fluctuations of caspian sea level beyond climatic variations the continued rising mode since about 1978 in the level of the caspian sea cannot be ascribed to a change in the hydrologic balance that is governed solely by runoff precipitation and evaporation such a change fails to explain some of the chemical links k cl rb cl ca cl sr cl and k rb between kara bogaz and caspian sea waters a more realistic model must include a tectono hydrodynamic factor that allows for subsurface addition of saline water to caspian sea and kara bogaz waters the subsurface water component could be akin to the coastal thermal springs in the area but must dissolve some evaporite deposits in the subsurface before addition to the waters of the inland sea a budget calculation gives an estimate of 2 to 9 subterranean addition of saline water to the seawater such an addition could cause a rise in the level of the caspian sea from 63 to as much as 225 cm within the past 20 yr

dielectric constant as a predictor of porosity in dry volcanic rocks x measurements of dielectric constant k are made on 34 samples of volcanic rocks at frequencies of 0 01 to 10 mhz

reconstructions of deltaic environments from holocene palynological records in the volga delta northern caspian sea new palynological and ostracod data are presented from the holocene volga delta obtained from short cores and surface samples collected in the damchik region near astrakhan russian federation in the northern caspian sea four phases of delta deposition are recognized and constrained by accelerated mass spectrometry ams radiocarbon ages palynological records show that erosive channels dunes baer hills and inter dune lakes were present during the period 11 500 8900 cal bp at the time of the mangyshlak caspian lowstand the period 8900 3770 cal bp was characterized regionally by extensive steppe vegetation with forest present at times with warmer more humid climates and with halophytic and xerophytic vegetation present at times of drought the period 3770 2080 cal bp was a time of active delta deposition with forest or woodland close to the delta indicating relatively warm and humid climates and variable caspian sea levels from 2080 cal bp to the present day aquatic pollen is frequent in highstand intervals and herbaceous pollen and fungal hyphae frequent in lowstand intervals soils and incised valley sediments are associated with the regional derbent regression and may be time equivalent with the medieval warm period fungal spores are an indicator of erosional or aeolian processes whereas fungal hyphae are associated with soil formation freshwater algae ostracods and dinocysts indicate mainly freshwater conditions during the holocene with minor brackish influences dinocysts present include spiniferites cruciformis caspidinium rugosum impagidinium caspienense and pterocysta cruciformis the latter a new record for the caspian sea the holocene volga delta is a partial analogue for the much larger oil and gas bearing mio pliocene palaeo volga delta

permittivity estimation over mars by using sharad data the cerberus palus area 1 cerberus palus is a thoroughly studied region of mars characterized by evident platy textures that were interpreted either as evidence for a frozen sea close to mars equator or as being resultant of lava mud or ice flows coming from cerberus fossae through athabasca valles radargrams provided by radar sounder sharad clearly show the presence of subsurface layers in the area by exploiting the great amount of available data authors have performed an accurate quantitative analysis aimed to estimate electromagnetic properties of surface and subsurface layers in terms of permittivity and attenuation to this aim a simplified electromagnetic approach has been used but taking into account effects of scattering due to surface roughness for avoiding overestimated results this has been done by using theory of electromagnetic scattering from fractal surfaces and by estimating needed parameters from topographic data provided by mola three distinct geologic formations have been analyzed namely a part of zephyria planum the cerberus plains and the bedrock beneath the plains the retrieved electromagnetic parameters have been also modeled as a mixture of volcanic rocks with either ice or air the zephyria planum material was found to be significantly porous 50 60 with an attenuation more likely compatible with empty pores ambiguous results were obtained for the plains material being the resulting porosity high in both the cases of empty 40 50 and of ice filled 80 pores the obtained results do not allow for evidence of a frozen sea on cerberus palus area

first cycle quartz arenites in the orinoco river basin venezuela and colombia modern first cycle quartz arenites are forming in the orinoco drainage basin by at least two distinct mechanisms common to both mechanisms is an environment of intense chemical weathering and extended time over which weathering can occur in the llanos andean foreland basin extended time is provided by temporary storage of orogenically derived sediments on extensive alluvial plains in lowland portions of the guayana shield long soil mineral residence times are produced by very low erosion and transport rates resulting from low relief and tectonic quiescence both weathering intensity and the duration of weathering are important in the modification of sand composition first cycle quartz arenites are produced in diverse tectonic settings and cannot be used by themselves to infer paleotectonic settings of ancient sequences furthermore although tectonic setting is of great importance in determining sand composition modifications during transport and deposition can overprint the effects of the tecto

the caspian lake history biota structure and function the elongate endorheic caspian lake has a north south orientation and its main freshwater inflow the volga river enters at the shallow north end two deep basins occupy its central and southern regions these facts lead to horizontal differences in temperature salinity and ecology nutrient levels and primary production are low historically lake level has fluctuated by 6 m but on the geological timescale fluctuations of 200 m have occurred the lake formed in the late miocene first went through a long shrinking phase expanded to three times its present size in the late pliocene and repeatedly rose and fell throughout the pleistocene with corresponding freshenings and salinizations the lake surface has remained below sea level since the last pleniglacial this dynamic history led to the assemblage of a set of euryhaline biota of tethyan and freshwater origin besides baltic elements that invaded with glacial meltwater endemism is as high as in lake baikal but typical marine groups are absent because the lake is oxygenated to the bottom its biota show a vertical zonation but without a true abyssal community suggesting cat o pollution of the volga ural and kura rivers and destruction of the spawning grounds of sturgeon signalling a forthcoming collapse of the world caviar market dumont 1995 the caspian is the endorheic terminus of the volga river which contributes 80 of its total inflow 237 km3 yr on average butorin 1979 with a range of 200 450 km3 the kura river is second in line and discharges only 16 8 km yr i the ural river is third with a discharge of 8 1 km yr i lake surface area situated below sea level is close to 400 000 km2 and lake volume is 78 000 km3 or 40 of the world s continental surface water here i attempt to provide insight into the nature of the caspian ecosystem including its eventful past i outline gaps in our knowledge and suggest research for the future

worldwide initiation of holocene marine deltas by deceleration of sea level rise radiocarbon dated deltaic sequences of holocene age from different parts of the world began to accumulate within a restricted time range from about 8500 to 6500 years ago evaluation of major delta processes indicates that deceleration in sea level rise was the key factor in holocene delta formation within many deltas there is as much as a 2000 year age range between basal deposits in seaward and landward cores this age difference records the progressive landward migration of near mean sea level depositional environments during the lower to mid holocene establishment of a chronostratigraphic framework for holocene delta development provides a fundamental global baseline for distinguishing sea level change from vertical land motion by tectonism and isostasy and for evaluating rates of future marine incursion into low lying deltas

late pleistocene to holocene evolution of the emba delta kazakhstan and coastline of the north eastern caspian sea sediment ostracods pollen and dinoflagellate cyst records six cores each approximately 10 m long of late pleistocene to holocene age were studied from the emba delta region in the north eastern caspian sea radiocarbon dates provide ages within the range of 47 820 to 12 020 cal bp for the middle sections and for post 1950 close to surface the ages fall within marine isotope stage mis 3 mis 2 and mis 1 with mis 4 also inferred four lithological units are present each separated by an erosional contact unit 4 is equated with mis 4 and consists of over consolidated east west trending aeolian sands deposited during the late pleistocene atelian lowstand unit 3 is equated with mis 3 and is a low energy shallow open water or lagoonal deposit based on ostracod faunas pollen from mesophilic trees is common confirming warm climatic conditions floristic elements such as engelhardia and carya were shared with east asia frequent taxodiaceae pollen occurs derived from glyptostrobus pensilis a seasonal freshwater swamp tree now found naturally only in isolated relict stands in east asia this suggests that the north eastern caspian region was a refugium supporting glyptostrobus swamp vegetation during mis 3 there is no evidence to indicate that these are reworked occurrences unit 2 consists of early khvalynian transgressive barrier sands and unit 1 of shoreface sands and muds of holocene age the late khvalynian highstand and the last glacial maximum lgm record are eroded by the mangyshlak unconformity after ca 12 500 cal bp the holocene interval contains frequent foraminifera and dinoflagellate cysts dinocysts of restricted marine affinity e g lingulodinium machaerophorum the dinocysts pterocysta cruciformis and impagidinium inaequalis are found commonly in the caspian sea for the first time results are compared with palynological and ostracod assemblages in surface samples from the eastern caspian sea coastal region

petrology of modern sands of the rios guaviare and inirida southern colombia tropical climate and sand composition immature lithic arenite 55 7 38 of the guaviare river in the andean foothills of southern colombia passes rapidly into sublithic arenite 87 3 10 as it travels eastward and downstream for 800 km across a low tropical savannah of the colombian llanos immediately east of the andes the sands of its long tributary the inirida river are exceptionally pure 99 0 1 because they are derived from weathered molassic sands that underlie the llanos small isolated precambrian crystalline monadnocks that pierce this andean molasse have little influence on sand composition this area has a seasonal rainfall of 2 to over 5 m and an average temperature of 26 to 27 c the petrology of these streams has great significance because it shows how effectively a seasonal tropical climate can alter the provenance and plate tectonic interpretation of ancient sandstones of foreland basins

diagenesis of the maxon sandstone early cretaceous marathon region texas a diagenetic quartzarenite abstract environments of deposition climate detrital mineral composition and stratigraphic position within a thick sequence of carbonate rocks were major controls on the diagenesis of maxon sandstones fluvial deltaic sands which were subjected to calichification and other pedogenic processes lost all macroporosity prior to burial most sands underwent compaction average of 14 porosity loss minor cementation by quartz and kaolinite possibly during invasion of meteoric water introduced during a low stand of sea level followed by extensive cementation and grain replacement by calcite c and o isotopic values of calcite suggest that carbonate was introduced by formation waters derived from adjacent limestones mass balance calculations on the loss and gain of chemical components during diagenesis show there was a major loss of silica from loss of feldspars and major gains in cao and co2 in calcite cement the overlap of calcite cement on detrital quartz grains gives the impression in thin section that the replacement of quartz by calcite was extensive however thin section and sem views of samples leached in hc1 show that even partial replacement of quartz is rare and is limited largely to the edges of tiny quartz overgrowths ignoring intraformational clasts most maxon sandstones now are quartzarenites q86f1r3 however compensating conservatively for feldspar grains replaced by calcite sands originally were subarkoses q86f10r3

sediment transport in the yellow sea and east china sea abstract eight survey cruises in different seasons have been conducted in the yellow sea ys and east china sea ecs during the period from 2000 to 2008 suspended sediment concentration ssc and hydrological data were collected during each cruise data analysis showed that total suspended sediment mass was approximately 0 18 109 tons in the surveyed area during spring and autumn seasons highly turbid waters were found in the shallow waters between the subei coast the changjiang estuary and the zhejiang coast with seasonal variations the investigation provided convincing evidence that suspended sediments were transported from the subei coast and the southern entrance of the yellow sea trough to the central ys muddy patches were found at the sea bed when tidal currents were too weak to erode the bottom sediments and water column stratification and eddies provided favorable conditions for trapping the fine grained suspended sediments the investigation indicated that the different front may have different effect on sediment transport during different seasons the front between the yellow sea cold water and the coastal water in the subei coast appeared to trap the high ssc sediments on the shallow water side of the front during summer the front along the zhejiang coast seemed to prevent suspended sediments from transport across the front due to circulation in the front zone and upwelling along the zhejiang coast during winter sediments were likely transported across the front to the central continental shelf of the ecs with the help of the downwelling and lateral ekman transport driven by monsoon winds

petrology chemistry and texture of modern river sands amazon river system key idea following the spirit of p d krynine the sands of the world s largest tropical river system are studied to reveal much about the general origin of sand and sandstone thin section and chemical study of 95 sand samples from the amazon river system in brazil peru ecuador and colombia a river system with great contrasts in climate and rock types reveals that sands derived from the andes are lithic arenites whereas sands derived from precambrian terrains are much richer in quartz as are sands in rivers draining tertiary molasse sand becomes more mature downstream along the main stem of the amazon solimoes maranon so that a sample analyzed at the mouth does not accurately reflect headwater composition dilution by quartz rich tributaries and quartz rich tertiary outcrops possible differential elimination of rock fragments and even possible weathering on the modern flood plain of the amazon contribute to enhanced maturity downstream we speculate that although data on modern large subarti

petrologic variations in quaternary volcanic rocks british columbia and the nature of the underlying upper mantle volcanic activity has produced late tertiary and quaternary cinder cones and flows between the snake river plain u s a and the yukon territory canada the rock types include basanites alkali olivine basalts high iron basalts hawaiites ankaramites nephelinites and olivine tholeiites the alkali olivine basalts basanites and hawaiites sampled are chemically similar to rocks from the mid atlantic islands associated with the volcanic rocks are xenoliths of ultramafic rocks gabbros granites and granulites

human influence and the changing geomorphology of mediterranean deltas and coasts over the last 6000 years from progradation to destruction phase the present geomorphology of the mediterranean s coasts is largely a product of an intricate long term relationship between nature and human societies a cradle of ancient civilisations the mediterranean has seen its shores occupied by humans since prehistory and is therefore a particularly pertinent unit of analysis the morphotectonic context and other forcing agents e g climate shaped out a highly diversified coastal morphology and generated a sediment supply regime potentially favourable to the formation of numerous open coast deltas and bay head deltas in infilled rias as sea level stabilised during the mid holocene this supply of riverine sediment has also been the key agent in mediating human occupation of the mediterranean s clastic coasts expressions of this relationship have been extensively archived in clastic coastal deposits including base level deltaic and estuarine sedimentary sinks which comprise records to explore the interactions between geosystems and the human environment the stratigraphic sequences in these coastal sedimentary archives comprise in many places a clearly identified anthropogenic signature notably in ancient harbours some of which underwent extremely rapid silting up due to massive sediment sourcing generated by new agricultural practices from the neolithic onwards increasing human influence especially over the last 3000 years has been in turn an important driver of changes in sediment supply strongly modulating deltaic development pulses of sediment supply from catchments rendered vulnerable by human perturbations during the roman period resulted in a new cycle of inception of many other deltas and in rapid delta growth e g the ebro the po the arno and the ombrone another progradation dynamic during the little ice age at a time of strong rural population growth river discharge increases technological developments and urbanisation further consolidated delta growth understanding the life cycle of these deltas since their initial formation is in turn key to unravelling the relative role of natural and anthropogenic forcing agents rapid climate changes are deemed to have contributed through both the stripping of landscapes rendered fragile by human activities and active fluvial sediment transport to the coast but disentangling climate change effects from human impacts in the mediterranean remains a challenge the patterns of subsequent deltaic growth and delta morphodynamics reflect adaptations to pulsed sediment supply river discharge variations the microtidal fetch limited context of the mediterranean and direct engineering interventions the progradation dynamic of the roman period and little ice age contrasts markedly with the situation of common coastal destabilisation over the last two centuries particularly well documented for the last 50 years this period has been characterised by reduced sediment flux to base level geosystems due to catchment reforestation retenion within reservoirs fluvial regulation and dredging resulting in the erosion of deltas and barrier lagoon and beach dune systems large stretches of shoreline and narrow coastal plains have been massively engineered for coastal defence and protection against erosion but also for the construction of marinas leisure harbours and artificial beaches resulting in the emergence of veritable artificial seafronts these interventions have collectively and progressively raised societies to a pervasive and overarching position in the geomorphic stability instability of the mediterranean s coasts a situation that will be exacerbated by pressures from sea level rise paving the way for rampant coastal erosion and delta destruction

abrupt deep sea warming palaeoceanographic changes and benthic extinctions at the end of the palaeocene a remarkable oxygen and carbon isotope excursion occurred in antarctic waters near the end of the palaeocene 57 33 myr ago indicating rapid global warming and oceanographic changes that caused one of the largest deep sea benthic extinctions of the past 90 million years in contrast the oceanic plankton were largely unaffected implying a decoupling of the deep and shallow ecosystems the data suggest that for a few thousand years ocean circulation underwent fundamental changes producing a transient state that although brief had long term effects on environmental and biotic evolution

relative alteration of microcline and sodic plagioclase in semi arid and humid climates abstract petrographic determination of the degree of alteration of holocene detrital feldspars from first order streams indicates that a broad overlap exists in the amount of alteration on detrital feldspars from contrasting wet and dry climates thus the amount of alteration of detrital feldspars from ancient sandstones is probably an invalid indicator of paleoclimate furthermore regardless of climate detrital plagioclase ab 80 95 generally is 15 20 percent more altered than potassium feldspar in light of this the paleoclimatic significance of the observed relation potassium feldspar more weathered than plagioclase in ancient sandstones todd 1968 needs re evaluation results of this study do suggest a possible preference of limonite plus kaolinite on detrital feldspars from humid climates versus limonite plus smectite on feldspars from semi arid climates however unequivocal substantiation of this difference is still lacking even if the compositional difference can be rigorously demonstrated an inability to distinguish diagenetic from climate controlled surface weathering induced alteration of feldspar will further decrease the utility of feldspar alteration relationships in paleoclimate interpretation

numerical heat and fluid flow modeling of the panorama volcanic hosted massive sulfide district western australia exceptional exposure of the archean pilbara block in western australia reveals a cross section through an archean massive sulfide hosting volcanic succession with underlying subvolcanic intrusion in the panorama district a numerical model based on available detailed geologic information has been constructed to simulate heat and fluid flow in the panorama district the modeling provides insight into the evolution of the hydrothermal system and evaluates key geologic parameters and their influence on fluid flow hydrothermal circulation and the genesis of massive sulfide orebodies the model simulates important aspects of the panorama massive sulfide district such as temperature distribution relative alteration zonation and the size and distribution of orebodies predicted temperatures ranging from 150oc at the top of the volcanic pile to 400oc at the andesite diorite interface are comparable to temperature estimates based on previously published oxygen isotope mapping modeled fluid discharge temperatures are highest for the sulphur springs deposit 300o 400oc and lower for the kangaroo caves and other deposits 250o 350oc the most favorable conditions to reproduce the orebodies and their related alteration zonation occur at anisotropic rock permeabilities comparable to the upper oceanic crust 10 15 10 14 m2 and higher fault permeabilities 10 14 10 13 m2 with a specific fault arrangement similar to that mapped in the field the 4 6 million metric tons mt sulphur springs orebody is predicted to form in less than 5 000 yr assuming a hydrothermal fluid with seawater salinity 10 ppm base metal concentration and a low deposition efficiency 10 other deposits form above the faults under similar conditions a large range of base metal concentrations in the fluids can account for the known orebodies but high temperatures 250oc and high flow velocities 10 7 m s are necessary to produce the observed alteration patterns and distribution of ore deposits results indicate that the establishment of a significant hydrothermal system capable of forming economic massive sulfide deposits is favored in fresh volcanic rock packages that have not been affected by earlier compaction or alteration under these conditions economic massive sulfide orebodies 5 mt of 10 zn cu may form in a few thousand years although the overall lifespan of the hydrothermal system may be between 30 000 and 200 000 yr depending on the variations in rock and fault permeability with time

small scale stratigraphy in a large ramp delta recent and holocene sedimentation in the volga delta caspian sea the volga delta differs from all other major deltas in the world by its extremely gentle onshore and offshore gradient f5 cm km and by being affected by the rapid sea level changes of the caspian sea at rates up to a hundred times the global sealevel rise this paper reports 1 the morphological and facies development of part of the lower delta during the last full sealevel cycle between 1929 and 1995 as monitored using remote sensing and field mapping and 2 the holocene development of the delta from outcrop data and augered transects during a sea level fall of 3 m between 1929 and 1977 rapid progradation of levees composed of fine sand took place along over 800 distributary channels along the delta front smaller distributaries became filled with clay and organics during the 3 m sea level rise from 1977 to 1995 aggradation occurred leading to deposition of silt and clay on the levees and minor filling of the flood basins sedimentation rates as established with 137 cs dating are up to 2 5 cm year total thickness of holocene deposits in the lower delta plain is 4 10 m

recent coastal evolution of the caspian sea as a natural model for coastal responses to the possible acceleration of global sea level rise abstract the caspian sea serves as an excellent natural laboratory for studies of coastal response patterns as it is highly variable in its water level over decadal and secular time scales coastal morphology presumably nearshore bottom slope and profiles of depositional coastal bodies or erosional scarps as well as rates and amplitudes of water level changes appear to be the most important factors of coastal response rates and patterns nearshore bottom slope determines not only shoreline retreat values according to the bruun rule but also the very patterns of coastal evolution for various morphological types of depositional coasts including deltaic coasts strict analytical prediction of coastal response to the accelerated sea level rise is yet to be solved analysis of every response pattern of depositional coasts to sea level changes requires a specific modification of the bruun rule however these equations should be regarded only as the means to estimate an order of magnitude of shoreline retreat or advance in many cases equations based on the bruun rule cannot be applied at all boundary conditions for each quantitative model should be thoroughly studied where possible longshore sediment drift sediment washover on to the landward slope of depositional coastal features and possible onshore or offshore aeolian sediment movement should be taken into account moreover applicability of the bruun rule based equilibrium approach will possibly diminish under the possible future acceleration of sea level rise

sefidrud delta and quaternary evolution of the southern caspian lowland iran abstract the southern caspian sea lowland in iran forms a thick sedimentary prism produced by interactions of marine deltaic and fluvial processes during the late neogene and quaternary deltaic and fluvial deposits have been developed mainly by the sefidrud which is the largest river of the country its drainage area ca 61 600 km 2 includes nearly the entire alborz mountain range and forms deep valleys gorges and a large delta at the southern coast of the caspian sea the sefidrud delta is so large that it covers one third of the large guilan mazanderan plain both from an aerial and volumetric point of view consequently the drainage network of the sefidrud represents the quaternary evolution of northern iran and can be used to test the hypothesized evolution of the region the sefidrud delta has been investigated using many short and long cores satellite images and lithofacies maps and the results show that this delta complex 1680 km 3 consists of a covered lower part and exposed upper deltaic sequences the lower and upper parts of the complex were formed during the early pleistocene and late pleistocene respectively the upper exposed alluvial and deltaic sediments represent a total progradation of approximately 50 km forming three separate delta subsequences d1 3 of which the last one d3 is the modern sefidrud delta the modern delta is a wave dominated blanket like sediment cover ca 30 m thick and 1550 km 2 produced during the last three millennia it was formed by 30 km progradation of six juxtaposed lobes each lobe corresponds to a long term sea level fluctuation of the caspian sea the active lobe ca 50 km 2 has been forming since 1550 ad late pleistocene deltaic sequences d1 3 particularly the modern one d3 were produced by relatively fast deposition due to high volume sediment load of the sefidrud it is suggested that they were produced after the opening of the rudbar gorge by river capture that in turn six times enlarged the drainage area previous deltaic progradation and marine transgressions were relatively slow and the development of the whole lowland at the southern caspian sea lasted ca 1 1 2 ma bp

equable climates during earth history eocene and cretaceous climate model experiments demonstrate that regardless of conditions of warm polar oceans differences in pole to equator surface temperature gradient or topography above freezing surface temperatures in winter for continental interiors at middle to high latitudes cannot be maintained continental interiors will have cold winter temperatures even during globally warm periods unless currently unrecognized forcing factors influenced past climates if model simulations of eocene and cretaceous climates are accurate the term equable as it applies to paleoclimate should be reconsidered

holocene vegetation history and fire regimes of pseudotsuga menziesii forests in the gulf islands national park reserve southwestern british columbia canada article i nfo pollen analysis of a 9 03 m long lake sediment core from pender island on the south coast of british columbia was used to reconstruct the island s vegetation history over the last 10 000 years the early holocene was characterized by open mixed woodlands with abundant pseudotsuga menziesii and a diverse understory in cluding salix and rosaceae shrubs and pteridium aquilinum ferns the establishment of quercus garryana savanna woodland with p menziesii and acer macrophyllum followed deposition of the mazama tephra until 5500 cal yr bp when these communities gave way to modern mixed p menziesii forest charcoal anal yses of the uppermost sediments revealed low charcoal accumulation over the last 1300 years with a mean fire return interval mfri of 88 years fires were more frequent mfri 50 yr during the medieval climate anomaly mca with warm dry conditions facilitating a higher fire frequency than during the little ice age when fires were infrequent given the projected warming for the next 50 100 years land managers considering the reintroduction of fire to the gulf islands national park reserve may want to consider using the mfri of the mca as a baseline reference in prescribed burning strategies

permittivity estimation of layers beneath the northern polar layered deposits mars 1 martian polar layered deposits most likely dusty ice are transparent to radar waves in the north pole bedrock has been detected by marsis up to a depth about 2 km whereas in the south pole such interface has been located at about 3 7 km the reflected signal is generally above the noise and can be used to estimate the dielectric properties of the bedrock assuming the permittivity of the first layer is known we use a simplified inversion method to extract the bedrock relative dielectric permittivity as 4 9 below the north pld s these values are coherent with the basalt nature and so the approach could be used to identify the lithology beneath the martian poles

quantification of l band insar coherence over volcanic areas using lidar and in situ measurements abstract interferometric synthetic aperture radar insar is a powerful tool to monitor large scale ground deformation at active volcanoes however vegetation and pyroclastic deposits degrade the radar coherence and therefore the measurement of 3 d surface displacements in this article we explore the complementarity between alos palsar coherence images airborne lidar data and in situ measurements acquired over the piton de la fournaise volcano reunion island france to determine the sources of errors that may affect repeat pass insar measurements we investigate three types of surfaces terrains covered with vegetation lava flows a a pahoehoe or slabby pahoehoe lava flows and pyroclastic deposits lapilli to explain the loss of coherence observed over the dolomieu crater between 2008 and 2009 we first use laser altimetry data to map topographic variations the lidar intensity which depends on surface reflectance also provides ancillary information about the potential sources of coherence loss in addition surface roughness and rock dielectric properties of each terrain have been determined in situ to better understand how electromagnetic waves interact with such media rough and porous surfaces such as the a a lava flows produce a higher coherence loss than smoother surfaces such as the pahoehoe lava flows variations in dielectric properties suggest a higher penetration depth in pyroclasts than in lava flows at l band frequency decorrelation over the lapilli is hence mainly caused by volumetric effects finally a map of lai leaf area index produced using spot 5 imagery allows us to quantify the effect of vegetation density radar coherence is negatively correlated with lai and is unreliable for values higher than 7 5

a strategy for an accurate estimation of the basal permittivity in the martian north polar layered deposits this paper deals with the investigation of the mars subsurface by means of data collected by the mars advanced radar for subsurface and ionosphere sounding working at few megahertz frequencies a data processing strategy which combines a simple inversion model and an accurate procedure for data selection is presented this strategy permits to mitigate the theoretical and practical difficulties of the inverse problem arising because of the inaccurate knowledge of the parameters regarding both the scenario under investigation and the radiated electromagnetic field impinging on the mars surface the results presented in this paper show that it is possible to reliably retrieve the electromagnetic properties of deeper structures if such strategy is accurately applied an example is given here where the analysis of the data collected on gemina lingula a region of the north polar layer deposits allowed us to retrieve permittivity values for the basal unit in agreement with those usually associated to the earth basaltic rocks

widespread excess ice in arcadia planitia mars the distribution of subsurface water ice on mars is a key constraint on past climate while the volumetric concentration of buried ice pore filling versus excess provides information about the process that led to its deposition we investigate the subsurface of arcadia planitia by measuring the depth of terraces in simple impact craters and mapping a widespread subsurface reflection in radar sounding data assuming that the contrast in material strengths responsible for the terracing is the same dielectric interface that causes the radar reflection we can combine these data to estimate the dielectric constant of the overlying material we compare these results to a three component dielectric mixing model to constrain composition our results indicate a widespread decameters thick layer that is excess water ice 104 km3 in volume the accumulation and long term preservation of this ice is a challenge for current martian climate models

solar forced 2600 bp and little ice age highstands of the caspian sea abstract the level of the caspian sea the largest inland sea in the world has fluctuated capriciously in history with amplitudes up to 3 m in the last century to 25 m in the last millennium and to over 150 m since the last glacial there is little consensus about the causes and forecasts are contradictory mainly due to a lack of solid data about past sea levels before 1837 ad when instrumental observation started we studied the holocene turali barrier complex along the western caspian shore in dagestan russia barrier dynamics during the last 3 m sea level cycle in the past century show that only lagoonal deposits overridden by highstand barriers are suitable for dating former highstands in the holocene barrier complex we selected the most suitable sites for dating using ground penetrating radar gpr profiles outcrops and gravel pits we obtained 14 accelerator mass spectrometry ams 14c data on in situ double valved molluscs from highstand lagoonal deposits the results suggest that the last major highstands occurred around 2600 bp and in the little ice age and coincide with global cooling events associated with minima in solar activity this suggests that millennial precipitation changes in the volga river drainage basin are also forced by solar activity

pleistocene climatic stratigraphy and environments of the terek kuma lowland nw caspian sea region inferred from palynological paleomagnetic and rodent records of the long otkaznoye sediment sequence abstract the paper presents the results of a high resolution palynological paleomagnetic and microtheriological study of the pleistocene sediment sequence at otkaznoye in the eastern ciscaucasian foreland a sequence which is unique in its stratigraphic completeness and thickness 160 m the sequence includes loess paleosol alluvial and alluvial proluvial beds the detailed climatostratigraphic subdivision of the otkaznoye sequence allows a correlation of the established paleoclimatic record with the global marine isotope stages the past climatically induced variability in the landscape of the terek kuma lowland is reconstructed for all neopleistocene i e middle and late pleistocene interglacial and glacial periods and for some intervals during the later early pleistocene stages

late pleistocene and holocene sea level change and coastal paleoenvironment evolution along the iranian caspian shore the authors published by elsevier b v this is an open access article under the cc by nc nd license http creativecommons org licenses by nc nd 4 0

development of the kura delta azerbaijan a record of holocene caspian sea level changes late holocene deposits of the kura delta indicate an alternating dominance of deltaic and shallow marine environments these major environment shifts are controlled by the high frequency sea level changes of the caspian sea the level of the caspian sea now at 27 m below global sea level gsl changes at rates of up to a hundred times as fast as global sea level allowing observation of sedimentary processes on a decadal scale that would take millennia in an oceanic environment the modern kura delta is a river dominated delta with some wave action along its north eastern flank and without tidal influence morphological and hydrological changes have been monitored for over 150 years continuing up to the present day using remote sensing imagery offshore sparker survey data onshore and offshore corings biostratigraphical analysis and radiometric dating enable a reconstruction of the holocene kura delta four phases of delta progradation alternating with erosional transgressive surfaces have been identified representing just as many cycles of sea level fall and rise the first cycle is represented by lowstand deposits truncated by a transgressive surface ts1 at ca 80 m below gsl ts1 is overlain by several metres of laminated clays and silts deposited during a late holocene forced regression h1 these deposits are truncated by the prominent reflector ts2 corresponding to the derbent lowstand around 1500 yr bp and subsequent transgression this transgressive surface is overlain by prograding shallowing upwards deposits h2 in turn truncated by a third transgressive surface ts3 correlated with a lowstand of ca 32 m below gsl the last phase h3 comprises an onshore progradational unit followed by an aggradational unit with an offshore veneer of clays and silts corresponding to the formation of the modern kura delta that started at the beginning of the 19th century

a full sea level cycle in 65 years barrier dynamics along caspian shores abstract the caspian sea being a closed basin shows much higher rates of sea level change up to 340 mm yr than the oceans it experienced a full sea level cycle with an amplitude of 3 m between 1929 and 1995 its coasts therefore present an attractive physical model to test predicted changes along oceanic coasts as a result of expected eustatic sea level rise and to validate sequence stratigraphical interpretations of ancient sediments along the wave dominated coasts with intermediate shore face slopes in dagestan low onshore bars were formed during the 1929 1977 sea level fall they represent minor short lived 1 2 years transgressive oscillations within the major regressional trend after the 1977 lowstand a prominent barrier lagoon system was formed which during the first phase of sea level rise 1977 1988 encroached landwards about 18 m each year by washover during storms continuous retreat between 1988 and 1995 however barrier size diminished lagoons widened and deepened apparently due to lack of coarse grained sediment supply discontinuous retreat the 1995 highstand prevented the barriers from being overstepped altogether sea level fall after 1995 again produced low bars without lagoons the caspian sea barrier coast demonstrates that for the formation of barrier lagoon complexes the combination of transgression and storms is essential barriers may show either continuous or discontinuous development at constant rate of sea level rise and constant offshore slope depending essentially on the availability of coarse grained sediments the rate of sea level rise as a factor in barrier behaviour cannot be viewed independently from barrier dimensions which in turn depend on wave base depth and maximum storm wave height relations between para sequence thickness and frequency and amplitude of sea level change in closed basins with an independent sea level regime may differ markedly from those in basins influenced by eustasy

absorption and scattering in ground penetrating radar analysis of the bishop tuff 1 ground penetrating radar gpr signals are attenuated by both absorption and scattering we performed low frequency 100 mhz gpr surveys at the volcanic tableland of the bishop california tuff to evaluate the factors that control gpr depth of investigation and to develop insight into the capabilities of such radars for mars the subsurface reflection character was very different for two different commercial systems used together they revealed both internal welding contacts in the tuff and an abundance of discrete scatterers attenuation coefficients were computed from profiles that showed distributed scattering the semilogarithmic signal decay is directly analogous to seismic coda the absorption intrinsic loss was determined to be 1 db m from low frequency vertical electric soundings the residual attenuation that is the attenuation in the absence of absorption is attributed to scattering scattering attenuation of 1 db m at 25 50 mhz corresponds to mean free paths as short as 4 m a fraction of the two way propagation distances of 20 40 m therefore the bishop tuff is formally a strong scatterer to gpr the mean free path is also comparable to the subsurface radar wavelength in this case maximizing scattering loss the scatterers themselves likely originate as welding heterogeneities contrasts in dielectric constant due to density differences may be supplemented by moisture variations on mars scattering is likely to contribute significant losses to gpr signals in all but the most uniform materials and unfrozen thin films of water in the lower cryosphere could influence both absorption and scattering

origin of modern quartzarenite beach sands in a temperate climate florida and alabama usa abstract quartzarenite coastal sands extending from eastern louisiana eastward to apalachee bay florida are anomalous their position 7 north of the tropic of cancer contrasts with most other known modern quartzarenites most of which are in a tropical setting to determine the origin of these quartzarenite beach sands we compared the mineralogy of samples taken from alabama and florida beaches rivers that supply sand to the coast and well cuttings representative of sandstone bedrock exposed in the alabama coastal plain to help assess the abundance of recycled quartz and accepting the conventional wisdom that rounded sand size quartz grains are recycled we quantified the roundness of quartz grains in thin sections of river beach and well samples we also determined the abundance of recycled grains with authigenic quartz using cathodoluminescence river sands on precambrian and paleozoic bedrock in the study area have subarkose and sublitharenite compositions however as far as 200 km inland from the coast river sands have attained quartzarenite composition and all rivers are presently delivering sand with at least 97 quartz to the coast rivers develop quartzarenite sand composition where they traverse poorly consolidated tertiary sandstones all of which we sampled are composed of 95 quartz published experimental work indicates that abrasional rounding of sand size quartz by rivers is insignificant and rounding in beaches is extremely slow hence the abundance of quartz grains with some degree of rounding 96 for beaches 75 for rivers further attests to the abundance of recycled quartz

physical properties of martian meteorites porosity and density measurements martian meteorites are fragments of the martian crust these samples represent igneous rocks much like basalt as such many laboratory techniques designed for the study of earth materials have been applied to these meteorites despite numerous studies of martian meteorites little data exists on their basic structural characteristics such as porosity or density information that is important in interpreting their origin shock modification and cosmic ray exposure history analysis of these meteorites provides both insight into the various lithologies present as well as the impact history of the planets surface we present new data relating to the physical characteristics of twelve martian meteorites porosity was determined via a combination of scanning electron microscope sem imagery image analysis and helium pycnometry coupled with a modified archimedean method for bulk density measurements our results show a range in porosity and density values and that porosity tends to increase toward the edge of the sample preliminary interpretation of the data demonstrates good agreement between porosity measured at 100 and 300 magnification for the shergottite group while others exhibit more variability in comparison with the limited existing data for martian meteorites we find fairly good agreement although our porosity values typically lie at the low end of published values surprisingly despite the increased data set there is little by way of correlation between either porosity or density with parameters such as shock effect or terrestrial residency further data collection on additional meteorite samples is required before more definitive statements can be made concerning the validity of these observations

global permittivity mapping of the martian surface from sharad abstract sharad is a subsurface sounding radar aboard nasa s mars reconnaissance orbiter capable of detecting dielectric discontinuities in the subsurface caused by compositional and or structural changes echoes coming from the surface contain information on geometric properties at metre scale and on the permittivity of the upper layers of the martian crust a model has been developed to estimate the effect of surface roughness on echo power depending on statistical parameters such as rms height and topothesy such model is based on the assumption that topography can be characterized as a self affine fractal and its use allows the estimation of the dielectric properties of the first few metres of the martian soil a permittivity map of the surface of mars is obtained covering several large regions across the planet surface the most significant correspondence with geology is observed at the dichotomy boundary with high dielectric constant on the highlands side 7 to over 10 and lower on the lowlands side 3 to 7 other geological correlations are discussed

the oscillation model of hydrothermal dynamics beneath aso volcano southwest japan after small eruption on may 2011 a new understanding model using repeated absolute and relative gravity measurement abstract at the end of 2010 the seismic activity in aso volcano intensely increased and water level in the nakadake crater decreased until early in 2011 then was followed by a small eruption in may 2011 after the eruption and heavy rain the volcanic activity subsided to calm period crater bottom was refilled with water and water level increased in the nakadake crater the next tremor reappeared in 2014 and tracked to eruption in november 2014 this eruptive pattern and water level variation in the crater repeatedly appeared on the surface and it should be related to the hydrothermal dynamics beneath aso volcano we initiated the gravity measurements in relation to hydrothermal dynamics in the subsurface of aso volcano using scintrex cg 5 549 and lacoste romberg type g 1016 relative gravimeter at 28 benchmarks in april 2011 one month before the eruption the repeated gravity measurements continue to monitor aso volcano with a series of the measurement after the eruption in every three months to a half year we analyze the gravity variation from 2011 to 2014 between the time of the phreatic and strombolian eruption the measurements covered the area more than 60 km 2 in the west side of aso caldera a new gravity network was also installed in may 2010 at seven benchmarks using a10 017 absolute gravimeter which re occupied in october 2010 june 2011 and two benchmarks in june 2014 as a result the gravity changes distinguish hydrothermal dynamic in the subsurface which has a direct correlation to water level fluctuation in the crater after the first eruption and before the second discharge the monitoring data notice large gravity changes between the surveys at benchmarks around nakadake crater and kusasenri area the simple 3d inversion models of the 4 d gravity data deduce the density contrast distribution beneath aso volcano the inversion and mass change result generate the oscillation typical as a new understanding model the variation of the mass shows a similar trend with the hydrothermal input rate to the crater of past research the third year monitoring from april 2013 displays a large gravity and mass variation while precipitation data in this period is smaller than the previous season the largest increased mass about 43 million tons by gaussian method occurred between may 2013 and september 2013 according to the three year gravity monitoring the calm period in aso volcano happens after may 2011 eruption until september 2013 which is followed by the active period before the november 2014 eruption this result will contribute to understand the process of eruption

rock water interaction in dielectric properties experiments with hydrophobic sandstones the dielectric constant of a partially saturated sandstone varies as a function of the level of water saturation experimental data indicate that rock water interaction at low saturations has a large effect on the measured dielectric response to theoretically predict the dielectric constant of the rock water air system this rock water interaction must be accounted for by including the effect of the water wetting the rock solid alternatively if the rock water interaction can be eliminated a three component dry rock water and air mixing law can be used to model the dielectric behavior in this laboratory study a chemical treatment is used to change four water wet sandstones into hydrophobic sandstones in three hydrophobic samples the rock water interaction seen in the data for the water wet samples is eliminated and the dielectric constant of the partially saturated sandstones can be simply modeled as a dry rock water air system this experimental study illustrates the importance of the chemical state of the rock surfaces in determining the dielectric behavior of sandstones

dielectric determination of rock fabric anisotropy abstract we have measured the dielectric anisotropy of specimens of a slate that formed by a single episode of metamorphism and deformation of a volcanic tuff the dielectric anisotropies can be represented by oblate ellipsoids that are comparable in shape with the strain ellipsoids determined from the changes in thickness of the rims of accretionary lapilli in the slate the rocks studied are largely made up of platy chlorite grains and discs cut parallel to the schistosity often exhibit an anomalous low frequency dispersion the magnetic susceptibility anisotropies are also oblate but their shapes do not compare as well with the strain as they have less extreme ellipsoidal shapes

natural and anthropogenic influences on depositional architecture of the ural delta kazakhstan northern caspian sea during the past 70 years abstract this paper focuses on the ural delta in the northern zone of the caspian sea an area with particular characteristics where intense influence from anthropogenic and natural factors exists which acts on the fragile delta system we built a database to integrate the data from the published sources bathymetric survey and recent images in the geographical information system gis environment the results were linked to the caspian sea level csl curve which had many variations changing the ural delta system s dynamics and in its architecture in addition the anthropogenic changes contribute to shaping the actual ural delta architecture through the link between the results and csl we reconstructed an evolution model for the ural delta system for the last century and identified three different architectures for the ural delta determined by the energy that acted on the system in the last century and by the anthropogenic changes this work identifies six different delta phases which are shaped by csl changes during the last 70 years and by anthropogenic changes the delta phases recognized are i a lobate delta phase shaped during high csl before 1935 ii natural elongate delta 1935 1950 formed during rapid csl fall iii anthropogenic elongate delta 1950 1966 formed during rapid csl fall and after the ural caspian sea canal construction which modified the sedimentary deposition on the delta iv anthropogenic elongate delta 1966 1982 shaped during low csl phase v anthropogenic elongate delta 1982 1996 formed during a rapid csl rise phase and vi anthropogenic elongate delta 1996 2009 shaped during high csl that represent the last phase and actual ural delta architecture

ranking welding intensity in pyroclastic deposits welding of pyroclastic deposits involves flattening of glassy pyroclasts under a compactional load at temperatures above the glass transition temperature progressive welding is recorded by changes in the petrographic e g fabric and physical e g density properties of the deposits mapping the intensity of welding can be integral to studies of pyroclastic deposits but making systematic comparisons between deposits can be problematical here we develop a scheme for ranking welding intensity in pyroclastic deposits on the basis of petrographic textural observations e g oblateness of pumice lapilli and micro fabric orientation and measurements of physical properties including density porosity point load strength and uniaxial compressive strength our dataset comprises measurements on 100 samples collected from a single cooling unit of the bandelier tuff and parallel measurements on 8 samples of more densely welded deposits the proposed classification comprises six ranks of welding intensity ranging from unconsolidated rank i to obsidian like vitrophyre rank vi and should allow for reproducible mapping of subtle variations in welding intensity between different deposits the application of the ranking scheme is demonstrated by using published physical property data on welded pyroclastic deposits to map the total accumulated strain and to reconstruct their pre welding thicknesses

radar sounding of subsurface structure in eastern coprates and capri chasmata mars we surveyed the subsurface structure in eastern coprates and capri chasmata in the equatorial region using high resolution visible images digital terrain models and radar sounding data we identi

bracketing ages for the formation of the ring creek lava flow mount garibaldi volcanic field southwestern british columbia the ring creek lava flow extending from opal cone generally is considered to be the youngest volcanic feature in the southern section of the mount garibaldi volcanic field southwestern british columbia an in situ stump dated 10 650 70 bp beta 43865 obtained from a raised delta partially overridden by the lava flow indicates that the lava was extruded after ca 10 7 ka at the skookum creek and mamquam river confluence sediments eroded from the ring creek lava flow form an alluvial fan that contains charcoal dated 9360 160 bp beta 38914 which indicates that the extrusion probably occurred before ca 9 3 ka thus these radiocarbon ages bracket the age of the ring creek lava flow and indicate that volcanic activity in the southern section of the mount garibaldi volcanic field has been dormant since at least ca 9 3 ka

deposition and flux of sediment from the po river italy an idealized and wintertime numerical modeling study abstract recent studies of sediment dynamics and clinoform development in the northern adriatic sea focused on winter 2002 2003 and provided the data and motivation for development of a detailed sediment transport model for the area near the po river delta we used both idealized test cases and more realistic simulations to improve our understanding of seasonal sediment dynamics there we also investigated the relationship between physical processes and the observed depositional products e g the accumulation of sediment very near the po river distributary mouths sediment transport near the po river was evaluated using a three dimensional ocean model coupled to sediment transport calculations that included wave and current induced resuspension suspended sediment transport multiple grain classes and fluvial input from the po river high resolution estimates from available meteorological and wave models were used to specify wind wave and meteorological forcing model results indicated that more than half of the discharged sediment remained within 15 km of the po river distributary mouths even after two months of intensive reworking by winter storms during floods of the po river transport in the middle to upper water column dominated sediment fluxes otherwise sediment fluxes from the subaqueous portion of the delta were confined to the bottom few meters of the water column and correlated with increases in current speed and wave energy spatial and temporal variation in wind velocities determined depositional patterns and the directions of sediment transport northeasterly bora winds produced relatively more eastward transport while southwesterly sirocco winds generated fluxes towards both the north and the south eastward transport accounted for the majority of the sediment exported from the subaqueous delta most likely due to the frequent occurrence of bora conditions progradation of the po river delta into the adriatic sea may restrict the formation of the western adriatic coastal current increasing sediment retention at the po delta and reducing the supply of sediment to the apennine margin a positive morphodynamic feedback may therefore be present whereby the extension of the delta into the adriatic increases sediment accumulation at the delta and facilitates further progradation

a pyroclastic flow deposit on venus explosive volcanism on venus is severely inhibited by its high atmospheric pressure and lack of water this paper shows that a deposit located near 16 s 144 e here referred to as scathach fluctus displays a number of morphological characteristics consistent with a pyroclastic flow deposit these characteristics particularly its lack of channelisation and evidence for momentum rather than cooling limited flow length contrast with fissure fed lava flow deposits the total erupted volume is estimated to have been between 225 km3 and 875 km3 but this may have been emplaced in more than one event interaction between scathach fluctus and a small volcanic cone constrain the flow velocity to 48 m s 1 and plausible volatile concentrations to at least 1 8 wt h2o 4 3 wt co2 or 6 1 wt so2 the latter two implying magma sourced directly from the mantle the deposit has radar characteristics particularly an exponential backscatter function that are similar to those of nearly half the planetary surface implying that pyroclastic deposits may be much more common on venus than has been recognised to date and suggesting both a relatively volatile rich mantle and a volcanic source for atmospheric so2

radar sounding of lucus planum mars by marsis italian space agency asi i 032 12 1 leibniz rechenzentrum garching germany 2013091832 european union 654367 283610

modeling river delta formation a model to simulate the time evolution of river delta formation process is presented it is based on the continuity equation for water and sediment flow and a phenomenological sedimentation erosion law different delta types are reproduced by using different parameters and erosion rules the structures of the calculated patterns are analyzed in space and time and compared with real data patterns furthermore our model is capable of simulating the rich dynamics related to the switching of the mouth of the river delta the simulation results are then compared with geological records for the mississippi river

anthropogenic influence on recent evolution of shorelines between the conero mt and the tronto r mouth southern marche central italy abstract a study of the shoreline evolution during the last two centuries along the southern portion of the marche region between the promontory of the conero mountain and the tronto river mouth has been carried out on the basis of historical data and taking into account the effects of both natural events and anthropogenic interventions the research started with searching acquiring georeferencing and digitizing all the available maps surveyed from 1835 to the present the above data set has been used to implement a vector geodatabase containing the successive position and shape of shorelines with particular attention to the neighboring river mouths since transitional and beach deposits have been almost completely eroded during the last decades the adoption of traditional techniques of geomorphologic and sedimentological analyses has not been possible the results of the above analyses have been correlated with the main natural events and human interventions occurring during the considered time span the results of this comparison highlights that the evolution of river mouths and neighboring beaches mostly depends on deforestation carried out in their hydrographic basins in the study area the progradation of river mouths continued after the end of the little ice age ended around 1850 namely it has been observed that the retreat coincided with the start of reforestation and agricultural development in the 20 s of the last century during the following decades further interventions such as construction of dams and check dams extraction of sediments from thalwegs fillings modifications of stream paths abandonment of agricultural practices etc contributed to a severe reduction of river solid load with subsequent retreat of both river mouths and beaches thus making it necessary to protect them with artifacts

anthropogenic effects on shoreface and shoreline changes input from a multi method analysis agadir bay morocco abstract in many situations the links between shoreline fluctuations and larger scale coastal change embracing the shoreface are not always well understood in particular meso scale years to decades sand exchanges between the shoreface and the shoreline considered as important on many wave dominated coasts are rather poorly understood and difficult to identify coastal systems where sediment transport is perturbed by engineering interventions on the shoreline and shoreface commonly provide fine examples liable to throw light on these links this is especially so where shoreface bathymetric datasets which are generally lacking are collected over time enabling more or less fine resolution of the meso scale coastal sediment budget agadir bay and the city of agadir together form one of the two most important economic development poles on the atlantic coast of morocco using a combined methodological approach based on wave current modelling bathymetric chart differencing determination of shoreline fluctuations and beach topographic surveying we highlight the close links between variations in the bed of the inner shoreface and the bay shoreline involving both cross shore and longshore sand transport pathways sediment budget variations and new sediment cell patterns we show that the significant changes that have affected the bay shoreline and shoreface since 1978 clearly reflect anthropogenic impacts notably blocking of alongshore sand transport by agadir harbour completed in 1988 and the foundations of which lie well beyond the depth of wave closure construction of the harbour has led to the creation of a rapidly accreting beach against an original portion of rocky shoreline updrift and to a net sand loss exceeding 145 000 m 3 year between 1978 and 2012 over 8 5 km 2 of the bay shoreface downdrift shoreline retreat has been further exacerbated by sand extraction from aeolian dunes and by flattening of these dunes to make space for tourist infrastructure digital elevation models of part of the bay beach between 2012 and 2014 confirm this on going sand loss these changes have involved the establishment of two divergent longshore bay sediment cells instead of the original single unidirectional cell a prospective view of these changes suggests that perturbation of longshore drift and the on going bay sediment budget deficit will eventual directly pose threats to the harbour access and to coastal tourism on which the economic growth of agadir has been built

dielectric measurements and radar attenuation estimation of ice basalt sand mixtures as martian polar caps analogues the nature of the materials underlying the superficial deposits of mars can be inferred applying an inversion algorithm from the data acquired by the orbiting hf radars marsis and sharad this approach requires the knowledge of the electromagnetic properties of the shallow deposits and an accurate evaluation of the signal attenuation the present work is focused on the determination of the dielectric parameters of several geo materials we performed the measurements of the complex permittivity in a wide range of temperature 150 250 k and frequency 20 hz 1 mhz on pure water ice dry basalt sand and ice basalt mixtures with different sand volume fractions the data are presented in terms of attenuation as a function of basalt volume fraction frequency and temperature and discussed in terms of extrapolation to marsis and sharad frequency bands the results show that besides the expected dependence of the attenuation from temperature the presence of the solid inclusions in the ice strongly affects the behaviour of the attenuation versus frequency

volcanology of the 2350 b p eruption of mount meager volcanic complex british columbia canada implications for hazards from eruptions in topographically complex terrain the pebble creek formation previously known as the bridge river assemblage comprises the eruptive products of a 2350 calendar year b p eruption of the mount meager volcanic complex and two rock avalanche deposits volcanic rocks of the pebble creek formation are the youngest known volcanic rocks of this complex they are dacitic in composition and con tain phenocrysts of plagioclase orthopyroxene amphi bole biotite and minor oxides in a glassy groundmass the eruption was episodic and the formation com prises fallout pumice bridge river tephra pyroclastic flows lahars and a lava flow it also includes a unique form of welded block and ash breccia derived from col lapsing fronts of the lava flow this merapi type brec cia dammed the lillooet river collapse of the dam triggered a flood that flowed down the lillooet valley the flood had an estimated total volume of 10 9 m 3 and inundated the lillooet valley to a depth of at least 30 m above the paleo valley floor 5 5 km downstream of the blockage rock avalanches comprising mainly blocks of plinth assemblage volcanic rocks an older formation making up part of the mount meager vol canic complex underlie and overlie the primary vol canic units of the formation both rock avalanches are unrelated to the 2350 b p eruption although the post eruption avalanche may have its origins in the over steepened slopes created by the explosive phase of the eruption much of the stratigraphic complexity evident in the pebble creek formation results from deposition in a narrow steep sided mountain valley containing a major river

dating modern deltas progress problems and prognostics 1 abstract radiocarbon dating is the method most frequently used to date holocene deltaic sequences but less than one quarter of 14c dates are within 500 years of predicted age such dates tend to be unreliable in other words often too old and commonly inverted upsection and core sample dates obtained near deltaic plain surfaces may be as old as mid to late holocene stratigraphic irregularities result primarily from downslope reworking of upland alluvial sediment with displacement of old carbon in the sediment that accumulates in lower valleys and deltaic plains use of dates that are too old results in inaccurately calculated rates most often too low of relative sea level rise and or land subsidence more reliable timing of deltaic sediment requires a multiple method dating approach including where possible identification of associated archaeological material developing an accurate dating strategy is a critical step for implementing reliable coastal protection measures needed for the rapi

mineralogical forms of silica and their sequence of formation in silcretes the paragenesis and the sequence of formation of silica polymorphs have been studied in three examples of silicification in the regolith of the paris basin and the central massif of france the initial silica deposits are most frequently opal with varying degrees of structural organization subsequently recrystallization produced varieties of progressively better organized quartz namely fibrous quartz chalcedony and lutecite which developed from deposits of microlaminated opal and microcrystalline quartz which formed from nodular opal however even during the formation of microcrystalline quartz facies dissolution and recrystallization processes continued resulting in progressively bigger quartz crystals in the final stages of silcrete development hyaline quartz crystals grew in voids these mineral sequences are determined by the solubility of each of the component parts solubility is controlled by the purity and the degree of order of the crystalline structure the most disordered minerals are the most soluble the degree of order is controlled in part by foreign ions incorporated into the lattice but also by the degree of supersaturation of silica in solution in the system which in turn controls the rate of formation of nuclei dissolution and recrystallization processes are dependent on the percolation of dilute solutions through the silcretes the concentrations of silica and other cations in these solutions is a function of the solubility of the silica phases in the host material and of the rate of percolation thus the porosity of the host material is important rapid percolation favors dissolution but in zones with slow percolation equilibrium is attained and no transformation of existing silica phases occurs it is in the zones of intermediate porosity that progressive recrystallization of quartz occurs the effect of rate of percolation on dissolution and recrystallization explains the vertical distribution of different silica polymorphs observed in numerous silcrete duricrusts

characterization of volcanic deposits with ground penetrating radar field based studies of surficial volcanic deposits are commonly complicated by a combination of poor exposure and rapid lateral variations controlled by unknown paleotopography the potential of ground penetrating radar gpr as an aid to volcanological studies is shown using data collected from traverses over four well exposed recent volcanic deposits in western canada the deposits comprise a pumice airfall deposit 3 4 m thick a basalt lava flow 3 6 m thick a pyroclastic flow deposit 15 m thick and an internally stratified pumice talus deposit 60 m thick results show that gpr is effective in delineating major stratigraphic contacts and hence can be used to map unexposed deposits different volcanic deposits also exhibit different radar stratigraphic character suggesting that deposit type may be determined from radar images in addition large blocks within the pyroclastic deposits are detected as distinctive point diffractor patterns in the profiles showing that the technique has potential for providing important grain size information in coarse poorly sorted deposits laboratory measurements of dielectric constant k are reported for samples of the main rock types and are compared with values of k for the bulk deposit as inferred from the field data the laboratory values differ significantly from the field values of k these results suggest that the effectiveness of gpr at any site can be substantially improved by initial calibration of well exposed locations

a new concept in modeling the dielectric response of sandstones defining a wetted rock and bulk water system experimental data for the real part of the dielectric constant k of three sandstone samples are considered as a function of the level of water saturation sw in the frequency range 60 khz to 4 mhz existing theoretical models have previously shown poor agreement with k versus sw data for rock samples undoubtedly due to the complexity involved in adequately accounting for geometrical and electrochemical effects in analyzing the data presented here we find a pronounced increase in k in the low saturation region which in all cases can be attributed to the establishment of geometrical and surface effects associated with the rock water interface when this increase in k is accounted for by defining wetted matrix parameters the data show excellent agreement with existing theoretical models

wave influence in the construction shaping and destruction of river deltas a review abstract waves are an important agent in the construction shaping and destruction of river deltas notwithstanding the commonality of waves in oceans and seas wave influence on deltas varies considerably depending on the coastal morphology and nearshore bathymetry although there have been advances in understanding the way waves approaching a delta shape its shoreline much still remains to be known of the interactions between waves and river deltas deltas are built essentially from sediments supplied by rivers sand sized and coarser sediments may also be derived from nearby abandoned delta lobes or from older relict nearshore deposits transported by wave reworking and longshore currents alternatively delta erosion by waves can also release sediment that is redistributed alongshore or that accumulates offshore the extent to which bedload is supplied to and sequestered in or lost by deltas through waves and longshore transport strongly depends on interactions between waves and fluvial discharge at the river mouth these interactions and the mutual adjustments they engender are not only important in the overall balance between delta retreat progradation or aggradation but also in processes such as avulsion and channel switching as well as in the eventual survival of a delta in the face of sea level rise where waves are important fluvial liquid discharge is high and sediment supply is rich in bedload two important aspects are the blocking of waves and longshore currents by strong river discharge and the formation of bars at the river mouth field studies of the complex interactive processes prevailing where river flows encounter waves are however non existent and numerical modelling though promising hampered by scale constraints and the difficulty of replicating them and generating mouth bars in the presence of longshore currents this interaction influences the seaward extent of the delta mouth protuberance and its stability this protuberance then forming the regional shoreline template to which waves and longshore currents adjust longshore currents can redistribute wave reworked mouth bar deposits emplaced during strong river flow transport may be either divergent from the mouth or may be regionally unidirectional but wherein the symmetry of some deltas probably rare may be maintained by a strong river blocking effect on transport from the updrift flank the mouth protuberance may be such as to foster transport reversal counter drift at the delta margins that contributes to sediment sequestering within the delta these interactions largely contribute in shaping delta shorelines and together with the abundance of sediment supply and grain size determine the resultant wave formed shoreline barrier types which include spits more or less closely spaced beach ridges and barrier islands and cheniers in situations of punctuated progradation or retreat where several distributary mouths occur pronounced longshore variability in wave processes and wave induced sediment transport may ensue resulting in multiple drift cells that assure the retention of sand and coarse grained sediments within the delta waves can also be an important agent in the reworking and retreat of mud rich deltas that generally conform in morphology to the river dominated such as the mississippi or tide dominated such as the ganges brahmaputra or chao phraya types resulting in the episodic formation of sandy cheniers and beach ridges although sea level rise is likely to lead to enhanced wave reworking of deltas the possible prevalence of aggradation in lieu of progradation channel switching and avulsion and washover processes may contribute to the disorganization of waves and longshore transport fostering deltaic sequestering of sand and coarser sized sediment and delta survival the weakening of river discharges resulting from human activities will invariably lead however to enhanced wave reworking of deltas and to deltaic sediment redistribution by longshore currents the massive swing towards significant reductions in fluvial sediment supply today may signify the ultimate demise of many deltas in the coming decades through a process of delta shoreline straightening by waves in addition to accelerated sinking these various foregoing aspects of the relationship between waves and river deltas are reviewed here across a range of timescales and new interaction concepts proposed using numerous examples of deltas in the world and on the basis of case studies conceptual studies and numerical modelling studies in the literature spanning more than forty years

sparse subsurface radar reflectors in hellas planitia mars abstract geomorphological features potentially related to subsurface ice such as scalloped depressions expanded craters pedestal craters and banded terrain are present in and around hellas planitia mars we present a radar survey of the region using the shallow radar sharad instrument on board the mars reconnaissance orbiter mro to identify candidate subsurface reflectors that may be due to the presence of potentially ice rich deposits we found that the majority of radar returns are likely from off nadir surface topography clutter arising from the rough topography of the region there is no widespread radar return from any subsurface interfaces however we identify a group of six reflectors adjacent to each other on a plateau in malea patera in which we have higher confidence landforms associated with a likely ice rich mantle are associated with the plateau but the thickness of this mantle does not correspond to the expected depth of the reflectors however layers beneath the mantle and marginal pitting at the edge of the plateau are similar to those associated with pedestal craters which may be ice rich and are a similar thickness to the expected depth of the reflectors malea patera has been interpreted to be a volcanic caldera so the reflectors may be associated with a volcanic deposit within the plateau although the evidence for this is inconclusive because this radar detection is localized and its origin ambiguous we cannot use it to make conclusions about the thickness of subsurface deposits in the hellas region as a whole the lack of widespread radar reflectors in this region as compared to the northern mid latitudes where extensive radar reflections have been mapped may be due in part to higher surface roughness which creates radar clutter that may obscure subsurface reflectors however on the southern rim of the basin and south of the basin the lack of reflectors may indicate that the possible ice rich deposits observed geomorphologically in this region are too thin to be resolved by sharad are dielectrically similar to the underlying unit or have a gradual vertical transition in ice content that is not reflective for the radar this would imply that recent climate processes may have favored widespread thick ice deposition or preservation in the northern hemisphere as compared to the southern hemisphere

the wandering of the volga delta a response to rapid caspian sea level change due to its very low gradient and absence of tide and surf the volga delta is an even more extreme example of the fluvially dominated type than the mississippi delta however it differs from all other large delta systems in that it borders a closed basin the caspian sea now at 26 m below global sea level caspian sea level is much more dynamic than that of the world oceans and rises at present about 1 5 cm yr a hundred time the eustatic rate within the quatemary sea level oscillations of at least 5 orders of magnitudes have been distinguished which seem grossly out of phase with eustatic sea level between the weichselian early khvalyn highstand of 50 m and the early holocene mangyshlak lowstand at 80 m the apex of the volga delta has wandered over 700 km alongstream the present day volga delta is not a highstand deposit but probably represents a minor transgression in a major regressional stage the delta does not show a coarsening upwards sedimentary sequence but consists of a weichselian transgressional fining upwards sequence topped by eolian deposits in which the delta distributary channels have been incised present day sedimentation is limited to a narrow fringe along the delta front and to deeper waters over 200 km offshore sea level changes outpaced aggradation to such an extent that volga sediment is spread over the whole north caspian plain sequence stratigraphical principles are difficult to apply because sea level cycles of five orders of magnitude are superimposed and because there is not enough sediment loading or tectonic subsidence to create sufficient accommodation space

anthropogenic influences on shoreline and nearshore evolution in the san francisco bay coastal system abstract analysis of four historical bathymetric surveys over a 132 year period has revealed significant changes to the morphology of the san francisco bar an ebb tidal delta at the mouth of san francisco bay estuary from 1873 to 2005 the san francisco bar vertically eroded an average of 80 cm over a 125 km 2 area which equates to a total volume loss of 100 52 million m 3 of fine to coarse grained sand comparison of the surveys indicates the entire ebb tidal delta contracted radially with the crest moving landward an average of 1 km long term erosion of the ebb tidal delta is hypothesized to be due to a reduction in the tidal prism of san francisco bay and a decrease in coastal sediment supply both as a result of anthropogenic activities prior research indicates that the tidal prism of the estuary was reduced by 9 from filling diking and sedimentation compilation of historical records dating back to 1900 reveals that a minimum of 200 million m 3 of sediment has been permanently removed from the san francisco bay coastal system through dredging aggregate mining and borrow pit mining of this total 54 million m 3 of sand sized or coarser sediment was removed from central san francisco bay with grain sizes comparable to the ebb tidal delta and its direct connection to the bay mouth removal of sediments from central san francisco bay may limit the sand supply to the delta and open coast beaches swan wave modeling illustrates that changes to the morphology of the san francisco bar have altered the alongshore wave energy distribution at adjacent ocean beach and thus may be a significant factor in a persistent beach erosion hot spot occurring in the area shoreline change analyses show that the sandy shoreline in the shadow of the ebb tidal delta experienced long term 1850s 1890s to 2002 and short term 1960s 1980s to 2002 accretion while the adjacent sandy shoreline exposed to open ocean waves experienced long term and short term erosion therefore the recently observed accelerating rates of bay sediment removal ebb tidal delta erosion and open coast beach erosion are all correlated temporally

processes reshaping the nile delta promontories of egypt pre and post protection abstract shoreline positions established from beach profile surveys combined with wave data are jointly analyzed as a function of their contribution to coastal processes to investigate the interaction between waves shoreline orientation and coastal structures along the nile delta promontories rosetta burullus and damietta repeated beach profile surveys along the promontory sectors 64 km long in total have been analyzed to determine rates of shoreline changes prior to construction 1971 1990 and after construction of protective structures 1990 2000 the behavior of coastline pre and post construction indicates that coastal erosion fronting protective structures has declined in the case of the seawalls at the tips of the rosetta and damietta promontories or has been partially replaced by sand accumulation in the case of detached breakwaters at baltim east of burullus promontory and at ras el bar west of the damietta promontory as a consequence downdrift erosion has been initiated in local areas adjacent to these structures in the direction of longshore sediment transport the 5 km long seawall protecting the rosetta promontory has stopped the dramatic erosion of this highly eroded area formerly shoreward retreated 88 m year with adverse local erosion at its west and east ends being 3 and 13 m year respectively similarly the 6 km long seawall built on the eastern tip of the damietta promontory still under construction has nearly stopped the severe erosion which was formerly 10 m year the detached breakwaters at both baltim and at ras el bar have accumulated sand at accretion rates of 37 and 14 m year respectively this sand accumulation is associated with downdrift erosion of 25 and 13 m year at baltim and ras el bar respectively results reaffirm that the original erosion accretion patterns along the nile delta promontories have been reshaped due to the massive protective structures built during the last decade this reshaping along the examined promontories is generally controlled by the temporal variability in the intensity and reversibility of wave directions and associated longshore currents coastline orientation and by the existing coastal protection structures

detection of welding in pyroclastic flows with ground penetrating radar insights from field and forward modeling data abstract we investigate the potential of ground penetrating radar gpr as a tool to delineate welded portions of pyroclastic flows by testing interpretations of field gpr data with numerical modeling specifically we test the hypothesis that regions of changing porosity with depth and regions of constant porosity are characterized by distinct signals in radargrams we model the propagation of electromagnetic waves through pyroclastic flow deposits with vertical variations in porosity the actual profiles are gradational but are represented in our models by a series of 1 cm thick homogeneous layers each layered porosity profile is converted into a layered k profile using an empirical law relating k to of dry volcanic rocks that is based on laboratory measurements the resulting synthetic traces indicate that moderate gradational changes in welding produce multiple low amplitude crests and troughs rather than strong individual reflections the lower the peak frequency of the source wavelet the greater the amplitude of the signal generated and thus the greater the potential signal to noise ratio extremely high rates of change in porosity with depth produce distinct strong reflections densely welded or unwelded portions where porosity is relatively constant produce sections of zero amplitude these preliminary results suggest that gpr can be used to map the effects of welding in pyroclastic flows specifically characteristic radar signals can be used to identify zones of changing degree of welding and zones of relatively constant degree of welding

rapid evolution of coastal lagoons in response to human interference under rapid sea level change a south caspian sea case study this research is part of the phd of the first author entitled evaluation of sefidrud delta south west caspian sea during the last millennium which was funded by brunel university london grant no r85104 the publication is a contribution to the inqua quicklakeh project no 1227 and to the european project marie curie climseas pirses ga 2009 247512

vesicle connectivity in pyroclasts and implications for the fluidisation of fountain collapse pyroclastic flows montserrat west indies abstract pyroclastic flows are noted for their highly mobile behaviour being able to flow on slopes as low as a few degrees and this has been attributed to fluidisation or partial fluidisation by escaping gases the three types of pyroclastic flows generated during the eruption of soufriere hills volcano on montserrat dome collapse fountain collapse and surge derived differ in their apparent mobility suggesting different degrees of fluidisation and friction reduction in the flowing granular materials several possible sources of fluidising gas operate in pyroclastic flows the purpose of this paper is to assess the feasibility of one mechanism the release during flow of pressurised gases trapped in the vesicles of juvenile clasts measurements with a helium pycnometer show that all vesicles in dense lava blocks from dome collapse pyroclastic flows are connected so that the mechanism is probably not viable for such flows on the other hand pumices from fountain collapse pyroclastic flows from soufriere hills and other volcanoes contain up to 10 vol of isolated vesicles this is confirmed by sem imagery which shows that soufriere hills pumices contain two vesicle populations with a bimodal size distribution the large vesicles are mostly interconnected whereas about two thirds of the smaller population

human induced changes in the geomorphology of the northeastern coast of the nile delta egypt abstract landsat enhanced thematic mapper imagery etm of 2002 and aerial photography of 1955 combined with published charts and field observations were used to interpret geomorphological changes in the coastal zone between kitchener drain and damietta spit in the northeastern nile delta previously recognized as a vulnerable zone to the effects of any sea level rise resulting from global warming the interpretation resulted in recognition of several changes in nine identified geomorphological land types beach and coastal flat coastal dunes agricultural deltaic land sabkhas fish farms manzala lagoon saltpans marshes and urban centers reclamation of vast areas of the coastal dunes and of manzala lagoon added about 420 km2 to the agricultural deltaic land about 48 km2 of sand dunes marshes sabkhas and salt pans have been converted to productive fish farms the main urban centers have expanded and new urban centers damietta harbor and the new damietta city have been constructed at the expense of vast areas of manzala lagoon coastal dunes and backshore flats as the consequence of human activities the size of manzala lagoon has been reduced to less than 50 short term shoreline changes along the coast of the study area established from beach profile survey spanning the years of 1990 to 2000 reveal longshore patterns of erosion versus accretion the rate of shoreline retreat has increased in the downdrift side of damietta harbor 14 m year whereas areas of accretion exist within the embayment of gamasa and in the shadow of ras el bar detached breakwater system with a maximum shoreline advance of 15 m year a sandy spit 12 km long has developed southeast of damietta promontory these erosion accretion patterns denote the natural processes of wave induced longshore currents and sediment transport in addition the impact of man made coastal protection structures

estimation of porosity and water saturation in dual porosity pyroclastic deposits from joint analysis of compression shear and electromagnetic velocities in situ measurements of porosity and water saturation of pyroclastic deposits have the potential to improve interpretations of geology and hydrology in volcanic regions and provide more accurate estimates of dense rock equivalent for volcanic eruptions however rock property models must consider the dual porosity structure of pyroclastic deposits i e vesicles within pumices and intergranular pores vesicularity intergranular porosity and water saturation all affect the density elasticity and dielectric properties of pyroclastic materials which control seismic and electromagnetic velocities the data from active seismic and ground penetrating radar techniques may improve porosity and water saturation estimation if the responses of seismic and electromagnetic waves to porosity and water saturation variations are complementary in pyroclastic rocks we develop a dual porosity petrophysical model to calculate seismic and electromagnetic velocities of pumice with known intergranular porosity vesicul

welded block and ash flow deposits from mount meager british columbia canada abstract the 2360 years b p eruption of mount meager british columbia produced a succession of rarely observed welded block and ash flow deposits and non welded equivalents we report on these rhyodacitic block and ash flow deposits by describing the deposits documenting the nature of the welding process and establishing the origins of these pyroclastic deposits variations in welding intensity are tracked by image analysis of field texture maps petrographic study of shard morphology and measurements of sample density and porosity pyroclast oblateness from image analysis of texture maps provides a qualitative record of welding intensity but underestimates the amount of compactional e g volume strain when compared to estimates from physical property measurements e g density porosity unconsolidated deposits have an average matrix porosity of 41 38 45 and clasts have an average porosity of 32 24 40 in unconsolidated deposits isolated porosity is pervasive 50 m shortening of the thickest deposit from 162 m to the current 112 m the pyroclastic flow deposits result from accumulation in a narrow confined river valley the accumulation was sufficiently rapid to keep the deposits above their glass transition temperature thereby allowing the succession to weld as a single cooling unit the nature and distribution of isolated porosity in the juvenile clasts of rhyodacite suggest an explosive rather than effusive origin for these block and ash flow deposits that may be analogous to some vulcanian eruption triggered dome collapse processes observed at soufriere hills volcano montserrat rather than gravitational collapse

the modern po delta system lobe switching and asymmetric prodelta growth the modern po delta system comprising five main delta lobes has been investigated by integrating vhr seismic surveys recorded offshore from water depths as shallow as 5 m to the toe of the prodelta in about 30 m with accurate historical cartography extending back several centuries previous studies give sedimentological and geochronological information from precisely positioned sediment cores this combined historical and stratigraphic reconstruction of the modern po prodelta allows volumetric reconstructions indicating an average sediment load of 9 4 10 6 ty r 1 for po di pila and po di goro gnocca lobes this estimate is remarkably consistent with the total sediment load of 11 5 10 6 ty r 1 available for parts of the last century from a gauge station at the apex of the delta plain in pontelagoscuro these integrated stratigraphic studies allow to explain the key characters of the po delta system a the marked asymmetry of the whole delta prodelta system reflecting prevailing sediment dispersal to the south of each individual delta outlet b the shoreparallel overlapping of successive prodelta lobes fed by distinct river outlets of ever changing relative importance c the delta outlets being artificially forced in a fixed position so that natural avulsion is prevented and delta lobes undergo headland retreat leaving a marked erosion on the prodelta d the presence of prodelta lobes showing widespread bcut and fillq features ranging from 100 to 300 m and depths up to 4 5 m filled with massive silt to very fine sand offshore of short lived very active distributary channels e g po di tolle lobe and suggesting that in some particular interval short lived episodes of submarine erosion are induced by catastrophic increases in river discharge of natural origin or induced by human maintenance the seismic stratigraphy of the modern po delta documents that markedly distinct prodelta architectures form when a newly activated lobe is located updrift north in this case or downdrift south of the one that is retreating in the first case the abandoned lobe becomes sheltered by the new rapidly advancing one in the opposite case the retreating lobe is updrift and a substantial portion of the sediment is cannibalized and transported to the new lobe downdrift d 2005 elsevier b v all rights reserved

a review of the delta po evolution italy related to climatic changes and human impacts abstract climate changes and sea level rise are important issues especially for deltas such as the po delta italy the evolution of the po delta shows a succession in space and a superposition in time of complex environmental natural processes during the last few centuries anthropogenic action has played a major role the formation of the po delta began about 2000 years ago and has undergone many phases of development between 1500 ad and 1600 ad the venetian technicians diverted the po river course with these interventions the renaissance delta was cut off from the hydraulic network and the modern delta began to form until the middle of the 20th century progradation of the delta was noticeable due to the abundant sediment supply in the following decades coastal erosion occurred this was caused by the reduction of the solid supply of the po due to dam and barrier construction and to river bed excavation these and other interventions e g reclamation methane extractions from superficial ground water table have deeply modified the physical and ecological characteristics of the po delta the morphological characteristics of the po delta make the largest italian wetland particularly unstable and very fragile when subjected to human pressure furthermore the delta evidences multiple threats that will probably be exacerbated in the following decades by the effects of expected climatic changes only the application of careful policies concerning coastal defence flood mitigation anthropogenic subsidence reduction and salt wedge intrusion control will allow reduction of the present or predicted negative effects this paper reviews how natural and human factors have controlled the po delta through time and discusses management strategies taking into account the importance of the human factor and the potential effects of climatic changes

dynamics of coupled human landscape systems a preliminary dynamical analysis of landscapes and humans as hierarchical complex systems suggests that strong coupling between the two that spreads to become regionally or globally pervasive should be focused at multi year to decadal time scales at these scales landscape dynamics is dominated by water sediment and biological routing mediated by fluvial oceanic atmospheric processes and human dynamics is dominated by simplifying profit maximizing market forces and political action based on projection of economic effect also at these scales landscapes impact humans through patterns of natural disasters and trends such as sea level rise humans impact landscapes by the effect of economic activity and changes meant to mitigate natural disasters and longer term trends based on this analysis human landscape coupled systems can be modeled using heterogeneous agents employing prediction models to determine actions to represent the nonlinear behavior of economic and political systems and rule based routing algorithms to represent landscape processes a cellular model for the development of new orleans illustrates this approach with routing algorithms for river and hurricane storm surge determining flood extent five markets home labor hotel tourism and port services connecting seven types of economic agents home buyers laborers home developers hotel owners employers hotel developers tourists port services developer and port services owners employers building of levees or a river spillway by political agents and damage to homes hotels or port services within cells determined by the passage or depth of flood waters the model reproduces historical aspects of new orleans economic development and levee construction and the filtering of frequent small scale floods at the expense of large disasters

quartz arenites review and interpretation abstract quartz arenites orthoquartzites are exceptional sands pettijohn et al 1972 that in the past have formed extensive and commonly thick formations they are somewhat enigmatic in that they do not appear to be forming at the present time this paper examines the origin of quartz rich sands documents the range of environments in which they are found and suggests a model for their genesis quartz sand is most commonly formed by tropical weathering of coarse grained quartz bearing rocks such as granite it may be deposited as texturally immature fluvial sandstones generally under a humid climate with drying of the climate quartz rich bauxitic soils and sandy alluvium can be a substantial source of poorly rounded dune sands for major deserts quartz sand when transported into shallow marine environments becomes very well rounded through reworking by tidal currents such sand may spill into deep oceanic environments and by sedimentary or tectonic transport may come to rest in both stable and active tectonic settings quartz rich sandstones can also be formed by diagenetic destruction of labile framework grains of immature sandstones precambrian orthoquartzites are commonly thick and widespread when compared to younger examples the thinness of post silurian quartz arenites may be largely due to the trapping effect of land vegetation and solution of quartz by organic acids in weathering profiles there is an abundance of shallow marine and fluvial quartz arenites in the early paleozoic and the cretaceous this is due to widespread continental flooding and a humid world climate following the disintegration of supercontinents the shallow marine examples are commonly associated with bituminous sometimes phosphatic shale glauconite and possibly chamositic ironstone there is an abundance of eolian quartz arenites in the permo triassic this is related to a widespread dry continental climate during assembly of the pangean supercontinent