cause of dominance by sheetflood vs debris flow processes on two adjoining alluvial fans death valley california two large adjoining alluvial fans of the panamint range piedmont death valley california are composed of different facies assemblages deposited by contrasting sedimentary processes the anvil spring fan was built solely by water flow processes incised channel floods and sheetfloods whereas the neighbouring warm spring fan has been constructed principally by debris flows the boundary between these fans delineates a sharp provincial piedmont contact between sheetflood dominated fans to the south and debris flow dominated fans to the north factors such as climate catchment area fan area catchment relief aspect vegetation types and density and neotectonic setting are essentially identical for these two fans the key difference between them is that their catchments are underlain by dissimilar bedrock types which weather to yield distinctive sediment suites weathering of the granite and andesite of the anvil fan catchment produces significant volumes of medium to very coarse sand granules pebbles cobbles and boulders but minimal silt and clay in contrast the shale quartzite and dolomite that dominate bedrock in the warm spring catchment weather to yield a wide suite of sedimentary particles spanning from clay to boulders the abundance of mud and the unsorted character of the yielded sediment cause precipitation induced slope failures in the warm spring catchment to transform readily into debris flows this propensity is due to the low permeability of the colluvial sediment which causes added water to become trapped quickly and pore pressure to rise rapidly promoting transformations to debris flows in contrast the limited volume of sediment finer than medium sand yielded from the anvil fan catchment causes the colluvium to have high permeability this factor prevents the transformation of wet colluvium to a debris flow during hydrologically triggered slope failures instead maintaining sediment transport as entrained bed load or suspended load in a water flow

circulation in the algerian basin during june 1986 hydrographic measurements made in the algerian basin during june 1986 as part of the western mediterranean circulation experiment together with satellite infrared images are used to describe the flow of major water types in the region modified atlantic water flows eastward along the algerian coast as the algerian current to 4 e where it breaks into a series of eddies and spreads far offshore it then flows partly northward into the ligurian provencal basin and partly eastward through the strait of sardinia the subsurface levantine intermediate water turns sharply northward after flowing westward through the strait of sardinia and forms a narrow vein along the sardinian coast winter intermediate water flows southward around the balearic islands its eastern branch recirculates back to the north whereas part of the western branch contributes to the algerian current by flowing eastward beneath the modified atlantic water two large long lived eddies are confirmed in the area the easternmost of these and other features with unresolved horizontal structure between sardinia and menorca extend from the surface through the pycnocline

alluvial fan deposition along a rift depocentre border from the neuquen basin argentina the interaction between hangingwall block rotation and alluvial deposition is examined from late triassic early jurassic successions exposed along the catan lil half graben border fault system in the neuquen basin argentina analysis of transport and depositional processes clast composition and rock body geometry allowed the identification of three distinctive fan shaped alluvial units the contrasting lithologic nature of the basement igneous metamorphic and syn rift fill volcanic and volcanic derived permits detailed studies of clast provenance the origin of each alluvial system footwall vs hangingwall derived can thus be verified a simple method was implemented to establish the geometry of each alluvial unit by comparing the stereographic projection of its bedding to that of an idealised fan shaped body results show that the three alluvial systems occupied the same relative location in the rift depocentre unit 1 is interpreted as an alluvial fan orientated transverse to the depocentre border fault system and fed from the footwall non cohesive debris flow deposition was the dominant process in this environment unit 2 is interpreted as a mainly hangingwall fed alluvial fan parallel to the depocentre border fault system and shows an upward decrease in footwall derived clasts hyperconcentrated flow was the principal transport process unit 3 represents a fan delta parallel to the depocentre border fault system its components are completely hangingwall derived and hyperconcentrated flow deposition was the dominant process differences in grain size composition transport directions and fan body geometry are proved to be directly linked to variations in ground tilting induced by the direction of hangingwall block rotation in an endorheic rift depocentre

spectral characterization of igneous rocks in the 8 to 12 μm region variation in the spectral response of silicates in the thermal infrared tir from 8 to 12 m is the foundation for potentially important applications in the lithologic characterization of terrestrial and extraterrestrial surfaces the purpose of this study is to elucidate the crystallo chemical basis for the variation in spectral behavior in terms which may be useful in remote sensing this has led to the definition of a new parameter scfm which is defined as the ratio sio2 sio2 cao feo mgo in minerals and rocks this parameter reflects the degree of depolymerization of the silica tetrahedra and is therefore highly correlated with the structure of tir reflectance spectra of major silicate minerals in both fine and coarse grained igneous rocks it is also a good numerical descriptor of igneous rock composition thus scfm is proposed as a very useful determinant for spectral identification of igneous rocks the scfm parameter was used to assess the effect of variations in location number and width of bands in discriminating rock composition an unfortunate ambiguity exists in the use of the term band which in spectroscopy indicates a feature in a spectrum and in remote sensing signifies a specific wavelength increment or channel the latter definition is used in this paper spectra of coarse particulate mineral and solid rock samples were acquired in the laboratory a regression analysis of bands varying in width from 0 2 to 1 4 m versus scfm results in coefficients of determination correlation coefficients r2 ranging from 0 88 for two 1 2 m wide bands to 0 97 for seven 0 2 m wide bands deletion of bands in the ozone absorption region 9 4 10 2 m results in a decrease in r2 by only 0 01 stimulation of system noise by addition of 5 random counts to the bands decreases r2 by only 0 03 because spectra structure is modified by weathering alteration and texture of the samples the validity of these results is limited to fresh igneous rocks with this constraint it is concluded that accurate spectral identification of igneous rock composition is not greatly affected by bandwidth or system noise it is the overall spectral envelope rather than the fine structure in the tir which contains most of the information diagnostic of igneous rock composition this permits design of remote sensing systems with broad bands and corresponding higher signal to noise which can be traded off against the important requirement for higher spatial resolution

the trollheim alluvial fan and facies model revisited widely held fundamental alluvial fan facies concepts generated in past literature based on the trollheim fan deep springs valley california are inconsistent with the actual characteristics of this fan previous publications have established mostly without field study that the trollheim fan consists of debris flow sieve lobe sheetflood and channel facies debris flow and sieve deposits comprise the proximal area giving way to channel or sheetflood deposits distally contrary to these views clayey and gravelly matrix supported debris flow deposits dominate all parts of the trollheim exposures suggesting that this fan has been built almost exclusively by mass wasting events channel fill deposits constitute only a small component of the fan and most are restricted to the proximal area where they have an inset relationship with debris flow sequences the channel facies consists of laterally restricted clast supported gravel lenses formed primarily through the winnowing of debris flow fines by streamflow the most widespread facies on the surface of the fan is a mantle of varnished matrix free pebbles cobbles and boulders that commonly are distributed in radially oriented lobes or levees characteristic of debris flow deposits this mantle was produced by the surficial winnowing of the fine fraction from debris flow deposits primarily by overland water flow in contrast to previous conclusions sheetflood and sieve deposits were not identified anywhere on the fan additionally many of the facies depicted in the widely cited trollheim vertical profile including ripple bedded sand cross bedded sand and overbank mud are not present on or in stratigraphic cuts of the fan after which the profile was named

close range ground based hyperspectral imaging for mining applications at various scales review and case studies abstract detailed mapping of mineral phases at centimeter scale can be useful for geological investigation including resource exploration this work reviews case histories of ground based close range hyperspectral imaging for mining applications studies of various economic deposits are discussed as well as techniques used for data correction integration with other datasets and validation of spectral mapping results using geochemical techniques machine learning algorithms suggested for automation of the mining workflow are reviewed as well as systems for environmental monitoring such as gas leak detection three new case studies that use a ground based hyperspectral scanning system with sensors collecting data in the visible near infrared and short wave infrared portions of the electromagnetic spectrum in active and abandoned mines are presented vertical exposures in a carlin style sediment hosted gold deposit an active cu au mo mine and an active asphalt quarry are studied to produce images that delineate the extent of alteration minerals at centimeter scale to demonstrate an efficient method of outcrop characterization which increases understanding of petrogenesis for mining applications in the carlin style gold deposit clay iron oxide carbonate and jarosite minerals were mapped in the copper porphyry deposit different phases of alteration are delineated some of which correspond to greater occurrence of ore deposits a limestone quarry was also imaged which contains bitumen deposits used for road paving aggregate review of current literature suggests use of this technology for automation of mining activities thus reducing physical risk for workers in evaluating vertical mine faces

temporal variability of currents in the eastern ligurian sea surface and intermediate waters enter the ligurian sea from the tyrrhenian and algero provencal basins via northward flows along the east and west coasts of corsica the temporal variability of these flows is examined by means of a 1 year time series of current data october 1986 to september 1987 and hydrographic data from december march and may cruises the flow through the corsica channel increases suddenly during december and then gradually decreases after march reaching its lowest values in late summer the seasonal variability in the channel seems associated mainly with the steric sea level differences between the tyrrhenian sea and ligurian sea the west corsican current appears more stable throughout the one year of data the two flows converge just north of corsica into the ligurian current because of the water masses differences between the two currents in the area of convergence considerable smaller scaled structure is observed during winter the less dense tyrrhenian water provides available potential energy to the ligurian shelf area and thereby helps sustain the large scale cyclonic circulation in the ligurian basin during the other seasons the spatial structures over the ligurian shelf are less organized and the spatial scale of the flow is a few tens of kilometers

integration of seismic and sedimentological methods for analysis of quaternary alluvial depositional systems due to the high potential of unconsolidated sedimentary bodies to form aquifers and reservoirs an identification of their exact geometry and location is of great importance current conceptual models of these bodies are often developed using scattered data from hydrogeological wells more reliable results can be achieved by application of methods that can provide continuous subsurface record of the actual geological situation in the investigated area in this article a combination of two different approaches is used on a case study of alluvial quaternary sediments from the east slovakian basin including the discussion how these methods contribute to the final geological interpretation first a sedimentological analysis was performed with the use of data acquired from auger drilled hydrogeological wells which enabled identification of depositional processes depositional systems and the possible source areas due to the shallow depth of the studied area a second approach based on the geophysical measurement using seismic refraction and tomography was applied this method provided information mainly about the geometry of these systems the position of the sediments within them and highlighted where the main changes in the sediment texture and composition occurred integration of both methods allows us to obtain a more precise image of the subsurface which contributes to a better understanding and prediction of the occurring sediments in the studied area

tectonics and sedimentation in the fohnsdorf seckau basin miocene austria from a pull apart basin to a half graben the miocene intramontane fohnsdorf seckau basin is situated at the junction of the sinistral mur murz fault system and the dextral pols lavanttal fault system the basin comprises a 2 400 m thick coal bearing fluviodeltaic lacustrine succession lower to middle miocene upper karpatian lower badenian which is overlain by a 1 000 m thick alluvio deltaic conglomeratic succession apfelberg formation middle upper badenian in the south a three stage model for the basin evolution has been reconstructed from structural analysis and basin fill geometries during a first pull apart phase subsidence occurred along ene trending sinistral strike slip faults of the mur murz fault system and ne sw to n s trending normal faults forming a composite pull apart basin between overstepping en echelon strike slip faults the seckau and fohnsdorf sub basins are considered as two adjacent pull aparts which merged into one basin during the second phase n s to nnw sse extension and normal faulting along the southern basin margin fault formed a half graben filled by wedge shaped alluvial strata apfelberg formation during the third phase after the end of basin sedimentation the dextral pols lavanttal fault system reshaped the western basin margin into a positive flower structure

characterizing kimberlite dilution by crustal rocks at the snap lake diamond mine northwest territories canada using swir 1 90 2 36 μm and lwir 8 1 11 1 μm hyperspectral imagery collected from drill core short wave infrared swir 1 90 2 36 m and long wave infrared lwir 8 1 11 1 m hyperspectral images collected using the sisurock system were used to develop an automated methodology for generating kimberlite dilution maps smoothed and denoised images from two snap lake northwest territories canada kimberlite drill cores were processed and swir and lwir spectral endmembers were extracted from the images with each mineralogical endmember assigned to one of four compositional groups undiluted kimberlite microdiluted kimberlite micro and macrodiluted kimberlite and crustal rocks these endmembers were used to classify the swir and lwir images and the results were validated using linescan data drill core logs petrology reports and the results of x ray diffraction raman spectroscopy and micro fourier transform infrared ftir spectroscopy this study demonstrates that hyperspectral imagery can be used to generate dilution maps for hypabyssal kimberlites that far supersede other current techniques in terms of spatial resolution

hyperspectral imaging of drill core from the steen river impact structure canada implications for hydrothermal activity and formation of suevite like breccias

pleistocene debris flow deposition of the hippopotamus bearing collecurti bonebed macerata central italy taphonomic and paleoenvironmental analysis abstract an integrated taphonomic sedimentological study provides insight into the origin preservation biases and paleobiological significance of the latest early earliest middle pleistocene bonebed of collecurti near colfiorito macerata central italy which represents an important benchmark in the european biochronological scale sedimentological evidence indicates that the bonebed is hosted in a debris flow deposit which was emplaced in a shallow lacustrine setting geologic and geomorphic controls on sedimentation in the intermontane colfiorito basin provided an ideal setting for the development of cohesive mass flows due to high relief and poorly integrated catchments along the basin margin and the abundance of detrital fines yielded by mesozoic sedimentary rocks of the local basement the fossil assemblage includes 496 bones with a minimum of 24 individuals representing 9 species and 8 genera dominated by hippopotamus antiquus the hippopotamus remains include partially articulated carcass parts as well as closely associated elements few disarticulated elements which are bones that can be more easily transported hydraulically were involved in pre debris flow winnowing and sorting and then entrained by the debris flows in nearby uplands transported a short distance down into a shallow pond or lake margin where the flow buried hippopotamus carcasses that had accumulated in the pond lake the hippopotamus carcasses were in an advanced state of decomposition when the debris flow entrained them their bones show no evidence of weathering trampling scavenging sorting or transportation prior to debris flow reworking which indicates that the animals were probably lying on the bottom of the pond where they lived or were already partially buried in mud previous palynological investigations have shown that the strata of interest at collecurti were deposited during a climatic trend toward ever increasing cooler conditions the low richness of the fauna confirms long exposure to harsh climatic and environmental conditions two are the plausible causes of the death of the collecurti animals i e severe cold and or drought taphonomic attributes rule out drought indicating that the assemblage accumulated in a short time as the result of a mass mortality event possibly due to a cold snap there are no other reported examples of quaternary debris flow hosted bonebeds in europe probably because this agent of taphonomic accumulation is rarely investigated in high energy paleogeomorphic settings it is likely that more such sedimentary events took place in the area and that similar fossil sites await to be discovered

the neogene fohnsdorf basin basin formation and basin inversion during lateral extrusion in the eastern alps austria the evolution of the early middle miocene fohnsdorf basin has been studied using borehole data reflection seismic lines and vitrinite reflectance the basin is located along the sinistral mur murz fault system and probably formed as an asymmetric pull apart basin which was subsequently modified by halfgraben tectonics as a consequence of eastward lateral extrusion sedimentation started with the deposition of fluvio deltaic sediments thick coal accumulated in the northwestern basin thereafter subsidence rates increased dramatically with the formation of a lake several hundred meters deep the lake was filled mainly from the north with more than 1500 m of sediments showing a coarsening upward trend due to southward prograding deltaic lobes a sequence of more than 1000 m of boulder gravels blockschotter in the southeastern part of the basin are interpreted as the upper part of a coarse grained fan delta succession which accumulated along a normal fault along the southern basin margin fan deltas reached the central basin only during the early stages of sedimentation and during the late stages of basin formation miocene heat flow was approximately 65 70 mw m2 which is significantly lower than in other basins along the mur murz fault system the present day southwestern basin margin is a recent feature which is related to transpression along the dextral pols lavanttal fault system it is formed by reverse faults constituting the northeastern part of a flower structure miocene sediments in the feeberg valley are preserved along its southwestern part uplift of the central part of the flower structure was at least 2 4 km north south compression resulted in the deformation of the basin fill uplift of the e w trending basement ridge separating the fohnsdorf and seckau basins and in the erosion of 1750 m of sediments along the northern basin margin

near infrared spectra of muscovite tschermak substitution and metamorphic reaction progress implications for remote sensing near infrared nir spectra of precambrian metagraywacke in the black hills south dakota demonstrate that reflectance spectroscopy can be used to monitor progressive changes in mineral chemistry as a function of metamorphic grade the wavelength of a combination al o h absorption band in muscovite measured using both laboratory and field portable nir spectrometers shifts from 2217 nm in the biotite zone to 2199 nm in the sillimanite k feldspar zone the band shift corresponds to an increase in the al vi content of muscovite determined by electron microprobe and is thus a monitor of al 2 si 1 fe mg 1 tschermak exchange spectroscopic measurements such as these are useful in the case of aluminum deficient rocks which lack metamorphic index minerals or appropriate assemblages for thermobarometric studies and in low grade rocks subgarnet zone which lack quantitative indicators of metamorphic grade and are too fine grained for petrographic or microprobe studies more important spectroscopic detection of mineral chemical variations in metamorphic rocks provides petrologists with a tool to recover information on metamorphic reaction histories from high spectral resolution aircraft or satellite remote sensing data

debris flow deposits in alluvial fans on the west flank of the white mountains owens valley california u s a abstract sections measured in incised channels on 10 alluvial fans show that debris flow beds mostly 30 200 cm thick are more important than stream flow deposits in construction of fans along the west flank of the white mountains the debris flow beds have a matrix supported fabric with a sandy mud matrix that comprises about 40 of individual beds complete grain size analyses of 19 debris flow beds show that they average 50 gravel 25 sand 11 silt and 4 clay inverse grading at the base of most beds is interpreted as due to a layer of high shear stress beneath an overlying semi rigid high strength plug that supported cobbles and boulders sticks and logs embedded in the plugs are oriented parallel with flow directions reflecting the laminar viscous motion of the plugs in the shear layer the average inclination of discoidal clasts is subhorizontal varying from 2 to 7 in the up flow direction in the plugs discoidal clasts have a subhorizontal fabric with average dips of 5 13 compared to the shear layer plugs have more scatter in clast orientation with numerous clasts dipping at 60 90 levees along the margins of debris flow lobes contain concentrations of the larger clasts in the flows in the leeves discoidal clasts have an average up flow dip of 21 31 with substantial variability in orientation similar to the plugs maximum clast size in individual debris flow beds is fairly constant down fan until the flows spread and thinned on the sandflat at the fan toe clast lithologies show that debris flows originate on steep slopes underlain by granitic and metavolcanic rocks at high elevations in the canyons in contrast stream flows obtained most of their clasts from talus slopes on metasedimentary rocks near the apices of the fans debris flows are generated during intense rainstorms in the spring and summer when landslides in the water saturated regolith move down slope shear dilate and by adding water are transformed into debris flows which then move with surging laminar motion along canyon flows to the fans the recurrence interval for debris flows is about 320 years as evidenced by 14c dates on plant material buried beneath debris flow beds

evolution of lacustrine systems along the miocene mur murz fault system eastern alps austria and implications on source rocks in pull apart basins tectonically controlled lakes developed during miocene lateral extrusion of the eastern alps mineralogy and the inorganic and organic geochemistry of rocks from three boreholes were investigated to reconstruct the evolution of lake ingering and lake groisenbach and to study the distribution of source rocks in pull apart basins gas prone coal and oil prone sapropelic shale accumulated during the initial shallow stages of lake ingering thereafter the lake deepened rapidly 125 m thick prodelta shale containing a type ii kerogen was deposited in the brackish several hundred meter deep hydrologically closed lake afterwards decreasing subsidence allowed the filling of the lake by prograding deltas during the advance of the deltaic systems the lake became shallower hydrologically open and the brackish influence terminated source rock quality decreased significantly during the filling stage of the lake a consequence of dilution of autochthonous organic matter and of enhanced input of land plants despite its considerable dimensions formation and filling of lake ingering lasted only two million years lake groisenbach was considerably smaller and more susceptible to high frequency changes in lake chemistry although the water body was temporarily oligosaline brackish conditions did not occur high sulphur contents were due to anoxic events and the inflow of ca rich waters abundant dissolved silica favoured diatoms blooms

inferring total organic carbon and major element geochemical and mineralogical characteristics of shale core from hyperspectral imagery hyperspectral systems that image drill core can capture detail mineralogical information at the millimeter scale and thus have the potential to enable investigators to characterize shale composition and heterogeneity complementing the direct chemical and x ray diffraction analysis of core samples and guiding detailed sampling this method provides insight into petrophysical and geomechanical properties because these properties are significantly correlated to rock composition we tested this approach on a continuous long core from the shale sequence of the horn river group in the horn river basin british columbia sampled at a spacing of 1 m 40 in and analyzed for geochemical composition these data enable the calibration of spectral imagery to rock composition and specifically predict total organic carbon toc and the abundance of sio2 al2o3 k2o and cao we then imaged nine samples from the woodford shale from the permian basin texas for a blind test to assess the predictive models the models were then used to predict toc and geochemical data over detailed imagery of 300 m 984 ft of horn river group shale core and portray their spatial variability downhole as images and profiles in its simplest form hyperspectral imagery can be enhanced to highlight fabric in shale core that otherwise is difficult to visualize because of low brightness in addition we show that spectral imagery of shale can also be processed to either convey mineralogical quartz clay and carbonate or geochemical information the resulting views can readily be used to guide the selection of samples and may provide tools for scaling reservoir properties from individual plugs to reservoir volumes

facies and depositional model of alluvial fan dominated by episodic flood events in arid conditions an example from the quaternary poplar fan north western china

source area and tectonic control on alluvial fan development in the miocene fohnsdorf intramontane basin austria middle miocene alluvial fans in the intramontane fohnsdorf basin of the eastern alps originated along normal faults and linked strike slip faults in a continental half graben setting the fans display considerable facies differences debris flows of the rachau fan are characterized by a sandy matrix and large boulders whereas debris flows of the apfelberg fan are characterized by higher silt and clay content and smaller clasts key control of debris flow facies is the lithology contrast in the fan source areas sand pebbles and large outsized boulders originated predominantly from the resistant augengneissand amphibolite dominated hinterland of the rachau fan whereas a significant higher proportion of mud and silt and smaller boulders have been derived from the apfelberg fan catchment which was dominated by mica schists and marble from harvey a m mather a e stokes m eds 2005 alluvial fans geomorphology sedimentology dynamics geological society london special publications 251 207 216 0305 8719 05 15 the geological society of

stratigraphic architecture and quaternary evolution of the val d agri intermontane basin southern apennines italy abstract the sedimentary record of the val d agri basin is of great importance for understanding the quaternary tectonic activity and climatic variability in the southern apennines changes in tectonic controls sediment supply and climatic input have been identified the interval from 56 to 43 ka was associated with asymmetric subsidence restricted to the north eastern actively faulted margin of the basin and development of axial braided river and transverse alluvial fan systems short lasting mediterranean type pedogenesis between 43 and 32 ka mis stage 3 coexisted with progradation aggradation of the southern alluvial fan deposits and southwards tilting of the basin floor aggradation ended with consumption of accommodation space after 32 ka during a subsequent stage of decline of vegetation cover possibly as a consequence of climatic cooling probably mis stage 2 active progradation of alluvial fans occurred breakthrough of the basin threshold and entrenchment of the drainage network must therefore be attributed to a latest pleistocene to holocene age the first stages of basin opening and fill predating 56 ka have only been inferred by stratigraphic considerations the earliest lacustrine sedimentation should be middle pleistocene or older in age the following south eastward basin widening allowed progradation of alluvial fan systems which completely filled the lacustrine area tentatively late middle pleistocene pedogenesis in mediterranean like climate conditions caused the final development of a highly mature fersiallitic paleosol at the top of the fan surfaces in areas of morpho tectonic stability plausibly during mis stage 5 the study results demonstrate the potential of applying a multidisciplinary approach in an intermontane continental settings marked by a relative rapid and constant tectonic subsidence and a high rate of sediment supply during the pleistocene glacial interglacial cycles

recent debris flow processes and resultant form and facies of the dolomite alluvial fan owens valley california abstract a multiphase debris flow triggered by an afternoon thunderstorm was deposited 22 august 1984 on the dolomite alluvial fan of owens valley california two tracts 10 300 cm thick accumulated during this event together covering 68 000 m2 26 of the fan with 50 000 m3 of sediment both tracts consist of numerous paired boulder rich levees 100 300 cm high on the proximal fan and multiple attached lobes 20 100 cm thick on the distal fan each levee lobe pathway was built by an individual surge with flow path switching caused by clogging of the frontal bouldery snout of the ensuing surge the levees consist of clast supported to matrix supported muddy pebbly cobbly boulder gravel displaying a well developed radially aligned a axis clast fabric the lobes mostly consist of matrix supported muddy pebbly cobble gravel the clast supported lobe margins are enriched in cobbles displaying a strongly preferred slope parallel a axis fabric along the sides that changes to a slope perpendicular fabric at the snout the distal ends of most of the clast rich lobes are overlain and offlapped by clast poor debris flow lobes of granular mud 10 30 cm thick the central zones of the levees and most lobes were surficially washed by recessional stage water flows that moved winnowed granules sand and mud off the fan the radial change from levees in the proximal fan to lobes distally is morphologically expressed as two intersecting slope segments the upper one sloping 9 12 and the lower one 3 5 this direct relationship between the constituent forms and slope values also is characteristic of pre 1984 deposits suggesting that the 1984 event is typical of the primary processes constructing the dolomite fan the pronounced radial change from levees to lobes and its manifestation as a slope inflection was caused by the selective loss on the upper fan of most of the boulders from the passing debris flow surges boulders were sorted from the surges because of their greater buoyancy which caused them to be preferentially concentrated in the part of the flow that subsequently was sheared off as levees this selective boulder removal depleted the flow of the clasts that provided lateral support facilitating flow expansion and the onset of lobe development thus the resultant facies assemblage is a function of the specific sediment grain size suite available in the catchment colluvium and the transport characteristics of this mix when transformed into a debris flow by the rapid addition of heavy rainfall during infrequent thunderstorms

tectonic and hydrologic controls on cyclic alluvial fan fluvial and lacustrine rift basin sedimentation jurassic lowermost cretaceous todos santos formation chiapas mexico abstract the nonmarine upper jurassic lowermost cretaceous todos santos formation of central chiapas mexico was deposited in half graben basins formed during the early rifting stage of the southern gulf of mexico basin this formation consists of alluvial fan fluvial and lacustrine sequences that were deposited under arid climatic conditions alluvial fans were built outwardly from the elongate basin margins by runoff that flowed transverse to the basin axis whereas fluvial units were deposited by rivers that flowed parallel to the basin axis lacustrine deposition took place in a topographic depression adjacent to the basin margin the presence of alluvial fan and fluvial or lacustrine deposits in vertically stacked cyclic megasequences hundreds of meters thick indicates that the basin opography changed through time this cyclicity denotes that periodically fluvial or lacustrine environments occupied the basin margin position and at other times alluvial fan sedimentation occurred there cyclicity was caused by periodic changes from high to low rates of basin subsidene the response of these three depositional environments to basin subsidence differed due to the unique hydrologic controls on sediment transport and deposition in each environment lakes were maintained by springs that emanated from the fractured fault margin and by fluvial discharge fluvial discharge and deposition resulted from precipitation or annual snowmelt anywhere in the river s expansive drainage basin whereas alluvial fan sedimentation occurred only when there was infrequent significant precipi ation in the small drainage basin from which fan sediment was derived as a result of these hydrologic controls the lacustrine or fluvial environments responded more quickly to periods of active tectonic subsidence and migrated over the fans to occupy the basin margin depression aided by a decrease in basin subsidence alluvial fans eventually prograded and displaced the fluvial or lacustrine environments away from the basin margin

oligo miocene alluvial fan evolution at the southern pyrenean thrust front spain oligocene to miocene conglomerate bodies interpreted as alluvial fan deposits are well exposed along the northern margin of the ebro basin in spain the source area was the southern pyrenean thrust front which was tectonically active at that time eleven separate conglomerate bodies have been identified and interpreted as the deposits of individual alluvial fans the smallest alluvial fan deposit is less than 0 8 km radius is about 460 m thick and has a calculated volume of 0 1 km 3 the largest is up to 5 5 km radius is at least 500 m thick and has a calculated volume of over 3 km 3 fan evolution was strongly controlled by the lithologies exposed by erosion of the emergent thrust front the size of the fan bodies was determined by the nature and extent of the bedrock lithologies which were in turn structurally controlled growth structures in the strata are common because deformation continued along the thrust front during fan sedimentation stepwise tectonic reconstructions of one of the alluvial fan conglomerate bodies and the adjacent thrust front suggest that the relief in the hinterland was around 500 m

alluvial fans and fluvial fans at the margins of continental sedimentary basins geomorphic and sedimentological distinction for geo energy exploration and development alluvial fans and fluvial fans are the most common depositional landforms along the margins of continental sedimentary basins their occurrence is determined by the area relief and hydrology of the catchment which ultimately control the relative ratios of sediment v flow discharge and runoff regimes fundamental morphological and process distinctions exist between these two kinds of deposystem which are seen as essentially different facies associations and internal architectures for the corresponding deposits alluvial fans commonly develop over short radial distances hundreds of metres to a few kilometres and are constructed by ephemeral flash flow events that lead to poor organization of the sedimentary facies and overall architecture of the corresponding deposits by contrast fluvial mega fans are fed by proper river systems which aggrade much larger volumes of clastic sediment over distances of up to a few hundred kilometres distinct channel belt and overbank domains are developed with a marked heterogeneity in the distribution of sedimentary facies represented by hierarchically well organized fluvial deposits the general properties of alluvial and fluvial fans reflect the different potentials for the corresponding successions to host economically attractive oil and gas resources and the different approaches required in exploration and prediction

the reflectance spectra of opal a 0 5 25 μm from the taupo volcanic zone spectra that may identify hydrothermal systems on planetary surfaces 1 opal a the main component of siliceous sinters in many terrestrial hydrothermal systems is a hydrated silicate that commonly incorporates silicified microorganisms the detection of opal a on the surface of mars therefore may carry important implications in the search for extraterrestrial life sinters from the discharge apron of ohaaki pool north island new zealand yielded reflectance spectra wavelengths between 0 5 25 m that indicate the presence of absorbed water trapped water and silanol in opal a two classes 1 and 2 of reflectance spectra were detected between the wavelengths of 6 13 m the class 1 spectrum is similar to existing opal spectra and was collected from well consolidated samples that had low porosity the class 2 spectrum is unique when compared to the spectra of other silica polymorphs and was collected from poorly consolidated samples that had high porosity

seismic reflection imaging of thin kimberlite dykes and sills exploration and deposit characterization of the snap lake dyke canada abstract seismic reflection techniques are for the first time used to image a thin diamondiferous kimberlite dyke from subcrop to depths greater than 1300 m exploration for vertical kimberlite pipes generally utilizes potential field techniques that often fail to reveal subhorizontal or shallow dipping intrusions in contrast seismic reflection methods are well suited for imaging targets with this geometry therefore in order to evaluate seismic reflection as a tool for subhorizontal kimberlite dyke sill exploration and mine planning a feasibility study and subsequent seismic survey were undertaken on the diamondiferous snap lake dyke northwest territories canada a substantial drilling program has mapped the dyke as a gently dipping sheet that averages 2 3 m in thickness the detailed structural and composition data available at snap lake provides a unique opportunity to test reflection techniques on a well sampled deposit the feasibility study involved measuring p velocities and densities of cores drilled from the kimberlite and host rocks these data were used to model reflection amplitudes evaluate resolution limitations and determine the acquisition parameters for the reflection survey two 2 d lines were acquired that provide comparative datasets for different sources explosive and vibroseis and ground types land and lake ice in addition the exploration scale survey incorporated high fold 40 260 nominal and long offsets 3260 m the explosive source profile recorded on land yielded a superb image of the dyke from depths of 60 m to more than 1300 m over a lateral distance of 5700 m the seismic image correlates well with adjacent drill hole data and adds considerable detail to the topography of the kimberlite sheet determined by drilling the vibroseis source also imaged the dyke but only when sources and geophones were on land the dyke was not imaged beneath the ice due to reverberation and attenuation effects the frequency response and unusually strong reflection amplitudes from the dyke indicate the importance of tuning effects and multiples for this type of target and acquisition environment apparent correlations between reflection amplitudes and dyke structure e g thickness feathering 3 d geometry suggest that seismic reflection data may be valuable for guiding drilling programs the results demonstrate that in the appropriate situation seismic methods have great potential for use in kimberlite exploration subsurface mapping and detailed imaging for mine development purposes

the use of near infrared spectroscopy to determine the degree of serpentinization of ultramafic rocks visible and near infrared 0 35 to 2 5 m bidirectional reflection spectra were recorded for a suite of particulate samples from mineralogically well characterized serpenatinized ultramafic rocks the reflection spectra typically exhibit well defined minima due to electronic and vibrational processes in the individual mineral constituents the contrast of near infrared spectral features of primary magnesian silicate minerals and secondary hydrous serpentine group minerals can be used to indicate the degree of serpentinization of the rock provided less than about 1 percent of finely divided magnetite is present the effect of magnetite apparent in rocks with more than 50 percent serpentine is to reduce the overall reflectance and the contrast of spectral bands near infrared spectrometry is potentially a rapid and reliable technique for detecting the highly serpentinized rocks which constitute target areas for asbestos exploration

the dachstein paleosurface and the augenstein formation in the northern calcareous alps a mosaic stone in the geomorphological evolution of the eastern alps the central and eastern areas of the northern calcareous alps nca are characterized by remnants of the dachstein paleosurface which formed in late eocene to early oligocene time and is preserved with limited modification on elevated karst plateaus in oligocene time the dachstein paleosurface subsided and was sealed by the augenstein formation a terrestrial succession of conglomerates and sandstones which are only preserved in small remnants on the plateaus some in an autochthonous position thermochronological data suggest a maximum thickness of the augenstein formation of 1 3 km possibly 2 km the age of the augenstein formation is constrained by the overall geological situation as early oligocene to earliest miocene fission track age data support an early oligocene age of the basal parts of the formation the source area of the augenstein formation consisted predominantly of weakly metamorphic paleozoic terrains greywacke zone and equivalents as well as the late carboniferous to scythian siliciclastic base of the nca to the south of the depositional area to the west the augenstein formation interfingered with the tertiary deposits of the inntal sedimentation of the augenstein formation was terminated in early miocene time in the course of the orogenic collapse of the eastern alps the augenstein sediments were eroded and redeposited in the foreland molasse zone from pannonian times 10 ma on the nca and the denuded dachstein surface experienced uplift in several pulses the dachstein paleosurface has been preserved in areas in which thick limestone sequences allowed subsurface erosion by cave formation and thus prevented major surface erosion

sedimentologic and geomorphic variations in storm generated alluvial fans howgill fells northwest england in june 1982 a storm with a return period greater than 100 yr but lasting less than 2 5 hr destabilized hillslopes and produced a suite of geomorphologically and sedimentologically diverse alluvial fans thirteen major fans were deposited at the tributary junctions between small 2 catchments and two north flowing headwater streams of the river lune northwest england storm generated fans spread over or became inset into older stable fans and produced localized vertical accretion of as much as 3 m and lateral accretion of as much as 100 m sedimentary processes operating during deposition involved debris flow transitional flow and streamflow six facies types are recognized on the basis of depositional topography sedimentary texture and fabric and matrix content viscous debris flow d1 dilute debris flow d2 transitional flow t1 fluvial bars and lobes s1 s2 and fluvial sheet gravels s3 regionally streamflow deposition prevails over debris flow deposition and type s3 facies has the greatest areal extent temporal and spatial variations in facies deposition during the storm however resulted from water sediment ratio variations fan deposition involved an early phase of debris flow to transitional flow due to large inputs of sediment from hillslope failures this was followed by a systematic change to more dilute conditions resulting in streamflow deposition and eventually in channel incision a significant amount of geomorphic work and complex variations in sedimentary processes during the storm resulted in part from extensive overland flow and hillslope destabilization discriminant analyses indicate that catchment size channel gradient and percentage of area eroded during the storm controlled whether debris flow or streamflow facies dominated a fan sequence smaller steeper catchments had a greater percentage of the area yielding sediment and are dominanted by debris flows whereas larger catchments produced more runoff resulting in dilution and streamflow the results indicate that the facies sequences and fan entrenchment in the howgill fells which are typically considered products of longer term climatic change or tectonics in other localities are here primarily affected by thresholds related to catchment geomorphology by the type of sediment available and by the position within the storm cell

the mineral chemistry near infrared and mid infrared reflectance spectroscopy of phengite from the olympic dam iocg deposit south australia article i nfo phengite is the main potassic dioctahedral mica identified at the olympic dam iron oxide copper gold iocg deposit south australia where its mineral chemistry is quite variable these differences can be explained by con trasting degrees of hydrothermal alteration in the heavily sericitized ore bearing rocks the phengites display a lower si content a higher al content and a lower mg number than the phengites from the weakly sericitized alter ation halo that surrounds the deposit variations are also observed in the near and mid infrared reflectance spectra collected from phengite bearing rocks in the near infrared high al phengite produces a spectral absorption feature at 2 206 m andthisfeature isdisplacedto2 213 m forlow al phengite inthe mid infrared high al phengite pro duces a strong reflectance peak at 9 59 m whereas this peak is observed at 9 57 mi n the spectra from low al phengite additional peaks were also identified at 10 98 12 22 and 13 33 m these were most intense in the spectra from high al phengite a drill core profile was produced using the results of the spectral analysis that shows the change in phengite mineral chemistry and phengite abundance as a function of depth in general near and mid infrared reflectance spectroscopy can be used to characterize the aluminum content of potassic dioctahedral micas like phengite and this information can be used to infer the degree of sericitic alteration that has occurred as a result of hydrothermal fluid flow

a topographic fingerprint to distinguish alluvial fan formative processes we demonstrate here a topographic fingerprint derived from a 1 m high resolution elevation model dem developed from airborne laser swath mapping alsm that distinguishes between formative processes from surface form in alluvial fans generated through relatively dry debris flows df and those surfaces formed primarily by fluvial sediment transport mf we selected alluvial fans with primarily holocene age surficial deposits along the eastern side of death valley california fans were initially classified in the field into df and mf types largely on the basis of sedimentological characteristics and surface morphometry trend surface analyses were performed on dems of the individual fans in order to remove the long wavelength trends both profile and planimetric from the residual data we found that high resolution surface data distinguishes process information in two ways 1 local relief increases as a function of length scale especially at length scales less than 40 60 m and 2 local relief is significantly higher for debris flow dominated fans than for fluvially dominated fans this fingerprint which is directly related to the dominant surface processes is unavailable from standard 30 m resolution data providing significant support for the acquisition of high quality high resolution data this fingerprint can be used to help calibrate numerical simulations of alluvial fan development and has the potential for similar applications to distinguish between processes of similar landforms on other planetary bodies within our solar system