unraveling tectonic and climatic controls on synorogenic growth strata northern apennines italy we develop a new high resolution stratigraphic age model to unravel the contributions of tectonic and climatic processes on early to late pleistocene synorogenic growth strata we capitalize on excellent continuous exposures along the flank of the po foreland in northern italy to elucidate hydrologic geomorphic and sedimentologic processes that are regularly attributed to but rarely proven to be caused by glacial interglacial climatic changes and unsteady rock uplift we perform our analysis on the enza section a succession of marine and terrestrial strata exposed along the enza river between parma and reggio emilia northern italy bedding in the enza section displays synorogenic growth strata geometry with bedding dips that range from 2 to 55 that becomes progressively shallower upsection we develop an age model that incorporates biostratigraphy magnetostratigraphy rock magnetic cyclostratigraphy cosmogenic radionuclide burial dating and optically stimulated luminescence dating and shows that the enza section spans the interval between 0 04 and 1 65 ma furthermore the age model pins the time of deposition for several lithostratigraphic units of regional significance and shows that sediment accumulation was unsteady ranging from 14 31 cm k y in the marine part of the section to 5 362 cm k y in the overlying littoral and terrestrial part of the section unsteady deposition is most pronounced in the terrestrial deposits where thick fluvial gravel packages accumulated in short 10 15 k y time periods that coincide with quaternary glacial intervals there is direct evidence for a dominant tectonic control in the older marine part of the section here sediment accumulation rates on the limb of the fold growing along this portion of the northern apennine mountain front show that between 1 07 and 1 65 ma repetitive progradation of neritic sand units directly followed pulses of rapid punctuated uplift in contrast the cyclic terrestrial facies variations in the enza section reveal that once the section became emergent at ca 1 ma and uplift slowed climate was the dominant control on sediment production and deposition

rare earth elements and neodymium isotopes in sedimentary organic matter abstract we report rare earth element ree and neodymium nd isotope data for the organic fraction of sediments collected from various depositional environments i e rivers n 25 estuaries n 18 open ocean settings n 15 and cold seeps n 12 sedimentary organic matter som was extracted using a mixed hydrogen peroxide nitric acid solution 20 h2o2 0 02 m hno3 after removal of carbonate and oxy hydroxide phases with dilute hydrochloric acid 0 25 m hcl a series of experimental tests indicate that extraction of sedimentary organic compounds using h2o2 may be complicated occasionally by partial dissolution of sulphide minerals and residual carbonates however this contamination is expected to be minor for ree because measured concentrations in h2o2 leachates are about two orders of magnitude higher than in the above mentioned phases the mean ree concentrations determined in the h2o2 leachates for samples from rivers estuaries coastal seas and open ocean settings yield relatively similar levels with ree 109 86 ppm mean s n 58 the organic fractions leached from cold seep sediments display even higher concentration levels 285 150 ppm mean s n 12 the h2o2 leachates for most sediments exhibit remarkably similar shale normalized ree patterns all characterized by a mid ree enrichment compared to the other ree this suggests that the distribution of ree in leached sedimentary organic phases is controlled primarily by biogeochemical processes rather than by the composition of the source from which they derive e g pore river or sea water the nd isotopic compositions for organic phases leached from river sediments are very similar to those for the corresponding detrital fractions in contrast the som extracted from marine sediments display end values that typically range between the end signatures for terrestrial organic matter inferred from the analysis of the sedimentary detrital fractions and marine organic matter inferred from the analysis of local surface seawater a notable exception is the case of organic matter om fractions leached from cold seep sediment samples which sometimes exhibit end values markedly different from both terrigenous and surface seawater signatures this suggests that a significant fraction of organic compounds in these sediments may be derived from chemosynthetic processes recycling pore water ree characterized by a distinct isotopic composition overall our results confirm that organic matter probably plays an important role in the oceanic ree budget through direct scavenging and remineralization within the water column both the high ree abundances and the shape of shale normalized patterns for leached som also suggest that om degradation in sub surface marine sediments during early diagenesis could control to a large extent the distribution of ree in pore waters benthic fluxes of organic bound ree could hence substantially contribute to the exchange processes between particulates and seawater that take place at ocean margins neodymium isotopes could provide useful information for tracing the origin terrestrial versus marine and geographical provenance of organic matter with potential applications in paleoceanography in particular future studies should further investigate the potential of nd isotopes in organic compounds preserved in sedimentary records for reconstructing past variations of surface ocean circulation

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

a genetic model of hydrocarbon derived carbonate chimneys in shelfal fine grained sediments the enza river field northern apennines italy abstract methane derived authigenic carbonate mdac concretions have been recently exposed in the pleistocene argille azzurre fm outcropping along the enza riverbanks northern apennines foothills italy the relations between the sediment deposition the coeval tectonic deformation and the mdac concretions have been investigated to unravel the mechanism of methane migration through the sediments and the processes leading to mdac occurrence the biogenic methane responsible for the formation of mdac chimneys and slabs has been generated in the organic rich pliocene sediments located in the po plain subsurface the gas migrated up dip towards the northern apennines foothills the mdac cements are mainly composed of dolomite whose precipitation requires thousand years and the absence of so 4 in the pore fluids according with the sedimentation rates of the mdac hosting pleistocene succession the sulphate methane transition zone migrated upwards faster than time required for dolomite precipitation therefore the connate water migrating together with the methane could have acted as second dic source allowing the mdac formation also in the methane rich zone

stable isotopes and rare earth element compositions of ancient cold seep carbonates from enza river northern apennines italy implications for fluids sources and carbonate chimney growth abstract cold seep carbonates are remarkable fossil records of hydrocarbon seepage and related conduits in the present research we analysed the carbon and oxygen isotopes rare earth element ree and trace element content of carbonate chimneys and concretions in the pleistocene argille azzurre formation northern apennines italy strong 13 c depletions values as low as 40 3 observed in both carbonate concretions and chimneys indicate that anaerobic oxidation of biogenic methane played a major role in the formation of these carbonates slightly higher 13 c values mostly found in the outer layers of the carbonate chimneys reflect a contribution of inorganic carbon from seawater ree patterns reveal the carbonates formed under mostly anoxic pore water conditions combined ree and trace element data reveal the growth of chimneys occurred from the outside in with the outer chimney walls experiencing rapid growth excellent correlations between ce ce ree contents and la n sm n and y ho ratios observed in the chimney walls provide additional evidence for the influence of seawater in the formation of the chimneys meanwhile o isotopic compositions of the samples suggest an 18 o depleted fluid was involved in carbonate precipitation this study has major implications for tracking fluid sources of seep carbonates and patterns of carbonate chimney growth

changing redox conditions at cold seeps as revealed by authigenic carbonates from alaminos canyon northern gulf of mexico anaerobic oxidation of methane in anoxic sediments at cold seeps often leads to formation of authigenic carbonates close to the seafloor along continental margins recent work however indicated that the redox conditions in sediments may vary to some degree during seepage activity in order to shed new light on the extent of this variability authigenic carbonates from alaminos canyon lease block 645 of the northern gulf of mexico have been characterized by means of inorganic and organic geochemistry the carbonates were collected from seep deposits representing various seafloor morphologies including extensive pavements mounds fractured carbonate slabs surrounded by dense bivalve shells and vestimentiferan tubeworm colonies the deposits almost entirely consist of aragonite the 18o values of aragonite vary from 2 6 to 5 8 v pdb suggesting precipitation in slight disequilibrium with the surrounding pore fluids the 13c values of aragonite between 33 9 and 20 4 v pdb agree with variable amounts of carbonate derived from oxidation of thermogenic methane and crude oil methane was primarily oxidized in an anaerobic process as revealed by the presence of 13c depleted molecular fossils of methane oxidizing archaea 13c values as negative as 118 and sulfate reducing bacteria 13c values as negative as 97 the syntrophic partners in the anaerobic oxidation of methane the observed inventories of molecular fossils in the authigenic carbonates mirror those of known consortia of anaerobic methane oxidizing archaea anme and sulfate reducing bacteria namely the anme 2 desulfosarcina desulfococcus dss and anme 3 desulfobulbus dbb consortia in contrast the same carbonates exhibit shale normalized rare earth elements patterns that all display real negative ce anomalies ce ce 0 78 suggesting that at least temporarily oxic conditions prevailed the episodic occurrence of oxic conditions is confirmed by the presence of molecular fossils of aerobic methanotrophic bacteria including 4 methylcholesta 8 14 24 dien 3 ol and two bacteriohopanepolyols aminotetrol and aminotriol the 13c values of the biomarkers of aerobic methanotrophs are as negative as 58 and are consequently less 13c depleted than the molecular fossils of the prokaryotes performing anaerobic oxidation of methane a pattern in accord with culture experiments overall our results suggest that redox conditions at cold seeps are variable this variability probably reflects changes in seepage flux the combination of an inorganic and an organic geochemical approach used here is promising to better assess the variability and diversity of past fluid and gas expulsion at seeps

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

marine cold seeps and their manifestations geological control biogeochemical criteria and environmental conditions characteristics of cold seeps at different geologic settings are the subject of this review primarily based on results of the research consortium sfb 574 criteria are drawn from examples on the erosive convergent margin off costa rica the accretionary margin off chile supplemented by examples from the transform margin of the golf of cadiz and the convergent hikurangi margin off new zealand others are from well studied passive margins of the black sea the golf of mexico the eastern mediterranean sea and the south china sea seeps at all settings transport water and dissolved compounds to the ocean through the seafloor by different forcing mechanism and from different depths of the submerged geosphere 10s of meters to 10s of km the compounds sustain oasis type ecosystems by providing bioactive reductants sulfide methane and hydrogen hereby the interaction between fluid composition flux rates and biota results in a diagnostic hydrocarbon metazoan microbe carbonate association currently well over 100 active sites are known the single most important reaction is microbially mediated anaerobic oxidation of methane with secondary reactions involving s biogeochemistry and carbonate mineral precipitation seep fluids and their seafloor manifestations provide clues as to source depth fluid sediment rock interaction during ascent lifetime and cyclicity of seepage events but less so on the magnitude of return flow at erosive margins cl depleted and b enriched fluids from clay dehydration provide criteria for source depth and temperature the upward material flow generates mud volcanoes at the seafloor above the projected location of dehydration at depth at accretionary margins fluids are derived from more shallow depths by compaction of sediments as they ride on the incoming oceanic plate they are emitted through thrust faults at highly sedimented margins organic rich and evaporite containing strata when present determine the final fluid composition by emitting characteristically gas hydrate derived methane brine associated non methane hydrocarbons or leached elements and their isotopes li 7li b ba from host sediments smectite illite transformation and associated cl depletion from release of interlayer water is a pervasive process at these margins rare earth element pattern in conjunction with redox sensitive metals retained in seep carbonates indicate whether or not they precipitated in contact with oxic bottom water or suboxic fluids clear environmental characterization though currently remains inconclusive more deeply sourced fluids as in transform margins may be characterized by their 87sr 86sr ratios from interaction with oceanic crustal rocks below quantification of flow and reliable estimates of total volatile output from fore arcs remain a challenge to seep research as does understanding the role of geologically derived methane in the global methane cycle

rare earth elements in cold seep carbonates from the southwestern dongsha area northern south china sea the circulation of methane rich fluids at cold seeps often leads to the precipitation of seep carbonates close to the seafloor along continental margins which can be used as records of past fluid seepage rare earth element ree concentrations in seep carbonates have been used to trace fluid sources and provide information on associated biogeochemical processes at cold seeps the ree concentrations of a series of carbonates collected from cold seeps in the southwestern dongsha area of the northern south china sea are analyzed in this study the total ree contents sigma ree of the seep carbonates analyzed show a wide variation from 17 ppm to 523 ppm with an average sigma ree value of 54 ppm which are higher than the carbonates from other cold seep areas a positive correlation between fe mn content and sigma ree was observed these results suggest that the seep carbonates of this study were primarily controlled by the methane derived fluid from which they precipitated the fe rich dolomite and siderite which are the main components of the carbonates are responsible for the enrichment of the ree a slight positive ce anomaly observed in the shale normalized ree patterns of the studied seep carbonates suggests that they formed in anoxic conditions and the correlations between ce ce and la n sm n ce ce and dy n sm n ce ce and sigma ree further reveal that the ree characteristics of most seep carbonate samples preserve the original redox conditions in which they precipitated and late diagenesis has had little effect on the ree however the ree characteristics of sub samples ds2 2b ds1 6a and ds1 7a are very different from those of the other sub samples indicating a greater impact of late diagenesis and post oxidation favored ree enrichment c 2014 elsevier ltd all rights reserved

recent and active tectonics of the external zone of the northern apennines italy we present a comprehensive study of the recent and active tectonics of the external part of the northern apennines italy by using morphotectonic geological structural and stratigraphic analysis compared with the current seismicity of the region this analysis suggests that the external part of the northern apennines is characterised by presence of three major systems of quaternary compressive structures corresponding to 1 the apenninic watershed 2 the apennines po plain margin pede apenninic thrust front and 3 the emilia ferrara and adriatic fold systems buried below the po plain geological data and interpreted seismic sections indicate a roughly n s quaternary deformation direction with rates 2 5 mm year the shortening decreased since the pliocene when our data indicate compression in a nnw sse direction and rates up to 7 mm year the trend and kinematics of the structures affecting the apennines po plain margin and the po plain subsoil fit well the pattern of the current seismicity of the area as well as recent gps and geodetic levelling data pointing to a current activity of these thrust systems controlled by an overall compressive stress field close to the apenninic watershed earthquake focal mechanisms indicate that shallow extension is associated to deep compression the extensional events may be related to a secondary extensional stress field developing on the hangingwall of the thrust system affecting the apenninic watershed alternatively this thrust system may have been recently deactivated and overprinted by active normal faulting deeper compressive events are related to the activity of both a major basement thrust that connects at surface with the pede apenninic thrust front and a major moho structure

diagenetic constraints on the use of cerium anomalies as palaeoseawater redox proxies an isotopic and ree study of cambrian phosphorites seawater rare earth element ree distributions show heavy ree enrichment and cerium depletion but these characteristics are only rarely found in ancient marine authigenic minerals such as carbonate fluorapatite and calcite this enigma may be due to changing ree distributions in seawater through time or to post depositional redistribution of ree differentiating between these two factors is however far from straightforward as their relative importance is likely to vary and evidence is often ambiguous in this article we present ree as well as strontium and sulphur isotope data for basal cambrian phosphorites of south china which confirm the emerging rule of thumb that granular phosphorites seldom reveal extreme departures from the seawater norm and tend to undergo therefore less diagenetic alteration of ree spectra than skeletal apatites and other phosphate types this study reveals stratigraphic trends in ce anomalies ce ce that could be taken to imply the preservation of a palaeoenvironmental signal however further investigation of our data shows that such trends in phosphorites can also be caused by post depositional alteration which tends to 1 increase ree contents 2 reverse ce depletion 3 alter eu anomalies and 4 concentrate preferentially the middle ree mree further alteration which may be due to weathering has led to hree depletion and positive la and y anomalies tetrad effect this is the first study where ceanom and phosphate bound sulphate s isotope values could be compared for one particular stratigraphic section which provides us with an additional tool for the interpretation of diagenetic redox conditions least altered phosphorites from meishucun that yield a strongly negative ceanom constrain early cambrian seawater 34s to about 33 we conclude that phosphorite ceanom primarily records variations in the local conditions of diagenesis while outlining some special cases in which diagenetic redox conditions may broadly reflect local bottom water redox conditions

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

the sedimentary flux of dissolved rare earth elements to the ocean abstract we determined pore fluid rare earth element ree concentrations in near surface sediments retrieved from the continental margin off oregon and california usa these sites represent shelf to slope settings which lie above within and below the oxygen minimum zone of the northeast pacific the sediments are characterized by varying degrees of net iron reduction with pore fluids from the shelf sites being generally ferruginous and the slope sediments having less pronounced iron reduction zones that originate deeper in the sediment package ree concentrations show maxima in shallow upper 2 10 cm subsurface pore fluids across all sites with concentrations that rise more than two orders of magnitude higher than seawater these pore fluid enrichments highlight the importance of a sedimentary source of rees to the ocean s water column here we use our measurements to estimate the diffusive flux of nd out of ocean sediments resulting in a global flux between 18 and 110 10 6 mol nd yr 1 while we do assume that our pore fluid profiles as well as the very limited data previously published are representative of a wide array of ocean environments this calculated flux can account for the modeled missing nd source flux 76 10 6 mol nd yr 1 in global budgets arsouze et al 2009 pore fluid normalized ree patterns show distinct variation in the middle ree and heavy ree enrichments with sediment depth and amongst sites these patterns show that the heavy ree enrichment of pore fluids at our deep slope site 3000 m water depth is closest to the heavy ree enrichment of seawater this observation supports the view that ree cycling within the upper ten centimeters of deep sea marine sediments as opposed to shallower continental shelf and slope sediments plays a significant role in controlling the integrated global ree flux from the pore fluids and consequently the broad scale ree pattern in seawater

authigenic carbonates from an active cold seep of the northern south china sea new insights into fluid sources and past seepage activity abstract site f also named formosa ridge represents the most vigorous cold seep on the northern south china sea continental slope in order to constrain the fluid sources and intensities of seepage we investigated the petrography mineralogy stable carbon and oxygen isotopic compositions element geochemistry and radiocarbon dating of authigenic carbonate rocks retrieved from the seafloor carbonate rocks mainly occurred as crusts nodules and nodular masses incorporated in carbonate breccias the carbonates were comprised mainly of high mg calcite and aragonite the 13 c of authigenic carbonate varied from 55 3 to 34 3 mean 48 5 n 47 vs v pdb suggesting biogenic methane is the dominant carbon source fuelling the system the 18 o carbonate values were from 3 6 to 4 8 mean 3 9 n 47 the observed 18 o enrichement in relation to calculated equilibrium values in the carbonates probably reflects dissolution of gas hydrates combination of seafloor observations and the obtained ams 14 c ages suggest that 1 initiation of methane seepage from at least 10 6 ka ago 2 environmental conditions may have been favorable for enhanced fluid seepage around 6 ka bp and 3 relatively low intensity of seepage from 2 ka bp till today

rare earth elements in seep carbonates as tracers of variable redox conditions at ancient hydrocarbon seeps marine hydrocarbon seeps are dynamic systems which are typically reflected in complex lithologies of limestones forming at these sites in order to test if seep limestones with their multiple generations of carbonate phases reflect variable redox conditions the rare earth element ree patterns of limestones from five ancient hydrocarbon seep localities hollard mound middle devonian iberg mississippian beauvoisin oxfordian canyon and satsop river oligocene and marmorito miocene have been investigated the total ree contents vary widely 0 3 43 7 p p m early microcrystalline phases tend to show higher contents than spatially associated later phases microspar sparite and blocky cement the shale normalized ree patterns of the carbonates show both negative and positive ce anomalies even for individual deposits suggesting that the redox conditions varied significantly it is apparent that in addition to anoxic conditions oxic conditions were common in some ancient seep environments intermittent oxygenation is presumed to have resulted from abrupt changes in fluid flow

cold seeps and authigenic carbonate formation in monterey bay california abstract authigenic carbonate associated with modern cold seep biological communities and their extinct analogues exhibit a broad range in stable isotope and mineral composition within the limited geographic area of monterey bay although such variations in ancient samples have been used to infer differing tectonic settings these carbonates all formed within a faulted continental margin environment and chemical variations reflect local differences in the sources and flux of carbon to sediment pore fluids the slow seepage of fluid and with it dissolved carbon along the transform faulted continental margin results in discrete areas of enhanced microbial sulfate reduction oxidation of methane from both biogenic and thermogenic origins as well as the active precipitation of both high mg calcite hmc and dolomite the authigenic carbonates include semicontinuous pavements of shallow cemented sediments surrounding benthic communities circular or pipe like chimneys interpreted as cemented conduits formed as a result of methane gas expulsion centimeter to meter scale rings doughnuts or slabs winnowed from variable depths within sediments and carbonate veins ankerite or calcite or cements in faulted basement rocks draped with bacterial mat abundant pyrite framboids preferentially filling the tests of the benthic foraminifer uvigerina peregrina and characteristic of the hmc bearing samples are products of a zone of shallow microbial sulfate reduction a process fundamental to the nourishment of the chemosynthetic cold seep communities sites on a sedimented ridge west of the san gregorio fault zone have carbon isotopic values between 35 and 56 that are strongly influenced by carbon derived from methane the higher values of 18 o more enriched in 18 o are found closer to the active fault zone carbonates from sites within the san gregorio fault zone or from monterey canyon floor exposures of miocene sediments have carbon isotope values between 7 and 26 that are mixtures of sedimentary organic carbon and microbially oxidized hydrocarbons from organic rich petroleum source rocks dolomite bearing samples are more enriched in both 18 o and 13 c bulk carbonate samples with heavier 18 o 18 o 3 5 result from the abundance of authigenic dolomite and low temperatures of formation local destabilization of clathrates might also create pore fluids that are more enriched in both 13 c and 18 o

magnetic stratigraphy and biostratigraphy of pliocene argille azzurre northern apennines italy abstract an integrated biomanetostratigraphic chronology for the mediterranean pliocene has been developed in the last five years mainly from land sections in southern italy calabria and sicily and odp leg 107 tyrrhenian sea cores in this paper the chronology is applied to terrigenous sediments from the northern apennine foredeep where reworking as well as sedimentation rate and facies variations limit the resolution of biostratigraphy and physical stratigraphy the integrated chronology gives improved stratigraphic control for a messinian to upper pliocene section exposed on the banks of the stirone near parma northern italy and for a short lower pliocene section located nearby at sant andrea bagni the sections are in the vicinity of stratotype sections for the tabianian lower pliocene and piacenzian upper pliocene and the chronology gives new insights into the complex pliocene sedimentation history in the northern apennine foredeep at this time at the stirone section the base of the pliocene record is in a normal polarity chronm correlated to the thvera subchron indicating a hiatus at the miocene pliocene boundary and the absence of the mpl1 foraminiferal zone at sant andrea bagni mpl1 is also missing in contrast to previous reports we conclude that this biozone is probably absent throughout the northern apennines where post messinian flooding appears to have occurred at the onset of mpl2 time during the gilbert chron sedimentation rates at stirone reached 104 cm kyr as nearly 300 m of argille azzurre blue clay were deposited in less than 0 5 myr very sporadic sedimentation is apparent from the late nunivak to the top of the section late gauss chron with a number of hiatuses being recognized within chron 2ar late gilbert and in the early gauss this interruption of sedimentation at about 4 1 ma is associated with a widely recognized early pliocene tectonic event involving thrusting and migration of the depocenter of the northern apennine foredeep

u th dating and post depositional alteration of a cold seep carbonate chimney from the campos basin offshore brazil abstract dating authigenic cold seep carbonates allows determining the timing of active seepage of hydrocarbon rich fluids at continental margins and ultimately the detection of the geological factors affecting it u th dating has been selected in this study the method having been successfully used before however incorporation of initial thorium in substantial amounts of detrital material due to the precipitation of carbonates within the seabed and post depositional alteration potentially pose a major problem violating the basic assumptions of the method here we report results from several samples from the campos basin off the coast of brazil they are unusual in their high 13 c values mean of 10 0 vpdb high detrital contents and being dominantly dolomite elevated 230 th 238 u activity ratios indicate that most of the carbonates lost uranium during diagenesis isochrones are obtained from the unaffected samples yielding an age of 140 4 3 1 ka vertical growth of the chimney must have been short and rapid since results from the top and bottom parts of the chimney concur within analytical uncertainties furthermore profiles of u th radioisotope specific activity 234 u and 232 th specific activity on two quarter slices of a carbonate chimney reveal the occurrence of three distinct diagenetic processes u loss u exchange with seawater and th gain

radiometric dating of submarine hydrocarbon seeps in the gulf of mexico massive abiotic carbonates and calcareous shells of the chemosynthetic mytilid bathymodiolus sp containing a detailed history of hydrocarbon seepage were investigated using radiocarbon and u series isotopes stable carbon isotopes and 87 sr 86 sr ratios were also determined in order to provide insights on the carbon source and the nature of the hydrocarbon rich fluids samples from five seepage sites on the northern gulf of mexico sea floor overlying subsurface salt diapirs and encompassing depths from 125 to 2000 m were selected as representative of the spectrum of active and extinct seeps examined from submersible dives in general paired 14 c and 230 th dates of carbonate buildups consisting of aragonite high mg calcite and dolomite mineralogies are highly discordant the cause of the discordance established on the basis of paired 14 c and 13 c values 14 c 898 to 992 13 c 9 5 to 53 3 for n 27 lies with the impairment of the radiocarbon dates resulting from dilution of the 14 c pool with fossil hydrocarbon derived carbon the validity of the ionium dates based on u rich 2 4 7 6 ppm samples is demonstrated by the concordance between 234 u 238 u and 230 th 234 u evolution in time and by the 234 u 238 u o activity ratios that are generally within the range of sea water value of 1 14 0 04 2 sigma some dolomite rich samples are exceptional because their 234 u 238 u o ratios are significantly higher 1 22 1 38 than sea water suggesting deposition from anoxic pore waters where the soluble u reached anomalous 234 u 238 u ratios the formation of the carbonates from sea water derived fluids rather than from formation fluids advecting from deep aquifers is supported by the 87 sr 86 sr composition of the samples mean 0 709145 19 10 6 n 14 that compares well with modern nonseep marine carbonates and the ambient gulf of mexico sea water 0 709171 8 10 6 calcareous shells the 13 c values of which indicate a carbon source in sea water 13 c 4 3 to 1 1 yield valid radiocarbon ages and show fair concordancy between their radiocarbon and ionium dates isotope migration attested by the observed u uptake in the fossil shells is likely to affect the accuracy of their ionium dates radiometric ages from extinct and senescent seep sites at upper bathyal depths indicate that hydrocarbon seepage occurred there during late pleistocene time 195 13 ka ages derived from nascent seep sites at mid bathyal and abyssal depths 12 3 0 0 ka indicate that currently vigorous seepage was initiated at the end of the last deglaciation these radiometric ages most likely reflect the time of sedimentary loading and associated salt diapirism that activated the fault conduits to the sea floor

the effect of diagenesis and fluid migration on rare earth element distribution in pore fluids of the northern cascadia accretionary margin analytical challenges in obtaining high quality measurements of rare earth elements rees from small pore fluid volumes have limited the application of rees as deep fluid geochemical tracers using a recently developed analytical technique we analyzed rees from pore fluids collected from sites u1325 and u1329 drilled on the northern cascadia margin during the integrated ocean drilling program iodp expedition 311 to investigate the ree behavior during diagenesis and their utility as tracers of deep fluid migration these sites were selected because they represent contrasting settings on an accretionary margin a ponded basin at the toe of the margin and the landward tofino basin near the shelf s edge ree concentrations of pore fluid in the methanogenic zone at sites u1325 and u1329 correlate positively with concentrations of dissolved organic carbon doc and alkalinity fractionations across the ree series are driven by preferential complexation of the heavy rees simultaneous enrichment of diagenetic indicators doc and alkalinity and of rees in particular the heavy elements ho to lu suggests that the heavy rees are released during particulate organic carbon poc degradation and are subsequently chelated by doc ree concentrations are greater at site u1325 a site where shorter residence times of poc in sulfate bearing redox zones may enhance ree burial efficiency within sulfidic and methanogenic sediment zones where ree release ensues cross plots of la concentrations versus cl li and sr delineate a distinct field for the deep fluids z 75 mbsf at site u1329 and indicate the presence of a fluid not observed at the other sites drilled on the cascadia margin changes in ree patterns the presence of a positive eu anomaly and other available geochemical data for this site suggest a complex hydrology and possible interaction with the igneous crescent terrane located east of the drilled transect

petrographic and geochemical characterization of seep carbonate from bush hill gc 185 gas vent and hydrate site of the gulf of mexico abstract authigenic carbonates are common at cold seep sites as a result of microbial oxidation of hydrocarbons seep carbonate samples were collected from the surface of the bush hill green canyon block 185 gulf of mexico a mound containing gas hydrate the carbonates consisted of oily porous limestone slabs and blocks containing bioclasts and matrix analysis by x ray diffraction shows that aragonite is the dominant mineral 89 99 wt with an average of 94 wt in the matrix of seep carbonate this cement occurs in microcrystalline microspar and sparite forms the moderate 13 c depletion of the seep carbonate the most depleted one has 13 c value of 29 4 and 26 of 38 subsamples have 13 c values 20 0 indicates that the non methane hydrocarbons was incorporated during seep carbonate precipitation relative enrichment of 18 o may be related to localized destabilization of gas hydrate or derived from 18 o enriched pore water originated from smectite illite transition in the deep sediments the total content of rare earth elements ree of the 5 hno 3 treated solution of the carbonates is from 0 40 ppm to 30 9 ppm the shale normalized ree patterns show varied ce anomalies from significantly negative slightly negative and no to positive ce anomalies variable content of trace elements total ree and ce anomalies in different samples and even in the different carbonate mineral forms microcrystalline microspar and sparite of the same sample suggest that the formation condition of the bush hill seep carbonate is variable and complex which is possibly controlled by the rate of fluid flux

authigenic carbonates from methane seeps of the northern congo fan microbial formation mechanism abstract authigenic carbonates were collected from methane seeps at hydrate hole at 3113 m water depth and diapir field at 2417 m water depth on the northern congo deep sea fan during rv meteor cruise m56 the carbonate samples analyzed here are nodules mainly composed of aragonite and high mg calcite abundant putative microbial carbonate rods and associated pyrite framboids were recognized within the carbonate matrix the 13c values of the hydrate hole carbonates range from 62 5 to 46 3 pdb while the 13c values of the diapir field carbonate are somewhat higher ranging from 40 7 to 30 7 pdb indicating that methane is the predominant carbon source at both locations relative enrichment of 18o 18o values as high as 5 2 pdb are probably related to localized destabilization of gas hydrate the total content of rare earth elements ree of 5 hno3 treated solutions derived from carbonate samples varies from 1 6 ppm to 42 5 ppm the shale normalized ree patterns all display positive ce anomalies ce ce 1 3 revealing that the carbonates precipitated under anoxic conditions a sample from hydrate hole shows a concentric lamination corresponding to fluctuations in 13c values as well as trace elements contents these fluctuations are presumed to reflect changes of seepage flux

tracing the composition fluid source and formation conditions of the methane derived authigenic carbonates in the gulf of cadiz with rare earth elements and stable isotopes abstract the mineral composition stable carbon and oxygen isotopes and rare earth element ree concentrations in methane derived authigenic carbonates collected from the gulf of cadiz were used to trace fluid sources and examine the controlling factors on ree composition during carbonate formation these authigenic carbonate samples are composed of a detrital fraction mainly quartz and clay cemented by authigenic carbonate minerals aragonite and mg calcite pure mg calcite or dolomite and mg calcite the 13c values of the whole rock samples vary between 45 8 and 9 7 vpdb and 18o values range from 3 7 to 6 9 vpdb the 13c values are indicative of a methane derived source for these carbonates most likely resulting from thermogenic gas or a mixture of thermogenic and biogenic gas the total ree content ree of these authigenic carbonate minerals range from 13 to 31 ppm all but four of the subsamples are lower than a typical marine carbonates 28 ppm this suggests that the ree composition of methane derived authigenic carbonates is controlled primarily by the methane rich fluids the results also show that the ree contents in carbonate mineral subsamples containing dolomite and mg calcite is higher than those subsamples with aragonite suggesting that the authigenic mineral composition and the formation environment are important factors the shale normalized ree patterns of the seep carbonates show no or slightly positive ce anomalies suggesting that the formation of these seep carbonates occurred under anoxic conditions and associated with rapid fluid seepage the correlation results of ce ce and lan smn ce ce and dyn smn and ce ce and ree suggest that the ree characteristics of most seep carbonate samples preserve the original redox conditions of their formation late diagenesis or post oxidation of the samples by their exhumation from the sediments into seawater has little effect on rees therefore it can be assumed these methane derived authigenic carbonates represent primary carbonate phases they have not undergone significant diagenesis and their geochemical and isotopic signatures mainly reflect their formation processes

rare earth elements in cold seep carbonates from the niger delta abstract the circulation of methane rich fluids at cold seeps often leads to precipitation of authigenic carbonates mediated by microbial activity which can be used as archives of fluid seepage on continental margins in this study we have investigated the potential of using rare earth element ree concentrations in authigenic carbonates for tracing fluid sources and providing information on associated biogeochemical processes at cold seeps we have examined various chemical procedures for the analysis of ree in authigenic carbonates and present a robust method using dilute acetic acid solution that allows the extraction of ree from carbonate phases with reduced contamination from fe mn oxides and detrital minerals using this method we analysed a series of carbonate samples collected at various deep sea sites of active fluid seepage on the niger delta for their ree and trace element concentrations 13c and 18o values and 87sr 86sr isotope compositions we show that the ree composition of cold seep carbonates is controlled primarily by that of the fluid from which they have precipitated our results also suggest that significant ree fractionation can occur during carbonate precipitation which can be related to various degrees of ree complexation by organic versus carbonate ligands in response to changing pore water chemical composition for parameters such as carbonate alkalinity

anaerobic methane oxidation and the formation of dolomite abstract we examine the link between organic matter degradation anaerobic methane oxidation amo and sulfate depletion and explore how these processes potentially influence dolomitization we determined rates and depths of amo and dolomite formation for a variety of organic rich sites along the west african margin using data from ocean drilling program odp leg 175 rates of amo are calculated from the diffusive fluxes of ch4 and so4 and rates of dolomite formation are calculated from the diffusive flux of mg we find that the rates of dolomite formation are relatively constant regardless of the depth at which it is forming indicating that the diffusive fluxes of mg and ca are not limiting based upon the calculated log iap values log ksp values for dolomite were found to narrowly range between 16 1 and 16 4 dolomite formation is controlled in part by competition between amo and methanogenesis which controls the speciation of dissolved co2 amo increases the concentration of co32 through sulfate reduction favoring dolomite formation while methanogenesis increases the pco2 of the pore waters inhibiting dolomite formation by regulating the pco2 and alkalinity methanogenesis and amo can regulate the formation of dolomite in organic rich marine sediments in addition to providing a mechanistic link between amo and dolomite formation our findings provide a method by which the stability constant of dolomite can be calculated in modern sediments and allow prediction of regions and depth domains in which dolomite may be forming

new insights into cerium anomalies and mechanisms of trace metal enrichment in authigenic carbonate from hydrocarbon seeps authigenic carbonates that form at marine hydrocarbon seeps provide a unique geological archive of past local environmental conditions and pore fluid geochemistry recent work on such carbonates revealed variable cerium ce anomalies and anomalous enrichments of certain trace metals however the mechanisms accounting for such anomalies remain poorly constrained here we characterize the rare earth element ree patterns of carbonate phases and the trace metal patterns of bulk carbonate rocks sampled at three hydrocarbon seeps located at congo fan pockmarks cf and the gulf of mexico sites ac645 and gb425 the analyzed cf gb425 and ac645 carbonates yielded different ree patterns displaying positive no as well as negative ce anomalies the covariation of molybdenum mo with uranium u including authigenic mo moauth and u uauth enrichments as well as mo u auth ratios proved useful to obtain new insight into the applicability of ce anomalies to constrain past redox conditions trace element patterns suggest that 1 cf carbonates formed in a restricted sulfidic environment while 2 the ac645 site experienced intermittent oxygenation causing negative ce anomalies and 3 environmental conditions were variable at the gb425 mud volcano site interestingly gb425 carbonates show significant mo arsenic as and antimony sb enrichments with the enrichment factor of as asef correlating well with the authigenic fe fraction these results suggest that iron oxyhydroxides played an important role in the adsorption of mo as and sb in the water column and their transfer to the sediment the combination of trace metal and ree geochemistry of authigenic carbonates used here is a promising tool to better assess past variability of redox conditions and biogeochemical processes at marine hydrocarbon seeps

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

rare earth elements in pore waters of marine sediments abstract the rare earth elements rees were measured in pore waters of the upper 25 cm of sediment from one site off peru and three sites on the california margin the pore water ree concentrations are higher than sea water and show systematic down core variations in both concentration and normalized pattern from these analyses and from comparison to other chemical species measured dissolved fe mn ba oxygen nitrate phosphate it is suggested that pore water rees can be grouped into three categories those that are from an fe source those that are from a poc source and cerium oxide rees from the fe source appear where anoxia is reached they have a distinctive middle ree mree enriched pattern the concentrations in this source are so elevated that they dominate ree trends in the fe oxide reduction zone the net result of flux from the poc source is relative enrichment of heavy rees hrees over light rees lrees reflecting remineralizing poc and complexation with doc a common linear ree pattern seen in both oxic and anoxic sediments is associated with this poc source as well as a hree enriched pattern that is seen in surficial sediments at the peru site overall the pore water results indicate that mn oxides are not an important carrier of rees in the oceans a ree biogeochemical model is presented which attempts to reconcile ree behavior in the water and sediment columns of the oceans the model proposes that poc fe oxide and ce oxide sources can explain the ree concentration profiles and relative abundance patterns in environments ranging from oxic sea water to anoxic pore water the model is also consistent with our observation that the ce anomaly of pore water does not exceed unity under any redox condition

tree ring responses to the 1978 earthquake at stephens pass northeastern california the 1978 earthquake at stephens pass northeastern california dropped a series of grabens that average 4 5 m in width extend up to 1 m in depth and are found intermittently along a 2 km long rupture zone the formation of this graben series killed or otherwise affected many trees growing in or immediately adjacent to the rupture zone nine trees responded to the 1978 earthquake with anomalously narrow ring widths beginning in 1979 and continuing for several years one tree responded with anomalously wide latewood relative to total ring width this example of tree ring responses to a normal fault earthquake complements other cases of tree growth responses to earthquakes of thrust and strike slip tectonic settings the 1978 earthquake at stephens pass was unique in that it caused tree ring responses even though it was only moderate magnitude 4 6 this study serves as a specific calibration example for dendrochronologically studying prehistoric earthquakes as well as eruptions at the nearby medicine lake highlands medicine lake has been seismically and volcanically active during the past 1000 yr and it supports a forest of several coniferous tree species that can be used for dendrochronologically studying geomorphological processes

seep carbonates and preserved methane oxidizing archaea and sulfate reducing bacteria fossils suggest recent gas venting on the seafloor in the northeastern south china sea seep carbonates formed by the synergistic metabolism of methane oxidizing archaea moa and sulfate reducing bacteria srb have been found in many places worldwide but have not been found to date in the south china sea mud volcanoes and shale diapirs have been reported in the south china sea however and microscope and geochernical analysis of carbonates dredged where bottom simulating reflectors bsr suggest the presence of gas hydrate on the northeastern continental slope of the south china sea suggest that the carbonates are hydrocarbon seep related carbonates the carbonates we dredged are chimney like and preserve moa srb fossils their very light carbon isotopic compositions 51 25 to 51 76 parts per thousand suggest that their carbon was derived from microbial methane oxidization these seep carbonates and their preserved moa srb fossils imply gas venting has occurred recently on the seafloor in the northeastern continental slopes in the south china sea c 2005 elsevier ltd all rights reserved

a multidisciplinary study of middle miocene seep carbonates from the northern apennine foredeep italy several pelitic intervals are intercalated at various levels within the marly arenaceous turbiditic successions of the middle miocene northern apennine foredeep they range in thickness from 30 to 200 m and represent sedimentation on top of ephemeral structural highs related to blind faults sediments are made up of hemipelagites and fine grained turbidites and include 13c depleted carbonates related to the rising of methane rich fluids hydrocarbon seep carbonates large portions of pelitic intervals are involved in chaotic masses by soft sediment deformation slumps slides intraformational breccias revealing an intense sediment instability during middle miocene a stratigraphic mineralogic and geochemical study was conducted on two of these pelitic intervals castagno d andrea mt citerna in order to reconstruct carbonate development the composition of fluids and to document the connections between fluid seepage and syndepositional tectonics this multidisciplinary approach has allowed us to discriminate between the two examined pelitic intervals in terms of age depositional rates and conditions organic carbon and post depositional processes seep carbonates are characterized by chemosymbiotic fossil communities autoclastic fractures and brecciation carbonate bodies show complex facies relationships as indicative of different stages in chemoherm growth the compositional study evidences the peculiar chemistry of chemoherm carbonates calcite low in mg and sr compared with carbonates in associated enclosing pelites and with modern chemoherms in general the non carbonate components within the chemoherms are enriched in detrital minerals and depleted in phyllosilicates with respect to the enclosing pelites the mineralogical changes in the clay component within the brecciated unit of the castagno d andrea chemoherms suggest authigenic precipitation of the mg rich phases isotopic analyses show the distinct carbon signature in the chemoherms from the two examined intervals castagno d andrea chemoherms more depleted from 15 8 up to 41 3 pdb than mt citerna from 5 2 up to 16 7 and the transitional 13c depletion trend observed moving from chemoherms to the enclosing pelites moderately depleted and te bouma sequence turbidites in the range of marine carbonates a slight but significant enrichment in 18o up to 1 4 pdb is observed for all chemoherms when compared to values of carbonate phases present in enclosing pelites geochemical data indicate that the brecciated facies of seep carbonates are related to an explosive release of gaseous fluids probably associated with the rise of deep hypersaline fluids

lower eocene carbonate cemented chimneys varna ne bulgaria formation mechanisms and the a biological mediation of chimney growth abstract in the area of pobiti kamani varna northeast bulgaria massive carbonate cemented columns chimneys up to 1 5 m diameter and 8 m high and horizontal interbeds 1 5 m thickness occur in dispersed outcrops over an area of 70 km2 within loose lower eocene sands field observations and petrographical and stable isotope geochemical characterisation of four studied locations reveal a relationship between these structures and processes of ancient hydrocarbon seepage column and interbed structures both consist of similar well sorted silt to sand sized nummulitic host sediments predominantly cemented by early diagenetic low magnesium calcite filamentous textures about 10 m in diameter and 80 650 m long are only locally detected within interparticle calcite cement of columns column samples from two sites reveal a similar linear and inverse covariant trend of 13c 18o values which was interpreted as a mixing trend between two end member fluid precipitation conditions i e 1 a methane and or higher hydrocarbon derived carbon member characterised by 13c values as low as 43 and marine controlled precipitation conditions with 18o of 1 0 5 v pdb and 2 a member with less contribution of methane which was mixed most likely with less depleted carbon sources explaining 13c values ranging up to 8 v pdb the corresponding depleted 18o values with many samples clustering around 8 v pdb are interpreted in terms of precipitation at elevated temperatures this suggests the venting system was not a true cold seep sensu stricto furthermore column cross transects often document an internal pattern consisting of concentric zones with distinct isotopic signatures which vary between the two end members the mixing and internal pattern of column isotopic data together with petrographical observations are qualitatively interpreted as evidence of alternating precipitation conditions controlled by varying seepage rates of a single fluid source at depth during build up of individual chimney pipes near the sediment surface based on several field observations migration of the hydrocarbon charged fluids in lower eocene times was possibly channelled along ne oriented faults isotopic signatures of calcite cemented horizontal interbeds with depleted 18o ratios as low as 8 88 v pdb and variable 13c 1 to 16 mainly around 5 to 7 suggest that ascending fluids contributed to their cementation or resetted the calcite cement isotopic signature predominantly during periods of active seepage of warmer fluids only few petrographical and preliminary lipid biomarker evidence has been found pointing to the presence or possibly former activity of microbiota involved in carbon cycling and calcite precipitation typical of cold seep settings this may result from diagenetic alteration of organic components however considering the processes of chimney formation a cementation process governed by the inorganic oxidation of hydrocarbons in which interstitial oxygen is rapidly consumed without bacterial mediation is considered

rare earth elements in authigenic methane seep carbonates as tracers for fluid composition during early diagenesis abstract authigenic carbonates forming at an active methane seep on the makran accretionary prism mainly consist of aragonite in the form of microcrystalline cryptocrystalline and botryoidal phases the 13 c carbonate values are very negative 49 0 to 44 0 v pdb agreeing with microbial methane as dominant carbon source the 18 o carbonate values are exclusively positive 3 0 to 4 5 v pdb and indicate precipitation in equilibrium with seawater at bottom water temperatures the content of rare earth elements and yttrium ree y determined by laser ablation inductively coupled plasma mass spectrometry la icp ms and solution icp ms varies for each aragonite variety with early microcrystalline aragonite yielding the highest cryptocrystalline aragonite intermediate and later botryoidal aragonite the lowest ree y concentrations shale normalised ree y patterns of different types of authigenic carbonate reflect distinct pore fluid compositions during precipitation microcrystalline aragonite shows high contents of middle rare earth elements mree reflecting ree patterns ascribed to anoxic pore water cryptocrystalline aragonite exhibits a seawater like ree y pattern at elevated total ree y concentrations indicating higher concentrations of rees in pore waters which were influenced by seawater botryoidal aragonite is characterised by seawater like ree y patterns at initial growth stages followed by an increase of light rare earth elements lree with advancing crystal growth reflecting changing pore fluid composition during precipitation of this cement conventional sample preparation involving micro drilling of carbonate phases and subsequent solution icp ms does not allow to recognise such subtle changes in the ree y composition of individual carbonate phases to be able to reconstruct the evolution of pore water composition during early diagenesis an analytical approach is required that allows to track the changing elemental composition in a paragenetic sequence as well as in individual phases high resolution analysis of seep carbonates from the makran accretionary prism by la icp ms reveals that pore fluid composition not only evolved in the course of the formation of different phases but also changed during the precipitation of individual phases

stratigraphic evidence of a middle pleistocene climate driven flexural uplift in the alps 1 this interdisciplinary study on the subsurface stratigraphy of the po plain northern italy brings new evidence in support of a climate driven erosional unloading of the alps since the middle pleistocene a newly acquired high resolution seismic profile and a critical review of industrial seismic lines were integrated with sedimentologic observations on four magnetostratigraphically dated continental cores to reconstruct a three sequence evolution of the pleistocene clastic infill in the northern po basin during the first sequence ps1 1 4 0 87 ma characterized by sedimentation rates of 34 cm kyr outpacing regional subsidence meandering river systems prograded over the basin passing downstream to a cyclothemic shelfal succession the second sequence ps2 0 87 0 45 ma heralded by a regional unconformity r surface correlated to the onset of the major pleistocene glaciations was characterized by widespread continental sedimentation of generally distal braidplain the third sequence ps3 0 45 ma to present marked at the base by another regional unconformity y surface is characterized by proximal braided fluvial deposition under combined conditions of confinement erosion and bypass we interpret the ps3 sequence as deposited under the effects of a flexural uplift of the northern po plain during the middle pleistocene starting at 0 45 ma in response to the long term erosional unloading of the alps triggered by the waxing and waning of alpine glaciers since the late early pleistocene global cooling 0 9 ma according to our modeling erosion on a relatively limited area of the alpine mountain chain ranging from 1 3 to 1 7 mm yr in the axial sector to 0 1 0 3 mm yr at the margins has been able to trigger rock uplift over a wider area including the proximal peripheral basins

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

rare earth element cycling in the pore waters of the bering sea slope iodp exp 323 abstract we studied the diagenetic behavior of rare earth elements rees in a highly productive passive margin setting of the bering sea slope site u1345 was drilled during the integrated ocean drilling program expedition 323 at a water depth of 1008 m currently in the center of an oxygen minimum zone pore water concentrations of fourteen rees were determined down to 140 meters below the seafloor mbsf the ree concentrations were higher in the pore water than the deep seawater indicating that there was significant liberation from the sediments during diagenesis there was a major peak at 10 mbsf that was more pronounced for the heavy ree hree this peak occurred below the sulfate methane transition zone 6 3 mbsf and coincided with high concentrations of dissolved iron and manganese at 2 mbsf there was a minor peak in ree and mn contents below 40 mbsf the ree concentration profiles remained constant the ce anomaly was insignificant and relatively constant paas normalized ce ce 1 1 0 2 throughout the depth profile showing that the ce depleted in seawater was restored in the pore water hree enrichment was observed over the entire 140 m except for the upper 1 m where a middle ree mree bulge was apparent ree release in shallow depths 2 4 mbsf is attributed to the release of light rees lrees and mrees during the organoclastic reduction of mn oxides in anoxic sediments the high hree concentrations observed at 10 mbsf can be attributed to the reduction of fe and mn minerals tied to anaerobic oxidation of methane or less significantly to ferromagnesian silicate mineral weathering the upward diffusion flux across the sediment water interface was between 3 for tm and 290 for ce pmol m 2 y 1

first dated human occupation of italy at 0 85 ma during the late early pleistocene climate transition abstract a candidate for the oldest human occupation site in italy is monte poggiolo where the lithic tool bearing levels are currently dated to 1 ma based on electron spin resonance esr the low analytical precision of 30 at 2 makes it unclear whether the date actually conflicts with a recent reassessment of age constraints on key hominin sites from italy france and spain pointing to a uniformly young timing for the earliest habitation of southern europe during the late early pleistocene climate transition within reverse magnetic polarity subchron c1r 1r 0 988 0 781 ma our new magnetostratigraphic and biostratigraphic results show a sequence of stable normal and reverse polarities in a regional lithostratigraphic context that indicate the monte poggiolo tool bearing site post dates the jaramillo normal polarity subchron most probably occurring at 0 85 ma immediately after the pronounced cooling that culminated with marine isotope stage 22 when the associated regression may have opened new migration routes through the po valley for large mammals and hominins

evidence for intense ree scavenging at cold seeps from the niger delta margin for many trace elements continental margins are the location of intense exchange processes between sediment and seawater which control their distribution in the water column but have yet to be fully understood in this study we have investigated the impact of fluid seepage at cold seeps on the marine cycle of neodymium we determined dissolved and total dissolvable td concentrations for ree and well established tracers of fluid seepage ch4 tdfe tdmn and nd isotopic compositions in seawater samples collected above cold seeps and a reference site i e away from any fluid venting area from the niger delta margin we also analyzed cold seep authigenic phases and various core top sediment fractions pore water detrital component easily leachable phases uncleaned foraminifera recovered near the hydrocast stations methane tdfe and tdmn concentrations clearly indicate active fluid venting at the studied seeps with plumes rising up to about 100 m above the seafloor depth profiles show pronounced ree enrichments in the non filtered samples td concentrations within plumes whereas filtered samples dissolved concentrations exhibit slight ree depletion in plumes relative to the overlying water column and display typical seawater ree patterns these results suggest that the net flux of ree emitted into seawater at cold seeps is controlled by the presence of particulate phases most probably fe mn oxyhydroxides associated to resuspended sediments at the reference site however our data reveal significant enrichment for dissolved ree in bottom waters that clearly relates to diffusive benthic fluxes from surface sediments neodymium isotopic ratios measured in the water column range from end 15 7 to 10 4 evidence that the end values for antarctic intermediate waters aaiw differed from those reported for the same water mass at open ocean settings shows that sediment water interactions take place in the gulf of guinea at each site however the bottom water end signature generally differs from that for cold seep minerals easily leachable sediment phases and detrital fractions from local sediments ruling out the possibility that seepage of methane rich fluids and sediment dissolution act as a substantial source of dissolved nd to seawater in the gulf of guinea taken together our data hence suggest that co precipitation of fe mn oxyhydroxide phases in sub surface sediments leads to quantitative scavenging of dissolved ree at cold seeps preventing their emission into bottom waters most probably it is likely that diffusion from suboxic surface sediments dominates the exchange processes affecting the marine nd cycle at the niger delta margin

authigenic carbon entombed in methane soaked sediments from the northeastern transform margin of the guaymas basin gulf of california extensive rov based sampling and exploration of the seafloor was conducted along an eroded transform parallel fault scarp on the northeastern side of the guaymas basin in the gulf of california to observe the nature of fluids venting from the seafloor measure the record left by methane venting on the carbonates from this area and determine the association with gas hydrate one gas vent vigorous enough to generate a water column gas plume traceable for over 800 m above the seafloor was found to emanate from a 10 cm wide orifice on the eroded scarp face sediment temperature measurements and topography on a sub bottom reflector recorded in a transform parallel seismic reflection profile identified a subsurface thermal anomaly beneath the gas vent active chemosynthetic biological communities cbcs and extensive authigenic carbonates that coalesce into distinct chemoherm structures were encountered elsewhere along the eroded transform parallel scarp the carbon isotopic composition of methane bubbles flowing vigorously from the gas vent 53 6 0 8 pdb is comparable to methane found in sediment cores taken within the cbcs distributed along the scarp 51 9 8 1 pdb however the 13c value of the co2 in the vent gas 12 4 1 1 pdb is very distinct from those for dissolved inorganic carbon dic 35 8 to 2 9 pdb found elsewhere along the scarp including underneath cbcs the 13c values of the carbonate rich sediments and rocks exposed on the seafloor today also span an unusually large range 40 9 to 12 9 pdb and suggest two distinct populations of authigenic carbonate materials were sampled unconsolidated sediments and some carbonate rocks which have lithologic evidence for near seafloor formation have negative 13c values while carbonate rocks that clearly formed in the subsurface have positive 13c values up to 23 0 close to that measured for co2 in the vent gas there appears to be two carbon sources for the authigenic carbonates 1 deeply sourced isotopically heavy co2 12 and 2 isotopically light dic derived from local anaerobic oxidation of methane at the sulfate methane interface in the shallow subsurface addition of isotopically light methane derived carbon at the seafloor may completely mask the isotopically heavy co2 signature 12 4 in the underlying sediments thus the authigenic carbonates may have formed from the same methane and carbon dioxide bearing fluid but under different migration and alteration conditions depending on how it migrated through the sediment column

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

u th systematics and ages of authigenic carbonates from hydrate ridge cascadia margin recorders of fluid flow variations uranium u concentrations and activity ratios 234u of authigenic carbonates are sensitive recorders of different fluid compositions at submarine seeps of hydrocarbon rich fluids cold seeps at hydrate ridge off the coast of oregon usa the low u concentrations mean 1 3 0 4 g g and high 234u values 165 317 of gas hydrate carbonates reflect the influence of sedimentary pore water indicating that these carbonates were formed under reducing conditions below or at the seafloor their 230th 234u ages span a time interval from 0 8 to 6 4 ka and cluster around 1 2 and 4 7 ka in contrast chemoherm carbonates precipitate from marine bottom water marked by relatively high u concentrations mean 5 2 0 8 g g and a mean 234u ratio of 166 3 their u isotopes reflect the 234u ratios of the bottom water being enriched in 234u relative to normal seawater simple mass balance calculations based on u concentrations and their corresponding 234u ratios reveal a contribution of about 11 of sedimentary pore water to the bottom water from the u pore water flux and the reconstructed u pore water concentration a mean flow rate of about 147 68 cm a can be estimated 230th 234u ages of chemoherm carbonates range from 7 3 to 267 6 ka 230th 234u ages of two chemoherms alvin and se knoll chemoherm correspond to time intervals of low sealevel stands in marine isotope stages mis 2 4 5 6 7 and 8 this observation indicates that fluid flow at cold seep sites sensitively reflects pressure changes of the hydraulic head in the sediments the 18o pdb ratios of the chemoherm carbonates support the hypothesis of precipitation during glacial times deviations of the chemoherm 18o values from the marine 18o record can be interpreted as to reflect temporally and spatially varying bottom water and or vent fluid temperatures during carbonate precipitation between 2 6 and 8 6 c

rare earth elements of seep carbonates indication for redox variations and microbiological processes at modern seep sites at marine seeps methane is microbially oxidized resulting in the precipitation of carbonates close to the seafloor methane oxidation leads to sulfate depletion in sediment pore water which induces a change in redox conditions rare earth element ree patterns of authigenic carbonate phases collected from modern seeps of the gulf of mexico the black sea and the congo fan were analyzed different carbonate minerals including aragonite and calcite with different crystal habits have been selected for analysis total ree content sigma ree of seep carbonates varies widely from 0 1 ppm to 42 5 ppm but a common trend is that the sigma ree in microcrystalline phases is higher than that of the associated later phases including micospar sparite and blocky cement suggesting that sigma ree may be a function of diagenesis the shale normalized ree patterns of the seep carbonates often show different ce anomalies even in samples from a specific site suggesting that the formation conditions of seep carbonates are variable and complex overall our results show that apart from anoxic oxic conditions are at least temporarily common in seep environments c 2012 elsevier ltd all rights reserved