identification of a late quaternary alluvial aeolian sedimentary sequence in the sichuan basin china abstract the late quaternary sedimentary sequence in the northwestern part of the sichuan basin consists of five lithological units and with increasing depth include the chengdu clay brown clay red clay sandy silt and basal muddy gravel the genesis provenance and age of the sediments as well as the possible presence of hiatuses within this sequence are debated measurements of grain size magnetic susceptibility quartz content quartz 18o values element composition and sr nd isotopic concentrations of samples from a typical sedimentary sequence in the area provides new insights into the genesis and history of the sequence the new data confirm that the sediments in study site are alluvial aeolian in origin with basal alluvial deposits overlain by aeolian deposits like the uppermost chengdu clay the underlying brown clay and red clay are aeolian in origin in contrast the silty sand like the basal muddy gravel is an alluvial deposit and not an aeolian deposit as previously thought moreover the succession of the aeolian deposits very likely contains two significant sedimentary hiatuses sedimentological analysis demonstrates that the source materials for the aeolian deposits in the northwestern part of the sichuan basin and those on the eastern tibetan plateau are different furthermore the loess deposits on the eastern tibetan plateau are derived from heterogeneous local sources

aminostratigraphy and faunal correlations of late quaternary marine terraces pacific coast usa recent studies using the extent of racemization of amino acids to date fossil mollusc shells in the arctic1 the british isles2 and on the atlantic3 4 and pacific5 13 coasts of north america have relied mainly on theoretical kinetic models of racemization ages generated in this fashion are highly model dependent and require estimates of integrated long term diagenetic temperatures we present here an alternative empirical approach to aminostratigraphy in which we plot amino acid enantiomeric ratios versus latitude for localities along the pacific coast of the united states and generate isochronal correlations by connecting data points of geographically proximal localities that have similar d l ratios and zoogeographic aspect isochrons are calibrated at a few localities by independent radiometric dates the diagenetic temperature effect on racemization is reflected in the slope of the isochrons but the need to quantify temperature is eliminated

two dimensional nonlinear diffusive numerical simulation of geomorphic modifications to cinder cones the temporal evolution of simple landforms such as cinder cones by nonlinear diffusive processes is studied through the use of a new 2d numerical model using well established and accurate numerical mathematics and high resolution digital elevation models dems extending 1d profile nonlinear diffusion analyses used in cinder cone hillslope and fault scarp evolution studies we have implemented a 2d numerical model with a spatially and temporally varying sediment transport rate coefficient scaled nonlinearly by the ratio of local slope to critical slope the high accuracy and efficient numerical implementation are documented in the paper and the matlab toolkit developed is used to solve for the developmentof an initial 2d cone form first we examine the nonlinear transport rule and suggest a refinement that accounts explicitly for flux at threshold slopes we find that the maximum diffusion necessarily introduced in the numerical model to avoid infinite rates at the critical slope controls the final morphology especially approaching steady state secondly solving the landscape evolution problem in 2d enables a natural accounting for sediment flux convergence or divergence in the profile thirdly the boundary behavior of a given landscape element controls much of what happens in that domain and so we allow for arbitrary flux magnitude or elevation boundary conditions fourthly landscapes are heterogeneous in their surface cover and so we allow for spatially and temporally varying transport rate k and we permit an arbitrary vertical displacement field within the model domain to test the new formulation for the nonlinear term the effect of variable diffusivity k and the numerical schemes implemented we apply the model to cinder cones built on the flanks of mount etna in 2001 and 2002 2003 we explore the effects of dem resolution with data from the 2001 cone and the utility of spatially variable diffusivity to explain the variation in erosion measured by differencing repeat light detection and ranging lidar surveys gathered in 2004 and 2007 over the 2002 2003 cone complex copyright 2013 john wiley sons ltd

the behavior of trace elements during schwertmannite precipitation and subsequent transformation into goethite and jarosite schwertmannite is a ubiquitous mineral formed from acid rock drainage ard and plays a major role in controlling the water chemistry of many acid streams the formation of schwertmannite was investigated in the acid discharge of the monte romero abandoned mine iberian pyrite belt sw spain schwertmannite precipitated from supersaturated solutions mainly owing to the oxidation of fe ii to fe iii and transformed with time into goethite and jarosite in a few hours schwertmannite precipitation removed more than half of the arsenic load from solution whereas the concentration of divalent trace metals zn cu pb cd ni and co remained almost unchanged in the laboratory natural schwertmannite was kept in contact with its coexisting acid water in a flask with a solid liquid mass ratio of 1 5 for 353 days during this time the ph of the solution dropped from 3 07 to 1 74 and the concentrations of sulfate and fe increased during the first 164 days schwertmannite transformed into goethite plus h3o jarosite but subsequently goethite was the only mineral to form some of the trace elements such as al cu pb and as were depleted in solution during the first stage as schwertmannite transformed into goethite plus h3o jarosite on the contrary the transformation of schwertmannite to goethite with no jarosite during the second stage released al cu and as to the solution despite the variation in their concentrations in solution approximately 80 of the total al and cu inventories and more than 99 as and pb remained in the solid phase throughout the entire aging process

active faulting and paleoseismology along the bree fault lower rhine graben belgium paleoseismic analysis of the 10 km long bree fault scarp in the lower rhine graben yields numerous lines of evidence of earthquake activity in the holocene and late pleistocene this active normal fault a part of the feldbiss fault system dips 70 ne and is expressed at the surface by a prominent nw se trending 7 to 20 m high scarp formed since the deposition of the maas river main terrace 700 kyr b p trenches and geophysical prospecting show that the fault which is known to have 100 m of vertical offset since the late pliocene breaks late pleistocene and holocene deposits ground penetrating radar seismic refraction and electric tomography suggest that at shallow depth the amount of displacement is larger than the youngest vertical offset visible in the trenches and corresponds to cumulative fault displacements the analysis of 36 leveling profiles across the scarp indicates that its height can be classified into three groups likely corresponding to different events a morphologic dating gives approximate ages of 2 1 5 kyr b p 14 5 kyr b p and 41 6 kyr b p for the past three surface faulting earthquakes analysis of faulted stratigraphy and earthquake induced deformation structures exposed in trenches suggests the occurrence of three large earthquakes during the past 45 l03 years and yields 0 07 mm yr of relative vertical deformation rate the most recent seismic event occurred between a d 610 and 890 the first identification of an active fault with surface ruptures in the lower rhine graben area emphasizes that large earthquake sources exist within intraplate europe and that at least some of these events are preserved in the geologic record

sea beam survey of an active strike slip fault the san clemente fault in the california continental borderland the san clemente fault located in the california continental borderland is an active northwest trending right lateral wrench fault sea beam data are used to map the major tectonic landforms associated with active submarine faulting in detail unavailable using conventional echo sounding or seismic reflection data in the area between north san clemente basin and fortymile bank the major late cenozoic faults are delineated by alignments of numerous tectonic landforms including scarps linear trenches benches and sags character and spatial patterns of these landforms are consistent with dextral wrench faulting although vertical offsets may be substantial locally the main trace of the san clemente fault cuts a straight path directly across the rugged topography of the region evidence of a steeply dipping fault surface basins or sags located at each right step in the en echelon pattern of faults are manifestations of pull apart basin development in a right slip fault zone seismic reflection profiles show offset reflectors and a graben in late quaternary turbidites of the navy fan where the fault zone follows a more northerly trend modern tectonic activity along the san clemente fault zone is demonstrated by numerous earthquakes with epicenters located along the fault s trend the average strike of the san clemente fault is parallel to the predicted pacific north american relative plate motion vector at this location therefore we conclude that the san clemente fault zone is a part of the broad pacific north american transform plate boundary and that the southern california region may be considered as a broad shear zone

original forms and initial modifications of the galway lake road scarp formed along the emerson fault during the 28 june 1992 landers california earthquake a remarkable scarp formed southeast of the galway lake road during the mw 7 3 landers california earthquake over the first 11 months following the earthquake we repeated topographic surveys and ground stereoscopic photography and interpreted the observations of original forms and initial modifications of the faulted landforms the complexity of the surface rupture influenced the geomorphic responses the principal shear zone consisted of en echelon right and left lateral generally left stepping fault segments with cumulative offsets of 5 m right lateral and 2 5 m vertical typical fault scarp profiles have different slope angles above and below the surface rupture and a small free face the surface rupture formed steep irregular knickpoints in channels crossing the scarp the original channel surfaces were warped as they stepped down over tilted and rotated fracture bounded blocks the landforms were modified measurably by the above average winter 1992 1993 rainfall over surfaces controlled by hillslope processes only fault scarp erosion was controlled by rainsplash and slumping originally sharp corners were rounded and loose sediment collected in colluvial wedges surface flows over simple ramp steps in channel profiles caused incision that drove knick points back by as much as 50 cm over more complex portions of the principal shear zone flow was diverted into open fractures and little modification of the scarp occurred the pre earthquake topography at the site provided no clear evidence of the last similar slip event simple diffusion erosion models of the time required to bring the new scarp to its pre landers event configuration indicate that the last major rupture may have been several thousand years ago

chemical weathering of a marine terrace chronosequence santa cruz california i interpreting rates and controls based on soil concentration depth profiles abstract the spatial and temporal changes in element and mineral concentrations in regolith profiles in a chronosequence developed on marine terraces along coastal california are interpreted in terms of chemical weathering rates and processes in regoliths up to 15 m deep and 226 kyrs old quartz normalized mass transfer coefficients indicate non stoichiometric preferential release of sr ca na from plagioclase along with lesser amounts of k rb and ba derived from k feldspar smectite weathering results in the loss of mg and concurrent incorporation of al and fe into secondary kaolinite and fe oxides in shallow argillic horizons elemental losses from weathering of the santa cruz terraces fall within the range of those for other marine terraces along the pacific coast of north america residual amounts of plagioclase and k feldspar decrease with terrace depth and increasing age the gradient of the weathering profile bs is defined by the ratio of the weathering rate r to the velocity at which the profile penetrates into the protolith a spreadsheet calculator further refines profile geometries demonstrating that the non linear regions at low residual feldspar concentrations at shallow depth are dominated by exponential changes in mineral surface to volume ratios and at high residual feldspar concentrations at greater depth by the approach to thermodynamic saturation these parameters are of secondary importance to the fluid flux qh which in thermodynamically saturated pore water controls the weathering velocity and mineral losses from the profiles long term fluid fluxes required to reproduce the feldspar weathering profiles are in agreement with contemporary values based on solute cl balances qh 0 025 0 17 m yr 1 during saturation controlled and solute limited weathering the greater loss of plagioclase relative to k feldspar is dependent on the large difference in their respective solubilities instead of the small difference between their respective reaction kinetics the steady state weathering rate under such conditions is defined as r q h m sol m total 1 s v b s the product of qh and the ratio of solubilized to solid state feldspar msat mtotal define the weathering velocity the weathering gradient bs reflects the kinetic rate of reaction where sv is the volumetric surface area of the residual feldspar both this rate expression and the spreadsheet calculations produce similar plagioclase weathering rates r 5 14 10 16 mol m 2 s 1 which agree with those reported for other environments of comparable climate and age weathering dependent concentration profiles are commonly described in literature the present paper provides methods by which these data can yield a more fundamental understanding of the weathering processes involved

degradation of unconsolidated quaternary landforms in the western north america abstract one of the major goals of geomorphology is to understand the rate of landscape evolution and the constraints that erosion sets on the longevity of land surfaces the latter has also turned out to be vital in modern applications of cosmogenic exposure dating and interpretation of lichenometric data from unconsolidated landforms because the effects of landform degradation have not been well documented disagreements exist among researchers regarding the importance of degradation processes in the dating techniques applied to exposures here we show that all existing qualitative data and quantitative markers of landform degradation collectively suggest considerable lowering of the surface of unconsolidated landforms over the typical life span of quaternary moraines or fault scarps degradation is ubiquitous and considerable even on short time scales of hundreds of years on steeply sloping landforms these conservative analyses are based entirely on field observations of decreasing slope angles of landforms over the typical range of ages in western north america and widely accepted modeling of landscape degradation we found that the maximum depth of erosion on fault scarps and moraines is on average 34 of the initial height of the scarp and 25 of the final height of the moraine although our observations are limited to fault scarps and moraines the results apply to any sloping unconsolidated landform in the western north america these results invalidate the prevailing assumption of no or little surface lowering on sloping unconsolidated landforms over the quaternary period and affirm that accurate interpretations of lichen ages and cosmogenically dated boulder ages require keen understanding of the ever present erosion in our view the most important results are twofold 1 to show with a large data set that degradation affects universally all sloping unconsolidated landforms and 2 to unambiguously show that even conservative estimates of the total lowering of the surface operate at time and depth scales that significantly interfere with cosmogenic exposure and lichen dating

computer simulation models of scoria cone degradation abstract long term erosional modifications of the relatively simple morphology of scoria cinder cones are ideally suited for study by field and computer simulation methods a series of temporally distinct cones in the san francisco and springerville volcanic fields of arizona provides the foundation for documenting the degradational evolution of scoria cones in a semi arid climate progressive changes due to erosion are illustrated by the systematic decrease with increasing age of various morphometric parameters including scoria cone height cone height width ratio hco wco crater depth width ratio and slope angle for example holocene latest pleistocene cones in the san francisco field have a mean hco wco value of 0 178 0 041 a mean maximum slope angle of 29 7 4 2 and a mean average slope angle of 26 4 7 3 whereas the group of pliocene cones have values of 0 077 0 024 20 5 5 8 and 8 7 2 7 respectively comparative morphology of scoria cones is a potentially useful dating tool for mapping volcanic fields in order to better understand the degradational modifications of these volcanic landforms we have developed a numerical approach to simulate the surficial processes responsible for the erosion of a typical scoria cone the simulation algorithm can apply either a linear diffusion equation model or a model with a nonlinear transport law using a finite difference formulation the simulation operates upon a three dimensional scoria cone input as a matrix of elevation values utilizing both field and model results the correlation between changing hco wco value cone age and computer time step was expressed graphically to derive comprehensive values of the transport or diffusion coefficient df for both volcanic fields for the san francisco volcanic field df had a calculated value of 21 4 m2 kyr for the linear model and 5 3 m kyr for the nonlinear model while for the springerville volcanic field df had a calculated value of 24 4 m2 kyr for the linear model and 6 3 m kyr for the nonlinear model

modification of wave cut and faulting controlled landforms from a casual observation that the form of degraded fault scarps resembles the error function this investigation proceeds through an elementary diffusion equation representation of landform evolution to the application of the resulting equations to the modern topography of scarplike landforms the morphologic observations can be analyzed either in the form of one or more cross strike elevation profiles or in the form of the slope offset plot a point plot of maximum scarp slope versus scarp offset working with either or both of these data representations for nine geologic structures which range in age from 3 to 400 ka b p and in offset from 1 to 50 m we apply analytical solutions for the vertical initial value scarp the vertical continuous offset scarp and the finite slope initial value scarp the model calculations are intrinsically ambiguous yielding as the final answer only the product t in the case of the initial value problem or the product a 1 in the case of the repeated faulting problem here t is the age of a single scarp forming event 2a is the vertical slip rate and is the mass diffusivity a single profile across three sea cliffs along the santa cruz california coast is analyzed as three separate initial value problems a reasonably constrained age for the sea cliff standing above the highway 1 platform returns 11 gkg 1 gkg 1 m2 ka with this we can date the two older sea cliffs in fact we do the converse age estimates for these two older sea cliffs based on a uniform rate of uplift both yield the same as for the lower sea cliff we treat a single profile of the raymond fault in pasadena san marino in terms of the repeated faulting problem for it the uplift rate of r crook and others yields 16 gkg the very substantial preexisting offset across the raymond fault must have been buried leveled some 230 ka b p when the modern topography began to form our analysis of the lake bonneville shoreline scarps reveals a dependence of t on 2a suggestive of nonlinear modification processes this appearance is treated with the finite slope initial value scarp model to determine 1 1 gkg for the lake bonneville shoreline scarps the suggestion of m n machette that approximately 100 000 year old meter high scarps are unobservable in weakly consolidated alluvial terranes of the basin and range and rio grande rift valley provinces can be formulated as 1 gkg the coincidence between this inequality and the lake bonneville shoreline is striking and it suggests that the value of 1 gkg may be generally applicable as a good first approximation to the modification of alluvial terranes within the semiarid regions of the western united states the lake bonneville shoreline is the basis for dating four sets of fault scarps in west central utah the drum mountains fault scarps can be modeled in several different circumstances but the most likely interpretation is that these fault scarps formed as the result of a single episode of normal faulting 3 6 to 5 7 ka b p the younger age is associated with quite low initial slope angles 25 the other three sets of fault scarps show no evidence for finite initial value slopes fault scarps along the eastern base of the fish springs range are very young 3 ka b p we estimate the age of fault scarps along the western flank of the oquirrh mountains to be 32 ka b p which meets the weak geologic constraint that they be older than the lake bonneville shoreline fault scarps along the northeastern margin of the sheeprock mountains are even older 53 ka b p an intriguing consequence of our single event analysis of these scarps is that an 11 5 m offset occurred in a single earthquake

exhumation of the inyo mountains california implications for the timing of extension along the western boundary of the basin and range province and distribution of dextral fault slip rates across the eastern california shear zone 1 new geologic mapping tectonic geomorphologic 10be terrestrial cosmogenic nuclide and u th he zircon and apatite thermochronometric data provide the first numerical constraints on late cretaceous to late quaternary exhumation of the inyo mountains and vertical slip and horizontal extension rates across the eastern inyo fault zone california the east dipping eastern inyo fault zone bounds the eastern flank of the inyo mountains a prominent geomorphic feature within the western basin and range province and eastern california shear zone u th he zircon and apatite thermochronometry yield age patterns across the range that are interpreted as indicating 1 two episodes of moderate to rapid exhumation associated with laramide deformation during the late cretaceous early tertiary 2 development of a slowly eroding surface during a prolonged period from early eocene to middle miocene 3 rapid cooling exhumation and initiation of normal slip along the eastern inyo fault zone accommodated by westward tilting of the inyo mountains block at 15 6 ma and 4 rapid cooling exhumation and renewed normal slip along the eastern inyo fault zone at 2 8 ma fault slip continues today as indicated by fault scarps that cut late pleistocene alluvial fan surfaces the second episode of normal slip at 2 8 ma also signals onset of dextral slip along the hunter mountain fault yielding a pliocene dextral slip rate of 3 3 1 0 mm a where a is years summing this dextral slip rate with estimated dextral slip rates along the owens valley death valley and stateline faults yields a net geologic dextral slip rate across the eastern california shear zone of 9 3 2 2 1 4 to 9 8 1 4 1 0 mm a

surface displacements in the 1906 san francisco and 1989 loma prieta earthquakes the horizontal displacements accompanying the 1906 san francisco earthquake and the 1989 loma prieta earthquake are computed from geodetic survey measurements the 1906 earthquake displacement field is entirely consistent with right lateral strike slip on the san andreas fault in contrast the 1989 loma prieta earthquake exhibited subequal components of strike slip and reverse faulting this result together with other seismic and geologic data may indicate that the two earthquakes occurred on two different fault planes

unexpected trend in the compositional maturity of second cycle sand abstract it is generally accepted that recycling of sandstone generates relatively more mature sand than its parent sandstone such maturity is accomplished mainly through chemical weathering as the chemically unstable minerals are eliminated because chemical weathering is ubiquitous on the earth s surface maturity due to recycling is expected in most geological settings however contrary to one s expectation second cycle holocene sand exclusively derived from sandy facies of the first cycle pennsylvanian permian cutler formation is actually less mature than its first cycle parent near gateway colorado both the cutler sandstone and holocene sand were the products of similar geological processes that controlled their respective composition in spite of such similarities a significant difference in composition is observed we propose that the unexpected immaturity in second cycle holocene sand may be due to mechanical disintegration of coarse grained feldspar and feldspar rich rock fragments into relatively smaller fractions results presented in this paper are the first quantitative estimation of recycling of parent sandstone into daughter sand and the first observed reverse maturity trend in second cycle sand these unexpected results suggest the need for further research to quantitatively understand the recycling process

mass accumulation rates in asia during the cenozoic summary this work establishes estimates of mass accumulation rates in 18 mostly offshore sedimentary basins in asia since the beginning of the cenozoic 66 ma the estimates were derived from isopach maps cross sections and drill holes or stratigraphic columns assuming regional similarity of the strata average solid phase volumes and accumulation rates were calculated for nine epochs approximately corresponding to geological periods palaeocene 66 58 ma eocene 58 37 ma oligocene 37 30 and 30 24 ma miocene 24 17 17 11 and 11 5 ma pliocene 5 2 ma and quaternary 2 0 ma these rates shed new light on the geological history of asia since the onset of the collision of india with asia 50 ma the overall average accumulation rates curve for asian sedimentary basins since the beginning of the tertiary shows an exponential form with slow accumulation rates less than 0 5 106 km3 myr 1 until the beginning of the oligocene more than 15 myr after the onset of the collision from the oligocene onwards rates increase quickly in an exponential manner reaching their maximum values in the quaternary more than 1 5 106 km3 myr 1 from these observations we suggest that extrusion and crustal shortening are complementary processes that have been successively dominant throughout the india eurasia collision history at smaller scales one may distinguish between independent histories at the subcontinental and basin scales this permits a comparison of the relative importance of tectonic and climatic erosion processes affecting the different mountain belts of asia during the cenozoic

field application of calcite dispersed alkaline substrate calcite das for passive treatment of acid mine drainage with high al and metal concentrations abstract passive treatment systems are widely used for remediation of acid mine drainage amd but existing designs are prone to clogging or loss of reactivity due to al and fe precipitates when treating water with high al and heavy metal concentrations dispersed alkaline substrate das mixed from a fine grained alkaline reagent e g calcite sand and a coarse inert matrix e g wood chips had shown high reactivity and good hydraulic properties in previous laboratory column tests in the present study das was tested at pilot field scale in the iberian pyrite belt sw spain on metal mine drainage with ph near 3 3 net acidity 1400 1650 mg l as caco3 and mean concentrations of 317 mg l fe 95 fe ii 311 mg l zn 74 mg l al 20 mg l mn and 1 5 0 1 mg l cu co ni cd as and pb the das tank removed an average of 870 mg l net acidity as caco3 56 of inflow 25 fe 93 al 5 zn 95 cu 99 as 98 pb and 14 cd but no mn ni or co average gross drain pipe alkalinity was 181 mg l as caco3 which increased total fe removal to 153 mg l 48 in subsequent sedimentation ponds unfortunately the tank suffered clogging problems due to the formation of a hardpan of al rich precipitates das lifetime could probably be increased by lowering al loads

northward migration of the southern diagonal fault of the hula pull apart basin dead sea transform northern israel abstract the hula valley located in northeastern israel is a 4 million year old pull apart basin bounded by two left stepped segments of the dead sea transform basic models of pull apart basins suggest four faults at all sides of the basin a situation which is not always the case in the hula pull apart basin the longitudinal n s faults are clearly evident while the transversal e w faults are less explicit an nw oriented lineament expressed as a north facing continuous scarp 1 3 m high was recognized in the southern part of the valley morphological seismic and sedimentary considerations suggest that this scarp is the surface expression of a deep seated fault this fault termed the yesod hama ala fault forms the present southern boundary of the hula pull apart basin and appears to be the southern diagonal fault which links the jordan fault in the east with the yammunneh fault in the west it is suggested that this fault scarp formed a shallow morphological barrier that partly blocked the southern outlet of the valley enabling a permanent lake in the southern part of the hula valley thus the uplifted southern block determined the sw shoreline of the lake it is proposed that the hula basin is a version of the classic pull apart model it is also suggested that in the absence of upwelling mantle material and extension along the length of the basin a crustal thinning and subsidence might have occurred through normal faulting of the upper brittle crust the thick depositional sequence within the southern part of the basin shows that the present margins have been a major depositional site for a long time and that the hula valley has thus developed as an asymmetric pull apart rhomb shaped basin bounded by steep north striking boundary normal as well as strike slip faults w nw striking and northward dipping normal faults and a south facing bending flexure as activity within the basin continued and northward migration of the faulting occurred a new fault developed according to this perception the present active fault is the yesod hama ala fault while the future fault will be located northward as can be presumed from the present micro seismic activity in the valley

statistical description of slope dependent soil transport and the diffusion like coefficient 1 for hillslopes undergoing diffusive soil transport it is often assumed that the soil flux is proportional to the local land surface gradient where the coefficient of proportionality is like a diffusion coefficient inasmuch as transport involves quasi random soil particle motions related to biomechanical mixing and similar dilational processes a slope dependent relation arises from a balance between particle fluxes that tend to loft a soil and gravitational settling of particles into available pore space a specialized form of the fokker planck equation adapted to such particle motions clarifies how the particle flux involves advective and diffusive parts this in turn contributes to a kinematic description of the diffusion like coefficient ingredients of this coefficient include an active soil thickness a characteristic particle size the porosity in excess of a consolidated porosity and the rate of particle activation as a function of depth these last two ingredients vertical porosity structure and activation rate in effect characterize the magnitude and frequency of settling particle motions related to biological activity and thereby set the rate constant of the transport process the significance of land surface slope is that it is a measure of the downslope component of slope normal lofting that is balanced by settling because the diffusion like coefficient contains the soil thickness the analysis suggests that the soil flux is proportional to the depth slope product the analysis is consistent with published profiles of soil creep displacement and with published estimates of soil flux obtained by downslope integration of soil production rates for hillslopes in california and australia

seasonal variations of ochreous precipitates in mine effluents in finland abstract ochreous precipitate and water samples were collected from the surroundings of seven closed sulphide mines in finland in the hammaslahti zn cu au mine otravaara pyrite mine and paroistenjarvi cu w as mine the collection was repeated in different seasons to study mineralogical and geochemical variations of precipitates the sampling was done in 1999 2002 from the ditches and drainage ponds of the tailings and waste rock piles that are susceptible to seasonal changes mineralogy of the precipitates was evaluated by x ray diffraction xrd and infrared spectroscopy ir and precipitate geochemistry was examined by selective extractions schwertmannite fe 8 o 8 oh 6 so 4 was the most typical fe hydroxide mineral found goethite was almost as common as schwertmannite was often poorly ordered and contained up to 10 wt of so 4 goethite and schwertmannite were commonly found as mixtures and they occurred in similar ph and so 4 concentrations ferrihydrite nominally fe 5 ho 8 4h 2 o was typically found in areas not influenced by acid mine drainage and also in acid mine waters with high organic matter or as content jarosite kfe 3 so 4 2 oh 6 was found only in one site in addition some gypsum caso 4 2h 2 o and aluminous sulphate precipitates presumably basaluminite al 4 so 4 oh 10 5h 2 o were identified selective extractions showed that acid extracts fe tot s tot ratios of schwertmannite and goethite samples were similar but the ratio of oxalate extractable to total fe fe ox fe tot of goethite samples were lower than those of the schwertmannite samples only al si and as were bound to precipitates in substantial amounts up to several wt in schwertmannites and goethites al cu co mn and zn were mostly structural substituting for fe in an fe oxyhydroxide structure or bound to surface adsorption sites in pores limited by diffusion in ferrihydrites heavy metals were also partly bound in adsorbed form dissolving in acid ammonium acetate ferrihydrites and goethites were more enriched in co mn and zn than schwertmannites but schwertmannites and ferrihydrites were more enriched in as than goethites mineralogical and geochemical evidence showed that in the spring after the snowmelt the acid mine drainage precipitates were predominantly schwertmannite and were partly transformed during warm summer months to goethite the phase transformation of precipitates was followed by a decrease in ph values and increase in so 4 concentrations of waters adsorbed as retarded the phase transformation

field multi step limestone and mgo passive system to treat acid mine drainage with high metal concentrations abstract passive treatment systems have become one of the most sustainable and feasible ways of remediating acid mine drainage amd however conventional treatments show early clogging of the porosity or and coating of the reactive grains when high acidity and metal concentrations are treated the performance of fine grained reagents dispersed in a high porosity matrix of wood shavings was tested as an alternative to overcome these durability problems the system consisted of two tanks of 3 m 3 filled with limestone sand and wood shavings and one tank of 1 m 3 with caustic magnesia powder and wood shavings separated by several oxidation cascades and decantation ponds the system treated about 1 5 m 3 day of amd containing an average of 360 mg l fe 120 mg l al 390 mg l zn 10 mg l cu 300 g l as and 140 g l pb a mean ph of 3 08 and a net acidity of 2500 mg l as caco 3 equivalent the water reached ph 5 and 6 in the first and second limestone tanks respectively suitable to remove trivalent metals and ph 8 9 in the mgo tank suitable to remove divalent metals after 9 months of operation the system achieved an average removal of 100 al cu as pb more than 70 fe about 25 zn and 80 acidity goethite schwertmannite hydrobasaluminite amorphous al oh 3 and gypsum were the main precipitates in the two limestone tanks precipitation of divalent metals fe ii zn and traces of cd ni and co were complete inside the third tank of mgo but preferential flow along the walls was responsible for its low treatment performance goethite gypsum zn schulenbergite and sauconite are the crystalline solid phases identified in the mgo tank

the natural attenuation of two acidic effluents in tharsis and la zarza perrunal mines iberian pyrite belt huelva spain the geochemical evolution of two acid mine effluents in tharsis and la zarza perrunal mines iberian pyrite belt huelva spain has been investigated in origin these waters present a low ph 2 2 and 3 1 and high concentrations of dissolved sulphate and metals fe al mn cu zn as cd co cr ni however the natural evolution of these acidic waters which includes the bacterial oxidation of fe ii and the subsequent precipitation of fe iii minerals represents an efficient mechanism of attenuation this self mitigating process is evidenced by the formation of schwertmannite which retains most of the iron load and by sorption toxic trace elements like as the later mixing with pristine waters rises the ph and favours the total precipitation of fe iii at ph 3 5 and subsequently al compounds at ph 4 5 along with the sorption of trace metals mn zn cu cd co ni until chemical equilibrium at circumneutral conditions is achieved

hillslope and channel evolution in a marine terraced landscape santa cruz california a flight of marine terraces along the central california coastline provides a unique setting for the study of topographic evolution wavecut platforms mantled by 2 6 m of marine terrace cover deposits are separated by 10 50 m tall decaying sea cliffs paleocliff edges become more rounded with age yet the details of the profiles and frequent bedrock exposure on the upper slopes imply weathering limited transport five bedrock stream channels etched through the marine terrace sequence display one to three distinct convexities in their longitudinal profiles detailed hand level surveys of the hillslopes and of the stream channel longitudinal profiles constrain hillslope evolution and channel incision components of a numerical model of landscape evolution we account for regolith production as a function of regolith depth in accord with the field observation that hillslope processes are presently dominated by the activities of burrowing rodents the transport process is taken to be diffusive stream incision is assumed to be controlled by stream power for which we use the surrogate of local drainage area slope product best fits of the numerical model to field data imply hillslope diffusivity is 10 m2 kyr 1 regolith production rate on bare bedrock is 0 3 m kyr 1 and falls off rapidly with regolith cover and the constant controlling the efficiency of stream incision is 5 to 7 10 7m 1 kyr1

hydrochemical performance and mineralogical evolution of a dispersed alkaline substrate das remediating the highly polluted acid mine drainage in the full scale passive treatment of mina esperanza sw spain acid mine drainage remediation is an unresolved matter in abandoned mining districts around the world development and implementation of passive treatment systems in these areas are commonly focused on engineering and water quality aspects neoformed mineral phases precipitated within the reactive material of these passive treatments account for the removal of pollutants but also can cause clogging and passivation of the reactive substrate after 20 months of operation and monitoring the limestone based passive treatment system implemented in mina esperanza sw spain was sampled to study the relationship between water chemistry mineral composition of the neoformed precipitates and treatment performance water chemical profiles show the existence of three precipitation zones controlled by fe al and zn hydrochemistry and also a migration with time of precipitation zones downward into the reactive material these precipitation zones were also confirmed by a mineral study performed on the solid samples where either schwertmannite and goethite or hydrobasaluminite and zn rich green rust were the mineral phases that controlled the metal removal in the three precipation fe al or zn zones iron and al precipitates were observed to play a critical role in the time evolution of the reactive material hydraulic conductivity furthermore al precipitates passivated to some extent the limestone grains by armoring although migration of the fe precipitation zone and al redissolution later activated the limestone grains a higher proportion of limestone in the reactive mixture and the addition of new reagents to the bottom section of the reactive material to enhance the reducing environment and to promote divalent metal removal are proposed on the basis of this hydrochemical and mineralogical study for a future design for the mina esperanza passive treatment system

tectonic versus chemical weathering controls on the composition of fluvial sands in tropical environments the compositions of fluvial sands collected in mountainous regions along the volcanic front in central america and along the andean front in venezuela and colombia correlate with the tectonic setting of their source terrains the sands derived from the central american volcanic arc are compositionally distinct from those derived from the andean terrains and minor variations in tectonic style can also be discriminated subtle differences in tectonic setting and source rock composition are recognizable only when modification by chemical weathering is slight they are strongest in sands from low order streams draining mountainous areas with modest alluvial plain development sands that have been exposed to weathering for extended periods during alluvial storage are progressively enriched in chemically stable phases with increased weathering sands from continental terrains converge toward a supermature quartz arenite end member and the imprint left by source rock composition and tectonic setting is obscured in intraoceanic terrains a similar but much less pronounced enrichment in stable phases relative to less stable phases is observed similarly overprinting the tectonic signal although detailed tectonic information is easily lost sands derived from intraoceanic terrains are distinguishable from those derived from continental terrains even after long exposure to intense chemical weathering conditions

seasonal variations in the formation of al and si rich fe stromatolites in the highly polluted acid mine drainage of agua agria creek tharsis sw spain abstract the study of the different biotic and abiotic processes involved in the current formation of fe stromatolites in rivers affected by acid mine drainage amd is essential not only to understand this unique and extreme environment but also to achieve a better understanding of the past iron formation on the earth and on mars the fe stromatolites studied in the highly polluted amd in tharsis sw spain revealed a unique mineral assemblage with jarosite and rostite as the most unexpected fe and al phases and goethite and schwertmannite as the main constituents seasonal variations in this region greatly affected the composition of the precipitates and the distribution of diatoms within the fe stromatolites drought and flood events were also recognized in the sedimentary textures and in the mineral assemblages observed of particular layers within the fe stromatolites the characterization of the chemical and mineralogical composition of fe stromatolites in tharsis as well as the different formation mechanisms proposed complement the existing literature on newly formed fe stromatolites and provides new observations to increase our understanding of those extreme environments

evaluating hillslope diffusion and terrace riser degradation in new zealand and idaho 1 the relationship of sediment flux to surface slope is a predominant control on the evolution of transport limited hillslopes although both linear and nonlinear sediment flux models have been proposed and widely debated this functional relationship remains one of the outstanding questions in geomorphology we examine degradation of fluvial terrace risers in new zealand and idaho in order to test the linear diffusion model and to better understand the relationship between sediment flux and slope we implement three techniques based on the linear diffusion model as well as a geometric scaling method that uses proportional relationships in riser geometry rather than a specific transport equation model to assess rates of degradation we show that techniques that utilize the riser midpoint slope as the primary metric of degradation as opposed to the full scarp profile offer the simplest and most reliable assessment of riser degradation our findings suggest that the linear diffusion model does not accurately describe terrace riser degradation except for low angle risers for which linear and nonlinear forms are indistinguishable results from the geometric scaling method show that degradation rates in both regions differ by a factor of two between equator and pole facing risers and that diffusion ages of idaho risers are approximately 2 times those of new zealand risers similar geometric trends in riser evolution from both regions reveal that terrace riser degradation is governed by a widely applicable relationship between sediment flux and slope

palaeoclimatic interpretation of a topographic profile across middle holocene regressive shorelines of longmu co western tibet most lakes and closed basins in tibet are surrounded by abandoned shorelines attesting for high water levels in the past two such lakes longmu co and sumxi co western tibet were the focus of detailed palaeoclimatic work during the 1989 sino french expedition based on the study of lake sediments and analysis of a piston core here it is shown that additional information may be deduced from the abandoned shorelines around longmu co a 1800 m long topographic profile was levelled from 75 m up to 230 m above the present lake elevation 5008 m on which the shorelines form a flight of horizontal terraces separated by more or less degraded scarps the elevations of the terraces were spaced regularly about 1 35 m except for 3 5 m high lacunae reccurring every 15 16 m the potential annual evapo transpiration was computed based on meteorological data collected at tien shui hai from 13 08 89 to 11 09 90 using a modified penman formula a value of 1 60 0 3 m yr was obtained under close system conditions no outlet and a synthetic curve of lake regression was derived which appears to be consistent with the measured shoreline heights it is concluded that the 1 35 m terraces represent annual regression of the lake level by contrast the 3 5 m high lacunae might reflect the periodic return about every 9 12 yr of particular climatic conditions responsible for a perturbation of the annual process of shoreline formation all the shorelines of this profile have formed probably within one century during a continuous and abrupt regression of the lake such evolution has also been identified in the sediments of a piston core collected at sumxi co and dated at about 6 5 5 kyr b p the lake level must have been at its highest stand shortly before that major regression the mechanism responsible for this middle holocene high stand and for the major sudden drop of the lake level remains uncertain

coupling effect of fe3 aq and biological nano sized fes coated limestone on the removal of redox sensitive contaminants as sb and cr implications for in situ passive treatment of acid mine drainage nano sized fes particles have been shown to improve the adsorption performance in permeable reactive barrier prb technologies that are used to treat acid mine drainage to investigate the coupling effect of fe3 and biological nano sized fes on removal of redox sensitive contaminants and the permeability of a limestone system fe reducing bacteria frb and sulfate reducing bacteria srb were used to form nano sized fes coatings on limestone grains for initial acidic solutions containing 0 5 mg l as v cr vi and sb v retardation factors increase from 26 5 and 7 respectively in a limestone only pristine system to 367 89 and 9 respectively in an fes coated limestone system and to 345 367 and 308 respectively in an fes fe3 aq system the permeability coefficient of the fes coated limestone system is better than that of the pristine limestone system but declines to two thirds of the pristine limestone system in the presence of fe3 aq possibly due to the formation of secondary ferric hydroxides xps analysis suggests that the fes particles are effective at reducing as v sb v and cr vi and removing them from solution these results demonstrate that fes particles improve retention of redox sensitive contaminants with and without fe3 aq these new findings give new insights on the coupling effect of redox systems used in prbs

late quaternary slip rates along the sierra nevada frontal fault zone california slip partitioning across the western margin of the eastern california shear zone basin and range province new geologic mapping tectonic geomorphologic and cosmogenic radionuclide geochronologic data provide the fi rst numerical constraints on late quaternary vertical slip and horizontal extension rates across the southern sierra nevada frontal fault zone california this fault zone exposes numerous nnw striking east facing normal fault scarps that offset seven distinct quaternary alluvial surfaces and a rockslide deposit beryllium 10 cosmogenic radionuclide surface exposure dating of these surfaces provides surface abandonment model ages of 123 7 16 6 ka 60 9 6 6 ka 25 8 7 5 ka 4 4 1 1 ka and 4 1 1 0 ka on alluvial fan surfaces and 18 7 3 9 ka on the rockslide deposit these age constraints combined with measurements of vertical surface offset across fault scarps yield preferred late pleistocene to holocene vertical and horizontal extensional slip rates of 0 2 0 3 mm yr and 0 1 0 2 mm yr vertical slip rate estimates in this study are comparable to late pleistocene vertical slip rate estimates across other prominent range front normal faults within the basin and range province these geologic and geochronologic results indicate that the eastern escarpment of the southern sierra nevada has remained tectonically active throughout the late quaternary combining our data with slip data from the owens valley and lone pine faults implies that slip along the eastern escarpment of the sierra nevada block is partitioned into three components dominantly dextral slip along the owens valley fault intermediate oblique slip along the lone pine fault and subordinate normal slip along the sierra nevada frontal fault zone these observations are consistent with global positioning system gps data which indicate that dextral shear strain accumulation dominates today along the western boundary of the eastern california shear zone and basin and range province

modelling the joint variability of grain size and chemical composition in sediments abstract the geochemical composition of siliciclastic sediments correlates strongly with grain size hence geochemical composition may serve as a grain size proxy in the absence of grain size variations geochemical data of siliciclastic sediments may be used to characterise size independent processes i e sediment provenance weathering mixing shape density sorting and diagenesis in general however geochemical data sets contain both types of information in order to formalise interpretation of geochemical data we propose a mathematical method to decompose the total geochemical variability of a series of genetically related specimens into a grain size dependent the shared signal and a grain size independent part the residual signal the former may serve as a proxy for grain size whereas the latter represents geochemical variability that would have been observed if all sediments would have had the same grain size distribution the two data sets are jointly decomposed by means of partial least squares pls and orthogonal projection subsequently the presence of significant grain size independent geochemical variability in the residual signal is determined in a statistically rigorous manner using a 2 test using a synthetic example we show that the residual record effectively reveals an imposed provenance signal which could not have been resolved from the geochemical or grain size data sets individually we analysed the relation between grain size and geochemical composition in three quaternary marine sediment cores located offshore west africa and south america geob7920 2 geob9508 5 and geob7139 2 both sites are characterised by biogenic sediment input in addition to fluvial and aeolian sediment input from the continent it was found that all cores show a strong but different correlation between the mean grain size and the bulk geochemical composition these results demonstrate that geochemical grain size proxies are empirical and site specific it was also found that the geochemical and grain size data in cores geob7920 2 and geob7139 2 do not contain unique information whereas in core geob9508 5 ti varies independently from the grain size this residual ti signal correlates with the transport mechanism as demonstrated by statistically different values of aeolian and fluvial dominated sediments however a unique interpretation of this residual signal in terms of the postulated grain size independent mechanisms could not be provided without additional information we conclude that the proposed model facilitates identification and validation of different element ratios as grain size proxies and more importantly as proxies for size independent processes for this reason the model paves the way for rigorous analysis of multi proxy data which are widely used in palaeoceanographic and palaeoclimatic research

constructing sandstone provenance and classification ternary diagrams using an electronic spreadsheet abstract we present and describe a microsoft excel based method of plotting sandstone provenance and classification related ternary diagrams although commercial software is available for plotting ternary diagrams none of these programs are especially designed to generate plots with specific provenance fields or classification schemes currently many sedimentologists use electronic spreadsheets for storing point count data and software for generating ternary diagrams and finally use separate image drafting software to generate publication quality figures the technique demonstrated in this paper does all in a single step requiring only widely available programs such as microsoft excel this spreadsheet will allow users to generate diagrams suitable for various other provenance related plots as well as develop new ideas for various geochemical ternary plots

the role of mineralogy on element mobility in two sulfide mine tailings from the iberian pyrite belt sw spain abstract a detailed study of two adjacent mine tailings impoundments comparing mineralogical and geochemical analyses of the solids with geochemical analysis of the pore water and gas was carried out in the monte romero sulfide mining district iberian pyrite belt sw spain since 1978 both facilities have been exposed to weathering in a semi arid climate with dry warm and wet rainy seasons in these impoundments sulfide oxidation releases sulfate and contaminants to the pore water that are transported and concentrated by evaporation in the top surface of the tailings causing precipitation of soluble iron sulfate salts in dry seasons these salts act as temporary sinks for minor elements such as cd co zn ni cu and mn which are again released during rainfall events in wet seasons stored flotation tailings have an average pyrite content of 30 wt although average amounts up to 80 are present in the upper 50 cm of one of the impoundments according to the results of the current study this difference is key to control the oxidation model in both tailings in the impoundment containing 30 wt of pyrite pore water ph increases in wet periods to 3 1 average by rainwater dilution causing supersaturation and precipitation of secondary fe iii phases such as jarosite goethite and schwertmannite consequently this impoundment shows a 20 25 cm thick yellowish oxidation layer in the top part in contrast in the impoundment containing 80 wt of pyrite in the top part extremely acidic pore waters ph

lake bonneville constraints on lithospheric thickness and upper mantle viscosity from isostatic warping of bonneville provo and gilbert stage shorelines the deformed shorelines of the late pleistocene lake bonneville provide an excellent opportunity to analyze the response of the earth to surface loads of relatively short wavelengths 400 km and short duration 30 kyr recently revised estimates of the lake loading history and an expanded compilation of shoreline elevations for the bonneville 1550 m provo 1440 m and gilbert 1300 m shorelines have prompted us to reexamine the deflection the earth model we use is identical with that employed by nakiboglu and lambeck and consists of an elastic plate overlying a maxwell viscoelastic channel and a rigid base our calculation differs from that of nakiboglu and lambeck in two respects we used a significantly more detailed load model and we compared our results with observations from three distinct shorelines the lake elevation history spans 32 kyr in 18 piecewise linear segments the water load is computed at each time step from a digital terrain model 4 4 km cell size and a specified lake elevation we find that the use of three separate shorelines significantly reduces the acceptable region of parameter space the effective elastic lithospheric thickness is 23 2 km the mantle viscosity is 1 2 0 2 1020 pa s and the depth to a significant viscosity increase is no less than 300 km though it might be much more examination of the residual deflections differences between observed and computed shoreline elevations reveals a regional tilt down to the ne of 6 10 5 which we attribute to collapse of the peripheral bulge produced by the laurentide ice sheet

metal retention mineralogy and design considerations of a mature permeable reactive barrier prb for acidic mine water drainage in northumberland u k mineralogical characterization of the precipitates developed in passive systems treating mine polluted waters is an essential tool to fully understand and control the removal processes taking place in these systems in 2008 after five years of operation a section of the permeable reactive barrier prb at shilbottle northumberland was subjected to a low intrusive non destructive solid sampling these solid samples were mineralogically characterized by xrd esem eds and sequential extractions in addition to the solid sampling 44 water samples obtained in the prb from january 2004 to august 2009 were used to study the mineral stability of some selected phases in these waters it was observed that the main iron phases in the prb were those associated with mineral phases typically developed in non reducing environments schwertmannite and goethite while the presence of a significant amount of pyrite was also observed the low residence time of the water within the prb from 10 to 40 h appears to be the reason for the absence of a more reducing and less acidic environment in the reactive substrate an increase of residence time in the prb by increasing reactive mixture porosity and resizing the prb changes in the reactive material employed smaller limestone grain size and inclusion of zerovalent iron and changes in the prb design isolating top layer and forced homogeneous flow upward through all the reactive material are proposed for future reconditioning of the system

paleoseismic results from the alpine site wasatch fault zone timing and displacement data for six holocene earthquakes at the salt lake city provo segment boundary

alluvial fan sedimentation of the cutler formation permo pennsylvanian near gateway colorado the permo pennsylvanian cutler formation near gateway colorado is the most complete 1 334 m proximal section of alluvial fan sediments deposited along the western flank of the ancestral uncompahgre uplift cutler facies can be correlated with depositional processes observed on modern dry alluvial fans proximal cutler facies include matrix supported bouldery debris flow and channel form streamflood conglomerates midfan sedimentation in the cutler is represented by trough cross bedded granular braided stream sandstones laterally continuous streamflood conglomerates and sheetflood deposits laterally continuous streamflood conglomerate was deposited at the mouth of large channels near the intersection point and consists of a cross bed set as much as 2 m thick with a basal boulder cobble lag rippled and laminated siltstone with gravel channels represents distal sheetflood sedimentation pedogenic features include rhizocretions and calcareous nodules vertical changes in facies and maximum clast size delineate three megasequences on the scale of hundreds of metres thick each mega sequence is composed of a coarsening upward sequence of proximal facies overlain by a fining upward sequence of more distal facies coarsening upward sequences record periods of tectonic uplift and fan progradation whereas fining upward sequences result from tectonic quiescence and weathering back of the mountain front small scale cycles on the scale of ten metres occur within the larger megasequences and represent changes inherent to the alluvial fan system autocyclic sedimentologic data on cutler alluvial fan sediments at gateway support previous interpretations of semiarid or arid paleoclimate during permian time along the western flank of uncompahgria and may act as a standard of comparison for tests of the role of tectonism on sedimentation trends in the paradox basin

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

high resolution spatial rupture pattern of a multiphase flower structure rex hills nevada new insights on scarp evolution in complex topography based on 3 d laser scanning fault scarps represent the most obvious expression of tectonic activity at the earth9s surface studies on scarp morphology place constraints on fault kinematics and scarp degradation processes and were often based on geomorphic dating techniques fault scarps exposed in areas of simple topography facilitate data acquisition and interpretation whereas little work had been done where fault scarps are superimposed on complex dissected topography fault scarps developed in complex topography are commonly observed along flower structures and at tips of strike slip faults such structures are important elements for evaluating the evolution and linking of strike slip fault systems and appear to be scale independent from several meters to hundreds of kilometers we examined the detailed meter to hundred meter scale structure and surface expression of a flank of one fault scarp bounded pressure ridge rex hills flower structure by combining field mapping with high resolution digital elevation model dem analysis based on terrestrial laser scanning we generated a detailed dem and extracted high resolution topographic cross sections which enabled us to identify fault scarps and to determine their relative ages and geometry our study site is located on the transpressional left bend between the pahrump and amargosa segments of the dextral stateline fault system the topography is characterized by alternating valleys and ridges each 100 m long relief of 4 m we observed the following the southern rex hills slope exhibits three fault scarps related to three reverse fault branches the basal scarp scarp 1 is most continuous and exhibits five segments the upper two scarps scarps 2 and 3 are less continuous furthermore fault scarps exposed on ridge crests are more numerous up to four to five scarps and smaller 5 m high valleys often exhibit single large 10 m high smoothed scarps to easily detect differences between the scarps we evaluated the height and slope angle of the scarps using topographic cross sections our analysis indicates that scarp shape is influenced by fault dip lithology and degradation processes resulting in large scatter and broad overlap in scarp height slope angle space the analysis further indicates that scarp degradation is stronger in the valleys and that the preservation potential of small individual fault scarps is therefore greater on the ridge crests we compared our fault scarp data with published calibrated data yielding an age of 2 ka for the rex hills scarps consistent with an earlier finding this suggests that the scarp shape mainly reflects progressive degradation since the most recent surface rupture our approach of analyzing high resolution topographic data of closely spaced fault scarps is promising especially when combined with subsurface data as well as geochronological and paleoseismic data and it provides a basic scheme for analyzing scarp populations in a complex topographic region despite the absence of subsurface data our approach allowed the study of complex high resolution fault scarp morphologies across a flower structure for the first time

escarpment evolution on high elevation rifted margins insights derived from a surface processes model that combines diffusion advection and reaction experiments with a surface processes model of large scale 1 1000 km long term 1 100 m y erosional denudation are used to establish the controls on the evolution of a model escarpment that is related to the rifting of a continent the model describes changes in topographic form as a result of simultaneous short and long range mass transport representing hillslope diffusive processes and fluvial transport advection respectively fluvial entrainment is modeled as a first order kinetic reaction which reflects the credibility of the substrate and therefore the fluvial system is not necessarily carrying at capacity one dimensional and planform models demonstrate that the principal controls on the evolution of an initially steep model escarpment are 1 antecedent topography drainage 2 the timescale or equivalently a length scale in the fluvial entrainment reaction 3 the flexural response of the lithosphere to denudation and 4 the relative efficiencies of the short and long range transport processes when rainfall and substrate lithology are uniform a significant amount of discharge draining over the escarpment top causes it to degrade only when the top of the model escarpment coincides with a drainage divide can escarpment retreat occur for these conditions an additional requirement for retreat of a model escarpment without decline is a long reaction time scale for fluvial entrainment this corresponds to a substrate that is hard to detach by fluvial erosion and therefore to fluvial erosion that is not transport limited continuous backtilting of an escarpment due to flexural isostatic uplift in response to denudational unloading helps maintain the scarp top as a divide it is essential if the escarpment gradient is to be preserved during retreat in a uniform lithology low flexural rigidities promote steep and slowly retreating escarpments for given rainfall and substrate conditions the morphology of a retreating model escarpment is determined by the ratio of the short range diffusive and long range advective transport efficiencies a low ratio which is interpreted to correspond to a relatively arid climate and weathering limited conditions promotes steep sharp topped escarpments with straight main slopes and escarpment retreat occurs over a wide range of height scales a high ratio interpreted to correspond to a more humid temperate climate produces a convex upper slope and concave lower slope morphology and only major escarpments are predicted to preserve a high scarp gradient lithological contrasts in the model produce more complex morphologies and predict the formation of scarps crowned by an erosionally resistant caprock however resistant caprocks are not an essential requirement for model scarps to retreat we conclude that the inferred controls and model behavior are both consistent with the present day morphology of rifted continental margins and with modern conceptual models of landscape evolution

paleoseismology and neotectonics of the shivwits section of the hurricane fault northwestern arizona the shivwits section of the hurricane fault in northwestern arizona has been largely ignored in evaluating the seismic hazard posed to the rapidly growing populations of southwestern utah to assess this hazard we conducted studies along the shivwits section using field observations and geomorphic modeling to understand the quaternary tectonism of this portion of the hurricane fault we have found evidence that it ruptured with up to 2 to 3 m of vertical displacement per event and likely produced m 7 earthquakes our results suggest that the slip rate along the southern hurricane fault has not decreased during the quaternary the moriah knoll basalt offset 150 to 200 m along the hurricane fault yielded a maximum long term slip rate of 0 15 to 0 25 mm yr estimated using a new 40ar 39ar age of 0 85 0 06 ma the late quaternary slip rates on alluvial fan surfaces offset 2 to 7 4 m were estimated using pedogenic carbonate rind thickness as a calibrated proxy for age these observations yielded slip rates of 0 05 to 0 3 mm yr paleoseismic trench investigations showed that two surface rupturing events occurred in the past 15 78 k y a radiocarbon sample from a most recent event mre fissure yielded a calibrated age of 8900 10 400 years b p the penultimate event was likely 10 k y before the most recent event slip rate estimates using the moriah knoll basalt 0 15 0 24 mm yr 850 ka surface offset 0 05 0 3 mm yr 100 ka morphologic modeling 0 06 0 21 mm yr 100 ka and observations from the trench 0 06 0 34 mm yr 15 75 ka suggest that there has been no detectable change in slip rate in the past 1 million years or so this implies a constant deformation rate for this portion of the colorado plateau margin therefore basin and range extension is actively encroaching manuscript received 24 november 2003

coastal slope terracing and relative sea level changes deductions based on computer simulations although a traditional geological survey of terraced coastal slopes is an essential part of studies aimed to reconstruct relative sea level changes the stratigraphic and chronological data so obtained frequently prove inadequate to completely unravel the sometimes very complex history of sea level fluctuation especially where erosion has prevailed over deposition and or deposits are difficult to date on the basis of our experience we think that much additional information can be gained through geomorphological interpretation of the profiles of those slopes in order to facilitate such interpretation a computer simulation model is developed that is able to predict the morphogenic response to a variety of possible relative sea level histories the results can be used to envisage some new interpretation keys for the analysis of real situations and hopefully as bases for the conception of general models of coastal slope evolution under the action of a variable sea level though preliminary the results so far obtained permit identification of the geomorphological consequences in terms of resulting slope profile of ordered successions of transgressions and regressions of different amplitude rate order and style moreover they provide interesting insights into the role that different styles of tectonic uplift may play in the phenomenon of multiple terracing of coastal slopes

andean growth and monsoon winds drive landscape evolution at sw margin of south america abstract in the atacama desert the driest place on earth located at the subduction margin of the andes the landscape evolves very slowly and changes in tectonic or erosion processes remain for a long time in the memory of topography at latitude 19 30 s a threshold between exoreic and endoreic drainage regimes is clearly associated with the latitudinal gradient imposed by the modern monsoon carrying humidity from the atlantic and disposed obliquely over catchments draining the andes to the pacific we summarize the geomorphic geological and climatic data in the threshold area we then use these data to constrain numerical experiments of drainage evolution data and experimental results are consistent with the development of a flat low energy morphology close to sea level interrupted at 10 ma by tectonic uplift prevailing to the present suggesting trench ward relief growth by incorporation of the coastal atacama region to the andes mountain belt