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

controls on the strength of coupling among climate erosion and deformation in two sided frictional orogenic wedges at steady state 1 many important insights regarding the coupling among climate erosion and tectonics have come from numerical simulations using coupled tectonic and surface process models however analyses to date have left the strength of the coupling between climate and tectonics uncertain and many questions unanswered we present an approximate analytical solution for two sided orogenic wedges obeying a frictional rheology and in a condition of flux steady state that makes explicit the nature and sensitivity of the coupling between climate and deformation we make the simplifying assumption that the wedge grows in a self similar fashion consistent with airy isostasy such that topographic taper is invariant with orogen width tectonic influx rate and climate we illustrate first how and why the form of the erosion rule matters to orogen evolution and then derive a physically based orogen scale erosion rule we show that steady state orogen width crest elevation and crustal thickness are controlled by the ratio of accretionary flux to erosional efficiency to a power dictated by the erosion process remarkably we show that for most combinations of parameters in the erosion law rock uplift rate is more strongly controlled by erosional efficiency than it is by the accretionary flux further assuming frontal accretion with no underplating the spatial distribution of erosional efficiency dictates the relative rock uplift rates on the pro wedge and retro wedge and the time averaged trajectories of rocks through the orogen the restriction to invariant frictional properties is conservative in these respects systems subject to positive feedback between erosion and rheology will exhibit even stronger coupling among climate erosion and deformation than shown here

a speleothem record of holocene paleoclimate from the northern wasatch mountains southeast idaho usa abstract a speleothem stable isotope record from minnetonka cave located in the northern wasatch mountains is shown to be a winter season biased record of holocene paleoclimate the season specific sensitivity of the record provides an opportunity to more robustly evaluate long term variability in large scale pacific teleconnection patterns such as enso and pdo as precipitation anomalies associated with these teleconnection patterns occur primarily in winter seasonal climate composite maps of high and low snowpack years at the study site demonstrate that winter precipitation is strongly linked to the relative strength of the aleutian low and the associated changes from to more meridional or more zonal steering level wind patterns minnetonka cave data suggest wetter cooler than modern early holocene winters and a dry middle holocene with a consistent warming trend from 7400 to 3800 bp after 4000 bp data suggest a return to wetter and or colder than modern winters for much of the late holocene prolonged winter dry intervals are identified from 7400 to 6000 bp and 4200 bp

influence of the diversion of bear river into bear lake utah and idaho on the environment of deposition of carbonate minerals bear river the largest river in the great basin had some of its flow diverted into bear lake through a series of canals constructed between 1911 and 1918 turning bear lake into a reservoir the prediversion lake had an unusually high mg2 c a2 ratio 38 by weight which resulted in precipitation of caco3 as aragonite the amount and mineralogy of the carbonate did not change immediately after the diversion but during the middle of the 20th century high mg calcite began to precipitate in contrast at the time of diversion there were very distinct changes in the isotopic composition of the carbonate that clearly define the time of diversion within the sediments sedimenttrap studies show that the caco3 polymorph that precipitates in the epilimnion of the lake today is high mg calcite samples in sediment traps placed 2 m above the bottom of the lake in 45 m of water bottom traps contain predominantly aragonite and quartz with lesser amounts of high mg and low mg calcite and dolomite isotopic evidence from the sediments shows that the aragonite that accumulated in the bottom sediment traps and that constitutes the bulk of postdiversion sediments is reworked and redistributed from shallow sites to deep sites

evaporation induced 18o and 13c enrichment in lake systems a global perspective on hydrologic balance effects growing pressure on sustainable water resource allocation in the context of global development and rapid environmental change demands rigorous knowledge of how regional water cycles change through time one of the most attractive and widely utilized approaches for gaining this knowledge is the analysis of lake carbonate stable isotopic compositions however endogenic carbonate archives are sensitive to a variety of natural processes and conditions leaving isotopic datasets largely underdetermined as a consequence isotopic researchers are often required to assume values for multiple parameters including temperature of carbonate formation or lake water delta o 18 in order to interpret changes in hydrologic conditions here we review and analyze a global compilation of 57 lacustrine dual carbon and oxygen stable isotope records with a topical focus on the effects of shifting hydrologic balance on endogenic carbonate isotopic compositions through integration of multiple large datasets we show that lake carbonate delta o 18 values and the lake waters from which they are derived are often shifted by 10 parts per thousand relative to source waters discharging into the lake the global pattern of delta o 18 and delta c 13 covariation observed in 70 of the records studied and in several evaporation experiments demonstrates that isotopic fractionations associated with lake water evaporation cause the heavy carbon and oxygen isotope enrichments observed in most lakes and lake carbonate records modeled endogenic calcite compositions in isotopic equilibrium with lake source waters further demonstrate that evaporation effects can be extreme even in lake records where delta o 18 and delta c 13 covariation is absent aridisol pedogenic carbonates show similar isotopic responses to evaporation and the relevance of evaporative modification to paleoclimatic and paleotopographic research using endogenic carbonate proxies are discussed recent advances in stable isotope research techniques present unprecedented opportunities to overcome the underdetermined nature of stable isotopic data through integration of multiple isotopic proxies including dual element c 13 excess values and clumped isotope temperature estimates we demonstrate the utility of applying these multi proxy approaches to the interpretation of paleohy droclimatic conditions in ancient lake systems understanding past present and future hydroclimatic systems is a global imperative significant progress should be expected as these modern research techniques become more widely applied and integrated with traditional stable isotopic proxies c 2015 elsevier ltd all rights reserved

sediment transport by burrowing mammals marin county california abstract field observations suggest that burrowing activity is the primary mode of sediment transport currently active in a small grassland drainage basin in marin county california spatial concentrations of the 1 150 gopher mounds surveyed vary from 0 16 mounds m on interfluves to 0 32 mounds m on sideslopes and in the topographic hollow with localized concentrations of up to 2 88 mounds m on the margins of the colluvial deposit simple models of sediment transport by burrowing activity yield estimates of between 0 91 and 2 33 cm3 cm yr for the basin as a whole with absolute minimum and maximum rates of 048 and 6 31 cm3 cm yr i these values are similar to those previously estimated for this area lehre 1982 and are nearly an order of magnitude less than average long term sediment transport rates at the same site reneau 1988 key words sediment transport erosion rates bioturbation introduction burrowing animals disturb and transport soil in environments ranging from alpine tundra to humid grasslands hansen and morris

controls on valley spacing in landscapes subject to rapid base level fall what controls the architecture of drainage networks is a fundamental question in geomorphology recent work has elucidated the mechanisms of drainage network development in steadily uplifting landscapes but the controls on drainage network morphology in transient landscapes are relatively unknown in this paper we exploit natural experiments in drainage network development in incised plio quaternary alluvial fan surfaces in order to understand and quantify drainage network development in highly transient landscapes i e initially unincised low relief surfaces that experience a pulse of rapid base level drop followed by relative base level stasis parallel drainage networks formed on incised alluvial fan surfaces tend to have a drainage spacing that is approximately proportional to the magnitude of the base level drop numerical experiments suggest that this observed relationship between the magnitude of base level drop and mean drainage spacing is the result of feedbacks among the depth of valley incision mass wasting and nonlinear increases in the rate of colluvial sediment transport with slope gradient on steep valley side slopes that lead to increasingly wide valleys in cases of larger base level drop we identify a threshold magnitude of base level drop above which side slopes lengthen sufficiently to promote increases in contributing area and fluvial incision rates that lead to branching and encourage drainage networks to transition from systems of first order valleys to systems of higher order branching valleys the headward growth of these branching tributaries prevents the development of adjacent ephemeral drainages and promotes a higher mean valley spacing relative to cases in which tributaries do not form model results offer additional insights into the response of initially unincised landscapes to rapid base level drop and provide a preliminary basis for understanding how varying amounts of base level change influence valley network morphology copyright 2015 john wiley sons ltd

the effects of lithology and base level on topography in the northern alpine foreland abstract the evolution of topography is driven by climate and tectonics and strongly influenced by substrate properties and different base levels the contributions of these factors may vary in space and time and are thus difficult to disentangle our study area the hausruck kobernauserwald range has a rather uniform climatic and tectonic history but is drained by rivers with different base levels and consists of contrasting sedimentary rocks mainly due to different sedimentation environments this makes them an ideal location to study the effects of lithology and base level on topography to decipher the roles of these influences we used a high resolution digital elevation model and performed a series of morphometric analyses longitudinal river profiles indicate that all channels in the study area independent from base level bed rock and overall morphological expression are well graded hypsometry shows no evidence for base level effects on the present topography while variations in the hypsometric curves coincide with lithological differences this is also reflected in contrasts of mean elevation and slope distributions lithology dependent variations in channel concavity and catchment wide hypsometric integrals show that lithology controls both channel incision and hillslope processes in the study area our results further indicate that variations in channel and catchment metrics are not linked to the prevalence of different rock types alone but to different successions of lithological units along the channels and within the catchments variations in channel slope and geomorphological mapping suggest that lithology dependent landsliding is the dominant process causing the observed large scale landscape diversity in the hausruck kobernauserwald range

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

the topographic signature of a major typhoon in august 2009 the typhoon morakot characterized by a cumulative rainfall up to 2884 mm in about three days triggered thousands of landslides in taiwan the availability of lidar surveys before 2005 and after 2010 this event offers a unique opportunity to investigate the topographic signatures of a major typhoon the analysis considers the comparison of slope area relationships derived by lidar digital terrain models dtms this approach has been successfully used to distinguish hillslope from channelized processes as a basis to develop landscape evolution models and theories and understand the linkages between landscape morphology and tectonics climate and geology we considered six catchments affected by a different degree of erosion three affected by shallow and deep seated landslides and three not affected by erosion for each of these catchments 2 m dtms were derived from lidar data the scaling regimes of local slope versus drainage area suggested that for the catchments affected by landslides i the hillslope to valley transitions morphology for a given value of drainage area is shifted towards higher value of slopes thus indicating a likely migration of the channelized processes and erosion toward the catchment boundary the catchment head becomes steeper because of erosion ii the topographic gradient along valley profiles tends to decrease progressively the valley profile becomes gentler because of sediment deposition after the typhoon the catchments without any landslides present a statistically indistinguishable slope area scaling regime these results are interesting since for the first time using multi temporal high resolution topography derived by lidar we demonstrated that a single climate event is able to cause significant major geomorphic changes on the landscape detectable using slope area scaling analysis this provides new insights about landscape evolution under major climate forcing copyright 2015 john wiley sons ltd

geomorphic response to an active transpressive regime a case study along the chaman strike slip fault western pakistan the chaman left lateral strike slip fault bounds the rigid indian plate boundary at the western end of the himalayan tibetan orogen and is marked by contrasting topographic relief deformed landforms along the fault provide an excellent record for understanding this actively evolving intra continental strike slip fault the geomorphic response of an active transpessional stretch of the chaman fault was studied using digital elevation model dem data integrated with advanced spaceborne thermal emission and reflection radiometer aster visible and near infrared short wave infrared vnir swir and images from geoeye 1 geologic and geomorphic mapping helped in reconstructing the late quaternary landscape history of this transpessional strand of the chaman strike slip fault and the associated spinatizha thrust fault in western pakistan topographic analysis of a part of the transpression the thrust bounded roghani ridge revealed northward growth of the spinatizha fault with the presence of three water gaps and two corresponding wind gaps geomorphic indices including stream length gradient index mountain front sinuosity valley floor width to valley height ratios and entrenchment of recent alluvial fan deposits were used to define the lateral growth and direction of propagation of the spinatizha fault left lateral displacement along chaman fault and uplift along the spinatizha fault was defined using topographic analysis of the roghani ridge and geomorphic mapping of an impressive alluvial fan the bostankaul fan the landforms and structures record slip partitioning along the indian plate boundary and account for the convergence resulting from the difference in the chaman fault azimuth and orientation of the velocity vector of the indian plate copyright 2012 john wiley sons ltd

how long is a hillslope hillslope length is a fundamental attribute of landscapes intrinsically linked to drainage density landslide hazard biogeochemical cycling and hillslope sediment transport existing methods to estimate catchment average hillslope lengths include inversion of drainage density or identification of a break in slope area scaling where the hillslope domain transitions into the fluvial domain here we implement a technique which models flow from point sources on hilltops across pixels in a digital elevation model dem based on flow directions calculated using pixel aspect until reaching the channel network defined using recently developed channel extraction algorithms through comparisons between these measurement techniques we show that estimating hillslope length from plots of topographic slope versus drainage area or by inverting measures of drainage density systematically underestimates hillslope length in addition hillslope lengths estimated by slope area scaling breaks show large variations between catchments of similar morphology and area we then use hillslope length relief structure of landscapes to explore nature of sediment flux operating on a landscape distinct topographic forms are predicted for end member sediment flux laws which constrain sediment transport on hillslopes as being linearly or nonlinearly dependent on hillslope gradient because our method extracts hillslope profiles originating from every ridgetop pixel in a dem we show that the resulting population of hillslope length relief measurements can be used to differentiate between linear and nonlinear sediment transport laws in soil mantled landscapes we find that across a broad range of sites across the continental united states topography is consistent with a sediment flux law in which transport is nonlinearly proportional to topographic gradient

tectonic geomorphology of the san andreas fault zone from high resolution topography an example from the cholame segment abstract high resolution topographic data along fault zones are important aids in the delineation of recently active breaks a 15 km long portion of the south central san andreas fault saf along the southern cholame segment contains well preserved tectonic landforms such as benches troughs scarps and aligned ridges that indicate recurring earthquake slip recently acquired lidar topographic data along the entire southern saf b4 project have shot densities of 3 4 m 2 computed from the lidar returns digital elevation models dems of 0 25 to 0 5 m resolution using local binning with inverse distance weighting and 0 8 m or larger search radii depict the tectonic landforms at paleoseismic sites well enough to assess them confidently mapping of recently active breaks using a lidar only based approach compares well with aerial photographic and field based methods the fault zone varies in width from meters to nearly 1 km and is comprised of numerous en echelon meter to kilometer length overlapping sub parallel fault surfaces bounding differentially moving blocks that elongate parallel to the saf the semantic variations of what constitutes active and the importance of secondary traces influence the breadth and complexity of the resulting fault trace maps

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

influences of temperature and mg ca ratio on caco3 precipitates from seawater the mg ca ratio at which the calcium carbonate mineral that has pseudohomogeneously precipitated from seawater changes from calcite to aragonite was experimentally determined as a function of temperature results indicate a dramatic change in the critical mg ca ratio over a relatively small temperature range for example in normal seawater with a mg ca of 5 1 the critical temperature is 6 3 c at a temperature of 25 c however mg ca must be less than 1 4 0 1 for calcite to form these data indicate that paleoclimatic conditions at the time of carbonate deposition must be considered when attempting to make inferences about variation in other factors such as paleo p co 2 p pressure and paleo mg ca ratios that may control carbonate mineral formation by abiotic processes however the inverse relation between inferred global paleoclimatic conditions and the dominant type of caco 3 polymorph being abiotically deposited i e warm conditions and low mg calcite versus cool conditions and aragonite suggest that substantial changes must have taken place in ocean chemistry over phanerozoic time

evaluation of the relative tectonic activity in the eastern lake van basin east turkey abstract the eastern part of the lake van basin van region turkey is controlled by reverse faults such as the gurpinar everek and alakoy faults these represent the major tectonic structures within the van region and have caused many devastating earthquakes based on quantitative analyses the quaternary activity and topographic relief control of each of these faults was investigated the gurpinar everek and alakoy faults are restricted to the southern slopes of the guzelsu everek and karasu basins respectively analyses of the mountain front sinuosity smf and valley floor width to height ratio vf suggest high activity along the gurpinar fault the everek fault and the western part of the alakoy fault furthermore based on the integration between smf and vf the estimated uplift rates were observed to increase from north to south the gurpinar and everek hanging wall blocks are characterized by uplift rates of 0 5 mm yr 1 whereas the alakoy fault exhibited a rate of 0 05 to 0 5 mm yr 1 these faults produce knickpoints or knickzones complex basin hypsometric curves and high values of the stream length gradient index based on these geomorphic analyses it was established that the tectonic activity of both the gurpinar and everek faults is greater than that of the alakoy fault

authigenic calcium carbonate flux in groundwater controlled lakes implications for lacustrine paleoclimate records groundwater dominated lakes are an important feature of many landscapes their sediments are a particularly valuable source of paleoenvironmental information in semiarid regions where perennial lakes may otherwise be scarce where groundwater and lake composition are favorable carbonate mineral precipitation evaporative concentration of lake water and microbial processes can combine to strongly deplete dissolved ca relative to influent groundwaters the authigenic carbonate flux acf can then become limited by water column cation availability and thereby be coupled to groundwater inflow rates and aquifer recharge here we analyze sedimentary records from two marl producing groundwater controlled lakes and demonstrate a link between one dimensional acf and the palmer drought severity index pdsi a measure of land surface wetness in a restricted outflow lake with high carbonate alkalinity acf is enhanced during historically wet climatic periods in response to increased aquifer recharge rates acf in this lake declines during droughts a neighboring dilute lake with a high rate of groundwater outflow shows comparatively weak coupling between acf and pdsi history ionic chemistry carbonate mineral equilibria and 13 c patterns of dissolved inorganic carbon show that the sensitivity of the acf signal depends on the degree of evaporative evolution of lake water and the mineral saturation state of the water column under conditions of stratification and ice cover copyright 2005 elsevier ltd

natural experiments in landscape evolution a natural experiment in landscape evolution is a case study of landform development in which only one element varies significantly and for which the driving forces initial conditions and or boundary conditions are well constrained natural experiments provide a means of testing landscape evolution theory on the large space and time scales to which that theory applies natural experiments can involve either steady or transient conditions cases with steady conditions allow one to test predictions about the relationships among topography erosion rates and various attributes related to climate and material properties transient cases are valuable for distinguishing between models whose predictions might be similar and therefore indistinguishable under steady conditions essential ingredients of a natural experiment include minimal variation in all but one factor good constraints on timing and or rates well characterized processes and high quality topographic data other useful ingredients include information about intermediate topographic states such as a former valley profile revealed by strath terraces and knowledge of the time history of erosion rates in order to deepen our understanding of the physics and chemistry of long term landscape evolution there is a pressing need to identify natural experiments and develop the necessary databases to take advantage of them copyright 2009 john wiley sons ltd

high resolution electromagnetic imaging of the san andreas fault in central california although there is increasing evidence that fluids may play a significant role in the earthquake rupture process direct observation of fluids in active fault zones remains difficult since the presence of an electrically conducting fluid such as saline pore water strongly influences the overall conductivity of crustal rocks electrical and electromagnetic methods offer great potential for overcoming this difficulty here we present and compare results from high resolution magnetotelluric mt profiles across two segments of the san andreas fault saf which exhibit very different patterns of seismicity parkfield which has regular small earthquakes and creep events and in the carrizo plain where the fault is seismically quiescent and apparently locked in both surveys electric fields were sampled continuously with 100 m long dipoles laid end to end across the fault from 100 to 0 1 hz the data from both profiles are consistent with a two dimensional 2 d fault parallel resistivity model when both transverse electric and magnetic te and tm mode data are included in the interpretation narrow approximately 300 endash 600 m wide zones of low resistivity extending to depths of 2 endash 4 km in the core of the fault are required at both locations however at parkfield the conductance conductivity thickness product of the anomalous region ismore an order of magnitude larger than at carrizo plain suggesting much higher concentrations of fluids for the more seismically active parkfield segment we also image structural differences between the two segments at carrizo plain resistive presumably crystalline rocks are present on both sides of the fault at depths below 3 endash 4 km in particular we clearly image resistive basement extending approximately 10 km or more east of the saf beneath the elkhorn hills and temblor range at parkfield the situation is quite different with a resistive block of salinian granite west of the fault and an electrically conductive presumably fluid rich franciscan complex to the east it is possible that these structural differences control the difference in mechanical behavior of the fault either directly by affecting fault strength or indirectly by controlling fluid supply copyright 1999 american geophysical union less

impact of wind erosion on detecting active tectonics from geomorphic indexes in extremely arid areas a case study from the hero range qaidam basin nw china abstract geomorphologic analysis has been used widely to detect active tectonics in regions where fluvial incision is the major erosional process in this paper however we assess the feasibility of utilizing these frequently used geomorphic indexes e g hypsometric curves longitudinal channel profiles normalized stream length gradient slk index to determine active tectonics in extremely arid areas where wind erosion also plays an important role the case study is developed on the hero range in the western qaidam basin one of the driest regions on earth with severe wind erosion since late pliocene the result shows that in the west and south sectors as well as the western part of the east sector of the hero range where fluvial incision prevails these geomorphic indexes are good indicators of active faulting and consistent with the geological result based on study of fault traces scarps faulted holocene fans and historical seismicity within the past four decades in contrast along the northeastern margin the ne and the se parts of the east sector of the range where wind erosion is also important the results from the geomorphic indexes show quite active tectonics contrary with the geological evidence favoring weakly active tectonics moreover the positive slk anomaly lies oblique to the fault trace and the anticline axis but parallel to the wind direction to reconcile the contradiction we propose that wind erosion caused by northwestern winds has a tendency to make geomorphic indexes exhibit anomalous values that indicate higher activities by way of 1 lowering the base level to generate knickpoints on the longitudinal channel profiles and therefore positive slk anomalies and 2 lateral erosion of the mountain front making the hypsometric curves and even the longitudinal channel profiles more convex and producing obvious slope breaks

lacustrine carbonates of iberian karst lakes sources processes and depositional environments abstract carbonates are the main components of iberian quaternary lake sediments in this review we summarize the main processes controlling carbonate deposition in extant iberian lakes located in mesozoic and tertiary carbonate dominated regions and formed through karstic activity during the late quaternary the lakes relatively small 1 ha to 118 ha and relatively shallow zmax 11 to 40 m provide examples of the large variability of sedimentary facies depositional environments and carbonate sources hydrology is dominated by groundwater inflow except those directly connected to the fluvial drainage nine lakes have been selected for this review and the main facies in palustrine littoral and profundal environments described and interpreted clastic carbonates occur in all iberian lakes due to the carbonate composition of the bedrocks surface formations and soils of the watersheds low temperatures and dilute meteoric waters seem responsible for the low carbonate content of sediments in high elevation lakes in the glaciated terrains in the pyrenees and the cantabrian mountains clastic carbonates are dominant in small karst lakes with functional inlets where sediment infill is dominated by fining upward sequences deposited during flood events re working of littoral carbonates is common in shallow environments and during low lake level stages in most lakes endogenic carbonate production occurs in two settings i littoral platforms dominated by chara and charophyte meadows and ii epilimnetic zone as biologically mediated calcite precipitates continuous preservation of varves since the mid holocene only occurs in one of the deeper lakes montcortes lake up to 30 m where calcite laminae textures massive fining upward and coarsening upward reflect seasonal changes in limnological conditions however varves have been formed and preserved in most of the lakes during short periods associated with increased water depth and more frequent meromictic conditions most iberian lakes are in a mature stage and karstic processes are not very active an outstanding example of a lake with intense karstic activity is banyoles lake where increased spring discharge after long rainy periods causes large remobilization and re suspension of the sediments accumulated in the deepest areas leading to the deposition of thick homogeneous layers homogeinites the iberian karst lake sequences underline the large variability of facies carbonate sources and depositional environments in small lake systems they illustrate how lake types evolve through the existence of a lake basin at centennial or even smaller time scales hydrology is the paramount control on facies and depositional environment patterns distribution and lake evolution and consequently a lake classification is proposed based on hydrology and sediment input a correct interpretation of carbonate sources and depositional history is a key for using lake sequences as archives of past global changes

multi phased uplift of the southern margin of the central anatolian plateau turkey a record of tectonic and upper mantle processes abstract uplifted neogene marine sediments and quaternary fluvial terraces in the mut basin southern turkey reveal a detailed history of surface uplift along the southern margin of the central anatolian plateau from the late miocene to the present new surface exposure ages 10be 26al and 21ne of gravels capping fluvial strath terraces located between 28 and 135 m above the goksu river in the mut basin yield ages ranging from ca 25 to 130 ka corresponding to an average incision rate of 0 52 to 0 67 mm yr published biostratigraphic data combined with new interpretations of the fossil assemblages from uplifted marine sediments reveal average uplift rates of 0 25 to 0 37 mm yr since late miocene time starting between 8 and 5 45 ma and 0 72 to 0 74 mm yr after 1 66 to 1 62 ma together with the terrace abandonment ages the data imply 0 6 to 0 7 mm yr uplift rates from 1 6 ma to the present the different post late miocene and post 1 6 ma uplift rates can imply increasing uplift rates through time or multi phased uplift with slow uplift or subsidence in between longitudinal profiles of rivers in the upper catchment of the mut and ermenek basins show no apparent lithologic or fault control on some knickpoints that occur at 1 2 to 1 5 km elevation implying a transient response to a change in uplift rates projections of graded upper relict channel segments to the modern outlet together with constraints from uplifted marine sediments show that a slower incision uplift rate of 0 1 to 0 2 mm yr preceded the 0 7 mm yr uplift rate the river morphology and profile projections therefore reflect multi phased uplift of the plateau margin rather than steadily increasing uplift rates multi phased uplift can be explained by lithospheric slab break off and possibly also the arrival of the eratosthenes seamount at the collision zone south of cyprus

erosion thresholds and land surface morphology we propose a graphical technique to analyze the entirety of landforms in a catchment to define quantitatively the spatial variation in the dominance of different erosion processes high resolution digital elevation data of a 1 2 km2 hilly area where the channel network had been mapped in the field were used in the digital terrain model topog to test threshold theories for erosion the land surface was divided into 20 m2 elements whose shapes were then classified as convergent planar or divergent the entire landscape plotted on a graph of area per unit contour length against surface gradient shows each planform plotting as a separate field a simple steady state hydrologic model was used to predict zones of saturation and areas of high pore pressure to mimic the extreme hydrologic events responsible for erosive instability of the land surface the field observation that saturation overland flow is rare outside convergent zones provided a significant constraint on the hydrologic parameter in the model this model was used in threshold theories to predict areas of slope instability and areas subject to erosion by saturation overland flow both of which can contribute to channel initiation the proportion of convergent elements predicted to exceed the threshold varies greatly with relatively small changes in surface resistance demonstrating a high sensitivity to land use such as cattle grazing overall the landscape can be divided using erosion threshold lines into areas prone to channel instability due to runoff and stable areas where diffusive transport predominates

testing glacial isostatic adjustment models of last interglacial sea level history in the bahamas and bermuda abstract part of the spatial variation in the apparent sea level record of the last interglacial lig period is due to the diverse response of coastlines to glacial isostatic adjustment gia processes particularly where coastlines were close to the laurentide ice sheet during the past two glacial periods we tested modeled lig paleo sea levels on new providence island npi bahamas and bermuda by investigating emergent coral patch reefs and oolitic peloidal beach deposits corals with closed system histories collected from patch reefs on npi have ages of 128 118 ka and ooids peloids from beach ridges have closed system ages of 128 116 ka elevations of patch reefs indicate a lig paleo sea level of at least 7 m to 9 m above present beach ridge sediments indicate paleo sea levels of 5 m to 14 m assuming subsidence 7 m to 16 m above present during the lig some though not all of these measurements are in good agreement with gia models of paleo sea level that have been simulated for the bahamas on bermuda corals with closed system histories collected from marine deposits have ages of 126 114 ka although coral bearing marine deposits on bermuda lack the precise indication of paleo sea level provided by patch reefs and oolitic beach ridges these sediments nevertheless provide at least a first order estimate of paleo sea level paleo sea level records on bermuda are consistently lower 2 m to 7 m than what gia models simulate for the lig the reason for the reasonable agreement with models for the bahamas and poor agreement for bermuda is not understood but needs further investigation in light of the probability of a higher sea level in the near future

surface uplift uplift of rocks and exhumation of rocks uplift of the surface of mountain belts requires forces that are comparable in magnitude to those associated with plate motion and therefore determination of rates of surface uplift could provide important information on the dynamics of mountain ranges rates of uplift of the surfaces of mountain ranges have not however been quantified sufficiently well that they provide useful constraints on those processes many reports off surface uplift in mountain ranges are based on mistaking exhumation of rocks or uplift of rocks for surface uplift and provide no information whatsoever on the rates of surface uplift

landscape evolution valley excavation and terrace development following abrupt postglacial base level fall many high latitude fluvial systems are adjusting to base level changes since the last glaciation channels that experienced base level fall may still be incising often through glacial diamictons tills these tills can be quite competent behaving more like weak bedrock than unconsolidated sediment and erode at a fast pace thus providing a unique opportunity to test models of channel incision and knickpoint migration in transient systems here we integrate light detection and ranging lidar topography strath terrace chronology and numerical modeling to determine knickpoint migration and incision history of the le sueur river in central minnesota usa results indicate that the le sueur river is best modeled as a detachment limited channel with downstream coarsening related to lag clasts from tills playing a critical factor in longitudinal profile development the le sueur river meanders as it incises so we coupled the best fit incision model to a meander model to determine valley excavation history the excavation history was used to determine a natural background erosion rate prior to land use changes associated with settlement and agricultural expansion in the mid 1800s we compared background fine sediment silt and clay erosion rates with historic decadal average annual suspended loads results show that modern fine sediment contributions from sources associated with valley excavation are three times higher than modeled presettlement loads recent changes in hydrology associated with land use and climate change have increased flows in rivers leading to higher sediment loads not just from field erosion but from increased bank and bluff erosion in the deeply incised valleys

integrated geomorphic and geodynamic modeling of a potential blind thrust in the san francisco bay area california abstract geometries and slip budgets of the faults in the san francisco bay area imply previously unrecognized fault linkages including examples of blind thrust structures that appear to connect segments of strike slip faults and accommodate along strike variations in slip rate along these structures displacement along linking faults may be associated with the development of topography and also may serve as earthquake sources in marin county california systematic spatial patterns in landscape topography and geomorphic indices suggest that the region north of mt tamalpais is experiencing differential rock uplift we suggest that a blind thrust underlies the elevated area creating the observed topography and possibly resolving a slip discrepancy between the hayward and san andreas fault in this region we have developed and implemented an integrative approach that combines observations from tectonic deformation and geomorphic properties to identify a potential blind thrust beneath marin county elastic displacement modeling has been tested for compatibility with the blind thrust hypothesis and to assess the sensitivity of observables to fault geometry and orientation from this a set of plausible blind thrust structures are defined we use a range of empirical relationships between channel steepness index and erosion rate to estimate spatial variations in erosion rate along bolinas ridge by coupling these erosion estimates with elastic displacement fault modeling we can use the resulting topographic envelopes to constrain the rate and duration of deformation these constraints along with spatial bounds on the possible fault models are used to calculate potential seismic moment and moment magnitude with an assumed recurrence interval of 100 years such blind thrusts can produce a mw 6 3 earthquake while a longer recurrence time 1000 years results in a maximum mw 7 0 earthquake although such events are not likely to be catastrophic they are large enough to cause significant strong ground motions in the san francisco bay area

geomorphic response to uplift along the dragon s back pressure ridge carrizo plain california we used high resolution topography geomorphic mapping of active surface processes and geologic mapping to study the topographic and erosional response of small drainage basins to rock uplift along the dragon s back pressure ridge along the san andreas fault in the carrizo plain california we infer the history of deformation experienced by 40 small drainage basins formed in poorly consolidated sedimentary rocks a space for time substitution directly images the erosional and topographic responses to deformation progressive deformation and rock uplift are accompanied by increases in channel steepness and basin relief as uplift ceases channel concavity rapidly increases causing channels to undercut hillslopes this undercutting promotes the consumption of hillslopes by landsliding this undercutting also causes basin relief to be greatest after uplift has stopped this analysis indicates that channels of the dragon s back pressure ridge respond to changes in rock uplift rates over thousands of years whereas hillslope processes may take more than an order of magnitude longer to adjust to changes in rock uplift rates our study directly measures changes in erosional processes due to the initiation and cessation of rock uplift which can typically only be inferred using numerical models by direct field observations

correlation of fluvial terraces and temporal steady state incision on the onshore makran accretionary wedge in southeastern iran insight from channel profiles and 10be exposure dating of strath terraces we describe and summarize the geomorphology of fluvial terraces along the four major rivers draining the central onshore makran accretionary wedge in iran and describe uplifted marine terraces on the coast of this region thirty five strath terraces at different sites were dated using in situ produced cosmogenic 10 be concentrations from surfaces and depth profiles these new measurements reveal abandonment ages between ca 15 and 380 ka the age distribution allows determining the chronology of terrace levels and establishing regional correlations between two major regional levels the geographically widespread correspondence suggests that these two levels result from a regional climatically driven force systematic dating also provides evidence for time and spatial variations in incision rate which enables distinguishing between a regionally uniform incision rate of 0 3 0 4 mm a and higher local incision and or uplift 0 8 mm a rates these spatial changes are consistent with where localized tectonic activity is recognized in the field we also dated using 14 c in shells four uplifted marine terraces on the coast of the study area comparing incision rates derived from strath terraces 0 3 mm a with published uplift estimates from marine terraces 0 2 mm a reveals that fluvial rivers responded to a regional long term incision and surface uplift pattern this rate reflects the tectonically steady state of the wedge on a regional scale locally high incision rates delineate active faults and folds indicating that perfect steady state is unlikely on short length scales

are two elements better than one dual isotope ratio detrending of evaporative effects on lake carbonate paleoelevation proxies 1 stable isotope based proxy methods enhance our ability to interpret geodynamical histories for tectonic provinces via paleoelevational reconstructions these methods require that the unmodified isotopic composition of meteoric water is recorded by authigenic minerals a critical assumption that has not been tested across wide ranging environmental and topographical contexts here we show that quaternary lake carbonate 18o values are not strongly nor significantly correlated with regional elevation due to the isotopic modification of in flow waters following entry into the lake environment these modifications are largely caused by surface water evaporation and can result in 3 km errors in paleoelevation estimates if not accounted for however our analysis suggests that positive shifts in surface water 18o are accompanied by similar magnitude shifts in 13c dic this positive co variation in 18o and 13c may be used to detrend lake carbonate compositions for the effects of surface water evaporation using a parameter we define here as the 13c excess when tibetan lakes are excluded from the data set 13c excess values are significantly correlated with mean up slope hypsometric altitude with an error of 500 m application of the13c excess approach to cenozoic lake carbonate records from the western u s cordillera both challenges and reinforces previous paleoelevational interpretations based on 18o alone

temporal changes in rock uplift rates of folds in the foreland of the tian shan and the pamir from geodetic and geologic data understanding the evolution of continental deformation zones relies on quantifying spatial and temporal changes in deformation rates of tectonic structures along the eastern boundary of the pamir tian shan collision zone we constrain secular variations of rock uplift rates for a series of five quaternary detachment and fault related folds from their initiation to the modern day when combined with gps data decomposition of interferometric synthetic aperture radar time series constrains the spatial pattern of surface and rock uplift on the folds deforming at decadal rates of 1 5 mm yr these data confirm the previously proposed basinward propagation of structures during the quaternary by fitting our geodetic rates and previously published geologic uplift rates with piecewise linear functions we find that gradual rate changes over 100 kyr can explain the interferometric synthetic aperture radar observations where changes in average uplift rates are greater than 1 mm yr among different time intervals 10 10 and 10 years