influences of quaternary climatic changes on processes of soil development on desert loess deposits of the cima volcanic field california summary soils formed in loess are evidence of both relict and buried landscapes developed on pliocene to latest pleistocene basalt flows of the cima volcanic field in the eastern mojave desert california the characteristics of these soils change systematically and as functions of the age and surface morphology of the lava flow four distinct phases of soil development are recognized phase 1 weakly developed soils on flows less than 0 18 m y old phase 2 strongly developed soils with thick argillic horizons on 0 18 0 7 m y old flows phase 3 strongly developed soils with truncated argillic horizons massively impregnated by carbonate on 0 7 to 1 1 m y old flows and phase 4 degraded soils with petrocalcic rubble on pliocene flows a critical aspect of the development of stage 1 soils is the evolution of a vesicular a horizon which profoundly affects the infiltration characteristics of the loess parent materials laboratory studies show that secondary gypsum and possibly other salt accumulation probably occurred during the period of phase 1 soil development slight reddening of the interiors of peds from vesicular a horizons of phase 1 soils and presence of weakly developed b horizons indicates a slight degree of in situ chemical alteration however clay and fe oxide contents of these soils show that these constituents as well as carbonates and soluble salts are incorporated as eolian dust in contrast to phase 1 soils chemical and mineralogical analysis of argillic horizons of phase 2 soils indicate proportionally greater degrees of in situ chemical alteration these data the abundant clay films and the strong reddening in the thick argillic horizons suggest that phase 2 and phase 3 soils formed during long periods of time and periodically were subjected to leaching regimes more intense than those that now exist flow age data and soil stratigraphic evidence also indicate that several major loess deposition events occurred during the past 1 0 m y loess events are attributed to past changes in climate such as the pleistocene to holocene climatic change that periodically caused regional desiccation of pluvial lakes reduction of vegetational density and exposure of loose unconsolidated fine materials during times of warmer interglacial climates precipitation infiltrates to shallower depths than during glacial periods extensive saline playas which developed in the mojave desert during the holocene are a likely source of much of the carbonates and soluble salts that are accumulating at shallow depths both in phase 1 soils and in the formerly noncalcareous nongypsiferous argillic horizons of phase 2 and 3 soils

crustal large scale serpentinized mantle peridotite body in the sulu ultrahigh pressure metamorphic belt eastern china evidence from gravity and magnetic anomalies abstract from analysis of the geological and geophysical data gravity magnetic seismic and petrophysics we propose that geophysical anomalies are produced by a serpentinized mantle peridotite body smpb situated in the middle to lower crust in the sulu belt the smpb was formed by crustal emplacement of mantle peridotites accompanied by ultrahigh pressure uhp metamorphism our finding suggests an emplacement mechanism for the serpentinized mantle wedge smw early in the subduction process this is different from the classic view which holds that the serpentinized forearc mantle is formed by in situ hydration processes blakely et al 2005 the petrophysical properties of the smpb are similar to those of the serpentinized forearc mantle or smw in modern subduction zones worldwide but the formation mechanisms for smpb and smw are different this observation is important for understanding the geodynamic processes that operated in the large uhp metamorphic belt in the dabie sulu area eastern china

two dimensional nonlinear diffusive numerical simulation of geomorphic modifications to cinder cones the temporal evolution of simple landforms such as cinder cones by nonlinear diffusive processes is studied through the use of a new 2d numerical model using well established and accurate numerical mathematics and high resolution digital elevation models dems extending 1d profile nonlinear diffusion analyses used in cinder cone hillslope and fault scarp evolution studies we have implemented a 2d numerical model with a spatially and temporally varying sediment transport rate coefficient scaled nonlinearly by the ratio of local slope to critical slope the high accuracy and efficient numerical implementation are documented in the paper and the matlab toolkit developed is used to solve for the developmentof an initial 2d cone form first we examine the nonlinear transport rule and suggest a refinement that accounts explicitly for flux at threshold slopes we find that the maximum diffusion necessarily introduced in the numerical model to avoid infinite rates at the critical slope controls the final morphology especially approaching steady state secondly solving the landscape evolution problem in 2d enables a natural accounting for sediment flux convergence or divergence in the profile thirdly the boundary behavior of a given landscape element controls much of what happens in that domain and so we allow for arbitrary flux magnitude or elevation boundary conditions fourthly landscapes are heterogeneous in their surface cover and so we allow for spatially and temporally varying transport rate k and we permit an arbitrary vertical displacement field within the model domain to test the new formulation for the nonlinear term the effect of variable diffusivity k and the numerical schemes implemented we apply the model to cinder cones built on the flanks of mount etna in 2001 and 2002 2003 we explore the effects of dem resolution with data from the 2001 cone and the utility of spatially variable diffusivity to explain the variation in erosion measured by differencing repeat light detection and ranging lidar surveys gathered in 2004 and 2007 over the 2002 2003 cone complex copyright 2013 john wiley sons ltd

the role of radiogenic heat production in the thermal evolution of a proterozoic granulite facies orogenic belt eastern ghats indian shield abstract the eastern ghats belt egb is a deeply eroded proterozoic orogenic belt juxtaposed against the archaean dharwar bastar singhbhum cratons in the indian shield the tectono metamorphic history of this belt is broadly similar to the grenvillian orogenic belts the egb exposes dominantly the granulite facies rocks such as charnockites khondalites and migmatitic gneisses with less abundant intermediate to mafic granulites the granulites are intruded by small plutons of granites syenites and anorthosites the northern and southern parts of the belt negb and segb have distinct crustal histories but 1600 1000 550 ma old tectono metamorphic events are common to both the belts in this research we attempt to understand the present day and past thermal state of this orogen on the basis of our radioelement k u and th measurements at 562 sites using in situ gamma ray spectrometry with other geological and geophysical constraints the dominant rock types of the negb and segb have similar radioelement abundances 3 k 3 ppm u and 30 ppm th and heat production heat production of charnockites gneisses khondalites and intermediate granulites of the negb is 2 9 2 8 2 9 and 1 1 w m 3 respectively in the segb they are 2 7 2 5 2 8 and 0 6 w m 3 respectively and the mafic granulites are the lowest in heat production 0 3 w m 3 on the basis of the heat production data and crustal petrologic models we show that the crustal contribution of the negb and segb is 54 and 45 mw m 2 respectively which are broadly in good agreement with the available surface heat flow data thermal models of the present day egb crust indicate that the temperature at the moho is 550 c radioelements and heat production of the eastern ghats granulites are higher than the other granulite belts in the indian shield the crustal radiogenic heat contribution and moho temperatures of the egb are higher than the adjoining archaean cratons this could also be responsible for the development of inverted metamorphic isograds in the tectonic boundary between the egb and the adjoining cratons during a collisional orogenic event at about 550 ma ago

influence of late quaternary climatic changes on geomorphic and pedogenic processes on a desert piedmont eastern mojave desert california radiocarbon dating of late quaternary deposits and shorelines of lake mojave and cation ratio numerical age dating of stone pavements dorn 1984 on the adjacent soda mountains piedmont provide age constraints for alluvial and eolian deposits these deposits are associated with climatically controlled stands of lake mojave during the past 15 000 yr six alluvial fan units and three eolian stratigraphic units were assigned ages based on field relations with dated shorelines and piedmont surfaces as well as on soil geomorphic data all but one of these stratigraphic units were deposited in response to time transgressive climatic changes beginning approximately 10 000 yr ago increased eolian flux rates occurred in response to the lowering of lake mojave and a consequent increase in fine sediment availability increased rates of deposition of eolian fines and associated salts influenced pedogenesis stone pavement development and runoff infiltration relations by 1 enhancing mechanical weathering of fan surfaces and hillslopes and 2 forming clay and silt rich surface horizons which decrease infiltration changes in alluvial fan source areas from hillslopes to piedmonts during the holocene reflect runoff reduction on hillslopes caused by colluvial mantle development and runoff enhancement on piedmonts caused by the development of less permeable soils inferred increased in early to middle holocene monsoonal activity resulted in high magnitude paleo sheetflood events on older fan pavements this runoff triggered piedmont dissection which in turn caused increased sediment availability along channel walls thus runoff infiltration changes during the late quaternary have occurred in response to eolian deposition of fines pedogenesis increased sheetflood activity in the holocene and vegetational changes which are related to many complicated linkages among climatic change lake fluctuations and eolian hillslope and alluvial fan processes

palaeomagnetic constraints on the collision and rotation of north and south china the eastern half of china is dominated by the north china block ncb and south china block scb separated by a complex fold system that trends roughly east west interpretation of the geology of this fold belt has led to a variety of estimates of the age of amalgamation of these two blocks1 7 palaeomagnetic results are few and have also been subject to conflicting interpretations8 11 here we present our own palaeomagnetic results for late permian rocks for both the scb and ncb and summarize other relevant palaeomagnetic data by reinterpreting the polarity given in some previous studies we are able to synthesize the results for the widespread emeishan basalts of the scb and to suggest a new model for the collision and relative rotation of the two blocks

size distribution of scoria cones within the egrikuyu monogenetic field central anatolia turkey abstract egrikuyu monogenetic field emf is one of the five clusters of monogenetic volcanoes in quaternary central anatolian volcanic province cavp emf consists mainly of scoria cones and a few maars e g kutoren obruk previous studies on monogenetic volcanoes of cavp mainly focused on petrologic evolution of scoria cones rather than the statistical analyses of their morphological parameters using the database compiled by arcasoy 2001 for the morphometric parameters of the scoria cones in the emf we present the power law behavior of their size distribution with respect to basal diameters wco of 77 scoria cones from the whole database both empirical maximum likelihood estimation mle and graphical log log plot methods are used for the estimation of scaling parameter b value of power law for the scoria cones which have basal diameter greater than or equal to 0 36 km however graphical method gives the precise result with the b value of 2 78 0 08 for 77 scoria cones over the width range 0 1 1 23 km herein b value indicates the relative number of the small scoria cones with respect to large ones for a given area the power law behavior of the size distribution of scoria cones in the emf suggests that their occurrence is self organized critical phenomena similar to earthquakes since the size distribution of scoria cones provides information about their eruptive magnitude and occurrence mechanism our results can be directly applied to future risk assessment of the cavp

violent strombolian or not using ground penetrating radar to distinguish deposits of low and high energy scoria cone eruptions scoria cones often grow by the accumulation of individual particles transported ballistically in strombolian type eruptions alternative models of cone formation suggest that cones are built primarily of fallout from the eruption column in more explosive eruptions often termed violent strombolian currently the distinction between normal strombolian and violent strombolian is based on direct observations of eruptions or by inference of eruption characteristics from mapping of tephra fall deposits unfortunately medial to distal tephra fall deposits erode rapidly leaving behind only the near vent facies of scoria cones which are thicker and less easily eroded therefore a tool that is capable of delineating differences between low energy strombolian deposits and higher energy violent strombolian deposits from investigation of the preserved scoria edifice is necessary ground penetrating radar imaging of cerro negro an active basaltic scoria cone in nicaragua has revealed details of cone deposits at depths of up to 12 m the record of the 1992 eruption which was observed to be violent strombolian shows quantifiable differences from normal strombolian near vent facies including reflections in the downwind profile that are continuous for hundreds of meters and through the slope break the ability to differentiate between tephra fallout and ballistically emplaced deposits at cerro negro suggests ground penetrating radar imaging may be useful in distinguishing eruptive style in older scoria cones where the medial to distal tephra deposits are eroded or buried

ultrahigh pressure metamorphic rocks from the chinese continental scientific drilling project i petrology and geochemistry of the main hole 0 2 050 m the main hole mh of the chinese continental scientific drilling project ccsd in southern sulu has penetrated into an ultrahigh pressure uhp metamorphic rock slice which consists of orthogneiss paragneiss eclogite ultramafic rock and minor schist recovered eclogites have a uhp metamorphic mineral assemblage of garnet omphacite rutile phengite kyanite coesite epidote ultramafic rocks contain garnet olivine clinopyroxene orthopyroxene ti clinohumite phlogopite gneisses and schists contain an amphibolite facies paragenesis but their zircons have coesite garnet omphacite or jadeite and phengite inclusions indicating that eclogites and gneisses have been subjected to in situ uhp metamorphism using available geothermobarometers p t estimates of 3 1 4 4 gpa and 678 816 c for eclogites were obtained if surface outcrops and neighboring shallow drill holes are considered together we suggest that a huge supracrustal rock slab 50 km long 100 km wide 5 km deep was subducted to a depth 100 km and then exhumed to the surface the depth interval 0 2 050 m of the ccsd mh can be divided into six lithological units unit 1 consists of alternating layers of quartz rich and rutile rich eclogites with thin interlayers of gneiss and schist eclogites of unit 1 are characterized by nb ta sr and ti depletions low mg number and general lree enrichment unit 2 comprises rutile and ilmenite rich eclogite and minor normal eclogite and is characterized by high tio2 total fe v co and sr and very low sio2 alkali zr ba nb ta and total ree contents and lree depleted ree patterns with slightly positive eu anomalies unit 3 contains ultramafic rock and minor mgo rich eclogite protoliths of uhp rocks from units 1 2 and 3 represent a layered mafic to ultramafic intrusion at crustal depth units 4 and 6 consist of interlayered eclogite and paragneiss the eclogites are characterized by th u nb ta and ti depletion and k enrichment and lree enriched ree patterns paragneisses show nb ta sr and ti depletions and lree enriched ree patterns occasionally with slightly negative eu anomalies indicating that their protoliths represent metamorphic supracrustal series unit 5 consists mainly of orthogneisses showing distinct nb ta sr and ti depletions and lree enriched ree patterns with pronounced negative eu anomalies suggesting granitic protoliths in conclusion it is proposed that the southern sulu uhp belt consists of a series of meta supracrustal rocks a layered mafic ultramafic complex and granites

electrical resistivity tomography revealing the internal structure of monogenetic volcanoes 1 eruptive activity of individual monogenetic volcanoes usually lasts a few days or weeks however their short lifetime does not always mean that their dynamics and structure are simple monogenetic cones construction is rarely witnessed from the beginning to the end and conditions for observing their internal structure are hardly reached we provide high resolution electrical resistivity sections 10 m electrode spacing of three monogenetic cones from northeastern spain comparing our results to geological observations to interpret their underground continuation the 100 m maximum depth of exploration provides information on almost the entire edifices highlighting the relationships between strombolian and hydromagmatic deposits in two multiphase edifices a main observation is a column of distinct resistivity centered on the puig d adri volcano which we interpret as the eruptive conduit this method can provide valuable information on the past volcanic dynamics of monogenetic volcanic fields which has real implications for the forecast of future activity

fitting degradation of shoreline scarps by a nonlinear diffusion model the diffusion model of degradation of topographic features is a promising means by which vertical offsets on holocene faults might be dated in order to calibrate the method we have examined present day profiles of wave cut shoreline scarps of late pleistocene lakes bonneville and lahontan it may be assumed that these scarps were initially at least as steep as the angle of repose offsets range from 1 to 12 m and present slope angles range from 9 to 29 a parameter called apparent diffusion age defined as half the mean square horizontal extent of the slope function of each profile is plotted as a function of scarp offset the points show a clear trend of apparent age increasing nearly linearly with offset if linear diffusion held and scarps were initially vertical apparent diffusion age would be the same for all the shoreline profiles the increasing trend can only partly be explained by nonvertical initial scarp slope and therefore the rate of transport of material downslope must increase significantly faster than a linear law in the range of slopes spanned by the data the transport law must become linear at small slope to reduce scatter between profiles with varying ambient slopes the transport law adopted for the purpose of dating is k0 1 5s2 where s is local slope the transport coefficient k0 is correlated inversely with fan slope suggesting that there is a dependence on the particle size distribution a table is included that allows easy application of the model to scarps with simple initial shape

sediment transport by dry ravel 1 dry ravel is a general term that describes the rolling bouncing and sliding of individual particles down a slope and is a dominant hillslope sediment transport process in steep arid and semiarid landscapes during fires particles can be mobilized by the collapse of sediment wedges that have accumulated behind vegetation on a daily basis particles may be mobilized by bioturbation and by small landslides experiments on a dry ravel flume indicate that a basic expression of the momentum equation predicts the distance traveled by particles propelled down a rough surface this equation is further elaborated to produce a nonlinear slope dependent transport equation for dry ravel that represents the rate at which sediment crosses a contour width of slope sediment traps installed on two hillslope transects near santa barbara california measured the flux from dry ravel initiated by bioturbation and the data support the form of the equation additionally a physical model based on the infinite slope stability analysis is proposed for the initiation of dry ravel by landsliding the analytical result from this model is supported by experiments and field data reported by others

eruptive style of the young high mg basaltic andesite pelagatos scoria cone southeast of mexico city the eruption of the pelagatos scoria cone in the sierra chichinautzin monogenetic field near the southern suburbs of mexico city occurred less than 14 000 years ago the eruption initiated at a fissure with an effusive phase that formed a 7 km long lava flow and continued with a phase of alternating and or simultaneous explosive and effusive activity that built a 50 m high scoria cone on the western end of the fissure and formed a compound lava flow field near the vent the eruption ended with the emplacement of a short lava flow that breached the cone and was accompanied by weak explosions at the crater products consist of a microlite rich high mg basaltic andesite samples were analyzed to determine the magma s initial properties as well as the effects of degassing induced crystallization on eruptive style although distal ash fallout deposits from this eruption are not preserved a recent quarry exposes a large section of the scoria cone detailed study of exposed layers allows us to elucidate the mode of cone building activity petrological and textural data combined with models calibrated by experimental work and melt inclusion analyses of similar magmas elsewhere indicate that the magma was initially hot 1 200 c gas rich up to 5 wt h2o crystal poor 10 vol fo90 olivine phenocrysts and thus poorly viscous 40 80 pa s during the early phase low magma ascent velocity at the fissure vent allowed low viscosity magma to degas and crystallize during ascent producing lava flows with elevated crystal contents at t 1 100 c and blocky surfaces later the closure of the fissure by cooling dikes focused the magma flow at a narrow section of the fissure this led to an increased magma ascent velocity rapid and shallow degassing 3 km deep triggered 40 vol microlite crystallization limited times for gas escape and higher magma viscosity 6 105 4 106 pa s drove strong explosions of highly 60 80 vol and finely vesicular magma coarse clasts broke on landing which implies brittle behavior due to complete solidification this requires sufficient time to cool and in turn implies ejection heights of over 1 km which is much higher than normal strombolian activity hence magma viscosity significantly impacts eruption style at monogenetic volcanoes because it affects the kinetics of shallow degassing the long lasting eruptions of jorullo and paricutin which produced similar magmas in western mexico were more explosive this can be related to higher magma fluxes and total erupted volumes implications of this study are important because basaltic andesites are commonly erupted to form monogenetic scoria cones of the trans mexican volcanic belt

geophysical profiling across the sulu ultra high pressure metamorphic belt eastern china abstract the largest ultra high pressure metamorphic uhpm belt in the world is located along the dabie sulu region which tectonically belongs to the east part of the central orogenic belt of china integrated geophysical investigations of using deep seismic reflection mt and geothermal observations have been carried out in the sulu area since 1997 the results of integrated interpretation suggest the existence of three features 1 a rift beneath the lianshui basin by the jiashan xionshui fault 2 a special crustal pattern called the magmatic multi arch structure occurs beneath the northern sulu uhpm zone and 3 a northwest dipping regional thrust crosses the sulu crust representing the intracontinental subduction of the yangtze craton beneath the sulu metamorphic belts after collision between the yangtze and sino korean cratons a magmatic multi arch structure consists of some arched reflectors that occur in both the lower and the upper crust where arched reflectors coincide with granitoid plutons the multi arch structures are common in eastern china where many mesozoic granitoid plutons of different scales occur the crustal structures in the sulu metamorphic belts resulted from intensive dynamic processes following the triassic collision between the yangtze and sino korean cratons the formation and exhumation of uhpm rocks followed the collision and then intracontinental subduction of the yangtze craton beneath the dabie sulu terranes took place in the early and middle jurassic in the late jurassic the sulu lithosphere turned to an extensional regime large scale granitic intrusions occurred in eastern china these likely resulted from lithospheric thinning and asthenospheric uplifting the granitic intrusions came to a climax during the cretaceous and were followed by rifting along existing faults in the early eogene resulting in many petroleum basins the granitoid emplacement that generated the magmatic multi arch structure and the rift were consequences of the lithospheric thinning process and deep intracontinental subduction of the yangtze craton beneath the sulu metamorphic belt might partially contribute to the lithospheric thinning

tectonic and magmatic controls on the location of post subduction monogenetic volcanoes in baja california mexico revealed through spatial analysis of eruptive vents post subduction 12 5 ma to less than 1 ma monogenetic volcanism on the baja california peninsula mexico formed one of the densest intra continental areas of eruptive vents on earth it includes about 900 vents within an area 700 km long n s and 70 to 150 km wide w e this study shows that post subduction volcanic activity was distributed along this arc and that modes exist in the volcano distribution indicating that productivity of the magma source region was not uniform along the length of the arc vent clustering vent alignments and cone elongations were measured within eight monogenetic volcanic fields located along the peninsula results indicate that on a regional scale vent clustering varies from north to south with denser spatial clustering in the north on the order of 1 9 10 1 vents km2 to less dense clustering in the south on the order of 7 8 10 2 vents km2 san quintin san carlos jaraguay and santa clara are spatially distinct volcanic fields with higher eruptive vent densities suggesting the existence of individual melt columns that may have persisted over time in contrast the san borja vizcaino san ignacio and la purisima vent fields show lower degrees of vent clustering and no obvious spatial gaps between fields thus indicating an area of more distributed volcanism insight into the lithospheric stress field can be gained from vent alignments and vent elongation measurements within the fields located along the extinct subduction related volcanic arc elongation patterns of cinder cones and fissure fed spatter cones vent clusters and vent alignments trend nw se and n s within the santa clara field located more to the west within the forearc elongation patterns of the same volcanic features trend ne sw these patterns suggest that magmatism was more focused in the forearc and in the northern part of baja california than in its southern region within the extinct arc magma ascent created volcano alignments and elongate cones parallel to nw se to n s oriented tectonic structures in the forearc the existence of n s and ne sw oriented volcanic features indicates a rotation in the stress field orientation compared to the arc

metamorphism and geochronology of granulites and migmatitic granulites from the magondi mobile belt zimbabwe the magondi mobile belt which crops out to the west of the zimbabwe archaean craton is an early to mid proterozoic feature within which sediments of the magondi supergroup were deformed and metamorphosed metamorphic grade increases northwards along the strike of the belt from greenschist facies in the south to granulite facies in the north the granulite facies rocks were partially melted during metamorphism at pressures of 5 7 kbar and temperatures of about 700 750 c with fluids buffered to low values of pfl late stages of partial melting were driven by vapour poor dehydration melting reactions an age for the metamorphism is indicated by rb sr ages of 1890 260 ma from enderbitic granulites at the rukomeshe river causeway east of makuti and of 1780 280 ma from garnet bearing and granitic granulites from the nyaodza region just east of lake kariba these ages confirm an early proterozoic age for the magondi orogeny which can be correlated with deformation in the kheis belt occupying a similar position on the western margin of the kaapvaal craton later brittle deformation and cataclasis distributed throughout the granulites but locally concentrated in n s striking shear zones are the result of deformation in the footwall of the south verging pan african thrust sheets

alteration history of mount epomeo green tuff and a related polymictic breccia ischia island italy evidence for debris avalanche this paper presents mineralogical chemical and textural data for the mount epomeo green tuff and an associated polymictic breccia on ischia island italy with the purpose of defining the alteration history of the two units and the emplacement origin of the polymictic breccia our results indicate that the green tuff trachytic ignimbrite experienced three alteration events that produced the following mineral assemblages 1 phillipsite randomly interstratified r0 illite smectite i s fe illite and smectite in situ green tuff 2 chabazite phillipsite r0 i s and fe illite proximal facies green tuff at scarrupata di barano and 3 analcime authigenic k feldspar fe illite r0 i s and smectite clasts of green tuff in polymictic breccia phillipsite chabazite and r0 i s within the in situ and proximal facies green tuff indicate low temperature alteration t 70 c alteration within a mostly closed chemical system these data suggest that the polymictic breccia represents a debris avalanche deposit created by a catastrophic volcanic collapse which was associated with low temperature hydrothermal alteration and thus structural weakening of the volcano the debris avalanche that produced the polymictic breccia on ischia may be related to nearby massive debris avalanche deposits recently discovered offshore of southern ischia the young age of the polymictic breccia 5 7 8 6 ka and the possibility of its catastrophic emplacement indicate an additional volcanic hazard for ischia island

atmospheric circulation during holocene lake stands in the mojave desert evidence of regional climate change it is commonly thought that the climate conditions that supported lakes over a period of years in the mojave desert in southern california only existed before 8 000 yr bp and that the environment has been arid since1 2 here we look at a drill core in the silver lake playa at the terminus of the mojave river and find holocene lake deposits which indicate that shallow lakes existed for at least a few decades these deposits were radiocarbon dated at 3620 70 and 390 90 yr bp corresponding to the early neo glacial and the little ice age respectively3 to identify the conditions necessary to produce these holocene lake events we have examined the modern climate and hydrological patterns that produce ephemeral lakes in this usually arid watershed available data indicate that there is a link between anomalous winter atmospheric conditions over the north pacific and mojave river floods that produced ephemeral lakes in the silver lake playa and that the mojave river filters out small to medium floods and allows only the extreme floods to reach the terminal playa and leave a record of the anomalous conditions we suggest that the late holocene lakes may have resulted from persistent similar atmospheric circulation patterns and winter floods

microtopographic evolution of lava flows at cima volcanic field mojave desert california microtopographic profiles were measured and power spectra calculated for dated lava flow surfaces at cima volcanic field in the eastern mojave desert of california in order to quantify changes in centimeter to meter scale roughness as a function of age for lava flows younger than about 0 8 m y roughness over all spatial scales decreases with age with meter scale roughness decreasing slightly more than centimeter scales flows older than about 0 8 m y show a reversal of this trend becoming as rough as young flows at these scales modeling indicates that eolian deposition can explain most of the change observed in the offset or roughness amplitude of power spectra of flow surface profiles up to 0 8 m y other processes such as rubbling and stone pavement development appear to have a minor effect in this age range changes in power spectra of surfaces older than about 0 8 m y are consistent with roughening due to fluvial dissection these results agree qualitatively with a process response model that attributes systematic changes in flow surface morphology to cyclic changes in the rates of eolian soil formation and fluvial processes identification of active surficial processes and estimation of the extent of their effects or stage of surficial evolution through measurement of surface roughness will help put the correlation of surficial units on a quantitative basis this may form the basis for the use of radar remote sensing data to help in regional correlations of surficial units

relationships between the petrophysical properties density seismic velocity heat generation and mineralogical constitution the petrophysical properties density p compressional wave velocity v p and heat generation a exhibit considerable variation with rock type to characterize a given rock quantitatively a single parameter the cation fraction expressed by the k value has been found to be suited best 100 crystalline rocks have been sampled to cover the widest possible range in k value from silicic types like granophyres and granites through granodiorites tonalites diorites gabbros amphibolites hornblendites pyroxenites to ultrabasic rocks p k a and v p were determined experimentally the latter at 0 5 kbar 50 mpa the interrelations between these properties were established by regression analysis the relation k and v p k show a linear dependence whereas a k a and a v p follow exponential laws in a w m 3 12 20 230 5 k mole cm 3 in a 22 5 8 15 g cm 3 and in a 16 5 2 74 v p km s all correlation coefficients are better than 0 9

radiogenic heat production in the upper third of continental crust from ktb the heat production rate of continental crystalline rocks was determined from cores and drill cuttings recovered from depths up to 9 1 km in boreholes drilled by the continental deep drilling program of germany ktb the drilled rocks are mainly gneisses and metabasites based on a large amount of data the comparison of laboratory and in situ determinations by logging shows good agreement the loss of radioactive elements in drill cutting samples at the shaker tables was minimized by using a broad range of available fragment sizes the data reveal a clear lithological dependence of the heat production rate of the metamorphic rocks at ktb the lithologically caused variations of the heat production rate have a wavelength in the order of the drilled depth and therefore they cover up any decreasing trend if there is one below 6 km tectonic elements such as fault zones play also an important role in the observed vertical distribution despite the availability of data for the upper third of the crust models to predict temperatures for greater depths still contain uncertainties

coesite bearing eclogite from the dabie mountains in central china coesite and coesite pseudomorphs are recognized in eclogite from the dabie mountains a collision zone between the sino korean and yangtze cratons in central china this third known occurrence of coesite in deep crustal rocks is within an archean gneiss terrane and is the first locality where coesite has been identified as an inclusion in both omphacite and garnet crystals at the same location coesite bearing eclogite is estimated to form at pressures of 28 kbar and temperatures from 600 to 710 c the dabie mountains eclogite underwent retrograde metamorphism to amphibolite facies after its formation the preservation of coesite in eclogite is found to be strongly controlled by the pressure temperature time path that coesite bearing eclogite followed during its uplift and retrograde metamorphism

post eruptive sediment transport and surface processes on unvegetated volcanic hillslopes a case study of black tank scoria cone cima volcanic field california abstract conical volcanic edifices that are made up from lapilli to block bomb pyroclastic successions such as scoria cones are widespread in terrestrial and extraterrestrial settings eruptive processes responsible for establishing the final facies architecture of a scoria cone are not well linked to numerical simulations of their post eruptive sediment transport using sedimentological geomorphic and 2d fragment morphology data from a 15 ky old scoria cone from the cima volcanic field california this study provides field evidence of the various post eruptive sediment transport and degradation processes of scoria cones located in arid to semi arid environments this study has revealed that pyroclast morphologies vary downslope due to syn eruptive granular flows along with post eruptive modification by rolling bouncing and sliding of individual particles down a slope and overland flow processes the variability of sediment transport rates on hillslopes are not directly controlled by local slope angle variability and the flank length but rather by grain size and morphological characteristics of particles such as shape irregularity of pyroclast fragments and block lapilli ratio due to the abundance of hillslopes degrading in unvegetated regions such as those found in the southwestern usa granulometric influences should be accounted for in the formulation of sediment transport laws for geomorphic modification of volcanic terrains over long geologic time

response of alluvial fan systems to the late pleistocene to holocene climatic transition contrasts between the margins of pluvial lakes lahontan and mojave nevada and california usa abstract dated shorelines of late pleistocene pluvial lakes lahontan great basin desert northwest nevada and mojave mojave desert eastern california provide timelines for the assessment of alluvial fan sedimentation at the lake margins during the late pleistocene to early holocene two sets of alluvial fan systems have been mapped the stillwater fans feeding lake lahontan and the zzyzx fans feeding lake mojave their contrasting morphologies suggest different responses of the two fan systems to late pleistocene to early holocene climatic change at the time the stillwater fan systems underwent minimal sedimentation with the catchment hillslopes apparently stable the zzyzx fans experienced major changes in water and sediment supply from the catchment hillslopes there was a major phase of hillslope debris flow activity followed by fanhead trenching and distal fan progradation both areas were wetter and colder in the late pleistocene than they are today but during the transition to the holocene the zzyzx area was more likely to experience intense rains associated with the monsoonal penetration of warm moist tropical air into the southwest vegetation reconstructions for the late pleistocene to the early holocene suggest that catchment hillslopes in the mojave supported a desert shrub vegetation but those in the stillwaters supported juniper woodland and grasses at low elevations and pine at higher elevations contrasts in hillslope vegetation cover together with storm activity may account for the different responses of the alluvial fans to climatic change during the pleistocene to holocene climatic transition after the falls in lake levels of lakes lahontan and mojave in the early holocene both areas underwent aridification resulting in reductions in hillslope vegetation cover increased storm runoff led to fanhead trenching and distal progradation of the alluvial fans variations in fan style at that time may relate primarily to base level conditions resulting from different gradients on the exposed lake shores

a heat generation model for continental crust based on deep drilling in the baltic shield abstract this paper presents a heat generation model for the old continental crust on the basis of a new petrological model on the origin evolution and deep structure of the crust in which petrological geochemical and geophysical data obtained from the kola superdeep borehole and other deep boreholes drilled into the crystalline basement of the east european platform are taken into account the petrological section obtained from the borehole observations was extrapolated down to the moho boundary taking into consideration the evolution and generalized seismic model of the continental crust in our model the continental crust is subdivided into three layers a granite gneiss layer 0 17 km a charnokite enderbite layer 17 30 km and a basic layer including autochthonous restites of the protocrust 30 40 km the boundaries between the layers correspond to seismic surfaces k1 and k2 the crustal contribution to heat flow is estimated to be about 25 mw m2 52 of the total heat flow for the baltic shield and the mantle heat flow is 22 24 mw m2 a comparison is made between the heat generation model obtained in this study and the ones estimated from seismic velocity structure the difference in the heat generation value between these models may originate from the differing geological and tectonic history of the sampling localities

the vesicular layer and carbonate collars of desert soils and pavements formation age and relation to climate change abstract the vesicular fine grained a horizon av is the widespread ubiquitous surficial horizon of desert soils in diverse landforms and parent materials of varying ages now known to form mostly through accumulation of eolian dust recent studies show that dust accumulation and concomitant soil development are genetically linked to stone pavement formation changes in the magnitude of eolian activity and effective leaching related to quaternary climatic changes are also hypothesized to have influenced the evolution of the av horizon numerical modeling geochronologic and field laboratory studies elucidate the nature of pedogenic processes controlling compositional evolution of av how the changing av horizon increasingly influences soil infiltration and carbonate translocation and accumulation and the control that clasts of the evolving pavement exert on pedogenic processes results of a model that determines soil bulk chemical composition based on mixing of estimated proportions of externally derived eolian material and parent materials imply that the evolution of the soil bulk composition is strongly influenced by av horizon formation the early development of a weakly to moderately developed av horizon directly over gravelly parent material in late and middle holocene soils moderately influences soil infiltration but significant leaching of very soluble materials and some carbonate in dust are permitted in older pleistocene soils however the texturally more mature av and underlying cumulic nongravelly horizons more strongly limit the rate and depth of leaching and soil bulk composition therefore more closely approximates a simple mixture of dust and parent material other aspects of av horizon development and its relations to the pavement are evaluated through studies of pavement clasts with coatings of soil carbonate referred to as carbonate collars development of a numerical model that integrates soil hydrology a co2 production diffusion model calcite kinetics and thermodynamic considerations composition and thermal characteristics of pavement clasts and the textural and structural properties of the surface horizon provides the basis for testing a hypothesis of collar formation model results combined with results of 13c and 18o analyses of collar carbonate demonstrate how precipitation of calcite on pavement clasts and within the av is favored at a depth much shallower than that indicated by the classic carbonate depth climate relationship of jenny and leonard jenny h j leonard c d 1935 functional relationships between soil properties and rainfall soil science 38 363 381 and arkley arkley r j 1963 calculations of carbonate and water movement in soil from climatic data soil science 96 239 248 or simulated by numerical models of carbonate accumulation simultaneous development of thick carbonate collars and the av horizon requires the sustained pavement clast av horizon coupling for at least centuries to possibly millennia new thermoluminescence ages also indicate that much of the av horizon formed in the holocene and that it is certainly much younger than the older pleistocene pavements this supports the previously proposed hypothesis that increased dust flux during the pleistocene to holocene transition triggered and or greatly accelerated av horizon development an understanding of the genesis of collars provides not just an understanding of how carbonate can accumulate in surface environments but it also provides important clues into processes of pavement evolution and preservation of av horizons during long glacial periods the av horizon is not merely an insignificant surficial zone of recent dust accretion instead its development profoundly influences the genesis of desert soils and pavements

quaternary soils and dust deposition in southern nevada and california eoliandustconstitutesmuchofthepedogenic material in late pleistocene and holocene soils of many arid regions of the world comparisonofthecompositionsand influx rates of modern dust with the eolian component of dated soils at 24 sites in southern nevada and california yields informationon 1 thecompositionandinflux rate of dust in late pleistocene and holocene soils 2 paleoclimate and its effects on the genesis of aridic soils especially with regard to dustfall events 3 the timing and relative contribution of dust from playa sources versus alluvial sources and 4 the effects of accumulation of dust in soil horizons the 2mmfractionsofaandbhorizons of soils formed on gravelly alluvial fan deposits in the study area are similar to moderndustingrainsize contentofcaco3and salt majoroxides andclaymineralogy thus they are interpreted to consist largely of dust the major oxide compositions of the shallow soil horizons are nearly identical to that of the modern dust but the compositions of progressively deeper horizons approachthatoftheparentmaterial theclay mineralogyofmoderndustatagivensiteis similar to that of the av horizons of nearby holocene soils but is commonly different from the mineralogies of deeper soil horizonsandoftheavhorizonsofnearbypleistocenesoils theseresultsareinterpretedto indicate that dust both accumulates and is transformed in av horizons with time changes in soil accumulation rates provide insights into the interplay of paleoclimate dustsupply andsoil formingprocesses modern dust deposition rates are more than large enough to account for middle and late holocene soil accumulation rates at nearly all sites however the early holocene soil accumulation rates in areas near late pleistocene pluvial lakes are much higher than modern rates and clearly indicate a dust deflation and deposition event that caused rapid formation offine grained shallow soil horizons on uppermost pleistocene and lower holocene deposits we interpret late pleistocene soil accumulation rates to indicate that dust deposition rates were low during this period but that increased effective moisture during the late wisconsinan favored translocation of clay andcaco3fromnearthesurfacetodeeper inthesoilprofile pre latepleistocenerates are very low in most areas mainly due to a pedogenic threshold that was crossed when accumulations of silt clay and caco3 began to inhibit the downward transport of eolian material but in part due to erosion

fluids in deeply subducted continental crust petrology mineral chemistry and fluid inclusion of uhp metamorphic veins from the sulu orogen eastern china abstract the complex vein associations hosted in southern sulu ultrahigh pressure uhp eclogites contain quartz omphacite or jadeite kyanite allanite zoisite rutile garnet these minerals have chemical compositions similar to those of host eclogites inclusions of polycrystalline quartz pseudomorphs after coesite were identified in vein allanite and garnet and coesite inclusions were found in vein zircon these facts suggest that the veins together with host eclogites have been subjected to synchronous uhp metamorphism the vein minerals contain relatively high concentrations of rare earth elements ree high field strength elements hfse and transition metal elements tme a kyanite quartz vein has a whole rock composition similar to adjacent uhp metamorphic granitic gneisses abundant primary multi solid fluid inclusions trapped within uhp vein minerals contain complex daughter minerals of muscovite calcite anhydrite magnetite pyrite apatite celestite and liquid and gas phase of h 2 o with solids up to 30 70 of the inclusion volume the presence of daughter minerals anhydrite and magnetite indicates the subduction fluids were oxidizing and provides a possible interpretation for the high oxygen fugacity of subduction zone magmas these characteristics imply that the uhp vein minerals were crystallized from supercritical silicate rich aqueous fluids that were in equilibrium with peak uhp minerals and that the fluids in deeply subducted continental crust may contain very high concentrations of silicate as well as hree hfse and tme such fluids might have resulted in major fractionation between nb and ta i e the uhp fluids have subchondritic nb ta values whereas the host eclogites after extraction of the fluids have suprachondritic nb ta values therefore voluminous residual eclogites with high nb ta ratios may be the complementary suprachondritic reservoir capable of balancing the subchondritic depleted mantle and continental crust reservoirs

geochronology and geochemistry of leucosomes in the north dabie terrane east china implication for post uhpm crustal melting during exhumation migmatites are widespread in the north dabie ultrahigh pressure metamorphic terrane ndt of dabie orogen east china idiomorphic and poikilitic amphibole grains in both leucosome and melanosome contain inclusions of plagioclase quartz and biotite suggesting formation of leucosome by fluid present melting of biotite plagioclase quartz bearing protoliths at p 5 7 kbar t 700 800 c precise sims zircon u pb dating indicates that migmatization of dabie orogen initiated at 140 ma and lasted for 10 ma coeval with the formation of low mg adakitic intrusions in dabie orogen based on mineralogical petrographic and geochemical data leucosomes in ndt can be subdivided into three groups 1 high la yb n medium sr y group group i whose high dy yb n but medium sr y ratios are caused by amphibole and plagioclase residual during partial melting of dioritic to granodioritic gneisses 2 low la yb n low sr y group group ii whose flat hree patterns are produced by entrainment of peritectic amphiboles into melts derived from partial melting of dioritic gneiss 3 high la yb n high sr y and eu group group iii whose extremely high sr and eu but low other ree concentrations are caused by accumulation of plagioclase and quartz although group i and iii fall in the adakitic fields on la yb n yb n and sr y y diagrams they are chemically distinct from contemporary high pressure adakitic intrusions in dabie orogen in a series of geochemical indexes for example lower dy yb n and or sr y ratios at given la yb n ratio lower sr cao ratios lower rb concentration but higher k rb ratios therefore leucosomes are produced by anatexis of the exhumed ultrahigh pressure metamorphic rocks at middle crustal level instead of partial melting of thickened lower crust with garnet rich and plagioclase poor residual the coeval occurrence of migmatites and high pressure adakitic intrusions in dabie orogen indicates large scale partial melting of middle to thickened lower crustal column in the early cretaceous the required heat source may be the mantle heat conducting through the lithospheric mantle whose lower parts have been convectively removed

syn eruptive morphometric variability of monogenetic scoria cones according to wood s model morphometric parameters such as slope angle can provide valuable information about the age of conical volcanic edifices such as scoria cones assuming that their initial slopes range from 30 to 33 measured manually on topographic maps and assuming that their inner architectures are homogenous this study examines the morphometric variability of nine young a few thousand years old small volume scoria cones from tenerife canary islands using high resolution digital elevation models in order to assess their slope angle variability because of the young age and minimal development of gullies on the flanks their morphometric variability can be interpreted as the result of syn eruptive processes including 1 pre eruptive surface inclination 2 vent migration and lava outflow with associated crater breaching and 3 diversity of pyroclastic rocks accumulated in the flanks of these volcanic edifices results show that slope angles for flank sectors differ by up to 12 among the studied volcanoes which formed over the same period of time this range greatly exceeds the 2 3 indicated by wood the greater than expected original slope range suggests that use of morphometric data in terms of morphometry based relative dating and detection of erosional processes and settings must be done with great care or detailed knowledge about absolute ages and eruption history especially in field scale morphometric investigation

geothermal modelling of the lithosphere in the central baltic shield and its southern slope lithospheric temperature and heat flow density hfd were studied in the central baltic fennoscandian shield and its subsurface continuation to the south along a transect trending from eastern finland to southern estonia the transect represents an example of a low hfd 30 mw m 2 archaean craton on a thick 150 190 km lithosphere surrounded by early and middle proterozoic mobile belts on a thinner 110 150 km lithosphere with slightly elevated hfd 35 55 mw m 2 numerical 2 d conductive models were constructed in which peridotite solidus temperatures were assigned to those depths which correspond to the seismically determined lithosphere asthenosphere boundary this technique was found to reduce the effect of uncertainties in heat production and thermal conductivity values on the simulation results upper crustal heat production values for the finnish terrain were taken from published geochemical analyses of outcropping rocks for the estonian terrain new heat production values were measured from core samples representing nineteen deep boreholes middle and lower crustal lithologies were estimated with the aid of the deep seismic vpvs data and corresponding heat production values were adapted from global xenolith averages and from data for granulites cropping out in other precambrian areas the results of the modelling suggest that the lithosphere and moho depth variations are only weakly reflected in the measured surface heat flow data which are mainly controlled by heat sources in the upper crust the simulated heat flow densities at 50 km depth approximately at the moho are relatively low and range from 12 mw m 2 at the archaean northeastern end to 19 mw m 2 on the proterozoic southwestern end of the transect simulated temperatures at 50 km depth increase from northeast to southwest ranging from 450 550 c in eastern finland to about 650 c in estonia sensitivity of the simulations to parameter changes was studied by varying the heat production and thermal conductivity values the extreme values for the moho temperature estimates thus obtained may be about 50 k lower or 100 k higher than the values above the corresponding sensitivity of the moho hfd is about 6 mw m 2 and of the surface hfd 5 20 mw m 2 respectively

determination of the crustal and thermal structure of the erzurum horasan pasinler basins eastern turkiye using gravity and magnetic data the erzurum horasan pasinler basin which surrounds miocene rocks is oriented approximately e w and is located in eastern anatolia turkiye east anatolia where ophiolitic and young volcanic rocks are widespread is situated in the alpine himalayan fold thrust fault belt the nw se trending north anatolian transform fault zone and the ne sw trending east anatolian transform fault zone formed by the compressional regime of east anatolia control the main tectonics of the study region while the moho and conrad depths of the study region are 43 0 and 20 9 km respectively the average sedimentary thickness has been determined to be 5 2 km by using the power spectrum method on the other hand it is found that the depth of the moho in the region varies from 41 0 to 44 5 km and the depth of the conrad discontinuity varies between 22 and 26 km as computed using empirical equations the basement of the sedimentary layer is calculated to be 6 km by using inversion results applied to the residual gravity data the curie point depth and average heat flow value in this region are calculated as 18 0 km and 89 1 m wm 2 respectively geotherm calculations reveal that the moho temperature is 1 028 0 c based on the crustal model the high heat flow values obtained are attributed to tectonic activities and melting of the lithospheric mantle caused by upwelling of the asthenosphere

new geothermal data from the kola superdeep well sg 3 abstract the kola superdeep well sg 3 reaches a depth of 12 262 m this provides the opportunity to obtain experimental data on thermal properties of deep horizons since 1985 a 8578 m deep borehole with a casing depth of 8278 m has been used as a geolaboratory the determination of the equilibrium temperature gradient and heat flow density hfd is more reliable than as published before to estimate hfd we used measurements of thermal conductivity from more than 8000 core samples below 4000 m rocks schists amphibolites gneisses and plagiogranites are characterized by significant anisotropy 1 17 2 10 this was taken into account when estimating the conductive hfd new experimental data on hfd in the interval of 0 4 0 9 km are in good agreement with previous results from 470 to 1675 m deep holes drilled near the sg 3 the 0 9 2 0 km interval shows abrupt increase in hfd up to an average value of 57 mw m 2 which differs significantly from the previously reported values of hfd from sg 3 from 37 to 44 mw m 2 as reported by different researchers the average hfd value of 63 mw m 2 in the 5 2 7 5 km interval is 17 43 higher than the previously estimated values within the depth interval from 7 6 to 8 2 km hfd shows a gradual decrease from 62 to 51 mw m 2 positive correlation between 1 and is observed only in the intervals of 2 5 4 3 km and 5 0 6 5 km as can be expected for a stationary conductive thermal regime analysis of the temporal variations of during the return of the hole to thermal equilibrium after its completion reveals that this parameter is capable of characterizing the permeability of a rock massif from the analyses of temporal variations of a lower permeability can be attributed to the part of the massif lying in the 3 0 4 5 km depth range it is proposed that the observed vertical variations in hfd are due to movement of fluids in the massif in some cases resulting in non stationary fields in particular the largest geothermal anomaly at 0 2 km depth is caused by a downward movement of meteoric waters in the zone of active water exchange the experimental results can be understood quantitatively if a permeability of 1 to 3 10 13 m 2 over a 1 2 km zone of exogenic fracturing is assumed an abrupt change of conductive hfd in the depth interval 1 7 2 2 km is attributed to a downward movement of fluids of 2 3 cm yr along inclined zones of fracturing at the boundary between igneous and sedimentary sequences this movement of fluids might be caused by a post glacial uplift of the baltic shield and would continue as lateral pressure in deep faults decreases

evaluation of morphometry based dating of monogenetic volcanoes a case study from bandas del sur tenerife canary islands morphometry based dating provides a first order estimate of the temporal evolution of monogenetic volcanic edifices located within an intraplate monogenetic volcanic field or on the flanks of a polygenetic volcano two widely used morphometric parameters namely cone height width ratio hmax wco and slope angle were applied to extract chronological information and evaluate their accuracy for morphometry based ordering based on these quantitative parameters extracted from contour based digital elevation models dems two event orders for the bandas del sur in tenerife canary islands were constructed and compared with the existing k ar paleomagnetic and stratigraphic data the results obtained suggest that the commonly used hmax wco ratio is not reliable leading to inappropriate temporal order estimates while the slope angle gives slightly better results the overall performance of such descriptive parameters was however generally poor i e there is no strong correlation between morphometry and age the geomorphic morphometric mismatches could be the result of 1 the diversity of syn eruptive processes i e diverse initial morphologies causing geomorphic morphometric variability 2 contrasting edifice specific degradation that depends partly upon the inner facies architecture of the volcanic edifices 3 various external environmental controls e g tephra mantling from pyroclastic density currents unrelated to the edifice evaluated and 4 differences in the scale resolution of input data the observed degradation trend and changes in morphometric parameters over time do not support a simple degradation model for monogenetic scoria cones volcanoes

seismic architecture and sediment distribution within the holocene barrier reef lagoon complex of mayotte comoro archipelago sw indian ocean twenty gravity cores and a large set of high resolution seismic profiles from various lagoonal settings were studied to determine the holocene sediment distribution and sequence architecture within the mayotte barrier reef lagoon complex the holocene seismic sequence comprises a type 1 sequence with lowstand transgressive and highstand systems tracts the lowstand systems tract consists of a paleosoil horizon formed during subaerial exposure the transgressive systems tract is composed of four depositional systems 1 inner transgressive layer 2 proximal and distal incised valley fills 3 mid lagoonal layer and 4 keep up or catch up fringing and barrier reef sequence the highstand systems tract comprises three depositional systems 1 of a proximal terrigenous wedge 2 mid lagoonal and distal carbonate sands or muds and 3 reefal carbonates our studies show that the nature of the holocene sequence is controlled by the rate and amplitude of sea level rise and environmental changes which are expressed by changes in clastic sediment supply and carbonate production the pre holocene topography and water dynamics steer the vertical and spatial sediment thickness distribution of the holocene additional important parameters are the proximity to a source area carbonate or terrigenous and the width of the depositional area climate dynamics are also of great importance while they determine carbonate production and terrigenous runoff sedimentation rates in the subtidal settings always lacked behind sea level rates thus a steep relief was created keeping most lagoonal parts within the deep subtidal realm in which sediment production was not efficient enough to fill up accommodation space in addition wave and or current energy might prevent the fill up of the lagoon this ultimately resulted in a typical empty bucket morphology only a high amplitude sea level fall would allow the subtidal lagoon to build up to base level unfilled accommodation space therefore must be a very common feature in the geologic record

influences of eolian and pedogenic processes on the origin and evolution of desert pavements well developed desert pavements are present above eolian deposits that mantle flows of the cima volcanic field located in the mojave desert california soil stratigraphic data and geochemical data demonstrate that eolian and pedogenic processes play major roles in the evolution of these pavements eolian dust 1 accelerates mechanical fragmentation of flow rock providing the source material for pavements and 2 accumulates slowly below basaltic colluvium in flow depressions eventually promoting development of cumulate soils below the evolving stone pavement an increase in dust flux during the holocene has raised ancient pleistocene pavements as much as 20 cm above the former land surface the results of our studies demonstrate for the first time that most desert pavements do not form by deflation by overland flow or by upward migration of stones through a slowly formed clayey argillic horizon desert pavements are born and maintained at the surface

intra and extra caldera volcaniclastic facies and geomorphic characteristics of a frequently active mafic island arc volcano ambrym island vanuatu abstract ambrym is one of the most voluminous active volcanoes in the melanesian arc it consists of a 35 by 50 km island elongated east west parallel with an active fissure zone the central part of ambrym about 800 m above sea level contains a 12 kilometre wide caldera with two active intra caldera cone complexes marum and benbow these frequently erupting complexes provide large volumes of tephra lapilli and ash to fill the surrounding caldera and create an exceptionally large devegetated plateau ash plain as well as sediment choked fluvial systems leading outward from the summit caldera deposits from fall subordinate base surge and small volume pyroclastic scoria flows dominate the volcaniclastic sequences in near vent regions frequent and high intensity rainfall results in rapid erosion of freshly deposited tephra forming small scale debris flow and modified grain flow dominated deposits box shaped channel systems are initially deep and narrow on the upper flanks of the composite cones and are filled bank to bank with lapilli dominated debris flow deposits these units spill out into larger channel systems forming debris aprons of thousands of overlapping and anastomosing long narrow lobes of poorly sorted lapilli dominated deposits these deposits are typically remobilised by hyperconcentrated flows debris rich stream flows and rare debris flows that pass down increasingly shallower and broader box shaped valleys lenses and lags of fines and primary fall deposits occur interbedded between the dominantly tabular hyperconcentrated flow deposits of these reaches aeolian sedimentation forms elongated sand dunes flanking the western rim of the ash plain outside the caldera initially steep sided immature box canyons are formed again conveying dominantly hyperconcentrated flow deposits these gradually pass into broad channels on lesser gradients in coastal areas and terminate at the coast in the form of prograding fans of ash dominated deposits the extra caldera deposits are typically better sorted and contain other bedding features characteristic of more dilute fluvial flows and transitional hyperconcentrated flows these outer flank volcaniclastics fill valleys to modify restricted portions of the dominantly constructional landscape lava flows and satellite cones of ambrym apparent maturity of the volcanic system has resulted in the subsidence of the present summit caldera at a similar rate to its infill by volcaniclastic deposits

volcanic geomorphological classification of the cinder cones of tenerife canary islands spain this paper proposes a method to establish a morphological classification of tenerife s cinder cones on the basis of a dual analysis of qualitative existence geometry and disposition of craters and quantitative morphometric parameters major and minor diameters and cone elongation major and minor diameters and crater elongation the result obtained is a morphological classification of the cinder cones of tenerife which can be sub divided into four types ring shaped cones horseshoe shaped volcanoes multiple volcanoes and volcanoes without crater in tenerife there is a clear dominance of horseshoe shaped volcanoes 69 0 over ring shaped cones 13 1 volcanoes without craters 11 4 and multiple volcanoes 6 4 the classification presented in this paper is characterized by its simplicity which makes it possible to include all morphological types of volcanoes found in tenerife this fact also renders our classification a useful tool to apply in other both insular and continental volcanic areas to eventually analyze and systematize the study of eruptive edifices with similar traits

monogenetic volcanism personal views and discussion monogenetic volcanism produces small volume volcanoes with a wide range of eruptive styles lithological features and geomorphic architectures they are classified as spatter cones scoria or cinder cones tuff rings maars maar diatremes and tuff cones based on the magma water ratio dominant eruption styles and their typical surface morphotypes the common interplay between internal such as the physical chemical characteristics of magma and external parameters such as groundwater flow substrate characteristics or topography plays an important role in creating small volume volcanoes with diverse architectures which can give the impression of complexity and of similarities to large volume polygenetic volcanoes in spite of this volcanic facies complexity we defend the term monogenetic volcano and highlight the term s value especially to express volcano morphotypes this study defines a monogenetic volcano a volcanic edifice with a small cumulative volume typically 1 km3 that has been built up by one continuous or many discontinuous small eruptions fed from one or multiple magma batches this definition provides a reasonable explanation of the recently recognized chemical diversities of this type of volcanism

thermal evolution of the upper yangtze craton secular cooling and short lived thermal perturbations abstract the upper yangtze craton uyc has stayed in a long term stabilization state its thermal history can be portioned into two parts secular evolutionary trend and short lived thermal perturbations the former is simulated by a two dimensional forward transient thermal model and the latter is discussed by reviewing previous studies the numerical modeling indicates the uyc tended to be cooling as it adjusted to the asynchronous rates of change in the internal radiogenic heat production and in the convecting mantle temperature below the cratonic root the average cooling rate of the uyc has been 58 c ga since the end of archean faster than that of the convecting mantle the surface heat flow presents a decreasing trend from 82 mw m2 at 2 5 ga to 53 mw m2 at present day which constructs the long term evolutionary path the thermal perturbations derived from the occasional tectono thermal events such as mantle plume activity and regional lithosphere extension serves as paroxysmal factors the thermal effects of the emeishan mantle plume were very strong yielding to the maximum heat flow anomaly of 100 mw m2 at the late permian in contrast the influences of regional lithosphere extension during both the early paleozoic period and the early permian middle triassic period were rather weak resulting in a surface heat flow increase of

a unique volcanic field in tharsis mars pyroclastic cones as evidence for explosive eruptions based on theoretical grounds explosive basaltic volcanism should be common on mars yet the available morphological evidence is sparse we test this hypothesis by investigating a unique unnamed volcanic field north of the shield volcanoes biblis patera and ulysses patera on mars where we observe several small conical edifices and associated lava flows twenty nine volcanic cones are identified and the morphometry of many of these edifices is determined using established morphometric parameters such as basal width crater width height slope and their respective ratios their morphology morphometry and a comparison to terrestrial analogues suggest that they are martian equivalents of terrestrial pyroclastic cones the most common volcanoes on earth the cones are tentatively interpreted as monogenetic volcanoes according to absolute model age determinations they formed in the amazonian period our results indicate that these pyroclastic cones were formed by explosive activity the cone field is superposed on an old elevated window of fractured crust which survived flooding by younger lava flows it seems possible that a more explosive eruption style was common in the past and that wide spread effusive plain style volcanism in the late amazonian has buried much of its morphological evidence in tharsis

one dimensional thermal modeling of the eastern pontides orogenic belt ne turkey the eastern pontides orogenic belt is one of the most complex geodynamic settings in the alpine himalayan belt due to the lack of systematical geological and geophysical data in this study 1d crustal structure and p wave velocity distribution obtained from gravity modeling and seismological data in the area has been used for the development of the thermal model of the eastern pontides orogenic belt the computed temperature depth profiles suggest a temperature of 590 60 c at a moho depth of 35 km indicates the presence of a brittle ductile transition zone this temperature value might be related to water in the subducted crust of the tethys oceanic lithosphere the curie temperature depth value of 29 km which may correspond to the crustal magma chambers is found 5 7 km below the moho depth surface heat flow density values vary from 66 5 and 104 7 mw m 2 high mantle heat flow density value of 48 mw m 2 is obtained for the area should be related to melting of the lithospheric mantle caused by upwelling of asthenosphere

flat mantle reflectors in eastern china possible evidence of lithospheric thinning abstract recent 24 s deep seismic reflection records revealed five flat reflectors in the lithospheric mantle in eastern china with increasing depth they are named m1 to m5 and can be seen on both field single shot and stacked records reflector m1 corresponds to the moho discontinuity whereas m5 may be the reflection from the bottom of the current lithosphere which is about 78 km deep according to geothermal measurements the other three reflectors seem peculiar and might result from interactions between the lithosphere and deeper mantle based on lithological and geochemical data it is suggested that the lithosphere has been thinned from about 150 km to about 60 km in the late mesozoic and then has been thickened to about 78 km during the cenozoic the thinning process produced a granulite layer in the old lower crust caused by magmatic underplating whereas an eclogite layer formed beneath owing to the subduction of the paleo tethys and yangtze craton during the permian and early mesozoic reflector m2 at about 12 s two way traveltime twt might result from the paleozoic moho which represents the boundary between the previous granulite and eclogite facies reflector m3 at about 14 s might correspond to the bottom of the eclogite layer beneath which the old lithospheric mantle remained the old and the newly developed mantle may have different compositions resulting in reflector m4 the multi layered mantle reflectors demonstrate a mantle structure that possibly correlates with the lithospheric thinning process that occurred in eastern china during the late mesozoic the discovery of multi layered mantle reflectors in the studied areas indicates a high heterogeneity of the upper mantle reflection seismology with improved technology together with velocity and resistivity imaging and rock physics measurements can provide more details of the heterogeneity and related dynamic processes that occurred in the lithospheric mantle

carboniferous and triassic eclogites in the western dabie mountains east central china evidence for protracted convergence of the north and south china blocks shrimp u pb dating and laser ablation icp ms trace element analyses of zircon from four eclogite samples from the north western dabie mountains central china provide evidence for two eclogite facies metamorphic events three samples from the huwan shear zone yield indistinguishable late carboniferous metamorphic ages of 312 5 307 4 and 311 17 ma with a mean age of 309 3 ma one sample from the hong an group 1 km south of the shear zone yields a late triassic age of 232 10 ma similar to the age of ultra high pressure uhp metamorphism in the east qinling dabie orogenic belt ree and other trace element compositions of the zircon from two of the huwan samples indicate metamorphic zircon growth in the presence of garnet but not plagioclase namely in the eclogite facies an interpretation supported by the presence of garnet omphacite and phengite inclusions zircon also grew during later retrogression zircon cores from the huwan shear zone have ordovician to devonian 440 350 ma ages flat to steep heavy ree patterns negative eu anomalies and in some cases plagioclase inclusions indicative of derivation from north china block igneous and low pressure metamorphic source rocks cores from hong an group zircon are neoproterozoic 780 610 ma consistent with derivation from the south china block in the western dabie mountains the first stage of the collision between the north and south china blocks took place in the carboniferous along a suture north of the huwan shear zone the major triassic continent continent collision occurred along a suture at the southern boundary of the shear zone the first collision produced local eclogite facies metamorphism in the huwan shear zone the second produced widespread eclogite facies metamorphism throughout the dabie mountains sulu terrane and a lower grade overprint in the shear zone

a time slice approach to the history of cenozoic sedimentation in the indian ocean abstract results from drilling at over 100 sites have been combined with a new plate tectonic model to produce a series of palinspastic maps which represent snap shots of the changing patterns of sediment accumulation in the indian ocean through the cenozoic the maps clearly delineate the main sedimentary depocenters and show how the sedimentary record has responded on an oceanwide scale to major changes in paleogeography tectonics paleocirculation and or climate paleogene sediment accumulation rates were generally low with significant accumulation in only limited areas suggesting weak ocean circulation and stable well stratified conditions by contrast the vigorous thermohaline circulation of the neogene resulted in substantial widespread sedimentation accumulation rates were generally high and displayed a wide range of values following rapid growth of the east antarctic ice sheet in the mid miocene carbonate sedimentation has been progressively restricted to the shallow ridges and plateaus of the western indian ocean but accumulates there with locally high rates the link between tectonics and terrigenous sedimentation is exemplified by the major deep sea fans off east africa zambezi fan and india indus and bengal fans which developed in response to uplift and erosion beginning in late oligocene time in the east african rift system and the himalayas respectively although maps from only five widely spaced times are shown the methodology is such that a continuous series of maps at intervals as close as 1 m y can readily be generated ultimately the combination of such time slice maps with the results of detailed time series studies will provide a powerful tool for understanding past oceanic environments

radiogenic heat production in the lithosphere of sulu ultrahigh pressure metamorphic belt abstract the chinese continental scientific drilling ccsd project is located at the sulu ultrahigh pressure metamorphic uhpm belt it offers a unique opportunity for studying the radiogenic heat production of both shallower and deeper rocks based on the concentrations of radiogenic elements u th and k on 349 samples from main hole of ccsd ccsd mh pilot holes and exposures we determined radiogenic heat productions of all major rock types in the sulu uhpm belt results show the mean values of orthogneiss and paragneiss are respectively 1 65 0 81 and 1 24 0 61 w m 3 due to different composition and grade of retrogressive metamorphism the eclogites display significant scatter in radiogenic heat production ranging from 0 01 to 2 85 w m 3 with a mean of 0 44 0 55 w m 3 the radiogenic heat production in ultramafic rocks also varies within a large range of 0 02 to 1 76 w m 3 and the average turns out to be 0 18 0 31 w m 3 based on the measurements and crustal petrologic model the vertical distribution model of heat production in sulu crust is established the resulting mean heat production 0 76 w m 3 contributes 24 mw m 2 to the surface heat flow 1 d thermal model indicates that the temperature at the moho reaches above 750 c and the thermal thickness of the lithosphere is 75 km in good agreement with the geophysical results the high teat flow 75 mw m 2 together with thin lithosphere presents strong support for the extension events during the late cretaceous and cenozoic

adakites the key to understanding lile depletion in granulites abstract for more than 20 years it has been argued that granulites of the lower continental crust are depleted in fluid mobile elements such as cs rb u and th either because they were removed by melting of the lower crust or through dehydration we argue that there is little evidence for a simple relationship between granulite facies metamorphism and element depletion and propose that for felsic orthogneisses the depletion may be a primary feature of crust generation processes modern adakites show a range of fluid mobile element ratios and adakites from the austral volcanic zone avz chile show fluid mobile element ratios very similar to those found in lower crustal felsic granulites this suite of adakites has a strong slab derived component we propose that modern adakites of the type found in the austral volcanic zone are analogous in their genesis to lower crustal felsic granulites and that their mafic precursors were already depleted in fluid mobile trace elements prior to melting an incremental melting model in which fluid mobile elements are released from an eclogitic slab prior to partial melting can explain the fluid mobile element behaviour of both modern adakites and lower crustal felsic granulites

calculation of mass accumulation rates in the absence of density or porosity measurements abstract synthetic mass accumulation rates have been calculated for odp site 707 using depth density and depth porosity functions to estimate values for these parameters with increasing sediment thickness at 1 ma time intervals determined on the basis of published microfossil datums these datums were the basis of the age model used by peterson and backman 1990 to calculate actual mass accumulation rate data using density and porosity measurements a comparison is made between the synthetic and actual mass accumulation rate values for the time interval 37 ma to the recent for 1 myr time intervals there is a correlation coefficient of 0 993 between the two data sets with an absolute difference generally less than 0 1 g cm 2 kyr we have used the method to extend the mass accumulation rate analysis back to the late paleocene 60 ma for site 707 providing age datums e g fossil or magnetic anomaly data are available the generation of synthetic mass accumulation rates can be calculated for any sediment sequence

magnetic petrology of high fe ti eclogites from the ccsd main hole implications for subduction zone magnetism 1 the high fe ti eclogites with exsolved lamellar in 530 600 m depths from the chinese continental scientific drilling ccsd main hole in the sulu ultra high pressure uhp metamorphic belt eastern china record an anomalously high susceptibility natural remanent magnetization nrm and koenigsberger ratio q nrm ji ji is induced magnetization this provides us with a good opportunity to study the effects of magnetic minerals and exsolution lamellae on the magnetic properties of deep rocks in this paper we have measured systematically magnetic properties and mineral assemblage and structure for three special samples no 83 no 86 and no 89 results show that these fe ti rich eclogites are the result of the fine grained titano magnetite exsolution in pyroxene and lamellar structure consisting of finely interlayered ilmenite and hematite in exsolved hemo ilmenite we found that the dominant fe bearing oxide minerals in samples studied are ilmenite hematite hem ilm up to 25 little titano magnetite and pyrite the ferromagnetic susceptibility is mainly controlled by fine grained titano magnetite and nrm is closely related to the exsolved lamellar structure we hence propose that the anomalous magnetism of these eclogites observed in our samples is the result of exsolution from homogenous pyroxene and ilmeno hematite during cooling and decompression processes these fe ti rich eclogites might be one of the sources of high magnetic anomalies observed in the sulu subduction zone eastern china

a review of water contents and ductile deformation mechanisms of olivine implications for the lithosphere asthenosphere boundary of continents abstract water plays an important role in the ductile deformation and evolution of the upper mantle water contents of natural olivine from 240 samples reveal a wide variation of 0 170 ppm h2o suggesting heterogeneous water distribution in the continental upper mantle the average water contents 17 13 ppm h2o in kimberlite nodules provide the best estimation of water concentrations in olivine in the lithosphere beneath cratons the very low water contents 7 9 ppm h2o of olivine from basalt xenoliths are caused by significant hydrogen loss during transport while the high values 44 34 ppm h2o in olivine megacrysts from kimberlites reflect restricted fluid rich conditions in the upper mantle to compare deformation in different tectonic environments the western superior province canada the dabie mountains and the north jiangsu basin china are selected to represent an archean craton an orogenic belt and a rift basin respectively using recent flow laws of olivine deformation maps of dry and wet olivine are constructed under p t conditions of the three tectonic units and in a continental subduction zone characterized by p 6 28 gpa and t 900 c for dry olivine diffusion creep is the dominant mechanism in all the cases which is contrary to the widely observed crystal preferred orientation of olivine in peridotites and seismic anisotropy observations for wet olivine only a small amount of water 50 h 106 si can remarkably decrease the stress of dislocation creep and increase contribution of dislocation creep to the deformation of olivine the strain rate profiles of olivine indicate a transition from dislocation creep to diffusion creep at a depth of 220 km which can be related with the lehmann discontinuity characterized by a rapid decrease in seismic anisotropy however the pressure induced fabric transition from 100 slip to 001 slip may be responsible for the lehmann discontinuity in subduction zones therefore rheology of the continental upper mantle is controlled by power law creep of wet olivine and diffusion creep is the dominant deformation mechanism in the deep upper mantle especially for fine grained peridotites the mechanical lithosphere asthenosphere boundary lab can be defined by the characteristic pressure derivative of effective viscosity the sharp lab beneath the dabie mountains and the sulu terrane favors the lithosphere asthenosphere decoupling while the diffuse lab beneath the western superior province will protect the continental root from convective erosion and mantle metasomatism the long term preservation of the continental roots can be attributed to a large viscosity contrast temperature contrast at a depth of 150 km

heat flow heat generation and crustal temperatures in the northern canadian cordillera thermal control of tectonics 1 the heat flow in the northern canadian cordillera between 59 and 64 n is very high 105 22 mw m2 the average upper crust heat generation is 4 6 2 4 microw m3 giving a reduced deep heat flow of 59 mw m2 similar to the southern canadian cordillera 49 53 n estimated moho temperatures of 800 1000 c and lithosphere only 50 60 km thick are substantiated by slow upper mantle seismic velocities and by high elevations associated with crust only 32 35 km thick the new data support the conclusion that all of the north and south america cordilleras are hot the paleoproterozoic wopmay orogen to the east has a remarkably high heat flow of 90 15 mw m2 for such an old and stable region however basement samples indicate high heat generation and estimated deep temperatures are intermediate between the cordillera and the slave craton further to the east heat flow from the yellowknife area of the slave craton 53 mw m2 implies low lithosphere temperatures in agreement with kimberlite xenolith p t data the high temperatures in the cordillera result in a very thin and weak lithosphere and may allow a lower crust detachment the north and central cordillera have been inland of the coastal queen charlotte transform fault since subduction stopped in the eocene thus some process has maintained high temperatures in the former back arc for more than 40 ma

k ar dating of the cima volcanic field eastern mojave desert california late cenozoic volcanic history and landscape evolution thirty four k ar ages and supporting paleomagnetic measurements from flows of the cima volcanic field provide a detailed volcanic history and a temporal basis for analysis of evolving landforms the cima field has undergone three periods of volcanic activity spanning late miocene through latest pleistocene time 1 7 6 to 6 5 2 4 5 to 3 6 and 3 1 0 to at least 0 015 m y ago these precisely dated sequences afford a unique opportunity to quantify the long term effects of pedogenesis and erosion on volcanic landforms in an arid environment morphologic and pedologtc data indicate that the most stable geomorphic surfaces in the field occur on flows between 0 25 and 0 75 m y old younger flows are dominated by eolian aggradation and outcrop rubbling and older flows are dominated by surface runoff and fluvial dissection a process response model involving progressive pedogenesis and a subsequent shift from infiltration to surface runoff is proposed to explain this temporal variation in land surface stability