testing the sensitivity of geomorphic indices in areas of low rate active folding eastern betic cordillera spain abstract active deformation structures have an incidence in topography that can be quantified by using geomorphic indices most of these indices have been checked in faulted regions with high deformation rates the application of several geomorphic indices hypsometric curve analysis normalized stream length gradient and valley width to valley height ratio to the drainage network of the southern limb of the sierra de las estancias antiform internal zones eastern betic cordillera where low rate active folding has been recognized allows us to investigate the suitability of these indices to identify active structures in such a scenario hypsometric curves clearly identify regions with recent uplift and young topography but they do not provide any constraint on the location of active folds local valley width to valley height index variations have been detected just coinciding whit the position of ene wsw active folds normalized stream length gradient index serves to locate active folds in areas of hard rock substratum but not in those areas with soft sediments neogene quaternary sedimentary basins this is most likely due to the fact that in the basins erosion is much more intense than in the hard rock sectors in view of these results we consider that geomorphic indices constitute a valuable tool for identifying sectors affected by low rate uplift related to active folding with the best results obtained in hard rock areas

relief and drainage evolution during the exhumation of the sierra nevada se spain is denudation keeping pace with uplift abstract we have performed a geomorphic analysis of the sierra nevada the highest range of the betic cordillera se spain with the aim to elucidate its late miocene to present day exhumation history the qualitative and quantitative analysis is based on filtered topography local relief swath profile analysis anomalies on stream orientation bulk erosion volume hypsometry and steepness index k sn all these parameters are intimately linked to river incision and development of drainage pattern having been calculated to assess the role of folding and faulting on the evolution of the sierra nevada moreover uplift rates in the core of the sierra nevada have been deduced from an extrapolation of the position of late tortonian to pliocene coastline deposits these data have been compared to apatite u th he fission track and 10 be cosmogenic data from se spain in order to evaluate the consistency among uplift thermal histories and denudation rates our preferred tectonic scenario is one that favors fast exhumation of the western sierra nevada in a nw se overall compressive setting produced by the convergence between the nubia and africa plates sub perpendicular to this compression a westward 4 mm year extensional hanging wall displacement promotes uplift and unroofing of the western part of sierra nevada

fault generated mountain fronts in southeast spain geomorphologic assessment of tectonic and seismic activity abstract tectonic activity of se spain is evaluated through the application of a general morphometric analysis over 17 different mountain fronts the selected fronts are distributed along the two most prominent crustal scale structures of the mediterranean sector of spain the eastern betic shear zone ebsz and the valencia trough geomorphic indexes used in this study are mountain front sinuosity index smf and valley floor width ratio vf this work is largely based on the smf vf regression analysis of the studied fronts together with previous available data from sw usa the development of mountain fronts in both different lithologies and tectonic contexts enabled characteristic morphometric signatures for different activity scenarios tectonic activity classes to be obtained this study thus indicates that variations of mountain front geomorphology triggered by different styles of faulting can be detected by morphometric analysis it is demonstrated that discrete uplift rates of 0 15 0 08 m ka are sufficient to keep relatively low smf values down to 1 4 in active fronts class 1 taking into account the reported uplift rates and preliminary palaeoseismic data for some of the class 1 studied fronts recurrence periods for surface rupture events can be theoretically bracketed for se spain recurrence periods for class 1 fronts could theoretically range between 10 000 and 12 500 years for maximum slip conditions and 1750 and 2600 years for minimum slip conditions inactive fronts class 3 develop under uplift rates down to 0 03 m ka and tested recurrence intervals for rupture events range between 25 000 and 50 000 years class 2 fronts of intermediate characteristics and activity display uplift rates between 0 07 and 0 03 m ka

the life cycle of thunderstorm gust fronts as viewed with doppler radar and rawinsonde data abstract this paper presents the time dependent analysis of the thunderstorm gust front with the use of project nimrod data rhi cross sections of reflectivity and doppler velocity are constructed to determine the entire vertical structure the life cycle of the gust front is divided into four stages 1 the formative stage 2 the early mature stage 3 the late mature stage and 4 the dissipation stage a new finding is a horizontal roll detected in the reflectivity pattern resulting from airflow that is deflected upward by the ground while carrying some of the smaller precipitation ahead of the main echo core of the squall line this feature is called a precipitation roll as determined from rawinsonde data the cold air behind the gust front accounts for the observed surface pressure rise calculations confirm that the collision of two fluids produce a nonhydrostatic pressure at the leading edge of the outflow the equation governing the propagation speed of a density current accurately predicts t

late quaternary large scale rotational slides induced by river incision the arroyo de gor area guadix basin se spain the arroyo de gor is a highly incised stream up to 200 m that has eroded into the pliocene pleistocene infill of the guadix basin in the betic cordillera se spain this paper concentrates on a particular reach of this stream namely the cenascuras gorafe reach where abundant inactive rotational slides can be recognized on both hillslopes of the canyon shaped valley the rotational slides have surface areas of 5 15 ha and volumes of mobilized material of 5 15 hm3 these rotational slides can be recognized by their main scarps which are still well featured at both margins of the valley as well as by the counter hillslope rotation of the strata in their bodies the surfaces of rupture are concave their width being greater than their length i e the landslides are elongated in a direction perpendicular to the landsliding displacement and parallel to the stream at depth the surfaces of rupture developed on fine grained sediments mostly clays underlying the conglomerates and sands affected by the rotational slides the clays at the surface of rupture are smectite rich and show several features produced by the landsliding such as striations and sigmoidal shaped structures the cenascuras gorafe canyon has been developed by a combination of entrenchment fracturing and landsliding initial deep entrenchment of the stream is attributed to a base level lowering related to the capture of the former endorheic basin by the gualdalquivir river in the late pleistocene this river incision created a canyon with subvertical unstable walls which due to gravitational instability would give way to vertical open tension cracks some distance from the canyon edge the tension cracks would end at depths equal to the base of the canyon which also coincides with the contact between the conglomerates and the underlying clays the rotational slides are thought to have occurred during heavy rains by a combination of piping which would have lengthened the tension cracks and infiltration which would reduce the shear strength along the gently dipping contact between conglomerates and the underlying clays thus the blocks bounded by the tension cracks and the subhorizontal lithological contact would slide under their own weight on the subhorizontal surfaces of reduced shear strength several age constraints lead us to tentatively assign the landslides to the isotope stage 5 around 32 ka an interglacial period agreed to be wetter and slightly warmer than the present day semi arid climate

recent large fold nucleation in the upper crust insight from gravity magnetic magnetotelluric and seismicity data sierra de los filabres sierra de las estancias internal zones betic cordillera abstract rheological heterogeneities in the upper crust have a close relationship with the fold position where rigid bodies could constitute initial perturbations that allow the nucleation of folds consequently establish the position and geometry of anomalous rocks located in the upper crust by geophysical studies help to understand the folded structure observed on surface new geological observations in the field along with gravity magnetic magnetotelluric and seismicity data reveal the subsurface structure in the sierra de los filabres sierra de las estancias folded region part of the alpine belt in southern spain the geometry of the upper crust is determined by geological field data 2d gravity models 2d magnetic models and 2d mt resistivity model while seismicity evidences the location of the deep active structures these results allow us to propose that a basic rock body at 4 to 9 km depth has determined the nucleation and development of the sierra de los filabres kilometric antiform n vergent large late folds are subjected to a variable present day stress field earthquake focal mechanisms suggest the presence in depth of a regional nw se compressive stress field however most of the seismogenetic structures do not extend up to the surface where nw se and wnw ese outcropping active normal faults are observed thus indicating a ne sw extension in the upper crust simultaneous to orthogonal nw se compression related to reverse faults and minor folds developed in the eastern almanzora corridor and in the nearby huercal overa basin the recent and active tectonic studies of cordilleras hinterland subjected to late folding greatly benefits from the integration of surface observations together with geophysical data

mesoscale analysis of heavy rainfall episodes from sowmex timrex abstractthe authors analyze the mesoscale structure accompanying two multiday periods of heavy rainfall during the southwest monsoon experiment and the terrain induced mesoscale rainfall experiment conducted over and near taiwan during may and june 2008 each period is about 5 6 days long with episodic heavy rainfall events within these events are shown to correspond primarily to periods when well defined frontal boundaries are established near the coast the boundaries are typically 1 km deep or less and feature contrasts of virtual temperature of only 2 3 c yet owing to the extremely moist condition of the upstream conditionally unstable air these boundaries appear to exert a profound influence on convection initiation or intensification near the coast furthermore the boundaries once established are long lived possibly reinforced through cool downdrafts and prolonged by the absence of diurnal heating over land in generally cloudy conditions these boundaries are linked phenomenologically with

plio pleistocene lacustrine evaporites of the baza basin betic chain se spain abstract the baza basin the eastern part of the guadix baza basin in se spain underwent a significant evaporitic sedimentation in non marine settings during the plio pleistocene the largest of these settings developed in the central part of the basin as a shallow saline lake system where abundant gypsum deposits occur benamaurel and galera gypsum units this paper studies these deposits from the cartographic stratigraphic sedimentologic petrographic and isotopic points of view all the gypsum has been preserved as primary enabling a good characterization of the environmental conditions of the original precipitates three interconnected subenvironments or zones inner intermediate and marginal are differentiated in this saline lake system in the inner zone shallow to relatively deeper central lake a regular alternation of gypsum and carbonate laminae accumulated suggesting a seasonal regime many of the gypsum laminae display size gradation both reverse and symmetrical indicating free precipitation in a stable brine body in the intermediate zone mosaic of shallow lakes carbonate dolomitic beds formed in association with dark lutite levels gypsum beds and gypsum nodules and micronodules moreover anoxic conditions developed in this zone which resulted in the formation of native sulphur occurrences of economic value in the marginal zone the evaporitic deposits are developed only locally the galera gypsum unit in particular the various gypsum lithofacies in these marginal deposits suggest the presence of a number of shallow to exposed settings saline mudflat saline marsh and gypsiferous pond the isotopic composition 34 s 18 o of the gypsum samples is consistent with a triassic origin of the sulphate as a result of chemical recycling these data also suggest that a similar recycling mechanism operated in the saline lake system where the gypsum sediments from the margins were coevally recycled towards the inner part both the evaporitic mineralogy and the gypsum and carbonate lithofacies suggest that semiarid conditions prevailed in this basin during the accumulation of the evaporite units

morphometric analysis of a reactivated variscan fault in the southern bohemian massif budějovice basin czech republic abstract quantitative geomorphic parameters are used to assess active vertical displacements at the nw se striking hluboka fault and the nne ssw striking rudolfov fault in the southern bohemian massif the faults are part of a late variscan fault system that was repeatedly reactivated in mesozoic miocene and pliocene times forming the margins of the bud jovice basin this basin is filled with up to 340 m thick cretaceous to quaternary sediments and forms morphological lowland surrounded by hill country we compared the basin facing hillslopes along the faults with other slopes that are not fault controlled all creeks and drainage basins share similar geological and hydrological settings and the common base level of the vltava river morphological differences in valley shapes stream profiles and drainage basin geometry therefore are likely to reflect different uplift of the crystalline basement with respect to the bud jovice basin all calculated geomorphic parameters characterise the hillslope along the hluboka fault as a very straight mountain piedmont junction with a morphology that is influenced by uplift along the fault differential uplift is indicated by extremely low values of mountain front sinuosity smf 1 01 to 1 06 high stream length gradients sl up to 200 and very low valley floor width to height ratios vf 0 05 to 0 26 the values are clearly distinct from the values observed at the other hillslopes streams showing convex up thalweg sections with marked single knickpoints close to the hluboka fault and previously published geodetic data vyskocil 1973 support the interpretation of active vertical fault displacement values observed at the hillslope crossing the rudolfov fault smf 1 17 to 2 20 sl up to 130 vf 0 29 to 2 5 and convex up stream profiles of creeks crossing the fault may classify the slope along the rudolfov fault as moderately active the interpretation is again corroborated by published geodetic data the analysed part of the margin of the bud jovice basin that is not fault controlled revealed geomorphic parameters that are not indicative for differential vertical displacements smf 1 30 to 4 16 sl up to 57 vf 2 10 to 4 80 concave up stream profiles of creeks draining into the basin are characteristic for equilibrated streams

high winds generated by bow echoes part i overview of the omaha bow echo 5 july 2003 storm during bamex abstract an analysis of a bow echo that produced damaging winds exceeding f1 in intensity on the fujita scale near omaha nebraska is shown part i of this study presents a combination of airborne doppler derived wind syntheses with a comprehensive damage survey in order to document the generation of strong winds at the surface a detailed kinematic analysis of the evolution of a quasi linear convective system into a bow shaped and subsequently a spearhead echo is shown for the first time it is hypothesized that a large cyclonic bookend vortex 70 80 km in diameter north of the bow apex enhanced the rear inflow jet and initiated the bowing process a hook shaped echo and mesovortex formed at the apex of a bowed segment of the convective line and was located to the north of the swath of strong damage rated greater than f1 in damage intensity the peak single doppler radial velocity recorded by the tail radar was 43 m s 1 in the low level outflow near the apex of the bow echo the regions of the str

buoyancy and pressure perturbations derived from dual doppler radar observations of the planetary boundary layer applications for matching models with observations abstract the technique developed by gal chen in 1978 is used to derive vertical velocities buoyancy and pressure perturbations from dual doppler radar observations of the planetary boundary layer pbl several approaches to verification are pursued they include a scan to scan temporal continuity of the derived fields b an objective test to find out how well the derived pressure perturbations balance the dynamical equations c comparison of dual doppler derived horizontally averaged fluxes of heat versus in situ measurements and other data sets and d a noteworthy improvement in the quality of the retrieved pressure when tendencies are included previous studies indicate that in order for the method to be viable the radars have to resolve the pbl with at least ten vertical levels one such event occurred on 27 september 1978 during project phoenix conducted at the boulder atmospheric observatory bao 300 m tower an inversion above a shallow boundary layer of height around 800 m was eroded

the role of forcing in cell morphology and evolution within midlatitude squall lines abstract this study assesses the role of mesoscale forcing on cell morphology and early evolution of midlatitude squall lines the forcing chosen was a cold front simulated to frontal collapse to produce a specific set of thermodynamic profiles at the leading edge of the front use of a realistic balanced and persistent forced state allowed a unique evaluation of its importance in thunderstorm evolution compared with a traditional homogeneous environment without forcing three dimensional squall lines were modeled with and without the front present in low and high bulk richardson number environments the forced convection evolved in significantly different ways than their isolated unforced counterparts in low shear conditions the line of isolated convective cells split with the adjacent split cells interfering destructively with neighboring cells in the line with forcing present differences in anticyclonic cell intensity and propagation prevented this interaction from occurring leading to longe

gis multi criteria decision analysis for assessment and mapping of neotectonic landscape deformation a case study from crete this study of drainage systems in a tectonically active region is based on the geographical information systems gis integration of data from an analytic hierarchy process ahp and a weighted linear combination wlc procedure with multiple criteria data a set of thematic maps were produced based on existing geological maps and freely available aster global dem elevation data using various geological information i e lineaments and lithologies geomorphometric indices i e slope gradient drainage density stream frequency and the topographic wetness index and morphotectonic indices i e amplitude of relief and stream length gradient that highlight areas of neotectonic landscape deformation the weights of the factors were determined using ahp and wlc a neotectonic landscape deformation index nldi is computed as the sum of the various weighted factors to provide a map of nldi distribution across the study region western crete the main objective of this study was to analyse and map the intra basin spatial variations in neotectonic landscape deformation five classes very low to very high were determined high to very high deformation zones are linked with known and newly detected active fault zones the methodology could be developed into a low cost technique for assessing seismic hazard guiding disaster risk reduction activities it can provide an alternative to the interferometric synthetic aperture radar insar approach for highlighting zones of neotectonic deformation particularly in regions where dense vegetation or snow cover renders insar ineffective

numerical simulation of an intense squall line during 10 11 june 1985 pre storm part ii rear inflow surface pressure perturbations and stratiform precipitation abstract an intense rear inflow jet surface pressure perturbations and stratiform precipitation associated with a squall line during 10 11 june 1985 are examined using a three dimensional mesoscale nested grid model it is found that the large scale baroclinity provides favorable and deep rear to front flow within the upper half of the troposphere and the mesoscale response to convective forcing helps enhance the trailing extensive rear inflow however latent cooling and water loading are directly responsible for the generation of the descending portion of the rear inflow the role of the rear inflow is generally to produce convergence ahead and divergence behind the system and thus assist the rapid acceleration of the leading convection when the prestorm environment is convectively favorable and the rapid dissipation of the convection when encountering unfavorable conditions in this case study the rear inflow jet appears to have caused the splitting of the surface wake low as well as the organized

a numerical study of three dimensional gravity waves triggered by deep tropical convection and their role in the dynamics of the qbo abstract a 3d mesoscale model is used to study the structure of convectively triggered gravity waves in the tropics and their role in the dynamics of the middle atmosphere simulations with three stratospheric background zonal wind cases are examined in the first case the background wind profile is constant the other two are representative of the easterly and westerly phases of the quasi biennial oscillation qbo spectral analysis is used to link the structure of the triggered gravity waves to the dominant vertical wavelength of the latent heating within the convection in the qbo wind shear cases upward propagating gravity waves are damped as they approach their critical layer the signature of critical layer absorption is clearly visible in the profiles of vertical momentum flux divergence in the simulations with open boundary conditions the response to vertical momentum flux divergence takes the form of large dynamic pressure differences between the east and west boundaries together with acceler

a numerical investigation of the organization and interaction of the convective and stratiform regions of tropical squall lines abstract a set of 13 two dimensional numerical simulations based on the 22 and 23 june soundings from the convectionprofonde tropicale in 1981 copt81 experiment in west africa is used to study the organization and interactionof the convective and stratiform regions of squall line type convective systems the initial wind profiles arecharacterized by the african easterly jet aej and the tropical easterly jet tej located at about 3 5 km and14 km respectively the physical processes that generate and maintain the mesoscale inflow at the rear of squall line type mesoscaleconvective systems are thereby examined horizontal potential temperature gradients generated by a combinationof latent heat release in the convective region and unsaturated mesoscale descent both modulated by evaporation cause a horizontal pressure gradient and generate horizontal line parallel vorticity the rear inflow is a consequenceof these processes the convective activity induces a significant upscale influence ahead of the

the formation of new england coastal fronts abstract coastal fronts are a frequent late fall and early winter feature of eastern new england weather data from a mesoscale observing network is used to describe the process of coastal frontogenesis and to determine the causes of formation three distinct types of coastal frontogenesis are found to occur in new england and examples of each are presented using mesoscale surface maps and time series type a coastal fronts form during cold air outbreaks as winds veer from offshore to onshore type b coastal fronts form in the evening as air temperatures over land fall below air temperatures over water both types of fronts represent thermally direct circulations which are created by heating from the warm sea surface often in combination with radiational cooling over land type c coastal fronts are caused by upstream blocking when a stable region of warm advection such as warm front approaches the appalachian mountains from the south type a and type b fronts are described in terms of land and sea bre

organization and environmental properties of extreme rain producing mesoscale convective systems this study examines the radar indicated structures and other features of extreme rain events in the united states over a 3 yr period a rainfall event is defined as extreme when the 24 h precipitation total at one or more stations surpasses the 50 yr recurrence interval amount for that location this definition yields 116 such cases from 1999 to 2001 in the area east of the rocky mountains excluding florida two kilometer national composite radar reflectivity data are then used to examine the structure and evolution of each extreme rain event sixty five percent of the total number of events are associated with mesoscale convective systems mcss while a wide variety of organizational structures as indicated by radar reflectivity data are seen among the mcs cases two patterns of organization are observed most frequently the first type has a line often oriented east west with training convective elements it also has a region of adjoining stratiform rain that is displaced to the north of the line the second type has a back building or quasi stationary area of convection that produces a region of stratiform rain downstream surface observations and composite analysis of rapid update cycle version 2 ruc 2 model data reveal that training line adjoining stratiform tl as systems typically form in a very moist unstable environment on the cool side of a preexisting slow moving surface boundary on the other hand back building quasistationary bb mcss are more dependent on mesoscale and storm scale processes particularly lifting provided by storm generated cold pools than on preexisting synoptic boundaries

pleistocene paleoenvironmental evolution at continental middle latitude inferred from carbon and oxygen stable isotope analysis of ostracodes from the guadix baza basin granada se spain abstract a representative paleoenvironmental reconstruction of continental middle latitude from ca 2 my to the upper part of middle pleistocene 279 77 ky was obtained from the carbon and oxygen stable isotopes analyzed in ostracode shells cyprideis torosa recovered in the guadix baza basin se spain an intramontaneous closed depression filled by alluvial and lacustrine sediments this study was performed along a 356 m thick composite section dated previously by paleomagnetism and the amino acid racemization method 13c and 18o profiles reflected changes in temperature the evaporation infill ratio in the water bodies and the amount of rain 13c is also affected by changes in plant biomass periods with high 13c and 18o values are associated with warm and dry regimes and with less vegetation which in some cases coincide with the development of displacive gypsum crystals whereas low 13c and 18o values correlate with cold and humid episodes which cause more vegetation biomass and therefore increasing the input of isotopically light carbon intermediate 18o values are linked to temperate dry or humid episodes when they coincide with high or low 13c values respectively 86 paleoclimatic events were distinguished in the pleistocene record from the 13c and 18o profiles from both the statistical analysis of the geochemical data and the geological observations four cold and humid long periods low 18o and four warm and dry long periods high 18o were defined this differs with respect to the paleoclimatological behavior established for the northern hemisphere where during cold periods glacial no water was available while permafrost conditions persisted whereas in warm episodes interglacial higher precipitation rates occurred good correspondences between the guadix baza basin paleoclimatic record and a marine oxygen isotope sequence two continental cores and other long mediterranean paleoenvironmental records pollen sequences from israel were found which suggested that climate changes in the guadix baza basin were in tune with global climatic changes

role of transverse structures in paleoseismicity and drainage rearrangement in rift systems the case of the valdecebro fault zone teruel graben eastern spain the e w trending nearly pure extensional valdecebro fault zone is a transverse structure at the central sector of the n s teruel graben it was activated by the late ruscinian early pliocene ca 3 7 ma giving rise to structural rearrangement of the graben margin until the late pleistocene it has accommodated a net slip ca 205 m with slip rate of 0 055 mm a paleoseismicity has been analysed in a 29 m long 5 m deep trench excavated through a fault branch that offsets a pleistocene pediment surface the paleoseismic succession includes a minimum of 6 7 events occurred since ca 142 ka bp although a model with 12 events could be more realistic the following paleoseismic parameters have been inferred assuming a minimum of 6 and a maximum of 12 events average coseismic slip 58 117 cm recurrence period 8 4 28 4 ka potential moment magnitude mw 5 8 5 9 the recorded displacement since ca 142 ka bp totalizes 7 0 m with slip rate of 0 05 0 07 mm a slip on the transverse valdecebro fault zone has critically contributed to bulk deformation under a prevailing multidirectional extensional regime drainage patterns have been rearranged recurrently switching between westward and southward directions as a consequence of diverse slip episodes at the valdecebro fault zone e w and the neighbouring la hita n s and concud nw se faults the ultimate westward drainage of the valdecebro depression incised and dismantled a southward sloping pleistocene pediment sourced at the valdecebro mountain front representing a capture by the alfambra river occurred between 124 and 22 ka bp

heavy precipitation associated with southern appalachian cold air damming and carolina coastal frontogenesis in advance of weak landfalling tropical storm marco 1990 abstract an analysis is presented of tropical storm marco 1990 a storm that dropped copious amounts of rain over the southeast united states marco was noteworthy because of its role in the formation and evolution of two distinct episodes of cold air damming and coastal frontogenesis over georgia and the carolinas these mesoscale features led to greater than 300 mm of precipitation in 2 days over the near coastal southeast united states much of the rain occurred while marco was over 400 km away this case is further complicated by two other nearby tropical cyclones which affected marco s track and the overall rainfall distribution synoptic and mesoscale analyses of the development of the coastal front and cold air damming episodes show that the location of marco helped to orient low level winds toward the appalachians as rain developed inland a pocket of relatively cool air the cool pool formed near the mountain slopes and was partially blocked by the higher terrain low level analyses show t

a numerical study of the along line variability of a frontal squall line during pre storm despite considerable progress in the understanding of two dimensional structures of squall lines little attention has been paid to the along line variability of these convective systems in this study the roles of meso and larger scale circulations in the generation of along line variability of squall lines are investigated using an 18 h prediction of a frontal squall line that occurred on 26 27 june 1985 during pre storm preliminary regional experiment for stormscale operational research meteorology it is shown that the canadian regional finiteelement rfe model reproduces reasonably well a number of surface and vertical circulation structures of the squall system as verified against available network observations these include the initiation propagation and dissipation of the squall system surface pressure perturbations and cold outflow boundaries a midlevel mesolow and an upper level mesohigh a front to rear ftr ascending flow overlying an intense rear to front rtf flow and a leading convective line followed by stratiform precipitation regions it is found that across line circulations at the northern segment of the squall line differ significantly from those at its southern segment including the different types of precipitation the absence of the rtf flow and midlevel mesolow and the early dissipation of organized convection in the northern part the along line variability of the squall s circulations results primarily from the interaction of convectively generated perturbations with a midlevel baroclinic trough the large scale trough provides an extensive rtf flow component in the southern portion of the squall system and an ftr flow component in the north whereas the midlevel mesolow tends to enhance the rtf flow to the south and the ftr flow to the north of the mesolow during the mature to decaying stages the along line variability of the squall s circulations appears to be partly responsible for the generation of different weather conditions along the line such as the development of an upper level stratiform region in the southern segment and a midlevel cloud region in the northern portion of the squall line

compartmentalization and time lapse geochemical reservoir surveillance of the horn mountain oil field deep water gulf of mexico oil is produced at the horn mountain field gulf of mexico mississippi canyon blocks 126 and 127 from middle miocene reservoirs m and j reservoir facies are characterized as sand filled channels and associated overbank deposits and are positioned in combination structural and stratigraphic traps prior to initial production several barriers and baffles were identified in both reservoirs by integrating geological geophysical petrophysical pressure pvt pressure volume temperature relationships and geochemical data and petroleum filling history a compartmentalization risk matrix was developed to facilitate and visualize the integrated evaluation of compartmentalization during production in addition to traditional surveillance technologies we applied time lapse geochemistry tlg to visualize petroleum sweep by monitoring changes in fluid composition and fingerprints across reservoirs in this technology appraisal and preproduction fluid samples are first analyzed to map fluid types across a static reservoir then a surveillance program in which fluid samples are taken from producing wells at regular time intervals is designed and executed the obtained production samples are geochemically fingerprinted and compared with preproduction fluids from the same well and surrounding wells at horn mountain interpretation of geochemical data allowed us to infer oil movement across reservoir m and helped to reevaluate reservoir models and reduce risks in managing reservoir performance in reservoir j an untapped compartment was identified and an additional producer was justified for future drilling time lapse geochemistry results were consistent with and complimentary to other surveillance data available to date our study demonstrates that tlg is a safe and cost effective technology which reduces uncertainties associated with other reservoir surveillance methods and appears to be valuable for reservoir management

oil composition variation and reservoir continuity unity field sudan abstract a suite of oils from stacked reservoirs in the unity field in sudan has been analyzed by various geochemical techniques for molecular information to elucidate the geological processes which cause variations in oil composition and their resulting oil fingerprints in different reservoir units analyses of these highly paraffinic oils indicate that the chromatographic fingerprint variations are due to differences in the abundances of saturated compounds including branched and cyclic alkanes neither aromatics nor nso compounds have any significant effect on the observed fingerprint variations this association of saturates instead of aromatics and nso compounds with the fingerprint variations precludes rock fluid interactions as a cause of the variations biomarker analyses show that variations in thermal maturity and organic facies of the source rock are responsible for the fingerprint variations thermal maturity increases with the depth of the reservoir suggesting a multiple charge process for the oils to fill these reservoirs over an extended period of time apparently the source rock generated and expelled progressively more mature oils and little mixing occurred during migration thus knowledge of oil compositional variations from one reservoir to another organic facies variation and source rock maturity combined with tectonic history may help explain charging and timing of oil emplacement

geomorphic evidence of quaternary tectonics within an underlap fault zone of southern apennines italy abstract a composite seismic source the irpinia agri valley fault zone located in the axial sector of the fold and thrust belt of southern apennines italy is investigated this composite source is made up of a series of nearly parallel nw striking normal fault segments which caused many historical earthquakes two of these fault segments known as the san gregorio magno and pergola melandro and the fault related mountain fronts form a wedge shaped right stepping underlap fault zone this work is aimed at documenting tectonic geomorphology and geology of this underlap fault zone the goal is to decipher the evidence of surface topographic interaction between two bounding fault segments and their related mountain fronts in particular computation of geomorphic indices such as mountain front sinuosity s mf water divide sinuosity s wd asymmetry factor af drainage basin elongation b s relief ratio r h hypsometry hi normalized steepness k sn and concavity is integrated with geomorphological analysis the geological mapping and structural analysis in order to assess the recent activity of the fault scarp sets recognized within the underlap zone results are consistent with the nw striking faults as those showing the most recent tectonic activity as also suggested by presence of related slope deposits younger than 38 ka the results of this work therefore show how the integration of a multidisciplinary approach that combines geomorphology morphometry and structural analyses may be key to solving tectonic geomorphology issues in a complex fold and thrust belt configuration

the evolution and structure of a bow echo microburst event part i the microburst abstract on 14 july 1982 a comprehensive multi doppler radar dataset was collected during the life cycle of an intense microburst producing thunderstorm during the joint airport weather studies jaws project this is believed to be one of the first attempts to study the temporal and spatial evolution of an entire microburst producing thunderstorm in addition the radar echo of the parent storm evolved into a bow shaped echo thus providing the first detailed dataset on this phenomenon this microburst was numerically simulated using srivastava s one dimensional downdraft model in an attempt to quantify microphysical processes and downdraft propagation in the subcloud layer analysis of the stormwide structure using a standard multi doppler kinematic analysis technique and the gal chen thermodynamic retrieval technique is stressed in this paper which is part 1 of a two part study part ii examines the evolution of the stormwide vorticity during the formation of the bow echo the microburst downdraft wa

estimation of net to gross from p and s impedance in deepwater turbidites the limitations of using low frequency 3 d seismic data for detailed reservoir characterization are well recognized nonetheless these data are very well suited for quantitative estimates of the net to gross n g which is a reservoir scale property critical in deepwater turbidite reservoir characterization and development projects the acoustic impedance inversion of 3 d seismic has been routinely used with varying success to estimate n g in many clastic reservoirs indeed when the shale baseline impedance can be estimated the departure from this trend can be argued to represent a certain measure of the hydrocarbon saturated sand volume on the reservoir scale we take this technique a step further by using both acoustic and shear impedance ai and si and applying them to horn mountain deepwater reservoirs gulf of mexico gom where six appraisal wells were available for calibration

long term control mechanisms of stream piracy processes in southeast spain the guadix basin developed as an endorheic depression during the upper miocene upper pleistocene its principal palaeogeographical characteristics are a large lake in the eastern sector an axial fluvial system and two fluvial systems transverse to it in the western sector the uplift of a central sector of the betic cordillera during the upper pleistocene affected the study area causing northward tilting from the internal zone of the cordillera sierra nevada and sierra de baza step faulting of the plio pleistocene infill of the ancient basin leaving more northern sectors in a lower topographical position alteration of fluvial current profiles and displacement of the ancient axial system to a position very close to the divide between the ancient endorheic guadix basin and the guadalquivir basin this facilitated capture of the endorheic basin by the headward erosion of a tributary of the guadalquivir river the region then began to be rapidly eroded as the new base level was now some 500 m lower than that of the ancient basin the present drainage network is similar to that of the ancient endorheic basin as regards the location of the main streams and the distribution of drainage patterns and fluvial styles although flow reversal is found in some stretches and a barbed drainage pattern appears locally as a result of the inheritance of drainage from the ancient basin fluvial superimposition is found in some stretches of the main streams 1997 by john wiley sons ltd

initiation and organizational modes of an extreme rain producing mesoscale convective system along a mei yu front in east china abstractthe initiation and organization of a quasi linear extreme rain producing mesoscale convective system mcs along a mei yu front in east china during the midnight to morning hours of 8 july 2007 are studied using high resolution surface observations and radar reflectivity and a 24 h convection permitting simulation with the nested grid spacing of 1 11 km both the observations and the simulation reveal that the quasi linear mcs forms through continuous convective initiation and organization into west east oriented rainbands with life spans of about 4 10 h and their subsequent southeastward propagation results show that the early convective initiation at the western end of the mcs results from moist southwesterly monsoonal flows ascending cold domes left behind by convective activity that develops during the previous afternoon to evening hours suggesting a possible linkage between the early morning and late afternoon peaks of the mei yu rainfall two scales of convective organization are found d

using biomarkers to improve heavy oil reservoir management an example from the cymric field kern county california for biodegraded oil accumulations field development can be optimized by using geochemical indicators of variations in the extent of bacterial alteration biodegradation typically reduces oil producibility by increasing oil viscosity in the cymric field kern county california sidewall core extracts reveal that the extent of oil biodegradation changes substantially over extremely short vertical distances in a shallow low permeability reservoir zones of more degraded oil can extend laterally for more than a mile the relationships between oil viscosity and biomarker biodegradation parameters in this field were calibrated from analyses of produced oils and these relationships were used to convert sidewall core biomarker analyses into quantitative predictions of lateral and vertical changes in oil viscosity and gravity compositional variations were also used to allocate production to discrete zones viscosity prediction and production allocation can be used to optimize 1 the placement of new wells 2 the placement of completion intervals 3 the thickness of steam injection intervals and 4 the spacing between injection intervals in the same well

diagnosed characteristics of precipitation systems over taiwan during the may june 1987 tamex abstract characteristics of mei yu precipitating cloud systems over taiwan during the may june 1987 taiwan area mesoscale experiment tamex have been studied using sounding surface precipitation and radar data vertical motion has been computed over the island at 6 h intervals from 13 may to 15 june using a modification of the kinematic method that takes into account the mountainous lower boundary within a four station sounding polygon two primary characteristics of the precipitation have been found first the major rainfall event were linked to the passage of midlatitude disturbances and typically consisted of both deep convective and stratiform components deep convection was primarily prefrontal or frontal while the stratiform precipitation was postfrontal presumably in association with overrunning and orographic lifting second there was a pronounced diurnal variability in the rainfall vertical motion heating q1 and moistening q2 profiles have been used to define the character of the pr

development and forcing of the rear inflow jet in a rapidly developing and decaying squall line during bamex abstract this study examines the development structure and forcing of the rear inflow jet rij through the life cycle of a small short lived squall line over north central kansas on 29 june 2003 the analyses were developed from airborne quad doppler tail radar data from the noaa and nrl p 3 aircraft obtained over a 2 h period encompassing the formation development and decay of the squall line during the bow echo and mesoscale convective vortex experiment bamex the strengthening of the system relative rear inflow to 17 m s 1 was concurrent with the formation of a bow echo an increased dynamic pressure gradient beneath the rearward tilted updraft and two counterrotating vortices at either end of the bow the later weakening of the rij to 8 m s 1 was concurrent with the weakening of the bow a decreased dynamic pressure gradient at midlevels behind the bow and the weakening and spreading of the vortices in a modeling study weisman quantified the forcing mechanisms responsible for the developm

geochronological position of badlands and geomorphological patterns in the guadix baza basin se spain abstract the guadix baza basin is one of a number of intramontane depressions located within the betic cordillera se spain where the geological and geomorphological evolution is controlled by tectonic activity the basin ceased to be closed after capture by the atlantic network when five main land systems developed late pleistocene geological evolution basically consisted of erosional modelling when badlands were deeply incised in highly erodible materials marls and silts three travertine platforms and several palaeolithic sites were used to determine that this main incision period fell within a 115 000 48 000 yr range there are few signs of geomorphological evolution of this basin in the last 48 000 yr based on these geomorphological data and soil development tectonic uplift of the basin probably played a secondary role in its evolution and climatic conditions in southern iberia in the 144 000 48 000 yr period were more humid and variable than later

application of aromatic compounds as maturity indicators in source rocks and crude oils concentration ratios of aromatic compounds such as naphthalenes phenanthrenes and dibenzothiophenes are at present attracting increasing attention as maturity indicators in sedimentary rocks and crude oils generally these indicators rely either on an increase with maturity in the degree of alkylation of a given parent compound or a shift in the isomer distribution of alkyl aromatic homologues towards thermally more stable isomers a combination of both concepts in the methylphenanthrene index mpi resulted in an excellent maturity parameter as demonstrated for rock extracts by an improved correlation with mean vitrinite reflectance rm between 0 65 and 1 4 i e in the zone of oil formation in cases that rm measurements were ambiguous this empirical relationship has proved useful in the calculation of theoretical vitrinite reflectance rc values from the mpi on the other hand for potential petroleum source rocks reaching maturity at relatively low temperatures the influence of the organic matter type on the aromatic distributions cannot be neglected consequently organic facies effects should be taken into account in the interpretation of aromatic distributions of such source rocks and related crude oils since the impact of the organic facies is strongly reduced with increasing maturity aromatic maturity parameters are particularly useful in the maturity evaluation of post mature crude oils and condensates in contrast to biological markers substantially higher concentrations of the key alkyl aromatics persist at elevated maturation levels thus aromatic maturity parameters should be considered as versatile tools in organic maturation studies and can complement established maturity indicators based on steranes and terpanes

active faulting in the central betic cordillera spain palaeoseismological constraint of the surface rupturing history of the baza fault central betic cordillera iberian peninsula abstract this paper on the baza fault provides the first palaeoseismic data from trenches in the central sector of the betic cordillera s spain one of the most tectonically active areas of the iberian peninsula with the palaeoseismological data we constructed time stratigraphic oxcal models that yield probability density functions pdfs of individual palaeoseismic event timing we analysed pdf overlap to quantitatively correlate the walls and site events into a single earthquake chronology we assembled a surface rupturing history of the baza fault for the last ca 45 000 years we postulated six alternative surface rupturing histories including 8 9 fault wide earthquakes we calculated fault wide earthquake recurrence intervals using monte carlo this analysis yielded a 4750 5150 yr recurrence interval finally compared our results with the results from empirical relationships our results will provide a basis for future analyses of more of other active normal faults in this region moreover our results will be essential for improving earthquake probability assessments in spain where palaeoseismic data are scarce

applications of petroleum geochemistry to exploration and reservoir management abstract petroleum geochemistry improves exploration efficiency by accounting for many of the variables that control the volumes of crude oil and natural gas available for entrapment including source rock distribution richness and quality thermal maturity and the timing of generation migration accumulation relative to trap formation it is most powerful when used with other disciplines such as seismic sequence stratigraphy and reservoir characterization four key technology milestones form the basis for most modern applications of geochemistry to exploration these are the concepts and applications of 1 petroleum systems and exploration risk 2 biomarkers stable isotopes and multivariate statistics for genetic oil oil and oil source rock correlation 3 calibrated three dimensional thermal and fluid flow modeling and 4 controls on petroleum composition by secondary processes petroleum geochemistry offers rapid low cost evaluation tools to aid in understanding development and production problems some technology milestones in reservoir geochemistry include 1 assessment of vertical and lateral fluid continuity 2 determination of proportions of commingled production from multiple zones and leaky casing 3 prediction of oil quality in reservoir zones and 4 prediction of gas oil and oil water contact locations as described in the conclusions future research will continue a trend toward predictive geochemistry examples of predictive tools that draw major research support include piston core surveys to assess deepwater petroleum systems prior to drilling and three dimensional basin modeling to predict the regional timing of generation migration and accumulation of petroleum among other research objectives models are needed to better predict the distribution and quality of petroleum in reservoirs

hydrothermal activity and its paleoecological implications in the latest miocene to middle pleistocene lacustrine environments of the baza basin betic cordillera se spain the continental sedimentary record of the baza basin guadix baza depression betic cordillera se spain shows six sedimentary units of lacustrine origin deposited from the latest miocene to the middle pleistocene depending on the interval considered the lacustrine deposits are mainly composed of marls carbonates or gypsiferous evaporites showing lithological mineralogical and geochemical features i e magnesium strontium and sulfur contents celestine deposits and travertine growths that are evidence of intense tectonically induced hydrothermal activity according to the high concentrations of strontium and sulfur as well as the abundance of travertines and magnesium clays the supply of hot waters was greater during the zanclean the gelasian and the calabrian as a result of tectonic activity hydrothermal activity has continued until the present time and is responsible of the hot springs that are nowadays active in the guadix baza depression the paleoenvironmental consequences of these sublacustrine hot springs were that during some intervals the lakes maintained a relatively permanent water table not subject to periodic desiccations in the dry season and warmer temperatures throughout the year this resulted in a high level of organic productivity especially for the calabrian which allowed the development of a rich and well diversified mammalian community similar to those of modern african savannas with tree patches in this mild environment the permanent water sheet favored the presence of drought intolerant megaherbivores such as the giant extinct hippo hippopotamus antiquus the high standing crop biomass of ungulates resulted in the availability of abundant carcasses for scavengers such as hyenas and hominins which explains the very high densities of skeletal remains preserved in the sediments distributed along the lake surroundings

heterogeneity of oil composition within a reservoir as a reflection of accumulation history abstract the unaltered petroleums of a small oil field in the f r germany reveal pronounced spatial heterogeneities in bulk and molecular composition over most of the field area the oil in high porosity high permeability sand intervals bears a higher proportion of saturated hydrocarbons and has a higher maturity chemical signature as compared to oils occupying lower porosity lower permeability zones for all sands with less than about 13 porosity a regular relationship was observed between oil composition and porosity permeability with a decrease of the latter petrophysical properties increasingly lower chemical maturities and increasingly different bulk chemical compositions lower proportions of saturated hydrocarbons and higher proportions of nso compounds were recorded maximum contrasts measured for chemical maturities are e g 0 63 versus 0 82 vitrinite reflectance equivalents rc values calculated on the basis of the methylphenanthrene index according to radke and welte 1983 0 31 versus 0 84 for the ratio of triaromatic to mono plus triaromatic steroid hydrocarbons and 0 38 versus 0 47 for the 20s 20s 20r ratio of c29 5 h 14 h 17 h steranes these spatial heterogeneities in the composition of the oils are interpreted to reflect 1 i successive stages of trap filling due to episodes of increasing burial and maturation of the relevant source rocks in combination with 2 ii low rates of in reservoir mixing of these individual oil charges by convection or diffusion recognition of compositional heterogeneities within the oil column of individual fields may not only provide a basis for the reconstruction of reservoir filling history but may also have important implications for improving petroleum production

formation and preservation of a giant petroleum accumulation in superdeep carbonate reservoirs in the southern halahatang oil field area tarim basin china giant petroleum accumulations worldwide with burial depths more than 7000 m 23 000 ft occur mostly in mesozoic and cenozoic reservoirs and yield predominantly natural gas recently however a giant oil accumulation with reservoir depths between 7000 m 23 000 ft and 8000 m 26 000 ft was discovered in the lower paleozoic section in the southern part of the halahatang region in the tarim basin china petroleum sourced from lower paleozoic rocks is contained in ordovician karst fracture cave reservoirs and sealed by middle upper ordovician limestones and mudstones the newly discovered superdeep accumulation is among the deepest black single phase oil accumulations worldwide and opens up new avenues for petroleum exploration in deep marine carbonate reservoirs reservoir pressures are between 75 mpa 10 878 psi and 85 mpa 12 328 psi with pressure coefficients between 1 2 and 1 7 and temperatures ranging between 140 c 284 f and 172 c 342 f charging and accumulation of petroleum occurred during the late hercynian orogeny followed by subsequent gradual deep burial which took place before rapid subsidence beginning circa 5 ma following subsidence the thickness of overlying strata increased by more than 2000 m 6600 ft before finally attaining current depth therefore this oil accumulation represents a well preserved ancient petroleum system based on the geochemical features of oils and gases the crude oils can be classified as mature sourced from mixed marine organofacies of shale marl and carbonate whereas the gases were cogenerated with oils despite very high present day reservoir temperatures no oil cracking has occurred because of the relatively short exposure of oils to high temperatures in a low geothermal gradient regime thus there is significant exploration potential under similar conditions for liquid petroleum in superdeep strata faults and reservoirs are major factors controlling petroleum accumulation interlayer karsts with excellent fracture cavity connectivity developed adjacent to faults generally resulting in the enrichment of oil and gas along fault zones high quality reservoirs in this area are easy to identify because they exhibit strong bead like amplitude features in seismic sections wells located near faults produce relatively large amounts of oil and gas effective karst fracture cave reservoirs with noncracked oil may exist below 8000 m 26 000 ft in the tarim basin and represent a significant exploration target in china

geochemistry of shale gases from around the world composition origins isotope reversals and rollovers and implications for the exploration of shale plays abstract we studied a large dataset of 2600 shale gas samples from 76 geological formations in 38 sedimentary basins located in eleven countries shale gases contain mostly hydrocarbons dominated by methane shale gases can have primary microbial secondary microbial and thermogenic origin however gases produced from most commercially successful shale plays e g the marcellus haynesville eagle ford and barnett in the usa the vaca muerta in argentina and the wufeng longmaxi in china are thermogenic it appears that formations with greater gas endowment such as the marcellus and the haynesville contain late mature thermogenic gas shale plays with early mature thermogenic and secondary microbial gas such as the antrim usa and the new albany usa formations have relatively low endowments of recoverable gas shale plays with primary microbial gas are not significant from commercial exploration perspective isotope reversals 13c of methane 13c of ethane are observed in shale plays with mature organic matter vitrinite reflectance 2 that experienced significant uplift 2 km it appears that isotope fractionation during desorption from depressurized late mature shales leads to isotope reversal in the residual gas produced from shale formations e g the wufeng longmaxi significant contribution of adsorbed gas enriched in 13c rich c2 hydrocarbons relative to the co occurring free gas in the production from some plays e g the fayetteville usa may result in isotope rollovers

the formation of a cooling induced mesovortex in the trailing stratiform region of a midlatitude squall line abstract there have been some ambiguities in recent observational studies as to whether midlevel mesovortices are induced by latent heating or cooling and develop in the descending or ascending portion of mesoscale convective systems mcs s in this study a comprehensive examination of a cooling induced mesovortex in the trailing stratiform region of a midlatitude squall line that occurred on 10 11 june 1985 during the preliminary regional experiment for storm central pre storm is presented using a 20 h high resolution simulation of the squall system this cooling induced midlevel vortex originates from the preexisting cyclonic vorticity associated with a traveling meso scale short wave the vortex is intensified in the descending rear to front rtf inflow as a result of continued sublimative melting and evaporative cooling in the stratiform region it decouples from the front to rear ftr ascending and anticyclonic flow in the upper troposphere during the formative stage the vortex tilts northw

recent fault controlled glacis deformation and its role in the fluvial capture of the guadix baza basin betic cordillera southern spain abstract this work is focussed on the geomorphological changes related to the pleistocene capture of the formerly endorheic guadix baza basin betic cordillera we explore the possible tectonic controls in the basin opening through a combined geomorphological and structural study for this we have selected a study area that includes the connecting zone between the former endorheic basin and the capture channel guadiana menor river this zone also includes the se end of the so called tiscar fault zone tfz that has been active during the upper miocene and onwards we use the glacis surface that marks the end of the endorheic sedimentation middle upper pleistocene as the main reference surface to identify recent deformation structures our results indicate that the main channel crossing the pozo alcon glacis guadalentin river shows evidence of high levels of fluvial incision and that some anomalies in the stream longitudinal profile could be correlated to the presence of pre glacis faults linked to the tfz conversely abrupt changes in the stream orientation seems to be related to post glacis downthrow faults we have identified that the dextral strike slip tiscar fault the northern boundary of the tfz propagates towards the se as far as the guadalentin river giving rise to a deformation band with oblique slip that descends the sw block down to 250 m and affects the glacis surface additionally the pozo alcon glacis has undergone distributed deformation mainly achieved by n s to ne sw downthrow faults and subordinate wnw faults the roughly e w extension within the pozo alcon glacis can be interpreted as developed in the extensional lobe at the tip of a dextral strike slip fault the tiscar fault according to the orientation wnw ese and location of the guadiana menor river following the southern boundary of the tfz and the relief attenuation and tilting produced by the extensional systems in the pozo alcon glacis we interpret that the later stages of tfz activity probably controlled and favoured the localisation of the basin capture

microseismicity and tectonics in the granada basin spain a microseismic experiment carried out in 1994 in the granada basin spain permitted the precise recording of more than 80 local earthquakes the dense distribution of the local network with 40 to 50 instrumental records for each event enabled us to have well controlled hypocenters and also 10 reliable focal mechanisms the above observations are interpreted together with topographic data neotectonics and sub surface information microtectonic observations in sierra elvira padul and zafarraya gave a set of fault planes and striae which were interpreted in terms of the recent regional stress tensor the actual stress tensor obtained from the microseismic campaign data gives a regime in radial extension with r1 vertical and r3 oriented ns to nne microtectonic information is coherent with these orientations but closer to 3 axial extension a set of 64 mechanisms obtained from the permanent andalusian network favors a ns orientation for r3 this results are interpreted in terms of the general model implying the lateral ejection of the betic ranges towards the atlantic d 2002 elsevier science b v all rights reserved

the baza fault a major active extensional fault in the central betic cordillera south spain in the guadix baza basin betic cordillera lies the baza fault a structure that will be described for the first time in this paper eight gravity profiles and a seismic reflection profile coupled with surface studies indicate the existence of a ne dipping normal fault with a variable strike with n s and nw se segments this 37 km long fault divides the basin into two sectors guadix to the west and baza to the east since the late miocene the activity of this fault has created a half graben in its hanging wall the seismic reflection profile shows that the fill of this 2 000 3 000 m thick asymmetric basin is syntectonic the fault has associated seismicity the most important of which is the 1531 baza earthquake since the late tortonian to the present i e over approximately the last 8 million years extension rates obtained vary between 0 12 and 0 33 mm year for the baza fault being one of the major active normal faults to accommodate the current ene wsw extension produced in the central betic cordillera the existence of this fault and other normal faults in the central betic cordillera enhanced the extension in the upper crust from the late miocene to the present in this regional compressive setting

architecture and tectono stratigraphic evolution of the intramontane baza basin betics se spain constraints from seismic imaging abstract the baza basin is a large neogene intramontane basin in the betic cordillera of southern spain that formed during the tortonian late miocene the betic cordillera was produced by nw se oblique convergence between the eurasian and african plates three seismic reflection lines each 18 km long vibroseis method were acquired across the baza basin to reveal the architecture of the sedimentary infill and faulting during basin formation we applied rather conventional cdp data processing followed by first arrival p wave tomography to provide complementary structural information and establish velocity models for the post stack migration these images show a highly asymmetric structure for the basin with sediments thickening westward reaching a maximum observed thickness of 2200 m near the governing baza fault zone bfz three major seismic units including several subunits on top of the acoustic basement could be identified we use stratigraphic information from the uplifted block of the bfz and other outcrops at the basin edges together with available information from neighboring betic basins to tentatively correlate the seismic units to the known stratigraphy in the area until new drilling or surface outcrop data is not available this interpretation is preliminary the seismic units could be associated to tortonian marine deposits and latest miocene to pleistocene continental fluvio lacustrine sediments individual strands of the bfz truncate the basin sediments strong fault reflections imaged in two lines are the product of the large impedance contrast between sedimentary fill and basement in the central part of the basin several basement faults document strong deformation related to the early stages of basin formation some of these faults can be traced up to the shallowest imaged depth levels indicating activity until recent times

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

improved interpretation of wireline pressure data modern wireline pressure data can have resolution and reproducibility sufficient to detect small fluid density changes and pressure barriers yet these features are commonly overlooked on conventional pressure depth plots the large pressure variation caused by weight of subsurface fluids hides these subtle features excess pressure is the pressure left after subtracting the weight of a fluid from the total pressure this concept is applied to wireline pressure data to remove effects of weight and emphasize subtle pressure differences caused by density variations and pressure barriers fluid density changes of 0 02 g cm3 or less can be resolved and within well pressure barriers in the order of 5 kpa 0 7 psi can be detected using good quality data effects of reservoir capillary displacement pressure can be detected by offset of the free water level from the petroleum water contact this effect can be used to estimate reservoir wettability subsurface fluid density measurements can also be used to evaluate oil or gas quality on a bed by bed scale in traps having variable oil or gas composition to detect compartmentalization by small petroleum density differences to verify quality of samples for pvt pressure volume temperature analysis and estimate salinity or temperature of unsampled water zones data quality limits barrier and fluid contact resolution thus quality control is essential pressure measurement errors on the 3 kpa 0 5 psi scale can be detected from behavior of the buildup pressure tests having the potential for small amounts of supercharge are identified from the overbalance and formation mobility examples illustrate identification of free water levels and fluid contacts fluid identification supercharge identification and water zone compartmentalization

the role of convectively generated rear inflow jets in the evolution of long lived mesoconvective systems abstract in this study the structure of convectively generated rear inflow jets and their role in the evolution of long lived mesoconvective systems are investigated through an analysis of idealized three dimensional simulations using a nonhydrostatic cloud model rear inflow jets are generated within these systems in response to the upshear tilting of the convective circulation as the horizontal buoyancy gradients along the back edge of the expanding system create a circulation that draws midlevel air in from the rear within this framework a wide range of rear inflow strengths and structures are produced depending on the magnitude of the ambient convective available potential energy cape and the vertical wind shear in general for environments characterized by weak to moderate vertical wind shear and weak to moderate cape the rear inflow jet descends and spreads along the surface well behind the leading edge of the gust front and the subsequent convective activity becomes weaker however for e

refining upon the climatic background of the early pleistocene hominid settlement in western europe barranco leon and fuente nueva 3 guadix baza basin se spain abstract the early pleistocene sites of barranco leon and fuente nueva 3 guadix baza basin se spain have yielded thousands of mode 1 or oldowan lithic artifacts both sites and one tooth in layer d formerly 5 of barranco leon today considered to be some of the earliest evidence of humans in western europe at ca 1 2 1 5 ma previous quantitative paleoclimatic reconstructions based on herpetile assemblages indicated that during the formation of these two sites the mean annual temperature and mean annual precipitation were higher than they are now in the southeastern iberian peninsula with lower continentality here we propose new climatic reconstructions where the mean monthly temperature and precipitation and the difference between the four driest months and the four rainiest months are estimated climatograms are built in order to specify the distribution and variation of temperature and precipitation during the year and the aridity indices of gaussen lautensach mayer dantin revenga and de martonne are used to characterize ombroclimatic differences according to these new climatic parameters rainfall distribution through the year shows considerably higher precipitation in every season except summer and early autumn which remain drier and thus consistent with a mediterranean climate pattern no change is observed in the duration of the aridity period which remains four months long however the value of the aridity index of de martonne is higher than 20 subhumid climate in barranco leon and fuente nueva 3 whereas today it is lower than 20 semi arid climate suggesting major changes in the ombroclimatic type these results yield a more precise scenario for the paleoclimatic conditions that prevailed during the late early pleistocene in the guadix baza basin and permit us to contrast the ages obtained from numerical dating and biochronology the very warm and humid climate reconstructed for both barranco leon and fuente nueva 3 suggests that in accordance with the numerical dating these two sites are contemporaneous with the particularly warm interglacial peaks of marine isotope stages 43 49 i e between 1 35 and 1 47 ma the similarity between reconstructed climates the high overlap between their estimated precipitation and between the difference of the driest from the rainiest season suggest that these sites may correspond to the same part of a climatic glacial interglacial cycle but because the evolutionary degree of the rodent mimomys savini shows a slightly more derived state for fuente nueva 3 than for barranco leon i e a short chronological difference between the two sites they may correspond to two consecutive warm interglacial peaks

glacis geometry as a geomorphic marker of recent tectonics the guadix baza basin south spain abstract the guadix baza basin occupies 4000 km 2 and constitutes the largest intramontane basin of the betic cordillera southern spain it has a well preserved geomorphic surface a glacis which started to be eroded when the basin conditions changed from endorheic to exorheic taking into account its large preserved surface area more than 1200 km 2 and its pre deformational geometry this geomorphic surface is a useful marker of recent deformation combining geological and geomorphological data and high resolution dem topographic profiles of the glacis have been produced to estimate vertical displacements caused by active compression and extension structures these structures have produced relative vertical displacements of up to 100 m from the late middle pleistocene to the present assuming an age for the glacis of between 205 and 600 ka it has been possible to estimate long term minimum and maximum vertical rates of the activity of normal faults and folds using this geomorphic surface as a marker vertical slip rates range from 0 07 to 0 49 mm year for the main active normal faults and vertical folding rates range from 0 05 to 0 17 mm year for several active folds these long term vertical slip and folding rates are in accordance with other values previously estimated in other sectors of the betic cordillera when present detailed geomorphic study of recent glacis is an excellent tool for evaluating active tectonics over large regions

development and applications of light hydrocarbon based star diagrams two star diagrams multivariate plots in polar coordinates have been developed to assess subtle chemical differences among oils the diagrams are based on analysis of c7 hydrocarbons of crude oils separated by gas chromatography the first of the c7 diagrams is used for distinguishing variations in oils caused by transformation e g water washing biodegradation and evaporation eight ratios are plotted on this diagram in order of decreasing sensitivity to biodegradation the ratios are designated tr1 through tr8 and the diagram is referred to as the c7 oil transformation star diagram c7otsd a second c7 based diagram consists of five ratios composed of compounds that are very resistant to the effects of transformation and thus are useful for correlation these ratios designated c1 through c5 are plotted on the c7 oil correlation star diagram c7ocsd this diagram can be used to correlate both transformed and primary oils based on source related chemical differences a task not easily accomplished through most conventional geochemical techniques for example condensates often contain no biomarkers due to their advanced maturity and therefore cannot be correlated with lower maturity oils however both condensates and oils usually contain light ends allowing correlation by c7 based star diagrams the division of star diagrams into two types allows one to assess the relative degrees of transformation among a set of oils that have been found to correlate based on the c7ocsd these microscale correlations detect small chemical differences between oils and therefore allow even slight variations among oils within the same reservoir to be recognized the technique has many applications that concern both exploration and production production related uses include reservoir compartmentalization studies investigating reservoir extent and connectivity determining the source of casing leakage and determining the extent of commingling of oils from different reservoirs in multicompletion wells or leaky single completion wells exploration problems that can be addressed are mechanisms and models of field fill history and evaluation of oil quality in untested pay zones most of these problems can be addressed through simple cost effective analyses on produced or tested crude oils for example a large advantage in production applications is the ability to assess reservoir connectivity without halting production from any well an additional use of the technique is for investigating contaminants or incompletely refined crudes in refinery streams in this paper i present several case studies that have already been done at saudi aramco these studies include three examples of behind casing leakage two examples of oil differentiation and a single example each of correlation of condensates and refinery contaminant tracing

spatial and temporal variation of palaeoseismic activity at an intraplate historically quiescent structure the concud fault iberian chain spain abstract several faults in the teruel and jiloca grabens iberian chain ne spain particularly the targeted concud fault show evidences of recent continuous activity despite their scarce instrumental and historic seismic record three trenches are studied in two locations central and southeastern sectors of the concud fault respectively after comparing with previous works we reconstruct a palaeoseismic succession with nine events distributed along a maximum time lapse bracketed between 81 6 and 14 0 ka this succession involves an average recurrence interval of 7 4 2 8 ka with individual interseismic periods between 4 and 11 ka the calculated coseismic displacements range from 0 6 to 2 7 m with an average value of 1 9 m that results in a slip rate of 0 26 mm a due to the incomplete sedimentary record for holocene times we cannot affirm that the youngest event detected was actually the last one we conjecture that some other events may have occurred during the period between 15 0 and 3 4 ka temporal and spatial variations have been detected in palaeoseismic activity specifically in the distribution of coseismic displacements first a non steady slip rate is evidenced during plio pleistocene times a long term tendency towards increasing slip rate is modulated in detail by the occurrence of minor cycles as the sequence of increasing decreasing activity recorded within the studied time window suggests secondly an asymmetric distribution of coseismic slip along the fault trace is observed paralleling the distribution of total fault throw which shows an absolute maximum close to the southeastern tip a combination of factors is proposed to explain this branching of the main fault dominant remote stress driven slip towards n 220 e on the nw se fault segment guided movement on the passive nnw sse segment giving rise to an oblique roll over monocline and decoupling of the hanging wall block owing to the transverse los mansuetos valdecebro fault zone

dedolomitization as an analogue process for assessing the long term behaviour of a co2 deep geological storage the alicun de las torres thermal system betic cordillera spain abstract carbon dioxide deep geological storage especially in deep saline aquifers is one of the preferred technological options to mitigate the effects of greenhouse gases emissions thus in the last decade studies characterising the behaviour of potential co 2 deep geological storage sites along with thorough safety assessments have been considered essential in order to minimise the risks associated with these sites the study of natural analogues represents the best source of reliable information about the expected hydrogeochemical processes involved in the co 2 storage in such deep saline aquifers in this work a comprehensive study of the hydrogeochemical features and processes taking place at the natural analogue of the alicun de las torres thermal system betic cordillera has been conducted thus the main water co 2 rock interaction processes occurring at the thermal system have been identified quantified and modelled and a principle conclusion is that the hydrogeochemical evolution of the thermal system is controlled by a global dedolomitization process triggered by gypsum dissolution this geochemical process generates a different geochemical environment to that which would result from the exclusive dissolution of carbonates from the deep aquifer which is generally considered as the direct result of co 2 injection in a deep carbonate aquifer therefore discounting of the dedolomitization process in any co 2 deep geological storage may lead to erroneous conclusions this process will also influence the porosity evolution of the co 2 storage formation which is a very relevant parameter when evaluating a reservoir for co 2 storage the geothermometric calculation performed in this work leads to estimate that the thermal water reservoir is located between 650 and 800 m depth which is very close to the minimum required to inject co 2 in a deep geological storage it is clear that the proper characterisation of the features and hydrogeochemical processes taking place at a natural system analogous to a man made deep geological storage will provide useful conceptual semi quantitative and even quantitative information about the processes and consequences that may occur at the artificial storage system

normal faulting driven by denudational isostatic rebound fluvial piracy in the guadix baza basin southeast spain promoted erosion of a high volume of sediments during the late quaternary after the former internal drainage of this basin changed to external due to headward erosion by the guadalquivir river as a response to load release this basin underwent uplift which in turn enhanced fluvial incision and erosional processes differential erosion within the guadix baza basin resulted in dissimilar isostatic rebound we numerically model the lithospheric response to sediment unloading and show a total rising of 15 m in the guadix subbasin compared to 2 m in the baza subbasin this differential uplift is likely to have been accommodated along the baza normal fault which has been active throughout the quaternary modeling results suggest that 13 of the total quaternary fault throw directly arises from the differential isostatic readjustment between subbasins this example is one of the first estimates of fault slip partitioning between tectonic and isostatic effects due to unloading driven by river incision

quaternary landscape evolution and erosion rates for an intramontane neogene basin guadix baza basin se spain abstract the landscape evolution in neogene intramontane basins is a result of the interaction of climatic lithologic and tectonic factors when sedimentation ceases and a basin enters an erosional stage estimating erosion rates across the entire basin can offer a good view of landscape evolution in this work the erosion rates in the guadix baza basin have been calculated based on a volumetric estimate of sediment loss by river erosion since the late pleistocene to do so the distribution of a glacis surface at ca 43 kyr characterised by a calcrete layer that caps the basin infilling has been reconstructed to support this age new radiometric data of the glacis are presented the volume of sediment loss by water erosion has been calculated for the entire basin by comparing the reconstructed geomorphic surface and the present day topography the resulting erosion rates vary between 4 28 and 6 57 m3 ha 1 yr 1 and are the consequence of the interaction of climatic lithologic topographic and tectonic factors individual erosion rates for the guadix and baza sub basins 11 80 m3 ha 1 yr 1 and 1 77 m3 ha 1 yr 1 respectively suggest different stages of drainage pattern evolution in the two sub basins we attribute the lower values obtained in the baza sub basin to the down throw of this sub basin caused by very recent activity along the baza fault

water flooding of the oseberg ost oil field norwegian north sea application of formation water chemistry and isotopic composition for production monitoring abstract this case study demonstrates how natural heterogeneities of formation and injection waters can be applied to a number of production related applications extending into the mature life of a reservoir break through of injection water identification and characterisation of production intervals and evaluation of responses to operational events are some of the possible applications during production the oseberg ost oil field in the north sea represents a complex situation with commingled production from all brent group formations the sr isotope composition is an excellent parameter for defining the natural baseline of formation water with a good spatial resolution and vertical stratification aquifer water from the utsira formation is injected for pressure support and reinjection of produced water has also been applied since the onset of water production utsira formation water has high mg low ba and low sr content compared to the reservoir formation waters isotopic compositions d and 87 sr 86 sr are also distinct a non reactive behaviour of ba and sr is verified from binary cross plots and geochemical modelling break through of injection water could be identified in five production wells based on ba mg ratios in one of the reservoir compartments beta saddle water injection points were changed after approximately three years the ba mg ratio could also identify the second injection water break through in one of the wells due to an intermediate period of higher formation water content since the sr content in the utsira water is low the 87 sr 86 sr ratio is a good natural tracer for formation water movements even at high ratios of injected water in particular the vertical stratification of 87 sr 86 sr is useful for quantifying production from different intervals in commingled wells a methodology for using operational events such as production allocations or shut ins for characterisation of production zones is discussed

mesoscale convective systems 1 mesoscale convective systems mcss have regions of both convective and stratiform precipitation and they develop mesoscale circulations as they mature the upward motion takes the form of a deep layer ascent drawn into the mcs in response to the latent heating and cooling in the convective region the ascending layer overturns as it rises but overall retains a coherent layer structure a middle level layer of inflow enters the stratiform region of the mcs from a direction determined by the large scale flow and descends in response to diabatic cooling at middle to low levels a middle level mesoscale convective vortex mcv develops in the stratiform region prolongs the mcs and may contribute to tropical cyclone development the propagation of an mcs may have a discrete component but may further be influenced by waves and disturbances generated both in response to the mcs and external to the mcs waves of a larger scale may affect the propagation velocity by phase locking with the mcs in a cooperative mode the horizontal scale of an mcs may be limited either by a balance between the formation rate of convective precipitation and dissipation of stratiform precipitation or by the rossby radius of the mcv the vertical redistribution of momentum by an mcs depends on the size of the stratiform region while the net vertical profile of heating of the large scale environment depends on the amount of stratiform rain regional variability of the stratiform rain from mcss affects the large scale circulation s response to mcs heating

the early to middle pleistocene boundary in the baza basin spain abstract the continental vertebrate fauna of cullar baza 1 granada spain occur immediately above the matuyama brunhes polarity boundary and therefore represent an initial record for the middle pleistocene all polarity zones for the late pliocene through middle pleistocene are found in an 80 m section which includes this fossil quarry the existing collection of abundant remains of micro mammals macro mammals and lithic artifacts indicating human activity can now be assigned an earliest middle pleistocene age of 0 75 ma another section 25 km across the neogene baza basin also has the matuyama brunhes polarity boundary however in this case the huescar 1 fossil quarry and the puerto lobo sites are both below the polarity boundary thus representing a record of the late early pleistocene at 0 9 ma differences in micro mammal species across these matuyama brunhes boundaries are significant and justify an approximately coincident biostratigraphic boundary between the biharian and toringian stages

recent and present day stresses in the granada basin betic cordilleras example of a late miocene present day extensional basin in a convergent plate boundary the diffuse convergent boundary between the eurasian and african plates in the western mediterranean is associated with a seismicity zone more than 300 km wide although the two plates are converging nw se the betic and rif cordilleras contain extensional structures that have been active since the miocene the extensional tectonics in the region which occurred simultaneously with the uplift of the cordillera have been analyzed in the southeastern sector of the late miocene to recent granada basin using earthquake focal mechanisms the determination of paleostresses from the study of the orientation and kinematics of microfaults and the study of the major structures both the geological surface data and the focal mechanisms indicate present day regional conditions of ne sw extension with triaxial to prolate stress ellipsoids however the stress field is heterogeneous with local variations in stress over time with different stresses sometimes even acting simultaneously in adjacent areas the most frequent changes consist of pluridirectional or ne sw extension favored by the prolate character of the stress ellipsoids and nw se subhorizontal compression favored by the regional tectonic setting strike slip faults are scarce even though they are the most likely structure to be expected in a region with sw ne extension and nw se compression seismicity is concentrated in the upper crust and may correspond to the activity of low to high angle normal faults similar to the surface faults although they can not be correlated with them the lower cutoff of this seismicity probably coincides with the 300 c isotherm and suggests a low thermal gradient for the region present day regional stresses have 1 vertical at the surface but in depth plunge toward the sw

rear inflow in squall lines with trailing stratiform precipitation abstract the relative airflow and accompanying precipitation structure of squall lines trailed by mesoscale regions of stratiform rain are examined with emphasis on the occurrence of rear inflow i e the intrusion of environmental air into these storms across the trailing precipitation boundary three cases from kansas and oklahoma provide examples of strong rear inflow which crosses the back edge of the stratiform precipitation area at relative speeds exceeding 10 m s 1 the vertical profiles of relative flow at the trailing precipitation boundary of these three systems were remarkably similar with the rear inflow confined to a jet like layer centered at about 550 mb doppler radar data for two of these cases showed that the rear inflow jet occupied a continuous channel extending from middle levels at the back edge of the stratiform region to lower levels of the leading convective region where it merged with outflow from convective downdrafts to bolster the leading gust front strong front to rea

genetic characterization of natural gases natural gases can be characterized genetically using four properties c2 concentration carbon and hydrogen isotope variations in methane and carbon isotope variation in ethane three diagrams for genetic characterization of gases have been designed in which the carbon isotopic composition of methane is correlated with the other parameters in these diagrams compositional fields have been defined for primary gases biogenic thermogenic associated and thermogenic nonassociated and for gases which result from mixing of these gases these fields are strictly empirical and comprise compositional variations found in about 500 natural gases the isotopic and compositional variations in natural gases can be described in terms of 1 processes during formation of the gases such as bacterial fermentation or maturation of organic matter and 2 processes during secondary migration mixing of primary gases is an important and common process migration of gases predominantly affects the c2 concentration whereas the isotopic properties of gaseous hydrocarbons primarily remain unchanged allowing an assessment of the origin of migrated gases and properties of their source rocks the formation of gas from humic organic matter and coals is not yet clear from published data the diagrams use data from various basins and areas interstitial gases from the gulf of california are entirely of bacterial origin traces of thermogenic gases are formed only in the vicinity of dolerite sills gases in the south german molasse basin and in the vienna basin are of bacterial mixed and thermogenic origins data from the north italian po basin provide examples for genetic characterization of migrated gases

geomorphologic evidence of the active baza fault betic cordillera south spain abstract the present work investigates a mountain front within the plio quaternary deposits belonging to the sedimentary fill of the guadix baza basin betic cordillera southern spain this 30 km long front developed in soft sediments and within a context of high erosion is generated by the recent activity of the baza normal fault the mountain front is the natural limit between the western and eastern sectors corresponding to the two sub basins of guadix and baza the two main glacis described in previous works in the area of the baza fault the old glacis in the guadix sub basin and the recent glacis in the baza sub basin are interpreted here as a single one displaced by the fault using this glacis as a marker we deduced that its age and the transition of the basin from endorheic to exorheic must be much older than previous estimations the baza fault may be considered as one of the most active faults of the central part of the betic cordillera according to the results of the general quantitative analysis of the mountain front relief using the smf vf ratio and the sl index

convection initiation associated with a sea breeze front a gust front and their collision abstract the initiation of convection associated with a sea breeze front a gust front and their collision is analyzed using data collected in east central florida during the convection and precipitation electrification project in conjunction with satellite surface and rawinsonde information dual doppler radar derived winds are used to determine the three dimensional kinematic factors critical to storm development the gust front which emanated from storms on the western half of the peninsula propagated more rapidly and was deeper than the sea breeze front which originated from the east coast and was characterized by a distinctly scalloped appearance convection associated with the sea breeze front appeared to develop preferentially at the vertices of this scalloped pattern where there were enhanced regions of convergence and upward motion on the gust front a helmholtz shearing instability produced an organized configuration of convergence and updraft maxima along its length however these were

reservoir geochemistry of south pass 61 field gulf of mexico compositional heterogeneities reflecting filling history and biodegradation abstract cluster analysis of gc data for gasoline and mid range hydrocarbon ratios from fifty one south pass 61 field oils reveals geochemically similar oil clusters corresponding to geographically coherent groups insight into the groupings is obtained from examination of indicators of geochemical processes e g anaerobic biodegradation aerobic biodegradation and extensive remigration of light ends six duplicate samples collected in 1986 and 1992 as well as replicate runs on a single sample showed excellent analytical reproducibility subtle but consistent differences in both gasoline and oil range hydrocarbon maturity indicators are observed between the east west and far west flanks of the field suggesting filling of different segments of the reservoir from different kitchens at slightly different stages of thermal maturity or with slightly different chemical character the west flank of the salt dome was charged with slightly more thermally mature petroleum than the east flank the stratigraphically oldest and deepest sand on the far west flank has received the most mature petroleum different fluid contacts and gors are observed in different sands and different fault blocks the stacked pay geometry of the field and widespread faulting have led to considerable remigration of gas and condensate as observed in other fields in the gulf of mexico thompson 1987 biodegradation varies in severity with depth and reservoir zone but is frequently overprinted by remigration of light end hydrocarbons anaerobic biodegradation by sulfate reducing bacteria is probably the cause of light to moderate alteration in intermediate depth pliocene sands which are hydraulically connected to the salt dome with dissolution of anhydrite from the salt dome providing the sulfate widespread late pyrite formation in reservoir sandstones is inferred to represent the ultimate sink for reduced sulfur from sulfate reduction during oil biodegradation co produced water compositions suggest no oxygenated freshwater infusion

a modeling study on the development of a bowing structure and associated rear inflow within a squall line over south china abstractthrough convection permitting simulations this study examines a large bowing structure within a squall line that occurred during the rainy season in south china the bowing structure is closely associated with a local enhancement of and balance between the cold pool and the line normal environmental low level vertical shear rear inflow plays an essential role in the formation and evolution of this large bowing structure it is found that the low level rear inflow is largely a natural consequence of the baroclinically generated horizontal vorticity near the surface while the midtropospheric rear inflow is forced by several pairs of bookend vortices vorticity budget and vortex line analyses show that the bookend vortices form mainly through the tilting of horizontal vorticity consolidation of these pairs of bookend vortices forms a broad zone of contiguous rear inflow the environmental flow and horizontal pressure gradient force associated with the midlevel pressure deficit induced by the re

origin of deep sour natural gas in the ordovician carbonate reservoir of the tazhong uplift tarim basin northwest china insights from gas geochemistry and formation water abstract deep sour gases are found in the ordovician carbonate reservoir of the tazhong uplift in the tarim basin northwest china all sour gases in this field are dominated by gas hydrocarbons c1 c4 with varying amounts of h2s most of the gases in the eastern tazhong are characterized by high gas dryness coefficients 0 95 13c enriched methane 13c1 ranging from 44 6 to 35 8 and small difference between values of the 13c2 and 13c1 13c2 1 in contrast the gases in the western tazhong are characterized by relatively low gas dryness coefficients mostly

distribution and mechanisms of orographic precipitation associated with typhoon morakot 2009 abstractusing a combination of doppler radar observations and rain gauge data this study documents detailed aspects of the orographic precipitation associated with typhoon morakot 2009 rainfall distribution over underlying topographical features and possible physical mechanisms responsible for the observed orographic enhancement are explored the study region constitutes an approximately two dimensional south north oriented orographic barrier with higher wider lower narrower terrain features in its northern southern portions i e the northern and southern barriers upstream conditions were characterized by abundant typhoon background precipitation embedded within strong nearly saturated westerly to west southwesterly oncoming flow the observations show that a wide area of topographically enhanced precipitation and the rainfall maxima were confined to the windward slopes of the northern barrier whereas the strongest rainfall tended to occur near and or slightly downstream of the mountain c

strain variations in a seismogenic normal fault baza sub basin betic chain insights from magnetic fabrics ams abstract ams and structural analysis are here applied to study the deformed zone associated with a large scale active normal fault in the central betic cordillera spain namely the baza fault system to determine i the kinematics of structures and their relation with fault zone architecture and segmentation degree ii the correlation between deformational structures and the different types of magnetic fabrics and iii the evolution of magnetic fabrics patterns from sedimentary to shear related associated with normal faults five outcrops 969 samples were analysed along the fault trace which shows different degrees of segmentation along strike and strong localization of deformation along narrow fault zones a first main set of magnetic fabric data corroborates the normal kinematics of the baza fault showing magnetic lineations parallel to the dip slip transport direction a second secondary set of magnetic lineations is parallel to the intersection lineation and can be related to less intense deformation in the fault rocks furthermore a detailed study 523 samples of a trench excavated across the fault zone where two fault splays tend to coalesce in a linkage relay zone indicates that i lithology and distance to fault planes are two factors that control the development of extension related magnetic fabrics in weakly deformed sediments ii the development of shear related fabrics in fault zones entails the mechanical rotation of minerals iii different orientation of magnetic lineations are related to different intensity of bulk deformation and iv magnetic lineation is useful to define local deviations of deformation axes produced by changes in the local extension direction from fault perpendicular to fault parallel extension in the linkage zone between adjacent fault splays

tectonics controls on fluvial landscapes and drainage development in the westernmost part of switzerland insights from dem derived geomorphic indices abstract this work focuses particularly on the geomorphological evidence for the tectonic controls on the development of the present day fluvial landscapes in the westernmost part of switzerland the tectonic deformation was evaluated on the basis of a combined analysis of several classical geomorphic indices hypsometric curves and integrals transverse topographic symmetry index and channel s bottom gradients through high precision dem processing a new optimization strategy was applied for defining geomorphic anomalies related to tectonic activity along the channels of three rivers based on a combined investigation of topographic swath longitudinal profiles geological and geophysical observations the results show that the abnormally high values of hypsometric integral are spatially occurred on the hanging walls of thrust faults while abnormally low ones are spatially observed in the same locations of paleo ice stream pathways observations obtained from transverse topographic symmetry index display asymmetries in the most of the studied drainage basins with a predominant se direction of lateral migration this direction is in agreement with the dominant dip direction of the bedding planes within the study area abnormal changes in the channel s bottom gradients which almost coincide in space with pronounced change in the depth of the subsurface geologic layers and in the geophysical properties are marked by distinct topographic relief in areas where rivers flow above blind and emergent faults our analysis not only confirms that there is a significant tectonic control on the evolution of drainage systems but also revealed a possible evidence for the reactivation of some inherited faults

geomorphic assessment of active tectonics in the acambay graben mexican volcanic belt spatial variations of quaternary deformation and tectonic activity of faults along the acambay graben are assessed using geomorphic and morphometric approaches the acambay graben is an east west trending structure of apparent quaternary age located in the central part of the mexican volcanic belt which gives rise to pronounced scarps over a distance of about 80 km continuing tectonic activity in the acambay graben is confirmed by recent well documented seismic episodes the intensity of active tectonics has been interpreted through a detailed geomorphic study of the fault generated mountain fronts and fluvial systems the combined geomorphic and morphometric data provide evidence for relative variations in tectonic activity among the acambay graben faults geomorphic indices suggest a relatively high degree of tectonic activity along the venta de bravo and the acambay tixmadeje faults followed in order of decreasing activity by the pastores temascalcingo and tepuxtepec faults spatial variations within faults have also been identified suggesting a higher level of tectonic activity at the tips of the faults this pattern of variation in the relative degree of tectonic activity is consistent with field evidence and seismic data for the acambay graben geomorphic evaluation of the acambay graben faults suggests that the acambay tixmadeje and venta de bravo faults and specifically the tips of these faults and a central segment near the town of venta de bravo should be considered as areas of potentially high earthquake risk 1998 john wiley sons ltd

the genesis of severe long lived bow echoes abstract a series of idealized simulations using a nonhydrostatic cloud model is used to investigate the genesis of bow echoes a bow shaped system of convective cells that is especially noted for producing long swaths of damaging surface winds it is hypothesized that severe long lived bow echoes represent a dynamically unique form of mesoconvective organization being produced for a restricted range of environmental conditions including a convective available potential energy cape of at least 2000 m2 s2 and vertical wind shears of at least 20 m s 1 over the lowest 2 5 5 km agl the key structural features include a 40 100 km long bow shaped segment of convective cells with a strong rear inflow jet extending to the leading edge of the bow at 2 3 km agl and cyclonic and anticyclonic eddies referred to as bookend vortices on the northern and southern flanks of the bowed segment respectively this structure characteristically develops three to four hours into the lifetime of a convective system a