shallow marine carbon and oxygen isotope and elemental records indicate icehouse greenhouse cycles during the early jurassic 1 for much of the mesozoic record there has been an inconclusive debate on the possible global significance of isotopic proxies for environmental change and of sequence stratigraphic depositional sequences we present a carbon and oxygen isotope and elemental record for part of the early jurassic based on marine benthic and nektobenthic molluscs and brachiopods from the shallow marine succession of the cleveland basin uk the invertebrate isotope record is supplemented with carbon isotope data from fossil wood which samples atmospheric carbon new data elucidate two major global carbon isotope events a negative excursion of 2 at the sinemurian pliensbachian boundary and a positive excursion of 2 in the late pliensbachian the sinemurian pliensbachian boundary event is similar to the slightly younger toarcian oceanic anoxic event and is characterized by deposition of relatively deepwater organic rich shale the late pliensbachian strata by contrast are characterized by shallow marine deposition oxygen isotope data imply cooling locally for both events however because deeper water conditions characterize the sinemurian pliensbachian boundary in the cleveland basin the temperature drop is likely of local significance in contrast a cool late pliensbachian shallow seafloor agrees with previous inference of partial icehouse conditions both the large scale long term and small scale short duration isotopic cycles occurred in concert with relative sea level changes documented previously from sequence stratigraphy isotope events and the sea level cycles are concluded to reflect processes of global significance supporting the idea of an early jurassic in which cyclic swings from icehouse to greenhouse and super greenhouse conditions occurred at timescales from 1 to 10 ma

global dinoflagellate event associated with the late paleocene thermal maximum the late paleocene thermal maximum or lptm ca 55 ma represents a geologically brief time interval 220 k y characterized by profound global warming and associated environmental change the lptm is marked by a prominent negative carbon isotope excursion cie interpreted to reflect a massive and abrupt input of 12 c enriched carbon to the ocean atmosphere reservoir possibly as a result of catastrophic gas hydrate release on time scales equivalent to present day rates of anthropogenic carbon input the lptm corresponds to important changes in the global distribution of biota including mass extinction of marine benthic organisms the dinoflagellate cyst record indicates that surface dwelling marine plankton in marginal seas also underwent significant perturbations during the lptm we report on the dramatic response of representatives of the genus apectodinium from two upper paleocene lower eocene sections in the southern new zealand and northern austria hemispheres where the dinoflagellate records are directly correlated with the cie benthic foraminifera extinction event and calcareous nannofossil zonation the results indicate that the inception of apectodinium dominated assemblages appears to be synchronous on a global scale and that the event is precisely coincident with the beginning of the lptm apectodinium markedly declined in abundance near the end of the lptm this apectodinium event may be associated with 1 exceptionally high global sea surface temperatures and or 2 a significant increase in marginal marine surface water productivity such a globally synchronous acme of dinoflagellate cysts is unprecedented within the dinoflagellate cyst fossil record

light hydrocarbon gases in guaymas basin hydrothermal fluids thermogenic versus abiogenic origin light hydrocarbon gases methane through pentane in high temperature hydrothermal fluids of the guaymas basin gulf of california are predominantly derived from thermocatalysis of organic carbon in sediments intruded by mid ocean ridge volcanic rocks the spectrum of c1 c5 gases in guaymas basin hydrothermal fluids is characterized by a preponderance of alkanes with essentially no alkenes present comparison with high temperature fluids from 21 n on the east pacific rise where geochemical evidence indicates a distinct lack of thermogenic gas and where methane is derived abiogenically from the basalts shows that the 21 n hydrocarbon gases are characterized by a prominent ethylene signature stable isotope compositions of guaymas basin m thane differ from 21 n gas guaymas basin has dgr13c values of 43 to 51 pmil vs pdb compared to 21 n where values as high as 15 pmil have been measured these differences reflect the different origins of light hydrocarbon gases in the two systems with guaymas methane being overwhelmingly of an organic thermogenic derivation and showing no evidence of the abiogenic basalt derived gas that characterizes the 21 n environment carbon isotope analyses of dissolved inorganic carbon in guaymas basin hydrothermal fluids indicate that high temperature hydrocarbon oxidation may be an important process acting in conjunction with high temperature thermocatalytic hydrocarbon generation

dissociation of oceanic methane hydrate as a cause of the carbon isotope excursion at the end of the paleocene isotopic records across the latest paleocene thermal maximum lptm indicate that bottom water temperature increased by more than 4 c during a brief time interval 104 years of the latest paleocene 55 6 ma there also was a coeval 2 to 3 excursion in the 13c of the ocean atmosphere inorganic carbon reservoir given the large mass of this reservoir a rapid 13c shift of this magnitude is difficult to explain within the context of conventional hypotheses for changing the mean carbon isotope composition of the ocean and atmosphere however a direct consequence of warming bottom water temperature from 11 to 15 c over 104 years would be a significant change in sediment thermal gradients and dissociation of oceanic ch4 hydrate at locations with intermediate water depths in terms of the present day oceanic ch4 hydrate reservoir thermal dissociation of oceanic ch4 hydrate during the lptm could have released greater than 1 1 to 2 1 1018 g of carbon with a 13c of approximately 60 the release and subsequent oxidation of this amount of carbon is sufficient to explain a 2 to 3 excursion in 13c across the lptm fate of ch4 in oceanic hydrates must be considered in developing models of the climatic and paleoceanographic regimes that operated during the lptm

mud volcanism in the gulf of cadiz results from the ttr 10 cruise a new deep water mud volcano field between 2000 and 3500 m water depth was discovered in the deep south portuguese margin as well as several new mud volcanoes in the south spanish and western moroccan margins of the gulf of cadiz during the ttr 10 training through research unesco ioc cruise in july august 2000 this work followed the discovery of a large mud volcano field in the gulf of cadiz first investigated during the ttr 9 cruise gardner 2001 geophys res lett 28 339 342 kenyon et al 2000 ioc technical series no 56 the discoveries were made based on a seamap side scan sonar mosaic and multibeam bathymetry seabeam collected in the area by the naval research laboratory nrl washington dc usa in 1992 kindly released for this purpose single channel seismics long range side scan sonar okean tv controlled grab hull mounted 3 5 khz profiler and coring were used to investigate several seafloor features observed on the side scan sonar imagery in the south iberia spanish and moroccan margins of the gulf of cadiz which were confirmed to be mud volcanoes the typical structures related to fluid venting in the gulf of cadiz are essentially represented by conical mud volcanoes with diameters ranging from several tens of meters to 4 km and heights that can reach 200 m some of these structures appear to be aligned along major conjugate ne sw and nw se trending faults that can be identified on the side scan sonar imagery the new field discovered in the south portuguese margin is the deepest in the gulf of cadiz area and includes three new mud volcanoes bonjardim olenin and carlos ribeiro which seem to be quite active with near surface gas hydrate occurrence and a high saturation in h2s and hydrocarbon gases mainly methane in the mud breccia and overlying pelagic sediments gas hydrates were recovered from the bonjardim mud volcano an intensely gassified mud breccia with one fragment of semi consolidated claystone with a thin bituminous veneer at the surface was recovered from the carlos ribeiro mud volcano the fauna recovered consists mainly of pogonophoran worms belonging to several species and undetermined species of foraminifera three new mud volcanoes were also discovered in the nw moroccan margin rabat student and jesus baraza these show a richer fauna that includes several species of molluscs polychaetes pogonophoran worms crustaceans echinoderms and some fragments of dead coral madrepora and lophelia carbonate crusts were recovered from the student mud volcano the ginsburg mud volcano discovered during the previous ttr 9 cruise was revisited and gas hydrates recovered once again a new mud volcano was also discovered in the spanish margin tasyo where evidence was found of coral build ups on the hard substratum of the mud volcanic edifice

discovery of hydrothermal vent fields on alarcon rise and in southern pescadero basin gulf of california author s paduan jb zierenberg ra clague da spelz rm caress dw troni g thomas h glessner j lilley md lorenson t lupton j neumann f santa rosa del rio ma wheat cg abstract 2018 the authors hydrothermal vent fields located in the gap between known sites in guaymas basin and 21 n on the east pacific rise were discovered on the alarcon rise and in southern pescadero basin the alarcon rise spreading segment was mapped at 1 m resolution by an autonomous underwater vehicle individual chimneys were identified using the bathymetric data vent fields were interpreted as active from temperature anomalies in water column data and observed and sampled during remotely operated vehicle dives the ja sit pericu and meyibo active fields are near the eruptive fissure of an extensive young lava flow vent fluids up to 360 c from meyibo have compositions similar to northern east pacific rise vents the tzab ek field is 850 m west of the volcanic axis and active chimneys rise up to 33 m above a broad sulfide mound the inactive field is 10 km north northeast along the rift axis and most sulfide chimneys are enriched in zn and associated elements that are transported at lower temperature compared to the more cu rich active fields in southern pescadero basin the auka field is on the margin of a sediment filled graben at 3 670 m depth discharging fluids are clear contain hydrocarbons and have neutral ph elevated salinity and temperatures up to 291 c they have deposited massive mounds of calcite with minor sulfide the fluids are compositionally similar to those in guaymas basin produced by high temperature basalt seawater interaction followed by reaction with sediment the paucity of sulfide minerals suggests subsurface deposition of metals

sediment hosted geothermal systems review and first global mapping abstract sediment hosted geothermal systems shgss are hybrid geological systems where volcanic and sedimentary domains interact leading to mixtures of inorganic and organic gases typically characterized by geothermal thermometamorphic or mantle derived co2 and biotic microbial or thermogenic ch4 shgss occur in sedimentary basins crossed by magmatic intrusions or involved in volcanic plumbing systems these systems can be of considerable interest for petroleum exploration and natural greenhouse gas emission studies but systematic studies for their characterization and worldwide distribution are missing here we provide a review of shgss identified so far and propose methodological criteria for their definition and identification based on integrated geological and gas geochemical parameters we find that shgss are typically characterized by a fluids dominated by mantle or decarbonation methamorphic co2 50 vol b considerable amounts of ch4 and heavier hydrocarbons at least 1 5 vol generally up to 30 40 vol produced by microbial or thermogenic degradation of organic matter hosted in sedimentary rocks c tectonically active sedimentary basins back arc rift zones and foredeep generally hosting petroleum fields and within 300 km from recent or ancient volcanic centers this analysis resulted in a global map including a first set of 33 shgss located in north america central and eastern europe far east eastern oceania and northern new zealand and a second set of potential shgs prone areas occurring also in south america north africa middle east and kamchatka the present shgs map can evolve on the basis of more detailed geological analysis and new gas geochemical data

a three dimensional model of the mean and seasonal circulation of the gulf of california 1 the mean and seasonal circulation of the gulf of california is simulated with a three dimensional numerical model forced by the pacific ocean through specifying the sea level the temperature and the salinity fields at its entrance at the sea surface the wind and the heat and freshwater fluxes are specified the model reproduces the observed mean and seasonal variability of sea level of heat and salt balances and the sea surface temperature sst climatology it also reproduces the general surface circulation of the northern gulf which consists of a seasonally reversing basin wide gyre it is found that tides and heat fluxes are both indispensable to reproduce the spatial structure and temporal evolution of the sst tides provide the mixing to upwell the cooler subsurface waters in the large islands area and the heating from the surface raises the sst the general circulation of the southern part of the gulf is due to the wind and the pacific forcing in the ekman layer two periods of anticyclonic circulation and one cyclonic per year occur below this layer two cyclonic periods develop in the northern part the tides play an important role in producing mean residual currents and both tides and winds compete against the pacific forcing to produce a cyclonic and anticyclonic circulation once a year contrary to conclusions of previous studies the thermohaline circulation is found to be unimportant in the gulf

an attempt to constrain the age duration and eruptive history of the karoo flood basalt naude s nek section south africa we have carried out paleomagnetic sampling of a similar to 750 m sequence of the karoo large igneous province naude s nek pass south africa k ar dating cassignol gillot has been performed on four samples from the 650 m upper unit mean age 179 2 1 8 ma and a sample from the lower unit 184 8 2 6 ma a succession of two phases of volcanism is suggested the lower 25 flows 115 m thick have recorded a reversed polarity the next 23 flows 135 m thick are transitional and contribute a detailed record of the van zijl 1962 jurassic reversal the upper 38 flows 500 m thick have normal polarity directional groups dgs of lava flows with quasi identical remanence directions indicate eruption durations too short to have recorded geomagnetic secular variation and hence are interpreted as single eruptive events altogether 19 dgs and 10 sheet lobes yield a sequence of 29 distinct directions this could correspond to a total eruptive activity shorter than 3000 years less than one per mil of the total duration over which the section was emplaced we obtain a new paleomagnetic pole for south africa at similar to 180 ma lambda 75 2 degrees n phi 276 4 degrees e a 95 5 8 degrees n 19 which is consistent with earlier reports

magma transport through the crust via interconnected sill complexes three dimensional seismic data from the volcanic margin offshore norway have been used to map the complex three dimensional geometry of two major sill complexes these data show that the complexes consist of bowl shaped or inclined sheetlike discordant sills that intersect with one another over a vertical distance of 8 12 km and transect basement and sedimentary rocks of the middle to upper crust using a simple graphical technique we demonstrate the interconnectedness of the sill complex and hence the maximum time for sill emplacement we show that sills are interconnected by junctions occurring systematically at the lowest points of the overlying sills and hence that the sill complex could have acted as a single throughgoing magmatic plumbing system transporting mafic melts from mid lower crustal depths to near surface based on this imaging of the magmatic plumbing system we conclude that sills can form viable and efficient conduits for crustal magma transport in volcanic margins and may play a role in feeding large extrusive complexes

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

rising arctic ocean temperatures cause gas hydrate destabilization and ocean acidification vast amounts of methane hydrates are potentially stored in sediments along the continental margins owing their stability to low temperature high pressure conditions global warming could destabilize these hydrates and cause a release of methane ch 4 into the water column and possibly the atmosphere since the arctic has and will be warmed considerably arctic bottom water temperatures and their future evolution projected by a climate model were analyzed the resulting warming is spatially inhomogeneous with the strongest impact on shallow regions affected by atlantic inflow within the next 100 years the warming affects 25 of shallow and mid depth regions containing methane hydrates release of methane from melting hydrates in these areas could enhance ocean acidification and oxygen depletion in the water column the impact of methane release on global warming however would not be significant within the considered time span

delimitation of ground failure zones due to land subsidence using gravity data and finite element modeling in the queretaro valley mexico abstract sedimentary basins of arid and semiarid zones are often subject to regimes of intense ground water withdrawal as it is normally the only source of water for development of communities an associated phenomenon is land subsidence which can develop to ground failures and consequently damage to infrastructure aquifer deformation can be analyzed using a stress strain or a flux force approach depending on the aquifer material compact or loose and on whether the water withdrawal forms a predominant flow direction toward a cone of depression geometry of the aquifer system also plays an important role as uneven thickness induces differential compaction and hence tensional and shear stresses on the ground mass in this work we present a stress strain approach to analyze subsidence for an unconfined aquifer of varying thickness this is done in two steps namely when the aquifer is in equilibrium and when it is totally depleted using this scheme in a region where ground failure is evident a portion of the aquifer system of the queretaro valley is analyzed the geometry of the hydrologic basement is first modeled using gravity measurements properly correlated with wells and field data then a stress analysis is implemented using the finite element method in order to identify probable zones of ground weakness which are calibrated with known ground failures the results indicate that both tensional and shear stress are present which induce ground failure in the form of surface faults

a blast of gas in the latest paleocene simulating first order effects of massive dissociation of oceanic methane hydrate carbonate and organic matter deposited during the latest paleocene thermal maximum is characterized by a remarkable 2 5 excursion in delta 13c that occurred over approximately 10 4 yr and returned to near initial values in an exponential pattern over approximately 2 x 10 5 yr it has been hypothesized that this excursion signifies transfer of 1 4 to 2 8 x 10 18 g of ch4 from oceanic hydrates to the combined ocean atmosphere inorganic carbon reservoir a scenario with 1 12 x 10 18 g of ch4 is numerically simulated here within the framework of the present day global carbon cycle to test the plausibility of the hypothesis we find that 1 the delta 13c of the deep ocean shallow ocean and atmosphere decreases by 2 3 over 10 4 yr and returns to initial values in an exponential pattern over approximately 2 x 10 5 yr 2 the depth of the lysocline shoals by up to 400 m over 10 4 yr and this rise is most pronounced in one ocean region and 3 global surface temperature increases by approximately 2 degrees c over 10 4 yr and returns to initial values over approximately 2 x 10 6 yr the first effect is quantitatively consistent with the geologic record the latter two effects are qualitatively consistent with observations thus significant ch4 release from oceanic hydrates is a plausible explanation for observed carbon cycle perturbations during the thermal maximum this conclusion is of broad interest because the flux of ch4 invoked during the maximum is of similar magnitude to that released to the atmosphere from present day anthropogenic ch4 sources

geomechanics of subsurface water withdrawal and injection land subsidence and uplift ground ruptures and induced seismicity are the principal geomechanic effects of groundwater withdrawal and injection the major environmental consequence of groundwater pumping is anthropogenic land subsidence the first observation concerning land settlement linked to subsurface processes was made in 1926 by the american geologists pratt and johnson who wrote that the cause of subsidence is to be found in the extensive extraction of fluid from beneath the affected area since then impressive progress has been made in terms of a recognizing the basic hydrologic and geomechanic principles underlying the occurrence b measuring aquifer compaction and ground displacements both vertical and horizontal c modeling and predicting the past and future event and d mitigating environmental impact through aquifer recharge and or surface water injection the first milestone in the theory of pumped aquifer consolidation was reached in 1923 by terzaghi who introduced the principle of effective intergranular stress in the early 1970s the emerging computer technology facilitated development of the first mathematical model of the subsidence of venice made by gambolati and freeze since then the comprehension measuring and simulation of the occurrence have improved dramatically more challenging today are the issues of ground ruptures and induced triggered seismicity which call for a shift from the classical continuum approach to discontinuous mechanics although well known for decades anthropogenic land subsidence is still threatening large urban centers and deltaic areas worldwide such as bangkok jakarta and mexico city at rates in the order of 10 cm yr

black shale formation during the latest danian event and the paleocene eocene thermal maximum in central egypt two of a kind abstract the paleocene eocene thermal maximum petm 55 8 ma is considered as the most severe of a series of transient warming events hyperthermals that occurred during the early paleogene however the extent and magnitude of environmental changes during the short lived warming events pre and post dating the petm are still poorly constrained in this study we focus on the latest danian event lde 61 7 ma and compare it to the petm we present high resolution micropaleontological geochemical and mineralogical data of the petm and the lde in two adjacent sections from the gebel qreiya area in egypt there both events are characterized by a distinct set of event beds overlying an unconformity they are associated with intense carbonate dissolution and substantial changes in the benthic foraminifera fauna moreover both show an abrupt drop of siliciclastic input sediment starvation correlative to the onset of black shale formation and a strong enrichment in redox sensitive trace elements the evidence for enhanced detrital input during the onset of the petm and a longer recovery phase with enhanced phosphorus sedimentation during the petm attests a stronger environmental impact of this event compared to the lde according to rock eval and elemental analysis the petm as well as the lde event beds have up to 4 wt organic carbon small amounts of volatile hydrocarbons but high amounts of highly weathered and inert organic matter black carbon during pyrolysis the extremely high temperatures for the maximum release of hydrocarbons of the petm and lde samples correspond to thermal heating of 170 c which is incompatible with the sediment burial history therefore we suggest that the organic matter in both event deposits does not reflect well preserved marine biomass but predominantly represents a mixture of heavily weathered autochthonous marine material and allochthonous combustion residues differences in preservation and or type of organic matter are also likely to account for the divergent stable isotope anomalies of organic carbon the well known negative carbon isotope anomaly at the petm and a positive anomaly at the lde although warming water column stratification and enhanced nutrient input may have promoted anoxic conditions on the shelf during the lde as well as during petm our results support rapid sea level rise and clastic starvation as one important mechanism for black shale formation and carbon sequestration for both events this result underlines the similarity of both hyperthermal events in terms of environmental changes recorded on the southern tethyan margin with the petm showing an additional early phase of strong detrital input not revealed at the lde

submarine hydrothermal vent complexes in the paleocene of the faroe shetland basin insights from three dimensional seismic and petrographical data this work presents a new method of coarse grained sediment input into a deep sedimentary basin and presents a new example of igneous processes controlling sedimentary facies the mesozoic cenozoic faroe shetland basin sediments are intruded by late paleocene igneous sills and dikes sill intrusions are frequently expressed on the paleosurface as hydrothermal mounds and vents occurring directly above sill tips three dimensional seismic data are used to image a paleocene submarine mounded structure that has been penetrated by an exploration well drilled in a d 1984 seismic morphology is combined with petrographic data to show that the mound was erupted from a central vent as a series of sediment pulses consisting of sediments disaggregated and recycled from depth a submarine sediment volcano

horizontal aquifer movement in a theis thiem confined system the skeletal matrix of an aquifer is known to move laterally toward a discharging well the mechanisms by which it moves relative to the well have been only partially studied in the past examining the relation of drawdown to volume strain for an assumed poroelastic solid has been a common approach by way of contrast the present study examines the relation of the velocity of solids aquifer matrix to their hydraulic driving forces the present approach can be considered darcian and allows the displacement field of the aquifer matrix to be calculated directly a new formulation of the darcy gersevanov law of water flowing relative to moving solids is applied to a theis thiem confined aquifer the aquifer is found to start with a maximum velocity when the pump is turned on and then to decelerate as time progresses dimensionless type curves of horizontal movement of the skeletal matrix are calculated the resulting equation of aquifer deformation is checked against 1 results from alternatively using the standard poroelastic stress strain approach and 2 the fundamental storage equation for transient groundwater flow

persistent environmental change after the paleocene eocene thermal maximum in the eastern north atlantic the paleocene eocene thermal maximum petm 56 ma is associated with abrupt climate change carbon cycle perturbation ocean acidification as well as biogeographic shifts in marine and terrestrial biota that were largely reversed as the climatic transient waned we report a clear exception to the behavior of the petm as a reversing climatic transient in the eastern north atlantic deep sea drilling project site 401 bay of biscay where the petm initiates a greatly prolonged environmental change compared to other places on earth where records exist the observed environmental perturbation extended well past the 13 c recovery phase and up to 650 kyr after the petm onset according to our extraterrestrial 3he based age model we observe a strong decoupling of planktic foraminiferal 18 o and mg ca values during the petm 13 c recovery phase which in combination with results from helium isotopes and clay mineralogy suggests that the petm triggered a hydrologic change in western europe that increased freshwater flux and the delivery of weathering products to the eastern north atlantic this state change persisted long after the carbon cycle perturbation had stopped we hypothesize that either long lived continental drainage patterns were altered by enhanced hydrological cycling induced by the petm or alternatively that the climate system in the hinterland area of site 401 was forced into a new climate state that was not easily reversed in the aftermath of the petm

splay fault branching from the hikurangi subduction shear zone implications for slow slip and fluid flow gns science s mbie funded contracts grant number co5x1204 and c05x0908 gas hydrates resources marsden fund project grant number gns0902

time dependent land uplift and subsidence in the santa clara valley california from a large interferometric synthetic aperture radar data set 1 we invert 115 differential interferograms derived from 47 synthetic aperture radar sar scenes for a time dependent deformation signal in the santa clara valley california the time dependent deformation is calculated by performing a linear inversion that solves for the incremental range change between sar scene acquisitions a nonlinear range change signal is extracted from the ers insar data without imposing a model of the expected deformation in the santa clara valley cumulative land uplift is observed during the period from 1992 to 2000 with a maximum uplift of 41 18 mm centered north of sunnyvale uplift is also observed east of san jose seasonal uplift and subsidence dominate west of the silver creek fault near san jose with a maximum peak to trough amplitude of 35 mm the pattern of seasonal versus long term uplift provides constraints on the spatial and temporal characteristics of water bearing units within the aquifer the silver creek fault partitions the uplift behavior of the basin suggesting that it acts as a hydrologic barrier to groundwater flow while no tectonic creep is observed along the fault the development of a low permeability barrier that bisects the alluvium suggests that the fault has been active since the deposition of quaternary units

numerical evaluation of mechanisms driving early jurassic changes in global carbon cycling the early jurassic early toarcian ca 183 ma carbon cycle perturbation is characterized by aabout 5 parts per thousand delta sup 13 c excursion in the exogenic carbon reservoirs a 1000 ppm rise in atmospheric co sub 2 and a 6 7 degrees warming two proposed explanations for this presumed global carbon cycle perturbation are the liberation of massive amounts of isotopically light ch4 from 1 gondwanan coals by heating during the intrusive eruption of the karoo ferrar large igneous province lip or 2 the thermal dissociation of gas hydrates carbon cycle modeling indicates that the release of ch4 from gondwanan coals synchronous with the eruption of the karoo ferrar lip fails to reproduce the magnitude or timing of the co sub 2 and delta sup 13 c excursions however sensitivity analyses constrained by a marine cyclostratigraphically dated delta sup 13 c record indicate that both features of geologic record can be explained with the huge input of about 15 340 24 750 gt c over about 220 k y a result possibly pointing to the involvement of hydrothermal vent complexes in the karoo basin the simulated release of 6000 gt c from gas hydrates also reproduces aspects of the early toarcian rock record but the large mass involved raises fundamental questionsmore about its formation storage and release less

heat flow and mineralogy of tag relict high temperature hydrothermal zones mid atlantic ridge 26 n 45 w submersible investigations employing heat flow measurements 12 stations sampling and imagery of the two relict high temperature hydrothermal zones of the tag field the alvin and mir sulfide zones elucidate relations between heat sources and mineralization including an active sulfide mound that has been the focus of prior studies values of heat flow in the mir zone and at the margin of the active mound are inversely proportional to distance from adjacent volcanic centers this observation supports the hypothesis that intrusions at volcanic centers adjacent to the high temperature hydrothermal zones supply the heat to drive hydrothermal activity the chronology of hydrothermal deposits in the different zones indicates that the intrusions are episodic with field wide high temperature hydrothermal events recurring at intervals of tens of thousands of years while activity at individual zones may recur at intervals of hundreds to thousands of years a sequence of hydrothermal deposits ranges to at least 140 000 years ago from massive sulfides forming at the active mound to recrystallization of sulfides in the active and relict zones to pyritization of an inactive mound in the alvin zone low temperature mineral phases precipitate before during and after the sulfides

the effects of pulsed pumping on land subsidence in the santa clara valley california abstract land subsidence caused by pulsed and constant pumping schemes was calculated and the results were compared to determine the possible advantages of pulsed pumping in reducing land subsidence pulsed pumping refers to pumping strategies involving alternation between periods of pumping and recovery in a well subsidence was calculated using a numerical model based on the santa clara valley ca the model accounts for delay in the release of water from storage in compressible interbeds as well as flow within aquifers for these tests the ratio of pumping period length to recovery period length was either 1 1 or 1 3 pulsing interval length length of one pumping period plus one recovery period ranged from 4 to 90 days pumping rates were adjusted so that pulsed pumping and constant pumping removed the same volume of water over the period under consideration pulsed pumping has the potential to concentrate subsidence around the pumping well for all simulations pulsed pumping caused greater subsidence near the test well than constant pumping under some conditions a transition point was reached beyond which pulsed pumping caused less subsidence than steady pumping the distance from the test well to the transition point decreases for a decreasing aquifer transmissivity b decreasing ratio of pumping period to recovery period and c increasing pulsing interval length the concentration of subsidence was reduced considerably when delay in release of water from storage in compressible aquitards was neglected indicating the importance of including delay effects in subsidence studies all pulsed pumping strategies caused a greater total volume of subsidence than steady pumping

methane escape from gas hydrate systems in marine environment and methane driven oceanic eruptions 1 huge quantities of ch4 are stored in marine sediment in the form of methane hydrate bubbles and dissolved ch4 in pore water here i discuss the various pathways for methane to enter the ocean and atmosphere including i methane hydrate dissolution or dissociation as it rises through seawater the dissociation rate can be 2 to 3 orders of magnitude greater than the dissolution rate ii the dissolution and expansion of a bubble with or without a hydrate shell as it rises through seawater there is a critical radius which depends on depth above which a bubble would reach the surface or even become larger as it rises i also propose and model the dynamics of a new type of terrestrial gas driven eruptions methane driven oceanic eruptions such eruptions not only represent a yet unrecognized geohazard but also provide a pathway for ch4 to rapidly enter the atmosphere as a greenhouse gas

evolution and origin of the ground fissures in xian china large scale extraction of ground water in xian has resulted in significant drawdown of the phreatic surface and in land subsidence across this ancient capital of china it has also triggered the rejuvenation of the normal faults in the upper portions of the quaternary deposits underlying the city leading to surface rupturing and the development of ground fissure zones across the city these ground fissure zones are structurally controlled in the sense that they are directly linked to the normal faults in the quaternary deposits all trending in an east northeasterly direction in essence they are the surface expressions of the deeper faults under current drawdown conditions the ground fissures have resulted in extensive property damage along their paths of propagation this paper describes their occurrence their possible causative mechanism and the resultant damage of necessity xian will still be dependent on ground water supply to a large extent in the years ahead however ground water extraction will have to be managed in an environmentally sustainable manner in order to minimize the geological hazards associated with the ground fissures

hierarchies of overpressure retardation of organic matter maturation case studies from petroleum basins in china the effects of overpressure on different aspects of organic matter maturation have been examined in three basins using multiple parameters overpressure in the yinggehai basin has retarded kerogen maturation hydrocarbon generation and thermal cracking of long chain normal hydrocarbons as well as evolution of isoprenoid hydrocarbons overpressure in the dongpu depression bohai bay basin seems to have retarded the maturation of bulk kerogens reflected by rock eval tmax the thermal cracking of long chain normal hydrocarbons and the evolution of isoprenoid hydrocarbons but seems to have had no detectable effects on vitrinite reflectance overpressure in the qiongdongnan basin has had no detectable retardation effects on all aspects of organic matter maturation the observed phenomena suggest differential retardation of organic matter maturation that is different organic matter maturation reactions and different maturity parameters have been retarded by overpressure to different degrees in the same overpressured system and four hierarchies of overpressure retardation hierarchy i retardation is defined as the state where the overpressure has retarded all aspects of organic matter maturation and is proposed to have been caused by the combination of high formation pressure and excess pressure a high water organic matter ratio and strong retention of reaction products in an early developed strong persistent overpressured system hierarchy ii retardation refers to the case in which all aspects of organic matter maturation except the maturation of hydrogen poor kerogens especially vitrinite have been retarded and seem to have been caused by early developed moderate to strong persistent overpressure hierarchy iii retardation refers to the situation where overpressure has retarded only the thermal cracking of liquid hydrocarbons but has had no detectable effect on the maturation of both hydrogen rich and hydrogen poor kerogens and is proposed to have been caused by moderate to strong persistent overpressures that began to develop around peak oil generation hierarchy iv retardation is defined as the situation where overpressure has had no detectable retardation on all aspects of organic matter maturation and may have been caused by cases wherein the overpressure developed too late the intensity of the overpressure was too low the duration of the overpressure was too short or overpressured fluids had been expelled frequently resulting from both the diversities of organic matter maturation reactions and the complexities of overpressure generation and development the hierarchies of overpressure retardation in different basins may be quite different and it is necessary to use multiple parameters to understand the evolution of the petroleum systems in overpressured basins

sea level humidity and land erosion records across the initial eocene thermal maximum from a continental marine transect in northern spain in two continental sections in the tremp basin northern spain the initial eocene thermal maximum also known as the paleocene eocene thermal maximum is registered by an 6 fall in 1 3 c values in soil carbonate nodules high resolution correlations using the 1 3 c excursion can be made to nearby shelf and bathyal marine settings allowing a detailed reconstruction of soil formation on land and transport of detritus to the sea during the initial eocene thermal maximum soils that formed before and after the initial eocene thermal maximum in the tremp region reflect arid to semiarid conditions with abundant evaporative minerals whereas initial eocene thermal maximum soils reflect seasonally wetter but generally dry conditions during the initial eocene thermal maximum land erosion was intensified and accumulation rates of terrigenous detritus in the sea increased this reflects both increased topographic relief associated with a prominent sea level lowstand and enhanced seasonal precipitation over a dry landscape with sparse vegetation deeper erosion led to an increase in the flux of kaolinite from buried mesozoic soils to the oceans the association of the initial eocene thermal maximum with a sea level lowstand in northern spain as well as at other marginal north atlantic sites may reflect coeval large scale magmatic activity in the northernmost atlantic

submarine volcanic mounds in the pearl river mouth basin northern south china sea a number of enigmatic km scale mound structures have been discovered in the baiyun sag of the pearl river mouth basin using high resolution 2d and 3d seismic data combined with multi beam bathymetry based on detailed seismic characterization we interpret these as sill fed volcanic mounds associated structures include igneous sills trans tensional faults lava flows and compactional drape folds the igneous intrusions and associated mounds were emplaced in the late early miocene c 18 5 ma or shortly thereafter constrained by the onlap relationship between the mounds and their overburden the volcanic mounds are preferentially developed above or adjacent to basement highs indicating a structural control on the igneous plumbing system we propose that the fractures and tectonic faults above the raised basement follow pre existing zones of weakness and may have acted as feeding conduits for the magmatic material the discovery of the early miocene igneous province has important implications for the understanding of the evolution of the pearl river mouth basin and for regional hydrocarbon prospectivity c 2014 elsevier b v all rights reserved

sedimentary response to paleocene eocene thermal maximum carbon release a model data comparison possible sources of carbon that may have caused global warming at the paleocene eocene boundary are constrained using an intermediate complexity earth system model confi gured with early eocene paleogeography we fi that 6800 pg c 13 c of 22 is the smallest pulse modeled here to reasonably reproduce observations of the extent of seafl oor caco 3 dis solution this pulse could not have been solely the result of methane hydrate destabilization suggesting that additional sources of co 2 such as volcanic co 2 the oxidation of sedimentary organic carbon or thermogenic methane must also have contributed observed contrasts in dissolution intensity between atlantic and pacifi c sites are reproduced in the model by reduc ing bioturbation in the atlantic during the event simulating a potential consequence of the spread of low oxygen bottom waters

diapiric ascent of magmas through power law crust and mantle there has never been a convincing explanation of the way in which diapirs of molten granite can effectively rise through mantle and crust we argue here that this is mainly because the country rocks have previously been assumed to be newtonian and we show that granitoid diapirs rising through thermally graded power law crust may indeed rise to shallow crustal levels while still molten the ascent velocity of diapirs is calculated through an equation with the form of the hadamard rybczynski equation for the rise of spheres through newtonian ambient fluids this well known equation is corrected by factors dependent on the power law exponent n of the ambient fluid and the viscosity contrast between the drop and the ambient fluid these correction factors were derived from results reported in the fluid mechanical and chemical engineering literature for the ascent of newtonian drops through power law fluids the equation allows calculation of the ascent rates of diapirs by direct application of rheological parameters of rocks the velocity equation is numerically integrated for the ascent of diapirs through a lithosphere in which the temperature increases with depth the depth of solidification of the diapir is systematically studied as a function of the geothermal gradient buoyancy of the body solidus temperature of the magma and rheological parameters of the wall rock the results show that when the wall rock behaves as a power law fluid the diapir s ascent rate increases without a similar increase in the rate of heat loss in this way diapirs rising at 10 to 102 m yr can ascend into the middle or upper crust before solidification strain rate softening rather than thermal softening is the mechanism that allows diapirism to occur at such rates the thermal energy of the diapir is used to soften the country rock only at late stages of ascent the transport of magmas through the lower crust and mantle as diapirs is shown to be as effective as magmatic ascent through fractures

western davis strait a volcanic transform margin with petroliferous features abstract we present a compilation of the western davis strait region offshore southeastern baffin island nunavut canada with new subsurface geological structural details and observations regarding past hydrocarbon occurrences from scientific and commercial exploration this consists of seismic mapping with archival data correlated with a filtered marine bouguer anomaly gravity compilation and magnetic data sets covering northern saglek basin the western part of the lady franklin basin and the ungava fault zone from south of baffin bay a regional seismic horizon for mapping basin architecture comes from the top of the paleogene volcanic syn magmatic zone where pervasive volcanic flows and intrusions are intermingled with the sedimentary section the seismic depth map to the top of the regional volcanic seismic horizon shows pre rift sedimentary basins having maximum depths of approximately 4 5 km flanking the shallower ungava fault zone correlation of bouguer anomaly gravity and magnetic data interpretations with the seismic mapping indicate that over some areas true crystalline basement is deeper than can be determined by reflection seismic as the base of the syn magmatic section is not resolvable for seismic mapping extensive paleogene mafic intrusives and extrusive basalts dominate the architecture of this volcanic rifted margin as seen by the dominant high amplitude magnetic anomalies associated with many deeper structures the over 250 km long davis strait fault is recognised as the key structural element of the ungava fault zone ufz and valley complex the adjoining davis strait high maps on seismic as a continuous structure running the length of davis strait plunging southwards to a bouguer gravity high feature that terminates the western end of the extinct eocene spreading zone south of davis strait this horn shaped structural feature establishes the presence of an accommodation zone with multiple faults and localised thrust faulting as required to fit the complex mechanics for strike slip motion that occurs along the south end of this transform fault system the revised marine bouguer anomaly gravity data set also defines two new near shore grabens east of cumberland sound the southern tariut basin and the northern imaqpik basin each extending over 100 km in length with sediment thicknesses of at least 4 km these pre rift basins most likely originate from the paleozoic based on seafloor dredge and nearby shallow drill cores from previous studies the hydrocarbon charge of a previously unexplained petroliferous shallow marine drill core that is adjacent the eastern edge of the tariut basin is attributed to paleozoic source rocks that have undergone enhanced thermal maturation from sill intrusion associated with rifting the imaqpik basin shows strong evidence of a hydrocarbon system from the proximity of clustered interpreted sea surface oil slicks mapped from satellite radar images and a local zone of anomalously high dissolved methane measured within the water column that originates from the seafloor immediately east of cape dyer at the northern limit of that basin the overlying cape dyer flood basalt field extends from limited onshore exposures into the offshore and maps with magnetic data over an area of approximately 13 000 km2 this extrusive feature and it s implicit underlying intrusive components are likely the unconventional heat source for the anomalous enhanced thermal maturation of paleozoic to paleogene source rocks in these pre rift basins that host this previously unrecognised petroleum system

carbon release by off axis magmatism in a young sedimented spreading centre continental rifting creates narrow ocean basins where coastal ocean upwelling and enhanced silicate weathering remove carbon dioxide from the atmosphere evidence from seismic data sonar backscatter and seafloor images and geochemical water analyses suggest that in young sedimented rifts active magmatism occurs in a broader region than appreciated and releases carbon from the sediments

isometamorphic variations in the reflectance and fluorescence of vitrinite a key to depositional environment abstract petrographic investigations of serial ply samples from five high to medium volatile bituminous coal seams from australia 4 and canada 1 reveal substantial in seam variations in the reflectance and monochromatic microfluorescence intensities of the maceral subgroup telovitrinite the variations consist of one case of reflectance enhancement and fluorescence suppression and four cases of reflectance suppression and fluorescence enhancement the single case of reflectance enhancement and fluorescence suppression is due to the oxidation of the vitrinite nuclei at the sequence boundary between the bayswater and upper wynn seams in new south wales the four cases of reflectance suppression and fluorescence enhancement result from the syn and epigenetic absorption by the vitrinite nuclei of hydrogen donated by presumably anaerobic bacteria generated lipids two of the coals are marine influenced the liskeard seam from the bowen basin by combined syngenetic and epigenetic effects and the greta seam from the sydney basin mainly by epigenetic contact with sea water for both coals the results are strong vitrinite reflectance suppression and fluorescence enhancement the remaining two coals the bulli seam from the sydney basin and a coal seam from the gates formation in british columbia show moderate epigenetic effects on the optical properties of telovitrinite by fresh water in the bulli seam which was studied in two adjacent localities the reflectance suppression and fluorescence enhancement of telovitrinite are stronger under sandstone roof than under shale roof in some cases the epigenetic effects are superimposed on syngenetic telovitrinite reflectance and fluorescence variations resulting from the cogeneration and mixing of different telovitrinite precursors for example autochthonous roots and hypautochthonous or allochthonous shoots a measure of the degree of dispersal and mixing is the coefficient of variation of telovitrinite reflectance and or fluorescence this coefficient correlates well with detrital minerals and dispersed macerals e g inertodetrinite and to a lesser extent sporinite some comments are made on slitted so called pseudovitrinite which is regarded as a telovitrinite that was subjected to very weak post coalification desiccation and possibly oxidation without losing much of its thermoplastic properties

north atlantic volcanic margins dimensions and production rates early tertiary lithospheric breakup between eurasia and greenland was accompanied by a transient 3 m y igneous event emplacing both the onshore flood basalts of the north atlantic volcanic province navp and huge extrusive complexes along the continent ocean transition on the rifted continental margins seismic data show that volcanic margins extend 2600 km along the early eocene plate boundary in places underlain by high velocity 7 2 7 7 km s lower crustal bodies quantitative calculations of navp dimensions considered minimum estimates reveal an areal extent of 1 3 106 km2 and a volume of flood basalts of 1 8 106 km3 yielding a mean eruption rate of 0 6 km3 yr or 2 4 km3 yr if two thirds of the basalts were emplaced within 0 5 m y the total crustal volume is 6 6 106 km3 resulting in a mean crustal accretion rate of 2 2 km3 yr thus navp ranks among the world s larger igneous provinces if the volcanic margins are considered the velocity structure of the expanded crust seaward of the continent ocean boundary differs from standard oceanic and continental crustal models based on seismic velocities this volcanic margin crust can be divided into three units of which the upper unit corresponds to basaltic extrusives the regionally consistent velocity structure and geometry of the crustal units suggest that the expanded crust including the high velocity lower crust which extends some distance landward of the continent ocean boundary was emplaced during and subsequent to breakup the volcanic margin crust was formed by excess melting within a wide zone of asthenospheric upwelling probably reflecting the interaction of a mantle plume and a lithosphere already extending

heat flow in the western mediterranean thermal anomalies on the margins the seafloor and the transfer zones the western mediterranean basin has been formed by miocene back arc extension and is underlain by a thin and young lithosphere this young lithosphere is warm as testified by an overall elevated offshore heat flow heat flow within the western mediterranean is however highly variable and existing data are unevenly distributed and poorly studied in the central part of the liguro provencal and algero balearic basins this central part is floored by a young oceanic crust bordered by different continental margins cut by transform faults and filled by up to 8 km of sediments we present a total of 148 new heat flow data collected during the medsalt and westmedflux cruises in 2015 and 2016 and aligned along seven regional profiles that show an important heat flow variability on the basin scale but also locally on the margins a new heat flow map for the western mediterranean outlines the following regional features 1 a higher average heat flow in the algero balearic basin compared to the liguro provencal basin 94 13 mw m2 and 78 16 mw m2 respectively and 2 a regional thermal asymmetry in both basins but with opposed heat flow trends up to 20 of this heat flow difference can be explained by sediment blanketing but age and heterogeneity of ocean crust due to an asymmetric and polyphased opening of the basins are believed to have given the major thermal imprint estimates of the age of the oceanic crust based on the new heat flow suggest a considerably younger west algerian basin 16 23 ma compared to the east algerian basin and the west sardinia oceanic floor 31 37 ma on the margins and ocean continent transitions of the western mediterranean the new heat flow data point out the existence of two types of local anomalies length scale 5 30 km 1 locally increased heat flow up to 153 mw m2 on the gulf of lion margin results from thermal refraction of large salt diapirs and 2 the co existing of both low 110 mw m2 heat flow areas on the south balearic margin suggests a heat redistribution system we suspect the lateral heat advection is resulting from a regional fluid circulation in the sediments associated to the widespread plio pleistocene volcanism on the south balearic margin

permanent scatterer insar reveals seasonal and long term aquifer system response to groundwater pumping and artificial recharge received 4 may 2007 revised 30 july 2007 accepted 10 october 2007 published 5 february 2008 1 permanent scatterer insar psinsark p rovides an ew high resolution methodology for detecting and precisely measuring long term and seasonal aquifer system response to pumping and recharge in contrast to conventional insar the permanent scatterer methodology utilizes coherent radar phase data from thousands of individual radar reflectors on the ground to develop displacement time series and to produce velocity field maps that depict aquifer system response with a high degree of spatial detail in this study we present the first results of a prototype study in las vegas valley nevada that demonstrate how this methodology can be utilized in heavily pumped groundwater basins to analyze aquifer system response to long term and seasonal pumping we have developed a series of velocity field maps of the valley for the 1992 1996 1996 2000 and 2003 2005 time periods that show that despite rising water levels associated with an artificial recharge program long term residual inelastic aquifer system compaction subsidence is continuing in several parts of the valley in other areas however long term subsidence has been arrested and locally reversed the seasonal elastic responses to alternating pumping and recharge cycles were segregated from the long term trends and analyzed for spatial and temporal patterns the results show oscillations in which the maximum seasonal responses are associated with the late stages of the annual artificial recharge cycles and that similar seasonal subsidence signals are related to summer pumping cycles the differentiation of the seasonal response through the use of time series data further allows the estimation of elastic and inelastic skeletal storage coefficients providing a basis for future work that could characterize the storage properties of an aquifer system with a high degree of spatial resolution

pockmarks in the witch ground basin central north sea marine sediments host large amounts of methane ch4 which is a potent greenhouse gas quantitative estimates for methane release from marine sediments are scarce and a poorly constrained temporal variability leads to large uncertainties in methane emission scenarios here we use 2d and 3d seismic reflection multibeam bathymetric geochemical and sedimentological data to i map and describe pockmarks in the witch ground basin central north sea ii characterize associated sedimentological and fluid migration structures and iii analyze the related methane release more than 1500 pockmarks of two distinct morphological classes spread over an area of 225 km2 the two classes form independently from another and are corresponding to at least two different sources of fluids class 1 pockmarks are large in size 6 m deep 250 m long and 75 m wide show active venting and are located above vertical fluid conduits that hydraulically connect the seafloor with deep methane sources class 2 pockmarks which comprise 99 5 of all pockmarks are smaller 0 9 3 1 m deep 26 140 m long and 14 57 m wide and are limited to the soft fine grained sediments of the witch ground formation and possibly sourced by compaction related dewatering buried pockmarks within the witch ground formation document distinct phases of pockmark formation likely triggered by external forces related to environmental changes after deglaciation thus greenhouse gas emissions from pockmark fields cannot be based on pockmark numbers and present day fluxes but require an analysis of the pockmark forming processes through geological time

does large igneous province volcanism always perturb the mercury cycle comparing the records of oceanic anoxic event 2 and the end cretaceous to other mesozoic events mercury hg is increasingly being used as a sedimentary tracer of large igneous province lip volcanism and supports hypotheses of a coincidence between the formation of several lips and episodes of mass extinction and major environmental perturbation however numerous important questions remain to be answered before hg can be claimed as an unequivocal fingerprint of lip volcanism as well as an understanding of why some sedimentary records document clear hg enrichment signals whilst others do not of particular importance is evaluating the impact of different volcanic styles on the global mercury cycle as well as the role played by depositional processes in recording global hg cycle perturbations here new mercury records of cretaceous oceanic anoxic event 2 oae 2 94 ma and the latest cretaceous 67 66 0 ma are presented oae 2 is associated with the emplacement of multiple predominantly submarine lips the latest cretaceous with subaerial volcanism of the deccan traps both of these connections are strongly supported by previously published trends towards unradiogenic osmium os isotope values in globally distributed sedimentary records hg data from both events show considerable variation between different locations attributed to the effectiveness of different sediment types in registering the hg signal with lithologically homogeneous records documenting more clear hg enrichments than sections with major changes in lithology such as limestones to claystones or organic rich shales crucially there is no geographically consistent signal of sedimentary hg enrichment in stratigraphic records of either oae 2 or the latest cretaceous that matches os isotope evidence for lip emplacement indicating that volcanism did not cause a global hg perturbation throughout the entire eruptive history of the lips formed at those times it is suggested that the discrepancy between os isotope and hg trends in records of oae 2 is caused by the limited dispersal range of hg emitted from submarine volcanoes compared to the global scale distribution of os a similar lack of correlation between these two proxies in uppermost cretaceous strata indicates that although subaerial volcanism can perturb the global hg cycle not all subaerial eruptions will do so these results highlight the variable impact of different volcanogenic processes on the efficiency of hg dispersal across the globe factors that could influence the impact of lip eruptions on the global mercury cycle include submarine versus subaerial volcanism volcanic intensity or explosivity and the potential contribution of thermogenic mercury from reactions between ascending magma and surrounding organic rich sediments

beyond methane towards a theory for the paleocene eocene thermal maximum abstract extreme global warmth and an abrupt negative carbon isotope excursion during the paleocene eocene thermal maximum petm have been attributed to a massive release of methane hydrate from sediments on the continental slope 1 however the magnitude of the warming 5 to 6 c 2 3 and rise in the depth of the ccd 2 km 4 indicate that the size of the carbon addition was larger than can be accounted for by the methane hydrate hypothesis additional carbon sources associated with methane hydrate release e g pore water venting and turbidite oxidation are also insufficient we find that the oxidation of at least 5000 gt c of organic carbon is the most likely explanation for the observed geochemical and climatic changes during the petm for which there are several potential mechanisms production of thermogenic ch4 and co2 during contact metamorphism associated with the intrusion of a large igneous province into organic rich sediments 5 is capable of supplying large amounts of carbon but is inconsistent with the lack of extensive carbon loss in metamorphosed sediments as well as the abrupt onset and termination of carbon release during the petm a global conflagration of paleocene peatlands 6 highlights a large terrestrial carbon source but massive carbon release by fire seems unlikely as it would require that all peatlands burn at once and then for only 10 to 30 ky in addition this hypothesis requires an order of magnitude increase in the amount of carbon stored in peat the isolation of a large epicontinental seaway by tectonic uplift associated with volcanism or continental collision followed by desiccation and bacterial respiration of the aerated organic matter is another potential mechanism for the rapid release of large amounts of co2 in addition to the oxidation of the underlying marine sediments the desiccation of a major epicontinental seaway would remove a large source of moisture for the continental interior resulting in the desiccation and bacterial oxidation of adjacent terrestrial wetlands

environmental impact of volcanic margin formation late rift stage uplift and subsequent massive transient volcanism during breakup of rifted volcanic continental margins constrain paleoenvironments by modifying basin geometry and the composition of the atmosphere hydrosphere and thus biosphere on regional and global scales the early tertiary north atlantic breakup history shows that lava emplacement was accompanied by regional ashfalls and that extrusive complexes influenced paleogene oceanic and continental margin circulation and sedimentation temporal correspondence with the terminal paleocene deep sea extinction event and the earliest eocene greenhouse suggests a global impact possibly by enhanced atmospheric co 2 levels leading to polar warming and thereby changing patterns of deep water formation in this context transient subaerial volcanism at continental margins should be considered with the much discussed continental flood basalt provinces and oceanic plateaus

sensing the ups and downs of las vegas insar reveals structural control of land subsidence and aquifer system deformation land subsidence in las vegas nevada united states between april 1992 and december 1997 was measured using spaceborne interferometric synthetic aperture radar the detailed deformation maps clearly show that the spatial extent of subsidence is controlled by geologic structures faults and sediment composition clay thickness the maximum detected subsidence during the 5 75 yr period is 19 cm comparison with leveling data indicates that the subsidence rates declined during the past decade as a result of rising ground water levels brought about by a net reduction in ground water extraction temporal analysis also detects seasonal subsidence and uplift patterns which provide information about the elastic and inelastic properties of the aquifer system and their spatial variability

new technique for dating igneous sills three dimensional seismic interpretation of tertiary sills within the northeast atlantic margin demonstrates that shallow level 20 km long the fill of the minibasin is dated biostratigraphically as 54 6 55 ma which fits well with radiometric dates for the timing of intrusion of sills around this basin ca 53 55 ma the recognition and dating of onlap fill seismic reflector packages that are delimited by forced folds form a new and useful method for dating shallow level igneous intrusions in sedimentary basins a method that provides independent constraints on radiometric dating techniques similar forced folds are recognized from other basins that have shallow level sills suggesting that the technique presented here may be similarly applicable in comparable geologic settings

evidence of a modern deep water magmatic hydrothermal system in the canary basin eastern central atlantic ocean new seismic profiles bathymetric data and sediment rock sampling document for the first time the discovery of hydrothermal vent complexes and volcanic cones at 4800 5200 m depth related to recent volcanic and intrusive activity in an unexplored area of the canary basin eastern atlantic ocean 500 km west of the canary islands a complex of sill intrusions is imaged on seismic profiles showing saucer shaped parallel or inclined geometries three main types of structures are related to these intrusions type i consists of cone shaped depressions developed above inclined sills interpreted as hydrothermal vents type ii is the most abundant and is represented by isolated or clustered hydrothermal domes bounded by faults rooted at the tips of saucer shaped sills domes are interpreted as seabed expressions of reservoirs of ch4 and co2 rich fluids formed by degassing and contact metamorphism of organic rich sediments around sill intrusions type iii are hydrothermal volcanic complexes originated above stratified or branched inclined sills connected by a chimney to the seabed volcanic edifice parallel sills sourced from the magmatic chimney formed also domes surrounding the volcanic cones core and dredges revealed that these volcanoes which must be among the deepest in the world are constituted by oib type basanites with an outer ring of blue green hydrothermal al rich smectite muds magmatic activity is dated based on lava samples at 0 78 0 05 and 1 61 0 09 ma k ar methods and on tephra layers within cores at 25 237 ky the subvent hydrothermal volcanic complex constitutes the first modern system reported in deep water oceanic basins related to intraplate hotspot activity

rifting under steam how rift magmatism triggers methane venting from sedimentary basins during opening of a new ocean magma intrudes into the surrounding sedimentary basins heat provided by the intrusions matures the host rock creating metamorphic aureoles potentially releasing large amounts of hydrocarbons these hydrocarbons may migrate to the seafloor in hydrothermal vent complexes in sufficient volumes to trigger global warming e g during the paleocene eocene thermal maximum petm mound structures at the top of buried hydrothermal vent complexes observed in seismic data off norway were previously interpreted as mud volcanoes and the amount of released hydrocarbon was estimated based on this interpretation here we present new geophysical and geochemical data from the gulf of california suggesting that such mound structures could in fact be edifices constructed by the growth of black smoker type chimneys rather than mud volcanoes we have evidence for two buried and one active hydrothermal vent system outside the rift axis the vent releases several hundred degrees celsius hot fluids containing abundant methane mid ocean ridge basalt morb type helium and precipitating solids up to 300 m high into the water column our observations challenge the idea that methane is emitted slowly from rift related vents the association of large amounts of methane with hydrothermal fluids that enter the water column at high pressure and temperature provides an efficient mechanism to transport hydrocarbons into the water column and atmosphere lending support to the hypothesis that rapid climate change such as during the petm can be triggered by magmatic intrusions into organic rich sedimentary basins

the paleocene eocene thermal maximum record in the organic matter of the claret and tendruy continental sections south central pyrenees lleida spain abstract the carbon isotope excursion cie associated with the paleocene eocene thermal maximum petm has been detected for the first time in the total organic carbon toc contained within the continental sediments of the tremp formation south central pyrenees lleida spain the 13 c toc magnitude of the cie is 4 3 in the claret section and 3 0 in the tendruy section with minimum values of 27 6 and 26 7 respectively previous studies have detected the cie in the south central pyrenees in both marine carbonates and within continental soil carbonate nodules these studies have located the onset of the cie either above or within the claret conglomerate interpreted as a megafan produced by a profound change in the precipitation regimen at the beginning of the petm our higher resolution 13 c toc study in the claret and tendruy sections places the onset of the cie below the base of the claret conglomerate and therefore suggests a 4 to 9 kyr time lag between the onset of the cie and an increase in intense seasonal precipitation rates furthermore this study suggests that the cie took place 30 55 kyr after the deposition of important late cernaysian tremp mammalian sites claret 4 tendruy v tendruy and palau which contain the youngest known occurrence of endemic paleocene mammalian taxa in europe before the mammalian dispersal event mde migration of new mammal groups such as perissodactyls artiodactyls primates marsupials carnivores creodonts and rodents the first immigrant mammals in europe are recorded at dormaal belgium above a hiatus the base of which has been dated to around the start of the cie our data indicate that the mde might have in fact occurred in europe within a time interval of about 67 kyr around the cie onset

chemical and carbon isotopic fractionations of gaseous hydrocarbons during abiogenic oxidation abstract the variations of chemical and carbon isotopic compositions in gaseous hydrocarbons upon abiogenic oxidation by sulfates hematite and both in laboratory studies were clearly demonstrated through a unique two step experimental approach in the first step a large number of small gold capsules containing gaseous hydrocarbons were prepared by kerogen pyrolysis experiments which were conducted under the same condition 450 c and 50 mpa for 72 h using the same kerogen the analytical results demonstrated that the chemical and carbon isotopic compositions of gases were almost identical among the capsules in the second step each of these gaseous hydrocarbon bearing capsules along with mineral oxidant hematite or magnesium sulfate heptahydrate or both and deionized water 15 of the amount of the oxidant was placed into a large gold capsule after welding sealing the small gaseous hydrocarbon bearing capsule was forced to leak while the large capsule remained undamaged by compressing the large capsule from the outside at the position where this small capsule was located then these large capsules containing gas and mineral reactants were heated isothermally at 350 c and 50 mpa for 72 144 216 and 288 h respectively the results of the oxidation experiments with increasing heating time can be outlined as follows 1 the amount of methane remained almost unchanged in the experiments using hematite and the mixed oxidants hematite mgso4 while it increased substantially in the experiment using mgso4 after 72 h indicating methane was one of the final products of c2 oxidation 2 the amounts of c2 c5 hydrocarbons decreased consistently and more rapidly in the experiment using mgso4 than that using hematite and the mixed oxidants 3 the oxidation rates of gas hydrocarbons increased with increasing carbon number of hydrocarbons 4 the oxidation rates of i butane and i pentane were substantially higher than those of the corresponding n butane and n pentane 5 the amount of h2s increased substantially in the experiment using mgso4 whereas it was below the detection level in the experiments using hematite and the mixed oxidants 6 the 13c values of c1 c5 hydrocarbons became less negative and the isotopic fractionation extent increased with increasing carbon number of hydrocarbons and oxidation extent 7 carbon isotopic fractionation factor k12 k13 decreased with increasing oxidation rate of gas hydrocarbons and 8 the rate of thermochemical sulfate reduction tsr was strongly dependent upon the presence and concentrations of h2s

enhanced hydrothermal processes at the new born lusi eruptive system indonesia abstract little is known about the processes taking place in new born hydrothermal systems we investigate the eruptive activity of lusi a sediment hosted hydrothermal system active since 2006 in east java indonesia we show that superimposed on the regular geysering activity lusi features periods of enhanced hydrothermal processes during which boiling mud breccia is violently discharged from the eruptive vents this results in sudden flooding lasting from several minutes to several hours and featuring almost instantaneous temperature peaks i e from 35 c to more than 65 c in less than 2 min such activity here named hydrothermal waves is marked by high frequency seismic radiations and is distinguished by sharp peaks of ch4 and co2 concentrations in the erupted fluids this suggests fluids upwelling from at least tents of meters below the near surface the injection into the shallow plumbing system of ch4 and co2 rich batches of fluids may promote instabilities in the mud breccia column leading to the hydrothermal waves our findings provide key insights into the deep charging dynamics of a new born hydrothermal system and highlight the effects imposed by subtle variations in fluid chemistry changes at depth

the mid cretaceous super plume carbon dioxide and global warming carbon dioxide releases associated with a mid cretaceous super plume and the emplacement of the ontong java plateau have been suggested as a principal cause of the mid cretaceous global warming the authors developed a carbonate silicate cycle model to quantify the possible climatic effects of these co sub 2 releases utilizing four different formulations for the rate of silicate rock weathering as a function of atmospheric co sub 2 they find that co sub 2 emissions resulting from super plume tectonics could have produced atmospheric co sub 2 levels from 3 7 to 14 7 times the modern pre industrial value of 285 ppm based on the temperature sensitivity to co sub 2 increases used in the weathering rate formulations this would cause a global warming of from 2 8 to 7 7c over today s global mean temperature altered continental positions and higher sea level may have been contributed about 4 8c to mid cretaceous warming thus the combined effects of paleogeographic changes and super plume related co sub 2 emissions could be in the range of 7 6 to 12 5c within the 6 to 14c range previously estimated for mid cretaceous warming co sub 2 releases from oceanic plateaus alone are unlikely to have been directly responsible for more than 20 of the mid cretaceous increase in atmospheric co sub 2

earth fissures and localized differential subsidence long linear tension cracks associated with declining groundwater levels at four sites in subsiding areas in south central arizona fremont valley california and las vegas valley nevada occur near points of maximum convex upward curvature in subsidence profiles oriented perpendicular to the cracks profiles are based on repeated precise vertical control surveys of lines of closely spaced bench marks association of these fissures with zones of localized differential subsidence indicates that linear earth fissures are caused by horizontal tensile strains probably resulting from localized differential compaction horizontal tensile strains across the fissures at the point of maximum convex upward curvature ranging from approximately 100 to 700 microstrains 0 01 to 0 07 per year were indicated based on measurements with a tape or electronic distance meter

high velocity breakup related sills in the voring basin off norway multichannel seismic reflection profiles in the hel graben v0ring basin reveal a sill complex at approximately 5 km depth it is associated with exceptionally high 7 4 km s 1 seismic wide angle velocities the existence of observable wide angle arrivals shows that the sills act as efficient waveguides seismic reflection data and amplitude modeling constrain the thickness of individual sills to approximately 100 m sonic logs from sills of similar thickness on the nearby utgard high show an average velocity of 7 0 km s 1 such high velocities require an olivine gabbroic sill composition and emplacement under conditions which allowed growth of relatively large crystal sizes a possible reason for such an emplacement environment is the hei graben s role as an intrusion center during breakup volcanism this would provide the necessary duration of the magmatic activity as well as locally increased melt volumes and cooling times sill complexes of this kind decrease the accuracy of determined velocity fields and crustal geometries below the top of the sill complex affecting depth conversion and gravity modeling furthermore the results question the concept of lower crustal bodies as large scale homogeneous accumulations of mafic melt

a surface vitrinite reflectance anomaly related to bell creek oil field montana u s a abstract vitrinite reflectance measurements from surface samples of mudrock and coal show anomalously high values over the bell creek oil field the average vitrinite reflectance rm increases to a peak of 1 2 over the field against background values of about 0 3 the rm anomaly coincides with a geochemical anomaly indicated by dgr13c in carbonate cemented sandstones these samples were taken from the upper cretaceous lance and paleocene fort union formations which form an essentially conformable sequence the depositional environment is apparently similar in both formations and we expect little variation in the source and composition of the organic matter rm should be rather constant across the field if conditions of diagenesis w re uniform the limited topographic relief 1 000 ft or 305 m over the shallow dipping homoclinal structure of the field and the poor correlation coefficient of rm regressed against sample locality elevation r 0 2 indicate that the rm anomaly is not due to burial deformation and subsequent erosion temperature studies over local oil fields with similar geologic conditions suggest the expected thermal anomaly would be less than 10 c 50 f which is too small to account for the significantly higher rank over the field coal clinkers are rare in the vicinity of the bell creek and widespread heating by burning of coal seams is unlikely we suggest that activity by petroleum metabolizing bacteria is a possible explanation of the rm anoma y microseepages from oil fields support large colonies of these organisms which could also metabolize aliphatic side chains on the kerogen molecule the loss of these side chains increases the aromaticity of the vitrinite and consequently increases its reflectance end of article last page 418

a new global paleocene eocene apparent polar wandering path loop by stacking magnetostratigraphies correlations with high latitude climatic data a new apparent polar wander path apwp from the beginning of the paleocene 65 ma to the middle of the mid eocene 42 ma is shown to be correlated with polar climatic data of the same time period rather than applying the classical method based on analysis of site based poles we stacked the apwps obtained from magnetostratigraphies magnetostratigraphies have the advantage of displaying an unbroken record of local apwps through time and for a magnetozone defined as the a combination of normal and reversed polarity intervals the instantaneous poles are synchronous seven magnetostratigraphies located on 4 different plates covered sufficient time to be used in the analysis an average apwp was then determined with respect to age at the magnetozone level for the african plate which was arbitrarily chosen as a reference frame virtual geomagnetic poles were transferred onto the african plate using ocean kinematic euler rotations the calculated apwp is characterized by a loop with two main changes of direction at magnetozones 26 25 61 5 56 5 ma and 24 22 56 5 48 6 ma distinct at a 95 level of probability and indistinct poles related to magnetozones 29 27 65 5 61 5 ma and 21 19 48 6 40 6 ma we also show that the implied rapid shift of the lithosphere with respect to the geographic pole possibly an episode of true polar wander was coeval with the time evolution of vertebrate occurrence on ellesmere island canadian arctic and with the tree ring growth rate in western antarctica

a transient rise in tropical sea surface temperature during the paleocene eocene thermal maximum the paleocene eocene thermal maximum petm has been attributed to a rapid rise in greenhouse gas levels if so warming should have occurred at all latitudes although amplified toward the poles existing records reveal an increase in high latitude sea surface temperatures ssts 8 to 10 c and in bottom water temperatures 4 to 5 c to date however the character of the tropical sst response during this event remains unconstrained here we address this deficiency by using paired oxygen isotope and minor element magnesium calcium ratios of planktonic foraminifera from a tropical pacific core to estimate changes in sst using mixed layer foraminifera we found that the combined proxies imply a 4 to 5 c rise in pacific sst during the petm these results would necessitate a rise in atmospheric pco 2 to levels three to four times as high as those estimated for the late paleocene

release of methane from a volcanic basin as a mechanism for initial eocene global warming a 200 000 yr interval of extreme global warming marked the start of the eocene epoch about 55 million years ago negative carbon and oxygen isotope excursions in marine and terrestrial sediments show that this event was linked to a massive and rapid approximately 10 000 yr input of isotopically depleted carbon it has been suggested previously that extensive melting of gas hydrates buried in marine sediments may represent the carbon source and has caused the global climate change large scale hydrate melting however requires a hitherto unknown triggering mechanism here we present evidence for the presence of thousands of hydrothermal vent complexes identified on seismic reflection profiles from the voring and more basins in the norwegian sea we propose that intrusion of voluminous mantle derived melts in carbon rich sedimentary strata in the northeast atlantic may have caused an explosive release of methane transported to the ocean or atmosphere through the vent complexes close to the palaeocene eocene boundary similar volcanic and metamorphic processes may explain climate events associated with other large igneous provinces such as the siberian traps approximately 250 million years ago and the karoo igneous province approximately 183 million years ago

groundwater pumping and land subsidence in the emilia romagna coastland italy modeling the past occurrence and the future trend 1 the emilia romagna coastland south of the po river delta italy has experienced a dramatic land settlement mainly due to the large groundwater withdrawal related to the local economic and tourist development started in the early 1950s although the use of surface water has reduced the settlement rate over the last three decades anthropogenic land subsidence still continues in a few kilometer wide coastal strip at a rate larger than the natural one the occurrence is reconstructed since 1946 with the aid of advanced finite element flow and poromechanical models implemented with a realistically detailed geology of the regional shallow multiaquifer system the models have been calibrated against the piezometric leveling and extensometer records observed over the last 50 years and a land subsidence prediction in 2016 is performed the results show that the extensive groundwater pumping that occurred in the past is most likely the main cause of the recent land settlement as well because of the delayed compaction of the clay aquitards comprised between the depleted aquifers however the available pumping data do not allow for a thorough understanding of the current local settlement process along the coastline which is the most vulnerable area of the emilia romagna region from an environmental viewpoint if the planned scenario of groundwater resource management will be implemented anthropogenic land subsidence is bound to become a marginal problem for the central and northern portion of the emilia romagna coastland

the suppression of inertinite reflectance abstract the suppression of reflectance of vitrinite with hydrogen rich composition compared to iso rank vitrinite of normal composition is widely recognized from a consideration of fluorescence alteration properties it is argued that inertinite macerals associated with hydrogen rich vitrinites in coal or dispersed organic matter will also show suppressed reflectance in dispersed organic matter in which vitrinite is rare or absent hydrogen rich unstructured inertinite may easily be misidentified as vitrinite if only reflectance data are available

seismic volcanostratigraphy of large volume basaltic extrusive complexes on rifted margins large volume extrusive basaltic constructions have distinct morphologies and seismic properties depending on the eruption and emplacement environments the presence and amount of water is of main importance while local rift basin configuration erosion and resedimentation determine the overall geometry of the volcanic constructions we have developed the concept of seismic volcanostratigraphy a subset of seismic stratigraphy to analyze volcanic deposits imaged on seismic reflection data the method places special focus on identification and mapping of seismic facies units and the volcanological interpretation of these units interpretation of seismic reflection data along the atlantic and western australia rifted margins reveals six characteristic volcanic seismic facies units named 1 landward flows 2 lava delta 3 inner flows 4 inner seaward dipping reflectors inner sdr 5 outer high and 6 outer sdr these units are interpreted in terms of a five stage tectonomagmatic volcanic margin evolution model comprising 1 explosive volcanism in a wet sediment broad basin setting 2 subaerial effusive volcanism forming gilbert type lava deltas along paleoshorelines 3 subaerial effusive volcanism infilling a fairly narrow rift basin 4 shallow marine explosive volcanism as the injection axis is submerged below sea level and finally 5 deep marine sheet flow or pillow basalt volcanism further erosion and resedimentation processes are particularly important during the shallow marine stages seismic volcanostratigraphy provides important constraints on rifted margin development in particular on the prevolcanic basin configuration relative timing of tectonomagmatic events total amount of volcanic rocks location of paleoshorelines and margin subsidence history these parameters give key boundary conditions for understanding the processes forming volcanic margins and other large volume basaltic provinces

seasonal subsidence and rebound in las vegas valley nevada observed by synthetic aperture radar interferometry analyses of areal variations in the subsidence and rebound occurring over stressed aquifer systems in conjunction with measurements of the hydraulic head fluctuations causing these displacements can yield valuable information about the compressibility and storage properties of the aquifer system historically stress strain relationships have been derived from paired extensometer piezometer installations which provide only point source data because of the general unavailability of spatially detailed deformation data areal stress strain relations and their variability are not commonly considered in constraining conceptual and numerical models of aquifer systems interferometric synthetic aperture radar insar techniques can map ground displacements at a spatial scale of tens of meters over 100 km wide swaths insar has been used previously to characterize larger magnitude generally permanent aquifer system compaction and land subsidence at yearly and longer timescales caused by sustained drawdown of groundwater levels that produces intergranular stresses consistently greater than the maximum historical stress we present insar measurements of the typically small magnitude generally recoverable deformations of the las vegas valley aquifer system occurring at seasonal timescales from these we derive estimates of the elastic storage coefficient for the aquifer system at several locations in las vegas valley these high resolution measurements offer great potential for future investigations into the mechanics of aquifer systems and the spatial heterogeneity of aquifer system structure and material properties as well as for monitoring ongoing aquifer system compaction and land subsidence

shelf to basin iron shuttle in the guaymas basin gulf of california abstract enrichments of highly reactive iron fe sum of fe oxyhydr oxide carbonate and sulfide minerals in marine sediments and sedimentary rocks are commonly interpreted as an indication of anoxic conditions in the bottom water at the time of deposition the model system for this proxy rationale is the semi restricted black sea where sediments underneath the anoxic and sulfidic i e euxinic deep water are enriched in reactive fe which was mobilized from the surrounding shelf areas to test whether such a shelf to basin fe shuttle can operate in semi restricted basins without euxinic deep water we investigated sedimentary fe speciation and fe isotope compositions in sediments of the guaymas basin gulf of california sediments on the slope underneath the eastern equatorial pacific oxygen minimum zone and sediments within the oxic deep basin are both enriched in reactive fe with reactive fe making up 45 11 of the total fe pool the following mechanisms may contribute to these fe enrichments 1 release of dissolved fe from anoxic shelf and slope sediments followed by lateral transport of dissolved and or particulate fe in the water column 2 preferential transport of fine grained terrigenous particles with a high reactive fe content into the basin 3 microbially mediated conversion of non reactive silicate minerals to reactive fe minerals during transport 4 hydrothermal venting and lateral fe transport within the deep water the first process can explain reactive fe enrichments in slope sediments whereas all processes may contribute to sedimentary fe enrichments in the deeper basin the 56 fe value of sediments increases from shelf to slope and decreases from the slope into the basin this lateral pattern of 56 fe as well as the pattern of fe enrichment is similar to that observed in other marine systems with a fe shuttle however the size of the fe enrichment and the range in 56 fe 0 06 to 0 16 is smaller this difference is due to higher terrigenous sedimentation rates in the guaymas basin and therefore more intense dilution of shuttle derived reactive fe we argue that depending on the extent of bathymetric restriction and terrigenous background sedimentation reactive fe enrichments can form under a broad range of redox conditions and in diverse sedimentary environments the concepts applied in this study can be used to identify those circumstances in the paleo record

discrepancies between anomalously low reflectance of vitrinite and other maturation indicators from an upper miocene oil source rock los angeles basin california abstract in the westernmost los angeles basin the nodular shale a distinctive richly organic bituminous and phosphatic mudstone occurs just above the unconformable base of the upper miocene modelo formation this 11 5 m y old bathyal oil source rock is present in wells to burial depths 3 810 m 12 500 ft and is inferred to be present within the central syncline of the basin beneath about 9 km 5 5 mi of late miocene to holocene clastic cover forty four subsurface samples of the nodular shale were collected from 14 selected wells located mostly between the playa del rey and crescent heights oil fields sites were selected to give the widest available range of sample depth and temperature where present burial depths are maximal and where geothermal gradients are firmly established median random reflectance ro of first cycle vitrinite is least in the shallowest samples clusters about 0 24 in the deeper samples and exceeds 0 30 only in the deepest and hottest samples extremes in the range of measured median ro are tabulated below with corresponding extremes of sample temperatures depths time temperature indices tti and calculated ro equivalents of the tti values table all measured values of ro are significantly depressed compared to other maturity criteria significantly second cycle and oxidized vitrinite from these same samples show normally elevated reflectance eight of the samples processed for reflectance measurements were analyzed for total organic carbon content which ranges from 2 21 to 9 41 most of the organic detritus is amorphous degraded algal material less than 10 is structured vitrinite thermal alteration index values for the amorphous material range from 2 to 2 corresponding with hypothetical conversion ro values between 0 45 and 0 75 again notably higher than the measured values the ratios of extractable hydrocarbons to toc in the 8 samples suggest mature levels of thermal evolution as do carbon preference indices of 0 93 and 1 14 from extracts of 2 samples striking similar patterns of vitrinite reflectance values have been described from alginites in some australian coalfields and oil shales the data suggest to us that hydrogen rich organic matter matures at lower temperatures and at a substantially faster rate and lower tti values than detritus dominated by structured organic matter of lower hydrogen content the depressed ro measurements evidently reflect the hydrogen rich nature of the dominant detritus and thus are not reliable indicators of either paleotemperature or thermal maturity in the most oilprone source rocks in fact depressed ro values may be indicators of ultra rich source rocks when normalized for other influences end of article last page 565

a novel approach to model earth fissure caused by extensive aquifer exploitation and its application to the wuxi case china initially observed in the semi arid basins of southwestern usa earth fissures due to aquifer over exploitation are presently threatening a large number of subsiding basins in various countries worldwide different mechanics have been proposed to explain this process such as differential compaction horizontal movements and fault reactivation numerical modeling and prediction of this major geo hazard caused by overuse of groundwater resources are challenging because of two main requirements shifting from the classical continuous to discontinuous geomechanics and incorporating 2 dimensional features the earth fissures into large 3 dimensional 3d modeling domain the subsiding basin in this work we proposed a novel modeling approach to simulate earth fissure generation and propagation in 3d complex geological settings a nested two scale approach associated with an original non linear elasto plastic finite element interface element simulator allows modeling the mechanics of earth discontinuities in terms of both sliding and opening the model is applied on a case study in wuxi china where groundwater pumping between 1985 and 2004 has caused land subsidence larger than 2 m the model outcomes highlight that the presence of a shallow 80 m deep bedrock ridge crossing the yangtze river delta is the key factor triggering the earth fissure development in this area bending of the alluvial deposits around the ridge tip and shear stress due to the uneven piezometric change and asymmetrical shape of the bedrock have caused the earth fissure to onset at the land surface and propagate downward to a maximum depth of about 20 30 m maximum sliding and opening are computed in the range of 10 to 40 cm in agreement with the order of magnitude estimated in the field

formation of conical fractures in sedimentary basins experiments involving pore fluids and implications for sandstone intrusion mechanisms large sand intrusions often exhibit conical morphologies analogous to magmatic intrusions such as saucer shaped or cup shaped sills whereas some physical processes may be similar we show with scaled experiments that the formation of conical sand intrusions may be favoured by the pore pressure gradients prevailing in the host rock before sand injection our experiments involve injecting air into a permeable and cohesive analogue material to produce hydraulic fractures while controlling the pore pressure field we control the state of overpressure in the overburden by applying homogeneous basal pore pressure and then adding a second local pore pressure field by injecting air via a central injector to initiate hydraulic fractures near the injection point in experiments involving small vertical effective stresses small overburden or high pore fluid overpressure the fracturing pressure lambda fract is supralithostatic and two dipping fractures are initiated at the injection point forming a conical structure from theoretical considerations we predict that high values of lambda fract are due to strong cohesion or high pore fluid overpressure distributed in the overburden such conditions are favoured by the pore pressure stress coupling induced by both pore pressure fields the dips of cones can be accounted for elastic stress rotation occurring around the source contrary to magmatic chamber models the aqueous fluid overpressure developed in a parent sandbody and prevailing before the formation of injectites may diffuse into the surrounding overburden thus favouring stress rotation and the formation of inclined sheets far from the parent source for experiments involving higher vertical effective stresses thick overburden or low pore fluid overpressure the fracturing pressure is lower than the lithostatic stress and a single fracture is opened in mode i which then grows vertically at a critical depth the fracture separates into two dilatant branches forming a flat cone we make use of a p i v particle imaging velocimetiy technique to analyse plastic deformation showing that these inclined fractures are opened in mixed modes close to the surface they change into steep shear bands where fluids can infiltrate the final morphology of the fracture network is very similar to the common tripartite architecture of various injection complexes indicating that different mechanisms may be involved in the formation of dykes feeder dykes under the sill zones may open as tensile fractures while overlying dykes may be guided by the deformation induced by the growth of sills these deformation conditions may also favour the formation of fluid escape structures and pockmarks c 2011 elsevier b v all rights reserved

seismic volcanostratigraphy of the norwegian margin constraints on tectonomagmatic break up processes voluminous volcanism characterized early tertiary continental break up on the mid norwegian continental margin the distribution of the associated extrusive rocks derived from seismic volcanostratigraphy and potential field data interpretation allows us to divide the more voring and lofoten vesteralen margins into five segments the central more margin and the northern voring margin show combinations of volcanic seismic facies units that are characteristic for typical rifted volcanic margins the lofoten vesteralen margin the southern voring margin and the area near the jan mayen fracture zone show volcanic seismic facies units that are related to small volume submarine volcanism the distribution of subaerial and submarine deposits indicates variations of subsidence along the margin vertical movements on the mid norwegian margin were primarily controlled by the amount of magmatic crustal thickening because both the amount of dynamic uplift by the icelandic mantle plume and the amount of subsidence due to crustal stretching were fairly constant along the margin thus subaerial deposits indicate a large amount of magmatic crustal thickening and an associated reduction in isostatic subsidence whereas submarine deposits indicate little magmatic thickening and earlier subsidence from the distribution of volcanic seismic facies units we infer two main reasons for the different amounts of crustal thickening 1 a general northward decrease of magmatism due to increasing distance from the hot spot and 2 subdued volcanism near the jan mayen fracture zone as a result of lateral lithospheric heat transport and cooling of the magmatic source region furthermore we interpret small lateral variations in the distribution of volcanic seismic facies units such as two sets of inner seaward dipping reflectors on the central voring margin as indications of crustal fragmentation

a high resolution benthic stable isotope record for the south atlantic implications for orbital scale changes in late paleocene early eocene climate and carbon cycling abstract the late paleocene and early eocene were characterized by warm greenhouse climates punctuated by a series of rapid warming and ocean acidification events known as hyperthermals thought to have been paced or triggered by orbital cycles while these hyperthermals such as the paleocene eocene thermal maximum petm have been studied in great detail the background low amplitude cycles seen in carbon and oxygen isotope records throughout the paleocene eocene have hitherto not been resolved here we present a 7 7 million year myr long high resolution orbitally tuned benthic foraminiferal stable isotope record spanning the late paleocene and early eocene interval 52 5 60 5 ma from ocean drilling program odp site 1262 south atlantic this high resolution 2 4 kyr record allows the changing character and phasing of orbitally modulated cycles to be studied in unprecedented detail as it reflects the long term trend in carbon cycle and climate over this interval the main pacemaker in the benthic oxygen isotope 18 o and carbon isotope 13 c records from odp site 1262 are the long 405 kyr and short 100 kyr eccentricity cycles and precession 21 kyr obliquity 41 kyr is almost absent throughout the section except for a few brief intervals where it has a relatively weak influence during the course of the early paleogene record and particularly in the latest paleocene eccentricity paced negative carbon isotope excursions 13 c cies and coeval negative oxygen isotope 18 o excursions correspond to low carbonate caco 3 and coarse fraction cf values due to increased carbonate dissolution suggesting shoaling of the lysocline and accompanied changes in the global exogenic carbon cycle these negative cies and 18 o events coincide with maxima in eccentricity with changes in 18 o leading changes in 13 c by 6 5 kyr in the 405 kyr band and by 3 1 kyr in the higher frequency 100 kyr band on average however these phase lags are not constant with the lag in the 405 kyr band extending from 4 5 kyr to 21 2 kyr from the late paleocene to the early eocene suggesting a progressively weaker coupling of climate and the carbon cycle with time the higher amplitude 405 kyr cycles in the latest paleocene are associated with changes in bottom water temperature of 2 4 c while the most prominent 100 kyr paced cycles can be accompanied by changes of up to 1 5 c comparison of the 1262 record with a lower resolution but orbitally tuned benthic record for site 1209 in the pacific allows for verification of key features of the benthic isotope records which are global in scale including a key warming step at 57 7 ma

a typical earth fissure resulting from loess collapse on the loess plateau in the weihe basin china abstract earth fissures are major geological hazards that frequently occur in the weihe basin in northwestern china and can cause severe damage to infrastructure this paper reports a case study of earth fissures resulting from loess collapse in the village of xibai in the weihe basin a series of geological investigations consisting of a site investigation trench excavation geological drilling exploratory well drilling and geotechnical testing were conducted to determine and analyze the characteristics of the xibai village earth fissures as well as the physical characteristics of the loess in the earth fissure development area the earth fissures were parallel to the village sewage pit and had a total length of 800 m with a maximum depth of 8 5 m the xibai village earth fissures were nearly vertical comparing the results of self weight collapsibility coefficient and three parameters void ratio dry density and water content of loess at different distances from the sewage pit the collapsibility of malan loess in this area and the effects of leakage from the sewage pit were determined the results revealed that a tilted seepage line was generated and the loess below this seepage line underwent varying degrees of self weight collapse deformation the nonuniform collapse settlement and rotation deformation of loess above the seepage line were thus generated while tensile stress was created in the upper part of the loess this rotation of loess similar to the deformation of the cantilever beam caused the formation of the earth fissures at the site with higher tensile stress based on the rotation mechanism this study explained the development process of collapse earth fissures and predicted that the xibai village earth fissures would continue to develop outward in the future

silicate weathering machine at work rock magnetic data from the late paleocene early eocene cicogna section italy we describe a scenario of climate forcing on sedimentation recorded in the late paleocene early eocene cicogna marine section from the belluno basin ne italy previously published magneto biostratigraphic data revealed that the 81 m cicogna section extends from chron c25r to chron c23r spanning the np7 np8 np12 nannofossil zones 52 2 56 6 ma using previously published rock magnetic data augmented by data from this study we describe and thoroughly discuss a pronounced increase of hematite relative to maghemite or magnetite between 54 9 and 54 6 ma immediately above the paleocene eocene boundary followed by a second long term increasing trend from 54 ma up to 52 2 ma in the early eocene this hematite is essentially of detrital origin insofar as it is associated with a strong shallow bias of paleomagnetic inclinations and is interpreted to have formed on land by the weathering of fe bearing silicates and other primary minerals we speculate that the warm and humid climate typical of the paleocene eocene thermal maximum petm 54 9 ma as well as of the warming trend leading to the early eocene climatic optimum eeco 52 50 ma enhanced continental weathering of silicate rocks with the consequent production transport and sedimentation of detrital hematite grains this hypothesis is confirmed by a statistical correlation between the rock magnetic properties and global climate as revealed by a standard benthic oxygen isotope record from the literature our temporal coupling between oxidation state of sedimentary magnetic phases and global climate is therefore consistent with the existence in the paleocene eocene of the silicate weathering negative feedback mechanism for the long term stabilization of the earth s surface temperature

a method to predict the group fissuring and faulting caused by regional groundwater decline ground fissuring is a recurrent problem in many countries where water extraction surpasses the natural recharge of aquifers due to differential settlement the soil layer undergoes deformation and cracks with serious consequences for civil infrastructure here we propose an approximate analysis of the fissuring process that can be used to predict the location of cracks which increasingly affect some middle and large sized cities in the world for that purpose the ground loss theory is applied to sediments overlying a sinusoidal shaped graben this analysis shows the existence of a tensile zone at the border of the graben with maximal values on its shoulder where tension cracks are more likely to appear it also shows that soil deformation under differential settlement may evolve into ground faulting if water withdrawal continues finally when a crack has completely developed the tensile zone shifts towards the center of the graben creating a new area for potential cracking and faulting

links between seawater paleoredox and the formation of sediment hosted massive sulphide shms deposits fe speciation and mo isotope constraints from late devonian mudstones abstract many models of sediment hosted massive sulphide shms deposit formation invoke basin restriction events that resulted in long term stagnation and anoxia in which sulphidic euxinic conditions ultimately prevailed euxinic conditions are then thought to provide a chemical trap for hydrothermally exhaled base metals here we present fe speciation and mo isotope data for organic rich mudstones from two drill holes intersecting upper devonian strata deposited along the passive margin of ancestral north america one drill hole intersects a 35 m thick sequence of shms mineralisation while the other intersects correlative un mineralised strata all samples have high fehr fet values 0 38 indicating water column anoxia for the majority of samples in the un mineralised drill hole the levels of pyritisation fall below the threshold typically used to define euxinic conditions fepy fehr 0 70 in contrast higher levels of pyritisation in the mineralised drill hole median fepy fehr 0 86 likely developed via diagenetic pyrite enrichment whereas pb and zn are negatively correlated with mo mo u co variation is consistent with fe oxyhydr oxide particulate shuttling in the water column in addition a weak correlation between toc p and mo provides further evidence that mo was sourced via authigenic rather than hydrothermal processes the 98mo values 0 66 to 1 02 are uniform between both drill holes and substantially lower than constraints for late devonian seawater 1 5 to 2 0 consistent with mo adsorption to fe oxyhydr oxides collectively the data provide evidence that local seawater was dominantly ferruginous anoxic non sulphidic at macmillan pass regional variability in the extent of ferruginous low toc p and euxinic high toc p conditions likely contributed to a balance between p regeneration and p enrichment that maintained nutrient availability and productivity in the selwyn basin during the late devonian we argue that high primary productivity and enhanced organic carbon burial are key variables for promoting sulphate reduction in the sub surface moreover how such conditions are maintained over long periods of basin evolution is more important for producing effective metal traps in shms systems rather than a specific localised redox condition of seawater i e euxinia

discussion on structure and evolution of hydrothermal vent complexes in the karoo basin south africajournal vol 163 2006 671 682 b e lock j a robey write we were interested to read the paper by svensen et al 2006 on south african hydrothermal vents within the karoo basin particularly concerning two vent complexes known as witkop ii and witkop iii one of us b e l had barely initiated a study of the stormberg diatremes when he left south africa to accept a faculty position in louisiana in 1977 and the project was not continued however the svensen paper reminded us of features we had seen in the field at the mackay s kop diatreme near jamestown in the mid 1970s this diatreme is in the same general area as those described by svensen et al but had not been visited by the latter because of their difficulty in locating the absentee landowner g marsh pers comm in particular we note the description of a partly undulating border zone typical for the pipes at witkop iii complex which the authors interpreted as a deformation zone based on figures in the original paper particularly their figure 7c a similar zone surrounds the mackay s kop diatreme but our interpretation differs significantly from that of svensen et al and bears on the mechanisms involved in diatreme formation and evolution the pipe at mackay s kop has a central fill consisting of a variety of lithofacies massive sandstone heterolithic breccias with sandstone and mudstone clasts and small pebble conglomerates consisting of well rounded sandstone clasts fig 1 a narrow marginal zone 15 40 cm wide of sandstone is the equivalent we believe of the deformation zone of svensen et al

thermal effects of igneous intrusions on maturity of organic matter a possible mechanism of intrusion abstract this paper assesses thermal maturation of organic matter near a well dated intrusion in the dsdp 41 368 hole near cape verde rise eastern atlantic and near some other intrusions from the u k u s a and east greenland the traditional numerical model with instantaneous intrusion satisfactorily describes the thermal evolution and thermal maturity aureoles of igneous bodies only if the initial temperature of intrusion is close to or even lower than the solidus temperature calculations in this model with more real values of the intrusion temperature and with consideration of latent heat effects lead to considerable over estimation of thermal influence of the intrusion models which consider formation of the intrusive body over time as distinct from instantaneous intrusion and especially models of emplacement of an intrusive body in the shell of relatively cool magmatic rocks show better agreement between the computed and observed vitrinite reflectance profiles consideration of convective heat flow due to hydrothermal activity arising in the vicinity of the intrusion during its formation and cooling helps to explain the difference between maturation profiles above and below some sills

fault controlled deformation and stress from pumping induced groundwater flow summary four two dimensional numerical model scenarios are developed to gain a better understanding of how earth fissures form under pumping induced stress the simulated aquifer aquitard system contains a low compressibility sub vertical 100 m wide fault zone that transects the hydrostratigraphic system that includes a 100 m thick vadose zone two scenarios represent constant and cyclical pumping over a 5 year period and two scenarios are used to evaluate the difference between using purely elastic aquitards versus elasto plastic aquitards the model provides for the analysis of the spatial distribution of deformation and normal and shear stress that potentially lead to the formation of earth fissures results indicate that this fault zone largely controls the deformation and stress regime of the system during pumping patterns of deformation and stress are similar for all scenarios with only the magnitudes being affected simulation results show that pumping induces a counterclockwise rotation of the fault plane on the footwall the distribution of deformation through the fault is damped and the deformation patterns are more subdued on the hanging wall but all deformation is directed toward the pumping well these deformation patterns result in two areas of stress accumulation that may lead to fissure formation a near the land surface in the fault zone and b near the saturated unsaturated interface on the hanging wall adjacent to the fault zone these results reveal the importance of both the fault and vadose zones in fissure genesis

geochemical characterization of deep sea sediments on the azores plateau from diagenesis to hydrothermal activity abstract the azores plateau is an active magmatic region in the central north atlantic ocean in this study we present a comprehensive data set of major element compositions and 87sr 86sr ratios of pore waters from surface sediments 0 9 mbsf of the azores plateau based on distinct geochemical signatures we can separate normal marine from hydrothermally affected sediments normal marine sediments can further be differentiated by their ash content pore waters of ash rich gravity cores gcs do not show any deviations from seawater values except of a minor increase in sr in contrast ash poor gcs generally show a trend for decreasing ca with increasing depth accompanied by a minor so4 decrease and a more pronounced sr increase we suggest that these deviations are caused by processes such as anaerobic oxidation of methane and carbonate recrystallization at four additional sample locations we observed a decrease in mg and so4 accompanied by a ca increase in the pore waters a pattern typical for hydrothermal fluids the existence of hydrothermal systems in this region are corroborated by multi channel seismic data suggesting that sill or dyke intrusions are present in the subsurface close to the core locations overall our observations offer preliminary indications for the existence of submarine hydrothermal systems on the azores plateau away from the mid atlantic ridge

three dimensional numerical simulation of fully coupled groundwater flow and land deformation due to groundwater pumping in an unsaturated fluvial aquifer system a series of three dimensional numerical simulations using a hydrogeomechanical numerical model is performed to analyze and predict fully coupled groundwater flow and land deformation due to groundwater pumping in an unsaturated fluvial aquifer system which has irregular lateral boundaries the aquifer system is composed of a loam layer underlain by a sand layer on bedrock a steady state numerical simulation is performed first to obtain initial spatial distributions of pressure head hydraulic head and groundwater flow velocity before groundwater pumping and its results are illustrated and validated reasonably with respect to field measurements of hydraulic head a transient state numerical simulation is then performed to obtain spatial and temporal distributions of pressure head hydraulic head groundwater flow velocity and land displacement vector during groundwater pumping and its results are also illustrated and validated reasonably with respect to field measurements of both hydraulic head and vertical displacement these numerical simulation results show that hydrogeomechanical numerical modeling can be a useful tool for analyzing and predicting long term groundwater level fluctuation and land deformation due to groundwater pumping in actual three dimensional aquifer systems