gravity data as a tool for landfill study this paper shows the potential of gravity data to map a buried landfill bottom topography to this end a gravity inversion method is presented for estimating the landfill s bottom depths at discrete points assuming a decrease of the density contrast with depth according to a hyperbolic law the method s efficiency was tested using synthetic data from simulated waste landfills producing estimated bottom topographies very close to the true ones the method s potentiality has been further evaluated in applying it to the gravity data from the abandoned thomas farm landfill site indiana usa whose bottom topography is known the estimated topography showed close agreement with the known thomas farm landfill s bottom topography

three dimensional model and late stage warping of the plattengneis shear zone in the eastern alps abstract the plattengneis shear zone is a 250 600 m thick flat lying cretaceous eclogite facies mylonitic shear zone with north over south transport direction that is exposed over almost 1000 km2 in the koralpe region along the eastern margin of the alps although the shear zone is one of the largest in the alps its role in the eoalpine metamorphic evolution and the subsequent exhumation of the region remain enigmatic and its large scale geometry is not well understood the outcrop pattern suggests that the shear zone is made up of a single sheet that is folded into a series of open syn and antiforms with wavelengths of about 10 km eclogite bodies occur above within and below the shear zone and there is no metamorphic grade change across the shear zone in the south the fold axes strike east west and plunge shallowly to the east in the north the fold axes are oriented in north south direction and form a dome shaped structure of the shear zone total shortening during this late stage warping event was of the order of 5 indirect evidence constrains this folding event to have occurred between 80 and 50 ma and the fold geometry implies that the final exhumation in the koralpe occurred somewhat later than further north interestingly the shear zone appears to strike out of the topography in the south and dip into the topography in the north so that north of the shear zone only hanging wall rocks are exposed and south of it only foot wall rocks possibilities for the geometric relationship of the plattengneis shear zone with the surrounding south dipping detachments are discussed

enhancement mechanisms of magnetic susceptibility in the chinese red clay sequence 1 little is known about the mechanisms of magnetic susceptibility enhancement for the red clay sequence on the chinese loess plateau clp in comparison to the overlying loess paleosol sequence here we present a rock magnetic study of the red clay sediments from the central clp our results show that frequency dependence of fd lf hf where lf and hf are measured at 470 hz and 4700 hz respectively lf and susceptibility of anhysteretic remanent magnetization arm are linearly correlated within the red clay sequence this linear correlation indicates that the pedogenic magnetic minerals of the red clay have a rather uniform grain size distribution as in the loess paleosol sequence and the grain size is independent of the degree of pedogenesis nevertheless red clay sediments are slightly more enriched in superparamagnetic magnetic particles than the overlying loess paleosol sediments as indicated by the higher slope of the regression line between fd and lf

significant effect of grain size distribution on compaction rates in granular aggregates we investigate the role of pressure solution in deformation of upper to mid crustal rocks using aggregates of halite as a room temperature analog for fluid assisted deformation processes in the earth s crust experiments evaluate the effects of initial grain size distribution on macroscopic pressure solution rate of the aggregate and compare the results to theoretical models for pressure solution we find that the grain size exponent deviates significantly from the theoretical value of 3 for diffusion controlled pressure solution models typically assume mono dispersed spherical particles in pseudo regular packing we infer that the discrepancy between experimentally determined grain size exponents and the theoretical values are a result of deviation of experimental and natural samples from regular packs of mono dispersed spherical particles moreover we find that compaction rates can vary by up to one order of magnitude as a function of the width of the grain size distribution for a given mean grain size wider size distributions allow for higher initial compaction rates increasing the macroscopic compaction rate with respect to more narrow grain size distributions grain sizes in rocks fault gouges and hydrocarbon reservoirs are typically log normal or power law distributed and therefore pressure solution rates may significantly exceed theoretical predictions spatiotemporal variations in pressure solution rates due to variations in grain size may cause the formation of low porosity zones which could potentially focus deformation in these zones and produce pockets of high pore pressures promoting nucleation of frictional instability and earthquake rupture

formal ratification of the quaternary system period and the pleistocene series epoch with a base at 2 58 ma in june 2009 the executive committee of the international union of geological sciences iugs formally ratified a proposal by the international commission on stratigraphy to lower the base of the quaternary system period to the global stratotype section and point gssp of the gelasian stage age at monte san nicola sicily italy the gelasian until then had been the uppermost stage of the pliocene series epoch the base of the gelasian corresponds to marine isotope stage 103 and has an astronomically tuned age of 2 58 ma a proposal that the base of the pleistocene series epoch be lowered to coincide with that of the quaternary the gelasian gssp was also accepted by the iugs executive committee the gssp at vrica calabria italy which had hitherto defined the basal boundary of both the quaternary and the pleistocene remains available as the base of the calabrian stage age now the second stage of the revised pleistocene in ratifying these proposals the iugs has acknowledged the distinctive qualities of the quaternary by reaffirming it as a full system period correctly complied with the hierarchical requirements of the geological timescale by lowering the base of the pleistocene to that of the quaternary and fully respected the historical and widespread current usage of both the terms quaternary and pleistocene copyright 2009 john wiley sons ltd

ichnology of a subaqueously prograding clastic wedge late pliocene morne l enfer formation fullarton trinidad implications for recognition of autogenic erosional surfaces and delineation of stress factors on irregular echinoids abstract the morne l enfer formation outcrops near fullarton trinidad expose an erosional surface between the shelf deposits below and a prograding clastic wedge of the late pliocene paleo orinoco system above the surface exhibits similarities as well as dissimilarities with examples of regressive surfaces of marine erosion rsmes in wave influenced shelf settings and also with incised valleys inherited from fluvial incision of shelf during a forced regression episode however detailed ichnological studies reveal that the surface is a subaqueous autogenically controlled erosional surface on a shelf dominated by the hyperpycnal and hypopycnal discharges with transient wave influence integration of ichnological and sedimentological characteristics also suggests complicated interrelationships among different stress factors affecting the infauna in different subenvironments especially the irregular echinoids the delta prograded subaqueously through autogenically establishing its lobe on the open shelf without stratigraphically significant erosional removal of sediments in the subaqueously prograding clastic wedge the fluvial influence pertains high stress conditions not only for the adult infauna but also for their larvae within the water column especially in and near the subaqueous distributary channels

a low order dynamical model of global climatic variability over the full pleistocene a previously formulated dynamical model of the late pleistocene ice ages based on the hypothesis that the global co sub 2 system can provide the instability to drive a natural oscillation involving feedbacks between the cryosphere atmosphere and ocean is extended to include 1 additive earth orbital forcing summer insolation changes at 65 degree n and 2 tectonic forcing in the form of a postulated variation in the multiplicative parameters rate constants of the model system the structural e g bifurcation properties of the model are examined in detail to reveal the regions of parameter space wherein the geologically inferred features of the full pleistocene can be simulated including the observed chronology the phase relationships between ice co sub 2 and north atlantic deep water formation and the mid pleistocene transition

final closure of panama and the onset of northern hemisphere glaciation abstract the greenland ice sheet is accepted as a key factor controlling the quaternary glacial scenario however the origin and mechanisms of major arctic glaciation starting at 3 15 ma and culminating at 2 74 ma are still controversial for this phase of intense cooling ravelo et al 1 a c ravelo d h andreasen m lyle a o lyle m w wara regional climate shifts caused by gradual global cooling in the pliocene epoch nature 429 2004 263 267 proposed a complex gradual forcing mechanism in contrast our new submillennial scale paleoceanographic records from the pliocene north atlantic suggest a far more precise timing and forcing for the initiation of northern hemisphere glaciation nhg since it was linked to a 2 3 c surface water warming during warm stages from 2 95 to 2 82 ma these records support previous models g h haug r tiedemann effect of the formation of the isthmus of panama on atlantic ocean thermohaline circulation nature 393 1998 673 676 2 claiming that the final closure of the panama isthmus 3 0 2 5 ma j groeneveld s steph r tiedemann d nurnberg d garbe schonberg the final closure of the central american seaway geology in prep 3 induced an increased poleward salt and heat transport associated strengthening of north atlantic thermohaline circulation and in turn an intensified moisture supply to northern high latitudes resulted in the build up of nhg finally culminating in the great irreversible climate crash at marine isotope stage g6 2 74 ma in summary there was a two step threshold mechanism that marked the onset of nhg with glacial to interglacial cycles quasi persistent until today

characterization of geothermally relevant structures at the top of crystalline basement in switzerland by filters and gravity forward modelling some of the major geothermal anomalies in central europe are linked to tectonic structures within the top of crystalline basement which modify strongly the top of this basement their assessment is a major challenge in exploration geophysics gravity has been proven to be suitable for the detection of mainly large scale lithological and structural inhomogeneities indeed it is well known and proven by different wells that for example in northern switzerland extended negative anomalies are linked to such structures due to depth limitation of wells there vertical extension is often unknown in this study we have investigated the potential of gravity for the geometrical characterization of such basement structures our approach consists in the combination of the series of butterworth filters geological modelling and best fitting between observed and computed residual anomalies in this respect filters of variable wavelength are applied to observed and computed gravity data the geological model is discretized into a finite element mesh near surface anomalies and the effect of the sedimentary cover were eliminated using cut off wavelength of 10 km and geological and seismic information we analysed the potential of preferential butterworth filtering in a sensitivity study and applied the above mentioned approach to part of the swiss molasses basin sensitivity analyses reveal that such sets of residual anomalies represents a pseudo tomography revealing the distribution of different structures with depth this finding allows for interpreting negative anomalies in terms of 3 d volumes best fitting then permits determination of the most likely 3 d geometries of such basement structures our model fits both geological observations and gravity among 10 deep boreholes in the studied area six reach the respective units and confirm our distribution of the negative and positive anomalies

the geothermal potential of buyuk menderes graben obtained by combined 2 5 d normalized full gradient results in this study the normalized full gradient nfg method was applied to the bouguer gravity data for western anatolia to identify the locations of the structures and the variations within the mediums the nfg values were calculated for different harmonics using bouguer gravity profile values and the locations of possible structures were determined in the next step for analyzing the continuity of these structures in detail 2 5 d nfg maps were created by combining the nfg results of the profiles for the same harmonics additionally the relationship between the structures obtained in this study and the geothermal sources was examined based on the study results the geothermal capacity of the region was estimated using the locations and the depths of the wells at the surroundings of kizildere saraykoy thus the possible fields with higher geothermal potential were identified throughout the region the structure borders obtained in this study were also evaluated with respect to the earthquakes that have occurred in aydin and denizli cities that contain high temperature geothermal basins and it was found that the regions which feed the geothermal sources are either non seismic or represent low seismicity

early onset and origin of 100 kyr cycles in pleistocene tropical sst records abstract the large 100 kyr cycles evident in most late pleistocene 0 0 6 ma paleoclimatic records still lack a satisfactory explanation previous studies of the nature of the transition from the early pleistocene 1 2 1 8 ma 41 kyr dominated climate regime to the 100 kyr world have been based almost exclusively on benthic foraminiferal oxygen isotopic 18o data it is generally accepted that the late pleistocene 100 kyr cycles represent a newly evolved sensitivity to eccentricity precession superimposed on an earlier and largely constant response to obliquity and precession forcing however orbitally resolved pleistocene sea surface temperature sst records from a variety of oceanic regions paint a rather different picture of the global climate transition across the mid pleistocene transition mpt 0 6 1 2 ma reanalysis of these sst records shows that 1 an early onset of strong 100 kyr like cycles in two low frequency bands 120 145 kyr and 60 80 kyr derived from the bundling of two three obliquity cycles into grand cycles obliquity subharmonics occurred in tropical sst records during the early pleistocene 2 these two early pleistocene periods converge into the late pleistocene 100 kyr period in tropical sst records 3 the dominance of 100 kyr sst power in the late pleistocene coincides with a dramatic decline in the 41 kyr sst power and 4 the correlation of timing of glacial terminations with eccentricity precession variation could well extend back into the early pleistocene we demonstrate that most of these features also occur in 18o records but in a much more subtle manner these features could be explained in two plausible ways a shift in climate sensitivity from obliquity to eccentricity precession a modified version of the conventional view or an increasingly nonlinear response to orbital obliquity across the mpt however our examination of the development of 100 kyr cycles favors an obliquity bundling mechanism to form late pleistocene 100 kyr cycles we therefore suggest that the late pleistocene 100 kyr climatic cycles are likely a nonlinear response to orbital obliquity although the timing of late pleistocene 100 kyr climatic cycles and their early forms appears to be paced by eccentricity precession

facies of slurry flow deposits britannia formation lower cretaceous north sea implications for flow evolution and deposit geometry mud rich sandstone beds in the lower cretaceous britannia formation uk north sea were deposited by sediment flows transitional between debris flows and turbidity currents termed slurry flows much of the mud in these flows was transported as sand and silt sized grains that were approximately hydraulically equivalent to suspended quartz and feldspar in the eastern britannia field individual slurry beds are continuous over long distances and abundant core makes it possible to document facies changes across the field most beds display regular areal grain size changes in this study fining trends especially in the size of the largest grains are used to estimate palaeoflow and palaeoslope directions in the middle part of the britannia formation stratigraphic zones 40 and 45 slurry flows moved from south west and south towards the north east and north most zone 45 beds lens out before reaching the northern edge of the field apparently by wedging out against the northern basin slope zone 40 and 45 beds show downflow facies transitions from low mud content dish structured and wispy laminated sandstone to high mud content banded units in zone 50 at the top of the formation flows moved from north to south or north west to south east and their deposits show transitions from proximal mud rich banded and mixed slurried beds to more distal lower mud content banded and wispy laminated units the contrasting facies trends in zones 40 and 45 and zone 50 may reflect differing grain size relationships between quartz and feldspar grains and mud particles in the depositing flows in zones 40 and 45 quartz grains average 0 30 0 32 mm in diameter 0 10 mm coarser than in zone 50 the medium grained quartz in zones 40 and 45 flows may have been slightly coarser than the associated mud grains resulting in the preferential deposition of quartz in proximal areas and downslope enrichment of the flows in mud in zone 50 flows mud was probably slightly coarser than the associated fine grained quartz resulting in early mud sedimentation and enrichment of the distal flows in fine grained quartz and feldspar mud particles in all flows may have had an effective grain size of 0 25 mm both mud content and suspended load fallout rate played key roles in the sedimentation of britannia slurry flows and structuring of the resulting deposits during deposition of zones 40 and 45 the area of the eastern britannia field in block 16 26 may have been a locally enclosed subbasin within which the depositing slurry flows were locally ponded slurry beds in the eastern britannia field are lumpy sheet like bodies that show facies changes but little additional complexity there is no thin bedded facies that might represent waning flows analogous to low density turbidity currents the dominance of laminar cohesion dominated shear layers during sedimentation prevented most bed erosion and the deposystem lacked channel levee and overbank facies that commonly make up turbidity current dominated systems britannia slurry flows although turbulent and capable of size fractionating even fine grained sediments left sand bodies with geometries and facies more like those deposited by poorly differentiated laminar debris flows

unusual occurrence and stratigraphic significance of the glossifungites ichnofacies in a submarine paleo canyon example from a pliocene shelf edge delta southeast trinidad abstract sedimentary rocks belonging to the upper slope shelf margin delta of the paleo orinoco river are present at the southeast coastline of trinidad in the columbus basin the pliocene mayaro formation exposed as foreshore cliffs represents the wave influenced delta front and mouth bar of this system these deposits consist of thick to very thick hummocky cross stratified sandstone beds and thin bedded to laminated heterolithic sediments they also contain abundant soft sediment deformation structures and sparse well preserved softground burrows e g ophiomorpha nodosa towards the north central part of the outcrop the delta front deposits are cut across by a paleo canyon filled with younger mud dominated prodeltaic sediments the rare exposure of the canyon wall exhibits an unusual occurrence of glossifungites ichnofacies contrastingly distinct from archetypal examples this monospecific suite contains a low abundance of firmground thalassinoides filled with mud rather than sand the tracemakers burrowed into a firm medium grained sandy substrate of the delta front and the burrows were subsequently passively filled by the mud from the overlying prodeltaic sediments filling the canyon the deep tier firmground thalassinoides suite crosscuts the pre existing softground trace fossils integration of ichnologic sedimentologic and sequence stratigraphic datasets indicates that the older delta front sediments are separated from the prodeltaic deposits by distinct episodes of fluctuating relative sea level controlled by the basin bounding growth fault activities and the development of the canyon whereas the entire shelf margin megasequence might have been deposited through a regional scale sea level lowstand the local fluctuations in accommodation space resulting from the growth fault movements and the incision of the canyon were responsible for the shifting positions of the depositional architectural elements of the shelf edge delta

solution doline development on glaciokarst in alpine and dinaric areas abstract in this study the evolution the development and the development environment of solution dolines of glaciokarst the alps and the dinarides are studied based on morphological observations partly with the help of literary data the dolines of sample sites were put into doline types giant solution doline small sized solution doline and schachtdoline the various features of the dolines belonging to different doline types were analysed and compared their size shape elongated nature and the slope angle of their side slope giant solution dolines are much more similar to the dolines of the temperate belt rather than to small sized solution dolines or schachtdolines at temperate climate giant solution dolines developed under the tree line similarly to dolines of the temperate belt and not above the tree line below the tree line the dolines grew horizontally to the effect of horizontal dissolution later in the glacials they developed laterally mainly along their longer axis by glacial erosion they got into their periglacial environment during the uplifting of the bearing area in mountains where they are absent the circumstances of their environment were not present either because the uplifting of the mountain was fast or it was covered by non karstic rock the shapes of small sized solution dolines and schachtdolines prove that their increase happened by deepening their deepening was caused by the meltwater of the snow patches of snow drifts which water does not move laterally because of the rock debris of the floor and thus solution works downwards in the features deepening and snow accumulation strengthen each other these karstic depressions are connected to the periglacial zone because treeless environment favours snow drifts if the depression is completely filled with snow in most part of the year the snow patch is wide thus dissolution affects the total width of the doline a doline schachtdoline with vertical sides and plain floor develops if snow fill is only partial in most part of the year the snow patch and thus dissolution will have a smaller area and a small sized solution doline with funnel shape develops

textural trends in turbidites and slurry beds from the oligocene flysch of the east carpathians romania deep water sandstone beds of the oligocene fusaru sandstone and lower dysodilic shale exposed in the buza uu valley area of the east carpathian flysch belt romania can be described in terms of the standard turbidite divisions in addition mud rich sand layers are common both as parts of otherwise normal sequences of turbidite divisions and as individual event beds eleven units interpreted as the deposits of individual flows were densely sampled and 87 thin sections were point counted for grain size and mud content s3 ta divisions which form the bulk of most sedimentation units have low internal textural variability but show subtle vertical trends in grain size most commonly coarse tail normal grading is associated with finetail inverse grading the mean grain size can show inverse grading normal grading or a lack of grading but sorting tends to improve upward in most beds fine tail inverse grading is interpreted as resulting from a decreasing effectiveness of trapping of fines during rapid deposition from a turbidity current as the initially high suspended load fallout rate declines if this effect is strong enough the mean grain size can show subtle inverse grading as well thus thick inversely graded intervals in deep water sands lacking traction structures do not necessarily imply waxing flow velocities if the suspendedload fallout rate drops to zero after the deposition of the coarse grain size populations the remaining finer grained flow bypasses and may rework the top of the s3 division forming well sorted coarser grained current structured tt units alternatively the suspended load fallout rate may remain high enough to prevent segregation of fines leading to the deposition of significant amounts of mud along with the sand mud content of the sandstones is bimodal either 3 13 or more than 20 two types of mud rich sandstones were observed coarser grained mud rich sandstones occur towards the upper parts of s3 ta divisions these units were deposited as a result of enhanced trapping of mud particles in the rapidly deposited sediment finer grained mud rich units are interbedded with ripple laminated very fine grained sandy tc divisions during deposition of these units mud floccules were hydraulically equivalent to the very fine sand and silt sized sediment the mud rich sandstones were probably deposited by flows that became transitional between turbidity currents and debris flows during their late stage evolution

three dimensional geometry and tectonostratigraphy of the pennine zone central alps switzerland and northern italy abstract continental collision during alpine orogenesis entailed a polyphase deformation history d1 d5 in the pennine zone of the central alps the regional tectonostratigraphy was basically developed during d1 and d2 characterised by isoclinal typically north closing recumbent anticlines separated by pinched in synclines on the scale of tens of kilometres later deformation phases d3 and d4 warped the stack into wavy to open folds exhumation of this zone resulted locally in later vertical shortening and folding of already steep fabrics d5 three dimensional models of the nappe pile were constructed based on geostatistical assessment of the regional foliation field and considering the abundant structural field data these models indicate the existence of five principal tectonostratigraphic levels developed during d1 and thus equivalent to nappe units s str the gotthard the leventina antigorio the maggia simano and probably the monte leone as well as the composite lepontine series lebendun soja and adula cima lunga levels all these tectonic units formed part of the passive continental margin of europe prior to the onset of the alpine orogenesis individual isoclinal post nappe folds reflect relative displacements on the order of 40 km or more the most prominent d2 post nappe structure is the wandfluhhorn fold structurally equivalent to the northern closure of the leventina lucomagno antiform the lebendun and monte leone folds are of similar magnitudes and also affect the whole nappe pile whereas the smaller mogno and molare synforms only refold the maggia simano nappe internally principal d3 and d4 structures are the tight mergoscia synform directly north of the insubric fault between bellinzona and locarno southern steep belt the maggia steep zone forming the steep western limb of the campo tencia synform and subdividing the lepontine dome into the simplon and ticino subdomes the chiera synform steepening the dominant foliation in the north northern steep belt and the vanzone and claro antiforms steepening the dominant foliation in the south southern steep belt the current geometry of the northern and southern steep belts reflects an interplay between d4 and d3 involving both fold interference and reactivation tightening

limestone dissolution processes in beke doline aggtelek national park hungary aggtelek national park hungary is a limestone karst upland characterized by karren dolines and river caves for a period of two years climatic and carbonate dissolution variables were monitored at four depths in a 7 5 m shaft through the soil fill in the floor of a typical large 150 m diameter doline results are compared to other monitoring stations in the shallow soils on side slopes runoff and groundwater flow are focused into the base of the doline soil fill where moisture is maintained at 70 90 per cent field capacity and temperatures permit year round production of soil co2 the capacity to dissolve calcite limestone ranges from c 3 g m 2 per year beneath thin soils on the driest slopes to 17 30 g m 2 per year in the top 1 2 m of doline fill and at its base 5 7 m below 1997 john wiley sons ltd

new gravity maps of the eastern alps and significance for the crustal structures abstract the deep seismic profile t ransalp crosses from north to south germany austria and italy the gravity measurements for each country were made by national agencies with different reference systems and data reduction methods within the frame of the t ransalp project a comprehensive database of the eastern alps was compiled covering an area of 3 5 by 4 in longitude and latitude 275 by 445 km respectively to increase the data coverage in the south alpine area two gravity surveys were carried out resulting in 469 areally distributed new stations of which 215 have been measured with the intent to improve the geoid in the area of the planned brenner basistunnel bbt the resulting gravity database is the best in terms of resolution and data quality presently available for the eastern alps here the free air bouguer and isostatic gravity fields are critically discussed the spatial density of existing gravity stations in the three countries is discussed on the italian side of the alps the spatial density is rather sparse compared to the austrian side the bouguer gravity field varies between 190 10 5 m s2 and 25 10 5 m s2 with the minimum located along the alpine high topographic chain but with a small offset a few tens of km to the greatest topographic elevation showing that the airy type local isostatic equilibrium does not fully apply here the maximum of the bouguer anomaly has an elongated shape of 100 by 50 km located between the towns of verona and vicenza and covers the venetian tertiary volcanic province vtvp a feature not directly related to the plate collision in the eastern alps the gravity high is only partly explainable by high density magmatic rocks and requires also a deeper source like a shallowing of the moho the isostatic residual anomalies airy model are in the range 50 10 5 m s2 with the greatest positive anomaly corresponding to the location of the vtvp indicating here under compensation of masses at last a discussion of a 2d density model based on reflection seismic data and receiver functions is made

living on the edge evaluating the impact of stress factors on animal sediment interactions in subenvironments of a shelf margin delta the mayaro formation trinidad abstract integrating sedimentological and ichnological characteristics of the gelasian mayaro formation along the se coast of trinidad allows recognition of a river dominated and wave influenced shelf edge deltaic succession of the paleo orinoco river developed under strong slope instability four main sedimentary settings and twelve subenvironments developed on and beyond the outer shelf i e at the shelf margin have been identified extreme paleoenvironmental conditions make the succession rarely and sporadically colonized ichnologic evidence suggests that shelf edge deltas are among the most stressful marine environments due to a combination of physicochemical factors in response to the intrinsic sedimentary processes and the relative hierarchy of their influences specific to every subenvironment within any particular subenvironment the relative dominance of the fluvial feeder system the action of waves and rare influence of tides and slope instability determine the combinations and ranking of stress factors river dominated shelf edge delta subenvironments demonstrate the extreme influence of stress factors related to channel activity e g salinity changes high sedimentation and erosion rates flocculation of mud seasonal variations of fluvial flux whereas subenvironments dominated by waves storms and oceanic swells away from the axial feeder s are mostly influenced by barform morphodynamics and its effects on local physiography the paleo orinoco delta is represented not only by the delta lobe s developed at the shelf edge but by delta lobe s formed on the outer shelf as well outer shelf deltaic subenvironments manifest typical ichno sedimentological signatures of a normal wave influenced in this case inner shelf delta being susceptible to extensive gravitational instabilities the delta system suffered from canyonization and smaller gullying and subsequent filling n b hereafter we use the term canyon for both canyons and smaller gullies the shelf edge delta system was also associated with shelf attached mass transport systems such depositional subenvironments dominated by slope instability and sediment gravity flows appear to be the most unconducive for benthic colonization resulting in almost complete absence of bioturbation characterization of the stress factors as the functions of parameters arising from specific sedimentary and or oceanographic processes chemical conditions and preservational constraints specific to each subenvironment leads to the construction of a comprehensive ichnological and depositional analog model for shelf edge deltas in general and for the accommodation driven low latitude shelf edge deltas at an active oblique foreland setting in particular

deep electrical resistivity tomography for the prospection of low to medium enthalpy geothermal resources summary the growth of the geothermal industry sector requires innovative methods to reduce explo ration costs whilst minimizing uncertainty during subsurface exploration until now geoelec trical prospection had to trade between logistically complex cabled technologies reaching a few hundreds meters deep versus shallow reaching prospecting methods commonly used in hydro geophysical studies we present a recent technology for geoelectrical prospection and show how geoelectrical methods may allow the investigation of medium enthalpy geothermal resources until about 1 km depth the use of the new acquisition system which is made of a distributed set of independent electrical potential recorders enabled us to tackle logistics and noise data issues typical of urbanized areas we acquired a 4 5 km long 2 d geoelectrical survey in an industrial area to investigate the subsurface structure of a sedimentary sequence that was the target of a 700 m geothermal exploration well geo 01 satigny in the greater geneva basin western switzerland to show the reliability of this new method we compared the acquired resistivity data against reflection seismic and gravimetric data and well logs the processed resistivity model is consistent with the interpretation of the active seismic data and density variations computed from the inversion of the residual bouguer anomaly the combination of the resistivity and gravity models suggest the presence of a low resistivity and low density body crossing mesozoic geological units up to palaeogene neogene units that can be used for medium enthalpy geothermal exploitation our work points out how new geoelectrical methods may be used to identify thermal groundwater at depth this new cost efficient technology may become an effective and reliable exploration method for the imaging of shallow geothermal resources

evolution of mg fe ratios in late variscan plutonic rocks from the external crystalline massifs of the alps france italy switzerland late variscan plutonic bodies are widespread in the external raumer et al 1993 menot et al 1994 from south to crystalline massifs of the alps argentera pelvoux belledonne north they are the argentera pelvoux belledonne grandes rousses mont blanc aiguilles rouges aar gotthard grandes rousses mont blanc and aiguilles rouges they can be classified on the basis of their mg fe mg ratio massifs western alps and the aar and gotthard massifs and mafic mineral content expressed by the b fe mg central alps fig 1 they appear as dome like structi parameter together with available ages of emplacement this tures of crystalline basement surrounded by a mostly classification highlights the existence of two plutonic suites one mesozoic sedimentary cover as a whole they define an early visean 330 340 ma and highly magnesian the other arcuate structure possibly inherited from the variscan later mainly stephanian 295 305 ma and more ferriferous orogeny bogdanoff et al 1991 this evolution from a magnesian plutonism to a more ferriferous during the variscan orogeny the ecm were part of one which also occurs in other variscan massifs e g corsica the helvetic moldanubian terrane of the internal zone might be accounted for by a combination of factors related to the of the variscides von raumer neubauer 1993 nature of the source of the magmas the physical and chemical precambrian metamorphic units and precambrian to conditions of melting and the late variscan geodynamic setting palaeozoic sediments interlayered with volcanic and as a basis for these considerations a comprehensive review is ultramafic rocks display in most areas a polymetamorphic presented of all the external crystalline massifs and their history and underwent a highly complex pre variscan late variscan intrusions and variscan evolution although they share a number of similarities the ecm each have also specific characteristics von raumer et al 1993 in addition to orthogneisses deriving from early palaeozoic plutonic and volcanic protoliths bussy von

quantifying postglacial sediment storage at the mountain belt scale sediment storage is an often neglected term in sediment budgets despite being the crucial link between rates of erosion and sediment yield mountain belts in particular host large valley fills that modulate fluxes of water and sediment buffer the geomorphic coupling between hillslopes and river channels reduce local valley relief and protect bedrock from fluvial incision here we propose a region growing algorithm based on a slope gradient criterion to automatically extract areas of postglacial fluvial and lacustrine valley fills from digital topography at the mountain belt scale applying this method to the european alps we find that the size frequency relationship of 17 766 individual sediment storage units expressed by either area or volume follows a power law over four and five orders of magnitude with scaling exponents 1 77 and 1 71 respectively we show that 90 of the area covered by sediment storage is in the lower quartile of the mountain belt9s elevation and below the median local relief on average low gradient valley fill occupies 6 of the studied drainage basins this fraction increases with basin size likely reflecting the larger accommodation space of trunk valleys generated by multiple glacial interglacial cycles comparison with sediment storage mapped in the southern alps new zealand indicates that rates of uplift and precipitation control the extent and spatial distribution of sediment storage at the mountain belt scale

subsoil carbonate dissolution rates and their determining factors in a karst drainage basin sw china subsoil carbonate dissolution is the drives of atmosphere co2 consumption underground water alkalinity and karst landform specifically the determining factors and corresponding dissolution models for subsoil carbonate dissolution rate text r text carb remain under researched in various seasons and soil profiles in situ with standard limestone tablets they are the results of both ecosystem dynamics and hydrological processes thus this study aimed to explore text r text carb under different seasons soil depths and water drainage conditions in a karst drainage basin and reveal the factors determining them six hundred eighty four standard limestone tablets were exposed to fields in the subsoil of 10 cm 20 cm 30 cm and 40 cm deep sixteen plots five sites over every 3 to 4 months in a total of 423 days in the basin of the miaoguang underground river in southwest china the determining factors including soil co2 concentration moisture content temperature and ph were monitored at the same time the results are summarized in the following statements text r text carb ranged from 0 39 to 18 15 mg cm 2 a 1 were in a clear seasonal pattern principal component analysis pca of the observed soil factors revealed the mechanisms that in hot and rainy summer high text r text carb occurred in an open system with continuously supplemented co2 period i and decreased with rainfall amount period iv low text r text carb occurred in a closed system with inactive biological co2 production under cold weather period ii and iii hence as soil temperature decreased text r text carb increased text r text carb increased with soil depths as the elevated soil co2 temperature and available acid water dissolution occurred in an open system on an annual average scale and a well fitting equation of text r text carb and soil factors were given local water drainage was critical in carbonate chemical dissolving with implications of formations of local karst landform due to no or less groundwater drain and spring seepage text r text carb measured in site b a flat saddle with underlying dolomite bedrock was nearly zero conversely with water retention text r text carb was higher in gentle limestone hillslope or depression than in steep hillside because of longer water rock interaction duration in general in karst drainage basin areas text r text carb was determined by multiple factors about seasons soil depths and water drainage

plio pleistocene climate evolution trends and transitions in glacial cycle dynamics abstract we describe the evolution of climate system dynamics by examining the climate response to changes in obliquity and precession over the last 5 3 myr in particular we examine changes in the shape of glacial cycles and the power of obliquity and precession response in benthic 18 o when the exponential trend in 18 o variance is removed its spectral power exhibits strong proportional responses to amplitude modulations in orbital forcing over most of the plio pleistocene precession responses correlate with modulations in forcing for the last 5 myr but 41 kyr response is sensitive to obliquity modulation only before 1 4 myr where responses are sensitive to modulations in forcing we demonstrate that glacial cycles are orbitally forced rather than being self sustained or paced by orbital changes the shapes of glacial cycles have several nonlinear properties which may be indicative of glacial interglacial differences in climate sensitivity or response time the saw tooth asymmetry of glacial cycles first appears shortly after the onset of major northern hemisphere glaciation and the relative duration of interglacial stages decreases at 1 4 myr collectively trends in the shape of glacial cycles and the sensitivity of 18 o to obliquity and precession are suggestive of major transitions in climate dynamics at approximately 2 5 and 1 4 myr but show no significant change associated with the appearance of strong 100 kyr cycles during the mid pleistocene transition

late pliocene pleistocene high resolution pollen sequence of colombia an overview of climatic change two long continental pollen records funza i 357 m and funza ii 586 m from the high plain of bogota colombia at 2550 m elevation have been studied palynologically fission track dates on zircon from intercalated volcanic ashes provided a chronological framework and showed the pollen records which correlate with high precision to be continuous over the interval from ca 3 2 ma to ca 27 ka the late pliocene pleistocene history of the montane forests and open alpine paramo vegetation is documented with a temporal resolution of ca 6 5 ka and for the upper 1 1 ma with a resolution of ca 1 2 ka the immigration of the northern hemisphere elements alnus at ca 1 ma and quercus at ca 0 33 ma which travelled along the panamanian landbridge caused significant changes in the composition of the andean montane forests the successive pleistocene glaciations forced the andean vegetation belts to an almost continuous altitudinal movement the upper forest line at present at ca 3200 m shifted between 1800 m glacials and ca 3500 m interglacials corresponding to a variation in temperature between ca 5 and 15 c at 2550 m altitude a provisional land sea correlation funza pollen odp site 677 18o is shown for the upper 1 2 ma stages 3 35 frequency analysis of several time series showed significant periods of the eccentricity 100 ka and precession 23 and 19 ka bands showing orbital forcing and a strong change in climatic variability around 800 ka at ca 2 7 ma a significant cooling of ca 5 c is documented reflecting the classical terrestrial pliocene pleistocene boundary which correlates to the reuverian praetiglian boundary of the nw european stratigraphical climatic subdivision

coupled 100 kyr cycles between 3 and 1 ma in terrestrial and marine paleoclimatic records earth s climate over the last one million years experienced several 100 kyr glacial cycles but no simple forcing mechanism has been identified numerous studies have tried to explain strong 100 kyr glacial cycles without recognizable forcing which has come to be known as the 100 kyr problem few studies have examined 100 kyr band paleoclimatic signals before 1 ma a recent study has demonstrated that benthic oxygen and carbon isotope records are phase locked and amplitude coupled at the 100 kyr band but that neither is phase locked to and amplitude coupled with the 100 kyr eccentricity signal between 3 and 1 ma this phasing and amplitude mismatch of the 100 kyr band between 3 and 1 ma between marine records and the eccentricity forcing signal has been called the late pliocene early pleistocene 100 kyr problem however it remains unknown whether terrestrial paleoclimate records are consistent with marine records at the 100 kyr band here i show that loess monsoon records from china are amplitude coupled with benthic oxygen and carbon isotope records at the 100 kyr band but not with the 100 kyr eccentricity forcing between 3 and 1 ma this observation provides further evidence in support of a free 100 kyr oscillation as the cause of the 100 kyr band amplitude variability in paleoclimatic records between 3 and 1 ma in contrast benthic oxygen isotope records and loess monsoon records at the 100 kyr band are not amplitude coupled with 100 kyr benthic carbon isotope records over the last 0 4 million years indicating that the late pleistocene 100 kyr climatic cycles may not result exclusively from a free oscillation

comparison of different digital elevation models and satellite imagery for lineament analysis implications for identification and spatial arrangement of fault zones in crystalline basement rocks of the southern black forest germany abstract gis based remote sensing techniques and lineament mapping provide additional information on the spatial arrangement of faults and fractures in large areas with variable outcrop conditions due to inherent censoring and truncation bias mapping of lineaments is still a challenging task in this study we show how statistical evaluations help to improve the reliability of lineament mappings by comparing two digital elevation models aster lidar and satellite imagery data sets in the seismically active southern black forest a statistical assessment of the orientation average length and the total length of mapped lineaments reveals an impact of the different resolutions of the data sets that allow to define maximum censoring bias and minimum truncation bias observable lineament length for each data set the increase of the spatial resolution of the digital elevation model from 30 m 30 m to 5 m 5 m results in a decrease of total lineament length by about 40 whereby the average lineament lengths decrease by about 60 lineament length distributions of both data sets follow a power law distribution as documented elsewhere for fault and fracture systems predominant ne n nnw and nw directions of the lineaments are observed in all data sets and correlate with well known mappable large scale structures in the southern black forest therefore mapped lineaments can be correlated with faults and hence display geological significance lineament density in the granite dominated areas is apparently higher than in the gneiss dominated areas application of a slip and dilation tendency analysis on the fault pattern reveals largest reactivation potentials for wnw ese and n s striking faults as strike slip faults whereas normal faulting may occur along nw striking faults within the ambient stress field remote sensing techniques in combination with highly resolved digital elevation models and a slip and dilation tendency analysis thus can be used to quickly get first order results of the spatial arrangement of critically stressed faults in crystalline basement rocks

evolution of solution dolines inferred from cosmogenic 36cl in calcite quantification of the development of solution dolines provides important information for understanding the long term evolution of karst landscapes this study reports the initial results of an investigation of the long term denudation rates along the side slopes of a solution doline based on analyses of cosmogenic 36 cl in calcite the denudation rates increase in proportion with increasing size of the topographic contributing area thereby supporting the hypothesis that the rate of surface lowering in carbonate terrains is controlled by water convergence in the epikarst a simple model based on the empirical correlation between denudation rate and contributing area is successful in explaining the form of several solution dolines located close to the analyzed doline the model reveals that these solution dolines which have varying diameters developed over similar time scales of the order of 10 5 yr

high frequency stacking pattern and stages of canyon gully evolution across a forced regressive shelf edge delta front abstract the succession of varying facies tracts filling within a canyon or a deep incised gully cutting across the delta front lobes at the shelf edge requires to be explained by high frequency allocyclic and or autocyclic events a fifth and sixth order sequence stratigraphic model for the shelf edge canyon fill or gully fill is here proposed for the first time the first gelasian cold phase and the renewal of transpressional uplift of basin margin occurring at the same time enforced regressive transit of the inner shelf paleo orinoco delta onto the paleo shelf edge its delta front developed along the shoulders of the major successive basin bounding growth faults the delivery of clastic sediments into the deeper slope and beyond in the columbus basin was through the gullies and canyons that incised and cannibalized across the shelf edge delta the mayaro formation of southeast trinidad furnishes the role of growth faulting during the first phase of delta front development at the paleo shelf edge thereby it serves as an example of several fifth order sequences within a fourth order equivalent episode which is contemporaneous to both the glacio eustatic episode the pretiglian and the renewal of transpressional uplift after a pause during the pliocene thus large incision and subsequent filling within the mayaro formation cover a passage of time fifth order equivalent that is unequivocally shorter than the span of the falling pretiglian eustatic sea level and second renewed phase of transpression tectonism the categorization of sedimentary facies of the canyon fill or gully fill and the encasing delta front outside the canyon gully cut into a series of sixth order genetic facies tracts shows variations of geomorphic stages of the canyon gully evolution from accommodation creation to the stages of filling these stages therefore should be attributed to the sixth order equivalent autogenic changes influenced by high frequency growth tectonics instead of assuming the stages to be related to the relatively lower frequency glacio eustatic allocyclicity of the earliest gelasian

chronostratigraphy and tectonostratigraphy of the columbus basin eastern offshore trinidad the columbus basin forming the easternmost part of the eastern venezuela basin is situated along the obliquely converging margins of the caribbean and south american plates the two primary structural elements that characterize the basin are 1 transpressional northeast southwest trending anticlines and 2 northwest southeast oriented down to the northeast extension normal faults the basin was filled throughout the pliocene and pleistocene by more than 40 000 ft 12 200 m of clastic sediment supplied primarily by the paleo orinoco delta system the delta prograded eastward over a storm influenced and current influenced shelf during the pliocene pleistocene depositing marine and terrestrial clastic megasequences as a series of prograding wedges atop a lower pliocene to pre pliocene mobile shale facies biostratigraphic and well log data from 41 wells were integrated with thousands of kilometers of interpreted two dimensional and three dimensional seismic data to construct a chronostratigraphic framework for the basin as a result several observations were made regarding the basin s geology that have a bearing on exploration risk and success 1 megasequences wedge bidirectionally 2 consideration of hydrocarbon system risk across any area requires looking at these sequences as complete paleofeatures 3 reservoir location is influenced by structural elements in the basin 4 the lower limit of a good quality reservoir in any megasequence deepens the closer it comes to the normal fault bounding the wedge in a proximal location 5 reservoir quality of deep marine strata is strongly influenced by both the type of shelf system developed bypass or aggradational and the location of both subaerial and submarine highs and 6 submarine surfaces of erosion partition the megasequences and influence hydrostatic pressure migration and trapping of hydrocarbons and the distribution of hydrocarbon type begin page 1906

three dimensional interface modelling with two dimensional seismic data the alpine crust mantle boundary summary we present a new approach to determine the 3 d topography and lateral continuity of seismic interfaces using 2 d derived controlled source seismic reflector data the aim of the approach is to give the simplest possible structure consistent with all reflector data and error estimates we define simplicity of seismic interfaces by the degree of interface continuity i e shortest length of ovsets and by the degree of interface roughness least surface roughness the method is applied to structural information of the crust mantle boundary moho obtained from over 250 controlled source seismic reflection and refraction profiles in the greater alpine region the reflected and refracted phases from the moho interface and their interpretation regarding crustal thickness are reviewed and their reliability weighted weights assigned to each reflector element are transformed to depth errors considering fresnel volumes the 2 d derived reflector elements are relocated in space 3 d migration and interpolation is performed between the observed reflector elements to obtain continuity of model parameters interface ovsets are introduced only where required according to the principle of simplicity the resulting 3 d model of the alpine crust mantle boundary shows two ovsets that divide the interface into a european an adriatic and a ligurian moho with the european moho subducting below the adriatic moho and with the adriatic moho underthrusting the ligurian moho each sub interface depicts the smoothest possible i e simplest surface fitting the reflector data within their assigned errors the results are consistent with previous studies for those regions with dense and reliable controlledsource seismic data the newly derived alpine moho interface however surpasses earlier studies by its lateral extent over an area of about 600 km by 600 km by quantifying reliability estimates along the interface and by obeying the principle of being consistently as simple as possible

orbital insolation ice volume and greenhouse gases abstract the specmap models of orbital scale climate change imbrie et al paleoceanography 7 1992 701 paleoceanography 8 1993 699 are the most comprehensive to date all major climatic observations were analyzed within the framework of the three orbital signals subsequently tuning of signals in vostok ice to insolation forcing has fixed the timing of greenhouse gas changes closely enough to permit an assessment of their orbital scale climatic role in addition evidence from several sources has suggested changes in the specmap 18 o time scale this new information indicates that the timing of co 2 changes at the periods of precession and obliquity does not fit the 1992 specmap model of a train of responses initiated in the north propagated to the south and later returning north to force the ice sheets in addition analysis of the effects of rectification on 100 000 year climatic signals reveals that all have a phase on or near that of eccentricity this close clustering of phases rules out the long time constants for 100 000 year ice sheets required by the 1993 specmap model a new hypotheses presented here revives elements of an earlier climap view hays et al science 194 1976a 1121 but adds a new assessment of the role of greenhouse gases as proposed by milankovitch summer mid july insolation forces northern hemisphere ice sheets at the obliquity and precession periods with an ice time constant derived here of 10 000 years changes in ice volume at 41 000 years drive ice proximal signals sst nadw dust that produce a strong positive co 2 feedback and further amplify ice volume changes at the precession period july insolation forces ice sheets but it also drives fast and early responses in ch 4 through changes in tropical monsoons and boreal wetlands and variations in co 2 through southern hemisphere processes these ch 4 and co 2 responses enhance insolation forcing of ice volume climatic responses at 100 000 years result from eccentricity pacing of forced processes embedded in obliquity and precession cycles increased modulation of precession by eccentricity every 100 000 years produces 23 000 year co 2 and ch 4 maxima that enhance ablation caused by summer insolation and drive climate deeper into an interglacial state when eccentricity modulation decreases at the 100 000 year cycle ice sheets grow larger in response to obliquity forcing and activate a 41 000 year co 2 feedback that drives climate deeper into a glacial state alternation of these forced processes because of eccentricity pacing produces the 100 000 year cycle the 100 000 year cycle began 0 9 myr ago because gradual global cooling allowed ice sheets to survive during weak precession insolation maxima and grow large enough during 41 000 year ice volume maxima to generate strong positive co 2 feedback the natural orbital scale timing of these processes indicates that ice sheets should have appeared 6000 3500 years ago and that co 2 and ch 4 concentrations should have fallen steadily from 11 000 years ago until now but new ice did not appear and co 2 and ch 4 began anomalous increases at 8000 and 5000 years ago respectively human generation of co 2 and ch 4 is implicated in these anomalous trends and in the failure of ice sheets to appear in canada

dissolution rates of subsoil limestone in a doline on the akiyoshi dai plateau japan an approach from a weathering experiment hydrological observations and electrical resistivity tomography abstract this study aims at estimating the controlling factors for the denudation rates of limestone which often forms solution dolines on karst tablelands our approaches include 1 electrical resistivity tomography ert to reveal shallow subsurface structures and hydrological settings 2 automated monitoring of volumetric water content in soil profiles and manual measurements of subsurface co2 concentrations and soil water chemistry and 3 a field weathering experiment using limestone tablets with the micro weight loss technique for determining current denudation rates the field experiment and monitoring were carried out over 768 days from 2009 2011 at four sites with varying topographic and hydrological conditions along the sideslope of a doline on the akiyoshi dai karst plateau in sw japan the installation depths of the limestone tablets were 15 cm or 50 cm below the slope surface the soil moisture conditions varied site by site water saturated conditions continued for 40 50 of the whole experimental period at 50 cm depth of upper and middle sites while only 0 10 of the experimental period was water saturated at the other sites chemical analysis revealed that the soil water was chemically unsaturated with calcite for all the sites spatial differences in concentrations of co2 in soil pore air were statistically less significant the denudation rates of the buried limestone tablets were 17 7 21 9 mg cm 2 a 1 at the upper and middle slopes where the soil was water saturated for a long time after precipitation the lowest denudation of 3 9 mg cm 2 a 1 was observed on lower slopes where soil was not capable of maintaining water at a near saturation level even after precipitation statistical analysis revealed that the denudation rates of the tablets were strongly controlled by the duration for which soil pores were saturated by water the conditions defined here are degrees of water saturation greater than 97 electrical resistivity tomography indicated that areas with high soil moisture conditions were located at the deeper zone on the lower slopes and the bottom of the doline where denudation would be faster

regional structure and tectonic history of the obliquely colliding columbus foreland basin offshore trinidad and venezuela abstract cenozoic eastward migration of the caribbean plate relative to the south american plate is recorded by an 1100 km long venezuela trinidad foreland basin which is oldest in western venezuela 65 55 ma of intermediate age in eastern venezuela 34 20 ma and youngest beneath the shelf and slope area of eastern offshore trinidad submarine columbus basin 15 0 ma recent in this study of the regional structure fault families and chronology of faulting and tectonic events affecting the hydrocarbon rich columbus foreland basin of eastern offshore trinidad we have integrated approximately 775 km of deep penetration 2d seismic lines acquired by the 2004 broadband ocean land investigations of venezuela and the antilles arc region bolivar survey 325 km of vintage gulfrex seismic data collected by gulf oil company in 1974 and published industry well data that can be tied to some of the seismic reflection lines top cretaceous depth structure maps in the columbus basin made from integration of all available seismic and well data define for the first time the elongate subsurface geometry of the 11 15 km thick and highly asymmetrical middle miocene recent depocenter of the columbus basin the main depocenter located 150 200 km east of trinidad and now the object of deepwater hydrocarbon exploration is completely filled by shelf and deepwater sediments derived mainly from the orinoco delta the submarine darien ridge exhibits moderate 20 140 m seafloor relief forms the steep 12 24 northern structural boundary of the columbus basin and is known from industry wells to be composed of 0 5 4 5 km thick folded and thrust imbricated hydrocarbon bearing section of cretaceous and early tertiary limestones and clastic rocks the eastern and southern boundaries of the basin are formed by the gently 1 7 4 5 northward dipping cretaceous paleogene passive margin of south america that is in turn underlain by precambrian rocks of the guyana shield interpretation of seismic sections tied to wells reveals the following fault chronology 1 middle miocene thrusting along the darien ridge related to highly oblique convergence between the caribbean plate and the passive margin of northern south america continuing thrusting and transpression in an oblique foreland basin setting through the early pleistocene 2 early pliocene recent low angle normal faults along the top of the cretaceous passive margin these faults were triggered by oversteepening related to formation of the downdip structurally and bathymetrically deeper and more seaward columbus basin large transfer faults with dominantly strike slip displacements connect gravity driven normal faults that cluster near the modern shelf slope break and trend in the downslope direction to the south no normal faults are present because the top cretaceous horizon has not been oversteepened as it is adjacent to the foreland basin 3 early pliocene recent strike slip faults parallel the trend of the darien ridge and accommodate present day plate motions

structure of the lithosphere beneath the eastern alps southern sector of the transalp transect abstract the interpretation of the seismic vibroseis and explosive transalp profiles has examined the upper crustal structures according to the near surface geological evidences and reconstructions which were extrapolated to depth only the southern sector of the transalp transect has been discussed in details but its relationship with the whole explored chain has been considered as well the seismic images indicate that pre collision and deep collision structures of the alps are not easily recognizable conversely good records of the neo alpine to present architecture were provided by the seismic sections two general interpretation models crocodile and extrusion have been sketched by the transalp working group 2002 both illustrate the continental collision producing strong mechanical interaction of the facing european and african margins as documented by giant lithosphere wedging processes arguments consistent with the extrusion model and with the indentation of adriatic southalpine lithosphere underneath the tauern window tw are according to the previous dss reconstructions the bouguer anomalies and the receiver functions seismological data the european moho descends regularly attaining a zone south of the periadriatic lineament pl the moho boundary and its geometry appear to be rather convincing from images of the seismic profile the tauern window intense uplift and exhumation is coherent with the strong compression regime which acted at depth thus originating the upward and lateral displacement of the mobile and ductile penninic masses according to the extrusion model the indentation of the penninic mobile masses within the colder and more rigid adriatic crust cannot be easily sustained wedging of the adriatic stiffened lower crust under high stresses and into the weaker penninic domain can be a more suitable hypothesis furthermore the intrusion of the european penninic crustal wedge underneath the dolomites upper crust is not supported by any significant uplifting of the dolomites the total average uplift of the dolomites during the neogene appears to be 6 7 times smaller than that recognized in the tw markedly the northward dip of the pl reaching a depth of approximately 20 km is proposed in our interpretation finally the adriatic upper crustal evolution points to the late post collision change in the tectonic grow up of the eastern alps orogenic chain the tectonic accretion of the northern frontal zone of the eastern and central alps was interrupted from the late miocene serravallian tortonian onward as documented by the molasse basin evolution on the contrary the structural nucleation along the s vergent tectonic belt of the eastern southern alps montello friuli thrust belt severely continued during the messinian and the plio pleistocene this structural evolution can be considered to be consistent with the deep under thrusting and wedge indentation of the adriatic lithosphere underneath the southern side of the eastern alps thrust and fold belt similarly the significance of the magmatic activity for the construction of the southern alps crust and for its mechanical and geological differentiation which qualified the evolution of the thrust and fold belt is highlighted starting with the permian triassic magmatism and progressing with the paleogene occurrences along the periadriatic lineament and in the venetian magmatic province lessini euganei hills

the interplay between eustacy tectonics and surface processes during the growth of a fault related structure as derived from sequence stratigraphy the govora ocnele mari antiform south carpathians abstract orogenic collision represents a moment when typical rules of thin skinned development are at odds with the generalized interaction between the upper and buoyant lower plate deriving the kinematics of these collisional features is usually difficult because of the large amounts of subsequent erosion study areas such as those that exist along the south carpathians foredeep where the syn and post collisional sediments are still preserved are important places to identify record and quantify out of sequence deformation here sequence stratigraphic techniques may be used in order to detect tectonic movements which are an order of magnitude higher resolution than those routinely identified by either standard structural analysis or isotope geochronology this study proves that what has been previously interpreted as a one stage growing anticline situated at the contact with the core of the orogen is in fact a gradually evolving antiform structure with at least four quantifiable pulses of vertical movements associated with various amounts of orogenic uplift during collision the interplay between the orogenic core and the anticline uplift controls the depositional area the effects of sea level variations being subordinated transversal shear zones such as strike slip faults are used as transport corridors by the progressive infill of large quantities of sediments from the source area towards the larger basins situated more to the foreland

sequence stratigraphy and architectural variability in growth fault bounded basin fills a review of plio pleistocene stratal units of the crotone basin southern italy field examples from the pliocene to pleistocene succession of the crotone basin document the variability of stratal architecture in syntectonic units deposited in normal fault bounded basins relatively thick trangressive intervals are common within these successions as shown in the zinga 2 zinga 3 and strongoli stratal units transgressive packages are formed by lagoonal mudstones that are abruptly overlain by shoreface sandstones aggradational highstand shallow marine packages are typical of the lower pliocene succession in half graben basins these deposits resulted from balanced conditions between the rate of sediment supply and the rate of creation of accommodation relatively thick forced regressive deposits are common within basins during phases where the accommodation supply ratio is low e g the middle pleistocene san mauro sandstone these deposits influenced by growth faulting and folding recorded base level lowering linked to glacio eustasy a complex stratal architecture may be the consequence of the alternation between tectonic subsidence and uplift e g the serra piani stratal unit such variations are thought to be related to the onset of an earliest mid pliocene transpressional tectonic phase the studied deposits therefore show a marked tectonic control that strongly influenced their stratal architecture these examples represent interesting cases of sequence stratigraphic analysis in growth faulted contexts

slow physics of large continental ice sheets and underlying bedrock and its relation to the pleistocene ice ages very simple two component models of the earth s cryosphere lithosphere system are analyzed the models consist of a continental ice sheet coupled to a responding earth model because of relatively long response times of the bedrock at least over shorter wavelengths long period of the order of 50 000 years internal or free oscillations in the system occur over a wide range of parameters and parameterizations the oscillatory mechanism operates primarily in the ablation zone and in particular at the firn line these free oscillations could play a dynamic role in the response of the climate system to eccentricity forcing a simple analysis presented strongly suggests that for the simplest rheological models of the earth response to pleistocence ice sheets elastic response is confined to a layer considerably less than the thermal thickness of the lithosphere furthermore because of the striking lack of geological evidence for large depressions of bedrock at the leading edge of growing continental ice sheets predicted by viscoelastic models of the earth more sophisticated rheological models of the earth s uppermost layer appear necessary

apatite fission track analysis in the argentera massif evidence of contrasting denudation rates in the external crystalline massifs of the western alps apatite fission track dating from a central transect in the argentera massif southernmost external crystalline massif ecm yielded ages between 8 05 0 6 and 2 4 0 2 myr with a positive age altitude correlation above 3 ma 1200 m recognising a thermal peak at c 250 c 33 ma based on stratigraphic metamorphic and 39ar 40ar data the present results suggest a slow cooling rate 8 5 c for the argentera massif during the oligocene early pliocene this rate compares with that from the pelvoux massif but contrasts with those observed in the northern ecm mont blanc and aar up to 14 c myr 1 for the same time interval this can be related to the different location of the ecm within the collided european margin at about 3 4 ma the denudation rate would have increased up to c 1 mm yr 1 in the argentera massif reaching the same value as in the belledonne and northern ecm likely a consequence of penninic thrust inversion

a high resolution model of the 100 ka ice age cycle significant improvements to the representation of climate forcing and mass balance response in a coupled two dimensional global energy balance climate model ebm and vertically integrated ice sheet model ism have led to the prediction of an ice volume chronology for the most recent ice age cycle of the northern hemisphere that is close to that inferred from the geological record most significant is that full glacial termination is delivered by the model without the need for new physical ingredients in addition a relatively close match is achieved between the last glacial maximum lgm model ice topography and that of the recently described ice 4g reconstruction these results suggest that large scale climate system reorganization is not required to explain the main variations of the north american na ice sheets over the last glacial cycle lack of sea ice and marine ice dynamics in the model leaves the situation over the eurasian ea sector much more uncertain the incorporation of a gravitationally self consistent description of the glacial isostatic adjustment process demonstrates that the na and ea bedrock responses can be adequately represented by simpler damped relaxation models with characteristic time scales of 3 5ka and 5 ka respectively these relaxation times agree with those independently inferred on the basis of postglacial relative sea level histories

origin of warm springs in banks peninsula new zealand abstract thermal springs present rare opportunities to locate and interpret the geological drivers of upper crustal fluid flow interpreting the conditions through which crustal fluids are heated and released to the surface is important for advancing our understanding of crustal deformation and geothermal resource potential across tectonic contexts in new zealand the majority of thermal springs are associated with magmatic hydrothermal systems in the central north island or with the rapidly uplifting bedrock in the south island s convergent fault systems however low enthalpy systems outside of these areas represent attractive targets for potential geothermal resource development the low enthalpy warm springs of banks peninsula located immediately adjacent to christchurch represent a highly understudied but potentially significant resource to the south island s most densely populated metropolitan area hosted within the eroded 11 5 8 ma volcanic complex of banks peninsula these warm springs 14 5 33 6 c represent an anomalous hydrothermal system that has been perturbed by the 2010 2016 canterbury earthquake sequence ces the february 22 2011 mw 6 2 earthquake induced observable changes to the banks peninsula warm springs system including the appearance of new warm springs within the peninsula s north western hillsborough valley we assess the origins of the volcanically hosted banks peninsula warm springs post ces using an integrated isotopic geochemical and soil gas flux approach additionally we elucidate the tectonic context and geological drivers of upper crustal fluid flow in the banks peninsula warm spring system aqueous phase emissions from the springs predominantly plot within the na k hco3 type waters and exhibit 18 o d and 13 c values of 8 30 to 9 26 v smow 60 15 to 64 19 v smow and 12 37 to 15 06 v pdb respectively soil gas flux surveys of the springs at rapaki bay revealed co2 fluxes that average 6 93 10 gm 2 day 1 with an average 13 c value of 19 81 5 v pdb and ch4 fluxes that average 5 58 12 gm 2 day 1 with an average 13 c value of 59 52 1 v pdb our results suggest that the banks peninsula warm springs are a structurally controlled upper crustal metamorphic hydrothermal heated system sourced from high altitude southern alps derived meteoric waters carbon isotope compositions of gaseous emissions associated with the banks peninsula thermal springs are consistent with an upper crustal metamorphic decarbonation and decarboxylation carbon source based on their geochemistry we propose that the banks peninsula warm springs should be considered an outboard extension of the south island s plate boundary hydrothermal system such connectivity implies that long lived low enthalpy geothermal resources may be associated with permeable and distributed fault networks in the periphery of convergent margins

3d gravity inversion through an adaptive learning procedure we have developed a gravity inversion method to estimate a 3d density contrast distribution producing strongly interfering gravity anomalies the interpretation model consists of a grid of 3d vertical juxtaposed prisms in the horizontal and vertical directions iteratively our approach estimates the 3d density contrast distribution that fits the observed anomaly within the measurement errors and favors compact gravity sources closest to prespecified geometric elements such as axes and points this method retrieves the geometry of multiple gravity sources whose density contrasts positive and negative values are prescribed by the interpreter through the geometric element at the first iteration we set an initial interpretation model and specify the first guess geometric elements and their target density contrasts each geometric element operates as the first guess skeletal outline of the entire homogeneous gravity source or any of its homogeneous parts to be reconstructed from the second iteration on our method automatically redefines a new set of geometric elements the associated target density contrasts and a new interpretation model whose number of prisms increases with the iteration the iteration stops when the geometries of the estimated sources are invariant along successive iterations tests on synthetic data from geometrically complex bodies and on field data collected over a mafic ultramafic body and a volcanogenic sedimentary sequence located in the tocantins province brazil confirmed the potential of our method in producing a sharp image of multiple and adjacent bodies

assessment of doline geometry using geophysics on the quercy plateau karst south france in the protection of karstic aquifers the role played by dolines is of interest as these shallow structures can be preferential infiltration pathways for groundwater recharge in this study three depressions in south france orniac lot were identified and characterized using combined geophysical methods apparent conductivity mapping allows precise definition of dolines corresponding to topographic depressions it also reveals other dolines that are hidden by soil cover electrical resistivity and seismic refraction tomography provide detailed cross sections even though the dolines studied are close one to another they exhibit great variability in shape and content moreover time lapse data show that the most saturated regions are on the edges of the first doline such information helps to evaluate human impacts and forecast potential groundwater contamination

integration of 3d geological modeling and gravity surveys for geothermal prospection in an alpine region abstract thermal sources are common manifestations of geothermal energy resources in alpine regions the up flow of the fluid is well known to be often linked to cross cutting fault zones providing a significant volume of fractures since conventional exploration methods are challenging in such areas of high topography and complicated logistics 3d geological modeling based on structural investigation becomes a useful tool for assessing the overall geology of the investigated sites geological modeling alone is however less effective if not integrated with deep subsurface investigations that could provide a first order information on geological boundaries and an imaging of geological structures with this aim in the present paper the combined use of 3d geological modeling and gravity surveys for geothermal prospection of a hydrothermal area in the western alps was carried out on two sites located in the argentera massif nw italy the geothermal activity of the area is revealed by thermal anomalies with surface evidences such as hot springs at temperatures up to 70 c integration of gravity measurements and 3d modeling investigates the potential of this approach in the context of geothermal exploration in alpine regions where a very complex geological and structural setting is expected the approach used in the present work is based on the comparison between the observed gravity and the gravity effect of the 3d geological models in order to enhance local effects related to the geothermal system it is shown that a correct integration of 3d modeling and detailed geophysical survey could allow a better characterization of geological structures involved in geothermal fluids circulation particularly gravity inversions have successfully delineated the continuity in depth of low density structures such as faults and fractured bands observed at the surface and have been of great help in improving the overall geological model

transition from storm wave dominated outer shelf to gullied upper slope the mid pliocene orinoco shelf margin south trinidad shelf edge deltas are a key depositional environment for accreting sediment onto shelf margin clinoforms the moruga formation part of the palaeo orinoco shelf margin sedimentary prism of south east trinidad provides new insight into the incremental growth of a pliocene storm wave dominated shelf margin relatively little is known about the mechanisms of sand bypass from the shelf break area of margins and in particular from storm wave dominated margins which are generally characterized by drifting of sand along strike until meeting a canyon or channel the studied st hilaire siltstone and trinity hills sandstone succession is 260 m thick and demonstrates a continuous transition from gullied with turbidites uppermost slope upward to storm wave dominated delta front on the outermost shelf the basal upper slope deposits are dominantly mass transport deposited blocks as well as associated turbidites and debrites with common soft sediment deformed strata the overlying uppermost slope succession exhibits a spectacular set of gullies which are separated by abundant slump scar unconformities tops of rotational slides then filled with debris flow conglomerates and sandy turbidite beds with interbedded mudstones the top of the study succession on the outer shelf area contains repeated upward coarsening sandstone rich parasequences 2 to 15 m thick with abundant hummocky and swaley cross stratification clear evidence of storm swell and storm wave dominated conditions the observations suggest reconstruction of the unstable shelf margin as follows i the aggradational storm wave dominated shelf edge delta front became unstable and collapsed down the slope ii the excavated scars of the shelf margin became gullied but gradually healed aggraded by repeated infilling by debris flows and turbidites and then new gullying and further infilling and iii renewed storm wave dominated delta front prograded out across the healed outer shelf re establishing the newly stabilized shelf margin the moruga formation study along with only a few others in the literature confirms the sediment bypass ability of storm wave dominated reaches of shelf edges despite river dominated deltas being by far the most efficient shelf edge regime for sediment bypass at the shelf break this article is protected by copyright all rights reserved

integrated 3d geophysical and geological modelling of the hercynian suture zone in the champtoceaux area south brittany france this paper combines geological knowledge and geophysical imagery at the crustal scale to model the 3d geometry of a segment of the hercynian suture zone of western europe in the champtoceaux area brittany france the champtoceaux complex consists of a stack of metamorphic nappes of gneisses and micaschists with eclogite bearing units the exhumation of the complex during early carboniferous times was accompanied by deformation during regional dextral strike slip associated with a major hercynian shear zone the south armorican shear zone sasz dextral shearing produced a km scale antiformal structure with a steeply dipping axial plane and a steeply eastward plunging axis armor 2 deep seismic profile shows that the regional structure was cut by a set of faults with northward thrusting components based on the seismic constraint direct 2d crustal scale modelling was performed throughout the champtoceaux fold on seven radial gravity profiles also using geological data and density measurements from field and drill hole samples the 3d integration of the cross sections the digitised geological map and the structural information foliation dips insure the geometrical and topological consistency of all sources of data the 2d information is interpolated to the whole 3d space using a geostatistical analysis finally the 3d gravity contribution of the resulting model is computed taking into account densities for each modelled geological body and compared to the bouguer anomaly the final 3d model is thus compatible with the seismic and gravity data as well as with geological data main geological results derived from the modelling are i the overall 3d geometry of the south dipping thrust system interpreted on the seismic profile emphasises northward thrusting and folding of the champtoceaux complex which was coeval with strike slip along the south armorican shear zone ii the gravity modelling suggests the presence of a relatively dense body below the champtoceaux complex that could be interpreted as a result of relative uplift of midcrustal material during thrusting along the e w trending wrench thrust system iii the northern limb of the champtoceaux anticline is a relatively shallow feature and iv vigneux synkinematic granitic body is a laccolith sheared and rooted along the southern branch of the sasz and spreads away from the strike slip zone within weak country rocks d 2004 elsevier b v all rights reserved

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

the alpine swiss french airborne gravity survey summary in february 1998 a regional scale airborne gravity survey was carried out over the french occidental alps within the framework of the geofrance 3 d research program the survey consisted of 18 ns and 16 ew oriented lines with a spacing of 10 and 20 km respectively covering the whole of the western french alps total area 50 000 km2 total distance of lines flown 10 000 km the equipment was mounted in a medium size aircraft dehavilland twin otter flowing at a constant altitude of 5100 m a s l and at a mean ground speed of about 280 km h 1 gravity was measured using a lacoste romberg relative air sea gravimeter type sa mounted on a laser gyro stabilized platform data from 5 gps antennae located on fuselage and wings and 7 ground based gps reference stations were used to determine position and aircraft induced accelerations the gravimeter passband was derived by comparing the vertical accelerations provided by the gravimeter with those estimated from the gps positions this comparison showed that the gravimeter is not sensitive to very short wavelength aircraft accelerations and therefore a simplified formulation for computing airborne gravity measurements was developed the intermediate and short wavelength non gravitational accelerations were eliminated by means of digital exponential low pass filters cut off wavelength 16 km an important issue in airborne gravimetry is the reliability of the airborne gravity surveys when compared to ground surveys in our studied area the differences between the airborne acquired bouguer anomaly and the ground upward continued bouguer anomaly of the alps shows a good agreement the rms of these differences is equal to 7 68 mgal for a spatial resolution of 8 km however in some areas with rugged topography the amplitudes of those differences have a striking correlation with the topography we then argue that the choice of an appropriate density reduction by a factor of 10 per cent for computing the ground topographic corrections over the highest mountains results in significantly reducing the differences between airborne and ground upward continued bouguer anomalies which shows that some of the misfit stems from errors in the ground data

late pleistocene ice age scenarios based on observational evidence ice age scenarios for the last glacial interglacial cycle based on observations of boyle and keigwin concerning the north atlantic thermohaline circulation and of barnola et al concerning atmospheric co sub 2 variations derived from the vostok ice cores are herein analyzed northern hemisphere continental ice sheets are simulated with an energy balance model ebm that is asynchronously coupled to vertically integrated ice sheets models based on the glen flow law the ebm includes both a realistic land sea distribution and temperature albedo feedback and is driven with orbital variations of effective solar insolation with the addition of atmospheric co sub 2 and ocean heat flux variations but not in their absence a complete collapse is obtained for the eurasian ice sheet but not for the north american ice sheet we therefore suggest that further feedback mechanisms perhaps involving more accurate modeling of the dynamics of the mostly marine based laurentide complex appears necessary to explain termination i 96 refs 12 figs 2 tabs

linked debrites in sand rich turbidite systems origin and significance abstract the outer parts of a number of small late jurassic sandy deep water fans in the northern north sea are dominated by the stacked deposits of co genetic sandy and muddy gravity flows sharp based structureless and dewatered sandstone beds are directly overlain by mudclast breccias that are often rich in terrestrial plant fragments and capped by thin laminated sandstones pseudonodular siltstones and mudstones the contacts between the clast rich breccias and the underlying sandstones are typically highly irregular with evidence for liquefaction and upward sand injection the breccias contain fragments up to metre scale of exotic lithologies surrounded by a matrix that is extremely heterogeneous and strewn with multiphase and variably sheared sand injections and scattered coarse and very coarse sand grains often coarser than in the immediately underlying sand bed markov chain analysis establishes that the breccias consistently overlie sandstones and the character of the breccias and their external contacts rule out a post depositional origin via in situ liquefaction intrastratal flowage or bed amalgamation and disruption the breccias are interpreted as debrites that rode on a water rich sand bed just deposited by a co genetic concentrated gravity current as such they are referred to as linked debrites to distinguish them from debrites emplaced in the absence of a precursor sand bed the distinction is important because these linked debris flows can achieve significant mobility through entrainment of both water and sediment from beneath and they ride on a low friction carpet of liquefied sand this explains the paradox presented by fan fringes in which there are common debrites when conventional thinking might predict that deposits of low concentration gravity currents should be more important here in fact evidence for transport by low concentration turbidity currents is rare in these systems several possible mechanisms might explain the formation of linked flows but the ultimate source of both sandy and clast rich flow components must be in shallower water on the basin margin the debrites are not triggered from distal slopes flow partitioning may have occurred by upslope erosion and retardation of the mudclast charged portion of an erosional sandy density current partial flow transformation of a precursor debris flow and or hydraulic segregation and reconcentration of the flaky clasts and carbonaceous matter during transport linked debrites are not restricted to small sand rich fans and similar mechanisms may be responsible for the long runout of debris flows in other systems the recognition of a distinct class of linked debrites is of wider importance for facies prediction reservoir heterogeneity and even carbon fluxes and sequestration on continental margins

3 d modelling of alpine mohos in southwestern alps summary we present and discuss a 3 d geometrical model of the moho topography in the southwestern alps to achieve this objective we used the potential of 3 d modelling software i e a 3 d geomodeller to combine gravity seismic and seismological constraints in a same and coherent 3 d space a new regional bouguer gravity anomaly map of the southwestern alps was calculated and filtered to isolate the moho signature in the southwestern alps then two alternative 3 d models were computed with data from the literature based on seismic and seismological constraints the first one represents an european lithospheric mantle decoupled from the european orogenic crust which is back thrusted by the ivrea body whereas the second 3 d model illustrates the subduction of a 20 km thick piece of lower continental crust coupled with the european upper mantle beneath the ivrea body according to the geological knowledge of these units we then assigned a density value to each modelled layer and we computed their gravity effects to compare them with the filtered moho map of the southwestern alps first of all the significant discrepancies of the moho gravity signature generated by these two geometrical models reveal that subduction of continental crust is no more active in the present day configuration of the southwestern alps therefore the first 3 d model was refined by a stochastic 3 d gravity inversion based on this processing our investigations confirm the presence of three superposed mohos in the southwestern alps and underline that

glacial variability over the last two million years an extended depth derived agemodel continuous obliquity pacing and the pleistocene progression abstract an agemodel not relying upon orbital assumptions is estimated over the last 2 ma using depth in marine sediment cores as a proxy for time agemodel uncertainty averages 10 ka in the early pleistocene 2 1 ma and 7 ka in the late pleistocene 1 ma to the present twelve benthic and five planktic 18 o records are pinned to the agemodel and averaged together to provide a record of glacial variability major deglaciation features are identified over the last 2 ma and a remarkable 33 out of 36 occur when earth s obliquity is anomalously large during the early pleistocene deglaciations occur nearly every obliquity cycle giving a 40 ka timescale while late pleistocene deglaciations more often skip one or two obliquity beats corresponding to 80 or 120 ka glacial cycles which on average give the 100 ka variability this continuous obliquity pacing indicates that the glacial theory can be simplified an explanation for the 100 ka glacial cycles only requires a change in the likelihood of skipping an obliquity cycle rather than new sources of long period variability furthermore changes in glacial variability are not marked by any single transition so much as they exhibit a steady progression over the entire pleistocene the mean variance skewness and timescale associated with the glacial cycles all exhibit an approximately linear trend over the last 2 ma a simple model having an obliquity modulated threshold and only three adjustable parameters is shown to reproduce the trends timing and spectral evolution associated with the pleistocene glacial variability

soil carbon dioxide and weathering potentials in tropical karst terrain peninsular malaysia a preliminary model co2 concentrations at depths of 15 30 and 50 cm were determined over a one year period in six karst soils in the malay peninsula evidence suggests that the highest single co2 value maxco2 per cent recorded at each site depth provides the best estimate of conditions during groundwater recharge events soil depth cm and bulk density bden are the best predictors of maxco2 with the equation loglo maxco2 1 146 bden 0 00698 depth 1 227 accounting for 86 per cent of the variation this equation is used to model maxco2 at seven more remote sites soil throughflow patterns and groundwater recharge points are estimated from slope pantometer and soil depth surveys in order to assess the co2 concentration with which soil waters ultimately equilibrate before entering the limestone limestone weathering seems to be predominantly of the open system type the overall mean maxco2 of 1 65 per cent corresponding with a weathering potential of 167 ppm caco3 weathering potentials vary markedly ranging from 62 82 ppm on rocky hilltops to more than 280 ppm on certain tower karst footslopes in selangor and the kinta valley and on moderate hillslopes developed in impure limestones in the boundary range

plio pleistocene ice volume antarctic climate and the global δ18o record we propose that from 3 to 1 million years ago ice volume changes occurred in both the northern and southern hemispheres each controlled by local summer insolation because earth9s orbital precession is out of phase between hemispheres 23 000 year changes in ice volume in each hemisphere cancel out in globally integrated proxies such as ocean 18 o or sea level leaving the in phase obliquity 41 000 years component of insolation to dominate those records only a modest ice mass change in antarctica is required to effectively cancel out a much larger northern ice volume signal at the mid pleistocene transition we propose that marine based ice sheet margins replaced terrestrial ice margins around the perimeter of east antarctica resulting in a shift to in phase behavior of northern and southern ice sheets as well as the strengthening of 23 000 year cyclicity in the marine 18 o record

3d cartographic modeling of the alpine arc we built a 3d cartography of the alpine arc a highly non cylindrical mountain belt using the 3d geomodeller of the brgm french geological survey the model allows to handle the large scale 3d structure of seventeen major crustal units of the belt from the lower crust to the sedimentary cover nappes and two main discontinuities the insubric line and the crustal penninic front it provides a unique document to better understand their structural relationships and to produce new sections the study area comprises the western alpine arc from the jura to the northwest up to the bergell granite intrusion and the lepontine dome to the east and is limited to the south by the ligurian basin the model is limited vertically 10 km above sea level at the top and the moho interface at the bottom we discarded the structural relationships between the alps sensus stricto and the surrounding geodynamic systems such as the rhine graben or the connection with the apennines the 3d model is based on the global integration of various data such as the dem of the alps the moho isobaths the simplified geological and tectonic maps of the belt the crustal cross sections ecors crop and nfp 20 and complementary cross sections specifically built to precise local complexities the database has first been integrated in a gis project to prepare their implementation in the geomodeller by homogenizing the different spatial referencing systems the global model is finally interpolated from all these data using the potential field method the final document is a new tri dimensional cartography that would be used as input for further alpine studies

rheological complexity in sediment gravity flows forced to decelerate against a confining slope braux se france abstract hybrid event beds are now recognized as an important component of many deep sea fan and sheet systems they are interpreted to record the passage of rheologically complex sediment gravity currents hybrid flows that comprise turbulent transitional and or laminar zones hitherto the development of hybrid flow character has mainly been recognized in system fringes and attributed to distal and lateral flow transformations and or declining turbulence energy expressed over lateral scales of several kilometers or more however new field data show that deposition from hybrid flows can occur relatively proximally where flows meet confining topography turbidity currents primed to transform to hybrid flows by up dip erosion and incorporation of clay may be forced to do so by rapid slope induced decelerations within 1 km of the slope local flow transformation and deposition of hybrid event beds offer an alternative explanation for unusual facies developed at the foot of flow confining seafloor slopes

spatial and temporal reconstructions of changes in the asian palaeomonsoon a new mineral magnetic approach abstract a new quantitative approach is proposed for estimating palaeoprecipitation across the chinese loess plateau at present there is a strong rainfall gradient across the plateau from 300 mm yr in the near desert conditions in the northwest to over 750 mm yr in the southeast just 700 km distant we find that the concentration of ferrimagnetic iron oxide minerals in nine modern soil types represented by 37 individual soil profiles is strongly correlated with this contemporary rainfall gradient the ferrimagnetic concentration rises along this gradient from 0 01 in the northwest to over 0 2 in the southeast the nine modern soil types have been used in the construction of a rainfall vs magnetic susceptibility least squares regression climofunction past variations of loess soil iron oxide content are easily established through magnetic susceptibility measurements and so can be used to reconstruct the rainfall of former interglacial and glacial periods the physical and pedological basis of the rainfall vs susceptibility relationship is discussed and potential limitations of our rainfall reconstruction method are explored our palaeoclimate reconstructions indicate dramatic changes in rainfall due to variations in the structure of the asian monsoon the rainfall variations are about four times greater than has been suggested for this region by atmospheric general circulation modelling our data indicate increased rainfall throughout central china both in interglacial periods and in the early holocene the increases in monsoonal rain were particularly pronounced at our westernmost sites adjacent to the northeastern edge of the tibetan plateau in contrast for glacial periods a reduction in rainfall is found across the whole loess area with the greatest decreases in the southeast

sensitivity of the lln climate model to the astronomical and co2 forcings over the last 200 ky the louvain la neuve climate model there referred to as the lln 2 d model has been used extensively to simulate the northern hemisphere ice volume under both the insolation and co2 forcings the period analysed here covers the last 200 ky first sensitivity analyses to constant co2 concentration were performed the model was accordingly forced by insolation changes only the co2 concentration being kept constant to respectively 210 250 and 290 ppmv results show that the simulated ice volume variations are comparable to the geological reconstructions only when the co2 concentration is low 210 ppmv and that the sensitivity of the simulated northern hemisphere ice volume to co2 is not constant through time second three co2 reconstructions were used to force the lln 2 d model in addition to insolation results show 1 a better agreement with the specmap oxygen isotope time series in particular as far as the amplitude of the signal is concerned and 2 that the simulated northern hemisphere ice volume is not very sensitive to the slight differences between these three reconstructions

north atlantic thermohaline circulation during the past 20 000 years linked to high latitude surface temperature during a surface cooling event 10 000 to 12 000 years ago higher cd ca and lower 13c 12c ratios are observed in benthic foraminifera shells from rapidly accumulating western north atlantic sediments data from sediment cores show that marked nutrient depletion of intermediate waters occurs in association with reduced glacial north atlantic deep water flux it is proposed that cold high latitude sea surface temperatures enhance intermediate water formation at the expense of deep water formation

absolute chronology of the pliocene quaternary sediment sequence of the bogota area colombia abstract a revised geochronological framework is presented for the sequence of unconsolidated sediments present in the bogota area eastern cordillera colombia this is based on 11 fission track dates on zircons that were obtained both from exposed ash layers and from a series of ashes from the funza ii borehole which reached 586 m below the surface of the high plain the 3 dates obtained from the exposed ash layers provide control for the older part of the sequence 6 2 5 ma the 8 dates from the funza ii core give control for the younger part of the sequence 3 0 ma acceptance of these new fission track dates on volcanic zircons means that many of the tephra dates obtained from the funza i core that included fission track dates on glass shards and k ar dates using the mineral fractions in the ashes published in 1984 are rejected it also confirms earlier climate stratigraphical dating the neogene quaternary sediments of the bogota area span a period of at least the last 6 ma the fluvial lacustrine sediment record registers major tectonic uplift of the eastern cordillera for the period between 5 and 3 ma the development of the large sedimentary basin of bogota after 3 5 ma with an important phase of tectonic adjustment at about 1 ma and a long period of strong climatic fluctuations that started shortly after 2 7 ma

initiation of turbidity currents outcrop evidence for eocene hyperpycnal flow turbidites abstract the most widely used although not as widely documented explanation for initiation of turbidites is the conversion of catastrophic sediment failures into turbidites such instantaneous sediment failures generate short lived surge type flows that deposit turbidite beds described as bouma sequences in this communication we present data from the eocene central basin of spitsbergen that shows turbidite systems that are volumetrically dominated by thick ungraded and laminated sandy turbidite beds deposited by gradual aggradation from sustained flows sustained flows are long lived and more or less continuous they can be generated by a variety of mechanisms e g 1 instability during volcanic eruptions and the consequent remobilisation of unconsolidated material 2 seismically triggered subaerial sliding within the drainage 3 storm surges 4 retrogressive slope failure 5 breaching and 6 hyperpycnal flows our database shows that in the eocene central basin the sustained flows were generated by hyperpycnal flows i e by direct river effluent the hyperpycnal flow turbidites have been recognized on the basis of 1 physical connection between fluvial and turbidite channels at the shelf edge 2 abundance of thick turbidite sandstone beds 3 sand prone nature of the turbidite systems 4 downslope changes of individual thick sandy turbidite beds and their collapsed pinch out segments 5 great abundance of continental material leaves coal fragments in turbidite beds 6 low abundance of associated slumped or debris flow beds and 7 the occurrence of turbidites in systematically accreted shelf margins these features strongly suggest that hyperpycnal flow generated by direct river effluent deposited significant number of turbidite beds in the documented slope and basin floor turbidite successions we also argue that the hyperpycnal flows are preferentially fed into the deepwater slopes beyond the shelf edge during the falling stage and lowstand of relative sea level the turbidite beds were studied in the context of seismic scale 1 15 km dip oriented outcrops by measuring detailed vertical sections following individual beds and packages of beds downslope for distances over 5 km lateral mapping and helicopter taken photomosaics

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

basal inflection controlled shelf edge wedges off new jersey track sea level fall a key marker for examining the latest pleistocene history of the new jersey margin is the high amplitude long recognized r horizon reflector this time transgressive surface was formed 47 33 ka and represents the integrated topographic and bathymetric surface developed during the complicated sea level oscillation associated with the regression that preceded the last glacial maximum lgm from landward to seaward across the outer shelf the r reflector changes from subhorizontal in most locations 9 m beneath the modern seafloor to seaward dipping forming the base of two offlapping sediment wedges the previously described outer shelf wedge and a deep shelf wedge seaward of it this transition occurs across two inflection zones where the dip of the r reflector steepens seaward that can be traced for tens of kilometers along strike and mark the landward limits of these wedges these inflection zones are possibly former wave dominated shorefaces these represent the primary topographic elements present during the last regression we speculate that these inflections dictated both the locations for deposition of the two prograding offlapping wedges that developed during the complex sea level fall prior to the lgm and their successive erosion before and after the lgm we suggest that such inflection zones and their associated wedges are important markers of regression in clastic dominated outer shelf settings along passive margins

hydrologic and geologic control of carbonate water chemistry in the subarctic nahanni karst canada there are six classes of water and five geologic environments in the subarctic nahanni karst during the summers of 1972 and 1973 214 water samples were collected from 15 of the 30 hydrogeologic categories linear discriminant function analysis using five measured and two derived chemical variables indicates that there are statistically significant 0 005 level differences in water chemistry between similar waters in different geologic environments between waters in the same geologic environment and between waters in different hydrogeological categories geological environment labels a natural water because it determines the availability of soil co2 and of soluble minerals measurements indicate that mean soil log pco2 is greatest in areas of shale mantled by till 2 39 and least in areas of sandy fluvioglacial drift 3 27 low values on the sandy drift are due to the sparse shrub vegetation and to the high degree of soil aeration soils in areas of shale are clay rich and support a dense boreal forest hydrology influences water chemistry because it determines how much co2 natural waters pick up from the environment and how much they subsequently lose to the atmosphere and as a result whether they dissolve or deposit soluble materials the similarity between mean calculated log pco2 in natural waters 2 92 and mean measured soil log pco2 2 80 suggests that natural waters in nahanni are dose to equilibrium with mean soil co2 levels

development of rheological heterogeneity in clay rich high density turbidity currents aptian britannia sandstone member u k continental shelf abstract upper aptian deep water sandstones in the witch ground graben of the north sea have been extensively drilled and cored in the britannia field the upper part of the britannia sandstone member comprises a series of thick 3 8 to 16 5 m sandstone beds that thin and pinch out against a paleoslope formed by the fladen ground spur to the north deposition was from unusually large volume flows that carpeted the deep basin floor and base of the lateral slope with sand the flows were able to heal significant seafloor topography produced during periods of local slope collapse the recognition of widespread early remobilization is new and results in a revised event bed correlation scheme and casts doubt on relationships between spatial patterns of grain size distribution facies distribution and paleoflow used to underpin previous models of deposit emplacement the beds are here interpreted as the deposits of large volume axially dispersing turbidity currents probably some 70 km from source and within 25 to 35 km of their run out limit to the south southeast of the britannia field single event beds contain a wide range of sand rich facies deposited progressively from turbulent suspension and clay rich facies previously termed slurry deposits deposited in cycles of en masse deposition from dilute laminar flow alternating with phases of suspension fallout from turbulent flow along the northern fringe of the system clay rich facies dominate but pass southward over six or seven km into progressively cleaner sand rich facies this trend in facies distribution is at a high angle to the inferred se dispersing paleoflow and is thought to reflect lateral suppression of flow turbulence from flow axes to flow margins controlled by relative changes in flow depth in addition the vertical arrangement of facies within beds always shows sand rich facies at bed bases passing upward often via distinctive banded facies into clay rich facies indicating a temporal flow transformation from dominantly turbulent to dominantly laminar with an intermediate phase of alternating laminar and turbulent flow this temporal transition in inferred flow conditions is similar to the inferred on axis to off axis spatial transition in conditions thus single clay rich sediment gravity flows can evolve in both time and space to develop different rheological zones of turbulent transitional and laminar character in addition certain debritic clay rich facies are now interpreted to result from post depositional remobilization from off the confining slope to the north and must be differentiated from the primary suite of depositional facies

oxygen and carbon isotope record of east pacific core v19 30 implications for the formation of deep water in the late pleistocene north atlantic abstract a detailed oxygen and carbon isotope record has been obtained from benthic foraminifera in core v19 30 from the carnegie ridge on the south side of the panama basin expressing these records and the oxygen and carbon isotope records previously published for atlantic core m 12392 on a common timescale it is apparent that the oxygen isotope records are very similar but that the carbon isotope records are quite different by obtaining the carbon isotope gradient between the two sites as a function of time we show that the production of north atlantic deep water has varied over a wide range during the late pleistocene and that the pattern of variation is not simply related to the well known oxygen isotope record although the two oxygen isotope records are very similar changes in the interoceanic gradient are detectable and support the hypothesis that in the glacial mode the north atlantic was colder and less oxygenated than it is today shackleton s 1 1977 interpretation whereby the carbon isotope record from the atlantic core reflects changes in the terrestrial biomass is an over simplification however the record from the pacific core v19 30 probably can be explained in these terms since it probably approximates the carbon isotope record of global mean oceanic dissolved co 2

geological modelling from field data and geological knowledge part ii modelling validation using gravity and magnetic data inversion the analysis of multiple data sets is required to select a realistic 3d geological model among an infinite number of possibilities an inverse method that aims at describing the 3d geometry of geological objects is presented the method takes into account the geology and the physical properties of rocks while respecting the topological properties of an a priori model the a priori model is built from the geological data set and its geometry is largely dependent upon assumptions about inaccessible geology at depth this method referred to as total litho inversion is a generalized 3d inversion that results in quantifying the lithology and the distribution of rock property in a probabilistic way its application is demonstrated through i a simple synthetic case and ii the relative distribution characterization of granites and diorites in an orogenic domain

partly pedogenic origin of magnetic variations in chinese loess quaternary sequences of interbedded aeolian silts loess and buried soils palaeosols potentially provide one of the best terrestrial records of past climates1 5 magnetic susceptibility variations in loess and palaeosol sequences from china are strongly correlated with climate induced fluctuations of oxygen isotope ratios in deep sea sediments2 4 6 8 as an explanation of this correlation it has been suggested that the recorded variations in magnetic susceptibility depend primarily on the degree of dilution by non magnetic bulk loess constituents of a uniform magnetic assemblage derived from remote but unknown sources6 8 it has also been suggested that such a model involving changes in the accumulation rate of loess superimposed on a constant flux of magnetic particles provides a relative geological timescale through the control of loess deposition by astronomically modulated climate fluctuations7 here we report a preliminary test of this model using rock magnetic properties especially sensitive to variations in magnetic grain size our results show that palaeosols are characterized by much finer magnetic grain size assemblages than are the intervening loess units this suggests that a simple model based on constant magnetic influx and dilution by variable amounts of non magnetic loess is inadequate our magnetic measurements establish the close comparability of the fine grained magnetic minerals in the palaeosol samples to those in contemporary soils and thus point to a partially pedogenic origin for the magnetic mineral assemblages in the palaeosols

rapid subsidence and preservation of fluvial signals in an otherwise wave reworked delta front succession early mid pliocene orinoco continental margin growth se trinidad abstract outcrops of the early mid pliocene orinoco delta succession on the atlantic facing trinidad continental margin demonstrate facies and stratigraphic architecture of a shelf margin developed in a setting of high sediment supply orinoco river and unusually rapid sediment accumulation subsidence averaging 1 km my the studied moruga clastic wedge of the orinoco margin consists of a series of topset to deepwater clinoforms with channelized sandstones river and mixed process delta front wave dominated delta front shoreface prodelta offshore transition shelf upper slope turbidite channels and mass transport deposits the succession is sand prone and generally consists of coarsening and thickening upward delta front lobes with hummocky swaley and wave ripple stratified sandstones indicating dominant storm wave reworking of the delta particularly when the delta lobes had reached outer shelf sites after long shelf transits the lower parts of distributary channels are well preserved and characterized by cross bedded to parallel laminated sandstones with mud clast lags the upper parts of channel fills were wave reworked during transgressions creating hummocky swaley cross stratified strata river dominated and mixed process wave and tide delta front deposits occur commonly within stacked coarsening upward units the river dominated delta front deposits exhibit parallel laminated to current ripple laminated intervals with normally graded thin beds changing upward to parallel and low angle cross lamination but mixed process delta front deposits also contain wave and bidirectional current ripples as well as discrete intervals of hummocky swaley cross stratification the preservation of the channel base as well as river and mixed process delta front deposits in the otherwise storm wave dominated atlantic facing setting suggests some sheltering of the coastal morphology and possibly low frequency of large storms but it is more likely that the unusually rapid subsidence at rates competing well with icehouse rates of eustatic sea level change and burial of deposits may have prevented the fluvial and tidal signals from being completely reworked by the storm waves in the studied outcrop area this study demonstrates an example of how the interactions of river tide and wave generated facies impacted stratigraphic architecture of a rapid subsiding shelf margin built by shelf edge deltas with high sediment supply

the lithospheric density structure of the eastern alps the three dimensional 3d lithospheric density structure of the eastern alps was investigated by integrating results from reflection seismics receiver function analyses and tomography the modelling was carried out with respect to the bouguer gravity and the geoid undulations and emphasis were laid on the investigations of the importance of deep lithospheric features although the influence of inhomogeneities at the lithosphere asthenosphere boundary on the potential field is not neglectable they are overprinted by the response of the density contrast at the crust mantle boundary and intra crustal density anomalies the uncertainties in the interpretations are in the same order of magnitude as the gravity field generated by the deep lithosphere after including the deep lithospheric geometry from the tomographic model it is shown that full isostatic equilibrium is not achieved below the eastern alps however calculation of the isostatic lithospheric thickness shows two areas of lithospheric thickening along the central axis of the eastern alps with a transition zone below the area of the transalp profile this is in agreement with the tomographic model which features a change in lithospheric subduction direction c 2005 elsevier b v all rights reserved

ambient noise tomography of the greater geneva basin in a geothermal exploration context the greater geneva basin is one of the key targets for geothermal exploration in switzerland until recently information about the subsurface structure of this region was mostly composed of well logs seismic reflection lines and gravity measurements as part of the current effort to further reduce subsurface uncertainty and to test passive seismic methods for exploration purposes we performed an ambient noise tomography of the greater geneva basin we used 1 5 years of continuous data collected on a temporary seismic network composed of 28 broadband stations deployed within and around the basin from the vertical component of the continuous noise recordings we computed cross correlation functions and retrieved rayleigh wave group velocity dispersion curves we then inverted the dispersion curves to obtain 2d group velocity maps and proceeded to a subsequent inversion step to retrieve a large scale 3d shear wave velocity model of the basin we discuss the retrieved features of the basin in the light of local geology previously acquired geophysical datasets and ongoing geothermal exploration the greater geneva basin is an ideal natural laboratory to test innovative geothermal exploration methods because of the substantial geophysical datasets available for comparison while we point out the limits of ambient noise exploration with sparse networks and current methodology we also discuss possible ways to develop ambient noise tomography as an affordable and efficient subsurface exploration method

mid pliocene asian monsoon intensification and the onset of northern hemisphere glaciation the late pliocene onset of major northern hemisphere glaciation nhg is one of the most important steps in the cenozoic global cooling although most attempts have been focused on high latitude climate feedbacks no consensus has been reached in explaining the forcing mechanism of this dramatic climate change here we present a key low latitude climate record the high resolution asian monsoon precipitation variability for the past fi ve million years reconstructed from south china sea sediments our results with supporting evidence from other records indicate signifi cant mid pliocene asian monsoon intensifi cation preceding the initiation of nhg at ca 2 7 ma ago this 1 4 million year long monsoon intensifi cation probably enhanced monsoon induced asian continental erosion and chemical weathering and in the process left fi ngerprints in marine calcium isotopes furthermore increased rock weathering and or organic carbon burial probably lowered the contemporary atmospheric co 2 and may have triggered the nhg onset

forced regressions in a sequence stratigraphic framework concepts examples and exploration significance sequence stratigraphic concepts suggest that stratal geometries develop and are largely controlled by changes in relative sea level on the shelf lowstand deposits which form during falls and subsequent stillstands of relative sea level can be recognized by the presence of an unconformity at the base the isolated and basinward position relative to the previous shoreline and the abrupt seaward translation of shallow water and shoreline facies into the basin across an unconformity surface this seaward translation of facies and shoreline regression in response to relative sea level lowering is termed a forced regression a forced regression is independent of variations of sediment flux and is in contrast with normal regressions that occur in response to excess sediment flux relative to space available on the shelf i e accommodation forced regressions commonly are associated with a zone of sedimentary bypass subaerial exposure and possible fluvial erosion between the newly formed and preceding shorelines certain shelf sands previously interpreted as offshore or mid shelf sand bodies thus can be reinterpreted as stranded lowstand shorelines associated with forced regressions this alternative interpretation has economic significance insofar as it suggests different subsurface correlations and reservoir geometries with the potential for development of new play types and enhanced recovery in o der fields examples of forced regression can be observed at a variety of scales and ages several such examples include the modern east coulee fan delta and the lower cretaceous viking formation in alberta canada the quaternary rhone delta and the quaternary hudson valley system

the crustal structure of the eastern alps from a combination of 3d gravity modelling and isostatic investigations abstract the transition between european and adriatic crust is an important feature related to the plate collision that formed the european alps the diversity of seismic and geological information allows the construction of two alternative 3d density models which both match the observed gravity field different seismic experiments suggest a thickness for the adriatic crust between 30 and 40 km the thick crust model requires an unusually dense lower crust 3050 kg m 3 to reproduce the observed bouguer anomaly to evaluate the two alternative models the isostatic implications of the geometry and density distribution within both 3d models are investigated using local airy and regional vening meinesz isostasy airy isostatic investigations show that the eastern alps are not isostatically compensated and the residuals correlate strongly with exposed geological formations subsequently subsurface loading is an important factor controlling isostatic processes the different geometry and densities in the two 3d models imply different loading at the crust mantle boundary the subsurface loads calculated from the 3d density models were used to estimate regional isostasy by a convolution method in general small rigidity values d 21 nm are determined for the eastern alpine lithosphere in the model with a 40 km thick adriatic crust high flexural rigidities are inferred for the adriatic plate 100 10 21 nm but these values are unusual for an active orogenic region the results point to the interfingering of european and adriatic crust that results in the squeezing of european crust between adriatic crust and mantle with additional contamination by mantle material

carbon dioxide concentrations in some tropical karst soils west malaysia summary regular measurements of carbon dioxide at depths of 15 30 and 60 cm were made over a period of one year in six karst soils of the malay peninsula the data exhibit wide spatial depth and temporal variations mean carbon dioxide concentrations increase with depth and differences in soil properties especially in air porosity account for much of the inter site variability with the highest carbon dioxide levels occurring in the denser soils formed on impure limestones and on colluvial or alluvial footslope deposits and the lowest being in the more porous hillslope soils formed on pure limestones carbon dioxide concentrations at individual sites vary directly with the amount of antecedent rainfall in periods of 1 32 1 64 or 1 128 days before sampling these findings indicate the difficulties of obtaining a reliable mean figure for carbon dioxide in tropical soils but do suggest that mean concentrations recorded in tropical karst soils probably underestimate the true solutional potential of percolation waters whereas over estimation is likely in temperate regions

results of a walk above vertical seismic profiling survey acquired at the thonex 01 geothermal well switzerland to delineate fractured carbonate formations for geothermal development abstract this paper deals with the design acquisition and processing of vertical seismic profiling data collected in 2016 at the directional thonex 01 geothermal well drilled in 1993 in the geneva canton switzerland the aim of the study was to obtain additional information from existing abandoned well for downhole geophysical characterization of potential geothermal reservoirs in the geneva area the main results obtained by this study allowed an improved subsurface image by multi offset acquisitions near and around the deviated well specifically we were able to 1 improve the velocity model of the geneva basin which at present is only constrained by one unique deep exploration well located at the south west of the basin far away from the study area 2 image the transition between the tertiary molasse siliciclastic sediments and the mesozoic carbonates 3 define an acquisition strategy for future vertical seismic profiling surveys in support of the geothermal exploration campaigns in the area this study has demonstrated the value of vertical seismic profiling method for the refinement of the subsurface geology at local scale and its usefulness to assist the planning of second well associated with geothermal doublets

simulating the impact of the panamanian seaway closure on ocean circulation marine productivity and nutrient cycling abstract the closure of the panama isthmus 14 3 ma caused large reorganizations of ocean circulation here we use a global climate ocean ecosystem model to investigate the effects of the closing gateway on ocean circulation marine productivity and nutrient distributions several sensitivity experiments with different sill depths and vertical diffusivities are performed consistent with previous model studies we find constricted throughflow due to shallowing of the sill leads to intensification of the north atlantic thermohaline overturning we demonstrate a strong coupling between the flows through the tropical gateways of panama and indonesia in a way that reduced outflow of upper ocean pacific waters via the panama gateway into the atlantic is compensated by increased flow through the indonesian archipelago the simulated rates of north atlantic deep water formation strongly depend on the vertical diffusion in the model particularly for a deep sill for the first time we document by model results shifts in nutrient distributions associated with reorganizations of ocean circulation with repercussions on marine productivity patterns reduced flow of nutrient rich sub surface waters from the pacific into the atlantic reduces biological productivity in the north atlantic in the eastern tropical pacific restriction of the nutrient rich outflow leads to nutrient accumulation which in turn maintains a strong increase in productivity these results seem to be largely consistent with the paleoproductivity proxy record a massive drop of opal accumulation rates however as found in north pacific sediments for the time of the final closure 2 75 ma cannot be simulated generally global marine net primary productivity npp is found to increase with proceeding gateway closure