high resolution surface and subsurface sequence stratigraphy of late middle to late ordovician late mohawkian cincinnatian foreland basin rocks kentucky and virginia the late middle to late ordovician late mohawkian to cincinnatian supersequence in kentucky and virginia was deposited in a tectonically active foreland basin during a transition from the ice free early ordovician to the glacial late ordovician this sequence was deposited in less than 12 m y is 250 500 m thick and is composed of four large third order sequences each 40 150 m thick that are regionally correlative in outcrops cores and gamma ray logs smaller scale third order parasequence sets up to 20 m thick and component parasequences 1 8 m thick make up the larger sequences and are only locally correlative subtidal dominated parasequences comprise the basal part of each sequence whereas shallower subtidal or peritidal dominated parasequences compose upper parts of sequences each large third order sequence is asymmetric and marked by lowstand transgressive and highstand systems tracts with unique lithologic and gamma ray log response characteristics ramp margin wedges rmw are poorly developed and consist of marine siltstone or grainstone packstone sheets extending into deep ramp settings these sheets have high gamma ray values in their base and lower blockier gamma ray responses in their tops transgressive systems tracts tst are thin composed of high energy locally phosphatic grainstone copyright 1997 the american association of petroleum geologists all rights reserved 1manuscript received february 7 1996 revised manuscript received may 27 1997 final acceptance june 16 1997 2department of geology virginia tech blacksburg virginia 24061 0420 present address department of earth atmospheric and planetary sciences massachusetts institute of technology cambridge massachusetts 02139 3department of geology virginia tech blacksburg virginia 24061 0420 this study was supported by nsf grant ear 9316057 to j f read a grant from mobil oil company and grants in aid of research from the geological society of america and appalachian basin industrial associates to mike pope we thank john haynes brian keith and rick major for thorough and insightful reviews of an earlier version of this manuscript

evidence of an extratropical atmospheric influence during the onset of the 1997 98 el nino the major 1997 98 el nino episode was initiated by a series of very energetic westerly wind bursts in late 1996 and early 1997 downwelling oceanic kelvin waves were subsequently generated and propagated rapidly eastward across the equatorial pacific ocean and induced significant warming in the eastern basin by analyzing newly available wind products derived from ssm i satellite observations we found indications that these westerly wind bursts were embedded within the active phase of the tropical intraseasonal oscillation the madden julian oscillation but their amplitudes were greatly enhanced in the western pacific sector the local enhancement involved the development of equatorial twin cyclones which themselves were induced by northerly cold surges from east asia western north pacific into the tropical pacific demonstrating an extratropical atmospheric influence on tropical processes

buried granites within the mid north sea high a gravity survey of the uk sector of the north sea reveals the presence of three gravity lows over the mid north sea high seismic data eliminate the possibility that these lows are due either to thicker sediments or to salt structures consequently the anomalies may be related to buried granites within the palaeozoic basement gravity modelling demonstrates that the amplitude and shape of the observed anomalies may be explained by buried batholith shaped bodies with densities appropriate for granites the tectonic influence of the buried granites may explain to some extent the continued stability of the mid north sea high throughout much of the development of the north sea basins

observations of rossby waves linked to convection over the eastern tropical pacific rossby wave activity propagating into the eastern tropical pacific from the midlatitudes during northern winter is examined in some detail these waves are associated with the intrusion of high potential vorticity air into low latitudes and they modulate cloudiness stability and vertical motion in the vicinity of the itcz in the upper troposphere and lower stratosphere the horizontal phase and group propagation of the wave activity are qualitatively like those of a nondivergent barotropic rossby wave as the waves move equatorward they become more shallow and propagate upward into the stratosphere the horizontal and vertical propagation is consistent with the tilts of the waves the large scale three dimensional background flow and with the signatures of momentum and heat fluxes associated with the wave activity in the lower troposphere paired cyclonic anomalies on either side of the equator accompany the upper level wave activity to the west of the itcz cloudiness signal these waves amplify following the peak in the itcz cloudiness and propagate westward along the equator this suggests that the upper level wave activity and possibly the associated convective heating can trigger the excitation of the equatorially trapped rossby modes the transient wave activity appears to be a crucial component of the momentum balance of the eastern tropical pacific circulation there is substantial interannual variability in the wave activity consistent with observed changes in the large scale basic state associated with the southern oscillation

structural development of the devono carboniferous plays of the uk north sea decades of oil and gas exploration across the north sea have led to a detailed understanding of its cenozoic mesozoic structure however the deeper basin architecture of paleozoic petroleum systems has been less well defined by seismic data this regional structural overview of the devono carboniferous petroleum systems incorporates interpretations from more than 85 000 line kilometres of 2d seismic data and 50 3d seismic volumes plus a gravity density and magnetic study from the central silverpit basin to the east orkney basin a complex picture of previously unmapped or poorly known basins emerges on an inherited basement fabric with numerous granite cored blocks these basins are controlled by devono carboniferous normal strike slip and reverse faults the main basins across quadrants 29 44 trend nw se influenced by the tornquist trend inherited from the caledonian basement north of quadrants 27 and 28 and the presumed iapetus suture the major depocentres are ne sw e g the forth approaches and inner moray firth basins to east west e g the caithness graben and wnw ese trending e g the east orkney basin reflecting the basement structural inheritance from seismic interpretation there are indications of an older north south fault trend in the inner moray firth that is difficult to image since it has been dissected by subsequent permo carboniferous and mesozoic faulting and rifting

an index for tropical temperate troughs over southern africa strong cases of the tropical temperate troughs ttt that are responsible for the most of the summer rainfall over subtropical southern africa are analyzed an index for identifying the ttt is introduced for the first time using anomalies of outgoing longwave radiation olr and the wind the ttt is associated with a ridge trough ridge wave like structure in the lower troposphere over southern africa and the adjoining indian ocean therefore the index considers physical processes that occur over southern africa adjoining the atlantic and indian oceans to depict the variability of the ttt events unusually strong ttt events are identified when the standard deviations of the ttt indices defined by the olr and wind anomalies in the selected regions are above 1 5 and 0 5 respectively after applying this criterion and filtering out consecutive events 55 ttt events are identified during the study period of december january february seasons from 1980 1981 to 2009 2010 from the composite analyses of those 55 events it is found that the ttts evolve with suppressed enhanced convection over the southwest indian ocean adjacent to madagascar southern africa the suppressed convection is in turn found to be associated with the enhanced convection around sumatra in the southeast tropical indian ocean this may explain why more ttt events occur in la nina years as compared to el nino years time evolution of the canonical ttt event shows that it starts 3 days prior to the mature phase of the event suggesting possible predictability after reaching a matured state the system moves east toward the indian ocean and decays within the subsequent couple of days in addition the intertropical convergence zone itcz structure changes over southern africa madagascar during the ttt event and remains similar to climatology over other regions the results indicate that the continental part of the itcz intensifies prior to the ttt event and then spreads southward following the mid latitude influence during and after the event

taconian orogeny in the new england appalachians collision between laurentia and the shelburne falls arc tectonic models of the ordovician taconian orogeny in western new england usually invoke a collision between the laurentian margin and a magmatic arc identified as the bronson hill arc however in central massachusetts and southern new hampshire rocks in the bronson hill arc are 454 to 442 ma and therefore younger than much of the taconian deformation and metamorphism in western new england and eastern new york which began by 470 ma u pb and single grain evaporation zircon ages combined with geochemical analyses reveal the presence of an older magmatic arc the shelburne falls arc that formed west of the bronson hill arc at 485 to 470 ma the shelburne falls arc formed above an east dipping subduction zone by the early ordovician the taconian orogeny was the result of the collision between laurentia and the shelburne falls arc beginning ca 475 to 470 ma the younger bronson hill arc formed above a west dipping subduction zone that developed along the eastern edge of the newly accreted terrane during the final stages of and subsequent to the taconian orogeny the taconian orogeny ended when plate convergence between laurentia and iapetus was accommodated by the newly developed west dipping subduction zone instead of by crustal shortening in the taconian thrust belt the tectonic history of the new england appalachians is inconsistent with a middle ordovician collision between laurentia and the proto andean margin of gondwana

characteristics of wave packets in the upper troposphere part i northern hemisphere winter abstract gridded data produced by the ecmwf reanalysis project have been analyzed to document the properties of wave packets in the northern hemisphere winter midlatitude upper troposphere based on results from earlier investigations 300 hpa meridional wind variations were chosen for analysis wave packet envelopes were also defined by performing complex demodulation on the wind data the properties of the wave packets are mainly illustrated using time lagged one point correlation maps performed both on and wave packet envelopes the results show that over most regions in the northern hemisphere winter with the exception of the deep tropics and near the aleutian low medium scale waves dominant wavenumber 5 8 exhibit the characteristics of downstream development and occur within wave trains that propagate with eastward group velocities much faster than the phase speeds of individual phases of the waves their group velocity is highly correlated with the local time mean 200 400 hpa wind while the

adjustment of the atmospheric circulation to tropical pacific sst anomalies variability of transient eddy propagation in the pacific north america sector nas a pattern that is shifted southward northward compared with climatology paths of coherent phase propagation of transient eddies and of the propagation of wave packets are analyzed a coherent path of propagation across the pacific towards north america is identified that is more zonal during el niwinters and during la nihas a dominant path heading northeastward to the pacific northwest a second path heading southeastward from the central pacific to the tropical east pacific is more accentuated during la ni nas than el ni nos these changes in wave propagation are reproduced in an ensemble of seasonal integrations of a general circulation model forced by a tropical pacific sea surface temperature pattern confirming that the changes are forced by changes in the mean atmospheric state arising from changes in tropical sea surface temperature a simplified model with a specified basic state is used to model the storm tracks for el ni no and la ni na winters the results suggest that the changes in transient eddy propagation and the eddy statistics can be understood in terms of the refraction of transient eddies within different basic states copyright c 2010 royal meteorological society

gigantic ordovician volcanic ash fall in north america and europe biological tectonomagmatic and event stratigraphic significance biostratigraphical geochemical isotopic and paleogeographic data suggest that the millbrig k bentonite one of the thickest and most widespread ordovician volcanic ash beds in eastern north america is the same as the so called big bentonite in baltoscandia this is the first time that the same k bentonite has been identified in both north america and europe and it serves as a unique event stratigraphic marker over a large portion of the northern hemisphere this eruption produced at least 340 km sup 3 of dense rock equivalent ash that was deposited in a layer up to 1 2 m thick over several million square kilometers as much as 800 km sup 3 of additional ash may have fallen into the iapetus ocean for a total of 1 140 km sup 3 trace element geochemistry shows that the ash was derived from a felsic calc alkalic magmatic source characteristic of volcanism in a continental crust based destructive plate margin setting this is one of the largest if not the largest ash falls recorded in earth s phanerozoic stratigraphic record but its recognizable effect on faunas and floras was minimal and it did not result in a global extinction event the millbrig big bentonite bed provides accurate time control for sedimentologic paleoecologic and paleogeographic reconstructions across plates positionedmore in tropical laurentia and temperate baltica latitudes during middle ordovician time less

correlation of the ordovician deicke and millbrig k bentonites between the mississippi valley and the southern appalachians 1 two widespread rocklandian age middle ordovician k bentonite beds the deicke and millbrig can be correlated from southern minnesota and northwestern iowa through eastern missouri across kentucky and central tennessee to the valley and ridge of the southern appalachian mountains they are equivalent to beds previously called t 3 or pencil cave and t 4 or mud cave metabentonites and thus constitute ordovician chronostratigraphic marker horizons throughout much of the eastern mid continent previous correlations of these beds in the mississippi valley by chemical fingerprinting is extended toward the southern appalachian basin by tracing in surface exposures and on wireline logs both beds thicken toward the southeast indicating a volcanic source area that was probably ast of south carolina the interval between the k bentonite beds also thickens toward the southeast owing to increased rates of carbonate deposition between the two volcanic episodes the areal extent of known correlatives of the deicke and millbrig is minimally estimated to be 600 000 sq km and at least 1122 cu km of pre compaction deicke k bentonite accumulated as ash in eastern north america the volume of both beds suggests they rank among the largest air fall ash deposits documented in the stratigraphic record

eustatic and far field tectonic control on the development of an intra platform carbonate shoal complex upper tongue of the tanglewood member upper ordovician lexington limestone central kentucky u s a abstract the lexington or trenton limestone is an upper ordovician chatfieldian edenian upper sandbian lower katian temperate water unit averaging about 60 m thick that was deposited in relatively shallow waters across the lexington platform in east central united states during the taconian orogeny lexington trenton shallow water deposition ended across most of the platform in late chatfieldian time and from that point deepened upward into the more shale rich clays ferry point pleasant and kope formations due to apparent sea level rise in central kentucky however deposition of the lexington limestone continued into early edenian time and includes up to 50 m of additional coarse calcarenites and calcirudites at the top which form the tanglewood buildup and reflect locally regressive conditions apparently related to local structural uplift consequently in central kentucky the lexington is more than 100 m thick and lexington deposition on the buildup continued into early edenian time as an intra platform shoal complex that tongues out into deeper water units in all directions in an attempt to understand how this shoal complex developed we examined the last major body of coarse skeletal sands in the central kentucky lexington limestone the upper tongue of the tanglewood member a 12 m thick succession of fossiliferous calcarenite and calcirudite that occurs across an area of 5200 km 2 near the center of the lexington platform although relatively homogeneous the upper tanglewood is divisible into five small scale fining upward sequence like cycles which contain prominent widespread deformed horizons facies analysis indicates that four lithofacies which reflect distinct depositional environments comprise the sequences across the shoal complex lithofacies were correlated across the shoal complex by integrating cyclicity and widespread deformed horizons in order to delineate the locations of major depositional environments facies analysis shows that the thickest and coarsest parts of each sequence and the shallowest depositional environments coincide with basement fault blocks which are known to have experienced uplift during earlier lexington limestone deposition the occurrence of thick coarse facies on the same blocks suggests that the blocks continued to experience uplift into shallow water where tides and waves redistributed sediments during upper tanglewood deposition although eustasy apparently controlled cyclicity taconian far field forces generated by orogeny in the east seem to have influenced facies distribution in each cycle through reactivation of basement fault zones as synsedimentary growth faults the example of the upper tanglewood member shows that tectonic far field forces can exert important influences on the development of carbonate depositional environments even in distal intracratonic settings like the lexington platform

far field tilting of laurentia during the ordovician and constraints on the evolution of a slab under an ancient continent during a brief period of 10 to 15 million years in the middle ordovician the michigan basin departed from its bull s eye subsidence pattern and tilted toward the east opening to the appalachian basin this tilting is observed in maps of tectonic subsidence estimated for the black river and trenton formations and extends over 300 km across the michigan basin and into eastern wisconsin contours of constant tectonic subsidence rate are approximately parallel to the inferred position of the laurentian iapetus convergent margin the distance between the inferred position of the subduction zone to the limit of tilting is approximately 1000 km three alternative models for the tilting are tested two relying on the rigidity of the continental lithosphere and a third on the viscous flow generated by a subducted slab in the first elastic model we assume the edge of the elastic plate is simply loaded from above by a fold and thrust sheet volcanic pile etc this model however cannot simultaneously satisfy the space of tectonic subsidence and subsidence rate even for lithospheres which have a rigidity of 10 28 nm in the second elastic model the laurentian continental margin descends into a trench of an eastward dipping slab that is a slab descending under the iapetus ocean this process cannot generate any significant far field displacements even for extremely rigid plates and must be rejected for the third model we use finite element solutions of a negatively buoyant slab in a viscous medium with a faulted lithosphere such slabs can easily generate not only realistic trenches on the under thrusting plate but also significantly tilt the lithosphere as much as 1000 km from the plate margin the magnitude and distribution of far field displacements depend on the age length and dip angle of the slab in contrast to the elastic models penetration of a west dipping slab beneath the continent can reproduce both the extent magnitude and rate of tectonic subsidence observed in the trenton and black river formations the observed data are best fit by an old slab 140 ma which initially descended at a moderate dip 20 30 for 10 15 m y which then steepened as the slab penetrated deeper into the mantle at the position of the previous ordovician plate margin there are narrow block faulted basins which underwent rapid subsidence 10 m y before the michigan basin tilted toward the east we propose that these earlier subsidence events were caused by the initial descent of the slab under the preexisting cambro ordovician passive margin the time lag of 10 m y may be due to the time it takes the slab to penetrate the upper mantle this result is important for understanding the time evolution of mantle convection and mechanisms for the initiation of subduction

a case study of the mechanics of extratropical influence on the initiation of the madden julian oscillation abstract mechanisms for extratropical influences on the initiation of the madden julian oscillation mjo are investigated using numerical simulations and a global reanalysis product previous simulations by a tropical channel model captured the timing and gross features of the initiations of two mjo events and suggested that the initiations were due to influences from the extratropics in this study latitudinal transport of momentum from the extratropics is found to be crucial in generating the lower tropospheric westerlies in the tropics associated with the mjo initiation the diagnoses of the zonal momentum budget for the mjo initiation region revealed that the advection by meridional winds could be important prior to the initiation of the mjo the time evolution of the wave activity identifies its source over the southern indian ocean where it grows by extracting kinetic energy from the mean flow the time scale of the lateral boundary conditions that is responsible for the mjo initiation is also inv

age and setting of the bronson hill magmatic arc a re evaluation based on u pb zircon ages in southern new england new u pb zircon ages of selected rocks from the bronson hill anticlinorium in southern new england are as follows microcline gneiss of the dry hill gneiss in the pelham dome believed to be metamorphosed alkali rhyolite is confirmed as late proterozoic yielding an age of 613 3 ma another sample shows strong evidence of zircon inheritance with a minimum mean age of 1402 ma plagioclase rich gneisses with associated amphibolites swanzey pauchaug monson and fourmile gneisses now believed to represent metamorphosed intrusive igneous rocks yield ages from 454 to 442 3 2 ma thus ranging from early late through latest ordovician consistent with other absolute ages of the oliverian plutonic series in the region quartz phyric rhyolite from the upper member of the ammonoosuc volcanics and rhyolite tuff from the partridge formation are dated at 453 2 ma and 449 3 2 ma respectively indicating that eruption of felsic lavas in the overlying volcanic section spanned an interval of approximately 4 m y additional zircon ages are reported from a crosscutting but deformed tonalite dike in the swanzey gneiss 381 3 ma and a coarse grained gabbro from the prescott intrusive complex 407 3 2 ma intrusive into the partridge formation metamorphic overprinting of the region during both the acadian and alleghanian orogenies is indicated by u pb titanite ages of 357 5 ma and 292 5 ma from a tonalite gneiss on prescott peninsula and the dry hill gneiss respectively the above ages and other zircon ages as well as petrography and geochemistry of the fourmile monson swanzey pauchaug and other plagioclase rich gneisses of the bronson hill anticlinorium suggest that they represent the plutonic root of a calc alkaline magmatic arc at least 250 km long that was produced partly or entirely on a continental margin in late ordovician time ca 454 442 ma the physically overlying cover sequence of chemically different tholeiitic arc volcanic and sedimentary rocks of the ammonoosuc volcanics and partridge formation previously thought to rest unconformably on the plagioclase rich plutonic gneisses is now shown to have had a magmatic history overlapping with them the zircon ages in the plutonic gneisses and the cover sequence indicate that both are the same age or slightly younger than the late ordovician caradocian emplacement of the giddings brook slice of the taconian allochthons and too young to have formed above an early and medial ordovician subduction zone

modulation of equatorial subseasonal convective episodes by tropical extratropical interaction in the indian and pacific ocean regions composite relationships among outgoing longwave radiation sea level pressure surface winds and upper tropospheric circulation are examined for northern winter during subseasonal episodes of eastward progression of convection from the indian ocean to the western pacific this evolution often culminates with westerly wind burst events and strong air sea interaction associated with regional scale convective blowups in the western equatorial pacific we first document some of these interactions in the composites for two timescales the submonthly 6 30 days and that of the madden julian oscillation mjo timescale 30 70 days we then analyze the december 1992 period during the tropical ocean global atmosphere coupled ocean atmosphere response experiment toga coare to illustrate how these composite relationships are manifested in a case study convection in the indian ocean for the composites is shown to be associated with a northern hemisphere wave train at 200 mbar arcing through the midlatitudes that can contribute to convective blowups farther east on the submonthly 6 30 days timescale in the intertropical convergence zone itcz in the eastern pacific the eastern asian trough that is part of this wave train is associated with pressure surges from the northern hemisphere and subsequent convection over southeast asia as the mjo convective envelope moves east to australasia midlatitude wave trains in either hemisphere include upper level troughs east of asia and australia and pressure surges from either hemisphere that contribute to pressure rises over the indonesian region and a subsequent shift of the convective envelope to the western pacific the vertical wind structure for the december 1992 case study is consistent with the composite surface and upper level winds and also shows strong vertical wind shear in the boundary layer a sharply defined westerly maximum near 700 mbar and an intensification of the upper level easterlies near 100 mbar very deep westerlies to 200 mbar are confined to shorter timescales the case study illustrates the various time and space scale interactions noted in the composites reciprocal interactions between the tropics and the midlatitudes on the submonthly and mjo timescales in both the composites and the case study involve pressure surges and wave interaction that influence subsequent convection as the convective envelope migrates eastward from the tropical indian to pacific ocean region

structure and characteristics of submonthly scale waves along the indian ocean itcz this study examines wave disturbances on submonthly 6 30 day timescales over the tropical indian ocean during southern hemisphere summer using japanese reanalysis jra25 jcdas products and national oceanic and atmospheric administration outgoing longwave radiation data the analysis period is december february for the 29 years from 1979 1980 through 2007 2008 an extended empirical orthogonal function eeof analysis of daily 850 hpa meridional wind anomalies reveals a well organized wave train pattern as a dominant mode of variability over the tropical indian ocean daily lagged composite analyses for various atmospheric variables based on the eeof result show the structure and evolution of a wave train consisting of meridionally elongated troughs and ridges along the indian ocean intertropical convergence zone itcz the wave train is oriented in a northeast southwest direction from sumatra toward madagascar the waves have zonal wavelengths of about 3 000 5 000 km and exhibit westward and southwestward phase propagation individual troughs and ridges as part of the wave train sequentially travel westward and southwestward from the west of sumatra into madagascar meanwhile eastward and northeastward amplification of the wave train occurs associated with the successive growth of new troughs and ridges over the equatorial eastern indian ocean this could be induced by eastward and northeastward wave energy dispersion from the southwestern to eastern indian ocean along the mean monsoon westerly flow in addition the waves modulate the itcz convection correlation statistics show the average behavior of the wave disturbances over the tropical indian ocean these statistics and other diagnostic measures are used to characterize the waves obtained from the composite analysis the waves appear to be connected to the monsoon westerly flow the waves tend to propagate through a band of the large meridional gradient of absolute vorticity produced by the mean monsoon westerly flow this suggests that the monsoon westerly flow provides favorable background conditions for the propagation and maintenance of the waves and acts as a waveguide over the tropical indian ocean the horizontal structure of the wave train may be interpreted as that of a mixture of equatorial rossby waves and mixed rossby gravity wavelike gyres

structural inversion and origin of a late ordovician trenton carbonate buildup evidence from the tanglewood and devils hollow members lexington limestone central kentucky usa abstract throughout east central united states lexington trenton limestones are largely late ordovician chatfieldian mid caradoc argillaceous skeletal calcarenites which are transgressive upward into late ordovician late chatfieldian edenian mid late caradoc shales and interbedded micrograined limestones in central kentucky however the same sequence is partially truncated by an unconformity and passes upward into a thicker younger edenian late caradoc regressive shoal complex of coarse calcarenites and calcirudites that is not generally typical of the lexington trenton sequence elsewhere the shoal complex is interpreted to have been a carbonate buildup and is partially bound by extant faults with basement precursors comparison of isopachous maps for pre and postunconformity buildup units with basement structural lineaments suggests that the buildup is related to reactivation and in one prominent case inversion of the basement structures the coincidence of structural reactivation inversion and buildup development with other major regional cratonic changes may reflect a reorganization of cratonic far field forces accompanying a nearly coeval reversal in the polarity of taconic subduction

global teleconnections in the 250 mb streamfunction field during the northern hemisphere winter abstract teleconnections of the streamfunction in the global domain based on ecmwf 250 mb winds for the 11 northern winters from 1978 79 through 1988 89 are documented in this study a zonal structure with a node near the equator indicating an out of phase relationship between the streamfunctions in the northern and southern hemisphere appears to mask the fluctuations of the asymmetric components of streamfunction after removing zonal means a global pattern emerges as the dominant structure in the low frequency band this pattern consists of several dipoles straddling either the exit region of midlatitude jets or the equator indicating the existence of teleconnections not only between the midlatitudes and the tropics but also between the northern and southern hemispheres teleconnection patterns in the intermediate frequency band are predominantly wavelike seven waveguides are identified based on the one point lag correlation maps for base points near the maximum teleconnectivity among them are thr

a case study of downstream baroclinic development over the north pacific ocean part ii diagnoses of eddy energy and wave activity the sequential development of a western and then an eastern north pacific cyclone is examined in terms of eddy energy and a phase independent wave activity based on the propagation of both a contiguous wave activity center and eddy energy the development of the western cyclone appears to influence its downstream neighbor a quantitative comparison of these two diagnoses is made in terms of group velocity and only minor differences are found during much of the initial evolution it is only once the tropopause undulations lose their wavelike appearance at which point application of the group velocity concept itself becomes quite tenuous that the downstream propagation of eddy energy seems faster than that of wave activity conventional methods of tracking this wave packet are also briefly discussed

soft sediment deformation in epicontinental carbonates as evidence of paleoseismicity with evidence for a possible new seismogenic indicator accordion folds abstract epicontinental seismicity is currently a subject of intense study by geologists and engineers particularly relative to triggering mechanisms epicentral areas and recurrence intervals aside from modern seismic events much of the evidence for previous events is in the form of soft sediment deformation which has often been systematically overlooked or misinterpreted carbonates have also been systematically ignored in most attempts to understand soft sediment deformation soft sediment deformation however is not a unique response to seismicity so how do we know when seismicity is implicated or not the concurrence of four criteria has been suggested as a way to confirm the likelihood of seismogenic origins for soft sediment deformation 1 presence of deformation consistent with a seismogenic origin 2 deformation that is widespread 3 deformation that can be temporally or stratigraphically constrained across its distribution and 4 deformation that is zoned across its distribution showing systematic increases in frequency size or intensity toward a likely epicentral area the greater the concordance of these criteria the more likely a seismogenic origin is in order to validate these criteria we scrutinized two very different examples of epicontinental carbonate soft sediment deformation which had been called seismites one from the shallow open marine upper ordovician lexington limestone of central kentucky usa and another from the peritidal dolomitic mesoproterozoic wumishan formation of northeast central china concurrence of criteria for lexington soft sediment deformation readily supports the case for a seismogenic origin whereas for wumishan deformation too few criteria were satisfied to implicate seismicity nonetheless after exclusion of all other possibilities for wumishan deformation seismicity stood out as the only likely cause although concurrence of the four noted criteria in soft sediment deformation almost certainly does indicate a seismogenic origin the co occurrence of criteria is rare and wholly dependent on past depositional environments and modern occurrence hence the four criteria cannot be used as universal seismogenic indicators and in the absence of such indicators we must continue to rely upon the integration of tectonic structural and paleoenvironmental clues for substitute corroboration

cold season synoptic scale waves over subtropical south america the most active winter synoptic scale wave patterns over south america are identified using an extended empirical orthogonal function eeof technique and are physically diagnosed using composite methods results show that the leading modes of short timescale variability propagate along two main paths over the subtropical jet latitudes 308s and over the subpolar jet latitudes 608s this research focuses on the subtropical mode and its evolution over south america the observed structure of the systems associated with the subtropical mode resembles that of midlatitude baroclinic waves both cyclonic and anticyclonic perturbations display significant modifications in their threedimensional structure as they evolve over extratropical and subtropical south america while the upper level perturbations are mostly unaffected when moving eastward the lower level perturbations advance following the shape of the andes mountains and exhibit an abrupt equatorward migration at the lee side of the mountains as a result of such detachment smaller eddy heat fluxes are observed in the vicinity of the orography and consequently a weaker eddy baroclinic growth is observed once the upper level system is on the lee side the perturbations acquire a more typical baroclinic wave structure and low level intensification of the system occurs the latter is largest around 1000 km east of the orography where enhanced moisture transports from tropical latitudes along the eastern portion of the low level cyclone favor precipitation occurrence over southeastern south america those precipitation processes seem to provide a diabatic source of energy that further contributes to the strengthening of the low level cyclone in addition an intensification of the cyclone once over the ocean was found in 60 of the situations considered which is consistent with previous research suggesting an additional source of moisture and heat flux due to the warm waters of the brazil current

large scale circulation associated with westerly wind bursts and deep convection over the western equatorial pacific the relationship between deep equatorial convection over the western pacific and atmospheric circulation during november to february 1986 1992 is studied using cross correlations between outgoing longwave radiation olr and national meteorological center global analyses we focus on intraseasonal convective events on the 6 to 30 day timescale over two regions just east of borneo and over the tropical ocean and global atmosphere toga coupled ocean atmosphere response experiment coare domain to the northeast of new guinea although comparatively little work has been done on this timescale we show that the bulk of the intraseasonal variability in both convection and low level circulation over the tropical western pacific occurs in this period range as a comparison with these higher frequency events the evolution of coare convection on the 30 to 70 day timescale is also considered the results of the historical data analysis are compared to a case study of deep convection associated with strong surface westerly winds during november 1989 this analysis is meant to serve as a benchmark for future case studies from the tropical ocean global atmosphere coare experiment and other periods in general 6 to 30 day equatorial convection in the regions studied occurs in conjunction with low level equatorial westerly wind anomalies paired anomalous cyclonic circulations straddling the equator and a strengthening of the sea level pressure gradient along the equator the increase in the pressure gradient appears most often tied to the simultaneous equatorward movement of high pressure systems originating over southeastern asia and australia a surge of trades over the central pacific also accompanies the development of convection over both study regions following the convective peak the low level westerlies slowly decay as the northern cyclone moves northwestward away from the equator in a track characteristic of a tropical depression it is also observed that low level westerly anomalies occur frequently without deep convection the vertical structure during convective events along the equator on the 30 to 70 day timescale and over indonesia in the 6 to 30 day band is baroclinic with easterly anomalies at upper levels overlying low level westerlies at 200 mbar a strengthened meridional outflow from the olr signal into a wave train on the equatorward side of the asian jet is observed to develop following the convective peak suggesting forcing of this circulation by the convection over the coare domain there is evidence that 6 to 30 day convection often occurs in conjunction with deep westerly flow it is suggested that these types of events are frequently characterized by vertical propagation of westerlies from the surface to the upper troposphere as is shown for a case study from november 1989 this westerly burst episode is shown to have many features in common with the typical case as defined from historical data

late middle to late ordovician seismites of kentucky southwest ohio and virginia sedimentary recorders of earthquakes in the appalachian basin synsedimentary ball and pillow beds breccias and faults in late middle to late ordovician foreland basin rocks of kentucky southwest ohio and virginia indicate broad zones of seismicity near the cincinnati arch and taconic orogenic front during deposition earthquake induced liquefaction formed seismites that include ball and pillow beds and rare sedimentary breccias that are correlative over large areas hundreds to thousands of square kilometers comparison of these features with liquefaction structures in holocene sediments indicates that the ordovician ball and pillow beds were probably generated by large earthquakes magnitudes 6 the ordovician seismites also provide information about epicenter location and the recurrence interval of large earthquakes in the ordovician foreland basin some were produced by faulting in the foreland and accretionary prism however horizons of resedimented lithoclastic breccias in the jeptha knob cryptoexplosive structure appear to correlate with several ball and pillow beds on jessamine dome along the cincinnati arch suggesting that some of the seismites may be genetically related to this enigmatic structure

barotropic wave propagation and instability and atmospheric teleconnection patterns abstract a global barotropic model linearized about the 300 mb climatological mean january flow is perturbed by applying a series of localized forcings distributed throughout the tropics and subtropics structures which resemble the observed pacific north american and east atlantic teleconnection patterns noted by wallace and gutzler 1981 tend to recur in the responses similar patterns are found to result from the dispersion of isolated initial perturbations placed at a variety of locations in the tropics and midlatitudes it is shown that these structures are related to the most rapidly growing mode associated with barotropic instability of the zonally varying climatological basic state in the absence of damping this mode has an e folding time of about a week and a period close to 50 days in localized regions the instantaneous growth rates can be competitive with those of baroclinic instability these episodes of rapid local barotropic growth are interspersed with intervals in which the local

seismic interpretation of dinantian carbonate platforms in the netherlands implications for the palaeogeographical and structural development of the northwest european carboniferous basin the northwest european carboniferous basin is characterized by a series of carbonate platforms and intervening shale dominated troughs during the dinantian sub period these structures have been mainly found along the margins of the basin here we present the results of an investigation of high quality 3d seismic surveys which has allowed the construction of a palaeogeographical and structural framework of the dinantian sub period in the centre of the northwest european carboniferous basin analysis of these data has revealed a series of structures characterized by flat tops well developed slopes and onlap by overlying strata these geometrical features suggest that the structures represent dinantian carbonate platforms an interpretation that is supported by recently published well data these findings suggest the following sequential depositional and structural model for the area 1 during the tournaisian stage carbonate sedimentation took place in basinal areas 2 continued subsidence probably induced by rifting resulted in the gradual onlap of carbonate deposition onto topographically higher areas 3 during the late visean stage rimmed shelf deposition took place by analogy with observations from the uk and belgium the seismically mapped structures represent these rimmed shelf carbonate platforms 2010 geological society of london

using black shales to constrain possible tectonic and structural influence on foreland basin evolution and cratonic yoking late taconian orogeny late ordovician appalachian basin eastern usa

extratropical tropical interaction during onset of the australian monsoon reanalysis diagnostics and idealized dry simulations abstract the onset of the australian monsoon is examined using i reanalysis data for seasons when enhanced observational networks were available and ii a 15 yr onset composite similar to previous findings onset is characterized by a sudden strengthening and deepening in tropical westerly winds which are overlain with upper tropospheric easterlies all onsets are preceded by up to a 7 day preconditioning period of enhanced vertical motion and moistening during the transition season the 6 weeks prior to onset a number of moist westerly events occur generally they are only sustained for short periods and overlain by upper level westerly winds suggesting an association with midlatitude troughs which protrude into the deep tropics for individual years and for a 15 yr composite monsoon onset is associated with major cyclogenesis events over the southwest indian ocean in the presence of a subtropical jet over the eastern indian ocean the proposed mechanism for extratropical tropical interaction i

the thor suture zone from subduction to intraplate basin setting the crustal seismic velocity structure of northwestern europe shows a low p wave velocity zone lvz in the lower crust along the caledonian thor suture zone tsz that cannot be easily attributed to avalonia or baltica plates abutting the tsz the lvz appears to correspond to a hitherto unrecognized crustal segment accretionary complex that separates avalonia from baltica explaining well the absence of avalonia further east consequently the northern boundary of avalonia is shifted 150 km southward our interpretation based on analysis of deep seismic profiles places the lvz in a consistent crustal domain interpretation a comparison with present day examples of the kuril and cascadia subduction zones suggests that the lvz separating avalonia from baltica is composed of remnants of the caledonian accretionary complex if so the present day geometry probably originates from pre variscan extension and eduction during devonian carboniferous backarc extension the reinterpretation of deep crustal zonation provides a crustal framework in which the northern limit of avalonia corresponds to the southern limit of the deep north german basin and the northern limit of prolific gas reservoirs and late mesozoic inversion structures 2016 geological society of america

extratropical forcing of tropical wave disturbances along the indian ocean itcz the role of extratropical waves in the excitation of tropical waves on submonthly timescales is explored along the indian ocean intertropical convergence zone itcz during the austral summer using japanese reanalysis products and noaa outgoing longwave radiation data the analysis period is december february of 1979 1980 to 2008 2009 the submonthly tropical waves are regarded as a type of rossby wave propagating along the mean monsoon westerly flow they play an important role in modulating the indian ocean itcz convection the linkage between the tropical and extratropical waves which is responsible for the formation and strengthening of tropical waves is examined composite analysis results linked to the tropical wave train development show that the midlatitude rossby wave train progresses eastward and northeastward from the south atlantic into the subtropical indian ocean as a trough and ridge that form part of the midlatitude wave train approach the southern africa southwest indian ocean swio region a southwest northeast oriented wave train is subsequently established originating from this feature and is strengthened across the tropical indian ocean the midlatitude wave propagation toward the subtropics induces the growth of the trough and ridge over the swio wave activity flux diagnostics indicate that the amplified trough and ridge over the swio act as an energy source for northeastward amplification of the tropical waves through the wave energy dispersion process the results suggest that the propagation of the midlatitude wave toward the swio is the fundamental mechanism behind the development of the tropical waves along the indian ocean itcz

interactions between enso transient circulation and tropical convection over the pacific abstract the interannual variability of transient waves and convection over the central and eastern pacific is examined using 30 northern winters of ncep ncar reanalyses 1968 69 1997 98 and satellite outgoing longwave radiation data starting in 1974 there is a clear signal associated with the el nino southern oscillation such that differences in the seasonal mean basic state lead to statistically significant changes in the behavior of the transients and convection with periods less than 30 days which then feed back onto the basic state during a warm event el nino phase the northern hemisphere subtropical jet is strengthened over the central pacific the region of upper tropospheric mean easterlies over the tropical western pacific expands eastward past the date line and the upper tropospheric mean westerly duct over the tropical eastern pacific is weakened the transients tend to propagate along the almost continuous waveguide of the subtropical jet equatorward propagation into the westerly

cross equatorial influences of submonthly scale southerly surges over the eastern indian ocean during southern hemisphere winter 1 lower tropospheric southerly surges occurring at submonthly timescales over the eastern indian ocean eio during southern hemisphere sh winter are extratropical tropical interaction phenomena involving various processes this study examined the physical mechanism driving equatorial wave disturbances associated with surge induced cross equatorial flow over the eio japanese 25 year reanalysis jra25 and tropical rainfall measuring mission satellite trmm 3b42 data products from june to august for the 7 years from 1998 to 2004 were analyzed composite analyses of low level wind and vorticity fields reveal that an equatorial clockwise gyre develops just after cross equatorial penetration of southerly surge winds this gyre is interpreted as an equatorially trapped rossby wave that develops asymmetrically around the equator in response to surge induced cross equatorial flow eddy vorticity budget analysis demonstrates the dynamic role of the southerly surge in the genesis of the equatorial clockwise gyre the result indicates that an injection of negative absolute vorticity into the equatorial tropics due to both advective and convergent processes associated with the surge winds is primarily responsible for the gyre genesis cross equatorial advection of basic state absolute vorticity by the surge eddy winds and vortex stretching by surge wind convergence are most effective in spinning up the equatorial clockwise gyre wave activity flux analysis further emphasizes that rossby wave energy propagation from the sh extratropics into the equatorial eio region is caused by the southerly surge these dynamic diagnostics suggest that the southerly surge plays a lateral forcing role in exciting the equatorial wave disturbance over the eio composite analyses of moisture flux and precipitation anomalies characterize the equatorial clockwise gyre as a convectively coupled equatorial rossby wave enhanced cross equatorial moisture transport due to the southerly surge appears to be linked to precipitation along the west coast of the southern indo china peninsula a case study of the southerly surge event during august 2000 illustrates the formation of the equatorial clockwise gyre and its convectively coupled equatorial rossby wave signature

overview of the meteorological conditions and atmospheric transport processes during indoex 1999 we give an overview of the regional meteorological situation during the indian ocean experiment indoex intensive field phase ifp in february and march 1999 the indoex domain reaching from 30 n to 30 s and from 50 e to 100 e was chosen because the low level outflow of pollution from india is carried by the northeasterly trades into the tropical convergence zone where cloud processing modifies the properties of the aerosols in contrast there is also an inflow of pristine southern hemispheric air by the southeasterly trades into the convergence zone however during the 1999 ifp some deviations from the climatological mean were observed in 1999 the intertropical convergence zone itcz was broken into a northern convergence zone and a southern convergence zone during february the northern zone was more active and the cross equatorial flow n s was weak both suggesting that less pollution was transported to the southern hemisphere in february it was occasionally possible to sample a southern hemispheric air mass on the southern side of the indoex domain during march 1999 the southern convergence zone became dominant and moved to a more southern position near 5 10 s it is shown that four channels carry pollution into the indoex domain 1 ne trades over the western arabian sea 2 nw ne flow along the west coast of india 3 ne trades over the west bay of bengal and 4 ne flow from se asia the strength of each channel is modulated by transients moving across pakistan and northern india western disturbances the heating of the indian subcontinent in march resulted in a eastern shift of the subtropical high from central india to the bay of bengal which also affected channels 2 3 and 4 episodes of high and low carbon monoxide concentrations as measured in kaashidhoo maldives during the 1999 ifp can qualitatively be explained by the operationality of the flow channels determined through trajectory analyses in combination with the intensity of the northern convergence zone

revised stratigraphic framework of pre westphalian carboniferous petroleum system elements from the outer moray firth to the silverpit basin north sea uk

revision and update of the stratigraphic nomenclature of netherlands in 1991 the geological survey of the netherlands started a project for revision and updating of the pre quaternary lithostratigraphy of netherlands this had not been done systematically since 1980 main objective of the study are 1 to bring the lithostratigraphic ideas into agreement with new findings and increased knowledge of dutch subsurface geology lithostratigraphy was extended into the lower carboniferous and devonian 2 expansion and standardization of the definitions and descriptions of existing lithostratigraphic units 3 application of modern concepts e g sequence stratigraphy in order to describe better the distribution of reservoir prone sediments and 4 to reach consensus on a number of stratigraphy related subjects such as a chronological time frame application of biozonations and the designation of the behavior of main structural elements through time eight working groups were formed each working on a specific aspect or stratigraphic interval under the supervision of a steering committee both working groups and steering committee were composed of persons from the geological survey several leading oil companies and in some cases universities several working groups have completed their tasks and updates of these stratigraphic intervals are available at the conference posters will display stratigraphic updates of lithostratigraphy for the carboniferous zechstein lower triassic more and upper jurassic lower cretaceous less

early carboniferous extension in east avalonia 350 my record of lithospheric memory abstract despite reactivations during variscan and alpine orogenies and the opening of the northern atlantic avalonia is one of the few regions where the initial mid paleozoic basin structure is still recognisable largely intact and well studied its kinematics and dynamics remain however largely unknown in particular in view of the successive late paleozoic to recent evolution of the basin consequently the importance of the mid palaeozoic tectonic evolution and structural controls are often overlooked and poorly understood in basin studies in this paper we reassess the importance of mid palaeozoic tectonics on subsequent sedimentary basin evolution of north western europe to this end we analyse the dynamics of early variscan extension in avalonia based on the integration and re evaluation of available geophysical and geological data from lithosphere to basin scales based on a revised crustal map of the thor suture zone we present a new paleo tectonic reconstruction and tectonic scenario for the devonian carboniferous rifting these findings are key for a better understanding of long lived tectonic segmentation and post rifting deformation phases our findings indicate that the structural grain of many crustal fault dominated sedimentary basin structures such as the north sea central graben were created in the early carboniferous consequently the main basement structuration of northwest europe was completed before the variscan orogeny and successive post variscan extension and inversion phases reactivated the existing basement structures without creating major new fault groups incorporation of the paleozoic structural grain allows for a consistent tectonic framework for the mesozoic contributing to fundamental understanding of basin evolution from our tectonic framework analysis avalonia therefore stands out as a fine example of long lived lithosphere memory spanning over 350 my of structural control in geodynamic evolution

interactions between synoptic intraseasonal and interannual convective variability over southern africa after removing the annual cycle a principal component analysis is applied to the daily outgoing longwave radiation anomaly field used here as a proxy for atmospheric convection the analysis is carried out over the southern african region 7 5 e 70 e 10 s 40 s for austral summer november through february for the period 1979 1980 to 2006 2007 the first five principal components pc are retained the first two pcs describe spatial patterns oriented north west to south east from tropical southern africa sa to the mid latitudes they are interpreted to be different possible locations for synoptic scale tropical temperate troughs ttt one dominant rainfall producing synoptic system in the region the phase relationship between these two pcs describes a tendency for these ttt to propagate eastwards from sa to the mozambique channel and southern madagascar the next three pcs describe convective fluctuations respectively located over the north west the south and the centre of sa their time series are significantly associated with madden julian oscillation mjo activity in the tropics however we find that ttt systems are statistically independent of the mjo i e they are equally liable to occur during any phase of the mjo three pcs out of five also show a significant association with el nino southern oscillation confirming that el nino years mostly coincide with suppressed convection at the intraseasonal time scales a result consistent with its impact on seasonal averages diagnosed in previous studies

geology and thermal maturity of namurian deposits in the němcicky sub basin as the south eastern continuation of the upper silesian coal basin czech republic abstract the southernmost documented occurrences of namurian coal bearing strata can be found in the n mcicky area se moravia that is considered to be the southern continuation of the upper silesian coal basin since the south eastern moravia belongs to the most prospective areas in terms of hydrocarbon exploration and production in the czech republic and namurian deposits are considered to be one of the potential source rocks there was a systematic evaluation of the southernmost occurrence of coal bearing carboniferous deposits in the czech republic during the hydrocarbon exploration within the area with regard to the regional geological setting and thermal maturity 2d and high quality 3d seismic surveys were used for a detailed thermal maturation analysis and a determination of the regional situation of heavily faulted eroded namurian strata cores and cuttings of coal and siltstones were used from 8 boreholes to investigate and measure the vitrinite reflectance the lithology and petrography definition was also done based on thin sections all new measurements were compared with archived data and older studies in the n mcicky sub basin the complete sedimentary succession occurs as part of typical cyclic development starting with basal conglomerates and followed by sandstones alternating with claystones siltstones and coal seams of marine and transitional origin samples from the nikolcice kurd jov ridge are showing significantly lower vitrinitte reflectance values with respect to their depths than those from the nesvacilka graben this fact is supporting the distinctive lateral movement along the western nesvacilka fault as presumed from the seismic interpretation dominant source from immature orogen is combined with the source from the mature continetal block i e opposite margin of the basin the seismic interpretation shows that the thicknesses of namurian deposits are not decreasing at all towards the recently deeper positions accordingly it is suggested that it is right within this erosionally untouched accommodational space of the n mcicky sub basin where we can find the interconnection to the uscb in the north

tropical extratropical interactions over southern africa three cases of heavy summer season rainfall abstract the synoptic evolution of three tropical extratropical te interactions each responsible for extreme rainfall events over southern africa is discussed in detail along with the consideration of previously studied events common features of these heavy rainfall producing tropical temperate troughs ttts over southern africa are discussed it is found that 2 days prior to an event northeasterly moisture transports across botswana set up by the angola low are diverted farther south into the semiarid region of subtropical southern africa the ttts reach full maturity as a te cloud band rooted in the central subcontinent which is triggered by upper level divergence along the leading edge of an upper tropospheric westerly wave trough convection and rainfall within the cloud band is supported by poleward moisture transports with subtropical air rising as it leaves the continent and joins the midlatitude westerly flow it is shown that these systems fit within a theoretical framework describing

recurrent daily olr patterns in the southern africa southwest indian ocean region implications for south african rainfall and teleconnections a cluster analysis of daily outgoing longwave radiation olr anomalies from 1979 to 2002 over the southern africa southwest indian ocean swio region for the november to february season reveals seven robust and statistically well separated recurrent patterns of large scale organized convection among them are three regimes indicative of well defined tropical temperate interactions linking the hinterland parts of southern africa to the mid latitudes of the swio preferred transitions show a tendency for an eastward propagation of these systems analysis of daily rainfall records for south africa shows that six of the olr regimes are associated with spatially coherent and significant patterns of enhanced or reduced daily rainfall over the country atmospheric anomalies from the ncep doe ii reanalysis dataset show that the olr regimes are associated with either regional or near global adjustments of the atmospheric circulation the three regimes representative of tropical temperate interactions being in particular related to a well defined wave structure encompassing the subtropical and temperate latitudes featuring strong vertical anomalies and strong poleward export of momentum in the lee of the location of the cloud band the time series of olr regimes seasonal frequency are correlated to distinctive anomaly patterns in the global sea surface temperature field among which are shown to be those corresponding to el nino and la nina conditions the spatial signature of el nino southern oscillation s enso influence is related to the combination of an increased decreased frequency of these regimes it is shown in particular that the well known dipole in convection anomalies contrasting southern africa and the swio during enso events arises as an effect of seasonal averaging and is therefore not valid at the synoptic scale this study also provides a framework to better understand the observed non linearities between enso and the seasonal convection and rainfall anomalies over the region

can thin coals be resolved in seismic data an example of the challenges for carboniferous visean to westphalian source rock definition across the elbow spit platform netherlands and the mid north sea high uk through well synthetic modelling