sedimentary pyrite formation an update sedimentary pyrite formation during early diagenesis is a major process for controlling the oxygen level of the atmosphere and the sulfate concentration in seawater over geologic time the amount of pyrite that may form in a sediment is limited by the rates of supply of decomposable organic matter dissolved sulfate and reactive detrital iron minerals organic matter appears to be the major control on pyrite formation in normal non euxinic terrigenous marine sediments where dissolved sulfate and iron minerals are abundant by contrast pyrite formation in non marine freshwater sediments is severely limited by low concentrations of sulfate and this characteristic can be used to distinguish ancient organic rich fresh water shales from marine shales under marine euxinic conditions sufficient h2s is produced that the dominant control on pyrite formation is the availability of reactive iron minerals calculations based on a sulfur isotope model indicate that over phanerozoic time the worldwide average organic carbon to pyrite sulfur ratio of sedimentary rocks has varied considerably high cs ratios during permo carboniferous time can be explained by a shift of major organic deposition from the oceans to the land which resulted in the formation of vast coal swamps at that time low cs ratios compared to today during the early paleozoic can be explained in terms of a greater abundance of euxinic basins combined with deposition of a more reactive type of organic matter in the remaining oxygenated portions of the ocean the latter could have been due to lower oceanic oxygen levels and or a lack of transportation of refractory terrestrial organic matter to the marine environment due to the absence of vascular land plants at that time

porosity development and the influence of pore size on the ch4 adsorption capacity of a shale oil reservoir upper cretaceous from colombia role of solid bitumen abstract the la luna formation of turonian santonian age has recently been described as a reservoir of shale oil type which is located in the middle magdalena valley basin mmv of colombia two of the members of this formation galembo gm at the top and salada sm at the bottom have previously been investigated by juliao et al 2015 to determine their organic composition maturity and hydrocarbon potential as well as their macro and mesoporosity characteristics by means of mercury intrusion porosimetry mip analysis the present work which is a continuation of the previous one focuses on the study of the porosity using low pressure n 2 and co 2 adsorption analysis of both members in the determination of ch 4 adsorption capacity and in the establishment of the corresponding relationships with the pore size micropore size the role played by the solid bitumen expressed as toc content of the lower sedimentary levels of both members gm and sm in the development of the porosity properties should be emphasized the results obtained from this work demonstrate that i the predominant types of organic populations kerogen and solid bitumen in the sedimentary levels of this shale oil reservoir that show a narrow degree of maturity are the main factors controlling porosity development and consequently ch 4 adsorption and storage capacity ii the kerogen rich levels upper part of gm and sm are mainly macro and mesoporous corresponding this porosity to that of the primary organic matter and the inorganics and there is no relationship between this porosity and the variation in toc content iii the amount of porosity measured by n 2 adsorption in the kerogen rich levels is influenced by the content of free hydrocarbons occluded in the pores s1 iv porosity mainly microporosity development in the lower levels of gm and sm seems to be linked to the presence absence and the amount of solid bitumen as demonstrated by the close relationship existing with the toc content therefore solid bitumen is the host of porosity v the microporosity developed in the sedimentary levels with solid bitumen content strongly influences the ch 4 adsorption capacity although the relationship has been found to be complex as it is influenced by the micropore size and therefore by the density of the ch 4 finally this study highlights the importance of organic petrography in detecting the solid bitumen which is the organic component that explains all variation in the textural properties of gm and sm and which eluded detection by all other techniques

calculation of petroleum masses generated and expelled from source rocks abstract an algebraic scheme for calculating the masses of petroleum formed in mature source rocks has been constructed the scheme exploits routine geochemical measurements and a basic understanding of the behaviour of sedimentary organic matter at elevated temperatures under both laboratory and subsurface conditions application of these techniques to data from a wide range of source rock types has led to the following general conclusions 1 1 major oil and gas generation from kerogen occurs between 120 and 150 c in the subsurface gas generation continues to temperatures 160 c 2 2 oil prone source rocks with average initial potential 5 kgt 1 of rock and average organic carbon contents 1 5 expel 60 90 of the total oil generated 3 3 oil expulsion from leaner source rocks is less efficient most of the oil generated remains in the source rock it is subsequently converted to lighter components at higher temperatures and expelled in the vapour state 4 4 the major loss of organic carbon from rich oil prone source rocks during generation and expulsion means that the petroleum potential and organic carbon content of mature source rocks are much less than their initial immature values hence the algebraic scheme must be used to calculate the initial values before expelled petroleum masses can be determined

sequence stratigraphy depositional history and middle to late quaternary sea levels of the ventura shelf california abstract high resolution shallow seismic profiles from the ventura shelf reveal two contrasting structurally controlled styles of deposition on the northern shelf folded plio pleistocene strata comprising the south limb of the ventura avenue anticline are unconformably overlain by undeformed late quaternary strata in contrast a thicker section of undeformed prograding deltaic sequences preserved on the subsiding southern shelf contains a detailed record of at least five middle and late quaternary glacioeustatic sea level oscillations a transgressive surface at 140 m in upper pleistocene saugus deposits is overlain by transgressive and highstand systems tracts a shelf margin systems tract subsequently developed as the sea level lowered marking the end of saugus deposition thereafter over 50 m of post saugus upper pleistocene sediment accumulated during a period of smaller scale sea level oscillations followed by the development of a pair of marine terraces presently at 50 and 33 m and a large fluvial channel now buried at 113 m correlations of saugus and terrace marker horizons with the middle to late quaternary paleosea level curve suggest development of the saugus marker horizons during oxygen isotopic stages 7 5e and formation of the terraces during wisconsinan high sea levels maximum rates of vertical separation on the oak ridge and pitas point faults are estimated to be 0 13 and 0 30 m 1000 yr respectively

convergence rates across a displacement transfer zone in the western transverse ranges ventura basin california three cross sections are balanced and retrodeformed to the top of the pleistocene saugus formation and to a horizon close to the base of the jaramillo subchron to yield crustal shortening and shortening rates for the western transverse ranges of california the cross sections compare the shortening that occurs along a transfer zone in which displacement is transferred eastward from a surface reverse fault red mountain fault to a blind thrust and from that to a combination of both a surface reverse fault san cayetano fault and the blind thrust using an age of 250 50 ka for the top of the saugus formation based on amino acid racemization of fossil mollusks crustal shortening rates appear to have abruptly accelerated through time from 3 4 3 to 5 4 mm yr between 250 and 975 ka to 20 6 to 28 1 mm yr since 250 50 ka using an age of 500 ka for the top of the saugus formation based on paleomagnetic stratigraphy there is little increase in deformation rates through time ranging from 5 5 to 8 6 mm yr between 975 500 ka and from 10 3 to 14 1 mm yr since 500 ka more crustal convergence rates determined by global positioning system surveys taken over 4 6 years indicate a shortening rate of 7 10 mm yr across the basin this is consistent with the slower rates of deformation calculated using an age of 500 ka for the top of the saugus formation less

burial of organic carbon and pyrite sulfur in sediments over phanerozoic time a new theory in present day marine sediments almost all of which are deposited in normal oxygenated seawater rates of burial of organic carbon c and pyrite sulfur s correlate positively and bear a constant ratio to one another c s 3 on a weight basis by contrast calculations based on the isotopic model of garrels and lerman 1981 indicate that at various times during the phanerozoic the worldwide burial ratio must have been considerably different than the present day value this ratio change is caused by the requirement that increases in the worldwide mass of organic carbon must be accompanied by equivalent decreases in the mass of sedimentary pyrite sulfur in order to maintain a roughly constant level of o2 in the atmosphere such apparently contradictory behavior can be explained if the locus of major organic carbon burial has shifted over time from normal marine environments as at present to non marine freshwater or to euxinic environments in the geologic past a shift to predominantly freshwater burial can help explain predicted high c s ratios in permo carboniferous sediments and a shift to euxinic environments can help explain predicted low c s ratios during the early paleozoic it is demonstrated that the three environments today exhibit distinguishably different average c s ratios

scales of stress heterogeneity near active faults in the santa barbara channel southern california the santa barbara channel represents the offshore portion of the ventura basin in southern california ongoing transpression related to a regional left step in the san andreas fault has led to the formation of e w trending en echelon fault systems that accommodate localized shortening across the basin recent studies have suggested that faults within the channel could be capable of a multisegment rupture and producing a m w 7 7 8 1 tsunamigenic earthquake however dynamic rupture models producing these results do not account for stress heterogeneity with only sparse information available on the stress field in this region further borehole derived stress constraints are essential for obtaining a more comprehensive understanding of the hazards related to the complex fault systems we used caliper logs from 19 wells obtained from industry to identify stress induced borehole breakouts beneath the holly and gail oil platforms in the channel our newly developed forward modeling technique provides constraints on the orientations and relative magnitudes of the three principal stresses at gail we determine a reverse faulting stress regime s hmax 1 7 s hmin 1 6 sv 1 0 and an s hmax azimuth of n45 e our results are consistent with local structures which reflect deeper regional scale trends and with similar studies onshore nearby at holly an s hmax rotation from n36 w to n57 e occurs across 100 m depth in a single well and differs from nearby results indicating that short length scale 10 km laterally and 1 km in depth stress heterogeneity is associated with complex changes in fault geometry

characterization of organic matter fractions in an unconventional tight gas siltstone reservoir abstract this paper on core samples collected from the triassic montney formation tight gas reservoir in the western canadian sedimentary basin wcsb illustrates that operationally defined s1 and s2 hydrocarbon peaks from conventional rock eval analysis may not adequately characterize the organic constituents of unconventional reservoir rocks modification of the thermal recipe for rock eval analysis in conjunction with manual peak integration provides important information with significance for the evaluation of reservoir quality an adapted method of the analysis herein called the extended slow heating esh cycle was developed in which the heating rate was slowed to 10 c per minute over an extended temperature range from 150 to 650 c for montney core samples within the wet gas window this method provided quantitative distinctions between major organic matter om components of the rock we show that the traditional s1 and s2 peaks can now be quantitatively divided into three components s1 esh free light oil s2a esh fluid like hydrocarbon residue fhr and s2b esh residual carbon solid bitumen more refractory consolidated bitumen pyrobitumen the majority of the total organic carbon toc in the studied montney core samples consists of solid bitumen that represents a former liquid oil phase which migrated into the larger paleo intergranular pore spaces physicochemical changes to the oil led to the precipitation of asphaltene aggregates subsequent diagenetic and thermal cracking processes further consolidated these asphaltene aggregates into lumps of solid bitumen or pyrobitumen at higher thermal maturity solid bitumen obstructs porosity and hinders fluid flow and thus shows strong negative correlations with reservoir qualities such as porosity and pore throat size although the fhr fraction constitutes a small portion of the total rock mass and volume in montney samples it has important implications for reservoir quality this fraction represents a thin film of condensed heavy molecular hydrocarbon residue covering surfaces of the present time pore spaces and may represent the lighter component of the paleo oil that migrated into tight interstices in the montney reservoir the fhr fraction potentially plays an important role in wettability alteration by creating hydrophobic matrix pore networks in portions of the reservoir that were not already filled with solid bitumen

origin of a thrust related fold geometric vs kinematic tests abstract geometric tests to determine the origin of fault related folds are common but as is typical in structural geology more than one fold origin may yield the final natural geometry thus the results of geometric tests are usually non unique in contrast kinematic tests of origin which employ both geometry and data about deformation commonly yield more constrained if not unique results unfortunately the necessary data collection requires much more work than for a geometric test in this study the thrust related barclay anticline is analyzed both geometrically and kinematically to determine which test is more effective geometric tests using angular relationships indicate three possible origins fault bend fault arrest and break thrust for the kinematic test predicted deformations for interlayer and flexural slip flexural flow simple shear and bending strains are compared to micro and mesostructural distributions solution strain and finite strain from the anticline strain measurements indicate that microscale deformation is uniformly distributed through the structure and is lithification dominated the microscale deformation does not match kinematic predictions and did not accommodate fold formation fold growth was achieved primarily through layer parallel slip restricted mostly to the forelimb and absent in the hinge which eliminates fault bend and fault arrest origins that require material transport from forelimb to backlimb the barclay anticline is therefore interpreted to be a break thrust structure interestingly a suite of contraction faults in the forelimb and hinge indicates material transport from forelimb to backlimb such transport has been discounted for break thrust folds the most important result of this study is that a kinematic test was a necessary step for distinguishing fold origin geometric testing alone was insufficient given that the barclay anticline has geometric characteristics typical of many thrust related folds kinematic testing appears necessary to determine their structural origin

the 1994 northridge earthquake sequence in california seismological and tectonic aspects the m w 6 7 northridge earthquake occurred on january 17 1994 beneath the san fernando valley two seismicity clusters located 25 km to the south and 35 km to the north northwest preceded the mainshock by 7 days and 16 hours respectively the mainshock hypocenter was relatively deep at 19 km depth in the lower crust it had a thrust faulting focal mechanism with a rake of 100 on a fault plane dipping 35 to the south southwest and striking n75 w because the mainshock did not rupture the surface its association with surficial geological features remains difficult to resolve nonetheless its occurrence reemphasized the seismic hazard of concealed faults associated with the contractional deformation of the transverse ranges the northridge earthquake is part of the temporal increase in earthquake activity in the los angeles area since 1970 the mainshock was followed by an energetic aftershock sequence eight aftershocks of m 5 0 and 48 aftershocks of 4 m 5 occurred between january 17 and september 30 1994 the aftershocks extend over most of the western san fernando valley and santa susana mountains they form a diffuse spatial distribution around the mainshock rupture plane illuminating a previously unmapped thrust ramp extending from 7 10 km depth into the lower crust to a depth of 23 km no flattening of the aftershock distribution is observed near its bottom at shallow depths above 7 10 km the thrust ramp is topped by a dense distribution of aftershock hypocenters bounded by some of the surficial faults the dip of the ramp increases from east to west the west side of the aftershock zoae is characterized by a dense steeply dipping and north northeast striking planar cluster of aftershocks that exhibited mostly thrust faulting these events coincided with the gillibrand canyon lateral ramp along the east side of the aftershock zone the aftershocks also exhibited primarily thrust faulting focal mechanisms the focal mechanisms of the aftershocks were dominated by thrust faulting in the large aftershocks with some strike slip and normal faulting in the smaller aftershocks the 1971 san fernando and the 1994 northridge earthquakes ruptured partially abutting fault surfaces on opposite sides of a ridge both earthquakes accommodated north south contractional deformation of the transverse ranges the two earthquakes differ primarily in the dip direction of the faults and the depth of faulting the 1971 north northeast trend of left lateral faulting chatsworth trend was not activated in 1994

fluid pressure induced seismicity at regional scales the role of high fluid pressure as a seismogenic agent has been the subject of intense study hubert and rubey 1959 hanshaw and bredehoeft 1968 healy and rubey 1968 simpson 1976 walder and nur 1984 sibson 1990 of particular interest is the so called fault valve mechanism sibson 1976 sibson 1990 a hypothesis whereby fluid pressure rises as a result of tectonic compression and pore volume reduction until crustal failure occurs triggering seismic activity and upward fluid discharge sealing and healing of the rock matrix richter and simmons 1977 sprunt and nur 1979 angevine et al 1982 following coseismic stress drop facilitates reaccumulation of fluid pressure initiating another loading cycle the fault valve mechanism is entertained as a plausible explanation for present day seismic activity in the western transverse ranges of california we provide a quantitative test of the fault valve hypothesis that uses geologic data and rates of active tectonics for a cross section through an active fold and thrust belt on the flank of a developing mountain range rates of fluid pressure buildup and average recurrence times of large earthquakes in the fold and thrust belt are estimated to be on the order of 104pa yrand hundreds of years respectively

seismicity and geometry of a 110 km long blind thrust fault 2 synthesis of the 1982 1985 california earthquake sequence during 1982 1985 three 5 4 mw 6 5 earthquakes migrated 65 km along the north half of a string of quaternary folds at the east front of the california coast ranges there is no surface fault associated with these earthquakes but the fold chain oriented parallel to the san andreas fault 30 km to the west takes up contraction normal to the san andreas fault identification of active blind thrust faults is hindered by the absence of a fault trace but may be revealed by the presence of growing folds at the surface and by earthquakes at depth because of excellent seismic geodetic and geologic data this earthquake sequence illuminates the geometry of the blind faults and enables us to probe their mechanics we relocate seismicity and compute focal mechanisms in a three dimensional velocity space and model the vertical deformation associated with the 1983 m 6 5 coalinga earthquake the aftershock zones abut at echelon offsets in the fold axes and the mainshocks display reverse slip perpendicular to the axes suggesting that the folds conceal a contiguous segmented thrust fault background seismicity concentrates at bends and breaks in the fold chain sites that may correspond to tears and ramps in the thrust fault at depth seismic reflection profiles reveal thrust and reverse faults dipping toward the san andreas fault at depths of 5 10 km with several kilometers of cumulative slip and high angle reverse faults in the anticlines with several hundred meters cumulative slip coseismic fold uplift accompanied the coalinga and kettleman hills north dome earthquakes suggesting that fold growth is episodic and coupled closely to repeated earthquakes on the underlying thrusts the north half of the fold chain has been the site of several 6 m 6 5 earthquakes since 1885 thus kettleman hills middle dome the next fold segment to the south has an elevated seismic potential the aftershock zones of the three main shocks are diffuse and occupy a region much larger than the site of seismic slip aftershocks occur 5 7 km from the fault regions where on the basis of a boundary element model the shear strain increase caused by the fault slip exceeds 20 ppm equivalent to about 0 7 mpa we argue that the broad aftershock zone is a product of high sustained off fault stress caused by repeated displacement on faults that do not cut the earth s surface the fault tip stresses lead to the formation of secondary faults which can become sites of aftershocks and postseismic creep

triassic oils and potential mesozoic source rocks peace river arch area western canada basin abstract triassic oils and their potential mesozoic source rocks in the peace river arch region western canada basin have been examined using various analytical techniques triassic oils are divided into two groups 1 and 2 on the basis of biomarker composition triassic outcrop samples from the rocky mountain foothills are mature to overmature and contain type ii iii organic matter with toc s ranging from 0 1 to 15 0 wt and hi values up to 445 subsurface core samples from the triassic montney formation are mature to overmature with toc s rarely up to 2 8 wt and hi values up to 398 the triassic doig formation has good to excellent source potential and moderate to high maturity with toc values over 5 0 wt and hi values commonly in excess of 300 the jurassic nordegg member ranges from early mature to overmature with toc s as high as 23 5 wt and hi values greater than 600 where maturity is low oil source rock correlations are established based on biomarker signatures between the group 1 oils and the doig formation group 2 oil was sourced by the nordegg member

experimental measurement of electromagnetic emissions possibly related to earthquakes in japan recent observations in the ussr appear to suggest that wide band electromagnetic radiation occurs just prior to earthquakes to apply this phenomenon to earthquake prediction measurements have been carried out at the sugadaira space radiowave observatory in japan under the ussr japan cooperation program in 1980 the recorded noise level at 81 khz is comparatively quiet throughout the day and night however about one half hour before the main shock of a magnitude 7 earthquake at 0733 ut on march 31 1980 the instrument recorded an anomalous amplitude increase to 15 db higher than the normal level vlf data recorded synoptically at sugadaira suggest that unusual impulsive radiation at frequencies below 1 5 khz also occurred shortly before the earthquake similar 81 khz emissions were observed prior to magnitude 5 and 6 earthquakes on september 25 1980 and january 28 1981

late quaternary history of the ventura mainland shelf california abstract the ventura mainland shelf off california provides an interesting example of sedimentary response to tectonic activity and eustatic sea level fluctuations during the late quaternary a network of 370 km of high resolution seismic reflection profiles provides the basis for the study the high local rates of uplift as well as local basin subsidence have resulted in two distinct styles of sedimentation a late pleistocene angular unconformity separates folded plio pleistocene strata from undeformed upper pleistocene and holocene strata on the northern shelf in contrast the southern shelf is characterized by a thick section of stacked progradational deltaic sequences containing a well preserved record of late quaternary sedimentation sediment overlying the unconformity north of the pitas point fault ranges from 10 to 40 m in thickness whereas the equivalent sequence in the adjacent southern shelf is 80 85 m thick the distribution of upper pleistocene and holocene deposits is controlled by structural features including the pitas point and oak ridge faults and the ventura avenue anticline as well as proximity to fluvial input from the santa clara and ventura rivers within upper pleistocene deposits a pair of buried marine terraces occur at depths of 33 and 50 m below present sea level b p s l terrace deposits consist of a basal coarse grained transgressive deposit which is transitional into a finer grained marine facies these deposits are associated with a period of aggradation during minor late wisconsinan sea level cycles deltaic deposits beneath the southern shelf 4 km north of hueneme submarine canyon suggest that the santa clara river debouched into the sea at this location during the late pleistocene the santa clara river shifted southward during the late wisconsinan and cut a large channel now buried near hueneme canyon this channel indicates that relative sea level was at least 113 m b p s l during the late wisconsinan a smaller channel indicates a fall in sea level to 46 m b p s l during the holocene the oak ridge fault displays a general increase in offset seaward across the shelf with a maximum vertical displacement of 17 m on the saugus upper pleistocene contact displacements on the pitas point fault increase shoreward attaining as much as 40 m of vertical displacement of the late pleistocene unconformity nearshore the pitas point fault vertically displaces the seafloor by 4 m

structure and seismic hazard of the ventura avenue anticline and ventura fault california prospect for large multisegment ruptures in the western transverse ranges abstract the ventura avenue anticline is one of the fastest uplifting structures in southern california rising at 5 mm yr we use well data and seismic reflection profiles to show that the anticline is underlain by the ventura fault which extends to seismogenic depth fault offset increases with depth implying that the ventura avenue anticline is a fault propagation fold a decrease in the uplift rate since 30 10 ka is consistent with the ventura fault breaking through to the surface at that time and implies that the fault has a recent dip slip rate of 4 4 6 9 mm yr to the west the ventura fault and fold trend continues offshore as the pitas point fault and its associated hanging wall anticline the ventura pitas point fault appears to flatten at about 7 5 km depth to a detachment called the sisar decollement then step down on a blind thrust fault to the north other regional faults including the san cayetano and red mountain faults link with this system at depth we suggest that below 7 5 km these faults may form a nearly continuous surface posing the threat of large multisegment earthquakes holocene marine terraces on the ventura avenue anticline suggest that it grows in discrete events with 5 10 m of uplift with the latest event having occurred 800 years ago rockwell 2011 uplift this large would require large earthquakes m w 7 7 8 1 involving the entire ventura pitas point system and possibly more structures along strike such as the san cayetano fault because of the local geography and geology such events would be associated with significant ground shaking amplification and regional tsunamis

active faulting and block rotations in the western transverse ranges california the geometry of faulting slip vectors of major earthquakes and results of very long baseline interferometry vbli are consistent with active clockwise rotation of crustal blocks in the western transverse ranges about vertical axes oblique left lateral thrust faults trending roughly east west across the western transverse ranges apparently separate long east west blocks of upper crust and the large components of lea lateral shear on east striking planes suggest that the blocks rotate with respect to the san andreas fault in the mojave region between the western transverse ranges and the mojave desert paleomagnetic declinations indicate some 35 and possibly 60 of clockwise rotation since about 10 ma and more importantly the relative velocity between the only two frequently measured vbli sites in the western transverse ranges is consistent with a rotation rate of 6 ma 3 ma during a 5 year period in the 1980s azimuths of slip vectors of major earthquakes are essentially orthogonal to the segment of the san andreas fault across the western mojave desert indicating that crustal shortening across the region is absorbed by crustal thickening and not by lateral translation extension of material parallel to that segment of the fault plate motions late quaternary offsets on the san andreas and san jacinto faults and geodetic measurements in the mojave region yield a calculated direction of relative motion between the san gabriel mountains and the pacific plate across the western transverse ranges that also is perpendicular to the san andreas fault in the mojave region rotation rates associated with simple mechanisms for applying essentially normal tractions to the lateral margins of blocks are not consistent with the observed geometry of faulting and with average rotation rates the rotation rate of 2 8 5 3 ma calculated assuming that the long east west blocks rotate in response to a uniform compression of a viscous substratum to the western transverse ranges however overlaps the range of observed average rotation rates thus the hypothesis that blocks of continental crust move as if carried passively by a substratum undergoing continuous deformation passes one test that can be made of it

unconventional shale gas systems the mississippian barnett shale of north central texas as one model for thermogenic shale gas assessment shale gas resource plays can be distinguished by gas type and system characteristics the newark east gas field located in the fort worth basin texas is defined by thermogenic gas production from low porosity and low permeability barnett shale the barnett shale gas system a self contained source reservoir system has generated large amounts of gas in the key productive areas because of various characteristics and processes including 1 excellent original organic richness and generation potential 2 primary and secondary cracking of kerogen and retained oil respectively 3 retention of oil for cracking to gas by adsorption 4 porosity resulting from organic matter decomposition and 5 brittle mineralogical composition the calculated total gas in place gip based on estimated ultimate recovery that is based on production profiles and operator estimates is about 204 bcf section 5 78 10 9 m 3 1 73 10 4 m 3 we estimate that the barnett shale has a total generation potential of about 609 bbl of oil equivalent ac ft or the equivalent of 3657 mcf ac ft 84 0 m 3 m 3 assuming a thickness of 350 ft 107 m and only sufficient hydrogen for partial cracking of retained oil to gas a total generation potential of 820 bcf section is estimated of this potential approximately 60 was expelled and the balance was retained for secondary cracking of oil to gas if sufficient thermal maturity was reached gas storage capacity of the barnett shale at typical reservoir pressure volume and temperature conditions and 6 porosity shows a maximum storage capacity of 540 mcf ac ft or 159 scf ton

do all fractions of organic matter contribute equally in shale porosity a case study from upper ordovician utica shale southern quebec canada abstract in many unconventional hydrocarbon systems organic matter om substantially contributes to total porosity of the rock that led to a positive correlation between total organic carbon toc and porosity while organic porosity is an important reservoir property of unconventional hydrocarbon systems toc of these rocks consists of different macerals or petrographic fractions these toc fractions can be geochemically divided and quantified by the revised extended slow heating esh rock eval analysis this study discusses the contribution of different fractions of om on porosity variation in the mature to overmature utica shale in southern quebec using esh rock eval analysis helium pycnometery scanning electron microscopy sem and x ray diffraction xrd mineralogy selected samples from three wells at depths of 400 700 and 2000 m covering a range of thermal maturity from late peak oil window vroeqv 1 to dry gas zone vroeqv 2 1 were analyzed in this study the predominant om constituents are solid bitumen chitinozoans and minor graptolites with mean toc of 1 1 0 4 wt the mean porosity for oil and gas window samples decreases with depth from 3 9 0 9 to 2 6 0 5 respectively the sem images reveal that organic porosity is limited to pores developed in solid bitumen while regardless of thermal maturity chitinozoans have a non porous structure throughout the oil to dry gas window this observation suggests that the impact of thermal maturity on porosity is different for different om fractions i e macerals leading to different contribution of om fractions to total porosity the latter conclusion is further supported by the improved correlation observed between the solid bitumen fraction and porosity compared to toc porosity correlation for oil window samples our entire data set suggests that om i e bitumen fraction especially in the dry gas window is not the major controlling factor on the total porosity in the utica shale whereas intergranular porosity has the dominant control on total porosity this observation suggests that the hydrocarbon storage potential may largely reside in inorganic pores rather than organic pores in the analyzed intervals of the utica shale the decrease in total porosity observed from shallower samples i e oil window to deeper samples i e dry gas window also suggests that intergranular porosity is the dominant porosity component which decreases with burial

artificial thermal maturation of source rocks at different thermal maturity levels application to the triassic montney and doig formations in the western canada sedimentary basin abstract artificial thermal maturation of petroleum source rocks is widely performed by either open or closed system pyrolysis these experiments are performed usually on immature source rock or isolated kerogen samples to quantify petroleum generation potential and to calculate kinetic parameters here we characterize a maturation series from the triassic montney and doig formations in the western canada sedimentary basin wcsb in order to investigate the evolution of the source rock properties and their corresponding kerogen kinetic parameters as a function of the thermal maturity organic petrography determined the thermal maturity and the spatial distribution of organic matter particles rock eval shale play analyses were then applied to assess the presence of both free and sorbed hydrocarbons still contained in the sample as well as the hydrocarbon generation potential based on vitrinite reflectance values three kerogen samples from the doig formation and one kerogen sample from the montney formation at different thermal maturity levels were selected for analysis of bulk kinetic parameters e g activation energy distribution frequency factor using programmed open system pyrolysis additionally we evaluated the type of hydrocarbons and determined the molecular composition of organic compounds that comprise the first two rock eval peaks sh0 and sh1 obtained during the improved thermovaporization td gc ms fid analyses were carried out on rock samples sequentially from 100 c to 200 c and then from 200 c to 350 c in order to characterize the composition of hydrocarbons represented by each rock eval shale play peak free and sorbed low to medium molecular weight aliphatic and aromatic hydrocarbons 20 are the main hydrocarbon components released in the temperature range corresponding to the rock eval shale play sh0 parameter medium and high molecular weight hydrocarbons c 10 c 30 aromatics and saturates are predominant components thermally released in the temperature range corresponding to the rock eval shale play sh1 parameter results show both an increasing activation energy and loss of petroleum generation potential as thermal degradation proceeds the shale play method has been developed to better discriminate the generated fluids sh0 sh1 from the residual kerogen sh2 providing a more accurate rock eval t max sh0 and sh1 parameters also offer a practical way for an early estimate of oil in place

unified structural representation of the southern california crust and upper mantle we present a new 3d description of crust and upper mantle velocity structure in southern california implemented as a unified structural representation usr the usr is comprised of detailed basin velocity descriptions that are based on tens of thousands of direct velocity vp vs measurements and incorporates the locations and displacement of major fault zones that influence basin structure these basin descriptions were used to developed tomographic models of crust and upper mantle velocity and density structure which were subsequently iterated and improved using 3d waveform adjoint tomography a geotechnical layer gtl based on vs30 measurements and consistent with the underlying velocity descriptions was also developed as an optional model component the resulting model provides a detailed description of the structure of the southern california crust and upper mantle that reflects the complex tectonic history of the region the crust thickens eastward as moho depth varies from 10 to 40 km reflecting the transition from oceanic to continental crust deep sedimentary basins and underlying areas of thin crust reflect neogene extensional tectonics overprinted by transpressional deformation and rapid sediment deposition since the late pliocene to illustrate the impact of this complex structure on strong ground motion forecasting we simulate rupture of a proposed m 7 9 earthquake source in the western transverse ranges the results show distinct basin amplification and focusing of energy that reflects crustal structure described by the usr that is not captured by simpler velocity descriptions we anticipate that the usr will be useful for a broad range of simulation and modeling efforts including strong ground motion forecasting dynamic rupture simulations and fault system modeling the usr is available through the southern california earthquake center scec website http www scec org

application of the global positioning system to crustal deformation measurements 3 result from the southern california borderlands five years of measurements from the global positioning system gps satellites collected between 1986 and 1991 are used to investigate deformation in the offshore regions of southern california gps provides the first practical technique to make precise geodetic measurements in the region the geodetic network is situated along the california coastline from vandenberg 120 6 w 34 6 n to san diego with additional sites on santa cruz san nicolas santa catalina santa rosa and san clemente islands the precision of horizontal interstation vectors is subcentimeter and the interstation vector rate between ovro and vandenberg agrees with the very long baseline interferometry derived rate to within one standard deviation no significant motion is observed in the western santa barbara channel between vandenberg and santa rosa island 0 5 1 6 mm yr where the quoted uncertainties are one standard deviation motions in the eastern santa barbara channel are consistent with compressional deformation of 6 1 mm yr at n16 3 e this motion is in agreement with seismicity and an independent geodetic analysis for the period 1971 1987 larsen 1991 san clemente island is moving relative to san diego at the rate of 5 9 1 8 mm yr at a direction of n38 20 w the motion between san nicolas island and san clemente island 0 8 1 5 mm yr is insignificant

grain assemblages and strong diagenetic overprinting in siliceous mudrocks barnett shale mississippian fort worth basin texas porosity permeability and total organic carbon toc in a heterogeneous suite of 21 high maturity samples vitrinite reflectance 1 52 2 15 from the barnett shale in the eastern fort worth basin display few correlations with parameters of rock texture fabric and composition these factors being mostly obscured by the effects of a protracted history of diagenesis diagenesis in these rocks includes mechanical and chemical modifications that occurred across a wide range of burial conditions compaction and cementation have mostly destroyed primary intergranular porosity the porosity average 5 vol by gas research institute helium porosimetry and pore size 8 nm median pore throat diameter are reduced to a degree such that pores are difficult to detect even by imaging ar ion milled surfaces with a field emission scanning electron microscope the existing porosity that can be imaged is mostly secondary and is localized dominantly within organic particulate debris and solid bitumen the grain assemblage is highly modified by replacement a weak pattern of correlation survives between bulk rock properties and the ratio of extrabasinal to intrabasinal sources of siliciclastic debris higher porosity permeability and toc are observed in samples representing the extreme end members of mixing between extrabasinal siliciclastic sediment and intrabasinal derived biosiliceous debris reservoir quality in these rocks is neither more strongly nor more simply related to variations in primary texture and composition because the interrelationships between texture and composition are complex and importantly the diagenetic overprint is too strong

geology and tsunamigenic potential of submarine landslides in santa barbara channel southern california abstract a large submarine landslide complex and four small landslides developed under the santa barbara channel suggesting a potential hazard from landslide generated tsunamis we integrate offshore stratigraphy and geologic structure multibeam bathymetric information and several kinds of seismic reflection data to understand how and when the submarine landslides formed seismic reflection data show that mass failure along the slope began at least 200 ka ago landslides appear as zones of poor reflectivity having an irregular upper surface and these zones alternate vertically with strong parallel reflections the emplacement ages of two of the three main landslide lobes are well established at 8 and 10 ka the source material for the youngest part of the landslide complex was sediment of probable late pleistocene and holocene age that accumulated in a shelf edge delta directly under this delta growth of faults and anticlines was particularly intense and tended to oversteepen the deltaic deposits these active structures also formed migration pathways and reservoirs for aqueous and hydrocarbon fluids from the deep basin tsunami deposits have been described from a low lying area near santa barbara and numerical modeling of tsunamis generated by hypothetical landslides in santa barbara channel indicates a moderate to severe threat borrero j c dolan j f and synolakis c e 2001 tsunamis within the eastern santa barbara channel geophys res lett 28 4 643 646 involving wave runups of 2 20 m for a range of assumed landslide volumes inundation from these waves however is expected to be highly focused so that only narrow 10 km sections of the shoreline would be affected

structural trend analysis by axial surface mapping discussion original article shaw j h s c hook and j suppre 1994 aapg bulletin v 78 p 700 721

neotectonics of the offshore oak ridge fault near ventura southern california the oak ridge fault is a large offset south dipping reverse fault that forms the south boundary of the ventura basin in southern california previous research indicates that the oak ridge fault south of the town of ventura has been inactive since 200 400 ka ago and that the fault tip is buried by 1 km of quaternary sediment however very high resolution and medium resolution seismic reflection data presented here show a south dipping fault on strike with the oak ridge fault that is truncated at 80 m depth by an unconformity that is probably at the base of late pleistocene and holocene sediment furthermore if vertically aligned features in seismic reflection data are eroded remnants of fault scarps then a subsidiary fault within the oak ridge system deforms the shallowest imaged sediment layers we propose that this subsidiary fault has mainly left slip offset these observations of holocene slip on the oak ridge fault system suggest that revision of the earthquake hazard for the densely populated santa clara river valley and the oxnard coastal plain may be needed

fault slip rates and interseismic deformation in the western transverse ranges california to better constrain fault slip rates and patterns of interseismic deformation in the western transverse ranges of southern california we present results from analysis of gps and interferometric synthetic aperture radar insar data and three dimensional mechanical and kinematic models of active faulting anthropogenic motions are detected in several localized zones but do not significantly affect the vast majority of continuous gps site locations gps measures contraction rates across the ventura basin of 7 mm yr oriented west northwest with rates decreasing to the west and east the santa barbara channel is accommodating 6 5 mm yr in the east and 2 5 mm yr in the western portions of n s contraction inversion of horizontal gps velocities highlights a zone of localized fast contraction rates following the ventura basin using a mechanical model driven by geodetically calculated strain rates we show that there are no significant discrepancies between short term slip rates captured by geodesy and longer term slip rates measured by geology mechanical models reproduce the first order interseismic velocity and strain rate patterns but fail to reproduce strongly localized contraction in the ventura basin due to the inadequate homogeneous elastic properties of the model existing two dimensional models match horizontal rates but predict significant uplift gradients that are not observed in the gps data mechanical models predict zones of fast contraction in the santa barbara channel and offshore near malibu suggesting that offshore faults represent a significant seismic hazard to the region furthermore many active faults throughout the region may produce little to no interseismic deformation making accurate seismic hazard assessment challenging 2013 american geophysical union all rights reserved

multi proxy approach to screen the hydrocarbon potential of the jurassic succession in the matruh basin north western desert egypt abstract this paper discusses the hydrocarbon potential of the jurassic succession in a mature basin in egypt as an important element of a larger petroleum system study prior to any organic petrographic and organic geochemical analyses a palynological age dating of the originally undifferentiated jurassic sequence was carried out to identify different formations under investigation this was based on key bioevents of some recovered dinoflagellate cysts and the identified lithology palynological toc rock eval pyrolysis including modified rock eval methods and vitrinite reflectance vro data from a total of 14 samples taken from the uppermost lower upper jurassic sequence represented by the wadi natrun toarcian aalenian khatatba late bathonian callovian and masajid oxfordian formations in the abu tunis 1 well are presented in addition two samples from the abu tunis 1 well and the proximal 32 km to the east siqueifa 1 well having the highest remaining hydrocarbon potential s2 yields were analyzed and their results were compared using modified pyrolysis programs although the data showed a good correlation between the tai of the palynomorph assemblage vitrinite reflectance and tmax from rock eval pyrolysis in the shallower intervals the correlation between vro and tmax was poor in the lower half of the studied succession middle khatatba and wadi natrun formations the very low tmax values indicate immature om while vro and tai indicated middle stage of oil window to past peak oil generation the reason for this discrepancy is that the deeper samples are reservoir rocks not source rocks and the majority of the organic matter is not composed of reactive kerogen but consists of migrated hydrocarbons and nso compounds contamination due to oil based mud obm was eliminated because the abu tunis 1 well was drilled in 1969 prior to the extensive use of obm in drilling this study showed that a multi proxy approach is the best way to screen the hydrocarbon potential in a thick succession that contains interbedded source and reservoir rocks

influence of igneous intrusions on thermal maturity and optical texture comparison between a bituminous marl and a coal seam of the same maturity abstract the impact of a 120 cm thick dike on dispersed organic matter in the triassic marry harbour mh bituminous marl in the raanes peninsula ellesmere island arctic canada was studied using reflected light microscopy and rock eval pyrolysis results were compared to a coal seam of similar maturity that was thermally altered by an igneous intrusion the mh bituminous marl is mature and within the oil window ro 0 94 whereas the coal is high volatile b bituminous rank ro 0 80 thermal alteration impacted differently the organic rich marl than the coal seam most of the heat generated by the intrusive emplacement in contact with coal is spent transforming coal to coke in the plastic layer zone similar to the process that coal undergoes in industrial coking operations in contrast the thermal alteration of sedimentary rocks occurs over longer distances as a result of the absence of a plastic layer zone the impact zone of the 120 cm thick igneous intrusion was greater in the mh bituminous marl which became thermally altered ro 2 34 at 190 cm from the contact with the dike on the contrary the coal became thermally altered ro 5 0 by a 240 cm alkali basalt intrusion twice the thickness of the mh dike and its impact zone was only 65 cm heat and hot volatile matter produced by the thermal decomposition of organic matter and minerals carbonate dehydration of clay minerals in contact with the igneous intrusion body is transferred through the sedimentary rock matrix by convection through fractures this transformation is evident by the occurrence of the pyrolytic carbon at various distances in the fractured mh marl from contact the hydrogen index hi shows a similar trend to that of the remaining source potential s2 both parameters decrease systematically toward the dike and go through a minimum at 20 cm from the dike contact as the indigenous organic matter is converted to hydrocarbons or devolatilized at the dike contact both s2 and hi have higher values these trends are similar to those of the volatile elements h and cl in the intruded coal seam the free hydrocarbons s1 showed a slightly different trend than s2 and hi it increased initially from 300 cm and reached a maximum at about 190 cm from the dike contact before decreasing continually and reaching a minimum at 20 cm from the contact at the dike contact the s1 increased slightly similar to the hi and s2 the presence of oil droplets trapped in carbonate concretions in combination with the highest value of oil expelled from the source rock based on s1 toc at distance of 190 cm from dike is an indication of the influence of contact metamorphism on oil generation locally furthermore it indicates that intrusion of igneous dikes into the bituminous mh marl resulted in an increase of organic matter maturation locally and in hydrocarbon generation

out of rock a new look at the morphological and geochemical preservation of microfossils from the 3 46 gyr old strelley pool formation abstract the biogenicity of most of the putative archean organic walled microfossils discussed in the literature remains debated here we report morphological and geochemical characterizations of an assemblage of microfossils isolated from the 3 46 gyr old strelley pool formation western australia thereby providing a new set of data on the oldest authentic microfossils on earth isolated microstructures microfossils were studied by combining scanning electron microscopy imaging and elemental analyses raman spectroscopy and nanoscale secondary ion mass spectrometry nanosims we identified four morphological types namely filaments films spheroids and lenses a minority of spheroids films and lenses exhibits a continuous wall cell surface and high n concentrations and substantial p contents as suggested by 31p 12c2 ionic ratios i e exceptionally high morphological and geochemical preservation levels in addition to the detection of p within microfossil walls p was also found within micrometric patches in lenses exhibiting a fusiform shape these patches may be remains of polyphosphate granules possibly formed during sporulation suggesting in turn that cellular organization appeared as soon as 3 46 gyr ago

effects of nanoporosity and surface imperfections on solid bitumen reflectance bro measurements in unconventional reservoirs abstract bitumen reflectance bro is an alternative maturity indicator to vitrinite reflectance vro in lower paleozoic and marine rocks where few higher plant macerals can be found in unconventional petroleum rocks locally exuded and or migrated oil are retained in the tight rocks and thermally and diagenetically consolidated into solid bitumen and pyrobitumen finding suitable bitumen macerals for bro measurements pose a challenge in indicating the proper thermal maturity this study reports the effects of surface imperfections caused by nanoporosity surface granularities and impurities on measuring bro in core samples from the jurassic nordegg shale shale oil and the triassic montney siltstone tight gas in the western canada sedimentary basin the degree that bitumen s surface imperfections influence any given reflectance measurement was controlled by changing the probe size area the larger the measuring probe the higher the degree of surface imperfections is included in bro readings the effect is quantified in this paper showing up to 27 diminishment of mean bro values when the probe size increased from 0 31 to 5 85 m2 the mode in which bitumen accumulates within the rock has a strong influence on the degree of surface imperfections bitumen which is disseminated within clay matrix introduces a high degree of nanoporosity and mineral interference and hence will result in lowest bro in contrast inclusions of high reflecting micrinite or diagenetic minerals such as pyrite result in higher bro these effects can vary at the microscopic scale leading to multiple populations of reflectance readings and difficult interpretations of thermal maturity

deformation in the santa barbara channel from gps measurements 1987 1991 geodesy is one of the few techniques that can be used to estimate strain rates across the submerged structures in the santa barbara channel by resolving relative surface velocities the global positioning system gps can be used to infer crustal deformation rates independent of geologic models gps measurements from the period 1987 1991 have been used to derive velocities for a 8 station network bounding the channel these estimates are based on 10 gps experiments each of several days in length over this 4 5 year period precision of individual determinations of intersite vectors range from 3 to 7 mm for the horizontal components and average 20 mm in the vertical the gps data indicate high rates of shortening in the eastern channel 6 1 mm yr at n16 3e and low rates of deformation in the western channel comparisons with previous geodetic studies suggest that deformation in the region has not been uniform over the last 100 years

solid bitumen as a determinant of reservoir quality in an unconventional tight gas siltstone play abstract in this study of the triassic montney tight gas siltstone play in the western canadian sedimentary basin petrophysical measurements of drill core samples porosity pore throat size water saturation and grain size are integrated with rock eval toc data organic petrography observations and sem imaging to show that reservoir quality in the gas window is strongly influenced by the pervasive presence of pore occluding solid bitumen and pyrobitumen at higher thermal maturity the solid bitumen formed as a pore filling liquid oil phase that was diagenetically and thermally degraded with further burial and increase in temperature the proportion of solid bitumen filling the intergranular paleopore network can be expressed as bitumen saturation and this attribute is found to be the dominant control on pore throat size and absolute permeability the samples with low bitumen saturation and large pore throat radius 0 01 m have water saturations that generally increase as pore throat size diminishes a relationship consistent with capillary theory for conventional water wet conditions the samples with high bitumen saturation and small pore throat radius

solid bitumen in the montney formation diagnostic petrographic characteristics and significance for hydrocarbon migration abstract the petrographic study of organic matter om in fine grained shale and tight rocks can be complicated by ambiguities in distinguishing primary kerogen deposited om from secondary solid bitumen migrated and solidified petroleum in this study complementary thin section field emission scanning electron microscopy fesem and organic petrology methods are used to examine core samples acquired from petroleum wells drilled into the triassic montney formation in western canada the results show that om in the medium to coarse grained siltstones of the montney tight gas and hydrocarbon liquids fairway is composed almost entirely of pore filling solid bitumen pyrobitumen here we document a range of petrographic characteristics that are diagnostic of the solid bitumen and its origin as migrated liquid petroleum these solid bitumen characteristics include 1 void filling habit 2 enclosure of earlier authigenic minerals 3 margins with smoothly curved meniscate form 4 internal flow structure 5 entrained and aligned clay minerals 6 isopachous rims along inorganic pore walls 7 globular granular aggregates and 8 fracture filling habit the petrographic results also show that the migration and flow of original oil through the thick montney formation up to 340 m was controlled at the micro scale by sedimentary ichnological diagenetic and structural features these features combined to form highly complex pathways and baffles for hydrocarbon migration petrographic recognition of om as secondary migrated solid bitumen rather than primary deposited kerogen has vital significance for assessing unconventional shale and tight hydrocarbon plays including om typing from rock eval pyrolysis interpreting depositional facies and environments and evaluating reservoir quality

kerogen composition and maturity assessment of a solid bitumen rich and vitrinite lean shale insights from the upper jurassic vaca muerta shale argentina abstract assessment of thermal maturity by solid bitumen reflectance measurements in vitrinite lean or vitrinite barren shales is widely used in unconventional shale gas and shale oil plays but the method is commonly challenged by the complexity in the measurements the upper jurassic marine vaca muerta shale in the neuquen basin in western argentina is both a prolific conventional source rock and a primary unconventional reservoir for oil and gas the shale is rich in solid bitumen and lean or barren in vitrinite and offers an excellent opportunity to gain insight into thermal maturity assessment of a shale with a complex organic matter composition the kerogen composition of a set of immature to highly mature vaca muerta shale samples was investigated by organic petrography and reflectance measurements were taken on vitrinite and solid bitumen the results were integrated with available rock eval data and stable carbon isotope values of shale gas ethane and propane collected at the same depth as the rock samples the maceral composition of immature vaca muerta shale is highly sapropelic and oil prone with hydrogen index values of 600 mg hc g toc or higher the liptinite macerals consist primarily of alginite with minor amounts of inertinite and or oxidized vitrinite indigenous vitrinite is generally scarce and in some samples absent vitrinite reflectance values range from 0 79 ro to more than 1 94 ro corresponding to early peak oil to dry gas maturity solid bitumen is abundant in all mature samples two general types of solid bitumen morphology were observed i br i a dark reflecting porous variant disseminated in the clayey mineral matrix and ii br ii a lighter reflecting more dense textured variant bands of denser solid bitumen were commonly seen flowing in more porous or weak zones in the matrix and around mineral grains degassing pores were frequently observed solid bitumen reflectance measurements on br i and br ii provided two populations with different reflectance ranges the correlation between vitrinite and br ii reflectances is considered to have highest confidence the correlation can be expressed by the equation vreqv br ii 0 3043 1 026 the established vreqv br ii correlation yields results comparable to other published correlations but also demonstrates significant discrepancy to others this warrants caution when assessing the maturity of complex unconventional shale gas and oil plays by translating solid bitumen reflectance values into vitrinite reflectance equivalents using correlations not calibrated to that specific shale play both hydrogen index values and ethane and propane stable carbon isotope values of vaca muerta shale gas show strong correlations to vreqv derived from br ii thus in cases with absence of vitrinite and questionable solid bitumen measurements reasonable maturities vitrinite reflectance equivalents can be inferred from these relationships

effects of nonplanar fault topology and mechanical interaction on fault slip distributions in the ventura basin california to assess the control of fault geometry and mechanical interactions on fault slip distributions in a complex natural system we present results from three dimensional mechanical models incorporating both nonplanar and rectangular planar representations of active faults within the ventura basin region of southern california we find that the incorporation of geologically constrained nonplanar fault surfaces into numerical models of active deformation results in a better match to available geologic slip rate data than models utilizing rectangular planar fault surfaces the model results demonstrate that nonplanar fault geometry and mechanical interactions exert a strong control on resultant slip distributions additionally we find that slip rates at most locations along the surface trace of ventura faults are not likely to rep resent average values for the entire fault surface we propose that results from three dimensional mechanical models using realistic i e nonplanar fault geometry can be used to both predict slip rates at specific locations and determine whether existing site specific slip rate estimates are representative of average fault slip rates although geo metric irregularities along fault surfaces should resist slip planar faults can have lesser slip than nonplanar faults due to the differing mechanical interactions among nearby faults in the two representations this suggests that models using simplified or planar fault geometry are likely to inaccurately simulate regional deformation we assert that detailed knowledge of three dimensional fault shape as well as the geometry and con figuration of deep fault intersections is essential for accurate seismic hazard char acterization of regions of complex faulting such as the ventura basin of southern california

the coal bearing strata of the lower cretaceous mannville group western canadian sedimentary basin south central alberta part 1 stratigraphic architecture and coal distribution controlling factors abstract this study aims to reconstruct the stratigraphic architecture of the subsurface coal bearing mannville group deposits lower cretaceous western canada sedimentary basin south and central alberta in order to characterize the occurrence of coal strata within this interval by focusing on their geometry extension and distribution two regional well correlation transects calibrated by core sedimentological analysis were established the mannville group was subdivided into system tracts a lowstand system tract lst which corresponds to the lower mannville fm a transgressive system tract tst corresponding to a backstepping phase of marine transgression and finally a highstand system tract hst that corresponds to the undivided upper mannville the geometry distribution and extension of the coal layers are examined within the sequential framework previously reconstructed four different zones where coal seams have occurred have been identified lst tst early hst middle hst and late hst thinner and more restricted coal layers are formed during the lowstand and transgressive system tracts and also during the late highstand system tract thicker more extensive coal layers are accumulated during early highstand as a result of the interaction with the topography which is partly smoothed during the deposition of the mannville group and the changes to the accommodation space through time

application of organic petrography in north american shale petroleum systems a review abstract organic petrography via incident light microscopy has broad application to shale petroleum systems including delineation of thermal maturity windows and determination of organo facies incident light microscopy allows practitioners the ability to identify various types of organic components and demonstrates that solid bitumen is the dominant organic matter occurring in shale plays of peak oil and gas window thermal maturity whereas oil prone type i ii kerogens have converted to hydrocarbons and are not present high magnification sem observation of an interconnected organic porosity occurring in the solid bitumen of thermally mature shale reservoirs has enabled major advances in our understanding of hydrocarbon migration and storage in shale but suffers from inability to confirm the type of organic matter present herein we review organic petrography applications in the north american shale plays through discussion of incident light photographic examples in the first part of the manuscript we provide basic practical information on the measurement of organic reflectance and outline fluorescence microscopy and other petrographic approaches to the determination of thermal maturity in the second half of the paper we discuss applications of organic petrography and sem in all of the major shale petroleum systems in north america including tight oil plays such as the bakken eagle ford and niobrara and shale gas and condensate plays including the barnett duvernay haynesville bossier marcellus utica and woodford among others our review suggests systematic research employing correlative high resolution imaging techniques and in situ geochemical probing is needed to better document hydrocarbon storage migration and wettability properties of solid bitumen at the pressure and temperature conditions of shale reservoirs

a new approach to investigate the correlation between geoelectrical time fluctuations and earthquakes in a seismic area of southern italy we propose a new approach to investigate the possible correlation between electrical signals and earthquakes good correlation has been found between the spectral power law exponent of geoelectrical signals and the hurst exponent of the seismicity of the area investigated a tendency of both parameters to converge toward unity typical of self organized critical dynamics is evident before the occurrence of the major event recorded in the area during the observation period

high resolution characterization of a core from the lower jurassic gordondale member western canada sedimentary basin abstract the gordondale member is a hydrocarbon source rock and potential unconventional reservoir that extends across northeastern british columbia and central northwestern alberta it is an organic rich calcareous fossiliferous mudstone with a median total organic carbon value of 6 0 wt a total of 230 samples were collected from approximately 25 m of gordondale member core for organic matter analysis using rock eval 6 analysis and organic petrology detailed core logging provides sedimentological context for organic matter characterization the predominant organic material in the samples is solid bitumen and liptinite with lesser zooclast and inertinite most kerogen is type ii autochthonous marine biomass with minimal dilution by inert organic carbon rock eval tmax values and random reflectance measurements of solid bitumen indicate the samples are within the oil generation window solid bitumen contributes a substantial amount of hydrocarbon potential to the interval a micro reservoir structure within the core is produced by thin intervals of impermeable displacive calcite that act as barriers to the upward migration of free hydrocarbons these free hydrocarbon accumulations could make excellent targets for horizontal wells within the gordondale member

emission of electromagnetic radiation preceding the ito seismic swarm of 1989 there have been several reports1 8 of electromagnetic radiation being detected in air and or underground before large earthquakes or volcanic eruptions unfortunately such measurements are often plagued by contamination from other sources of noise we have developed an electrode system that is effective at filtering out urban and atmospheric background noise here we report the detection of anomalous electromagnetic signals several hours before the occurrence of large earthquakes near ito city japan about 150 km from the location of the electrodes we have also detected anomalous signals about one day before an undersea volcanic eruption that constituted part of the same seismic swarm near ito although the mechanism responsible for such signals is still unclear these results indicate that their monitoring could be valuable for the prediction of seismic activity

triangle zones geometry kinematics mechanics and the need for appreciation of uncertainties abstract triangle zones are important structures found in foreland fold and thrust belts all over the world and are commonly associated with tectonic wedging however tectonic wedging and consequently the formation of passive hinterland verging roof thrusts requires particular mechanic conditions such as pre fractured rocks syntectonic sedimentation or a specific stratigraphic layering with variable mechanically weak and rigid formations in this contribution models of triangle zones and hypotheses regarding their formation are reviewed our results show that the term triangle zone is often used in a contradictory sense and interpretations are affected by large uncertainties passive roof thrusts are not necessarily required in all cases and suggested models of triangle zones even if they are geometrically and kinematically viable are hampered by their mechanical implications with respect to a large number of published triangle zones and associated kinematic as well as mechanic models we present a new definition and classification scheme which is discussed and applied to natural examples worldwide we show that natural examples of triangle zones can be separated into two types 1 detachment dominated and 2 ramp dominated triangle zones both types imply particular mechanic conditions of involved detachments and regional dynamics regarding the large uncertainties associated with triangle zone interpretation we suggest to only use the term triangle zone in a very stringent manner and only if irrefutable evidences for stratigraphic repetitions within a duplex are given the results should then be validated with additional kinematic and mechanic considerations geometric and kinematic uncertainties as well as implications of the proposed model explaining observed triangular structures should be reflected in the nomenclature used

mineral and organic material in matrices and coatings of framboidal pyrite from pennsylvanian sediments england abstract analytical sem observations show that the inorganic fraction of interstitial matrix and coatings of pyrite framboids consists only of a1 and si compounds xrd patterns from bulk concentrates of the pyrite reveal the presence of both kaolinite and quartz in this fraction from marine and nonmarine mud rocks and dominantly quartz with little or no kaolinite from coal these minerals are inferred to be present within framboidal interstices and coatings and can be alternate to or in association with organic matter in these positions the strata are of westphalian c age at the gastrioceras listeri marine horizon near sheffield england the mineral and organic material are regarded as early diagenetic the kaolinite and quartz being syndepositional with the pyrite the organic com onent may be of this age or later probably having undergone some subsequent maturation

late quaternary slip rate on the oak ridge fault transverse ranges california implications for seismic risk abstract the slip rate on the oak ridge fault at south mountain in the densely populated lower santa clara valley california is estimated as 6 15 to 12 3 mm yr since the end of saugus deposition at 0 4 to 0 2 ma slightly lower slip rate estimates result from a different projection of the top of the saugus in the hanging wall block of the fault an assumed displacement of 3 m per event gives an average recurrence interval of 250 to 500 yr with the major uncertainty being the age of the top of the saugus displacement of 2460 m of the top of the saugus at south mountain includes piercing point displacement and distributed displacement from drag folds near the fault both are the near surface expression of faulting at potential mainshock depths beneath well control slip rates for the nearby san cayetano and red mountain faults are not well constrained because post miocene strata are absent in their hanging wall blocks but available evidence suggests that their slip rates are about the same as that for the oak ridge fault earthquake return times measured in hundreds of years have been shown by others for the 1971 san fernando fault and a small fault near the red mountain fault and comparable return times are suggested for a normal fault in the hanging wall block of the oak ridge fault a trench on the harmon alluvial fan near the ventura county government center revealed evidence of cracks filled with sediments from below suggesting liquefaction during an earthquake the lower santa clara valley has not had a large damaging earthquake in 200 years of record keeping but one is expected there in the near future the december 21 1812 earthquake may have occurred on the offshore continuation of the oak ridge or red mountain fault

petroleum retention in the mandal formation central graben norway abstract upper jurassic organic matter rich marine shales of the mandal formation have charged major petroleum accumulations in the north sea central graben including the giant ekofisk field which straddles the graben axis recent exploration of marginal basin positions such as the mandal high area or the sogne basin has been less successful raising the question as to whether charging is an issue possibly related to high thermal stability of the source organic matter or delayed expulsion from source to carrier the mandal formation is in part a very prolific source rock containing mainly type ii organic matter with

a physical model for the precursory magnetic anomalies of the m5 4 alum rock and m6 0 parkfield earthquakes here we propose an alternative physical model based on the concept of criticality for the explanation of the observed magnetic signals prior to the m6 0 parkfield and the m5 4 alum rock earthquakes motivated by an analogous experience from major earthquakes in greece where both magnetic field variations and seismic electric signals were also recorded few weeks before the main shock we suggest that in all these cases similar dynamic processes characterized by critical behaviour should govern the corresponding pre focal areas when the relevant precursory signals emerged

oak ridge fault ventura fold belt and the sisar decollement ventura basin california abstract the rootless ventura avenue san miguelito and rincon anticlines ventura fold belt in pliocene pleistocene turbidites are related to south dipping reverse faults rising from a decollement in underlying miocene shale to the east sulphur mountain anticlinorium comprises the upper plate of a south dipping set of thrusts sisar big canyon lion that merge downward into a decollement in mudstone of the rincon formation named here the sisar decollement shortening of the miocene and younger sequence is 3 km greater than that of the underlying competent vaqueros sespe and marine eocene sequence in the ventura fold belt and 7 km greater farther east at sulphur mountain cross section balancing requires that this difference be taken up by the paleogene sequence at the oak ridge fault to the south convergence is ne to nne based on earthquake focal mechanisms and piercing point offset of the south mountain seaknoll by the oak ridge fault a ne trending line connecting the west end of oak ridge and the east end of the sisar fault separates an eastern domain where late quaternary displacement is taken up entirely on the oak ridge fault and a western domain where displacement is transferred to the sisar decollement and its overlying rootless folds this implies that 1 the oak ridge fault near the coast presents as much seismic risk as it does farther east despite negligible shallow post 0 2 ma movement 2 ground rupture hazard is high for the sisar fault set in the upper ojai valley and 3 the decollement could fail on a low angle thrust at depth and produce an earthquake analogous to the 1987 whittier narrows event in los angeles

ulf electromagnetic precursors for an earthquake at biak indonesia on february 17 1996 ulf electromagnetic emissions associated with a large earthquake occurred at biak island indonesia at 5h 59m ut on february 17 1996 magnitude mw 8 2 and depth 20 km from usgs catalog have been investigated on the basis of ulf magnetic observations at two stations biak and darwin in australia about 1 200 km apart though a simple analysis of magnetic field intensity horizontal and vertical magnetic field components at both stations was found to be closely correlated with geomagnetic kp activity a detailed analysis of the difference of h and z components at the two stations the polarization analysis z h and fractal analysis frequency spectrum slope at these two stations has yielded that the ulf emissions in the frequency range from 5 mhz to 30 mhz about 1 5 1 0 months before the quake are likely to be a precursory signature of the quake with its intensity on the order of 0 2 0 3 nt

the scec southern california reference three dimensional seismic velocity model version 2 we describe version 2 of the three dimensional 3d seismic velocity model of southern california developed by the southern california earthquake center and designed to serve as a reference model for multidisciplinary research activities in the area the model consists of detailed rule based representations of the major southern california basins los angeles basin ventura basin san gabriel valley san fernando valley chino basin san bernardino valley and the salton trough embedded in a 3d crust over a variable depth moho outside of the basins the model crust is based on regional tomographic results the model moho is represented by a surface with the depths determined by the receiver function technique shallow basin sediment velocities are constrained by geotechnical data the model is implemented in a computer code that generates any specified 3d mesh of seismic velocity and density values this parameterization is convenient to store transfer and update as new information and verification results become available

deformation across the western united states a local estimate of pacific north america transform deformation we obtain a locally based estimate of pacific north america relative motion and an uncertainty in this estimate by integrating deformation rate along three different paths leading west across southwestern north america from east of the rio grande rift to near the continental escarpment data are primarily quaternary geologic slip rate estimates and resulting deformation determinations therefore are instantaneous in a geologic sense but long term with respect to earthquake cycles we deduce a rate of motion of the pacific plate relative to north america that is 48 2 mm yr a rate indistinguishable from that predicted by the global kinematic models rm2 and nuvel 1 however we obtain an orientation that is 5 9 counterclockwise of these models a more westerly motion of the pacific plate with respect to north america is calculated from all three paths the relatively westerly motion of the pacific plate is accommodated by deformation in the north american continent that includes slip on relatively counterclockwise oriented strike slip faults including the san andreas fault which is especially relevant in and south of the transverse ranges and a margin normal component of net extension across the continent which is especially relevant north of the transverse ranges deformation of the sw united states occurs in regionally coherent domains within which the style of deformation is approximately uniform in the vicinity of the transverse ranges two important shear systems splay from the san andreas fault the eastern california shear zone trending nnw from the eastern transverse ranges and the trans peninsular faults trending sse from the western and central transverse ranges within the transverse ranges the right lateral san andreas fault steps left seemingly requiring large amounts of convergence there however most of this convergence is avoided through a funneling flow of the crust toward the western transverse ranges and into the relatively narrow central california coast ranges and the northern motion of the mojave the former process involves an alternation of rotation direction from counterclockwise in and south of the central transverse ranges to clockwise in the western transverse ranges

active tectonic studies in the united states 1987 1990 the techniques and instrumentation used in active tectonic studies are discussed and recent results are reviewed it is suggested that a critical mass of data on several particular regions has been accumulated making possible critical debates and attempts to assess earthquake hazards particular attention is given to studies of the pacific northwest region basin and range deformation studies and distributed deformation and hidden earthquake sources also included is a comprehensive bibliography for the period

recent deformation along the offshore malibu coast dume and related faults west of point dume southern california offshore faults west of point dume southern california are part of an important regional fault system that extends for about 200 km from near the city of los angeles westward along the south flank of the santa monica mountains and through the northern channel islands this boundary fault system separates the western transverse ranges on the north from the california continental borderland on the south previous research showed that the fault system includes many active fault strands consequently the entire system is considered a serious potential earthquake hazard to nearby los angeles we present an integrated analysis of multichannel seismic and high resolution seismic reflection data and multibeam bathymetric information to focus on the central part of the fault system that lies west of point dume we show that some of the main offshore faults have cumulative displacements of 3 5 km and many faults are currently active because they deform the seafloor or very shallow sediment layers the main offshore fault is the dume fault a large north dipping reverse fault in the eastern part of the study area this fault offsets the seafloor showing holocene displacement onshore the malibu coast fault dips steeply north is active and shows left oblique slip the probable offshore extension of this fault is a large fault that dips steeply in its upper part but flattens at depth high resolution seismic data show that this fault deforms shallow sediment making up the hueneme fan complex indicating holocene activity a structure near sycamore knoll strikes transversely to the main faults and could be important to the analysis of the regional earthquake hazard because the structure might form a boundary between earthquake rupture segments

earthquake rupture as a critical point consequences for telluric precursors abstract earthquakes are related to rupture phenomena in complex statistical systems of cracks we first review some available information suggesting that rupture in earthquakes is a critical point the consequences of this hypothesis on several phenomena are then discussed in particular we focus our attention on a simple theory of electroseismic activity based on mechano electrical transduction effects such as the piezoelectric or the pressure induced polarization effect the neighbourhood of the rupture threshold is characterized by a specific response which could correspond to telluric wave activity observed as precursors of earthquakes

depositional and diagenetic controls on deeply buried cambrian carbonate reservoirs longwangmiao formation in the moxi gaoshiti area sichuan basin southwestern china abstract this study is about factors controlling dolostone reservoir quality and the material studied is cores mainly from two wells in deeply buried early cambrian longwangmiao formation in a recently discovered gas field in the sichuan basin the vertical distribution of porosity in the formation was highly related to the presence of grainy lithofacies in manifold cycles and dissolution vugs which in turn were controlled by multiple order of sea level fluctuations and paleotopography the transgressive sections have very low porosity values whereas the regressive sections demonstrate significantly better porosities pore networks are dominated by vugs intercrystalline pores and residual intergranular pores the major diagenetic processes that affect reservoir quality include cementation dissolution dolomitization and emplacement of bitumen primary intergranular pores were substantially decreased by marine and burial cementation early freshwater related dissolution produced predominant vugs and locally enhanced intergranular pores a key factor controlling the distribution of porosity intercrystalline pores are interpreted to be inherited from precursor rocks by rearrangement during dolomitization most pores were occluded partly largely or completely by bitumen in the latest diagenetic stage resulting substantial reduction in porosity this work contributes to a better understanding of processes and controlling factors that have affected the longwangmiao reservoir property which may serve as an analog for many dolostone reservoirs worldwide especially other infra cambrian neoproterozoic early cambrian carbonate reservoirs

reconciling rapid strain accumulation with deep seismogenic fault planes in the ventura basin california global positioning system measurements across the east central ventura basin transverse ranges southern california before the nearby 1994 northridge earthquake show high strain rates interpreting this rapid strain accumulation using the usual model of deep slip on a dislocation in a uniform elastic half space requires slip to extend to within 5 km of the surface such shallow slip is difficult to reconcile with the substantial coseismic displacement at depths from 7 to 19 km during the northridge earthquake here we model the displacement and velocity fields throughout the earthquake cycle using a two dimensional finite element model with a viscoelastic rheology displacements are driven by far field and basal velocity boundary conditions and by imposed periodic earthquakes on the thrust faults bounding the basin the thrust faults rupture through an elastic upper crust to a depth of 15 km after a transient stage during which stresses and strains build up to quasi equilibrium values the behavior of the model becomes periodic the sum of the coseismic displacement divided by the repeat interval plus the average interseismic velocity is equal to the geologic velocity the temporal variation in surface velocity depends mainly on the elsasser relaxation time proportional to the product of the maxwell time of the lower crust and the ratio of the thicknesses of the entire crust and viscoelastic lower crust we are able to match the observed high strain rate only if we include the observed variations in elastic modulus associated with the deep basin sediments the model reconciles geologic geodetic and seismological observations of deformation there are trade offs among the far field convergence rate the elsasser time the earthquake repeat time and the time into the earthquake cycle acceptable convergence rates range from 8 mm yr for a relaxation time of the lower crust of 300 years to 12 mm yr for a 30 year relaxation time

thin skinned tectonics of the upper ojai valley and sulphur mountain area ventura basin california by integrating surface mapping with subsurface well data and drawing cross sections and subsurface maps the geometry of shallow structures and their geologic history of the upper ojai valley of california can be reconstructed the geometry of shallow structures the geologic history and the location of earthquake foci then offer constraints on the deep structure of this complex area the upper ojai valley is a tectonic depression between opposing reverse faults its northern border is formed by the active north dipping san cayetano fault which has 6 0 km of stratigraphic separation in the silverthread area of the ojai oil field and 2 6 km of stratigraphic separation west of sisar creek the fault dies out farther west in ojai valley where the south vergent shortening is transferred to a blind thrust the southern border of the upper ojai valley is formed by the quaternary lion fault set sisar big canyon and lion faults which dips south and merges into the sisar decollement within the south dipping ductile lower miocene rincon formation folds with north dipping axial planes including the lion mountain anticline and reeves syncline are middle pleistocen or older and are related to movement on an unnamed fault in the footwall block of the san cayetano fault and on the san cayetano fault respectively by the middle pleistocene the sulphur mountain anticlinorium and the big canyon syncline began forming as a fault propagation fold the fault propagation fold is rooted in the sisar decollement a passive backthrust rising from a blind thrust at depth the formation of the sulphur mountain anticlinorium was followed closely by the ramping of the south dipping lion fault set to the surface over the nonmarine upper pleistocene saugus formation to the east the san cayetano fault overrides and folds the lion fault set near the surface area balancing of the deformation shows shortening of 15 5 km and suggests a 17 km depth to the brittle d ctile transition

pyrite formation in the water column and sediments of a meromictic lake we compared concentrations of organic carbon partitioning of iron and sulfur stable isotopic ratios of major sulfur species and pyrite morphologies in the water column and sediments of oxic and euxinic portions of a sulfate rich meromictic lake green lake near fayetteville new york in order to examine the effects of euxinic conditions on pyrite formation and sedimentary fe s c relations about 15 of the pyrite in sediments of the euxinic basin of green lake forms in the water column the bulk of pyrite in both euxinic and oxic sediments forms in the upper 10 cm of the sediment and is limited by availability of reactive iron oxic and euxinic sediments in green lake cannot be clearly distinguished on the basis of concentrations of organic carbon or pyrite degree of pyritization or sulfur isotopic ratios of pyrite but can be distinguished by using size distributions of pyrite framboids therefore fe s c relations in ancient shales must be used with caution when attempting to reconstruct paleoenvironmental redox conditions

geochemical screening of source rocks and reservoirs the importance of using the proper analytical program abstract geochemical screening is routinely integrated into larger exploration and sometimes development programs that also include assessments of the geological setting petrophysics mechanical properties of the rock etc the rock eval analytical equipment and its classical basic bulk rock method have been developed mainly to characterize potential source rock intervals in petroleum systems however with the increasing interest in unconventional plays it has been recently demonstrated that the use of modified pyrolysis temperature regimes improves the quantification of hydrocarbons still present in oil impregnated samples in spite of their availability the use of such modified pyrolysis temperature regimes still remains scarce among users of pyrolysis data e g exploration geologists and geochemists reservoir engineers petrophysicists and other geoscientists several cases were selected to portray how different analytical programs are necessary to obtain less biased and more accurate answers to critical questions during prospect and play evaluations and appraisals samples originating from conventional and unconventional plays in the greater permian basin of west texas wolfcamp spraberry formations the dj basin in colorado niobrara formation the williston basin lower bakken shale and source rock reservoirs in the middle east were analysed each using three known different pyrolysis methods namely the institut fran ais du petrole s basic bulk rock reservoir and shale play the shale play and reservoir pyrolysis methods yield oil in place estimates 20 42 higher than those yielded by the basic bulk rock method on the same sample e g for the niobrara formation 87 bbl oil ac ft bulk method 118 bbl oil ac ft reservoir method 119 bbl ac ft shale method for the lower bakken 194 bbl oil ac ft bulk method 246 bbl oil ac ft shale method in addition a mature source rock interval believed to contain gas prone organic matter type iii based solely on toc and pyrolysis data was re interpreted as composed mainly of amorphous oil prone kerogen following a multi component study which included transmitted and reflected light organic petrography these results present unequivocal evidence that underestimating the importance of selecting the proper analytical program can change interpretations dramatically