the influence of constitutive models on self boring pressuremeter interpretation in clay a comparison of the elastic perfectly plastic epp and hyperbolic hb theories for interpreting loading and unloading parts of self boring pressuremeter sbp tests in clay is presented computer aided modelling cam is used to analyze 60 sbp tests in clay to obtain shear modulus g undrained shear strength su and in situ total horizontal geostatic stress ho it is shown that the technique of cam is consistent repeatable and simple to use for all tests analyzed by both models the inferred horizontal geostatic stresses are identical and comparable to lift off measurements a small systematic difference is found between the two models for the undrained shear strength of soft and stiff clays the shear modulus valves derived from the epp model are unrelated to the true modulus of the soil there is however a semiempirical relationship between the hb model and pressuremeter unload reload ur shear modulus key words clay self boring pressuremeter elastic perfectly plastic hyperbolic

observational evidence for westward propagation of temperature inversions in the southeastern arabian sea 1 a warm pool forms in the southeastern arabian sea seas prior to the onset of the summer monsoon over india in early june the core of this warm pool is in the lakshadweep sea ls xbt and surface salinity data collected in the ls during may 2002 april 2003 show that temperature inversions occur off the southwest coast of india in early december with the arrival of low salinity waters from the bay of bengal the low salinity waters and the inversions propagate westward along with the downwelling rossby waves that constitute the lakshadweep sea level high inversions occur in the western ls 73 e about 40 days after they occur near the coast in the eastern ls 75 5 e they disappear in april when the tropical convergence zone moves over the seas and the warm pool engulfs the region ocean dynamics and air sea fluxes are together responsible for the formation and westward propagation of the inversions

structural setting of the bay of naples italy seismic reflection data implications for campanian volcanism abstract this paper focuses on the recent tectonic evolution of the bay of naples with the aim of exploring the connection between local tectonics and volcanism we reprocessed the seismic reflection dataset acquired in the area in the late 1973 the new processing was highly successful in obtaining a decisive strong reduction of random noise removal of coherent noise and reduction of spatial aliasing classical interpretative schemes and complex attributes of seismic traces were used to reconstruct fault kinematics and reflector patterns the results show that the faults affecting the bay of naples exhibit prevailing ne structural strikes with the exception of the pozzuoli caldera where nw patterns are also common many faults are subvertical and show seismic evidence of volcanic activity along them a main alignment of conjugate ne sw faults named here as magnaghi sebeto line intersects several submarine volcanic banks and separates the bay into two sectors characterized by important geological geophysical and petrochemical differences the structural configuration of the bay may reflect the occurrence of either oblique extension or a transfer zone of the nw se fault system along which in the campanian lucanian apennine chain great vertical displacements occur

florida straits deglacial temperature and salinity change implications for tropical hydrologic cycle variability during the younger dryas temperature and d 18 osw a proxy for surface salinity records based on mg ca ratios and oxygen isotope measurements in the planktonic foraminifera globigerinoides ruber from a sediment core located on the western margin of the florida straits as a proxy for meltwater discharge influence on florida straits surface water salinity we also measured ba ca ratios in g ruber from the same core results show that riverine influence on florida straits surface water started by 17 2 ka bp and ended by 13 6 ka bp 600 years before the start of the younger dryas yd cold interval the initiation of the yd is marked by an abrupt increase in florida straits d 18 osw values indicating a shift to elevated sea surface salinity occurring in 130 years most likely resulting from increased regional aridity and or reduced precipitation in order to resolve the timing of tropical atmospheric circulation change relative to amoc variability across this transition we compare the timing of surface water changes to a recently published record of florida current variability in the same core reconstructed from benthic oxygen isotope measurements we find synchronous changes in atmospheric and ocean circulation on the transition into the yd consistent with an abrupt reduction in amoc as the driver of tropical atlantic atmospheric circulation change at this time

a tropical mechanism for northern hemisphere deglaciation 1 we investigate the role of the tropics in the melting and reforming of the laurentide ice sheet on glacial timescales using an atmospheric general circulation model it is found that warming of tropical sea surface temperatures ssts from glacial boundary conditions as observed at the end of glacial periods causes a large increase in summer temperatures centered over the ice sheet forming regions of canada this highlatitude response to tropical change is due to relatively small changes in the circulation of the extratropical atmosphere which lead to changes in the vertical profiles of temperature and moisture in the extratropical atmosphere the maximum perturbation in the summer radiative balance over the laurentide ice sheet 25 w m 2 due to the changes in the local atmospheric water vapor inventory is much larger than that induced by glacial to interglacial changes in atmospheric co2 these changes via an atmospheric bridge between the tropics and extratropics represent a mechanism for deglaciations which is consistent with timing constraints in contrast a cold perturbation to tropical sst for interglacial boundary conditions results in only very small changes in the delivery of water vapor to the laurentide region and therefore almost no cooling over the canadian region this implies that tropical ssts could play a more important role in melting ice sheets in the northern hemisphere than in reforming them possibly providing a mechanism which could help to explain the rapidity of deglaciation relative to glacial inception

last glacial interglacial productivity and associated changes in the eastern arabian sea abstract we reconstruct paleo productivity and bottom water oxygenation changes during the past 32 ka from the southeastern arabian sea using absolute abundance of planktic foraminifera relative abundance of globigerina bulloides angular asymmetrical benthic foraminifera aabf measurements of total organic carbon c org caco 3 and globigerinoides ruber 18 o and 13 c the faunal and geochemical proxies suggest that productivity in the southeastern arabian sea was high during mis 3 a distinct decrease in productivity is inferred during the last glacial maximum 19 23 ka lgm bottom water was well oxygenated during mis3 only to become oxygen depleted during the lgm productivity decreased abruptly during heinrich stadial 1 hs 1 but the response to heinrich stadial 2 hs 2 was different low productivity during the early deglaciation is also synchronous with an increase in ice volume corrected 18 o 18 o sw ivc a salinity proxy between 18 9 18 3 18 9 ka bp and 15 9 15 0 16 3 ka bp and a concomitant decrease in 13 c between 18 2 17 5 18 7 ka bp and 16 4 15 3 16 7 ka bp these patterns suggest that the global 13 c minimum event during the last deglaciation was associated with the weak monsoon interval during hs 1 and a drop in productivity in tropical regions a progressive increase in productivity is observed throughout the holocene with a distinct jump at 5 4 3 8 6 3 ka bp we infer that although productivity was higher in the eastern arabian sea during most of the last glacial interval the overall resultant carbon sequestration was confined only to a restricted zone and not large enough to substantially alter atmospheric co 2

a simple evaluation of cleaning procedures on fossil benthic foraminiferal mg ca 1 recent studies suggest that benthic foraminiferal mg ca may be useful in reconstructing deep water temperature changes during the quaternary and on longer timescales rosenthal et al 1997 lear et al 2000 martin et al 2002 because changes in deep water temperature may be small sample preparation could play an important role in reconstructing accurate temperatures from shell mg ca a simple examination of changes in measured shell chemistry of benthic foraminifera from two intervals subjected to increasingly rigorous cleaning reveals that fossil benthic foraminiferal samples cleaned by oxidation yield lower mg ca values than samples only rinsed and weak acid leached reductive cleaning further lowered the shell mg ca of one of the two benthic species examined lower mg ca values following oxidation and reduction appear to reflect removal of contaminant mg associated with remnant organic matter and adsorbed phases

the cause of carbon isotope minimum events on glacial terminations the occurrence of carbon isotope minima at the beginning of glacial terminations is a common feature of planktic foraminifera carbon isotopic records from the indo pacific sub antarctic and south atlantic we use the 13 c record of a thermocline dwelling foraminifera neogloboquadrina dutertrei and surface temperature estimates from the eastern equatorial pacific to demonstrate that the onset of 13 c minimum events and the initiation of southern ocean warming occurred simultaneously timing agreement between the marine record and the 13 c minimum in an antarctic atmospheric record suggests that the deglacial events were a response to the breakdown of surface water stratification renewed circumpolar deep water upwelling and advection of low 13 c waters to the convergence zone at the sub antarctic front on the basis of age agreement between the absolute 13 c minimum in surface records and the shift from low to high 13 c in the deep south atlantic we suggest that the 13 c rise that marks the end of the carbon isotope minima was due to the resumption of north atlantic deep water influence in the southern ocean

preconsolidation pressure of champlain clays part ii laboratory determination a series of conventional and special consolidation tests was carried out on clay samples from 11 sites in the champlain sea basin the results show that for a given clay at a given depth there is a unique preconsolidation pressure strain rate relationship independent of the tests carried out and that the relationships obtained in different champlain clays can be normalized correlations between the preconsolidation pressure values obtained from the different special consolidation tests and the conventional test are established and a method of estimating in situ preconsolidation pressure is suggested keywords preconsolidation pressure laboratory testing techniques strain rate

thermal fronts and attracting lagrangian coherent structures in the north bay of bengal during december 2015 march 2016 abstract we investigate two dimensional advective stirring by satellite derived ocean surface currents in the north bay of bengal during december 2015 march 2016 using the framework of lagrangian coherent structures lcs the forward and backward finite time lyapunov exponent fftle and bftle respectively fields indicate that freshwater parcels from the river run off are subjected to intense stirring by the ocean surface currents which contain both geostrophic and wind forced ekman currents large scale thermal fronts present in the satellite based sea surface temperature sst fields are then shown to closely resemble attracting lcs alcs that govern horizontal advective stirring on subseasonal time scales statistical estimates of the angle between the thermal fronts of all spatial scales present in the sst data and the alcs from the entire north bay of bengal show a preference to align with each other significantly in the presence of sufficiently strong alcs in their neighbourhood thermal fronts are shown to have a strong preference to align with them finite time advection of fluid particles over around a week to compute the bftle fields results in the strongest alignment between the thermal fronts and neighbouring alcs the robustness of our results are established by presenting analyses of i geostrophic currents from altimeter data and ii a reanalysis based fine scale salinity field attracting lcs identified as sufficiently strong ridges in the bftle fields are argued to represent reasonable estimates of the location and orientation of fronts thermal or salinity formed by advective stirring over subseasonal time scales

effects of disturbance on undrained strengths interpreted from pressuremeter tests although the cylindrical cavity expansion theory should provide a sound basis for obtaining the undrained shear strength of clays from pressuremeter tests the interpreted strengths are often inconsistent with data measured in high quality laboratory tests this paper investigates how the pressuremeter results are affected by disturbances that inevitably occur during device installation the installation of self boring and displacement type pressuremeters is simulated using strain path analyses with realistic effective stress strain strength properties described by the mit e3 model whittle and kavvadas 1994 derived strengths obtained from the simulated expansion of displacement type pressuremeters tend to underestimate the in situ cavity expansion strength by amounts that depend on the relative volume of soil displaced the time delay prior to testing and the initial overconsolidation ratio of the clay interpretation procedures using the simulated contraction curves give much more reliable estimates of the true undrained shear strength the simulated disturbance effects of self boring lead to derived peak shear stresses that are significantly higher than the reference undrained shear strengths this overestimate depends on the volume of soil removed during installation and is enhanced when the finite membrane length is included in the analyses self boring pressuremeter data from a well documented test site in boston massachusetts confirm the general character of the predicted pressuremeter stress strain behavior the theoretical analyses underestimate the peak strengths derived from self boring pressuremeter sbpm expansion tests but match closely the measured postpeak resistance in the strain range of 3 6 saddle point condition saddle point strengths are similar in magnitude to the shear strengths measured in laboratory undrained triaxial compression tests at this site the current predictions are not able to explain the very high shear strengths derived from the sbpm contraction curves

reevaluation of the oxygen isotopic composition of planktonic foraminifera experimental results and revised paleotemperature equations cultured planktonic foraminifera orbulina universa symbiotic and globigerina bulloides nonsymbiotic are used to reexamine temperature 18o relationships at 15 25 c relationships for both species can be described by linear equations equations for o universa grown under low light ll and high light hl share a slope of 4 80 0 21 c 1 with a hl ll offset of 0 33 due to symbiont photosynthetic activity the effect of co32 on o universa is 0 002 mol 1 kg 1 and is insensitive to temperature for g bulloides ontogenetic effects produce size related trends in temperature 18o whereby larger shells are enriched in 18o relative to smaller specimens the o universa temperature 18o relationships are more accurate than previously published equations for describing plankton tow data our equations do not explain planktonic core top data with the same precision but provide a good fit to benthic cibicidoides data below 10 c temperature 18o relationships for g bulloides provide good agreement with field data for this species from the northeast pacific

the 1245 yr bp asososca maar eruption the youngest event along the nejapa miraflores volcanic fault western managua nicaragua abstract the asososca tephra comprises the asymmetrically distributed well stratified phreatomagmatic products of the 1245 125 120 yr bp asososca maar eruption west of managua nicaragua it is the youngest eruptive unit related to the monogenetic volcanism concentrated along the n s trending nejapa miraflores active fault and intersecting e w to ne sw and nw se minor faults the close relationship between monogenetic volcanism and the structural local tectonic framework is evidenced by the lineament domains and vent alignment patterns identified by remotely sensed images and dems of the research area the asososca maar lake bathymetry suggests that the crater was formed by coalescing vents migrating during the eruptive event the asososca tephra dominantly consists of accidental lithics disrupted from the underlying stratigraphic units observed inside and around the maar crater dry base surge bedsets are dominant throughout the eruptive unit showing facies variation from proximal cross stratified beds to mid distal plane parallel and wavy parallel beds grain size analyses indicate that base surges transported dominantly 1 0 and 1 sized particles at the bedload in form of traction carpets while fine ash material in continuous suspension was minimal juvenile fragments were only identified in the finer fractions varying from vesiculated scoriae to dense sideromelane fragments sem analyses suggest that the asososca eruption resulted from a highly efficient fuel coolant interaction between a tholeiitic basaltic melt and an aquifer hosted in a shallow level between 50 and 200 m of olivine bearing scoria ash and lapilli beds the explosion triggered the country rock comminution and the production of moss like fused shaped and blocky ash shards with stepped surfaces quenching cracks pitting alteration skins and adhered particles all indicative of phreatomagmatic fragmentation the very recent age of the asososca maar eruption confirms that the densely inhabited managua area is volcanically active and that hazard studies should focus on the potential for phreatomagmatic eruptions

self boring pressuremeter study of san francisco bay mud discussion and closure the discussers comment on the use of s sub u p ratios from the laboratory uu and vane tests and on the comparisons with similar ratios from cu triaxial tests the second discusser notes that the instrument used by the authors the cambridge type self boring pressuremeter is now considerably improved recent work has also shown that it is possible to be more certain in the initial setting of the cutter this coupled with cutter geometry have meant that it is no longer a procedure of trial and error to determine the correct cutter setting it is also possible even in stiff clay to attain driving rates up to a meter of drilling in ten minutes the authors comment on the issues raised the authors observe that the self boring pressuremeter offers promise as a means to define the properties of soft clay soil the device is useful because it not only can determine the shear strength of a soil but also the stress strain and pore pressure response and the lateral stress in the ground

constraint of the co2 rise by new atmospheric carbon isotopic measurements during the last deglaciation 1 the causes of the 80 ppmv increase of atmospheric carbon dioxide co2 during the last glacial interglacial climatic transition remain debated we analyzed the parallel evolution of co2 and its stable carbon isotopic ratio 13co2 in the european project for ice coring in antarctica epica dome c ice core to bring additional constraints agreeing well but largely improving the taylor dome ice core record of lower resolution our 13co2 record is characterized by a w shape with two negative 13co2 excursions of 0 5 during heinrich 1 and younger dryas events bracketing a positive 13co2 peak during the bolling allerod warm period the comparison with marine records and the outputs of two c cycle box models suggest that changes in southern ocean ventilation drove most of the co2 increase with additional contributions from marine productivity changes on the initial co2 rise and 13co2 decline and from rapid vegetation buildup during the co2 plateau of the bolling allerod

evidence of transpressional tectonics on the uruk sulcus region ganymede abstract the surface of ganymede is characterized by intense tectonic deformation the two terrains light and dark show morphotectonic features namely grooves and furrows these represent kilometric systems at the regional scale interpreted as extensional structures e g horst and graben systems currently evidence of significant compression has not yet been recognized leaving open the opportunity to clarify the tectonic balance of ganymede s surface debate still exists on the geodynamics responsible for surface deformation and the investigation of these features contributes to understanding the internal processes to understand the deformation that shapes the surface of the satellite we explore the tectonic setting of the light terrain region of uruk sulcus using structural geology methodologies by remote sensing and systematic analysis of grooves we recognize three groove systems within the sulcus and one furrow system in the neighboring dark terrain uruk sulcus is also characterized by the presence of two domains of lineaments subtle linear texture anisotropies related to the influence of tectonic processes on morphology comparison of the combined results from the analyses of the recognized groove systems with the lineament domains allowed us to infer the stress field responsible for their development in the studied area according to these results an evolutionary tectonic scenario for uruk sulcus is proposed a tectonic corridor characterized by dextral transpression with 58 of the internal compressional component approximately n s oriented and responsible for localized e w extensional features among crustal blocks of the shear zone

ba ca in neogloboquadrina pachyderma as an indicator of deglacial meltwater discharge into the western arctic ocean 1 down core samples of the planktonic foraminifer neogloboquadrina pachyderma sinistral from the mendeleyev ridge in the western arctic ocean have been analyzed for ba ca and 18o the apparent distribution coefficient for n pachyderma sin is estimated at dba 0 22 0 02 a meltwater event is identified at around 11 8 14c kyr bp and is coincident with elevated ba ca ratios the barium enrichment is believed to be the result of enhanced weathering and erosion following glaciation additionally barium may have desorbed from shelf sediments as sea level rose changes in ba ca correlate with the retreat of the laurentide ice sheet and the evolution of the mackenzie river drainage basin therefore maximum ba ca in arctic surface waters at 11 8 ka may be indicative of an increase in the export of freshwater from the arctic to the north atlantic potentially contributing to the onset of the younger dryas this work suggests that ba ca in planktonic foraminifera may be a useful indicator of the timing and processes associated with deglaciation

tectonic stresses seaward of an aseismic ridge trench collision zone a remote sensing approach on the loyalty islands sw pacific abstract the loyalty islands are a series of limestone karstified islands on the australian plate that are presently approaching the vanuatu subduction zone sw pacific they are deformed due to the combined effects of the bulging of the subducting lithosphere and the beginning collision between the loyalty ridge and the vanuatu subduction zone therefore they constitute a series of markers for early phases of ridge arc collision lineaments deduced from remote sensing images aerial photos spot3 spot4 and envisat data termed here as fractures are analyzed by comparison with planar structures measured during field studies and termed as geological data fracture data indicate a stable main n110 direction with a large variance of nearly 15 in rms and two minor directions 45 apart which may constitute shear directions associated to the major one a scale dependent analysis shows that fractures longer than 2000 m are close to the n110 direction and that their orientation shifts progressively to reach the n125 direction for l

independence of geostatic stress from overconsolidation in some beaufort sea clays reply since 1982 extensive use has been made of the self bored pressuremeter in arctic offshore site investigations one finding of this work is that the in situ geostatic stress ratio k0 of beaufort sea clays is apparently unrelated to the overconsolidation ratio ocr the procedures and data to support this finding are documented and the finding is discussed in light of the present geological understanding for the area it is concluded that the independence of k0 from ocr may be quite widespread a finding that contradicts the widely held tenet regarding the existence of a single valued function relating k0 and ocr if k0 is regarded as important then it should be measured in situ key words self bored pressuremeter geostatic stress ratio k0 beaufort shelf geologic history overconsolidation ratio

observational evidence for remote forcing of the west india coastal current 1 circulation in the north indian ocean is influenced by both local and remote wind forcing so far however determining the contribution of these two forcing mechanisms at a location has been possible only in numerical experiments here we separate remote and local forcing in observations using field measurements current sea level and wind for a month during march april 2003 off goa in the near coast regime of the west india coastal current wicc we show that the current was driven by local winds only at periods less than 10 days with remote forcing contributing at longer periods the high passed hp period less than 10 days component of the along shore current was strongly correlated with the hp component of the along shore wind the current lagging the wind by half a day the low passed lp components of the wind and current were not correlated the former was unidirectional but the latter reversed during the period of observation the relationship between the hp wind and current was used to estimate the locally forced lp current permitting an estimate of the remote current the lp residual this separation of locally forced and remotely forced currents showed that remote forcing contributed as much as local forcing to the wicc the local current behaved like a classical eastern boundary current forced by local winds the reversal in the remote current was due to winds 700 km farther south along the coast frictional damping had an impact only at periods less than 10 days there being no remotely forced hp current

drainage network geometry versus tectonics in the argentera massif french italian alps abstract the argentera massif french italian alps with its uniform lithology was selected to evaluate how known plio pleistocene tectonics have conditioned the drainage network geometry the drainage network was automatically derived and ordered from a 10 m resolution dem on hillshade images alignments of morphological features were identified the massif was subdivided into 22 domains of 50 km 2 within which the directions of every river channel segment and the direction of the aligned morphological features were compared and contrasted with the strike of tectonic structures measured in the field results suggest that the argentera drainage system is variously controlled by recent tectonics depending on the massif sector taken into account in the nw sector the vertical uplift is less because the strain has been accommodated in an oblique direction along a lateral thrust in the se sector strain in a predominantly vertical direction along a frontal thrust has resulted in a major vertical displacement accordingly the nw sector is characterized by i a strong geometric relationship between the main tectonic structures and the directions of river channels ii longitudinal main rivers bordering the massif and iii a general trellis pattern within the domains in the se sector the prolonged uplift has forced an original longitudinal drainage system to develop as a transverse system this change has occurred by means of fluvial captures that have been identified by the presence of windgaps fluvial elbows and knickpoints at the domain scale intense uplift of the se sector has prompted the drainage pattern to evolve as a dendritic type with no clear influence of structure in the channel orientations

deglaciation in the tropical indian ocean driven by interplay between the regional monsoon and global teleconnections abstract high resolution climate records of the ice age terminations from monsoon dominated regions reveal the interplay of regional and global driving forces speleothem records from chinese caves indicate that glacial terminations were interrupted by prominent weak monsoon intervals wmi lasting a few thousand years deglacial wmis are interpreted as the result of cold temperature anomalies generated by sea ice feedbacks in the north atlantic most prominently during heinrich events recent modeling results suggest however that wmis reflect changes in the intensity of the indian rather than the east asian monsoon here we use foraminiferal trace element mg ca and ba ca and stable isotope records from a sediment core off the malabar coast in the southeastern arabian sea with centennial scale resolution to test this hypothesis and to constrain the nature and timing of deglacial climate change in the tropical indian ocean the malabar deglacial sst record is unique in character and different from other tropical climate records sst at the last glacial maximum was 2 7 0 5 c colder than pre industrial sst deglacial warming started at 18 6 95 ci range 18 8 18 1 kyr bp within error of the onset of warming at other tropical sites as well as in antarctica and the southern ocean and either coeval with or up to 1 kyr before the atmospheric co 2 rise warming took place in two steps separated by an interval of stable sst between 15 7 16 2 14 9 and 13 2 13 9 12 0 kyr bp the 18 o water record and the ba ca record which is a measure of indian sub continent riverine runoff indicate that the last ice age termination was marked by a prominent weak indian monsoon interval interrupted by an intense monsoon phase as seen in speleothem records and predicted by modeling a strong correspondence between the timing of the malabar 18 o sw record and the hulu cave monsoon record suggests that deglacial 18 o changes in both localities dominantly reflect compositional changes in precipitation likely driven by changes in the north atlantic

vertical variation of oxygen isotope in bay of bengal and its relationships with water masses 1 we present here for the first time comprehensive depth specific near surface to 1800 m oxygen isotope 18o data set of 175 water samples collected from 22 different locations in the bay of bengal bob during july august 2009 and december january 2012 2013 the study is aimed to constrain the water mass parameters using oxygen isotope and salinity four water masses are identified on the basis of temperature salinity relationship a bay of bengal water bobw 0 50 m b mixed zone mz 60 120 m c indonesian throughflow itf 200 500 m and d indian ocean deep water idw 600 1800 m our study shows 1 18o salinity correlation slope 0 15 0 01 intercept 4 58 0 24 r2 0 89 n 54 for the bobw is found to be consistent with surface bob water reported earlier 2 relatively lower correlation r2 0 24 n 47 in underlying mixed zone suggesting mixing of various water masses 3 significant linear correlation between 18o and salinity in idw r2 0 70 indicating depleted less saline water from southern hemisphere spread up to 18 n and 4 vertical profiles at various sampling locations showing a continuous enrichment of 18o 0 6 0 8 within top 60 100 m irrespective of their proximity to coastline in conjunction with a sharp decrease in 14c data below the same depth zone 60 100 m as reported earlier we suggest the 18o value reaches to its acme at a zone of mixing between younger bobw and relatively older itf this preliminary study indicates oxygen isotope and salinity together can be used to identify different water masses in the bob

the role of transfer structures on volcanic activity at campi flegrei southern italy abstract the tyrrhenian margin of central italy underwent extension during pliocene and quaternary extension occurred mainly through nw se normal faults bordering a sequence of plio quaternary basins these basins are offset by coeval ne sw faults which show strike slip and normal motions and have been interpreted as transfer faults plio quaternary volcanic activity along the margin occurred along a nw se belt systematically in correspondence with ne sw transverse systems the campi flegrei volcanic district cfvd on the southern tyrrhenian margin consists of an active ne sw volcanic ridge developed along ne sw fractures we performed a structural field analysis with analogue and mechanical models to investigate the role of transverse structures upon volcanism at campi flegrei field analysis at campi flegrei recognized ne sw and to a lesser extent coeval nw se active fractures analogue experiments have simulated the development of transfer fault systems in brittle extensional domains the experiments show that subvertical transfer faults connect offset adjacent normal faults dipping 60 the mechanical model is based on the stress equations in uniaxial lithostatic conditions and absence of regional stresses it shows how pre existing subvertical fractures require the smallest magmatic pressures to be penetrated for a given magmatic pressure subvertical fractures might be penetrated more deeply tapping more easily primitive magmas these results suggest that the cfvd is located along a ne sw transfer zone connecting nw se regional normal faults volcanic activity along such ne sw trend would be induced by the subvertical dip of the transfer faults the subvertical dip of transfer faults also suggests an explanation for the emission of the more primitive products along ne sw systems at campi flegrei these considerations find a wider application on the remaining volcanic districts of the margin located in the same overall structural setting

topographic lineament swarms clues to their origin from domain analysis of italy regional scale subparallel linear topographic features characterize almost all planetary surfaces this experiment concerns their tectonic meaning by focusing on map limits or domains through which individual swarms of these linear features are developed these domain limits are contrasted with map boundaries of better known structural features in a tectonically active region italy to seek clues to stress environments and times of origin of the lineaments the study uses regional raised relief maps to filter the lineament data to a very simple subset those strictly topographic features of a length and prominence capable of retaining detectability through generalizations required by relief map production a total of 5 372 lineaments were drawn using 4 differently lighted images of 1 1 000 000 scale relief maps of italy seven different tests were used for reliability and reproducibility of the data rose diagrams were prepared for 86 subareas by computer fitting of gaussians to azimuth frequency histograms individual azimuthal petals of these roses were then correlated to delimit the general area over which a given azimuthal swarm is developed the precise swarm boundaries were then located by computer contouring the population density of lines of each swarm on the original data set in this way 48 local swarms were mapped boundaries of these swarms correlate poorly with traditional litho tectonic provinces instead they seem to be associated with basin axes broad arches coastal flexures areas of normal fault swarms and projections of structural grain from adjacent sea floors the 48 domains may be grouped into 8 noncontiguous but azimuthally compatible super swarms covering much of italy the most prominent of the super swarms are greatly expanded versions of regional structural grains trend of the po basin axis of the upper adriatic basin zone of south alpine underthrusting and landward extensions of structural grain of the tyrrhenian sea from these relationships a model for lineament swarm origins is proposed involving very minor regional stretching of the thin brittle carapace of extremely large sometimes subtle structures deforming by ductile mechanisms at depth

structural control on geothermal circulation in the cerro tuzgle tocomar geothermal volcanic area puna plateau argentina abstract the reconstruction of the stratigraphical structural framework and the hydrogeology of geothermal areas is fundamental for understanding the relationships between cap rocks reservoir and circulation of geothermal fluids and for planning the exploitation of the field the cerro tuzgle tocomar geothermal volcanic area puna plateau central andes nw argentina has a high geothermal potential it is crossed by the active nw se trans andean tectonic lineament known as the calama olacapato toro cot fault system which favours a high secondary permeability testified by the presence of numerous springs this study presents new stratigraphic and hydrogeological data on the geothermal field together with the analysis from remote sensed image analysis of morphostructural evidences associated with the structural framework and active tectonics our data suggest that the main geothermal reservoir is located within or below the pre palaeozoic ordovician basement units characterised by unevenly distributed secondary permeability the reservoir is recharged by infiltration in the ridges above 4500 m a s l where basement rocks are in outcrop below 4500 m a s l the reservoir is covered by the low permeable miocene quaternary units that allow a poor circulation of shallow groundwater geothermal fluids upwell in areas with more intense fracturing especially where main regional structures particularly nw se cot parallel lineaments intersect with secondary structures such as at the tocomar field away from the main tectonic features such as at the cerro tuzgle field the less developed network of faults and fractures allows only a moderate upwelling of geothermal fluids and a mixing between hot and shallow cold waters the integration of field based and remote sensing analyses at the cerro tuzgle tocomar area proved to be effective in approaching the prospection of remote geothermal fields and in defining the conceptual model for geothermal circulation

the digital elevation model of italy for geomorphology and structural geology abstract the geomorphological setting and main geo structural features of the central southern italian peninsula have been investigated by creating and analyzing a digital elevation model dem and derived slope aspect and shaded relief images the dem has been assembled from the mean heights archive provided by the italian geological survey for the whole country the elevation data exhibit a grid mesh spacing of 7 5 latitude and 10 longitude firstly three different methods for calculating from a dem slope and aspect are discussed the four contiguous right triangles the maximum downward gradient and the bicubic spline first derivative the resulting maps have been compared with each other at regional scale and for a small area with a slope map obtained by using classical techniques the main goal of the comparison has been the choice of the best technique for the computation of the digital slope map of italy the four contiguous right triangles method yields better results both at local and at regional scale and is being used to create from the dem a slope map and a shaded relief of the whole country which will be published by the italian geological survey secondly the integrated analysis of dem derived slope digital map and shaded relief has permitted verification for the italian peninsula of the trends of already mapped fractures and faults and detection of previously unmapped structures showing morphological evidence the analysis of 1520 regional structural features has showed that the morphological setting of the studied area is strictly related to the tectonics about 90 of the mapped faults and folds are detectable on the shaded relief which proved to be the most useful byproduct of the dem for morphological analysis

brittle deformations in the upper pleistocene deposits of the crotone peninsula calabria southern italy abstract the structural setting of the crotone peninsula calabria southern italy is discussed in this paper structural analyses were carried out both on a regional and an outcrop scale to detect the main structural systems and the stress field which affected the area during the late pleistocene the tectonic features observed in the area are represented by normal faults and extensional joints the regional scale faults are arranged in five main systems striking ene wsw nne ssw e w nw se and nnw sse they are responsible for the dislocation of four marine depositional units cutro terrace correlatable with the isotopic stage 7 s leonardo campolongo isola di capo rizzuto terrace correlatable with the isotopic substage 5e le castella capo rizzuto terrace correlatable with the isotopic substage 5c and capo colonne terrace correlatable with the isotopic substage 5a in several distinct terraces from the studies carried out on a mesostructural scale it is possible to conclude that for the last 200 000 yrs the crotone peninsula was affected by an extensional stress field the comparison between the average uplift rates calculated for the crotone peninsula terraces and those computed for several upper pleistocene deposits located in sicily calabria and campania suggests that the intense tectonics which affected the crotone peninsula can be related to the geodynamic activity of the calabrian arc

spring warming of the eastern arabian sea and bay of bengal from buoy data observations from moored buoys during spring of 1998 2000 suggest that the warming of the mixed layer similar to20 m deep of the north indian ocean warm pool is a response to net surface heat flux q net similar to100 w m 2 minus penetrative solar radiation q pen similar to45 w m 2 a residual cooling due to vertical mixing and advection is indirectly estimated to be about 25 w m 2 the rate of warming due to typical values of q net minus q pen is not very sensitive to the depth of the mixed layer if it lies between 10 m and 30 m

uav based surveying in volcano tectonics an example from the iceland rift abstract in the present work we applied the use of an unmanned aerial vehicle uav a quadcopter and the aerial structure from motion digital photogrammetry image processing technique asfm to study volcano tectonics and tectonic features in an active icelandic rift data have been collected in order to evaluate the holocene deformation in the northern volcanic zone of iceland we mapped 397 structures mainly related to extension fractures and subordinately normal faults in the theistareykir fissure swarm obtaining 1098 and 21 structural data respectively this allowed to reconstruct an overall spreading direction of n108 during holocene times and to calculate a stretch of 1 013 regarding 8 10 ka old lava units deformation in the area is related to both dyke intrusions and extensional tectonics furthermore detailed geological structural field and uav surveys were also performed in two test areas in order to determine data accuracy and the associated reliability of this approach in addition to the above different flight heights were tested suggesting that photo collection with a 12 4 mpx camera at 100 m is efficient to study fracture dilation and kinematics

geomorphic expression of midcrustal extension in convergent orogens 1 channel orientation gradient drainage basin spacing drainage patterns and alluvial fan sedimentology define a set of geomorphic observables for fingerprinting modes of extensional tectonism in convergent settings anomalous finely textured trellis drainage patterns in the alps are spatially coincident with the low angle simplon and brenner detachments the detachment footwalls are characterized by numerous high angle brittle faults which are etched out by low order stream gullies and channels we quantify the relationship between these faults and watershed scale geomorphology using high resolution digital topography to extract channel and basin metrics topographic data are complemented by a field data set of channel gradients and the integrated erosional response of the watersheds preserved in valley bottom alluvial fans in footwall regions adjacent to the detachments channels are steeper more closely spaced have statistically coherent orientations and feed coarse steep alluvial fans drainage spacing increases in the footwall away from the detachment and the trellis pattern diminishes in the detachment hanging walls which typically lack high angle brittle faults there is a poor correlation between channel steepness density or orientation and hanging wall alluvial fans tend to be relatively larger gentler and debris flow dominated comparisons are made to the ticino dome region of the alps as well as to the pioneer core complex of central idaho in both cases our analysis suggests high angle brittle faulting of the footwall is particularly well preserved in the region adjacent to a detachment these results are consistent with a subvertical simple shear model for footwall extrusion as well as annealing or a lack of reactivation of brittle structures in the footwall distal to the rolling hinge

modulation of chlorophyll concentration by downwelling rossby waves during the winter monsoon in the southeastern arabian sea abstract signatures of rossby waves that are evident in satellite ocean colour data in the southeastern arabian sea seas are more prominent during the winter than the summer monsoon during the winter the sea level is high and the conditions are less conducive for the injection of nutrients through the eddy pumping mechanism in this study we use satellite observations and a physical ecosystem model to examine the role of horizontal advection associated with rossby waves in enhancing chlorophyll concentration in the seas zonal advection dominates over meridional advection and its effect is more prominent in the south of indian subcontinent and west of the maldives except along the coast and around the islands the vertical processes are weak and do not lead to a substantial increase in chlorophyll model simulations show that the currents associated with the rossby wave also transport nutrients and other physicochemical properties of water along the path of the wave the advected water decreases the concentration of arabian sea high salinity water mass and replenishes the oxygen in the oxygen minimum zone in the seas

role of synoptic scale forcing in cyclogenesis over the bay of bengal the cyclone frequency distribution over the bay of bengal during 1990 2009 was distinctly bimodal with a primary post monsoon peak and a secondary pre monsoon peak despite the very high convective available potential energy cape during the pre monsoon the location of the monsoon trough over the bay is a primary factor in tropical cyclogenesis because the trough was in the northernmost bay during the pre monsoon season cyclogenesis was inactive in the southern bay where a strong southwesterly wind shear was found in this season moreover a hot dry air mass extending vertically from 950 to 600 hpa was advected from northwestern india toward the bay moist warm southwesterly winds penetrating below the deep dry air mass caused a prominent dryline to form aloft on the northwestern side of the bay the synoptic scale hot dry air forcing to the bay suppressed the active convection necessary for cyclogenesis the strength of the stable environmental layer represented by convective inhibition cin was extremely large and acted as a cap over the northern and northwestern bay conversely during the post monsoon there were no horizontal temperature or moisture gradients and cape and cin were fairly modest the entire bay was covered by a very deep moist layer from the surface to 700 hpa transported from the east the monsoon trough position and the environmental cin in combination can explain the lower frequency of cyclogenesis during the pre monsoon compared with the post monsoon season

indian ocean warming of 1997 1998 the indian ocean underwent substantial changes in 1997 1998 the observations show not only the appearance of a dipole mode in the tropical region but also a persistent basin scale warming we present in this study an analysis of the basin scale sea surface temperature sst variations during 1997 1998 using satellite observations in situ temperature measurements and national centers for environmental prediction reanalyses we find that the indian sst anomaly peaks occurred at two periods i e november december january coinciding with the nino3 peak and the following april may june and were phase locked to the indian ocean seasonal cycle the changes of sst in the equatorial ocean were related to a coupled interaction between the atmosphere and the ocean oceanic upwelling in the east and downwelling in the west played a major role in giving rise to the sst anomalies associated with the dipole mode structure the upwelling off the coast of sumatra elevated the regional thermocline by more than 80 m in december 1997 on the other hand the changes of sst in the southern indian ocean were largely induced by the changes of local latent flux during boreal fall winter of 1997 the southeasterly trades were displaced and abnormally prolonged in their northernmost equatorial position this shifted the center of the trades toward the equator weakened the winds in the central southern ocean reduced the latent heat flux in the region and subsequently induced a surface warming the total change of the sst anomalies integrated over the two periods july december 1997 and january may 1998 were explained well by the same period latent flux integral in both intensity and pattern the cross basin upper ocean temperature sections show that the extratropical warming was rather uniformly distributed in the upper 60 m further supporting the role of mixed layer processes in the warming

a model to explain joint patterns found in ignimbrite deposits the study of fracture systems is of paramount importance for economic applications such as co2 storage in rock successions geothermal and hydrocarbon exploration and exploitation and also for a better knowledge of seismogenic fault formation understanding the origin of joints can be useful for tectonic studies and for a geotechnical characterisation of rock masses here we illustrate a joint pattern discovered in ignimbrite deposits of south america which can be confused with conjugate tectonic joint sets but which have another origin the pattern is probably common but recognisable only in plan view and before tectonic deformation obscures and overprints it key sites have been mostly studied by field surveys in bolivia and chile the pattern is represented by hundreds of meters up to kilometre long swarms of master joints which show circular to semi circular geometries and intersections that have x and y patterns inside each swarm joints are systematic rectilinear or curvilinear in plan view and as much as 900 m long in section view they are from sub vertical to vertical and do not affect the underlying deposits joints with different orientation mostly interrupt each other suggesting they have the same age this joint architecture is here interpreted as resulting from differential contraction after emplacement of the ignimbrite deposit above a complex topography the set of the joint pattern that has suitable orientation with respect to tectonic stresses may act to nucleate faults

interplay between fracturing and hydrothermal fluid flow in the ason valley hydrothermal dolomites basque cantabrian basin spain in ason valley hydrothermal dolomite area basque cantabrian basin northern spain an overlapping stepover area between two major basement faults the cabuerniga and ruahermosa transtensional faults was the location for different scales and types of extensive frac tures this fracture mesh affected the albian ranero limestone and was formed in a dilational jog a regional fluid throughflow area it acted as pathway for overpressured fluids that controlled the dolomite mineralization in the ranero massif area the study of synchronous structural features fluid flow channelling and dolomitization processes indicated their tectonic control the fluid cir culated and concentrated preferentially in more fractured areas with increased permeability such as extensional chimneys creating dolomite bodies repeated extensive tectonic activity enhanced fracture porosity promoting overpressured fluid migration and cyclical dolomitization events the studied fracture pattern suggests the presence of sinistral transtension during the formation of extensional joint sets that channellized the mineralizing fluid flow a gradation in structural fea tures and dolomite facies and textures is visible from the main pozalagua fault dolomite body to peripheral dolomite bodies as the breccia body and ranero megajoints these differences could reflect a proximal distal trend from the main fluid flow area along the pozalagua fault to the ranero megajoints

lineament domain of regional strike slip corridor insight from the neogene transtensional de geer transform fault in nw spitsbergen lineaments on regional scale images represent controversial features in tectonic studies published models explain the presence of the lineament domains in most geodynamic environments as resulting from the enhanced erosion along strikes normal to the upper crustal regional extension despite their success in many tectonic frameworks these models fail to explain the existing lineament domains in the regional strike slip corridors that separate regional blocks including the transform faults the present paper investigates the lineament distribution in such environments and specifically presents the results from a study along the shear corridor of the de geer transform fault in the north atlantic responsible for the separation and drifting away between northern greenland and the svalbard archipelago since oligocene times the study spans from satellite image analysis and outcrop scale investigations to a more regional analysis on a digital bathymetric model of the north atlantic arctic ocean lineaments were automatically detected in the spectral band 8 0 52 0 9 m of a landsat 7 image 15 m pixel resolution a total of 320 image lineaments were extracted from both the regional and the local scale investigations and statistically analyzed results from the multi scalar lineament analyses revealed the existence of a main n s lineament domain regionally persistent from the de geer corridor to the western margin of northern spitsbergen where it relates to the youngest post oligocene tectonics observed onshore this is confirmed by field observations showing that the n s faults represent the youngest brittle deformation system and systematically cut the deformations associated with the building of the tertiary west spitsbergen fold and thrust belt the n s lineament domain is the result of the activity of a larger regional scale tectonic feature nw se oriented and responsible for the localized extension within its deformation corridor the de geer transform fault a model is presented that involves the presence of a thin upper crust with brittle behavior lying above a deeper crustal layer characterized by a more ductile deformation the lower layer suffers more diffuse homogeneous strain this strain is transmitted to the upper brittle layer forming clusters of enhanced fracturing zones aligned following the induced stress trajectories lineaments develop along these weaker fractured zones preferentially etched by erosional processes and align perpendicular to the least horizontal compression sigma3 which in turn forms an angle to the shear kinematics in the western part of spitsbergen this angle is smaller than 45 due to the transtensional tectonic regime the proposed model for lineament domain origin in strike slip environments well integrates the existing models in literature and could be applied to other similar geodynamic contests

the post eocene evolution of the doruneh fault region central iran the intraplate response to the reorganization of the arabia eurasia collision zone

origin of the adventure subglacial trench linked to cenozoic extension in the east antarctic craton abstract the antarctic plate occupies a unique geodynamic setting being mostly surrounded by divergent or transform margins major intracontinental basins and highlands characterize its bedrock buried under the 34 ma east antarctic ice sheet eais their formation atop of the cratonic lithosphere in the interior of east antarctica remains a major open question post mesozoic intraplate extensional tectonic activity has been proposed for their development and is supported by this work here we focus on the adventure subglacial trench ast whose origin is poorly constrained and controversial as currently available geophysical models suggest either extensional or compressional tectonic origin the ast is an over 250 km long 60 km wide subglacial trough elongated in the nnw sse direction adjacent to the westernmost flank of the wilkes subglacial basin and is parallel to regional scale alignments of magnetic and gravimetric anomalies geophysical campaigns allowed better definition of the ast physiography showing its typical half graben geometry the rounded morphology of the western flank of the ast was simulated through tectonic numerical modelling we consider the subglacial landscape to primarily reflect a preserved relict of the tectonic processes affecting the interior of east antarctica in the cenozoic due to the negligible erosion deposition capability of the eais the bedrock morphology was replicated through the activity of the listric adventure fault characterized by a basal detachment at the base of the crust 34 km and a vertical displacement of 2 5 km this length suggests its regional crustal importance the predicted displacement is interpreted either as a newly formed fault or as the partial reactivation of a weaker zone along a major precambrian crustal scale tectonic boundary the extensional regime in the ast is part of a more extensive 800 km long intraplate corridor characterized by nearly along strike extension in cenozoic times with a left lateral transpressional component this corridor may represent the effect of far field stresses induced by plate motions

strike slip fault propagation cleavage in carbonate rocks the mattinata fault zone southern apennines italy disjunctive spaced solution cleavage in carbonate rocks is genetically associated with the propagation of the left lateral strike slip mattinata fault in the gargano promontory italy typical cleavage development is restricted within the 200 300 mwide fault zone which is bounded by virtually unfractured wall rocks the cleavage consists of sub parallel solution surfaces which are often reactivated as sheared solution planes geometrical and kinematic relationships exist between the fault and the associated cleavage planes thus 1 cleavage fault intersection lines lie parallel to the fault and the sheared cleavage rotational axes and 2 the cleavage fault angle is almost constantly equal to 408 a model for the development of the mattinata fault is proposed in which the cleavage surfaces are interpreted as fault propagation deformations cleavage nucleates as solution planes at the front of the advancing fault as the result of stress concentration in this region two distinct time sequential processes are shown to operate during the fault propagation 1 typical millimetre to centimetre spaced solution surfaces form in the distal tip zone of the advancing fault plane 2 as the tip advances the fault plane breaks through the cleavage as minor shear displacements reactivate some of these nascent surfaces these observations may prove useful in understanding mechanisms for fault controlled enhanced reduced permeability and fluid pathways 1999 elsevier science ltd all rights reserved

analysis and interpretation of landsat synthetic stereo pair for the detection of active fault zones in the abruzzi region central italy considerable enhancement of landsat imagery for geologic and morphotectonic interpretation can be obtained through generation of a synthetic stereo pair by means of the integration of the spectral data with a digital elevation model photointerpretation of the enhanced landsat images allows one to detect morphotectonic landforms of regional extension and to analyze their geomorphic characteristics at a small scale field geologic and structural surveys are then extensively used to crosscheck the image interpretation and to establish the relationships between location orientation and estimated age of the regional structures and the local evidences of active tectonics an application of landsat stereo pair creation and interpretation is presented for an area characterized by high rates of tectonic activity in central italy the work results in the definition of the location and extension of an active seismotectonic source whose geomorphic expression at the surface strongly suggests that it is capable of generating earthquakes of magnitude 7

core top calibration of mg ca in tropical foraminifera refining paleotemperature estimation 1 optimal use of mg ca as a paleotemperature proxy requires establishing calibrations for different species of foraminifera and quantifying the influence of dissolution to achieve this goal we have measured mg ca and 18o in a series of tropical and subtropical core tops including four depth transects the ceara rise the sierra leone rise and the rio grande plateau in the atlantic and the ontong java plateau in the pacific focusing on spinose mixed layer dwelling species globigerinoides ruber and globigerinoides sacculifer and nonspinose thermocline dwelling neogloboquadrina dutertrei shell mg ca in g sacculifer is 5 15 lower than in g ruber while n dutertrei mg ca is 49 55 lower than in g ruber this statistically significant offset has allowed us to establish different calibrations for each species multilinear regression analysis was used to develop calibration equations that include a correction term for the dissolution effect on mg ca in foraminiferal calcite presented in this paper are two sets of calibrations one set using core depth as a dissolution correction and another using co32 as a dissolution parameter the calibrations suggest that g ruber is the most accurate recorder of surface temperature while g sacculifer records temperatures below the surface at 20 30 m the depth habitat of n dutertrei is more uncertain owing to the wide range in habitat depths depending on hydrographic conditions but on average mg ca and 18o data suggest it is at 50 m of the three species n dutertrei is the most sensitive to dissolution up to 23 decrease in shell mg ca per km while g sacculifer is the most resistant

pore pressure response to barometric pressure change in champlain clay prediction of the clay elastic properties abstract champlain sea clay deposits play a crucial role in limiting contaminant migration to underlying aquifers in the saint lawrence river valley champlain sea clays are well known as being prone to landslide and sample disturbance estimation of their elastic properties using their in situ loading efficiency would provide mechanical properties for the soil dynamic analyses and immediate settlement calculations encountered in geotechnical projects determination of loading efficiency can be envisioned as a very small strain test in this paper we describe a detailed monitoring program for 10 vibrating wire piezometers installed within sealed boreholes on 5 study sites near montreal in quebec canada the pore pressure response to barometric pressure variation was analyzed with three methods linear regression visual inspection and multiple regression which gave loading efficiencies between 0 7 and 0 95 these values were then used to estimate the elastic properties of the clay formation vertical compressibility and specific storage on the order of 1 10 6 kpa 1 and 1 10 5 m 1 were respectively obtained for most of the monitoring sites a comparison of compressibility values derived from the in situ loading efficiency method with those obtained with pressuremeter oedometer and pulse tests confirmed that clay compressibility is strain dependent the pore pressures measured on the study sites have been corrected by applying the multiple regression and visual inspection methods for most piezometers both methods provided nearly identical results however for deep piezometers the multiple regression method provided smoother pore pressure time series than the visual inspection method the vertical hydraulic gradient obtained with corrected pressure data was shown to change significantly on some test sites during the monitoring period

high resolution record of northern hemisphere climate extending into the last interglacial period high resolution record of northern hemisphere climate extending into the last interglacial period

cenozoic noncoaxial transtension along the western shoulder of the ross sea antarctica and the emplacement of mcmurdo dyke arrays field data on cenozoic faults and the mcmurdo dyke arrays in the reeves glacier mawson glacier area victoria land antarctica allow us to support noncoaxial transtensional tectonics along the n s trending western shoulder of the ross sea dyke injection within a crustal scale right lateral strike slip shear zone is testified by magma filled tension gash like arrangements within some master fault zones and by the left stepping arrangements of dykes in the intrafault zones the noncoaxiality of deformation is shown by the re activation of many dyke walls as right lateral strike slip faults this suggests an increase in the strike slip component over time along the western shoulder of the ross sea our data support the relevance of transtensional to strike slip tectonics for triggering melting and controlling the geometry and modes of magma emplacement

fissural volcanism polygenetic volcanic fields and crustal thickness in the payen volcanic complex on the central andes foreland mendoza argentina shield volcanoes caldera bearing stratovolcanoes and monogenetic cones compose the large fissural payen volcanic complex located in the andes foreland between latitude 35 s and 38 s the late pliocene pleistocene and recent volcanic activity along e w trending eruptive fissures produced basaltic lavas showing a within plate geochemical signature the spatial distribution of fractures and monogenetic vents is characterized by self similar clustering with well defined power law distributions vents have average spacing of 1 27 km and fractal exponent d 1 33 defined in the range 0 7 49 3 km the fractal exponent of fractures is 1 62 in the range 1 5 48 1 km the upper cutoffs of fractures and vent fractal distributions about 48 49 km scale to the crustal thickness in the area as derived from geophysical data this analysis determines fractured media crust thickness associated with basaltic retroarc eruptions we propose that the payen volcanic complex was and is still active under an e w crustal shortening regime

the cenozoic fold and thrust belt of eastern sardinia evidences from the integration of field data with numerically balanced geological cross section newly collected structural data in eastern sardinia italy integrated with numerical techniques led to the reconstruction of a 2 d admissible and balanced model revealing the presence of a widespread cenozoic fold and thrust belt the model was achieved with the forc software obtaining a 3 d 2 d time numerical reconstruction of the continuous evolution of the structure through time the mesozoic carbonate units of eastern sardinia and their basement present a fold and thrust tectonic setting with a westward direction of tectonic transport referred to the present day coordinates the tectonic style of the upper levels is thin skinned with flat sectors prevailing over ramps and younger on older thrusts three regional tectonic units are present bounded by two regional thrusts strike slip faults overprint the fold and thrust belt and developed during the sardinia corsica block rotation along the strike of the preexisting fault ramps not affecting the numerical section balancing this fold and thrust belt represents the southward prosecution of the alpine corsica collisional chain and the missing link between the alpine chain and the calabria peloritani block relative ages relate its evolution to the meso alpine event eocene oligocene times prior to the opening of the tyrrhenian sea tortonian results fill a gap of information about the geodynamic evolution of the european margin in central mediterranean between corsica and the calabria peloritani block and imply the presence of remnants of this double verging belt missing in the southern tyrrhenian basin within the southern apennine chain the used methodology proved effective for constraining balanced cross sections also for areas lacking exposures of the large scale structures as the case of eastern sardinia

morphostructural analysis and cenozoic evolution of elephant island southern scotia arc antarctica elephant island located in the vicinity of the present day active boundary of the south shetland block and the antarctic and scotia plates is a region of particular interest for understanding the past and present geodynamic evolution of the southern scotia arc lineament from different data sources field measured fractures and geomorphological evidences have been analysed in this context the lineaments extracted from aerial photographs 1 624 from a dem 348 and from radarsat 2 satellite data 1 365 indicate four dominant lineament sets with ne sw nw se n s and w e strikes all data sources identified similar lineament families but differences in the frequency distributions and subsequently on the dominant orientations were observed the measurements direct of fractures were obtained from 23 sites in the field at which 278 planes were measured fracture planes indicate main modes trending in the nne ssw and nnw sse directions and a secondary mode in the e w the major trends of the fracture measurements and the lineaments display a good correlation in the e w direction however there is an angular variation in the azimuth values of the nne sse and nnw sse fractures with respect to the n s ne sw and nw se orientations of the lineaments of approximately 20 this trend deviation may be due to the fact that mapped lineaments are composed of small fracture sets that may be related to shear fractures that cannot be distinguished at the aerial photograph or radar satellite data scales submerged sea floor morphological feature orientations match the studied morphostructures on the island and the main tectonic structures in this part of the scotia arc a linkage of the main lineament families to the tectonic stages from the oligocene to the present has been proposed taking into account the information of the orientation and sense of movement of the fractures and stresses in the elephant island region

sensitivity of the thermohaline circulation to tropical and high latitude freshwater forcing during the last glacial interglacial cycle recent studies indicate that the tropical freshwater budget of the atlantic is modulated by changes in el nine southern oscillation enso if anomalies of the atlantic freshwater balance persist on the order of decades these might have a large influence on the north atlantic thermohaline circulation thc here we present a sensitivity study in which we use a model scenario for enso behavior during the last 120 kyr to force a simplified model of the thc with corresponding freshwater exchange between the tropical atlantic and pacific if the steady state strength of the north atlantic thc is similar to the present day its response to the forcing is of the order of 1 3 sv 1 sv 10 6 m 3 s 1 no mode changes of the thc are simulated for reasonable values of the coupling constant between freshwater exchange and enso if on the other hand the steady state overturning is significantly weaker a collapse of the thc occurs due to forcing from the tropics the modeled thc variation due to tropical freshwater perturbations are compared to those resulting from middle and high latitude freshwater forcing due to long term growth and decay of northern hemisphere ice sheets it is found that both forcings are of similar amplitude except during the deglaciation when high latitude forcing dominates a possible out of phase relationship between deep water formation in the north pacific and north atlantic is also explored

the last glacial termination a major puzzle of paleoclimatology is why after a long interval of cooling climate each late quaternary ice age ended with a relatively short warming leg called a termination we here offer a comprehensive hypothesis of how earth emerged from the last global ice age a prerequisite was the growth of very large northern hemisphere ice sheets whose subsequent collapse created stadial conditions that disrupted global patterns of ocean and atmospheric circulation the southern hemisphere westerlies shifted poleward during each northern stadial producing pulses of ocean upwelling and warming that together accounted for much of the termination in the southern ocean and antarctica rising atmospheric co2 during southern upwelling pulses augmented warming during the last termination in both polar hemispheres

moored observations of upper ocean response to the monsoons in the arabian sea during 1994 1995 the role of surface forcing in the semiannual evolution of the upper ocean temperature salinity and velocity fields in the arabian sea is examined to do so variability in the upper ocean in the central arabian sea was observed from an array of moorings deployed from october 1994 to october 1995 the northeast ne monsoon was characterized by moderate winds clear skies and dry air sea surface temperature sst dropped by 31c the ocean lost an average of 19 7 w m 2 and the mixed layer deepened by 100 m in response the southwest sw monsoon was accompanied by strong winds cloudy skies and moist air the ocean gained an average of 89 5 w m 2 but sst dropped by 5 51c and the mixed layer deepened to almost 80 m the response to the ne monsoon included daily cycling in the depth of the mixed layer in response to the diurnal cycle in the buoyancy forcing and a weak local wind driven response stronger windforcing during the sw monsoon dramatically reduced diurnal restratification and a clearer signal of local wind driven flow in the upper ocean was found the strongest velocity signal in the upper ocean however was the flow associated with mesoscale geostrophic features that passed slowly through the moored array dominating the current meter records in the first part of the ne monsoon and again in the latter part of the sw monsoon one dimensional heat and freshwater balances which held at other times through the year broke down during the passage of these features r 2002 published by elsevier science ltd

estimating the seaward extent of sea breeze from quikscat scatterometry 1 we present an objective method for quantifying the seaward extent of the sea breeze the underlying assumption is that the offshore decay in the strength of the sea breeze results in an offshore decay of the vector correlation between the wind vectors near and away from the coast the degradation in the vector correlation coefficient is used to estimate the seaward extent of the sea breeze using quikscat data

volcano tectonics of the al haruj volcanic province central libya abstract the al haruj intra continental volcanic province ahvp located at the south western margin of the sirt basin hosts the most extensive and recent volcanic activity in libya which is considered typical for plate interiors from north to south the ahvp is divided into two subprovinces namely al haruj al aswad and al haruj al abiyad the total area of the ahvp is around 42 000 km 2 despite the great size of the ahvp its volcano tectonic evolution and activity have received very little attention and are poorly documented and understood here we present new field data and analytical and numerical results on the volcano tectonics of the ahvp the length thickness ratio of 47 dykes and volcanic fissures were measured to estimate magmatic overpressure at the time of eruption the average dyke length thickness ratio of 421 indicates magmatic overpressures during the associate fissure eruptions of 8 19 mpa depending on host rock elastic properties spatial distributions of 432 monogenetic eruptions sites points lava shields pyroclastic cones in the ahvp reveal two main clusters one in the south and another in the north aligned eruptive vents show the dominating strike of volcanic fissures feeder dykes as wnw ese to nw se coinciding with the orientation of one of main fracture fault zones numerical modelling and field observations suggest that some feeder dykes may have used steeply dipping normal fault zones as part of their paths to the surface

spatial distribution of cones and satellite detected lineaments in the pali aike volcanic field southernmost patagonia insights into the tectonic setting of a neogene rift system abstract the relationships between the distribution and morphometric features of eruptive structures scoria and spatter cones maar tuff rings and the fracture network were investigated in the pliocene quaternary pali aike volcanic field southernmost patagonia argentina chile the alkali basaltic basanitic magmas which erupted in this area have nearly primary magma compositions and often bear mantle xenoliths hence magma ascent from deep seated reservoirs was probably very fast with no significant stagnation at crustal levels field surveys and satellite image analysis led to the identification of up to 467 eruptive structures and four main nw se ne sw e w and n s fracture systems the spatial distribution of eruptive cones and fractures was investigated through the computation of power law exponents df for self similar clustering the self similarity of cones and fractures was defined between lower and upper cut offs which were in turn related to the thickness of the fractured mechanical layer the fractal character of cones and fracture distribution clustering in the pali aike volcanic field area was thus correlated with crustal thickness the self similarity of fractures was used to establish the relative chronology of the detected fracture systems the self similar clustering exponent is highest in the e w and nw se fracture systems df 1 78 and 1 77 respectively and lowest in the n s system df 1 65 the self similar clustering of eruptive structures is well defined df 1 45 the intense volcano tectonic activity in the pali aike area marks a major pliocene quaternary phase in the development of the magellan neogene rift system

structural controls of the domuyo geothermal field southern andes 36 38 s argentina abstract geothermal fields in subduction related orogens are closely linked to areas characterized by young magmatic and tectonic activity both in arc and back arc settings the spatio temporal interaction of quaternary volcanic complexes with regional extensional and transtensional structures might favor a hydrothermal circuit between meteoric water and magmatic fluids this study encompasses a kinematic analysis of fault structures from the high enthalpy system located at the western flank of the domuyo volcano in argentina an analysis of remote sensing data was applied to detect regional lineaments lineament density and to identify fracture patterns possibly associated with the different deformational stages documented in the area these results were combined with detailed fracture analysis and kinematic study of mesoscale faults as well as existing geological structural and geophysical data the integration suggests that the fluid dynamics of the domuyo geothermal field are directly conditioned by pre existing basement structures that were reactivated as normal faults during pliocene to quaternary times furthermore the intensely fracture late triassic early jurassic units are interpreted as the potential level for the reservoir the fault reactivation was likely associated with the accommodation of regional extension along pre existing fault structures and locally enhanced by hydrothermal effects of the domuyo geothermal field

analysis of the cone pressuremeter test in clay the cone pressuremeter test is a new in situ test which combines a standard cone penetrometer with a pressuremeter an analysis of the cone pressuremeter test in clay is presented the analysis shows that important information about soil properties can be gained from the unloading section of the pressuremeter curve as well as the loading section seven tests using a prototype cone pressuremeter are analysed using the new method and the derived soil parameters are compared with other tests at the same site the analysis is shown to fit closely the behaviour observed in the tests and the derived values of shear modulus and undrained strength agree well with the results of other tests le nouvel essai au pressiometre a cone combine un penetrometre a cone de type standard avec un pressiometre l article presente une analyse de l essai au pressiometre a cone dans l argile l analyse demontre que des indications importantes au sujet des proprietes du sol peuvent s acquerir a partir des zones de dechargement

formation mechanisms of temperature inversions in the southeastern arabian sea numerical simulations using a high resolution 0 25 0 0 25 0 40 levels ogcm of the indian ocean are used to study the formation mechanisms of temperature inversions ti in the southeastern arabian sea seas during winter to the west and south of india haline stratification is a necessary pre requisite for ti formation off the southern tip of india low salinity water advected from the bay of bengal is cooled by strong winds and leads to ti formation in the southern part of the seas advection of this cooler low salinity water over warm salty seas water leads to the formation of ti and occur at a deeper depth sim 80 m due to the downwelling within the lakshadweep high in the northern part ti occur at a much shallower depth sim 20 m and are caused by shortwave radiation penetrating below the mixed layer of about 12 m

changes in surface productivity and subsurface denitrification during the holocene a multiproxy study from the eastern arabian sea spatial and temporal variations in the intensity of subsurface denitrification in the water column of the eastem arabian sea have been investigated using chemical and isotopic proxies the data show a steady increase in the denitrification intensity from 10 ka to 2 ka bp probably caused by changes in surface productivity fuelled by strengthening of upwelling monsoonal intensity in addition changes in redox conditions and detrital material input are assessed using abundances of a suite of major and trace elements the temporal variations in some of the monsoonal proxies are characterized by periodicities of 1400 and 700 years similar to those reported in the south asian chinese monsoon and high latitude climate north atlantic region

coupled sea surface temperature seawater δ18o reconstructions in the arabian sea at the millennial scale for the last 35 ka two sediment cores from the western 905 10 46 9 n 51 56 4 e water depth 1586 m and eastern sk17 15 15 n 72 58 e water depth 840 m arabian sea were used to study past sea surface temperatures sst and seawater 18o 18ow variations for the past 35 ka we used coupled mg ca 18o calcite variability in two planktonic foraminiferal species globigerinoides ruber which thrives throughout the year and globigerina bulloides which occurs mainly when surface waters contain high nutrients during upwelling or convective mixing ssts in both areas based on mg ca in g ruber were 3 to 4 c lower during the last glacial maximum lgm 21 ka than today and the holocene period the sst records based on g bulloides also indicate general cooling down to 18 c in both areas ssts in the western arabian sea based on g bulloides were always lower than those based on g ruber indicating the presence of strong seasonal temperature contrast during the holocene and lgm we interpret the consistent presence of this seasonal temperature contrast to reflect a combination of seasonal summer upwelling sw monsoon and winter convective mixing ne monsoon in the western arabian sea in the eastern arabian sea g bulloides based ssts were slightly lower about 1 c than g ruber based ssts during the holocene indicating the almost absence of a seasonal temperature gradient similar to today however a large seasonal temperature contrast occurred during the lgm which favors the assumption that strong ne monsoon winds forced winter upwelling or convective mixing offshore goa sst and 18ow reconstructions reveal evidence of millennial scale cycles particularly in the eastern arabian sea here the stadial periods northern hemisphere cold periods such as younger dryas and heinrich events are marked by increasing ssts and salty sea surface conditions relative to those during the interstadial periods indeed the 18ow record shows evidence of low saline surface waters during interstadial periods indicating increased freshwater runoff from the western ghats as a consequence of enhanced sw monsoon intensity

diversity and distribution of echinoderms in the south eastern arabian sea shelf under the influence of seasonal hypoxia abstract the south eastern arabian sea seas margin represents a tropical eastern boundary upwelling system which is subjected to intense seasonal hypoxia in the continental shelf and impingement of oxygen minimum zone omz along the continental slope this paper provides the first comprehensive information on abundance diversity and distribution patterns of echinoderms which are highly sensitive to oxygen deficiency and anthropogenic disturbances in the continental shelf 20 250 m of the seas results are based on depth stratified and seasonally resolved sampling at 241 sites representing 8 latitudinal grids 4 depth strata from inner shelf to shelf edge using naturalist dredge and smith mcintyre grab echinoderms were the numerically dominant group among epifauna 42 with significant seasonal variations in relative abundance 71 during winter and 17 during summer monsoon fifty five species of echinoderms were identified among which ophiuroids showed highest diversity 24 species followed by echinoids 11 species and asteroids 8 species species richness of echinoderms was higher in the inner and mid shelf 20 80 m while the group was nearly absent in the shelf edge 150 250 m a significant negative correlation was noted between species richness and latitude and three distinct sub regions could be delineated based on species diversity and abundance the observed distribution patterns were found to be determined chiefly by sediment texture and bottom water dissolved oxygen along with anthropogenic disturbances bottom trawling echinoderms showed maximum abundance and species richness in the well oxygenated sandy sediments of the southern seas and very low species richness and abundance in relatively silty sediments of the northern seas which were characterised by high seasonal fluctuations in dissolved oxygen seasonal hypoxia the near absence of echinoderms in the shelf edge despite the availability of sandy substrates indicates that this group is more sensitive to the perennially low oxygen conditions prevailing here

sensitivity of the atlantic intertropical convergence zone to last glacial maximum boundary conditions 1 recent paleoproxy records suggest that the mean latitude of the atlantic intertropical convergence zone itcz varied synchronously with north atlantic climate over a range of timescales throughout the holocene and last glacial maximum we show that the present day meridional mode of atmosphere ocean variability in the tropical atlantic is a potentially useful model for understanding these paleoclimate changes the tropical atlantic in a coupled atmospheric general circulation and slab ocean model responds to last glacial maximum conditions with a southward displacement of the itcz this response arises primarily through the land ice sheet that forces increased north atlantic trades analogous to the forcing on the present day meridional mode changes to sea ice coverage and to ocean heat transport associated with a weakened atlantic thermohaline circulation also cause a meridional mode response though through different mechanisms our results highlight the potential for tropical atlantic paleoclimate to be driven from the high latitude influences in particular land ice on glacial interglacial timescales

calibration of mg ca thermometry in planktonic foraminifera from a sediment trap time series 1 paired mg ca and 18o measurements on planktonic foraminiferal species g ruber white g ruber pink g sacculifer g conglobatus g aequilateralis o universa n dutertrei p obliquiloculata g inflata g truncatulinoides g hirsuta and g crassaformis from a 6 year sediment trap time series in the sargasso sea were used to define the sensitivity of foraminiferal mg ca to calcification temperature habitat depths and calcification temperatures were estimated from comparison of 18o of foraminifera with equilibrium calcite based on historical temperature and salinity data when considered together mg ca mmol mol of all species except two show a significant r 0 93 relationship with temperature t c of the form mg ca 0 38 0 02 exp 0 090 0 003 t equivalent to a 9 0 0 3 change in mg ca for a 1 c change in temperature small differences exist in calibrations between species and between different size fractions of the same species o universa and g aequilateralis have higher mg ca than other species and in general data can be best described with the same temperature sensitivity for all species and pre exponential constants in the sequence o universa g aequilateralis g bulloides g ruber g sacculifer other species this approach gives an accuracy of 1 2 c in the estimation of calcification temperature the 9 sensitivity to temperature is similar to published studies from culture and core top calibrations but differences exist from some literature values of pre exponential constants different cleaning methodologies and artefacts of core top dissolution are probably implicated and perhaps environmental factors yet understood planktonic foraminiferal mg ca temperature estimates can be used for reconstructing surface temperatures and mixed and thermocline temperatures using g ruber pink g ruber white g sacculifer n dutertrei p obliquiloculata etc the existence of a single mg thermometry equation is valuable for extinct species although use of species specific equations will where statistically significant provide more accurate evaluation of mg ca paleotemperature

fractal analysis of fracturing in two african regions from satellite imagery to ground scale abstract in two test areas of africa the fractal character of fracture fields was analyzed at very different scales on fracture maps from satellite images and from interpretation of drainage networks on topographical maps aerial photographs and ground photographs three different methods were used and the results criticized it was generally found that the area studied in western africa displays more fractal features than the area examined in central africa this might be related to the number and mechanism of fracturing phases in each region

assessment of self boring pressuremeter tests in sensitive clay the present paper analyzes field test results obtained by means of the cambridge self boring pressuremeter sbpm in a sensitive champlain clay of quebec it is shown that although the undrained shear strengths deduced from the sbpm tests are higher than the values obtained with the field vane the observed discrepancy is reduced by taking into account progressive failure effects it is not the sbpm test that overestimates the undrained shear strength but rather the vane test that underestimates it in this sensitive clay total and effective field stress paths are inferred from the sbpm tests and it is shown that the effective stress paths approach the tension zone of the mohr coulomb failure diagram before heading towards the large strain failure envelope of the clay the pressuremeter interpretation has been thoroughly worked through for various uncertainties like undrained test conditions plane strain conditions and disturbance basing the final judgment on a comparison of the effective stress adj

analysis of lineaments and their relationship to neogene fracturing se viti levu fiji the fiji archipelago lies along a complex active section of the pacific and australian plate boundary zone in the sw pacific the availability of a range of remotely sensed imagery and recent field studies have permitted the exploration of the link between lineaments as seen on such imagery and tectonic fractures observed on the ground in se viti levu the main island of fiji comparisons of statistical orientation peaks as well as the spatial extent of lineaments with field mapped fractures indicate that the lineaments are largely a reflection of tectonic fractures in the bedrock emphasized on the surface by topography drainage and vegetation surface lineaments correspond to broad zones of intense fracturing and strongly influence the landform features of the area it appears that surface fracture sets are open upward splay zones that merge downward into single planar discontinuities represented by sparse uninterrupted magnetic lineaments at depth fault correlated lineament sets extend over greater geographical distances than the equivalent mapped fault zones and these lineament sets represent more complex regional structural patterns than previously known this study provides an approach to mapping fracture patterns where outcrop is limited and where conventional field mapping techniques of structural geology are impractical it highlights the benefits of mapping lineaments from multiple sets of remote sensing imagery of the surface and bedrock mapping them at regional and larger scales as well as linking lineaments to detailed field mapped structures lineament data derived using such an approach can be used effectively to characterize regional structural patterns which in turn may provide better understanding of the structural and tectonic evolution and seismic hazards of the region this approach may also find useful application in groundwater mineral and oil and gas exploration

incorporating surface indicators of reservoir permeability into reservoir volume calculations application to the colli albani caldera and the central italy geothermal province abstract the quaternary roman volcanic province extends for over 200 km along the tyrrhenian margin of the italian peninsula and is composed of several caldera complexes with significant associated geothermal potential in spite of the massive programs of explorations conducted by the then state owned enel and agip companies between the 1970s and 1990s and the identification of several high enthalpy fields this resource remains so far unexploited although it occurs right below the densely populated metropolitan area of roma capital city the main reason for this failure is that deep geothermal reservoirs are associated with fractured rocks the secondary permeability of which has been difficult to predict making the identification of the most productive volumes of the reservoirs and the localisation of productive wells uncertain as a consequence almost half of the many exploration deep bore holes drilled in the area reached a dry target this work reviews available data and re assesses the geothermal potential of caldera related systems in central italy by analysing in detail the case of the colli albani caldera system the closest to roma capital city a gis based approach identifies the most promising reservoir volumes for geothermal exploitation and uses an improved volume method approach for the evaluation of geothermal potential the approach is based on a three dimensional matrix of georeferenced spatial data the a axis accounts for the modelling of the depth of the top of the reservoirs based on geophysical and direct data the b axis accounts for the thermal modelling of the crust i e t with depth based on measured thermal gradients both a and b data are necessary but not sufficient to identify rock volumes actually permeated by geothermal fluids in fractured reservoirs we discuss the implementation of a c axis that evaluates all surface data indicating permeability in the reservoir and actual geothermal fluid circulation we consider datasets on i distribution and density of tectonic lineaments ii temperature and iii electric conductivity of shallow groundwaters iv partial pressure of dissolved co2 in shallow groundwaters the geothermal potential of colli albani and the implications for caldera related geothermal systems in central italy are discussed based on the role of the geometry and structure of reservoirs in relationship with volcano tectonic structures and deep geothermal fluid migration paths

strain rate effects in model pressuremeter testing a series of one eighth scale strain controlled model pressuremeter tests were performed using an automated flexible wall calibration chamber testing system undrained model pressuremeter tests were performed with and without the internal pore water pressure measuring piezometer needles at radial strain rates ranging from 1 to 8 min in a controlled laboratory setup in beds of kaolin clay prepared with known stress histories reference strength and deformation properties were determined using one dimensional consolidation isotropically consolidated undrained compression and k sub 0 consolidated undrained compression laboratory tests and comparisons were made with the interpreted values from the pressuremeter test data interpretations of the undrained shear strength initial shear modulus shear stress radial strain variation limit pressure and horizontal stress for each net pressuremeter curve were evaluated via various interpretation procedures using the marquardt levenberg algorithm based on the laboratory test data and the analytical interpretations several conclusions were made regarding the effects of the rate of probe expansion on the deduced shear modulus undrained shear strength and limit pressure in the pressuremeter testing of clays

evaporation precipitation changes in the eastern arabian sea for the last 68 ka implications on monsoon variability 1 variations in sea surface temperature sst 18o of sea water 18ow and salinity were reconstructed for the past 68 ka using a sediment core aas9 21 from the eastern arabian sea eas in order to understand the changes in evaporation and precipitation associated with the monsoon system the mg ca derived sst record varies by 4 c it shows that marine isotope stage mis 4 was warmer than mis 3 that the last glacial maximum was 4 c cooler than the present and that there was a 2 c increase within the holocene mis 4 records higher 18ow and salinity values than mis 2 suggesting variable flow of low salinity bay of bengal flow into the eas during glacial periods the transition from mis 4 to mis 3 was marked with a conspicuous shift from higher to lower 18ow values which reflects a decrease in the evaporation precipitation budget in the eas perhaps due to the strengthening of southwest monsoon monsoon reconstructions based on 18ow reveal that monsoon driven precipitation was higher during mis 3 and mis 1 and was lower during mis 2 and mis 4 this is consistent with earlier monsoon reconstructions based on upwelling indices from the western arabian sea however the amplitude of monsoon fluctuations derived through upwelling indices and 18ow varies significantly which may indicate spatial variability of monsoon rainfall

tectonic causes of landslides the relationship between mass movements and tectonic lineaments is investigated in the pliocene sand and clay terrains of montepulciano central italy satellite images and aerial photographs show six families of lineament in southern tuscany all of which are present in the montepulciano area the orientation location and density of these are related to corresponding attributes of morphological phenomena such as retrogressive slumps drainage density and slope angle rose diagrams stereographic plots and statistical analysis all reveal a close correspondence between slumping mass movements and the directions and spatial concentrations of fracture traces although slopes and valley trends respond more closely to apennine nw trending and anti apennine ne trending lineaments the longitudinal axes of landslides are strongly orientated nnw to n the direction of one of the most significant lineament groups in western central italy and the local study area copyright 1993 john wiley sons ltd

effect of strain rate on undrained strength derived from pressuremeter tests a method is presented for evaluating the effect of strain rate on pressuremeter tests it can analyse the combined effects of higher strain rate and variation of strain rate across the soil mass on the undrained strength derived from pressuremeter tests the results of a parametric study using this method indicate that the stress strain curves derived from the pressuremeter curves differ from the true material stress strain curves and that the undrained strength is overestimated these differ ences are quantified l article presente une methode pour evaluer i effet du taux de deformation sur les essais pressiometriques en utilisant la mkthode il est possible d analyser les effects combines d un taux de deformation plus eleve et d une variation dans le taux de deformation a travers la masse du sol sur la resistance non drainee obtenue a partir d essais pressiometriques les resultats d une etude parametrique utilisant cette methode indiquent que les courbes de contrainte deformation obtenues a partir des

late tectonic reorientation of lineaments and fabrics in the northern eastern ghats province india evaluating the role of the mahanadi shear zone abstract south of the msz that cuts across the eastern ghats province egp of india lineament trends and early granulite facies fabrics rotate from nne ssw in the south towards the wnw ese striking northerly dipping mahanadi shear zone msz in the north using field microstructural and ebsd techniques we demonstrate that d1 and d2 planar fabrics are reoriented by an e w trending northerly dipping d3 extensional shear zone that has a subordinate sinistral strike slip component d3 microstructures are pervasive with quartz and feldspar microstructures characteristic of amphibolite facies metamorphism monazite chemical ages from the d3 shear zone yield ages in the range 730 680 ma the msz representing d4 deformation in the area is a predominantly dextral strike slip deformation during d4 microstructures evolve exclusively through plastic deformation of quartz and culminates in s4 mylonitic fabric formation in high d4 strains zones under greenschist facies conditions these microstructures are restricted to the msz and localized high d4 strain zones unlike the d3 microstructures we conclude that the earlier post granulite extensional deformation d3 and not the msz was responsible for the swing in lineament and fabric trends in the northern egp

morphological and geochemical evidence of neotectonics in the volcanic area of monti vulsini latium italy interdisciplinary research has been carried out to contribute to the definition of the neotectonic arrangement of the eastern area of monti vulsini affected by upper pleistocene volcanic activity particularly geochemical and geomorphological inquiries have been performed to identify tectonic elements whose recent activity could be related to the volcanic history of this area the morphological field evidence of tectonics as well as the analysis of azimuthal distribution of stream channels and the statistical analysis of the amplitude of relief ar revealed the eastern monti vulsini volcanic area to be controlled by different tectonic alignments at the same time the geochemical contribution focused on geostatistical elaboration of soil gas data has attempted to process unbiased criteria to define soil gas anomalies and to infer correlation with their fault related linear geometry in particular rose diagrams of anomalous gas concentration alignments and azimuthal distribution of stream channels performed for each hierarchical order were compared to obtain information about the location and orientation of tectonic elements as well as about the possible reconstruction of their activity in recent times by means of relative chronology

remote forcing annihilates barrier layer in southeastern arabian sea 1 time series measurements of temperature and salinity profiles were made every two hours at 74 30 e 9 13 n in the southeastern arabian sea seas during 22 march 7 april and 23 may 7 june 2003 as part of the arabian sea monsoon experiment armex the observations show that a 20 m thick barrier layer bl exists during march april owing to a surface layer of low salinity waters advected earlier during december january from the bay of bengal the bl is almost annihilated by 7 april owing to upwelling the relic bl that survives is annihilated later in may by upwelling and by the inflow of high salinity waters from the north and by mixing due to stronger winds which deepen the mixed layer we present evidence from satellite data and arguments based on existing theories to show that both the upwelling and the advection of high salinity waters are remotely forced

new geomorphic data on the active taiwan orogen a multisource approach a multisource and multiscale approach of taiwan morphotectonics combines different complementary geomorphic analyses based on a new digital elevation model dem side looking airborne radar slar and satellite spot imagery aerial photographs and control from independent field data this analysis enables us not only to present an integrated geomorphic description of the taiwan orogen but also to highlight some new geodynamic aspects well known major geological structures such as the longitudinal valley lishan pingtung and the foothills fault zones are of course clearly recognized but numerous previously unrecognized structures appear distributed within different regions of taiwan for instance transfer fault zones within the western foothills and the central range are identified based on analyses of lineaments and general morphology in many cases the existence of geomorphic features identified in general images is supported by the results of geological field analyses carried out independently in turn the field analyses of structures and mechanisms at some sites provide a key for interpreting similar geomorphic features in other areas examples are the conjugate pattern of strike slip faults within the central range and the oblique fold and thrust pattern of the coastal range furthermore neotectonic and morphologic analyses drainage and erosional surfaces have been combined in order to obtain a more comprehensive description and interpretation of neotectonic features in taiwan such as for the longitudinal valley fault next at a more general scale numerical processing of digital elevation models resulting in average topography summit level or base level maps allows identification of major features related to the dynamics of uplift and erosion and estimates of erosion balance finally a preliminary morphotectonic sketch map of taiwan combining information from all the sources listed above is presented