internal structure of aeolian dunes in abu dhabi determined using ground penetrating radar a ground penetrating radar survey of aeolian dunes in the al liwa area of abu dhabi reveals a variety of dipping reflectors which are interpreted as primary sedimentary structures the interpretation of the radar profiles has been confirmed by bulldozing trenches through the study area and comparing logged sections in the trenches with the radar profiles nnw sse orientated radar profiles approximately parallel to the prevailing wind direction show two sets of dipping reflectors which are interpreted as sets of cross stratification and second and third order bounding surfaces radar profiles orientated wsw ene across the prevailing wind direction are dominated by concave up reflectors which are interpreted as trough shaped scours and sets of trough cross stratification produced by oblique progradation of barchanoid dunes nested troughs with small sets of trough cross stratification within larger troughs may be due to reactivation following wind reversal or the superposition of small dunes on larger dunes and the fill of large dune troughs by smaller dunes convex upwards reflectors are interpreted as linear spurs on the convex portions of sinuous dunes or erosional remnants between troughs overall there is a tendency for the larger second order bounding surfaces to dip downwind which confirms brookfield s ideas of the relative migration paths of dunes and draa

geochemistry of the thermal springs of mount taftan southeastern iran abstract thermal and cold water chemistry from the southern flank of mount taftan was investigated in order to discriminate among hydrochemical facies isotopic characteristics geothermal reservoir and identify the major geochemical processes that affect water composition the waters from both the hot and cold springs show high total dissolved solids content and are strongly to lightly acidic calcium is the dominant cation in terms of anions the taftan hot springs are cl so 4 type there is also a hco 3 type cold spring the so 4 cl ratios on an so 4 cl hco 3 diagram confirm the volcanic origin of the hot waters conservative elements indicate that the three types of analysed water have similar origin and the difference in concentration is due to dilution of thermal water with almost shallow fresh groundwater not affecting the elements proportions also the retrogressive 18 o enrichment with respect to the meteoric water line mwl confirms that thermal waters andesitic water have been diluted by shallow waters of meteoric origin comparison of the chemistry of thermal and cold springs and other evidences are indicative of an immature hydrothermal water system in taftan volcano because of waters immaturity temperatures in the geothermal reservoir in taftan region cannot be estimated accurately by applying na k k mg and quartz geothermometers

the possible role of humans in the early stages of machair evolution palaeoenvironmental investigations in the outer hebrides scotland abstract low altitude sandy plains machair are a distinctive feature of the atlantic coasts of the scottish outer hebrides they formed as a result of shoreward movement of sediment consequent upon a rise in holocene sea levels during the long period over which machair has been forming the earliest date proposed for their human occupation is the neolithic the natural origins of the machair are not disputed but examination of deposits at sites in the islands of benbecula and grimsay encourages us to advance a possible anthropogenic role in the process of machair development and also to suggest that human involvement may date from the mesolithic period pre 5000 bp ca 5730 cal bp a time for which archaeological evidence is lacking from the outer hebrides the presence of charcoal might suggest that burning of the vegetation cover of the machair was an additional factor to the supposedly dominant marine and aeolian processes in sand mobility removal of shrub vegetation may also have left sand surfaces open to deflation there remains a difficulty in separating natural from human causes in investigations of long term coastal evolution

structure of the makran subduction zone from wide angle and reflection seismic data abstract makran is one of the largest accretionary wedges on the globe formed by the convergence between the eurasian and the arabian plates it is characterised by an extremely high sediment input of 7 km and a shallow subduction angle we present seismic velocity models from four wide angle seismic lines that image the wedge sediments and the subducted oceanic crust three strike lines show complex but rather one dimensional structures where the observed seismic phases have been studied with the reflectivity method a 160 km long dip line was surveyed coincident with a mcs line collected by cambridge university in 1986 prestack depth migration of this data with the new wide angle velocities shows improved images compared to earlier results interpretation of the wide angle and the mcs data indicates that a decollement is developed along a bright reflector within the turbiditic sequence more than 3 km of sediment bypasses the first accretionary ridges underthrusting and is transported to greater depth this might help to explain the sparse earthquake activity associated with subduction here in the strike lines low velocity layers occur landward of the deformation front in zones where active thrusting or underplating takes place the oceanic crust is characterised by a strong velocity contrast between layer ii and layer iii

crustal thickness of iran inferred from converted waves the iranian plate is part of the alpine himalayan orogenic belt which has been formed by the continental collision between the arabian and eurasian plates the present day iranian plate is characterized by diverse tectonic domains including mountain belts e g zagros and alborz kopeh dagh and oceanic plate subduction e g makran here we present the lateral variations of the moho discontinuity beneath iran using a detailed p receiver function study our results allow for more precise estimations of the crustal thickness and enable us to provide a detailed moho depth map for all of iran for the first time we used the teleseismic events recorded from 1995 to 2011 at 77 national permanent stations 24 broadband and 53 short period stations our results show significant variations in the crustal thickness which are related to the different geological features within iran in general the average crustal thickness beneath iran is about 40 45 km a relatively thick crust of about 54 2 km due to the shortening is observed beneath the alborz mountain ranges the crust beneath the alborz zone shows a thickness changing from 47 2 to 45 2 km from west to east and reaches a thickness of about 50 2 km beneath the kopeh dagh mountain range we find the thinnest crust of about 33 2 km beneath the makran subduction zone in southeast iran showing a normal continental crust which has not been influenced by collisional processes the thickest crust 66 2 km is locally observed beneath the sanandaj sirjan zone which is considered the suture zone of the collision between the arabian and eurasian plates

magmatic degassing of multicomponent vapors and assessment of magma depth application to vulcano island italy degassing of magmatic h2o co2 and rare gases plays a major role in understanding large scale earth processes and in the assessment of volcanic activity here we describe a quantitative model for magmatic degassing of h2o co2 noble gas n2 mixtures our modeling takes into account non ideal behaviors by adopting recently developed approaches for the solubility of h2o co2 mixtures in silicate liquids and for noble gas partitioning in h2o co2 bearing magmas this new approach allows quantitative treatment of inert gas fractionation throughout the degassing of any h2o co2 bearing natural magma in a wide range of thermo baric conditions magma degassing simulations performed by our model have clearly displayed that dissolved h2o and co2 in the melt strongly affect inert gas degassing due to their modest solubility differences in h2o rich magmas all the inert gases are strongly partitioned into vapor at early degassing extents after the quick exhaustion of co2 in contrast co2 rich melts retain dissolved helium longer because co2 has firstly to be released from magma whereas nitrogen and heavy noble gases undergo a similar or higher exsolution than co2 at early magma degassing extents we have successfully applied the degassing model to the active volcanic system of vulcano island italy where several geochemical parameters have been monitored over the last decade by quantitatively assessing magma pressure over time the model has allowed us to reconstruct the rise of magma towards the surface the results clearly show that the magma has reached low pressure and depth beneath vulcano thus interaction with the hydrothermal system as well catastrophic magma rises may result in hazardous future scenarios

effect of the volcanic front migration on helium nitrogen argon and carbon geochemistry of hydrothermal magmatic fluids from hokkaido volcanoes japan abstract active volcanoes from hokkaido are distributed along the sw ne trending volcanic front where the subducting pacific plate changes direction from n s to wsw ese one exception is the tokachi volcano which is located approximately 50 km to the north west of the current volcanic front the tokachi oki slab cracking zone represents the transitional zone between the honshu and kurile trenches this change is responsible for the rapid lateral variation of the subduction angle and slab shape we investigate the consequence of this change on the chemical and isotopic compositions from hydrothermal magmatic fluids and mineral separates collected from three volcanoes of hokkaido northern japan namely tarumae tokachi and meakan our data show that these volcanoes have a distinct range of he n and c isotopic compositions meakan fumaroles have a 3he 4he ratio that ranges from 4 46ra to 6 88ra 15n from 2 2 to 3 5 and 13c co2 from 8 47 to 9 81 consistent with subducted sediment contribution tarumae fumaroles have a particularly low 3he 4he ratio 3 08ra in comparison with their hot springs up to 5 24ra and are associated with high co2 3he ratios 2 2 5 3 1011 hydrothermal crustal interactions from the dome or from a deeper hydrothermal system are the main mechanisms that control the 3he 4he and co2 3he ratios in tarumae fumaroles the 15n and 13c co2 values for tarumae volcano range from 0 6 to 3 1 and from 6 34 to 6 43 respectively tokachi fumaroles are characterized by high 3he 4he up to 7 38ra low 15n 2 4 0 1 and low 13c co2 up to 5 32 consistent with mantle contribution and minor subducted sediment contribution the limestone sediment mantle ratio shows a decreasing contribution from subducted sediments starting from tokachi 1 9 to meakan 3 4 and finally tarumae 5 3 this change of isotopic compositions from the sw ne of hokkaido is the result of the tokachi oki slab cracking zone slab dehydration under tokachi occurs at a deeper level 150 200 km than in other hokkaido volcanoes 100 km which produces the migration of the volcanic front therefore we argue that the isotopic signature of tokachi is the result of i a lower sediment contribution from the slab ii a deeper dehydration of the slab and iii a lower degree of partial melting

sand drift and soil formation along an exposed north atlantic coastline 14 000 years of diverse geomorphological climatic and human impacts this paper sets out the history of aeolian deposition and soil formation over the last 14 15 000 calendar years along the exposed and gale prone atlantic coastlines of the southern isles of the outer hebrides of scotland detailed palaeoenvironmental interpretation and chronological control have been provided by field mapping soil micromorphological analyses and radiocarbon and optically stimulated luminescence osl dating programmes two dominant types of aeolian sands are described in this region quartzose sands are shown to originate mainly as periglacial wind blown sands derived from glacial and periglacial deposits of late devensian age which were formerly exposed on the present continental shelf this aeolian deposition did however continue into the early holocene with re working perhaps by slope wash taking place as recently as the 4th millenniumbp quartzose sands mantle valley floors and hillslopes by the end of the devensian and early holocene a variety of soil types with extensive horizonation had developed upon them including podzolic brown earths peaty gleys and peat soils radiocarbon and osl dating demonstrate that the carbonate sands of the machair sand sheets which characterize the present atlantic shorelines began to accumulate very early for a european shoreline from approximately 8700 calendar years ago on benbecula and north uist whereas further south deposition began later osl dating suggests that non sequences and diastems are common in greater part these machair sand sheets are best interpreted as a composite of separate slivers of sand reflecting small scale and local episodes of sand drift rather than distinct layers of region wide distribution which might reflect past major storms or significant palaeoclimatic fluctuations the new evidence presented here provides little support for the following explanatory geomorphic or stratigraphic models which have previously sought to explain the development of these coastal machair landscapes continuous development layer cake or step wise prograding coastal barrier qualified support is given for the explanations that emphasize i the long term spasmodic input and re cycling of sands and ii that the present smoothed landscapes and distinctive machair grassland vegetation are essentially recent in age and reflect the interactions of natural and human processes in a stormy environment characterized by re working widespread layers of thick organic materials within the carbonate sands in the study area which have previously been regarded as dune palaeosols dating to the bronze age and iron age are suggested by soil micromorphological analysis to be in significant part anthropogenic in origin they are organically enriched layers or midden soils the consequence of human activities notably the disposal of organic wastes and other forms of soil modification during times of significant settlement in these coastal sands these periods of relatively intense human activity are therefore shown to be associated at least locally with periods of soil formation and stability not universal instability and dune drift along these shorelines in general these extensive layers of midden soil do not necessarily imply periods of decreased storminess relatively widespread soil formation in these coastal dunes did however take place in the period between 400 and 100 years ago essentially within the period of increased storminess associated with the little ice age it is suggested that at some point s within the following periods of time broadly defined in calendar yearsbp notable sand drift affecting the quartzose sands the carbonate sands or both took place within the study area 13 700 13 000 11 000 10 500 9000 8300 7500 7000 6900 6400 5800 4200 one of the most notable episodes of drift in the outer hebrides as well as elsewhere on the coast of north west europe 3800 3300 1700 1300 600 200 with individual great storms being recorded in the 17th and 18th centuries and 100 present day limited drift associated with machair stratification

an approach to mapping buried prehistoric palaeosols of the atlantic seaboard in northwest europe using gpr geoarchaeology and gis and the implications for heritage management abstract widespread layers of well preserved organically and archaeologically rich palaeosols dating to the bronze age and iron age are known from across the atlantic seaboard of scotland including the western isles orkney and shetland the survival of these soils has been facilitated by an overburden of aeolian sand forming dunes above them whilst these soils display archaeological importance they are constantly under threat from erosion through storm damage due to their exposed coastal position this presents certain challenges with regard to heritage management since their extents are largely unknown normally only being identified when exposed by wind and storm erosion consequently following such damage mitigation can only be reactionary in response to archaeological deposits being uncovered and left open to threat without accurately mapping the extent of these important deposits archaeological landscape management is compromised this paper presents a case study aimed at enabling proactive management of these deposits through rapid three dimensional mapping undertaken using a combination of borehole calibrated gpr survey and gis modelling the results demonstrate how effective baseline data can be generated to highlight areas of greater or lesser risk thereby providing the potential for quantifying and predicting the effects of damage from future storm events

large scale sediment underplating in the makran accretionary prism southwest pakistan field relations in the emergent part of the makran accretionary prism show that a mid miocene to early pliocene slope and shelf sedimentary sequence was deposited directly on abyssal plain turbidites without any detectable stratigraphic or structural discordance sedimentological evidence for rapid shoaling however indicates that the underlying sediment column was tectonically thickened by a factor of between two and three during this period this can be explained by large scale underthrusting and underplating of sediment a mode of accretion that is also favored by mass balance considerations the visible deformation in the coastal makran occurred when the region was 70 100 km north of the contemporary prism front

rare earth elements geochemistry in springs from taftan geothermal area se iran abstract concentrations of rare earth elements rees were determined in springs and andesitic dacitic rocks of taftan geothermal field hydrochemical results of major ions indicate that thermal springs are na so 4 cl and ca so 4 cl types concentrations of rees are in ranges of 10 4 to 1 2 and 49 to 62 times of chondrite for springwater and rock samples respectively the thermal sts and tts and the cold aps springs with low ph values exhibit a very high ree contents 0 64 to 3 15 mg l saturation index indicates that fe and al phases can control dissolved ree concentration in fts and pf cold springs the speciation of ree complexes indicates dominant presence of lnso 4 and free ion in the taftan thermal springs in aps cold spring with ph 4 fluoride complexes are dominate over the free ion and sulfate species while in pf and fts cold springs with ph 6 4 and 7 respectively carbonate complexes lnco 3 are predominant species chondrite normalized pattern for the low ph waters show very distinctive gull wing patterns characteristic feature of acid sulfate geothermal systems and are similar to those of the host rocks chemical characteristics of rare earth elements in spring and volcanic rock samples indicate that rees are originated from the andesitic dacitic host rocks whole rock normalized ree patterns and petrographic evidences show that rare earth elements leached mainly from marginal alteration of minerals and matrix decomposition in volcanic rocks in chondrite normalized ree patterns significant negative eu anomaly in the cold springs compare to the thermal and acidic springs indicates that alteration of plagioclase is more intense in the later corresponding to increasing in temperature and acidic state of reactant water

origin of fluids discharged from mud volcanoes in se iran abstract onshore and offshore mud volcanism in the makran accretionary prism is related to convergence of the arabian and eurasian plates this study describes the chemical and isotopic composition of hydrocarbon rich fluids from four active on shore mud volcanoes located along the makran coast southern iran namely borborok ain napag and sand mirsuban makran coast southern iran as well as pirgel mud volcano se iran that is located between the taftan and bazman igneous volcanoes the main aim was to provide insights into the source region s of gases and waters discharged from these systems and the secondary processes controlling their chemical features the four on shore mud volcanoes emitted ch4 dominated gases with significant concentrations of c2 alkanes suggesting a dominant thermogenic origin as confirmed by their 13c ch4 values carbon dioxide was present at relatively low concentrations 0 78 2 33 with an isotopic signature 13c co2 from 34 2 to 11 1 vs v pdb in the range of that typical of thermogenic gases hence the geochemical features of these mud volcanoes point to the occurrence of a deep gas source rich in hydrocarbons although the occurrence of an exploitable gas reservoir has to be confirmed by geophysical measurements and detailed geostructural surveys gas chemistry from pirgel mud volcano completely differs with respect to that of the previous ones since the former emits gases dominated by co2 and showing relatively high r ra values 1 6 suggesting a significant fluid contribution from the nearby volcanic systems moreover waters from the on shore mud volcanoes showed a na cl composition typically associated with mud volcanism whereas those discharged from pirgel were na hco3 type and rich in chemical species typical of hydrothermal fluids such as as waters from the on shore volcanoes were characterized by a strong 18o positive shift and high b and li concentrations likely indicating clay mineral dehydration and long term water rock interaction such geochemical features were also shown by the waters from pirgel where the high concentrations of b and li were possibly related to volcanic source estimated temperatures for the on shore mud volcanoes estimated using the mg li and mg k geothermometers range from 84 to 165 c corresponding to 3 7 km depth

origin of carbon in fumarolic gas from island arcs abstract we have measured 3 he 4 he ratios 13c values and co 2 3 he ratios of fumaroles and hot spring gases in three volcanic areas in japan the 3 he 4 he ratios 13c values and co 2 3 he ratios vary from 02 05 ratm 9 7 to 2 7 and from 7 74 109 to 1 18 1011 respectively based on these data and those in the literature we present the first quantitative estimates of the upper mantle sediment and limestone including slab components in co2 of volcanic and hydrothermal fluids from subduction zones taking compiled c isotopic data of limestone and organic sediment assuming that the co 2 3 he ratio and 13c value of mid ocean ridge basalt morb are representative of the upper mantle component and that later isotopic and elemental fractionations are minimal it is possible to deconvole each fraction of c on the basis of simple mixing equations up to 20 of the carbon in high temperature volcanic gases in subduction zones is derived from a morb type source while the major fraction of the gases is attributable to co2 produced by decarbonation of subducted marine limestone and slab carbonate

chemical and isotopic composition of fumarolic gases and the so2 flux from volcan de colima mexico between the 1994 and 1998 eruptions volcan de colima is the most active volcano in mexico including a significant effusive eruption in 1991 and a weak explosive event in 1994 geochemical monitoring of the volcano started in january 1996 with collection of fumarolic gases approximately every 3 months from two sites in the summit crater z3 800 c and z2 400 c chemical compositions of volcanic gases from the z2 fumarole showed a peak in s cl in the middle of 1997 14 15 months before the start of the 1998 lava eruption high temperature volcanic vapors from z3 changed progressively in water isotopic composition and showed a weak trend of increasing hcl hf and a peak in s cl at the same time starting from the summer of 1997 the volcanic water became gradually enriched in deuterium which probably indicated an increasing contribution from deep less degassed magma a negative correlation between d and cl content for the z3 fumarolic gases is explained by shallow degassing of the colima hot lava plug this hypothesis is consistent with published data on cl contents and solubilities in magmas and supported by the observed positive trends of s cl and hcl hf with d for the z3 fumarole until september 1998 the so2 flux from the volcano was at a low level 100 tons day and often below the detection limit of the instrument 30 tons day a sharp increase in the so2 flux was recorded 1 month before the eruption started it jumped from 400 50 tons day to 1600 tons day 2 days before new lava emerged on 20 november 1998 the so2 flux correlated well with seismicity

origin of heavy fe isotope compositions in high silica igneous rocks a rhyolite perspective abstract the origin of heavy fe isotope compositions in high silica 70 wt sio 2 igneous rocks remains a highly controversial topic considering that fluid exsolution in eruptive rocks is more straight forward to constrain than in plutonic rocks this study addresses the problem of fe isotope fractionation in high silica igneous rocks by measuring fe isotope compositions of representative rhyolitic samples from the neoproterozoic volcanic sedimentary basins in southern china and the triassic tu le basin in northern vietnam the samples show remarkably varied 56 fe irmm014 values ranging from 0 05 0 05 to 0 55 0 05 which is among the highest values reported from felsic rocks the extensional tectonic setting and short melt residence time in magma chambers for the studied rhyolites rule out soret diffusion and thermal migration processes as causes of the high 56 fe values effects of volcanic degassing and fluid exsolution on bulk rock 56 fe values for the rhyolites are also assessed using bulk rock geochemical indicators and rayleigh fractionation models and these processes are found to be insufficient to produce resolvable changes in fe isotope compositions of the residual melt the most probable mechanism accounting for heavy fe isotope compositions in the high silica rhyolites is narrowed down to fractional crystallization processes in the magma before rhyolite eruption removal of isotopically light fe bearing minerals i e ulvospinel rich titanomagnetite ilmenite and biotite is proposed as the main cause of fe isotope variation in silicic melts during magmatic evolution this study implies that crystal fractionation is the dominant mechanism that controls fe isotope fractionation in eruptive rocks and fe isotopes could be used to study magmatic differentiation of high silica magmas

melt composition control of zr hf fractionation in magmatic processes zircon zrsio4 and hafnon hfsio4 solubilities in water saturated granitic melts have been determined as a function of melt composition at 800 and 1035 c at 200 mpa the solubilities of zircon and hafnon in metaluminous or peraluminous melts are orders of magnitude lower than in strongly peralkaline melt moreover the molar ratio of zircon and hafnon solubility is a function of melt composition although the solubilities are nearly identical in peralkaline melts zircon on a molar basis is up to five times more soluble than hafnon in peraluminous melts accordingly calculated partition coefficients of zr and hf between zircon and melt are nearly equal for the peralkaline melts whereas for metaluminous and peraluminous melts dhf dzr for zircon is 0 5 to 0 2 consequently zircon fractionation will strongly decrease zr hf in some granites whereas it has little effect on the zr hf ratio in alkaline melts or similar depolymerized melt compositions the ratio of the molar solubilities of zircon and hafnon for a given melt composition temperature and pressure is proportional to the hf zr activity coefficient ratio in the melt the data imply that this ratio is nearly constant and probably close to unity for a wide range of peralkaline and similar depolymerized melts however it changes by a factor of two to five over a relatively small interval of melt compositions when a nearly fully polymerized melt structure is approached for most ferromagnesian minerals in equilibrium with a depolymerized melt dhf dzr typical values of dhf dzr range from 1 5 to 2 5 for clinopyroxene amphibole and titanite because of the change in the hf zr activity ratio in the melt the relative fractionation of zr and hf by these minerals will disappear or even be reversed when the melt composition approaches that of a metaluminous or peraluminous granite it is thus not surprising that fractional crystallization of such granitic magmas leads to a decrease in zr hf whereas fractional crystallization of depolymerized melts tends to increase zr hf there is no need to invoke fluid metasomatism to explain these effects results demonstrate that for ions with identical charge and nearly identical radius crystal chemistry does not alone determine relative compatibilities rather the effect of changing activity coefficients in the melt may be comparable to or even larger than elastic strain effects in the crystal lattice

petrogenesis of late permian silicic rocks of tu le basin and phan si pan uplift nw vietnam and their association with the emeishan large igneous province abstract major and trace elements and whole rock sr nd isotope data of late permian silicic plutonic and volcanic rocks from the phan si pan tu le region in nw vietnam were collected in order to establish their petrogenetic relationship with the magmatic rocks of the song da zone nw vietnam and the alkaline silicic rocks of the panxi area of the emeishan large igneous province elip in sw china the granites and rhyolites have geochemical characteristics of anorogenic granites e g high fe and high ga al and are further subdivided based on mineralogy the phu sa phin and muong hum granites contain sodic to sodic calcic amphiboles and sodic pyroxene while the phan si pan granite does not the phu sa phin and muong hum granites occasionally show peralkaline to metaluminous compositions while the phan si pan granites and the tu le rhyolites have metaluminous to peraluminous compositions the chondrite normalized ree patterns la yb n 3 6 51 3 gd yb n 1 4 3 4 and the primitive mantle normalized spidergrams enrichment in high field strength elements are similar to those of the song da silicic rocks and the panzhihua and taihe granites in the panxi area rhyolite melts modeling suggest that the silicic magmas were likely generated by fractionation of the song da high ti basalts the end t values range from weakly negative to moderately positive values 2 2 to 2 2 suggesting the silicic rocks may be assimilated by basement rocks during magma emplacement permian magmatic rocks in the phan si pan tu le region are petrologically geochemically and geochronologically comparable to those of the inner zone of elip although permian lithospheric mantle and lower crustal structure of the phan si pan tu le region may be destroyed by a lithospheric removal in response to cenozoic india eurasia collision our results along with recent geophysical analyses in nw vietnam suggest that the upper to middle crust of phan si pan tu le region represent a remnant upper to middle crust of inner zone of elip

ground penetrating radar of northern lacustrine deltas ground penetrating radar gpr was used in several selected deltaic sedimentary environments to better understand subsurface stratigraphy and reconstruct former depositional environments the profiles provide high resolution continuous subsurface data on facies thickness and depths orientation of major sedimentary structures postdepositional failure planes and depth of peat deposits field experiments were carried out on six river deltas records from four of the deltas exhibit sedimentary facies a record from one delta shows a possible slump and records from another delta reveal the thickness and stratigraphic relationships of peat deposits the delta types are i sandy wave influenced ii sandy immature wave influenced steeper middle and lower shoreface iii sandy braided and iv gravelly fan foreset in areas of limited subsurface control stratigraphic logs from drill core cutbank exposure or geophysical logs radar profiles can provide big picture perspectives of the subsurface

hydrological effects of buried palaeosols in eroding landscapes a case study in south africa abstract palaeosols have long been studied as valuable records of past climate and landscape changes the influence of palaeosols on the functioning of present day landscapes is receiving closer attention due to the relevance of palaeosols on long term hydrological processes and the future hydrological and erosive response of catchments this study describes a sequence of interbedded colluvial sedimentary deposits and buried palaeosols exposed by gully erosion in the drakensberg escarpment foothills in kwazulu natal province south africa model simulations are presented that explore present day hydrological effects of pedogenetic and textural differentiation under conditions of groundwater lowering caused by gully erosion at 14 sites the results suggest that the colluvial deposits and palaeosols cause a significant increase in total annual drainage from most of the 14 studied sites compared with similar sites without texturalor structural differentiation in the simulations sediment deposition not palaeosol formation has the most profound influence on the present day hydrological functioning of the catchment a true deposystem service effects of the limited palaeosol development on soil water holding capacity and actual soil water storage appear to be negligible

volcanic gas emissions from taftan and damavand the iranian volcanoes abstract volcanic gas sampling and so2 flux measurements were performed on taftan volcano 3920 m height se iran makran volcanic arc and damavand volcano 5610 m height northern iran alborz mountains both volcanoes possess near summit fumarolic fields with moderately intensive gas jets and temperatures up to 160 c taftan and 175 c damavand gases of both volcanoes contain mmol mol h2o 910 930 co2 50 80 so2 3 7 h2s 2 5 5 hcl 5 8 2 and hf 0 1 0 13 both volcanoes are also similar in terms of minor gas species mmol mol he 0 0005 0 0011 h2 0 00077 0 0046 n2 ex 0 15 0 30 and ar ex 0 0006 0 0012 where subscript ex denotes non atmospheric fraction d 18o systematics has shown that damavand fumarolic gases contain 60 65 of magmatic fraction whereas the taftan emissions correspond to almost pure magmatic andesitic vapor low amount of nitrogen in taftan gases and its isotopic composition may be explained by low input of nitrogen containing organic matter with the subducting slab due to specific geometry of the makran subduction zone namely by the presence of an accretionary prism of a considerable size the origin of high ch4 content in damavand gases and very low concentrations of c2h6 and higher hydrocarbons 0 65 mmol mol co2 ch4 80 ch4 c2h6 104 is unclear fumaroles of taftan volcano are poor in ch4 similar to many other arc volcanoes co2 ch4 105 3he 4he isotopic composition expressed as r ra was measured at 7 0 7 5 for taftan and 6 65 for damavand corresponding to the co2 3he ratio of 1 0e 10 the 34s of the total sulfur is 7 6 2 2 for taftan fumaroles and 8 1 2 2 for damavand fumaroles 13c co2 is 5 9 2 0 damavand and 4 3 0 15 taftan concentrations of major gas species h2o co2 s hcl ratios and isotopic data r ra co2 3he 34s show that the volcanic gas composition on both volcanoes have a distinct arc signature this conclusion is especially important for the intraplate damavand volcano which has an uncertain tectonic affinity but according to the latest geochemical studies was considered having hotspot rift origin mini doas measurements of the so2 fluxes showed 20 12 t d so2 at taftan and 43 20 t d so2 at damavand which places both volcanoes as small so2 emitters

chemical and isotopic composition of magmatic gases from the 1988 eruption of klyuchevskoy volcano kamchatka abstract gas samples have been collected at the place of magma effusion during the 1988 flank eruption of klyuchevskoy for the first time in the course of studies at this volcano the high temperature gases 1000 1100 c are rich in water and halogens but depleted in sulphur their molar composition is close to chemical equilibrium at the collection temperature while their oxidation state corresponds to redox conditions between fmo and nno buffers the isotopic composition of the water d 71 to 44 18 o 6 3 to 8 4 versus smow plots within the field of primary magmatic waters the isotopic composition of h 2 d 187 to 160 is consistent with isotopic equilibrium between h 2 and h 2 o in the conditions of emission both the chemistry of the gases and the low 13 c of carbon dioxide 11 6 pdb suggest extensive magma outgassing occurred during the course of the eruption

gas geochemistry of the magmatic hydrothermal fluid reservoir in the copahue caviahue volcanic complex argentina abstract copahue volcano is part of the caviahue copahue volcanic complex ccvc which is located in the southwestern sector of the caviahue volcano tectonic depression argentina chile this depression is a pull apart basin accommodating stresses between the southern liquine ofqui strike slip and the northern copahue antinir compressive fault systems in a back arc setting with respect to the southern andean volcanic zone in this study we present chemical inorganic and organic and isotope compositions 13c co2 15n 3he 4he 40ar 36ar 13c ch4 d ch4 and d h2o and 18o h2o of fumaroles and bubbling gases of thermal springs located at the foot of copahue volcano sampled in 2006 2007 and 2012 helium isotope ratios the highest observed for a southern american volcano r ra up to 7 94 indicate a non classic arc like setting but rather an extensional regime subdued to asthenospheric thinning 13c co2 values from 8 8 to 6 8 vs v pdb 15n values 5 3 to 5 5 vs air and co2 3he ratios from 1 4 to 8 8 109 suggest that the magmatic source is significantly affected by contamination of subducted sediments gases discharged from the northern sector of the ccvc show contribution of 3he poor fluids likely permeating through local fault systems despite the clear mantle isotope signature in the ccvc gases the acidic gas species have suffered scrubbing processes by a hydrothermal system mainly recharged by meteoric water gas geothermometry in the h2o co2 ch4 co h2 system suggests that co and h2 re equilibrate in a separated vapor phase at 200 220 c on the contrary rock fluid interactions controlling co2 ch4 production from sabatier reaction and c3h8 dehydrogenation seem to occur within the hydrothermal reservoir at temperatures ranging from 250 to 300 c fumarole gases sampled in 2006 2007 show relatively low n2 he and n2 ar ratios and high r ra values with respect to those measured in 2012 such compositional and isotope variations were likely related to injection of mafic magma that likely triggered the 2000 eruption therefore changes affecting the magmatic system had a delayed effect on the chemistry of the ccvc gases due to the presence of the hydrothermal reservoir however geochemical monitoring activities mainly focused on the behavior of inert gas compounds n2 and he should be increased to investigate the mechanism at the origin of the unrest started in 2011

acid sulfate chloride volcanic waters formation and potential for monitoring of volcanic activity abstract this paper deals mainly with acidic sulphate chloride asc waters that are discharged at volcanic edifices generally not associated with crater lakes geographically the largest number of such manifestations were found on japanese and kuril islands these waters are formed by 1 condensation of magmatic vapor under shallow conditions and or 2 dissolution of magmatic gases in underground waters 3 near surface mixing of steam heated sulphate waters with sodium chloride waters of deeper formation 4 interaction of sodium chloride waters with the rocks undergone by argillic and advanced argillic alteration including hydrolysis of elemental sulfur 5 a combination of several of the listed processes criteria to assess the nature of such waters using their chemical and isotopic composition are based on the relative abundances of major species and trends in isotopic compositions generally controlling by mixing of magmatic host rock meteoric endmembers an overview of available data on temporal chemical variations of such waters shows that usually volcanic activity is marked by an increase in the so4 cl ratio during or after the eruptive event the response on the volcanic activity depends on hydrogeological conditions that control the appearance of the asc springs

the geology of damavand volcano alborz mountains northern iran damavand volcano located in northern iran is a large 400 km 3 composite cone that is currently dormant it shows fumarolic activity near the summit but no evidence of eruption in the past 1000 yr the volcano represents an isolated focus of magmatism of uncertain tectonic affinity although geophysical and geochemical constraints point toward a local hotspot plume origin possibly associated with lithospheric delamination rather than any association with subduction new u th he and 40 ar 39 ar geochronological constraints indicate that the present cone young damavand has been constructed over 600 k y on an older eroded edifice of indistinguishable composition younger than 1 8 ma damavand activity has been characterized by the eruption of radially directed trachyandesite lava flows almost exclusively from summit vents limited pyroclastic activity has yielded thin fallout pumice lapilli layers and a few pyroclastic flows only one significant pyroclastic event is recognized in the remnants of a welded ignimbrite ponded and preserved along the haraz river drainage relatively short periods of volcanic eruptive activity were interspersed with longer periods of erosion in which volcanic products were transported particularly as hyperconcentrated flows into the surrounding drainage systems to be further reworked into epiclastic deposits occasional catastrophic events punctuated this interplay between volcanism and erosion at least one sector collapse is signified by the presence of a large debris avalanche deposit and the regional drainage systems appear to have been frequently dammed by incursions of volcanic material

palaeosols and their cover sediments of a glacial landscape in northern central europe spatial distribution pedostratigraphy and evidence on landscape evolution abstract knowledge of the distribution types and properties of buried soils i e palaeosols is essential in understanding how lowlands in northern central europe have changed over past millennia this is an indispensable requirement for evaluating long term human impact including soil erosion and land cover dynamics in the serrahn area 62 km2 a young glacial landscape representative for northeastern germany and part of the muritz national park 26 pedosedimentary sections were documented and analysed to this end a multiproxy approach was applied using pedology micromorphology geochronology and palaeoecology statistical and spatial analyses of c 5200 soil profiles of which 10 contain palaeosols show that buried soils cover an area of 5 7 km2 i e 9 of the area studied most palaeosols are cambisols arenosols and gleysols palaeosols are mainly covered by aeolian and colluvial sands as well as by lacustrine sands and peat radiocarbon and luminescence dating together with palynological and anthracological data reveal that former land surfaces were dominantly buried through erosion triggered by human activity in the late holocene in addition but to a clearly smaller extent lateglacial early holocene palaeosols and cover sediments occur following medieval clear cutting and intensive land use the study area is today again widely forested the high share of buried land surfaces detected here is expected to be representative for the hilly glacial landscapes even in the wider region i e in northern central europe and should be considered in soil mapping soil carbon budgeting and assessments of past human impact

nitrogen isotopes in thermal fluids of a forearc region jalisco block mexico evidence for heavy nitrogen from continental crust 1 the jalisco block jb is a geologically and tectonically complex part of northwestern mexico characterized by active subduction type volcanism rifting and old stable structures thermal springs and groups of springs are widely distributed over jb bubbling gas from seven thermal springs located within different tectonic environments of the jb was analyzed for he 20ne and n2 concentrations and 15n ratios all gases are n2 dominant 84 with the exception of one sample rio purificacion which has a significant ch4 content about 50 all collected gas samples are relatively high in he up to 1500 ppm vol and with 3he 4he values ranging from 0 6 to 4 5 ra all measured nitrogen isotope ratios are heavier than air with 15n values ranging from 0 5 to 5 0 the relative n2 excess with respect to air saturated water computed on the basis of n2 and 20ne contents indicates the contribution of a nonatmospheric n2 source all the samples show a good correlation between 15n and the relative excess of n2 with 15n 5 3 for the maximum n2 excess of 100 due to a presumed lack of seafloor sediment involved in the subduction process such a 15n positive value seems to reflect the addition to the fluids of a heavy nitrogen originating from metamorphism processes of rocks occurring within the overlying continental crust