high resolution magnetic stratigraphy across the oligocene miocene boundary in an alluvial lacustrine succession ebro basin northeast spain abstract the study of a late oligocene early miocene 300 m thick section of alluvial and shallow lacustrine sediments in the ebro basin has allowed a high resolution magnetic polarity stratigraphy for the oligocene miocene boundary to be established the samples studied include alluvial sandstones and mudstones as well as shallow lacustrine and paludine micritic and microsparitic limestones two hundred and fifty specimens were stepwise thermally or magnetically demagnetized following standard procedures magnetic imprints of the distinct lithologies present sharp contrasts especially for the stability of the secondary components the vgp data show 18 reversal events defining a sequence of 16 polarity intervals lateral and vertical continuity of the sequences studied has enabled a correspondence between the local paleomastological biozones and the magnetostratigraphic succession to be established the high resolution chronology of this magnetostratigraphic succession provides valuable information that allows the non marine european biochronological scales to be correlated to the global polarity time scale gpts the magnetic polarity zonation of the section has been correlated to the gpts using the distinct sequence and pattern polarity reversals as well as by considering the fossil mammal assemblages as a preliminary result chrons 8 7a 7 and 6c have been identified

transient luminous events above two mesoscale convective systems storm structure and evolution 1 two warm season mesoscale convective systems mcss were analyzed with respect to their production of transient luminous events tles mainly sprites the 20 june 2007 symmetric mcs produced 282 observed tles over a 4 h period during which the storm s intense convection weakened and its stratiform region strengthened tle production corresponded well to convective intensity the convective elements of the mcs contained normal polarity tripole charge structures with upper level positive charge 40 c midlevel negative charge 20 c and low level positive charge near the melting level in contrast to previous sprite studies the stratiform charge layer involved in tle production by parent positive cloud to ground cg lightning resided at upper levels this layer was physically connected to upper level convective positive charge via a downward sloping pathway the average altitude discharged by tle parent flashes during tle activity was 8 2 km above mean sea level msl 25 c the 9 may 2007 asymmetric mcs produced 25 observed tles over a 2 h period during which the storm s convection rapidly weakened before recovering later unlike 20 june tle production was approximately anticorrelated with convective intensity the 9 may storm which also had a normal tripole in its convection best fit the conventional model of low altitude positive charge playing the dominant role in sprite production however the average altitude discharged during the tle phase of flashes still was higher than the melting level 6 1 km msl 15 c based on these results it is inferred that sprite production and sprite parent positive charge altitude depend on mcs morphology

hydrocarbon source rock variability within the austin chalk and eagle ford shale upper cretaceous east texas u s a abstract the austin chalk and eagle ford shale are upper cretaceous deposits that extend across texas from the northeast to southwest these formations contain organic carbon enriched mudstones and chalks that were deposited during transgressions of the cretaceous epeiric sea in north america recent workers in petroleum geochemistry have demonstrated that these organic enriched rocks possessed attributes common to oil source rocks the present study of these austin chalk and eagle ford shale rocks is from the perspective of organic petrology and it augments the earlier geochemical work that documented source variability within units of these formations as with the earlier work the results of this study show that both formations contain intervals that are when mature capable of generating commercial quantities of liquid hydrocarbons however this work further revealed that eagle ford rocks not only exhibit greater or ganic carbon contents but also have greater quantities of oil prone kerogen fluorescent amorphinite and exinite when compared with rocks from the austin chalk these source rock differences relate to levels or degrees of organic preservation dysaerobic to oxic depositional settings seem to be more characteristic of the austin chalk than of the eagle ford shale such oxic environments do not consistently favor the preservation of organic matter usually well preserved kerogen forms under more anoxic conditions such as those that occurred during deposition of some eagle ford units these anoxic conditions suggest that the geographically more extensive eagle ford shale is a more important source for oil than is the austin chalk

the silurian qusaiba hot shales of saudi arabia an integrated assessment of thermal maturity abstract the lower silurian qusaiba hot shales qhs are proven source rocks for oil within the paleozoic and possibly some of the mesozoic reservoirs in saudi arabia moreover these shales have oil shale potential where they are immature and shallow enough for mining as well as unconventional shale oil and shale gas potential in areas where they are within oil maturity and gas maturity levels respectively the qhs were deposited in relatively shallow marine environments under anoxic water conditions resulting in accumulation of amorphous kerogen organic walled graptolites and acritarchs across the arabian basin organic matter quality does not show much variation for the qhs but the maturity varies greatly as a result of varying burial history thermal maturity assessment of shale source rocks that lack vitrinite such as the qusaiba hot shales continues to be challenging especially where conflicting measurements are obtained from different sources this paper presents an integrated assessment of qhs thermal maturity parameters based on cores from 13 carefully selected boreholes that based on regional basin models are believed to cover a wide maturity range ca 0 5 to 2 0 ro we conducted some analyses on kerogen maceral petrography graptolite reflectance uv fluorescence whole rock pyrolysis raman spectroscopy of graptolite and other analyses on bitumen extracts gc and gc ms of saturate and aromatic fractions and ftir spectroscopy of the asphaltene fraction we show that using many thermal maturity parameters reduces uncertainty significantly and we therefore recommend that graptolite reflectance analyses should be conducted in support of other maturity indicators proper reflectivity measurements of the graptolites set the reference for comparison of other maturity parameters obtained from petrographic geochemical and spectroscopic techniques our work provides a template by which qusaiba thermal maturity can be more accurately estimated when only a limited set of maturity parameters is available

a new chronology for the middle to late miocene continental record in spain abstract the first detailed chronology for the middle to late miocene continental record in spain is presented based on high resolution magnetostratigraphic data of mammal bearing sections which were studied in several basins calatayud daroca teruel valles penedes duero and jucar cabriel our results indicate that these sections compose an almost complete magnetostratigraphic succession from the lower aragonian mn4 to the middle turolian mn12 seven successive mammal neogene mn zone boundaries are directly dated in these sections which often contain faunas of two successive zones in superposition the three oldest boundaries are dated in the aragonian type area calatayud daroca basin the mn4 mn5 boundary vargas section occurs in chron c5cr o with a corresponding age of 17 26 0 01 ma the mn5 mn6 boundary aragon section in chron c5acn 0 8 with an age of 13 75 0 03 ma and the mn6 mn7 8 boundary aragon section in the interval c5ar 1n c5ar 3r with an age of 12 75 0 25 ma the mn7 8 mn9 aragonian vallesian boundary occurring in chron c5r 1n at 11 1 ma and the mn9 mn10 boundary in chron c4ar 3r at 9 7 0 1 ma are recorded in the valles penedes basin vallesian type area and are supported by the results from the duero basin torremormojon section in the turolian type area teruel basin the mn10 mn11 vallesian turolian boundary la gloria section occurs in chron c4an y at 8 7 0 1 ma taking into account the pre existing data from the jucar cabriel basin the mn11 mn12 boundary cabriel valley section is recalibrated to c4n 1n at an age of 7 5 0 1 ma

magnetostratigraphic calibration of the european neogene mammal chronology abstract this paper presents first a discussion on the status of the subdivisions of the european neogene mammal chronology and second it synthesizes all available magnetostratigraphic data from europe to provide chronological framework for mammal localities mammalian events and mammalian biochronologic units of the european neogene because of the lack of their rock equivalents the subdivisions of the european neogene based on mammals have not attained the stage status in terms of reliability except the vallesian and turolian therefore they are designated as the european land mammal ages elma magnetostratigraphic data on mammal bearing deposits in europe is still scarce in time and space consequently it is not yet possible to correlate accurately all elma and mn zones with the geomagnetic polarity time scale gpts nevertheless several studies dealing with mammal localities and their deposits around the oligocene miocene boundary in the middle and late miocene provide reliable correlations of some elma and mn zone boundaries thus the calibration of the oligocene miocene boundary at the base of chron c6cn 2n is in agreement with its age in marine deposits the well known hipparion datum astaracian vallesian boundary is now dated as about 10 8 ma occurring slightly above the base of chron c5n 2n this paper also reviews magnetostratigraphic correlations of some late miocene and pliocene mammal localities in the paratethys area taking into account the chronological assessments in other parts of europe for some key mammalian events new correlations with the gpts have been proposed for these localities thus some new ages are suggested for the late miocene and pliocene paratethys stages

polarimetric and electrical characteristics of a lightning ring in a supercell storm abstract on 30 may 2004 a supercell storm was sampled by a suite of instrumentation that had been deployed as part of the thunderstorm electrification and lightning experiment telex the instrumentation included the oklahoma lightning mapping array ok lma the national severe storms laboratory s band weather surveillance radar 1988 doppler wsr 88d polarimetric radar at norman oklahoma and two mobile c band shared mobile atmospheric research and teaching radars smart r combined datasets collected by these instruments provided a unique opportunity to investigate the possible relationships among the supercell s kinematic microphysical and electrical characteristics this study focuses on the evolution of a ring of lightning activity that formed near the main updraft at approximately 0012 utc matured near 0039 utc and collapsed near 0050 utc during this time period an f2 intensity tornado occurred near the lightning ring region lightning density contours computed over 1 km layers are over

variations in cloud to ground lightning characteristics among three adjacent tornadic supercell storms over the tennessee valley region the contrasting behavior of cloud to ground cg lightning associated with three adjacent supercell thunderstorms observed on 18 may 1995 is examined thunderstorm characteristics and anvil interactions are related to north south variations in cg lightning properties while tornadic activity was not consistently related to variations in cg properties radar reflectivity factor area greater than 65 db z was generally inversely related to cg frequency it is hypothesized that suppression of cg activity was produced by reduction of large number concentrations of precipitation sized particles i e presence of large hail in the particle interaction mixed phase region it is further hypothesized that seeding from upstream storm anvil ice was associated with nearly coincident enhancement of cg activity in downstream storms likewise it is hypothesized that the reduction in 65 dbz echo area inferred suppression of hail is related to this inferred anvil seeding process

evolution of the total lightning structure in a leading line trailing stratiform mesoscale convective system over houston texas 1 line normal vertical cross sections of houston lightning detection and ranging ldar vhf radiation sources and radar reflectivity provide new insights into the three dimensional total lightning structure and evolution of a leading line trailing stratiform llts mesoscale convective system mcs over houston texas on 31 october 2005 previous research examining only the mature stage of an mcs showed that the overwhelming majority of vhf lightning sources occurred in the convective region with a lightning pathway extending rearward and descending in altitude into the stratiform region this descending pathway was most likely associated with small charged ice particles advected from the convective line unlike previous research the lightning pathway observed during the evolution of the mcs on 31 october 2005 initially extended rearward 40 km at a nearly constant height of 9 10 km in less than an hour the lightning pathway evolved into a sloped pathway similar to that found by previous research with a horizontal extent between 50 to 60 km and downward descent of 4 to 5 km during the lightning pathway evolution radar analysis showed an increase of reflectivity in the midlevels of the stratiform region consistent with increased depositional and aggregational growth above the melting layer broadening increased range of values of radar reflectivity above the melting layer was most likely an indication of a strengthening mesoscale updraft in the stratiform region this strengthening updraft may have contributed to an increase in the growth of the small charge carrying ice crystals giving them a greater fall speed in addition the mesoscale updraft may have promoted an environment conducive to local stratiform region charge generation in the mixed phase region just above the melting layer

coordinated observations of sprites and in cloud lightning flash structure 1 the temporal and spatial development of sprite producing lightning flashes is examined with coordinated observations over an asymmetric mesoscale convective system mcs on 29 june 2011 near the oklahoma lightning mapping array lma sprites produced by a total of 26 lightning flashes were observed simultaneously on video from bennett colorado and hawley texas enabling a triangulation of sprites in comparison with temporal development of parent lightning in particular negatively charged stepped leaders in three dimensional space in general prompt sprites produced within 20 ms after the causative stroke are less horizontally displaced typically 30 km however both prompt and delayed sprites are usually centered within 30 km of the geometric center of relevant lma sources with affinity to negative stepped leaders during the prior 100 ms interval multiple sprites appearing as dancing jumping events associated with a single lightning flash could be produced either by distinct strokes of the flash by a single stroke through a series of current surges superposed on an intense continuing current or by both our observations imply that sprites elongated in one direction are sometimes linked to in cloud leader structure with the same elongation and sprites that were more symmetric were produced above the progression of multiple negative leaders this suggests that the large scale structure of sprites could be affected by the in cloud geometry of positive charge removal based on an expanded dataset of 39 sprite parent flashes by including more sprites recorded by one single camera over the same mcs the altitude above mean sea level msl of positively charged cloud region tapped by sprite producing strokes declined gradually from 10 km msl 35 c to around 6 km msl 10 c as the mcs evolved through the mature stage on average the positive charge removal by causative strokes of sprites observed on 29 june is centered at 3 6 km above the freezing level or at 7 9 km above ground level

magnetostratigraphy and small mammals of the late oligocene banovici basin in ne bosnia and herzegovina article i nfo a combined magnetostratigraphic and small mammal investigation was carried out to acquire better age control on the sedimentary infill of the banovici basin in bosnia and herzegovina although the dinarides occupy a crucial paleogeographic position bridging central europe and anatolia no detailed records of its small mammal fauna have been published until now a rich small mammal assemblage with over 500 molars was excavated from a section exposing marls and clays just underlying the basins main coal layer the fauna of this turija small mammal locality compares best with the uppermost oligocene to lowermost miocene localities from the european mp30 mn1 mammal zones and with anatolian zone b from central turkey a 160 m thick series of lacustrine sediments overlying the main coal layer in the nearby grivice section was sampled for paleomagnetic purposes the magnetostratigraphic pattern of the grivice section comprises a long reversed interval a subsequent short normal interval and another reversed interval the most logical correlation of this pattern to the late oligocene part of the geomagnetic polarity time scale gpts is to chrons c6cr c6cn 3n and c6cn 2r 24 to 23 2 ma this correlation implies a sedimentation rate of 20 cm kyr for the banovici basin and an age of approximately 24 ma for the turija mammal site the proposed correlation fits well with other magnetostratigraphically calibrated mammal records in western and central europe as well as anatolia and with the recalibrated ages of 24 95 0 05 ma and 24 72 0 04 ma for two basalt flows bracketing the enspel mp28 site in southern germany our results indicate that a limited exchange of fauna from central asia to western europe existed in late oligocene and miocene times

geodynamic evolution of the northern dinarides and the southern part of the pannonian basin abstract most of the recent geodynamic interpretations of the pannonian basin focus on its relation to the formation of the carpathians and the alpine orogeny however also the dinarides were severely affected by neogene tectonics related to the formation of the pannonian basin especially in the northernmost dinarides neogene deformation played a very important role in the evolution of this mountain chain geological records clearly show evidence of two phases of plate convergence along the northern and eastern margins of the present day dinarides at the end of the jurassic the dinaridic parts of the tethys ophiolites were obducted onto the northeastern margins of the apulian microplate the second phase is documented in the central part of the northernmost dinarides it is genetically related to an ancient volcanic arc as indicated by late cretaceous palaeogene trench sediments with blueschist olistolithes which are interlayered by basalt rhyolites pyroclastics medium pressure metamorphosed trench sediments and associated synkinematic granitoids in the northern part of the dinarides subduction processes terminated with the eocene compressional event which caused the uplift of the dinarides numerous intramontane basins with shallow marine fluviatile and lacustrine deposits were generated during the oligocene penecontemporaneous andesites which are found along the drava and sava depressions of the south pannonian neogene basin can be correlated with the easternmost periadriatic tonalites however observations do not indicate strike slip faulting at that time in this area the neogene rift stage initiated the evolution of the pannonian basin it is marked by extruded submarine trachyandesites of karpathian age badenian basalts andesites dacites and rhyolites and pannonian alkali basalts which are interlayered by coeval sedimentary rocks main evidence for the large scale tectonic transport of large dinaridic blocks into the pannonian basin area are the periadriatic sava and zagreb zemplen fault systems and subparallel faults the late sarmatian global sea level drop which coincided with a compressional phase is regionally marked by an unconformity throughout the pannonian basin as reported by horvath horvath f 1995 phases of compression during the evolution of the pannonian basin and its bearing on hydrocarbon exploration mar pet geol 12 8 837 844 due to thermal subsidence during the pliocene more than 2000 m of lacustrine freshwater sediments were deposited in the south pannonian basin the pliocene compression phase can be observed in the transdanubian zone and also south of the mura and drava rivers by south and southwest dipping reverse fault systems

a gps based three dimensional lightning mapping system initial observations in central new mexico a gps based system has been developed that accurately locates the sources of vhf radiation from lightning discharges in three spatial dimensions and time the observations are found to reflect the basic charge structure of electrified storms observations have also been obtained of a distinct type of energetic discharge referred to as positive bipolar breakdown recently identified as the source of trans ionospheric pulse pairs tipps observed by satellites from space the bipolar breakdown has been confirmed to occur between the main negative and upper positive charge regions of a storm and found to be the initial event of otherwise normal intracloud discharges the latter is contrary to previous findings that the breakdown appeared to be temporally isolated from other lightning in a storm peak vhf radiation from the energetic discharges is observed to be typically 30 db stronger than that from other lightning processes and to correspond to source power in excess of 100 kw over a 6 mhz bandwidth centered at 63 mhz

strokes of upward illumination occurring within a few milliseconds after typical lightning return strokes 1 correlated data for natural cloud to ground lightning flashes were obtained with a high speed video camera 54000 frames per second five stations of electric field change antennas and a seven station vlf lf lightning network linet along with operational lightning and electric field networks at kennedy space center florida four observed flashes at 25 55 km distance had return stroke like upward illumination ui from the ground just after within 2 ms of a return stroke rs but in a separate channel connection to ground 0 7 to 2 5 km apart the ui events were visible for short duration 0 5 ms or less and short length to 1 7 km altitude or less and they had slow propagation speed 1 6 2 6 107 m s 1 and no apparent connection to the rs channel in one case the rs was no longer visible to the ground when the ui began 1 30 ms later although mid level channel was still distinct in another case the main rs had dimmed over the 0 52 ms interval before the ui but was still visible the remaining two cases had the entire length of the prior rs channel no longer visible for 40 and 240 s before the ui began 1 32 and 1 87 ms later electric field change data for the ui events resemble those of weak return strokes these events were not located by the operational ground strike and vhf detection systems all four ui events were detected by linet as negative ground strokes with small less than 7 ka peak current magnitude

middle eocene late oligocene climate variability calcareous nannofossil response at kerguelen plateau site 748 a major deterioration in global climate occurred through the eocene oligocene time interval characterized by long term cooling in both terrestrial and marine environments during this long term cooling trend however recent studies have documented several short lived warming and cooling phases in order to further investigate high latitude climate during these events we developed a high resolution calcareous nannofossil record from odp site 748 hole b for the interval spanning the late middle eocene to the late oligocene 42 to 26 ma the primary goals of this study were to construct a detailed biostratigraphic record and to use nannofossil assemblage variations to interpret short term changes in surface water temperature and nutrient conditions the principal nannofossil assemblage variations are identified using a temperate warm water taxa index twwt from which three warming and five cooling events are identified within the middle eocene to the earliest oligocene interval among these climatic trends the cooling event at 39 ma cooling event b is recorded here for the first time variations in fine fraction 18o values at site 748 are associated with changes in the twwt index supporting the idea that significant short term variability in surface water conditions occurred in the kerguelen plateau area during the middle and late eocene furthermore odp site 748 calcareous nannofossil paleoecology confirms the utility of these microfossils for biostratigraphic paleoclimatic and paleoceanographic reconstructions at southern ocean sites during the paleogene

mapping the lateral development of lightning flashes from orbit optical lightning measurements from the lightning imaging sensor lis are used to map the lateral development of lightning flashes and produce statistics that describe their motion through the electrified cloud this is accomplished by monitoring the frame by frame group level evolution of the optical signals produced during each flash while the optical flash properties recorded by lis gravitate towards the most exceptional optical signals produced during the flash group level data describe the evolution and lateral development of the flash resulting from physical lightning process that emits enough light out of the top of the cloud to be detected from orbit the groups that comprise lis flashes constitute examples of complex lateral flash structure that can extend 80 km in length with dozens to hundreds of visible branches the lateral development of individual flashes is described in terms of its speed and direction of motion whether the development extends the overall length of the flash or reilluminates an existing segment and whether it is directed inbound or outbound with respect to the origin sixty five percent of propagating groups are directed outbound from the origin 22 extend the length of the flash and 3 5 reilluminate an existing branch lis flashes are commonly oriented from east to west and develop at speeds ranging from 104 to 106 m s consistent with large scale leader development these results provide evidence that lightning imagers may be used in conjunction with lightning mapping array systems to document physical lightning phenomena across global domains

controls of surface erosion on the evolution of the alps constraints from the stratigraphies of the adjacent foreland basins the combined information about the stratigraphies from the foreland basins surrounding the swiss alps exhumation mechanisms and the structural evolution of the alpine orogenic wedge allow an evaluation of the controls of erosion rates on large scale alpine tectonic evolution volumetric data from the molasse basin and fining upward trends in the gonfolite lombarda indicate that at 20 ma average erosion rates in the alps decreased by 50 it appears that at that time erosion rates decreased more rapidly than crustal uplift rates as a result surface uplift occurred because of surface uplift the drainage pattern of the alpine hinterland evolved from an across strike to the present day along strike orientation furthermore the decrease of average erosion rates at 20 ma coincides with initiation of a phase of thrusting in the jura mountains and the southern alpine nappes at 50 km distance from the pre 20 ma thrust front coupled erosion mechanical models of orogens suggest that although rates of crustal convergence decreased between the oligocene and the present the reduction of average erosion rates at 20 ma was high enough to have significantly influenced initiation of the state of growth of the swiss alps at that time

correlated observations of three triggered lightning flashes a cooperative analysis of three triggered lightning flashes initiated during the thunderstorm research international program trip 81 at langmuir laboratory new mexico has resulted in the determination of three dimensional return stroke propagation speeds and peak currents for 56 subsequent strokes we find a nonlinear relationship between the return stroke propagation speed and the stroke peak current that is qualitatively similar to that proposed by both lundholm and wagner a nonlinear correlation is also found between the return stroke propagation speed and the dart leader propagation speed for 32 strokes linear correlation coefficients are evaluated for the following quantities dart leader propagation speed and ensuing return stroke peak current 32 strokes r 0 84 stroke peak current and interstroke interval 69 strokes r 0 57 return stroke propagation speed and interstroke interval 56 strokes r 0 49 dart leader propagation speed and interstroke interval 32 strokes r 0 43 the weak positive correlation found between the dart leader propagation speed and the interstroke interval contradicts previous corresponding natural lightning observations the mean three dimensional return stroke propagation speed for 56 strokes is 12 107 m s with a range of 6 7 107 m s to 17 107 m s the mean three dimensional propagation speed found for 32 dart leaders is 20 106 m s with a range of 9 5 106 m s to 43 106 m s the mean dart length measured is 50 m with a range of 15 90 m in two of the three flashes the downward propagating dart leaders appear to meet upward propagating streamers at heights of approximately 20 and 30 m respectively

radio interferometric observations of cloud to ground lightning phenomena in florida radio frequency observations of cloud to ground lightning in florida have been analyzed to document a number of features of the lightning the observations have been made using an interferometer system which determined the direction to the lightning radiation as a function of time during close lightning discharges observations are presented for about 50 radiating events during five multiple stroke normal polarity flashes to ground the results confirm and extend results of a similar study of new mexico lightning by rhodes et al 1994 dart leaders in cloud k events and attempted leaders are found to be the same phenomena namely a negative polarity streamer that propagates horizontally and or vertically to ground at estimated speeds of about 10 7 ms 1 down to 10 6 ms 1 the step or impulsive fast electric field change produced by some k events is found to be caused by positive breakdown back at the starting point of the negative streamer after the streamer has progressed over some or all of its distance this breakdown appears to initiate a forward stroke along the streamer channel which can renew the breakdown at the front end of the channel k breakdown which happens to occur during a continuing current discharge to ground produces an m event channel brightening when it connects with the conducting channel to ground the step fast field change of the m events is found to be produced at the time of connection inside the cloud no fast field change is detected when this breakdown reaches ground that would be associated with a return stroke m events can also be initiated by fast 10 7 ms 1 positive streamers which often propagate away from the leader source region within a few milliseconds of the arrival of a return stroke back in the source region these streamers often generate an even faster negative recoil event back along their extent which propagates down the channel to ground as the m event in all cases the current increase or channel brightening produced by k and m events is predicted to occur in a forward direction that is toward or down the channel to ground in the same direction as the initiating negative streamer positive breakdown is detected only immediately following return strokes or during some k streamers in both cases the electric stresses are expected to be very large suggesting that positive breakdown which produces a conducting channel is difficult to initiate results for one flash suggest that negative charge was left at low altitude by the initial stroke to ground this forced the subsequent leaders to develop a new path to ground first as series of attempted leaders and then as a dart stepped leader

flash propagation and inferred charge structure relative to radar observed ice alignment signatures in a small florida mesoscale convective system a series of vertical cross sections taken through a small mesoscale convective system mcs observed over florida by the dual polarimetric smart radar were combined with vhf radiation source locations from a lightning mapping array lma to examine the lightning channel propagation paths relative to the radar observed ice alignment signatures associated with regions of negative specific differential phase kdp additionally charge layers inferred from analysis of lma sources were related to the ice alignment signature it was found that intracloud flashes initiated near the upper zero kdp boundary surrounding the negative kdp region the zero kdp boundary also delineated the propagation path of the lightning channel with the negative leaders following the upper boundary and positive leaders following the lower boundary very few lma sources were found in the negative kdp region we conclude that rapid dual polarimetric radar observations can diagnose strong electric fields and may help identify surrounding regions of charge

magneto biostratigraphy and paleoenvironments of the miocene freshwater sediments of the sarajevo zenica basin abstract the sarajevo zenica basin of bosnia herzegovina was part of the dinaride lake system a large network of miocene long lived freshwater basins in southeastern europe the basin contains a thick sedimentary succession of carbonates coals and mixed siliciclastic deposits that reflects the paleoclimatic and tectonic evolution of the region in this study we present novel integrated magneto bio stratigraphic and sedimentological data and reconstruct the paleoenvironmental evolution of the sarajevo zenica basin during its two main evolutionary phases thrusting and extension the basal oligo miocene freshwater paleoenvironments are characterized by alternating palustrine shallow lacustrine and distal fluvial phases the base level fluctuations are largely controlled by syn sedimentary pulses of tectonic loading during the final phase of thrusting in the internal dinarides the majority of this succession is considered early miocene in age which contrasts with previous oligocene age estimates the subsequent extensional phase initiated not later than 18 4 ma this coarsening upward sequence of lacustrine carbonates silts sands and conglomerates is correlated between 17 2 and 15 ma c5cr c5br by means of integrated bio magnetostratigraphy during this upper extensional phase subsidence and sediment influx was generally controlled by activity along the basin bounding normal fault overruling smaller scale climatic influences we conclude that the existence of the long lived sarajevo lake is coeval with other dinaric and southern pannonian lakes and overlaps in time with the miocene climatic optimum sedimentation in the sarajevo zenica basin terminated at 15 14 ma which concurs with both the end of the climatic optimum as well as the cessation of extension in the dinarides these results will help to better quantify the paleoclimatic changes in the dinaride lake system as well as the regional tectono sedimentary events such as potential migrations of deformation across the dinarides

using lightning observations as a volcanic eruption monitoring tool lightning commonly occurs in the eruption columns produced by explosive volcanic eruptions there are several different kinds of lightning detection instruments that could be employed to help monitor volcanoes each with their own advantages and disadvantages very low frequency vlf instruments have the ability to detect lightning at long ranges but tend to have low sensitivity due to network geometry and typically can provide only the time and 2 d location of a cloud to ground return stroke or similar high amplitude pulse produced by an intracloud discharge low frequency lf and medium frequency mf instruments typically have more sensitivity than a vlf network but can only be used for detection on a regional scale very high frequency vhf lightning mapping instruments also provide only regional coverage but detect all lightning within their range during the 2009 eruption of redoubt volcano alaska usa each of these types of instruments detected lightning from redoubt s ash plume the vhf system consistently detected lightning before the other two during each distinct explosive event and also detected more lightning than the others by one or two orders of magnitude lightning observations could be used to confirm and in some cases detect explosive volcanic activity the rapid response provided by lightning monitoring is a valuable tool for fast identification of potentially hazardous ash clouds

a calibrated mammal scale for the neogene of western europe state of the art abstract a magnetobiostratigraphically calibrated mammal scale for the neogene of western europe is presented in this paper the mammal neogene mn units originally proposed by mein report on activity rcmns working groups 1975 have been re defined here on the basis of first appearances of selected small and large mammal taxa the chronology of the lower boundaries of each unit had been established mostly after the significant magnetobiostratigraphic framework developed in the last decade in a number of spanish basins ebro calatayud daroca valles penedes teruel fortuna cabriel and guadix baza in the case of the early and middle miocene particularly mn 1 mn 2 and mn 3 the authors have also taken into account the magnetobiostratigraphic framework developed in the north alpine foreland basin some alternative correlations of the magnetostratigraphic data from this last basin are proposed in order to achieve a higher degree of consistence with the data from the iberian basins a quite well established magnetostratigraphic calibration of the mn boundaries can be proposed for most of the neogene from middle miocene to late pliocene on the other hand the chronological boundaries of the early miocene mn units are still poorly constrained due to 1 scarcity of well studied continuous thick magnetostratigraphic sections 2 the difficulty in defining the boundaries of the mn zones for this time span due to the relative homogeneity and persistence of the fossil rodent faunas and the absence of significant large mammal dispersal events some of the troubles which arise with the application of the mn units strengthen the need to take into account the palaeobiogeographical meaning of these units and their real suitability to date and correlate through extensive geographic areas

aragonian stratigraphy reconsidered and a re evaluation of the middle miocene mammal biochronology in europe abstract the recently collected fauna of armantes 1a in chron c5br of the armantes section necessitates reinterpretation of the previous bio and magnetostratigraphical correlations between the armantes and vargas sections calatayud daroca basin central spain w krijgsman m garces c g langereis r daams j van dam a j van der meulen j agusti l cabrera a new chronology for the middle to late miocene continental record in spain earth planet sci lett 142 1996 367 380 the long reversal in the vargas section is now correlated to c5br instead of to c5cr on the basis of the biostratigraphical correlation of armantes 1a to the faunas of fuente sierra 2 and 3 in the vargas section which are situated in the basal part of the middle aragonian mn5 this leads to the revised age of 16 0 ma for the early middle aragonian mn 4 5 boundary our age estimate of the mn5 6 boundary is maintained at ca 13 75 ma the vargas section is now considered to start in chron c5cn 2r and to end in c5bn 1n as a result of the revised correlation the duration of the time gap between the fossiliferous parts of vargas and the younger aragon section previously estimated as ca 1 5 myr is now reduced to less than 200 000 years the tie points of the european mammal units mn4 mn6 to the geomagnetic polarity time scale f f steininger w a berggren d v kent r l bernor s sen j agusti circum mediterranean neogene miocene and pliocene marine continental chronologic correlations of european mammal units in r l bernor v fahlbusch h w mittmann eds the evolution of western eurasian neogene mammal faunas columbia univ press new york 1996 pp 7 46 are evaluated our age estimates of the mn4 5 and mn5 6 boundaries are compatible with the new magnetostratigraphic calibration of middle miocene mammal zones in the swiss molasse basin o kempf t bolliger d kalin b engesser a matter new magnetostratigraphic calibration of early to middle miocene mammal biozones of the north alpine foreland basin in j p aguilar s legendre j michaux eds actes du congres biochrom 97 mem trav e p h e 21 1997 547 562

triggered lightning sky waves return stroke modeling and ionosphere effective height ground waves and sky waves measured 209 km and 250 km south of six triggered lightning flashes containing 30 strokes that occurred in the half hour before sunset on 27 august 2015 are presented and analyzed we use a cross correlation technique to find the ionospheric effective reflection height and compare our results to previous techniques that calculate effective height based on the time delay between ground wave and sky wave time domain features from the first flash to the last flash there is on average a 1 6 km increase in effective ionospheric height whereas no change in effective ionospheric height can be discerned along the individual strokes of a given flash we show to what extent the triggered lightning radiation source can be described using channel base current channel geometry and channel luminosity versus time and height and speculate that a well characterized source could allow a more accurate determination of the electromagnetic fields radiated toward the ionosphere than has been done to date we show that both channel geometry and the change in return stroke current amplitude and waveshape with channel height inferred from measured channel luminosity versus height and time determine the waveshape of the ground wave and presumably the upward propagating wave that results in the sky wave and that the waveshape of the ground wave does not appear to be related to the current versus time waveform measured at the channel base other than a roughly linear relationship between the two peak values

magnetostratigraphy of the vallesian late miocene in the valles penedes basin northeast spain the magnetostratigraphic analysis of the late miocene continental deposits from the valles penedes basin combined with its well documented fossil mammal record has provided a well resolved chronology for the upper basin infill the study is based on the biostratigraphic and magnetostratigraphic cross correlation of 12 sections throughout the alluvial sequences in the western valles area the biostratigraphic framework consists of 21 mammal localities corresponding to the mammal neogene mn9 and mn10 units the composite magnetic polarity sequence is based on 400 paleomagnetic sites correlation with the geomagnetic polarity time scale gpts has led to an absolute dating of the faunal events and a precise chronostratigraphy of the vallesian mammal stage in its type area the hipparion first appearance datum fad at the mn8mn9 boundary is dated at 11 1 ma in the valles penedes basin this age compared to other radiometrically dated localities in europe north africa and turkey is consistent with an isochronous dispersal of this equid through the mediterranean region a possible isochrony at a larger geographical scale old world mesogea must await more reliable ages of the hipparion fad in asia and africa the cricetulodon fad mn9amn9b boundary is dated to 10 4 ma in chron c5n the progonomys fad mn9mn10 boundary corresponding to the intra vallesian faunal crisis is dated at 9 7 ma c4ar 3r the vallesian spans 2 4 myr from 11 1 ma c5r 1n to 8 7 ma c4an and correlates to the early tortonian

the vallesian mammal succession in the valles penedes basin northeast spain paleomagnetic calibration and correlation with global events abstract the integrated lithostratigraphic biostratigraphic and magnetostratigraphic study of new and classical alluvial fan sequences in the valles penedes basin northeast spain western mediterranean enabled a considerable refinement of the vallesian mammalian succession in this basin and its correlation with the magnetic polarity time scale up to 12 new sections were logged and sampled in a search of mammal remains and a paleomagnetic analysis was carried out the correlation among these sections was based on the small mammal content and the succession of magnetozones enabling the establishment of four main composite sections les fonts montagut terrassa and viladecavalls as a result the vallesian in the valles penedes basin appears punctuated by four main mammalian events which coincide with the appearance of the genera hipparion cricetulodon progonomys and rotundomys the hipparion event did not coincide with any further change in the associations of small and large mammals the dispersal of the cricetid cricetulodon in its turn involved the first set of extinctions in the vallesian affecting the rodent and carnivore and artiodactyl associations the main break during the vallesian coincided with the dispersal of the murids of the genus progonomys and implied a sudden drop in the diversity of the rodent and artiodactyl species of warm wet forested affinities this phase is characterized by the association of the murid progonomys and the cricetid cricetulodon and includes the last record of hominoids in the basin the replacement of cricetulodon by the sigmodont cricetid rotundomys was associated with the entry of some typical early turolian species according to the correlation established it is concluded that the fad of hipparion in the valles penedes basin is dated at 11 1 ma at the base of chron c5r 1n this data is congruent with other datings in northern africa and eastern europe suggesting the isochrony of this event in the mediterranean regions the cricetulodon fad is dated to 10 4 ma in chron c5n the progonomys dispersal coincident with the late vallesian crisis is dated at 9 7 ma in chron c4ar 3r the rotundomys fad is dated at 9 2 9 3 ma in the upper part of chron c4ar 1n the vallesian mammal bioevents affected the peri mediterranean zones including northern africa and other regions in northern and western eurasia these paleofaunistic changes were caused by temperature descent from subtropical to warm temperate conditions as well as by changes in the aridity balance and seasonality this climatic evolution was the result of the interplay of diverse global events cooling of the high latitude regions growing of the antarctica ice sheet and enhancement of the thermohaline oceanic circulation and of large scale tectonic and paleogeographic processes surface uplift of the himalayas the tibetan plateau and other tectonic reliefs closing of gateways between the mediterranean marine regions and the world ocean the magnetobiochronology resulting from the study of the western valles sequences suggests a close chronological correlation between some of these global and regional processes and the vallesian bioevents recorded

statistics and characteristics of cloud to ground lightning with multiple ground contacts 1 during the summer of 1997 386 cloud to ground cg lightning flashes were recorded on videotape near tucson arizona within this sample 136 flashes 35 struck the ground in two or more places that were separated by tens of meters or more within this subset of 136 which we term multiple channel flashes mcfs 88 exhibited two or more separate and distinct channels between the cloud base and the ground a type that we term a new channel flash ncf 37 forked or produced channels that struck the ground in two or more places and shared a common channel at higher altitudes a type that we term an altered channel flash acf and 11 exhibited both types of behavior the ratio of ncfs to acfs in arizona was 99 48 or 2 1 a value that is consistent with measurements in florida after allowing for differences in the cloud base heights altogether the 386 cg flashes produced 558 different strike points therefore the average number of strike points per cg flash was 1 45 67 of the new strike points were produced by the second stroke in the flash and 72 of the changes in channel geometry occurred after there had been just one stroke in the previous channel ten of the 48 acfs 21 developed along a visible branch of the previous channel and seven of the 136 mcfs 5 contained strokes that reilluminated the first channel after a second channel had formed the presence of a long continuing luminosity during the initial three or more consecutive video frames appeared to lower the probability of forming either a new or altered channel on the second stroke from 47 to 33 but the statistics are limited and our ability to identify individual strokes is biased by poor time resolution

palaeoenvironmental evolution of lake gacko southern bosnia and herzegovina impact of the middle miocene climatic optimum on the dinaride lake system in the early to middle miocene a series of lakes collectively termed the dinaride lake system dls spread out across the north western part of the dinaride anatolian continental block its deposits preserved in numerous intra montane basins allow a glimpse into the palaeoenvironmental palaeobiogeographic and geodynamic evolution of the region lake gacko situated in southern bosnia and herzegovina is one of the constituent lakes of the dls and its deposits are excellently exposed in the gracanica open cast coal mine a detailed study of the sedimentary succession that addresses facies sediment petrography geophysical properties and fossil mollusc palaeoecology reveals repetitive changes in lake level these are interpreted to reflect changes in the regional water budget first order chronologic constraints arise from the integration of radio isotopic and palaeomagnetic data 40ar 39ar measurements on feldspar crystals from a tephra bed in the upper part of the sedimentary succession indicate a 15 31 0 16 ma age for this level the reversed magnetic polarity signal that characterises the larger part of the investigated section correlates to chron c5br of the astronomically tuned neogene timescale guided by these chronologic data and a detailed cyclostratigraphic analysis the observed variations in lake level evident as two 40 m and seven 10 m scale transgression regression cycles are tuned to 400 kyr and 100 kyr eccentricity cycles from the tuning it can be inferred that the sediments in the gacko basin accumulated between 15 8 and 15 2 ma the economically valuable lignite accumulations in the lower part of the succession are interpreted to indicate the development of swamp forests in conjunction with lake level falls corresponding to 100 kyr eccentricity minima pedogenesis rhizoliths and palustrine carbonate breccias in the upper part of the section reveal long term aridity coinciding with a 400 kyr eccentricity minimum eccentricity maxima are interpreted to trigger lake level high stands these are accompanied by eutrophication events caused by enhanced denudation of the surrounding basement and increased detrital input into the basin the presented age model proves that lake gacko arose during the middle miocene climatic optimum and that the optimum climatic conditions triggered the formation of this long lived lake

magnetic detection and characterization of biogenic magnetic minerals a comparison of ferromagnetic resonance and first order reversal curve diagrams australian research council grant number dp120103952 australia new zealand iodp consortium anzic grant number le0882854

lower silurian hot shales in north africa and arabia regional distribution and depositional model abstract lowermost silurian organic rich hot shales are the origin of 80 90 of palaeozoic sourced hydrocarbons in north africa and also played a major role in petroleum generation on the arabian peninsula in most cases the shales were deposited directly above upper ordovician peri glacial sandstones during the initial early silurian transgression that was a result of the melting of the late ordovician icecap deposition of the main organic rich shale unit in the north african arabian region was restricted to the earliest silurian rhuddanian stage acuminatus atavus and probably early cyphus graptolite biozones during this short period 1 2 m y a favourable combination of factors existed which led to the development of exceptionally strong oxygen deficiency in the area in most countries of the study area the post rhuddanian silurian shales are organically lean and have not contributed to petroleum generation the distribution and thickness of the basal silurian hot shales have been mapped in detail for the whole north african region using logs from some 300 exploration wells in libya tunisia algeria and morocco in addition all relevant accessible published and unpublished surface and subsurface data of the lower silurian shales in north africa and arabia have been reviewed including sedimentological biostratigraphic and organic geochemical data the lowermost silurian hot shales of northern gondwana are laterally discontinuous and their distribution and thickness were controlled by the early silurian palaeorelief which was shaped mainly by glacial processes of the late ordovician ice age and by pan african and infracambrian compressional and extensional tectonism the thickest and areally most extensive basal silurian organic rich shales in north africa occur in algeria tunisia and western libya while on the arabian peninsula they are most prolific in saudi arabia oman jordan and iraq the hot shales were not deposited in egypt which was a large palaeohigh at that time the depositional model presented may help in better understanding the source potential of the basal silurian shales in less explored regions of north africa and arabia including morocco northern niger and the kufra basin in southeast libya

alternating field demagnetization of rocks and the problem of gyromagnetic remanence abstract alternating field a f demagnetization has proved to be a very reliable technique for separating the magnetization components of rock samples the method is subject to errors caused by either imperfection of the technique or by intrinsic properties of a rock recently stephenson 1 2 introduced the term gyroremanent magnetization grm for a disturbing remanent magnetization that can be acquired by magnetic material during tumbling or stationary a f demagnetization the implications for the routine a f demagnetization of anisotropic rock samples seemed to be very serious here however a method is presented on how to avoid the effect of grm on results obtained from stationary a f demagnetization

lightning return stroke velocities in the thunderstorm research international program trip we have used high speed streaking photographic techniques to time resolve the luminous components of cloud to ground lightning flashes two dimensional return stroke velocities have been measured for 63 strokes representing we believe the largest set of return stroke velocity measurements obtained to date all recordings were made during our participation in the thunderstorm reseach international program conducted at the kennedy space center florida during the summers of 1977 and 1978 and at the langmuir laboratory near socorro new mexico during the summer of 1979 the mean return stroke velocity near ground channel length 1 3 km was found to be 11 107 m s with a maximum relative error estimate in most cases of 35 or less the distribution of velocities peaks strongly at approximately 9 107 m s thirty two of the 63 values 51 fall within the interval of 8 12 107 m s the range of observed velocities spans the interval of 2 9 24 107 m s based on the presence of branches in the time resolved recordings 17 strokes are considered to be first return strokes with a mean velocity near ground of 9 6 107 m s the mean velocity for subsequent strokes is 12 107 m s a further breakdown of the results for florida and new mexico respectively reveals mean first return stroke velocities of 6 6 107 m s and 15 107 m s as well as mean subsequent stroke velocities of 11 107 m s and 13 107 m s velocity variations for 17 of the best events are presented with the return stroke velocity observed to decrease with height in every case except one the velocity reduction can be substantial velocities in upper channel lengths were often reduced by 25 or more relative to velocities near ground even for subsequent strokes the variation of velocity between strokes in multistroke flashes was found to be significant in some cases and minor in others the results of this study are compared with the earlier major works of schonland and of mceachron substantial disparities are found and examined we show in fact that schonland s south african return stroke velocity measurements were obtained in part from a lightning storm atypical of the region it should be noted however that our minimum return stroke velocity value of 2 9 107 m s is in excellent agreement with the results of schonland and of mceachron despite the fact that our work schonland s and mceachron s were obtained in widely differing geographical areas by using different instrumentation and spanning a period of 50 years

statistical analysis of storm electrical discharges reconstituted from a lightning mapping system a lightning location system and an acoustic array in the framework of the european hydrological cycle in the mediterranean experiment project a field campaign devoted to the study of electrical activity during storms took place in the south of france in 2012 an acoustic station composed of four microphones and four microbarometers was deployed within the coverage of a lightning mapping array network on the 26 october 2012 a thunderstorm passed just over the acoustic station fifty six natural thunder events due to cloud to ground and intracloud flashes were recorded this paper studies the acoustic reconstruction in the low frequency range from 1 to 40 hz of the recorded flashes and their comparison with detections from electromagnetic networks concurrent detections from the european cooperation for lightning detection lightning location system were also used some case studies show clearly that acoustic signal from thunder comes from the return stroke but also from the horizontal discharges which occur inside the clouds the huge amount of observation data leads to a statistical analysis of lightning discharges acoustically recorded especially the distributions of altitudes of reconstructed acoustic detections are explored in detail the impact of the distance to the source on these distributions is established the capacity of the acoustic method to describe precisely the lower part of nearby cloud to ground discharges where the lightning mapping array network is not effective is also highlighted

a numerically calibrated reference level mp28 for the terrestrial mammal based biozonation of the european upper oligocene the fauna of the enspel westerwald and the neighbouring karlich neuwied basin fossil deposits correspond to the upper oligocene mammal paleogene mp reference level 28 and 28 30 respectively basaltic flows and a trachyte tuff terminating and predating the fossil deposit sedimentation allow to numerically calibrate the mp reference levels by radioisotope dating laser fusion 40ar 39ar step heating on volcanic feldspars yield a time interval of 24 9 24 5 ma for reference level mp28 at enspel and a maximum age of 25 5 ma for the time interval mp28 mp30 at karlich interpolation between the time intervals determined for the enspel reference level mp28 and the age of the global oligocene miocene boundary of 24 0 0 1 ma taken from literature results in time intervals of 24 5 24 2 ma and 24 2 23 9 ma for the younger reference levels mp29 and mp30 respectively these intervals of 0 4 m y for mp reference levels of the latest oligocene are short relative to older oligocene mp reference levels 21 27 between 34 and 25 ma since subdivision into mp reference levels essentially is based on assemblages of mammal taxa and on evolutionary changes in tooth morphology of mammals short mp time intervals during the latest oligocene indicate a rapid evolutionary change relative to the early oligocene

radar and lightning analyses of gigantic jet producing storms 1 an analysis of thunderstorm environment structure and evolution associated with six gigantic jets five negative polarity one positive was conducted three of these gigantic jets were observed within detection range of very high frequency lightning mapping networks all six were within range of operational radars and two dimensional lightning network coverage five within the national lightning detection network and one within the global lightning detection gld360 network most of the storms producing the jets formed in moist tropical or tropical like environments precipitable water ranged from 37 to 62 kg m 2 and 0 6 km shear from 3 5 to 24 8 m s 1 featuring high convective available potential energy 1200 3500 j kg 1 and low lifted indices 2 8 to 6 4 the storms had maximum radar reflectivity factors of 54 to 62 dbz and 10 dbz echo contours reached 14 17 km storms covered by three dimensional lightning mappers were near peak altitude of lightning activity modes of the vertical distributions of radio sources were at altitudes colder than 50 c and vertical reflectivity intensity with overshooting echo tops around the times of their jets two of the other three jet producing storms produced their jet around the time of a convective surge as indicated by radar data and likely featured overshooting tops the observations suggest a link between convective surges overshooting tops and the occurrence of gigantic jets similar to prior modeling studies

cenozoic continental climatic evolution of central europe continental climate evolution of central europe has been reconstructed quantitatively for the last 45 million years providing inferred data on mean annual temperature and precipitation and winter and summer temperatures although some regional effects occur the european cenozoic continental climate record correlates well with the global oxygen isotope record from marine environments during the last 45 million years continental cooling is especially pronounced for inferred winter temperatures but hardly observable from summer temperatures correspondingly cenozoic cooling in central europe is directly associated with an increase of seasonality in contrast inferred cenozoic mean annual precipitation remained relatively stable indicating the importance of latent heat transport throughout the cenozoic moreover our data support the concept that changes in atmospheric co2 concentrations although linked to climate changes were not the major driving force of cenozoic cooling

lightning subsequent stroke electric field peak greater than the first stroke peak and multiple ground terminations for 46 multiple stroke flashes in which each stroke ground termination was located using a tv camera network and thunder ranging 15 flashes 33 had one or more subsequent return strokes whose initial electric field peak normalized to 100 km was greater than the first stroke field peak of the flash in 9 of these 15 flashes the subsequent strokes with field peaks greater than the first stroke followed the same channel as the first stroke in five flashes the subsequent strokes with the greater peaks followed a different channel to ground and in one flash the subsequent strokes with the greater peaks occurred both in the first stroke channel and in a different channel the interstroke intervals immediately preceding the 13 larger subsequent strokes that followed the first stroke channel had a geometric mean gm duration of 98 ms 1 7 times greater than the gm of 57 ms for all 199 interstroke intervals 46 flashes without any selection eight of the 13 larger subsequent strokes for which leader durations were measurable had a gm leader duration of 0 55 ms 3 3 times smaller than the gm of 1 8 ms for 117 subsequent leaders with measurable duration in a previously formed channel of the 46 multiple stroke flashes for the six larger subsequent strokes that created a new channel to ground the preceding interstroke interval had a gm of 130 ms and the leader duration had a gm of 15 ms no subsequent stroke with peak field exceeding the first in any category had a preceding interstroke interval less than 35 ms analysis of direct current measurements from switzerland shows that subsequent stroke currents exhibit many features similar to those of florida subsequent stroke electric fields in 22 florida single stroke and multiple stroke ground flashes the distances between multiple channel terminations in a given flash 33 measurements ranged from 0 3 km to 7 3 km with a gm of 1 7 km

a basin modeling study of the jafurah sub basin saudi arabia implications for unconventional hydrocarbon potential of the jurassic tuwaiq mountain formation abstract the middle upper jurassic organic rich carbonate mudrocks of the tuwaiq mountain formation in the jafurah sub basin of the central arabian basin have long been recognized as the source of hydrocarbons trapped primarily in upper jurassic carbonate reservoirs of saudi arabia e g giant ghawar field with the recent development of commercial hydrocarbon production from unconventional reservoirs in north america these organic rich carbonate mudrocks are now recognized as potential shale gas and shale oil plays three conventional source rock intervals the tuwaiq mountain tqmn hanifa and jubaila formations exist within the jurassic petroleum system of the jafurah sub basin the tqmn formation is being evaluated for shale gas and shale oil potential by saudi aramco because the tqmn fm holds excellent unconventional gas characteristics such as high total organic carbon content toc and low clay content and proper maturity window for oil and gas generation five wells representing the first unconventional gas exploration wells drilled in the jafurah sub basin have been selected for 1d and 2d basin modeling work the work was performed to investigate the burial and thermal maturity evolution of the tqmn formation in the jafurah sub basin the maturity of the tqmn formation in the study wells varies from 0 8 to 1 25 vre covering peak oil to wet gas generation stage despite only slight differences in present day burial depths the present day temperature gradients have been calculated to be higher at well locations where the source rock is at higher maturity modeling results suggest that higher temperature gradient areas of the basin probably has higher basement heat flow which leads to satisfactory match between measured and predicted maturity and temperature at present day this increased basement heat flow in areas of higher temperature gradient correspond to the interpreted change in crustal composition most likely granitic basement generating more radiogenic heat the modeling results suggest that tqmn source rocks started generating oil at about 100 ma and they reached the peak oil generation at about 70 ma present day they are in the wet gas generation window in the northern and eastern parts of the jafurah sub basin where the thermal gradients are 28 c km or higher the central and southwestern parts of the sub basin are cooler and here the tqmn source rocks are within the peak oil generation window the warmer parts of the sub basin have higher shale gas potential compared to the cooler parts of the basin we note that proper modeling and estimation of gas content in these source rocks and probably in unconventional resource estimation work in general some skilled modifications in basin modeling parameters are necessary variation of the oil saturation threshold is necessary until a gas saturation level equal to or higher than the gas adsorption capacity of the source rock is obtained otherwise modeling will lead to overestimation of the oil migration out of the source rock and thus the amount of the oil that can be retained and cracked to gas at higher temperatures will be miscalculated therefore the eventual gas content estimations will may be severely underestimated following our basin modeling study we note that improvement of the present day subsurface temperature data will be necessary in the future to estimate the maturity and shale gas potential of the tqmn source rocks in the jafurah sub basin

the lower marine to lower freshwater molasse transition in the northern alpine foreland basin oligocene central switzerland south germany age and geodynamic implications the wilhelmine alpe section near immenstadt allgau south germany which represents one of the best continuously exposed outcrops within the northern alpine foreland basin has been analyzed for magnetostratigraphic and palynostratigraphic signals the section comprises the marine to terrestrial transition from lower marine umm to lower freshwater molasse usm sediments based on the correlation of the local magnetic pattern with the geomagnetic polarity timescale gpts and palynostratigraphic data an age of about 31 ma is suggested for the umm usm transition in the wilhelmine alpe section a comparison with coeval magnetostratigraphic sections from central and eastern switzerland indicates that the regression of the umm sea along the southern margin of the molasse basin occurred strongly heterochronously between 31 5 and 30 ma the heterochroneity is attributed to the deposition of fan delta and alluvial fan sediments which document that the overall marine conditions during the umm were accompanied by strong clastic input derived from the rising alps this clastic contribution had a much stronger influence on the depositional pattern than previously thought

a comparative study of fossil and extant algaenans using ruthenium tetroxide degradation in this study the chemical structure of algaenans isolated from the freshwater algae tetraedron minimum pediastrum boryanum and botryococcus braunii are compared with their fossil counterparts by means of ruo4 oxidation the results show that the algaenans investigated are preserved in sediments with only minor structural alterations however product mixtures from ruo4 degradation of the fossil algaenans exhibit a broader distribution of oxidation products than freshly isolated algaenans indicating that the fossil biopolymers contain a greater proportion of ether cross links which maybe an effect of diagenetic alteration or different algal strains despite these differences fossil algaenans can still be recognised chemically on the basis of the specific ruo4 oxidation products even after 50 ma of sediment burial

magnetostratigraphic constraints on relationships between evolution of the central swiss molasse basin and alpine orogenic events magnetostratigraphic chronologies together with lithostratigraphic sedimentological and petrological data enable detailed reconstruction of the oligocene to miocene history of the north alpine foreland basin in relation to specific orogenic events and exhumation of the alps the molasse of the study area was deposited by three major dispersal systems rigi hohronen napf distinguished by characteristic heavy mineral suites conglomerate clast populations and the presence of key clasts these systems record three major phases of denudation of the alpine edifice the rigi system eroded the austroalpine and penninic nappes of eastern switzerland from 30 to 25 5 ma as a result of backthrusting and uplift of these units along the insubric line subsequent uplift of the aar massif some 40 km to the north appears to have controlled the duration of the hohronen and napf dispersal systems spanning 24 22 ma and 21 5 15 ma respectively they record downcutting into the crystalline cores of the penninic and austroalpine nappes of eastern hohronen and western napf switzerland high resolution reconstruction of the structural and geometrical evolution of the proximal molasse reveals in sequence and out of sequence thrusting events at the alpine front and incorporation of the molasse into the orogenic wedge by in sequence thrusting and underplating furthermore it reveals close relationships between periods of rapid denudation in the central alps and phases of increased sediment accumulation rates at the proximal basin border an initial increase in molasse accumulation rates to 1 km m y occurred between 30 and 25 5 ma and coincides with the insubric phase of backthrusting along the eastern insubric line where 10 km of vertical displacement is interpreted during the same time span the alpine wedge propagated forward along the basal alpine thrust as indicated by the coarsening and thickening upward megasequence and by occurrence of bajada fans derived from the alpine border the end of this tectonic event is marked by a basinwide unconformity interpreted to have resulted from crustal rebound after initial loading a subsequent increase in accumulation rates to 1 km m y between 23 and 21 5 ma coincides with initial uplift of the eastern aar massif by at least 4 km this phase of high accumulation rates is associated with incorporation of early chattian conglomerates into the orogenic wedge the third advance of the alpine wedge between 21 and 15 5 ma caused underplating of molasse deposits resulting in synsedimentary backthrusting of previously deposited molasse sequences and in the development of a progressive unconformity a rapid increase in accumulation rates from 0 35 to 1 km m y between 15 5 and 15 ma marks the final loading event in the wedge which may be caused by further major displacement and loading of the aar massif this deformation is coeval with out of sequence thrusting of the helvetic border chain and of the piggyback stack of north penninic and ultrahelvetic flysch nappes along the basal alpine thrust

lightning development associated with two negative gigantic jets 1 we report observations of two negative polarity gigantic jets sufficiently near very high frequency vhf lightning mapping networks that the associated lightning characteristics and charge transfer could be investigated in both cases the gigantic jet producing flash began as ordinary intracloud lightning with upper level channels attempting to exit the cloud and then produced the upward gigantic jet neither flash had developed channels to ground confirming that the major charge transfer during gigantic jets occurred between the cloud and ionosphere the leader progression of one event was detected at altitudes above 20 km demonstrating the possibility of detecting and tracking the propagation of negative jets above the cloud with vhf techniques citation lu g et al 2011 lightning development associated with two negative gigantic jets geophys res lett 38 l12801

characteristics of a negative lightning with multiple ground terminations observed by a vhf lightning location system propagation characteristics of a negative cloud to ground lightning with four leader return stroke sequences exhibiting four ground terminations referred to as multiple termination flash are analyzed using a two dimensional mapping system of lightning radiation sources in vhf band along with broadband electric field change records the four stepped leader stroke sequences were produced from two different branches of the preliminary breakdown process inside the cloud and the time intervals between each adjacent two leader stroke sequences were 82 9 ms 81 4 ms and 152 2 ms respectively the first two stroke sequences were multiple termination strokes mtss and each mts showed two different ground terminations induced by two leader branches the corresponding electric field changes exhibited two fast rising waveforms separated by 1 5 ms and 2 7 ms respectively and the second peak was 3 4 times smaller than the first the second grounding branch in each mts occurred when its channel was in poor connection conditions to the main stroke channel the third and fourth leader stroke sequences connected to the ground with one of the different grounded channels of the second mts the dart leaders before these two strokes exhibited chaotic pulse trains cpts with significant slow electric field variations accompanying strong and continuous vhf radiations the cpts only occurred in the dart leader stage which propagated with a speed in an order of 107 m s different from dart leader attempted leader was associated with regular pulse trains and propagated at a speed order of 106 m s along the previous channel

a multidisciplinary approach in determining the maceral kerogen type and mineralogical composition of upper cretaceous eagle ford formation impact on pore development and pore size distribution abstract maceral kerogen or organic matter type and mineralogical composition with the associated porosity of the upper cretaceous eagle ford formation karnes county texas was investigated in karnes county the calcareous mudstone of the eagle ford formation was deposited in an open marine outer shelf to upper slope environment to adequately characterise all components of this mudrock a multidisciplinary approach was implemented to analyse 26 core samples from a single producing well that completed within the eagle ford formation analyses included organic petrology organic geochemistry light and electron microscopy and spectroscopy pore size distribution analyses and x ray diffraction the bitumen reflectance ranges between 1 94 and 2 08 calculated vr o 1 60 1 69 indicating the mudrock is in the condensate rich gas window the toc content ranges between 1 7 and 7 2 with an average of 3 9 mineral composition is dominated in descending order by calcite clay quartz and plagioclase calcite varies between 32 and 87 with an average of 57 porosity measured by helium pycnometry ranges between 3 5 and 10 3 with an average of 7 5 organic petrology coupled with backscattered and field emission scanning electron microscopy indicates matrix bitumen as the most significant contributor to the toc content and porosity matrix bitumen contains significant meso and microporosity and is enhanced by the secondary cracking of the bitumen an increase in bioclastic mostly foraminifera and siliciclastic components correlates with lower toc content due to the lower volume of organic rich matrix peloids fecal pellets are calcareous organic rich and lack terrigenous sediment indicating a zooplankton source pelagic deposition of peloids is interpreted as a primary mechanism of amorphinite deposition which is converted to hydrocarbons and matrix bitumen the mixed siliciclastic calcareous matrix that surrounds the peloids is comprised of matrix bitumen and dispersed organics from land plants vitrinite fusinite and inertodetrinite the siliciclastic component increases in the middle of the eagle ford and marks the boundary maximum flooding surface between the lower tst and upper hst section of the formation the inorganic and organic components suggest a mixed terrigenous and marine source with both inorganic and organic sediments being derived from the proximal ouachita thrust belt and from pelagic organisms within the overlying water column the lower tst eagle ford formation contains more micro and mesopores than the upper hst eagle ford formation due to higher toc content in the lower eagle formation these results illustrate that a multidisciplinary approach is necessary to identify how pore network are distributed within mudrocks and how this distribution is controlled by organic inorganic deposition and hydrocarbon generation processes

depositional and structural evolution of a foreland basin margin in a magnetostratigraphic framework the eastern swiss molasse basin this integrated study of the sedimentology magnetostratigraphic chronology and petrography of the mostly continental clastics of the oligocene to miocene swiss molasse basin underpins a reconstruction of facies architecture and delineates relationships between the depositional evolution of a foreland basin margin and exhumation phases and orogenic events in the adjacent orogen a biostratigraphically based high resolution magnetostratigraphy provides a detailed temporal framework and covers nearly the whole stratigraphic record of the molasse basin 31 5 13 ma three transverse alluvial fan systems evolved at the southern basin margin they are characterized by distinct petrographic compositions and document the exhumation and denudation history of the growing eastern swiss alps enhanced northward propagation of the orogenic wedge is interpreted to have occurred between 31 5 and 26 ma during the period 24 19 ma intense in sequence and out of sequence thrusting took place as molasse strata were accreted to the orogenic wedge a third active tectonic phase possibly caused by backthrusting of the plateau molasse probably occurred between ca 15 and 13 ma fan head migration between 31 5 and 13 ma is probably controlled by the structural evolution of the thrust front due to molasse accretion and backthrusting

a novel nmr surface relaxivity measurements on rock cuttings for conventional and unconventional reservoirs abstract surface relaxivity is an intrinsic rock property that makes low field nmr a valuable tool for determining pore size distribution of geological formations its value can vary considerably in different rocks depending on the type and distribution of the rock minerals rock surface wettability and petrophysical properties therefore laboratory measurement of is required on a case by case basis however existing nmr methods are expensive complex and most often require supplementary and expensive non nmr measurements rock samples are also required to be well consolidated and cylindrical so that experiments can be run at high pressures a barrier for measurements of unconsolidated and thinly laminated unconventional rocks this study proposes a new nmr method termed nmr grain sizing method that uses different grain sizes of a given rock to generate pores of corresponding sizes using a geometric constant grain specific surfaces are transformed to pore surfaces and the governing nmr equation is rearranged so that we have a method that measures from only nmr measurements on rock cuttings this approach is simple inexpensive and does not require supplementary measurements it offers an added advantage for characterizing thinly laminated formations a proof of concept is demonstrated for three unconventional rocks qusaiba shale jafurah carbonate mudrock and eagle ford and two conventional rocks berea sandstone and indiana limestone the ranges of surface relaxivity are 96 9 134 5 m s qusaiba shale 62 07 106 m s jafurah carbonate mudrock 55 9 68 72 m s eagle ford 35 51 43 2 m s berea sandstone and 33 2 40 54 m s indiana limestone all measurements are reproducible with 95 confidence interval the measured values for indiana limestone and berea sandstones were validated with micro ct based pore network models and also compare well with literature data measurement of qusaiba shale and jafurah carbonate source rocks are apparently reported for the first time here

the impact of wettability and connectivity on relative permeability in carbonates a pore network modeling analysis 1 we use pore network modeling to study the impact of wettability and connectivity on waterflood relative permeability for a set of six carbonate samples four quarry samples are studied indiana portland guiting and mount gambier along with two subsurface samples obtained from a deep saline middle eastern aquifer the pore space is imaged in three dimensions using x ray microtomography at a resolution of a few microns the images are segmented into pore and solid and a topologically representative network of pores and throats is extracted from these images we then simulate quasi static displacement in the networks we represent mixed wet behavior by varying the oil wet fraction of the pore space the relative permeability is strongly dependent on both the wettability and the average coordination number of the network we show that traditional measures of wettability based on the point where the relative permeability curves cross are not reliable good agreement is found between our calculations and measurements of relative permeability on carbonates in the literature this work helps establish a library of benchmark samples for multiphase flow and transport computations the implications of the results for field scale displacement mechanisms are discussed and the efficiency of waterflooding as an oil recovery process in carbonate reservoirs is assessed depending on the wettability and pore space connectivity

geochemical petrographic and petrophysical characterization of the lower bakken shale divide county north dakota abstract the lower bakken shale is a key member of the bakken petroleum system which is a prolific unconventional accumulation in north america unconventional accumulations have unpredictable lateral variations in hydrocarbon production due to a variety of factors including porosity permeability and other rock properties therefore understanding the geochemical source rock potential petrological and petrophysical properties of these units is essential in evaluating the hydrocarbon potential for the lower bakken shale this study utilized cores from four wells within three fields in divide county north dakota with samples collected for rock eval pyrolysis organic petrology petrographic thin section studies xrd sem porosity pore size and pore fluid distribution helium porosimetry and nmr t2 porosity techniques were used to estimate porosity and also to check the quality of the results and avoid discrepancies results showed that maturity in the study area varies from immature to early mature using tmax and solid bitumen reflectance organic petrology showed the dominance of solid bitumen and marine alginites which confirms the type ii kerogen identified from pyrolysis and marine depositional environment in the study area major organic matter types identified from sem studies involve stringy om om mineral admixture particulate om and pure om which host the majority of the organic matter pores furthermore pore types identified from sem include mineral matrix pores organic matter pores and microfracture pores porosity values based on both helium and nmr varies but the difference was nominal and attributed to the presence of abundant clay minerals pore sizes are distributed within micropores mesopores and macropores with thermal maturity toc and clay mineral proportion having a major influence on pore distribution clay bound water was identified to be the dominant fluid within the shale samples using the t2 cutoff values and supporting evidence from the abundance of clay matrix porosity

horizontal lightning propagation preliminary breakdown and electric potential in new mexico thunderstorms 1 characteristics of lightning flashes in three storms are compared to simultaneous electric field e measurements at various altitudes to examine three hypotheses the first is the idea that horizontal lightning branches propagate at altitudes near potential extrema or wells the analyses show that horizontal lightning activity and potential extrema are coincident in time and altitude and so are consistent with the idea that lightning moves charges into potential wells as a means of using a storm s electrostatic energy to drive a lightning flash s dielectric breakdown processes second these data are used to verify the usual interpretation of breakdown polarity of lightning radiation sources detected by the lightning mapping array the third hypothesis investigated is that normal cloud to ground flashes have a period of preliminary breakdown if and only if a potential well for negative charge exists between the altitudes of flash initiation and ground the analyses show that in 14 flashes when a low level well was indicated the period of preliminary breakdown before the first return stroke lasted an average of 117 ms considerably longer than the average lifetime of a stepped leader in 15 flashes in which no low level well was indicated the time between initiation and first return stroke averaged 15 ms

global plate motion frames toward a unified model 1 plate tectonics constitutes our primary framework for understanding how the earth works over geological timescales high resolution mapping of relative plate motions based on marine geophysical data has followed the discovery of geomagnetic reversals mid ocean ridges transform faults and seafloor spreading cementing the plate tectonic paradigm however so called absolute plate motions describing how the fragments of the outer shell of the earth have moved relative to a reference system such as the earth s mantle are still poorly understood accurate absolute plate motion models are essential surface boundary conditions for mantle convection models as well as for understanding past ocean circulation and climate as continent ocean distributions change with time a fundamental problem with deciphering absolute plate motions is that the earth s rotation axis and the averaged magnetic dipole axis are not necessarily fixed to the mantle reference system absolute plate motion models based on volcanic hot spot tracks are largely confined to the last 130 ma and ideally would require knowledge about the motions within the convecting mantle in contrast models based on paleomagnetic data reflect plate motion relative to the magnetic dipole axis for most of earth s history but cannot provide paleolongitudes because of the axial symmetry of the earth s magnetic dipole field we analyze four different reference frames paleomagnetic african fixed hot spot african moving hot spot and global moving hot spot discuss their uncertainties and develop a unifying approach for connecting a hot spot track system and a paleomagnetic absolute plate reference system into a hybrid model for the time period from the assembly of pangea 320 ma to the present for the last 100 ma we use a moving hot spot reference frame that takes mantle convection into account and we connect this to a pre 100 ma global paleomagnetic frame adjusted 5 in longitude to smooth the reference frame transition using plate driving force arguments and the mapping of reconstructed large igneous provinces to core mantle boundary topography we argue that continental paleolongitudes can be constrained with reasonable confidence

tectonic evolution of the northwestern internal dinarides as constrained by structures and rotation of medvednica mountains north croatia this paper attempts to explain the tectonic history and the possible reasons for the change of trend of the northwestern part of internal dinarides in a transitional area between the southern eastern alps central dinarides and tisia north of zagreb structural and palaeomagnetic data collected in pre neogene rocks at medvednica mts combined with palaeomagnetic data available form neogene rocks in the surrounding area point to the following conclusions 1 the reason for dramatic deflection in structural trend of the internal dinarides in the area north of zagreb is a 130o clockwise rotation and eastward escape of a tectonic block comprising medvednica mts and the surrounding inselbergs bounded to the north by the easternmost tip of the periadratic lineament in medvednica mts the main period of tectonic escape and associated clockwise rotation occurred in late palaeogene possibly in oligocene earliest miocene 2 when rotated into the original position the trend of observed pre neogene structures of medvednica mt becomes parallel to the major structural trend of the central dinarides in view of their original orientation these structures are interpreted in the following way a the first d1 deformational event is attributed to the aptian albian nappe stacking in the central northern dinarides that was accommodated by a top to the north directed shearing and northward propagation of already obducted ophiolites of the central dinaridic ophiolite zone this nappe stacking which resulted in a weak regional metamorphism in tectonic units underlying the ophiolites was orogen parallel or at a very acute angle to known structural and possibly palaeogeographic trends this implies a major left lateral shear component along the former adriatic margin and obducted dinaridic ophiolite zone b this was followed by early albian orogen perpendicular shortening d2 that was accommodated by folding and top to the west thrusting this deformation resulted in gradual cooling of the metamorphic stack and also in uplift and erosion of the higher structural units c d3 deformational event was driven by renewed e w shortening that took place after the paleocene most probably during the middle eocene oligocene i e synchronous with the main dinaridic tectonic phase of the external dinarides this shortening was probably triggered by collision and thrusting of tisia over the northern segment of the internal dinarides d this was finally followed by d4 pervasive right lateral n s shearing that is tentatively interpreted as being related to the right lateral shearing of the sava zone during the eocene oligocene e following the main period of tectonic escape and induced clockwise rotation in late palaeogene possibly in oligocene earliest miocene the medvednica mts and the surrounding area were affected by repeated extensions and inversions since the early miocene to recent times palaeomagnetic data suggest that in the early miocene but probably before the karpatian this area was part of a regional block that shifted northwards and rotated in counter clockwise sense a second episode of counter clockwise rotation occurred at the present latitude in post pontian times since ca 5 ma driven by the counter clockwise rotating adriatic plate

comparison of ground based 3 dimensional lightning mapping observations with satellite based lis observations in oklahoma 3 dimensional lightning mapping observations obtained in central oklahoma by the new mexico tech lightning mapping array lma have been compared with optical observations of the discharges from space obtained by nasa s lightning imaging sensor lis excellent spatial and temporal correlations were obtained between the two sets of observations all lightning discharges seen by lis were mapped by the lma most of the detected optical events were associated with lightning channels that extended into the upper part of the storm cloud to ground discharges that were confined to mid and lower altitudes were less well detected than intracloud discharges and tended to be detected late in the discharge intracloud discharges were readily detected by lis as soon as they extended into the upper part of the storm and often extensively illuminated the cloud at the end or part way through the discharge the extensive illumination was impulsive in nature and was also seen at the end of some cloud to ground discharges

observations of two sprite producing storms in colorado two sprite producing thunderstorms were observed on 8 and 25 june 2012 in northeastern colorado by a combination of low light cameras a lightning mapping array polarimetric and doppler radars the national lightning detection network and charge moment change measurements the 8 june event evolved from a tornadic hailstorm to a larger multicellular system that produced 21 observed positive sprites in 2 h the majority of sprites occurred during a lull in convective strength as measured by total flash rate flash energy and radar echo volume mean flash area spiked multiple times during this period however total flash rates still exceeded 60 min sup 1 and portions of the storm featured a complex anomalous charge structure with midlevel positive charge near 20degc the storm produced predominantly positive cloud to ground lightning all sprite parent flashes occurred on the northeastern flank of the storm where strong westerly upper level flow was consistent with advection of charged precipitation away from convection providing a pathway for stratiform lightning the 25 june event was another multicellular hailstorm with an anomalous charge structure that produced 26 positive sprites in less than 1 h the sprites again occurred during a convective lull with relatively weaker reflectivity and lower total flash rate but relatively larger mean flash area however all sprite parents occurred in or near convection and tapped charge layers in adjacent anvil cloud the results demonstrate the sprite production by convective ground strokes in anomalously charged storms and also indicate that sprite production and convective vigor are inversely related in mature storms

lightning location relative to storm structure in a leading line trailing stratiform mesoscale convective system 1 horizontal and line normal vertical cross sections and composite images of dallas fort worth lightning detection and ranging ldar ii vhf radiation sources and radar reflectivity over a 30 min period provide a unique perspective on lightning pathways within a leading line trailing stratiform llts mesoscale convective system mcs on 16 june 2002 the overwhelming majority of vhf lightning sources occurred within the leading convective line in a bimodal pattern in the vertical assuming that vhf source density maxima were most likely associated with positive charge then the ldar ii observations suggest that the gross charge structure of the convective region of the mcs was characterized by a tripole with net positive charge centered at 4 5 km agl 3 c and 9 5 km agl 35 c and net negative charge centered roughly in the relative minimum of the vhf source density maximum at 7 km agl 17 c a persistent lightning pathway and inferred positive charge zone sloped rearward by 40 50 km and downward by 4 5 km from the upper vhf source maximum in the convective line through the transition zone and into the radar bright band of the stratiform region in the stratiform region vhf lightning sources and inferred positive charge were concentrated in three layers centered at 4 5 6 and 9 km agl 2 c 11 c and 31 c respectively consistent with past electric field studies of symmetric llts mcss positive cloud to ground lightning flashes in the stratiform region were initiated in the convective line and followed the slanting pathway from the top of convective cores to the stratiform precipitation where they were horizontally extensive layered and highly branched the sloping lightning pathway was identical to hypothetical trajectories taken by snow particles these observations provide further support for the advection of charge on snow along the sloping pathway and the in situ generation of charge in the horizontal lightning layers as primary contributors to electrification and positive lightning production rearward of the convective line

total lightning signatures of thunderstorm intensity over north texas part i supercells abstract it is shown that total lightning mapping along with radar and national lightning detection network nldn cloud to ground lightning data can be used to diagnose the severity of a thunderstorm analysis of supercells some of which were tornadic on 13 october 2001 over dallas fort worth texas shows that lightning detection and ranging ldar ii lightning source heights quartile median and 95th percentile heights increased as the storms intensified most of the total cloud to ground and intracloud lightning occurred where reflectivity cores extended upward within regions of strong reflectivity gradient rather than in reflectivity cores a total lightning hole was associated with an intense nontornadic supercell on 6 april 2003 none of the supercells on 13 october 2001 exhibited a lightning hole during tornadogenesis the radar and ldar ii data indicated updraft weakening the height of the 30 dbz radar top began to descend approximately 10 min 2 volume scans before tornado touchdow

paleomagnetic and geochronologic constraints on the geodynamic evolution of the central dinarides the geodynamic evolution of the dinaride mountains of southeastern europe is relatively poorly understood especially in comparison with the neighboring alps and carpathians here we construct a new chronostratigraphy for the post orogenic intra montane basins of the central dinarides based on paleomagnetic and 40ar 39ar age data a first phase of basin formation occurred in the late oligocene a second phase of basin formation took place between 18 and 13 ma concurrent with profound extension in the neighboring pannonian basin our paleomagnetic results further indicate that the dinarides have not experienced any significant tectonic rotation since the late oligocene this implies that the dinarides were decoupled from the adjacent adria and the tisza dacia mega units that both underwent major rotation during the miocene the dinaride orogen must consequently have accommodated significant shortening this is corroborated by our ams data that indicate post middle miocene shortening in the frontal zone wrenching in the central part of the orogen and compression in the hinterland a review of paleomagnetic data from the adria plate which plays a major role in the evolution of the dinarides as well as the alps constrains rotation since the early cretaceous to 48 10 counterclockwise and indicates 20 of this rotation took place since the miocene it also shows that adria behaved as an independent plate from the late jurassic to the eocene from the eocene onwards coupling between adria and africa was stronger than between adria and europe adria continued to behave as an independent plate the amount of rotation within the adria dinarides collision zone increases with age and proximity of the sampled sediments to undeformed adria these results significantly improve our insight in the post orogenic evolution of the dinarides and resolve an apparent controversy between structural geological and paleomagnetic rotation estimates for the dinarides as well as adria

unusual features of negative leaders development in natural lightning according to simultaneous records of current electric field luminosity and high speed video the development of downward and upward leaders that formed two negative cloud to ground return strokes in natural lightning spaced only about 200 s apart and terminating on ground only a few hundred meters away was monitored at morro do cachimbo station brazil the simultaneous records of current close electric field relative luminosity and corresponding high speed video frames sampling rate of 20 000 frames per second reveal that the initiation of the first return stroke interfered in the development of the second negative leader leading it to an apparent continuous development before the attachment without stepping and at a regular two dimensional speed based on the experimental data the formation processes of the two return strokes are discussed and plausible interpretations for their development are provided

chronology and integrated stratigraphy of the miocene sinj basin dinaride lake system croatia article i nfo ar 39 ar dating mollusk evolution conohyus in the miocene the intra montane basins of the dinaric mountain chain harbored a series of long lived lakes constituting the so called dinaride lake system the thick lacustrine sedimentary records of these lakes provide an excellent opportunity to study evolution and radiation of mollusks in an isolated environment the 500 m thick infill that accumulated in the sinj basin is one of the key records because of its excellent mollusk preservation recent studies on the depositional history pollen assemblages and large mammals have enhanced the understanding not only of lake sinj but also of the regional climatic developments and faunal migratory patterns a reliable chronology of the development of lake sinj which is crucial for global correlation of its endemic realm was still lacking in this paper we present a detailed time frame for the miocene sinj basin based on palaeomagnetic and 40 ar 39 ar data we conclude that deposition took place between 18 0 to 15 0 ma a time span that correlates with the upper burdigalian and lower langhian mediterranean stages and ottnangian karpatian and lowermost badenian paratethys stages furthermore we determined the timing of several events in mollusk evolution important for correlation across the dinarides an age of 15 0 ma is attributed to the large mammals conohyus and gomphotherium preserved in the upper part of the basin stratigraphy 2010 elsevier b v all rights reserved