interpretation of tectonic versus magmatic processes for resetting apatite fission track ages in the nigde massif turkey abstract apatite fission track aft ages may record the timing of exhumation related cooling of formerly deeper rocks or the timing or simple cooling of rocks already at or near the earth s surface the interpretation of aft ages is therefore challenging in regions that experienced coeval or sequential bedrock exhumation and magmatism the nigde massif central turkey is an example of a metamorphic complex for which the tectonic significance of the aft ages has been questioned owing to the location of the massif in a volcanic province the metamorphic rocks of the nigde massif have miocene aft ages of 17 9 ma 30 50 million years younger than the timing of initial unroofing of the rocks to the earth s surface at 60 45 ma according to one model fission tracks in apatite may have been completely reset when the massif was partly to entirely reburied in the tertiary however the massif is located in a region of major neogene volcanism during which ignimbrite was deposited on exhumed metamorphic basement and there is disagreement as to whether the miocene aft ages represent cooling related to final exhumation via denudation or cooling following heating by volcanism or other magmatic activity to evaluate different cooling scenarios we examine aft age and track length characteristics in the context of model temperature time paths integrated thermal modeling modeling of apatite fission track age and track length data and geological observations suggest that the aft ages represent final exhumation and cooling in the miocene and few to no thermal effects from volcanic deposits or other neogene magmatic activity

the interaction between aegean back arc extension and anatolia escape since middle miocene the aegean domain is a key area for understanding the processes of back arc extension observed deformation pattern and present day kinematics result from the interaction between the southward retreat of the hellenic trench and the westward escape of anatolia lithosphere scale analogue models were employed to display that the overall pattern of aegean extension requires not only the combination of trench retreat and anatolia escape since middle miocene but also the presence of an inherited lithosphere scale mechanical discontinuity the vardar suture zone vsz the reactivation in dextral shear of the eastern branch of the vsz accommodates both the trench retreat ns stretching and the westward escape of anatolia ew shortening in the cyclades area since middle miocene additionally our model shows that the north anatolian fault naf is a late structure in the evolution of the aegean initiated around 10 ma after the onset of anatolia escape the displacement field at the surface of the model allows the identification of sub domains which result from strain partitioning instead of being rigid microplates directly comparable to the present day displacement field gps of the aegean and western anatolia our model provides a simple but powerful way to look at the dynamics of aegean extension in two main stages from middle eocene to middle miocene extension was only driven by the southward retreat of the hellenic trench at a rate lower than 1 cm y 1 since middle miocene the combination of slab rollback with anatolia westward escape resulted in a southwest direction of trench retreat with an accelerating rate of up to 3 cm y 1

unraveling middle crust conductive layers in paleozoic orogens through 3d modeling of magnetotelluric data the ossa morena zone case study sw iberian variscides 1 in recent years a number of magnetotelluric mt surveys have been carried out in the southern branch of the iberian variscan massif namely in the ossa morena zone omz and its neighboring areas the south portuguese zone spz and the central iberian zone ciz in order to determine the geoelectrical structure of this transpressive orogen and gain insight into its internal architecture new mt data collected across the omz complete a dense database that covers the whole belt and its boundaries this paper presents an integrative three dimensional model of the available mt data from the apparent resistivities four components impedance phases and geomagnetic transfer functions from 61 stations given the location of the study area near the atlantic ocean coast effect on the data was analyzed as well as the stability of the mesh due to the strong resistivity contrasts a mesh of 80 77 76 cells was finally used with an average cell size of 4 4 km in the horizontal direction and increasing thickness in the vertical direction from 25 m in the shallower layers to 5 km in the deepest ones the most striking feature is in addition to the conductive anomalies associated with the sutures between the spz omz and the omz ciz a conductive layer which spans the whole ossa morena middle to lower crust the top of this conductive layer is interpreted as a major decollement between the granulitic basement and the overlying meta sedimentary pile

dating the exhumation of a metamorphic dome geological evidence for pre eocene unroofing of the nigde massif central anatolia turkey the timing of exhumation of metamorphic rocks and granitoids of the nigde metamorphic dome at the southern tip of the central anatolian crystalline complex is a matter of debate according to some authors the metamorphic rocks are overlain nonconformably by a sedimentary sequence of late maastrichtian to late palaeocene age in contrast other authors recently argued that the nigde dome represents an extensional core complex of oligocene early miocene age finally unroofed during late miocene times on the one hand the results of our study contradict the latter interpretation a sedimentary sequence of earliest eocene to early middle eocene age nonconformably overlies the high grade rocks of the nigde dome on its southeastern flank pebbles from the metamorphic rocks are ubiquitous in the conglomerates of this sequence as a result the nigde metamorphic rocks must have reached the surface before eocene times or at the very beginning of the eocene at the latest the uckapili granite whose crystallization age has been inferred to be early miocene has intruded the metamorphic complex during exhumation the granite is also found as pebbles within the conglomerates of the eocene sedimentary sequence and thus is actually older than the eocene apatite fission track dates of 12 11 ma across the nigde dome do not indicate that the metamorphic rocks were still on their way to the surface at that time instead they must reflect a later event which is most probably heating during late neogene magmatism lastly there is no ductile then brittle extensional detachment in the two areas where it has been invoked that is on the western and southern flanks of the dome an extensional detachment nevertheless exists at the top of the nigde dome best documented in its northern part where the detachment fault superposes a superficial unit made up of massive ophiolitic rocks onto the high grade metamorphic sequence field evidence indicates that this detachment developed before eocene times on the other hand our observations do not confirm the nonconformity of the sedimentary sequence dated as late maastrichtian late palaeocene onto the nigde high grade rocks field relations show either a tectonic contact between the two or the direct nonconformity of the eocene sediments onto the metamorphic rocks the lack of coarse clasts originating from the nigde high grade rocks within the maastrichtian palaeocene sequence further suggests that the metamorphic dome did not reach the surface before late palaeocene times these results compare well with available data from the northwestern part of the central anatolian crystalline complex suggesting that exhumation has been broadly synchronous on the scale of the massif as a result of an episode of high magnitude extension that affected the region in campanian to palaeocene times

crustal rheology of the himalaya and southern tibet inferred from magnetotelluric data the collision between the indian and asian continents which began about 70 million years ago involved a convergence of at least 1 400 km and raised the tibetan plateau since crustal material is too buoyant to be transported downwards into the earth s interior the mechanisms at work in plateau formation are important in understanding the evolution of the continents yet still a matter of debate geophysical observations in the himalaya and tibet using ultra low frequency radio waves now reveal that a partially molten layer is present along the entire length of the himalaya this weak layer implies that widespread crustal flow is occurring and explains many features of plateau evolution the cenozoic collision between the indian and asian continents formed the tibetan plateau beginning about 70 million years ago since this time at least 1 400 km of convergence has been accommodated1 by a combination of underthrusting of indian2 and asian lithosphere crustal shortening3 horizontal extrusion4 and lithospheric delamination5 rocks exposed in the himalaya show evidence of crustal melting1 6 and are thought to have been exhumed by rapid erosion and climatically forced crustal flow7 8 magnetotelluric data can be used to image subsurface electrical resistivity a parameter sensitive to the presence of interconnected fluids in the host rock matrix even at low volume fractions here we present magnetotelluric data from the tibetan himalayan orogen from 77 e to 92 e which show that low resistivity interpreted as a partially molten layer is present along at least 1 000 km of the southern margin of the tibetan plateau the inferred low viscosity of this layer is consistent with the development of climatically forced crustal flow in southern tibet

revealing the electrical properties of a gneiss dome using three dimensional magnetotellurics burial and exhumation cycles associated with faulting in central anatolia turkey abstract the nigde massif is a small scale exhumed lithospheric entity in central anatolia formed as a result of metamorphism driven by crustal thickening and migmatization its thermal and structural history records two burial and unroofing episodes induced by oblique tectonics related to an adjacent wrench zone of the ecemis fault to show the complex tectonic history of the events of this area its electrical resistivity structure was determined using three dimensional magnetotellurics forty seven high quality soundings within a frequency range of 320 hz 5000 s were utilized for this purpose the dimensionality of the data was investigated via phase tensor analyses and induction vectors a hydrothermal system that might be related to mt hasan was delineated as a widespread conductive zone in addition interpretation of the electrical resistivity models found a rheology seismicity relationship in the study area the nigde massif was depicted as a highly resistive dome like anomaly bounded by low angle detachment faults as indicated by the resistivity contrast between the massif and the adjacent features the lower boundary of the massif is defined by a resistive to conductive transition situated at 25 30 km depth beneath this transition a widespread low resistivity zone was interpreted as a partially melting lower crust this crustal feature is connected to a shallower anomaly beneath the ecemis fault zone which may infer the ascension of fluids that may be contributing to earthquake generation seismicity along the ecemis fault is overtly heterogeneous in that it tends to form a step approaching south along the fault where the lower crustal conductor is absent relevance between the seismicity and resistivity pattern denotes the presence of a fault configuration that is necessary for the yo yo tectonics

the afar depression transition between continental rifting and sea floor spreading abstract detailed geophysical and geological studies were undertaken in the 1970 s in the afar depression ethiopia in order to study the processes of continental break up occurring in this unique setting the afar is located between the ethiopian and somali plateaus and the red sea we have re evaluated the available seismic refraction and gravity data using modern interpretation techniques and incorporated new information derived from magnetic gravity seismicity and seismic refraction data the results of the re evaluation indicate that the afar depression is a transition zone between the continental rifts of kenya and the present ongoing sea floor spreading of the red sea and the gulf of aden in the depression itself the crust is greatly attenuated and is underlain by a low velocity 7 4 7 5 km s high temperature upper mantle material however it is still a continental crust which thins to the northeast and east towards the red sea and the gulf of aden it is not a newly formed oceanic crust as has been suggested in the past the trends of the areas of crustal thinning are indicated by the gravity anomalies the trend of the ethiopian rift reaches south afar where the trend of crustal thinning changes and becomes parallel to the red sea trend it is offset en echelon from the spreading area of the red sea which is marked by an alignment of gravity maxima the gulf of aden trend continues west towards the ethiopian rift the gravity trends coincide with areas of maximum crustal thinning and may thus suggest a possible triple junction in development

a new intracontinental transcurrent structure the central anatolian fault zone turkey abstract recent neotectonic studies including remote sensing aerial photographs geological field mapping on various scales and measured stratigraphic section substantiate the existence of a large sinistral intracontinental transcurrent structure which we call the central anatolian fault zone cafz this is an approximately 730 km long 2 km to 80 km wide ne trending active sinistral strike slip fault zone that cuts across the anatolian plateau between duzyayla in the northeast and anamur county in the southwest it continues onward beneath the eastern mediterranean sea and determines the boundary of the antalya and adana basins as far as to the west of cyprus the cafz is a very young neotectonic structure it resulted from the reactivation and propagation of an older paleotectonic structure the so called ecemi s corridor in both nne and sw directions across the inner tauride suture in the plio quaternary times based on geometric discontinuities the cafz is divided into 24 segments each of them is characterized by a number of strike slip morphotectonic features reflecting recent motions the easternmost part of the anatolian platelet is being deformed internally by several dextral to sinistral intraplate strike slip faults these are the lake salt fault zone lsfz the salanda fault sf the cafz the goksu yazyurdu fault zone gyfz and the malatya ovacik fault zone mofz they take up lesser motion and are younger than boundary faults of the anatolian platelet the gyfz and mofz splay from the natf cut across the anatolian platelet and then meet to the eatf whereas other faults are confined into the anatolian platelet and seem to be independent structures however present day structural pattern of all these intraplate faults and boundary faults of the anatolian platelet indicates a regional strain pattern of nnw sse directed shortening and ene wsw directed extension and they seem to have developed to accommodate northward motion of the arabian plate since late early pliocene times

magnetotelluric measurements in sw iberia new data for the variscan crustal structures 1 thirty new mt soundings were carried out in sw iberia allowing the investigation of the lateral continuity of some major structures and lithological features that are believed to control decisively the deep architecture of the ossa morena zone belts results of the two dimensional inversion of the data reveal high conductivity zones in the middle lower crust interpreted as the signal of a granulitic basement with grain boundary interconnected films of graphite the resistive features located preferentially in the upper middle crust are ascribable to igneous complexes of variable age

core complex development in central anatolia turkey tectonic models for the central anatolian segment of the alpine himalayan orogen have not considered this region as part of the aegean extensional province we have found evidence however for oligocene miocene extension and exhumation of midcrustal rocks in a metamorphic dome nigde massif that is structurally and petrologically similar to miocene core complexes 500 km to the west strong correspondence in the timing and kinematic development of the menderes western turkey and nigde core complexes suggests that extensional tectonics and exhumation of mid to lower crustal rocks affected much of the eastern mediterranean region in the nigde massif supracrustal rocks were buried to depths of 16 20 km at high temperatures 700 c during contraction associated with closure of neo tethyan seaways in late mesozoic early cenozoic time following cooling and decompression to 600 c and 10 km metasedimentary rocks underwent a second heating event at low pressures during miocene magmatism that postdated much of the unroofing of the massif development of the nigde core complex was related to exhumation of thickened and thermally weakened continental crust in the upper plate of a north dipping subduction zone the partial subduction of the tauride carbonate platform in the eocene resulted in choking of the subduction zone followed by isostatic rebound and exhumation of the buoyant platform this in turn caused a rapid emergence of the upper plate resulting in erosion of upper crustal rocks and exhumation of midcrustal rocks along the northern edge of the inner tauride suture zone although northern regions of central anatolia contain the same protoliths as the nigde massif and underwent extensive tertiary magmatism they did not undergo similar extension suggesting that core complex development in south central turkey was controlled by the location of thickened and thermally weakened crust adjacent to a suture zone

tectonic burial and exhumation cycles tracked by muscovite and k feldspar 40ar 39ar thermochronology in a strike slip fault zone central turkey abstract muscovite and k feldspar 40ar 39ar ages from the eastern margin of the nigde massif in central anatolia track the timing of initial exhumation reburial and final exhumation and cooling of metamorphic rocks deformed within a strike slip fault zone although the ages of initial and final cooling were known from previous studies our new results document the timing of the reheating reburial event muscovite from four of eight gneiss samples have late cretaceous 40ar 39ar ages that date initial cooling at 75 ma the remaining samples have perturbed spectra that climb to late cretaceous ages with increasing extraction temperatures during analysis these perturbed samples are located beneath a faulted unconformity overlain by paleogene sedimentary deposits that were derived in part from the metamorphic rocks then buried metamorphosed and deformed under greenschist facies conditions samples close to the faulted unconformity are more perturbed than structurally deeper samples the age of the thermal perturbation is determined at 30 5 ma using multi diffusion domain modeling of k feldspar 40ar 39ar data from two gneiss samples one located close to the unconformity and one at a structurally deeper level muscovite 40ar 39ar results and modeled k feldspar temperature time histories show that the eastern margin of the nigde massif experienced a reheating event that peaked at 30 ma the thermal pulse has been attributed to reburial associated with transpression in the ecemis segment of the central anatolian fault zone along the eastern margin of the nigde massif activity of this fault zone may represent a far field expression of the onset of collision of arabia with eurasia in se anatolia

crustal scale geometry and kinematics of late orogenic extension in the central aegean cyclades and ewia island abstract the aegean continental domain is known to be the site of widespread back arc extension since at least the middle miocene overprinting structures related to the mesozoic cenozoic hellenic orogeny features attributed to early thrusting include the overall ductile deformation within two broad belts that have suffered hp lt metamorphism across the aegean this study summarizes the results of a structural study in the central aegean area cyclades and evvia island examining in particular the relationship between ductile and brittle deformation on a regional scale extension appears to be responsible for most of the ductile deformation within hp rock units that have experienced penetrative greenschist facies and higher grade metamorphic overprinting on each island studied progressive extensional deformation has occurred through the development of a major normal sense detachment zone down to depths of about 18 25 km the geometry of the extensional system on the scale of the central aegean is described taking into account the characteristic features of the regional scale ductile strain field at least two probably three subparallel major north dipping detachment zones are identified trending nw se in the northwestern cyclades and e w in the southeastern cyclades both with initial dips estimated at around 30 45 the present geometry of the extensional system implies that these detachment zones and related metamorphic core complexes interfere with each other two main evolutionary models are considered which can account for such a kinematic link between parallel detachment zones structural data favour the sequential development of synthetic major detachments zones in a direction opposite to the sense of dip of the detachments early oligocene lower miocene detachment type extension in the area studied is related to a late orogenic post thickening back arc setting

electromagnetic imaging of variscan crustal structures in sw iberia the role of interconnected graphite abstract the western part of the iberian peninsula iberian massif is the best exposed fragment of the variscan orogen in europe its southern half was generated by an oblique collision between three continental terranes belonging to the margins of laurassia avalonia the south portuguese zone spz and gondwana the ossa morena zone omz and the central iberian zone ciz the boundaries between them are considered to be suture zones a 200 km long magnetotelluric profile across the three variscan terranes was done in a nne direction approximately perpendicular to the main tectonic features the results of two dimensional inversion of the mt dataset reveal high conductivity zones coinciding with the transitions spz omz and omz ciz these conductive bodies related to the sutures at depth were interpreted as graphite enrichments along shear planes formed due to the overall transpressive regime a high conductivity layer extending along the whole omz was found at a depth of 15 25 km the top of which spatially correlates with a broad reflector detected by a recently acquired deep seismic reflection profile the high conductivity was interpreted as caused by the precambrian serie negra graphite rich rocks carbon and oxygen x ray mapping with electron microprobe on polished sections of serie negra samples from omz revealed the presence of interconnected graphite which supports the hypothesis that graphite is determinant for the high conductivity two graphite types which help to record the geological evolution were identified graphite accumulations in the schistosity surfaces produced by folding and metamorphism and metallic films of graphite developed along late faults the conductive layer shows blobs of higher conductivity suggesting macro anisotropy additional mylonitisation and shearing produced by thrusting at depth can be the origin of these zones of enhanced conductivity given that the detachment level is located within the serie negra several high resistivity features were found in the upper crust related to devonian and carboniferous successions and probably to some unexposed plutons in the spz and the palaeozoic series of omz plus some granitic intrusions in the ciz a high resistivity zone extending to the whole crust is correlated with extensive late variscan granite intrusions

gneiss domes metamorphic core complexes and wrench zones thermal and structural evolution of the nigde massif central anatolia 1 the nigde massif a migmatite cored structural dome in south central turkey was metamorphosed deformed intruded and exhumed in an oblique tectonic regime involving a switch from transpression prograde metamorphism to transtension exhumation an 80 ma history of transpression and transtension is recorded in metamorphic rocks of the massif and the last 50 ma are recorded in both basement and overlying basin deposits nigde metamorphic rocks record a high temperature top to north syntranspression ductile fabric that was overprinted by lower grade top to south syntranstension ductile shear zones the 40ar 39ar data for hornblende muscovite and biotite document rapid late cretaceous cooling with the oldest ar hornblende ages 88 79 ma overlapping u pb ages in monazite and zircon 92 78 ma muscovite ar ages are dominantly 81 79 ma suggesting a short time between crystallization of high temperature metamorphic rocks and their cooling biotite ar ages are 79 74 ma with the exception of disturbed samples from the eastern margin of the massif and from eocene granitic stocks in the dome core the eastern margin adjacent to the sinistral central anatolian fault zone records another cycle of burial and exhumation that overprinted earlier fabrics and disturbed isotopic systems these two cycles of burial exhumation took place repeatedly along the same zone this may be characteristic of highly oblique tectonic regimes in the nigde massif burial and exhumation became more localized and of lower amplitude over time suggesting stabilization of the crust

new insights into the late amazonian zonal shrinkage of the martian south polar plateau the martian south polar plateau planum australe comprises the largest known water ice surface deposit on the planet here we present evidence for an episode of extensive polar plateau retreat during the late amazonian which affected regions flanking circum polar terrains located between cavi angusti and sisyphi montes

constraints on the crustal structure of the internal variscan belt in sw europe a magnetotelluric transect along the eastern part of central iberian zone iberian massif 1 the iberian massif is the best exposed segment of the european variscan belt it includes relatively well preserved terranes that were accreted by transpression along time and resulted in a number of geotectonic units that formed part of the late paleozoic assembly of the pangaea supercontinent in sw iberia these units are the central iberian zone ciz ossa morena zone omz and the south portuguese zone spz a 210 km long ne sw magnetotelluric profile was carried out through the ciz from the omz ciz boundary toward the north reaching the tagus cenozoic basin data dimensionality analysis resulted in a suitable 2 d electrical resistivity structure allowing a 2 d inversion of the data set complementary available geophysical data deep seismic gravity and aeromagnetic and a comparison with a detailed geological cross section led us to constrain the interpretation of the 2 d electrical resistivity structure of the ciz crust the results show for the upper crust the existence of diverse conductive resistive bodies that correlate well with known geological features sedimentary basins faults granitic plutons mineralized systems a mild but steady conductive band is located along the middle and lower crust that is interpreted as a mafic granulite basement the upper section of this band connects with several elongated shallow conductors providing further evidence for the existence in the central iberian zone of a complex decollement system where the major faults are rooted such a crustal architecture is viewed as the northward continuation of the variscan large scale structures previously recognized in the southern sectors omz and spz

very high electrical conductivity beneath the munchberg gneiss area in southern germany implications for horizontal transport along shear planes summary new magnetotelluric data from the munchberg gneiss complex in southern germany reveal a zone of extremely high electrical conductivity 1 d modelling of the data is justified in the period range 0 01 to 10 s at least three layers are required to explain the steepness of the apparent resistivity curves and the best fitting models comprise four layers with successively higher conductivities the layers of highest conductivity at depths between 2 2 and 3 6 km correlate with pronounced bands of high seismic reflectivity profile dekorp 85 4n the munchberg complex is today widely recognized as a tectonic klippe consisting of rocks whose metamorphic and stratigraphic order is inverted rather than overturned the material was transported into its present position by predominantly horizontal tectonic forces along shear zones we interpret the high conductivity and high reflectivity as remnants of this transport process

conductive crust imaged in western turkey by mt wide band magnetotelluric mt data across the izmir ankara suture zone iasz the bornova flysch zone and the menderes massif of western turkey images shallow and deep crustal structures inversions of the mt data reveals two subzones of the crust with varying thickness the viscoelastic lower crust appears as a conductive zone 2000 ohm m at a depth from 5 km to 25 km under the iasz a hypocentral cross section of earthquakes along the profile shows more dense seismic activity in and around the twin core structure due to this correspondence we interpret that decoupling of the twin core structure could be responsible for the denser seismic activity around the iasz the depth of the lithosphere asthenosphere boundary is rather shallow in the geoelectrical model about 45 km at the se and nw end of the profile and 55 km in the middle

the geoelectrical structure of northwestern anatolia turkey the magnetotelluric method has been employed to generate a geoelectrical model that will reveal the rich geological pattern and dynamic character of western and northwestern anatolia turkey magnetotelluric data were collected from 53 sites along a profile of 290 km from the dardanelles to the alasehir graben magnetotelluric data were in the range of 0 00055 hz to 320 hz the models were obtained through 2 d joint inversion of transverse electric and transverse magnetic modes lateral changes in geoelectrical models are verified by using gravity and magnetic data in addition some of the seismological data presented here agree with proposed models that suggest a brittle ductile structure boundary at a depth of 20 km generally speaking a regional extensional regime caused reduction in the thickness of the crust and consequent uplift towards the south the constructed model delineates the western part of the north anatolian fault zone along the biga peninsula the current patterns of volcanic activity on the biga peninsula and at kula are related to conductive spots presented in the models the border of the gordes basin located between the izmir ankara suture zone and the menderes massif is also well delineated the north anatolian fault zone presents a pattern in which density and susceptibility anomalies attain relatively high values fillings covering most of the surface have lower density and susceptibility values than those of underlying structures

the east anatolian fault geometry segmentation and jog characteristics a detailed account is given of the fault geometry and segment structure of the east anatolian fault zone as a whole based on mapping of active faults supported by available seismological and palaeoseismological data we divide the east anatolian fault into two main strands southern and northern the main southern strand is c 580 km long between karliova and antakya and connects with the dead sea fault zone and the cyprus arc via the amik triple junction the northern strand termed the surgu misis fault system is c 350 km long and connects with the kyrenia misis fault zone beneath the gulf of iskenderun we infer that slip partitioning between the main and northern strands of the east anatolian fault accommodates 2 3 and 1 3 of the slip rate of the lateral motion between the arabian and anatolian plates respectively in the celikhan adana antakya region taking account of the time elapsed from the latest events on the east anatolian fault we suggest that the pazarcik and amanos segments have the potential to produce destructive earthquakes in the near future

coeval extensional shearing and lateral underflow during late cretaceous core complex development in the nigde massif central anatolia turkey 1 the nigde massif at the southern tip of the central anatolian crystalline complex consists of two structural units foliations in the lower unit define a dome cored by migmatites the contact between the two units bears all the elements of a ductile to brittle extensional detachment hence the nigde massif represents an extensional metamorphic core complex top to ne ene shearing at higher levels of the lower unit relates to displacement along the detachment deeper levels of the lower unit display high temperature top to ssw ductile shearing the two shearing deformations show a difference in the mean trend of stretching lineations of up to 58 new 40ar 39ar ages combined with previously published data enable us to infer that the two shears were contemporaneous in our favored interpretation oblique shearing in the core of the dome reflects lateral underflow i e horizontal flowing of the lower crust in a direction highly oblique to the direction of extension as a result of the interaction between lateral underflow and downdip shearing along the overlying detachment distinct structural domains are expected to exist within the migmatitic part of the core complex with observed counterparts in the nigde dome lateral underflow may reflect inward flow on the scale of the core complex regional scale channel flow is an alternative that would better account for the record of non coaxial deformation in the core of the dome more generally we suspect that the development of lateral underflow in a metamorphic core complex more likely reflects regional channel flow rather than local inward flow

late miocene ductile extension and detachment faulting mykonos greece the geometry and style of structural relations at map to microscopic scale on mykonos cyclades aegean sea greece suggests ductile extension and detachment faulting during the late miocene this island is dominated by granitic rocks that have a well developed shallowly dipping mylonitic foliation and a northeast southwest trending mineral elongation lineation kinematic indicators in these rocks exhibit a top to the northeast down dip sense of shear textural relations suggest that conditions during mylonitic deformation were greenschist to amphibolite facies and published k ar geochronology suggests a late miocene age for this deformation event mylonitic rocks lie in the footwall of a low angle fault and fault striae parallel to the elongation lineation suggest kinematic coordination between mylonitic deformation and movement along the fault translation along the fault juxtaposes younger tilted sedimentary rocks of low metamorphic grade upon the once deeper mylonitic rocks the style and geometry of deformational fabrics and map relations on this island are strikingly similar to those observed in metamorphic core complexes of the western united states