delineation of groundwater potential zones in araniar river basin tamil nadu india an integrated remote sensing and geographical information system approach the paper presents the development of a groundwater potential index gwpi map of the araniar river basin india through an overlay analysis of climatic geologic geomorphic soil and land use land cover features of the basin using landsat5 thematic mapper tm data and arcgis9 2 a correlation analysis of the developed gwpi map was carried out with a yield map of the basin to standardize the weights assigned to each theme a maximum correlation coefficient of 0 922 was obtained when rainfall geology soil slope geomorphology and land use land cover maps were overlaid with standardized weights of 0 49 0 20 0 17 0 05 0 05 and 0 04 respectively the gwpi map showed groundwater potential zones as excellent very good good moderate and poor with yield values in the ranges 293 361 210 292 126 209 43 125 and 15 42 lpm respectively the analysis of post and pre monsoon water table depths also showed pronounced groundwater level fluctuations in the central and eastern part of the basin the gwpi map when combined with the post and pre monsoon water table depth maps may also help in locating suitable sites for artificial recharge for effective and efficient groundwater resource exploration and management of the basin

rock magnetic properties and relative paleointensity stack between 13 and 24 kyr bp calibrated ages from sediment cores lake moreno patagonia argentina we conducted a detailed study of natural remanence and rock magnetic properties on three sediment cores from lake moreno patagonia argentina based on these measurements we constructed a relative paleointensity stack for the period 13 24 kyr bp calibrated ages rock magnetic properties of the sediment cores showed uniform magnetic mineralogy and grain size suggesting that they were suitable for relative paleointensity studies the remanent magnetisation at 20 mt nrm20 mt was normalised using the anhysteretic remanent magnetisation at 20 mt arm20 mt the saturation of the isothermal remanent magnetisation at 20 mt sirm20 mt and the low field magnetic susceptibility k spectral analysis showed that the normalised records were not affected by local environmental conditions the recorded pseudothellier paleointensity was compared with records obtained from conventional normalising methods comparing the paleointensity curves with others obtained previously in other lakes in the area has allowed us to reach reliable conclusions about centennial scale features 2008 elsevier b v all rights reserved

evidence for multiple paleomagnetic intensity lows between 30 and 50 ka bp from a western equatorial pacific sedimentary sequence abstract a paleomagnetic study was carried out on the radiocarbon dated md97 2134 core located in the western equatorial pacific southern papua new guinea margin rock magnetic investigations revealed changes of the magnetic mineralogy along the hemi pelagic sedimentary sequence but the reconstruction of past direction and relative paleointensity variations of the geomagnetic field remained feasible four successive paleointensity drops are recorded between 30 and 50 ka bp the largest one is associated with an abrupt swing of declination and inclination interpreted as a smoothed signature of the laschamp excursion 41 ka bp the succession of four events of weak intensity between 30 and 50 ka bp introduces a complex behaviour of the geomagnetic field in the time interval spanning over the laschamp and the mono lake excursions

integration of ground subsidence hazard maps of abandoned coal mines in samcheok korea integrated techniques were developed applied and validated for the analysis of ground subsidence hazards by abandoned coal mines in samcheok korea using a geographic information system gis slope depth of drift distance from drift groundwater level permeability geology and land use were extracted or calculated from the digital elevation model topographic drift distribution borehole geologic and land use database by using the constructed spatial database the relations between the ground subsidence location and seven related factors were identified and quantified by frequency ratio fr weights of evidence woe logistic regression lr and artificial neural network ann models the relations were used as factor ratings in the overlay analysis to create ground subsidence hazard indices and maps the four ground subsidence hazard maps were reflected as the new input factors and integrated using fr woe lr and ann models to make a hazard map all of the subsidence hazard maps were validated by comparison with known ground subsidence locations that were not used in the analysis as a result the integrated ground subsidence hazard maps used four new subsidence related input factors that showed a greater accuracy 96 46 for fr 97 22 for woe 97 20 for lr and 96 70 for ann respectively than the individual ground subsidence maps 95 54 for fr 94 22 for woe 96 89 for lr and 94 45 for ann respectively using the first seven factors

delineation of groundwater potential zone in chhatna block bankura district west bengal india using remote sensing and gis techniques groundwater is one of the most valuable natural resources which is an immensely important and dependable source of water supply in all climatic regions over the world groundwater is in demand in areas where surface water supply is inadequate and nonsexist in the chhatna block bankura district and is located on the eastern slope of chotonagpur plateau which is mapped on 73 i 15 73 i 16 and 73 m 3 and falls between latitude 23 10 23 30 n and longitude 86 47 87 02 e it represents plain land and gentle slope which is responsible for infiltration and groundwater recharge the groundwater in this region is confined within the fracture zones and weathered residuum the present investigation is therefore undertaken to delineate potential zones for groundwater development with the help of a remote sensing study irs liss iii data along with other data sets e g existing toposheets and field observation data have been utilized to extract information on the hydrogeomorphic features which include valley fills buried pediment moderate buried pediment shallow and structural hills lineament density contour and slope map of this hard rock terrain the target of this study is to delineate the groundwater potential zones in chhatna block bankura district west bengal satellite imagery along with other data sets has been utilized to extract information on the groundwater controlling features of this study area three features hydrogeomorphology slope and lineaments that influence groundwater occurrences were analyzed and integrated all the information layers have been integrated through gis analysis and the groundwater potential zones have been delineated the weighted index overlay method has been followed to delineate groundwater potential zones the results indicate that good to excellent groundwater potential zones are available in almost the entire block the results show that there is good agreement between the predicted groundwater potential map and the existing groundwater borehole databases the area is characterized by hard rock terrain still due to the presence of planation surface along valley fills it became the prospective zone the area has been categorized into four distinct zones excellent good fair and poor excellent groundwater potential zones constitute 30 35 of the total block area good groundwater potential zones occupy a majority of the block covering approximately 55 60 and the fair potential zones occupy about 10 15 of the total block poor potential zones occupy a very insignificant portion less than 1

gis based groundwater spring potential mapping in the sultan mountains konya turkey using frequency ratio weights of evidence and logistic regression methods and their comparison summary in this study groundwater spring potential maps produced by three different methods frequency ratio weights of evidence and logistic regression were evaluated using validation data sets and compared to each other groundwater spring occurrence potential maps in the sultan mountains konya turkey were constructed using the relationship between groundwater spring locations and their causative factors groundwater spring locations were identified in the study area from a topographic map different thematic maps of the study area such as geology topography geomorphology hydrology and land use cover have been used to identify groundwater potential zones seventeen spring related parameter layers of the entire study area were used to generate groundwater spring potential maps these are geology lithology fault density distance to fault relative permeability of lithologies elevation slope aspect slope steepness curvature plan curvature profile curvature topographic wetness index stream power index sediment transport capacity index drainage density distance to drainage land use cover and precipitation the predictive capability of each model was determined by the area under the relative operating characteristic curve the areas under the curve for frequency ratio weights of evidence and logistic regression methods were calculated as 0 903 0 880 and 0 840 respectively these results indicate that frequency ratio and weights of evidence models are relatively good estimators whereas logistic regression is a relatively poor estimator of groundwater spring potential mapping in the study area the frequency ratio model is simple the process of input calculation and output can be readily understood the produced groundwater spring potential maps can serve planners and engineers in groundwater development plans and land use planning

a new rock magnetic approach to selecting sediments for geomagnetic paleointensity studies application to paleointensity for the last 4000 years the hypothesis that the ratio of detrital remanent magnetization to anhysteretic remanent magnetization drm arm for sediment samples is a measure of relative geomagnetic paleointensity is critically evaluated by two distinct approaches one approach is a detailed rock magnetic examination of the implicit assumptions of the drm arm method and the construction of a selection process by which to identify sediments that conform to requirements satisfying these assumptions sediments are uniform with respect to drm arm ratio if they contain magnetite in the 1 15 ym particle size range as the predominant magnetic mineral and have variations in magnetite content of less than 20 30 times the minimum concentration the drm arm ratios of these sediments should provide estimates of relative geomagnetic paleointensity relative particle size variations in magnetite are detected with a plot of anhysteretic susceptibility xarm versus low field susceptibility x and the size range 1 15 m is approximately identified by high field hysteresis parameters a rock magnetic evaluation of leboeuf lake sediments with these techniques indicates that these sediments are suitable for a relative plaeointensity study the second approach to evaluating the drm arm ratio as a measure of relative paleointensity is direct comparison with absolute paleointensity data a comparison between the leboeuf lake estimates and thellier thellier results from the western united states supports the conclusion that suitable sediments can record geomagnetic paleointensity fluctuations

sedimentary records of relative paleointensity of the geomagnetic field theory and practice sediments have proved irresistible targets for attempts at determining the relative variations in the earth s magnetic field because of the possibility of long and continuous sequences that are well dated and have a reasonable global distribution the assumption underlying paleointensity studies using sedimentary sequences is that sediments retain a record reflecting the strength of the magnetic field when they were deposited early theoretical work suggested that because the time required for an assemblage of magnetic particles in water to come into equilibrium with the ambient magnetic field was quite short no dependence on magnetic field was expected nonetheless a number of experiments showed that sedimentary magnetizations varied in accordance with the field albeit not always in a simple linear fashion experiments in which the sediments were stirred in the presence of a field to simulate bioturbation showed a reasonably linear relationship with the applied field and these results spurred the hope that variations in the earth s magnetic field might indeed be recoverable from appropriate sedimentary sequences examination of existing paleointensity data sets allows a few general conclusions to be drawn it appears that sedimentary sequences can and do provide a great deal of information about the variations in relative paleointensity of the earth s magnetic field the dynamic range of sedimentary data sets is comparable to those acquired from thermal remanences moreover when compared directly with such independent measures of magnetic field variations as beryllium isotopic ratios and thermally blocked remanences there is considerable agreement among the various records when viewed over timescales of hundreds to thousands of years relative paleointensity data sets from more than a few thousand kilometers apart bear little resemblance to one another suggesting that they are dominated by nondipole field behavior when viewed over timescales of a few tens of thousands to hundreds of thousands of years however the records show coherence over large distances at least thousands of kilometers and may reflect changes in the dipole field on the basis of a sequence spanning the brunhes and matuyama chrons the magnetic field has oscillated with a period of about 40 ka for the last few hundred thousand years but these oscillations are not clear in the record prior to about 300 ka thus they are probably not an inherent feature in the geomagnetic field and the correspondence of the period of oscillation to that of obliquity is probably coincidence

geomagnetic paleointensity dating of south china sea sediments for the last 130 kyr relative paleointensity records from the northern south china sea northwest pacific ocean were studied in two gravity piston cores continuous mineral magnetic and paleomagnetic measurements were made using discrete sediment samples detailed rock magnetic parameters such as thermomagnetic and high field hysteresis data indicate that pseudo single domain magnetite in a narrow range of grain size and concentration is the main contributor to the remanent magnetization the uniform magnetic mineralogy meets the commonly accepted criteria for establishing relative paleointensity records the relative paleointensity rpi curves were constructed by normalizing the natural remanent magnetization nrm with isothermal remanent magnetization irm both in the 20 60 mt demagnetization state dating constraints have been provided by radiocarbon ages in the upper 400 cm of both cores furthermore we have correlated our paleointensity records with napis 75 s atlantic 1089 sint 200 and nopapis 250 to determine the chronological rpi framework for the south china sea scs pis although some temporal offsets of paleointensity features between the different records have been recognized their similar shape suggests that relative paleointensity on the 10 3 10 4 year scale is globally coherent and can provide an age framework for sediments independent of delta 18 o ages c 2009 elsevier b v all rights reserved

geomagnetic paleointensity for the last 100 kyr from the sub antarctic south atlantic a tool for inter hemispheric correlation abstract we report relative paleointensity proxy records from four piston cores collected near the agulhas ridge and meteor rise south atlantic the mean sedimentation rate of the cores varies from 24 cm kyr to 11 cm kyr the two cores with mean sedimentation rates over 20 cm kyr record positive remanence inclinations at 40 41 ka coeval with the laschamp event age models are based on oxygen isotope data from three of the cores augmented by radiocarbon ages from nearby core rc11 83 and by correlation of paleointensity records for the one core with no oxygen isotope data the relative paleointensity proxy records are the first from the south atlantic and from the high to mid latitude southern hemisphere prominent paleointensity lows at 40 ka and 65 ka as well as many other features can be correlated to paleointensity records of comparable resolution from the northern hemisphere the records are attributable in large part to the global scale field and therefore have potential for inter hemispheric correlation at a resolution difficult to achieve with isotope data alone

evidence for a geomagnetic excursion recorded in the sediments of lac st front france a link with the laschamp excursion anomalous paleomagnetic directions accompanied by low intensities of natural remanent magnetization are recorded at 17 m depth in the sediments cored from lac st front massif central france the rock magnetic properties and the parameters characterizing anisotropy of susceptibility of samples taken from the sediment horizons carrying these anomalous directions spanning some 30 40 cm are identical to those of samples taken from the other stratigraphic intervals carrying a record of normal geomagnetic secular variation therefore the sequence of anomalous directions is interpreted as a geomagnetic excursion furthermore it is concluded that this excursion occurred at a time when the paleointensity field was low the excursion is dated at about 33 14c 37 ka b p by correlating the susceptibility and paleomagnetic logs from lac st front with the corresponding logs from the nearby lac du bouchet sedimentary sequence the excursional directions in lac st front can be averaged out with a triangular window of 20 cm these smoothed excursional directions resemble the directional variations observed in the corresponding lac du bouchet interval this finding indicates that the absence of this excursion in lac du bouchet may be due to a larger smoothing of the geomagnetic signal

geomagnetic field evolution during the laschamp excursion abstract since the last geomagnetic reversal 780 000 years ago the earth s magnetic field repeatedly dropped dramatically in intensity this has often been associated with large variations in local field direction but without a persistent global polarity flip the structure and dynamics of geomagnetic excursions and especially the difference between excursions and polarity reversals have remained elusive so far for the best documented excursion the laschamp event at 41 000 years bp we have reconstructed the evolution of the global field morphology by using a bayesian inversion of several high resolution palaeomagnetic records we have obtained an excursion scenario in which inverse magnetic flux patches at the core mantle boundary emerge near the equator and then move poleward contrary to the situation during the last reversal leonhardt r fabian k 2007 paleomagnetic reconstruction of the global geomagnetic field evolution during the matuyama brunhes transition iterative bayesian inversion and independent verification earth planet sci lett 253 172 195 these flux patches do not cross the hydrodynamic boundary of the inner core tangent cylinder while the last geomagnetic reversal began with a substantial increase in the strength of the non dipolar field components prior to the laschamp excursion both dipolar and non dipolar field decay at the same rate this result suggests that the nature of an upcoming geomagnetic field instability can be predicted several hundred years in advance even though during the laschamp excursion the dipolar field at the earth s surface was dominant the reconstructed dynamic non dipolar components lead to considerable deviations among predicted records at different locations the inverse model also explains why at some locations no directional change during the laschamp excursion is observed

combining geophysical techniques and multi criteria gis based application modeling approach for groundwater potential assessment in southwestern nigeria a new approach of modeling very low frequency electromagnetic vlf em and vertical electrical sounding ves data with a view of evaluating groundwater resources potential via application of gis based multi criteria technique is investigated in this study on eight vlf em traverses established in the site 40 ves locations were combed the acquired geophysical data vlf em and ves were processed applying fraser karous hjelt filter and win resist program geophysical software to determine the area subsurface geophysical parameters five hydrogeologic maps were produced based on the results of the interpreted geophysical parameters the produced hydrogeologic maps were assigned suitable weights and different rankings to the individual classes boundary within the maps using the standard saaty s scale principle in the context of analytical hierarchy process ahp data mining technique a raster based empirical gis model was developed for integrating the hydrogeologic maps to compute the groundwater potential index gwpi values in the range of 1 02 2 82 for the study area based on the estimated gwpi results a final map zoning the area into low 0 0930 1 3922 medium 1 3922 1 9109 and high 1 9109 2 8173 groundwater potential classes was produced in gis environment the prediction accuracy of the produced potential map was established via cross validation and in situ well correlation analysis the results of the study established a new approach of modeling geophysical data for exploring groundwater productivity potential in the study area

northeastern pacific oxygen minimum zone variability over the past 70 kyr impact of biological production and oceanic ventilation 1 during the last glacial period the oxygen minimum zone omz within the northeastern pacific ocean strengthened and weakened on a millennial time scale demonstrating a tight linkage with northern high latitude climate although the precise mechanisms responsible remain unknown core md02 2508 retrieved off baja california was analyzed for major and trace elements br ca ti fe mn and sr using a xrf scanner and redox sensitive trace elements cu ni cd as v cr mo and u using the icp ms the trace element content the fe ti ratio and br based organic carbon exhibit higher values during the holocene and during warm dansgaard oeschger events than during the last glacial maximum lgm stadials and heinrich h events a principal component analysis of the element al ratio indicated that the following two main factors controlled the chemical composition of the sediments 1 export production as represented by organic carbon that was lower during cold periods and 2 regional intermediate water oxygenation as represented by u and mo variability that was not supported by a change in export production the latter suggests that intermediate water oxygenation improved during h events but slightly deteriorated during late marine isotope stage mis 3 and mis 2 a local biogeochemical effect forced by atmospheric processes impacted the lgm and h events in the same manner whereas regional intermediate oceanic circulation varied in an opposite manner during the lgm and h events possibly as a result of the global reorganization of intermediate water circulation during the lgm

overview of the shuttle imaging radar b preliminary scientific results the shuttle imaging radar b experiment consisted of a large number of scientific investigations in the earth sciences nine oceanographic experiments were conducted to study the generation and propagation of surface waves the dynamics of internal waves oil slick detection and the properties of southern polar ice stereo imaging from space allowed three dimensional viewing of surface features geologic experiments were conducted to study subsurface penetration structural mapping and lithologic classification imaging radar angular scatterometry was used in the vegetation cover forest type and urban areas classification experiments this article provides an overview of the scientific results some of which are also presented in this issue

chlorine 36 evidence for the mono lake event in the summit grip ice core abstract a distinct peak has been discovered in the 36 cl data from the grip ice core between the dansgaard oeschger d o events 6 and 7 at approximately 32 kyr bp this peak can be attributed to a minimum of the geomagnetic dipole field associated with the mono lake event since the 36 cl peak reflects a higher production rate of all cosmogenic radionuclides it has an impact on the 14 c dating of the last ice age furthermore it provides an additional time marker similar to a peak found earlier corresponding to the laschamp event at approximately 39 kyr bp

timing of quaternary geomagnetic reversals and excursions in volcanic and sedimentary archives abstract we review the ages of quaternary magnetic polarity reversals and magnetic excursions improvements in radioisotopic 40ar 39ar dating of reversals and excursions reflect the use of multi collector mass spectrometers along with ultra low backgrounds laser based incremental heating methods and adoption of 28 201 ma for the fish canyon sanidine fcs standard age kuiper et al 2008 these improvements have brought 40ar 39ar ages of reversals and excursions into close correspondence with astrochronological ages based on the correlation of 18o data to lr04 lisiecki and raymo 2005 and in a few cases correlation to ice core chronologies ages of two polarity reversals the matuyama brunhes boundary and base olduvai are at odds with ages given in popular geomagnetic polarity timescales sedimentary records of the laschamp and iceland basin excursion are numerous and widespread and attest to global manifestation and global synchronicity of these excursions records of other quaternary excursions are less numerous the blake excursion 115 ka has been recorded in north atlantic sediments chinese loess indian ocean volcanics and spanish speleothems the santa rosa excursion 932 ka has been recorded in north atlantic and phillipine basin sediments as well as in volcanic rocks from new mexico and galapagos the punaruu excursion 1115 ka has been observed in sediments from the north atlantic and california margin as well as in volcanic rocks on tahiti uniformity of individual excursion ages using astrochronological 40ar 39ar and u th methods argues for synchronous global manifestation of excursions strengthening the usefulness of magnetic excursions and reversals in quaternary stratigraphy

mono lake excursion in mono basin california and at carson sink and pyramid lake nevada summary a restudy of the mono lake excursion in the mono basin california using two new localities 20 km apart shows that the palaeomagnetic record in the basin is the most complete and accurate for the entire excursion the excursion is also recorded in exposed sediment from pleistocene lake lahontan in northwestern nevada about 250 km north of the mono basin sampling of the lake lahontan sediment was done at pyramid lake and in the carson sink following the initial discovery of the mono lake excursion by denham cox 1971 liddicoat coe 1979 showed that the excursion consists of two parts split by a volcanic ash bed at pyramid lake and in the carson sink the older half of the excursion is not recorded but the younger half can be recognized two factors appear to have contributed to the partial recording of the excursion at pyramid lake and in the carson sink 1 the relative strength of the palaeomagnetic field low during the older half of the excursion and high during the younger half and 2 the slower sedimentation in lake lahontan estimated to be about half the rate of deposition for the lacustrine sediment in the mono basin tephrochronology and carbon 14 dates indicate an age of 28 000 yr for the middle of the mono lake excursion on the assumption that the sedimentation rate was a constant 25cm kyr 1 in the mono basin the span of the full excursion is about 2000 yr

paleointensity of the earth s magnetic field during the laschamp excursion and its geomagnetic implications the reversed paleomagnetic direction of the laschamp and olby flows represents a specific feature of the geomagnetic field this is supported by paleomagnetic evidence showing that the same anomalous direction was recorded at several distinct sites including scoria of the laschamp volcano to examine this anomalous geomagnetic fluctuation we studied the paleointensity of the laschamp and olby flows using the thellier method twenty five samples were selected for the paleointensity experiments and from seven we obtained reliable results because the paleointensity results of the olby and laschamp flows as well as laschamp scoria are very similar they can be represented by a single mean paleointensity f 7 7 t considering that this low paleointensity is less than 1 6 of the present geomagnetic field and is more characteristic of transitional behavior our results suggest that the paleomagnetic directions of the laschamp and olby flows were not acquired during a stable reversed polarity interval a more likely explanation is that the laschamp excursion represents an unsuccessful or aborted reversal

magnetic properties of sedimentary greigite fe3s4 new data are presented here that document the previously poorly known magnetic characteristics of sedimentary greigite fe3s4 several diagnostic magnetic properties can be used in conjunction to rapidly screen sediments to detect the presence of greigite such discriminants are necessary because greigite displays a similar or higher range of coercivities compared to most ferrimagnetic minerals and the commonly used method of alternating field demagnetization cannot be used to distinguish between palaeomagnetic remanence components due to greigite and other ferrimagnetic minerals sedimentary greigite has high ratios of the saturation isothermal remanent magnetization to magnetic susceptibility mrs which are accompanied by hysteresis ratios of mrsms 0 5 and bcr bc 1 5 ms is the saturation magnetization bc is the coercive force and bcr is the coercivity of remanence greigite has no low temperature phase transition whereas the ferrimagnetic iron sulphide pyrrhotite undergoes a major phase transition at about 34 k and unoxidized magnetite displays the verwey transition at 118 k low temperature measurements may therefore prove valuable in distinguishing between magnetite pyrrhotite and greigite although the absence of a low temperature transition cannot be taken as definitive evidence for the presence of greigite greigite also displays characteristic high temperature behaviour with a major drop in magnetization between 270 and 350 c determination of the mrs ratio is an excellent means of rapidly screening sediments to identify stratigraphic intervals that may contain greigite subsequent low and high temperature analyses can then provide unambiguous identification of greigite and enable the evaluation of the presence of other magnetic minerals

on the age of the laschamp geomagnetic excursion abstract the laschamp geomagnetic excursion is a critical tie point found directly in deep sea sediment cores and revealed in polar ice as an abrupt change in the rate of cosmogenic nuclide flux despite the importance of this excursion to quantifying paleoclimate proxy records archived in sediment and ice and to providing an independent calibration of the radiocarbon calendar its timing remains poorly known previous k ar 40 ar 39 ar and u th isochron determinations from lava flows at the type locality in the massif central france vary widely are imprecise and suggest a mean age of about 46 2 2 5 ka 2 results of 6 new unspiked k ar and 13 40 ar 39 ar incremental heating experiments on subsamples from three sites on the laschamp and olby flows are concordant and give a weighted mean age of 40 4 1 1 ka 2 uncertainty including analytical sources only that is 10 younger than the previous estimates considering that the 40 k 40 ar decay constant is not known to a precision better than 2 4 the most probable radioisotopic age for the laschamp excursion is 40 4 2 0 ka 2 analytical plus decay constant uncertainties this new age for the laschamp excursion agrees precisely with that deduced from the napis 75 deep sea sediment paleointensity stack when calibrated against the gisp2 ice core chronology using the o isotopes in ice and the magnetic properties of the marine cores

geomagnetic moment variation and paleomagnetic excursions since 400 kyr bp a stacked record from sedimentary sequences of the portuguese margin abstract a paleomagnetic study was performed in clayey carbonate sedimentary sequences deposited during the last 400 kyr on the portuguese margin northeast atlantic ocean declination and inclination of the stable remanent magnetization present recurrent deviations from the mean geomagnetic field direction the normalized intensity documents a series of relative paleointensity rpi lows recognized in other reference records three directional anomalies occurring during rpi lows chronologically correspond to the laschamp excursion 42 kyr bp the blake event 115 122 kyr bp and the icelandic basin excursion 190 kyr bp a fourth directional anomaly recorded at 290 kyr bp during another rpi low defines the portuguese margin excursion four non excursional rpi lows are recorded at the ages of the jamaica pringle falls mamaku calabrian ridge 1 and levantine excursions the rpi record is characterized by a periodicity of 100 kyr paleointensity lows often coinciding with the end of interglacial stages this record sets the basis of the construction of an authigenic 10be 9be record from the same sedimentary sequences carcaillet et al this issue

inferring the heterogeneity transmissivity and hydraulic conductivity of crystalline aquifers from a detailed water table map abstract estimating the transmissivity or hydraulic conductivity field to characterize the heterogeneity of a crystalline aquifer is particularly difficult because of the wide variations of the parameters we developed a new approach based on the analysis of a dense network of water table data it is based on the concept that large scale variations in hydraulic head may give information on large scale aquifer parameters the method assumes that flux into the aquifer is mainly sub horizontal and that the water table is mostly controlled by topography rather than recharge it is based on an empirical statistical relationship between field data on transmissivity and the inverse slope values of a topography reduced water table map this relationship is used to compute a transmissivity map that must be validated with field measurements the proposed approach can provide a general pattern of transmissivity or hydraulic conductivity but cannot correctly reproduce strong variations at very local scale less than10 m and will face of some uncertainties where vertical flows cannot be neglected the method was tested on a peridotite ultramafic rock aquifer of 3 5 km 2 in area located in new caledonia the resulting map shows transmissivity variations over about 5 orders of magnitude average logt 5 2 0 7 comparison with a map based on measured water level data n 475 shows that the comparison between logt computed values and logt data deduced from 28 hydraulic tests is estimated with an error less than 20 in 71 of cases logt 0 4 and with an error less than 10 logt 0 2 on average in 39 of cases from this map a hydraulic conductivity map has been computed showing values ranging over 8 orders of magnitude the repeatability of the approach was tested on a second data set of hydraulic head measurements n 543 the mean deviation between both logt maps is about 11 these encouraging results show that the method can give valuable parameter estimates and can characterize aquifer heterogeneity the computed logt and logk maps highlight the spatial distribution of parameters that show a pattern clearly controlled by the fault network of this ultramafic massif however the faults are mainly characterized by low permeability zones this differs from results on other crystalline aquifers and may be due to the fact that weathering products of peridotite are clay like materials the resulting transmissivity map can be used as a starting point for modelling or to direct additional fieldwork

gis based multi criteria analysis and vulnerability method for the potential groundwater recharge delineation case study of manouba phreatic aquifer ne tunisia groundwater resources in semi arid climate like manouba region north of tunisia have experienced deterioration of available water resources in terms of both quantity and quality managers and water engineers developed techniques to compensate for the high exploitation and remedy the poor quality of groundwater resources one of the most important solutions is to focus on the recharge capacity of the aquifer this paper aims to locate potential groundwater recharge areas using the multi criteria approach delineation of groundwater potential recharge zones relies on physical parameters and groundwater vulnerability geographical information system can provide tools for handling multidisciplinary data used for each parameter in this work weighting coefficients attributed for parameters are assigned based on local conditions in the region using the analytic hierarchy process by applying the intelligent decision system software results show that most of the study area has a groundwater recharge rate potentially moderate to high only 24 of the study area have low groundwater recharge rate located especially in sebkhat essijoumi and its vicinity that mainly match to the least permeable and hilly areas considering both the vulnerability to pollution and the potential groundwater recharge capacity the most suitable recharge sites are located in the north west of the study area

re evaluation of greek archaeomagnitudes a new technique is used to determine the secular variation of the geomagnetic ancient field in athens the results indicate that published greek archaeomagnitudes were seriously affected by alteration it is shown that all intensities obtained using modifications of the thellier method may be affected by alteration and are therefore suspect

archeomagnetic results from southwest united states and mesoamerica and comparison with some other areas abstract archeomagnetic am results from southwestern united states can be represented by an archeomagnetic apparent polar curve aapc that is distributed near the axis of rotation and contained within 75 n latitude the aapc for the past 1600 yr is located mostly on the near side with mainly easterly declinations it is characterized by loops extending outward from the axis of rotation about 10 15 every 250 300 yr at 1350 1100 800 500 and 200 ad inclination of the magnetic field varied from a minimum of 40 to a maximum of 62 with maximum values occurring at 600 1100 1350 ad and modern minimum values occurred at 800 1250 and 1500 ad declination ranged from 18 e to 14 w with maximum easterly values occurring at 500 ad and during the nineteenth century the most westerly declination occurred about 1100 ad the maximum and minimum values of declination and inclination correspond in age with loop like extension of the aapc archeomagnetic paleointensity results suggest changes from 1 5 to 0 8 times the present field with variations occurring generally in unison with the changes in direction comparison of archeomagnetic data from mesoamerica england france japan bulgaria and china with the data from the southwest united states suggests some similarities and dissimilarities of the spatial and temporal position of the aapc early age archeomagnetic results to 8500 bc from the united states confirm a similar pattern of secular variation and limit the time of the most recent reversal some available global data suggest that 200 ad may have been a time of small divergence from an axial field inclined by 7 5 from the rotational axis

geomagnetic assisted stratigraphy and sea surface temperature changes in core md94 103 southern indian ocean possible implications for north south climatic relationships around h4 abstract new records of past sea surface temperatures ssts were derived in the 30 50 kyr b p time interval from a core located at 45 s in the southern indian ocean md94 103 to investigate the climatic phasing between the southern indian ocean the greenland and the antarctic ice the magnetic signal of core md94 103 was synchronized at better than millennial accuracy in the vicinity of the laschamp geomagnetic to a reference record napis 75 already placed on the gisp2 age model coccolithophorid and diatom species abundances both point to a cooling of surface waters during h4 specific diatoms also indicate lower salinity waters during the same time interval these observations do not support the idea that the south hemisphere warmed 1 5 2 kyr before the north hemisphere nature 394 1998 739 rather alkenone derived ssts suggest that cold conditions have characterized the surface waters in the south latitudes during h4 and h5 and that temperature at evaporation sites contributed to the isotopic events a1 and a2 visible in the isotopic records of central antarctica earth planet sci lett 177 2000 219 ssts obtained from foraminifera assemblages depict somewhat different temperature patterns possibly indicative of water stratification

geospatial and geostatistical approach for groundwater potential zone delineation over the past few decades groundwater has become an essential commodity owing to increased demand as a result of growing population industrialization urbanization and so on the water supply situation is expected to become more severe in the future because of continued unsustainable water use and projected change in hydrometeorological parameters due to climate change this study is based on the integrated approach of remote sensing geographical information system and multicriteria decision making techniques to determine the most important contributing factors that affect the groundwater resources and to delineate the groundwater potential zones ten thematic layers namely geomorphology geology soil topographic elevation digital elevation model land use land cover drainage density lineament density proximity of surface water bodies surface temperature and post monsoon groundwater depth were considered for the present study these thematic layers were selected for groundwater prospecting based on the literature discussion with the experts of the central ground water board government of india field observations geophysical investigation and multivariate techniques the thematic layers and their features were assigned suitable weights on saaty s scale according to their relative significance for groundwater occurrence the assigned weights of the layers and their features were normalized by using the analytic hierarchy process and eigenvector method finally the selected thematic maps were integrated using a weighted linear combination method to create the final groundwater potential zone map the final output map shows different zones of groundwater potential namely very good 16 good 35 moderate 28 low 17 and very low 2 1 the groundwater potential zone map was finally validated using the discharge and groundwater depth data from 28 and 98 pumping wells respectively which showed good correlation copyright 2014 john wiley sons ltd

some evidence for sharp changes in the archaeomagnetic intensity variation during the last 2000 years abstract an assessment of archaeomagnetic intensities from greek and bulgarian data sets during the last 2000 years indicates sharp changes in their variation particular emphasis is given to the reliability of these data and the results are discussed in terms of a latitude effect

shuttle imaging radar sir b investigations of the canadian shield initial report two of the 43 shuttle imaging radar sir b experiments carried out from the 41 g shuttle mission in 1984 involved a 2600 km swath across the canadian shield with the objectives of studying the structure of province boundaries and developing techniques for the geologic use of orbital radar despite degraded single incidence angle imagery resulting from system problems valuable experience has been obtained with data over a test site near bancroft ontario it has been found that even subdued glaciated topography can be effectively imaged variations in backscatter being caused by variations in local incidence angle rather than shadowing it has been demonstrated that small incidence angles are more sensitive to topography than large angles backscatter is extremely sensitive to look direction topographic features nearly normal to the illumination being highlighted and those nearly parallel to it being suppressed it is concluded that orbital radar can provide a valuable tool for geologic studies of the canadian shield and similar areas if suitable look angles and at least two look directions can be utilized for each area

south atlantic and north atlantic geomagnetic paleointensity stacks 0 80 ka implications for inter hemispheric correlation recent coring of high deposition rate atlantic sediments has led to the development of north atlantic napis and south atlantic sapis geomagnetic paleointensity stacks the sapis stack comprises five records from the sub antarctic south atlantic 41 471s 6 101e four are from piston cores collected during the ocean drilling program odp leg 177 site survey cruise earth planet sci lett 175 2000 145 the other is odp site 1089 leg 177 j geophys res 2001 submitted for publication all but one 4 pc03 of the sapis cores have oxygen isotope records which are used in conjunction with lithologic and geomagnetic variability to derive an optimized correlation to site 1089 the site 1089 age model is derived by mapping the benthic and planktic isotope data to those from nearby core rc11 83 which has 14 calibrated radiocarbon ages in the 11 41 ka interval below this level the chronology is derived by matching the site 1089 benthic oxygen isotope data to the specmap stack the napis stack comprises six records from a wide area of the north atlantic philos trans r soc ser a 358 2000 1009 correlation between cores was based on marine isotopic stage boundaries augmented by millennial scale features heinrich events and fluctuations in concentration dependent magnetic parameters napis was placed on the gisp2 chronology using the marine to ice core oxygen isotope correlation proposed by voelker et al radiocarbon 40 1998 517 for one of the napis cores in the resulting age model the laschampevent recorded in five of six cores falls in a very narrow o1 kyr age range and coincides with the 10 be and 36 cl peak measured in the ice cores comparison of the two stacks placed on their own independent age models indicates that common millennial scale paleointensity features are preserved although more work is needed to define the true global content of the paleointensity record as well as the precise age of many features it is readily apparent that paleointensity can provide a global correlation tool at a resolution unattainable from isotope data alone r 2002 published by elsevier science ltd

archaeomagnetic paleointensity in the american southwest during the past 2000 years abstract an archaeomagnetic paleointensity study was carried out on pottery samples from the hohokam anasazi and mogollon cultures of the american southwest the thellier thellier paleointensity experiment was used on 187 specimens from 77 different sherds derived from 23 archaeological sites interpretations were made for 127 specimens from 54 sherds about a two thirds success rate the median value for the quality factor was 12 the results were corrected for magnetic anisotropy owing to a fabric in the pottery using an easy plane model of magnetization the anisotropy of the hard axis relative to the easy plane of magnetization averaged 31 the correction factor for the paleointensity was typically 5 4 and systematically increased the paleointensities because the laboratory heatings were applied within the easy plane the sample average paleointensities were compiled along with other data from north america the hohokam data were kept as a separate set because of uncertainties concerning the hohokam chronology curves of the virtual axial dipole moment vadm variation for the hohokam and non hohokam data sets were derived using a moving window smoothing technique the hohokam and non hohokam curves show good agreement regardless of which hohokam chronology is used relative paleointensity records from north american lake sediments are also congruent with the archaeointensity results despite the scatter in the archaeomagnetic data the correlation of these records suggests that the secular variation pattern is being recovered the field strength at 300 bc is 30 40 higher than at present a low from 250 to 1250 ad is 10 15 weaker than at present and a peak at 1500 ad is about 30 higher than at present the low from 250 to 1250 ad in comparison with global paleointensity compilations suggests a substantial non dipole field in north america at that time the rate of change of the archaeomagnetic vadm is similar to rates observed today

incidence angle considerations for spacecraft imaging radar the value of radar imagery for most geologic applications is greatest when obtained with relatively large incidence angles it is infeasible to attain these large angles from spacecraft altitudes a study is being conducted to assess the usefulness of imagery collected at smaller angles radar image simulation is employed to create imagery for platform scenarios at numerous angles of incidence for specific geologic features preliminary analyses and results are provided

research note mono lake excursion in the lahontan basin nevada summary in the lahontan basin of north western nevada the mono lake excursion is recorded in a wave cut bank at pelican point on the west side of pyramid lake the record is almost identical to one across the lake near pyramid island 10 km away and in the carson sink 60 km further to the east at each locality the older half of the excursion is present only as a reduction in the relative field intensity while the younger half shows the expected easterly declination and steep positive inclination that result in a small counterclockwise loop of the virtual geomagnetic poles the younger half occurs during high relative field intensity and the entire intensity pattern is similar to the one for the excursion in the mono basin california 250 km to the south the presence of only part of the mono lake excursion in the lahontan basin might have resulted from the slow sedimentation rate in pyramid lake estimated to be about 12 cm kyr 1 with the field behaviour being more extensively integrated in the subsamples used in an alternate explanation the absence of the older part of the excursion can be attributed to overprinting when magnetic grains that were free to rotate in unconsolidated sediment were realigned during the high relative field intensity in the younger part of the excursion

the geology and geomorphology of the venus surface as revealed by the radar images obtained by veneras 15 and 16 a region by region condensed description of almost all of the area that was radar photographed by veneras 15 and 16 is presented using some generalizations the diversity of terrain was reduced to a discrete set from which a geological morphological map was constructed the predominant type of terrain of the studied area is a plain that was tentatively subdivided into five morphological types ridge and band patchy rolling plain dome and butte plain smooth plain and high smooth plain stratigraphically the ridge and band plains are the oldest and the smooth plains are the youngest the stratigraphic position of the other types is yet to be determined large sections of the plains show similarities to the mare type basaltic plains of the moon mercury and mars other types of terrain are combinations of ridges and grooves in various patterns linear parallel orthogonal diagonal or chevron like and chaotic in some places the ridge and groove terrain is stratigraphically below the plain material but in other places it appears to be plain material that has been subsequently deformed near the eastern and western boundaries of ishtar terra large several hundred kilometers in diameter ring like features can be seen that are named coronae or ovoids evidence of tectonic deformation and the presence of flow like patterns support their designation as volcano tectonic features beta regio seems to be an uplifted plain showing evidence of rifting and volcanism all types of terrain are sparesely peppered with craters of obvious impact morphology their average density gives the plain an age range of 0 5 to 1 109 years the fact that many impact craters are still in the pristine state indicates a very low rate of surface reworking at least for the last 0 5 to 1 109 years no evidence for water erosion sedimentation processes has been found the tectonic activity of venus has no equivalent on the moon mercury or even mars and can be compared only with that of the earth intensive horizontal deformation previously known only on earth occurs on venus but in a characteristic venusian style

a high resolution authigenic 10be 9be record of geomagnetic moment variations over the last 300 ka from sedimentary cores of the portuguese margin a high resolution study of authigenic be isotopes 10be and 9be combined with continuous relative paleointensity records has been performed along the same marine sedimentary sequences from the portuguese margin n e atlantic covering the past 300 ka in order to assess relationships between geomagnetic moment variations and 10be production rate variations a carefull examination of the various ways of taking into account environmental disturbing effects on the authigenic 10be concentration leads to the conclusion that the most reliable proxy of cosmonuclide production rates is presently the authigenic 10be 9be ratio eight intervals of significant authigenic 10be 9be enhancement evidence geomagnetic moment drops related to global paleomagnetic excursions some being already admitted others being proposed as new geomagnetic features since contrarily to sedimentary magnetic remanence the authigenic 10be 9be records dipole moment variations without significant acquisition delay it provides better constraints on their timing comparison of 10be 9be and benthic 18o records from the same cores suggests that dipole moment lows preferentially occured during or at the end of interglacial episodes with a quasi period of 100 ka

exploring former subglacial hodgson lake antarctica paper ii palaeolimnology direct exploration of subglacial lakes buried deep under the antarctic ice sheet has yet to be achieved however at retreating margins of the ice sheet there are a number of locations where former subglacial lakes are emerging from under the ice but remain perennially ice covered one of these lakes hodgson lake 72 00 549 s 068 27 708 w has emerged from under more than 297 465 m of glacial ice during the last few thousand years this paper presents data from a multidisciplinary investigation of the palaeolimnology of this lake through a study of a 3 8 m sediment core extracted at a depth of 93 4 m below the ice surface the core was dated using a combination of radiocarbon optically stimulated luminescence and relative palaeomagnetic intensity dating incorporated into a chronological model stratigraphic analyses included magnetic susceptibility clast provenance organic content carbonate composition siliceous microfossils isotope and biogeochemical markers based on the chronological model we provisionally assign a well defined magnetic polarity reversal event at ca 165 cm in the lake sediments to the mono lake excursion ca 30 34 ka whilst osl measurements suggest that material incorporated into the basal sediments might date to 93 9 ka four stratigraphic zones a d were identified in the sedimentological data the chronological model suggests that zones a c were deposited between marine isotope stages 5 2 and zone a during stage 1 the holocene the palaeolimnological record tracks changes in the subglacial depositional environment linked principally to changing glacier dynamics and mass transport and indirectly to climate change the sediment composition in zones a c consists of fine grained sediments together with sands gravels and small clasts there is no evidence of overriding glaciers being in contact with the bed reworking the stratigraphy or removing this sediment this suggests that the lake existed in a subglacial cavity beneath overriding lgm ice in zone d there is a transition to finer grained sediments characteristic of lower energy delivery coupled with a minor increase in the organic content attributed either to increases in allochthonous organic material being delivered from the deglaciating catchment a minor increase in within lake production or to an analytical artefact associated with an increase in the clay fraction evidence of biological activity is sparse total organic carbon varies from 0 2 to 0 6 and cannot be unequivocally linked to in situ biological activity as comparisons of 13c and c n values with local reference data suggest that much of it is derived from the incorporation of carbon in catchment soils and gravels and possibly old co2 in meteoric ice we use the data from this study to provide guidelines for the study of deep continental subglacial lakes including establishing sediment geochronologies determining the extent to which subglacial sediments might provide a record of glaciological and environmental change and a brief review of methods to use in the search for life

groundwater favorability map using gis multicriteria data analysis on crystalline terrain sao paulo state brazil summary this paper presents the groundwater favorability mapping on a fractured terrain in the eastern portion of sao paulo state brazil remote sensing airborne geophysical data photogeologic interpretation geologic and geomorphologic maps and geographic information system gis techniques have been used the results of cross tabulation between these maps and well yield data allowed groundwater prospective parameters in a fractured bedrock aquifer these prospective parameters are the base for the favorability analysis whose principle is based on the knowledge driven method the multicriteria analysis weighted linear combination was carried out to give a groundwater favorability map because the prospective parameters have different weights of importance and different classes of each parameter the groundwater favorability map was tested by cross tabulation with new well yield data and spring occurrence the wells with the highest values of productivity as well as all the springs occurrence are situated in the excellent and good favorability mapped areas it shows good coherence between the prospective parameters and the well yield and the importance of gis techniques for definition of target areas for detail study and wells location

age of the mono lake excursion and associated tephra abstract the mono lake excursion mle is an important time marker that has been found in lake and marine sediments across much of the northern hemisphere dating of this event at its type locality the mono basin of california has yielded controversial results with the most recent effort concluding that the mle may actually be the laschamp excursion earth planet sci lett 197 2002 151 we show that a volcanic tephra ash 15 that occurs near the midpoint of the mle has a date not corrected for reservoir effect of 28 620 300 14c yr bp 32 400 gisp2 yr bp in the pyramid lake basin of nevada given the location of ash 15 and the duration of the mle in the mono basin the event occurred between 31 500 and 33 300 gisp2 yr bp an age range consistent with the position and age of the uppermost of two paleointensity minima in the napis 75 stack that has been associated with the mle philos trans r soc london ser a 358 2000 1009 the lower paleointensity minimum in the napis 75 stack is considered to be the laschamp excursion philos trans r soc london ser a 358 2000 1009

cosmogenic 10be production records reveal dynamics of geomagnetic dipole moment gdm over the laschamp excursion 20 60 ka documenting accurately amplitude and rhythms of geomagnetic variations is a prerequisite to understand the mechanisms triggering geomagnetic excursions and reversals we present new authigenic 10be 9be ratio be ratio results covering the 60 20 ka time interval from equatorial core md05 2920 the most significant be ratio peak is located 18 cm above the main relative paleointensity rpi minimum recorded in this sequence these are interpreted as two independent recordings of the geomagnetic dipole moment gdm decrease linked to the laschamp excursion dated at ca 41 ka the stratigraphic offset is assignable to post depositional magnetization lock in processes resulting in time delay of 1 6 ka the be ratio and rpi records show comparable asymmetric behavior before and after the dipole low the be ratio record is combined with three other series to construct a global record of 10be paleoproduction variations this compilation demonstrates the strong coherence of low and mid latitudes data sets and its comparison with 10be flux records from polar regions fully supports the hypothesis of a global atmospheric 10be production doubling during the laschamp the be ratio stack is converted in terms of gdm using both a theoretical model and a reconstruction of gdm values using absolute paleointensities measured on lava flows both methods provide similar results the dipole moment record derived from this approach bedm 20 60 shows the following characteristics high field values 11 1022 am2 prior to a sharp two steps dipole decrease until reaching minimum values 1 8 0 7 1022 am2 between 41 6 and 40 9 ka at the time of the laschamp excursion the gdm partly recovers up to values of 6 3 1022 am2 and oscillates in this range without showing any sharp decreases that could be associated with excursions reported within the 38 20 ka time interval e g the mono lake excursion

upscaling and regionalizing hydraulic conductivity and effective porosity at watershed scale in deeply weathered crystalline aquifers two innovative approaches for upscaling and regionalizing hydraulic conductivity and effective porosity at watershed scale are proposed they are based on the concept that large scale variations in hydraulic head may characterize large scale properties and were tested on an unconfined granitic aquifer exposed to deep weathering located in south india maheshwaram watershed 53 km2 both methods are based on field data such as water levels discharge rates of irrigation wells geological observations and the results of small scale hydraulic tests the resulting hydraulic conductivity map uses the statistical empirical relationship between log normal distributions of hydraulic conductivity from small scale tests and linear discharge rates from exploited wells i e the ratio between discharge rate and the saturated aquifer thickness the empirical relationship agrees with thiem dupuit s assumption for unconfined aquifers the performance of the method was compared to the values of local hydraulic conductivity estimates deduced from small scale tests not used for drawing the map about 90 of simulated values varies less than 20 from local measurements logk 0 4 on average which is reasonable considering the complexity of the studied fractured aquifer the regionalization of the effective porosity was based on a method that combines both water table fluctuation and groundwater budget techniques in the absence of recharge from rainfall however the use of these techniques at cell scale requires a good knowledge of groundwater flux to and from the cells which here is unknown to avoid this difficulty a coarse graining method was used assuming that increasing the cell size for such computations leads to a negligible contribution of these flux compared to net groundwater abstraction from the cell our results show that cell sizes over 520 520 m achieve a negligible balance in addition porosity maps provide average values of around 1 5 that are almost identical to the ones previously found at watershed scale the proposed methods for regionalizing hydraulic conductivity and porosity fields provide access not only to the average large scale values but also to their spatial distribution which is of prime interest in terms of flux and contaminant transport in a hard rock environment the uncertainty introduced by field data the choice of the computation scale as the impact of cell size on the calculated effective porosity value and the possible meaning of their spatial variations are also discussed

late quaternary paleomagnetic secular variation recorded in deep sea sediments from the demerara rise equatorial west atlantic ocean abstract we have carried out a paleomagnetic rock magnetic study of two gravity cores and two multicores from the demerara rise 8 n adjacent to ne south america the magnetic measurements indicate that there is a stable natural remanent magnetization nrm carried primarily by detrital magnetite titanomagnetite that preserves the local pattern of paleomagnetic secular variation psv the two gravity cores have consistent patterns of directional variability the rock magnetic intensities in both gravity cores vary by less than a factor of three relative paleointensity estimates have been derived by normalizing the nrm to chi arm and sirm both gravity cores show the same pattern of relative paleointensity variability 27 calibrated radiocarbon dates from our studied gravity cores and one additional piston core huang et al 2014 have been used to build chronologies for the two gravity cores core 25ggc has bulk sedimentation rates varying from 18 to 22 cm ky and contains a psv record for the last 19 ka core 9ggc has bulk sedimentation rates of 9 17 cm ky and contains a psv record for the last 28 ka there are no other published good quality well dated full vector psv records within 4000 km of the sites a region which constitutes almost 20 of the earth s surface area our relative paleointensity records are consistent with other global records under the assumption of field intensity being largely a global scale process we have compared our directional psv data statistically with eight other good quality well dated low latitude psv records our statistical analysis shows that our demerara rise directional psv records are consistent with those other studies and that the late quaternary equatorial field variability is significantly lower than much longer duration 780 ka to 5 ma variability

geologic interpretation of space shuttle radar images of indonesia the national aeronautics and space administration nasa space shuttle mission in november 1981 acquired images of parts of the earth with a synthetic aperture radar system at a wavelength of 23 5 cm 9 3 in and spatial resolution of 38 m 125 ft this report describes the geologic interpretation of 1 250 000 scale images of irian jaya and eastern kalimantan indonesia where the all weather capability of radar penetrates the persistent cloud cover the inclined look direction of radar enhances subtle topographic features that may be the expression of geologic structures on the indonesian images the following terrain categories are recognizable for geologic mapping carbonate clastic volcanic alluvial and coastal melange and metamorphic as well as undifferentia ed bedrock regional and local geologic structures are well expressed on the images in the vogelkop region of irian jaya the major tectonic elements tamrau mountains sorong fault kemum block bintuni basin and lengguru foldbelt are readily mapped on the image of the sorong fault geomorphic features offset drainage shutterridges aligned notches provide clear evidence for left lateral strike slip displacement several lineaments on the image correlate with previously mapped faults other lineaments may be the expression of previously unrecognized faults on the image of the mainland of irian jaya a belt of metamorphic and melange terrain marks the zone of collision between the pacific plate and the australian plate the high central range of irian jaya is located south of the metamorphic and melange belt the generally homoclinal structure of the central range is interrupted in the paniai lake region by a series of southward directed thrust plates indicated by belts of carbonate terrain new guinea limestone group that alternate with belts of clastic terrain kembelangan formation in the image of eastern kalimantan several major foldbelts are clearly expressed these limited examples of space shuttle radar images demonstrate their value for geologic interpretation of indonesia it is recommended that future shuttle missions acquire complete radar coverage of the main islands of indonesia for use in geologic mapping and energy exploration shuttle radar images would also be valuable for other cloud covered forested regions

extension of the lac du bouchet palaeomagnetic record over the last 120 000 years a high resolution profile of the palaeomagnetic variations recorded in the upper 20 m of the lac du bouchet sedimentary sequence has been reconstructed from several parallel mackereth and livingstone type cores inter core correlations were established by comparing individual core profiles of magnetic susceptibility individual records of af cleaned directions were then stretched to a common depth scale and merged the mean record was then filtered and smoothed in order to reduce the background noise accelerator radiocarbon determinations and pollen analyses show that the sequence covers the last interglacial glacial cycle back to ca 120 kyr b p and allow to perform a depth to time transformation there is a noted absence of widely divergent directions back to 90 kyr b p it is estimated that the recorded signal a pdrm signal represents the geomagnetic input signal attenuated by about 19 it follows that the excursions reported for the laschamp and olby lavas if they existed at all must have been of rather short duration two durable excursions appear in narrow diameter sections at the base of three independent cores b c and d while a reverse to normal transition is possibly documented in the lowermost meter core d this part of the sequence is dated from the recognition of major climatic events related to the 18 o isotopic stages defined in the oceanic record between 116 and 95 kyr this introduces the possibility of new excursions at ca 104 and 95 kyr i e immediately after the recovery of normal polarity documenting the end of the blake event

high resolution paleomagnetic secular variations and relative paleointensity since the late pleistocene in southern south america abstract paleomagnetic inclination declination and relative paleointensity were reconstructed from the sediments of laguna potrok aike in the framework of the international continental scientific drilling program icdp potrok aike maar lake sediment archive drilling project pasado here we present the u channel based full vector paleomagnetic field reconstruction since 51 2 ka cal bp the relative paleointensity proxy rpi was built by normalising the natural remanent magnetisation with the anhysteretic remanent magnetisation using the average ratio at 4 demagnetisation steps part of the chrm interval nrm arm 10 40 mt a grain size influence on the rpi was removed using a correction based on the linear relationship between the rpi and the median destructive field of the natural remanent magnetisation mdf nrm the new record is compared with other lacustrine and marine records and stacks from the mid to high latitudes of the southern hemisphere revealing consistent millennial scale variability the identification of the laschamp and possibly the mono lake geomagnetic excursions and a direction swing possibly associated to the hilina pali excursion at 20 ka cal bp nonetheless a global scale comparison with other high resolution records located on the opposite side of the earth and with various dipole field references hint at a different behaviour of the geomagnetic field around southern south america at 46 ka cal bp

absolute palaeointensity study of the mono lake excursion recorded by new zealand basalts abstract one of the geomagnetic excursions recorded in basalts of the auckland volcanic field new zealand has recently been correlated unequivocally with the mono lake excursion making it the only confirmed record from the southern hemisphere this record is also exceptional in occurring in five separate monogenetic basaltic volcanoes absolute palaeointensity determinations using the microwave technique based on a comprehensive suite of samples of the auckland basalts recording the excursion show that the geomagnetic field in new zealand at the time of the mono lake excursion was reduced to about 14 t i e to 30 of its normal value this result confirms previous estimates based on more limited sampling in addition it provides a comparison of the microwave and ldt dht shaw methods of measuring palaeointensity which give results that are statistically indistinguishable the palaeointensities determined from the five different volcanoes are also indistinguishable though the palaeodirection data suggest that a very small segment of the vgp path may have been recorded this study confirms the reliability of palaeointensity and palaeodirection determinations from these particular new zealand basalts which together with their definitive 40ar 39ar ages establishes this record of the mono lake excursion as one of the best documented consequently there is significant potential in searching for records of this excursion elsewhere in the pacific region for use as a stratigraphic marker in studies of recent volcanism and palaeoclimate reconstructions

use of synthetic aperture radar sar for geologic reconnaissance in arctic regions an example from the arctic national wildlife refuge alaska satellite based synthetic aperture radar sar can provide an additional remote sensing tool for regional geologic studies in arctic regions although sar data do not yield direct information on rock type and do not replace traditional optical data sar data can provide useful geologic information in arctic regions where the stratigraphic column includes a wide range of lithologies and bedrock exposures have been reduced to rubble by frost action for example in ers 1 sar data from the arctic national wildlife refuge anwr of the northeastern brooks range alaska carbonate and clastic rocks can give remarkably different radar responses on minimally reprocessed sar data the different radar response of different lithologies can be attributed to variations in surface roughness specifically the size and angularity of scree in talus slopes additional postacquisition processing can both remove many of the negative terrain effects common in sar data and enhance contrasts in bedrock lithology because of this ability to discriminate between gross lithologic packages the ers 1 sar data can be used to provide a regional view of anwr and a detailed look at specific areas a mosaic of ers 1 sar data from all of anwr provides a synoptic copyright 1997 the american association of petroleum geologists all rights reserved 1manuscript received august 30 1995 revised manuscript received march 11 1996 final acceptance august 15 1996 2geophysical institute university of alaska fairbanks alaska 99775 3alaska sar facility geophysical institute university of alaska fairbanks alaska 99775 this study was supported by sponsors of the tectonics and sedimentation research group of the university of alaska fairbanks including arco alaska bp alaska chevron exxon japan national oil co mobil phillips and unocal the alaska sar facility provided support for richard guritz and reprocessing of the ers 1 sar data ers 1 sar data were provided by the european space agency under a research agreement with nasa we would like to thank steve ahlgren lyn mcnutt and ken dean for stimulating discussions on sar and its potential geologic applications in the arctic wes wallace for discussions on the regional geology of northeastern alaska and weathering characteristics of the different stratigraphic units and wes wallace ken dean bill stringer larry lane m c erskine jr h r hopkins and k biddle for helpful reviews of the manuscript

hydro environmental assessment of a regional ground water aquifer hirakud command area india a hydro environmental assessment has been performed for hirakud command area india in terms of quantity and physicochemical quality analysis of groundwater quantity analysis has been performed in terms of water level variation and groundwater potential zone identification groundwater table fluctuation analysis reveals that water level is declining rapidly due to insufficient recharge owing to frequent recession of monsoon and excessive pumping of groundwater inefficient distribution of canal water especially in the tail end of the hirakud command is accentuating the high dependency on ground water the groundwater potential zone index map is generated using analytic hierarchy process along with different influencing features e g land use cover soil type geology three zones have been identified for hirakud command area poor 21 15 moderate 46 32 and good 32 53 physical and chemical parameters of groundwater e g electrical conductivity ph total dissolved solids total hardness nitrate iron sodium potassium calcium magnesium chlorine bicarbonate and fluoride are analyzed for the study area piper analysis is used to identify dominant hydrochemical facies united states salinity laboratory and wilcox diagram are used to determine the irrigation water quality principal component analysis is utilized to find out key groundwater quality parameters the chemical analysis shows that values of all parameters are within permissible limit however nitrate iron and fluoride are found above permissible limit in some areas the assessment reveals the state of the aquifer in terms of quantity and quality

a gis based model of potential groundwater yield zonation for a sandstone aquifer in the juye coalfield shangdong china abstract resolving the potential groundwater yield zonation of sandstone aquifers occurring at depths of several hundred meters has been an important and challenging objective of the hydrogeological research focused on preventing flood hazards in coal mines using accessible geological exploration data we put forward a method of predicting the spatial distribution of groundwater storage potential in sandstone aquifers from permian age coal deposits in juye coalfield shangdong china a geological tectonic and lithological composition index gtlci model was created using the following parameters sandstone depth and thickness faults length density fald faults density fad fault frequency density fafd fault scale density fasd variation coefficient of the slope vcs of the coal seam intensity index of folds in horizontal direction iifoh and lithological composition index lci each of these factors was subsequently divided into 5 classes the analytic hierarchy process ahp and trapezoidal fuzzy number tfn method was applied to calculate the weight of the conditioning factor and their respective sub classes groundwater yield potential contour map which was initially constructed using the gtlci values revealed four groundwater abundance zones the map was further refined by taking into account hydrogeologic data collected during mining activities the gtlci model predictive success rate of 80 was explained by the limited number of boreholes available for validation it is considered that the gtlci model is effective at predicting zonation of groundwater yield in the sandstone aquifers from permian age coal deposits in juye coalfield china

evidence of synchronous climate change across the northern hemisphere between the north atlantic and the northwestern great basin united states from ca 50 to 20 ka summer lake oregon rose and fell in tune with north atlantic interstadial and stadial climatic oscillations respectively this record exhibits the complete morphology of the north atlantic millennial scale climate change signal including dansgaard oeschger oscillations heinrich events and bond cycles the phase relationship of these climate change records high summer lake during warm north atlantic low during cold is demonstrated at millennial scale resolution by the relative positions of the mono lake and laschamp paleomagnetic excursions in these records these results in conjunction with comparisons of historical climate records also presented here imply a direct temporal connection at the subcentury scale between the north atlantic and the northwestern great basin via an atmospheric teleconnection

a methodology for regionalizing 3 d effective porosity at watershed scale in crystalline aquifers 13 an innovative approach for regionalizing the 3 d effective porosity field is presented and 14 applied to two large overexploited and deeply weathered crystalline aquifers located in 15 southern india the method derives from earlier work on regionalizing a 2 d effective 16 porosity field in that part of an aquifer where the water table fluctuates which is now 17 extended over the entire aquifer using a 3 d approach a method based on geological and 18 geophysical surveys has also been developed for mapping the weathering profile layers 19 saprolite and fractured layers the method for regionalizing 3 d effective porosity 20 combines water table fluctuation and groundwater budget techniques at various cell sizes 21 with the use of satellite based data for groundwater abstraction the structure of the 22 weathering profile and geostatistical techniques the approach is presented in detail for the 23 kudaliar watershed 983 km 2 and tested on the 730 km 2 anantapur watershed at watershed 24 scale the effective porosity of the aquifer ranges from 0 5 to 2 in kudaliar and between 25 0 3 and 1 in anantapur which agrees with earlier works results show that i depending 26 on the geology and on the structure of the weathering profile the vertical distribution of 27 effective porosity can be very different and that the fractured layers in crystalline aquifers are 28 not necessarily characterized by a rapid decrease in effective porosity and ii that the lateral 29 variations in effective porosity can be larger than the vertical ones these variations suggest 30 that within a same weathering profile the density of open fractures and or degree of 31 weathering in the fractured zone may significantly varies from a place to another 32 the proposed method provides information on the spatial distribution of effective porosity 33 which is of prime interest in terms of flux and contaminant transport in crystalline aquifers 34 implications for mapping groundwater storage and scarcity are also discussed which should 35 help in improving groundwater resource management strategies 36 37

paleoclimatic context of geomagnetic dipole lows and excursions in the brunhes clue for an orbital influence on the geodynamo the hypothesis of an influence of the astronomical precession on the geodynamo energy budget was recently reappraised by theoreticians paleomagnetic indications of such an influence remain controversial because reconstructions of paleointensity variations from sediments are suspected to be contaminated by lithological paleoclimatically induced influences three sets of complementary indicators are however available 1 records of the direction of magnetization in sediments 2 records of magnetic anomalies of the deep sea floor basalts and 3 records of production variations of cosmogenic isotopes from sediment and ice cores these records confirm the genuine geomagnetic origin of paleointensity lows and their narrow link with excursions or short reversals recorded in various materials and often dated by radiometric methods the analysis of these time series and their comparison with 18o records of the paleoclimate suggest that such globally recorded geomagnetic dipole lows have preferentially occurred in the context of interglacial or transitional paleoclimates at the time of low or decreasing obliquity the dominant periods extracted with the complex continuous wavelet transform technique range from 40 to 125 ka further suggesting a link with orbital parameters these results encourage future efforts of research to improve the precision the resolution and the dating of the time series of geomagnetic dipole low in order to better decipher orbital signatures and understand their origin an important implication of this topic is that the next geomagnetic dipole low should be related with the present interglacial

mono lake geomagnetic excursion found at summer lake oregon a 25 cm zone of anomalous paleomagnetic directions from lacustrine sediments near summer lake oregon has the same age and the same paleomagnetic signature as the younger part of the proposed mono lake geomagnetic excursion both field observations and rock magnetic studies support the hypothesis that the anomalous directions represent actual geomagnetic field behavior thereby confirming the existence of the mono lake excursion at the oregon site although confirmation of its existence at this site does not make the mono lake excursion any more suitable as a chronostratigraphic horizon this excursion may now be used as an additional constraint on models of geomagnetic field behavior including those that predict the morphology of transitional geomagnetic fields

climate variability in the salawusu river valley of the ordos plateau inner mongolia china during marine isotope stage 3 fluctuations in climatic proxies of the milanggouwan section in the salawusu river valley of the ordos plateau inner mongolia china during marine isotope stage 3 mis 3 coincide well with sedimentary cycles for palaeo mobile dune sands alternating with fluvial lacustrine facies and palaeosols we compared the palaeo mobile dune sands with modern mobile dune sands products of a cold and dry climate dominated by the east asian winter monsoon whereas the fluvial lacustrine facies and palaeosols were controlled by a wet warm climate similar to that of the east asian summer monsoon the mis 3 climate of the salawusu river valley appears to have experienced at least nine wet warm and ten cold dry fluctuations divided into five stages mis 3e 58 900 49500 yr bp mis 3d 49 500 40 700 yr bp mis 3c 40 700 36 900 yr bp mis 3b 36 900 27 000 yr bp and mis 3a 27 000 22 300 yr bp the 19 cold warm climatic fluctuations corresponded roughly to the grip and guliyan records and with fluctuations in the north atlantic climate notable peaks in the spectral analysis occurred at 19 500 yr 1020 yr 640 yr and 500 yr our results show that the millennial centennial climate was closely related to the relative strengths of east asian monsoons which are controlled by the north atlantic thermohaline circulation and which is also closely linked to the sun s precession period copyright 2008 john wiley sons ltd

age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr