reservoir characteristics and their effects on hydrocarbon accumulation in lacustrine turbidites in the jiyang super depression bohai bay basin china abstract a great difference exists between the hydrocarbon charging characteristics of different tertiary lacustrine turbidites in the jiyang super depression of the bohai bay basin east china based on wireline log data core observation and thin section analyses this study presents detailed reservoir property data and their controlling effects from several case studies and discusses the geological factors that govern the hydrocarbon accumulation in turbidite reservoirs the lacustrine fluxoturbidite bodies investigated are typically distributed in an area of 0 5 10 km2 with a thickness of 5 20 m the sandstones of the tertiary turbidites in the jiyang super depression have been strongly altered diagenetically by mechanical compaction cementation and mineral dissolution the effect of compaction caused the porosity to decrease drastically with the burial depths especially during the early diagenesis when the porosity was reduced by over 15 the effect of cementation and mineral dissolution during the late stage diagenesis is dominated by carbonate cementation in sandstones high carbonate cement content is usually associated with low porosity and permeability carbonate dissolution secondary porosity zone and primary calcite dissolution is believed to be related to thermal maturation of organic matter and clay mineral reactions in the surrounding shales and mudstone two stages of carbonate cementation were identified the precipitation from pore water during sedimentation and secondary precipitation in sandstones from the organic acid dissolved carbonate minerals from source rocks petrophysical properties have controlled hydrocarbon accumulation in turbidite sandstones high porosity and permeability sandstones have high oil saturation and are excellent producing reservoirs it is also noticed that interstitial matter content affects the oil bearing property to some degree there are three essential elements for high oil bearing turbidite reservoirs excellent pore types low carbonate cement 15 and average permeability 10 md

a retreating fan delta system in the neoproterozoic chattisgarh rift basin central india major controls on its evolution a thick wedge of immature siliciclastics characterizes the basal part of the basin fill succession in the eastern part of the neoproterozoic chattisgarh basin it comprises a mosaic of mass flow deposited conglomerate and pebbly sandstone coarse grained sandy braided stream deposits wave lag pebble sheets high energy wave dominated foreshore and upper shoreface facies and wave and tide dominated lower shoreface facies the succession is characterized by strong lateral and vertical facies variation the facies associations and stacking pattern point to the development of an alluvial fan to fan delta complex with outbuilding of delta lobes onto a high energy shallow marine shelf via a high gradient narrow delta plain the delta front deposits of coarse grained sand interfinger and grade into prodelta mud in the seaward direction the dominance of coarse grained sandy detritus with a high content of fresh feldspar grains points to mechanical weathering of granites and gneisses of the cratonic basement and a semiarid climate the sediment caliber and the climate exerted a major control on the facies and on processes of sediment transfer from the fan to the shelf a critical balance between progradation aggradation and retrogradation controlled the evolution of delta successions within an overall transgressive regime related to the extension of a cratonic rift basin repeated fault controlled uplift of the source followed by subsidence and transgression generated multiple fining upward cycles and a retreating fan delta system the marked variations in thickness of the delta succession and the stacking pattern in different measured profiles reflect the overriding tectonic controls on delta evolution the accumulated fault displacement in active sectors created higher accommodation and thicker delta sequences intermittent uplift of fault blocks exposed fresh bedrock to mechanical weathering generated a large amount of detritus and resulted in forced regressions repeatedly disrupting the fining upward pattern the controls of source rock lithology or climate were of secondary importance to tectonic effects retreating fan deltas are rarely reported and may be a stratigraphic response of marine connected rift basins at the early stage of extension the delta stratigraphy is analogous to the submarine fan stratigraphy in the case where basin shales act as hydrocarbon sources the fan deltas are potential hydrocarbon reservoirs the coarse grained lobes can be excellent reservoirs with the enclosing prodelta muds acting as seals to vertical migration of hydrocarbon the coarse grained deposits of the delta plain and proximal delta front occurring as laterally coalesced large sand bodies blanketed by transgressive prodelta mud might also form good reservoirs

relationships between magnetic and structural fabrics revealed by variscan basement rocks subjected to heterogeneous deformation a case study from the klodzko metamorphic complex central sudetes poland

1891 1883 ma southern bastar cuddapah mafic igneous events india a newly recognized large igneous province abstract a newly recognized remnant of a paleoproterozoic large igneous province has been identified in the southern bastar craton and nearby cuddapah basin from the adjacent dharwar craton india high precision u pb dates of 1891 1 0 9 ma baddeleyite and 1883 0 1 4 ma baddeleyite and zircon for two se trending mafic dykes from the bd2 dyke swarm southern bastar craton and 1885 4 3 1 ma baddeleyite for a mafic sill from the cuddapah basin indicate the existence of 1891 1883 ma mafic magmatism that spans an area of at least 90 000 km2 in the south indian shield this record of 1 9 ga mafic ultramafic magmatism associated with concomitant intracontinental rifting and basin development preserved along much of the south eastern margin of the south indian shield is a widespread geologic phenomenon on earth similar periods of intraplate mafic ultramafic magmatism occur along the margin of the superior craton in north america 1 88 ga molson large igneous province and in southern africa along the northern margin of the kaapvaal craton 1 88 1 87 ga dolerite sills intruding the waterberg group existing paleomagnetic data for the molson and waterberg 1 88 ga large igneous provinces indicate that the superior and kalahari cratons were at similar paleolatitudes at 1 88 ga but a paleocontinental reconstruction at this time involving these cratons is impeded by the lack of a robust geological pin such as a limpopo like 2 0 ga deformation zone in the superior province the widespread occurrence of 1 88 ga intraplate and plate margin mafic magmatism and basin development in numerous archean cratons worldwide likely reflects a period of global scale mantle upwelling or enhanced mantle plume activity at this time

holocene vegetation and volcanic activity auckland isthmus new zealand a 12 000 to 4000 yr bp pollen and tephra bearing profile from auckland new zealand provides insights into the vegetation history and evidence for early holocene volcanic activity in this area centred on the mount wellington basaltic volcano possibly 500 yr separated initial scoriaceous ash deposition ca 9500 yr ago and subsequent major lava flows ca 9000 yr ago from mount wellington the local vegelation topography and drainage patterns were substantially modified during this time and damming by the lava flows resulted in the formation of lake waiatarua in a shallow valley head ca 9000 yr ago diatom evidence indicates that this lake was initially deep 5 m but was shallowing around 4000 yr ago in contrast to the mount wellington eruptions tephra deposition resulting from distant rhyolitic volcanic activity of the central north island and mayor island has had little effect on the auckland vegetation during this time interval 12 000 4000 yr ago between ca 12 000 and 10 000 yr ago conifer angiosperm forest was the predominant vegetation cover on auckland isthmus but during the early holocene forest dominated by metrosideros expanded probably on to fresh volcanic surfaces resulting from the mount wellington eruptions at this time swamp forest communities developed in waiatarua valley basin and included species indicative of moist mild relatively frost free climates some taxa show histories consistent with other records from the northern new zealand region including the rise of ascarina lucida ca 11 000 to 9000 yr ago and its subsequent decline and the expansion of agathis australis kauri forest communities from ca 6000 yr ago taken together the history of local and regional vegetation points to a mild moist and weakly seasonal early holocene climate which subsequently became drier with greater seasonal temperature extremes

lidar based quantification of lava flow susceptibility in the city of auckland new zealand abstract lava flows represent one of the most significant volcanic hazards from basaltic monogenetic volcanoes such as spatter cones scoria cones maars and tuff rings they are common features emanating from parasitic vents on the flanks of polygenetic volcanoes and in dominantly flat lying intraplate volcanic fields the auckland volcanic field avf is a volcanic field that has been active for the last ca 250 ka hosting at least 50 monogenetic volcanoes morphometric parameters of lava flows such as volume length thickness and area were used to quantify the potential lava flow inundation susceptibility to new zealand s most densely populated area the city of auckland based on an airborne light detection and ranging lidar digital surface model dsm the morphometric parameters of fifteen studied flows included average length of 2 5 km range 0 7 6 5 km overall average thickness of 14 8 m range 3 4 43 8 m average of maximum thicknesses of 48 2 m range 18 3 180 5 m average area occupied of 5 1 km 2 range 0 4 25 1 km 2 and average volume of 0 12 km 3 range 0 005 1 km 3 based on these parameters and a lidar derived dsm the present topography was classified into sea topographic depressions low lying areas prone to inundation by an average lava flow buffer zones prone to inundation only by extremely thick lava flows and peaks or ridges which are unlikely to be overtopped in monogenetic fields each new vent occurs in a new location creating uncertainty around the spatial location of the volcanic hazard thus this research provides a general vent location independent approach to describe the lava flow susceptibility for a potentially active monogenetic volcanic field what this analysis reveals is that the city of auckland can be divided into two distinct areas with strongly different susceptibility to lava flow inundation the southern part of the city is predominantly flat without hindrance to lava flow whereas the hilly northern and central part has many ridges that can limit or channelise lavas these contrasting properties must be accounted for in scenario based or probabilistic hazard and risk models developed for the avf

reply to the discussion of deb 2013 on the paper of saha et al 2013 entitled tectono magmatic evolution of the mesoproterozoic singhora basin central india evidence for compressional tectonics from structural data ams study and geochemistry of basic rocks abstract we appreciate that our attempt to document deformation pattern within the mesoproterozoic singhora group india and to resolve some key stratigraphic issues in chhattisgarh geology patranabis deb and chaudhuri 2008 dhang and patranabis deb 2012 in recent times has attracted the attention of deb we whole heartedly welcome the keen interest shown by deb in our paper and discussions attempted by him on different aspects of the paper here we offer our strong rebuttal of his imaginative discussions principally because the claims made by deb are neither supported by outcrop based field data nor through any available subsurface geophysical data it appears that the key concern of deb 2013 was to force fit the structural grains of the sonakhan greenstone belt within the deformation pattern of singhora cover sediments upholding an unsubstantiated assumption that the sonakhan greenstones belt constitutes the basement for the singhora basin without citing any evidence outcrop geophysical or bore hole showing sonakhan metamorphics in the basement of the singhora basin he plotted the structural data of the sonakhan greenstone belt and attempted comparison of those with the bedding attitudes of the singhora cover sediments and claimed that the possible rejuvenation of basement faults triggered folding in the singhora cover sediments leaving aside the issues of lack of any field support available geophysical results 3 layer gravity survey by srinivas et al 2000 magnetic survey by srinivas et al 2004 and short borehole observations pers comm mukherjee a 2012 all clearly demonstrates unclassified archean paleoproterozoic granites and gneisses of the bastar craton as basement for the singhora basin not the sonakhan greenstones neither is the presence of any basin scale fault inferred from the basement of the singhora basin in any geophysical model the result of magnetic survey along the basna sohela transect carried out by srinivas et al 2004 which represents the singhora basement in particular clearly shows granites as immediate basement for the singhora as the very assumption of deb 2013 i e that the sonakhan represents the basement to the singhora basin does not stand either on his own field data or on any strong reasoning we refrain from any further discussion on this topic instead we frame our reply on the doubts raised by deb 2013 on the mapping field analysis and concepts used in our paper saha et al 2013

carbonate cementation patterns and diagenetic reservoir facies in the campos basin cretaceous turbidites offshore eastern brazil massive turbidite arkoses contain more than 80 of the oil reserves of the campos basin the main petroleum province of brazil the porosity and permeability distribution in the namorado albian cenomanian and carapebus turonian santonian sandstones is

strength capacity of a no tension portal arch frame under combined seismic and ash loads abstract in some previous papers the seismic response of a simple structural system has been studied namely a masonry arch portal baratta et al 1996 seismic risk of historic centres modelled by the classical rules of mono dimensional structures and complex structural systems made of combinations of several elementary arch portals in this paper the seismic response of a simple masonry arch portal under the combined action of horizontal seismic forces and vertical overload due to volcanic ash fall subsequent to an eruption is discussed decay of the collapse coefficient of the horizontal load is evaluated for ash fall load increasing

risk assessment of residential buildings for an eruption of furnas volcano sao miguel the azores this paper presents the results of a study of the risks to human settlements of a future eruption of the furnas volcano in the azores it makes use of previous geological studies to estimate the likely impact of the volcanic hazards on the surrounding settlements given an eruption comparable with the last major eruption in the island in 1630 it presents the results of a comprehensive building by building survey of the settlements at risk to determine the exposure of the residential building stock to these hazards and it uses data from recent experience of volcanic eruptions elsewhere to estimate the vulnerability of the buildings to each hazard and the likely scale of human casualties and building damage the paper concludes with some recommendations for preparedness and protective measures which could be taken before an eruption to reduce the risk of human casualties from roof and building collapses principal among these are recommendations for strengthening the lateral load resistance of buildings built with the traditional vernacular techniques to better resist groundshaking during eruptions and earthquakes upgrading local building code requirements with view to increasing the live load resistance of roofs to levels similar to those applied in areas of heavy snowfalls to prevent roof collapse from tephra loading other preparedness measures are also discussed with respect to volcanic earthquakes volcanic bomb impact pyroclastic flows and tephra falls many aspects of this paper are relevant to other volcanic areas around the world

growth destruction and facies architecture of effusive and explosive volcanics in the miocene shama basin southwest of saudi arabia subaqueous subaerial volcanism in a lacustrine setting abstract this paper presents for the first time detailed stratigraphical and petrographical analyses of the harrat shama volcanic basin hsvb of miocene age in sw saudi arabia this basin is filled by abundant volcanics intercalated with fluvio lacustrine sedimentary successions these successions are characterized by a syneruptive intereruptive cycle which results from the intercalation periods of volcanics and volcaniclastic sedimentation along with periods of fluvial incision two depositional sequences showing an overall fining upward trend are preserved within the hsvb the first comprises hyaloclastites zeolite bearing bedded tuffs and bedded accretionary lapilli tuffs interpreted as deep lake whereas the second is made up of extensive pumiceous pyroclastic flows peperitic breccias and basaltic lava flows which are in turn capped by siliciclastic deposits of lacustrine deposits the passage between two sequences is defined by lateral variations of the lithofacies and textural features reflecting a change in paleogeography the fining upward volcaniclastic deposits of the hsvb sequence are interpreted to represent the sedimentation pattern induced by tectonic subsidence with the influence of volcaniclastic sediment input indicating well established proximal distal relationship hsvb was evolved through three stages including pre syn and post caldera stages the first two stages correspond to proximal aggradational syn eruptive event whereas the latter stage refers to distal degradational inter eruptive event these stages overlap in time as shown by the alternation of explosive effusive and their resedimented deposits reflecting diverse eruptive sequences formed by different fragmentation processes the difference in the latter coupled with the variability in the magma water interaction and the nature of substrate are responsible for such diversity resulting in progressive environmental changes from subaqueous to subaerial regime from bottom to top the development of such contrast in the depositional sequences reflects variation in the sediment flux and subsidence rate during the evolution of the hsvb

basal tuffs and contemporaneity of the chattisgarh and khariar basins based on new dates and geochemistry abstracttime bracketing of thousands of meters thick unmetamorphosed fossil free sedimentary successions is a long standing challenge in indian proterozoic stratigraphy limited geochronologic ages from either the basal or the upper part of the successions prevent workers from constraining the precise age interval for individual basin fill leaving aside the issue of correlatability between different basin sequences this article deals with silicic tuff units from the basal part of two areally separated proterozoic sedimentary successions of central india the singhora group of the chattisgarh supergroup and the khariar group the singhora tuff is enriched in large ion lithophile rb ba th etc elements and light rare earth elements and in a discrimination diagram falls within the volcanic arc granite field u th pb electron probe microanalyzer geochronology of monazite and zircon grains from the singhora tuff revealed several age data clusters namely 2500 2100 1800 1500 and 1000 ma in c

impacts of the 1945 and 1995 1996 ruapehu eruptions new zealand an example of increasing societal vulnerability over the past 50 yr the risk to society from volcanic eruptions has increased sharply due to an increased population more developed and diversified economies and a more technologically advanced infrastructure this fact is demonstrated vividly by the impacts from the two largest eruptions of the twentieth century from the cone volcano of ruapehu which suggest that the vulnerability of key sectors in new zealand society has increased by one to two orders of magnitude over this period both the 1945 and 1995 1996 eruptions included explosive phases that dispersed ash over a wide area of the north island for a period of several months individual ash falls were only a few millimeters thick in communities within 150 km of the volcano and only trace amounts were found in communities farther away the 1995 1996 eruption caused similar physical effects to the 1945 eruption but had considerably greater social and economic impacts the greatest contribution to the cost of the 1995 1996 eruption estimated in excess of 130 million new zealand dollars was the impact on the alpine tourist industry in the central north island essentially nonexistent in 1945 other significant impacts were felt by the rapidly growing aviation and electricity generation sectors the cost of any future eruption of the same magnitude is likely to grow as the vulnerability of our society increases at a rapid rate

economic impact of explosive volcanic eruptions a simulation based assessment model applied to campania region volcanoes abstract plinivs study centre of university of naples federico ii has developed a methodology that aims to estimate in probabilistic terms the direct and the indirect economic impacts of a sub plinian i or strombolian type eruption of vesuvius the economic model has been implemented as a complementary tool of the volcanic impact simulation model a tool developed at plinivs center available to the italian civil protection department dpc decision makers to quantify the potential losses consequent to a possible eruption of vesuvius or campi flegrei along the expected time history of the eruptive event all the possible direct costs and the factors indirect costs impacting the economic growth in the event area have been identified each cost factor is built up through a specific algorithm that is fed by various providers in order to run software that will estimate the global amount of economic damage from a volcanic event the model does not include the economic evaluation of intangibles e g human casualties while the evaluation of damage to the local cultural heritage historical buildings archeological sites monuments etc is linked to the economic impact on tourism estimated into indirect costs the architecture of the model is based on a simulation logic which allows an evaluation of different economic impact scenarios through input changes allowing the model to be used as a tool to support the decision making process

forced folds and fractures this volume is concerned with defining the major similarities and difference between forced folds and buckle folds in order that these differences can be used to recognize the type of folding and therefore the expected fracture pattern present in regions of poor exposure or where the geologist has to rely on seismic images an understanding of the differences between the two fold types their 3d geometry spatial organization fracture patterns etc provides an invaluable tool for earth scientists concerned with assessing the possible role of folds and their associated fracture patterns in controlling fluid migration and concentration within the crust the papers presented here are grouped into 4 sections contributions in the first section describe the use of numerical analyses to investigate the formation of fractures in forced folds including compaction folds and the section contains a description of large scale compaction folding in which the associated fracturing has given rise to the development of large sandstone dykes the papers in the second section deal with the formation of forced folds as a result of normal faulting in various geological environments including along a classical graben margin and around a resurgent caldera the third section contains papers relating to forced folding in compressional and strike slip regimes the final section considers the temporal and spatial relationships between forced folds and buckle folds the formation of crustal scale folds and a method of determining the distribution of strain on any folded surface a key parameter controlling the distribution of fractures

superposed deformation fabrics in the precambrian metabasic rocks of the iron ore group singhbhum craton eastern india evidences from anisotropy of magnetic susceptibility studies abstract anisotropy of magnetic susceptibility ams data have been utilized to build up the multiple deformation sequences and strain variation from an apparently undeformed metabasic lava sequence of the basal part of the paleo mesoarchean greenstone succession of the iron ore group rocks in the western iron ore basin singhbhum craton eastern india the basal lava crops out bordering the regional horseshoe shaped outcrop the horseshoe synclinorium structure of the overlying bif rocks ams data of 892 cylindrical specimens drilled from 83 samples collected from different structural domains within the synclinorium structure are presented in the analysis ams orientation data have been analyzed in the light of superposed fold type 1 interference fabrics developed within bif as a result of successive deformation episodes d1 and d2 it is found that the lava samples ubiquitously present two consistent magnetic fabrics homogeneous over smaller sub areas which have been successfully correlated with the d1 and d2 deformation fabrics from the bif rocks moreover a regional scale variation in intensity and nature of strain is noticed from the ams data which have been utilized to decipher folding mechanism as well as the changing deformation pattern during successive folding events

discussion of saha et al 2012 precambrian research tectono magmatic evolution of the mesoproterozoic singhora basin central india evidence for compressional tectonics from structural data ams study and geochemistry of basic rocks abstract the discussion of saha et al precambrian research 2012 doi 101016 j precamres 2012 03 004 2012 tectono magmatic evolution of the mesoproterozoic singhora basin central india evidence for compressional tectonics from structural data ams study and geochemistry of basic rocks in precambrian research is placed within the broader context of what is known and what is unknown about the shallow crustal deformation structures and the interplay of deformation in the basement and cover rocks

forecasting transitions in monogenetic eruptions using the geologic record spatial forecasting of volcanism and associated hazards in intraplate monogenetic volcanic fields is subject to large uncertainties in both data and models we demonstrate a novel logistic regression method for mapping phreatomagmatic magmatic eruption transition susceptibility using near surface hydrologic topographic and geologic data the method is illustrated on the auckland volcanic field the location of new zealand s largest city auckland environmental factors examined for possible influence included the thickness of water saturated and porous sediments substrate type and geology vent elevation and distance from the nearest fault by comparing these factors with the volumes and styles of past eruption sequences a location specific eruption sequence forecasting model was constructed recognizing that larger and or longer eruptions are more likely to exhaust vent area sources of water estimating volcanic hazard susceptibility in this way allows more effective planning and improved preeruption preparedness between eruptions and during future volcanic crises

tephra cushioning of ballistic impacts quantifying building vulnerability through pneumatic cannon experiments and multiple fragility curve fitting approaches abstract ballistic projectiles are the most frequently lethal volcanic hazard close to the vent recent eruptions of ontake in 2014 and kusatsu shirane in 2018 showed that un reinforced timber framed buildings those typically considered highly vulnerable to the dangerous penetration of ballistics provided life saving shelter from ballistic impact modelled kinetic energies of some non penetrating impacts were an order of magnitude above expected penetration thresholds it has been hypothesised that a pre existing layer of tephra on the roofs cushioned impacts to quantitatively test this and improve our understanding of how buildings respond to projectile impacts we used a pneumatic cannon to simulate block impacts to clay tiles and reinforced concrete roof slabs covered with tephra layers 0 20 cm thick substantially higher impact energies were resisted when tephra was present with 5 cm of tephra approximately tripling the penetration threshold of both building materials fragility curves which relate ballistic hazard intensity with the probability of building damage were developed from our experimental data following three curve fitting approaches generalised link models cumulative link models and data binning a key benefit of these approaches is that confidence in these curves can be robustly quantified from the data the first time that this has been attempted for volcanic fragility curves this study shows how the extent of building damage can be strongly influenced by the sequence of volcanic hazards and provides an example of proactive risk management through testing of physical mitigation strategies in a laboratory environment

compaction of lithic sands experimental results and applications compaction experiments showed that the degree of physical compaction of a lithic sand is related to the amount and type of lithic material present these experiments produced a product that is texturally indistinguishable from natural lithic sandstones generally sedimentary lithic fragments are more ductile than metamorphic lithic fragments volcanic lithic fragments when altered to phyllosilicate minerals by weathering or diagenesis are extremely ductile mineralogy and intragranular microporosity influence ductility ratios based on weight percent of soft ductile minerals clay and micas to hard brittle minerals quartz and feldspar within the lithic fragments provides a good indication of ductility a ratio greater than 1 indicates the lithic material will be h ghly ductile microporous lithic fragments are more ductile than dense lithic fragments physical compaction models were developed based on experimental data from well sorted lithic sandstones for which the percentage of preserved porosities were functions of the effective stress the type of lithic material and the quantity of lithic material these models are derived from laboratory sandstones with at least 25 lithic grains in the following categories moderately ductile metamorphic lithic fragments highly ductile shale lithic fragments and extremely ductile altered volcanic lithic fragments application of the compaction models of the experimental compaction techniques to modern subsurface sand samples or outcrop equivalents can provide valuable estimates of the preserved porosities i e reservoir potential for lithic sandstones that may be exploratory objecti es in frontier basins examples using the models and experimental compaction techniques for exploration are given experimental data showed that precompaction cement and overpressure may be beneficial to porosity preservation an early formed partial cement can retard compaction and preserve porosity by stabilizing the sand pack a later cement does not have this beneficial effect overpressure when developed early retards compaction by reducing the effective stress of course a late developing overpressure is not effective at preserving porosity because compaction is an irreversible process

volcanz a volcanic loss model for auckland new zealand abstract volcanz is a probabilistic volcanic loss model developed for the auckland region in new zealand that currently considers tephra fall hazards from the auckland volcanic field avf tuhua volcano okataina volcanic centre taupo volcano tongariro volcanic centre and egmont volcano in this first version of the model structural and non structural damage to residential building envelopes and associated cleanup costs are calculated using monte carlo simulation volcanz assigns a minimum and maximum damage value to groups of buildings for every simulation dependent on tephra thickness a central damage value representing loss as a percentage of total replacement cost is then randomly selected between these limits even with small thickness falls non structural damage is expected to roof and wall coatings air conditioning units aerials and satellite dishes due to the corrosive and abrasive properties of tephra an average loss of 583 attributed to non structural damage was assigned to all residential buildings impacted by any thickness of tephra greater than 0 1 mm the costs of tephra removal from buildings cleaning of building exteriors and tephra transport and disposal are also calculated within the model assuming much of the cleanup process will be carried out by homeowners losses from all simulations are plotted against calculated average recurrence intervals aris to produce loss curves structural damage does not become apparent until aris of approximately 8000 years 1 billion losses due to structural damage occur at about 35 000 years and this increases to about 26 billion at 1 million years loss due to non structural damage is constant at approximately 160 million for aris above about 600 years between 600 and 3000 years cleanup loss is approximately 50 million increasing to over 450 million at a return period of 1 million years at aris between 600 and 3000 years total loss is approximately 210 million increasing to 10 billion at 100 000 years and over 26 billion at 1 million years because we only consider residential building damage and associated cleanup these values greatly underestimate total loss from the next volcanic event to impact auckland loss calculations will be improved by adding additional hazard and loss modules to volcanz resulting in a complete catastrophe loss model

quantitative evaluation of the reservoir potential and controlling factors of semi deep lacustrine tempestites in the eocene lijin sag of the bohai bay basin east china abstract ancient lacustrine storm deposits that act as petroleum reservoirs are seldom reported the lijin sag which is located in the southeastern corner of the bohai bay basin in east china is a ne sw trending cenozoic half graben basin some of its eocene deposits bindong deposits were interpreted as lacustrine tempestites the bindong tempestites which developed in the lower part of the upper fourth member of the shahejie formation es41 constitute a new kind of petroleum reservoir and are novel petroleum exploration targets in the bindong area however the characteristics of the es41 bindong tempestite reservoirs and their controlling factors are poorly understood point count analyses of thin sections scanning electron microscope image analyses x ray diffractometry data and the petrophysical parameters of the bindong tempestite reservoirs were utilized to estimate the reservoir quality the reservoirs have undergone significant diagenetic alteration which can be divided into negative and positive aspects the negative alteration includes compaction authigenic minerals and cementation such as carbonates clay minerals and overgrowths of quartz and feldspar the uneven distribution of carbonate cement increased the reservoir s heterogeneity with carbonate cement commonly precipitating along the sandstone mudstone contacts the primary porosity was severely reduced because of compaction and extensive carbonate cementation positive alteration includes dissolution carbonate cementation undercompaction and fractures carbonate cementation exhibited both positive and negative effects on the reservoir quality overall the objective reservoir quality is quite poor a quantitative evaluation of the reservoirs potential was conducted the cutoff values of several of the reservoir s parameters were calculated the lower limits of the porosity and permeability are 8 35 5 85 and 1 2587 0 2753 10 3 m2 respectively depending on the depth the upper limits of the carbonate and mud content are approximately 18 5 and 9 10 respectively a fundamental understanding of these characteristics will provide necessary information for extracting hydrocarbons from analogous subsurface reservoirs

distal record of multi sourced tephra in onepoto basin auckland new zealand implications for volcanic chronology frequency and hazards we have documented 80 tephra beds dating from ca 9 5 to 50 ka contained within continuously deposited palaeolake sediments from onepoto basin a volcanic explosion crater in auckland new zealand the known sources for distal 190 km from vent tephra include the rhyolitic taupo volcanic centre 4 and okataina volcanic centre 14 and the andesitic taranaki volcano 40 and tongariro volcanic centre 3 the record provides evidence for four new events between ca 50 and 28 ka mangaone subgroup suggesting okataina was more active than previously known the tephra record also greatly extends the known northern dispersal of other mangaone subgroup tephra ten rhyolitic tephra pre date the rotoehu eruption ca 50 ka and some are chemically dissimilar to post 50 ka rhyolites some of these older tephra were produced by large magnitude events however their source remains uncertain eight tephra from the local basaltic auckland volcanic field avf are also identified interpolation of sedimentation rates allow us to estimate the timing of 12 major explosive eruptions from taranaki volcano in the 27 5 9 5 ka period in addition 28 older events are recognised the tephra are trachytic to rhyolitic in composition all have high k2o contents 3 wt and there are no temporal trends this contrasts with the proximal lava record that shows a trend of increasing k2o with time by combining the onepoto tephra record with that of the previously documented pukaki crater 15 avf basaltic fall events are constrained at 34 6 30 9 29 6 29 6 25 7 25 2 24 2 23 8 19 4 19 4 15 8 and 14 5 ka and three pre 50 ka events this provides some of the best age constraints for the avf and the only reliable data for hazard recurrence calculations the minimum event frequency of both distal and local fall events can be estimated and demonstrates the auckland city region is frequently impacted by ash fall from many volcanoes

probabilistic tephra fall simulation for the auckland region new zealand abstract the auckland region new zealand is at significant risk from tephra falls originating both from the local auckland volcanic field avf and several distant large volume centres we use geological data and observations of historical eruptions to develop a catalogue of simulated tephra dispersal patterns for the auckland region using the ashfall model simulated patterns relate to individual eruptive phases and can be combined to simulate events that vary in volume and duration avf eruption parameters were chosen to replicate fine tephra fall dispersed from small volume phreatomagmatic eruptions modelling of eruptions from distant volcanoes was carried out in two stages first the sensitivity of modelled tephra thickness to various model parameters was tested by far the largest thickness variations were the result of varying wind conditions followed by eruption volume the second stage involved modelling volumes that best replicated thicknesses of preserved events within the auckland region allowing the catalogue to be created only about 1 of simulations from distant volcanoes reached the auckland region suggesting that preserved tephra layers are either the result of reasonably long lived eruptions or a number of eruptive phases for eruptions originating within the avf mean modelled tephra thickness on land is small approximately 1 6 mm near the coast and thinning rapidly inland mean andesitic thicknesses are dominated by eruptions from egmont volcano which typically deposit tephra over a narrow section of the auckland region with a maximum thickness of approximately 1 7 mm rhyolitic eruptions are more widespread with mean thickness varying from 30 mm in the south of the region to 9 mm in the north when all centres are combined and weighted by their conditional likelihood of occurrence mean thickness ranges from 7 mm in the south to 1 5 mm in the north however maximum thicknesses of 150 mm for the avf 12 mm for andesitic centres and 830 mm for rhyolitic centres all have the potential to cause much greater damage within parts of the auckland region

volcanic ashfall accumulation and loading on gutters and pitched roofs from laboratory empirical experiments implications for risk assessment abstract volcanic ash load is dependent on the migration and accumulation of ash on roofing surfaces and guttering of which limited research has been conducted this study investigates this knowledge gap through the empirical experimental testing of volcanic ash on variably pitched metal sheet roofs with modern pvc gutter systems highlighting the relative importance of accumulation migration remobilization saturation and subsequent load a testing rig delivered ash onto variably pitched roofs pitches 15 25 30 35 and 45 with two 45 tests involving a wet surface with subsequent ashfall and the second of ashfall with periods of wetting followed by wetting until failure in testing dry ash on a dry roof accumulates at pitches up to 35 above this pitch the percentage of ash accumulating reduces with greater percentages infilling guttering and or lost to the ground with the introduction of a wet roof surface at 45 pitch adherence of dry ash greatly increases increasing accumulated ash thickness as compared to dry tests from 8 to 38 for testing involving periods of wetting at 45 roof pitch accumulation percentages further increased to 50 ash migrating from the roof surface filled guttering more rapidly at greater pitches which once full resulted in further migrating ash to spill over the front or back gutter lips collapse of guttering did not occur during testing but deformation and bracket detachment did occur at loads 1 kpa this study provides data on load calculations on roofing and pvc guttering through the quantification and utilization of relationships between ash fate pitch and the influence of water in the development of two scenarios for both roof and gutter these two scenarios then enable the estimation of ash accumulation and thus the load and collapse thresholds for roof and gutter at different roof pitch which could be adopted for volcanic risk modeling or risk management

tephra fall clean up in urban environments abstract tephra falls impact urban communities by disrupting transport systems contaminating and damaging buildings and infrastructures and are potentially hazardous to human health therefore prompt and effective tephra clean up measures are an essential component of an urban community s response to tephra fall this paper reviews case studies of tephra clean up operations in urban environments around the world spanning 50 years it identifies methods used in tephra clean up and assesses a range of empirical relationships between level of tephra accumulation and clean up metrics such as collected tephra volume costs and duration of operations results indicate the volume of tephra collected from urban areas is proportional to tephra accumulation urban areas with small tephra accumulations 1 000 m 3 km 2 or an average of 1 mm thickness may collect 50 000 m 3 km 2 or an average of 50 mm thickness remove up to 80 this relationship can inform impact and risk assessments by providing an estimate of the likely response required for a given tephra fall no strong relationship was found between tephra fall accumulation and clean up cost or duration for urban environments which received one off tephra falls suggesting that these aspects of tephra fall clean up operations are context specific importantly this study highlights the advantage of effective planning for tephra clean up and disposal in potentially exposed areas

porosity permeability and textural heterogeneity of reservoir sandstones from the lower cretaceous putaohua member of yaojia formation weixing oilfield songliao basin northeast china abstract with the granulometric analyses mineral composition x ray diffraction xrd analyses porosity and permeability measurements scanning electron microscopy sem observations and mercury porosimetry measurements of the reservoir sandstones from four wells in the weixing oilfield songliao basin ne china the porosity permeability and pore structural heterogeneity features of the putaohua member sandstone of the lower cretaceous yaojia formation have been investigated in this paper the sandstones are mostly characterized by a similar deposition in continental detrital environments with quartz and feldspar taking the majority 97 and argillaceous minerals illite kaolinite and chlorite the minority 3 however their granule size sorting index porosity and permeability vary significantly in contrast to the generality that high porosity permeability often corresponds to large grain sizes and sorting indexes the porosity and permeability here show no good correlations to the grain size and sorting index suggesting the presence of a remarkable textural heterogeneity in terms of sequential change in permeability along the well depth cyclic sedimentation modes have been identified in some sub layers despite the porosity data showing little response to those scenarios this may be ascribed to the sandstone s peculiar intergranular pore structures in which the cementation occurred in pore lining and filling manners to different extents depending on their depositional environments the distributary channel facies tends to have lowest detrital clay content and rather open packed texture in pore lining cementation manner whereas sand sheet facies has pore filling manner the hg porosimetry analytical data are in fairly good agreement with the heterogeneous pore structures observed by sem large sized pores and channels connecting them though only accounting for a low percentage of the total porosity are believed to contribute mostly to the effective permeability in the sandstone reservoir such textural heterogeneities should be closely associated with the dynamic changing sedimentary facies of sandstones in the continental environment

volcanic hazards in auckland new zealand a preliminary assessment of the threat posed by central north island silicic volcanism based on the quaternary tephrostratigraphical record

magnetic fabric methods and applications fabric is a ubiquitous and significant feature of geological materials the processes involved in the formation and deformation of rocks and sediments leave their mark on the orientations of the constituent mineral grains petrofabrics thus provide essential keys to understanding the history of geological materials magnetic anisotropy is directly related to petrofabric and has become one of the most rapid sensitive and widely used tools for its characterization the relationship between magnetic fabric and petrofabric is complex and depends on various factors including the composition concentration and grain size of mineral grains ongoing research in geological applications is paralleled by studies of the fundamental mineral magnetic phenomena involved the papers in this book represent the current state of investigations in magnetic anisotropy studies as a discipline that integrates geological interpretations mineral fabric development technical advances and rock magnetic properties

depositional history of the chhattisgarh basin central india constraints from new shrimp zircon ages a reply abstract the indian shield includes the singhbhum bastar and east and west dharwar cratons proterozoic sedimentary basins formed on these cratons have preserved rocks with a range of degrees of metamorphism and deformation in the chhattisgarh basin within the bastar craton the ca 2200 2500 m thick chhattisgarh supergroup has been preserved in nearly pristine condition previous work has shown that the sukhda tuff located about 2200 m from the base of the section was formed ca 1007 ma new u pb shrimp age determinations show that the singhora tuff located about 100 m above the base of the basin is not older than ma thus most of the chhattisgarh supergroup was deposited between 1400 and 1000 ma age data for detrital zircons from sandstones show that regardless of their stratigraphic position there is a unimodal age peak near 2500 ma the typical age of adjacent granitic and rhyolitic basement rocks indicating that these constituted the principal provenance of the sediments in the chhattisg

the anisotropy of magnetic susceptibility ams in low grade cleaved pelitic rocks influence of cleavage bedding angle and type and relative orientation of magnetic carriers

deformation pattern of the nw terrane boundary of the eastern ghats mobile belt india a tectonic model and correlation with antarctica abstract thrusts interspersed with lateral ramp and wrench structures mark the join between proterozoic eastern ghats mobile belt and archaean cratons of the eastern india the join referred to as terrane boundary shear zone exhibits an arcuate geometry at the nw margin of the eastern ghats where the mobile belt shows the presence of northwesterly verging nappes based on this the area has been described to represent the salient part of a fold thrust belt juxtaposition of the granulites over the low grade craton is largely attributed to thrusting along the terrane boundary shear zone as the folds are disoriented and the granulites are retrograded along the thrusts the terrane boundary shear zone is interpreted to be a retrograde shear zone the shear zone hosts a number of synkinematic alkali intrusive rocks that constrain the age of thrusting to 1 4 ga in the correlative framework of gondwanaland the terrane boundary shear zone is very likely to be contiguous with the rayner napier boundary of antarctica

the purana basins of southern cratonic province of india a case for mesoproterozoic fossil rifts abstract since its cratonization in the palaeoproterozoic southern peninsular india witnessed the development of a number of large intracratonic sedimentary basins traditionally referred to as purana basins spanning in age from late palaeoproterozoic through neoproterozoic the localization of these intracratonic basins namely pranhita godavari pg chattisgarh and cuddapah basins is apparently controlled by pre existing sutures and or weak zones the pg basin and the cuddapah basin host unconformity bound thick sediment dominated successions attesting to several cycles of fluvial shallow marine to shelf slope basin sedimentation deposition was punctuated by block uplifts resulting in local hiatuses and or volcanic upheavals leading to intercalation of thin but persistent basaltic flows and acid tuffs and ignimbrites basin margin deep faults apparently played a role in the facies distribution in these basins based on these features we propose that these basins initiated as continental rifts which however never opened up into a full fledged ocean basin but links with open seaway are evident from frequent occurrence of deposits representing tidal and storm influence particularly in upper part of the chattisgarh succession spatial distribution of facies and sediment thickness in the cuddapah and pg basins suggest that an open seaway existed to the east of the south indian cratonic province during the mesoproterozoic while similar criteria point to the existence of an open seaway north of the chattisgarh basin development history including nature of inversion suggest that the southern cratonic province of india existed as a single large continental mass since the mesoproterozoic in spite of episodes of supercontinent build up and fragmentation involving india and east gondwana during the proterozoic

horizontal and vertical variations in sedimentation and resuspension rates in a stratifying lake effects of internal seiches the temporal and spatial variations in the rate of sedimentation and sediment resuspension in lake rehtijarvi southern finland were studied by sediment traps deployed in the stratifying and non stratifying regions of the lake both the gross sedimentation rate and the resuspension rate recorded by near bottom traps were significantly higher in the stratifying region 20 m depth than in the shallow part of the lake 2 m depth these rate changes were caused by temporarily elevated hypolimnetic resuspension rates exceeding 40 g dry weight m 2 day 1 in july 2005 whereas in the shallow station no such peak was observed and the resuspension rate remained below 30 g dry weight m 2 day 1 throughout the study the elevated resuspension rate in the hypolimnion could not be attributed to surface wave action or sediment disturbance by fish but was due to the occurrence of internal seiches the seiche amplitude was on average the highest in july although the wind velocities were low this was because winds temporarily were blowing along the longitudinal axis of the lake due to the steep slopes the sediments of lake rehtijarvi are prone to redistribution and sediment focusing towards the accumulation areas also affected trap catches in the deep stations

forced regressive wedges on a neoproterozoic siliciclastic shelf chandarpur group central india abstract outcrop based sequence analysis across the transition from the chaporadih to the kansapathar formation of chandarpur group chattisgarh supergroup central india resolved a long standing uncertainty on occurrence of depositional discontinuity through undoubted identification of a forced regressive wedge and associated intraformational unconformity process based facies analysis identified eleven different facies types that are grouped into five different facies associations paleoenvironments range from shelf shoreface foreshore and beach tide influenced estuary and delta bounded between the surface of marine erosion at its base and subaerial unconformity marked by paleosol development at its top the coarse grained wedges of shoreface sandstone is interpreted as forced regressive in origin the basinward downstepping of two such regressive wedges bears evidence for lowering of wavebase in connection with relative fall in sea level the valley created during the falling sea level was filled by sediments in lowstand transgressive and highstand depositional motif the aggradational to weakly progradational bedsets of foreshore beach sediments record the history of early slow rise in base level with steepening in the rate of relative sea level rise the coastline transformed from wave dominated to tide dominated wide variability in the balance between sediment supply and accommodation is recorded in the facies types and stacking motif of transgressive estuarine sections at different studied locations the highstand tidal delta is a supply driven normal regressive product at stable or marginally rising base level

a physical model of cementation and its effects on single phase permeability in this paper we present a mathematical model to quantify the effects of cements on the single phase permeability estimate of clastic rocks the model represents pore filling pore lining and pore bridging cements by treating the cement particles as rectangular crystals attached radially to detrital grains these clusters influence permeability through an increase in effective specific surface area and tortuosity because the model is based on physical principles it is largely devoid of empiricism and should be applicable to a wide range of rock types permeability estimates by our model match experimental data from two sets of sandstone samples of five hydrocarbon bearing formations in the north sea the model also confirms the well known result that the effect of pore bridging cement is a factor of ten greater in reducing the single phase permeability compared to pore lining and pore filling cements

impact of the ad 79 explosive eruption on pompeii i relations amongst the depositional mechanisms of the pyroclastic products the framework of the buildings and the associated destructive events abstract a quantitative and qualitative evaluation of the damage caused by the products of explosive eruptions to buildings provides an excellent contribution to the understanding of the various eruptive processes during such dramatic events to this end the impact of the products of the two main phases pumice fallout and pyroclastic density currents of the vesuvius ad 79 explosive eruption onto the pompeii buildings has been evaluated based on different sources of data such as photographs and documents referring to the archaeological excavations of pompeii the stratigraphy of the pyroclastic deposits and in situ inspection of the damage suffered by the buildings the present study has enabled the reconstruction of the events that occurred inside the city when the eruption was in progress in particular we present new data related to the c j polibius house a large building located inside pompeii from a comparison of all of the above data sets it has been possible to reconstruct in considerable detail the stratigraphy of the pyroclastic deposits accumulated in the city to understand the direction of collapse of the destroyed walls and to evaluate the stratigraphic level at which the walls collapsed finally the distribution and style of the damage allow us to discuss how the emplacement mechanisms of the pyroclastic currents are influenced by their interaction with the urban centre all the data suggest that both structure and shape of the town buildings affected the transport and deposition of the erupted products for instance sloping roofs drained a huge amount of fall pumice into the impluvia a rectangular basin in the centre of the hall with the function to collect the rain water coming from a hole in the centre of the roof thus producing anomalous deposit thicknesses on the other hand flat and low sloping roofs collapsed under the weight of the pyroclastic material produced during the first phase of the eruption pumice fall in addition it is evident that the walls that happened to be parallel to the direction of the pyroclastic density currents produced during the second eruptive phase were minimally damaged in comparison to those walls oriented perpendicular to the flow direction we suggest that the lower depositional parts of the pyroclastic currents were partially blocked locally reflected and slowed down because of recurring encounters with the closely spaced walls within buildings locally the percentage of demolished walls decreases down current which has been interpreted as a loss in kinetic energy within the depositional system of the flow however it seems that the upper transport system by passed these obstacles then supplied new pyroclasts to the depositional system that restored its physical characteristics and restored enough kinetic energy to demolish the next walls and buildings further along its path

diagenesis and reservoir quality of the sherwood sandstone triassic corrib field slyne basin west of ireland abstract the triassic sherwood sandstone in the corrib field slyne basin west of ireland on the european continental margin is a dry gas reservoir with a mercia mudstone top seal petrographic analysis combined with x ray diffraction stable isotope fluid inclusion and core analysis have been used to assess timing of growth and origin of mineral cements whether sandstone diagenesis involved mass flux the controls on reservoir quality and how reservoir quality is likely to vary in more deeply buried sections depositional and early diagenetic characteristics of the sherwood in corrib are typical of a semi arid fluvial environment containing groundwater of meteoric origin early diagenesis included the development of copious dolomite cement in the form of dolocrete as well as the formation of abundant clay while less volumetrically important grain coating haematite and k feldspar cement also grew burial diagenesis witnessed the initial growth of minor chlorite and albite quartz overgrowths and ankerite followed and are the most important burial cements growing over a temperature interval between 100 and 1165 c albite commenced growth at about 90 c quartz cement at 100 c and ankerite at 110 c these cements reached the zenith of their development at 105 110 c for albite 125 130 c for quartz and 135 145 c for ankerite siderite and anhydrite are relatively minor late stage cements the formation water has been consistently highly saline during burial and in terms of mineral cement derived oxygen stable isotope values is likely to be a diagenetically evolved version of the initial depositional water suggesting long term stagnation of the pore fluids the diagenetic reactions that formed burial cements all seem to be essentially isochemical including the ankerite that has carbon isotope characteristics of the cannibalisation of dolocrete reservoir quality is mainly controlled by early diagenetic dolomite and clay although grain size is also important because only sandstones with 200 m grain size have 50 md permeability both shallower and deeper sections than corrib may have similar porosity and permeability since temperature dependent diagenetic controls on reservoir quality e g quartz and illite cement are peripheral

porosity depth trends in reservoir sandstones theoretical models related to jurassic sandstones offshore norway abstract theoretical models of compaction and porosity modification in sandstones during burial are discussed theory predicts that mechanical compaction is the dominant porosity reducing mechanism during burial from 0 to 2 5 3 km porosity depth trends are at this stage mainly controlled by the stability of the grain framework and the effective stress time and temperature also influence the porosity depth gradients at shallow to moderate depths but are probably less important than effective stress and framework grain composition at greater burial depths below 2 5 3 km chemical compaction including pressure solution can explain most of the porosity reduction in well sorted clean arenites theoretical modelling of the intergranular pressure solution suggests that sandstones may lose porosity rapidly by this mechanism below 2 5 3 km and that factors capable of retarding pressure solution and quartz cementation are required to maintain prospective porosities below 4 km this theory and comparisons with empirical data from jurassic sandstones from offshore norway indicate that high porosity is favoured by 1 overpressures approaching the lithostatic pressure gradient 2 a short residence time below 3 km burial 3 coatings on grains of clay or microcrystalline quartz which prevent quartz dissolution and precipitation and 4 a high content of feldspar and early diagenetic secondary pores early hydrocarbon emplacement may retard quartz cementation and preserve porosity but chemical compaction probably continues after oil emplacement except at very high hydrocarbon saturations

volcanic risk ranking for auckland new zealand ii hazard consequences and risk calculation in a companion paper a methodology for ranking volcanic hazards and events in terms of risk was presented and the likelihood and extent of potential hazards in the auckland region new zealand investigated in this paper the effects of each hazard are considered and the risk ranking completed values for effect are proportions of total loss and as with likelihood and extent are based on order of magnitude

building damage in rabaul papua new guinea 1994 damage information on 173 buildings was collected in the immediate aftermath of the september 1994 eruption which destroyed large sections of rabaul town papua new guinea the extent of damage is presented on a five point scale and related to construction characteristics and tephra load total roof loads in rabaul town ranged from 2 to 16 kn m 2 about 100 to 950 mm tephra thickness most buildings which collapsed completely experienced loads 7 5 kn m 2 but many buildings sustained half this load with little more than cosmetic damage timber framed buildings suffered more than buildings with at least some concrete block walls however some old steel framed buildings experienced severe damage with tephra loads as low as 2 kn m 2 comparisons with tephra loads and building damage elsewhere are limited but suggest that rabaul buildings experiencing roof loads of 2 5 kn m 2 generally survived reasonably well however the comparisons are unsatisfactory because of inadequate data on tephra unit weights roof design building ages the quality of workmanship and the natural variability of construction materials particularly timber the rabaul data suggest that concrete block walls increase building resistance to tephra loads but it is doubtful that conventional residential buildings can be designed to sustain tephra loads exceeding 7 kn m 2 the rabaul experience also indicates that building codes for volcanic areas need to consider mudfills and post eruption corrosion of sheet metal roofs and wall cladding most importantly had the majority of buildings in rabaul survived the september 1994 tephra falls wet season mudflows a few months later would still have made most of the town unsafe and uninhabitable