numerical modelling of sea surface temperature and circulation in the great australian bight abstract the blumberg mellor 3d numerical ocean model was employed to investigate the seasonal cycle of sea surface temperature sst and circulation within the great australian bight gab an idealised representation of the gab was modelled results indicated that a warm water mass could be established within the gab with features comparable to observation due to the application of a positive net heat flux at the surface and forcing from the west to east passage of anticyclonic weather systems these systems had a north south migration representative of the shifting subtropical high pressure ridge over southern australia an anticyclonic gyre was established within the gab as a result of the imposed wind stress which contributed towards the formation of a warm tongue spreading across the gab from west to east and a pool of significantly colder water in the eastern gab the sst distribution was found to be sensitive to the bottom topography and north south gradient of heat flux applied to the model domain intrusion of an external current through the western boundary in winter representing the leeuwin current revealed that warm water associated with the intrusion did not penetrate into the gab to any great distance

residence of ree y th and u in granites and crustal protoliths implications for the chemistry of crustal melts a systematic study with laser ablation icp ms scanning electron microscopy and electron microprobe revealed that 70 95 wt of ree except eu y th and u in granite rocks and crustal protoliths reside within reeythu rich accessories whose nature composition and associations change with the rock aluminosity the accessory assemblage of peraluminous granites migmatites and high grade rocks is composed of monazite xenotime in low ca varieties apatite zircon thorthosilicate uraninite and betafite pyrochlore metaluminous granites have allanite sphene apatite zircon monazite and thorthosilicaie peralkaline granites have aeschinite fergusonite samarskite bastnaesite fluocerite allanite sphene zircon monazite xenotime and th orthosilicate granulite grade garnets are enriched in nd and sm by no less than one order of magnitude with respect to amphibolite grade garnets granulitegrade feldspars are also enriched in lree with respect to amphibolite grade feldspars accessories cause non henrian behaviour of ree y th and u during melt solid partitioning because elevated fractions of monazite xenotime and zircon in common migmatites are included within major minerals their behaviour during anatexis is controlled by that of their host settling curves calculated for a convecting magma show that accessories are too small to settle appreciably being separated from the melt as inclusions within larger minerals biotite has the greatest tendency to include accessories thereby indirectly controlling the geochemistry of ree y th and u we conclude that ree y th and u are unsuitable for petrogenetical modelling of granitoids through equilibrium based trace element fractionation equations

experimental resetting of the u th pb systems in monazite abraded fragments 200 400 m of a large chemically homogeneous and non metamict brazilian monazite crystal characterised by a concordant u pb ages of 474 1 ma 208pb 206pb 19 5 were hydrothermally treated at varying temperatures with solutions of different compositions product monazites were analysed with scanning electron microscope sem electron microprobe emp secondary ion mass spectrometer sims and isotope dilution thermal ionisation mass spectrometer id tims experiments with pure water over a temperature range of 800 1200 c at 700 mpa and durations ranging from 5 to 60 days showed that even at 1200 c any dissolution and recrystallization of new monazite is confined to the outermost surface of the grain neither pb diffusion at the emp scale nor significant discordancy were observed we performed experiments at 800 and 1000 c for different durations using different fluid compositions at quartz saturation a 10 wt cacl2 fluid a 10 wt srcl2 fluid a 10 wt nacl fluid and a fluid containing nbs 982 pb standard 208pb 206pb 1 for all runs emp traverses revealed no pb diffusion profiles significant overgrowths of newly formed monazite are documented by sem analyses they occurred only in the 1000 c experiments when either cacl2 or pb bearing fluids were present in the cacl2 experiment two zones could be distinguished within the crystal a core possessing the initial monazite composition and a rim consisting of newly formed monazite produced by dissolution precipitation which was enriched in ca and pb free id tims dating of single grains treated with srcl2 and cacl2 solutions at 1000 c are significantly discordant experiments employing the nbs pb standard produced sub concordant monazite for which the 207pb 206pb apparent age has become older than prior to the experiment 544 ma at 800 c and 495 ma at 1000 c the newly grown monazite rim had obviously incorporated pb from the fluid none of our reaction products contained a detectable diffusion profile the only resetting mechanism we detected involved dissolution precipitation the extent of the dissolution precipitation process depends on fluid composition and is a more efficient mechanism than diffusion for controlling the resetting of monazite in natural rocks

the effects of vegetative ash on infiltration capacity sediment transport and the generation of progressively bulked debris flows abstract through the alteration of the physical characteristics of a landscape such as the destruction of vegetation and the formation of a hydrophobic layer a fire can dramatically amplify erosion rates on the basis of field observations it has been proposed that the deposition of a layer of ash on the ground surface can enhance the erosion of mountainous terrain by surface runoff and might even be a necessary condition for the generation of progressively bulked debris flows in this study a flume was constructed to investigate the role of ash in increasing both the volume and the transport capacity of runoff the experiments demonstrated that the presence of ash on the soil surface reduces the ability of flowing water to infiltrate this effect is even greater when the ash has been pre wetted in addition the ability of ash slurries to infiltrate decreases with increasing ash concentration the results also indicate that the transport capacity of runoff is enhanced by the incorporation of ash into the flow because of the increased fluid density however the addition of ash reduces the boundary reynolds number such that at high ash concentrations and with fine grained sediment sediment transport declines as the flow becomes hydraulically smooth the experimental results were also used to evaluate the ability of steep flow fronts a common characteristic of debris flows and flash floods to increase sediment transport rates finally it is proposed that ash slurries may evolve into progressively bulked debris flows through a positive feedback between fluid density transport capacity and erosivity

the mean summertime circulation along australia s southern shelves a numerical study abstract for the first time a high resolution regional model is developed for the slope and shelf circulation within the great australian bight and for the gulfs region of south australia the results indicate the extent nature and dynamical interaction of a variety of circulation features that are most likely to be important for the region in particular the positive wind stress curl south of australia leads to an equatorward sverdrup transport in the deep ocean westward flinders current along the slope and upwelling of the 600 m deep permanent thermocline the wind stress curl also leads to a seaward topographic sverdrup transport within the wide sloping shelf of the bight and results in an anticyclonic gyre that is intensified off the eyre peninsula and reduced in magnitude by the joint effect of baroclinicity and topographic relief in the western half of the bight the seaward surface ekman and topographic transports are shown to converge with the onshore component of the flinders current lea

low pressure metamorphism of palaeozoic pelites in the aspromonte southern calabria constraints for the thermal evolution in the calabrian crustal cross section during the hercynian orogeny during hercynian low pressure high temperature metamorphism of palaeozoic metasediments of the southern aspromonte calabria a sequence of metamorphic zones at chlorite biotite garnet staurolite andalusite and sillimanite muscovite grade was developed these metasediments represent the upper part of an exposed tilted cross section through the hercynian continental crust p t information on their metamorphism supplements that already known for the granulite facies lower crust of the section and allows reconstruction of the thermal conditions in the calabrian crust during the late hercynian orogenic event three foliations formed during deformation of the metasediments the peak metamorphic assemblages grew mainly syntectonically s2 during regional metamorphism but mineral growth outlasted the deformation this is in accordance with the textural relationships found in the lower part of the same crustal section exposed in the northern serre pressure conditions recorded for the base of the upper crustal metasediments are c 2 5 kbar and estimated temperatures range from 350 c in the chlorite zone increasing to 500 c in the lower garnet zone and reaching 620 c in the sillimanite muscovite zone geothermal gradients for the peak of metamorphism indicate a much higher value for the upper crust c 60 c km 1 than for the granulite facies lower crust 30 35 c km 1 the small temperature difference between the base of the upper crust 620 c at c 2 5 kbar and the top of the lower crust 690 c at 5 5 kbar can be explained by intrusions of granitoids into the middle crust which in this crustal section took place synchronously with the regional metamorphism at c 310 295 ma it is concluded that the thermal structure of the calabrian crust during the hercynian orogeny as it is reflected by peak metamorphic assemblages was mainly controlled by advective heat input through magmatic intrusions into all levels of the crust

centrifuge modelling of hillslope debris flow initiation physical modelling of hillslope debris flow initiation was undertaken using the geotechnical beam centrifuge at the university of dundee the tests were carried out on model slopes consisting of soils with known properties prepared with constant initial density and material thickness the results showed that soils with a higher silt fraction can sustain a higher increase in pore water pressure and thus a greater reduction in effective stress before failure is induced this suggests that sand rich soils with lower fines content are geotechnically more susceptible to slope failure and that observed higher spatial frequencies of debris flow on slopes with coarse grained bedrocks can be partially explained in terms of lower critical pore pressure failure thresholds amongst the sandier soil matrixes produced from such lithologies differences in rates of water ingress into the model soils required to trigger a critical rise in pore pressures during the tests provide insights into the varying synoptic conditions and antecedent rainfall characteristics that are likely to trigger debris flows in different soil types

a northern boundary current along australia s southern shelves the flinders current 1 south of australia the monthly mean wind stress curl is positive during both summer and winter and leads to ekman pumping and downwelling throughout the region sverdrup dynamics indicates that this downwelling should lead to a northward transport of around 5 10 sv 1 sv 10 m3 s 1 classical arguments for western boundary currents are adapted to show that this transport should be deflected into an upwelling favorable boundary current that flows from east to west along australia s southern shelves the flinders current support for this proposition is obtained from results of the ocean circulation and climate advanced modelling project occam sverdrup transports and limited observations for the region in addition the occam results show that the northward transport leads to upwelling at depths below 400 m and that the flinders current 1 intensifies from victoria to western australia transport 8 sv with speeds up to 15 cm s 1 2 can extend from the surface to depths of 800 m and 3 is found during both summer and winter during winter the winds are downwelling favorable and lead to a coastal current that flows from west to east and opposes the flinders current further support for the origin and nature of the flinders current is obtained from simple numerical experiments made using a rectangular domain and idealized representations of the summer and winter wind stress

flow around a coastal bend a model of the santa barbara channel eddy a steady equatorward wind stress is applied over a two layer ocean infinitely deep lower layer west of an otherwise straight meridional coast with a right angle bend initial t 10 days response consists of an equatorward current kelvin wave that triggers a cyclone around the bend through viscous production and advection of vorticity a process akin to eddy shedding in flows without rotation the response at large times is governed by a kelvin wave forced by the equatorward weakening of the assumed positive wind stress curl which produces a poleward current near the coast application to the santa barbara channel cyclone is discussed and the cyclone formation process is further demonstrated with a three dimensional model with topography and stratification

u pb single zircon pb evaporation and sm nd isotopic study of a granulite domain in se madagascar madagascar is a poorly known precambrian domain at the eastern border of the mozambique belt strongly affected by the pan african orogeny this large island represents a key part of gondwanaland and the accurate dating of the major metamorphic event is critical for the reconstruction of that supercontinent in the southeastern zone of the island metamorphism has reached high temperature and low pressure conditions 850 c and 5 kbar with moderate retrogression a u pb conventional multigrain single zircon stepwise pb evaporation and sm nd geochronological study on meta felsic rocks has shown that basement of at least lower proterozoic age was strongly metamorphosed around 570 580 ma this tectometamorphic event nearly obliterated any pre pan african zircon isotopic memory the granulite facies metamorphism is associated with the syn metamorphic emplacement of the anosyan charnock ites and granites a strong channelized fluid contribution at 545 ma has produced the re crystallization of biotite apatite

experimental study on initiation of gully type debris flow based on artificial rainfall and channel runoff debris flows usually occur abruptly and rapidly in mountainous areas and it is difficult to observe their occurrence progress therefore an experiment has become an important method to study debris flow initiation mechanism in recent years in this paper taking xiongjia gully in sw china as an example and on the basis of artificial rainfall experiment the author has studied the initiation of gully type debris flow experiment results indicate some relation between rainfall intensity and gully erosion failure mode of soil mass initiation mechanism and characteristics of debris flow based on several groups of experiments conclusions were drawn as follows 1 under strong precipitation the infiltration rate and soil water content in different depths are inversely proportional to the rainfall intensity intense rainfall favors the overland flow gully runoff and erosion but is not conducive to water infiltration 2 slope failure modes and initiation mechanism of debris flow vary with different rainfall and runoff conditions under the condition with the rainfall intensity of 55 mm h the slope failure mode presents a soil liquefaction and landslide accordingly the debris flow initiation mechanism belongs to landslide transformation however under the condition of intense rainfall and runoff gully beds are easy to be eroded and slopes are prone to collapse then debris flows occurred with initiation mechanism of entrainment 3 in terms of debris flow characteristics the debris flow occurrence process consists of several intermittent flows in addition the debris flow magnitude and flow viscosity are not consistent with rainfall intensity on the contrary under condition of intense rainfall of 65 and 75 mm h debris flows tend to be watery however under the rainfall condition of 55 mm h the flow viscosity is higher the experiment results are consistent well with the natural debris flow occurrence from xioangjia gully

modelling the thermal perturbation of the continental crust after intraplating of thick granitoid sheets a comparison with the crustal sections in calabria italy thick granitoid sheets represent a considerable percentage of palaeozoic crustal sections exposed in calabria high thermal gradients are recorded in upper and lower crustal regional metamorphic rocks lying at the roof and base of the granitoids ages of peak metamorphism and emplacement of granitoids are mostly overlapping suggesting a connection between magma intrusion and low pressure metamorphism to analyse this relationship thermal perturbation following granitoid emplacement has been modelled the simulation indicates that in the upper crust the thermal perturbation is short lived in contrast in the lower crust temperatures greater than 700 c are maintained for 12 ma explaining granulite formation anatexis and the following nearly isobaric cooling an even longer perturbation can be achieved introducing the effect of mantle lithosphere thinning into the model

contrasted monazite hydrothermal alteration mechanisms and their geochemical implications in spite of the major importance of monazite as a repository for the rare earths and th in the continental crust for u th pb geochronology and as a possible form for high level nuclear waste very little work has been carried out so far on the behaviour of this mineral during fluid rock events this contribution describes two contrasting examples of the hydrothermal alteration of monazite the first case comes from a sample of the carnmenellis granite cornwall southwest england chloritized at 284 16 c whereas the other occurs in the skiddaw granite lake district northwest england which underwent greisenization at 200 30 c an integrated study involving backscattered scanning electron microscopy electron microprobe analyses and laser ablation inductively coupled plasma mass spectrometry la icp ms reveals that the chloritization event was characterized by the coupled substitution 2ree3 th4 ca2 in the altered parts of the monazite thus leaving the p o framework of the crystal untouched in contrast greisenization led to the coupled substitution ree3 p5 th4 si4 and therefore involved a partial destruction of the phosphate framework the resulting rare earth element patterns are quite different for these two examples with a maximum depletion for dy and er in the altered parts of the carnmenellis monazite whereas the skiddaw monazite shows a light rare earth depletion but an yb and er enrichment during alteration this latter enrichment accompanied by an increase in u but roughly unchanged pb concentrations probably resulted from a decrease in the size of the 9 coordinated site in monazite thereby favouring the smaller rare earths these contrasted styles of monazite alteration show that the conditions of fluid rock interaction will not only affect the aqueous geochemistry of the lanthanides actinides and lead and the relative stability of the different minerals holding these elements variations in these conditions will also lead to various possible chemical exchanges between the crystalline phases and the hydrothermal fluids the occurrence of common lead along penetrative cracks in the carnmenellis monazite shows that only a leaching prior to the u pb analyses of the whole grain will permit an accurate determination of the magmatic crystallization age in contrast for the skiddaw case it may be possible to date the fluid rock event by in situ 207pb 206pb geochronology the observation that the altered parts of both monazite examples display nd leaching and no significant sm nd fractionation indicates that they should not affect the host whole rock nd isotopic signatures finally it appears that monazite like ceramics designed for the containment of high level nuclear wastes will retain th and the geochemically equivalent transuranic elements during fluid rock events similar to those documented in this study but may release nd u and the corresponding radionuclides to the environment

a mechanism for enhanced upwelling off central chile eddy advection 1 a regional numerical model is developed for the mid chile shelf and ocean circulation 30 s to 43 s the model is forced with mean summertime wind stress and transports from a global model over the first 10 days deep 250 300 m peru undercurrent puc water is upwelled to depths of 170 270 m after this time upwelling by the steady winds is largely shut down and a 55 km diameter cyclonic eddy is found to grow in deep water off punta lavapie the mechanism for eddy growth is identified to be baroclinic instability of an initial offshore meander of the equatorward chile coastal current ccc over a period of more than 100 days the onshore arm of the deep water eddy upwells puc water to depths of 150 m toward the shelf a shallow headland eddy then sweeps this puc water to depths of less than 50 m and into the gulf of arauco the net upwelling of 200 m is the largest found for the region observational evidence is cited for the existence of the deep water cyclonic eddy over a period of 4 months a spatially intermittent puc is also found to lie below the ccc in agreement with observational studies the model also predicts the existence of an offshore branch of the ccc that is directed to the northwest

δ18o and δ13c variability in brachiopods from modern shelf sediments and its utility for understanding complex oceanography southern australian shelf abstract the 18o and 13c values of brachiopod shell calcite are commonly used as proxies for ancient environmental marine conditions and secular changes in ancient ocean chemistry the variability of 18o and 13c across modern shelf settings is however not well documented this study presents 18o and 13c data from 407 holocene 5000 yr bp and living brachiopods collected from 220 sites across 3000 km along australia s southern shelf the largest cool water carbonate shelf in the modern world significant isotopic variability is present in separate specimens at individual sites and across the entire region individual specimens analyzed at multiple shell positions have an isotopic range of values up to 1 3 and 1 9 for 18o and 13c respectively multiple brachiopods at a single site have values that vary as much as 2 1 for 18o and 1 8 for 13c regional variability ranges on the order of 3 6 and 3 4 for 18o and 13c respectively the distribution of intrasite variability can be divided into areas of high and low variability areas characterized by low variability occur in zones of relatively consistent shelf water conditions high variability zones usually correspond to areas of seasonal upwelling onto the shelf and this aspect is interpreted to be the main cause of isotopic variability upwelling waters are cold leading to higher 18o values and are commonly rich in respired dissolved inorganic carbon dic and nutrients promoting active phytoplankton growth and leading to variable 13c values the extensive spatial coverage across this vast latitude parallel region provides a valuable baseline illustrating the isotopic range that could occur in a single layer in the rock record furthermore changes in isotopic signatures measured across stratigraphy might not necessarily reflect secular changes in ocean chemistry but instead could be recording local changes in shelf circulation and upwelling intensity

modelling of the initiation of rainfall induced debris flows in the cardoso basin apuan alps italy abstract a case study is being carried out in relation to the event of june 19 1996 when an intense rainstorm hit the cardoso area in the apuan alps italy the catastrophe triggered several gravitational movements mainly characterized by soil slip debris flows a dataset coming from field and laboratory surveys allowed a complete parameterization of the event and consequently the realization of a physically based dynamic model related to the initiation of the rainfall induced landslides the aim of the study is to analyze the processes involved in the light of the modelling results and to assess the spatio temporal activity of the landslides both in terms of location of the triggering sites and of determination of the critical rainfall conditions the critical rainfall input thresholds obtained with a deterministic approach are then compared with the thresholds obtained by an empirical analysis of the main rainfall events occurred in the southern apuan area in the period from 1975 to 2002

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

petrology and u th pb geochronology of the sapphirine quartz bearing metapelites from rajapalayam madurai block southern india evidence for polyphase neoproterozoic high grade metamorphism abstract strongly migmatitic sapphirine bearing granulites occur as dm to m sized enclaves in garnetiferous leucogranites in the southeastern part of the madurai block mb the largest section of neoproterozoic crust in the southern granulite terrain of india sgt early mineral assemblages biotite sillimanite quartz garnet biotite quartz break down via successive dehydration melting reactions to high t and high p phase assemblages e g garnet melt orthopyroxene sillimanite melt orthopyroxene cordierite melt melt consuming reactions along the retrograde path led to partial resorption of garnet to orthopyroxene sillimanite orthopyroxene sapphirine and or orthopyroxene cordierite as well as orthopyroxene sillimanite assemblages to cordierite biotite quartz symplectites the occurrence of uht metamorphism is indicated by the presence of small inclusions of sapphirine quartz intergrowths in garnet this reaction sequence is interpreted in a kfmash partial petrogenetic grid taking both melt producing and melt consuming reactions into account which yields a clockwise heating cooling decompression p t path culminating at 8 11 kbar and 1000 1100 c in situ u th pb monazite dating has been performed to more precisely constrain the ages given by chemical electron microprobe on monazite in various textural positions monazite inclusions in garnet often yield a bimodal distribution of early 950 850 ma and late neoproterozoic 600 500 ma ages which is in good agreement with the results of u pb and epma zircon dating in other places of the southeastern madurai block by contrast monazite inclusions in other mafic minerals orthopyroxene cordierite biotite or as interstitial phase exclusively yield ages between 550 and 480 ma the early neoproterozoic population is interpreted to reflect the timing of migmatisation and peak uht metamorphism whereas the late neoproterozoic ages are inferred to date cooling and exhumation with granitic magmas to a higher crustal level of the madurai block

u pb zircon rb sr and sm nd geochronology of high to very high pressure meta acidic rocks from the western alps three meta acidic rocks from the western italian alps a magnesiochloritoid bearing metapelite from the monte rosa massif a coesite pyrope quartzite from the dora maira massif and the monte mucrone granite in the sesia zone have been studied by u pb zircon rb sr on whole rock apatite and phengite and sm nd wholerock methods the mineral parageneses of the investigated rocks indicate high to very high pressure and medium to high temperature metamorphism this combined isotopic study has enabled us to constrain the ages of magmatic and metamorphic events and also to compare the behaviour of u pb zircon systems in three intensely metamorphosed areas of the pennine domain the u pb zircon data have yielded a magmatic age for the monte mucrone granite at 286 2 ma this result confirms the occurence of late hercynian magmatism in the sesia zone as in other austro alpine units and in other areas of the european crystalline basement in the monte rosa massif a geologically meaningless lower intercept age of 192 2 ma has been interpreted as an artefact due to a complex evolution of the u pb zircon system the magmatic shape of the zircons implies a magmatic or volcano sedimentary protolith for this rock originally considered as a metasediment the very high pressure metamorphism in the dora maira quartzite has produced an opening of the u pb zircon system at 121 12 29 ma the rb sr data support the occurence of high grade metamorphism during cretaceous times phengites model ages are slightly younger than the u pb zircon lower intercept ages due to cooling phenomena or possible response of the phengites to a later deformation the nd model ages from the whole rock samples as well as the u pb upper intercept ages from zircons of all three investigated rocks indicate the presence of proterozoic crustal components inherited from the precursors of these meta acidic rocks the studied zircon populations and their u pb systems apparently showed open system behaviour only when affected by extreme metamorphic conditions 700 750 c 28 kbar whereas eclogite facies conditions of 500 550 c and 14 16 kbar were not enough to disturb significantly the u pb zircon evolution it is also probable that the sedimentary or magmatic origin of the protoliths of these meta acidic rocks which involved different characteristics such as grain size and fluid phase concentration and composition could be another important factor controlling the u pb zircon system behaviour during metamorphic events

analysis of rainstorm induced slide debris flows on natural terrain of lantau island hong kong abstract lantau island the largest outlying island of the territory of hong kong experienced a severe rainstorm on 4 5 november 1993 which induced 800 slope failures on natural terrain there detailed field investigations were carried out to study the failure modes in relation with various influencing factors it was found that the occurrence of slide debris flows has a close relationship with bedrock geology slope gradient vegetation cover and micro landform the failure modes of slide debris flows may be classified into translational slides and rotational slides and the former are predominant analysis of the hydrological response of colluvial slopes during the rainstorm indicated that the majority of the failures were caused by the development of a perched water table in the thin surface layer of colluvium of volcanic origin due to infiltration during the heavy rain undisturbed soil samples from south lantau have been subjected to anisotropically consolidated undrained compression tests at comparatively low stress levels constant deviatoric stress path tests cqd simulating the stress path in the field at in situ stress levels have been performed to investigate soil behavior the cqd test results indicate that the material of slopes at undisturbed state is brought to dilation because of the increase in pore water pressure caused by infiltration of rain water for a translational slide the displacement resulting from dilation may destroy cohesion along the failure surface and locally within the interior of the slide the surplus water during the intense rainstorm was able to equilibrate the reduction in pore pressure caused by dilation and the dilation and displacement may be further increased the strain softening after significant strains triggered debris flow mobilization however for a rotational slide the increase in pore water pressure caused by surplus water infiltration during the intense rainstorm could not equilibrate the reduction in pore pressure caused by dilation much or even all of the sliding block could not mobilize into a debris flow

size of a debris flow deposition model experiment approach the prediction of the dangerous extent of a debris flow deposition is of vital importance but difficult to achieve precise prediction of the depositional boundary of a debris flow event is impossible but the size of a debris flow deposition could provide some estimates of the area length width and thickness of a debris flow deposition based on in situ depositional experiments performed on a debris flow creek just after debris flows a rule of thumb expressed by a group of equations containing the multiple variate nonlinear functions is proposed in this paper the interrelationships between the size and the causation also are discussed and some empirical formulae to calculate the causative parameters for different regions are presented

geochronology of the medium to high grade metamorphic units of the peloritani mts sicily the peloritani mountains are a fragment of an orogen variably attributed to the alpine or hercynian orogeny on the basis of 39ar 40ar u pb and rb sr dating the main metamorphism of the two medium high grade metamorphic units the mela and aspromonte units and most of the thrusting responsible for stacking the orogenic edifice are seen to be hercynian the main thrusting of the aspromonte unit over the lower grade units took place at 301 2 ma brittle deformation during tertiary reactivation of hercynian thrust planes did not generate any rejuvenation of white micas in the studied sector our dataset shows a great complexity and we propose to unravel it by considering different levels of information to first order the mela and aspromonte units differ in their metamorphic paths and their geochronological evolution the mela unit shows generally younger ages carboniferous than the aspromonte unit and unlike the latter was extensively retrogressed in greenschist facies the aspromonte unit is itself geochronologically heterogeneous proterozoic ages are preserved both in titanite and in amphibole relics of one tectonic subunit devonian to carboniferous amphibole ages are found in different other subunits tertiary overprint is minor and spatially limited we propose to consider the chronologically heterogeneous subunits as accreted pre hercynian terranes amalgamated late during the hercynian orogeny micas in both units give scattered mesozoic 39ar 40ar and rb sr ages with evidence for heterochemical mica generations we interpret them as a result of widespread hydrothermal circulation event s tertiary overprint is generally absent with the exception of a small area near messina where biotite and muscovite underwent a complex recrystallisation history in the interval between 48 and 61 ma

ocean circulation in the great australian bight in an eddy resolving ocean reanalysis the eddy field seasonal and interannual variability abstract the ocean circulation in the great australian bight gab is dominated by the surface intensified leeuwin current lc over the outer continental shelf and the flinders current farther offshore in the gab the lc flows eastwards and varies seasonally with strongest currents of up to 0 8 m s at 130 5 e bringing warm and salty waters as far east as western tasmania the flinders current flows westwards as an undercurrent at depths of around 500 m over the continental slope and at the surface offshore of the lc off the shelf the gab is rich in mesoscale eddies with surface intensified currents of up to 0 4 m s that are coherent over the full water depth getting weaker with depth within deep water eddies isotherms are displaced vertically by up to 200 m eddies in the eastern gab are most energetic in austral winter and spring coincident with the seasonal weakening of the lc the eastern most penetration of gab eddies occurs in austral winter when the lc starts to weaken we hypothesise that the horizontal shear associated with the lc generates eddies in the eastern gab the volume transport of the lc at the head of the gab is typically between 1 and 7 sv with a clear seasonal cycle and the interannual variability of lc transport is up to 2 sv

petrogenesis of contrasting hercynian granitoids from the calabrian arc southern italy abstract the granitoids of the southern calabrian arc have been investigated for whole rock and phase chemistry zircon typology ree sr and nd isotopes two distinct granitoid associations which are related in time and partly in space are present a calc alkaline one and a peraluminous one the prevailing calc alkaline association is compositionally expanded sio2 48 70 and biotite dominated with tonalites and granodiorites as predominant rock types the peraluminous association is compositionally restricted sio2 67 76 and contains two mica al silicates distinct peraluminous typologies occur also as core facies within the calc alkaline types all granitoids are ilmenite bearing the cittanova cn villa s giovanni vsg and capo rasocolmo cr peraluminous granites display zircon typology ree patterns srt 51 to 113 and ndt values 8 5 to 4 6 at 290 ma suggesting a dominantly quartzofeldspathic metasedimentary source in more detail the cn types and the cr vsg types require heterogeneous and different sources the calc alkaline granitoids display very variable ree patterns cen 25 227 and ybn 3 5 18 5 in the tonalites granodiorites and variable age corrected ndt values 8 5 to 0 25 whereas sr values vary little 82 to 93 thus in terms of ndt srt covariation the data points define a vertical array which is inconsistent with a model involving crustal contamination by mantle derivatives a more viable mechanism seems to be the melting of hydrous and heterogeneous mafic lower crust and or basic underplate producing distinct magma batches evolving independently crustal contamination mingling and fractionation processes may all have contributed to the observed geochemical variations within the granitoids the peraluminous granodiorites occurring within the serre and capo vaticano multipulse calc alkaline plutons exhibit isotopic ratios ndt 6 11 to 0 33 and srt 93 to 97 which are similar to those of the calc alkaline host rocks suggesting a possible genetic link geologic and geochemical data indicate a continental collision setting for this plutonic activity the magmas were produced during late thickening to exhumation phases following collision and moderate crustal overthickening and were emplaced subsequently during a short time span a mantle contribution should have favoured melting which affected various sectors of the continental crust

different age response of zircon and monazite during the tectono metamorphic evolution of a high grade paragneiss from the ruhla crystalline complex central germany results of tims sims and sem analyses show that zircon and monazite in a high grade paragneiss of the ruhla crystalline complex central germany were formed and or altered during different stages of a tectono metamorphic history between early devonian and permian times detrital zircon cores of 460 ma place an older limit on the age of anatexis and show that the paragneiss sequence contains rocks at least as young as early cambrian metamorphic zircon growth commenced at 365 ma peaking at 360 355 ma at the same time that granite dykes were emplaced in contrast monazite in the paragneiss preserves little record of the metamorphic peak most monazite grains grew or were recrystallised in the lower carboniferous at 339 ma contemporaneous with the emplacement of voluminous diorite and granite bodies these intrusions and related tectonics caused some of the high u zircon overgrowths to undergo moderate to severe pb loss a second pb loss event between 300 and 280 ma can be related to late carboniferous early permian large scale block faulting

petrological evidence for crustal thickening and extension in the serre granulite terrane calabria southern italy the paper presents the metamorphic trajectory recorded by metapelitic migmatites of the upper part of the hercynian lower continental crust of the serre southern calabria italy the relict minerals reaction textures and phase equilibria define a clockwise p t path the prograde metamorphism from temperature of about 500 c and pressure of 4 5 kbar to t 700 ca nd p 8 kbar stabilized the assemblage grt ky bt ms si 11ox 3 26 3 29 in the uppermost metapelites of the profile progressive heating led to h2o fluxed and dehydration melting first of ms then of bt at t 700 c in the stability field of sillimanite this process was followed by nearly isothermal decompression producing additional melt with a transition from grt to a grt crd stability field further decompression caused the formation of crd corona around garnet nearly isobaric cooling led to rehydration and retrogression across the stability field of andalusite up to the stability field of kyanite the lowermost metapelites of the studied profile have lost most of the memory of the prograde p t path they record decompression and cooling high temperature mylonites occur in which boudinage elongation and pull aparts characterize the porphyroclasts the pull aparts in the high t mylonites are filled with low p minerals crd spl the hercynian metamorphic trajectory and the microtextures are consistent with crustal thickening and subsequent extensional regime during extension an important tectonic denudation probably caused the isothermal decompression extension also occurred in post hercynian times as documented by pull aparts in sillimanite porphyroclasts filled with chloritoid within a low grade mylonite

observations of divergence and upwelling around point loma california 1 historical records of near surface water temperatures in the southern californian bight often show a preferential cooling in the lee of headlands such as point dume palos verdes and point loma at times this cooler water is associated with an increase in chlorophyll a as is evident in satellite images of ocean color from the region here we combine hydrographic data from a 1 day cruise aboard the rv roger revelle a precursor to the 0304 california cooperative oceanic fisheries investigations calcofi cruise with high frequency hf radar codar measurements satellite images and long term thermistor records of near surface temperature to identify a small scale isolated upwelling in the lee of point loma 32 5 n associated with the more saline water downstream of the headland are higher nutrient concentrations an increase in chlorophyll a concentration and a bloom of chain forming diatoms indicative of a mature upwelling system it is suggested that this upwelling is not primarily due to local or remote wind forcing but rather to the divergence of the prevailing southerly flow as it passes the point loma headland time series of surface vorticity calculated from hf radar measurements of sea surface velocity show that as the flow separates from the headland relative vorticity increases offshore of the cape inshore the time series of divergence convergence shows a tendency toward divergence at the surface indicating a preferential upwelling which appears to raise the thermocline thus resulting in a flux of cold nutrient rich water to the surface in the presence of high nutrients and light photosynthetic organisms bloom in these upwelled waters as they are advected away from the headland and offshore by the prevailing surface currents

transient wind driven upwelling in a submarine canyon a process oriented modeling study 1 a hydrodynamic model is employed to study flow near a submarine canyon during conditions of upwelling favorable coastal winds findings reveal that up canyon flow is the rapid geostrophic adjustment to barotropic pressure gradients establishing across the canyon stratification leads to the formation of a cyclonic eddy within the canyon trapping neutrally buoyant matter and limits the upwelling depth only when a strong seasonal pycnocline is located below shelf break depth typical speeds of up canyon flow are 10 30 cm s constrained by the timescale of synoptic weather patterns 5 days only stronger events high upwelling index can move slope water from a depth 300 m onto the continental shelf and close toward the coast where it can be lifted into surface layers during a subsequent upwelling event

rainfall induced debris flows in pyroclastic deposits campania southern italy abstract a combination of empirical and physically based hydrological models has been used to analyze historical data on rainfall and debris flow occurrence in western campania to examine the correlation between rainfall and debris flow events rainfall data from major storms recorded in recent decades in western campania were compiled including daily series from several rain gauges located inside landslide areas supplemented by hourly rainfall data from some of the principal storms a two phase approach is proposed during phase 1 soil moisture levels have been modelled as the hydrological balance between precipitation and evapotranspiration on a daily scale using the method of thornthwaite geograph rev 38 1948 55 phase 2 is related to the accumulation of surplus moisture from intense rainfall leading to the development of positive pore pressures these interactions take place on an hourly time scale by the leaky barrel lb model described by wilson and wiezoreck env eng geoscience 1 1995 11 in combination with hourly rainfall records the lb model has been used to compare hydrological effects of different storms the critical level of retained rain water has been fixed by the timing of debris flow activity related to recorded storm events new rainfall intensity duration thresholds for debris flow initiation in western campania are proposed these thresholds are related to individual rain gauge and assume a previously satisfied field capacity condition the new thresholds are somewhat higher than those plotted by previous authors but are thought to be more accurate and thus need less conservatism

boundary effect on the hydraulic characteristics of gravelly soil slopes in physical model tests abstract the stability of a residual gravelly soil slope during heavy rainfall is closely related to the seepage field which is directly affected by the seepage boundaries of the slope to examine the boundary effect a novel model flume that can implement permeable and impermeable boundary conditions was designed with this flume hydraulic model tests of a gravelly soil slope considering those two seepage boundaries were carried out the results show that distinct spatial morphology of seepage fields is reflected by the hydraulic characteristics of the slope models with different seepage boundaries the slope with permeable boundaries generally exhibits a larger average infiltration rate as well as a relatively smaller moving speed of wetting front in the lower part compared to the slope with impermeable boundaries the residual moisture content in the deep lower part of the slope with permeable boundaries is 6 6 cm3 cm3 smaller than that of the slope with impermeable boundaries nevertheless the maximum pore water pressure in the middle part of the slope with permeable boundaries is 1 2 kpa higher than that in the corresponding part of the slope with impermeable boundaries it is noted that regional pore water pressures in the shallow lower and shallow middle parts of the slope with impermeable boundaries exhibit large fluctuations with an amplitude over 0 5 kpa the seepage field in the slope with permeable boundaries presents a multi dimensional development which may lead to a local failure of the slope the results are of great significance in studying the similarity of seepage boundary condition in the field of similarity theory on landslide model tests and provide an experimental basis for establishing rainfall induced landslide theory

water mass analysis and alongshore variation in upwelling intensity in the eastern great australian bight 1 a study of climatological and conductivity temperature depth ctd data for 2004 is made to provide a conceptual model of upwelling for the eastern region of the great australian bight in particular the data and other studies provide strong evidence that shelf break upwelling is confined to the southwest kangaroo island region and does not occur farther to the west off the eyre peninsula rather the upwelled water is likely to remain in a kangaroo island pool until subsequent upwelling events draw the water to the shallower and surface coastal regions of the eastern bight in this manner the surface upwelling apparent off the bonney coast kangaroo island and the eastern great australian bight gab can appear to be simultaneous moreover it appears likely that the water within the kangaroo island pool remains nutrient rich support for this model comes from ctd sections collected in 2004 that show that the upwelled signal cool 26 kg m 3 diminishes in width and intensity with increasing distance from kangaroo island the pattern of fluorescence is similar to that for temperature in the upwelled plume and indicates that the kangaroo island pool remains nutrient rich relatively low oxygen concentrations may indicate a previous bloom the warmest water is found near the shelf break along with very low values of fluorescence and relatively higher levels of oxygen suggesting nutrient limited growth of phytoplankton these data also support the notion that the upwelled nutrient rich water is supplied from the kangaroo island pool and not by shelf break upwelling in the eastern gab anomalously salty and fresh water is identified as resulting from evaporation in coastal bays and groundwater aquifer discharge

spatial and temporal variation in cores from lake titicaca bolivia peru during the last 13 000yrs we compared the stratigraphy of sediment cores that span the last 13 000 yrs from three sites in the main basin of lake titicaca boliva peru as indicators of regional paleoclimate the cores show similar patterns of change after 6400 calendar yrs before present cal yr bp but differ before that time site ne98 pc2 which is near the rio illave and its delta shows differences in diatom species composition and in calcium carbonate concentrations relative to cores from the other two sites particularly during times of inferred high precipitation in contrast the carbon isotopic stratigraphy of the three sites is relatively similar the magnetic susceptibility data suggest that the proximity of site ne98 pc2 to the river and delta resulted in higher loads of detrital sediment prior to 6400 yr bp whereas pelagic sources contributed most of the sediment at the other sites these differences highlight the potential for spatial heterogeneity of sediment records in large lake systems and the importance of evaluating multiple cores for robust interpretation of paleoenvironmental history

pressure temperature evolution of the late hercynian calabria continental crust compatibility with post collisional extensional tectonics the late hercynian tectonic evolution of the calabria crust is characterized by peak metamorphic conditions up to 800 c and 1000 mpa and coeval mid crustal granitoid emplacement at 304 300 ma to check if a post collisional extensional framework similar to that of other hercynian massifs can explain petrologic data we model the pressure temperature evolution of the crust during extension following granitoid emplacement model parameters are constrained by petrologic geochemical and structural data computed p t paths are characterized by nearly isothermal decompression followed by isobaric cooling which show a good fit to petrologic p t paths for duration of extension between 5 and 10 ma the model results therefore support an interpretation of the magmatic and metamorphic evolution of the calabria crust in terms of the late hercynian extension in this framework slab break off is a reasonable explanation for the common evolution of the southern european hercynian massifs

multi stage melting in the lower crust of the serre southern italy the lower crustal section exposed in the serre southern italy consists part of the section the most depleted metagreywackes underwent melt extraction of about 9 13 vol the two stage melting mainly of al rich metasediments which underwent granulite facies metamorphism partial melting and melt extraction the paper occurred during the prograde metamorphism and continued during the isothermal decompression considers the formation of melts in metapelites and metagreywackes leucosomes and host rocks have been studied to investigate the melting process biotite rich and biotite free melanosomes with scarce felsic components are present the biotite rich types are widespread in the upper part of the section and the two types may occur side

middle precambrian provenance of jurassic sandstone in the mino terrane central japan th u total pb evidence from an electron microprobe monazite study precise electron microprobe analyses have been made on detrital monazites in jurassic sandstones of the mino terrane central japan and their th u pb relations are examined in terms of pbo and tho2 tho2 tho2 plus the equivalent of uo2 the pbo tho2 ratios of most detrital monazites 403 of 581 grains cluster in the range from 0 0763 to 0 0618 other grains show the ratio of about 0 0541 46 grains 0 0364 29 grains 0 0170 24 grains and 0 0116 79 grains the pbo tho2 ratio of 0 0763 0 0618 is nearly identical with that of monazites in a middle precambrian 1740 ma gneiss clast from the kamiaso conglomerate of the mino terrane this strongly suggests that the detrital monazites were derived from gneisses and or granitoids of middle precambrian age the ratio of 0 0116 is nearly the same as that of monazites in a permian 274 ma paragneiss of the hida terrane north to the mino terrane the pbo tho2 monazite data coupled with palaeocurrent analyses and petrological characteristics of sandstones show that middle precambrian high grade metamorphic rocks and granitoids were widespread both in the northern and southern source regions of the e w trending jurassic basin of the mino terrane the pbo tho2 ratio of detrial monazites is a useful new measure for the provenance analysis of clastic rocks

geochronological constraints on the timing of granitoid magmatism metamorphism and post metamorphic cooling in the hercynian crustal cross section of calabria exposed cross sections of the continental crust are a unique geological situation for crustal evolution studies providing the possibility of deciphering the time relationships between magmatic and metamor phic events at all levels of the crust in the cross section of southern and northern calabria u pb rb sr and k ar mineral ages of granulite facies metapelitic migmatites peraluminous granites and amphibolite facies upper crustal gneisses provide constraints on the late hercynian peak metamorphism and granitoid magmatism as well as on the post metamorphic cooling monazite from upper crustal amphibolite facies paragneisses from southern calabria yields similar u pb ages 295 293 4 ma to those of granulite facies metamorphism in the lower crust and of intrusions of calcalkaline and metaluminous granitoids in the middle crust 300 10 ma monazite and xenotime from peraluminous granites in the middle to upper crust of the same crustal section provide slightly older intrusion ages of 303 302 0 6 ma zircon from a mafic to intermediate sill in the lower crust yields a lower concordia intercept age of 290 2m a which may be interpreted as the minimum age for metamorphism or intrusion u pb monazite ages from granulite facies migmatites and peraluminous granites of the lower and middle crust from northern calabria sila also point to a near synchronism of peak metamorphism and intrusion at 304 300 0 4 ma at the end of the granulite facies metamorphism the lower crustal rocks were uplifted into mid crustal levels 10 15 km followed by nearly isobaric slow cooling c 3 cm a 1 as indicated by muscovite and biotite k ar and rb sr data between 210 4 and 123 1 ma the thermal history is therefore similar to that of the lower crust of southern calabria in combination with previous petrological studies addressing metamorphic textures and p t conditions of rocks from all crustal levels the new geochronological results are used to suggest that the thermal evolution and heat distribution in the calabrian crust were mainly controlled by advective heat input through magmatic intrusions into all crustal levels during the late hercynian orogeny

analysis of hydrographic and stable isotope data to determine water masses circulation and mixing in the eastern great australian bight 1 hydrographic and stable isotope data from waters in the eastern great australian bight gab sampled during march april 1998 indicate that both mixing and evaporative processes are important on the shelf five water masses are defined on the basis of their temperature salinity 2h and 18o values two of these are end members the flinders current fc and the great australian bight plume gabp whereas the other three are a result of mixing between these two end members water mass distribution reflects an anticyclonic gyre in the eastern gab cool and fresh water present at depth along the eyre peninsula is sourced from upwelling of flinders current water directly from the shelf break this water is progressively heated evaporated and mixed with warmer and more saline shelf waters as it flows around the gyre high temperatures salinities and 2h values in surface waters in the central gab suggest that the great australian bight plume has a greater spatial extent than previously recorded also occurring along the shelf edge between 130 e and 133 e a high temperature high salinity low 2h water mass that is isotopically similar to the flinders current occurs in the west of the study area indicating intrusion of flinders current water into the central gab differences in isotopic compositions of off shelf water suggest that the great australian bight plume is flowing off the shelf and mixing with flinders current water at 132 e however this outflow does not generate an eastward flowing current during the period when samples were collected

lower crustal rejuvenation and growth during post thickening collapse insights from a crustal cross section through a variscan metamorphic core complex the variscan lower crust of europe acquired its main features seismic layering intrusion of mantle derived magmas granulite grade metamorphism when the upper crust underwent post thickening extension through gravitational collapse we suggest that post thickening collapse is a geodynamic process that contributes to the growth and differentiation of continental lithosphere in collapsed mountain belts

age constraints on late paleozoic evolution of continental crust from electron microprobe dating of monazite in the peloritani mountains southern italy another example of resetting of monazite ages in high grade rocks in situ monazite microprobe dating has been performed for the first time on trondhjemite and amphibolite facies metasediments from the peloritani mountains in order to obtain information about the age of metamorphism and intrusive magmatism within this still poorly known sector of the hercynian belt all samples show single stage monazite growth of hercynian age one migmatite and one biotitic paragneiss yielded monazite ages of 311 4 and 298 6 ma respectively these ages fit with previous age determinations in similar rocks from southern calabria indicating a thermal metamorphic peak at about 300 ma at the same time as widespread granitoid magmatism the older of the two ages might represent a slightly earlier event possibly associated with the emplacement of an adjacent trondhjemite pluton previously dated by shrimp at 314 ma no evidence for pre hercynian events and only a little indication for some monazite crystallization starting from ca 360 ma were obtained from monazite dating of the metasediments suggesting either a single stage metamorphic evolution or a significant resetting of the monazite isotope system during the main hercynian event ca 300 ma rare monazite from a trondhjemite sample yields evidence for a late hercynian age of about 275 ma this age is interpreted as representing a post magmatic stage of metasomatic monazite crystallization which significantly postdates the emplacement of the original magmatic body

initiation process of debris flows on different slopes due to surface flow and trigger specific strategies for mitigating post earthquake in old beichuan county china the 12 may 2008 wenchuan earthquake ms 8 0 in china produced an estimated volume of 28 108 m3 loosened material which led to debris flows after the earthquake debris flows are the dominant mountain hazards and serious threat to lives properties buildings traffic and post earthquake reconstruction in the earthquake hit areas it is very important to understand the debris flow initiation processes and characteristics for designing debris flow mitigation the main objective of this article is to examine the different debris flow initiation processes in order to identify suitable mitigation strategies three types of debris flow initiation processes were identified designated as types a b and c by field survey and experiments in a type initiation the debris flow forms as a result of dam failure in the process of rill erosion slope failure landslide dam or dam failure this type of debris flow occurs at the slope of 10 2 with a high bulk density and several surges following dam failure b type initiation is the result of a gradual increase in headward down cutting bank and lateral erosion and then large amount of loose material interfusion into water flow which increases the bulk density and forms the debris flow this type of debris flow occurs mainly on slopes of 15 3 without surges c type debris flow results from slope failures by surface flow infiltration loose material crack slope failure and fluidization this type of debris flow occurs mainly on slopes of 21 4 and has several surges of debris flow following slope failure and a high bulk density to minimize the hazards from debris flows in areas affected by the wenchuan earthquake the erosion control measures such as the construction of grid dams slope failure control measures the construction of storage sediment dams and the drainage measures such as construction of drainage ditches are proposed based on our results it is recommend that the control measures should be chosen based on the debris flow initiation type which affects the peak discharge bulk density and the discharge process the mitigation strategies discussed in this paper are based on experimental simulations of the debris flows in the weijia huashiban and xijia gullies of old beichuan city the results are useful for post disaster reconstruction and recovery as well as for preventing similar geohazards in the future

the processes and mechanism of failure and debris flow initiation for gravel soil with different clay content clay content can influence gravel soil mass failure and debris flow initiation significantly but quantification of the clay content influence in the published literature is lacking this paper describes the experiments carried out to explore soil mass failure and debris flow initiation with different clay contents the whole process of gravel soil mass failure and debris flow initiation can be grouped into five phases i infiltration excess runoff ii fracture extending iii initial slip iv large scale slip v debris flow triggering in the experiments when the clay content of soil mass is lower than 2 5 no soil failure and debris flow are triggered only the soil masses with moderate clay contents 5 10 show the clear processes of the five phases that need the shortest rainfall duration among different clay contents soil masses with high clay content 10 and low clay content 2 5 5 need longer rainfall duration to cover the five phases for partially triggering soil failure and debris flows clay content is closely linked with the soil failure and debris flow initiation under rainfall the key mechanism can be grouped into two reasons i the clay particles absorb the moisture and dilate to fill the soil pores and the content of the clay has a direct link with the filled pores ii the gravel soil masses with different clay content differ in their structure for the low clay content soil mass group 2 5 5 the coarse grains of the gravel soil form large pores and saturated clay particles are too few to block most soil pores as a result pore water pressure of soil mass is released easily in the raining process therefore inner friction holds strong and soil mass is hard to mobilize into slip and debris flows on the other hand for soil masses with high 10 clay contents soil failure and debris flow are triggered under the aid of surface runoff flux to reduce the cohesion of the soil whereas only for the soil masses with moderate clay contents 5 10 large scale soil failure and debris flow can be triggered within the shortest duration in this case the debris flow is of the form of soil mechanics which is triggered after soil masses slip and liquefaction the others are of the form of hydraulic mechanics the experiments provide valuable evidence for quantifying clay content impact on gravel soil failure and debris flow initiation because they were carried out in a flume the research results are applicable to the soil failure and debris flow initiation in bedrock gully situations

debris flow initiation and sediment recharge in gullies landslides that enter gullied low order drainages can either initiate debris flow or stop depositing sediment in the channel this process is one of the most common ways that debris flows initiate but little attention to date has been paid to evaluating the factors that affect whether or not the initial landslide will become a debris flow or deposit sediment in the channel statistically significant parameters that determine whether slope failures become debris flows or act to recharge in channel sediment are channel gradient angle of entry of failure into the channel initial failure volume and the amount of in channel stored sediment steeper channels low angles of entry lower volumes of in channel sediment and larger initial failures were more likely to result in debris flows this study found that as the volume of in channel stored sediment increased the volume of initial failure required to initiate a debris flow also increased this result calls into question the simple supply limited model of cyclical debris recharge and debris flow in low order gullied drainages and suggests a negative feedback mechanism between debris accumulation and debris flow susceptibility

alpine debris flows triggered by a 28 july 1999 thunderstorm in the central front range colorado on 28 july 1999 about 480 alpine debris flows were triggered by an afternoon thunderstorm along the continental divide in clear creek and summit counties in the central front range of colorado the thunderstorm produced about 43 mm of rain in 4 h 35 mm of which fell in the first 2 h several debris flows triggered by the storm impacted interstate highway 70 u s highway 6 and the arapahoe basin ski area we mapped the debris flows from color aerial photography and inspected many of them in the field three processes initiated debris flows the first process initiated 11 of the debris flows and involved the mobilization of shallow landslides in thick often well vegetated colluvium the second process which was responsible for 79 of the flows was the transport of material eroded from steep unvegetated hillslopes via a system of coalescing rills the third which has been termed the firehose effect initiated 10 of the debris flows and occurred where overland flow became concentrated in steep bedrock channels and scoured debris from talus deposits and the heads of debris fans these three processes initiated high on steep hillsides 30 in catchments with small contributing areas 8000 m2 however shallow landslides occurred on slopes that were significantly less steep than either overland flow process based on field observations and examination of soils mapping of the northern part of the study area we identified a relation between the degree of soil development and the process type that generated debris flows in general areas with greater soil development were less likely to generate runoff and therefore less likely to generate debris flows by the firehose effect or by rilling the character of the surficial cover and the spatially variable hydrologic response to intense rainfall rather than a threshold of contributing area and topographic slope appears to control the initiation process in the high alpine of the front range because debris flows initiated by rilling and the firehose effect tend to increase in volume as they travel downslope these debris flows are potentially more hazardous than those initiated by shallow landslides which tend to deposit material along their paths

frequency of debris flows and their relation with precipitation a case study in the central alps italy abstract debris flows are very important and widespread mass movements and represent a remarkable geomorphological hazard this research deals with debris flows in an alpine environment studied using dendrogeomorphological dating techniques outlining their relation with precipitation and analysing possible changes in their frequency and intensity over time the study area is the upper valle del gallo northern italy a typical high mountain environment dominated by mass wasting processes where many debris flow fans occupy the valley bottom dendrogeomorphological research was conducted on twelve of these fans and two channels located on slopes tree growth anomalies abrasion scars compression wood and abrupt growth changes were used as dating methods two hundred and thirty nine debris debris flow events between 1875 and 2003 were dated using 757 trees pinus montana mill analysis between dated events and precipitation suggests that debris flows in the study area could be triggered by 20 30 mm of rain concentrated in a few hours the debris flow frequency tends to increase gradually but the highest value seems to have occurred in the period 1974 1983 this trend agrees with the historical occurrence of flooding events in northern italy as inferred by literature and with similar studies conducted in the swiss alps the results of this research are intended as a contribution for understanding the response of geomorphological processes to climatic changes

cross shelf seawater exchange controls the distribution of temperature salinity and neritic carbonate sediments in the great australian bight the seasonally averaged wind stress of the great australian bight gab during the austral winter is directed to the east along the shelf and results in downwelling that extends to depths of 250 m this downwelling is enhanced in the eastern gab through the outflow of cold saline water formed in the broad shallow regions of the gab and gulfs during the austral summer the averaged wind stress field of the gab is anticyclonic with upwelling favorable winds along much of the coastline in general however significant slope upwelling is only observed in the eastern and western gab where the shelf is narrow upwelling there provides nutrients to support the planktic and pelagic communities and the observed distribution of benthic invertebrate communities that lead to the formation of neritic carbonate sediments at the shelf break of the central gab where the shelf is very wide the observed cross shelf distributions of temperature salinity and sediments indicate that downwelling occurs year round the implied lack of nutrients is argued to explain the smaller communities of invertebrates found at the shelf edge 100 250 m in these areas a previous numerical study is cited to show that summer downwelling very likely results from a convergence of the deep ocean and poleward sverdrup transports the unique aspect of this integrated oceanographic sedimentological investigation is to tie outcomes of that numerical study with extant observations and benthic habitat to provide a consistent picture of how cross shelf exchange regulates water properties and benthos in the gab

the influence of mixing on primary productivity a unique application of classical critical depth theory mixing and primary productivity was examined in upwelling influenced nearshore waters off south western eyre peninsula swep in the eastern great australian bight egab the economically and ecologically important shelf region off southern australia that forms part of the southern and indian oceans mixing stratification in the region was highly temporally variable with a unique upwelling circulation in summer autumn november april and downwelling through winter spring may september highest productivity was associated with upwelled stratified water up to 2958 mg c m

evidence of a large seasonal coastal upwelling system along the southern shelf of australia 1 we report observational existence of a large seasonal coastal upwelling system that establishes in austral summer december april along australian southern shelves wind driven upwelling events occur simultaneously in three upwelling centres spanning a distance of 800 km during each summer period there are 2 3 major upwelling events each lasting 1 week the simultaneous rapid response of sst to wind forcing in the upwelling centres which display vastly different shelf widths points to the existence of a larger scale process that carries cold water onto the shelf prior to the upwelling season exploration of a major upwelling event in march 1998 shows the evolution of peak surface chlorophyll a concentrations of 4 g l lagging the onset of upwelling by 1 week the associated exponential growth rate can be estimated at 0 4 d 1 another week later we found a distinct sub surface chlorophyll a maximum at a depth of 50 m centred along the upwelling front reasons for the formation of this maximum are not fully understood

thermal history vs fabric anisotropy in granitoids emplaced at different crustal levels an example from calabria southern italy the sila and serre granitoids of calabria were emplaced in the late carboniferous at depths ranging from 6 to 23 km in a postcollisional extensional regime their fabric which developed during and after final crystallization up to the solid state strongly increases in intensity with emplacement depth this relationship is attributed to the thermal history of the calabrian basement cooling histories of granitoids constrained by geological data and rb sr cooling ages on micas demonstrate that residence times of rocks at temperatures greater than those of the brittle ductile transition vary greatly as a function of initial emplacement depth this explains why shallow level granitoids that remained for about 10 myr at temperatures above those of the brittle domain retain their original magmatic fabric by contrast the strong fabrics of the deep seated granitoids are explained by solid state strain overprint that lasted more than 100 myr at temperatures above those of the brittle domain

the relationship between tectono metamorphic evolution and argon isotope records in white mica constraints from in situ 40ar 39ar laser analysis of the variscan basement of sardinia the basement of sardinia represents a nearly complete section of a segment of the variscan belt that experienced a polyphase tectonometamorphic evolution and barrovian metamorphism this basement is well suited to investigate the relationship between tectono metamorphic evolution and argon isotope records in white mica micaschists from the garnet zone maximum t of up to 520 560 c contain two texturally and chemically resolvable generations of white mica 1 deformed celadonite rich flakes defining a relict s1 foliation preserved within the main s2 foliation or enclosed in rotated albite porphyroblasts 2 celadonite poor white micas aligned along the main s2 foliation the s1 foliation developed earlier and at a deeper crustal level with respect to that at which the thermal peak was reached from the staurolite zone t of up to 590 625 c to the sillimanite k feldspar zone white mica is nearly uniform in composition muscovite and is predominantly aligned along the s2 foliation or is of later crystallization in situ ar ar laser analyses of white mica yielded ages of 340 315ma in the garnet zone and 320 300ma in the staurolite and sillimanite k feldspar zones results highlight a close link between argon isotope records in white mica and both textures and structure forming major elements the oldest ages were detected in samples where the earlier syn d1 white mica generation did not texturally and chemically re equilibrate at upper crustal levels this study suggests that the white micas that escaped recrystallization retain argon isotope records of an earlier metamorphic stage that survived a later event characterized by temperatures higher than 500 c

equilibration and disequilibration between monazite and garnet indication from phase composition and quantitative texture analysis the integration of information which can be gained from accessory i e age t and rock forming minerals i e temperature t and pressure p requires a more profound understanding of the equilibration kinetics during metamorphic processes this paper presents an approach comparing conventional p t estimate from equilibrated assemblages of rock forming minerals with temperature data derived from yttrium garnet monazite ygm and yttrium garnet xenotime ygx geothermometry such a comparison provides an initial indication on differences between equilibration of major and trace elements regarding this purpose two migmatites two polycyclic and one monocyclic gneiss from the central alps switzerland northern italy were investigated while the polycyclic samples exhibit trace element equilibration between monazite and garnet grains assigned to the same metamorphic event there are relics of monazite and garnet obviously surviving independent of their textural position these observations suggest that surface processes dominate transport processes during equilibration of those samples the monocyclic gneiss on the contrary displays rare isolated monazite with equilibration of all elements despite comparably large transport distances with a nearly linear crystal size distribution of the garnet grain population growth kinetics related to the major elements were likely surface controlled in this sample in contrast to these completely equilibrated examples the migmatites indicate disequilibrium between garnet and monazite with a change in ree patterns on garnet transects the cause for this disequilibrium may be related to a potential disequilibrium initiated by a changing bulk chemistry during melt segregation while migmatite environments are expected to support high transport rates i e high temperatures and melt presence the evolution of equilibration in migmatites is additionaly related to change in chemistry as a key finding surface controlled equilibration kinetics seem to dominate transport controlled processes in the investigated samples this may be decisive information towards the understanding of age data derived from monazite

a review of the shelf slope circulation along australia s southern shelves cape leeuwin to portland abstract a review is presented of the ocean circulation along australia s southern shelves and slope uniquely the long zonal shelf is subject to an equatorward sverdrup transport that gives rise to the flinders current a small sister to the world s major western boundary currents the flinders current is strongest near the 600 m isobath where the current speeds can reach 20 cm s and the bottom boundary layer is upwelling favourable it is larger in the west but likely intermittent in both space and time due to possibly opposing winds thermohaline circulation and mesoscale eddies the flinders current may be important to deep upwelling within the ubiquitous canyons of the region during winter the leeuwin current and local winds act to drive eastward currents that average up to 20 30 cm s the currents associated with the intense coastal trapped wave field 6 12 day band are of order 25 30 cm s and can peak at 80 90 cm s wintertime winds and cooling also lead to downwelling to depths of 200 m or more and the formation of dense coastal water within the great australian bight and the south australian sea within the great australian bight the thermohaline circulation associated with this dense water is unknown but may enhance the eastward shelf edge south australian current the dense salty water formed within spencer gulf is known to cascade as a gravity current to depths of 200 m off kangaroo island this dense water outflow and meanders in the shelf circulation also fix the locations of a sequence of quasi permanent mesoscale eddies between the eyre peninsula and portland during summer the average coastal winds reverse and surface heating leads to the formation of warm water in the western great australian bight and the south australian sea no significant exchange of shelf water and gulf water appears to occur due to the presence of a dense nutrient rich sub surface pool that is upwelled off kangaroo island the winds lead to weak average coastal currents increasing evidence suggests that el nino events 4 7 year period can have a major impact on the winter and summer circulation these events propagate from the pacific ocean and around the shelf slope wave guide of west australia and into the great australian bight during winter el nino events the average shelf currents may be largely shut down during summer the thermocline may be raised by up to 150 m the nature and role of tides and surface waves is also discussed along with uncertainties in the general circulation and future research

effects of soil aggregates on debris flow mobilization results from ring shear experiments abstract rates and styles of landslide motion are sensitive to pore water pressure changes caused by changes in soil porosity accompanying shear deformation soil may either contract or dilate upon shearing depending upon whether its initial porosity is greater or less respectively than a critical state porosity attained after sufficiently high strain we observed complications in this behavior however during rate controlled 0 02 m s 1 ring shear experiments conducted on naturally aggregated dense loamy sand at low confining stresses 10 6 and 40 kpa the aggregated soil first dilated and then contracted to porosities less than initial values whereas the same soil with its aggregates destroyed monotonically dilated we infer that aggregates persisted initially during shear and caused dilation before their eventual breakdown enabled net contraction an implication of this contraction demonstrated in experiments in which initial soil porosity was varied is that the value of porosity distinguishing initially contractive from dilative behavior can be significantly larger than the critical state porosity which develops only after disaggregation ceases at high strains in addition post dilative contraction may produce excess pore pressures thereby reducing frictional strength and facilitating debris flow mobilization we infer that results of triaxial tests which generally produce strains at least a factor of 4 smaller than those we observed at the inception of post dilative contraction do not allow soil contraction to be ruled out as a mechanism for debris flow mobilization in dense soils containing aggregates

particle interaction inside debris flows evidence through experimental data and quantitative clast shape analysis abstract results of analytical experiments related to the dynamic behavior of debris flows are presented particle interaction and the amount and type of fines content present in the matrix aspects that govern debris flow behavior are studied via the morphological evolution of constituent particles four different mixtures of water and sediment with compositions resembling debris flows were prepared and put into a rotating drum known as a los angeles standard abrasion machine and studied at different time intervals for each sampling time quantitative shape analysis was performed using three morphological coefficients mc 2 mc 3 8 and mc 30 34 coefficient mc 2 gives information about particle ellipticity mc 3 8 is related to basic irregularities at a macro scale such as roundness mc 30 34 is related to microscale irregularities like surface texture coefficient mc 3 8 was shown to be very sensitive to silt content in the matrix and coefficient mc 30 34 to the presence of clay all three coefficients point to the fact that changes in shape between granulometric classes are gradual and follow a power law coarse granulometric classes acquire more circular and smooth profiles while small particles maintain their irregular profiles this phenomenon is the result of clast interaction processes within mixtures clast collisions between particles produce comminution of the coarsest fractions while finer particles fracture along their entire surface the rate at which these changes occur is related to the type of fine sediment present in the matrix changes in particle shape are an important tool for revealing internal dynamics because they are related to clast interaction and affect sedimentation processes inside these flows this type of experiment although not on a real scale provides important physical information for understanding the phenomena that occur inside debris flows enabling the study of a variety of textural parameters and their changes at regular time intervals the experimental patterns observed offer new insights into clast clast interaction rounding and comminuting theory with important implications for understanding rheological behavior and kinematics of flows and related hazards