laboratory experiments simulating the geomorphic response to tectonic uplift 1 we present the results of an experimental study of topography dynamics under conditions of constant precipitation and uplift rate the experiment is designed to develop a complete drainage network by the growth and propagation of erosion instabilities in response to tectonic perturbations the quantitative analysis of topographic evolution is made possible by using telemetric lasers that perform elevation measurements at an excellent level of precision we focus our study on the effect of initial surface organization and of uplift rate on both the transient dynamics and the steady state forms of topography we show that the transient phase is strongly dependent on the initial internally drained area which is found to decrease exponentially with time the topography always reaches a steady state whose mean elevation depends linearly on uplift rate with a strictly positive value when uplift is zero steady state surfaces are characterized by a well defined slope area power law with a constant exponent of 0 12 and an amplitude that depends linearly on uplift rate with a strictly positive value when uplift is zero these results are consistent with a stream power law erosion model that includes a nonnegligible threshold for particle detachment uncertainty regarding the sediment transport length is resolved by calibrating the transient dynamics with a surface process model reappraising published results on the linear dependency between mean elevation or relief and denudation rate we suggest that an erosion threshold is worth considering for large scale systems

meteoric like fabrics forming in marine waters implications for the use of petrography to identify diagenetic environments petrographic fabrics have long been used to identify meteoric diagenesis of carbonate sediments however on the basis of oxygen isotopic data we document similar fabrics forming in marine pore fluids in the shallow subsurface of great bahama bank therefore petrographic fabrics alone are not reliable indicators of diagenetic environments even for shallow water sediments in our study skeletal grainstones show two distinct diagenetic assemblages either dissolution of aragonitic grains and minimal cementation high permeability intervals or abundant blocky spar cement and neomorphism of aragonitic skeletal grains low permeability intervals these marine burial fabrics are present as shallow as 110 m below sea level well above the aragonite compensation depth a feature that must be considered for models of diagenesis in ancient carbonate sediments marine burial diagenesis may be important in ancient carbonate sediments deposited in moderate water depths or in shallow water during rising sea level where meteoric diagenesis is suppressed

geometry and kinematics of recent deformation in the mondy tunka area south westernmost baikal rift zone mongolia siberia we used satellite imagery and field data to investigate the south westernmost baikal rift zone we focus our study in the mondy and ikhe ukhgun valleys site of an mw 6 9 seismic event in 1950 surface deformations are observed along the e w trending mondy strike slip fault and along the ikhe ukhgun thrust the mondy fault system is 80 km long and is composed of four segments 10 15 km long these segments are characterized by subvertical planes with left lateral movements the ikhe ukhgun thrust is 20 km long dips 40 to the south and shows reverse movement with a left lateral component these observations are consistent with the present day regional nne ssw compression and with the focal mechanism of the 1950 mondy earthquake that was recently re evaluated these features like those observed in the tunka basin demonstrate a recent change of regional strain regime from transtension to transpression that we place before the late pleistocene

landsliding and the evolution of normal fault bounded mountains much of the tectonic and climatic history in high relief regions such as the mountains of the western u s basin and range province is contained in the morphology of hillslopes drainage networks and other landforms that range in scale from 10 1 to 101km to understand how these landforms evolve we have developed a numerical landscape evolution model that combines a detailed tectonic displacement field with a set of physically based geomorphic rules bedrock landsliding long recognized as a significant geomorphic process in mountainous topography is for the first time explicitly included in the rule set in a series of numerical experiments we generate synthetic landscapes that closely resemble mountainous topography observed in the basin and range the production of realistic landscapes depends critically on the presence of bedrock landslides and landsliding yields rates of long term erosion that are comparable in magnitude to those of fluvial erosion the erosive efficiency of bedrock landsliding implies that hillslopes may respond very quickly to changes in local base level and that fluvial erosion is the rate limiting process in steady state experimental landscapes our experiments generate power law distributions of landslide sizes somewhat similar to both field and laboratory observations thus even a simple model of bedrock landsliding is capable of quantitatively reproducing mountainous topography and landslide distributions and represents a significant step forward in our understanding of the evolution of normal fault bounded ranges

climate tectonics and the morphology of the andes large scale topographic analyses show that hemisphere scale climate variations are a first order control on the morphology of the andes zonal atmospheric circulation in the southern hemisphere creates strong latitudinal precipitation gradients that when incorporated in a generalized index of erosion intensity predict strong gradients in erosion rates both along and across the andes cross range asymmetry width hypsometry and maximum elevation reflect gradients in both the erosion index and the relative dominance of fluvial glacial and tectonic processes and show that major morphologic features correlate with climatic regimes latitudinal gradients in inferred crustal thickening and structural shortening correspond to variations in predicted erosion potential indicating that like tectonics nonuniform erosion due to large scale climate patterns is a first order control on the topographic evolution of the andes

depositional architecture of growth fault related wave dominated shelf edge deltas of the oligocene frio formation in corpus christi bay texas abstract growth faults within the frio formation define six subbasins on the south texas shelf and add to the complexity of the sediment dispersal along the shelf margin these growth faults influenced sediment pathways controlled sediment partition and provided increased accommodation for deltaic depocenters rollover and thickening of sediments occur on the downthrown side of growth faults with offsets of at least 150 m and up to 750 m growth strata are indicated by intervals that thicken landward by several tens of meters from anticline crests individual 4th order 100 500 ky regressive cycles expand about five to seven times across growth faults expansion ratios as great as 10 are observed the shelf edge is associated with the largest displacement expansion ratios and thickness of prograding deltaic sequences sedimentary structures and trace fossil associations identified in cores from nueces encinal and red fish bay subbasins indicate deposition on a wave dominated deltaic shoreline the cores exhibit highly bioturbated muddy sandstones alternating with decimeter thick clean sandstones with hummocky cross stratification alternation of fair weather wave deposits with sandy storm beds in two successive fault zones suggests that all subbasins developed under similar conditions during growth fault development high sediment supply conditions favored accumulation of thicker sediments on the downthrown sides of the faults wave dominance of deltas on the outer shelves in the growth compartments suggest that building of the upper slope rather lowers slope margin and decreases the likelihood of the presence of sandy deep water fans correlation of about 700 well logs integrated with seismic data provided the areal distribution and relative timing of sediment filling of the growth faulted compartments to unravel the evolution of higher order fourth and fifth sequences affected by these growth faults core data were used to recognize depositional environments to calibrate lithology to well logs and to characterize seismic amplitude anomalies within this shoreface succession the clean sandy storm beds will make attractive hydrocarbon reservoirs especially on the crest of rollover anticlines in downthrown compartments these sandstone bodies pinch out seaward into open marine shelf mudstones and are sealed by overlying shelf mudstones deposited during transgressive episodes

geometry and rate of faulting in the north baikal rift siberia we present a detailed morphotectonic analysis of late quaternary faulting in the north baikal rift nbr a region characterized by ranges and basins distributed over more than 800 km along strike in eastern siberia remote sensing techniques spot meteor scenes and aerial photographs are used to map the active fault network which displays a general en echelon distribution from the northern lake baikal to the easternmost basin with 30 km spaced overstepping segments of 10 80 km in length most faults have a dominant dip slip component over their cenozoic history the inherited crustal fabric strongly influences the overall geometry of the rifted basins we use 54 14c ages of postglacial terraces near the foot scarps of the muya basin to date offsets measured inside alluvial fans the last main postglacial event in this area appears to be the early holocene optimum dated at 10 2 ka following the onset of deglaciation at 13 ka using these time constraints a detailed leveling across two terraces offset by the taksimo fault west muya basin shows consistent minimum vertical slip rates of 1 6 0 6 mm yr 1 using 30 other active scarps analyzed in the field we find a lower bound for horizontal velocity of 3 2 0 5 mm yr 1 across the nbr a rate close to the one found in the southern rift from global positioning system measurements we then compare directions of slip vectors from holocene field data and slip directions from earthquake fault plane solutions although local discrepancies appear the mean directions of lesser horizontal stress 3 inverted from theses values are n130 e and n155 e respectively which are comparable within uncertainties and favor a rifting obliquity of 30 40 extrapolating our holocene rates we estimate basin ages younger than those generally believed less than 7 ma and propose a spatial and temporal evolution of rifted basins consistent with experimental models of oblique rifting total amounts of extension and vertical throw 7 and 12 km respectively across major faults appear rather constant from the central to the northern rift these results favor a progressive development of asymmetric grabens in a rift zone that widens with times and they indicate a strong rheological control on deformation which seems enhanced by other contributions than the far field effects of the indo eurasian collision

drainage basin evolution in the rainfall erosion facility dependence on initial conditions four experiments in alluvial drainage basin evolution were carried out in the rainfall erosion facility ref at colorado state university to investigate the dependence of basin evolution on initial topography basins were initially undissected each experiment began with a unique initial condition representing various end members of relief and hypsometry drainage network development hillslope processes basin denudation and basin response to base level lowering all depended strongly on the initial topography no classic model of drainage network evolution was found to be generally applicable initially planar slopes first developed subparallel channels that extended headward dendritically during an early phase of extension channel incision occurred first in the interior of the basin where saturation overland flow was greatest not at the basin outlet as assumed in most classic models of network development channels widened over time initiating lateral migration and drainage capture in the downslope portion of the watershed before transferring lateral migration upslope planar basins of larger initial gradient grew headward more quickly and become more deeply entrenched inhibiting late stage lateral migration an experiment with initial relief concentrated at a plateau edge evolved in several unique ways a high ratio of subsurface to surface flow gave rise to mass movements at the plateau edge and outlet channels deep channels were quickly cut initially but did not extend far upslope because slope instability undermined channel head migration leaving the plateau undissected and hence very slow to erode these results suggest that the distribution of relief within a basin exerts an important control on drainage network pattern and basin denudation in addition erosional basins may evolve in several distinct modes characterized by particular combinations of hypsometry hillslope processes and mean denudation rate

fluvial landscape response time how plausible is steady state denudation whether or not steady state topography and denudation are probable states depends on the timescale of system response to tectonic and climatic perturba tions relative to the frequency of those perturbations this paper presents analytical derivations of algebraic relations for the response time of detachment limited fluvial bedrock channel systems both to tectonic and climatic perturbations detachment limited fluvial erosion is described by the stream power incision model and the derivations are limited to the applicability of that model all factors likely to influence system response time that are not adequately captured by the stream power incision model will tend to increase the response time the calculations presented thus provide minimum estimates of landscape response time and therefore over predict the prob ability of attaining and sustaining steady state topography and denudation the central range of taiwan is used as a case study to estimate response times in a landscape often argued to be in steady state model parameters are fit to modern stream profiles by assuming that the topography represents a quasi steady state form estimated response times generally range from 0 25 to 2 5 ma depending on the non linearity of the incision rule and the magnitude and type of perturbation thus it may be reasonably argued that steady state topography and denudation are likely to prevail during periods of climatic stability response time is sufficiently short compared with plate tectonic timescales however rapid climatic fluctuation in the quaternary appears to preclude the attainment of steady state conditions in modern orogens motivation

post 4 ma initiation of normal faulting in southern tibet constraints from the kung co half graben the timing of e w extension of the tibetan plateau provides a test of mechanical models of the geodynamic evolution of the india asia convergence zone in this work we focus on the kung co half graben southern tibet china bounded by an active n s normal fault with a minimum vertical offset of 1600 m to estimate the onset of normal faulting we combined high and medium temperature u pb ar ar and low temperature u th he thermochronometry of the kung co pluton a two mica granite of the northern himalayan granitic belt that outcrop in the footwall of the fault biotite and muscovite ar ar ages are close from each other 16 ma 0 2 ms and 15 0 4 ma bt which is typical of fast cooling the zircon and apatite u th he ages range from 11 3 to 9 6 ma and 9 9 to 3 7 ma respectively these he ages are indicative of 1 fast initial cooling from 11 3 to 9 ma gradually decreasing with time and 2 a high geothermal gradient 400 c km close to the surface at 10 ma the kung co pluton was emplaced at about 22 ma u pb on zircon at less than 10 km depth and 520 545 c subsequent to its shallow emplacement the pluton underwent fast thermal re equilibration ending around 7 5 ma followed by a period of slow cooling caused either by the end of the thermal re equilibration or by very slow exhumation 0 02 0 03 mm yr from 7 5 ma to at least 4 ma in either case the data suggest that the exhumation rate increased after 4 ma we infer this increase to be related to the initiation of the kung co normal fault a critical examination of previously published data show that most n s tibetan normal faults may have formed less than 5 ma ago rather than in the miocene as assumed by several authors such a young age implies that e w extension is not related to the neogene south tibetan magmatism 25 to 8 ma consequently models relating e w extension to magmatism such as convective removal of the lower lithosphere may be inappropriate we rather think that this extension is related with local accommodation of boundary forces and displacements 2007 elsevier b v all rights reserved

mechanical and chemical compaction in fine grained shallow water limestones abstract artificial compaction of in situ cores of modern sediments from differing sedimentary environments resulted in 1 reduction of sediment thickness by 50 percent and more 2 reduction of initial porosities of 65 to 75 percent to 35 to 45 percent 3 creation of megascopic textures almost identical to many ancient lime mud and wackestones 4 creation of organic wispy stylolite like layers that in nature probably would initiate dissolution and stylolite development given burial and time 5 chemical compaction evidenced by thin sections showing quartz grains piercing mollusc shells without causing fractures and sem evidence of solutional interfitting of 1 to 4 m size aragonitic carbonate grains 6 obliteration of pellets and birdseye or fenestral voids in those sediments here early cementation was lacking pellets were preserved in slightly cemented bahama bank muds compacted to half the original thickness 7 obliteration of identifiable marine grasses and vertical root tube voids 8 mashing of sediment filled circular burrows to produce ellipsoidal structures significant mechanical compaction resulted from pressures simulating less than 1 000 ft 305 m of burial increasing loads to an equivalent of more than 10 000 ft 3 400 m did not significantly increase compaction or reduce sediment core length chemical compaction pressure dissolution was detected only in sediment cores compacted to pressures greater than 10 000 ft 3 400 m of burial these short term experiments suggest that chemical compaction would begin at much shallower depths given geologic time compaction experiments that caused chemical compaction lend support to the well established hypothesis that cement required to produce a low porosity low permeability fine grained limestone is derived internally dissolution ion diffusion and reprecipitation are considered the m st likely processes for creating significant thicknesses of dense limestones in the geologic record continuation of chemical compaction after significant porosity reduction necessitates expulsion of connate fluids possibly including hydrocarbons

transient fluvial incision in the headwaters of the yellow river northeastern tibet china 1 we utilize topographic analysis of channel profiles combined with field measurements of erosion rates to explore the distribution of channel incision in the anyemaqen shan a broad mountainous region in the northeastern tibetan plateau tributary channels to the yellow river display systematic downstream increases in channel gradient associated with convex upward longitudinal profiles steep lower reaches of channels are associated with rapid 1 m ka incision rates along the yellow river while upstream reaches are associated with relatively slow 0 05 0 1 m ka erosion of soil mantled uplands covariance between erosion rates and channel steepness indices suggest that channels are adjusted to match long wavelength differential rock uplift across the range geologic constraints indicate that rapid incision downstream of the range is associated with excavation of basin fill driven by changes in relative base level farther downstream the upstream limit of this wave of transient incision is marked by a series of knickpoints that are found at nearly the same elevation throughout the watershed consistent with knickpoint migration as a kinematic rather than diffusional wave tributary channel gradients downstream of knickpoints however display a progressive adjustment to increased incision rates that may reflect the influence of increased sediment flux comparison of observed channel profiles to a stream power model of fluvial behavior reveals that the rate of knickpoint propagation can only be explained if the erosional efficiency coefficient k increases during incision our results thus highlight the utility of channel profile analysis to reconstruct the fluvial response to both active tectonism and external changes in base level

drainage network evolution and patterns of sedimentation in an experimental wedge in fold and thrust belts drainage organization and patterns of sedimentation depend conceptually on the ability or not for preexisting reaches to incise uplifting thrust sheets in this study we investigate experimentally the dynamics of drainage network in a wedge submitted to shortening and erosion it allows us to reproduce and to monitor the interactions between tectonics erosion and sedimentation during the development of up to five successive thrust sheets in the experiments channels adjust to uplift rate by both increasing their slope and narrowing their channels as it is observed in nature the series of experiments shows that the proportion of persistent preexisting transverse channels increases with the ratio of rainfall over shortening rates the experiments confirm the view that the competition between discharge and tectonic uplift controls along strike variations in sediment flux in sedimentary basins by controlling the drainage organization if the transverse channels draining a wedge are not diverted a line source dispersal system develops in front of the active structure if channels are diverted in the backlimb of the frontal structure it results in point sourced depositional systems separated by areas fed only by small channels developing in the front of the wedge fans accumulated in front of the active structures reveal two stages of sedimentation one of progradation while the frontal structure is active and a second one of valley backfilling and thrust sealing during internal deformation of the wedge the experiments also suggest that spatial variations in rock uplift rate along a thrust front may be evidenced by minimum discharge variations of persistent transverse channels

transformation of aragonite dominated lime muds to microcrystalline limestones scanning electron microscopy of textures in several well lithified pleistocene micrites mixed micrite and microspar from south florida and the bahamas shows significant diagenetic alteration of the lime mud precursors the dominance of aragonite in those precursor muds is supported by the surprising presence of abundant aragonite relics in the neomorphic calcite crystals confirmed by feigl stain x ray and electron diffraction polished very lightly etched surfaces of neomorphic calcite crystals even in the microspar show aragonite relics and pits both absent in coexisting void fill cements similarities between micrite and microspar crystals indicate their common origin through a one step neomorphic process of calcitization that is the mud did not first calcitize to micrite and then alter to microspar by aggrading neomorphism this conclusion has more general implications for the interpretation of the origins of other older microsparitic carbonates both early calcitization and concurrent early meteoric cementation were significant in producing the florida bahamas micrites studied which have low porosities similar to those found in most ancient fine grained limestones these low porosities despite the absence of significant overburden indicate that major porosity reduction without compaction can occur in calcitized aragonite dominated muds

small is beautiful upscaling from microscale laminar to natural turbulent rivers 1 the use of microscale experimental rivers with flow depths of the order of a few millimeters to investigate natural processes such as alluvial fans dynamics knickpoints migration and channel morphologies such as meandering and braiding has become increasingly popular in recent years this raises the need to address the issue of how to extrapolate results from the experimental microscale at which flow is laminar to the scale of natural turbulent rivers we address this question by performing measurements of average flow velocity and sediment transport in an experimental laminar river the average flow velocity is correctly predicted from the navier stokes equation solved for a steady uniform laminar flow laminar sediment transport is found to be consistent with the law of meyer peter and muller 1948 commonly used to describe sediment transport in natural turbulent rivers we also show that surface tension is important only if the microscale river width is on the order of or smaller than the capillary length these results allow us to demonstrate that the evolution of longitudinal bed profiles of turbulent and laminar rivers are governed by identical dimensionless equations and therefore follow the same dynamics differences of time and length scales at work in experimental and natural rivers are mainly encoded in the expression of two parameters a diffusion coefficient and a threshold slope on the basis of this analysis we derive a set of equations allowing us to rescale bed elevation downstream distance time and uplift rate from an experimental microscale river to the field scale finally we show how this set of equations can be used to rescale these same parameters in the case of a temporally varying discharge

slope distributions threshold hillslopes and steady state topography digital elevation models of two steady state mountain ranges the olympic mountains om and oregon coast range ocr are used to examine relationships between slope distributions the development of threshold hillslopes and steady state topography plots of drainage area versus slope for these mountain ranges exhibit substantial scatter that complicates comparison of range form to analytical theories and landscape evolution models contour plots of the density of such data reveal an attractor at the scale of the transition from hillslope processes to channel processes and log bin averaging reveals trends that parallel predictions of steady state erosion laws but with different rate laws for five distinct process domains hillslopes valley heads and colluvial bedrock and alluvial valley segments slope histograms computed for 100 km2 areas defined by a 10 10 km grid throughout the om exhibit approximately normal or exponential distributions in areas of active rock uplift and depositional topography respectively local slope distributions in the ocr also tend to be normally distributed but some are left skewed in areas with gentler slopes mean slopes determined both over the above referenced grid and a 10 km diam moving window are relatively invariant in the core of the om in spite of strong contrasts in bedrock erodibility and gradients in long term rock uplift rates in contrast the mean slopes in the ocr parallel latitudinal gradients in rock uplift rates and bedrock erodibility hence the slope distributions in the om and ocr reflect distinct relationships between development of threshold bedrock and soil mantled hillslopes and steady state topography

a new experimental material for modeling relief dynamics and interactions between tectonics and surface processes abstract we developed a new granular material mativ to study experimentally landscape evolution in active mountain belt piedmonts its composition and related physical properties have been determined using empirical criteria derived from the scaling of deformation erosion transport and sedimentation natural processes mativ is a water saturated composite material made up with 4 granular components silica powder glass microbeads plastic powder and graphite whose physical mechanical and erosion related properties were measured with different laboratory tests mechanical measurements were made on a modified hubbert type direct shear apparatus erosion related properties were determined using an experimental set up that allows quantifying the erosion sedimentation budget from tilted relaxation topographies for mativ we also investigated the evolution of mean erosion rates and stream power erosion law exponents in 1d as a function of slope our results indicate that mativ satisfies most of the defined criteria it deforms brittlely according to the linear mohr coulomb failure criterion and localizes deformation along discrete faults its erosion pattern is characterized by realistic hillslope and channelized processes slope diffusion mass wasting channel incision during transport eroded particles are sorted depending on their density and shape which results in stratified alluvial deposits displaying lateral facies variations to evaluate the degree of similitude between model and nature we used a new experimental device that combines accretionary wedge deformation mechanisms and surface runoff erosion processes results indicate that mativ succeeded in producing detailed morphological and sedimentological features drainage basin channel network terrace syntectonic alluvial fan geometric kinematic and dynamic similarity criteria have been investigated to compare precisely model to nature although scaling is incomplete it yields particularly informative orders of magnitude with all these characteristics mativ appears as a very promising material to investigate experimentally a wide range of scientific questions dealing with relief dynamics and interactions between tectonics erosion and sedimentation processes

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

orogeny and orography the effects of erosion on the structure of mountain belts a numerical model of the coupled processes of tectonic deformation and surface erosion in convergent orogens is developed to investigate the nature of the interaction between these processes crustal deformation is calculated by a two dimensional finite element model of deformation in response to subduction and accretion of continental crust erosion operates on the uplifted surface of this model through fluvial incision which is taken to be proportional to stream power the relative importance of the tectonic and erosion processes is given by a dimensionless erosion number relating convergence velocity rock erodibility and precipitation rate this number determines the time required for a system to reach steady state and the final topographic shape and size of a mountain belt fundamental characteristics of the model orogens include asymmetric topography with shallower slopes facing the subducting plate and an asymmetric pattern of exhumation with the deepest levels of exhumation opposite to subduction these characteristics are modified when the regional climate exhibits a dominant wind direction and orographically enhanced precipitation on one side of the mountain belt the two possible cases are dominant wind in the direction of motion of the subducting plate and dominant wind direction in the opposite direction of the subducting plate velocity models of the former case predict a broad zone of exhumation with maximum exhumation in the orogen interior models of the latter case predict a focused zone of exhumation at the margin of the orogen and at high erosion number a reversal in the topographic asymmetry natural examples of these two cases are presented the southern alps of new zealand exhibits the climate and exhumation asymmetry characteristic of wind in the direction opposite to motion of the subducting plate the asymmetry of topography suggests that erosion is not efficient enough to have reversed the topographic asymmetry the contrasting example of dominant wind in the direction of subduction motion is provided by the olympic mountains of washington state in this case exhumation of deep levels of the cascadia accretionary wedge shows a broad domal pattern consistent with the observed orographic precipitation

mechanical compaction versus early cementation in fine grained limestones differentiation by the preservation of organic microfossils abstract in many fine grained limestones the differentiation of mechanical compaction and early cementation is difficult because of the frequent lack or ambiguity of compaction indicators here a new complementary criterion is proposed for the assessment of compaction in fine grained carbonates the deformation of thin walled organic microfossils within the sediment it is shown that they are reliable indicators of compaction two general styles of preservation can be distinguished early cemented limestones contain spherical to slightly deformed microfossils whereas mechanically compacted carbonates always show flattened specimens

dem based morphometry of range front escarpments in attica central greece and its relation to fault slip rates in this paper we apply current geological knowledge on faulting processes to digital processing of digital elevation models dem in order to pinpoint locations of active faults the analysis is based on semiautomatic interpretation of 20 and 60 m dem and their products slope shaded relief in northern eastern attica five normal fault segments were recognized on the 20 m dem all faults strike wnw ese the faults are from west to east thriassion thfs fili fifs afidnai affs avlon avfs and pendeli pefs and range in length from 10 to 20 km all of them show geomorphic evidence for recent activity such as prominent range front escarpments v shaped valleys triangular facets and tilted footwall areas however escarpment morphometry and footwall geometry reveal systematic differences between the bexternalq segments pefs thfs and avfs and the binternalq segments affs and fifs which may be due to mechanical interaction among segments and or preexisting topography in addition transects across all five escarpments show mean scarp slope angles of 22 18f0 78 for both carbonate and metamorphic bedrock the slope angle equation for the external segments shows asymptotic behaviour with increasing height we make an empirical suggestion that slope angle is a function of the long term fault slip rate which ranges between 0 13 and 0 3 mm yr the identified faults may rupture up to magnitude 6 4 6 6 earthquakes the analysis of the 60 m dem shows a difference in fault patterns between western and northern attica which is related to crustal rheology variations d 2004 elsevier b v all rights reserved

shrinking and splitting of drainage basins in orogenic landscapes from the migration of the main drainage divide climate and in particular the spatial pattern of precipitation is thought to affect the topographic and tectonic evolution of mountain belts through erosion numerical model simulations of landscape erosion controlled by horizontal tectonic motion or orographic precipitation result in the asymmetric topography that characterizes most natural mountain belts and in a continuous migration of the main drainage divide the effects of such a migration have however been challenging to observe in natural settings here i document the effects of a lateral precipitation gradient on a landscape undergoing constant uplift in a laboratory modelling experiment in the experiment the drainage divide migrates towards the drier leeward side of the mountain range causing the drainage basins on the leeward side to shrink and split into smaller basins this mechanism results in a progressively increasing number of drainage basins on the leeward side of the mountain range as the divide migrates such that the expected relationship between the spacing of drainage basins and the location of the main drainage divide is maintained i propose that this mechanism could clarify the drainage divide migration and topographic asymmetry found in active orogenic mountain ranges as exemplified by the aconquija range of argentina

footwall topographic development during continental extension 1 we examine the progressive development of footwall topography associated with a set of active normal faults in the northeastern basin and range province of the western united states fault length and displacement increase monotonically from northeast to southwest in the study area allowing us to track both variations in footwall morphology with increasing displacement and along strike changes in morphology on a single fault we show that patterns of catchment area footwall relief and catchment outlet spacing vary predictably and are related to the growth of the range bounding normal fault array in this semiarid region full parsing of footwall drainage area and removal of antecedent topography do not occur until fault arrays grow beyond two crustal scale segments multiple segment faults with lengths of up to 150 km have footwall relief that is limited to 1000 m in the center of the footwall and that decays to zero at the fault tips over a length scale of 15 km we hypothesize that this relatively uniform footwall relief is erosionally limited and reflects the efficacy of surface processes in removing footwall material in the center of the footwall if the fault array grows by relatively steady propagation of the tips we suggest that the 15 km length scale required to reach uniform relief is related to a timescale of relief generation by the fault tip propagation rate while such propagation rates are poorly known an average rate of 10 mm yr 1 would imply footwall relief generation over a timescale of 1 myr

ubiquity of wave dominated deltas in outer shelf growth faulted compartments abstract growth faults and deltaic coastlines are common features along basin margins with a high flux of sediment delivery it has been observed in previous studies that wave dominated deltas are the characteristic and long lived coastline type in such growth faulted extensional basins during deltaic progradation the structural and depositional systems migrate and adjust as sedimentation rates keep pace with fault displacement rates a numerical model indicates that increased subsidence along growth faults slows the progradation rate of deltas as new accommodation is being created the decrease in forward delta growth results in a longer period of wave reworking per unit of sediment due to the retention of large fetch and water depth since subsidence is maintained through time sediments tend to accumulate on delta topsets creating thick wave dominated delta front successions on the downthrown sides of faults the proposed model may guide subsurface interpretations where it is difficult to assess the shoreline type without cores it is proposed here to use values of expansion index derived from seismic reflection profiles or well log correlations as a proxy for the likelihood of wave dominance on the delta shoreline

landscape response to tectonic forcing digital elevation model analysis of stream profiles in the mendocino triple junction region northern california the topographic evolution of orogens is fundamentally dictated by rates and patterns of bedrock channel incision quantitative field assessments of process based laws are needed to accurately describe landscape uplift and denudation in response to tectonics and climate we evaluate and calibrate the shear stress or similar unit stream power bedrock incision model by studying stream profiles in a tectonically active mountain range previous work on emergent marine terraces in the mendocino triple junction region of northern california provides spatial and temporal control on rock uplift rates digital elevation models and field data are used to quantify differences in landscape morphology associated with along strike northwest to southeast changes in tectonic and climatic conditions analysis of longitudinal profiles supports the hypothesis that the study area channels are in equilibrium with current uplift and climatic conditions consistent with theoretical calculations of system response time based on the shear stress model within uncertainty the profile concavity of the trunk streams is constant throughout the study area 0 43 as predicted by the model channel steepness correlates with uplift rate these data help constrain the two key unknown model parameters the coefficient of erosion k and the exponent associated with channel gradient n this analysis shows that k cannot be treated as a constant throughout the study area despite generally homogeneous substrate properties for a reasonable range of slope exponent values n best fit values of k are positively correlated with uplift rate this correlation has important implications for landscape evolution models and likely reflects dynamic adjustment of k to tectonic changes due to variations in orographic precipitation and perhaps channel width sediment load and frequency of debris flows the apparent variation in k makes a unique value of n impossible to constrain with present data

channel initiation and the problem of landscape scale since the 1940s it has been proposed that landscape dissection into distinct valleys is limited by a threshold of channelization that sets a finite scale to the landscape this threshold is equal to the hillslope length that is just shorter than that necessary to support a channel head a field study supports this hypothesis by showing that an empirically defined topographic threshold associated with channel head locations also defines the border between essentially smooth undissected hillslopes and the valley bottoms to which they drain this finding contradicts assertions that landscapes are scale independent and suggests that landscape response to changes in climate or land use depends on the corresponding changes in the threshold of channelization

evolution of neotectonic activity of east anatolian fault system eafs in bingol pull apart basin based on fractal dimension and morphometric indices abstract this study is an attempt of a semi automatic geomorphological gis analysis based on morphometric indices in the study 10 m resolution digital elevation models dems are used to assess the neotectonic signals regarding the recent topographic developments and to attach additional significance to active tectonics in the bingol basin area the methodology incorporates the determination of the structural similarities of the faults in the basins using fractal concepts and the application of four morphometric indices stream power index sp multi resolution index of valley bottom flatness mrvbf terrain ruggedness index tri and valley width to height ratio vf in order to detect the deviation from spatial randomness of the applied indices the weighted correlation coefficient moran s i is used and the results are interpreted at a confidence interval of 99 the spatial distribution of integrated index values is evaluated with the tectonically active fault zones in order to determine the probable activity and the structural deformation in the basin the applied methodology reveals that the fractal analysis of the fault lines and the spatial analysis of the morphometric indices proved to be effective tools in analyzing the tectonic influence of the fault system on the basin area within the basin area a relatively lesser degree of tectonic activity is observed in contrast with the high tectonic activity outside the basin

experimental modelling of tectonics erosion sedimentation interactions in compressional extensional and strike slip settings tectonically controlled landforms develop morphologic features that provide useful markers to investigate crustal deformation and relief growth dynamics in this paper we present results of morphotectonic experiments obtained with an innovative approach combining tectonic and surface processes erosion transport and sedimentation coupled with accurate model monitoring techniques this approach allows for a qualitative and quantitative analysis of landscape evolution in response to active deformation in the three end member geological settings compression extension and strike slip experimental results outline first that experimental morphologies evolve significantly at a short time scale numerous morphologic markers form continuously but their lifetime is generally short because erosion and sedimentation processes tend to destroy or bury them for the compressional setting the formation of terraces above an active thrust appears mainly controlled by narrowing and incision of the main channel through the uplifting hanging wall and by avulsion of deposits on fan like bodies terrace formation is irregular even under steady tectonic rates and erosional conditions terrace deformation analysis allows retrieving the growth history of the structure and the fault slip rate evolution for the extensional setting the dynamics of hanging wall sedimentary filling appears to control the position of the base level which in turn controls footwall erosion two phases of relief evolution can be evidenced the first is a phase of relief growth and the second is a phase of upstream propagation of topographic equilibrium that is reached first in the sedimentary basin during the phase of relief growth the formation of triangular facets occurs by degradation of the fault scarp and their geometry height becomes stationary during the phase of upstream propagation of the topographic equilibrium for the strike slip setting the complex morphology of the wrench zone composed of several interacting fault segments enhances the interactions with the drainage network because of the widening of the main fault zone toward the surface a significant amount of distributed deformation is observed along the wrench zone locally where two terminations of fault segments interact less than a quarter of the far field displacement can remain measurable using fault offsets leading to a systematic underestimation of the real fault slip rate these different experimental examples illustrate the great potential of the approach coupling deformation mechanisms and erosion transport sedimentation processes to investigate qualitatively and quantitatively the morphotectonic evolution of tectonically controlled landscapes

spatial variations in catchment averaged denudation rates from normal fault footwalls we test the spatial correspondence between rock uplift in active normal fault footwalls in the western usa and catchment averaged denudation rates from cosmogenic radionuclide crn analysis we find that denudation rates vary along strike depending on the fault length and displacement for the 18 km long sweetwater fault foot wall relief is largely inherited from the prefaulting topography and denudation rates are only partly reflective of fault displacement for the 130 km long wassuk fault all inherited topography has been removed by erosion in response to fault displacement denudation rates however show little along strike consistency and no correlation with catchment size or morphology we argue that in the early stages of fault growth crn derived denudation rates reflect inherited prefaulting relief with an overprint of fault controlled erosion in later stages of fault growth rates are decoupled from fault displacement through the impact of stochastic landsliding events and longer term measures of denudation such as low temperature thermochronometry that integrate over multiple earthquakes may provide a better record of spatial variations in rock uplift

mesoscale fluvial erosion parameters deduced from modeling the mediterranean sea level drop during the messinian late miocene 1 after a base level drop rivers are the first components of the landscape to respond by incising into topography a base level drop results in a knickpoint in the downstream part of river longitudinal profiles whether knickpoints are preserved or erased during the upstream propagation of incision is still debated preservation and erasure of knickpoints are two end member processes that work in natural systems at different timescales different length scales and different places the huge 1500 m and fast tens of kiloyears sea level drop in the mediterranean during the messinian resulted in the fast propagation of incision far inland this is especially the case in the rhone valley southern france where the knickpoint is 300 km from the mediterranean coast numerical modeling of this event has been performed using the ros model which simulates both erosional and depositional processes in rivers the best fit between numerical results and geological data is obtained for a nonlinear relation between incision and drainage area and for a small transport length of sediment this small transport length at least 2 orders of magnitude lower than the length of the rhone suggests that the longitudinal profile relaxed in a diffusive way so that the initial knickpoint was not preserved finally after a base level fall the propagation of fluvial incision is very fast at geological timescales hundreds of kiloyears despite this the diffusive response implies that the time required for restoration of an equilibrium profile is very long

experimental modelling of orogenic wedges a review abstract experimental modelling applied to the study of orogenic wedge dynamics has been a subject of fruitful research for more than 30 years although the technique dates back as far as the early xix th century on one hand several first order parameters controlling the structural evolution of mountain belts have been intensively investigated using the classic tectonic sandbox models the main parameters are the properties of the basal decollement the deforming material the backstop and fluxes kinematics and surface processes on the other hand the morphological evolution of a mountain relief subjected to changing tectonic or climatic forcing has been addressed using another kind of approach called geomorphic models nowadays the literature is extremely rich particularly for the sandbox technique so that it becomes difficult to have an exhaustive view of the effects of the above parameters on mountain evolution in this article we propose a detailed review of the main results obtained using both tectonic and geomorphic approaches our goal is to provide an almost complete state of the art in the experimental study of relief dynamics to guide present and future researchers in their understanding of mountain belt evolution

quaternary extension in southern tibet field observations and tectonic implications we summarize evidence for quaternary and active faulting collected in the field during three sino french expeditions to southeastern tibet 1980 1982 detailed mapping of quaternary and active faults as well as microtectonic measurements indicate that normal faulting has been the dominant tectonic regime north of the himalayas in the last 2 0 5 m y the maximum horizontal principal stress in south tibet appears to be only the intermediate principal stress 2 1 being vertical south of the chord joining the eastern and western syntaxes of the himalayan arc extensional strains are principally localized within seven regularly spaced rift zones three of which have been studied in some detail the extension direction is determined to be n96 e 7 mainly from statistical averaging of strikes of newly formed normal faults throw rates on normal faults are evaluated for different time spans 2 0 5 m y 60 40 kyr and 10 2 kyr b p using structural and topographic reliefs as well as synglacial and postglacial vertical offsets the rate of quaternary extension is about 1 m y 1 along an 1100 km long ese traverse across south tibet this corresponds to a spreading rate of 1 0 6 cm yr this rate and the divergent horizontal projections of slip vectors of earthquakes along the himalayan front constrain the rate at which rigid india underthrusts southern tibet to be 2 1 cm yr although most of the normal faults appear to be independent of and nearly orthogonal to the e w mesozoic tertiary tectonic fabric the yadong gulu rift appears to be guided for over 130 km by the older oblique ne sw nyainqentanglha range and fault zones along it this reactivated zone is the most prominent left lateral strike slip fault system in se tibet excepting this zone and the vicinity of the se extremity of the karakorum fault quaternary strike slip faulting is rare in south tibet i e south of the chord between the syntaxes of the himalayan arc north of the chord the tectonic style is different there minor conjugate strike slip faulting is widespread and appears to control quaternary normal faulting which is more diffuse and subdued than in south tibet along the chord the presence of a major zone of active right lateral en echelon strike slip faults karakorum jiali fault zone probably reflects the greater facility of eastward extrusion in north central tibet in response to the northward push of india the eastern himalayan syntaxis may be an obstacle to such extrusion movements south of the chord

a possible normal fault rupture for the 464 bc sparta earthquake surface ruptures have been identified for some normal faulting earthquakes in the aegean region1 3 but for most historical earthquakes the associated faults are unknown this hampers the evaluation of the rates and styles of present day deformation and the assessment of seismic hazard in the region4 here we examine the famous earthquake that destroyed sparta in 464 bc using spot satellite images and fieldwork we have mapped a 20 km long normal fault scarp trending approximately north south a few kilometres east of the ancient city our observations combined with an examination of historical descriptions of the earthquake damage suggest that the sparta earthquake ruptured this fault scarp in an event of magnitude ms 7 2 the holocene slip rate and the recurrence time for such large events on the sparta fault would be 1 mm yr 1 and 3 000 yr respectively

relationships among climate erosion topography and delamination in the andes a numerical modeling investigation cordilleran orogenic systems such as the andes are controlled by shortening rates climatically controlled erosion rates and in some cases eclogite production and delamination all of these processes are coupled however making it diffi cult to uniquely determine the relative importance of each process and the feedbacks among them in this paper we develop a massbalanced numerical model that couples an actively shortening orogen and crustal root with eclogite production delamination and climatically controlled erosion the model provides a fi rst order quantifi cation of the sources shortening and sinks erosion and eclogite production and delamination of crustal volume during the cenozoic in the andes as a function of latitude and time given reasonable estimates for the rates of eclogite production and the threshold size of the eclogitic root required for delamination the model suggests that in the central andes between 5 s and 32 s the orogen has grown to a suffi cient height to produce and maintain eclogite which in turn has promoted delamination in the lower crust and mantle in this region climatically controlled erosion rates infl uence the size of the orogen through two separate mechanisms by exporting mass via surface processes and by controlling the lithostatic pressure in the lower crust which modulates the rates of eclogite production and or delamination to the north and south of the central andes relatively low shortening rates and high precipitation and erosion rates have slowed eclogite production such that delamination likely has not occurred during the cenozoic

using the aster global dem to derive empirical relationships among triangular facet slope facet height and slip rates along active normal faults abstract the advent of global dems provided a uniform elevation dataset for studying geomorphic parameters in a variety of settings in this paper aster dem data 30 m pixel size are used to derive empirical relationships between triangular facet attributes and slip rates along active normal faults we sampled 232 triangular facets along 10 normal faults in greece and bulgaria that slip with rates from 0 1 mm yr up to 1 3 mm yr the studied normal faults accumulate quaternary tectonic strain in well known extensional provinces such as central greece crete and sw bulgaria the normal fault footwalls analyzed herein have been developed under similar long term climatic conditions it is suggested that two key geometrical features of the youngest generation of triangular facets slope angle and height can provide useful metrics to assess rates of deformation when seismological and geodetic data are lacking or not found in sufficient quantity to make reasonable assessments our derived empirical relation between slip rate and facet slope angle is y 0 057 x 1 where y is the fault slip rate mm yr and x is the facet slope angle degrees with an r 2 0 728 it is envisaged that our analysis may be helpful in assessing seismic hazard along normal faults with similar facet characteristics in other extensional settings

interaction between normal fault slip and erosion on relief evolution insights from experimental modelling the growth of relief in active tectonic areas is mainly controlled by the interactions between tectonics and surface processes erosion and sedimentation the study of long lived morphologic markers formed by these interactions can help in quantifying the competing effects of tectonics erosion and sedimentation in regions experiencing active extension river long profiles and faceted spurs triangular facets can help in understanding the development of mountainous topography along normal fault scarps in this study we developed analogue experiments that simulate the morphologic evolution of a mountain range bounded by a normal fault this paper focuses on the effect of the fault slip rate on the morphologic evolution of the footwall by performing three analogue experiments with different fault slip rates under a constant rainfall rate a morphometric analysis of the modelled catchments allows comparing with a natural case tunka half graben siberia after a certain amount of fault slip the modelled footwall topographies of our models reaches a dynamic equilibrium i e erosion balances tectonic uplift relative to the base level close to the fault whereas the topography farther from the fault is still being dissected due to regressive erosion we show that the rates of vertical erosion in the area where dynamic equilibrium is reached and the rate of regressive erosion are linearly correlated with the fault throw rate facet morphology seems to depend on the fault slip rate except for the fastest experiment where faceted spurs are degraded due to mass wasting a stream power law is computed for the area wherein rivers reach a topographic equilibrium we show that the erosional capacity of the system depends on the fault slip rate finally our results demonstrate the possibility of preserving convex river long profiles on the long term under steady external tectonic uplift and rainfall conditions

the growth of geological structures by repeated earthquakes 2 field examples of continental dip slip faults a strong test of our understanding of the earthquake cycle is the ability to reproduce extant fault bounded geological structures such as basins and ranges which are built by repeated cycles of deformation along strike slip faults the coseismic and interseismic deformation can be nearly equal in magnitude and opposite in sign resulting in little permanent deformation except for the fault offset for dip slip faults portions of the crust are lifted and dropped and so buoyancy forces are exerted the seismic and interseismic deformations do not balance and structures grow and become subject to erosion and deposition we consider three examples for which the structure and fault geometry are well known the white wolf reverse fault in california site of the 1952 kern county m 7 3 earthquake the lost river normal fault in idaho site of the 1983 borah peak m 7 0 earthquake and the cricket mountain normal fault in utah site of quaternary slip events basin stratigraphy and seismic reflection records are used to profile the structure and coseismic deformation measured by leveling surveys is used to estimate the fault geometry to reproduce these structures we add the deformation associated with the earthquake cycle the coseismic slip and postseismic relaxation to the flexure caused by the observed sediment load treating the crust as a thin elastic plate overlying a fluid substrate the cumulative deformation is principally dependent on the elastic plate thickness modestly sensitive to the sediment substrate density difference and insensitive to the fluid viscosity for the 4 to 8 ma structures we deduce a longterm flexural rigidity of 2 15 1019 nm this is equivalent to an elastic plate thickness of 2 4 km for a young s modulus of 2 5 1010 nm 2 this value is found where independent estimates of the elastic thickness from the coherence between surface topography and gravity yield values of about 4 km but where coseismic fault slip extends to a depth of 10 15 km thus much of the seismogenic crust must weaken substantially during the life of active faults causing the fault bounded basins to narrow over time

tectonic evolution and stress pattern of south wagad fault at the kachchh rift basin in western india we describe a study of the e w trending south wagad fault swf complex at the eastern part of the kachchh rift basin krb in western india this basin was filled during late cretaceous time and is presently undergoing tectonic inversion during the late stage of the inversion cycle all the principal rift faults were reactivated as transpressional strike slip faults the swf complex shows wrench geometry of an anastomosing en echelon fault where contractional and extensional segments and offsets alternate along the principal deformation zone pdz geometric analysis of different segments of the swf shows that several conjugate faults which are a combination of r synthetic and r antithetic propagate at a short distance along the pdz and interact generating significant fault slip partitioning surface morphology of the fault zone revealed three deformation zones a 500 m to 1 km wide single fault zone a 5 6 km wide double fault zone and a c 500 m wide diffuse fault zone the single fault zone is represented by a higher stress accumulation which is located close to the epicentre of the 2001 bhuj earthquake of m w 7 7 the double fault zone represents moderate stress at releasing bends bounded by two fault branches the diffuse fault zone represents a low stress zone where several fault branches join together our findings are well corroborated with the available geological and seismological data

long river profiles tectonism and eustasy a guide to interpreting fluvial terraces along three rivers at the mendocino triple junction northern california strath cut and fill terraces have formed in response to tectonic and eustatic processes detailed surveying and radiometric dating at multiple sites indicate that lower reaches of the rivers are dominated by the effects of oscillating sea level primarily aggradation and formation of fill terraces during sea level high stands alternating with deep incision during low stands a eustasy driven deposi tional wedge extends tens of kilometers upstream on all rivers tapering to zero thickness this distance is greater than expected from studies of the effects of check dams on much smaller streams elsewhere due in part to the large size of these rivers however the change in gradient is nearly identical to other base level rise studies the depositional gradient is about half that of the original channel middle to upper reaches of each fiver are dominated by the effects of long term uplift primarily lateral and vertical erosion and formation of steep unpaired strath terraces exposed only upstream of the depositional wedge vertical incision at a rate similar to that of uplift has occurred even during the present sea level high stand along rivers with highest uplift rates strath terraces have steeper gradients than the modem channel bed and do not merge with marine terraces at the river mouth consequently they cannot be used to determine altitudes of sea level high stands strath formation is a continuous process of response to long term uplift and its occurrence varies spatially along a river depending on stream power and hence position upstream strath terraces are found only along certain parts of a coastal stream upstream of the aggradational effects of oscillating sea level and far enough downstream that stream power is in excess of that needed to transport the prevailing sediment load for a given size fiver the greater the uplift rate the greater the rate of vertical incision and consequently the less the like lihood of strath terrace formation and preservation

experiments on faulting in a two layer cover sequence overlying a reactivated basement fault with oblique slip abstract two series of experiments were undertaken to investigate the development of faults in a cover sequence overlying a reactivated basement fault with oblique slip the experiments represent physical models properly scaled to account for gravitational forces brittle behaviour of the upper cover and ductile behaviour of evaporites in the lower cover models were made with a coulomb layer sand overlying a newtonian ductile layer silicone putty in each series the thickness of the silicone layer was varied from each experiment to the next in all normal wrench experiments a domain of faults appeared in the brittle layer vertical offsets were mostly of normal sense but some reverse faults occurred in experiments with thick silicone layers the thicker the silicone the wider the fault domain the deformation zone was in all cases limited to the faulted domain in the reverse wrench experiments discrete reverse riedel faults appeared without a silicone layer as the silicone layer became thicker the importance of the reverse faults diminished with the thickest layer of silicone 3 cm no faults appeared in the overburden but a monoclinal flexure accommodated the dip slip component in the presence of silicone the deformation zone was not limited to a faulted domain and the strike slip component was accommodated by a bulk shearing of the overburden in the uplifted compartment these experiments demonstrate that in basins deformed in oblique slip mode any deformation that is localized along discrete faults at the basement level becomes distributed over a much wider zone of overburden when this overlies an interval of evaporites

active faulting in sw bulgaria possible surface rupture of the 1904 struma earthquakes two destructive earthquakes a main shock preceded by a large foreshock occurred in 1904 in the balkan region these events have long been recognized as the largest earthquakes ever recorded in europe and the mainshock was assigned a magnitude up to 7 8 the region affected by the shaking straddles the present border between bulgaria and the republic of macedonia with the immediate epicentral area close to krupnik in the struma valley neither the surface break nor the source faults of the 1904 events have yet been identified using satellite imagery and field observations we mapped active faults close to or within the epicentral area the most prominent ones are three 20 35 km long normal faults the kocani fault in the eastern part of the republic of macedonia and the two neighbouring krupnik and bansko faults in south west bulgaria the latter two are the closest to the immediate epicentral area of the 1904 events geologic and morphologic observations allow us to estimate the age of initiation 13 ma and the long term slip rate 0 15 mm year 1 of the krupnik fault the onset and rate of faulting suggest that the region experienced a limited amount of stretching 100 per cent deduced from regional models involving extension on low angle detachments faults along the krupnik fault we found a recent 2 m high scarp that may have formed in 1904 a possible rupture of the krupnik fault compatible with our observations would account for a moment mo 2 8 1019 nm and a magnitude ms 6 9 significantly smaller than the previous estimates

influence of piedmont sedimentation on erosion dynamics of an uplifting landscape an experimental approach models of relief development generally assume that eroded products are evacuated far from the landscape whereas in nature they are often deposited at the foot of mountain belts within continental environments because piedmont aggradation can modify the base level for erosion we investigate the influence of piedmont sedimentation on the dynamics of an upstream relief we developed an experimental study of relief dynamics using laboratory scale models submitted to uplift under runoff driven erosion we compare the dynamics of topographies surrounded or not by a depositional belt made of eroded products coming from upstream piedmont aggradation acts on the dynamics of the upstream relief by modifying the relative uplift rate applied uplift rate minus aggradation rate that denudation tends to balance relief denudes at a lower rate than the applied uplift rate so the mean elevation of the uplifting topography rises when the time scale of aggradation is higher than the time scale of relief development the topography cannot reach a steady state between denudation and the applied uplift rate as long as aggradation occurs however in this case denudation balances a continuously varying relative uplift rate during a dynamic equilibrium phase of the topography

large scale geomorphology classical concepts reconciled and integrated with contemporary ideas via a surface processes model linear systems analysis is used to investigate the response of a surface processes model spm to tectonic forcing the spm calculates subcontinental scale denudational landscape evolution on geological timescales 1 to hundreds of million years as the result of simultaneous hillslope transport modeled by diffusion and fluvial transport modeled by advection and reaction the tectonically forced spm accommodates the large scale behavior envisaged in classical and contemporary conceptual geomorphic models and provides a framework for their integration and unification the following three model scales are considered micro meso and macroscale the concepts of dynamic equilibrium and grade are quantified at the microscale for segments of uniform gradient subject to tectonic uplift at the larger meso and macroscales which represent individual interfluves and landscapes including a number of drainage basins respectively the system response to tectonic forcing is linear for uplift geometries that are symmetric with respect to baselevel and which impose a fully integrated drainage to baselevel for these linear models the response time and the transfer function as a function of scale characterize the model behavior numerical experiments show that the styles of landscape evolution depend critically on the timescales of the tectonic processes in relation to the response time of the landscape when tectonic timescales are much longer than the landscape response time the resulting dynamic equilibrium landscapes correspond to those envisaged by hack 1960 when tectonic timescales are of the same order as the landscape response time and when tectonic variations take the form of pulses much shorter than the response time evolving landscapes conform to the penck type 1972 and to the davis 1889 1899 and king 1953 1962 type frameworks respectively the behavior of the spm highlights the importance of phase shifts or delays of the landform response and sediment yield in relation to the tectonic forcing finally nonlinear behavior resulting from more general uplift geometries is discussed a number of model experiments illustrate the importance of fundamental form which is an expression of the conformity of antecedent topography with the current tectonic regime lack of conformity leads to models that exhibit internal thresholds and a complex response

modeling the shape and evolution of normal fault facets facets formed along the footwalls of active normal fault blocks display a variety of longitudinal profile forms with variations in gradient shape degree of soil cover and presence or absence of a slope break at the fault trace we show that a two dimensional process oriented cellular automaton model of facet profile evolution can account for the observed morphologic diversity the model uses two dimensionless parameters to represent fault slip progressive rock weathering and downslope colluvial soil transport driven by gravity and stochastic disturbance events the parameters represent rock weathering and soil disturbance rates respectively scaled by fault slip rate both can be derived from field estimated rate coefficients in the model s transport limited regime slope gradient depends on the ratio of disturbance to slip rate with a maximum that represents the angle of repose for colluvium in this regime facet evolution is consistent with nonlinear diffusion models of soil mantled hillslope evolution under the weathering limited regime bedrock becomes partly exposed but microtopography helps trap some colluvium even when facet gradient exceeds the threshold angle whereas the model predicts a continuous gradient from footwall to colluvial wedge under transport limited behavior fully weathering limited facets tend to develop a slope break between footwall and basal colluvium as a result of reduced transport efficiency on the rocky footwall slope to the extent that the model provides a reasonable analogy for natural facets its behavior suggests that facet profile morphology can provide useful constraints on relative potential rates of rock weathering soil disturbance and fault slip

landslide distribution and size in response to quaternary fault activity the peloritani range ne sicily italy landslides contribute to dismantle active mountain ranges and faults control the location of landslides yet evidence of the long term regional dependency of landslides on active faults is limited previous studies focused on the transient effects of earthquakes on slope stability in compressive and transcurrent regimes here we show that in the peloritani range ne sicily italy one of the fastest uplifting areas in the mediterranean a clear geographical association exists between large bedrock landslides and active normal faults of the messina straits graben by interpreting aerial photographs we mapped 1590 landslides and sackungs and 626 fault elements and their facets in a 300 km2 area in the eastern part of the range we used the new landslide and fault information in combination with prior geological and seismic information to investigate the association between bedrock landslides and faults we find that the distribution and abundance of landslides is related to the presence of large active normal faults and matches the pattern of the local historical seismicity landslide material is more abundant along the east peloritani fault system where the long term activity of the faults measured by the average yearly geological moment rate is larger than in the west peloritani fault system where landslides are less abundant along the fault systems landslide material concentrates where the cumulated fault throws are largest we conclude that large landslides and their cumulated volume are sensitive to local rates of tectonic deformation and discriminate the deformation of the single fault segments that dissect the peloritani range our findings are a direct test of landscape evolution models that predict higher rates of landslide activity near active faults our work opens up the possibility of exploiting accurate landslide and fault maps in combination with geological and seismic information to characterize the long term seismic history of poorly instrumented active regions copyright 2015 the authors earth surface processes and landforms published by john wiley sons ltd

quaternary evolution of the corinth rift and its implications for the late cenozoic evolution of the aegean summary we present geological and morphological observations at different scales to constrain rates of faulting and the distribution of deformation in the seismically active aegean region we focus first on the 130 km long corinth rift an asymmetric graben where a flight of terraces of marine origin are uplifted we show that the edges of the terraces lie in the footwall of the normal fault bounding the corinth rift and correspond to sea level highstands of laic pleistocene age using a detailed analysis of aerial and spot imagery supported by field observations we have mapped 10 terrace platforms and strandlines ranging in elevation from 10 to 400 m over distances of 2 to 20 km from the fault the elevation of the terraces inner edges was estimated at 172 sites with an error of 5m this data set contains a precise description of the uplift and flexure of 10 different palaeohorizontal lines with respect to the present sea level to date the deformation we correlate the corinth terraces with late pleistocene oxygen isotope stages of high sea level stands and with global sea level fluctuations using a thick elastic plate model consistent with our current understanding of the earthquake cycle and a boundary element technique we reproduce the geometry of the shorelines to constrain both mechanical parameters and the slip on the fault we show that the seismogenic layer behaves over the long term as if its elastic modulus were reduced by a factor of about 1000 all the terraces are fitted for fault slip increasing in proportion to terrace age and the component of regional uplift is found to be less than 0 3 mm yr 1 the best fits give a slip rate of 11 3 mm yr 1 on the main rift bounding fault over the last 350 kyr other geological and morphologic information allows us to estimate the total age of the main fault 1 ma and to examine the mechanical evolution of the corinth rift the minimum observed sediment thickness in the gulf places an extreme check on the results of the modelling and a lower bound on slip rate of 6 7 mm yr 1 40 per cent less than estimated with modelling even this slip rate is nearly 10 times higher than for comparable features in most of the aegean and elsewhere in the world at a larger scale the spacing and asymmetry of the rift systems in the aegean suggest strain localization in the upper mantle with slow extension starting 15 myr ago or earlier the more recent 1 myr rapid phase of rifting in corinth partly reactivated this earlier phase of extension the younger faulting in corinth appears to result from its present location in the inhomogeneous stress field process zone of the south westward propagating tip of the southern branch of the north anatolian fault we extend these relations to propose a mechanical model for the late cenozoic evolution of the aegean as the arabia europe collision progressed in eastern turkey it caused anatolia to move to the west and the north anatolian fault to propagate into the aegean where the early slow extension started to be modified about 5 ma ago the process of propagation dramatically increased the activity of some but not all of the earlier rifts the model we present is compatible with tectonic observations as well as with the seismicity the palaeomagnetic rotations and the displacement field now observed with gps and slr

new microtextural criterion for differentiation of compaction and early cementation in fine grained limestones mechanisms of porosity reduction in fine grained limestones micrites the most abundant type of limestone have been difficult to evaluate because of the fine crystal sizes scanning electron microscopy reveals common minute voids termed microfenestrae approximately 1 5 40 mu m diameter in holocene lime muds from all marine carbonate environments studied experimental compaction of lime muds greatly reduces abundance of microfenestrae at pressures less than 10 bar thus the abundance of cement filled microfenestrae in micrites appears to be a widely applicable criterion for recognition of the extent of cementation prior to significant compaction in any given micrite microfenestrae in most phanerozoic micrites studied are about as common as in holocene lime muds suggesting that early cementation is a more important mechanism in micrite porosity reduction than recent views have suggested

the growth of geological structures by repeated earthquakes 1 conceptual framework in many places earthquakes with similar characteristics have been shown to recur if this is common then relatively small deformations associated with individual earthquake cycles should accumulate over time to create geological structures following this paradigm we show that existing models developed to describe leveling line changes associated with the seismic cycle can be adapted to explain geological features associated with a fault in these models an elastic layer containing the fault overlies a viscous half space with a different density fault motion associated with an earthquake results in immediate deformation followed by a long period of readjustment as stresses relax in the viscous layer and isostatic equilibrium is restored deformation is also caused as a result of the loading and unloading due to sediment deposition and erosion in this paper the parameters that control the growth of dip slip structures are identified we find that the flexural rigidity of the crust or the apparent elastic thickness provides the main control of the width of a structure the loading due to erosion and deposition of sediment determines the ratio of uplift to subsidence between the two sides of the fault the flexure due to sediment load is much more important in this respect than whether the fault is normal or reverse in character we find that in general real structures are associated with apparent elastic thicknesses of 4 km or less and thus with very low flexural rigidities

holocene paleoseismicity of the tunka fault baikal rift russia the tunka fault is a major normal oblique transform fault within the nne trending baikal rift that displays geomorphic evidence of recurrent quaternary movement a flight of six fanhead terraces of the kyngarga river is displaced by several parallel faults and has scarps up to 32 m high at arshan the main fault zone is exposed in an abandoned gravel quarry about 1 km east of the kyngarga river thirteen radiocarbon dates from the quarry a shallow trench in a graben and natural streamcuts constrain the timing of the latest two or three holocene paleoearthquakes the latest earthquake is bracketed by the 1024 1315 calendar years cal year b p age of an unfaulted terrace and by the 1947 2179 cal year b p age of a soil buried by scarp colluvium in the graben trench the penultimate earthquake is also relatively well constrained assuming that the displacement event slightly younger than 7091 7867 cal year b p in the upper quarry exposure is the same as the fissuring event slightly older than 6733 7385 cal year b p in the lower quarry exposure evidence for earlier event s between 9 2 12 7 ka depends on ambiguous stratigraphic evidence in the lower quarry exposure on the basis of only the two well dated earthquakes the recurrence interval at arshan may range from 2 9 to 6 8 ka for earthquake displacements of at least 1 3 m or a slip rate of 0 19 0 44 mm yr intermediate term 100 ka and long term circa 500 ka slip rates computed from terrace age estimates and fault scarp heights are 0 08 0 16 mm yr and 0 07 0 11 mm yr respectively rates that are considerably lower than the late holocene rate and the approximately 0 5 mm yr that might be inferred from the tectonic geomorphology of the tunka range front

new constraints on sediment flux dependent river incision implications for extracting tectonic signals from river profiles we present new field data from rivers draining across active normal faults that incise across the same lithology at the fault have been subjected to similar climatic regimes and tectonic settings and were perturbed by a well documented increase in fault slip rate ca 1 ma in spite of these similarities the rivers exhibit markedly different long profiles and patterns of catchment incision we use channel slope and hydraulic geometry data for each river to calculate bed shear stresses b and show that there is no simple relationship between peak b and the relative uplift rates across the faults u which differ by a factor of four the long term average sediment supply to each channel q s estimated from time averaged catchment erosion rates can explain the b versus u data if bedload modulates bedrock incision rate e in a strongly nonlinear way together these field data allow us for the first time to evaluate theoretical predictions of the role of sediment on river profile evolution and to quantify the magnitude of the effect in natural systems

effect of drainage area on hypsometry from an analysis of small scale drainage basins in the siwalik hills central nepal hypsometry of drainage basins area elevation analysis has generally been used to infer the stage of geomorphic development and to study the influence of varying forcing factors i e tectonics climate lithology on topography however the scale dependence of hypsometry has generally been neglected in order to assess the scale dependence of hypsometry this study focuses on the sensitivity of hypsometry to different digital elevation model dem resolutions and on the influence of drainage area hypsometry inferred from different dems is shown to be robust against variations of their resolution however hypsometry appears to be dependent on drainage area we propose that this scale dependence may reflect the varying importance of river and hillslope processes with basin area copyright 1999 john wiley sons ltd

geomorphic significance of postglacial bedrock scarps on normal fault footwalls the existence of well preserved holocene bedrock fault scarps along active normal faults in the mediterranean region and elsewhere suggests a dramatic reduction in rates of rock weathering and erosion that correlates with the transition from glacial to interglacial climate we test and quantify this interpretation using a case study in the italian central apennines holocene rates are derived from measurements of weathering pit depth along the magnola scarp where previous cosmogenic cl 36 analyses constrain exposure history to estimate the average hillslope erosion rate over similar to 10 5 years we introduce a simple geometric model of normal fault footwall slope evolution the model predicts that the gradient of a weathering limited footwall hillslope is set by fault dip angle and the ratio of slip rate to erosion rate if either slip or erosion rate is known the other can be derived applying this model to the magnola fault yields an estimated average weathering rate on the order of 0 2 0 4 mm yr more than 10 times higher than either the holocene scarp weathering rate or modern regional limestone weathering rates a numerical model of footwall growth and erosion in which erosion rate tracks the oxygen isotope curve reproduces the main features of hillslope and scarp morphology and suggests that the hillslope erosion rate has varied by about a factor of 30 over the past one to two glacial cycles we conclude that preservation of carbonate fault scarps reflects strong climatic control on rock breakdown by frost cracking

mechanisms of active folding of the landscape southern tian shan china 1 we explore the kinematic mechanisms of active large scale folding based on analysis of two adjacent major anticlines in tian shan central asia that share an acceleration of shortening rate leading to topographic emergence and folded geomorphic surfaces their folding mechanisms are fundamentally different yakeng anticline is a gentle pure shear detachment fold with 1200 m of shortening and a well constrained history of growth beginning at 5 5 ma with an order of magnitude increase in shortening rate from 0 16 to 1 2 1 6 mm yr at 0 16 0 21 ma the shape of the deformed topographic surface and of subsurface horizons deposited during deformation is a linearly proportional image at reduced amplitude of the deeper structure which shows that instantaneous uplift rates have been pointwise linearly proportional to the current finite fold amplitude in contrast quilitak anticline is a complex fault bend fold with uplift rates proportional to the sine of the fault dip showing discontinuities in uplift rate across active axial surfaces the 10 to 20 km wide anticline is topographically emergent only in a central 5 to 7 km wide mountainous uplift the abrupt southern edge of which is marked by 600 to 700 m high triangular facets that result from active folding of a pediment across an active axial surface the giant facets are shown to form by kink band migration and record postemergence deformation since an order of magnitude acceleration in shortening rate from 0 6 to 4 5 mm yr apparently contemporaneous with yakeng sections logged across the active 115 m wide hinge zone show that recent strata provide a bed by bed record of fold scarp growth which is quantitatively deciphered by fitting bed shapes to a finite width kink band migration model

the silurian of gotland sweden facies interpretation based on stable isotopes in brachiopod shells the silurian of gotland sweden consists of 440 m of carbonate deposits repeatedly uniform sequences of micritic limestones and marls are interrupted by complex structured reefs and by adjacent platform sediments generally the alteration of facies is interpreted as the result of sea level fluctuations caused by a gradual regression with superimposed minor transgressive pulses the purpose of this study is a facies interpretation based on both field observations and stable isotope measurements of brachiopod shells approximately 700 samples from stratigraphically arranged localities in different facies areas have been investigated the carbon and oxygen isotopes show principally parallel curves and a close relationship to the stratigraphic sequence lower values occur in periods dominated by deposition of marly sequences higher values are observed in periods dominated by reefs and extended carbonate platforms the oxygen isotope ratios are interpreted to reflect paleosalinity changes due to varying freshwater input rather than to paleotemperature carbon isotope ratios are believed to have been connected to global changes in the burial of organic carbon in black shales during periods of euxinic deep water conditions consequently the facies succession on gotland results from global paleoclimatic conditions changes in terrigenous input due to different rates of weathering and freshwater runoff rather than sea level fluctuations control the carbonate formation of the silurian on gotland

measurements of friction coefficients and cohesion for faulting and fault reactivation in laboratory models using sand and sand mixtures abstract simple laboratory tests have been made on dry quartz sand and on mixtures of sand and clay and sand and cement tests were made on both low and high density specimens of each mixture as determined by physical handling techniques the tests included measurements of density estimates of the coefficient of internal friction based on fault orientation and estimates of the friction coefficients and cohesion values for fault initiation and reactivation in a shear frame apparatus which was also used to test artificial fault zones made from pure clay glass microspheres and wheat flour the results suggest that density is determined more by handling technique than by composition and that friction coefficients and perhaps cohesion both increase with increasing density the shear testing revealed a consistent drop in cohesion for fault reactivation in all densely packed mixtures tested although small this drop may be significant for some types of laboratory models

erosion as a driving mechanism of intracontinental mountain growth in nature mountains can grow and remain as localized tectonic features over long periods of time 10 m y by contrast according to current knowledge of lithospheric rheology and neglecting surface processes any intracontinental range with a width that exceeds that which can be supported by the strength of the lithosphere should collapse within a few tens of millions of years for example assuming a quartz dominated crustal rheology the relief of a range initially 3 km high and 300 400 km wide is reduced by half in about 15 m y as a result of lateral spreading of its crustal root we suggest that surface processes might actually prevent such a subsurface collapse removal of material from topographic heights and deposition in the foreland oppose spreading of the crustal root and could eventually drive a net influx of material toward the orogeny we performed a set of numerical experiments in order to validate this hypothesis a section of a lithosphere with a brittle elasto ductile rheology initially loaded by a mountain range is submitted to horizontal shortening and to surface processes if erosion is intense material is removed more rapidly than it can be supplied by crustal thickening below the range and the topography is rapidly smoothed for example a feature 3 km high and 300 400 km wide is halved in height in about 15 m y for an erosion coefficient k 10 3 m 2 yr the erosion rate is of the order of a few 0 1 mm yr this regime might be called erosional collapse if erosion is not active enough the crustal root spreads out laterally and subsurface collapse occurs in the third intermediate regime removal of the material by erosion is dynamically compensated by isostatic rebound and inward flow in the lower crust so that the range can grow in this mountain growth regime the range evolves toward a characteristic graded shape that primarily depends on the erosion law the erosion rate may be high e g 0 5 0 9 mm yr close to the rate of tectonic uplift e g 0 7 1 1 mm yr and few times higher than the rate of topographic uplift 0 15 0 2 mm yr these experiments show that surface processes can favor localized crustal shortening and participate in the development of an intracontinental mountain surface processes must therefore be taken into account in the interpretation and modeling of long term deformation of continental lithosphere conversely the mechanical response of the lithosphere must be accounted for when large scale topographic features are interpreted and modeled in terms of geomorphologic processes

implications of sediment flux dependent river incision models for landscape evolution 1 developing a quantitative understanding of the factors that control the rate of river incision into bedrock is critical to studies of landscape evolution and the linkages between climate erosion and tectonics current models of long term river network incision differ significantly in their treatment of the role of sediment flux we analyze the implications of various sediment flux dependent incision models for large scale topography in an attempt 1 to identify quantifiable and diagnostic differences between models that could be detected from topographic data or from the transient responses of perturbed systems and 2 to explain the apparent ubiquity of mixed bedrock alluvial channels in active orogens although certain forms of the various models can be discarded as inconsistent with morphological data we find that the relative intrinsic concavity indices of detachment and transport limited systems defined herein largely dictate whether the various models can be tied to distinctive steady state morphologies preliminary data suggest that no such diagnostic differences may exist and other methods must be developed to test models accordingly we develop and explore differences in the scaling behavior of topographic relief and the extent of detachment versus transport limited channels as a function of rock uplift rate that may allow discrimination among various models further we explore potentially diagnostic differences in the rates and patterns of transient channel response to changes in rock uplift rate in addition to general differences between detachment and transport limited systems our analysis identifies an interesting hysteresis in landscape evolution hybrid channels at the threshold between detachment and transport limited conditions are expected to act as detachment limited systems in response to an increase in rock uplift rate or base level fall and as transport limited systems in response to a decrease in rock uplift rate especially during postorogenic topographic decline the analyses presented set the stage for field studies designed to test quantitatively the various river incision models that have been proposed

macroscale dynamics of experimental landscapes abstract we review results from laboratory scale modelling of erosion and relief dynamics under variable uplift and rainfall rates under constant values of these forcing parameters an experimental landscape typically evolves towards a steady state between uplift and erosion and we show how the geometry of the steady state landscape adjusts to the rates of uplift and rainfall the comparison between these laboratory scale landscapes and the natural ones is not straightforward because contrary to analogue modelling in tectonics natural conditions of relief evolution cannot be downscaled to the laboratory without any scale distortions laboratory scale modelling in geomorphology is therefore only experimental not analogue despite these limitations experimental models may be used to provide physical tests for numerical models and they give insights into first order behaviours and directions for future research

statistical separation of tectonic and inflation driven components of deformation on silicic reservoirs laguna del maule volcanic field chile abstract the reconstruction of the structural history of inflating silicic systems is challenging because their faulting record encompasses tectonic and inflation driven deformation and separating the two can rarely be accomplished here we present and utilize a statistical methodology to differentiate tectonic from inflation driven deformation in the laguna del maule ldm a post glacial rhyolitic volcanic field southern volcanic zone chile latitude 36 s ldm is cut by the troncoso fault a major normal fault that strikes ne and dips to the nw the troncoso hanging wall contains abundant young 19 9 4 ka where normal faults are developed on the troncoso hanging wall during shoreline based inflation

tracking silica in earth s upper mantle using new sound velocity data for coesite to 5 8 gpa and 1073 k the compressional and shear wave velocities for coesite have been measured simultaneously up to 5 8 gpa and 1073 k by ultrasonic interferometry for the first time the shear wave velocity decreases with pressure along all isotherms the resulting contrasts between coesite and stishovite reach 34 and 45 for p and s wave velocities respectively and 64 and 75 for their impedance at mantle conditions the large velocity and impedance contrasts across coesite stishovite transition imply that to generate the velocity and impedance contrasts observed at the x discontinuity only a small amount of silica would be required the velocity jump dependences on silica d lnvp d sio2 0 38 wt 1 and d lnvs d sio2 0 52 wt 1 are utilized to place constraints on the amount of silica in the upper mantle and provide a geophysical approach to track mantle eclogite materials and ancient subducted oceanic slabs

landscape stress and reorganization from χ maps insights from experimental drainage networks in oblique collision setting several recent studies have suggested that maps of flow length normalized for drainage area called chi could reveal landscapes in a transient state which are prone to reorganizations of basin geometry flow line topology and water divide locations however the potentially long timescales associated with the evolution of basin geometry make the capability of to predict such reorganization challenging to test in natural settings here we investigate the evolution of experimental drainage networks developed on a wedge coupled to a piedmont and growing in oblique convergence we use this experimental setting to investigate the relationships between maps the imposed tectonic deformation and the drainage network evolution as deposition can occur within channels or in the piedmont our experimental streams deviate from purely bedrock channels for which the metric has been initially developed yet we show that the large scale pattern of the experimental drainage network is consistent with the imposed deformation field as 2 3 of the observed gradients across water divide are oriented in the expected direction with respect to the imposed deformation this suggests that maps can be used to infer the horizontal component of regional deformation in large scale natural mountainous fluvial landscapes in addition we observe that when a divide affected by a gradient migrates the orientation of the gradient correctly anticipates the sense of landscape reorganization for 2 3 of these divides

a physical explanation for an observed area slope elevation relationship for catchments with declining relief a general relationship between the contributing area slope and mean elevation of catchments with relief declining after a tectonic uplift event is presented this relationship is based on the continuity equation for runoff and erosion processes in the catchment the key hypothesis underlying this relationship is that as a catchment declines the nondimensionalized catchment approaches a constant form this hypothesis is verified for computer simulated catchments the area slope elevation relationship covers several cases catchments declining toward a peneplain catchments declining from a high slope dynamic equilibrium resulting from a high rate of tectonic uplift to a low slope one resulting from a lower rate of tectonic uplift and catchments declining from an elevated initial condition as for example in the decline of a mine spoil heap a previously published relationship between slope and area for catchments in dynamic equilibrium and based on runoff and erosion physics is shown to be a special case of this general relationship the new area slope elevation relationship is compared with data from simulated catchments and a field catchment it is thus shown that for declining catchments the area slope elevation relationship is a good predictor of catchment form for catchments with declining relief it is argued that the slope area elevation relationship is sufficient with the planiform drainage pattern to completely define the elevation properties of the catchment such as for instance the hypsometric curve

height of faceted spurs a proxy for determining long term throw rates on normal faults evidence from the north baikal rift system siberia 1 we present new results on the long term throw rates of active normal faults in the north baikal rift nbr eastern siberia based on a statistical analysis of triangular faceted scarps fault bounded ridges in the nbr display typical morphologies with several contiguous facets separated by fault perpendicular catchments over a range of 20 fault segments analyzed triangular facet heights vary from 200 to 900 m as fault scarps have been developing under similar long term climatic conditions we infer that the scatter in mean facet height arises from long term differences in fault throw rate we compare the morphology of nbr facets with results obtained in a previously published numerical model of facet growth using facet height as an input model results provide estimates of the long term fault throw rate nbr throw rates vary between 0 2 and 1 2 mm yr 1 the throw rates are then compared with the cumulated throw which has been constrained by geophysical and stratigraphic data in the basins this provides an estimate of the age of fault and basin initiation we show that the modern stage of basin development started circa 3 myr ago except for the north baikal basin 8 ma our results also suggest that a proportion of the observed throw is inherited from an earlier tectonic stage

geologic constraints on bedrock river incision using the stream power law denudation rate in unextended terranes is limited by the rate of bedrock channel incision often modeled as work rate on the channel bed by water and sediment or stream power the latter can be generalized as ka m s n where k represents the channel bed s resistance to lowenng whose variation with lithology is unknown a is drainage area a surrogate for discharge s is local slope and m and n are exponents whose values are debated we address these uncertainties by simulating the lowering of ancient river profiles using the finite difference method we vary m n and k to match the evolved profile as closely as possible to the corresponding modern river profile over a time period constrained by the age of the mapped paleoprofiles we find at least two end member incision laws ka 0 3 0 5 s for australian rivers with stable base levels and k f a 0 1 0 2 s n for rivers in kauai subject to abrupt base level change the long term lowering rate on the latter expression is a function of the frequency and magnitude of knickpoint erosion characterized by k f incision patterns from japan and california could follow either expression if they follow the first expression with m 0 4 k varies from 10 7 10 6 m 0 2 yr for granite and metamorphic rocks to 10 5 10 4 m 0 2 yr for volcaniclastic rocks and 10 4 10 2 m 0 2 yr for mudstones this potentially large variation in k with lithology could drive strong variability in the rate of long term landscape change including denudation rate and sediment yield

faceted spurs at normal fault scarps insights from numerical modeling 1 we present a combined surface processes and tectonic model which allows us to determine the climatic and tectonic parameters that control the development of faceted spurs at normal fault scarps sensitivity tests to climatic parameter values are performed for a given precipitation rate when hillslope diffusion is high and channel bedrock is highly resistant to erosion the scarp is smooth and undissected when instead the bedrock is easily eroded and diffusion is limited numerous channels develop and the scarp becomes deeply incised between these two end member states diffusion and incision compete to produce a range of scarp morphologies including faceted spurs the sensitivity tests allow us to determine a dimensionless ratio of erosion f for which faceted spurs can develop this study evidences a strong dependence of facet slope angle on throw rate for throw rates between 0 4 and 0 7 mm a facet height is also shown to be a linear function of fault throw rate model performance is tested on the wasatch fault utah using topographic geologic and seismologic data a monte carlo inversion on the topography of a portion of the weber segment shows that the 5 ma long development of this scarp has been dominated by a low effective precipitation rate 1 1 m a and a moderate diffusion coefficient 0 13 m2 a results demonstrate the ability of our model to estimate normal fault throw rates from the height of triangular facets and to retrieve the average long term diffusion and incision parameters that prevailed during scarp evolution using an accurate 2 d misfit criterion

decoding temporal and spatial patterns of fault uplift using transient river long profiles we present detailed observations of rivers crossing active normal faults in the central apennines italy where excellent constraints exist on the temporal and spatial history of fault movement we demonstrate that rivers with drainage areas 10 km2 and crossing faults that have undergone an increase in throw rate within the last 1 my have significant long profile convexities in contrast channels that cross faults that have had a constant slip rate for 3 my have concave up profiles and have similar concavities and steepness indices to rivers that do not cross any active fault structures this trend is consistent across the central apennines and cannot be explained by appeal to lithology or regional base level change the data challenge the belief that active faulting must always be reflected in river profiles instead the long profile convexities are best explained as a transient response of the river system to a change in tectonic uplift rate moreover for these rivers we demonstrate that the height of the profile convexity as measured from the fault scales with the magnitude of the uplift rate increase on the fault and we establish that this relationship holds for throw rate variation along strike for the same fault segment as well as between faults these findings are shown to be consistent with predictions of channel response to changing uplift rate rates using a detachment limited fluvial erosion model and they illustrate that analysis of the magnitude of profile convexities has considerable predictive potential for extracting tectonic information we also demonstrate that the migration rate of the profile convexities varies from 1 5 10 mm y and is a function of the slip rate increase as well as the drainage area this is consistent with n 1 for the slope exponent in a classical detachment limited stream power erosion law but could potentially be explained by incorporating an erosion threshold or an explicit role for sediment in enhancing erosion rates finally we show that for rivers in extensional settings where the response times to tectonic perturbation are long in this case 1 my attempts to extract tectonic uplift rates from normalised steepness indices are likely to be flawed because topographic steady state has not yet been achieved

rheology of petrolatum paraffin oil mixtures applications to analogue modelling of geological processes abstract paraffins have been widely used in analogue modelling of geological processes petrolatum and paraffin oil are commonly used to lubricate model boundaries and to simulate weak layers in this paper we present rheological tests of petrolatum paraffin oil and several homogeneous mixtures of the two the results show that petrolatum and all petrolatum paraffin oil mixtures are strain strain rate and temperature dependent under typical experimental strain rates 10 3 10 1 s 1 for the same conditions pure paraffin oil is a slightly temperature dependent linear newtonian fluid all mixtures have yield stress and flow stress strain softening values that decrease with decreasing shear rate and with increasing relative amounts of paraffin oil the degree of strain rate dependence shear thinning also decreases with increasing paraffin oil content because these materials have rheologies that can be characterized and controlled they are suitable for use in a large number of analogue model settings either as a lubricant or to simulate weak layers when used as a lubricant mixtures with higher paraffin oil content should perform better than pure petrolatum

10be erosion rates controlled by transient response to normal faulting through incision and landsliding abstract quantifying erosion rates and how they compare to rock uplift rates is fundamental for understanding landscape response to tectonics and associated sediment fluxes from upland areas the erosional response to uplift is well represented by river incision and the associated landslide activity however characterising the relationship between these processes remains a major challenge in tectonically active areas in some cases because landslides can preclude obtaining reliable erosion rates from cosmogenic radionuclide crn concentrations here we quantify the control of tectonics and its coupled geomorphic response on the erosion rates of catchments in southern italy that are experiencing a transient response to normal faulting we analyse in situ 10be concentrations for detrital sediment samples collected along the strike of faults with excellent tectonic constraints and landslide inventories we demonstrate that 10be derived erosion rates are controlled by fault throw rates and the extent of transient incision and associated landsliding in the catchments we show that the low relief sub catchments above knickpoints erode at uniform background rates of 0 10 mm yr while downstream of knickpoints erosion removes 50 of the rock uplifted by the faults at rates of 0 10 0 64 mm yr despite widespread landsliding crn samples provide relatively consistent and accurate erosion rates most likely because landslides are frequent small and shallow and represent the integrated record of landsliding over several seismic cycles consequently we combine these validated 10be erosion rates and data from a geomorphological landslide inventory in a published numerical model to gain further insight into the long term landslide rates and sediment mixing highlighting the potential of crn data to study landslide dynamics

dating bedrock gorge incision in the french western alps ecrins pelvoux massif using cosmogenic 10be terra nova 22 18 25 2010 abstract we report in situ produced 10be data from the gorge du diable french western alps to date and quantify bedrock gorge incision into a glacial hanging valley we sampled gorge sidewalls and the active channel bed to derive both long term and present day incision rates 10be ages of sidewall profiles reveal rapid incision through the late holocene ca 5 ka at rates ranging from 6 5 to 13 mm yr 1 present day incision rates are significantly lower and vary from 0 5 to 3 mm yr 1 within the gorge our data imply either delayed initiation of gorge incision after final ice retreat from internal alpine valleys at ca 12 ka or post glacial surface reburial of the gorge our results suggest that fluvial incision rates 1 cm yr 1 into crystalline bedrock may be encountered in transient landscape features induced by glacial interglacial transitions

a comparison of experimental and natural drainage basin morphology across a range of scales 1 numerous quantitative models have been developed to simulate the long term evolution of river basin topography most of these models reach an equilibrium state when the base level is lowered at a constant rate and the substrate and climate are constant in time at equilibrium the erosion balances the base level lowering so the topography remains frozen in time however some recent laboratory experiments contradict this behavior in these experiments the space time mean erosion rate balances the base level lowering rate but the actual erosion rates are highly variable in space and time consequently the channel networks are substantially mobile the experimental flow conditions are approximately similar but not dynamically equivalent to those in nature so it is unclear whether the observed dynamics are representative this paper examines whether the processes occurring in the experiments produce basins that are geometrically similar to typical natural basins to make this comparison the conceptual framework of scaling invariance is used many similarities are observed but we find that the experimental basins are slightly more elongated across a range of scales than the natural basins we consider and the relationship between channel slope and drainage area exhibits a break that is not found in the natural basins we analyze in the experiments the slopes of small channels also depend on the proximity of large channels this dependency is more pronounced for experiments with more mobile channel networks and it is not observed in most of the natural basins we analyze

landscape response to climate change insights from experimental modeling and implications for tectonic versus climatic uplift of topography we present the results of an experimental investigation of the concurrent action of tectonic uplift and climate variation on relief evolution we designed an experimental apparatus that allows the study of erosion of laboratory scale topographies that evolve under given uplift and rainfall rates for constant uplift and rainfall rates the experimental topography evolves toward a statistical steady state defined by a mean elevation constant with time starting from such a steady state and keeping the input uplift rate constant a subsequent change in the rainfall rate yields a change in the mean elevation of the landscape to a new equilibrium elevation an increase in precipitation yields a lower mean steady state elevation whereas for a decrease in precipitation the surface is uplifted we define this phenomenon as a climatically induced surface uplift as opposed to a tectonically induced surface uplift the climatically and tectonically induced surface uplifts correspond to different dynamics of denudation so that it is theoretically possible to differentiate between the climatic or tectonic causes of surface uplift from records of output sediment fluxes