interactions between the ebb tidal delta and landward shoreline price inlet south carolina abstract patterns of erosion and deposition along the shoreline of price inlet south carolina are strongly influenced by ebb tidal delta processes the ebb delta goes through cycles of growth and decay 15 20 change in volume which last from 4 to 7 years in the growth phase large intertidal bar complexes are formed on both sides of the main ebb channel by the coalescence of landward migrating swash bars during this stage waves refracting around the southern bar complex produce a reversal in the longshore transport direction on the downdrift shoreline this results in little sediment escaping the inlet and delta system the sand trapping mechanism ceases and the delta reduces in volume when the bar complexes migrate onshore and attach to the beach the inlet shoreline also goes through cycles of 7 to 42 years duration in which its offset configuration changes the shift in shoreline alignment is controlled by the orientation of the main ebb channel and the resulting ebb tidal delta morphology when the inlet has a downdrift offset configuration the ebb tidal delta is skewed along the updrift shoreline in this position bar complexes preferentially accrete along the updrift beach causing a progradation of the shoreline at the same time the downdrift shoreline erodes due to little sediment bypassing the inlet this pattern of sedimentation eventually produces an updrift offset inlet the erosional depositional processes are reversed when the ebb flow in the channel thalweg is deflected off the prograding updrift inlet shore ine this causes a clockwise rotation of the main ebb channel and a shift in the ebb delta to a position along the downdrift shoreline in this configuration the updrift shoreline erodes and the downdrift shoreline accretes this study documents the close relationship that exists at price inlet south carolina between the ebb tidal delta and landward shoreline evidence is presented to show that this relationship may hold for other mixed energy tidal inlets as well

age and tectonic significance of metamorphic rocks along the axis of the sierra nevada batholith a critical reappraisal metamorphic rocks in many roof pendants along the axis of the sierra nevada batholith snb between 36 and 38 degree n lat have been considered part of the kings sequence of probable mesozoic age however most of the pendants are in fact undated by fossils and may contain paleozoic or precambrian strata a critical reappraisal of new and existing data on these pendants has led to the following hypotheses 1 a continental crustal silver referred to as the snow lake block with the approximate dimensions of the salinian block and represented by metamorphosed proterozoic and cambrian miogeoclinal rocks extends 120 mi 200 km southeastward from northern ynp to the kaweah river drainage and includes rocks in the following pendants snow lake piute mountain glen aulin may lake iron mountain shuteye peak dinkey creek patterson mountain boyden cave and sequoia park this silver was displaced about 400 km northward along an intrabatholithic dextral strike slip fault during the early cretaceous time 2 based on reconnaissance studies the authors propose that the shoo fly complex which lies west of the snow lake block continues southeastward to 36 degree n lat and includes parts of the following pendants oakhurst lower kings river kaweah river tule river and kernmore canyon the apparent juxtaposition of the shoo fly complex with the snow lake block requires the presence of a major tectonic break between them this structure now largely obliterated by cretaceous plutons of the snb may be the equivalent of the golconda thrust in north central nevada less

spatial analysis of fluoride concentration in groundwaters of shivani watershed area karnataka state south india through geospatial information system hydrogeochemical investigations with emphasis on groundwater fluoride concentrations were carried out in the shivani watershed area karnataka south india this drought prone watershed is characterised by poor groundwater potential and is composed of different lithounits like gneisses migmatites tonalites mafics ultramafics conglomerates and quartzites analysis of spatial variation of groundwater fluoride concentration through the use of gis technology software platforms like arcview 3 2a and mapinfo professional 8 5 has enabled the identification of low fluoride and high fluoride areas within the watershed geochemical data indicates that 38 of groundwater samples have excessive fluoride concentration which poses a health risk to the population of the area correlation studies indicate that higher groundwater alkalinity activates leaching of fluoride resulting in elevated concentrations of fluoride no other significant geochemical interrelationship could be identified between fluoride and rest of the physico chemical parameters owing to the lack of any significant correlation coefficients this holds good in the case of both low fluoride 1 5 mg l groundwaters of the watershed however differential or non uniform type positive or negative of coefficient of correlation is observed between fluoride at different levels and other physico chemical parameters among the different lithounits of the study area gneisses house comparatively more number of high fluoride groundwaters fluoride bearing minerals biotite hornblende and apatite are the probable natural sources of groundwater fluoride

the gem lake shear zone cretaceous dextral transpression in the northern ritter range pendant eastern sierra nevada california the gem lake shear zone is a northwest striking steeply dipping dextral transpressional shear zone that provides the first direct evidence for dextral deformation in wall rock pendants in the central part of the sierra nevada batholith the gem lake shear zone is a minimum of 30 km in length and extends at least from the north end of the northern ritter range pendant to the southeast edge of the ritter range pendant the amount of displacement on the zone is uncertain but matching fault slivers of pennsylvanian marble in the northern ritter range pendant to similar exposures north of the mount morrison pendant suggests a minimum dextral offset of 20 km the gem lake shear zone was active in early late cretaceous time from before 91 ma the age of the syntectonic granodiorite of kuna crest to at least 80 ma 40ar 39ar age of syndeformational mica from the shear zone in the ritter range pendant deformation in the gem lake shear zone is characterized by combined dextral simple shear and subvertical stretching which are variably partitioned in anastomosing high strain zones in the shear zone at gem lake predominantly dextral deformation is indicated by porphyroclast asymmetries s c fabric and asymmetric crenulations a component of subvertical stretching is indicated by a moderately to steeply plunging stretching lineation in a segment of the shear zone at kuna crest a strongly developed stretching lineation indicates predominantly subvertical stretching with a lesser component of dextral strike slip the gem lake shear zone is considered to be part of a proposed regional system of shear zones in the eastern sierra nevada the sierra crest shear zone system this dextral transpressional system was active prior to and synchronous with intrusion of the late cretaceous sierra nevada batholiths deformation ceased shortly after pluton emplacement the sierra crest shear zone system includes possibly related shear zones as far north as saddlebag lake pendant and at least as far south as oak creek pendant and the owens valley indicating a possible strike length greater than 150 km

dynamic transfer of simulated altimeter data into subsurface information by a numerical ocean model a global eddy resolving capability to predict the ocean circulation is technologically feasible within the next decade for this purpose the satellite altimeter is the most promising operational source of oceanic data with global coverage but only at the surface a comparable source of subsurface data is not on the horizon this investigation demonstrates the ability of a numerical ocean model to dynamically transfer simulated altimeter data into subsurface information this was done for a variety of dynamical regimes with 1 barotropic baroclinic mixed and episodic instabilities 2 flat bottoms or large amplitude topography 3 relatively vigorous or gentle exchange of energy between the layers and 4 major time scales that are short 60 days long 1 year or both in all cases the pattern of the deep pressure field is much different from the one for the current related variations in the sea surface elevation and sometimes not obviously related to it the model was able to reconstruct the deep pressure field even in situations with energetic shallow and deep circulations baroclinic instability and a vigorous vertical exchange of energy however in such experiments the frequency of updating for the free surface elevation was critical in this study the maximum update interval that allowed successful dynamic surface to subsurface transfer was about half the shortest major time scale smts e g 50 60 days in the experiments with baroclinic instability without knowledge of the deep pressure field numerical predictions of the surface pressure field and the depth of the pycnocline typically were better than climatology for 1 4 to 1 2 the smts but with successful dynamic surface to subsurface transfer forecasts without updating were better than climatology for the smts or more the time scale for predictive skill can be substantially longer than the maximum update interval permitted because the update interval must be short enough to allow decreasing error in the deep pressure field from one free surface update to the next until the error asymptotes at some acceptable level approximately 30 50 in these results forecasts of nondispersive isolated eddies with beta rossby number o 1 demonstrated predictive skill for 3 months or more even when the subsurface initial state was unknown a serendipitous result of the study is some progress in understanding the generation of cyclonic eddies associated with the loop current in the eastern gulf of mexico section 5 5

devonian mississippian sinistral transcurrent faulting along the cratonic margin of western north america a hypothesis in the northern canadian cordillera three major proterozoic assemblages show a distinct sinistral separation along the long lived richardson hess fault zone it is suggested that this separation resulted from displacements along a mid paleozoic sinistral fault system connecting the devonian mississippian ellesmerian orogen of the arctic with the antler orogen of the western united states composite displacement of possibly hundreds of kilometres along this fault system created transpressional and transtensional deformation along the western outer margin of the north american craton deformation was accompanied by eastward progradation of turbiditic chert quartz arenites local igneous activity and exhalative ore deposition extensive late mesozoic and cenozoic compression and extension probably greatly modified mid paleozoic fault related deformation patterns

eureka quartzite in mexico tectonic implications at cerro cobachi 90 km east of hermosillo sonora an ordovician to permian miogeoclinal assemblage and an ordovician to permian siliceous deep water assemblage were juxtaposed by thrust faulting between mid permian and latest cretaceous time both assemblages resemble counterparts in the great basin one formation an ultramature quartzite unit in the miogeoclinal assemblage closely resembles the middle ordovician eureka quartzite in the southern great basin isopach lines of the eureka trend south southwestward from a maximum thickness of 134 m near owens lake california the eureka thins and splays northward in the southern inyo mountains and thins southeastward in the nopah range but south southwestward parallel with the isopach lines it apparently ends abruptly as if faulted because the paleozoic stratigraphy of the western great basin and that of west texas have elements in common it is quite possible that the southwest trending facies belts of the great basin originally wrapped around the southern border of the continent through northern mexico and joined corresponding belts in texas two hypotheses are suggested 1 the cerro cobachi terrane of which the quartzite is a part is indigenous to northern mexico and 2 the cerro cobachi terrane is indigenous to california and was displaced tectonically to northern mexico the second hypothesis is favored by the apparently abrupt termination of the eureka quartzite near owens lake the nearly identical thickness of the two quartzites and their nearly identical lithic composition and texture

early permian thrust faults in east central california one exposed and another inferred thrust fault in the southeastern inyo mountains of east central california are interpreted as early permian in age these faults both apparently of local extent are temporally and geographically related to a major episode of basin formation which occurred along a southeast trending segment of the permian north american plate margin the close relationship between basin formation and thrust faulting supports a previous interpretation by us that this segment of the margin was undergoing active wrench tectonism during the early permian resulting in the essentially simultaneous development of local extensional and compressional structures similar to those now forming in the california continental borderland

large magnitude miocene extension in the central mojave desert implications for paleozoic to tertiary paleogeography and tectonics this is the published version copyright 1990 american geophysical union all rights reserved

world wide delivery of river sediment to the oceans new data and new estimates from old data show that rivers with large sediment loads annual discharges greater than about 15 times 10 6 tons contribute about 7 times 10 9 tons of suspended sediment to the ocean yearly extrapolating available data for all drainage basins the total suspended sediment delivered by all rivers to the oceans is about 13 5 times 10 9 tons annually bedload and flood discharges may account for an additional 1 2 times 10 9 tons about 70 of this total is derived from southern asia and the larger islands in the pacific and indian oceans where sediment yields are much greater than for other drainage basins

the geomorphology of the mississippi river chenier plain abstract the chenier plain of the mississippi river is a shore parallel zone of alternating transgressive clastic ridges separated by progradational mudflats the term chenier is derived from the cajun term chene for oak the tree species that colonizes the crests of the higher ridges the mississippi river chenier plain stretches 200 km from sabine pass texas to southwest point louisiana and ranges between 20 and 30 km wide with elevations of 2 6 m the timing and the process of formation could be re evaluated in the light of new chronostratigraphic findings in the mississippi river delta plain the stratigraphic relationship between the teche and lafourche delta complexes and ship shoal offshore indicates that these delta complexes belong to different delta plains that developed at different sealevels it appears that the teche delta complex is associated with the late holocene delta plain which developed 7000 to 3000 yrs b p when sealevel stood 5 6 m lower than present a regional transgression occurred between approximately 3000 bp and 2500 yrs b p leading to the transgressive submergence of the late holocene delta plain producing the regional teche shoreline the timing of this transgression conforms to the age of the most landward ridge in the chenier plain the little chenier little pecan island trend which dates at about 2500 yrs b p this ridge trend was originally interpreted as representing the teche delta complex switching event with the landward holocene pleistocene contact representing the high stand shoreline the implication of this new interpretation is that the little chenier little pecan island trend represents the high stand shoreline a continuation of the teche shoreline separating the late holocene and recent delta plains and that the holocene pleistocene contact represents the leading edge of the marshes transgressing onto the prairie terrace significant mudflat progradation seems to require a westerly position of the mississippi river but the numerous different forms and ages of cheniers do not correspond well to the timing of major delta complex switching progradation of the chenier plain appears to be associated with building of the recent delta plain and not the teche complex of the late holocene delta plain the occurrence of individual ridges appears to be primarily tied to delta lobe switching within the lafourche complex and variations in sediment supply from local rivers the recent development of the atchafalaya delta complex to the west is the closest position of an active distributary to the chenier plain since sealevel stabilization a new episode of rapid mudflat progradation is thus taking place

assimilation of altimeter data in a two layer primitive equation model of the gulf stream abstract a two layer finite depth primitive equation model of the gulf stream region is used to study the effect of updating the model with simulated altimeter data as observations in this study both a complete field of sea surface height ssh and ssh sampled along satellite tracks are used as observations a simulated 17 day repeat orbit corresponding to the geosat erm and a 10 day repeat period corresponding to topex poseidon are used satellite observations give only information about the sea surface height but previous studies have shown that it is important to transfer the surface information to the lower layer as fast as possible in order for the model to have a realistic evolution a statistical inference technique is therefore used to update the lower layer pressure field the velocity fields in both layers are updated using a geostrophic correction calculated from the change in the pressure fields it is shown that updating the velocities is important for the assimilation to be successful w

pennsylvanian and early permian paleogeography of east central california implications for the shape of the continental margin and the timing of continental truncation pennsylvanian and early permian paleogeographic features in east central california include a southeast trending carbonate shelf edge and turbidite basin that we infer paralleled a segment of the western margin of the north american continent this segment of the continental margin was oblique to an adjoining segment on the north that trended southwestward across nevada into easternmost california we propose that the southeast trending segment of the margin originated by tectonic truncation of the originally longer southwest trending segment in early or middle pennsylvanian to late early permian time significantly earlier than a previously hypothesized late permian or early triassic continental truncation event we interpret the truncating structure to have been a sinistral transform fault zone along which a continental fragment was removed and carried southeastward into the caborca hermosillo region of northern mexico where it is now represented by exposures of late proterozoic and paleozoic miogeoclinal rocks

the early permian thysanophyllum coral belt another clue to permian plate tectonic reconstructions early permian species of the related massive coral genera thysanophyllum stylastraea and protowentzelella are restricted geographically to a narrow belt stretching discontinuously from the southern ural mountains to texas by way of vestspitsbergen canadian arctic islands and the western cordillera british columbia and the basin and range of idaho utah nevada arizona and california in addition limited data suggest that this belt may have extended as far south as peru this coral belt developed at low and intermediate latitudes during early permian time along the northwestern and western margins of the pangaean supercontinent land a very wide paleopacific ocean and temperature barriers prevented these tropical to subtropical shallow water corals from invading similar warm water environments in the tethys ocean on the opposite coast of pangaea where faunas including different types of massive corals developed today the thysanophyllum association is represented in several geosynclinal belts which in the past have been difficult to relate to one another this coral belt therefore may constitute an important key for understanding the relationships between several of these great belts of sediment accumulation and in locating the position of permian continental margins and interpreting some subsequent plate margin tectonic events

coastal open ocean exchange in the black sea observations and modelling the interaction between physical and biological processes in the areas of continental margins governs the variability of ecosystems the complexity of processes in these areas requires detailed studies combining modelling and surveying efforts one promising step in this direction was undertaken in the framework of the eros 21 project focusing on the shelf part of the north western black sea in the present paper we focus on the results of physical studies aiming to improve the understanding of the fundamental exchange processes in the ocean margins as well as to quantify some of them in the black sea we illustrate the capabilities of circulation models to reproduce physical processes with different time and space scales coastal waves internal waves baroclinic rossby and topographic waves another class of important phenomena in the coastal zone is associated with convection sources at the sea surface and in the outflow areas give rise to plume dynamics that play a crucial role in the vertical mixing and provide the mechanism for water mass formation most of the results are illustrated for the shelf part of the black sea the verification of simulations is performed by comparison with survey data altimeter data from the topex poseidon mission and radiotracer observations the latter in combination with simulations from circulation models are used to trace the penetration of tracers into the intermediate and deep layers we show that although most 90sr is introduced by river runoff large amounts of this signal penetrate the halocline in the bosphorus straits area and along the southern coast another important fraction of the river water penetrates the intermediate layers at the shelf edge in the north western black sea

assimilating altimetric data into a south china sea model sea surface heights from the topex poseidon altimeter are assimilated into a three dimensional primitive equation model to derive the circulation in the south china sea with data assimilation the model resolves not only the basin wide circulation but also a dipole off vietnam and a low high feature near the luzon strait mesoscale features are missing in the simulation without data assimilation because of poor resolution in the wind field and inadequate knowledge of the transport through the luzon strait compared to the case without data assimilation data assimilation reduces the root mean square error between the simulated and observed sea surface heights by a factor of 2 3 circulation derived from data assimilation under climatological conditions is contrasted with that during el nino in the normal winter of 1993 1994 flow at 50 m depth is strong and cyclonic flow at 900 m depth is cyclonic as well the deep cyclone persists into the following summer during the 1994 1995 el nino winter features in the flow field at 50 m depth either weaken or disappear and circulation at 900 m depth is anticyclonic in the summer of 1995 the dipole and the eastward jet off vietnam at 50 m depth are missing and the anticyclonic circulation at 900 m depth persists temperature at 65 m shows significant warming from fall 1994 to summer 1995 a weakened flow field and warming in the upper ocean are consistent with findings from earlier el nino events

evidence of uppermost proterozoic to lower cambrian miogeoclinal rocks and the mojave snow lake fault snow lake pendant central sierra nevada california this is the published version copyright 2010 american geophysical union all rights reserved

evolution of the ordovician through middle pennsylvanian carbonate shelf in east central california carbonate shelf rocks marked by various sedimentary features suggesting intertidal to supratidal deposition or bearing rich benthic faunas and their corresponding slope and basin rock sequences containing planktic fossils and sediment gravity flow deposits have been identified in the inyo mountains argus range region of east central california for all of the paleozoic from ordovician through middle pennsylvanian four major depositional sequences each beginning with a marine transgression and all but the third ending with a progradation were developed representing 1 early ordovician into early silurian time 2 early silurian into earliest middle devonian time 3 middle to late devonian time and 4 early to middle late mississippian time a period of basinal infilling in the late mississippian was followed by a fifth major marine transgression in the early pennsylvanian the carbonate shelf itself evolved from a homoclinal ramp in the ordovician to an accretionary rimmed margin by the early devonian this margin was drowned probably in the middle devonian by the early mississippian a new homoclinal ramp had been developed before the end of the mississippian this ramp became distally steepened and then was transformed into an accretionary rimmed margin the early to middle pennsylvanian marine transgression gave rise to still another homoclinal carbonate ramp subsidence of 2 300 m occurred between early ordovician and middle pennsylvanian time in the area immediately east of the inyo mountains it increased westward to probably 3 500 m at the edge of the owens valley as the continental margin subsided and bent downward 1 between early ordovician and middle late mississippian time as a result of subsidence and relatively low rates of sedimentation the water depth in the western part of the study area increased from close to sea level at the beginning of the ordovician to as much as 3 000 m in the late mississippian because of higher rates of sediment accumulation and lower rates of subsidence in the eastern part of the region shallow water environments were maintained throughout most of this time interval even so the shelf slope break retreated at least 45 km southeastward from middle ordovician to middle late mississippian time and at least 35 km farther southeastward by middle pennsylvanian time

continuation of antler and sonoma orogenic belts to the eastern sierra nevada california and late triassic thrusting in a compressional arc strong stratigraphic and structural similarities exist between metamorphic rocks of the saddlebag lake pendant eastern sierra nevada california and rocks of the antler and sonoma orogenic belts in west central nevada these similarities indicate that the roberts mountains and golconda allochthons can be traced to the eastern edge of the sierra nevada batholith in california newly recognized thrust faults that imbricate the antler and sonoma rocks and younger metamorphic rocks are of late triassic age and are cut by a 219 ma pluton these thrusts apparently were active during a major episode of late triassic arc volcanism and they constrain the age of the golconda thrust as pre latest triassic the continuation of the antler and sonoma orogenic belts to the saddlebag lake pendant means that large strike slip displacements cannot have occurred on northwest trending faults along the eastern edge of the sierra nevada however a large structural break may terminate the antler and sonoma belts at or near the western edge of the saddlebag lake pendant

observations of nearshore wave dissipation over muddy sea beds 1 wave propagation on the louisiana inner shelf is studied using concurrent measurements at two shallow water ocean observatory sites in sedimentary environments dominated by mud at one site and sand at the other contrary to the widely accepted hypothesis that mud induced wave dissipation is important only for long waves observations show significant damping of high frequency short waves which interact weakly with the bottom the mechanism of short wave dissipation is not understood numerical simulations show that other dissipative processes such as refraction or depth limited breaking do not account for the magnitude of the observed effects independent observations of strong sediment re working during storms suggest that these effects are related to sediment resuspension processes

roberts mountains allochthon and the western margin of the cordilleran miogeocline in the northern ritter range pendant eastern sierra nevada california the truncated southwestern edge of the roberts mountains allochthon is exposed in the northern ritter range pendant in the eastern sierra nevada structurally overlying parautochthonous rocks of the cordilleran miogeocline the northern ritter range pendant exposes units that have the same stratigraphic affinities and structural relationships as rocks of the antler orogenic belt in nevada paleozoic metasedimentary rocks exposed in the pendant consist of two major units 1 a structurally complex disrupted chert and argillite unit interpreted to be correlative with the roberts mountains allochthon and 2 a stratigraphically coherent siliceous and calcareous unit the rush creek sequence that is interpreted to be part of a transitional outer shelf and slope assemblage of the lower paleozoic cordilleran miogeocline in the northern ritter range pendant the roberts mountains allochthon structurally overlies the rush creek sequence along a north striking steeply dipping fault zone that may be a preserved remnant of the roberts mountains thrust which in north central nevada emplaced the allochthon over outer shelf and slope strata of the cordilleran miogeocline during the late devonian early mississippian antler orogeny these stratigraphic and structural belts are truncated on the southwest side of the pendant by the gem lake shear zone a northwest trending dextral strike slip fault associated with the cretaceous sierra nevada batholith the northern ritter range pendant thus defines both the southwestern limit of the antler orogenic belt and the westernmost exposures of parautochthonous miogeoclinal rocks in the central cordillera

satellite altimetry observations of the black sea level the paper is devoted to the application of satellite altimetry from the topex poseidon and ers 1 missions to the black sea we use the nasa ocean altimeter pathfinder project collinear data set and monthly climatic hydrography to restore the dynamical sea level that which connected with the black sea circulation two realizations are created from collinear and grid data sets the black sea hydrographic survey data collected by the cooperative marine science programme for the black sea are used for validation of both products the estimated rms accuracy of the black sea dynamical level is about 3 cm the grid data product is used for the analysis of seasonal and mesoscale variability of the black sea level the observations show that the black sea circulation has strong seasonal variation it attenuates in summer to autumn and intensifies in winter to spring this variability is accompanied by a western phase propagation of the sea level a simple two layer model of the wind induced circulation in the rectangular basin provides an interpretation of these results it is shown that the seasonal variability of the geostrophic circulation is most likely produced by the annual changes of the wind stress curl the western phase propagation is treated as the radiation of rossby waves from the eastern coast of the basin typical periods of the mesoscale oscillations of the dynamical sea level are estimated from the topex poseidon altimeter time series in different parts of the black sea by means of a spectral analysis the strongest mesoscale oscillations have periods of about 120 days and are located in the southeastern part of the basin where the rim current bifurcates and off the crimean peninsula where the rim current meanders as a result of the local orography

danube river sediment input and its interaction with the north western black sea abstract the influence of the river danube is determinant to the sedimentation of the north western and western black sea area after 1970 following the building of the iron gates dam the danube river sediment discharge diminished to 30 40 of its previous value after a 12 000 year evolution marked by active progradation the danube delta has become mainly inactive over the last few decades partly due to interventions of man made origin the deficit of sediment influx has led to the intense erosional processes of the deltaic littoral on the black sea north western shelf two main areas with contrasting sedimentary processes have been identified the internal danube sediment fed shelf and the external sediment starved shelf the modern highstand sedimentary history of the north western black sea deep area is marked by the cessation of the danube deep sea fan active development the main depositional units within the north western black sea are described

prevalence of fluorosis in the fluoride enriched groundwater in semi arid parts of eastern india geochemistry and health implications abstract fluorosis is becoming a global environmental toxicological problem and is most commonly found in water stressed regions in order to evaluate the geochemical mechanism of fluoride enrichment in groundwater and health implications in the padwakodari environs of eastern part of india a total of twenty two samples were collected and analysed for physico chemical parameters spreading across the study area geologically the area mainly comprises of phyllites granite gneiss mica schist and sandstone high fluoride concentrations found mainly in the granite gneisses which are situated central to northwestern parts of the study area the concentration of fluoride in the groundwater samples ranges from 0 3 to 11 mg l with an average of 2 mg l 64 of the groundwater samples containing fluoride concentration that exceed the who drinking water guidelines value of 1 5 mg l chronic ingestion of high doses has been linked to the development of dental fluorosis and in extreme cases skeletal fluorosis the dominant geochemical facies present in water are na ca mg hco 3 11 samples na mg ca hco 3 5 samples ca na mg hco 3 5 samples and ca mg na hco 3 1 sample sodium and bicarbonate ions being major component in majority of the water types located mostly in the granite gneiss formation has a tendency to increase fluoride concentration in groundwater by dissolving the fluoride from fluoride bearing minerals the oversaturation of half of the samples with respect to calcite and majority of samples undersaturation with respect to fluorite makes it feasible for fluoride to get released in to the groundwater decreasing ca activity downgradient recharge to discharge leads to a dominance of fluorite unsaturated conditions and consequently to mobilization of fluoride in groundwater the results indicate that the fluoride concentration in groundwater is mainly governed by high weathering of fluoride bearing minerals i e apatite and biotite in granite gneiss contains abundant fluoride alkaline hydrogeological environment high temperature low rainfall evapotranspiration and ion exchange

magnitude and significance of miocene crustal extension in the central mojave desert california the newly recognized waterman hills detachment fault whdf of the central mojave desert california is significant because it provides the first unambiguous evidence for large scale core complex style crustal extension in the central mojave desert and because it has significantly rearranged the pre miocene paleogeography of the mojave desert the whdf places steeply dipping to overturned miocene volcanic and sedimentary rocks upon mylonitic pre tertiary basement the mylonites which apparently formed during extension are predominantly l tectonites which manifest top to northeast shear the whdf dips to the northeast beneath dominofaulted ranges of the central mojave desert and detachment faults of the colorado river trough forming an imbricated early miocene system of detachment faults extension continued in the colorado river trough after extension had ceased in the central mojave desert tentative correlations of mesozoic intrusions suggest about 40 km of slip across the whdf which carries eugeoclinal paleozoic rocks in its hanging wall and cratonal miogeoclinal paleozoic rocks in its footwall restoration of 40 km of slip 1 removes a prominent kink in the boundary between eugeoclinal and cratonal miogeoclinal facies 2 aligns cratonal miogeoclinal strata near victorville more closely with the late paleozoic continental margin farther north 3 places cratonal miogeoclinal rocks structurally beneath eugeoclinal rocks implying that the facies were stacked by thrusting and 4 straightens the western margin of the late jurassic independence dike swarm

facies and evolution of the modern brazos delta texas wave versus flood influence abstract in order to better define the facies architecture and processes controlling the evolution of wave dominated deltas a detailed sedimentary and geomorphologic study was undertaken on the brazos delta texas the delta has formed since 1929 when the brazos river was diverted by the u s army corps of engineers the brazos delta is composed primarily of fine grained sediments prodelta clay constitutes more than half of the sediment volume thick sands are restricted to the narrow delta front environment whereas back bar lagoonal clays are a significant component of the delta plain sequence the facies architecture is not representative of the classic strandplain model for wave dominated deltas this is due to the strong influence of floods on deltaic evolution in early 1992 statewide flooding gave rise to a major constructional phase of the delta significant quantities of fine grained sediments were deposited in the prodelta one year after the onset of flooding a channel mouth bar emerged offshore of the river mouth and enabled progradation of the delta similar flood events that occurred during 1941 1957 and 1965 were recorded as ridge trough pairs in the delta headland the brazos delta is therefore fluvially influenced during floods and wave influenced during intervening periods

geodynamics of dobrogea romania new constraints on the evolution of the tornquist teisseyre line the black sea and the carpathians abstract dobrogea is the only place south of poland where the tornquist teisseyre line europe s longest lineament outcrops to characterize and date the tectonic activity of this line and to understand its relations with the neighboring structures e g the carpathians and the black sea basin the fracturing of late jurassic to neogene rocks in north central and south dobrogea is analyzed these paleostress reconstructions indicate that the dobrogea orogen was built under a n s compression with strain partitioning between thrusting at its front and dextral reverse slip along the peceneaga camena and capidava ovidiu faults during the late jurassic barremian from aptian to coniacian the dobrogea platform was characterized by se directed extension compatible with the aptian cenomanian rifting of the western black sea followed by the se directed drifting of a part of the moesian block i e the istanbul block on its southern extremity the tornquist teisseyre line does not show evidence for any large scale alpine strike slip movements postulated by many the peceneaga camena fault being reactivated in latest cretaceous paleogene as a pure reverse fault during the late tertiary the carpathian compression was poorly transmitted to dobrogea extension dominated the neogene deformation which indicates a weak coupling between the carpathians and its foreland

assimilation of geosat altimetric data in a nonlinear reduced gravity model of the indian ocean part 1 adjoint approach and model data consistency abstract geosat sea level variations are assimilated into a nonlinear shallow water model of the indian ocean after spinup the model forced by observed winds over 1985 1988 provides a first guess for initial conditions on november 1986 and a mean thermocline depth used as a reference surface for altimetric observations data are assimilated during one year and north of 20 s the model data misfit is minimized using the adjoint model with respect to the initial conditions and the reference surface the assimilation algorithm converges fast and steadily the monthly rms difference between model and data is reduced from 21 to 16 m the optimal thermocline surface is significantly affected by assimilation large changes occur along the paths of the throughflow and south equatorial current it is found that the optimal mean state is valid only for the period of assimilation it degrades the agreement between observations and simulations for the following year because of the large interannual event that took

cretaceous sinistral strike slip along nacimiento fault in coastal california the san andreas and nacimiento faults of coastal california both separate granitic and metamorphic basement rocks of the salinian block from partly coeval but contrasting mesozoic terranes underlain by the franciscan subduction complex by analogy with neogene dextral strike slip along the san andreas fault cretaceous sinistral strike slip can be inferred along the nacimiento fault in preference to hypotheses for tectonic erosion during subduction or for dextral strike slip of unspecified amount following restoration of known san andreas and inferred proto san andreas dextral displacements reversal of about 560 km 350 mi of postulated sinistral slip on the nacimiento fault brings four major mesozoic lithotectonic belts of california and baja california into simple al gnment as subparallel terranes related to mesozoic subduction along the continental margin neogene deformation within the san andreas transform system involved a elongation of the salinian block by dextral slip along subsidiary faults that branch from the san andreas fault and b dextral rotation of crustal panels within the transverse ranges latest cretaceous and or earliest paleogene dextral slip along a proto san andreas fault followed the san andreas course in central california but diverged westward in southern california nacimiento sinistral displacements occurred in mid cretaceous to early or medial late cretaceous time after cretaceous emplacement of plutons now within the salinian block but prior to deposition of uppermost cretaceous sedimentary sequences in central california available data on mesozoic relative and absolute plate motions in the mesoameric n region support the likelihood of cretaceous sinistral strike slip subparallel to the california continental margin paleotectonic reconstruction of crustal blocks in california and baja california to their inferred mid cretaceous relative positions shows the salinian block inserted on a bias between the flanking mojave and peninsular ranges blocks salinian granitic rocks thus formed an interior part of the mesozoic batholith belt and their initial strontium isotopic ratios are compatible with the gradients displayed by values from the adjoining blocks the similar mesozoic terranes that now lie east and west of the salinian block were then adjacent to one another west of the sierra nevada block available paleomagnetic data neither support nor preclude the reconstruction but additional work together with future detailed lithotectonic comparisons potentially can confirm or refute the hypothesis i represents a correct interpretation of the nacimiento fault is important for understanding the overall tectonic framework of petroliferous basins both onshore and offshore in coastal california

southern extension of the independence dike swarm of eastern california new geochronologic data show that jurassic dikes in the western mojave desert and eastern transverse ranges are part of the independence dike swarm of eastern california these occurrences extend the length of the dike swarm to more than 500 km u pb zircon concordia intercept ages for dikes near stoddard well in the western mojave desert and big wash in the eagle mountains are identical within analytical uncertainties to 148 ma zircon ages for independence dikes north of the garlock fault recognition of this widespread magmatic and tectonic event with a restricted age has important ramifications 1 crosscutting relations between the dikes and pre upper jurassic and cretaceous rocks help establish relative ages 2 persistence of dikes across several inferred terrane boundaries constrains terrane accretion ages 3 the dike rocks represent magmatic processes in a wide range of wall rock settings 4 the dikes are structural markers that record translations and rotationsof crustal flakes 5 regional persistence and dilational emplacement of the independence dike swarm suggest that it is the last extension in a series of alternating extensional and compressional events during the jurassic the tectonic regime responsible for the independence dikes may be related to arc normal extension changes in plate motions or oblique subduction with left lateral shear

high fluoride in groundwater of an industrialized area of eastern india odisha inferences from geochemical and isotopic investigation an assessment of fluoride distribution in groundwater of an industrialized area talchir odisha india was carried out to understand the potential sources and processes this study is significant as the water resources are being endangered by the mining and other industrial activities in this region high concentration of fluoride 4 4 mg l was observed in groundwater of this area which was attributed mainly to mining activities additional source for high fluoride is the basement granitic rock containing fluoride bearing minerals like amphibole biotite and fluorite the dominant chemical types are found to be na ca hco3 na mg hco3 ca mg hco3 and ca na hco3 the groundwater facies variation was found in accordance with the local lithology there was no marked difference in the fluoride concentration of groundwaters between near and far off mining zone geochemical modeling indicated precipitation of calcite and dolomite as the driving force for the release of fluoride from the formation in addition to the precipitation of calcite and dolomite evapotranspiration also contributes to high fluoride in groundwater environmental stable isotopes inferred that there was no clear isotopic distinction between high and low fluoride groundwater and the groundwater was found to be evaporated environmental tritium data suggested that the groundwater was modern and fluoride enrichment was facilitated by long residence time of groundwater statistical methods also corroborate the geochemical and isotopic inferences the study highlights that natural geogenic source is the main cause for high fluoride in groundwater refuting earlier theories that attribute mining activities as the only source for high fluoride in this region

stable isotope systematics in mesozoic granites of central and northern california and southwestern oregon 18o d and h2o contents were measured for whole rock specimens of granitoid rocks from 131 localitics in california and southwestern oregon with 41 new determinations in the klamath mountains and sierra nevada initial strontium isotope ratios are known for 104 of these samples large variations in 18o 5 5 to 12 4 d 130 to 31 water contents 0 14 to 2 23 weight percent and initial strontium isotope ratios 0 7028 to 0 7095 suggest a variety of source materials and identify rocks modified by secondary processes regular patterns of variation in each isotopic ratio exist over large geographical regions but correlations between the ratios are generally absent except in restricted areas for example the regular decrease in d values from west to east in the sierra nevada batholith is not correlative with a quite complex pattern of 18o values implying that different processes were responsible for the isotopic variations in these two elements in marked contrast to a good correlation between 87sr 86sr o and 18o observed in the peninsular ranges batholith to the south such correlations are lacking except in a few areas d values on the other hand correlate well with rock types chemistry and 87sr 86sr o except in the coast ranges where few of the isotopic signatures are primary the uniformly low d values of samples from the mojave desert indicate that meteoric water contributed much of the hydrogen to the rocks in that area even so the 18o values and 18o fractionations between quartz and feldspar are normal in these same rocks

radiocarbon dating of danube delta deposits abstract the holocene history of the danube delta has been studied using 14c analyses of faunal material the principal phases of development include 1 initial letea caroarman spit 11 700 9800 yr b p in its central part 8800 5500 yr b p in its southern part 2 sf gheorghe i delta 8900 7200 yr b p 3 sulina delta 7200 2000 yr b p and 4 sf gheorghe ii delta chilia delta 2000 yr b p present other smaller scale features have also been dated including secondary deltas cosna and sinoe deltas and littoral bars age determinations carried out on whole samples were erratic and it was found that individual species had to be separated and dated in all cases the older dates were of transported material whereas the younger dates gave the true age of the formation

genesis of high f groundwaters southern india abstract high f groundwaters are common in the dry parts of the indian peninsula constituting a serious health problem the f originates mainly from hydroxypositions in biotite and hornblende and is concentrated through evapotranspiration in soil and groundwater exhibiting residual alkalinity such waters are common in areas with generally alkaline soils along the flow paths of the water from hilltops to valley bottoms calcite dolomite and fluorite seem to precipitate in that order a practical solution to the health problem may be to locate drinking water wells in upslope positions

a speculative reconstruction of the middle paleozoic continental margin of southwestern north america geologic relations and data from strontium and oxygen isotopic studies are used together to speculate on the paleogeographic positions of various crustal blocks or terranes in southwestern north america with respect to the middle paleozoic continental margin the southwestern margin of the middle paleozoic continent based on these data is quite irregular in its present configuration but most of the irregularities can be accounted for by strike slip displacement of continental fragments during several post middle paleozoic tectonic events we conclude that large scale late paleozoic sinistral displacements and mesozoic and cenozoic dextral displacements have been the major events affecting the configuration of this margin our preferred model includes the following elements 1 500 km of left lateral displacement of a large part of the margin during a late paleozoic truncation 2 slivering of the margin by right lateral faulting during the mesozoic amounting to about 275 km of total displacement and 3 further deformation of the margin during the cenozoic primarily by right lateral faulting oroclinal bending and crustal extension

the geology of the mccoy mountains formation southeastern california and southwestern arizona the mccoy mountains formation is a 7 3 km thick metasedimentary sequence exposed in at least 6 mountain ranges in southeastern california and southwestern arizona the siliciclastic mccoy mountains formation is deposited on and interbedded at its base with a jurassic volcanic terrane and is intruded by undeformed upper cretaceous plutons it has been assigned a cretaceous paleocene age on the basis of fossil angiosperm wood found within the upper third of the sequence presently known exposures of mccoy mountains formation define a west northwest trending basin 140 km long by 25 km wide which was filled from the north by predominantly alluvial processes the mccoy mountains formation is divided into six members each containing distinctive stratigraphy and sedimentary petrology sandstone consists of quartz feldspar and lithics and each member has a different composition the source evolved from volcanic sedimentary to plutonic sedimentary composition with time much thinner laterally equivalent clastic sequences are now known on the craton adjacent to the basin s northern margin the mccoy mountains formation is homoclinal and south dipping and its uppermost strata are deformed into a north verging overturned syncline with sympathetic south dipping cleavage northern exposures of mccoy mountains formation and underlying jurassic volcanic terrane contain a north dipping cleavage and south verging overturned folds sympathetic to the cleavages and folding are north and south bounding faults which limit mccoy mountains formation exposures and place the north american craton north side and the mojave sonora complex or tujunga terrane south side onto mccoy basin rocks structural analysis and paleomagnetic data strongly suggest that the thrusting over and folding of the mccoy basin rocks took place in late jurassic time as a single event the fault along the southwestern margin of the mccoy basin is thus apparently a jurassic terrane boundary and may be a northern extension of the jurassic mojave sonora megashear if true proposed early tertiary accretion of the tujunga terrane must have occurred farther to the southwest

interpretation of the last chance thrust death valley region california as an early permian decollement in a previously undeformed shale basin abstract the last chance thrust discontinuously exposed over an area of at least 2500 km2 near the south end of the cordilleran foreland thrust belt in the death valley region of east central california is controversial because of its poorly constrained age and its uncertain original geometry and extent we interpret this thrust to be early permian in age to extend throughout a sedimentary basin in which deep water mississippian shale overlain by pennsylvanian and earliest permian limestone turbidites accumulated to represent about 30 km of eastward displacement and to be related to convergence on a northeast trending segment of the early permian continental margin last chance deformation occurred between the times of the antler and sonoma orogenies of late devonian early mississippian and late permian ages respectively and followed early to middle pennsylvanian truncation of the continental margin by transform faulting in the western part of the mississippian shale basin in east central california the originally recognized exposures of the last chance thrust show neoproterozoic and early paleozoic strata above lower plate mississippian shale farther east faults subparallel to bedding above below and within the mississippian shale are interpreted to mark the thrust zone and to represent a regional decollement at the eastern margin of the basin upper plate thrust slices of deep water late paleozoic strata are interpreted to have piled up against the margin of the mississippian carbonate shelf to form a large antiformal stack above the lee flat thrust which we regard as the easternmost exposure of the last chance thrust thrust loading depressed the western part of the shelf creating a new sedimentary basin in which about 3 5 km of younger early permian deep water strata were deposited against the antiformal stack later probably in the late permian other thrusts including the inyo crest thrust which was subsequently overlapped by early to middle triassic marine strata cut across the last chance thrust we interpret the last chance thrust as similar in many ways to appalachian type decollements in which the zone of thrusting is localized along a shale interval the last chance thrust however has been dismembered during later geologic events so that its original geometry has been obscured our model may have unrecognized analogs in other structurally complex shale basins in which the initial deformation was along a major shale unit

assimilation of sea surface height data into an isopycnic ocean model abstract two different methods for assimilating sea surface height data into an isopycnic primitive equation model were developed and tested for the idealized case of an analytical gaussian warm core anticyclonic eddy then implemented using remotely sensed data from the brazil malvinas confluence region the first method makes a geostrophic assumption about the flow to relate sea surface height field gradients to the model velocities the second method nudges the model sea surface height itself toward the observed values using a linear vertical influence function in the upper layers the relationship between the surface height observations and the layer interface displacements is derived from observations of eddies in different regions of the atlantic ocean both assimilation methods were successful in transferring the dynamical influence of the sea surface height measurements deep into the water column but a combination of both gave the best results the application of both methods reproduced the det

holocene evolution of the western orinoco delta venezuela the pristine nature of the orinoco delta of eastern venezuela provides unique opportunities to study the geologic processes and environments of a major tropical delta remote sensing images shallow cores and radiocarbon dating of organic remains form the basis for describing deltaic environments and interpreting the holocene history of the delta the orinoco delta can be subdivided into two major sectors the southeast sector is dominated by the rio grande the principal distributary and complex networks of anastomosing fluvial and tidal channels the abundance of siliciclastic deposits suggests that fluvial processes such as overbank flooding strongly influence this part of the delta in contrast the northwest sector is represented by few major distributaries and overbank sedimentation is less widespread relative to the southeast sector peat is abundant and occurs in herbaceous and forested swamps that are individually up to 200 km 2 in area northwest directed littoral currents transport large volumes of suspended sediment and produce prominent mudcapes along the northwest coast mapping of surface sediments vegetation and major landforms identified four principal geomorphic systems within the western delta plain 1 distributary channels 2 interdistributary flood basins 3 fluvial marine transitional environments and 4 marine influenced coastal environments coring and radiocarbon dating of deltaic deposits show that the northern delta shoreline has prograded 20 30 km during the late holocene sea level highstand progradation has been accomplished by a combination of distributary avulsion and mudcape progradation this style of deltaic progradation differs markedly from other deltas such as the mississippi where distributary avulsion leads to coastal land loss rather than shoreline progradation the key difference is that the orinoco delta coastal zone receives prodigious amounts of sediment from northwest moving littoral currents that transport sediment from as far away as the amazon system 1600 km late holocene progradation of the delta has decreased delta plain gradients increased water levels and minimized overbank flooding and siliciclastic sedimentation in the northwest sector these conditions coupled with large amounts of direct precipitation have led to widespread peat accumulation in interdistributary basins because peat forming environments cover up to 5000 km 2 of the delta plain the orinoco may be an excellent analogue for interpreting ancient deltaic peat deposits

permian and triassic rocks of the mojave desert and their implications for timing and mechanisms of continental truncation upper paleozoic and lower mesozoic rocks in the mojave desert and adjacent areas record the change from a passive continental margin to a subduction margin in the southwestern united states this change was apparently accompanied by truncation and reorientation of the continental margin in the mojave desert and western basin and range province from late proterozoic to mississippian time the western margin of north america had a northeast southwest trend through nevada and eastern california truncation of the margin began in pennsylvanian time when a northwest trending left lateral strike slip fault zone formed across the antler orogenic belt the cordilleran miogeocline and the more cratonal character mojave desert rocks of the antler belt were apparently displaced southward from east central california to their present position in the northwestern mojave desert sedimentary rocks deposited during this interval record an active continental borderland characterized by alternately subsided and uplifted marine basins this transcurrent faulting continued to late permian time magmatic activity and deformation started in the mojave desert in late permian time and affected both miogeoclinal cratonal and displaced antler rocks magmatic activity ceased and marine sedimentation resumed in early triassic time lower triassic rocks constitute an overlap sequence on both deformed and undeformed miogeoclinal cratonal rocks and possibly on displaced antler rocks facies trends in these rocks are northwest southeast indicating the new margin trend truncation and reorientation of the margin were completed therefore by early triassic time or possibly as early as late permian time upper permian magmatism and deformation in the mojave desert are older than and distinct from the early triassic sonoma orogeny of nevada lower triassic rocks in the mojave desert are post tectonic with respect to deformation in that region whereas correlative lower triassic rocks in nevada are pretectonic to syntectonic with respect to the sonoma orogeny this difference reflects the variation in deformation and tectonic setting along a newly developed cordilleran margin the southern part of the cordillera was apparently a subduction margin as early as late permian or middle triassic time while the central nevada segment was the site of collision tectonics

u pb zircon strontium and oxygen isotopic and geochronological study of the southernmost sierra nevada batholith california the southernmost sierra nevada offers a view into the deep levels of the mesozoic batholithic belt which constitutes much of the range to the north and represents one of the major tectonic features of western north america the main crystalline rocks of the study area are 1 the intrusive suite of bear valley a middle cretaceous tonalite batholith complex with coeval gabbroic intrusives and 2 the gneiss complex of the tehachapi mountains which consists of early cretaceous orthogneiss and subordinate paragneiss with local domains having granulite facies metamorphic assemblages the orthogneisses are dominantly tonalitic in composition with significant layers of granodioritic to granitic and lesser dioritic to gabbroic gneiss quartz rich and psammitic metasedimentary rocks with subordinate marble constitute the main framework assemblage into which the plutonic rocks were emplaced field relations demonstrate assimilation of metasedimentary material into the orthogneiss and tonalite batholith magmas and magma mixing between mafic tonalitic and granitic materials significant domains of both homogenization and inhomogenization are recognized isotopically within the mixed rocks u pb zircon studies have resolved two major igneous suites and a third suite of postdeformational intrusives all lying between 90 and 120 ma the first suite gneiss complex of the tehachapi mountains was emplaced at 115 ma and exhibits penetrative high temperature deformation developed at or near solidus conditions a number of discordance patterns along with the physical properties of the zircon suggest minor inheritance of proterozoic zircon and limited open system behavior in response to a major 100 ma plutonic event the 100 3 ma intrusive suite of bear valley crosscuts the older suite but also exhibits significant synplutonic deformation mainly concordant zircon ages indicate the igneous crystallization age but some discordances occur due to inheritance or entrainment of proterozoic zircon the high temperature deformation fabrics in these suites and within the metasedimentary framework rocks were crosscut by the granodiorite of claraville 90 ma and pegmatite dikes 95 ma the granodiorite of claraville shows strong inheritance of proterozoic zircon and high initial 87 sr 86 sr and 18 o zircon populations from paragneiss and quartzite samples are dominated by proterozoic detrital grains strontium and oxygen isotopic data on the zircon geochronology sample suite suggest simple twocomponent mixing of mantle derived gabbroic to tonalitic magmas with partial to complete melt products from the metasedimentary framework rocks sedimentary admixtures for some granitic rocks may be as high as 45 but for the tonalitic batholithic complex are no higher than about 15 modeled values of 10 20 metasediment are typical for the orthogneisses initial 87 sr 86 sr correlates directly with 18 o and generally correlates inversely with sr content some subtle complexities in the sr and o isotopic data suggest the involvement of a third cryptic component such a component could be early phanerozoic ensimatic accretionary terranes that were structurally beneath the observed metasedimentary sequence or altered oceanic crust and sediments introduced into the mantle magma source area by subduction one of the initial aims of this study was to seek out remnants of proterozoic sialic crystalline rocks within the gneiss complex of the tehachapi mountains no such remnants were found and our studies strongly suggest that sialic components within this link of the mesozoic batholithic belt were introduced into mantle derived magraatic systems by anatexis of continent derived sedimentary rocks

controls on the genesis of some high fluoride groundwaters in india india has an increasing incidence of fluorosis dental and skeletal with some 62 million people at risk high fluoride groundwaters are present especially in the hard rock areas south of the ganges valley and in the arid north western part of the country the phenomenon is related to groundwater with residual alkalinity ca2 hco3 fluoride concentrations are governed by adsorption equilibria and by fluorite solubility evapotranspiration leads to a precipitation of calcite a lowering of ca activity and increase in na ca ratios and this allows an increase in f levels in southern india mg seems to be controlled by dolomite while sepiolite and palygorskite are mg sinks in rajasthan but may then release f under alkaline conditions the latter two minerals are probably also important sources and sinks for f in the hydroxy positions the increase in the extent of sodic soils as a result of irrigation is a contributing factor to the increasing incidence of fluorosis remedial measures including addition of gypsum and rainwater harvesting are needed even in areas where the sodicity does not cause structural problems in the soil

seasonal interannual and mesoscale variability of the black sea upper layer circulation derived from altimeter data 1 topex poseidon and ers altimeter data comprising the period from may 1992 to may 1999 are assimilated into a shallow water model for providing a dynamically consistent interpretation of the sea surface height variations and estimation of the temporal and spatial characteristics of the upper layer circulation in the black sea these 7 year long observations offer a new capability for interpretation of major transient and quasi permanent features of the upper layer circulation the instantaneous flow fields involve a complex eddy dominated system with different types of structural organizations in which the eddies and the gyres of the interior cyclonic cell interact continuously among themselves and with meanders and filaments of the rim current the circulation possesses a distinct seasonal cycle whose major characteristic features repeat every year with some year to year variability an organized two gyre winter circulation system disintegrates gradually into a series of interconnecting eddies in the summer and autumn months which are also characterized by more pronounced and complex mesoscale activity in the peripheral flow system our analyses suggest a revised schematic circulation picture of the major quasi permanent and recurrent elements of the black sea

proterozoic and lower cambrian miogeoclinal rocks of snow lake pendant yosemite emigrant wilderness sierra nevada california evidence for major early cretaceous dextral translation detailed stratigraphic and structural studies at snow lake pendant have established new evidence for the presence of uppermost precambrian and lower cambrian miogeoclinal strata within the axial region of the sierra nevada batholith lithologic and stratigraphic data along with trace fossils a distinctive triassic overlap sequence fairview valley formation dikes probably related to the jurassic independence dike swarm and structural history suggest that the older rocks of snow lake pendant correlate with the stirling quartzite wood canyon formation zabriskie quartzite and carrara formation in the western mojave desert and san bernardino mountains this correlation implies approximately 500 km of dextral transport of the rocks of snow lake pendant along the proposed mojave snow lake fault movement on the fault probably took place after 148 ma the age of the independence dike swarm and prior to 110 ma the age of plutons in the central part of the sierra nevada batholith

genesis and geochemistry of high fluoride bearing groundwater from a semi arid terrain of nw india occurrence of fluoride in natural water resources and the associated health hazards have been reported from many parts of india during the last decade with the objective of organizing a systematic scientific programme to understand the geochemical behaviour of fluoride in natural water resources in relation to the local hydrogeological climatic conditions and agricultural use a typical semi arid terrain in the northwestern part of india was chosen for detailed study the present work is an attempt to study the fluoride contamination in groundwater in parts of jaipur district rajasthan state and to assess the origin and genesis of fluoride in groundwater the area falling under the semi arid tract of central rajasthan is geologically occupied by alluvial formations and precambrian rocks gneisses and schists where groundwater occurs under unconfined to semi confined conditions a total of 66 groundwater samples was collected during the pre monsoon period and analysed which gave a concentration of fluoride in water in the range of 0 35 to 9 3 mg l with 62 of the samples in excess of permissible limit of 1 5 mg l as compared to alluvial formations fluoride enrichment in groundwater is higher in hard rock areas the samples collected from the granite gneissic terrain show higher values when compared to those in the schist the groundwater of the shallow aquifers soil clay complex weathered zone has a higher concentration of fluoride than the deep fractured hard rock aquifer does the possible sources of fluoride are chemical weathering and leaching of fluorine bearing minerals present in hard rocks and alluvial formations under the alkaline environment in arid to semi arid conditions high ph as well as alkalinity and low levels of ca mg and total hardness suggest favourable chemical conditions for the fluoride dissolution process a higher rate of evapotranspiration intensive and long term irrigation and heavy use of fertilizers are the supplementary factors that further increase the fluoride content in the groundwater a groundwater management programme is suggested

fluoride dynamics in the granitic aquifer of the wailapally watershed nalgonda district india high concentrations of fluoride up to 7 6 mg l are a recognized feature of the wailapally granitic aquifer of nalgonda district andhra pradesh india the basement rocks provide abundant sources of f in the form of amphibole biotite fluorite and apatite the whole rock concentrations of f in the aquifer are in the range 240 990 mg kg calcretes from the shallow weathered horizons also contain comparably high concentrations of f 635 950 mg kg the concentrations of water soluble f in the granitic rocks and the calcretes are usually low 1 of the total or less but broadly correlate with the concentrations observed in groundwaters in the local vicinity the water soluble fraction of fluoride is relatively high in weathered calcretes compared to fresh calcretes groundwater major ion composition shows a well defined trend with flow downgradient in the wailapally aquifer from na ca hco3 dominated waters in the recharge area at the upper part of the catchment through to na mg hco3 and ultimately to na hco3 and na hco3 cl types in the discharge area in the lowest part the evolution occurs over a reach spanning some 17 km groundwater chemistry evolves by silicate weathering reactions although groundwaters rapidly reach equilibrium with carbonate minerals favouring precipitation of calcite and ultimately dolomite in the lower parts of the watershed this precipitation is also aided by evapotranspiration decreasing ca activity downgradient leads to a dominance of fluorite undersaturated conditions and consequently to mobilisation of f despite the clear downgradient evolution of major ion chemistry concentrations of f remain relatively uniform in the fluorite undersaturated groundwaters most being in the range 3 0 7 6 mg l the rather narrow range is attributed to a mechanism of co precipitation with and or adsorption to calcrete in the lower sections of the aquifer the model may find application in other high f groundwaters from granitic aquifers of semi arid regions

paleogeographic and structural significance of an upper mississippian facies boundary in southern nevada and east central california discussion and reply a major facies boundary separating meramecian lower upper mississippian shallow water carbonate platform rocks to the south east from coeval to slightly younger relatively deep water siliciclastic rocks to the northwest can be traced throughout southern nevada and east central california although the precise depositional relation between the two facies is not entirely clear the outer margin of the shallow water carbonate rocks almost certainly marks the edge of the carbonate platform in earliest late meramecian time this facies boundary is distinct and unambiguous enough that it and a parallel subfacies boundary within the carbonate platform rocks can be used to estimate amounts of displacement on cenozoic right slip faults in the region the carbonate siliciclastic facies boundary is offset by about 170 km in a right lateral sense parallel to the death valley furnace creek fault zone between the west side of that fault zone and the northeast side of the las vegas valley shear zone this offset is cenozoic in age and is interpreted to be distributed as follows 45 50 km on the las vegas valley shear zone 80 km on the death valley furnace creek fault zone 30 km on the stewart valley fault and an additional 10 15 km that is not specifically accounted for restoration of these offsets successfully reconstructs the meramecian carbonate shelf edge and aligns several thrust faults now exposed on opposite sides of the right slip faults

isotopic evidence for the origin of mesozoic and cenozoic granitic plutons in the northern great basin sup 18 o sup 16 ratios of granitic rocks in western north america reflect source rock lithologies providing insight into the geology of the deep continental crust in a 400 km wide 800 km long east west transect through the northern great basin the mesozoic and cenozoic plutons define three zones western low sub 18 o zone wz delta sup 18 o 6 to 8 5 central high sup 18 o zone cz delta sup 18 o 9 to 13 eastern zone ez utah delta sup 18 o 7 to 9 the wz cz boundary is analogous to the delta sup 18 o step in the peninsular ranges batholith prb a similarly abrupt sup 87 sr sup 86 sr sub i step 0 710 to the east defined by farmer and depaolo 1983 lies 150 200km east of the wz cz sup 18 o sup 16 o step dividing the cz into two subzones v type in the west corresponding to the eastern half of the prb but much wider due to regional cenozoic extension and s type to the east a plausible source for the high sup 87 sr low epsilon sub nd s type subzone is a late precambrian miogeoclinal metasedimentary section whereas the v type source appears to be a phanerozoic volcanogenic eugeoclinal accreted terrane both source regions have very high delta sup 18 o 9 to 16 butmore radically different sup 87 sr sup 86 sr and epsilon sub nd thus the authors would not place the buried edge of the 1 5 ga craton beneath the sup 87 sr sup 86 sr step but farther east near the ez boundary the authors instead that this step is a sharp lithologic and age boundary a suture zone within the giant prism of sediments and volcanics in nevada less

the evolution of middle america and the gulf of mexico caribbean sea region during mesozoic time a plate tectonic model for the evolution of middle america and the gulf of mexico caribbean sea region is presented the model which is based upon the existence of the mojave sonora megashear incorporates into the triassic pangea reconstruction three microplates between north and south america thus avoiding the overlap of the bullard fit these plates are the yaqui bounded on the north by the mojave sonora megashear the east and west maya plates bounded on the north by the mexican volcanic zone and on the south by a predecessor of the motagua fault zone and the chortis plate parts of guatemala and honduras during late jurassic time as north america split away from europe africa and south america shear with left lateral sense of displacement occurred along the transform faults that bounded the micro plates if 800 km of left lateral displacement along the mojave sonora megashear 300 km along the mexican volcanic belt and 1 300 km along a proto motagua megashear are restored and if yucatan and cuba are rotated to fit against northern south america then 1 a curvilinear belt of late paleozoic rocks that show lithologic as well as paleontologic similarities extends across the reconstruction and links outcrops in texas eastern mexico nuclear central america and colombia 2 a mediterranean like sea is delineated that was a precursor of most of the present gulf of mexico 3 correlation is implied between the distinctive quartzose san cayetano formation of cuba and the caracas and juan griego groups of venezuela geometric constraints suggest that probably shear initially occurred along the mexican volcanic zone near the end of the middle jurassic subsequently probably about 160 m y ago displacements that total 800 km began along the mojave sonora megashear contemporaneously yucatan and fragments of pre cretaceous rocks that compose parts of central and western cuba migrated northward toward their present positions rotation of yucatan was facilitated by considerable displacement along the proto motagua zone and along a zone that is probably coincident with the modern salina cruz fault accumulation of widespread major salt units of late jurassic callovian to early oxfordian age in the gulf basin probably occurred contemporaneously with the arrival of these blocks at their present positions clastic units that interfinger with some of the youngest salt units and rim the gulf of mexico have not recorded major recognized translations since their accumulation clockwise rotation of south america and the chortis plate occurred during early cretaceous time this movement which was manifested by subduction of jurassic ocean floor against the previously rifted precursor of the island of cuba and under parts of hispaniola and puerto rico is recorded by circum caribbean orogeny abrupt changes in the relative motions between north and south america during late cretaceous time may have resulted in extension and outpourings of basalt upon the jurassic rocks of the ocean floor of the venezuelan basin west of beata ridge sea floor spreading formed the colombian basin related subduction occurred as the chortis plate including part of central america the nicaraguan rise and southeastern cuba was sutured against the maya east plate along the present motagua fault and cayman trench our model is constrained by published geologic data the relative positions of north and south america from atlantic sea floor magnetic anomalies and the requirement that the major transform faults be compatible with the poles of rotation for the appropriate relative motions between north and south america paleomagnetic data from middle america are sparse but do not conflict with the predicted motions of some of the microplates especially chortis

speculative reconstruction of the mojave snow lake fault implications for paleozoic and mesozoic orogenesis in the western united states available evidence suggests that the mojave snow lake fault a major early cretaceous dextral fault with up to 400 km displacement formerly existed in what is now the axial part of the sierra nevada batholith regional relations suggest that the fault formerly continued in western nevada the mojave desert and in rocks now exposed in the salinian block restoration of 400 km of early cretaceous dextral displacement on the mojave snow lake fault leads to speculative but testable reconstructions of mesozoic and paleozoic tectonic features of california and nevada insights derived from these reconstructions include the following 1 two regionally extensive jurassic thrust belts of opposed vergence appear to have intersected in the northern sierra nevada the eastern east vergent thrust belt which includes the fencemaker and liming thrusts in western nevada and several east vergent thrusts in the northern sierra may be a contractional belt along which an early jurassic interarc or marginal basin was closed in middle to late jurassic time the western west vergent thrust belt is part of the classic nevadan orogen of the western klamath mountains and the western sierra metamorphic belt in which collisions and or thrusting of various island arc terranes occurred during middle and late jurassic time 2 the early mesozoic continental arc included paired belts of triassic jurassic blueschist and melange and igneous rocks including late triassic and younger plutons and volcanic rocks this conclusion is not new but the reconstruction provides a slightly different geometry than previously thought 3 sonomia the late paleozoic island arc terrane of the western u s may have formed a relatively narrow belt extending from northwestern nevada to the latitude of the western mojave desert the geologic development of the paleozoic basement complex of sonomia was very different from that of the cordilleran miogeocline in death valley and the mojave desert requiring that a continuation of the sonoma suture belt or golconda thrust must have extended southward through the sierra nevada batholith to the mojave region 4 a heterogeneous belt of permian to triassic or triassic deformation in the mojave and eastern sierra nevada together with the golconda allochthon in nevada may represent the protracted response to the collision of sonomia with the western margin of north america the contractional deformation continued during the evolution of the early mesozoic continental arc 5 several predictions can be made about the nature of concealed basement within the sierra nevada batholith and within western nevada the reconstruction suggests that elements of the antler and sonoma orogenic belts should underlie areas of the batholith and western nevada as a result of northward displacement along the mojave snow lake fault from the western mojave and southern sierra nevada

climatostratigraphic scheme of the black sea pleistocene and its correlation with the oxygen isotope scale and glacial events abstract new evidence from the asov sea black sea region shows that after the cobb mountain magnetic event 1 1 myr there were 8 saline water events with mediterranean molluscs penetrating into the asov sea five times farther than the western manych strait and 7 or 10 cold freshwater events during the freshening phase the caspian sea molluscan fauna penetrated into the black sea each time the caspian mollusc assemblage was characterized by a new species of didacna thus some 18 20 bioclimatostratigraphic units can be distinguished in the asov sea black sea section for the last 1 myr their numerical age is estimated by some dozen thermoluminescence dates and 12 magnetic polarity datum planes the karangatian s lato corresponds to the interval 300 000 50 000 yr the uzunlarian to 580 000 300 000 yr and the chaudian to 1 100 000 600 000 yr the karangatian and tyrrhenian marine terraces correspond to marine isotope stages 5 and 7 the uzunlarian and milazzian to stages 11 15 and the chaudian and sicilian to stages 16 28 the number and ages of glacial interglacial cycles in continental europe are identical to the climatic cycles in the black sea and mediterranean

processes reshaping the ebro delta abstract due to the limited supply of sediment from the ebro river its delta is mainly subject to reshaping processes in the form of alongshore alternation of erosive and accretive coastal stretches without a significant change in the overall subaerial surface of the delta the main agents presently forcing these processes waves and mean water level oscillations are analysed in detail as a function of their contribution to coastal processes in this manner waves are characterised in terms of short term seasonal changes longshore sediment transport pattern long term cross shore transport at the shoreface and storm impacts although the study area is a microtidal one and waves are the main agent forcing coastal evolution at yearly scales mean water level oscillations meteorological tides and long term relative mean sea level variations play a non negligible role additionally a joint analysis of waves and storm surges has been done in order to characterise conditions inducing an impulsive type of coastal response at last the classical ternary classification of deltas has been applied in a dynamical way by considering the river vertex in terms of the variation in sediment supply moreover the effects of considering mean water level variations other than tides on the deltaic classification has also been tested the inclusion of rslr influence becomes relevant for river independent deltas since it indicates the inability of the delta to withstand it the main problem to include this agent in the ternary classification is that rslr is more of a passive factor whereas the other considered agents are active in the sense that they induce more perceivable morphological processes

seismic stratigraphy of late quaternary deposits from the southwestern black sea shelf evidence for non catastrophic variations in sea level during the last 10 000 yr abstract detailed interpretation of single channel seismic reflection and huntec deep tow boomer and sparker profiles demonstrates that the southwestern black sea shelf formed by a protracted shelf edge progradation since the miocene pliocene five seismic stratigraphic units are recognized unit 1 represents the last phase of the progradational history and was deposited during the last glacial lowstand and holocene it is divided into four subunits subunit 1a is interpreted as a lowstand systems tract 1b and 1c are interpreted as a transgressive systems tract and subunit 1d is interpreted as a highstand systems tract the lowstand systems tract deposits consist of overlapping and seaward prograding shelf edge wedges deposited during the lowstand and the subsequent initial rise of sea level these shelf edge wedges are best developed along the westernmost and easternmost segments of the study area off the mouths of rivers the transgressive systems tract deposits consist of a set of shingled shore parallel back stepping parasequences deposited during a phase of relatively rapid sea level rise and include a number of prograded sediment bodies including barrier islands beach deposits and thin veneers of seismically transparent muds showing onlap onto the flanks of older sedimentary features a number of radiocarbon dates from gravity cores show that the sedimentary architecture of unit 1 contain a detailed sedimentary record for the post glacial sea level rise along the southwestern black sea shelf these data do not support the catastrophic refilling of the black sea by waters from the mediterranean sea at 7 1 ka postulated by ryan pitman major shimkus maskalenko jones dimitrov gorur sakinc yuce mar geol 138 1997 119 126 ryan pitman touchstone book 1999 319 pp and ballard coleman rosenberg mar geol 170 2000 253 261

updrift river mouth migration on cuspate deltas two examples from the coast of tuscany italy the configuration of the arno and ombrone deltas italy is evaluated the terminal courses of the rivers forming these deltas face the dominant wave orthogonal this configuration came about during rapid delta progradation as a consequence of increased river sediment input due to widespread deforestation within the catchment area a prevailing phenomenon from the early middle ages to the xviii century the rivers attained and maintained their directions as the result of the increased accretion rate on the less exposed downdrift side of the delta on the more exposed updrift side delta growth caused the shoreline to gradually rotate so that it directly faced the waves approaching the coast here due to the lower refraction wave energy per shore unit increased whilst accretion rate decreased this rotation of the shoreline induced longshore inversion on the updrift side whereas today cusp erosion is restoring the original drift direction

fluoride occurrence and mobilization in geo environment of semi arid granite watershed in southern peninsular india plausible forms of fluoride f responsible for the persistence of fluoride toxicity in ground water of a granitic terrain of semi arid region which is the main source of drinking water have been studied the study area in anantapur district of andhra pradesh india is one of the chronic regions with excess fluoride in groundwater and the region is under transformation into aridity due to poor rainfall and over exploitation of groundwater geochemical analysis of soil groundwater and rock samples of the study area revealed the presence of other toxic elements also in addition to fluoride which need to be addressed in drinking water sector in near future soil fluoride leaching experiments demonstrated the probable mode of mobilization of f into the groundwater through natural recharge process during monsoon analysis of saturation indices indicates that the fluorite solubility alone is not attributable to the high fluoride content in groundwater the groundwater flow controls fluoride mobilization in the study area as it is evidenced through fluoride concentration and electrical conductivity increase from catchment to downstream region creation of lesser fluoride groundwater sources through rainwater harvesting and artificial recharge of groundwater in catchment areas is suggested as a long term sustainable safe drinking water strategy