variation of velocity with effective stress in chalk null result from north sea well data wireline log data and pore pressure measurements from eight wells have been analysed to investigate how velocity in the chalk of the central graben north sea depends on porosity and vertical effective stress the main conclusion is that velocity shows no detectable dependence on vertical effective stress when porosity and vertical effective stress are treated as independent variables this result contrasts with the behaviour of shales which exhibit a reduction in velocity on unloading the significance is that velocity in the chalk cannot be used to detect the presence of any overpressure caused by unloading it is suggested that the absence of an observable velocity reduction in unloaded chalk is due to cementation

varves of the dead sea sedimentary record abstract the sedimentary record of the dead sea provides an exceptional high resolution archive of past climate changes in the drought sensitive eastern mediterranean levant a key region for the development of humankind at the boundary of global climate belts moreover it is the only deep hypersaline lake known to have deposited long sequences of finely laminated annually deposited sediments i e varves of varied compositions including aragonite gypsum halite and clastic sediments vast efforts have been made over the years to decipher the environmental information stored in these evaporitic clastic sequences spanning from the pleistocene lake amora to the holocene dead sea a general characterisation of sediment facies has been derived from exposed sediment sections as well as from shallow and deep water sediment cores during high lake stands and episodes of positive water budget mostly during glacial times alternating aragonite and detritus laminae aad facies were accumulated whereas during low lake stands and droughts prevailing during interglacials laminated detritus ld facies and laminated halite lh facies dominate the sequence in this paper we i review the three types of laminated sediments of the dead sea sedimentary record aad ld and lh facies ii discuss their modes of formation deposition and accumulation and their interpretation as varves and iii illustrate how dead sea varves are utilized for palaeoclimate reconstructions and for establishing floating chronologies

dependence of sonic velocity on effective stress in north sea mesozoic mudstones abstract overpressure estimation methods that use sonic velocity as a proxy for porosity only account for excess pressure due to undercompaction so the influence of unloading processes in generating overpressure is ignored we have used wireline log data and pore pressure measurements in mudstones of the cromer knoll group and the heather formation in the north sea to investigate whether velocity is sensitive to the contribution of unloading processes to observed overpressures our approach was to fit the data by four alternative linear relationships with sonic velocity as the dependent variable the independent variables necessarily included porosity and vertical effective stress and optionally the natural log response and depth our preferred results are v p 3746 3744 11 1 v 4 7 in the cromer knoll mudstones and v p 4035 4269 8 6 v 5 5 in the heather mudstones for vertical effective stress over the range 10 30 mpa the sensitivity of sonic velocity to vertical effective stress is therefore around 10 m s 1 mpa 1 this sensitivity should be sufficient to improve estimates of pore pressure while drilling by using sonic density and natural logs in combination to make use of this sensitivity for pore pressure estimation robust empirical relationships with vertical effective stress as the dependent variable would have to be established for the formations of interest

recent climate driven river incision rate fluctuations in the mercantour crystalline massif southern french alps abstract we present a new geomorphological analysis of the tinee river tributaries in the southern french alps based on numerical inverse and forward modelling of their longitudinal profiles we model their relative uplift history with respect to the main channel hence the incision rate history of this channel inverse models show that all tributaries have consistent incision rate histories with alternating high and low values a comparison with global temperature curves shows that these variations correlate with quaternary climate changes we suggest that during warm periods a wave of regressive erosion propagates in the tinee river while its tributaries deeply incise their substratum to catch up with the falling base level we also show that the post 140 ka history of this landscape evolution is dominated by fluvial incision we then perform forward models of river incision and simulate the incision of the tinee river system over a time span of 600 ka this model allows us to extract time and space incision rate variations of the tinee river with a background of a few mm yr 1 incision rate can increase up to more than 1 cm yr 1 during short periods of time due to climatic oscillations this result is compatible with published cosmogenic nuclide based dating which evidenced incision rates from 0 2 to 24 mm yr 1 the part of the channel located between 12 and 20 km downstream from the source has undergone several periods of rapid incision rates which could explain the steep hillslopes and the triggering of a landslide 10 ka ago

origin of turbidites in deep lake geneva france switzerland in the last 1500 years abstract turbidites in lacustrine sediments are commonly used to assess the frequencies of flood events and or earthquakes understanding the origin of those deposits is key to adequately assess the sources and triggers of such events in large lacustrine systems ca ti x ray fluorescence core scanner and magnetic susceptibility values on sediment cores of the deep basin of lake geneva are used as a provenance indicator of the turbidites either from the dranse or rhone deltas or from the slopes not influenced by deltaic input this tool is validated by mineralogical analyses x ray diffraction major and trace element geochemistry x ray fluorescence based on this discrimination method the turbidites deposited in the central part of the deep basin can be classified regarding their origin from all identified turbidites four turbidites are chosen based on their large depositional area and volumes and are studied in more detail in order to better understand the processes leading to turbidite deposition in the deep basin the age intervals of these turbidites were compared to the historical records of extreme events in the region of lake geneva these turbidites can be related to extreme floods earthquakes and spontaneous delta collapses the cause of two turbidites could not be identified precisely due to large dating intervals that did not allow attributing a specific historical event to the turbidite layer overall this study provides a tool in classifying the turbidites in deep lake geneva and exemplifies that defining the cause of turbidites is complex although it remains a prerequisite for paleohydrology and paleoseismology studies

mechanics of fold and thrust belts and accretionary wedges cohesive coulomb theory a critically tapered fold and thrust belt or submarine accretionary wedge is one that is on the verge of coulomb failure everywhere including its base where frictional sliding along a decollement is assumed to be occurring cohesion within a wedge can add significantly to the overall strength near the toe the effect of this is to decrease the near toe taper leading to a critical topographic profile that is concave upward if the decollement is planar we obtain an approximate self consistent solution for the state of stress within a thin skinned cohesive critical coulomb wedge and determine the relationship between the wedge taper and its strength and basal friction the theory is then applied to the presently deforming fold and thrust belt of western taiwan fitting of theoretical critical wedge shapes to topographic profiles and measurements of the step up angles of thrust faults from the basal decollement are used to constrain the taiwan wedge strength parameters an attractive assertion fully consistent with all the observations is that the mechanics of fold and thrust belts and accretionary wedges is governed by normal frictional and fracture strengths of rocks measured in the laboratory in particular if byerlee s law b 0 85 is adopted as the coefficient of sliding friction on the base we find a coefficient of internal friction 0 9 1 0 in the wedge and a wedge cohesion so 5 20 mpa other solutions having strengths and ambient stresses up to 4 times lower than this can also however satisfy the data

holocene climate variability as reflected by mid european lake level fluctuations and its probable impact on prehistoric human settlements abstract a data set of 180 radiocarbon tree ring and archaeological dates obtained from sediment sequences of 26 lakes in the jura mountains the northern french pre alps and the swiss plateau was used to construct a holocene mid european lake level record the dates do not indicate a random distribution over the holocene but form clusters suggesting an alternation of lower and higher climatically driven lake level phases they provide evidence of a rather unstable holocene climate punctuated by 15 phases of higher lake level 11 250 11 050 10 300 10 000 9550 9150 8300 8050 7550 7250 6350 5900 5650 5200 4850 4800 4150 3950 3500 3100 2750 2350 1800 1700 1300 1100 750 650 cal bp and after 1394 ad a comparison of this mid european lake level record with the gisp2 polar circulation index pci record the north atlantic ice rafting debris ird events and the 14 c record suggests teleconnections in a complex cryosphere ocean atmosphere system correlations between the gisp2 pci the mid european lake level the north atlantic ird and the residual 14 c records suggest that changes in the solar activity played a major role in holocene climate oscillations over the north atlantic area

stress constraints and hydrofracturing stress data for the continental crust faulting and seismicity in the upper continental crust require considerable differential stresses application of experimentally developed friction fracture and flow laws shows that high differential stresses can only exist in the uppermost crust direct hydraulic fracturing measurements in deep boreholes seem to support this rock mechanics conclusion the experimental data base presently consists of approximately 500 hydrofrac tests conducted in about 100 boreholes at about 30 different geographical locations to illustrate the variation of measured stresses with depth the data are expressed as dimensionless horizontal stresses in the forms h h sv z wheres v gz extrapolation of the experimental data to greater depth shows that the minor horizontal stress approaches the values h sv 0 5 which limits friction on wet faults and that the major horizontal stress approaches a value close tos h sv 1 at rather shallow depth 5 to 10 km this limits faulting and seismicity in most of the upper crust to either strike slip or normal faults the lower boundary for seismicity is mainly dependent on tectonic strain accumulation and rock creep at the environmental conditions at depth

mid to late holocene flood frequency changes in the northeastern alps as recorded in varved sediments of lake mondsee upper austria abstract annually laminated varved lake sediments with intercalated detrital layers resulting from sedimentary input by runoff events are ideal archives to establish precisely dated records of past extreme runoff events in this study the mid to late holocene varved sediments of lake mondsee upper austria were analysed by combining sedimentological geophysical and geochemical methods this approach allows to distinguish two types of detrital layers related to different types of extreme runoff events floods and debris flows and to detect changes in flood activity during the last 7100 years in total 271 flood and 47 debris flow layers deposited during spring and summer were identified which cluster in 18 main flood episodes fe 1 18 with durations of 30 50 years each these main flood periods occurred during the neolithic 7100 7050 vyr bp and 6470 4450 vyr bp the late bronze age and the early iron age 3300 3250 and 2800 2750 vyr bp the late iron age 2050 2000 vyr bp throughout the dark ages cold period 1500 1200 vyr bp and at the end of the medieval warm period and the little ice age 810 430 vyr bp summer flood episodes in lake mondsee are generally more abundant during the last 1500 years often coinciding with major advances of alpine glaciers prior to 1500 vyr bp spring summer floods and debris flows are generally less frequent indicating a lower number of intense rainfall events that triggered erosion in comparison with the increase of late holocene flood activity in western and northwestern nw europe commencing already as early as 2800 yr bp the hydro meteorological shift in the lake mondsee region occurred much later these time lags in the onset of increased hydrological activity might be either due to regional differences in atmospheric circulation pattern or to the sensitivity of the individual flood archives the lake mondsee sediments represent the first precisely dated and several millennia long summer flood record for the northeastern ne alps a key region at the climatic boundary of atlantic mediterranean and east european air masses aiding a better understanding of regional and seasonal peculiarities of flood occurrence under changing climate conditions

integrating the holocene tephrostratigraphy for east asia using a high resolution cryptotephra study from lake suigetsu sg14 core central japan abstract tephra volcanic ash layers have the potential to synchronise disparate palaeoenvironmental archives on regional to hemispheric scales highly productive arc regions like those in east asia offer a considerable number of widespread isochrons but before records can be confidently correlated using these layers a refined and integrated framework of these eruptive events is required here we present the first high resolution holocene cryptotephra study in east asia using the lake suigetsu sedimentary archive in central japan the holocene tephrostratigraphy has been extended from four to twenty ash layers using cryptotephra extraction techniques which integrates the deposits from explosive eruptions from north korea china south korea and along the japanese arc this lake suigetsu tephrostratigraphy is now the most comprehensive record of east asian volcanism and the linchpin site for correlating sequences across this region major element glass geochemical compositions are presented for the tephra layers in the sequence which have been compared to proximal datasets to correlate them to their volcanic source and specific eruptions this study has significantly extended the ash dispersal of many key holocene marker layers and has identified the first distal occurrence of isochrons from ulleungdo and changbaishan volcanoes utilising the high precision lake suigetsu chronology we are able to provide constrained eruption ages for the tephra layers which can be transferred into other site specific age models containing these markers this new framework indicates that several isochrons stratigraphically bracket abrupt climate intervals in japan and could be used to precisely assess the regional and hemispheric synchronicity of these events

appalachian stress study 2 analysis of devonian shale core some implications for the nature of contemporary stress variations and alleghanian deformation in devonian rocks detailed stress measurements in three boreholes penetrating horizontally bedded devonian silt stones sandstones and limestones above a prominent salt decollement in the appalachian plateau of western new york have revealed variations in horizontal stress magnitudes which correlate with lithologic and stratigraphic units in all wells high differential stress levels up to 20 mpa were found in shales of very high clay content contrary to the proposition that such materials have negligible long term strength elastic modulus data show that stiffer beds generally host higher stress levels and suggest that sand shale stress contrasts result in large part from elastic shortening of the section in response to regional ene compression no correlation between stress and poisson s ratio was found however a major systematic drop in stress level within the generally massive shales which occurs across a group of sand beds near the base of the rhinestreet formation appears to be of different origin the stress offset corresponds to the top of a section which we conclude on the basis of local and regional total strain data derived from chlorite fabric measurements once hosted abnormally high pore pressures the total strain data also suggest the entire section above the salt has been uniformly shortened during alleghanian compression to explain the stress discontinuity two kinematic patterns for alleghanian deformation of the devonian section are proposed both involving abnormal pore pressure development in the sub rhinestreet section in response to limited drainage of fluid drainage of this paleo overpressure is the best available explanation of the stress offset although an additional remnant stress component must also be present to satisfy the stress data precisely

review and assessment of in situ rock stress in hong kong for territory wide geological domains and depth profiling abstract hydraulic fracturing is a favorably used technique to measure in situ rock stress orientation and magnitude for the design of underground excavations in hong kong studies prior to 2000 revealed a general wnw ese maximum horizontal stress orientation and established stress ratio depth profile however there is a paucity of geological assessment on the in situ stress by examining 380 no of in situ stress test results from 65 boreholes at depth ranging between 18 and 300 mbgl and the review of the associated raw data such as pressure time records and impression packer test results in the test reports this study updates the map of hong kong regional major principal stress orientation besides the study also reviews whether the major geological domains in hong kong have any major impact or influence on in situ stress magnitudes and orientations depth relationships on principal in situ stress orientation is also explored from the study the following conclusions can be drawn high kh and kh at shallow depth and the overall wnw ese orientation of maximum horizontal stress are observed the results are consistent with the published measurements in previous studies the rock type imposes no prominent effect on the stress magnitude no apparent depth relationship on principal in situ stress orientation is observed

processes of flood triggered detrital layer deposition in the varved lake mondsee sediment record revealed by a dual calibration approach a succession of 23 sub millimetre to maximum 12 mm thick mostly flood triggered detrital layers deposited between 1976 and 2005 was analysed in 12 varved surface sediment cores from meso scale peri alpine lake mondsee applying microfacies and high resolution micro x ray fluorescence analyses detailed intrabasin comparison of these layers enabled identification of i different source areas of detrital sediments ii flood triggered sediment flux and local erosion events and iii seasonal differences of suspended flood sediment distribution within the lake basin additional calibration of the detrital layer record with river discharge and precipitation data reveals different empirical thresholds for flood layer deposition for different parts of the basin at proximal locations detrital layer deposition requires floods exceeding a daily discharge of 40 m3 s 1 whereas at a location 2 km more distal an hourly discharge of 80 m3 s 1 and at least 2 days of discharge above 40 m3 s 1 are necessary furthermore we observe a better correlation between layer thickness and flood amplitude in the depocentre than in distal and proximal areas of the basin although our results are partly site specific the applied dual calibration approach is suitable to precisely decipher flood layer formation processes and thereby improve the interpretation of long flood time series from lake sediments

persistent positive north atlantic oscillation mode dominated the medieval climate anomaly the medieval climate anomaly mca was the most recent pre industrial era warm interval of european climate yet its driving mechanisms remain uncertain we present here a 947 year long multidecadal north atlantic oscillation nao reconstruction and find a persistent positive nao during the mca supplementary reconstructions based on climate model results and proxy data indicate a clear shift to weaker nao conditions into the little ice age lia globally distributed proxy data suggest that this nao shift is one aspect of a global mca lia climate transition that probably was coupled to prevailing la nina like conditions amplified by an intensified atlantic meridional overturning circulation during the mca

deformation along the san andreas fault 1982 1986 as indicated by frequent geodolite measurements frequent 4 12 times per year measurements of six 3 line lengths 10 40 km strain networks located along the locked sections of the san andreas fault in southern and central california provide a time history of deformation along the fault in the interval 1982 1986 the standard error in measurement ranges from 0 4 ppm in line length for the shortest lines to 0 2 ppm for the longest lines except for one example of coseismic offset and postseismic relaxation the observations are at least marginally consistent with uniform in time deformation the records of deformation at the networks closest to the epicenters of two recent magnitude 6 california earthquakes 1984 morgan hill and 1986 north palm springs were particularly stable in the year preceding the earthquakes thus it is unlikely that these earthquakes were triggered by regional strain events however marginally significant anomalies were observed 12 18 months before both earthquakes

quantifying cretaceous cenozoic exhumation in the otway basin southeastern australia using sonic transit time data implications for conventional and unconventional hydrocarbon prospectivity in prospective basins affected by exhumation uncertainty commonly exists regarding the maximum burial depths of source reservoir and seal horizons one such basin is the otway basin an important gas province in southeastern australia which has witnessed several exhumation events here we present estimates of net exhumation magnitudes for 110 onshore and offshore petroleum wells based on the sonic transit time analyses of lower cretaceous fluvial shales our results show significant post albian net exhumation in the eastern onshore otway basin 1500 m 4920 ft and a generally minor net exhumation 200 m 655 ft elsewhere in the otway basin consistent with estimates based on thermal history data the distribution of net exhumation magnitudes in relation to mid cretaceous and neogene compressional structures indicates that exhumation was dominantly controlled by short wavelength basin inversion driven by plate boundary forces deeper burial coupled with high geothermal gradients in the onshore eastern otway basin and along the northern basin margin during the early cretaceous have rendered lower cretaceous source rocks mostly overmature with any remaining hydrocarbons from the initial charge likely to be trapped in tightly compacted reservoirs and or secondary fracture related porosity however the embrittlement of these reservoirs during their deeper burial may present opportunities for the development of low permeability plays through hydraulic fracturing where smectite clay minerals are illitized source rocks at near maximum burial at present day are at temperatures suitable for gas generation with key controls on prospectivity in these areas including the sealing potential of faulted traps and the relationship between charge and trap development

reconstruction of sea level pressure fields over the eastern north atlantic and europe back to 1500 spatially and temporally high resolution estimates of past natural climate variability are important to assess recent significant climate trends the mid latitude atmospheric circulation is the dominant factor for regional changes in temperature rainfall and other climatic variables here we present reconstructions of gridded monthly sea level pressure slp fields back to 1659 and seasonal reconstructions from 1500 1658 for the eastern north atlantic european region 30 w to 40 e 30 n to 70 n these were developed using principal component regression analysis based on the combination of early instrumental station series pressure temperature and precipitation and documentary proxy data from eurasian sites the relationships were derived over the 1901 1960 calibration period and verified over 1961 1990 under the assumption of stationarity in the statistical relationships a transfer function derived over the 1901 1990 period was used to reconstruct the 500 year large scale slp fields systematic quality testing indicated reliable winter reconstructions throughout the entire period lower skill was obtained for the other seasons although meaningful monthly reconstructions were available from around 1700 onwards when station pressure series became available the quality and the reconstructed slp fields for two exceptionally cold years 1573 1740 are discussed and climatologically interpreted an eof analysis of the 1500 1999 winter slp revealed firstly a zonal flow pattern with pronounced decadal to centenial time scale variations secondly a monopole pattern over northwest europe and thirdly a pattern modulating the meridional flow component over europe these 500 year slp reconstructions should be useful for modelling studies particulary for analyses of low frequency atmospheric variability and for circulation dynamics

climate variability in se europe since 1450 ad based on a varved sediment record from etoliko lagoon western greece to achieve deeper understanding of climate variability during the last millennium in se europe we report new sedimentological and paleoecological data from etoliko lagoon western greece the record represents the southernmost annually laminated i e varved archive from the balkan peninsula spanning the little ice age allowing insights into critical time intervals of climate instability such as during the maunder and dalton solar minima after developing a continuous ca 500 year long varve chronology high resolution xrf counts stable isotope data measured on ostracod shells palynological including pollen and dinoflagellate cysts and diatom data are used to decipher the season specific climate and ecosystem evolution at etoliko lagoon since 1450 ad our results show that the etoliko varve record became more sensitive to climate change from 1740 ad onwards we attribute this shift to the enhancement of primary productivity within the lagoon which is documented by an up to threefold increase in varve thickness this marked change in the lagoon s ecosystem was caused by i increased terrestrial input of nutrients ii a closer connection to the sea and human eutrophication particularly from 1850 ad onwards and iii increasing summer temperatures integration of our data with those of previously published paleolake sediment records tree ring based precipitation reconstructions simulations of atmospheric circulation and instrumental precipitation data suggests that wet conditions in winter prevailed during 1740 1790 ad whereas dry winters marked the periods 1790 1830 ad dalton minimum and 1830 1930 ad the latter being sporadically interrupted by wet winters this variability in precipitation can be explained by shifts in the large scale atmospheric circulation patterns over the european continent that affected the balkan peninsula e g north atlantic oscillation the transition between dry and wet phases at etoliko points to longitudinal shifts of the precipitation pattern in the balkan peninsula during the little ice age

hydrological thresholds and basin control over paleoflood records in lakes the scarcity of long term hydrological data is a barrier to reliably determining the likelihood of floods becoming more frequent and or intense in a warmer world lake sediments preserve characteristic event layers offering the potential to develop widely distributed and unique chronologies of historical floods inferring flood magnitude remains a greater challenge previously overcome in part by analyzing sharply laminated polar or alpine sequences here we demonstrate an approach to obtain flood frequency and magnitude data from an unexploited resource the largely visually homogeneous organic sediments that typify most temperate lakes the geochemical composition and end member modeling of sediment trap and adjacent short core particle size data for brotherswater northwest england discriminates the signature of infrequent coarse grained flood deposits from seasonal and longer term allogenic enhanced discharge and sediment supply during winter and autogenic summer productivity thermal mixing depositional processes comparing the paleoflood reconstruction to local river discharges shows that hydrological thresholds censor event signature preservation with 4 yr recurrence intervals detectable in delta proximal sediments declining to 9 yr in the lake center event threshold discharge and process characterization are essential precursors to discerning flood magnitude from sediment archives implementation of our approach in globally prevalent temperate lakes offers a vast unique repository of long term hydrological data for hydrologists climate modelers engineers and policy makers addressing future flood risks

orbital and solar forcing of shifts in mid to late holocene flood intensity from varved sediments of pre alpine lake ammersee southern germany abstract microfacies analyses and x ray fluorescence scanning xrf at sub mm resolution were conducted on the varved mid to late holocene interval of two sediment profiles from pre alpine lake ammersee southern germany the coring sites are located in a proximal as10prox and distal as10dist position towards the main tributary river ammer in 1 8 km distance from each other to shed light on sediment distribution within the lake particular emphasis was 1 the detection of intercalated detrital layers and their micro sedimentological features and 2 intra basin correlation of these event deposits detrital layers were dated by microscopic varve counting verified by accelerator mass spectrometry 14c dating of terrestrial plant macrofossils since 5500 varve years vyr bp in total 1573 detrital layers were detected in either one or both of the investigated sediment profiles based on their microfacies geochemistry and proximal distal deposition pattern detrital layers were interpreted as river ammer flood deposits earlier studies on flood layer seasonality have proven that flood layer deposition occurs predominantly during spring and summer the flood season at lake ammersee most prominent features of the record are the onset of regular flood layer deposition at 5500 vyr bp in as10prox and 2800 vyr bp in as10dist as well as three major increases in mean flood layer thickness at 5500 2800 and 400 vyr bp integrating information from both sediment profiles allowed to interpret these changes in terms of shifts towards higher mean flood intensity proposed triggering mechanisms are gradual reduction in northern hemisphere orbital summer forcing and superimposed centennial scale solar activity minima likely responses to this forcing are enhanced equator to pole temperature gradients and changes in synoptic scale atmospheric circulation the consequences for the ammersee region are more intense cyclones leading to extremer rainfall and flood events in spring and summer

stress field determinations in france by hydraulic tests in boreholes the stress field has been determined at eight different sites in france four in crystalline or metamorphic rocks four in sedimentary formations by hydraulic tests in boreholes for seven of these sites the complete stress field has been determined using the hydraulic tests on pre existing fractures htpf inversion method validity of the results is demonstrated by the good fit between a priori and a posteriori values for the data and by the low values of the a posteriori standard deviation on the unknowns for four sites results have been compared with those derived according to the hydraulic fracturing theory the two methods yield comparable results for the orientation of the maximum horizontal principal stress h a generally satisfactory fit for the magnitude of the minimum horizontal principal stress h but a very poor agreement for the magnitude of h this latter misfit has been attributed to the effect of fluid percolation prior to the actual opening of the fractures below a depth of 500 m a homogeneous h direction n150 e has been determined at the crystalline sites auriat echassieres le mayet de montagne chassoles all located in the northern massif central for three of these sites the vertical stress is significantly lower than the weight of overburden as computed from the rock density and the depth of the corresponding measurement at auriat and echassieres the stress field is consistent with a mostly strike slip faulting regime at le mayet de montagne and chassoles the maximum stress is vertical but nearly equal to h the stress field has been found to be much more heterogeneous at two of the four sites in sedimentary rocks because of the large variability in mechanical rock properties in such heterogeneous formations inversion with the htpf method must be limited to those data which pertain to the same rock horizon however because of its structure this heterogeneity does not restrict the possibility of defining large scale uniform principal stress directions all the results are consistent with the local seismotectonics

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

an examination of in situ rock stress estimation using the kaiser effect abstract when rock cores are loaded in uniaxial compression acoustic emission occurs when the stress reaches a level greater than that which the rock has previously experienced this phenomenon known as the kaiser effect has been used as an indirect method of estimating the in situ stress field in rock masses if the procedure is valid then the kaiser effect method has the advantage that the stress field can be estimated through laboratory tests on rock cores rather than the field drillhole methods of overcoring and hydraulic fracturing however the kaiser effect method is an enigma on the one hand there are good reasons why the method cannot be valid on the other hand there are reports in the literature of it being successfully applied in this paper we explore the variety of geological and mechanical factors involved and report on a case example for the olkiluoto crystalline rock site in western finland we conclude that the kaiser effect method for stress measurement is only likely to be successful if it is supported by key geological and other stress measurement information and if certain procedures are followed as explained in the paper

stable oxygen and carbon isotopes of carbonates in lake sediments as a paleoflood proxy lake sediments are increasingly explored as reliable paleoflood archives in addition to established flood proxies including detrital layer thickness chemical composition and grain size we explore stable oxygen and carbon isotope data as paleoflood proxies for lakes in catchments with carbonate bedrock geology in a case study from lake mondsee austria we integrate high resolution sediment trapping at a proximal and a distal location and stable isotope analyses of varved lake sediments to investigate flood triggered detrital sediment flux first we demonstrate a relation between runoff detrital sediment flux and isotope values in the sediment trap record covering the period 2011 2013 ce including 22 events with daily hourly peak runoff ranging from 10 24 m3 s 1 to 79 110 m3 s 1 the three to ten fold lower flood triggered detrital sediment deposition in the distal trap is well reflected by attenuated peaks in the stable isotope values of trapped sediments next we show that all nine flood triggered detrital layers deposited in a sediment record from 1988 to 2013 have elevated isotope values compared with endogenic calcite in addition even two runoff events that did not cause the deposition of visible detrital layers are distinguished by higher isotope values empirical thresholds in the isotope data allow estimation of magnitudes of the majority of floods although in some cases flood magnitudes are overestimated because local effects can result in too high isotope values hence we present a proof of concept for stable isotopes as reliable tool for reconstructing flood frequency and although with some limitations even for flood magnitudes less

rheological characterization of a sedimentary formation from a stress profile inversion summary detailed stress measurements have been carried out within a sedimentary sequence composed of a hard clay formation laying horizontally between two limestone units in the eastern paris basin france orientations of the minor and major horizontal principal stresses are found to be in good agreement with the direction of major shortening that prevailed during the last tectonic stage however their magnitudes exhibit an intriguing evolution with depth while the magnitude of the maximum horizontal stress slowly but regularly increases with depth the magnitude of the minimum horizontal one is larger in the hard clay formation than in the surrounding limestone units contrary to expectation from simple elastic considerations an analytical calculation demonstrates that the genesis of the current stress state may be reproduced by taking into account horizontal strains in two different directions and simulating erosion of part of the overburden with a viscoelastic model for the hard clay and an elastic behaviour for the limestone however the elastic constants that are derived for the limestone in order to fit the measured stress field correspond to a material that is more deformable and has a lower poisson s ratio than predicted by laboratory tests this discrepancy may be explained by a slow long term deformation process in the limestone possibly associated with pressure solution

a millennial long record of warm season precipitation and flood frequency for the north western alps inferred from varved lake sediments implications for the future abstract the recent warming of the global climate is well recognized however does a warmer climate also mean a moister climate does dry get drier and wet get wetter there are important questions as they relate to changes in the water cycle and impacts the water resources as well as the frequency and intensity of storms and floods in the near future in europe regional climate models do not show consistent and robust results for future hydroclimatic changes and how extreme events will evolve in response to future climate change paleo hydroclimatic data from natural archives are one of the few means to assess such changes in the longer context here we present an annually resolved record of warm season mjja precipitation and summer flood frequency from the varved annually laminated sediments of proglacial lake oeschinen 46 30 n 7 44 e 1580 m nw swiss alps back to ad 884 these data sets are inferred from the thickness of annual sediment deposits and the occurrence of flood event layers in the sediments the chronology of the sediment record is based on multiple varve counts and validated with historical floods chronicled in written documents back to the 14th century and 14c ams dates the precipitation record shows pronounced interannual to centennial variability with humid warm season phases between ad 920 950 ad 1100 1180 ad 1300 1400 ad 1590 1650 ad 1700 1790 ad 1820 1880 and ad 1960 2008 driest conditions are reconstructed for ad 960 1080 ad 1250 1300 and for ad 1880 1900 our precipitation record is consistent with the few multi centennial warm season precipitation records available for europe we did not find a persistent relationship between warm season precipitation and temperature in contrast results show that the relation between precipitation and temperature has oscillated between positive correlations warmer gets wetter cooler gets drier and negative correlations warmer gets drier cooler gets wetter with a highly significant 2 99 multidecadal 60 70 yrs periodicity over the last millennium possible explanations for this phenomenon are changes in the weather type statistics or the within weather type variability which influence the combinations between precipitation and temperature over continental central europe and operate at multidecadal scales such multidecadal effects might also be important for precipitation scenarios in the alpine area under future warming our record of flood frequency suggests more frequent floods under cool and humid climate during the warm seasons this picture is consistent with other studies from small and medium size catchments at mid and high elevations in the alpine area however the 13th century reveals a period with high flood frequency during warm and moderately dry average precipitation conditions this anomalous situation is currently not understood nonetheless this is also one out of several possible scenarios for the future from the different combinations found in our record we conclude that the relation between floods precipitation and temperature and in consequence future projections remain poorly constrained

a 450 year record of spring summer flood layers in annually laminated sediments from lake ammersee southern germany 1 a 450 year spring summer flood layer time series at seasonal resolution has been established from the varved sediment record of lake ammersee southern germany applying a novel methodological approach the main results are 1 the attainment of a precise chronology by microscopic varve counting 2 the identification of detrital layers representing flood triggered fluxes of catchment material into the lake and 3 the recognition of the seasonality of these flood layers from their microstratigraphic position within a varve tracing flood layers in a proximal and a distal core and correlating them by application of the precise chronology provided information on the depositional processes comparing the seasonal flood layer record with daily runoff data of the inflowing river ammer for the period from 1926 to 1999 allowed the definition of an approximate threshold in flood magnitude above which the formation of flood layers becomes very likely moreover it was possible for the first time to estimate the completeness of the flood layer time series and to recognize that mainly floods in spring and summer representing the main flood seasons in this region are well preserved in the sediment archive their frequency distribution over the entire 450 year time series is not stationary but reveals maxima for colder periods of the little ice age when solar activity was reduced the observed spring summer flood layer frequency further shows trends similar to those of the occurrence of flood prone weather regimes since a d 1881 probably suggesting a causal link between solar variability and changes in midlatitude atmospheric circulation patterns

the origin of tectonic stress in the lithosphere abstract the sources of lithospheric stress and their distinctive features are briefly reviewed it is suggested that there are two main categories of lithospheric stress renewable stress which persists despite continuing stress relaxation and non renewable stress which can be dissipated by relief of the initial strain the two most important types of renewable stress arise from plate boundary forces and from isostatically compensated loads non renewable stress systems include bending stresses membrane stresses and thermal stresses an important phenomenon generating large stresses at shallow depth is stress amplification caused by lower lithospheric creep this applies to renewable stresses but not to the non renewable type it is suggested that only renewable stresses contribute significantly to tectonic activity however bending and thermal stresses are locally important in subducting lithosphere

a 45 kyr laminae record from the dead sea implications for basin erosion and floods recurrence abstract recording and analyzing how climate change impacts flood recurrence basin erosion and sedimentation can improve our understanding of these systems the aragonite detritus laminae couplets comprising the lacustrine formations that were deposited in the dead sea are considered as faithful monitors of the freshwater supply to the lakes we count a total of 5600 laminae couplets deposited in the last 45 kyr mis3 mis1 at the dead sea center which encompass the upper 142 m of the icdp core 5017 1 the present study shows that aragonite and detritus laminae are thinner and occur at high frequency during mis 3 2 while they are much thicker and less frequent during mis 1 by analyzing multiple climate connected factors we propose that significant lake level drops enhanced dust input and low vegetative cover in the drainage basin during the last deglaciation 22 11 6 ka have considerably increased erodible materials in the dead sea watershed we find a decoupling existed between the significant lake level drop lake size reduction and lamina thickness change during the last deglaciation we argue that during the last glacial and the holocene the variation of lamina thickness at the multiple millennium scale was not controlled directly by the lake level size change we interpret this decoupling implying the transport capacity of flash floods is low and might be saturated by the oversupply of erodible materials and indicating a transport limited regime during the time period we suggest the observed thickness and frequency distribution of aragonite detritus laminae points to the high frequency of small magnitude floods during the last glacial in contrast to low frequency but large magnitude floods during the holocene

annually resolved lake record of extreme hydro meteorological events since ad 1347 in ne iberian peninsula abstract we present an annual reconstruction of extreme rainfall events interpreted from detrital layers and turbidites interbedded within a varved sediment record since the 14 th century in montcortes lake ne spain 1027 m a s l clastic microfacies intercalated within the biochemical calcite varves were characterized and their depositional dynamics interpreted using high resolution geochemical and sedimentological analyses annual number of detrital layers was compared against instrumental records of extreme daily rainfalls providing minimum rainfall thresholds and return periods associated to the identified types of clastic microfacies non continuous detrital layers were deposited during rainfall events higher than 80 mm 2 year return period while graded detrital layers and turbidites were associated with higher magnitude rainfall events 90 mm and 4 year return period the frequency distribution of extreme hydro meteorological events is not stationary and its pattern coincides with historical floods from the nearby segre river high frequency of heavy rainfalls occurred during the periods ad 1347 1400 and ad 1844 1894 a lower frequency of heavy rainfall was found during the periods ad 1441 1508 1547 1592 1656 1712 1765 1822 and 1917 2012 the 20 th century stands out as the longest interval within the studied period of very low number of extreme rainfall events variability in extreme rainfall events prior to the 20 th century is in phase with solar activity suggesting a mechanistic link in mid latitude atmospheric circulation patterns that ceased during the 20 th century

in situ stress amplification due to geological factors in tunnels the case of pajares tunnels spain geological and geomechanical anisotropies can significantly increase the magnitude of in situ stress in a rock mass excavated for tunnelling purposes four tunnels for the new high speed railway lines in pajares in the cantabrian mountains n spain were analysed and significant deformations was found to have occurred in forty specific zones of these tunnels during excavation requiring much more support than envisaged before construction local factors influencing in situ stress have been identified in these zones of the tunnels related to geological structures of high compressive tectonic stress regimes including thrust faults folds with steep flank dip orwith geomechanical anisotropies in contact zones between rock formations of different strengths amethodological procedurewas applied to four tunnels to assess the influence of the geological anisotropies on the insitu stress magnitudes this procedure is based on the analysis of tunnel deformations and the support pressure needed to stabilise the excavations affected by geological anisotropies the increase of in situ stress due to local factors is expressed by the stress amplification factor saf defined by the ratio between the k h v local value estimated in a particular rock mass tunnel zone and the mean k h v regional value representative of the whole rock mass tunnel kregional was estimated from hydrofracture tests and from the tsi index klocal was calculated from the back analysis of the support pressure required to stabilise the deformed tunnel zones saf values for the forty specific tunnel zones ranged from 1 1 to 2 5 this significant increase in the magnitude of in situ stress emphasises the influence of geological and geomechanical anisotropies in tunnel stability and support design the results provide a quantitative approach for assessing structural stresses in rock masses for tunnelling excavations

quantification of principal horizontal stresses inside a tunnel an application of fracture induced electromagnetic radiation femr technique in the darjeeling sikkim himalayas abstract characterization of recent stresses delineation of the locations of active faults landslide prone slip planes and forecasting earthquakes are some of the emerging applications of the fracture induced electromagnetic radiation femr technique it is believed that such radiation is polarized along the direction of maximum compression and proportional to the maximum applied shear stress in this paper we have demonstrated the use of the femr technique to calculate the magnitude and directions of principal horizontal stresses inside a tunnel of 240 m length over a hilly road between jorethang and mayong near the village of miyong in sikkim india by taking 11 cross sectional measurements using a portable femr recording device called angel m although a reverse stress regime is obvious and established over the himalayas the results show a normal stress regime prevailing over this shallow near surface region of the tunnel and the direction of maximum shear stress changes along the tunnel length the results were explained with the aid of a simple clay analogue model where normal reactivation of a thrust plane with changing dips was simulated with this communication we hope to encourage scientists and engineers to deploy the femr technique which is lesser known but quicker non destructive cheaper and more accessible than conventional methods in evaluating tunnel safety by calculating shallow stresses locally modified inside a tunnel

on the state of stress in the near surface of the earth s crust five models for near surface crustal stresses induced by gravity and horizontal deformation and the influence of rock property contrasts rock strength and stress relaxation on these stresses are presented three of the models the lateral constraint model the model for crustal stresses caused by horizontal deformation and the model for the effects of anisotropy are linearly elastic the other two models assume that crustal rocks are brittle or viscoelastic in order to account for the effects of rock strength and time on near surface stresses it is shown that the lateral constraint model is simply a special case of the combined gravity and deformation induced stress field when horizontal strains vanish and that the inclusion of the effect of rock anisotropy in the solution for crustal stresses caused by gravity and horizontal deformation broadens the range for predicted stresses it is also shown that when stress levels in the crust reach the limits of brittle rock strength these stresses become independent of strain rates and that stress relaxation in ductile crustal rocks subject to constant horizontal strain rates causes horizontal stresses to become independent of time in the long term

reconstruction of temperature in the central alps during the past 2000 yr from a δ18o stalagmite record the precisely dated isotopic composition of a stalagmite from spannagel cave in the central alps is translated into a highly resolved record of temperature at high elevation during the past 2000 yr temperature maxima during the medieval warm period between 800 and 1300 ad are in average about 1 7 8c higher than the minima in the little ice age and similar to present day values the high correlation of this record to d 14 c suggests that solar variability was a major driver of climate in central europe during the past 2 millennia d 2005 elsevier b v all rights reserved

varves in lake sediments a review abstract downcore counting of laminations in varved sediments offers a direct and incremental dating technique for high resolution climatic and environmental archives with at least annual and sometimes even seasonal resolution the pioneering definition of varves by de geer 1912 had been restricted to rhythmically deposited proglacial clays one century later the meaning of varve has been expanded to include all annually deposited laminae in terrestrial and marine settings under favourable basin configurations and environmental conditions limnic varves are formed due to seasonality of depositional processes from the lake s water column and or transport from the catchment area subsequent to deposition of topmost laminae the physical preservation of the accumulating varved sequence requires the sustained absence of sediment mixing for example via wave action or macrobenthic bioturbation individual sub laminae in varved lake sediments typically express contrasting colours always differ in terms of their organic chemical and or mineralogical compositions and often also differ with regard to grain size various predominating climatic and depositional conditions may result in clastic biogenic or endogenic incl evaporitic varved sediments and their mixtures to reliably establish a varve chronology the annual character of laminations needs to be determined and verified in a multidisciplinary fashion sources and influences of possible errors in varve chronologies are best determined and constrained by repeated varve counts and by including radioisotopes and correlation with historically documented events a well established varve chronology greatly enhances the scientific value of laminated limnic archives by securely anchoring the wealth of multi proxy palaeoenvironmental information in the form of time series for multidisciplinary investigations applications of varved records are discussed with special reference to advances since the 1980s these span fields like calibrating radiometric dating methods reconstructing past changes of the earth s magnetic field or detecting fluctuations in solar forcing once a varve chronology is established it can be applied to precisely date events like volcanic ash layers earthquakes or human impact as well as short and long term climate temperature precipitation wind hydroclimatic conditions or flooding and environmental changes eutrophication pollution due to their exceptional high temporal resolution and in combination with their robust and accurate internal time scale in calendar years annually laminated sediments can be regarded as one of the most precious environmental archives on the continents these records are necessary to extend temporally limited instrumental records back in time as such they have societal relevance with regard to risk assessments related to natural hazards arising from e g flooding or volcanic eruptions

evidence for higher than average air temperatures after the 8 2 ka event provided by a central european δ 18 o record the so called 8 2 ka event represents one of the most prominent cold climate anomalies during the holocene warm period accordingly several studies have addressed its trigger mechanisms absolute dating and regional characteristics so far however knowledge about subsequent climate recovery is still limited although this might be essential for the understanding of rapid climatic changes here we present a new sub decadally resolved and precisely dated oxygen isotope o record for the interval between 7 7 and 8 7 ka bp 10 calendar years before ad 1950 derived from the calcareous valves of benthic ostracods preserved in the varved lake sediments of pre alpine mondsee austria besides a clear reflection of the 8 2 ka event showing a good agreement in timing duration and magnitude with other regional stable isotope records the high resolution mondsee lake sediment record provides evidence for a 75 year long interval of higher than average o values directly after the 8 2 ka event possibly reflecting increased air temperatures in central europe this observation is consistent with evidence from other proxy records in the north atlantic realm thus most probably reflecting a hemispheric scale climate signal rather than a local phenomenon as a possible trigger we suggest an enhanced resumption of the atlantic meridional overturning circulation amoc supporting assumptions from climate model simulations

links between flood events in central europe since ad 1500 and large scale atmospheric circulation modes 1 based on documentary sources incidence variations of flood events can be reconstructed back to ad 1500 for several catchment areas in central europe links to atmospheric circulation modes derived from reconstructed large scale sea level pressure slp grids for the last 500 years have been identified on climatic time scales monthly to seasonal these relations are expressed in terms of several indices describing the particular importance of atmospheric circulation modes as a dynamical background for the varying incidence of flood events during winter the zonal circulation mode covers the largest part of these events in relation to mode frequency however other circulation modes become important during historical periods of increased flood frequency e g modes characterised by atlantic low and russian high pressure centres different subtypes of this mode reached maxima in flood association during different climatic periods of the past

integrating chronological uncertainties for annually laminated lake sediments using layer counting independent chronologies and bayesian age modelling lake ohau south island new zealand abstract annually resolved varved lake sequences are important palaeoenvironmental archives as they offer a direct incremental dating technique for high frequency reconstruction of environmental and climate change despite the importance of these records establishing a robust chronology and quantifying its precision and accuracy estimations of error remains an essential but challenging component of their development we outline an approach for building reliable independent chronologies testing the accuracy of layer counts and integrating all chronological uncertainties to provide quantitative age and error estimates for varved lake sequences the approach incorporates 1 layer counts and estimates of counting precision 2 radiometric and biostratigrapic dating techniques to derive independent chronology and 3 the application of bayesian age modelling to produce an integrated age model this approach is applied to a case study of an annually resolved sediment record from lake ohau new zealand the most robust age model provides an average error of 72 years across the whole depth range this represents a fractional uncertainty of 5 higher than the

event layers in the japanese lake suigetsu sg06 sediment core description interpretation and climatic implications event layers in lake sediments are indicators of past extreme events mostly the results of floods or earthquakes detailed characterisation of the layers allows the discrimination of the sedimentation processes involved such as surface runoff landslides or subaqueous slope failures these processes can then be interpreted in terms of their triggering mechanisms here we present a 40 ka event layer chronology from lake suigetsu japan the event layers were characterised using a multi proxy approach employing light microscopy and xrf for microfacies analysis the vast majority of event layers in lake suigetsu was produced by flood events 362 out of 369 allowing the construction of the first long term quantitative with respect to recurrence and well dated flood chronology from the region the flood layer frequency shows a high variability over the last 40 ka and it appears that extreme precipitation events were decoupled from the average long term precipitation for instance the flood layer frequency is highest in the glacial at around 25 ka bp at which time japan was experiencing a generally cold and dry climate other cold episodes such as heinrich event 1 or the late glacial stadial show a low flood layer frequency both observations together exclude a simple straightforward relationship with average precipitation and temperature we argue that especially during glacial times changes in typhoon genesis typhoon tracks are the most likely control on the flood layer frequency rather than changes in the monsoon front or snow melts spectral analysis of the flood chronology revealed periodic variations on centennial and millennial time scales with 220 yr 450 yr and a 2000 yr cyclicity most pronounced however the flood layer frequency appears to have not only been influenced by climate changes but also by changes in erosion rates due to for instance earthquakes

a 1600 yr seasonally resolved record of decadal scale flood variability from the austrian pre alps we present a record of extreme spring summer runoff events for the past 1600 yr preserved in the varved sediments of lake mondsee austrian pre alps combined sediment microfacies analyses and high resolution micro x ray fluorescence element scanning allow us to identify 157 detrital event layers deposited in spring summer and to discriminate between regional flood and local debris flow deposits higher spring summer flood activity with a mean event recurrence of 3 5 yr occurred in several well confined multidecadal episodes during the dark ages cold period and medieval time a d 450 480 590 640 700 750 and 1140 1170 as well as during the early little ice age lia a d 1300 1330 and 1480 1520 in contrast lowest spring summer flood activity with an event recurrence of only 30 100 yr is observed during the medieval climate anomaly a d 1180 1300 and the coldest interval of the lia a d 1600 1700 these findings indicate a complex relationship between temperature conditions and extreme hydro meteorological events and suggest that enhanced summer mediterranean cyclogenesis triggers large scale floods in the northeast alps during climatic transitions the lake mondsee data demonstrate the climatic sensitivity of spring summer floods and prove the potential of varved sediment records to investigate the impact of changing climate boundary conditions on seasonal flood activity for pre instrumental time

performance based support design for horseshoe shaped rock caverns using 2d numerical analysis abstract excavation in rock may change the stress field and induce excavation damaged zones edz in the surrounding rock mass to consider the development of the edz the support design could be evaluated using the convergence confinement method ccm in this paper an efficient approach is proposed to evaluate the support design based on rock cavern performance 2d plane strain models are adopted to simulate the excavation effects of horseshoe cross section rock caverns using the progressive core replacement method the performance of rock cavern is investigated using ccm parameteric studies are carried out to analyze the effects of rock condition and sequential excavation it shows the roof displacement is not changing significantly during excavation if q 10 it also presents the sequencial excavation can reduce the range of the edz but there are no obvious relationships for different subdivision methods using the data from numerical analysis the relationships among the rock conditions the sequential excavation parameters and the cavern performances are mapped using artificial neural network ann an evaluation chart for the support design of a rock cavern is proposed by integrating the ann models into excel software a case study is presented to verify the accuracy of the proposed method it illustrates the feasibility of the proposed approach for practical applications with much less computing time

physical properties of shale at temperature and pressure deformational properties p wave and s wave velocities and electrical resistivity were measured for three north sea malm shales in the laboratory under pressures to 800 bars and temperatures to 100 c these data were used to evaluate how factors such as mineralogy microstructure compaction and pore fluid conductivity affect a shale s seismic and electrical responses deformation in the shales is dominated by inelastic processes which cause time dependent changes in velocity resistivity and pore pressure overall shales are less sensitive to pressure changes as compared to sandstones of similar porosity however changes in temperature result in large changes in physical properties as compared to sandstones or shaly sands p wave and s wave velocities may decrease by as much as 10 percent over the temperature range studied and calculated activation energies for surface conduction are nearly twice those observed in shaly sands these comparisons emphasize fundamental differences in fabric among the

abnormal formation pressure and shale porosity an abnormally pressured jurassic shale from the north sea viking graben has a fluid pressure over burden ration close to 0 8 at a depth of more than 4 000 m and is associated with low porosity and high density the porosity and fluid pressure history of the shale involves three successive stages 1 normal gravitational compaction prevailed during the first few hundred meters of burial 2 the shale porosity was severely reduced by carbonate cementation in conjunction with a major break in sedimentation but the fluid pressure remained hydrostatic and finally 3 the porosity was further reduced by compaction and possibly cementation and the fluid pressure increased to above hydrostatic in response to renewed subsidence and the cretaceous and tertiary overburden lo d

generation of pseudo synthetic seismograms from gamma ray well logs of highly radioactive formations the conventional synthetic seismogram is created with a sonic and a density log however the sonic log can be replaced with the resistivity neutron gamma ray or spontaneous potential log to produce a pseudo sonic ps log more recent techniques involve combining an sp log and a gr log to produce a ps log in the past a drawback in using gr logs for the ps is the presence of highly radioactive and often organic rich layers possessing abnormally high gr readings to improve the pseudo sonic log produced from the gamma ray log a technique was developed to statistically treat the outliers from the wells in the hugoton embayment that encountered predominantly shale sandstone limestone and dolomite and whose logged sections included both normal and abnormally high gr readings to demonstrate a wider range application of our method the procedure was applied to wells from the hugoton embayment central kansas uplift sedgwick basin salina basin forest city basin and nemaha uplift the correlation coefficients between the ps and the conventional sonic for the six basins were 0 75 0 92 0 86 0 91 0 77 and 0 70 respectively also the match between the resulting conventional synthetic seismogram and the pseudo synthetic seismogram from a blind test well for each area was quite good provided the outliers have been properly treated the gr log is a viable tool for creating pseudo sonic logs and pseudo synthetic seismograms for exploration in oil and gas basins where there are few wells with sonic logs or where sonic log quality is poor

thermal stresses due to cooling of a viscoelastic oceanic lithosphere theories based upon thermal contraction of cooling oceanic lithosphere provide a successful basis for correlating seafloor bathymetry and heat flow the horizontal components of the contraction of the lithosphere as it cools potentially give rise to large thermal stresses current methods to calculate these stresses assume that on the time scales of cooling the lithosphere initially behaves as an inviscid fluid and instantly freezes into an elastic solid at some critical temperature these instant freezing methods inaccurately predict transient thermal stresses in rapidly cooling silicate glass plates because of the temperature dependent rheology of the material the temperature dependent rheology of the lithosphere may affect the transient thermal stress distribution in a similar way and for this reason the authors use a thermoviscoelastic model to estimate thermal stresses in young oceanic lithosphere this theory is formulated here for linear creep processes that have an arrhenius rate dependence on temperature results show that the stress differences between instant freezing and linear thermoviscoelastic theory are most pronounced at early times 0 20 m y when the instant freezing stresses may be twice as large the solutions for the two methods asymptotically approach the same solution with time a comparison with intraplate seismicity shows that bothmore methods underestimate the depth of compressional stresses inferred from the seismicity in a systematic way less

slip rate earthquake recurrence and seismogenic potential of the rodgers creek fault zone northern california initial results instrumental seismicity defines a seismic gap along the rodgers creek fault zone rcfz between santa rose and san pablo bay results of a paleoseismicity study within the gap using offset channels in late holocene alluvial deposits as piercing points indicate a minimum slip rate of 2 1 to 5 8 mm yr for the past 1 300 years a preferred range for the maximum recurrence interval of 248 to 679 years and a surface offset of 2 0 3 minus 0 2 m during the most recent event the rcfz has produced past m7 earthquakes and historical seismicity data indicate a minimum elapsed time of 182 years since the most recent earthquake of this size

environmental responses to lateglacial climatic fluctuations recorded in the sediments of pre alpine lake mondsee northeastern alps investigation of the sedimentary record of pre alpine lake mondsee upper austria focused on the environmental reaction to rapid lateglacial climatic changes results of this study reveal complex proxy responses that are variable in time and influenced by the long term evolution of the lake and its catchment a new field sampling approach facilitated continuous and precisely controlled parallel sampling at decadal to sub annual resolution for mu xrf element scanning carbon geochemistry stable isotope measurements on ostracods pollen analyses and large scale thin sections for microfacies analysis the holocene chronology is established through microscopic varve counting and supported by accelerator mass spectrometric 14 c dating of terrestrial plant macrofossils whereas the lateglacial age model is based on delta 18 o wiggle matching with the greenland ngrip record using the gicc05 chronology microfacies analysis enables the detection of subtle salimentological changes proving that depositional processes even in rather large lake systems are highly sensitive to climate forcing comparing periods of major warming at the onset of the lateglacial and holocene and of major cooling at the onset of the younger dryas reveals differences in proxy responses reflecting threshold effects and ecosystem inertia temperature increase vegetation recovery decrease of detrital flux and intensification of biochemical calcite precipitation at the onset of the holocene took place with only decadal leads and lags over a ca 100 a period whereas the spread of woodlands and the reduction of detrital flux lagged the warming at the onset of the lateglacial interstadial by ca 500 750a cooling at the onset of the younger dryas is reflected by the simultaneous reaction of delta 18 o and vegetation but sedimentological changes reduction of endogenic calcite content increase in detrital flux were delayed by about 150 300 a three short term lateglacial cold intervals corresponding to greenland isotope substages gl 1d gl 1c2 and gl 1b also show complex proxy responses that vary in time copyright c 2011 john wiley sons ltd

use of bathymetry and clay mineralogy of reservoir sediment to reconstruct the recent changes in sediment yields from a mountain catchment in the western high atlas region morocco abstract the dam of takerkoust located at the outlet side of n fis basin western high atlas of morocco is one of the strategic reservoirs in morocco facing a serious problem of siltation due to soil erosion a paleo hydrology approach combining chronological and sedimentological analyses is conducted to understand the evolution of the depositional sediment history of the takerkoust reservoir between 1988 and 2016 first a series of 8 bathymetric surveys in the takerkoust reservoir was used to determine the chronology of flood event deposits second grain size distribution clay mineralogy xrd and organic matter content were analyzed in 2 cores drilled in the takerkoust reservoir and the newly build ouirgane reservoir in upstream from which 46 samples were taken third soils samples collected from the uppermost soil horizons first 5 cm of different localities of the n fis watershed were also analyzed to identify sediments origins eleven couplets with different textures and thickness are identified in the takerkoust reservoir corresponding to the period 1988 2016 the highest correlation is observed between instantaneous maximum flow and thickness of the sandy component of the couplets the variation of the siltation rate allows highlighting two distinct periods the oldest period 1988 1999 characterized by a high sediment yield sy 908 6 t km 2 yr 1 and a youngest one 1999 2016 characterized by a low sy 203 9 t km 2 yr 1 the newly built ouirgane dam seems to be responsible for the decreasing siltation rate and change of the clay assemblages of the sedimentary series in takerkoust reservoir

near surface in situ stress introduction from plots of in situ stress versus depth it is apparent that horizontal stress is several times the vertical stress at depths of 100 m within the earth s crust hast 1958 herget 1973 haimson 1978 brown and hoek s 1978 compilation of earth stress shows that the average of principal horizontal stresses at zero depth varies between 2 7 and 40 5 mpa the literature contains no consensus on why the horizontal stresses should be so high at shallow depths possible mechanisms include plastic yield and subsequent elastic deformation accompanying unloading on removal of overburden seagar 1964 topography voight 1966 and creep under tectonic forces hast 1969

gravity induced stresses near topography of small slope topographic modification of gravity induced near surface stresses results in significant departures from a lithostatic state a perturbation scheme provides approximate analytical solutions for plane strain of an elastic half space with an irregularly shaped free surface of small characteristic slope e the leading order effect of the topography is equivalent to that of a distributed normal load on a plane boundary and the correction at order e is due to a distributed shear traction on a plane boundary in the near surface region these two effects contribute at the same order to departures from the lithostatic stress field the contribution of the shearing has been neglected in most previous analyses we present explicit solutions for several particular geometries a symmetric ridge or valley an adjacent ridge and valley a shelf and a sharp crested ridge notable features include 1 for a sufficiently steep ridge the horizontal normal stress is compressive at the crest and decreases possibly becoming tensile with depth 2 large horizontal tension is induced in a valley bottom at greater depth these effects vanish and the stresses approach lithostatic similar analysis is applied to a half space under a far field tectonic compression or tension the result shows that the leading order effect of topography is equivalent to a distributed shear traction on a plane surface regional horizontal compression can be significantly reduced or even change to tension in the neighborhood of a topographic high

a new rock mass classification system qhlw for high level radioactive waste disposal abstract in this paper a new rock mass classification system named q hlw system is proposed with the purpose of evaluating the suitability of the host rock for high level radioactive waste hlw disposal in the system the rock suitability evaluation of two different scales is considered namely the repository and tunnel scales the system is developed on the basis of q system and considers both the long term safety and constructability requirement of the host rock for disposal thus some additional parameters including the fracture zone groundwater chemistry and thermal effect are also taken into account in light of their significant influence on the long term safety of hlw disposal the avoidance strategy is highlighted in the proposed system by excluding the rock volume with unfavorable conditions particularly adjacent to the large scale fracture zones in the proposed system the q index the product of the first four parameters in q method is considered as the basic constructability index by incorporating the influence of other parameters the q hlw system is established in which the suitability of host rock is classified into three classes at the repository and tunnel scales as a preliminary validation the system is applied to the beishan area a potential region for hlw disposal in china using the classification method at the repository scale the most suitable disposal site in xinchang block of the beishan area is identified the rock classification at the tunnel scale is also carried out along two deep boreholes the proposed system is found to be a usable tool in identifying suitable rock volume of different scales for hlw disposal

an 825 year long varve record from lillooet lake british columbia and its potential as a flood proxy abstract lillooet river in southwest british columbia has produced damaging floods many times during the past century the floods are recorded in lillooet lake into which the river flows as anomalously thick clastic varves in order to determine whether an 825 year long varve record obtained from 12 percussion and vibracores can be used as flood proxy we compare river discharge records dating back to 1914 to the thickness of the varves deposited during the same time period correlations between varve thickness and a variety of historical discharge measures are low to moderate for the periods 1914 2004 r 2 0 37 and 1914 1945 r 2 0 40 but higher for the period 1946 2004 r 2 0 55 the best correlation r 2 0 55 is between maximum fall discharge and varve thickness during the most recent period 1946 2004 varve thickness for the earlier period of hydrometric data 1914 1946 which is a time of rapid glacier retreat and warmer temperatures in british columbia is best explained with a discharge proxy combining nival runoff glacier runoff and maximum fall discharge landslides glacier fluctuations river dyking artificial lowering of lillooet lake as well as lag effects of storms are responsible for the considerable unexplained variance in the relation between discharge measures and varve thickness over the historic period the cores contain many anomalously thick varves some of which we attribute to previously dated prehistoric landslides in the watershed or to local landslides into the lake we conclude that many historic and prehistoric floods are faithfully recorded as anomalously thick clastic varves but that other processes operating in the watershed preclude using this record as a reliable paleo flood proxy

anthropogenic and climate controls on vegetation changes between 1500 bce and 500 ce reconstructed from a high resolution pollen record from varved sediments of lake mondsee austria abstract this study reports a precisely dated pollen record with a 20 year resolution from the varved sediments of lake mondsee in the north eastern european alps 47 49 n 13 24 e 481 m above sea level the analysed part of core spans the interval between 1500 bce and 500 ce and allows changes in vegetation composition in relation to climatic changes and human activities in the catchment to be inferred intervals of distinct but modest human impact are identified at ca 1450 1220 740 490 and 340 190 bce and from 80 bce to 180 ce while the first two intervals are synchronous with prominent salt mining phases during the bronze age and early iron age at the nearby unesco world heritage site of hallstatt the last two intervals fall within the late iron age and roman imperial era respectively comparison with published records of extreme runoff events obtained from the same sediment core shows that human activities including agriculture and logging around lake mondsee were low during intervals of high flood frequency as indicated by a higher number of intercalated detrital event layers but intensified during hydrologically stable intervals comparison of the pollen percentages of arboreal taxa with the stable oxygen isotope and potassium ion records of the ngrip and gisp2 ice cores from greenland reveals significant positive correlations for fagus and negative correlations for betula and alnus this underlines the sensitivity of vegetation around lake mondsee to temperature fluctuations in the north atlantic as well as to moisture fluctuations controlled by changes in the intensity of the siberian high and the north atlantic oscillation nao regime

fundamentals of seismic rock physics during the past 50 years or so tremendous progress has been made in studying physical properties of rocks and minerals in relation to seismic exploration and earthquake seismology during this period many theories have been developed and many experiments have been carried out some of these theories and experimental results have played important roles in advancing earth sciences and exploration technologies this tutorial paper attempts to summarize some of these results

ultrasonic compressional and shear velocities in dry clastic rocks as a function of porosity clay content and confining pressure summary for clastic silicate rocks sampled from a rotliegendes well core the velocities up and us were obtained at 10 pressures up to 300mpa using a pulse transmission technique the porosities of all rocks 57 sandstones 26 siltstones five claystones ranged from 0 01 and 0 15 by volume fraction and the clay content varied from less than 0 01 to 0 88 by volume fraction both velocities increase with pressure in the low pressure range the rate of increase is large non linear and is greater for up than for us above 120 mpa both velocities increase linearly velocities porosity and clay content were fitted by least squares regression for pressures of 8 24 60 120 200 and 300 mpa the fractional effect of porosity and clay on the velocities for dry clastic silicate rocks can be described above 120 mpa by u a b ccluy where v is the velocity of the p wave or s wave is the volume fraction of pores and clay is the volume fraction of clay from this it is possible to obtain pressure dependent velocity functions u a pb c exp dp where u is the crack free velocity linear in porosity and clay b is the velocity slope under high pressure u c is the zero pressure velocity and d is related to closure of cracks

resolution limits of fluid overpressures from mineralogy porosity and sonic velocity variations in north sea mudrocks pore pressure identification in mudrocks largely relies on indirect methods including analyses of sonic velocity data the magnitude of pore pressure changes that can be resolved from such data depends on the impact of fluid pressures on well log responses and on the velocity responses to lithological variations that could be mistaken for indications of pore pressure changes analysis of relationships between sonic velocity mineralogy and porosity from 11 north sea wells demonstrated porosity variations of up to 5 from the mean value in mudrocks at any given depth between 1 and 3 5 km 3300 11 500 ft comparisons of these wells with seven wells from the norwegian sea demonstrated that the sonic velocity and density variations are influenced by the content of silica with a biogenic origin but that they can otherwise not in general be related to mineralogy and pore pressure variations the sonic velocity deviations from the mean value are of the same magnitude as those that would be caused by porosity changes of 8 in mudrocks of uniform lithology furthermore the deviations are not significantly reduced when the velocity data are compensated for changes in density porosity detection limits for mechanically compacting mudrocks that are at their maximum effective stress are equivalent to static mud density changes of 0 1 0 15 g cm3 these numbers apply to mudrocks with similar lithological variability to those analyzed in our data set but should be much higher when significant amounts of silica with a biogenic origin are present the impact of effective stress changes on the sonic velocities of chemically compacting as well as of mechanically unloading rocks is much less because small or no porosity changes follow from the effective stress changes in such cases the velocity responses for mechanically unloading and stress insensitive chemical compaction can only be identified from four dimensional time lapse seismic data unless the rocks are close to the fracturing limit these observations imply that reasonably accurate velocity based pore pressure identification in north sea mudrocks requires a knowledge of local mudrock heterogeneity and compaction that cannot easily be obtained as a result sonic velocity data should be treated with considerable caution in pore pressure evaluation

a new method of estimating the ratio between in situ rock stresses and tectonics based on empirical and probabilistic analyses this paper describes a new procedure for assessing the ratio between in situ stresses in rock masses by means of k k h v being h and v principal stress and tectonics for purposes of engineering geology and rock mechanics the method combines the use of the logic decision tree and the empirical relationship between the tectonic stress index tsi and a series of k in situ values obtained from an extensive database the decision tree considers geological and geophysical factors affecting stress magnitudes both on the regional and local scale the tsi index is defined by geological and geomechanical parameters the method proposed provides an assessment of the magnitude of horizontal stresses of tectonic origin results for several regions of europe are presented and the possible applications of the procedure are discussed

flood stratigraphies in lake sediments a review abstract records of the frequency and magnitude of floods are needed on centennial or millennial timescales to place increases in their occurrence and intensity into a longer term context than is available from gauged river flow and historical records recent research has highlighted the potential for lake sediment sequences to act as a relatively untapped archive of high magnitude floods over these longer timescales abyssal lake sediments can record past floods in the form of coarser grained laminations that reflect the capacity for river flows with greater hydrodynamic energy to transport larger particles into the lake this paper presents a framework for investigating flood stratigraphies in lakes by reviewing the conditioning mechanisms in the lake and catchment outlining the key analytical techniques used to recover flood records and highlighting the importance of appropriate field site and methodology selection the processes of sediment movement from watershed to lake bed are complex meaning relationships between measureable sedimentary characteristics and associated river discharge are not always clear stratigraphical palaeoflood records are all affected to some degree by catchment conditioning fluvial connectivity sequencing of high flows delta dynamics as well as within lake processes including river plume dispersal sediment focussing re suspension and trapping efficiency with regard to analytical techniques the potential for direct e g laser granulometry and indirect e g geochemical elemental ratios measurements of particle size to reflect variations in river discharge is confirmed we recommend care when interpreting fine resolution geochemical data acquired via micro scale x ray fluorescence xrf core scanning due to variable down core water and organic matter content altering x ray attenuation we also recommend accounting for changes in sediment supply through time as new or differing sources of sediment release may affect the hydrodynamic relationship between particle size and or geochemistry with stream power where these processes are considered and suitable dating control is obtained discrete historical floods can be identified and characterised using palaeolimnological evidence we outline a protocol for selecting suitable lakes and coring sites that integrates environmental setting sediment transfer processes and depositional mechanisms to act as a rapid reference for future research into lacustrine palaeoflood records we also present an interpretational protocol illustrating the analytical techniques available to palaeoflood researchers to demonstrate their utility we review five case studies of palaeoflood reconstructions from lakes in geographically varied regions these show how lakes of different sizes and geomorphological contexts can produce comprehensive palaeoflood records these were achieved by consistently applying site validated direct and proxy grain size measurements well established chronologies validation of the proxy process interpretation and calibration of the palaeoflood record against instrumental or historical records