early hydrothermal carbon uptake by the upper oceanic crust insight from in situ u pb dating it is widely thought that continental chemical weathering provides the key feedback that prevents large fluctuations in atmospheric co2 and hence surface temperature on geological time scales however low temperature alteration of the upper oceanic crust in off axis hydrothermal systems provides an alternative feedback mechanism testing the latter hypothesis requires understanding the timing of carbonate mineral formation within the oceanic crust here we report the first radiometric age determinations for calcite formed in the upper oceanic crust in eight locations globally via in situ u pb laser ablation inductively coupled plasma mass spectrometry analysis carbonate formation occurs soon after crustal accretion indicating that changes in global environmental conditions will be recorded in changing alteration characteristics of the upper oceanic crust this adds support to the interpretation that large differences between the hydrothermal carbonate content of late mesozoic and late cenozoic oceanic crust record changes in global environmental conditions in turn this supports a model in which alteration of the upper oceanic crust in off axis hydrothermal systems plays an important role in controlling ocean chemistry and the long term carbon cycle

u th dating of striated fault planes direct dating of brittle fault activity is of fundamental importance to tectonic reconstructions and paleoseismic studies one way to address this issue is by constraining the timing of fault striations but this requires a better understanding of the striation formation mechanism and associated mineralization we present results from a microstructural geochemical and geochronological study of calcite precipitates associated with striated fault planes from the dead sea fault zone in northern israel we recognize four types of coexisting calcite precipitates including calcite cement in dilation breccia calcite in striated groove morphology calcite gouge associated with hydraulic fracturing and pressure solution and calcite coating of the fault surface carbon oxygen isotopes 87sr 86sr ratios and rare earth element and yttrium rey patterns indicate various precipitation mechanisms associated with formation of syntectonic calcite cement and striations coseismic calcite gouge and interseismic calcite coating precipitates in the fault zone using u th dating of samples from three adjacent fault planes we delineate four welldefined deformation ages in the period from 220 to 60 ka we conclude that these ages constrain the timing of activity along the dead sea fault zone in northern israel and argue that a similar methodological approach could potentially shed light on the timing of deformation in other brittle fault zones

allochthonous slope sequence at lobster cove head evidence for a complex middle ordovician platform margin in western newfoundland the upper part of an intact sequence of lower to middle ordovician deep water sediments which now form a large disrupted raft within the rocky harbour melange at lobster cove head is interpreted as having been deposited downslope from a drowned carbonate platform margin the entire 50 m thick section is arenig late canadian or ibexian to early whiterock in age graptolite biostratigraphy demonstrates a correlation with upper parts of the cow head group to the north the basal part of the section is a proximal facies of the cow head group shallow bay formation factory cove member beds 9 10 and part of bed 11 the upper part of the section consists of interbedded dolostone and shale and is unlike any other sequence in the cow head group this upper sedimentary sequence is defined as the lobster cove head member of the shallow bay formation cow head group contact between the two sedimentary packages is also marked by a faunal break and coincides with emplacement of megaconglomerate bed 12 at cow

a condensed lower to middle ordovician graptolite succession at matane quebec canada the highly condensed lower to middle ordovician deep water succession from the cap des rosiers group at matane bears three conspicuous graptolite faunas of late tremadoc to mid darriwilian age the tremadoc fauna belongs to the aorograptus victoriae zone in the castlemainian isograptus victoriae maximodivergens zone fauna the earliest pseudisograptus species pseudisograptus initialis n sp appears together with the ancestral arienigraptus gracilis a darriwilian fauna with holmograptus spinosus and bergstroemograptus crawfordi represents the youngest pre nemagraptus gracilis zone fauna described from the quebec appalachians

the faroe shetland basin a regional perspective from the paleocene to the present day and its relationship to the opening of the north atlantic ocean the faroe shetland basin is located offshore nw scotland on the se margin of the atlantic ocean and comprises numerous sub basins and intra basin highs that are host to a number of significant hydrocarbon discoveries the principal hydrocarbon discoveries are in palaeocene eocene strata though earlier ones are known and therefore their existence is intimately linked to the opening and evolution of the north atlantic from 54 ma the final rifting and separation of greenland from eurasia is commonly attributed to the arrival of a mantle plume which impacted beneath greenland in the early tertiary moreover the ensuing plate separation is commonly described in terms of instantaneous unzipping of the north atlantic whereas in reality proto plate boundaries were more diffuse during their inception and the linked rift system including connections with the arctic which we see today was not established until late palaeogene early neogene time from a regional analysis of ocean basin development including the stratigraphic record on the adjacent continental margins the significance of the greenland iceland faroe ridge and the age and role of iceland we propose a dual rift model whereby north atlantic breakup was only partial until the oligo miocene with true final breakup only being achieved when the reykjanes and kolbeinsey ridges became linked as final breakup coincides with the appearance of iceland this model negates the need for a plume to develop the north atlantic with rifting reliant on purely plate tectonic mechanisms lithospheric thinning and variable decompressive upper mantle melt along the rifts

lower ordovician arenig llanvirn graptolites from the notre dame subzone central newfoundland many lower paleozoic rocks in the notre dame subzone of central newfoundland are of unknown or imprecise age several new lower ordovician graptolite occurrences are here reported and earlier records revised new graptolite localities in the balsam bud cove formation at snooks arm on the baie verte peninsula previously recorded as early ordovician arenig have yielded an assemblage identical to that found in the middle part of bed 11 of the cow head group western newfoundland indicating a probable lower didymograptus bifidus zone age at corner pond southeast of corner brook an abundant diverse fauna from the corner pond formation indicates a marginally older age for the black shales than those at snooks arm pendeograptus fruticosus zone equivalent to lower bed 11 black shales associated with felsic volcanics and limestone breccia belonging to the cutwell group at lushes bight on long island western notre dame bay which were previously assigned to the widespread black shales of the lawrenc

u pb geochronology of calcite mineralized faults absolute timing of rift related fault events on the northeast atlantic margin constraining the timing of brittle faulting is critical in understanding crustal deformation and fluid flow but many regional scale fault systems lack readily available techniques to provide absolute chronological information calcite mineralization occurs in crustal faults in many geological settings and can be suitable for u pb geochronology this application has remained underutilized because traditional bulk dissolution techniques require uncommonly high u concentration because u and pb are distributed heterogeneously throughout calcite crystals high spatial resolution sampling techniques can target domains with high u and variable u pb ratios here we present a novel application of in situ laser ablation inductively coupled plasma mass spectrometry la icp ms to basaltic fault rock geochronology in the faroe islands northeast atlantic margin faults that are kinematically linked to deformation associated with continental break up were targeted acquired ages for fault events range from mid eocene to mid miocene and are therefore consistently younger than the regional early eocene onset of ocean spreading highlighting protracted brittle deformation within the newly developed continental margin calcite geochronology from la icp ms u pb analysis represents an important and novel method to constrain the absolute timing of fault and fluid flow events

vein calcite dating reveals pyrenean orogen as cause of paleogene deformation in southern england an improved method of u pb dating of vein calcite formed during deformation is used to determine the age and cause of folding along the south coast of england fractures arising from folding of late cretaceous chalk of southern england occurred 34 7 1 7 myr ago underlying jurassic strata have veins within fractures with ages of 55 48 42 39 37 34 31 and 25 ma with 34 31 ma being the tectonic culmination folding was slightly younger than the age of the youngest strata in the overlying solent group suggesting that folding terminated basin sedimentation this age of north south shortening is inconsistent with attribution to intraplate forces from the mainly younger alps but is plausibly a result of the pyrenean orogen which evolved from 50 to 28 myr ago with a late eocene culmination a modified method for carbonate laser ablation inductively coupled plasma mass spectrometry u pb dating is presented that uses measured 232 th and 208 pb as a better monitor of common pb and it has distinct advantages over existing methods initial common lead determined on samples conforms closely to model compositions calculated by earlier workers with free regressions giving the most robust dates the modified method is applicable to structural geology carbonate diagenesis and to dating of carbonate relevant to palaeo environmental and archaeological studies supplementary material details of sample locations and characteristics photographs of sample localities microscopic images of veins details of the experimental procedure and u pb data for all samples and reference materials are available at https doi org 10 6084 m9 figshare c 3997086

quartz arenites of the cambro ordovician kamouraska formation quebec appalachians canada ii eolian sands in deep sea sedimentary gravity flow deposits the kamouraska formation is a quartz arenitic unit of latest cambrian earliest ordovician age in the quebec appalachians that was deposited by hyperconcentrated to concentrated density flows in a meandering submarine canyon on the continental slope bordering the iapetus ocean as outlined in a companion paper detailed petrographic study of the quartz arenites of the kamouraska formation combined with scanning electron microscopy of grain surface textures suggests that the quartz sands are of eolian origin having been derived from an inland desert or less likely a barrier beach dune system transport of the mature quartz arenitic sand onto the shelf and deposition into the deep sea was not accompanied by substantial mixing with material from other sources thus preserving the inherited eolian characteristics a modern analogue for the eolian interpretation of the deep sea quartz arenite beds is as follows thick late pleistocene eolian sand beds on a modern abyssal plain in the east atlantic referred

la icp ms u pb geochronology and clumped isotope constraints on the formation and evolution of an ancient dolomite reservoir the middle permian of northwest sichuan basin sw china abstract recent advances in laser ablation inductively coupled plasma mass spectrometry la icp ms in situ u pb radiometric dating and clumped isotope thermometry 47 of carbonate minerals provide potential for refining the fluid flow and diagenetic history of carbonate successions in this study the middle permian dolomites proximal to the longmenshan fold and thrust belt in northwest sichuan basin southwest china were investigated using combined u pb geochronology clumped isotope thermometry and routine isotopic 13c 18o and 87sr 86sr and elemental geochemistry in an attempt to reveal the possible relevance of carbonate diagenesis and porosity evolution to the basin scale tectonic fluid flow events in the framework of absolute time overall formation and evolution of these dolomites temporally correlated well with major tectonic episodes of the longmenshan fold and thrust belt contrary to the previously assumed volcanic related model u pb dating and 47 analyses suggest a mid to late triassic replacive dolomitization event u pb ages of 240 12 ma to 233 8 6 4 ma by a hot 47 temperatures 88 104 c basinal brine which was likely driven by thrust related compression of the longmenshan fold and thrust belt during the triassic replacive dolomitization was immediately followed by cementation of euhedral dolomites u pb age of 228 10 ma and blocky calcites u pb ages of 224 8 1 8 ma to 213 4 3 3 ma precipitated from the basinal brine in the same tectonic regime afterwards there was long term cessation of diagenesis that was coincident with and thus may well be attributed to tectono thermal quiescence during most of the mesozoic era and paleogene finally saddle dolomite cements yield miocene ages u pb ages of 16 40 0 74 ma to 12 3 1 2 ma and precipitated in pre existing vugs representing a hydrothermal fluid flow event 47 temperatures up to 170 c during the reactivation of thrusting in addition similarities in u pb ages and geochemical signatures between host rocks replacive dolomites and the vug lining dolomite cements suggest that most porosity in these dolomite reservoirs was inherited from the precursor limestones which probably experienced meteoric leaching during late permian uplift this study highlights that there are geodynamic controls on fluid flow and consequent diagenetic evolution of carbonates in tectonically active sedimentary basins it illustrates that burial alone in this setting is not a sufficient driver for diagenetic alteration and porosity reduction the combination of u pb radiometric dating clumped isotope thermometry and routine geochemical analyses is a useful approach in refining the diagenetic and porosity evolution history of ancient carbonate successions

assemblages de chitinozoaires dans l ordovicien inferieur de l est du canada from a description of middle arenig chitinozoa from the levis formation zone c and the cow head group a succession of the main lower ordovician chitinozoan assemblages is proposed this succession is compared with the main assemblages described in the literature this comparison allows recognition of taxa with potential stratigraphie value

clumped isotope palaeothermometry and la icp ms u pb dating of lava pile hydrothermal calcite veins calcite veins are a common product of hydrothermal fluid circulation clumped isotope palaeothermometry is a promising technique for fingerprinting the temperature of hydrothermal fluids but clumped isotope systematics can be reset at temperatures of ca 100 c to model whether the reconstructed temperatures represent calcite precipitation or closed system resetting the precipitation age must be known la icp ms u pb dating of calcite is a recently developed approach to direct dating of calcite and can provide precipitation ages for modelling clumped isotope systematics in calcite veins in this study clumped isotope and la icp ms u pb calcite analyses were combined in basalt hosted calcite veins from three settings in scotland samples from all three localities yielded precipitation temperatures of ca 75 115 c from clumped isotope analysis but veins from only two of the sites were dateable yielding precipitation ages of 224 8 ma and 291 33 ma 2 modelling from the dated samples enabled confident interpretation that no closed system resetting had occurred in these samples however the lack of a precipitation age from the third location meant that a range of possible thermal histories had to be modelled meaning that confidence that resetting had not occurred was lower this highlights the importance of coupling clumped isotope thermometry and la icp ms u pb calcite dating in determining the temperature of hydrothermal fluids recorded in calcite veins this paired approach is shown to be robust in constraining the timing and precipitation temperature of calcite formation and thus for tracking hydrothermal processes

radiogenic isotopes record a drop in a bucket a fingerprint of multi kilometer scale fluid pathways inferred to drive fault valve behavior abstract minerals precipitated from fluids carry a chemical signature of fluid origin and transport history we use this concept to test the hypothesis that a subset of veins precipitated in the loma blanca fault zone rio grande rift nm usa record fault valve behavior previous studies of this site show syntectonic calcite veins formed in response to post seismic fluid discharge following repeated ground rupturing earthquakes u th ages on veins constrain the timing of fault slip over a period of 400 000 years the radiogenic isotope sr pb and u data we report here demonstrate that a cluster of earthquakes that occurred at 430 ka when fault slip frequency increased by nearly one order of magnitude corresponds with a brief period of particularly large and rapid variations in post seismic fluid chemistry isotopic variations are consistent with fluid input from the socorro magma body a large active mid crustal basalt intrusion 19 km below the surface the short duration of the earthquake cluster

the onset of the dead sea transform based on calcite age strain analyses the onset and evolution of the dead sea transform are re evaluated based on new in situ u pb dating and strain analyses of mechanically twinned calcites direct dating of 30 syn faulting calcites from 10 different inactive fault strands of the transform indicates that the oceanic to continental plate boundary initiated between 20 8 and 18 5 ma within an 10 km wide distributed deformation zone in southern israel ages from the northern dead sea transform 17 1 12 7 ma suggest northward propagation and the establishment of a well developed 500 km long plate bounding fault in 3 m y the dominant horizontal shortening direction recorded in the dated twinned calcites marks the onset of left lateral motion along the evolving plate boundary the observed changes in the strain field within individual fault strands cannot be simply explained by local weakening effects along strands of the dead sea transform or by gradual changes in the euler pole through time

temporal and spatial relations between large scale fault systems evidence from the sinai negev shear zone and the dead sea fault abstract in the major zones of crustal deformation within the arabia sinai nubia plates the interactions between the sinai negev shear zone snsz and the dead sea fault system dsf shed light on the interplay between neighboring large scale fault systems the snsz is composed of several e w to ene wsw trending mainly normal and dextral strike slip faults that are tens to hundreds of kilometers long these faults form a 120 km wide shear zone in the sinai sub plate on reaching the plate bounding dead sea fault system dsf individual lineaments of the snsz are observed in the arabian plate offset left laterally by 105 km which is the total estimated offset of the dsf in this contribution we review the geologic setting of the snsz and its complex relations with the dsf in light of newly obtained age strain analyses for this we use in situ u pb geochronology in conjunction with twin analysis of syn faulting calcite from both systems the results indicate that the deformation along the snsz initiated in the campanian maastrichtian or earlier as the oldest dates are 73 71 ma the main phase of fault activity began in the late oligocene early miocene 27 22 ma as documented by numerous dates that were obtained along several lineaments of the snsz the activity continued until 10 ma after which no direct ages have been obtained the dominant phase of activity along the snsz at 27 22 ma preceded the timing of initiation of lateral faulting along the dsf at 20 18 ma by a few myr for the overlapping period of activity between 20 and 10 ma episodes of fault activity along the snsz followed by episodes of fault activity along the dsf moreover dominant episodes of activity along one fault system were associated with a decrease in activity along the other system the temporal relations between the snsz and dsf highlight the possibility that these fault systems are mechanically interrelated but the exact mechanism for this fault interaction needs further study we consider the paleo strain or paleo stress that control the evolution and style of the snsz and assess them at the central sinai negev region during the cenozoic we show that the formation of new plate boundaries at the region i e the red sea suez rift and the dsf affected the strain field within the snsz the proximity of the two systems indicates that the dsf related stress originated within the snsz and possibly caused structural and style changes in the latter system syn faulting calcite twins analyses within the snsz show pronounced spatial and temporal variations of the principal strain directions between and along individual faults this observation demonstrates that the imposed stress within the central sinai negev were not uniform over time the high angle 70o between the traces of the snsz and the direction of the dsf related maximum shortening likely suppressed the dextral motion along the snsz post 20 ma field evidence u pb dates and recent seismicity shows that the current snsz is a long lived structure that has been active during the miocene alongside the dominantly dsf and may still be sporadically active today

isotopic evidence for microbial production and consumption of methane in the upper continental crust throughout the phanerozoic eon microorganisms produce and consume methane in terrestrial surface environments sea sediments and as indicated by recent discoveries in fractured crystalline bedrock these processes in the crystalline bedrock remain however unexplored both in terms of mechanisms and spatiotemporal distribution here we have studied these processes via a multi method approach including microscale analysis of the stable isotope compositions of calcite and pyrite precipitated in bedrock fractures in the upper crust down to 1 7 km at three sites on the baltic shield microbial processes have caused an intriguing variability of the carbon isotopes in the calcites at all sites with 13c spanning as much as 93 1 related to anaerobic oxidation of methane to 36 5 related to methanogenesis spatiotemporal coupling between the stable isotope measurements and radiometric age determinations micro scale dating using new high spatial methods la icp ms u pb for calcite and rb sr for calcite and co genetic adularia enabled unprecedented direct timing constraints of the microbial processes to several periods throughout the phanerozoic eon dating back to devonian times these events have featured variable fluid salinities and temperatures as shown by fluid inclusions in the calcite dominantly 70 85 c brines in the paleozoic and lower temperatures 50 62 c and salinities in the mesozoic preserved organic compounds including plant signatures within the calcite crystals mark the influence of organic matter in descending surficial fluids on the microbial processes in the fracture system thus linking processes in the deep and surficial biosphere these findings substantially extend the recognized temporal and spatial range for production and consumption of methane within the upper continental crust

a calcite reference material for la icp ms u pb geochronology u pb dating of calcite is an emerging but rapidly growing field of application in geochronology with great potential to inform problems in landscape basin and mountain belt evolution through age determination of diagenetic cements vein mineralisation and geological formations difficult to date otherwise in this brief we present isotope dilution u pb isotope measurements on a sample of calcite wc 1 that has been and will continue to be used as a reference material for in situ u pb laser ablation inductively coupled plasma mass spectrometry la icp ms dating and which is suitable to be distributed to the geochronological community we present in situ measurements using la icp ms to demonstrate the suitability of wc 1 for use as a u pb dating reference material in spite of it not being isotopically homogeneous the wc 1 calcite sample is 254 4 6 4 ma old and comprised of 85 to 98 radiogenic lead it presents a suitable reference material that can facilitate dating of calcite ranging in age from precambrian to late neogene age

u pb dating of calcite in ancient carbonates for age estimates of syn to post depositional processes a case study from the upper ediacaran strata of finnmark arctic norway results of in situ u pb dating of calcite spherulites cone in cone cic calcite and calcite fibres from a calcareous concretion of the upper ediacaran of finnmark arctic norway are reported ca

new biostratigraphic information from the western part of the hamburg klippe pennsylvania and its significance for interpreting the depositional and tectonic history of the klippe biostratigraphic investigation of the graptolite and conodont faunas of the western part of the hamburg klippe of eastern pennsylvania permits a revised stratigraphic framework and new conclusions regarding its likely tectonic setting graptolite and conodont data reveal an almost complete lower to lower upper ordovician zonal section no cambrian strata appear to be present with the possible exception of the uppermost part during early to early middle ordovician time medium to fine grained siliciclastics and minor carbonate sediments were deposited in a lower slope and rise setting these sediments were consolidated and incorporated as olistoliths in an olistostrome possibly as a trench fill complex during the middle ordovician darriwilian 3 4 this olistostrome which contains large lower and lower middle ordovician fragments within a matrix of shales siltstones and sandstones of da 3 4 age is herein named the shellsville member of the dauphin formation turbidites here assigned to the nyes road member of the dauphin formation were also deposited during da 3 4 time these rocks interfinger with red beds of the here named manada hill member of the dauphin formation the red shales cherts and associated rocks of the manada hill member are pelagic deposits that range in age from at least early arenig through middle llanvirn time these allochthonous rocks were emplaced as a gravity generated klippe into the martinsburg foreland basin during late climacograptus bicornis or early dicranograptus clingani time these three members compose the dauphin formation new in the western part of the klippe area prior to emplacement of the allochthon syntectonic flysch and scattered wildflysch of the martinsburg formation were deposited some graptolite faunas from the martinsburg formation where contiguous with the klippe may be slightly older than those known from areas farther from the klippe this could indicate an earlier start of deposition in the martinsburg foreland basin in advance of the allochthon the klippe occupied a large space in the martinsburg foreland basin and it diverted deposition in this area until it was finally covered by late martinsburg age sediment the dauphin formation is now structurally interleaved and folded with the martinsburg formation as a result of late taconian and later alleghenian tectonism

middle ordovician late dapingian darriwilian conodonts from the cow head group and lower head formation western newfoundland canada1this article is one of a series of papers published in cjes special issue in honour of ward neale on the theme of appalachian and grenvillian geology middle ordovician late dapingian darriwilian conodonts from the shallow bay and green point formations cow head group and the lower head formation are recorded from three sections in gros morne national park the collection was investigated to clarify local age relationships between the uppermost part of the cow head group and the interbedded to overlying sediments of the lower head formation conodonts from st pauls inlet north section indicate a middle dapingian age for the upper lower bed 13 latest dapingian to early darriwilian age for the upper bed 13 an early darriwilian dw 1 age for the top beds or bed 15 of the shallow bay formation at lower head and the lower head formation is referred to the darriwilian the uppermost part of the lower bed 13 contains periodon hankensis n sp gothodus sp a and diaphorodus delicatus followed by periodon macrodentatus ansella longicuspica erraticodon n sp a and spinodus wardi n sp in the lowermost part of upper bed 13 the fauna with p macrod

u pb dating of calcite veins reveals complex stress evolution and thrust sequence in the bighorn basin wyoming usa reply we report u pb absolute ages of calcite cements from a diffuse vein network documented in the bighorn basin wyoming usa where distinct systematic vein sets developed at the front of the thin skinned sevier orogen during laramide layer parallel shortening and during thick skinned laramide thrusting and folding the u pb age distribution illustrates 1 an outward eastward transmission of sevier orogenic stress from 89 7 2 9 ma 2 in the west and from 75 3 2 8 ma in the east and 2 an inward westward development of laramide related fracturing and folding 72 3 0 ma and 45 4 1 8 ma respectively in the east 60 5 4 6 ma and 27 9 1 1 ma respectively in the west which is in accordance with the known sequence of exhumation of the major laramide basement arches our results also show that the stress related to laramide compression first overprinted the stress related to sevier compression in the sedimentary cover around major basement uplifts this study highlights the utility of u pb calcite geochronology as a powerful tool for constraining complex sequences of deformation in orogenic forelands

chitinozoaires de l arenig superieur zone d de la formation de levis quebec canada the shumardia limestone that forms the upper part of the levis formation zone d yields well preserved assemblages of chitinozoans these assemblages seem to be characterized by a new species cono

sources of ca2 in the major carbonate cements in eocene sandstones and conglomerates evidence from sr isotopes sr ca ratios and rare earth elements abstract different sources of calcium have important effects on the formation and distribution of carbonate cements on the basis of identifying all possible sources of calcium comprehensive quantitative analyses of sr c and o isotopic values and trace elements including rare earth elements were conducted to determine the ca2 sources and their changes in the same type of carbonate cements at different vertical positions in the same reservoirs ferroan calcite and ankerite were the major types of carbonate cements ca2 in ferroan carbonate cements in the sandstones near the mudstone sandstone m s interfaces was derived primarily from diagenetic fluids mixed with ca2 originating from the transformation of smectite to illite and from original sedimentary water in the adjacent mudstones however ca2 in the ferroan carbonate cements in the sandstones away from the m s interfaces originated from the transformation of smectite to illite the dissolution of carbonate minerals and original sedimentary water in source rocks the gradual change of ca source of the same type of ferroan carbonate cements indicates the diversity of migration direction of diagenetic paleo fluid in the same period during the transformation of smectite to illite concentration gradients were created from mudstones to sandstones ca2 mg2 fe2 and other cations in the mudstones diffused to the adjacent sandstones and provided sources of ferroan carbonate cements at the edge of the sandstones pore water with ca2 mg2 fe2 co32 and other cations in the source rocks was collectively charged into sandstones during oil emplacement and promoted the precipitation of ferroan carbonate cements in residual pore water due to oil emplacement and material supplied by the adjacent mudstones the content of ferroan carbonate cements in the sandstones was lower and the reservoir porosity was higher at a greater distance from the m s interfaces however in thick bedded sandstones due to lack of material supply from the adjacent mudstones ca2 mg2 fe2 and co32 in the ferroan carbonate cements were mainly derived from source rocks as a result no significant changes were observed in the content of ferroan carbonate cements and reservoir porosity in the vertical direction

a tectonic model for the norwegian passive margin with implications for the ne atlantic early cretaceous to break up a sub regional tectonic study of the mid norwegian margin has been assimilated into a broader regional study of the ne atlantic margin the ne atlantic margin experienced several extensional events between devonian post orogenic collapse and break up in early tertiary this paper focuses on the extensional events between early cretaceous and early tertiary it is suggested that ne trending early cretaceous rifting followed the entire margin from the southern rockall trough to the bjornoya basin of the sw barents sea this rift had a markedly different trend than the preceding n trending late jurassic rift of e g the north sea seamounts may have been emplaced in the highly thinned basin axes during early cretaceous rifting subsequent rift events followed the early cretaceous rift trend an enigmatic 9mid9 cretaceous event probably extensional is observed in the northern part of the mid norwegian margin the event is expressed by faulting in the inner voring basin and by uplift of the outer voring and lofoten margins uplift is associated with a widespread unconformity uplift of the gjallar ridge in the voring basin culminated during the latest cretaceous to early tertiary rifting with structural geometries broadly similar to those seen in core complexes a new tectonic model for ne atlantic margin is proposed based on these observations and builds on analogues from the modern rift system in the red sea and woodlark basin of papua new guinea

a critical analysis of the structure and tectonic significance of rift oblique lineaments transfer zones in the mesozoic cenozoic succession of the faroe shetland basin ne atlantic margin abstract nw se trending rift oblique lineaments transfer zones9 occur along the length of the ne atlantic margin previous workers have suggested that these lineaments played an important role in providing conduits and or barriers to sedimentation during the cretaceous and palaeocene it has also been suggested that they were active as discrete basin wide strike slip faults this study uses a well calibrated 3d seismic survey of regional extent to critically assess the structural and stratigraphic evidence for three rift oblique lineaments in the uk sector of the faroe shetland basin victory clair and judd lineaments structures previously attributed to basin wide strike slip deformation can be more simply explained as igneous intrusions hydrothermal vent complexes gas chimneys and or faults that transfer extensional strain between en echelon rift segments there is little evidence to suggest that activity along discrete basin wide lineaments controlled palaeocene sedimentation within the faroe shetland basin rather sediment transport and deposition at this time are likely to have been controlled by along and across strike variations in the magnitude of thermal subsidence which in turn reflect the 3d nature of the underlying mesozoic rift architecture

age and composition of the ruisseau isabelle melange along the shickshock sud fault zone constraints on the timing of melanges formation in the gaspe appalachians melanges are common in the humber and dunnage zones of the quebec appalachians humber zone melanges are spatially associated with taconian nappes and believed to be of tectonic origin dunnage zone melanges are interpreted as relicts of an ordovician accretionary prism the ruisseau isabelle melange rim in the gaspe ap palachians was first interpreted as a dunnage zone melange because of its tectonic position along the baie verte brompton line and lithological components such as dark mudstone blocks of ultramafic rocks and greenish chromite bearing sandstone the rim comprises sedimentary rock assemblages composite shale black shale and chromite bearing sandstone assemblages an exotic block a pebbly mudstone assemblage and slivers of serpentinized peridotite and metamorphic tectonite most melanges of the dunnage zone in the quebec appalachians contain partly similar rocks but their age is not well constrained recent work on the rim and cap chat melange of the humber zone and new fossil finds in the rim rock assemblages allow us to conclude that previous distinction between melanges of the dunnage and humber zones on the basis of rock type associations is not valid according to the age of the rim rock assemblages melanges in the northern gaspe appalachians continued forming after the mid caradocian later than the dunnage zone melanges of southern gaspe appalachians the juxtaposition and structural features of the rim rock assemblages result from repeated faulting along the shickshock sud fault from late ordovi cian to middle devonian

a precise worldwide correlation of early ordovician graptolite sequences fourteen early ordovician tremadoc llandeilo graptolite sequences from around the world are precisely infrazonally correlated based on the stratigraphic ranges of 130 species and species groups the composite standard sequence css of graptolites has been determined from the six best regional sequences by a nonparametric graphic correlation two data sets were selected one comprised first appearance events of 103 taxa the other first and last appearance events of 45 taxa the results of the two runs accord well and reveal respectively 66 and 73 successive bioevents in early ordovician time event spacing averages 0 7 0 8 ma and enables fine subdivision correlation and homotaxial testing for diachroneity the strong correlation between each of the six regional sequences and the css indicates the high level of accordance among graptolite successions around the world

genesis of the gaosong sn cu deposit gejiu district sw china constraints from in situ la icp ms cassiterite u pb dating and trace element fingerprinting abstract the gaosong sn cu deposit in the gejiu ore district sw china is a large cassiterite sulfide deposit hosting total ore reserves of 67 4 mt 1 3 sn and 19 0 mt 1 1 cu two types of mineralization developed in the deposit i e cassiterite sulfide ore within the proximal skarn in contact with the gaofengshan biotite granite and fault controlled stratiform like cassiterite iron oxide sulfide ore in the distal carbonate country rock cassiterite grains are disseminated in both ores in situ u pb dating of one cassiterite sample from the cassiterite sulfide ore and two from the cassiterite iron oxide sulfide ore yielded weighted mean 206pb 238u ages of 84 3 1 4 ma 85 1 1 0 ma and 83 5 2 1 ma respectively the three mineralization ages are consistent with the emplacement age of the gaofengshan granite 85 8 0 6 ma within error suggesting a close temporal link between tin mineralization and granitic magmatism cassiterite grains can be divided into two types based on cathodoluminescence cl illustrations namely euhedral cst i and veinlet like cst ii in the cassiterite sulfide ore cst i has clear oscillatory zonation and is dull luminescing in the cassiterite iron oxide sulfide ore cst i core is dull luminescing blue in om cl and surrounded by a bright luminescing cst i rim yellow in om cl cst i is replaced by cst ii veinlets with bright luminescing yellow in om cl the sem cl luminescing intensity of cassiterite is mainly controlled by ti content elevated w and fe but low nb ta zr and hf concentrations of cassiterites from the gaosong deposit are distinctly different from those of cassiterites in vms sedex tin deposits but similar to those from granite related tin deposits the late cretaceous crystallization ages and trace element characteristics demonstrate that cassiterites from both ores were formed in a magmatic hydrothermal system associated with the gaofengshan granite and preclude the sedex origin of the stratiform like cassiterite iron oxide sulfide ore

absolute ages of multiple generations of brittle structures by u pb dating of calcite direct dating of brittle structures is challenging especially absolute dating of diagenesis followed by a series of superimposed brittle deformation events we report 22 calcite u pb ages from tec

arenig biostratigraphy of the pointe de levy slice quebec appalachians canada the pointe de levy slice includes a nearly complete arenig graptolite succession a conspicuous gap exists in the yapeenian ya to lower darriwilian da part ya 1 da 1 the lithological column is compiled from several sections at levis quebec that yield only parts of the complete succession the graptolite zonation can be compared closely with that from the cow head group of western newfoundland and the deep kill formation of eastern new york the shumardia limestone is differentiated into four graptolite zones and subzones of which the youngest zone clearly belongs to the llanvirn the araneograptus murrayi and holmograptus lentus zones are documented for the first time from the levis area the undulograptus dentatus zone of the latest arenig is introduced

classification and conodont based age of the ordovician trilobite ellsaspis middle arenigian ville guay quebec ellsaspis rasetti 1945 occurs in a thin intraclast granule and echinoderm hash packstone in continental slope facies at ville guay presence of an anterior median glabellar node and assignment of

directly dating geologic events u pb dating of carbonates 1 carbonates are ubiquitous forming in a variety of settings including caves soils the oceans during burial from hydrothermal fluids and along faults u pb dating of carbonates is applicable to almost the entire geologic time scale with results from pleistocene speleothems showing great promise for dating records 1 ma old here we review studies of u pb dating of carbonates from a range of depositional and diagenetic environments and consider published results with regard to stratigraphic associations and the behavior of u and pb in various fluids we detail the steps required to select suitable samples summarize current laboratory techniques and provide directions for improvement of analytical protocols the u pb dating of carbonates has tremendous potential for dating events of geologic interest and is virtually untapped

seismic cycles recorded in late quaternary calcite veins geochronological geochemical and microstructural evidence southwest turkey is seismically active as a result of the hellenic subduction process in the eastern mediterranean we conducted high resolution micro sampling high precision u series dating and microchemical analysis on an extensional vein system in a tectonically active but non hydrothermal area u th age data and microscopic observations provide evidence of repeated fracturing of a previously sealed crack system followed by a new increment of veining repeated injection of veinlets suggests that the vein system was formed by the crack seal mechanism four major u th age groups for the emplacement of the vein system fall between 23 9 0 2 ka and 23 2 0 4 ka 21 7 0 4 ka and 19 2 0 2 ka 17 3 0 1 ka and 16 2 0 3 ka and at 11 8 0 2 ka stable and sr isotope geochemistry of the calcite vein samples indicates that surface water interacting with the soil cover was the major component of the groundwater system from which the extensional veins precipitated trace element and 0 isotope data of the vein system are interpreted to reflect carbonate precipitation associated with seismic cycles involving fluids with different trace element compositions and co2 contents initial carbonate precipitation during a single seismic cycle occurred from co2 dominated fluids that were degassed from the original co2 water mixture this was followed consecutively by carbonate precipitation from the remaining water which was relatively impure with higher trace element contents millimetre to submillimetre scale u series dating in conjunction with geochemistry of carbonate veins related to active tectonism offers an innovative means of constraining the absolute timing of late quaternary seismic and inter seismic events c 2010 elsevier b v all rights reserved

integrated chitinozoan conodont and graptolite biostratigraphy from the upper part of the cape cormorant formation middle ordovician western newfoundland the cape cormorant formation of the table head group exposed on the port au port peninsula western newfoundland is composed of dark brown to black shales with interbeds of thin calcareous silty and sandy distal turbidites distinctive carbonate conglomerates and breccias derived from the foundering shelf are occasionally found in the formation the sediments accumulated in the foreland basin formed during the early stage of the taconic orogeny the faunas from the upper part of the cape cormorant formation include graptolites conodonts and chitinozoans the graptolites are well preserved but are of low diversity and are referred to the darriwil pterograptus elegans zone conodonts recorded from the distal turbidites are rare and fragmented the faunas include taxa that are known from the st george and table head groups the conodont fauna is tentatively assigned to the histiodella kristinae phylozone and to the younger unzoned interval the chitinozoans are well preserved and the yield is high the

holmograptus spinosus and the middle ordovician darriwilian graptolite biostratigraphy at les mechins quebec canada the les mechins region in quebec provides a unique opportunity to understand the darriwilian graptolite suc cession in eastern north america the graptolite faunas of the upper member of the anse au crapaud formation include the arienigraptus gracilis oncograptus upsilon undulograptus austrodentatus and holmograptus spinosus biozone fau nas and thus complement the well known darriwilian faunas of the cow head table head and goose tickle groups of western newfoundland in particular the holmograptus spinosus biozone interval of calcarenitic limestones bears a rare combination of benthic shelly and planktic graptolitic faunas with conodonts brachiopods ostracods sponge spicules and algal remains associated with common graptolites that allow an inter continental correlation the holmograptus spino sus biozone is introduced for the interval based on a diverse and characteristic graptolite fauna the fauna includes among others atopograptus woodwardi recognized for the first time in north america the holmograptus spinosus biozone fauna can be found worldwide and is easily correlated into the conodont biofacies using species of the genus histiodella ties between graptolite and conodont biozonations are discussed for the darriwilian silicified ostracods are illustrated for the first time from the interval hustedograptus quebecensis is described as new resume au quebec la region de les mechins fournit une occasion unique de comprendre la succession de graptolites du darriwilien dans l est de l amerique du nord les faunes graptolites du membre superieur de la formation de l anse au crapaud comprennent les faunes des biozones aarienigraptus gracilis aoncograptus upsilon aundulograptus austro dentatus et aholmograptus spinosus ces fossiles s ajoutent ainsi aux faunes bien connues des groupes darriwilien de cow head de table head et de goose tickle de l ouest de terre neuve l intervalle de la biozone aholmograptus spi nosus des calcaires calcarenitiques comporte notamment une association rare de faunes benthiques acoquilles et de planctons agraptolites avec des conodontes des brachiopodes des ostracodes des spicules d eponges et des restes d algues associes aux graptolites communs qui permettent une correlation intercontinentale la biozone aholmograptus spinosus est introduite pour l intervalle en se basant sur une faune de graptolites diversifiee et caracteristique la faune comprend entre autres atopograptus woodwardi reconnu pour la premiere fois en amerique du nord la faune de la bio zone aholmograptus spinosus peut etre trouvee partout atravers le monde et il est assez facile de la faire correspondre au biofacies de conodontes en utilisant des especes du genre histiodella les liens entre les biozones agraptolites et acono dontes sont discutes pour le darriwilien des ostracodes silicifies sont illustres pour la premiere fois apartir de l intervalle hustedograptus quebecensis est decrit en tant que nouveau fossile traduit par la redaction

a tale of both sides of iapetus upper darriwilian ordovician graptolite faunal dynamics on the edges of two continents ordovician graptolite faunal compositions between the laurentia and baltica margins of the iapetus ocean differ considerably in the upper darriwilian da 3 da 4 upper middle ordovician detaile

graptolite conodont biostratigraphy and biofacies of the middle ordovician cerro viejo succession san juan precordillera argentina abstract high resolution graptolite conodont biostratigraphy and biofacies analysis have been carried out for the lower member of the los azules formation exposed in the cerro viejo area san juan precordillera western argentina the rock succession is composed of alternating rich fossiliferous argillites and virtually barren volcanic ash beds k bentonites of darriwilian da2 age graptolite and conodont collections from the los azules and amarilla creeks sections are studied graptolites are the most common fossils in the lower member of the los azules formation and represent the undulograptus dentatus and holmograptus lentus zones a diverse conodont fauna recovered from the uppermost limestones of the underlying san juan formation and conodont elements preserved on bedding plane surfaces in the lower los azules formation indicate the lenodus variabilis and eoplacognathus suecicus zones micaceous siltstone with bergstroemograptus crawfordi harris and abundant biserial graptolites close to the top of the lower member is notable this bed yielded the first specimens of polonodus magnum albanesi this species precedes the entrance of pygodus anitae bergstrom which is typical from the upper part of the e suecicus zone characteristic graptolites of the diplograptus decoratus zone da3 or equivalent faunas were not recorded in the studied sections suggesting the presence of a hiatus between the lower and middle members which may indicate a critical event in the history of the basin a rich conodont assemblage dominated by planktic pelagic forms periodon paroistodus protopanderodus drepanoistodus an abundant shelly fauna and scarce graptolites are recorded in the upper san juan limestone after drowning of carbonate platform the conodont diversity dramatically dropped becoming graptolites the dominant elements of the faunas in the lower member of the los azules formation the periodon pygodus biofacies represents a low diversity deep water conodont community present both in the upper part of the lower member and the middle member graptolite faunas represent the isograptid biofacies including pandemic and pacific forms of the epipelagic and deep water biotopes they are related to a transgressive event that diachronically flooded the precordilleran carbonate platform during the early middle ordovician

the norway basin revisited from continental breakup to spreading ridge extinction abstract we re evaluate the structure and spreading evolution of the southeastern norway basin nb based on a new high resolution aeromagnetic survey nb 07 the survey covers a complete oceanic spreading segment from the continental oceanic transition of the more margin off norway to the aborted aegir ridge the new survey documents a transform margin an orthogonally rifted segment and an oblique sheared volcanic margin formed during the onset of breakup observed from the east jan mayen fracture zone to the faroe platform the detailed fabric of the nb revealed by the new data indicates that two distinct tectonic phases have reshaped the basin before the cessation of seafloor spreading and abortion of the aegir ridge in the late oligocene after continental breakup phase i from c24 to c21r 52 to 49 ma marks the earliest phase of spreading probably initiated in the central and outer part of the more basin during this period competing oceanic segments led to the formation of overlapping systems and pseudo fault development we observe a significant change in the nb s oceanic spreading system in the late early eocene and based on observations from surrounding areas we suggest that this is a record of a major tectonic event in the norwegian greenland sea around c21r 49 47 9 ma during phase ii from c21r to c10 48 to 28 ma of nb s development spreading rates decreased spreading direction changed and the number of faulting with large displacement increased leading to the formation of unexpected n s oriented oceanic fracture zones the fan shaped development of the spreading system initiated around c21r 49 47 9 ma instead of c18 c17 40 38 ma or c24 53 3 52 3 ma as previously proposed these new observations were used to re evaluate the tectonic evolution of the norwegian greenland sea and discuss some implications on the syn and post breakup development of the surrounding continental margins and the evolution of the jan mayen microcontinent

dating and characterizing primary gas accumulation in precambrian dolomite reservoirs central sichuan basin china insights from pyrobitumen re os and dolomite u pb geochronology abstract primary gas accumulation with trillions of cubic meters of gas volumes was discovered recently in the precambrian dengying formation of the gaoshiti moxi block central sichuan basin china in this study we investigated the pervasive saddle dolomite cements and solid bitumens within karst vugs in the dengying dolomite reservoirs using laser ablation inductively coupled plasma mass spectrometry la icp ms in situ u pb dating we obtained a high precision absolute age of 259 4 3 0 ma for the saddle dolomite cementation consistent in timing with the eruption of emeishan flood basalts 262 251 ma combined with high homogenization temperatures th and salinities of primary fluid inclusion as well as rare earth element ree compositions we consider that the saddle dolomite precipitation was likely related to hydrothermal activity driven by the emeishan mantle plume the identification of rare surviving oil inclusions and extensive solid bitumens within the dolomite vugs is indicative of the presence of paleo oil reservoirs these bitumens are characterized by high equivalent vitrinite reflectance requ no fluorescence and deformed fibrous textures typical of highly mature pyrobitumens gas geochemistry data indicates that only minor thermochemical sulfate reduction tsr has occurred thus the pyrobitumen was interpreted to result mainly from the thermal cracking of paleo oils and its associated re os isochron age of 154 21 ma representing the timing of dry gas formation petrographical evidence suggests that the paleo oil charge must have taken place after sparry dolomite cementation but prior to pyrobitumen generation this combined with coeval aqueous inclusion th data and published thermal burial models constrains the time of paleo oil emplacement to ca 222 205 ma suggesting an oil filling event related to the indosinian orogeny this study documented the first chronological data constraining the complex evolution history of a petroleum system in one of the oldest primary gas reservoirs in the world

biostratigraphy and palaeoecology of lower ordovician graptolites from the fezouata shale moroccan anti atlas abstract the fezouata shale fezouata formation has produced the most complete lower ordovician graptolite succession known from the african continent which was studied from 32 sections located along the western central and eastern moroccan anti atlas a composite biostratigraphic and chronostratigraphic scheme is presented for the entire formation that in ascending order comprises the anisograptus matanensis rhabdinopora flabelliformis anglica zones uppermost lower tremadocian adelograptus tenellus and aorograptus victoriae zones middle tremadocian araneograptus murrayi and hunnegraptus copiosus zones upper tremadocian cymatograptus protobalticus zone lower floian baltograptus jacksoni zone middle floian and the baltograptus minutus zone plus an azygograptus interval upper floian most of these zones or biozones are recorded for the first time in africa together with important graptolite species such as ancoragraptus bulmani spjeldnaes cym protobalticus monsen b jacksoni rushton clonograptus multiplex nicholson b minutus tornquist and azygograptus eivionicus elles a correlation with the graptolite sucession from the algerian sahara is also suggested reinforced by the common record of the minute anisograptid choristograptus louhai legrand providing its second world occurrence in the tremadocian of morocco the prior late tremadocian dating of the fezouata lagerstatte is here extended to the middle floian as revealed by the graptolite biochronology the repeated record along the lower and middle parts of the fezouata formation of deep water mesopelagic species of the genera araneograptus with mass occurrences of conical colonies together with large horizontal rhabdosomes of paratemnograptus paradelograptus clonograptus tetragraptus and holograptus schizograptus do not fit the sedimentological interpretation of deposition of these strata in much shallower inshore to mid shelf environments this inconsistency has implications when inferring the living conditions of the fezouata soft bodied assemblages

fault zone permeability structure evolution in basalts a combination of field microstructural and experimental static permeability characterization is used to determine fault permeability structure evolution in upper crustal basalt hosted fault zones in the faroe islands the faults comprise lower strain fracture networks to higher strain breccias that form tabular volumes around a principal slip zone hosting gouge or cataclasite samples representative of these fault zone components are used for static experimental permeability measurement results indicate that within the appropriate effective pressure depth range 10 90 mpa 0 3 to 3 0 km basalt hosted faults evolve from low strain 10 17 m2 structures sample analyses reveal that static permeability is controlled by the development of a fault parallel clay alteration decreasing permeability and b porous zeolite vein connectivity due to hydrofracture increasing permeability fault parallel permeability is increased relative to the host rock while fault normal permeability is low throughout fault rock evolution this configuration will tend to promote across fault compartmentalization and along fault fluid flow facilitating migration between relatively high permeability horizons e g vesicular flow unit tops and siliciclastic horizons bypassing the bulk of the stratigraphy

fractures in mudrocks advances in constraining timing and understanding mechanisms abstract recent advances in fracture timing techniques have led to new insights about sequences and mechanisms of fracture formation in mudrocks methods to constrain fracture timing in mudrocks include i field evidence including crosscutting relationships and evidence of compaction ii petrographic evidence including signs of soft sediment deformation and diagnostic mineral assemblages or textures iii stable isotopic evidence iv thermometric dating using burial history modelling and v radiometric age dating in this contribution we briefly review each method with salient examples from the literature many documented examples of mudrock hosted fractures formed during early burial a non intuitive finding that demands a re assessment of our assumptions about what types of materials can develop opening mode fractures in general the style and distribution of fractures varies dramatically based on fracture timing highlighting the importance of constraining timing for predicting fracture patterns and interpreting their mechanisms including the role of fluid flow

chronologic constraints on hominin dispersal outside africa since 2 48 ma from the zarqa valley jordan abstract recent discoveries constrain the presence of hominins in north africa since ca 2 4 ma and in china since ca 2 1 ma providing a new temporal framework for the earliest migration out of africa no paleolithic sites of such age exist in the levant the natural corridor between africa and asia the dawqara formation in the zarqa valley jordan has been known since the early 1980s because of the presence of artifacts at different stratigraphic levels within its fluvial sediments consisting of choppers cores and flakes although most of the artifacts display signs of transport they bear unambiguous evidence of manufacture and document hominin presence in the zarqa valley during the deposition of dawqara formation based on integrated chronology provided by paleomagnetic 40ar 39ar and u pb dating methods our study shows that the dawqara formation was deposited between 2 52 0 01 ma and the matuyama olduvai geomagnetic reversal 1 95 ma by linear interpolation the artifact bearing stratigraphic levels within the dawqara formation have ages of ca 2 48 ma 2 24 ma 2 16 ma 2 06 ma and 1 95 ma respectively possibly documenting continuous hominin presence in the zarqa valley these new ages for the dawqara assemblage constrain the earliest hominin dispersal out of africa to the beginning of the pleistocene and pre date by ca 300 kyr the hominin occupation of chinese loess plateau

palaeocene recent plate boundaries in the ne atlantic and the formation of the jan mayen microcontinent abstract breakup and sea floor spreading between greenland and eurasia established a series of new plate boundaries in the north atlantic region since the late palaeocene a conventional kinematic model from pre breakup to the present day assumes that eurasia and greenland moved apart as a two plate system however new regional geophysical datasets and quantitative kinematic parameters indicate that this system underwent several adjustments since its inception and suggest that additional short lived plate boundaries existed in the ne atlantic among the consequences of numerous plate boundary relocations is the formation of a highly extended or even fragmented jan mayen microcontinent and subsequent deformation of its margins and surrounding regions the major oligocene plate boundary reorganization and microcontinent formation might have been precluded by various ridge propagations and or short lived triple junctions ne and possibly sw of the jan mayen microcontinent from the inception of sea floor spreading 54 ma to c18 40 ma our model implies a series of failed ridges offshore the faeroe islands a northern propagation of the aegir ridge ne of the jan mayen microcontinent and a series of triple junctions and or propagators in the southern greenland basin

an image mapping approach to u pb la icp ms carbonate dating and applications to direct dating of carbonate sedimentation we present a new approach to laser ablation inductively coupled plasma mass spectrometry la icp ms u pb dating of carbonates based on selection and pooling of pixels from 2 d elemental and isotopic ratio maps this image mapping technique is particularly useful for targeting subdomains in samples with complex geological histories key major and trace elements that are sensitive to detrital components postformational fluid ingress mineralogical changes or diagenetic overprinting are measured along with the pb and u isotopic data laser sampling is undertaken along successive linear rasters that are compiled into maps using the monocle add on for iolite with one pixel in the map corresponding to one time slice of the time resolved signal these element element ratio and isotope ratio maps can be overlain over photomicrographs or scanning electron microscopy images to spatially link compositional data to textural and structural features the pixels corresponding to likely homogeneous age domains can be isolated by applying appropriate selection criteria e g th 0 3 ppm mg ca 0 004 and pooled into pseudo analyses using a proxy for the parent daughter ratio e g 207pb 235u 238u 208pb to retrieve the largest possible spread of the data points on isochron diagrams the approach is best suited for analytical setups capable of rapidly or simultaneously scanning over a large mass range and can yield a precision of 1 or better on quadrupole instruments depending on u concentration 238u 204pb and age of the sample the sample specific filtering criteria for selection and rejection of data and their rationale can be reported resulting in more transparency with regard to data processing

the lower ordovician fezouata konservat lagerstatte from morocco age environment and evolutionary perspectives abstract the lower ordovician fezouata konservat lagerstatte from southern morocco has been one of the major palaeontological discoveries of the last decade it provides a unique insight into one of the most critical periods in the evolution of marine life the cambrian ordovician transition however its potential for deciphering key trends in animal diversification was hitherto largely limited by major uncertainties concerning its stratigraphic position age and environmental setting based on extensive fieldwork fossil evidence and facies recognition our study provides clarification on these three crucial issues exceptional preservation is limited to two intervals within the fezouata shale graptolites indicate a late tremadocian age for the fezouata konservat lagerstatte as a whole which is supported by biostratigraphical evidence provided by acritarchs sedimentological features and reconstructed patterns of relative sea level changes indicate relatively shallow water environmental conditions under distal storm influence in an offshore to lower shoreface siliciclastic ramp setting the fezouata biota represents a unique and exceptional window into the palaeobiodiversity in open marine conditions thus contrasting with the other ordovician konservat lagerstatten presently known in our analyses of this new set of data we pave the way for accurate temporal faunal and environmental comparisons with other lower palaeozoic konservat lagerstatten and unlock the full potential of the fezouata biota to better understand the processes and scenarios of early animal radiations

onshore evidence for progressive changes in rifting directions during continental break up in the ne atlantic abstract current models for the palaeogene aged continental break up in the north atlantic invoke a nw se extension vector throughout the rift to drift process accommodated by margin parallel normal faults and margin oblique strike slip transfer zones however palaeogene and younger faults in the faroe islands provide evidence for a progressive anticlockwise rotation in extension vectors immediately prior to and following north atlantic break up six deformation stages are recognized 1 east west to ne sw extension accommodated by dip slip north south and nw se trending faults 2 continued ne sw extension accommodated by nw se and nne ssw oriented dykes 3 north south extension accommodated by ene wsw and ese wnw conjugate dykes 4 crustal extrusion involving both east west shortening and further north south extension along ene wsw dextral and ese wnw sinistral conjugate strike slip faults 5 during the final stages of rifting the regional extension vector became nw se and was accommodated predominantly by slip along ne sw dextral oblique slip faults 6 pre existing structures were locally reactivated as tensional and extensional shear features characterized by the entrainment of clastic material along fault planes the present study reveals a distinct period of margin parallel extension immediately prior to break up that is not accounted for by existing models illustrating the importance of conducting field based studies to validate otherwise widely accepted margin scale models worldwide

u pb dating of geodic calcite new insights on western europe major tectonic events and associated diagenetic fluids this study presents the first application of the u pb dating method to highly pb depleted diagenetic geodic calcites of the jurassic formations of the paris basin that leads to a reappraisal of the palaeohydrological history of this region composite u pb ages from multiple geodes combined with 18 o analyses reveal two main phases of diagenetic fluid circulations linked with major regional tectonic events dogger formations recorded a first diagenetic fluid episode at 147 8 3 8 ma i e at the very beginning of the emersion of the basin during the tithonian period and 30 ma earlier than previously assumed 18 o results confirmed that most of the calcitic cement phases that closed the porosity of these formations precipitated at the beginning of the cretaceous period oxfordian formations recorded another major meteoric fluid circulation at 33 5 2 8 ma related to the initial stage of the european cenozoic rift system ecris consequently the porosity of the mesozoic formations of the studied area may have been closed sooner than previously thought before the main ecris rifting phase of oligocene age this study shows that u pb dating of secondary geodic calcite offers a new powerful way for reconstructing the coupled palaeohydrological and diagenetic history of sedimentary basins supplementary material pb pb diagrams 238 u and 235 u series isochron diagrams and effect of blank correction on u and pb isotopic compositions and on ages calculation are available at https doi org 10 6084 m9 figshare c 3886885

the development of cavities and clastic infills along fault related fractures in tertiary basalts on the ne atlantic margin field based geological observations have revealed the hitherto unrecognised development of post magmatic brittle deformation structures cutting tertiary volcanic rocks in the faroe islands these faults and fractures are characteristically associated with different styles of clastic sedimentary infill including 1 0 3 1 0 m thick clastic units infilling open fractures formed along pre existing steeply dipping to sub vertical faults 2 0 1 0 6 m thick sub horizontal clastic units displaying internal features consistent with deposition from flowing water passing through complex open subterranean cavity systems within fractured basalts 3 anastomosing mm scale and planar dm scale clastic intrusion features mobilised and emplaced during transient fault related overpressuring events along pre existing fractures cutting the surrounding volcanic units the infill features provide evidence for the existence of sustained open cavities in the sub surface the clastic materials are commonly internally affected by later fault related deformation and lack mineralisation unlike all preceding faulting episodes in the faroes region perhaps reflecting their near surface development we believe structures equivalent to these features may occur widely in other parts of the ne atlantic margin particularly along the outer arcs of gentle regional scale fold hinges the uncemented fracture hosted clastic infills potentially represent important fluid migration pathways within the otherwise low permeability cenozoic volcanic sequences of the ne atlantic region

dating of anatase forming diagenetic reactions in rotliegend sandstones of the north german basin diagenetic conditions controlling authigenic formation of anatase and in situ la icp ms u pb isotope dating of this phase are studied in upper rotliegend ii sandstones from two wells in nw germany anatase grew after breakdown of detrital ti phases e g ilmenite although local scale ti transport and mobilization from detrital clay hematite coats or condensed hydrocarbons cannot be ruled out the anatase forming reaction marks the change from a regime of reducing conditions imposed by first hydrocarbon generation to oxidizing conditions probably caused by influx of a fluid from evaporitic zechstein rocks this change in fluid influx is interpreted as response to enhanced normal faulting and halokinesis during accelerated burial in triassic times isotope data of u and pb indicate incorporation of crustal common pb from mesozoic pore fluids but precisely mark diagenetic growth of anatase at 224 3 5 1 5 6 ma in a tera wasserburg plot locally u pb isotope signatures are consistent with either additional incorporation of u and pb from detrital precursor phases or with uptake of uranogenic pb from hydrocarbons generated prior to 224 ma anatase is shown to be a valuable authigenic phase suitable for u pb chronometry of diagenetic events which appears to be unaffected by protracted burial and temperatures exceeding temperatures of crystallization

yapeenian early ordovician graptolites in the quebec appalachians a newly discovered oncograptus upsilon fauna occurs in a sequence of turbiditic siltstones within the lower ordovician ste anne river nappe in the gaspe area of quebec this is the first discovery

an emerging thermochronometer for carbonate bearing rocks 47 u pb assessing the thermal evolution of sedimentary basins is critical for understanding the origin of natural resources including ores geothermal fluids or hydrocarbons and for deciphering larger scale tectonic and geodynamic evolutions modern reconstructions of past subsurface temperatures mostly rely on thermochronometers that are not applicable to carbonate rocks e g fission track and u th he analyses here by coupling carbonate clumped isotope 47 thermometry and laser ablation u pb geochronology on a complete paragenetic sequence we demonstrate the applicability of an emerging thermochronometer for carbonate bearing rocks paired 47 and u pb data were obtained for calcite and dolomite phases precipitated in a middle jurassic carbonate hydrocarbon reservoir of the paris basin depocenter france the absolute thermochronological data allow the precise reconstruction of the thermal history of these rocks from shallow burial temperatures 40 c occurring in the late jurassic toward a progressive burial and heating stage up to 87 c during the cretaceous followed by a cooling stage down to 69 c during the tertiary uplift of the basin the inferred time temperature path based on 47 u pb data is mostly consistent with the thermal scenario independently deduced from organic maturity indicators from the underlying lower jurassic shales the 47 u pb thermochronological data also highlight a thermal anomaly during aptian albian time that requires revisiting the accepted timing for hydrocarbon migration in the middle jurassic reservoir carbonates

u pb dating of cements in mesozoic ammonites dating sedimentary carbonates using the u pb method can help improve the phanerozoic timescale using a novel combination of laser ablation multi collector inductively coupled plasma mass spectrometry la mc icp ms and thermal ionization multi collector mass spectrometry tims u pb numerical ages were obtained on early diagenetic calcite cements in jurassic ammonites in which concentrations of u range from 0 47 to 5 3 ppm the calcite cements of two ammonites is1 and is2 from the uppermost bifrons zone of the toarcian 179 180ma of the uk gave tims normalized la u pb dates of 164 9 5 3 ma and 166 7 4 8ma respectively normalizing la icp mc ms data to an in house calcite standard gave a more precise date of 165 5 3 3 ma for is1 cement an unzoned ammonite ss2 of bajocian age 168 170 ma yield a tims normalized la u pb age of 158 8 4 3 ma for its early diagenetic cement both the combined la mc icp ms and tims approach and the use of a calcite laser ablation standard can result in accurate ages of cements with uncertainties of 2 3 2 the later however is more efficient and precise these u pb dates of cements are 10 to 20 myr younger than the numerical ages of the biostratigraphic intervals from which the ammonites derive the u pb dates are taken to represent the time at which the aragonite shell of the ammonite inverted to calcite and released its u to precipitate in a late diagenetic alteration of early diagenetic fringing cements concentrations of u and pb in a range of other pristine biogenic carbonateswere found too low u b 0 01 ppm for meaningful dating using laser ablation method

combined zircon and cassiterite u pb dating of the piaotang granite related tungsten tin deposit southern jiangxi tungsten district china abstract the large low grade piaotang w sn deposit in the southern jiangxi tungsten district of the eastern nanling range south china is related to a hidden granite pluton of jurassic age the magmatic hydrothermal system displays a zonation from an inner greisen zone to quartz veins and to peripheral veinlets stringers five floor zonation model most mineralization is in quartz veins with wolframite cassiterite the hidden granite pluton in underground exposures comprises three intrusive units i e biotite granite two mica granite and muscovite granite the latter unit is spatially associated with the w sn deposit combined la mc icp ms u pb dating of igneous zircon and la icp ms u pb dating of hydrothermal cassiterite are used to constrain the timing of granitic magmatism and hydrothermal mineralization zircon from the three granite units has a weighted average 206pb 238u age of 159 8 0 3 ma 2 mswd 0 3 the cathodoluminescence cl textures indicate that some of the cassiterite crystals from the wolframite cassiterite quartz vein system have growth zonations i e zone i in the core and zone ii in the rim dating on cassiterite zone ii yields a weighted average 206pb 238u age of 159 5 1 5 ma 2 mswd 0 4 i e the magmatic and hydrothermal systems are synchronous this confirms the classical model of granite related tin tungsten mineralization and is against the view of a broader time gap of 6 myr between granite magmatism and w sn mineralization which has been previously proposed for the southern jiangxi tungsten district the elevated trace element concentrations of zr u nb ta w and ti suggest that cassiterite zone ii formed in a high temperature quartz vein system related to the piaotang granite pluton

improving paleohydrological and diagenetic reconstructions in calcite veins and breccia of a sedimentary basin by combining δ47 temperature δ18owater and u pb age abstract in sedimentary basins the precise temperature and timing at which relatively shallow

climacograptus pungens ruedemann 1904 and the definition of the darriwilian ordovician graptolite genus archiclimacograptus mitchell 1987 the genus archiclimacograptus represents one of the earliest taxa of axonophoran graptolites with geniculate the cae but its current status and evolutionary relationships are difficult to access even after a number of cladistic analyses have been executed archiclimacograptus pungens ruedemann a poorly known little species from the lower darriwilian of eastern north america is interpreted as a possible member of the genus the species belongs to a group of axonophorans with highly asymmetrical proximal end and pattern c astogeny characterized by the lack of an apertural spine on th1 2 rang ing from the levisograptus dentatus biozone darriwilian to the nemagraptus gracilis biozone sandbian specimens are common in north america and the argentinian precordillera but have not been reported from any atlantic faunal realm localities the distribution of the group indicates a restriction to the pacific faunal realm providing the earliest indication of a developing biogeographic differentiation of axonophoran graptolites after their origin in the oceanic biofacies during the upper dapingian to lower darriwilian time interval archiclimacograptus ambiguus is described as a new species resume si le genre archiclimacograptus represente un des taxons les plus anciens de graptolites axonophores dotes de theques geniculees son statut actuel et ses liens evolutionnaires sont difficiles a evaluer et ce meme apres diverses analyses cladistiques archiclimacograptus pungens ruedemann une petite espece meconnue du darriwilien inferieur de l est de l amerique du nord est interprete faisant possiblement partie de ce genre l espece appartient a un groupe d axonophores presentant une extremite proximale tres asymetrique et une astogenie de type c caracterisee par l absence d une epine apertu rale sur th12 dont la distribution va de la biozone a levisograptus dentatus darriwilien a la biozone a nemagraptus graci lis sandbien des specimens sont repandus en amerique du nord et dans la precordillere argentine mais leur presence dans des localites du domaine faunique atlantique n a jamais ete signalee la distribution du groupe indique qu il se limite au domaine faunique pacifique constituant l indice le plus ancien d une differentiation biogeographique des graptolites axo nophores apres leur apparition dans le facies oceanique durant l intervalle allant du dapingien superieur au darriwilien infe rieur archiclimacograptus ambiguus est decrit comme etant une nouvelle espece traduit par la redaction

ten million years of activity within the eastern california shear zone from u pb dating of fault zone opal abstract reconstructions of long term fault activity are essential for understanding both the mechanisms controlling fault behavior and accurate earthquake hazard assessments increasing evidence for temporal variations in strain accumulation suggests non uniform strain rates over a range of historic to geologic timescales the paucity of long term records of fault activity has limited our ability to resolve these variations we present a method for constraining long term fault activity based on u pb dating of fault related opal from secondary fault segments within the eastern california shear zone ecsz the presence of sheared and breccia cemented opaline silica within well exposed faults at near surface conditions suggest that opal formation is associated with high magnitude earthquakes capable of surface rupture 6 m temporal constraints from massive and sheared syntectonic opal n 74 on related secondary faults from this study provide new insights on the timing of fault initiation reactivation and longevity the oldest dates obtained indicate that ecsz activity commenced at or before 10 ma multiple deformation events dated within a single structure on episodically deposited and sheared opal up to six generations demonstrate that fault reactivation occurred over 105 yr timescales 0 7 0 1 myr relative probabilities of dated deformation events can be used to evaluate changes in fault activity in the past 2 5 ma n 60 this analysis indicates enhanced fault activity starting at 2 ma and peaking around 1 ma possibly due to fault interactions and distribution of deformation between the ecsz and the san andreas fault

u pb dating of calcite cement and diagenetic history in microporous carbonate reservoirs case of the urgonian limestone france microporous carbonates can constitute excellent hydrocarbon reservoirs if their micro pore and or nanopore structure is sufficiently developed and continuous in such deposits assessing the exact timing of reservoir property stabilization is critical to better understand the postdepositional processes favorable to the creation or preservation of porosity however placing reliable and accurate chronological constraints on the formation of microporosity in these reservoirs is a major challenge in this study we performed absolute u pb dating of calcite cements occurring in the urgonian microporous limestone northern tethys margin of southeastern france u pb ages ranging between 96 7 4 9 ma and 90 5 1 6 ma were obtained on the major calcitic phase responsible for the cementation and therefore the stabilization of microporosity indicating that this diagenetic process occurred synchronously at the regional scale following an extended subaerial exposure our results show that 1 the mineralogical stabilization process responsible for the formation of an excellent pervasive microporous network took place relatively early and 2 the so acquired reservoir quality was preserved for more than 90 m y these observations emphasize the importance of long exposure periods and associated meteoric influx for the formation and preservation of good microporous reservoirs

pore geometry as a control on rock strength the strength of rocks in the subsurface is critically important across the geosciences with implications for fluid flow mineralisation seismicity and the deep biosphere most studies of porous rock strength consider the scalar quantity of porosity in which strength shows a broadly inverse relationship with total porosity but pore shape is not explicitly defined here we use a combination of uniaxial compressive strength measurements of isotropic and anisotropic porous lava samples and numerical modelling to consider the influence of pore shape on rock strength micro computed tomography ct shows that pores range from sub spherical to elongate and flat ellipsoids samples that contain flat pores are weaker if compression is applied parallel to the short axis i e across the minimum curvature compared to compression applied parallel to the long axis i e across the maximum curvature numerical models for elliptical pores show that compression applied across the minimum curvature results in relatively broad amplification of stress compared to compression applied across the maximum curvature certain pore shapes may be relatively stable and remain open in the upper crust under a given remote stress field while others are inherently weak quantifying the shape orientations and statistical distributions of pores is therefore a critical step in strength testing of rocks

calcite twinning strains from syn faulting calcite gouge small offset strike slip normal and thrust faults we have evaluated the stress strain behavior of calcite precipitated and mechanically twinned in small offset strike slip normal and thrust faults of a variety of ages and from a variety of tectonic settings n 3001 twin measurements 63 strain analyses from 18 field sites five strike slip faults with syn faulting horizontally striated calcite rake 0 were studied and we report the orientations of the contemporaneous stress strain field associated with each fault intrusion of the marathon large igneous province mafic dikes 2 1 ga in archean crust minnesota usa post keweenaw rift 1 1 ga faulting island lake fault central ontario canada subduction associated with metamorphic core complex formation cretaceous china subduction cretaceous to miocene italy and continental extension recently active furnace creek fault death valley california usa seven normal faults with synfaulting dip slip striated calcite were studied and are from the following tectonic settings a normal fault slip surface in an ordovician piedmont fold appalachian s paleo subduction associated with cretaceous metamorphic core complex formation china 3 sites the paleo extensional atlantic margin 55 ma ireland 1 site with a u pb calcite age continental extension 1 active site mojave desert a transcurrent margin jamaica 1 active fault site and subduction 2 active faults along the eur african margin in italy with calcite u th disequilibria ages and crete respectively six thrust fault examples are all from convergent orogenic settings the basal thrust of the penokean 1850 ma fold and thrust belt the penokean orogen foreland in mesabi range banded iron formation folds an offset breccia body in the permian gondwanide belt ellsworth mountains antarctica the frontal thrust of the gondwanide cape belt south africa the paleocene frontal prospect thrust sevier belt wyoming and an alpine foreland back thrust lulworth cove u k for each strike slip fault system the twinning shortening strain is horizontal and at an angle of 0 60 to the respective fault plane dextral or sinistral although in the majority of cases the shortening axis is parallel to fault strike 13 of 23 results in each normal fault example dip slip kinematic striations dominate the faulted surface yet the orientation of the maximum principal compressive stress 1 and shortening strain axis e1 are not 45 to the fault plane as predicted but are sub horizontal and either strike parallel 25 of 35 results or strike normal 10 of 35 results thrust faults preserve shortening strain axes parallel to the dip slip kinematic direction within the fault plane plane strain and not at 45 to the principal plane 5 of 5 results none of the fault stress strain field results reported here support the andersonian or mohr coulomb criteria for stress strain relations predicted along faults

graptolite biozone correlation charts charts are presented showing the correlation of graptolite biozonations for the lower ordovician to lower devonian i e for the entire stratigraphical range of the planktonic graptoloid graptolites regions chosen are those for which the most detailed biostratigraphical studies have been undertaken for baltica average graptolite zone chron duration appears to vary from c 300000 years ludlow epoch to 2 4 ma lochkovian epoch

modeling gpr radiation and reflection characteristics for a complex temperate glacier bed we demonstrate that ground penetrating radar gpr reflection data from a temperate glacier are accurately modeled using a helmholtz kirchhoff diffraction integration technique that incorporates the radiation characteristics of point dipoles on a half space interface this is accomplished by comparing field data to simulated data our 40 mhz field data are from a 100 340 m x and y dimensions respectively survey grid containing 51 parallel survey lines the field data were collected with the dipole oriented perpendicular to the survey line x dipole the synthetic data used isotropic x dipole and y dipole antennas and reflections were calculated using a bed topography previously defined by 3d kirchhoff migration the comparisons between the real and synthetic waveforms show excellent agreement including reflection arrival times amplitude trends interference patterns and false layering from out of plane reflections the location of reflectors determined from exploding reflector rays explains t

hematite fault rock thermochronometry and textures inform fault zone processes abstract minerals on fault surfaces record fluid rock interaction strain and or heat during fault slip fault hosted hematite is amenable to u th he he thermochronometry hematite he dates reflect fault related processes or exhumation depending on hematite growth above or below the grain size controlled closure temperature and processes that promote open system behavior deconvolving these phenomena requires multi scale hematite textural characterization and constraints on the ambient thermal history from conventional thermochronometry two examples of this approach include investigations of hematite coated fault surfaces from exhumed damage zones in the seismically active wasatch fault zone wfz ut and painted canyon fault pcf paralleling the southern san andreas fault mecca hills ca wfz fault mirrors preserve sub m scale polygonal grain textures and hematite he data patterns that together with host rock apatite he data are consistent with localized friction generated heat hematite he loss and hematite recrystallization during damage zone seismicity