effects of topography on the curvature of fold and thrust belts during shortening of a 2 layer model of continental lithosphere abstract we have used analogue experiments to investigate the effects of surface topography on the curvature of fold and thrust belts under conditions of 1 initial relief but no erosion and 2 no initial relief but differential erosion sedimentation and transport in experiments where a 2 layer model lithosphere shortened and thickened in front of an advancing straight piston the geometry of the developing thrust wedge was very sensitive to variations in surface topography in models with an initially flat horizontal surface and in the absence of erosion and sedimentation thrusts were straight propagated forwards and nucleated at buckle folds far in front of an advancing piston around an initial topographic high plateau or cone thrusts tended to be arcuate forming salients towards the foreland initial plateaux and cones tended to behave rigidly while arcuate thrust slices formed around them to accommodate differential slip transfer zones developed on both sides of initial highs fault blocks rotated about vertical axes and thrusts moved in oblique slip within transfer zones in models with initially horizontal surfaces which were subject to differential erosion sedimentation and transport thrusts initially were straight but then progressively rotated around non eroded thickened and stronger areas these worked as indenters in front of which new thrusts nucleated at curved buckle folds these thrusts were also curved their apices being in front of the thickened non eroded areas in nature arcuate structural patterns are to be found around the altiplano of the central andes and around the tromen volcanic ridge in the neuquen basin of northern patagonia we infer that these areas behaved in quasi rigid fashion protected as they were by their high elevations and that differential erosion at the scale of the entire andes may have contributed to oroclinal bending

synchronous detachment folds and coeval sedimentation in the prepyrenean external sierras spain a case study for a tectonic origin of sequences and systems tracts this paper reports on the structural and sedimentary evolution of the middle to late eocene of the prepyrenean external sierras southern pyrenees spain the initiation duration and kinematics of a set of growth structures that developed in a shallow marine depositional setting is documented the detailed analysis of the syntectonic marine sediments not only confirms the already known east to west progression of deformation but also reveals the continued growth of the early formed structures as later ones propagate towards the foreland the sedimentary units coevally deposited with these growth structures are arranged in four depositional sequences their boundaries correspond to flooding surfaces which grade basinwards into correlative conformities they are also indicated by the presence of both angular unconformities and onlap geometries each depositional sequence generally consists of two systems tracts the lower one or transgressive systems tract is formed by up to 400 m of azoic marls deposited in outer ramp areas the upper one or highstand systems tract mainly consists of shallow siliciclastic and carbonate facies up to 200 m thick deposited in middle to inner ramp areas these depositional sequences are interpreted to be controlled by regional tectonic pulses an increase of tectonic activity resulted in the flooding of the basin and in the subsequent deposition of a thick succession of nearly azoic blue marls i e transgressive systems tract the overlying highstand systems tract developed following periods of diminished tectonism with the consequent growth and progradation of shallow carbonate platform facies

detachment folding fold amplification and diapirism in thrust wedge experiments 1 the relations between detachment folding fold amplification and salt diapirism in contractional settings have been investigated by means of scaled analogue models the viscosity of the silicone layer simulating salt in nature and the shortening rates were combined in order to reproduce weak type 1 models and strong type 2 models decollements deformation patterns in the roof sequence exhibited two contrasting styles 1 outward propagation of detachment folding along the decollement ofp mode and 2 passive roof duplex prd mode in type 2 models detachment folding propagated away from the most external thrust in the floor sequence while in type 1 models long lived detachment folds almost invariably localized amplified above a floor thrust tip as a result of strain localization a silicone wall intruded occasionally into the crestal graben of detachment folds in type 1 and ofp models best fitting of transition models data points indicates nonlinear relations with regression curves close to the equilateral hyperbola equation for both ofp prd and amplified detachment folds box folds transitions a quantitative comparison of model results with nature has been attempted by plotting salt based fold and thrust belts data points on the scaled transition curves obtained from the modeling such a comparison relates shear stress products and ratios to the conditions favoring the amplification of detachment folds and the potential emplacement of ductile diapirs in their core by reducing the roof sequence strength pore fluid pressure b is inferred to shift the equilibrium of fold and thrust belts toward the field of ofp and diapirism

centrifuged models of gulf of mexico profiles abstract physical models dynamically scaled in a centrifuge are used to explore the importance of slope progradation in driving internal salt structures much further horizontally than they rise large increments of ductile plastic overburden added at normal gravity values simulated primary clastic sedimentary progradation of a clastic slope over a layer of buoyant fluid simulating salt during load increments at a nominal 800 g in a centrifuge this ductile topographic slope spread over the ductile decollement except for down to basin growth faults all the structures considered to be distinctive in the northern gulf of mexico are simulated in the models that are scaled such that 1 mm and 60 s in the model correspond to 1 1 5 km and 2 6 ma in the prototype ratios of the rate of advance to the rate of rise of the shelf break compared with the rate of advance and increase in relief of salt structures control how much of the deep autochthonous salt is squeezed ahead of the advancing shelf and the paths this salt takes to shallow structural levels the few three dimensional diapiric stocks which developed from many two dimensional mullions in the models spread stock canopies which advanced huge distances before some became tongue canopies by climbing over clastic sediments already aggraded in front of them the models emphasize the significance of ductile spreading of the clastic sediments now being discerned by backstripping

experimental and field study of the effects of lithological contrasts on thrust related deformation 1 the influence of mechanical contrasts related to stratigraphy on thrust related deformation are investigated by sandbox modeling using combinations of granular materials possessing different mechanical properties and by structural analysis of a natural example from the spanish pyrenees the models used in this study consist of loose sand and glass microbeads in varied stratigraphic thicknesses and sequences and the natural example consists of a weakening upward sequence of sandstones and carbonates in both cases layers of different composition had a mechanical significance and accommodated shortening differently model sand and natural sandstone exhibited most shortening by thrust imbrication irrespective of stratigraphic position whereas glass microbeads and carbonates exhibited wider deformation zones and enhanced folding accompanied by displacement reduction along thrust surfaces cutting them transitions of structural style were guided by the stratigraphy rather than by a simple unidirectional propagation from a step up layer parallel shortening was accommodated by diverse mechanisms but did not vary significantly in layers which had different properties the magnitude with which mechanical contrasts were expressed in the models was influenced by the strength at the decollement zone the effect of mechanical contrast was more profound in models shortened above a low friction decollement

formation of orogen perpendicular thrusts due to mechanical contrasts in the basal decollement in the central external sierras southern pyrenees spain two series of analogue models are used to explore the effect of ductile frictional contrasts of the basal decollement on the development of oblique and transverse structures during thin skinned shortening these models simulate the evolution of the central external sierras ces southern pyrenees spain which constitute the frontal emerging part of the southernmost pyrenean thrust the ces are characterised by the presence of n s to nw se anticlines perpendicular to the pyrenean structural trend and developed in the hanging wall of the thrust system they detach on unevenly distributed triassic materials evaporitic dolomitic interfingering the models simulated the effect of adjacent ductile versus frictional decollements during shortening model series a tests the thickness ratio between overburden and the ductile layer whereas model series b tests the width perpendicular to the shortening direction of frictional decollement model results confirms that deformation reaches further in areas detached on a ductile layer whereas above frictional decollement areas shortening is accommodated by additional uplift and penetrative strain this replicates the structural style of the ces higher structural relief of n s anticlines with regard to orogen parallel structures absence of a representative ductile decollement in the core plunging towards the hinterland and foreland side closure not thrusted by the south pyrenean thrust

deformation patterns and structural vergence in brittle ductile thrust wedges an additional analogue modelling perspective abstract scaled physical models of brittle ductile thrust wedges investigated the causes leading to the development of the various structural styles observed in fold and thrust belts and accretionary prisms this study focused on some potential controlling factors such as 1 relative strength between the brittle overburden and the viscous decollement layer brittle ductile coupling 2 the effect of very low basal friction and 3 pre shortening rheological stratigraphy including decollement strength type 1 models had a single basal decollement whereas in type 2 models the decollement was embedded in brittle material simulating an upper roof sequence and a lower floor sequence other models investigated the effects produced by an horizon of mechanical weakness at the base of the viscous decollement type 1a and the role of decollement offset type 3 the experiments suggest the occurrence of a genetic relationship between the absolute values of shear stresses and the development of dominating hinterland or foreland verging thrust faults or dually verging thrusts by controlling the orientation of the 1 axis basal friction and decollement offset is found to effectively influence the deformation pattern and structural vergence and could explain the development of dominating backthrusts in cascadian type margins the decoupling of a frontal monocline via the upper decollement type 2 models produced passive roof duplex structures termed composite roof duplex when the frontal monocline coexists with outward fold propagation

recess drawn by the internal zone outer boundary and oblique structures in the paleomargin derived units subbetic domain central betics an analogue modelling approach abstract the subbetic domain comprising the south iberian paleomargin derived units is a fold and thrust belt developed over a ductile substrate showing a complex structural pattern in the central betics a main trend can be defined with respect to which frequent oblique structures are observed these oblique structures often subperpendicular to the main trend are not located along transfer zones but rather are present everywhere in the fold and thrust belt moreover they are coetaneous with those drawing the main trend this complex pattern is situated in front of a recess marked by the outer boundary of the internal zones the alboran domain which acted as backstop analogue models were designed to study the influence of such a recess on a ductile brittle multilayer one of the models in which the backstop recess is symmetric with respect to its direction of movement shows a high variation in the orientation of the resulting structures being not only qualitatively but also quantitatively similar to the studied natural case

modelling the geometry of coulomb thrust wedges internal geometry and detachment of coulomb thrust wedges is examined in a combined gravity and pressure force field under various boundary conditions and coulomb parameters frontally buttressed sand wedges accreted with narrow tapers above soles with negligible friction in these models serial imbricates stepped up in conjugate sets which operated synchronously or serially with increases in sole friction model coulomb wedges accreted in piggyback style with enhanced taper but narrower spacing of imbricates in this mode flat topped box fold anticlines nucleated at the frontal tip of a sole thrust prior to the fore limb failing as a ramp the initial ramp thrusts subsequently rotated and steepened to acquire concave upwards listric geometry when cohesion was a significant component of strength and the sand grains interlocked thoroughly ramp climb during piggyback thrusting occurred through the generation of a stack of backthrusts the taper of cohesionless sand wedges which lack any length scale was consistent with the critical cohesionless coulomb wedge taper in contrast the taper of experimental cohesive sand wedges which are scale dependent was consistent with the theoretical cohesive coulomb narrow taper only when the cohesive length scale was lr sr rar 10 6 this was constrained by comparing geometry of cohesive sand wedges shortened at different body force per unit mass

experimental insights on the geometry and kinematics of fold and thrust belts above weak viscous evaporitic decollement abstract this paper discusses the differences in mechanical properties and kinematics between fold and thrust belts detaching on evaporitic decollements and those detaching on stronger detachments physical experiments are described that model shortening of a thick brittle cover overlying a weak viscous decollement to gain a better understanding of these differences we tested the influence of 1 the decollement layer thickness and 2 the presence of a deformable backstop on the hinterland side and of a decollement pinch out on the foreland side because of the very low shear strength of the viscous decollement folds and thrusts did not propagate according to a piggy back sequence but by centripetal back and forth propagation additional shortening was accommodated by growth of all existing structures fold symmetry and thrust vergence varied between experiments models confined between two rigid vertical endwalls always deformed by symmetric folding and thrusting in models having a deformable backstop and a foreland decollement pinch out forethrusting initially dominated folds were asymmetric and fault blocks rotated in models having a thick decollement layer folds kept growing asymmetrically diapirism also depended on the initial decollement geometry diapirs formed only in models having a deformable backstop and were restricted to the hanging wall of a fault related fold finally the implications of such kinematics on the thermal history are discussed as well as the likelihood of hydrocarbon maturation and preservation

tracing tectonic deformation using the sedimentary record the study of sediments and sedimentary basins in terms of their tectonic environment requires a multidisciplinary approach and has increasingly drawn both techniques and objectives from fields outside sedimentology the application of different theoretical experimental and empirical resources provided by structural geology geochemistry geophysics scale modelling and field geology complement sedimentological methods with the combined aim of achieving a deeper understanding of the origins evolution and significance of sedimentary sequences in terms of their tectonic history studies presented in this volume range across a wide spectrum from the analysis of sedimentary sequence architecture at basin scale down to the chemical properties of individual grains and include studies from a range of tectonic settings the volume will be of interest to those involved with or contemplating studies involving the linkages between tectonics and sedimentation as well as a wider audience to whom the results of such studies may provide fresh insight

conical folds and apparent rotations in paleomagnetism a case study in the southern pyrenees abstract the so called apparent rotation was defined as the angular deviation between a local paleomagnetic direction after the standard bedding correction and their corresponding paleomagnetic reference j geophys res 85 1980 3659 in this paper we make a theoretical exploration on this concept and we conclude that depending on the number sequence orientation and magnitude of the deformation axes that have affected to the rock volume the apparent rotation may be the addition of a vertical axis rotation plus a spurious rotation the later is an error whose origin is the inappropriate application of the bedding correction during the restoration which does not fit the reverse sequence of deformations then apparent rot s l spurious rot vertical axis rot conical folds are complex geometries that cannot be restored by using the bedding correction however appearance of apparent and spurious rotations has not been studied even though the presence of this kind of folds is very common in fold and thrust belts in this paper we show a way to restore these structures and its associated paleomagnetic data by means of forward modelling on a stereographic projection the modelling has to be based on a good characterization of the geometry fold axis orientation and understanding of the kinematics of the fold general modelling has also allowed us to predict the apparent rotation in conical synclines its magnitude depends on the semiapical angle and on the degree of development of the fold the sense of the rotation clockwise or counter clockwise will depend on the sense of rotation the fold axis the western external sierras provide an excellent case study of apparent rotations due to the presence of a conical fold in the footwall ebro foreland basin of the south pyrenean sole thrust in addition a vertical axis clockwise rotation up to 47 32 in average has been detected in the hagingwall an apparent rotation up to 28 20 in average is observed in the footwall of the structure when a simple bedding correction is used this deviation does not fit with the expected ebro basin direction reference and is caused by the effect of the riglos conical syncline developed by the flexure of the foot wall ramp of the south pyrenean sole thrust the forward modelling carried out considering the geometry and kinematics non significant rotations in the autochthonous foot wall of this structure predicts very well the paleomagnetic observations in the field geographic coordinates with angular departures of only 5 in average the only application of the bedding correction would introduce errors spurious rotations up to 21 12 in average related to the conical geometry that would not allow the differentiation of these distinct structural units

deformation transfer in viscous detachments comparison of sandbox models to the south pyrenean triangle zone deformation transfer in viscous detachments comparison of sandbox models to the south pyrenean triangle zone

geometries of syntectonic sediments associated with single layer detachment folds abstract three kinematic models have been proposed to account for the geometry and kinematics of detachment folds involving a homogeneous competent layer detached over a ductile unit model 1 variable limb dip constant limb length model 2 constant limb dip variable limb length and model 3 variable limb dip variable limb length because the same fold shape can be generated by any of the above mechanisms fold kinematics are best determined by the geometries of syntectonic sediments in single layer detachment folds growth strata patterns are controlled by axial surface activity limb rotation limb lengthening fold uplift rates sedimentation rates and deformation mechanisms of the syntectonic sediments asymmetric kink folds have been modelled and compared with natural examples from the southern spanish pyrenees under conditions of high sedimentation rates model 1 folds produce characteristic fanning growth stratal wedges that initially onlap and then progressively overlap the detachment anticline whereas at low sedimentation rates anticlines with fanning growth wedges on both limbs are formed model 2 folds under conditions of high syntectonic sedimentation rates form anticlines with growth strata largely parallel to the pre growth units and thinned over the fold crest in contrast at low sedimentation rates model 2 folds show offlapping growth strata onto both limbs model 3 growth folds under conditions of high syntectonic sedimentation rates form anticlines with intermediate features from model 1 and model 2 at low sedimentation rates anticlines are formed with offlapping growth structures

structural evolution of a fold and thrust belt generated by multiple decollements analogue models and natural examples from the northern apennines italy this study analyses the role played by the mechanical proprieties of the rocks involved in a thrust system focusing on the problem of multiple decollements and of related compressional structures integration of geophysical seismic reflection profiles and geological data and scaled sandbox models are used to study the deformation style of two areas of the northern apennines italy the po plain and the umbria marche apennines both areas are characterised by a complex stratigraphy consisting of decollements located at different depths that influence the geometry and kinematics of the thrust system the main characteristic of the models presented here is the presence of two decollement horizons situated at the base and in an intermediate level of the models during deformation of the models these two decollement horizons generate two sets of structures with different geometrical characteristics and significance through the joint analysis of geophysical and geological data and model results wavelengths of the compressional structures analysed show that the structural style of the two analysed areas is almost similar moreover model results prove that the final configuration of the thrust system follows the general rules of evolution of a wedge deformed above a weak decollement and is largely governed by the larger deep seated structures

modeling of thrust fronts above ductile and frictional detachments application to structures in the salt range and potwar plateau pakistan series of scaled sandbox models are used to simulate the development of thin skinned simultaneous shortening above adjacent ductile and frictional substrates these models simulate the evolution of the potwar plateau and salt range in pakistan where pale

transverse fold evolution in the external sierra southern pyrenees spain fault slip data are used to reconstruct varying tectonic regimes associated with transverse fold development along the eastern and southern margins of the jaca basin southern pyrenees spain the spanish pyrenean foreland consists of thrust sheets and leading edge decollement folds which developed within piggyback basins guara formation limestones on the margins of the jaca basin were deposited synchronously with deformation and are exposed in the external sierra within the transverse folds principal shortening axes determined from p and t dihedra plots of fault slip data show a shift from steep shortening in stratigraphically older beds to nne ssw horizontal shortening in younger beds older strata are characterized by extensional faults interpreted to result from halotectonic salt tectonics deformation whereas younger strata are characterized by contraction and strike slip faults interpreted to result from thrust sheet emplacement the interpretation of the timing for the shortening axes in the younger strata is supported by the observation that these axes are parallel to shortening axes determined from finite strain analysis calcite twins and regional thrusting directions determined from fault related folds and slickenlines this study shows that fault population analysis in syntectonic strata provides an opportunity to constrain kinematic evolution during orogeny

episodic accretion and strain partitioning in a model sand wedge we model led thrust wedge accretion and deformation partitioning in a passively layered sand detached and shortened above a smooth rigid decollement the thrust wedge accretes in piggyback style during forward advance of a rear wall the passively layered sand accommodates the shortening penetratively by kinking ramp folding and by imbrication in single layers the style of compression changes with time and or stratigraphic position within the sand prism initial penetrative layer shortening above a slipped zone of decollement is succeeded by formation of monoclinal or conjugate shear bands at temporary terminations of decollement the shear bands subsequently narrow down and lock as thrust ramps the model sand wedge accrets episodically rather than steadily episodicity is controlled by the stick slip mode of decollement propagation and by volume loss and compaction of the wedge material in response to convergence this results in formation of a wedge with a convex upwards cross sectional topography

relationships between lightning and properties of convective cloud clusters 1 satellite observations of convective system properties and lightning flash rate are used to investigate the ability of potential lightning parameterizations to capture both the dominant land ocean contrast in lightning occurrence and regional differences between africa the amazon and the islands of the maritime continent as found in previous studies the radar storm height is tightly correlated with the lightning flash rate a roughly second order power law fit to the mean radar echo top height above the 0 c isotherm is shown to capture both regional and land ocean contrasts in lightning occurrence and flash rate using a single set of parameters recent developments should soon make it possible to implement a parameterization of this kind in global models parameterizations based on cloud top height convective rain rate and convective rain fraction all require the use of separate fits over land and ocean and fail to capture observed differences between continental regions

role of lateral thickness variations on the development of oblique structures at the western end of the south pyrenean central unit abstract the montsec unit is one of the most important detached south verging nappes within the south pyrenean central unit spcu southern pyrenees a n s cross section of its western sector based on seismic reflection profiles shows a hangingwall ramp geometry in mesozoic strata overlain by a syntectonic series of lower eocene sediments with growth geometry the geometry of growth strata constrains the age of its movement between the paleocene and the middle eocene the geometry of the western oblique ramp of the south pyrenean central unit is defined by a series of n s folds in some cases associated with underlying west verging thrusts as indicated by seismic reflection profiles and field data in this paper we propose that the geometry of the thrust wedge of mesozoic units progressively thinning from east to west strongly contributed to constrain the location and geometry of the western termination of the montsec thrust the hypothesis proposed is checked by a series of experimental wedges developed in a sandpack with lateral and three dimensional thickness variations oblique structures form as thrusting progresses at the tip of the sand wedge

experimental modeling of role of gravity and lateral shortening in zagros mountain belt dynamically scaled analogs of the geologic structures of the zagros mountain belt are used to argue that different parts of the zagros mountains of iran record different combinations of the effects of a gravity driven overturn and a southwest northeast lateral shortening superimposed on the zagros overturn partially scaled material models have been used to simulate the zagros geodynamics which involve layer parallel compression of a 6 to 7 km thick phanerozoic carbonate cover containing a pattern of preshortening diapirs the folds in the zagros form rapidly 1 5 mm yr in a 20 to 30 km wide zone reactive some of the preshortening diapirs and generate new synshortening listric diapirs a third set of postshortening diapirs rises from the hormuz decollement behind the fold thrust front model buckle folds superimposed on diapirs or pillows tend to avoid and curve around preshortening diapirs which flatten in the synclines model profiles show that lateral shortening induces residual salt at depth to flow toward and rise through the anticlinal cores as synshortening or postshortening diapirs i suggest that any salt pillows in currently diapir free zones of the zagros fold thrust belt may surface as diapirs through the anticlines in the future in the absence of well data seismic and field observations i have used only three map pattern criteria to recognize the timing of diapirs these are locally obscured by extrusive salt sheets preshortening diapirs are generally small and elongate parallel to fold axes and are restricted to synclines synshortening diapirs are elongate perpendicular to the fold axes and are restricted to anticlines postshortening diapirs can be the same size as synshortening diapirs or larger and can be circular they are more common in the anticlines

3d evolution of fold and thrust belts formed by oblique convergence abstract this paper presents the results of a series of scaled analogue models designed to simulate thrust belt development formed by orthogonal and oblique convergence the models were constructed to produce doubly vergent orogenic wedges with a pro wedge and a retro wedge separated by an uplifted orogenic core models were constructed from homogeneous layered sandpacks in a 3 m 1 3 m deformation rig the progressive evolution of the models was recorded using digital photography and the photographs were animated for analysis the experiments investigated convergence obliquities from orthogonal 90 to as low as 15 obliquity orthogonal models produced long linear critically tapered pro wedge fold and thrust belts parallel to the convergence margin together with a narrow uplifted core and a steep retro wedge thrust system the taper angle of the pro wedge was typically 11 12 whereas the retro wedge maintained a steeper taper of 38 42 models where the convergence vector was oblique at angles of 60 and 45 to the margin produced doubly vergent thrust wedges with thrust faults trending parallel to the margin there was little evidence of linked penetrative strike slip faulting but en echelon riedel like shear systems developed in the 45 oblique model subordinate oblique slip motion was observed on some thrust faults in contrast for 30 and 15 oblique convergence models strong deformation partitioning developed with steeply sloping pro wedges that did not have critical tapers through going linked strike slip faulting was developed that cut the uplifted axial zones of these models analysis of the models by animation of the digital photographs shows how the thrust systems initiated and propagated in particular it is clear that at any one time several thrusts were moving simultaneously serial cross sections through the moderately oblique convergence models 60 45 are almost indistinguishable from the orthogonal model cross sections the results of orthogonal convergence experiments compare well to the map patterns of faults and folds in the salt range pakistan 60 and 45 oblique convergence models compare well to the zagros where some strain partitioning on strike slip faults occurs the highly oblique models show very strong strain partitioning with penetrative margin parallel strike slip faulting similar to that found in ne venezuela

regional and local controls on postglacial vegetation and fire in the siskiyou mountains northern california usa article i nfo the siskiyou mountains of northwestern california and southwestern oregon are a floristic hotspot and the high diversity of conifers there likely results from a combination of geological ecological climatological and historical factors to evaluate how past climate variability has influenced the composition structure and fire regime of the siskiyou forests pollen charcoal and lithological evidence was examined from two lakes along a moisture gradient to reconstruct the vegetation fire and climate history the late glacial period was characterized by subalpine parkland and infrequent fire at both sites during the late glacial early holocene transition period subalpine parkland was replaced by a closed forest of pinus cupressaceae abies and pseudotsuga and more frequent fires a 1000 years earlier at the wetter site and it is likely that reduced pacific ocean upwelling created warmer drier conditions at the coast in the early holocene pinus cupressaceae were less abundant and fire less frequent at the coastal site during a period of increased coastal upwelling and fog production in the late holocene abies pseudotsuga pinus and quercus vaccinifolia increased in the forest at both sites suggesting a widespread response to cooling fewer fires at the wetter site may account for the abundance of picea breweriana within the last 1000 years the comparison of the two records implies that large scale controls in climate during the last 14 000 cal yr bp have resulted in major changes in vegetation and fire regime asynchrony in the ecosystem response of wetter and drier sites arises from small scale spatial variations in effective moisture and temperature resulting from topographically influenced microclimates and coastal to inland climate gradients

reverse modelling of detachment folds application to the pico del aguila anticline in the south central pyrenees spain abstract a simple method to estimate fold amplification and thrust movement rates for detachment folds is documented and illustrated by its application to a symmetrical detachment fold in the southern pyrenees spain the technique provides a complete record of the kinematic evolution of detachment folds and is based on the application of equations for detachment folds involving limb rotation the method uses the stratal pattern of the syntectonic sediments and assumes that these growth strata were deposited horizontally that the folds involve a homogeneous competent unit detached over a ductile horizon and that the folds can be represented by chevronkink bands the procedure is applicable to any detachment fold with associated growth strata that display wedge geometries progressive unconformities indicating limb rotation through time this method can be used for both detachment folds formed with constant limb length or variable limb length and it can also accommodate undecompacted or decompacted growth strata