sedimentology of quaternary perched springline and paludal tufas criteria for recognition with examples from guadalajara province spain outcrop scale geometries and bed relationships of ambient temperature freshwater carbonates are poorly understood because many described tufas have been dismantled by erosion and present only part of a particular depositional model at the field scale four end member models encompass the tufa continuum 1 perched springline 2 paludal 3 fluvial and 4 lacustrine tufas individual bed types can occur with variable dominance within several of these models but one or more beds are characteristically dominant only within a single tufa model so it can be differentiated from relatively isolated outcrop fragments two models perched springline tufas and paludal tufas are known in outline only in the literature despite being present within the quaternary deposits of most karstic regions perched springline tufas generally form lobate fan shaped mound morphologies on hillslopes and develop from single or multiple spring resurgences mature deposits show a subhorizontal top and a steep face on the downflow side the steep outer zones of tufa mounds may be developed into cascades with moss curtains or can be dominated by shallow rimstone pools according to face angle tufa deposits lying downslope of the mounds are usually detrital in nature especially if some dismantling of the mound has occurred the relatively thin subhorizontal lobe top deposits commonly contain organic rich deposits paludal tufas develop predominantly in waterlogged valley bottom situations where line sourced waters emerge from valley side and bottom aquifers lime mud precipitation predominates in these sites mud is deposited as subhorizontal laminites that thin towards the valley axis and downstream of resurgences tufa spring mounds may form where lesser volumes of water are involved individual tussocks phytoherm cushions of grasses and rushes are the most diagnostic feature of the model but sapropels and peats may be intercalated diagenesis in both models is rapid lithification of individual beds is virtually instantaneous and always occurs before the decay of the associated living vegetation the resulting highly porous and permeable fabrics remain fresh in holocene tufas but aggrading neomorphism and partial spar infill of vegetation moulds is common in older deposits dissolution in many perched springline tufas is small scale many large cavities are primary but with later coatings of speleothems early removal of organics from paludal tufas is responsible for autobrecciation and differential compaction

three dimensional modelling of a holocene tufa system in the lathkill valley north derbyshire using ground penetrating radar unlithified and partly lithified carbonate sequences are ideally suited to the application of ground penetrating radar gpr augmented by percussion augering and shallow seismic techniques all tied to present day topography using global positioning system gps methods this methodology provides the first clear information on the distribution and geometry of lithofacies within buried tufa complexes the approach has been applied to a thick succession of holocene tufas filling a gorge site along a 3 5 km length of the river lathkill north derbyshire earlier studies have demonstrated the presence of up to 16 m of tufas and sapropels associated with two transverse tufa dams barrages these strata have been accumulating throughout the holocene although tufa developments at present are of minor extent internal tufa morphologies are recorded by gpr as bright laterally continuous reflections for lithified concretionary and lithoclast rich horizons the brightest reflectors occur within well cemented barrages and delineate core areas and prograding buttress zones in contrast unlithified lime muds and sapropels produce low contrast reflections lithostratigraphic control and depth calibration of the gpr profiles was provided by percussion augering at selected sites six distinct lithofacies and four secondary barrages are identified in the study constructional and destructional events can be identified and correlated within the gpr profile network and the internal growth morphologies of the barrages are apparent gpr profiles also clearly define the evolution of the facies geometries three phases of tufa development can be recognized within the gpr data and greatly extend our understanding of holocene tufa forming processes in valley sites a early holocene barrage build ups but with limited paludal deposition b middle holocene ponding and sapropel accumulation under warm conditions and c late holocene barrage termination and valley levelling probably coincidental with anthropogenic activity this type of multidisciplinary approach should be considered as an essential prerequisite to all biostratigraphic and geochemical studies of holocene freshwater carbonate sites

viscosity and other rheological properties of bitumen from the upper devonian grosmont reservoir alberta canada viscosity is directly related to the mobility and quality of hydrocarbons in reservoirs and its distribution is commonly heterogeneous therefore viscosity has a great impact on the exploitation of heavy oil and bitumen reservoirs previous studies showed that viscosity measurements are problematic and are often inconsistent mainly because of the challenges of sample preparation and lack of a standard procedure for measuring viscosity in the oil and gas industry this study aims to improve the characterization of reservoir viscosity by understanding the rheological properties of bitumen using bitumen samples from the upper devonian grosmont reservoir alberta canada this study shows that grosmont bitumen is essentially a non newtonian fluid exhibiting a distinctive shear thinning behavior at low temperatures of less than 40c with increasing temperature however the bitumen changes from a non newtonian fluid to a newtonian fluid at low temperatures the viscosity variations can be divided into four stages a standard viscosity called zero shear viscosity is obtained from the viscosity variations and can be used throughout the reservoir as characteristic viscosity for grosmont bitumen the viscosity distribution in the grosmont reservoir is complex and appears to be stratigraphically related bitumen samples from formation boundaries tend to have higher viscosities suggesting more severe biodegradation at these locations possible causes for the observed patterns in the grosmont include 1 oil water contacts migrating up and down over time 2 oil migration and or biodegradation controlled by aquitards that divide the reservoir into hydrostratigraphically separated units and 3 differences in microbial activity that is aerobic versus anaerobic possibly controlled by the level of oxygenation over time

origin and morphology of limestone caves limestone caves form along ground water paths of greatest discharge and solutional aggressiveness flow routes that acquire increasing discharge accelerate in growth while others languish with negligible growth as discharge increases a maximum rate of wall retreat is approached typically about 0 01 0 1 cm yr determined by chemical kinetics but nearly unaffected by further increase in discharge the time required to reach the maximum rate is nearly independent of kinetics and varies directly with flow distance and temperature and inversely with initial fracture width discharge gradient and pco2 most caves require 104 105 yr to reach traversable size their patterns depend on the mode of ground water recharge sinkhole recharge forms branching caves with tributaries that join downstream as higher order passages maze caves form where 1 steep gradients and great undersaturation allow many alternate paths to enlarge at similar rates or 2 discharge or renewal of undersaturation is uniform along many alternate routes flood water can form angular networks in fractured rock anastomotic mazes along low angle partings or sponge work where intergranular pores are dominant diffuse recharge also forms networks and spongework often aided by mixing of chemically different waters ramiform caves with sequential outward branches are formed mainly by rising thermal or h2s rich water dissolution rates in cooling water increase with discharge co2 content temperature and thermal gradient but only at thermal gradients of more than 0 01 c m can normal ground water co2 form caves without the aid of hypogenic acids or mixing artesian flow has no inherent tendency to form maze caves geologic structure and stratigraphy influence cave orientation and extent but alone they do not determine branch work versus maze character

comparison of the quaternary travertine sites in the denizli extensional basin based on their depositional and geochemical data abstract in the denizli basin turkey located in the western anatolian extensional province travertine and tufa deposition has been an ongoing process for at least 600 000 years travertine bodies which are 30 to 75 m thick and each covers areas of 1 to 34 km2 are up to 1 km3 in volume today spring waters in this area have temperatures of 19 to 57 c are of the ca mg hco3 so4 type in the pamukkale kelkaya and pinarbasi areas and the ca mg so4 hco3 type at cukurbag thermal waters along the northern margin of the basin are generally hotter than those in the east southeast and south the 18o and d values of the spring waters indicate a meteoric origin the average temperatures of the hydrothermal systems in the denizli basin appear to have decreased from pleistocene to holocene travertine which formed from the hotter water is more widespread than the tufa that formed in the cooler spring waters deposition of the travertine which formed largely on slopes in depressions and along fissure ridges mostly on northern basin margins was controlled by the interplay between various intrinsic and extrinsic parameters the travertines are formed largely of calcite with only minor amounts of aragonite in some of the vertically banded crystalline crust raft and pisoid travertines found in some of the northern sites the aragonitic samples rich in sr are typically found around the spring orifices and along the central axis of the fissure ridges the stable isotope values of the travertine found in the northwest and southeast parts of the basin are different the 13c values of the northern travertine deposits are more positive 3 7 to 11 7 vpbd than those found in the south southeast areas 4 to 5 8 vpdb in contrast the travertine and tufa in the southeastern areas have higher 18o values 15 2 to 7 8 vpdb than those of the northern areas 16 6 to 4 8 vpdb available evidence indicates that spring activity and associated travertine precipitation in the denizli basin were controlled largely by tectonic activity rather than by climatic conditions

recognition and delineation of paleokarst zones by the use of wireline logs in the bitumen saturated upper devonian grosmont formation of northeastern alberta canada the upper devonian grosmont formation in northeastern alberta canada is a shallow marine carbonate platform complex that was subaerially exposed for hundreds of millions of years between the mississippian and cretaceous during this lengthy exposure period an extensive karst system developed that is characterized by an irregular erosional surface meter size several feet dissolution cavities collapse breccias sinkholes paleosols and fractures the karsted grosmont formation which contains giant reserves of bitumen subcrops beneath cretaceous clastic sediments of the giant athabasca tar sands deposit the paleokarst in the grosmont formation can be recognized on wireline logs in relatively nonargillaceous carbonate intervals 30 api units on the gamma ray log as excursions of the caliper log off scale neutron density porosity readings and severe cycle skipping of the acoustic log the paleokarst is more prevalent in the upper units of the grosmont formation and the effects of karstification decrease toward stratigraphically older and deeper units the paleokarst usually occurs within 35 m 115 ft of the erosional surface the reservoir properties of the grosmont formation e g thickness porosity permeability and seal effectiveness are significantly influenced by karstification depending upon the location karstification has either benefited or degraded the reservoir characteristics benefits include porosity values greater than 40 up to 100 in caverns and permeability values of 30 000 md in severely fractured intervals detrimental reservoir characteristics include erosion porosity and permeability reduction and seal ineffectiveness

regional scale porosity and permeability variations in upper devonian leduc buildups implications for reservoir development and prediction in carbonates upper devonian carbonate rocks of the rimbey meadowbrook reef trend in the subsurface of central alberta are characterized by a wide range of porosity and permeability values dolostones show the highest values of absolute and average horizontal and vertical permeability for all rock types horizontal permeability averages tens of times to several hundred times the vertical permeability if considered irrespective of burial depth limestones and dolomitic limestones are more porous than dolostones there is an overall decrease of porosity and permeability in leduc formation carbonates with increasing burial depth and thermal maturity along the reef trend at relatively shallow burial depths 2000 m dolostones are significantly more porous and permeable than limestones dolostones appear to retain their porosity and permeability much better than limestones during burial indicating that dolostones are more resistant to porosity and permeability reducing processes particularly pressure solution thus reservoir quality in dolostone reservoirs decreases less severely with depth in addition porosity enhancement in dolostones by leaching in the burial environment during and after dolomitization is important although these significant relationships arenot new concepts they appear to be underappreciated the better porosity and permeability of dolostones relative to limestones at greater depths is of economic significance for exploration in upper devonian carbonates of the deep alberta basin and probably other carbonate areas where reservoirs are mostly found in dolostones and where limestones have a low reservoir potential and pose a considerable exploration risk the best reservoir potential in the leduc formation of the deep alberta basin occurs in dolomitized buildups that were connected to a regional conduit system

a sedimentary facies model for stepped fluvial tufa systems in the iberian range spain the quaternary piedra and mesa valleys stratigraphic and sedimentological analyses of the quaternary tufa and associated deposits in the piedra and mesa river valleys allowed a number of stages of their sedimentary evolution to be characterized and a depositional sedimentary model for this north central sector of the iberian range spain to be established the proposed sedimentary facies model may explain tufa arrangements in other medium to high gradient stepped fluvial tufa systems with narrow transverse profiles occurring in temperate semi arid areas in both recent and past scenarios there are several tufa deposits within the piedra and mesa river valleys that over a maximum thickness of about 90 m record one or more stages of tufa deposition produced following the fluvial incision of the bedrock or previous tufa deposits each depositional stage begins with coarse detrital sedimentation six fundamental vertical sequences of tufa facies with small amounts of detrital material reveal the sedimentary processes that occurred in different fluvial environments channel areas with i free flowing water ii barrages and or cascades and iii dammed water and palustrine floodplains the proposed sedimentary model involves narrow stepped fluvial valleys in which tufa cascades were common alternating intervals of bryophyte and stromatolite facies commonly formed at some cascades many of these represented barrage cascade structures that consisted of phytoclast rudstones thick phytoherms of mosses and associated stromatolites and curtain shaped phytoherms of stems upstream of these structures dammed areas with bioclastic sands and silts developed and palustrine vegetation grew the channel stretches between barrages and or cascades were loci for extensive stromatolite growth in fast flowing water the palustrine floodplain was home to pools and drainage channels the model also explains the growth of some barrages in the river piedra that surpassed the height of the divide with the diffluence of the main channel into a secondary course forming other tufa deposits in the area the distribution and abundance of certain types of tufa facies in fluvial basins may be an indicator of differences in their gradients the facies studied in this work suggest that the gradient of the ancient river piedra was steeper than that of the ancient river mesa assuming similar scenarios for climate and hydrology the depositional settings mentioned above and their dimensions would have been determined mainly by the gradient and width of the associated river valleys this sedimentary model may also be useful for inferring variations in other river basin slopes as well as accounting for the presence of tufas in areas that normally have no permanent water input

synthesis and model of formation water flow alberta basin canada based on a large amount of publicly available data several studies have previously examined the flow of formation waters in different parts of the alberta basin offering various interpretations as to the causes of the observed pressure regime and flow pattern however there has been no synthesis of these diverse studies on a basin wide basis accordingly these studies are critically reviewed in this paper and synthesized in a new basin scale model of the flow of formation waters in the alberta basin the proposed regional scale model has significant implications for understanding hydrocarbon migration pathways ore genesis the geothermal regime and deep waste disposal in the alberta basin several flow systems each one driven by a different mechanism are identified together with the main processes leading to the nonhydrostatic pressures observed in the basin two megahydrostratigraphic successions and associated flow systems are recognized the first succession corresponds to the pre cretaceous passive margin stage of basin development and consists of thick carbonate dominated aquifer systems separated by shaly aquitards and evaporitic aquicludes a northeastward basin scale flow system is driven by basin topography with recharge in montana and discharge in northeastern alberta southwest to northeast regional scale flow adjacent to the fold and thrust belt is probably the result of past tectonic processes the salinity of formation water in pre cretaceous aquifers is high and generally increases both northward and with depth this variability is the result of increased water rock reactions mineral solubility with increased temperatu e and of incomplete flushing by meteoric water as a result of salinity variations flow retarding buoyancy effects can be important the second megahydrostratigraphic succession corresponds to the post jurassic foreland stage of basin evolution and consists of thick shaly aquitard systems and relatively thin sandstone aquifers in the southwestern part of the basin flow in isolated aquifers is driven southwestward by erosional rebound in the thick intervening shales downdip toward the fold and thrust belt the salinity of formation waters in the post jurassic aquifers is low mixing of waters and interference between the major flow systems takes place along the pre cretaceous unconformity where successively older pre cretaceous aquifers subcrop from west to east flow in shallow lo al systems at the top of the sedimentary succession is driven by local topography

searching for travertines calcretes and speleothems in deep time processes appearances predictions and the impact of plants common models for modern calcite precipitation in and around caves soils springs and streams involve co 2 supplied by thick high p co 2 biogenic soils which were probably thin or non existent before vascular plants indeed plant influenced chemical weathering might have caused accelerated terrestrial carbonate production from the devonian onwards however terrestrial carbonates have also been documented from the archaean proterozoic cambrian ordovician and silurian mechanisms which could have caused non marine carbonates to precipitate without organic rich soils are described and some geological events likely to have influenced non marine carbonate precipitation up to the origin of vascular plants are highlighted as organisms have evolved so have the petrographic characteristics of non marine carbonates some examples of this are also given here

unconformities and porosity development in carbonate strata ideas from a hedberg conference the purpose of this paper is to highlight ideas from a hedberg conference concerning detection of unconformities and associated porosity in carbonate strata many types of information including cores and outcrops seismic data eustatic sea level curves wireline logs biostratigraphic data stable isotope trends cycle stacking patterns and tectonic and basin evolution models can be used to predict and or detect subaerial unconformities all methods of detecting subaerial exposure with these types of information have limits and pitfalls detailed analysis of the stratigraphy sedimentology and diagenetic history of a rock sequence from outcrop or core data is considered the most reliable means of detecting subaerial exposure though an integrated approach using all a ailable information is recommended the relationship between subaerial exposure and subsurface porosity in carbonates is not simple or easily predicted subsurface porosity is the product of many factors operating during deposition subaerial exposure and burial several concepts should be recognized when evaluating porosity associated with subaerial unconformities 1 carbonate diagenesis during subaerial exposure rearranges pore networks but usually does not increase the total porosity near surface dissolution can simply lower a topographic surface without increasing porosity within the host limestone in many cases total porosity in carbonates under unconformities is actually reduced during subaerial exposure 2 permeability is likely to change more than porosity during subaerial exposure increasing in some c ses but decreasing in others 3 pore systems evolve with time during subaerial exposure short periods of subaerial exposure 10 000 400 000 yr are often associated with greater porosity than long intervals of subaerial exposure 1 20 million yr prolonged subaerial exposure may change permeability less than porosity because high permeability karst related conduits can form quickly and persist for millions of years 4 many carbonates subjected to subaerial exposure have little or no porosity in the deep subsurface because compaction cementation and stratal collapse reduce porosity during burial 5 unconformity related diagenesis may enhance reservoir potential by creating pore systems that are resistant to compaction during deeper burial 6 vugs caverns and breccias can fo m in the deep subsurface because of dissolution by basinal fluids independent of subaerial exposure 7 lithologic changes at unconformities like shales overlying carbonates can influence the flow of subsurface fluids during end page 857 deeper burial resulting in deep burial dissolution localized along unconformities if subaerial exposure and exposure surfaces are integrated into a sequence stratigraphic paleogeographic and climatic framework systematic and hopefully predictable patterns will emerge however we do not fully understand the complex interplay between the factors critical to creating and preserving porosity in carbonates additional research is needed to quantify critical processes and products so we can reliably predict porosity associated with subaerial exposure during exploration in frontier basins and on a smaller scale during reservoir analysis

hydrogeology of formation waters northeastern alberta basin the hydrogeological study of formation waters in the northeastern part of the alberta basin defined as the area from 55 to 58 n and from 110 to 114 w is based on information from 12 475 wells 3187 formation water analyses 2531 drill stem tests and 452 030 core plug analyses because the study area covering approximately 76 000 km2 is located at the feather edge of the basin local topography and physiographic features particularly the athabasca river system exert a strong influence on the flow of formation waters in most of the aquifers generally temperature seems to be the main controlling factor on salinity distributions the salinity of formation waters increases in the vicinity of evaporitic beds and decreases close to the surface beca se of mixing with fresh meteoric water introduced through local flow systems the lower and middle devonian pre prairie aquifer systems beneath the regionally extensive prairie aquiclude are characterized by regional topographically driven flow updip to the northeast this updip flow is opposed by buoyancy forces caused by salinity increase with temperature downdip to the southwest the post prairie devonian aquifers are characterized by transitional flow regimes because of erosion at the sub cretaceous unconformity and outcrop at the athabasca river local physiographic influences are superimposed on basin scale regional flow in these aquifers hydraulic communication between the beaverhill lake cooking lake and grosmont aquifers is inferred in places caused by cooking lake reefs penetrating the intervening shales of the lower ireton aquitard finally the retaceous aquifers all can be described as having local flow regime characteristics with no buoyancy effects as a result of recharge in topographically high areas and discharge in low regions along the valleys of the athabasca river system the flow of formation waters in northeastern alberta played an important role in the formation of the huge athabasca oil sands deposits hydrocarbons that migrated into the area from the west were trapped into local reservoirs and biodegraded and washed by fresh meteoric water introduced by local flow systems environmentally the subsurface hydrogeology in the area imposes specific constraints on waste disposal in deep formations mostly because of the absence of a thick continuous regional aquitard and because most aquifers subcrop at shallow depth or crop out and discharge along the valleys of the athabasca river system and at the basin edge

sulfuric acid speleogenesis of carlsbad cavern and its relationship to hydrocarbons delaware basin new mexico and texas sulfur isotope data and ph dependence of the mineral endellite support the hypothesis that carlsbad cavern and other caves in the guadalupe mountains were dissolved primarily by sulfuric acid rather than by carbonic acid floor gypsum deposits up to 10 m thick and native sulfur in the caves are significantly enriched in 32 s isotope 34 s values as low as 25 8 per mil cdt indicate that the cave sulfur and gypsum are the end products of microbial reactions associated with hydrocarbons a model for a genetic connection between hydrocarbons in the basin and caves in the guadalupe mountains is proposed as the guadalupe mountains were uplifted during the late pliocene pleistocene oil and gas moved updip in the basin the gas reacted with sulfate anions derived from dissolution of the castile anhydrite to form h 2 s co 2 and castile limestone the hydrogen sulfide rose into the capitan reef along joints forereef carbonate beds or bell canyon siliciclastic beds and there reacted with oxygenated groundwater to form sulfuric acid and carlsbad cavern a sulfuric acid mode of dissolution may be responsible for large scale porosity of some delaware basin reservoirs and for oil field karst reservoirs in other petroleum basins of the world

sedimentology of coexisting travertine and tufa deposits in a mounded geothermal spring carbonate system obruktepe turkey the recent discoveries of deeply buried cretaceous reservoir bodies in the atlantic ocean revealed that relationships between the distribution of spring carbonate deposits and faults are poorly understood the well exposed quaternary deposits at obruktepe denizli basin turkey provide an opportunity to reconstruct the three dimensional sedimentary architecture of such a system integration of sedimentological lithofacies and geochemical analyses reveals complexity in the lateral relationships between sedimentary environments faults and geothermal spring carbonates five environmental systems are distinguished based on the lithofacies analysis i vent ii smooth slope iii travertine terrace iv tufa barrage and v flood systems encrusting baffling and settling sedimentary processes are reflected in data acquired at several scales from lithofacies observations to the morphology and arrangement of geobodies together with microfabrics and stable carbon and oxygen isotope data mean values of 4 9 parts per thousand delta c 13 and 8 74 parts per thousand delta o 18 vienna peedee belemnite reflect geothermal circulation of springwaters the environmental distribution and lithofacies indicate a lateral continuum between travertine and tufa deposits within this hot spring system this finding supports two depositional models in which water flow variation is the main control on both caco3 precipitation and the resulting formation of travertine and tufa the proposed models address the factors responsible for the development of these complex mound shaped carbonate spring deposits and how they are related to fluid circulation at depth and in association with faults

origin and diagenesis of quaternary travertine shrub fabrics rapolano terme central italy millimetre to centimetre sized arborescent shrub like calcite precipitates are common constituents of hot water travertine shallow pool deposits of quaternary age at rapolano terme tuscany italy in the presently forming travertines the shrubs consist of apparently random associations of i micrite aggregates and ii subhedral to euhedral rhombic spar crystal aggregates in thin section the micrite aggregates appear dark and the spar rhomb aggregates light giving the shrubs a mottled appearance travertines are basically produced by caco3 precipitation due to degassing and evaporation of the spring waters although biological influence may also stimulate precipitation the formation of masses of erect shrubs rather than dense crystal crusts that form on slopes is probably due to limited water flow in the pool environments microbes including bacteria and diatoms are important influences on shrub microfabric and external shape the micrite aggregates are associated with bacteriform bodies seen as tiny rods and spheres the micrite precipitates around these bodies and in adjacent biofilm spar rhomb precipitation appears to be external to the biofilm and may be related to the presence of diatoms which are locally closely associated with the spar rhombs although an essentially inorganic origin particularly for the more euhedral rhombs cannot be ruled out in the older quaternary travertines the original microfabric of the shrubs has been diagenetically altered the original mottled appearance of the shrubs has become uniformly dark and micritic and the evidence for the dual micritic and spar rhomb origin of the shrubs is obscured or destroyed spar micritization of the shrubs is probably due to abiotic and locally biotic dissolution previous studies did not recognize the diagenetic micritization and attributed shrub formation entirely to bacterial activity

seismic reflection imaging of karst in the persian gulf implications for the characterization of carbonate reservoirs karstification positively and negatively affects the quality of carbonate reservoirs for example dissolution and brecciation can increase porosity and permeability whereas cavern collapse or cementation driven by postkarstification fluid flow may occlude porosity and reduce permeability karst may also pose challenges to drilling because of the unpredictable and highly variable porosity and permeability structure of the rock and the corresponding difficulty in predicting drilling mud weight when combined outcrop petrographic and geochemical data can constrain the style distribution and origin of seismic scale karst which may provide an improved understanding of carbonate reservoir architecture and allow development of safer drilling programs however relatively few studies have used seismic reflection data to characterize the regional development of seismic scale karst features in this study we use time migrated two dimensional seismic reflection data to determine the distribution scale and genesis of karst in a 3 km thick 9800 ft thick jurassic miocene carbonate dominated succession in the persian gulf we map 43 seismic scale karst features which are expressed as vertical pipe columns of chaotic reflections capped by downward deflected depressions that are onlapped by overlying strata the columns are up to 2 km 6500 ft tall spanning the upper jurassic to upper cretaceous succession and are up to 5 5 km 18 000 ft in diameter we interpret these pipes to have formed in response to hypogene karstification by fluids focused along preexisting faults with hypogene generated depressions enhanced by epigene processes during key intervals of exposure our study indicates that seismic reflection data can and should be used in conjunction with petrographic and geochemical techniques to determine the presence of hypogene karst plays and to help improve the characterization of carbonate reservoirs and associated drilling hazards

geothermal exploration of paleozoic formations in central alberta this study explores the distribution of paleozoic formations in the central alberta basin and investigates rock properties with regard to their usability as geothermal reservoirs the study area of this regional scale investigation is about 160 km 200 km in size and located around edmonton where the basin depth ranges between 1 8 and 3 5 km a three dimensional 3d geological model was developed based on stratigraphic tops from about 7000 wells from the database of the alberta geological survey ags spatial distribution and thickness of deep formations were established in the 3d geological model porosity and permeability of four devonian carbonate formations cooking lake leduc and nisku formations and wabamun group were investigated using data from more than 50 000 core analyses average porosity of the devonian strata in the study area ranges from 4 5 nisku to 8 7 wabamun average permeability is between 3 5 10 15 m2 wabamun and 26 10 15 m2 leduc the distribution of both param

fracture networks and strike slip deformation along reactivated normal faults in quaternary travertine deposits denizli basin western turkey abstract the denizli basin in the west anatolian extensional province in western turkey is known for its numerous quaternary travertine occurrences travertine morphology is often dependant on the relative position of the deposition with respect to basin bounding faults the travertine occurrences examined in this study are situated at the intersection of the locally e w oriented denizli basin and the adjacent ne sw oriented baklan graben in the ne based on an extensive field campaign including lidar scanning several high resolution fault fracture maps of five large quarries 300 m in length and 60 m in height are constructed in which this world class travertine deposit is currently excavated a structural analysis is performed in order to determine the tectonic overprinting of the travertine body and to derive the stress states of the basin after travertine deposition the mostly open non stratabound joints are several tens of metres long and often bifurcate creating a dense fracture network minor infill of the joints resulted in the presence of a few colour banded calcite veins based on the e w ne sw and nw se orientation of three dominant joint sets it is concluded that the joint network is caused by local n s extension alternated by nw se and ne sw extension exemplifying the presence of stress permutations in the quaternary high angle e w to wnw ese faults cross cut the quarries faults are filled with travertine debris and clastic infill of above lying sedimentary units indicative of the open nature of the faults the specific e w fault orientation in the locally e w trending denizli basin indicates that they initiated as normal faults a paleostress inversion analysis performed on kinematic indicators such as striations on the clayey fault infill and the sinistral displacement of paleosols shows that some of the normal faults were reactivated causing left lateral deformation in a transient strike slip stress field with a ne sw oriented 1

corals on seamount peaks provide evidence of current acceleration over deep sea topography geological and physical studies of seamounts have suggested the existence of distinct deep sea habitats characterized by exposed rocky bottom and a unique current regime1 9 however few biological data have been collected for deep seamounts10 12 here we present some of the first quantitative observations of hard bottom non hydrothermal fauna in the deep sea these observations show that black corals antipatharians and horny corals gorgonians present on the slopes of a multi peaked seamount are more abundant near peaks compared with mid slope sites at corresponding depths on narrow peaks corals are most abundant on the crest whereas on wide peaks coral densities are highest at the edge of the crest the abundance of corals also increases on knobs and pinnacles physical models and observations2 4 9 13 15 together with our direct measurements suggest that the seamount topography affects the local current regime corals appear to benefit from flow acceleration and some of their patterns of distribution can be explained by current conditions these results suggest that suspension feeders have some potential as indicators of prevailing currents at deep hard bottom sites

characterization and discrimination of paleokarst breccias and pseudobreccias in carbonate rocks insight from ordovician strata in the northern tarim basin china abstract ordovician carbonates in the central and southern halahatang area of the tarim basin host highly productive hydrocarbon reservoirs previous studies suggest that the yingshan and yijianfang formations the primary producing intervals have been extensively karstified however the current author has not observed significant karst features in the formations based on the detailed study of 380 m long cores from 16 wells in the current study true breccias are only identified in two wells in the lianglitage formation including crackle and mosaic breccias as well as chaotic clast supported breccias the breccias are interpreted as karst related breccias that formed in near surface environments during pre silurian subaerial exposure and timing of karstification probably coincided with eustatic sea level fall caused by the middle katian glaciation widespread karst features of the yijianfang and yingshan formations identified as breccias or sediment filled cavities in many previous studies are actually only a mottled fabric pseudobreccia caused by selective diagenetic alteration and infiltration of bitumen in the deeper subsurface the color difference between pseudoclasts and pseudomatrix does not reflect a mixture of clasts and cave sediments but instead is characterized by distinct nevertheless commonly subtle variations in the limestone texture and whether bitumen is present one the basis of core and thin section observations sem scanning electron microscope and xrd x ray diffraction analyses the author presents criteria to distinguish karst breccias and pseudobreccias that can be applied to other similar carbonate deposits discrimination between karst breccias and nodular limestones is also presented differentiation of karst and pseudokarst features serves not only an academic interest but also has important applications for the exploration and development of carbonate reservoirs

geologic and resource assessment of the upper devonian grosmont and upper ireton formations central grosmont shelf complex alberta canada the devonian grosmont and upper ireton gui formations of northeastern alberta contain between 300 and 574 billion bbl of in situ bitumen the gui stratal succession shallows upward and is partitioned into five progradational shallow marine sequences although matrix porosity is highest within intertidal deposits commonly 20 30 matrix permeability is similar for subtidal and intertidal facies commonly 10 3000 md reservoir zones are 29 98 ft 9 30 m thick and from oldest to youngest include the a1 a2 b c1 c2 d1 d2 d3 and upper ireton because of truncation beneath the sub cretaceous unconformity the gui thins from 656 ft 200 m within the western part of the study area to an erosional edge within the easternmost part intertidal facies most commonly underlie the sub cretaceous unconformity and are commonly karsted karst breccia and associated fractures occur within thin 3 20 ft 1 6 m intervals that are parallel to bedding and most abundant in proximity 164 328 ft 50 100 m to the unconformity within the study area bitumen is concentrated above 475 ft 145 m above sea level and in place bitumen is estimated at 58 billion bbl 9 2 106 m3 the greatest in place bitumen volume 66 is associated with the d2 d3 and upper ireton intervals a proof of concept numerical model evaluates the potential effectiveness of steam assisted gravity drainage enhanced oil recovery within the gui the model suggests bitumen recovery as high as 189 000 bbl over a 20 yr period with an injector producer spacing between 33 and 41 ft 10 and 12 m

dolomitization and calcitization of the devonian grosmont formation northern alberta abstract the grosmont formation upper devonian comprises a platform carbonate sequence which extends over 100 000 sq km in the subsurface of alberta and contains extensive areas of calcitized dedolomitized dolomite reservoir rocks hydrocarbon content of the grosmont formation is estimated to be 50 109 m3 of 7 api gravity oil with bitumen recovery rates as high as 70 percent using thermally enhanced recovery environments of deposition in the grosmont formation range from subtidal and intertidal to supratidal early stratigraphically controlled and later cross cutting dolomites are observed dissolution fabrics are generally related to the uppermost dolomitized units of the grosmont formation below an unconformity which overlies paleozoic rocks calcitization textures are found in limestone and dolomite units and do not bear any relationship to the unconformity petrographic examination shows that calcitization of dolomite occurs in different forms large 0 25 0 5 mm dolomite rhombs observed floating in micrite or at calcitic micrite dolomite contacts have cores replaced by calcite dolomite rhombs that are not calcitized contain cloudy cores with abundant calcite inclusions in some samples fragments of dolomite rhombs are observed with the cores dissolved away indicating that part of the calcitization process involves dissolution a complete range from dolomitic rocks that show no evidence of calcitization to calcitic rocks with the textures of sucrosic dolomites are observed late calcite cements filling the remaining available pore space are also related to the calcitization process there is a strong tendency for dolomites from stratigraphic units to be grouped by their isotopic compositions three phases of dolomitization are interpreted in the grosmont formation an early sabkha dolomite upper grosmont 3 dolomites formed during reflux of hypersaline brines upper grosmont 2 and dolomites related to waters expelled from shales during burial lower grosmont further dolomites in each unit tend to be depleted in the heavy isotopes of both carbon and oxygen with increasing degree of dissolution and or calcitization the geological and geochemical evidence indicates that calcitization was early and related to dolomitization probably with a later stage that took place during uplift and the entry of meteoric water along the unconformity

detailed topography of the devonian grosmont formation surface from legacy high resolution seismic profiles northeast alberta abstractthe devonian grosmont formation in northeastern alberta canada is the world s largest accumulation of heavy oil in carbonate rock with estimated bitumen in place of 64 5 109 m3 much of the reservoir unconformably subcrops beneath cretaceous sediments this is an eroded surface modified by kartstification known as the sub mannville unconformity smu we studied the reanalysis and integration of legacy seismic data sets obtained in the mid 1980s to investigate the structure of this surface standard data processing was carried out supplemented by some more modern approaches to noise reduction the interpretation of these reprocessed data resulted in some key structural maps above and below the smu these seismic maps revealed substantially more detail than those constructed solely on the basis of well log data in fact the use of only well log information would likely result in erroneous interpretations although features smaller than about 40 m in radius cannot be easily discerned at the smu

parasequence architecture in a low accommodation setting impact of syndepositional carbonate epikarstification mcmurray formation alberta canada abstract the sparrow paleovalley spv is situated in the southwest corner of the mcmurray sub basin alberta canada and drained a portion of the grosmont highlands on a sub cretaceous paleotopographic surface the regional stratigraphic architecture of the lower cretaceous mcmurray formation in spv comprises a series of regressive parasequences ps organized into depositional units du the latter of which are separated by regionally mappable flooding surfaces isopach maps of individual dus show that in general they have a consistent thickness although stratal thickening of dus occurs in the landward part of the spv and extends over an area of 400 km2 this stratal thickening ranges from 21 to 45 and is accompanied by increases in both the abundance of soft sediment deformation structures ssd and normal micro faults in pss and an increase in the number and thickness of pss the thickness disparity between the over thickened zone compared to the rest of the spv is statistically significant and points to an external control on the accumulation of dus the mcmurray formation unconformably overlies a complex distribution of devonian strata that subcrop at the sub cretaceous unconformity below the spv devonian strata include from east to west oldest to youngest the beaverhill lake woodbend and winterburn groups in the western reaches of the spv mcmurray fm deposits overlie and are flanked by strata of the woodbend and winterburn groups the latter of which experienced erosion and carbonate epikarstification when subaerially exposed subsidence through epikarstification of devonian carbonates generated localized deepening in the mcmurray sub basin which was infilled during deposition of dus and resulted in over thickening of mcmurray strata the correspondence of topographic lows on the sub cretaceous unconformity and over thickening of dus overlying these topographic lows indicates that active carbonate epikarstification of devonian strata was contemporaneous with deposition of the mcmurray formation

stability of shallow karstic caverns in blocky rock masses abstract the limiting relationship is explored between underground opening span and required cover height for stability in blocky rock masses characterized by a network of horizontal bedding planes and vertical joints understanding this relationship is crucial for the design of mining excavations in karstic terrain as typically encountered in carbonate rock masses we perform numerical analysis of multiple roof spans vs cover height geometries using the dda method to obtain the boundary curve between stable and unstable opening geometries our results indicate that for cavern spans of up to 18 m a low cover height vs opening span ratio of h b 0 33 is sufficient for stability for spans greater than 18 m the demand for cover height rapidly increases and it appears to stabilize at h b 1 0 for b 26 m and above to validate our numerical analysis results a unique case study is analyzed wherein a 40 m span karstic cavern the ayalon cave has been preserved below an active open pit mine in central israel with cover height of only 30 m thus rendering the cave marginally stable according to our model prediction indeed there is ample evidence of partial collapse of the roof in the cave the predictive capability of our model is further confirmed using two additional case studies in blocky rock masses each of which possesses very different mechanical parameters such as intact rock strength density and deformability suggesting that our model predictions remain valid as long the rock mass maintains a blocky structural configuration

pore size and pore throat types in a heterogeneous dolostone reservoir devonian grosmont formation western canada sedimentary basin the devonian grosmont formation in northeastern alberta canada is a giant heavy oil reservoir the main reservoir rocks are dolomitized and karstified platform and ramp carbonates and the best reservoir facies occur in the upper grosmont ugm units 3 and 2 in these units reservoir properties are highly heterogeneous hand specimen thin section uv and sem petrography as well as grading scales mercury capillary pressure curve analysis and statistics have been used to characterize reservoir heterogeneity our investigation led to a new pore size classification for carbonate reservoirs this new classification has four pore sizes microporosity pore diameters 256 mm a combination of microscopic observations and capillary pressure curve characteristics led to the recognition of four pore throat texture types on the microporosity scale and to five types on the mesoporosity scale microporosity pore types include 1 intracrystal dissolution porosity 2 pervasive intercrystal and intracrystal dissolution porosity 3 intergranular and or intercrystal porosity in grainstones and 4 primary or solution microporosity in mud matrix only in limestones mesoporosity pore types include 1 intercrystal porosity 2 solution enhanced intercrystal porosity 3 oversized porosity 4 intragranular solution porosity and 5 intergranular solution porosity some of these types are homogeneous e g non fabric selective dissolution porosity and inte crystal primary porosity whereas others are heterogeneous generally hydrocarbon recovery efficiency is good in the homogeneous pore throat types but poor in the heterogeneous types reservoir heterogeneity has further been characterized by comparison and statistical analysis of plug and full diameter core fdc data that indicate 1 plug porosities on average are higher than fdc porosities 2 plug permeabilities on average are higher than fdc permeabilities 3 plug porosity and permeability show relatively good linear relationships in certain core intervals but fdc data do not and 4 generally the more homogeneous reservoir rocks have relatively high matrix porosity heterogeneity is common in grosmont dolostone reservoir rocks and affects overall reservoir quality at the megascopic scale the reservoir properties can be classified as homogeneous dual porosity and multilayered the dual porosity model has three subcategories fractured channeled and pressure solution derived

bacterial shrubs crystal shrubs and ray crystal shrubs bacterial vs abiotic precipitation hot water travertine deposits commonly contain shrub like morphologies on the centimeter to meter scale that range from highly irregular forms bacterial shrubs to features that display regular geometric patterns crystal shrubs and ray crystal crusts the bacterial shrubs have been previously recognized as the product of bacterially induced precipitation whereas the ray crystal crusts have been described as due to dominantly abiotic precipitation the bacterial shrubs have a highly irregular morphology similar to woody plants in contrast end member crystal shrubs display distinct crystal habits and regular repeating morphologies i e they commonly have attributes of noncrystallographic as well as crystallographic dendrites there is a complete gradational relationship between the bacterial shrubs and crystal shrubs ray crystal crusts are large fan shaped features composed of subparallel extremely coarse bladed crystals of calcite all three types bacterial shrubs crystal shrubs and ray crystal crusts contain either a dense tangle of bacterial body fossils and or micron sized pores the micropores are bacterial molds the immediately enveloping spar crystals around all three morphologic types are devoid of bacterial body fossils and micropores the bacterial shrubs crystal shrubs and ray crystal crusts are to differing degrees the product of bacterially induced precipitation as well as abiotic mineral precipitation the differences in morphology are due to the relative contribution of bacterially induced precipitation as compared with that of abiotic mineral precipitation bacterially induced precipitates can form in environments too chemically harsh or otherwise inhospitable for other taxa to thrive epiphyton and renalcis commonly formed in occult environments under conditions inhospitable to other taxa consideration of the published descriptions and interpretations concerning epiphyton and renalcis and by analogy the origin of bacterial shrubs have led to the conclusion that epiphyton and renalcis also are bacterially induced precipitates

deposition and diagenesis of mammoth hot springs travertine yellowstone national park wyoming u s a strata forming a 113 m long core through mammoth hot springs record the holocene evolution of this travertine accumulation from deposition as part of a lacustrine to a terraced mound environment the deposit is readily divided into four intervals 113 67 m carbonate cemented volcaniclastic with intercalated layers of travertine 67 60 m moderately pure travertine with some volcaniclastics 60 50 m carbonate cemented volcaniclastic rich interval and 50 0 m essentially pure travertine lithologic composition sedimentary structures and the rare ostracode fossils indicate that the lower 67 m predominantly accumulated in a lacustrine environment whereas the upper 40 m are terraced mound deposits all of the travertine is calcite some after aragonite layers of shrubs oncoids and peloids all bacterial in origin form the dominant allochems within the travertine stable isotopic carbon and oxygen values n 128 are strongly positively correlated and decrease up core 4 and 8 respectively reflec