feldspathic clasts in yamato 86032 remnants of the lunar crust with implications for its formation and impact history abstract low concentrations of th and fe in the yamato y 86032 bulk meteorite support earlier suggestions that y 86032 comes from a region of the moon far distant from the procellarum kreep terrain pkt probably from the lunar farside 39 ar 40 ar rb sr sm nd and sm isotopic studies characterize the chronology of y 86032 and its precursors in the mega regolith one of the rock types present in a light gray breccia lithology is an anorthosite characterized by plagioclase with an 93 i e more sodic than lunar fans but with very low 87 rb 86 sr and 87 sr 86 sr similar to those of fans fan stands for ferroan anorthosite this an93 anorthosite has nd isotopic systematics similar to those of nearside norites a fan like an97 anorthosite is present in a second light colored feldspathic breccia clast and has a more negative e nd value consistent with residence in a lree enriched environment as would be provided by an early plagioclase flotation crust on the lunar magma ocean lmo this result contrasts with generally positive values of e nd for apollo 16 fans suggesting the possibility of assymetric development of the lmo other possible explanations for the dichotomy in e nd values are advanced in the text the y 86032 protolith formed at least 4 43 0 03 ga ago as determined from a sm nd isochron for mineral fragments from the breccia clast composed predominantly of an93 anorthosite and a second clast of more varied composition we interpret the mineral fragments as being predominatly from a cogenetic rock suite an 39 ar 40 ar age of 4 36 4 41 0 035 ga for a third clast composed predominantly of an97 anorthosite supports an old age for the protolith initial 143 nd 144 nd in that clast was 0 64 0 13 e units below 143 nd 144 nd in reservoirs having chondritic sm nd ratios consistent with prior fractionation of mafic cumulates from the lmo a maximum in the 39 ar 40 ar age spectrum of 4 23 0 03 ga for a second sample of the same feldspathic breccia clast probably reflects some diffusive 40 ar loss lack of solar wind and lunar atmosphere implanted ar in the light gray breccia clast allows determination of an 39 ar 40 ar age of 4 10 0 02 ga which is interpreted as the time of initial brecciation of this litholgy after correction for implanted lunar atmosphere 40 ar impact melt and dark regolith clasts give ar ages of 3 8 0 1 ga implying melt formation and final breccia assembly 3 8 ga ago some breccia lithologies were exposed to thermal neutron fluences of 2 10 15 n cm 2 only about 1 of the fluence experienced by some other lunar highlands meteorites other lithologies experienced neutron fluences of 1 10 15 n cm 2 thus y 86032 spent most of the time following final brecciation deeply buried in the megaregolith the neutron fluence data are consistent with cosmogenic 38 ar cos cosmic ray exposure ages of 10 ma variations among differing lithologies in the amount of several regolith exposure indicators including cosmogenic noble gas abundances neutron capture induced variations in sm isotopic abundances and ir contents are consistent with a period of early 3 8 ga ago lunar regolith exposure subsequent deep burial at 5 m depth and ejection from the moon 7 10 ma ago

modeling of rainfall triggered shallow landslide by integrating hydrological modeling with the infinite slope stability analysis a rainfall triggered shallow landslide model was developed by iverson water resour res 36 1897 1910 2000 in iverson s model the infiltration capacity is assumed to be equivalent to the saturated hydraulic conductivity for finding pressure heads analytically however for general infiltration process the infiltration capacity should vary with time during the period of rain and the infiltration rate is significantly related to the variable infiltration capacity to avoid the unrealistically high pressure heads iverson employed the beta line correction by specifying that the simulated pressure heads cannot exceed those given by the beta line in this study the suitability of constant infiltration capacity together with the beta line correction for hydrological modeling and landslide modeling of hillslope subjected to a rainfall is examined by amending the boundary condition at ground surface of hillslope in iverson s model the modified iverson s model with considering general infiltration process is developed to conduct this examination the results show that the unrealistically high pressure heads from iverson s model occur due to the overestimation of infiltration rate induced from the assumption that the infiltration capacity is identical to the saturated hydraulic conductivity considering with the general infiltration process the modified iverson s model gives acceptable results in addition even though the beta line correction is applied the iverson s model still produces greater simulated pressure heads and overestimates soil failure potential as compared with the modified iverson s model therefore for assessing rainfall triggered shallow landslide the use of constant infiltration capacity together with the beta line correction needs to be replaced by the consideration of general infiltration process

parameterization of soil properties for a model of topographic controls on shallow landsliding application to rio de janeiro a key problem in the use of physically based models of landslide hazards is how to parameterize the representation of soil properties we applied a physically based model for the topographic control on shallow landsliding shalstab to two catchments in rio de janeiro to investigate the accuracy of model results in relation to parameterization of soil properties in so doing we address the relevance of values derived from laboratory tests to the field problem as well as the trade offs inherent in model parameterization we ran the model for all combinations of reasonable cohesion bulk density and friction angle values and compared model predictions to mapped landslides scars we rank sorted model performance through the proportion of the total area of landslide scars correctly predicted as potentially unstable application of the model to an area where soil properties are not well known can be based on either a standard parameterization that emphasizes topographic controls or on local calibration of soil parameters against a map of known landslide locations our analysis suggests that in general acquisition of high quality digital elevation models dems is more important than generation of spatially detailed soil property values for reconnaissance level assessment of shallow landslide hazards

flow and solute transport through the soil matrix and macropores of a hillslope segment subsurface flow from various portions of a soil profile on a steep forested hillslope was evaluated by two sets of step change miscible displacement tests at different application rates and antecedent hydrologic conditions solutions of nacl 1000 mg l 1 cl were applied at steady state rates equivalent to 20 and 30 mm h 1 of standing water over the entire plot area using a line irrigation source located 1 5 m upslope lateral distance from an excavated soil pit subsurface flow and tracer breakthrough from five portions the organic rich soil layer including macropores the mineral soil matrix and three groups of macropores in the mineral soil layer of the soil profile were individually measured and analyzed using a convective dispersive model matrix flow dominated discharge from the soil pit during tracer tests 70 93 of total discharge however during wet periods with upslope drainage macropores including organic rich soil contributed proportionally more flow than during periods when upslope drainage was minimal outflow from macropores during the test with wet antecedent conditions had lower cl concentrations than drainage from the soil matrix suggesting dilution in macropores from upslope drainage effective pore volumes calculated for the flow averaged breakthrough data from the entire profile were much less 40 than the estimates measured by tensiometers of total volume of pore water suggesting that preferential flow significantly contributed to subsurface transport of tracer the pore volume for the entire profile increased only slightly with increasing application rate however the relative proportions of pore volumes calculated for individual portions varied proportionally to antecedent hydrologic conditions these changes are attributed to the expansion of individual macropores with surrounding soil and the lateral extension of macropore networks during wetter conditions

field variability of landslide model parameters a data set of parameters slope soil depth and soil shear strength relevant to spatially distributed modelling of shallow landslides triggered by rain and snowmelt events was determined from field measurements in 250 grid elements of dimensions 25 m downslope 10 m across slope in an area of 250 m 250 m on a hillslope in scotland these data provide an unusually detailed basis for the evaluation of spatial variability and uncertainty in model parameterisation the variations in slope and soil strength are represented adequately by normal distributions a weibull distribution is suggested for the soil depth data the factor of safety calculated at each point in the grid was shown partially to identify observed landslides with a number of false predictions of occurrence trend analysis and semivariogram analysis of the data set suggest that the use of kriging could improve upon this approach to landslide prediction by providing areal estimates of parameters at the grid element scale with associated error bounds

limits on the validity of infinite length assumptions for modelling shallow landslides the infinite slope method is widely used as the geotechnical component of geomorphic and landscape evolution models its assumption that shallow landslides are infinitely long in a downslope direction is usually considered valid for natural landslides on the basis that they are generally long relative to their depth however this is rarely justified because the critical length depth l h ratio below which edge effects become important is unknown we establish this critical l h ratio by benchmarking infinite slope stability predictions against finite element predictions for a set of synthetic two dimensional slopes assuming that the difference between the predictions is due to error in the infinite slope method we test the infinite slope method for six different l h ratios to find the critical ratio at which its predictions fall within 5 of those from the finite element method we repeat these tests for 5000 synthetic slopes with a range of failure plane depths pore water pressures friction angles soil cohesions soil unit weights and slope angles characteristic of natural slopes we find that 1 infinite slope stability predictions are consistently too conservative for small l h ratios 2 the predictions always converge to within 5 of the finite element benchmarks by a l h ratio of 25 i e the infinite slope assumption is reasonable for landslides 25 times longer than they are deep but 3 they can converge at much lower ratios depending on slope properties particularly for low cohesion soils the implication for catchment scale stability models is that the infinite length assumption is reasonable if their grid resolution is coarse e g 25 m however it may also be valid even at much finer grid resolutions e g 1 m because spatial organization in the predicted pore water pressure field reduces the probability of short landslides and minimizes the risk that predicted landslides will have l h ratios less than 25

regional gravity anomalies depth of the foreland basin and isostatic compensation of the new guinea highlands the new guinea highlands form an active thrust belt advancing southward over the australian continental margin surface geology indicates thin skinned deformation of sediments and continental basement building mountains 2 4 km in average elevation the depth of the adjacent foreland basin is no more than 1500 m in papua new guinea and in many places only 100 200 m indicating little deflection of the australian lithosphere beneath the load of the mountains calculations of elastic loading in which the topographic load of the entire mountain range is supported by australian lithosphere of uniform flexural rigidity d predict a basin 2 10 times deeper than observed in eastern new guinea for a wide range of flexural rigidities 1021 1025 nm bouguer gravity anomalies in the eastern highlands between 143 e and 144 e are consistent with local airy compensation of the mountains and preclude a continuous plate with d 1022 nm underlying any significant portion of the mountains in contrast the observed broad foredeep flexure in central new guinea near 141 142 e requires a strong lithosphere d 1024 1025 nm and limited gravity and sediment thickness observations farther west indicate similar flexural rigidities bouguer gravity measurements and observed foreland basin depths throughout new guinea can be explained by a strong and continuous lithosphere beneath the foreland basin extending no more than 20 60 km north of the range front implying that the plate has weakened beneath the thrust belt collateral evidence for plate weakening beneath the highlands may be found in earthquakes at 10 25 km depth with high angle thrust mechanisms and in widespread quaternary volcanism throughout the eastern thrust belt a 50 mgal positive residual anomaly over the northern 100 km of the eastern highlands cannot be explained by local compensation or mechanical support from the south indicating either a large excess mass at depth or some additional form of support for the northeastern highlands the gravity observations in eastern new guinea require 10 15 km of crustal thickening but observed sediment thicknesses can only account for 0 5 km necessitating 5 15 km of thickening in the basement

gis techniques and statistical models in evaluating landslide hazard geographical information systems gis and numerical cartography may greatly facilitate the development and use of statistical models for the assessment of regional landslide hazard from a small drainage basin located in central italy relevant geological and geomorphological factors were collected and processed by applying gis technology in particular modules were used which both generate high fidelity digital terrain models and automatically partition the terrain into main slope units the resulting information was then analysed by discriminant analysis which enabled landslide hazard and risk to be evaluated in each slope unit although not lacking drawbacks the method proved to be a feasible and cost effective approach to landslide susceptibility assessment and mapping

tectonic evolution of the meatiq infrastructure central eastern desert egypt the pan african basement exposed in the meatiq area central eastern desert egypt was found to possess tectonic styles belonging to infrastructure transition and super structure levels tectonic style of the infrastructure was developed during an old orogeny in the lower pan african and overprinted by those of the transition and superstructure levels of a younger orogeny in the middle and upper pan african respectively in the lower pan african old sequences of sediments and volcanics together with ophiolitic rocks were intensely deformed and regionally highly metamorphosed into gneisses and amphibolites in the infrastructure level such rocks were migmatized plastically deformed and intruded by synkinematic granitoid diorite to alkali granite lenses sheets and plutons which were probably crystallized as amphibolite facies gneisses later on these infrastructural rocks were cut by mafic to intermediate dykes and sills isostically uplifted and cratonized parts were exposed to erosion in the middle pan african the cratonized rocks sank into a transition tectonic level where they underwent large scale thrusting varying degrees of cataclasis and mylonitization and low to medium grade regional metamorphism an episode of plutonism guided by thrusts followed mainly in the form of synkinematic intrusion of tonalite granodiorite and quartz monzodiorite in the upper pan african isostatic uplift occurred and the mylonitic rocks attained the superstructure level there they were subjected to two main phases of folding resulting in the major meatiq domal structure subsequently the folded rocks were intruded by a postkinematic quartz monzonite pluton

hydrologic effects of clearcutting and wildfire on steep granitic slopes in idaho many of the environmental impacts of logging and wildfire are caused by changes in the hydrologic response of slopes after disturbances this study was conducted to evaluate changes in inflow storage and outflow for 3 year periods before and after clearcut logging and wildfire on two steep granitic microwatersheds in idaho clearcutting alone and clearcutting plus wildfire increased annual peak snow water equivalent and snowmelt rates an average of 41 and 30 respectively the greater volume and rate of snowmelt caused respective increases in the peak piezometric rise and in total piezometric storage amounting to 47 and 27 accordingly the total volume of subsurface flow intercepted by the roadcut was increased 96 and was accompanied by 27 greater peak flow rates none of the above responses were detectable on an adjacent watershed that was burned by wildfire alone evapotranspiration was reduced on both watersheds after clearcutting or wildfire as indicated by increases in the unsaturated soil water content at the end of the growing season amounting to 44 and 72 respectively accelerated mass erosion on clearcut slopes and accelerated surface and mass erosion on roads and in channels below roads can result from such changes

structure of the papuan fold belt papua new guinea 1 the structure of the papuan fold belt differs substantially from the classical thin skinned structures of the canadian rockies mainly due to the weak and broken papuan lithosphere and incompetent clastic section compared to the strong cratonic lithosphere in canada overlain by limestones and quartzites the papuan margin was dissected by mesozoic extensional faults in part reactivated during neogene compression which created basement involved anticlines or elevated plateaus in the papuan fold belt the sedimentary section in the fold belt is deformed into large ramp anticlines in the southwest smaller miocene and mesozoic duplexes in the center and fault propagation folds in the northeast hydrocarbon discoveries to date have occurred in the southwestern anticlines which are interpreted as reactivated extensional structures the precursor rollover anticlines trapped oil generated in the late cretaceous such that present accumulations probably result from preservation of that oil during neogene thrusting mesozoic duplex structures are likely to be prospective but difficult to define and fault propagation folds rely upon unproven upper cretaceous sandstones as a reservoir

mapping landslide hazards in forest watersheds a physically realistic methodology is presented for estimating and mapping landslide hazards for watersheds this methodology also considers the variability of the controlling factors a demonstration of this methodology on an area in southeast alaska is described

experimental investigation of rainfall criteria for shallow slope failures a theory of the internal response based rainfall criterion for predicting slope failure is proposed based on artificial rainfall tests for a sandy slope key elements in a generic model describing shallow slope failure are identified from the tests with extensive soil moisture and piezometric measurements the observed retrogressive slope failure was triggered by a toe failure followed by an abrupt increase in debris discharge the onset of the failure was preceded by a clear transition point on the soil moisture vs time curve at the soil bedrock interface both external and internal responses of slopes to rainfall can be expressed using widely adopted i d rainfall intensity duration plots experimental results from the tests indicate close relationships between the internal based and external based i d envelopes for critical slope states the theory of the internal based i d criterion proposed here will be useful for more accurate slope failure predictions

the muller anticline papua new guinea basement cored inverted extensional fault structures with opposite vergence abstract throughout the nw se trending papuan foldbelt two dominant structural styles are present in the northeast the 1 km thick thrust imbricate slices of miocene limestone attest to the classical thin skinned nature of the deformation in the southwest adjacent to the undeformed foreland fold structures are 1 or 2 orders of magnitude greater in size are strongly asymmetrical and commonly have relatively thicker stratigraphie sections on the crests such structures are the result of mio pliocene compression that caused thrusting along faults that are hypothesized to have been extensional in the mesozoic and palaeogene geological traverses from the undeformed foreland heading northeast across the 150 km by 50 km muller range in western papua new guinea provided detailed surface structural data when combined with analysis of existing geological maps exploration wells regional gravity surveys and extensive seismic in the foreland moderately constrained balanced and restorable cross sections through the muller anticline could be constructed interpretations of gravity data are consistent with the muller anticline being cored by basement and seismic data extrapolated beneath the mountains show the outcrop of basement in the centre of the muller range to be elevated 8 km above regional the eastern muller anticline ema has a shallow northeast limb and steeper southwest limb suggesting a ne dipping fault below such that basement was thrust to the southwest the cecilia wai asi juha and lavani anticlines to the southwest of the ema are interpreted to be formed by shortening of the whole sedimentary section to balance the shortening in basement there are no such structures to the southwest of the western muller anticline wma where the southwest limb is gently dipping and the northeast limb is steep hence the wma is interpreted as having formed above a sw dipping fault along which basement was thrust to the northeast the marked difference in shortening of the southwest limbs requires a tear fault between the ema and wma the tear fault is here interpreted to coincide with the northwestern end of the cecilia and lavani anticlines and the marked change in strike of the muller anticline by analogy with other very large asymmetrical basement involved structures in the papuan foldbelt it is suggested that the faults underlying the muller anticline were active as extensional faults in the mesozoic soling at a mid crustal detachment the extensional faults beneath ema and wma had opposite vergence and were separated by a transfer zone subsequent compressional reactivation of the extensional faults in the pliocene gave rise to the present muller anticline

analysis of hillslope erosion rates using dated colluvial deposits hollows are sites of long term deposition of colluvium and contain a valuable record of the timing and rates of hillslope erosion a model is presented that uses measured depositional rates of colluvium in hollows to calculate transport rates of colluvium and bedrock lowering rates on the surrounding slopes this model has been applied to eight dated colluvial deposits in the clearwater river basin of western washington the calculated average transport rate is about 34 cm 3 cm yr and the calculated average bedrock lowering rate is about 0 04 mm yr equivalent to an average sediment yield of 90 t km 2 yr for the holocene there is significant variability in erosion rates between sites which may be due to local lithologic variations although the average values are similar to an independent estimate of modern erosion rates for this area multiple stratigraphic levels have been dated in five deposits and document that the deposits are cumulative and that deposition has been active through the

a contour based topographic model for hydrological and ecological applications a digital model for discretizing three dimensional terrain into small irregularly shaped polygons or elements based on contour lines and their orthogonals is described from this subdivision the model estimates a number of topographic attributes for each element including the total upslope contributing area element area slope and aspect this form of discretization of a catchment produces natural units for problems involving water flow as either a surface or subsurface flow phenomenon the model therefore has wide potential application for representing the three dimensionality of natural terrain and water flow processes in the fields of hydrology sedimentology and geomorphology three example applications are presented and discussed they are the prediction of zones of surface saturation the prediction of the distribution of potential daily solar radiation and the prediction of zones of erosion and deposition in a catchment

late cretaceous to oligocene burial and collision in western papua new guinea indications from low temperature thermochronology and thermal modelling abstract recent field and analytical work have considerably improved our understanding of the structure of the muller range along the frontal trend of the papuan fold and thrust belt pftb in western papua new guinea png however numerous questions remain unresolved concerning the geological evolution of the region in particular the late cretaceous to oligocene history of the region is largely unknown due to the absence of a continuous stratigraphic record here we use both new and existing low temperature thermochronology data to investigate the geological history of the muller range thermal history models based on these data suggest two major cenozoic cooling episodes the youngest and best constrained is clearly recorded in the stratigraphic record and relates to neogene collision at the northern margin of the australian continent an older episode of comparable or greater magnitude occurred in the eocene to oligocene and may relate to the removal of 1500 3000 m of late cretaceous to eocene section across the muller range prior to the widespread deposition of the shelfal darai limestone we suggest that extension along major faults beneath the muller range accommodated sedimentation from the late cretaceous to the eocene consistent with long lived extensional structures observed in neighbouring regions in contrast to the muller range area an almost continuous late cretaceous to eocene stratigraphic sequence is preserved in the hinterland

northern new guinea wrench fault system a manifestation of late cenozoic interactions between australian and pacific plates abstract cenozoic plate interactions between the australian and pacific plates have yielded a variety of convergent tectonic styles two major products of this convergence are the sorong fault zone of irian jaya and the ramu markham fault zone of papua the sorong fault system has been documented to extend westward more than 500 mi 800 km from teluk sarera to kep banggai as a left lateral strike slip fault the ramu markham fault system is of disputed displacement and has been previously interpreted to extend from over 310 mi 500 km just east of the sepik river into the huon gulf a consideration of australian pacific cenozoic plate kinematics holocene vectors earthquake focal mechanisms photogeologic lineation analyses and the assimilation of other pertinent geologic data suggests that the ramu markham fault zone is an extension of the sorong fault system and that together they represent significant left lateral strike slip motion in rigid crustal basement this motion has produced large scale en echelon surface expressed faults and folds in detached overlying neogene sediments furthermore this wrench fault system has led to the transcompressional development and deformation of the meervlakt piore sepik and ramu basins of northern new guinea an understanding of the tectonic evolution of these basins is tantamount to an assessment of their evolving hy rocarbon potential end of article last page 980

incorporation of the effect of concentration of flow into the kinematic wave equations and its applications to runoff system lumping abstract the usual kinematic wave equations are revised to consider the interaction between surface flow and subsurface flow in mountainous watersheds having curved surfaces covered with a layers of uniform thickness a function which represents watershed surface geometry which is called the geometric pattern function in the paper is incorporated into the basic equations of the kinematic wave model and the depth flow relation equation for the surface subsurface flow system is derived when the watershed surface is linearly converging or diverging its geometric pattern function has a linear form and numerical simulations for such cases are given here if the geometric pattern function is regarded as a new parameter of the kinematic wave model then the kinematic wave flow model becomes very flexible in fact when the lateral inflow is spatially uniform the model may be used as a simple model of a stream network system using this simplified model a method of transformation of the kinematic wave flow model of a stream system into a lumped runoff model which we call a reservoir cascade model is developed

a distributed slope stability model for steep forested basins a distributed physically based slope stability model dslam based on an infinite slope model a kinematic wave groundwater model and a continuous change vegetation root strength model is presented it is integrated with a contour line based topographic analysis and a geographic information system gis for spatial data extraction and display the model can be run with either individual rainfall events or long term sequences of storms these inputs can be either actual storm records or synthesized random events based on monte carlo simulation the model is designed to analyze rapid shallow landslides and the spatial distribution of safety factor fs in steep forested areas it can investigate the slope stability problem in both temporal and spatial dimensions for example the impact of timber harvesting on slope stability either at a given time or through an extended management period the probability of landslide occurrence for a given year and the delivery of landslide sediments to headwater streams the dslam model was applied in a steep forested drainage of cedar creek in the oregon coast ranges using actual spatial patterns of timber harvesting and measured rainfall during a major storm which triggered widespread landslides in that area in 1975 simulated volume and number of failures were 733 m3 and 4 respectively these values agreed closely with field measurements following the 1975 storm however the effect of parameter uncertainty may complicate this comparison for example when soil cohesion values of 2 0 and 3 0 kpa were used the failure volume changed by factors of 2 04 and 0 41 respectively compared with the average condition of 2 5 kpa used in the simulation for soil depths 30 higher and lower than the standard condition the failure volume changed by factors of 2 0 and 0 27 respectively when maximum root cohesion changed from 12 5 kpa average condition to 10 kpa the failure volume increased 1 73 fold for the case of 15 kpa the failure volume changed by a factor of 0 55 the simulated failures caused by the storm were mostly in hollows the simulations show that the spatial distribution of fs is controlled mainly by topography and timber harvesting patterns and is greatly affected by groundwater flow patterns during major rainstorms most areas with fs 3 0 corresponded with the distribution of blocks clear cut in 1968 and all elements with fs 2 0 were in areas clear cut in 1968 areas with low fs 1 0 1 6 expanded dramatically during the rainstorm and decreased at a slow rate after the storm factors of safety in hollows declined sharply during the storm

kinematic subsurface stormflow this paper builds on the analysis of henderson and wooding 1964 in comparing simplified models of subsurface stormflow for the case of a sloping soil mantle in which the hydraulic conductivity is constant throughout it is shown that models based on a kinematic wave formulation may be good approximations for those based on the extended dupuit forchheimier assumptions for values of the nondimensional parameter 4i cos k sin2 less than about 0 75 in terms of predicting both water table profiles and subsurface stormflow hydrographs by using this critical value of the range of values of slope angle and saturated hydraulic conductivity for which the kinematic approximation is valid can be specified a comparison is made with slope angles and hydraulic conductivities at field sites where subsurface stormflow has been shown to be an important component of catchment storm response it is concluded that the kinematic approximation may be useful for cases of practical interest

predicting deposition of debris flows in mountain channels an empirical model for predicting deposition of coarse textured debris flows in confined mountain channels is developed based on field measurements of 14 debris flows in the pacific northwest u s a the model uses two criteria for deposition channel slope less than 3 5 and tributary junction angle greater than 70 the model is tested by predicting travel distances of 15 debris flows in the oregon coast range and six debris flows in the washington cascades u s a the model is further tested on 44 debris flows in two lithological types in the oregon coast range using aerial photos and topographic maps on these flows only the approximate travel distance is known the model can be used by resource professionals to identify the potential for impacts from debris flows key words debris flow deposition travel erosion

analysis of a small debris slide in coastal alaska on october 1 1980 a moderately intense storm at trap bay alaska triggered a small debris slide in a forested midslope depression that was instrumented to record the maximum piezometric rise although the return period for the storm was 2 years 54 3 68 cm of the total rain fell during the final 3 h causing the soil mantle to become nearly saturated this resulted in an average maximum pore water pressure of 2 2 kpa at the sliding surface causing failure analysis of the mechanics of the failure showed that an apparent cohesion of 2 0 kpa probably due to rooting strength was acting on the 43 hillslope calculated factors of safety for such thin partially saturated soils are very sensitive to small changes in apparent cohesion and should be used with caution on such sites

rifting of the northern margin of the australian continent and the origin of some microcontinents in eastern indonesia abstract continental australia is bounded on the east south and west sides by passive margins and the geological histories of these are well documented falvey and mutter 1981 the northern margin of the australian continent is now an active collision margin its previous history as a passive margin has rarely been examined this paper shows how the late palaeozoic to mesozoic sequence which forms the northern margin of the australian continent in the island of new guinea is readily related to the tectonic stages of a rift drift sequence rifting start of breakup began at about 230 m y ago at the permian triassic boundary the onset of seafloor spreading is marked by a post breakup unconformity and ranges in age along the northern margin of the continent from 185 m y in papua new guinea to 170 m y in irian jaya from there the age of the post breakup unconformity continues to young in a southwesterly direction along the western margin of the australian continent reflecting the opening of the indian ocean off western australia the timing of the onset of spreading in central papua new guinea is consistent with the timing of the initiation of spreading in the proto pacific ocean proposed by nur and ben avraham 1977 by the end of the jurassic the northern margin of the australian continent faced a seaway which linked the proto indian and proto pacific oceans this newly formed ocean was separated from the pre existing oceans of the neo tethys and panthalassa by a screen of continents or microcontinents the identity of this screen is discussed and it is suggested that part of it is preserved in the microcontinents of eastern indonesia

structure of the alice anticline papua new guinea serial balanced cross sections and their restoration abstract the structure of the western part of the papuan fold belt is characterised by both thin skinned thrusting and basement involved structures basement involvement is attributed to inversion of earlier formed extensional faults the alice anticline is a frontal structure of the papuan fold belt and formed due to inversion of a tertiary extensional fault system complex forelimb geometry of the alice anticline changes markedly along strike and suggests varying amounts of shortening in this part of the structure balanced cross sections quantify differential shortening along the anticline whereas palinspastic restoration shows that the differential shortening is compatible between cross sections three dimensional restoration of the alice anticline makes use of a series of balanced cross sections and is based on a line length method paradoxically the restoration reveals non plane strain in the balanced cross sections upon which it relies however the restoration also reveals and quantifies a component of rotation about vertical axes which would not be detected by application of conventional methods of structural analysis rotations about vertical axes are attributed to pinning of progressive foreland propagating deformation the distribution of rotations about vertical axes suggest that zones of pinning are coincident with relay zones in the early extensional fault geometry two relay zones associated with the original geometry acted as obstructions to deformation and have effectively pinned contractional structures during their formation causing the rotations about vertical axes such rotations are not manifested in changing fold axis orientations and have only been derived from a consideration of material balance during deformation

the structure of mountain fronts commonly the part of a mountain front which is visible at the surface consists of foreland dipping thrust belt rocks elevated above their regional structural position and overlain more or less conformably by molasse several explanations for their geometry are possible 1 major detachments exist within or beneath the molasse resulting in transport of the foreland basin examples of this geometry come from the swiss molasse plain the southern pyrenees and the mackenzie mountains of canada 2 displacement is lost on major backthrusts beneath the frontal monocline examples cited here are the rockies of alberta the sulaiman ranges of pakistan the mackenzies and the andes in peru 3 thrust sheets travelled over an old land surface and syntectonic molasse contemporaneously offlaps the topographic high of the thrust front this phenomenon occurs along the alpine thrust front in haute provence 4 the frontal fold represents deformation above a large scale thrust tip no unequivocal example of tip line strain at this scale has been recorded although this type of deformation may occur in the brooks range of alaska in many areas mountain fronts show a combination of these idealized geometries

rainfall ground water flow and seasonal movement at minor creek landslide northwestern california physical interpretation of empirical relations simple ground water flow analyses can clarify complex empirical relations between rainfall and landslide motion here we present detailed data on rainfall ground water flow and repetitive seasonal motion that occurred from 1982 to 1985 at minor creek landslide in northwestern california and we interpret these data in the context of physically based theories we find that landslide motion is closely regulated by the direction and magnitude of near surface hydraulic gradients and by waves of pore pressure caused by intermittent rainfall diffusive propagation of pore pressure waves accompanies downward ground water flow along nearly vertical hydraulic gradients that exist in most of the landslide field data combined with a pore pressure diffusion analysis show that single rainstorms typically produce short period waves that attenuate before reaching the landslide base in contrast seasonal rainfall cycles produce long period waves that modify basal pore pressures but only after time lags that range from weeks to months such tune lags can depend on antecedent moisture storage and can explain variable delays between the onset of the wet season and seasonal landslide motion limit equilibrium analysis shows that when seasonal pressure waves reach the landslide base they establish a critical distribution of effective stress that delicately triggers landslide motion the critical effective stress balance is extremely sensitive to the direction and magnitude of hydraulic gradients although pervasively downward gradients instigate seasonal motion we infer from theory and limited data that ground water also may circulate locally in near surface cells the circulation can further reduce the landslide s frictional strength particularly in areas of nearly horizontal ground water flow that occur beneath steep faces of hummocks hummocky topography that results from slope instability may therefore cause ground water flow that perpetuates instability

sediment transport capacity of sheet and rill flow application of unit stream power theory theoretical equations for calculating the unit stream power of both sheet and rill flow were developed and used to predict the sediment transport capacity of such flows independent data sets from three sources representing both finely aggregated clay soils and coarse textured nonaggregated soils sheet rill and composite sheet rill flow systems and a range of slopes were used to test the utility of the method the results were very good and demonstrated the simplicity and robustness of the method for shallow overland flow the best results were obtained when the critical unit stream power at incipient sediment motion was treated as a constant value that was independent of slope the results also suggest that a unique value of critical unit stream power for rill initiation exists that is independent of soil type for noncohesive loams or fine sands and finely aggregated clay soils the sediment transport capacity can be accurately predicted from a knowledge of the physical characteristics of the soil or bed material alone for aggregated clay soils this requires information on the aggregate size distribution and the effects of soil particle size differentiation as flow rates and unit stream powers increase with the transition from sheet to rill flow

structure of the irian jaya mobile belt irian jaya indonesia image interpretation and field investigation over the central ranges of irian jaya has provided a structural overview of the inaccessible and largely unmapped irian jaya mobile belt ijmb in the region bounded by longitudes 136 30 e and 141 00 e throughout much of the southern para autochthonous part of the belt structural facing directions are visible on imagery through selective illumination of hogbacks and cuestas formed on thick bedded mesozoic siliciclastics and extensive late cretaceous neogene platform carbonate sequences north of the regional derewo fault zone the derewo metamorphics are regarded in part as correlatives of the metamorphosed om beds in western papua new guinea and display a regional structural grain parallel to the orogen the limited extent of spectrally anomalous features associated with ultramafic rocks indicate that ophiolites are confined to the southern part of the irian jaya ophiolite belt which may be largely composed of metamorphic rocks interpreted macroscopic and megascopic structures suggest the presence of seven discrete structural domains in the ijmb from north to south these are 1 north coast basin region consisting of paleogene neogene volcanics and sediments overlain by a pliocene pleistocene successor basin sequence 2 an allochthonous terrane composed of ophiolites and high grade metamorphic rocks 3 the derewo metamorphic assemblage displaying polyphase deformation 4 a complex marginal zone within mesozoic paleogene miogeoclinal sediments which includes steep duplex structures and remnant klippen 5 a 40 to 50 km wide partly inverted synclinorium composed of miogeoclinal sediments 6 a regional south vergent overturned anticlinorium formed by incompetent paleozoic sediments and 7 a foreland thrust domain involving both mesozoic cenozoic miogeoclinal cover and a deformed neogene foreland molasse basin sequence the regional disposition of interpreted structures in the irian jaya mobile belt and reference to published mapping in western irian jaya and western papua new guinea strongly indicates polyphase deformation late oligocene miocene docking of metamorphics island arc assemblages and ophiolites produced tectonically stacked e w trending structures thrust on to the north margin of the australian continent with its miogeoclinal cover late miocene pliocene collision with the melanesian arc brought the accreted australian margin into contact with the westward moving pacific plate and instituted a regime of oblique transpressional convergence resulting structures include e w sinistral wrenching and nw thrusts along lateral e w ramps

passive roof duplex geometry in the frontal structures of the kirthar and sulaiman mountain belts pakistan abstract exploration for hydrocarbons over the past few years has greatly improved our understanding of the geometry of frontal mountain belt structures in this study we introduce and discuss the concept of the passive roof duplex using as the main example the kirthar and sulaiman ranges in the baluchistan province of pakistan structures similar to those described here have been recognized previously in other mountain belts and they appear to exist as a common feature in many more frontal regions of mountain belts our example of a passive roof duplex which we describe from pakistan is compared briefly with similar structures reported by others the passive roof duplex is here defined as a duplex whose roof thrust has backthrust sense passive roof thrust and whose roof sequence those rocks lying above the roof thrust remains relatively stationary during foreland directed piggy back style propagation of horses within the duplex