adiabatic westward drift of indian monsoon depressions a large fraction of the rain received by continental india is produced by cyclonic vortices with outer radii of about 1000 km that are contained within the larger scale south asian monsoon flow the more intense occurrences of these vortices are called monsoon depressions these consist of bottom heavy columns of relative vorticity that propagate to the northwest in time mean low level eastward flow previous studies have argued that this apparent upstream propagation is caused by dynamical lifting west of the vortex centre with the resulting ascent producing vortex stretching that shifts the vortex to the west here analysis of over 100 indian monsoon depressions is used to show that low level vortex stretching has a spatial structure inconsistent with the observed propagation and is balanced by other terms in the low level vorticity budget instead monsoon depressions are shown to consist of potential vorticity maxima that have peak amplitude in the middle troposphere and propagate westward by nonlinear horizontal adiabatic advection i e beta drift the precipitating ascent in monsoon depressions makes a more minor contribution to the total storm motion and primarily acts to maintain the upright structure of the vortex these results suggest a new view of indian monsoon depressions as potential vorticity columns that propagate primarily by adiabatic dynamics

intraplate deformation in western europe deduced from an analysis of the international terrestrial reference frame 1997 itrf97 velocity field although tectonic deformation in western europe is essentially concentrated in the appenines and alpine alps pyrenees mountain ranges several large historical and instrumentally recorded earthquakes m 6 are known in the supposedly stable part of europe because of its accuracy and internal consistency at a global scale the international terrestrial reference frame 1997 itrf97 velocity field allows testing of intraplate rigidity in western europe at a millimeter per year level using the full statistical information available on the itrf97 velocities we identify a subset of sites located in central europe that satisfies a rigid cap rotation with residual velocities 1 mm yr and therefore provide a stable europe reference frame serf in this reference frame we find residual velocities at european itrf sites that are consistent with known active tectonic features we identify a northward motion at sites located in italy with internal deformation of the adriatic block rather than rigid plate motion and a westward motion of the westernmost part of europe of the order of 1 2 mm yr relative to central europe the relative motion of the adriatic block and western europe agrees with the current extension known in the tyrrhenian sea and the apennines in central europe we find active deformation 1 mm yr in the eastern alps and western carpathians in the alpine range our results indicate e w extension across the western alps and n s compression across the central and eastern alps in agreement with the strain regime deduced from seismotectonic observations in belgium and the netherlands we find residual velocities of 1 1 5 mm yr to the northwest at all the sites most likely accommodated along the upper and lower rhine graben structures an important outcome of this study is the identification of internal deformation of the order of 1 2 mm yr in an area usually interpreted as stable europe this result should be further checked as new denser and more accurate space geodetic data sets with longer observation time spans become available for europe

modeling dynamic marine gas hydrate systems dynamically changing marine gas hydrate systems are the subject of this study the changes may result from varying pressure or temperature at the seafloor exploration and exploitation operations rapid sedimentation or wasting at the seafloor etc pressure and temperature may not be used as independent state variables at the same time to specify the overall state of such dynamic systems consequently a pressure enthalpy gas concentration salinity phase balance model is constructed for calculating phase distribution and transition of the system of marine gas hydrate which is assumed to contain a liquid phase consisting of water gas and salt a vapor phase consisting of gas only solid halite and solid gas hydrate consisting of gas and water calculations of phase transition processes demonstrate various dynamic feedback mechanisms involved in dynamically evolving marine gas hydrate systems a comprehensive model of fluid flow and transport of heat water salt and gas in marine sediment is developed simulations show that gas hydrate dissociation resulting from increasing temperature or decreasing pressure at the seafloor may lead to the development of a three phase zone with coexistent gas hydrate free gas and liquid solution and excess pore pressure in marine gas hydrate systems the changes considered in this study are rapid 5 years with respect to the geological time scale but are sufficiently slow 10 2 years to allow thermodynamic equilibrium throughout the applicable pressure temperature and salinity ranges for the calculations used in this study are sufficiently wide to cover those likely occurring in gas hydrate bearing marine sediments

blocking highs over asia and monsoon droughts over india severe summer droughts of the indian subcontinent have been found to accompany prolonged breaks in the south west monsoon data from the years of severe drought suggest that the associated breaks were due to upper tropospheric blocking ridges over east asia we present here a model for the evolution of two such blocking ridges the east asia eabr and the west asia wabr apparently an intense wabr the initiator of the monsoon break precedes the formation of the eabr this cycle could be a way of predicting years of intense drought or monsoon activity

stress tensor orientation derived from fault plane solutions in the southwestern alps gephart and forsyth s method has been applied to estimate stress orientations from earthquake fault plane solutions of the southwestern alps a region where the tectonic stress regime is known to be fairly complex fault plane solutions have been either taken from the literature or computed using data from local and regional networks data refer to seismic events of magnitude in the range 2 5 5 3 which occurred in the last decades at depths between 0 and 25 km two zones with a different stress orientation have been identified in the studied area 44 0 45 5 n 6 5 8 5 e the western zone corresponding to the crest of the alpine belt where a high dip maximum compressive stress is found and the eastern zone alps chain to po plain transition characterized by an almost horizontal e w 1 and a nearly vertical 3 hypocenters of earthquakes used for stress inversion lie in the depth ranges 0 15 km and 5 25 km in the western and eastern zones respectively the transition between the two stress domains is very sharp and this is also indicated by space distribution of earthquake individual misfits to the respective stress models the findings of the present study are a good match for tectonic models which assume e w compression derived from the adria europe interaction and producing 1 major thrusting processes in the eastern side of the chain and 2 secondary tensional effects at very shallow depth beneath the alpine belt crest western zone of the area studied in this work

understanding the revival of the indian summer monsoon after breaks abstractin this paper the authors suggest a dynamical mechanism involved in the revival of the summer monsoon after breaks in this context the authors carry out a diagnostic analysis using the datasets from national centers for environmental prediction reanalysis 2 for the period 1979 2007 to identify a robust mechanism that typifies breaks and subsequent revival of monsoon the authors find during the peak of significant breaks an anomalous southward shift of the subtropical westerly jet stream which is invariably accompanied by an anomalous northward shift of a stronger than normal easterly jet these major changes during a break facilitate an instability mechanism which apparently leads to formation of a synoptic disturbance formation of such a disturbance is critical to the subsequent revival of the summer monsoon in 61 of the observed break to active revivals computations of energetics and correlation analysis carried out suggest an increase in the eddy kinetic energy at the expense of the mea

tectono thermal evolution of a distal rifted margin constraints from the calizzano massif prepiedmont brianconnais domain ligurian alps the thermal evolution of distal domains along rifted margins is at present poorly constrained in this study we show that a thermal pulse most likely triggered by lithospheric thinning and asthenospheric rise is recorded at upper crustal levels and may also influence the diagenetic processes in the overlying sediments thus representing a critical aspect for the evaluation of hydrocarbon systems the thermal history of a distal sector of the alpine tethys rifted margin preserved in the ligurian alps case tuberto calizzano unit is investigated with thermochronological methods and petrologic observations the studied unit is composed of a polymetamorphic basement and a sedimentary cover providing a complete section through the prerift synrift and postrift system zircon fission track analyses on basement rocks samples suggest that temperatures exceeding 240 25 c were reached before 150 160 ma upper jurassic at few kilometer depth neoformation of green biotite stable at temperatures of 350 to 450 c was synkinematic with this event the tectonic setting of the studied unit suggests that the heating cooling cycle took place during the formation of the distal rifted margin and terminated during late jurassic 150 160 ma major crustal and lithospheric thinning likely promoted high geothermal gradients 60 90 c km and triggered the circulation of hot deep seated fluids along brittle faults causing the observed thermal anomaly our results suggest that rifting can generate thermal perturbations at relatively high temperatures between 240 and 450 c at less than 3 km depth in the distal domains during major crustal thinning preceding breakup and onset of seafloor spreading

climatically versus tectonically forced erosion in the alps thermochronometric constraints from the adamello complex southern alps italy abstract we apply u th sm he dating and fission track thermochronometry of apatites to the adamello complex located in the southern european alps our goal is to constrain exhumation rates since the miocene in particular to determine whether the increase in sedimentation documented in the foreland basins since 5 ma is recorded in cooling rates of the southern alps thermochronometry provides a cooling rate for rocks which can be converted to an exhumation rate through thermal modeling thereby quantifying the amount of rock exhumed at different time scales apatite fission track and u th sm he analyses all record miocene ages we find no evidence for an increase in exhumation rate during the plio pleistocene the results of our exhumation rate estimates and tectono geomorphic modeling suggest that unroofing during thrust propagation of the southern alps in the late miocene drove most of the exhumation while changes in relief mainly associated with plio pleistocene climate change likely did not affect the adamello complex the findings from this study combined with other studies highlight that there appears to be a gradient across the alps with more intensive plio pleistocene erosion in the western and central alps compared to the eastern and southern alps

detection of overpressure zones and a statistical model for pore pressure estimation from well logs in the krishna godavari basin india abnormally high pressures measured by repeat formation tester rft and detected by well log data from 10 wells in the krishna godavari k g basin occur in the vadaparru shale of miocene and raghavapuram shale of early cretaceous age overpressures generated by disequilibrium compaction and pore pressures have been estimated using the conventional eaton sonic equation with an exponent of 3 0 the observed abnormal pore pressure gradient ranges from 11 85 to 13 10 mpa km whereas fracture pressure gradient varies from 17 40 to 19 78 mpa km the magnitude of vertical stress sv has a gradient from 21 00 to 23 10 mpa km the minimum horizontal principal stress sh magnitude is found to vary from 64 to 77 of the sv in normally pressured to overpressured sediments a multiple linear regression model with a squared multiple correlation coefficient r2 of 0 94 is proposed for pore pressure prediction from gamma ray density and sonic logs to focus on efficient drilling operations and to prevent borehole instability the statistical model has been calibrated with the rft data from five wells covering about 3400 sq km area of the onshore k g basin the model predicted pore pressure values are in close agreement with the actual rft data for another four wells including a well in the offshore k g basin hence the proposed regression model may be useful for predicting pore pressure from other well logs in the k g basin

widespread extension in the core of the western alps revealed by earthquake analysis the western alps are an active collision belt whose current stress field is inhomogeneous muller et al 1992 we report new seismological data which significantly improve our knowledge of this stress field about 1600 earthquakes which occurred in the western alps during the last 10 years were precisely located and 79 new focal solutions were computed the analysis of this database shows that widespread extension affects all the internal zones of the belt to better constrain the associated stress regime six stress tensors were computed using the gephart and forsyth 1984 method they show that the current tectonics of the western alps are contrasted with close variation in the stress regime transpression to the front of the belt contrasting with extension in the core of the belt the extensional direction is radial to the arcuate geometry of the belt and bounded outboard by the former thrust of the internal zones onto the external zone suggesting extensional reactivation of this inherited crustal discontinuity such widespread extension within the inner part of an actually ongoing collision belt cannot be explained by simple collision related tectonics we propose that intrabelt buoyancy forces such as those produced by a slab retreat or slab break off interfere with the boundary forces driven by the ongoing europe africa convergence

crystallographic and geochemical properties of natural gas hydrates accumulated in the national gas hydrate program expedition 02 drilling sites in the krishna godavari basin off india abstract this study presents the crystallographic and geochemical properties of different types of pore space natural gas hydrate recovered by pressure core operations during the national gas hydrate program nghp expedition 02 at three study areas in the krishna godavari basin off eastern india the gas hydrate is structure i with hydration number n 6 1 6 2 formed predominantly from microbial methane and small amounts of heavier hydrocarbons up to c3 hydrate crystal lattice constants are nearly uniform regardless of sediment pore space size ethane concentration varies with clay content and to some extent depth and its measurement helps resolve the contributions of gases dissolved in pore water to hydrate formation we also assess the disturbance of the core through drilling using diffraction techniques and visual observation of hydrate bearing sediments

apatite u th he age constraints on the development of the great escarpment on the southeastern australian passive margin the southeast australian margin like other high elevation passive margins is characterised by a steep escarpment that separates a dissected coastal plain from a low relief inland plateau quantitative constraints on the generation of escarpments can be provided by apatite u th he ages here we use a coast perpendicular traverse across the coastal lowlands escarpment and plateau to test the three prevailing models of se australian escarpment formation namely retreat into a downwarped rift shoulder escarpment retreat and down wearing on high elevation rift shoulder with flexural rebound apatites from the coastal plain have he ages of between 87 and 112 ma suggesting that the coastal lowlands developed very rapidly after rifting and continental break up at 85 100 ma the he age data are inconsistent with the erosion of a downwarped rift margin and cannot be explained by a constant post break up rate of lateral escarpment retreat across the coastal plain or by constant down wearing the data require either rapid escarpment retreat or rapid in place excavation of the escarpment soon after break up in response to rifting and the lowering of base levels on the margin of the new continent at break up followed by a period of landscape stability and low erosion combined with the existing apatite fission track record the he data are consistent with erosion of 3 4 km within a maximum of 28 myr of break up at a minimum vertical erosion rate of 130 m myr 1 along the coast the rapid denudation period across the coastal plain in this region took less than 48 myr from the coast to the escarpment base which corresponds to an average vertical erosion rate of 45 m myr 1 this is equivalent to a mean escarpment retreat rate of 5 10 km myr 1 apatite he ages from the plateau 183 247 ma indicate that the highlands remained stable throughout continental break up experiencing average erosion rates of less than 10 m myr 1 since the late palaeozoic early mesozoic

chronology causes and progression of the messinian salinity crisis the messinian salinity crisis is widely regarded as one of the most dramatic episodes of oceanic change of the past 20 or so million years 1 3 earliest explanations were that extremely thick evaporites were deposited in a deep and desiccated mediterranean basin that had been repeatedly isolated from the atlantic ocean1 2 but elucidation of the causes of the isolation whether driven largely by glacio eustatic or tectonic processes have been hampered by the absence of an accurate time frame here we present an astronomically calibrated chronology for the mediterranean messinian age based on an integrated high resolution stratigraphy and tuning of sedimentary cycle patterns to variations in the earth s orbital parameters we show that the onset of the messinian salinity crisis is synchronous over the entire mediterranean basin dated at 5 96 0 02 million years ago isolation from the atlantic ocean was established between 5 59 and 5 33 million years ago causing a large fall in mediterranean water level followed by erosion 5 59 5 50 million years ago and deposition 5 50 5 33 million years ago of non marine sediments in a large lago mare lake sea basin cyclic evaporite deposition is almost entirely related to circum mediterranean climate changes driven by changes in the earth s precession and not to obliquity induced glacio eustatic sea level changes we argue in favour of a dominantly tectonic origin for the messinian salinity crisis although its exact timing may well have been controlled by the 400 kyr component of the earth s eccentricity cycle

eastward propagating mjo during boreal summer and indian monsoon droughts improved understanding of underlying mechanism responsible for indian summer monsoon ism droughts is important due to their profound socio economic impact over the region while some droughts are associated with external forcing such as the el nino and southern oscillation enso many ism droughts are not related to any known external forcing here we unravel a fundamental dynamic process responsible for droughts arising not only from external forcing but also those associated with internal dynamics we show that most ism droughts are associated with at least one very long break vlb breaks with duration of more than 10 days and that the processes responsible for vlbs may also be the mechanism responsible for ism droughts our analysis also reveals that all extended monsoon breaks whether co occurred with el nino or not are associated with an eastward propagating madden julian oscillation mjo in the equatorial indian ocean and western pacific extending to the dateline and westward propagating rossby waves between 10 and 25 n the divergent rossby wave associated with the dry phase of equatorial convection propagates westward towards indian land couple with the northward propagating dry phase and leads to the sustenance of breaks thus the propensity of eastward propagating mjo during boreal summer is largely the cause of monsoon droughts while short breaks are not accompanied by westerly wind events wwe over equatorial western pacific favorable for initiating air sea interaction all vlbs are accompanied by sustained wwe the wwes associated with all vlb during 1975 2005 initiate air sea interaction on intraseasonal time scale extend the warm pool eastward allowing the convectively coupled mjo to propagate further eastward and thereby sustaining the divergent circulation over india and the monsoon break the ocean atmosphere coupling on interannual time scale such as el nino can also produce vlb but not necessary

a closing ligurian sea two earthquakes occurred in the ligurian sea in december 1989 and april 1990 both were widely felt along the french and italian rivieras thus reminding us of the seismic risk in this region the significant increase in the number of seismic stations in the area facilitated the study of these two shocks and their related aftershocks using different techniques absolute and relative hypocentral locations doublet analysis and waveform modeling we computed accurate hypocentral locations and estimated the location error range for earthquakes in this area we also computed the focal mechanisms for both mainshocks and we present here a synthesis that integrates previous data the reactivation in compression of the ligurian sea sphenochasm is confirmed which would eventually result in the closing of an aborted oceanic domain as the seismic activity is clearly restricted to the northern margin we suggest it locally results from the lateral expulsion of the south western alps along the apulian indenter

seismic imaging of a fractured gas hydrate system in the krishna godavari basin offshore india gas hydrate was discovered in the krishna godavari kg basin during the india national gas hydrate program nghp expedition 1 at site nghp 01 10 within a fractured clay dominated sedimentary system logging while drilling lwd coring and wire line logging confirmed gas hydrate dominantly in fractures at four borehole sites spanning a 500 m transect three dimensional 3d seismic data were subsequently used to image the fractured system and explain the occurrence of gas hydrate associated with the fractures a system of two fault sets was identified part of a typical passive margin tectonic setting the lwd derived fracture network at hole nghp 01 10a is to some extent seen in the seismic data and was mapped using seismic coherency attributes the fractured system around site nghp 01 10 extends over a triangular shaped area of 2 5 km2 defined using seismic attributes of the seafloor reflection as well as seismic sweetness at the base of the gas hydrate occurrence zone the triangular shaped area is also showing a polygonal nearly hexagonal fault pattern distinct from other more rectangular fault patterns observed in the study area the occurrence of gas hydrate at site nghp 01 10 is the result of a specific combination of tectonic fault orientations and the abundance of free gas migration from a deeper gas source the triangular shaped area of enriched gas hydrate occurrence is bound by two faults acting as migration conduits additionally the fault associated sediment deformation provides a possible migration pathway for the free gas from the deeper gas source into the gas hydrate stability zone it is proposed that there are additional locations in the kg basin with possible gas hydrate accumulation of similar tectonic conditions and one such location was identified from the 3d seismic data 6 km nw of site nghp 01 10

fault system and thermal regime in the vicinity of site nghp 01 10 krishna godavari basin bay of bengal abstract drilling coring activities onboard joides resolution for hydrate resource estimation have confirmed gas hydrate in the continental slope of krishna godavari kg basin bay of bengal and the expedition recovered fracture filled gas hydrate at the site nghp 01 10 in this paper we analyze high resolution multi channel seismic mcs high resolution sparker hrs bathymetry and sub bottom profiler data in the vicinity of site nghp 01 10 to understand the fault system and thermal regime we interpreted the large scale fault system 5 km predominantly oriented in nnw sse direction near nghp 01 10 site which plays an important role in gas hydrate formation and its distribution the increase in interval velocity from the baseline velocity of 1600 m s to 1750 1800 m s within the gas hydrate stability zone ghsz is considered as a proxy for the gas hydrate occurrence whereas the drop in interval velocity to 1400 m s suggest the presence of free gas below the ghsz the analysis of interval velocity suggests that the high concentration of gas hydrate occurs close to the large scale fault system we conclude that the gas hydrate concentration near site nghp 01 10 and likely in the entire kg basin is controlled primarily by the faults and therefore has high spatial variability we also estimated the heat flow and geothermal gradient gtg in the vicinity of nghp 01 10 site using depth and temperature of the seafloor and the bsr we observed an abnormal gtg increase from 38 c km to 45 c km at the top of the mound which remarkably agrees with the measured temperature gradient at the mound nghp 01 10 and away from the mound nghp 01 03 we analyze various geological scenarios such as topography salinity thermal non equilibrium of bsr and fluid gas advection along the fault system to explain the observed increase in gtg the geophysical data along with the coring results suggest that the fluid advection along the fault system is the primary mechanism that explains the increase in gtg the approximate advective fluid flux estimated based on the thermal measurement is of the order of few tenths of mm yr 0 37 0 6 mm yr

late miocene to present exhumation in the ligurian alps southwest alps with evidence for accelerated denudation during the messinian salinity crisis detrital apatite u th he and fission track thermochronometry are applied to constrain the exhumation history of the ligurian alps southwest alps exhumation of the ligurian alps is recorded from ca 11 ma and continues until present more than 4 km of exhumation is recorded at an average rate of 0 4 0 2 mm yr exhumation is accommodated along a north dipping thrust at the foot of the ligurian margin combined u th he and fission track thermal modeling show a phase of accelerated denudation between 7 and 5 ma associated with the base level drop during the messinian salinity crisis

from nappe stacking to out of sequence postcollisional deformations cretaceous to quaternary exhumation history of the se carpathians assessed by low temperature thermochronology 1 apatite fission track aft and u th he ahe thermochronology have been combined to constrain the exhumation history of the se carpathians cooling ages generally decrease from cretaceous for the internal basement nappes aft ages to miocene quaternary aft and ahe respectively for the external sedimentary wedge the aft and ahe data show a paleogene age cluster which confirms a suspected but never demonstrated tectonic event the new data furthermore suggest that the se carpathians have been affected by a middle miocene exhumation phase related to continental collision which occurred at rates of 0 8 mm yr similar to the one previously inferred for the east carpathians the se carpathian tectonic evolution however is overprinted by two younger exhumation events in the pliocene pleistocene the first exhumation phase latest miocene early pliocene occurred at high exhumation rates 1 7 mm yr and is interpreted as a tectonic event and or associated with a sea level drop in the paratethys basins during the messinian low stand the youngest recorded tectonic phase suggests rapid pleistocene exhumation 1 6 mm yr and is interpreted to represent crustal scale shortening different in mechanics from collisional processes the data suggest that the se carpathians did not develop as a typical double vergent orogenic wedge instead exhumation was related to a foreland vergent sequence of nappe stacking during collision and was subsequently followed by a large out of sequence shortening event truncating the already locked collisional boundary

current strain regime in the western alps from continuous global positioning system measurements 1996 2001 four to six years of continuous measurements at 10 permanent global positioning system sites in the western alps show horizontal residual velocities of 2 mm yr with respect to stable europe uncertainties range from 0 3 to 1 4 mm yr these velocities and the associated strain rate field indicate that the central part of the range is currently dominated by east west extension whereas the southern part shows north south to northwest southeast compression the geodetic and seismotectonic data are consistent with a model where strain is essentially controlled by the counterclockwise rotation of the adriatic microplate with respect to eurasia this rotation together with the arcuate shape of the contact between the adriatic microplate and the alps induces dextral shear kinematic boundary conditions across the western alps with an additional divergence component in their central part and in switzerland and a convergence component in their southern part

paleoenvironmental change in a precession paced succession across the onset of the messinian salinity crisis insight from element geochemistry and molecular fossils abstract in marginal mediterranean sub basins the early phase of the messinian salinity crisis msc is recorded by cyclic successions of gypsum and shales which in deeper parts of the sub basins make lateral transition into organic rich shales marls and carbonates the cyclic stacking pattern of the gypsum bearing sequences is assumed to reflect periodic paleoenvironmental change induced by precession driven climate perturbations with the assumption that shales reflect humid climate precession minima while gypsum reflects arid conditions precession maxima however this correlation has not been verified to date mostly because of the scarcity of microfossils the most commonly used tools for the reconstruction of precession driven paleoenvironmental change such change can instead be reconstructed through the study of the deeper water counterparts of gypsum marly and carbonate layers with geochemical indicators major and trace elements molecular fossils which provide insight on climate and aquatic productivity we used this approach to study a section from the piedmont basin nw italy where the onset of the msc is archived in a sequence of organic rich sediments this sequence displays distinct lithological cyclicity evidenced by the repetition of couplets of organic rich shales and marls either bioturbated in the pre msc part of the section or laminated during the msc the influence of orbitally driven precession climate oscillations is demonstrated by fluctuations of ti al si al mg al k al zr al and ba al ratios that are in phase with lithological cyclicity these fluctuations are interpreted to reflect alternation of humid shales deposited during precession minima and arid bioturbated and laminated marls deposited during precession maxima phases dominated by fluvial and aeolian transport of detrital material respectively the cyclicity of the element ratios is mirrored by changes in organic carbon content and molecular fossil inventory in particular the distribution of long chain n alkanes and their degree of preservation reveal that humid phases at times of precession minima were typified by the maximum input of degraded terrestrial organic matter driven by enhanced riverine runoff which promoted water column stratification coeval increase in ba content a common paleoproductivity proxy agrees with enhanced nutrient supply during humid periods promoting phases of eutrophication in the basin lithological and geochemical changes are observed in msc sediments deposited at times of precession maxima evidenced by the replacement of pre msc bioturbated marls by laminated marls rich in filamentous fossils corresponding to the remains of probable colorless sulfide oxidizing bacteria such changes reflect an intensification of water column stratification after the onset of the msc possibly related to the combined effect of persistent freshwater inflow and basin isolation preluding the advent of gypsum precipitation

first paleomagnetic data from the sedimentary cover of the french penninic alps evidence for tertiary counterclockwise rotations in the western alps abstract we present a paleomagnetic study performed in the brianconnais sedimentary cover of the western alpine arc france sampling was focused on upper jurassic rocks of the brianconnais cover in the briancon guillestre area more than 100 samples from 11 sites were collected essentially from ammonitico rosso limestones and sedimentary dykes of the upper jurassic thermal and alternating field demagnetizations revealed three components of magnetization carried dominantly by magnetite 1 a low temperature component with present day magnetic field direction of viscous origin 2 a well defined reverse polarity component with a maximum unblocking temperature of 440 c a component and 3 a weak high temperature component b component that experienced a viscous overprint during heating and was difficult to isolate the a component exhibits a negative fold test and shows a better clustering when corrected for tilting associated with late alpine extension this component is interpreted as a secondary remagnetization acquired during the cooling path related to late eocene early oligocene metamorphism the mean a component direction corrected for late alpine extensional tilting is d 142 i 57 k 44 95 8 this direction significantly differs by 47 13 from the expected direction for eurasia we interpret this difference to be related to a post eocene counterclockwise rotation about a vertical axis of the penninic zone relative to stable europe

toward understanding the post collisional evolution of an orogen influenced by convergence at adjacent plate margins late cretaceous tertiary thermotectonic history of the apuseni mountains 1 the relationship between syn to post collisional orogenic shortening and stresses transmitted from other neighboring plate boundaries is important for understanding the kinematics of mountain belts but has received little attention so far the apuseni mountains are an example of an orogen in the interference zone between two other subduction systems located in the external carpathians and dinarides this interference is demonstrated by the results of a combined thermochronological and structural field study that quantifies the post collisional latest cretaceous tertiary evolution the exhumation history derived from apatite fission track and u th he thermochronology indicates that the present day topography of the apuseni mountains originates mainly from latest cretaceous times modified by two tectonic pulses during the paleogene the latter are suggested by cooling ages clustering around 45 ma and 30 ma and the associated shortening recorded along deep seated fault systems paleogene exhumation pulses are similar in magnitude 3 5 km and are coeval with the final collisional phases recorded in the dinarides and with part of the carpathian rotation around the moesian promontory these newly quantified paleogene exhumation and shortening pulses contradict the general view of tectonic quiescence subsidence and overall sedimentation for this time interval the miocene collapse of the pannonian basin did not induce significant regional exhumation along the western apuseni flank nor did the subsequent carpathian collision this is surprising in the overall context of pannonian basin formation and its subsequent inversion in which the apuseni mountains were previously interpreted as being significantly uplifted in both deformation stages

dem analyses and morphotectonic interpretation the plio quaternary evolution of the eastern ligurian alps italy abstract the ligurian alps italy straddle a complex and ill defined tectonic transition that accommodates eurasia adria shortening driving concurrent growth of the western alps and northern apennines we focus on the plio quaternary landscape evolution of the eastern part of the ligurian alps with the goal of defining the active tectonics through an analysis of topography drainage networks and river long profiles the ligurian alps have a steep seaward facing escarpment with topographic features reminiscent of the geomorphic markers preserved on both actively uplifting coastlines and passive margins for example there are seaward facing benches that are thought to be uplifted marine terraces common to active margins but the drainage divide of the seaward escarpment shows clear evidence of recent northward migration into the po foreland a process consistent with escarpment retreat characteristic of passive or subsiding margins this study explores the active tectonics consistent with these diverse landscape evolution pathways our analysis reveals that rock type strongly throttles the development of topographic relief drainage networks and northward migration of the drainage divide however we also identify segments of the escarpment that indicate recent base level falls through an analysis of modeled channel steepness and comparison with mean hillslope gradient the base level falls are consistent with numerous barbed tributaries that are best explained as recent stream captures no significant correlation among the stream captures at the drainage divide suspected marine terraces at the coast ligurian sea bathymetry and active seismicity indicates that the escarpment is the footwall of a segmented normal fault this normal fault is embedded in a regionally subsiding margin where actively uplifting segments lead to a straightened pinned drainage divide whereas relatively inactive segments permit divide migration into the footwall block these results are broadly consistent with rock uplift increasing eastward toward genova across the long suspected alps apennine sestri voltaggio fault zone they highlight the respective roles of legacy structures rock type and localized rock uplift in constructing a landscape in an otherwise extending and subsiding crustal retrowedge of an active subduction plate boundary

clustering of synoptic activity by indian summer monsoon intraseasonal oscillations 1 active and break phases of the indian summer monsoon are characterized by enhancement and decrease of precipitation over the monsoon trough region using genesis data of monsoon low pressure systems lps and circulation data for the period 1954 to 1993 it is shown that the frequency of occurrence of lps is nearly 3 5 times higher in the active phase of monsoon as compared to the break phase in addition the tracks of these synoptic systems are also strongly spatially clustered along the monsoon trough during the active phase of the monsoon the enhanced decreased frequency of occurrence of lps during active break phases is due to modulation of meridional shear of zonal winds and cyclonic vorticity along the monsoon trough by the intraseasonal oscillations iso

synthesis of deep multichannel seismic and high resolution sparker data implications for the geological environment of the krishna godavari offshore eastern continental margin of india abstract proven hydrocarbon occurrence in the krishna godavari kg basin a part of the eastern continental margin of india initiated intense exploration activities to discern the potential hydrocarbon bearing structures payoff zones recent discovery of gas hydrates in its offshore triggered detailed exploration measures adopting advanced seismic data acquisition techniques supported by deep drilling to understand its genesis interpretation of multichannel seismic mcs sections highlighted several distinct horizons from lower cretaceous to recent in the sediment overburden and the nature and configuration of the underlying crust the sections also depicted the presence of growth faults shale bulging toe thrust faulting delta progradation active sliding slumping buried channels pinchout structures and reflection free zones indicating the different types of sedimentary processes varied geological environments and neotectonic activity in the kg offshore high resolution sparker hrs data revealed subsidence gas fluid expulsion pathways occasional diapiric intrusions and growth faulting in the upper slope and toe thrust faulting upthrust and diapiric intrusions in the lower slope the mid slope is characteried by a well stratified e w trending basin bounded by upthrust and diapirism the entire region is associated with gas escape features blanking zones columnar type gas vents fault controlled mud shale diapirs large dimension gas saturated zones and pockmarks the growth faults shale bulging and toe thrusting seen in the mcs data since oligocene time could be linked to shale diapirism upthrust gas fluid expulsion subsidence and mini basin formation observed on the shallow hrs records synthesis of these datasets suggests that the distribution of gas hydrate in the shallow sediments may be controlled by the deeper structural and tectonic configuration therefore knowledge about shallow sedimentary column and its connectivity with deeper strata through faults fractures and other structural features and the geological architecture are significantly important to evaluate the genesis of gas hydrates

evidence of marine isotope stage 5 5 highstand in liguria italy and its tectonic significance abstract the quaternary shoreline displacements in liguria are still poorly known this paper completely revises and reinterprets the literature on this topic taking into account only those markers that allow precise estimates of altitude and age of sea level highstands among the sites showing geomorphological evidence of mis 5 5 present in liguria three were considered reliable in eastern liguria a beach deposit with a terrace inner margin at 28 m a s l villa monteverde was dated by osl in western liguria in a site close to the french border balzi rossi a notch present inside two caves indicating a sea level altitude of 12 m is associated with a deposit containing a faunal assemblage with strombus bubonius this gastropod appeared in the italian seas only during the last interglacial highstand and provides a unique marker of the mis 5 5 horizon eastward near imperia another site madonna dell arma shows similar evidence but in this case the notch is not preserved because the cave is carved in a very soft oligocene conglomerate late quaternary tectonic movements along the different tracts of the ligurian coast seem to have occurred apparently with different although rather low uplift rates the connection between the alpine and apennine chains sestri voltaggio line divides the ligurian arch into two parts the alpine sector can be considered stable whereas the apennine relief displays in its central part an uplift rate of 0 16 mm yr

relationship between stationary planetary wave activity and the east asian winter monsoon 1 the variability of both the stationary planetary wave activity and the east asian winter monsoon is strongly associated with the thermal contrast between oceans and landmasses in this study we explore the interannual relationship between the monsoon and the wave activity defined by an index of the difference in the divergence of eliassenpalm flux between 50 n at 500 hpa and 40 n at 300 hpa it is found that compared to the winters of low wave activity the equatorward propagation of planetary waves in the middle and upper troposphere is stronger in the high wave activity winters during these high activity winters the upward wave propagation from the troposphere into the stratosphere becomes weaker this is accompanied by a smaller perturbation in the polar vortex which tends to be colder and stronger in the meantime the east asian westerly jet stream the east asian trough the siberian high and the aleutian low all become weaker apparently in particular the weakening of the siberian high and the aleutian low decreases the northeasterly wind over east asia leading to a warming condition in the region especially in northeastern asia a further analysis reveals that the zonal wavenumber 2 pattern of planetary waves contributes dominantly to the variability of the east asian winter monsoon

grain scale imaging and compositional characterization of cryo preserved india nghp 01 gas hydrate bearing cores abstract we report on grain scale characteristics and gas analyses of gas hydrate bearing samples retrieved by nghp expedition 01 as part of a large scale effort to study gas hydrate occurrences off the eastern indian peninsula and along the andaman convergent margin using cryogenic scanning electron microscopy x ray spectroscopy and gas chromatography we investigated gas hydrate grain morphology and distribution within sediments gas hydrate composition and methane isotopic composition of samples from krishna godavari kg basin and andaman back arc basin borehole sites from depths ranging 26 to 525 mbsf gas hydrate in kg basin samples commonly occurs as nodules or coarse veins with typical hydrate grain size of 30 80 m as small pods or thin veins 50 to several hundred microns in width or disseminated in sediment nodules contain abundant and commonly isolated macropores in some places suggesting the original presence of a free gas phase gas hydrate also occurs as faceted crystals lining the interiors of cavities while these vug like structures constitute a relatively minor mode of gas hydrate occurrence they were observed in near seafloor kg basin samples as well as in those of deeper origin 100 mbsf and may be original formation features other samples exhibit gas hydrate grains rimmed by nacl bearing material presumably produced by salt exclusion during original hydrate formation well preserved microfossil and other biogenic detritus are also found within several samples most abundantly in andaman core material where gas hydrate fills microfossil crevices the range of gas hydrate modes of occurrence observed in the full suite of samples suggests a range of formation processes were involved as influenced by local in situ conditions the hydrate forming gas is predominantly methane with trace quantities of higher molecular weight hydrocarbons of primarily microbial origin the composition indicates the gas hydrate is structure i

extensional neotectonics around the bend of the western central alps an overview the western alps active tectonics is characterized by ongoing widespread extension in the highest parts of the belt and transpressive compressive tectonics along its borders we examine these contrasting tectonic regimes using a multidisciplinary approach including seismotectonics numerical modeling gps morphotectonics fieldwork and brittle deformation analysis extension appears to be the dominant process in the present day tectonic activity in the western alps affecting its internal areas all along the arc shortening in contrast is limited to small areas located along at the outer borders of the chain strike slip is observed throughout the alpine realm and in the foreland the stress orientation pattern is radial for 3 in the inner extensional zones and for 1 in the outer transcurrent tranpressional ones extensional areas can be correlated with the parts of the belt with the thickest crust quantification of seismic strain in tectonically homogeneous areas shows that only 10 20 of the geodesy documented deformation can be explained by the alpine seismicity we propose that alpine active tectonics are ruled by isostasy buoyancy forces rather than the ongoing shortening along the alpine europe adria collision zone this interpretation is corroborated by numerical modeling the neogene extensional structures in the alps formed under increasingly brittle conditions a synthesis of paleostress tensors for the internal parts of the west alpine arc documents major orogen parallel extension with a continuous change in 3 directions from ene wsw in the simplon area to n s in the vanoise area and to nnw sse in the briancon area minor orogen perpendicular extension increases from n to s this second signal correlates with the present day geodynamics as revealed by focal plane mechanisms analysis the orogen parallel extension could be related to the opening of the ligurian sea during the early middle miocene and to compression rotation of the adriatic indenter inducing lateral extrusion

modeling of the temperature sensitivity of the apatite u th he thermochronometer apatite u th he apparent ages will generally reflect residence for extended periods at temperatures where helium is neither quantitatively retained nor lost by diffusion to characterize the response of apatite he ages to thermal histories involving partial he retention we explored solutions to the he production diffusion equation under thermally static conditions the analytical solution to this equation coupled with published diffusivity data demonstrates that the zone of partial he retention extends from about 40 c to 85 c this zone lies at temperatures 35 c cooler than the analogous fission track partial annealing zone he ages within the partial retention zone ultimately achieve a balance between he production and loss yielding a steady state age both the ultimate age and the time it takes to achieve this age are temperature dependent for example an apatite held at 75 c equilibrates to an age of 2 ma after 17 myr regardless of whether equilibrium is approached from a higher or a lower initial he age for representative dynamic thermal histories we evaluated apatite he ages using a numerical solution to the ingrowth diffusion equation the results illustrate the sensitivity of he ages to various geologic histories and are useful for understanding he age elevation relationships and for testing time temperature paths derived from apatite fission track length distributions in addition although he diffuses rapidly from apatite at shallow crustal temperatures modeling of ambient temperature fluctuations indicates that he ages are nearly unaffected by surficial processes

tsunami mapping related to local earthquakes on the french italian riviera western mediterranean the ligurian coast located at the french italian border is densely populated as well as a touristic area it is also a location where earthquakes and underwater landslides are recurrent the nature of the local tsunamigenesis is therefore a legitimate question because no tsunami warning system can resolve tsunami arrival times of a few minutes which is the case for the area as far as the seismicity of the area is concerned the frequent recurrent earthquakes are generally of moderate magnitude most of them are lower than mw 5 however the relatively large mw 6 9 earthquake larroque et al in geophys j int 2012 doi 10 1111 j 1365 246x 2012 05498 x that occurred on the february 23 1887 offshore of imperia italian riviera is quite emblematic this unusual event for the region merits a complete study the quantification of its rupture mechanism is essential 1 to understand the regional active deformation but also 2 to evaluate its tsunamigenesis potential by deriving relevant rupture scenarios obtained from our knowledge of the event for that purpose the event is extensively described here the first point has been the subject of quite a few studies based on the seismotectonics of the area the last documented approach has been completed by larroque et al geophys j int 2012 doi 10 1111 j 1365 246x 2012 05498 x who proposed a rupture scenario involving a reverse faulting along a north dipping fault and favoring a mw 6 9 magnitude in the present paper 1 we study the accuracy of their solutions in relation to the computational grid spacing and the dispersive nondispersive parameterization 2 based on an uncertainty on the recorded wave amplitude of the genoa tide gauge they used we propose a mw 6 7 earthquake magnitude solution for the event the kinematics is unchanged co existing with the mw 6 9 3 we evaluate the tsunami coastal impact of the 1887 event and 4 we test a range of possible ruptures that local faults may undergo in order to propose a synoptic mapping of the tsunami threat in the area the spatial distribution of the maximum wave height mwh is provided with a tentative identification of the processes that are responsible for it this latter issue is imperative in order to make our mapping as generic as possible in the framework of our deterministic approach based on realistic scenarios and not on ensemble statistics the predictions suggest that the wave impact is mostly local considering the relatively moderate size of the rupture planes although the present day seismicity in this region is moderate stronger earthquakes m 6 5 have occurred in the past the studied scenarios show that for such events specific localities along the french italian riviera may experience very significant mwh related to the shallow focal depth tested for such scenarios we may reasonably conclude that the tsunami threat is relatively significant and uniform at the italian side of the riviera from ventimiglia to imperia while it is more localized sporadic at the french side from antibes to menton with however higher local level of inundation e g nice city center

active deformation at the southwestern alps ligurian basin junction france italy boundary evidence for recent change from compression to extension in the argentera massif abstract several hundred earthquakes of small and moderate magnitude occur each year at the southwestern alps ligurian basin junction in addition the historical seismicity data attests for earthquakes of magnitude close to 6 5 despite the seismic hazard and the vulnerability of this region the present day driving mechanism of deformation and the major structures accommodating these deformations remain unclear this littoral area presents a strong topographic gradient from 3000 masl on the argentera alpine massif to 2500 m u s l in the ligurian basin and a strong structural inheritage resulting from 50 my geological evolution combining different processes such as continental collision and ocean basin opening we present new results about the kinematics of the corsica sardinia continental block with respect to the western alpine belt from 7 years of continuous gps measurements we show that a small part of the nubia eurasia convergence is certainly transferred northward of the maghrebides deformation belts to the corsica sardinia block in the southwesternmost alps from torino to the mediterranean coast the baselines reveal differential motions of lengthening between the po plain and the argentera and shortening between the argentera and the ligurian domain in a region where few focal solutions are available we determine seven new focal mechanisms located in the argentera massif these new data underline a quaternary change from compression to extension in that part of the western alpine belt the focal mechanisms calculated attest for extensional faulting at shallow level between 1 and 11 km depth we add 7 focal mechanisms from the literature to calculate the stress tensor a homogeneous solution indicates a direction of extension broadly perpendicular to the topographic axis culmination of the argentera in contrast the earthquakes recorded below 15 km at the northwestern margin of the po plain testify reverse faulting and a compressional state of stress in the deep crust thus we point out that the stress field is vertically heterogeneous in the crust of the argentera area the ligurian domain is mainly characterized by reverse and strike slip faulting the major earthquakes are located in the northern margin and at the ocean continent transition these earthquakes are assumed to result from the reactivation in a compressional state of stress of the structures formed during the oligo miocene opening of the ligurian basin finally we propose three hypotheses to explain the current deformation at the alps ligurian basin junction taking into account the far field kinematics between the nubia and the eurasia plates the topographic gradient between the argentera massif and the ligurian oceanic floor and the distribution of the deformations

long lasting transcurrent tectonics in sw alps evidenced by neogene to present day stress fields abstract the sw alps are an active orogen undergoing intra mountainous extension and peripheral compression we discuss the significance of syn orogenic extension based on a comparison of paleo stress derived from fault slip data inversion reflecting the long term

methane sources and production in the northern cascadia margin gas hydrate system abstract the oceanographic and tectonic conditions of accretionary margins are well suited for several potential processes governing methane generation storage and release to identify the relevant methane evolution pathways in the northern cascadia accretionary margin a four site transect was drilled during integrated ocean drilling program expedition 311 the 13c values of methane range from a minimum value of 82 2 on an uplifted ridge of accreted sediment near the deformation front site u1326 1829 mbsl meters below sea level to a maximum value of 39 5 at the most landward location within an area of steep canyons near the shelf edge site u1329 946 mbsl an interpretation based solely on methane isotope values might conclude the 13c enrichment of methane indicates a transition from microbially to thermogenically sourced methane however the co existing co2 exhibits a similar trend of 13c enrichment along the transect with values ranging from 22 5 to 25 7 the magnitude of the carbon isotope separation between methane and co2 ec 63 8 5 8 is consistent with isotope fractionation during microbially mediated carbonate reduction these results in conjunction with a transect wide gaseous hydrocarbon content composed of 99 8 by volume methane and uniform dch4 values 172 8 that are distinct from thermogenic methane at a seep located 60 km from the expedition 311 transect suggest microbial co2 reduction is the predominant methane source at all investigated sites the magnitude of the intra site downhole 13c enrichment of co2 within the accreted ridge site u1326 and a slope basin nearest the deformation front site u1325 2195 mbsl is 5 at the mid slope site site u1327 1304 mbsl the downhole 13c enrichment of the co2 is 25 and increases to 40 at the near shelf edge site u1329 this isotope fractionation pattern is indicative of more extensive diagenetic alteration at sites with greater 13c enrichment the magnitude of the 13c enrichment of co2 correlates with decreasing sedimentation rates and a diminishing occurrence of stratigraphic gas hydrate we suggest the decreasing sedimentation rates increase the exposure time of sedimentary organic matter to aerobic and anaerobic degradation during burial thereby reducing the availability of metabolizable organic matter available for methane production this process is reflected in the occurrence and distribution of gas hydrate within the northern cascadia margin accretionary prism our observations are relevant for evaluating methane production and the occurrence of stratigraphic gas hydrate within other convergent margins

dynamics of breaks in the indian summer monsoon abstract in this paper the authors present results of diagnostic analysis of observations and complementary experiments with a simple numerical model that enable them to synthesize the morphology and dynamics of breaks in the indian summer monsoon ism almost one week ahead of the onset of a break spell over india a monotonically decreasing trend in convective activity is found to occur over the bay of bengal in response to a steady eastward spreading of dry convectively stable anomalies from the equatorial indian ocean a major intensification of the convectively stable anomalies over the bay of bengal is seen about 2 3 days prior to commencement of a monsoon break both observations and modeling experiments reveal that rapid northwest propagating rossby waves are triggered in response to such a large strengthening of the convectively stable anomalies it is shown that an abrupt movement of anomalous rossby waves from the bay of bengal into northwest and central india marks the initiation of a break

intraseasonal convection and air sea fluxes over the indian monsoon region revealed from the bimodal iso index the present study aims to elucidate the intraseasonal oscillations iso of atmospheric convection and air sea fluxes over the indian region during summer monsoon season to accomplish this the study employs the extended empirical orthogonal function based bimodal iso index developed by kikuchi et al clim dyn 38 9 10 1989 2000 2012 the propagation of deep convective anomalies and air sea fluxes are explored during the different phases p1 p8 of the bimodal index this is achieved by examining the tropical rainfall measuring mission satellite rainfall outgoing long wave radiation olr sea surface temperatures sst downward shortwave radiation dsr and reanalysis products of 850 hpa winds potential vorticity and latent heat fluxes lhfs composite analysis of the anomalies depicts the strong weak northward eastward propagation of convective anomalies over the indian region equatorial indian ocean over the indian region active suppressed or weak convection is evident during the phases of p4 and p5 p1 p2 and p7 p8 enhanced deep convection is lead by a phase of 850 hpa westerly winds and negative sst anomalies signatures of iso during different phases are examined from research moored array for african asian australian monson analysis and prediction rama buoy observations over the bay of bengal rainfall sst and lhf anomalies from rama buoy measurements are in concurrence with the spatial composites of bimodal iso phases plausible drivers for the variability of intraseasonal convection and air sea fluxes were reviewed using published observational and modelling studies findings from the present study advocate the applicability of kikuchi bimodal index clim dyn 38 9 10 1989 2000 2012 over the indian region and have practical application for the validation of ocean atmospheric coupled models

impact of mjo on the intraseasonal variation of summer monsoon rainfall over india the summer monsoon rainfall over india exhibits strong intraseasonal variability earlier studies have identified madden julian oscillation mjo as one of the most influencing factors of the intraseasonal variability of the monsoon rainfall in this study using india meteorological department imd high resolution daily gridded rainfall data and wheeler hendon mjo indices the intra seasonal variation of daily rainfall distribution over india associated with various phases of eastward propagating mjo life cycle was examined to understand the mechanism linking the mjo to the intraseasonal variability during mjo phases of 1 and 2 formation of mjo associated positive convective anomaly over the equatorial indian ocean activated the oceanic tropical convergence zone otcz and the resultant changes in the monsoon circulation caused break monsoon type rainfall distribution associated with this negative convective anomalies over monsoon trough zone region extended eastwards to date line indicating weaker than normal northern hemisphere inter tropical convergence zone itcz the positive convective anomalies over otcz and negative convective anomalies over itcz formed a dipole like pattern subsequently as the mjo propagated eastwards to west equatorial pacific through the maritime continent a gradual northward shift of the otcz was observed and negative convective anomalies started appearing over equatorial indian ocean during phase 4 while the eastwards propagating mjo linked positive convective anomalies activated the eastern part of the itcz the northward propagating otcz merged with monsoon trough western part of the itcz and induced positive convective anomalies over the region during phases 5 and 6 the dipole pattern in convective anomalies was reversed compared to that during phases 1 and 2 this resulted active monsoon type rainfall distribution over india during the subsequent phases 7 and 8 the convective and lower tropospheric anomaly patterns were very similar to that during phase 1 and 2 except for above normal convective anomalies over equatorial indian ocean a general decrease in the rainfall was also observed over most parts of the country the associated dry conditions extended up to northwest pacific thus the impact of the mjo on the monsoon was not limited to the indian region the impact was rather felt over larger spatial scale extending up to pacific this study also revealed that the onset of break and active events over india and the duration of these events are strongly related to the phase and strength of the mjo the break events were relatively better associated with the strong mjo phases than the active events about 83 of the break events were found to be set in during the phases 7 8 1 and 2 of mjo with maximum during phase 1 40 on the other hand about 70 of the active events were set in during the mjo phases of 3 to 6 with maximum during phase 4 21 the results of this study indicate an opportunity for using the real time information and skillful prediction of mjo phases for the prediction of break and active conditions which are very crucial for agriculture decisions

geological and geophysical features of and controls on occurrence and accumulation of gas hydrates in the first offshore gas hydrate production test region in the shenhu area northern south china sea abstract integrated three dimensional seismic logging sediment cores and geochemical testing data were collected from guangzhou marine geological survey 3 and 4 hydrate drilling expeditions and used in this study for a comprehensive investigation of the geological and geophysical features and accumulation mechanism of hydrates in the first offshore gas hydrate production test region ghptr in the shenhu area of the south china sea seismic signatures indicative of disseminated hydrates and free gas include the bottom simulating reflector bsr gas chimney and mud diapir associated with enhanced seismic reflections acoustic blanking masking and chaotic appearance have been observed the acoustic travel time responses density and compensated neutron three porosity log analysis high precision grid tomography inversion analysis and constrained sparse spike inversion confirm the presence of free gas below the gas hydrate bearing zone ghbz free gas bearing zones have significantly different p wave impedances and low velocity anomalies than the overlying ghbz and surrounding strata these anomalous zones are controlled by the structural attitude of the reservoir strata which are characterized as inter bedded stratigraphic units variations in the type and geological characteristics of the hydrocarbon migration pathways were observed between sites w18 and w19 on the western ridge and sites w11 and w17 on the eastern ridge in the gmgs study area the efficiency of gas migration in the western ridge may be higher than that in the eastern ridge resulting in variations in hydrate gas types thickness of the ghbz and gas migration flux and accumulation except for site w11 hydrates were recovered below the structure i inferred bsr at sites w17 w18 and w19 the gas hydrate stability zone calculations reveal that the structure i hydrate stability zone differs from the bsr depth and is generally shallower than the base of the logging anomaly indicating the coexistence of structure i and ii hydrates the bsr is not indicative of the bghsz it is rather regarded as a transitional indicator of structure i and ii gas hydrates in the ghptr the appearance of free gas and hydrates below the structure i inferred bsr indicates that the shenhu area is characterized by a complex hydrate formation and accumulation system resulting from the supply of biogenic and thermogenic gases despite fine grained host sediments predominating the ghptr the coupling of favorable conditions including efficient hydrocarbon generation sufficient gas supply multiple pathways for gas migration and relatively high reservoir porosity have led to the development of highly saturated gas hydrate accumulations within relatively thick sedimentary sections which demonstrates a significant resource potential

western alpine back thrusting as subsidence mechanism in the tertiary piedmont basin western po plain nw italy abstract basin formation dynamics of the tertiary piedmont basin tpb are here investigated by means of cross section numerical modelling previous works hypothesised that basin subsidence occurred due first to extension oligocene and then to subsequent loading due to back thrusting miocene however structural evidence shows that the tpb was mainly under contraction from oligocene until post pliocene time while extension played a minor role furthermore thermal indicators strongly call for a cold flexure induced mechanism but are strictly inconsistent with a hot thermally induced mechanism our new modelling shows that the tpb stratigraphic features can be reproduced by flexure of a visco elastic plate loaded by back thrusts active in the western alps in oligo miocene times far field compression contributed to the tpb subsidence and controlled the basin infill geometry by enhancing basin tilting forebulge uplift and erosion of the southern margin of the basin these results suggest that the tpb subsidence is the result of a combination of mechanisms including thrust loading and far field compressional stresses

solving the production diffusion equation for finite diffusion domains of various shapes part i implications for low temperature u th he thermochronology abstract we propose an accurate fast and easy to use method to derive numerical solutions for production diffusion equations for finite diffusion domains of various shapes and arbitrary cooling histories previous studies provide solutions for spheres infinite cylinders and infinite sheets we extend this range and provide solutions for finite bodies i e finite cylinders and rectangular blocks of any aspect ratio this approach is important as recently it has become clear that for example the physical grain is the diffusion domain for he diffusion in apatite and titanite j geophys res 105 2000 2903 geochim cosmochim acta 63 1999 3845 we discuss the use of the new approach for forward modelling u th he production diffusion in apatite taking results with finite cylinders as a good approximation for apatite crystals it is found that approximating instead with spheres or infinite cylinders having the same radius yields differences in calculated ages that can easily be as large as 20 35 the relative differences are most pronounced in thermal histories that spend significant time at or near the closure temperature on the other hand reasonable agreement is found with spheres having the same surface to volume ratio

geologic implications of gas hydrates in the offshore of india krishna godavari basin mahanadi basin andaman sea kerala konkan basin gas hydrate resource assessments that indicate enormous global volumes of gas present within hydrate accumulations have been one of the primary driving forces behind the growing interest in gas hydrates gas hydrate volumetric estimates in recent years have focused on documenting the geologic parameters in the gas hydrate petroleum system that control the occurrence of gas hydrates in nature the primary goals of this report are to review our present understanding of the geologic controls on the occurrence of gas hydrate in the offshore of india and to document the application of the petroleum system approach to the study of gas hydrates national gas hydrate program of india executed the national gas hydrate program expedition 01 nghp 01 in 2006 in four areas located on the eastern and western margins of the indian peninsula and in the andaman sea these areas have experienced very different tectonic and depositional histories the peninsular margins are passive continental margins resulting from a series of rifting episodes during the breakup and dispersion of gondwanaland to form the present indian ocean the andaman sea is bounded on its western side by a convergent margin where the indian plate lithosphere is being subducted beneath southeast asia nghp 01 drilled logged and or cored 15 sites 31 holes in the krishna godavari basin 4 sites 5 holes in the mahanadi basin 1 site 2 holes in the andaman sea and 1 site 1 hole in the kerala konkan basin holes were drilled using standard drilling methods for the purpose of logging while drilling and dedicated wireline logging as well as through the use of a variety of standard coring systems and specialized pressure coring systems nghp 01 yielded evidence of gas hydrate from downhole log and core data obtained from all the sites in the krishna godavari basin the mahanadi basin and in the andaman sea the site drilled in the kerala konkan basin during nghp 01 did not yield any evidence of gas hydrate most of the downhole log inferred gas hydrate and core recovered gas hydrate were characterized as either fracture filling in clay dominated sediments or as pore filling or grain displacement particles disseminated in both fine and coarse grained sediments geochemical analyses of gases obtained from sediment cores recovered during nghp 01 indicated that the gas in most all of the hydrates in the offshore of india is derived from microbial sources only one site in the andaman sea exhibited limited evidence of a thermogenic gas source the gas hydrate petroleum system concept has been used to effectively characterize the geologic controls on the occurrence of gas hydrates in the offshore of india

dynamical response of the south asian monsoon trough to latent heating from stratiform and convective precipitation simulation experiments using a simplified atmospheric gcm and supplementary diagnostic analyses of observations are performed to understand how the south asian monsoon trough mt responds dynamically to latent heating from mesoscale convective systems mcss observations reveal that the mt during active monsoons is characterized by a deep cyclonic vorticity extending from the surface to 350 hpa and organized mcss covering over 3500 4000 km along the indo gangetic plains the mcss during active monsoons are composed of a relatively higher abundance of stratiform type precipitation mostly nimbostratus as compared to the convective type the results suggest that a stratiform type heating profile is very effective in promotingupward development of continental scale cyclonic circulation well above the midtroposphere over the mt region the vertical development involves a dynamical uplift of the layer of cyclonic circulation and is induced by midlevel 600 500 hpa convergence and vorticity stretching above 500 hpa by varying the population of stratiform and convective rain types in the simulation the horizontal scale of midlevel vorticity response is shown to increase significantly with stratiform population in contrast the midlevel response is more localized when the mcs is dominated by deep convective clouds for large stratiform populations the midlevel responseis found to extend far westward up to the northernflanks of the africanitcz indicativeof rossby wave dispersion of pv anomalies that are generated near the level of maximum heating gradient from the present findings one can conclude that the vertical deepening of mt during active monsoons is not merely a localized phenomenon instead it represents a large scale dynamical response to organized mcss that exert pivotal influence on the upward development of cyclonic circulation well above the midtroposphere

oligocene to present kilometres scale subsidence and exhumation of the ligurian alps and the tertiary piedmont basin nw italy revealed by apatite u th he thermochronology correlation with regional tectonics the ligurian alps segment of the alpine apennine orogen in nw italy is unconformably covered by upper eocene to holocene sediments in the tertiary piedmont basin tpb and po plain these sediments dip towards the north demonstrating the erosional nature of the southern border of the succession and implying that the adjacent orogenic belt formed the substratum rather than the margin of the sedimentary basin apatite u th he and fission track thermochronology shows that the orogen first subsided and was buried at 4 km from 30 to 26 ma and began its exhumation thereafter from 26 ma to present this upward movement was contemporaneous with subsidence in the northern tpb the couple exhumation in the s and subsidence in the n migrated northwards through time vertical movements in the area are similar to those reconstructed in corsica in both cases the onset of exhumation b

effect of thermal non equilibrium seafloor topography and fluid advection on bsr derived geothermal gradient abstract the seafloor and bottom simulating reflectors bsrs are interpreted from the 3d seismic data acquired in krishna godavari kg offshore basin in the vicinity of sites drilled cored during national gas hydrate program nghp expedition 01 the shallow structures such as inner toe thrust fault system regional and local linear fault systems and mass transport deposits are inferred from attributes of seafloor time structure as well as from the seismic profiles the geothermal gradient is estimated from the depths and temperatures of the seafloor and the bsr the temperature at the bsr depth is estimated from the methane hydrate and seawater salinity phase boundary assuming that the bsr represents the base of the gas hydrate stability zone the spatial variations in geothermal gradient gtg show a strong correlation with seafloor topography in the kg basin the gtg decreases by 13 30 over the topographic mounds formed due to inner toe thrust faults and recent mass transport deposits the gtg decreases by only 5 10 over the mounds likely due to defocusing of heat flux based on one dimensional topographic modeling hence the gtg perturbation due to topography alone cannot explain the observed gtg anomaly the temperature profile beneath these mounds may not be in equilibrium with the surroundings either due to the recent upliftment of sediments along the inner toe thrust faults or rapid deposition of sediments due to slumping sliding in contrast an increase in gtg by 10 15 is observed in the vicinity of major fault systems we presume that the likely mechanism for the increase in gtg is fluid advection from a deeper part of the basin a detailed thermal modeling involving the effect of surface topography high sedimentation rates fluid advection and sediment thickening due to tectonics is required to understand the thermal profile in kg offshore basin

river incision and migration deduced from 36cl cosmic ray exposure durations the clue de la cerise gorge in southern french alps abstract we estimate recent 20 ka incision and lateral migration rate on a spectacular n s striking gorge cross cutting n dipping limestones in a fold and thrust belt of the external southern french alps upstream of the gorge the river makes a right angle turn and follows the limestone surface parallel to the bedding direction ew eighteen samples were gathered along two vertical river polished profiles and three others on the denuded north dipping surface layer in order to determine river incision and lateral migration timing and rates surface age exposures of polished river cliff and bedding surface have been obtained from 36cl cosmogenic nuclide dating and allow us to constrain the rate of vertical incision and of surface denudation of the jurassic limestone layer fifteen 36cl exposure ages have been obtained and range from 21 ka to 3 ka samples clearly define two age height linear trends which slopes correspond to incision rates of 1 and 0 3 mm yr respectively the transition from low to high incision rate occurs at about 12 ka i e during the younger dryas glacial phase data also indicate that the vertical incision of the n s branch of the gorge is coeval with the lateral northward river migration of its e w branch associated with the denudation of the limestones surface extrapolating incision rates deduced from 36cl exposure ages through time suggests that the incision of the clue and denudation of the jurassic limestones started about 500 600 ka ago

solving the production diffusion equation for finite diffusion domains of various shapes part 2 application to cases with alpha ejection and non homogeneous distribution of the source abstract in this paper numerical methods derived in part i chem geol 2002 are expanded to accommodate the effects of emission and zonation of u and th as relevant for u th he thermochronology expressions for the required coefficients are derived for spheres finite and infinite cylinders and rectangular blocks for parent nuclide distributions which are either uniform or have stepwise zoning we show that the effects of emission and zonation on the he retention in a nonspherical crystal of modest aspect ratio can be approximated by a sphere of identical surface to volume ratio s v if the zonation is transposed on to the sphere the currently usual correction method is to perform first a diffusive calculation without considering emission and zonation and to multiply afterward with a correction factor that has been derived originally for nondiffusive calculations our results demonstrate that more accurate calculations yield different results and that the differences are often too large to be ignored in practice especially for thermal histories that include a protracted residence in the partial retention zone the difference between the usual correction and our correction can be as high as 20 for homogeneous sources for zoned crystals the difference can be even larger

late stages of exhumation constrained by structural fluid inclusion and fission track analyses sesia lanzo unit western european alps in metamorphic areas paleogeothermal gradients are difficult to properly estimate leading to great uncertainty in exhumation rate calculations based on fission track analysis in this work a new multidisciplinary approach based on fluid inclusion analysis structural analysis and fission track dating has proven to be able to constrain the late stages of exhumation of metamorphic rocks the study area is located in the sesia lanzo unit of the western european alps along the hone shear zone kinematic analysis at different scales unraveled a polyphase postmetamorphic deformation history constrained in the p t space thanks to laboratory investigation of kinematically referenced fluid inclusions coupled with the analysis of the rheological behavior of quartz and feldspar inside syn kinematic veins the resulting p t path points to an increasing paleogeothermal gradient from 18 to 30 c km 1 after greenschist facies metamorphic conditions and provides a reference framework for a quantitative interpretation of fission track data in terms of exhumation rates and fault throws according to fission track data throws accommodated by the hone shear zone between 33 and 30 ma are on the order of 4 5 km and would be underestimated by 25 if a normal steady gradient was assumed for the whole post metamorphic history of the area the deepest portions of this structure were exhumed thanks to the activity of the e w fault system that accommodated a throw of 4 km between 28 and 20 ma and a throw of 0 8 km during the last 20 myr

evidence of slumping sliding in krishna godavari offshore basin due to gas fluid movements abstract the krishna godavari kg offshore basin is one of the promising petroliferous basins of the eastern continental margin of india drilling in this basin proved the presence of gas hydrate deposits in the shallow marine sediments beyond 750 m water depths and provided lithologic and stratigraphic information we obtained multibeam swath bathymetry covering an area of about 4500 km 2 in water depths of 280 1800 m and about 1260 line km of high resolution seismic hrs records the general lithology of midslope deposits is comprised of nannofossil rich clay nannofossil bearing clay and foraminifera bearing clay the hrs records and bathymetry reveal evidence of slumping and sliding of the upper and midslope sediments which result in mass transport deposits mtd in the northwestern part of the study area these deposits exhibit 3 9 5 km widths and extend 10 13 km offshore the boundaries of the mtds are often demarcated by sharp truncation of finely layered sediments fls and the mtds are characterized by acoustically transparent zones in the hrs data average thickness of recent mtds varies with depth i e in the upper slope the thickness is about 45 m while in the lower slope it is about 60 m and in deeper offshore locations they attain a maximum thickness of about 90 m a direct indication for slumping and mass transportation of deposits is provided by the age reversal in 14 c ams dates observed in a sediment core located in the midslope region seismic profiling signatures provide indications of fluid gas movement we propose that the presence of steep topographic gradients high sedimentation rates a regional fault system diapirism fluid gas movement and neotectonic activity may have facilitated the slumping sliding of the upper slope sediments in the kg offshore basin

presence of a long term lithospheric thermal anomaly evidence from apatite fission track analysis in northern new england abstract apatite fission track aft ages from 56 samples of paleozoic and mesozoic crystalline rocks in new hampshire northeastern vermont and western maine range from 70 to 140 ma and reflect widespread early to late cretaceous cooling the regional aft age distributions determined in this study suggest that reactivation of preexisting orogen parallel faults and the presence of a long lived thermal anomaly in the lithospheric mantle controlled the late unroofing history of this part of the northern appalachians a northeast trending zone of young dominantly late cretaceous aft ages 70 118 ma extends from southwestern new hampshire through the central white mountain region and continues into northern new hampshire northeastern vermont and western maine providing evidence for regional nw se extension and cooling at this time significantly older aft ages 125 140 ma in the region bounded by the bill little ammonoosuc and northey hill faults in northwestern new hampshire suggest a normal sense r

late orogenic vertical movements within the arc of the sw alps and ligurian alps abstract mainly on the basis of seismic data we reconstruct magnitude and timing of miocene to present vertical movements in the region of the savigliano basin an up to 4 km thick succession of neogene to quaternary sediments accumulated inside the alpine arc at the western termination of the po plain we focus in particular on the margins of the basin which are the link between the mountain range and the subsiding basin seismic data from these regions allow for the definition of upward and downward vertical movements uplift exhumation and subsidence with a spatial and temporal resolution which cannot be attained by other methods the eastern southern and western margins of the savigliano basin display very different geometries of the sedimentary bodies and therefore document different vertical movements during miocene to present times the eastern part of the savigliano basin and the regions to the e experienced subsidence followed by exhumation the southern margin of the basin in the cuneo area was much more stable with miocene to present formations all pinching out close to the present day outcropping position of the basement sedimentary cover contact in the w seismic sections record a stage of tilting until the burdigalian followed by generalized subsidence which affected also the adjacent regions of the sw alps the overall pattern of vertical movements is essentially controlled by the nw ward migration of a syncline anticline couple with the synclinal axis presently located in the center of the savigliano basin the width of the folds is in the order of 30 60 km 1 2 wavelength in map view the trace of the fold axes changes from n s in the savigliano basin to e w in the alessandria basin

seabed morphology and gas venting features in the continental slope region of krishna godavari basin bay of bengal implications in gas hydrate exploration abstract increased oil and gas exploration activity has led to a detailed investigation of the continental shelf and adjacent slope regions of mahanadi krishna godavari kg and cauvery basins which are promising petroliferous basins along the eastern continental margin of india in this paper we analyze the high resolution sparker subbottom profiler and multibeam data in kg offshore basin to understand the shallow structures and shallow deposits for gas hydrate exploration we identified and mapped prominent positive topographic features in the bathymetry data these mounds show fluid gas migration features such as acoustic voids acoustic chimneys and acoustic turbid layers it is interesting to note that drilling coring onboard joides in the vicinity of the mounds show the presence of thick accumulation of subsurface gas hydrate further geological and geochemical study of long sediment cores collected onboard marion dufresne in the vicinity of the mounds and sedimentary ridges shows the imprints of paleo expulsion of methane and sulfidic fluid from the seafloor to understand the origin of the mounds and their relationship with gas hydrate cold seep formation we analyzed the multi channel seismic reflection mcs data close to the mounds the mcs data show that the subsurface layers beneath the mounds are folded below the folded overburden we observe zones of no coherent reflections probably originating from miocene sequence since the study area is located in shale tectonics regime where miocene sequences are known to be overpressured we interpret the zones of no coherent reflections as miocene shale diapirs the upward movement of shale diapirs has folded the overburden layer and resulted in the formation of numerous faults fractures these faults act as permeable pathways for fluid gas movement facilitating the formation of gas hydrate and cold seeps close to shale diapiric mound

the messinian diatomite deposition in the mediterranean region and its relationships to the global silica cycle abstract diatomites constitute a widely represented lithology in the messinian sections of the circum mediterranean neogene marginal basins although traditionally interpreted as genuine evidence of the gradually restricted conditions that characterized the mediterranean just before the messinian salinity crisis their coeval occurrence with a global intensification of the opaline production in the world oceans late miocene early pliocene biogenic bloom suggests that an integrative analysis of the origins of these sediments is necessary a comprehensive analysis of the geological and paleontological records suggests that the synergistic intervention of abiotic tectonic and climate reconfigurations and biotic expansion of grass dominated opal rich biomes controlling factors may have promoted a remarkable enhancement of silica flux from continents to oceans which in turn can explain the opaline burst that occurred during the late miocene at both the global and mediterranean scale the finely laminated pattern and the rich fossil content of diatomaceous deposits that are usually considered to be byproducts of anoxic conditions are briefly discussed some studies seem to indicate that instead of anoxia the aggregation and sedimentation of diatom tests may play a critical role in these processes the lower messinian diatomites of the mediterranean region are generally interbedded with organic rich sediments sapropels clearly attesting prolonged precessionally controlled periods of basin stratification and bottom water anoxia or hypoxia a causal relationship between sapropel and diatomite deposition in the mediterranean is proposed considering the possible interplay between stratification adapted diatoms and anaerobic bacteria and their respective role in influencing the marine silica cycle

sedimentation rates from calcareous nannofossil and planktonic foraminifera biostratigraphy in the andaman sea northern bay of bengal and eastern arabian sea abstract in this study we determined calcareous nannofossil and planktonic foraminifera events in sediments recovered during the 2006 indian national gas hydrate program nghp expedition 01 selected bioevents permitted the assignment of orbitally calibrated ages derivative sedimentation rate estimates and identification of sedimentary discontinuities in the andaman sea at hole nghp 01 17a a late miocene to recent record was recovered but with a significant hiatus during the latest miocene and pliocene sedimentation rates here vary from 50 m myr during the pleistocene to 130 m myr for the late miocene in the northern bay of bengal at hole nghp 01 19a the base of the cored record also reaches the late miocene and extends to recent but the same hiatus missing the pliocene is present at this hole a the early pleistocene at hole nghp 1 19a shows sensible variation in sedimentation rates ranging between 130 m myr and 10 m myr during the last 0 5 ma for the late miocene the sedimentation rate was ca 50 m myr in the western bay of bengal at hole nghp 01 10b d calcareous nannofossils were sparse and only foraminifera datums are available the base of the section is latest early pliocene to late pliocene and the majority of the record is considered younger than late pliocene due to the scarcity of calcareous nannofossils and the few foraminifera datums sedimentation rates were not determined here however hole nghp 01 16a in the same region recorded the highest occurrence of pseudoemiliania lacunosa an event that confirms a pleistocene age allowing us to estimate a sedimentation rate between 110 m myr and 450 m myr along the western peninsular indian margin at hole nghp 01 01a a continuous record from the holocene to the early oligocene indicates sedimentation rates of ca 25 m myr until the middle miocene and a sensible reduction downward reaching 4 m myr in the early miocene to the early oligocene no hiatuses were observed the large changes in sedimentation rates observed in these cores reflect long timescale changes in the environment likely induced by changes in the strength of the indian monsoon system

tertiary cooling and exhumation history in the maramures area internal eastern carpathians northern romania thermochronology and structural data the tertiary kinematic history of the maramures area is constrained by integrating thermochronological fission track and uth he analysis data with field based structural investigations this study focuses on the tectonic evolution of the northern rim of the tisza dacia block during collision with the european margin cretaceous nappe stacking related metamorphism as well as late cretaceous exhumation are evidenced by zircon fission track data subsequent palaeogene to early miocene sedimentation led to burial heating and annealing of fission tracks in apatite final tectonic uplift was initiated during the convergence of tisza dacia with the european margin associated with transpressional deformation 16 to 12 ma this led to mid miocene exhumation recorded by apatite fission track cooling ages in the western part of the study area transtension between 12 and 10 ma caused brittle deformation along ew trending strike slip faults and swne trending normal faults delimiting blocks that were tilted towards the sw this fragmentation of the crust led to enhanced exhumation at rates of 1 mm a in the central part of the study area as is documented by middle to late miocene cooling ages 13 to 7 ma the outside estimate for the total amount of exhumation since middle miocene times is 7 km

gas hydrate distribution and carbon sequestration through coupled microbial methanogenesis and silicate weathering in the krishna godavari basin offshore india abstract the national gas hydrate program expedition 01 cored ten sites in the krishna godavari basin located on the southeastern margin of india a comprehensive suite of pore water solute concentrations and isotope ratios were analyzed to investigate the distribution and concentration of gas hydrate along the margin in situ diagenetic and metabolic reactions and fluid migration and flow pathways gas hydrate was present at all of the sites cored and in situ microbial methanogenesis leads to estimates of depth integrated average gas hydrate saturations that are typically

the exhumation history of the european alps inferred from linear inversion of thermochronometric data thermochronometric data collected across the alps over the last three decades allows for investigation of the evolution of this orogen which is subject to changes in climate and geodynamics exhumation rates are inferred from the thermochronometric ages using a statistical inversion method based on the fact that the distance a sample traveled since closure is equal to the integral of the exhumation rate from the present day to the age of the sample exhumation rates are assumed to be spatially correlated but are free to vary through time this results in the quantification of exhumation rates across the alps since 32 ma along with assessments of the quality of these inferences we find that exhumation rates are initially fast in the internal arc of the western alps at rates up to 0 8 km myr at 30 ma decreasing at 20 ma to 0 3 km myr to remain slow to the present at the same time around 20 ma rates across the external crystalline massifs of western alps increase to 0 6 km myr we also find that the onset of high exhumation rates in the tauern window and the lepontine dome occurs at around 20 ma a time characterized by major reorganizations in the alpine chain a general increase in exhumation rates at around 5 ma over the entire alps is not confirmed instead we find that the western alps exhibit a 2 to 3 fold increase in exhumation rate over the last 2 ma during a recent event not seen further east in spite of very similar topographic characteristics we attribute this strong signal to detachment of the european slab in the western alps combined with efficient glacial erosion

testing models of orogen exhumation using zircon u th he thermochronology insight from the ligurian alps northern italy testing models of orogen exhumation requires precise constraint of the time temperature paths of the exhumed rocks the zircon u th he zhe thermochronometer has a closure temperature of 140 210 c and can provide temporal constraints on the exhumation history of rocks through a thermal range which crucially corresponds the onset of brittle behaviour of an exhuming orogen we performed zhe analyses to test the existing contradictory models for the exhumation of the ligurian alps the zhe ages indicate a very rapid 1 3 6 8 mm yr and southward migrating exhumation of the orogen between 32 and 25 ma these high exhumation rates are unique within the alpine belt and cannot be reconciled with existing geodynamic models of the evolution of the ligurian alps we propose a model of tectonic denudation via detachment accomplished in the shallowest crust 5 km as a result of the last orogenic phase of extension

dominant synoptic disturbance in the extreme rainfall at cherrapunji northeast india based on 104 years of rainfall data 1902 2005 abstractthe characteristics of active rainfall spells arss at cherrapunji northeast india where extreme high rainfall is experienced and their relationships with large scale dynamics were studied using daily rainfall data from 1902 to 2005 and japanese 55 year reanalysis from 1958 to 2005 extreme high daily rainfalls occur in association with arss the extremely large amounts of rainfall in the monsoon season are determined by the cumulative rainfall during arss arss start when anomalous anticyclonic circulation aac at 850 hpa propagates westward from the south china sea and western north pacific and covers the northern bay of bengal the aac propagates farther westward and suppresses convection over central india during arss at cherrapunji and continues for 3 to 14 days consequently a northward shift of the monsoon trough during the break in the indian core region occurs the westerly wind which prevails in the northern portion of the aac transports moisture toward northeast india and en

exhumation controlled by transcurrent tectonics the argentera mercantour massif sw alps new apatite fission track aft and u th he ages from the argentera mercantour external crystalline massif of the sw alps document an exhumation history along transcurrent dextral faults significant aft age differences across the strikes of the main faults have been obtained from the ne 12 9 ma to the sw 5 2 ma and are linked to vertical uplifts along these right lateral transpressional structures such segmentation is not observed in ahe ages ahe ages have preserved younger ages 4 5 ma on the eastern hangingwall side of the high durance extensional system such an exhumation history is interpreted to result from a transition of transpressional to transtensional regimes at 8 5 ma during continuing adria europe convergence these data show that recent extensional deformation in the sw alps can be related to the development of a transtensional domain in the ubaye embrunais depression linked to ongoing strike slip deformation along the argentera mercantour

morphology and tectonics of mahanadi basin northeastern continental margin of india from geophysical studies abstract the bathymetry total intensity magnetic and satellite free air gravity data over the eastern continental margin of india between the latitudes 18 30 n and 20 n within the water depths of 25 2300 m between paradip and gopalpur were analyzed and interpreted onshore aeromagnetic and bouguer gravity data over the adjacent coastal region are also supplemented in the present analysis the basement configuration inferred from the bathymetry magnetic and gravity data resembles a series of coast parallel structural highs and depressions and their shearing pattern in the mahanadi offshore basin the chilika offshore lineament and dhamara offshore lineament constitute the southern and northern boundaries of the offshore basin respectively in this sector the inferred continent ocean boundary cob around 170 km from the coast approximately mimics the 2000 m isobath the width of the inferred offshore basin between the chilika offshore lineament and dhamara offshore lineament is around 240 km and it extends approximately up to 170 km from coast to offshore perhaps up to the cob the inferred tectonics of the northeastern continental margin of india suggests pull apart and sheared transform mechanisms during the breakup of india from antarctica the model studies suggest that the northern part of the 85 e ridge abuts the coast at chilika lake the shape of 2000 m isobath over the northeastern continental margin of india closely resembles to that of 2000 m isobath off the lambert graben of east antarctica this inference appears to further support the theory that the eastern continental margin of india and east antarctica are closely aligned in the pre breakup tectonic setting of the eastern gondwanaland

assessment of gas hydrate saturation in marine sediments from resistivity and compressional wave velocity log measurements in the mahanadi basin india abstract gas hydrate was recovered in the mahanadi basin along the eastern continental margin of india during the india national gas hydrate program nghp expedition 01 in 2006 infrared imaging of recovered core confirmed gas hydrate occurs predominantly in discrete layers pore water chemistry electrical resistivity and acoustic velocity down hole logs were used to estimate gas hydrate saturations at three of the sites in the mahanadi basin sites nghp 01 08 09 and 19 gas hydrate saturation estimated from pore water chloride concentrations shows values up to 10 of the pore space at 200 m below seafloor just above the base of the gas hydrate stability zone bghsz gas hydrate saturations estimated from electrical resistivity and acoustic velocity logs using standard relations and modeling approaches are comparable to each other and saturations are 10 15 of the pore space seismic reflection data were also analyzed for the evidence of gas hydrate and a bottom simulating reflector bsr was imaged along the seismic profiles in the study area the depth of the bsr is varying from 200 m to 300 m below seafloor depending on water depth in the mahanadi basin the occurrence of gas hydrate was observed to be associated with deep water channel and levee complexes especially at site nghp 01 19 based on the regional seismic data but the cored logged section at each site lacked any significant sand fraction which does not allow for higher gas hydrate saturations as identified from seismic time slice data all sites drilled in the mahanadi basin are within the steeper slope region of the channel system and any sand bypassed this region significant sand deposition would occur further down slope where typical fan type deposits can be inferred from the seismic data and thus higher accumulations of gas hydrate would be expected

methanogenic biodegradation of petroleum in the west siberian basin russia significance for formation of giant cenomanian gas pools approximately 1700 tcf 48 trillion m3 of dry gas 99 methane reserves and resources occur in western siberia mostly in shallow 1500 m 4921 ft cenomanian pools in the northern part of the basin this dry gas constitutes about 11 of the world s conventional gas endowment and about 17 of the annual gas production the origin of the dry gas has been debated extensively over the last 45 yr but remains controversial widely discussed hypotheses on the origin include early mature thermogenic gas from coal primary microbial gas from dispersed organic matter or coal and thermogenic gas from deep source rocks however all these hypotheses are in some ways inconsistent with the molecular or isotopic composition of the gases or the results of basin and petroleum systems modeling here i present geochemical and geological evidence that a significant although yet not quantified part of the shallow dry gas in the northern west siberian basin originated from methanogenic biodegradation of petroleum circumstantial evidence includes the occurrence of heavily biodegraded oil legs and residual oil in many cenomanian gas pools as well as geochemical evidence of heavy to slight biodegradation in jurassic albian reservoirs commonly underlying the cenomanian pools direct evidence includes most importantly 13c enriched co2 in pools with biodegraded oil although data are limited which indicates 40 70 wt conversion of oil derived co2 to secondary microbial methane distinctive hydrocarbon molecular and isotopic compositions of most gases in cenomanian pools average dryness c1 sum c1 c5 is 0 9976 average 13c of methane is 51 8 suggest that they represent mixtures of biodegraded thermogenic gases from deep mainly jurassic source rocks and secondary microbial methane with an occasional small addition of primary microbial methane contribution of early mature coal derived gas is possible in areas with the most significant thermal stress of hauterivian aptian sediments but remains speculative review of petroleum habitats of five representative oil gas condensate fields in western siberia including the world s second largest gas field urengoyskoe suggests that methanogenic biodegradation may best explain the observed distribution and properties of fluids in the shallow reservoirs of those fields recognition of secondary microbial gas in western siberia helps explain the observed dominance of gas in the shallow cool northern part of the basin where conditions were more favorable for prolonged petroleum biodegradation than in the central and southern parts of the basin secondary microbial gas has been recognized worldwide and may 1 represent a volumetrically significant exploration target in shallow reservoirs perhaps more significant than primary microbial gas and 2 indicate effective thermogenic petroleum systems in the deeper sections large volumes up to 66 500 tcf 1884 trillion m3 of secondary microbial methane could have been generated from biodegraded petroleum accumulations worldwide although a part of that gas accumulated as oil dissolved free and hydrate bound gas most gas apparently escaped into the overburden atmosphere and ocean and could have affected global climate in the geologic past

origin of natural gases and associated gas hydrates in the shenhu area northern south china sea results from the china gas hydrate drilling expeditions abstract geochemical data for hydrate gases acquired from the gmgs3 and gmgs4 gas hydrate drilling expeditions conducted by the guangzhou marine geological survey gmgs are used to explore the origin of hydrate gases and their relationship to deep hydrocarbon reservoirs and to evaluate the contribution of different genetic types of gases to the formation and accumulation of gas hydrates in the shenhu area of the northern part of the south china sea scs compositionally methane is the dominant gas 90 in the void gas and pressure core gas in addition as much as 3 of the gas is composed of c2 hydrocarbons including ethane propane iso butane butane iso pentane and n pentane the 13c ch4 and d ch4 values indicate a mixed biogenic thermogenic origin for the hydrate forming gas the methane isotope correlation indicates that the source of the hydrate gas is closely related to the deep conventional gas reservoirs discovered in the baiyun sag panyu low uplift area both the hydrate gases and the deep reservoir gases are sourced from the hydrocarbon kitchens in the baiyun sag revealing a paragenetic relationship within the same petroleum system the composition of the hydrocarbons and the isotopic variation of methane with depth suggest that the thermogenic gas was likely affected by compositional and isotopic fractionation during the long distance migration from the deep source rocks to the shallow gas hydrate stability zone ghsz the impact of biodegradation on a solely thermogenic gas could also affect the final composition of the hydrate forming gas analysis of the ghsz based on gas hydrate compositions suggests that the occurrence of thermogenic gas could also indicate the coexistence of structure i si and structure ii sii gas hydrates in the shenhu area with the sii hydrates accumulating in or below the lower part of the si ghsz the confirmed presence of sii hydrates in the shenhu area relocated the base of the ghsz deeper than was indicated by the bottom simulating reflector which warrants further study in future explorations for gas hydrates in the shenhu area

gas geochemistry of the mount elbert gas hydrate stratigraphic test well alaska north slope implications for gas hydrate exploration in the arctic abstract gases were analyzed from well cuttings core gas hydrate and formation tests at the bpxa doe usgs mount elbert gas hydrate stratigraphic test well drilled within the milne point unit alaska north slope the well penetrated a portion of the eileen gas hydrate deposit which overlies the more deeply buried prudhoe bay milne point west sak and kuparuk river oil fields gas sources in the upper 200 m are predominantly from microbial sources c1 isotopic compositions ranging from 86 4 to 80 6 the c1 isotopic composition becomes progressively enriched from 200 m to the top of the gas hydrate bearing sands at 600 m the tested gas hydrates occur in two primary intervals units d and c between 614 0 m and 664 7 m containing a total of 29 3 m of gas hydrate bearing sands the hydrocarbon gases in cuttings and core samples from 604 to 914 m are composed of methane with very little ethane the isotopic composition of the methane carbon ranges from 50 1 to 43 9 with several outliers generally decreasing with depth gas samples collected by the modular formation dynamics testing mdt tool in the hydrate bearing units were similarly composed mainly of methane with up to 284 ppm ethane the methane isotopic composition ranged from 48 2 to 48 0 in the c sand and from 48 4 to 46 6 in the d sand methane hydrogen isotopic composition ranged from 238 to 230 with slightly more depleted values in the deeper c sand these results are consistent with the concept that the eileen gas hydrates contain a mixture of deep sourced microbially biodegraded thermogenic gas with lesser amounts of thermogenic oil associated gas and coal gas thermal gases are likely sourced from existing oil and gas accumulations that have migrated up dip and or up fault and formed gas hydrate in response to climate cooling with permafrost formation

a diode laser system for heating minerals for u th he chronometry we have developed a diode laser 25 w 808 nm system for he extraction from minerals for u th he chronometry the laser beam is delivered via a 600 m fiber cable and focused using a binocular microscope temperatures necessary for he release from apatite 500 600 c and zircon 1100 1300 c encapsulated in pt foil tubes are attained by heating to 0 5 w for 30 s and 1 25 2 5 w for 20 min respectively using a defocused beam heating at these powers does not result in measurable u and or th loss from apatite as noted by the preservation of the distinct th u in multiple splits of two different durango apatite crystals analyses of durango and the california institute of technology internal standard apatite 97mr22 yield u th he ages of 32 8 1 8 ma 1 n 11 and 4 6 0 5 1 n 5 respectively well within accepted ages the u th he age and th u of five fish canyon tuff zircon aliquots yield 29 3 2 2 ma 1 and 0 6 0 03 respectively and are indistinguishable from ages produced by resistance furnace he extraction heating of unencapsulated minerals shows that the diode laser couples well with optically opaque minerals e g hornblende biotite muscovite garnet and basalt groundmass suggesting that diode lasers offer a cheap small low maintenance alternative to nd yag and ar ion lasers for 40ar 39ar cosmogenic noble gas and stable isotope studies

marine pore water sulfate profiles indicate in situ methane flux from underlying gas hydrate marine pore water sulfate profiles measured in piston cores are used to estimate methane flux toward the sea floor and to detect anomalous methane gradients within sediments overlying a major gas hydrate deposit at the carolina rise and blake ridge u s atlantic continental margin here sulfate gradients are linear implying that sulfate depletion is driven by methane flux from below rather than by the flux of sedimentary organic matter from above thus these linear sulfate gradients can be used to quantify and assess in situ methane flux which is a function of the methane inventory below

national gas hydrate program expedition 01 offshore india gas hydrate systems as revealed by hydrocarbon gas geochemistry abstract the national gas hydrate program expedition 01 nghp 01 targeted gas hydrate accumulations offshore of the indian peninsula and along the andaman convergent margin the primary objectives of coring were to understand the geologic and geochemical controls on the accumulation of methane hydrate and their linkages to underlying petroleum systems four areas were investigated 1 the kerala konkan basin in the eastern arabian sea 2 the mahanadi and 3 krishna godavari basins in the western bay of bengal and 4 the andaman forearc basin in the andaman sea upward flux of methane at three of the four of the sites cored during nghp 01 is apparent from the presence of seafloor mounds seismic evidence for upward gas migration shallow sub seafloor geochemical evidence of methane oxidation and near seafloor gas composition that resembles gas from depth the kerala konkan basin well contained only co2 with no detectable hydrocarbons suggesting there is no gas hydrate system here gas and gas hydrate from the krishna godavari basin is mainly microbial methane with 13c values ranging from 58 9 to 78 9 with small contributions from microbial ethane 52 1 and co2 gas from the mahanadi basin was mainly methane with lower concentrations of c2 c5 hydrocarbons c1 c2 ratios typically 1000 and co2 carbon isotopic compositions that ranged from 70 7 to 86 6 for methane and 62 9 to 63 7 for ethane are consistent with a microbial gas source however deeper cores contained higher molecular weight hydrocarbon gases suggesting a small contribution from a thermogenic gas source gas composition in the andaman basin was mainly methane with lower concentrations of ethane to isopentane and co2 c1 c2 ratios were mainly 1000 although deeper samples were

the tripoli libya earthquake of september 4 1974 implications for the active tectonics of the central mediterranean source parameters have been determined for the earthquake ms 5 6 that occurred offshore of tripoli libya on september 4 1974 one nodal plane of its focal mechanism has dip 37 strike 297 and rake 141 indicating oblique normal faulting this nodal plane is subparallel to many west northwest striking normal faults in the epicentral area and is most likely the fault plane indicating a component of right lateral strike slip with slip vector azimuth n84 e inversion of long period teleseismic body waves indicates 12 km centroid depth and 0 4 1018 n m seismic moment a much larger earthquake ms 7 0 on april 19 1935 that occurred in the same zone of active oblique normal faults 400 km farther southeast near sirte probably involved similar slip sense this zone for which the name tunisia libya seismic zone appears appropriate has overall northwest southeast extent 1000 km from northern libya to between tunisia and sicily it takes up a change in motion direction relative to stable europe from west of north inside the african plate to between n30 e and n50 e in the ionian sea between sicily southernmost peninsular italy southwest greece and libya this suggested motion direction of sicily relative to stable europe agrees with independent estimates from fault slip rates and senses elsewhere in italy

influence of total organic carbon deposition on the inventory of gas hydrate in the indian continental margins abstract total organic carbon toc content of marine sediments represents residual carbon originally derived from terrestrial and marine sources which has survived seafloor and shallow subseafloor diagenesis ultimately its preservation below the sulfate reduction zone in marine sediments drives methanogenesis within the gas hydrate stability zone ghsz methane production along continental margins can supersaturate pore fluids and lead to the formation of gas hydrate in this paper we examine the inventory and sources of toc in sediments collected from four regions within the ghsz along the indian continental margins the recovered sediments vary in age from oligocene to recent mean toc abundance is greatest in the krishna godavari k g basin and decreases progressively to the mahanadi basin andaman wedge and kerala konkan k k basin this decrease in toc is matched by a progressive increase in biogenic caco3 and increasing distance from terrestrial sources of organic matter and lithogenic materials organic carbon sources inferred from c n and 13ctoc range from terrestrial k g basin to mixed marine and terrestrial mahanadi basin to marine dominant andaman wedge and k k basin in the k g basin variation in the bulk 13ctoc is consistent with changes in c3 and c4 vegetation driven by monsoon variability on glacial interglacial timescales whereas in the mahanadi basin a shift in the 13ctoc likely reflects the onset of c4 plant deposition in the late miocene a large shift the 13ctoc in the k k basin is consistent with a change from c3 to c4 dominated plants during the middle miocene we observe a close relationship between toc content and gas hydrate saturation but consider the role of sedimentation rates on the preservation of toc in the zone of methanogenesis and advective flow of methane from depth although toc contents are sufficient for in situ methanogenesis at all the sites where gas hydrates were observed or inferred from proxy data seismic borehole log pressure core and gas composition data coupled with relatively high observed gas hydrate saturations suggest that advective gas transport may also play a role in the saturation of methane and the formation of gas hydrates in these regions although toc content may be a first order indicator for gas hydrate potential the structural and stratigraphic geologic environment along a margin will most likely dictate where the greatest gas hydrate saturations will occur

gas hydrate systems at hydrate ridge offshore oregon inferred from molecular and isotopic properties of hydrate bound and void gases abstract we report and discuss molecular and isotopic properties of hydrate bound gases from 55 samples and void gases from 494 samples collected during ocean drilling program odp leg 204 at hydrate ridge offshore oregon gas hydrates appear to crystallize in sediments from two end member gas sources deep allochthonous and in situ as mixtures of different proportions in an area of high gas flux at the southern summit of the ridge sites 1248 1250 shallow 0 40 m below the seafloor mbsf gas hydrates are composed of mainly allochthonous mixed microbial and thermogenic methane and a small portion of thermogenic c2 gases which migrated vertically and laterally from as deep as 2 to 2 5 km depths in contrast deep 50 105 mbsf gas hydrates at the southern summit sites 1248 and 1250 and on the flanks of the ridge sites 1244 1247 crystallize mainly from microbial methane and ethane generated dominantly in situ a small contribution of allochthonous gas may also be present at sites where geologic and tectonic settings favor focused vertical gas migration from greater depth e g sites 1244 and 1245 non hydrocarbon gases such as co2 and h2s are not abundant in sampled hydrates the new gas geochemical data are inconsistent with earlier models suggesting that seafloor gas hydrates at hydrate ridge formed from gas derived from decomposition of deeper and older gas hydrates gas hydrate formation at the southern summit is explained by a model in which gas migrated from deep sediments and perhaps was trapped by a gas hydrate seal at the base of the gas hydrate stability zone ghsz free gas migrated into the ghsz when the overpressure in gas column exceeded sealing capacity of overlaying sediments and precipitated as gas hydrate mainly within shallow sediments the mushroom like 3d shape of gas hydrate accumulation at the summit is possibly defined by the gas diffusion aureole surrounding the main migration conduit the decrease of gas solubility in shallow sediment and refocusing of gas by carbonate and gas hydrate seals near the seafloor to the crest of the local anticline structure

miocene lateral extrusion in the inner western alps revealed by dynamic fault analysis 1 from early miocene to the present day the core parts of the western european alps experienced brittle extensional deformations mostly in a strike parallel direction here we present new data constraining the brittle deformation of the vanoise area french alps and a synthesis of 312 paleostress tensors in the whole arc of the internal western alps the data show a continuous change in the direction of extension from n065 simplon area to n s vanoise area and to nnw sse briancon area the abundance of orogen perpendicular 3 axes increases from the north to the south in the brianconnais area an extensional reactivation of the basal penninic thrust seems to be the origin of the e w to ne sw oriented 3 in light of these new data and the regional paleostress synthesis we propose a predominant orogen parallel extension in the internal zone as a whole this orogen parallel extension is related to the indentation rotation of the apulian microplate and to the opening of the ligurian sea during the lower middle miocene the locally observed orogen perpendicular extension is interpreted as an effect of the exhumation of the internal crystalline massifs the uplift of the external crystalline massifs and or the present day geodynamics postorogenic gravitational collapse some transcurrent tectonics older than the extension in the valais area and younger than the extension farther south is observed in the entire inner western alps strike slip movements are correlated with the apulian rotation and local permutation of stress axes

intraseasonal variability of the low level jet stream of the asian summer monsoon abstract the strong cross equatorial low level jet stream llj with its core around 850 hpa of the asian summer monsoon june september is found to have large intraseasonal variability during the monsoon onset over kerala india and during break monsoon periods when the convective heating of the atmosphere is over the low latitudes of the indian ocean the axis of the llj is oriented southeastward over the eastern arabian sea and it flows east between sri lanka and the equator and there is no llj through peninsular india this affects the transport of moisture produced over the indian ocean to peninsular india and the bay of bengal in contrast during active monsoon periods when there is an east west band of strong convective heating in the latitudes 10 20 n from about longitude 70 to about 120 e the llj axis passes from the central arabian sea eastward through peninsular india and it provides moisture for the increased convection in the bay of bengal and for the monsoon depressions forming there

hydrothermal petroleum in the sediments of the andaman backarc basin indian ocean abstract recent sediments of the andaman backarc basin indian ocean between the andaman nicobar islands and the malay peninsula have been analyzed for biomarker lipids three cores were selected one each from the fault zone in a deep basin a graben between two fault systems another from a location adjacent to the fault and the third from the topographic high in the rift valley the molecular composition of the lipid classes n alkanes isoprenoids alkylbenzenes alkylcyclohexanes hopanoids polycyclic aromatic hydrocarbons steranes alcohols sterols and fatty acids was examined by gas chromatography gc and gc mass spectrometry to understand the nature and source of the hydrocarbons present and the processes of maturation of organic matter the data show that the hydrocarbons are of hydrothermal origin derived from thermal alteration of sedimentary organic matter consisting of a mixture predominantly of marine derived components with some terrestrial inputs normal alcohols and fatty acids also corroborate the distribution of n alkanes the distribution profiles and various parameters computed from the concentration of the target compounds suggest that oxidative reactions and microbial degradation in this environment are insignificant triterpane and pah compositions indicate that the thermal maturity of the bitumen in the samples is comparable to or lower than that found at other hydrothermal regions such as the northern juan de fuca ridge guaymas basin and escanaba trough

neogene kinematics of the central and western alps evidence from fission track dating zircon and apatite fission track analysis has established the continuation of a zone of rapid change in mineral ages extending from the simplon fault zone in the simplon alps through the rhone valley and along the southeastern side of the mont blanc and belledonne massifs apatite fission track ages to the northwest of this zone generally range from 1 4 to 6 ma whereas those to the southeast range from 6 to 13 ma corresponding values for zircon are 11 13 and 16 26 ma respectively the zone corresponds to the position of the frontal pennine thrust in the mont blanc belledonne region this structure a prominent feature on recent deep seismic profiles may have been reactivated in the neogene with an important normal fault component this is suggested by apatite and zircon fission track ages in the footwall that are younger than those in the hanging wall and by the observed elimination of the lower pennine or simplon nappes along this fault zone in the rhone valley mont blanc belledonne region resulting in the juxtaposition of north penninic and helvetic ultra helvetic nappes at the current erosion level the distribution of fission track ages reflects this movement and the related neogene exhumation of the mont blanc and belledonne external massifs which has continued until less than 1 4 m y ago i e it is almost certainly still active and has tilted the overlying nappe sequence

the 30 50 day mode at 850 mb during monex abstract the analyzed wind field at 850 mb during the summer monsoon experiment monex is subjected to a time series analysis to confirm the existence of a peak in the time range of 30 50 days having established that this study presents a mapping of the motion field for this time scale in this short paper we illustrate the steady meridional propagation of a train of troughs and ridges that seem to form near the equator and dissipate near the himalayas the meridional scale of this mode is around 300 km and its meridional speed of propagation is 0 75 latitude per day the amplitude of the wind for this mode is around 3 6 m s 1 the salient contributions here are the mapping and the demonstration of a very regular behavior of this mode its existence is here noted from a period well before the onset of monsoon i e from early may to late july three major storms during monex were noted to form within the trough line of this system and the period of major cessation of rains over the indian subconti

the syn and post collisional evolution of the romanian carpathian foredeep new constraints from anisotropy of magnetic susceptibility and paleostress analyses abstract the first results of anisotropy of the magnetic susceptibility ams data from the romanian carpathian foredeep reveal compression directions generally perpendicular to the highly bended carpathian orogenic arc the distribution of the present day stress field in the pannonian carpathian region reflects pre imposed plate boundaries that were established during late miocene collision analysis of the ams along the eastern and southern carpathian foredeep at the contacts of the orogenic nappe pile the lower plate and the overlying sedimentary rocks indicates that two factors are critical for the distribution of the stress field during and after collision i e 1 the inherited highly bended plate geometry and 2 the quaternary deformation that lead to differential vertical and horizontal movements in the se carpathians the ams analysis was successfully used in the weakly deformed mio pliocene sedimentary rocks from the carpathian foredeep revealing information about the deformation history of the soft non competent rocks where the poor preservation of traditional kinematic indicators e g faults and folds is difficult

role of topography in isotherm perturbation apatite u th he and fission track results from the malta tunnel tauern window austria 1 apatite u th he and fission track age determinations of samples from a 20 km long near horizontal tunnel in the hochalm ankogel dome eastern tauern window austria are presented in order to determine the role of paleo topography in perturbing isotherms in the shallow crust apatite fission track ages 26 8 ma show no systematic correlation with distance along the tunnel or elevation two age components in the fission track data indicate cooling through 120 c at approximately 20 ma and 80 c at approximately 6 ma surface and tunnel u th he ages 17 9 ma and 13 5 ma respectively are consistently younger than the equivalent fission track ages u th he ages vary systematically along the tunnel with older ages at the northern and southern tunnel portals and younger ages in the central section geological factors faulting lithology appear to have had little effect on this age distribution the u th he age pattern is inconsistent with rock cooling underneath the present day hochalm ankogel dome topography the age minimum is interpreted to coincide with a paleotopographic maximum in the hochalm ankogel dome and suggests that the 40 60 c isotherms were warped sufficiently to affect apatite u th he ages the tunnel apatite u th he ages match synthetic he ages derived from a two dimensional numerical model of landscape evolution integrating the thermal model results with the data allows the relief development to be constrained and we calculate that the present day hochalm ankogel dome topography was formed at 7 to 10 ma

lithofacies characterization of gas hydrate prospects discovered during the national gas hydrate program expedition 02 offshore krishna godavari basin india abstract lithofacies of host sediments associated with gas hydrate reservoirs may have a significant influence on the formation of hydrates the type of sediments and the depositional processes responsible for the gas hydrate bearing sediments along the eastern margin of the india have been studied by integrating core data and logging while drilling downhole logs borehole data correlated with seismic data were used for the interpretation of geological process responsible for gas hydrate formation the acquired seismic profiles were correlated with the downhole logs by identifying the shape of the well logs curves that indicate finning up and blocky patterns turbidite sands and debris flows were also identified from the log and core sediment studies this study identified two prominent types of depositional systems 1 turbidity currents and 2 debris flows were mainly responsible for the deposition of gas hydrate bearing reservoirs in the study area based on these studies two well developed gas hydrate systems have been identified in the krishna godavari basin and hydrates were determined to be distributed mostly in sand dominated facies fine grained sand in the identified turbidite deposits were shown to be a good hydrate reservoir the hydrate bearing sediments in the central part of the krishna godavari basin area c in d6 block consist of mostly debris flows which is consistent with scattered gravel and sand silt sized grains in channel levee systems