hydrochemical and isotopic characteristics of groundwater in the yanqi basin of xinjiang province northwest china in this study hydrochemical and isotope investigations were conducted in the yanqi basin to determine the chemical composition and to gain insight into the groundwater recharge process in the yanqi basin it mainly used hydrochemistry environmental isotopes and a series of comprehensive data interpretation e g statistics ionic ratios and piper diagram to obtain a better understanding of the functioning of the system the following hydrochemical processes were identified as the main factors controlling the water quality of the groundwater system weathering of silicate minerals dissolution ion exchange and to a lesser extent evaporation which seemed to be more pronounced down gradient of the flow system as groundwater flows from the recharge to discharge areas chemical patterns evolve in the order of ca2 hco3 ca2 mg2 hco3 to ca2 mg2 cl so4 2 na k cl so4 2 and na cl according to lithology the environmental isotope 18o 2h 3h measurements further revealed that precipitation was the main recharge source for the groundwater system some local values indicated high levels of evaporation tritium and cfc analysis were used to estimate the ages of the different groundwater the tritium values of the groundwater samples varied from 2 82 to 29 7 tu the age of the groundwater at depths of 120 m is about 30 50 years cfc values obtained for six samples to determine groundwater age the age of the groundwater is about 20 50 years

retraction note the hydrochemical framework of surface water basins in southern ghana surface water resources play a crucial role in the domestic water delivery system in ghana in addition sustainable food production is based on the quality and quantity of water resources available for irrigation purposes to supplement rain fed agricultural activities in the country the objective of this research was to determine the main controls on the hydrochemistry of surface water resources in the southern part of ghana and assess the quality of water from these basins for irrigation activities in the area r mode factor and cluster analyses were applied to 625 data points from 6 river basins in southern ghana after the data had been log transformed and standardized for homogeneity this study finds that surface water chemistry in the south is controlled by the chemistry of silicate mineral weathering chemistry of rainfall fertilizers from agricultural activities in the area as well as the weathering of carbonate minerals a gibb s diagram plotted with total dissolved solids tds on the vertical axis against na k ca2 k na on the horizontal axis indicates that rock weathering plays a significant role in the hydrochemistry activity diagrams for the cao na2o al2o sio2 h2o and cao mgo al2o3 sio2 h2o systems suggest that kaolinite is the most stable clay mineral phase in the system in addition an assessment of the irrigation quality of water from these basins suggests that the basins are largely low sodium low to medium salinity basins delivering water of acceptable quality for irrigation purposes

bed by bed fold growth by kink band migration sant llorenc de morunys eastern pyrenees ahstract rowth strata deposited over and against the flank of the sant llorenc de morunys fold during its final stages of deformation have been mapped at high resolution as the basis for unraveling the kinematics of fold growth we use restoration techniques based on normal balancing assumptions to decipher the detailed kinematic history of folding the progressive restorations as well as balanced forward modeling show that the last few hundred meters of fold growth were dominated by kink band migration of a sort that is typical of much faultrelated folding the kink band migration has produced complex anticlinal hinge zone geometry including segmented fold hinges linked by disconformities and unconformities which has direct and detailed explanation in terms of fluctuations in deposition rate relative to curved hinge kink band migration rate large fluctuations in the convolution of non steady sedimentation and deformation are demonstrated although the absolute fluctuations in deformation and sedimentation are unknown at a length scale of 100 m kink band migration with little or no deposition is interspersed with sedimentation with little or no deformation at the length scale of 500 m deposition ranges from 200 to 50 of uplift 0 1997 elsevier science ltd all rights reserved

strains developed in the hangingwalls of thrusts due to their slip propagation rate a dislocation model reply abstract fault planes propagate radially from a point source and this failure propagation process is very similar to the movement of a dislocation through a crystal lattice an elastic strain represented by an extra half plane is necessarily imparted to the lattice at an edge dislocation and this is equivalent to the ductile bead which accompanies the propagating tip of a thrust fault this ductile bead migrates with the fault tip and imparts a characteristic internal strain to the thrust sheet a two dimensional model is presented to illustrate the inter relationship between fault plane slip fault tip propagation and internal strain in multilayered sequences internal strain is usually represented by asymmetric folds verging in the thrust transport direction a simple technique the displacement distance plot utilizes the fact that displacement dies out towards the fault tip this plot can be used to quantify the relative stretch measured parallel to the fault movement which is dependent on the slip propagation rate and it may be used to define exactly the position of the fault tip on a cross section examples of fold thrust structures from devon england and pembrokeshire wales are used to illustrate the technique

distal tephras of the eastern lake victoria basin equatorial east africa correlations chronology and a context for early modern humans abstract the tephrostratigraphic framework for pliocene and early pleistocene paleoanthropological sites in east africa has been well established through nearly 50 years of research but a similarly comprehensive framework is lacking for the middle and particularly the late pleistocene we provide the first detailed regional record of late pleistocene tephra deposits associated with artifacts or fossils from the lake victoria basin of western kenya correlations of late pleistocene distal tephra deposits from the wasiriya beds on rusinga island the waware beds on mfangano island and deposits near karungu mainland kenya are based on field stratigraphy coupled with 916 electron microprobe analyses of eleven major and minor element oxides from 50 samples at least eight distinct distal tephra deposits are distinguished four of which are found at multiple localities spanning 60 km over an approximately north to south transect new optically stimulated luminescence dates help to constrain the late pleistocene depositional ages of these deposits our correlation and characterization of volcaniclastic deposits expand and refine the current stratigraphy of the eastern lake victoria basin this provides the basis for relating fossil and artifact bearing sediments and a framework for ongoing geological archaeological and paleontological studies of late pleistocene east africa a crucial time period for human evolution and dispersal within and out of africa

progressive evolution of a fault related fold pair from growth strata geometries sant llorenc de morunys se pyrenees abstract new structural stratigraphical mapping constrains the three dimensional kinematics and mechanisms of eocene oligocene growth folding at sant llorenc de morunys ne ebro basin spain a 1 km wide sub vertical panel of syntectonic alluvial gravels passes southwards via a highly asymmetrical growth fold pair to shallowlydipping strata the axial surface of the anticline comprises either continuous or en echelon segments while that of the syncline is concave and usually continuous while converging upwards the axial surfaces do not define growth triangles principal and subsidiary growth unconformities and thickness changes occur across both axial surfaces and the common limb dips within the common limb decrease up stratigraphy and up dip mesostructures indicate that internal deformation was ongoing during folding at all stratigraphical levels and concentration of cleavage in the syncline indicates that this hinge was essentially fixed sequential restoration of three profiles shows that folds amplified principally by limb rotation but incorporated minor passive hinge migration particle movement vectors generated by section restoration are arcuate about a hinterland pinpoint a new trishear model of fault propagation folding involving non rigid limb rotation reproduces the rounded hinge forms thickening geometries and limb dip variations observed simple kink band migration models fixed axis and constant thickness theories do not replicate these features

numerical modeling of trishear fault propagation folding in contrast to kink band migration modeling methods trishear numerical models produce fault propagation folds with smooth profiles and rounded hinges modeled fold hinges tighten and converge downward within a triangular zone of distributed deformation which is focused on the fault tip such features have been reported from field studies and are also seen in analogue models of compressional deformation however apart from its initial application to laramide folds little quantitative work has been undertaken on trishear fault propagation folding in other settings in addition no study has been undertaken into the growth strata which might be associated with such structures this paper uses an equivalent velocity description of the geometric model of trishear together with models of erosion and sedimentation to investigate trishear fault propagation folding of both pregrowth and growth strata the trishear model is generalized to include a variety of fault propagation to slip ratios and fault propagation from a flat decollement the models show continuous rotation of the forelimb with the characteristic development of cumulative wedges within growth strata when total slip on a structure is high the model predicts overturned pregrowth and growth strata during the initial stages of deformation beds in the forelimb thicken but later thin when they become steep or overturned the effect of variations in fault propagation to slip ratios on two dimensional finite strain in the models is assessed by the use of initially circular strain markers high fault propagation to slip p s ratios lead to narrow zones of high finite strain while lower p s ratios lead to more ductile deformation and broader zones of high strain in all cases hanging wall anticlines and footwall synclines originate as early ductile folds which are later cut by the propagating fault modeled structures are compared with natural examples

simulation of groundwater flow in a crystalline rock aquifer system in southern ghana an evaluation of the effects of increased groundwater abstraction on the aquifers using a transient groundwater flow model monitored groundwater level data well logs and aquifer data as well as the relevant surface hydrological data were used to conceptualise the hydrogeological system of the densu basin in southern ghana the objective was to numerically derive the hydraulic conductivity field for better characterization of the aquifer system and for simulating the effects of increasing groundwater abstraction on the aquifer system in the basin the hydraulic conductivity field has been generated in this study through model calibration this study finds that hydraulic conductivity ranges between a low of 2 m d in the middle sections of the basin and about 40 m d in the south clear differences in the underlying geology have been indicated in the distribution of aquifer hydraulic conductivities this is in consonance with the general assertion that the hydrogeological properties of the aquifers in the crystalline basement terrains are controlled by the degree of fracturing and or weathering of the country rock the transient model suggest aquifer specific storage values to range between 6 0 10 5 m 1 and 2 1 10 4 m 1 which are within acceptable range of values normally quoted for similar lithologies in the literature there is an apparent subtle decrease in groundwater recharge from about 13 of the annual precipitation in 2005 to about 10 3 of the precipitation in 2008 the transient model was used to simulate responses of the system to annual increment of groundwater abstraction by 20 at the 2008 recharge rates for the period 2009 2024 the results suggest that the system will not be able to sustain this level of abstraction as it would lead to a basin wide drawdown in the hydraulic head by 4 m by the end of the prediction period it further suggests a safe annual increment in groundwater abstraction by 5 under business as usual recharge conditions identification and protection of groundwater recharge areas in the basin are recommended in order to safeguard the integrity of the resource under the scenario of increased abstraction for commercial activities in the basin copyright 2012 john wiley sons ltd

thrust surface geometry implications for thrust belt evolution and section balancing techniques abstract the application of modern concepts of thrust tectonics to orogenic belts has yielded many detailed restorable sections thrusts generally restore with a staircase geometry onto the undeformed stratigraphic template since the work of rich 1934 it has been generally assumed that thrusts have propagated with a staircase trajectory and that hangingwall structures result from the movement of the thrust sheet up footwall ramps however thrusts often cut through previously folded strata with a smooth trajectory smooth trajectory thrusts can be identified from footwall geometry and strain state once a smooth trajectory thrust has been identified it is insufficient to produce a balanced deformed section and its restored counterpart sequential balanced sections must be constructed reversing the deformation history the restoration of thrusts to a staircase trajectory has no mechanical significance as the thrust is merely acting as a marker if restored back beyond the time at which it propagated thrust ramps are not necessarily actual steps in the thrust surface they are often just zones where the thrust cuts through bedding in a smoothly curving trajectory ductile deformation in thrust belts can reduce bed length at depth thus removing the need for structures which are necessary to preserve constant bed lengths ductile deformation in the internal zones of orogenic belts renders the construction of balanced sections in these zones highly problematical

ages estimated from a diffusion equation model for scarp degradation the diffusion equation derived from the continuity equation for hillslopes is applied to scarp erosion in unconsolidated materials solutions to this equation allow direct calculation of the product of the rate coefficient and the age of the scarp from measurements of scarp morphology where the rate coefficient can be estimated or can be derived from scarps of known age this method allows direct calculation of unknown ages of scarps

the origin of fluoride in the granitic aquifer of porto alegre southern brazil the porto alegre region southern brazil comprises a fractured aquifer system constituted by pre cambrian granitic and gneissic rocks and a porous aquifer system formed by cenozoic muddy sandy to sandy sediments a model is presented for the origin of the fluoride in the groundwater of the fractured aquifer system based on ionic interrelations a statistical analysis of physicochemical parameters and geochemical modeling the fluoride is present at levels of up to 6 13 mg l in groundwater and it arises due to the dissolution of secondary fluorite filling fractures in the granitic and gneissic rocks the dissolution of fluorite occurs at the same time as calcite and dolomite solubilization the statistical analysis identified three chemically distinct groups named 1 2 and 3 and two subgroups 1a and 1b of groundwater in the fractured aquifer the most significant differences between these groups are the different concentration ranges of fluoride calcium bicarbonate magnesium total dissolved solids and chloride and ph values as well as the correlations between them the compositional evolution of each groundwater group is governed mainly by how much high salinity groundwater from the porous aquifer system is mixed with them and the different thermodynamic equilibrium conditions of calcite dolomite and fluorite

numerical modelling of the response to variable stretching rate of a domino fault block system abstract using a numerical model of domino fault block development the effects of a variable stretching rate during rifting were investigated it is shown that a varable stretching rate can have an important influence on synrift sequence geometries this can lead to complex synrift sequences composed of wedge shaped units formed during periods of high stretching rate and more symmetrical units formed during periods of relative tectonic quiescence at the fault block crest increases in stretching rate can produce offlapping synrift sequences whereas decreases in stretching rate allow onlap onto the fault block crest if the rifting period contains multiple pulses of stretching complex intra synrift unconformities can be formed the initial bathymetry is also shown to have an important influence on the modelled synrift stratigraphy the modelled stratigraphies are similar to those thought to result from variations in absolute sea level pseudo facies markers based on the combined initial depth and slope of deposition of the modelled sediments are shown to be a useful tool and graphically illustrate the response of the system to pulses of tectonic activity

a kinematic model for the origin of footwall synclines abstract the origin of footwall synclines at the base of thrust ramps can be related to the kinematic evolution of fault propagation folds the conventional fault propagation fold model does not predict the development of footwall synclines because it assumes a high propagation to slip ratio for development of the lower flat which does not allow for folding before the thrust cuts up section an alternative model where the propagation to slip ratio remains finite throughout the development of the fault propagation fold produces a detachment fold at the thrust tip during propagation of the thrust along the lower flat if the thrust cuts up through the ductile core of the detachment fold during ramp formation it will leave behind the forelimb of the detachment fold as part of a footwall syncline

geochemical and statistical evidence of deep carbonate groundwater within overlying volcanic rock aquifers aquitards of southern nevada usa abstract samples collected from springs and wells in southern nevada were analyzed for major solutes and trace elements as part of a larger study to characterize the geochemical signatures of these groundwaters in this study principal component analysis pca was used to reduce the large data sets including the four major cations ca mg na k and 27 trace elements analyzed in these groundwater samples principal components analysis of the major cation data indicates that groundwaters from cenozoic felsic volcanic rock aquifers aquitards of southern nevada exhibit strong chemical associations to each other but weak relationships to groundwaters from the regional carbonate aquifer which were instead chemically similar to each other however pca of the trace element data demonstrates that some groundwaters from the volcanic aquifers aquitards are chemically similar to those of the underlying regional carbonate aquifer the pca also reveals that these groundwaters from the volcanic aquifers aquitards have significantly different trace element compositions than perched groundwaters contained within similar felsic volcanic rocks moreover rare earth element ree data from groundwaters collected from wells finished in the volcanic aquifers aquitards of southern nevada have similar concentrations and similar shale normalized patterns to the carbonate aquifer groundwaters as well as local carbonate rocks these same southern nevada well waters do not exhibit ree concentrations or shale normalized signatures that resemble the perched volcanic groundwaters or the tuffs of southern nevada the ree data and trace element pca along with previous carbon isotope analyses water temperature data hydraulic head relations and results of a recent pump test of a well near yucca mountain suggest close contact of the regional carbonate groundwaters and groundwaters from the overlying volcanic rocks of southern nevada and possible upwelling of the carbonate groundwaters into the overlying volcanic rock units in the vicinity of yucca mountain

influence of syntectonic sedimentation on thrust wedges in analogue models scaled analogue sandbox models have been used to simulate the growth of coulomb thrust wedges that include syntectonic sedimentation during thrusting increases in the syncontractional sedimentation rate dramatically change the shape of the coulomb thrust wedge decreasing the number of thrust slices the internal shortening and the critical taper of the wedge thrust trajectories change from ramp flat to sigmoidal with increased syncontractional sedimentation the analogue models show many similarities to thrust fault geometries in accretionary prisms and foreland fold and thrust belts in which thrust slices prograded into basins with active sedimentation

strains and folds within thrust sheets an analysis of the heilam sheet northwest scotland abstract the changes of shape and orientation of fossil worm burrows have been used to carry out a detailed strain analysis of the heilam thrust sheet in the moine thrust zone northwest scotland the strains have been factorised into components of layer parallel shear 1 layer normal shear 2 and layer parallel shortening or elongation variations in the 1 shear are largely lithologically controlled some strain is due to flexural processes as the thrusts and overlying beds change dip over thrust ramps or are tightened by later deformation while there may also be a component of drag which increases towards the overlying thrust this predating the shear due to flexure a contoured map of the values suggests that major folds within the thrust sheet developed as a result of stick or drag on the floor thrust prior to ramp climb this led to differential movement in the transport direction causing layer parallel shortening accompanied or followed by buckling of the layers a map showing layer normal shear strains 2 suggests that the heilam sheet forms a major surge zone the central part having moved further wnw than the northern and southern parts this has led to components of lateral shear along parts of the sheet especially in the north producing curvature of the imbricate faults

multivariate statistical analysis of geochemical data as indicative of the hydrogeochemical evolution of groundwater in a sedimentary rock aquifer system summary the study of groundwater hydrogeochemistry of the paleozoic basses laurentides sedimentary rock aquifer system in quebec produced a large geochemical dataset groundwater samples were collected at 153 sites over a 1500 km2 study area and analyzed for major and minor ions the large number of data can lead to difficulties in the integration interpretation and representation of the results two multivariate statistical methods hierarchical cluster analysis hca and principal components analysis pca were applied to a subgroup of the dataset to evaluate their usefulness to classify the groundwater samples and to identify geochemical processes controlling groundwater geochemistry this subgroup consisted of 144 samples and 14 parameters ca2 mg2 na k hco 3 cl so 4 2 fe2 mn2 br sr2 f ba2 hs seven geochemically distinct clusters c1 c7 resulted from the hca samples from clusters c3 c4 c6 and c7 are mostly located in preferential recharge areas the majority of these samples have ca mg hco3 recharge groundwater c3 c6 c7 and na hco3 evolved groundwater c4 samples from the other three clusters c1 c2 c5 are characteristic of an aquifer system under confined conditions the majority of these samples have na hco3 evolved groundwater c1 c5 and na cl ancient groundwater that exhibits elevated concentrations in br c2 in addition to recognizing the importance of hydrogeological conditions on groundwater geochemistry the distribution of clusters also showed the importance of the geological formations on minor and trace elements such as fe2 mn2 sr2 f and ba2 the first five components of the pca account for 78 3 of the total variance in the dataset component 1 is defined by highly positive loadings in na cl and br and is related to groundwater mixing with champlain sea water and solute diffusion from the marine clay aquitard the high positive loadings in ca2 and mg2 of component 2 suggest the importance of dissolution of carbonate rocks in this aquifer system from their characteristic loadings the first two components are defined as the salinity and hardness components respectively components 3 5 are related to more local and geological effects the integration of the hca and the pca with conventional classification of groundwater types as well as with the hydrogeological and geological contexts allowed the division of the region into four main geochemical areas providing an improved regional picture of the aquifer system dynamics and hydrogeochemical evolution of groundwater the following factors were recognized as influencing the evolution of groundwater identified in every geochemical area 1 geological characteristics including sedimentary rock type and till mineralogy 2 hydrogeological characteristics represented by the level of confinement and the hydraulic gradient and 3 the geological history including the latest glaciation and the champlain sea invasion with its integrated approach this hydrogeochemical study contributes to the characterization and understanding of complex groundwater flow systems and provides an example of the long term geochemical evolution of hydrogeological systems after a major perturbation in this case seawater invasion

characterization of the groundwater flow regime and hydrochemistry of groundwater from the buem formation eastern ghana this study demonstrates the application of multivariate statistical methods in definition of groundwater recharge and discharge areas in a sedimentary basin in ghana q mode hierarchical cluster analysis hca was applied to 57 hydrochemical data from the buem formation in the northern part of the volta region in ghana r mode hca and r mode factor analysis were then applied to the same dataset to reveal the processes controlling the hydrochemistry of groundwater from this hydrogeological formation results of both the q and r mode analyses were backed by graphical methods the analyses revealed two major water types differentiated by salinity levels into four spatial groundwater associations the characteristics of the four groundwater types are discussed the recharge areas are characterized by cahco3 low salinity waters which evolve through rock water interactions to nahco3 high salinity waters in the discharge areas this study finds that the hydrochemistry of groundwater from this formation is mainly controlled by the weathering of minerals principally silicates in the aquifer matrix the effects of the chemistry of recharging precipitation are higher in the recharge areas while mineral weathering tends to be severe close to the discharge areas in the groundwater flow regime all the four spatial groundwater associations have low sodium content but salinity levels increase towards the discharge areas such that some of wells in the discharge areas may not be acceptable for irrigation on grounds of high salinities which might affect the osmotic potentials of plants copyright 2011 john wiley sons ltd

hydrogeological and hydrochemical characterization of the voltaian basin the afram plains area ghana in the afram plains area groundwater is the main source of water supply for most uses the area is underlain by aquifers of the southern voltaian sedimentary basin which are predominantly sandstones mudstones conglomerates and shale ordinary least squares regression analysis using 41 well test data from aquifers in the afram plains portion of the voltaian system reveals that transmissivity t exists in a non linear relationship with specific capacity sc the analysis reveals that t 0 769sc1 075 with r 2 0 83 for aquifers in the area the mudstone conglomerate aquifer in the area appears to be the most variable in terms of both specific capacity and transmissivity with transmissivity ranging from 0 18 to 197 7 m2 day and 0 5 and 148 5 m3 day m respectively horizontal fractures and joints resulting from secondary fracturing appear to be the main determinants of both transmissivity and specific capacity in the area phreeqc modeling and mineral stability diagrams indicate that groundwater quality in the afram plains area is controlled by the incongruent weathering of silicate minerals in the aquifers these processes concentrate calcium sodium magnesium potassium bicarbonate ion and quartz leading to calcite dolomite and aragonite supersaturation at most locations hierarchical cluster analysis performed on the raw chemical data reveals two main water types or facies the calcium sodium chloride bicarbonate facies and the magnesium potassium sulfate nitrate facies for the southern and northern sections of the afram plains area respectively

spatio temporal evaluation of the groundwater quality in kafr al zayat district egypt eighteen groundwater well sites located in kafr al zayat egypt were sampled monthly from january 2009 to november 2011 for microbial content mn 2 fe 2 total dissolved solids tds total hardness no3 and turbidity the data were analyzed combining the integrated use of factor and cluster analyses as well as the geostatistical semi variogram modeling the prime objectives were to assess the groundwater suitability for drinking to document the factors governing the spatio tempral variability and to recognize distinctive groundwater quality patterns to help enable effective sustainability and proactive management of the limited resource the groundwater microbial mn 2 fe 2 tds and total hardness contents violated the drinking water local standards while the turbidity and the nitrate content complied with them factor analysis indicated that the microbial content is the most influential factor raising the variability potential followed in decreasing order by mn2 fe2 tds no3 turbidity and finally the total hardness turbidity resulting from urban and agricultural runoff was strongly associated with most of the quality parameters quality parameters fluctuate sporadically without concrete pattern in space and time while their variability scores peak in november every year three spatially distinctive quality patterns were recognized that were consistent with and affected by the cumulative effects of the local topography depth to water table thickness of the silty clay cap layer surface water and groundwater flow direction and hence the recharge from contaminated surface canals and agricultural drains copyright 2013 john wiley sons ltd

origin of the shallow groundwater system in the southern voltaian sedimentary basin of ghana an isotopic approach the development and management of groundwater resources require an ability to understand and identify the recharge source to the groundwater system stable and radioactive isotope data have been used to investigate the source of recharge and the age of the shallow groundwater system within the southern voltaian sedimentary basin svsb of ghana as part of an on going groundwater development project the tritium concentrations in the groundwater samples are very low and range from less than 1 7 2 t u while measured 14c content ranges from 43 to 108 modern carbon the tritium concentration of rainfall ranges from less than 1 4 t u the 18o values of groundwater samples range from 4 2 to 2 6 while the d values range from 21 to 10 stable isotopic data of the groundwater samples lie either on or close to the global meteoric water line gmwl on the d 18o plot and indicate that the shallow groundwater in the area is derived from meteoric water that has undergone no significant degree of kinetic evaporation during recharge no indication of paleo recharge can be inferred from the 18o and 2h composition of the groundwater current tritium concentration in the groundwater is generally low however it proved useful in the qualitative identification of modern recharge radiocarbon deduced ages range from about b p to modern and indicate young recharge to the shallow groundwater system

geometric and numerical model of progressive limb rotation in detachment folds a simple area balanced geometric model of progressive limb rotation in detachment folds allows the quantification of displacement uplift and rotation and the assessment of their effect upon growth strata geometries translation of this geometric model into a velocity model of deformation allows the modeling of associated growth strata resulting from background sedimentation and local erosion transport and deposition we show that with constant displacement and sedimentation rate this model predicts a progressive unconformity indicating the onlap and eventual overlap of the fold limb caused by a decreasing uplift rate this decrease is a consequence of the kinematics of progressive limb rotation increases in displacement rate with sedimentation rate kept constant can lead to offlap and angular unconformities although subsequent onlap does not necessarily reflect a return to a lower displacement rate modeled growth strata geometries exhibit many of the features reported from the literature

mathematical modelling of sedimentary basin processes abstract mathematical models of various sedimentary basin processes including hanging wall deformation evaporite deposition carbonate platform sedimentation and sequence development on active domino style fault blocks are presented many of these processes may be formulated using the equation of continuity of an open system as a starting point sedimentary and tectonic processes may be combined into a single mathematical formulation provided that an eulerian coordinate system is used and this ensures that tectonics and sedimentation are modelled as simultaneous rather than sequential processes the resulting algorithms are fast robust and applicable to many geologically very different situations but may be limited to relatively simple examples the conditions under which the models are numerically stable are also easily found the abstract nature of the mathematical models requires that simply determined properties such as palaeo water depth and palaeo slope must be used as proxy facies markers the main limitation of the method is that it is restricted to modelling processes which change slowly with time and space and the method can therefore not cope properly with episodic or chaotic processes

experimental models of extensional forced folds we have used single layer and multilayer clay models to study the development of forced folds above normal faults our modeling results show that the deformation patterns associated with extensional forced folding depend on the dip of the underlying normal fault and the presence of layer parallel detachments in single layer clay models extensional forced folds are upward widening monoclines anticlinal axial surfaces dip in the same direction as underlying master normal faults and synclinal axial surfaces dip in the opposite direction of master normal faults most secondary faults are upward steepening normal faults if master normal faults are steeply dipping however many secondary normal faults become high angle reverse faults at shallow depths the propagation and linkage of secondary faults into through going normal faults terminates the development of extensional forced folds more folding occurs prior to fault linkage if the master normal fault is steeply dipping rather than gently dipping most dipping beds and secondary faults are preserved in the hanging walls of the through oing normal faults in multilayer clay models with layer parallel detachments extensional forced folds are also upward widening monoclines slip on the lowest detachment laterally transfers extension induced by normal faulting and forced folding from the master normal fault to the detachment edge slip on overlying detachments accommodates minor thickness changes associated with upward widening of the fold secondary faults include low angle normal faults near the anticlinal axial surface minor thrust faults near the synclinal axial surface and high angle normal faults above the detachment edge the model predicted deformation patterns are similar to those of extensional forced folds from the gulf of suez and offshore norway this similarity suggests that our modeling results apply to extensional forced folds and can provide guidelines for interpreting field well and seismic data

salinization of groundwater in arid and semi arid zones an example from tajarak western iran study of the groundwater samples from tajarak area western iran was carried out in order to assess their chemical compositions and suitability for agricultural purposes all of the groundwaters are grouped into two categories relatively low mineralized of ca hco3 and na hco3 types and high mineralized waters of na so4 and na cl types the chemical evolution of groundwater is primarily controlled by water rock interactions mainly weathering of aluminosilicates dissolution of carbonate minerals and cation exchange reactions calculated values of pco2 for the groundwater samples range from 2 34 10 4 to 1 07 10 1 with a mean value of 1 41 10 2 atm which is above the pco2 of the earth s atmosphere 10 3 5 the groundwater is oversaturated with respect to calcite aragonite and dolomite and undersaturated with respect to gypsum anhydrite and halite according to the ec and sar the most dominant classes c3 s1 c4 s1 and c4 s2 were found with respect to adjusted sar adj sar the sodium na content in 90 of water samples in group a is regarded as low and can be used for irrigation in almost all soils with little danger of the development of harmful levels of exchangeable na while in 40 and 37 of water samples in group b the intensity of problem is moderate and high respectively such water when used for irrigation will lead to cation exchange and na is adsorbed on clay minerals while calcium ca2 and magnesium mg2 are released to the liquid phase the salinity hazard is regarded as medium to high and special management for salinity control is required thus the water quality for irrigation is low providing the necessary drainage to avoid the build up of toxic salt concentrations