carbon dioxide and radon gas hazard in the alban hills area central italy abstract the sudden and catastrophic or slow and continuous release at surface of naturally occurring toxic gases like co 2 h 2 s and rn poses a serious health risk to people living in geologically active regions in general this problem receives little attention from local governments although public concern is raised periodically when anomalous toxic gas concentrations suddenly kill humans or livestock for example elevated co 2 concentrations have been linked to the death of at least 10 people in the central italian region of lazio over the last 20 years while it was the co 2 asphyxiation of 30 cows in a heavily populated area near rome in 1999 which prompted the present soil gas study into the distribution of the local health risk a detailed geochemical survey was carried out in an area of about 4 km 2 in the ciampino and marino districts whereby a total of 274 soil gas samples were collected and analysed for more than 10 major and trace gas species data were then processed using both statistical and geostatistical methods and the resulting maps were examined in order to highlight areas of elevated risk general trends of elevated co 2 and rn concentrations imply the presence of preferential pathways i e faults and fractures along which deep gases are able to migrate towards the surface the co 2 and rn anomalous trends often correspond to and are usually elongated parallel to the apennine mountain range the controlling structural feature in central italy because of this fundamental anisotropy in the factors controlling the soil gas distribution it was found that a geostatistical approach using variogram analysis allowed for a better interpretation of the data with regard to the health risk to local inhabitants it was found that although some high risk areas had been zoned as parkland others had been heavily developed for residential purposes for example many new houses were found to have been built on ground which has soil gas co 2 concentrations of more than 70 and radon values of more than 250 kbq m 3 it is recommended that land use planners incorporate soil gas and or gas flux measurements in environmental assessments in areas of possible risk i e volcanic or structurally active areas

soil gas survey for tracing seismogenic faults a case study in the fucino basin central italy soil gas he rn co2 and ch4 surveys were performed to test their sensitivity for locating fault or fracture systems when masked by unconsolidated lithologies and to investigate the gas bearing properties of seismogenic faults the fucino basin central italy was chosen as a test site because it displays a network of surface and shallow buried active faults within the valley floor which were partially reactivated during the 1915 avezzano earthquake ms 7 0 the highest radon values were found aligned along the most important faults especially along the san benedetto gioia dei marsi fault sbgmf to the east and in the northwestern sector where the avezzano celano fault acf meets the northwestern prolongation of the 1915 coseismic rupture moderately anomalous values of radon occur along the faults located in the depression of the historical lake trasacco fault tf and ortucchio fault of anomalous values of co2 rn and he were detected north of borgo ottomila in a zone where coseismic scarps and liquefaction phenomena were responsible for a pervasive brittle deformation during the 1915 earthquake highest helium values prevail in the western part of the plain in correspondence with a horst structure bounded by the tf and considered to be the extension of the vallelonga trasacco ridge results of this research confirm the possible usefulness of soil gas methods for locating some tectonic faults when covered by unconsolidated deposits the study provides some clues on the spatial influence of tectonics and geology on deeply seated gas migration toward the surface

atmospheric volcanic loading derived from bipolar ice cores accounting for the spatial distribution of volcanic deposition 1 previous studies have used small numbers of ice core records of past volcanism to represent hemispheric or global radiative forcing from volcanic stratospheric aerosols with the largest ever assembly of volcanic ice core records and state of the art climate model simulations of volcanic deposition we now have a unique opportunity to investigate the effects of spatial variations on sulfate deposition and on estimates of atmospheric loading we have combined 44 ice core records 25 from the arctic and 19 from antarctica and goddard institute for space studies modele simulations to study the spatial distribution of volcanic sulfate aerosols in the polar ice sheets we extracted volcanic deposition signals by applying a high pass loess filter to the time series and examining peaks that exceed twice the 31 year running median absolute deviation our results suggest that the distribution of volcanic sulfate aerosol follows the general precipitation pattern in both regions indicating the important role precipitation has played in affecting the deposition pattern of volcanic aerosols we found a similar distribution pattern for sulfate aerosols from the 1783 1784 laki and 1815 tambora eruptions as well as for the total b activity after the 1952 1954 low latitude northern hemisphere and 1961 1962 high latitude northern hemisphere atmospheric nuclear weapon tests this confirms the previous assumption that the transport and deposition of nuclear bomb test debris resemble those of volcanic aerosols we compare three techniques for estimating stratospheric aerosol loading from ice core data radioactive deposition from nuclear bomb tests pinatubo sulfate deposition in eight antarctic ice cores and climate model simulations of volcanic sulfate transport and deposition following the 1783 laki 1815 tambora 1912 katmai and 1991 pinatubo eruptions by applying the above calibration factors to the 44 ice core records we have estimated the stratospheric sulfate aerosol loadings for the largest volcanic eruptions during the last millennium these loadings agree fairly well with estimates based on radiation petrology and model simulations we also estimate the relative magnitude of sulfate deposition compared with the mean for greenland and antarctica for each ice core record which provides a guideline to evaluate the stratospheric volcanic sulfate aerosol loading calculated from a single or a few ice core records

post caldera activity in the alban hills volcanic district italy 40ar 39ar geochronology and insights into magma evolution we present 24 40ar 39ar ages for the youngest volcanic products from the alban hills volcanic district rome combined with petrological data on these products we have attempted to define the chronology of the most recent phase of activity and to investigate the magma evolution of this volcanic district the early mainly explosive activity of the alban hills spanned the interval from 561 1 to 351 3 ka after approximately 50 kyr of dormancy a mainly effusive phase of activity took place accompanied by the strombolian activity of a small central edifice monte delle faete this second phase of activity spanned the interval 308 2 to 250 1 ka after another dormancy period of approximately 50 kyr a new hydromagmatic phase of activity started at 200 ka at several centers located to the southwest of the monte delle faete edifice after an initial recurrence period of approximately 50 kyr which also characterized this new phase of activity the longest dormancy period approximately 80 kyr in the history of the volcanic district preceded the start of the activity of the albano and giuturna centers at 70 1 ka results of our study suggest a quasi continuous magmatic activity feeding hydromagmatic centers with a new acme of volcanism since around 70 ka based on data presented in this paper we argue that the alban hills should not be considered an extinct volcanic district and a detailed re assessment of the volcanic hazard for the area of rome is in order

process based approach to co2 leakage detection by vadose zone gas monitoring at geologic co2 storage sites a critical issue for geologic carbon sequestration is the ability to detect co2 in the vadose zone here we present a new process based approach to identify co2 that has leaked from deep geologic storage reservoirs into the shallow subsurface whereas current co2concentration based methods require years of background measurements to quantify variability of natural vadose zone co2 this new approach examines chemical relationships between vadose zone n2 o2 co2 and ch4 to promptly distinguish a leakage signal from natural vadose zone co2 the method uses sequential inspection of the following gas concentration relationships 1 o2 versus co2to distinguish in situ vadose zone background processes biologic respiration methane oxidation and co2 dissolution from exogenous deep leakage input 2 co2 versus n2 to further distinguish dissolution of co2 from exogenous deep leakage input and 3 co2 versus n2 o2 to assess the degree of respiration ch4 oxidation and atmospheric mixing dilution occurring in the system the approach was developed at a natural co2 rich control site and successfully applied at an engineered site where deep gases migrated into the vadose zone the ability to identify gas leakage into the vadose zone without the need for background measurements could decrease uncertainty in leakage detection and expedite implementation of future geologic co2 storage projects

carbon dioxide earth degassing and seismogenesis in central and southern italy 1 we present the first regional map of co2 earth degassing from a large area most of central and south italy derived from the carbon of deep provenance dissolved in the main springs of the region the investigation shows that a globally significant amount of deeply derived co2 10 of the estimated global co2 emitted from subaerial volcanoes is released by two large areas located in western italy the anomalous flux of co2 suddenly disappears in the apennine in correspondence to a narrow band where most of seismicity concentrates here at depth the gas accumulates in crustal traps generating co2 overpressurized reservoirs which induce seismicity

seismicity seismogenic structures and crustal stress fields in the greater rome area central italy 1 instrumental seismicity of the greater rome area is analyzed using the most recent seismological database the aim of this study is to identify potential seismogenic structures responsible for the moderate seismicity that characterizes this sector where no surface faulting is expected on the basis of the absence of strong local earthquakes as evidenced by the 2000 year long historical record nevertheless in light of the great value and the high vulnerability of the architectural and monumental patrimony of rome even the occurrence of moderate events imposes a careful assessment of the hazard linked to the presence of active faults that are undetectable by means of classic geological field investigation seismic data here analyzed belong to the period 1997 2008 and show local magnitude ml ranging from 1 5 to 4 7 to better constrain the hypocentral depths we computed the vp vs ratio using a modified wadati method and the minimum 1 d velocity model that approximates the seismic structure of the study area moreover we applied a double difference hypocentral determination technique to improve earthquake locations most of the located seismicity appears to be concentrated within seven main clusters spatial distribution of the seismicity allowed us to identify several seismogenic structures corresponding to previously undetected or only supposed active faults the stress tensor obtained by inverting the focal mechanisms computed in this study is in agreement with the ne sw extensional tectonic stress active in the inner chain of the apennines although there is evidence of some local stress field heterogeneities

carbon dioxide degassing from the albani hills volcanic region central italy the albani hills are affected by strong co2 degassing processes the amount of co2 which rises from the depths and subsequently dissolves into shallow groundwater has been estimated to be more than 4 2 109 mol year 1 most of the gas is released in localised anomalous spots lavinio solforata and ciampino albano nemi areas generated by fluid leakage processes from buried pressurized reservoirs hosted by structural highs of the calcareous siliceous marly basement the groundwater circulating in the anomalous areas becomes co2 oversaturated generating observable gas manifestations whose composition is mainly controlled by gas liquid separation processes a gas flow rate of 6 1 108 mol year 1 has been measured from the two larger manifestations using the accumulation chamber technique the presence at shallow level of co2 oversaturated groundwater can explain several episodes of sudden release of gas which was documented by historical chronicles from roman times until now

stable isotope geochemistry of coals humic kerogens and related natural gases isotope systematics are well defined for conventional sapropelic type i ii kerogens and their associated bacterial and thermogenic natural gas products these geochemical tools are used to estimate source type maturity and depositional environment and as a correlation technique in many cases the natural gas signatures in near surface samples and drill cuttings can be used to classify or predict a deeper lying source rock or reservoir corresponding interpretative schemes for coals type iii kerogens and their associated hydrocarbons are progressing quickly the shift in attention to humic sources is driven primarily by depletion of conventional oil and gas resources and the economic and societal requirements of coal and coal bed methane carbon hydrogen and nitrogen stable isotope variations can be large between different coals and humic kerogens these differences can often be recognized in their bulk 13corg dorg and 15norg values isotope signatures of coals can be diagnostic of several factors including deposit age type geographic location maturity and generation history however these characteristic isotopic variations are substantially better defined by the c h and n isotope ratios of the separate maceral groups such as vitrinite exinite and inertinite this new application of stable isotopes at the maceral and compound levels have great potential to improve the interpretative precision over conventional whole coal or bulk techniques hydrocarbon gases including coal gases derived from coals and humic kerogens can be distinguished from type i ii sources based on their molecular rations i e c1 c2 c3 and by comparing their stable isotope compositions especially 13cch4 and dch4 the 13cc2h6 can also be valuable but ethane is generally present in small amount 1 vol and requires

a proposal for the kinematic modelling of w dipping subductions possible applications to the tyrrhenian apennines system in w dipping subduction zones there is a general eastward progression of the back arc basin accretionary wedge foredeep complex with the forward progression early stages of the complex are revealed by slices of upper crust and sedimentary cover abandoned to the west left floating above a new section of mantle a major shear zone should form at the new moho separating upper crust slices of earlier accretionary stages and the eastward flowing mantle the mantle wedging at the top of the subduction plane could be responsible for the uplift of the central parts of the belt the retreating of the subduction hinge is interpreted as due to the push generated by the eastward mantle flow detected in the hot spot reference frame the foredeep depth is mainly a function of the radius of curvature of the subduction hinge the frontal wedge is constructed from the stacking of the upper layers of the subducting plate and the syntectonic clastics that fill the foredeep which are progressively involved in thrusting and later by extension in order to preserve volume balance the lithosphere of the eastern plate before subduction has to be the same size as that which has been subducted due to the longer length of the arc with respect to the original length of the linear margin between the two converging plates laterally stretched subducted lithosphere is predicted at depth w dipping subductions usually have a short life probably due to their inherent capability to produce new lateral heterogeneities of the lithosphere the thin back arc which are a key factor in controlling and generating new subductions both e and w dipping this model is applied to the apennines tyrrhenian sea system

geochemical evidence for and characterization of co2 rich gas sources in the epicentral area of the abruzzo 2009 earthquakes abstract we describe the results of a detailed hydrogeochemical campaign on the groundwater circulating in two regional aquifers located in the area of the abruzzo 2009 earthquakes the influx of deeply derived co2 rich gases into the two aquifers is highlighted by the 13c isotopic composition of dissolved carbon species the source of the gas is roughly localised beneath the epicentral area of the earthquakes where the presence of sources of fluids under high pressure is suggested by seismological investigations the carbon isotopic mass balance of the aquifers indicates that the amount of the deep co2 dissolved and transported by the groundwaters is 530 t day the chemical and isotopic composition of the gas entering the aquifers named abruzzo gas has been derived by comparing the data measured in the springs with the results of a gas water rock reaction model that simulates the evolution of the chemical and isotopic composition of groundwater affected by the input of a deeply derived co2 rich gas phase the composition of abruzzo gas is compared to that of 40 large gas emissions located in central italy the gas becomes progressively richer in radiogenic elements 4he and 40ar and in n2 from the volcanic complexes in the west to the apennines in the east the abruzzo gas in agreement with its location well matches the composition of the gases emitted in the pre apennine region these geochemical features consistent with the structural setting of the region indicate increasing residence times of the gas in the crust moving from west to east in particular we suggest that the strong increase in radiogenic crustal gases reflects the occurrence of deep traps where the gas is stored at high pressures for a long time and that such high pressure gas pockets play a major role in the generation of apennine earthquakes

a newly emerged august 2013 artificially triggered fumarole near the fiumicino airport rome italy abstract early in the morning of 24 august 2013 following by hours the drilling of a shallow borehole in the same spot a new fumarole producing emissions of co2 rich gas water and mud suddenly appeared at a crossroad along the fenced area of the fiumicino international airport of rome italy similar episodes have been scientifically documented or simply reported in recent and past years to understand why gases are easily entrapped in the shallow subsurface of the fiumicino area we used five borehole cores drilled by us analyzed the stratigraphy of these and other nearby cores acquired a 2d seismic refraction tomogram and performed chemical and isotopic analyses of water samples collected from aquifers intercepted by two drilled boreholes our boreholes were realized with proper anti gas measures as while drilling we recorded the presence of pressurized gases at a specific permeable gravel level results show that in the study area gases become mainly entrapped in a mid pleistocene gravel horizon at about 40 50 m depth this horizon contains a confined aquifer that stores the endogenous upwelling gases the gravel is interposed between two silty clayey units the lower unit very hard and overconsolidated is affected by fractures that allow ascending gases to bypass the otherwise impermeable shale permeate the gravel and dissolve into the aquifer in contrast the upper unit is impermeable to fluids and seals the gas pressurized aquifer which therefore constitutes a source of hazard during human activities such as well drilling quarrying and various building related excavations as the stratigraphy of the fiumicino area is very common in large portions of the densely populated roman area and as the adjacent volcanic districts are hydrothermally active we conclude that phenomena similar to that observed at fiumicino could again occur both at fiumicino and elsewhere in the surrounding region as a prompt confirmation of our conclusion we signal that while writing this paper new artificially triggered degassing phenomena occurred off fiumicino in connection with the construction of the new harbor

role of the brittle ductile transition on fault activation abstract we model a fault cross cutting the brittle upper crust and the ductile lower crust in the brittle layer the fault is assumed to have stick slip behaviour whereas the lower ductile crust is inferred to deform in a steady state shear therefore the brittle ductile transition bdt separates two layers with different strain rates and structural styles this contrasting behaviour determines a stress gradient at the bdt that is eventually dissipated during the earthquake during the interseismic period along a normal fault it should form a dilated hinge at and above the bdt conversely an over compressed volume should rather develop above a thrust plane at the bdt on a normal fault the earthquake is associated with the coseismic closure of the dilated fractures generated in the stretched hangingwall during the interseismic period in addition to the shear stress overcoming the friction of the fault the brittle fault moves when the weight of the hangingwall exceeds the strength of the dilated band above the bdt on a thrust fault the seismic event is instead associated with the sudden dilation of the previously over compressed volume in the hangingwall above the bdt a mechanism requiring much more energy because it acts against gravity in both cases the deeper the bdt the larger the involved volume and the bigger the related magnitude we tested two scenarios with two examples from l aquila 2009 italy and chi chi 1999 taiwan events gps data energy dissipation and strain rate analysis support these contrasting evolutions our model also predicts consistently with data that the interseismic strain rate is lower along the fault segment more prone to seismic activation

the determination of deep temperatures by means of the co co2 h2 h2o geothermometer an example using fumaroles in the campi flegrei italy chromatographic analyses of fumarolic gases collected in sampling bottles containing an alkaline solution have been carried out using a thermal conductivity detector and a flame ionization detector after catalytic conversion of co and ch4 the latter method enables the concentration of carbon monoxide to be measured with sufficient accuracy for use in a co co2 h2 h2o geothermometer application of this geothermometer to fumaroles in the crater of solfatara in the campi flegrei italy indicates that they are fed from a steam reservoir at 250 15 c and at 10 36 2atm of oxygen on the other hand the ch4 co2 h2 h2o geothermobarometer seems to re equilibrate at superficial temperatures and cannot be used for infering thermodynamic conditions at depth regular sampling of these fumaroles together with a geothermometric interpretation of the gas analyses provides a means of monitoring with comparative accuracy the chemical and thermal evolution of the hydrothermal reservoir below the solfatara crater such monitoring would probably detect an increase in temperature at depth and the injection of magmatic gas into the reservoir

the history of the monti sabatini and alban hills volcanoes groundwork for assessing volcanic tectonic hazards for rome abstract the volcanic rocks of rome provide chronostratigraphic constraint that is of use to geologists archaeologists and paleontologists identifying the areal distribution of these rocks their mode of emplacement and a detailed chronology of the eruptive events also is crucial for assessing local natural hazards in a volcanic tectonic context and for recognizing whether the volcanoes may erupt again in the future we have identified and dated many of the volumetrically significant eruptive units from the monti sabatini and alban hills colli albani and propose a formalized volcanic stratigraphy for rome it is probable that seismic events triggered some eruptions as several ignimbrites from the two volcanoes have statistically indistinguishable ages following a 200 kyr period of dormancy that was coincident with a pulse of regional uplift the alban hills appears to have begun recently circa 45 ka a new eruptive cycle therefore accurate assessment of volcanic tectonic hazards and estimation of possible future volcanic activity is necessary for the safety of the five million people living near these volcanoes

the first ml scale for north of vietnam abstract the first local magnitude scale ml for northern vietnam has been derived using a portable broadband seismic network in northern vietnam as part of the cooperation between the vietnam institute of geophysics and the institute of earth sciences at academia sinica taiwan the composite horizontal peak amplitude data used in this study is comprised a total of 202 amplitude records from 14 broadband stations which measure 36 shallow earthquakes with focal depths less than 36 km occurred in and around north western vietnam during 01 2006 10 2007 the new distance correction function obtained in this study is log a 0 1 74 log r 0 00048 r 0 522 where a0 and r are the empirically determined distance correction and hypocentral distance respectively this distance correction relation for northern vietnam is quite similar to one for southern california implying relative efficient attenuation with distances the correlation between the new ml and duration magnitudes md which is still being used for making the official earthquake bulletin in vietnam is expressed as m l 0 955 m d 0 17

gas blowout from shallow boreholes at fiumicino rome induced hazard and evidence of deep co2 degassing on the tyrrhenian margin of central italy abstract a borehole drilled at fiumicino rome down to only 27 m depth in a zone where no gas emission at the surface was known caused a gas blowout from a pressurized gas pocket confined beneath a clay cover gas slowly diffused from the borehole within superficial permeable sand seven persons living in three ground floor flats of a near building had to be hospitalized due to co2 exposure all the houses in the proximity were evacuated at the request of the fire brigade two additional boreholes were drilled nearby hoping that this could rapidly exhaust the gas stored underground to the contrary the soil gas flux near houses increased and indoor co2 air concentration rapidly rose to lethal values 15 to 30 vol as a remediation we suggested to restore the continuity of the impervious gas cover by squeezing quick setting cement into the formation through new boreholes to be drilled near the existing ones although the first cement squeeze reduced drastically the co2 soil flux and indoor concentration six additional squeezes had to be carried out in order to lower the gas emission below the gas hazard threshold the gas was mostly made of co2 98 vol with minor n2 and ch4 its chemical and isotopic composition 13cco2 1 55 3he 4he 0 314 ra is similar to that of the gas manifestations of mts sabatini and alban hills volcanic areas though being somewhat contaminated by crustal and shallow organic volatiles these gases likely have a component originated in the mantle that beneath the volcanic roman comagmatic province is probably deeply contaminated with crustal material the fiumicino gas blowout indicates that the area of central italy characterized by strong co2 degassing extends westerly to include the tyrrhenian coast

new gps constraints on the kinematics of the apennines subduction abstract we present the velocity field of the italian area derived from continuous gps observations from 2003 to 2007 the gps sites were installed by different institutions and for different purposes they cover the whole country with a mean inter site distance of about 60 km and provide a valuable source of data to map the present day kinematics of the region the absolute itrf2005 rotation poles and rates of eurasia africa and adriatic plates are estimated to study the kinematics along their boundaries in the apennines belt the corsica sardinia block coherently moving as the eurasia plate is used as reference of the upper plate for the apennines subduction zone we apply a simple kinematic model to estimate the rates and spatial pattern of the subduction along the apennines we identify at least four different independently moving lower plates i e the adriatic diverging and internally segmented ionian sicily and africa converging plates with different subduction rates the conservative estimates of the subduction rate are 5 mm yr in the calabrian arc 1 5 mm yr in sicily and 0 9 mm yr in the northern apennines this variegate mixture of behaviors seems to reflect the variable lithospheric thickness and composition of the lower plates inherited from the mesozoic rifting an unexpected along strike contraction is observed along the western side of the central northern apennines velocities are estimated both relative to eurasia and relative to the deep and shallow hotspot reference frames hsrf the hotspot representation seems more coherent with the geophysical and geological constraints along the subduction system in which the adriatic and ionian plates move sw ward and their deeper slab portions provide an obstacle to the opposite relative mantle flow all these patterns better reconcile if the subduction process is conceived as a passive feature controlled by the far field plate velocities and the relative eastward mantle flow acting on a disrupted slab

deformation of the 125 ka marine terrace in italy tectonic implications in peninsular italy marine terraces and shorelines created during oxygenisotope substage 5e known historically as the tyrrhenian highstand provide a reliable and homogeneous datum of vertical motions during the past 125 000 years published accounts of 121 locations on the tyrrhenian inner edge were reinterpreted and used to calculate both local and regional uplift rates the data show arching of southern italy between the tyrrhenian and the adriatic coasts and of the calabrian arc between the sangineto and the longi taormina tectonic lineaments at rates of up to 1 2 mm yr for the past 125 ka they also suggest that the present configuration of the southern apennines is the product of post early pleistocene regional uplift superimposed on tortonian to early pleistocene thrusting uplift patterns are characterised by different wavelength in different geodynamic settings suggesting a close link with the depth of the causative tectonic sources

mantle derived co2 migration along active faults within an extensional basin margin fiumicino rome italy abstract fluid migration along faults can be highly complex and spatially variable with the potential for channeled flow accumulation in capped porous units fault cross flow lateral migration along strike or complete sealing extensional basin margins can be important for such migration given the associated crustal thinning and decompression that takes place combined with potential geothermal or mantle gas sources one such example is near the urban area of rome situated along the active extensional continental margin of the tyrrhenian back arc basin and surrounded by middle upper pleistocene k rich and arc related volcanoes recent research activities in the area around fiumicino a town 25 km to the west of rome has highlighted the close spatial link between degassing co 2 and the faults that provide the necessary vertical migration pathways in particular detailed soil gas and gas flux surveys have highlighted the release at surface of large volumes of asthenospheric mantle co 2 in correspondence with normal faults observed in a new seismic reflection profile acquired along the tiber river detailed reconstruction of the pleistocene holocene stratigraphy of the area dates fault activity from 20 000 to 9000 years bp it is proposed that the gas migrates preferentially along the cataclastic tectonic breccias of the faults until it encounters recent unconsolidated sediments porous units within this shallow stratigraphy act as temporary secondary traps for the leaking gas with local gas release at the ground surface occurring where the sealing of the overlying aquitards has been compromised degassing and active faults confirm the extensional tectonics affecting the area and the geodynamic scenario of a mantle wedge beneath the western apennines associated with ongoing w directed subduction moreover degassing highlights the potential geochemical and seismic risks for the highly populated urban areas near rome

the transition from wave dominated estuary to wave dominated delta the late quaternary stratigraphic architecture of tiber river deltaic succession italy abstract this paper presents a detailed description of the stratigraphic architecture of the late pleistocene holocene tiber delta succession in order to document the passage from wave dominated estuary to wave dominated delta in the broader context of late quaternary sea level fluctuations this succession constitutes a sequence stratigraphic unit known as tiber depositional sequence tds which was deposited during the last glacial interglacial cycle last 120 ka our study is based on the examination of an enormous amount of data derived from the stratigraphy of about 300 wells petrographical and paleontological data foraminifera ostracoda pollen and plant macrofossils 14 c dating and from the integration of geomorphological and geoarcheological data recently a 100 m deep core pesce luna well was studied through a multidisciplinary approach and a detailed description of sedimentary facies foraminifer and ostracod assemblages pollen and 14 c dating is presented in this paper the new data allowed to produce three new correlation panels and to describe in more detail with respect to previous interpretations the stratigraphic depositional architecture of the tds which internally shows the preservation of sediment deposited during the early and late lowstand the transgressive and the highstand systems tracts alluvial and coastal depositional systems characterize the early lowstand phase of the tds which developed during the eustatic sea level fall between about 120 and 30 26 yr bp during the late lowstand phase which is characterized by stillstand and slow eustatic sea level rise a prograding delta and an aggrading incised valley fluvial fill developed the tiber incised valley was transformed into a wave dominated estuary during the transgressive phase tst whereas a coastal shelf sedimentation took place during the subsequent highstand phase hst this study confirms the lithofacies distribution resulting from transgression and infilling of the wave dominated estuaries but also shows how the transition to a wave dominated delta prograding at the time of sea level highstand occurred changes in sediment input climatic variations and more recently human activities played a major role in the development of the tiber delta during the last 20 000 yr bp in the last 3000 years a relationship between progradational phases of the delta and flood events of the tiber river has been highlighted suggesting also the formation and merging of barrier spits to the mainland

flux measurements of nonvolcanic co2 emission from some vents in central italy in central italy nonvolcanic co2 is discharged from many areas of focused degassing vents and associated strong diffuse emission and from high pco2 groundwater we estimate that there are at least 100 co2 vents in central italy many of which have a history of lethality to animals and humans the gas vents are extremely efficient pathways for transporting large amounts of deeply derived co2 from gas reservoirs to the surface as co2 fluxes from these vents were heretofore unmeasured several complementary methods were developed to measure the co2 flux from seven of these vents which cumulatively discharge 3 1 109 mol yr 1 co2 472 t d 1 considering all of the vents in central italy the total co2 flux from vents alone may be similar to the co2 emission from the taupo volcanic zone in new zealand 1010 mol yr 1 1200 t d 1 and other areas of high heat flow summing the co2 discharged from vents areas of diffuse co2 degassing and degassing of high pco2 groundwater we provisionally estimate that the total nonvolcanic co2 flux to the atmosphere in central italy may be 1011 mol yr 1 12 000 t d 1

recurrence of volcanic activity along the roman comagmatic province tyrrhenian margin of italy and its tectonic significance 1 the roman comagmatic province rcp developed along the nw se striking extensional tyrrhenian margin of italy since middle pleistocene and includes ultrapotassic small eruptive centers and large volcanic districts by means of a review and statistical analysis of a large data set of radiometric ages we demonstrate that in the rcp major eruptive cycles occurred at different volcanic districts almost simultaneously and with an almost constant recurrence time our analysis started with the alban hills volcanic district where a detailed 40ar 39ar chronology of the eruptive cycles has been recently achieved and then extended to include a database of 264 radiometric ages of the rcp volcanics published since 1980 statistical treatment of the data set shows a marked non poissonian behavior of volcanic activity through the whole magmatic province with climax of each major eruptive cycle occurring simultaneously at the different districts approximately every 48 kyr the concomitant eruption of many volcanic districts spreading over a 250 km long chain implies a control mechanism acting at a regional scale after discussing the possible relationship between tectonics sea level changes and volcanic activity we hypothesize that constant rates of slab retreat during middle pleistocene could have been a key factor controlling the rate of magma upwelling and the major cycles of recharge of the magma chambers as a working hypothesis we propose that the duration of the cycles may be related to 1 progressive weakening of the crust due to magma underplating or 2 cyclic injection of convective plumes into the mantle wedge

the deep structure of the eolian arc filicudi panarea vulcano sector in light of gravity magnetic and volcanological data abstract the magnetic and gravimetric methods of investigation have been applied to the central sector of the eolian arc combined with geovolcanological data for the purpose of defining the structural framework in which the volcanism developed the processing of the magnetic and gravimetric data involved 3d modeling of the volcanic bodies and the application of a depth separation filter in order to subtract from the measured field the effect caused by the subaerial and submarine volcanic edifices and by all surface inhomogeneities magnetic and gravimetric 2 5d modeling on selected profiles has also been done in a joint interpretation of the magnetic and gravimetric data constrained by volcanological knowledge the interpretation of the final maps and profiles has demonstrated the existence of extensional tectonics resulting in the development of horst and graben volcanism occurs in the graben areas in particular the salina lipari vulcano magmatic axis has developed in a very deep articulated graben of lithospheric importance and completely filled by volcanic deposits and intrusive bodies the origin of this structure and of the associated igneous activity is suggested to be related to trans tensional tectonics along a plio pleistocene regional strike slip fault system

volcaniclastic sedimentation in coastal environments the interplay between volcanism and quaternary sea level changes central italy abstract the geometry and facies characteristics of volcaniclastic and marine sequences have been investigated in relation to synvolcanic and intervolcanic episodes and to quaternary sea level changes in an area of relative recent tectonic stability the studied area is a coastal sector of northern latium where the products of three different quaternary volcanoes reached the coast during a period ranging between 0 45 and 0 1 ma the onshore sedimentation area includes lowland situated between pre existing structural and volcanic constructional highlands with no clearly defined structural basin margins called the tuscania basin detailed stratigraphic field work has allowed analysis of lateral facies relationships between marine and volcaniclastic sediments using volcanic horizons mainly geochronologically dated pyroclastic flow deposits and fallout deposits as stratigraphical markers the successions have been organized in unconformity bounded stratigraphic units and the synthems are bounded by primary order unconformities recognized throughout the continental area down to the coast the stratigraphies have been compared with the oxygen isotope scale of pisias et al marine geol 59 1994 217 the analysis of the components and of the lithofacies of each synthem has proven to be a powerful tool to correlate marine and volcano sedimentary successions in areas affected by the interaction between volcanic activity and sea level changes