palaeomagnetism and magnetic properties of the cappadocian ignimbrite succession central turkey and neogene tectonics of the anatolian collage abstract the cappadocian ignimbrite succession of central southern anatolia comprises at least nine major and two minor calc alkaline rhyolitic sheets emplaced at 1 2 ma intervals between 11 2 and 1 1 ma it records the last phase of neotethyan subduction during final emplacement of the tauride orogen in southern turkey this study reports magnetostratigraphy and describes associated rock magnetic properties remanence resides in ti poor titanomagnetites haematisation is locally produced by post emplacement oxidation but does not contribute significantly to the palaeomagnetic signature although secondary processes within the ignimbrite sheets have produced composite isothermal remanent magnetisation spectra and variable intensities of magnetisation weak anisotropy of magnetic susceptibility describes tensors with maximum axes close to bedding and minimum axes perpendicular to this plane directions of kmax with weak imbrication mostly suggest flow away from centres of eruption located by gravity and remote sensing older ignimbrites upper and lower goreme akdag zelve from the cardak centre are all of normal polarity later ignimbrites partly erupted from the derinkuyu centre comprise the sarimaden r cemilkoy r tahar r kizilkaya r incesu n and valibaba sofular r ignimbrites the overall reversed group mean is d i 174 51 n 10 units r 9 84 95 6 6 k 55 and all magnetisation directions from the upper goreme 9 0 ma onwards are rotated anticlockwise with respect to eurasian and african palaeofields this sense of rotation characterises most of central anatolia and averages 9 5 in this sector the rotation rate from 8 to 1 ma bp was 1 25 ma but it appears to have accelerated during the latter part of the quaternary to about an order higher than rates determined from gps rotation has resulted from extrusion of fault blocks during tectonic escape of the anatolian collage to the southwest and followed crustal thickening as the afro arabia plate has continued to impinge differentially into eurasia cenozoic magnetic inclinations are systematically shallower across anatolia than inclinations expected from the geocentric dipole model and the apparent polar wander of bordering major plates only part of this difference 400 km can be accommodated by northward movement and crustal thickening in central anatolia since mid miocene times shallow inclinations observed in the aegean region extend into turkey they are observed in young volcanics and appear to reflect a regional geomagnetic anomaly the pattern of neotectonic declinations across anatolia shows rotations that are strongly anticlockwise rotated in the east near the arabian pincer but diminish towards the west to become zero or slightly clockwise at the western extremity of the collage rotations also seem 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 and by inference the cyprus arc

unraveling the electrical conductivity structure to decipher the hydrothermal system beneath the mt hasan composite volcano and its vicinity sw cappadocia turkey abstract to comprehend the hydrothermal potential beneath the mt hasan composite volcano and its vicinity three dimensional analyses of magnetotelluric data collected at 27 sounding locations were utilized to develop electrical conductivity or its reciprocal resistivity images in southwest cappadocia central anatolia turkey a low resistivity anomaly associated with a clay cap was observed in the resulting numerical models that followed the characteristics of the earlier theoretical models developed for the electromagnetic interpretation of hydrothermal systems the observed anomaly appeared in the form of a deep smectite smectite illite and illite chlorite sequence buried under the cover layers made up of welded ignimbrites contemporaneous sediments and monogenetic quaternary volcanism products further evidence was observed that indicated the presence of a relatively deep 4 6 km single magmatic chamber beneath mt hasan and the surrounding system the tuz golu fault and some other auxiliary faults within this system present a high correlation with the low to high resistivity interfaces in the vicinity of mt hasan

neogene ignimbrites of the nevsehir plateau central turkey stratigraphy distribution and source constraints abstract in anatolia turkey extensive calc alkaline volcanism has developed along discontinuous provinces from neogene to quaternary times as a consequence of plate convergence and continental collision in the nevsehir plateau which is located in the central anatolian volcanic province volcanism consists of numerous monogenetic centres several large stratovolcanoes and an extensive mainly neogene rhyolitic ignimbrite field vent and caldera locations for the neogene ignimbrites were not well known based on previous studies in the neogene ignimbrite sequence of the nevsehir plateau we have identified an old group of ignimbrites kavak ignimbrites followed by five major ignimbrite units zelve sarimaden tepe cemilkoy gordeles kizilkaya and two smaller less extensive ones tahar sofular other ignimbrite units at the margin of the plateau occur as outliers of larger ignimbrites whose main distributions are beyond the plateau excellent exposure and physical continuity of the units over large areas have allowed establishment of the stratigraphic succession of the ignimbrites as from bottom to top kavak zelve sarimaden tepe cemilkoy tahar gordeles sofular kizilkaya our stratigraphic scheme refines previous ones by the identification of the zelve ignimbrite and the correlation of the previously defined akkoy ignimbrite with the sarimaden tepe ignimbrite correlations of distant ignimbrite remnants have been achieved by using a combination a field criteria 1 sedimentological characterisitics 2 phenocryst assemblage 3 pumice vesiculation texture 4 presence and characteristics of associated plinian fallout deposits and 5 lithic types the correlations significantly enlarge the estimates of the original extent and volume of most ignimbrites volumes range between 80 km 3 and 300 km 3 for the major ignimbrites corresponding to 2500 10 000 km 3 in areal extent the major ignimbrites of the nevsehir plateau have an inferred source area in the derinkuyu tectonic basin which extends mainly between nevsehir and the melendiz dag volcanic complex the kavak ignimbrites and the zelve ignimbrite have inferred sources located between nevsehir and derinkuyu coincident with a negative gravity anomaly the younger ignimbrites sarimaden tepe cemilkoy gordeles kizilkaya have inferred sources clustered to the south between the erdas dag and the melendiz dag volcanic complex we found evidence of collapse structures on the northern and southern flanks of the erdas dag volcanic massif and of a large updoming structure in the sahinkalesi tepe massif the present day derinkuyu tectonic basin is mostly covered with quaternary sediments and volcanics the fault system which bounds the basin to the east provides evidence that the ignimbrite volcanism and inferred caldera formation took place in a locally extensional environment while the basin was already subsiding drilling and geophysical prospecting are necessary to decipher in detail the presently unknown internal structure of the basin and the inferred probably coalesced or nested calderas within it

estimation of curie point temperature and geothermal structure of island arcs of japan abstract curie depth analysis from aeromagnetic data was performed in a nationwide project to assess the geothermal resources of japan creation of a curie depth map of japan was completed in 1984 and it agrees well with thermal structures such as the high temperature gradient regions of volcanic chains low temperature regions of the forearc basins and the intermediate temperature regions of the backarc basins measured temperature gradient t data were gathered in order to estimate the curie temperature from the t and the curie depths when t is assumed to be constant with respect to depth a remarkable difference is found in the estimated curie temperature t e c of the backarc and forearc side of the basins in the backarc side an average t e c of 450 c is reasonable for both the curie depth estimated from aeromagnetic data average depth of about 10 km in the backarc side and the temperature gradients average gradient of 4 5 c 100 m the average t e c on the forearc side was found to be low at about 300 c the difference in the curie temperatures between the two areas may be due to a regional difference in rock type e g granite as opposed to basalt in the case of the northeast japan arc as suggested by some authors the isotherms may suddenly fall between the volcanic front and the trench based on model studies we recognized that a curie depth map obtained by the algorithm we developed should include an averaging effect this suggests that the inferred curie depth curve across the line marking the sudden fall in the curie isotherm should gradually increase towards the trench therefore the low curie temperature that we estimated may indicate an apparent shallow curie depth caused by the averaging effect against an area bearing deep curie depths hence the reasons for the inconsistency of the estimated curie temperature between the forearc side and backarc side may be as follows 1 the averaging effect of the curie depth estimate which makes the curie depth apparently shallower in the forearc side and 2 the lower curie temperature of basaltic rocks which are assumed to be distributed along the east side of the aseismic front

vent distribution and its relation to regional tectonics cappadocian volcanics turkey abstract the distribution of polygenetic and monogenetic volcanoes of the neogene quaternary cappadocian volcanic province cvp is analyzed to investigate the relationship between vent location and regional tectonic lineaments two fault systems exist in the province one system miocene quaternary tuzgolu ecemis system is oblique whereas the other system late miocene pliocene cvp system is parallel to the long axis of the cvp the polygenetic volcanoes are aligned parallel to the second system but concentrate around the major faults of the first system regional offsets are proposed along the first fault system based on the distribution of the polygenetic volcanoes the monogenetic volcanoes group into five geographically distinct clusters in the western part of the cvp the monogenetic cones are aligned parallel to the cvp system whereas in the central part the cones are fed by dikes injected along the recent fractures of the tuzgolu ecemis system in the eastern part the monogenetic cones form along the radial fractures of the erciyes composite volcano

thermal investigation in the cappadocia region central anatolia turkey analyzing curie point depth geothermal gradient and heat flow maps from the aeromagnetic data in this study curie point depth cpd heat flow geothermal gradient and radiogenic heat production maps of the cappadocian region in central anatolia are presented to reveal the thermal structure from the aeromagnetic data the large circular pattern in these maps matches with previously determined shallow 2 km in average depression estimated cpds in this depression filled with loose volcano clastics and ignimbrite sheets of continental neogene units vary from 7 to 12 km while the geothermal gradient increases from 50 to 68 c km heat flows were calculated using two different conductivity coefficients of 2 3 and 2 7 wm 1 k 1 the radiogenic heat production was also obtained between 0 45 and 0 70 w m 3 in this area heat flow maps were compared with the previous regional heat flow map of turkey and significant differences were observed in contrast to linear heat flow increment through the northeast in the previous map in the literature produced maps in this study include a large caldera like circular depression between nevsehir aksaray nigde and yesilhisar cities indicating high geothermal gradient and higher heat flow values in addition active deformation is evident with young magmatism in the neogene and quaternary times and a large volcanic cover on the surface boundaries of volcanic eruption centers and buried large intrusions are surrounded with the maxspots of the horizontal gradients of magnetic anomalies analytic signal as map pointing out exact locations of causative bodies is also presented in this study circular region in the combined map of as and maxspots apparently indicates a possible caldera

magnetic mineralogy of the lower continental crust rocks that were once present in the deep continental crust can be found in surface exposure as xenoliths as parts of high grade metamorphic and plutonic terrains and as obducted lower crustal cross sections a review of magnetic and mineralogic studies of samples representing all such occurrences shows that magnetite is the only magnetic phase present in significant amounts in these rocks thermodynamic considerations indicate that tipoor magnetite is the expected magnetic oxide under equilibrium conditions that exist in the lower crust regardless of the primary magmatic composition of the spinel phase furthermore it seems unlikely that serpentinites with metal alloys contribute significantly to the magnetization of the lower crust or mantle thus magnetite in the deep crust is the most likely candidate for the source of the long wavelength magnetic anomalies observed in regional aeromagnetic and satellite magnetometer surveys if so the entire crust should be magnetic in most continental areas including shields in areas of high heat flow the bottom of the magnetic crust may lie considerably above the moho

interpretation of the gravity and magnetic anomalies of the cappadocia region central turkey the cappadocia region located in central turkey is characterized by widespread lava flows and volcanoclastic deposits dating from miocene to quaternary gravity and aeromagnetic anomalies of the region appear to present similar high and low amplitude regions although the aeromagnetic anomalies exhibit a rather complex pattern which is thought to be caused by remanent magnetization the low pass filtered aeromagnetic map shows a deep seated magnetic anomaly which may be linked to the widespread volcanic activity at the surface the pseudogravity transformation of the upward continued anomaly has been constructed the pseudogravity anomaly demonstrates some form of clockwise rotation this anomaly was modelled by means of a three dimensional method the top and bottom of the body are at 6 3km and 11km including the flight height from the ground surface respectively this deep body is ellipsoidal and extends along an e w direction which is in line with the regional stress direction deduced from gps measurements a new mobilistic dynamo tectonic system appears to explain the body s e w elongation the modelled body may be the source for the inferred geothermal energy of the region magnetic measurements were carried out on oriented rock samples collected from outcrops of ignimbrites and basalts providing directions and intensities of remanent magnetization susceptibilities and koeningsberger q ratios standard deviations of remanent directions of the natural remanent magnetization nrm display a wide scatter implying unreliability of the surface data reduction to pole rtp transformation of magnetic anomalies was successful with the induced magnetization angle despite the complex pattern of magnetic anomalies

investigation of the deep structure of the sivas basin innereast anatolia turkey with geophysical methods abstract sivas basin is the easternmost and third largest basin of the central anatolian basins in this study gravity aeromagnetic and seismic data are used to investigate the deep structure of the sivas basin together with the well seismic velocity data geological observations from the surface and the borehole data of the celalli 1 well basement depth is modeled three dimensionally 3d using the gravity anomalies and 2d gravity and magnetic models were constructed along with a n s trending profile densities of the rock samples were obtained from the distinct parts of the basin surface and in situ susceptibilities were also measured and evaluated in comparison with the other geophysical and geological data additionally seismic sections in spite of their low resolution were used to define the velocity variation in the basin in order to compare depth values and geological cross section obtained from the modeling studies deepest parts of the basin 12 13 km determined from the 3d model are located below the settlement of hafik and to the south of zara towns geometry extension and wideness of the basin together with the thickness and lithologies of the sedimentary units are reasonably appropriate for further hydrocarbon exploration in the sivas basin that is still an unexplored area with the limited number of seismic lines and only one borehole

interpretation of magnetic anomalies and estimation of depth of magnetic crust in slovakia the magnetic map of slovakia used in the paper was compiled as part of a project titled atlas of geophysical maps and profiles in 2001 the residual magnetic data were analyzed to produce curie point estimates to remove distortion of magnetic anomalies caused by the earth s magnetic field reduction to pole transformation was applied to the magnetic anomalies using the magnetization angle of the induced magnetization anomalies reduced to the pole tend to be better correlated with tectonic structures we applied a 3 km upward continuation to the residually compiled magnetic anomalies in order to remove effects of topography the depth of magnetic dipoles was calculated by an azimuthally averaged power spectrum method for the entire area such estimates can be indicative of temperatures in the crust since magnetic minerals lose their spontaneous magnetization according to curie temperature of the dominant magnetic minerals in the rocks the computed curie point depths in the slovakia region vary between 15 2 km and 20 9 km heat flow higher than 100 mwm 2 occurs at the central volcanics and eastern part of slovakia where the curie point depths values are shallow the correlation between curie point depths heat flow and crust depth was investigated for two e w cross sections heat flow and curie point depth values are correlated with each other however these values could not be correlated with crust depth the curie point isotherm which separates magnetic and non magnetic parts of the crust is represented in two cross sections

statistical analysis for thermal data in the japanese islands abstract we calculated statistical average of thermal data to speculate regional thermal structure of the forearc area of the japanese islands the three thermal statistical averages show a difference of a high thermal regime in the western part of forearc inner zone and a low in the kanto forearc outer zone the kanto zone marks 18 k km 1 for mean geothermal gradient 44 mw m 2 for mean heat flow while the western inner zone shows 27 k km 1 for mean geothermal gradient 63 mw m 2 for mean heat flow the geothermal gradients of the nobi plain and the osaka plain in the western inner zone are 29 and 36 k km 1 respectively while the value of the kanto plain in the kanto zone is 21 k km 1 taking account of the effect of accumulation of sediments we see the difference in the thermal regime between the plains and conclude that the difference is significant heat flux in the crust depends on the volume of granite rich in radioactive elements there are few granitic rocks in the kanto zone while granitic rocks are dominant in the western inner zone the heat flow of 20 mw m 2 is attributed to the granitic rocks of about 8 km in thickness there are two oceanic plate subductions of the pacific plate and the philippine sea plate under the kanto zone while only the philippine sea plate has been subducting under the western inner zone the model simulation based on thermal and subduction model shows a heat flow ranging 50 60 mw m 2 in the southwest japan forarc area and a low value of about 20 mw m 2 in the northeast japan forearc area the heat flux from the cooling oceanic lithosphere depends on the age of plate the shikoku basin a part of the philippine sea plate off the western inner zone is 15 30 ma while the pacific plate off the kanto zone is 122 132 ma theoretically heat flux values of 15 and 50 ma oceanic plates range 60 120 mw m 2 and those of 122 132 ma could be about 10 mw m 2 if the heat flux contribution from the philippine sea plate under the kanto zone is smaller than the plate under the western inner zone there could be a thermal regime difference in order of several tens of mw m 2 conclusively the cause of the difference of heat flux could be the uneven granitic rocks distribution and or the difference of heat flux between the two subducting plate

curie point depth of the island of crete greece the aeromagnetic data of the island of crete were inverted to produce curie point estimates the data were high pass filtered to remove components arising from topography and magnetic core fields which were not adequately modeled by igrf the depth to the centroid z 0 of the deepest distribution of the magnetic dipoles was obtained by computing a least squares fit to the lowest fre quency segment of the azimuthally averaged log power spectrum the depth to the top of the deepest crustal block was computed as the depth z t to the centroid of the second deepest distribution using the second lowest frequency segment of the spectrum the depth to the bottom of the deepest dipoles the inferred curie point depth is then z b 2z 0 z t the curie depth estimates range between 24 and 28 km this is in accordance with the depths inferred by extrapolating heat flow values measured in boreholes

hidden calderas evidenced by multisource geophysical data example of cappadocian calderas central anatolia abstract the cappadocian volcanic field in central anatolia turkey is characterised by a sequence of 10 neogene ignimbrites the associated calderas have been partly dismantled and buried by subsequent tectonic and sedimentary processes and therefore cannot be readily recognized in the field recent progress in the understanding of the stratigraphic correlations and flow patterns has identified two main probable source areas for the ignimbrites detailed study of these areas based on gravity surveys remote sensing data spot and ers1 images and digital elevation models dem has provided evidence for two major caldera complexes and their relationship to old stratovolcanoes and neogene tectonics the older nevsehir acigol caldera complex located between the towns of acigol nevsehir and cardak is inferred to be the source of the kavak and zelve ignimbrites the nevsehir acigol caldera complex is defined mainly by a 35 mgal circular gravimetry anomaly about 15 km in diameter the boundaries of this now buried caldera complex are shown by high gradients on the bouguer gravity anomaly map the younger derinkuyu caldera complex located between the erdas stratovolcano and the ciftlik basin is inferred to be the source of the sarimaden cemilkoy gordeles and kizilkaya ignimbrites it is well defined by a rectangular 35 23 km gravity low 30 mgal with a positive high 20 mgal in the center gravity remote sensing data and the dem provide evidence that the erdas stratovolcano on the northern margin of the derinkuyu caldera complex represents the remnants of a large stratovolcano partly cut by one or more caldera collapses the positive anomaly within the derinkuyu caldera complex is centered on the 15 km wide sahin kalesi volcanic massif field evidence and structural features inferred from the dem and remote sensing data strongly suggest that this massif is a resurgent doming associated with the gordeles ignimbrite eruption high resolution ers1 spot and dem images reveal that the transtensive regime active at least since the miocene influenced the location of eruptive centers and caldera complexes in cappadocia the two caldera complexes are located in transtensive grabens the subsidence of these grabens continuing after the caldera collapse events most likely resulted in the burying of the calderas and could explain the difficulties in identifying them in the field

magnetization of lower crust and interpretation of regional magnetic anomalies example from lofoten and vesteralen norway the interpretation of regional magnetic anomalies commonly observed over continental crust in both satellite and near surface magnetic data has remained enigmatic in its requirement for laterally extensive thick highly magnetic and deep seated sources presented here are the results of a detailed field analytical and experimental study of the magnetic mineralogy and magnetic properties of rocks from lofoten and vesteralen norway a province of deep seated origin with associated regional magnetic and gravity anomalies these rocks have a bulk magnetic character of surprising uniformity with susceptibilities hysteresis and curie temperatures defined solely by coarse grained magnetite stable remanence is observed in samples from sw lofoten but is not of significant magnitude the thermal enhancement of magnetic susceptibility the hopkinson effect is not important rocks from the deepest part of the section have the largest average susceptibilities 6 10 2 si and magnitudes of natural remanent magnetization nrm 5 10 4 a m2 kg these values of susceptibility together with the oft observed viscous character of the nrm suggest that these granulite facies lithologies particularly those of sw lofoten are perfect examples of lower crustal sources of typical regional magnetic anomalies furthermore these intermediate pressure granulites define a unique magnetic petrology especially for mafic compositions at higher grades of metamorphism high pressure granulites and eclogites or lower grades greenschist and amphibolite facies such magnetite bearing assemblages will be unstable and their high or low grade equivalents will be only weakly magnetic this evidence and these conclusions may be used to constrain models of lower crustal sources of regional magnetic anomalies over stable cratons it portrays the lower crust as a highly magnetic unit defined by metamorphic grade with a curie isotherm of 575 c magnetite and magnetization parallel to the ambient geomagnetic field induced and viscous components

geophysical investigation of the geothermal potential under the largest volcanic cover in anatolia kars plateau ne turkey in this study curie point depth cpd geothermal gradient radiogenic heat production and heat flow maps were constructed based on different thermal conductivity coefficients using magnetic anomaly data for the kars plateau which has the largest volcanic cover in turkey the bottom depths of the magnetic crust in the research area were revealed by the cpd map for the first time in this investigation there are two apparent magnetic anomaly trends in the study area the first is the horasan senkaya sarikamis selim arpacay trend in the ne sw direction and the other is the hanak ardahan arpacay trend in the nw se direction two other prominent elongations extend into the ardahan gole senkaya and kars digor axes all these trends represent mountain chains and or stratovolcanoes in the region and no anomalies are observed around the non volcanic outcrops curie depths are shallow up to 14 km between horasan and kagizman towns and 12 km in the northwestern part of the study area gradient values can reach 50 c km 1 in the northwestern sector together with the high heat flows represented by the 150 wm 1 k 1 contours the deepest cpd region lies between gole and susuz towns where the geothermal gradient decreases to 27 c km 1 heat flows decrease 60 wm 1 k 1 in the same area an apparent gap around the kars plateau was observed in previous regional heat flow maps of turkey by other authors who used the bottom hole temperatures of boreholes and hot springs temperatures this gap has been accurately filled from the results of this study and geothermal exploration areas and the geothermal potential of the kars plateau have thus been determined for future exploration activity on the basis of the tectonic elements and earthquake data

effects of the karacadag volcanic complex on the thermal structure and geothermal potential of southeast anatolia the karacadag volcanic complex kvc is the largest volcanic unit in se turkey it is also defined as a shield volcano on the northernmost part of the arabian plate the main goal of this study is to investigate the geothermal potential of this region associated with the magnetic signature of this volcanic complex and surrounding area besides this primary objective the possibility of there being volcanic intrusion into the buried fault zones under the volcanic cover are also investigated to determine the interrelations between the active tectonics and heat flow in the area a spectral analysis method is applied to the magnetic anomalies of the volcanic rocks to identify the curie point depth cpd and geothermal gradient as well as to estimate heat flow and radiogenic heat production of radioactive minerals in the complex a tilt angle map is also presented in correlation with instrumentally recorded earthquake magnitudes to indicate tectonic trends that are consistent with the maps of the thermal parameters in this study in contrast with expectations for the kvc area the region around akcakale and suruc grabens is the most prolific zone for geothermal potential despite them not showing strong magnetic anomalies curie point depths are shallow down to 18 km around the akcakale graben and deeper down to 22 km around the bitlis zagros suture zone where the geothermal gradients increase from 26 to 32 c km 1 through the graben area heat flows in this zone are in the range from 75 to 90 mw m 2 depending on the thermal conductivity coefficient 2 3 2 5 2 7 and 3 0 w m 1 k 1 used radiogenic heat production values also indicate slightly changing spectra in the range 0 19 to 0 25 w m 3 none of these parameters are focused around mt karacadag however the earthquake epicenters generally m 4 are aligned with the boundary faults of the akcakale graben where the cpd geothermal gradient and heat flow maps indicate relatively high potential we thus suggest that this graben area would be good for future geothermal exploration on the contrary considering the low geothermal gradient and heat flow values mt karacadag can be accepted as being an extinct volcano despite its apparent high magnetic anomalies

curie point depth investigation of central anatolia turkey the residual aeromagnetic total field intensity anomalies in central anatolia were calculated from the regional aeromagnetic anomalies surveyed by the mineral research and exploration mta of turkey the residual aeromagnetic data were analyzed to produce curie point estimates by the method of okubo et al 1985 the curie point depth of central anatolia varies from 7 9 km and 22 6 km the shallowest curie point depths were observed around the cappadocia and erciyes volcanic complexes in central anatolia a good correlation was deduced between the curie point depths and the heat flow data measured previously which is most certainly important for the geothermal resources of the region the shallow curie point depths also correlate well with the hot spring locations in central anatolia

further analysis of the relationship between circulation anomaly patterns and tropical convection tropical extratropical connections are investigated for 250 mbar stream function fluctuations in both intraseasonal and interannual bands the principal modes of anomalous 250 mbar stream function are computed and related to anomalous outgoing longwave radiation olr which is used as a proxy for deep tropical convection the leading mode for both boreal winter and summer displays a large zonally symmetric component which appears in both the intraseasonal is and interannual ia bands in the is band the dominant mode is an oscillation with a period of 48 days correlations between the principal component of this mode and olr anomalies indicate that this pattern is directly related to convection in the tropical pacific the second mode for the boreal winter consists of a wave train from the pacific ocean east northeastward to western north america and then east southeastward to the subtropical atlantic ocean this mode also exists in both ia and is bands simultaneous and lagged correlations between the amplitude time series of this mode and olr anomalies indicate that extreme amplitudes of this wave train are preceded by extremes in the olr anomalies cloud band activity in the subtropical north pacific enhanced cloud band activity in the vicinity of hawaii associated with an anomalousmore cyclonic 250 mbar circulation in the same region precedes the maximum development of a 250 mbar ridge south of the aleutian islands trough over western north america and another ridge along the east coast of the united states the second mode for boreal summer june august is associated with variations of the asian monsoon 36 refs 11 figs 1 tab less

curie point depths of the island of kyushu and surrounding areas japan as part of a comprehensive nationwide evaluation of geothermal resources for japan the first of the curie point depth maps covering the island of kyushu has been prepared the map was created by inverting gridded regional aeromagnetic data two satisfactory algorithms were developed to invert the gridded data based upon a distribution of point dipoles the first algorithm estimates x0 y0 and z0 the coordinates of the centroid of the distribution by computing a least squares fit to the radial frequency of the fourier transform the second algorithm estimates centroid depth only by computing a least squares fit to the squared amplitude of the frequency estimates the average depth to the top zt of the collection of point dipoles was estimated by a variation of the second algorithm the depth to the bottom of the dipoles inferred curie point depth is zb 2z0 zt the depth estimates are hand contoured to produce the final map the curie point depth map is then compared to regional geology and heat

tropical plumes and extreme precipitation in subtropical and tropical west africa three cases of extreme precipitation in october january and march april over subtropical north western and tropical west africa have been selected in order to study the moisture transports precipitation generation mechanisms and large scale dynamics involved all cases show strong tropical extratropical interactions and elongated cloud bands extending from the tropics into the subtropics usually referred to as tropical plumes tps investigations are based on observational data and high resolution output from simulations using the university of wisconsin nonhydrostatic modeling system trajectory analyses show that moisture is transported from the tropical easterly mid level flow the monsoonal southerlies and the north easterly trade winds to provide precipitable water and potential instability at mid tropospheric levels the instability is released through ascent related both to weak quasi geostrophic forcing to the east of an upper level trough and to the strong inertially unstable and highly divergent upper level subtropical jet stj accompanying the tp in the january and march cases the passage of a precursor upper level trough over the same location precedes the development and initiates the moisture transport from the deep tropics the associated north westerly cold advection supports the generation of precipitation by triggering convection over the tropical atlantic ocean whose outflow feeds into the stj over africa and by enhancing the vertical mass transport within the intertropical discontinuity over and near west africa in october when the still active african monsoon facilitates the extraction of tropical moisture a wave in the tropical easterlies and strong trade winds from the southern hemisphere are dominant factors low level cyclogenesis and frontogenesis only play roles in the late stages of the developments the elongated mostly positively tilted potential vorticity pv streamers associated with the observed troughs form as a result of an equatorward transport of high pv air downstream of a large ridge over the north atlantic the rapid amplification of the ridge is achieved through a combination of negative horizontal pv advection and diabatic reduction of upper level pv through latent heating within a cloud band that forms in connection with an explosive baroclinic development near the east coast of north america copyright 2005 royal meteorological society

tropical plumes over eastern north africa as a source of rain in the middle east tropical plumes tps reflect tropical extratropical interaction associated with the transport of moisture from the tropics to extratropical latitudes they are observed in satellite images as continuous narrow cloud bands ahead of upper level subtropical troughs at times when the subtropical jet is highly perturbed rainstorms usually develop in the exit regions of tps so their presence over northern africa has an impact on the precipitation regime in the southeastern mediterranean based on satellite images and rainfall measurements from israel 10 tps over eastern north africa between 1988 and 2005 in which considerable rain was recorded were selected using the ncep ncar reanalysis data the structure and evolution of these tps were characterized and their regional canonical features were identified a typical tp that occurred in march 1991 is described in detail the main canonical characteristics are as follows the tp development is preceded by an incubation period expressed either as a stationary upper level trough persisting 2 6 days or as two consecutive tp pulses the preferred location for tp origin is 5 15 n 5 w 15 e the tp is separated from the underlying dry saharan pbl the subtropical trough undergoes a phase locking with the lower tropical trough the cloudiness in the tp induced rainstorm is mostly stratified with continuous moderate rain originating from midlevel moisture and the tp tends to be followed by a midlatitude cyclogenesis over the eastern mediterranean this analysis proposes several explanations for the efficiency of the tps in transporting moisture over a 2000 km distance

palaeomagnetism of the cappadocian volcanic succession central turkey major ignimbrite emplacement during two short miocene episodes and neogene tectonics of the anatolian collage abstract the central anatolian volcanic province in cappadocia includes 13 high volume calc alkaline ignimbrite sheets emplaced by plinian eruptions within a succession the urgup formation after 10 ma recording the last phase of neotethyan subduction and accompanying emplacement of the tauride orogen in southern turkey to evaluate magnetostratigraphy in the context of recent revisions of the chronostratigraphy we have extended palaeomagnetic investigation to 32 new sites yielding significant chrm directions integrated rock magnetic and palaeomagnetic investigations identify magnetic remanence residing predominantly in ti poor titanomagnetites although secondary processes within the ignimbrite sheets notably post emplacement oxidation have locally produced hematisation expressed by composite irm spectra and variable reduction in intensity of magnetisation the ignimbrite sheets possess weak anisotropies of magnetic susceptibility ams mostly 3 of pyroclastic deposits during polarity chron c4r 1n between 9 31 and 9 43 ma subsequent activity from the acigol centre further to the south west cemilkoy gelveri gordeles and kizilkaya produced in excess of 620 km 3 of pyroclastic deposits during polarity chrons between 5 3 and 7 1 ma the younger incesu ignimbrite was sourced in the sultansazligi pull apart basin to the east during the gauss chron 2 58 3 60 ma all pre incesu ignimbrites are rotated uniformly anticlockwise and the overall reversed group mean direction of magnetisation is d i 170 8 52 4 n 9 r 8 91 95 5 4 k 91 the implied tectonic rotation in this sector of central anatolia 16 4 relative to eurasia is young and postdates the 5 3 7 1 ma acigol centre whilst largely predating emplacement of the incesu ignimbrite whilst rotational deformation within anatolia is young it proves to be distributed with a temporal variation from block to block it is embraced by a complex post miocene tectonic regime of strike slip and extension during tectonic escape and suction towards the hellenic arc to the west

a wet heterogeneous lunar interior lower mantle and core dynamo evolution while recent analyses of lunar samples indicate the moon had a core dynamo from at least 4 2 3 56 ga mantle convection models of the moon yield inadequate heat flux at the core mantle boundary to sustain thermal core convection for such a long time past investigations of lunar dynamos have focused on a generally homogeneous relatively dry moon while an initial compositionally stratified mantle is the expected consequence of a postaccretionary lunar magma ocean furthermore recent re examination of apollo samples and geophysical data suggests that the moon contains at least some regions with high water content using a finite element model we investigate the possible consequences of a heterogeneously wet compositionally stratified interior for the evolution of the moon we find that a postoverturn model of mantle cumulates could result in a core heat flux sufficiently high to sustain a dynamo through 2 5 ga and a maximum surface dipolar magnetic field strength of less than 1 t for a 350 km core and near 2 t for a 450 km core we find that if water was transported or retained preferentially in the deep interior it would have played a significant role in transporting heat out of the deep interior and reducing the lower mantle temperature thus water if enriched in the lower mantle could have influenced core dynamo timing by over 1 0 gyr and enhanced the vigor of a lunar core dynamo our results demonstrate the plausibility of a convective lunar core dynamo even beyond the period currently indicated by the apollo samples

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

aeromagnetic anomaly modeling of central zone structure and magnetic sources in the chicxulub crater abstract the analytic signal method and forward modeling in three dimensions are applied to magnetic field data over the chicxulub crater in order to determine and document the main magnetic anomaly sources and crater structure in the central zone aeromagnetic data over the structure reveal three strong well defined concentric patterns with a central 40 km diameter zone of high amplitude anomalies magnetic anomalies are interpreted to be associated with the melt sheet upper breccias and central uplift which present three to four orders of magnitude contrasts with the surrounding carbonate units the limited number of magnetic property measurements apparent wide range in the remanent intensity and susceptibility in the upper breccias and possible yet unconstrained zones of hydrothermal systems have restricted our ability to determine the characteristics and distribution of major structural elements of the chicxulub crater the amplitude of the analytic signal produces maxima over magnetization contrasts independent of the direction of magnetization interpretation of maxima location and depth distribution is used in a second stage as a priori information in the construction of an input prism assemblage magnetic configuration and its properties for three dimensional forward modeling results indicate that magnetic sources extend to a radial distance of 45 km from the center of the structure with average depths ranging between 2 and 4 km the magnetic anomaly sources in the central structural uplift zone are located in the range from 3 5 to 8 km depth with dominant contributions from an apparent large body forming the basement uplift

fission track dating obsidians in central and northern anatolia twenty obsidian samples from central and north anatolia were dated by the fission track method split samples analyzed in two different laboratories give consistent results data presented refer to three volcanic fields and are summarized as follows orta sakaeli northern anatolia obsidians with ages from 21 23 ma gollu dagi dome complex near ciftlik central anatolia has given ages between 1 33 0 98 ma acigol caldera central anatolia shows three age groups 1 eruptions of precaldera bogazkoy obsidians with ages 0 18 0 15 ma 2 formation of the large intracaldera dome kocadag taskesiktepe at about 0 08 ma uncorrected apparent age of 0 075 ma and 3 acigol peripheral obsidian domes with plateau ages of 0 020 and 0 019 ma and an additional uncorrected age of 0 018 ma form a distinct age group this fission track parameters discriminate between the various obsidian sources of prehistoric obsidian artifacts

linkages between 200 mb tropical and extratropical circulation anomalies during the 1986 1989 enso cycle abstract nmc operational wind analyses have been used to document the 200 mb circulation anomalies during the solstice seasons of the 1987 1989 enso cycle using the one level vorticity balance diagnostic approach the 200 mb rossby wave anomalous source distribution was derived as departures from a three year mean for the single warm phase season january march 1987 the effective rossby wave anomaly sources were found to be generally quite small within 15 of the equator poleward of about 15 the anomalous 200 mb divergence through the planetary vorticity divergence anomaly stretching term is the dominant factor in determining the anomalous 200 mb vorticity source distribution its jfm standard deviation around 30 35 n was an order of magnitude larger than that found in the deep tropics the january march and june august 200 mb circulation differences between the warm and cold phase of the 1987 1989 enso cycle are described the enso cycle linkages between the equatorial pacific convection anomali

curie point depths of macedonia and thrace n greece the aeromagnetic data of macedonia and thrace were used to produce curie point estimates the data were high pass filtered to remove components arising from topography and magnetic core fields which were not adequately modeled by a dgrf the depth to the centroid z 0 of the deepest distribution of the magnetic dipoles was obtained by computing a least squares fit to the lowest frequency segment of the azimuthally averaged log power spectrum the average depth to the top of the deepest crustal block was computed as the depth to the top z t of the second lowest frequency segment of the spectrum the depth to the bottom of the deepest magnetic dipoles the inferred curie point depth was then calculated from z b 2z 0 z t the curie depth estimates for macedonia and thrace range between 11 2 and 17 3 km these results are consistent with the depths inferred by extrapolating known geothermal gradient and heat flow values

geoelectromagnetic and geothermic investigations in the ihlara valley geothermal field abstract the ihlara valley is situated within a volcanic arc that is formed by the collision of the eastern mediterranean plate system with the anatolian plate in this study we will present data from a reservoir monitoring project over the ihlara ziga geothermal field located 22 km east of aksaray in central anatolia although identified geothermal resources in the ihlara valley are modest substantial undiscovered fields have been inferred primarily from the volcanic and tectonic setting but also from the high regional heat flow 150 200 mwm 2 on the kirsehir massif in 1988 and 1990 geoelectromagnetic surveys were undertaken by mta ankara to confirm the presence of a relatively shallow 0 5 1 km hydrothermally caused conductive layer or zone csamt and schlumberger resistivity data show good correspondence with each other and 2 d geoelectric models are also in harmony with geologic data and gravity anomalies the depth of the resistive basement which is interpreted as paleozoic limestone is 200 250 m in the western part and increases eastward 600 750 m this may imply n s oriented normal faulting within the survey area the parameters of the top layer are a resistivity of 25 to 95 ohm m and a thickness of between 100 and 250 m the thickness of the conductive tuffs between the top layer and the basement whose resistivity is about 4 5 o hmm also increases eastward from 100 to 450 m the apparent resistivity maps for the frequencies between 32 and 2 hz reveal a localized low resistivity anomaly to the east of belisirma

curie point depth from spectral analysis of magnetic data in taiwan abstract this study constructs an integrated magnetic anomaly map of taiwan and its vicinity that combines land magnetic data and marine magnetic data the reduction to pole rtp correction method was applied to the integrated magnetic anomaly data the corrected magnetic anomaly results for a region roughly 880 km in width and 660 km in length fit well with geological tectonic signatures and are used to estimate the curie point isotherm the adopted curie point depth method provides a relationship between the 2 d fft power spectrum of the magnetic anomalies and the depth of magnetic sources by transforming the spatial data into the frequency domain the basal depth of the magnetic sources is calculated from the magnetic data finally the curie point depth of taiwan is obtained the highest value of 17 km is located in northern taiwan and the lowest value of 6 km is located at southern taiwan and also has the highest thermal gradient of 88 c km the curie point depth is consistent with heat flow measurements with correlation coefficient 0 62

formation of cloud bands associated with the american subtropical jet stream and their interaction with midlatitude synoptic disturbances reaching europe abstract this study describes the evolution of very large cloud bands originating from the eastern subtropical pacific ocean and their relation to the american subtropical jet stream in many cases these cloud bands interact with polar lows and then give rise to a very large typical midlatitude cyclone the cloud pattern associated with this cyclone is very similar to that described by the norwegian cyclone model although its origin is quite different

curie point depths based on spectrum analysis of aeromagnetic data west anatolian extensional province turkey the curie point depth map of western anatolia was constituted from spectral analysis of the aeromagnetic data the curie point depth values from 53 overlapping blocks 90 90 km in size have been estimated from the band pass filtered data the slope of the longest wavelength part of the radially averaged log power spectrum divided by the radial frequency produced the depth to the centroid z0 for the deepest crustal block the depth to the top zt was obtained by the slope of the second longest wavelength part of the spectrum from these depths the curie point depth was then calculated by using zb 2z0 zt the curie point depth estimates for western anatolia range between 8 2 and 19 9 km

the geology of mount hasan stratovolcano central anatolia turkey mount hasan is a double peaked stratovolcano located in central anatolia turkey the magmas erupted from this multi caldera complex range from basalt to rhyolite but are dominated by andesite and dacite two terminal cones big mt hasan and small mt hasan culminate at 3253 m and 3069 m respectively there are four evolutionary stages in the history of the volcanic complex stage 1 kecikalesi volcano 13 ma stage 2 palaeovolcano 7 ma stage 3 mesovolcano and stage 4 neovolcano the eruptive products consist of lava flows lava domes and pyroclastic rocks the later include ignimbrites phreatomagmatic intrusive breccias and nuees ardentes sometimes reworked as lahars the total volume is estimated to be 354 km 3 the area extent 760 km 2 textural and mineralogical data suggest that both magma mixing and fractional crystallization were involved in the generation of the andesites and dacites the magmas erupted from the central volcanoes show a transition with time from tholeite to calc alkaline three generations of basaltic strombolian cones and lava flows were emplaced contemporaneously with the central volcanoes the corresponding lavas are alkaline with a sodic tendency

modeling of shallow structures in the cappadocia region using gravity and aeromagnetic anomalies abstract in this study shallow structures and bodies creating gravity and magnetic anomalies in the cappadocia volcanic complex region in central anatolia were investigated in order to determine the tectonic origin and structural setting of young volcanic units the shallow geological structures in the region are depressions filled with mainly low density loose volcano clastics and ignimbrite sheets associated with the continental neogene deposits these units together with other volcanic products are originated from the large neogene and quaternary volcanoes of the central anatolia particularly in the cappadocia region at first spectral analysis to obtain the cut off frequencies for the high pass filter was performed in this investigation then gravity and magnetic data were high pass filtered to remove the deep and regional effects on anomalies and to unveil only shallow structures effects subsequently upward and downward continuations were carried out to determine how these shallow structures influence the total anomalies and their contribution in the confining total potential field in addition three and two dimensional gravity models 3d and 2d of the study area were also constructed to obtain the bottom depth of shallow bodies according to spectral analysis results shallow structures could be separated into two groups from the power spectrums and bottom depth of deeper structure was commonly determined about 2 km in gravity and magnetic spectrum both more shallow structure is at the depth around 0 317 km according to the gravity power spectrum obviously 3d and 2d models are consistent with the spectral analysis results for the deeper unit depth a circular large depression 70 50 km 2 surrounds mount melendiz with a 1 2 7 km depth range 2 km in average because the depressions around the central volcanoes of mount melendiz and mount hasan cover very large areas in the basin scale the shallow and low density volcanic units can hardly be claimed that they are the products of a large caldera system in contrast to the expectations however this idea in any case is still worth to pondering over and should be investigated with further volcanological methods

continental arc volcanism and tectonic setting in central anatolia turkey abstract the neogene and quaternary volcanism of central anatolia represents the central sector of the anatolian volcanic arc related to continental collision between the afro arabian and eurasian plates it is closely associated with a complex system of tectonic depressions related to brittle deformations of transtentional type and which commenced in the late miocene the volcanism here considered can be divided into three main periods of activity separated by important deformative and erosive events the first period is represented by a mostly andesitic effusive activity the second period is characterized by the emplacement of a thick ignimbritic sequence and shows an areal distribution up to 11 000 km 2 seven ignimbrite units have been recognized the three main units were found at a distance of more than 100 km from the presumed source area geological and sedimentological data lead us to recognize the melendiz dag volcanic complex and the ciftlik caldera as the probable ignimbrites source vent during the third period great andesitic basaltic stratovolcanoes and a number of prevalently acid monogenic centres developed the relationship between the volcanic activity is clearly conditioned by the main transcurrent fault systems present in central anatolia the neogene quaternary volcanic activity prevalently developed along the ene wsw karaman sivas lineament most of the great central volcanoes developed at the intersection between the ene wsw trends and the ecemis and tuz golu transcurrent faults the structural interpretation of the quaternary monogenic centres is more difficult probably they are related to the very recent n s fault swarms which cross the anatolides and the taurus range