impacts of various toc distributions on hydrocarbon generation abstract this study used numerical basin modeling methods to examine how various total organic carbon content toc distributions in formations with a fixed average toc impact the overall oil and gas generation ability different geological and geochemical conditions such as thickness and burial depth of the source formation thermal gradient organic richness degree of spread and types of kerogen are considered in this investigation the results show that there is a significant impact on the overall oil and gas generation capability especially when the source rocks are in the peak generation windows the magnitudes of oil and gas generation rates can vary by up to 5 10 times in some cases the general rules are that the more dispersion of toc in the formation or the thicker the formation and the greater the thermal gradient the larger the difference of generation rates between the distributions which favor hydrocarbon generation therefore in addition to the average toc richness the toc distribution in a source rock formation must also be considered when the petroleum potential of a basin is evaluated

integrated computer aided basin modeling applied to analysis of hydrocarbon generation history in a northern italian oil field abstract the application of reaction kinetics to the analysis of hydrocarbon hc generation processes requires a detailed temperature history of potential source rocks in order to obtain optimum results the necessary accuracy can be obtained by employing integrated computer aided basin modeling techniques to simulate the depositional history resulting in a continuous record of temperatures throughout the study area the technique has been applied to the analysis of an on off structure hc generation problem in a northern italian oil field the simulation of the geologic processes shows that low sedimentation rates and more importantly the high thermal conductivities of the carbonate rocks resulted in low temperatures throughout most of the geologic history of the study area which were followed by a sudden rapid temperature increase in the off structure area during the last 6 5 ma the calculated temperature history enables an accurate determination of the hc generation history using a kinetic approach which shows how hc generation is closely controlled by the sedimentation history and structural development and which also describes its relation to trap formation it also shows why hcs are generated at very low vitrinite reflectance levels i e peak oil generation at approximately 0 6 r o determination of the hc generation rate gives additional critical information as even source rocks located in apparently good potential zones at present i e in the on structure area can be of minor importance for a trap due to slow generation rates and consequent low expulsion efficiencies

hydrocarbon potential and depositional environment of the lower cretaceous black mudstones and shales in the coastal guangdong province china abstract the mesozoic especially the cretaceous sequences in the northern south china sea scs are important potential targets of oil and gas exploration however they are currently poorly understood we use organic petrology and geochemistry to evaluate the hydrocarbon potential and study depositional environment of the cretaceous black mudstones and shales from the dayawan section in the guangdong province china these mudstones and shales yield total organic carbon toc contents of 0 63 2 76 and most samples meet the requirement for higher toc source rocks organic matters in the mudstones and shales were sourced mainly from higher plants as well as subordinate benthic macroalgae organic petrology and geochemical data suggested that the organic matters were dominated by type iii and minor type ii and generally have low thermal maturity thus we evaluated the black mudstones and shales have a potential for hydrocarbon generation especially gas prone pr ph trace elements and mixture source of organic matter suggested that these black mudstones and shales formed in a coastal lacustrine environment characterized by weakly oxidizing weakly reducing conditions and low salinity a marine transgression developing in the middle part of the section was recognized generally the northern scs which exhibits the more marine influence likely contains source rocks with higher toc contents and better organic matter types the cretaceous source rocks with higher liquid hydrocarbon generation potential may occur locally in the pearl river mouth basin

thermal basin modelling of the arauco forearc basin south central chile heat flow and active margin tectonics abstract the arauco basin is part of the coastal forearc domain in south central chile during its evolution since the late cretaceous it was subject to multiple deposition cycles and the erosion of lower bathyal to beach and lagoon sediments these different environments were established in alternating accretional and erosive subduction tectonic settings along the south andean active margin whereas the general development is well understood inconsistencies arise regarding the origin of the high thermal maturity of eocene coals and the estimates of vertical movements of the whole area during the cenozoic thermal modelling of this forearc basin provides new insights regarding its thermal evolution and evaluation of the magnitudes of subsidence and inversion results are based on the analysis of coal samples from surface outcrops mines and drill cores of ten onshore wells from enap sipetrol newly derived vitrinite reflectance vr r measurements indicated a temperature in the range of 135 150 c for the oldest sediment unit of the arauco basin which was reached in post eocene times furthermore 1d basin modelling techniques indicate scenarios that could explain the coalification values in the basin s sediments the models were calibrated against vr r data from drill core samples supplied by enap sipetrol a miocene and an oligocene subsidence inversion scenario were considered while neither could be securely discarded based on the modelling results furthermore it can be shown that the current thermal maturity was not reached by an increased heat flow hf or a deep subsidence only consequently a structural inversion accompanied by the erosion of 3 0 0 4 km depending on the locality in combination with a high hf of 64 4 mw m 2 is the best explanation of the available data the hf which is high for a forearc setting can be attributed to the increased temperature of the relatively young subducted nazca plate and an additional influence of ascending hot fluids from the subduction zone the maximum temperature gradient inferred is

the thermal history of the bowen basin queensland australia vitrinite reflectance and clay mineralogy of late permian coal measures abstract the thermal history of the bowen basin queensland australia has been investigated using vitrinite reflectance data and clay mineralogy vitrinite reflectance data combined with a study of clay mineral reactions indicates that the maximum temperatures which induced organic maturation of the bowen basin coals and extensive clay mineralisation are not related to deep burial metamorphism during the latest middle triassic earliest late triassic as previously believed the results of the present study indicate that the development of a zone of high heat flow in the latest late triassic had a major control on the thermal history of the bowen basin high palaeogeothermal gradients estimated in the northern bowen basin are interpreted to result from convective heat transfer during a hydrothermal event variable heat distributions due to localised fracture enhanced permeable zones acting as hot reservoirs in the deeper part of the basin may have been responsible for some significant local thermal anomalies in the lower coal measures the estimated palaeogeothermal gradients in the southern bowen basin also indicate high heat flow in the lower sections of the stratigraphy sections in the southern bowen basin however are believed to reflect a rock dominated semi closed system with low water rock ratio where rocks are impervious to circulating fluids and thus heat transfer may have occurred by conduction the correlation between vitrinite reflectance and clay mineralogy shows a delay in illitisation reaction relative to organic maturity for many illite smectite i s mixed layer clays in the northern bowen basin this phenomenon can be explained as a result of insufficient time for the completion of mineral reactions and a variable potassium supply in relatively impermeable rocks the relationship between i s expandability and vitrinite reflectance for the bowen basin data compared to basins with known tectonic regimes suggests a thermal history in a rift setting for the bowen basin the effect of thin igneous intrusions on clay mineral reactions is very limited intensive illitisation due to heating of intrusions can only be observed in narrow zones immediately adjacent to intrusive bodies this further demonstrates that mineral reactions are too slow to record the effect of extremely short heating duration in contrast to organic maturity indicators these differences between mineral and organic parameters aid in the identification of local contact metamorphic effects

influence of the conditions of deposition on the chemistry and the reflectance variations of the brent coals specular reflectance infrared i r microspectroscopy was performed in order to account for reflectance anomalies in the brent coal series bituminous coals of the upper jurassic of the north sea main bands of i r spectra recorded on a nicolet system 800 coupled with a nic plan microscope were integrated these data allowed us to relate two distinct reflectance trends top and basal brent coals to depositional conditions top brent coals may originate from reducing environments where organic matter was well preserved for this series defined as a reference series good correlations were obtained between the i r data based on oh aromatic and aliphatic c h as well as c o band intensity and maturity parameters such as vitrinite reflectance vr o and relative depth basal brent coals associated with coastal and upper delta plain environments may originate from more oxidizing depositional settings where organic matter was altered spectra exhibited strong oxygen bearing bands oh and c o and weak aliphatic c h bands because of such variations in the chemistry of vitrinites the reflectance measurements were strongly biased aromatic c h 3000 3100 cm 1 i r bands were also accurately studied the results suggest that aromatic c h concentration is rank controlled and independent of depositional setting large intra brent vr c variations observed in a single well 0 2 in 4 m depth were possibly related to a diagenetic oxidation process providing that all the samples were extracted from oxidizing environments those variations may also strongly correlate with an increasing degree of oxidation of the upper and coastal delta plain depositional settings these data suggest that vitrinite reflectance may be strongly influenced by oxidation and must be carefully handled when extrapolating r o data to the reconstruction of the thermal history of sedimentary basins infrared microspectroscopy is demonstrated to be particularly adapted to establish the oxidation of vitrinite that may lead to overestimation of r o values

development of microporosity in a micritic limestone reservoir lower cretaceous middle east abstract abundant intercrystalline microporosity is developed within the matrix of micritic limestones over several hundreds of meters of section in the thamama group lower cretaceous at sajaa field eastern u a e sediments in the upper shuaiba formation uppermost tamama group include muddy rudist algal coralgal and orbitolina dominated lithofacies matrix is composed of euhedral to subhedral micro rhombic low mg calcite crystals with average diameters of about 5 m microporosity development was not related to leaching chalkification of lithified micrite during post depositional emergence of the shuaiba formation features diagnostic of emergence are lacking in core below the upper contact of the unit matrix microporosity is believed to have been an early developed property of micritic limestones trace element compositions of matrix reflect a diagenetic process that involved conversion of a calcitic lime mud into micro rhombic micrite and microspar using a closed system geochemical model the observed matrix oxygen isotope compositions 18 o of 4 to 5 pdb are compatible with dissolution of aptian lime mud 18 o of 2 pdb and reprecipitation of calcite in fluids of marine composition under conditions corresponding to burial depths of 550 800 m porosity of 30 50 at 40 50 c closed system conditions are consistent with textural constraints for limited or arrested cementation in the matrix chemical compaction was responsible for partial occlusion of matrix microporosity as microporosity is decreased in zones of intense stylolitization slight corrosion of matrix crystals and leaching of peloids and orbitolina postdated cementation and chemical compaction during deep burial

coalification in the northern wildhorn nappe and adjacent units western switzerland implications for tectonic burial histories abstract vitrinite reflectance of fourteen eocene coal samples from the northern wildhorn nappe in the kander valley have been analyzed and compared to nine agewise similar coals from adjacent tectonic units the degree of coalification decreases regularly from semi anthracite in the kander valley to lignite in the plateau molasse the degree of coalification in the tertiary coals appears to be solely dependent on their tectonic history and indicates and estimated 6 km of burial by higher pennine nappes for the kander valley the rank at this locality low volatile bituminous to semi anthracite is significantly higher than in the border chain at beatenberg high volatile a bituminous the latter locality therefore was never buried deeper than about 4 km a further decrease in rank is found in the subalpine flysch and molasse high volatile b bituminous which in turn is significantly more mature than lignites from the folded plateau molasse at linden two samples of dogger coal from the pennine prealpes medianes are medium to low volatile bituminous that is intermediate between the kander valley and beatenberg their rank however was achieved before their final emplacement north of the wildhorn nappe by comparing calculated tti time temperature indices values for time depth burial curves with measured vitrinite reflectances maximum burial temperatures were estimated for the various tectonic units for the wildhorn nappe 160 180 c were obtained in the kander valley and 100 130 c in the border chain as a result of tectonic burial due to the thrusting by the pennine prealps sedimentary burial led to temperatures of 100 120 c in the subalpine molasse below the border chain prior to its thrusting

a theoretical study of large sea level oscillations in the western mediterranean large sea level oscillations up to 1 m amplitude and around 10 min period have been observed in several bays and harbors of the western mediterranean these oscillations appear to be associated with short period 10 min atmospheric pressure fluctuations amplitude of 1 5 mbar using a model with a flat shelf and a sloping bottom harbor we found that these oscillations were the result of a three way resonant coupling between an atmospheric gravity wave a coastally trapped edge wave and the normal modes of a harbor the amplification mechanism was studied for the harbor of ciutadella good agreement between the predicted and the observed frequencies and amplitudes is found

paleomagnetic dating of postglacial sediment offshore lake superior minnesota wisconsin u s a abstract four gravity cores and two piston cores obtained from offshore regions of lake superior were analyzed for variations in geomagnetic declination and inclination in natural remanent magnetization nrm sedimentation rates in offshore lake superior 20 cm 1000 yr are much slower than in great lakes environments where paleomagnetic dating has been applied before typically 1 m 1000 yr five of the six cores could be correlated on the basis of declination and four of the six could be correlated on the basis of inclination absolute age assignment to declination events by correlation to a radiocarbon dated core from lake st croix minnesota tentatively shows that sedimentation rates in lake superior have changed from relatively fast to relatively slow to intermediate values in postglacial times

thermal effects of zechstein salt and the early to middle jurassic hydrothermal event in the central polish basin deep gas potential in the polish basin may factor significantly in european geopolitics and thermal effects can influence that outcome there and elsewhere deep 3 km 9843 ft well data from the kujawy area of the central polish basin reveal average geothermal gradient 36c km thermal conductivity of mesozoic strata k 2 29 w m k and present day heat flow q 82 4 mw m2 that is 3 less than that obtained using the entire borehole the extrapolated surface temperature 6 2c is in good agreement with temperatures during the weichselian glaciation the thermal conductivity of the upper permian zechstein 4 89 w m k is in good agreement with values from the north sea and northern germany steady state heat flow theory one dimensional 1 d predicts present day temperature 199c at the base of zechstein cap rock at 6 km 19 685 ft depth in kujawy this is reduced just more than 10c by low zechstein thermal gradients 16 8c km because of thermal refraction two dimensional and three dimensional models of zechstein salt pillows can significantly negate this cooling effect however such effects appear absent in the kujawy wells studied a widespread early to middle jurassic 195 175 ma hydrothermal event appears to have reached maximum in the kujawy area a 455c paleotemperature at 7 km 22 966 ft depth carboniferous is predicted by 1 d conductive heat transfer however geologic evidence does not support this result the discrepancy is reconciled by convective heat transfer with upward fluid flow 3 3 10 10 m s 10 8 10 10 ft s resulting in a maximum paleotemperature of 273c at 7 km 22 966 ft depth despite a paleoheat flow of 142 mw m2 the trend of intensity of the hydrothermal event correlates with the present day heat flow trend hydrothermal event sites are subparallel to the major northwest southeast structural and regional heat flow trend whereas other sites as close as 14 km 45 932 ft and without hydrothermal event are not the decay of the hydrothermal event is consistent with localized cylindrical plumes 10 km 32 808 ft radius that cool by conduction results suggest a long term 185 m y structural control on heat flow linear regression to vitrinite paleotemperatures yields a 185 ma jurassic surface temperature of approximately 21 3c that is approximately 13c higher than the present day temperature for warsaw poland the duration of maximum reservoir and source rock paleotemperature 50 m y is contrary to the kinetics of nitrogen and co2 producing wells equilibrium thermodynamics predicts approximately 60 methane for present day kujawy reservoirs with considerable uncertainty that should be removed by anticipated new deep drilling

calculation of vitrinite reflectance from thermal histories a comparison of some methods vitrinite reflectance values ro calculated from commonly used methods are compared with respect to time invariant temperatures and constant heating rates two monofunctional methods one involving a time temperature index to vitrinite reflectance correlation tti ro and the other involving a log ro to depth correlation yield vitrinite reflectance values that are similar to those calculated by recently published arrhenius based methods such as easy ro the approximate agreement between these methods supports the perception that the easy ro algorithm is the most accurate method for the prediction of vitrinite reflectances throughout the range of organic maturity normally encountered however calibration of the e methods against vitrinite reflectance data from two basin sequences with well documented geologic histories indicates that although the easy ro method has wide applicability it slightly overestimates vitrinite reflectances in strata of low to medium maturity up to a ro value of 0 9 the two monofunctional methods may be more accurate for prediction of vitrinite reflectances in similar sequences of low maturity an older but previously widely accepted tti ro correlation consistently overestimates vitrinite reflectances with respect to other methods underestimation of paleogeothermal gradients in the original calibration of time temperature history to vitrinite reflectance may have introduced a systematic bias to the tti ro correlation used in this method also incorporation of tai thermal alteration index data and its conversion to ro equivalent values may have introduced inaccuracies

petroleum generation and accumulation in the golfo san jorge basin argentina a basin modeling study abstract the golfo san jorge basin located in patagonia is very important for the oil and gas production of argentina in spite of the long history of exploration and production few geochemical studies were performed until now for this study a set of possible source rocks was analyzed by organic geochemical and petrographical methods the samples of the pozo d 129 fm range from mature to overmature and contain from less than 0 5 to 2 45 toc there is some evidence indicating an algal origin of the more hydrogen rich kerogen present in part of the basin almost all the samples of pozo anticlinal aguada bandera and pozo cerro guadal fm are overmature toc values range from less than 0 5 to 2 5 the maturation of source rocks and generation expulsion and migration of hydrocarbons was evaluated by means of 1d and 2d basin models the 1d models constructed for the western part of the basin and 2d models applied for the eastern part both indicate maximum burial in miocene times the thickness of the tertiary at times of maximum burial ranged from 1000 to 1500 m and the generally small tertiary thickness now present in the fold belt region is assumed to be the result of erosion the main tectonic inversion took place in the late neogene the models strongly suggest that a magmatic event between 20 and 30 ma combined with the maximum burial at miocene times produced a very important pulse in hydrocarbon generation within the major part of the basin dated intrusive and extrusive magmatic rocks extended all over the basin account for this period of elevated heat flow migration pathways are extensively discussed for the 2d model probably major faults acted as important conduits for petroleum

the antarctic margin and its possible hydrocarbon potential abstract geological and geophysical data over the antarctic margin are reviewed to define those areas where thick sedimentary sequences occur which may have potential to source hydrocarbons where possible the waples lopatin model has been used to calculate whether the degree of maturation of the sediments is sufficient for hydrocarbons to have been generated significant sedimentary sequences occur along the continental margins of wilkes land western dronning maud land antarctic peninsula and ellsworth land and as basins or troughs on the continental shelf of prydz bay weddell sea and ross sea maturation assessments are possible for western dronning maud land eastern weddell sea western antarctic peninsula ellsworth land and ross sea regions within the great limitations of the data only western weddell sea and ross sea basins have maturation values sufficient for the generation of hydrocarbons

numerical modelling of the destructive meteotsunami of 15 june 2006 on the coast of the balearic islands a destructive tsunami like event locally known as rissaga waves occurring on 15 june 2006 in ciutadella harbour menorca balearic islands is reproduced by a numerical model forced by a travelling atmospheric disturbance the disturbance is reconstructed from microbarograph measurements being the only available instrumental data at the time of the event the model is verified based on two weaker 1997 events which were recorded by a number of bottom pressure recorders operating at that time on the menorca shelf in ciutadella inlet and adjacent platja gran inlet both 1997 events are numerically simulated and good agreement is achieved with observations in time frequency including eigenfrequencies of the affected inlets and wave heights subsequently the same model is applied to simulate the 2006 event the vigorous currents with speeds up to 400 cm s are found to occur specifically at those areas of the harbour where the most severe damage and sinking of boats had been reported maximum simulated sea level heights of 2 5 m were about one half of those reported by eyewitnesses this difference is apparently caused by quality and spatial resolution of bathymetry data however in general the model is capable of reproducing the event fairly well and can probably be used for future assessment and mitigation activities on the coasts of the balearic islands

odessa tsunami of 27 june 2014 observations and numerical modelling on 27 june a 1 2 m high wave struck the beaches of odessa the third largest ukrainian city and the neighbouring port town illichevsk northwestern black sea throughout the day prominent seiche oscillations were observed in several other ports of the black sea tsunamigenic synoptic conditions were found over the black sea stretching from romania in the west to the crimean peninsula in the east intense air pressure disturbances and convective thunderstorm clouds were associated with these conditions right at the time of the event a 1 5 hpa air pressure jump was recorded at odessa and a few hours earlier in romania we have utilized a barotropic ocean numerical model to test two hypotheses 1 a tsunami like wave was generated by an air pressure disturbance propagating directly over odessa experiment 1 2 a tsunami like wave was generated by an air pressure disturbance propagating offshore approximately 200 km to the south of odessa and along the shelf break experiment 2 both experiments decisively confirm the meteorological origin of the tsunami like waves on the coast of odessa and imply that intensified long ocean waves in this region were generated via the proudman resonance mechanism while propagating over the northwestern black sea shelf the odessa tsunami of 27 june 2014 was identified as a beach meteotsunami similar to events regularly observed on the beaches of florida usa but different from the harbour meteotsunamis which occurred 1 3 days earlier in ciutadella baleares spain mazara del vallo sicily italy and vela luka croatia in the mediterranean sea despite that they were associated with the same atmospheric system moving over the mediterranean black sea region on 23 27 june 2014

post alleghanian unroofing history of the appalachian basin pennsylvania from apatite fission track analysis and thermal models results of apatite fission track analyses on 29 ordovician through permian sandstones from the appalachian basin in pennsylvania are presented ages range from 111 17 to 184 10 ma mean track lengths of 10 71 0 29 to 13 10 0 17 m with unimodal negatively skewed length distributions are indicative of slow cooling the data separate into two groups on an age versus mean length plot the younger group 111 144 ma is found in the structural depressions of the anthracite basin and the broad top basin and adjacent appalachian plateau the older group 144 184 ma is found in the structurally higher southwestern appalachian plateau and juniata culmination and adjacent central plateau fission track data suggest that the basin cooled slowly after the alleghanian orogeny with culminations cooling earlier than depressions cooling histories modeled from apatite fission track data with maximum temperatures constrained by vitrinite reflectance indicate cooling beginning soon after the alleghanian orogeny except in the juniata culmination which apparently experienced synorogenic cooling and unroofing during formation of the underlying duplex model cooling histories and available geologic information indicate that the foreland basin did not experience mesozoic reheating unroofing histories were modeled from fission track cooling histories using heat flow estimates and burial depths derived from vitrinite reflectance profiles the models suggest that the unroofing history of the appalachian basin in pennsylvania can be divided into three episodes an initial episode of relatively rapid cooling and unroofing late permian early jurassic is attributed to flexural rebound of the foreland in response to erosional removal of alleghanian topographic load initial unroofing rates are higher in eastern pennsylvania than in the west consistent with a flexural model an episode of little to no unroofing middle jurassic late oligocene began contemporaneously with the inception of drift at the atlantic continental margin at this time unloading of the orogen was replaced by subsidence and sedimentation on the new margin without flexural rebound the driving force for unroofing of the basin was removed and unroofing slowed greatly an episode of rapid unroofing over the full width of the basin occurred from the miocene to the present although the driving mechanism for unroofing at this time has not been identified it is consistent with increased sedimentation rates in the middle atlantic offshore basins for the same period

a common source rock for egyptian and saudi hydrocarbons in the red sea the northern red sea area hosts a classic triple junction of the red sea gulf of aqaba and gulf of suez rifted basins the sedimentary succession here can be divided into prerift pre miocene and synrift miocene and post miocene megasequences the prerift section has been penetrated in only a few wells drilled on the western egyptian side of the red sea whereas the synrift section is known on both the egyptian and the saudi sides of the red sea although the synrift units on both sides of the water are similar in facies thicknesses and depositional environments they have different stratigraphic nomenclatures the northern red sea consists of elongated troughs separated by elongated structural highs both of which trend northwest southeast gulf of suez trend these highs are dissected by cross elements trending northeast southwest gulf of aqaba trend and east northeast west southwest and are looked upon as strike slip faults dislocating these highs identified rich source rocks are present in the upper senonian carbonates the sudr and duwi formations on the western side of the sea the early miocene rudeis formation burqan group and the middle miocene kareem and belayim formations maqna group the pre miocene and the early miocene source rocks host oil prone kerogen whereas the middle and late miocene source rocks contain oil and gas prone kerogen all of these source rocks are sufficiently mature copyright 1997 the american association of petroleum geologists all rights reserved 1manuscript received january 18 1996 revised manuscript received october 11 1996 final acceptance march 21 1997 2faculty of science uae university p o box 17551 al ain united arab emirates we are especially grateful to the egyptian general petroleum corporation for supplying the materials and the necessary data on which the present work is based and the permission to publish it we also thank c g st c kendall and a e m nairn who read the early draft of this paper and offered valuable comments thanks to aapg reviewers d waples r j murris w maze and an anonymous reviewer for their constructive comments which we have used to improve our paper we acknowledge g cole bhp petroleum for granting permission to use some of his previous work

chalk porosity and sonic velocity versus burial depth influence of fluid pressure hydrocarbons and mineralogy seventy chalk samples from four formations in the overpressured danish central north sea have been analyzed to investigate how correlations of porosity and sonic velocity with burial depth are affected by varying mineralogy fluid pressure and early introduction of petroleum the results show that porosity and sonic velocity follow the most consistent depth trends when fluid pressure and pore volume compressibility are considered quartz content up to 10 has no marked effect but more than 5 clay causes lower porosity and velocity the mineralogical effect differs between p wave and shear velocity so that smectite bearing chalk has a high poisson s ratio in the water saturated case but a low value in the dry case oil bearing chalk has up to 25 units higher porosity than water saturated chalk at similar depth but similar velocity probably because hydrocarbons prevent pore filling cementation but not pore structure stiffening cementation in this presumably water wet chalk these results should improve the modeling of chalk background velocity for seismic inversion analysis when describing the porosity reducing process pore volume compressibility should probably be disregarded when correcting for fluid pressure because the cementing ions originate from stylolites which are mechanically similar to fractures we find that cementation occurs over a relatively short depth interval

migration of orogenic fluids through the siluro devonian helderberg group during late paleozoic deformation constraints on fluid sources and implications for thermal histories of sedimentary basins abstract fluid inclusion data and fracture filling cement fabrics in deformed but non overthrusted carbonate and siliciclastic rocks of the siluro devonian helderberg group central appalachians indicate post cementation late paleozoic migration of high pressure high temperature fluids void filling quartz and calcite cements contain secondary two phase fluid inclusions liquid vapor which occur in annealed microfractures most melting temperatures last occurrence of ice are 20 to 25 c which correspond to salinities of greater than 22 equivalent wt nacl pressure corrected liquid vapor homogenization temperatures are 200 to 300 c and greatly exceed maximum paleotemperatures 150 c given by conodont cai values vitrinite reflectance illite crystallinity or temperatures calculated from known sedimentary overburden completely cemented sandstone and limestone also have multiple crosscutting trains of secondary hydrocarbon inclusions hydrocarbon inclusions occur along deformation microstructures in cements some hydrocarbon inclusion trains crosscut cement filled fractures the nature of occurrence of the secondary inclusions suggests that fluids moved along intracrystalline deformation microstructures either during or after late paleozoic deformation rare fractures contain transported skeletal grains exotic clasts lithologies different from wall rock recemented clasts of fracture filling cement and mud cement clasts contain solid inclusions of mud and skeletal fragments and indicate several episodes of particle transport cementation and refracturing prior to final fracture filling and cementation these fracture fills locally crosscut stylolites coarse grained poorly sorted clastic fracture fills suggest migration of rapidly moving fluids which were capable of transporting clasts through fracture conduits under deep burial conditions conduction calculations place upper limits on size and duration of thermal anomalies which were caused by extrabasinal fluids these calculations indicate that hot fluid migration events most likely were short lived heat transfer by extraformational fluids moving along faults and fractures may have been the mechanism by which thermal anomalies developed in the helderberg group stratigraphic constraints suggest that likely sources for the hot brines are overthrusted terranes to the east of the study area possible stratigraphic horizons which were sources for the overpressured hot fluids may have been thick cambrian shales which are important detachment horizons for major late paleozoic thrust sheets in the eastern valley and ridge province east of the study area fluids may have migrated during thrusting along thrust faults which ramp upwards from east to west into stratigraphically higher units thrust faults ultimately die out in devonian units some of the dissolved ions in the secondary two phase inclusions may have been incorporated when shale derived fluids moved through silurian evaporites or cambro ordovician carbonates which contain evidence of cryptic evaporites potential source rocks for secondary hydrocarbon inclusions may have been lower silurian through lower devonian strata based on lopatin modeling and assuming that migration occurred during late paleozoic deformation this study may help to explain many apparently anomalous geologic phenomena in deformed foreland basin sediments it also has implications for tracking migration pathways for fluids which facilitate regional scale deformation in fold and thrust belts and how tectonic fluids may affect the rocks through which they move

determination of critical parameters for evaluating coal measure shale gas in china abstract coal measure shale is one of the most abundant types of marine continental shales in china two sets of typical coal measure shales in china are developed in the shanxi formation ordos basin and in the longtan formation guizhou province in this study thermal simulation rock pyrolysis and x ray diffraction experiments were used to analyze four coal measure shale samples collected from typical areas of china based on the study of hydrocarbon generation process of the samples the lower limits of thermal maturity ro of favorable and target areas for coal measure shale were 1 8 and 2 5 respectively the threshold ro value of oil generation in coal measure shale was preliminarily inferred to be 0 6 the gaseous hydrocarbon production per unit of s1 s2 after the gas generation threshold was linearly and positively correlated with ro the lower limits of total organic carbon toc corresponding to the favorable and target areas were 2 45 wt and 2 84 wt respectively combined with x ray diffraction experiments the diagenetic stage and the hydrocarbon generation model of coal measure shale were established and could be divided into four evolutionary stages the results of this study have direct scientific and practical significance for the evaluation of gas content and selection of areas in china for the extraction of coal measure shale

seismic stratigraphic analysis of the punta del este basin offshore uruguay south america the punta del este basin of offshore uruguay is one of a series of mesozoic sedimentary basins along the eastern seaboard of south america the basin resulted from continental rifting of an older gondwana landmass this rifting led to the initiation of the south atlantic ocean the tectonic and stratigraphic history of the basin can be characterized by a three phase evolution with each phase involving a separate and distinct basin geometry style of faulting and lithostratigraphic succession the rift phase deposited predominantly continental siliciclastics of neocomian age arranged in a number of syndepositional assymetric trap door grabens this phase is overlain by a largely unfaulted succession of continental to marine rocks of the sag basin phase of aptian to maastrichtian age these rocks record an overall marine transgression the passive margin phase is represented by a thick sequence of tertiary sediments that postdate rift related tectonism and correspond to sedimentation along the margin of the newly opened south atlantic ocean the punta del este part of the greater salado basin is relatively unexplored with only two wells having been drilled both in the updip part of the basin these two wells have contributed some understanding of the stratigraphic succession but have failed to adequately assess the basin s true hydrocarbon potential this paper constitutes one of the first detailed comprehensive published accounts of this basin and is a prerequisite for future exploration in the area

fresh evidence relating the great adriatic surge of 21 june 1978 to mesoscale atmospheric forcing 1 on the morning of 21 june 1978 exceptional sea level oscillations with a trough to crest height of 6 m and a period of 10 20 min were observed in vela luka bay slightly less pronounced variability was observed in a wider middle and south adriatic east coastal area and with some delay along the west coast in this paper one of the original hypotheses put forward to interpret the event relating it to a mesoscale air pressure disturbance is reconsidered by using all the available data as well as state of the art meteorological and oceanographic models a fresh look at the meteorological data confirms that the atmospheric disturbance propagated at about 22 m s in a northeastward direction additionally the data suggest that it had the shape of the boxcar function characterized by an air pressure offset of 3 mbar and duration of 10 min the meteorological model employed weather research and forecasting wrf advanced research wrf proves unable to reproduce the mesoscale disturbance coinciding with the surge but it shows that the background atmospheric conditions were favorable for the development of such disturbances the oceanographic model advanced circulation model for shelves coasts and estuaries two dimensional depth integrated forced by the described air pressure disturbance successfully reproduces sea level variability in vela luka bay reaching a few meters and thus surpassing the inverted barometer response by two orders of magnitude the enhancement appears to be due to a four phase process the model also suggests that the scattering due to the variable bathymetry and the reflection from the east adriatic coast resulted in waves that returned towards the west coast and generated considerable sea level activity there

possible atmospheric origin of the 7 may 2007 western black sea shelf tsunami event 1 the paper examines the possibility that tsunami event recorded in the western black sea on 7 may 2007 was triggered by a traveling atmospheric disturbance as meteotsunamis are favored by specific synoptic conditions we inspected available ground and sounding observations european centre for medium range weather forecasts reanalysis fields and satellite based products and compared them to the documented mediterranean meteotsunamis we found an atmospheric disturbance traveling toward 30 nne with amplitude of 2 3 hpa and propagation speed of about 16 m s passing through few tens of kilometers wide pathway over the region affected by the tsunami this disturbance occurred in the lower troposphere but it was capped by instable convective cell that preserved gravity disturbance s coherence over a region at least 150 km long an ocean modeling study showed that such a disturbance is capable of generating large tsunami waves and strong currents over the shallow regions following the observations over the region where maximum sea level oscillations have been documented therefore this event has a potential to be classified as a meteotsunami the first of such kind in the black sea

on the reconstruction of the transfer function for atmospherically generated seiches a method recently proposed to separate source and topographic effects in observed tsunami spectra is revised and applied to atmospherically generated seiches the method is used to investigate the origin of abnormal seiche events rissaga waves recorded in the region of ciutadella balearic islands the reconstructed open sea source spectra and the observed atmospheric pressure spectra are combined to estimate the transfer function between the atmosphere and the sea surface this function is used to predict sea level spectra for given locations near to the coast theoretically computed spectra for two rissaga events are in good agreement with observations

misr based passive optical bathymetry from orbit with few cm level of accuracy on the salar de uyuni bolivia abstract we demonstrate that under ideal circumstances passive optical measurements can yield surface water depth estimates with an accuracy of a few centimeters our target area is the salar de uyuni in bolivia it is a large active salt flat or playa which is maintained as an almost perfectly level and highly reflective surface by annual flooding to a mean depth of 30 50 cm we use misr data to estimate spatial and temporal variations in water depth during the waning portion of the 2001 flooding cycle we use a single icesat laser altimetry profile to calibrate our water depth model though the salt surface is probably the smoothest surface of its size on earth with less that 30 cm rms height variations over an area of nearly 104 km2 it is not completely featureless topography there includes a peripheral depression or moat around the edge of the salt and several sets of prominent parallel ridges with 5 km wavelength and 30 cm amplitude the process by which these features form is still not well characterized

petroleum geology of southern iraq subsurface relations of the albian rocks in southern iraq are postulated from the study of lithofacies electrical well logs petroleum occurrences geothermal source rocks maturation and hydrogeologic mapping from these studies an evaluation of the commercial potential for oil in the nahr umr formation became feasible it appears that a petroliferous belt exists in the marine marginal facies of the lower albian nahr umr sandstone the oil in the nahr umr reservoirs has probably been generated in deep lower cretaceous source rocks and may have started to generate as early as paleocene time the upper shale beds of the nahr umr formation supersedes the ahmadi shale formation which acts as a cap rock to the albian reservoirs in kuwait and neutral zone hitherto no economic oil trap has been discovered in the upper albian mauddud formation that overlies the nahr umr and underlies the ahmadi in southern iraq

time and temperature in petroleum formation application of lopatin s method to petroleum exploration n v lopatin in the soviet union has developed a method for taking both time and temperature into account as factors in thermal maturation of kerogen lopatin s time temperature index of maturity tti values correlate with the thermal regimes corresponding to generation and preservation of hydrocarbons because such information is potentially of great interest for oil exploration a calibration and evaluation have been made of lopatin s method within the limitations of the data presently available the following statements can be made 1 the rate of the chemical reactions involved in thermal maturation of organic material appears to double with every 10 c 18 f rise in temperature 2 threshold values of lopatin s time temperature index of maturity tti are 15 onset of oil generation 75 peak oil generation 160 end oil generation 500 40 oil preservation deadline 1 000 50 oil preservation deadline 1 500 wet gas preservation deadline 65 000 dry gas preservation deadline 3 tti values calculated from lopatin reconstructions consistently agree with other maturation parameters commonly used by petroleum geochemists potential applications of lopatin s method for oil exploration include timing of oil generation calculation of volume of hydrocarbons generated within a basin and determination of economic deadlines

side scan targets in lake superior evidence for bedforms and sediment transport a high resolution side scan sonar survey of the lake bed off the keweenaw peninsula lake superior demonstrates that bottom currents are affecting lake bed morphology at depths up to 240 m numerous lineations which run parallel to the shore appear to be sand ribbons a field of sedimentary furrows which occurs in one area demonstrates the long term directional stability of the near bottom flow large 100 300 m in diameter 2 5 m deep unusual ring like or arcuate depressions are common throughout the western half of lake superior these rings themselves do not appear to have been formed by bottom currents but may have developed as water was released by the rapid compaction of glacial sediments which underlie the lake bed off the keweenaw peninsula the forms of the rings have been modified by bottom currents the bottom currents which have modified the lake bed are probably generated when storms cross the lake at times when it is poorly stratified

palynofacies analysis of sediments from the cote d ivoire ghana transform margin preliminary correlation with some regional events in the equatorial atlantic abstract analyses of the palynofacies and sporomorph thermal alteration indices tai of sediments from ocean drilling program odp sites 959 to 962 in the cote d ivoire ghana transform margin west africa were undertaken to 1 determine the source and depositional conditions of the organic matter in the sediments 2 refine a paleobathymetric curve derived from other data for site 959 which drilled the most continuous sedimentary sequence from pleistocene to albian and 3 interpret the paleothermal history of the area twelve types of dispersed organic matter were identified amorphous organic matter aom marine palynomorphs algae resins black debris yellow brown fragments black brown fragments cuticles plant tissue wood sporomorphs and fungi the relative abundances of these organic matter components at each site were analyzed using cluster analysis resulting in the identification of seven palynofacies assemblages at site 959 five each at sites 960 and 961 and four at site 962 amorphous organic matter which is chiefly marine derived black debris and wood have played the most significant role in defining palynofacies assemblages the palynofacies assemblages show some correlation with lithologic units sediment sources and depositional environments previous palynofacies studies in passive margins have demonstrated that changes in the ratio of aom to terrestrial organic matter are related primarily to proximal distal positions of depositional environments relative to the shoreline however this assumption does not always hold true for a transform margin where tectonic factors play an important role in the organic matter distribution at least in the early stages of evolution lithofacies ccd paleodepths for the north atlantic trace fossil association benthic foraminifera and palynofacies data were the criteria used for reconstructing a paleobathymetric curve for site 959 a cyclicity in the organic matter distribution of the upper miocene to lower pliocene pelagic sediments could be related to fluctuations in productivity of biosiliceous and calcareous organisms and sedimentation rates a drastic increase in the amount of aom and a decrease in black debris and wood in the carbonate and clastic rocks lithologic unit iv overlying the tectonized albian sediments lithologic unit v at sites 959 and 960 coincide with the presence of an unconformity qualitative color analysis of palynomorphs was undertaken for all sites although the main focus was on site 959 where detailed organic geochemical data were available at site 959 tai values indicate an immature stage of organic maturation 2 except for the claystone samples between 1012 52 and 1036 5 mbsf and one limestone sample at 1043 4 mbsf reaching peak levels of 2 58 to 3 0 in the tectonized albian sediments below the unconformity these tai values show a positive correlation with the tmax values derived from rock eval pyrolysis data the highest values recorded in the basal tectonized units at all the sites sites 960 962 have mean values between 2 25 and 3 13 may be related to high heat flow during the intracontinental to syntransform basin stage in the region

the mad sea phenomenon in the strait of sicily sea level observations at cape bon tunisia and mazara del vallo sicily show that large coherent oscillations exist across the strait of sicily with significant energy bands centered at periods of 35 3 41 6 50 6 75 8 and 134 5 min whose possible structure is confirmed by a numerical approximation to the gravitational barotropic normal modes with realistic topography it is observed that these oscillations are related to the passage of synoptic weather systems over the region an investigation on the configuration phase velocity and direction of approach of atmospheric disturbances over the region suggests that the oscillations in the strait of sicily could be forced by instabilities that develop in large scale low pressure fronts that propagate as pressure gravity waves with an approximate phase speed between 24 and 30 m s21

paleolimnological records of climatic change in north america lacustrine fossil records provide long time series of data on limnological and climatic conditions these data are useful for establishing natural patterns of climate variability and for generating testable hypotheses about atmospheric circulation and climate ecosystem linkages shoreline features can indicate past lake level fluctuations that may reflect changes in moisture balance but often these records are discontinuous and are evidence of only extreme conditions the organisms geochemistry and sedimentology of lake sediments may provide a more continuous sequence of direct and indirect lake climate interactions in the past the most clearly interpretable paleolirnnological records of climatic change are those that use several lines of evidence to corroborate a climatic hypothesis and are from sites near an ecotone or in regions of extreme climate in all cases hydrologic setting mediates a lake s response to climate and must be considered in interpreting sedimentary sequences discussion of the impact of recent and future climatic changes necessitates a baseline against which the magnitude of observed or predicted changes can be measured commonly we look to recent history as a reference point for comparison however the landscape of recent decades or in some cases even centuries has been altered greatly by human activities thus to determine whether recent or future climatic change is unique or unusual we need long natural preanthropogenic time series against which observed or predicted climatic states and variability can be compared paleolimnological archives are a tool for looking at environmental patterns prior to anthropogenic impact and show a range of climatic states far greater than those documented by written records former strand lines of pluvial lakes bonneville and lahontan in the western u s for example testify to moisture extremes unsurpassed in recent centuries or even millennia in addition one can us the paleolimnological record as an independent climatic proxy against which patterns and rates of terrestrial response to climatic change can be compared here i present a broad overview of paleoclimatic reconstruction in north america from lacustrine records with a focus on the late quaternary the review is limited to climatic inference from paleolirnnological records a term i use in a restrictive sense to refer to records of past lake states physical biological and geochemical as opposed to records of past stream hydrology e g ely et al 1993 knox 1993 or terrestrial conditions i summarize paleolimnological tools available for reconstruction of past climate the capabilities and limitations of these tools

estimating kinetic parameters for organic reactions from geological data an example from the gippsland basin australia abstract an examination has been made of strategies to estimate kinetic parameters activation energy and pre exponential factor for organic reactions from geological data least squares regression and a direct search algorithm were applied to a set of sterane isomerization data from volador 1 an oil exploration well in the gippsland basin australia the best fit kinetic parameters depend on the number and quality of data points used as well as the thermal history because both the data and thermal history have intrinsic uncertainties a range of kinetic parameters can explain the data to a specified level of misfit for reasonable variations in the thermal history the effective kinetic parameters for the data from volador 1 are e 75 100kj mol and a 10 1 10 5 s it is observed that the range of acceptable parameter pairs has a linear relation of the form ln a a be and the slope b is dependent on the thermal history small departures of either parameter from this relation lead to significant variations in the predicted values for the reaction progress

sedimentary processes in the great lakes sediments in the great lakes are subject to four general categories of processes input transport deposition and postdepositional alteration sedimentary input is from coastal erosion 64 riverine input 26 atmospheric transport 3 and several lesser sources 7 once in the lake sediments are transported to their place of deposition along the bottom and or in suspension depending upon grain size and density the rate of deposition in the great lakes is variable and ranges from zero in some areas to over 6000 g m sup 2 yr sup 1 in the eastern basin of lake erie after deposition sediments undergo bioturbation dissolution of carbonate and opal remobilization of many metals followed by reprecipitation within the surficial oxidized layer and degradation of organic compounds

atmospheric gravity waves and the rissaga phenomenon the atmospheric forcing of large sea level oscillations up to 1 5 m amplitude with about a 10 min period in some bays and inlets of the balearic islands is described using simultaneous measurements of pressure and sea level elevation in the port of ciutadella at the end of a large and narrow inlet during 5 7 july 1989 the influence of atmospheric pressure oscillations on these large sea level variations locally known as rissaga is investigated coherence and cross correlation functions reveal that the large oscillations in the inlet are associated with and probably forced by a 10 min gravity wave in the atmosphere the effect of longer period waves on the inlet is seen in the well known inverted barometric effect forcing small oscillations in the water level of just some centimetres these latter waves have a period of around 50 min and an unusually large amplitude of some 3 mb the phase spectrum between sea level and pressure suggests that the inlet may behave as a damped harmonic oscillator which during rissaga is externally forced by the atmospheric pressure oscillations

possible causes of abnormal vitrinite reflectance values in paralic deposits of the carboniferous in the achterhoek area the netherlands abstract vitrinite reflectance data r m are presented for coals from two wells in the netherlands these data are grouped according the allied sedimentary sequences three groups of sedimentary sequences are distinguished thin coal seams covered by sands show suppressed r m values relatively high values are found in thick coal seams covered by shales coal seams with irregular sequences do not show abberant values it is suggested that the low reflectance values are caused by relatively more intense biodegradation during the early diagenesis due to continuous refreshment of te ambient watermass in sediments covered by a stagnant watermass biodegradation has not progressed as far leaving vitrinite precursors relatively rich in oxygen vitrinites produced in these environments have a high r m value the redoxpotential is a predominant factor governing the diagenetic processes

enhanced atmospheric circulation over north america during the early holocene evidence from lake superior profiles of grain sizes in five cores recovered from lake superior show that grain size increased with burial depth to the postglacial glacial contact the results reflect a substantial reduction in bottom current velocity and the corresponding wind velocity from 9500 to 6500 years ago

pressure forced seiches of large amplitude in inlets of the balearic islands 2 observational study in part 1 of this study gomis et al 1993 proposed a possible mechanism for the generation of large amplitude seiches observed in inlets of the balearic islands in part 2 we revise the proposed mechanism in light of recent observations these consist of simultaneous records of sea level bottom pressure measured at three locations inside and outside ciutadella inlet and atmospheric pressure measured at four sites inland nearby first results that support the existence of offshore surface waves of atmospheric origin are shown next a detailed analysis of atmospheric data reveals the passage of non dispersive waves with a predominant direction and phase speed that seem to be about the same during seiche events finally coherence phase difference and admittance functions estimated for different pairs of instruments are compared with the theoretical results all observations indicate that large amplitude seiches observed in ciutadella are likely the result of a resonant coupling between offshore surface waves generated by atmospheric disturbances and the fundamental mode of that inlet as suggested in part 1 however the analytical model used in part 1 is clearly too simple to explain the observed characteristics of the offshore surface waves

relationships between thermal maturity indices calculated using arrhenius equation and lopatin method implications for petroleum exploration thermal maturity can be calculated with time temperature indices tti based on the arrhenius equation using kinetics applicable to a range of types ii and iii kerogens these ttis are compared with tti calculations based on the lopatin method and are related theoretically and empirically via vitrinite reflectance to the petroleum generation window the ttis for both methods are expressed mathematically as integrals of temperature combined with variable linear heating rates for selected temperature intervals heating rates control the thermal maturation trends of buried sediments relative to arrhenius ttis lopatin ttis tend to underestimate thermal maturity at high heating rates and overestimate it as low heating rates complex burial histories applicable to a range of tectonic environments illustrate the different exploration decisions that might be made on the basis of independent results of these two thermal maturation models

source of the 2007 ist meteotsunami adriatic sea 1 siroka bay on the island of ist in the northern adriatic was struck by a severe inundation around 1530 utc on 22 august 2007 the maximum wave height reached 4 m and substantial material damage was induced this paper investigates the generating force of the inundation data analysis indicates that the inundation was provoked through a double resonance mechanism with initiation by a pronounced atmospheric disturbance that generated open ocean waves through the proudman resonance the waves were then further amplified inside the affected bay the air pressure disturbance which propagated at a speed of about 21 24 m s 1 over the northern adriatic shelf was investigated through both data analysis and atmospheric numerical modeling apparently the air pressure disturbance was a surface manifestation of a ducted gravity wave which propagated through the atmosphere from the apennines to the eastern adriatic coast over the northern adriatic according to the model simulation the wave was trapped in a stable layer adjacent to the ground which was capped by a dynamically unstable layer with wind speeds of about 22 m s 1 this made the unstable layer also a critical layer for gravity waves propagating with the same speed and allowed for their ducting in the layer below

radionuclide dating of recent sediment and the validation of pollen environment reconstruction in a small watershed reservoir in southeastern china abstract a 76 cm sediment core was collected from the huangdong reservoir southeastern china the radionuclides 137 cs and 210 pb and sediment grain size analysis were applied to establish the chronology and modern sedimentation rates the chronology established by the 137 cs time markers was consistent with the constant flux constant sedimentation cfcs model and the known time of dam construction 1960 ad recognized from the curve of sediment grain size at the depth of 54 cm the results show that the sedimentation rate of the huangdong reservoir is relatively high implying that soil erosion and water loss were strong the sedimentation rate before the construction of the reservoir was approximately 1 5 cm a which belongs to the fluvial flooding deposit the rate decreased to approximately 1 0 cm a during the reservoir deposition since 1960s pollen and micro charcoal analysis were performed to test the reliability of pollen based environment reconstruction including vegetation cover deforestation planting and fire disasters the results of pollen and micro charcoal indicated that the herbs primarily gramineae ferns such as dicranopteris and several trees mainly pinus varied following chorography or historical records we discovered that the most important indicators for local forest cover changes are pollen concentration and the ap nap value ratio of arboreal pollen to non arboreal pollen human impact on forests is manifested by a sharp decrease in pollen percentage of trees and absolute pollen concentration forest fire events were recorded by the peaks of charcoal concentration and the c p value ratio of charcoal concentration to pollen concentration for example the massive deforestation and intensive fires during the great leap forward movement and the cultural revolution are reflected by pollen and micro charcoal spectra this work testifies that radionuclide use as a dating method is applicable in southern china and the 137 cs method has demonstrated its reliability in the small reservoir setting in spite of low absolute values the environmental proxies such as grain size pollen and charcoal are sufficiently sensitive to reveal local ecosystem changes caused by natural disasters or human activity

empirical relation between carbonate porosity and thermal maturity an approach to regional porosity prediction reply to brown discussion i thank ray 1985 for the interest shown in my paper schmoker 1984 his analysis illustrated mathematical relations not specifically addressed in my manuscript 1 do not believe however that these results are significant or that they weaken my arguments he demonstrated only the obvious point that if two variables correlate with a third variable they will correlate with each other further more his analysis and conclusions are based on the assumption of an exponential porosity depth relation i would argue that such a relation is an effect of subsurface diagenesis that does not explain the cause and that ray has approached the problem backward the proper con clusion would be that for certain simple basins an expo nential porosity depth relation follows logically from the idea that porosity decreases in the subsurface as a function of thermal maturation perhaps the point that should be emphasized here is that depth z in and of itself does not affect or control geologic

role of diffusion in primary migration of hydrocarbons the following effective diffusion coefficients d cm2 sec were determined for the diffusion of light hydrocarbons through the water saturated pore space of shales methane 2 12 10 6 ethane 1 11 10 6 propane 5 55 10 7 iso butane 3 75 10 7 n butane 3 01 10 7 n pentane 1 57 10 7 n hexane 8 20 10 8 n heptane 4 31 10 8 and n decane 6 08 10 9 on the basis of these new data a deterministic dynamic model was set up to simulate the diffusive transport of light hydrocarbons c1 to c10 from source rocks for eight documented source rock units representing a wid range of geologic conditions maturities of 0 40 to 1 35 mean vitrinite reflectance oil to gas prone kerogens the cumulative amounts of hydrocarbons escaping with time were calculated thus it was shown that diffusion represents an effective process for primary migration of gas but not for oil the rate of mass transport for gas from source rocks with geologic time can be sufficiently high to account for the origin of commercial size gas fields for example a cumulative amount of 109 kg of methane 1 5 109 std m3 or 5 3 1010 scf has escaped by diffusion in 540 000 years from a certain volume 1 000 km2 by 200 m thick of a high mature gas prone mesozoic source rock in western canada the origin of hydrocarbon accumulations with high gas to oil ratios in low mature sediments in geologically young basins early gases and condensates can be explained by an early phase of primary migration predominantly based on diffusion during the initial stages of the accumulation history of those fields extending up to millions of years under certain conditions the reservoir gas changes with geologic time from a methane rich to a wet gas composition at low maturity levels below about 0 6 rm even oil prone source rocks yield methane rich light hydrocarbon mixtures by migration through diffusion compositional trends among reservoir gases of several multiple pay gas fields in louisiana represent evidence for diffusive transport of hydrocarbons the variation in gas composition between the individual pay zones is controlled by increasing distances of diffusive transport of the hydrocarbons from a uniform source rock at depth to their present accumulation sites in the shallow pay zones compounds of high diffusivity are enriched for example in the sligo gas field of louisiana the methane ethane and the iso butane n butane ratios increase from 10 2 to 36 0 and from 0 86 to 1 13 respectively from the deepest to the shallowest of the five productive reservoir sands which are spread over a a depth interval of 5 500 ft 1 676 m diffusion of light hydrocarbons in the subsurface can also have economically adverse effects for example existing gas accumulations can be destroyed by dissipation the rate of this destruction was calculated for the harlingen gas field holland by diffusive loss through 400 m of shale cap rock the initial amount of methane in place of 1 93 109 std m3 6 8 1010 scf is reduced by one half over a period of 4 5 million years this leads us to propose the concept that large gas accumulations can persist through extended periods of geologic time only as dynamic systems reaching some kind of steady state equilibrium between diffusive loss through the cap rock and continuous replenishment from the source rock

subsidence crustal structure and thermal evolution of georges bank basin a geophysical study of georges bank basin defines a deep crustal structure that is interpreted in terms of the basin s tectonic and thermal history gravity models along three basin cross sections delineate two zones of crustal thinning at the basement hinge zone and oceanic crustal margins these two zones bound rift stage crust about 25 km thick which underlies the central portion of the basin subsidence analysis of the basin using data from multichannel seismic reflection lines and two cost wells suggests a rifting and uniform extensional origin two dimensional finite difference modeling of the basin defines a crustal structure that concurs with the gravity and subsidence studies the resulting isotherms show no major changes in the thermal structure since the ate jurassic in some areas of the basin temperatures sufficient for oil generation are determined from maturation studies of jurassic sediments hydrocarbon generation is questionable however because of the probable lack of proper and sufficient kerogen in the jurassic deposits

basin analysis predictions of known hydrocarbon occurrences the north sea viking graben as a test case abstract basin analysis can assimilate structural burial and thermal histories to predict hydrocarbon prone zones in speculative areas the validity of the modelling approach was field tested in the north sea viking graben an area for which good data are available a recent birps deep seismic reflection profile across tectonic strike of the graben was interpreted and depth converted with good well control the burial and structural histories were determined by backstripping the chronostratigraphic layers using a one dimensional fluid flow compaction model on pseudo wells after removal of each sequence the section was manually reconstructed the thermal history was examined using thermal indicator tomography extensional models and calculations of depth to detachment lack of resolution required that three different paleo heat flow trends be tested to encompass the range in variability a gradual warming trend a constant heat flow through time and a low heat flow until the cretaceous tertiary boundary where a heat pulse occurred basement subsidence extension depth to detachment calculations and thermal indicator inversions all suggest that the uk side of the graben has developed differently to the norwegian section the generation modelling predicts the position of the oil window in the cross section the areas where this window enveloped the draupne formation kimmeridge clay source rock broadly correlate with the positions of the gullfaks statfjord and thistle oilfields of the uk sector however in the norwegian sector the draupne formation was generally overmature except in the area around the troll oilfield predicted middle to late cretaceous generation in the rift axis may have caused updip oil migration towards the horda platform the correct prediction of oil prone zones validates the use of quantitative basin analysis as a tool for evaluating frontier areas where data are limited

the timing of regional lateglacial events and post glacial sedimentation rates from lake superior abstract we analyze both new and previously published paleomagnetic records of secular variation psv from lake superior sediment cores and compare these records to correlated rhythmite varve thickness records to determine post glacial sedimentation rates and to reassess the termination of glaciolacustrine varves in the basin the results suggest that offshore sedimentation rates have exhibited considerable spatial variation over the past 8000 years particularly during the mid holocene we attribute offshore mid holocene sedimentation changes to alterations in whole basin circulation perhaps precipitated by a greater dominance of the gulf of mexico air mass during the summer season nearshore bays are characterized by high sedimentation rates for at least 1000 years after varve cessation and during a period between around 4500 and 2000 cal bp after 2000 cal bp sedimentation rates subsided to earlier rates the increases between 4500 and 2000 cal bp are probably due to lake level fall after the nipissing ii highstand the older glaciolacustrine varve thickness records suggest that the influx of glacially derived sediment ended abruptly everywhere in the lake except near the lake nipigon inlets multiple sediment cores reveal 36 anomalously thick varves previously ascribed to the formation of the nakina moraine which were deposited just prior to varve cessation in the open lake the psv records support the observation that the cessation of these thick varves is a temporally correlative event occurring at 9035 170 cal bp calibrated years before 1950 ca 7950 8250 14 c bp this date would correlate to the eastern diversion of lake agassiz and glacial meltwater into lake ojibway

long barotropic waves generated by a storm crossing topography abstract storms crossing topography are shown to radiate long surface gravity waves the waves are transients generated by changes in the depth dependent amplitude of the atmospherically forced pressure wave beneath a storm this generation mechanism for long waves known as meteorological tsunamis or rissaga does not appear to have been previously discussed the transients have periods equal to the passage time of the storm of order 30 min for small fast moving storms a 1d model is used to give the amplitudes of the transient waves generated by a small fast moving storm crossing a topographic step on to a continental shelf and across a ridge large transients are generated by storms whose translation speed is subcritical in deep water and supercritical in shallow water that is faster than the shallow water wave speed surprisingly when the depth difference between the deep water and the continental shelf is large a gentle transition from deep to shallow water over 10 storm widths only slightly r

oil generation and migration in the gifhorn trough nw germany abstract the origin and migration of oils from selected oil fields in the gifhorn trough nw germany was investigated by geochemical analysis of crude oils and possible lower and middle jurassic source rocks productive reservoir sandstones in the gifhorn trough occur in the dogger beta zone of the middle jurassic bajocian and are interbedded with shales that contain 1 2 toc mostly type iii kerogen in the lower jurassic toarcian organic matter rich shales 9 12 toc whose kerogen has a type ii composition form the best quality oil prone source rocks biomarker and stable isotope analyses of oils and source rock extracts reveal that all oils analysed are derived from the lower toarcian shales lias epsilon the timing of oil generation and migration was investigated by reconstructing the geothermal history of the source rock in specific drainage areas and determining the availability of migration pathways through geological time hydrocarbon generation started in the central part of the gifhorn trough in upper cretaceous time differences in the maturity of the oils display separate small drainage areas close to the reservoirs variations in oil composition within deep buried reservoirs indicate the preservation of different migration phases

biomarker geochemistry of the miocene monterey formation west san joaquin basin california implications for petroleum generation abstract much of the miocene monterey formation of california is rich in biogenic sediment especially organic matter and silica because of the geologic structure the monterey in the subsurface near lost hills in the san joaquin basin forms a natural laboratory for the study of the diagenetic responses of these materials rocks of similar age and lithology are buried to depths ranging between 500 and 3500 m and are thus exposed to a temperature range of 45 130 c the diagenetic progression of silica from opal a to opal ct to microquartz is well documented in monterey burial history studies however diagenetic indicators need to be established below the depth of complete conversion of opal ct to quartz which may be very shallow 1500 m or less at lost hills conventional maturity indicators are problematic the scarcity of vitrinite in many monterey samples hampers reflectance measurements in addition values that are measured may be anomalously low maximum pyrolysis temperatures are depressed due in part to high heavy bitumen content biomarker geochemistry provides effective alternative maturity indicators of particular interest are the stereochemical variations observed in the assemblages of steranes and triterpanes extracted from oil well core samples for example the 20s 20r ratio of 5 h 14 h 17 h 24 ethylcholestane increases from 0 09 to 0 56 over the depth range cited samples from petroleum accumulation zones are distinguished by anomalously mature biomarker assemblages considering their depth of burial this indicates that these bitumens are as mature as the deepest non production zone sample 3430 m even though they are from much shallower depths 580 1572 m other maturity and or migration indicators confirm this such as the relative increases in amounts of 14 h 17 h steranes rearranged steranes and tricyclic terpanes thus it appears that any immature indigenous bitumen in production zone samples is overwhelmed by a mature component which presumably migrated updip from deeper warmer strata since much oil is produced from shallow organic rich fractured monterey shales early in situ generation has previously been hypothesized however while both source and reservoir rock are lithologically similar and lie within the same formation biomarker geochemistry indicates that substantial generation occurs only in deeply buried monterey shales

evidence of stream response to holocene climatic change in a small wisconsin watershed abstract during the holocene moderate climatic and vegetational changes triggered several episodes of adjustment in the brush creek fluvial system the alluvial chronology includes an episode of erosion at 7800 5700 yr b p corresponding to the mid holocene precipitation minimum and an episode of floodplain construction at 5700 5000 yr b p corresponding to a rapid increase in precipitation holocene climatic changes have influenced the sedimentology of the alluvial deposits and soil development on them fluvial adjustment is caused primarily by hydrologic and hydraulic changes related to climatic change but there is no simple model for fluvial response to climatic change the relationship between the direction of climatic change and the type of fluvial response is complex

coalification and thermal histories of tertiary basins in relation to late alpidic evolution of the eastern alps the thermal histories of tertiary basins situated around and within the eastern alps are examined using coalification data waples method is used to estimate paleogeothermal conditions the data suggest that the basins thermal histories are intimately related to late alpidic geodynamics of the eastern alps

effects of smectite on the oil expulsion efficiency of the kreyenhagen shale san joaquin basin california based on hydrous pyrolysis experiments the amount of oil that maturing source rocks expel is expressed as their expulsion efficiency which is usually stated in milligrams of expelled oil per gram of original total organic carbon oil expulsion efficiency can be determined by heating thermally immature source rocks in the presence of liquid water i e hydrous pyrolysis at temperatures between 350 c and 365 c for 72 hr this pyrolysis method generates oil that is compositionally similar to natural crude oil and expels it by processes operative in the subsurface consequently hydrous pyrolysis provides a means to determine oil expulsion efficiencies and the rock properties that influence them smectite in source rocks has previously been considered to promote oil generation and expulsion and is the focus of this hydrous pyrolysis study involving a representative sample of smectite rich source rock from the eocene kreyenhagen shale in the san joaquin basin of california smectite is the major clay mineral 31 wt in this thermally immature sample which contains 9 4 wt total organic carbon toc comprised of type ii kerogen compared to other immature source rocks that lack smectite as their major clay mineral the expulsion efficiency of the kreyenhagen shale was significantly lower the expulsion efficiency of the kreyenhagen whole rock was reduced 88 compared to that of its isolated kerogen this significant reduction is attributed to bitumen impregnating the smectite interlayers in addition to the rock matrix within the interlayers much of the bitumen is converted to pyrobitumen through crosslinking instead of oil through thermal cracking as a result smectite does not promote oil generation but inhibits it bitumen impregnation of the rock matrix and smectite interlayers results in the rock pore system changing from water wet to bitumen wet this change prevents potassium ion transfer and dissolution and precipitation reactions needed for the conversion of smectite to illite as a result illitization only reaches 35 to 40 at 310 c for 72 hr and remains unchanged to 365 c for 72 hr bitumen generation before or during early illitization in these experiments emphasizes the importance of knowing when and to what degree illitization occurs in natural maturation of a smectite rich source rock to determine its expulsion efficiency complete illitization prior to bitumen generation is common for paleozoic source rocks e g woodford shale and retort phosphatic shale member of the phosphoria formation and expulsion efficiencies can be determined on immature samples by hydrous pyrolysis conversely smectite is more common in cenozoic source rocks like the kreyenhagen shale and expulsion efficiencies determined by hydrous pyrolysis need to be made on samples that reflect the level of illitization at or near bitumen generation in the subsurface

hydrocarbon prospects across narmada tapti rift in deccan trap central india inferences from integrated interpretation of magnetotelluric and geochemical prospecting studies abstract as the mesozoic sediments contribute most of the oil and gas reserves of the world we present an integrated interpretation approach using magnetotellurics mt and surface geochemical prospecting studies to demarcate hydrocarbon prospective gondwana mesozoic formations underneath the deccan flood basalts of late cretaceous age across narmada tapti rift between bhusawal and barwah in central india the mt interpretation shows deep 5 km basement structure between southern and central part of the mt profile however it gradually becomes shallower to either ends of the profile with a predominant basement depth reduction in the northern end compared to the southern end the geophysical results suggest thick 2 3 5 km mesozoic sediments in the area characterized by deep basement structure the geochemical analysis of the near surface soil samples indicate higher concentrations of light gaseous hydrocarbons constituents over the area marked with thick sub basalt mesozoic formations analyses of the geochemical data imply that these hydrocarbons are genetically related generated from a thermogenic source and these samples fall in the oil producing zone the temperature depth estimations in the region supports favorable temperature conditions 80 120 c for oil generation at basement depths

atmospheric origin of the devastating coupled air sea event in the east adriatic enhanced sea level oscillations with devastating effects occurred on 26 27 june 2003 in the east adriatic the phenomenon was recognized as a resonantly coupled air sea interaction where the sea wave is forced by the propagating atmospheric pressure disturbance this study examines the dynamics and predictability of the atmospheric component of the coupled system first the initiation amplification and maintenance of the system are examined the source of the perturbation is traced back to the alpine region where the potentially unstable air in the westerly current lifts over the alps resulting in convection and wave development the wave and convective activity apparently couple in a wave cisk manner and propagate southeastward down the eastern adriatic coast due to the potentially unstable air above the adriatic the system additionally amplifies along its track the dissipation of the system occurs after the landfall second the performance of the numerical model at the resolution that is similar to operational nwp model resolution is examined this severe event is highly susceptible to the details of the model configuration presumably due to the sensitivity in coupling of the wave and mcs thus although the model is able to reproduce and forecast this kind of event at a fairly coarse resolution the details of the spatial structure as well as the time of onset are questionable in this case the greatest sensitivity is primarily in the treatment of moist and convective processes

resonant coupling of a traveling air pressure disturbance with the east adriatic coastal waters 1 exceptional sea level oscillations and strong current reversals observed in the east adriatic on 27 june 2003 are analyzed using available meteorological and tide gauge measurements and numerical model results it is shown that the variability in the atmosphere sea system was characterized by high frequencies 0 01 0 1 min 1 and sea level and current amplitudes surpassing 1 m and 1 m s 1 respectively the event was related to the occurrence of a gravity disturbance in the atmosphere above the adriatic the disturbance traveled toward the east southeast at a speed of 22 m s 1 and was resonantly coupled with a wave in the sea 50 m deep the resulting forced wave was further amplified when entering funnel shaped bays opened to it there are indications that the forcing disturbance and its counterpart in the sea excited normal modes of the bays and harbors in the area moreover nonlinear steepening of the forced wave seemingly occurred resulting in the formation of high frequency wave trains this process along with the generation of coastal seiches could explain the observed and modeled differences between the spectra of coastal variability and the spectrum of forcing wave

summer breakout of trapped bottom dense water from the northern adriatic 1 the paper deals with an intriguing dense water breakout episode in mid august 2004 which has been observed in the bottom layers of the oil rig located in the middle of the northern adriatic various data temperature series and vertical t s profiles currents meteorological measurements and satellite images have been analyzed in order to understand conditions which preceded were active and followed the breakout episode a stationary bottom pool of dense water generated during the previous winter has been suspected to be a source of the dense water observed during the breakout with a permanent position established by a stationary northern adriatic cyclonic anticyclonic gyre system the breakout lasted for 3 days advecting the bottom waters more than 2 c colder than residing waters at the oil rig site the main result of modeling experiments concerns the generative force for the observed breakout which was found to be a mesoscale storm that occurred over the open north adriatic on 8 august 2004 the storm has been reproduced by the coupled ocean atmosphere mesoscale prediction system coamps atmospheric model which was then used to force the princeton ocean model pom at the surface results of simulations reveal the capability of the storm to break the thermohaline fronts through the wind induced baroclinic transport and downwelling at the exposed shorelines this is the first study in the adriatic which evaluates the impact of mesoscale summer storm to the sea driving bottom layer circulation through the convergence divergence dynamics in addition to the direct impact on the sea surface through the wind stress forcing

effects of subduction parameters on geothermal gradients in forearcs with an application to franciscan subduction in california geothermal gradients in forearcs are often suppressed below normal values because of the cooling effect of the relatively cold downgoing plate in this paper finite difference thermal modeling is used to evaluate the influence on forearc gradients of variations in six potentially important subduction zone parameters variations in forearc radiogenic heat production over the general range likely in forearc rocks 0 to 1 5 10 6 w m 3 cause only minor changes in temperatures at the base of the forearc about 2 to 35 depending on other parameters and thus have relatively little effect on pressure temperature pt conditions of metamorphism however their effect on gradients at shallow levels and thus on surface heat flows may be greater up to about 100 likely variations in forearc thermal conductivity 1 5 to 3 5 w m 1 c 1 similarly change temperatures at the base of the forearc only modestly 10 25 but change surface heat flows more substantially 1 45 1 75 times decreasing the subduction angle from 27 to 3 6 increases gradients by about a factor of 2 at both deep and shallow levels decreasing the subduction rate by a factor of 8 160 to 20 km m y increases gradients by about a factor of 2 when frictional heating at the plate contact is excluded and less when modest amounts of frictional heating are included forearc gradients increase virtually linearly with the presubduction geothermal gradient in the subducting slab and thus are higher above a younger slab when frictional heating is excluded forearc gradients are 2 0 2 8 times higher above a 10 m y old slab than above a 150 m y old slab again the relative effect is lessened when frictional heating is incorporated the amount of frictional heating at the plate contact potentially has the greatest influence on forearc gradients the frictional heat production h is given by h vs where is the shear stress along the plate contact and vs is the subduction rate the modeling shows that forearc gradients increase linearly with unless plate contact shear stresses are only a small fraction of those expected with frictional sliding of dry rocks outer parts of forearcs would be the sites of pervasive low p t metamorphism greenschist facies rather than high p t metamorphism blueschist facies very high fluid pressures along the plate contact are probably the way shear stresses are reduced pressure temperature conditions of blueschist facies metamorphism in the franciscan subduction complex of california are easily explained with typical subduction rates and slab ages with plate contact shear stresses of the order of 10 mpa equivalent to around 3 of lithostatic pressure but stresses within the range zero to a few tens of megapascals are probably permitted by the thermal constraints speculative application of the modeling results assuming a shear stress of 4 of lithostatic pressure to plate motion reconstructions for the franciscan forearc suggests that forearc gradients were about 8 c km around 85 ma when the subducting slab was perhaps 145 m y old and the subduction rate was perhaps 95 km m y gradients increased moderately through the latest cretaceous to middle tertiary as subduction became slower and the subducting slab became younger reaching about 16 c km at 28 ma when the slab age was about 11 m y and the subduction rate was about 48 km m y the slab age subduction rate and forearc gradient then remained fairly constant until 5 ma when subduction slowed to about 32 km m y and the slab age decreased to about 8 m y causing gradients to rise to about 20 c km

documented international enquiry on solid sedimentary fossil fuels coal definitions classifications reserves resources and energy potential abstract this paper deals with all solid sedimentary fossil fuels i e coal the main one for geological reserves and resources peat and oil shales definitions of coal the 50 ash limit already adopted by un ece for coal definition allows the creation of a new category the organic shales 50 75 ash comprising energetic materials still valuable for thermal use coal shales or to be retorted for oil production oil shales geological relations between coals oil shales solid bitumen liquid hydrocarbons natural gas and coalbed methane are also examined together with environmental problems as a final synthesis of all topics the paper discusses the problems related with a modern geological classification of all solid sedimentary fuels based on various rank parameters moisture content calorific value reflectance maceral composition and mineral matter content and washability finally it should be pointed out that the paper is presented as series of problems some of them old ones but never resolved until now in order to facilitate the next generation of coal geologists to resolve these problems on the basis of international agreements all sections begin with documented introductions for further questions opening an international enquiry the authors hope that the answers will be abundant enough and pertinent to permit synthetic international solutions valuable for the new millennium with the help of interested consulted authorities international pertinent organisations and regional experts

multi meteotsunami event in the adriatic sea generated by atmospheric disturbances of 25 26 june 2014 a series of meteotsunamis hit a few locations in the mediterranean and black seas during 22 27 june 2014 meteotsunamis were particularly numerous on 25 and 26 june in the adriatic sea where at least six harbours and bays were stricken by powerful waves strongest events occurred in vela luka korcula island a known meteotsunami hot spot where waves reached height of 3 m and in rijeka dubrovacka bay where strong 5 m s currents accompanied 2 5 m high waves intensification of high frequency sea level activity was observed at both the eastern and western adriatic tide gauge stations with maximum recorded wave heights reaching 68 cm ortona italy a series of individual air pressure disturbances characterized by pronounced rates of air pressure change up to 2 4 hpa 5 min limited spatial extent 50 km and high temporal variability propagated over the adriatic on 2 days in question numerical hydrodynamic model schism forced by measured and idealised air pressure disturbances was utilised to reproduce the observed adriatic sea level response several important conclusions were reached 1 meteotsunamis occurring at various parts of the coast were generated by different atmospheric air pressure disturbances 2 topographic influence can be removed from sea level spectra by computing spectral signal to background ratios the result being related to the external forcing resembles atmospheric pressure spectra 3 sea response is strongly dependant on details of atmospheric forcing and 4 over complex bathymetries like the middle and south adriatic ones numerous effects including proudman resonance edge waves strong topographical enhancement and refractions on the islands placed on the pathway of atmospheric disturbances should be taken into account to fully understand meteotsunami generation and dynamics an in depth numerical study is planned to supplement the latter conclusion and to quantify contribution of each process

high frequency sea level oscillations in the mediterranean and their connection to synoptic patterns abstract this paper contains a basin wide assessment of high frequency sea level oscillations in the mediterranean sea for the period from 2010 to 2014 sea level series with temporal resolutions of 1 min were taken from 29 tide gauges that had been operational for at least 4 years with high quality time series the contribution of high frequency sea level variance 2 min 6 h to the total and residual sea level variance was estimated to vary between 0 4 and 9 5 and between 0 6 and 12 1 respectively but to become dominant at some stations during extreme high frequency events a total of 36 high frequency sea level events were extracted from the series with some occurring locally in one of the four selected regions of spain sardinia sicily and the greece ionian sea 6 events some occurring over two or three regions 19 events and some occurring in all of the selected regions within a period of 1 3 days 11 events the basin wide events normally propagate from the western to the eastern parts of the basin with an average velocity of approximately 30 km h synoptic patterns associated with high frequency events were analysed and a high resemblance to patterns associated with meteotsunamis was observed i a cyclone with a centre w nw from the affected area ii a strong thermal front in the lower troposphere and iii a forefront of an unstable strong mid tropospheric jet placed over the affected area the strong coherence between high frequency sea level events and synoptic patterns introduces the possibility of a timely forecast of these events

thermal history of michigan basin the elevated organic maturity observed in shallowly buried units from the michigan basin implies that higher temperatures and thicker overburdens once existed in the basin evidence from sediment accumulation rates regional dips and maturity of pennsylvanian age coals suggests that up to 1 000 m 3 280 ft of sediment were removed by erosion prior to the late jurassic when the basin became stable geothermal gradients during paleozoic basin subsidence probably ranged from 35 to 45 c km 19 to 25 f 1 000 ft in contrast to the average present value of 25 c km 14 f 1 000 ft depths to the top of the oil window ranged from 1 900 to 2 300 m 6 230 to 7 540 ft during the paleozoic post pennsylvanian erosional uplift and further thermal m turation of the basin have combined to raise the top of the oil window to its present level of 500 m 1 640 ft

the use of free radicals of organic matter to determine paleogeothermal gradient abstract free radicals in 60 kerogen samples from 5 wells in the qiongdongnan tarim and liaohe basins in china were analyzed by electron spin resonance esr for use in geothermometry based on esr data for 44 kerogen samples from the tertiary qiongdongnan basin a regression curve was shown to fit free radical densities n g with burial depth of samples for use in geothermal gradient estimation using this curve the highest geothermal gradients experienced by carboniferous permian strata well tmc1 in the tarim basin and oligocene eocene strata well lr16 in the liaohe basin were estimated concurrently five samples from liaohe basin were examined by apatite fission track analysis to assess the reliability of the esr kerogen method for geothermal gradient determination results of esr analyses match those of vitrinite reflectance and apatite fission track analysis indicating that maximum geothermal gradients obtained from the esr curve are reliable this paper presents a useful esr kerogen method for estimating paleogeothermal gradients which is especially useful where vitrinite and apatite are not present

lake type controls on petroleum source rock potential in nonmarine basins based on numerous empirical observations of lacustrine basin strata we propose a three fold classification of lacustrine facies associations that accounts for the most important features of lacustrine petroleum source rocks and provides a predictive framework for exploration in nonmarine basins where lacustrine facies are incompletely delineated 1 the fluvial lacustrine facies association is characterized by freshwater lacustrine mudstones interbedded with fluvial deltaic deposits commonly including coal shoreline progradation dominates basin fill resulting in the stacking of indistinctly expressed cycles up to 10 m thick in map view the deposits may be regionally widespread but laterally discontinuous and contain strong facies contrasts transported terrestrial organic matter contributes to mixed type i iii kerogens that generate waxy oil type i kerogen is hydrogen rich and oil prone type iii kerogen is hydrogen poor and mainly gas prone the luman tongue of the green river formation wyoming and the honyanchi formation junggar basin china provide examples of this facies association which is also present in the songliao basin of northeastern china the central sumatra basin and the cretaceous doba doseo basins in west central africa 2 the fluctuating profundal facies association represents a combination of progradational and aggradational basin fill and includes some of the world s richest source rocks deposits are regionally extensive in map view having relatively homogenous source facies containing oil prone type i kerogen examples include the laney member of the green river formation wyoming the lucaogou formation junggar basin china the bucomazi formation offshore west africa and the lagoa feia formation campos basin brazil 3 the evaporative facies association represents dominantly aggradational fill related to desiccation cycles in saline to hypersaline lakes and may include evaporite and eolianite deposits sublittoral organic rich mudstone facies are relatively thin but may be begin page 1034 quite rich and widespread the highest organic enrichment coincides with the deepest lake stages low input of land plant organic matter results in minimal lateral contrasts in organic content in some cases a distinctive type i s sulfur rich kerogen may generate oil at thermal maturities as low as 0 45 vitrinite reflectance equivalent examples include the wilkins peak member of the green river formation wyoming the jingjingzigou formation junggar basin china the jianghan and qaidam basins china and the blanca lila formation argentina

metamorphic evolution of a very low to low grade metamorphic core complex danubian window in the south carpathians the danubian window characterized by diagenetic to low greenschist facies conditions at a high thermal gradient is evidently of great interest for methodological studies because high metamorphic thermal gradient conditions during low grade metamorphism have received little attention so far the general increase in metamorphic grade from sw to ne in the danubian window is indicated by mineral parageneses studies as well as by illite kubler index ki measurements and organic matter reflectance omr for the first time this study distinguishes between metamorphic conditions related to jurassic ocean floor cretaceous nappe stacking post collisional accommodation and syn kinematic getic detachment metamorphism and cooling after oligocene exhumation the occurrence of the prehnite pumpellyite facies in the severin cosustea units in the southeastern area is the result of cretaceous metamorphism remnants of ocean floor metamorphism prevailed the highest pressure is constrained by the upper stability limit of prehnite to be at around 4 0 kbar the danubian units situated within the diagenetic zone were not below 200 8c due to epidote formation the ki omr and mineral data indicate diagenetic conditions assuming temperatures between 200 and 250 8c pressures between 1 8 and 2 6 kbar were calculated using kinetic and numerical maturity models orogenic collisional cretaceous peak pressure conditions of 4 0 1 0 kbar are found in the danubian nappes not altered by a subsequent syn detachment metamorphic overprint highest temperatures in chloritoid schists and epidote hornblende bearing mylonites have been inferred for samples from the northern border of the danubian window between 300 and 400 8c along a synto post detachment retrograde pressure path post dating the chloritoid formation the occurrence of clinozoisite chlorite quartz suggests temperatures 300 8c in the northwest while the association andalusite quartz and biotite muscovite indicates temperatures between 370 and 400 8c at 3 5 kbar in the northeast it is demonstrated that the slope of the regression lines between ki and omr data gives valuable qualitative information about the relative magnitudes of p and t the slope of the regression line for the danubian window samples indicates normal heat flow conditions during nappe stacking and hyperthermal conditions during the formation of the getic detachment high thermal gradient conditions can easily be explained by partly isothermal decompression during the getic detachment event the elevation of the geotherm being caused by crustal thinning and rapid exhumation of the danubian units probably also a higher heat flux prevailed at the end of the getic detachment at a time when the retrograde chloritoid decomposition reactions took place documenting late stage ht greenschist facies metamorphism from siegesmund s fugenschuh b froitzheim n eds tectonic aspects of the alpine dinaridecarpathian system geological society london special publications 298 281 315 doi 10 1144 sp298 14 0305 8719 08 15 00 the geological society of london 2008 location of the study area and

effects of bottom currents and fish on sedimentation in a deep water lacustrine environment sands and muds accumulating under the influence of apparently strong bottom currents in a deep water environment of lake superior were studied in detail using 3 5 khz echo sounding side scan sonar piston gravity and box coring and lake floor photography the study area includes a well defined slope and basin environment bottom currents maintain a scoured trough 20 m deep and 2 km wide at the base of the slope and modify the shapes of large ringlike depressions that are common in many regions of lake superior side scan sonar records reveal lineations subparallel to the direction of bottom current flow that are interpreted in different areas to be sand ribbons slight depressions or depositional furrows the sediments range from silty sand in the scoured trough to sandy clays farther offshore radiocarbon dating and 210 pb dating show the sediments to be postglacial rather than relic glacial lacustrine sediments grain size distributions are affected by bottom currents and a nearby source of sand some sedimentary structures including plane laminations and interbedded sands and muds are due to bottom currents fish create dish laminations however that often obscure the effects of the bottom currents fish and fish scour depressions are common in lake floor photographs whereas evidence for bottom currents is not biological activity therefore appears to erase traces of intermittent currents

a new windstorm proxy from lake sediments a comparison of geological and meteorological data from western germany for the period 1965 2001 1 the feasibility of detecting windstorm layers in lake sediments is explored by comparing quartz grain size data from a freeze core obtained from the schalkenmehrener maar eifel region western germany to recent meteorological wind data the schalkenmehrener maar is appropriate for such a calibration study because the morphological settings of the lake allow the conservation of windstorm layers in particular there is no fluvial sediment inflow and long term wind measurements are available from nearby stations the age model for the uppermost 30 cm of the sediment core is based on measurements of 137cs and 210pb concentrations an ultra high resolution grain size analysis is performed digitally on thin sections and reveals distinct 1 mm thick layers with increased quartz grain content and sharp gaussian grain size distributions which are shifted to larger grain sizes compared to the normal lake sediment in order to compare the occurrence of these layers with meteorological wind data a windstorm index is developed combining data from meteorological stations in the eifel region and reanalyses from the european centre for medium range weather forecast a statistical evaluation of matches between the windstorm index and the core s silt fraction data indicates that the sediment layers very likely coincide with the major windstorm events in the eifel region during the last decades six historical storm are identified this pilot study identifies the main requirements and proposes a novel methodological approach for using sediment data from lakes with similar settings as the schalkenmehrener maar as a new proxy to reconstruct the windstorm record of the geological past

barotropic waves generated by storms moving rapidly over shallow water 1 in the falls of both 1999 and 2000 waves with characteristics similar to tsunami hit the southeast coast of newfoundland canada the waves were large enough to cause local flooding damage to docks and other destruction there is however no evidence of seismic events underwater landslides or slumping events on either occasion other explanations such as storm surge also appear unlikely and local weather conditions at the coast were not exceptional at the time on both occasions tropical storms moved rapidly across the grand banks of newfoundland from southwest to northeast with a translation speed of 30 m s 1 a significant nonisostatic response to atmospheric pressure forcing can be expected over the shallow water of the banks since the translation speed of the storms is comparable to the local shallow water gravity wave speed we speculate that the atmospheric pressure forcing associated with the storms generated a barotropic wake and we use a numerical model to argue that as the storm moved back over the deep ocean the wake was refracted and or reflected by the variable bathymetry at the edge of the banks and that it was the refraction of the wake toward the coast that led to the unusual sea level events in southeastern newfoundland the numerical model results are in general agreement with the eye witness reports the model computed wave activity hits the southeast coast of newfoundland at about the right time and in the right areas for both events although for the 1999 event the model response is weaker than is observed at port rexton in trinity bay the reason for the poorer model performance in the 1999 case is not known although we do find that the model results are sensitive to uncertainty in the exact track taken by the storm across the banks the model results demonstrate that the period and wavelength of the gravity waves comprising the wake are in general proportional to the length scale of the pressure forcing an exception being the model response in conception bay newfoundland where a resonant seiche response is found to dominate index terms 4504 oceanography physical air sea interactions 0312 4564 oceanography physical tsunamis and storm surges 4219 oceanography general continental shelf processes 3339 meteorology and atmospheric dynamics ocean atmosphere interactions 0312 4504 4255 oceanography general numerical modeling keywords tsunami barotropic tropical storm modeling air sea

past present and future of basin and petroleum system modeling basin and petroleum system modeling bpsm has had increasing impact on industry decisions related to exploration and new venture opportunities over the last decade basin and petroleum system modeling technology usability and user group size have grown as a result of its capacity to reduce exploration risk based on current statistics improvements in bpsm have significant potential to reduce future well failures particularly when caused by lack of petroleum charge to bring bpsm practitioners from academia and industry together an aapg hedberg research conference was organized to discuss the latest developments and issues in this field a survey was conducted during the conference in santa barbara california april 2016 and this paper summarizes the results a key takeaway was an overarching consensus throughout the bpsm community that improved understanding of hydrocarbon migration and more flexible workflows are necessary to better assess charge and migration risk in exploration and new ventures in addition bpsm is increasingly used to predict pore pressure and porosity at field scales which opens new opportunities to integrate bpsm workflows with other technologies such as seismic rock property analysis and reservoir quality modeling in this paper we discuss these and other issues that arose from in depth discussion and an online survey

construction of type curves of geomagnetic secular variation for dating lake sediments from east central north america type curves of palaeomagnetic secular variations of declination and inclination through the last 12 000 radiocarbon years have been constructed by combining data from the minnesota lakes with paral

meteotsunami tide interactions and high frequency sea level oscillations in the eastern yellow sea while an air pressure jump was moving southeastward over the shallow water region of the eastern yellow sea in march 2007 a long ocean wave meteotsunami was generated and amplified due to the proudman resonance the long wave arrived at the coast during high tide with wave amplitude of 1 4 m and seawater overflew seawalls and inundated the land high frequency sea level oscillations continued for 8 9 h after the long wave hit a local coast the moon s age was 12 days and the tidal range was about 4 m between neap and spring tides two dimensional numerical simulations were performed to reproduce amplification of the long ocean wave in offshore and oscillations of sea level at the coast both tidal elevation and tidal currents were found to affect the growth of the long wave amplitude by the interactions between tides and the long wave long wave tides interactions are important processes for the accurate prediction of long wave arrival time and maximum height and for the reduction of coastal hazards in the macrotidal region after the long wave hit the coast of remote regions reflected waves propagated radially from remote regions to a local coast the high frequency sea level oscillations at a local observation station continued until all of the reflected waves from remote regions had passed by it was concluded that high frequency oscillations of sea level are generated not only by local reflection of the long wave but also by propagation of the reflected waves from remote regions

pressure forced seiches of large amplitude in inlets of the balearic islands large amplitude harbor seiches usually occur in summer in the balearic islands a significant correlation between sea level oscillations and atmospheric pressure disturbances has been found though a proved physical mechanism to account for this atmosphere ocean interaction is still missing using a flat bottom shallow water model we show that a direct coupling between atmospheric pressure and the free mode of an inlet is unlikely but that an oceanic wave of atmospheric origin can act as an intermediate mechanism and adequately force the inlet by resonance the phase relationship derived from this mechanism is in good agreement with observations provided the whole spectrum of oceanic waves is in opposite phase to the generating atmospheric disturbance we also show that the very large oscillations observed at ciutadella an elongated shallow inlet in the west coast of menorca balearic islands can be explained in terms of the particular shape of this inlet

a study of resonant oscillations in the split harbour adriatic sea abstract the study examines the occurrence of proudman resonance in front of the split harbour adriatic sea the dataset comprises air and sea pressure sea level data collected at the harbour entrance during august to october 2000 and is characterized by rather strong synoptic disturbances that took place over the harbour the analyses encompass empirical tools such as time series analysis high and band pass filtering spectral and wavelet analyses while the theoretical approach includes the conceptual model of the resonance resonance appears in front of the harbour and then propagates inward covering periods between 7 7 and 28 5 min as a result of complex atmospheric gravity wave structure gain between sea level and air pressure equals 0 05 0 40 dbar hpa 5 40 cm hpa

hydrocarbon potential of the lower cretaceous mudstones in coastal southeastern china the cretaceous hosts the highest hydrocarbon potential among all geological stratigraphic sequences worldwide and the lower cretaceous in coastal southeastern china with the development of black mudstones and shales has potential for hydrocarbon generation this potential therefore is of significance to regional hydrocarbon exploration both onshore and offshore however it has not been investigated in detail here we address this issue based on the results of integrated organic geochemistry and petrology of four representative outcrop sections in the region results show that there are two possible source rock sequences in the lower cretaceous of coastal southeastern china that is a lower sequence represented by the bantou formation black mudstones in the fujian province and an upper interval represented by the guantou formation black mudstones or calcareous mudstones in the zhejiang province the organic matter abundance of these two formations reaches levels of poor to good source rocks the kerogen is dominated by type iii whereas type ii can also be found locally in the northwestern fujian province most samples are highly mature to overmature except for the samples with less influence of volcanism in the northern guangdong province comparatively the organic matter abundance of the early stage source rocks is higher than for the late stage rocks and the kerogen type is less favorable however the maturity shows little correlation with age and is largely related to volcanism therefore the lower cretaceous in coastal southeastern china seems to have hydrocarbon potential gas in particular in local areas including the northern guangdong province and its analog in offshore basins for the early stage and the northwestern fujian province and its analog in offshore basins for the late stage these results and understanding provide insights for expanding new hydrocarbon exploration targets in southeastern china both onshore and offshore and may also have implications for understanding the regional cretaceous geology