complex concentric granitoid intrusions in the coastal mobile belt espirito santo brazil the santa angelica pluton an example the brazilian coastal mobile belt in southern espirito santo consists of archean to upper proterozoic units which have been metamorphosed and deformed to a gneiss migmatite and granulite facies rock assemblage during archean and proterozoic tectono thermal events

the fluid dynamics of a basaltic magma chamber replenished by influx of hot dense ultrabasic magma this paper describes a fluid dynamical investigation of the influx of hot dense ultrabasic magma into a reservoir containing lighter fractionated basaltic magma this situation is compared with that which develops when hot salty water is introduced under cold fresh water theoretical and empirical models for salt water systems are adapted to develop a model for magmatic systems a feature of the model is that the ultrabasic melt does not immediately mix with the basalt but spreads out over the floor of the chamber forming an independent layer a non turbulent interface forms between this layer and the overlying magma layer across which heat and mass are transferred by the process of molecular diffusion both layers convect vigorously as heat is transferred to the upper layer at a rate which greatly exceeds the heat lost to the surrounding country rock the convection continues until the two layers have almost the same temperature the compositions of the layers remain distinct due to the low diffusivity of mass compared to heat the temperatures of the layers as functions of time and their cooling rate depend on their viscosities their thermal properties the density difference between the layers and their thicknesses for a layer of ultrabasic melt 18 mgo a few tens of metres thick at the base of a basaltic 10 mgo magma chamber a few kilometres thick the temperature of the layers will become nearly identical over a period of between a few months and a few years during this time the turbulent convective velocities in the ultrabasic layer are far larger than the settling velocity of olivines which crystallise within the layer during cooling olivines only settle after the two layers have nearly reached thermal equilibrium at this stage residual basaltic melt segregates as the olivines sediment in the lower layer depending on its density the released basalt can either mix convectively with the overlying basalt layer or can continue as a separate layer the model provides an explanation for large scale cyclic layering in basic and ultrabasic intrusions the model also suggests reasons for the restriction of erupted basaltic liquids to compositions with mgo 10 and the formation of some quench textures in layered igneous rocks

significance of ferrodioritic liquids in magma mixing processes a general model to explain the various igneous associations found in mixed magma intrusives and extrusives belonging to high level volcanic centres is presented this model is based on detailed mapping in the british tertiary volcanic centre on skye which suggests that basic and acid magmas were continually available throughout its development new major and trace element data from these rocks indicate that they were co genetic and that the basic magmas which combined with acid magmas to produce hybrid magmas were ferrodioritic in composition and not basaltic as had previously been thought

effects of confining stress density and initial static shear stress on the cyclic shear response of fine grained unclassified tailings a constant volume direct simple shear apparatus was used to investigate the effects of confining stress initial static shear stress and void ratio on the liquefaction resistance of fine grained tailings the cyclic resistance ratio also expressed as the overburden stress correction factor was found to decrease with increasing confining stresses in the range 100 400 kpa and to gradually increase from 400 kpa onwards when samples were tested at the same initial void ratio the presence of an initial static shear stress decreased the liquefaction resistance a key outcome of the work was to reveal the critical importance of density on liquefaction susceptibility of compressible tailings thus a combined correction factor to account for overburden stress and density on cyclic resistance was proposed

petrogenesis of a basalt rhyolite tephra from the west central afar ethiopia the cindery tuff is an unusual tephra fall deposit that contains evidence for the mixing of basaltic and rhyolitic liquids prior to eruption it contains clear rhyolitic glass shards together with brown basaltic glass spheres and a broadly bimodal phenocryst assemblage brown glasses are ferrobasaltic in composition and are similar to the voluminous pliocene tholeiites of the surrounding west central afar volcanic field both are enriched in the light rare earth and incompatible elements and possess higher 87sr 86sr and lower 143nd 144nd than morb rhyolitic glasses are subalkaline and compared to the basaltic glasses are strongly depleted in the compatible elements and enriched in the incompatible elements both glass types have similar incompatible element and isotopic ratios and with the rhyolite glass showing a 2 fold parallel enrichment in rare earth element abundances over the basaltic glass these observations suggest that the two glasses are genetically related

a laboratory model of a replenished magma chamber abstract it has recently been suggested that periodic influxes of hot but heavy magma into the base of a basaltic magma chamber can remain isolated from the rest of the chamber while the new magma cools and crystallization proceeds when thermal equilibrium is almost complete the suspended crystals settle out and the residual less dense liquid can then mix with the fluid above in the present paper the basic fluid dynamical processes underlying this model have been investigated in laboratory experiments using aqueous solutions the lower layer was hot kno3 solution for which saturated solutions become less dense as the temperature decreases with a cold deeper layer of less dense nano3 or k2co3 above the lower layer there was strong convective transfer of heat through a sharp interface separating the layers at a rate which is predicted here drawing on previous studies carried out with oceanographic applications in mind once crystallization began non equilibrium effects became important and the observed temperatures differ somewhat from those predicted in the experiments crystals grew mainly from the bottom rather than while in suspension but this is not an essential aspect of the model the important fact is that the density of the residual liquid in the lower layer decreased until it became equal to that of the upper layer and then the interface broke down so that the two layers mixed thoroughly together leaving a layer of kno3 crystals at the base no crystallization at all occurred when the hot input liquid was forced to mix initially with the cold solution already in the chamber

interaction between coeval mafic and felsic melts in the st francois terrane of missouri usa abstract in the eastern st francois mountains of missouri a 1 48 ga subvolcanic ring pluton known as the silvermine granite hosts swarms of dark pillow shaped enclaves exhibiting classical features of mafic melt globules trapped in granitic magma the pillows formed by turbulent injection of near liquidus mafic melt into a resident visco plastic granitic magma exchange of crystals fluids and ions between the two melts produced a hybrid tonalite granite enclave series and modified host granite composition several lines of evidence suggest interaction between granitic melt that produced the granophyric cap of the pluton and basaltic melt that formed dikes in the area rapid cooling of the pillows re melted the host creating back veins in many enclaves mineral chemistry indicates the hybrid rocks have undergone extensive subsolidus re equilibration

influence of strain history on postliquefaction deformation characteristics of sands abstract an experimental study aimed at improving the understanding of the role of maximum cyclic strain during earthquake loading on the subsequent response of liquefied sands is presented the behavior of two sands one generally strain hardening and the other strain softening over a range of stress and density states during virgin monotonic loading is presented to demonstrate that regardless of whether a sand is contractive or dilative in preliquefaction loading its response following liquefaction is dilative it is shown that postliquefaction stress strain behavior can be characterized by four distinct phases the influence of relative density confining stress and the level of maximum shear strain during earthquake loading prior to liquefaction preliquefaction strain preliq on the response of liquefied sand varies during each of these phases the first phase of deformation essentially at zero stiffness is highly dependent on the level of preliquefaction strain but is not significantly affec

interactions between basaltic and granitic magmas in a svecofennian postorogenic granitoid intrusion aland southwest finland abstract the lemland intrusion is one of four postorogenic 1815 1770 ma granitoid intrusions occurring in southwestern finland the intrusions are dominated by porphyritic granite and basic intermediate rocks they show features of a bimodal magmatism causing net veining and formation of mixed rocks the current investigation of the southern part of the lemland intrusion reveals that the basic intermediate rocks form a ring like structure in which the rocks can be divided in three tentative units 1 fine grained mafic pillows in porphyritic granite 2 mixed rocks with mafic inclusions in a hybrid matrix and 3 medium grained mafic rock it is suggested that the ring like structure with the different units was emplaced from a disrupted zoned magma chamber and the different rock units were created due to differences in chemical and physical properties of the magmas the process started with the intrusion of basic magma into overlying acid magma creating basic pillows within it during the upward movement the basic magma left behind an area where the basic and the acid magma were intimately commingled and mixed this mixed magma intruded into the area inside the mafic pillows which formed an isolated barrier against the cooler acid magma the medium grained mafic rock in the middle of the ring structure is regarded as the same rock as the fine grained mafic rock the coarser grain size depending on the longer time for crystallization this rock was back veined and brecciated by the mixed magma creating a mega breccia when this process ended the acid magma was still active and formed cutting dykes in the mafic and mixed rocks

origin of hybrid ferrolatite lavas from magic reservoir eruptive center snake river plain idaho the mineralogy and geochemical characteristics of intermediate composition ferrolatites and related lavas from the magic reservoir eruptive center central snake river plain have been investigated to evaluate the origin and petrologic significance of these hybrid lavas the ferrolatites are chemically uniform but contain a disequilibrium phenocryst xenocryst assemblage derived in part from mixed rhyolitic and basaltic magmas that are closely represented by extrusive units in the area the hybrid lavas also contain xenoliths of archean granulites and have high 87sr 86sr and low 143nd 144nd ratios all of which suggest significant magma crust interaction quantitative models including magma mixing minor crystal fractionation and crustal contamination very closely reproduce the observed compositions of these ferrolatites closed system fractionation and or simple bulk contamination models are not as successful and can be ruled out it appears that preexisting mafic and silicic magmas from distinct sources e g mantle and crust encounter one another in crustal level magma chambers under conditions where intimate mixing may occur despite wide differences in the physical properties of these liquids

cyclic behaviour of reconstituted and desiccated rewet thickened gold tailings in simple shear a simple shear apparatus norwegian geotechnical institute ngi type has been used to investigate the mechanical behaviour of gold tailings under monotonic cyclic and post cyclic loading specimens were prepared either by reconstituting the tailings at different water contents or by employing a dry wet preparation technique the latter technique attempted to simulate a realistic stress history for thickened tailings deposition by preparing the specimen at the pumping water content and subsequently allowing it to settle and then desiccate to a target water content subsequently these specimens are rewetted and then consolidated cyclic resistance ratios for specimens prepared by the dry wet preparation technique were considerably higher than those of specimens prepared by the standard technique though there appears to be no advantage in drying the tailings past the shrinkage limit in general the tailings could experience significant deformation during cyclic and post cyclic loading irrespective

an evaluation of direct simple shear tests on clay normally consolidated samples of kaolin have been tested in two direct simple shear apparatuses the first apparatus is specially instrumented with load cells in the horizontal boundaries to investigate the uniformity of the stresses acting on the samples the internal deformations and strains are determined using radiographic techniques the radial stress is determined from membranes reinforced with resistance wire the second apparatus is a standard commercially available device supplied by geonor the stresses and strains are shown to be uniform in the central region of the sample away from the vertical boundaries until failure values of the stress and strain variables determined from the central region are representative of a uniform simple shear deformation in plane strain in all tests the samples fail by developing approximately horizontal ruptures values of the shear modulus and shear strength estimated from the average stresses in the geonor apparatus underestimate by approximately 10 the

petrogenetic interpretation of granitoid rock series using multicationic parameters abstract granitoid rock compositions from a range of tectonic environments are plotted on a multicationic diagram devised by de la roche and his coworkers this shows that there is a systematic change through an orogenic cycle which leads progressively to the ultimate development of alkaline magmas possible source materials and mechanisms of magma generation are considered from analysis of mineral compositional vectors these suggest that most granitoid series result from a two stage process first fractional crystallisation of clinopyroxene olivine and calcic plagioclase from a basic source with tholeiitic affinities produces a magma of intermediate composition this magma then undergoes periodic mixing with a felsic magma followed by in situ fractionation to generate individual intrusions within granitoid series

composite minor intrusions as windows into subvolcanic magma reservoir processes mineralogical and geochemical evidence for complex magmatic plumbing systems in the british tertiary igneous province the rudh a chromain sill is a composite minor intrusion emplaced into jurassic sandstones on the south coast of the ross of mull nw scotland and is part of a suite of basic silicic sheets associated with the early development of the 58 56 ma mull central igneous complex new whole rock major and trace element data combined with sr nd pb isotope data indicate that two distinct magma end members were involved in the formation of the sill a tholeiitic basaltic andesite magma generated by contamination and fractional crystallization of regionally available olivine tholeiite basaltic magma and a rhyolitic magma produced predominantly through crustal melting of basement metasediments intermediate compositions at the gradational boundaries between the basic margins and silicic interior of the sill formed by high temperature diffusive hybridization within a compositionally zoned magma reservoir prior to sheet emplacement the basic portions of the sheet are replete with a large variety of crustal xenoliths as well as numerous gabbroic and noritic cumulate fragments the rudh a chromain sill therefore preserves evidence for the complex interplay between a number of magmatic processes which when combined with data from the remainder of the suite suggests that the magmatic plumbing system which fed the sill complex was not simply one large long lived magma chamber but rather a plexus of variably connected sheet like magma reservoirs

magmatic evolution of the skye igneous centre western scotland modelling of assimilation recharge and fractional crystallization the skye igneous centre forming part of the british tertiary magmatic province developed over a 7 myr period 61 54 ma and is characterized by a complex suite of lavas hypabyssal and intrusive rocks of picritic to granitic composition the intrusion of magma from mantle to crust at 2 10 3 km 3 yr 6 mt yr advected magmatic heat of roughly 0 2 gw averaged over the period of magmatism supporting an excess heat flux of about 130 mw m 2 or about twice the present day average continental heat flow the volume of new crust generated at skye 15 000 km 3 spread over the present day area of skye corresponds to 9 km of new crust the geochemical evolution of the skye magmatic system is constrained using the energy constrained recharge assimilation and fractional crystallization ecrafc model to understand variations in the sr and pb isotopic and sr trace element composition of the exposed magmatic rocks with time the character composition and specific enthalpy of both assimilant and recharge magma appears to change systematically up section suggesting that the magma reservoirs migrated to progressively shallower levels as the system matured the model of the magma transport system that emerges is one in which magma batches are stored initially at lower crustal levels where they undergo rafc evolution residual magma from this stage then migrates to shallower levels where mid crustal wall rock is assimilated the recharge magma at this level is characterized by an increasingly crustal signature for some of the stratigraphically youngest rocks the data suggest that the magma reservoirs ascended into and interacted with upper crustal torridonian metasediments

the loch scridain xenolithic sill complex isle of mull scotland fractional crystallization assimilation magma mixing and crustal anatexis in subvolcanic conduits

effects of gravel content on shear resistance of gravelly soils abstract shallow landslides in colluvium which generally consists of wide particle gradation in a loose state occur in steep slope terrains to perform stability analyses shear strength parameters that represent soil constituents in situ stress state and shearing mode are needed this experimental study investigates the effects of gravel content on the shearing characteristics of gravelly soils based on the intergrain state concept a series of drained simple shear tests was performed on reconstituted specimens of gap and well graded sands with various gravel content levels the results reveal that 1 the shear strength of gravelly soils depends on the packing condition of dominant particles with the intergrain granular void ratio being a more representative parameter for the soil packing condition than the global void ratio 2 the drained shear strength of loose gravelly sand is dominated by sand matrix properties with the inclusion of gravel content reducing the strength by no more than 20 compared to that of pure sand 3 the strength parameters of sand like gravelly soils can be estimated from the sand matrix with proper reduction

sr isotope variations in a composite sill crystal liquid processes and the origin of the skye granites sr isotope data from the rubh an eireannaich sill one of a suite of composite mafic silicic minor intrusions associated with the 59 ma skye intrusive centre nw scotland indicate that both crystal liquid fractionation and magma mixing processes have played important roles in its genesis the data indicate that two distinct magmas were involved in the formation of the sill a ferrobasaltic andesite magma generated by contamination and fractional crystallization of regionally available basaltic magma and a rhyolite magma which has a significant crustal component hybrid intermediate compositions at the gradational boundaries between the mafic and silicic components of the sill formed by mixing prior to or during emplacement whilst fractional crystallization of the unmixed silicic magma occurred almost exclusively after mixing the identification of a significant crustal component within the silicic portion of the sill suggests that the compositionally related granites of the skye intrusive centre have a similar origin

geochemical evolution of the tertiary mull volcano western scotland the early tertiary mull volcano western scotland is one of the most dissected and best exposed igneous complexes of the north atlantic province the new and published geochemical data enable us to chart the magmatic evolution of the mull volcano from the oldest lavas through the intrusive rocks of three overlapping igneous centres to the youngest dykes in this study we identify four successive magma types within the remnant volcano the earliest type the mull plateau group comprises mildly alkaline basaltic rocks with steep chondrite normalized rare earth element ree patterns this type is succeeded within the lava succession and dyke swarm by the coire gorm magma type with essentially flat chondrite normalized ree patterns a third magma type represented within the lava and dykes the central mull tholeiites is more depleted in incompatible trace elements than the preceding types and has flat to lree depleted chondrite normalized patterns the major intrusions and cone sheets of mull centre 1 and early centre 2 belong to this magma type midway through the igneous activity associated with centre 2 the magma type changed to become more alkalic and more enriched in incompatible trace elements this magma type the late mull type is found to persist through the cone sheets and major intrusions of centre 3 to the youngest dykes these changes in magma composition were related to variations in the mantle source and depth of partial melting beneath mull and or differences in the efficiency of melt pooling before ascent through the lithosphere with the exception of the early staffa magma sub type part of the mull plateau group the location of magma chambers in which the bulk of contamination occurred changed with time from deep lower crustal lewisian gneiss to shallow upper crustal moine schist intermediate members of the plateau group and the late mull magma type are enriched in fe ti and p relative to the central mull tholeiites we attribute this difference to the more alkalic nature of these suites lower fo2 and the formation of fe3 p complexes in the magma the intermediate rocks were important in magma mixing processes with two types of mixing identified on mull 1 cryptic mixing between basalts and low fe intermediate magmas typified by lavas and early basic cone sheets of the central mull tholeiite magma type 2 observable mingling between rhyolitic magmas and high fe intermediate magmas of the late mull type shown by the mixed magma bodies of the glen more and loch ba ring dykes the main factor in determining which type of mixing occurred appears to have been the density contrast between the various magmas it may safely be maintained that mull includes the most complicated igneous centre as yet accorded detailed examination anywhere in the world bailey et al 1924 memoir of the geological survey of great britain scotland hmso edinburgh 1924

sedimentary and volcano tectonic processes in the british paleocene igneous province a review research on the british paleocene igneous province bpip has historically focused on the emplacement chemistry and chronology of its elaborate central intrusive complexes and lava fields however the bpip has also been dramatically shaped by numerous erosion sedimentation and volcano tectonic events the significance of which becomes ever clearer as localities in the bpip are re investigated and our understanding of volcano sedimentary processes advances the resultant deposits provide important palaeo environmental palaeo geographical and stratigraphical information and highlight the wide range of processes and events that occur in ancient volcanic settings such as the bpip in this paper we review the sedimentary and volcano tectonic processes that can be distinguished in the bpip and conceptualize them within a generalized framework model we identify and describe the sedimentary responses to four broadly chronological stages in the history of the bpip volcanoes 1 the development of the lava fields 2 early intrusion induced uplift 3 caldera collapse and 4 post volcano denudation and exhumation of central complexes we highlight and illustrate the range of sedimentary processes that were active in the bpip these operated on and helped shape a dynamic landscape of uplands and lowlands of alluvial fans braided rivers lakes and swamps and of volcanoes torn apart by catastrophic mass wasting events and or caldera collapse

magma mixing the marsco suite isle of skye scotland magma mixing has been proposed as a major mechanism for the origin of a wide variety of rock suites in mid ocean basalts there are few obstacles to mixing because of the similarities in chemical and physical properties of the proposed end members however in calc alkaline rocks the proposed end members have disparate properties and these present obstacles to mixing

pre eruptive magma mixing in ash flow deposits of the tertiary rum igneous centre scotland the northern marginal zone of the rum igneous centre is a remnant of an early caldera and its infill it is composed of intra caldera breccias and various small volume pyroclastic deposits overlain by prominent rhyodacite ash flow sheets of up to 100 m thickness the ash flows were fed from a feeder system near the caldera ring fault and intrusive rhyodacite can locally be seen grading into extrusive deposits a variety of features suggest that the ash flows were erupted from a magma chamber that contemporaneously hosted felsic and mafic magmas i chilled basaltic inclusions in rhyodacite ii formerly glassy basaltic to andesitic enclaves with fluid fluid relationships iii feldspars with thick reaction rims enclosed in the basaltic to andesitic inclusions yet with cores chemically resembling those of the rhyodacite iv trace element compositions of the rhyodacite and the mafic enclaves form a mixing line between the end member rhyodacite and basalt compositions additionally textural and chemical features in the rhyodacite feldspar phenocrysts are consistent with magma mixing v feldspars with resorption embayments cutting through internal zonation of the crystals vi complexly zoned crystals with sieve textured zones that are overgrown with euhedral zones vii oscillatory zonation of feldspar phenocrysts in the rhyodacite showing sharp increases in anorthite an 10 followed by gradual decrease in an content an 4 this evidence points to eruption of ash flows from a felsic magma chamber that was periodically replenished by injection of mafic magma diffusional mixing between the two magmas was permitted by temperature and compositional differences but was slow due to the contrast in viscosities and densities the fe ti p enriched basic magma that replenished the chamber was degassing on entering the lower temperature environment and soon equilibrated thermally followed by chemical exchange between the two end member magmas this process formed hybrid andesite enclaves enriched in trace elements beyond that caused by simple mixing implying trace element diffusion in addition to bulk mixing eruption was caused by replenishment with and degassing of the basic magma and the chamber partially evacuated while the process of hybridisation was underway the erupted products record magma mixing by chamber replenishment blending of two magmas and elemental exchange in the magma chamber and also physical mingling in the eruptive conduit

effect of static shear stress on the cyclic resistance of sands in simple shear loading an experimental study of the effect of initial static shear stress on the undrained simple shear response of sands is presented liquefaction resistance of two sands one generally contractive and the other dilative over a wide range of density and effective stress levels was evaluated at various density and stress states at a given density the effect of static shear on the cyclic resistance of sands is dependent on the type of stress strain response that ensues during loading the general notion that static shear increases the cyclic resistance of sands at relatively high densities is not valid if the sand is contractive at the denser state the k correction factor for sand at 80 relative density may be as low as about 0 6 for strain softening sand depending on the initial stress state the routine industry practice of disregarding the k factor in dense sands may thus lead to unsafe designs in such materials the k values measured under cyclic simple shear loading are compared to the k values

replenished magma chambers effects of compositional zonation and input rates several recent publications have reported investigations of the dynamical effects and geological consequences of the replenishment of a homogeneous magma chamber by the rapidinjection of hot relatively dense fresh magma the new magmaforms a separate layer at the base of the chamber whereit cools and crystallizes until the density of the residual liquid in the lower layer becomes equal to that of the upperlayer at which time the fluid in the two layers becomes intimately mixed the fluid dynamical aspects of this modelwere confirmed by laboratory experiments using aqueous solutions this paper reports three experimental variations on the basic theme which examine the effects of the rate of injection into homogeneous and compositionally stratified chambers first the rapid injection of a hot dense layer beneath a fluid with a lower temperature and a vertical compositional gradient is considered a series of layers gradually builds up from the base of the upper gradient region while the lower layer cools crystallizes and finally overturns in this situation however the rise of the lower layer fluid is restrained by the density gradient and mixing takes place with only part of the upper fluid second the slow influx of a hot dense liquid beneath a cold less dense homogeneous layer is considered a considerable quantity of the input fluid coolsand crystallizes immediately releasing some lighter fluid to mix with the fluid in the homogeneous layer with time some dense input fluid spreads along the bottom so that locally the situation is the same as the one considered in the previous studies with a local overturning occurring when the density of the lower fluid has decreased sufficiently the deposition of crystals continues and some rather fine chimney like structures can develop which bear a resemblance to the black smokers recently discovered on the sea floor third a combination of the first two variations is studied by the consideration of the slow influx of hot dense liquid beneath a uniformly cooler fluid with a vertical compositional gradient the input fluid is constrained in its rise by the density gradient as the influx continues the additional thermal energy is also confined and causes the crystals to redissolve and build up a lower layer as was observed in the case of a rapid injection beneath a compositional gradient

structure transitions of clay fills in north western bohemia laboratory investigations of a clayey material from a fill created during open cast coal mining are presented standard laboratory experiments direct shear box oedometer have been supplemented by large scale testing the mechanical behaviour of the fragmentary soil is influenced by the presence of macrovoids and shows further size and time effects which makes the description of the clay fill behaviour difficult the initially fragmentary structured soil changes with time back to a homogeneous material due to weathering processes and through geostatic load partial saturation of the fragments also contributes to the peculiar behaviour of the clay fill material

the hydrogeological attributes and mechanisms of a receding sedimentary terrain in the anambra basin southern nigeria this research investigated the hydrogeological aspects associated with severe gulling and landsliding on a vulnerable sedimentary terrain in the context of the newly identified deformation patterns and large numbers of recently discovered scars clustering slopes on identical coordinates results of field survey remote sensing vertical electrical sounding and experimental analyses were presented to explain the causes and mechanisms of the mass movements ravaging the terrain a digital elevation model accurately captured the diverse geomorphologic elements including landslide scars hills ridges valleys plains and rivers that matched field observations the model aided the identification of previously unknown steep incised channels active headcuts unstable side walls and a seasonal river flowing near the slopes having large number of landslide scars it was observed that areas that lay on higher elevations where the clusters occur were dominated by fresh scars while the moderate to low elevations were dominated by older ones majority of the slope failures initiated within the sandstone as shallow slides 1 m to the sliding surface covering 104 m2 with short runout distances bigger landslides although few occurred as isolated individual events initiated at the sandstone shale boundary on distinct slopes the steepness of the slopes seemed controlled by slope morphology concavity which probably influenced the number and distribution of landslide events the steeper slopes were more concave and had the highest concentration of scars shallow water table 4 11 m and increased instability brittleness index under increasing over consolidation ratio are the critical failure factors

orbitolina episodes in carbonate platform evolution the early aptian model from se spain abstract among the orbitolininae palorbitolina lenticularis blumenbach is a common facies marker in upper barremian lower aptian shallow water mesogean deposits and was hitherto ascribed to specific but contrasting paleoenvironments within the carbonate platform facies suites the albacete prebetic area se spain illustrates a model in which the palorbitolina facies spread over the whole platform system the development of the palorbitolina sediments coincided with a transgressive trend at the end of an important terrigenous period this model could also be applied to similar middle crotaceous orbitolina facies