clouds and hazes vertical structure of a saturn s giant vortex from cassini vims v data analysis abstract we studied the evolution of a giant tropospheric vortex formed in the wake of the storm that encircled saturn from december 2010 to july 2011 fletcher et al 2011a science 332 1413 1417 fletcher et al 2012 icarus 221 560 586 sanchez lavega et al 2011 nature 475 71 74 sanchez lavega et al 2012 icarus 220 561 576 sayanagi et al 2013 icarus 223 460 478 fischer et al 2011 nature 475 75 77 taking advantage of the observations acquired by the instruments on board the cassini spacecraft in particular the visual and infrared mapping spectrometer vims imaged the vortex several times in this work we analyzed two observations registered by the visual channel of vims vims v on 08 24 2011 and 01 04 2012 both after the active phase of the storm and characterized quantitatively the vertical structure of the clouds and hazes above the vortex until now vims v dataset has been scarcely exploited to perform such an analysis the ir channel of vims has always been preferred since it covers wavelengths containing spectral information on a wider range of altitudes in the atmosphere nevertheless in our analysis we investigate the information content of vims v observations and demonstrate that the covered spectral range contains valuable information that are helpful to improve our knowledge on the properties of saturn s upper atmosphere we developed a forward radiative transfer model to describe saturn s atmosphere and simulate vims v spectra in the 0 35 1 05 m wavelength range the analysis has then been performed by means of an inverse model that we built on the basis of the bayesian approach spatial distributions of effective radii column number densities and top pressures of the cloud decks have been mapped and as a by product of our analysis we also suggest a modified spectral shape for the imaginary part of the refractive index of the tropospheric haze with respect to the shape described in the study of karkoschka and tomasko 2005 icarus 179 195 221 the results suggest that the processes responsible for the formation and persistence of the vortex weakened between august 2011 and january 2012 even if the differences that we observe could be due to the fact that the vortex has moved in different positions between the two dates we found that in august 2011 the upper haze was arranged in a dome like structure with the center at 8 mbar and the boundaries at 12 mbar moreover we detected a zone in the lower haze at 135 mbar characterized by higher optical thickness with respect to the surrounding regions located at 85 mbar in january 2012 the dome in the upper layer has diluted into a more homogeneous structure and the haze appears to be overall shifted to less than 6 mbar similarly the 135 mbar high optical depth zone previously detected in the lower layer has disappeared

a new look at the saturn system the voyager 2 images voyager 2 photography has complemented that of voyager i in revealing many additional characteristics of saturn and its satellites and rings saturn s atmosphere contains persistent oval cloud features reminiscent of features on jupiter smaller irregular features track out a pattern of zonal winds that is symmetric about saturn s equator and appears to extend to great depth winds are predominantly eastward and reach 500 meters per second at the equator titan has several haze layers with significantly varying optical properties and a northern polar collar that is dark at short wavelengths several satellites have been photographed at substantially improved resolution enceladus surface ranges from old densely cratered terrain to relatively young uncratered plains crossed by grooves and faults tethys has a crater 400 kilometers in diameter whose floor has domed to match tethys surface curvature and a deep trench that extends at least 270 around tethys circumference hyperion is cratered and irregular in shape iapetus bright trailing hemisphere includes several dark floored craters and phoebe has a very low albedo and rotates in the direction opposite to that of its orbital revolution with a period of 9 hours within saturn s rings the birth of a spoke has been observed and surprising azimuthal and time variability is found in the ringlet structure of the outer b ring these observations lead to speculations about saturn s internal structure and about the collisional and thermal history of the rings and satellites

diagenetic history of tight sandstones and gas entrapment in the yulin gas field in the central area of the ordos basin china abstract the ordos basin is a large cratonic basin with an area of 250 000 km2 in central china upper paleozoic coals and shales serve as gas source rocks with peak generation and migration at the end of the early cretaceous recent exploration has verified the huge gas potential in the basin centered gas accumulation system bcgas however the mechanism for the gas accumulation is controversial with an integrated approach of thin section petrography ultra violet fluorescence microscopy fluid inclusion microthermometry raman microspectrometry scanning electron microscopy and x ray diffractometry we identified diagenetic trapping and evaluated the diagenetic history of sandstone reservoirs in the yulin gas field in the central area where structural stratigraphic and or sedimentary lithologic traps have not been found it was revealed that three phases of diagenesis and hydrocarbon charging occurred respectively in the late triassic late jurassic and at the end of the early cretaceous in the first two phases acidic water entered the reservoir and caused dissolution and cementation resulting in porosity increase however further subsidence and diagenesis including compaction and cementation markedly reduced the pore space at the end of the early cretaceous the bulk of the gas migrated into the tight reservoirs and the bcgas trap was formed in the updip portion of this system cementation continued to occur due to low gas saturation and has provided effective seals to retain gas for a longer period of time than water block in the bcgas the mechanism for the gas entrapment was changed from water block by capillary pressure in the bcgas to diagenetic sealing the diagenetic seals in the updip portion of the sand body were formed after gas charging which indicates that there is a large hydrocarbon exploration potential at the basin centered area

a probabilistic assessment of earthquake hazard parameters in nw himalaya and the adjoining regions the maximum likelihood estimation method is applied to study the geographical distribution of earthquake hazard parameters and seismicity in 28 seismogenic source zones of nw himalaya and the adjoining regions for this purpose we have prepared a reliable homogeneous and complete earthquake catalogue during the period 1500 2010 the technique used here allows the data to contain either historical or instrumental era or even a combination of the both in this study the earthquake hazard parameters which include maximum regional magnitude mmax mean seismic activity rate the parameter b or b log e of gutenberg richter g r frequency magnitude relationship the return periods of earthquakes with a certain threshold magnitude along with their probabilities of occurrences have been calculated using only instrumental earthquake data during the period 1900 2010 the uncertainties in magnitude have been also taken into consideration during the calculation of hazard parameters the earthquake hazard in the whole nw himalaya region has been calculated in 28 seismogenic source zones delineated on the basis of seismicity level tectonics and focal mechanism the annual probability of exceedance of earthquake activity rate of certain magnitude is also calculated for all seismogenic source zones the obtained earthquake hazard parameters were geographically distributed in all 28 seismogenic source zones to analyze the spatial variation of localized seismicity parameters it is observed that seismic hazard level is high in quetta kirthar sulaiman region in pakistan hindukush pamir himalaya region and uttarkashi chamoli region in himalayan frontal thrust belt the source zones that are expected to have maximum regional magnitude mmax of more than 8 0 are quetta southern pamir caucasus and kashmir himanchal pradesh which have experienced such magnitude of earthquakes in the past it is observed that seismic hazard level varies spatially from one zone to another which suggests that the examined regions have high crustal heterogeneity and seismotectonic complexity

evidence of fluid flow in microfractures in geopressured shales petrographic and microprobe analyses of geopressured shales from the oligocene frio formation brazoria county texas provide direct evidence of hydraulic fracturing and significant fluid flow in the shales the optical continuity of the fracture margins and their higher al si ratios indicate that the fracture margins have undergone more complete alteration of smectite to illite than the interiors of the fracture blocks crosscutting relationships between calcium sulfate and the organic material that fills the fractures indicate that calcium sulfate was emplaced before the organic material and thus was precipitated in the subsurface the calculated fracture permeabilities of the shales on the order of 10 13 m2 are similar in magnitude to that of he frio sandstone reservoirs which suggests that these fractured shales could support flow comparable to that in the sandstones fracture fill deposits or collapse could in turn reduce this flow in addition the more extensive alteration of the fracture margins suggests that fluid in these shales flowed preferentially through the microfractures rather than through the matrix

depositional and diagenetic controls of source rock characteristics of the lower jurassic nordegg member western canada petrographic mineralogical and bulk geochemical xrd xrf and rock eval data indicate that depositional and early diagenetic processes were the principal controls on the organic and inorganic characteristics of the lower jurassic nordegg member source rock this unit comprises organic rich calcareous mudstones to marlstones and marly limestones that were deposited in a predominantly anoxic hypersaline silled marine basin during two transgressive regressive t r events sediments deposited during marine transgression have a higher content of carbonate calcite and dolomite and organic matter fe mainly as pyrite content varies inversely with carbonate content the basal nordegg member is phosphatic with stratiform apatite laminae and phosphatic nodules early diagenetic phosphatogenesis was probably mediated by bacteria under variably dysoxic conditions during the initial transgressive event regressive parts of t r cycles are expressed as an increase in abundance of silicate quartz illite kaolinite and minor k feldspar and lower organic carbon contents deposition of abundant marine organic matter fueled vigorous bacterial reduction of sulfate and almost total bacterial reworking of the sedimented organic matter resulting in significant production of reduced sulfur species and predominantly amorphous kerogen pyrite formation was ubiquitous but limited by the abundance of fe where fe contents fell below 3 wt excess sulfides were incorporated into the kerogen this process resulted in the early diagenetic formation of the sulfur rich kerogen type i ii s that typifies the nordegg thus fe availability in the depositional environment exerted an important control on the amount of s available for incorporation into the kerogen furthermore content of organic s increases with increasing hydrogen index indicating the importance of type and reactivity of organic matter on the extent of incorporation of sulfur into the kerogen during early diagenesis

saturn s cloud structure and temporal evolution from ten years of hubble space telescope images 1994 2003 abstract we present a study of the vertical structure of clouds and hazes in the upper atmosphere of saturn s southern hemisphere during 1994 2003 about one third of a saturn year based on hubble space telescope images the photometrically calibrated wfpc2 images cover the spectral region between the near uv 218 255 nm and the near ir 953 1042 nm including the 890 nm methane band using a radiative transfer code we have reproduced the observed center to limb variations in absolute reflectivity at selected latitudes which allowed us to characterize the vertical structure of the entire hemisphere during this period a model atmosphere with two haze layers has been used to study the variation of hazes with latitude and to characterize their temporal changes both hazes are located above a thick cloud putatively composed of ammonia ice an upper thin haze in the stratosphere between 1 and 10 mbar is found to be persistent and formed by small particles radii 0 2 m the lower thicker haze close to the tropopause level shows a strong latitudinal dependence in its optical thickness typically 20 40 at the equator but 5 at the pole at 814 nm this tropospheric haze is blue absorbent and extends from 50 to 100 mbar to about 400 mbar both hazes show temporal variability but at different time scales first there is a tendency for the optical thickness of the stratospheric haze to increase at all latitudes as insolation increases second the tropospheric haze shows mid term changes over time scales from months to 1 2 years in its optical thickness typically by a factor of 2 such changes always occur within a rather narrow latitude band width 5 10 affecting almost all latitudes but at different times third we detected a long term 10 year decrease in the blue single scattering albedo of the tropospheric haze particles most intense in the equatorial and polar areas long term changes follow seasonal insolation variations smoothly without any apparent delay suggesting photochemical processes that affect the particles optical properties as well as their size in contrast mid term changes are sudden and show various time scales pointing to a dynamical origin

uncertainties in plate reconstructions relative to the hotspots pacific hotspot rotations and uncertainties for the past 68 million years summary a method previously used for estimating the uncertainty in rotation of a plate relative to the hotspots is shown to be insufficient because of the neglect of the uncertainty in one of the three degrees of freedom of a rotation two new methods for estimating best fitting rotations and associated uncertainties for the rotation of a plate relative to the hotspots are presented both methods require a priori estimates of the uncertainties in the locations of individual hotspots and their ancient tracks for a particular age the use of a priori uncertainties permits the hypothesis of hotspot fixity to be tested the first method the two hotspot method leads to simple geometrical interpretations of best fitting rotations and of the eigenvectors and eigenvalues of the appropriate covariance matrix this simplicity comes at the cost of using only two hotspots and their associated tracks with assumed equal circular uncertainties the second method the n hotspot method allows use of an arbitrary number of hotspots 2 with unequal elliptical uncertainties this generality and power comes at the cost of losing the simple geometrical interpretation of the first method elliptical uncertainties are generally more appropriate because hotspot tracks are less well known along strike than across strike because of gaps and uncertainties in ages along the tracks when both methods are applied to the estimate of the pacific hotspot rotation since the age of the hawaiian emperor elbow using the tracks of both the hawaiian and louisville hotspots they produce similar rotations and similar uncertainties the n hotspot method is further applied to estimate pacific hotspot motion at six additional ages from 10 9 ma to 67 7 ma corresponding to the ages of key magnetic anomalies used in global plate reconstructions the goodness of the resultant fit shows that the assigned uncertainties and assumption of hotspot fixity are mutually consistent the pre elbow i e pre 47 9 ma or emperor pole of rotation is shown to differ significantly from the post elbow i e post 47 9 ma or hawaiian pole of rotation moreover rotation over the past 47 9 ma is shown to have occurred in at least three statistically distinct stages from 47 9 to 20 1 ma from 20 1 ma to 6 ma and from 6 ma to the present the change in pole position at 20 1 ma is accompanied by a highly significant 50 per cent increase in the rate of rotation of the pacific plate relative to the hotspots these encouraging results suggest that the new methods can be used to improve and to quantify plate motions relative to the hotspots for a wide variety of applications

historic seismicity near the source zone of the great 2008 wenchuan earthquake implications for seismic hazards article i nfo in the past 500 years 14 historical earthquakes including one that caused a maximum intensity of ix oc curred over a distance of more than 300 km along the longmen shan thrust belt including portions that did not rupture during the devastating wenchuan earthquake sequence of may 12 2008 estimated locations of epicenters and trends of faulting during historical events complement information gathered after the 2008 sequence in particular in addition to the two fault splays that ruptured in 2008 there are additional seismogenic faults across the longmen shan belt including those in the hinterland and in the foreland in the latter case the occurrence of moderate sized historical earthquakes and the disproportionally wide re gion of reported damage in the sichuan basin from large events within the longmen shan belt probably an effect of low attenuation in the stable basin calls for attention to the potential of seismic hazard in the heavily populated chengdu basin moreover long recurrence intervals of great events estimated from trenching of colluvium along the ruptures of the 2008 sequence should not be taken as reliable estimates for somewhat smaller but nonetheless highly destructive events along the longmen shan thrust belt

geochemical constraints on models for secondary petroleum migration along the upper devonian rimbey meadowbrook reef trend in central alberta canada abstract the upper devonian rimbey meadowbrook reef trend of central alberta canada is one of the classical examples that was originally used to support gussow s model of differential hydrocarbon entrapment however the clear discrepancies existing between the ideal hydrocarbon distribution predicted by this model and the one actually observed led to several alternative geological models most of which have not been constrained by organic geochemical data the present study uses a wide range of bulk and molecular parameters to determine the oil source characteristics and thermal maturity along the reef trend the concentrations and isomeric distributions of alkylcarbazoles and non alkylated benzocarbazoles in oils are employed to study petroleum migration pathways and to constrain the existing secondary petroleum migration models the data indicates that gussow s principle is generally applicable as the oils in the up dip direction generally have longer implied migration distances although this is not always the case other factors not recognized previously such as the presence of two subfamilies of the duvernay formation sourced oils may also have contributed significantly to the discrepancies in the oil and gas distributions between the model predictions and the actual observational data

keck adaptive optics images of jupiter s north polar cap and northern red oval abstract we present observations at near infrared wavelengths 1 5 m of jupiter s north polar region and northern red oval nn lrs 1 the observations were taken with the near infrared camera nirc2 coupled to the adaptive optics system on the 10 m w m keck telescope on ut 21 august 2010 at 5 m jupiter s disk reveals considerable structure including small bright rings which appear to surround all small vortices it is striking though that no such ring is seen around the northern red oval in de pater et al 2010a icarus 210 742 762 we showed that such rings also exist around all small vortices in jupiter s southern hemisphere and are absent around the great red spot and red oval ba we show here that the vertical structure and extent of the northern red oval is very similar to that of jupiter s red oval ba these new observations of the northern red oval therefore support the idea of a dichotomy between small and large anticyclones in which ovals larger than about two rossby deformation radii do not have 5 m bright rings in de pater et al 2010a icarus 210 742 762 we explained this difference in terms of the secondary circulations within the vortices we further compare the brightness distribution of our new 5 m images with previously published radio observations of jupiter highlighting the depletion of nh 3 gas over areas that are bright at 5 m

deep water niger delta fold and thrust belt modeled as a critical taper wedge the influence of elevated basal fluid pressure on structural styles we use critical taper wedge mechanics theory to show that the niger delta toe thrust system deforms above a very weak basal detachment induced by high pore fluid pressure the niger delta exhibits similar rock properties but an anomalously low taper sum of the bathymetric slope and dip of the basal detachment compared with most orogenic fold belts this low taper implies that the niger delta has a very weak basal detachment which we interpret to reflect elevated pore fluid pressure 0 90 within the akata formation a prodelta marine shale that contains the basal detachment horizon the weak basal detachment zone has a significant influence on the structural styles in the deep water niger delta fold belts the overpressured and thereby weak akata shales ductilely deform within the cores of anticlines and in the hanging walls of toe thrust structures leading to the development of shear fault bend folds and detachment anticlines that form the main structural trap types in the deep water fold belts moreover the low taper shape leads to the widespread development of backthrust zones as well as the presence of large relatively undeformed regions that separate the deep water fold and thrust belts this study expands the use of critical taper wedge mechanics concepts to passive margin settings while documenting the influence of elevated basal fluid pressures on the structure and tectonics of the deep water niger delta

fracture patterns and petrophysical properties of carbonates undergoing regional folding a case study from kurdistan n iraq abstract the zagros taurus fold and thrust belt hosts a prolific hydrocarbon system most hydrocarbon reserves are stored in naturally fractured reservoirs and such fracture systems can therefore have a significant impact on reservoir performance fractures are one of the most important paths for fluid flow in carbonate reservoirs and industrial geoscientists and engineers therefore need to understand and study fracture patterns in order to optimise hydrocarbon production the observed fracture patterns in outcrops may have implications on fluid flow and reservoir modelling in subsurface reservoirs and we have therefore undertaken a case study of fracturing associated with regional folding in iraqi kurdistan in this area some exploration wells currently target upper triassic dolostones kurra chine formation and or lower jurassic limestones and dolomitised limestones sehkaniyan formation in both units hydrocarbon production comes mainly from secondary porosity created by dolomitisation dissolution and fracturing both formations have undergone multiple phases of deformation associated with burial uplift folding and thrusting we investigate some fracture pattern characteristics and some petrophysical properties of these units using selected outcrops around the gara ora and ranya anticlines that form folds directly traceable for 25 70 km our outcrop data is compared with subsurface fracture and petrophysical datasets reported from wells in the nearby shaikhan and swara tika fields the 1 2 3d fracture attributes collected from outcrops are fracture orientation type spacing intensity length and cross cutting and abutting relationships fracture orientations show a clear relationship to the local fold axis in both the outcrop and subsurface although in some cases they appear to relate more to the present day in situ maximum horizontal stress direction or local strike slip faulting three stages of fracturing are proposed pre folding early folding and post folding fractures in addition we report petrophysical properties porosity permeability and acoustic velocity of both the kurra chine and sehkaniyan formations in relation to their structural position within folds and faults and stratigraphic level the highest porosities and permeabilities are recorded in the hinges and backlimbs of the gara anticline the best reservoir quality highest porosity and permeability is often found in areas associated with replacement dolomite i e solution vugs and intercrystalline porosity the kurra chine formation displays similar trends in velocity porosity data at both outcrop and the subsurface however the sehkaniyan formation displays lower acoustic velocity for a given porosity at outcrop compared to the subsurface

petrology and k ar ages of dredged samples from laysan island and northampton bank volcanoes hawaiian ridge and evolution of the hawaiian emperor chain summary the hawaiian emperor volcanic chain is made up of at least 107 indentifiable shield volcanoes chase and others 1970 bargar and jackson 1974 clague and others 1980 and is the longest linear island and seamount chain in the pacific fig 1 beginning at the active volcanoes kilauea and mauna loa on the island of hawaii this chain of volcanoes extends west northwestward along the hawaiian ridge for a distance of 3 500 km where it turns northward and continues another 2 300 km as the emperor seamounts ending near the intersection of the aleutian and kurile trenches it is now thought that the hawaiian emperor chain was formed as the pacific lithospheric plate moved first northward and then northwestward relative to the hawaiian hot spot a more or less stable melting anomaly in the asthenosphere and that the bend in the chain reflects a major change in pacific plate motion several mechanisms have been proposed to explain the hawaiian and other hot spots including a propagating fracture betz and hess 1942 jackson and wright 1970 diapiric upwelling along a line of structural weakness green 1971 mcdougall 1971 thermal morgan 1972a 1972b or chemical anderson 1975 plumes of gravitationally unstable material rising from the deep mantle shear melting coupled with thermal feedback shaw 1973 and geographically stabilized by gravitational sinking of refractory residua shaw and jackson 1973 and extrusion induced by lateral motion along plate boundaries handschumacher 1973 despite the variety of dynamic models proposed there has yet to be devised a definitive experiment to test any of them all these mechanisms are however encompassed by the general or kinematic hot spot hypothesis which when used in the broadest sense implies neither mechanism nor excess heat

the great white spot and disturbances in saturn s equatorial atmosphere during 1990 a giant storm the great white spot erupted at the end of september 1990 as a localized bright cloud system close to saturn s equator its evolution produced a complex planetary disturbance which affected the whole equatorial region a month later similar spots have appeared approximately once every saturnian year about 30 earth years implying that a seasonal change in solar heating for example may be responsible for their occurrence

holocene paleoseismicity in the fold and thrust belt of the hikurangi subduction zone eastern north island new zealand abstract along the 500 km long eastern coastline of the north island new zealand there are at most seven distinct holocene marine terraces aged 7 ka b p or less the highest of the terraces is 27 m above present day mean sea level the coastal region is subdivided into fourteen distinct subregions based on radiocarbon ages of marine deposits overlying wave cut shore platforms and geographic distribution of similarly aged terraces holocene marine terraces are the result of uplift associated with large earthquakes co seismic deformation this conclusion is based on characteristic stepped terrace morphology clustering of ages of terrace deposits within subrogions and the occurrence of co seismic uplift in historic time differential uplift across structures and distinct age variations at subregion boundaries are also characteristic recurrence intervals of uplift in any one terrace sequence vary from 0 4 ka to 2 0 ka and individual amounts of uplift vary from 1 0 m to 4 0 m in the past 2 5 ka ages from all terraces within subrogions indicate at least 21 paleoseismic events affecting coastal areas of eastern north island in that period these events cluster in time and in separate parts of eastern north island several earthquakes occurred 0 3 0 6 1 0 1 5 2 1 and 2 3 ka b p our data strongly support the concept of segmentation of deformation along the subduction margin the likely cause of coastal uplift is movement on steep reverse faults local structures rather than the subduction thrust that propagate from or near the subduction thrust some 20 25 km below the region earthquakes of moment magnitude 7 3 8 0 are estimated to be associated with these fault movements

geography and history of the louisville hotspot chain in the southwest pacific the louisville ridge is a 4300 km long late cretaceous and cenozoic hotspot chain the south pacific equivalent of the hawaiian emperor chain its northwestern end is being consumed by the tonga kermadec subduction zone but seabeam and magnetic mapping shows that the chain still includes more than 60 major volcanoes of both normal and reversed polarity distributed along a 75 km wide band that can be fitted to small circles about three successive poles of pacific plate hotspot rotation this band obliquely crosses fracture zones of the eltanin system but there is little interaction and no evidence of any genetic connection between the two structures forty of the louisville volcanoes grew above sea level and are preserved as high latitude i e coral free guyots they are spaced less than 100 km apart along most of the chain but there are none within 750 km of the inferred present location of the hotspot beneath a swell at the southeast end of the chain the rate of volcano building by the louisville hotspot declined sharply about 20 m y ago after being remarkably constant at 3 4 103 km3 m y for the previous 50 m y and none of the louisville volcanoes built during the past 10 12 m y the time of most profuse hawaiian volcanism has reached sea level however a seamount from which pleistocene lavas were dredged rises to within 540 m of the sea surface from the crest of the hotspot swell at 50 5 s 139 2 w guyot heights demonstrate that a hotspot swell several hundred meters high has persisted throughout the known life of the chain and sometimes had an isostatic depression on its loaded crest the depths of guyot shelf breaks increase systematically to the northwest from 530 to 2100 m proportional to the square root of volcano age with some scatter and tilting caused by plate boundary tectonism and local isostatic subsidence and uplift

basin centered gas systems basin centered gas systems bcgss are potentially one of the more economically important unconventional gas systems in the world in the united states they contribute as much as 15 of the total annual gas production these regionally pervasive gas accumula tions are different from conventionally trapped accumulations in several respects the basin centered gas accumulations bcgas associated with bcgss are typically characterized by regionally pervasive accumulations that are gas saturated abnormally pres sured commonly lack a downdip water contact and have low permeability reservoirs the accumulations range from single isolated reservoirs a few feet thick to multiple stacked reservoirs several thousand feet thick two types of bcgss are recognized a direct type characterized by having gas prone source rocks and an indirect type characterized by having liquid prone source rocks during the burial and thermal histories of these systems the source rock differences between the two types of bcgss result in strikingly different characteristics that impact exploration strategies the majority of known bcgas are the direct type exploration activity for bcgas is in the early stages and thus far has been focused in north america in other parts of the world concepts of basin centered gas systems are poorly known and exploration activity focused on basin centered gas accumulations is minimal

the origin and evolution of saturn s 2011 2012 stratospheric vortex the planet encircling springtime storm in saturn s troposphere december 2010 july 2011 fletcher l n et al 2011 science 332 1413 1414 sanchez lavega a et al 2011 nature 475 71 74 fischer g et al 2011 nature 475 75 77 produced dramatic perturbations to stratospheric temperatures winds and composition at mbar pressures that persisted long after the tropospheric disturbance had abated thermal infrared ir spectroscopy from the cassini composite infrared spectrometer cirs supported by ground based ir imaging from the visir instrument on the very large telescope and the mirsi instrument on nasa s irtf is used to track the evolution of a large hot stratospheric anticyclone between january 2011 and march 2012 the evolutionary sequence can be divided into three phases i the formation and intensification of two distinct warm airmasses near 0 5 mbar between 25 and 35 n b1 and b2 between january april 2011 moving westward with different zonal velocities b1 residing directly above the convective tropospheric storm head ii the merging of the warm airmasses to form the large single stratospheric beacon near 40 n b0 between april and june 2011 disassociated from the storm head and at a higher pressure 2 mbar than the original beacons a downward shift of 1 4 scale heights approximately 85 km post merger and iii the mature phase characterised by slow cooling 0 11 0 01 k day and longitudinal shrinkage of the anticyclone since july 2011 peak temperatures of 221 6 1 4 k at 2 mbar were measured on may 5th 2011 immediately after the merger some 80 k warmer than the quiescent surroundings from july 2011 to the time of writing b0 remained as a long lived stable stratospheric phenomenon at 2 mbar moving west with a near constant velocity of 2 70 0 04 deg day 24 5 0 4 m s at 40 n relative to system iii longitudes no perturbations to visible clouds and hazes were detected during this period with no direct tracers of motion in the stratosphere we use thermal windshear calculations to estimate clockwise peripheral velocities of 200 400 m s at 2 mbar around b0 the peripheral velocities of the two original airmasses were smaller 70 140 m s in august 2011 the size of the vortex as defined by the peripheral collar was 65 longitude 50 000 km in diameter and 25 latitude stratospheric acetylene c2h2 was uniformly enhanced by a factor of three within the vortex whereas ethane c2h6 remained unaffected the passage of b0 generated a new band of warm stratospheric emission at 0 5 mbar at its northern edge and there are hints of warm stratospheric structures associated with the beacons at higher altitudes p 0 1 mbar than can be reliably observed by cirs nadir spectroscopy analysis of the zonal windshear suggests that rossby wave perturbations from the convective storm could have propagated vertically into the stratosphere at this point in saturn s seasonal cycle one possible source of energy for the formation of these stratospheric anticyclones

practical kinetic modeling of petroleum generation and expulsion abstract models for petroleum generation used by the industry are often limited by a sub optimal laboratory pyrolysis methods for studying hydrocarbon generation b over simple models of petroleum generation c inappropriate mathematical methods to derive kinetic parameters by fitting laboratory data d primitive models of primary migration expulsion and its coupling with petroleum generation and e insufficient use of subsurface data to constrain the models problems a b and c lead to forced compensation effects between the activation energies and frequency factors of reaction kinetics that are wholly artificial and which yield poor extrapolations to geological conditions simple switch or adsorption models of expulsion are insufficient to describe the residence time of species in source rocks yet the residence time controls the thermal stresses to which the species are subjected for cracking to lighter species the shellgenex model for petroleum generation and expulsion has been developed since 1988 in this multi species model the rate limiting step of primary migration is treated as the slow diffusion of the petroleum through the kerogen itself other key aspects of the model are the reaction and transport behaviour of the heavy compounds the role of free radicals in the cracking kinetics of hydrocarbon species in the model and the evolving free volume of the kerogen the last of these has a particularly strong effect on the primary migration of the generated petroleum molecules some implications of this model are that a compositions of expelled petroleum vary more strongly than the standard parallel reaction model suggests and b expulsion is not immediately extinguished by waning temperatures and pressures but continues with decreasing gor of the expelled petroleum and increasing density of the expelled oil

atmospheric dynamics of saturn s 2010 giant storm great white spot a rare planet encircling storm raged on saturn in 2010 2011 analyses of high resolution spacecraft imagery and numerical modelling reveal a dynamic storm head powered by sustained convection in the zonal flow of saturn s atmosphere

rapid formation of the small isles tertiary centre constrained by precise 40ar 39ar and u pb ages the relative chronology of magmatic and tectonic events is key to an understanding of the influence of the iceland plume on the north atlantic in particular the location and duration of magmatism is of fundamental importance initial widespread flood basalt formation occurred in baffin island greenland and britain before complete plate break up at 56 ma after which time magmatism became concentrated in the active rift zone historically the british tertiary igneous province btip has been instrumental in advancing many concepts of igneous petrology however the absolute age and duration of the province remains unresolved here we present new internally consistent 40ar 39ar ages that help to constrain the volcanic activity in the small isles centre to within 2 my this short duration has implications for the onset of magmatism in the larger north atlantic province the rapid unroofing of the rum volcano and more significantly some of the evidence used to propose pulsing of the iceland plume

geochemical evidence for oxygenated bottom waters during deposition of fossiliferous strata of the burgess shale formation abstract deciphering the oxygenation potential of bottom waters during deposition of the fossiliferous strata of the burgess shale is key to understanding the paleoecology of the organisms preserved as fossils and the processes involved in their preservation methods of paleo redox determination that are based upon trace fossils organic carbon content or size analysis of pyrite framboids are problematic when applied to the burgess shale fortunately patterns in redox sensitive trace elements hold great potential for determining paleo redox conditions for these greenschist facies rocks because they are independent of both age and metamorphic grade four burgess shale type bst fossil bearing sections were studied three lie within the burgess shale formation whereas one lies within the slightly younger duchesnay unit of the middle chancellor formation the geochemical proxies of seawater redox conditions that were used are mo u th v cr v v ni ni co and v sc each of these redox sensitive indices suggests that oxygenated conditions prevailed in the overlying seawater during deposition of beds within which bst preservation developed non fossiliferous beds at the base of the mt stephen trilobite beds yield three geochemical indices v v ni v sc ni co that indicate deposition under dysoxic to anoxic conditions thus the only beds to have been deposited under anoxic conditions are barren of fossils of soft bodied taxa further contradicting the notion that bottom water anoxia is a factor in bst preservation the laminated nature of the burgess shale and evidence for subsurface anoxia coupled with evidence for oxygenated bottom waters presence of bacterial mats and surficial trace fossils suggest that the burgess shale was deposited in the exaerobic zone oxic anoxic boundary at the water sediment interface implications of this reinterpretation of the depositional environment of the burgess shale include 1 taphonomic models for bst preservation must account for the presence of oxygen in bottom waters 2 paleoecological interpretations of the burgess shale need to account for a probable autochthonous benthic component in what is a complex assemblage of fossils that includes elements derived from the platform and 3 the possibility of burgess shale communities based upon chemosynthesis and or bacteria grazing must be considered

history of the sevier orogenic wedge in terms of critical taper models northeast utah and southwest wyoming problems with applying critical taper models to ancient orogenic wedges are overcome in the late cretaceous late paleocene sevier orogenic wedge in utah and wyoming by a symptomatic approach in which wedge behavior is inferred from the time space distribution of thrust faulting erosion and synorogenic sediment accumulation in association with the orogenic wedge in turn the causes of wedge behavior are interpreted in terms of features that are known about the sevier wedge such as the locations of major decollements and the lithologic constituents of major thrust sheets from coniacian through late paleocene time 35 m y basement and cover rocks in the sevier wedge were shortened by 100 km in three major and one minor events an overall eastward progression of thrusting was punctuated by several episodes of out of sequence and hinterland vergent thrusting over the long term wedge taper was controlled by internal wedge strength initial taper and changes in the durability of the upper surface of the wedge and its internal lithostratigraphy critical taper was maintained by the offsetting effects of basement duplexing in the rear of the wedge and forward imbrication at the front of the wedge while the basal decollement was mainly in basement rocks the wedge was highly tapered and thrust spacing was relatively close 15 km beginning ca 75 ma the basal decollement ramped upward and eastward into weak cambrian shale and jurassic salt thrust spacing increased to 25 45 km and wedge taper decreased drastically the highly tapered rear part of the wedge carried strong basement rocks above moderately weak mylonitic and cataclastic decollements whereas the frontal lower taper part of the wedge carried sedimentary rocks above extremely weak salt and shale decollements through time internal strength of the wedge decreased as it incorporated an increasing proportion of sedimentary rocks the thrust belt was able to advance eastward in spite of its decreasing internal strength and decreasing taper because the basal decollement of the wedge also became weaker through time both by strain softening beneath the rear of the wedge and by propagating along extremely weak rocks beneath the front of the wedge provenance data from associated synorogenic conglomerates indicate that the durability of the upper surface of the wedge probably increased over the long term history of the sevier wedge as an increasing proportion of the erosional surface became occupied by resistant precambrian quartzite and basement rocks this would have had the effect of decreasing the rate of erosion through time and maintaining a steeper surface slope which would have helped the wedge to remain at critical to supercritical taper the sevier wedge also exhibits several shorter term 10 km and 3 was subjected to regional erosion marked by major unconformities that ultimately caught up with tectonic thickening and caused the wedge to stall this cyclicity is attributed to the need for wedges to become supercritical before they can propagate forward over large distances and a lag time between wedge thickening and uplift and wedge erosion erosion eventually catches up to the rate of uplift the wedge stalls and the locus of deformation shifts to the rear of the wedge in order to rebuild taper this analysis suggests that orogenic wedges continually deform and find a way to maintain taper sufficient to allow forward propagation as long as a sufficient push from the rear exists the actual taper value may change substantially through time as lithostratigraphy internal strength upper surface durability and presence absence of weak potential stress guides conspire to maintain a critical taper

stratigraphic controls on production from a basin centered gas system lower cretaceous cadotte member deep basin alberta canada in this article we examine the controls on gas production from cretaceous clastic strand plain deposits in an area the deep basin of alberta that was instrumental in the development of the basin centered gas concept by integrating core wireline logs three dimensional seismic data petrophysical measurements pressure and production data we show that the best gas production comes from stratigraphic sweet spots consisting of chert rich shoreface and beachface deposits that alternate between tight quartzose sandstone the physical properties of the chert rich and quartzose units are sufficiently different that they can be distinguished seismically seismic modeling and observations show that high amplitude areas correspond to porous and productive chert rich shoreface and beachface deposits a map of seismic amplitudes for the cadotte member shows narrow 0 5 km 0 3 mi width curvilinear high amplitude anomalies corresponding to cherty shoreface and beachface deposits that are parallel to depositional strike east northeast west southwest and correlate precisely with production trends wells drilled outside the high amplitude anomalies do not have sufficient permeability to produce gas at economic rates the shore parallel stratigraphic sweet spots are locally compartmentalized by shale filled channels that cut at high angles through the strand plain like other cretaceous units in this area the cadotte member is wet structurally updip from gas charged rocks the contact between these two phases traversing through our study area and its location is controlled by the interplay of regional structural dip and depositional processes that controlled the lithology and stratigraphic architecture of the rocks

properties of a martian local dust storm in atlantis chaos from omega mex data abstract in this study we present the analysis of the dust properties of a local storm imaged in the atlantis chaos region on mars by the omega imaging spectrometer on march 2nd 2005 we use the radiative transfer model mitra to study the dust properties at solar wavelengths between 0 5 m and 2 5 m and infer the connection between the local storm dynamics and the topography we retrieve maps of effective grain radius reff optical depth at 9 3 m 9 3 and top altitude ta of the dust layer our results show that large particles reff 1 6 m are gathered in the centre of the storm lat 33 5 s lon 183 5 w where the optical depth is maximum 9 3 7 0 and the top altitude exceeds 18 km outside the storm we obtain 9 3 we speculate that a low thermal inertia region at the western border of atlantis chaos is a possible source of the dust storm moreover we find evidence that topography plays a role in confining the local storm in atlantis chaos the vertical wind component from the gcm does not provide any hint for the triggering of dust lifting on the other hand the combination of the horizontal and vertical wind profiles suggests that the dust once lifted is pushed eastward and then downward and gets confined within the north east ridge of atlantis chaos from our results the thickness of the dust layer collapsed on the surface ranges from about 1 m at the storm boundaries up to more than 100 m at its centre we verify that a layer of dust thicker than 1 m deposited on the surface can prevent the detection of mafic absorption features however such features are still present in omega data of atlantis chaos registered after the storm hence we deduce that once the storm is over the dust deposited on an area larger than the one where it has been observed

a seismic sequence from northern apennines italy provides new insight on the role of fluids in the active tectonics of accretionary wedges abstract we analyze a seismic sequence which occurred in 2000 along the northern apennines accretionary wedge italy the sequence developed within the cretaceous triassic limestones of the tectonic wedge where methane rich and oil reservoirs are stored ruptures mainly developed on wnw ese striking thrusts the compressive stress field is consistent with that acting at regional scale in northern apennines seismic parameters indicate that fluids are involved in the seismogenic process the amplitudes of the p and s phases and data from some stations evidence a p to s conversion within v p v s 2 1 layer the attenuation properties of crust show a higher attenuation zone located west of the epicentral cloud eight hundred aftershocks delineate a sub vertical cloud of events between 7 and 14 km depth the space time evolution of the aftershocks is consistent with a diffusive spreading diffusivity 1 9 m 2 s along vertically superimposed thrusts diffusion also controls the time evolution of the sequence fluid pressure is estimated to be roughly equal to the vertical lithostatic stress the overpressure within reservoirs develops by tectonic compaction processes the fluids upraise along sub vertical fractures related to the shortening of the wedge the 2000 sequence occurred in an area that separates a thermal and deeper petroleum system from a shallower biogenic system the divider of these systems controls the attenuation properties of the crust the fluid rock interaction at seismogenetic depth is related to hydrothermal processes more than to compaction in accretionary wedges seismicity activating superimposed thrusts may drive methane and oil upraising from the upper crust

the onset and growth of the 1990 equatorial disturbance on saturn abstract the development of cloud structures at low saturnian latitudes in september 1990 can be divided into three phases the onset and expansion of the initial disturbance popularly known as the great white spot the eastward and westward expansion of the bright cloud and the eventual formation of wave like structures encircling the equator the three phases of this storm are consistent with a single convective event this event is evaluated within the historical context of previous occurrences and general seasonal mechanisms are considered

saturn s zonal wind profile in 2004 2009 from cassini iss images and its long term variability abstract five years of cassini imaging science subsystem images from 2004 to 2009 are analyzed in this work to retrieve global zonal wind profiles of saturn s northern and southern hemispheres in the methane absorbing bands at 890 and 727 nm and in their respective adjacent continuum wavelengths of 939 and 752 nm a complete view of saturn s global circulation including the equator at two pressure levels in the tropopause 60 mbar to 250 mbar with the mt filters and in the upper troposphere from 350 mbar to 500 mbar with the cb filter set is presented both zonal wind profiles available at the supplementary material section show the same structure but with significant differences in the peak of the eastward jets and the equatorial region including a region of positive vertical shear symmetrically located around the equator between the 10 c

industrial structural geology principles techniques and integration an introduction the authors wish to acknowledge the generous financial support provided in association with this volume to the geological society and the petroleum group by badley geoscience ltd bp cgg robertson dana petroleum ltd getech group plc maersk oil north sea uk ltd midland valley exploration ltd rock deformation research schlumberger and borehole image core specialists wildcat geoscience walker geoscience and prolog geoscience we would like to thank the fine team at the geological society s publishing house for the excellent support and encouragement that they have provided to the editors and authors of this special publication

dynamics of saturn s great storm of 2010 2011 from cassini iss and rpws saturn s quasi periodic planet encircling storms are the largest convecting cumulus outbursts in the solar system the last eruption was in 1990 sanchez lavega a 1994 chaos 4 341 353 a new eruption started in december 2010 and presented the first ever opportunity to observe such episodic storms from a spacecraft in orbit around saturn fischer g et al 2011 nature 475 75 77 sanchez lavega a et al 2011 nature 475 71 74 fletcher l n et al 2011 science 332 1413 here we analyze images acquired with the cassini imaging science subsystem iss which captured the storm s birth evolution and demise in studying the end of the convective activity we also analyze the saturn electrostatic discharge sed signals detected by the radio and plasma wave science rpws instrument the storm s initial position coincided with that of a previously known feature called the string of pearls sops at 33 n planetocentric latitude intense cumulus convection at the westernmost point of the storm formed a particularly bright head that drifted at 26 9 0 8 m s 1 negative denotes westward motion on january 11 2011 the size of the head was 9200 km and up to 34 000 km in the north south and east west dimensions respectively rpws measurements show that the longitudinal extent of the lightning source expanded with the storm s growth the storm spawned the largest tropospheric vortex ever seen on saturn on january 11 2011 the anticyclone was sized 11 000 km by 12 000 km in the north south and east west directions respectively between january and september 2011 the vortex drifted at an average speed of 8 4 m s 1 we detect anticyclonic circulation in the new vortex the vortex s size gradually decreased after its formation and its central latitude shifted to the north the storm s head moved westward and encountered the new anticyclone from the east in june 2011 after the head vortex collision the rpws instrument detected that the sed activities became intermittent and declined over 40 days until the signals became undetectable in early august in late august the sed radio signals resurged for 9 days the storm left a vast dark area between 32 n and 38 n latitudes surrounded by a highly disturbed region that resembles the mid latitudes of jupiter using iss images we also made cloud tracking wind measurements that reveal differences in the cloud level zonal wind profiles before and after the storm

motions in saturn s atmosphere observations before voyager encounters abstract a summary is presented of all the telescopic observations of the clouds in saturn s atmosphere made prior to the voyager encounters with the planet saturn displays a pattern of belts and zones like jupiter although they are practically constant in latitude and without significant changes over the last century some dark and white spots with diameters of about 6000 to 10 000 km have been observed allowing us to ascertain the atmospheric rotational period only a strong equatorial jet can be inferred from these measurements the most obvious features of saturn are the great white spots gws with diameters of 20 000 km or more but only five outbursts have been detected since 1876 corrected measurements have been obtained of the zonal velocities at different latitudes u with variations between 430 and 14 msec 1 with respect to the magnetic rotation of the planet m l kaiser m d desch j w warwick and j b pierce science 209 1238 1240 1980 the expansion velocities of some gws have been measured to be u 30 to 100 msec 1 and their lifetimes l from 30 to 150 days a possible subatmospheric origin for the gws is proposed in which it is due to a temporary and local anisotropy in the internal heat source a hot spot in the deeper atmosphere all the multiple features seen in both 1903 and 1933 appear to be linked to a unique system of longitudes rotating with the magnetic period

mechanical stability of the triangle zone the backthrust wedge the triangle zone arrangement of faults that commonly develops at the foreland margin of fold and thrust belts is one of the few places in this structural setting that backthrusts of significant dimensions are observed even in this setting the backthrust may be a relatively ephemeral feature as it can be cannibalized by the foreland advance of thrusting in an active fold and thrust system one of the factors that determines the longevity of a specific backthrust and triangle zone in an active system is the mechanical stability of the backthrust wedge the wedge of rock that forms the hangingwall to the backthrust upper and lower stability limits for this backthrust wedge can be determined using the critical wedge concept for a cohesive coulomb material the configuration of the backthrust wedge developed in triangle zones along the southern and central alberta portion of the canadian cordillera agrees well with the stability limits derived for reasonable rock properties and normal fluid pressures in contrast a low taper triangle zone interpretation for northeastern british columbia does not fall within the calculated stability limits even when abnormally high fluid pressures and extreme rock properties are assumed however a similar low taper geometry may be achieved by the shingling of stable backthrust wedges upper crustal delamination and passive roof duplexing are both processes that serve to sustain a mechanically stable backthrust wedge configuration suggesting that they are both viable paths for the progressive advance of the mountain front triangle zone

estimating basal friction and fluid pressure from the geometry and spacing of frontal faults in naga fold thrust belt india abstract naga fold thrust belt is an emerging destination for petroleum exploration in eastern india it is a thin skinned ftb where new initiatives are being taken after a long gap of initial discoveries in absence of sufficient drilling or quality seismic data in the southern part of the fold thrust belt fluid pressure regimes remain largely speculative using the concept and the formulation for efficient coefficient of basal friction we have revisited the method and concept of pressure dependent coulomb wedge theory for thin skinned thrust belts for deriving the fluid pressure ratio in naga fold thrust belt the efficient coefficient of basal friction on the decollement and the fluid ratio of naga fold thrust belt are estimated to be 0 22 and 0 85 respectively this indicates an overpressure situation in the wedge this method of estimating basal friction and fluid pressure is more case specific and can be obtained from the data of thrust initiation angle and thrust spacing

cassini imaging of saturn southern hemisphere winds and vortices high resolution images of saturn s southern hemisphere acquired by the cassini imaging science subsystem between february and october 2004 are used to create maps of cloud morphology at several wavelengths to derive zonal winds and to characterize the distribution frequency size morphology color behavior and lifetime of vortices nonequatorial wind measurements display only minor differences from those collected since 1981 and reveal a strong prograde flow near the pole the region just southward of the velocity minimum at 40 7 s is especially active containing numerous vortices some generated in the proximity of convective storms the two eastward jets nearest the pole display periodicity in their longitudinal structure but no direct analogs to the northern hemisphere s polar hexagon or ribbon waves were observed characteristics of winds and vortices are compared with those of saturn s northern hemisphere and jupiter s atmosphere

unsteady evolution of the bolivian subandean thrust belt the role of enhanced erosion and clastic wedge progradation abstract the subandean fold and thrust belt of bolivia constitutes the easternmost part of the andean orogen that reflects thin skinned shortening and eastward propagation of the andean deformation front the exact interplay of tectonics climate and erosion in the deposition of up to 7 5 km of late cenozoic strata exposed in the subandes remains unclear to better constrain these relationships we use four w e industry seismic reflection profiles eight new zircon u pb ages from mio pliocene sedimentary strata and cross section balancing to evaluate the rates of thrust propagation shortening and deposition pinch out migration eastward thrusting arrived in the subandean belt at 12 4 0 5 ma and propagated rapidly toward the foreland unit approximately 6 ma this was followed by out of sequence deformation from ca 4 to 2 1 ma and by renewed eastward propagation thereafter our results show that the thrust front propagation and deposition pinch out migration rates mimic the sediment accumulation rate the rates of deposition pinch out migration and thrust propagation increased three and two fold respectively 8 mm a 3 3 mm a at 8 6 ma the three fold increase in deposition pinch out migration rate at this time is an indication of enhanced erosional efficiency in the hinterland probably coupled with flexural rebound of the basin following the pulse of pinch out migration the subandean belt witnessed rapid 80 km eastward propagation of thrusting to the la vertiente structure at 6 ma as there is no evidence for this event of thrust front migration being linked to an increase in shortening rate the enhanced frontal accretion suggests a shift to supercritical wedge taper conditions we propose that the supercritical state was due to a drop in basal strength caused by sediment loading and pore fluid overpressure this scenario implies that climate controlled variation in erosional efficiency was the driver of late miocene mass redistribution which induced flexural rebound of the subandean thrust belt spreading of a large clastic wedge across the basin and subsequent thrust front propagation

saturn s cloud structure inferred from cassini iss abstract using high resolution cassini iss images with wavelengths ranging from the ultraviolet to the near infrared we have retrieved saturn s atmospheric aerosol structure and properties for a broad range of latitudes in the southern hemisphere the observations are consistent with two distinct layers of haze above a scattered cloud each layer is characterized by a vertical location an optical thickness and an effective mean particle size all of which vary with latitude the tropospheric haze is optically thickest and extends to the greatest heights 40 mbar over the equator its top surface is at significantly greater depths 150 mbar at mid latitudes the height of the haze correlates well with position of the tropopause as indicated by the temperature field beneath this haze we find a scattered denser cloud responsible for small scale contrasts at an average depth of 1 75 0 4 bar with some features as deep as 2 5 bar or greater

tests of fixity of the indo atlantic hot spots relative to pacific hot spots rates of inter hot spot motion have been debated for decades herein we present updated predictions for the tracks of the tristan da cunha reunion and iceland hot spots assuming them to be fixed relative to pacific hot spots uncertainties in pacific hot spot rotations which include uncertainties in the current locations of hot spots of 100 200 km are combined with uncertainties in relative plate motions accumulated through the plate circuit to obtain the final uncertainty in the predicted positions including uncertainties of 150 200 km in the current locations of the indo atlantic hot spots improvements to reconstruction methods to relative plate reconstructions to age dates along the tracks and to the geomagnetic reversal timescale lead to significant changes from prior results when compared with the observed tracks the predicted tracks indicate nominal rates of motion of only 2 6 mm a 1 of these indo atlantic hot spots relative to pacific hot spots over the past 48 ma within the uncertainties the rates range from no motion to rates as high as 8 13 mm a 1 for reconstructions prior to 48 ma b p however the apparent rates of inter hot spot motion are much larger 46 55 20 mm a 1 if the motion occurred entirely between 68 ma b p and 48 ma b p either hot spots moved rapidly before 48 ma b p and slowed drastically at 48 ma b p or global plate circuits through antarctica become less reliable as one goes increasingly further into the past most paleomagnetic data favor the latter explanation

source rock contributions to the lower cretaceous heavy oil accumulations in alberta a basin modeling study the origin of the immense oil sand deposits in lower cretaceous reservoirs of the western canada sedimentary basin is still a matter of debate specifically with respect to the original in place volumes and contributing source rocks in this study the contributions from the main source rocks were addressed using a three dimensional petroleum system model calibrated to well data a sensitivity analysis of source rock definition was performed in the case of the two main contributors which are the lower jurassic gordondale member of the fernie group and the upper devonian lower mississippian exshaw formation this sensitivity analysis included variations of assigned total organic carbon and hydrogen index for both source intervals and in the case of the exshaw formation variations of thickness in areas beneath the rocky mountains were also considered all of the modeled source rocks reached the early or main oil generation stages by 60 ma before the onset of the laramide orogeny reconstructed oil accumulations were initially modest because of limited trapping efficiency this was improved by defining lateral stratigraphic seals within the carrier system an additional sealing effect by biodegraded oil may have hindered the migration of petroleum in the northern areas but not to the east of athabasca in the latter case the main trapping controls are dominantly stratigraphic and structural our model based on available data identifies the gordondale source rock as the contributor of more than 54 of the oil in the athabasca and peace river accumulations followed by minor amounts from exshaw 15 and other devonian to lower jurassic source rocks the proposed strong contribution of petroleum from the exshaw formation source rock to the athabasca oil sands is only reproduced by assuming 25 m 82 ft of mature exshaw in the kitchen areas with original total organic carbon of 9 or more

thermal structure and dynamics of saturn s northern springtime disturbance saturn s slow seasonal evolution was disrupted in 2010 2011 by the eruption of a bright storm in its northern spring hemisphere thermal infrared spectroscopy showed that within a month the resulting planetary scale disturbance had generated intense perturbations of atmospheric temperatures winds and composition between 20 and 50 n over an entire hemisphere 140 000 kilometers the tropospheric storm cell produced effects that penetrated hundreds of kilometers into saturn s stratosphere to the 1 millibar region stratospheric subsidence at the edges of the disturbance produced beacons of infrared emission and longitudinal temperature contrasts of 16 kelvin the disturbance substantially altered atmospheric circulation transporting material vertically over great distances modifying stratospheric zonal jets exciting wave activity and turbulence and generating a new cold anticyclonic oval in the center of the disturbance at 41 n

cloud structure of saturn s 2010 storm from ground based visual imaging abstract we present a study of the vertical cloud structure for the initial stage of the great white spot gws a giant storm that developed in saturn in december 2010 using ground based visual images we focus in the characterization of the undisturbed atmosphere preceding the storm and the disturbed region in the wake of the gws the observations were taken at calar alto spain and pic du midi france observatories on 27 december 2010 and 13 january 2011 about 1 month after the detection of the outbreak they cover a spectral range from the ultraviolet at 375 nm to the near infrared at 954 nm including the deep methane absorption band at 890 nm and a number of increasingly weaker methane absorption bands limb to limb scans of the absolute reflectivity of the regions preceding and following the storm at different wavelengths are compared to those produced by a radiative transfer model atmosphere our model assumes three layers of gas and particles stratospheric and tropospheric hazes and a deep cloud we find that the most notorious changes in the wake of the gws occurred in the top level of the semi infinite bottom cloud which ascended from an altitude level p 1 bar in the undisturbed region to p 300 300 100 mbar in the stormy area representing a rise of more than 40 km the density of the tropospheric haze does not change substantially but tropospheric particles are found to be more reflectant at all wavelengths suggesting that they are coated by fresh material putatively coming from deeper levels of the atmosphere