coastwise transport reconsidered lateral displacements in oblique subduction zones and tectonic consequences coastwise transport margin parallel displacement of arc and forearc slivers is a common feature of zones of oblique subduction today but at rates that rarely exceed a few tens of kilometers per million year paleomagnetic studies strongly indicate that coastwise transport in the north american cordillera went on during late cretaceous early tertiary time at rates several times higher than this other studies have shown that obliquity is commonly partitioned between oblique subduction and coastwise transport of a detached sliver of over riding crust the analysis developed here indicates that in the absence of a buttress a physical impediment to sliver motion at its leading edge sliver motion should obey the relationship tan p r tan 1 1 r2 sin2 12 where is the angle of obliquity is the angle of subduction and r rfrs is the ratio of resistance to slip on strike slip faults cutting the over riding plate to resistance to slip on the subduction zone in this equation p is a partitioning factor 0 p 1 where p 1 implies oblique subduction and no sliver motion and p 0 is the case in which the sliver moves at velocity v sin equivalent to the transverse component of relative motion rates of coastwise transport calculated from this relationship are systematically too high presumably indicating that most modern subduction zones are buttressed key factors in the buttress effect are 1 the greater strength of oceanic vs continental lithosphere and 2 the energy required to thicken continental crust large scale tectonic transport in the north american cordillera probably was the result of a combination of favorable factors long continued highly oblique convergence and a plate margin geometry that avoided the buttress problem

paleomagnetism and geochronology of the late cretaceous paleogene island arc complex of the kronotsky peninsula kamchatka russia kinematic implications the remnants of ancient island arcs are exposed in the achayvayam valagina and east peninsulas tectonic zones of the olutor kamchatka region northeast russia geochemically late cretaceous to paleogene island arc complexes of the east peninsulas zone are similar to intraoceanic island arcs and the east peninsulas zone is regarded as the extinct kronotsky island arc paleomagnetic and biostratigraphic studies of late cretaceous and paleogene island arc rocks were carried out at 21 sites in the eastern part of the kronotsky peninsula which belongs to the east peninsulas zone characteristic remanent magnetizations of both polarities isolated from most sites pass reversal and fold tests the cretaceous result is also supported by a positive conglomerate test on lava boulders from an intraformational conglomerate mean inclinations of late cretaceous ypresian and bartonian rocks correspond to paleolatitudes of 44 8 8 0 n 38 6 3 5 n and 45 1 7 0 n respectively these values are 20 lower than the corresponding reference values for the north american plate for the cretaceous and ypresian and 14 lower for the bartonian therefore northward transport of the kronotsky island arc is indicated kinematic evolution of the kronotsky island arc in the late cretaceous paleogene was reconstructed using published kinematic parameters in addition we incorporated into analysis the geological and published paleomagnetic data for the late cretaceous and tertiary island arc complexes of the cape kamchatka peninsula from the east peninsulas zone and the late cretaceous island arc complexes of the achayvayam valagina zone as a result two alternative scenarios of kinematic evolution for the kronotsky island arc are proposed according to both of them the kronotsky island arc was moving with the continental plate in late cretaceous time and with the pacific plate from the beginning of the paleocene until docking with the eurasian margin in miocene pliocene time

geotraverses across the swiss alps the alpine chain marks the collision zone between the european and african lithospheric plates the earth s crust below the alps has been thickened by tectonic activity to form a root of crustal material which extends to a depth of approximately 60 km here we present the initial results of three seismic reflection traverses across the alps which show large scale crustal indentations resulting from collision between continental plates as well as the nappeforming style of deformation produced by compression of attenuated ocean crust the data suggest that the gross structural deformation of the collision zone results from large scale crustal indentations the descending european crust is delaminated and deformed by wedges of the african crust protruding northwards below the alps the nappe forming deformation seems to be restricted to the upper 10 20 km of the penninic domain in the core of the alps

constraints on the moho in japan and kamchatka abstract this review collects and systematizes in one place a variety of results which offer constraints on the depth and the nature of the moho beneath the kamchatka peninsula and the islands of japan we also include studies of the izu bonin volcanic arc all results have already been published separately in a variety of venues and the primary goal of the present review is to describe them in the same language and in comparable terms for both regions we include studies using artificial and natural seismic sources such as refraction and reflection profiling detection and interpretation of converted mode body waves receiver functions surface wave dispersion studies in kamchatka and tomographic imaging in japan the amount of work done in japan is significantly larger than in kamchatka and resulting constraints on the properties of the crust and the uppermost mantle are more detailed japan and kamchatka display a number of similarities in their crustal structure most notably the average crustal thickness in excess of 30 km typical of continental regions and the generally gradational nature of the crust mantle transition where volcanic arcs are presently active

use of ground probing radar and resistivity surveys for archaeological investigations in japan geophysical methods are normally used to estimate the distribution of cultural relics before digging objects of archaeological interest are usually located within a few meters of the surface therefore geophysical methods suitable for archaeological exploration are those which provide high resolution at shallow depths the most commonly used geophysical methods are ground probing radar resistivity and magnetometry of these methods we used mainly ground probing radar and resistivity surveys in archaeological investigations at four sites three of the sites were in gumma prefecture japan they were covered with volcanic deposits loam or pumice using ground probing radar we were able to locate ancient dwellings burial mounds and a distribution of archaeologically significant culture layers at the other site in nara prefecture we located part of the remains of an ancient city in this investigation the resistivity method and ground probing radar were combined to determine the loc

forensic geoscience applications of geology geomorphology and geophysics to criminal investigations abstract one hundred years ago georg popp became the first scientist to present in court a case where the geological makeup of soils was used to secure a criminal conviction subsequently there have been significant advances in the theory and practice of forensic geoscience many of them subsequent to the seminal publication of forensic geology by murray and tedrow murray r tedrow j c f 1975 republished 1986 forensic geology earth sciences and criminal investigation rutgers university press new york 240 pp our review places historical development in the modern context of how the allied disciplines of geology mineralogy sedimentology microscopy geophysics soil science microbiology anthropology and geomorphology have been used as tool to aid forensic domestic serious terrorist and international crime investigations the latter half of this paper uses the concept of scales of investigation from large scale landforms through to microscopic particles as a method of categorising the large number of geoscience applications to criminal investigation forensic geoscience has traditionally used established non forensic techniques 100 years after popp s seminal work research into forensic geoscience is beginning to lead as opposed to follow other scientific disciplines

fast monostatic gpr modeling we propose the exploding reflector method to simulate a monostatic survey with a single simulation the exploding reflector used in seismic modeling is adapted for ground penetrating radar gpr modeling by using the analogy between acoustic and electromagnetic waves the method can be used with ray tracing to obtain the location of the interfaces and estimate the properties of the medium on the basis of the traveltimes and reflection amplitudes in particular these can provide a better estimation of the conductivity and geometrical details the modeling methodology is complemented with the use of the plane wave method the technique is illustrated with gpr data from an excavated tomb of the nineteenth century

aquisgrani terrae motus factus est part 1 the aachen cathedral germany built on weak ground charlemagne charles the great placed the centre of his kingdom during carolingian times in aachen germany aquisgrana this medieval period and his regency are associated with a period of extensive constructions in aachen including the carolingian part of the aachen cathedral the cathedral was the first building in germany to join the unesco world heritage list the foundations and construction ground of the cathedral were excavated during recent archaeological and geotechnical investigations the cathedral is founded on pillars and piles in devonian blue limestone and shale covered by pleistocene loess sediments remains of roman buildings such as thermae are situated below this part of the cathedral the pillars are connected by up to 5 m deep foundation walls and are up to 2 4 m thick even though information about the construction site is important for the assessment of structural health and remediation measures it is often rare for old historical buildings documentations from construction time concentrate on the construction progress and financial aspects detailed descriptions on the foundation ground and techniques are usually not preserved this information is of relevance for assessment of earthquake related structural damages and site effects on construction investigations in the course of remediation measures or archaeological surveys fill this information gap they provide insights in the ancient foundation techniques and can be used for identifying earthquake related phenomena in the construction site furthermore a direct insight into potential seismic effects associated with the ground and building response on seismic shaking becomes possible in the case of the aachen cathedral typical geotechnical investigation methods including drilling and laboratory tests were applied together with gpr measurements to evaluate the construction ground and evaluate potential seismological effects

electromagnetic surveying in current middle eastern archaeology application and evaluation since 1977 the smithsonian institution has had a major research program on the human biological history of the near east as part of this program electromagnetic em surveying methods have been extensively used to identify anomalies of potential archaeological significance below the surface an em 31 noncontacting terrain conductivity meter was used in jordan bahrain kuwait and egypt with excellent results in addition to the successful application of em equipment to archaeological problems we investigated the equipment s response to changing environmental and climatic conditions we have developed efficient methods for recording em data the following results were obtained recording accuracy is better than previously reported 0 97 percent repeatability error between two observers the degree of accuracy is primarily a function of operator error and less a function of equipment reliability and the em 31 produces helpful highly reproducible results in the arid and semiarid environment of the mi

grustal shortening in the alpine orogen results from deep seismic reflection profiling in the eastern swiss alps line nfp 20 east the deep crustal seismic line nfp 20 east crosses almost the entire swiss alps despite the complex geometry of the well exposed nappe structure and the considerable axial plunge of some of the units the vibroseis survey yielded coherent reflections from several individually identifiable nappe contacts in the northern part of the survey the vibroseis data closely match the internal structure of the helvetic nappes and the underlying autochthonous parautochthonous mesozoic sediments on the northern flank of the aar massif an external basement uplift these mesozoic sediments seem to rise from a depth of approximately 7 8 km below sea level to the surface in a series of steps which is interpreted to represent crustal shortening achieved by a combination of folding and thrusting in the southern part of the survey it was possible to image a number of thin slivers of mesozoic carbonates pinched between slabs of penninic basement nappes as well as nappe contacts between lithologically contrasting units in addition it seems that the insubric fault zone which marks the contact between the penninic zone and the southern alps and which outcrops about 30 km to the south of the survey shows up as steeply north dipping reflections the lower european crust in the northern part of the survey is relatively transparent as opposed to the adriatic lower crust whose reflective nature may stem from shear zones associated with mesozoic crustal stretching the base of both the european and adriatic crust coincides with a 1 s thick band of laterally discontinuous reflections this reflection moho drops to greater depths going from the north toward the center of the alpine chain where it disappears with a steep southerly dip the moho reappears as a reflection band farther south this moho gap is situated above the lithospheric root and may be caused by perturbations related to subduction of lower crustal material the crustal scale structure obtained from the vibroseis data may be interpreted as a continent continent collision with wedge shaped indentation of a piece of adriatic crust into the european crust and vertical escape of the material in the core of the orogen along steeply dipping faults

estimates of modern arc parallel strain rates in fore arcs deflections of slip vectors of interplate thrust earthquakes from expected directions are used to estimate arc parallel strain rates within the overriding plates at the world9s major convergent plate margins arc parallel extension strain rates between 10 8 yr and 10 7 yr and significant at 2 standard deviations are observed in the fore arcs of the aegean aleutian mariana sumatran southern kuriles new hebrides scotia and southern central american lat 8 to 12 n subduction zones and the himalayas northern chile lat 17 to 31 s and central america lat 11 to 18 n show arc parallel compression available geologic and geodetic estimates of fore arc slip and strain rates agree within a factor of two with slip vector estimates arc parallel strain in fore arcs is rapid enough to produce geologically significant effects such as unroofing of high grade metamorphic rocks and disruption of transported fore arc terranes fore arcs deform even where convergence is perpendicular to curved margins demonstrating that head on subduction can produce a three dimensional strain field

geophysical remote sensing of historical aboriginal gravesites in southwestern western australia many suspected historical aboriginal gravesites are throughout southwestern western australia where individual burial locations remain unknown because of the cultural and historical importance of these heritage sites there is an increasing effort to identify such locations to enable better site preservation and appropriate commemoration gravesite reconnaissance routinely requires the investigation of large areas and it is inefficient and disrespectful to excavate large volumes in search of burials geophysical remote sensing offers a noninvasive alternative for identifying and delineating gravesites to these ends the university of western australia uwa society of exploration geophysicists seg student chapter has been working with the south west aboriginal land and sea council swalsc in a pilot study to acquire several near surface geophysical surveys at two historically documented aboriginal gravesites in quairading and toodyay western australia the resulting ground penetrating radar gpr magnetics conductivity mapping and resistivity profiling data sets identify subsurface anomalies that are consistent in location with historical documentation and elders recollections and with the expected geophysical signatures of historical burials and early development activities the geophysical survey results have been relayed to the swalsc and community decision makers to assist in upcoming preservation and commemoration efforts the pilot study could be helpful in identifying other aboriginal gravesites throughout western australia and would represent a positive step toward resolving key longstanding issues among different community interests surrounding the uncertainties of some sites of suspected aboriginal heritage

deep seismic reflection profiling in the swiss alps explosion seismology results for line nfp 20 east in september 1986 a 120 km long seismic line was recorded through the swiss alps the line traverses major units involved in thin and thick skinned alpine tectonics our preliminary interpretation indicates that 1 lithologic boundaries such as basement cover contacts although severely deformed during the alpine orogeny can be identified on the seismic sections 2 the top of the aar massif an external basement massif extends deep into the alpine orogen 3 the upper and lower parts of the crust are more or less transparent but are separated by a swarm of reflectors at mid crustal level 4 these mid crustal reflectors might be related to trapped fluids from alpine metamorphism and 5 the moho appears as a bright reflection that steepens from the north toward the south and terminates abruptly near the center of the alpine chain perhaps because of alpine deformation

synthetic seismograms for a complex crustal model the algorithm of the original reflectivity method has been vectorized and implemented on a cdc cyber 205 computer calculation times are shortened by a factor of 20 to 30 compared with a general purpose computer with a capacity of several million floating point operations per second mflop the rapid calculation of synthetic seismograms for complex models high frequency sources and all offset ranges is a provision for modeling not only particular phases but the whole observed wavefield as an example we model refraction data of the black forest southwest germany and are able to derive rather tight constraints on the physical properties of the lower crust

model for late mesozoic early tertiary tectonics of coastal california and western mexico and speculations on the origin of the san andreas fault cretaceous and early tertiary arc and forearc rocks found along the coast in southern california and baja california have been shown by paleomagnetic measurements to have originated many hundreds or even several thousands of kilometers south of their current locations northward transport also is found in cretaceous batholithic rocks near the edge of the continent in washington and british columbia the consistency of this pattern suggests that slices of arc and forearc rock originating on the western edge of north america have been translated along the coast by strike slip faulting strike slip faults are shown to be an expected response to north oblique subduction of the farallon and or kula plates faulting and subduction probably were concurrent activities i e the arc and forearc grew and were displaced simultaneously because displacement was dominantly parallel to subduction related lithic belts arc and forearc rocks may have traveled large distances without producing either significant hiatuses in the rock record or conspicuous disruptions in the distribution of lithic belts subduction related strike slip faulting is shown to be favored by high angles of oblique convergence shallow dip of the subducting slab relatively easy slip on potential faults within the arc or forearc and the existence of a place for the moving sliver to go it is suggested that these conditions are not difficult to satisfy and that subduction related strike slip faulting may thus be a common feature of convergent orogens the location of the san andreas fault inboard from the continental margin may be attributable to localization of the pacific north american transform by a system of precollision subduction related faults

results of nfp 20 seismic reflection profiling along the alpine section of the european geotraverse egt summary recent deep crustal seismic reflection profiling across the central alps of eastern and southern switzerland has provided a detailed image of this continental collision zone as part of the swiss national science project nfp 20 a series of reflection profiles was recorded during two phases along n s transects crossing the alpine edifice the eastern and southern profiles coincide with the alpine segment of the european geotraverse egt and in part with the earlier swiss geotraverse these data together with other geophysical and extensive geologic information form a unique and comprehensive volume of crustal information for this region of the alps on a larger scale the new reflection data also add to a growing set of profiles crossing the alpine fold belt which includes an additional traverse carried out by nfp 20 across the western swiss alps and the ecors crop profile across the western alps the initial results of the reflection data across the central alps outline a crustal framework involving northward indentation of the adriatic hinterland into the subducting european foreland this occurs beneath the collapsed oceanic basins of the penninic allochthon which is defined by its highly reflective crystalline nappes the present crustal thickness within the alpine collision zone has doubled to about 60 km by both vertical and horizontal displacements along an inferred complex detachment system controlled by the adriatic wedge the south plunging european foreland implies that portions of the thickened crust have been subducted into the upper mantle this general framework of flake tectonics is laterally consistent with the ecors crop results from the western alps however the western alps show a higher degree of crustal imbrication which may be related to the presence of the rigid ivrea body and an overall greater amount of crustal shortening compared to the central alps

discrimination between earthquakes and chemical explosions by multivariate statistical analysis a case study for switzerland a data set of 43 confirmed earthquakes and 42 explosions 1 3 m l 3 8 is analyzed by multivariate statistical analysis the explosion events include quarry blasts and explosions detonated for seismic experiments as well as an explosion of an ammunition storage site the events of this training data set are mainly located in the alpine mountains and central switzerland with the seismic sources having excellent distance r 300 km and azimuthal coverage for the recording stations multivariate statistical analysis is used to derive general discriminant functions based on regional waveform data for the training set the discriminant functions are then tested for consistency on the events of the training data set with the result that 97 of these events are correctly identified by the multivariate discriminant functions of the total training data set 17 is classified as ambiguous cases based on marginal discriminant functions the method is subsequently applied to an extended data set including nighttime events from 1992 1996 which are hence regarded as earthquakes and a set of presumed explosions from the years 1984 1997 for central switzerland the events of the extended data set can clearly be identified with the discriminant functions derived from the training data set the identification rate is lower for other regions in switzerland which can be related to tectonic units for these regions considered to have a laterally homogeneous crust a linear correction term in the discriminant function providing for station corrections can be found that significantly decreases the misidentification rate online material table of earthquake and explosion events manuscript received 11 may 2001

reconstruction of subduction and back arc spreading in the nw pacific and aleutian basin clues to causes of cretaceous and eocene plate reorganizations the eocene 50 45 ma major absolute plate motion change of the pacific plate forming the hawaii emperor bend is thought to result from inception of pacific plate subduction along one of its modern western trenches subduction is suggested to have started either spontaneously or result from subduction of the izanagi pacific mid ocean ridge or from subduction polarity reversal after collision of the olyutorsky arc that was built on the pacific plate with ne asia here we provide a detailed plate kinematic reconstruction of back arc basins and accreted terranes in the northwest pacific region from japan to the bering sea since the late cretaceous we present a new tectonic reconstruction of the intraoceanic olyutorsky and kronotsky arcs which formed above two adjacent oppositely dipping subduction zones at 85 ma within the north pacific region during another pacific wide plate reorganization we use our reconstruction to explain the formation of the submarine shirshov and bowers ridges and show that if marine magnetic anomalies reported from the aleutian basin represent magnetic polarity reversals its crust most likely formed in an 85 to 60 ma back arc basin behind the olyutorsky arc the olyutorsky arc was then separated from the pacific plate by a spreading ridge so that the 55 to 50 ma subduction polarity reversal that followed upon olyutorsky ne asia collision initiated subduction of a plate that was not the pacific hence this polarity reversal may not be a straightforward driver of the eocene pacific plate motion change whose causes remain enigmatic

geophysics and burials field experience and software development abstract in the uk geophysical survey methods have been increasingly applied in the search for clandestine burials and in the elimination of land from murder enquiries as part of a broader spectrum of systematic search techniques this paper considers recent forensic search work and stresses the general resources and intelligence needed for a successful search and the role played by geophysics the main emphasis however is to discuss the applicability of ground penetrating radar gpr in grave detection and to review recent developments in software particularly the importance of high resolution mapping the paper also discusses the use of image analysis of both planes through blocks of buried landscape together with predictive modelling and the value of 3 d analysis for data manipulation

magnetic mapping ground penetrating radar surveys and magnetic susceptibility measurements for the study of the archaeological site of serra di vaglio southern italy in this work we present the results of a multidisciplinary study for characterising the archaeological site of serra di vaglio basilicata region southern italy the site includes an ancient native settlement arisen between the 8th and the 3rd century bc the investigation has been performed by means of the integrated use of three different high resolution and no invasive geophysical techniques magnetic mapping ground penetrating radar profiling gpr and magnetic susceptibility measurements the integrated approach allows us to detect buried archaeological structures in particular our results helped to define spatial pattern of the buried remains to define the geometry of the anthropogenic settlements and to obtain detailed information about the composition and the manufacturing processes of different building materials the archaeological excavations carried out in one of the investigated sites confirm the usefulness and the reliability of the integrated employment of different geophysical techniques for the archaeological study of ancient buried structures

precise time and conditions of peak taconian granulite facies metamorphism in the southern appalachian orogen u s a with implications for zircon behavior during crustal melting events abstract the time of peak thermal conditions in the granulite facies zone of the southern appalachian orogen corresponds to the time of formation of garnet bearing leucosomes generated by biotite dehydration melting in garnet sillimanite gneisses leucosomes contain unusually abundant zircon occurring as inclusions in euhedral plagioclase phenocrysts and garnet isotope dilution thermal ionization mass spectrometric analysis of 13 elongate euhedral zircon crystals from the leucosome yields a concordant u pb age of documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 normalfont selectfont declaretextfontcommand textcyr cyr pagestyle empty declaremathsizes 10 9

ground penetrating radar surveys used in archaeological investigations during 1982 and 1983 two ground penetrating radar surveys were carried out in conjunction with archaeological investigations in canada the first survey was a detailed high resolution radar survey at the site of a sixteenth century basque whaling station on the labrador coast designed to locate the graves of the basques the second was a rapid low resolution reconnaissance survey as part of a prehistory impact assessment program at the site of the new national museum of man in hull quebec both surveys were experimental and were designed to see whether ground penetrating radar would be useful for identifying and locating anomalies of archeological significance radar was successful in detecting archeological anomalies several meters in size at both locations and the high resolution survey was moderately successful in identifying basque graves ongoing work involves comparing radar results with the archaeological investigations to increase the understanding of how radar can be applied to archaeology a

structure of an active arc continent collision area the aleutian kamchatka junction abstract the plate boundary between the north american and pacific plates along the westernmost portion of the aleutian arc is formed by several active dextral strike slip fracture zones fracturing is expressed by fault escarpments visible in reflection seismic profiles and narrow zones of high seismicity the seismicity changes from the aleutian arc where shallow earthquakes occur to intermediate to deep earthquakes in the kamchatka aleutian junction area and to the south in the vicinity of this junction the distribution of earthquakes follows the traces of major aleutian fracture zones down to a depth of 100 km south of the kronotsky peninsula the distribution of earthquakes changes and is similar to other subduction zones the fracture zones cut the western aleutian arc into individual blocks which move along strike slip faults to the west and collide with kamchatka related transtension and transpression has led to the development of pull apart basins and block tilting the fracture zones splay into numerous strike slip faults to the west where they meet the kamchatka margin the main faults of the aleutian fault system can be traced on the kamchatka mys peninsula where deformed pleistocene sediments high uplift rates recent thrust faulting and changes in the drainage system provide evidence for neotectonic activity the fault pattern onshore and offshore in the junction area supports an indentation tectonic model of the collision of aleutian arc slivers with kamchatka

eocene arc continent collision and crustal consolidation in kamchatka russian far east the age and origin of high grade metamorphic rocks of the sredinnyi range kamchatka have been the subject of a long and controversial debate based on geochronologic data and its association with a collage of accreted oceanic terranes leading interpretations argue that the sredinnyi range metamorphic rocks represent an accreted precambrian or mesozoic microcontinent in this contribution we present new data that indicate that these metamorphic rocks were formed from the cretaceous paleocene sedimentary margin of northeast russia when it was overridden during eocene obduction of the olyutorsky arc a far travelled oceanic island arc our data include new mapping and structural observations along the northern and eastern flanks of the sredinnyi range and shrimp zircon and monazite u th pb age data from 15 key samples these new isotopic data demonstrate that paragneissic units were formed from sediments with depositional ages locally no older than late cretaceous to paleocene furthermore the statistical similarity of zircon u pb grain ages from the kamchatka schist with very low grade turbidite sandstones of the ukelayat and khozgon groups indicate that metasediments of the sredinnyi range are upgraded stratigraphic equivalents of northeast russian marginal strata shrimp u pb ages of zircon overgrowths and metamorphic monazite extracted from migmatite and gneiss indicate that peak metamorphism occurred at 52 ma which is synchronous with the onset of the olyutorsky arc continent collision heating and cooling occurred rapidly at rates approaching 80 c m y rapid heating is attributed to syn collisional subduction related magmatism thermochronology and structural observations indicate that exhumation was due to a combination of ductile and brittle thinning of the crust we speculate that this thinning was caused by diapiric ascent of a low density low viscosity continental material beneath a dense structural lid of the obducted island arc

the komandorsky basin as a product of spreading behind a transform plate boundary abstract a long term study of the komandorsky basin in particular by the cruises of r vvulkanolog and r vdmitry mendeleev in the summer of 1988 made it possible to describe in detail the main structural features of this marginal basin several ne and n s trending spreading axes were detected in the basin in the rear of the transform sector of the aleutian arc spreading axes are shifted relative to each other along nw striking transform faults there is variation in style from north to south along the strike of the spreading axes and a less well defined symmetry compared to that typical of mid oceanic ridges the tectonic pattern and heat flow reflect several stages starting from the eocene in the history of the opening of the basin caused by the changes in the velocity and direction of the relative motion between the pacific and north american plates

geophysical surveys of burial sites a case study of the oaro urupa a maori family burial site was surveyed using shallow electromagnetic em magnetometer gradiometer and ground penetrating radar gpr techniques the locations of some older graves are no longer known partly through the loss of markers and partly through the loss of the oral record there are at least 150 such burial sites throughout new zealand and similar problems occur elsewhere in the world the knowledge that maori graves are traditionally set out facing east made survey design easier background trends are removed and possible anomalous features are identified despite the complicating presence of metal fencing the em in phase response the vertical gradient of the total magnetic field and the gpr response were particularly useful in combination gpr surveys were carried out using two frequencies 450 and 200 mhz the higher frequency radar surveys were limited in extent because these data had a limited depth of penetration and were prone to signal ringing in the surficial clay the lower

multidisciplinary approaches to the geoarchaeological evaluation of deeply stratified sedimentary sequences examples from pleistocene and holocene deposits in southern england united kingdom archaeological evaluation of deeply stratified sedimentary sequences from lowland river valleys can be problematic because of the often excessive depth of the deposits the associated high level of the water table and ground instability in such situations conventional archaeological survey techniques are inappropriate and alternative methodologies are required one suitable approach is to model subsurface stratigraphy in an attempt to determine potential locations for buried archaeology using an integrated borehole and geophysical program of ground investigation information of this type is often available in the form of geotechnical data that can be usefully augmented by geoarchaeological targeting of selected areas of the site for further information in this paper we show how such techniques can be used to model buried gravel surfaces peats within alluvial stacks and buried former clifflines in holocene and pleistocene sediments from southern england

geodynamics of an early eocene arc continent collision reconstructed from the kamchatka orogenic belt ne russia abstract the principal structures of the central and eastern ranges of the kamchatka orogenic belt were formed during collision of an upper cretaceous lower paleocene island arc with the asian continental margin during the early eocene two major syncollisional tectonic events are recognized westward thrusting of the island arc onto the continental margin and eastward thrusting on the eastern side of the deformed arc accompanied by tectonic accretion of eastward derived slices of oceanic crust both tectonic processes occurred under upper to middle crustal conditions syntectonic high temperature medium pressure metamorphism up to amphibolite and granulite facies affected the units of the arc its oceanic basement and the continental margin synkinematic gabbro plagiogranite intrusions occurred along major decollements of both vergences according to the geodynamic model both of the observed tectonic events i e westward overthrusting of the arc and eastward thrusting at its eastern side represent incremental stages of a single processes that lasted over 7 ma and was initiated by the arc continent collision the first stage corresponds to southeastward continent subduction under the arc which was soon blocked followed by reversal of subduction polarity and the beginning of northwestward oceanic subduction

integrated geophysical studies at ancient itanos greece the results of an integrated geophysical survey at the archaeological site of itanos crete are presented and discussed at hellenistic itanos which is located near the seashore the buried ruins are partially under the saline water table the purpose of this geophysical survey was to map buried relics of buildings streets and walls of ancient itanos in particular the usefulness of combining conventional geophysical mapping techniques and high resolution imaging methods in delineating shallow targets of archaeological interest at such complex archaeological sites is studied magnetic gradient soil resistance and electromagnetic measurements were taken in grids covering an area of approximately 16 000 m2 processing of geophysical maps included filtering with the gradient and first derivative operators in the space domain and the upward continuation and butterworth filters in the wavenumber domain emphasis is given to the mathematical description of the processing steps the integration of the geophysical measurements revealed the existence of a well and three parallel walls verified by excavation ground probing radar and electrical tomography sections crossing the parallel walls showed the vertical extent of these features ground penetrating radar time slices and 3d electrical tomography depth slices were used for the verification of specific anthropogenic anomalies which were detected on the geophysical maps a shallow seismic survey was carried out in an effort to locate and map the ancient port the combination of a wide spectrum of geophysical prospecting techniques was successful in delineating the buried relics enhancing the information context regarding the hellenistic settlement of itanos together with its port and necropolis the geophysical survey at itanos demonstrates that the integrated approach is appropriate for archaeological investigations at complex sites like itanos

400 my of basic magmatism in a single lithospheric block during cratonization ion microprobe study of plagioclase megacrysts in mafic rocks from transbaikalia russia post ordovician magmatism occurred within the ordovician accreted elements and d 18 o and simultaneous increase in high field strength terrane of transbaikalia during its 400 my of cratonization basic elements and k we speculate on tectonic implications of the magmas may be critical in the generation of k rich silicic magma established chemical trends as reflecting progressive incompatible yet only subordinate volumes of coeval mafic rocks in the silicic element depletion and devolatilization of a mantle source and plutons and synchronous volcanics are present most of the mafic increasing prevalence of alkali basalt from the sublithospheric mantle rocks contain plagioclase megacrysts 1 5 mm and these were in the course of cratonization used to reconstruct the primary basic magma chemistry and its evolution with time optical and scanning electron microscopy studies and electron microprobe profiling through plagioclase megacrysts of diverent ages revealed unzoned ca rich cores in a number of crystals key words anorogenic cratonization ion microprobe stable isotopes in each sample several crystals within each rock in a number of trace elements rocks within each age group were studied several ion microprobe analyses inside each of these cores were made for concentrations of li be b f mg p cl k ti fe co rb sr y zr nb cs introduction ba la ce pr nd sm eu and pb in addition partition coeycients for the same trace elements and the relevant compositional range of plagioclase were used to convert trace element concentrations secondary ion mass spectrometry studies in transbaikalian plagioclase to parental magmatic values wholeof liquidus phases

japan sea opening history and mechanism a synthesis the respective tectonic effects of back arc spreading and continental collision in asia are considered either as two independent processes or as closely interrelated extrusion tectonics assumes that the opening of the south china sea and the left lateral motion along the red river fault are geometrically linked in a pull apart manner this model is not accepted by several workers because the structural link between the two processes is not clearly demonstrated in the case of the japan sea we can show without ambiguity that back arc opening was controlled by large intracontinental strike slip faults which can be easily understood as effects of the india asia collision far from the indenter the japan sea opened in the early miocene in a broad pull apart zone between two major dextral strike slip shear zones the first one extends from north sakhalin to central japan along 2000 km it has accommodated about 400 km of finite displacement deformation along it varies from dextral transpression in the north to dextral transtension in the south the second is between korea and sw japan and has accommodated a smaller displacement of about 200 km the extensional domain in between lies in the back arc region of japan distributed stretching of the arc crust resulted in the formation of most of the japan sea while localized oceanic spreading at the southern termination of the eastern transpressional shear zone shaped the japan basin the first oceanic crust was formed in a small triangle based on the eastern shear zone and spreading propagated westward inside the pull apart region timing of oceanic crust formation of formation of the dextral shear zones and of block rotation in between as well as the internal structure of the basins and the geometry of deformation along the master shear zones are used to reconstruct the opening history this evolution is discussed by comparison to other manifestations of the arc and back arc activity such as the history of sedimentation and volcanism the paper then suggests that the collision of india can have tectonic consequences as far north as japan and sakhalin and describes the geometrical relation of back arc opening there and diffuse extrusion

gravity interpretation of a unified 2 d acoustic image of the central alpine collision zone summary four individual deep seismic reflection profiles across the eastern and southern swiss alps have been combined along the trend of the bouguer gravity anomalies onto the european geotraverse the profiles were migrated ray theoretically with the migration velocity model derived from a smoothed reinterpretation of the seismic wide angle profiles running parallel to the strike of the alpine arc the contours of this velocity model were ray theoretically depth migrated together with the combined digitized line drawings of the seismic reflection profiles the resulting acoustic image depicts the subduction of parts of the lower crust of the european plate beneath the adriatic promontory of the african plate at a low angle of 15 based on the interpretation of the seismic data orogenic crustal thickening is attributed to the stacking of crystalline nappes onto the upper crust of the european plate and wedging of the european and adriatic middle and lower crusts the latter being ill constrained by the seismic evidence alone the south vergent thrusting of the southern alps can be accounted for by the observed downbending of the adriatic moho and the lower crust in conjunction with the inferred wedging at mid crustal levels using the geometric constraints provided by seismic data gravity modelling of the alpine lithosphere asthenosphere system relative to stable central european platform clearly favours a gently inclined subduction zone reaching down to at least 200 km depth such a gently dipping subduction zone is at odds with prominent models on alpine geodynamics which favour a near vertical orientation of the subducting lithosphere verschluckung in agreement with the wedging hypothesis indirectly inferred from the seismic data the short wavelength part of the alpine gravity anomaly requires a middle crust of anomalously high density in the axial zone of the orogen both seismic and gravimetric evidence therefore suggest that late orogenic lithospheric shortening and crustal thickening was governed by the mechanical decoupling of the upper middle and lower parts of the crust the amount of subducted lower crustal material cannot be constrained by gravity modelling since its gravity effect cannot be separated from the effect of the subducting slab

the pre cretaceous deep seated tectonics of the abukuma massif and its place in the structural framework of japan abstract the structures and microstructures of the takanuki and hitachi areas in the abukuma massif northeast japan are described in the takanuki area the basic gosaisho series thrusts the pelitic takanuki ones in a hp metamorphic context the nappe structure is afterwards refolded by a migmatitic dome the samegawa dome in a ht metamorphic context microtectonic analysis shows that the nappe was transported from south to north along the stretching lineation geometric features suggest that the samegawa dome was emplaced by diapirism the role of the thrust surface as an instable interface promoting the doming is emphasized the hitachi metamorphic rocks composed of basic schist limestone and sandstone shist thrust the pelitic rocks of the western hitachi gneisses as for the takanuki area the thrusting occurred in ductile synmetamorphic conditions with a north or northeastward displacement owing to lithologic petrologic structural similitudes the nappe of the hitachi metamorphic rocks and that of the gosaisho series are unified into a unique nappe with a northward motion the emplacement occurred between late permian and late cretaceous likely in late jurassic the allochthonous units of the abukuma massif are correlated with the green schist nappe described in southwest japan since they are surrounded by the same zones namely the tanba zone and the kurosegawa kitakami one moreover both in southwest and northeast japan the emplacement of the green schist nappes is due to a shear deformation inducing rotational structures along the stretching lineation indicating the same sense of transport that is eastward in southwest japan and northward in northeast japan owing to the late bending of the japanese islands the late jurassic nappe structure is obliquely overprinted by a ht metamorphism ryoke in southwest japan abukuma in northeast japan and afterwards cut by late faults as the median tectonic line or the tanakura fault giving rise to the present complexity

archean protolith and accretion of crust in kamchatka shrimp dating of zircons from sredinny and ganal massifs abstract we used an ion microprobe shrimp rg for u pb dating of individual zircons in high grade metamorphic basements of the felsic sredinny and mafic ganal massifs in kamchatka thirty percent of zircons from paragneisses of the sredinny massif contain archean 2800 2500 ma early proterozoic 1700 2100 ma and late proterozoic 1000 ma detrital cores in addition a broad and almost uninterrupted range of phanerozoic detrital cores 460 175 ma is present with jurassic to lower cretaceous 150 96 ma zircons forming the youngest detrital age group ubiquitous documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 normalfont selectfont declaretextfontcommand tex

ground penetrating radar survey finalized to the recovery of the s agata alla badia church in catania eastern sicily italy numerous archaeological sites dating to the greek roman period have been found in the underground of the city of catania eastern sicily italy their presence is a testimony of the several settlements that have followed in this area over time in this work we have conducted electromagnetic surveys consisting of ten georadar profiles inside the church of s agata alla badia damaged during the earthquake occurred in eastern sicily on 13 december 1990 the aim was to investigate the area where the church is located to obtain information useful for its structural recovery mechanical drillings were also carried out to reconstruct the local stratigraphy which could be complicated by the presence of underground cavities and artefacts as evidenced by recent excavations beneath the catania cathedral in the nearby piazza duomo from the interpretation of the gpr data the presence of ancient masonry structures underlying the recent foundations was highlighted in addition the gpr survey allowed us to identify and locate reflective horizons in the subsurface probably due to the presence of materials with different state of aggregation and or to buried structures

determining geophysical responses from burials in graveyards and cemeteries abstractgraveyards and cemeteries around the world are increasingly designated as full therefore there is a requirement to identify vacant spaces for new burials or to identify existing ones to exhume and then reinter if necessary geophysical methods offer a potentially noninvasive target detection solution however there has been limited research to identify optimal geophysical detection methods against burial age we have collected multifrequency 225 900 mhz ground penetrating radar gpr electrical resistivity and magnetic susceptibility surface data over known graves with different burial ages and soil types in three uk church graveyards results indicate that progressively older burials are more difficult to detect but this decrease is not linear and is site specific medium to high frequency gpr and magnetic susceptibility was optimal in clay rich soils medium to high frequency gpr and electrical resistivity in sandy soils and electrical resistivity and low frequency gpr in coarse sand

the deep thermal field of the upper rhine graben abstract the upper rhine graben has a significant socioeconomic relevance as it provides a great potential for geothermal energy production the key for the utilisation of this energy resource is to understand the controlling factors of the thermal field in this area we have therefore built a data based lithospheric scale 3d structural model of the upper rhine graben and its adjacent areas in addition 3d gravity modelling was performed to constrain the internal structure of the crystalline crust consistent with seismic information based on this lithosphere scale 3d structural model the present day conductive thermal field was calculated and compared to measured temperatures our results show that the regional thermal field is mainly controlled by the configuration of the upper crust which has different thermal properties characteristic for the variscan and alpine domains temperature maxima are predicted for the upper rhine graben where thick insulating cenozoic sediments cause a thermal blanketing effect and where the underlying crustal units are characterised by high radiogenic heat production the comparison of calculated and measured temperatures overall shows a reasonable fit while locally occuring model deviations indicate where a larger influence of groundwater flow may be expected

constraints on the upper crustal structure of the long valley mono craters volcanic complex eastern california from seismic refraction measurements during the summers of 1982 and 1983 field work was completed on 10 new seismic refraction profiles in the long valley mono craters region located within the technically active zone between the eastern sierra nevada and the basin and range province the four profiles presented here sample the upper 7 10 km of the crust within the western half of long valley cladera the mono craters ring fracture system and the normal crust north and northeast of long valley the entire area shares a common crystalline basement consisting primarily of mesozoic granitic rocks at a depth of 2 km beneath the topographic surface the p wave velocity is uniformly 5 6 km s beneath which the velocity increases with a gradient of about 0 1 s 1 clear secondary arrivals observed on a profile crossing the west part of the caldera support evidence from 1972 seismic refraction profiles for a reflecting boundary at a depth of 7 8 km beneath the west margin of the resurgent dome which may represent the top of a magma chamber structural details resolved in the upper 2 km of the crust lead to the following conclusions 1 p wave velocities in the crystalline basement at depths shallower than 2 km vary from 3 6 to 5 0 km s this variation reflects differences in the degree of fracturing of the upper portion of the basement 2 an apparently homogeneous basement in the upper 7 10 km beneath the mono craters ring fracture system indicates that any extensive magma chamber must be at least 10 km deep there 3 the downdropped crystalline basement beneath the western half of long valley caldera dips genty 5 10 to the northeast apparent offsets along steeply dipping caldera bounding faults are 1 0 1 7 km along the northern western and southern sides of the caldera with largest offsets in the north 4 rocks forming the caldera fill fall into essentially three p wave velocity groups from the surface downward these velocity groups are 100 400 of 1 2 1 8 km s material corresponding to unconsolidated fluvial or lacustrine deposits or highly fractured rhyolite flows 200 400 m of 2 8 3 1 km s material corresponding to sparsely jointed postcaldera rhyolite rhyodacite and basalt flows and approximately 1000 m of 3 9 4 4 km s material corresponding to deposits of bishop tuff

the latest cretaceous early paleogene rapid growth of accretionary complex and exhumation of high pressure series metamorphic rocks in northwestern pacific margin episodic growth of accretionary complexes along the northwestern pacific margin is well documented from detailed biostratigraphy and radiometric dating of metamorphic rocks the latest cretaceous to early paleogene rapid growth of the accretionary complexes observed in hokkaido and sakhalin islands was caused by the supply of a large amount of terrigenous sediments from an intracontinent collision zone the mongolia okhotsk zone in the northern asian continent rapid growth of the accretionary prism resulted in episodic tectonic events in the forearc and magmatic arc rapid underplating caused uplift and exhumation of previously accreted complexes along with high pressure series metamorphic rocks now exposed as the kamuikotan complex in hokkaido and the susunai complex in sakhalin the forearc basin shallowed as a result of the uplift the uplift collapsed the old accretionary complex and supplied olistoliths onto the forearc region magmatic activity along the continental margin was also active at the same time subduction of a large amount of terrigenous sediments into the mantle may have contributed to active magmatism at that time a large supply of water trapped in the subducted sediments entered the mantle and increased partial melting of the mantle wedge

moho depth and poisson s ratio in the western central alps from receiver functions summary current knowledge about deep crustal structure of the alpine orogen has mainly been derived from p wave velocity models obtained from active and passive seismic experiments a complementary s wave model to provide lithological constraints necessary for unique structural interpretation has been missing to date in this paper we present important new information on s wave velocity model in the alps we applied the receiver function method using 6 yr of high quality data from 61 permanent and temporary stations sampling the western central alps we determined first order crustal features moho depth h and average vp vs ratio with the h stacking technique that uses timing of direct and multiple p to s converted phases from the moho interface synthetic tests reveal a dipping moho interface expected beneath an orogen causes a systematic bias of h and potentially leading to misinterpretation we thus applied corrections determined from synthetic data to remove the bias providing better fit of recovered moho depths with active seismic estimates for each site we also obtained independent h and estimates based on the timing of the strong ps phase our results show a gently south southeast dipping european moho at a depth of 24 30 km beneath the northern alpine foreland steepening rapidly towards the europe africa suture zone to reach a maximum depth of 55 km south of the suture the moho of the adriatic crust promontory of the african plate is at 35 45 km depth in the previously ill constrained western alps we found the european moho at 30 km depth beneath the more external units dipping east northeast to reach 50 55 km in the inner core of the alps the poisson s ratio clearly correlates with the tectonic units that comprise the alps average crustal values in the european alpine foreland are close to 0 25 in the alps we observe low values 0 22 in the highly deformed nappes of the mesozoic helvetic and southern alps indicating a thickening of felsic upper crustal material in contrast the poisson s ratio is significantly higher 0 26 in the penninic and austroalpine units near the suture zone this rapid and significant change marks a clear rupture between the alpine forelands and the suture domain we assign this high poisson s ratio to doubling of mafic lower crust consistent with results from previous active seismic experiments a continuation of the lower crustal wedge into the central part of the western alps however seems unlikely based on low observed poisson s ratios

reduction of topography effect in inductive electromagnetic profiles application on coastal sambaqui shell mound archaeological site in santa catarina state brazil we present results of electrical conductivity profiles obtained with inductive electromagnetic geophysical method in santa marta archaeological site santa catarina state southern brazil this site is a sambaqui shell mound in which several human occupation remains are found during pre colonial period such as buried lithic and bone artifacts fire place etc most of these mounds include as well many human burials which in many cases point to funerary ritual as a main agency for mound building a set of profiles of apparent electrical conductivity and magnetic susceptibility was acquired in two sites aiming the identification of geophysical anomalies with potential interest for excavation to enhance conductivity data we applied an effective procedure to remove topographical effects in the apparent conductivity measurements which are rather conditioned by the presence of a variable water table depth or conductive sediment layer a linear dependence among conductivity values and the site elevation provided a simple linear model to remove the influence of topography corrected electric conductivity maps substantially improved the definition of anomalies many of them rather subtle in raw data images corrected maps also show a better adherence with magnetic susceptibility maps both of them identifying archaeological structures of interest a well structured fire place and a concentration of ceramic fragments

an interpretation of wide angle compressional and shear wave data in southwest germany poisson s ratio and petrological implications shear wave velocity especially when used with compressional wave velocity is an important constraint on estimates of the composition and physical state of the continental lithosphere we present shear velocity s models derived from high quality s wave data along three profiles in southwest germany which combine with existing p wave velocity p models to give poisson s ratio in the crust and uppermost mantle we then construct a laterally varying petrological model of the crust by comparing our p and s models with published laboratory measured rock velocities in general poisson s ratio is 0 25 in the uppermost crust 0 22 0 23 in the mid crust but reaching a low of 0 15 in the black forest low p zone and varies laterally from 0 24 to 0 30 in the lower crust the average poisson s ratio of the whole crust is everywhere about 0 25 the laminated signature of the lower crust prominent on reflection and p wave refraction data is absent on the s wave refraction data implying a strong high low alternation of poisson s ratio in the lower crust this suggests that the lower crustal laminae represent mafic silicic compositional layering for example basic sills in an originally more quartz rich lower crust rather than alternating zones of high and low pore pressure there is no evidence for a shear wave low velocity zone lvz in the black forest mid crust despite the presence of a strong p wave lvz this suggests high quartz content and the presence of pore fluids at low not high pore pressure a clear p to s converted moho reflection pm s is visible on several shots indicating that the moho is at least locally a first order discontinuity no shear wave refractions from the upper mantle are present even where strong p wave refractions are observed possibly indicating an increase of poisson s ratio with depth in the upper mantle the petrological modeling indicates that the upper and middle crust are probably of granitic composition that the mid crustal low p zones have high quartz content and that the lower crust probably consists of granulites of laterally varying bulk composition from granodioritic to gabbroic the lower crust is more mafic in areas of high reflection density on seismic reflection profiles suggesting that the laminations are caused by mafic intrusions into the lower crust either prior to the variscan orogeny or during tertiary volcanic activity

surveying batavia s graveyard geophysical controlled experiments and subsurface imaging of archaeological sites on an indian ocean coral island abstractwe conducted geophysical surveys on beacon island in the houtman abrolhos archipelago offshore western australia to investigate areas of archaeological interest related to the 1629 batavia shipwreck mutiny and massacre we used three complementary near surface geophysical survey techniques total magnetic intensity electromagnetic induction mapping and ground penetrating radar to identify anomalous target zones for archaeological excavation interpreting near surface geophysical anomalies is often complex and nonunique although it can be significantly improved by achieving a better understanding of site specific factors including background conditions natural variability detectability limits and the geophysical response to and spatial resolution of buried targets these factors were not well understood for beacon island nor indeed for the australian coastal environment we have evaluated the results of controlled experiments in which we bury known targets at representative depths and a

imaging skeletal remains with ground penetrating radar comparative results over two graves from viking age and medieval churchyards on the stora seyla farm northern iceland detailed ground penetrating radar surveys were conducted at separate viking age and medieval churchyards on the stora seyla farm in skagafjor ur northern iceland surveying over a previously unknown site ca ad 1000 that is located just a few meters above the skagafjor ur valley bottom delineated the remnants of a buried circular turf wall that encloses a church structure and several graves the radar profiles over the graves contain strong hyperbolic reflections that emanated from the skeletal remains over one of the graves an air filled void within the chest cavity had been detected as noted by reflections with normal polarity which indicated a boundary towards increasing microwave velocity during excavation the soil surrounding an intact rib cage collapsed thus confirming the presence of the void in general the skeletal remains were very well preserved and yielded strong reflections which permitted the orientation of the body to be determined conversely the radar profiles over a grave from a more recent churchyard ca ad 1200 show ground disturbance but lack hyperbolic reflections upon excavation only teeth were recovered the poor preservation of the skeletal remains is attributed to increase contact with infiltrating groundwater from an overlying gravel layer interpretations were aided by time slice overlay imaging forward modeling and analysis of the reflection coefficient

a lithospheric cross section through the swiss alps ii constraints on the mechanical structure of a continent continent collision zone summary the calculation of strength profiles along the european geotraverse egt through the swiss alps yields constraints on the large scale vertical and lateral mechanical structure through the alpine continent continent collision zone strength profiles are evaluated for different assumptions on petrological stratification and strain rate and are based on temperature depth profiles derived from transient thermo kinematic modelling of the neoalpine orogeny the main contribution to the total strength results from the mantle lithosphere which is strongly controlled by temperature in contrast the crustal contribution is mainly determined by variations in petrological stratification a direct correlation between surface heat flow and the total strength of the crust the mantle lithosphere and the entire lithosphere crust and mantle lithosphere is not observed our results demonstrate that in tectonically active areas a transient thermal model along with detailed knowledge of the deep structure and petrology is necessary to evaluate lithospheric strength envelopes inside the collision zone strain rate has a strong control on the bottom of the mechanically strong crust whereas outside the collision zone the effect is less significant the cut off depth of seismicity along the profile which correlates largely with the bottom of the mechanically strong crust deviates from the 300 400 c isotherm the inferred effective elastic thickness for the molasse basin north of the alps is in agreement with flexural modelling results whereas for the southern alps the predictions deviate

crustal structure beneath the northern margin of the swiss alps abstract the structure of the earth s crust under the northern margin of the swiss alps was determined by means of seismic refraction and reflection measurements the profile runs northeast from montreux on lake geneva along the helvetic nappes on the southern edge of the molasse basin to the rhine valley south of lake constance with two shotpoints 165 km apart we derived a two dimensional p wave velocity model from these data using data from two fans perpendicular to the profile at a distance of 110 km from the shotpoints we migrated the overcritical moho reflections laterally to their proper position the complicated sedimentary structure was mainly taken from various exploration surveys and earlier shallow research main features of the crust are the 3 km thick upper basement has an average velocity of 6 0 km s which is followed by 2 km with a reduced velocity of 5 6 km s at 10 km depth the velocity increases to 6 15 km s no significant structural changes occur in the depth range between 10 and 26 km with an average velocity of 6 2 km s at a depth of 26 km in the west and 24 km in the east the velocity increases to 6 6 km s for about 3 km followed by a low velocity zone of 6 4 km s with an average thickness of 6 km the crust mantle boundary is reached at 34 km depth under shotpoint jaunpass and deepens to 35 km near shotpoint saentis the southeastward downdip of the moho observed on the p m p fans migrates the derived deeper crustal structure laterally to the northwest by about 9 km from the surface position of the profile the velocity depth structure derived from the refraction and wide angle reflection data agrees well with a short near vertical reflection profile near shotpoint jaunpass

detection and characterisation of black death burials by multi proxy geophysical methods the construction of the new crossrail railway discovered 25 well preserved skeletons shallowly buried in central london in 2013 subsequent carbon dating and adna analysis confirmed the archaeological age and presence of the yersinia pestis black death plague epidemic strain here we present the non invasive multi proxy geophysical survey of the adjacent charterhouse square rapidly undertaken to detect any further burials and characterise the site historical records suggested the area was a burial ground for black death plague victims before subsequent cemetery and urban land use following initial trial surveys surveys imaged 200 isolated and similar sized burials in the south west of the site there were also two contrasting burial orientations present at various depths which suggested a series of controlled phased burials a well defined eastern burial boundary taking the form of a ditch and bank was also discovered geophysical surveys also identified a subsequent complex site history with multiple aged features this study revises knowledge of black death aged burials and provides important implications for successful geophysical burial detection with significant time and space limited site constraints

mesozoic evolution of northeast asia and the collision of the okhotsk microcontinent abstract tectonic models of northeast japan generally involve the progressive subduction of the paleo pacific oceanic crust during the mesozoic and collision of the okhotsk microcontinent at the end of the cretaceous with eurasia however these models are not based on a precise knowledge of the overall structure and succession of deformations in the collision zone our survey leads us to propose structural maps and cross sections of the hokkaido central belt and a tectonic description of each tectonic stage it appears that at the end of the jurassic until the early cretaceous an important event of nappe emplacement occurred we interprete this event as the collision of the okhotsk block with eurasia much earlier than in classical models during this collision the oceanic crust of a marginal basin was obducted with an east vergence and partly metamorphosed contemporaneously with the collision an important volcanism linked with the pacific subduction started and continued during the whole of the cretaceous period the continental margin was affected by strike slip faults running parallel to the margin with a left lateral motion the main fault was the tanlu fault which accommodated the northward movement of the eastern part of the asian continent which led to the closing of an oceanic domain between siberia and the okhotsk block this tectonic scenario ended 70 m y ago contemporaneously with the cessation of the volcanism in the okhotsk uda margal volcanic belt from the eocene to the middle miocene a right lateral strike slip motion along sakhalin and hokkaido gave rise to the hidaka shear zone and finally led to the opening of the sea of japan

an introduction to the european geotraverse project first results and present plans abstract the european geotraverse egt is an international multidisciplinary project focused on a north south orientated lithospheric profile 4000 km long and of varying width extending from northernmost scandinavia to north africa this profile consists of three interlinking segments northern central and southern comprising a continuous succession of tectonic provinces ranging from the oldest precambrian areas of the baltic shield to the currently active area of the western mediterranean the broad aim of the egt project is to obtain a better three dimensional picture of the structure state and composition of the continental lithosphere to use as a basis for an understanding of its evolution and dynamics all of the 12 major projects that constitute the egt joint programme have now been initiated and several of these projects are nearing completion along the northern segment data from the fennoscandian long range project fennolora a 2000 km long seismic profile across the precambrian baltic shield show that except beneath southern sweden the shield is characterized by a high velocity 40 50 km thick crust including a 5 10 km thick crust mantle transition zone an alternating series of 4 6 high and low velocity zones is present in the subcrustal lithosphere the base of which increases in depth from ca 110 km to ca 230 km from south to north beneath the shield the top of the mantle transition zone lies at a depth of about 450 km the second major project along this segment the eugeno s european geotraverse northern segment southern part project is a multidisciplinary study of the fennoscandian border zone and was largely completed in 1984 with the realization of a large scale seismic experiment preliminary interpretation of the excellent data obtained indicate the presence of strong lateral variations in internal crustal structure beneath the danish basin field work for a third major project a multidisciplinary transect of the archaean and early proterozoic terrains in the northernmost part of the shield the polar profile was carried out in 1985 a series of deep seismic reflection lines has so far been realized in the area of the central segment in the context of german national programmes first interpretations of the seismic data from a 260 km long profile across the two main intra variscan hercynian lineaments have shown the presence of numerous horizons making up a highly reflective zone in the lowermost 10 km of the crustal section studied and distinct changes in reflectivity between the main variscan tectonic zones in 1986 the entire segment will be investigated in detail in an ambitious international programme of integrated geological and geophysical studies a series of seismic experiments termed egt s have been carried out across the southern segment in 1982 1983 and 1985 interpretation of data from the 1982 and 1983 experiments have led to several interesting results including 1 1 the suggestion that two crust mantle like interfaces exist beneath the po basin at depths of about 35 and 50 km and adjacent tectonic units these interfaces marking a deep contact zone between the adriatic and european plates 2 2 in the area between genoa and corsica the ligurian sea is underlain by a greatly thinned distinctly layered section of continental crust and 3 3 corsica and sardinia are underlain by bowl shaped typically variscan continental crusts the 1985 phase of seismic surveys focused on crustal structure beneath tunisia and the adjacent seas in addition two off traverse projects are being realized first a wide aperture network of autonomously recording seismic stations nars installed along the line gothenburg malaga between 1982 and 1984 is already yielding high quality data on the upper 600 700 km of the mantle second an investigation of lithospheric seismic anisotropy in the area of the iberian peninsula is being organized for 1987 1988 finally of great importance are the systematic compilation of existing data and where needed in critical regions collection of new geophysical and geological data presently being carried out for the entire area encompassed by the egt it is expected that these compilations will be completed by 1987 at about the same time that full results from the main large scale seismic experiments become available enabling the construction of an integrated lithospheric cross section along the egt requiring a final phase of intensive multidisciplinary collaboration

an unrecognized major collision of the okhotomorsk block with east asia during the late cretaceous constraints on the plate reorganization of the northwest pacific abstract interactions at plate boundaries induce stresses that constitute critical controls on the structural evolution of intraplate regions however the traditional tectonic model for the east asian margin during the mesozoic invoking successive episodes of paleo pacific oceanic subduction does not provide an adequate context for important late cretaceous dynamics across east asia including continental scale orogenic processes significant sinistral strike slip faulting and several others the integration of numerous documented field relations requires a new tectonic model as proposed here the okhotomorsk continental block currently residing below the okhotsk sea in northeast asia was located in the interior of the izanagi plate before the late cretaceous it moved northwestward with the izanagi plate and collided with the south china block at about 100 ma the indentation of the okhotomorsk block within east asia resulted in the formation of a sinistral strike slip fault system in south china formation of a dextral strike slip fault system in north china and regional northwest southeast shortening and orogenic uplift in east asia northeast striking mountain belts over 500 km wide extended from southeast china to southwest japan and south korea the peak metamorphism at about 89 ma of the sanbagawa high pressure metamorphic belt in southwest japan was probably related to the continental subduction of the okhotomorsk block beneath the east asian margin subsequently the north northwestward change of motion direction of the izanagi plate led to the northward movement of the okhotomorsk block along the east asian margin forming a significant sinistral continental transform boundary similar to the san andreas fault system in california sanbagawa metamorphic rocks in southwest japan were rapidly exhumed through the several kilometer wide ductile shear zone at the lower crust and upper mantle level accretionary complexes successively accumulated along the east asian margin during the jurassic early cretaceous were subdivided into narrow and subparallel belts by the upper crustal strike slip fault system the departure of the okhotomorsk block from the northeast striking asian margin resulted in the occurrence of an extensional setting and formation of a wide magmatic belt to the west of the margin in the campanian the block collided with the siberian margin in northeast asia at about 77 ma a new oceanic subduction occurred to the south of the okhotomorsk block ending its long distance northward motion based on the new tectonic model the abundant late archean to early proterozoic detrital zircons in the cretaceous sandstones in kamchatka southwest japan and taiwan are interpreted to have been sourced from the okhotomorsk block basement which possibly formed during the late archean and early proterozoic the new model suggests a rapidly northward moving okhotomorsk block at an average speed of 22 5 cm yr during 89 77 ma it is hypothesized that the okhotomorsk east asia collision during 100 89 ma slowed down the northwestward motion of the izanagi plate while slab pull forces produced from the subducting izanagi plate beneath the siberian margin redirected the plate from northwestward to north northwestward motion at about 90 89 ma

mapping the moho of the western alps by wide angle reflection seismics abstract a new picture of the moho beneath the western alps could be obtained using wide angle reflection seismic data this picture in addition to its increased sharpness clearly shows how the moho deepens down to the root zone of the chain 55 km a 25 30 km deep reflector with upper mantle characteristics is discovered under the brianconnais zone where it overlies the autochthonous moho this unit does not seem to connect to the so called ivrea body situated much shallower and farther into the chain it supports a hypothetical flaking of the european lithosphere beneath the western alps farther east the moho beneath the po plain is clearly mapped too with a crustal thickness increasing in steps from 25 to 35 km this p wave moho picture is compared with an s wave picture and major differences appearing in the middle crust are discussed finally the seismic response of the moho is investigated and is shown to be shifted towards low frequencies in the inner zones of the chain this could partly explain why the ecors crop vertical seismic line equipped with high frequency geophones faltered over the identification of the deep alpine moho

new temple discovery at the archaeological site of nysa western turkey using gpr method abstract we carried out a ground penetrating radar gpr study at specific sites around the nysa city western turkey to assess the potential of detection method and imaging of buried archaeological features as a major educational and cultural aegean city during the hellenistic and roman times nysa has been the focus of archaeological investigations for the last 100 yrs past and ongoing excavations have revealed major ancient buildings such as theatres amphitheatres a library and shops however it is suspected that the original city may have extended further and reached a larger size we collected 22 profiles using a gpr system equipped with two shielded antennas of 250 and 500 mhz central frequencies after processing steps gpr results revealed the existence of buried walls located at 50 m west of the library they systematically display a characteristic signature hyperbolic shaped point source reflections in gpr profiles and may be described in terms of location geometry and dimension to a certain extent of construction style excavations made after our study confirmed our results and unearthed a previously unknown temple hence shallow geophysical investigations helped in gathering crucial archaeological information to better characterize the extent and richness of the city of nysa

simultaneous use of electrostatic quadrupole and gpr in urban context investigation of the basement of the cathedral of girona catalunya spain there is a growing demand for nondestructive geophysical investigation in archaeology especially in an urban context this is a result of taking our heritage more seriously than in the past since excavations are possible only over a very limited area any a priori information brought by geophysical methods can help to focus these excavations the classical geophysical methods used in archaeology resistivity magnetism are not applicable in an urban context with problems of accessibility and inherent electromagnetic noise the potential of the combined use of ground penetrating radar gpr and electrostatic es quadrupole data is demonstrated in the investigation of the floor of the cathedral of girona in northern spain a 1 3 1 3 m electrostatic quadrupole was towed continuously over a set of parallel profiles to produce a resistivity map for a 20 60 m area a set of resistive anomalies corresponds with known structures probably graves the largest observed anomalies appear to be related to fou

the search for graves over the decades grave markers in old cemeteries have been lost geophysical exploration can sometimes locate the unmarked burials the two techniques which may be best for this search are a ground penetrating radar survey and a soil conductivity survey a ground penetrating radar survey with its capability for estimating the depth and shape of buried objects is particularly suitable with an electromagnetic induction survey the disturbed soil in the grave shaft can sometimes be detected as a change in electrical conductivity both of these surveys also can locate large metal objects these surveys have limitations at some sites the radar cannot profile deeply enough at others the soil strata are so complex that graves cannot be distinguished a conductivity survey can be degraded by metallic trash and other small objects in the topsoil it can give the best results where the earth is distinctly stratified results from nine surveys are illustrated here the sites are all in the u s a and the gra

the search for graves with ground penetrating radar in connecticut the search for unmarked and clandestine graves is a labor intensive time consuming and often frustrating task several geo physical methods are available which can be expediently used with little or no disturbances to sites among which ground penetrating radar gpr is often considered the most useful tool to delineate possible graves this paper is the result of many years of gpr testing for unmarked graves in connecticut natural and cultural conditions are considered in the failure and or success of detection and the use of gpr in archaeological studies

okhotsk sea ice coverage and kamchatka glaciation over the last 350ka evidence from ice rafted debris and planktonic δ18o high resolution records of ice rafted debris ird and oxygen isotope records spanning an e w trending transect across the okhotsk sea unravel the marine and terrestrial cryogenic history of ne siberia over the last 350 kyr ird predominantly dispersed basin wide by sea ice shows lowest fluxes during interglacial periods implying a reduced and seasonal sea ice coverage highest ird accumulation rates are observed during glacial and deglacial periods with a more extended but highly dynamic ice cover although being rather synchronous ird fluxes are on average higher in the western okhotsk sea than in the eastern part pointing to a persistent but mobile particle supplying sea ice cover even during full glacial conditions presumably less dense in the eastern parts mis 6 is exceptional in this respect asynchronous fluxes of ird which vary spatially reflect rapid paleoclimatic and paleo glaciomarine changes ird accumulation rates were by factor 2 3 higher during mis 6 as compared to the last glacial maximum and the ird depositional center shifted from the western okhotsk sea early mis 6 toward kamchatka late mis 6 synchronous to a distinct change in the ird mineral composition both the characteristic composition of late mis 6 ird originating from the sredinny mountain range of kamchatka and their significantly enhanced accumulation rates refer to intensified iceberg dispersal across the eastern part of the okhotsk sea at 138 ka 135 ka 129 ka and 128 ka bp this scenario affords the presence of extended mountain glaciers protruding down to sea level on the western side of kamchatka anomalously light planktonic stable oxygen isotopes during mis 6 3 termination ii and mis 5 5 5 4 suggest significant freshwater supply related to the westward drainage of kamchatka glaciers the intensified kamchatka glaciation observed during late mis 6 was repeated during mis 3 iceberg discharges into the eastern okhotsk sea are observed at 60 ka 51 ka 42 ka 38 ka 36 ka and 31 ka and may partly correspond to n atlantic heinrich events

ground penetrating radar survey of a prehistoric site in southern italy abstract in this paper we present and discuss the results of a ground penetrating radar gpr study carried out in an area of southern italy where a karst cave with prehistoric remains was found the aim of the study involved the imaging of the subsurface stratigraphy both inside and outside the cave in order to assist archaeologists in an excavation programme the survey grid comprised 18 intersecting gpr profiles problems associated with the use of the gpr within a cave environment are highlighted and the data processing sequence designed to extract useful geo archaeological signatures is described interpretation of the radar sections was controlled by the excavation of two trenches inside and outside the cave allowing detailed outlining the complex stratigraphy and the reconstruction of palaeolithic and neolithic subsurface horizons

use of ground penetrating radar for assessment of potential sinkhole conditions an example from ghor al haditha area jordan sinkholes are near surface indicators of active karst features at depth such as cavities conduits and solutionally enlarged fractures this study tests the usefulness of ground penetrating radar gpr to identify and locate buried sinkholes as a means of interpreting the existence of these subsurface hydraulically active karst features gpr survey was made at the ghor al haditha area west of the jordan dstf in the jordan valley escarpment at the eastern dead sea shoreline gpr profiles 100 mhz made along the eastern dead sea shoreline showed a trough like pattern of radar reflections outlining a series of possible filled sinkholes this feature is about 38 m wide and about 12 m deep its width is consistent with the width of the feature obtained from the topographic map of the area the gpr survey suggests that this feature has been filled with relatively dense and resistive materials this structure lies almost directly above a major water bearing zone

evolution of the darling range batholith yilgarn craton western australia a shrimp zircon study ma and slow cooling indicated by marginal recrystallization and primary and secondary internal structures observed in zircons from continued pb loss from the zircons until 2628 2616 ma granites from the late archaean darling range batholith record stages in the evolutionary history of the granites and provide a basis for a shrimp u pb study on the timing of granite evolution many granite zircons contain cores a few low u cores retain concordant to slightly discordant u pb ages of 2 8 ga some show discordant intermediate ages but most have nearly concordant

main fault systems of the soviet far east the analysis of the distribution of thrusts normal faults and strike slip faults of various ages has allowed us to determine the character of lithospheric block displacements in the soviet far east the early mesozoic late mesozoic and cainozoic kinematics were each essentially different the early mesozoic dzhagdinsk fault system appeared as a result of the collision of the bureinsk khankaisk microcontinent with the siberian continent the largest faults of the system are neither longstanding nor deep but were formed during the latest stage of the structural evolution the multistage formation of the faults of the dzhagdinsk system is conditioned by its position at the margin of the continent the late mesozoic faults are mainly strike slip faults caused by the subduction of the oceanic crust at an acute angle with respect to the strike of the active continental margin the cainozoic faults were formed under compression on the boundary between the siberian platform and the bureinsk massif but under tension in the east of the region

a fine structural section through the crust and lower lithosphere along the axial region of the alps summary a unified two dimensional lithospheric model has been derived for the p wave velocity structure beneath the alpine longitudinal profile alp 75 main line by making new phase correlations and using ray tracing and ray theoretical seismogram calculations in laterally inhomogeneous media due essentially to an increase in thickness of the lower crust the total crustal thickness increases from 30 40 km in the peripheral regions to about 50 km in the central region of the alps the thickness change is more abrupt at the eastern end than at the western end of the line the boundary between the upper and lower crust occurs at 18 20 km depth except in the peripheral region at the eastern end of the line where it occurs at 14 16 km depth along the whole line the seismic basement has velocities averaged over some tens of kilometres of 5 85 6 15 km s 1 with individual values having uncertainties of 0 05 0 1 km s 1 at least east of shot point b the lower part of the upper crust has been modelled as a low velocity layer which is most pronounced beneath the peripheral regions and which is generally underlain by a transition zone at the base of which the top of the lower crust occurs the top of the lower crust has been modelled with velocities ranging from 6 25 6 5 km s 1 beneath the peripheral regions to 6 5 6 65 km s 1 beneath the central alps velocity uncertainties at the top of the lower crust are estimated to be around 0 2 km s 1 beneath the central alps a low velocity layer has also been modelled in the lower crust the top 6 km of the mantle has been modelled with velocities of 8 0 8 2 km s 1 with individual estimates having uncertainties of 0 15 km s 1 below this the upper mantle down to almost 100 km depth has been modelled as a series of high velocity layers embedded in material with lower velocities of 8 0 8 2 km s 1 the combined effects of tectonic overthrusting and uplift and erosion have probably led to the lower crust being apparently thicker than the upper crust in the central alps at the present day

origin transport and emplacement of an exotic island arc terrane exposed in eastern kamchatka russia the regional stratigraphy of eastern kamchatka includes an exotic early late cretaceous ophiolite and late cretaceous island arc volcanic sequence integrating the existing geologic and geophysical data we examine the origin transport emplacement and postemplacement deformation of the island arc terrane which is named the olyutorsky island arc results from several paleomagnetic studies consistently indicate that the island arc terrane originated 1000 km to the south of where it is presently exposed although the formative paleolatitudes of the island arc rocks approximately correspond to the location of the izanagi farallon subduction zone the age of the volcanic rocks postdates the cessation of izanagi farallon convergence thus indicating that an unnamed plate or back arc basin existed in the northwest pacific during late cretaceous time we examine two possible models for northward transport of the island arc terrane to kamchatka 1 infra oceanic transport with the pacific or kula plates and 2 coastwise translation of the island arc terrane after accretion to the eurasian margin far to the south of kamchatka for both models the dominant eocene and miocene deformation ages observed in eastern kamchatka are used as two possible age limits for the cessation of northward transport although the observed paleolatitudes from paleomagnetic data correspond best with the infra oceanic transport model the provenance of the paleogene transport stratigraphy indicates a near shore sediment supply our preferred interpretation is that the island arc terrane 1 accreted onto the eurasian margin concurrent with cessation of island arc volcanism maastrichtian danian and 2 underwent northward coastwise translation along a major strike slip fault zone ending by middle late eocene time 43 50 ma it is unclear whether the ophiolite was exposed during arc continent collision or whether the ophiolite was obducted onto the island arc prior to collision a consequence of either infra oceanic transport or coastwise translation is that an open corridor between the western terminus of the aleutian arc and kamchatka must have existed until middle to late eocene time spreading within the komandorsky basin subduction of sea mounts and collision of the aleutian arc with kamchatka are proposed to have instigated the second miocene phase of deformation which uplifted and reexposed the island arc terrane

arc continent collision and subduction reversal in the cenozoic evolution of the northwest pacific an example from kamchatka ne russia abstract the principal new feature in the cenozoic evolution of the northwest pacific is based on the fact that two arc terranes of upper cretaceous paleogene age were incorporated in the kamchatka orogen during the early tertiary and at the end of the miocene respectively these two arc terranes so called achaivayam valaginskaya campanian lower paleocene and kronotskaya coniacian eocene arcs are separated by a suture zone that contains deformed slices of young paleocene lower eocene oceanic crust paleomagnetic data on the original paleolatitudes of the arc positions as well as geochemical data characterized the arcs as intraoceanic originated in the northwest pacific the arcs were separated by the vetlovka oceanic plate suggested to be a trapped fragment of the kula plate in which a new spreading zone developed in the early tertiary the principal event in the reconstructed evolution is the eocene collision of the extended achaivayam valaginskaya arc terrane with the continental margin of asia the margin is interpreted as the southeastern facing the pacific cretaceous accretionary boundary of the okhotsk microplate docked against the asian continent at 55 65 ma the arc continent collision developed progressively northward from the end of the paleocene early eocene in southern kamchatka to the middle eocene in the olutorka region the different stages of the collision occurred simultaneously along strike of the achaivayam valaginskaya arc according to the geodynamic model based on geological data for southern kamchatka collision included 1 the entrance of the continental margin in the subduction zone deformation of the overriding plate and subduction of fore arc block 2 arc obduction on the continental margin blocking of continental margin subduction and 3 subduction reversal with onset of oceanic subduction at the eastern side of the deformed arc this subduction reversal produced deformation and reverse faulting along the eastern side of the arc thus allowing accretion of tectonic slices of young oceanic crust of the vetlovka plate which began to subduct during the subduction reversal the subducted plate dipping to the southeast was broken off and detached at depth under the arc area the subduction polarity reversal the most characteristic feature of the collision model is strongly supported by structural and geologic data of southern kamchatka and explains the main tectonic metamorphic and magmatic events related to and postdating the collision

provenance of proterozoic garnet biotite gneiss recovered from elan bank kerguelen plateau southern indian ocean at elan bank of the kerguelen plateau in the southeast indian ocean leg 183 of the ocean drilling program recovered clasts of garnet biotite gneiss in a fluvial conglomerate intercalated with basalt flows u pb and pb pb dates of zircons and monazites in these clasts and an overlying sandstone range from 534 to 2547 ma which is much older than the surrounding indian ocean seafloor these dates show that old continental crust resides in the shallow crust of the oceanic kerguelen plateau and that the breakup of gondwana dispersed continental fragments into the nascent indian ocean lithosphere

crustal structure of the southern alps beneath the intersection with the european geotraverse abstract newly digitized and amplitude controlled record sections from the 1977 southern alps refraction campaign permitted a reinterpretation of the crustal structure in the area between western lombardy and the giudicaria fault the resulting model exhibits considerable lateral heterogeneity in the west below 7 5 km of sediments of the lombardy basin the crust reaches a depth of only 31 km whereas it thickens towards the more mountainous area in the east reaching a depth of 46 km below the adamello massif although the signal character of the corresponding reflections is somewhat erratic the data are satisfied best by models with a low velocity zone in the upper crust an additional small velocity discontinuity from 6 2 to 6 4 km s was found in the middle crust at around 20 km earlier interpretations based on travel times alone included a layer with a velocity of about 7 km s at this depth this high velocity layer was then interpreted as lower crustal material of the adriatic african plate which had been overthrust onto the european plate during the alpine orogeny thus explaining the uplift of the southern alps however this model of crustal doubling is questionable because such a mid crustal high velocity layer is not in agreement with the amplitude data the relatively thin crystalline part of the crust under the lombardy basin is interpreted in accordance with geological evidence as a relic of a late hercynian rifting event

deep structure of the alps what do we really know abstract in the last five decades the deep structure of the alps has been probed by every geophysical method applicable and the resulting amount of data is unmatched for any other orogen in this study an attempt is made to review the data and the proposed structural models with the aim of separating the certain from the probable and from the speculative information this can be achieved by first reviewing the theoretical resolving power and ambiguity of the applied interpretation methods and then analysing the proposed models the methods reviewed are inversion of surface wave data teleseismic and local earthquake seismic tomography near vertical reflection seismology wide angle reflection and refraction seismology and gravity modelling all information about the moho rated as certain is combined to give a moho map of the alpine area the information rated as certain and probable and additional qualitative arguments are used to discuss a crustal model of the western and central alps represented by two cross sections major structural elements in this crustal model are a thick overthrust penninic nappe system wedging at mid to lower crustal levels a discontinuous moho and strong variations along the strike of the orogen whereas the structures of the european upper crust and of the penninic nappe system are well constrained only few and isolated lower crustal structural elements are rated as certain finally the shape of the lower lithosphere in the alps is discussed by review and comparison of the results from surface wave teleseismic travel time residual and tomographic studies qualitative arguments suggest the existence of a lithospheric root or slab beneath the alps probable tomographic information suggests a south vergent european lithospheric slab beneath the southern alps and the po plain despite the considerable number of studies aimed at resolving the deepest part of alpine orogeny the available quantitative information on the sub moho structure cannot be rated as certain