human environment interaction during the holocene along the shoreline of the ancient lake ladoga a case study based on palaeoecological and archaeological material from the karelian isthmus russia this paper presents the results of pollen diatom charcoal and sediment analyses from lake bol shoye zavetnoye situated between the gulf of finland and lake ladoga on the karelian isthmus north

late holocene sea level changes along the southern coast of finland baltic sea abstract lake isolation studies provide a reliable method for reconstructing the sea level history of areas affected by the glacio isostatic land uplift in this study late holocene relative sea level changes were investigated along the southern coast of finland gulf of finland in the baltic sea by studying 11 isolation basins in four areas kirkkonummi orslandet tenhola and prastkulla which extend across 120 km of finnish coastline that is characterised by a narrow archipelago the methods employed were lithostratigraphic interpretation diatom analyses and radiocarbon dating also used in this work are the results from three previously studied isolation basins with four 14 c dates the sea level history varies within the study area the 3000 yr old baltic sea shoreline is located about 11 m above present sea level a s l in prastkulla and about 8 m a s l in kirkkonummi these differences are due to the differences in isostatic uplift rates which have been slower in the east the main trend in relative sea level along the southern coast of finland is one characterised by a generally decreasing uplift rate during the late holocene however we identify the uplift anomalies in two areas where our data show phases of relative sea level lowering they are the first verified late holocene land uplift anomalies detected in finnish sea level data

moho vs crust mantle boundary evolution of an idea abstract the concept that the mohorovicic discontinuity moho does not necessarily coincide with the base of the continental crust as defined by rock type compositions was introduced in the early 1980s this had an important impact on understanding the nature of the crust mantle boundary using information from seismology and from deep seated samples brought to the surface as xenoliths in magmas or as tectonic terranes the use of empirically constrained p t estimates to plot the locus of temperature vs depth for xenoliths defined a variety of geotherms depending on tectonic environment the xenolith geotherms provided a framework for constructing lithological sections through the deep lithosphere and revealed that the crust mantle boundary in off craton regions commonly is transitional over a depth range of about 5 20 km early seismic reflection data showed common layering near the moho correlating with the petrological observation of multiple episodes of basaltic intrusion around the crust mantle boundary developments in seismology petrophysics and experimental petrology have refined interpretation of lithospheric domains the expansion of in situ geochronology especially zircon u pb ages and hf isotopes os isotopes of mantle sulfides has defined tectonic events that affected whole crust mantle sections and revealed that the crust mantle boundary can change in depth through time however the nature of the crust mantle boundary in cratonic regions remains enigmatic mainly due to lack of key xenoliths or exposed sections the observation that the moho may lie significantly deeper than the crust mantle boundary has important implications for modeling the volume of the crust mapping the crust using seismic techniques alone without consideration of the petrological problems may lead to an overestimation of crustal thickness by 15 30 this will propagate to large uncertainties in the calculation of elemental mass balances relevant to crust formation processes and the composition of the convecting mantle

the present rate of uplift of fennoscandia implies a low viscosity asthenosphere the rate of displacement in fennoscandia has been intensively discussed for many years it is now widely accepted to be an isostatic response of the glacial history of the area the earth s present response to deglaciation in fennoscandia is simulated using a three dimensional 3d viscoelastic model in which the asthenosphere and mantle viscosity are allowed to vary so that the maximum rate of present uplift matches its observed value the deglaciation history is considered to be known and the c14 datings are converted to sidereal years the pattern of the present uplift gives a firm match with the observed data when a low viscosity asthenosphere is introduced assuming a 15 000 years load cycle i e the glacier was applied to the surface for 15 000 years before the melting started the best fitting earth viscosity model is a 1024 nm lithosphere overlying a 75 km thick 2 0 1019 pas asthenosphere and a 1 2 1021 pas mantle the simulations suggest a remaining maximum uplift of 40 m

the early holocene sea level rise the causes anatomy and consequences of the early holocene sea level rise ehslr are reviewed the rise of ca 60m took place over most of the earth as the volume of the oceans increased during deglaciation and is dated at 11 650 7000 cal bp the ehslr was largely driven by meltwater release from decaying ice masses and the break up of coastal ice streams the patterns of ice sheet decay and the evidence for meltwater pulses are reviewed and it is argued that the ehslr was a factor in the ca 8470 bp flood from lake agassiz ojibway patterns of relative sea level changes are examined and it is argued that in addition to regional variations temporal changes are indicated the impact of the ehslr on climate is reviewed and it is maintained that the event was a factor in the 8200 bp cooling event as well as in changes in ocean current patterns and their resultant effects the ehslr may also have enhanced volcanic activity but no clear evidence of a causal link with submarine sliding on continental slopes and shelves can yet be demonstrated the rise probably influenced rates and patterns of human migrations and cultural changes it is concluded that the ehslr was a major event of global significance knowledge of which is relevant to an understanding of the impacts of global climate change in the future

measured and calculated elastic wave velocities for xenoliths from the lower crust and upper mantle jackson i rudnick r l o reilly s y and bezant c 1990 measured and calculated elastic wave velocities for xenoliths from the lower crust and upper mantle in j h leven d m finlayson c wright j c doohey and b l n kennett editors seismic probing of continents and their margins tectonophysics 173 207 210

determination of shale stiffness tensor from standard logs a technique allowing inversion of the shale stiffness tensor from standard logging data sonic velocities density porosity and clay content is developed the inversion is based on the effective medium theory the testing of the technique on laboratory measurements of the elastic wave velocities in shale samples shows that the inversion makes it possible to predict the elastic wave velocities vp vs1 and vs2 in any direction within an error of a few per cent the technique has been applied for the stiffness tensor inversion along a well penetrating a shale formation of the mississippian age altered by thin layers of limestone it is demonstrated that the symmetry of a stiffness tensor inverted at the sonic frequency 2 khz is slightly orthorhombic and taking into account the experimental errors can be related to the vertical transverse isotropy symmetry for the productive interval of the shale formation the thomsen parameters and average respectively 0 32 0 25 and 0 21 which indicate anelliptic behaviour of the velocities in this shale the coefficients of anisotropy of this shale interval are around 24 and 20 for the compressional and shear waves respectively the values of the inverted velocities in the bedding plane for this interval are in good agreement with the laboratory measurements the technique also allows inversion of the water saturation of the formation sw and the inverted values are in agreement with the sw values available for this formation a backus like upscaling of the inverted stiffness tensors is carried out for the lower and upper bounds of the frequency band used in the crosswell tomography 100 hz and 500 hz these results can serve as an initial velocity model for the microearthquake location during hydrofracking of the shale formation

ice age paleotopography a gravitationally self consistent theory of postglacial relative sea level change is used to infer the variation of surface ice and water cover since the last glacial maximum lgm the results show that lgm ice volume was approximately 35 percent lower than suggested by the climap reconstruction and the maximum heights of the main laurentian and fennoscandian ice complexes are inferred to have been commensurately lower with respect to sea level use of these ice age boundary conditions in atmospheric general circulation models will yield climates that differ significantly from those previously inferred on the basis of the climap data set

elasticity of single crystal orthoferrosilite the elastic moduli of a synthetic single crystal of pure fesio3 orthoferrosilite have been measured at 1 bar and 20 c by brillouin spectroscopy the moduli are in megabars c11 1 98 c22 1 36 c33 1 75 c44 0 59 c55 0 58 c66 0 49 c12 0 84 c13 0 72 c23 0 55 a comparison of the pyroxene crystal structure with elasticity data shows that distortion of the tetrahedral chains parallel to c is related to c33 straight or extended chains increase c33 and highly kinked chains weaken the structure however the ferrosilite data show that beyond a certain degree of distortion the tetrahedral chains are essentially passive previous models of pyroxene elasticity have indicated that c11 should be most sensitive to composition this is supported by the current study and is reflected in the elasticity data via a positive linear correlation of c11 with the size of the m1 octahedron as measured by the average m1 0 distance the average longitudinal modulus c 11 c11 c22 c33 3 varies linearly with composition in the system orthoenstatite orthoferrosilite whereas the average shear moduli c 44 and c 12 are constant for fe contents of at least 20 by comparison data for the solid solution forsterite fayalite are consistent with a linear variation of modulus versus composition between the end members for all three average moduli we suggest that this difference between orthopyroxene and olivine is due to a strong preference of fe2 for the m2 octahedral site in pyroxene the isotropic shear modulus is 30 lower for ferrosilite than enstatite despite a similar contrast in end member values of the olivine data are consistent with a linear variation of between fo100 and fa100 at high temperatures fe and mg in orthopyroxene will be randomly distributed and a linear variation of with molar content of fe is expected a comparison of laboratory elasticity data with observed mantle properties shows that vp vs and of the upper mantle are satisfied by pure olivine however the data strongly suggest that without the coexistence of a garnet phase no more than 10 orthopyroxene may be present in a model mantle assemblage ca clinopyroxene increases the upper limit on mantle garnet content but does not greatly affect constraints on the quantity of orthopyroxene in the upper mantle

measured and calculated elastic wave speeds in partially equilibrated mafic granulite xenoliths implications for the properties of an underplated lower continental crust ultrasonic compressional wave velocities measured at 1 0 gpa and room temperature are compared with calculated velocities based on single crystal data and modal mineralogy for a suite of mafic granulite xenoliths from the chudleigh volcanic province north queensland australia the xenoliths have nearly constant major element compositions but widely variable modal mineralogy reflecting recrystallization under variable pressure temperature conditions at depth in the continental crust 20 45 km they thus provide an excellent opportunity to investigate velocity variation with depth in a mafic lower crust measured p wave velocities corrected for the decompression induced breakdown of garnet range from 6 9 to 7 6 km sec and correlate with derivation depth these velocities are 5 12 lower than the calculated velocities 7 5 8 0 km sec apparently as a result of grain boundary alteration as well as irreversible changes that occurred in the xenoliths during rapid decompression calculated p wave velocities are similar to those estimated by furlong and fountain 1986 and sobolev and babeyko 1989 for mafic granulites formed through basaltic underplating of the continental crust depending upon in situ temperature p wave velocities in the deepest samples may be interpreted as crustal e g 7 3 7 6 km sec if heat flow is high or mantle 7 7 7 8 km sec in areas of low heat flow the range of velocities in the xenolith suite is larger than predicted for a fully equilibrated underplated basaltic layer highlighting the importance of kinetic effects in determining the ultimate velocity profile of magmatically underplated crust comparison of our results with seismic profiles illustrates that the lower crust rarely reaches such high velocities suggesting quartz bearing rocks country rocks are present within magmatically underplated layers of the deep crust

the inference of mantle viscosity from an inversion of the fennoscandian relaxation spectrum summary a formal inverse theory for mantle viscosity is here applied to a relaxation spectrum derived from the post glacial uplift of fennoscandia the spectrum represents the set of eigenfrequencies or inverse decay times for the fundamental mode of viscous gravitational relaxation between the spherical harmonic degrees 14 to 45 and 65 to 80 theoretical predictions of the eigenfrequencies are based upon the determination of the zeroes of the secular determinant function derived for a spherically symmetric self gravitating visco elastic planet differential kernels relating shifts in the eigenfrequencies to arbitrary perturbations in the radial viscosity profile i e frechet kernels are computed using the variational principle derived by peltier 1976 the inversions are performed within the framework of non linear bayesian inference and the problem has been parameterized in terms of the logarithm of viscosity the inversions have yielded a set of robust constraints which all models for the radial viscosity profile below fennoscandia must satisfy the a posteriori estimates and variance reduction are found to be insensitive to the a priori variance ascribed to the model layers the constraints have furthermore been summarized into a set of a posteriori estimates of the average model viscosity value in radial regions consistent with the resolving power of the data which decreases from a radial length scale of approximately 120km at the base of the lithosphere to 1200km at 1000km depth the data provide essentially no information regarding the mantle rheology below 1200km depth for example for earth models with a lithospheric thickness lt of 100 km the volumetric average logarithm of viscosity in regions in the depth ranges 1040 400 km 670 210 km and 235 100 km is constrained to be respectively 21 03 0 09 20 70 0 08 and 20 37 0 19 we have repeated the inversions for a number of assumed lithospheric thicknesses and have found that a relatively low viscosity layer in the sublithospheric region with respect to the underlying upper mantle is required for lt 120km in this respect we have quantified the previously described trade off between a decrease in the viscosity of this region and a decrease in lt cathles 1975 in forward analyses of the glacial isostatic adjustment data set it is common to use earth models with isoviscous upper and lower mantle regions to investigate this two layer case we have also performed inversions which assume perfect correlation amongst the model layers in the upper and separately the lower mantle under this strict model space limitation the inversions yield models with upper and lower mantle viscosities in the range 3 7 1020 4 5 1020 pa s and 2 2 1021 1 9 1021 pa s respectively the ranges are obtained from a suite of inversions using lithospheric thickness from 70 km to 145 km the a posteriori constraints generated from the bayesian inversions are used together with a statistic based on the computed misfit to the fennoscandian relaxation spectrum to rule out a number of previously published viscosity models

recent postglacial rebound gravity change and mantle flow in fennoscandia summary the recent postglacial rebound of fennoscandia is investigated using sea level data levelling data and gravity data in particular an analysis is made of the repeated data obtained hitherto on the fennoscandian land uplift gravity line along latitude 63 methods for this analysis include an iterative procedure for computing the relation between gravity change and absolute land uplift the mass flow parameter and the geoid rise the remaining land uplift is also estimated the mass flow parameter c is used to characterize the relation between additional mass and additional volume due to rebound it is a number between 0 and 1 1 corresponding to full inflow of mantle below the rising crust and 0 to no inflow but some kind of decompression the main result is that c is significantly different from 0 at the 99 per cent level we find c 0 8 this means that models proposed of the present uplift based on pure decompression must be ruled out and that a viscous inflow of mantle is a necessary part of the ongoing uplift process on the other hand this process might be more complicated than a pure viscous flow

viscosity and thickness of the asthenosphere detected from the fennoscandian uplift the earth s response to the deglaciation in fennoscandia is modelled using a layered viscous model with an elastic lithosphere the modelled tilting of palaeoshorelines at particular locations peripheral to the former ice load and the pattern of the present rate of uplift consistent with the observations strongly suggest a low viscosity asthenosphere earth models without a low viscosity asthenosphere give significant mismatch to the present rate of uplift and are unable to mimic the observed tilting of palaeoshorelines models with a viscosity of the lower mantle of 1 0 2 0 1021 pa s and a viscosity of the upper mantle of 0 7 1 0 1021 pa s overlain by low viscosity asthenosphere with a thickness ranging from 25 to 100 km fit equally well with the observations it is suggested strongly that the asthenosphere has a thickness of less than 150 km and a viscosity of less than 7 0 1019 pa s

estimation of ancient and future shoreline positions in the vicinity of olkiluoto an island on the western coast of finland the difference between grid and tin based gis approaches abstract the rise of gis data and spatial modelling techniques has brought new insights into shore displacement and palaeogeographical studies during recent years the aim of this study was to compare the capabilities of a raster data and map algebra based technique with those of a vector data triangulated irregular network tin based technique in the reconstruction of ancient and future shoreline positions in the vicinity of olkiluoto an island on the rapidly uplifting western coast of finland the first two models were carried out using a raster subtraction technique with grid cell sizes of 200 m and 30 m and a third model utilised a tin intersection technique where the shoreline is derived from the intersection of the tin representing the modern topography and the tin representing the water plane of the reconstructed phase the results show that the raster based technique has limited capability in recognition of important landscape features common to glacially sculptured coastal areas subject to glacial isostatic adjustment gia whereas the tin intersection technique provides more detailed information about the shoreline features comparison of the results reveals that the advantage of the tin intersection technique is more obvious the finer the scale is novel spatial modelling techniques improve the reconstructions of palaeolandscapes and shoreline positions of different time periods

main environmental changes since the weichselian glaciation in the danish waters between the north sea and the baltic sea as reflected in the molluscan fauna abstract the danish waters forming the transition zone between the north sea and the baltic sea are described through changes in the molluscan fauna and bottom communities during the holocene the major change in the fauna at the pleistocene holocene boundary is thought to be caused by changes in the palaeocurrents at this time a sudden sea level rise marked by floodwaters is recorded at the levels from 24 5 to 4 0 m between ca 8600 and 7800 cal years bp corresponding to a sea level rise of around 3 5 m every 100 years an expiring tide is identified in the early subboreal affecting the prolific fjord faunas of the atlantic time

comparison of seismic upscaling methods from sonic to seismic the term upscaling used here means a prediction of elastic wave velocities at lower frequencies from the velocities at higher frequencies three different methods of upscaling are considered including the simple averaging backus averaging and pair correlation function methods these methods are applied to upscale the elastic wave velocities measured at sonic frequencies 2 khz logging data available for a well penetrating layers of gas bearing shales and carbonates as a result a velocity distribution over depth for vp and vs is found in the frequency range of 50 500 hz the difference in the results obtained for a particular depth by the three theoretical methods in the surface seismic frequency bandwidth 50 100 hz is 600 m s for p wave and 260 m s for s wave velocity this difference is attributed to different theoretical backgrounds underlying these methods

effects of sand shale anisotropy on amplitude variation with angle ava modelling the sawan gas field pakistan as a key case study for south asia s sedimentary basins amplitude variation with angle ava is a technique widely used in the characterisation of hydrocarbon reservoirs and assumes the earth s crust to be an isotropic medium yet anisotropy is ubiquitous in stratigraphic sequences and has first order effects on seismic ava responses when investigating subsurface prospects this work analyses the effects of anisotropic strata on ava responses using the lower goru formation middle indus basin pakistan as a case study in the study area shale intervals are interbedded with reservoir sands of the sawan gas field shales in this field form laminae or are dispersed within reservoir sands making the lower goru formation an example of a vertically transversely isotropic vti medium in this work we calculate the effective saturated mechanical properties of the lower goru formation based on rock physics templates the backus 1962 average typically designed for layered media combined with the empirical relations of brown and korringa 1975 and wood 1955 the input data used in our rock physics modelling is based on detailed petrophysical analyses of well data using the saturated effective mechanical properties of the lower goru formation we generate angle dependent reflection coefficient curves and seismic ava responses based on exact and approximate solutions for both isotropic and anisotropic reservoir scenarios our results suggest that the effects of lithological anisotropy are more pronounced in places with thick shale beds within reservoir sands conversely angle dependent reflection curves and seismic ava responses based on isotropic or anisotropic cases give similar solutions in the presence of thin shale beds as a corollary of this work we present a bayesian inversion method for the estimation of porosity in vti media

holocene isostatic uplift of the south shetland islands antarctic peninsula modelled from raised beaches we present new isobases constraining the holocene isostatic uplift of the south shetland islands northern antarctic peninsula based on evidence from raised shorelines holocene shorelines were described and surveyed at fifteen sites to determine the spatial variability of relative sea level rsl change across the south shetland islands and provide new spatial rsl change corrections for the region results show that the highest shoreline is a transgressive feature correlated by geomorphological evidence on most exposed coastlines of the archipelago its surveyed height was corrected for local variability in wave energy by subtracting the measured altitude of the present day shoreline these corrected surveyed heights of the highest raised beach were modelled using quadratic polynomial trend surface analysis to constrain differing rates of regional isostatic uplift we present two isobase models of isostatic uplift since formation of the highest holocene raised beach circa 7360 7000 years ago these models suggests a maximum uplift of ca 20 m was centred on an area north of greenwich island with isobases implying an elongate zone of uplift orientated east southeast to west northwest along the spine of the island chain this corresponds well with previously published geomorphologically based estimates of palaeo ice extent and the deglaciation history of the south shetland islands and gives new context to the palaeo ice extent and glacial history of the region

the abrupt termination of the younger dryas climate event previous studies on two deep greenland ice cores have shown that a long series of climate oscillations characterized the late weichselian glaciation in the north atlantic region1 and that the last glacial cold period the younger dryas ended abruptly 10 700 years ago2 here we further focus on this epoch defining event and present detailed heavy isotope and dust concentration profiles which suggest that in less than 20 years the climate in the north atlantic region turned into a milder and less stormy regime as a consequence of a rapid retreat of the sea ice cover a warming of 7 c in south greenland was completed in about 50 years

upscaling of elastic properties of anisotropic sedimentary rocks summary in this paper the term upscaling means the theoretical prediction of rock s elastic properties at lower frequency seismic or cross well data using higher frequency logging data on sonic velocities vp vs1 and vs2 porosity and density the mineral composition and water saturation derived from other logs are used due to the special treatment of sonic logging data provided by the dipole sonic probe all the sonic velocities are obtained in the principal coordinate system of the rock s stiffness tensor the upscaling procedure includes two steps the first step involves the solution of an inverse problem on reconstruction of the parameters of the rock s microstructure from the logging data the inversion is based on the effective medium theory as a result of the inverse problem solution the effective stiffness tensor is found for depths at which the sonic wave velocities are measured at the second step the velocities of waves at given lower frequencies are calculated as propagating in a layered medium the number of layers in the medium depends on the given frequency and logging step each layer of the medium has the stiffness tensor found at the first step this upscaling procedure has been applied to a wellbore for which the dipole sonic data are available the rocks penetrated by the well are shales in general the resulting medium exhibits orthorhombic symmetry at sonic frequency this symmetry results from the preferential orientation of clay platelets and grain related cracks and vertical cracks the existence of the latter is indicated by the dipole sonic tool depending on the microstructure parameters orientation of clay platelets and cracks pore crack connectivity and shale mineralogical composition the shales at lower frequency have either transversely isotropic symmetry with the vertical axis of symmetry a k a vti or orthorhombic symmetry

seismic properties of lower crustal xenoliths from el hoyazo se spain experimental evidence up to partial melting abstract seismic techniques provide unique tools to investigate the structure and in combination with petrological geochemical and petrophysical study the composition of the lower crust controversies can be solved with comparative study of metamorphic terrains or xenoliths that occur adjacent to areas where seismic refraction reflection data are available xenoliths represent a direct sampling of the inaccessible lower crust at the time of the volcanism whilst exposed crustal sections can only be used as analogue of present day lower crust the present study is focused on the measurements of compressional wave velocities up to conditions exceeding the beginning of melting 950 c at 500 mpa confining pressure on three garnet biotite sillimanite metapelitic xenoliths recovered from the neogene dacites of el hoyazo se spain they preserve widespread interstitial rhyolitic glass as evidence of primary melt extraction and represent the best example of partially molten lower crust in the alboran domain the influence of glass on vp is primarily reflected by anomalous positive dvp dt while heating with velocity increasing at 500 mpa from 4 98 to 5 50 km s 1 at room temperature to 5 85 6 79 km s 1 at 650 700 c this corresponds to the glass transition where all the grain boundaries and most of the pores within the glass are closed after this point the velocity decreases to 6 2 6 5 km s 1 at 950 c where re melting of the glass is achieved and additional partial melt produced on cooling the behavior is normal with negative dvp dt after the thermal treatment velocities are 30 higher 6 07 7 21 km s 1 and reveal that in the presence of intergranular melt velocity measurements at room temperature cannot be extrapolated to high temperatures p waves measured at melting conditions are in agreement with deep seismic refraction data and tomography in the area and corroborate the hypothesis that partial melts are actually present in alboran lower crust

long wave seismic anisotropy of heterogeneous reservoirs summary borehole logs often show considerable variation over small lengths consistent with fine layering of the formation elastic upscaling allows layering on a fine length scale to be replaced by thicker homogeneous equivalent transversely isotropic layers thus creating a model with far fewer layers in this paper the evect of inclusions of finite lateral extent on elastic upscaling is examined for inclusions with a small thickness to width ratio backus averaging gives a good approximation to the long wavelength elastic properties of the medium however for larger thickness to width ratios the anisotropy of the medium can be significantly reduced for inclusions that are long in comparison to their width azimuthal anisotropy may result if the inclusions show a preferential orientation this could result from the presence of flow during deposition the azimuthal anisotropy increases with increasing thickness to width ratio of the inclusions and vanishes when this ratio is zero for larger thickness to width ratios the magnitude of the azimuthal anisotropy may be of similar magnitude to that commonly seen in sedimentary basins azimuthal anisotropy is usually attributed to the presence of aligned fractures within the formation the present results suggest a further source of azimuthal anisotropy that may be significant

diatom and stable isotope records of late holocene lake ontogeny at indrepollen lofoten nw norway a response to glacio isostasy and neoglacial cooling borg indrepollen is a coastal lake on the island of vestvagoy lofoten nw norway a sedimentary sequence spanning the last 4500 cal yr bp was analysed for diatom c n and stable isotopes 13c and 15 n the record provides clear evidence of glacio isostatic rebound in the lofoten region five distinct lithostratigraphic geochemical zones i v and four major diatom zones a d were identified the early record i iii a biii 4500 550 cal yr bp contains coarse sedimentary material and diatoms indicative of more marine conditions the correlation between the isotopic data high 13c and low c n and trends in the biological data marine brackish flora suggest the marine influence on the indrepollen basin is a controlling factor of the source of organic material the latter part of the record iv c 550 cal yr 550 226 indicates a transitional phase from marine dominated diatom to brackish taxa and is coincident with a section of microlaminations in the core the youngest zone v d 226 cal yr bp

holocene sea level changes and glacio isostasy in the gulf of finland baltic sea abstract shoreline displacement in the eastern part of the gulf of finland during the past 9000 radiocarbon years was reconstructed by studying a total of 10 isolated lake and mire basins located in virolahti in southeastern finland and on the karelian isthmus and in ingermanland in russia study methods were diatom analyses sediment lithostratigraphical interpretation and radiocarbon dating in southeastern finland the marine litorina transgression maximum occurred ca 6500 6200 14 c yr bp 7400 7100 cal yr bp in areas of the slower land uplift rate on the karelian isthmus and in ingermanland the transgression maximum occurred ca 6400 6000 14 c yr bp 7300 6800 cal yr bp the highest litorina shoreline is located at ca 23 m above present sea level in southeastern finland whereas in the eastern part of the karelian isthmus near st petersburg it is located at ca 8 m above present sea level the amplitude of the litorina transgression in virolahti area is ca 4 m whereas on the karelian isthmus and in ingermanland the amplitude has varied between 5 and 7 m the regional differences between areas are solely due to different glacio isostatic land uplift rates the seven basins studied in this research were connected to the baltic sea basin during the litorina sea stage and their diatom and lithostratigraphical records indicate a single smooth litorina transgression

seismic velocity heterogeneity and the composition of the lower crust abstract many wide angle seismic experiments attempt to constrain lower crustal seismic velocity and thus composition deep near normal incidence seismic data recorded during the past decade suggest a widely varying and highly complex pattern of lower crustal heterogeneity synthetic seismic modelling indicates that velocities measured from wide angle experiments may depend significantly upon the geometrical arrangement and scale of the heterogeneities heterogeneities with a correlation length considerably large than the seismic wavelength will tend to produce observed velocities biased towards high values heterogeneities much smaller than the seismic wavelength can lead to a velocity bias of either sense depending upon their arrangement seismic velocities greater than 7 3 km s measured near the base of the crust in underplated and intruded passive continental margins suggest compositions that are markedly more mafic than mantle melting calculations predict our seismic modelling suggests that the mismatch between modelled and observed velocities at passive margins may be attributable to large scale correlation length greater than seismic wavelength heterogeneities

the last glacial maximum of svalbard and the barents sea area ice sheet extent and configuration abstract the timing extent and configuration of the late weichselian barents ice sheet has been debated for several decades this debate has arisen largely because of the limited or conflicting field evidence on which most models have been based in particular reconstruction of the marine parts of the former barents ice sheet has been controversial this paper aims to review the geological observations and interpretations regarding the size and timing of the late weichselian ice sheet combined with numerical modelling of its formation in order to produce a reconstruction of ice sheet extent and behaviour sub glacial till with overlying glacimarine deposits dated to the late weichselian is found over most of the barents sea floor and the continental shelf west of svalbard glacially induced debris flow deposits on the large bjonoya and isfjorden trough mouth fans strongly support the idea of ice sheet extension to the shelf edge during maximum glaciation isobase maps show a centre of post glacial uplift in the north central barents sea and glaciological and isostatic modelling suggest that the ice sheet was 2000 3000 m thick in this area the ice sheet was confluent with ice over the kara sea but the interaction between the barents and kara ice sheets is not yet fully understood the deglaciation of the barents ice sheet started ca 15 ka probably by calving within the deeper troughs by 12 ka most of the central barents sea was ice free and ice remained over the svalbard franz josef land and novaja zemlya archipelagos and adjacent shallow shelf areas the coasts and fjords of these islands were ice free by 10 ka

course and origin of the fennoscandian uplift the case for two separate mechanisms the classical glacial isostatic uplift paradigm of fennoscandia is in need of a thorough revision as to its course and origin the total uplift amounts to 830 m not 300 m the centre of uplift started to rise 13 000 bp not 9300 bp the uplift appears to be composed of two separate mechanisms one true glacial isostatic rebound and one linear uplift factor possibly representing a phase boundary adjustment calculations and modelling must treat these two factors independently which has not been the case

holocene coastal evolution and uplift mechanisms of the northeastern raukumara peninsula north island new zealand abstract the coastal geomorphology of the northeastern raukumara peninsula new zealand is examined with the aim of determining the mechanisms of holocene coastal uplift elevation and coverbed stratigraphic data from previously interpreted coseismic marine terraces at horoera and waipapa indicate that despite the surface morphology there is no evidence that these terraces are of marine or coseismic origin early holocene transgressive marine deposits at hicks bay indicate significant differences between the thickness of preserved intertidal infill sediments and the amount of space created by eustatic sea level rise therefore uplift did occur during early holocene evolution of the estuary the palaeoecology and stratigraphy of the sequence shows no evidence of sudden land elevation changes beach ridge sequences at te araroa slope gradually toward the present day coast with no evidence of coseismic steps the evolution of the beach ridges was probably controlled by sediment supply in the context of a background continuous uplift rate no individual dataset uniquely resolves the uplift mechanism however from the integration of all evidence we conclude that holocene coastal uplift of this region has been driven by a gradual aseismic mechanism an important implication of this is that tectonic uplift mechanisms do vary along the east coast of the north island this contrasts with conclusions of previous studies which have inferred holocene coastal uplift along the length of the margin was achieved by coseismic events this is the first global example of aseismic processes accommodating uplift at rates of 1 mm yr 1 adjacent to a subduction zone and it provides a valuable comparison to subduction zones dominated by great earthquakes

drumlins subglacial meltwater floods and ocean responses drumlins and erosional marks in bedrock give evidence for broad subglacial meltwater floods that have discharge rate estimates of about 10 6 m 3 s similar discharge rates are obtained for other late glacial catastrophic floods the total volume of meltwater that is thought to have formed the livingstone lake saskatchewan drumlin field is estimated at 8 4 x 10 4 km 3 this volume is equivalent to a eustatic rise of 0 23 m in global sea level meltwater release and roughly contemporaneous formation of drumlin fields in north america and europe could have involved several metres of sea level rise in a few years the implications of such floods for the generation of myths and the interpretation of the oxygen isotopic record of the oceans are discussed high meltwater discharges are of potential importance to the generation of a lid of cold fresh water over the north atlantic and its effects on late glacial climate

glacial isostasy and long term crustal movements in fennoscandia with respect to lithospheric and asthenospheric processes and properties comment recently morner discussed his model of glacio isostatic compensation in the light of new seismological models of the upper mantle below fennoscandia he concluded that the p wave velocity distribution is in full agreement with his estimate of the viscosity distribution as inferred from glacio isostatic relaxation whereas the consistency of seismological and geodynamical earth models is a necessary condition for their soundness the particular type of agreement sought by morner is not required or expected nor can his method of attaining such agreement be approved for easier understanding of my criticism i briefly recall the type of information provided by the seismological and by the glacio isostatic evidence

a consistent map of the postglacial uplift of fennoscandia a consistent map of the recent postglacial rebound of fennoscandia is constructed on the basis of sea level records lake level records and repeated high precision levellings the uplift rates calculated from the sea level series form a consistent framework of the map the sea level stations used are 56 reliable stations in the baltic sea and adjacent waters with series spanning 60 years or more many of them about 100 years using a reference station in the baltic sea and another one outside the baltic all results are reduced to a common time span the 100 year period 1892 1991 in order to eliminate oceanographic changes inland uplift differences are obtained from the repeated national levellings and in four of the large lakes from long water level series in pairs the levellings however yield less accurate land uplift values than the sea level and lake level data the resultant map shows a fairly smooth phenomenon with a maximum apparent uplift in the gulf of bothnia of 9 0 mm yr 1 the standard error is typically 0 2 mm yr i close to the sea level stations larger inland finally the pattern of the present uplift as determined here is observed to be very similar to that of the past uplift as determined from ancient shore lines of the litorina sea however the ratio between the past uplift and the present uplift rate tends to increase somewhat towards the uplift centre this might reflect a non uniform mantle viscosity also the uplift maximum seems to have migrated towards nne

the lower crust of se belarus petrological geophysical and geochemical constraints from xenoliths abstract highly altered alkaline lamprophyre tuffs of devonian age from se belarus contain lower crustal xenoliths that vary from feldspar rich mafic granulites to rarer feldspar poor eclogitic granulites together with coarse grained hornblendites textural evidence mineral compositions and t p data 700 800 c 0 9 1 1 gpa of the garnet granulite xenoliths indicate that equilibration occurred in the lower crust and therefore we consider that these xenoliths represent samples of the in situ lower crust they are highly altered but the main primary minerals are almandine garnet diopside and andesine plagioclase k feldspar scapolite biotite apatite ilmenite ti magnetite and rutile are accessory minerals a subsequent metasomatic event post dating the granulite facies metamorphism has introduced widespread pargasitic amphibole the granulites are basic in composition are enriched in the most incompatible trace elements and have large negative nb anomalies la n nb n range from 3 to 12 inferring a subduction related origin ree patterns show variable lree enrichment la yb 6 27 and some positive eu anomalies indicating plagioclase accumulation trace element and ree patterns for one sample suggest a melt composition the granulites may represent a gabbroic underplate of unknown age and may be petrogenetically related to the osnitsk mikashevichi plutonic belt hornblendite xenoliths are relatively unaltered and consist of pargasite or pargasite plus magnetite and apatite amphibole compositions are very homogeneous and resemble those in the granulite xenoliths the 40 ar 39 ar plateau age is 381 2 ma lree enriched patterns low 87 sr 86 sr ratios and textural constraints suggest that these hornblendites precipitated from a magma formed from a small degree partial melt of a garnet bearing mantle they may be petrogenetically related to the host lamprophyres possibly as a cumulate from an earlier flux of magma and related to the metasomatic event that affected the granulites whole rock vp values calculated from modal mineralogies of the granulite xenoliths range from 6 7 to 7 5 km s assuming equilibration at 800 c 1 0 gpa they are compatible with seismic velocity measurements of the lower crust beneath se belarus which reach 7 2 km s xenoliths with the least modal plagioclase and to some extent the most modal clinopyroxene and garnet give the highest whole rock vp values calculated vp values for hornblendite xenoliths 6 75 km s at 800 c 1 0 gpa suggest that identification of hornblendite in the lower crust from vp values alone would be difficult

observation of azimuthal anisotropy from the seismic reflectivity of a tertiary turbidite sand p wave data from a time lapse 3d obc survey have been analysed to estimate and interpret azimuthal seismic anisotropy this is achieved by careful processing to preserve the azimuthal signature the survey images a major reservoir body in a channelized turbidite field in the gulf of mexico three distinct and significant anisotropy anomalies are discovered on or around this particular 4500 ft sand all of which change intensity but not orientation with hydrocarbon production these anomalies are distributed along the highest concentration of cumulative sand thickness with their symmetry axes aligned with the main channel axis we suspect that this time lapse anisotropy could be caused by the alignment of the depositional grain fabric theoretical calculation predicts that this mechanism when combined with fluid saturation changes can generate the observed pattern of behaviour if further supported by other researchers this result would indicate that appropriately designed seismic surveys could be a useful tool for palaeo direction studies in clastic reservoirs and also a useful constraint for directional permeability in the reservoir flow simulation model

gravity change geoid change and remaining postglacial uplift of fennoscandia the result obtained hitherto on the fennoscandian land uplift gravity line indicates that the postglacial uplift process might be more complicated than a pure horizontal flow of mantle bouguer model simple formulae valid for a more arbitrary model are developed for the change of the geoid and for the remaining land uplift numerical applications yield a geoid change of about 0 4 mm yr 1 and a remaining land uplift of the order of 50 m but the latter quantity is very difficult to determine with reasonable accuracy

a review of the history of the baltic sea 13 0 8 0 ka bp abstract the dynamic history of the baltic sea during the millennia following the last deglaciation has been one of the main topics for many generations of quaternary geologists around the baltic sea based on the present state of knowledge and certain hypotheses a model for the development during the baltic ice lake yoldia sea and ancylus lake stages are presented the oresund strait was the threshold of the initial stage of the baltic ice lake and was eroded down to bedrock as a result of the isostatic uplift the emerging threshold forced the baltic ice lake to rise above sea level at ca 12 0 ka bp this gradual up damming ended at ca 11 2 ka bp when the large glacial lake was lowered 5 10m by possible subglacial drainage at mt billingen a glacial readvance during the younger dryas ended a ca 400 year long land bridge between sweden and the continent by blocking the former drainage route once again the baltic ice lake had to rise above sea level to be drained over the oresund strait at ca 10 5 ka bp a gradual ice recession began and 200 years later when the receding ice sheet could not withhold the up dammed water masses the final drainage of the baltic ice lake occurred which rapidly lowered the water level within the baltic basin with ca 25 m and ended the baltic ice lake stage the next stage the yoldia sea was characterized by a complex pattern of relative sea level changes with large differences within the baltic basin a very restricted baltic sea in the south and thus an extensive landbridge at ca 9 9 ka bp a short 100 200 years saline ingression is seen in the baltic sediment records from stockholm in the north to the southernmost parts of the yoldia sea the gradually shallower strait in south central sweden the narke strait ended the saline influence 300 400 years later the two remaining outlets west of lake vanern gota alv and otteid steinselva had become too shallow to swallow the outflowing yoldia sea waters at this stage the baltic lake vanern level could thus not fall in pace with the relative sea level fall outside the outlet areas this was the isolation of lake vanern and the baltic from the sea and the beginning of the ancylus lake since the water depth of the larger gota alv outlet had to be more or less maintained the ancylus lake level had to rise in pace with the uplift of the outlet region this caused a significant and rapid transgression 10 30 m in ca 300 years in the southern baltic which flooded large areas with recently immigrated pine forests since the oresund strait during the yoldia sea stage had been uplifted more than southerly areas the ancylus transgression ended with a new drainage pathway at ca 9 2 ka bp through the darss sill area in the southern baltic and northwards through the store belt strait this so called dana river had cut off the former large land bridge the quaternary deposits of this new threshold were eroded and a fairly rapid regression set in at ca 9 0 ka bp the dana river had eroded down to the sea level which isolated lake vanern from the ancylus lake and created a land bridge between southern sweden and northwards ca 800 years later when the sea level rose above the oresund threshold marine water could enter the baltic and at ca 8 0 ka bp brackish water characterized the southern baltic this marks the end of the ancylus lake

eemian sea level highstand in the eastern baltic sea linked to long duration white sea connection abstract revised diatom and new dinoflagellate cyst and benthic foraminiferal data from the eastern baltic sea have refined our understanding of eemian last interglacial 131 119 5 ka sea level change on the russian karelia a former seaway linking the baltic to the white sea results from peski eastern baltic show the initiation of marine conditions just before 131 ka in the latest saalian after the opening of a connection to the north sea following the onset of the eemian marine highstand and the opening of the white sea connection at around 130 25 ka near fully marine conditions persisted in the eastern baltic area for ca 6 kyr until ca 124 ka for most of the eemian a strong thermal stratification in the eastern baltic resulted from an arctic and possible north atlantic water component from the white sea merging with warmer waters from the north sea from ca 124 ka decreasing salinity indicates the end of the marine highstand and a simultaneous closure of the baltic sea white sea connection i e a duration of ca 6 kyr for this seaway the main influence of white sea inflow appears to be restricted to the eastern baltic area although a large submerged area in the russian karelia associated with temperate atlantic waters could have assisted in creating a more oceanic climate for central europe

relationships between compressional wave and shear wave velocities in clastic silicate rocks new velocity data in addition to literature data derived from sonic log seismic and laboratory measurements are analyzed for clastic silicate rocks these data demonstrate simple systematic relationships between compressional and shear wave velocities for water saturated clastic silicate rocks shear wave veloci ty is approximately linearly related to compressional wave velocity and the compressional to shear velocity ratio decreases with increasing compressional velocity laboratory data for dry sandstones indicate a nearly constant compressional to shear velocity ratio with rigidity approximately equal to bulk modulus ideal models for regular packings of spheres and cracked solids exhibit behavior similar to the observed water saturated and dry trends for dry rigidity equal to dry bulk modulus gassmann s equations predict velocities in close agreement with data from the water saturated

equilibration temperatures and elastic wave velocities for upper mantle rocks from eastern australia implications for the interpretation of seismological models abstract this study integrates available geological geophysical and petrophysical data for deep seated lithologies which occur beneath eastern australia and which are accessible at the surface as xenoliths in basaltic host rocks it is shown that spinel lherzolite mantle wall rock occurs over a depth range commencing at about 30 km and extending to about 55 km this represents a temperature range of 850 1000 c acoustic wave velocity measurements were carried out on three types of spinel lherzolites and one mantle derived garnet pyroxenite the acoustic velocities range from 7 7 to 7 9 km s 1 for the pressure and temperature conditions beneath eastern australia derived from xenolith geothermobarometry these values demonstrate that the use of dunite as a generalised mantle rock results in overestimation of model mantle vp especially when used with a standard continental model geotherm the measured spinel lherzolites also show variable anisotropy in acoustic wave velocity 5 8 for these moderately foliated samples it is demonstrated that by using a combination of the measured acoustic velocities and single crystal elasticity data for constituent minerals it is possible to interpolate vp for a wide modal range of rock types relevant to the lower crust and upper mantle triangular grids which allow graphical estimation of vp for spinel lherzolites garnet lherzolites and garnet pyroxenites have been constructed the petrologic and petrophysical results are used to constrain models of the lower crust and upper mantle profiles based on available seismic data for eastern australia

compressional wave velocity of granite and amphibolite up to melting temperatures at 1 gpa abstract compressional wave velocities vp at above solidus temperatures and at 1 gpa were obtained for a granite and amphibolite which are considered to be major constituents of the continental crust the temperature variation of velocities showed that the vp values of granite decreased with rising temperature but substantially increased beyond the melting temperature 850 900 c such an increase may be caused by the transition of quartz the velocities of amphibolite decreased linearly with increasing temperature and dropped sharply at temperatures above the solidus 700 c indicating that partial melting of amphibolite acts to significantly lower the seismic velocities

pleistocene deglaciation and the global gravity field the present day global geoid and free air gravity anomaly signals induced by pleistocene deglaciation have been computed along with their secular variations a revised green function has been derived for the free air gravity anomaly and we find that an earth model with a lower mantle viscosity moderately larger than the upper mantle value satisfies observations of the anomaly over both hudson s bay and fennoscandia using this preferred earth model the predicted global geoid anomaly map is characterized by peak negative values of 36 7 9 4 and 21 9 m over hudson s bay northern europe and antarctica respectively and by a smooth small amplitude 2 5 m upwarping over the major ocean basins although the field has an order of magnitude less power than the observed there is a significant spatial correlation between the two inferences of mantle viscosity based upon comparisons between the observed geoid and the computed deglaciation induced anomaly are hampered by the large contribution from the convective circulation in the earth s mantle we have subtracted a predicted convection signal based on seismic tomography from the observed field however the residual geoid thus obtained is still too inaccurate to allow a useful comparison in contrast a filtered version of the observed geoid over canada which retains harmonic coefficients in the degree range 10 22 provides a relatively uncontaminated by convection datum that is indeed satisfied by the preferred earth model secular variations in the earth s gravitational field are naturally dominated by the signal from pleistocene deglaciation in this respect we compute zonal harmonics in the expansion of the present day rate of change of the geopotential and in particular we predict amplitudes comparable to that for the previously analysed j2 for j4 j5 j7 and j9 all of which reflect in large part the response due to the melting of the massive laurentide ice sheet this analysis suggests that measurement of these higher order secular variations of the zonal harmonics based upon analysis of long time series of lageos ranging data could provide very useful additional constraints on the radial variation of mantle viscosity these constraints along with all others described in this paper are shown to be relatively insensitive to assumptions concerning the deflection during the glacial isostatic adjustment process of the 400 and 670 km density discontinuities within the mantle

seabed geodiversity in a glaciated shelf area the baltic sea abstract geodiversity describes the heterogeneity of the physical terrain we have performed basin wide geodiversity analysis on a glaciated epicontinental seabed to assess geodiversity measures and patterns locate areas with high geodiversity and draw conclusions on contributing processes geodiversity quantification is a rather new topic and is mainly practiced in land areas we applied geodiversity methods developed for terrestrial studies to a seabed environment three geodiversity parameters including the richness patchiness and geodiversity index of the baltic sea were assessed in a gis environment based on broad scale datasets on seabed substrates structures and bedrock a set of environmental and geological variables which were considered to reflect geological processes under seabed conditions were compared with the geodiversity to identify some of its drivers we observed differences in the geodiversity levels of the baltic subbasins which are mainly due to basement type bedrock roughness shore density and glacier derived processes the geodiversity of the baltic sea generally increases from south to north and from open sea to high shore density areas archipelagos crystalline bedrock areas provide more diverse seabed environments than sedimentary rock areas the analysis helps to inform scientists marine spatial planners and managers about abiotic conservation values the dynamics of the seabed environment and potential areas with elevated biodiversity

effects of transverse isotropy on p wave avo for gas sands velocity anisotropy should be taken into account when analyzing the amplitude variation with offset avo response of gas sands encased in shales the anisotropic effects on the avo of gas sands in transversely isotropic ti media are reviewed reflection coefficients in ti media are computed using a planewave formula based on ray theory we present results of modeling special cases of exploration interest having positive reflectivity near zero reflectivity and negative reflectivity the avo reflectivity in anisotropic media can be decomposed into two parts one for isotropy and the other for anisotropy zero offset reflectivity and poisson s ratio contrast are the most significant parameters for the isotropic component while the difference between shale and gas sand is the most important factor for the anisotropic component for typical values of tl anisotropy in shale positive and e both difference and e difference e amplify avo effects for small angles of incidence plays a

relative sea level change and evidence for the holocene storegga slide tsunami from a high energy coastal environment cocklemill burn fife scotland uk a site in the cocklemill burn valley on the north shore of the firth of forth scotland provides evidence of relative sea level changes during the holocene from ca 7970 to ca 5090 radiocarbon years bp and of the holocene storegga slide tsunami dated here as having taken place after ca 7215 radiocarbon years bp marine sediments associated with two shorelines widely present in mainland scotland the main postglacial shoreline and the blairdrummond shoreline are recorded the holocene storegga slide tsunami deposits are unique here in the record of such sediments in eastern scotland in that they occur within marine sands of which the upper horizons are intertidal sandflat deposits the tsunami deposits probably accumulated shortly after a period of accelerated relative sea level rise the pattern and timing of which could have played a role in triggering the holocene storegga slide

a dinoflagellate cyst record of holocene climate and hydrological changes along the southeastern swedish baltic coast a high resolution well dated dinoflagellate cyst record from a lagoon of the southeastern swedish baltic sea reveals climate and hydrological changes during the holocene marine dinoflagellate cysts occurred initially at about 8600 cal yr bp indicating the onset of the littorina transgression in the southeastern swedish lowland associated with global sea level rise and thus the opening of the danish straits both the species diversity and the total accumulation rates of dinoflagellate cysts continued to increase by 7000 cal yr bp and then decreased progressively this pattern reveals the first order change in local sea level as a function of ice volume equivalent sea level rise versus isostatic land uplift superimposed upon this local sea level trend well defined fluctuations of the total accumulation rates of dinoflagellate cysts occurred on quasi 1000 and 500 yr frequency bands particularly between 7500 and 4000 cal yr bp when the connection between the baltic basin and the north atlantic was broader a close correlation of the total accumulation rates of dinoflagellate cysts with gisp2 ice core sea salt ions suggests that fluctuations of baltic surface conditions during the middle holocene might have been regulated by quasi periodic variations of the prevailing southwesterly winds most likely through a system similar to the dipole oscillation of the modern north atlantic atmosphere

laboratory wave velocity measurements on lower crustal xenoliths from calcutteroo south australia abstract seismological and petrologic studies have suggested the presence of mafic granulite eclogite and amphibolite as the major components of the lower crust in southeastern australia elastic wave velocity measurements conducted to 400 mpa confining pressure of selected nodules from one kimberlite pipe in south australia range after corrections for estimated in situ crustal pressures and temperatures from v p 6 9 7 7 km s 1 and v s 3 9 4 3 km s 1 these values fall between previous measurements for more silicic crustal granulites and mafic eclogites and coincide with the published velocities determined by seismic studies for southeastern australia it is possible that these types of compositions may be widespread components of the lower continental crust and may require revision of currently accepted models of crustal evolution

anisotropic velocity analysis1 results from walkaway vsp and shale laboratory experiments show that shale anisotropy can be significantly anelliptic heterogeneity and anellipticity both lead to non hyperbolic moveout curves and the resulting ambiguity in velocity analysis is investigated for the case of a factorizable anisotropic medium with a linear dependence of velocity on depth more information can be obtained if there are several reflectors the method of dellinger et al for anisotropic velocity analysis in layered transversely isotropic media is examined and is shown to be restricted to media having relatively small anellipticity a new scheme based on an expansion of the inverse squared group velocity in spherical harmonics is presented this scheme can be used for larger anellipticity and is applicable for horizontal layers having monoclinic symmetry with the symmetry plane parallel to the layers the method is applied to invert the results of anisotropic ray tracing on a model sand shale sequence for transversely isotropic media with small anisotropy the scheme reduces to the method of byun et al and byun and corrigan the expansion in spherical harmonics allows the p phase slowness surface of each layer to be determined in analytic form from the layer parameters obtained by inversion without the need to assume that the anisotropy is weak

holocene relative shore level changes and stone age palaeogeography of the parnu bay area eastern baltic sea the shore displacement and palaeogeography of the parnu bay area eastern baltic sea during the stone age were reconstructed using sedimentological and archaeological proxies and gis based landsc

amplitude versus offset variations in gas sands seismic reflections from gas sands exhibit a wide range of amplitude versus offset avo characteristics the two factors that most strongly determine the avo behavior of a gas sand reflection are the normal incidence reflection coefficient r0 and the contrast in poisson s ratio at the reflector of these two factors r0 is the least constrained based on their avo characteristics gas sand reflectors can be grouped into three classes defined in terms of r0 at the top of the gas sand class 1 gas sands have higher impedance than the encasing shale with relatively large positive values for r0 class 2 gas sands have nearly the same impedance as the encasing shale and are characterized by values of r0 near zero class 3 sands have lower impedance than the encasing shale with negative large magnitude values for r0 each of these sand classes has a distinct avo characteristic an example of a gas sand from each of the three classes is presented in the paper the class 1 example involves a hartshorn channel s

effective media for transversely isotropic models based on homogenization theory with applications to borehole sonic logs sonic log records including measurements of wave speeds in boreholes provide critical input to the geological geophysical and petrophysical studies of a region under exploration 1d background models are routinely built based on sonic log records for applications such as seismic imaging of hydrocarbon reservoirs and microseismic source inversions smoothing or upscaling techniques are required to produce models in coarser scales than the very fine layers in the raw log data in this paper we follow the recently popular homogenization theory derive its application to the special case of 1d ti models for both p sv and sh waves and show that it is consistent with the backus averaging technique commonly used to upscale 1d fine layered models we examine a study case of sonic log data from a well in the horn river basin in northeastern british columbia a region known for its tight shale gas deposit we demonstrate the computational accuracy and efficiency gained by proper upscaling procedures for spectral element simulations of seismic wave propagation and discuss the effect of control parameters on wavefield recovery