microbial fabrics from neogene cold seep carbonates northern apennine italy abstract a number of hydrocarbon seep carbonate masses are hosted within miocene and pliocene siliciclastic units along the apennine range and sicily and are mainly composed of micritic and microsparitic textures geomicrobiological analysis of some of these deposits shows that preserved microbial processes are few and the contribution of microbe derived textures to their construction is volumetrically very limited in the carbonate groundmass of two northern apennine miocene and pliocene seep carbonate deposits uncommon and well preserved features suggest direct and indirect evidence of microbial activity some of these features are interpreted as the mineralization products of microbial textures and include complex alveolar textures and fossilized biofilms that line and fill microconduits pores and other voids similar to living bacterial aggregations recovered in modern seep carbonates other mineral structures such as spheroids and rhombs with concentric fabrics composed of calcite dolomite alternations abound as cement components and suggest a nucleation via bacterial sulfate reduction processes a similar origin is also assumed for the acicular aragonite bundles that in the miocene seep carbonate mass enclose dense clusters of millimeter size filamentous morphologies of biological origin

seep carbonates in a thrust related anticline at the leading edge of an orogenic wedge the case of the middle late miocene salsomaggiore ridge northern apennines italy abstract seep carbonates are important indicators of submarine fluid expulsion and dewatering of sediments along convergent margins and accretionary prisms in the northern apennine compressional wedge seep carbonates usually occur in pelitic successions from different settings of the middle late miocene foreland basin system in serravallian foredeep deposits of the salsomaggiore area seep carbonates cemented and or encrusted coarse grained sandstones and conglomerates fluid expulsion strictly related to variable intensities in tectonic stresses generated seep carbonate facies and sediment instabilities depending on the position of the fluid pathway feeders within the salsomaggiore ridge a middle late miocene intra basinal high at the leading edge of the apenninic orogenic wedge this site provides a unique opportunity for analyzing depositional characters and the three dimensional distribution and evolution of a seepage system in a thrust related anticline the resulting evolutionary model shares common features with recent ridges in other accretionary wedges in this model a strict relationship between tectonics seepage and sediment instability during a major tectonic phase is outlined

comparison of superdarn radar boundaries with dmsp particle precipitation boundaries 1 auroral boundary algorithms for superdarn ionospheric convection observations are introduced both the equatorward boundary of scatter ebs and the convection reversal boundary crb are found and compared with boundaries based on dmsp particle precipitation observations these comparisons provide an intercalibration between the two schemes and insight into the relationship between disparate phenomena the ebs is reliably poleward of the equatorward boundary of precipitation ebp at most local times but centers well on the equatorwardmost precipitation between 1600 and 2200 mlt when within 8 latitude of the radar station indicating a correspondence with the slerps slow long lived e region plasma structures of jayachandran near dawn the ebs coincides better with the structured unstructured boundary sub than the ebp as one might expect if the ionospheric irregularities responsible for this scatter were produced by the gradient drift instability the crb correlates well with the open closed boundary ocb as seen by dmsp there is however an equatorward offset of the crb relative to the ocb that varies from zero near noon to 1 near dawn and dusk and is largest near midnight this offset is consistent with a small viscous like interaction between the magnetosheath and the low latitude boundary layer resulting in a degree of antisunward flow on closed field lines the offset decreases under the influence of southward interplanetary magnetic field as one might expect if increased dayside merging interfered with this effect

the pliocene age stirone river hydrocarbon chemoherm complex northern apennines italy abstract the stirone river section in the italian northern apennines hosts a rare example of pliocene age hydrocarbon imprinted carbonates in the mediterranean basin associated with deep water hemipelagic lithologies these include meter sized dolomite cemented chimneys micritic brecciated limestones lucina mudstones and chemosymbiotic bivalve shells some such chimneys show 13 c values as low as 37 5 vpdb suggesting subsurface precipitation of authigenic dolomite induced by anaerobic oxidation of methane triggered by consortia of sulphate reducing bacteria these carbonates are interpreted as part of the plumbing system related to hydrocarbon expulsion onto the seafloor resulting from hydrocarbon enriched defluidization processes dated at an interval at 3 6 3 3 ma and associated with the thrust related salsomaggiore structure

cenozoic dolomites of carbonate islands their attributes and origin abstract dolomites found on and below carbonate islands atolls and oceanic platforms provide useful insights into the origin of dolomite insights that may not be attainable from the study of more ancient cratonic dolomites for this reason they have been the subject of study for decades a critical mass of case studies now exist and some significant conclusions can be drawn from the cumulative data in most cases the association with an island is causal and not genetic nevertheless these dolomite occurrences are referred to herein as island dolomites one type of dolomite on carbonate islands is penecontemporaneous dolomite a phase that forms while the host sediment is in its original depositional setting island examples are holocene in age occur in holocene sediments and originate as a direct precipitate from either normal or evaporated seawater these are microcrystalline poorly ordered ca rich 18o enriched and geochemically unstable phases that are susceptible to recrystallization in the setting in which they formed post depositional dolomite is the other type of dolomite associated with carbonate islands this type of dolomite replaces older precursors and forms as cement distinctive characteristics include a dominance of fabric preserving texture pore lining cement rims that may exhibit micron scale banding with low mg calcite and formation in association with precursor dissolution sr isotopic dating indicates that all examples are neogene or quaternary in age those formed during the middle miocene through pliocene are massive laterally continuous and often multigenerational in contrast younger examples tend to be localized partial replacements of a single generation sr isotope ages also suggest global synchroneity in many dolomitization events which suggests a connection between dolomitization global eustacy and or global climatic factors geochemical attributes of post depositional island dolomites are ca enrichment positive 18o and 13c low sr contents 150 300 ppm and low fe global similarity in petrography and geochemistry of replacive island dolomites argues for a similar origin inferred origins however depend primarily on how 18o and sr data are interpreted values for 18o and dsr must be assumed due to uncertainties in oxygen isotope fractionation and sr partitioning there is no consensus or uniformity in those assumptions thus interpretations can vary and be biased to a desired result covariant trends in 13c and 18o some negative 13c values and high sr all favor a mixing zone origin but examples with these attributes are few lack of covariance in the isotopes mean 18o of 2 0 to 3 5 and low sr future studies should standardize the type of data collected and the analytical techniques employed multiple geochemical attributes should be measured on microsampled components and quantitative modeling should be employed in order to constraint interpretations as much as possible also needed are a better understanding of the kinetic processes that form these dolomites more careful assessment of their recrystallization status and an improved understanding of dsr and 18o at low temperature

methane derived carbonate conduits from the late aptian of salinac marne bleues vocontian basin france petrology and biosignatures abstract peculiar carbonate bodies occur in distinct marl layers of the marnes bleues formation aptian albian vocontian basin southern france the carbonate conduits exhibit pipe or sausage like forms and a central channel their sizes range between 30 and 60 cm in length and 5 10 cm in diameter the conduit carbonates consist of automicrite authigenically formed within the sediment millimeter sized aggregates of framboidal pyrite are abundant within the conduit automicrites probably representing former colonies of sulfate reducing bacteria the central channel reflects former pathways of reduced fluids in the carbonate conduit ni enrichments at the margins of the central cavity are may be due to the activity of methane related metabolism as ni is an important bio element for respective microbes light stable carbon isotope ratios of the conduit automicrites 25 86 to 23 10 vpdb point to carbonate precipitation linked to anaerobic oxidation of methane aom while less depleted stable carbon isotope ratios of microspar in marginal zones of the central opening 8 96 vpdb are in line with microbial sulfate reduction a methane related origin of the conduit carbonates is confirmed by the presence of authigenic lipid biomarkers tentatively sourced by archaea most of which are characterized by strong 13 c depletions 13 c values down to 104 the presence of organically bound sulfur is well in line with microbial sulfate reduction isorenieratane potentially point to the presence of brown pigmented green sulfur bacteria the methane was probably sourced by older oae black shales which are known to contain isotopically 13 c heavy biomarkers of archaea as reported elsewhere

authigenic carbonate formation and its impact on the biomarker inventory at hydrocarbon seeps a case study from the holocene black sea and the plio pleistocene northern apennines italy carbonates are widespread at methane and petroleum seeps and are often precipitated as consequence of an alkalinity increase due to the anaerobic oxidation of methane aom or less often reported of higher hydrocarbons these carbonates are taphonomic windows into earth s history because they excellently protect the in situ formed microbial signatures e g lipid biomarkers from diagenetic destruction a complication for paleoreconstructions however is that seep carbonates also encapsulate variable amounts of allochthonous organic matter sometimes even completely obscuring authigenic microbial signatures seep carbonates from the holocene black sea the pleistocene enza river and the pliocene san lorenzo both northern apennines italy provide hints to better understand i the importance of processes other than aom for the formation of seep carbonates and ii the controls of allochthonous and autochthonous contribution of biomarkers to organic matter in seep carbonates biomarker distributions in different parts of a black sea carbonate clearly demonstrate that high allochthonous organic matter is entrapped if aom carbonates are formed intrasedimentary particularly if methane supply is relatively low and external organic matter input high high allochthonous contributions were also found in the biomarker inventory of ancient seep carbonates from the italian northern apennines enza river and san lorenzo pointing at their precipitation within the sediment specific and complex conditions were indicated from our data for the enza river location carbonate facies and particularly biomarker compositions with abundant signatures of sulfate reducing bacteria suggest that sulfate reduction using alkaline and eventually sulfate and higher hydrocarbon enriched fluids triggered the growth of these seep carbonates our and other data suggest that this process has to be more considered if interpreting seep settings particularly where microbial processes rely on rising fluids from deep petroleum reservoirs

a study of the chemistry of pore fluids and authigenic carbonates in methane seep environments kodiak trench hydrate ridge monterey bay and eel river basin analyses of the chemical and isotopic composition of carbonates rocks recovered from methane seepage areas of the kodiak trench hydrate ridge monterey bay clam flats and the eel river basin coupled with the studies of the chemistry of the pore fluids have shown that these carbonates have grown within the sediment column geochemical profiles of pore fluids show that in deep water seeps kodiak trench 4450 m monterey bay 1000 m hydrate ridge 650 m 13c dic values are low isotopically light whereas in the eel river area 350 500 m 13c dic values are much higher isotopically heavier in all cases the 13c values indicate that processes of methane oxidation associated with sulfate reduction are dominant in the shallow sediments data on the isotopic composition of authigenic carbonates found at sites in kodiak trench eel river basin south and eel river basin north indicate a variable composition and origin in different geochemical environments some of the authigenic carbonates from the study sites show a trend in their 13c values similar to those of the pore fluids obtained in their vicinity suggesting formation at relatively shallow depths but others indicate formation at greater sediment depths the latter usually consist of high magnesium calcite or dolomite which from their high values of 13c up to 23 and 18o up to 7 5 suggest formation in the deeper horizons of the sediments in the zone of methanogenesis these observations are in agreement with observations by other workers at hydrate ridge in monterey bay and in the eel river basin

when did the northern apennine become a mountain chain abstract the purpose of the present paper is to bracket the age of the initial uplift of the northern apennine chain by means of all the available evidence the collected data show that the age of the lacustrine or fluvio lacustrine units which have aggraded in the intramontane basins is late pliocene in the northwestern tip of the northern apennine and mostly early pleistocene elsewhere the age of the oldest terraced fluvial deposits showing the initiation of incision is mostly middle pleistocene the uplift of the summit areas of low relief most likely took place during the middle pleistocene it is concluded that the uplift occurring during middle and upper pleistocene caused an area of rather low relief to become the northern apennine mountain chain an eastward shift of the uplift through time is likely

productivity generated annual laminae in mid pliocene sapropels deposited during precessionally forced periods of warmer mediterranean climate abstract paleoproductivity estimates for a sequence of five mid pliocene mediterranean sapropels illustrate the importance of insolation maxima in enhancing organic carbon accumulation well laminated sapropelitic intervals in the northern apennines have been studied by a combination of sedimentological and micropaleontological analysis detailed electron microscope description bulk chemical composition carbon isotopic composition and elemental ratios each sapropel formed during precessional minima lasted 7 5 to 10 kyr which is the same duration calculated for coeval counterparts in odp sites in the eastern mediterranean the organic carbon mass accumulation rates of the studied sapropels show the same values of those calculated in the coeval mediterranean sapropels suggesting that the same productivity conditions were controlling sapropel formation in the whole mediterranean despite the differences in depositional setting and the strong variations in sedimentation rate mat forming diatoms play an important role in increasing the settling velocity allowing rapid sinking of organic matter and preventing bacterial remineralization in the water column the consequent partial oxygen depletion at the seafloor increases preservation which is therefore considered an effect rather than a cause of the organic carbon accumulation

fission track reconstruction of the front of the northern apennine thrust wedge and overlying ligurian unit in the northern apennines foreland the marnoso arenacea formation ma fm records post depositional burial temperatures overlapping with those of the zone of partial annealing of apatite fission tracks because the stratigraphy sedimentology petrography and structural evolution of this turbidite succession has been intensively studied over the last 40 years the ma fm provides an ideal case to apply the apatite fission track method the data show a general decrease of the maximum paleotemperature undergone by the ma samples toward the foreland area the maximum burial calculated using a geothermal gradient of 20 c km spans from more than 5 km to less than 2 5 km and indicates that the reconstructed total thickness of the ma succession is not enough to justify the determined burial values stratigraphic data indicates that the missing section consisted of a lower component foredeep successions and an upper allocthonous component composed of disrupted and chaotic oceanic sediments and minor ophiolites ligurian unit the ligurian unit overrode the foredeep succession during deposition its advancement toward the foreland area was associated with subsidence and only locally contrasted by thrust growth the reconstructed wedge shape of the ligurian unit in its final and pre erosional configuration at time of the maximum bunal of the ma succession shows a flat upper surface which corresponds to a paleosurface of early pliocene age this surface marks at 4 to 5 ma the onset of the exhumation phase which occurred at a mean rate of 1 2 mm yr

biodetrital carbonates on the adriatic continental shelf imprinted by oxidation of seeping hydrocarbons abstract the gas productive bonaccia area located at ca 80 90 m below sea level offshore ancona central adriatic sea is site of hydrocarbon derived carbonate production the carbonates include large dm sized slabs bryozoan limestone smaller concretionary aggregates mudstones and pipes the mudstones and botryoidal aragonite cements within limestones show 13c values as low as 47 8 vpdb consistent with seepage of isotopically light hydrocarbons e g methane these hydrocarbon derived carbonates commonly incorporate abundant shell remains deriving from the prevalently coarse bioclastic rich muddy deposits from post glacial transgressive units it is therefore hypothesized that hydrocarbon rich fluids permeated the post glacial sediments resulting in seafloor seeps that were inhabited by chemosymbiotic lucinid bivalves and burrowing callianassid shrimps fossils and traces of which have been found in the bonaccia carbonates microbial oxidation of the reduced compounds contained in the seep fluids led to a locally patchy carbonate cementation of the sediments at the seep sites the pipes are interpreted as decapod burrows that subsequently served as conduits for hydrocarbon leakage seepage is probably still active at present as testified by gas production at the study site interestingly seep carbonates exhumed by erosion served as hard substrate for fouling benthos i e bryozoans oysters and red algae in the holocene the main products of the processes at the bonaccia study site are composite bryozoan dominated limestones whose multi step and complex history was unfold thank to radiocarbon dating of key components and precise stratigraphic control the bonaccia case study can serve as a model for the interpretation of ancient analogs such as bryozoan dominated limestones and mudstones of paleozoic to mesozoic age which are not uncommon in the geological record it further calls for caution in assuming that the presence of dominant macrobenthic fossil in old hydrocarbon derived limestones implies its ecological connection to active seepage

a new model of the petroleum system in the northern apennines italy a geochemical study on fluids from selected spontaneous seepages and drilled wells was carried out together with geologic investigation and deep cross sections reconstruction to examine the petroleum system in the western northern apennines foothills the hydrocarbons occurring in the miocene foredeep units that form the reservoirs are commonly interpreted as generated in a source reservoir system however the low total organic carbon its elevated dilution in the sediment pile and the limited amount of successions that entered in the oil window indicate a low potential for the hydrocarbons generation the structures deformation in the northern apennines foothills is mainly late miocene to pliocene in age and involves successions that are progressively younger towards southeast the earlier structure forms the salsomaggiore anticline in the western sector the comparison of the fluids from the wells and the mud volcanoes shows high geochemical and thermal history similarities saline waters originate from the connate pore water entrapped in the miocene reservoir rocks during their deposition the gaseous hydrocarbons are a mixture of secondary biogenic methane and primary and secondary thermogenic gases the associated oils show both early and late maturities these evidences account for different generation and migration steps depending on burial conditions and deformation time the various reservoirs appear confined by the thrust detachment at different depths and by the occurrence of reactivated lateral ramps these results suggest the occurrence of a common source rock deeper than the tertiary reservoir units which progressively entered in the oil window this source rock could have wide lateral extension at least comparable with the width of the studied area and represent a prime exploration target to evaluate the undiscovered oil and gas resources

the geochemistry of carbonate diagenesis the past present and future stable carbon and oxygen isotopes 18o and 13c values and trace elements have been applied to the study of diagenesis of carbonate rocks for over 50 years as valuable as these insights have been many problems regarding the interpretation of geochemical signals within mature rocks remain for example while the 18o values of carbonate rocks are dependent both upon the temperature and the 18o value of the fluid and additional information including trace element composition aids in interpreting such signals direct evidence of either the temperature or the composition of the fluids is required such information can be obtained by analysing the 18o value of any fluid inclusions or by measuring the temperature using a method such as the clumped isotope technique such data speak directly to a large number of problems in interpreting the oxygen isotope record including the well known tendency for 18o values of carbonate rocks to decrease with increasing age unlike the 18o 13c values of carbonates are considered to be less influenced by diagenesis and more a reflection of primary changes in the global carbon cycle through time however many studies have not sufficiently emphasized the effects of diagenesis and other post depositional influences on the eventual carbon isotopic composition of the rock with the classic paradigm that the present is the key to the past being frequently ignored finally many additional proxies are poised to contribute to the interpretation of carbonate diagenesis although the study of carbonate diagenesis is at an exciting point with an explosion of new proxies and methods care should be taken to understand both old and new proxies before applying them to the ancient record

mineralogy geochemistry and petrography of methane derived authigenic carbonates from enza river northern apennines italy abstract a remarkable exposure of carbonate pipe like and slab concretions occurs along the enza riverbanks on the northern apennines foothills italy based upon geochemical and field evidences their genesis has been attributed to microbial governed carbonate precipitation from hydrocarbon enriched fluids the pipe like concretions are thus interpreted as former conduits chimneys marking sites of methane ascent onto the seafloor the resulting enza river chimney field is arranged in a palisade fashion a rare example of such mineralogical and petrographic analyses of some chimneys and slabs document that the dominant cement is dolomite although the chimneys show a rather homogeneous texture a clear zonation is observed in the relative distribution of major and minor elements in their internal and external parts the occurrence of sulphide minerals in the stratigraphically upper samples indicates possible renewal of fluids leakage after a major erosive event

genetic characterization of natural gases natural gases can be characterized genetically using four properties c2 concentration carbon and hydrogen isotope variations in methane and carbon isotope variation in ethane three diagrams for genetic characterization of gases have been designed in which the carbon isotopic composition of methane is correlated with the other parameters in these diagrams compositional fields have been defined for primary gases biogenic thermogenic associated and thermogenic nonassociated and for gases which result from mixing of these gases these fields are strictly empirical and comprise compositional variations found in about 500 natural gases the isotopic and compositional variations in natural gases can be described in terms of 1 processes during formation of the gases such as bacterial fermentation or maturation of organic matter and 2 processes during secondary migration mixing of primary gases is an important and common process migration of gases predominantly affects the c2 concentration whereas the isotopic properties of gaseous hydrocarbons primarily remain unchanged allowing an assessment of the origin of migrated gases and properties of their source rocks the formation of gas from humic organic matter and coals is not yet clear from published data the diagrams use data from various basins and areas interstitial gases from the gulf of california are entirely of bacterial origin traces of thermogenic gases are formed only in the vicinity of dolerite sills gases in the south german molasse basin and in the vienna basin are of bacterial mixed and thermogenic origins data from the north italian po basin provide examples for genetic characterization of migrated gases

modelling transient temperature distribution for injecting hot water through a well to an aquifer thermal energy storage system summary heat storage systems are usually used to store waste heat and solar energy in this study a mathematical model is developed to predict both the steady state and transient temperature distributions of an aquifer thermal energy storage ates system after hot water is injected through a well into a confined aquifer the ates has a confined aquifer bounded by aquicludes with different thermomechanical properties and geothermal gradients along the depth consider that the heat is transferred by conduction and forced convection within the aquifer and by conduction within the aquicludes the dimensionless semi analytical solutions of temperature distributions of the ates system are developed using laplace and fourier transforms and their corresponding time domain results are evaluated numerically by the modified crump method the steady state solution is obtained from the transient solution through the finalvalue theorem the effect of the heat transfer coefficient on aquiclude temperature distribution is appreciable only near the outer boundaries of the aquicludes the present solutions are useful for estimating the temperature distribution of heat injection and the aquifer thermal capacity of ates systems

fluid sources and stable isotope signatures in authigenic carbonates from the northern apennines italy abstract authigenic carbonates are frequently associated with methane cold seep systems which extensively occur in various geologic settings worldwide of interest is the relation between the fluids involved in their formation and the isotopic signals recorded in the carbonate cements along the northern apennines foothills italy hydrocarbons and connate waters still seeping nowadays are believed to be the primary sources for the formation of fossil authigenic carbonate found in plio pleistocene marine sediments four selected outcrops of dolomitic authigenic carbonates were analysed to compare signature of seeping fluids with fractionation of stable carbon and oxygen isotopes recorded in the carbonate along the foothills deep methane rich fluids spontaneously rise to the surface through mud volcanoes or are exploited in wells drilled nearby to the fossil plio pleistocene authigenic carbonates the plumbing system providing fluids to present day cold seeps was structurally achieved in late miocene and plio pleistocene 13 c values of methane which vary from 51 9 to 43 0 vpdb indicate that gas composition from the deep hydrocarbon reservoirs is relatively uniform along the foothills on the contrary 13 c in fossil authigenic carbonates strongly varies among different areas and also within the same outcrop the different carbon sources that fed the investigated carbonates were identified and include thermogenic methane from the deep miocene reservoirs 13 c enriched co 2 derived from secondary methanogenesis and microbial methane from pliocene successions buried in the po plain the 13 c variability documented among samples from a single outcrop testifies that the authigenic carbonates might represent a record of varying biogeochemical processes in the hydrocarbon reservoirs the sources of stable oxygen isotopes in authigenic carbonates are often ascribed to marine water oxygen isotopic fractionation in the dolomite cements indicates that marine pore water couldn t be the sole source of oxygen 18 o values provide a preliminary evidence that connate waters had a role in the carbonates precipitation the concomitant occurrence of active cold seepages and fossil record of former plumbing systems suggests that generation and migration of hydrocarbons are long lasting and very effective processes along the northern apennines foothills

methane derived carbonates and authigenic pyrite from the northwestern black sea abstract methane seeps in the northwestern black sea are accompanied by carbonate and pyrite precipitates sediments were sampled at locations on the romanian 120 m depth and ukrainian 180 200 m depth shelf and slope layered carbonate crusts are formed of i carbonate cemented siliciclastic sediment containing dreissenoid bivalves ii microcrystalline high mg calcite or aragonite and iii aragonitic cement the dreissena sediment is subrecent and was deposited during the freshwater phase of the black sea it has been affected by seepage of methane rich fluids which induced intergranular precipitation of authigenic carbonates the microcrystalline carbonates exhibit an intense autofluorescence high mg calcite contains 11 14 mol mgco3 the aragonitic cement 8300 9500 ppm sr forms either isopachous layers or botryoids microbial filaments about 10 20 m in diameter and up to 900 m in length are preserved within and on carbonate crusts the carbonates are depleted in 13c microcrystalline carbonate ranges from 27 to 41 pdb and botryoidal aragonite ranges from 26 to 38 pdb the 13c depletion indicates that the carbonates predominantly derive from the microbial oxidation of methane carbonate deposits do not project up into the oxic water column they are restricted to the anoxic water column and to anoxic sediments revealing the crucial role of anaerobic methane oxidation for carbonate precipitation 14c contents give apparent radiocarbon ages of 20 640 180 a bp for a sample of botryoidal aragonite and 19 110 180 a bp for a sample of microcrystalline carbonate compatible with minimum ages of carbon derived from a fossil hydrocarbon source the 18o values of methane derived carbonates show a narrow range from 1 2 to 0 2 pdb 87sr 86sr ratios of microcrystalline carbonate mean 0 70927 and aragonitic cement mean 0 70918 are indistinguishable from ambient seawater mean 0 70917 and thus indicate a shallow sr source higher 87sr 86sr ratios of the dreissena sediment mean 0 71005 are probably caused by sr derived from detrital mica carbonates are accompanied by blocks and crusts composed of pyrite the framboidal sulphide exhibits a palisade like fabric with framboids arranged to parallel pillars sulphur isotopic ratios 34s ranging from 16 8 to 19 7 cdt indicate that the sulphur derives not from the 34s depleted h2s of the water column or the uppermost sediment layers most likely pyrite formed in the lacustrine sediments after the first incursion of mediterranean seawater

petroleum exploration in italy a review abstract petroleum exploration in italy began in the second half of the 19th century but the first consistent discoveries were only made after world war ii at present the original reserves of the italian petroleum fields amount to about 160 million tons of oil and 720 billion cubic metres of gas domestic production in 1990 was 4 6 million tons of oil and 17 3 billion cubic metres of gas the lithology of the italian sedimentary sequences was controlled by the geodynamic evolution of the western margin of the adria plate the permian triassic continental and shallow water environments pre dating the break up of pangea were followed by subsiding carbonate platforms and basins in the mesozoic tertiary compressive tectonics induced by the subduction of the adria continental margin produced a complex thrust belt bordered by a migrating foredeep filled with clastic sediments most of the oil and a minor part of the gas were generated by middle triassic lower jurassic shaly and carbonate source rocks most of the gas was sourced by pliocene pleistocene clays in the foredeep turbiditic deposits and has a bacterial origin a short review integrated with some actual examples of typical fields cortemaggiore costa molina settala agostino porto garibaldi barbara candela palino rospo vega exemplifies the different plays in the main tectonic domains