a dna tracer used in column tests for hydrogeology applications tracing techniques are commonly used to investigate groundwater quality and dynamics as well as to measure the hydrogeological parameters of aquifers the last decade has seen a growing interest in environmentally friendly tracers including single stranded dna molecules in this study an electrolytic tracer and a synthetic dna tracer are comparatively evaluated in laboratory scale tests to assess their potential application in field studies aimed at investigating groundwater environments a real time quantitative polymerase chain reaction assay was developed and optimized to detect and quantify the dna tracer while tracer column tests were performed to investigate the dna tracer behavior and to compare it to the electrolytic tracer the results show that the dna tracer has an almost pure convective flow while the kcl tracer experiences dispersive behavior the tracing method proposed can be applied in hydrogeological field studies involving calcareous fractured rock systems with the dna tracer particularly suitable in tracing karst systems which are often characterized by several conduits of flow to test the dna tracer in operation a preliminary test was conducted in the field

global magsat anomaly maps at ground level abstract four maps of the vertical component of the magnetic anomaly field are derived at ground level from magsat data at satellite altitude measurements performed below and above an altitude of 425 km are treated as two independent datasets by two different methods 1 a local downward continuation inverse method and 2 a global spherical harmonic decomposition for each map one and two dimensional energy density spectra are obtained and correlation coefficients are computed it is shown that anomalies with wavelengths as short as 700 km can be significantly recovered at ground level corresponding to a ground resolution of 350 km the improved correlation between anomalies and geodynamic features achieved with downward continued maps is illustrated with the example of southeast asia

experimental tests for particle size dependent bioturbation in the deep ocean the potential for particle size dependent bioturbation rates was experimentally tested at 1 240 m in the santa catalina basin eastern pacific spherical glass bead tracers in five size classes 816 17 31 32 62 63 125 and 126 420 m were spread over the sediment surface and tube cored 997 d later downcore concentrations of glass beads were enumerated in each of the five size categories and page s l test was used to test the null hypothesis of equal vertical penetration of all size classes of tracer in all cores the null hypothesis was rejected finer tracers penetrated deeper into the sediment in two of the three cores vertical biodiffusivities were computed from concentration profiles of downcore tracers these also showed size dependence with biodiffusivities ranging from 1 cm2 yr for the 8 1 6 pm fraction to 0 1 cm2 yr for the 1 25 420 pm size class these data demonstrate that vertical bioturbation rates are particle size dependent in santa catalina basin the likely cause is preferential ingestion and downward transport of fine particles by deposit feeders

long wavelength magnetic anomalies in the caribbean plate boundaries and allochthonous continental blocks vector magnetic anomaly maps are derived at satellite altitude from magsat data over the caribbean and middle america to minimize smoothing of the anomaly field caused by averaging the data over the whole altitude range of magsat measurements two maps are derived in two nonoverlapping altitude ranges 350 420 and 420 550 km a composite map of the vertical component of the anomaly field is then computed at ground level this map displays large positive anomalies associated with fast subduction zones these anomalies define discontinuities in the downgoing slab associated with seismic gaps positive anomalies are also consistently observed above allochthonous blocks of continental origin in the caribbean area and suggest that the average magnetization is larger in the continental lithosphere elongated magnetic lows are observed above transform boundaries of the caribbean plate the cayman trough anomaly is consistent with magnetization of the order of 1 a m in the upper mantle demagnetization of the lithosphere along the bocono el pilar fault system which bounds the caribbean plate to the south may be accounted for by frictional heating along shear zones the pattern of anomalies along the southern margin of the united states is related to its accretionary tectonic history various estimates of the vertically integrated magnetization of both oceanic and continental lithospheres are computed using these anomalies and provide constraints on the vertical distribution of lithospheric sources of magsat anomalies

geophysical interpretation of the magnetic anomalies of china derived from magsat data the ambiguities about geophysical implications based on the correlation of scalar magnetic anomalies and geological features were investigated a method was developed to convert scalar magnetic anomalies into a map of the lateral variations of magnetic susceptibility of the lithosphere this map is directly correlated with the causative sources the method is based on spherical harmonic analysis of lateral variations seen on the scalar magnetic anomaly map and those of the lithospheric magnetic susceptibility the harmonic coefficients are related through the fundamental causality relationship governing a magnetized body and its associated scalar magnetic anomaly the main features of the resulting magnetic susceptibility anomalies are outlined

transport of suspended solids from a karstic to an alluvial aquifer the role of the karst alluvium interface this study focuses on the coupled transport of dissolved constituents and particulates from their infiltration on a karst plateau to their discharge from a karst spring and their arrival at a well in an alluvial plain particulate markers were identified and the transport of solids was characterised in situ in porous and karstic media based on particle size analyses sem and traces transport from the sinkhole to the spring appeared to be dominated by flow through karst particulate transport was apparently conservative between the two sites and there was little difference in the overall character of the particle size distribution of the particulates infiltrating the sinkhole and of those discharging from the spring qualitatively the mineralogy of the infiltrating and discharging material was similar although at the spring an autochthonous contribution from the aquifer was noted chalk particles eroded from the parent rock by weathering in contrast transport between the spring and the well appears to be affected by the overlying alluvium particles in the water from the well showed evidence of considerable size sorting additionally sem images of the well samples showed the presence of particles originating from the overlying alluvial system these particles were not found in samples from the sinkhole or the spring the differences between the particulates discharging from the spring and the well indicate that the water pumped from the alluvial plain is coming from the karst aquifer via the very transmissive complex geologic interface between the underlying chalk formation and the gravel at the base of the overlying alluvial system

can the thermal thickness of the continental lithosphere be estimated from magsat data abstract the long wavelength magnetic anomaly field derived from magsat data is modelled by large scale lateral magnetization variations in the continental lithosphere of europe central and southeast asia a simple model with six domains with uniform magnetization is shown to be consistent with this long wavelength anomaly field in this model all major alpine mountain belts are associated with magnetization lows and proterozoic cratons with magnetization highs in particular a significant contrast of magnetization is associated with the tornquist tesseyre line the structural boundary between the paleozoic western part of europe and the proterozoic eastern domain it is thus proposed that the magnetization contrasts and their associated long wavelength magnetic anomalies may be attributed to differences of tectono thermal age of the lithosphere the main magnetization contrasts displayed by the model are then shown to be associated with seismic velocity contrasts this observation supports the hypothesis that magnetization variations are generated by magnetic sources distributed over the whole upper lithosphere down to the depth of the 600 c isotherm to support this conclusion it is shown that the magnetic thickness predicted by the magnetization model obtained is in good agreement with the depth of the 600 c deduced from heat flow measurements

the downward continuation of magsat crustal anomaly field over southeast asia a general method for the local downward continuation at ground level of geopotentials measured by low orbiting satellites at different altitudes is proposed such a continuation is the inverse solution of the external dirichlet problem the stability of the solution with respect to the altitude and the distribution of data points is discussed principal component analysis is shown to perform well and leads to a stable solution the method proposed has the advantage of being directly applicable to measured data points which are not evenly spaced and at different altitude as an illustration it is applied to magsat data over southeast asia two independent maps of the vertical component of the anomaly field at a constant altitude near ground level are derived for dawn descending orbits and dusk ascending orbits data separately the two maps reveal similar anomalies and confirm the correlation of the magsat derived anomaly field with the mosaic structure of the continental crust in southeast asia stable continental blocks are associated with positive anomalies and intervening collision belts correspond to well defined negative anomalies a very prominent low is observed above the himalaya and extends over the tibet plateau confirming an anomalous crustal and thermal structure of the plateau

dna labeled clay a sensitive new method for tracing particle transport the behavior of mobile colloids and sediment in most natural environments remains poorly understood in part because characteristics of existing sediment tracers limit their widespread use here we describe the development of a new approach that uses a dna labeled montmorillonite clay as a highly sensitive and selective sediment tracer that can potentially characterize sediment and colloid transport in a wide variety of environments including marine wetland ground water and atmospheric systems characteristics of dna in natural systems render it unsuitable as an aqueous tracer but admirably suited as a label for tracing particulates the dna labeled clay approach using techniques developed from molecular biology has extremely low detection limits very specific detection and a virtually infinite number of tracer signatures furthermore dna labeled clay has the same physical characteristics as the particles it is designed to trace it is environmentally benign and it can be relatively inexpensively produced and detected our initial results show that short 500 base pair strands of synthetically produced dna reversibly adsorb to both na montmorillonite and powdered silica surfaces via a magnesium bridge the dna montmorillonite surface complexes are stable in calciumbicarbonate spring waters for periods of up to 18 days and only slowly desorb to the aqueous phase whereas the silica surface complex is stable only in distilled water both materials readily release the adsorbed dna in dilute edta solutions for amplification by the polymerase chain reaction pcr and quantification the stability of the dna labeled clay complex suggests that this material would be appropriate for use as an extremely sensitive sediment tracer for flow periods of as long as 2 weeks and possibly longer

magnetization of the pacific ocean lithosphere deduced from magsat data magsat anomalies over the pacific ocean are related to volcanic plateaus and the edge effect of the pacific cretaceous quiet zone pcqz four prominent plateaus shatsky rise the mid pacific mountains hess rise and manihiki plateau are considered in this study the major lateral magnetization contrasts associated with these plateaus are considered to arise from the topographic swells and the crustal roots with root thicknesses estimated from topography using an airy isostatic model shatsky rise and the mid pacific mountains are older than the cretaceous quiet period and their natural remanent magnetization nrm is not a significant component of the magnetization contrasts that cause the magsat anomalies associated with these plateaus their magnetic properties are characterized by effective magnetic susceptibility contrasts of 0 07 0 01 s i per unit volume averaged over their topographic swells and crustal roots equivalent to 0 04 if averaged over the entire crustal thicknesses swell plus root plus intervening layer this value agrees well with the estimates of previous investigators for these plateaus and for similar plateaus in other oceans two plateaus of cretaceous quiet period age within the pcqz hess rise and manihiki plateau have origins similar to those of shatsky rise and the mid pacific mountains and they probably have similar effective susceptibility contrasts but they may also carry cretaceous quiet period nrm magnetic anomalies due to hess rise and manihiki plateau calculated from the effective susceptibility contrast deduced for shatsky rise and the mid pacific mountains are substantially larger than the observed magsat anomalies of these plateaus there are also magsat anomalies over parts of the pacific where no plateaus exist some of these anomalies are demonstrated as probably due to a contrast in nrm between the pcqz and its surroundings the total remanent magnetization contrast magnetization contrast in amperes per meter times thickness in meters equivalent to the dipole moment per unit area of the pcqz is 14 000 20 000 amperes 30 which cannot be simply explained by the absolute values of remanent magnetization predicted by conventional models of oceanic crustal magnetic properties modelling of the cretaceous quiet zones in the northern atlantic indicates a similar total remanent magnetization contrast these results may be explained by including uppermost mantle remanent magnetization with an intensity of about 1 2 a m 1 if magnetization persists to a depth of 7 below the seismic moho i e down to the depth of the crustal roots of the plateaus including nrm in the uppermost mantle of the pcqz also serves to reduce the calculated amplitude of the hess rise and manihiki plateau magsat anomalies if the nrm of the crustal roots is less than the nrm of the surrounding uppermost mantle on this basis the estimated intensity of nrm in the uppermost 7 km of the pcqz mantle is 1 3 a m 1 in very good agreement with the intensity estimated from the pcqz edge effect anomalies these estimates of uppermost mantle nrm are probably a maximum limit recognizing that other sources may also contribute to the total remanent magnetization contrasts of the cretaceous quiet zones

the global continent ocean magnetization contrast abstract a schematic global model for the distribution of magnetization in the lithosphere is devised this model is characterized by a uniform stepwise change of radially integrated susceptibility at continent ocean boundaries and an axial dipolar inducing field a spherical harmonic expansion of the magnetic field produced by this source distribution is computed then the standard method of truncation at degree n 13 is used to determine the respective contribution of this field to the main field and to the lithospheric anomaly field the latter is shown to display significant anomalies near continental margins as well as within continents and oceanic basins the energy density spectrum of this field is shown to be very similar to the spectrum of the magsat derived lithospheric anomaly field furthermore several features of this field are shown to account for unexplained anomalies of the magsat field this supports the hypothesis that such an abrupt magnetization variation may occur at several continental margins and contribute to the signal in the magsat derived long wavelength anomaly maps this hypothesis provides an order of magnitude estimate for the magnetization difference between oceanic and continental lithospheres finally it is argued that the synthetic anomaly field produced by this model provides an upper bound to the energy density spectrum of the lithospheric field at low harmonic degrees and concluded that the lithospheric field does not contribute significantly to the earth s field below degree 13

fingerprinting and tracing the sources of soils and sediments earth and ocean science geoarchaeological forensic and human health applications abstract fine grained sediment is perhaps the most widespread and pervasive contaminant in aquatic systems reflecting its role in influencing the quality of the water e g turbidity vector of chemicals and other pollutants and its detrimental effect on infrastructure e g dams turbines and aquatic habitats e g salmonid spawning grounds through sedimentation determining the sources of fine grained sediment thus represents an important requirement for watershed and coastal management as well as for understanding the evolution of landscapes and ocean basins sediment source fingerprinting utilizes the diagnostic physical chemical and biological properties i e tracers of source materials to enable samples of collected sediment to be apportioned to these sources this review examines the development of the technique within the earth and ocean sciences focusing mainly on agricultural landscapes however the development of new tracers such as compound specific stable isotopes has allowed the technique to be applied in a growing number of environmental settings including forested including wildfire impacted forests urban and estuarine coastal settings this review also describes other applications of the fingerprinting approach such as geoarchaeological e g archaeological site formation forensic e g identifying the sources of soil sediment particles in criminal investigations and human health e g identifying the sources of airborne particulate matter pm 2 5 applications identifying commonalities in methods and approaches between environments and disciplines should foster collaboration and the exchange of ideas furthermore refinement of the sediment source fingerprinting technique requires that several methodological issues be addressed these methodological issues range from the initial sampling design to the interpretation of the final apportionment results this review also identifies and assesses these methodological concerns

quantification of controls on regional rockfall activity and talus deposition kananaskis canadian rockies abstract rockfall is a significant geomorphic process in many mountainous regions that also poses a notable natural hazard risk most previous studies of rockfall erosion have investigated the mechanics and rates of local rockwall retreat and talus deposition with only a few investigations of rockfall and or associated talus considering larger spatial scales i e drainage basin mountain range the purpose of the current research is to investigate the areal extent of rockfall talus and controlling factors of its distribution over regional spatial scales of order 102 km2 in kananaskis canadian rockies to inform our understanding of its significance in mountain development to achieve this goal a large talus inventory is collected and analyzed for 11 steep tributaries of the kananaskis river canadian rockies talus accumulations associated with rockfall provide evidence about the nature and rates of rockfall activity that supplies sediment to these deposits and are the focus of the present study to quantify the controls of rockfall talus activity in this region we analyze the association of talus deposits with structural geology glacial topography and temperature related weathering i e frost cracking a total of 324 talus polygons covering a surface area of 28 51 km2 are delineated within the 11 study basins with the number of talus polygons in each study basin ranging from 1 to 73 analysis of the talus inventory shows that cirques and glacially sculpted valleys are locations of notable talus accumulation in kananaskis with other locations of significant talus deposition being associated with thrust faults we also found that the upper elevations at which talus deposits are typically found are the general range of elevations experiencing a notable number of days in the frost cracking window when this window is defined as 3 to 15 c no such association is found for the frost cracking window of 3 to 8 c estimates of average erosion rates for all study basins combined are between 0 15 mm y 1 lower estimate to 3 1 mm y 1 upper estimate rockfall activity is expected to have been most active for the several millennia following deglaciation during the paraglacial period when hillslopes were oversteepened

small scale features in the earth s magnetic field observed by magsat a spherical harmonic expansion to degree and order 29 is derived using a selected magnetically quiet sample of magsat data global maps representing the contribution due to terms of the expansion above n 13 at 400 km altitude are compared with previously published residual anomaly maps and shown to be similar even in polar regions an expansion with such a high degree and order displays all but the sharpest features seen by the satellite and gives a more consistent picture of the high order field structure at a constant altitude than do component maps derived independently the appendix is available with the entire article on microfiche order from american geophysical union 2000 florida avenue n w washington dc 20009 document b83 008 2 50 payment must accompany order

new global vector magnetic anomaly maps derived from magsat data new global maps of the vector magnetic anomaly field of earth are derived from magsat data improvement on earlier published vector and scalar maps is achieved with the following procedure 1 the noise level of vector measurements associated with the discontinuities of the in flight sensor attitude determination is reduced by selecting the data 2 a monthly model of the main field is computed to account for secular variation using only quiet day data 3 the time dependence of the ring current effect is taken into account using hourly values of the dst index based on ground obseivations 4 sectorial indices based on ground observations are introduced to select profiles corresponding to low magnetic activity these indices provide a better discrimination of quiet data than the global kp index usually used for that purpose 5 a time and longitude dependent dynamic model of the equatorial electrojet is derived and used to correct magnetic measurements at low latitudes anomaly maps of x and z components are obtained using selected measurements within the reduced altitude range 350 425 km these maps are compared with earlier magsat anomaly maps and their respective resolutions are discussed these maps evidence large anomalies of lithospheric origin within the oceanic domain in particular the z map displays a characteristic pattern of long wavelength anomalies in these areas it is first shown that some of these anomalies particularly in the north atlantic and indian oceans may be correlated with the age of the lithosphere then a significant similarity between magnetic and geoid anomalies above ocean basins is evidenced this suggests that long wavelength oceanic magnetic anomalies may also be attributed to variations of the thickness of the magnetized layer associated with ocean floor topography

magnetic anomaly modeling at the indo eurasian collision zone abstract one of the consistent features of satellite crustal magnetic anomaly maps is the large negative anomaly in the indo eurasian collision zone this region is modeled by the introduction of magnetic blocks representing the tibetan asian and himalayan mountain regions the crustal thickness of these blocks is based on the principle of isostasy it has been shown that the removal of the core field from the magsat data removes most of the long wavelength anomalies associated with the ocean continent susceptibility contrast and that some of the observed anomalies after processing of the satellite data are a manifestation of this contrast to account for this the final model is a superposition of the above block model on a global model of typical continent and ocean susceptibility called a standard earth magnetization model semm a combination of the three blocks superposed on the semm reproduces the major features of the observed magsat anomalies block model susceptibilities of the asian and himalayan regions are the same as for the continental portion of the semm albeit with a greater crustal thickness thus the crust in these regions is typical by contrast the satellite magnetic data require an integrated susceptibility in the tibetan region which is considerably lower than typical two possible explanations are suggested one that the origin and tectonic history of the tibetan region differs from the neighboring regions in such a way as to result in lower susceptibility this is consistent with current thinking that the tibetan plateau is made up of several fragments or micro continents which were attached to asia prior to the collision of india with asia the other possible explanation is that the curie isotherm in the tibetan region is elevated compared to the asian and himalayan regions

magsat scalar anomalies and major tectonic boundaries in asia the distribution of magsat scalar anomalies is compared with locations of major tectonic boundaries in asia foldbelts separate large scale positive and negative anomalies inside and outside the siberian platform and sediment filled aulacogens within the platform separate the anomalies into two parts which overlie the anabar and aldan shields tectonic boundaries appear to exercise some control over the extent and distribution of the satellite observed crustal anomalies

magnetic measurements aboard a stratospheric balloon abstract we have measured the total intensity of the earth s magnetic field above the western mediterranean along a 2000 km profile flown at an altitude of 40 km a proton magnetometer was aboard a cnes centre national d etudes spatiales stratospheric balloon the core field and transient external field contributions have been carefully determined and removed from the data the resulting profile reveals significant anomalies of 10 20 nt amplitudes with 100 1200 km wavelengths these anomalies have a clear crustal origin and can be related to heterogeneities in magnetisation in the oceanic algero provencal basin and to major faults of the spanish continental crust comparison of our new data with previous data obtained over the same area at about 1 km altitude aeromagnetic surveys and about 400 km altitude magsat demonstrates the potential of stratospheric balloon measurements in bridging the 200 1500 km gap that exists in the knowledge of crustal anomalies a gap that is unavoidable if only aeromagnetic and satellite like magsat data are used

using concurrent dna tracer injections to infer glacial flow pathways author s dahlke he williamson ag georgakakos c leung s sharma an lyon sw walter mt abstract 2015 john wiley a sons ltd catchment hydrology has become replete with flow pathway characterizations obtained via combinations of physical hydrologic measurements e g streamflow hydrographs and natural tracer signals e g stable water isotopes and geochemistry in this study we explored how our understanding of hydrologic flow pathways can be improved and expanded in both space and time by the simultaneous application of engineered synthetic dna tracers in this study we compared the advective dispersive transport properties and mass recovery rates of two types of synthetic dna tracers one consisting of synthetic dna strands encapsulated into biodegradable microspheres and another consisting of free dna i e not encapsulated the dna tracers were also compared with a conservative fluorescent dye all tracers were injected into a small 3 2 km2 valley glacier storglaciaren in northern sweden seven of the nine dna tracers showed clear recovery during the sampling period and similar peak arrival times and dispersion coefficients as the conservative fluorescent dye however recovered dna tracer mass ranged only from 1 to 66 while recovered fluorescent dye mass was 99 resulting from the cold and opaque subglacial environment provided by the glacier mass loss associated with microbial activity and photochemical degradation of the dna is likely negligible leaving sorption of dna tracers onto suspended particles and loss of microtracer particles to sediment storage as probable explanations despite the difference in mass recovery the advection and dispersion information derived from the dna tracer breakthrough curves provided spatially explicit information that allowed inferring a theoretical model of the flow pathways that water takes through the glacier

minimal crustal magnetizations from satellite data abstract the minimum amplitude crustal magnetization needed to explain magsat vector anomaly data is found using harmonic splines as basis functions shure et al 1982 phys earth planet inter 28 215 229 and choosing a subset of the original basis parker and shure 1982 geophys res lett 9 812 815 to represent magnetization we suggest the optimum model of this type is obtained by associating representers only with north and vertically downwards data points given the larger uncertainties associated with east component magsat data following parker et al 1987 rev geophys 25 17 40 we find a model minimizing the r m s volume integral of magnetization over the magnetized lithosphere the numerical effort involved in producing a regional or continental scale model with given horizontal spatial detail with our method is less than that for an equivalent source dipole model when the magnetization is not assumed induced approximately equal to that for an induced magnetization equivalent dipole model and considerably less than that for a spherical harmonic apparent susceptibility model the method is demonstrated by producing a solution for two regions the contiguous usa for comparison with previously published models and africa and its continental margins magnetization models fit the data slightly worse than those of the downward continued anomaly field at the earth s surface comparison of our component of magnetization for the usa in the direction of the core field with the induced magnetization equivalent dipole model of mayhew 1984 earth planet sci lett 71 290 296 is very good as expected for magnetization either induced by or frozen remanently in an approximately dipole field either parallel or antiparallel to the current rotation axis the east component of magnetization is much smaller than the north and vertically downwards components we make no assumptions about the relative contributions of remanent and induced magnetization and the resulting models have a substantial remanent component however our models suffer from the severe non uniqueness common to all magnetization models whereby magnetization in a uniform susceptibility and thickness shell concentric with the earth s centre owing to any internal magnetic field that is then switched off generates no external magnetic field

mean ionospheric field correction for magsat data to obtain a meaningful anomaly map showing magnetic fields of crustal origin from satellite observations it is necessary to account adequately for and subtract the fields generated by the currents flowing in the ionosphere conventionally corrections are made separately for each path by empirical methods of fitting and subtracting linear quadratic or harmonic functions from the original data this procedure however lacks a sound physical basis we examined the field components after the main field and the magnetospheric field were subtracted from magsat data and found certain structures in the residual field the residual fields at 0600 and 1800 local times were separately averaged over longitude to obtain the effective contribution of ionospheric current system at these local times which is called the mean ionospheric field mif to obtain the crustal anomalies the mif was subtracted from the residual fields to account for the day to day variation in the ionospheric current system and for the difference in satellite altitude anomaly maps are constructed on 5 5 grid averages the dawn and dusk anomaly maps after the correction agree well with each other showing that the effect of the ionospheric field is well taken care of by the mif correction the amplitude of anomalies is large even at comparatively long wavelength and the maps successfully represent these crustal anomalies which have been greatly reduced in the previous maps

uniform sense normal simple shear of the continental lithosphere geophysical studies suggest that the thin crust characteristic of the basin and range province extends eastward beneath the west margin of the colorado plateau and rocky mountain regions in arizona and utah zones perhaps over 100 km wide may be defined bounded on the west by the east limit of upper crustal normal faults that account for more that 10 extension and on the east by the east limit of thinning beneath the colorado plateau a discrepancy exists within these zones between the negligible extension measurable in the upper crust and the substantial extension apparent from crustal thinning assuming the discrepant zone crust was as thick as or thicker than the colorado plateau rocky mountain crust prior to extensional tectonism if various theories appealing to crustal erosion are dismissed mass balance problems evident in the discrepant zones are most easily resolved by down to the east normal simple shear of the crust moving lower and middle crustal rocks that initially were within the zones up and to the west to where they now are locally exposed in the basin and range province west of the discrepant zones in both arizona and utah east directed extensional allochthons with large displacement are exposed these geophysical and geological observations complement one another if it is accepted that the entire crust in both arizona and utah failed during extension on gently east dipping east directed low angle normal faults and shear zones over a region several hundred kilometres wide large scale uniform sense normal simple shear of the crust suggests the entire lithosphere may do the same such a hypothesis predicts major lithospheric thinning without crustal thinning will occur in plateau areas in the direction of crustal shear in the case of the arizona utah and red sea extensional systems and possibly the death valley extensional terrain a broad topographic arch typically 1500 2000 m higher than the extended terrain is present suggesting lithospheric thinning in areas predicted by the hypothesis

contribution of induced and remanent magnetization to long wavelength oceanic magnetic anomalies the magsat mission has provided very precise measurements of earth s magnetic field which have been used to derive accurate maps of the long wavelength magnetic anomaly field analyses of this field over localized areas have shown that induced magnetization is mainly responsible for the anomalies and that remanent magnetization is rarely detectable at magsat altitude a careful analysis of the data taking into account the various effects due to non lithospheric sources allows this field to be better described and consequently suggests two observations 1 long wavelength oceanic anomalies display many similarities with the distribution of seafloor topography suggesting a relationship between crustal thickening and magnetization enhancement 2 age related pattern i e ridge parallel of anomalies is observed in two of the larger oceanic basins indian and north atlantic oceans several forward models are constructed to investigate these correlations in the first model the effect of variations in crustal thickness was modeled assuming uniform susceptibility and that thickness varies proportionally to the seafloor topography in the second model the field due to remanent magnetization acquired during the cretaceous long normal period was modeled and shown to contribute significantly to the magsat field in order to make the modeled and observed maps fully comparable several effects must be taken into account a global magnetization contrast exists between oceans and continents and induces widely distributed anomalies because of the truncated spherical harmonic analysis the spectral content of the observed map in the north south direction is reduced because of the along track filtering due to the polar orbit of magsat when these effects are taken into account the model combining the contribution of induced and remanent magnetization display remarkable similarity to observed data this comparison constrains both induced and remanent magnetization of oceanic lithospheric rocks

seafloor spreading anomalies in the magsat field of the north atlantic we show that a simple magnetization model for the crust of the north atlantic basin will explain the major anomalies of the magsat intermediate wavelength magnetic field over the basin our seafloor spreading model incorporates anomalous skewness and enhanced magnetization near the spreading axis and at the cretaceous quiet zones the anomalies over the young oceanic crust indicate a decrease in susceptibility away from the spreading axis the enhanced magnetization over the cretaceous quiet zone could be due to an increased main field intensity or a change in the spreading center processes during the cretaceous though similar observations are not readily apparent for other basins the north atlantic correlation indicates that an investigation of the remanent magnetization of the ocean crust could provide a standard for the evaluation of the intermediate wavelength magnetic field the models presented in this paper demonstrate that a sizable percentage of the intermediate wavelength energy in the magsat field is derived from sources within the earth s crust it also demonstrates that remanent magnetization is an important source of the magsat field over oceanic areas we seek to demonstrate in this paper that although components of the main field are likely to contribute to the intermediate wavelength scalar field we can correlate the anomaly field over the north atlantic to the well studied thermal remanent magnetization of the oceanic crust with a minor component of induced magnetization associated with younger oceanic crust

water quality and sediment geochemistry in lakes of yunnan province southern china yungui plateau lakes in southwestern china are economically important although few have been studied previously water and sediments of 24 lakes throughout yunnan province were sampled in october 1994 we describe the chemical and physical characteristics of yunnan lakes and address effects of regional geology and human influences on water quality and sediment type water quality differs between deep yunnan lakes of tectonic origin and shallow solution basins shallow lakes generally have higher nutrient concentrations and appear to be more susceptible to riparian disturbance than deeper lakes shallow lakes with high macrophyte standing crops nevertheless exhibit nutrient poor waters principal ions ca2 mg2 and hco3 reflect regional carbonate geology except in cheng hai which is a sodium bicarbonate lake specific conductance and 18o are positively correlated indicating that evaporation concentrates both solutes and 18o large shallow lakes in southeastern yunnan exhibit 18o enriched waters because of substantial evaporation whereas small deep lakes are 18o depleted lake waters are 18o depleted in small shallow basins that receive substantial rainwater input relative to their small volumes 18o enrichment in cheng hai suggests that a recent 5 m water level decline in this lake was caused by increased evaporation or diversion of freshwater inflow yunnan watersheds have undergone substantial deforestation agricultural cultivation soil erosion and industrialization limnetic nutrient concentrations indicate that human activities have affected water quality organic matter content is low in sediments because of increased non carbonate clastic sediment yield from watersheds environmental policies are needed to balance ecological contraints with economic activities that impact water quality

band limited global scalar magnetic anomaly map of the earth derived from magsat data the magnetometer satellite magsat data are separated into two distinct sets the dawn and the dusk sets the two sets are analyzed independently because of the dawn dusk asymmetry of the external magnetic field components of the data two scalar magnetic anomaly maps the dawn and the dusk maps are derived using the spherical harmonic expressions of the respective data set the significant correlation of the two maps in the harmonic range of 18 41 indicates the repeatability of the magsat data in these harmonics the shortest repeatable wavelength is about 920 km a band limited global scalar magnetic anomaly map is derived at about 410 km altitude by arithmetic averaging of the dawn and the dusk maps the map is then downward continued to about 10 km altitude the downward continued magnetic anomalies are relatively more localized the main features of the anomalies are as follows 1 continents have relatively stronger magnetic anomalies than oceans especially the younger oceans 2 many circum pacific subduction zones have magnetic signatures and 3 there is no overall correlation between anomalies and major shields