co2 depleted fluids from mid ocean ridge flank hydrothermal springs hydrothermal spring fluids were collected from baby bare a basement outcrop on the sediment covered eastern flank of the juan de fuca ridge overlying 3 5 ma old crust these waters are venting at 25 c but have cooled from 64 c within the upper 200 300 m of the upflow zone during their ascent unlike ridge axis hydrothermal vent fluids previously sampled the total co2 content of the endmember spring fluids 0 85 mol kg 1 is depleted with respect to bottom seawater the very low alkalinities 0 43 meq l 1 and high ca2 concentrations 55 mmol kg 1 of endmember spring fluids suggest that the removal of c in the spring fluids is associated with carbonate precipitation in the igneous basement assuming that 8 20 of the total ridge flank heat loss rate of 50 1018 cal yr 1 6 6 tw is removed by porewater advecting from the sediment at 25 c an upper limit dictated by the global input rate of mg 2 to the oceans mottl and wheat 1994 a maximum global carbon sink of 1 0 2 6 1011 mol yr 1 1 2 3 1 mton c yr 1 and a maximum global alkalinity sink of 140 340 109 eq yr 1 are calculated for warm 25 c ridge flank hydrothermal circulation this carbon flux is only 2 5 of current estimates of subaerial and submarine volcanic co2 emissions 50 1011 mol yr 1 indicating that hydrothermal alteration of oceanic crust on young mid ocean ridge flanks at temperatures of a few tens of degrees celsius is only a relatively minor sink for carbon on a global basis it is still possible however that ridge flank alteration at lower temperatures 25 c is an important component of the global carbon budget

mechanism of groundwater bursting in a deep rock salt mine region a case study of the anpeng trona and glauber mines china this paper investigated two incidents which occurred in anpeng trona and glauber mines in china to understand the mechanism of groundwater bursting there are two locations in the anpeng mines where groundwater bursting occurred since mid november 2008 and february 2009 respectively a systematic exploration of the geological conditions operation of the mines the hydrogeochemistry of groundwater bursting and groundwater conducted passageways was implemented the result reveals that the solution mining leakage was serious and the leaked water was the source for groundwater bursting the fractures cracks faults and mining wells formed connections with one another during solution mining such solution welled up and rose along the conducted passages and recharged shallow aquifers before finally reaching the ground surface as groundwater bursting the impacts of groundwater bursting on the environment are serious thus this study provides a basis for effective prevention of groundwater bursting and rational design of solution mining drainage plans

chemosynthetic origin of 14 c depleted dissolved organic matter in a ridge flank hydrothermal system hydrothermal fluids circulate through the upper portion of the oceanic crust isotopic analyses suggest that chemosynthetic microbial communities in the crust synthesize dissolved organic carbon in hydrothermal ridge flank fluids

efficient removal of recalcitrant deep ocean dissolved organic matter during hydrothermal circulation oceanic dissolved organic carbon doc is an important carbon pool similar in magnitude to atmospheric co2 but the fate of its oldest forms is not well understood hot hydrothermal circulation may facilitate the degradation of otherwise un reactive dissolved organic matter playing an important role in the long term global carbon cycle the oldest most recalcitrant forms of doc which make up most of oceanic doc can be recovered by solid phase extraction here we present measurements of solid phase extractable doc from samples collected between 2009 and 2013 at seven vent sites in the atlantic pacific and southern oceans along with magnesium concentrations a conservative tracer of water circulation through hydrothermal systems we find that magnesium and solid phase extractable doc concentrations are correlated suggesting that solid phase extractable doc is almost entirely lost from solution through mineralization or deposition during circulation through hydrothermal vents with fluid temperatures of 212 401 c in laboratory experiments where we heated samples to 380 c for four days we found a similar removal efficiency we conclude that thermal degradation alone can account for the loss of solid phase extractable doc in natural hydrothermal systems and that its maximum lifetime is constrained by the timescale of hydrothermal cycling at about 40 million years

deformation mechanisms of deeply buried and surface piercing late pre cambrian to early cambrian ara salt from interior oman we compared microstructures of late pre cambrian to early cambrian ara salt diapirs from the deep subsurface 3 5 5 km of the south oman salt basin and from surface piercing salt domes of the ghaba salt basin laterally these basins are approximately 500 km apart but belong to the same tectono sedimentary system the excellent data situation from both wells and outcrops allows a unique quantification of formation and deformation mechanisms spanning from sedimentation to deep burial and via re activated diapir rise to surface piercement microstructures of gamma irradiated and etched thin sections indicate dislocation creep and fluid assisted grain boundary migration as the main deformation mechanisms operating in the deep subsurface microstructures from the surface are characterised by large old subgrain rich crystals these old grains are partly replaced by new subgrain free and subgrain poor crystals which show gamma irradiation decorated growth bands and fibrous microstructures indicative of pressure solution creep and static recrystallisation most likely due to surface piercement and exposure using subgrain size piezometry the maximum differential stresses for the subsurface salt is 1 7 mpa and those for the surface piercing salt is 3 4 mpa the latter value displaying the high stress conditions in the diapir stem as the salt rises on its way to the surface

3 d numerical simulations of earthquake ground motion in sedimentary basins testing accuracy through stringent models summary differences between 3 d numerical predictions of earthquake ground motion in the mygdonian basin near thessaloniki greece led us to define four canonical stringent models derived from the complex realistic 3 d model of the mygdonian basin sediments atop an elastic bedrock are modelled in the 1d sharp and 1d smooth models using three homogeneous layers and smooth velocity distribution respectively the 2d sharp and 2d smooth models are extensions of the 1 d models to an asymmetric sedimentary valley in all cases 3 d wavefields include strongly dispersive surface waves in the sediments we compared simulations by the fourier pseudo spectral method fpsm the legendre spectral element method sem and two formulations of the finite difference method fdm s and fdm c up to 4hz the accuracy of individual solutions and level of agreement between solutions vary with type of seismic waves and depend on the smoothness of the velocity model the level of accuracy is high for the body waves in all solutions however it strongly depends on the discrete representation of the material interfaces at which material parameters change discontinuously for the surface waves in the sharp models an improper discrete representation of the interfaces can cause inaccurate numerical modelling of surface waves for all the numerical methods considered except sem with mesh of elements following the interfaces a proper implementation of interfaces requires definition of an effective medium consistent with the interface boundary conditions an orthorhombic effective medium is shown to significantly improve accuracy and preserve the computational efficiency of modelling the conclusions drawn from the analysis of the results of the canonical cases greatly help to explain differences between numerical predictions of ground motion in realistic models of the mygdonian basin we recommend that any numerical method and code that is intended for numerical prediction of earthquake ground motion should be verified through stringent models that would make it possible to test the most important aspects of accuracy

strain and competence contrast estimation from fold shape a new method to estimate strain and competence contrast from natural fold shapes is developed and verified by analogue and numerical experiments strain is estimated relative to the nucleation amplitude an which is the fold amplitude when the amplification velocities caused by kinematic layer thickening and dynamic folding are identical an is defined as the initial amplitude corresponding to zero strain because folding at amplitudes smaller than an is dominantly by kinematic layer thickening for amplitudes larger than an estimates of strain and competence contrast are contoured in thickness to wavelength h l and amplitude to wavelength a l space these quantities can be measured for any observed fold shape contour maps are constructed using existing linear theories of folding a new nonlinear theory of folding and numerical simulations all for single layer folding the method represents a significant improvement to the arc length method the strain estimation method is applied to folds in viscous newtonian power law non newtonian and viscoelastic layers also strain partitioning in fold trains is investigated strain partitioning refers to the difference in strain accommodated by individual folds in the fold train and by the whole fold train fold trains within layers exhibiting viscous and viscoelastic rheology show different characteristic strain partitioning patterns strain partitioning patterns of natural fold trains can be used to assess the rheological behaviour during fold initiation d 2001 elsevier science b v all rights reserved

the concentration and isotopic composition of carbon in basaltic glasses from the juan de fuca ridge pacific ocean the abundance and 13c12c ratios of carbon were analyzed in basaltic glass from twenty locations along the juan de fuca ridge using a 3 step combustion extraction technique carbon released during the first two combustion steps at 400 500 c and 600 650 c is interpreted to be secondary and only the carbon recovered during a final combustion step at 1200 c is thought to be indigenous to the samples for carbon released at 1200 c glasses analyzed as 1 2 mm chips contained 23 146 ppm c with 13c values of 4 8 to 9 3 whereas samples crushed to 38 63 m or 63 90 m yielded 56 103 ppm c with 13c values of 6 1 to 9 2 the concentrations and isotopic compositions of the primary carbon dissolved in the glasses and present in the vesicles are similar to those previously reported for other ocean ridge basalts the juan de fuca basaltic magmas were not in equilibrium with respect to carbon when they erupted and quenched on the sea floor evidence of disequilibrium includes 1 1 a large range of carbon contents among glasses collected at similar depths 2 2 a highly variable calculated carbon isotopic fractionation between melt and vapor determined by comparing crushed and uncrushed splits of the same sample and 3 3 a lack of correlation between vesicle abundance carbon concentration and depth of eruption variations in carbon concentration and 13c ratios along the ridge do not correlate with major element chemistry the observed relationship between carbon concentrations and 13c values may be explained by late stage variable degrees of open system rayleigh like degassing

evolution of boudins under progressively decreasing pore pressure a case study of pegmatites enclosed in marble deforming at high grade metamorphic conditions naxos greece during ductile deformation of marbles under high grade metamorphic conditions on naxos greece pegmatites enclosed in the marbles were deformed in a brittle fashion forming blocky boudins with quartz crystallized in the interboudin zones we studied the three dimensional geometry of the boudins in the field and in two large samples the first sample was serially sectioned to observe the structural and microstructural evolution in the second sample we mapped the surface morphology of the deformed pegmatite in profile the boudins can be classified as symmetric torn type boudins evolving towards asymmetric boudins with a later domino boudin component in three dimensions however the morphology of the boudinaged pegma tite is a simple set of normal faults with mode i fractures in the fault tips and rotation of the fault blocks to accommodate the extension in the marble deformation history was constrained by petrology and microstructures in combi nation with simple order of magnitude calculations of both the cooling and pore fluid pressure evolution the dynamically recrystallized coarse grained calcite of the marble provides clear evidence that after the pegmatite intruded the marble and solidified it was deformed at peak conditions of m2b metamorphism 670 c and 0 6 gpa such pegmatitic melts contain 10 percent h2o which is released during crystalliza tion we infer that after crystallization of the pegmatite the pore fluid pressure in the pegmatite remained close to lithostatic due to the very low permeability of the surrounding marble and the pegmatite was deformed at very low effective stress which led to brittle deformation of feldspar and mode i fracturing of the pegmatite forming torn type boudins with time the pore fluid pressure slowly decreased increasing the effective stress ongoing n s extension thus resulted in slip along the quartz filled interboudin zones and in block rotation producing domino boudins

the late messinian erosional surface and the subsequent reflooding in the mediterranean new insights from the melilla nador basin morocco new field investigations in the cape des trois fourches peninsula northern morocco allow us to bring new insights on the late messinian erosional surface and the overlying marine deposits our results show that the late messinian erosional surface characterized by an erosional plateau is interrupted by an up to 70 m deep paleovalley thought to result from a landslide the minimum relative sea level drop is 70 m probably much more with regard to the indication that a large scale landsliding has occurred the post erosional deposits cycle 3 comprise one major depositional sequence composed of two high order sedimentary subcycles deposits of the first subcycle 3a filled in the erosional basin and the paleovalleys deposits of the second subcycle 3b overflowed the paleovalleys and the erosional plateau we found evidence of the transgressive systems tract of the deposits corresponding to the post messinian crisis reflooding for which a latest messinian onset can neither be proved nor entirely ruled out because the rare biostratigraphic data are not sufficiently conclusive the uppermost part of the reflooding deposits subcycle 3a is shown to be definitely pliocene in age based on the occurrence of globorotalia puncticulata and the composition of the assemblage of pectinids

induced seismicity of the groningen gas field history and recent developments abstract induced seismicity of the groningen gas field is caused by the production of gas because of the large areal extent of the reservoir the long history of depletion and the available data sets which exist as a result of consequences and public unrest caused by induced seismicity the field presents a valuable case for studying the relationships among geologic flow dynamic geomechanical and seismological models gas production from the groningen field started in 1963 induced seismicity of the field first was recorded in 1991 ml 2 4 during the subsequent 10 years induced seismicity stayed at a rate of about five events ml 1 5 per year starting in 2003 the number of events and magnitudes started to increase in 2012 the largest event ml 3 6 occurred which caused the most damage to date as a consequence studies carried out in 2013 have fundamentally changed the way to look at the relationship between induced seismicity and gas depletion there appears to be a close link between

modeling the influence of sinking anhydrite blocks on salt diapirs targeted for hazardous waste disposal due to the low permeability and high ductility of rock salt many salt diapirs such as those in germany and the netherlands are targeted as long term repositories for disposal of high level radioactive and chemical wastes geophysical and subsurface data show that the gorleben salt diapir which is one of the most extensively investigated diapirs in the world and other salt diapirs of the zechstein formation in germany contain large blocks 80 m thick of high density anhydrite inclusions these blocks which were carried upward by the rising salt are considered to be detached segments of intercalated layers that initially were deposited with the salt results of physical and numerical models presented here show that such detached high density blocks which were entrained and carried upward by the diapir at an earlier stage tend to sink in the late stages of diapiric evolution when the rate of diapiric rise slows down during their descent these high density competent blocks deform by folding and create shear zones at the immediate contact with the less competent salt the descending blocks initiate a secondary internal flow within the salt diapirs they descend and they may deform any repository built within such diapirs which would otherwise be considered as tectonically inactive

the composition of gases in fluid inclusions of late permian zechstein marine evaporites in northern germany abstract in order to understand the generation of gases in late permian marine evaporites and the migration of gases in salt domes 428 gas bearing fluid inclusions of the gorleben salt dome northern germany were analysed using laser raman spectrometry lrs the investigations were divided in two parts in the first part only gas rich inclusions were analysed involving samples from different stratigraphic layers of the zechstein 2 stasfurt serie and zechstein 3 leine serie and from different locations within the salt dome for the second part only the gaseous components in brines rich inclusions of the zechstein 2 were measured the compositional range of all inclusions investigated can be subdivided into two main groups with rare exceptions the first group of n 2 and n 2 o 2 inclusions reveals a n 2 o 2 ratios close to that of modern atmosphere thus indicating trapped paleoatmosphere the second group is represented by inclusions that contain mixtures of n 2 ch 4 occasionally h 2 and or h 2 s the most abundant subgroups are n 2 ch 4 and n 2 ch 4 h 2 mixtures these gas mixtures can be produced by the decomposition of organic material under anoxic conditions it is noted that n 2 in both main groups can also be generated by degassing of underlying early permian rotliegendes or carboniferous c org rich sedimentary rocks and an entrapment in early stages of the zechstein halokinesis the different origin of both main groups is supported by stratigraphic correlation in the stratigraphic layers which contain mainly mixtures of n 2 and o 2 or pure n 2 inclusions of the n 2 ch 4 h 2 h 2 s group are rare and vice versa layers which are rich in n 2 ch 4 h 2 h 2 s do not contain many n 2 o 2 inclusions the majority of layers investigated frequently contains inclusions of the n 2 o 2 group only two anhydrite rich layers of zechstein 3 main anhydrite and anhydrite intercalated salt contain mainly inclusions of the second group the zechstein 3 potash seam as well as secondary halites contain more or less the same population of inclusions from every main group a comparison of the gas rich inclusions and the gases in the brine rich inclusions of the zechstein 2 layer main rock salt 3 shows distinct differences whereas the gas rich inclusions are of the n 2 o 2 group the gases from the brine rich inclusions are of the n 2 ch 4 group emphasising different origins the latter is a product of anhydrite rich parts or potash seams that have migrated later into the overlying main rock salt 3

paleostresses of the groningen area the netherlands results of a seismic based structural reconstruction article i nfo we describe a novel workflow to reconstruct paleostresses in the subsurface where the traditional outcrop based method that uses fault slip measurements is not possible we use 3d seismic data and structural restoration to determine fault surfaces and slip vectors these data are then used as input for paleostress reconstruction algorithms the study area of ca 750 km 2 is situated in the groningen block the netherlands excellent quality 3d seismic data were used to interpret 11 horizons and approximately 80 faults between the tertiary and the top rotliegend indicators of fault slip direction are fault undulations sedimentary structures offset by faults and shapes of horizon cut outs these indicators were used as a basis of 3d restoration of the interpreted horizons a stepwise restoration approach was chosen that removed younger deformation to obtain slip vectors for older deformation events in a following work step numeric dynamic analysis nda was used to calculate paleostress tensors for the middle and lower tertiary upper cretaceous and upper rotliegend sequences the results presented in this paper are consistent with existing paleostress interpretations for nw europe however in contrast to previous studies they are derived from a subsurface volume where paleostress information was lacking until now issues that need further study include the effect of the size of the study area on the assumptions of a homogenous stress field and an analysis of the ambiguity of the interpretation of fault slip indicators on 3d seismic data

deformation characteristics of rock salt with mudstone interbeds surrounding gas and oil storage cavern abstract this paper discusses the deformation differences that occur due to the presence of thin mudstone layers in underground storage caverns in rock salt both plasticity and viscosity are considered in the displacement calculations the results show that both creep deformation and deformation distinction i e the differences in the creep behavior between the salt rock and the mudstone are very large under the condition of high effective stresses when the inner diameters of salt caverns are 40 60 m the maximum radial convergence can reach 24 m and the deformation distinction can reach up to 6 m 30 years after the completion of cavern by solution mining the affected areas are however are restricted to the vicinity of the cavern the tightness of the cavern may not be violated if the distance between the caverns is greater than this amount the extension of plastic and dilatancy zones in rock salt is limited to three times the cavern diameter when elasto plastic mudstone interbeds are included tensile failure zones are present in the vicinity of the cavern and the plasticity zone stretches through the entire layer this could cause a loss of cavern tightness or stability if the mudstone interbeds creep although the creep rate is 2 orders lower than that of rock salt yielding is strongly de escalated but the deformation distinction is not affected

anatomy of mushroom shaped diapirs we produced more than 100 mushroom shaped diapirs in eight centrifuged models under acceleration of 1200 g the modelling results allow natural examples to be recognized mushroom diapirs have an overhanging bulb fringed by one or more skirts which can curl inward to form vortices capable of entraining cover material to various degrees most of the internal folds are downward facing the oldest buoyant unit occurs in the skirt and in the diapiric core younger buoyant units or their immediate cover are infolded in crescentic patterns external mushroom diapirs have skirts that infold cover material with greater maturity the skirts can curl inward to form an external vortex entraining cover in contrast internal mushroom diapirs have skirts confined entirely within the intrusion again with greater maturity these confined skirts may curl inward but they entrain only diapiric material internal mushroom structure results from toroidal circulation confined within the diapir where isoviscosity prevails external mushroom structure results where source and entrained cover have similar effective viscosities entrained inclusions of more permeable country rock threaten the integrity of a mined cavern by creating a plumbing system

dissolved organic carbon in basalt hosted deep subseafloor fluids of the juan de fuca ridge flank abstract marine dissolved organic carbon doc is highly depleted in radiocarbon and thus inferred to be largely refractory to removal processes that operate on less than millennial timescales however a growing number of reports have shown that a large fraction of marine doc can be effectively removed during circulation through submarine hydrothermal systems what is not clear however is whether the doc that remains in hydrothermal fluids is remnant non reactive doc from recharged seawater or doc that has been largely produced in the subsurface we collected and characterized warm 65 c hydrothermal fluids from deep 18 40 73 200 m within the basalt hosted basement of the juan de fuca ridge flank in the northeast pacific ocean doc concentrations in hydrothermal fluids were 9 to 18 m much lower than measured in local deep seawater 37 5 m doc 14 c values of 683 to 856 were much lower than the 14 c dissolved inorganic carbon dic values of 880 to 918 while doc 13 c values of 23 6 to 27 0 were much heavier than that of the particulate organic carbon poc pool 34 suggesting that biological production in the subsurface is not a primary source of doc rather our data suggest that isotopically enriched doc are selectively removed from recharged seawater leaving doc that is very isotopically depleted in the basaltic basement fluids despite the removal of 50 75 of doc in the subsurface nuclear magnetic resonance nmr functional group analyses indicate that aromatic compounds were added to basaltic basement fluids during passage through the deep subseafloor and may partly contribute to the depleted 14c doc in the ridge flank basement fluids

initiation and growth of gypsum piercement structures in the zechstein basin abstract the importance of tectonic processes in initiating halite diapirs has become much better understood in recent years less well understood is the development of diapiric structures involving rocks composed predominantly of gypsum below about 1000 m gypsum dehydrates to anhydrite which often obscures primary sedimentary textures if the strain associated with diapiric rise in the rock induces the transition to anhydrite obliteration of primary features in the gypsum can be expected in our study we infer that the diapiric movement in the werra anhydrite member of cycle 1 of the zechstein formation of europe occurred before the initial transition of gypsum to anhydrite based on the presence of pseudomorphs of bedded primary gypsum crystals the overburden lithologies and depositional environment and the mechanical properties of gypsum anhydrite and carbonate rocks faulting and differential loading of a shallow overburden were the key components in initiating the gypsum diapirism the transition to anhydrite occurred after burial and after cessation of diapirism in comparison the diapirism of calcium sulfate of the leine anhydrite into the leine halite members of cycle 3 of the zechstein formation probably occurred much later after burial and appears to have been triggered by halite diapirism which in turn triggered the dehydration reaction causing the calcium sulfate to become the incompetent phase relative to the halite

coeval folding and boudinage in four dimensions scaled analogue experiments have been carried out incrementally to demonstrate the growth of constrictional folds and boudins through space and time pure constriction acted on a single stiff layer that was embedded in a weak matrix with the layer trending parallel to the x axis of the constrictional strain ellipsoid the viscosity ratio between non linear viscous layer and matrix was set at ca 13 three dimensional images of the incrementally deformed layer have been obtained using computer tomography they yielded clear evidence that d1 folds and d1 boudins show striking interactions when growing simultaneously at low to moderate finite strain the axes of d1 folds are subparallel and the axes of d1 boudins are subperpendicular to the x axis of the constrictional strain ellipsoid the normalized wavelengths of d1 folds and d1 boudins and the amplitudes of d1 folds are fixed already at low finite strain 5 and do not significantly change as deformation proceeds the normalized wavelength of both structures is not so in line as suggested by theoretical studies at higher degrees of finite strain d1 boudins are affected by d2 folds and rotated limbs of the latter show d2 boudinage resulting in complex deformation patterns that are difficult to identify in the field the model results are important for the analysis and interpretation of deformation structures in rheologically stratified rocks undergoing dislocation creep under bulk constriction tectonic settings where constrictional folds and boudins may develop simultaneously are stems of salt diapirs subduction zones or thermal plumes

finite difference calculation of travel times the travel times of the first arriving seismic waves through any velocity structure can be rapidly computed on a two or three dimensional numerical grid by finite difference extrapolation from point to point wavefronts rather than the traditional rays are tracked head waves are properly treated and shadow zones are filled by the appropriate diffractions differences of less than 0 03 per cent are found between the results of this technique and raytracing for a complex two dimensional model this scheme is useful for the windowing of finite difference calculations to increase computing speed and promises to aid in earthquake location tomographic inversion and kirchhoff migration in structures that have strong lateral velocity gradients

surface processes recorded by rocks and soils on meridiani planum mars microscopic imager observations during opportunity s first three extended missions the microscopic imager mi on the mars exploration rover opportunity has returned images of mars with higher resolution than any previous camera system allowing detailed petrographic and sedimentological studies of the rocks and soils at the meridiani planum landing site designed to simulate a geologist s hand lens the mi is mounted on opportunity s instrument arm and can resolve objects 0 1 mm across or larger this paper provides an overview of mi operations data calibration and analysis of mi data returned during the first 900 sols mars days of the opportunity landed mission analyses of opportunity mi data have helped to resolve major questions about the origin of observed textures and features these studies support eolian sediment transport rather than impact surge processes as the dominant depositional mechanism for burns formation strata mi stereo observations of a rock outcrop near the rim of erebus crater support the previous interpretation of similar sedimentary structures in eagle crater as being formed by surficial flow of liquid water well sorted spherules dominate ripple surfaces on the meridiani plains and the size of spherules between ripples decreases by about 1 mm from north to south along opportunity s traverse between endurance and erebus craters

sequence stratigraphy and cyclic development of basal zechstein carbonate evaporite deposits with emphasis on zechstein 2 off platform carbonates upper permian northeast germany abstract although the basal zechstein is classically subdivided into two cycles z1 and z2 lower part it can alternatively be subdivided into three complete third order depositional sequences zs1 zs3 and the associated lowstand systems tract transgressive systems tract of a fourth sequence zs4 third and higher order sea level fluctuations influenced the depositional and diagenetic history of the carbonate evaporite alternations within the basal zechstein the main subject of the present study the zechstein 2 carbonate stassfurt carbonate or ca2 is interpreted to encompass both transgressive predominantly in slope and basinal settings and highstand systems tracts of zechstein sequence zs3 as well as part of the lowstand systems tract of the fourth zechstein sequence zs4 in northeastern germany hydrocarbon reservoirs of the ca2 developed along both northern and southern margins of the southern permian basin on top of the topography of the zechstein 1 cycle z1 this z1 topography resulted from deposition of the werra anhydrite a1 the highstand systems tract of the second zechstein sequence zs2 the northern ca2 carbonate platform is consistently narrow and fringed by coated grain and composite grain bars and shoals it is characterized by a steep fault controlled slope which precluded the formation of in situ shallow water grain dominated carbonates during relative sea level lowstands displaced shallow water coated grain and composite grain packstones wackestones may however occur as slope fan deposits turbidites in contrast the southern carbonate platform is wide tectonically dissected and fringed by grain dominated shallow water carbonates coated grain and composite grain bars and shoals zechstein 2 shallow water carbonates detectable by basal zechstein seismic anomalies also developed on pre existing topographical highs in off platform positions three depositional cycles ca2 cycles i ii and iii most probably reflecting high amplitude fourth order sea level fluctuations can be identified within the stassfurt carbonate our observations suggest that sea level variations possibly reflecting cyclicity in the milankovitch frequency band 0 1 0 4 ma and the pre zechstein topography pronounced during formation of the werra anhydrite were the most important factors in controlling the depositional as well as the diagenetic history of the zechstein 2 carbonate in off platform positions

subseafloor seawater basalt microbe reactions continuous sampling of borehole fluids in a ridge flank environment 1 integrated ocean drilling program iodp hole 1301a was drilled cased and instrumented with a long term subseafloor observatory cork on the eastern flank of the juan de fuca ridge in summer 2004 this borehole is located 1 km south of odp hole 1026b and 5 km north of baby bare outcrop hole 1301a penetrates 262 m of sediment and 108 m of the uppermost 3 5 ma basaltic basement in an area of warm 64 c hydrothermal circulation the borehole was instrumented and those instruments were recovered 4 years later here we report chemical data from two continuous fluid samplers osmosamplers and temperature recording tools that monitored changes in the state of borehole formation fluids these changes document the effects of drilling fluid overpressure and flow seawater basalt interactions and microbial metababolic activity initially bottom seawater flowed into the borehole through a leak between concentric cork casing strings eventually the direction of flow reversed and warm altered formation fluid flowed into the borehole and discharged at the seafloor this reversal occurred during 1 week in september 2007 3 years after drilling operations ceased the composition of the formation fluid around hole 1301a generally lies within bounds defined by springs on baby bare outcrop to the south and fluids that discharged from hole 1026b to the north deviations likely result from reactions with drilling products simple conservative mixing of two end member fluids reveals reactions occurring within the crust including nitrate reduction presumably by denitrifying microbes the observed changes in borehole fluid composition provide the foundation for a conceptual model of chemical and microbial change during recharge of a warm ridge flank hydrothermal system this model can be tested through future scientific ocean drilling experiments

a deformation apparatus for three dimensional coaxial deformation and its application to rheologically stratified analogue material abstract a new apparatus is described that supports all types of three dimensional coaxial deformation from pure constriction to pure flattening up to 78 shortening is possible at strain rates ranging from 4 10 6 to 1 10 2 s 1 the apparatus has been used to study the influence of the deformation regime on the geometry of a deforming stiff layer embedded in a weak matrix layer and matrix consist of plasticine the apparent viscosity and stress exponent n of which vary from 2 10 6 to 2 10 7 pa s and 6 9 respectively first results suggest a considerable influence of the deformation regime on the geometry of the deformed layer including its thickness if the viscosity ratio between layer and matrix is small 2 1 5 folding is restricted to the flattening and plane strain regime the latter if the layer is initially oriented perpendicular to the long axis x of the finite strain ellipsoid if the layer is oriented perpendicular to the intermediate y axis under plane and constrictional strain low viscosity ratios result in boudinage but folding is hardly developed however simultaneous growth of folds and boudins is possible under pure constriction at a viscosity ratio of 10 three dimensional images based on computer tomography suggest a strong interaction between such coeval folds and boudins resulting in characteristic deformation patterns that should not occur if both structures form in sequence during polyphase deformation

palaeokarst influenced depositional and diagenetic patterns in upper permian carbonates and evaporites karstryggen area central east greenland the karstryggen area of eastern greenland represents the western edge of sedimentation in the jameson land basin an arm of the northern zechstein seaway upper permian strata of this area were deposited as two major sequences the first marine incursion transgressed largely peneplaned lower permian strata and deposited thin paralic conglomerates sandstones and shales the huledal formation followed by a thick package of carbonates and evaporites the karstryggen formation although the karstryggen formation represents the transgressive maximum of this sequence it contains only marginal or restricted marine strata including micritic stromatolitic and peloidal carbonates and thick but localized bedded gypsum deposits these lithofacies indicate that relatively arid climates prevailed in this basin as in most of the zechstein region a major regression associated with a change to a more humid climate terminated karstryggen sedimentation pre existing evaporites and carbonates underwent diagenetic alteration including widespread calcitization and dissolution of gypsum more importantly topographic relief in excess of 120 m was generated by fluvial drainage systems and karstic sinkholes a second marine incursion accompanied by a return to a semi arid climate drowned this high relief topography producing a complex sequence of strata the wegener halvo formation in which sedimentation was greatly influenced by the rugged underlying terrain marine cemented algal molluscan grainstones draped pre existing palaeotopography during the initial stages of flooding continued drowning led to differential sedimentation on highs and in lows oolitic and bryozoan brachiopod grainstones formed as shoals on the crests of most prominences whereas shales conglomeratic debris flows evaporites or oolitic turbidites were deposited in the lows more restricted sedimentation took place in the westernmost areas which lay closest to the mainland shoreline and were situated to the west of a palaeotopographic ridge there oolitic stromatolitic and evaporitic strata were deposited under hypersaline conditions indicative of a return to more arid climatic conditions three subcycles mark smaller scale relative changes of sea level that occurred during deposition of the wegener halvo formation they are delimited by regional surfaces with moderate relief 5 20 m developed during subaerial exposure widespread diagenetic changes including leaching of aragonitic grains dissolution collapse brecciation of evaporites and meteoric calcite cementation occurred in association with these smaller scale sequence boundaries again reflecting climatic oscillations relative sea level fluctuations coupled with regional climate changes played a dominant role in determining both depositional and diagenetic relations in these strata these features undoubtedly extend into subsurface parts of this basin as well as into yet unexplored areas of the northern zechstein basin and barents shelf and may have economic significance for the localization of hydrocarbons

salt redistribution during extension and inversion inferred from 3d backstripping abstract a 3d backstripping approach considering salt flow as a consequence of spatially changing overburden load distribution isostatic rebound and sedimentary compaction for each backstripping step is used to reconstruct the subsidence history in the northeast german basin the method allows to determine basin subsidence and the salt related deformation during late cretaceous early cenozoic inversion and during late triassic jurassic extension in the northeast german basin the deformation is thin skinned in the basinal part but thick skinned at the basin margins the salt cover is deformed due to late triassic jurassic extension and late cretaceous early cenozoic inversion whereas the salt basement remained largely stable in the basin area in contrast the basin margins suffered strong deformation especially during late cretaceous early cenozoic inversion as a main question we address the role of salt during the thin skinned extension and inversion of the basin in our modelling approach we assume that the salt behaves like a viscous fluid on the geological time scale that salt and overburden are in hydrostatical near equilibrium at all times and that the volume of salt is constant because the basement of the salt is not deformed due to decoupling in the basin area we consider the base of the salt as a reference surface where the load pressure must be equilibrated our results indicate that major salt movements took place during late triassic to jurassic e w directed extension and during late cretaceous early cenozoic nne ssw directed compression moreover the study outcome suggests that horizontal strain propagation in the salt cover could have triggered passive salt movements which balanced the cover deformation by viscous flow in the late triassic strain transfer from the large graben systems in west central europe to the east could have caused the subsidence of the rheinsberg trough above the salt layer in this context the effective regional stress did not exceed the yield strength of the basement below the rheinsberg trough but was high enough to provoke deformation of the viscous salt layer and its cover during the late cretaceous early cenozoic phase of inversion horizontal strain propagation from the southern basin margin into the basin can explain the intensive thin skinned compressive deformation of the salt cover in the basin the thick skinned compressive deformation along the southern basin margin may have propagated into the salt cover of the basin where the resulting folding again was balanced by viscous salt flow into the anticlines of folds the huge vertical offset of the pre zechstein basement along the southern basin margin and the amount of shortening in the folded salt cover of the basin indicate that the tectonic forces responsible for this inversion event have been of a considerable magnitude

carbon isotope composition of organic compounds produced by abiotic synthesis under hydrothermal conditions although it is widely believed that production of organic compounds by fischer tropsch synthesis and related processes occurs in many geologic environments unambiguous identification of compounds with an abiotic origin in natural samples has been hampered by a lack of means to discriminate between abiotic compounds and organic matter from biological sources while isotopic compositions might provide a means to discriminate between biologic and non biologic sources of organic matter there are few data presently available to constrain the isotopic composition of compounds produced by abiotic processes in geologic systems here we report results of laboratory experiments conducted to evaluate the isotopic composition of organic compounds synthesized abiotically under hydrothermal conditions we find the organic products are depleted in 13c to a degree typically ascribed to biological processes indicating that carbon isotopic composition may not be a particularly effective diagnostic means to differentiate between biologic and non biologic sources furthermore our results suggest that the isotopic compositions of reduced carbon compounds found in many ancient rocks that have heretofore been attributed to biological sources could be consistent with an abiotic origin in a hydrothermal setting

three dimensional simulations of seismic wave propagation in the taipei basin with realistic topography based upon the spectral element method we use the spectral element method to simulate strong ground motion throughout the taipei metropolitan area mesh generation for the taipei basin poses two main challenges 1 the basin is surrounded by steep mountains and 2 the city is located on top of a shallow low wave speed sedimentary basin to accommodate the steep and rapidly varying topography we introduce a thin high resolution mesh layer near the surface the mesh for the shallow sedimentary basin is adjusted to honor its complex geometry and sharp lateral wave speed contrasts variations in moho thickness beneath northern taiwan are also incorporated in the mesh spectral element simulations show that ground motion in the taipei metropolitan region is strongly affected by the geometry of the basin and the surrounding mountains the amplification of ground motion is mainly controlled by basin depth and shallow shear wave speeds although surface topography also serves to amplify and prolong seismic shaking

rock mechanics for gas storage in bedded salt caverns abstract liquefied petroleum gases and natural gas have been stored in caverns solution mined in domal and bedded salt for many years the majority of the natural gas storage caverns in the united states have been developed in domal salt this paper is a case history of three caverns that were developed specifically for natural gas storage in bedded salt in an area that has historically known only lpg storage in similar caverns coring and rock mechanics studies indicated that the salt could be divided into two distinctive types one of which could not support an underground excavation rock mechanics testing was limited to salt cores but insoluble ledges and intercalated redbed clay played a great part in the ultimate cavern shapes and spans based upon development of storage space in the three caverns conclusions have been reached that will simplify future cavern development

rayleigh wave phase velocity maps of tibet and the surrounding regions from ambient seismic noise tomography ambient noise tomography is applied to the significant data resources now available across tibet and surrounding regions to produce rayleigh wave phase speed maps at periods between 6 and 50 s data resources include the permanent federation of digital seismographic networks five temporary u s program for array seismic studies of the continental lithosphere passcal experiments in and around tibet and chinese provincial networks surrounding tibet from 2003 to 2009 totaling 600 stations and 150 000 interstation paths with such a heterogeneous data set data quality control is of utmost importance we apply conservative data quality control criteria to accept between 5000 and 45 000 measurements as a function of period which produce a lateral resolution between 100 and 200 km across most of the tibetan plateau and adjacent regions to the east misfits to the accepted measurements among passcal stations and among chinese stations are similar with a standard deviation of 1 7 s which indicates that the final dispersion measurements from chinese and passcal stations are of similar quality phase velocities across the tibetan plateau are lower on average than those in the surrounding nonbasin regions phase velocities in northern tibet are lower than those in southern tibet perhaps implying different spatial and temporal variations in the way the high elevations of the plateau are created and maintained at short periods 20 s very high velocities are imaged in the tarim basin the ordos block and the sichuan basin these phase velocity dispersion maps provide information needed to construct a 3 d shear velocity model of the crust across the tibetan plateau and surrounding regions

the internal geometry of salt structures a first look using 3d seismic data from the zechstein of the netherlands abstract we present a first look at the large scale complexly folded and faulted internal structure of zechstein salt bodies in nw europe using 3d reflection seismic reflection data from two surveys on the groningen high and the cleaver bank high we focus on a relatively brittle folded and boudinaged claystone carbonate anhydrite layer the z3 stringer enclosed in ductile salt a first classification of the structures is presented and compared with observations from salt mines and analogue and numerical models z3 stringers not only are reservoirs for hydrocarbons but can also present a serious drilling problem in some areas results of this study could provide the basis for better prediction of zones of drilling problems more generally the techniques presented here can be used to predict the internal structure of salt bodies to estimate the geometry of economic deposits of all kinds and locate zones suitable for storage caverns structures observed include an extensive network of zones with increased thickness of the stringer these we infer to have formed by early diagenesis karstification gravitational sliding and associated local sedimentation later this template was deformed into large scale folds and boudins during salt tectonics salt flow was rarely plane strain producing complex fold and boudin geometries deformation was further complicated by the stronger zones of increased thickness which led to strongly non cylindrical structures we present some indications that the thicker zones also influence the locations of later suprasalt structures suggesting a feedback between the early internal evolution of this salt giant and later salt tectonics this study opens the possibility to study the internal structure of the zechstein and other salt giants in 3d using this technique exposing a previously poorly known structure which is comparable in size and complexity to the internal parts of some orogens

internal kinematics of salt diapirs the internal structure of intrusive and extrusive salt bodies elucidates their external shape and the mechanism and history of diapiric emplacement information relevant to petroleum exploration trace amounts of brine can act like heat to weaken salt and promote geologic creep by solution transfer mechanisms we compare natural strain markers in salt with the artificial markers used by fluid dynamicists stream lines are the smooth flow paths followed by fluid particles stream surfaces separate flow laminae and contain the stream lines grain shape fabrics in salt anneal readily and have strain memories so short that lineations map the stream lines and foliations map the stream surfaces of the last stages of deformation by contrast larger structures like folded beddi g have much longer strain memories as a result multiple generations of tonguelike recumbent flow folds formed by unsteady flow in the mother source layer rotate to upright sheath folds or spines in the stems of diapirs here they are constricted and refolded into steep curtain folds to form crescentic and other interference patterns visible in the roofs of salt mines mature diapirs can form crestal bulbs which may be balloon or mushroom shaped and which potentially form larger petroleum traps than previously supposed screens of country rock may be entrained between the stem and peripheral overhanging lobes caused by episodic sedimentation

messinian subaerial erosion of the proto nile delta abstract the evaporitic drawdown and subsequent dessication of the mediterranean basins during the messinian salinity crisis has been confirmed by detailed seismic mapping of the ensuing erosion surface in the nile delta region the basal messinian unconformity determined by seismic analysis and borehole correlation extends from almost sea level in the southern delta area to depths of at least 5 km in the nile cone the onlap of the contemporaneously deposited fluvio deltaic clastics of the qawasim formation occurs at between 2 5 to 4 km below present gradual initial drawdown of the mediterranean sea with occasional sudden sporadic falls is implied by the presence of entrenched meanders and impaired rejuvenation terraces in the nile canyon formed as the proto nile river cut down into the pre existing tortonian delta complex the former tortonian delta slope became an extensive linear erosional front with over 3 km of vertical relief the uppermost levels of which were protected by tabular oligocene basalt flows preserved as mesas and buttes the lower slopes were the site of coalescing piedmont fans fed by upper slope wadi systems the piedmonts merged into the qawasim fluvio deltaic deposits of the proto nile fluvial flood plain the subcrop beneath the basal messinian unconformity reveals a remarkable diversity of rock type each with its own distinctive control on the geomorphology and geometry of the ensuing messinian erosional surface fracture patterns within the oligocene basalts produced a trellis drainage network which became later captured by a dendritic system developed on less resistant prodelta shales of the former tortonian delta slope close study of seismic profiles clearly demonstrates that the basal messinian erosional disconformity can be traced northwards to depths of at least 2 5 3 0 km before becoming affected by later pliocene faulting this validates a deep dessication model for the evolution of the messinian evaporites

solution precipitation creep and fluid flow in halite a case study of zechstein z1 rocksalt from neuhof salt mine germany zechstein z1 rocksalt from the fulda basin from the immediate vicinity of the hessen potash bed is folded into tight to isoclinal folds which are cut by an undeformed 1 cm thick coarse grained halite vein microstructures were investigated in etched gamma irradiated thin sections from both the wall rock and the vein the lack of synsedimentary dissolution structures and the widespread occurrence of plate shaped and hopper grains in the wall rock suggests that the sedimentary environment was perennial lake deformation microstructures are in good agreement with solution precipitation creep process and salt flow under very low differential stress strength contrast between anhydrite rich and anhydrite poor layers caused the small scale folding in the halite beds the vein is completely sealed and composed mainly of euhedral to subhedral halite grains which often overgrow the wall rock grains those microstructures together with the presence of occasional fluid inclusion bands suggest that the crystals grew into a solution filled open space based on considerations on the maximum value of in situ differential stress the dilatancy criteria the amount of released fluids from the potash bed during metamorphism and the volume change it is proposed that the crack was generated by hydrofracturing of the rocksalt due to the presence of the salt metamorphic fluid at near lithostatic pressure

structural evolution timing and tectonic style of the sole pit inversion abstract the nw se oriented sole pit high located in the western half of the southern north sea basin is the result of three different structural processes initiated during the late palaeozoic basin subsidence probably related to late hercynian pull apart movements led to continuous sedimentation from the permian to the middle jurassic mid jurassic doming of its eastern flank followed by erosion transtensional movements and differential subsidence until the early cretaceous reflect the mid and late kimmerian crustal distension and fragmentation of the north sea rift basinwide inversion occurred between the turonian and the campanian and was repeated in the oligocene resulting in a total uplift of some 1500 m the present structural style is represented by a complex network of transpressional and transtensional faults at permian rotliegend levels which are thought to represent the upward termination of a series of wrench induced flower structures with a right lateral sense of displacement these faults are detached by zechstein and triassic salt from more orderly transtensional faults systems at shallower levels in areas where salt is absent late kimmerian normal faults became reactivated in a reverse sense during inversion however the relationship of these shallow mappable tectonic components to the deeper pre permian structure of the sole pit high and to the underlying crustal configuration remains speculative

numerical modelling of rise and fall of a dense layer in salt diapirs this thesis uses results of systematic numerical models to argue that externally inactive salt structures which are potential targets for radioactive waste disposal might be internally active due to the presence of dense layers or blocks within a salt layer the three papers that support this thesis use the gorleben salt diapir nw germany which was targeted as a future final repository for high grade radioactive waste as a general guideline the first two papers present systematic studies of the parameters that control the development of a salt diapir and how it entrains a dense anhydrite layer results from these numerical models show that the entrainment of a dense anhydrite layer within a salt diapir depends on four parameters sedimentation rate viscosity of salt perturbation width and the stratigraphic location of the dense layer the combined effect of these four parameters which has a direct impact on the rate of salt supply volume area of the salt that is supplied to the diapir with time shape a diapir and the mode of entrainment salt diapirs down built with sedimentary units of high viscosity can potentially grow with an embedded anhydrite layer and deplete their source layer salt supply ceases however when salt supply decreases dramatically or ceases entirely the entrained anhydrite layer segments start to sink within the diapir in inactive diapirs sinking of the entrained anhydrite layer is inevitable and strongly depends on the rheology of the salt which is in direct contact with the anhydrite layer during the post depositional stage if the effective viscosity of salt falls below the threshold value of around 1018 1019 pa s the mobility of anhydrite blocks might influence any repository within the diapir however the internal deformation of the salt diapir by the descending blocks decreases with increase in effective viscosity of salt the results presented in this thesis suggest that it is highly likely that salt structures where dense and viscous layer blocks are present undergo an internal deformation processes when these dense blocks start sinking within the diapir depending on size and orientation of these blocks deformation pattern is significantly different within the diapir furthermore model results applied to the gorleben diapir show that the rate of descent of the entrained anhydrite blocks differs on different sides of the diapir this suggests that if the anhydrite blocks descent within the gorleben diapir they initiate an asymmetric internal flow within it

tracing iron fueled microbial carbon production within the hydrothermal plume at the loihi seamount the loihi hydrothermal plume provides an opportunity to investigate iron fe oxidation and microbial processes in a system that is truly fe dominated and distinct from mid ocean ridge spreading centers the lack of hydrogen sulfide within the loihi hydrothermal fluids and the presence of an oxygen minimum zone at this submarine volcano s summit results in a prolonged presence of reduced fe within the dispersing non buoyant plume in this study we have investigated the potential for microbial carbon fixation within the loihi plume we sampled for both particulate and dissolved organic carbon in hydrothermal fluids microbial mats growing around vents and the dispersing plume and carried out stable carbon isotope analysis on the particulate fraction the 13 c values of the microbial mats ranged from 23 to 28 and are distinct from those of deep ocean particulate organic carbon poc the mats and hydrothermal fluids were also elevated in dissolved organic carbon doc compared to background seawater within the hydrothermal plume doc and poc concentrations were elevated and the isotopic composition of poc within the plume suggests mixing between background seawater poc and a 13 c depleted hydrothermal component the combination of both doc and poc increasing in the dispersing plume that cannot solely be the result of entrainment and doc adsorption provides strong evidence for in situ microbial productivity by chemolithoautotrophs including a likelihood for iron oxidizing microorganisms

engineering properties of rock salt and simplified closed form deformation solution for circular opening in rock salt under the true triaxial stress state abstract underground structures and storage caverns are increasingly being constructed in rock salt due to its unique self healing ability and impervious nature rock salts are likely to experience and develop time dependent behavior deformation hence the characterization of rock salt for its properties including viscosity are pertinent for design of these structures in addition the material in underground openings experiences true triaxial stresses and hence it is vital to study the behaviour of such structures under true triaxial loading conditions this paper presents results of extensive laboratory testing carried out on specimens of khewra rock salt for its physico mechanical properties physical and engineering properties such as mineralogy density sonic wave velocity resistivity point load index and shear strength properties were measured a simplified closed form solution which deploys three dimensional strength criterion mogi coulomb with maxwell viscoelastic behaviour is developed to assess the stress and deformation behaviour of circular opening in plane strain condition the closed form solution assumes that the material exhibits the maxwell behavior when the stresses are lower than the yield stress and the material behavior is the combination of maxwell and mogi coulomb elastoplastic material when the stresses are equal to the yield stress in addition a cylindrical wellbore problem is solved with the proposed closed form solution and the deformation of the wellbore was estimated for the different time intervals

experimental deformation of a single layer anhydrite in halite matrix under bulk constriction part 1 geometric and kinematic aspects a new deformation apparatus has been used to model the internal kinematics of salt diapirs composite natural samples consisting of a single layer of anhydrite embedded in halite matrix were constrictionally deformed at temperature t 345 c strain rate 10 7 s 1 maximum viscosity 2 1013 pa s and maximum finite strain ex 122 the anhydrite layer oriented parallel to the major stretching axis x was deformed by fracturing whereas halite behaved viscously at advanced state of constriction ex 90 a strong increase in strain hardening of halite led to a transient tension fracture that healed up and was shortened by folding during the final phase of viscous deformation tiny prismatic anhydrite inclusions disseminated inside the halite matrix were reoriented during constriction resulting in a linear grain shape fabric 3d images of the anhydrite layer based on computer tomography revealed rare kink folds with axes subparallel to x and boudins which result from tension fracture with increasing layer thickness hi the width of boudins wa increases linearly wa 0 3 1 3 hi the normalized width of boudins wd wa hi is almost constant at 1 5 1 0 these geometrical parameters can be used to reveal fracture boudinage under bulk constriction the oblique orientation of most of the boudins with respect to the principal strain axes results from folding of the boudins by a second generation of folds the latter with axes subperpendicular to the layer

how did the messinian salinity crisis end the cause of the desiccation of the mediterranean sea during the messinian salinity crisis has been widely debated but its re flooding remains poorly investigated interpretations generally involve tectonic collapse of the strait of gibraltar or global sea level rise or even a combination of both the dramatic sea level fall in the mediterranean has induced deep fluvial incision all around the desiccated basin we investigate erosion dynamics related to this base level drop by using the numerical simulator eros we show that intense regressive erosion develops inevitably in the gibraltar area eventually inducing the piracy of the atlantic waters by an eastward flowing stream and the subsequent re flooding of the mediterranean

defining folds on three dimensional surfaces we present a new method for the structural analysis of folded surfaces the method requires a generalized definition of a fold as a patch consisting of contiguous points with gaussian curvature and mean curvature of consistent sign four classes of folds result from this definition antiforms and synforms each of synclastic and anticlastic forms this new analysis is illustrated with reference to several examples

structural evolution of inverted basins in the dutch offshore abstract the structural evolution of the dutch central north sea graben and the fault bounded broad fourteens basin is discussed graben formation started during the early triassic and culminated in strong differential subsidence during the late jurassic early cretaceous narrow fault bounded grabens and troughs and broad intervening highs were formed as a result of crustal distension and associated transtensional deformations the thickness of the late jurassic to early cretaceous fill of these basins may have exceeded 3000 m concurrent with the filling of these basins the bordering highs became deeply truncated during the late cretaceous and early tertiary compressive stresses resulted in inversion of these basins whereby movements along their bounding normal faults were reversed giving rise locally to overthrusting as for instance in the broad fourteens and west netherlands basins the timing of these compressional deformations has been palaeontologically dated and coincides with major orogenic events in the alps

modeling of grabens extending above evaporites in canyonlands national park utah abstract grabens in canyonlands national park utah began extending above a layer of evaporites when the colorado river cut through the overburden two dimensional finite element models simulate the effects of geometry and rock properties on graben configuration and spacing only those models having a progressively increasing slope or no slope mimicked the natural upslope graben propagation typical rock properties produced the most realistic fault patterns an initial friction angle of 31 a cohesion of 1 mpa and strain weakening comprising cohesion loss and decrease of friction angle to 26 a tensile stress limit narrowed the grabens and reproduced the vertical upper portion of the natural faults the viscous salt resisted overburden spreading and controlled its rate modeled grabens spread at typical rates of 1 2 mm a 1 for a salt viscosity of 1 10 18 pa s and the entire system strained at rates from 6 0 10 14 s 1 to 0 5 10 14 s 1 the faults bounding a graben formed nearly simultaneously at the top surface and propagated downward salt rose beneath the grabens as reactive diapirs overburden adjacent to the canyon flexed as salt was expelled and formed an arching horst and graben a corresponding horst has been found in the field the model results scale to larger dimensions except for the steep upper part of the faults reduced dimensions create vertical or no faults

development of n w europe s southern permian gas basin summary the southern permian basin contains over 4 1 10 12 m 3 of recoverable non associated gas most of which is found in early permian rotliegend sandstones the most important source of this gas is carboniferous coal deposited in a proto tethys foredeep basin where the coals were overlain by rotliegend desert sands and by late permian zechstein halite the scene was set for creating important reservoirs for gas deformation of the reservoir and seal to create a trap and the generation and migration of carboniferous gas resulted from the structural history of the area which was shaped in part by underlying crustal blocks and zones of crustal weakness much of this history was related to events most clearly expressed beyond the limits of n w europe in the north atlantic and tethys 1 e w tension which gave rise to the oblique slip induced subsidence of many sub basins within the southern permian basin caused the consecutive creation of the viking central graben system and rockall trough and ended with the crustal spreading of the atlantic ocean and 2 the early mesozoic opening of tethys its cretaceous closure and ensuing alpine orogeny which induced inversion in many areas of the southern permian basin that are now gas bearing

wave propagation modelling of induced earthquakes at the groningen gas production site gas extraction from the groningen natural gas field situated in the netherlands frequently induces earthquakes in the reservoir that cause damage to buildings and pose a safety hazard and a nuisance to the local population due to the dependence of the national heating infrastructure on groningen gas the short term mitigation measures are mostly limited to a combination of spatiotemporal redistribution of gas production and strengthening measures for buildings all options become more effective with a better understanding of both source processes and seismic wave propagation detailed wave propagation simulations improve both the inference of source processes from observed ground motions and the forecast of ground motions as input for hazard studies and seismic network design the velocity structure at the groningen site is relatively complex including both deep high velocity and shallow low velocity deposits showing significant thickness variations over relatively small spatial extents we performed a detailed 3 d wave propagation modelling study for an induced earthquake in the groningen natural gas field using the spectral element method we considered an earthquake that nucleated along a normal fault with local magnitude of ml 3 we created a dense mesh with element size varying from 12 to 96 m such that with a dominant source frequency of 7 hz waveforms with a frequency content up to 10 hz could be accurately modelled the velocity density model is constructed using a 3 d geological model of the area including both deep high velocity salt deposits overlying the source region and shallow low velocity sediments present in a deep and narrow tunnel valley the results show that the 3 d density velocity model in the groningen area clearly plays a large role in the wave propagation and resulting surface ground motions and causes significant lateral variations in site response the highvelocity salt deposits have a dispersive effect on the radiated wavefield reducing the seismic energy reaching the surface near the epicentre in turn the presence of low velocity tunnel valley deposits can locally cause a significant increase in peak ground acceleration here we study induced seismicity on a local scale and use specfem3d to conduct full waveform simulations and show how local velocity variations can affect seismic records the author s 2018

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

developing an application specific ground motion model for induced seismicity abstract a key element of quantifying both the hazard and risk due to induced earthquakes is a suite of appropriate ground motion prediction equations gmpes that encompass the possible shaking levels due to such events induced earthquakes are likely to be of smaller magnitude and shallower focal depth than the tectonic earthquakes for which most gmpes are derived furthermore whereas gmpes for moderate to large magnitude earthquakes are usually derived to be transportable to different locations and applications taking advantage of the limited regional dependence observed for such events the characteristics of induced earthquakes warrant the development of application specific models a preliminary ground motion model for induced seismicity in the groningen gas field in the netherlands is presented as an illustration of a possible approach to the development of these equations the gmpe is calibrated to local recordings of small magnitude events and captures the epistemic uncertainty in the extrapolation to larger magnitude considered in the assessment of the resulting hazard and risk

the influence of initial fold geometry on type 1 and type 2 interference patterns an experimental approach abstract experiments on superposed folding were performed in a plane strain pure shear rig using paraffin wax as an analogue for rocks a series of pre formed cylindrical folds were refolded with the compression direction acting parallel to the initial fold hinge direction the intermediate axis perpendicular to the first fold axial plane and the extension direction parallel to the first fold axial plane and perpendicular to its axis type 1 interference geometry roundness tightness and amplitude were varied to investigate the influence of first fold geometry on the interference patterns experimental folding of an initially planar layer oriented parallel to the first fold envelope provides a reference geometry for comparison the results suggest that hinge roundness has less influence on the interference pattern than other factors close initial folds refold into type 2 interference patterns which become even more pronounced as the tightness increases open folds produce type 1 interference patterns folds with the same interlimb angle and the same roundness produce different interference patterns depending on relative amplitude folds with relatively large amplitude are refolded into type 2 patterns whereas folds with small amplitude give clear dome and basin structures in a second set of experiments the compression direction also acted parallel to the first fold hinge but the orientations of the intermediate and extension axes were interchanged the interference patterns obtained are very similar to those in type 1 interference geometry suggesting that the major factor in determining whether type 1 or type 2 interference patterns develop is the initial fold geometry and not the kinematics of the second deformation

inorganic chemistry gas compositions and dissolved organic carbon in fluids from sedimented young basaltic crust on the juan de fuca ridge flanks abstract the permeable upper oceanic basement serves as a plausible habitat for a variety of microbial communities there is growing evidence suggesting a substantial subseafloor biosphere here new time series data are presented on key inorganic species methane hydrogen and dissolved organic carbon doc in ridge flank fluids obtained from subseafloor observatory corks circulation obviation retrofit kits at integrated ocean drilling program iodp boreholes 1301a and 1026b these data show that the new sampling methods cowen et al 2012 employed at 1301a result in lower contamination than earlier studies furthermore sample collection methods permitted most chemical analyses to be performed from aliquots of single large volume samples thereby allowing more direct comparison of the data the low phosphate concentrations 0 06 0 2 m suggest that relative to carbon and nitrogen phosphorus could be a limiting nutrient in the basement biosphere coexisting sulfate 17 18 mm hydrogen sulfide 0 1 m hydrogen 0 3 0 7 m and methane 1 5 2 m indicates that the basement aquifer at 1301a either draws fluids from multiple flow paths with different redox histories or is a complex environment that is not thermodynamically controlled and may allow co occurring metabolic pathways including sulfate reduction and methanogenesis the low doc concentrations 11 18 m confirm that ridge flank basement is a net doc sink and ultimately a net carbon sink based on the net amounts of doc oxygen nitrate and sulfate removed 30 m 80 m 40 m and 10 mm respectively from entrained bottom seawater organic carbon may be aerobically or anaerobically oxidized in biotic and or abiotic processes

a monte carlo method for probabilistic hazard assessment of induced seismicity due to conventional natural gas production abstract a monte carlo approach to probabilistic seismic hazard analysis is developed for a case of induced seismicity associated with a compacting gas reservoir the geomechanical foundation for the method is the work of kostrov 1974 and mcgarr 1976 linking total strain to summed seismic moment in an earthquake catalog our monte carlo method simulates future seismic hazard consistent with historical seismic and compaction datasets by sampling probability distributions for total seismic moment event locations and magnitudes and resulting ground motions ground motions are aggregated over an ensemble of simulated catalogs to give a probabilistic representation of the ground motion hazard this approach is particularly well suited to the specific nature of the time dependent induced seismicity considered we demonstrate the method by applying it to seismicity induced by reservoir compaction following gas production from the groningen gas field a new ground motion prediction equation gmpe tailored to the groningen field has been derived by calibrating an existing gmpe with local strong motion data for 2013 2023 we find a 2 chance of exceeding a peak ground acceleration of 0 57 g and a 2 chance of exceeding a peak ground velocity of 22 cm s above the area of maximum compaction disaggregation shows that earthquakes of m w 4 5 at the shortest hypocentral distances of 3 km and ground motions two standard deviations above the median make the largest contributions to this hazard uncertainty in the hazard is primarily due to uncertainty about the future fraction of induced strains that will be seismogenic and how ground motion and its variability will scale to larger magnitudes

geological and tectonic investigations in the former morsleben salt mine germany as a basis for the safety assessment of a radioactive waste repository abstract the safety assessment of a repository for radioactive waste is based on the results of model simulations and scenario analysis to obtain a well founded geological basis for this extensive geological and structural studies have been carried out for the morsleben repository the morsleben repository for radioactive waste was constructed in zechstein strata the location of the werra formation z1 was located in boreholes and the stassfurt z2 leine z3 and aller z4 formations are exposed in the repository mine the zechstein salt has a total thickness in the western part of the salt body of 580 m in the eastern part it is only 380 m thick the morsleben repository is in the allertal zone salt structure the root zone of a deeply eroded salt body this is evidenced by the relatively small thickness of the zechstein salt as well as by the many blocks of the hauptanhydrit z3ha in the salt which are present mostly in the synclinal hinge zones i e in the deeper parts of the structure as a result of tectonic separation of ductile salt from competent anhydrite the tectonics of the structure are documented by polyphase folds characteristic of the deformation of ductile material the general trend of the fold axes is horizontal nw se parallel to the trend of the allertal zone the western part of the salt structure is characterised by high ne vergent isoclinal folds the z2 to z4 strata involved in the folding extend from the salt table top of the salt body down to the lowest synclinal trough in the eastern part the folds are open and symmetric with considerably smaller amplitude correspondingly z4 strata mostly occur just below the salt table z3 at the repository level and z2 below that the different styles of folding in the east and west are due to the structure of the rocks beneath the zechstein salt the boundary between the two types of folds lies above a major fault in the rocks below the zechstein salt separating a downthrown block in the west from an upthrown block in the east ne vergent isoclinal folds occur above the downthrown block where the major ascent of the salt occurred in contrast the folding in the upthrown eastern block has hardly been affected by the ascending salt hence the wide open symmetrical folds thus the structure of the rocks beneath the zechstein determined the folding style in the overlying salt the present day fold structures chiefly result from late cretaceous compression that affected the north german basin the salt body is therefore primarily a tectonic structure and is not halokinetic

halite cementation and carbonate diagenesis of intra salt reservoirs from the late neoproterozoic to early cambrian ara group south oman salt basin late neoproterozoic to early cambrian carbonates of the ara group form important intra salt stringer reservoirs in the south oman salt basin differential loading of thick continental clastics above the six carbonate to evaporite cycles of the ara group led to the formation of salt diapirs encasing a predominantly self charging hydrocarbon system within partly highly overpressured carbonate bodies stringers these carbonates underwent a complex diagenetic evolution with one stage of halite cementation in a shallow early and another in a deep late burial environment early and late halite cements are defined by their microstructural relationship with solid bitumen the early phase of halite cementation is post dated by solid reservoir bitumen this phase is most pervasive towards the top of carbonate stringers where it plugs nearly all available porosity in facies with initially favourable poroperm characteristics bromine geochemistry revealed significantly higher bromine contents up to 280 p p m in the early halite compared with the late halite 173 p p m the distribution patterns and the high bromine contents of early halite are consistent with precipitation caused by seepage reflux of highly saturated brines during deposition of the overlying rock salt interval later in burial history relatively small quantities of early halite were dissolved locally and re precipitated as indicated by inclusions of streaky solid bitumen within the late halite cements late halite cement also seals fractures which show evidence for repeated reopening initially these fractures formed during a period of hydrothermal activity and were later reopened by a crack seal mechanism caused by high fluid overpressures porosity plugging by early halite cements affects the poroperm characteristics of the ara carbonates much more than the volumetrically less important late halite cement the formation mechanisms and distribution patterns of halite cementation processes in the south oman salt basin can be generalized to other petroliferous evaporite basins

convection experiments in high prandtl number silicones part 2 deformation displacement and mixing in the earth s mantle the evolution of structures in the earth s convecting mantle is studied in a simple but carefully scaled laboratory flow the geometrical scaling is constrained by the various geometries of convection cells possible in the earth s interior two layered mantle convection with a superposed small scale circulation in the top is favoured here the model flow has a rayleigh number 104 a prandtl number 108 and approximately axially symmetric cells with aspect ratio of unity the rheology and boundary conditions are aimed to be dynamically similar to that occurring in the mantle the flow is analysed on the basis on snapshots showing the progressive deformation and displacement of passive flow markers which allow the reconstruction of velocity vectors strain rate and vorticity inferences can be made about 1 1 the progressive deformation in individual rock masses and 2 2 the nature of the large scale mixing process caused by a combination of deformation and displacement in a convecting mantle this is discussed in terms of the kinematic vorticity number both geological and fluid mechanical studies of low inertia flows may benefit from the new experimental technique and analyses presented here until now it has been impossible to visualize and quantify the finite strains and rotation components of deformation in flowing fluids by other than numerical methods the laboratory method advocated here is quick and involves equipment which is relatively cheap if compared with those required for numerical analyses basic understanding of elementary fluid dynamics is sufficient to perform innovative investigations in this new field

ductile creep compaction and rate and state dependent friction within major fault zones the shear traction on major strike slip faults during earthquakes is much lower than that expected on a frictionally sliding surface in equilibrium with hydrostatic pressure the low shear traction is explained if the fluid pressure at the time of the earthquake is much greater than hydrostatic pressure ductile creep within mostly sealed fault zones compacts the matrix and thus increases fluid pressure between earthquakes frictional dilatancy during earthquakes decreases fluid pressure below hydrostatic and over the earthquake cycle the fault zone is in long term equilibrium with the country rock this ductile mechanism is formally unified with rate and state theory for time dependent friction when the difference between a critical porosity where the rock loses all strength and the actual porosity of cracks is used as a state variable this choice is justified by percolation theory of mostly broken lattices time dependent behavior associated with changes in normal traction in the laboratory is explained by the formalism instability earthquakes sometimes occurs in the numerical experiments however fairly small amounts of frictional dilatancy during initial frictional creep decrease fluid pressure and preclude unstable sliding two coupled mechanisms for producing dilatancy on faults once an instability is well underway are evident 1 expansion of pore fluids associated with frictional heating increases fluid pressure offsetting the effects of increased pore volume during earthquakes there is some tendency for pore volume increase to balance fluid expansion so that fluid pressure stays relatively constant 2 production of isolated voids that do not immediately decrease fluid pressure throughout the fault zone during earthquakes can occur to the extent that the fault zone is not significantly strengthened although the extent of both processes is constrained by energy considerations the variation of fluid pressure during earthquakes is not yet well enough understood to predict stress drop from observable material properties

dissolved hydrogen and methane in the oceanic basaltic biosphere abstract the oceanic basaltic crust is the largest aquifer on earth and has the potential to harbor substantial subsurface microbial ecosystems which hitherto remains largely uncharacterized and is analogous to extraterrestrial subsurface habitats within the sediment buried 3 5 myr old basaltic crust of the eastern juan de fuca ridge flank the circulating basement fluids have moderate temperature 65 c and low to undetectable dissolved oxygen and nitrate concentrations sulfate present in high concentrations is therefore expected to serve as the major electron acceptor in this subsurface environment this study focused on the availability and potential sources of two important electron donors methane ch4 and hydrogen h2 for the subseafloor biosphere high integrity basement fluids were collected via fluid delivery lines associated with integrated ocean drilling program iodp circulation obviation retrofit kits corks that extend from basement depths to outlet ports at the seafloor two new corks installed during iodp 327 in 2010 1362a and 1362b were sampled in 2011 and 2013 the two corks are superior than earlier style corks in that they are equipped with coated casing and polytetrafluoroethylene fluid delivery lines reducing the interaction between casing materials with the environment additional samples were collected from an earlier style cork at borehole 1301a the basement fluids are enriched in h2 0 05 1 8 mol kg suggesting that the ocean basaltic aquifer can support h2 driven metabolism the basement fluids also contain significant amount of ch4 5 32 mol kg revealing ch4 as an available substrate for subseafloor basaltic habitats the 13c values of ch4 from the three boreholes ranged from 22 5 to 58 while the 2h values ranged from 316 to 57 the isotopic compositions of ch4 and the molecular compositions of hydrocarbons suggest that ch4 in the basement fluids is of both biogenic and abiotic origins varying among sites and sampling times the 2h values of ch4 in cork 1301a fluid samples are much more positive than found in all other marine environments investigated to date and are best explained by the partial microbial oxidation of biogenic ch4 in conclusion our study shows that ch4 and h2 are persistently available to fuel the deep biosphere and that ch4 is both produced and potentially consumed by microorganisms in the oceanic basement