strain partitioning in the northern walker lane western nevada and northeastern california abstract paleomagnetic studies constrain both the kinematics and the timing of neogene intracontinental strain in the walker lane of northwestern nevada northeastern california the northwest trending walker lane is a zone of complex faulting and dextral offset along the boundary between the sierra nevada and the basin and range here an extensive tertiary volcanic section provides a paleomagnetic test for vertical axis rotation the 25 1 ma nine hill tuff covered the two structural domains of northern walker lane and parts of the adjacent provinces in the northernmost domain the pyramid lake domain the nine hill tuff is unrotated or rotated slightly counter clockwise in contrast nine hill tuff is rotated 35 44 clockwise in the northeastern part of the adjacent carson domain usable exposures of the tuff are lacking elsewhere in the carson domain but 9 13 ma basalts record 37 51 clockwise vertical axis rotation these basalts were sampled at three sites encompassing the n s length of the carson domain younger basalts from the carson domain show smaller clockwise rotations the paleomagnetic studies show that the deformation in the northern walker lane is partitioned into domains dominated by translation rotation and extension dextral slip along the walker lane is accommodated primarily by northwestward translation in the pyramid lake domain and by clockwise vertical axis rotation in the carson domain some neogene extension is also accommodated in the walker lane but most of it is occurring to the west of the walker lane along the edge of the sierra nevada comparison of paleomagnetic results from rocks of different ages constrains the timing of the present deformation regime in the walker lane the similar rotations recorded in 25 ma and 9 13 ma rocks indicates that virtually all of the rotation in the carson domain occurred after the eruption of the 9 13 ma basalts smaller rotations recorded in younger rocks constrain rotation rate

paleomagnetism of early paleogene marine sediments in southern tibet china implications to onset of the india asia collision and size of greater india article i nfo we report a paleomagnetic study of paleocene marine sediments in the gamba area of the tethyan himalayan terrane southern tibet which aims to accurately locate the position of the northern margin of greater india and further constrain timing of initial contact between india and asia following detailed rock magnetic and paleomagnetic experiments on a total of 675 drill core samples collected from the zongpu and upper jidula formations characteristic remanent magnetizations chrms were successfully isolated from most samples following alternating field af or integrated thermal and af demagnetization the chrms are of dual polarity and pass fold and reversal tests indicating a pre folding origin together with detailed biostratigraphic investigation of the sampling section a magnetic polarity sequence is constructed from data at 167 sampled horizons and satisfactorily correlates with polarity chrons c24r to c27r dating the zongpu formation between 56 2 and 61 8 ma on the geomagnetic polarity time scale the chrm directions from the zongpu formation are grouped stratigraphically into 33 sites and yield two paleopoles of 71 6 n 277 8 e a95 2 5 and 67 3 n 266 3 e a95 3 5 for the time intervals comprising 56 to 59 ma and 59 to 62 ma respectively these new paleopoles imply that the tethyan himalayan terrane was sited at low latitudes in the northern hemisphere during the interval 62 56 ma suggestingthatinitial contact between thetethyanhimalayaand lhasa terranes was established before60 5 1 5 ma and verylikelyoccurred nearthecretaceous tertiary boundary at least in the central partof the suturezone the results alsoindicate that atleast 1500 480 kmof post collisionalcrustal shortening occurred within the himalayas from the analysis of available paleomagnetic data obtained on both sides of the suture zone we propose a conceptional collision model for the india asia collision

anisotropy of magnetic susceptibility of eocene and miocene sediments in the qaidam basin northwest china implication for cenozoic tectonic transition and depocenter migration the cenozoic evolution of the qaidam basin especially its paleostress field can provide a better understanding of the dynamistic process of the northern tibetan plateau under certain conditions anisotropy of magnetic susceptibility ams holds great potential for investigating early tectonic events even where macroscopic and microscopic evidence of deformation is invisible a basin scale ams study of the middle to late eocene xiaganchaigou formation and the early to middle miocene xiayoushashan formation from seven locations was conducted covering most outcrops of these two formations within the qaidam basin in the western qaidam basin principal stress directions inferred from ams ellipsoids consist with those inferred from fold axial traces while at eboliang and in the northern qaidam basin most principal stress directions reflected by ams ellipsoids are different from those reflected by fold axial traces two epochs of compressive strain have been identified an early n s strain no later than oligocene and a late ne sw strain since miocene the early n s compression is more intense in the northern qaidam basin than that in the western qaidam basin while the late ne sw compression which dominates the modern nw se trending fold axial traces is more intense in the western qaidam basin than that in the northern qaidam basin the stress transfer provides a reasonable explanation for the southeastward migration of the deposition center in the qaidam basin during cenozoic moreover the appearance of e component compression may be in close relationship with the beginning of the left lateral strike slip kunlun fault or the eastward channel flow to the south of the kunlun fault

effects of geology and human activity on the dynamics of salt water intrusion in three coastal aquifers in southern spain mathematical modelling of salt water intrusion processes in three aquifers on the southern coast of spain rio verde rio velez and castell de ferro reveals that although all three systems are subject to the same climate and seasonal over exploitation geological and human factors have very different effects on the dynamics of contamination in the rio verde aquifer the most important influence is the high volume of extractions occurring during the dry season in rio velez the intrusion is strongly controlled by infiltration of water from the river to the aquifer and in the castell de ferro system an intensely karstified carbonate massif lying in contact with both the sea water and the detrital aquifer represents the main entrance point for influx of sea water and subsequent washing of the aquifer we have undertaken a mathematical simulation of various possible measures to counteract intrusion according to the specific characteristics of the process in each aquifer these measures include artificial recharge use of natural recharge from the river as a hydraulic barrier and the construction of a low permeability barrier

late quaternary to decadal velocity fields in asia 1 fields of crustal velocity and strain rate within asia averaged over horizontal distances of 300 km are calculated from estimates of quaternary slip rates on faults and rates of change of lengths of baselines between gps sites the calculated fields fit strain rate components estimated from quaternary slip rates within 95 confidence limits and fit the gps data with an rms residual of 2 5 mm yr 1 the strain rate field constrained only by quaternary slip rates of faults differs from the combined solution at the level of 20 nstrain yr 1 and the differences are explicable by the limited accuracy of geological estimates of slip rate therefore the strain rate fields determined by geodetic measurements taken on the 10 year timescale are consistent with geological observations on the 104 year timescale the combined solution for velocities shows plate or block like motion within deforming asia only in tarim south china and the amurian region elsewhere the kinematics of rigid blocks does not provide a useful description of the motion in particular velocities relative to eurasia point at high angles to contours of their magnitudes not parallel to them as they would if large regions moved as rigid blocks the axes of principal horizontal compressional strain align with topographic gradients in agreement with previous suggestions that asia deforms as a continuum under the influence of gravity

dispersion patterns of the ground roll in eastern saudi arabia seismic surveys on land must be designed so that the source generated noise such as ground roll is preferentially attenuated before p wave signal amplification and recording the correct specification of spatial and frequency filters requires prior knowledge of the noise properties in the area we show that the strong rayleigh wave component of source generated noise has a wavelength range which is predictable on a regional scale using widespread p wave velocity measurements in shallow upholes this predictive capability decreases the number of noise analyses required to map the boundaries between areas with different rayleigh wave properties the case history presented is for northeastern saudi arabia an area of roughly 150 000km2 the data comprise 80 noise analyses and a data base of over 10 000 up hole measurements of p wave velocities supplemented by maps of topography and geologic outcrops examples show that the frequency wavenumber transforms of time offset records can be interpreted in detai

geophone array formation and semblance evaluation the performance of a variety of areal geophone arrays was evaluated using seismic data recorded on a dense receiver grid in a walkaway survey conducted in the permian basin of west texas surface waves trapped waves and scattered energy have long been recognized as a significant noise problem in this area arrays were formed by extracting sets of traces from the main data set and stacking them to produce individual traces of a receiver gather we calculated semblance of each receiver gather to evaluate array performance high values of semblance indicate that an array effectively removes surface waves while preserving reflections differences in data quality associated with variations in geophone array design are often subtle and difficult to discern through simple inspection of field records by calculating frequency dependent semblance we were able to detect and quantify differences in array performance

exploring the interplay between infiltration dynamics and critical zone structures with multiscale geophysical imaging a review abstract infiltration is the process of water entering into and routings through the subsurface it has a profound impact on water flux in the earth s critical zone cz influencing phenomena such as overland flow stream generation plant available water and groundwater recharge as well as the associated cz processes and functions of weathering erosion slope stability and food production however reliable measurement of infiltration in structured geomedia soils and regolith with hidden subsurface features remain challenging the increasing availability of geophysical techniques has helped them emerge as viable options for minimally invasive determination of infiltration at the pedon to hillslope or catchment scales geophysical methods replace the educated guesswork of interpreting field data from traditional infiltrometers with direct visualization and quantification this paper provides a comprehensive literature review of various applications of geophysical techniques used to 1 visualize infiltration relevant structures 2 monitor non uniform or preferential infiltration patterns and 3 map soil moisture distribution after infiltration it then proposes a new conceptualization form and function dualism for subsurface hydrology to link preferential infiltration to cz structures with the goal of formulating more realistic infiltration theories related to subsurface structural heterogeneity the characterization of both subsurface structures form and infiltration dynamics function via geophysical imaging should help infiltration models currently emphasizing macroscale behaviors rooted in the continuum concept expand to accommodate the microscale nature of preferential flow integrating multiple geophysical approaches and developments into the new generation of geophysical techniques will further enhance our ability to see into the fabric of the subsurface and capture the dynamics of non uniform infiltration through the hidden half of the cz this approach offers exciting opportunities for understanding the complex interactions between cz structures and cz processes

radiocarbon dated sediment sequences from the belgian coastal plain testing the hypothesis of fluctuating or smooth late holocene relative sea level rise the late holocene deposits of the coastal lowlands bordering the southern north sea were formed by a renewed expansion of the tidal environment replacing freshwater peats the sea level history during the last 2500 years inferred from the post peat deposits containing little to no datable organic material is characterized by two conflicting schools of thought the first one supports a smooth sea level curve the second approach underpins fluctuating sea level changes the fluctuating approach also uses facies variations recorded in the post peat deposits to provide a chronostratigraphical subdivision linked to transgressions and regressions this paper examines the controlling factors responsible for the facies variations in the post peat deposits in order to test the approach of the fluctuating sea level the results of sedimentological investigation coupled with radiocarbon dates of intertidal shells from four shallow outcrops located in nearby sand filled late holocene tidal channels in the belgian

cenozoic structural inversion from transtension to transpression in yingxiong range western qaidam basin new insights into strike slip superimposition controlled by altyn tagh and eastern kunlun faults abstract a cenozoic structural inversion event from transtension to transpression involving salt tectonics has been uncovered in the yingxiong range the western qaidam basin seismic reflection data show that there are two common structural styles in the yingxiong range 1 the positive flower structure 2 the thrust controlled fold at shallow depth and the positive inverted flower structure at deep levels which are separated by a salt layer in the upper xiaganchaigou formation the yingxiong range experienced a first stage of transtension in the eocene induced by the altyn tagh fault and a second stage of transpression from the early miocene to present jointly controlled by the altyn tagh and eastern kunlun faults the eocene transtension produced numerous nw striking right stepping en echelon transtensional normal faults or fractures in the yingxiong range at the same time evaporites and mudstone were deposited in the vicinity of these faults in the early miocene the eocene transtensional normal faults were reactivated in a reverse sense and the thrust controlled folds at shallow depth started to form simultaneously with transpression enhanced in the late cenozoic positive flower structures directly formed in places without evaporites the cenozoic transtension to transpression inversion of the yingxiong range is the result of strike slip superimposition controlled by the altyn tagh and eastern kunlun faults in time and space

saline intrusion and refreshening in a multilayer coastal aquifer in the catania plain sicily southern italy dynamics of degradation processes according to the hydrochemical characteristics of groundwaters the catania plain is a large alluvial depression which represents one of the most important hydrogeological units in eastern sicily a detailed hydrochemical and hydrogeological investigation focussed on its north eastern corner has provided new insights into the past and present relationship between freshwater and seawater in shallow and deep aquifers according to hydrochemical data over the last centuries the area has been affected by local variations of the sea level giving rise to sequential processes of re equilibration of the exchangeable complex involving freshwater and seawater in both surficial and deep aquifers these ongoing processes consist in the refreshening of both deep aquifers 500 m from the shoreline and to a lesser extent due to lower freshwater influx shallow aquifers in the former case there is a shift of the groundwater compositions towards the na hco3 type and a significant drop in the salt contents while in the latter case the salt contents do not drop significantly at a distance 500 m from the shoreline the exchangeable complex of deep aquifers is presently subject to salinization according to the temporal variabilities in the hydrochemical data over the period 1995 96 the apparent dualism can be attributed to a general worsening of the current freshwater seawater relationship in deep aquifers this new tendency appears to be related to a sharp increase in water consumption by the local industrial plant which has reversed the natural refreshening tendency giving rise to a new saline intrusion that is particularly severe close to the shoreline

the estimation of fault slip from map data the separation pitch diagram although an essential feature of faults is that they produce a relative movement of two blocks the total or net slip is known only for a very small percentage of faults this note proposes a diagram for the graphical determination of net slip from the strike separation of markers recorded on geological maps with or without knowledge of the net slip direction the strike separation of one marker allows the drawing of a solutions line on the diagram depicting the range of slip vectors compatible with the measured separation the net slip vector can be obtained by either the intersection of two or more solutions lines or from a single solutions line if the direction of slip is independently known the diagram gives a visual appreciation of the effects of data uncertainty on the estimate of net slip and is a useful device for the representation of the kinematic characteristics of a collection of faults the use of the diagram is illustrated with examples from the south wales coalfield and the moine thrust zone

dissipation of fast strike slip faulting within and beyond northeastern tibet structural patterns global positioning system gps velocities and quaternary fault slip rates in northeastern tibet indicate a transfer of left lateral slip from the kunlun fault northeast to the haiyuan fault and minor crustal shortening and rotation within a 200 km wide stepover zone related deformation also continues at least a few hundred kilometers north of the haiyuan fault into a region of diffuse extensional shear or rotation underlain by average thickness crust fast localized slip along the central kunlun fault transforms into distributed deformation across a 500 km wide zone where the lower crust is weak the distribution of fault parallel gps velocities across this region suggests a decrease in fault slip toward eastern fault tips and progressive dissipation of slip to the north rather than east of the tibetan plateau as previously suggested

analogue modelling of intraplate strike slip tectonics a review and new experimental results abstract intraplate strike slip zones commonly display intricate 3 d geometries with rapid changes in structural style along strike and with depth strike slip deformation typically results in complex vertical and horizontal sections that can be difficult to interpret coherently physical modelling of strike slip fault systems is a powerful and graphic tool to help in providing a unified picture of the evolution of strike slip zones with considerable spatial and temporal detail a large number of experimental studies have investigated different aspects of strike slip tectonics using materials such as dry sand wet clay or silicone the choice of analogue material and experimental design exerts a strong control on the structures that form in the model here we present a review of different experimental setups used to investigate intraplate strike slip tectonics from the classical riedel experiment to more sophisticated setups using brittle and viscous analogue materials we review our current understanding from models of distributed shear transtension transpression pull apart basins formed in releasing stepovers and popups formed in restraining stepovers in addition we present the results of two new experimental series that investigated 1 the effect of crustal weak zones on strike slip fault zone segmentation and 2 strike slip and transpressional reactivation of extensional basins

a direct comparison of emi data and borehole data on a 1000 ha data set abstract increasingly the frequency domain electromagnetic induction emi method is used to study soil properties and hydrological properties on different scales yet emi data are most often used as they are or with the low induction number approximation moreover reported studies have been fairly small

a new evaluation approach of world war one s devastated front zone a shell hole density map based on historical aerial photographs and validated by electromagnetic induction field measurements to link the metal shrapnel phenomenon since the end of world war one only few research is performed to understand the extent of the destruction of the first meters of soil archive at the former belgian front zone the only existing sources identifying the by artillery destroyed landscape are maps indicating destruction at the level of administrative communities based on war damage inventories even a century after the war there is a need to gain more detail in the historical destruction at a landscape or parcel scale unlike in neighboring country france the belgian authorities allowed a complete repopulation of the front zone which results in an ongoing confrontation between ground workers farmers construction workers archaeologists etc the war s heritage trenches bunkers graves etc and its dangers unexploded ordnances uxo metal shrapnel and the high rate of unexploded shells up to 30 of the fired projectiles are typical remnants of this trench warfare the localization of these phenomena is also useful to simulate the extent of the war s environmental impact and the intensity of possible uxo finds to inventorize destruction and the related metal shrapnel pollution msp we propose a new mapping method based on a sampling strategy to digitize shelling densities derived from historical aerial photographs this data source allows us to characterize almost every single parcel in this mainly agricultural area by classifying the derived shelling densities destruction classes can be distinguished to describe the impact on landscape and soil archive the translation of the destruction map into a map indicating the level of buried metal shrapnel was possible due to the direct relation between shells metal shrapnel and shell holes a validation with the buried metal objects was performed with metal parameters derived from electromagnetic induction field surveys these scan results indicated a strong relation between shelling densities and the buried metal clutter based on the findings in this research we offer tools to create an accurate destruction map that can be directly related to the occurrence of ww1 relicts within the soil archive

transpressional salt tectonic system in western qaidam basin western china in this paper high resolution three dimensional seismic data are used to interpret a transpressional salt tectonic structure in the yingxiongling area qaidam basin china the geometries of the salt structure and the shizigou fault system that intersects it are precisely depicted the shizigou fault system is composed of suprasalt and subsalt components the suprasalt component is a y shaped reverse fault and the subsalt component is a complex flower structure in previous studies suprasalt and subsalt components were interpreted as two independent fault systems this paper proposes instead that the suprasalt and subsalt faults are kinematically related and decoupled across the salt layer

present day crustal motion within the tibetan plateau inferred from gps measurements 1 using the measurements of 726 gps stations around the tibetan plateau we determine the rigid rotation of the entire plateau in a eurasia fixed reference frame which can be best described by an euler vector of 24 38 0 42 n 102 37 0 42 e 0 7096 0 0206 ma the rigid rotational component accommodates at least 50 of the northeastward thrust from india and dominates the eastward extrusion of the northern plateau after removing the rigid rotation to highlight the interior deformation within the plateau we find that the most remarkable interior deformation of the plateau is a glacier like flow zone which starts at somewhere between the middle and western plateau goes clockwise around the eastern himalayan syntaxis ehs and ends at the southeast corner of the plateau with a fan like front the deformation feature of the southern plateau especially the emergence of the flow zone could be attributed to an eastward escape of highly plastic upper crustal material driven by a lower crust viscous channel flow generated by lateral compression and gravitational buoyancy at the later developmental stage of the plateau the first order feature of crustal deformation of the northeastern plateau can be well explained by a three dimensional elastic half space dislocation model with rates of dislocation segments comparable to the ones from geological observations in the eastern plateau although gps data show no significant convergence between the eastern margin of the plateau and the sichuan basin a small but significant compressional strain rate component of 10 5 2 8 nstrain yr exists in a relatively narrow region around the eastern margin in addition a large part of the eastern plateau northeast of the ehs is not undergoing shortening along the northeastward convergence direction of the ehs but is stretching

partitioning of oblique convergence coupled to the fault locking behavior of fold and thrust belts evidence from the qilian shan northeastern tibetan plateau oblique plate convergence is common but it is not clear how the obliquity is achieved by continental fold and thrust belts we address this problem in the qilian shan northeastern tibetan plateau using fieldwork observations geomorphic analysis and elastic dislocation modeling of published geodetic data a thrust dips ssw from the northern range front and underlies steeper thrusts in the interior cenozoic thrust related shortening across the qilian shan is 155 175 km based on two transects elastic dislocation modeling indicates that horizontal strain in the interseismic period is consistent with oblique slip on a single low angle detachment thrust below 26 km depth dipping ssw at 17o we suggest this detachment is located above north china block crust originally underthrust during paleozoic orogeny horizontal shear strain is localized directly above the up dip limit of creep on the detachment and is coincident with the left lateral haiyuan fault this configuration implies oblique slip on the detachment below seismogenic depths is partitioned in the shallow crust onto separate strike slip and thrust faults this is consistent with strain partitioning in oceanic subduction zones but has not previously been found by dislocation models of continental interiors the marginal strike slip altyn tagh fault influences thrusting within the qilian shan for 100 200 km from the fault but does not control the regional structure where paleozoic basement faults have been reactivated the qilian shan resembles the main tibetan plateau in nascent form active thrusts are marginal to an interior that is developing plateau characteristics involving low relief and low seismicity

marine and human activity influences on the groundwater quality of southern korinthos area greece in this paper the groundwater quality of the southern part of korinthos region north east peloponnese is discussed the geology is characterized by a thick sequence of neogene marls alternating with sandstones overlain by superficial quaternary deposits the latter consist of a mixture of loose materials such as conglomerates marly sandstones sands and clay to silty sands the area is crossed by a fault system parallel to the coastline and the quaternary sediments have formed extended tyrrhenian marine terraces two aquifers have been identified in the area the first is unconfined and occurs within the quaternary sediments whereas the other is a deep confined aquifer occurring within the underlying neogene marl series analysis of hydrochemical evolution over the past 30 years has indicated significant deterioration of quality owing to seawater intrusion and nitrate pollution the various sources of pollution have rendered to a large extent shallow groundwater unsuitable not only for potable water supply but also for irrigation purposes however this is not the case for the deeper confined aquifer statistical analysis was used to explore the evolution of salinization during the years 1968 and 1998 in view of the alarming conditions caused by the documented groundwater quality deterioration the need for integrated water resources management is stressed to maintain the socio economic growth of the region studied copyright 2003 john wiley sons ltd

active deformation of asia from kinematics to dynamics using estimated strain rates across the actively deforming region of asia to infer variations in viscous stress it is shown that gradients of stress point uphill toward the center of tibet where gravitational potential energy per unit surface area reaches a maximum thus the dynamics of the deformation seem to obey the equation of creeping flow which expresses a balance between gradients in stress and the gravitational body force this balance in the region of the tibetan plateau yields an estimate of 10 22 pascal second for the average viscosity of the tibetan lithosphere which is only about 10 to 100 times greater than the viscosity of the convecting upper mantle

geochemical processes and solute transport at the seawater freshwater interface of a sandy aquifer geochemical processes occurring at a seawater freshwater interface were studied in a shallow coastal siliclastic aquifer containing minor amounts of calcite data were collected from 106 piezometers in a 120 m transect from the coastline and landward in the first 40 m from the coastline a wedge of saltwater is intruding below the freshwater aquifer the aquifer is strongly reduced with mineralization of organic matter by methanogenesis in the freshwater aquifer and sulfate reduction dominating in the most seaward part of the saline aquifer the spatial separation of cations in the aquifer indicated a slow freshening process where ca2 from freshwater displaced the marine cations na and mg2 from the exchanger complex the resulting loss of ca2 from solution decreases the saturation state for calcite and possibly causes calcite dissolution a storm flooding event was recorded where pulses of dense seawater sank through the fresh aquifer as a result the terminal electron accepting process switched from methanogenesis to sulfate reduction the pulses of sinking seawater also triggered cation exchange reactions where ca2 was expelled from the exchanger by seawater na and mg2 the released ca2 is being flushed from the aquifer by groundwater flow and this export of ca2 will in the long term cause decalcification of the sediment the water composition in the aquifer is in a transient state as the result of various processes that operate on different timescales oxidation of organic matter occurs continuously but at a rate decreasing on a geological time scale the freshening of the aquifer operates on the timescale of a few years the episodic flooding and sinking of seawater through the aquifer proceeds in the course of days to weeks but occurs irregularly with years in between

structural deformation pattern within the nw qaidam basin in the cenozoic era and its tectonic implications abstract the qaidam basin is located in the northeastern tibetan plateau and provides an excellent field laboratory in understanding the history and mechanism of the plateau growth it deformed widely over the northwest during the cenozoic but with little thrust loading along the margins where no foreland depression is observed based on satellite images seismic and borehole data we investigated the structural deformation pattern including the structural style and timing of deformation and its formation mechanism within the northwestern qaidam basin during the cenozoic era mapping of surface geology shows that the modern qaidam basin is characterized by five se trending anticlinal belts each belt consists of several right step en echelon anticlines with plenty of normal and strike slip faults crossing the crests those anticlines are generally dominated by double fault systems at different depths an upper thrust fault system controlling the anticlines identified on the surface and a lower dextral transpressional fault system characterized by typical flower structures they are separated by weak layers in the upper xiaganchaigou or the shangganchaigou formations the upper system yields shortening strain 2 5 times larger than that of the lower system and the additional strain is interpreted to be accommodated by hinge parallel elongation in the upper system growth strata indicate that deformation within the qaidam basin initiated in the middle miocene 15 ma and accelerated in the late miocene 8 ma a simple riedel p shear model is used to explain the deformation mechanism within the northwestern qaidam basin

groundwater chemistry patterns in the phreatic aquifer of the central belgian coastal plain the holocene geological evolution of the belgian coastal plain is dominated by a transgression of the north sea silting up of the coastal plain and human intervention impoldering this has led to a typical pattern in groundwater quality which is discussed here for the central part of the coastal plain therefore a database with available groundwater samples is composed water type according to the stuyfzand classification is determined and different hydrosomes and their hydrochemical facies are identified based on this the origin and evolution of the water types is explained using piper plots and geochemical calculations with phreeqc before the impoldering salinising and freshening conditions alternated with a general salinisation of the aquifer after about 3400 bp this results in a dominance of brackish and salt nacl subtypes which are still found in the deeper part of the aquifer the subsequent impoldering resulted in an major freshening of the aquifer leading to nahco3 mghco3 and cahco3 subtypes overall mixing cation exchange carbonate mineral dissolution and oxidation of organic matter are identified as the major processes determining the general water quality the close link between geological evolution water quality and what is still observable today is illustrated with this example of the belgian coastal plain

cenozoic deformation history of the qaidam basin nw china results from cross section restoration and implications for qinghai tibet plateau tectonics abstract the deformation and uplifting history of the qinghai tibet plateau is a controversial issue and so far there has been insufficient evidence for interpretation investigations of the cenozoic deformation in the northeastern edge of this plateau may provide some relevant information in this paper the cenozoic deformation history of the qaidam basin has been studied based on results from the balanced cross section restoration of six geological sections they indicate that 1 the qaidam basin has been undergoing continuous shortening since the beginning of cenozoic with two relatively fast shortening phases the first during 42 8 40 5 ma and the second during 2 8 ma present 2 the shortening rate of the qaidam basin reached its maximum value since 2 8 ma and approximately 32 of the average total cenozoic shortening took place in this period and 3 the shortening of all sections reached approximately 50 of their respective total shortening by miocene the cenozoic deformation history of the qaidam basin shows good synchroneity with uplifting history of the qinghai tibet plateau it is therefore proposed that the deformation and uplifting in the south and north edges of the qinghai tibet plateau was almost synchronous with the altyn tagh fault formed at the beginning of india asia collision accordingly it is postulated that since the india asia collision at the beginning of cenozoic the indian plate moved northward continuously with two relatively fast phases the first during 42 8 40 5 ma and the second during 2 8 ma present approximately 50 of the total cenozoic northward displacement of the indian plate of the total amount of crustal shortening and uplifting of the qinghai tibet plateau and of the total cenozoic strike slip displacement of the altyn tagh fault were probably reached by the early miocene moreover another 30 40 might have taken place during 2 8 ma present the periods during 42 8 40 5 ma and during 2 8 ma present may also be the two fast phases for crustal shortening and uplifting of the qinghai tibet plateau and strike slip displacement of the altyn tagh fault

reconstructing the paleotopography beneath the loess cover with the aid of an electromagnetic induction sensor abstract during the last glacial period weichselian wind blown loess was deposited over the undulating landscape of central belgium which had been formed in surfacing tertiary marine sediments since valleys were filled up with a thicker loess layer than hill tops the present topography is much smoother this smoothing was enhanced by subsequent erosion processes reconstructing the paleolandscape at a detailed scale is almost impossible by conventional procedures based on soil augerings therefore the use of the electromagnetic induction sensor em38dd was evaluated as an alternative for mapping the depth to the tertiary clay substrate on our 2 7 ha study site located in the loess belt of central belgium a strong non linear relationship r 2 0 86 was found between the apparent electrical conductivity eca measured by the vertical dipole orientation of the em38dd and the depth to a tertiary clay substrate these predictions were validated by independent observations of the depth to the tertiary clay and a correlation coefficient of 0 83 with an average error of 0 22 m was found so our dense eca measurements 2 by 2 m resolution allowed us to build a three dimensionall surface of the depth to the tertiary substrate reconstructing the paleotopography beneath the loess cover this paleotopography revealed distinct erosion patterns on the surface of the tertiary clay the continuity of these was confirmed by an analysis of surface flow patterns conducted on the reconstructed paleotopography the non invasive time and cost effective electromagnetic induction sensor was found to offer new perspectives to reconstruct and analyse in detail the quaternary paleotopography beneath the loess cover

measurement of interseismic strain across the haiyuan fault gansu china by insar the haiyuan fault is part of a major left lateral fault system at the northeastern edge of the tibet qinghai plateau two m8 earthquakes 1920 and 1927 occurred along the fault bracketing an unbroken section of the fault identified as the tianzhu seismic gap we use interferometric synthetic aperture radar data from descending orbits of the ers satellites acquired between 1993 and 1998 along two adjacent tracks covering the gap to measure the current surface movements and better understand the present day mechanical behavior of this fault section the analysis of the radar data involves first the combined correction of orbital errors and errors associated with the phase delay through the troposphere a subset of the data is then selected based on the analysis of the residual noise spectra for each pair of data the selected interferograms are stacked and the average phase change rate is converted in fault parallel velocity assuming that the ground movement is horizontal and parallel to the fault velocity maps from both tracks show a zone of high velocity gradient across the fault a few kilometers wide consistent with left lateral slip on the haiyuan fault the average velocity field from the two tracks in their overlapping area is well fit with a single screw dislocation model in an elastic half space the derived fault slip rate at depth 4 2 8 mm yr is consistent with recent gps results the corresponding shallow apparent locking depth 0 4 2 km can be explained by a current low stress accumulation on the fault due to creep almost on the entire fault plane however unless it is transient this creep would be paradoxical with the occurrence of past large earthquakes along this fault section as revealed by paleoseismology an alternative model implying both shallow creep in the brittle upper crust and deep aseismic slip beneath the seismogenic layer separated by a locked section would be consistent with insar observations and with the potential for large earthquakes on the fault as well a two dislocation model with slip at 5 mm yr beneath 15 km and a transient creep rate of 11 mm yr between 2 and 7 km fits the insar data however the width and creep rate of the shallow creeping zone and their possible along strike variations are still poorly resolved with the present data set

depth slicing of multi receiver emi measurements to enhance the delineation of contrasting subsoil features abstract mobile multi receiver electromagnetic induction sensors provide simultaneous readings of the apparent electrical conductivity eca from overlapping soil volumes therefore small contrasting features can be difficult to identify because they have a limited contribution to the bulk measurement especially if they are present in the subsoil i e beneath the topsoil integrating eca data from simultaneous measurements with multiple coil configurations has the potential to elucidate the variability within the soil profile as it enables modelling the electrical conductivity ec for distinct depth intervals therefore it was our objective to develop a methodology to enhance the delineation of contrasting subsoil features such as in filled gullies and archaeological features we selected a 3 5 ha study site where contrasting features were expected a three layered build up was taken as the initial ec slicing model after varying the interface depths the shallowest and deepest ec depth slice showed a clear minimum of their combined variances at interface depths of 0 36 m which corresponded to the ploughing depth and 0 86 m this implies that the ec depth slice in between these depths contained a demonstrably higher variability a sub area of 0 85 ha was completely excavated to a depth of 0 7 m revealing the subsoil features and the host material an automated edge detection algorithm showed that the ec depth slice was superior to any individual eca measurement for delineating the contrasting subsoil features therefore we concluded that depth slicing by integrating simultaneous eca signals from a multi receiver emi sensor clearly improved the identification of subsoil features

unveiling the prehistoric landscape at stonehenge through multi receiver emi abstract archaeological research at stonehenge uk is increasingly aimed at understanding the dynamic of the wider archaeological landscape through the application of state of the art geophysical techniques unprecedented insight is being gathered into the buried archaeological features of the area however applied survey techniques have rarely targeted natural soil variation and the detailed knowledge of the palaeotopography is consequently less complete in addition metallic topsoil debris scattered over different parts of the stonehenge landscape often impacts the interpretation of geophysical datasets the research presented here demonstrates how a single multi receiver electromagnetic induction emi survey conducted over a 22 ha area within the stonehenge landscape offers detailed insight into natural and anthropogenic soil variation at stonehenge the soil variations that were detected through recording the electrical and magnetic soil variability shed light on the genesis of the landscape and allow for a better definition of potential palaeoenvironmental and archaeological sampling locations based on the multi layered dataset a procedure was developed to remove the influence of topsoil metal from the survey data which enabled a more straightforward identification of the detected archaeology the results provide a robust basis for further geoarchaeological research while potential to differentiate between modern soil disturbances and the underlying sub surface variations can help in solving conservation and management issues through expanding this approach over the wider area we aim at a fuller understanding of the human landscape interactions that have shaped the stonehenge landscape

temporal and spatial patterns of cenozoic deformation across the qaidam basin northern tibetan plateau we conducted a systematic analysis of the temporal and spatial patterns of cenozoic deformation of the northeastern ne and southwestern sw parts of the qaidam basin the largest and thickest cenozoic sedimentary basin within the tibetan plateau by constructing balanced cross sections traversing the whole basin using high resolution seismic reflection data we found that that these two parts deformed synchronously with similar temporal patterns involving nearly constant ne sw contraction before c 2 5 ma and much more intense shortening possibly enhanced by fierce wind erosion since then however the spatial deformation patterns of these two areas differ markedly an eastward weakening trend in the sw part is not observed in the ne part we believe that this difference is due to their different boundary conditions this result places new constraints on the formation mechanisms of the northern tibetan plateau

cenozoic tectonic evolution of the qaidam basin and its surrounding regions part 3 structural geology sedimentation and regional tectonic reconstruction the qaidam basin is the largest topographic depression inside the tibetan plateau because of its central position understanding the tectonic origin of the qaidam basin has important implications for unraveling the formation mechanism and growth history of the tibetan plateau in order to achieve this goal we analyzed regional seismic reflection profiles across the basin and a series of thickness distribution patterns of cenozoic strata at different time slices the first order structure of the basin is a broad cenozoic synclinorium which has an amplitude ranging from 16 km in the west to 48 in the west to 15 s 1 to 1 3 10 17 s 1 the eastward decrease in upper crustal shortening requires a progressive shift in crustal thickening mechanisms across qaidam basin from dominantly upper crustal shortening in the west to dominantly lower crustal shortening in the east although sedimentation began synchronously at 65 50 ma across the entire basin the initiation ages of the southern and northern basin bounding structures are significantly different deformation started at 65 50 ma in the north and at 29 24 ma in the south this information and the existing inference that the uplift of the eastern kunlun range south of qaidam basin began after 30 20 ma imply that the paleogene 65 24 ma qaidam and hoh xil basins on both sides of the eastern kunlun range may have been parts of a single topographic depression 500 km wide in the north south direction between the qilian shan and fenghuo shan thrust belts in the north and south the development of this large paleogene basin in central tibet and its subsequent destruction and partitioning by the neogene uplift of the eastern kunlun range requires a highly irregular sequence of deformation possibly controlled by preexist ing weakness in the tibetan lithosphere

ground penetrating radar measurements of subsurface structures of lacustrine sediments in the qaidam basin nw china possible implications for future in situ radar experiments on mars abstract the stratigraphic profile of paleolakes on mars preserves a record of past climatic hydrological and sedimentary environment radar could be used to detect the structure and distribution of buried lacustrine sediments but orbiter radar sounders rarely detect the internal structure or the bottom of the ancient martian lake deposits future martian missions will employ ground penetrating radar gpr onboard rovers to investigate the shallow subsurface structure of paleolake basins in this case ground experiments are necessary to test the potential of gpr detection this study reports on gpr experiments operating at 100 mhz and 200 mhz carried out in the qaidam basin one of the analogue sites for martian paleolake environments to detect the subsurface structure of lacustrine sediments and measure the relative permittivity of sediments with both laboratory instrument and gpr data two gpr measurements were performed on top of yardangs representing layered lacustrine sedimentary outcrops another survey site is a polygonal patterned ground which is a common landform in the qaidam basin and on mars the observations revealed by gpr experiments show that 1 sediments of three sites have varied compositions density and porosity and have a wide range of relative permittivity values from 1 56 to 4 56 2 the detection depth of our measurements could reach 20 m 3 the interfaces between sedimentary layers can be seen in radargrams but reflectors in radargrams may not always match with exposed layers of the yardang outcrops due to the undetected change of permittivity values or thin thickness of layers 4 a distinct and continuous reflector is observed beneath the polygonal terrain which we interpret as a subsurface layer with low water brine content our ground experiments suggest that a similar gpr on martian rover could detect the near surface structure of lacustrine sediments e g deposition anomaly interfaces of drastic permittivity change such as buried ice brine considering that the design frequency is close to our equipment

hydrogeochemical analysis of salinization processes in the coastal aquifer of oropesa castellon spain the coastal aquifer of oropesa is affected by salinization processes undoubtedly associated with intense groundwater exploitation for agriculture supply the aquifer corresponds geologically to a tectonic depression with plioquaternary fill hydrogeologically this aquifer is detrital with intergranular porosity which receives substantial recharge from adjacent mesozoic aquifers contact with the sea in addition to the presence of cultivated soil requiring extreme exploitation of groundwater frequently give rise to processes of seawater intrusion the present research is an attempt to understand the saltwater intrusion in this aquifer using hydrochemical analyses of the behavior of certain minor ions that could help in the characterization process in the case of the oropesa sector groundwater salinization does not appear to be attributable solely to the intrusion of seawater but there are also anomalies related largely to the geology of the sector and its surroundings the type of recharge the hydrodynamic conditions in the specific area etc

tectonic history of the altyn tagh fault system in northern tibet inferred from cenozoic sedimentation the active left slip altyn tagh fault defines the northern edge of the tibetan plateau to determine its deformation history we conducted integrated research on cenozoic stratigraphic sections in the southern part of the tarim basin fission track ages of detrital apatites existing biostratigraphic data and magnetostratigraphic analysis were used to establish chronostratigraphy whereas composition of sandstone and coarse clastic sedimentary rocks was used to determine the unroofing history of the source region much of the detrital grains in our measured sections can be correlated with uplifted sides of major thrusts or transpressional faults implying a temporal link between sedimentation and deformation the results of our studies together with existing stratigraphic data from the qaidam basin and the hexi corridor suggest that crustal thickening in northern tibet began prior to 46 ma for the western kunlun shan thrust belt at ca 49 ma for the qimen tagh and north qaidam thrust systems bounding the north and south margins of the qaidam basin and prior to ca 33 ma for the nan shan thrust belt these ages suggest that deformation front reached northern tibet only 10 5 m y after the initial collision of india with asia at 65 55 ma because the aforementioned thrust systems are either termination structures or branching faults of the altyn tagh left slip system the altyn tagh fault must have been active since ca 49 ma the altyn tagh range between the tarim basin and the altyn tagh fault has been a long lived topographic high since at least the early oligocene or possibly late eocene this range has shed sediments into both the tarim and qaidam basins while being offset by the altyn tagh fault its continuous motion has made the range act as a sliding door which eventually closed the outlets of westward flowing drainages in the qaidam basin this process has caused large amounts of oligocene miocene sediments to be trapped in the qaidam basin the estimated total slip of 470 70 km and the initiation age of 49 ma yield an average slip rate along the altyn tagh fault of 9 2 mm yr remarkably similar to the rates determined by gps global positioning system surveys this result implies that geologic deformation rates are steady state over millions of years during continental collision

a block model of distributed deformation by faulting it is clear from palaeomagnetic evidence that large and hitherto unexpected rotations about a vertical axis are common in regions of distributed continental deformation we propose a simple two dimensional model to illustrate how fault movement and block rotation within a zone of distributed deformation may be related to the relative motion of the rigid plates that bound the zone one surprizing feature of this model is that the component of strike slip motion on the faults within the deforming zone is in the opposite sense to the strike slip component across the zone as a whole thus slip vectors within the zone are not the same as that between the bounding rigid plates in contrast to deformation at oceanic plate boundaries examples of active fault geometries similar to those of our model can be seen in greece iran and the western usa

oblique stepwise rise and growth of the tibet plateau two end member models of how the high elevations in tibet formed are i continuous thickening and widespread viscous flow of the crust and mantle of the entire plateau and ii time dependent localized shear between coherent lithospheric blocks recent studies of cenozoic deformation magmatism and seismic structure lend support to the latter since india collided with asia 55 million years ago the rise of the high tibetan plateau likely occurred in three main steps by successive growth and uplift of 300 to 500 kilometer wide crustal thrust wedges the crust thickened while the mantle decoupled beneath gently dipping shear zones did not sediment infilling bathtub like of dammed intermontane basins formed flat high plains at each step the existence of magmatic belts younging northward implies that slabs of asian mantle subducted one after another under ranges north of the himalayas subduction was oblique and accompanied by extrusion along the left lateral strike slip faults that slice tibet s east side these mechanisms akin to plate tectonics hidden by thickening crust with slip partitioning account for the dominant growth of the tibet plateau toward the east and northeast

can a primary remanence be retrieved from partially remagnetized eocence volcanic rocks in the nanmulin basin southern tibet to date the india asia collision paleomagnetic dating of the india asia collision hinges on determining the paleogene latitude of the lhasa terrane southern tibet reported latitudes range from 5 n to 30 n however leading to contrasting paleogeographic interpretations here we report new data from the eocene linzizong volcanic rocks in the nanmulin basin which previously yielded data suggesting a low paleolatitude 10 n new zircon u pb dates indicate an age of 52 ma negative fold tests however demonstrate that the isolated characteristic remanent magnetizations with notably varying inclinations are not primary rock magnetic analyses end member modeling of isothermal remanent magnetization acquisition curves and petrographic observations are consistent with variable degrees of posttilting remagnetization due to low temperature alteration of primary magmatic titanomagnetite and the formation of secondary pigmentary hematite that unblock simultaneously previously reported paleomagnetic data from the nanmulin basin implying low paleolatitude should thus not be used to estimate the time and latitude of the india asia collision we show that the paleomagnetic inclinations vary linearly with the contribution of secondary hematite to saturation isothermal remanent magnetization we tentatively propose a new method to recover a primary remanence with inclination of 38 1 35 7 40 5 95 significance and a secondary remanence with inclination of 42 9 41 5 44 4 95 significance the paleolatitude defined by the modeled primary remanence 21 n 19 8 n 23 1 n is consistent with the regional compilation of published results from pristine volcanic rocks and sedimentary rocks of the upper linzizong group corrected for inclination shallowing the start of the tibetan himalaya asia collision was situated at 20 n and took place by 50 ma

cenozoic tectonic evolution of asia a preliminary synthesis abstract asia has been a major testing ground for various competing models of continental deformation due to its relatively well understood plate boundary conditions in the cenozoic exceptional exposure of active structures and strain distribution and widespread syn collisional igneous activity as a proxy for the thermal state of the mantle and crust two cenozoic orogens dominate the continent the himalayan tibetan orogen in the east induced by the india asia collision and the turkish iranian caucasus orogen in the west induced by the arabia asia collision the development of the two orogens was accomplished by shortening in the early stage followed by strike slip faulting and extension in the late stage in the himalayan tibetan orogen shortening across two discrete thrust belts at 55 30 ma in southern and northern tibet created a large intracontinental basin the paleo qaidam basin in between subsequent crustal thickening and a possible thermal event in the mantle e g convective removal of central tibetan mantle lithosphere may have raised the elevation of this early intra plateau basin up to 2 3 km to its current height collision between india and asia also caused lateral extrusion of southeast asia between 32 ma and 17 ma the latest stage of the india asia collision was expressed by north trending rifting and the development of trench facing v shaped conjugate strike slip faults in central mongolia central tibet eastern afghanistan and southeast asia in the turkish iranian caucasus orogen early crustal thickening in the orogenic interior began at or prior to 30 20 ma this style of deformation was replaced by strike slip faulting at 15 5 ma associated with further northward penetration of arabia into asia westward extrusion of the anatolia turkey block and rapid extension across the sea of crete and sea of aegean the late stage extension in both orogens was locally related to extensional core complex development the continental margin extension of east asia was developed in two stages initially in a widely distributed zone that has an east west width of 500 800 km during 65 35 ma which was followed by localized extension and opening of back arc basins associated with the development of spreading centers at 32 17 ma e g japan sea or east korea sea bohai bay and south china sea opening of the back arc basins could be induced by 1 rapid eastward migration of the western pacific trench system or 2 oblique subduction of pacific plate beneath asia that had produced a series of en echelon right slip primary shear zones linking with back arc spreading centers oriented obliquely to the strike of the nearby trench since 15 ma the eastern margin of asia became contractional in the east west direction as indicated by the collapse of back arc basins in the western pacific and the development of fold thrust belts along the eastern continental margin coeval with the contraction is widespread east west extension in siberia north china and the tibetan plateau the above observations can be explained by a change in boundary condition along the eastern margin of asia that allowed the thickened asian continent to spread eastward causing east west extension in its trailing edge and east west compression in its leading edge in west asia continental margin extension started at about 25 20 ma in the aegean and cretan regions which was associated with a rapid southward retreat of the hellenic arc the complex evolution of cenozoic deformation in asia may be explained by a combined effect of temporal changes in plate boundary conditions thermal evolution of the upper mantle perturbed by collisional tectonics and the built up of gravitational energy through crustal thickening and thermal heating although the past research in asia has treated the india asia and arabia asia convergence as separate collisional processes their interaction may have controlled the far field cenozoic deformation in asia the most pronounced result of this interaction is the creation of a northeast trending 300 400 km wide and 1500 km long zone of northwest striking right slip faults which extends from the zagros thrust belt in the south to western mongolia in the north and links with the active tian shan and altai shan intracontinental orogens cenozoic deformation and coeval igneous activity spatially overlap with one another in the himalayan tibetan and turkish iranian caucasus orogens a large cenozoic magmatic gap exists between tibet in the south and mongolia in the north where cenozoic deformation has not been associated with any coeval igneous activity finally cenozoic igneous activity is always associated with jurassic cretaceous magmatic arcs suggesting a causal relationship between the early arc magmatism and later syn collisional magmatism

salinization processes in the unconfined aquifer of bou areg ne morocco a geostatistical geochemical and tomographic study hydrogeological and geochemical data in conjunction with the results of an electrical imaging tomographic survey were examined to determine the main factors and mechanisms controlling the groundwater chemistry and salinity of the unconfined aquifer of bou areg on the mediterranean coast of ne morocco in addition statistical and geochemical interpretation methods were used to identify the distribution of the salinity multivariate statistical analysis cluster and principal component factors revealed the main sources of contamination groups a b and c in the cluster analysis and factors 1 3 factor 1 ce cl k so42 and mg2 factor 2 ca2 hco3 and ph factor 3 no3 represent the signature of seawater intrusion in the coastal zone the influence of marly gypsum outcrops in the upstream zone and anthropogenic sources respectively the ionic delta the ionic ratio the saturation index and stuyfzand s method were applied to evaluate geochemical processes the results obtained indicate on the one hand the phenomenon of salinization in both the coastal and the upstream zones and on the other the dilution of groundwater by recharge cation exchange is shown to modify the concentration of ions in groundwater locally with respect to salinization processes in the coastal zone the results of electrical imaging tomography show that salinity increases both with depth and laterally inland from the coastline due to seawater intrusion

geochemical evolution and timescale of seawater intrusion into the coastal aquifer of israel this study is an attempt to quantify the geochemical processes and the timescale of seawater intrusion into a coastal aquifer from changes in the major ionic composition of the water and the natural distribution of the cosmogenic isotopes 14c and 3h for that purpose we sampled saline and brackish groundwaters from the israeli coastal aquifer a multilayer sampler mls was used to obtain very high resolution 10 cm profiles across the fresh saline water interface fsi the chemical and stable isotope data revealed three distinct water types end members that are located in different zones on the route to the coastal aquifer 1 slightly modified mediterranean seawater sws 2 slightly diluted with up to 20 fresh groundwater saline groundwater sds and 3 fresh groundwater fgw the sws samples generally show an excess of total alkalinity and total dissolved inorganic carbon dic and a depletion of 13cdic and 14cdic with respect to normal seawater indicating that anaerobic oxidation of organic matter is the first diagenetic reaction that affects seawater during its penetration into the bottom sediments sds waters appear when sws is slightly diluted gain ca2 and sr2 and is depleted in k suggesting that the main processes that transform sws into sds are slight dilution with fresh groundwater and cation exchange at the fresh saline water interface sds generally shows conservative mixing with fgw inspection of chemical data from coastal aquifers around the world indicates that intensive ion exchange in slightly diluted saline groundwater is a globally important phenomenon of seawater intrusion most of our saline groundwater samples contain substantial amounts of 3h suggesting that penetration of mediterranean seawater and its inland travel to a distance of 50 100 m onshore occurred 15 30 yr ago this is supported by the 14cdic mass balance that explains the relatively low 14cdic activities in the sds as influenced by diagenesis and not by simple radioactive decay

reconstructing palaeochannel morphology with a mobile multicoil electromagnetic induction sensor abstract field methods to map and reconstruct the morphology of buried river systems are highly dependent on spatial interpolation conventional methods such as standard borehole survey allow a detailed vertical reconstruction of the shallow subsurface but leave lateral connections between sample locations open to interpretation geophysical survey techniques have recently introduced more detail mobile electromagnetic induction emi survey combines high density sampling with full lateral coverage but fails to produce detailed information about vertical facies changes recently multicoil emi survey added vertical discrimination potential to this lateral continuity in this study we present an integrated approach for reconstructing the morphology of a known palaeochannel segment by modelling the depth to the sandy substrate in addition a calibration method based on a limited number of auger data is proposed in a first phase the modelling procedure was evaluated along two transects on a test site showing palaeochannel depths ranging from 1 to 4 m beneath the surface in a second phase the morphology of the entire site was reconstructed these three resulting depth models were then compared with auger observations and electrical resistivity tomography ert data the high correlation coefficients 0 9 between observed and modelled depths showed that even in complex pedological environments palaeochannel morphology could be predicted precisely using multicoil emi data therefore we concluded that a multicoil emi survey proves to be an efficient and reliable solution for mapping and reconstructing the morphology of the shallow subsurface

the growth of northeastern tibet and its relevance to large scale continental geodynamics a review of recent studies recent studies of the northeastern part of the tibetan plateau have called attention to two emerging views of how the tibetan plateau has grown first deformation in northern tibet began essentially at the time of collision with india not 10 20 myr later as might be expected if the locus of activity migrated northward as india penetrated the rest of eurasia thus the north south dimensions of the tibetan plateau were set mainly by differences in lithospheric strength with strong lithosphere beneath india and the tarim and qaidam basins steadily encroaching on one another as the region between them the present day tibetan plateau deformed and its north south dimension became narrower second abundant evidence calls for acceleration of deformation including the formation of new faults in northeastern tibet since 15 ma and a less precisely dated change in orientation of crustal shortening since 20 ma this reorientation of crustal shortening and roughly concurrent outward growth of high terrain which swings from nne ssw in northern tibet to more ne sw and even ene wsw in the easternmost part of northeastern tibet are likely to be in part a consequence of crustal thickening within the high tibetan plateau reaching a limit and the locus of continued shortening then migrating to the northeastern and eastern flanks these changes in rates and orientation also could result from removal of some or all mantle lithosphere and increased gravitational potential energy per unit area and from a weakening of crustal material so that it could flow in response to pressure gradients set by evolving differences in elevation

new paleomagnetic constraints on middle miocene strike slip faulting along the middle altyn tagh fault knowledge of the evolution of the altyn tagh fault atf has significant implications for our understanding of the tectonic deformation of the tibetan plateau controversy exists regarding the formation of the orocline like arcuate structures or curved thrust faults south of the atf in this paper we conducted a paleomagnetic rotation study of the akatengnengshan ak and youshashan yss anticlines to determine whether the changes in the anticlines axes were caused by frictional drag associated with sinistral strike slip faulting along the atf no significant paleomagnetic rotations during the last 20ma were observed at the xichagou and laomangai localities which are situated along the yss anticline whereas significant counterclockwise ccw rotations of similar to 50 degrees that occurred between similar to 16 2 and 11 1ma were noted at the yitunbulake locality which lies along the western edge of the ak anticline this amount of ccw rotation is consistent with the difference in axes between the ak and yss anticlines combined with other geological evidence we believe that the middle atf was active between similar to 16 and 11ma frictional drag associated with sinistral strike slip motion likely resulted in the similar to 50 degrees ccw rotation of the ak anticline which was originally straight or parallel to the yss anticline there was concentrated or insignificant strike slip faulting along the middle atf before similar to 16ma but rapid and distributed 40km strike slip faulting occurred between similar to 16 and 11ma at a rate of 10mm yr and the minimum displacement was similar to 50km

high resolution magnetostratigraphic study of the paleogene neogene strata in the northern qaidam basin implications for the growth of the northeastern tibetan plateau abstract the cenozoic terrestrial intermontane qaidam basin on the northeastern edge of the tibetan plateau contains 12 km of sedimentary rocks that potentially document the accommodation of india asia convergence and the growth of the plateau the chronology remains incomplete hindering cross basin correlation between lithostratigraphic units and their further interpretation here we present a high resolution magnetostratigraphy spanning 5 km of paleogene neogene sequence at dahonggou in the northern qaidam basin based on correlation with the geomagnetic polarity time scale gpts we have dated the section to being between 52 and 7 ma the bottom conglomeratic unit ranging from 52 ma to 44 ma was deposited in high energy environments e g alluvial fan or braided river reflecting the earliest deformation and uplift of the basin bounding qilian shan fold thrust belt in response to india asia collision in addition we identified two major increases in sedimentation rate at 25 16 ma and after 9 5 ma and three phases of lesser increases at 52 44 ma 38 33 ma and 14 6 12 0 ma these increases in sedimentation rate are consistent with regional thermochronology and basin analysis studies which revealed enhanced motion on basin bounding thrust faults we argue that these accelerated sedimentation rates indicate pulsed tectonism in the northeastern tibetan plateau the pulse at 25 16 ma may further relate to phases of strong rainfall linked to an intense monsoon at that time

slip rate gradients along the eastern kunlun fault 1 whether strike slip fault systems in eurasia accomplish eastward extrusion of tibetan crust and lithosphere depends largely on the kinematics of deformation at the fault tip here we present new slip rate determinations using millennial scale geomorphic markers from sites along the easternmost segment of the kunlun fault in north central tibet this fault system represents one of the major strike slip faults within the indo asian collision zone has been argued to exhibit uniform slip rates along much of its length and plays a central role in models for eastward extrusion of tibetan lithosphere displaced fluvial terrace risers along tributaries of the yellow river coupled with 14c ages of terrace material provide constraints on slip rates over late pleistocene to holocene time results indicate that slip rates decrease systematically along the eastern 150 km of the fault from 10 to 2 mm yr these data challenge the view that slip along the kunlun fault remains uniform along the entire length of the fault and instead reveal gradients in displacement similar to those expected at fault tips moreover slip along the fault appears to terminate within the thickened crust of the plateau and therefore any extrusion of tibetan lithosphere accomplished by slip along the kunlun fault must be absorbed by internal deformation of the plateau surrounding the fault tip

two stage evolution of the altyn tagh fault during the cenozoic new insight from provenance analysis of a geological section in nw qaidam basin nw china introductionthe 1600 km long active altyn taghfault atf de nes the northern edgeof the tibetan plateau links thewestern kunlun eastern kunlun andqilian orogenic belts fig 1a and gures prominently in constrainingthe timing mechanism and stress dis sipation of the tibetan uplift e g yinand harrison 2000 tapponnier etal 2001 cowgill et al 2003 aspectof its cenozoic evolution has beenattracting hot debate zhou and gra ham 1996 yue and liou 1999 yinet al 2002 liu et al 2007 and akey issue is the initiation of left slipmovement on the fault which wasconsidered to occur i during lateeocene early oligocene evidenced bythermochronology in the altynmountain chen et al 2001 andsedimentology adjacent to the fault meng et al 2001 yue et al 2001 ritts et al 2004 or ii since middlemiocene through structural analysisin the qaidam basin yuan et al 2008 wang et al 2010 apatite s sion track result along the atf wanet al 2001 chen et al 2002 andcomprehensive analysis of the north ern tibetan plateau burch el et al 1989 wang 1997 meyer et al 1998 yin et al 2002 argued a much earlierinitiation age 49 ma of the westernand central segments of the atf butwith questionable proofs ritts et al 2004 two factors probably lead tothis uncertainty i the atf is toolarge to allow us to nd an appropri ate proxy deciphering accurately itsevolution and ii most extant studiesshare a bias that the atf has beenalways a left slip fault during thecenozoic which we regard as a mis understanding in this paper provenance analysis has beenproved e ective on revealing theuplifting history of mountains andevolution of major faults e g lindseyet al 2007 miao et al 2008 linet al 2009 marsaglia et al 2010 the qaidam basin is the largest sed imentary basin inside the tibetan pla teau and accumulated thick terrestrialsediments during the cenozoic rieseret al 2006 making itself an idealplace for deciphering the uplift andpropagation of the plateau yin et al 2007 2008 as it is bounded by theatf to the northwest fig 1b itssedimentation has possibly been tiedto the development of this large scaleintracontinentalfault fewworkshavebeen done on this subject due to thetough geographic conditions in thispaper we investigated a geologicalsection spanning eocene pliocene inthe nw qaidam basin and analysedin detail provenance of the sediments we link the result to cenozoic evolu tion of the atf and try to illustrate together with some other evidences that the atf was used to be a basalshear zone before its initiation of left slip since middle miocene which rec onciles the two contrasting viewpointson the cenozoic initiation of the atfabovementioned geological settingthe study section is seated at thesouthern side of the atf and incisesthe western limb of the nw trendingganchaigou anticline bounded to thenorth by a north directed reversefault a branch fault of the atf fig 1c the cenozoic strata are wellexposed in the section including thexiaganchaigou xg shangganchai gou sg xiayoushashan xy shangyoushashan sy and shizigou szg formations in an ascendingorder the xg formation consists of redmudstone siltstone and sandstoneattaining bed thickness of 0 2 1 m interbedded with conglomerate andpebble sandstone layers 10 20 cmthick figs 2 and 3a the stratumeven comprises more than 100 mthick calcareous mudstones in theupper part in the drillhole chaishen 3 about 6 km east of the sectionabstract

northward growth of the qimen tagh range a new model accounting for the late neogene strike slip deformation of the sw qaidam basin abstract situated along the western termination of the eastern kunlun mountains the qimen tagh range represents a key area to understand the cenozoic basin range interactions between the northeastern tibetan plateau and the qaidam basin within that region several huge bow like fault systems such as the kunbei and qimen tagh fault systems accommodate the transpressive deformation but their kinematic evolution is still highly debated newly acquired seismic profiles and isopach maps of the late eocene sediments strongly suggest that the kunbei fault system consisting of the kunbei arlar and hongliuquan faults in the southwestern qadaim basin was initially a left lateral strike slip fault system rather than a thrusting system growth strata indicate an early miocene onset age for this strike slip deformation however earthquake focal mechanisms show that the present day tectonic pattern of this fault system is dominated by ne sw transpression as for the qimen tagh fault system numerous linear geomorphic features and fault scarps indicate that it was again a strike slip fault system deformed sediments within the adatan valley prove that strike slip motion prevailed during the pleistocene yet the present day deformation is marked by ne sw transpression collectively the kunbei and qimen tagh fault systems were initially left lateral strike slip fault systems that formed during early miocene and pleistocene respectively colligating with these southward younging left lateral strike slip faulting ages and the fact that these convex northward structures converge to the center segment of active kunlun fault in the east we thus considered the kunbei and qimen tagh fault systems as former western segments of the kunlun fault once located further south in the present day location of that fault these faults gradually migrated northward since the early miocene while their kinematics changed from left lateral strike slip motion to ne sw transpression

deformation within a strike slip fault network at westward ho devon u k domino vs conjugate faulting abstract a system of ne trending left lateral faults and nw trending right lateral faults at westward ho north devon u k cut steeply dipping 60 strata faults were accurately mapped in the field and from aerial photography and lateral separations of marker beds measured along the fault traces these data are used to examine the displacements within the network of interacting faults and to calculate variations in the density and relative proportions of the fault sets the displacements are also used in a tensor analysis of the strain and together with block rotations used to restore the deformation the results show a range of heterogeneity within the fault network both in terms of the fault patterns and strain some sub areas show a dominance of one fault set with regularly spaced larger displacements separating relatively weakly deformed blocks with smaller antithetic faults within these areas up to 20 rotation of the faults and bedding produces a domino style deformation that accommodates up to 15 extension the domino regions are separated by areas of conjugate faulting in which both sets of faults are equally developed and have similar displacement ranges conjugate areas have little or no rotation of the bedding and generally lower strains than domino regions

continental deformation accommodated by non rigid passive bookshelf faulting an example from the cenozoic tectonic development of northern tibet abstract collision induced continental deformation commonly involves complex interactions between strike slip faulting and off fault deformation yet this relationship has rarely been quantified in northern tibet cenozoic deformation is expressed by the development of the 1000 km long east striking left slip kunlun qinling and haiyuan faults each have a maximum slip in the central fault segment exceeding 10s to 100 km but a much smaller slip magnitude

transforming the miocene altyn tagh fault slip into shortening of the north western qilian shan insights from the drainage basin geometry although it has long been proposed that active crustal shortening within the qilian shan accommodates slip along the altyn tagh fault questions regarding the temporal and spatial amount of slip transfer remain debated traditional shortening calculations cannot yet be made accurately because the geology is not known well enough following the view that long linear drainage basins in the north western qilian shan developed in response to internal shortening associated with slip transfer along the altyn tagh fault we targeted this special irregular drainage basin geometry to develop an alternative way to estimate shortening we infer a total of 66 km of shortening in the western qilian shan with a north eastward decrease in the magnitude of shortening this 39 shortening strain is comparable to previous estimates estimates of dates of initiation support the view that significant shortening and topographical growth within the north western qilian shan occurred in post middle miocene time

paleomagnetism indicates no neogene vertical axis rotations of the northeastern tibetan plateau 1 paleomagnetic data were obtained from 108 paleomagnetic sites collected in cretaceous to tertiary red beds from seven localities distributed in three general regions adjacent to the altyn tagh fault at the northern edge of the tibetan plateau in the hexi corridor 12 sites in oligocene strata at yaoquanzi 39 97 n 97 68 e yield a mean paleomagnetic direction i 33 0 d 8 6 95 6 0 with concordant declination and 36 sites in early cretaceous mudstones of the longshou shan 39 09 n 100 50 e provide a concordant paleomagnetic direction i 53 4 d 6 8 95 3 8 across the nan shan fold thrust belt miocene paleomagnetic directions from 39 sites distributed among four localities have a concordant mean declination i 40 6 d 7 2 95 5 8 in the altyn tagh range 21 sites in oligocene strata at xorkoli 38 93 n 91 43 e yield a paleomagnetic direction with concordant declination i 49 7 d 5 0 95 5 4 these results combined with existing regional paleomagnetic data indicate that 1 the hexi corridor along with the north china block has not undergone tectonic vertical axis rotation since at least early cretaceous time and is separated from the xining lanzhou basin and eastern tibet by an important post early cretaceous tectonic boundary 2 the nan shan fold thrust belt and the qaidam basin have not experienced wholesale vertical axis rotation during neogene time and 3 absence of vertical axis rotations in areas adjacent to the altyn tagh fault indicates that sinistral shear strain between the tarim basin and the northern tibetan plateau is concentrated on the fault these results are consistent with asian tectonic models that combine distributed lithospheric deformation and thickening with narrow and weak shear zones

water quality changes in the dunes of the western belgian coastal plain due to artificial recharge of tertiary treated wastewater abstract since july 2002 tertiary treated waste water has been used to artificially recharge the phreatic aquifer of the dunes in the belgian western coastal plain the purpose of this project is to develop a sustainable water source and thereby minimize lowering of the water table while maintaining production capacity the recharged water is extracted via production wells located south and north of two ponds used for the recharge the uniqueness of this system is that the total dissolved solids in this recharge water is low 50 mg l in comparison with natural dune water 550 mg l in this paper water quality of recharge water groundwater between ponds and extraction wells extracted water and dune water is analysed the extraction water quality is determined by mixing of recharged water and dune water mineralisation of the recharge water occurs mainly by carbonate dissolution further o2 consumption no 3 reduction and oxidation of fe sulfide minerals are distinguished at the beginning of 2007 clogging of the ponds began to occur and it was observed that extraction rates and temperature of the recharge water influenced the amount of water which could be recharged using cl data it is confirmed that all the recharged water is recovered by the extraction wells finally it is concluded that the quality of the extracted water does not change significantly as a function of time

strike slip fault network of the huangshi structure sw qaidam basin insights from surface fractures and seismic data abstract the huangshi structure as one of the nww trending s shaped structures in the southwestern qaidam basin holds important implications for unraveling the regional structural pattern there are four dominant sets of surface strike slip fractures at the core of the huangshi structure the fractures with orientations of n28 e n47 e and n65 e correlate well with conjugate riedel shears r tension fractures t and riedel shears r in the riedel shear model respectively two conjugate strike slip fracture sets occur at the surface of the hongpan structure secondary to the huangshi structure and the southwestern part of the huangshi structure in seismic sections the huangshi structure is present as a positive flower or y shaped structure governed by steeply dipping faults whereas hongpan and xiaoshaping structures located symmetrically to the huangshi structure are thrust controlled anticlines the riedel shear pattern of surface strike slip fractures the positive flower or y shaped structure in seismic sections and the nw trending secondary compressional anticlines consistently demonstrate that the huangshi structure is dominated by left lateral strike slip faults which comprise a strike slip fault network considering the similar s shaped configuration and nww trend of structures across the southwestern qaidam basin it can be further speculated that these structures are also predominantly of left lateral strike slip types

right lateral shear and rotation as the explanation for strike slip faulting in eastern tibet the convergence of two continents can be accommodated by crustal thickening and by lateral transport of crust out of the path of the converging continents1 3 the principal features suggesting that lateral transport is important are major strike slip faults striking roughly orthogonally to the orientation of convergence between the continents displacement on such faults is imagined to allow lateral transport of material with respect to the converging continents possibly accounting for a large fraction of the convergence between the two continents the most spectacular example of such strike slip faulting is in the eastern part of the tibetan plateau where three major left lateral faults with slip rates of 10 mm yr 1 and several smaller roughly parallel faults dominate the regional strain field2 3 cobbold and davy4 suggested that these faults may be rotating in a clockwise fashion here we put bounds on that rate of rotation and conclude that the image of lateral transport on such faults2 known also as continental escape extrusion or expulsion is an illusion and that instead the left lateral slip on east striking planes in eastern tibet is a manifestation of north striking right lateral simple shear if this conclusion is correct the east striking left lateral faults and the crustal blocks between them are rotating clockwise at 1 2 myr 1 the east west dimension of eastern tibet is shortening at 10 20 mm yr 1 and little material is moving eastward out of india s path into eurasia by left lateral simple shear

relative motion across the eastern tibetan plateau contributions from faulting internal strain and rotation rates abstract a kinematic model comprising 14 rotating elastic plastic blocks is used to represent the modern deformation of eastern tibet and neighboring regions block rotations fault slip rates and permanent strain rates within the blocks are constrained by inverting gps velocities slip vector azimuths derived from earthquakes and fault slip rates derived from geology the calculated internal strain rates of blocks in eastern tibet amounts to 10 to 30 10 9 yr in contrast to relatively low rates

lateral extrusion along the altyn tagh fault qilian shan ne tibet insight from a 3d crustal budget the lithospheric strike slip altyn tagh fault has accommodated hundreds of kilometers of displacement between the qaidam and tarim blocks since its eocene reactivation however the way the deformation is accommodated in the qilian shan and further east remains uncertain based on 360 km of northeastward migration of the relatively rigid qaidam block along the altyn tagh fault and 3d isovolumetric balancing of the crustal deformation within the altyn tagh fault qilian shan system we demonstrate that 250 28 km 43 8 49 4 of n20e directed crustal shortening and an additional 250 to 370 km of eastward motion of the qilian shan crust must be accounted for by strike slip faulting in the qilian shan and crustal thickening in the qinling area as well as by extension in the adjoining north china block graben systems

exploring the potential of multi receiver emi survey for geoarchaeological prospection a 90 ha dataset article i nfo article history the archaeological evaluation of landscapes in the framework of developer led archaeology is often based on extensive trenching programmes complemented with auger surveys in wetland environments during the archaeological evaluation of a 90 ha polder site in the north west of belgium a mobile multi receiver electro magnetic induction emi survey was used as a main prospecting technique the use of a mobile survey allowed to map the entire study area at a very fine resolution over 25 measurements per m 2 incorporating a multi receiver emi instrument enabled measuring the apparent electrical conductivity eca and the appar ent magnetic susceptibility msa of four different soil volumes simultaneously at each location the detailed maps provided insight into the archaeological and geomorphological features of the site among the detected structures were a large medieval farmstead a palaeoriver system and a number of military remains from world war i wwi the vertical discrimination potential added insight into the vertical facies changes which allowed modeling the palaeolandscape and helped determining the depth of detected medieval features the different msa measurements gave additional insight into the wwi structures in this paper we give an overview of the possibilities of combining multiple eca measurements for interpreting vertical soil variability together with an example of the added information from simultaneously gathered msa data more generally the diverse potential of multi receiver emi survey for geoarchaeological research is demonstrated

intracrustal detachment within zones of continental deformation geologic mapping of active to recently active geologic structures in panamint valley western united states and in the haiyuan region and northern tibetan plateau china suggests detachment in the middle and lower crust on a scale of tens of kilometres to at least several hundred kilometres detachment occurs similarly in predominantly extensional panamint valley and in predominantly compressional china environments it involves structures with displacements of more than 10 km and displacement rates of more than 3 mm yr perhaps more than 10 mm yr the steeply dipping strike slip faults present in all three areas hunter mountain fault haiyuan fault and altyn tagh fault zone terminate in zones of extension or compression and geometric relations indicate that all structures including strike slip faults are thin skinned and restricted to the upper crust in panamint valley and in the haiyuan region deformation within these systems can be reconstructed in three dimensions displacement on the strike slip faults is absorbed by extension or compression occurring at the termination of the faults so strike slip displacement is roughly equal to and in the same direction as shortening or extension we propose that left slip on the altyn tagh fault zone in northern tibet is similarly absorbed by shortening southeast of the fault zone within the qaidam basin and the nan shan

paleomagnetism of eocene and miocene sediments from the qaidam basin implication for no integral rotation since the eocene and a rigid qaidam block the qaidam basin is the largest topographic depression inside the tibetan plateau and it is a key factor to understanding the cenozoic evolution of the northern tibetan plateau paleomagnetic data was obtained from the middle to late eocene xiaganchaigou formation and the early to middle miocene xiayoushashan formation from seven localities the paleomagnetic results indicate that the qaidam basin has not undergone obvious basin scale vertical axis rotation with respect to the eurasia plate since the eocene local clockwise rotation took place only at a few special locations along the northern margin of the qaidam basin the uniform paleomagnetic results at different localities support that the qaidam basin is a relatively rigid block regional paleomagnetic and geodetic observations also suggest that crust south of the kunlun fault moves eastward faster than crust north of the kunlun fault

cenozoic tectonic evolution of qaidam basin and its surrounding regions part 1 the southern qilian shan nan shan thrust belt and northern qaidam basin cenozoic qaidam basin the largest active intermountain basin inside tibet figures importantly in the debates on the history and mechanism of tibetan plateau formation during the cenozoic indo asian collision to determine when and how the basin was developed we conducted detailed geologic mapping and analyses of a dense network of seismic reflection profiles from the southern qilian shan nan shan thrust belt and northern qaidam basin our geologic observations provide new constraints on the timing and magnitude of cenozoic crustal thickening in northern tibet specifically our work shows that the southernmost part of the qilian shan nan shan thrust belt and contractional structures along the northern margin of qaidam basin were initiated in the paleocene early eocene 65 50 ma during or immediately after the onset of the indo asian collision this finding implies that stress was transferred rapidly through tibetan lithosphere to northern tibet from the indo asian convergent front located 1000 km to the south the development of the thrust system in northern qaidam basin was driven by motion on the altyn tagh fault as indicated by its eastward propagation away from the altyn tagh fault the eastward lengthening of the thrust system was spatially and temporally associated with eastward expansion of qaidam basin suggesting thrust loading was the main control on the basin formation and evolution the dominant structure in northern qaidam basin is a southwest tapering triangle zone which started to develop since the paleocene and early eocene 65 50 ma and was associated with deposition of an overlying southwest thickening growth strata sequence recognition of the triangle zone and its longevity in northern qaidam basin explains a long puzzling observation that cenozoic depocenters have been located consistently along the central axis of the basin this basin configuration is opposite to the prediction of classic foreland basin models that require the thickest part of foreland sediments deposited along basin edges against basin bounding thrusts restoration of balanced cross sections across the southern qilian shan nan shan thrust belt and northern qaidam basin suggests that cenozoic shortening strain is highly inhomogeneous varying from 20 to 60 both vertically in a single section and from section to section across the thrust belt the spatially variable strain helps explain the conflicting paleomagnetic results indicating different amounts of cenozoic rotations in different parts of qaidam basin the observed crustal shortening strain also implies that no lower crustal injection or thermal events in the mantle are needed to explain the current elevation 3000 3500 m and crustal thickness 45 50 km of northern qaidam basin and the southern qilian shan nan shan thrust belt instead thrusting involving continental crystalline basement has been the main mechanism of plateau construction across northern qaidam basin and the southern qilian shan nan shan region

seawater intrusion and associated processes in a small coastal complex aquifer castell de ferro spain an attempt to identify the hydrogeochemical processes that accompany current or past intrusion of seawater in the castell de ferro coastal aquifer se spain was made using ionic deltas ionic ratios and saturation indices alluvial and coastal quaternary sediments and triassic marbles constitute this complex aquifer cation exchange dolomitization and calcite dissolution were identified as operating in the aquifer the cation exchange processes in the detrital materials are different from those in the marbles in addition it was determined that while the processes of marine intrusion associated with periods of low groundwater levels still persist in the detrital aquifer in the carbonate sector the flushing process characteristic of wetter conditions has begun

interpretation of magnetic and gravity gradient tensor data using normalized source strength a case study from mcfaulds lake northern ontario canada in this paper we present a case study on the use of the normalized source strength nss for interpretation of magnetic and gravity gradient tensors data this application arises in exploration of nickel copper and platinum group element ni cu pge deposits in the mcfaulds lake area northern ontario canada in this study we have used the normalized source strength function derived from recent high resolution aeromagnetic and gravity gradiometry data for locating geological bodies in our algorithm we use maxima of the normalized source strength for estimating the horizontal location of the causative body then we estimate depth to the source and structural index at that point using the ratio between the normalized source strength and its vertical derivative calculated at two levels the measurement level and a height h above the measurement level to discriminate more reliable solutions from spurious ones we reject solutions with unreasonable estimated structural indices this method uses an upward continuation filter which reduces the effect of high frequency noise in the magnetic case the advantage is that in general the normalized magnetic source strength is relatively insensitive to magnetization direction thus it provides more reliable information than standard techniques when geologic bodies carry remanent magnetization for dipping gravity sources the calculated normalized source strength yields a reliable estimate of the source location by peaking right above the top surface application of the method on aeromagnetic and gravity gradient tensor data sets from mcfaulds lake area indicates that most of the gravity and magnetic sources are located just beneath a 20 m thick on average overburden and delineated magnetic and gravity sources which can be probably approximated by geological contacts and thin dikes come up to the overburden

geometry and kinematics of the arlar strike slip fault sw qaidam basin china new insights from 3 d seismic data abstract the right stepping en echelon kunbei fault system consisting of the hongliuquan arlar xiii and kunbei faults features importantly in the tectonic evolution of the southwest qaidam basin the 3d seismic cross section interpretation and key horizon similarity attribute analysis show that the nww striking arlar fault is composed of two steeply dipping faults f1 and f2 in cross sectional view and branches eastward into two west dipping faults f5 and f6 in map view the fact that the strata above t 2 the base of the early miocene xiayoushashan formation become dramatically thinner toward the high points of the arlar fault suggests an early miocene initiation ca 22 0 ma for this fault as indicated by the windowed amplitude related attribute maps the arlar fault and f5 one branch of the arlar fault have cumulative sinistral offsets of 8 6 8 7 km and 5 2 5 4 km respectively these considerably greater strike slip components in conjunction with the respective maximum true dip slip displacements of