geometric and kinematic models for detachment folds with fixed and variable detachment depths abstract detachment folds are defined by competent rock units and are cored by incompetent units deformed internally above a detachment horizon we have developed two geometric models to constrain possible geometries and kinematic paths for ideal detachment folds the models each independently relate fold geometry to shortening and to detachment depth model assumptions include plane strain constant competent bedlength constant cross sectional area chevron fold geometry and no bed parallel shear outside the fold detachment depth is constant in one model but may vary in the other thus allowing evaluation of the implications for fold geometry and kinematics of fixed vs variable detachment depth detachment folds formed above a detachment unit of constant thickness constant detachment depth must be initially symmetrical and cannot grow with fixed hinges fixed arc length or a self similar geometry detachment folds formed above a detachment unit of variable thickness variable detachment depth must also be initially symmetrical but any one fold geometry can have a range of possible initial and final detachment depths kinematic paths for folds with fixed hinges fixed arc lengths migrating hinges variable arc lengths and selfsimilar geometries are all possible if detachment depth varies the change in detachment depth during deformation can be determined using the variable detachment depth model if either initial or final detachment depth is known the models demonstrate a wider range of variability in the geometry and kinematics of ideal detachment folds particularly for the variable depth model than is the case for ideal fault bend and fault propagation folds this variability limits the usefulness of simple geometric models for reconstructing the geometry of natural detachment folds balancing cross sections over a sufficient area and evaluating strain may compensate for these limitations

chemical weathering indices applied to weathering profiles developed on heterogeneous felsic metamorphic parent rocks abstract chemical weathering indices are commonly used for characterizing weathering profiles by incorporating bulk major element oxide chemistry into a single metric for each sample generally on homogeneous parent rocks weathering indices change systematically with depth however the weathering of heterogeneous metamorphic rocks confounds the relationship between weathering index and depth in this paper we evaluate previously defined chemical weathering indices for their suitability in characterizing weathering profiles developed on felsic heterogeneous metasedimentary bedrock from coweeta hydrologic laboratory north carolina usa among the weathering indices evaluated here the weathering index of parker wip is the most appropriate for application to weathering profiles on heterogeneous and homogeneous parent rock because the wip includes only the highly mobile alkali and alkaline earth elements in its formulation it yields values that differ greatly from those of the parent rock in addition the wip allows for aluminum mobility unlike other weathering indices these characteristics combine to make the weathering index of parker the most applicable index for studying the weathering of heterogeneous metasedimentary rocks however the wip should be applied judiciously as alkali and alkaline earth metals may be readily depleted during weathering in addition to reflecting weathering the chemical index of alteration cia chemical index of weathering ciw plagioclase index of alteration pia and vogt s residual index v may be sensitive to subtle geochemical changes such as hydrothermal alteration along a fault and or alteration at the water table weathering indices that include iron in their calculations were not included in this study because they do not distinguish between ferric and ferrous iron the oxidation state and distribution of iron in a weathering profile is influenced by the proportion of oxidation states in the pre weathered metamorphic rock and interaction with groundwater during weathering

a weathering intensity index for the australian continent using airborne gamma ray spectrometry and digital terrain analysis abstract weathering intensity largely controls the degree to which primary minerals are altered to secondary components including clay minerals and oxides as weathering intensity increases there are changes in the hydrological geochemical and geophysical characteristics of the regolith thus once calibrated weathering intensity can be used to predict a range of regolith properties a weathering intensity index wii over the australian continent has been developed at a 100 m resolution using regression models based on airborne gamma ray spectrometry imagery and the shuttle radar topography mission srtm elevation data airborne gamma ray spectrometry measures the concentration of three radioelements potassium k thorium th and uranium u at the earth s surface the total gamma ray flux dose is also calculated based on the weighted additions of the three radioelements regolith accounts for over 85 of the australian land area and has a major influence in determining the composition of surface materials and in controlling hydrological and geomorphological processes the weathering intensity prediction is based on the integration of two regression models the first uses relief over landscapes with low gamma ray emissions and the second incorporates radioelement distributions and relief the application of a stepwise forward multiple regression for the second model generated a weathering intensity index equation of wii 6 751 0 851 k 1 319 relief 2 682 th k 2 590 dose the wii has been developed for erosional landscapes but also has the potential to inform on deposition processes and materials the wii correlates well with site based geochemical indices and existing regolith mapping interpretation of the wii from regional to local scales and its application in providing more reliable and spatially explicit information on regolith properties are described

predicting regolith thickness in the complex weathering setting of the central mt lofty ranges south australia abstract we describe a model to predict regolith thickness in a 128 000 ha study area in the central mt lofty ranges in south australia the term regolith encompasses soil a and b horizons and highly weathered bedrock c horizon the thickness of the regolith has a major control on water holding capacity for plant growth and movement of water through the landscape and as such is important in hydropedological modelling and in evaluating land suitability e g for forestry and agriculture thickness estimates also have direct application in mineral exploration and seismic risk assessment geology and landscape evolution within the study area is complex reflecting the variable nature of bedrock materials and the partial preservation of deeply weathered profiles as a consequence of weathering processes dating to the cenozoic or possibly older these characteristics together with strong climatic gradients make the study area an ideal location to understand environmental and landscape evolution controls on weathering depth the area also features weathered landscape analogues to many parts of southern australia we use a digital soil mapping rules based approach to develop a model to predict regolith thickness this model uses statistically based relationships established between 714 regolith thickness measurements and 29 geographic environmental covariates including geology geochemistry terrain and climate themes and with a ground resolution of 10 m accuracy testing based on a 75 25 training test data split on the resulting map established a correlation r 2 of 0 64 this result is encouraging and is a significant advance over regolith depth mapping by traditionally based regolith landscape mapping methods finally it leads the way towards a nationally consistent regolith thickness map for landscape scale environmental simulation modelling and decision support

geometric analysis of fold development in overthrust terranes abstract fault bend folding fault propagation folding and detachment or decollement folding are three distinct scenarios for fold thrust interaction in overthrust terranes simple kink hinge models are used to determine the geometric associations implicit in each scenario bedding maintains constant thickness in the models except in the forelimb of the fold the forelimb is allowed to thicken or thin without limit the models address individual folds and the calculated fold geometries are balanced structures each mode of fold thrust interaction has a distinct set of geometric relationships final fold geometry is adequate in itself to discern many fault bend folds this is not the case for fault propagation and detachment folds these two fold forms have very similar geometric relationships some knowledge of the nature of the underlying thrust or decollement zone is usually needed to distinguish between them the geometry of a fold is altered in a predictable fashion by transport through an upper ramp hinge and by fault parallel shearing of the structure the shearing results in a tighter fold whereas transport through the ramp hinge produces a broader fold the viability of the geometric analysis technique is demonstrated through its application to a pair of detachment folds from the canadian cordillera the geometric analysis is also used to evaluate cross sections through subsurface structures in an example from the turner valley oil field the analysis indicates how the interpretation should be altered so as to balance the cross section the analysis reveals hidden assumptions and specific inconsistencies in structural interpretations

a rheological model for fractured rock we propose a rheological model for rock deforming in plane strain by slip on two sets of intersecting weak surfaces we assume that the normals to the surfaces lie within the deformation plane and that the surfaces are unbounded and experience noninterfering slip where slip rate is linearly proportional to resolved shear stress the rock behaves as an incompressible anisotropic fluid for the simplest case where the intrinsic slip behavior along the two sets is identical the principal axes of anisotropy are parallel and perpendicular to the bisectors of the intersurface angles for deformation rates parallel and perpendicular to these axes three behaviors may occur depending on the magnitude of the intersurface angle 2 if 0 2 45 or 135 2 180 the rock is weaker in shear than in shortening or extension if 45 2 135 it is stronger in shear than in shortening or extension finally if 2 45 or 135 the rock behaves isotropically as applications we use the derived constitutive relations to examine the response of a fractured layer to two commonly modeled types of folding forced folding above a vertical fault and buckling of a layer embedded in an isotropic medium undergoing shortening

understanding the utility of aerial gamma radiometrics for mapping soil properties through proximal gamma surveys abstract historical aerial gamma radiometrics have been proposed to be an important covariate for characterizing soil properties because it provides information about soil parent material pre existing aerial gamma radiometrics within the united states however can exhibit coarse spatial resolutions and therefore may be unhelpful for soil mapping studies therefore the objective of this work was to test the hypothesis that aerial gamma radiometrics can reliably map soil properties the hypothesis was tested using proximal radiometrics and soil sampling proximal or ground surveys were conducted within four different heterogeneous landscapes and 112 soil samples were collected and characterized for texture i e particle size fractions and or calcium carbonate equivalent proximal and soil relationships were assessed in terms of significance using pearson correlation coefficient testing and stepwise backwards linear regression proximal data were then weighted and averaged within the aerial sensor field of view and subsequently tested for significance with historical aerial data using pearson correlation tests proximal and aerial sensors were then compared in their ability to predict nearby measurements of clay and sand content relationships between texture and proximal gamma measurements were significant p

sedimentary and structural evolution of a pleistocene small scale push moraine in eastern poland new insight into paleoenvironmental conditions at the margin of an advancing ice lobe abstract recent studies of push moraines have focused on the interplay between the dynamics of ice margins and the environmental variables of the foreland into which they advance these studies showed that the spatial distribution geometry and style of the glaciotectonic deformation of push moraines are controlled by ice induced stresses the strain rate the rheology of the deposits and hydraulic conductivity in this work we provide new insight into this interplay at a small spatio temporal scale specifically the ancient glacial system of the liwiec ice lobe within the younger saalian ice sheet in eastern poland the paleoenvironmental variables that are analysed here refer to the dynamics of the hydrological processes that affected the patterns and sediment deposition rate on the terminoglacial fan and the resulting mechanical stratigraphy and hydraulic conductivity of the foreland we document the progradational sequence of the fan deposits that developed as a result of the ice lobe thickening and the steepening of its stationary front the sedimentary features of the fan the lithology of its basement and the hydraulic conductivity of the foreland strongly influenced the geometry and kinematics of fold growth during the advance of the ice lobe the predominance of flexural slip and the development of fractures including fold accommodation faults were interpreted to be an effect of buckle folding due to horizontal shortening induced by ice advance the partial overriding of the push moraine by the ice lobe and thus the submarginal conditions for deformation were inferred from the significant hinge migration and internal deformation of the strata under undrained conditions in one of the folds the synfolding deposition pattern of the fan growth strata allowed us to suggest that the push moraine was probably formed by a sustained advance rather than surge

a unified kinematic model for the evolution of detachment folds abstract detachment folds represent a major structural element in a number of fold belts they are common in the jura mountains the zagros fold belt the central appalachian fold belt the wyoming fold belt the brooks range the parry islands fold belt and parts of the subandean belt these structures form in stratigraphic packages with high competency contrasts among units the competent upper units exhibit parallel fold geometries whereas the weak lower unit displays disharmonic folding and significant penetrative deformation two distinct geometric types disharmonic detachment folds and lift off folds have been recognized however these structures commonly represent different stages in the progressive evolution of detachment folds the structures first form by symmetric or asymmetric folding with the fold wavelength controlled by the thickness of the dominant units volumetric constraints require sinking of units in the synclines and movement of the ductile unit from the synclines to the anticlines continuing deformation results in increasing fold amplitudes and tighter geometries resulting from both limb segment rotation and hinge migration initially limb rotation occurs primarily by flexural slip folding but in the late stages of deformation the rotation may involve significant internal deformation of units between locked hinges the folds eventually assume tight isoclinal geometries resembling lift off folds variations in the geometry of detachment fold geometry such as fold asymmetry significant faulting and fold associated with multiple detachments are related to variations in the mechanical stratigraphy and pre existing structure

fold generated imbricates examples from the caledonides of southern norway abstract the cambro silurian sequence of the oslo region contains fold trains and closely spaced imbricate thrust faults the imbricates could be interpreted as having ramped off the sole detachment and generated fault propagation folds several imbricate thrusts however appear to die out both downwards and upwards into folds this suggests that the thrusts were generated within the cambro silurian sequence and propagated down to the sole thrust rather than propagating upwards from the sole thrust the mechanical stratigraphy is apparently responsible for this style where during folding relatively brittle limestone members faulted in the highly strained fold forelimbs prior to through going faulting developing in the shales understanding the origin of such imbricates is important when choosing a method of section restoration

early mesozoic deformations of the eastern yanshan thrust belt northern china the yanshan thrust belt ytb is located at the northern edge of the north china plate because of the intense thicking and subsequent delamination of the lithosphere in north china geologists have been focused on the late mesozoic deformation in the yanshan belt the yanshan belt has been regarded as part of a stable craton from the proterozoic to the early mesozoic in this paper the authors present that the yanshan area was deformed during the early mesozoic this deformation could be related to ocean basin closure along the northern margin of north china or related to the collision between the north china and yangtze plates along the qinling dabie ultrahigh pressure belt three stages of early mesozoic deformation are identified in the eastern yanshan at lingyuan county the first stage is characterized by westward thrusting d1 the second stage comprises a top to east thrust system d2 and the third stage comprises extensional gravity induced collapse and landsliding d3 the timing of these evens is constrained by both the crosscutting relationships of faults and the isotopic dating of volcanic rocks and gravels the d1 and d2 events took place in the late triassic and early jurassic whereas d3 event occurred at the end of the middle jurassic the dengzhangzi formation was deposited during the d1 d2 period and recorded a rapid uplift erosion and deposition sequence these early mesozoic contractional deformations in the ytb were probably related to the closure of ancient asian ocean and ancient qinling ocean the later crustal extension was caused by gravitational collapse of the eastern china plateau during early mesozoic

above the weathering front contrasting approaches to the study and classification of weathered mantle abstract weathered mantle comprises the materials above bedrock and below the soil it can vary in thickness from millimeters to hundreds of meters depending primarily on climate and parent material study of the weathered mantle comes within the realms of four disciplines geology geomorphology soil science and civil engineering each of which uses a different approach to describe and classify the material the approaches of engineers geomorphologists and geologists are contrasted and compared using example papers from the published literature soil scientists rarely study the weathering profile as such and instead concentrate upon soil forming processes and spatial distribution primarily in the solum engineers including engineering geologists study the stability and durability of the weathered mantle and the strength of the materials using sophisticated procedures to classify weathered materials but their approach tends to be one dimensional furthermore they believe that the study of mineralogy and chemistry is not useful geomorphologists deal with weathering in terms of process how the weathered mantle is formed and with respect to landform evolution using a spatial approach geologists tend to ignore the weathered mantle because it is not bedrock or to study its mineralogy and or chemistry in the laboratory i recommend that the approaches of the various disciplines be integrated geomorphologists and geologists should consider using engineering weathering classifications and geologists should adopt a spatial perspective to weathering as should engineers and engineering geologists

numerical modeling of trishear fault propagation folding in contrast to kink band migration modeling methods trishear numerical models produce fault propagation folds with smooth profiles and rounded hinges modeled fold hinges tighten and converge downward within a triangular zone of distributed deformation which is focused on the fault tip such features have been reported from field studies and are also seen in analogue models of compressional deformation however apart from its initial application to laramide folds little quantitative work has been undertaken on trishear fault propagation folding in other settings in addition no study has been undertaken into the growth strata which might be associated with such structures this paper uses an equivalent velocity description of the geometric model of trishear together with models of erosion and sedimentation to investigate trishear fault propagation folding of both pregrowth and growth strata the trishear model is generalized to include a variety of fault propagation to slip ratios and fault propagation from a flat decollement the models show continuous rotation of the forelimb with the characteristic development of cumulative wedges within growth strata when total slip on a structure is high the model predicts overturned pregrowth and growth strata during the initial stages of deformation beds in the forelimb thicken but later thin when they become steep or overturned the effect of variations in fault propagation to slip ratios on two dimensional finite strain in the models is assessed by the use of initially circular strain markers high fault propagation to slip p s ratios lead to narrow zones of high finite strain while lower p s ratios lead to more ductile deformation and broader zones of high strain in all cases hanging wall anticlines and footwall synclines originate as early ductile folds which are later cut by the propagating fault modeled structures are compared with natural examples

hydrodynamics and equilibrium of a multiple inlet system although it is generally acknowledged that most multiple inlets are unstable and cannot coexist there is evidence to suggest that such inlets can indeed be stable over decadal time scales multiple inlet systems servicing a single embayment in contrast to single inlet systems confer particular hydrodynamic characteristics such as the potential existence of residual discharges and currents between the inlets this paper presents detailed measurements of hydrodynamic variables obtained over complete spring and neap tidal cycles in a multiple inlet system in southern portugal ria formosa the results indicate that the two main interconnected inlets servicing an embayment can coexist at least over a time scale of several decades however their coexistence cannot be explained simply using empirical equilibrium relations or inlet hydraulics although residual flow between the inlets appears to play an important role enhancing their stability it is the availability of sediment stored in the ebb tidal deltas and its capacity to be carried into the inlets during storm events that ultimately dictates the overall equilibrium independently of the flushing capability provided by the hydraulics such movement of sediment leads to the obstruction of the inlet channels thereby affecting the hydraulic efficiency and eventually leading to inlet closure in the long term the results augment existing knowledge concerning multiple inlet systems and improve understanding of their short to medium term stability

boolean and fuzzy methods for identifying lateritic regoliths in the brazilian amazon using gamma ray spectrometric and topographic data abstract airborne gamma ray spectrometry is relatively well understood when associated with rocks but the response and radioelement distribution in weathered materials is less known this work used airborne gamma ray spectrometry and altimetry to identify domains with higher probability of occurrence of lateritic crust and dismantling products in an area located in the west of the brazilian amazon map algebra was used through the boolean and fuzzy techniques to create predictability digital models highlighting favorable areas for the occurrence of lateritic crusts the index overlay method was used in the boolean technique the fuzzy technique used the fuzzy algebraic product operator fuzzy algebraic sum operator and fuzzy gamma operator both models showed good correlation between the favorability predicted and the presence of crusts in the field however the fuzzy model showed higher correlation and highlighted areas not identified by the boolean model in contrast the boolean model allowed the visualization of the areas related to the influence of each variable or its possible combinations individually on the final map thus the identification of lateritic crusts based on mathematic models applied to altimetric and airborne gamma ray spectrometric data is a new tool that will contribute significantly to geological mapping and to the understanding related to the response and radioelement distribution in weathered materials

backlimb trishear a kinematic model for curved folds developed over angular fault bends abstract numerous analog models and some natural examples display smoothly curving backlimb fold hinges over sharp angular bends in the underlying thrust surface we present a new kinematic model that can reproduce this geometry by defining a triangular zone focused on the fault bend the model presupposes incompressible flow in the triangular zone and makes common assumptions about velocities on either side of the fault bend either symmetric or asymmetric triangular zones can be defined with parallel kink folding and similar folding being special cases of the two respectively where the apical angle of the triangular zone is zero the results of the numerical model compare well to analog experiments the model is conceptually analogous to forelimb trishear at the tip of a propagating fault and hence we refer to it as backlimb trishear

mechanical models of trishear like folds previous workers have formulated velocity descriptions of the trishear kinematic model of fault propagation folds which are inherently non unique we present two complete mechanical models of fault related folding and assess the validity of the assumptions used in the assignment of velocities in the trishear description and to eliminate the untenable situation of an infinite number of possible solutions for velocity fields the mechanical model of forced folding forced fold based on viscous folding theory is used to derive the velocity fields in an anisotropic sedimentary cover overlying faulted and displaced rigid basement blocks the solution of displacements around a stress free fault in an elastic body is used to model fault arrest folds that form around a fault imbedded in a deformed medium the results indicate that the velocity fields assumed in the trishear model more closely resemble the velocities derived in the mechanical forced fold model than the mechanical model of fault arrest folding the forced fold model produces a triangular region of concentrated deformation similar to the trishear region assumed in the kinematic models while the deformation produced by the fault arrest model is not concentrated within a triangular zone

long term landscape evolution in australia the main features of the australian physical landscape are of the order of 107 108 years old this contradicts the widely held view that little of the earth s topography predates the quaternary and that erosion cycles are carried to planation within tens of millions of years much of the australian landscape must have developed over similar timescales to that of the tectonic evolution of the continent itself the study of the geomorphology of such ancient terrains may therefore be seriously deficient unless it is considered within the context of continental scale tectonic development application of this approach shows that there are strong links between the geomorphology of australia and plate movements ocean spreading plate convergence tectonostratigraphic terranes orogenesis and epeirogenesis the most important factor contributing to the survival of ancient landscapes in australia is the low rate of denudation which the continent has experienced during the mesozoic and cenozoic this is largely a consequence of orogenic stability although the absence of significant quaternary glaciation may also be of importance however in order for landforms to have survived over such timespans denudation must not only have been low but must also have been highly localized over space and time this has been the case both on a regional scale with long term denudation rates of 0 2 m ma 1 in central australia contrasting with higher rates along the continental margins and on a local scale with denudation confined to valleys leaving divides and interfluves almost unscathed

mathematical block motion model for deformation of a layer above a buried fault of arbitrary dip and sense of slip abstract an analytic series solution is obtained for the stress and deformation in an isotropic viscous or incompressible elastic layer subjected to rigid block motion at its base the block motion approximates slip on a pre existing basement fault of arbitrary dip and sense of slip deformation in the layer due to horizontally separating and horizontally converging blocks slip on a vertical basement fault and slip on 45 dipping reverse and normal basement faults is examined above horizontally diverging and converging blocks a symmetric syncline and anticline form respectively monoclines form above dipping basement faults the location of the monocline and to a lesser degree its form vary systematically with fault attitude and sense of slip for a given fault displacement the region of brittle failure in a basement normal fault model is larger than that in a reverse fault model new faults formed in the layer are arcuate in profile model results agree with observations of stress orientation and deformation from laboratory models

can multiple tidal inlets be stable abstract the gorge stability of inlets connecting the same bay to the ocean is analysed the basic premise is that when the tidal maximum of the bottom shear stress in an inlet is larger than the equilibrium shear the inlet is in a scouring mode and when smaller than the equilibrium shear stress the inlet is in a shoaling mode the tidal maximum of the bottom shear stress equals the equilibrium shear stress when the inlet is in equilibrium with the hydraulic environment an inlet is called stable when after a small change the cross sectional area returns to its equilibrium value using a linearized lumped parameter model for the flow in the inlets it is shown that for a two inlet bay system neither of the two inlets can be stable this implies that when assuming the inlets to be in equilibrium with the hydraulic environment a small change in the cross sectional area of one or both of the inlets will result in the closure of one or both of the inlets starting with the results for the two inlet bay system arguments are presented that suggest a similar conclusion holds for multiple inlets i e ultimately all inlets will close or at best one will remain open

gamma ray spectrometry and geological maps as tools for cadmium risk assessment in arable soils abstract farmers in some parts of sweden have problems achieving quality assurance certification for their products due to frequently excessive cadmium cd concentrations in wheat grain such problems are most frequent in areas where soils are affected by sedimentary rock containing alum shale in this study we used aerial and ground based gamma radiometry to assess cd risk in food production at regional and field scale in one such area a regional risk map for cd in arable soils in the south eastern tip of sweden was created using aerial gamma ray spectrometry measurements 238 u 232 th and 40 k combined with maps on bedrock geology and quaternary soil deposits the map had 5 hypothetical risk categories category 1 areas highest risk had 5 ppm 238 u category 2 had 3 5 ppm 238 u category 3 till on cambrian sandstone category 4 fluvial deposits downstream from risk categories 1 3 and category 5 other arable soils low risk the high uranium u levels were caused by inclusion of alum shale fragments which may also contain high amounts of cd the cambrian sandstone is a possible source of high soil cd concentrations but low in u since it in this area contains sphalerite zns which is high in cd directed sampling revealed very high cd concentrations in both soil and winter wheat grain in the higher risk categories the r 2 value for the positive correlation between cd and estimated 238 u in topsoil was 0 59 the risk categories based on soil properties were also useful in predicting cd concentration in wheat but there were no differences between categories 2 3 and 4 so for wheat three risk classes appeared more relevant the spatial variation in cd in the study area is considerable according to the risk classification and many farms include both high and low cd areas use of a ground based gamma ray sensor for detailed mapping of fields at two farms in high cd risk areas gave a fairly strong correlation between 238 u and soil cd r 2 0 68 when 232 th 238 u ratio was used instead the relationship was even stronger r 2 0 75 the th u ratio can remove some of the noise in gamma recordings and may be useful in depicting high u areas airborne gamma ray scanning also outlined the cd risk areas fairly well r 2 0 39 at the field level the results show that geological maps and gamma radiation mapping calibrated with a few analyses of cd concentrations in soils and crops can be used for risk classification of soils at the regional scale in this type of landscape using gamma ray data many areas that would have been overlooked when using geological maps alone were classified as high risk ground based gamma ray scanning could be useful for farmers to identify fields and parts of fields where special consideration is needed to reduce the risk of high cd in crops

fold accommodation faults fold accommodation faults are secondary faults that accommodate strain variations related to structural and stratigraphic position during fold evolution four main types of fold accommodation faults are commonly found out of syncline and into anticline thrusts form primarily because of an increase in bed curvature within fold cores although differential layer parallel strain at different scales also contributes to fault slip depending on the kinematic evolution of the major fold the thrusts may propagate along the steep or gentle limb of an asymmetric fold or along the hinge of symmetric folds wedge thrusts are primarily formed in competent units because of variations in penetrative layer parallel strain between adjacent units limb wedges occur as hanging wall and or footwall fault bend and fault tip folds whereas hinge wedges occur as multiple nested faults that tend to thicken the more competent units forelimb and backlimb thrusts form by a variety of mechanisms forelimb space accommodation thrusts are low displacement thrusts that resolve strain discontinuities resulting from increased curvature in fold cores forelimb shear thrusts form in the late stages of folding because of rotation and layer parallel extension on the steep forelimbs of folds most backlimb thrusts originate as out of syncline thrusts they may eventually link with forelimb thrusts to form forelimb backlimb thrusts back thrusts accommodate hanging wall strain during the formation of fault related folds they either form selectively in competent units or propagate through the section at the same rate as the main thrust although fold accommodation faults are secondary features they are important elements that define the geometry and size of structural traps in fold thrust structures accurate mapping of these structures is therefore critical in interpreting the structural geometry of fold and thrust belts shankar mitra holds the monnett chair and professorship of energy resources at the university of oklahoma he received his ph d in structural geology from johns hopkins university in 1977 he spent 19 years at arco research and exploration as senior and principal research geologist director of structural geology manager of geological research and senior exploration research advisor his primary research interests are in the development of structural concepts and methods and their application to exploration and production problems he is a recipient of aapg s wallace pratt and cam sproule awards

interactions between perched and saprolite aquifers on a small salt affected and deeply weathered hillslope a small hillslope was chosen to investigate the role of throughflow as a mechanism responsible for the movement of soil water and solutes towards a saline seep and as a source of recharge to a permanent regional aquifer at depth the hydraulic properties chemical characteristics and physical responses of both systems were studied on a deeply weathered salt affected hillslope additional data were also obtained from other sites in south western australia regional groundwater flow occurred in a variably textured deeply weathered material in which the hydraulic conductivity varied from 0 001 to 0 14m day 1 perched groundwater flow throughflow occurred in the higher permeability 1 5 m day 1 near surface soil materials throughflow occurred throughout winter contributing approximately 530 m3 of fresh 160 mg l 1 cl water to a saline seep by contrast the deep aquifer discharged approximately 1100 m3 of waters with salt concentrations of 2000 6000 mg l 1 cl recharge and discharge rates to and from the deep aquifer were estimated to be of the order of 5 20 mm a 1 and 50 300 mm a 1 respectively saturated conditions existed throughout winter within the seep and the immediately adjacent non saline area with up to 60 per cent of the hillslope soils becoming saturated after major rainfall events 20 mm day 1 in the mid slopes in particular along a central depression saturation of the shallow soils caused macropore channel recharge to take place through the clay textured subsoils water level responses suggest that approximately 25 30 per cent of annual recharge occurred from one storm studied in september 1984 recharge through macropore channels is a significant mechanism in the concave slope areas on the hillslope throughflow was found to be a major source of water but not salt contributing to the saline seep in general the contribution of throughflow was found to decrease further inland at other sites studied however at inland sites where perennial perched aquifers have developed in deep sands saline areas have been caused by throughflow and not by deep aquifer discharge

can γ radiometrics predict soil textural data and stoniness in different parent materials a comparison of two machine learning methods abstract the use of radiometrics for soil proximal sensing is strongly site specific because of the influence of parent material mineralogy on the rays emitted from the soil the work wants to propose a non linear and multivariate computational approach to predict soil textural data and surficial stoniness based on spectroscopy the spectroscopy survey was performed in heterogeneous soils in terms of parent material pedogenesis morphology coarse material and moisture content the radiometrics survey was performed by the mole sensor the netherlands and ray spectra were analysed by a full spectrum analysis 70 experimental points were described and classified according to parent material and surficial stoniness the 70 experimental sites were also sampled during the ray survey and analysed for soil texture and moisture content an explorative pca in the experimental points based on the ray data and the elevation showed 3 groups of cases relating to the three groups of bedrock i calcareous flysch ii feldspathic sandstone and iii other lithologies namely marly shales marine and fluvio lacustrine deposits two machine learning models were used to predict sand clay and surficial stoniness the models were support vector machines svm and artificial neural networks ann an independent validation set of 20 soil samples was used to check the accuracy of the prediction models both svm and ann showed good prediction accuracy for sand and clay although svm showed the lowest errors both models showed lower accuracy for stoniness prediction mainly due to high prediction errors in several sampling points probably the high errors in stoniness prediction were due the strong heterogeneity of rock types and mineralogy however prediction model of stoniness spatial variability is very important in order to an adequate farming management

a morphological behaviour model for the outer delta of mixed energy tidal inlets abstract the long term evolution of the seaward part of mixed energy tidal inlet systems is analysed and modelled mathematically in terms of aggregated morphological parameters the model is an adapted version of a two line model in which empirical information on the equilibrium state of the outer delta is included thus detailed computations of the water and sediment motion at the hydrodynamic time scale are avoided the viability of the concept is tested and the model is verified against data from one of the inlets of the western wadden sea the results of a number of practice based applications are shown and discussed

modelling the abundance of soil calcium carbonate across australia using geochemical survey data and environmental predictors abstract soil calcium carbonate is a key component of the regolith particularly in arid and semi arid regions it influences soil properties is an important terrestrial carbon store and is used in mineral exploration previous national overviews of soil carbonate distribution have been compiled from regional soil regolith or geological maps with varying degrees of confidence and consistency here we develop a decision tree approach based on a piecewise linear regression model to map soil calcium carbonate abundance at the continental scale the model is based on relationships established from 1311 field sites sampled across australia at two depths 0 10 and 60 80 cm and 49 national environmental predictor datasets reflecting fundamental soil formation processes e g climate parent material relief the resulting map of soil calcium carbonate distribution is based on the median results of twenty model runs generated by randomly selecting 90 training and 10 validation splits of the input data results present an average coefficient of determination r2 of 0 5 on the validation dataset the predictors used in the modelling are consistent with our understanding of the controls on the sources inputs formation and preservation of soil calcium carbonate across australian landscapes the model produces a continuous internally consistent quantitative prediction of soil calcium carbonate abundance in surficial regolith at a resolution of 90 m with associated uncertainty estimates this type of analysis provides a framework for better understanding environmental controls on regolith processes and has the potential to also be used to predict other soil geochemical properties furthermore the methodology has utility globally where geochemical survey data are available

geometry and kinematics of buried structures in the piedmont of the central longmen shan implication for the growth of the eastern tibetan plateau structural geometry and kinematics are important to understand the growth of the tibetan plateau margins in this study several high resolution seismic reflection profiles were combined with well data and the fault bend fold theory to determine the geometric and kinematic characteristics of the pengxian buried structures located in the piedmont of central longmen shan lms seismic interpretations indicate that the pengxian buried structures were involved in multi period superimposed deformation during the cenozoic the structural deformation of the frontal lms was controlled by a triassic detachment fault f2 which extended forward at a gentle angle and formed a fault bend fold during the late miocene the steep angle pengxian blind fault developed on the f2 with a few offsets during the pleistocene 3d imaging of the pengxian buried structures shows that the f2 horizontally propagated into the western sichuan basin with a fault slip of approximately 3 3 3 5 km the longquan shan lqs anticline has a total slip of approximately 3 0 km since its initiation our study suggests that the average slip rate of the f2 is

natural radionuclides in the soils of a small agricultural basin in the canadian prairies and their association with topography soil properties and erosion summary samples taken from the a and b horizons of the soil at 160 sites in a small 178 ha cultivated drainage basin in central saskatchewan were analysed by gamma spectroscopy to determine the concentration of a number of natural radionuclides in the soil the concentration of 40k the 238u daughters 226ra 214pb and 214bi and the 232th daughters228ac 212bi and 208tl was determined a variety of soil properties and topographic variables were measured at each sampling site earlier studies in the basin provided net soil erosion estimates i e net loss or gain for each site the association of isotope activities with topography soil properties and net erosion was evaluated mean isotope activities for the basin were very close to mean values reported earlier for native soils in southern saskatchewan differences in isotope concentrations between the a and b horizons of the soils were related to differences in the degree to which the different isotopes are taken up by plants isotope concentrations in the surface soil were inversely correlated with soil particle size variation in isotope activities within the basin appeared to be linked to soil redistribution by erosion but in a complex manner which reflects size sorting of soil particles by erosion processes erosion processes seem to be at least as important as leaching processes in determining the spatial distribution of natural radionuclides in the surface soils of the study area

cambrian river terraces and ridgetops in central australia oldest persisting landforms fluvial sediments in paleovaileys cut in the ashburton surface of the davenport province of central australia form terrace remnants that appear to retain their original depositional tops and have probably existed as subaerial landforms since their inception marine fossils in sediments conformable with the fluvial sediments near the southeast margin of the province give a cambrian age for the terraces the ashburton surface forming the ridgetops between the paleovalleys is cambrian or older

breaking ground pedological geological and ecological implications of soil bioturbation abstract soil and its biota are fundamental components of the critical zone earth s living skin that most directly sustains life within that zone geologically rapid soil and saprolite displacement by biota particularly invertebrate meso and macrofauna affects a large proportion of earth s soils this was first recognised by late 19th century observers on both sides of the atlantic ocean who regarded bioturbation as fundamental to soil formation throughout much of the 20th century however the agronomical focus of soil scientists and the dominant paradigm of landscape evolution relegated bioturbation as a result many aspects of bioturbation are still not widely appreciated only in the last few decades has a re evaluation commenced in a range of disciplines primary effects of bioturbation which we quantify herein include soil production from saprolite the formation of surface mounds soil burial and downslope transport rates of bioturbation can be as rapid as sustained maximum rates of tectonic uplift in concert with surface geomorphic processes bioturbation alters fundamental properties of soil including particle size distribution porosity the content of carbon and other nutrients and creep flux rate the precise influence of biotic mixing is regulated by its depth function earth s incredibly diverse soil biota also perform a number of functions at a range of spatial and temporal scales that extend beyond soil to landscape evolution ecosystem engineering niche construction and carbon cycling understanding these linkages which have operated since the evolution of trees in the devonian period is of growing importance as we seek a fuller picture of earth s history to predict and manage its future

contributions of gamma ray spectrometry to terrestrial impact crater studies the example of serra da cangalha northeastern brazil 1 several geophysical methods have been used for decades for the identification and exploration of impact craters most of them are based on seismic potential fields and electrical data focusing on exploration of anomalies caused by changes in physical properties or by structures associated with the formation of the crater gamma ray spectrometry is usually not mentioned among the geophysical methods employed in crater studies although it is known that impact cratering processes cause a number of physical chemical changes in the country rocks these changes include the remobilization of hydrothermal fluids which directly modify the composition of target rocks and subsidiarily of soils related to these rocks therefore the distribution of radioactive elementsk th and uhas the potential to map such modifications we present the analysis of gamma ray signatures at the serra da cangalha impact structure located in northeastern brazil using methods for enhancingkanomalies and also the overall gamma ray signatures these results provide valuable information on the distinct zones within the crater and might contribute to the understanding of hydrothermal enrichment processes produced as a result of the impact event

digital soil pattern recognition in the lower namoi valley using numerical clustering of gamma ray spectrometry data abstract digital soil mapping involves the use of ancillary data e g proximal and remotely sensed as surrogates for soil information to produce maps of soil type or classes two of the most popularly used sources of ancillary data are the proximally sensing electromagnetic em induction instruments and remotely sensed digital elevation model data dem however these data have limitations at the catchment level and are of limited use on predominantly flat alluvial landscapes respectively another option is the use of remotely sensed gamma ray ray spectrometry data which has successfully been used to map the regolith in this paper the use of ray spectrometry data i e potassium k uranium u thorium th and total count tc coupled with a numerical clustering algorithm i e fuzzy k means fkm algorithm is explored in order to identify geological and geomorphological units at the district and soil mapping units at a broader catchment level we do this by using the euclidean distance and the measures of fuzziness performance index fpi and normalized classification entropy nce to identify k 11 classes and a fuzziness exponent 2 0 for interpretation the k 11 classes produce contiguous classes which are consistent with geological and geomorphological interpretations of an eroded landscape alluvial lands and dust mantled alluvial lands at the district level at the sub catchment level the k 11 classes also match broad soil mapping units and also elucidate subtle differences of the alluvial lands which characterise the agriculturally significant parts of the lower namoi valley fuzzy canonical analysis shows that k and tc contribute most to the discrimination of the classes associated with the trachyte rich parts of the eroded landscape the alluvial lands and most of the dust mantled alluvial lands whilst u and th discriminate the basaltic outliers and other geomorphological units of the eroded lands we conclude that the approach allows soil management and landscape units to be identified with the information used as a first approximation to determine where soil sample locations need to be collected to validate the map units identified in order to better incorporate and characterise subsoil properties the inclusion of em signal data e g em38 or dualem 1 may also be appropriate

the 3d distribution of phyllosilicate clay minerals in western victoria abstract the mineralogy of the clay fraction of soils is a major determinant of the behavior of soil conventionally these clay minerals have been determined using techniques such as x ray diffraction xrd but new complementary methods such as infrared spectroscopy can be used to rapidly and economically predict these minerals this paper presents a methodology to predict these clay minerals at high resolution that adhere to globalsoilmap gsm standards mid infrared mir spectroscopic models were formulated for clay minerals kaolinite illite and smectite using partial least squares regression plsr and legacy quantitative xrd determinations very strong models were achieved for kaolinite illite and smectite and the root mean square error of cross validation rmsecv were all

effect of subseabed salt domes on tidal residual currents in the persian gulf geological studies in the persian gulf pg have revealed the existence of subseabed salt domes with suitable filtering of a high resolution pg seabed topography it is seen that the domes leave their signature in the seabed i e numerous hills and valleys with amplitudes of several tens of meters and radii from a few up to tens of kilometers it was suspected that the shark skin of the pg seabed may affect the tidal residual flow the interaction of tidal dynamics and these obstacles was investigated in a nonlinear hydrodynamic numerical tidal model of the pg the model was first used to characterize flow patterns of residual currents generated by a tidal wave passing over symmetric elongated and tilted obstacles thereafter it was applied to the entire pg the model was forced at its open boundary by the four dominant tidal constituents residing in the pg each tidal constituent was simulated separately results i e tidal residual currents in the pg as depicted by lagrangian trajectories reveal a stationary flow that is very rich in eddies each eddy can be identified with a topographic obstacle this confirms that the tidal residual flow field is strongly influenced by the nonlinear interaction of the tidal wave with the bottom relief which in turn is deformed by salt domes beneath the seabed different areas of maximum residual current velocities are identified for major tidal constituents the pattern of trajectories indicates the presence of two main cyclonic gyres and several adjacent gyres rotating in opposite directions and a strong coastal current in the northern pg

thrusting in a folded regime fold accommodation faults in the ruhr basin germany abstract the late carboniferous ruhr basin in germany has been described as an authochtonous foreland basin of the variscan orogen the structure of the basin is fold dominated with fold accommodation faults as secondary elements vast and excellently documented 3d mining exposures provide extensive data on the geometry of thrusts and the relationship between thrusting and folding stratigraphic throw is the determining factor in the geometry of thrusts and displacement and shortening are functions of throw material behaviour and bedding dip built up on a basic geometric model a complex system of different fault types can be described linked regularly to each other and developed during the folding process

understanding airborne radiometric survey signals across part of eastern england a low level airborne radiometric survey provides data on the concentrations of gammaemitting elements including potassium k thorium th and uranium u in the upper half metre of the soil where weathering has not penetrated much beyond this depth as in the young soils that cover much of england and wales the signal is likely to be related to the soil s clay content and its parent material in these situations radiometric survey could be valuable for mapping soil digitally we wished to understand how the radiometric signal relates to parent material and soil geochemistry and to identify the spatial structure if not the sources of any unexplained variation we analysed the joint spatial variation of the airborne gamma signal and high resolution soil geochemical survey data across part of eastern england by modelling their coregionalization we also used reml to assess the joint effects of soil geochemistry and parent material on the radiometric signals of k and th the overall correlations of radiometric estimates with soil survey data for k and th were large as were the structural correlations for components of variation spatially dependent up to 49 and 16 km for k and th respectively this suggests that the radiometric signals for these two elements provide effective estimates of the amounts in the soil and their patterns of distribution although class of parent material accounted for a third of of the variance in the radiometric k signal much of the variation within the classes is explained by geochemistry suggesting that subtler changes can be detected a larger proportion of the th signal was accounted for by parent material this supports our expectation that radiometric signals for k and th provide information on parent material in the young landscapes of england and wales we are therefore confident that airborne radiometric surveys would be useful for making thematic maps of soil particularly the soil s texture and closely related properties across england and wales copyright 2007 natural environment research council published in 2007 by john wiley sons ltd

identifying the characteristic signatures of fold accommodation faults abstract hand specimen and outcrop scale examples of folds are analyzed here to identify the characteristic signatures of fold accommodation faults we describe and analyze the geometric and kinematic relationships between folds and their associated faults in detail including the structural position and spatial distribution of faults within a fold the displacement distribution along the faults by applying separation distance plots for the outcrop scale examples and the change of cut off angle when the fault cut across folded layers a comparison between fold accommodation faults and fault related folds based on their separation distribution plots and the problem of time sequence between faulting and folding are discussed in order to distinguish fold accommodation faults from the reverse faults geometrically and kinematically similar to them the analysis results show that fold accommodation faults originate and terminate within a fold and usually do not modify the geometry of the fold because of their limited displacement the out of syncline thrust has a diagnostically negative slope separation value decreasing away from the upper fault tip in the separation distance graph the change of cut off angle and the spatial distribution of faults display a close relationship with the axial surface of the fold our analyses show that fold accommodation faults are kinematically consistent with the flexural slip of the fold the interbedded strata with competence contrast facilitate formation of fold accommodation faults these characteristic signatures are concluded as a set of primary identification criteria for fold accommodation faults

analysing the proximal gamma radiometry in contrasting mediterranean landscapes towards a regional prediction of clay content abstract the analysis of radiometric data from proximal soil sensing measurements can be used to predict key soil properties for environmental and agricultural issues these predictions require prior calibrations that use a large sampling of field data that could be significantly reduced if regional predictions can be established however such predictions may be challenging for mediterranean regions because of the highly contrasted soils and specific geopedological characteristics sedimentary rocks low weathering etc our study focuses on the regional prediction of a key soil property clay content within highly contrasting geopedological groups gpg from the languedoc region the aims of the research were i to understand the relationship between radiometric data and the clay content within the different complex gpgs and ii to predict the clay content from radiometry with a regional calibration based on the gpg as an auxiliary variable a proximal soil survey using the radiometer called the mole was conducted in 8 areas of the languedoc region the plots were selected over different gpgs that are representative of the soil diversity and materials according to their weathering intensity and igneous components in total 242 sites were sampled based on a random grid cell for soil laboratory measurements the soil texture and stoniness were analysed and the particle size fractions were separated for mineral identification via x ray diffraction the activity of 232th 1 to 71 bq kg and 40k 40 to 771 bq kg exhibits the largest range between the different gpgs which spans the range of values measured in previous european studies the relationship between the clay content and 232th is significant at a regional level r2 0 60 rmse 42 g kg the residuals are significantly distributed according to the different gpgs a new linear model based on the 232th activity and the gpgs improves the prediction of the clay content r2 0 72 rmse 35 g kg our study showed that ground radiometry can be used to predict the clay content within a complex mediterranean sedimentary context the 232th radionuclide is the best predictor the disturbance of the relationship between the 232th and the clay content corresponds to the fine earth mineralogy type and the proportion of igneous pebbles

identifying large scale erosion and deposition processes from airborne gamma radiometrics and digital elevation models in a weathered landscape patterns of erosion and deposition are difficult to identify and measure at catchment and regional scale but it may be possible to infer their distribution from remote sensing using easily measured surrogate variables airborne geophysical surveys provide data on gamma ray emissions from surface and near surface material and allow estimation of k th and u content gamma ray signatures are largely determined by lithology but also change with weathering and with erosion and deposition and may be used as a partial surrogate for those processes comparison of gamma ray signatures with topographic characteristics closely related to sediment transport capacity downstream sorting of sediments and the extent of erosion and deposition shows strong linkages studies in four small catchments in southeastern australia indicate that k consistently increases as slopes become steeper while th and u may either increase or decrease this suggests the presence of fresh rock rather than weathered material and implies removal of material by erosion although some patterns may result from systematic changes in lithology across catchments analysis by lithology confirms the increase in k with slope in granites metamorphosed sediments and basalt and also shows a tendency for u to decrease with slope in the granites and basalt gamma ray emissions vary only slightly with catchment area a surrogate measure of water discharge suggesting that water erosion is limited or that discharge is not closely related to area gamma radiometric profiles down hillslopes averaged across the full range of gradients show that in most cases radioelements initially decrease probably reflecting increased weathering but then increase close to valley floors because of accumulation of fine sediments analysis by lithology confirms the increase in radioelements close to valley floors in granites and metamorphosed sediments but the trend is less clear in basalt gamma ray profiles down floodplains are variable and indicate the amount of deposition and accumulation of weathered material in valley openings and exposure of bedrock in valley constrictions simple erosion and deposition models based on the conservation of mass equation and applied to the four catchments show that all radioelements increase as the potential for deposition increases they reach a low point in zones of no net erosion or deposition and subsequently increase as erosion becomes more intense and weathered material is lost from slopes analysis by lithology largely confirms this pattern the usefulness of airborne geophysical survey data is limited by flight line spacing with most data being flown at a 200 400 m spacing in australia however general trends in erosion and deposition can still be distinguished and there is capacity for calibrating long term erosion and deposition models once better approaches to interpretation of gamma ray data have been developed copyright 2000 john wiley sons ltd

estimation of fault propagation distance from fold shape implications for earthquake hazard assessment a numerical grid search using the trishear kinematic model can be used to extract both slip and the distance that a fault tip line has propagated during growth of a fault propagation fold the propagation distance defines the initial position of the tip line at the onset of slip in the santa fe springs anticline of the los angeles basin we show that the tip line of the underlying puente hills thrust fault initiated at the same position as the 1987 magnitude 6 0 whittier narrows earthquake

application of airborne gamma ray imagery to assist soil survey a case study from thailand abstract airborne gamma ray imagery agri provides coarse resolution approximately 400 400 m pixel spatial information on gamma ray emitting elements i e potassium k thorium th and uranium u in the upper half meter of the soil these radioelements are a potential information source for soil mapping since their abundance is related to soil geochemistry specifically the chemical composition of parent materials and their weathering products resulting from geomorphic and pedogenic processes the aim of this study was to evaluate the potential of agri for improving digital soil survey process in two phases 1 a preliminary phase where hypotheses of soil landscape relationships are developed and 2 a phase where soil map unit boundaries are placed or revised the study also evaluated the match between agri and existing lithologic geopedologic and soil series maps the study was conducted in a well characterized complex soil landscape the 560 km2 upper pa sak watershed in petchaboon province thailand the relationship between gamma ray data and geological units was examined with box and whisker plots and confirmed by rock and soil samples rock and soil sample classifications were compared with the gamma ray image and to typical radioelement responses found in the literature to interpret agri data in terms of regolith and soil genesis we compared agri to two existing soil maps geopedologic and soil series maps first the geopedologic map was split into four maps according to the geopedologic hierarchy landscape lithology relief and landform at the latter lowest level soil units are also associated secondly soil series and geopedologic soil units were used to examine the distribution of radioelement response to selected soil characteristics parent material texture mineralogy and thickness the interpretations from best correlation in both soil maps were described in terms of the radioelement changes during pedogenic and geomorphic processes based on a review of literature and supported by soil samples in the hypotheses generating stage agri provided useful information in three forms single signal ratio and ternary images enhanced with a hill shaded dem by relating these to lithology material transport and internal pedogenetic processes agri correlated well with the classes of the geopedologic map 1 50 000 at the two higher levels landscape and lithology but to a lesser degree at the two lower levels relief and landform in geopedologic approach in the mapping stage agri showed deficiencies in the soil series map 1 50 000 made by conventional aerial photo analysis and limited field surveys especially in inaccessible areas but also in low relief terraces and flood plains which provided a basis for future field sampling to correct these deficiencies agri suggested new boundaries differentiating topsoil properties and the presence of plinthite despite its coarse resolution clustering of gamma ray and elevation data dem was carried out using fuzzy logic to generate various classification layers final map was produced using total weighted inverse distance of all the classes in a 3 by 3 window class label was assigned to the one with the largest total inverse distance over the entire set of fuzzy classification bands the result shows relatively higher classification accuracy for soil parent material differentiation overall accuracy of 72 as compared to the classification for soil types 67

a regolith depth map of the australian continent abstract the regolith is defined as weathered in situ and transported material overlying unweathered bedrock as fresh bedrock exposures form a small proportion of the landscape regolith is common in australia and varies in depth from less than a metre in upland settings to many hundreds of metres e g the cenozoic basins because of crucial fluxes in gases water nutrients and dissolved salts and variation in permeability and connectivity knowledge of the nature and depth of regolith is important to many land based industries including agriculture and forestry the minerals industry sees regolith as a barrier to discovery of mineralised rock at depth or as a host of minerals in economic concentrations there are clearly a range of important characteristics of regolith depth and therefore the quantity of regolith is fundamental for resource inventory and biophysical modelling applications a method is described that maps the depth of regolith with estimates of mapping uncertainty to the moderately weathered saprock boundary for the whole of australia our approach draws on an extensive legacy of publically available drillhole data of variable attribute consistency and applies an environmental correlation style of digital mapping prediction that utilises relevant spatial covariates e g terrain analysis climate and gamma radiometric datasets from the original database of 350 000 records we filtered and harmonised a useable dataset of 128 000 records key predictive datasets used in the depth model included weathering intensity lithology age distance to out crop elevation and relief shallowest cover corresponded to high relief erosional landscapes and deepest corresponded to cenozoic basin sediments the final map with a ground resolution of approximately 90 m 3 arcsec was generated using 100 bootstrap model iterations the reliability of the model was assessed using measures of r square 0 38 lin s concordance 0 51 mean error 5 73 m and root mean squared error 24 56 m calculated on a withheld test dataset the regolith depth map is consistent with known areas of deep in situ weathering and accumulation of recent sediment associated with the distribution of cenozoic basins and provides a testable estimate in areas with little drilling or survey history the predictive modelling approach provides a framework to further build and improve regolith depth prediction across varying spatial scales where sufficient quality drillhole data and environmental predictors exist and set priorities for new data acquisition

mechanical models of fault propagation folds and comparison to the trishear kinematic model abstract faults propagating through the earth generate a wave of deformation ahead of their tip lines we have modeled this process to understand the relationship between fold geometry and fault propagation using finite element modeling fem we investigate the response of incompressible frictionless and frictional materials and a compressible frictional material with associated flow to vertical and dipping faults whose tip lines propagate at rates 3 3 5 times their slip rates the fold geometries finite strain and velocity fields in models with incompressible materials are very similar to those produced by the trishear kinematic model even though the latter uses a purely ad hoc linear velocity field furthermore when the trishear grid search is applied to the final geometry of the mechanical folds the best fit kinematic models have approximately the same propagation to slip ratio as was used in the fem experiments however when the compressible frictional material is used the mechanical models exhibit a main triangular shear band in front of the tip line and a conjugate shear band in the fold backlimb both migrating with the propagating tip line the conjugate shear band antithetic to the fault produces a gentle anticlinal back limb even though there is not a bend in the fault

predictive geochemical mapping using environmental correlation abstract the distribution of chemical elements at and near the earth s surface the so called critical zone is complex and reflects the geochemistry and mineralogy of the original substrate modified by environmental factors that include physical chemical and biological processes over time geochemical data typically is illustrated in the form of plan view maps or vertical cross sections where the composition of regolith soil bedrock or any other material is represented these are primarily point observations that frequently are interpolated to produce rasters of element distributions here we propose the application of environmental or covariate regression modelling to predict and better understand the controls on major and trace element geochemistry within the regolith available environmental covariate datasets raster or vector representing factors influencing regolith or soil composition are intersected with the geochemical point data in a spatial statistical correlation model to develop a system of multiple linear correlations the spatial resolution of the environmental covariates which typically is much finer e g 90 m pixel than that of geochemical surveys e g 1 sample per 10 10 000 km 2 carries over to the predictions therefore the derived predictive models of element concentrations take the form of continuous geochemical landscape representations that are potentially much more informative than geostatistical interpolations environmental correlation is applied to the sir samuel 1 250 000 scale map sheet in western australia to produce distribution models of individual elements describing the geochemical composition of the regolith and exposed bedrock as an example we model the distribution of two elements chromium and sodium we show that the environmental correlation approach generates high resolution predictive maps that are statistically more accurate and effective than ordinary kriging and inverse distance weighting interpolation methods furthermore insights can be gained into the landscape processes controlling element concentration distribution and mobility from analysis of the covariates used in the model this modelling approach can be extended to groups of elements indices element ratios isotopes or mineralogy over a range of scales and in a variety of environments

resonance and morphological stability of tidal basins the paper describes the concept of a network model for the morphological behaviour of a near resonant multiple inlet tidal basin as part of a model system which includes the barrier island coasts and the outer deltas it addresses the question whether a small interference somewhere in such a basin can have major effects on sediment transport and morphology elsewhere in the system in order to explain the basic ideas of the model only the main tidal constituent m2 and the associated topography induced residual current are considered not the overtides furthermore the model concerns only non cohesive sediment sand in spite of these simplifications the model concept is shown to be effective in that it results in a morphological evolution equation for each branch of the network and a picture of the influence of each branch on the resonance sensitivity of the system as a whole

quantitative resolution of the debate over antiquity of the central australian landscape implications for the tectonic and geomorphic stability of cratonic interiors we report the first measure of long 100 myr and short 1 myr term denudation rates from key geologically stable landforms in the davenport range central australia these landforms have previously been assigned a cambrian age which arguably places them amongst the oldest persistent landforms on the continent if not on earth our results from combined apatite fission track thermochronology and in situ cosmogenic radionuclide analyses using 10 be and 26 al show that while average exhumation rates are low the denudation history for this cratonic region is incompatible with extreme sub aerial longevity and long term tectonic and geomorphic stability our revised model for the landscape evolution of this region is consistent with one of maximum burial prior to and during the mesozoic followed by a phase of kilometre scale exhumation that was largely complete by the beginning of the cainozoic we suggest that a similar process of burial and exhumation has probably been responsible for the sub aerial preservation of seemingly ancient landforms elsewhere in australia

landscape scale exploratory radiometric mapping using proximal soil sensing abstract the soil s gamma radiometric signal is known to be a crucial indicator of the heterogeneity of soil properties most likely directly related to the mineralogy and geochemistry of the parent material however fine resolution radiometric data sourced from geophysical surveys are often not available in our study area in the lower hunter valley australia only coarse scale based on 2 km line spacing aerial radiometric maps are available an alternative solution could be to implement a smart ground based gamma ray survey when detailed radiometric information is required on larger extent the work presented here therefore details a vehicle borne gamma ray soil survey conducted in the lower hunter valley to investigate if a proximal soil sensing device with a footprint much smaller than airborne gamma ray spectrometers can be employed for regional extent mapping and still capture the soil s fine scale heterogeneity to do so we designed an algorithm for the delineation of irregular transects drive lines based on ancillary environmental information intended to be used specifically for wide ranging exploratory surveys wires at the regional scale the wires algorithm creates transects from randomised starting points that terminate at boundary points the path is defined with directional constraints that collectively ensure that the environmental variability within the domain of study is accessed and sampled the design was delineated for the entire 220 km2 study area in this exploratory work we surveyed a sub catchment of the area 15 km2 to trial the feasibility of wires we produced radiometric maps based on a regression kriging approach an external validation of the maps showed good results we also validated the maps produced with existing detailed radiometric maps across a landholding 140 ha that is situated within the sub area investigated in this study both surveys were comparable which gives us useful insights into understanding the scaling properties of the geophysical properties of soil across environments

the formation of representative lateritic weathering covers in south central guangxi southern china the mineralogy and geochemistry have been studied in three representative lateritic weathering covers close to the tropic of cancer guangxi south china with the purpose of studying formation and evolution processes of lateritic covers in this region the x ray diffraction and scanning electron microscope analysis results indicate that the contents particle sizes shapes and structures of secondary minerals such as iron and clay minerals are distinctly different in ferruginous nodular horizon and mottled clay layer of lateritic profiles the ferruginous nodules are characterized by high concentrations of iron and aluminum and low contents of silicon the energy analysis suggests that there are element exchanges between hematite crystal and clay minerals the mass balance calculation results show that there is exogenetic input of iron into lateritic covers especially within the ferruginous nodular horizon compared to the bottom layer of the profile the scanning electron microscope images also confirm that voids and fractures in ferruginous nodules were filled with ferruginous material derived from soil solution this could be a significant interpretation for the negative correlations between fe2o3 and al2o3 the iron and manganese oxides in ferruginous nodular horizon have an apparent effect on the adsorption and precipitation of cerium strontium compared to other alkali metal and alkali earth metal elements concentrates in mottled clay layer variation in the he gt ratio reflected by the o fe ratio in a small ferruginous concretion indicates that climate changes altered aqueous activity of the soil environment finally a model for the formation and evolution of typical lateritic weathering covers in south central guangxi supported by all the data was proposed

combining geomorphometry feature extraction techniques and earth surface processes research the way forward abstract in recent years the wealth of technological development revolutionised our ability to collect data in geosciences due to the unprecedented level of detail of these datasets geomorphologists are facing new challenges giving more in depth answers to a broad er range of fundamental questions across the full spectrum of the earth s and planetary processes this contribution builds on the existing literature of geomorphometry the science of quantitative land surface analysis and feature extraction translate land surface parameters into extents of geomorphological elements it provides evidence of critical themes as well as emerging fields of future research in the digital realm supporting the likely effectiveness of geomorphometry and feature extractions as they are advancing the theoretical empirical and applied dimension of geomorphology the review further discusses the role of geomorphometric legacies and scientific reproducibility and how they can be implemented in the hope that this will facilitate action towards improving the transparency and efficiency of scientific research and accelerate discoveries in geomorphology in the current landscape substantial changes in landforms ecosystems land use hydrological routing and direct anthropogenic modifications impact systems across the full spectrum of geomorphological processes although uncertainties in the precise nature and likelihood of changes exist geomorphometry and feature extraction can aid exploring process regimes and landscape responses taken together they can revolutionise geomorphology by opening the doors to improved investigations crossing space and time scales blurring the boundaries between traditional approaches and computer modelling and facilitating cross disciplinary research ultimately the exploitation of the available wealth of digital information can help to translate our understanding of geomorphic processes which is often based on observations of past or current conditions into the rapidly changing future

defining element associations and inferring geological processes from total element concentrations in australian catchment outlet sediments multivariate analysis of continental scale geochemical data abstract in this paper the geochemical composition of surficial regolith is statistically analysed and compared to independent geoscientific datasets to infer processes governing regolith composition surface 0 10 cm depth and sub surface 60 80 cm depth transported sediment samples from the national geochemical survey of australia were analysed for total element content in both coarse censored data

stability analysis of a two inlet bay system abstract the stability analysis for a double inlet bay system is applied to an inlet system resembling big marco pass and capri pass on the lower west coast of florida since the opening of capri pass in 1967 the length of big marco pass has increased from 2000 m in 1967 to 3000 m in 1988 and the cross sectional area has decreased from 1200 m 2 in 1967 to 1000 m 2 in 1988 since 1967 the cross sectional area of capri pass has steadily increased and in 1988 was 700 m 2 tides off the inlets are of the mixed type with a diurnal range of 1 m the gross littoral transport rate in the vicinity of the inlets is estimated at 150 000 m 3 yr 1 for each inlet the maximum tidal velocities are calculated as a function of the gorge cross sectional areas using a lumped parameter model to describe the hydrodynamics of the flow in the model it is assumed that the bay level fluctuates uniformly and the bay surface area remains constant the velocities are used to calculate the tidal maximum of the bottom shear stress in each inlet as a function of the cross sectional areas of the two inlets closure surface values of the equilibrium shear stress are derived from an empirical relationship between cross sectional area and tidal prism for stable inlets along the west coast of florida closure surfaces and equilibrium stress values are calculated for values of friction factors ranging from f 4 10 3 to f 6 10 3 using the closure surfaces and equilibrium stress values the equilibrium flow curve for each inlet is determined the equilibrium flow curve represents the locus of the combination of cross sectional areas for which the actual bottom shear stress in the inlet equals the equilibrium shear stress based on the equilibrium flow curves and the known values of the cross sectional areas of the two inlets in 1988 it is expected that ultimately big marco pass will close and capri pass will remain as the sole inlet with a cross sectional area of 1250 m 2 and a maximum tidal velocity pertaining to a diurnal tide of 0 85 m s 1

automated regolith landform mapping using airborne geophysics and remote sensing data burkina faso west africa abstract we have studied the regolith landform distribution in the area of gaoua western burkina faso using an integration of geophysical and remote sensing data concentration maps of k th u as well as their ratios were computed from airborne gamma ray spectrometry data to assess the geochemical composition of the regolith the mineralogy of the surfaces was mapped via the analysis of multispectral aster and landsat scenes pauli decomposition data retrieved from polarimetric alos palsar and radarsat 2 images were included to characterize the surface properties of the regolith material morphometric variables such as slope curvature and relative relief were derived from the srtm digital elevation model to quantify the topographic parameters of the different regolith landforms an artificial neural network implementation advangeo was then employed to extract four basic regolith landform units from the satellite and airborne data relic ferruginous duricrusts rich in hematite and goethite belonging to the high glacis erosional surfaces represented by rock outcrops and suboutcrops alluvial sediments and soft pediment materials of the middle and low glacis were mapped successfully in the region the results were compared with the existing geomorphological maps an independent visual classification and field observations we found that the distribution and shape of the iron rich duricrusts are more accurate than portrayed in the current maps the best results with an overall accuracy of 94 21 and a kappa value of 0 92 were obtained for a dataset consisting of gamma ray spectrometry data combined with derivatives of the srtm digital elevation model augmented by landsat and polarimetric radar data the approach demonstrates for the first time the potential of machine learning in regolith landform mapping the proposed combined analysis of airborne geophysics and remote sensing data can be adopted easily in other regions with similar long term lateritic weathering histories worldwide

chemical weathering in subtropical basalt derived laterites a mass balance interpretation misiones ne argentina abstract subtropical laterites are partially found in the argentinian province of misiones covering the jurassic cretaceous serra geral flood basalts known as posadas formation in argentina two hypotheses have been proposed to explain the origin of these laterites the autochthonous theory attributes the origin of these deposits to the chemical weathering of the underlying tholeiitic basalts however during the last decade an allochthonous tropical loess model was proposed several mineralogical geochemical characteristics of a lateritic profile 2 m thick 26 9 58 s 54 35 3 w are analyzed in this paper in order to constrain the nature of weathering processes in this region and the provenance of the lateritic layer the basaltic bedrock at the sampling site exhibits intergranular texture and is mainly composed of clinopyroxene plagioclase and opaque minerals likely titanomagnetite and ilmenite altered glass and apatite were also identified in lower proportions the x ray diffraction of the clay size fraction shows prevailing kaolinite and hematite in the most altered samples complemented by amorphous fe al hydr oxides serra geral basalts normalized spidergrams and mass balance calculations confirmed almost complete losses of all major oxides i e 50 g of material was removed by weathering from each 100 g of the original basalt and depletions of some trace elements e g sc v sr cr ni rb and u in the uppermost and intermediate layers of the lateritic profile reflecting the weathering of feldspars clinopyroxenes volcanic glass and apatite in contrast some elements are enriched in the topmost and intermediate layers due to intrinsic immobility during weathering e g zr hf ta th or adsorption onto clays e g cs rare earth elements rees are depleted in the top layers and enriched in the middle section of the profile the preferential leaching of rees from the uppermost levels during weathering and its accumulation in the middle section can be caused by a ph increase in this level the decomposition of organic matter and the consequent precipitation of rees which exhibit an affinity to form aqueous organic complexes or the presence of fe and mn hydr oxides in the intermediate level weathering intensity was appraised by means of different alteration indices which showed the extreme leaching endured by the basaltic bedrock the index of lateritization iol which ranges between 35 and 55 and the accompanying saf ternary plot sio2 al2o3 fe2o3 indicate an increasing weathering trend towards the profiles top reflecting the modest loss of sio2 relative to al2o3 and fe2o3 during kaolinitization the geochemical approach used to constrain the origin of the lateritic mantle that partially covers misiones province clearly relates the analyzed laterites to the underlying tholeiitic basalts supporting the autochthonous origin theory

lithology and soil relationships for soil modelling and mapping abstract relationships between parent material and soil are not well understood and generally only reported in qualitative form we present a classification of parent material for pedologic purposes which includes twelve lithology classes based on mineralogical and chemical composition the relationships of these lithology classes with six key soil properties soil organic carbon ph cation exchange capacity sum of bases total p and clay were examined in a case study over new south wales australia we used multiple linear regression random forest and cubist tree models based on a soil dataset of over 3200 points semi quantitative estimates are derived of change in these soil properties with a change in lithology class and an associated silica index for example a 22 relative decrease in soil organic carbon with each 10 rise in silica broadly equivalent to a change from shale to granite assuming other factors remain constant parent material covariates are essential for the effective modelling and mapping of soil properties widely available lithology data have the potential for greater use in digital soil modelling and mapping dsmm programs we compared the performance of the classified lithology data with other continuous geophysical parent material covariates such as gamma radiometrics in digital soil models and maps over nsw the lithology covariate was demonstrated to exert the greatest influence on all six soil properties coming well ahead of all geophysical parent material and other environmental covariates validation statistics demonstrated strong improvement in both model and map quality when the lithology covariate was included for example lin s concordance for the cubist sum of bases model rose from 0 46 with no parent material covariates to 0 58 with the continuous geophysical covariates to a high of 0 77 when lithology was also used the improvement was typically slightly less marked in the final digital maps than for the calibration models probably due to the lower reliability of the lithology grid derived from broad scale polygonal geological and soil data a process is suggested for the application of lithology data into dsmm programs despite the potential drawbacks of using polygonal data properly organised categorical lithology data can be a strong covariate to complement other continuous geophysical data sources in dsmm programs particularly where reliable and fine scale geological and soil data are available

distribution of fault slip in outcrop scale fault related folds appalachian mountains abstract current kinematic models of ramp related folds predict a direct relationship between ramp angle and fold shape and imply specific sequences of deformation analyses of outcrop scale structures in the valley and ridge province of the appalachians reveal configurations that depart from model predictions the models fail to account for the presence of footwall synclines and are inconsistent with measured displacement distributions on some natural faults observations support the interpretation that faults can grow by propagation both up and down dip from a nucleation point fault propagation in either direction may result in the formation of folds primarily on the side of the fault that is displaced in the direction of fault propagation