curie isotherm depth from aeromagnetic data constraining shallow heat source depths in the central aeolian ridge southern tyrrhenian sea italy the salina lipari and vulcano volcanic ridge and the surrounding sea sectors aeolian archipelago southern tyrrhenian sea italy are characterized by vents responsible for a recent 40 ka 1889 1890 ad effusive and explosive subareal activity and repeated 56 to 7 ka in age submarine explosive eruptions from source areas located between lipari and vulcano a spectral depth estimation of the magnetic bottom using a fractal method on aeromagnetic data from vulcano lipari and salina volcanic ridge allows us to constrain the curie isotherm depth the elevated portion of the isotherm is between 2 and 3 km below salina and vulcano and about 1 km below lipari the curie depth results in the context of other geological and geophysical evidence suggest that the rise of the curie isotherm is mainly due to the occurrence of shallow heat sources such as magma ponds and associated hydrothermal systems the short wavelength magnetic anomaly field reflects magnetic contrasts from highly magnetized volcanic bodies low magnetization sediments and hydrothermally altered rocks borehole temperature data verify the curie temperature derived from the magnetic methods on the island of vulcano we conclude that the whole vulcano lipari and salina volcanic ridge is active and should be monitored

on the origin and post depositional history of widespread massive ash deposits the case of intermediate brown tuffs ibt of lipari aeolian islands italy abstract we analysed a widespread massive ash unit outcropping on the island of lipari which belongs to the intermediate brown tuffs ibt succession of the aeolian islands italy the use of a multidisciplinary approach that integrates textural petrological and pedological methods allows us to discriminate between syn eruptive and post depositional features the deposits are dominated by uncrystallised blocky glass fragments of homogeneous shoshonitic composition confirming a provenance from hydromagmatic eruptions on the island of vulcano many glass fragments are surrounded by a coating separated by a thin void of syn eruptive origin due to alteration by aggressive acid gases in the eruptive cloud the lack of this coating in the northern part of lipari can be explained as a progressive dispersion of the gases far from the vent and or to post depositional processes the degree of soil development significantly increases from south soil profiles p1 and p2 at valle muria to north p3 and p4 at madoro and chiesa vecchia sites respectively as a response to a decrease in slope steepness which has brought about a progressive deepening of the pedogenetic front on gentler landforms and conversely its rejuvenation on steep slopes the relatively poor to moderate degree of pedogenic evolution of the studied ibt unit is consistent with its emplacement during part of the last glacial period

impact of early dolomitization on multi scale petrophysical heterogeneities and fracture intensity of low porosity platform carbonates albian cenomanian southern apennines italy abstract petrographic petrophysical and fracture analyses were carried out on middle cretaceous platform carbonates of the southern apennines italy that represent an outcrop analogue of the val d agri and tempa rossa reservoirs of the basilicata region the studied outcrops which are made of interlayered limestones and dolomites of inner platform environment were selected to study the impact of dolomitization on reservoir properties and the control of dolomite texture on fracture development two types of dolomites both formed during very early diagenesis were found interlayered at a metre scale with micrite rich limestones mainly mudstones and wackestones dolomite a is fine to medium crystalline and makes non planar mosaics dolomite b is coarse crystalline and makes planar s and planar e mosaics the intercrystalline space of the planar e subtype of dolomite b is either open or filled by un replaced micrite or by late calcite or saddle dolomite cement dolomite a and dolomite b have similar average porosities of 3 7 and 3 1 respectively which are significantly higher than the average porosity of limestones 1 4 their poro perm relationships are similar with the notable exception of planar e type b dolomites which generally display higher permeability values the intensity of top bounded fractures is distinctly lower in coarse crystalline dolomites than in fine crystalline dolomites and limestones both at the macro and the micro scale on the other hand neither lithology i e limestone vs dolomite nor dolomite crystal size control the intensity of perfect bed bounded fractures which is strictly controlled by the fracture layer thickness our results provide information that could be used as guidance for the characterization and modelling of fractured carbonate reservoirs made of interlayered limestones and dolomites

dolomites and dolomites in mesozoic platform carbonates of the southern apennines geometric distribution petrography and geochemistry abstract a multidisciplinary study of the dolomitized bodies present among the late triassic to late cretaceous carbonate deposits of the monti lattari belt southern apennines of italy compares the different dolomitization styles present within this succession of these mesozoic platform carbonates and furnishes an overview of their formative genetic models the revealing traces of the diverse modes of diagenesis in this region include both surface and subsurface mechanisms utilizing a geometric reconstruction of the dolomitized bodies an integrated facies and petrographic analysis of the components and a geochemical characterization of the sediments including detailed mineralogy and associated stable isotope values the data presented demonstrate that some intervals are characterized by surface related dolomitization processes middle late triassic and cretaceous while others latest triassic to lower middle jurassic and are mainly dominated by later large scale subsurface dolomitization processes all of the middle late triassic norian successions are pervasively dolomitized exhibit fabric preserving textures and have a distinctly heavy stable isotope signature their origin has been related to diagenesis due to particular climatic and palaeoceanographic conditions leading to the formation of extended blankets of shallow warm saline seawater this setting was terminated by climatic and palaeoceanographic changes during the latest triassic which dramatically reduced the significance of surface related dolomitization on a regional scale the overlying latest triassic rhaetian outcrops consist of a widespread coarse fabric destructive massive dolomite with a lighter isotopic signature these dolomites seem genetically related to the ones of the lower middle jurassic which share the same geometrical petrographic and geochemical characteristics caused by large scale fluid circulation this diagenetic pattern apparently started in the early jurassic during burial driven by thermal convection due to the different temperatures between the oceanic waters and the warmer carbonate platform the middle upper jurassic units feature local episodes of early dolomitization that partially replaced the muddy carbonate facies due to tidal pumping and reflux mechanisms dolomitization is not a pervasive feature during this phase of deposition in the cretaceous portion of the succession dolomites have a totally different and distinct character and are generally related to bedding and show variability in textures and mg ca ratios local association with evaporites geometry of dolomitized bodies and stable isotope geochemistry suggest processes comprising evaporative pumping and reflux all related to the surface environment this evidence points to a renewal of a climatic context more favorable for early dolomitization thus this study permits recognition of the presence of three quite different dolomitization styles within the carbonate platform succession of the southern apennines fold thrust belt one ascribed to the norian one to the rhaetian lower jurassic and one to the cretaceous

wet surge deposits at la fossa di vulcano depositional and eruptive mechanisms abstract wet surge deposits of different volcanic cycles of the recent fossa activity at vulcano have been measured on a bed by bed basis with data recorded to millimeter detail the wet surge layers are varicoloured with variable thickness with the most recurrent thickness being about 1 cm the beds consist of fine ash without internal structures textural features include a accretionary lapilli of maximum size of 0 5 cm dispersed thoroughout the layer or forming continuous layers of submillimeter size b vesiculated layers which represent 10 to 65 of the total deposit vesicles have different shapes and smooth walls varying in volume from 1 to 15 20 c soft sediment types of bedding deformation such as gravity flowage ripples load cast and slumps the slope angle has not influenced either the concentration and size of the accretionary lapilli or the shape size and distribution of vesicles only the thickness of the layers decreases with distance from the vent sem investigations show features indicating the hydromagmatic origin of the deposits and stressing the role of the fluid phase noteworthy is the presence of vesiculated grains produced by magmatic exsolution which show chilling effects on the internal walls of the broken bubbles grain size analyses reveal that the layers are not graded and most of the samples have a median size finer than 50 m the grain size distributions are frequently polymodal suggesting several closely timed explosions as all the beds exhibit the same textures grain size and particle morphology a single mechanism can explain their deposition the depositional unit formed at the base of the cloud through the lateral expansion on the ground of a sticky muddy medium consisting of ash and fluid in general each layer lost its plasticity before the deposition of the next layer the deposition occurred in a nearly continuous sequence without periods of rest long enough to permit erosional discontinuity the eruptions are hydromagmatic and occur where magma at least partially fragmented comes into effective contact with subsurface water the process follows a model suggested by wohletz 1983b 1986 developing in more than one fragmentation event in the turbulent surge cloud both severe hydration and alteration of glassy grains and the formation of accretionary lapilli occur

magnetic fabric and remanent magnetization of pyroclastic surge deposits from vulcano aeolian islands italy abstract tufi di grotte dei rossi inferiori are unwelded fine grained pyroclastic deposits of hydromagmatic origin emplaced between 21 and 11 8 6 ka at vulcano aeolian islands italy by deposition through surges spreading laterally from inside the la fossa caldera in this study the deposit s magnetic properties were investigated and interpreted in terms of eruptive and emplacement dynamics rock magnetism data were supplemented by grain size and textural characteristic analyses as well as scanning electron microscope sem investigations curie point measurements isothermal remanent magnetization and microprobe analyses showed that magnetization is carried by low ti titanomagnetite the size of the grains ranges from about 20 to 300 micrometres their shape from equidimensional to highly elongated the magnetic fabric is typical of fine grained pyroclastics foliation is well developed and in most sites lineation is directed towards the source area of the la fossa caldera the remanent magnetization consists of two components whose blocking temperature spectra partially overlap the direction of the low temperature component is close to that of the axial dipole and consistent with the palaeosecular variation curve for the aeolian islands the high temperature component is systematically shallowed and close to the direction of the magnetic lineation the overall results suggest that the high temperature component was acquired before and the low temperature component after the actual deposition of grains immediately after eruption the grains cooled and moved as free particles in the turbulent cloud during the expansion of the surge flows those particles with high blocking temperatures acquired a thermal remanence they were then deposited and shear at the very base of the flow oriented them and imprinted the rock s fabric and high temperature magnetization component volcanological and magnetic data suggest turbulent transportation and traction deposition of particles finally the rock cooled down and acquired the low temperature magnetization according to this model remanence acquisition in pyroclastic rocks deposited at temperatures lower than the curie point of their ferromagnetic grains depends on both the fluid dynamic forces and cooling history and must therefore be more complex than in pyroclastics deposited at higher temperatures such as welded ignimbrites

volcanic geomorphology and tectonics of the aeolian archipelago southern italy based on integrated dem data the geomorphological and morphometric analysis of the sea floor topography surrounding the aeolian islands south tyrrhenian sea italy provides insights into the relationships between the volcanological evolution of the islands and their tectonic features we constructed geomorphological maps of the submarine portions of the seven large edifices constituting the islands on the basis of a dem with a 5 m resolution step these maps include constructional and destructional landforms such as submarine volcanic vents located west of lipari and north of alicudi and hummocky surfaces recognised north of lipari and salina the latter landforms together with the occurrence of large scars affecting the main edifices on land suggest that sector collapses affected some islands geomorphological data indicate that the location of subaerial and submarine vents is strongly controlled by local tectonic structures striking wnw ese alicudi filicudi sector nnw sse salina lipari vulcano sector and ne sw panarea stromboli sector the islands can be divided into two groups on the basis of some morphometric parameters a first group with a pancake like shape dp d abrasion platform diameter basal diameter higher than 0 40 and h d total height basal diameter lower than 0 13 and a second group with a conical shape characterised by dp d lower than 0 34 and h d higher than 0 14 these ratios and other morphometric parameters reflect the different volcanological and structural evolution of the aeolian islands the pancake like shaped complexes have been created in addition to their submarine stage by extrusive and highly explosive activity whereas the cone shaped edifices have been characterised by effusive or moderate explosive activity

an approach for investigating the depositional mechanism of fine grained surge deposits the example of the dry surge deposits at la fossa di vulcano abstract fine grained thinly laminated surge deposits have been studied in order to understand the physical properties of pyroelastic deposits with a large tractional component and to investigate on type and number of laminae deposited from a single surge cloud the examples are taken from the dry surge deposits of the fossa cone vulcano island where there is a good knowledge of the stratigraphy good exposures of the deposits and an absence of secondary structures analysis of texture and structure allows all the bed facies to be grouped into 4 principal types type 1 is made up of a loose coarse and medium ash in dark grey gently undulating laminae sometimes with cross laminae that alternate with pale grey laminae type 2 consists of grey ash in beds characterized by limited lateral continuity normal grading and a flat non erosive base type 3 is made up of submillimeter ochreous laminae plane parallel or gently undulating type 4 consists of massive beds of fine ash ochre in colour characterized by notably lateral continuity and constant thickness determination of the nature morphology and size of the grains shows that a close relationship exists between the relative abundance and shape of components and the textural and grain size characteristics of the bed facies the results suggest that a single surge event could deposit either a set of plane parallel to transverse laminae as type 1 and type 3 or a pair of laminated beds as type 2 and 4 depending on the flow velocity the effective grain size and density of the solid phase and the particle concentration in the eruptive cloud the almost complete lack of lithics suggests that magma water interaction occurred in sub surface conditions across a fragmented magma surface the efficiency of the interaction was primarily controlled by the ascent velocity of the magma in the conduit and its physical properties

rock magnetism and compositional investigation of brown tuffs deposits at lipari and vulcano aeolian islands italy abstract a rock magnetic investigation was carried out on the nonwelded ash deposits of the brown tuffs aeolian islands southern tyrrhenian sea to improve the stratigraphic correlation between the deposits cropping out on lipari and vulcano islands and locate their source area the study was supplemented by petrographical and geochemical analyses on selected strata with the intent to compare the brown tuffs to other rocks emplaced at vulcano in the same time span more than 30 levels were sampled in the intermediate 56 4 ka ibt 21 22 ka and upper 21 22 ka ubt parts of the brown tuffs sequences on the two islands their characteristic remanent magnetization chrm directions were derived from stepwise thermal demagnetization and the magnetic fabric from measurements of the anisotropy of magnetic susceptibility the levels with indistinguishable chrm directions were regarded as coeval and to form an individual stratigraphic unit the units were referred to the brown tuffs sequence of lucchi et al 2008 on the grounds of their emplacement age provided by comparison of their mean paleomagnetic direction with the paleosecular variation curves of the southern tyrrhenian region as well as the field constraints the closer correlation between the sequences of lipari and vulcano contributes to a better understanding of the volcanic activity that produced the brown tuffs and shows that most of the ibt and the oldest ubt levels were emplaced in a short time span between 24 and 20 17 ka the magnetic fabric is typically well developed but at most sites the magnetic foliation is very close to horizontal and no imbrication is defined the source area of the brown tuffs parent pyroclastic flows as constrained from the intersection of the magnetic lineations falls in the northeastern part of la fossa caldera structure although limited to major elements compositional data provide further indication about the parent plumbing system and its behaviour magma batch es involved in the ibt eruptions have homogeneous features and underwent frequent refilling and tapping processes conversely those involved in the early ubt eruptions are compositionally more variable this suggests more complex evolution and plumbing system activity the ubt eruptions represent either residual mafic magmas from the previous eruptions or the arrival of new fresh shoshonitic magma in the system

a permeability model for naturally fractured carbonate reservoirs abstract based on a detailed structural study performed on a reservoir surface analogue a fracture permeability model for carbonate reservoirs is proposed this involves four hierarchical systems each one assumed to convey fluids exclusively to that of immediately higher order new basic equations are then provided simulating hydrodynamic reservoir response the large scale first order structures consist of faults to which high permeability structures damage zones are associated at the meter scale stratabound joint systems together with bedding joints bounding the mechanical layers form a connected network transporting fluids to the fault system at a lower scale down to crystal size non stratabound joints constitute a pervasive and capillary fracture network which conveys fluids within the rock mass the non fractured host rock constitutes the lower permeability system at the crystal scale as no published works include an effective integration of detailed structural and numerical models the present study aims at covering a significant gap in the literature also providing appropriate theoretical basis for subsequent studies on fracture network modeling and reservoir simulation besides its application in the field of reservoir development and management the illustrated model may also be useful in environmental studies involving ground fluids such as e g in the field of special toxic nuclear waste management

palaeomagnetism of holocene and late pleistocene sediments from lago di mezzano and lago grande di monticchio italy initial results abstract palaeomagnetic records of the geomagnetic secular variation reaching back to 31 and 102 kyr cal bp respectively were obtained from two sediment cores from lago di mezzano central italy and two cores from lago grande di monticchio southern italy intra lake correlation was based on continuous high resolution susceptibility measurements and discrete dry density samples characteristic remanent magnetization chrm of all 4800 samples was determined by analysis of the results of progressive alternating field af demagnetization intra lake comparison of the resulting chrm directions confirms that the inclination and declination records reflect the palaeosecular variation of the local geomagnetic field composite curves of geomagnetic palaeosecular variations psv were created for each lake in order to compare the reconstructed psv records with those from lac du bouchet massif central france and lac de joux switzerland the good agreement in the general patterns of the inclination and declination records of all lakes mentioned above confirms the reconstructed psv records of the italian lakes investigated

low angle normal faulting and focused exhumation associated with late pliocene change in tectonic style in the southern apennines italy in the southern apennines low temperature thermochronometry data indicate that exhumation of previous tectonically buried sedimentary units started at around 10 ma and took place mostly during the last 6 ma relatively high exhumation rates are obtained from apatite fission track aft and u th he ahe analysis pointing to a substantial contribution of tectonic processes to rock exhumation besides erosion exhumation rates derived from new apatite u th he data ahe for the last 3 ma are generally lower than rates determined by aft data and almost in line with erosion rates inferred from cosmogenic nuclides and sediment yield thus suggesting that tectonic exhumation was dominant during the older exhumation stages of this region however younger cooling ages in the monte alpi area from both aft and ahe analyses point out focused exhumation during the last 3 ma structural and morphotectonic analyses indicate that fast exhumation occurred specifically in this area where the apulian platform reservoir carbonates elsewhere buried beneath a several kilometer thick allochthonous cover are exposed at the surface as a result of a complex interplay between steep rooted reverse faulting and shallow low angle extension this deformation involved the development of foreland dipping low angle normal faults affecting the allochthonous cover units during the late stages of reverse fault related anticlinal growth in the underlying buried carbonates extension of the region triggered focused exhumation in the footwall of the extensional low angle faults which was followed by widespread crustal extension and associated development of high angle normal faults leading to surface uplift of monte alpi

frequent activity on vulcano italy spanning the last 80 ky new insights from the chemo stratigraphy of the brown tuffs abstract the brown tuffs bt are widespread reddish brown to grey ash rich pyroclastic deposits recognized in the stratigraphic sequences of the aeolian islands and capo millazzo peninsula sicily that span the last 80 ky they have very homogeneous lithological textural and sedimentological features which make it difficult to reliably correlate units on the islands to proximal units in the source areas here we carefully re interpret the stratigraphic profiles of the bt on vulcano and lipari where the deposits are thickest and present the most complete succession the investigation is based on a large dataset of major and minor element geochemistry of juvenile glass components for the majority of the recognized bt depositional units whilst also providing new radiocarbon ages the distinctive chemical groupings observed within the glass analyses both temporally and spatially allow us to fingerprint the three main stratigraphically defined macro units in which the bt succession can be sub divided using prominent tephra marker beds the ischia tephra monte epomeo green tuff 56 ky and monte guardia pyroclastics from lipari herein radiocarbon dated to 27 26 ky the lower 80 56 ky lbt intermediate 56 27 ky ibt and upper bt here dated at 24 6 ky ubt macro units display k series volcanic glasses ranging from basaltic trachy andesites through trachy andesites to more evolved trachytes all consistent with an origin on vulcano the ubt are clearly distinguished from the lower macro units by their higher sio2 trachy andesite to trachytic glasses which extend to noticeably lower tio2 cao and mgo contents these features make it possible to re define the geochemical evolutionary boundary between ibt and ubt as corresponding to the 24 ky spiaggia lunga scoria bed on vulcano which is stratigraphically higher and younger than the previous boundary marker monte guardia the glass compositions of the lbt ibt and ubt are used to 1 assess links to known proximal eruption units outcropping on vulcano 2 validate medial distal bt occurrences across the aeolian archipelago salina filicudi and panarea and on capo millazzo 3 confirm that the bt are responsible for distal volcanic ash layers preserved in central mediterranean marine sedimentary archives interestingly the glass compositions of the ubt are very similar to those of the punte nere unit the earliest pyroclastic products erupted from the currently active la fossa cone on vulcano indicating the corresponding magmatic system has likely erupted similar melts and products over the last 24 ky and thus extending its life cycle such information is crucial for evaluating the long term eruption scenarios underpinning hazard assessment of the la fossa caldera magmatic system

evolution of the fossa cone vulcano abstract in decreasing order of abundance the principal emplacement mechanisms for deposits of the fossa edifice of vulcano include dry surge wet surge pyroclastic fall lahar lava flow pyroclastic flow and epiclastic processes most samples from pyroclastic beds on fossa contain two grain size populations the coarser mode at 0 5 1 5 resulted from modified ballistic transport whereas the finer mode at 2 5 3 5 is related to surge transport reconstruction of the entire stratigraphy of the cone permits the beds to be grouped into five principal eruptive cycles all of which postdate the lower pilato ash of lipari dated at 11 000 to 8 500 y b p pte nere cycle palizzi cycle commenda cycle pietre cotte cycle and the modern cycle additional cycles may be present but exposures on the cone are insufficient for their adequate definition all cycles follow a similar stochastic pattern starting with surge eruptions and ending with effusion of lava from the crater rim the frequency of pyroclastic fall events increases with time throughout each cycle this progressive decrease in the efficiency of water melt interaction through the duration of each cycle may be due to a gradual rise of each new magma column coupled with an increase in magmatic volatiles tectonism and magma mixing both play a role in triggering eruptions on fossa the present crater lies at the intersection of two prominent tectonic trends a nnw fracture system parallels the main eruptive centers and an ene set aligns with the migration of minor vents the silicic lavas of fossa contain a mixture of two components xenocrysts of plagioclase augite and olivine surrounded by a dark glass are intimately dispersed into an evolved rhyolitic matrix

magnetic fabric flow directions and source area of the lower miocene peach springs tuff in arizona california and nevada we have used anisotropy of magnetic susceptibility ams to define the flow fabric and possible source area of the peach springs tuff a widespread rhyolitic ash flow tuff in the mojave desert and great basin of california arizona and nevada the tuff is an important stratigraphic marker from the colorado plateau to barstow california a distance of 350 km however the location of its source caldera is unknown dated at 18 5 ma by 40ar 39 ar the tuff erupted during the early stages of miocene extension along the lower colorado river the thicker accumulations 100 m occur at kingman arizona and in the piute mountains california on opposite sides of the colorado river extensional corridor our ams studies produced well defined magnetic lineations in 30 of 42 sites distributed throughout the tuff typical ratios of the principal ams axes are 1 01 for the magnetic lineation kmax kint and 1 02 for the foliation kint kmin the bulk magnetic susceptibility of the peach springs tuff averages 2 0 10 3 in the si unit system the subhorizontal lineations which presumably parallel the flow directions form a pattern radiating outward from the approximate center of the outcrop area magnetic foliations define an imbrication that generally dips away from the distal margins and toward the center of the outcrop of the tuff the lineation and imbrication indicate a source region near the southern tip of nevada defining the best intersection of the ams lineations required restoration of major extension strike slip faulting and associated tectonic rotation in the disrupted tuff the optimum intersection of magnetic lineations lies in the southern black mountains of arizona on the eastern side of the colorado river extensional corridor no caldera structures are known from that area but the area contains thick sections of the peach springs tuff above a silicic volcanic center the caldera may be buried under younger deposits in the mohave valley of arizona tertiary granite in the newberry mountains may represent a deeper level of the peach springs tuff vent that has been exhumed by detachment faulting

reply to comments to volcanic geomorphology and tectonics of the aeolian archipelago southern italy based on integrated dem data by favalli et al bull volcanol 68 157 170 2005 doi 10 1007 s00445 005 0429 3 by calanchi et al 2007 bull volcanol doi 10 1007 s00445 007 0134 5

a method for correcting geographically separated remanence directions for the purpose of archaeomagnetic dating summary spatial variations in the geomagnetic field must be taken into account if secular variation master curves and directional magnetic dates are to be optimized two methods for relocating remanence vectors have been proposed and in this paper their relative accuracies are compared using a numerical model based on the present day field a method which converts archaeomagnetic directions via a virtual geomagnetic pole is shown to be the more efficient transformation for an archaeomagnetic region the size of the british isles 900 km radius the maximum error in relocating vectors to a central location is predicted to be of the order of 1 2

paleomagnetic secular variation at vulcano aeolian islands during the last 135 kyr abstract paleosecular variation psv of the earth s magnetic field during the last 135 kyr has been investigated in lavas scoriae and pyroclastic rocks of vulcano aeolian islands about 1000 samples have been collected at 77 sites from 25 distinct volcanic units whose age is either known from published isotopical data or constrained on the grounds of statigraphical relationships magnetic mineralogy investigation shows that ti magnetite is the main ferromagnetic mineral at most sites secondary magnetization components are either absent or easily removed by stepwise thermal or alternating field demagnetization the mean site direction of the characteristic remanent magnetization is usually well defined since the semi angle of confidence is greater than 5 at only four sites the mean paleomagnetic direction over the last 135 kyr d 9 4 i 53 2 95 3 5 differs from the geocentric axial dipole gad at vulcano d 0 i 57 8 and might be interpreted as the effect of a long term non axial dipolar component the psv record from vulcano agrees well with those from the lacustrine sediments of lago grande di monticchio 100 kyr bp and lago di mezzano 30 kyr bp located in the italian peninsula brandt et al quat sci rev 18 1999 961 976 the inclination anomaly i found at vulcano corresponds to about half of the shallowing observed in the sediments of the two lakes and the declination anomaly d may be used to tie the declination values derived from azimuthally unoriented cores to the geographical reference system in order to find the optimum site to be used as reference for psv studies in italy the angular values of the earth s magnetic field measured at the 113 repeat stations of the italian geomagnetic network coticchia et al boll geod sci aff 40 2001 277 291 have been analyzed with the relocation via pole method noel and batt geophys j int 102 1990 753 756 the viterbo station lat 42 27 n long 12 02 e proved the best since the mean error is 0 3 for both declination and inclination wherever the original psv site is located in italy a preliminary composite psv curve for the last 30 kyr bp is thus proposed merging and relocating to viterbo the data from vulcano and the curve from lago di mezzano corrected for the gad deviation found at vulcano

meandering flow of a pyroclastic density current documented by the anisotropy of magnetic susceptibility ams in the quartz latite ignimbrite of the pleistocene monte cimino volcanic centre central italy abstract a pattern of shifting current direction is revealed by the anisotropy of magnetic susceptibility ams in the quartz latite ignimbrite associated with the pleistocene cimini dome complex in central italy high field ams documents that both paramagnetic and ferrimagnetic minerals contribute to the magnetic fabric of the ignimbrite the results of low field ams studies suggest that the pyroclastic density current changed both direction and character during deposition of each flow unit that makes up the ignimbrite the meandering behaviour of the currents can be observed on the scale of 15 cm increments in the fine grained basal layer 2a of one flow unit in an area lacking significant palaeotopography ams data from 1 2 and 4 metre increments through the flow units also show complex changes in flow direction throughout the deposition of each unit studied the most closely aligned ams fabrics occur near the bases of flow units and dispersion increases upward this trend may represent decreased shear between the flow and the substrate or increased turbulence in the upper depositional zone of the pyroclastic density current or both suggesting a progressively waning current in terms of capacity or particle concentration the phenomena observed in this study have broad implications for the general methodology of ams studies detailed vertical profiles made up of several individual sample sites within 1 metre thickness intervals can reveal small scale current flow variations that may not be evident if sampling is done more sparsely

integration of controlled source and radio magnetotellurics electric resistivity tomography and reflection seismics to delineate 3d structures of a quick clay landslide site in southwest of sweden abstractquick clay which is the main cause of landslides that occur in the northern countries liquefies easily and its presence implies an increased risk of landslide geophysical methods have been increasingly used in landslide investigations three dimensional electric resistivity tomography radio magnetotelluric rmt controlled source rmt csrmt and high resolution reflection seismic data were acquired at a quick clay landslide site in the southwest of sweden the main objectives were to evaluate the capability of each method in delineating different subsurface geologic structures that controlled a peculiar and hazardous retrogressive type landslide in the study area a 3d resistivity model from the inversion of csrmt data showed the best correlation with the reflection seismic data and borehole information thanks to the broad frequency range of the data set it better imaged the resistive crystalline bedrock underlying the marine conductive clays and showed considerable correlations with the

a review of deformation pattern templates in foreland basin systems and fold and thrust belts implications for the state of stress in the frontal regions of thrust wedges aesthetically appealing thrust systems and related large scale anticlines in both active and fossil foreland fold and thrust belts and the economic potential associated with the m have captured the interest of structural geologists for many decades as a consequence a large amount of data on sub seismic deformation patterns from thrust related an ticlines is available in the literature we provide a review of deformation pattern templates from fi eld data in foreland fold and thrust belts and show that the most frequent tre nds of sub seismic syn orogenic deformation structures hosted in km scale thrust related folds frequently and pa radoxically indicate a syn th rusting strike slip stress fi eld con fi guration with a near vertical 2 and a sub horizontal 3 rather than a contractional one where the latter is expected to be the vertical principal axis of the stress ellipsoid this a pparent inconsistency between sub seismic syn orogenic deformation structures and stress fi eld orientation is here named the 2 paradox field data support a possible expla nation of the paradox provided by the major role played by i nherited early orogenic extensional deformation struc tures on thrust fault nucleation nucleation of major thru sts and their propagation is facilitated and driven by the positive inversion and linkage of the early orogenic sub s eismic extensional inheritance developed in the foreland basin this process eventually leads to the development of l argereversefaultzonesandcanoccurbothincontractional and strike slip stress fi eld con fi gurations

age and petrology of the late pleistocene brown tuffs on lipari italy late pleistocene volcanic products on lipari consist mainly of pyroclastic surge deposits monte guardia sequence and fine grained brown tuffs radiometric age determination on carbon from thin soils at the top of the tuffs indicate that they have several ages of emplacement ranging from more than 35 000 to 16 800 years ago chemical and microprobe data on glass and mineral fragments from these tuffs show that they belong to a shoshonite or high k series this composition is compatible with an origin related to the magma system of vulcano but not with the magma system on lipari

volcanic history of lipari aeolian islands italy during the last 10 000 years abstract examination of the volcanic stratigraphy of deposits younger than 10 000 years on lipari indicates four principal periods of volcanic activity related to specific centers the products from each different volcanic center are defined as volcano stratigraphic unit vsu from the oldest these are the canneto dentro gabellotto fiume bianco forgia vecchia and monte pilato rocche rosse vsus the study of textures and dispersal of the deposits permitted the vents to be localized and the recent volcanic history of lipari to be reconstructed the oldest event formed a small explosion breccia cone with a final obsidian lava in the canneto dentro area immediately afterward a complex series of explosions produced the widespread dry surge deposits of the gabellotto fiume bianco sequence this activity ended with the extrusion of a domical lava flow the renewal of activity occurred in the pirrera area with an explosive eruption that produced explosion breccia deposits the last eruptions from this vent were coeval with the first eruption of m pilato the rim of the explosion breccia cone was partially destroyed by the forgia vecchia lava flow m pilato cone grew in a very short period of time due to a continuous swarm of explosive events after a short repose time a series of more energetic and superficial explosions occurred through a vent slightly to the south the extrusion of the rocche rosse lava flow about 729 a d ended this cycle of activity all the volcanic centers follow a quite similar stochastic pattern starting with a fall or surge eruption and ending with effusion of viscous rhyolitic lavas the four centers are aligned along either nw se or ne sw fault systems according to the structural pattern of the island they can be placed into two groups the canneto dentro gabellotto centers and the forgia vecchia m pilato centers a long quiescence 3 500 years separates the activity of these two groups while inside of each the activities were nearly contemporaneous or in rapid succession

monte guardia sequence a late pleistocene eruptive cycle on lipari italy this paper documents a complex sequence of interbedded lapilli fall base surge and pyroclastic flow deposits here named the monte guardia sequence that erupted from volcanic centers in the southern part of lipari aeolian island arc radiocarbon data from ash flow tuffs above and below this sequence bracket its eruption between 22 600 and 16 800 years ago geologic evidence however suggests that this single eruptive cycle had a more restricted duration of years to tens of years the basis for our interpretations comes from data measured at 38 detailed sections located throughout the island the monte guardia sequence rests on a series of lower rhyolitic endogenous domes in the southern part of lipari and it covers the oldest lavas lahars and pyroclastic flows in the north only in the northeast part of the island is it covered by younger deposits which there consist of lapilli tuffs and lavas of the monte pilato rhyolitic cycle the deposit ranges in thickness from more than 60 m surrounding the vents in the south to less than a few decimeters at 10 km distance in the north throughout most of the island the monte guardia sequence overlies a thin andesitic lapilli fall layer which is a key bed for correlation this lapilli tuff probably erupted from a volcanic center on another island of the aeolian arc possibly salina the principal activity of the monte guardia sequence started with an explosion that formed a continuous breccia blanket covering most of the island some pumiceous blocks within this breccia are composed of alternating bands of acidic and andesitic composition suggesting that the initiation of pyroclastic activity could have been triggered by magma mixing typical monte guardia sequence consists of explosive products that grade from magmatic pumice fall to phreatomagmatic base surge character the eruptive cycle is characterized by a number of energy decreasing megarhythms that start with a lapilli fall bed and end with a base surge set that progresses through sand wave massive and planar beds isopach maps of the fall and surge deposits indicate that both types were directed to the northwest by prevailing winds existing topographic relief was an additional factor that affected the emplacement of surge products at the end of the cycle andesitic pyroclastic flows and rhyolitic endogenous domes were emplaced above the monte guardia deposits near the vent

temporal evolution of a three component system the island of lipari aeolian arc southern italy the volcanic products from lipari define an evolutionary trend with a high gradient of k enrichment similar to the calc alkaline to potassic volcanism of other islands in the aeolian arc stratigraphic reconstruction of the island based on field and geochronological data indicate that the volcanic activity can be subdivided in two stages the first stage from 223 to 42 ka consists of six eruptive cycles and is characterized by basalts and basalt andesites showing progressive increase in both sio2 and k2o contents with time the second stage consists of four cycles erupted since 42 ka and is marked by an apparent rejuvenation of the geochemical system with the appearance of the first rhyolitic products fractional crystallization assimilation and mixing models suggest that the geochemistry of lipari volcanism evolved with time by a complex interplay between two mantle derived components one sub alkaline and the other alkaline in addition to crustal melts and or crustally derived materials a petrogenetic model in which fractional crystallization was subordinate to mixing best fits the geochemical data and petrographic observations of macro and microscopic features melts from the crustal and mantle end members are almost always present in the system but the relative proportions appear to vary with time the sub alkaline mantle component source of tyrrhenian tholeiites is an important contributor to the early evolution of the volcanism in lipari input from the alkaline mantle component source of the roman comagmatic province increases with time and the crustal component becomes dominant in the later activity the preferred petrogenetic model for the temporal evolution of the volcanic system in lipari involves melting initially caused by an increase in the thermal input related to the opening of the tyrrhenian sea and or to subduction processes the quick rise of the isotherms and almost contemporaneous melting of source materials with different compositions favored complex mixing during ascent of the melts

stratigraphy and significance of brown tuffs on the aeolian islands southern italy abstract brown tuffs bt are volcaniclastic ash deposits prominently represented in the stratigraphic profiles of all the aeolian islands and capo milazzo on the northern coast of sicily detailed stratigraphy and tephrochronology together with available radiometric ages suggest that they were emplaced over a long time interval spanning from the end of the last interglacial period ca 80 ka bp up to 4 5 ka bp age of the overlying punte nere pyroclastic products on vulcano the most complete bt succession is documented on lipari where 14 distinct and successive units are subdivided by the interbedding of widespread tephra layers local volcanic products paleosols and epiclastic deposits and the occurrence of local erosive surfaces inter island occurrence of ischia tephra a widely known tephra layer in the aeolian archipelago dated at 56 ka bp and monte guardia pyroclastics from lipari dated at 22 20 ka bp subdivides the bt succession in upper ubt intermediate ibt and lower bt units lbt which can be correlated at regional level the lbt was emplaced between 80 and 56 ka bp the ibt between 56 and 22 ka bp and the ubt between 20 and 4 5 ka bp on the basis of stratigraphy similarity in lithology and textural features morphology of glass fragments composition and consistency of thickness and grain size variations ubt units correlate with piano grotte dei rossi tuffs on vulcano island they were generated by pulsating hydromagmatic explosive activity giving rise to pyroclastic density currents spreading laterally from a source located inside the la fossa caldera on vulcano island composition is in agreement with this hypothesis since ubt compositional features match those of vulcano magmas erupted in that period the effect of co ignimbrite ash clouds or associated fallout processes from sustained eruptive columns is seen to explain the presence of ubt in areas further away from the suggested source e g salina and lipari islands and capo milazzo the origin of ubt exposed on panarea island is still a matter of debate due to contrasting compositional data due to large uniformity of lithological textural and componentry characters with respect to the ubt the lower portions of the bt succession lbt ibt are considered to be the result of recurrent large scale hydromagmatic eruptions of similar type moreover for the ibt units the correlation with monte molineddo 3 pyroclastics of vulcano island on the basis of lithological compositional and stratigraphic matching again suggests source s related to the vulcano plumbing system and located within the la fossa caldera

a distant magmatic source for cretaceous karst bauxites of southern apennines italy revealed through shrimp zircon age dating karst bauxites occur at a late cretaceous hiatus on a bahamiantype platform in southern apennines italy in contrast to the well defined stratigraphic context their origin remains controversial detrital zircon grains preserve textures and th u ratios consistent with crystallization from a melt occasionally around older cores u pb isotopic data collected using shrimp ii record several age populations the youngest 90 ma falls into the age interval of bauxite formation as defined by stratigraphic criteria the zircons must therefore be derived from a contemporary cretaceous volcanic source the older zircons may be interpreted as xenocrysts associated with the cretaceous magmas or derived from different sources because the bauxite occurs on a isolated carbonate platform the grains must come from far away sources most probably transported by wind the age palaeogeography and inferred cretaceous wind pattern are consistent with a prevailing origin from the dinaric and carpatho balkan orogenic belts with its cretaceous bimodal volcanism

composite detrital and thermal remanent magnetization in tuffs from aeolian islands southern tyrrhenian sea revealed by magnetic anisotropy this paper reports on the complex relation between rock emplacement and remanence acquisition in tuffs deposited by pyroclastic density currents disclosed by systematic measurements of the anisotropy of magnetic susceptibility and natural remanent magnetization nrm thermal demagnetization shows that the nrm consists of two components with different blocking temperature spectra the direction of the low temperature component is consistent with the geocentric axial dipole value whereas the high temperature component has dispersed directions the magnetic fabric is oblate the magnetic foliation is close to the bedding and the lineations are generally dispersed along a girdle within the foliation plane the directions of the magnetic lineation and the high temperature remanence component of individual specimens are close to each other this correspondence suggests that the high blocking temperature grains acquired a remanence aligned to their long dimension before deposition while cooling within the explosive cloud and the moving pyroclastic current thereafter during deposition the traction processes at the base of the current oriented the grains along the flow direction and affected both fabric and high temperature remanence this nrm component results from mechanical orientation of previously magnetized grains and is thus detrital in origin a second thermal component was then acquired during the cooling of the low blocking temperature grains after deposition these results show that nrm in fine grained pyroclastic rocks is affected by the earth s magnetic field as well as the emplacement processes and that magnetic fabric data are essential to unravel its complex nature

development of rudist lithosomes in the coniacian lower campanian carbonate shelves of central southern italy high energy vs low energy settings abstract the late cretaceous shallow water depositional areas of southern tethys were complexes of unprotected shelves occupied by foramol assemblages that produced loose diagenetically stable bioclastic debris not involved in significant in situ cementation processes both storm and wind induced currents and waves exercised a strong control on the distribution of the shifting biogenic sediments which covered the open sea floor constituting large coalescing sheets of winnowed fine to coarse skeletal sands rudists spread over all shelf sectors from more open and external areas to more internal ones occupying different substrata and furnishing the bulk of the skeletal component by means of bioerosion processes they colonised mobile sediments giving rise to complex bodies with peculiar characteristics related to environmental parameters of the different sectors of the shelf on the basis of detailed sedimentological taphonomic and palaeontological data we recognised two main rudist rich depositional settings end members in the southern italy senonian rudist bearing successions in successions pertaining to hypothesised marginal shelf sectors characterised by high energy regime deposits rudist lithosomes are metric in thickness and lateral extent and lens like in morphology rich in bioerosion derived skeletal sand and silt rudists are highly diversified large elongated cylindro conical hippuritids mostly pertaining to the genera hippurites and vaccinites thick shelled radiolitids and plagioptychids largely dominate rudists clustered in life position are subordinate they often form small bouquets more commonly these organisms appear fallen but only barely reworked the rudist rich bodies laterally pass into clean bioclastic grainstone in which sedimentary structures related to current and or storm erosional action are common no evidence of significant original relief of the rudist bodies in respect of the neighbouring sediment can be recognised the submarine erosion and or the high energy processes operating presumably inhibited the aggradation of the tidal sediments above the marginal ones as a consequence the vertical facies organisation shows widespread subtidal cycles as commonly recognised in open shelves with ramp like morphologies in successions pertaining to more internal and or low energy sectors rudist rich beds rhythmically alternate with finer grained foraminiferal limestones small elevator radiolitids with oligospecific diversity are dominant mostly concentrated in clumps rudists in growth position are abundant although a large quantity of shells appear toppled with little reworking they may form laterally continuous biostromal shell beds sedimentary structures such as cross lamination and gradation are only occasionally present the resulting facies are commonly arranged in peritidal shallow subtidal cycles in which evidence of subaerial up to pedogenic modifications on a large and small scale and less frequently submarine exposure is common intermediate successions have been recognised characterised by deposits of silty sand plains which present intercalations of graded bioclastic storm related beds sedimentological characteristics seem to document more open conditions in which submarine erosion was intermittently prevalent in these successions rudist species that are commonly found both in high energy and low energy assemblages coexist

eruptive and emplacement mechanisms of widespread fine grained pyroclastic deposits on vulcano island italy tufi di grotte dei rossi inferiori are thick ash deposits representing the most voluminous stratigraphic unit on vulcano island the deposits are related to hydromagmatic eruption which occurred under shallow water inside a caldera depression grain size data and results of sem investigation allow the character of the transporting medium solid material concentration in the cloud during the lateral expansion and the nature and role of the fluids present at the time of deposition to be constrained we suggest that the eruption was characterized by closely timed hydromagmatic pulses giving rise to eruption clouds rich in water vapor and steam the coarser material was not significantly transported in the eruptive cloud and it probably deposited in the caldera depression area the finer material was extensively transported in the cloud creating turbulent flows which surmounted the caldera rim barrier and dispersed in a southward direction forming widespread deposits in the piano area lower concentrated flows produced laminated deposits of more limited dispersion whereas higher concentrated flows formed more dispersed thicker massive layers

complex remanent magnetization in the kizilkaya ignimbrite central anatolia implication for paleomagnetic directions abstract pyroclastic flow deposits known as ash flow tuffs or ignimbrites are invaluable materials for paleomagnetic studies with many applications for geological and tectonic purposes however little attention has been paid to evaluating the consistency and reliability of the paleomagnetic data when results are obtained on a single volcanic unit with uneven magnetic mineralogy in this work we investigate this issue by concentrating on the kizilkaya ignimbrite the youngest large volume unit of the neogene ignimbrite sequence of the central anatolian volcanic province in turkey bringing evidence of significant magnetic heterogeneities in ignimbrite deposits magnetic mineralogy susceptibility magnetic remanence coercivity etc and emphasizing the importance of a stratigraphic sampling strategy for this type of volcanic rocks in order to obtain reliable paleomagnetic data six sections were sampled at different stratigraphic heights within the devitrified portion of the ignimbrite isothermal remanence measurements point to low ti titanomagnetite as the main magnetic carrier at all sites at some sites the occurrence of oxidized ti magnetite and hematite is disclosed the bulk susceptibility k m decreases vertically at two out of six sections its value for the topmost samples is commonly one order of magnitude lower than that of the samples at the base in most cases low k m values relate to high coercivity of remanence b cr values which range from 25 to 400 mt and to low s ratios measured at 0 3 t between 0 28 and 0 99 these data point to the occurrence of oxidized magnetic phases we therefore consider the k m parameter as a reliable proxy to check the ignimbrite oxidation stage and to detect the presence of oxidized ti magnetite and hematite within the deposit the characteristic remanent magnetization is determined after stepwise thermal and af demagnetization and clearly isolated by principal component analysis at most sites for these sites the site mean paleomagnetic direction is consistent with data from the literature at a few other sites the remanence is more complex the direction moves along a great circle during demagnetization and no stable end point is reached the occurrence of oxidized ti magnetite or hematite as well as two remanence components with overlapping coercivity and blocking temperature spectra suggest that the kizilkaya ignimbrite acquired first a thermal remanent magnetization and then during the final cooling or a short time later a secondary remanent magnetization component which is interpreted as a crm acquired during post emplacement devitrification processes notwithstanding the kizilkaya ignimbrite is a single cooling unit its magnetic properties suffered substantial variations laterally and vertically within the deposit the kizilkaya case shows that thick pyroclastic deposits should be sampled using a stratigraphic approach at different sites and different stratigraphic heights at each individual sampling location otherwise under sampling may significantly affect the paleomagnetic results when sampling is performed on a short duration or on very poorly preserved deposits we recommend drilling the lower central portion in the most strongly welded and devitrified facies such sampling strategy avoids complications arising from the potential presence of a pervasive secondary crm masking the original chrm

the geometry and petrogenesis of dolomite hydrocarbon reservoirs the wide distribution of dolomite rocks in north american middle and far eastern hydrocarbon reservoirs is reason enough for their intensive study in this volume dolomite enthusiasts review progress and define the current boundaries of dolomite research related particularly to the importance of these rocks as reservoirs as might be expected reviews provide critical analyses of past ideas on origins and why many are no longer tenable discussions range between conceptual models and numerical simulations of the flow paths of dolomitizing fluids geochemical modelling and microbial mediation case studies from areas as diverse as north america the middle east se asia and australia provide a solid background but illustrate important differences in views on the origins of these enigmatic rocks