geodynamic evolution of the sw europe variscides 1 the early evolution of sw europe variscides started by opening of the rheic ocean at 500 ma splitting avalonia from armorica iberia subduction on the se side of rheic generated the paleotethys back arc basin 430 390 ma splitting armorica from iberia with development of porto tomar ferreira do alentejo ptfa dextral transform defining the boundary between continental armorica and finisterra microplate to the w obduction of paleotethys was followed by armorica iberia collision and emplacement of nw iberian allochthonous units at 390 370 ma whereas toward the west of ptfa there was antithetic ophiolite obduction beja acebuches and rheic ophiolites plus finisterra continental slices on top of ossa morena zone with simultaneous development of eclogites and orogenic magmatism under a flake double wedge tectonic regime continued convergence 370 ma proceeded by intracontinental deformation with progressive tightening of the ibero armorican arc through dextral transpression on the cantabrian indentor from iberia to armorica the proposed model is discussed at the light of the driving mechanism of soft plate tectonics

cyclical behavior of thrust wedges insights from high basal friction sandbox experiments scaled sandbox experiments with high basal friction simulating the growth of accretionary wedges display cycles alternating between frontal imbricate thrusting and underthrusting of long undeformed sheets by contrast low basal friction experiments with otherwise similar and constant initial conditions produce a classic frontal imbricate fan through repeated failure along frontal thrusts the cyclical behavior observed in high basal friction experiments is expressed by three quantities 1 the average spacing between frontal thrusts 2 the advance and retreat of the deformation front and 3 the frontal slope alpha of the actively deforming wedge as a long sheet is underthrust the front is steepened through slumping until the maximum critical angle is reached then frontal thrusting resumes and the accretion of imbricate slices builds the wedge forward thereby lowering the taper to the minimum critical angle at shallow tapers a long unit is underthrust and subsequently uplifts shortens and steepens the overlying wedge through backthrust deformation thus completing the cycle underthrusting of long units offers a simple mechanism for underplating overlying units it also provides a possible explanation for temporally and spatially varying wedge geometries in nature when basal frictions attain 80 90 of the internal friction

pollen distribution in marine sediments on the continental margin off northern california abstract pollen analysis of 84 samples from surface sediment of the continental margin off northern california between 38 and 39 n and 123 and 124 w shows that the composition of pollen assemblages in this part of the north pacific ocean reflects the regional vegetation of the russian river and other local drainage basins of the northern coast of california systematic trends in the quantitative and qualitative variations in these marine pollen assemblages show that fluvial and marine transport are important factors in determining the nature of pollen assemblages offshore these conclusions are supported by the analyses of pollen in rivers of the north coast of california and in particulate matter collected in a mid slope sediment trap

mesozoic extension controlling the southern alps thrust front geometry under the po plain italy insights from sandbox models in the southern alps fold and thrust belt east west mesozoic rifting controlled the development of extensional faults the deposition of the sedimentary sequences and the thickness and distribution of the main detachment levels vertical and lateral heterogeneities strongly influenced the structural style of the subsequent north south contractional phase as revealed by surface mapping and by subsurface maps derived from seismic data along the strike of the chain lateral terminations of thrust faults occur at syn rift extensional faults trending normal with respect to the contractional structures from west to east the thrust sheet number decreases and the order of structures and their wavelength changes on a regional scale the effects produced by pre existing heterogeneities on the development of contractional alpine tectonic structures in the external area of the southern alps were evaluated by means of scaled sandbox analogue models modelled lateral heterogeneities produced different wavelength thrust sheets salients and recesses whereas vertical heterogeneities facilitated the development of structures of different orders first order structures detached at the base of the model and second order structures detached at the intermediate relatively weak layers comparison of analogue model results with nature showed good geometrical similarities 2006 elsevier ltd all rights reserved

vegetation evolution based hydrological climate history since lgm in southern south china sea abstract the reconstruction of vegetation evolution and climate changes at low latitudes since the last glacial maximum lgm remains incomplete in this study we reconstructed the palynological history of vegetation changes since the lgm using a sediment core collected from the slope in the southern south china sea scs the chronology of the core was based on eight ams14c dates and 85 stratigraphic samples were palynologically analyzed our results denote that the vegetation reconstructed during the lgm in the southern scs was characterized by a relatively high percentage of herb pollen and a modest decrease in the number of fern spores suggesting a temperature decline and humidity change in this region further the preservation of a rich diversity of pollen from the tropical lowland rainforest indicated that the rainforests might have covered large areas of the exposed sunda shelf during the lgm the dynamic concentration of the pinus pollen in the core which is a proxy for the east asian winter monsoon eawm satisfactorily matched the changes in the atlantic meridional overturning circulation and australian indonesian summer monsoon especially during the heinrich stadial 1 this suggests that the climate at the high latitudes of the northern hemisphere can drive the intertropical convergence zone itcz southwards based on the enhanced eawm the southward shifting itcz may change the hydrological climate of the equator and the southern hemisphere the pteridophyte spores which are good regional precipitation indicators were positively correlated with the warm pool convection and inversely related with the eawm possibly indicating the considerable impact of the high latitude climate in the northern hemisphere on precipitation in the tropical regions our results indicate that during the last deglaciation the tropical hydrological changes were relatively moderate when compared with the drastic change observed at high latitudes and were attributed to the regulation of the el nino southern oscillation like state our sequence of pollen and spores from the southern scs can be used to observe the detailed dynamics of climatic evolution in tropical regions the results of this study are essential to understand the complicated climate processes and the relation between high and low latitudes

kinematics of orocline and arc formation in thin skinned orogens the regional traces of folds faults and foliations found in many fold thrust belts are bent in plan view it proves valuable to distinguish between two types of bent orogens based on their kinematic evolution oroclines or rotational arcs are bent orogens in which segments of the orogen change strike during the evolution of the bend and nonrotational arcs are bent orogens in which segments of the orogen do not change strike during development of the bend the kinematic evolution of a bend that forms in a thin skinned orogen can be described in terms of three parameters the displacement path trajectories followed by points along the strike of the orogen the magnitude and distribution of tangential extension along the strike of the orogen and the change in position of the endpoints of the orogen with respect to a reference line only slight differences in the displacement path trajectory pattern determine whether an orogen evolves as a nonrotational arc or as an orocline thus the distinction between these two types of bends is not always of major tectonic significance compressional deformation along irregular continental margins or the impact of indentors on continental margins during collisional orogenies more likely leads to formation of nonrotational arcs as can be simulated with a sand wedge model interaction between a fold thrust wedge with obstacles in the foreland or with a wrench fault more likely leads to orocline formation orocline formation is also associated with noncoaxial reactivation of thrust faults tangential extension is a necessary consequence of certain displacement path trajectory patterns and can accompany development of either nonrotational arcs or oroclines two examples one from the umbrian apennines and one from the makran range demonstrate how movement on cross strike fault arrays can accommodate tangential extension in thin skinned bends

balanced cross sections and their implications for the deep structure of the northwest alps reply abstract the structure of the northwest external french alps around the internal belledonne and mont blanc massifs in the beaufortain area can be explained by foreland wnw propagating thrust tectonics the internal belledonne massif is interpreted as having developed by imbrication of an originally thin skin of basement with a mesozoic cover above this massif all thrusts tend to climb lateral sections to the south to converge with the frontal pennine thrust the southern termination of the mont blanc massif is merely a spectacular example of such a lateral ramp

the cenozoic evolution of the roer valley rift system integrated at a european scale the roer valley rift system rvrs is located between the west european rift and the north sea rift system during the cenozoic the rvrs was characterized by several periods of subsidence and inversion which are linked to the evolution of the adjacent rift systems combination of subsidence analysis and results from the analysis of thickness distributions and fault systems allows the determination of the cenozoic evolution and quantification of the subsidence during the early paleocene the rvrs was inverted laramide phase the backstripping method shows that the rvrs was subsequently mainly affected by two periods of subsidence during the late paleocene and the oligocene quaternary time intervals separated by an inversion phase during the late eocene during the oligocene and miocene periods the thickness of the sediments and the distribution of the active faults reveal a radical rotation of the direction of extension by about 70 80j counter clockwise integration of these results at a european scale indicates that the late paleocene subsidence was related to the evolution of the north sea basins whereas the oligocene quaternary subsidence is connected to the west european rift evolution the distribution of the inverted provinces also shows that the early paleocene inversion laramide phase has affected the whole european crust whereas the late eocene inversion was restricted to the southern north sea basins and the channel area finally comparison of these deformations in the european crust with the evolution of the alpine chain suggests that the formation of the alps has controlled the evolution of the european crust since the beginning of the cenozoic

the oligocene miocene tectonic evolution of the northern outer carpathian fold and thrust belt insights from compression and rotation analogue modelling experiments this paper presents the different analogue scenarios of the tectonic evolution of the northern outer carpathians i e the western and northern eastern outer carpathians which formed as an accretionary wedge in front of the east alpine carpathian pannonian alcapa block during oligocene miocene times currently this fold and thrust belt forms an arc which is asymmetrically convex to the north and wider in its eastern part palaeomagnetic investigations have suggested that the rocks of the arc underwent counter clockwise rotation along almost the whole arc which is difficult to explain as an effect of simple indentation of the triangular indenter in this case two branches of the arc should be rotated in the opposite directions the structural evolution of the western outer carpathians is characterized by superposition of two successive tectonic shortening events directed n s and ne sw the results of the presented analogue modelling suggest that two scenarios of the geodynamic evolution of the studied belt could explain the occurrence of such differently oriented shortening events 1 two phases of differently directed indentation first to the n then to the ne and 2 indenter movement to the ne with simultaneous counter clockwise rotation however the experiment in which the moving indenter is simultaneously rotated produces the most suitable model the counter clockwise rotation of the material is only possible in front of both sides of the convex indenter in this model the results of the analogue modelling also prove that rotation of the alcapa block started after formation of the magura nappe the innermost nappe of the western outer carpathians

the relation between regionally consistent stretching lineations and plate motions abstract regional stretching lineations in the himalayas and southern tibet coincide with the known relative motions of the converging plates this relation is used to infer plate motions from the stretching lineations in the variscan and caledonian belts of europe and in the late proterozoic belts of northeast and east africa in each region high angle convergence of plates produced transverse stretching lineations and high angle collision was followed by or combined with large displacements first by ductile shear and later by brittle fractures parallel to the plate boundaries apparent stretching as a result of volume loss ramsay wood 1973 is common but recognisable as such reorientation by later deformations must be allowed for ramsay 1967 in ductile shear zones simple shearing leads to the progressive approach towards the shear plane of the xy plane of the strain ellipsoid and progressive approach of x the extension axis to the shear line ramsay graham 1970 thus large extensions approximate to the shear line large extensions tend to produce sheath folds whose acutely curved axes approach the stretching direction quinquis et al 1978 also the pre existence of a strong linear fabric predisposes the development of later folds with axes parallel to the earlier linear fabric for all of these reasons the extension axis x rather than the fold axis is of prime significance

material transfer in accretionary wedges from analysis of a systematic series of analog experiments the structural evolution of accretionary wedges was modeled in a series of analog experiments with systematically varying initial boundary conditions the two principle parameters investigated were basal friction and thickness of sediment input relative to subducted sediment output material transfer in terms of degree and location of accretion and erosion is quantified as a function of these two parameters low basal friction produces long thin wedges by continuous frontal accretion of imbricate thrusts simultaneously substantial basal erosion may occur with little influence on the frontal dynamics the formation of an outer arc high with an accompanying forearc basin depends upon the relative amount of basal erosion the opening of the subduction window spacing of thrust faults is proportional to the layer thickness confirming the principle of self similar wedge growth from critical wedge theory high basal friction typically generates steep wedges marked by an erosional mass wasting frontal slope in the cases i o this is due to underthrusting and or subduction of the entire sedimentary section the case i o also features the late development of normal faulting and an extensional forearc basin for both low and high basal friction the material balance affects the wedge slope erosive conditions i o for low basal friction the primary modes of material transfer are frontal accretion and basal erosion for high basal friction the primary modes of material transfer are underthrusting underplating and frontal erosion applying the experimental results to active convergent margins parallels may be drawn thus the barbados ridge complex is interpreted to be a good example of a low basal friction wedge with an accretionary material balance while the japan and mariana margins provide examples of an erosive material balance

kinematics of orocline tightening in the core of an arc paleomagnetic analysis of the ponga unit cantabrian arc northern spain 1 paleomagnetic and structural analyses of the western european variscan belt wevb suggest that the most viable kinematic model for variscan deformation in northern iberia is oroclinal bending of an originally linear belt in a two stage tectonic history this history represents two regional compression phases e w in the late carboniferous and n s in the permian both in present day coordinates which resulted in the refolding about steeply plunging axes of initially north south trending thrusts and folds in the hinge zone and oroclinal tightening due to vertical axis rotation of the belt s limbs however the orocline model has yet to be critically tested in the wevb s core this study reports new paleomagnetic rock magnetic and structural data from the inner core of the wevb in order to test opposing kinematic models for the well documented fault and fold interference structures formed by late stage variscan deformation and to better understand the overall development of the wevb arc map scale structural features within the wevb core have a highly sinuous geometry characterized by transverse and thrust parallel fold systems formed by fault bend folding over footwall ramps the intersections of these two fold systems produce steeply plunging interference folds which are best exposed in the ponga thrust unit a total of 67 paleomagnetic sites were collected in the barcaliente formation of the ponga unit with emphasis placed on detailed spatial coverage of individual structural domains a multicomponent paleomagnetic remanence was measured which is interpreted to be composed of two components a low unblocking temperature recent viscous magnetization and a high unblocking temperature ancient magnetization that was acquired in the latest stephanian to early permian after initial d1 thrusting and folding bur prior to major secondary rotation rock magnetic experiments show that the characteristic remanence magnetization is carried by secondary authigenic pseudosingle domain magnetite these paleomagnetic results are used to determine the kinematics and geometry of postmagnetization deformation by restoring in situ magnetic vectors back to a defined reference direction on the basis of the restored ponga unit geometry the steeply plunging interference folds found in the wevb core are best described by a combination of secondary buckling of frontal ramp parallel hanging wall anticlines and modification of d1 lateral oblique ramps as frontal ramps during late stage north south shortening this combination of structural modification of the inner core of the wevb was necessary to accommodate oroclinal bending during the final amalgamation of pangea in the late paleozoic

behaviour of minor arcuate shapes hosted in curved fold and thrust belts an example from the northern apennines italy s satolli et al minor arcs in curved fold and thrust belts arcuate fold and thrust belts have been extensively studied in the literature less attention however has been paid to the characteristics of local scale arcuate structures meaning 5 10 km long fold or thrust traces that display map view curvature nevertheless detailed investigation of small arcuate structures hosted in major arcs can contribute to understanding the pervasiveness of deformation mechanisms we performed a combined geological and palaeomagnetic study on 21 sites from a c 60 km 2 area in the northern apennines in order to analyse minor arcs at a kilometric scale as evidenced by the geological and structural analysis performed on the 21 sites the fold axial trend changes from n s to nw se in the study area the comparison with palaeomagnetic results shows the lack of correlation between vertical axis rotations and fold axial trends as a consequence the minor arcuate shapes of thrusts and related folds are interpreted as mostly primary features inherited from the geometry of the palaeomargin represented by pre orogenic faults according to a context of inversion tectonics

anthropogenic changes in the landscape of west java indonesia during historic times inferred from a sediment and pollen record from teluk banten palynological and charcoal analyses of shallow marine core 98 28 from the northern coastal area of west java provide a regional vegetation history during the last few centuries reliable chronostratigraphical control is provided by 210pb analyses and the occurrence of the 1883 krakatau ash tsunami layer as a time marker the results permit the distinction of four successive stages reflecting increased disturbance and land clearance with some evidence for the presence of deciduous lowland forests in the banten area during the early holocene the establishment of coconut and pine plantations and the severe loss of biodiversity in the last few decennia are also echoed in the pollen record the effect of the krakatau eruption was insignificant compared with human impact on vegetation in the banten area copyright 2004 john wiley sons ltd

strain displacement and rotation associated with the formation of curvature in fold belts the example of the jura arc abstract a new simplified genetic classification scheme for arcuate fold thrust belts is proposed based on total strain patterns and displacement vector fields we distinguish three extreme end member models 1 oroclines pure bending of an initially straight belt 2 piedmont glacier with divergent transport directions and 3 primary arcs a simple geometric model set up for the simulation of strain patterns in primary arcs with uniform transport direction demonstrates that divergent strain trajectories and rotations of passive marker lines do not require any divergence in displacement directions these often quoted arguments are insufficient for the identification of oroclinal bending or piedmont glacier type of arc formation only three dimensional restorations of an arc provide the critical information about displacement directions in their absence arc parallel stretches and rotations in comparison with total strains provide the most useful criteria for the distinction of arc formation modes as an example the jura fold thrust belt of the external alps is discussed a large set of strain data includes total shortening estimates based on balanced cross sections local strain axes orientations from the inversion of fault populations homberg c 1996 unpublished phd thesis universite de paris vi france tectonic stylolites and micro strains from twinning in sparry calcite strain trajectories maximum shortening direction computed from these data define a strongly divergent fan with a 90 opening a complete displacement vector field for the entire jura has been determined from balanced cross sections augmented with three dimensional block mosaic restorations philippe y 1995 unpublished phd thesis universite de chambery france displacement vectors diverge by about 40 markedly less than strain trajectories the non parallelism between strain trajectories and transport directions indicates that considerable wrenching deformation did occur in both limbs of the jura arc paleomagnetically determined clockwise rotations of 0 13 from ten sites kempf o et al terra nova 10 6 10 behind the right hand half of the jura arc and two sites with a combined 23 anticlockwise rotation behind the left hand half of the arc are and additional argument in favor of such a wrenching deformation we conclude that the jura arc formed as a primary arc with a minor component of piedmont glacier type divergence in transport directions

antarctic temperatures over the past two centuries from ice cores 1 we present a reconstruction of antarctic mean surface temperatures over the past two centuries based on water stable isotope records from high resolution precisely dated ice cores both instrumental and reconstructed temperatures indicate large interannual to decadal scale variability with the dominant pattern being anti phase anomalies between the main antarctic continent and the antarctic peninsula region comparative analysis of the instrumental southern hemisphere sh mean temperature record and the reconstruction suggests that at longer timescales temperatures over the antarctic continent vary in phase with the sh mean our reconstruction suggests that antarctic temperatures have increased by about 0 2 c since the late nineteenth century the variability and the long term trends are strongly modulated by the sh annular mode in the atmospheric circulation

experiments on shortening of a 4 layer model of the continental lithosphere davy ph and cobbold p r 1991 experiments on shortening of a 4layer model of the continental lithosphere in p r cobbold editor experimental and numerical modelling of continental deformation tecronophysics 188 l 25 we present an experimental method for modelhng lithospheric deformation the method is based on a simplified profile of lithosphere rheology where only four layers are considered brittle crust ductile crust brittle mantle and ductile mantle the strengths of the four layers calculated from laboratory determined flow laws depend strongly on geothenns and slightly on strain rates and deformation regimes the rheological profiles of the lithosphere have been recreated in experimental models built with analog materials sand silicone putty and golden syrup which flow under their own weight during lithospheric shortening the style of deformation depends on the relative strengths of the four layers especially those in the mantle of special importance is the existence or non existence of a brittle mantle the initial stages of compression often produce flexures or buckles without local isostatic compensation buckling exerts a strong control on the localisation of thrust faults in later stages the thrusts tend to form at the inflexion points of buckles the style of crustal thickening depends on the relative thicknesses and resistances of the lithospheric layers in 2 layer lithospheric models without resistant mantle shortening was concentrated upon a small number of thrusts widely spaced in 3 layer models shortening was concentrated into a large number of reverse faults more closely spaced and more steeply dipping than before in clayer models a single thrust formed in the brittle mantle motion on this thrust dragged the crustal layers down forming an asymmetric crustal root with steep imbricate slices

pollen stratigraphic evidence of human activity at dieng central java abstract the pollen stratigraphy of a small lake at 2000 m elevation in the dieng highlands of central java where a large hindu javanese religious center flourished from about 1250 to 700 b p indicates substantial and nearly continuous clearance of the montane forest since about 1350 b p a core to the base of organic sediments is 14 m long and has a basal date of 1340 b p a zone of abundant pollen of the weedy herb plantago major corresponds well in time with the occupation of the religious center after about 700 b p the pollen of secondary forest species shifted in composition suggesting a different pattern of vegetation use in the highlands in the mid 19th century european observers reported that the forest on the mountains at dieng was closed and mature but evidence in the pollen is lacking by the 1920s the expanding human population had stripped the landscape of trees and the first pollen of cultivated plants appears in the stratigraphy because of local protection and forest replanting trees have again increased on the steepest slopes and the pollen assemblage today differs in composition from the previous zones

erosion driven uplift of the modern central alps abstract we present a compilation of data of modern tectono geomorphic processes in the central european alps which suggest that observed rock uplift is a response to climate driven denudation this interpretation is predominantly based on the recent quantification of basin averaged late holocene denudation rates that are so similar to the pattern and rates of rock uplift rates as determined by geodetic leveling furthermore a gps data based synthesis of adriatic microplate kinematics suggests that the central alps are currently not in a state of active convergence finally we illustrate that the central alps have acted as a closed system for holocene redistribution of sediment in which the peri alpine lakes have operated as a sink for the erosional products of the inner central alps while various hypotheses have been put forward to explain central alpine rock uplift e g lithospheric forcing by convergence mantle processes or ice melting we show with an elastic model of lithospheric deformation that the correlation between erosion and rock uplift rates reflects a positive feedback between denudation and the associated isostatic response to unloading thus erosion does not passively respond to advection of crustal material as might be the case in actively converging orogens rather we suggest that the geomorphic response of the alpine topography to glacial and fluvial erosion and the resulting disequilibrium for modern channelized and associated hillslope processes explains much of the pattern of modern denudation and hence rock uplift therefore in a non convergent orogen such as the central european alps the observed vertical rock uplift is primarily a consequence of passive unloading due to erosion

structural evolution in thrust belts and relative plate motion the upper pennine piemont zone of the internal alps southwest switzerland and northwest italy the earliest ll extension lineation of the polyphase deformation sequence in the combin and zermatt saas fee units of the piemont zone of the upper pennine nappes trends roughly nw se and the geochronological and stratigraphical constraints indicate that the nappe transport and the associated stretching lineation occurred between about 100 and 70 ma this accords in a general way with the relative motion of the african plate to the european plate during the late cretaceous as determined from reconstructions of the opening of the atlantic ocean and suggests that late cretaceous thrusting in the swiss alps was driven fairly directly by the africa europe plate motion

the western alps from the jurassic to oligocene spatio temporal constraints and evolutionary reconstructions abstract despite extensive research in the last 150 years the regional tectonic reconstruction of the western alps has remained controversial the curved orogenic belt consists of several ribbon like continental terranes sesia austroalpine internal crystalline massifs brianconnais which are separated by two or more ophiolitic sutures piemonte valais antrona lanzo canavese high pressure hp metamorphism of each terrane occurred during distinct orogenic episodes at 65 ma in the sesia austroalpine at 45 ma in the piemonte zone and at 35 ma in the internal crystalline massifs it is suggested that these events reflect individual accretionary episodes which together with kinematic indicators and the speed and direction of plate motions provide constraints for the discussed reconstruction model the model involves a prolonged orogenic history that took place during relative convergence of europe and adria here considered as a promontory of the african plate the first accretionary event involved the sesia austroalpine terrane final closure of the piemonte ocean occurred during the eocene 45 ma and involved ultra high pressure uhp metamorphism of the piemonte oceanic crust incorporation of the brianconnais terrane in the accretionary wedge occurred thereafter possibly during or after subduction of the valais ocean in the late eocene 45 35 ma this subduction was terminated at ca 35 ma when the internal crystalline massifs i e the assumed internal parts of the brianconnais terrane were buried into great depths and underwent hp and uhp metamorphism

mechanical stratigraphy as a factor controlling the development of a sandbox transfer zone a three dimensional analysis abstract in thrust belts fold fault terminations are common features of the structural architecture and can pose complicated problems to unravel in particular when two or more terminations are in close proximity such terminations usually reflect pre existing attributes amongst the many factors lateral variations in the mechanical stratigraphy can control along strike geometry and kinematics of fault related folds a displacement transfer zone was produced in a compressional sandbox model by means of two adjacent mechanically different stratigraphic domains the experiment allowed two discrete chains to develop in the different domains so that a complex structural setting occurred in the connecting area periclinal folds oblique thrust fronts and oblique ramps developed in the resulting transfer zone the interaction between periclines in the transfer zone produced lateral culminations in the folded structures the analysis of displacement across the structural domains revealed that a significant loss of slip along the faults occurred in the relay zone in this area imbricate faulting was partially replaced by layer parallel shortening a linear relationship appears to exist between the bed length of the thrust sheet and the related fault slip

enso driven carbon see saw in the indo pacific 1 the sediment trap experiments have been carried out during the 2001 2002 el nino la nina transition in the monsoon driven and freshwater influenced upwelling system off south java the results indicate that enhanced precipitation rates and associated river discharges increase the co2 uptake of the biological pump by increasing the organic carbon export and reducing the carbonate precipitation the freshwater furthermore forms a buoyant low salinity surface layer that caps off the nutrient and co2 rich subsurface waters which shortens the upwelling season during wet la nina conditions a reduced capping effect during dryer el nino conditions strengthens the upwelling and as shown by our model results increase co2 emission into the atmosphere along the freshwater influenced continental margins in se asia by contrast el nino weakens upwelling and reduces the co2 emission in the equatorial pacific ocean

structural analysis of the lombard thrust sheet and adjacent areas in the helena salient southwest montana usa abstract the helena salient is a prominent craton convex curve in the cordillera thrust belt of montana usa the lombard thrust sheet is the primary sheet in the salient structural analysis of fold trends cleavage attitudes and movement on minor faults is used to better understand both the geometry of the lombard thrust and the kinematic development of the salient early w e to wnw ene shortening directions in the lombard sheet are indicated by fold trends in the center of the thrust sheet the same narrow range of shortening directions is inferred from kinematic analysis of movement on minor faults and the orientations of unrotated cleavage planes along the southern lateral ramp boundary of the salient as the salient developed the amount and direction of shortening were locally modified as listric detachment faults rotated some tight folds to the nw and as right lateral simple shear caused by lock up and folding of the jefferson canyon fault above the lateral ramp rotated other folds northeastward where the lateral ramp and frontal oblique ramp intersect folds were rotated back to the nw our interpretation of dominant w e to wnw ese shortening in the lombard sheet later altered by local rotations supports a model of salient formation by primary parallel transport modified by interactions with a lateral ramp

the role of salt in fold and thrust belts davis d m and engelder t 1985 the role of salt in fold and thrust belts in n l carter and s uycda editors collision tectonics deformation of continental lithosphere tectonophysics 119 67 88 the style of deformation in thin skinned fold and thrust belts is critically dependent upon the resistance to sliding along the detachment between the mass of deforming sediments and the underlying rocks evaporites can provide an extremely weak horizon within which a basal detachment can form and along which only a relatively small shear traction can be supported fold and thrust belts that form atop a salt layer such as the appalachian plateau the franklin mountains in northwestern canada and the jura of the alps among others share several readily observable characteristics as predicted by a simple mechanical model for fold and thrust belts a detachment in salt permits a thrust belt to have an extremely narrow cross sectional taper in addition predicted orientations of the principal stress axes over a salt dtcollement are consistent with the commonly observed lack of a consistently dominant vergence direction of structures within the thrust belt other common attributes of salt basal thin skinned deformation include the presence of several widely but regularly spaced folds and abrupt changes in deformational style at the edge of the salt basin

palynology of eastern indonesian marine piston cores a late quaternary vegetational and climatic record for australasia abstract pollen analyses of late quaternary sediments from nine marine piston cores reveal a continuous vegetation and environmental record for eastern indonesia and northern australia on the island of halmahera a montane oak forest largely replaced the tropical lowland vegetation during the last glacial period while fern cover was strongly reduced during its maximum 18 000 yr b p climate was cooler and slightly drier than today around 10 000 yr b p mangrove vegetation expanded following the rising sea level in our western new guinea record at 14 000 yr b p climate grew warmer and slightly wetter until it stabilised around 10 000 yr b p at that time the mid to upper montane forests expanded to their full altitudinal range and fern cover increased while montane oak forest grassland and woodland areas had contracted in our marine pollen records during the last glacial the climate of northern australia was distinctly drier than today grassland vegetation with sedges increased considerably at 38 000 and 24 000 yr b p replacing eucalypt forest and culminating in a maximum grassland cover at the height of the last glaciation 18 000 yr b p the rapid sea level rise allowed the expansion of mangrove forests and salt bush marshes which had become established on the large tidal flats of the drowning sahul shelf around 12 000 yr b p one piston core g6 4 extends to 300 000 yr b p and shows that glacial periods are characterized by high pollen concentrations in marine sediments recording expanding grassland vegetation during interglacial woodland and fern cover increased while pollen concentrations in the sediments were low after 190 000 yr b p a more open vegetation suggests that conditions were in general much more arid than before repeated mangrove vegetation expansions suggest major rises in sea level at around 244 000 220 000 and 130 000 yr b p

eleven month high resolution pollen and spore sedimentation record off sw java in the indian ocean abstract settling particles collected in a sediment trap 60 km off sw java in the indian ocean at a 2200 m deep site about 830 m above the sea floor between december 2001 and november 2002 intervals of 16 days for 11 months were analyzed for the abundance and taxa composition of pollen and spores several factors control their deposition such as the monsoon driven reversal of the wind directions and ocean currents as well as flowering periods long distance transport plays a particular role during the monsoon seasons during the nw monsoon mid december beginning of march maxima of picea type alnus pinus and quercus pollen occur in the trap samples which correspond to wind and marine currents coming from the north probably the equatorial counter current and southern java current transporting pollen from the southern part of continental asia and sumatra to the research area during the se monsoon end of july mid november an increase of pollen originating from southeast indonesia and australia was observed pollen grains were probably transported by the south equatorial current and partly by the leeuwin current casuarina and in part eucalyptus are most abundant during this period during the intermonsoon period assemblages are mainly composed of pollen originating from west java maxima of some pollen taxa such as elaeocarpus myrica dacrycarpus type casuarina eucalyptus and podocarpus type probably reflect their flowering periods the transportation time from the pollen source area to the sediment trap is about 1 2 months the extrapolated pollen accumulation rate of the marine sediment trap would be about 1670 grains cm 2 yr the trap collected low concentrations of mangrove pollen which might be the result of the strong destruction of the mangrove belt in java during recent decades high values of poaceae pollen are probably related to the land use forest canopy opening and development of the secondary vegetation in west java the majority of the pollen and spores collected by the sediment trap reflects the vegetation of sw java but long distance transport in particular by the marine currents during the se and ne monsoons needs to be considered when interpreting marine pollen records off sw java in the eastern indian ocean

pollen distribution in marine sediments from the south eastern indonesian waters abstract pollen analysis on box core sediments from the south eastern indonesian waters provide information on trends in pollen transport and on pollen distribution in the marine surface sediments pollen and at a lower rate pteridophyta spore concentration values tend to decrease with increasing distance from the shoreline as a result pteridophyta percentages tend to increase with increasing distance from the shoreline mangrove pollen shows very little export from its distribution area while pollen from the mid upper montane group shows a substantial export from its onshore distribution area in general despite the complex nature of vegetation patterns and pollen transport in this region the onshore distribution of individual taxa and major vegetation types is well reflected in the pollen distribution in the marine sediments

deformation of accretionary wedges in response to seamount subduction insights from sandbox experiments sandbox experiments using a two dimensional and a three dimensional approach are used to study the deformation of margins in response to seamount subduction successive mechanisms of deformation are activated during the subduction of conical seamounts first reactivation of the frontal thrusts and compaction of the accretionary wedge is observed then back thrusting and conjugate strike slip faulting develops above the leading slope of the subducted seamount the basal d6collement is deflected upward in the wake of the subducting high and a large shadow zone develops behind the seamount trailing slope consequently frontal accretion is inhibited and part of the frontal margin is dragged into the subduction zone when the main d6collement returns to its basal level in the wake of the seamount the margin records a rapid subsidence and a new accretionary wedge develops closing the margin reentrant the sediments underthrusted in the wake of the seamount into the shadow zone are underplated beneath the rear part of the accretionary wedge substantial shortening and thickening of the deformable seaward termination of the upper plate basement associated with basal erosion is observed seamount subduction induces significant material transfer within the accretionary wedge favors large tectonic erosion of the frontal margin and thickening of the rear part of the margin the subduction and underplating of relatively undeformed water ladden sediments associated with fluid expulsion along the fractures affecting the margin could modify the fluid pressure along the basal ddcollement consequently significant variations of the effective basal friction and local mechanical coupling between the two plates could be expected around the subducting seamount

lateral displacement during neogene convergence in the western and central alps although major deformation in the western alps is clearly the result of north northwest directed thrust tectonics there is evidence suggesting that orogen parallel deformation may have been important in the late tectonic history of the western alps the authors propose that this northeast trending deformation includes 1 southwest directed normal fault movement along the simplon line 2 a diffuse zone of northeast striking dextral strike slip deformation along the rhone valley in switzerland between the mont blanc and aiguilles rouges massifs and through the belledonne massif and 3 southwest directed thrusting in the embrunais ubaye and digne nappe systems of southeastern france the correlation of these three broad regions of deformation is based on similar amounts of minimum displacement consistent kinematics and timing of deformation

change of direction of overthrust shear in the helvetic nappes of western switzerland abstract the lowest of the helvetic nappes in western switzerland the morcles and the doldenhorn nappes are large scale recumbent folds in equivalent tectonic positions in the alpine chain a comparison of the orientations of stretching lineations in both nappes shows that the lineations in the two stratigraphically normal sequences trend n s whereas those in the two stratigraphically inverted sequences trend nw se a similar geometrical relationship has been found from an analysis of the calcite c axis directions of these limestones the two normal sequences show nw se directed c axes whereas the two inverted sequences show w e directed c axes these observations lead to the following conclusions 1 regionally consistent shear movements occurred over a strike distance of more than 60 km and these gave rise to similar deformation patterns in both nappes 2 a progressive rotation of these shear movements from a northerly direction in the earlier formed limbs to northwesterly in the later formed inverted limbs can be deduced the finite strain stretching lineations lag behind the crystallographic fabric axes formed in the later part of the deformation history

crescent like large scale structures in the external zones of the western gibraltar arc betic rif orogenic wedge the external wedge of the gibraltar arc orogenic system western mediterranean is a natural case of a fold and thrust salient although at the scale of the arc a swing of the structural trend can be observed the presence of closed crescent like structures some of them more than 25 km long and scattered over an area of 3500 km 2 characterize the gibraltar arc external wedge this feature makes it very different from a classical arc shaped fold and thrust belt detailed structural maps of representative crescent like structures are presented synorogenic sediments reveal that they probably formed during a short time interval most probably during a single shortening event the crescent like structures are localized in front of a recess formed by the internal zones that acted as backstop this backstop shape and a viscous substrate essentially triassic evaporites below the fold and thrust external wedge constrain the experimental setting of an analogue model in which we were able to reproduce structures that developed originally with a highly non cylindrical shape during a single straight convergence moreover the tectonic transport directions along the thrusts are broadly comparable in the natural case and the model

a record of fire vegetation and climate through the last three glacial cycles from lombok ridge core g6 4 eastern indian ocean indonesia abstract charcoal elemental carbon and clastic particle analyses have been undertaken on tropical marine core g6 4 collected from the eastern indian ocean between the lesser sunda islands of indonesia and northwestern australia to help interpret an existing pollen record in addition a new oxygen isotope record has been constructed and several radiocarbon dates produced to allow a refinement of the chronology of the core the record covers the last 300 000 years with three clear glacial interglacial cycles however the new oxygen isotope record and radiocarbon dates suggest a hiatus and it appears that most isotope stage 3 is missing interglacials are characterised by higher values of mangrove fern and rainforest pollen indicating wetter conditions than intervening glacials which have higher cyperaceae and chenopodiaceae values gramineae percentages are also generally higher during glacials but there is a sustained increase in grasses relative to eucalyptus about 185 000 years ago originally interpreted as a change to drier conditions an increase in burning from about 200 000 years ago from charcoal evidence suggests that fire may have been an important contributing factor this and subsequent increases in charcoal may reflect anthropogenic burning and are considered in relation to archaeological evidence for possible times of arrival of people within australia the elemental carbon record shows major differences to that from charcoal and further research is needed to interpret its meaning little consistent evidence for changes in climate or vegetation disturbance is provided by clastic particle influx which may well reveal a record of volcanicity within the region

arcuate thrust systems in sandbox experiments a comparison to the external arcs of the western alps in the external western alps two regional structural arcs were generated during tertiary northwest directed collision between the apulian indenter and the european passive margin these arcs distinguished by their geographic position and their age are examined by using a new compilation of structural data and comparing these to the results of sandbox analogue experiments the principal western alpine arc comprises two orthogonal synchronous thrust systems in the late eocene early miocene major shortening 105 km was toward the northwest to west northwest and minor shortening 11 km was toward the southwest shortening in each branch decreased toward the core of the arc during the late miocene and pliocene the jura arc accommodated 35 km of northwest directed shortening while 10 5 km of southwest to south southwest directed shortening was accommodated on the digne thrust system sandbox experiments were used to investigate the role of the motion vector of a rigid rectangular indenter orthogonal diagonal curved or rotational paths and the mechanical stratigraphy of the foreland in the evolution of upper crustal arcuate systems e g presence of a basal easy slip silicone horizon comparison of experimental results with the external alpine arc suggests that the indenter followed a slightly diagonal path with respect to the european margin from the eocene to the early miocene and curved counterclockwise by 10 15 in the middle miocene mechanical stratigraphy experiments support the hypothesis that thick triassic evaporites played a primary role in the evolution of the jura arc the influence of mechanical stratigraphy was most prominent during weak deformation at the external boundaries of the alpine orogen jura fold and thrust belt digne thrust

arcuate accretionary wedge formation at convex plate margin corners results of sandbox analogue experiments abstract indentation of a rigid box into a sand layer leads to accretion of sand into a wedge which has an arcuate shape in map view curvature of the wedge is most pronounced at the corners of the indentor where deformation has been investigated in detail in this study several features of the arcuate wedge in the corner region depend on the indentation angle i e the angle between the indentation direction and the normal to the frontal face of the indentor a the ratio between the widths of the lateral and frontal parts of the wedge increases linearly with increasing indentation angle b orogen parallel extension ope in the corner area is initially high and leads thus to large finite ope in the firstly formed nappes but decreases and attains a stable level during progressive convergence finite ope in the corner region is smaller at larger indentation angles c displacement vectors of accreted material exhibit fanning around the arc but in oblique indentation the spread of their orientation is smaller than the change of structural strike nappe traces and fold axes displacement vectors trend mainly in such positions normal to structural strike where displacement is parallel to the indentation direction the results from these experiments can be applied to natural arcuate fold thrust belts if natural conditions do not differ much from experimental boundary conditions such an application may give information about the former plate movement direction across an arcuate plate margin in the example of the eastern carpathian arc a tertiary plate movement direction of approx 125 130 was determined this direction is in accordance with current models of large scale tectonics of the carpathian region which indicates the applicability of the experimental results to natural examples

overthrust shear deformation of a foreland basin structural studies south east of the pelvoux massif se france abstract the late tertiary champsaur prapic fold zone lies to the southeast of the pelvoux basement massif in the footwall of the frontal pennine thrust of the western alps the 0 8 1 3 km thick late eocene oligocene foreland basin succession lies directly on crystalline basement and was deformed by wsw directed shear below the overthrusting internal alpine units on the frontal pennine thrust this deformation decouples from the basement in a top to wsw sw basal shear zone above the turbidite sequence gres du champsaur is folded in chevron like folds a 12 km long continuous profile across the champsaur fold zone documents variations in chevron fold shape axial plane dips and zonal distribution of folding which indicate progressively higher shear strains towards the frontal pennine thrust in the east chevron fold axes trend generally nnwsse except close to the pelvoux massif where fold axes curve to n s possibly due to lateral drag in the western part of the investigated area sw directed thrusting on the champsaur thrust almost doubles the tertiary stratigraphy the champsaur thrust and chevron folding in its footwall deform the overlying internal thrust sheets the champsaur prapic fold zone is a particular example of overthrust shear deformation in the footwall of internal alpine nappes in which deformation is concentrated in diffuse ramp zones to the north late alpine deformation changes to wnw directed partly post dating the wsw sw directed deformation further south therefore in the core of the external western alpine are two sub perpendicular transport directions which barely overlap can be distinguished

a kinematic evolutionary model for the penninic sector of the central ligurian alps the nappe pile presently cropping out in the central sector of the ligurian alps is represented by some principal groups of tectonic units starting from the foreland the outer and lower weakly metamorphic up to 0 3 gpa brianconnais units support the high pressure up to 1 3 gpa ensemble of inner brianconnais nappes in turn overridden by the prepiedmont units sourced from the european continental margin prepiedmont units form two superposed groups the lower is composed only of a pre namurian basement alpine metamorphism up to 0 6 gpa and the upper is mainly composed of a slightly metamorphic greenschist facies post namurian cover at the top lie the high pressure metamorphosed up to 0 8 gpa in the sector here considered ophiolitic units the group of the non metamorphic helminthoid flysch nappes original stratigraphic cover of the ophiolitic units has travelled the greatest distance and is presently mainly set onto the outer part of the chain only events up to the stacking of the nappe pile are discussed disregarding late stage deformation as the examined sector is located at a considerable distance from the collisional zone late processes did not change the overall order of superposition formerly acquired the model proposes the development of two major subhorizontal detachment surfaces the first shallower one confines at the base a very thin skinned set of nappes nearly totally made up of prepiedmont sedimentary covers that are bounded at their top by the helminthoid flysch units both these groups underwent a mainly horizontal outwards transport in contrast the underlying prepiedmont crust and the adjoining brianconnais inner sector separated by the second deeper major detachment surface were progressively dragged into the subduction zone under the ophiolitic units and duplexes were generated exhumation of the metamorphic units occurred along the subduction channel as did stacking of the nappe pile

neogene lateral extension during convergence in the central alps evidence from interrelated faulting and backfolding around the simplonpass switzerland abstract the simplon fault zone occurs at the western end of the lepontine metamorphic dome in the central alps and represents a major low angle 25 dip normal fault associated with wsw ene directed lateral extension movement began in the early miocene and continued until at least 3 ma accumulating a total vertical throw of around 10 km corresponding to 24 km displacement parallel to the fault this displacement is partitioned between a broad zone of ductile mylonites in the footwall and a more discrete cataclastic detachment fault the simplon line in the central region simplon village to zwischbergen some 3 km of the total vertical displacement is accommodated by the discrete cataclastic zone due to the higher exposed structural level the importance of the cataclastic component increases towards the northwest in the northern steep belt around the simplonpass retrograde greenschist facies mylonite formation and younger cataclastic faulting associated with lateral extension occurred contemporaneously with sse vergent large scale backfolding representing nnw sse shortening and crustal thickening the combined effect was an overall shortening across the orogen accommodated by an extension parallel to the orogen allowing lateral escape of continental material normal faulting and the resultant lateral escape was not just superficial it extended to depths of at least 15 km and probably to depths exceeding 25 km the overall geometry and kinematics of the simplon fault zone and in particular the interplay between folding and faulting is very similar to that described from the metamorphic core complexes and detachment faults of the cordillera of the southwestern usa within the central alps extension was associated with rapid exhumation of the lepontine metamorphic dome as evidenced by very rapid cooling rates determined from mineral ages in the footwall similar to the cenozoic tectonics of the himalayas and tibet orogen parallel extension in the mountain belt may have been promoted by an overall reduction in the horizontal compressive stress in this direction more limited extension of the same age and orientation is known from a large area of the european foreland greater extension in the mountain belt compared with the foreland was accommodated by major strike slip transfer fault systems and was linked to coeval overthrusting of the lowlands towards the southwest in the external southwestern alps of haute provence france coeval folding and orogen parallel extension such as at the simplonpass were developed in a dextral transpressive regime due to oblique wnw ese convergence across the alps during the neogene

the restoration of thrust systems and displacement continuity around the mont blanc massif nw external alpine thrust belt abstract foreland propagating external thrust belts may be considered as essentially plane strain phenomena so that displacements can be correlated throughout their linked three dimensional fault geometry this approach has been applied to part of the northwest external french swiss alps around the mont blanc basement massif imbricates of basement and cover sequences on the sw margin of this massif restore to a width in excess of 77 km with an implicit shortening of at least 67 km these displacements can be correlated with those in the neighbouring helvetic nappes by transferring movements via lateral branch lines onto the mont blanc thrust by reappraising thrust geometries the helvetic ultrahelvetic nappe complex has been restored to a width of 114 km to the ese of the aiguilles rouges basement massif displacements on the internal se margin of the mont blanc massif estimated by balanced sections and a restoration of the ultrahelvetic klippen in the sub alps exceed 59 km thrust continuity incorporating the restorations of nappes and imbricate geometries around the mont blanc massif is illustrated on a crude restored branch line map which also serves as a preliminary palaeogeographic reconstruction external thrust systems to the east of the external belledonne aiguilles rouges massif restore to a width of at least 140 km in the footwall to the frontal pennine thrust

new constraints for indentation mechanisms in arcuate belts from the jura mountains france the mechanism of indentation in arcuate belts is discussed using the jura mountains as an example using fault inversion analysis from numerous sites the miocene pliocene stress pattern is reconstructed two superimposed compressional stress fields have been recognized considering the theoretical distribution of compression in front of a rigid indenter we interpret the complex stress pattern in the jura mountains as a result of a major change in the mechanism of indentation of the jura by its hinterland initially the indenter was narrower and limited in the southwest by the vuache transfer fault with time it expanded to the southwest and included the entire molasse basin this evolution highlights the importance of decoupling along faults which here controlled the indenter shape

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

quantifying vertical axis rotation in curved orogens correlating multiple data sets with a refined weighted least squares strike test 1 map scale curvature is a fundamental feature of most contractional orogenic belts and is central to understanding the kinematic and dynamic evolution of mountain systems paleomagnetic analysis combined with detailed structural studies is the most robust means of quantifying vertical axis rotations that produce curvature over a range of temporal and spatial scales this paper explores how vertical axis rotations can best be evaluated for multiple data sets by applying a weighted least squares method to the classic strike test this refined method provides measures of best fit slope confidence interval and goodness of fit between map scale structural trend paleomagnetic rotations and deformation fabric orientations structural trend is estimated by averaging fold axial trace formation contact and bed strike data over kilometer scale areas paleomagnetic and deformation fabric site mean orientations and measurement uncertainties are estimated using vector and bootstrap statistics weighting factors are estimated from combined measurement uncertainty structural noise related to small scale block rotation and stress strain refraction and variations in restoration paths the number of sites needed to obtain a significant confidence interval in strike test slope is a function of combined uncertainty in paleomagnetic or deformation fabric directions and the total range in structural trend around a curved orogen improved estimates of strike test slope and rotation thus require systematic sampling with a wide distribution of sites evaluation of appropriate weighting factors and statistical analysis a case study is presented that highlights application of this refined method to paleomagnetic and deformation fabric data sets from the wyoming salient of the sevier thrust belt paleomagnetic data yield a strike test slope of 0 76 0 11 indicating that the wyoming salient is a progressive arc with 3 4 secondary curvature related to vertical axis rotation synchronous with large scale thrusting and 1 4 initial curvature finite strain anisotropy of magnetic susceptibility and mesoscopic structural orientations which are related to early layer parallel shortening all yield strike test slopes of 0 9 0 1 comparing these slopes with paleomagnetic results indicates that deformation fabrics had initial curvature and thus cannot be used alone to accurately estimate rotations by integrating systematic paleomagnetic and structural data using statistical analysis curvature models for the wyoming salient are closely constrained

pollen and fern spores recorded in recent and late holocene marine sediments from the indian ocean and java sea in indonesia fossil pollen and spore diversity in marine sediment cores from the coasts off sw kalimantan and ne java java sea as well as modern pollen assemblages collected off west java in the se indian ocean in a marine sediment trap are documented in this paper in total photographic images of 138 pollen and 41 spores including 14 pollen and 32 unidentified spore types are presented in morphological order illustrated pollen and spore taxa list may help pollen and spore identification of future palynological investigations focused on the reconstruction of past vegetation climate and environment dynamics in se asia

deformation of brittle ductile thrust wedges in experiments and nature 1 even though the rheology of thrust wedges is mostly frictional a basal ductile decollement is often involved by comparison with purely frictional wedges such brittle ductile wedges generally display anomalous structures such as backward vergence widely spaced thrust units and nonfrontward sequences of thrust development laboratory experiments are used here to study the deformation of brittle ductile thrust wedges results are compared with natural systems in the jura mountains and the northern pakistan salt range and potwar plateau two series of three models are used to illustrate the effects of varying the basal wedge angle and shortening rate v these two parameters directly control variations in relative strength between brittle and ductile layers bd coupling wedges with strong bd coupling low and high v give almost regular frontward sequences with closely spaced thrust units and as such are not significantly different from purely frictional wedges weak bd coupling high and low v gives dominantly backward thrusting sequences intermediate bd coupling produces frontward backward oscillating sequences the spacing of thrust units increases as coupling decreases back thrusts develop in parts of a wedge where bd coupling is weak regardless of the thrust sequence wedges with weak bd coupling need large amounts of bulk shortening more than 30 to attain a state of equilibrium at which stable sliding along the base occurs on this basis we argue that a state of equilibrium has not yet been attained in at least some parts of the jura mountains and eastern salt range and potwar plateau thrust systems

characterization of stress perturbations near major fault zones insights from 2 d distinct element numerical modelling and field studies jura mountains abstract we consider and discuss the presence of discontinuities in the crust as a major source of stress perturbations based on 2 d distinct element modelling we reconstruct the local stress field around a vertical discontinuity in various geological contexts the resulting stress distribution reveals that major directional stress changes occur near the tips of the discontinuity so that stress deviations can reach values as large as 50 we establish simple relationships controlling stress changes around a pre existing fault zone as a function of 1 the remote differential stress magnitude 1 3 2 the friction coefficient on the discontinuity and 3 the strike of the discontinuity relative to the far field stress as a geological example we present the morez fault zone in the internal jura paleostress reconstruction in forty two sites indicates that the trends of the mio pliocene compression are n110 on average near the fault whereas they are n130 in the surrounding areas a comparison between the results of the tectonic study and those of theoretical modelling suggests that the 20 counterclockwise deviation is directly related to the reactivation of this large weak zone we thus evaluate the role of mechanical decoupling along pre existing zones of weakness especially with consideration to the accommodation of the alpine deformation in the jura belt

kinematic model for the curvature of the northern subalpine chain france abstract analyses of cross sectional shortening mapped faults and calcite twin strain are used in conjunction with geometric kinematic modeling to interpret the mechanism of curvature formation in the northern subalpine chain of france there is a 45 change in strike around the chain that is convex towards the foreland northwest five models for fold thrust belt curvature are applied to the northern subalpine chain they can reproduce the geometry and the kinematic history of a curved fold thrust belt and can be used to predict the magnitude and orientations of strains and the three dimensional geometry of the curvature the models are pure bending radial thrusting curve parallel simple shear uniform displacement uniform shortening and transport parallel simple shear two principal criteria for distinguishing among the models geometrically are the horizontal tangential strain extension or contraction parallel to strike and cross sectional shortening the transport parallel simple shear model predicts no tangential extension in the central domain and greater radial shortening and significant tangential extension in the northeastern and southern domains this is the pattern observed in the northern subalpine chain therefore the curvature of the northern subalpine chain is attributed to a transport parallel simple shear mechanism

complex proximal deposition during the plinian eruptions of 1912 at novarupta alaska proximal 3 km deposits from episodes ii and iii of the 60 h long novarupta 1912 eruption exhibit a very complex stratigraphy the result of at least four transport regimes and diverse depositional mechanisms they contrast with the relatively simple stratigraphy and inferred emplacement mechanisms for the previously documented better known medial distal fall deposits and the valley of ten thousand smokes ignimbrite the proximal products include alternations and mixtures of both locally and regionally dispersed fall ejecta and numerous thin complex deposits of pyroclastic density currents pdcs with no regional analogs the locally dispersed component of the fall deposits forms sector confined wedges of material whose thicknesses halve radially from and concentrically about the vent over distances of 100 300 m cf several kilometers for the medial distal fall deposits this locally dispersed fall material and many of the associated pdc deposits is rich in andesitic and banded pumices and richer in shallow derived wall rock lithics in comparison with the coeval medial fall units of almost entirely dacitic composition there are no marked contrasts in grain size in the near vent deposits however between locally and widely dispersed beds and all samples of the proximal fall deposits plot as a simple continuation of grain size trends for medial distal samples associated pdc deposits form a spectrum of facies from fines poor avalanched beds through thin bedded landscape mantling beds to channelized lobes of pumice block rich ignimbrite the origins of the novarupta near vent deposits are considered within a spectrum of four transport regimes 1 sustained buoyant plume 2 fountaining with co current flow 3 fountaining with counter current flow and 4 direct lateral ejection the novarupta deposits suggest a model where buoyant stable regime 1 plumes characterized most of episodes ii and iii but were accompanied by transient and variable partitioning of clasts into the other three regimes only one short period of vent blockage and cessation of the plinian plume occurred separating episodes ii and iii which was followed by a single pdc interpreted as an overpressured blast involving direct lateral ejection in contrast regimes 2 and 3 were reflected by spasmodic sedimentation from the margins of the jet and perhaps lower plume which were being strongly affected by short lived instabilities these instabilities in turn are inferred to be associated with heterogeneities in the mixture of gas and pyroclasts emerging from the vent of the parameters that control explosive eruptive behavior only such sudden and asymmetrical changes in the particle concentration could operate on time scales sufficiently short to explain the rapid changes in the proximal 1912 products

short paper kinematics of the alpine arc is there a continuous sweep in direction of alpine orogenic displacements around the alpine arc or does the overlap of a few distinct directions give this impression the thrust evolution of the sw alps which supports the latter view does not accord with the hypothesis of indenter induced body forces two displacement realms one with directions determined by intraplate configuration and another with directions related simply to the body forces maycoexist within the orogen but this is not yet established one of the longest standing disagreements in alpine geology concerns the nature of the radial pattern of orogenic displacements outwards from the alpine arc in one view there is a continuum of displacement directions sweeping from approximately southward in the maritime alps through west and northwest to approximately northward in austria in the other view there is no continuum but a small number of distinct directions of orogenic displacements each dominating a particular sector which relay one to another around the alpine arc recent papers mark a significant development in both sides of this argument which is given additional importance by the attempt of platt et al 1989 a to use displacement data to constrain plate motions this paper is intended as a contribution to the discussion and suggests one possible resolution of the argument sophisticated syntheses of alpine structure have for a long time accepted the possibility that both of the above views have some validity and goguel 1963 is a good starting point for discussion his displacements of crystalline basement of

multi stage thrusting at the penninic front in the western alps between mont blanc and pelvoux massifs the different segments of the tectonic boundary between external european and internal penninic units in the western alps the so called penninic front pf formed at different times and according to different kinematic scenarios during a first episode eocene the pf corresponds to a transpressive suture zone between penninic and european units north to nnw trending stretching lineations found along internal nappe contacts within the penninic units are related to this episode this subduction zone was sealed by the priabonian flysch of the aiguilles d arves a detrital trench formation that formed during the final stages of subduction during a second episode starting in mid oligocene times the pf imaged along the ecors crop profile acted as a wnw directed thrust this thrust the roselend thrust rt only partially coincides with the pf south of moutiers the rt propagates into the dauphinois units carrying the former eocene pf including the priabonian flysch passively in its hangingwall south of the pelvoux massif the rt finds its continuation along the brianconnais front an out of sequence thrust behind the embrunais ubaye nappes on a larger scale our findings indicate oblique sinistral collision within the future western alps during the eocene followed by westward indentation of the adriatic block

a 135 000 year record of vegetational and climatic change from the bandung area west java indonesia sedimentological and palynological analyses of sediment cores from the intramontane bandung basin west java indonesia provide a first palaeoclimatic record for the indonesian region covering continuously the last 135 000 years our data on palaeosol development indicate anomalously dry conditions for the final part of the penultimate glacial period around 135 000 yr b p and very warm and humid interglacial conditions from 126 000 to 81 000 yr b p during the transition to the last glacial period around 81 000 yr b p freshwater swamp forest of the bandung plain was replaced by an open swamp vegetation dominated by grasses and sedges indicating a change to considerably drier conditions possibly related to reduced moisture uptake by the nw monsoon as a consequence of lower sea levels at the onset of glacial conditions a strong reduction in asplenium ferns from 81 000 to 74 000 yr b p suggests that drier conditions may also have occurred in the mountains of the bandung area while increased numbers indicate that from 74 000 to 47 000 yr b p it was slightly wetter again inferred depression of montane vegetation zones and reduced fern percentages suggests distinctly cooler and possibly drier climatic conditions prevailed in the bandung area from 47 000 to approximately 20 000 yr b p for the last glacial maximum 4 7 c lower temperatures are recorded

the curved translation path of the parpaillon nappe french alps the parpaillon nappe is one of the two helminthoid flysch nappes emplaced on the external dauphinois zone of the western alps a structural analysis of the nappe is presented two superposed deformations d1 and d2 are described that are mainly characterized by large scale recumbent folds whose axes are quasi orthogonal ne sw for d1 and nw se for d2 their vergence is northwestward for d1 and southwestward for d2 during the d2 deformation the nappe was separated into two units one of these being thrusted over the other an analysis of incremental strain using quartz and calcite fibre growth indicates that d2 follows d1 without discontinuity therefore the superposition of d1 and d2 structures is interpreted as a progressive deformation instead of two distinct phases of deformation the emplacement of the nappe is discussed under two aspects the relations between displacement and strain and the role of gravity it is concluded that the translation has been twofold first towards the nw and then towards the sw and that the displacement result essentially from gravity forces kinematic implications for the alpine collision are suggested

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

high resolution palynological record for vegetation and environment change during mis 2 in the southern south china sea abstract vegetation evolution and corresponding climate changes during marine isotope stage mis 2 on the exposed shelves in the southern south china sea scs region are still controversial palynomorph data including percentage concentration and influx were used to reconstruct the history of vegetation and environment changes during mis 2 and mis 1 it recommends three significant changes occurred during these periods at 21 51 cal kyr b p 17 82 cal kyr b p and 12 36 cal kyr b p the findings indicate that during mis 2 and the start of mis 1 the northeastern part of exposed shelves were covered with tropical rainforests ferns were present in ground flora and sub canopy of tree cover in the rainforests in the coastal areas mangrove forests survived up to the start of mis 1 and then disappeared due to the rapid rise in sea level grassland was present to a limited extent and probably in the beach areas only winter monsoon was strong although the temperature was lower than at present from 11 70 cal kyr b p ferns were the dominating vegetation while herbs disappeared completely trees of lower and upper montane rainforests were present to some extent the climate was warm sea level rose the continental shelf was submerged in the ocean and the summer monsoon became stronger than in previous times this study supports the previous works from the southern scs region and suggests that a combination of pollens with other proxies give a better understanding of vegetation and climatic dynamics in the past

mechanics of the salt range potwar plateau pakistan a fold and thrust belt underlain by evaporites the salt range and potwar plateau are part of the active foreland fold and thrust belt of the himalaya in northern pakistan in this region the distance from the main boundary thrust mbt to the front of the fold and thrust belt is very wide 100 150 km because a thick evaporite sequence forms the zone of decollement recent studies have combined seismic reflection profiles petroleum exploration wells bouguer gravity anomalies and surface geology to construct cross sections in the eastern central and western salt range potwar plateau areas in this study the sections are compared with a model that considers the mechanics of a fold and thrust belt to be analogous to that of a wedge of snow or soil pushed in front of a bulldozer chapple 1978 davis et al 1983 dahlen et al 1984 dahlen 1984 models which include the effects of evaporites at the base chapple 1978 davis and engelder 1985 suggest that these thrust belts will have 1 narrow 1 cross sectional tapers 2 larger widths than areas not underlain by evaporites 3 symmetrical structures and 4 changes in deformational style at the edge of the evaporite basin the section across the eastern potwar plateau most closely resembles this latter model having 1 a taper of 0 8 0 1 2 a width of 100 150 km 3 thrust faults that verge both to the north and south and 4 structures rotated 30 counterclockwise with respect to the salt range from the observed taper and pore fluid pressures of the eastern potwar plateau estimates of the values for the yield strength of the evaporites o and the coefficient of internal friction of the overlying wedge are calculated as o 1 33 1 50 mpa and 0 95 1 04 which are then applied to the other cross sections in the central and western sections a basement uplift the sargodha high interferes with the front of the fold and thrust belt this feature causes the ramping of the salt range thrust and produces a relatively steep basement slope 2 4 beneath the potwar plateau this dip in the presence of the weak evaporite decollement is sufficient to provide critical taper no topographic slope is necessary and the thrust wedge of the southern potwar plateau is pushed over the decollement without significant internal deformation the northern potwar plateau is strongly folded and faulted yet the topographic slope remains flat although the deformation suggests that evaporites are not present there the observed taper in the northern potwar plateau is best fitted by the model with evaporites at the decollement combining this with published paleomagnetic and geologic constraints a model for the evolution of the northern potwar plateau suggests that the area deformed as a steeply tapered 3 5 5 5 thrust wedge until approximately 2 million years ago when the southward propagating decollement encountered the evaporites between 2 ma and the present the northern potwar plateau has been pushed along the salt decollement without deformation and erosion has reduced its original steep topographic slope to a nearly level surface

an oceanic box model of the miocene mediterranean sea with emphasis on the effects of closure of the eastern gateway 1 the early miocene mediterranean sea had two gateways toward the open ocean the indian ocean in the east and the atlantic ocean in the west closure of the eastern connection during the middle miocene had important effects on the water properties and circulation of the mediterranean sea to gain insight into the circulation of the mediterranean sea during the miocene and the effects of closure we apply a box model the model has three boxes representing the atlantic ocean the mediterranean sea and the indian ocean the boxes exchange water heat and salt through surface and deep flow the deep flow is driven by the density contrast between the boxes we analyze the variation of 1 temperature salinity and residence time and 2 magnitude and configuration of the gateway flows in response to changes in the gateways and in atmospheric forcing freshwater and heat fluxes the analysis is presented in three parts preclosure closure and postclosure model results are compared with observations reported in literature the model analysis indicates that 1 prior to closure of the eastern gateway deep flow was most likely west to east in both gateways provided the density of the indian ocean was relatively low 2 the preclosure system was not very sensitive to freshwater and heat flux 3 the response of the mediterranean water properties and flow to gradual closure is nonlinear 4 closure probably resulted in cooling and a rise of salinity and residence time of the mediterranean sea if evaporation exceeded freshwater input and 5 multiple equilibrium states are possible i e different surface and deep flow for the same value of freshwater flux in the case of two gateways in addition we tentatively propose a best fit scenario for the history of closure linking the available data and our model results

vegetation and climate change in west java indonesia during the last 135 000 years abstract sedimentological and palynological analyses of two sediment cores from the intramontane bandung basin java indonesia provide the first palaeoclimatic record for the indonesian region covering the last 135 000 years our data indicate anomalously dry conditions for the penultimate glacial and very warm and humid conditions during the last interglacial during the last glacial period fresh water swamp forests of the bandung plain were replaced by open swamp vegetation dominated by grasses and sedges indicating a change to considerably drier climatic conditions possibly as a consequence of lower sea levels at the onset of glacial conditions for the last glacial maximum temperatures 4 7 c lower than at present are recorded

pollen distribution in hemipelagic surface sediments of the south china sea and its relation to modern vegetation distribution abstract this paper analyses the distribution of pollen in the surface sediments of the south china sea as recorded in 28 samples from the area 6 09 20 07 n and 112 05 119 45 e at water depths of 329 4307 m pollen concentrations range from 444 kgrains g dry wt on the lower part of the continental slope in the northeast to zero in the central basin below 4000 m water depth pollen distribution patterns in the concentration and percentage isopolls incorporating data from the literature reflect the routes and mechanisms of pollen transport pollen source areas and considerable systematic differences between north and south the northern scs is distinguished by very high concentrations due to the high production and effective long distance transport of pine pollen and fern spores the maximum of their concentration occurs in the north adjacent to the convergence of the bashi and taiwan straits rather than near the estuaries of big rivers and stretches as a saddle from ne to sw consistent with the direction of the ne winter monsoon and sea current this pattern implies that pine pollen and fern spores adapted to wind transport and water flotation come from the northeast through the straits borne on the winter monsoon and sea current forced by it their source areas should cover large regions probably including south and southeast china most pollen of tropical and subtropical broad leaved trees found in the northern part of the scs occur in low concentrations however these concentrations decrease uniformly offshore implying a fluvial discharge from nearby lowlands in south china in the southern part of the scs pollen of tropical and subtropical broad leaved trees predominate total pollen concentrations however are much lower only 1 10 of those of the northern part the greatest concentrations occur offshore north borneo and decrease toward deep water suggesting fluvial input from relatively local sources on the adjacent islands e g borneo

the arc of the western alps in the light of geophysical data on deep crustal structure recently two international deep seismic campaigns in the western and central alps etude continentale et oceanique par reflexion et refraction sismique progetto strategico crosta profonda ecors crop roure et al 1996b and national research program 20 nrp 20 pfiffner et al 1997 have been completed here we present a synoptic interpretation of the wealth of geophysical data about deep crustal structure of the alps collected during the past 40 years including the two above mentioned geophysical projects the tectonic reinterpretation of the ecors crop high resolution seismic transect is based on an evaluation of the deep crustal structure by integrating new and literature data on surface geology combined with previously published interpretations regarding the central alps schmid et al 1996 this study reveals substantial differences in geometry and kinematics between transects across the western and central alps respectively at depth the transition between the central and western alps is marked by the western limits of an adriatic lower crustal wedge shaped structure and the northeastern limits of a similar structure made of european lower crustal material at the surface it coincides with a corridor of dextral strike slip along the tonale and simplon lines in addition the thickness of the seismogenic zone shows a remarkable variation from over 40 km beneath the penninic realm of the western alps to less than 20 km in the central alps the formation of the western alpine arc was initiated during convergence and collision before 35 myr ago when the adriatic micro plate moving northward with respect to the european foreland caused sinistral transpression in the western alps while the central and eastern alps underwent head on convergence and collision during the post collisional stage i e after 35 myr ago the arcuate shape of the western alps was accentuated by wnw directed movement and anticlockwise rotation of the adriatic microplate decoupled from the central and eastern alps along the tonale simplon dextral shear zone this led to wedging of lower crustal slices both in the western alps and in the central alps the new tectonic interpretation of the ecors crop transect allows a kinematic model to be established for crustal shortening in the western alps during the past 35 myr the ivrea mantle plays the role of a backstop in our tectonic model we distinguish three episodes of post collisional crustal shortening along the ecors crop transect from 35 to 30 ma the brianconnais basement was back thrusted over the gran paradiso units leading to 30 km of crustal shortening first episode in the early miocene movements concentrated mainly along the penninic frontal thrust and resulted in about 60 km shortening second episode post 12 ma shortening within the external massifs is associated with folding in the jura mountains when the crust was shortened by an additional 30 km third episode

mechanical and fracture stratigraphy using examples from core studies this article shows that separate identification of mechanical stratigraphy and fracture stratigraphy leads to a clearer understanding of fracture patterns and more accurate prediction of fracture attributes away from the wellbore mechanical stratigraphy subdivides stratified rock into discrete mechanical units defined by properties such as tensile strength elastic stiffness brittleness and fracture mechanics properties fracture stratigraphy subdivides rock into fracture units according to extent intensity or some other observed fracture attribute mechanical stratigraphy is the by product of depositional composition and structure and chemical and mechanical changes superimposed on rock composition texture and interfaces after deposition fracture stratigraphy reflects a specific loading history and mechanical stratigraphy during failure because mechanical property changes reflect diagenesis and fractures evolve with loading history mechanical stratigraphy and fracture stratigraphy need not coincide in subsurface studies current mechanical stratigraphy is generally measurable but because of inherent limitations of sampling fracture stratigraphy is commonly incompletely known to accurately predict fractures in diagenetically and structurally complex settings we need to use evidence of loading and mechanical property history as well as current mechanical states

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

thrust zone kinematics in a basement cover imbricate stack eastern pelvoux massif french alps abstract thrust imbrication is now widely accepted as a major process in controlling basement cover relationships in the external parts of the western alps complications in the simple geometries expected from thrusting alone arise from alpine deformation affecting pre existing extensional faults inherited from the old mesozoic basins this contribution describes the structural geology of part of the eastern pelvoux massif centred on the rocher de l yret where alpine deformation has masked any pre existing structures a series of major thrusts carry basement onto cover these lie west of and in the footwall to the pennine front a major zone of thrusting which carries the internal alps onto the external zones stretching lineations in calc mylonites derived from eocene limestones deposited on the basement indicate a tectonic transport axis of wnw ese plunging ca n100 e this direction is supported by the orientation of striae and corrugations on faults which cut basement rocks shear criteria in the calc mylonites imply top to the wnw shearing despite this simple kinematic picture basement cover relationships cannot be explained by thrusting alone a series of faults cut down through the thrust stack towards the wnw and show net extensional offsets with respect to the tectonic pile these faults and associated shears in the calc mylonites cannot be traced to depth rather they appear to branch onto earlier thrust surfaces this geometry is interpreted as due to distributed shearing in the hanging wall to the local floor thrust perhaps reflecting late reactivation of the pennine front

present day and future tectonic underplating in the western swiss alps reconciliation of basement wrench faulting and decollement folding of the jura and molasse basin in the alpine foreland abstract the western alps form a geodynamically active mountain belt showing the typical features of an evolving orogenic wedge with its pro wedge geometry to the nnw and its retro wedge structures to the sse renewed tectonic underplating of european continental crust occurred after the orogenic wedge underwent major dynamic disequilibrium following the break off of the southward subducting slab of the european passive margin the most important of these basement imbricates are the mont blanc aiguilles rouges and gastern aar crystalline massifs also forming the alps highest mountains the upper plate present day orogenic wedge of the western alps includes the molasse basin and the jura fold and thrust belt both decoupled from the basement over a basal decollement surface the overall geometry of this wedge appears to be strongly unstable according to simple wedge models in its attempt to regain stability out of sequence thrusts form in the existing basement nappes but also new basement nappes should develop beneath the southern portion of the molasse basin new out of sequence thrusts in the cover trigger higher than average uplift rates concentrated around the newly forming structures and are accompanied by a concentration of earthquakes tectonic underplating is further corroborated by neotectonics and the tectonic structures observed in the prealpes molasse basin and jura similarly uplift rates and earthquakes along the southern edge of the jura mountains seem to witness the development of a new incipient basement nappe at depth partial inversion of former permo carboniferous grabens in the basement a possible spatial coincidence of areas with strong earthquake activity and zones with uplift rates above surrounding values suggest a common mechanism for their origin in the western swiss alpine foreland combined with information from basement geometry and wedge dynamics it is proposed that the common mechanism is the development of basement imbricates by tectonic underplating the proposed model for ongoing and possible future tectonic underplating beneath an active alpine orogenic wedge also allows to reconcile the models of basement wrench faulting in the molasse basin and jura with the distant push theory where the molasse basin and jura develop over a basal decollement horizon

glacial conditions in the northern molucca sea region indonesia abstract palynological planktonic foraminiferal and stable isotope data from a sediment core in the northern mollucca sea have been used to evaluate regional glacial climatic and hydrographic conditions the palynological record shows that in glacial time the climate was drier than today indicating a weakened influence of the northwesterly winds at that time the drier climatic conditions at glacial time were associated with a higher lapse rate which together with a lower sea level resulted in a large expansion of the lower montane oak forests on the nearby island of halmahera glacial mollucca sea surface water salinities were probably higher than today while glacial surface water temperatures might have been close to present day values the deep chlorophyll maximum dcm layer in the northern molucca sea at glacial time was more productive and cooler than today probably the result of the inflow of cooler and nutrient enriched subtropical lower water from the pacific the less asymmetrical high latitude ice coverage at glacial time and the particularly strong increase in the pole to equator thermal gradient on the northern hemisphere provides theoretical evidence that the intertropical convergence zone itcz shifted equatorwards and oscillated over a more narrow latitudinal range than today this inferred configuration of the itcz at glacial time however fails to explain the observed increased aridity in the study area at that time we propose therefore that the drier glacial climatic conditions are related to a possible disturbance in the el nino southern oscillation enso system

kinematics of the alpine arc and the motion history of adria the alps have been interpreted traditionally in terms of north or northwest directed convergence between africa and europe1 with adria the continental underpinnings of the adriatic sea and northern italy acting as a promontory of the african continent2 this has been supported by recent analyses of africa europe relative plate motions3 5 which indicate dominantly north south directed convergence during the tertiary phase of intracontinental shortening we show here however that kinematic indicators from alpine tectonites are difficult to reconcile with this motion history figs 1 and 2 and are explained best by roughly west northwest directed adria europe motion since about 70 million years ago combined with an arc normal pattern of motion driven by local body forces this implies that adria has moved independently of both africa and europe since at least the late cretaceous

controls on the geometry of fold thrust belt salients salients convex to the foreland curves in the map traces of orogens typically involve fold thrust belts formed along the foreland margin of orogens an examination of the map view shape degree of asymmetry dimensions and structural trend line patterns i e the variation in fold trend and fault strike along the length of the belt of 20 fold thrust belt salients worldwide illustrates relationships between salient geometry and the geologic setting in which the salient formed in order to understand these relationships we used simple sandbox models to simulate the formation of three of the several types of salients specifically we examined indenter controlled salients the geometry of which reflects interaction of a fold thrust belt with a hinterland indenter basin controlled salients the geometry of which reflects lateral variations in the thickness of predeformational basin fill and detachment controlled salients the geometry of which reflects lateral variations in the strength of a detachment surface our models demonstrate that thrusts in these three types of salients initiate with a curved shape and that rocks within thrust sheets on the limbs of salients can undergo a vertical axis rotation in response to simple shear without requiring major rotation of the fault trace furthermore trend line patterns distinguish basin controlled from indenter controlled salients specifically structural trend lines in basin controlled salients converge at the end points of the curve while in indenter controlled salients they diverge at the end points of the curve the asymmetry of a salient correlates with the asymmetry of the predeformational basin and or of the indenter and with the convergence direction thus our results explain geometric characteristics of individual salients and address controversies concerning paleomagnetic data in salients they also may help prioritize petroleum exploration targets in salients foreland basin oil fields concentrate at the apex of basin controlled salients because the geologic factors that generate the salient also contribute to localizing oil fields

evolution and variability of the asian monsoon system state of the art and outstanding issues the asian monsoon is comprised of the indian and east asian subsystems these two components are linked to one another in varying degrees by regions of strong sensible heating indo asian landmass and strong latent heat export the western pacific warm pool and the southern subtropical indian ocean variability within the indian and east asian subsystems interactions among them and the extent to which they interact with other climate phenomena e g enso are current topics of modern and paleoclimate research this work provides an overview of past and current paleomonsoon research on tectonic to interannual time scales with a primary focus on marine sediment records while past and current work has contributed greatly to our understanding of paleomonsoon variability at all time scales additional efforts are required to make further progress in two critical areas 1 additional efforts are needed in terms of proxy development and evaluation requiring concerted efforts at long term sediment trap deployments in key monsoon influenced regions as well as development of adequate and widely available core top databases these are necessary to assess the impact of modern oceanographic and seafloor processes on potential monsoon proxies 2 additional effort is also needed in acquiring a sufficient geographic distribution of downcore records to assess linkages among the subsystems and their role in the context of extratropical climate change these records should have high sedimentation rates including varved sections this requires substantial survey support to identify the most appropriate coring and drilling targets c 2004 elsevier ltd all rights reserved