tracing of water masses using a multi isotope approach in the southern indian ocean anthropogenic radionuclides 3 h 14 c and 129i stemmed from nuclear weapons tests were found in 1999 to be very abundant in the surface of the southern indian ocean comparable to those in the subtropical northwest pacific ocean the observed radionuclide variations with latitude longitude in the southern indian ocean are not due to deposition patterns of global fallout but due to transport of water masses from the western pacific through the indonesian seas and different water fronts present in the crozet basin of the indian ocean high radionuclide concentrations observed in the latitudinal belt of 20 40 s are associated with the indian ocean subtropical gyre which acts as a reservoir of radionuclides maintaining their high concentrations on a time scale of several decades 14 c data documents that the southern indian ocean is an important for sink of anthropogenic carbon the isotopic tracers reveal the evidence of the most intense surface gradients and presence of several water masses in the southern indian ocean which makes the region one of the most dynamic places of the world ocean

structural analysis and interpretation of the surface deformations of the el asnam earthquake of october 10 1980 the el asnam earthquake of october 10 1980 represents the major seismotectonic event of these last decades in the west mediterranean area it has induced a large amount of surface breaks this earthquake reveals the importance of compressional phenomena that characterize nowadays the tectonics of north africa the tectonic analysis of surface rupture shows the complexity of the deformation mechanism the principal mechanism consists of the activation of a nw se trending thrust fault accompanied with a left lateral motion and with an intense deformation of the northwestern overthrusting block an accurate description of these deformations shows that for a large part the breaks geometry depends closely on the substratum structure finally the analysis of the dislocations on irrigation ducts just above the fault traces allowed a quantitative study of the deformation

relations between surface deformation fault geometry seismicity and rupture characteristics during the el asnam algeria earthquake of 10 october 1980 abstract the el asnam earthquake of october 10 1980 ms 7 3 produced surface faulting on a northeast trending thrust fault of 30 km length with displacements of up to 6 5 m though average displacements were about 3 m in addition widespread tensional features were formed some in clear association with folding above the thrust and others in an area beyond the exposure of the thrust at the surface which may be related to buried reverse faults the observed thrust fault is split into southern central and northern segments local and teleseismic data are examined to show that the main shock nucleated at the southwest end of the fault and propagated 12 km northeast where a second rupture of approximately equal moment occurred continuing the faulting a further 12 km northeast along the central segment both ruptures nucleated at about 8 10 km depth displacements were largest on the central segment where they were probably enlarged by aftershocks including one of mb 6 1 three hours after the main shock the northern segment was much shorter than the other two and showed smaller displacement the junctions between fault segments are marked by distinct geomorphological characteristics and a change in strike of the faulting as well as a sudden drop in the observed displacement it appears that the rupture development is influenced by the changes in fault geometry between segments and that such junctions or barriers have persisted through much of the late quaternary

a quasi synoptic view of the frontal circulation in the crozet basin during the antares 4 cruise abstract with the major objective of estimating the secondary vertical circulation a fine grid survey of hydrographic and current fields across the crozet basin frontal zone was made as a physical component of the multidisciplinary antares 4 cruise this frontal zone forms the boundary of the antarctic circumpolar current and the agulhas return current with the quasi permanent existence of strong eddy activity prior to any quantitative diagnosis of the vertical circulation from the fine grid data it is necessary to place the mesoscale circulation and its time variability of the survey area within the basin wide context we give a quasi synoptic view of the ambient frontal circulation during the cruise period using satellite derived chlorophyll concentrations and sea surface temperature particular emphasis is placed on evaluation of the degree of synopticity of our fine grid measurements by comparing mesoscale features on satellite images the limited survey area 1 5 latitude 2 longitude lies precisely within the southernmost and easternmost convergent zone of the two current systems cutting across mesoscale meanders having typical wavelengths of 400 km and periods of 4 months both these satellite images and topex poseidon sea surface height data indicate little temporal variability of the survey area during the 14 days of measurement although fortuitous this quasi steady state of circulation enables us to use the ensemble of fine grid data as a set of synoptic data for diagnosing the vertical circulation using quasi geostrophic dynamics preliminary analysis of the horizontal and vertical hydrographic structure of the fine grid hints at the existence of wave like cross frontal intrusions having a mean along front wavelength of about 30 km

the 2002 denali fault earthquake alaska a large magnitude slip partitioned event the mw moment magnitude 7 9 denali fault earthquake on 3 november 2002 was associated with 340 kilometers of surface rupture and was the largest strike slip earthquake in north america in almost 150 years it illuminates earthquake mechanics and hazards of large strike slip faults it began with thrusting on the previously unrecognized susitna glacier fault continued with right slip on the denali fault then took a right step and continued with right slip on the totschunda fault there is good correlation between geologically observed and geophysically inferred moment release the earthquake produced unusually strong distal effects in the rupture propagation direction including triggered seismicity

weathering of the oporto granite geotechnical and physical properties abstract this paper characterizes the weathering products of the two mica oporto granite in terms of its mineralogical chemical geotechnical and physical properties this information is used to identify a physical property that can be used as an index of the degree of weathering and to estimate other properties in outcrop the oporto granite is always weathered and weathering profiles frequently exceed 20 m within these profiles granitic saprolites are composed of quartz feldspars and some mica with kaolinite and gibbsite as final weathering products the average percentage of secondary minerals determined by bulk x ray diffraction xrd is low in both weathered rock 2 4 and saprolite 8 7 geotechnically the saprolites exhibit no or low plasticity plasticity index pi 12 the skeleton character of the saprolites is reflected in the significant proportion of fines 29 5

engineering and geological characteristics of granite weathering profiles in south china granite weathering profiles are widely distributed in south china their engineering and geological characteristics are major geotechnical subjects that are important in the design and construction of civil engineering projects this paper presents a summary of the weathering characteristics and zoning of granite weathering profiles in south china and discusses their engineering and geological properties a five grade scheme has been adopted in the zoning of a granite weathering profile studies have shown that the completely weathered granites cwg in south china have the following characteristics low moisture content low to medium plasticity w l 22 5 39 0 i p 6 5 11 8 medium void ratio 0 36 1 29 weak shrinkage and medium compressibility a 1 2 0 24 0 8 mpa 1 and high shear strength phi 20 30degrees c 20 40 kpa the cwgs are usually at a low or high plastic state and most of them are over consolidated soils a majority of the physical and mechanical properties have good statistical correlations with the degree of weathering the data presented in the paper are important in geotechnical engineering projects such as slope stability evaluation in china c 2002 elsevier science ltd all rights reserved

gps measurements of crustal deformation in the baikal mongolia area 1994 2002 implications for current kinematics of asia 1 we present new geodetic results of crustal velocities over a large part of northern asia based on gps measurements in the baikal rift zone and mongolia spanning the 1994 2002 period we combine our results with the gps velocity field for china of wang et al 2001 and derive a consistent velocity field for most of asia we find contrasted kinematic and strain regimes in mongolia with northward velocities and n s shortening in westernmost mongolia but eastward to southeastward motion and left lateral shear for central and eastern mongolia this eastward to southeastward motion of central and eastern mongolia is accommodated by left lateral slip on the e w trending tunka bolnay and gobi altay faults 2 1 2 mm yr 1 2 6 1 0 mm yr 1 and 1 2 mm yr 1 respectively and by about 4 mm yr 1 of extension across the baikal rift zone consequently 15 of the india eurasia convergence is accommodated north of the tien shan by n s shortening combined with dextral shear in the mongolian altay and by eastward displacements along major left lateral strike slip faults in central and eastern mongolia we find a counterclockwise rotation of north and south china as a quasi rigid block around a pole north of the stanovoy belt which rules out the existence of an amurian plate as previously defined and implies 2 mm yr 1 of left lateral slip on the qinling shan fault zone

internal tides and vertical mixing over the kerguelen plateau within the context of the natural iron fertilization study keops time series measurements of ctd and ladcp profiles at a site 50 6 s 72 e 528 m coinciding with an annual phytoplankton bloom over the kerguelen plateau were made during the january february 2005 keops cruise an important activity of highly nonlinear semidiurnal internal tides having peak to peak isopycnal displacements of up to 80 m is identified these internal tides appear to be a principal agent for promoting elevated vertical mixing indispensable for upward transfer of iron within the seasonal thermocline we estimate local vertical eddy diffusivities of the order of 4 10 4 m2 s 1 using a thorpe scale analysis although this estimate is higher by an order of magnitude than the canonical value o 0 1 10 4 m2 s 1 in the open ocean away from boundaries it is consistent with nonlinear internal wave wave interaction theories as verified by independent diffusivity estimates using the vertical wavenumber spectral methods for shear and strain it is also suggested that the general ocean circulation may play an important role in preconditioning the bloom in that the relatively sluggish circulation over the shallow plateau compared to the much more dynamic neighbouring deep ocean may foster the bloom s observed annual recurrence over the plateau

rapid late quaternary slip repeated prehistoric earthquake rupture and widespread landsliding associated with the karakudzhur thrust central kyrgyz tien shan field studies have shown that active faulting in the sw tien shan is distributed across a series of e w reverse faults along the range fronts and within basin interiors with summed shortening rates that are consistent with gps measurements in contrast few field studies have been undertaken to determine the distribution and the average slip rates of faults in the central and eastern parts of the tien shan in this paper we use remote and field based observations to characterize the active faulting and tectonic geomorphology of the karakudzhur basin in the central tien shan of kyrgyzstan we use radiocarbon luminescence and uranium series dating to provide ages on three fluvial terraces that are vertically displaced across the basin bounding reverse fault and estimate fault slip rates using a 20 s dipping fault exposure we find that the fault has a slip rate of 2 4 5 9 mm year averaged over the holocene indicating that it accommodates a major part of the shortening measured by gps in contrast to the relatively uniform distribution of n s shortening in the sw tien shan significant shortening may instead be concentrated at present on a few active faults in the northern part of the central tien shan the fresh geomorphic expression of the karakudzhur fault suggests that it has ruptured in recent prehistory in a large magnitude mw 7 earthquake from palaeoseismic trenching we show that two significant surface rupturing earthquakes have occurred since 2 4 ka the most recent earthquake was potentially accompanied by widespread landsliding and faulting in the surrounding highlands

the armenian earthquake of 1988 december 7 faulting and folding neotectonics and palaeoseismicity summary the spitak earthquake of 1988 december 7 is the first well documented event directly associated with surface breaks in the transcaucasian regions of the ussr the earthquake was located within the ese wnw oriented pambak sevan thrust and fold zone corresponding to the southern front of the lesser caucasus the mechanism of the earthquake is consistent with the nearly ns compressive tectonics due to the active continental collision between the arabian block and the russian platform the rupture is composed by several branches two of which reach the surface the first branch oriented n140 begins near the village of alavar has a length of 11 km and disappears at about 4 km se of spitak it consists of a right lateral en echelon system of strike slip faults with a maximum offset of 50 cm the second branch is the main one and breaks for about 8 km between spitak and gekhasar with a general orientation n120 showing reverse faulting dipping to the north with a right lateral component surface ruptures between gekhasar and spitak show either a narrow band of pressure ridges in alluvial deposits and soil or a fault scarp in the bed rocks when soil is absent maximum displacements observed between spitak and gekhasar attain 160 cm of vertical motion and 90 cm of horizontal dextral offset the displacement also varies within this branch showing finer segmentation few secondary deformations are observed some normal faults near gekhasar correspond to the collapse of the uplifted block an anticline fold oriented parallel to the fault scarp and situated along its northwestern prolongation emphasizes the regional compressive tectonics landslides were activated on its flanks a 200 m long reverse fault break observed along the hinge of a secondary fold suggests the occurrence of a blind thrust at depth and that the hidden branches which continue the main central segment towards the nw are associated to surface folding therefore the total length of the fault and fold zone is about 40 km in agreement with the rupture length and seismic moment obtained on the basis of surface wave modelling well developed uplifted terraces in the northern block and subsiding valleys in the southern block indicate past quaternary activity in the fault region palaeoseismological evidence of ancient earthquakes has been recognized in trenches across the spitak fault one old event occurred between 17 000 years bp and the beginning of the formation of present day soil

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

intensive surveys of the azores front 2 inferring the geostrophic and vertical velocity fields the geostrophic and vertical velocity fields are inferred using density and horizontal velocity data from three seasoar acoustic doppler current profiler surveys of the azores front the analysis is a two step procedure consisting of 1 objective analyses to reflect the observed length scales and 2 dynamical adjustments so that the density field is statically stable and the velocity field is in geostrophic balance the vertical velocity is inferred using a version of the quasi geostrophic omega equation in which the stratification is allowed to vary in the horizontal the resulting vertical velocity peaks at 2 10 4 m s 1 at 200 300 m there is a tendency for the denser water to the north of the front to be downwelled while the warmer water to the south is upwelled the implied heat flux exceeds 10 w m 2 near 100 m depth so the upper 100 m is warmed while the lower water column is cooled tending to stratify the upper ocean ageostrophic horizontal flow is toward the dense side of the front at the surface the dominant terms in the density balance are time rate of change and horizontal advection the inferred circulation cells may be an important mechanism of subduction in the upper ocean

pseudomorphic transformation of plagioclases during the weathering of granitic rocks in galicia nw spain abstract microscopic study of twelve weathering profiles developed on granitic rocks in galicia nw spain showed that in most cases the transformation of the parent rock into saprolite occurs with pseudomorphic alteration of the plagioclases it was seen that the transformation and the retention of plagioclases in the alteration profile are directly related to the conservation of the general structure of the rock and this in its turn depends on the mineralogical composition and texture the most unstable constituents in the galician environment are biotites and plagioclases there being a clear difference in the rate of alteration between the plagioclases and the k feldspars this implies that a large part of the fabric of the rock remains unaltered when the plagioclases are completely weathered so that the pores caused by the weathering of the plagioclases are filled by their own alteration products with regard to the influence of the texture it was observed that fine grained rocks are altered more easily than coarse grained ones especially if they are rich in biotites in this study we show various examples in which even with high levels of alteration the morphological features of the original plagioclase crystals are preserved twins original zoning myrmekitic textures and perthites the pseudomorphic transformation of plagioclase is independent of the products to which it gives rise and here we show examples where gibbsite 1 1 dioctahedral phyllosilicate or a mixture of both appear as secondary minerals the mineralogical nature of a newly formed product depends mainly on the intensity of the leaching to which the profile is subjected which is influenced by the rainfall in the area where they are found as well as the size of existing voids in the material

sr z sbnd nd isotopic record of multi stage interactions between mantle derived magmas and crustal components in a collision context the ultramafic granitoid association from vivero hercynian belt nw spain late stage epizonal calc alkaline granitoids of the hercynian belt are often associated with coeval more basic rocks such granitoids have been the focus of special attention when studying the role of mantle derived magmas in granitoid genesis these studies conclude that basic magmas are involved in granitoid production but their contribution to the chemical composition of granitoids is often controversial the vivero massif nw spain includes calc alkaline granitoids and coeval ultramafic and mafic rocks but these granitoids are syntectonic and intruded into middle crustal levels during an early stage scattered major and trace element chemistry together with heterogeneous sr nd isotopic results preclude an origin of this ultramafic to granitoid association by any closed system fractionation process ultramafic rocks include peridotites pyroxenites and homblendites with endi from 3 5 to 1 3 and 87sr86sr i ratio from 0 7059 to 0 7080 they are interpreted as cumulates formed by in situ fractional crystallization from contaminated basaltic magmas particularly by interaction with 87sr enriched fluids mafic rocks comprise biotite amphibole diorites quartz diorites and tonalites with ndi from 3 8 to 0 0 and 87sr86sr i ratio from 0 7058 to 0 7073 they represent either cumulates or more evolved magmas of calc alkaline affinity these rocks display an inverse correlation between the degree of differentiation and the degree of contamination inferred from isotope data this points to wall rock assimilation by thermal erosion during ascent of basic magmas up to the middle crust and supports the participation of mantle sources with positive end and 87sr86sr i 0 7058 granitoids range from amphibole biotite tonalites through biotite granodiorites to monzonitic granites they show an isotopic trend which diverges from that of ultramafic and mafic rocks endi 6 0 to 1 9 decreases while 87sr86sr i ratio 0 7061 to 0 7082 increases from tonalites to monzonitic granites reflecting an increasing contribution of crustal components in more differentiated rocks assimilation and fractional crystallization mixing included account for such an evolution contamination of basic magmas by this process occurring at deeper crustal level produced hybrid tonalites and related mafic magmatic enclaves only monzonitic granites are interpreted as pure crustal melts their hree fractionated patterns gd yb 4 5 suggest equilibrium with a garnet rich residuum partial melting of moderate time integrated rb sr protolith such as greywackes and or meta igneous rocks of intermediate acid composition could account for the isotopic composition of these monozogranites this example shows that at least some calc alkaline granitoids of collisional setting are not produced by pure intra crustal melting they are formed through a complex multi stage hybridization process involving mantle derived magmas crustal components and several concomitant magmatic processes

identifying a reference frame for calculating mass change during weathering a review and case study utilizing the c program assessing element immobility and critical ratio methodology abstract the first step in calculating mass changes that occur during the transformation of plutonic rock to saprock involves the determination of a reference frame i e an immobile element whose mass was conserved during the alteration process procedures for identifying the statistical properties of immobile elements have been available since 1990 but have not generally been applied we therefore developed the c program assessing element immobility aei that allows for rapid assessment of those elements possessing the statistical properties of immobility aei utilizes algorithms that test for equal distributions and unchanging means of ratios subcompositional independence and subcompositional invariance following discussion of the general mathematical and statistical procedures implemented in aei we utilize it in a case study involving three sites in an 30 m thick section of regolith zr i is located near the base of the regolith while zr ii and zr iii are located at depths of 20 m and 5 m respectively from each site previous workers chemically analyzed a number of samples from saprock and adjacent unweathered corestones in addition xrd work showed that from zr i to zr ii to zr iii biotite was altered to vermiculite vermiculite kaolinite and vermiculite mixed layer biotite vermiculite kaolinite respectively at zr iii the most dominant clay mineral is kaolinite aei performs a series of tests to assess whether or not a given set of elements possess the statistical properties for immobility it identified the following elements as a potential reference frame al na fe mg ti and p at zr i si al fe mn mg ti and p at zr ii and mg and mn at zr iii however critical ratio methodology indicated that the precision as measured by the smallest 95 confidence interval is greatest for al2o3corestone al2o3saprock and na2ocorestone na2osaprock at zr i for sio2corestone sio2saprock at zr ii and for mgocorestone mgosaprock at zr iii mass balance results using al2o3 and na2o at zr i were nearly identical and as a result only the results derived from al2o3 are reported here using al2o3 sio2 and mgo as reference frame elements for zr i zr ii and zr iii respectively revealed the following statistically significant losses of k mass 14 9 8 at zr i 28 11 9 at zr ii and 33 8 7 at zr iii in addition at zr iii the statistically significant loss of 36 13 11 p mass is attributed to the dissolution of apatite and the small nominal loss of 6 5 5 ca mass may reflect incongruent leaching of plagioclase and or apatite in contrast the small additions of 5 5 4 al 5 2 2 fe and 4 2 2 ti mass at zr iii are likely the result of the translocation of kaolinite and kaolinitized biotite particles into the crack system by downward percolating fluids and the exchange and adsorption of al fe and ti ions onto the illuviated clay lining as it evolved over time overall the interplay between eluviation and illuviation at zr iii translates into a statistically significant 5 3 3 increase in bulk mass

chemical weathering in granitic environments abstract factors controlling chemical weathering in granitic environments are deduced using an extensive database from the literature based on a transition state theory model we evaluated the effects on chemical weathering of runoff temperature and ph the dependence between temperature and runoff and chemical weathering is complicated by other factors such as the presence depth of soil cover soil cover favors chemical weathering when it is thin and rich in weatherable minerals in contrast it reduces chemical weathering when is thick and poor in primary minerals processes that increase the contact time and the surface of the water rock interactions such as physical denudation increase chemical weathering rates in granitic environments the effect of temperature can be quantified assuming an apparent activation energy value of 48 7 kj mol to describe chemical weathering of silica in granitic crystalline environment under high runoff conditions

prediction of some weathering trends of plutonic and volcanic rocks based on thermodynamic and kinetic considerations abstract the exposed crust consists mainly of plagioclase 35 quartz 20 k feldspar 11 volcanic glass 12 biotite 8 and muscovite 5 quartz is a resistate thus feldspars and glass represent approximately 75 percent of the labile minerals the weathering characteristics of these constituents are summarized in the context of thermodynamic mass balance and kinetic considerations experimentally determined release rate constants were used to predict the proportions of ca na and k released by feldspars of plutonic rocks granites to gabbros to weathering solutions the chemical weathering trends of the weathered residues calculated from the kinetic data conform closely to the initial trends observed in some recent weathering profiles demonstrating the accuracy of the predictions since the weathering of feldspars is controlled by processes that should not change through geological time the relative release rates of ca na and k from the feldspars of granitic rocks can be calculated for future and past episodes of continental weathering experimentally determined release rate constants are not available for a wide range of volcanic glass compositions but the limited data indicate that compositional trends are predictable in weathering profiles developed on volcanic rocks the kinetic data available for rhyolitic glasses accurately predict the initial weathering trends observed in a recent rhyolite weathering profile

crustal thickening and deformation sequence in the footwall to the suture of the variscan belt of northwest spain abstract the sequence of formation and propagation of structures as well as the evolution of crustal thickening in the variscan belt of northwest spain are proposed in this paper the foreland of this mountain belt shows thin skinned tectonics a polyphase deformation with associated regional metamorphism is recognized in the hinterland zones two important culminations the narcea and lugo antiforms are present in an e w cross section through the footwall to the suture of this orogen such culminations are derived from the stacking of several thrust systems generated during two successive periods the sequence of thrust emplacement helps to clarify the formation of different types of structures at the same time in different places in the orogen

slip rates along active faults estimated with cosmic ray exposure dates application to the bogd fault gobi altai mongolia dating morphological features displaced along active faults presents a major difficulty in evaluation of slip rates we used in situ produced 10 be to calculate minimum ages for alluvial surfaces misaligned by movement along a major active fault in the gobi altai western mongolia the maximum slip rate of 1 2 mm yr suggested by this method contrasts strongly with rates of 20 mm yr that we estimated by correlation of alluvial deposition with warm humid periods associated with the last glacial termination estimated to have occurred about 12 ka in western tibet the 10 be based slip rate indicates that strong earthquakes can occur along faults with low slip rates and demonstrates the contribution of cosmic ray exposure dating in quaternary tectonic analyses

holocene hydrological changes inferred from alluvial stream entrenchment in north tian shan northwestern china abstract we analyze the possible contribution of climate change or tectonics on fluvial incision from the study of a case example along the northern flank of tian shan the rivers that exit the high range fed large alluvial fans by the end of the last glacial period they have since deeply entrenched the piedmont by as much as 300 m we have surveyed several terraces that were cut and abandoned during river entrenchment providing information on intermediate positions of the riverbed during downcutting they suggest a gradual decline in river slope during a major phase of incision throughout the holocene tectonic uplift affects only a zone about 5 km wide corresponding to a growing anticline and is shown to account for about 10 of total incision incision was therefore most probably driven by climate change from observed fluvial incision we estimate the water discharge in excess of that needed to carry the sediments supplied by hillslope erosion in the headwaters we used a model based on a transpor

surface subsidence induced by groundwater drainage tunneling in granite residual soils burata railway tunnel spain abstractunderground tunneling besides raising geotechnical challenges can often modify the hydrological regime around an excavated area this fact entails not only the modification of superficial aquifers but also the appearance of subsidence phenomena as a consequence of the decrease in pore pressure in the end this may jeopardize the structural integrity of the construction leading to delays and undesirable secondary effects this paper documents the problems arising from the construction of a railway tunnel for a high speed train in the province of orense in the northwest of spain the tunnel was excavated through a highly weathered granitic massif using conventional methods the drawdown in the water table caused by the tunnel advance was analyzed and monitored the initial lowering of the water level was followed by a period of soil subsidence with deflections reaching up to 104 mm these differential settlements happened along a 150 m strip on both sides of the tunnel axes which affected urban

cross frontal exchange of antarctic intermediate water and antarctic bottom water in the crozet basin abstract the hydrographic survey made across the antarctic circumpolar current acc in the southwestern crozet basin during the april may 1993 antares 1 cruise revealed unprecedented strong cross frontal injections of newly formed antarctic intermediate water aaiw into the subtropical zone north of the acc the acc in this area is mostly associated with the subantarctic front saf and subtropical front stf which are tightly merged into one structure bordered to the north with the eastward extension of the agulhas return current the oxygen and salinity extrema of the newly injected aaiw at a depth of 1200 m well north of the stf reach as high as 6 17 ml l 1 and 34 15 these values coincide almost exactly with those in the aaiw source found at a depth of 500 m just south of the saf but surpass considerably oxygen by 1 35 ml l 1 and salinity by 0 23 psu those values corresponding to the old aaiw at the nearby subtropical stations such spectacular cross frontal injections of new aaiw were not continuous in space and time but were found to be rather local intermittent and impulsive this was closely correlated with the highly perturbed meandering frontal zone due to the frequent passages of strong atmospheric depressions during the cruise there is also clear evidence of the northward penetration of antarctic bottom water aabw through the crozet kerguelen gap and its northward flow along the deep western boundary of the crozet basin supporting previous observations moreover our observations indicate more precisely the bottom water pathway which is concentrated against the continental rise west of 56 e following roughly the 4000 m isobath it is concluded that the crozet basin frontal zone acts as a barrier only for the upper layer water masses and that it is dynamically transparent for the cross frontal exchange of intermediate and deeper layer water masses of potential density anomalies greater than 27 1 including aaiw and aabw

grouting experiment in a completely weathered granite dam abutment case study on grouting technique and test analysis anti seepage grouting of earth rock dams is an important aspect of dam construction projects completely weathered granite is a typical porous granular soil traditional grouting techniques cannot meet the requirements of completely weathered granite grouting therefore pulsating grouting which combines drilling and grouting is proposed and grouting experiments were performed on a completely weathered granite reservoir abutment in combination with traditional clay cement slurry materials the results show that single row 1 m hole spacing of the permeability after grouting was less than 10 lu the acoustic wave velocity increased by 17 3 52 5 moreover the core sample was relatively complete and the compressive strength of the core reached 7 3 mpa on average the proposed technique significantly reduces the unit cost is applicable to completely and strongly weathered granite and similar formations thus this work provides an engineering reference for these formations

smectite formation produced by weathering in a coarse granite saprolite in galicia nw spain abstract weathering of a calcalkaline granite was studied in the south of galicia nw spain where the average annual precipitation is 1400 mm and the average annual temperature is 12 c the original rock contains perthitic k feldspars plagioclases with inclusions of muscovite and opaque minerals quartz and chloritized biotite with apatite zircon sphene and opaques as accessories in the saprolite the structure of the rock is preserved the plagioclases show up to grade 4 weathering and the biotites between 2 and 3 weathering in quartz and potassium feldspar crystals is manifested only by fracturing biotite changes following the parallel linear model and its weathering products are interstratified biotite vermiculite and iron oxyhydroxides the plagioclases change to a microgranular material by pseudomorphic transformation this material which substitutes the plagioclase includes small clearly delimited units which retain zones with the optic characteristics of muscovite x ray diffraction analyses of microsamples show that they are formed by 1 1 diocthaedral phyllosilicate smectite and a small quantity of mica from these facts we concluded that smectite is formed inside the plagioclase crystals and probably originates from the inclusions of muscovite contained in these crystals as it is suggested by the microscopic study which shows the increase in volume which occurs when the crystals of muscovite are transformed

relic permafrost structures in the gobi of mongolia age and significance relict permafrost structures ice wedge casts and cryoturbation structures are present in the gobi of southern mongolia luminescence dates of sediments are presented to constrain the age of formation of permafrost structures these data show that there was a phase of permafrost development during the latter part of the last glacial after about 22 to 15 ka that resulted in cryoturbated sediments and ice wedge casts furthermore permafrost degradation occurred during late pleistocene times 13 10 ka and was absent during the early holocene these permafrost structures mark the southernmost evidence of permafrost in northern asia during late quaternary times and indicate that the mean annual air temperature was below approximately 6 c during their formation 1998 john wiley sons ltd

paleoclimatic evolution of the uvs nuur basin and adjacent areas western mongolia abstract the investigations presented in this paper focus on the shifts in pleistocene glaciations and the geomorphic changes in landforms as well as lake level changes and aeolian deposits of the last glacial interglacial cycle including the holocene geomorphic evidence and high lake levels show that the climate was more humid before the last glacial maximum lgm however at least one arid phase also occurred during the second half of the lgm the climate was dry and cold turning to wet and cold during the late glacial of the last ice age fluctuations in humidity and temperature occurred during the holocene since about 2000 yr bp the impact of human activity has increased

frontal structure water masses and circulation in the crozet basin due to topographic steering by the crozet and kerguelen plateaus the antarctic circumpolar current acc core in the crozet basin area is shifted to its northernmost position in the southern ocean along the southern limb of the south indian subtropical gyre here the jet like current is embedded within a narrow band 26 5 kg m3 in the western half of the basin and heavier mode 26 7 kg m3 in its eastern half these different varieties of crozet basin mode water are closely correlated with the degree of exchange and mixing between subtropical and subantarctic waters along the dynamically active frontal zone the area north of the kerguelen plateau appears to be an important source of water mass modification antarctic intermediate water advected from the west also undergoes there significant modification by intrusions across the frontal zone of fresher oxygen richer colder subantarctic water energetic eddy activities observed along the frontal zone likely enhance such cross frontal exchange of water masses equatorward spreading of the modified thermocline water masses mode water antarctic intermediate water occurs as part of the anticyclonic circulation in the south indian subtropical gyre which is centered within the basin strong injection of north indian deep water into the acc south of amsterdam island is clearly evidenced for the first time this deep oxygen minimum water centered at about 3000 m can be traced to the east of madagascar from where it spreads southward through the eastern part of the crozet basin due to the influence of this water mass north atlantic deep water characteristics of the circumpolar deep water are significantly altered in kerguelen amsterdam passage our results indicate a cyclonic deep level circulation pattern in the crozet basin with a northward flow 9 sv of circumpolar deep water antarctic bottom water as a deep western boundary current and a partially compensating southward flow 3 sv of north indian deep water through the eastern part of the basin it is concluded that the crozet basin constitutes an important passage for the exchange of water masses between the southern ocean and the indian ocean

a 900 k y record of strath terrace formation during glacial interglacial transitions in northwest china the timing of the development of strath terraces with respect to climatic variability remains equivocal previous studies attribute strath terrace formation to glacial or interglacial climates or to variations in sediment and water fluxes that cause lateral erosion followed by vertical incision a chronology of strath terrace formation spanning similar to900 k y has been generated on the basis of loess paleosol couplets and paleomagnetic thermoluminescence and radiocarbon dating of strath terraces in the qilian shan of northeastern tibet repetitive stratigraphic and geomorphic patterns on each terrace indicate that they formed during glacial interglacial transitions long term bedrock incision rates and inferred rock uplift rates appear steady and unrelated to strath formation over the past 900 k y

active intracontinental transpressional mountain building in the mongolian altai defining a new class of orogen abstract mountain ranges that are actively forming around the western and northern perimeter of the indo eurasia collisional deformational field such as the mongolian altai comprise a unique class of intracontinental intraplate transpressional orogen with structural and basinal elements that are distinct from contractional and extensional orogens late cenozoic uplift and mountain building in the mongolian altai is dominated by regional scale dextral strike slip faults that link with thrust and oblique slip faults within a 300 km wide deforming belt sandwiched between the more rigid junggar basin block and hangay precambrian craton dominant orogenic elements in the mongolian altai include double restraining bends terminal restraining bends partial restraining bends single thrust ridges thrust ridges linked by strike slip faults and triangular block uplifts in areas of conjugate strike slip faults the overall pattern is similar to a regional strike slip duplex array however the significant amount of contractional and oblique slip displacement within the range and large number of historical oblique slip seismic events renders the term transpressional duplex more accurate intramontane and range flanking basins can be classified as ramp basins half ramp basins open sided thrust basins pull apart basins and strike slip basins neither a classic fold and thrust orogenic wedge geometry nor a bounding foredeep exists the manner in which upper crustal transpressional deformation is balanced in the lower crust is unknown however crustal thickening by lower crustal inflation and northward outflow of lower crustal material are consistent with existing geological and geodetic data and could account for late cenozoic regional epeirogenic uplift in the russian altai and sayan regions

cumulative right lateral fault slip rate across the zagros makran transfer zone role of the minab zendan fault system in accommodating arabia eurasia convergence in southeast iran the zendan minab zone is the transition zone between the zagros collision to the west and makran subduction to the east it is also linked to the north with the nayband gowk fault system that bounds the lut block to the east the total convergence rate between arabia and eurasia is estimated to range between 23 and 35 mm yr 1 in a nne trending direction the deformation through the minab zendan system is accommodated within two fault systems the western n160 e trending minab zendan fault system and the eastern north south sabzevaran jiroft fault system the study area is characterized by a well defined succession of quaternary deposit levels the age of these deposits was estimated by archaeological data regional palaeoclimate correlations and constrained by additional in situ10be dating in another paper in this study these deposits exhibit offsets both lateral and vertical that are evaluated by satellite image analysis and gps profiles thanks to offsets and ages the strike slip rates associated with the minab zendan and the sabzevaran jiroft fault systems are calculated to be 5 1 1 3 or 6 6 1 5 and 6 2 0 7 mm yr 1 respectively these results allow an evaluation of the velocity vector of the musandam peninsula oman with respect to the lut block of 11 4 2 0 or 12 9 2 2 mm yr 1 in a n10 15 e direction close to the gps estimates this study also constrains the in plane slip rates for each fault previous works indicate that the zagros accommodates only 10 mm yr 1 of shortening while 10 mm yr 1 should be accommodated by the alborz mountains in northern iran this last 10 mm yr 1 may be accommodated through the nayband gowk system and the east iranian ranges implying that the two fault systems constituting the zagros makran transfer zone have different geodynamic roles the western minab zendan fault system links the makran and zagros deforming zones whereas the northwestern jiroft sabzevaran fault system is transmitting the deformation to the nayband gowk system and then to the alborz ranges the presence of another such strike slip zone within the makran seems to indicate that the accommodation zone between the zagros and makran is wide of the order of 400 km we interpret this deformation pattern that accompanies the genesis of the immature transform zone by a flexure of the slab under the zagros makran transfer zone instead of a tear in the slab that may be expected to induce a sharper transition zone

linking foraging behaviour to physical oceanographic structures southern elephant seals and mesoscale eddies east of kerguelen islands in the southern ocean mesoscale features such as fronts and eddies have been shown to have a significant impact in structuring and enhancing primary productivity they are therefore likely to influence the spatial structure of prey fields and play a key role in the creation of preferred foraging regions for oceanic top predators optimal foraging theory predicts that predators should adjust their movement behaviour in relation to prey density while crossing areas with sufficient prey density we expect predators would change their behaviour by for instance decreasing their speed and increasing their turning frequency diving predators would as well increase the useful part of their dive i e increase bottom time thereby increasing the fraction of time spent capturing prey southern elephant seals from the kerguelen population have several foraging areas in antarctic waters on the kerguelen plateau and in the interfrontal zone between the subtropical and polar fronts this study investigated how the movement and diving behaviour of 22 seals equipped with satellite relayed data loggers changed in relation to mesoscale structures typical of the interfrontal zone we studied the links between oceanographic variables including temperature and sea level anomalies and diving and movement behaviour such as displacement speed diving duration and bottom time correlation coefficients between each of the time series were calculated and their significance tested with a parametric bootstrap we focused on oceanographic changes both temporal and spatial occurring during behavioural transitions in order to clarify the connections between the behaviour and the marine environment of the animals we showed that a majority of seals displayed a specific foraging behaviour related to the presence of both cyclonic and anticyclonic eddies we characterized mesoscale oceanographic zones as either favourable or unfavourable based on the intensity of foraging activity as identified by the behavioural variables our findings highlight the importance of mesoscale features for top predators behaviour and introduce a new approach for evaluating the importance to the seals of the origin and intensity of these features

determination of the surface geostrophic velocity field from satellite altimetry 1 presently available marine geoid models are not accurate enough to extract the mean surface circulation directly from satellite altimetry a novel method for estimating the mean velocity field of major ocean current systems is derived from the free surface boundary condition with a given quasi geostrophic balance for the horizontal surface flow a scaling analysis of this boundary condition indicates that although the vertical velocity w is mostly balanced by the local change of the free surface t useful information on the mean current is contained in a small ageostrophic departure t w our method consists in the development of a simple algebraic equation with two unknowns and an adjustable parameter associated with t assuming that the latter is proportional to t w most interestingly t and all other coefficients of the equation can be determined from altimetry the altimeter data used is combined topex poseidon ers gridded data and the solution is obtained by least squares minimizing the contribution from the time variable part of the parameter and prescribing the zonal direction of the mean current the method which is found to be particularly useful for quasi zonal high energy current systems has been validated against direct observations in the gulf stream and southern ocean comparisons with direct observations and monte carlo experiments suggest an overall solution error of about 10 cm s 1 once calibrated against regional velocity statistics this method will be able to determine from altimetry the mean or instantaneous surface velocity field down to the frontal scale with a realism that has been inaccessible because of the geoid constraint

a generalized 3 d geological and hydrogeological conceptual model of granite aquifers controlled by single or multiphase weathering summary the weathered layers of crystalline rocks form aquifers that are of prime interest for water supply in hard rock areas these weathering profiles generally develop under both stable geodynamic conditions weathering rate erosion rate and a hydrolysing climate they are composed of thick stratiform layers that follow the paleo landscape paleotopography and thus present a gently dipping sequence at a regional scale the structure and the hydrodynamic properties of the weathering profile of a granitic area 53 km 2 maheshwaram catchment state of andhra pradesh india were characterized in detail and mapped from observations on outcrops 80 vertical electric soundings and lithologs from 45 borewells in which flowmeter measurements and injection tests were also performed to characterize the hydraulic conductivities of the conductive fissure zones the structure of the weathering profile results from a multiphase process an ancient weathering profile was partly eroded down to its fissured layer it was later re weathered more or less parallel to the current topographic surface this peculiar structure is linked to the geodynamic history of the indian peninsula that underwent alternate weathering and erosion dominated phases the profile is thus composed from top to bottom up to a total depth of 35 m of sandy regolith saprolite 1 3 m 10 15 m of laminated saprolite containing unusual preserved fissures and a 15 20 m thick fissured layer by comparing various case studies in similar terrain a generalized 3 d geological and hydrogeological conceptual model of granite type aquifers granites gneisses etc is proposed in granite type rocks single weathering or multiphase weathering and erosion processes induce similar geological structures a few main geological differences arise from the comparison of single phase and multiphase weathering profiles i in the later the respective thicknesses of the various layers can be deeply modified ii the ancient fissured layer can be re weathered and the resulting new laminated layer may contain quite well preserved and conductive ancient fissures and iii the upper part of the fissured layer is more densely fissured as a result of the same weathering processes the fissures from the fissured layer of single phase or multi phase profiles exhibit very similar hydraulic conductivities and show both a higher density of conductive fissures at the top of the layer the preserved ancient fissures within the laminated layer of a multiphase profile are partly obliterated by the recent weathering their hydraulic conductivity is thus significantly reduced nevertheless they do significantly contribute to borewell yield these weathering induced fissures provide most of the aquifer permeability the use of such a conceptual model for the precise geological mapping of the weathering structure appears to be a prerequisite for groundwater development and management in hard rock areas as it answers to several key issues

fronts transport and weddell gyre at 30 e between africa and antarctica a detailed description of the frontal structure of major currents and estimates of transport between africa and antarctica at 30 e were made on the basis of a finely resolved hydrographic section made during the 1996 civa 2 cruise particular emphasis was put on a refinement of the eastern boundary of the weddell gyre by analyzing also supplementary hydrographic data from the 1993 civa 1 cruise and the best available historical hydrographic data in the weddell and enderby basins contrary to the general belief our results show that the weddell gyre extends far beyond 30 e reaching at least as far east as the enderby land promontory 53 e from this point westward currents along the antarctic continental margin constitute the gyre s southern boundary thus closing the cyclonic circulation of the gyre at its easternmost end as the most convincing evidence for this refined circulation scheme significant westward transport south of 65 s has been identified from the civa 1 acoustic doppler current profiler data we have shown also using an inertial jet model that the blocked feature of the weddell cold regime 57 s to the west of 25 e is due to the topographic control of flow by local bathymetry during the civa 2 cruise 70 of the antarctic circumpolar current acc was concentrated near the polar front 51 s with surface speeds reaching up to 70 cm s 1 the baroclinic current field in the subpolar area south of the weddell front 58 s for civa 2 and 57 s for civa 1 is featureless 3 cm s 1 but yielding a nonnegligible eastward transport of 15 sv 1 sv 106 m3 s 1 this bottom referenced baroclinic transport is entirely compensated by a substantial westward barotropic transport south of 65 s the acc transport across the 30 e section during the civa 2 cruise is estimated to be 160 sv

dating faulted alluvial fans with cosmogenic 10be in the gurvan bogd mountain range gobi altay mongolia climatic and tectonic implications the gurvan bogd mountain range is a fault system characterized by strong earthquakes m 8 separated by long periods of quiescence further to the previous works in the area our study provides new data concerning the tectonic and climatic processes in the gobi altay to quantify the slip rates along the faults we dated offset alluvial fans analysing the in situ produced 10 be along profiles at depth the slip rates along the bogd strike slip fault and its associated thrust faults over the upper pleistocene holocene period are 0 95 0 29 mm yr 1 and comprised between 0 12 0 02 and 0 13 0 02 mm yr 1 respectively the surfaces ages account for a cyclic formation of the fans over the past 360 ka in correlation with the terminations of the marine isotope stages 2 6 8 and 10

vorticity and vertical circulation at an ocean front abstract density and velocity data with 4 km horizontal resolution from a survey of a front during fasinex frontal air sea interaction experiment are combined to describe the structure of the top 300 m of the ocean the geostrophic velocity field is derived and is used to examine the relative importance of stratification relative vorticity and twisting terms in ertel s potential vorticity q tenfold isopycnic changes in q are found across a horizontal scale of only 10 km these changes are confined to isopycnals that outcrop from the seasonal thermocline into the mixed layer the ageostrophic velocity field is quantified by solution of the omega equation and vertical velocities of up to 40 m day 1 are found small 40 km surface trapped top 200 m eddies are found to play a crucial role in the transport and effective diffusion of properties across the thermocline out of the mixed layer

weathering of granites in a temperate climate nw portugal granitic saprolites and arenization abstract saprolites or in situ weathering products from granitoid rocks of northwest portugal were studied by means of x ray diffraction xrd of their clay fraction and observations of polished thin sections combined with transmission electron microscopy tem scanning electron microscopy with energy dispersive spectrometer sem eds microanalyses their principal features are 1 depths of more than 10 m 2 mean material loss of 40 as calculated by an isovolumetric method 3 low clay content mean value of 7 and a high degree of mineralogical evolution the clay fraction is characterized by a predominance of kaolinite and gibbsite with subordinate 2 1 minerals illite chlorite vermiculitic mixed layers vermiculite the significance of the secondary minerals in granitic saprolites from northwest portugal is compared to published data from atlantic europe this allows the definition of a climatic zonality for weathering products and identifies arenization as an important weathering process

co seismic strike slip and rupture length produced by the 2001 ms 8 1 central kunlun earthquake field investigations show that the surface wave magnitude ms 8 1 central kunlun earthquake tibetan plateau of 14 november 2001 produced a nearly 400 kilometer long surface rupture zone with as much as 16 3 meters of left lateral strike slip along the active kunlun fault in northern tibet the rupture length and maximum displacement are the largest among the co seismic surface rupture zones reported on so far the strike slip motion and the large rupture length generated by the earthquake indicate that the kunlun fault partitions its deformation into an eastward extrusion of tibet to accommodate the continuing penetration of the indian plate into the eurasian plate

circulation pathways and transports of the southern ocean in the vicinity of the southwest indian ridge circulation pathways and transports of the antarctic circumpolar current acc and agulhas return current arc around the complex bathymetry of the southwest indian ridge and del cano rise have been established from two hydrographic surveys and two year long moorings after crossing the southwest indian ridge in a 110 sv 1 sv 106 m3s 1 flow concentrated at 48 s the acc fragments before being reconcentrated into several branches by the bathymetry in particular 30 40 sv turns north around the eastern flank of the del cano rise turns west as part of anticyclonic flow round the del cano rise finally returning eastward as part of the crozet front eddy variability from both satellite data and moorings is low over the bathymetry of the del cano rise so the strong currents found between the del cano rise and the crozet plateau are believed to be permanent features this largely barotropic time independent transport is the major pathway for the acc to enter the crozet basin the anticyclonic flow also transfers water from the mozambique basin across the southwest indian ridge to the south side of the del cano rise given the evidence for fragmentation of the acc where it crosses the southwest indian ridge and the concentration of several jets into the crozet front from the acc subtropical front and agulhas return current it is misleading to relate standard frontal definitions such as the polar front and subantarctic front to the major transport pathways

deep weathering of granitic rocks a case of tunnelling in nw spain abstract this paper highlights a case of extensive development of saprolith from granitic bedrock in nw spain the weathering front at the study area extends to more than 250 m in depth the drilling of a railway tunnel madrid galicia high speed line through the bedrock and saprolith resulted in significant technical issues and economic losses cross sections revealing the 3d complexity of saprolith development are mainly based on fieldwork boreholes laboratory tests and the excavation works saprock is always observed overlying unweathered igneous bedrock two saprolite facies one clay rich and the other clay poor overlie the saprock the recognition is based on several criteria these deposits gradually thicken from the boundaries between the granitoid and metasedimentary roof pendants factors controlling saprolith development are discussed and the chemical and mineralogical changes and trends that occur are described variations in some geotechnical properties and the loss of quality of the rock masses from an engineering perspective are also quantified

assessing volumetric strains and mass balance relationships resulting from biotite controlled weathering implications for the isovolumetric weathering of the boulder creek granodiorite boulder county colorado usa abstract an important process often cited in the development of saprock and saprolite is the isovolumetric weathering of granitic bedrock evidence for isovolumetric weathering includes the observation that the texture of the granitic protolith often remains recognizable in its weathered products in contrast to the above often cited view we present results from a study of two sites located on the 1 65 ga boulder creek granodiorite near boulder colorado usa in which weakly chemically altered saprock derived from tonalitic and granodioritic tonalitic bedrock records volumetric strains on the order of 7 6 8 5 and 7 9 8 2 respectively we show that dilation is likely due to the alteration of biotite to vermiculite during the early stages of weathering and is associated with an expansion normal to the 001 cleavage of 40 theoretical calculations of volumetric strains based on the modal biotite present in the protolith support such an interpretation

diachronous variscan tectonothermal activity in the nw iberian massif evidence from 40ar 39ar dating of regional fabrics abstract multigrain concentrates of hornblende and muscovite together with whole rock slate phyllite samples have been dated 27 analyses using 40ar 39ar incremental release methods along a systematic traverse across the various lithotectonic structural elements which comprise northwestern sectors of the variscan iberian massif hornblende concentrates from amphibolites in the allochthonous ordenes complex yield plateau isotope correlation ages of 425 ma and 377 ma muscovite concentrates and whole rock slate phyllite from this and the cabo ortegal complex yield plateau ages which range from 367 ma to 295 ma analyses of similar material from the relative autochthon yield plateau ages between 359 ma and 275 ma muscovite concentrates from three late to post kinematic granitic stocks yield plateau ages between 309 ma and 274 ma at least seven of the 40ar 39ar analyses from metamorphic rocks record variable thermal rejuvenation of intracrystalline argon systems associated with emplacement of proximal granitic stocks the remaining analyses may be used to constrain the local age of various variscan tectonothermal events the oldest fabric ages are recorded in allochthonous units whereas the youngest fabric ages occur along the boundary between internal and external zones middle devonian ages are recorded in the allochthon and suggest a chronological continuity with deformational events in the relative autochthon where variscan deformation initiated in the upper devonian and diachronously prograded eastward the first deformational events recorded in the limit within the internal and external zones occured ca 20 25 ma later lower namurian variscan deformation systematically prograded diachronously eastward across the orogen as new crustal material was added along the front of the developing orogenic wedge however the entire orogen remained tectonically active with different structural features forming at different times and at different places an average propagation rate of ca 5 km m y is suggested by consideration of a 20 25 ma difference in correlative fabric ages and present separations

cenozoic normal faulting and regional doming in the southern hangay region central mongolia implications for the origin of the baikal rift province abstract the hangay dome in central mongolia is a mountainous region covering more than 200 000 km2 with numerous flat topped peaks over 3000 m that preserve a late cretaceous paleogene erosion surface doming began in the middle oligocene producing more than 2000 m of regional topographic uplift the range represents an important kinematic link between the baikal rift province to the north and altai transpressional ranges to the south and west structural field investigations of major faults visible on satellite imagery indicate that the southern hangay dome region is dominated by late cenozoic normal faults that bound small half graben most faults are ne striking and faults at the highest elevations are the most recently active most graben appear to be isolated systems that constitute small sediment sinks perched on the flanks and crests of the dome the first order feature is the dome itself and most sediment eroded off of the dome is deposited in the mongolian valley of lakes or is carried northwards by the selenga river and its extensive tributaries the basement of the dome is a precambrian craton although the shape and dimensions of the craton are poorly constrained to the north and east late cenozoic uplift of the southern dome region appears to be confined to the area underlain by cratonic basement whereas the altai region to the south and west is underlain by mechanically weaker palaeozoic arc and accretionary belts with respect to the regional northeast directed shmax the hangay craton appears to have acted as a rigid passive indentor focusing late cenozoic transpressional deformation around its west and southern margins models invoking a late cenozoic plume as the driving force for doming and widespread alkaline volcanism on the dome are not strongly supported by geochemical and isotopic data on neogene recent volcanics and the spatial correlation between areas that are domed and older cratonic crust appears too coincidental to be ignored convective removal of an overthickened lithospheric root leading to adiabatically decompressed asthenosphere could explain regional doming and volcanism however major crustal thickening last occurred in the permian in the southern hangay region and the time lag between thickening and postulated root removal and plateau uplift 200 myr appears too long an alternative model is explored based on speculated lithospheric mantle flow patterns driven by india s continued northeastward indentation it is suggested that lithospheric mantle flow diversion around the overthickened hangay craton crustal keel could cause lithospheric thinning beneath the craton and passive asthenospheric upwarp leading to regional topographic uplift and decompression melting alkali volcanism in general the angular relationship between precambrian craton boundaries and the prevailing northeasterly shmax appears to control the kinematics of late cenozoic deformation throughout the hangay altai sayan and baikal regions

dissolved iron in the vicinity of the crozet islands southern ocean the annual phytoplankton bloom occurring north of the crozet plateau provides a rare opportunity to examine the hypothesis that natural iron fertilization can alleviate high nutrient low chlorophyll hnlc conditions normally associated with the southern ocean therefore during crozet natural iron bloom and export experiment crozex a large multidisciplinary study performed between november 2004 and january 2005 measurements of total dissolved iron dfe0 2 m were made on seawater from around the islands and atmospheric iron deposition estimated from rain and aerosol samples dfe concentrations were determined by flow injection analysis with n n dimethyl p phenylenediamine dihydrochloride dpd catalytic spectrophotometric detection dfe concentrations varied between 0 086 and 2 48 nm with low values in surface waters enrichment of dissolved iron 1 nm at close proximity to the islands suggests that the plateau and the associated sediments are a source of iron waters farther north also appear to be affected by this input of coastal and shelf origin although dissolved iron concentrations decrease as a function of distance to the north of the plateau with a gradient of 0 07 nm km 1 at the time of sampling using lateral and vertical diffusion coefficients derived from ra isotope profiles and also estimates of atmospheric inputs it was then possible to estimate a dfe concentration of 0 55 nm to the north of the islands prior to the bloom event which is sufficient to initiate the bloom the lateral island source being the largest component a similar situation is observed for other sub antarctic islands such as kerguelen south georgia that supply dissolved iron to their surrounding waters thus enhancing chlorophyll concentrations

mineralogical variability in weathering microsystems of a granitic outcrop of galicia spain summary several products of weathering have been studied in a granitic outcrop in galicia n w spain spain alteration took place under a humid temperate climate the various materials and the microsystems in which they occur are 1 fissures containing gibbsite and or 1 1 sheet silicates of varying degrees of crystallinity 2 fissures containing 2 1 sheet silicates of beidellite type 3 encrustations of siliceous material showing varying degrees of structural order with or without organic matter and 4 encrustations of non crystalline matter composed chiefly of al p and si the results demonstrate the importance of considering the different microsystems which contribute to the formation of secondary products in a given weathering system

controlling factors of gullying in the maracuja catchment southeastern brazil hundreds of gullies vocorocas of huge dimensions up to 400 500 m long 150 m wide and 50 m deep are very common in the small maracuja catchment in southeastern brazil these erosional features which occur with an uneven intensity throughout the area started due to bad soil management practices at the beginning of european settlement at the end of the 17th century and nowadays are still evolving but at a slower rate as surface soils are usually very resistant to erosion the outcrop of the more erodible basement saprolites seems to be an essential condition for their beginning an analysis of well known erosion controlling factors was performed aiming to explain the beginning and evolution of these gullies and to understand the reasons for their spatial distribution data shows that geology and mainly geomorphology are the main controlling factors since gullies tend to be concentrated in basement rock areas with lower relief domain 2 of maracuja catchment mainly at the fringes of broad and flat interfluves at the detailed scale 1 10 000 gullies are more common in amphitheatre like headwater hollows that frequently represent upper quaternary gullies paleogullies which demonstrate the recurrence of channel erosion so gullies occur in areas of thicker saprolites domain 2 in places with a natural concentration of surface and underground water hollows saprolites of the preserved non eroded hollows are usually pressurized confined aquifer due to a thick seal of quaternary clay layer in a similar configuration to the ones found in hollows of mass movement mudflow sites in southeastern brazil therefore the erosion of the resistant soils by human activities such as road cuts and trenches valos or their mobilization by mudflow movements seem to be likely mechanisms of gullying initiation afterwards gullies evolve by a combination of surface and underground processes such as wash and tunnel erosion and falls and slumps of gully walls copyright 2005 john wiley sons ltd

137cs water profiles in the south indian ocean an evidence for accumulation of pollutants in the subtropical gyre abstract the 137 cs seawater transect along the 20 s latitude in the indian ocean sampled during the round the globe beagle2003 blue ocean global expedition clearly shows a presence of two cores of higher 137 cs concentrations at 100 e and 55 e in water column depths between 100 and 200 m the subsurface maximum of 137 cs activity concentration 2 1 mbq l observed near 100 e is the highest level found in southern hemisphere seawater which is comparable to the maximum 137 cs concentration observed in north pacific surface water this transect represents the first high density sight of 137 cs distribution in south indian ocean waters the estimated 137 cs water column inventories up to 1240 bq m 2 normalized for the 1000 m water depth along the 20 s latitude are by a factor of three higher than would be expected from global fallout in the south indian ocean the estimated residence time of 137 cs in surface waters of the south indian ocean 30 years is by about a factor of two higher than for the north pacific the 137 cs data confirm a transport of surface waters from the north pacific via indonesian seas to the south indian ocean and to the subtropical gyre the subtropical gyre is an important reservoir of anthropogenic pollutants that have been transported from the north pacific and indian oceans to the south on a time scale of several decades

lithosphere rheology and active tectonics in mongolia relations between earthquake source parameters gravity and gps measurements in this paper we use observations of earthquake source parameters and gravity to investigate the mechanical properties and the active faulting of the lithosphere in mongolia well determined earthquake centroid depths including 10 from inversions of p and sh waveforms that are presented here for the first time show that the seismogenic thickness ts within mongolia itself is less than 20 km however to both the east in parts of the lake baikal rift system and the west adjacent to the junggar basin and kazakhstan platform the seismogenic thickness is considerably greater and includes essentially the whole crust from the admittance between the free air gravity and the topography and also from profiles across a flexural foreland basin we determine the effective elastic thickness te in central mongolia to be 30 km in both mongolia and its surroundings te is comparable with ts and where it is well determined te ts these data are consistent with the view that the strength of the continental lithosphere resides in its seismogenic part which in mongolia is the upper crust but to both the east and west appears to be the whole crust the earthquake source parameters also allow us to ask how the active faulting in mongolia accommodates the velocity field revealed by gps measurements it is likely that the entire mongolian altay range in the west rotates counter clockwise relative to stable asia and is responsible for the distributed e w left lateral shear seen further east in central mongolia the admittance observations show no evidence at the present day for convective mantle support or a hotspot responsible for the elevated region of the hangay dome in central mongolia even though the geochemical data from nodules in late cenozoic basalts and seismic tomography studies suggest elevated temperatures at shallow depths 125 km and probably thinned lithosphere

forebergs flower structures and the development of large intra continental strike slip faults the gurvan bogd fault system in mongolia the gurvan bogd mountains of the gobi altay mongolia contain a system of strike slip faults with a reverse component part of which moved in a large earthquake mw 8 0 in 1957 adjacent and sub parallel to the main ranges are numerous thrust related folds thrust faults and elongated low ridges forebergs all of which result from the shortening component on the fault zone the appearance of these thrust related structures is varied depending on their stage of development preservation and exposure evidence from geomorphology and surface ruptures suggests that they may all serve a common function which is to broaden the deforming zone by creating new structures that are able to accommodate both the strike slip and the shortening components of motion the geomorphology further suggests that these new structures then evolve by lateral propagation and increase in amplitude to eventually merge and form through going new faults subparallel to the old in their early stages the new faults and related structures appear to be influenced by the underlying sediments adjacent to the main range which may include weak layers such as lake beds that can ultimately cause the collapse of foreberg ridges in landslides the migration of faulting away from the main range is likely to be driven by stresses associated with topography which in turn is a consequence of the shortening component the evolution described here is thus peculiar to strike slip faults with a reverse component and can form many of the features of the flower structures that are often described in such oblique shortening zones although the shortening component is often localized in restraining bends its origin may ultimately be related to rotations about vertical axes which are common in deforming continental regions

transport and scavenging of pu in surface waters of the southern hemisphere oceans abstract the distribution of 239pu in atlantic and indian ocean waters about four decades after their main injection from atmospheric nuclear weapons tests is discussed recent data obtained in the framework of the shots southern hemisphere ocean tracer studies projects are evaluated and compared with previous investigations seawater samples were collected during the round the globe beagle2003 blue ocean global expedition along the 30 s transect in the atlantic and the 20 s transect in the indian ocean the results indicate transport of surface waters labelled with 239pu from the western north pacific via the indonesian seas to the south indian ocean and then to the south atlantic ocean along the whole beagle2003 sampling route the atlantic ocean has the lowest 239pu content due to its particle scavenging on the long way from the western north pacific on the other hand concentrations of the conservative 137cs tracer are in all three oceanic basins comparable the primary productivity reflected by the chlorophyll content in surface waters has similar longitudinal distribution as 239pu radioactive and chlorophyll tracers revealed that the most important current system in each southern oceanic basin is represented by the subtropical gyre while the main streams of the gyres maintain high concentrations of tracers inside the loops the tracer concentrations are the lowest

field examples of strike slip fault terminations in mongolia and their tectonic significance deformation at the ends of large intracontinental strike slip faults that do not simply link other major structures often involves rotations about a vertical axis we use earthquake slip vectors surface rupture in earthquakes and geomorphology to examine the ends of three major strike slip faults in mongolia in these places a simple pattern is seen consisting of a thrust fault on one side with a displacement that decreases away from the strike slip fault consistent with local rotational deformation strike slip faults that terminate in this way allow the style of faulting to change spatially within a deforming area for example from dominantly strike slip to dominantly dip slip while still accommodating the overall deformation required by larger scale regional motions such a change in fault style should also be accompanied by a change in the rotation rate about a vertical axis which may be detected paleomagnetically the kind of strike slip fault termination described here may have consequences for how large strike slip fxaults evolve and grow and for the variation in displacement along their length

geomorphology and structure of the jid right lateral strike slip fault in the mongolian altay mountains abstract we describe the late cenozoic structure and evolution of the jid right lateral strike slip fault in the northern mongolian altay mountain chain parts of the jid fault have a vertical component of motion introduced by bending along the fault some locations show additional structural complexity at the earth s surface with parallel strands having strike slip normal and reverse faulting probably indicating a spatial separation of dip slip and strike slip components of motion in cross section the jid fault shows indications of recent movements at scales ranging from drainage re organisation at the kilometre scale to ground deformations likely to result from movements during the last earthquake which occurred 870 980 years ago based on osl dating of deposits exposed in trenching from the scale of the ruptures the earthquake would have had a magnitude of 7 5 with an estimated right lateral slip of 5 m numerous horizontal offsets of about 10 15 m and vertical scarps of 5 m in the youngest alluvial deposits show the likely cumulative movement over the last 15 000 years and suggest a maximum slip rate of roughly 1 mm yr the minimum cumulative right lateral slip on the jid fault is 1 km which would accumulate in 1 ma at present day rates of slip the relatively small vertical component of motion on the jid fault is not sufficient to generate topography in the adjacent kharkhiraa and turgen uul mountains with relief of over 2000 m the high mountains may therefore result from localised uplift on thrust faults rather than by oblique slip on the jid fault