaceous period when ophiolite was emplaced on the arabian platform this event was not the consequence of a continental collision the ophiolite obduction onto the arabian platform was followed by a regionwide extension and a new marine transgression over the platform immediately after the ophiolite obduction the second episode of deformation occurred during middle eocene miocene time in two distinct stages as a result of the progressive elimination and complete closure of the ocean s which led to the collision between the zone of nappes located to the north being a part of eurasia and the arabian plate the maden marginal basin formed north of the subduction zone that eliminated the ocean between eurasia and arabia along the southern margin of the taurus belt and abutted the arabian plate much later during the final collision the second episode of deformation formed the present orogenic segment leading to the amalgamation of different tectonic units these amalgamated nappes collided with the arabian plate and welded onto it at the latest stage of the orogenic evolution during the miocene epoch

statistical significance of the fold test in palaeomagnetism summary the significance of the change in direction dispersion on applying the fold test in palaeomagnetism is used as the criterion for deciding whether or not the fold test has statistical significance a set of tables is compiled which can be used for quick application of the test

structure of a fossil ridge transform intersection in the troodos ophiolite recent palaeomagnetic studies of sheeted dykes adjacent to the east west trending southern troodos transform fault of cyprus have demonstrated significant clockwise block rotations which are most easily interpreted as being due to drag induced by dextral strike slip faulting along the transform1 6 we show here that such rotations have not occurred along the entire length of the transform instead to the west of the areas previously studied the sheeted dykes have been subjected to simple tilting only indicating normal faulting but no strike slip the changeover between these two domains of differing structural styles near the village of mandria is approximately in line with the centre of the solea graben a north south trending structure within the troodos massif which has previously been interpreted as a fossil ridge axis7 we suggest that the mandria area represents a fossilized ridge transform intersection and present the results of a detailed field investigation of the area together with preliminary palaeomagnetic data to determine the relationship between tectonism and magmatism at such plate boundary zones we use our findings to test a recent theoretical model8 of deformation processes at ridge transform intersections and show that distributed deformation due to block rotation is largely confined to the ridge transform corner itself

extreme tectonic rotations within an eastern mediterranean ophiolite baer bassit syria palaeomagnetic results from 27 sites at five localities within the dismembered bae r bassit ophiolite of northern syria are presented the ophiolite forms part of a series of thrust sheets emplaced over mesozoic carbonates of the arabian platform in the middle maastrichtian a positive inclination only area wide tilt test applied to four locality mean remanences and positive fold and reversal tests from palaeohorizontal units pillow lavas lava flows within one of these localities indicate that the ophiolite preserves pre deformation magnetisations variable directions of remanence between localities demonstrate that the ophiolite has experienced extreme relative anticlockwise rotations on a kilometric scale within the most extensively sampled ophiolite massif bassit sheet there is a progressive increase in rotation from north to south the southernmost units at the lowest structural level in the imbricate thrust stack record the highest rotation exceeding 200 although tectonic rotation during imbricate thrusting has been reported in a number of orogenic belts the pattern of rotations in the bassit sheet is difficult to explain by differential thrust sheet rotation instead regional comparisons with the hatay ophiolite of southern turkey and the troodos ophiolite of cyprus suggest that a significant component of rotation may be ascribed to intraoceanic deformation of a coherent region of oceanic crust within the southern neotethyan basin prior to ophiolite emplacement the partially rotated bae r bassit ophiolite was then emplaced and structurally dismembered by thrust faulting during the late tertiary the ophiolitic units were further rotated during the initiation and development of a major sinistral strike slip fault zone linking the cyprus subduction zone to the dead sea transform system the extreme rotations observed in the study are therefore of composite origin and reflect the complex development of structural fabrics within the ophiolite 2002 elsevier science b v all rights reserved

kinematics of oceanic thrusting and subduction from basal sections of ophiolites the structural analysis of high stress deformation at the base of the peridotite section in many ophiolites in suture zones enables the kinematics of oceanic convergence responsible for the suture to be defined this deformation results from the thrusting over oceanic crust of a young lithosphere involved in a subduction process flow plane flow line sense of shear related to the thrusting are geometrically deduced from the study of mineral preferred orientations in the basal peridotite and in the quartzites belonging to the amphibolite sole

palaeorotation of the troodos microplate cyprus the troodos ophiolite represents one of the best preserved fragments of ocean floor crust that is exposed on land as the extrusive series of the ophiolite retains a stable magnetization that is directed westward the ocean crust is considered to have rotated anticlockwise through 90 since its formation in the late cretaceous1 to determine the timing of the rotation event over 3 000 orientated samples have been collected from the ophiolite and from its in situ turonian to recent sedimentary cover here we report that pelagic chalks immediately overlying the highest extrusive lava units of the ophiolite complex give reliable magnetic vector directions indicating that at least 60 of rotation occurred before the lower eocene and that rotation was completed by the end of the lower eocene rotation cannot have occurred within a single late miocene event as reported previously2 regional geological considerations support the rotation of only a small fragment of oceanic crust that was stranded adjacent to an active continental margin in this tectonic setting the oblique consumption of oceanic crust beneath troodos crust could provide the necessary driving force for tectonic rotation

revised and synthetic apparent polar wander paths of the african eurasian north american and indian plates and true polar wander since 200 ma we have reviewed paleomagnetic data available for the eurasian african north american and indian plates over the last 200 ma selection criteria are those generally accepted with an emphasis on evidence for lack of remagnetization accurate dating and proper structural analysis this results in 23 35 51 and 2 poles for eurasia africa north america and india respectively we believe that this limited set of higher quality data is more likely to reveal key features of apparent polar wander apw paths than averaging of larger data sets involving less stringent selection criteria we propose and describe revised apw paths but more importantly we next use relative motion models to transfer all data in a common reference frame we find good agreement between transferred data when they are averaged separately for each plate in independent 20 ma windows this is a check on consistency of paleomagnetic data kinematic models and of the geocentric dipole hypothesis transferred data from all plates are averaged in 20 ma windows to generate synthetic apw paths for all plates studied these synthetic paths are in agreement with the original revised apw paths that use only data from a single plate moreover both geographic and time resolution are improved spatial confidence intervals are of the order of 5 the synthetic paths display interesting features such as a previously ill recognized apw loop for eurasia paleomagnetic and hotspot apw are next compared and a determination of true polar wander tpw is derived we find significant tpw amounting to over 20 in the last 200 ma tpw appears to be episodic with a standstill between 180 and 110 ma there is general agreement with a previous study of livermore et al 1984 the tpw standstill appears to correlate with a time of decreasing reversal frequency ending with the cretaceous long normal superchron other periods of fast tpw would seem to correspond to increasing reversal frequency however it is suggested that the major tpw hairpin at 50 ma might correspond to the collision of india with eurasia tentative correlations with core or mantle indicators can be understood as a result of couplings between the core mantle and lithosphere we believe primarily related to episodic evolution of the d layer

jurassic cretaceous paleomagnetism and paleogeography of the pontides turkey published paleomagnetic data from the pontides indicate anomalously low jurassic and early cretaceous paleolatitudes compatible with the southern neo tethyan african continental margin and significantly different from paleolatitudes predicted for the northern eurasian neo tethyan margin we present a new set of paleomagnetic data from 50 late cretaceous sites mainly from the western pontides and from the eastern pontides and 11 early jurassic sites mainly from the eastern pontides fold tests indicate that the characteristic magnetization components predate eocene folding late cretaceous site mean declinations are northerly in the eastern pontides and rotated to the west by a few tens of degrees in the western pontides late cretaceous site mean declinations are affected by local clockwise rotation in one sampling region close to the north anatolian fault the mean late cretaceous inclinations and resulting paleolatitudes are 41 1 23 5 n and 43 7 25 5 n for the western and eastern pontides respectively for the eastern pontides the early jurassic liassic mean inclination is 60 5 yielding a paleolatitude of 41 4 n considerably further north than previous paleolatitude estimates for the eastern pontides at this time the paleolatitude estimates for the western and eastern pontides are consistent with these units being close to the eurasian continental margin during liassic and late cretaceous time

reply to comment on tectonics of the akamas and mamonia ophiolites western cyprus magnetic petrofabrics and paleomagnetism by g j borradaile and k lucas

constructing a stacked benthic δ18o record composite stacks were constructed by superimposing 6 to 13 benthic foraminiferal 1 8 o records covering the period 0 850 ka an initial timescale for each core was established using radioisotopic age control points and assuming constant sedimentation rates between these points the average of these records is our 13 core untuned stack next we matched the 41 kyr component of each record individually to variations in earth s obliquity four of the 13 records produced timescales that were inconsistent with one or more of the known radioisotopic ages the nine remaining cores were averaged to create a minimally tuned stack six of the minimally tuned cores were assembled into a tropical stack for each stack we estimated the uncertainty envelope from the standard deviation of the constituents spectral analysis of the three stacks indicates that benthic 1 8 o is dominated by a 100 kyr oscillation that has a narrow spectral peak the contribution of precession to the total variance is small when compared to prior results from planktic stacks

a sustained 21 m sea level highstand during mis 11 400 ka direct fossil and sedimentary evidence from bermuda abstract a small protected karstic feature exposed in a limestone quarry in bermuda preserved abundant sedimentary and biogenic materials documenting a transgressive phase still stand and regressive phase of a sea level in excess of 21 3 m above present during marine isotope stage mis 11 400 ka as determined by u th dating and amino acid racemization cobbles and marine sediments deposited during the high energy transgressive phase exhibit rim cements indicating a subsequent phreatic environment this was succeeded stratigraphically by a still stand deposition of fine calcareous lagoonal sediments containing bioclasts of red algae and benthic and planktonic foraminifera that was intensely burrowed by marine invertebrates probably upogebiid shrimp that could not be produced under any condition other than sustained marine submergence overlying this were pure carbonate beach sands of a low energy regressive phase containing abundant remains of terrestrial and marine vertebrates and invertebrates the considerable diversity of this fauna along with taphonomic evidence from seabird remains indicates deposition by high run up waves over a minimum duration of months if not years the maximum duration has yet to be determined but probably did not exceed one or two thousand years the most abundant snails in this fauna are two species indicative of brackish water and high tide line showing that a ghyben herzberg lens must have existed at 20 m the nature of these sediments and fossil accumulation is incompatible with tsunami deposition and given the absence of evidence for tectonic uplift of the bermuda pedestal or platform provide proof that sea level during mis 11 exceeded 20 m a fact that has widespread ramifications for geologists biogeographers and human demographics along the world s coastlines

uranium lead isotopic ages of plagiogranites from the troodos ophiolite cyprus and their tectonic significance zircon populations from two plagiogranites in the plutonic section of the troodos ophiolite yield u pb dates between 90 3 0 7 and 92 4 0 7 ma zircons from one of the two samples yield u pb dates of 90 3 0 7 and 92 1 0 7 ma this difference is greater than our analytical error and the zircons are therefore considered to be slightly discordant two fractions from another sample are internally and externally concordant and have an average date of 91 6 1 4 ma this date is adopted as the age of plagiogranite crystallization the plutonic section of the troodos ophiolite is complex in that several generations of intrusion can be identified the plagiogranites occur at the top of the intrusive section and represent fractionated residua of magma chambers related to the lower pillow lavas they are possibly slightly older than small ultramafic layered complexes that represent the final intrusive episode within the troodos ophiolite there is good agreement between our results and the ages of radiolaria which occur in umbers intercalated with the upper pillow lavas of troodos blome and irwin 1985 this shows that the 75 to 85 ma k ar dates on the lavas and sheeted dikes desmet et al 1978 delaloye and desmet 1979 delaloye et al 1980 staudigel et al 1986 represent age resetting unrelated to ophiolite formation the troodos u pb zircon ages are slightly lower than u pb zircon ages from the samail ophiolite in oman which vary between 93 5 and 97 9 ma and average 95 ma tilton et al 1981 the small difference in age between the troodos and the samail ophiolites and the geochemical similarities of basalts from both complexes to island arc volcanic rocks imply that a 3000 km axis of rift related island arcs formed between 91 and 98 ma emplacement of the ophiolites followed during the early maastrichtian

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

carbonate dissolution in a modern mixing zone the potential for dissolution of calcite and aragonite and precipitation of dolomite by the mixing of fresh and saline ground waters has been demonstrated theoretically1 3 although geologists have used these processes in the explanation of the diagenesis of recent4 7 and ancient8 12 carbonates there has been only limited investigation of the geochemical processes of modern mixing zones13 14 here we report the results of chemical and rock profiling through a modern mixing zone on andros island in the bahamas our results demonstrate undersaturation of the waters in the mixing zone with respect to aragonite and calcite and corresponding pervasive dissolution of the carbonate rocks at this level undersaturation is significantly enhanced by bacterial processes which are also responsible for precipitation of an iron rich crust despite chemical supersaturation precipitation of dolomite was not observed thereby casting some doubt on the mixing zone model of dolomitization

timing of uplift of the troodos massif cyprus constrained by sedimentary and magnetic polarity evidence abstract plio pleistocene sediments exposed around the ophiolitic troodos massif document spectacular uplift from below sea level to a maximum height of c 2000 m sedimentation reflects a dominant control of focused tectonic uplift modified by the effects of glacio eustatic sea level change and climatic change understanding the uplift and controls on deposition has been hindered by an inadequate age model here we present a preliminary investigation of the polarity of remanent magnetizations recorded within the upper part of the pliocene succession in the pissouri and mesaoria basins and from the pleistocene marine terrace deposits that border the troodos massif when integrated with available lithostatigraphic and biostratigraphic data the main results are as follows focused uplift of the troodos massif began during the late pliocene either between 2 14 and 1 95 ma or immediately prior to 1 77 ma shallow marine ophiolite derived clastic and bioclastic sediments accumulated in both the mesaoria and pissouri basins implying that the troodos massif was uplifted as a single tectonic entity non marine deltaic and fluvial facies prograded into both of the basins during the pleistocene 1 77 ma recent marine terraces in sw and south cyprus were cut and covered by littoral sediments from

mesozoic sedimentary and magmatic evolution of the arabian continental margin northern syria evidence from the baer bassit melange one of the few detailed records of mesozoic deep water sedimentation and volcanism preserved along the tectonically emplaced arabian continental margin is from the baer bassit region of northern syria south tethyan units there occur as blocks broken formation and disrupted thrust sheets within the bear bassit melange two overall composite successions are identified the first comprises mainly sedimentary successions ranging from late triassic to late cretaceous cenomanian in age the second is dominated by middle jurassic lower cretaceous alkaline per alkaline volcanic and minor intrusive igneous rocks the extrusives are intercalated with radio larian sediments and capped by cenomanian ferromanganese rich pelagic limestone facies compari sons and the regional setting suggest that the triassic to cenomanian mainly sedimentary units formed in deep water near the base of the slope of the arabian continental margin the contrasting volcanogenic successions developed in a more distal off margin setting regional comparisons e g with southwestern cyprus and southwestern turkey suggest that continental break up to form a south tethyan oceanic basin took place in late triassic time associated with alkaline volcanism similar alkaline volcanism of middle jurassic to early cretaceous age could reflect the activity of a mantle plume beneath the arabian plate overall sedimentation was mainly controlled by an interplay of post rift thermal subsidence plume related uplift siliceous oceanic productivity climatic change and eustatic sea level change the south tethyan marginal to oceanic units in northern syria were detached from an inferred oceanic basement in latest cretaceous time emplaced onto the arabian continental margin then transgressed by maastrichian and younger autochthonous successions

palaeomagnetic insights into the evolution of neotethyan oceanic crust in the eastern mediterranean abstract a synopsis of palaeomagnetic data from three late cretaceous eastern mediter ranean tethyan ophiolites troodos hatay and baer bassit and their sedimentary coversequences is presented these data provide valuable insights into the role of regional andlocal scale tectonic rotations in the geodynamic evolution of neotethyan oceanic crust thegeologically earliest phases of tectonic rotation are documented in the troodos ophiolite where rotations around both subvertical and subhorizontal axes are readily related to thedevelopment of the spreading fabrics and structures during crustal genesis subsequent c 74 anticlockwise intra oceanic rotation of a troodos microplate has been quantified throughanalysis of the in situ sedimentary cover of the troodos ophiolite results indicate that bulkanticlockwise rotation began soon after the cessation of spreading and ended by the end ofthe eocene with c 50 60 of microplate rotation being over by the maastrichtian the timeat which ophiolite thrust sheets were emplaced onto the arabian continental margin to theeast of troodos recent results from the emplaced structurally dismembered baer bassitophiolite indicate extreme anticlockwise rotations of ophiolitic thrust sheets varying on akilometre scale new data from the post emplacement sedimentary cover confirm that onlya small component of these rotations is due to post emplacement tectonism baer bassitrepresents the leading edge of the emplaced ophiolitic sheet new data from the morecoherent section preserved in the hatay ophiolite to the north demonstrate significantanticlockwise rotation this is equivalent to the rotation of the most northerly part of thebaer bassit units to the south and is of the same sense and magnitude as the pre maastrichtian phase of microplate rotation documented in the troodos this suggests acommon intra oceanic origin for the majority of the troodos and hatay rotations and asignificant component of the more variable rotations observed in baer bassit overall therefore the data support a model involving 1 intra oceanic rotation of a coherent regionof crust within the southern neotethyan basin this rotated unit is more areally extensivethan has previously been inferred from consideration of data from the troodos ophiolitealone 2 emplacement of part of the rotated unit onto the arabian platform 3 subsequentlocalized post emplacement modification related to the development of the current plateconfiguration

kinematic evolution of the tethys belt from the atlantic ocean to the pamirs since the triassic abstract we present an updated series of kinematic reconstructions of the major plates around the tethys from the atlantic ocean to the pamirs between the early jurassic and the present this set is used elsewhere as a basis for paleogeographic maps of the entire region the problems related to the positions of the continents in the lower triassic are also discussed no direct analyses of magnetic anomalies and fracture zones in the atlantic have been made rather all available poles and rotations have been tested in order to eliminate or minimize possible kinematic errors the reconstructions are shown for nine key geological periods which correspond to well recognized magnetic anomalies except for the jurassic cretaceous boundary and the cretaceous tertiary boundary which correspond to interpolated positions paleolatitudes have been drawn using the study of westphal et al 1986 an attempt has been made to take into account the displacements caused by formation of the continental margins and basins by stretching the resulting relative vector of motions along the northern boundary of the tethys shows a significant change 80 m y ago left lateral motion with compression dominates before whereas right lateral motion with compression dominates after to the east rates of motion vary by a factor of three with time and four maxima can be clearly related to tectonic events in the late jurassic late cretaceous eocene and post middle miocene to the west north of apulia on the contrary the motion rate has not changed significantly since the early cretaceous and is close to 1 cm yr as an average these rather complex adjustments in rates and directions of relative motion are produced in great part through a complex migration of the africa eurasia pole of rotation and seem to be mostly governed by the tectonics of the tethys plate boundary

palaeomagnetic timing of the rotation and translation of cyprus abstract the geological evolution of the mesozoic troodos ophiolite complex in cyprus and the tectonic nature and timing of the palaeomagnetically indicated anticlockwise rotation of cyprus of some 80 and ca 15 northward translation have been open for debate for some time new palaeomagnetic data from 18 sites 180samples in the post ophiolite sediments ranging in age from upper cretaceous to upper miocene are presented most of the sites are of normal geomagnetic polarity but indications of reversed polarity have been found in an older group of sediments the lefkara formation of upper palaeocene age six sites from the older group of sediments upper cretaceous to eocene in age give a site mean direction of the af cleaned sediments of d i 323 29 with 95 18 while 5 sites from a younger group of sediments oligocene to miocene in age give a cleaned site mean direction of d i 334 58 with 95 9 these and published data suggest that an anticlockwise rotation of cyprus of 60 10 occurred early during the post igneous evolution of the cyprus oceanic crust between 90 and 50ma leaving only a minor anticlockwise rotation of 20 10 to occur during the last 50 ma it is furthermore concluded that the northward translation of cyprus of 15 mostly took place during the last 30ma it thus appears that a fairly rapid rotation of the cyprus microplate first took place in the late cretaceous and early tertiary time with an average angular velocity of 1 2 ma during which the northward translation was minor or negligible in the latter half of the tertiary the sense of movement appears to have radically changed the northward translation now being dominant with an average velocity of 5 6cm yr this temporal evolution is found to be in good agreement with the mesozoic and tertiary movements of the african lithospheric plate relative to europe as evidenced from the atlantic sea floor magnetic anomaly spreading history

troodos extrusive series of cyprus a comparison with oceanic crust the extrusive section on the northern flank of the troodos ophiolite is 1 000 to 1 500 m thick and consists of about 12 lithologic units of pillowed and massive lava and breccia some pillowed units which average 100 to 200 m in thickness vary systematically from lava tubes up to 6 m in diameter at the base through common pillows less than 1 m in diameter to small pillows and extrusive breccias at the top these assemblages appear to be individual volcanoes suggesting episodic volcanic accretion the upper 100 to 200 m of the section is pervasively altered and oxidized but fresh volcanic glass is preserved throughout most of the extrusive section the lavas are subdivided on geochemical evidence into a lower differentiated andesite to dacitic andesite series resembling evolved island arc tholeiites and an upper series of picrite mafic basalt and basaltic andesite very low in tio2 k2o p2o5 nb rb and ba the highly depleted basalt and basaltic andesite resemble lavas from ocean crust near island arcs lateral continuity of lithologic units interpreted as individual volcanoes and the relatively constant dips of the extrusive rocks suggest that tilting and rotation have not played major roles in the accretion process the occurrence of fractionated lavas at the base and primitive lavas at the top suggests a broad zone of accretion located above a subduction zone

radiolarian biochronology of mesozoic deep water successions in nw syria and cyprus implications for south tethyan evolution new radiolarian biostratigraphical data have shed light on the mesozoic tectonic evolution of south tethys in the baer bassit region of nw syria radiolarian assemblages of late triassic middle jurassic and early cretaceous age were extracted from radiolarites in five measured sections the results are compared with published radiolarian ages from the mamonia complex western cyprus these two areas are interpreted as preserved fragments of the conjugate margins of a small south tethyan oceanic basin formed by triassic rifting in the southerly i e arabian margin proximal successions were dominated by shallow water derived carbonate whereas distal successions reveal seamount type alkaline peralkaline volcanism dated as both late triassic and middle jurassic early cretaceous along the inferred northern margin i e western cyprus proximal successions are dominantly terrigenous whereas distal settings include late triassic oceanic crust and seamount type lavas

comment on tectonics of the akamas and mamonia ophiolites western cyprus magnetic petrofabrics and paleomagnetism by g j borradaile and k lucas

did the kyrenia range of northern cyprus rotate with the troodos hatay microplate during the tectonic evolution of the eastern mediterranean previous palaeomagnetic studies have allowed the recognition of a distinctive area of neotethyan oceanic rocks including the troodos ophiolite in cyprus and the hatay ophiolite to the east in southern turkey that underwent 90 of anticlockwise rotation between late cretaceous campanian and early eocene time the southern and western boundaries of this rotated troodos hatay microplate have been inferred to lie within or adjacent to zones of deformed oceanic and continental margin rocks that are now exposed in southern and western cyprus however the northern boundary of the microplate remains undefined relevant to this problem palaeomagnetic data are presented here from basaltic lavas exposed along the kyrenia range mostly from late cretaceous maastrichtian sites and one eocene site a positive inclination only fold test demonstrates that remanences are pre deformational in age and positive conglomerate tests show that magnetic remanences were acquired before late eocene early oligocene time together suggesting that primary magnetizations are preserved data from the eastern kyrenia range and the karpas peninsula the easternmost extension of the kyrenia range document significant relative tectonic rotation between these localities with no rotation in the eastern range versus 30 of anticlockwise rotation of the karpas peninsula unfortunately palaeomagnetic sites from the western kyrenia range did not yield tectonically interpretable magnetization directions probably due to complex poly phase thrusting and folding and the central range also yielded no interpretable data however the available palaeomagnetic data are sufficient to demonstrate that the kyrenia terrane underwent a separate rotation history to the troodos hatay microplate and also implies that the northern boundary of the troodos hatay microplate was located between the troodos ophiolite and the kyrenia range the former microplate margin has since been overridden and concealed by two phases of southwards thrusting and folding of the kyrenia range units mid eocene latest miocene earliest pliocene the likely cause of the anticlockwise rotation affecting the karpas peninsula and by implication the curvature of the kyrenia range as a whole relates to regional late stage subduction and diachronous continental collision the southern neotethys sutured in se turkey during the early miocene whereas a relict ocean basin remained further west in the easternmost mediterranean allowing a remnant n dipping subduction zone to retreat southwards and so induce the present day arcuate shape of the kyrenia range

tectonic rotations in extensional regimes and their paleomagnetic consequences for oceanic basalts paleomagnetic samples of many deep sea drilling project dsdp basalts have shallower inclinations than would be inferred from the paleolatitude at which the basalts were extruded at mid ocean ridges rather than arising from peculiarities of the geomagnetic field the anomalous magnetic directions may result from tectonic rotations along the listric normal faults which often characterize extensional tectonic regimes several lines of evidence support this conclusion observations of the basin and range province an extensional tectonic regime occurring in continental crust observations of the troodos complex cyprus an oceanic extensional tectonic regime now exposed on land and analysis of possible fault patterns associated with the magma chambers postulated to occur at some mid oceanic ridges the tectonic rotations resulting from movement along the listric normal faults occur about a horizontal axis generally perpendicular to the extension direction and typically amount to 30 to 50 although rotations as large as 70 to 90 are not uncommon the paleomagnetic consequences of these rotations can be calculated for dsdp basalts if the original strike and latitude of a ridge are known at four dsdp sites for which adequate data are available namely sites 319 332 410 and 417 rotations ranging from 50 to 70 are required to explain the paleomagnetic results if the original strike and location of the ridge are not known as is the case for most of the older parts of the pacific ocean the paleomagnetic data and the inferred rotation determine a relationship between possible ridge strikes and locations this information combined with a similar but independent relationship derived from the marine magnetic anomalies puts severe constraints on the original strike and location of the ridge

evidence from the kyrenia range cyprus of the northerly active margin of the southern neotethys during late cretaceous early cenozoic time sedimentary geology and planktonic foraminiferal biostratigraphy have shed light on the geological development of the northern active continental margin of the southern neotethys in the kyrenia range following regional triassic rifting a carbonate platform developed during jurassic cretaceous time followed by its regional burial deformation and greenschist facies metamorphism the platform was exhumed by late maastrichtian time and unconformably overlain by locally derived carbonate breccias passing upwards into upper maastrichtian pelagic carbonates in places the pelagic carbonates are interbedded with sandstone turbidites derived from mixed continental basic volcanic neritic carbonate and pelagic lithologies in addition two contrasting volcanogenic sequences are exposed in the western central kyrenia range separated by a low angle tectonic contact the first is a thickening upward sequence of campanian lower maastrichtian pelagic carbonates silicic tuffs silicic lava debris flows and thick bedded to massive rhyolitic lava flows the second sequence comprises two intervals of basaltic extrusive rocks interbedded with pelagic carbonates the basaltic rocks unconformably overlie the metamorphosed carbonate platform whereas no base to the silicic volcanic rocks is exposed additional basaltic lavas are exposed throughout the kyrenia range where they are dated as late maastrichtian and late paleocene middle eocene in age in our proposed tectonic model related to northward subduction of the southern neotethys the kyrenia platform was thrust beneath a larger tauride microcontinental unit to the north and then was rapidly exhumed prior to late maastrichtian time pelagic carbonates and sandstone turbidites of mixed largely continental provenance then accumulated along a deeply submerged continental borderland during late maastrichtian time the silicic and basaltic volcanogenic rocks erupted in adjacent areas and were later tectonically juxtaposed the campanian early maastrichtian silicic volcanism reflects continental margin type arc magmatism in contrast the upper maastrichtian and paleocene middle eocene basaltic volcanic rocks erupted in an extensional or transtensional setting likely to relate to the anticlockwise rotation of the troodos microplate

magnetic properties of marine limestones numerous paleomagnetic investigations have been carried out on limestones but their rock magnetic properties have often been neglected in this review geological and rock magnetic factors which determine whether marine limestones are suitable for paleomagnetic study are summarized and laboratory techniques for the identification of the magnetic mineralogy are evaluated the conditions under which pelagic limestones form are especially favorable for the acquisition of a stable primary natural remanence nrm probably by a postdepositional alignment process the effectiveness and timing of acquisition of this remanence are influenced by the thoroughness of bioturbation other remanence components can be acquired during diagenesis in the soft sediment right after deposition or much later even in the indurated limestone the magnetic mineralogy of a limestone is difficult to describe optically because of the small grain size and low concentration magnetic techniques are more convenient direct analysis of extracted magnetic minerals is handicapped by the difficulty of obtaining a representative extract a particularly useful technique involves combined observations of isothermal remanent magnetization irm acquisition in strong fields up to at least 4 t and the subsequent destruction of this irm during stepwise or continuous thermal demagnetization the magnetic minerals most commonly identified by these techniques are magnetite goethite hematite and maghemite these magnetic minerals occur in different combinations in the marine limestones of central europe and the mediterranean realm pyrite is common in certain limestones where it can be the precursor of an unwelcome late goethite pyrrhotite may be responsible for unstable magnetization in the swiss helvetic limestones but otherwise is rare thermal demagnetization of some limestones causes changes of susceptibility and coercivity at quite low temperatures 300 400 c due to the breakdown of a metastable mineral such as maghemite goethite or pyrrhotite at high temperatures above 500 c pronounced changes of magnetic mineralogy occur in all limestones because of the growth of new magnetite this necessitates great care in interpretation of thermal demagnetization of high blocking temperature components and often results in observational difficulties due to viscous remanent vrm behavior of the newly formed magnetite vrm is a widespread component of nrm in many limestones but it can usually be removed effectively by standard magnetic cleaning techniques the susceptibility serves as a simple control of mineralogical change during heating and can serve as an indicator of lithologic variation of magnetic mineral concentration and type in magnetostratigraphic profiles the susceptibility is anisotropic and shows a classical depositional pattern of the distribution of principal axes however the probable postdepositional mechanism of nrm acquisition especially in bioturbated sediments implies that the anisotropy pattern results from postdepositional compaction of the sediment

foraminifera and testate amoebae thecamoebians in an anchialine cave surface distributions from aktun ha carwash cave system mexico surface sediment samples from aktun ha carwash cave system mexico were analyzed for microfossils carbonate isotopes and organic matter content saline water flooded the cave during the sangamon interglacial highstand 124 119 kyr hosting a marine assemblage dominated by saline foraminifera bolivina sp 73 and elphidium sp 11 with a mean 13c 25 5 and a mean 18o 22 7 this assemblage was found distal to sinkholes 75 m upstream 150 m downstream and in yellow orange sediment mean total organic carbon toc 3 6 late pleistocene 95 15 kyr sea level fall reestablished vadose conditions in the cave allowing for localized speleothem flowstone to seal in the marine assemblage holocene sea level rise completely reflooded the cave with freshwater by 6 5 kyr providing a suitable habitat for a freshwater assemblage of living testate amoebae centropyxis aculeata 38 arcella vulgaris 10 and the foraminifer ammonia tepida var juvenile 35 with a mean 13c 210 8 and a mean 18o 24 9 on the ostracod cytheridella ilosvayi this assemblage was found proximal to sinkholes 75 m upstream 150 m downstream and in black to brown sediment mean toc 17 5 foraminifera and testate amoebae colonize aquatic cave environments respond to physicochemical conditions in the cave similarly to other coastal settings and thereby provide promise for the application of protists as proxies in flooded caves

reconstructing global overturning from meridional density gradients despite the complexity of the global ocean system numerous attempts have been made to scale the strength of the meridional overturning circulation moc principally in the north atlantic with large scale basin wide hydrographic properties in particular various approaches to scaling the moc with meridional density gradients have been proposed but the success of these has only been demonstrated under limited conditions here we present a scaling relationship linking overturning to twice vertically integrated meridional density gradients via the hydrostatic equation and a rotated form of the geostrophic equation this provides a meridional overturning streamfunction as a function of depth for each basin using a series of periodically forced experiments in a global coarse resolution configuration of the general circulation model nemo we explore the timescales over which this scaling is temporally valid we find that the scaling holds well in the upper atlantic cell at 1000 m for multi decadal and longer timescales accurately reconstructing the relative magnitude of the response for different frequencies and explaining over 85 of overturning variance on timescales of 64 2048 years despite the highly nonlinear response of the antarctic cell in the abyssal atlantic between 76 and 94 of the observed variability at 4000 m is reconstructed on timescales of 32 years and longer the scaling law is also applied in the indo pacific this analysis is extended to a higher resolution stochastically forced simulation for which correlations of between 0 79 and 0 99 are obtained with upper atlantic moc variability on timescales 25 years these results indicate that meridional density gradients and overturning are linked via meridional pressure gradients and that both the strength and structure of the moc can be reconstructed from hydrography on multi decadal and longer timescales provided that the link is made in this way