new results and a palaeomagnetic overview of the pontides in northern turkey summary palaeomagnetic results are reported from 16 sites within volcanic and volcano sedimentary rocks of cretaceous and eocene age from the central pontides in northern turkey the sampled area is bounded by the north anatolian fault naf to the south and the black sea to the north the palaeomagnetic data collected demonstrate the presence of both non rotated and anticlockwise rotated regions i declination directions including lower upper cretaceous and eocene sites do not indicate any significant rotations north of where the naf exhibits an arcuate shape ii 20 anticlockwise rotation was observed in the sinop peninsula the northernmost extremity of the central pontides iii in the west of the central pontides two sites with normal and reversed antipodal directions indicate a 20 anticlockwise rotation and iv another region lies to the east of the study area and shows a rotation in an anticlockwise sense of about 5 30 the upper cretaceous and eocene directions reported in this paper and other palaeomagnetic studies show that there is not much difference between the inclination values of the upper cretaceous i 40 1 95 7 2 and the eocene sites i 39 6 95 8 1 furthermore the values of the inclination available from both sedimentary and volcanic upper jurassic lower cretaceous formations are shallower than the upper cretaceous ones this suggests that the entire pontides have undergone a northward drift of over 2000 km since the upper jurassic

geometric changes of plate boundaries along part of the northern dead sea transform geochronologic and paleomagnetic evidence the korazim block an elevated pressure ridge along with the faults bounding the sea of galilee and hula pull apart basins are internal structures of the dead sea transform plate boundary k ar dates and paleomagnetic data from basalt flows and sedimentary strata are utilized to determine the stratigraphy and the deformation of the region the integration of the two methods together with structural data yield high resolution age determination of the stratigraphic sequence and provides insight into the timing and style of deformation the korazim block is covered in its southern and central areas by pliocene basalt flows the cover basalt 5 1 3 6 ma and ruman basalt 2 9 2 2 ma formations and in its northern area by basalts yarda basalt 0 9 0 8 ma and sediments 3 0 2 3 and 1 6 0 9 ma of plio pleistocene age the magnetic polarity of a total of 29 lava flows and intercalated sedimentary strata is mixed the mean magnetic declination of the 29 sites shows an anomalous direction which yields 11 4 4 0 counterclockwise rotation with respect to the expected field the mean inclination of 46 0 4 1 does not significantly deviate from the expected field the anomalous declination is interpreted as the consequence of faulting and block rotation accommodating internal deformation this deformation did not begin before late pliocene to early pleistocene probably not before 0 9 ma and may still be active simultaneous right lateral slip of 50 175 m with a small reverse component of 30 90 m along nw trending faults and 11 counterclockwise rotation created internal deformation of the korazim pressure ridge this deformation is the consequence of left lateral slip along the almagor strand of the dead sea transform subparallel to the plate slip vector thus a compression component was formed which presumably led to the internal deformation of the korazim block the recent deformation of the korazim block in relation to the age of adjacent structures and to the age of the dead sea transform permits temporal resolution of geometric changes which must typify transform boundaries such as the dead sea transform internal structures within transforms may change along with the transform internal geometry and become inactive while new structural features may develop

palaeomagnetic and geochronological evidence for a major middle miocene unconformity in soke basin western anatolia and its tectonic implications for the aegean region cenozoic convergence between the eurasian and african plates and concurrent slab roll back processes have produced a progressive extension in back arc areas such as the aegean region and western anatolia there is still a long standing controversy as to whether this was a continuous or stepwise process to shed light on this controversy and on the driving mechanism of regional extension we present palaeomagnetic and geochronological results from the soke basin located at the southeastern rim of the izmir balikesir transfer zone our improved geochronology shows that volcanic activity in the region occurred between 11 66 and 12 85 ma middle to late miocene palaeomagnetic data for the soke basin show a c 23 clockwise rotation whereas early miocene data show a c 28 counterclockwise rotation the primary nature of the magnetization is indicated by a positive tilt test the resulting c 51 counterclockwise rotations during the middle miocene signify a major tectonic reorganization during a period when an interruption of exhumation of metamorphic massifs has been reported we suggest that the izmir balikesir transfer zone is the main driver of the reorganization in the region the regional fingerprint of this tectonic reorganization coincides with the acceleration of trench retreat and illustrates the surface impact of tearing of the hellenic slab supplementary material details of 40 ar 39 ar analysis including heating steps and the output pmag file including details of paleomagnetic analysis performed in this study are available at https doi org 10 6084 m9 figshare c 3690871

source parameters of the 2005 2008 balâ sirapinar central turkey earthquakes implications for the internal deformation of the anatolian plate abstract active tectonics of central anatolia is mainly governed by the collision of the african arabian and anatolian plates which causes westward escape of anatolia along the north and east anatolian fault zones and the counterclockwise rotation of the kirsehir block with insignificant internal deformation the formation of the present day tectonic processes in this region can be deduced from geophysical prospecting and seismological data although the seismicity in central anatolia is distinctively lower than that in the northern and eastern parts of the anatolian plate small and moderate earthquakes 2 5 mw 6 0 mostly occurred in the region in the past decades or so for example intense earthquake activity was observed in the bal afsar sirapinar ankara central anatolia region in the period of 2005 to 2008 with destructive earthquakes of july 30 2005 mw 5 2 december 20 2007 mw 5 7 and december 26 2007 mw 5 6 therefore these earthquakes are crucial to analyze the shallow crustal deformation in the central anatolian block in the present study we obtained source parameters of 2005 2008 earthquake sequence using the regional moment tensor rmt inversion method we analyzed complete broad band waveforms recorded at near field distances 0 45 3 6 our results reveal nw se directed right lateral strike slip faulting and ne sw directed left lateral strike slip faulting mechanisms which are clearly correlated with the conjugate fault systems in the bal afsar sirapinar region however some earthquakes also have e w directed normal faulting components we suggest that the major characteristics of 2005 2006 and 2007 2008 earthquake activity could have been dominantly associated with left lateral and right lateral strike slip faulting mechanisms respectively the seismogenic depth is found to be about 8 10 km this result implies that earthquakes in the study region occurred mostly in the upper crust which accommodates the strain by brittle deformation furthermore our results are consistent with neotectonic features and available geophysical data e g gravity aeromagnetic and paleomagnetic reported by previous studies it may be envisioned that the joint interpretation of earthquake source parameters with those observations will shed light into the complex deformation processes for future studies

palaeomagnetic study of the karaman and karapinar volcanic complexes central turkey neotectonic rotation in the south central sector of the anatolian block abstract in the anatolian sector of the afro eurasian collision zone a palaeotectonic collisional phase paleocene to miocene responsible for emplacement of the pontide and tauride orogens has been replaced by a neotectonic phase of continental deformation late miocene early pliocene to recent the latter phase appears to have been accommodated mainly by crustal thickening during late miocene and pliocene times but was succeeded by complex differential rotations of fault blocks during crustal extrusion in late pliocene and quaternary times in this study we have investigated palaeomagnetism of miocene recent volcanic rocks comprising the western extension of the central anatolian volcanic province located in the south central part of the anatolian block with the aim of resolving deformations near to the border with the tauride orogen rock magnetic investigations identify low ti magnetite assemblages of primary cooling related origin these have predominant multidomain structures but significant fractions of single domains are always present low temperature alteration is largely absent the karaman volcanic complex late pliocene shows a net rotation of 5 7 6 9 not significantly different from the regional field axis during recent times the karapinar volcanic field brunhes epoch identifies a larger net rotation of 23 1 12 0 in a restricted sample the adjoining karacadag volcanic complex late miocene pliocene and middle miocene lavas beneath the hasandag complex define net rotations of 8 1 5 9 and 16 4 8 9 respectively analysis of palaeomagnetic results from late cretaceous recent rock units emplaced in anatolia during the palaeotectonic and neotectonic regimes shows that rates of rotation have accelerated in post pliocene times as crustal thickening has given way to tectonic escape a near uniform anticlockwise rotation of 25 35 has characterised much of this block during the most recent phase of deformation and appears to have occurred in common with the eurasian plate to the north of the north anatolian fault zone whilst this rotation appears to extend south eastwards across the ecemis fault zone towards the east anatolian fault the present study shows that smaller differential anticlockwise rotations have characterised the south central region of the block where it has interacted at its southwestern margin with oroclinal bending focussed on the isparta angle

evidence of late cretaceous oroclinal bending in north central anatolia palaeomagnetic results from mesozoic and cenozoic rocks along the izmir ankara erzincan suture zone

paleomagnetism of cretaceous volcanic rocks from central chile and implications for the tectonics of the andes the mean direction of remanent magnetization in well dated structurally and petrologically simple cretaceous ash flow tuffs from the central valley of chile near santiago indicates that the region has undergone a small about 14 clockwise rotation two other paleomagnetic studies on cretaceous rocks from coastal chile give a similar result we tentatively attribute these rotations to dextral shear caused by oblique subduction of the nazca plate beneath south america in contrast cretaceous rocks from peru seem from paleomagnetic evidence to have been rotated counterclockwise relative to the stable interior of the continent this sense of apparent rotation agrees with the sense of deflection of geologic trends from north south to north northwest at about the peru chile border the arica deflection on the basis of these observations several authors have suggested that the arica deflection is an orocline however uncertainty in all such paleomagnetic interpretations is introduced by what seems to be a very streaked distribution of cretaceous reference poles from the south american craton the cause of this streaking is not known

a model for tectonic rotations about a vertical axis abstract the rotation of a rigid ellipsoidal inclusion within a highly viscous fluid orientated so that two of the principal axes remain horizontal is used as a model for the rotation of crustal inclusions in wide zones of continental deformation this model is also applicable to other geological problems involving the rotation of inclusions in a matrix the pattern of behaviour in such a model is shown to be complex in general the rotation rate of the inclusion is a function of all components of the velocity field of the deforming medium and the horizontal aspect ratio of the inclusion however for a given velocity field this aspect ratio must exceed a critical value before the inclusion can rotate continuously inclusions with lower aspect ratios will rotate for a certain range of orientations in an opposite direction to the sense of shear in the deforming zone the possibility of the inclusion changing shape during rotation adds to the complexity of behaviour

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

neotectonic deformation in the western sector of tectonic escape in anatolia palaeomagnetic study of the afyon region central turkey abstract following final closure of the neotethyan ocean during the late miocene deformation in central turkey has led to crustal thickening and uplift to produce the anatolian plateau followed by westward extrusion of terranes by strike slip widespread volcanism has accompanied this latter neotectonic phase and palaeomagnetic study of the volcanism shows a coherent record of differential block rotations indicating that the anatolian region is not a plate or platelet sensu stricto but is undergoing distributed internal deformation to evaluate the scale of neotectonic rotations in the transition zone near the western limit of tectonic escape and the border of the extensional domain in central west turkey we have studied the palaeomagnetism at 82 sites in volcanic suites distributed along a 140 km lineament with north south trend and ranging in age from 18 to 8 ma comparable deflection of magnetic remanence from the present field direction is identified along the full length of the lineament a mean clockwise rotation of 12 3 4 2 is determined for this western sector of the anatolian strike slip province since similar rotations are observed in the youngest and oldest units this cumulative rotation occurred after the late miocene when interpreted together with results elsewhere in anatolia it is inferred that the rotation is later than crustal thickening and uplift of the anatolian plateau and entirely a facet of the tectonic escape inclinations are mostly 10 shallower than the predicted miocene field and are considered to reflect the presence of a persistent inclination anomaly in the mediterranean region larger rotations departing from the regional trend are also observed within the study region but are confined to the vicinity of major faults notably those bounding the afyon aksehir graben the pattern of neotectonic declinations across anatolia identifies strong anticlockwise rotation in the east near the arabian pincer with progressive reduction in the amount of rotation towards the west it becomes zero or slightly clockwise at the western extremity of the accreted terrane collage rotations also appear to become generally younger towards the south crustal deformation has therefore been distributed and the net effect of terrane extrusion to the west and south has been to expand the curvature of the tauride arc the westward radial expansion of the extruded terranes is inferred to combine with backroll on the hellenic arc to produce the contemporary extensional province in western turkey

regional clockwise rotation of the armutlu peninsula western turkey resolved from palaeomagnetic study of eocene volcanics abstract the north anatolian fault naf one of the major tectonic entities of turkey is a dextral fault system lying within an intracontinental transform zone up to 100 km in width this shear zone is composed of continental blocks delimited by strike slip faults with the armutlu peninsula being one of the largest of these blocks and surrounded by two main branches of the naf such fault bounded blocks typically display rotations and a variety of different kinematic models have been proposed to explain these in this study eocene volcanic rocks of the armutlu peninsula have been sampled from 50 palaeomagnetic sites following alternating field and thermal demagnetisation and component analysis a dual polarity axis is resolved which shows that the peninsula has rotated 16 6 8 clockwise relative to the predicted field direction at this location in eocene times this clockwise block rotation is interpreted in terms of dextral motion of a tectonic block bounded by two strands of the naf the palaeomagnetic data also indicate that the eocene rocks of the armutlu peninsula were emplaced at a palaeolatitude statistically identical to the present and we conclude that northward movement of this sector of the anatolides since eocene times has been below the limits of palaeomagnetic detection

block rotation by strike slip faulting structural and paleomagnetic evidence geometric analysis shows that motion of sets of strike slip faults should cause block rotation otherwise the distorted fault domain would not fit with its surrounding the sense of the block rotation depends on the sense of fault slip and the spacing and orientation of the faults all of which can be obtained from structural data the predictions of the geometric model can then be independently tested by paleomagnetic measurements the model was tested in northern israel structural data reveal several domains of contemporaneous right and left lateral strike slip faults paleomagnetic measurements show that in a domain of nnw trending left lateral faults blocks rotated 23 3 8 2 clockwise and in a domain of right lateral faults blocks rotated 22 4 9 0 anticlockwise these results are in agreement with the prediction of the geometric analysis of the structure the combined results of the heterogenous deformation of the area resembles a pure shear which allows n s extension by about 1 3 in other domains rotations of 34 6 9 1 and 53 1 11 0 were found in their original orientation the left and right lateral faults intersected at angles of 60 70 enclosing the principal axis of shortening in accordance with theories of brittle failure as a result of block rotations this angle is now larger and may reach 110 the results demonstrate large block rotations in different senses in domains of strike slip faults the independent structural and paleomagnetic data can be interpreted within the framework of a simple geometric model northern israel is considered to be a good model for this efficient mechanism of intraplate deformation which is expected to occur in similar tectonic settings elsewhere

crustal disequilibrium of the central pontides northern turkey due to oroclinal bending revealed by gravity modelling abstract the turkish pontide orogenic belt belongs to the former eurasian margin which is the result of two major successive processes of the closure of the tethyan oceans subduction followed by collision this almost e w trending large mountain range shows an arc shaped geometric structure in the northern turkey according to previous studies based on geological and paleomagnetic data oroclinal deformation was proposed as a result of the geodynamic evolution due to the africa eurasia convergence in the region the aim of study is to determine how this important evolution is expressed in the lithosphere beneath the region by gravity modelling a bouguer gravity anomaly map was constructed and from this a gravity model is presented that reveals the general crustal structure underneath the northern turkey the results present a significant crustal thickness change that occurs in the n s and as well as in the e w directions from s to n a significant sharp crustal thickness decrease 20 km was found while from e to w the crustal thickness beneath the pontides increases by approximately 7 km while an average thickness of 37 km was calculated in the east it reached a maximum value of 44 km in the west although the reason for the increase in crustal thickness from north to south is logical in terms of the geodynamic evolution the increase from east to west is probably caused by the nature of the continental collision the most plausible explanation is an oblique nw indentation of the kirsehir block into the pontides

correlation of clayey gouge in a surface exposure of serpentinite in the san andreas fault with gouge from the san andreas fault observatory at depth safod abstract magnesium rich clayey gouge similar to that comprising the two actively creeping strands of the san andreas fault in drill core from the san andreas fault observatory at depth safod has been identified in a nearby outcrop of serpentinite within the fault zone at nelson creek each occurrence of the gouge consists of porphyroclasts of serpentinite and sedimentary rocks dispersed in a fine grained foliated matrix of mg rich smectitic clays the clay minerals in all three gouges are interpreted to be the product of fluid assisted shear enhanced reactions between quartzofeldspathic wall rocks and serpentinite that was tectonically entrained in the fault from a source in the coast range ophiolite we infer that the gouge at nelson creek connects to one or both of the gouge zones in the safod core and that similar gouge may occur at depths in between the special significance of the outcrop is that it preserves the early stages of mineral reactions that are greatly advanced at depth and it confirms the involvement of serpentinite and the mg rich phyllosilicate minerals that replace it in promoting creep along the central san andreas fault

deformational behaviour of continental lithosphere deduced from block rotations across the north anatolian fault zone in turkey abstract theoretical considerations of lithosphere deformation across transform plate boundaries predict an expression in terms of 3istributed deformation the magnitude of rotation is expected to diminish away from the fault zone in a way which depends on the length of the fault the amount of displacement and the ductility of the lithosphere palaeomagnetic studies across the north anatolian transform fault zone which separates the eurasian plate and anatolian block in northern turkey show that clockwise rotations predicted from the sense of dextral motion are indeed present and have attained finite rotations of up to 270 during the 5 ma history of neotectonic deformation such rotations are however confined to narrow 10 km wide zones between system bounding faults and appear to have resulted from rotation in ball bearing fashion of equidimensional blocks a few kilometres in size outside of this zone only anticlockwise rotations are observed these are unrelated to deformation across the fault zone and record regional anticlockwise rotation of turkey which is complementing clockwise rotation of greece and accompanying neogene opening of the aegean sea the observed behaviour of continental lithosphere satisfies no plausible value of power law behaviour we therefore conclude that relative motion across this transform boundary occurs as a discrete zone of intense deformation within a brittle layer comprising the seismogenic upper crust this is presumed to be detached from a continuum deformation response to shearing in the lower crust and mantle beneath

paleomagnetism and crustal rotations along a shear zone las vegas range southern nevada in southern nevada paleozoic isopachs mesozoic structures and mountain ranges trend north south but as they approach the right lateral west northwest trending las vegas valley shear zone lvvsz they are bent clockwise up to 90 in oroflexes 30 km long in the las vegas range the declination of the characteristic magnetization of the cambrian bonanza king formation has likewise been rotated clockwise more than 50 for samples from eight sites 13 23 samples per site in the las vegas range and in its extension south of the lvvsz stepwise thermal demagnetization to 600 c removed recent and tertiary overprints revealing a nearly horizontal late paleozoic viscous partial thermoremanent magnetization vptrm which predates both the tertiary oroflexural bending and the sevier thrusting in the area the declination of the characteristic magnetization after correcting for the dip of bedding varies from 133 2 at a site 24 km north of the shear zone to 196 4 13 km north of it and 204 4 11 km south of the shear zone this parallels a similar change in the structural trend the paleomagnetic data indicate that the las vegas range is broken into rather small blocks 5 km which rotate in response to more continuous deformation at depth this deformation of the upper crust can be modelled using a thin non newtonian viscous plate model which when applied to the las vegas valley shear zone predicts rotations similar to those seen in the las vegas range

phyllosilicates in hydrothermally altered basalts from dsdp hole 504b leg 83 a tem and aem study phyllosilicates occurring as replacements of olivine clinopyroxene and interstitial materials and as veins or fracture fillings in hydrothermally altered basalts from dsdp hole 504b leg 83 have been studied using transmission and analytical electron microscopy the parageneses of phyllosilicates generally change systematically with depth and with the degree of alteration which in turn is related to permeability of basalts saponite and some mixed layer chlorite smectite are the dominant phyllosilicates at the top of the transition zone chlorite corrensite and mixed layer chlorite corrensite occur mainly in the lower transition zone and upper levels of the sheeted dike zone chlorite talc and mixed layer talc chlorite are the major phyllosilicates in the sheeted dike zone although replacement of talc or ohvine by saponite is observed the phyllosilicates consist of parallel or subparallel discrete packets of coherent layers with packet thicknesses generally ranging from 100 a to a few hundred a the packets of saponite layers are much smaller or less well defined than those of chlorite corrensite and talc indicating poorer crystal linity of saponite by contrast chlorite and talc from the lower transition zone and the sheeted dike zone occur in packets up to thousands of a thick the si si al ratio of these trioctahedral phyllosilicates increases and fe fe mg decreases in the order chlorite corrensite saponite and talc these relations reflect optimal solid solution consistent with minimum misfit of articulated octahedral and tetrahedral sheets variations in composition of hydrothermal fluids and precursor minerals especially in si si al and fe fe mg ratios are thus important factors in controlling the parageneses of phyllosilicates the phyllosilicates are generally well crystallized discrete phases rather than mixed layered phases where they have been affected by relatively high fluid rock ratios as in high permeability basalts in veins or areas adjacent to veins intense alteration in basalts with high permeability indicating high fluid rock ratios is characterized by pervasive albitization and zeolitization minimal alteration in the basalts without significant albitization and zeolitization is characterized by the occurrence of saponite mixed layer chlorite smectite in the low temperature alteration zone and mixed layer chlorite corrensite or mixed layer talc chlorite in the high temperature alteration zone textural non equilibrium for phyllosilicates is represented by mixed layering and poorly defined packets of partially incoherent layers the approach to textural equilibrium was controlled largely by the availability of fluid or permeability

sequential rotation of stretching axes and block rotations a structural and paleomagnetic study along the north anatolian fault abstract fault kinematics of the western part of the north anatolian fault an active transcurrent fault were investigated consistent successive counterclockwise rotation of incremental stretching directions was derived from the seven areas investigated we assumed that the changes in stretching directions correlate to the consistent rotation of one or several blocks caused by interaction of major fault segments in order to test this hypothesis we compared magnetic remanence directions measured within tertiary calc alkaline volcanic rocks with the changes in stretching direction in spite of the successive changes in stretching systematic changes in remanence directions were not observed most of the latter show no or low angular distances to the reference direction of d 335 i 50 both positive and negative signs are inferred for movements about subhorizontal and subvertical axes where magnetic remanence directions suggest rotation we conclude that changes in the overall deformation explain the systematic changes in incremental directions better than consistent external rotation a deformation path is proposed that includes ne sw and n s shortening during the paleogene and possibly lower miocene nw se shortening and penecontemporaneous local n s extension for the miocene and nw se to e w shortening and sw ne to n s extension for the pliocene until the present

late cretaceous to paleocene oroclinal bending in the central pontides turkey 1 the turkish pontide fold and thrust belt formed since the paleozoic and is an important element in the africa eurasia convergence and the resulting closure of the neo tethys ocean it has a peculiar arc shaped geometry in its central part along the black sea coast which may have resulted from oroclinal bending we have determined the vertical axis rotation history of this area using paleomagnetism on cretaceous to eocene rocks from 47 sites and critically analyzed previously published data we applied the same reliability criteria to all data our results show that late cretaceous sites have clockwise and counterclockwise rotations perpendicular to the structural trend in the central pontides in the eastern pontides they show only local rotations paleocene to eocene rocks in the central and eastern pontides show no rotation we conclude that the central pontide northward arc shaped geometry results from oroclinal bending in latest cretaceous to earliest paleocene times the timing and scale of geological processes that occurred in the region make it likely that orocline formation resulted from neo tethys closure between the pontides and the metamorphic promontory of the anatolide tauride block earlier studies on the southerly located cankiri basin reveal that clockwise and counterclockwise rotations occurred in eocene oligocene times this implies that the entire region underwent continuous deformation from late cretaceous to eocene caused by convergence of the pontides and the anatolide tauride block with a southward moving deformation front deformation was first localized in the northern part of the central pontides until the paleocene resulting in oroclinal bending and from at least eocene times it shifted toward the cankiri basin region

behavior of the brittle crust in wide plate boundary zones in wide and active continental plate boundary zones ductile flow in the deeper and strong parts of the lithosphere may control crustal deformation this is likely if average resistive shear stresses on faults in the brittle crust are much less than 108 pa and the underlying bulk effective viscosity is much greater than 1021 pa s in this case a simple model of distributed deformation referred to as the floating block model may be useful this treats the crust as an array of rotating and translating rigid blocks which are floating on an underlying continuous flow with a constant rheology the model is analyzed in detail in this paper because it has the potential to link detailed observations of crustal deformation with the large scale flow crustal blocks are defined by at least two sets of faults the kinematics of crustal deformation can be described in terms of the motions of these blocks both the relative motion on block boundaries faults and block tilting about a horizontal axis can be described in terms of the underlying flow and block rotation about a vertical axis however rotations about a vertical axis which are an important component of the crustal deformation will depend not only on the underlying flow but also on the shape orientation and arrangement of the crustal blocks the average rotation rate about a vertical axis over finite rotations will be significantly different from that predicted at any instant also the rotation history is considerably complicated if as is likely the underlying flow field or block shape has changed with time these aspects of crustal deformation are discussed with reference to real zones of active deformation in new zealand greece and western north america

comparative mineral chemistry and textures of safod fault gouge and damage zone rocks abstract creep in the san andreas fault observatory at depth safod drillhole is localized to two foliated gouges the central deforming zone cdz and southwest deforming zone sdz the gouges consist of porphyroclasts of serpentinite and sedimentary rock dispersed in a foliated matrix of mg smectite clays that formed as a result of shearing enhanced reactions between the serpentinite and quartzofeldspathic rocks the cdz takes up most of the creep and exhibits differences in mineralogy and texture from the sdz that are attributable to its higher shearing rate in addition a 0 2 m wide sector of the cdz at its northeastern margin ne cdz is identical to the sdz and may represent a gradient in creep rate across the cdz the sdz and ne cdz have lower clay contents and larger porphyroclasts than most of the cdz and they contain veinlets and strain fringes of calcite in the gouge matrix not seen elsewhere in the cdz matrix clays in the sdz and ne cdz are saponite and corrensite whereas the rest of the cdz lacks corrensite saponite is younger than corrensite reflecting clay crystallization under declining temperatures and clays in the more actively deforming portions of the cdz have better equilibrated to the lower temperature conditions

paleomagnetic reconstruction of the cenozoic evolution of the eastern mediterranean abstract a total of 113 paleomagnetic sites were sampled along an anatolian s n transect from the arabian platform the hatay region the eastern taurides the kirsehir block the sivas basin and the eastern pontides reliable characteristic remanent paleomagnetic directions were retrieved from 37 of these sites spanning in time from paleocene to miocene in a general way declinations are westerly deviated and inclinations are shallower than the geocentered dipole value at the present latitudes when combined with previously published results these data indicate that a large scale counterclockwise rotation of anatolia of some 25 has occurred since the miocene assuming that the pole of rotation of anatolia with respect to europe has remained constant in time at the location given by macclusky et al j geophys res 105 2000 5695 on the basis of the geodetic data this rotation implies that a large westward displacement 500 km at the average latitude of 40 has taken place assuming that the rotation was initiated by the arabia europe collision about 12 ma ago this corresponds to an average displacement of about 40 mm year together with previous results from the western part of the aegean arc these results indicate that the main trends of the cenozoic evolution of the eastern mediterranean appear to consist of two post early miocene rotations of opposite senses a clockwise rotation of the western part of the aegean tectonophysics 146 1988 183 around a pole situated in northern albania and a counterclockwise rotation around the pole given by mcclusky et al j geophys res 105 2000 5695 comparison with gps data suggest that both rotations are still active today

the north anatolian fault a new look dedicated to the memory of three pioneers ihsan ketin sirri erinc and melih tokay and a recent student aykut barka who burnt himself out in pursuit of the mysteries of the north anatolian fault abstract the north anatolian fault naf is a 1200 km long dextral strike slip fault zone that formed by progressive strain localization in a generally westerly widening right lateral keirogen in northern turkey mostly along an interface juxtaposing subduction accretion material to its south and older and stiffer continental basements to its north the naf formed approximately 13 to 11 ma ago in the east and propagated westward it reached the sea of marmara no earlier than 200 ka ago although shear related deformation in a broad zone there had already commenced in the late miocene the fault zone has a very distinct morphological expression and is seismically active since the seventeenth century it has shown cyclical seismic behavior with century long cycles beginning in the east and progressing westwa

talc bearing serpentinite and the creeping section of the san andreas fault the section of the san andreas fault located between cholame valley and san juan bautista in central california creeps at a rate as high as 28 mm yr 1 ref 1 and it is also the segment that yields the best evidence for being a weak fault embedded in a strong crust serpentinized ultramafic rocks have been associated with creeping faults in central and northern california and serpentinite is commonly invoked as the cause of the creep and the low strength of this section of the san andreas fault however the frictional strengths of serpentine minerals are too high to satisfy the limitations on fault strength and these minerals also have the potential for unstable slip under some conditions here we report the discovery of talc in cuttings of serpentinite collected from the probable active trace of the san andreas fault that was intersected during drilling of the san andreas fault observatory at depth safod main hole in 2005 we infer that the talc is forming as a result of the reaction of serpentine minerals with silica saturated hydrothermal fluids that migrate up the fault zone and the talc commonly occurs in sheared serpentinite this discovery is significant as the frictional strength of talc at elevated temperatures is sufficiently low to meet the constraints on the shear strength of the fault and its inherently stable sliding behaviour is consistent with fault creep talc may therefore provide the connection between serpentinite and creep in the san andreas fault if shear at depth can become localized along a talc rich principal slip surface within serpentinite entrained in the fault zone

palaeomagnetic evolution of the cankiri basin central anatolia turkey implications for oroclinal bending due to indentation p alaeomagnetic data in combination with palaeostress data and anisotropy of magnetic susceptibility orientations are utilized to develop a tectonic evolutionary model for the early tertiary part of the omega shaped ca nkiri basin turkey the results reveal clockwise rotations in the northeast and anticlockwise rotations in the west and southeastern corner of the basin the magnetic inclinations indicate a northward drift of the ca nkiri basin and support an indentation model for the kirsehir block it is proposed that the shape of the cankiri basin was the result of indentation of the kirsehir block into the sakarya continent during northwards migration accompanying closure of neotethys it appears that the indentation started prior to eocene and ended before middle miocene times

the origin of neogene tectonic rotations in the galatean volcanic massif central anatolia a paleomagnetic study was carried out on neogene volcanic rocks at 30 sites within the galatean massif 40 4 n 31 5 e to determine possible block rotations due to stress variations two phases of rotation could be characterized as the result of neogene volcanic activity we suggest that the first stage of rotation was isolated in early middle miocene calc alkali rocks with a relative counterclockwise rotation of r r 20 2 9 3 with respect to eurasia this accommodates the south westward rotational collapse of the western anatolia peninsula across a pole on the bitlis suture in the neotectonic period on other hand a relative clockwise rotation of r r 27 3 6 4 with respect to eurasia is predicted in contrast to the uniform clockwise rotations extremely large clockwise rotations up to 264 are restricted in a narrow zone between two dextral faults we believe that the second stage rotations support the idea of individual microblock rotations due to deformation along the north anatolian fault zone

neotectonic deformation in the eurasia arabia collision zone the east anatolian plateau e turkey evidence from palaeomagnetic study of neogene quaternary volcanic rocks palaeomagnetic studies of the neogene quaternary rocks of anatolia have been mostly interpreted in the light of its westward escape as a result of the collision between the arabian and eurasian plates along the bitlis zagros suture during the neotectonic period however within the collision zone in east anatolia palaeomagnetic data are not available in order to help understand the deformational history of eastern anatolia during the neotectonic period we have carried out a palaeomagnetic study of miocene quaternary volcanic rocks from 100 sites selected on the basis of their geographical position and known age the results indicate that the study area can be divided into five principal tectonic blocks based on earthquake activity and the rotation that the blocks underwent these blocks are the van block vb the kars block kb the anatolian block ab the pontide block pb and the arabian block arb the largest counterclockwise ccw tectonic rotations were encountered in the ab and pb whereas the largest clockwise cw rotations were recorded in the vb the sinistral east anatolian fault and the erzurum fault zone form the present boundary of these two contrasting cw and ccw rotating domains both the ab and the pb exhibit similar amount of rotation until the quaternary during which the ab rotated 13 ccw while the pb remained stable the quaternary rotation of the ab is attributed to the activity of the north anatolian fault the kb shows the smallest amount of cw rotation during all of the time intervals studied all of the blocks studied indicate an acceleration in the amount of rotations during the quaternary which was preceded by a period of relative tectonic stability during the late pliocene following the collision of the arabian plate with the eurasian plate during the mid miocene the crust was initially thickened by thrusting and folding this was followed by lateral extrusion and differential rotation of the crustal blocks during late miocene pliocene in response to ongoing indentation of the arabian plate our data show that strike slip faults that commonly separate wedge shape crustal blocks are the most significant means of accommodating the tectonic escape and rotation of crustal blocks in east anatolia delamination of the lower crust and the lithospheric mantle may have contributed to the deformation by thermally weakening the crust

chemical controls on fault behavior weakening of serpentinite sheared against quartz bearing rocks and its significance for fault creep in the san andreas system 1 the serpentinized ultramafic rocks found in many plate tectonic settings commonly are juxtaposed against crustal rocks along faults and the chemical contrast between the rock types potentially could influence the mechanical behavior of such faults to investigate this possibility we conducted triaxial experiments under hydrothermal conditions 200 350 c shearing serpentinite gouge between forcing blocks of granite or quartzite in an ultramafic chemical environment the coefficient of friction of lizardite and antigorite serpentinite is 0 5 0 6 and increases with increasing temperature over the tested range however when either lizardite or antigorite serpentinite is sheared against granite or quartzite strength is reduced to 0 3 with the greatest strength reductions at the highest temperatures temperature weakening and slowest shearing rates velocity strengthening the weakening is attributed to a solution transfer process that is promoted by the enhanced solubility of serpentine in pore fluids whose chemistry has been modified by interaction with the quartzose wall rocks the operation of this process will promote aseismic slip creep along serpentinite bearing crustal faults at otherwise seismogenic depths during short term experiments serpentine minerals reprecipitate in low stress areas whereas in longer experiments new mg rich phyllosilicates crystallize in response to metasomatic exchanges across the serpentinite crustal rock contact long term shear of serpentinite against crustal rocks will cause the metasomatic mineral assemblages which may include extremely weak minerals such as saponite or talc to play an increasingly important role in the mechanical behavior of the fault our results may explain the distribution of creep on faults in the san andreas system

neogene anticlockwise rotation of central anatolia turkey preliminary palaeomagnetic and geochronological results abstract a palaeomagnetic and geochronological study was carried out on fifty sites from the neogene volcanic province of central anatolia results from this analysis show that there has been a progressive anticlockwise rotation of this region over the period spanning at least the last 10 12 ma we interpret this rotation as having resulted from the collision of arabia with anatolia along the bitlis suture if we assume a constant rate of rotation we obtain a rate of 2 4 ma this value is significantly higher than the present day rotation rate obtained from gps 1 3 0 1 ma and also implies that these rocks have been rotating at their present rate since well before collision occurred along the bitlis suture 12 ma a geologically unreasonable conclusion if however we combine these data with data from other palaeomagnetic studies with good age control the resultant curve seems to show three distinct linear segments 1 0 5 ma with a very slow rate of rotation 1 2 ma 2 5 12 ma where we observe a rapid increase of rotation rate to 6 5 ma and 3 12 ma when the rotation rate is again essentially zero 0 041 ma these results are generally consistent with a model calling for middle miocene collision along the bitlis suture and late plio pleistocene initiation of motion along the north and east anatolian fault zones

a block model of distributed deformation by faulting it is clear from palaeomagnetic evidence that large and hitherto unexpected rotations about a vertical axis are common in regions of distributed continental deformation we propose a simple two dimensional model to illustrate how fault movement and block rotation within a zone of distributed deformation may be related to the relative motion of the rigid plates that bound the zone one surprizing feature of this model is that the component of strike slip motion on the faults within the deforming zone is in the opposite sense to the strike slip component across the zone as a whole thus slip vectors within the zone are not the same as that between the bounding rigid plates in contrast to deformation at oceanic plate boundaries examples of active fault geometries similar to those of our model can be seen in greece iran and the western usa

the relationship between strain rates crustal thickening palaeomagnetism finite strain and fault movements within a deforming zone the deformation of continental lithosphere generally does not occur on a single fault but is distributed over a zone up to a few hundred kilometers wide if the deformation rate is constant throughout the zone and if the velocity is continuous everywhere and does not change with time the deformation gradient tensor can be obtained analytically this tensor directly determines the amount of crustal thickening and is related in a complicated manner to the finite strain tensor the declination of remnant magnetization measured within the zone can also be rotated by the deformation because palaeomagnetic measurements are generally made on rigid blocks which have not been deformed there is no simple relationship between such rotations and the finite strain expressions for all these quantities are obtained in terms of the velocity gradients which are taken to be constant the history of western north america is used to illustrate the relationship between the present deformation by strike slip and thrust motions the rotations of the remnant magnetization vectors and the shape of accreted terranes at the surface distributed deformation is taken up by motion on faults which separate the zone into blocks the displacement rate on the faults their strike and the finite rotations of the blocks are all controlled by the velocity gradients analytic expressions relating these quantities are obtained a deforming zone containing normal faults which crosses central greece takes up both strike slip and extension and illustrates the relationship between the structures within and the motion across the zone a similar but more complicated zone in northeastern iran involves both strike slip and shortening

crustal deformation and kinematics of the eastern part of the north anatolian fault zone turkey from gps measurements abstract the north anatolian fault zone nafz is a 1200 km long dextral strike slip fault zone forming the boundary between the eurasian and anatolian plates it extends from the gulf of saros north aegean in the west to the town of karliova in eastern turkey although there have been numerous geodetic studies concerning the crustal deformation velocity field and the slip rate of the nafz along its western and central segments geodetic observations along the eastern section of the nafz are sparse in order to investigate the gps velocities and the slip rate along the eastern part of the nafz a dense gps network consisting of 36 benchmarks was installed between tokat and erzincan on both sides of the fault zone and measured from 2006 to 2008 measurement results indicate that the slip rate of the nafz increases westwards within about 400 km from 16 3 2 3 mm year to 24 0 2 9 mm year in consistence with the observation that the anatolian block is being pulled by the hellenic trench rather than being pushed by the arabian plate as a result of continental collision between the arabian and eurasian plates in eastern turkey since late miocene modelling the gps velocities shows that fault locking depth increases also in the same direction from 8 1 3 3 km to 12 8 3 9 km slip rate decreases as moving off the hellenic trench an average slip rate of 20 1 2 4 mm year and a locking depth of 12 5 3 5 km are also estimated for the entire study area by using all of the gps measurements obtained in this study the gps velocities are in good agreement with the kinematic models created by paleomagnetic studies in the region and complete the overall picture

global evaluation of large earthquake energy from 1997 through mid 2010 1 we develop an updated radiated seismic energy e catalog of global earthquakes with seismic moment m0 1019 nm mw 6 7 from 1997 through mid 2010 recording 342 events using 17849 seismograms station specific corrections and event duration dependent total p wave group calculations allow for improved e determinations for large and long duration earthquakes we find the global mean energy to moment ratio log10 e m0 4 59 0 36 robust deviations are found for thrust t 4 74 strike slip ss 4 44 and normal n 4 51 faulting events for two regions with recent energy deficient tsunami earthquakes tse we examine all large thrust earthquakes with m0 5 1017 nm mw 5 7 to identify a regional characterization in their relative radiated energy to moment ratio while thrust events along java indonesia the site of two tse events in 1994 and 2006 are comparable t jv 4 91 to the global thrust average events along the middle america trench mat the site of the 1992 nicaragua tse are consistently deficient t mat 5 15 along the mat a trend of increased deficiency in radiated energy to the southeast occurs in the direction of more rapid plate convergence global thrust mechanisms become increasingly deficient in radiated seismic energy at shallow depths with tse events representing the shallowest and most energetically deficient end member of the events in the study results suggest thrust events are highly variable but tend to increase in apparent stress from about 15 kpa near the surface to 2 mpa near 70 km depth

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

esr in the 21st century from buried valleys and deserts to the deep ocean and tectonic uplift abstract electron spin resonance esr dating can date many materials including hydroxyapatite in enamel and some fish scales aragonite and calcite in corals molluscs some travertine and calcrete and quartz from ash fluvial deposits and some flint dating studies using these materials have numerous potential applications in many varied quaternary settings esr dating uses signals resulting from trapped charges created by radiation in crystalline solids ages are calculated by comparing the accumulated radiation dose in the dating sample with the internal and external radiation dose rates produced by natural radiation in and around the sample and produced by cosmic radiation when compared to other dating techniques age agreement has been excellent for teeth corals molluscs and quartz recent improvements have included using a more complex modelling technique to calculate the cosmic dose rates and more detailed modelling techniques for dealing with variable external dose rates methods in development include using quartz from buried fluvial valleys to date geomorphic surfaces and using the signals in barnacles and benthic foraminifera for dating fossils or their associated sediment new chronometer applications recently developed include using coral and mollusc dates to build sealevel curves and to monitor volcanic activity and tectonic uplift using tooth and mollusc dates to assess water availability in deserts and using isochron data to assess u uptake processes into teeth when coupled with other geochemical and geomorphological techniques esr can provide the chronometric control to build paleoclimatic and other paleoenvironmental records many other applications are possible from heating studies for artefacts to dating sulphates and other minerals on distant planets

palaeomagnetic study of block rotations in the niksar overlap region of the north anatolian fault zone central turkey abstract this palaeomagnetic study investigates crustal deformation within and adjacent to the niksar overlap area of the north anatolian fault zone nafz in central east turkey the studied rock formations comprise 1 red limestones of late cretaceous age 3 sites 2 mafic lavas of eocene age on the north side 13 sites and south side 9 sites of the nafz and 3 volcanic rocks of pliocene quaternary age from the niksar pull apart basin within the nafz 8 sites comparisons with reference palaeofield directions computed from apparent polar wander paths of the eurasian and afro arabian plates identify two scales of regional and local tectonic rotation 1 1 a pre tilting remanence in the eocene volcanic rocks south of the nafz d i 144 1 47 5 95 7 6 is interpreted to reflect counterclockwise rotation by 30 40 from the reference palaeofields contemporaneous volcanic rocks from the north side of the nafz have the same reverse polarity recorded in pre tilting magnetisations the remanence is also rotated counterclockwise d i 152 4 42 5 95 11 3 but by about 8 less than the volcanics on the south side of the nafz hence similar amounts of rotation are observed on both sides of the nafz and are interpreted to reflect motions during the pre middle miocene collisional history in this sector of the pontides no distributed clockwise rotations anticipated from subsequent dextral motion along the nafz intracontinental transform are observed the slightly larger anticlockwise rotation found on the south side of the nafz probably records relative rotation of en echelon wedges by continental escape during post middle miocene strike slip along the transform 2 2 within the narrow zone of intense deformation along the nafz cretaceous limestones appear to be rotated clockwise by dextral strike slip motion whilst plio quaternary lavas within a fault bounded block in the overlap region associated with the niksar pull apart basin have magnetisations consistently directed 240 270 e magnetic inclinations are not diagnostic of polarity but both polarity solutions identify rapid clockwise rotation at rates in excess of 50 m y a normal polarity solution is favoured and implies that a block ca 5 km across has undergone a strike slip displacement of around 12 km within the nafz during the last polarity chron cretaceous eocene palaeolatitudes are closer to those predicted from eurasia than afro arabia but a study of older rocks is required to resolve affinities of this sector of the anatolian block theoretical models of crustal deformation across intracontinental transforms obeying power law behaviour and treating the lithosphere as a viscous medium predict that distributed clockwise rotations should be observed about as broad across the nafz these rotations are not observed instead intense clockwise rotation is confined to a narrow zone close to the major fault break the concentration of historic seismic activity here also implies that the bulk of the dextral motion between the eurasian plate and the anatolian block is accommodated by slip along faults close and parallel to the main trace of the nafz

a palaeomagnetic study of the sivas basin central turkey crustal deformation during lateral extrusion of the anatolian block abstract the sivas basin is a complex collage of eocene and younger rocks located within the wedge shaped eastern margin of the anatolian block between the dextral north anatolian fault zone and the sinistral eastern anatolian fault zone it has been subject to ongoing deformation by movement of the arabian block into eurasia and concomittant sideways expulsion of the anatolian block post collisional deformation since mid miocene times has been dominated by n s to nw se compression expressed by thrusting and strike slip faulting cretaceous and eocene rocks were magnetically overprinted to variable degrees during the collisional phase although these overprints have since been rotated mostly anticlockwise rocks emplaced during the neotectonic history are high fidelity palaeomagnetic recorders of subsequent block movements regional anticlockwise rotation is recognised across the basin with differential rotation of fault and thrust bounded blocks an absence of perceptible differences between group mean rotations identified from miocene pliocene and quaternary units shows that most regional rotation has been concentrated within the latest phase of the neotectonic history during quaternary times at an average rate of 10 ma commencement of this rotation postdates initiation of the north anatolian fault zone implying that compression following collision was accomodated initially by crustal thickening during late miocene and pliocene times subsequent anticlockwise rotations have resulted from sideways expulsion of blocks to the south of the central anatolian thrust along major ne sw sinistral faults to achieve the crustal shortening resulting from n s compression these fault orientations and their sense of motion are explained by a prandtl model involving deformation of a triangular plastic terrane the anatolian block between two rigid plates eurasia and afro arabia the variations in regional rotation identified by palaeomagnetism show that average contemporary anticlockwise rotation of anatolia revealed by gps data 1 2 ma is achieved by variable and locally large block rotations between major thrusts and strike slip faults

differential neotectonic rotations in anatolia and the tauride arc palaeomagnetic investigation of the erenlerdaǧ volcanic complex and isparta volcanic district south central turkey abstract in the anatolian sector of the alpine himalayan collisional belt a palaeotectonic phase of terrane accretion has been succeeded by a neotectonic phase of intracontinental deformation as the afro arabian plate has continued to impinge differentially into the accreted collage the resulting tectonic escape has during the last few million years extruded and rotated blocks in a southwesterly direction this paper reports a palaeomagnetic investigation of the erenlerda volcanic complex and isparta alkaline volcanic district undertaken to extend analysis of crustal rotation into the southwestern part of the anatolian region and investigate the interaction with the isparta angle and the extensional province of western turkey the erenlerda volcanism comprises three phases of volcanism the oldest sille volcanics 11 7 11 4 ma yield a mean d 150 i 52 rotated anticlockwise during early stages of crustal thickening and deformation before a later miocene episode c 10 9 8 9 ma d 183 i 47 and a mio pliocene episode d 179 i 51 the latter two episodes indicate that no significant rotation has resulted during the neotectonic crustal extrusion in this southwestern sector of anatolia further to the west within the isparta angle a 4 7 4 0 ma alkaline episode yields a mean of d 186 i 53 rotated slightly clockwise the pattern of palaeomagnetic declinations across anatolia shows rotations that are strongly anticlockwise in the east near the arabian pincer and diminish towards the west to become zero or slightly clockwise at the western extremity of the collage the timing of rotation also appears to become younger towards the south crustal deformation has therefore been distributed and the net effect of terrane extrusion to the west and south has been to expand the curvature of the tauride arc and by inference the cyprian arc where good age control exists in cappadocia and the sivas basin rotations are found to be concentrated within the last few million years and are up to an order higher than rates deduced from global positioning system the palaeomagnetic data imply that the neotectonic deformation following collision initially produced crustal thickening resulting in uplift of the anatolian plateau and was only subsequently accommodated by major differential block rotation during tectonic escape

palaeomagnetic evidence for substantial rotation of the almacik flake within the north anatolian fault zone nw turkey summary palaeomagnetic data on eocene rocks from within the almacik flake bounded by two strands of the north anatolian right lateral fault indicate that the flake has undergone an apparent counterclockwise rotation of about 148 on average we interpret this as a real 212 clockwise rotation because the almacik flake is entirely delimited by the right lateral north anatolian fault strands the only dominant post eocene structure in the area and because areas surrounding the flake do not show the same rotation this rotation must have occurred since the north anatolian fault originated in the late medial miocene late serravallian 11 5 ma and if so may imply either a larger total slip along it than hitherto estimated or that the almacik flake is the surface expression of a flower structure rotating above a shear zone narrower than the present width of the flake

middle eocene paleomagnetic data from the eastern sakarya zone and the central pontides implications for the tectonic evolution of north central anatolia 1 a paleomagnetic investigation has been carried out on middle eocene volcanic rocks at 23 sites in the eastern sakarya zone and the central pontides of north central anatolia in order to better understand the regional tectonic evolution of the main zones of northeastern anatolia in the middle eocene the results constrain the tectonic evolution of the area when evaluated in conjunction with earlier published paleomagnetic directions from 92 localities small counterclockwise rotations in the range of r r 1 3 1 4 to r r 17 2 16 8 with respect to eurasia are observed in the central pontides on the northern side of the north anatolian fault naf clockwise rotations ranging between r r 8 5 15 1 and r r 29 7 12 0 are observed between the naf and the sungurlu fault sf in the eastern sakarya zone counterclockwise rotations of r r 18 9 12 4 to r r 42 2 6 9 are observed to the south of the sf our findings combined with previous data support the indentation model of kaymakci et al 2000 2003a 2003b which postulates the collision and northeast directed indentation of the kirsehir block into the sakarya zone this model which was developed to explain the evolution of the cankiri basin can also explain the variable magnitudes of paleomagnetically determined rotations thrust directions and the curvature of the north anatolian ophiolite belt

palaeomagnetic study of the erciyes sector of the ecemis fault zone neotectonic deformation in the southeastern part of the anatolian block

present day strain distribution across a segment of the central bend of the north anatolian fault zone from a persistent scatterers insar analysis of the ers and envisat archives

corrensite and mixed layer chlorite corrensite in metabasalt from northern taiwan tem aem empa xrd and optical studies many chloritic minerals in low grade metamorphic or hydrothermally altered mafic rocks exhibit abnormal optical properties expand slightly upon glycolation expandable chlorite and or have excess alvi relative to aliv as well as significant ca k and na contents chloritic minerals with these properties fill vesicles and interstitial void space in low grade metabasalt from northern taiwan and have been studied with a combination of tem aem empa xrd and optical microscopy the chloritic minerals include corrensite which is an ordered 1 1 mixed layer chlorite smectite and expandable chlorite which is shown to be a mixed layer chlorite corrensite corrensite and some mixed layer chlorite corrensite occur as rims of vesicles and other cavities while later formed mixed layer chlorite corrensite occupies the vesicle cores the tem observations show that the mixed layer chlorite corrensite has ca 20 and the corrensite has ca 50 expandable smectite like layers consistent with xrd observations and with their abnormal optical properties the aem analyses show that high si and ca contents high alvi aliv and low fevi fe mg vi ratios of chlorites are correlated with interstratification of corrensite or smectite like layers in chlorite the aem analyses obtained from 200 500 a thick packets of nearly pure corrensite or chlorite layers always show that corrensite has low aliv siiv and low fevi fe mg vi while chlorite has high aliv siiv and high fevi fe mg vi this implies that the trioctahedral smectite like component of corrensite has significantly lower aliv siiv and fevi fe mg vi the ratios of fevi fe mg vi and aliv siiv thus decrease in the order chlorite corrensite smectite the proportions of corrensite or smectite like layers relative to chlorite layers in low grade rocks are inferred to be controlled principally by fe mg ratio in the fluid or the bulk rock and by temperature compositional variations of chlorites in low grade rocks which appear to correlate with temperature or metamorphic grade more likely reflect variable proportions of mixed layered components the assemblages of trioctahedral phyllosilicates tend to occur as intergrown discrete phases such as chlorite corrensite corrensite smectite or chlorite corrensite smectite a model for the corrensite crystal structure suggests that corrensite should be treated as a unique phase rather than as a 1 1 ordered mixed layer chlorite smectite

frictional properties and sliding stability of the san andreas fault from deep drill core the strength of tectonic faults and the processes that control earthquake rupture remain central questions in fault mechanics and earthquake science we report on the frictional strength and constitutive properties of intact samples across the main creeping strand of the san andreas fault saf california united states recovered by deep drilling we find that the fault is extremely weak friction coefficient 0 10 and exhibits both velocity strengthening frictional behavior and anomalously low rates of frictional healing consistent with aseismic creep in contrast wall rock to the northeast shows velocity weakening frictional behavior and positive healing rates consistent with observed repeating earthquakes on nearby fault strands we also document a sharp increase in strength to values of 0 40 over 1 m distance at the boundary between the fault and adjacent wall rock the friction values for the saf are sufficiently low to explain its apparent weakness as inferred from heat flow and stress orientation data our results may also indicate that the shear strength of the saf should remain approximately constant at 10 mpa in the upper 5 8 km rather than increasing linearly with depth as is commonly assumed taken together our data explain why the main strand of the saf in central california is weak extremely localized and exhibits aseismic creep while nearby fault strands host repeating earthquakes

reinterpretation of the ordovician rotations in nw argentina and northern chile a consequence of the precordillera collision early paleozoic paleomagnetic data from nw argentina and northern chile have shown large systematic rotations within two domains one composed of the western puna that yields very large up to 80 counter clockwise rotations and the other formed by the famatina ranges and the eastern puna that shows 40 clockwise rotations around vertical axes in several locations lack of significant rotations in younger rocks constrains this kinematic pattern to have occurred during the paleozoic previous tectonic models have explained these rotations as indicative of rigid body rotations of large para autochthonous crustal blocks or terranes a different but simple tectonic model that accounts for this pattern is presented in which rotations are associated to crustal shortening and tectonic escape due to the collision of the allochthonous terrane of precordillera in the late ordovician this collision should have generated dextral shear zones in the back arc region of the convergent sw gondwana margin where systematic domino like clockwise rotations of small crustal blocks accommodate crustal shortening the western puna block bordering the precordillera terrane to the north might have rotated counterclockwise as an independent microplate due to tectonic escape processes in a fashion similar to the present day relationship between the anatolia block and the arabian microplate

counterclockwise rotation of the anatolian block abstract seismological and other data from the boundaries of anatolia are used to discuss the motion and plate tectonics of this block models which include a rotation of anatolia around a single pole are shown to be inconsistent with much of this data in particular a westward motion of anatolia which is the most commonly used model should be reconsidered models which use a single pole of rotation fail because they assume the north anatolian fault to be an ideal transform fault which describes all of the motion between anatolia and the black sea in effect internal deformation in the form of extension in western anatolia and for the most part strike slip faulting in eastern anatolia are important and account for some of the relative motion thus a more appropriate model for this region is one which not only stresses the dominance of the north anatolian fault but also recognises the importance of internal deformation and the limitation of classic plate tectonic models which this deformation implies the preferred model for the motion of anatolia is a nonuniform tight counterclockwise rotation approximated by the shape of the north anatolian fault as well as by the faults which splay from it to the south such a model is consistent with data from the boundaries of anatolia including the source mechanism of earthquakes and depth of benioff zone along the southern boundary of the block counterclockwise rotation of anatolia is the natural consequence of the collision of arabia with eastern anatolia coupled with subduction in the eastern mediterranean

strike slip faulting topographic growth and block movements as deduced from drainage anomalies the yesilirmak river basin northern turkey abstract this study aims to understand the various effects of known tectonism on a fluvial network and to interpret the tectonic deformations using described and analysed systematic anomalies in the drainage basin of the yesilirmak river in northern turkey at countermarch this region which is divided into several faulted wedges by right lateral strike slip faulting of the north anatolian fault zone and its individual splays has experienced several moderate to large earthquakes with high amounts of surface ruptures during the historical and instrumental periods the yesilirmak river basin includes several geomorphic imprints of such widespread and frequent strike slip deformations offsets between 750 m and 19 km aligned drainages and linear valleys 170 km are expected geomorphic and tectonic responses to strike slip faulting in the fluvial system we used such indicators to determine the long term effects of strike slip faulting in the yesilirmak river drainage network the measured stream offsets represent decreasing values toward southern splay faults consistent with published geodetic data for the region however some other large scale geomorphic anomalies extracted from the drainage network are not explainable by only strike slip tectonics compressional structures i e anticlines synclines in the region are responsible for such large scale drainage diversions 20 24 km along the river courses although these diversions the north anatolian fault zone is the main driving force shaping present geomorphology on a regional scale the sungurlu ezinepazari fault also plays a critical role in landscape evolution their activities and associated block movements have resulted with tilting processes on the other hand the entire fluvial network should be modified by the sea level changes of the black sea particularly in the late quaternary

why are there no clockwise rotations along the north anatolian fault zone mechanical analysis of lithospheric deformation associated with an intracontinental transform fault suggests that it should be associated with a pattern of vertical axis rotations governed by the length of the fault its displacement and the mechanical properties of the lithosphere paleomagnetic results from two transects across the north anatolian fault zone indicate that there have been no measurable clockwise rotations on a regional scale associated with neogene dextral strike slip motion along the fault the data come from two groups of volcanic rocks that have been dated by k ar whole rock geochronology and have yielded ages ranging from 45 3 3 1 m y to 41 8 1 3 m y eocene and 21 7 1 5 m y to 7 5 0 2 m y miocene the absence of clockwise rotations suggests one of the following explanations 1 in contrast to the assumptions underlying current mechanical analyses deformation in the upper crust may not directly reflect the flow in the lithosphere and is localized along a single fault trace 2 deformation is distributed but rotations have been prevented by the presence of elongate fault blocks subparallel to the trace of the main fault 3 displacement along the north anatolian fault may be too small or the rheologic properties of the lithosphere such that rotations about vertical axes cannot be resolved instead of the predicted clockwise rotations measured declinations show that there has been approximately 30 of anticlockwise rotation of both the eocene and miocene volcanic rocks this suggests that no significant rotation occurred between eocene and miocene times and that the anticlockwise rotation occurred either immediately before or concurrent with the plio pleistocene slip on the north anatolian fault

global positioning system constraints on plate kinematics and dynamics in the eastern mediterranean and caucasus we present and interpret global positioning system gps measurements of crustal motions for the period 1988 1997 at 189 sites extending east west from the caucasus mountains to the adriatic sea and north south from the southern edge of the eurasian plate to the northern edge of the african plate sites on the northern arabian platform move 18 2 mm yr at n25 5 w relative to eurasia less than the nuvel 1a circuit closure rate 25 1 mm yr at n21 7 w preliminary motion estimates 1994 1997 for stations located in egypt on the northeastern part of africa show northward motion at 5 6 2 mm yr also slower than nuvel ia estimates 10 1 mm yr at n2 4 e eastern turkey is characterized by distributed deformation while central turkey is characterized by coherent plate motion internal deformation of 2 mm yr involving westward displacement and counterclockwise rotation of the anatolian plate the anatolian plate is de coupled from eurasia along the right lateral strike slip north anatolian fault naf we derive a best fitting euler vector for anatolia eurasia motion of 30 7 0 8 n 32 6 0 4 e 1 2 0 1 myr the euler vector gives an upper bound for naf slip rate of 24 1 mm yr we determine a preliminary gps arabia anatolia euler vector of 32 9 1 2 n 40 3 1 1 e 0 8 0 2 myr and an upper bound on left lateral slip on the east anatolian fault eaf of 9 1 mm yr the central and southern aegean is characterized by coherent motion internal deformation of 2 mm yr toward the sw at 30 1 mm yr relative to eurasia stations in the se aegean deviate significantly from the overall motion of the southern aegean showing increasing velocities toward the trench and reaching 10 1 mm yr relative to the southern aegean as a whole

block versus continuum deformation in the western united states abstract the relative role of block versus continuum deformation of continental lithosphere is a current subject of debate continuous deformation is suggested by distributed seismicity at continental plate margins and by cumulative seismic moment sums which yield slip estimates that are less than estimates from plate motion studies in contrast block models are favored by geologic studies of displacement in places like asia a problem in this debate is a lack of data from which unequivocal conclusions may be reached in this paper we apply the techniques of study used in regions such as the alpine himalayan belt to an area with a wealth of instrumental data the western united states by comparing plate rates to seismic moment release rates and assuming a typical seismogenic layer thickness of 15 km it appears that since 1850 about 60 of the pacific north america motion across the plate boundary in california and nevada has occurred seismically and 40 aseismically the san francisco bay area shows similar partitioning between seismic and aseismic deformation and it can be shown that within the seismogenic depth range aseismic deformation is concentrated near the surface and at depth in some cases this deformation can be located on creeping surface faults but elsewhere it is spread over a several kilometer wide zone adjacent to the fault these superficial creeping deformation zones may be responsible for the palaeomagnetic rotations that have been ascribed elsewhere to the surface expression of continuum deformation in the lithosphere our results support the dominant role of non continuum deformation processes with the implication that deformation localization by strain softening must occur in the lower crust and probably the upper mantle our conclusions apply only to the regions where the data are good and even within the western united states i e the basin and range deformation styles remain poorly resolved nonetheless we maintain that block motion is the deformation style of choice for those continental regions where the data are best

palaeomagnetically defined rotations of fault bounded continental blocks in the north anatolian shear zone north central anatolia abstract the 1200 km long north anatolian transform fault connects the east anatolian post collisional compressional regime in the east with the aegean back arc extensional regime to the west this active dextral fault system lies within a shear zone reaching up to 100 km in width and consists of southward splining branches these branches which have less frequent and smaller magnitude earthquake activity compare to the major transform cut and divide the shear zone into fault delimited blocks comparison of palaeomagnetic data from 46 sites in the eocene volcanics from different blocks indicate that each fault bounded block has been affected by vertical block rotations although clockwise rotations are dominant as expected from dextral fault bounded blocks anticlockwise rotations have also been documented these anticlockwise rotations are interpreted as due to anticlockwise rotation of the anatolian block as indicated by gps measurements and the effects of unmapped faults or pre north anatolian fault tectonic events

estimates of seismic potential in the marmara sea region from block models of secular deformation constrained by global positioning system measurements we model the geodetically observed secular velocity field in north western turkey with a block model that accounts for recoverable elastic strain ac cumulation the block model allows us to estimate internally consistent fault slip rates and locking depths the northern strand of the north anatolian fault zone nafz carries approximately four times as much right lateral motion 24 mm yr as does the southern strand in the marmara sea region the data show strain accu mulation to be highly localized we find that a straight fault geometry with a shallow locking depth of 6 7 km fits the observed global positioning system velocities better than does a stepped fault geometry that follows the northern and eastern edges of the sea this shallow locking depth suggests that the moment release associated with an earthquake on these faults should be smaller by a factor of 2 3 than previously inferred assuming a locking depth of 15 km online material an updated version of velocity field data

continuum calculations of continental deformation in transcurrent environments a thin viscous sheet approximation is used to investigate continental deformation near a strike slip boundary the vertically averaged velocity field is calculated for a medium characterized by a power law rheology with stress exponent n driving stresses include those applied along boundaries of the sheet and those arising from buoyancy forces related to lateral differences in crustal thickness calculations are performed with either velocity or stress prescribed on the transcurrent boundary exact and approximate analytic solutions for a region with a sinusoidal strike slip boundary condition are compared with solutions for more geologically relevant boundary conditions obtained using a finite element technique the across strike length scale of the deformation is approximately 1 4 n 1 2 times the dominant wavelength of the imposed strike slip boundary condition for both the analytic and the numerical solutions this result is consistent with length scales observed in continental regions of large scale transcurrent faulting an approximate linear relationship between displacement and rotation is found that depends only on the deformation length scale and the rheology calculated displacements finite rotations and distribution of crustal thicknesses are consistent with those observed in the region of the pacific north america plate boundary in california

compositional variations in mafic phyllosilicates from regional low grade metabasites and application of the chlorite geothermometer mafic phyllosilicates in metabasites affected by low grade regional metamorphism from wales and eastern north greenland show variations in their structure and chemistry these variations are related to four mineral zones in these metabasites which are recognized on the presence absence of various key calc silicate minerals and also actinolite zones 1 and 2 equate with the zeolite facies zone 3 with the prehnite pumpellyite facies or prehnite actinolite facies in rocks with appropriate bulk rock composition and zone 4 with the greenschist facies whilst variations in fe fe mg in chlorite correlate closely with fe fe mg ratios in the whole rock other chemical variations are clearly unrelated to whole rock compositions contents of aliv are seen to increase systematically in samples from zone 1 through to zone 4 which relate to an increase in temperature calibration of alteration temperatures calculated using the chlorite geothermometer based on aliv contents developed for meta andesites in the los azufres geothermal system mexico against x values an estimate of the proportion of chlorite to swelling component in the mafic phyllosilicates shows a decrease in the swelling component in passing from zone 1 to zone 4 i e with an increase in temperature calculated temperatures compare favourably with published stability estimates for the various key calc silicates and actinolite these data indicate that the chlorite geothermometer although developed for meta andesites from a hydrothermal system does show a correlation with temperatures estimated from calc silicate assemblages in metabasites affected by low grade metamorphism developed on a regional scale