evolution of faulting and plate boundary deformation in the southern taranaki basin new zealand abstract faulting and folding in the southern taranaki basin constrain the evolution of the new zealand plate boundary since 80 ma sedimentary rocks up to 8 km thick record multiple phases of deformation which have been examined using 2d and 3d seismic reflection data resulting in fault displacement time curves and basin wide isopach maps with temporal resolutions of 5 10 myr and 1 4 myr pre and post 23 ma respectively three main phases of tectonic activity have been recognised late cretaceous and palaeocene extension 80 55 ma mainly oligocene and younger contraction and plio pleistocene 3 7 0 ma extension most of the largest faults e g cape egmont fault accrued displacement during the late cretaceous and were reactivated one or more times during subsequent episodes of deformation the oldest phase of extension occurred during gondwana break up and was ubiquitous throughout the basin contraction along the eastern boundary of the basin associated with the onset of hikurangi margin subduction commenced as early as late eocene the zone of contraction widened and migrated westward during the miocene with reverse faults and folds in westernmost parts of the basin formed in the late miocene 7 5 ma initiation and episodic widening of this zone of contraction may have been partly triggered by changes in the rate of plate convergence contraction is now mainly confined to the northern south island and has been succeeded to the north by plio pleistocene extension the present day transition zone between extension in the north and contraction in the south is defined by a wnw trending line across the basin the extension contraction transition migrated southward during the late miocene and pliocene consistent with steepening of the subducting plate and associated southward movement of the southern termination of the hikurangi subduction system

controls on reservoir quality of lower cretaceous tight sandstones in the laiyang sag jiaolai basin eastern china integrated sedimentologic diagenetic and microfracturing data abstract the jiaolai basin fig 1 is an under explored rift basin that has produced minor oil from lower cretaceous lacustrine deltaic sandstones the reservoir quality is highly heterogeneous and is an important exploratory unknown in the basin this study investigates how reservoir porosity and permeability vary with diagenetic minerals and burial history particularly the effects of fracturing on the diagenesis and reservoir deliverability the laiyang sandstones are tight reservoirs with low porosity and permeability

exceptional reservoir quality in hpht reservoir settings examples from the skagerrak formation of the heron cluster north sea uk abstract as the exploration of hydrocarbons moves into more complex and deeper basinal settings the need to understand the effect of high temperatures and high pressures on reservoir quality and rock properties becomes even more important the fluvial channel sandstone reservoirs of the skagerrak formation in the central north sea exhibit anomalously high porosities and permeabilities considering their depth of burial 3500 m below sea floor despite the complex depositional setting diagenetic history high overpressure and temperatures encountered in the skagerrak formation hydrocarbons are currently being produced the skagerrak formation reservoirs used in this study have encountered overpressures of 40 mpa and temperatures up to 185 c at present day maximum burial to identify the role played by the high pressure and high temperature encountered in the reservoir sandstones a multidisciplinary approach involving petrographic fluid inclusion and burial history modelling studies has been adopted our interpretation of the results is that the generation of shallow overpressure in these fields limited mechanical compaction and also played an important role in minimizing pressure solution in the chemical compaction regime as evidenced by reduced quartz cementation fluid inclusions found in the quartz overgrowths indicate late stage development with temperatures of formation in the range 130 to 170 c coincident with late stage deeper burial hydrocarbon emplacement occurred after quartz cementation and has had little to no effect on porosity preservation the formation of well developed authigenic chlorite 70 surface coating and to a lesser extent illite clay coats with burial had a positive effect on porosity preservation even though permeability was marginally reduced in the illite rich sandstones a schematic porosity and quartz cement evolution model has been developed which allows for pre drill prediction of reservoir quality in the heron cluster and provide valuable insights for other complex high pressure high temperature reservoirs

reservoir potential of late cretaceous terrestrial to shallow marine sandstones taranaki basin new zealand abstract late cretaceous coals and coaly source rocks are the main source of hydrocarbons in the taranaki basin yet to date there have not been any hydrocarbon discoveries within cretaceous strata and sandstone distribution and reservoir quality for this interval have been poorly understood the late cretaceous sediments were deposited in several sub basins across taranaki with their distribution largely determined by sediment supply subsidence and sea level change in this study we describe potential reservoir facies in well penetrations of cretaceous strata in taranaki as well as from outcrop in northwest nelson on the southern edge of the basin study of cretaceous outcrop has shown that facies distribution is a major control on reservoir quality shoreface intertidal and estuarine depositional facies contain both excellent well sorted sandstone reservoir facies as well as low net to gross reservoir poor facies these contrast with deposits from generally less well sorted and more heterolithic coastal plain environments much of the facies distribution is attributed to relative sea level fluctuations which occurred throughout deposition late cretaceous sandstones display a range of mean grain sizes and compositions with the latter related to geographic location and sediment source burial depths are highly variable across the basin ranging from 6 km and this has had a profound effect on reservoir quality the main petrographic controls on reservoir quality are sandstone composition volume of clay minerals degree of mechanical compaction related to maximum burial depth and proximity to a source of acidic pore fluids for the generation of secondary porosity results from this study suggest that cretaceous strata are a viable reservoir play over much of the western part of the taranaki basin and into parts of the south eastern basin palaeogeographic maps and textural compositional data can be used to high grade regions for further exploration

the 8 2 ka event from greenland ice cores we present a collection of high resolution chemistry and stable isotope records from the plateau of the greenland ice cap during the cold event 8200 yr ago using a composite of four records the cold event is observed as a 160 5 yr period during which decadal mean isotopic values were below average within which there is a central event of 69 yr during which values were consistently more than one standard deviation below the average for the preceding period four cores in north south and central greenland show differences at decadal and shorter timescales it is not yet clear if this represents significant spatial differences in response the results show clear evidence for colder temperatures and a decrease in snow accumulation rate however the changes in chemical concentrations for the ions looked at here are small suggesting only minor changes in atmospheric circulation for this event apart from the decrease in methane concentration greenland ice cores give only weak evidence for effects outside the north atlantic region

terrestrial climate signal of the 8200 yr b p cold event in the labrador sea region accelerated melting of greenland ice has raised concern about the future impact of enhanced freshwater discharge on regional climate through its effect on ocean circulation an abrupt cooling event ca 8200 cal yr b p has been linked to meltwater from the decaying north american ice sheet oxygen isotopic analyses of cellulose from subfossil sphagnum mosses isolated from a newfoundland peat core reveal a pronounced anomaly ca 8350 yr b p with a duration of 150 years the maximum estimated 18 o precipitation change 4 53 1 05 vienna standard mean ocean water is the largest observed in the circum north atlantic region the magnitude of change exceeds that predicted by recent paleoclimate simulations comparisons with recent records of surface and deep ocean proxies in the labrador sea and the wider north atlantic region suggest synchroneity however an 200 year delay between the responses of the labrador sea region and the greenland ice sheet to the effects of meltwater release remains to be explained

perspectives on cretaceous gondwana break up from detrital zircon provenance of southern zealandia sandstones detrital zircon u pb ages in 37 sandstones from late early late cretaceous marine and non marine successions across southern zealandia indicate a provenance from local basement within present day zealandia samples from taranaki basin were derived from median and karamea batholith granitoids with transport directions from west to east samples from west coast western southland and great south basins contain components derived more locally and more variably from median batholith and rahu suite granitoids and or the palaeozoic buller terrane west coast basin samples have more plutonic contributions and great south basin localities have more albian aged c 110 100 ma zircons samples from canterbury basin were sourced from torlesse composite terrane basement the provenance variations are present in both marine and non marine sandstones and suggest localized watersheds this fits an interpretation of late cretaceous deposition in rift controlled basins across southern zealandia during pre gondwana break up regional extension more speculatively some additional source areas may have been created at the rifted margins of zealandia during this break up

sequence stratigraphy and controls on reservoir sandstone distribution in an eocene marginal marine coastal plain fairway taranaki basin new zealand abstract middle to upper eocene strata in taranaki basin new zealand consist of terrestrial marginal marine shallow marine and offshore sediments deposited in a series of transgressive and regressive cycles within a passive margin setting coastal plain facies are largely confined to eastern and southern sides of the basin and marine mudstones to western and northern parts shoreface to fluvial sandstones within a ne sw oriented coastal facies belt form the pre eminent petroleum reservoir fairway in taranaki basin and provide the bulk of new zealand production the terrestrial coastal plain part of the succession also contains coal rich proven source rocks we have interpreted twelve depositional sequences 3rd and 4th order within the middle to upper eocene strata the base of our study interval marks a relative transgression within the middle eocene and is overlain by composite sequences and parasequences represented by cyclically stacked packages overall regression occurs up to the top of the middle eocene which is overprinted by intermittent shorter term transgressions the overlying upper eocene strata are characterised by overall shoreline retreat with final transgression over the entire taranaki basin in the latest eocene early oligocene stratigraphic cyclicity within the terrestrial to shallow marine facies is noted from paleoenvironmental interpretations determined from well log core biostratigraphic and coal sulphur data whilst eustasy may have played a role in development of the taranaki stratigraphy tectonically induced subsidence was probably the over riding factor especially in the upper eocene petroleum producing reservoirs occur at several distinct horizons within the middle to upper eocene succession interpreted here to represent significant events during sequence development most reservoir sandstones were deposited as channelised facies following 3rd order lowstands sequence boundaries are interpreted at the base of many of these sandstone intervals some of which may represent type 1 boundaries developed as incised valley systems this regional study has used an integrated approach to show how sequence stratigraphy can be applied to a non marine to shallow marine succession to assist with exploration and reservoir development through our recent and multi disciplinary work we have been able to discriminate subtle base level fluctuations and greater marine control of depositional architecture than has previously been recognised with implications for source rock quality fairway exploration reservoir charge and production effectiveness

effects of sandstone provenance on reservoir quality preservation in the deep subsurface experimental modelling of deep water sand in the gulf of mexico deep water turbidite sandstone reservoirs in the gulf of mexico have been sourced from a variety of provenance terrains as a result the framework composition of each reservoir in the basin varies widely including volcanic rich litharenite oligocene vicksburg feldspathicrich lithic arkose oligocene frio metamorphic rich feldspathic litharenite palaeogene wilcox lithic poor quartzarenite miocene quartz rich sublitharenite cretaceous and quartzand feldspar rich subarkose norphlet provenance driven differences in composition have a complex but critical influence on how each of these reservoirs responds to burial induced changes in depth fluid pressure effective stress and temperature a combination of petromod and touchstone modelling programs are used in this study to simulate the influence of provenance on compaction and cementation of the main reservoir types in the gulf of mexico for example modelling results predict that at higher levels of thermal exposure some lithic rich sands although more ductile and highly compacted will experience less quartz cementation than less ductile quartz rich sands thereby preserving a higher range of porosity and permeability furthermore modelling results predict that temperature effective stress depth windows for optimal reservoir quality preservation vary widely depending on sandstone provenance the evaluation of sandstone grain composition and subsequent interpretation of sand provenance has proven to be a useful methodology for oil and gas exploration for many years specific applications of provenance studies are varied and have included the following assistance in the interpretation of basin evolution and tectonic setting dickinson 1985 help in discriminating sandstone petrofacies and source areas ingersoll 1990 interpretation of relief and climate of source areas folk 1980 help with the interpretation of palaeo drainage and sediment dispersal patterns lowe et al 2011 and help with improving stratigraphic correlation morton hurst 1995 recent workers have used provenance as a means of discriminating potential areas of basins with higher reservoir quality potential vincent et al 2010 2013 provenance reconstruction has also become a critical step in selecting the most appropriate analogues for predictive reservoir quality modelling using diagenetic modelling software such as exemplarw lander walderhaug 1999 and touchstone lander et al 2008 what has not been reported as yet is the degree to which provenance affects predictive modelling results with this in mind we pose a question could provenance related differences in sandstone composition within a single basin be large enough to significantly affect predictive modelling results this study is intended to address that question by comparing a variety of sandstone compositions across a wide range of simulated burial histories specifically sandstone compositions representing the mesozoic through tertiary gulf of mexico reservoirs of the deep water basin are used in a series of test cases this basin provides a natural laboratory for testing the effects of provenance on reservoir quality prediction and the findings from this study are intended to be used for global application provenance and reservoir quality modelling provenance transport distance climate and depositional setting all affect the initial detrital composition and to some extent the textural attributes of sandstone reservoirs at the onset of burial depositional texture and composition greatly control the rate and style of compaction and other diagenetic processes that occur during burial specific subsurface processes that are affected by initial sand composition include the following 1 mechanical compaction 2 chemical compaction 3 dissolution of unstable minerals 4 precipitation of quartz cement 5 precipitation of other cements e g carbonates zeolites sulphates from scott r a smyth h r morton a c richardson n eds 2014 sediment provenance studies in hydrocarbon exploration and production geological society london special publications 386 27 47 first published online september 12 2013 http dx doi org 10 1144 sp386 17 the geological society of london 2014 publishing disclaimer www geolsoc org uk pub ethics at conocophillips on august 28 2014 http sp lyellcollection org downloaded from

origin of the torlesse terrane and coeval rocks south island new zealand the carboniferous to lower cretaceous torlesse terrane and haast schist derivatives constitute the major part of the complexly deformed facies of the eastern province of new zealand strata consist mainly of quartzofeldspathic graywacke and mudstone intercalated with minor but widely distributed conglomerate and volcanics with associated chert and limestone clastic rocks were deposited largely by sediment gravity flow mechanisms in a deep marine environment also present are a few highly fossiliferous shallow marine and terrestrial deposits of limited areal extent which rest unconformably on or in fault contact with torlesse flysch several periods of deformation are recognized and melange is present on both local and regional scales metamorphism ranges from zeolite to greenschist facies the bulk of the rocks fall into five areally extensive and mutually exclusive fossil zones of the following ages permian atomodesma middle triassic early late triassic torlessia late triassic monotis and late jurassic early cretaceous contacts between major fossil zones are mainly tectonic petrographic analysis permits subdivision of torlesse sandstones into five major petrofacies that correspond in age to the five major fossil zones the sandstone petrofacies mainly arkosic together with the composition of conglomerate clasts mainly indurated torlesse rocks indicate that the source terrane was a continental volcano plutonic arc probably part of gondwanaland coupled with autocannibalistic reworking of older uplifted torlesse rocks in contrast to the quartzofeldspathic nature of the torlesse coeval sedimentary rocks of the eastern province are volcanogenic they are thought to represent related forearc basin maitai murihiku terranes and trench complex caples terrane deposits derived from a volcanic island arc brook street terrane three petrofacies are established for maitai murihiku and caples sandstones the petrofacies indicate a common evolving immature to submature volcanic island arc source for these terranes a reconstruction of new zealand s eastern and western provinces is proposed in permian and triassic times the torlesse was deposited in trench slope or borderland basins along a trench transform margin fronting a continental volcano plutonic arc source western province gondwanaland deposition was spasmodic but voluminous and was accompanied by concurrent deformation and accretion resulting in parallel belts of torlesse rock younging outward from the gondwanaland margin at the same time the brook street terrane volcanic arc and associated terranes were forming to the west of the torlesse site separated from gondwanaland by a marginal sea in latest triassic or early jurassic times the torlesse was rafted into the volcanic arc system via transform faulting approximately parallel to the gondwana margin the collision event resulted in tectonic thickening of torlesse and caples rocks at the plate interface and metamorphism to haast schist the source was then dominated by older partly metamorphosed torlesse terrane newly uplifted along the collision front closing of the marginal sea behind the brook street terrane in late jurassic early cretaceous times resulted in juxtapositioning with the western province gondwanaland along the median tectonic line

eustatic variations during the paleocene eocene greenhouse world we reconstruct eustatic variations during the latest paleocene and earliest eocene 58 52 ma dinoflagellate cysts grain size fractions and organic biomarkers in marine sections at four sites from three continents indicate an increased distance to the coast during the paleocene eocene thermal maximum petm the same trend is recognized in published records from other sites around the world together the data indicate a eustatic rise during the petm beginning 20 to 200 ka before the globally recorded negative carbon isotope excursion cie at 55 5 ma although correlations are tentative we recognize other global transgressions during chrons c25n and c24n the latter may be associated with eocene thermal maximum 2 53 5 ma or the x event 52 ma these results suggest a link between global sea level and hyperthermal intervals potentially because of the melting of small alpine ice sheets on antarctica thermal expansion of seawater or both however the early onset of sea level rise relative to the cie of the petm suggests contributions from other mechanisms perhaps decreasing ocean basin volume on sea level rise copyright 2008 by the american geophysical union

diagenesis and burial history modeling of heterogeneous marginal marine to shoreface paleocene glauconitic sandstones taranaki basin new zealand paleocene marginal marine to shoreface glauconitic sandstones f sands of the farewell formation from the maui field in taranaki basin new zealand demonstrate a diagenetic evolution driven by major shifts in acidic pore water composition rate of burial and clay mineral authigenesis mechanical compaction is the principal porosity reducing mechanism during the first 2500 m of burial of the f sands continued mechanical compaction with long grain contacts concavo convex contacts and deformed liable grains are common throughout the f sands late stage flow of dissolved co2 in the pore fluids of the farewell formation is thought to have been generated from thermal decarboxylation of coaly source rocks the circulation of these co2 rich fluids will have dissolved into undersaturated pore fluids and partially catalyzed dissolution of feldspar and quartz producing ions for the precipitation of kaolinite and chlorite timing of the diagenetic reactions as determined using paragenetic observations fluid inclusion analysis and burial history modeling suggests that the quartz cements formed at a late stage 100 c corresponding to 0 7 ma and is consistent with the migration of hydrocarbons and associated co2 into the f sand reservoir significant secondary porosity is generated through the dissolution of feldspar which is preserved due to late stage of occurrence at close to present day maximum burial dissolved solutes in the f sands sandstones are being preferentially precipitated in interbedded and surrounding fine grained heterolithic siltstone to very fine grained sandstone beds leading to enhanced heterogeneity and preservation of secondary porosity this study provides an improved understanding for diagenetic reconstruction of marginal marine to shoreface facies

the 10a phase a high pressure expandable sheet silicate stable during subduction of hydrated lithosphere h2o storage and release in deep subducting lithosphere is controlled by complex reaction suites involving a variety of hydrous phases as a result of its relatively large thermal stability and intermediate composition the 10a o phase mg3si4o10 oh 2wnh2o has been regarded as a relevant h2o reservoir in a wide range of rock compositions and mineral assemblages high pressure syntheses of the 10a o phase were carried out at 6 7 gpa and 650 c under fluidsaturated conditions in a walker type multi anvil apparatus from 5 min to 430 h x ray powder diffraction of large platy hexagonal crystals of the 10a o phase up to 100 wm were indexed on the basis of a trioctahedral type structure long term run products s 110 h reveal sensitivity of the 10a o phase to treatment with acetone leading to the appearance of diffractions at greater d spacings 10 2 11 6 a o with respect to the basal peak of the 10a o phase 9 64 10 07 a o this swelling behavior is strongly related to synthesis run duration the raman spectrum of the 10a o phase at frequencies less than 800 cm 31 shows a strong similarity to talc in the si o stretching region 800 1100 cm 31 the 10a o phase exhibits three modes 909 992 and 1058 cm 31 as compared to two in talc the bending mode of water x2 i s found at 1593 cm 31 in the oh stretching region peaks at 3593 3622 and 3668 cm 31 were observed the acetone treated sample shows a c h stretching mode at 2923 cm 31 while the double bond cno signal is absent the swelling behavior of the 10a o phase is interpreted as due to intercalation of acetone with pre existing interlayer water the efficiency of this process is dependent on the amount of the interlayer water which in turn depends on run duration the relation between the response to acetone treatment and run duration is therefore interpreted as a time dependent hydration of the 10a o phase the fractions transformed from non expandable to expandable fractions was fitted to the avrami empirical law which suggests that kinetics are mainly controlled by diffusion rather than phase boundary reactions the ability to accommodate variable amounts of h2o makes the 10a o phase a major h2o sink whenever a hydrous phase such as chlorite and serpentine breaks down during prograde transformations in the subducted lithosphere under h2o saturated conditions a fully hydrated 10a o phase occurs when h2o undersaturated conditions prevail a h2o deficient 10a o phase incorporates the volatile component available the exchange capacity of interlayer molecules in the 10a o phase structure opens new scenarios on the control of fluid compositions escaping from subducted

seismic stratigraphy of a buried volcanic arc northland new zealand and implications for neogene subduction abstract for over 6 million years in the early miocene the northland peninsula of new zealand s north island was the site of a volcanic arc comprising north westerly trending twin belts of marine and subaerial andesitic volcanoes approximately 50 volcanic edifices from major massifs to small cones have been newly identified on marine seismic profiles of the western belt which is largely buried the volcanoes were important point sources of sediment and the volcaniclastic deposits of each of the major and intermediate sized volcanoes form distinct seismic sequences the three main elements of the volcanic sequence are i a main body ii a sloping apron and iii a wide almost flat ring plain the downlap of the oldest discernible internal clinoform reflector relative to a known regional marker reflector underlying it indicates the approximate time of onset of activity whereas downlap of the top bounding reflector relative to those of other volcanic sequences provides a relative order of extinction sequence stratigraphic principles and super position determine relative stratigraphic hierarchy the volcanoes studied here were active only in the early miocene with few exceptions most were active by 22 ma and extinct by 16 ma with many extinct by 19 ma there was no pattern in their order of inception or extinction although a few became dominant burying or surrounding their neighbours at the south eastern end of the chain there is a rapid change over a short distance in both age and orientation from the northwest trending early miocene volcanism in the northland basin to north east trending middle and late miocene volcanism in the contiguous taranaki basin the northland volcanoes are interpreted to have been an arc facing the south westwards subducting south fiji basin whereas the taranaki volcanoes are interpreted to have been part of a separate pacific facing volcanic arc the lau colville ridge

thermal history and exhumation of basement rocks from mesozoic to cenozoic subduction cycles central north island new zealand a new thermochronological study of the basement rocks of the central north island new zealand records thermal and exhumation histories related to two subduction cycles since the latest jurassic the basement comprises metasedimentary terranes accreted onto eastern gondwana during mesozoic subduction since the oligocene these terranes have been located on the hanging wall of the hikurangi subduction margin overriding the pacific plate results of zircon fission track 121 264 ma analysis yield detrital or slightly reset ages apatite fission track 19 8 122 ma and u th sm he 10 3 95 2 ma ages are fully reset results from inverse thermal history modeling of the data of individual and stacked samples imply the following 1 after their accretion the basement rocks were cooled and exhumed to shallow depths of the crust in the early cretaceous by 150 135 ma this was followed by an episode of reheating until 100 ma which we interpret to be the result of burial by sedimentation above the accretionary wedge during extensional deformation caused by continued underplating and thickening of the wedge from beneath 2 from 100 ma our data indicate thermotectonic quiescence until the oligocene 27 ma 3 during initiation of the hikurangi margin the fore arc proto axial ranges began to exhume during the late oligocene to early miocene 27 20 ma subduction triggered unroofing removed 1 2 2 8 km of overburden most of which was probably the less lithified passive margin sediments 4 along the western central north island the exhumational response to the hikurangi subduction was limited with a total magnitude of erosion 1 5 km in the cenozoic

equation of state of gold and its application to the phase boundaries near 660 km depth in earth s mantle the pressure volume temperature equation of state eos of gold is fundamental to high pressure science because of its widespread use as an internal pressure standard in particular the eos of gold has been used in recent in situ multi anvil press studies for determination of phase boundaries related to the 660 km seismic discontinuity these studies show that the boundaries are lower by 2 gpa than expected from the depth of the 660 km discontinuity here we report a new p v t eos of gold based on the inversion of quasi hydrostatic compression and shock wave data using the mie gru neisen relation and the birch murnaghan debye equation the previously poorly constrained pressure derivative of isothermal bulk modulus and the volume dependence of gru neisen parameter q d lnq d ln v are determined by including both phonon and electron effects implicitly kp0t 5 0 0 2 and q 1 0 0 1 this combined with other accurately measured parameters enables us to calculate pressure at a given volume and temperature at 660 km depth conditions this new eos yields 1 0 0 2 gpa higher pressure than anderson et al s eos which has been used in the multi anvil experiments however after the correction there still exists a 1 5 gpa discrepancy between the post spinel boundary measured by multi anvil studies and the 660 km discontinuity other potential error sources such as thermocouple emf dependence on pressure or systematic errors in spectroradiometry should be investigated theoretical and experimental studies to better understand electronic and anharmonic effects in gold at high p t are also needed 2002 elsevier science b v all rights reserved

holocene climatic instability a prominent widespread event 8200 yr ago the most prominent holocene climatic event in greenland ice core proxies with approximately half the amplitude of the younger dryas occurred 8000 to 8400 yr ago this holocene event affected regions well beyond the north atlantic basin as shown by synchronous increases in windblown chemical indicators together with a significant decrease in methane widespread proxy records from the tropics to the north polar regions show a short lived cool dry or windy event of similar age the spatial pattern of terrestrial and marine changes is similar to that of the younger dryas event suggesting a role for north atlantic thermohaline circulation possible forcings identified thus far for this holocene event are small consistent with recent model results indicating high sensitivity and strong linkages in the climatic system

thermochronology of northern murihiku terrane new zealand derived from apatite ft analysis murihiku terrane is the least deformed of a series of tectonostratigraphic terranes that have been amalgamated to form the basement underlying new zealand apatite fission track ft thermochronology has been applied to the youngest beds late jurassic hettangian tithonian stages of this terrane located at port waikato in western north island which are broadly folded the apatite ft ages are partially annealed are younger than their stratigraphic ages and remarkably decrease in age upsection interpretation and modelling of the maximum palaeotemperatures experienced by the sample horizons and the timing of cooling requires a wedge of cretaceous sedimentary rocks to have accumulated within the axis of the major fold kawhia syncline deposition of murihiku terrane sequences continued therefore into the cretaceous and probably until c 100 ma deposition may have ended as late as 85 10 ma when cooling via denudation started the upper parts of the former succession probably accumulated during folding in addition interpretation of the ft data require a marked increase in palaeogeothermal gradient from a subnormal value of 15 c km 1 during the late jurassic up to c 30 c km 1 at 85 10 ma this is attributed to the termination of subduction along the pacific margin of gondwanaland and a transition to a rift transform tectonic setting in western new zealand during tasman sea spreading the latest cretaceous palaeocene eastward tilting of the murihiku basement at port waikato may have been accommodated on the taranaki fault or another coast parallel fault the waikato fault probably acted as a transfer fault at that time accumulating a significant amount of throw

impact of regional variation in detrital mineral composition on reservoir quality in deep to ultradeep lower miocene sandstones western gulf of mexico abstract future exploration in lower miocene sandstones in the gulf of mexico will focus increasingly at depths greater than 4 5 km and reservoir quality will be a critical risk factor in these deep to ultradeep reservoirs the goal of this study was to understand the variation in reservoir quality of lower miocene sandstones across the western gulf of mexico to do this we examined regional variation in detrital mineral composition diagenesis and reservoir quality in five areas 1 louisiana 2 upper texas coast 3 lower texas coast 4 burgos basin mexico and 5 veracruz basin mexico using petrographic and petrophysical data from depths of 0 9 7 2 km there are strong variations in mineralogical composition within the study area lower miocene sandstones from offshore louisiana have an average composition of quartz 86 feldspar 12 and rock fragments 2 q 86 f 12 r 2 feldspar and rock fragment content increase southward as source areas shifted to include volcanic and carbonate rocks composition of samples from offshore texas ranges from q 67 f 24 r 9 in the upper texas coast to q 58 f 24 r 19 in the lower texas coast lower miocene sandstones from the onshore burgos basin northern mexico have an average composition of q 54 f 22 r 23 whereas sandstones from the veracruz basin southern mexico contain the highest proportion of rock fragments q 33 f 12 r 55 main diagenetic events in quartz rich lower miocene sandstones in louisiana were mechanical compaction and precipitation of quartz cement compactional porosity loss increased to the south with increasing rock fragment content calcite is the most abundant cement in the south and is strongly related to reservoir quality loss at moderate burial depths the best reservoir quality occurs in quartz rich sandstones in louisiana and decreases with increasing lithic content in texas and mexico porosity is higher in louisiana and upper texas than in lower texas and mexico at all depths and temperatures but at depths 5 km and temperatures 175 c porosity differences are lessened the lower miocene sandstone trend in the western gulf of mexico from louisiana to mexico is an example of the importance of variation in detrital mineralogy as a control on diagenesis and reservoir quality

a geochemical and biostratigraphic approach to investigating regional changes in sandstone composition through time an example from paleocene eocene strata taranaki basin new zealand

reservoir characterisation of syn rift and post rift sandstones in frontier basins an example from the cretaceous of canterbury and great south basins new zealand abstract a paucity of well data in frontier basins presents serious challenges for reservoir characterisation studies around the world in this paper we provide the first regional study addressing reservoir distribution composition and quality in the frontier canterbury basin cb and great south basin gsb of new zealand and show how the results can be used to help reduce uncertainties associated with reservoir presence and effectiveness cretaceous strata in canterbury and great south basins represent two stages of basin history the oldest cenomanian coniacian mid cretaceous strata are syn rift deposits that developed in response to the breakup of the eastern margin of gondwana while overlying santonian maastrichtian late cretaceous strata are post rift deposits that signify the start of rift drift transgression these cretaceous deposits are characterised by a change in facies from predominantly alluvial fluvial to marginal shallow marine that is recognisable in outcrop and wells and from seismic response based on our petrographic examination of 99 cretaceous samples from well and outcrop locations we conclude that there are significant differences in sandstone texture and mineralogy that are related to differences in depositional facies basin stratigraphy geographic location and degree of diagenetic alteration sandstones from the earliest part of the syn rift succession largely reflect the composition of the underlying basement geology typically granitoid or quartzose western province rocks in gsb and lithic rich eastern province metasedimentary rocks in cb younger strata representing part of the post rift succession are generally better sorted with detrital compositions reflecting sediment mixing of several basement source areas based on available data reservoir quality is directly related to sandstone texture and detrital composition factors of provenance and facies compaction a factor of burial depth temperature and degree or type of diagenetic alteration best quality sandstones are predicted to occur in the late cretaceous post rift succession of gsb and locally in cb either where sediment is derived from local granitoids or where high energy depositional processes have resulted in quartz enriched compositions

satellite gravity measurements confirm accelerated melting of greenland ice sheet using time variable gravity measurements from the gravity recovery and climate experiment grace satellite mission we estimate ice mass changes over greenland during the period april 2002 to november 2005 after correcting for the effects of spatial filtering and limited resolution of grace data the estimated total ice melting rate over greenland is 239 23 cubic kilometers per year mostly from east greenland this estimate agrees remarkably well with a recent assessment of 224 41 cubic kilometers per year based on satellite radar interferometry data grace estimates in southeast greenland suggest accelerated melting since the summer of 2004 consistent with the latest remote sensing measurements

provenance of the sedimentary rakaia sub terrane torlesse terrane south island new zealand the use of igneous clast compositions to define the source abstract the permian to late triassic rakaia sub terrane part of the torlesse superterrane of the new zealand eastern province is an accretionary complex that comprises an enormous volume of quartzofeldspathic sandstones and mudstones with subsidiary conglomerates plus minor oceanic assemblages the field of provenance analysis has undergone a revolution with the development of single crystal isotope dating techniques using mainly silt to sand sized single mineral grains fine sand and mud may be transported over thousands of kilometres with potential problems for provenance studies reinforcing the need for caution when interpreting provenance evidence from single heavy mineral grains this study focuses on coarser grained rocks notably conglomerates which involve much shorter transport distances and therefore may be used to trace proximal sources a detailed rock sampling programme and geochronological geochemical and sr nd isotope analysis of igneous clasts from four conglomerates boundary creek te moana mckenzie pass and lake hill have broadly characterised the igneous source for the rakaia sub terrane shrimp u pb zircon ages of rakaia sub terrane igneous clasts define three distinct periods of magmatic crystallisation the first period ranges in age from 292 to 243 ma permian to middle triassic with two clusters recognisable a minor early permian one ranging in age from 292 to 277 ma and a major late permian to middle triassic one from 258 to 243 ma all these clasts are confined to the kazanian permian te moana the dorashamian permian mckenzie pass and the carnian late triassic lake hill conglomerates the clasts which are subduction related calc alkaline to high k calc alkaline and metaluminous to peraluminous range in lithology from andesite to rhyolite and their plutonic equivalents many clasts at lake hill have chemical compositions characteristic of partial melts of a source of basaltic composition in equilibrium with amphibole pyroxene garnet adakites indicative of a thick crust in the clast source area the second period comprises carboniferous calc alkaline metaluminous to weakly peraluminous clasts of the permian boundary creek conglomerate ranging in age from 356 to 325 ma the third group consists of two cambrian clasts a monzogranite from te moana c 497 8 ma and a dacite from lake hill c 517 ma geochronology geochemistry and sr nd isotopes of rakaia igneous clasts correlate broadly with those of permian to triassic plutons and volcanics from the amundsen and ross provinces of marie byrd land thus the antarctic sector of the panthalassan margin of gondwana is the probable source for the rakaia sub terranes as opposed to the other postulated sources in eastern australia

the 8k event cause and consequences of a major holocene abrupt climate change abstract a prominent abrupt climate event about 8200 years ago brought generally cold and dry conditions to broad northern hemisphere regions especially in wintertime in response to a very large outburst flood that freshened the north atlantic changes were much larger than typical climate variability before and after the event with anomalies up to many degrees contributing to major displacement of vegetative patterns this 8k event provides a clear case of cause and effect in the paleoclimatic realm and so offers an excellent opportunity for model testing the response to north atlantic freshening has the same general anomaly pattern as observed for older events associated with abrupt climate changes following north atlantic freshening and so greatly strengthens the case that those older events also reflect north atlantic changes the north atlantic involvement in the 8k event helps in estimating limits on climate anomalies that might result in the future if warming caused ice melt and hydrologic cycle intensification at high latitudes lead to major changes in north atlantic circulation few model experiments have directly addressed the 8k event and most studies of proxy records across this event lack the time resolution to fully characterize the anomalies so much work remains to be done

changes in reservoir heterogeneity and quality as a response to high partial pressures of co2 in a gas reservoir new zealand abstract the kapuni field is the largest onshore petroleum field in new zealand and produces co2 rich gas c 40 45 mol co2 diagenesis within the reservoir is dominated by co2 related reactions that have resulted in localised precipitation of kaolin abundant quartz calcite dolomite and siderite along with localised generation of secondary porosity most of the co2 in the reservoir is thought to have been sourced from intraformational coals with subsequent up dip migration to the crest of the kapuni structure during migration co2 will have dissolved into undersaturated pore fluids and the resulting acidic pore fluids catalysed feldspar and minor carbonate dissolution thereby providing ions for precipitation of authigenic minerals timing of the diagenetic reactions as determined by paragenetic observations and fluid inclusion analysis suggests that both quartz and carbonate formed at a very late stage 100 c corresponding to 0 4 ma which is consistent with modelled maturation and expulsion of co2 from intraformational source rocks 5 ma to present the carbon isotope composition of carbonate cements median 13cpdb 12 4 is similar to that of the reservoired co2 13cpdb 14 5 and this is supportive of late stage cement formation with carbon sourced primarily from thermal maturation reactions the degree of co2 related reactions observed within the kapuni field appears dependent upon grain size lithofacies and stratigraphic position in the reservoir coarse grained high energy facies have undergone the most feldspar dissolution coupled with formation and local preservation of secondary porosity this is interpreted to be due to preferential migration of large volumes of co2 rich fluids through permeable beds thereby further enhancing reservoir quality by comparison much less feldspar reaction but locally significant authigenic mineral precipitation occurs within finer grained lower energy sandstone facies this is considered to be due to relatively low permeability prior to co2 circulation restricting the degree of fluid circulation and resulting in net mineral precipitation authigenic kaolin has precipitated close to the mineral source whilst ions required to precipitate calcite dolomite cements are likely to have migrated further resulting in a complex distribution of carbonate cements with pervasive cements observed at gas water contacts results from this study demonstrate how co2 related reactions are dependent on grain size and mineralogy we show that these reactions can affect vertical heterogeneity of a reservoir by increasing the degree of compartmentalisation through development of sweet spots due to mineral dissolution and tight beds due to mineral cementation

the effect of ductile lithic sand grains and quartz cement on porosity and permeability in oligocene and lower miocene clastics south china sea prediction of reservoir quality ductile clay rich sand grains control porosity and permeability in the fluvio deltaic oligocene and lower miocene sandstones of the south china sea ductile grains account for between approximately 5 and 50 of the original sand grain population there is a pronounced loss of porosity with increasing burial depth in the basin at depths of less than 3000 m this is due solely to ductile grain compaction where the rate of porosity loss with depth increases with increasing ductile grain content at depths greater than 3000 m the steep porosity loss with depth is due to combined ductile grain compaction and quartz cementation the amount of quartz cement increases with increasing burial depth however cleaner sandstones tend to have greater amounts of quartz cement at any given depth below 3000 m this leads to convergence of porosity evolution for the clean and ductile rich sandstones below 3000 m there is a rapid loss of permeability with decreasing porosity because compaction of ductile grains smears them between rigid quartzose grains leading to blocked pore throats a consequence of this process is that the lowest permeabilities are found in sandstones with the highest ductile grain contents quartz cement does not have a clear and discernible control on permeability the pronounced loss of porosity with increasing depth and permeability with decreasing porosity leads to low permeability at relatively shallow burial depths reservoir quality is thus controlled by the nature of the primary sand and depth of burial the sediment supply system led to systematic changes in ductile grain content across the basin with ductile content increasing into the more distal part of the sediment system the consequence is that depth of economic basement in terms of porosity or permeability can be predicted as a function of ductile grain content and burial depth for prospects across the basin

surface and deep ocean interactions during the cold climate event 8200 years ago evidence from a north atlantic deep sea sediment core reveals that the largest climatic perturbation in our present interglacial the 8200 year event is marked by two distinct cooling events in the subpolar north atlantic at 8490 and 8290 years ago an associated reduction in deep flow speed provides evidence of a significant change to a major downwelling limb of the atlantic meridional overturning circulation the existence of a distinct surface freshening signal during these events strongly suggests that the sequenced surface and deep ocean changes were forced by pulsed meltwater outbursts from a multistep final drainage of the proglacial lakes associated with the decaying laurentide ice sheet margin

early paleogene temperature history of the southwest pacific ocean reconciling proxies and models we present a new multiproxy tex86 18o and mg ca marine temperature history for canterbury basin eastern new zealand that extends from middle paleocene to middle eocene including the paleocene eocene thermal maximum petm and early eocene climatic optimum eeco in light of concerns that proxy based sea surface temperature sst estimates are untenably warm for the southwest pacific during the eocene we review the assumptions that underlie the proxies and develop a preliminary paleo calibration for tex86 that is based on four multiproxy eocene records that represent an sst range of 15 34 c for the southwest pacific paleogene we show that tex86l exhibits the best fit with the eocene paleo calibration ssts derived from related proxies tex86h 1 tex86 exhibit a systematic warm bias that increases as tex86 values decrease a warm bias of 4 7 c where tex86 0 7 the tex86l proxy indicates that southwest pacific sst increased by 10 c from middle paleocene to early eocene with sst maxima of 26 28 c tropical during the petm and eeco and an sst minimum of 13 16 c cool warm temperate at the middle late paleocene transition 58 7 ma the base of the eeco is poorly defined in these records but the top is well defined in canterbury basin by a 2 5 c decrease in sst and bottom water temperature bwt in the latest early eocene 49 3 ma bwt falls from a maximum of 18 20 c in the eeco to 12 14 c in the middle eocene overall cooler temperatures are recorded in the mid waipara section which may reflect a deeper 500 m water depth and less neritic depositional setting compared with hampden and odp 1172 200 m water depth the high ssts and bwts inferred for the petm and eeco can be reconciled with eocene coupled climate model results if the proxies are biased towards seasonal maxima and the likely effect of a proto east australian current is taken into account

freshwater outbursts to the oceans from glacial lake agassiz and their role in climate change during the last deglaciation abstract lake agassiz was the largest lake in north america during the last deglaciation as the laurentide ice sheet lis retreated large volumes of water stored in this proglacial lake were episodically released into the oceans these waters were variably routed to the gulf of mexico arctic ocean north atlantic ocean and hudson bay during this period the three largest cooling events in the northern hemisphere closely followed 4 of the 5 largest outbursts from lake agassiz 1 the younger dryas which was preceded by a release of 9500 km 3 2 the preboreal oscillation preceded by releases of 9300 km 3 and 5900 km 3 and 3 the 8 2 ka cold event preceded by a 163 000 km 3 outburst these are respectively fluxes of 0 30 sv 0 29 sv 0 19 sv and 5 2 sv if released in 1 year because the influx of freshwater reaching the north atlantic ocean can inhibit thermohaline circulation partly depending on whether the ocean was in a glacial interglacial or transitional mode of circulation we believe that at least these large outbursts from lake agassiz may have provided the triggers for changes in ocean circulation and in turn for widespread climate change

an 8500 cal year multi proxy climate record from a bog in eastern newfoundland contributions of meltwater discharge and solar forcing analyses of plant macrofossils testate amoebae and the degree of peat humification have been combined into a single composite reconstruction of bog surface wetness bsw on a coastal plateau bog in eastern newfoundland the reconstruction reveals 14 distinctive phases of near surface water tables commencing at 8270 7500 6800 5700 5200 4900 4400 4000 3100 2500 2050 1700 600 and 200 cal bp which may be used to infer changes in the atmospheric water balance of eastern newfoundland the first two major phases of pool development follow the final drainage of glacial lake agassiz at 8400 cal bp and the ungava lakes between ca 7500 6900 cal bp respectively from 7500 cal bp to the present there appears to be a strong correlation within dating errors between reconstructed bsw and the stacked ice rafted debris ird record in the north atlantic ocean both records may reflect long term changes in air masses comparisons of the bsw reconstruction with records of cosmogenic isotope flux also suggest a persistent link between reduced solar irradiance and increased bsw during the holocene

sandstone provenance and sediment dispersal in a complex tectonic setting taranaki basin new zealand abstract mineralogical geochemical and detrital zircon data from key reservoir intervals in taranaki basin are integrated with paleogeography and basement maps to provide a synthesis of changes in sediment provenance and sandstone composition through time results show that sandstone composition and quality in taranaki is strongly related to sediment provenance and basin history late cretaceous syn rift deposits display clear evidence for first cycle erosion from local basement rocks dominated by granites of the median batholith a ne sw trending shoreline belt developed through the paleocene which was associated with a gradual increase in sandstone maturity that peaked during the eocene passive margin phase sediment provenance continued to be primarily from granitoids with transport directions from the s sw to n ne progressive quartz enrichment is interpreted to be a result of cleaning through longshore drift longer transport distances and enhanced chemical weathering due to warmer paleoclimates we also invoke a component of eroded and recycled cretaceous paleocene sediment linked to an episode of uplift in the south a transition period ensued from the late eocene to early miocene associated with a change in basin tectonics from passive margin to active margin compositional and detrital zircon u pb data indicate that rocks to the east of taranaki basin became emergent with progressive erosion of cretaceous eocene cover rocks and underlying basement terranes minor southward propagating uplift of the eastern basin margin was initiated in the latest eocene and by the late oligocene provenance and sedimentation patterns had clearly changed with the earliest miocene strata sourced from eastern metasedimentary basement rocks the eastern province continued to be a major sediment source through the active margin phase but mixed with the re appearance of granite reworked sources and miocene volcaniclastic detritus these changes in sediment provenance through time are displayed on a set of eight sediment dispersal maps which can be used to help predict composition and hence reservoir quality in undrilled parts of the basin

triassic turbidites in the west qinling mountains nw china part of the collisional songpan ganzi basin or an active forearc basin abstract lower to middle triassic clastic rocks in the west qinling mountains along ne margin of the qinghai tibet plateau are generally regarded as part of the songpan ganzi flysch basin however relatively little attention has been paid to the age and provenance of these units new petrological and geochemical results demonstrate that these sediments accumulated along an active continental margin and are dominated by feldspathic litharenite and lithic arkose with low mineral and compositional maturity they were derived primarily from a continental arc source dominated by intermediate to felsic igneous rocks with a minor contribution from older metamorphosed and sedimentary sources turbidite samples yielded two primary detrital zircon u pb age populations of ca 273 ma and ca 435 ma which is different from the early triassic ca 252 ma and middle silurian ca 427 ma age populations that dominate the songpan ganzi basin these data together with paleocurrent results indicate that the south qilian belt was the primary source origin because this belt contains both early paleozoic andean type igneous and magmatic rocks and has a basement of precambrian metamorphosed rocks regionally an andean type arc traverses the south qilian belts and extends into the west qinling mountains and kunlun orogen which formed by north directed subduction of the paleo tethyan ocean during the early to middle triassic voluminous detritus that originated from the qilian and kunlun orogens as they were uplifted and eroded was transported to the south and deposited in the forearc area in front of the a nimaqen mianlue suture

subduction platform subsidence and foreland thrust loading the late tertiary development of taranaki basin new zealand borehole seismic and gravity data are used to investigate deformation of continental lithosphere at a miocene collisional zone deformation is manifested in the three following principal forms a long wavelength 500 km platform subsidence ascribed to mantle convection flexural deformation on a scale of 100 200 km due to crustal thrusting at the eastern boundary of the taranaki basin and a ductile thickening evident on the deep seismic section of taranaki basin that occurs on a scale of 10 km evidence for flexural deformation principally comes from the deep seismic section that shows a 150 km wavelength bending of the moho down toward the major zone of thrusting within the taranaki fault zone paleowater depths however provide evidence for an initial early miocene regional subsidence that is too long in wavelength to be explained by flexure induced from thrust sheet loading instead we propose that this broad platform subsidence was driven by loading from a deep source probably subduction induced flow in the mantle by 22 19 ma 1 2 km of water existed over most of the area now occupied by south taranaki basin by 19 17 ma the water depth in the zone east of the taranaki basin the taranaki fault zone had been replaced by rock due to submarine thrusting and crustal thickening this build up of submarine topography in the taranaki fault zone constitutes part of the load 25 8 mpa that created and maintains south taranaki basin gravity data place further constraints on loading at the thrust front and point to an additional intracrustal loading equivalent to 15 7 mpa over a 50 km wide zone this intracrustal load is explained as being due to thick skinned thrusting bringing denser lower crustal rocks nearer to the surface in the thrust zone the complete load on the taranaki foreland is therefore in three parts the submarine topographic load the intracrustal load and the loading of infilling sediments

rapid early holocene deglaciation of the laurentide ice sheet the demise of the laurentide ice sheet during the early holocene epoch is the most recent and best constrained disappearance of a large ice sheet in the northern hemisphere and thus allows an assessment of rates of ice sheet decay as well as attendant contributions to sea level rise here we use terrestrial and marine records of the deglaciation to identify two periods of rapid melting during the final demise of the laurentide ice sheet when melting ice contributed about 1 3 and 0 7cm of sea level rise per year respectively our simulations with a fully coupled ocean atmosphere model suggest that increased ablation due to enhanced early holocene boreal summer insolation was the predominant cause of laurentide ice sheet retreat although the surface radiative forcing in boreal summer during the early holocene is twice as large as the greenhouse gas forcing expected by the year 2100 the associated increase in summer surface air temperatures is very similar we conclude that our geologic evidence for a rapid retreat of the laurentide ice sheet may therefore describe a prehistoric precedent for mass balance changes of the greenland ice sheet over the coming century

a new greenland ice core chronology for the last glacial termination 1 we present a new common stratigraphic timescale for the north greenland ice core project ngrip and grip ice cores the timescale covers the period 7 9 14 8 kyr before present and includes the bolling allerod younger dryas and early holocene periods we use a combination of new and previously published data the most prominent being new high resolution continuous flow analysis cfa impurity records from the ngrip ice core several investigators have identified and counted annual layers using a multiparameter approach and the maximum counting error is estimated to be up to 2 in the holocene part and about 3 for the older parts these counting error estimates reflect the number of annual layers that were hard to interpret but not a possible bias in the set of rules used for annual layer identification as the grip and ngrip ice cores are not optimal for annual layer counting in the middle and late holocene the timescale is tied to a prominent volcanic event inside the 8 2 kyr cold event recently dated in the dye 3 ice core to 8236 years before a d 2000 b2k with a maximum counting error of 47 years the new timescale dates the younger dryas preboreal transition to 11 703 b2k which is 100 150 years older than according to the present grip and ngrip timescales the age of the transition matches the gisp2 timescale within a few years but viewed over the entire 7 9 14 8 kyr section there are significant differences between the new timescale and the gisp2 timescale the transition from the glacial into the bolling interstadial is dated to 14 692 b2k the presented timescale is a part of a new greenland ice core chronology common to the dye 3 grip and ngrip ice cores named the greenland ice core chronology 2005 gicc05 the annual layer thicknesses are observed to be log normally distributed with good approximation and compared to the early holocene the mean accumulation rates in the younger dryas and bolling periods are found to be 47 2 and 88 2 respectively

paleohydraulics of the last outburst flood from glacial lake agassiz and the 8200 bp cold event abstract during the last deglaciation of north america huge proglacial lakes formed along the southern margin of the laurentide ice sheet the largest of these was glacial lake agassiz which formed about 11 7 14 c kyr and drained into hudson bay about 7 7 14 c kyr 8 45 cal kyr overflow from these lakes was variably directed to the mississippi st lawrence and mackenzie drainage systems and it is thought that switches in routing were accompanied by a response in ocean circulation that produced abrupt climate events when the ice dam across hudson bay finally was breached a massive flood drained lake agassiz which was routed through hudson strait to the labrador sea in terms of stored water volume the largest reservoir was associated with the kinojevis level of lake agassiz for this maximum filling the impounded water volume available to produce floods is estimated as 40 000 151 000 km 3 depending on the location of the ice margin and route used the timing of this rapid release of stored freshwater just precedes the early holocene cooling event at 8 2 cal kyr bp we use the spring hutter theory to simulate flood hydrographs for floods that originate in subglacial drainage conduits and find that flood magnitude and duration are 5 sv and 0 5 yr multiple fillings and floods are possible as are single floods having a complex multipulse structure modelling results suggest that the outburst flood from lake agassiz may have terminated before the lake surface elevation dropped to sea level and that the flood ended when a stable drainage channel was established connecting lake agassiz to the tyrrell sea

the cold event 8200 years ago documented in oxygen isotope records of precipitation in europe and greenland stable oxygen isotope ratios of ostracod valves in late glacial and holocene sediments of core as 92 5 from deep lake ammersee southern germany reflect variations of mean oxygen isotope ratios in past atmospheric precipitation the record reconfirms the strong similarity of climate evolution in europe and greenland during the last deglaciation for the first time in europe we find a 200 year long negative 18o excursion which is contemporaneous with the strongest negative 18o excursion in the greenland ice around 8 2 ky before present the 8 2 ky isotopic event on both sides of the north atlantic ocean is interpreted as a cold period most probably induced by a perturbation of the north atlantic thermohaline circulation we discuss two possible triggering mechanisms 1 weak forcing as proposed by alley et al and 2 forcing by a strong and sudden freshwater pulse from the collapse of the hudson ice dome

the greenland ice core chronology 2005 15 42 ka part 2 comparison to other records a new greenland ice core chronology gicc05 based on multi parameter counting of annual layers has been obtained for the last 42 ka here we compare the glacial part of the new time scale which is based entirely on records from the northgrip ice core to existing time scales and reference horizons covering the same period these include the grip and northgrip modelled time scales the meese sowers gisp2 counted time scale the shackleton fairbanks grip time scale sfcp04 based on 14c calibration of a marine core the hulu cave record three volcanic reference horizons and the laschamp geomagnetic excursion event occurring around greenland interstadial 10 gicc05 is generally in good long term agreement with the existing greenland ice core chronologies and with the hulu cave record but on shorter time scales there are significant discrepancies around the last glacial maximum there is a more than 1 ka age difference between gicc05 and sfcp04 and a more than 0 5 ka discrepancy in the same direction between gicc05 and the age of a recently identified tephra layer in the northgrip ice core both sfcp04 and the tephra age are based on 14c dated marine cores and fixed marine reservoir ages for the laschamp event gicc05 agrees with a recent independent dating within the uncertainties

replicability and variability of the recent macrofossil and proxy climate record from raised bogs field stratigraphy and macrofossil data from bolton fell moss and walton moss cumbria england replication of results is a basic tenet of science but in palaeoecology this is very time consuming and the signal is subject to noise the derivation of proxy climate signals from ombrotrophic peat was carried out originally using samples from open peat faces where the stratigraphic relationships could be easily observed now that such sections are rare and often degraded there is a need to demonstrate that data can be replicated from core profiles ten short cores taken from two adjacent bogs have been analysed for macrofossils and show a coherent series of changes which are also similar to previous profiles from the same sites it is concluded that variation between profiles is slight and less than observations of present vegetation mosaics might suggest recommendations for a standard approach to fieldwork on raised bogs that emphasises the utility of subfossil pool layers are proposed and the need for a secure chronology is stressed 1998 john wiley sons ltd

a regional 8200 cal yr bp cooling event in northwest europe induced by final stages of the laurentide ice sheet deglaciation the most notable change in 18o in greenland ice cores during the holocene occurs at 8200 cal yr bp here we present a new high resolution marine record from the northern north sea along with tree ring data from germany which contain evidence of a pronounced temperature drop 2 c contemporaneous with that of the greenland ice core records the synchronous timing of the cooling event in the greenland ice cores marine record and tree ring data from northwest europe reflects a regional influence on the north atlantic ocean atmospheric system suggesting a prominent role of the north atlantic thermohaline circulation the operation of the north atlantic ocean circulation is sensitive to variation in the freshwater budget implying that any change in freshwater flux is capable of altering the north atlantic circulation system we hypothesise minor but long term freshwater fluxes in the final stages of the deglaciation of the laurentide ice sheet as a forcing mechanism 1998 john wiley sons ltd

provenance of permian triassic and ordovician metagraywacke terranes in new zealand evidence from 40ar 39ar dating of detrital micas single crystal 40 ar 39 ar ages of detrital micas from greenland group ordovician low grade metagraywackes of the west coast south island new zealand indicate a source area having muscovite age patterns of 490 515 ma the detrital muscovite ages are characteristic of granitoid and gneiss terranes of the ross adelaide fold belt of antarctica therefore the source area for the greenland group sedimentary rocks was the immediately adjacent pacific margin of gondwana similar age determinations for rakaia terrane permian triassic torlesse supergroup metagraywackes of the wellington and canterbury regions of new zealand indicate that their source area included rocks having prominent muscovite cooling ages populations of 210 290 ma 80 and 410 460 ma 15 the torlesse detrital muscovite age data thus suggest that the source area of the metagraywackes was not within the lachlan fold belt of southeast australia and analogues in antarctica nor in the adjacent ross adelaide fold belt rather the rakaia terrane of the torlesse metagraywackes is a true suspect terrane derived from a source area within the hunter bowen fold belt of northeast australia and the immediately adjacent older orogens of eastern queensland

pressure temperature studies of talc plus water using x ray diffraction x ray diffraction measurements of natural talc plus water at combined pressures and temperatures of 0 15 gpa and 23 400 degrees c reveal the presence of a structural change that could be interpreted as a new high pressure phase at 4 0 0 5 gpa and raise the possibility that the newly inferred phase transition takes place in cold subducting stabs as a precursor to appearance of the 10 angstrom phase of talc

pre requisites processes and prediction of chlorite grain coatings in petroleum reservoirs a review of subsurface examples abstract deeply buried reservoirs containing chlorite coated quartz sand grains commonly have higher than expected porosity and permeability although prediction of such positive anomalies still remains elusive a total of 54 published examples based on information and data from 62 scientific papers was collated quantification of some of the most common parameters including depositional environment age and latitude of sand deposition effect on reservoir quality and chemical composition of chlorite is presented the dataset indicates that chlorite coats are found in sandstones deposited in a range of depositional environments but most commonly occur in delta related environments 44 with fluvial environments the second most common 19 age relationships indicate that there is an overall exploration bias in published examples with chlorite coats becoming increasingly common through time the latitude at the time of deposition of sands with chlorite coats is wide 60 n 60 s and indicates that temperate and tropical climates are important for the generation of this clay mineral chlorite can have a variable effect on reservoir quality but is typically positive iron rich chlorites occur overwhelmingly in coastal environments while mixed iron and magnesium rich chlorites are principally found in marine and terrestrial sandstones analysis of these factors suggests that hinterland geology basinal soil development and geochemical weathering and proximity to river systems are essential to the formation of chlorite precursor phases these characteristics have been combined to define situations where chlorite coats were more likely or more unlikely to form these parameters will provide insights into the formation of chlorite and to further refine predictive models for the presence or absence of chlorite coated sandstones

diagenesis and reservoir quality of paleocene sandstones in the kupe south field taranaki basin new zealand paleocene reservoir sandstones in the kupe south field taranaki basin contain a diagenetic mineral assemblage that records major shifts in pore water composition during the burial history of the basin early calcite formed at shallow burial largely from meteoric depositional pore waters whereas later chlorite smectite records the downward passage of marine pore waters into the sandstones from overlying marine mudrocks prior to significant sandstone compaction during the late miocene late calcite and ferroan carbonates may record the presence of connate meteoric water expelled upward from nonmarine sedimentary rocks of the underlying cretaceous sequence whereas later kaolinite and secondary porosity formation are related to localized meteoric influx resulting from la e miocene to early pliocene uplift and erosion of the reservoir section hydrocarbon entrapment occurred during further pliocene to holocene sediment accumulation labile grain alteration has been less severe in the lower part of the hydrocarbon bearing section lower sands than in the upper part upper sands with the result that the lower sands contain mainly chlorite smectite and the upper sands contain mainly ferroan carbonates and kaolinite formed by extensive alteration of labile grains and earlier formed chlorite smectite reservoir quality in the lower sands is controlled mostly by grain size and the presence of chlorite smectite but in the upper sands the presence of kaolinite is the single most important cause of poor reservoir quality

centennial scale climate cooling with a sudden cold event around 8 200 years ago the extent of climate variability during the current interglacial period the holocene is still debated temperature records derived from central greenland ice cores show one significant temperature anomaly between 8 200 and 8 100 years ago which is often attributed to a meltwater outflow into the north atlantic ocean and a slowdown of north atlantic deep water formation this anomaly provides an opportunity to study such processes with relevance to present day freshening of the north atlantic anomalies in climate proxy records from locations around the globe are often correlated with this sharp event in greenland but the anomalies in many of these records span 400 to 600 years start from about 8 600 years ago and form part of a repeating pattern within the holocene more sudden climate changes around 8 200 years ago appear superimposed on this longer term cooling the compounded nature of the signals implies that far field climate anomalies around 8 200 years ago cannot be used in a straightforward manner to assess the impact of a slowdown of north atlantic deep water formation and the geographical extent of the rapid cooling event 8 200 years ago remains to be determined

an interdisciplinary approach to reservoir characterisation an example from the early to middle eocene kaimiro formation taranaki basin new zealand abstract the kaimiro formation is an early to middle eocene ne sw trending reservoir fairway in taranaki basin and comprises a range of coastal plain through to shallow marine facies a time of regional transgression is observed across the paleocene eocene transition which is linked to a general global warming trend and to regional thermal relaxation related subsidence in new zealand the earliest eocene transgressive deposits pass upwards into a series of cyclically stacked packages interpreted as 3rd and 4th order sequences maximum regression occurred within the early eocene and was followed by punctuated retrogradational stacking patterns associated with shoreline retreat and subsequent regional transgression in the middle eocene the kaimiro formation is considered a good reservoir target along most of the reservoir fairway which can largely be attributed to a consistently quartz rich lithic poor composition and reasonably coarse sand grain size correlations demonstrate that within the early eocene the main reservoir facies are channel fill sandstones overlying candidate sequence boundaries in paleoenvironmentally landward proximal settings and upper shoreface shoreline sandstones in relatively basinward distal settings middle eocene reservoir facies are not represented in distal wells due to overall transgression at this time yet they form a significant target in more proximal well locations particularly on the taranaki peninsula depositional facies is one of the principal controls on sandstone reservoir quality however while reservoir facies have been proven along the length of the reservoir fairway it is evident that diagenesis has significantly impacted sandstone quality relatively poor reservoir properties are predicted for deeply buried parts of the basin maximum burial 4 5 km due to severe compaction and relatively abundant authigenic quartz and illite in contrast good reservoir properties are locally represented in reservoir facies where present day burial depths are these results illustrate how an interdisciplinary approach to regional reservoir characterisation are used to help reduce risk during prospect evaluation assessment of both reservoir distribution and quality is necessary and can be undertaken through integrated studies of facies sequence stratigraphy burial modelling and petrography

early holocene glacial lake meltwater injections into the labrador sea and ungava bay 1 in this paper we analyze drainage routes and estimate fluxes of meltwater released from labrador ungava glacial lakes into the labrador sea ungava bay and hudson bay between 7 5 and 6 0 kyr bp 8 4 7 0 calendar cal years ka the analysis and estimates are based on landform based reconstructions of the laurentide ice sheet lis decay pattern and the associated glacial lake evolution geomorphological data constraining the spatial extent of glacial lakes are coupled to a digital terrain model for meltwater volume calculations the lis ice recession between 7 5 and 6 0 kyr bp led to the formation of a large number of glacial lakes which drained in approximately 30 meltwater pulses with fluxes exceeding 0 015 sv 1 sv 106 m3 s 1 into labrador sea ungava bay and hudson bay the inferred rapid ice margin retreat during late stages of deglaciation indicates that these drainage events were relatively short lived the early holocene glacial lakes of labrador ungava released meltwater resulting in a total inflow of 6000 km3 freshwater to the north atlantic the pulsed nature of meltwater release from the lakes is likely to have resulted in rapid repeated cooling of the labrador sea surface water

late eocene early miocene facies and stratigraphic development taranaki basin new zealand the transition to plate boundary tectonics during regional transgression eight latest eocene to earliest miocene stratigraphic surfaces have been identified in petroleum well data from the taranaki basin new zealand these surfaces define seven regional sedimentary packages of variable thickness and lithofacies forming a mixed siliciclastic carbonate system the evolving tectonic setting particularly the initial development of the australian pacific convergent margin controlled geographic stratigraphic and facies variability this tectonic signal overprinted a regional transgressive trend that culminated in latest oligocene times the earliest influence of active compressional tectonics is reflected in the preservation of latest eocene early oligocene deepwater sediments in the northern taranaki basin thickness patterns for all mid oligocene units onwards show a shift in sedimentation to the eastern taranaki basin controlled by reverse movement on the taranaki fault system this resulted in the deposition of a thick sedimentary wedge initially of coarse clastic sediments later carbonate dominated in the foredeep close to the fault in contrast oligocene active normal faulting in a small sub basin in the south may represent the most northerly evidence for rifting in southern zealandia related to emerald basin formation the early miocene period saw a return to clastic dominated deposition the onset of regional regression and the southward propagation of compressional tectonics

deep focus earthquakes and recycling of water into the earth s mantle for more than 50 years observations of earthquakes to depths of 100 to 650 kilometers inside earth have been enigmatic at these depths rocks are expected to deform by ductile flow rather than brittle fracturing or frictional sliding on fault surfaces laboratory experiments and detailed calculations of the pressures and temperatures in seismically active subduction zones indicate that this deep focus seismicity could originate from dehydration and high pressure structural instabilities occurring in the hydrated part of the lithosphere that sinks into the upper mantle thus seismologists may be mapping the recirculation of water from the oceans back into the deep interior of our planet

provenance analysis using conglomerate clast lithologies a case study from the pahau terrane of new zealand abstract the field of provenance analysis has undergone a revolution with the development of single crystal isotope dating techniques using mainly silt to sand sized single minerals this study focuses on coarser grained rocks notably conglomerates which involve much shorter transport distances and therefore may be used to trace proximal sources the torlesse terranes part of the new zealand eastern province are accretionary complexes that comprise an enormous volume of quartzofeldspathic sandstones and mudstones with subsidiary conglomerates plus minor oceanic assemblages two terranes are recognised in the south island the permian to late triassic rakaia terrane and the late jurassic to early cretaceous pahau terrane geochronology geochemistry and sr nd isotopes of igneous clasts from pahau terrane conglomerates identify the median tectonic zone s l as a major contributor of detritus to the pahau depositional basin shrimp u pb zircon ages of igneous clasts range from 128 to 123 ma and from 147 to 135 ma calc alkaline clasts of the latter range are indistinguishable in age chemical composition and petrogenesis from the calc alkaline granitoids of the darran suite whereas alkaline clasts correlate with the electric granite both parts of the median tectonic zone an early jurassic calc alkaline rhyolite clast from kekerengu 188 3 ma correlates with the bounty island granite campbell plateau the petrography and geochemistry of pahau terrane sandstone clasts indicate the recycling of permian to early late triassic older rakaia terrane rocks this is further supported by the detrital zircon age data igneous conglomerate clasts are capable of placing exceptionally tight constraints on pahau provenance and on its mesozoic tectonic setting within the southwest pacific margin of gondwana they provide the best evidence yet that the pahau terrane is locally derived

lake agassiz final drainage event in the northwest north atlantic 1 the 8 2 ka climate event recorded in greenland ice cores is subject of debates with respect to causal linkage with a collapse of the atlantic meridional overturning due to the drainage of the late glacial lake agassiz here we present records from the nw north atlantic down current the flood discharge route showing that the 9 5 8 ka interval was marked by a succession of events the drainage itself corresponds to a twin layer of carbonate rich turbidites deposited within the calibrated 8 35 8 5 ka interval proxies of sea surface and deep current conditions do not indicate significant concomitant changes in the nw north atlantic the dataset however supports the concept that the 8 2 ka climate event may represent one of the manifestations of climate instability during an interval with major changes of land drainage in ne america due to the collapse of the laurentide ice sheet subsequent fast sea level rise and large scale reorganization of the north atlantic thermohaline circulation pattern

a synchronized dating of three greenland ice cores throughout the holocene as part of the effort to create the new greenland ice core chronology 2005 gicc05 a synchronized stratigraphical timescale for the holocene parts of the dye 3 grip and ngrip ice cores is made by using volcanic reference horizons in electri cal conductivity measurements to match the cores the main annual layer counting is carried out on the most suited records only exploit ing that the three ice cores have been drilled at locations with different climatic con ditions and differences in ice flow however supplemental counting on data from all cores has been performed between each set of reference horizons in order to verify the valid ity of the match after the verification the main dating is transferred to all records us ing the volcanic reference horizons as tie points an assessment of the mean annual layer thickness in each core section confirms that the new synchronized dating is consistent for all three cores the data used for the main annual layer counting of the past 7900 years are the dye 3 grip and ngrip stable isotope records as the high accumulation rate at the dye 3 drill site makes the seasonal cycle in the dye 3 stable isotopes very resistant to firn diffusion an effort has been made to extend the dye 3 holocene record the new syn chronized dating relies heavily on this record of 75 000 stable isotope samples the dat ing of the early holocene consists of an already established part of gicc05 for grip and ngrip which has now been transferred to the dye 3 core gicc05 dates the younger dryas termination as defined from deuterium excess to 11 703 b2k 130 years earlier than the previous grip dating

diagenesis porosity evolution and petroleum emplacement in tight gas reservoirs taranaki basin new zealand abstract tight gas reservoirs have become popular targets in petroleum exploration in recent years due largely to the increasing market demand for gas and also to technology advances used in extraction reservoir quality is typically poor due to deep burial diagenesis resulting in significant compaction cementation and illitization however analysis of tight reservoirs using integrated techniques can improve our understanding about the controls on reservoir quality and these results can potentially be used to help predict reservoir quality at other sites the use of integrated analysis of diagenetic and burial history is here shown for the eocene k3e kapuni group reservoir in cardiff 1 taranaki basin new zealand the k3e belongs to a deep gas play that was considered uncommercial in the early 1990 s due to poor reservoir quality associated with extensive authigenic illite potassium argon dating has shown that destruction of the reservoir through illitization occurred in the pliocene associated with a late stage heating and or fluid flow event timing of illite authigenesis in the k3e reservoir postdates the likely circulation of co2 rich fluids that caused reaction of feldspar to form kaolinite and quartz homogenization temperatures from two phase aqueous fluid inclusions within quartz cements together with 1d basin models of co2 expulsion from coaly source rocks indicate that feldspar reactions may have started in the mid miocene the co2 rich fluids are thought to have been generated by thermal decarboxylation of intraformational paleocene eocene coals at the same time oil was being expelled from older cretaceous coals and migrated into the mid late eocene reservoirs evidence for oil migration is demonstrated by the presence of residual oil and by the local occurrence of abundant oil bearing fluid inclusions the products of feldspar dissolution appear to be in reasonable balance with the amount of dissolved feldspar suggesting a relatively closed diagenetic system with little improvement in reservoir quality despite the large volume of feldspar dissolved petrographic evidence of reservoir sandstones at cardiff 1 demonstrates the presence of some illite free secondary macropores lined by residual oil this local preservation of porosity may be replicating the original distribution of oil saturated pores in the pliocene at the time when authigenic kaolinite underwent reaction to form illite remobilization of the oil probably occurred by gas flushing after the main phase of illitization at c 5 ma the data presented in this study are consistent with redistributed liquid petroleum into up dip traps and represent the potential for a new exploration play the eocene reservoir at cardiff 1 is currently gas charged with the pore system composed of approximately one third large macropores connected by a tortuous microporous network however it is possible that with the currently buoyant gas market and modern hydraulic fracturing techniques it may now be economic to flow gas from the locally large pores identified in the k3e reservoir

the 8 2 kyr bp event simulated by a global atmosphere sea ice ocean model seven freshwater perturbation experiments were performed with a global atmosphere sea ice ocean model to study the mechanism behind the 8 2 kyr bp holocene cooling event these experiments differed in initial state and duration of the applied freshwater pulse while the amount of freshwater was kept constant 4 67x10 14 m 3 one of the scenarios with freshwater added to the labrador sea at a rate of 0 75 sv during 20 years resulted in weakening of the north atlantic thermohaline circulation during 320 years and surface cooling varying from 1 to 5 degreesc over adjacent continents this result is consistent with proxy data suggesting that a meltwater induced weakening of the thermohaline circulation caused the event moreover our results indicate that the time scale of the meltwater release and the initial state are important as both have a strong effect on the magnitude and duration of the produced model response

anisotropic thermal properties of talc under high temperature and pressure abstract the anisotropic thermal conductivity and diffusivity of talc were simultaneously measured up to 5 3 gpa and 900 k using the pulse transient method although significant anisotropy was observed in the thermal conductivity of talc the average thermal conductivity is comparable to that of olivine and roughly three times greater than that of antigorite from the ratio of the thermal conductivity to the thermal diffusivity the heat capacity of talc was evaluated the pressure derivative of heat capacity was found to be positive which is related to the anomaly of thermal expansivity of talc above 50 c at atmospheric pressure

calcite cement in permian deep water sandstones delaware basin west texas origin distribution and effect on reservoir properties calcite cement is the dominant control on reservoir quality in turbidite sandstones of the upper permian bell canyon formation delaware basin these well sorted very fine grained arkoses were deposited in a basin floor setting by channel levee systems terminating in broad lobes calcite cement distribution in the east ford and geraldine ford fields was mapped using core log and thin section data calcite is concentrated in tightly cemented zones that are mostly less than 1 ft 0 3 m thick areas that have high percentages of calcite cemented sandstone 20 occur along the margins of the sandstone bodies in overbank and lobe deposits where sandstone pinches out into siltstone areas that have the lowest percentage of calcite cemented sandstone 10 occur where the sandstone is thickest in the channel facies isotopic composition of the calcite 13c 1 8 to 3 0 relative to the peedee belemnite pdb 18o 4 6 to 6 3 pdb is consistent with the source of calcium carbonate being from dissolution of detrital carbonate rock fragments and marine skeletal debris because internal sources of calcite were apparently insufficient to account for the cement volume cement components are interpreted as having been transported into the sandstones from organic rich basinal siltstones and limestones feldspars buffered acidic formation waters near where they entered the sandstone resulting in calcite concentrated near the sandstone margins the calcite formed near maximum burial depths of 4800 ft 1 5 km and temperatures of 104f 40c from marine pore waters with 18o of approximately 0 relative to standard mean ocean water most of the calcite cemented zones are interpreted as being concretions that extend no more than a few meters laterally production data and geophysical log correlations suggest that some cemented zones are laterally continuous at least 1000 ft 300 m and cause vertical reservoir compartmentalization laterally extensive calcite layers may be associated with the base of turbidite deposits

the impact of diagenesis on the heterogeneity of sandstone reservoirs a review of the role of depositional facies and sequence stratigraphy diagenesis exerts a strong control on the quality and heterogeneity of most clastic reservoirs variations in the distribution of diagenetic alterations usually accentuate the variations in depositional porosity and permeability linking the types and distribution of diagenetic processes to the depositional facies and sequence stratigraphic framework of clastic successions provides a powerful tool to predict the distribution of diagenetic alterations controlling quality and heterogeneity the heterogeneity patterns of sandstone reservoirs which determine the volumes flow rates and recovery of hydrocarbons are controlled by geometry and internal structures of sand bodies grain size sorting degree of bioturbation provenance and by the types volumes and distribution of diagenetic alterations variations in the pathways of diagenetic evolution are linked to 1 depositional facies hence pore water chemistry depositional porosity and permeability types and amounts of intrabasinal grains and extent of bioturbation 2 detrital sand composition 3 rate of deposition controlling residence time of sediments at specific near surface geochemical conditions and 4 burial thermal history of the basin the amounts and types of intrabasinal grains are also controlled by changes in the relative sea level and therefore can be predicted in the context of sequence stratigraphy particularly in paralic and shallow marine environments changes in the relative sea level exert significant control on the types and extent of near surface shallow burial diagenetic alterations which in turn influence the pathways of burial diagenetic and reservoir quality evolution of clastic reservoirs carbonate cementation is more extensive in transgressive systems tract tst sandstones particularly below parasequence boundaries transgressive surface and maximum flooding surface because of the abundance of carbonate bioclasts and organic matter bioturbation and prolonged residence time of the sediments at and immediately below the sea floor caused by low sedimentation rates which also enhance the formation of glaucony eogenetic grain coating berthierine odinite and smectite formed mostly in tst and early highstand systems tract deltaic and estuarine sandstones are transformed into ferrous chlorite during mesodiagenesis helping preserve reservoir quality through the inhibition of quartz cementation the infiltration of grain coating smectitic clays is more extensive in braided than in meandering fluvial sandstones forming flow barriers in braided amalgamated reservoirs and may either help preserve porosity during burial because of quartz overgrowth inhibition or reduce it by enhancing intergranular pressure dissolution diagenetic modifications along sequence boundaries are characterized by considerable dissolution and kaolinization of feldspars micas and mud intraclasts under wet and warm climates whereas a semiarid climate may lead to the formation of calcrete dolocrete cemented layers turbidite sandstones are typically cemented by carbonate along the contacts with interbedded mudrocks or carbonate mudstones and marls as well as along layers of concentration of carbonate bioclasts and intraclasts commonly hybrid carbonate turbidite arenites are pervasively cemented proximal massive turbidites normally show only scattered spherical or ovoid carbonate concretions improved geologic models based on the connections among diagenesis depositional facies and sequence stratigraphic surfaces and intervals may not only contribute to optimized production through the design of appropriate simulation models for improved or enhanced oil recovery strategies as well as for co2 geologic sequestration but also support more effective hydrocarbon exploration through reservoir quality prediction

comparative in situ x ray diffraction study of san carlos olivine influence of water on the 410 km seismic velocity jump in earth s mantle a comparative study of the equation of states of hydrous 0 4 wt h2o and anhydrous san carlos olivine 30 ppm h2o was conducted using synchrotron x rays up to 11 gpa in a diamond anvil cell dac at ambient temperature both samples were loaded in the same high pressure chamber of the dac to eliminate the possible pressure difference in different experiments the obtained compression data were fitted to the third order birch murnaghan equation of state yielding a bulk modulus k 123 3 gpa for hydrous olivine and k 130 4 gpa for anhydrous olivine as k is fixed at 4 6 therefore 0 4 wt h2o in olivine results in a 5 reduction in bulk modulus previous studies reported bulk modulus reduction by water in olivine s high pressure polymorph wadsleyite to which the transformation from olivine gives rise to the seismic discontinuity at 410 km depth the new data results in a reduction in the magnitude of the discontinuity by 50 in v p and 30 in v s for 1 5 water partitioning between olivine and wadsleyite with respect to anhydrous mantle previous knowledge of the influence of water on this phase transition has been in opposition to a large amount of water e g 200 ppm by wood 1995 existing at 410 km depth calculation of the seismic velocities based on newly available elasticity data of the hydrous phases indicates that the presence of water is favorable for the mineral composition model pyrolite and seismic observations in terms of the magnitude of the 410 km discontinuity

early oligocene marine canyon channel systems implications for regional paleogeography in the canterbury basin new zealand abstract the oligocene is a time of maximum submersion of the zealandia landmass it coincides with changes in oceanographic currents as well as with the inception of the cenozoic plate boundary through new zealand our analysis of offshore wells and seismic reflection lines in the canterbury basin reveals condensed oligocene strata

the 8200 year b p event in the slope water system western subpolar north atlantic 1 stable isotope trace metal alkenone paleothermometry and radiocarbon methods have been applied to sediment cores in the western subpolar north atlantic between hudson strait and cape hatteras to reveal the history of climate in that region over the past 11 kyr we focus on cores from the laurentian fan which is known to have rapid and continuous accumulation of hemipelagic sediment although results among our various proxy data are not always in agreement the weight of the evidence alkenone sea surface temperature sst 18o and abundance of globigerinoides ruber indicates a continual cooling of surface waters over laurentian fan from about 18 c in the early holocene to about 8 c today alternatively mg ca data on planktonic foraminifera indicate no systematic change in holocene sst the inferred long term decrease in sst was probably driven by decreasing seasonality of northern hemisphere insolation two series of proxy data show the gradual cooling was interrupted by a two step cold pulse that began 8500 years ago and lasted about 700 years although this event is associated with the final deglaciation of hudson bay there is no 18o minimum anywhere in the labrador sea yet there is some evidence for it as far south as cape hatteras finally although the 8200 year b p event has been implicated in decreasing north atlantic ventilation and hence widespread temperature depression on land and at sea we find inconsistent evidence for a change at that time in deep ocean nutrient content at 4 km water depth