seismic anisotropy in the crystalline upper crust observations and modelling from the outokumpu scientific borehole finland summary seismic velocity anisotropy measurements are made of a fractured metamorphic formation from the 2 5 km deep international continental scientific drilling programme icdp borehole in outokumpu finland three component walk away vertical seismic profile vsp measurements are made along two source line azimuths at three receiver depths 1000 1750 and 2500 m and incidence angle dependent qp and qs wave velocities are extracted with a p method the highest qp wave anisotropy 13 6 per cent vfast 6160 m s 1 vslow 5370 m s 1 is measured between 1000 and 1750 m depth with anisotropy of up to 9 4 per cent vfast 6090 m s 1 vslow 5540 m s 1 measured between 1750 and 2500 m depth the top 1300 m of the region is composed of a homogeneous strongly intrinsically anisotropic biotite rich schist and is sampled by the shallowest walk away profile anisotropy of up to 11 1 per cent vfast 5950 m s 1 vslow 5320 m s 1 is measured by the walk away vsp between 50 and 1000 m depth along with shear wave splitting averaging 5 per cent 180 m s 1 laboratory derived intrinsic anisotropy of the schist cannot by itself explain the degree or orientation of the anisotropy measured in the walk away vsps however a model which modifies the intrinsic stiffnesses by the inclusion of a single set of dipping aligned cracks allows the observed in situ velocities to be reproduced forward modelling of the qp wave walk away vsp measurements from 50 to 1000 m depth is undertaken using an effective medium model to develop a 3 d velocity model of this region an orthorhombic medium is used to represent the intrinsic anisotropy of the biotite rich schist and a single set of aligned cracks is added to give a bulk elastic stiffness the resulting model predicts the schist to have an overall anisotropy of 16 8 per cent with qp wave velocities of up to 6315 m s 1 the accuracy of the model is assessed through its fit to the walk away vsp measurements as well as a comparison to known geology of the region

holocene rate of slip and tentative recurrence interval for large earthquakes on the san andreas fault cajon pass southern california abstract detailed mapping of the san andreas fault zone where it crosses cajon creek southern california has revealed a number of late quaternary deposits and geomorphological features offset by the fault radiocarbon dates from alluvial and swamp deposits provide a detailed chronology with which to characterize the activity of the san andreas fault four independent determinations of the slip rate on the san andreas fault yield an average rate of 24 5 3 5 mm yr for the past 14 400 years the similarity of the four values which span different intervals of time from 5900 to 14 400 years ago suggest that the slip rate has been constant during this period the slip rate confirms that the san andreas fault is accumulating slip faster than any other fault in the plate boundary throughout california also the sum of the slip rates on the san andreas 24 5 mm yr and the san jacinto 10 mm yr faults south of their junction is the same as the san andreas north of their junction 35 mm yr an excavation provided evidence for at least two and up to four earthquakes that caused rupture on the fault between 1290 and 1805 a d and tentative evidence for six earthquakes in about the last 1000 years both lines of evidence imply an average recurrence interval for large earthquakes of about 1 to 2 centuries combined with the historic record this investigation indicates that the last major earthquake at cajon creek was probably at the beginning or middle of the 18th century while the record at cajon creek may suggest that the next major earthquake on the san andreas fault is overdue the data can be interpreted to indicate that the recurrence interval for earthquakes on the san andreas south of the 1857 rupture is 3 to 4 centuries and that the anticipated event should not be expected until the next century

intrinsic elasticity of a textured transversely isotropic muscovite aggregate comparisons to the seismic anisotropy of schists and shales 1 the anisotropic properties of phyllosilicate rocks are investigated through the modeling of the pore free intrinsic elasticity of a textured muscovite aggregate the elastic constants were calculated for textures as defined using orientation distribution functions odfs ranging from perfectly aligned to completely random the odfs were described using a gaussian distribution the width of which is controlled by the standard deviation of the orientations of the crystal c axis with respect to the sample foliation plane under the assumption that the sample has hexagonal transversely isotropic symmetry the values were obtained using the widely used voigt reuss hill averaging techniques as well as the geometric mean average gma the gma is more physically meaningful in that it requires that the elastic constants determined in either the stiffness or the compliance domains be invertible comparisons between these different averages indicate that strictly the voigt and reuss values do not necessarily provide the limiting bounds as is expected for the isotropic case despite this some characteristics of the elastic wave p wave anisotropy are only weakly dependent on the averaging procedure employed the calculated elastic constants are converted to the anisotropic and parameters in order to allow for comparison to existing measurements in the literature however these intrinsic results are not intended to provide a measure of the properties of phyllites per se but to provide a reference against which more sophisticated models that incorporate porosity layering and composition may be constructed

transversely isotropic phase velocity analysis from slowness estimates near offset vertical seismic profiling vsp is an established technique to obtain interval velocities for lithology characterization time to depth calibrations and seismic data processing unfortunately these velocities are often insufficient to distinguish lithology types and can disagree with surface seismic stacking velocities multiple source offset vsps provide additional travel time information for calculating interval anisotropic velocities that can help discriminate lithology in this paper a technique is developed for computing transversely isotropic phase velocities over intervals less than the dominant seismic wavelength independent estimates of vertical and horizontal slowness are made for each receiver depth and source offset pair these provide the magnitude and direction of phase velocity for calculating the in situ elastic properties of a transversely isotropic medium this technique requires the assumption of lateral homogeneity because horizontal slowness components are related to surface properties between sources and not to rock properties between receivers at depth factors that violate this assumption such as source elevation differences and dipping layers are evaluated with synthetic data six impulsive source p wave offset vsps in a 663 m well in east texas are analyzed and a near offset sh wave vibrator vsp provides vertical shear wave phase velocities strong transversely isotropic velocity variations observed in the tertiary and cretaceous sediments penetrated by this well correlate with lithology types suggesting that this technique is sensitive to local properties at the receiver these results may not indicate exact intrinsic elastic properties and could be due in part to dipping layers vertical heterogeneities and unknown local surface variations percent phase velocity anisotropy appears to increase from 6 to 20 for p wave and 10 to 50 for sv wave with increasing amounts of calcareous material and shale in the rock percentage anisotropy is defined as the ratio of the horizontal to vertical velocity for p waves and the ratio of velocity at 45 to vertical velocity for sv waves sandstones and chalk exhibit the least amount of anisotropy while the shales and calcareous shales exhibit the most

ultrasonic velocity and anisotropy of hydrocarbon source rocks an experimental study of the physical properties of black kerogen rich shales also including maturation analysis scanning electron microscope sem observations and physical modeling revealed fairly peculiar petrophysical parameters specifically these rocks have very low porosity and density but most importantly both p and s ultrasonic velocities normal to bedding are extremely low whereas they are much higher parallel to bedding giving rise to a strong anisotropy even at high confining pressures we found that these parameters primarily reflect kerogen content microstructure and maturation level of these rocks we found also that microcracks inferred from ultrasonic velocity measurements occur only in mature shales these microcracks are parallel to the bedding plane and further enhance strong intrinsic anisotropy notably at low effective pressure our results show that on a small scale kerogen rich shales are transversely isotropic rocks and can be effectively modeled using the thin laye

geometry and rate of faulting in the north baikal rift siberia we present a detailed morphotectonic analysis of late quaternary faulting in the north baikal rift nbr a region characterized by ranges and basins distributed over more than 800 km along strike in eastern siberia remote sensing techniques spot meteor scenes and aerial photographs are used to map the active fault network which displays a general en echelon distribution from the northern lake baikal to the easternmost basin with 30 km spaced overstepping segments of 10 80 km in length most faults have a dominant dip slip component over their cenozoic history the inherited crustal fabric strongly influences the overall geometry of the rifted basins we use 54 14c ages of postglacial terraces near the foot scarps of the muya basin to date offsets measured inside alluvial fans the last main postglacial event in this area appears to be the early holocene optimum dated at 10 2 ka following the onset of deglaciation at 13 ka using these time constraints a detailed leveling across two terraces offset by the taksimo fault west muya basin shows consistent minimum vertical slip rates of 1 6 0 6 mm yr 1 using 30 other active scarps analyzed in the field we find a lower bound for horizontal velocity of 3 2 0 5 mm yr 1 across the nbr a rate close to the one found in the southern rift from global positioning system measurements we then compare directions of slip vectors from holocene field data and slip directions from earthquake fault plane solutions although local discrepancies appear the mean directions of lesser horizontal stress 3 inverted from theses values are n130 e and n155 e respectively which are comparable within uncertainties and favor a rifting obliquity of 30 40 extrapolating our holocene rates we estimate basin ages younger than those generally believed less than 7 ma and propose a spatial and temporal evolution of rifted basins consistent with experimental models of oblique rifting total amounts of extension and vertical throw 7 and 12 km respectively across major faults appear rather constant from the central to the northern rift these results favor a progressive development of asymmetric grabens in a rift zone that widens with times and they indicate a strong rheological control on deformation which seems enhanced by other contributions than the far field effects of the indo eurasian collision

kinematic evolution of the ama drime detachment insights into orogen parallel extension and exhumation of the ama drime massif tibet nepal abstract the ama drime massif is a north south trending antiformal structure located on the southern margin of the tibetan plateau that is bound by the ama drime and nyonno ri detachments on the western and eastern sides respectively detailed kinematic and vorticity analyses were combined with deformation temperature estimates on rocks from the ama drime detachment to document spatial and temporal patterns of deformation deformation temperatures estimated from quartz and feldspar microstructures quartz c axis fabrics and two feldspar geothermometry of asymmetric strain induced myrmekite range between 400 and 650 c micro and macro kinematic indicators suggest west directed displacement dominated over this temperature range mean kinematic vorticity estimates record early pure shear dominated flow 49 66 pure shear overprinted by later simple shear 1 57 pure shear high strain 36 50 shortening and 57 99 down dip extension dominated flow during the later increments of ductile deformation exhumation of the massif was accommodated by at least 21 42 km of displacement on the ama drime detachment samples from the nyonno ri detachment were exhumed from similar depths we propose that exhumation on the nyonno ri detachment during initiation of orogen parallel extension 11 13 ma resulted in a west dipping structural weakness in the footwall that reactivated as the ama drime detachment

gps measurements of crustal deformation in the baikal mongolia area 1994 2002 implications for current kinematics of asia 1 we present new geodetic results of crustal velocities over a large part of northern asia based on gps measurements in the baikal rift zone and mongolia spanning the 1994 2002 period we combine our results with the gps velocity field for china of wang et al 2001 and derive a consistent velocity field for most of asia we find contrasted kinematic and strain regimes in mongolia with northward velocities and n s shortening in westernmost mongolia but eastward to southeastward motion and left lateral shear for central and eastern mongolia this eastward to southeastward motion of central and eastern mongolia is accommodated by left lateral slip on the e w trending tunka bolnay and gobi altay faults 2 1 2 mm yr 1 2 6 1 0 mm yr 1 and 1 2 mm yr 1 respectively and by about 4 mm yr 1 of extension across the baikal rift zone consequently 15 of the india eurasia convergence is accommodated north of the tien shan by n s shortening combined with dextral shear in the mongolian altay and by eastward displacements along major left lateral strike slip faults in central and eastern mongolia we find a counterclockwise rotation of north and south china as a quasi rigid block around a pole north of the stanovoy belt which rules out the existence of an amurian plate as previously defined and implies 2 mm yr 1 of left lateral slip on the qinling shan fault zone

high pressure rocks of the acatlan complex southern mexico large scale subducted ordovician rifted passive margin extruded into the upper plate during the devonian carboniferous abstract high pressure hp rocks in the paleozoic acatlan complex of southern mexico occur in a median belt extruded into the complex which is the root zone of a klippe to the west these hp rocks are predominantly clastic metasedimentary rocks and include a bimodal suite of amphibolites and granitoids u pb la icpms zircon dating indicates that one of the amphibolites was intruded at or before 461 2 ma and a megacrystic granitoid yielded an intrusive age of 488 8 7 ma which is within the 490 450 ma range of other dated hp megacrystic granitoids the amphibolites have a tholeiitic transitional to alkalic within plate chemistry derived from a heterogeneous mantle by various degrees of partial melting the host metasedimentary rocks contain detrital zircons derived both from the acatlan granitoids and the ca 1 0 1 3 ga oaxacan complex and are inferred to represent rifted passive margin sediments an age of 348 4 1 ma from zircons in a migmatized amphibolite is interpreted as the time of migmatization and dates decompression melting following peak pressure at depths of 45 55 km retrogression from 530 c to 370 c occurred between 343 and 335 ma the predominance of reasonably coherent rifted passive margin rocks over a surface area of 10 90 km suggests removal of a large slice of the upper plate during flat slab subduction this slice was subducted to depths of ca 45 55 km where it was underplated and transferred to the overriding plate the absence of oaxacan complex rocks in the hp belt suggests the oaxacan basement was subducted to greater depths underplating was followed by extrusion facilitated by extension in the upper plate that produced mississippian rift basins east of the median hp belt westward overthrusting of the hp rocks produced a klippe that overrode mississippian clastic wedge sediments

cenozoic deformation of the tarim basin and surrounding ranges xinjiang china a regional overview abstract with its central position between the tibetan plateau and the tian shan range the tarim basin is a key element of the cenozoic asian orogenic system however a comprehensive regional study and more particularly the quantification of shortening through this basin and its margins are still needed to understand its role in the cenozoic deformation of asia from a compilation of previous works together with an extensive dataset of satellite field seismic and well data we provide a tectonic map of the cenozoic structures and four balanced geological transects of the tarim basin and its surrounding ranges based on this map and these cross sections we characterize the cenozoic deformation of the original proterozoic tarim block from structural restorations and crustal budgets we also quantify the compressive component of this deformation most of the cenozoic compressive deformation from 94 to 100 is concentrated in the ranges along the block margins to the west up to 78 23 km and 54 24 18 km of crustal shortening are accommodated across the compressive western kunlun and southwestern tian shan ranges while to the east up to 38 6 18 km and 15 20 15 km are accommodated across the transpressive altyn tagh and southeastern tian shan ranges a non negligible amount of compressive deformation up to 6 is also accommodated within the tarim basin by large basement cored uplifts with a vergence synthetic to the deformation of the tibetan plateau edge to the west the bachu uplift absorbs 5 km of the total crustal shortening of the western kunlun thrust system while to the south the tanan uplift accumulates 0 6 km of the altyn tagh strike slip system structural inheritance has a major influence on the cenozoic deformation since 33 3 to 100 of the total shortening is accommodated by reactivated basement structures inherited from the protero paleozoic history of the tarim block finally we argue that the basement cored uplifts in the centre of the basin imply a deformation transfer from the tibetan plateau to the tian shan above a deep crustal decollement decoupling the deforming crust from an underlying rigid mantle

velocity anisotropy of shales and depth estimation in the north sea basin it is known that in the north sea basin the depths to major reflectors as determined from surface seismic data are often larger than the well log depths from a study of data sets which tie 21 wells i found a strong correlation between the occurrence of the depth error and the presence of shales in the subsurface assuming that the error is caused by elliptical velocity anisotropy in shales i measured the anisotropy from a comparison of the well log sonic data and the interval velocity profile obtained from the surface seismic data and also from a comparison of the seismic depth and the well log depth it was found that the two methods of measurements agree with each other and also agree qualitatively with the previous laboratory measurements of anisotropy in shale samples the results strongly suggest that the depth anomaly in the north sea basin is caused by the velocity anisotropy of shales a simple method to correct the seismic depth is given

denitrification in the recharge area and discharge area of a transient agricultural nitrate plume in a glacial outwash sand aquifer minnesota 1 recharge rates of nitrate no3 to groundwater beneath agricultural land commonly are greater than discharge rates of no3 in nearby streams but local controls of no3 distribution in the subsurface generally are poorly known groundwater dating cfc 3h was combined with chemical ions and gases and stable isotope n s and c analyses to resolve the effects of land use changes flow patterns and water aquifer reactions on the distributions of o2 no3 so4 and other constituents in a two dimensional vertical section leading from upland cultivated fields to a riparian wetland and stream in a glacial outwash sand aquifer near princeton minnesota within this section a plume of oxic no3 rich groundwater was present at shallow depths beneath the fields and part of the wetland but terminated before reaching the stream or the wetland surface groundwater dating and hydraulic measurements indicate travel times in the local flow system of 0 to 40 years with stratified recharge beneath the fields downward diversion of the shallow no3 bearing plume by semiconfining organic rich valley filling sediments under the wetland and upward discharge across the valley and stream bottom the concentrations and 15n values of no3 and n2 indicate that the no3 plume section was bounded in three directions by a curvilinear zone of active denitrification that limited its progress however when recalculated to remove the effects of denitrification the data also indicate changes in both the concentrations and 15n values of no3 that was recharged in the past isotope data and mass balance calculations indicate that fes2 and other ferrous fe phases were the major electron donors for denitrification in at least two settings 1 within the glacial fluvial aquifer sediments beneath the recharge and discharge areas and 2 along the bottom of the valley filling sediments in the discharge area combined results indicate that the shape and progress of the oxic no3 plume termination were controlled by a combination of 1 historical and spatial variations in land use practices 2 contrast in groundwater flow patterns between the agricultural recharge area and riparian wetland discharge area and 3 distribution and abundance of electron donors in both the sand aquifer and valley filling sediments the data are consistent with slow migration of redox zones through the aquifer in response to recharging oxic groundwater during holocene time then an order of magnitude increase in the flux of electron acceptors as a result of agricultural no3 contamination in the late twentieth century to which the redox zone configuration still may be adjusting the importance of denitrification for no3 movement through formerly glaciated terrains should depend on the source areas and depositional environments of the glacial sediments as well as geomorphology and recent stream valley sediment history

the oligocene miocene stratigraphic evolution of the majella carbonate platform central apennines italy abstract the stratigraphic architecture of the bolognano formation documents the evolution of the majella carbonate platform in response to global and local changes that affected the mediterranean area during the oligocene miocene interval the bolognano formation consists of a homoclinal ramp that developed in a warm subtropical environment five different lithofacies associations have been identified lepidocyclina calcarenites cherty marly limestones bryozon calcarenites hemipelagic marls and marly limestones and lithothamnion limestones each association corresponds to a single lithostratigraphic unit except for the lepidocyclina calcarenites that form two distinct lithostratigraphic units lepidocyclina calcarenites 1 and 2 these six units reflect alternation of shallow water carbonate production and drowning specifically two of the three stages of shallow water carbonate production regard the development of wide dune fields within the middle ramp one stage dominated by red algae and a sea grass carbonate factory whereas the two drowning phases are represented by marly cherty limestones and calcareous marls a new biostratigraphic framework for bolognano formation is presented based on high resolution analysis of calcareous nannofossil assemblages which proved to be very useful for biostratigraphic constraints also in shallow water settings using this approach we have linked the first drowning phase late chattian aquitanian p p in age to western mediterranean volcanism and the mi 1 event and the second drowning phase late burdigalian serravallian in age to the closure of the indo pacific passage and the occurrence of the global monterey event these results permit a new deciphering in terms of sequence stratigraphy of the bolognano formation that is interpreted as a 2nd order super sequence that can be subdivided into 3 transgressive regressive sequences

erosion triangular facets as markers of order in an open dissipative system the complexity and non linearity of the morphogenetic system which is responsible for shaping the earth s surface have been widely recognised by many authors who have documented the fractal nature of erosion in this paper two peculiar kinds of landforms are compared to point out ordered structures i e triangular facets that arise in different geomorphic systems due to the principle of morphologic convergence occurrence of triangular facets has been documented in mountainous areas in relation to base level changes and hydrographical network evolution similarly shaped landforms are present even in recent tectonic uplift areas along faults the spatial distribution of the two kinds of facets has been investigated in two river basins located in liguria northern italy and in a mountainous area in oman the results of this analysis document the different spatial features of the two kinds of facets

anisotropic velocity analysis for lithology discrimination a new velocity analysis technique is presented for analyzing moveout of signals on multichannel surface seismic or vsp data an approximate skewed hyperbolic moveout formula is derived for horizontally layered transversely isotropic media this formula involves three measurement parameters the average vertical velocity and horizontal and skew moveout velocities by extending dix type hyperbolic moveout analysis we obtain improved coherence over large source geophone offsets for more accurate moveout correction compared with the stacking velocity obtained by simple hyperbolic analysis methods the three velocity parameters estimated by this technique contain more physically meaningful geologic information regarding the anisotropy and or velocity heterogeneity of the subsurface synthetic p wave model experiments demonstrate that the skewed hyperbolic moveout formula yields an excellent fit to time distance curves over a wide range of ray angles consequently the measurement parameters are shown to re

estimation of slip rates in the southern tien shan using cosmic ray exposure dates of abandoned alluvial fans cosmic ray exposure dates based on in situ produced 10 be in combination with measured heights of fault scarps that cut three abandoned fans imply a slip rate of less than 2 mm yr on the bounding thrust fault along a segment of the southern flank of the tien shan of central asia this rate somewhat lower than those for the segment farther west and for the northern margin of the belt implies that the distribution of shortening across the tien shan must change markedly along the belt the date of abandonment of the smallest of the three fans is consistent with fan formation since the last glacial maximum but the other two fans appear to have been formed and abandoned prior to that time these and other results suggest that advances and retreats of alpine glaciers may not be synchronized with continental ice sheets and that not all prominent geomorphological features in arid asian regions have formed since the last glacial maximum in this study we have assessed the relationship between cosmogenic nuclide content of individual clasts and the time since their deposition on a surface cosmogenic nuclide accumulation represents the integrated total surface exposure of rocks in source regions during transport and since deposition postdepositional processes erosion burial bioturbation and cryoturbation all of which decrease the quantity of cosmogenic nuclides produced in a rock in a given time and hence the apparent exposure age also cause significant scatter among apparent ages of samples from the surfaces very low 10 be concentrations in material from active streambeds and at depth below one of the fan surfaces indicate that exposure prior to deposition onto fan surfaces was minimal

measured anisotropy in pierre shale the five elastic coefficients which characterize a transversely isotropic medium have been measured for the pierre shale the first arrival times deduced from two closely spaced vertical seismic profiles provide values of magnitude and direction of the phase velocity at a given depth for different locations of the sources from these velocities we can estimate the five elastic coefficients by assuming that the p and sv wave velocities have only a small dependence on the angle of propagation on the other hand it is shown that the accuracy in the difference between the directions of propagation and particle motion is not sufficient to determine the anisotropy this work was industrially sponsored through the integrated geophysics project

a refraction seismic field study to determine the anisotropic parameters of shales shales are known to be transversely isotropic ti which can lead to incorrect subsurface imaging if isotropic behavior is assumed by knowing the anisotropic parameters of the shales it is possible to correct for the anisotropic effects in seismic data thereby obtaining a more correct subsurface image two p wave refraction seismic field studies were undertaken in areas of steeply dipping marine shales of the wapiabi formation to determine the anisotropic parameters of these shales in situ the first survey was located in jumpingpound creek alberta canada and the other location was west of longview alberta canada seismic lines were laid out parallel perpendicular and 45 to the local strike directions at both locations the compressional headwave velocities along strike were determined to be faster than the velocities perpendicular to strike analysis of the jumpingpound creek data location yielded anisotropic parameters of e 0 14 0 05 and 0 00 0 08 whereas at longview the anisotr

is the wasatch fault footwall utah united states segmented over million year time scales the wasatch fault zone utah is a 370 km long segmented normal fault system with topographic salients depths of footwall exposure geomorphic properties and geophysical anomalies that suggest differential long term footwall uplift and exhumation on segments that are partitioned by long lived structural segment boundaries apatite u th he ages from footwall samples along the range front from the five central footwall segments av erage 5 3 6 1 0 ma coupled two dimensional thermokinematic and helium diffusion mod els suggest average long term 5 m y exhumation rates of 0 2 0 4 mm yr for most of the wasatch front the exception is the southern end of the salt lake city segment where exhumation rates are two times as great as elsewhere along the wasatch front the rel atively invariant he ages and exhumation rates imply that most of the wasatch did not behave kinematically as independent footwall segment blocks with differential exhumation amounts over the past 5 m y the structural boundaries such as salients and intrabasin highs that partially delineate segments may have persisted since the pliocene and con trolled the locations of the surface rupture segments

slip rates along active faults estimated with cosmic ray exposure dates application to the bogd fault gobi altai mongolia dating morphological features displaced along active faults presents a major difficulty in evaluation of slip rates we used in situ produced 10 be to calculate minimum ages for alluvial surfaces misaligned by movement along a major active fault in the gobi altai western mongolia the maximum slip rate of 1 2 mm yr suggested by this method contrasts strongly with rates of 20 mm yr that we estimated by correlation of alluvial deposition with warm humid periods associated with the last glacial termination estimated to have occurred about 12 ka in western tibet the 10 be based slip rate indicates that strong earthquakes can occur along faults with low slip rates and demonstrates the contribution of cosmic ray exposure dating in quaternary tectonic analyses

the interplay between subduction and lateral extrusion a case study for the european eastern alps based on analogue models a series of analogue experiments simulating intra continental subduction contemporaneous with lateral extrusion of the upper plate are performed to study the interference between these two processes at crustal levels and in the lithospheric mantle the models demonstrate that intra continental subduction and coeval lateral extrusion of the upper plate are compatible processes leading to similar deformation structures within the extruding region as compared to the classical setup lithosphere scale indentation strong coupling across the subduction boundary allows for the transfer of stresses to the upper plate where strain regimes are characterized by crustal thickening near a confined margin and dominated by lateral displacement of material near a weak lateral confinement the strain regimes propagate laterally during ongoing convergence creating an area of overlap characterized by transpression when subduction is oblique to the convergence direction the upper plate is less deformed and as a consequence the amount of lateral extrusion decreases in addition strain is partitioned along the oblique plate boundary resulting in less subduction in expense of right lateral displacement close to the weak lateral confinement both oblique and orthogonal subduction models have a strong resemblance to lateral extrusion tectonics of the eastern alps europe where subduction of the adjacent adriatic plate beneath the eastern alps is debated our results imply that subduction of adria is a valid mechanisms to induce extrusion type deformation within the eastern alps lithosphere furthermore our findings suggest that the oligocene to late miocene structural evolution of the eastern alps reflects a phase of oblique subduction followed by a later stage of orthogonal subduction conform a miocene shift in the plate motion of adria oblique subduction also provides a viable mechanism to explain the rapid decrease in slab length of the adriatic plate beneath the eastern alps towards the pannonian basin

identification of groundwater flowpaths and denitrification zones in a dynamic floodpain aquifier abstract the groundwater flow system in the thick sand and gravel aquifer of the wide forested floodplain along the lower wisconsin river was characterized using major ion and oxygen and deuterium stable isotope analyses to explain nitrate attenuation in the floodplain critical to the groundwater flow system are the 60 90 m bluffs the pleistocene river terrace and the modern floodplain with ridge and swale microtopography upland nitrate concentrations reached 12 mg no 3 n l but were largely below the detection limit in the downgradient floodplain wetlands a transect of monitoring wells and multilevel samplers with depths of up to 6 m were installed to characterize spatial and temporal variability in the floodplain groundwater flowpaths results showed that the topography induces deep intermediate and shallow flow systems and that temporal variability causes mixing between water from different sources nitrate attenuation in this system is likely a combination of dilution plant uptake and denitrification the absence of dissolved oxygen and nitrate and presence of high soluble iron concentrations in the lower floodplain indicate an ample supply of electron donors for oxygen consumption denitrification and subsequent iron reduction the data indicate that conditions created by the topography and temporal variability of the system are suitable for denitrification to occur at depth

strike slip kinematics in central and eastern iran estimating fault slip rates averaged over the holocene 1 according to gps measurements the right lateral shear between central iran and afghan blocks amounts to 16 mm yr a model based on very long term estimates of fault rates suggests the current shear originated about 5 ma ago and has been accommodated by strike slip faulting limited to the western 2 mm yr gowk nayband fault and eastern 14 mm yr sistan system fault edges of the lut block we have used high resolution spot5 pixel size 2 5 m images to measure recent cumulative offsets and estimate slip rates over shorter time periods that average several seismic cycles only recent offsets a few tens of meters have been found along the anar fault inside the central iran plateau and along the sistan faults east of the lut the offset morphologies postdate the last incision of the network and are most probably of holocene age 12 2 ka the corresponding slip rates range between 0 5 0 75 mm yr 1 75 2 5 mm yr 1 5 mm yr 1 2 5 mm yr for the anar east neh west neh and asagie fault respectively these estimates suggest the gps shear rate across the lut may not extrapolate over the holocene they also indicate strike slip faulting is not confined to the lut edges but also occurs in central iran suggesting the ongoing strike slip tectonics might have originated between 8 and 22 ma ago earlier than considered previously and consistent with observations in ne iran

do river profiles record along stream variations of low uplift rate environments 1m m yr 1 where climate changes may have erased tectonic features we evaluate the respective contribution of low uplift rate 0 1 mm yr 1 and pleistocene climate oscillations on gradient variations of two comparable river profiles crossing different uplift zones in the southern upper rhine graben we compare the observed points of discontinuity in river profile knickpoints and convex portions knickzones with those predicted by a detachment limited model that includes stochastic short term and cyclic long term variations in climate a bedrock detachment threshold and rock uplift the detachment limited model is chosen as it predicts the development of persistent knickpoints differing values of the shear stress exponent erosion threshold climate variability and uplift pattern have been checked our modeling suggests that climate changes had no significant effects on profiles and that anomalies are more likely due to anticline growth this surprising result arises from the combination of a very low regional uplift rate and the detachment limited assumption the detachment limited model implies an upstream propagation of knickpoints and knickzones generated by uplift at the outlet during dry climate periods of low erosion the greater the uplift rate the larger the variations in river bed elevation thus for high uplift rate knickpoints and knickzones generated by climate oscillations are more likely to hide tectonic features this result seems counterintuitive because it suggests that tectonic knickzones will be better preserved in low uplift rate environments provided that the lithology is homogeneous

ultrasonic velocities in cretaceous shales from the williston basin compressional and shear wave velocities were measured in the laboratory from 1 bar to 4 kbar confining pressure for wet undrained samples of cretaceous shales from depths of 3200 and 5000 ft in the williston basin north dakota these shales behave as transversely isotropic elastic media the plane of circular symmetry coinciding with the bedding plane for compressional waves the velocity is higher for propagation in the bedding plane than at right angles to it and the anisotropy is greater for the 5000 ft shale for shear waves the sh wave perpendicular to bedding and the sv wave parallel to bedding propagate with the same speed which is about 25 percent lower than that for the sh wave parallel to bedding in general compressional and shear velocities are higher for the indurated 5000 ft shale than for the friable 3200 ft shale all velocities increase with in increasing confining pressure to 4 kbar the 3200 ft shale exhibits velocity hysteresis as a function of pressure whereas this effect is a

using the aster global dem to derive empirical relationships among triangular facet slope facet height and slip rates along active normal faults abstract the advent of global dems provided a uniform elevation dataset for studying geomorphic parameters in a variety of settings in this paper aster dem data 30 m pixel size are used to derive empirical relationships between triangular facet attributes and slip rates along active normal faults we sampled 232 triangular facets along 10 normal faults in greece and bulgaria that slip with rates from 0 1 mm yr up to 1 3 mm yr the studied normal faults accumulate quaternary tectonic strain in well known extensional provinces such as central greece crete and sw bulgaria the normal fault footwalls analyzed herein have been developed under similar long term climatic conditions it is suggested that two key geometrical features of the youngest generation of triangular facets slope angle and height can provide useful metrics to assess rates of deformation when seismological and geodetic data are lacking or not found in sufficient quantity to make reasonable assessments our derived empirical relation between slip rate and facet slope angle is y 0 057 x 1 where y is the fault slip rate mm yr and x is the facet slope angle degrees with an r 2 0 728 it is envisaged that our analysis may be helpful in assessing seismic hazard along normal faults with similar facet characteristics in other extensional settings

interaction between normal fault slip and erosion on relief evolution insights from experimental modelling the growth of relief in active tectonic areas is mainly controlled by the interactions between tectonics and surface processes erosion and sedimentation the study of long lived morphologic markers formed by these interactions can help in quantifying the competing effects of tectonics erosion and sedimentation in regions experiencing active extension river long profiles and faceted spurs triangular facets can help in understanding the development of mountainous topography along normal fault scarps in this study we developed analogue experiments that simulate the morphologic evolution of a mountain range bounded by a normal fault this paper focuses on the effect of the fault slip rate on the morphologic evolution of the footwall by performing three analogue experiments with different fault slip rates under a constant rainfall rate a morphometric analysis of the modelled catchments allows comparing with a natural case tunka half graben siberia after a certain amount of fault slip the modelled footwall topographies of our models reaches a dynamic equilibrium i e erosion balances tectonic uplift relative to the base level close to the fault whereas the topography farther from the fault is still being dissected due to regressive erosion we show that the rates of vertical erosion in the area where dynamic equilibrium is reached and the rate of regressive erosion are linearly correlated with the fault throw rate facet morphology seems to depend on the fault slip rate except for the fastest experiment where faceted spurs are degraded due to mass wasting a stream power law is computed for the area wherein rivers reach a topographic equilibrium we show that the erosional capacity of the system depends on the fault slip rate finally our results demonstrate the possibility of preserving convex river long profiles on the long term under steady external tectonic uplift and rainfall conditions

depositional and tectonic framework of the rift basins of lake baikal from multichannel seismic data recent multichannel seismic reflection data from lake baikal located in a large active continental rift in central asia image three major stratigraphic units totaling 3 5 to 7 5 km thick in four subbasins a major change in rift deposition and faulting between the oldest and middle rift units probably corresponds to the change from slow to fast rifting in early pliocene time inferred from on land studies a minor modification of fault patterns characterizes the youngest unit a brief comparison of the basins of lake baikal with those of the east african rift system highlights differences in structural style that can be explained by differences in age and evolution of the surrounding basement rocks

tectonic beheading of fluvial valleys in the maestrat grabens eastern spain insights into slip rates of pleistocene extensional faults abstract interaction between faulting and landscape evolution in regions of active tectonics allows us to use subtle geomorphological markers for estimating fault slip rates geomorphic features of two valleys connected with the bottom of the alcala de xivert graben at the maestrat graben system eastern spain suggest that they correspond to the lowest segments of ancient valleys whose original heads were located at the axis of the neighbouring irta range they were beheaded owing to displacement of the torreblanca and irta faults during a period of active extensional faulting in middle pleistocene times these faults produced a negative inversion of the relief sinking a narrow graben the ametler graben at the middle of the irta range whose alluvial infill buried the midsegments of the beheaded valleys this hypothesis has been tested by applying two geomorphic indices the stream gradient index sl and the valley width height ratio vf as well as by considering surface and subsoil information about the sedimentary infill of the ametler graben from this evolutionary model after reconstructing hypothetical longitudinal profiles of the ancient rivers and taking into account a new absolute age obtained for the alluvial infill of the ametler graben slip rates at the northern segment of the torreblanca fault have been approached the throw rate has been constrained between a minimum of 0 04 0 07 mm year for the last 1 9 to 2 6 ma and a maximum of 0 26 0 30 mm year for the last 253 3 18 0 ky these values are comparable to those averaged on other active faults in the central eastern iberian chain for the overall late pliocene pleistocene times nevertheless the torreblanca fault shows exceptionally high activity within the context of the maestrat and catalonian grabens which can explain its deep imprint in landscape evolution

a multioffset vertical seismic profiling experiment for anisotropy analysis and depth imaging a multioffset vertical seismic profile vsp was carried out in the rocky mountain foothills of southern alberta canada the purpose of this experiment was to investigate whether the dipping shale strata exhibit p wave velocity anisotropy and if so to calculate the thomsen anisotropy parameters for use in anisotropic depth migration traveltime inversion of first arrival data from the multioffset vsp revealed that the dipping mesozoic clastics in the area exhibit seismic velocity anisotropy of about 10 the anisotropy parameters derived from this experiment were then used in anisotropic prestack depth migration of data from a surface seismic line close to the vsp well comparison of the anisotropic migration with the corresponding isotropic prestack depth migration showed that the target was imaged incorrectly in the isotropic case a lateral shift of 180 m in the updip direction of the overlying beds was observed the image obtained with an anisotropic velocity model was also better focused than that obtained assuming isotropic velocities

late holocene slip rate for the north anatolian fault turkey from cosmogenic 36cl geochronology implications for the constancy of fault loading and strain release rates geomorphologic mapping and cosmogenic radionuclide 36cl dating of an offset fluvial terrace yield a preferred late holocene slip rate of 20 5 5 5 mm yr for the central part of the north anatolian fault turkey an independent slip rate constrained by 14c ages is 20 5 8 5 mm yr these rates are generally similar to but possibly slightly slower than the short term rate of elastic strain storage of 25 1 measured geodetically across this major strike slip fault reilinger et al 2006 1 suggesting that loading and strain release on this part of the north anatolian fault have been relatively constant when averaged over the past 2 2 5 k y we attribute this consistency to the relatively simple structure of the anatolia eurasia plate boundary in north central turkey where almost all plate boundary strain is accommodated along the north anatolian fault the absence of other moderate to high slip rate faults and the earthquakes they produce leads to a relatively simple stress evolution for the fault dominated by steady tectonic loading 1 ref 10

the structure and development of the baikal rift depression abstract the baikal rift depression located in southeastern siberia is one of the best investigated intra continental rift structures in the world in addition to being the site of comprehensive studies by russian geo scientists for decades the baikal depression is now the subject of new international investigations using advanced technical means and technologies the present paper summarizes the principal results concerning the morphostructure of the baikal rift the stratigraphy of the cenozoic deposits and the stages of the baikal depression development based on cross sections which exhibit the impact of both tectonic and climatic processes the development of the baikal depression occurred through two stages i the pre crypto rift stage of the late cretaceous eocene and ii active rifting of the oligocene recent the second stage is divided into several steps and substeps separated by tectonic phases formation of the baikal rift zone appears to be related to the indo eurasian plate collision related to a model of passive rifting the uplifted shoulders of the depression have a complex morphostructure overlain by cenozoic deposits which are thin and restricted in area the near marginal zones of the rift are largely defined by the system of longitudinal blocks of different width surfaces of the blocks are inclined either to the uplifted shoulder of the rift bound by listric faults typical for western edges of the depression or to the axis of the depression cenozoic deposits on the blocks consist of accumulative plains composed primarily of thick lacustrine sequences

cenozoic exhumation history of south china a case study from the xuefeng mt range abstract new apatite fission track aft dating was applied to the xuefeng mt range and yuanma basin to constrain the cenozoic exhumation process of the southeastern yangtze block south china the analyzed samples in this study have aft ages ranging from 27 9 2 5 to 61 5 5 9 ma which are younger than the deposition or crystallization ages of the host rocks the aft analysis and thermal history modeling indicate that both the xuefeng mt range and the yuanma basin underwent significant exhumation during the early cenozoic ca 60 40 ma these samples were rapidly exhumed to near the surface during this period our results suggest that an important tectonic event occurred along or near regional fault zones e g the qinhang fault in south china during the early cenozoic ca 60 40 ma however it is difficult to relate this event to the eastern sichuan fold belt which is much older and is characterized by large scale folding and thrusting combined with fieldwork in the yuanma xupu and xinning basins we refute the cretaceous pan yangtze basin that was proposed to have been separated by the uplifted xuefeng mt range after the late cretaceous the exhumation stage from ca 60 ma to 40 ma was an important period during which plate movements across the eastern asian and pacific regions were reorganized the early cenozoic tectonothermal event in south china can be attributed to a change in the direction and speed of the subduction of the pacific plate beneath the eurasian plate an oligocene miocene cooling event was also recorded in the eastern xuefeng mt range which we tentatively attribute to the activity of dextral faults in this area as a far field effect of the collision between the indian and eurasian plates

tectonic geomorphology of the spildagi high ranges western anatolia abstract the spildagi high ranges represent the footwall block of the manisa fault zone mfz which is one of the nw se to e w trending active dip slip normal fault systems in western anatolia the spildagi high ranges were uplifted by approximately 1500 m with respect to the lowland manisa basin following the late miocene the plio quaternary active tectonics was interpreted through a detailed geomorphic study of the fault generated mountain fronts and drainage pattern of the spildagi high ranges the combined geomorphic and morphometric data provide evidence for relative variations in tectonic activity along the mfz morphometric measures such as axial river profiles drainage basin geometry triangular facets and mountain front lineament patterns document the impact of active tectonics on the landscape evolution of the mfz which resulted in the subdivision of western central and eastern sectors an axial river flowing in the manisa basin is represented by the gediz river that exhibits a meandering braided transition pattern the relative positions of the palaeochannels and oxbows evidence the south westward migration of the gediz river towards the mfz we infer that the source of axial river migration is tilting of the manisa plain due the listric nature of the mfz quantitative measurement of geomorphic indices such as mountain front sinuosity s mf 1 11 1 14 valley floor width to height ratios v f 0 033 0 947 facet heights 25 1060 m and facet slopes 5 77 40 21 suggest a relatively high degree of tectonic activity along the mfz hypsometric curves for all sector slopes mostly exhibit straight or concave shapes indicating the presence of the young and weakly eroded mountain front of the spildagi high ranges the combined geomorphic indices and field data suggest that the analysed dip slip normal fault segments are linear and highly active

velocity anisotropy in shale determined from crosshole seismic and vertical seismic profile data crosshole and vertical seismic profile vst data made possible accurate characterization of the elastic properties including noticeable velocity anisotropy of a near surface late tertiary shale formation shear wave splitting was obvious in both crosshole and vsp data in crosshole data two orthologonally polarrized shear s waves arrived 19 ms in the uppermost 246 ft 75 m vertically traveling s waves of the vsp separated about 10 ms in the uppermost 300 ft 90 m but remained at nearly constant separation below that level a transversely isotropic model which incorporates a rapid increase in s wave velocities with depth but slow increase in p wave velocities closely fits the data over most of the measured interval elastic constants of the transvesely isotropic model show spherical p and s2 wave velocity surfaces but an ellipsoidal s1 wave surface with a ratio of major to minor axes of 1 15 the magnitude of this s wave anisotropy is consistent with and lends credence to s wave anisotropy magn

a coupled vertically integrated model to describe lateral exchanges between surface and subsurface in large alluvial floodplains with a fully penetrating river this paper presents a vertically averaged model for studying water and solute exchanges between a large river and its adjacent alluvial aquifer the hydraulic model couples horizontal 2d saint venant equations for river flow and a 2d dupuit equation for aquifer flow the dynamic coupling between river and aquifer is provided by continuity of fluxes and water level elevation between the two domains equations are solved simultaneously by linking the two hydrological system matrices in a single global matrix in order to ensure the continuity conditions between river and aquifer and to accurately model two way coupling between these two domains the model is applied to a large reach about 36 km2 of the garonne river south western france and its floodplain including an instrumented site in a meander simulated hydraulic heads are compared with experimental measurements on the garonne river and aquifer in the floodplain model verification includes comparisons for one point sampling date 27 piezometers 30 march 2000 and for hydraulic heads variations measured continuously over 5 months 5 piezometers 1 january to 1 june 2000 the model accurately reproduces the strong hydraulic connections between the garonne river and its aquifer which are confirmed by the simultaneous variation of the water level in the river and in piezometers located near the river bank the simulations also confirmed that the model is able to reproduce groundwater flow dynamics during flood events given these results the hydraulic model was coupled with a solute transport component based on advection dispersion equations to investigate the theoretical dynamics of a conservative tracer over 5 years throughout the 36 km2 reach studied meanders were shown to favour exchanges between river and aquifer and although the tracer was diluted in the river the contamination moved downstream from the injection plots and affected both river banks

tracking the multi stage exhumation history of the western chinese tianshan by apatite fission track aft dating implication for the preservation of epithermal deposits in the ancient orogenic belt abstract the western chinese tianshan located in the southern domain of the central asian orogenic belt caob was originally established by multiple accretion collision processes in the paleozoic and was modified by complicated intracontinental tectonic evolution in the mesozoic to cenozoic understanding the timing and mechanism of the latter geological processes is critical to unravel the preservation conditions of the epithermal deposits in the western chinese tianshan this work presents new apatite fission track aft data for three mountain ranges keguqinshan wusunshan and nalatishan of the western chinese tianshan to track their exhumation history our aft data gave a wide range of ages from 76 8 5 5 ma to 182 3 9 9 ma and the mean confined fission track lengths are between 9 8 0 5 m and 12 3 0 2 m the new data in combination with the thermal history modeling results allow us to summary three main episodes of exhumation in the western chinese tianshan including the early permian 300 280 ma late triassic late jurassic 230 140 ma and late oligocene early miocene 30 20 ma the first episode may have been caused by terrane accretion collision in the late paleozoic leading to uplift of the keguqinshan that supplied abundant sediments to form a critical cover of ca 4 km thick on these epithermal deposits the second episode was likely related to closure of the mongol okhotsk ocean in the mesozoic and an extremely slow exhumation rate ca 0 0083 mm y as well as a moderate erosion of ca 0 8 km thick are estimated the last episode is regarded to be the result of collision between the indian plate and the eurasia plate in the cenozoic and this significant tectonic event triggered rapid exhumation up to ca 0 1 mm y of the whole region in the western chinese tianshan which removed more than ca 3 2 km pre cenozoic sedimentary cover and sent the epithermal deposits to the subsurface level

new constraints on sediment flux dependent river incision implications for extracting tectonic signals from river profiles we present new field data from rivers draining across active normal faults that incise across the same lithology at the fault have been subjected to similar climatic regimes and tectonic settings and were perturbed by a well documented increase in fault slip rate ca 1 ma in spite of these similarities the rivers exhibit markedly different long profiles and patterns of catchment incision we use channel slope and hydraulic geometry data for each river to calculate bed shear stresses b and show that there is no simple relationship between peak b and the relative uplift rates across the faults u which differ by a factor of four the long term average sediment supply to each channel q s estimated from time averaged catchment erosion rates can explain the b versus u data if bedload modulates bedrock incision rate e in a strongly nonlinear way together these field data allow us for the first time to evaluate theoretical predictions of the role of sediment on river profile evolution and to quantify the magnitude of the effect in natural systems

modeling fluvial incision and transient landscape evolution influence of dynamic channel adjustment 1 channel geometry exerts a fundamental control on fluvial processes recent work has shown that bedrock channel width depends on a number of parameters including channel slope and is not solely a function of drainage area as is commonly assumed the present work represents the first attempt to investigate the consequences of dynamic gradient sensitive channel adjustment for drainage basin evolution we use the channel hillslope integrated landscape development child model to analyze the response of a catchment to a given tectonic perturbation using as a template the topography of a well documented catchment in the footwall of an active normal fault in the apennines italy that is known to be undergoing a transient response to tectonic forcing we show that the observed transient response can be reproduced to first order with a simple detachment limited fluvial incision law transient landscape is characterized by gentler gradients and a shorter response time when dynamic channel adjustment is allowed the differences in predicted channel geometry between the static case width dependent solely on upstream area and dynamic case width dependent on both drainage area and channel slope lead to contrasting landscape morphologies when integrated at the scale of a whole catchment particularly in presence of strong tilting and or pronounced slip rate acceleration our results emphasize the importance of channel width in controlling fluvial processes and landscape evolution they stress the need for using a dynamic hydraulic scaling law when modeling landscape evolution particularly when the relative uplift field is nonuniform

seismic attributes for monitoring of a shallow heated heavy oil reservoir a case study in production geophysics detecting the zones of production or constraining the in situ conditions within a reservoir are often of greater importance than obtaining highly resolved seismic structural images standard seismic data processing distorts the signal and limits the potential for extracting additional information especially for shallow targets an alternative shift stack procedure is applied in the processing of a shallow 12 fold 1 m common midpoint cmp spacing reflection profile acquired over a heated athabasca heavy oil sand reservoir the shift stack involves summing of cmp traces which have been flattened to an appropriate reference event simple modeling confirms that the prestack waveforms are better preserved by this process amplitude and frequency attributes are extracted from the reflection profile amplitudes of a continuous reservoir event vary by 600 over 35 m intervals along the profile bright spots correlate with heated regions apparent frequencies as measured by the instantaneous frequency and by short time window power spectral estimates of the subreservoir event are 20 30 hz lower in these same regions these diminished apparent frequencies most probably result from interference of the subreservoir reflection with events related to structural changes within the reservoir a complete interpretation of the results has not been attempted as knowledge of the in situ conditions is incomplete however changes in the seismic response at the well locations suggest that these attributes are useful in detection and mapping of heated zones the shiftstack procedure may also be useful in environmental and geotechnical applications

sedimentation and subsidence patterns in the central and north basins of lake baikal from seismic stratigraphy comparison of sedimentation patterns basement subsidence and faulting histories in the north and central basins of lake baikal aids in developing an interbasinal seismic stratigraphy that reveals the early synrift evolution of the central portion of the baikal rift a major continental rift system although there is evidence that the central and northern rift basins evolved at approximately the same time their sedimentation histories are markedly different primary sediment sources for the initial rift phase were from the east flank of the rift two major deltas developed adjacent to the central basin the selenga delta at the south end and the barguzin delta at the north end the barguzin river system located at the accommodation zone between the central and north basins also fed into the southern part of the north basin and facilitated the stratigraphic linkage of the two basins a shift in the regional tectonic environment in the mid pliocene created a second rift phase distinguished by more rapid subsidence and sediment accumulation in the north basin and by increased subsidence and extensive faulting in the central basin the barguzin delta ceased formation and parts of the old delta system were isolated within the north basin and on academic ridge these isolated deltaic deposits provide a model for the development of hydrocarbon plays within ancient rift systems in this second tectonic phase the dominant sediment fill in the deeper and more rapidly subsiding north basin shifted from the flexural eastern margin to axial transport from the upper angara river at the north end of the basin

geomorphic significance of postglacial bedrock scarps on normal fault footwalls the existence of well preserved holocene bedrock fault scarps along active normal faults in the mediterranean region and elsewhere suggests a dramatic reduction in rates of rock weathering and erosion that correlates with the transition from glacial to interglacial climate we test and quantify this interpretation using a case study in the italian central apennines holocene rates are derived from measurements of weathering pit depth along the magnola scarp where previous cosmogenic cl 36 analyses constrain exposure history to estimate the average hillslope erosion rate over similar to 10 5 years we introduce a simple geometric model of normal fault footwall slope evolution the model predicts that the gradient of a weathering limited footwall hillslope is set by fault dip angle and the ratio of slip rate to erosion rate if either slip or erosion rate is known the other can be derived applying this model to the magnola fault yields an estimated average weathering rate on the order of 0 2 0 4 mm yr more than 10 times higher than either the holocene scarp weathering rate or modern regional limestone weathering rates a numerical model of footwall growth and erosion in which erosion rate tracks the oxygen isotope curve reproduces the main features of hillslope and scarp morphology and suggests that the hillslope erosion rate has varied by about a factor of 30 over the past one to two glacial cycles we conclude that preservation of carbonate fault scarps reflects strong climatic control on rock breakdown by frost cracking

baikal rift zone structure and geodynamics abstract the cenozoic baikal rift zone is superimposed on the caledonian baikal fold belt representing the suture between the precambrian siberian craton and several microcontinents the baikal rift zone consists of a system of disconnected fault bounded basins and extensional and wrench faults that straddles a major arch having a topographic relief of 2 3 km rifting activity commenced during the oligocene and is still active as evident from high seismicity of the baikal rift zone across the baikal rift zone upper crustal extension is considerably smaller than would be expected from its crustal thickness which decreases by 8 11 km across the baikal basins as compared to the adjacent unextended areas the discrepancy between upper and lower crustal attenuation could be attributed to intrusion of a major diapir indeed geophysical data indicate that the sayan baikal dome coincides with such a diapir the top of which is located at the crust mantle boundary this intrusion is held responsible for oligocene and quaternary doming of the rift zone development of the intra continental baikal rift system is thought to be related to asthenospheric diapirism active rifting however intra plate stresses in conjunction with the himalayan collision may have played some role

using chemical hydrologic and age dating analysis to delineate redox processes and flow paths in the riparian zone of a glacial outwash aquifer stream system 1 a combination of chemical and dissolved gas analyses chlorofluorocarbon age dating and hydrologic measurements were used to determine the degree to which biogeochemical processes in a riparian wetland were responsible for removing no3 from groundwaters discharging to the otter tail river in west central minnesota an analysis of river chemistry and flow data revealed that no3 concentrations in the river increased in the lower half of the 8 3 km study reach as the result of groundwater discharge to the river groundwater head measurements along a study transect through the riparian wetland revealed a zone of groundwater discharge extending out under the river on the basis of combined chemical dissolved gas age date and hydrologic results it was determined that water chemistry under the riparian wetland was controlled largely by upgradient groundwaters that followed flow paths up to 16 m deep and discharged under the wetland creating a pattern of progressively older more chemically reduced low no3 water the farther one progressed from the edge of the wetland toward the river these findings pose challenges for researchers investigating biogeochemical processes in riparian buffer zones because the progressively older groundwaters entered the aquifer in earlier years when less no3 fertilizer was being used no3 concentrations originally present in the groundwater had also decreased in the upgradient aquifer as a result of denitrification and progressively stronger reducing conditions there the resulting pattern of decreasing no3 concentrations across the riparian zone may be incorrectly interpreted as evidence of denitrification losses there instead of in the upgradient aquifer consequently it is important to understand the hydrogeologic setting and age structure of the groundwaters being sampled in order to avoid misinterpreting biogeochemical processes in riparian zones

long term slip rate of the southern san andreas fault from 10be 26al surface exposure dating of an offset alluvial fan we determine the long term slip rate of the southern san andreas fault in the southeastern indio hills using 10 be and 26 al isotopes to date an offset alluvial fan surface field mapping complemented with topographic data air photos and satellite images allows precise determination of piercing points across the fault zone that are used to measure an offset of 565 80 m a total of 26 quartz rich cobbles from three different fan surfaces were collected and dated the tight cluster of nuclide concentrations from 19 samples out of 20 from the offset fan surface implies a simple exposure history negligible prior exposure and erosion and yields an age of 35 5 2 5 ka the long term slip rate of the san andreas fault south of biskra palms is thus 15 9 3 4 mm yr this rate is about 10 mm yr slower than geological 0 14 ka and short term geodetic estimates for this part of the san andreas fault implying changes in slip rate or in faulting behavior this result puts new constraints on the slip rate of the san jacinto and on the eastern california shear zone for the last 35 kyr our study shows that more sites along the major faults of southern california need to be targeted to better constrain the slip rates over different timescales

velocity anisotropy observed in wellbore seismic arrivals combined effects of intrinsic properties and layering a method of estimating velocity anisotropy by the t p inversion of seismic traveltimes observed in a multidepth and offset vsp experiment is developed in the method a set of seismic traces observed at afixed depth in the wellbore are transformed to the t p domain incidence angle dependent interval velocities are extracted from the resulting curves using coherency measures after accounting for the effects of the overlaying layers to test the method we obtained seismic records from a shallow borehole drilled through a flat lying sedimentary sequence one depth interval that consists of a homogeneous bioturbated shale is nearly isotropic a second interval characterized by an alternation of thin 1 m sands and shales displays an anisotropy of 15 withvelocitiesincreasingfromthenearvertical 0 308 to the oblique 30 8 0 558 angles of incidence oblique velocities were always larger the observation thattheshale sanddepthintervaldisplayingthegreatest anisotropy also is the most heterogeneous in the sonic logs suggests that the thin layering produces the anisotropy the theoretical vertical to horizontal velocity anisotropy for this interval computed assuming isotropic layering is 14 2 comparing this theoretical value to the vertical to oblique value obtained over a smaller range of incidence angles indicates that the theoretical valueistoosmall thisdiscrepancyispossiblybecauseof the intrinsic anisotropy of the shale layers themselves that is not considered in the theoretical calculations

monitoring active fumaroles through time lapse electrical resistivity tomograms an application to the pisciarelli fumarolic field campi flegrei italy abstract volcanoes are usually monitored through observations of many physical and chemical phenomena in the most dangerous cases as the one of the campi flegrei caldera italy great amount of data are collected both in discrete or continuously and regularly stored however how to transform such mass of data in a deeper understanding of the volcano dynamics is still an open question dissimilar information are in fact always hard to compare but just integrating all the available knowledge hazardous events could be prevented in a reliable way fluids as water and gasses mobilized in the subsoil by the heat induced by deep magmatic sources are widely recognized as the first engine of similar occurrences and the volcanic gas emissions represent together with the seismic activity one of the most considered precursors at the same time the electrical geophysical methods are the most applied in order to detect and characterize the fluid patterns in the subsoil so the integration of geoelectrical and geochemical observations should represent one of the most pursued approach in volcanoes monitoring on the contrary standard way to compare such data has been not yet codified the ert tomograms capability to individuate that parts of the subsoil where gasses cumulate is well understood in literature however we look for indications about its proficiency in associating the electrical resistivity changes relative to these zones once compared to the geochemical time series to deep related contributes distinguishing them from the seasonal ones the electrical signature of the fluid patterns reconstructed through a time lapse ert approach could be of relevance to better characterize the volcanic phenomena and their origins in this paper a first test of ert and geochemical time series integration was performed to enhance the understanding of the pisciarelli fumarolic field evolution now the most active area in the whole campi flegrei caldera

increasing shallow groundwater co2 and limestone weathering konza prairie usa in a mid continental north american grassland solute concentrations in shallow limestone hosted groundwater and adjacent surface water cycle annually and have increased steadily over the 15 year study period 1991 2005 inclusive modeled groundwater co2 verified by measurements of recent samples increased from 10 2 05 atm to 10 1 94 atm about a 20 increase from 1991 to 2005 the measured groundwater alkalinity and alkaline earth element concentrations also increased over that time period we propose that carbonate minerals dissolve in response to lowered ph that occurs during an annual carbonate mineral saturation cycle the cycle starts with low saturation during late summer and autumn when dissolved co2 is high as dissolved co2 decreases in the spring and early summer carbonates become oversaturated but oversaturation does not exceed the threshold for precipitation we propose that groundwater is a co2 sink through weathering of limestone soil generated co2 is transformed to alkalinity through dissolution of calcite or dolomite the annual cycle and long term increase in shallow groundwater co2 is similar to but greater than atmospheric co2 2008 elsevier ltd all rights reserved

first break vertical seismic profiling tomography for vinton salt dome building laterally depth varying velocity models for vertical seismic profiling vsp imaging is challenging because of the narrow ray angle coverage of vsp data especially if only first arrivals are used this study explores the potential of a new deformable layer tomography dlt for building velocity models with a vsp data set acquired over the vinton salt dome in southwestern louisiana the dlt method uses first breaks to constrain the geometry of velocity interfaces from an initial model of flat constant velocity layers parameterized using a priori geologic and geophysical information a progressive multiscale inversion loop gradually updates the interface geometry the final solution model containing 3d geometry is well supported by resolution and reliability tests and closely matches the long wavelength trends of area sonic logs the presence of velocity anisotropy is also indicated

cenozoic normal faulting and regional doming in the southern hangay region central mongolia implications for the origin of the baikal rift province abstract the hangay dome in central mongolia is a mountainous region covering more than 200 000 km2 with numerous flat topped peaks over 3000 m that preserve a late cretaceous paleogene erosion surface doming began in the middle oligocene producing more than 2000 m of regional topographic uplift the range represents an important kinematic link between the baikal rift province to the north and altai transpressional ranges to the south and west structural field investigations of major faults visible on satellite imagery indicate that the southern hangay dome region is dominated by late cenozoic normal faults that bound small half graben most faults are ne striking and faults at the highest elevations are the most recently active most graben appear to be isolated systems that constitute small sediment sinks perched on the flanks and crests of the dome the first order feature is the dome itself and most sediment eroded off of the dome is deposited in the mongolian valley of lakes or is carried northwards by the selenga river and its extensive tributaries the basement of the dome is a precambrian craton although the shape and dimensions of the craton are poorly constrained to the north and east late cenozoic uplift of the southern dome region appears to be confined to the area underlain by cratonic basement whereas the altai region to the south and west is underlain by mechanically weaker palaeozoic arc and accretionary belts with respect to the regional northeast directed shmax the hangay craton appears to have acted as a rigid passive indentor focusing late cenozoic transpressional deformation around its west and southern margins models invoking a late cenozoic plume as the driving force for doming and widespread alkaline volcanism on the dome are not strongly supported by geochemical and isotopic data on neogene recent volcanics and the spatial correlation between areas that are domed and older cratonic crust appears too coincidental to be ignored convective removal of an overthickened lithospheric root leading to adiabatically decompressed asthenosphere could explain regional doming and volcanism however major crustal thickening last occurred in the permian in the southern hangay region and the time lag between thickening and postulated root removal and plateau uplift 200 myr appears too long an alternative model is explored based on speculated lithospheric mantle flow patterns driven by india s continued northeastward indentation it is suggested that lithospheric mantle flow diversion around the overthickened hangay craton crustal keel could cause lithospheric thinning beneath the craton and passive asthenospheric upwarp leading to regional topographic uplift and decompression melting alkali volcanism in general the angular relationship between precambrian craton boundaries and the prevailing northeasterly shmax appears to control the kinematics of late cenozoic deformation throughout the hangay altai sayan and baikal regions

tectonic characteristics of the lishan piedmont fault in the se weihe graben central china as revealed by the geomorphological and structural analyses abstract the fault kinematics slip rate and paleoseismicity along the approximate ew trending lishan piedmont fault lpf in the se weihe graben central china have been determined the results of geomorphological analysis field investigations and radiocarbon 14 c age dating indicate that i slope angles of the observed triangular facets cluster around 20 ii empirical correlations yield a vertical slip rate throw rate of 0 11 0 25 mm yr 1 which is lower than the neighboring active faults iii the lpf is characterized by almost purely normal slip and was active within the past 18 000 yr these findings can provide a basis for the assessment of seismic risk in and around the densely populated city of xi an an old capital of china however we suggest more precise constraints on the fault slip rate and detailed paleoseismological studies on the timing of the most recent earthquake and the repeat time of paleo earthquakes are needed in order to better understand the seismogenic behaviors of the active lpf

influence of nested groundwater systems on reduction oxidation and alkalinity gradients with implications for plant nutrient availability in four new york fens summary this study compares hydrologic investigations of four new york fens designed to characterize spatial variability in groundwater flow gwf and the resulting hydrochemical patterns that influence plant nutrient availability at the marl fen and two rich fen sites hydrometric data and pore water samples collected from nested piezometers set along the gwf path showed spatial patterns consistent with a mixing gradient established by the intersection of local i e hill slope relatively dilute groundwater discharge and mineral rich groundwater discharged from a larger scaled i e intermediate system distinct redox and carbonate gradients along the gwf paths of three rich fens reflected strong interactions between groundwater supply of terminal electron acceptors and microbial processes affecting speciation of iron nitrogen and phosphorus decreased nitrate concentrations increased dissolved iron and removal of sulfate along flowpaths indicated that redox conditions became more reduced as groundwater moved down gradient nitrate removal occurred across the interface between the upland mineral soil and the organic rich fen peat lack of ammonium accumulation indicated that denitrification limits n supply to plants in down gradient fen areas further down gradient sulfate enriched groundwater discharge sustained sub oxic conditions and enhanced phosphorus mobility through effects on iron sulfur phosphorus dynamics alkalinity generation and dissolution of mineral bound p in contrast the poor fen was sustained by an isolated surficial groundwater system a thick lacustrine clay aquitard limited intermediate or regional scaled groundwater discharge as a result water table fluctuations were more responsive to short term weather events and imposed the strongest influence on redox status a redox gradient evidenced by increasing iron and ammonium concentrations extended downward with depth from the aerated peat surface the dilute water supply and lack of additional internal alkalinity generation limited buffer capacity and decomposition overall ammonium accumulation increased n availability whereas reduced decomposition rates further limited p availability our results show that interaction of multiple gwf systems within the fens was the critical determinant of water table stability rich fens or fluctuation poor fen as well as the supply of dissolved ions that influence geochemical processes affecting plant nutrient availability together these factors accounted directly or indirectly for observed spatial patterns in redox and alkalinity gradients which in turn controlled speciation of phosphorus reactive minerals differences among fens in spatial patterns could be accounted for by differences in the geomorphometry of the basins within which the fens developed and the stratigraphy and hydraulic characteristics of underlying sediments results suggest that fe s dynamics rather than carbonate precipitation likely influences inorganic phosphorus pools and release mechanisms

height of faceted spurs a proxy for determining long term throw rates on normal faults evidence from the north baikal rift system siberia 1 we present new results on the long term throw rates of active normal faults in the north baikal rift nbr eastern siberia based on a statistical analysis of triangular faceted scarps fault bounded ridges in the nbr display typical morphologies with several contiguous facets separated by fault perpendicular catchments over a range of 20 fault segments analyzed triangular facet heights vary from 200 to 900 m as fault scarps have been developing under similar long term climatic conditions we infer that the scatter in mean facet height arises from long term differences in fault throw rate we compare the morphology of nbr facets with results obtained in a previously published numerical model of facet growth using facet height as an input model results provide estimates of the long term fault throw rate nbr throw rates vary between 0 2 and 1 2 mm yr 1 the throw rates are then compared with the cumulated throw which has been constrained by geophysical and stratigraphic data in the basins this provides an estimate of the age of fault and basin initiation we show that the modern stage of basin development started circa 3 myr ago except for the north baikal basin 8 ma our results also suggest that a proportion of the observed throw is inherited from an earlier tectonic stage

faceted spurs at normal fault scarps insights from numerical modeling 1 we present a combined surface processes and tectonic model which allows us to determine the climatic and tectonic parameters that control the development of faceted spurs at normal fault scarps sensitivity tests to climatic parameter values are performed for a given precipitation rate when hillslope diffusion is high and channel bedrock is highly resistant to erosion the scarp is smooth and undissected when instead the bedrock is easily eroded and diffusion is limited numerous channels develop and the scarp becomes deeply incised between these two end member states diffusion and incision compete to produce a range of scarp morphologies including faceted spurs the sensitivity tests allow us to determine a dimensionless ratio of erosion f for which faceted spurs can develop this study evidences a strong dependence of facet slope angle on throw rate for throw rates between 0 4 and 0 7 mm a facet height is also shown to be a linear function of fault throw rate model performance is tested on the wasatch fault utah using topographic geologic and seismologic data a monte carlo inversion on the topography of a portion of the weber segment shows that the 5 ma long development of this scarp has been dominated by a low effective precipitation rate 1 1 m a and a moderate diffusion coefficient 0 13 m2 a results demonstrate the ability of our model to estimate normal fault throw rates from the height of triangular facets and to retrieve the average long term diffusion and incision parameters that prevailed during scarp evolution using an accurate 2 d misfit criterion

decoding temporal and spatial patterns of fault uplift using transient river long profiles we present detailed observations of rivers crossing active normal faults in the central apennines italy where excellent constraints exist on the temporal and spatial history of fault movement we demonstrate that rivers with drainage areas 10 km2 and crossing faults that have undergone an increase in throw rate within the last 1 my have significant long profile convexities in contrast channels that cross faults that have had a constant slip rate for 3 my have concave up profiles and have similar concavities and steepness indices to rivers that do not cross any active fault structures this trend is consistent across the central apennines and cannot be explained by appeal to lithology or regional base level change the data challenge the belief that active faulting must always be reflected in river profiles instead the long profile convexities are best explained as a transient response of the river system to a change in tectonic uplift rate moreover for these rivers we demonstrate that the height of the profile convexity as measured from the fault scales with the magnitude of the uplift rate increase on the fault and we establish that this relationship holds for throw rate variation along strike for the same fault segment as well as between faults these findings are shown to be consistent with predictions of channel response to changing uplift rate rates using a detachment limited fluvial erosion model and they illustrate that analysis of the magnitude of profile convexities has considerable predictive potential for extracting tectonic information we also demonstrate that the migration rate of the profile convexities varies from 1 5 10 mm y and is a function of the slip rate increase as well as the drainage area this is consistent with n 1 for the slope exponent in a classical detachment limited stream power erosion law but could potentially be explained by incorporating an erosion threshold or an explicit role for sediment in enhancing erosion rates finally we show that for rivers in extensional settings where the response times to tectonic perturbation are long in this case 1 my attempts to extract tectonic uplift rates from normalised steepness indices are likely to be flawed because topographic steady state has not yet been achieved

escarpment evolution on high elevation rifted margins insights derived from a surface processes model that combines diffusion advection and reaction experiments with a surface processes model of large scale 1 1000 km long term 1 100 m y erosional denudation are used to establish the controls on the evolution of a model escarpment that is related to the rifting of a continent the model describes changes in topographic form as a result of simultaneous short and long range mass transport representing hillslope diffusive processes and fluvial transport advection respectively fluvial entrainment is modeled as a first order kinetic reaction which reflects the credibility of the substrate and therefore the fluvial system is not necessarily carrying at capacity one dimensional and planform models demonstrate that the principal controls on the evolution of an initially steep model escarpment are 1 antecedent topography drainage 2 the timescale or equivalently a length scale in the fluvial entrainment reaction 3 the flexural response of the lithosphere to denudation and 4 the relative efficiencies of the short and long range transport processes when rainfall and substrate lithology are uniform a significant amount of discharge draining over the escarpment top causes it to degrade only when the top of the model escarpment coincides with a drainage divide can escarpment retreat occur for these conditions an additional requirement for retreat of a model escarpment without decline is a long reaction time scale for fluvial entrainment this corresponds to a substrate that is hard to detach by fluvial erosion and therefore to fluvial erosion that is not transport limited continuous backtilting of an escarpment due to flexural isostatic uplift in response to denudational unloading helps maintain the scarp top as a divide it is essential if the escarpment gradient is to be preserved during retreat in a uniform lithology low flexural rigidities promote steep and slowly retreating escarpments for given rainfall and substrate conditions the morphology of a retreating model escarpment is determined by the ratio of the short range diffusive and long range advective transport efficiencies a low ratio which is interpreted to correspond to a relatively arid climate and weathering limited conditions promotes steep sharp topped escarpments with straight main slopes and escarpment retreat occurs over a wide range of height scales a high ratio interpreted to correspond to a more humid temperate climate produces a convex upper slope and concave lower slope morphology and only major escarpments are predicted to preserve a high scarp gradient lithological contrasts in the model produce more complex morphologies and predict the formation of scarps crowned by an erosionally resistant caprock however resistant caprocks are not an essential requirement for model scarps to retreat we conclude that the inferred controls and model behavior are both consistent with the present day morphology of rifted continental margins and with modern conceptual models of landscape evolution

accommodating large scale intracontinental extension and compression in a single stress field a key example from the baikal rift system the baikal rift system in southern siberia is one of the main intracontinental extensional features on earth the rift system represents the northwestern boundary of the amuria plate and in that respect can be considered as an evolving plate boundary the baikal rift system has been widely studied both in terms of geology and geophysics and many models have been proposed for its formation and evolution however the age of the initiation of deformation and the mechanism driving this deformation are still largely debated while major extension has occurred since the late miocene pliocene the onset of extension seems older than the india asia collision implying that several driving mechanisms may have acted together or in relay through time in this work we review the available data and models for deformation in an area encompassing the baikal rift system the sayan ranges to the west and the transbaikal to the east using a synthesis of this data and our own field and mapping observations we show that the baikal rift system along with transpressional deformation in the sayan ranges and transtension in the transbaikal area can be explained through major left lateral strike slip systems the deformation is strongly controlled by inherited crustal and lithospheric structures and is distributed over a wide area within the western amuria plate that consequently cannot be considered as a rigid block such distributed deformation is likely to have a strong effect on the structure of the future continental margin if extension evolves towards the formation of oceanic crust

geometry of the pamir hindu kush intermediate depth earthquake zone from local seismic data 1 we present new seismicity images based on a two year seismic deployment in the pamir and sw tien shan a total of 9532 earthquakes were detected located and rigorously assessed in a multistage automatic procedure utilizing state of the art picking algorithms waveform cross correlation and multi event relocation the obtained catalog provides new information on crustal seismicity and reveals the geometry and internal structure of the pamir hindu kush intermediate depth seismic zone with improved detail and resolution the relocated seismicity clearly defines at least two distinct planes one beneath the pamir and the other beneath the hindu kush separated by a gap across which strike and dip directions change abruptly the pamir seismic zone forms a thin approximately 10 km width curviplanar arc that strikes east west and dips south at its eastern end and then progressively turns by 90 to reach a north south strike and a due eastward dip at its southwestern termination pamir deep seismicity outlines several streaks at depths between 70 and 240 km with the deepest events occurring at its southwestern end intermediate depth earthquakes are clearly separated from shallow crustal seismicity which is confined to the uppermost 20 25 km the hindu kush seismic zone extends from 40 to 250 km depth and generally strikes east west yet bends northeast toward the pamir at its eastern end it may be divided vertically into upper and lower parts separated by a gap at approximately 150 km depth in the upper part events form a plane that is 15 25 km thick in cross section and dips sub vertically north to northwest seismic activity is more virile in the lower part where several distinct clusters form a complex pattern of sub parallel planes the observed geometry could be reconciled either with a model of two sided subduction of eurasian and previously underthrusted indian continental lithosphere or by a purely eurasian origin of both pamir and hindu kush seismic zones which necessitates a contortion and oversteepening of the latter

dip moveout error in transversely isotropic media with linear velocity variation in depth levin 1990 modeled the moveout within common midpoint cmp gathers of reflections from plane dipping reflectors beneath homogeneous transversely isotropic media for some media when the axis of symmetry for the anisotropy was vertical he found departures in stacking velocity from predictions based upon the familiar cosine of dip correction for isotropic media here i do similar tests again with transversely isotropic models with vertical axis of symmetry but now allowing the medium velocity to vary linearly with depth results for the same four anisotropic media studied by levin show behavior of dip corrected stacking velocity with reflector dip that for all velocity gradients considered differs little from that for the counterpart homogeneous media as with isotropic media traveltimes in an inhomogeneous transversely isotropic medium can be modeled adequately with a homogeneous model with vertical velocity equal to the vertical rms velocity of the inhomogeneous medium in practice dip moveout dmo is based on the assumption that either the medium is homogeneous or its velocity varies with depth but in both cases isotropy is assumed it turns out that for only one of the transversely isotropic media considered here shale limestone would v z dmo fail to give an adequate correction within cmp gathers for the shale limestone more fortuitously the constant velocity dmo gives a better moveout correction than does the v z dmo less

late quaternary tectonics of the vallo di diano basin southern apennines italy italian ministry of university and research project firb research and development of new technologies for protection and defence of territory from natural risks w p c3 crustal imaging in italy

sedimentation processes and new age constraints on rifting stages in lake baikal results of deep water drilling with this paper we present a first attempt to combine the direct results on lithology composition and age dating in the boreholes bdp 93 bdp 96 and bdp 97 with geological and seismic data from the areas where those sections were drilled the sedimentary environments represented by the bdp boreholes are markedly different and possess characteristic lithological features the results of the deep drilling provide the essential means for testing numerous age models used in geological reconstructions of the lake baikal rifting dynamics neither the basin wide unconformity interpreted from seismic data nor the interpreted change from shallow water to deep water facies at the boundary of the seismic stratigraphic complexes were found in the bdp 96 boreholes on academician ridge also lithology does not support the proposed reconstructions of intense lake level fluctuations and transgressions during the pliocene at academician ridge the continuous deep water hemipelagic sedimentation at academician ridge has existed for the past 5 ma the beginning of an intense rifting phase of the neobaikalian sub stage and related drastic changes in sedimentation processes were interpreted on seismic sections as the basin wide unconformity b10 different age estimates for this boundary ranged from late pliocene 3 5 ma to plio pleistocene boundary as shown by bdp 96 borehole b10 is associated with a lithological change from diatomaceous ooze to dense silty clay and not with an erosional contact the new age for this boundary in bdp 96 is approximately 2 5 ma this new age constraint suggests that the upper sedimentary strata of northern baikal 1 5 1 7 km thick have formed during the past 2 5 ma with average sedimentation rates of 60 70 cm ka the bdp 93 boreholes at buguldeika suggest that uplift in primorsky range took place prior to 1 07 1 31 ma a date which exceeds the age of previous geological models