shredding of environmental signals by sediment transport 1 landscapes respond to climate tectonic motions and sea level but this response is mediated by sediment transport understanding transmission of environmental signals is crucial for predicting landscape response to climate change and interpreting paleo climate and tectonics from stratigraphy here we propose that sediment transport can act as a nonlinear filter that completely destroys shreds environmental signals this results from ubiquitous thresholds in sediment transport systems e g landsliding bed load transport and river avulsion this morphodynamic turbulence is analogous to turbulence in fluid flows where energy injected at one frequency is smeared across a range of scales we show with a numerical model that external signals are shredded when their time and amplitude scales fall within the ranges of morphodynamic turbulence as signal frequency increases signal preservation becomes the exception rather than the rule suggesting a critical re examination of purported sedimentary signals of external forcing citation jerolmack d j and c paola 2010 shredding of environmental signals by sediment transport geophys res lett 37 l19401 doi 10 1029 2010gl044638

quantifying differential rock uplift rates via stream profile analysis despite intensive research into the coupling between tectonics and surface processes our ability to obtain quantitative information on the rates of tectonic processes from topography remains limited due primarily to a dearth of data with which to test and calibrate process rate laws here we develop a simple theory for the impact of spatially variable rock uplift rate on the concavity of bedrock river profiles application of the analysis to the siwalik hills of central nepal demonstrates that systematic differences in the concavity of channels in this region match the predictions of a stream power incision model and depend on the position and direction of the channel relative to gradients in the vertical component of deformation rate across an active fault bend fold furthermore calibration of model parameters from channel profiles argued to be in steady state with the current climatic and tectonic regime indicates that 1 the ratio of exponents on channel drainage area and slope m n is 0 46 consistent with theoretical predictions 2 the slope exponent is consistent with incision either linearly proportional to shear stress or unit stream power n 0 66 or n 1 respectively and 3 the coefficient of erosion is within the range of previously published estimates mean k 4 3 10 4 m 0 2 yr application of these model parameters to other channels in the siwalik hills yields estimates of spatially variable erosion rates that mimic expected variations in rock uplift rate across a fault bend fold thus the sensitivity of channel gradient to rock uplift rate in this landscape allows us to derive quantitative estimates of spatial variations in erosion rate directly from topographic data

buffers barriers and blankets the dis connectivity of catchment scale sediment cascades abstract catchment configuration and the nature of connectivity within and between landscape compartments affect the operation of sediment cascades and geomorphic responses to disturbance events of differing magnitude and frequency this paper introduces the concept of landform impediments termed buffers barriers and blankets that impede sediment conveyance by limiting the connectivity between landscape compartments buffers restrict sediment delivery to channels barriers inhibit sediment movement along channels and blankets drape channel or floodplain surfaces affecting the accessibility of sediment to entrainment these features operate as a series of switches which turn on off processes of sediment delivery determining the effective catchment area at any given time using previously documented examples the role of these features in affecting the operation of sediment cascades in a low relief passive landscape setting such as the australian landmass is contrasted to examples from high relief uplifting settings in new zealand the australian examples are further explored by examining how changes to landscape connectivity brought about by human disturbance since european settlement have impacted upon landscape sensitivity and prospects for river recovery this approach to analysis of impediments to sediment conveyance is generic and can be applied in any environmental setting

shelf edge tide correlated eddies along the southeastern united states 1 high frequency radar observations in the southeastern united states have revealed sequences of small short lived cyclonic eddies along the shoreward edge of the gulf stream that spin up as the local tide turns alongshelf antiparallel to the stream eddies propagate equatorward along the shelf edge sometimes progressing shoreward before dissipating one to three hours later they are distinctly different from gulf stream meander eddies which propagate poleward in this article radar and mooring data are used to establish three important aspects of these new eddies they represent an instability process operating at a previously unidentified frequency scale and cross stream position they contribute to shoreward momentum fluxes defining a link between gulf stream and outer shelf subtidal variability and illustrating a mechanism to justify locally large horizontal eddy viscosity estimates and they transport properties across the shelf edge importing nutrients onto the shelf and transferring heat between the gulf stream and the coastal ocean

quantifying fluvial non linearity and finding self organized criticality insights from simulations of river basin evolution abstract a numerical study was undertaken to investigate non linearity and the potential for self organized criticality soc in the evolution of river basins twenty three simulations were carried out using the authors caesar landscape evolution model in which the magnitude of storm events variability of storm events sediment heterogeneity sources of sediment supply and catchment morphology are systematically varied to evaluate their importance as possible drivers for non linear behavior and soc temporal fluctuations in simulated sediment yield show notable non linear behavior storm magnitude and occurrence of landslides appear to have little impact on variability of the sediment yield when compared to the impacts of sediment heterogeneity rainfall variability and catchment morphology particularly it appears that the non linearity of sediment yields results from the manner in which the catchment processes the variable rainfall rather than just the rainfall variability itself the variations in sediment yield show a power law magnitude frequency distribution which is a possible but inconclusive indicator of soc however several other more qualitative arguments can be made to support the case for soc in these simulations specifically we identify the nature of the critical state and suggest two cascade mechanisms by which the system can organize itself around this critical state combined these arguments indicate that simulated evolution of river basins indeed exhibits soc at least with respect to sediment yield the critical state appears to be an indicator of the connectivity of the drainage network thus the simulations indicate that unlike traditional soc systems the critical state of the system can vary in time as sudden changes in drainage network connectivity may result in sudden changes in the soc behavior of the system

weichselian palynostratigraphy palaeovegetation and palaeoenvironment the record from lago grande di monticchio southern italy abstract the palynostratigraphic record from lago grande di monticchio s italy is presented an independent sedimentation rate based chronology provides an age of 101 530 calendar years bp for the lowermost sediments sampled this chronology enables assessment of the rapidity of vegetation changes during the last glacial contrary to widely held views the vegetation showed numerous large magnitude changes in periods of

characterization of controls on high resolution stratigraphic architecture in wave dominated shoreface shelf parasequences using inverse numerical modeling abstract a new inverse numerical modeling method is used to constrain the environmental parameters e g relative sea level sediment supply and wave climate histories that control stratigraphic architecture in wave dominated shallow marine deposits the method links a process response forward stratigraphic model that simulates wave and storm processes barsim to a combination of inverse methods formulated in a bayesian framework that allows full characterization of uncertainties this method is applied for the first time to a real geologic dataset collected at outcrop from two shoreface shelf parasequences in the aberdeen member blackhawk formation of the book cliffs east central utah usa the environmental parameters that controlled the observed stratigraphic architecture are quantified and key aspects of stratigraphic architecture are successfully predicted from limited data stratigraphic architecture at parasequence stacking and intra parasequence scales was driven principally by relative sea level varying by up to about 55 m and sediment supply varying by up to 70 m2 yr whose interplay determines the shoreline trajectory within zones of distinctive shoreline trajectory variations in wave climate of up to about 3 m in fairweather wave height controlled superimposed variations in sandstone and shale content e g the development of upward coarsening and upward fining bedsets the modeling results closely match the observed stratigraphic architecture but their quality is limited by 1 the formulation and assumptions of the forward modeling algorithms and 2 the observed data distribution and quality which provide poor age constraint

time scales of tectonic landscapes and their sediment routing systems abstract in regions undergoing active tectonics the coupling between the tectonic displacement field the overlying landscape and the redistribution of mass at the earth9s surface in the form of sediment routing systems is particularly marked and variable coupling between deformation and surface processes takes place at a range of scales from the whole orogen to individual extensional fault blocks or contractional anticlines at the large scale the attainment of a steady state between the overlying topography and the prevailing tectonic conditions in active contractional orogens requires an efficient erosional system with a time scale dependent on the vigour of the erosional system generally in the range 10 6 10 7 years the catchment fan systems associated with extensional fault blocks and basins of the western usa are valuable natural examples to study the coupling between tectonic deformation landscape and sediment routing systems even relatively simple coupled systems such as an extensional fault block and its associated basin margin fans have a range of time scales in response to a tectonic perturbation these response times originate from the development of uniform steady state relief during the accumulation of displacement on a normal fault c 10 6 years the upstream propagation of a bedrock knickpoint in transverse catchments following a change in tectonic uplift rate c 10 6 years or the relaxation times of the integrated catchment fan system in response to changes in climatic and tectonic boundary conditions 10 5 10 6 years the presence of extensive bedrock or alluvial piedmonts increases response times significantly the sediment efflux of a mountain catchment is a boundary condition for far field fluvial transport but the fluvial system is much more than a simple transmitter of the sediment supply signal to a neighbouring depocentre fluvial systems appear to act as buffers to incoming sediment supply signals with a diffusive time scale c 10 5 10 6 years dependent on the length of the system and the extent of its floodplains stream channels and proximal gravel fans the vocabulary for explaining landscapes would benefit from a greater recognition of the importance of the repeat time and magnitude of perturbations in relation to the response and relaxation times of the landscape and its sediment routing systems landscapes are best differentiated as buffered or reactive depending on the ratio of the response time to the repeat time of the perturbation furthermore landscapes may be regarded as steady or transient depending on the ratio of the response time to the time elapsed since the most recent change in boundary conditions the response of tectonically and climatically perturbed landscapes has profound implications for the interpretation of stratigraphic architecture

neogene subsidence pattern in the multi episodic extension systems insights from backstripping modelling of the okinawa trough abstract extensional systems of back arc basins have been widely recognized and studied in se asia however the interactions between extensional tectonics and spatial temporal distributions of tectonic subsidence in an active back arc basin are poorly known using a backstripping technique we analysed 33 multichannel seismic profiles to calculate the neogene tectonic subsidence across the entire okinawa trough ot for the first time reconstruction of the tectonic subsidence shows that the ot can be roughly divided into four subsidence stages with variable rate by comparing the temporal spatial distribution of the intensive subsidence area we confirmed that rifting events first occurred in the northern segment not and middle segment mot from the miocene to late pliocene and then propagated to the southern segment sot after the late pliocene the factors controlling the rapid tectonic subsidence over the entire ot can be classified into two categories 1 ne to nne trending normal faulting related to extension of the ot and nw to nww trending strike slip faulting i e the tokara fault and the miyako fault related to subduction of the philippine sea plate under the eurasian plate 2 the anomalous rapid subsidence occurred in the southernmost part of the sot is likely related to the subducted gagua ridge which caused magma intrusion resulting from partial melting we suggest that magmatic bodies produced by partial melting of subducted materials intruded into the crust and created a dense lithosphere causing this rapid tectonic subsidence

sedimentary and tectonic evolution of plio pleistocene alluvial and lacustrine deposits of fucino basin central italy abstract the fucino basin was the greatest lake of the central italy which was completely drained at the end of 19th century the basin is an intramontane half graben filled by plio quaternary alluvial and lacustrine deposits located in the central part of the apennines chain which was formed in upper pliocene and in quaternary time by the extensional tectonic activity the analysis of the geological surface data allows the definition of several stratigraphic units grouped in lower units and upper units the lower units upper pliocene are exposed along the northern and north eastern basin margins they consist of open to marginal lacustrine deposits breccia deposits and fluvial deposits the upper units lower pliocene holocene consist of interbedded marginal lacustrine deposits and fluvial deposits thick coarse grained fan delta deposits are interfingered at the foot of the main relief with fluvial lacustrine deposits most of the thickness of the lacustrine sequences more than 1000 m thick is buried below the central part of the fucino plain the basin is bounded by e w wsw ene and nw se fault systems velino magnola fault e w and tremonti celano aielli fault wsw ene and s potito celano fault nw se in the north the trasacco fault the pescina celano fault and the serrone fault nw se in the south east the geometry and kinematic indicators of these faults indicate normal or oblique movements the study of industrial seismic profiles across the fucino basin gives a clear picture of the subsurface basin geometry the basin shows triangular shaped basin fill geometry with the maximum deposits thickness toward the main east boundary fault zones that dip south westward serrone fault trasacco fault pescina celano fault on the basis of geological surface data borehole stratigraphy and seismic data analysis it is possible to recognize and to correlate sedimentary and seismic facies the bottom of the basin is well recognized in the seismic lines available from the good and continuous signals of the top of meso cenozoic carbonate rocks the shape of sedimentary bodies indicates that the filling of the basin was mainly controlled by normal slip along the nw se boundary faults in fact the continental deposits are frequently in on lap contact over the carbonate substratum several disconformable contacts occurred during the sedimentary evolution of the basin the main faults with antithetic and synthetic fault planes displace the whole sedimentary sequence up to the surface indicating a recent faults activity 1915 avezzano earthquake ms 7 0 the stratigraphic and tectonic setting of the fucino basin and neighboring areas indicates that the extensional tectonic events have had an important role in driving the structural sedimentary evolution of the plio quaternary deposits the geometry of the depositional bodies of the fault planes and their relationships indicate that the fucino basin was formed as a half graben type structure during plio quaternary extensional events some internal complexities are probably related to the fold and thrust structures of the apenninic orogeny formed in messinian time in this area and to a different activity timing of the e w and wsw ene fault systems and the nw se fault systems we believe based on the similarity of the surface characteristics that the structural setting of the fucino basin can be extrapolated to the other great intramontane basins in central italy e g rieti l aquila sulmona sora isernia basins

a spatially lumped model to investigate downstream sediment flux propagation within a fluvial catchment abstract a spatially lumped process response model pacmod is presented which calculates long time series 103 106 years of fluvial water discharge and sediment load at the river catchment outlet based on climatic data drainage basin characteristics and user defined parameters key aspects of the model are i the lumped approach allowing for fast simulations and preserving the same resolution from palaeoclimatic conditions and geomorphological reconstructions ii the parameterization of sediment routing and storage within the catchment pacmod was successfully tested on observed data from three present day fluvial systems the meuse the waipaoa and the po rivers moreover the simulated sediment flux for the meuse and for the waipaoa rivers in the late quaternary is in agreement with published field and modelling work pacmod experiments show how the downstream propagation of the original climatic signal is hampered by sediment routing and storage within the catchment

inverse modeling of post last glacial maximum transgressive sedimentation using 2d sedflux application to the northern adriatic sea abstract a coupled simulation of the hydrologic model hydrotrend and the stratigraphic model 2d sedflux is applied to transgressive deposits in the north adriatic sea area over the last 21 000 years synthetic sediment discharge from the po river which increases more than 70 during late pleistocene compared to those during holocene due to glacier melt and enlarged drainage area is employed in the simulation of sediment deposition by the process based forward model 2d sedflux paleo morphology is reconstructed in a pseudo inverse manner by comparing the predicted deposit distribution and the modern morphology accommodation for thick prograding deposits in the modern po delta and the po lowstand delta are created by drawing back the modern bathymetric profile the bathymetric profile is then adjusted for aggradational deposits these sequential simulations produced a likely profile of the paleo morphology which had accommodation matching with the sediment supply evaluation of effects of waves however suggested that the predicted rate of sediment input was too low to produce a prograding delta a good match with the observation of the modern po delta was achieved when further adjustments in basin width was properly made

drainage basin responses to climate change recent investigations have shown that the extent of the channel network in some drainage basins is controlled by a threshold for overland flow erosion the sensitivity of such basins to climate change is analyzed using a physically based model of drainage basin evolution the golem model simulates basin evolution under the action of weathering processes hillslope transport and fluvial bedrock erosion and sediment transport results from perturbation analyses reveal that the nature and timescale of basin response depends on the direction of change an increase in runoff intensity or a decrease in vegetation cover will lead to a rapid expansion of the channel network with the resulting increase in sediment supply initially generating aggradation along the main network followed by downcutting as the sediment supply tapers off by contrast a decrease in runoff intensity or an increase in the erosion threshold will lead to a retraction of the active channel network and a much more gradual geomorphic response cyclic changes in runoff intensity are shown to produce aggradational degradational cycles that resemble those observed in the field cyclic variations in runoff also lead to highly punctuated denudation rates with denudation concentrated during periods of increasing runoff intensity and or decreasing vegetation cover the sediment yield from threshold dominated basins may therefore exhibit significant variability in response to relatively subtle environmental changes a finding which underscores the need for caution in interpreting modern sediment yield data

influence of the st lawrence island polynya upon the bering sea benthos the influence of a polynya a persistent ice free region on water column production and subsequent transport to the shallow continental shelf benthos of the bering sea was evaluated by studying spatial patterns of organic material deposition benthic biomass community sediment metabolism benthic population structure and other potential indicators of enhanced organic carbon transport to benthic communities underlying the st lawrence island polynya despite suggestions that polynyas may be important localized centers of primary production in polar waters we found that the st lawrence island polynya does not obviously enhance the biomass of benthic communities directly below the polynya however southward flowing baroclinic currents generated as a result of brine injection at the polynya edge do appear to have an influence on the biomass and ecological structure of bering sea benthic communities south of st lawrence island these currents appear to affect mean sediment oxygen consumption surface organic carbon nitrogen ratios total organic content and bottom water ammonia by sweeping phytodetrital matter south and to the west of the island a particle reactive short lived natural radioisotope 7be used as an indicator of rapid days to weeks deposition of particulate material from the water column was detected only in surface sediments to the southwest of the island indicating enhancement of particle deposition to the southwest of the island finally the 18o content of tunicate cellulose was highest in the polynya region consistent with increased filter feeding in the late winter when the polynya is present and presumably promoting primary production in the open water the anadyr current consisting of nutrient rich deeper bering sea water that is upwelled onto the shelf in the gulf of anadyr flows west to east in the region south of st lawrence island throughout the year and is the major forcing function for high production in the region the interaction of anadyr water with the winter spring ephemeral polynya and associated baroclinic currents combine to positively influence benthic communities

geomorphic limits to climate induced increases in topographic relief recognition of the potential for strong dynamic coupling between atmospheric and tectonic processes has sparked intense cross disciplinary investigation and debate on the question of whether tectonics have driven long term climate change or vice versa it has been proposed that climate change might have driven the uplift of mountain summits through an isostatic response to valley incision because isostasy acts to compensate mean elevations the debate hinges on the question of whether climate change can significantly increase topographic relief or more precisely increase the volume of missing mass between summits and ridges here we show that in tectonically active mountain ranges geomorphic constraints allow only a relatively small increase in topographic relief in response to climate change thus although climate change may cause significant increases in denudation rates potentially establishing an important feedback between surficial and crustal processes neither fluvial nor glacial erosion is likely to induce significant isostatic peak uplift

development and response of a coupled catchment fan system under changing tectonic and climatic forcing sediment fans are a potentially useful and underexploited recorder of earth s climatic and tectonic history but historical observations have led to conflicting views on the importance of tectonic climatic and lithologic variables in controlling fan morphology and deposition a one dimensional model of a sediment fan and its associated catchment is used to explore the sensitivity of such simple sediment routing systems to perturbations in fault slip and precipitation rates a transport limited catchment is coupled to a fan whose surface slope is set by the balance between catchment sediment efflux and the available tectonically generated basin accommodation rock uplift rate is spatially variable across the model space increasing the fault slip rate or decreasing the precipitation rate leads to an increase in fan slope temporary back stepping of the fan toe and a pronounced angular unconformity conversely a decrease in slip rate or an increase in precipitation rate results in a decrease in fan slope and progradation and eventual stabilization of the fan toe once perturbed the system evolves toward a new equilibrium state with time constants of 0 5 to 2 myr these response times are insensitive to slip rate but are strongly dependent on precipitation rate variations in fan slope are well described by a dimensionless parameter that expresses equilibrium slope as a function of slip rate precipitation rate system size and catchment lithology this parameter holds promise as a predictive tool in inverting the morphology of natural fans for environmental variables

the impact of milankovitch scale climatic forcing on sediment supply abstract stratigraphy is the main technique to predict the occurrence of potential reservoirs and seals in the oil industry stratigraphic tools used are stratigraphic observations from drilled wells rock samples and wireline logs and seismic interpretation nowadays computer modelling allows scenario forecasting of the sequence to be expected application of these tools indicates that the key input parameters are initial basin topography subsidence eustasy and sediment supply the first three parameters are usually well constrained or can readily be deduced from well and seismic data however the fourth sediment supply is loosely defined and because of that it is used to calibrate the model in the present article the controls on sediment supply are reviewed and the impact of in particular milankovitch scale climatic forcing on sediment supply is tested on the neogene of the niger drainage and delta system sediment supply is controlled by a complex interplay of geographic and climatic factors such as 1 relief or mountain height 2 the size and temporal storage capacity of the drainage area 3 overall climate 4 amount and seasonality of precipitation and 5 vegetation cover studies in geomorphology have indicated that although complex computer models can be made to predict erosional product for the present a large scale sediment supply prediction should be based on the combination of palaeogeographical palaeoclimatological and erosion potential maps more detailed sediment supply predictions should include milankovitch scale variations the climatic impact of these variations is mainly felt when we are in a transition between two climates then the area will experience regular climatic changes from e g wet rainforest to dry monsoonal climate or low to high sediment supply respectively this concept was tested in the forward modelling package stratagem on the neogene of the niger delta four scenarios were evaluated using various combinations of large and milankovitch scale sediment supply curves combined with global or milankovitch scale eustatic sea level curves the results confirm the impact of both large scale and milankovitch scale climatic forcing on sediment supply however in an icehouse world the various scenarios also suggest that the effect of eustatic sea level fluctuations overshadows the impact of milankovitch scale sediment supply by contrast in a greenhouse world the impact of milankovitch scale sediment supply is expected to be more significant in the absence of significant sea level fluctuations

tectonic and climatic controls on knickpoint retreat rates and landscape response times 1 the rate at which transient knickpoints propagate through a landscape fundamentally controls the rate of geomorphic response to tectonic and climatic perturbation here we present knickpoint retreat rates upstream of active faults for 19 bedrock catchments in turkey and 11 bedrock catchments in italy where we have very good constraints on both the magnitude and timing of the tectonic perturbation and where climate histories are well documented we show that the knickpoints have average retreat rates of between 0 2 and 2 mm yr for catchments with drainage areas between 6 and 65 km2 and we test whether differences in rock mass strength and catchment size are sufficient to explain this range in retreat rates our analysis suggests that even accounting for these two variables knickpoint propagation velocities differ markedly and we show that channels crossing faults with higher throw rates have knickpoints that are retreating faster the dependence of knickpoint retreat velocity on throw rate is at least as important as catchment drainage area these results indicate counterintuitively that landscapes forced by large amplitude tectonic perturbations will have shorter response times than those perturbed by smaller amplitude changes the link between the knickpoint propagation velocity and throw rate is largely but not completely explained by channel narrowing in areas of high uplift rate channel steepening upstream of the active faults may explain all of the residual dependency of knickpoint retreat rate on fault throw rate but only if the slope exponent n in the standard stream power model is greater than 1 3 however we cannot rule out a role for sediment supply in driving enhanced knickpoint retreat rate in addition to the well documented channel narrowing effect finally we find that mean knickpoints retreat rates in turkey are only half of those in italy for catchments of equivalent size crossing faults with similar throw rates this difference in fluvial response time is accounted for by long term differences in the ratio of precipitation to infiltration in the two areas over the last 1 my

cosmogenic nuclides topography and the spatial variation of soil depth abstract if the rate of bedrock conversion to a mobile layer of soil depends on the local thickness of soil then hillslopes on uniform bedrock in a landscape approaching dynamic equilibrium should be mantled by a uniform thickness of soil conversely if the depth of soil varies across an actively eroding landscape then rates of soil production will also vary and consequently the landscape will not be in morphologic equilibrium the slow evolution of hillslopes relative to the tempo of climatic variations and tectonic adjustments would suggest that local morphologic disequilibrium may be expected in many landscapes here we explore this issue of equilibrium landscapes through a previously developed model that predicts the spatial variation in thickness of soil as a consequence of the local balance between soil production and erosion first we confirm the assumption in the model that soil production varies inversely with the thickness of soil using two independent methods one method uses the theoretical prediction that at local steady state soil production equals removal the depth of soil should vary inversely with hillslope curvature the second method relies on direct measurements of in situ produced concentrations of cosmogenic 10 be and 26 al in bedrock at the base of the soil column for our study site in northern california the two methods agree and yield the expression that the rate of soil production declines exponentially with the thickness of soil from 0 077 mm year with no soil mantle to 0 0077 mm year under 1 m of soil we then use this function of soil production in a coupled production and diffusive model of sediment transport to explore the controls on the spatial variation of the depth of soil on four separate spur ridges noses where we measured the data for the function of soil production model predictions are sensitive to boundary conditions grid scale and run time nonetheless we found good agreement between predicted and observed depths of soil as long as we used the observed function of soil production the four noses each have spatially varying curvature and consequently have varying depths of soil implying morphologic disequilibrium we suggest that our study site has been subjected to a wave of incision and varying intensities of erosion because of tectonic and climatic oscillations that have a frequency shorter than the morphologic response time of the landscape

transformation of tectonic and climatic signals from source to sedimentary archive sedimentary rocks reflect past tectonic and climatic events numerical simulations suggest that changes in precipitation and in the rate of tectonic uplift affect the grain size and the distribution of sediments deposited downstream

geology geography and humans battle for dominance over the delivery of fluvial sediment to the coastal ocean abstract sediment flux to the coastal zone is conditioned by geomorphic and tectonic influences basin area and relief geography temperature runoff geology lithology ice cover and human activities reservoir trapping soil erosion a new model termed bqart in recognition of those factors accounts for these varied influences when applied to a database of 488 rivers the bqart model showed no ensemble over or underprediction had a bias of just 3 across six orders of magnitude in observational values and accounted for 96 of the between river variation in the long term 30 years sediment load or yield of these rivers the geographical range of the 488 rivers covers 63 of the global land surface and is highly representative of global geology climate and socioeconomic conditions based strictly on geological parameters basin area relief lithology ice erosion 65 of the between river sediment load is explained climatic factors precipitation and temperature account for an additi

delayed delivery from the sediment factory modeling the impact of catchment response time to tectonics on sediment flux and fluvio deltaic stratigraphy the sediment flux from a catchment is driven by tectonics and climate but is moderated by the geomorphic response of the landscape system to changes in these two boundary conditions consequently catchment response time and the non linear behavior of landscapes in response to boundary condition change control the downstream propagation of climatic or tectonic perturbations from catchments to neighboring basins in order to investigate the impact of catchment response time on sediment flux we integrated a spatially lumped numerical model pacmod with new routines simulating the evolution of landscape morphology and erosion rates under tectonic and climatic forcing we subsequently applied the model to reconstruct the sediment flux from a tectonically perturbed catchment in central italy finally we coupled our model to deltasim a process response model simulating fluvio deltaic stratigraphy and investigated the impact of catchment response time on stratigraphy using both synthetic scenarios and a real world system fucino basin central italy our results demonstrate that the differential response of geomorphic elements to tectonic and climatic changes induces a complex sediment flux signal and produces characteristic stratigraphic architectures and shoreline trajectories copyright 2014 john wiley sons ltd

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

a cellular model of holocene upland river basin and alluvial fan evolution coulthard t j macklin m g kirkby m j 2002 a cellular model of holocene upland river basin and alluvial fan evolution earth surface processes and landforms 27 3 269 288

how plausible are high frequency sediment supply driven cycles in the stratigraphic record abstract this paper is an attempt to quantify the plausible time scales of clastic sediment supply variations at the entrance of sedimentary basins our approach is based on the sedimentary system concept which simplifies natural systems by dividing them into three zones of dominant processes the erosion the transfer and the sedimentation subsystems we examine recent results from geomorphology which show that frequent climate changes can induce high frequency sediment flux variations at the outlet of the source area we put forward the crucial role of the transfer subsystem which conveys sediment from the erosion zone to the basin by applying a diffusive model to a number of worldwide rivers we extend from large 1000 km to intermediate 300 km rivers the previous finding that the transfer subsystem acts as a buffer for short periods sediment pulses tens to hundreds of kiloyears this implies that high frequency stratigraphic cycles in clastic accumulations fed by large drainage systems are unlikely to reflect sediment supply cycles of tens to hundreds of thousands of years of periodicities

self organized criticality in river basins challenging sedimentary records of environmental change for many years researchers have linked increases in sediment and bedload from drainage basins to external factors such as increased rainfall however natural systems have always shown a high degree of scatter or nonlinearity in this response which has made prediction of sediment yields difficult we identify and describe a mechanism for self organized criticality in the bedload sediment output from a simple drainage basin evolution model this implies that identical floods will give considerably different sediment yields which effectively renders the system unpredictable therefore existing empirical methods for estimating sediment yields may need to be radically reevaluated furthermore sedimentary records used to infer past climate or environmental conditions could simply reflect the internal system dynamics instead of external drivers

modeling fluvial incision and transient landscape evolution influence of dynamic channel adjustment 1 channel geometry exerts a fundamental control on fluvial processes recent work has shown that bedrock channel width depends on a number of parameters including channel slope and is not solely a function of drainage area as is commonly assumed the present work represents the first attempt to investigate the consequences of dynamic gradient sensitive channel adjustment for drainage basin evolution we use the channel hillslope integrated landscape development child model to analyze the response of a catchment to a given tectonic perturbation using as a template the topography of a well documented catchment in the footwall of an active normal fault in the apennines italy that is known to be undergoing a transient response to tectonic forcing we show that the observed transient response can be reproduced to first order with a simple detachment limited fluvial incision law transient landscape is characterized by gentler gradients and a shorter response time when dynamic channel adjustment is allowed the differences in predicted channel geometry between the static case width dependent solely on upstream area and dynamic case width dependent on both drainage area and channel slope lead to contrasting landscape morphologies when integrated at the scale of a whole catchment particularly in presence of strong tilting and or pronounced slip rate acceleration our results emphasize the importance of channel width in controlling fluvial processes and landscape evolution they stress the need for using a dynamic hydraulic scaling law when modeling landscape evolution particularly when the relative uplift field is nonuniform

tectonic uplift threshold hillslopes and denudation rates in a developing mountain range studies across a broad range of drainage basins have established a positive correlation between mean slope gradient and denudation rates it has been suggested however that this relationship breaks down for catchments where slopes are at their threshold angle of stability because in such cases denudation is controlled by the rate of tectonic uplift through the rate of channel incision and frequency of slope failure this mechanism is evaluated for the san bernardino mountains california a nascent range that incorporates both threshold hillslopes and remnants of pre uplift topography concentrations of in situ produced cosmogenic 10 be in alluvial sediments are used to quantify catchment wide denudation rates and show a broadly linear relationship with mean slope gradient up to 30 above this value denudation rates vary substantially for similar mean slope gradients we propose that this decoupling in the slope gradient denudation rate relationship marks the emergence of threshold topography and coincides with the transition from transport limited to detachment limited denudation the survival in the san bernardino mountains of surfaces formed prior to uplift provides information on the topographic evolution of the range in particular the transition from slope gradient dependent rates of denudation to a regime where denudation rates are controlled by rates of tectonic uplift this type of transition may represent a general model for the denudational response to orogenic uplift and topographic evolution during the early stages of mountain building

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

nonequilibrium regolith thickness in the ouachita mountains abstract interpretations of regolith and soil thickness in the context of landscape evolution are typically based on the notion that thickness is controlled by the interaction of weathering rates and erosion and tuned to topography on sideslopes of the ouachita mountains arkansas however there is a high degree of local spatial variability that is largely unrelated to topography this indicates nonequilibrium in the sense that there is no evidence of a balance between rates of weathering and removal as is postulated in some conceptual models in geomorphology and pedology johnson s soil thickness model is applied as an alternative to interpret local variations in regolith thickness at the study sites regolith thickness is not generally related to slope curvature elevation or pedogenic development in the solum this indicates that variability in thickness is related chiefly to processes and controls acting in the lower regolith below the solum the primary controls of variability are local lithol

channel response to tectonic forcing field analysis of stream morphology and hydrology in the mendocino triple junction region northern california abstract an empirical calibration of the shear stress model for bedrock incision is presented using field and hydrologic data from a series of small coastal drainage basins near the mendocino triple junction in northern california previous work comparing basins from the high uplift zone huz uplift rates around 4 mm year to ones in the low uplift zone luz 0 5 mm year indicates that the huz channels are about twice as steep for a given drainage area this observation suggests that incision processes are more effective in the huz it motivates a detailed field study of channel morphology in the differing tectonic settings to test whether various factors that are hypothesized to influence incision rates discharge channel width lithology sediment load change in response to uplift or otherwise differ between the huz and luz analysis of regional stream gaging data for mean annual discharge and individual floods yields a linear relationship between discharge and drainage area increased orographic precipitation in the huz accounts for about a twofold increase in discharge in this area corresponding to an assumed increase in the erosional efficiency of the streams field measurements of channel width indicate a power law relationship between width and drainage area with an exponent of 0 4 and no significant change in width between the uplift rate zones although interpretation is hampered by a difference in land use between the zones the huz channel width dataset reveals a scaling break interpreted to be the transition between colluvial and fluvial dominated incision processes assessments of lithologic resistance using a schmidt hammer and joint surveys show that the rocks of the study area should be fairly similar in their susceptibility to erosion the huz channels generally have more exposed bedrock than those in the luz which is consistent with protection by sediment cover inhibiting incision in the luz however this difference is likely the result of a recent pulse of sediment due to land use in the luz therefore the role of sediment flux in setting incision rates cannot be constrained with any certainty to summarize of the four response mechanisms analyzed the only factor that demonstrably varies between uplift rate zones is discharge although this change is likely insufficient to explain the relationship between channel slope and uplift rate the calibrated model allows us to make a prediction of channel concavity that is consistent with a previous estimate from slope drainage area data we show that the inclusion of nonzero values of critical shear stress in the model has important implications for the theoretical relationship between steady state slope and uplift rate and might provide an explanation for the observations this analysis underscores the importance of further work to constrain quantitatively threshold shear stress for bedrock incision

regolith thickness instability and the formation of tors in arid environments 1 we present model results suggesting that a physical erosion bedrock weathering feedback is responsible for the development of isolated bedrock knobs tors inselbergs that often punctuate otherwise smooth pediments of homogeneous basement lithology tors and larger more heavily jointed and morphologically complex exposures inselbergs may arise as a consequence of fluctuations in rainfall and sediment transport conditions combined with a bedrock weathering mechanism that depends on regolith thickness hydrogeochemical considerations and field observations in arid granitic environments suggest that the relationship between weathering rate and regolith thickness exhibits a maximum for a finite thickness of cover we have encapsulated this simple erosion weathering feedback in a numerical model simulating arid semiarid landscape evolution that produces low sloping pediments punctuated by tors tors form during periods of higher effective moisture resulting in local base level incision and regolith thinning on pediments invoking a transition in which mantled surfaces lower at rates exceeding the bare bedrock weathering rate this condition favors the emergence and growth of tors in areas covered by regolith thickness less than a threshold value subsequent shifts in climate or local base level that restore sediment surface lowering rates less than the bare bedrock weathering rate will lead to a progressive decrease in tor height and ultimately their disappearance thus according to this model tors in arid environments represent possibly transient features related to fluctuations in climate or local transport conditions rather than palimpsests of an ancient landscape derived from differential subsurface weathering followed by regolith stripping

chemical heterogeneity on mercury s surface revealed by the messenger x ray spectrometer 1 we present the analysis of 205 spatially resolved measurements of the surface composition of mercury from messenger s x ray spectrometer the surface footprints of these measurements are categorized according to geological terrain northern smooth plains deposits and the plains interior to the caloris basin differ compositionally from older terrain on mercury the older terrain generally has higher mg si s si and ca si ratios and a lower al si ratio than the smooth plains mercury s surface mineralogy is likely dominated by high mg mafic minerals e g enstatite plagioclase feldspar and lesser amounts of ca mg and or fe sulfides e g oldhamite the compositional difference between the volcanic smooth plains and the older terrain reflects different abundances of these minerals and points to the crystallization of the smooth plains from a more chemically evolved magma source high degree partial melts of enstatite chondrite material provide a generally good compositional and mineralogical match for much of the surface of mercury an exception is fe for which the low surface abundance on mercury is still higher than that of melts from enstatite chondrites and may indicate an exogenous contribution from meteoroid impacts

erosion dynamics modelling in a coupled catchment fan system with constant external forcing article i nfo recent alluvial fan models have suggested that deep alluvial fan entrenchment could occur without any change in sediment and water influx moreover other studies have shown that the evolution of a fan could strongly depend on feedback between the fan and the mountain catchment we evaluate if natural entrenchment still occurs in a coupled catchment fan system and we evaluate its possible impact on the evolution of mountain erosion we use a landscape evolution model where the mountain corresponds to an uplifting block and where fans form over an initial horizontal surface our experiments confirm that deep entrenchment at the fan apex can occur without a change in climate or in uplift rate under two conditions 1 the transport threshold critical shear stress is significant and 2 the downstream boundary condition corresponds to an open boundary with fixed elevation which stops the progradation of alluvial fans a stable entrenchment occurs when sediments reach this limit the entrenchment can be explained by a strong nonlinear dependence of the transport law on the slope when the shear stress is close to critical a fan slope increase occurs when sediments reach the model limit and this drives entrenchment fan entrenchment drives strong erosion in the mountain with intensity and a response time similar to those observed for the initial mountain uplift these results indicate that determining how much of natural erosion is from autogenic mechanisms is essential in order to link landscape entrenchment with past external changes 2010 elsevier b v all rights reserved

effective timescales of coupling within fluvial systems this paper presents a review of the coupling concept in fluvial geomorphology based mainly on previously published work coupling mechanisms link the components of the fluvial system controlling sediment transport down the system and the propagation of the effects of base level change up the system they can be viewed at several scales at the local scale involving within hillslope coupling hillslope to channel coupling and within channels tributary junction and reach to reach coupling at larger scales coupling can be considered as zonal coupling between major zones of the system or as regional coupling relating to complete drainage basins these trends are illustrated particularly by the examples of hillslope to channel coupling in the howgill fells northwest england badland systems in southeast spain alluvial fans in spain usa and uae and base level induced dissection of neogene sedimentary basins in southeast spain as the spatial scales increase so do the timescales involved effective temporal scales relate to magnitude and frequency characteristics recovery time and propagation time the relative importance changing with the spatial scale for downsystem coupling at the local scale the first two are important with propagation time increasing in importance in larger systems especially in those involving upsystem coupling related to base level change the effective timescales range from the individual event with a return period of decades through decadal to century timescales for downsystem coupling to tens to hundreds of thousands of years for the basinwide response to base level change the effective timescales influence the relative importance of factors controlling landform development

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

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