paleomagnetism of archean rocks from northwestern ontario iii rock magnetism of the shelley lake granite quetico subprovince the shelley lake granite of northwestern ontario contains five magnetic phases deuteric and post crystallization hematites which are relatively abundant but carry only 1 4 of the natural remanent magnetization nrm primary magnetite in coarse 50 500 m grains both optically homogeneous and subdivided by hematite lamellae micrometre size secondary magnetite in chloritized biotites and submicrometre size magnetite whose presence is inferred from low blocking temperatures in thermal decay curves of the nrm the nrm is a composite of type 1 and type 2 remanences which differ in direction by about 90 see companion paleomagnetic paper both nrm components occur in normal n and reverse r polarities type 1 remanences 1n 1r have the hallmarks of multidomain md behaviour high blocking temperatures but low coercivities exponential alternating field af decay curves generally md results of the lowrie fuller test and md to transitional values 0 3 10 of the koenigsberger qn ratio further

effect of low temperature treatments on pseudo thellier paleointensity determination 1 in paleointensity determination on multidomain md magnetite demagnetization is always easier than restoring remanence in companion acquisition steps as a result paleointensity results follow a convex down curve on the arai plot in an attempt to overcome this problem the effect of systematic low temperature demagnetization ltd on pseudo thellier results was examined ltd was applied not only to the initial anhysteretic remanent magnetization arm simulating natural remanent magnetization or nrm but also after each partial anhysteretic remanent magnetization parm acquisition step three practical benefits of systematic ltd were discovered 1 ltd treated pseudo thellier results always yielded more accurate intensity values regardless of grain size and sample lithology 2 ltd improved the behavior of md magnetite in paleointensity determination although not as much as for single domain and pseudosingle domain grains 3 an unanticipated bonus was a more even distribution of data points on the arai plot resulting from the fact that ltd causes a shift of points toward the upper end of the arai curves constructing a three dimensional map of the distributions and ltd was successful in quantitatively explaining behavior on the arai plots

on the resolution of multivectorial remanences abstract low temperature demagnetization ltd promotes single domain sd like alternating field af and thermal demagnetization properties of anhysteretic remanent magnetization arm and thermoremanent magnetization trm by eliminating low coercivity or low unblocking temperature fractions of remanence we have investigated the effectiveness of ltd in improving the independence of partial arms parms independence of parms and of partial trms ptrms is crucial because multivectorial directional analyses and paleointensity determinations are otherwise compromised in normalized vector plots of af demagnetization of orthogonal parms ltd treated samples showed universal improvement in the degree of independence the greatest improvement was for synthetic sd and pseudo single domain magnetites and natural lake sediments on the other hand independence barely improved for synthetic multidomain magnetite granites and gabbros in general ltd provides a better resolution of superimposed vectors in multicomponent remanence the direction of the original arm corresponding to primary nrm in nature is perfectly recovered however the parm the overprint is not perfectly resolved especially for overprinting coercivities

using natural maturation series to evaluate the utility of parallel reaction kinetics models an investigation of toarcian shales and carboniferous coals germany abstract open system pyrolysis is routinely performed on immature samples in order to determine the kinetic parameters of petroleum generation at both bulk and molecular levels this study tested such predictions for type ii and type iii organic matter by making calibrations with both artificial and natural maturity sequences of toarcian shales posidonia shale 0 48 1 44 rr and carboniferous vitrains 0 74 2 81 rr both natural series showed little or no compositional variability attributable to kerogen type artificially matured samples were prepared by non isothermal heating 0 7 k min of the least mature samples up to end temperatures between 375 and 470 c under either closed or open system conditions measured generation rate versus temperature curves were analyzed assuming a distributed system of activation energies and a single frequency factor in each case the resulting kinetic parameters were then used to assess bulk petroleum formation rates for geological heating conditions in the case of all artificially matured samples measured and predicted bulk petroleum formation rate vs temperature curves for each maturation stage remain within the original envelope defined by the least mature sample despite an upward shift of tmax temperatures this confirms that the reactions taking place during both the pyrolysis measurements and simulated maturation processes are the same involving mainly homolytic cracking a similar pattern of measured and predicted rate curves is reproduced by the natural maturation sequence of the toarcian shales in the maturity range of 0 53 to 1 44 rr suggesting that petroleum generation within these natural systems also results from cracking reactions and therefore that petroleum generation over geological time can be reliably extrapolated from open system pyrolysis of the appropriate immature sample by contrast significant deviations are observed for the natural coal series with measured and predicted rate curves extending beyond the immature envelopes in accordance with the pronounced increase of frequency factors and of protonated aromatic carbon concentrations this behavior is attributed to solid state aromatization reactions which compete with product generation during natural coalification but which are not reproducible to the same extent by experimental heating it is concluded that petroleum generation from vitrinitic coals over geological time cannot be reliably extrapolated from open system pyrolysis of low rank samples

palaeomagnetism and geochronology of the proterozoic dolerite dyke from southwest greenland indication of low palaeointensity summary intensity of the geomagnetic field during the archaean can potentially be used to study an evolution of the dynamo activity in the earth s core in order to investigate this issue we present new palaeomagnetic and geochronological results from the dolerite dyke which have been intruded into the archaean gneisses of nuuk area southwest greenland 40ar 39ar dating of the pyroxene grains from dolerite yield an age of 2585 21 ma the high temperature component which has been recognized as a characteristic direction is identified in 24 dolerite samples comparison of the palaeomagnetic directions from dolerite dykes with those from host gneisses suggests a primary origin for this component magnetic mineralogical and grain size investigations revealed a pseudo single domain magnetite as a dominant career of magnetization thellier palaeointensity determinations of 14 dolerite specimens yield a mean field value of 13 9 2 5 t strength of the virtual dipole moment 2 30 0 42 1022 am2 obtained from this study is about one quarter of the present earth s filed value a simulation based numerical model of the thellier experiments suggests that the presence of multidomain grains can play a role in enhancing the strength of palaeointensity even after taking in to account the effects of multidomain grains an intensity value 13 9 t from this study suggests that the strength of geomagnetic field at about 2 6 ga was much lower than that of the present time

free oscillation of the japan sea excited by earthquakes ii modal approach and synthetic tsunamis summary the free oscillations of the japan sea excited by the 1964 niigata and the 1983 japan sea earthquakes are examined adopting a modal approach normal mode solutions with periods longer than 50 min are obtained numerically for the actual bathymetry provided by the grids of 20km in size the eigenvectors or water height distributions obtained show that the modes with longest eigenperiods are determined by the size and depth of the whole japan sea many modes with shorter eigenperiods are regionally trapped in a shallow part such as the continental shelf where the amplitude of eigenvectors is large the niigata earthquake excites mainly the regional modes whereas the japan sea event excites both kinds of modes equally the difference in excitation is attributed to the different water depth at the source the niigata earthquake occurred on a continental shelf about 100 m deep whereas the depth at the source area of the japan sea event is about 2500 m the synthetic tsunami is computed by a superposition of the normal modes the spectra agree well with those observed in the period range of 50 to 210 min

petroleum systems in the jiangling dangyang area jianghan basin china source related geochemical data define at least four petroleum systems in the jiangling dangyang area of the jianghan basin eocene paleocene anoxic evaporitic lacustrine source rocks generated most of the crude oils in the area eocene qianjiang rock from the sha 13 well 1322 m contains fast reacting sulfur rich type is organic matter and its extract is most similar to the sha 13 oil sand bitumen qianjiang reservoir lower eocene paleocene xingouzhui rocks from the xin 73 well 842 and 862 m contain slow reacting low sulfur type i organic matter and their extracts are most similar to the sha 26 oil sand bitumen eocene jinsha reservoir and the ling 2 sha 24 and tuo 3 oils xingouzhui reservoirs two unidentified middle triassic or older marine carbonate evaporite source rocks or different facies of the same source rock generated the daxiakou oil triassic jialingjiang formation outcrop xingshan county and the moderately biodegraded tianwan seep oil permian changxing outcrop chengxi county respectively one or more unidentified marine source rocks which could include the lower permian qixia or the upper sinian doushantuo formations generated the miaoshi and yanmenkuo seep oils permian qixia outcrops the jingshan seep oil ordovician baota outcrop probably is related to these oils but could represent another petroleum system different kinetics for hydrocarbon generation among eocene qianjiang and lower eocene paleocene xingouzhui formation source rocks and chemical differences among the related oils are caused by organic facies variations high salinity and low eh enhanced the preservation of oil prone organic matter in these lacustrine settings and facilitated incorporation of sulfur into the organic matter anoxia and the unusual presence of abundant sulfate as gypsum resulted in the microbial reduction of sulfate to sulfide and incorporation of this sulfur into the kerogen for example biomarkers show that source rock in the sha 13 well 1322 m was deposited under more saline lower eh conditions than that in the ling 80 well 1808 m although both are from the qianjiang formation the sha 13 rock sample is more organic rich 6 62 vs 1 27 wt toc and has a higher hydrogen index 794 vs 501 mg hc g toc and faster reaction kinetics than the ling 80 sample kerogen from the sha 13 sample is type is because it has a high hydrogen index and an atomic s c ratio 0 074 in the range of sulfur rich fast reacting kerogens of the monterey formation s c 0 040 organic rich lower jurassic coaly rocks from outcrops at daxiakou contain immature to mature gas prone organic matter that is not related to any oils in the study several organic rich upper sinian to permian samples could have been source rocks in the past but are now highly mature based on high tmax 464 540 c and estimated vitrinite reflectance ro values mass balance calculations were used to estimate the original toc toc c in these samples prior to maturation these samples could not be correlated with the oils using biomarkers because of high maturities and low extract yields however stable carbon isotope type curves suggest that the miaoshi yanmenkuo permian qixia formation and the jingshan ordovician baota formation seep oils originated from source rocks in the lower permian qixia 3 00 wt toc or upper sinian doushantuo formations 5 96 wt toc lack of triaromatic dinosteroids in the miaoshi and yanmenkuo seep oils supports but does not prove a permian source rock very negative stable carbon isotope ratios for kerogens from the lower cambrian shuijintuo formation 33 5 to 33 6 8 85 16 64 wt toc show that they are not related to any of the analyzed oils

thermal cracking of kerogen in open and closed systems determination of kinetic parameters and stoichiometric coefficients for oil and gas generation abstract the purpose of the study is to compare artificial maturation of kerogens representative of the main types of organic matter kerogen types i ii ii s and iii in open and anhydrous closed pyrolysis systems the generated compounds are fractionated according to their thermal stability into six chemical classes c 1 c 2 c 5 c 6 c 14 c 15 saturates c 15 aromatics and nsos which include resins and asphaltenes in both systems primary cracking of kerogen can be described by two main reactions oil generation together with early gas generation followed by late gas production mass balances obtained in the two pyrolysis systems are reasonably similar although some secondary cracking of the nsos and underestimation of methane potential due to incomplete pyrolysis may occur in the open system kinetic parameters of thermal cracking are derived from experiments in the open system using an optimization procedure which determines a unique frequency factor and a weight distribution of chemical classes for a discrete series of activation energies the resultant frequency factors are checked with those obtained for specific molecular tracers such as n c 12 and n c 24 alkanes generated from kerogens in open and closed systems under isothermal conditions the results show that using a unique frequency factor as determined by optimization is correct for type i ii and ii s kerogens this factor is more questionable however when the distribution of activation energies is very broad such as for type iii coals based on this study a strategy for determination of kinetic parameters on any new source rock sample is proposed

paleomagnetism of the red lake greenstone belt northwestern ontario possible evidence for the timing of gold mineralization we report paleomagnetic results from 1 largely unaltered batholiths and 2 sheared and altered units in the archean red lake greenstone belt a major gold producing region in the uchi subprovince of northwestern ontario group 1 includes the hammell lake killala baird trout lake and little vermilion lake batholiths which were intruded between 2730 and 2700 ma ago u pb zircon group 2 includes the howey diorite the dome stock and dikes and andesites from the dickenson mine these units from the mineralized deformation zones dzs between the batholiths were sheared and hydrothermally altered in the same event that caused gold mineralization in supracrustal units the batholiths carry a stable reversed remanence rlr withd 159 i 74 k 20 95 16 n 4 units 14 sites rlr has high coercivities unblocking temperatures and remanence intensities and appears to be a primary thermal remanence dating from 2700 ma the altered units from the gold bearing dzs carry a different remanence rlg withd 180 i 57 k 23 95 3 n 3 units 6 sites rlg also has relatively high coercivities and unblocking temperatures but its magnetization intensities are 1 2 orders of magnitude lower than those of rlr opaque minerals and silicates observed in thin section are highly altered rlg is therefore believed to be a chemical or thermochemical remanence acquired 2580 ma ago during the late stages of cooling and gold mineralization seeing as rlg characterizes the shear zone rocks but is absent from unaltered rocks outside the dzs it could be used as a rapid prospecting tool in delineating areas of alteration and possible mineralization the paleopoles for rlr 2700 ma and rlg 2580 ma link with those of the shelley lake granite 2580 ma 40ar 39ar hornblende and biotite and the matachewan hearst dikes 2450 ma u pb zircon and baddeleyite the sense of motion on the late archean early proterozoic apparent polar wander path for laurentia as defined by this sequence of paleopoles is opposite to that previously accepted

archean regional transpression and paleomagnetism in northwestern ontario canada abstract the archean metamorphic rocks of the superior province of the canadian shield occur in lithologically defined belts or subprovinces the tectonically more stable interiors of belts possess consistent primary components of magnetic remanence in the case of the quetico belt these stable directions are tightly grouped about 005 55 with some minor dispersion and most were acquired during the cooling that followed syntectonic recrystallisation this study examines the directions of primary remanence components for rocks along the margins of the quetico belt within 4 km of the strongly deformed vertical ene trending boundaries the boundaries are known to have experienced dextral transpression involving penetrative single phase deformation which out lasted metamorphism within a few kilometres of the belt boundaries the primary remanence components are re distributed along a vertical ene trending great circle girdle which is nearly parallel to the plane of transpressive shear and regional schistosity it is suggested that the effects of transpression have mechanically deflected the components of primary remanence toward this plane

apparent polar wander paths and the close of late archean crustal transpression northern ontario 1 lamprophyre dikes of the southern superior province of the canadian shield crosscut archean structures including a late archean unconformity and its overlying younger archean timiskaming sedimentary and volcanic rocks the dikes also cut the single schistosity that formed in these rocks nevertheless the lamprophyre dikes show a weak internal tectonic fabric that is approximately parallel to the schistosity in the bedrock and oblique to dike walls the consistent orientation of this internal tectonic fabric has been recognized in every lamprophyre dike using anisotropy of magnetic susceptibility ams thus the lamprophyre dikes provide a useful chronological marker trapping the last pulse of archean tectonism unfortunately our previous attempts to compare the lamprophyre paleopoles with those of the age calibrated apparent polar wander path apwp failed because it was not possible to isolate separate young and old components of magnetization that failure occurred due to the overlap of blocking temperatures or coercivities for the different characteristic vector components borradaile et al 1994a using new cores from the same specimens here we distinguish successfully between consistently oriented vector components by using low temperature demagnetization ltd before thermal demagnetization although the paleopoles appear well defined comparisons with published apwps for the superior province from late archean irving 1979 dunlop 1983 symons et al 1994 to early proterozoic buchan et al 2000 are difficult moreover the earlier parts of the paths are progressively less precise and complete nevertheless a component remanences for the dikes give a paleopole near the path at 2650 ma for a timiskaming volcanic breccia with a u pb age of 2696 ma the a component paleopole may lie between 2600 and 2650 ma b component remanences yield paleopoles in the nw pacific region incompatible with any proposed archean path but perhaps representing some much younger proterozoic remagnetization event e g keweenawan 1100 ma

ocean signals in tide gauge records tide gauges are designed to measure changes in water level relative to land however vertical motions of the earth s crust manifest themselves as apparent water level changes in tide gauge records these crustally induced changes are often small in amplitude relative to the wide range of oceanic processes which affect water level in coastal regions vertical crustal motion can best be studied by first removing oceanic variability from the time series in this paper we summarize the major oceanic signals in tide gauge records we take the approach that the oceanic signals are unwanted noise in the data methods are described for removing or at least reducing the various oceanic signals these oceanic signals span a broad range of time scales from tides to interannual variability associated with the el nino phenomenon and secular sea level change from a number of oceanographic effects

organic geochemistry of freshwater and alkaline lacustrine sediments in the green river formation of the washakie basin wyoming u s a abstract two members of the green river formation in the washakie basin have been analysed by organic geochemical and organic petrographic techniques and the results placed in a sequence stratigraphic framework one of these members the laney shale was deposited in a hydrologically closed alkaline lake under an arid climate and was characterized by high concentrations of alginite rich organic matter whereas the other the luman tongue was deposited in a hydrologically open freshwater lake under a humid climate and consisted of organic poor profundal lake mudstones and coaly lake margin sediments potential source rocks in both lake types have the potential for generating high wax oil at high subsurface temperatures 150 175 c at a heating rate of 5 k ma but the alkaline system is clearly more prolific the most abundant biological marker hydrocarbons were the 4 methylsteranes in both lake types though dinosteranes were found only in the laney shale oleanane was absent from the luman tongue despite an abundance of angiosperm palynomorphs intraformational heterogeneities were best documented for the laney shale where molecular differences in kerogen type occur at the parasequence level with early transgression maximum transgression and rejuvenation stages of lake history having its own kerogen type and distinctive high wax oil fingerprint thermal lability was shown to be linked to kerogen structure in particular the presence of alicyclic and oxygen containing moieties and these in turn are correlated with total organic carbon content and thence productivity degree of preservation some kerogen components appear to have originated via selective preservation whereas others may have been formed by diagenetic condensation reactions

differences in paleomagnetic interpretations due to the choice of statistical demagnetization and correction techniques kapuskasing structural zone northern ontario canada abstract the kapuskasing structural zone ksz reveals a section through the archean lower crustal granoblastic gneisses our new paleomagnetic data largely agree with previous work but we show that interpretations vary according to the choices of statistical demagnetization and field correction techniques first where the orientation distribution of characteristic remanence directions on the sphere is not symmetrically circular the commonly used statistical model is invalid fisher r a proc r soc a217 1953 295 any tendency to form an elliptical distribution indicates that the sample is drawn from a bingham type population bingham c 1964 distributions on the sphere and on the projective plane phd thesis yale university fisher and bingham statistics produce different confidence estimates from the same data and the traditionally defined mean vector may differ from the maximum eigenvector of an orthorhombic bingham distribution it seems prudent to apply both models wherever a non fisher population is suspected and that may be appropriate in any tectonized rocks non fisher populations require larger sample sizes so that focussing on individual sites may not be the most effective policy in tectonized rocks more dispersed sampling across tectonic structures may be more productive second from the same specimens mean vectors isolated by thermal and alternating field af demagnetization differ which treatment gives more meaningful results is difficult to decipher especially in metamorphic rocks where the history of the magnetic minerals is not easily related to the ages of tectonic and petrological events in this study thermal demagnetization gave lower inclinations for paleomagnetic vectors and thus more distant paleopoles third of more parochial significance tilt corrections may be unnecessary in the ksz because magnetic fabrics and thrust ramp are constant in orientation to the depth at which they level off at approximately 15 km depth with archean geothermal gradients primary remanences were blocked after the foliation was tilted to rise on the thrust ramp therefore the rocks were probably magnetized in their present orientation tilting largely or entirely predates magnetization

evaluation of the petroleum composition and quality with increasing thermal maturity as simulated by hydrous pyrolysis a case study using a brazilian source rock with type i kerogen abstract hydrous pyrolysis hp experiments were used to investigate the petroleum composition and quality of petroleum generated from a brazilian lacustrine source rock containing type i kerogen with increasing thermal maturity the tested sample was of aptian age from the araripe basin ne brazil the temperatures 280 360 c and times 12 132 h employed in the experiments simulated petroleum generation and expulsion i e oil window prior to secondary gas generation from the cracking of oil results show that similar to other oil prone source rocks kerogen initially decomposes in part to a polar rich bitumen which decomposes in part to hydrocarbon rich oil these two overall reactions overlap with one another and have been recognized in oil shale retorting and natural petroleum generation during bitumen decomposition to oil some of the bitumen is converted to pyrobitumen which results in an increase in the apparent kerogen i e insoluble carbon content with increasing maturation the petroleum composition and its quality i e api gravity gas oil ratio c 15 fractions alkane distribution and sulfur content are affected by thermal maturation within the oil window api gravity c 15 fractions and gas oil ratios generated by hp are similar to those of natural petroleum considered to be sourced from similar brazilian lacustrine source rocks with type i kerogen of lower cretaceous age api gravity of the hp expelled oils shows a complex relationship with increasing thermal maturation that is most influenced by the expulsion of asphaltenes c 15 fractions i e saturates aromatics resins and asphaltenes show that expelled oils and bitumen are compositionally separate organic phases with no overlap in composition gas oil ratios gor initially decrease from 508 131 m 3 m 3 during bitumen generation and remain essentially constant 81 84 m 3 m 3 to the end of oil generation this constancy in gor is different from the continuous increase through the oil window observed in anhydrous pyrolysis experiments alkane distributions of the hp expelled oils are similar to those of natural crude oils considered to be sourced from similar brazilian lacustrine source rocks with type i kerogen of lower cretaceous age isoprenoid and n alkane ratios i e pristane n c 17 and phytane n c 18 decrease with increasing thermal maturity as observed in natural crude oils pristane phytane ratios remain constant with increasing thermal maturity through the oil window with ratios being slightly higher in the expelled oils relative to those in the bitumen generated hydrocarbon gases are similar to natural gases associated with crude oils considered to be sourced from similar brazilian lacustrine source rocks with type i kerogen of lower cretaceous with the exception of elevated ethane contents the general overall agreement in composition of natural and hydrous pyrolysis petroleum of lacustrine source rocks observed in this study supports the utility of hp to better characterize petroleum systems and the effects of maturation and expulsion on petroleum composition and quality

comparison of petroleum generation kinetics by isothermal hydrous and nonisothermal open system pyrolysis this study compares kinetic parameters determined by open system pyrolysis and hydrous pyrolysis using aliquots of source rocks containing different kerogen types kinetic parameters derived from these two pyrolysis methods not only differ in the conditions employed and products generated but also in the derivation of the kinetic parameters i e isothermal linear regression and non isothermal nonlinear regression results of this comparative study show that there is no correlation between kinetic parameters derived from hydrous pyrolysis and open system pyrolysis hydrous pyrolysis kinetic parameters determine narrow oil windows that occur over a wide range of temperatures and depths depending in part on the organic sulfur content of the original kerogen conversely open system kinetic parameters determine broad oil windows that show no significant differences with kerogen types or their organic sulfur contents comparisons of the kinetic parameters in a hypothetical thermal burial history 2 5 c my show open system kinetic parameters significantly underestimate the extent and timing of oil generation for type iis kerogen and significantly overestimate the extent and timing of petroleum formation for type i kerogen compared to hydrous pyrolysis kinetic parameters these hypothetical differences determined by the kinetic parameters are supported by natural thermal burial histories for the naokelekan source rock type iis kerogen in the zagros basin of iraq and for the green river formation type i kerogen in the uinta basin of utah differences in extent and timing of oil generation determined by open system pyrolysis and hydrous pyrolysis can be attributed to the former not adequately simulating natural oil generation conditions products and mechanisms

partial anhysteretic remanent magnetization in magnetite 2 reciprocity 1 one necessary condition for successful determination of relative paleomagnetic field intensity using anhysteretic remanent magnetization arm methods is reciprocity a partial arm produced by a steady field h applied over a narrow interval 2 1 of alternating field af must demagnetize over the same interval 2 1 experimentally we find that partial arms of single domain sd and pseudosingle domain psd grains demagnetize mainly between 2 and 1 whereas 50 of partial arms of large psd and multidomain md grains are erased below 1 giving a low field tail in the coercivity distribution natural pumices granites and oceanic basalts violated reciprocity but lake sediments gabbros andesite and red scoria had relatively small low coercivity tails and are better candidates for paleointensity work using total arm to simulate natural remanence we carried out pseudo thellier paleointensity determinations for coarse psd and md grains arm demagnetization outweighed partial arm acquisition at the same af step resulting in convex down curves of arm remaining versus partial arm gained pseudo arai plot pseudo arai plots predicted from experimentally determined distributions of blocking and unblocking fields agreed well with measured pseudo thellier results in particular explaining convex down md curves

are arm and trm analogs thellier analysis of arm and pseudo thellier analysis of trm abstract we test the possibility of using the pseudo thellier method as a means of determining absolute paleointensity thellier analysis of anhysteretic remanent magnetization arm and pseudo thellier analysis of thermoremanent magnetization trm have been carried out on a large collection of sized synthetic magnetites and natural rocks in all samples the intensity of trm is larger than that of arm and the ratio r trm arm is strongly grain size dependent the best fit slope b ta from pseudo thellier analysis of trm shows a linear correlation with r the ratio b ta r yielded approximately correct paleointensities although uncertainties are larger than in typical thellier type determinations for single domain and multidomain magnetites alternating field and thermal stabilities of arm and trm are fairly similar however for 0 24 m magnetite arm is both much less intense and less resistant to thermal demagnetization than trm reflecting different domain states for the two remanences and resulting in severely non linear arai plots for thellier analysis of arm

archean uplift of a subprovince boundary in the canadian shield revealed by magnetic fabrics abstract a high strain zone reported elsewhere as a subprovince or tectonic terrane boundary shows evidence of uplift during a penetrative d 1 event some outcrops reveal this by conventional l s petrofabric observations however all outcrops permit measurements of the anisotropy of low field magnetic susceptibility ams which here records the preferred crystallographic orientation of chlorite biotite and amphibole furthermore anisotropy of anhysteretic magnetic remanence aarm reflects the preferred orientation of ferromagnetic grains magnetite and pyrrhotite all three types of fabric show that the rocks were shortened in a north south direction perpendicular to the terrane boundary and stretched upwards in a nearly coaxial strain history a few anomalous magnetic fabrics may indicate some late d 1 subhorizontal e w extension compatible with transpression along the boundary we conclude that this boundary is a zone of high strain associated with the uplift of the high grade plutonic rocks of the winnipeg river subprovince with only slight evidence of minor components of late transpression during the penetrative d 1 fabrics

secular and earthquake related vertical crustal movements in japan as deduced from tidal records 1951 1981 abstract monthly tidal records for the last 31 years from about 100 tidal stations are used to delineate vertical crustal movements in japan a new computer aided processing system was created for this purpose its principle is differential use of tidal records in a region so that the oceanographic disturbances of common causes may be eliminated from the sea level data this method enables us to observe nearly absolute vertical land movement at tidal stations with a precision of a few centimeters the japanese islands are divided into nine regions taking oceanographic conditions into account general discussion on recent vertical movements has yielded several notable features and trends as follows 1 1 rapid and stationary subsidence in the northeastern part of japan presumably of tectonic origin 2 2 a complex pattern of uplift and subsidence in the southwestern part of japan which seems to reflect subduction of the philippine sea plate against the honshu block 3 3 relatively stable land on the japan sea side of honshu movements related to the earthquakes during the period 1951 1981 are also discussed although few of the cases show clear cut premonitory movements if abnormal movements in a coastal area appeared with an amplitude exceeding 2 or 3 cm we could detect them by the present system

paleomagnetic evidence for post 2 55 ga tectonic tilting and 1 1 ga reactivation in the southern kapuskasing zone ontario canada we report paleomagnetic results from two traverses in the southern part of the kapuskasing structural zone ksz of north central ontario which is hypothesized to be an oblique cross section through upper and middle archean crust exposed by uplift and tilting anorthosites and granulite grade gneisses were sampled to the east in the shawmere traverse while amphibolite grade tonalitic gneisses were sampled to the west in the racine traverse three distinct remanent magnetization rm components were isolated by alternating field and thermal demagnetization the a rm has mean directions d 50 i 62 k 138 95 5 n 5 sites 23 samples for the shawmere traverse and d 23 i 53 k 49 95 7 n 8 sites 46 samples for the racine traverse because of the high 500 c laboratory unblocking temperatures of the a rm in the shawmere granulite grade rocks we believe this magnetization was acquired in early slow uplift without tilting from about 24 km to about 16 km depths and has survived the later main ksz uplift and tilting event the racine a rm has laboratory unblocking temperatures down to 400 c and was blocked prior to uplift from a shallower crustal level about 8 km with tilt corrections of 30 and 15 respectively about the 35 striking axis of the ksz the shawmere and racine a paleomagnetic poles fall on the laurentian apparent polar wander path around 2 55 ga dating the time of initial uplift crustal tilting in the ksz occurred after 2 55 ga and was greater in the east than in the west the b rm found mainly in shawmere anorthosites has d 115 i 68 k 17 95 17 n 4 sites 14 samples with a paleopole at 144 w 49 n near 1 1 ga keweenawan reverse poles and the normal pole of the nearby 1 0 ga nemegosenda carbonatite the b rm is probably a thermochemical overprint related to reactivation of the ksz at the time of keweenawan rifting and volcanism in the lake superior region a novel c rm with d 64 i 2 k 18 95 13 n 6 sites 10 samples is either an unresolved hybrid of the a and b rms or an earliest keweenawan 1 3 ga overprint

partial anhysteretic remanent magnetization in magnetite 1 additivity 1 we have tested the additivity of partial anhysteretic remanent magnetization parm for suites of eight synthetic magnetites with mean grain sizes from 65 nm to 18 m and 18 natural samples including lake sediments oceanic and continental volcanic rocks gabbros and granites in both synthetic and natural sample suites domain states inferred from hysteresis and other magnetic properties vary from single domain sd through pseudosingle domain psd to multidomain md for each sample total arm intensity was compared with sums of partial arms of three different types four conjugate pairs of parallel parms four pairs of perpendicular parms and one set of five neighboring parallel parms in each case the intervals of alternating field af over which a steady field h was applied to produce the partial arms are nonoverlapping and cover the entire af range 0 100 mt used to produce the total arm additivity of partial arms was verified to better than 3 for all the samples whatever the domain state sd psd and md or composition ranging from pure magnetite to x 0 6 titanomagnetite the universality of parm additivity is unexpected because its analog partial thermoremanent magnetization ptrm deviates from ideal behavior as the grain size increases and the domain structure becomes md the different behaviors probably result from the fact that parm is produced at ordinary temperatures over short times whereas the most intense ptrm is produced at temperatures approaching the curie point with significant dwell times promoting such processes as isothermal remanence acquisition domain nucleation and domain wall reequilibration verification of the law of additivity of parms is an encouraging first step toward validating pseudo thellier and other methods of paleointensity determination that use arm in place of or in addition to trm

free oscillation of the japan sea excited by earthquakes i observation and wave theoretical approach summary tsunamis caused by the 1964 niigata and the 1983 japan sea earthquakes continued for a long time and appeared to have excited the free oscillation of the almost closed japan sea the spectral analysis of the tide gauge records of those tsunamis shows that there are distinct peaks above the noise level in the frequency range between 0 08 and 0 4mhz finitedifference computations of tsunami for the whole japan sea using a supercomputer reproduce those peaks and confirm that they represent the free oscillation of the japan sea the computation is also made for a region including only the se half of the japan sea with an artificial radiation condition on the n and w boundaries a comparison between the results of these two computations shows the effect of reflections from the nw coast and of the geometry and size of the whole japan sea the simulated spectrum from the se half region almost agrees with that from the whole japan sea for the niigata tsunami indicating that the niigata earthquake excites mainly the regional oscillations for the 1983 japan sea earthquake only a few peaks are reproduced by the computation for the se half region indicating that the free oscillation of the whole japan sea is the essential part of the spectrum for the japan sea event thus the excitation of the free oscillation depends on the earthquake location

on partial thermoremanent magnetization tail checks in thellier paleointensity determination 1 coarse magnetite grains of multidomain md or large pseudo single domain psd size 10 m approximately cause nonlinearity and other problems in paleomagnetic field intensity determination and can lead to spurious paleointensity values one suggested method of detecting their presence is to carry out an additional zero field heating step following the acquisition of partial thermoremanent magnetization ptrm to check for complete demagnetization of the ptrm residual undemagnetized ptrms ptrm tails are characteristic of md and large psd grains and cause nonideal behavior in thellier type paleointensity experiments we have measured ptrm tails in synthetic and natural magnetites of many sizes and domain states including psd and md starting from two different initial states first a thermally demagnetized sample was given a ptrm by cooling in a field h from the blocking temperature tb the ptrm tail is the remanence mptr remaining after zero field reheating to tb mptr is most prominent for large grain sizes and when tb 500 c we next measured ptrm tails mptr produced in a thellier paleointensity experiment the initial state in this case is a total thermoremanent magnetization gradually reduced by double heatings zero field followed by in field to a set of increasing tb for all synthetic and natural samples containing large psd and md magnetites regardless of grain size or lithologic differences mptr is significant but mptr is negligible that is the ptrm tail checks are always zero in our model thellier experiments however in practical paleointensity studies the ptrm tail check method has been shown to be successful in detecting md grains the reason for these contrasting results is that our experiments were carried out with the field hlab that produced ptrm equal in intensity and parallel to the field h that produced natural remanent magnetization nrm in this special situation the ptrm tail is completely masked for the ptrm tail check method to be most effective either hlab should be applied at a large angle to the nrm direction or hlab should be larger than twice or more the paleofield h this will highlight the ptrm tail in the first case by deflecting the apparent nrm direction after the tail check step and in the second case by increasing the apparent nrm intensity

the mechanism of the 1983 japan sea earthquake as inferred from long period surface waves and tsunamis abstract the source process of the japan sea earthquake of may 26 1983 is studied by using the long period surface waves and tsunamis the moment tensor inversion of rayleigh waves which consider the lateral heterogeneity of the earth is developed and applied to the ida records of this event the moment tensor solution and first motion data indicate that the mechanism is dip slip and the seismic moment is 7 6 1027 dyne cm the fault is estimated to be 120 km in length 40 km in width and dips eastward with a dip angle of 30 from the aftershock distribution tsunami simulation for an actual topography is made to restrain the slip on the fault the aftershock area and the tsunami records suggest that the fault is divided into two segments the northern part strikes nnw and slips 4 m while the southern part strikes nne and slips 5 m the fault geometry the aspect ratio and the stress drop of this event are similar to those of the 1964 niigata earthquake but differ from those of the earthquakes in the pacific coast of japan

paleomagnetic evidence for proterozoic tectonism in the kapuskasing structural zone ontario the kapuskasing structural zone ksz in the superior province of north central ontario is thought to be an oblique cross section through middle archean crust samples from 30 sites in granulite gneisses and anorthosites of the ksz have been analyzed using alternating field and thermal demagnetization methods three remanent magnetization components were found with mean directions of d 23 i 50 k 52 95 11 n 5 sites for the a component d 73 i 68 k 50 95 5 n 18 for the b component and d 332 i 59 k 53 95 17 n 3 for the c component v constanzo alvarez and d j dunlop found similar a and b components in less metamorphosed rocks from the same units to the immediate west they attributed the a component to uplift at 2 55 ga with subsequent 15 to 30 wnw tilt and the b component to thermochemical overprinting at 1 1 ga as the ksz was reactivated during keweenawan rifting and volcanism we also attribute the a component to uplift during the 2 55 ga kenoran orogeny with concomitant 10 5 wnw downward tilting before intrusion of the 2 45 ga matachewan dikes to give its present paleopole of 33 e 67 dp 6 dm 9 n 13 using data from both studies we attribute acquisition of the b component to uplift at about 1 88 ga as suggested by recent thermal modeling and tectonic syntheses to give a paleopole of 124 w 30 n dp 7 dm 8 n 20 the c component is found in only three sites and may be either an hybrid of a 1 1 ga keweenawan crm with the b component or a fault block tilted b component near the ivanhoe lake cataclastic zone

paleomagnetism of archean rocks from northwestern ontario iv burchell lake granite wawa shebandowan subprovince the late archean burchell lake granite of the shebandowan greenstone belt in northwestern ontario has a characteristic natural remanent magnetization nrm resembling the type 1 nrm of the nearby shelley lake granite of the quetico gneiss belt of 36 stably magnetized samples 21 had predominantly normal polarity 1n nrm and 15 had reverse polarity 1r the mean direction based on stable end point and vector subtracted directions is d 2 3 i 48 9 k 23 9 95 10 0 n 10 sites intersecting remagnetization circles gave a similar direction the corresponding paleopole bl1 lies at 83 2 e 71 1 n near track 6 of the laurentian apparent polar wander path around 2600 ma although the burchell lake pluton is not dated radiometrically neighbouring granites give k ar biotite ages of 2550 2600 ma and it is reasonable to suppose that the nrm dates from the time of intrusion or shortly thereafter a type 2 nrm like that of the shelley lake granite was isolated in 12 samples its mean direction is d

simple kinetic models of petroleum formation part i oil and gas generation from kerogen modern basin analysis uses kinetic models to predict the extent of petroleum generation within potential source rocks the global kinetic model presented here assigns kinetic parameters based on gross depositional environment and stratigraphic age this is useful in areas of low geochemical knowledge including exploration frontiers five kerogen kinetic organofacies each characterized by a specific organic matter input and early diagenetic overprint can broadly be related to sedimentary facies age associations even using seismic sequence stratigraphy alone a aquatic marine siliceous or carbonate evaporite any age b aquatic marine siliciclastic any age c aquatic non marine lacustrine phanerozoic d e terrigenous non marine ever wet coastal mesozoic and younger and f terrigenous non marine coastal late palaeozoic and younger routine pyrolysis data allow partitioning of organic carbon in the immature source rock into four initial components oil oil generative gas generative and inert separate kinetic parameters for the oil and gas generative fractions allow computation of the evolving concentration and composition of the products it was assumed that the activation energy distributions for each fraction were normally distributed non linear regression of large combined laboratory and field data sets varying by up to 12 orders of magnitude in heating rate established optimum values for the required ten 5 2 kinetic parameter sets a emean e differences in kinetic parameters can be reconciled with known chemical properties although our knowledge base is still inadequate to construct kinetic models from first principles mean activation energies governing oil generation increase systematically in the order a f causing a corresponding increase in generation temperature at a reference heating rate 2 c ma 1 the oil generation window 10 90 oil generative kerogen degraded increases from ca 95 135 c to 145 175 c organofacies c has the tightest energy distribution and narrowest oil generation window the gas generation window ranges from ca 105 155 c to 175 220 c thermal stress results from a combination of temperature and time an order of magnitude increase decrease in heating rate elevates depresses reaction temperatures by ca 15 c heating rates in subsiding sedimentary basins can vary by two orders of magnitude dramatic differences in generation temperature can result if the heating rate and organofacies effects compound thus global oil and gas generation temperature thresholds constitute blunt instruments with which to screen the petroleum potential of sedimentary basins because unexpelled oil provides a potential feedstock for oil to gas cracking in the source rock quantitative models of petroleum generation become really useful only when coupled with models of oil gas cracking and expulsion for example the frequently observed association between gas provinces and coals cannot be explained solely by their generation behaviour

tilting and transpression of an archaean anorthosite in northern ontario abstract an archaean anorthosite complex crops out over more than 300 km 2 at the junction between an archaean metasedimentary accretionary prism quetico belt and a volcanic greenstone terrain to the north wabigoon belt the anorthosite is feebly deformed and weakly foliated however anisotropies of low field susceptibility ams and anhysteretic remanence aarm define consistent magnetic fabric directions extending over subareas 25 km 2 in extent whereas magnetic fabrics cannot define strain magnitudes they normally provide reliable indications of finite strain orientations even where the fabrics developed by stress controlled nucleation during a progressive noncoaxial strain history the field schistosity s 1 being the oldest foliation rotated closest to the shear plane ams foliation due to preferred crystallographic orientation of silicates and pyrrhotite as well as preferred dimensional orientation of magnetite lies at a greater angle to the shear plane because it formed late then s 1 had less time to rotate the few measurements of the youngest aarm foliation caused by magnetite and pyrrhotite suggest that it may lie at a still greater angle to the shear plane thus s 1 and succeeding magnetic foliations provide a cryptic shear sense indicator they reveal relative motions along the terrain boundary that include transpression due to nw se shortening causing dextral e w shear with a north side up component palaeomagnetic data confirm a progressive northwards steepening of the anorthosite sills that is consistent with northwards subduction of the accretionary prism to the south

guidelines for kinetic input to petroleum system models from open system pyrolysis abstract reliable basin and petroleum system models bpsm require accurate kinetic parameters for the conversion of source rock kerogen to petroleum the purpose of this paper is to dispel widespread uncertainty about kinetic input to bpsm by providing guidelines based on interpretation of previously published data for 81 worldwide source rocks containing various kerogen types kinetic response is unrelated to kerogen type as defined by rock eval pyrolysis hydrogen index default kinetics in bpsm software may differ from that for the same kerogen type in different study areas use default kinetics with caution when appropriate measured kinetics are unavailable measure kinetic parameters using thermally immature equivalents of the source rock which may require multiple samples because kerogen kinetics can vary laterally and vertically in each source rock descriptions of depositional environment are insufficient to define kerogen type or kinetic response in different basins optimize multiple run programmed pyrolysis results for both the activation energy ea and frequency factor a assuming a universal value of a rather than optimizing both ea and a can yield temperature errors of 20 c or more when extrapolated to geologic time alternative kinetic models to calculate vitrinite reflectance ro may be more accurate than easy ro for bpsm calibration in the aurora 1 and inigok 1 wells in alaska basin ro and easy rodl more accurately replicates the dogleg in vitrinite reflectance versus depth commonly observed in wells at depths corresponding to 0 7 1 0 ro

kerogen asphaltene sulfur relationships in sulfur rich monterey oils abstract monterey oils in the santa maria basin onshore and offshore are generally low maturity oils because of low thermal exposure relatively shallow burial for short times they are generated as heavy high sulfur oils because of the composition of the unusual type ii source kerogens which are exceptionally rich in organic sulfur 8 14 these high sulfur kerogens which we designate type ii s appear to generate oil at significantly lower thermal exposures than ordinary type ii kerogens with less than 6 s in contrast to common type ii kerogens which generate oil largely by cleavage at oxygen bridge groups and carbon carbon bonds eliminating co2 h2o and hydrocarbon fragments type ii s kerogens have an additional complement of weak bonds associated with bound sulfur the preferential cleavage at weak sulfur linkages tends to produce larger fragments leading to high initial amounts of asphaltenes resins and sulfur rich aromatics together with smaller amounts of saturated hydrocarbons elemental analyses of monterey kerogens and asphaltenes clearly support the concept that the asphaltenes are essentially fragments of kerogen cleaved sufficiently to be soluble or peptized in this heavy oil system solubilization of asphaltenes is attributed to their interactions with the abundant resins and aromatics this sysstem is sufficiently stable under source and reservoir conditions to allow expulsion and migration for reasonable distance without significant fractionation or changes in gross properties initial asphaltenes have essentially the same atomic h c ratios as the source kerogen but have significantlyy lower o c ratios and slightly lower s c ratios the n c ratios are nearly the same for kerogens and their derived asphaltenes with increasing maturity the h c ratios in asphaltenes decrease much like maturation changes in kerogen the s c ratio also decreases significantly however the o c ratios initially low in asphaltenes and n c ratios increase slightly due to material balance caused by other losses these element composition and atomic ratio relationships allow some important inferences concerning source kerogen composition from analysis of asphaltenes alone this can be useful when potential source rock samples are not available for analysis and or when a choice between alternate source rock possibilities must be made

paleoremanence dispersal across a transpressed archean terrain deflection by anisotropy or by late compression the quetico belt is an archean metasedimentary terrain sandwiched between greenstone subprovinces a single regional schistosity is subparallel to magnetic foliation defined by anisotropy of low field magnetic susceptibility ams and anisotropy of anhysteretic remanence aarm aligned micas are the primary cause of ams aligned pyrrhotite is the sole cause of aarm each magnetic subfabric is due to minerals that grew in overlapping intervals in the strain history their slight obliquity may be due to crystallization during noncoaxial strain magnetic fabric ellipsoids suggest varying severity of flattening very strong flattening on the northern boundary less severe on the southern boundary and least severe in the interior the interior and the southern boundary of the belt stretched horizontally and the shortening direction varies gradually from ns in the north to nnw in the south the paleomagnetic record carried by pyrrhotite shows characteristic remanences dispersed around a great circle subparallel to the regional schistosity and magnetic foliations late stress effects rotated paleoremanences into this pattern we discount deflection of the paleofield by anisotropy the pattern of dispersal indicates uniaxial oblate flattening of the region with nnw sse shortening late in the metamorphic cooling history 300 c this postdates schistosity ams and aarm fabrics but it is controlled by the same kinematic pattern

new discoveries in dynamics of an m8 earthquake phenomena and their implications from the 2003 tokachi oki earthquake using a long term monitoring cabled observatory at the 2003 tokachi oki earthquake of m8 seafloor phenomena such as a generation process of tsunami seafloor uplifts turbidity current etc were observed using a cabled observatory installed on the seafloor the turbidity current was observed as a benthic storm caused presumably by the mainshock the seafloor uplifts were observed at the mainshock and continuously after the mainshock the uplifts were 0 35 0 37 and 0 12 m for epicentral distances of 25 5 31 4 and 81 7 km respectively after the mainshock a continuous uplift of the seafloor is observed at all three pressure gauge locations indicating that there was a change in the state of friction on the plate boundary interface by the mainshock in this paper we first show what was observed using the cabled observatory installed right above the focal area of the earthquake and then we discuss to summarize these phenomena associated with the earthquake its possible causes and future directions in long term monitoring of seismogenic processes

a five years super slow aseismic precursor model for the 1994 m8 3 hokkaido toho oki lithospheric earthquake based on tide gauge data 1 here we present a super slow aseismic event model prior to the magnitude 8 3 kurile island hokkaido toho oki earthquake on 4 october 1994 based on data recorded by two tide gauges located 50 150 km from the earthquake epicenter both instruments recorded several cm of subsidence during a five year period prior to the earthquake the observed signals are consistent with a precursory quasi stable slip on the western half of the hokkaido toho oki fault plane when recognized such aseismic events can considerably improve our intermediate term several years prediction capability

detectability of very slow earthquake from tide gauge records a very slow earthquake or crustal deformation with a rise time longer than the period of the free oscillation of the earth is difficult to observe on seismograms however we show that it can be detected from tide gauge records because the free oscillation of an ocean basin such as the japan sea contains longer eigenperiods than those of the solid earth actually such an oscillation was excited by the niigata earthquake of 1964 and recorded on tide gauges comparison of the tide gauge spectra of the free oscillation with the noise spectra shows that the free oscillation of the japan sea excited by a magnitude 7 class earthquake can be detected in the present tide gauge observation system further a simulation for a very slow earthquake with a source process time of 1 hour shows that the slow event which cannot be detected on seismograms is detectable on tide gauges however the smaller the slip the more difficult it is to detect the movement because of the limited dynamic range of the existing tide gauge system if a slow deformation precedes a large earthquake tide gauge records would be useful for earthquake prediction so improvements in the observation system are desirable

normal modes of the world ocean part ii description of modes in the period range 8 to 80 hours abstract we have calculated normal modes with period between 8 and 80 h for a domain consisting of the arctic atlantic indian and pacific oceans in this period range the numerical model has 56 modes of which 13 are topographic vorticity waves all slower than 30 h the trapping sites for these modes are the siberian shelf the icelandic plateau the grand banks the falkland plateau and patagonian shelf the kerguelen plateau the new zealand and fiji plateaus and the hawaiian ridge predominantly planetary vorticity waves do not appear in the model at periods less than 80 h the 41 modes found between 30 and 8 h include basin modes in the north atlantic indian and equatorial pacific quarter wave resonances in the arabian sea bay of bengal and gulf of guinea and kelvin waves on the antarctic coast the pacific north american coast and the new zealand coast several vorticity and gravity modes exhibit an eastward circumglobal flow of energy that is confined to equatorial latitudes except where defl

state of the art of research in kinetic modelling of oil formation and expulsion abstract the last ten years have seen a rapid development in the understanding of petroleum generation and expulsion by a combined use of natural series and experimental simulation this knowledge is now used to develop mathematical models which reproduce the kinetics of petroleum generation and migration in the purpose of basin evaluation by a combination of observation of homogeneous geochemical series experimental simulation and mathematical modelling it has been now established that parameters governing the quantity and composition of petroleum are temperature type of organic matter time or heating rate catalysis by clay minerals which would produce important amounts of isoalkanes is not necessary to produce petroleum the role of minerals although still controversial is rather to retain the heavy fraction of petroleum pressure seems to have a limited influence within the range for effective source rocks kerogen is a tremendously complex macromolecule which is now insufficiently characterized to develop fundamental predictive models of thermal cracking i e involving intermediates such as radicals and olefins such models presently apply only to the cracking of simple molecules hexane hexadecane at limited degrees of cracking for this reason kinetic models are still empirically calibrated on pyrolysis experiments and or on natural maturation trends the most popular models involve a series or a continuous distribution of parallel reactions to describe primary cracking i e direct formation of mobile compounds from kerogen these are generally calibrated against open system pyrolysis with various temperature programs consideration of natural maturation trends i e decrease in petroleum potential may be used also for calibration but discrepancies of organic matter properties availability of deep samples and uncertainties on thermal history limit the effectiveness of such methods whatever the method main activation energies are found in the range 45 60 kcal mol secondary cracking which refers generally to cracking of mobile compounds cannot be modelled from open system pyrolysis nor from natural series unknown residence times but only from closed system pyrolysis although models of primary and secondary cracking still need experimental improvements and more realistic kinetic schemes their ability to predict quantities and composition of petroleum depends primarily on migration which is poorly known indeed migration controls the residence time of petroleum in hot zones of sedimentary basins and thus determines the extent of oil conversion into gas as reproduced by recent numerical models preliminary studies documenting the interactions between thermal cracking and expulsion are shown from haltenbanken area and paris basin in the last few years a kind of agreement has been reached that primary migration was most likely occuring in a separate phase from water and that a sufficient concentration of petroleum must be generated for expulsion to start indeed high expulsion efficiencies over 50 are systematically found for rich and mature source rocks a further understanding of primary migration requires observations of natural series petrophysical studies of source rocks porosities under 10 permeabilities in the nanodardy range thermodynamic investigation of unconventional multiphase organic systems kerogen liquid s gas and experimental simulation under stress this on going research should enable models to track correctly migration paths and thermal history of petroleum fluids as necessary to model their composition

temporal variation of crustal deformation during the days preceding a thrust type great earthquake the 1944 tonankai earthquake of magnitude 8 1 japan the temporal variation in precursory ground tilt prior to the 1944 tonankai japan earthquake which is a great thrust type earthquake along the nankai trough is discussed using the analysis of data from repeated surveys along short distance leveling routes sato 1970 pointed out that an anomalous tilt occurred one day before the earthquake at kakegawa near the northern end of the focal region of the earthquake from the analysis of additional leveling data sato s result is re examined and the temporal change in the ground tilt is deduced for the period of about ten days beginning six days before the earthquake a remarkable precursory tilt started two or three days before the earthquake the direction of the precursory tilt was up towards the south uplift on the southern nankai trough side but the coseismic tilt was up towards the southeast perpendicular to the strike of the main thrust fault of the tonankai earthquake the postseismic tilt was probably opposite of the coseismic tilt the preseismic tilt is attributed to precursory slip on part of the main fault if similar precursory deformation occurs before a future earthquake expected to occur in the adjacent tokai region the deformation may help predict the time of the tokai earthquake

decay rate dependence of anhysteretic remanence fundamental origin and paleomagnetic applications 1 we have measured the intensity of anhysteretic remanent magnetization arm as a function of alternating field af decay rate for synthetic and natural single domain sd and pseudo single domain psd magnetites arm intensity increases as decay rate decreases multidomain md magnetites have the opposite response arm increasing as the decay rate increases these are identical to the sd psd and md dependences of thermoremanent magnetization on cooling rate for all grain sizes and domain structures arm intensity increases as the af decay rate used to achieve an initial demagnetized state decreases decay rate differences in arm intensity are a property of low and medium coercivity grains as shown by annealing and by stepwise af demagnetizing samples we interpret the sd results to mean that increased af exposure time permits a closer approach to equilibrium magnetization an approximate thermal activation theory based on neel 1949 and an exact theory by egli and lowrie 2002 predict 6 11 increases in arm for an order of magnitude decrease in decay rate in reasonable accord with the observed 12 increase for 0 065 m sd grains for md grains we hypothesize that increased exposure time slower decay permits more efficient self demagnetization reducing arm low coercivity grains experience the largest self demagnetizing fields and therefore have the largest decay rate response initial state decay rate response is attributed to longer exposure times leaving domain walls more strongly pinned in deeper potential wells the net self demagnetizing field is zero in the demagnetized state acquisition decay rate annealing and initial state responses of psd grains are a blend of sd and md responses because arm is the most frequently used normalizer in relative paleointensity determination it is important either to use a standard decay rate or else to remove the decay rate dependence by demagnetizing the arm to 30 of its initial value arm0 3 a standard demagnetization level for the normalizing arm is particularly important when comparing paleointensity records from different laboratories

total moment spectra of fourteen large earthquakes total moment spectra mt m where m is the moment rate tensor are computed for 14 large earthquakes recorded by the international deployment of accelerometers ida network using the scalar moment retrieval method proposed by silver and jordan 1982 for each event we obtain estimates of mt averaged over the 10 disjunct 1 mhz intervals in the low frequency band 1 11 mhz typical ida record sets from events with mt 0 2 a 1 a 1027 dyne cm yield standard errors on the 1 mhz averages that are generally less than 20 our multiple band estimates of mt are usually consistent with comparable single band values found by other investigators from the total moment spectra we derive the zero frequency static moment mt 0 and the characteristic source duration c 2 var f t where f t is the time function of the moment rate tensor assumed to be the same for all components the parameter c formally depends on the second degree temporal spatial and mixed spatial temporal moments of an extended source but calculations with realistic source geometries indicate that the interpretation of tc strictly in terms of the second temporal moment leads to very little error a plot of c against shows considerable scatter some events lie significantly above the empirical scaling curve of kanamori and given 1981 slow earthquakes and some below fast earthquakes examples of the former include all three deep focus events analyzed here as well as the 1970 colombia and 1963 peru bolivia deep focus earthquakes whose total moment spectra are calculated from the moment tensor solutions of gilbert and dziewonski 1975 an example of the latter is the great sumbawa earthquake of august 9 1977 24 3 a which is inferred to have a relatively shallow spatial centroid 20 km and a nearly flat moment spectrum suggesting that the faulting was confined to the upper more brittle portion of the oceanic lithosphere three other large earthquakes tonga june 22 1977 23 2 a kuril islands december 6 1978 3 6 0 2 a and tumaco december 12 1979 25 2 a exhibit moment spectra which significantly decrease toward higher frequencies indicating larger values of c the aftershocks of both the tonga and kuril islands events are distributed over a considerable range of depths consistent with rupture into the lower more ductile portions of the oceanic lithosphere we speculate that the characteristic source duration may be causally related to the depth of coseismic rupturing within the lithosphere