quaternary blind thrusting in the southwestern sacramento valley california patterns of microearthquakes and quaternary surface deformation suggest that the tectonic setting of the sw sacramento valley is similar to areas of the western san joaquin valley known to be underlain by seismogenic blind thrust faults on the basis of previous work and analysis of geologic and seismic reflection data the following late cenozoic tectonic features and processes are identified 1 uplift of the northern coast ranges beginning approximately 3 4 ma and eastward propagation of uplift into the southwestern sacramento valley by 1 0 ma 2 uplift and homoclinal flexure of plio pleistocene strata at the eastern coast ranges mountain front 3 uplift and folding above blind thrusts approximately 15 km east of the mountain front in the southwestern sacramento valley similar associations of structures and processes have been observed in thrust belts in pakistan the peruvian andes and the canadian cordillera and are commonly attributed to thrusting within an intercutaneous wedge or triangle zone by using other thrust belts as analogs the propagation of an eastward tapering triangle zone is interpreted to be the principal mechanism for uplift and homoclinal flexure at the eastern coast ranges mountain front seismic reflection profiles reveal that 1 the triangle zone consists primarily of east vergent blind thrusts and 2 west vergent backthrusts exposed in the the eastern coast ranges and southwestern sacramento valley are rooted in the east vergent thrusts transfer of slip from the east vergent blind thrusts to the west vergent backthrusts occurs locally beneath the southwestern sacramento valley fault bend folding in the hanging walls of the backthrusts has created a north northwest striking chain of low hills approximately 15 km east of the mountain front the folds deform 3 4 1 0 ma fluvial sediments and thus are middle pleistocene in age or younger local variations in strike suggest that the fold chain is segmented like the new idria coalinga kettleman hills segmented fold chain in the southwestern san joaquin valley stein and ekstrom 1989 these data have implications for seismic hazard assessment anecdotal accounts indicate that two m 6 0 events of the 1892 winters vacaville earthquake sequence probably occurred beneath the eastern coast ranges dale 1977 toppozada et al 1981 ground cracking was observed following the main shocks along the mountain front in the southwestern sacramento valley we propose that the earthquakes were generated by slip on a blind thrust beneath the coast ranges and that the ground cracking in the valley represents propagation of the eastward tapering triangle zone the 1892 earthquake sequence suggests that blind thrusts beneath the southwestern sacramento valley are active and capable of generating moderate to large magnitude earthquakes

the quaternary evolution of the gulf of corinth central greece coupling between surface processes and flow in the lower continental crust abstract the gulf of corinth in central greece is an active normal fault zone with particularly clear evidence of isostatic footwall uplift constrained by quaternary marine terraces and hanging wall subsidence and sedimentation it is bounded to the south by a pliocene to early pleistocene sedimentary basin which is now eroding into the gulf previous work has suggested that the relief across this region has increased dramatically since the early pleistocene due to the isostatic response to increased rates of footwall erosion and hanging wall sedimentation it is indeed assumed here that incision accompanying the draw down of global sea level at 0 9 ma during the first major pleistocene glaciation initiated the erosion of the basin south of the gulf of corinth and so abruptly increased the sedimentation rate in the gulf the resulting transient thermal and isostatic response to these changes is modelled with the subsiding depocentre and eroding sediment source coupled by flow in the lower continental crust the subsequent enhancement of relief involving an increase in bathymetry from near zero to 900 m and 500 m of uplift of the eroding land surface in the sediment source is shown to be a direct consequence of this change the model is sensitive to the effective viscosity of the lower crust and can thus resolve this parameter by matching observations a value of 6 1019 pa s is indicated suggesting a viscosity at the moho no greater than 1018 pa s similar transient topographic effects caused by increased rates of sedimentation and erosion are likely to be widespread within the geological record suggesting that this coupling process involving flow in the weak lower crust may be of major geological and geomorphological importance

seismically active fold and thrust belt in the san joaquin valley central california structural analysis of late cenozoic folds along the western and southern margins of the san joaquin basin suggests that the folds are related to development of a fold and thrust belt rather than to wrench tectonics the folds have formed by the processes of fault bend folding and fault propagation folding which commonly occur in fold and thrust belts our structural interpretation attributes the seismically active coalinga and kettleman hills north dome anticlines to fault bend folding above a thrust fault s that steps up from a detachment within the franciscan assemblage to a detachment at the base of the great valley group this thrust does not reach the surface blind thrust and its slip is consumed in backthrusting and formation of subsurface folds under the san joaquin valley movement on the postulated thrust s would explain the cause of the may 2 1983 coalinga earthquake and the august 15 1985 avenal earthquake and would account for the lack of significant surface rupture or shallow subsurface faulting during both earthquakes well documented examples of fault bend and fault propagation folding also occur at wheeler ridge in the san emigdio mountains and at kettleman hills south dome deformation associated with fold and thrust belts can be extremely complicated considerable fault movement can occur without accompanying surface rupture or shallow level faulting conversely surface rupture can occur that has no direct relationship to fault slip at depth an example would be flexural slip folding wherein the slip planes reach the surface but do not root into any significant faults at depth consequently traditional geologic approaches to seismic risk evaluation which rely largely on surface data are subject to numerous pitfalls when applied to fold and thrust belts our interpretation of the structural style that developed in central california during the late cenozoic requires that the strain associated with the transpressive motion between the pacific and north american plates be resolved into normal and tangential components thrust faulting and folding normal to the plate boundary and strike slip faulting parallel to the plate boundary san andreas fault the thrust faults root in a deecollement at the brittle ductile transition zone above which shortening is associated with folding and thrust faulting and beneath which shortening in the lower crust is accommodated by ductile processes of tectonic thickening or incipient subduction

thermal mechanical and chemical influences on the performance of optical fibres for distributed temperature sensing in a hot geothermal well structural well bore integrity is an important issue for sustainable provision of geothermal energy raman scattering based fibre optic distributed temperature sensing dts can help to monitor the status of a well and therefore help to optimize expensive work over activities this study reports on the installation of a fibre optic cable in the cemented annulus behind the anchor casing in the high temperature geothermal well he 53 hellishei i geothermal field sw iceland although the cable has been damaged during the installation temperature data could be acquired during the entire length of installation down to 261 3 m temperature measurements were performed during the installation in spring 2009 during the onset of a flow test in summer 2009 and after a 8 5 month shut in period in summer 2010 during the flow test maximum temperatures of 230 c were measured after 2 weeks fluid production using optical time domain reflectometry otdr attenuation measurements at 850 and 1 300 nm enabled to identify mechanical thermal and chemical degradation along the optical fibre the observed degradation led to erroneous temperature readings and limits due to the optical budget of the dts system the accessible length of the fibre the characteristics and the influence of the different degradation mechanisms on the accuracy of the dts measurements are discussed and recommendations for an optimized installation are given

the history of the major rivers of southern britain during the tertiary the evolution of the drainage system of lowland britain is discussed on the basis of available geological evidence including that from terrestrial sites and that which has more recently become available from offshore exploration of the north sea the english and bristol channels and the irish sea tertiary stratigraphy throws considerable light on landform and river development paleocene destruction of a chalk cover which seems to have been incomplete in western britain was accompanied by basin sedimentation under a tropical climate the major elements the thames solent hampshire proto avon river irish sea river and possibly an early trent river existed almost throughout the cenozoic the influence of atlantic rifting and thermal doming in nw britain appears to have been stronger and more temporally focused than the persistent flexuring that determined and maintained tertiary drainage lines in the se here also the folded mesozoic terrains on the surface contrast with the more dominant block faulted relief of the palaeozoic oldlands the rivers of the se can be shown to have extended or reduced their lengths in response to relative sea level change and gentle warping drainage antecedence the destruction of the solent system and the breaching of the english channel are also evident by contrast the major river systems of the west are now entirely submerged long term stability of the drainage pattern reflects a persistent tectonic regime in the south with a subdued low relief landscape having a weathered regolith and dense vegetation cover meandering river channels and alluvial styles predominated although channel forms varied according to sediment load slope and discharge variability coarse gravel dominated accumulations are rare and localized chemically stable lithologies dominate the clastic component throughout it is apparent that the deeply incised river valleys seen today are related to high predominantly coarse sediment yields encouraged by substantial rapid climate changes in the pleistocene this emphasizes the significance of mechanical compared with chemical weathering for the rate and nature of landscape dissection and the modifications that have arisen as a result of glaciation frost climate weathering rapidly changing climates and sea levels the stratigraphical evidence here reviewed is at variance with older largely geomorphologically based landform evolution models denudational chronology but gives considerable support to the recent proposals emphasizing the significance of paleocene erosion and enduring low relief landscapes and drainage systems evolving alongside fold development during the paleogene given the depobasin evidence now available postulated fluvially active episodes can and must be linked to contemporaneous deposition some at least of the many controversies involving the identity of erosion surfaces the dating of them using only residual deposits and weathering mantles and the selection of particular tertiary episodes as ones of landscape development can now be resolved

rheological differences between archaean and younger crust can determine rates of quaternary vertical motions revealed by fluvial geomorphology surface uplift is widely observed in subaerial regions of continental crust that are distant from plate boundaries often revealed by river terrace staircases with altitude ranges of several hundred metres which typically span the quaternary this characteristic geomorphology has been explained by forcing of flow in the weak lower crustal layer by surface processes non steady state erosion and cyclical loading by ice sheets and sea level fluctuations this study tests this interpretation by showing that analogous river terrace staircases are absent in archaean crust which lacks the weak lower crustal layer found elsewhere

inversion of field data in fault tectonics to obtain the regional stress iii a new rapid direct inversion method by analytical means summary a new method for determining the reduced stress tensor with four degrees of freedom the orientations of the three principal stress axes as well as the ratio of principal stress differences using fault slip data or focal mechanisms of earthquakes is presented from a computational point of view the inversion of fault slip data is made in a direct way by purely analytical means as a result the determination process is extremely fast and adaptable on small microcomputers from a physical point of view the method aims at simultaneously i minimizing the angles between theoretical shear stress and actual slip vector and ii having relative magnitudes of shear stress large enough to induce slip despite rock cohesion and friction examples of application to actual fault slip data sets with good or poor variety of fault slip orientations are shown the double significance of the basic criterion adopted results in a more realistic solution of the inverse problem than the single minimization of the shear stria angle

the structure and evolution of the wessex basin southern england an example of inversion tectonics abstract the wessex basin of southern england consists of four main sub basins each sub basin is thought to be fundamentally controlled by the normal reactivation of hercynian basement thrust and wrench or transfer faults post hercynian polyphase reactivation of both east west thrust and northwest southeast transfer faults tended to compartmentalise the basement thereby leading to the initiation of discrete permian cretaceous depocentres while rifting was confined to the western portions of the area during the permo triassic easterly migration in the mesozoic allowed the initiation of the weald and channel basins the sub basins represent therefore simple sinistral pull apart basins opening along northwest southeast faults this same fault direction is postulated to have also played a major role in controlling and or modifying the development of european basins in general major pre aptian uplift and erosion is largely attributed to the thermal effects and hence the isostatic uplift of the basin associated with continental rifting of the bay of biscay and the north atlantic margins major inversion and hence basin destruction began in the late cretaceous early tertiary with the uplift of the channel weald and vale of pewsey basins and culminated in the oligocene miocene synchronous with the helvetic phase of alpine deformation wessex basin inversion was facilitated by the thrust reactivation of variscan faults above an intracrustal detachment surface the same surface which allowed upper crustal extension and hence basin initiation in the permo triassic the structural development of the wessex basin both during extension basin formation phase and compression inversion phase was ultimately controlled by the plate motion of africa relative to europe such plate motions successfully predict the observed nw se sinistral motion from the stephanian to the aptian e w sinistral motion during the aptian cenomanian and largely nw se dextral motion from the cenomanian to the present day

the multiple inverse method a new technique to separate stresses from heterogeneous fault slip data abstract a new inverse technique is presented here to separate stresses from heterogeneous fault slip data without a priori information on the stresses or on the classification of faults according to the stresses four parameters are determined by the inversion one for the shape of the stress ellipsoid and three for the direction of the stress axes accordingly the inversion is equivalent to the projection of the fault slip data to a point in four dimensional parameter space the data are divided into k element subsets to which the inverse technique is applied where k 4 or 5 is the optimal choice for the stability of solutions and for the reduction of computation significant solutions are identified as clusters in parameter space the technique is demonstrated first by simulated fault slip data as an example field data obtained from miocene fore arc sediments in western japan were processed by the method

river response to an active fold and thrust belt in a convergent margin setting north island new zealand high resolution digital elevation data topsar 10 m grid are used to reconstruct late quaternary growth histories of subtle folding in the wairarapa fold and thrust belt north island new zealand outcrop data of deformed latest miocene and younger strata are combined with observations of warped and faulted late quaternary terrace surfaces to unravel the geomorphic and structural history of the huangarua river valley optically stimulated luminescence osl dating of loess that accumulated on these strath terraces and paleosol stratigraphy allow temporal correlation among the terraces and with glacial climate cycles since the last interglaciation these data indicate that five intervals of strath cutting occurred at 125 60 70 30 15 and 10 ka strath beveling is largely independent of local folding or regional base level change we hypothesize that straths are cut when an increase in sediment supply during cool climatic periods brings river sediment load and river transport capacity into balance in the wairarapa strath cutting events appear to occur near the end of cool climatic cycles this study shows that the identification of subtle departures from regional topographic trends becomes practical when a high resolution dem is available after subtraction of an average valley gradient from the digital topography the residual topography on the terrace treads reveals cross valley and longitudinal tilting although rates of folding are slow and the magnitude of deformation is commonly limited to less than a few tens of meters these topographic anomalies define fold axes that coincide with subsurface structures when combined with time control these anomalies serve to define the patterns and rates of fold growth over the past 125 kyears

a simple heat flow quality function and appraisal of heat flow measurements and heat flow estimates from the uk geothermal catalogue abstract a comprehensive database of temperature heat flow thermal conductivity and geochemistry is the basis of geothermal modelling the latest revision 1987 of the uk geothermal catalogue ukgc contains over 2600 temperatures at over 1150 sites and over 200 observations of heat flow about 93 of the temperature data are from depths less than 2000 m and about 50 are bottom hole temperatures bht heat flow density distribution models can be expanded to include estimates of heat flow derived from bht and thermal conductivity data contained in the ukgc a simple quantitative assessment of the quality of individual heat flow measurements has been devised based on the type and frequency of temperature and conductivity measurements and the borehole depth the dimensionless quality function hfq has been defined so that for a heat flow borehole with two equilibrium temperature measurements made across an interval with a mean depth of 1 km or greater with complementary thermal conductivity determinations made at intervals of 1 m across this zone the heat flow quality function is 1 0 over 50 of the uk heat flow dataset has a hfq function less than 0 10 the 4 highest quality observations have values above 1 0 the same function can be used to assess the quality of estimates of heat flow by assigning quality functions to various types of temperature and thermal conductivity observation schemes appraisal of the uk heat flow dataset indicates that some of the observational data have a similar quality rating to estimates of heat flow derived from convolution of temperature and thermal conductivity data for deep boreholes within the catalogue in eastern england the heat flow density pattern is significantly modified by incorporation of estimates of heat flow from deep boreholes which have hfq values comparable with early heat flow measurements made in this region

an integrative geothermal resource assessment study for the siliciclastic granite wash unit northwestern alberta canada this study explores the siliciclastic granite wash unit in northwestern alberta as a potential geothermal reservoir the approach covers regional 3d structural geological modelling of a 90 km 70 km area based on well log and legacy 2d seismic data the fault strike was interpreted from lineaments which were identified with the refined trend surface analysis method the stress state of the granite wash reservoirs was determined by an integrated approach of 3d fault modelling stress ratio definition based on frictional constraints and slip tendency analysis the results show that the best site for a geothermal application is located in the southwestern study area where the highest temperatures above 70 c coincide with the largest thickness above 20 m and zones of elevated porosity and permeability the integrated stress analysis indicates an in situ stress regime from normal to strike slip faulting maintaining a non critically stressed reservoir or faults therein assuming a friction coefficient of 0 7 the granite wash reservoirs could be used for heating of greenhouses domestic warm water provision and district heating

thames river sediments of the british early and middle pleistocene abstract the thames drainage system contains the most complete record of fluvial sediments in the british quaternary the kesgrave sands and gravels form the main body of this sediment having been deposited over an interval that spans the later part of the early pleistocene and most of the middle pleistocene conventional stages pre pastonian a through to early anglian ca 1 2 ma this deposit provides a stratigraphic context for related bio morpho and pedostratigraphic evidence and for the recognition of pre anglian pre oi stage 12 upland glaciation in the welsh mountains and intense periglaciation in lowland england it also facilitates correlation with the stratigraphy of northern europe and the global pattern of orbitally forced climatic change this paper describes the first catchment wide correlation of thames river sediments and proposes a formal redefinition of the lithostratigraphic units concerned the scheme outlined here is based on two lithologically distinctive formations defined at type areas reflecting significant changes in catchment dimensions the earlier sudbury formation was formed when the thames catchment extended into wales and drained northwards across east anglia the later colchester formation was formed after the upper catchment had been reduced in extent to that of the present river but continued to flow across east anglia the whole sediment body is now named the kesgrave group

an inverse problem in microtectonics for the determination of stress tensors from fault striation analysis abstract a method is proposed to compute some characteristics of a possible stress tensor related to striations measured in a given faulted area if several tectonic phases are responsible for the striations the method separates and determines the successive stress tensors the iterative algorithm consists of alternatively a sorting the data attributed to a tectonic phase and b computing the characteristics of the stress tensor of this phase the method is tested using an application to synthetic and actual data

pleistocene evolution of the solent river of southern england abstract the solent river no longer exists since most of its course was drowned by eustatic sea level rise during the flandrian stage holocene previously it flowed eastwards across southeast dorset and south hampshire as an extension of the river frome as such it formed the axial major stream of the hampshire basin a sequence of fluvial aggradations ranging in height from 125 m o d to below sea level provide evidence of the former courses of this substantial river and its tributaries detailed study of the deposits supported by analysis of clast lithological assemblages provide the basis for the recognition of a series of lithostratigraphical units throughout the area the facies and sedimentary structures indicate that the bulk of the deposits accumulated in a braided river environment under periglacial climates late pleistocene fossiliferous sediments of ipswichian and flandrian age provide a biostratigraphical framework the results demonstrate that the solent river was a substantial system comparable in size to the present thames and was a tributary of the channel river during periods of low sea level cold stages evolution of the river reflects its response to climatic change local geological structure and long term tectonic activity although datable deposits limit determination of the age of the solent river sequence it is undoubtedly of considerable antiquity and potentially extends back to the early pleistocene discussion of the sequence includes placing the events within their regional context

flow in the lower continental crust as a mechanism for the quaternary uplift of south east england constraints from the thames terrace record abstract the sequence of terraces of the river thames in south east england has been shown to date from the early pleistocene onwards and to provide an indication of the quaternary uplift history of the region using this evidence supplemented by altitudes of pliocene and early pleistocene marine sediments we have determined the pliocene and quaternary uplift histories of five representative localities clacton colchester and dartford for the lower thames and cookham and reading for the middle thames these uplift histories have been modelled using a physics based technique which calculates the isostatic response involving flow in the lower continental crust induced by cyclic loading at the earth s surface our results suggest that the late pliocene and early pleistocene part of the uplift history of our study region was initiated following the deterioration in climate starting at 3 1 ma which marked the start of upland glaciation elsewhere in europe the later increase in uplift rates in the middle pleistocene followed the start of intensified cyclic loading by very large continental ice sheets during and after oxygen isotope stage ois 22 at 0 87 ma dartford cookham and reading in the interior of south east england are all shown to have begun to uplift quite rapidly at rates of up to 0 1 mm a 1 following the start of forcing at 3 1 ma they have since uplifted by distances which increase gradually westward from 200 to 250 m of which a uniform 70 m has occurred since ois 22 at 0 87 ma in contrast clacton and colchester near the present north sea coastline experienced slow subsidence until the late early pleistocene but have nonetheless uplifted since ois 22 by similar distances to the other sites

application of the geomechanical facies approach and comparison of exploration and evaluation methods used at soultz sous forets france and spa urach germany geothermal sites earth reservoirs are increasingly exploited today with the extraction of resources such as heat and hydrocarbons and the large scale emplacement of waste such as co2 sequestration the characterization site investigation predictive modeling and long term monitoring are dependent on the processes being investigated and modeled in most cases complex coupled processes have to be addressed in a geologically complex rock mass system in this paper we present a conceptual holistic framework known as geomechanical facies linking all the scales of investigation characterization and reservoir development methods we demonstrate this concept on the work undertaken during the design and development of the enhanced geothermal systems egs systems at the forefront of european hot dry rock hdr technology soultz sous forets france and spa urach germany soultz sous forets is situated within granitic rocks and an active tectonic graben system in the central part of the rhine graben it presents conditions of lithology temperature stress hydraulics and geochemistry that are very different from those at spa urach located in a very dense gneiss formation in the south german crystalline complex spa urach exhibits more elastic behavior and is set tectonically within an almost inactive strike slip stress field described in more detail in sects drill core analysis and hydraulic stimulation at spa urach this paper compares the exploration and field development methods used at these two sites against the back drop of the geomechanical facies concept issues addressed include the key parameters for flow and heat transport properties coupled hydro mechanical process identification the success of the hdr reservoir as a heat exchanger and exploration techniques applicable to the different facies identification of the key geomechanical facies gives an indication as to which technologies will prove more efficient in the application of hdr technology the results of this study will hopefully help in developing heat recovery schemes for the long term economical operation of future hdr plants and egs as well as assist in the understanding of engineered geosystems

late quaternary evolution of the upper reaches of the solent river southern england based upon marine geophysical evidence geological evidence suggests that during the late quaternary a river system the solent river drained a large part of central southern england its upper reaches flowed in a west east direction flanked to the south by a chalk ridge the purbeck isle of wight chalk ridge today only part of the upper reaches of the river9s tributary channels remain as the area was inundated during the flandrian transgression forming an embayment system poole and christchurch bays in order to map the offshore buried channels of the upper reaches of the solent river an extensive set of shallow marine geophysical data was analysed and interpreted the results of this investigation show that the solent river system was disrupted irreversibly by southerly capture of its upstream section before the flandrian transgression this disruption was the result of the fluvial breaching of the southern barrier of the system the purbeck isle of wight ridge at three points probably during late devensian time poole bay was first to be submerged during the transgression the estuaries which resulted from the drowning of the fluvial palaeovalleys of poole bay were infilled with transgressive facies sequences which have been preserved within the buried palaeovalleys in contrast christchurch bay was submerged at a later time but because of the abrupt manner of its inundation no transgressive facies have been preserved within its buried palaeovalleys

sensitivity of weichselian fluvial systems to climate change nochten mine eastern germany abstract this paper aims to contribute to the understanding of fluvial system response to climate change during the last glacial interglacial cycle fluvial and aeolian successions have been studied in the opencast brown coal mine nochten in eastern germany an absolute chronology was established by luminescence and 14 c dating enabling to demonstrate the relations between depositional units and changes in sedimentary environment over time with regional climatic and vegetational changes it is concluded that the major climatic periods coinciding with the oxygen isotope stages are generally reflected in the fluvial sequence by distinct fluvial environments major climatic changes oxygen isotope stage boundaries have been preserved in the fluvial record as erosional bounding surfaces and by changes in fluvial style rapid climate changes like the middle pleniglacial dansgaard oeschger cycles are in general not reflected in the fluvial succession these cycles were too short or with too low amplitude to cause a strong vegetational response and related changes in water and sediment supply it is emphasized that also the preservation potential of short lived climatic warming events in high energy fluvial systems is low warming events may however have been preserved in lacustrine successions in former thermokarst lakes a strong cooling event at ca 40 ka leading to continuous permafrost conditions and changes in the water and sediment budget was reflected in the fluvial archive by a change from sandy anabranching to braided river conditions

the quaternary uplift history of central southern england evidence from the terraces of the solent river system and nearby raised beaches abstract we have used fluvial solent river system and marine terraces to reconstruct the uplift history of central southern england in the case of the former we make the assumption that fluvial incision has been a direct response to surface uplift with its precise timing controlled by climatic forcing of fluvial activity such that height of terrace gravel above modern river is a consequence of uplift since deposition in the case of the marine sequence we take the height of interglacial raised beaches above a calculated contemporaneous sea level as a measure of uplift the calculation involving an adjustment from modern sea level using the deep oceanic oxygen isotope signal as an indication of global ice volume at the time of deposition this exercise requires some degree of dating constraint which is problematic for both environments the solent terraces have yielded little biostratigraphical evidence whereas the south coast raised beaches have either been poorly exposed in recent years or their ages have been controversial because of disputes between biostratigraphy and geochronological data we have supplemented the evidence available from these sources by using key aspects of the archaeological record as dating constraints in particular the first appearances of levallois technique a marker for mis 9 8 and of bout coupe handaxes mis 3 the first of these has been particularly useful in modelling of the middle pleistocene parts of the river terrace staircases of the solent system in undertaking this reappraisal we have noted several inconsistencies and disagreements between past correlation schemes for the terraces of the solent and its various tributaries we find that versions involving shallower downstream gradients in the main solent river are most likely to be correct and that revisions on this basis solve a number of problems in interpretation encountered previously our results show that most of this region has uplifted by 70 m since the late early pleistocene and by 150 m since the middle pliocene there being a high degree of consistency between uplift histories inferred for river terraces and marine terraces uplift rates increase gradually westward such that along the river frome at the western end of the hampshire basin 80 m of uplift since the late early pleistocene is indicated this variation is interpreted as a consequence of a regional scale variation in crustal properties about 80 m of uplift is also indicated on this timescale by raised beaches in the portsdown area and adjacent terraces of the river test and solent in the vicinity of the portsdown anticline to the north of southampton we interpret this as a consequence of 10 m of vertical slip in the past million years on the blind reverse fault beneath this anticline this dataset thus provides the first clear indication of measurable quaternary structural development in crustal basement in the onshore uk the solent has formed more than a single terrace per 100 ka milankovitch cycle leading us to attribute terraces to isotopic substages potentially improving upon the resolution available from sequences in which terraces formed once per cycle athough the first appearence of levallois technique was initially considered to date from the mis 9 8 transition based on evidence from the thames we found that there was a better modelling fit if this was taken as having occurred slightly earlier in mis 9b perhaps in association with the post mis 9e or 9c marine regression which could have permitted immigration into a previously insular britain of people versed in levallois technology

the inverse problem in microtectonics and the separation of tectonic phases abstract the algorithm of inverse problems is applied to three cases in microtectonics a collection of striations measured on pre existing faults may be processed automatically and interpreted in terms of tectonic stress a comparison is made between two different methods formerly proposed by the authors both methods are tested with field data the theoretical results agree with independent field criteria for a separation of tectonic phases

investigation of a new hdr system with horizontal wells and multiple fractures using the coupled wellbore reservoir simulator tough2mp well eos3 geothermal energy is renewable sustainable and available in large amounts the hot dry rock hdr systems in particular have the largest potential for long term sustainability and therefore draw a lot of attention the combination of horizontal wells and the technology of multiple transverse fractures technology is an attractive approach of such hdrs which is called in this paper as the specific egs enhanced geothermal system the main objective of this paper is to study the heat extraction over a period of 20 years by water circulating in a deep geothermal reservoir using this specific egs the wellbore flow module t2well eco2n is implemented in the parallelized simulator tough2mp as a new code tough2mp well eos3 which enables coupled wellbore reservoir simulations using this newly developed code the sensitivity of heat extraction against various parameters of the formation and fractures is assessed the influences of the fracture geometry and the space of two neighborhood fractures on the geothermal energy performance are analyzed according to the results in this paper the injection rate the wellbore radius and the fracture permeability are three main influence factors for the distribution of total flow through individual fractures a large injection rate a small wellbore radius and a large fracture width will cause the short circuit effect which reduces the performance of this specific egs compared with the classic hdr system doublet or triplet vertical wells single fracture this specific egs has a much higher performance and a longer duration of the economic production furthermore the horizontal wells can also be drilled in both directions of the minimum horizontal stress instead of in just one direction so that the energy performance is doubled and the investment cost per kw energy production is decreased and the advantage of this specific egs is significantly enlarged

the somme valley terrace system northern france a model of river response to quaternary climatic variations since 800 000 bp recent research on the somme valley terrace deposits that began in 1987 has resulted in an integrated sequence of geological and geomorphological evidence for this area that is of particular significance for prehistoric investigations this has been achieved using previous evidence and new results from archaeological and geological excavations these include longitudinal profiles cartography and detailed synthesis of sections of alluvial deposits stratigraphy of river deposits and overlying loess sequences the work based on a study of the geometry of the terrace system has resulted in the identification of ninestepped alluvial formations that occur along 70 km of the valley detailed study permits the integration of the various alluvial sequences this suggests that each alluvial sequence results from sedimentation through a single glacial interglacial climatic cycle this hypothesis is confirmed by investigation of soil and loess sequences of the deposits overlying the fluvial sediments the synthesis presented provides a basis for understanding the deposition of the terrace system and an initial chronostratigraphic interpretation for the deposits

uplift driven valley incision and river terrace formation in southern england outside the limits of middle pleistocene glaciation the river basins of southern england contain long cenozoic terrestrial sedimentary records of greatest importance are the river terrace sequences which contain biostratigraphical and sedimentary evidence that testifies to the high amplitude climatic changes of the quaternary however trends in valley development cannot easily be accommodated within the framework of quaternary climatic change it is argued in this paper that episodic incision and terrace development result from uplift a consequence of the interplay between continuing alpine orogenic movements and erosion driven isostasy using a simple linear model height age an uplift rate of ca 7 cm ka 1 is estimated for the terrace sequence in the upper thames valley this preliminary model is evaluated using the records of adjacent basins 1997 john wiley sons ltd

tectonic analysis of fault slip data sets using data that include the direction and the sense of motion on individual fault surfaces determined by slickenside lineations it is possible to reconstruct reduced stress tensors that correspond to the orientation of stress axes and to the ratio 2 3 1 3 between principal stress values 1 2 3 compression being positive no assumption is made concerning the orientation of fault planes relative to stress axes so that reactived faults are taken into account as well as newly created ones qualitative and quantitative methods for analysis of fault slip data were developed during the last 10 years the practical limitation of the methods and the necessity for critical field observations are emphasized these methods can be applied to focal mechanisms of earthquakes a more complex analysis of heterogeneous data sets involving an iterative separation of different stress systems is also discussed this analysis enables one to distinguish successive faulting events careful qualitative study in the field is in all cases essential

the seismic reflection moho beneath the united kingdom and adjacent areas abstract onshore and offshore deep seismic reflection data have been integrated to produce two way travel time and depth maps of the seismic reflection moho beneath the uk moho travel times are mostly in the range 9 5 11 5 s showing only weak correlation with specific upper crustal structural features but decreasing generally northwestward towards the atlantic margin moho depths show a much stronger correlation with upper crustal structure than do travel times there is pronounced crustal thinning moho depths 32 km are found generally beneath basement massifs particularly onshore short wavelength topographic features on the moho are quite rare and are generally restricted to ancient zones of continental collision and or subduction some of these ancient collision and or subduction zones are spatially associated with a highly reflective moho this is particularly evident where low angle shear zones in the lower crust or uppermost mantle converge with or intersect the moho it is suggested that development of a moho detachment surface can tectonically smooth the moho and thereby markedly increase its reflectivity a tendency in certain areas for the moho to remain at roughly constant two way travel time though not constant depth beneath both sedimentary basins and intervening basement massifs is interpreted as indicating that structural features on the scale of several tens of kilometres are in regional isostatic equilibrium conversely travel time perturbations beneath smaller features 10 km across indicate that these are at least partially uncompensated the uk crust is therefore weak but not sufficiently weak to attain local airy isostasy basement massifs west of scotland show systematically smaller moho two way travel times than similar structures farther south within the constraints of regional isostasy this can be interpreted in two main ways greater rigidity and strength of lewisian rocks within the west scottish massifs manifest as higher seismic velocity relative to density could be a cause of the observed travel time differences alternatively low density material beneath the crust could buoy up the western scottish massifs if this buoyancy were the consequence of igneous underplating then any underplated material would have to lie beneath the seismic reflection moho

the role of neotectonics and glaciation on terrace formation along the nysa klodzka river in the sudeten mountains southwestern poland the nysa klodzka river drainage basin in the sudeten mts sw poland preserves a complex late cainozoic succession that includes eight fluvial series or terraces and deposits from two glacial episodes as well as local volcanic rocks slope deposits and loess fluvial sedimentation took place during the late pliocene and from the early middle pleistocene cromerian with a long erosion phase gap during the early pleistocene fluvial series are dated to the late pliocene cromerian holsteinian late saalian eemian weichselian and the holocene glacial deposits represent the early elsterian and early saalian stages almost all these stratigraphic units have been observed in all geomorphic zones of the river the mountainous klodzko basin the bardo mts bardo gorge and in the mountain foreland the main phase of tectonic uplift and strong erosion was during the early pleistocene minor uplift is documented also during the post early saalian and probably the post elsterian the post early saalian and post elstrian uplift phases are probably due to glacio isostatic rebound the quaternary terrace sequence was formed due to base level changes epigenetic erosion after glaciations and neotectonic movements the cromerian fluvial deposits terraces do not indicate tectonic influence at all all other quaternary terraces indicate clear divergence and the post early saalian terraces also show fault scarps the fluvial pattern remained stable once formed during the pliocene with only minor changes along the uplifted block along the bardo gorge inferring an antecedent origin for the bardo gorge only during the post glacial times have epigenetic incisions slightly modified the valley

migration of hydrocarbons and secondary porosity in sandstones a unified hypothesis concerning generation and migration of hydrocarbons and development of secondary porosity in sandstones is presented carbonic acid is considered to be the primary reagent responsible for dissolution in the development of secondary porosity in sandstones the degree to which reservoir quality is enhanced by development of secondary porosity may be proportional to the amount of hyrocarbons generated as well as to the amount of unstable constituents during diagenesis in some cases formation of secondary porosity may be responsible not only for development of reservoir but also for a significant element of entrapment by the partial but areally and stratigraphically selective dissolution of sandstone in the migration path of hydrocarbons jmt

sedimentology palaeontology and archaeology of late middle pleistocene river thames terrace deposits at purfleet essex uk middle pleistocene fluvial deposits of the corbets tey formation at purfleet essex provide evidence of an un named and previously poorly recognized interglacial thought to corrrelate with oxygen isotope stage ois 9 previous attributions of the sediments to the ipswichian last interglacial stage are refuted new investigations have yielded rich molluscan mammalian and ostracod assemblages that indicate fully temperate conditions and the distal influence of marine transgression pollen analyses suggest a previously unrecorded phase of interglacial vegetational development clast composition geomorphological evidence and the occurrence of molluscs that favour large rivers all point to deposition by the thames rather than in a minor tributary as suggested previously three separate palaeolithic industries in stratigraphical superposition are recognized at purfleet these being clactonian acheulean and levallois purfleet is therefore a key locality in the understanding of the early human occupation and exploitation of southern britain as well as for the interpretation and correlation of the terrace sequence in the thames valley

preliminary geological geochemical and numerical study on the first egs project in turkey geothermal energy is attracting more and more attention due to its large capacity and lack of dependency on the weather currently many countries have planned enhanced geothermal system egs projects in this paper the first egs project in turkey which is being implemented at the license area of sds energy inc in dikili of the izmir province is introduced extensive geological paleostress 279 fault slip data from 33 locations geophysical magnetotelluric and vertical electrical sounding at 80 and 129 locations respectively and geochemical studies as well as paleostress measurements have been conducted in this area within the scope of this project in the light of all these studies it has been determined that the dikili region is remarkable in terms of its high thermal gradient of about 7 c 100 m the geothermal reservoir formation the kozak granodiorite is a homogeneous crystalline volcanic rock mass with high radiogenic heat production and suitable for an egs application the analysis shows that the dominating fault system is normal and the corresponding primary stress regime is extensional based on the geological geophysical surveys and the estimated in situ stresses numerical studies were carried out to assess the results of the hydraulic fracturing and geothermal energy production using the numerical codes flac3dplus and tough2mp respectively in the area a of the dikili site the simulation results show that the stimulated reservoir volume and area could reach 44 5 million m3 and 1 km2 respectively with an injection volume of 122 931 m3 assuming the fractured zone has a height of 1000 m and a half length of 1200 m the distance between injection and production wells being 1000 m an average overall geothermal capacity of 83 7 mwth in 20 years could be reached with an injection rate of 250 l s the injection strategy and design parameters of the reservoir stimulation and geothermal production will be further optimized with the project running

the chronology palaeogeography and archaeological significance of the marine quaternary record of the west sussex coastal plain southern england u k abstract the quaternary sediments of the west sussex coastal plain have produced a wide range of floral faunal and archaeological remains these sediments consist of marine sands and gravels exhibiting transgressive and regressive trends which occur from present day sea level to c 43 0 m o d and are overlain by terrestrial silts and cold climate periglacial sediments at the present day coastline channel fill deposits occur below modern beach levels new field observations coupled with a re investigation of old sites and literature suggest that five discrete high stands of sea level may be preserved in the area of the west sussex coastal plain age estimates for these deposits suggest that they span large parts of the middle and upper pleistocene oxygen isotope stages 13 to 5 conformable relationships between many of the marine and terrestrial sediments suggest that the potential exists within the area to correlate the marine and terrestrial quaternary stratigraphic records in addition sediments associated with two of these high sea level stands are associated with extensive buried landsurfaces covering large areas of the coastal plain at some locations these intact landsurfaces are associated with evidence for human activity and represent stratigraphic and cultural resources of international importance

the palos verdes terraces california bathtub rings from a buried reverse fault uplift of the palos verdes peninsula has long been associated with a northwest trending southwest dipping reverse fault unfortunately the palos verdes hills fault has no obvious surface displacement and little background seismicity to substantiate its dimension orientation or earthquake potential in this paper we investigate the tectonic style and slip rate of the palos verdes hills fault and the uplift history of the palos verdes hills by analyzing the geometry of 13 marine terraces that encircle the peninsula in a bathtub ring configuration elevations of 211 terrace remnants constrain a fault model with 3 0 to 3 7 mm yr 1 of oblique dextral reverse slip on a fault dipping 67 at 6 to 12 km depth beneath the peninsula if the rate was constant through time fault inception would have occurred 2 4 3 0 ma we propose that the largest credible earthquakes on the fault have magnitude 6 and could revisit every 2000 years

the mid pleistocene climate transition onset of 100 ka cycle lags ice volume build up by 280 ka the mid pleistocene climate transition mpt is the complex climatic change which brought the late pleistocene ice ages we explore the mpt in the time and frequency domains by new methods of time series analysis high resolution oxygen isotope records reveal that the ice volume related increase in 18o mean amplitude 0 29 0 05 1 transition midpoint 922 12 ka duration 40 9 ka significantly preceded the abrupt increase in the amplitude of the 100 ka cycle at 641 9 ka this finding can be quantitatively simulated using a simple ice bedrock model in which due to the additional ice the calving threshold is exceeded the simulated calving events prior to 650 ka are separated by 77 ka whereas after 650 ka they occur pseudo periodically with a mean period of nearly 100 ka the cause for the delay of the 100 ka calving cycle was not a slow bedrock relaxation rather the coincidental combination of insolation existing ice mass and bedrock depression