observations of a cut off low over southern australia the structure and evolution of an intense cut off low is documented in detail unprecedented for the australian region by combining high time resolution radiosonde profiles with co located wind profiler observations and routine australian bureau of meteorology analyses the cut off low develops over the ocean south of australia and subsequently interacts with a subtropical frontal system over the central part of the continent throughout the period of observation the strongest temperature gradients lay through the subtropics moreover the subtropical temperature gradients strengthened while the midlatitude temperature gradients associated with the cut off low weakened the australian bureau of meteorology s 150 km regional assimilation and prognosis system analyses capture the broad scale structure and evolution of the system reasonably well the system documented here is similar in structure to the instant occlusion investigated by browning and hill 1985 the major difference being that our cut off low develops poleward of a subtropical front the cut off low was cold cored and produced a very deep tropopause fold over adelaide the tropopause descended to an altitude of about 5 km and the temperature at 500 hpa fell to 30 c the western edge of the low level cold dome was marked by a strong secondary warm front which passed over adelaide about 8 hours after the tropopause height minimum the warm front was characterized at the surface by an absolute minimum in the pressure and a temperature rise of about 7 c significantly this increase in temperature took place in the early hours of the morning against the diurnal trend the cut off low produced very high rainfalls resulting in flash flooding and much damage in the adelaide hills area the most severe convection took place in the region behind the lowered tropopause around the passage of the warm front

australian east coast cyclones part i synoptic overview and case study abstract the meteorological conditions for the development of australian east coast cyclones are described the main synoptic precursor is a trough or dip in the easterly wind regime over eastern australia the cyclones are a mesoscale development which occurs on the coast in this synoptic environment they form preferentially at night in the vicinity of a marked low level baroclinic zone and just equatorward of a region of enhanced convection resulting from flow over the coastal ranges three different types of east coast cyclone have been identified types 1 and 3 are very small systems which can have lifetimes as short as 16 hours during which hurricane force winds have been observed to develop the other type 2 system is a meso synoptic scale cyclone that can bring sustained strong winds and flood rainfall over several days because of their intensity rapid development and occasional tiny size these systems are a major forecast problem

mid cretaceous sequence stratigraphy and sedimentary cyclicity in the western paris basin abstract cenomanian and turonian depositional patterns of the western paris basin are interpreted in terms of sequence stratigraphy a system tract analysis of the epicontinental normandie basin with pelagic chalks and of the maine platform covered by clastics provides evidence for relative changes in coastal onlap various minor uncomformities are related to these changes of sea level the four global cycles uza or zc 2 2 2 5 of haq et al 1987 1988 are recognised while an additional one is proposed for the geslinianum zone in addition periodic rhythmic cycles are commonly registered within the chalk expressed by the repitition of various facies enhanced both by biosedimentary processes and diagenetic alteration these elementary climatic cycles allow accurate lithostratigraphic correlations during this period when the sea level peaked on the tectonically passive border of the armorican block the paris basin appears to record a detailed set of events which can be correlated with those in the atlantic boreal and tethyan provinces

tsunamis in the aeolian islands southern italy a review the aeolian islands located in the south tyrrhenian sea to the west of calabria and to the north of sicily constitute the aeolian volcanic arc characterized by a relevant volcanic activity with an established tsunamigenic potential according to the documentary sources that are available for the aeolian tsunamis and that cover unfortunately only about the last 100 years stromboli is responsible for the majority of the events some cases are also known to have occurred at the islands of salina and vulcano in terms of intensities the most destructive events are those originated by the stromboli volcano reported to have produced severe destruction to boats and houses and to have even caused injuries and fatalities in this work we focus on the historical events and discard the paleotsunami occurrences that were probably associated with the ascertained flank collapses of the volcanic cones we also neglect the recent destructive tsunamis of 30 december 2002 which were caused by a series of mass failures at the sciara del fuoco since observations and analyses are of such an amount that deserve to be illustrated in devoted papers the bulk of the present research consisted in collecting all the available data on the historical cases the first in order of time is the july 1916 stromboli tsunami with the purpose of casting more light on their generation mechanism and on their effects and consequently of contributing to the studies on assessment of tsunami hazard and risk in the aeolian islands and in the southern tyrrhenian sea

facies architecture and sequence stratigraphy in glacially influenced basins basic problems and water level glacier input point controls with an example from the quaternary of ontario canada abstract sequence architecture is controlled by two fundamental factors the water level relative to the depositional surface which controls accommodation space and the points or areas of sediment injection which control how this space is filled in relative water level accommodation space and injection points normally vary together and various genetic terms are used to define systems tracts but in glacially influenced basins accommodation space is controlled not only by water level but also by the glacier injection points are similarly dually controlled by water level and by the terminus of the glacier during high lake levels the injection point of the glacier may be underwater at the base of the slope genetic terms like highstand and lowstand therefore are meaningless in successions controlled by sediment input points which are independent of water levels and accommodation space distinct water level and glacier input point systems can occur side by side the water level system controlled by lake level or sea level the glacier input point system controlled by the position of the subaqueous glacier front and both can form juxtaposed systems passing laterally into each other a bewildering and incompatible terminology is needed if the terms of genetic sequence stratigraphy are used for both water level and glacier input point systems because the sedimentary injection points and sequence boundaries of the two systems fluctuate out of phase with one another sequences developed by movement of the glacier are completely independent of those controlled by water levels if genetic sequence stratigraphy is applied to a basin with both lake level and glacier input point systems then each needs separate genetic terminologies to describe them which leads only to confusion however descriptive sequence stratigraphy allostratigraphy can be readily applied to successions like the quaternary of lake ontario we therefore suggest that genetic sequence terms be discarded and simpler allostratigraphic terminology used in glacially influenced basins

central australian cold fronts abstract this paper presents an observational study of the structure and behavior of cold fronts over central australia during the late dry season a time of year when the prefrontal convectively well mixed layer is particularly deep the study is based on the results of the central australian fronts experiments cafe held in 1991 three fronts were documented in unprecedented detail for the australian region using a greatly enhanced surface observing network and a boundary layer wind profiler as well as serial upper air soundings data on the surface energy balance were obtained also a common feature of the fronts observed during cafe was that they were dry shallow 1 km deep and moved into a deep 4 km convectively well mixed boundary layer one of them initiated major dust storms across central australia a prominent feature of the fronts was the marked diurnal variation of their surface signature as they moved through the network noteworthy was the tendency during the night for the initiatio

numerical simulation of the landslide induced tsunami of 1988 on vulcano island italy on 20 april 1988 a landslide of approximately 200 000 m3 occurred on the northeastern flank of the volcano la fossa on the island of vulcano the landslide fell into the sea producing a small tsunami in the bay between punte nere and punta luccia that was observed locally in the neighbouring harbour called porto levante the slide occurred during a period of unrest at the volcano that was monitored very accurately the study of this event is composed of two parts the simulation of the landslide and the simulation of the ensuing tsunami the former is studied by means of a lagrangian type numerical model in which the landslide is seen as a multibody system an ensemble of material deforming blocks interacting together during their motion the latter is simulated according to the eulerian view by solving the shallow water approximation to navier stokes equations of fluid dynamics with the incorporation of a forcing term depending on the slide motion technically the slide evolution is computed first and this result is then used to evaluate the excitation term of the hydraulic equations and to calculate the tsunami propagation computed wave fronts radiate both toward the open sea with rapid amplitude decay and along the shore in the form of edge waves that lose energy slowly comparison between model outputs and observations can be carried out only in a qualitative way owing to the absence of tide gauge records and results are satisfactory

numerical modeling of the september 13 1999 landslide and tsunami on fatu hiva island french polynesia 1 on september 13 1999 omoa bay fatu hiva island french polynesia was struck by 2 to 5 m high water waves several buildings were flooded and destroyed but no lives were lost observations gathered during a post event survey revealed the recent collapse into the sea of a 300 300 m2 at least 20 m thick cliff located 5 km southeast of omoa this cliff failure most certainly triggered the tsunami waves since the cliff was reported intact 45 min earlier we simulate the tsunami generation due to a subaerial landslide using a finite difference model assimilating the landslide to a flow of granular material numerical modeling shows that a 0 0024 km3 landslide located in the presumed source area accounts for the tsunami waves reported in omoa bay we show that the striking amplification observed in omoa bay is related to the trapping of waves due to the shallow submarine shelf surrounding the island

climatology and dynamics of the link between dry intrusions and cold fronts during winter part ii front centred perspective the conceptual picture of an extratropical cyclone typically includes a cold front and a dry intrusion di behind it by objectively identifying fronts and dis in ecmwf era interim data for 1979 2014 part i quantified the climatological relationship between cold fronts and dis driven by the finding that front intensity and frontal precipitation are enhanced in the presence of dis here we employ a front centred perspective to focus on the dynamical and thermodynamical environment of cold fronts with and without dis in the northern hemisphere winter distinguishing between trailing fronts that connect to a parent cyclone and isolated fronts examples of dis behind each type illustrate the baroclinic environment of the trailing front and the lack of strong temperature gradients across the isolated front composite analyses of north atlantic and north pacific fronts outline the major differences in the presence of dis compared to similar fronts but without dis in their vicinity the magnitude and spatial structure of the modification by dis depends on the front intensity yet generally with dis trailing fronts occur with stronger slp dipole deeper upper tropospheric trough stronger 10 m wind gusts enhanced ocean sensible and latent heat fluxes in the cyclone cold sector and heavier precipitation isolated weak fronts exhibit similar behaviour with different spatial structure this study highlights the central role of dis for shaping the variability of fronts and their associated environment and impact

response to high frequency sea level change in a fluvial to estuarine succession cenomanian palaeovalley fill bohemian cretaceous basin

retreat rates modalities and agents responsible for erosion along the coastal chalk cliffs of upper normandy the contribution of terrestrial laser scanning in order to follow all the changes affecting the coastal chalk cliff face in upper normandy and improve knowledge about cliff erosion repeated terrestrial laser scanning tls surveys were carried out frequently between 2010 and 2013 every 4 5 months they were conducted at two sites with similar lithostratigraphic characteristics but different exposures to marine actions the former being an abandoned cliff and the latter an active cliff they provide a quantification of the production of debris with centimeter precision from 0 01 to 0 04 m these surveys provided three major outcomes 1 cliff retreat rates were measured at high spatial resolution with retreat values unsurprisingly 3 4 times higher for an active cliff than for an abandoned cliff this result highlights that marine actions should be seen as not only a transport agent but also a particularly effective erosion agent 2 a significant proportion of debris fall production about 25 in the total active cliff retreat was identified and 3 one of the modalities of retreat was visualized as the creation of a basal notch which propagates instability towards the upper part of the cliff face later this instability generates rock falls coming from the whole cliff face

tsunami wave height dependence on landslide volume tsunami generation from submarine landslides depends mainly on the volume of the slide material and also on other factors which include angle of the slide water depth density of the slide material the speed with which the material moves duration of the slide etc based on an incomplete data set of volume v of slide versus maximum amplitude h of the resulting tsunami waves gleaned through available literature a simple linear regression relationship was developed another partial data set was developed also from published literature on v versus h values based on numerical models it was found that the agreement between the results of the numerical simulations and the observations is rather poor it is not clear why this is so and which data set is of questionable relevance this is not to cast doubt on numerical models that do not use volume of the slide in an explicit manner

linear and nonlinear computations of the 1992 nicaragua earthquake tsunami numerical computations of tsunamis are made for the 1992 nicaragua earthquake using different governing equations bottom frictional values and bathymetry data the results are compared with each other as well as with the observations both tide gauge records and runup heights comparison of the observed and computed tsunami waveforms indicates that the use of detailed bathymetry data with a small grid size is more effective than to include nonlinear terms in tsunami computation linear computation overestimates the amplitude for the later phase than the first arrival particularly when the amplitude becomes large the computed amplitudes along the coast from nonlinear computation are much smaller than the observed tsunami runup heights the average ratio or the amplification factor is estimated to be 3 in the present case when the grid size of 1 minute is used the factor however may depend on the grid size for the computation

application of wavelet transform analysis to landslide generated waves the aim of this paper is to illustrate the results of a preliminary study on aerial landslide generated waves which has been mainly intended to establish a method for analyzing water surface records some simple physical experiments reproducing the scott russell s wave generator were carried out in a small two dimensional wave flume the wavelet transform wt is applied to analyze wave measurements and it is shown that useful information can be obtained by means of this technique the celerity of impulsively generated waves reflection by an overflow structure and seiching phenomena of the flume are studied a discussion of the results along with some remarks about ongoing research is also given

detecting compositional spatial and temporal attributes of glaucony a tool for provenance research abstract a reliable interpretation of glaucony bearing units requires the characterization of compositional spatial and temporal attributes of glaucony the criteria that can readily determine the differentiation of the various types of glaucony autochthonous parautochthonous or allochthonous intrasequential and detrital or allochthonous extrasequential are discussed in detail autochthonous vs allochthonous glaucony may be often detected on the basis of detailed sedimentological investigations including facies interpretation of glaucony bearing deposits and careful examination of spatial distribution of glaucony textural and morphological features although generally not diagnostic on their own provide a significant contribution to glaucony interpretation the distinction between parautochthonous and detrital glaucony can be sometimes performed by radiometric dating more commonly it requires that compositional attributes of glaucony be matched against those of putative sources glauconies from distinct parent rocks generally have different maturity and carry unique geochemical and mineralogical fingerprints that may contribute definitive data for provenance research previous work on glaucony and examples from units formed in tectonically stable areas cretaceous eocene deposits of paris basin and hampshire basin and active tectonic basin settings miocene strata of southern alps and northern apennines provide the opportunity to discuss the validity of the proposed criteria across different structural domains and emphasize the need for an integrated approach to the study of glaucony

large scale potential vorticity anomalies and deep convection the effect on deep convection of large scale potential vorticity pv anomalies and their associated tropospheric stable layers is complex and not well understood this article examines the meteorological events of 9 july 2007 iop7b of the convective and orographically induced precipitation study cops which was dominated by an upper level pv anomaly that stretched from the uk to southern france and as far northeast as denmark three precipitation regions were identified from the case lines of intense storms beneath the pv anomaly less intense more widespread convective precipitation to the east of the pv anomaly and in between a region of no precipitation the latter of these coincided with the high resolution measurements and model analyses from cops the extensive and varied data analyzed in this investigation show that convective available potential energy cape was present in this region the distribution of cape and convective inhibition cin is presented via an innovative pseudo 3d visualization that allows horizontal and vertical interactions to be considered however convection was capped by a complex arrangement of dry layers the base of the key layer was at 750 hpa these dry layers descended separately from the upper troposphere moving around the pv anomaly as it developed from a breaking rossby wave to the west during the seven days before the iop this case adds to other studies that show that descent of complex dry layers is an important mechanism for forming convection inhibiting atmospheric lids in western europe a simple conceptual model is developed that synthesizes the effect of large scale pv anomalies on deep convection from a series of consistent case studies this model has significant implications for storm forecasting and projections of storminess in future climates as it highlights the importance of thin structures that can advect hundreds of km before having an impact copyright 2012 royal meteorological society

the cenomanian turonian boundary event ctbe in northern lebanon as compared to regional data another set of evidences supporting a short lived tectonic pulse coincidental with the event abstract constrained by both foraminifera and isotope data the zeitoun and nahr ibrahim sections in northern lebanon record a steady flooding of the cenomanian carbonate platform during the uppermost cenomanian lower turonian interval the flooding began just before the inception of the ctbe 13c positive shift it is marked by the deposition of finely bedded to laminated fine grained limestone overlying platformal carbonates this scenario is entirely different to what has been published in northern israel where repeated emergences are instead recorded during the event a survey of published data from nearby middle east countries to north africa suggests that the ctbe is accompanied on a larger scale especially along the syrian arc by tectonic disturbances responsible for sequence stratigraphic heterogeneity and palaeogeographic changes detailed analysis of available data makes it possible to extract from the sedimentary record four sequence stratigraphic scenarios implying two phases of heterogeneity bounding the event and responsible for the outphasing of relative sea level changes in some sensitive areas these disturb a stepped early cenomanian to early turonian overall transgressive trend recorded in some large stable areas often used to support the concept of mesozoic eustasy the discussion focuses on the global processes that are possibly involved the hypothesized tectonic pulse does not explain the ctbe it is just another set of data to be taken into account in the search for causes

mesoscale analysis of a polar trough interacting with a polar front the interaction of a polar trough with a polar front can lead to a characteristic satellite cloud pattern commonly referred to as an instant occlusion the detailed structure and development of an event rather resembling an instant occlusion is analysed in this paper using routine data supplemented by additional radiosondes soundings and cloud imagery from noaa 7 and meteosat and radar network pictures the event presented differs from an instant occlusion as described by anderson and others in that a band of polar front cloud developed simultaneously with the band of cloud associated with the polar trough rather than being a pre existing feature thus we refer to it under the different name of pseudo occlusion in order to keep this distinction in mind a conceptual model of the pseudo occlusion is developed in which the key elements are i a moist relatively warm low level jet associated with the polar trough referred to as the polar trough conveyor belt and ii a major upper level jet streak associated with the polar front referred to as the polar front conveyor belt the two conveyor belts intersect almost at right angles precipitation associated with the polar front is predominantly from stratiform cloud whereas that associated with the polar trough is a mixture of stratiform and convective just on the poleward side of the upper jet the cloud top drops abruptly here dry air having recently descended beneath the tropopause fold suppresses the depth of the moist air associated with the polar trough conveyor belt this leads to a minimum in the intensity of precipitation between the rain areas associated with the trough and the front although the air overrunning the trough just on the poleward side of the polar front is dry as a result of earlier descent the air in this location is likely to have begun ascending as part of the indirect circulation in the exit region of the upper level jet streak the polar trough low level jet probably forms part of this circulation

a dynamic model for rainfall induced landslides on natural slopes assessment of landslide hazard often requires a good knowledge of the landslide characteristics and runout mechanics in this paper a quasi three dimensional model using lagrangian finite element method lfem is formulated to reproduce the dynamic runout process caused by landslides a case study of rainfall induced landslide on a natural slope in 1993 in lantau island hong kong is presented voellmy rheology is adopted to characterize the multi dimensional runout behaviour for engineering applications the selection of appropriate rheology and the determination of relevant key parameters associated with the failure mechanisms and runout mechanics are highlighted details of the mathematical formulation particularly with respect to the stability of the numerical scheme and quality control of the mesh are provided the close correlation between the calculation results and the field observations shows that if an appropriate rheological relationship is selected for the simulation a reasonable description of the runout behaviour can be obtained using the present model implications of the potential hazard from natural terrain landslides to downslope development are also discussed used in conjunction with geographical information system gis database the model can also be applied to the preliminary hazard zoning of terrain and land use management in mountainous areas

cyclone anticyclone couplets over north america part ii analysis of a major cyclone event over the eastern united states abstract the evolution of a major cyclone over eastern north america in march 1971 is described a noteworthy feature of the development in addition to the extreme baroclinity was the substantial thermal advection upward from the middle troposphere to the lower stratosphere in conjunction with a strongly sloping tropopause strong cold air advection into the trough aloft was associated with subsidence and vortex tube stretching above 500 mb the vorticity so generated was advected downstream to support exceptional surface development a deep layer of air with potential vorticity values characteristic of stratospheric air was advected downward to 600 mb immediately upstream of the deepening surface cyclone the region of positive potential vorticity advection coincided with the area of computed quasi geostrophic height falls and lay along the leading edge of the massive cold advection zone aloft a strong sloping tropopause led to a sloping level of nondivergence across the trough axis with substantial

foraminiferal evidence for cenomanian sequence stratigraphy and palaeoceanography of the boulonnais paris basin northern france abstract a middle to upper cenomanian chalk succession in the northwestern european paris basin escalles section was investigated with respect to its sediment composition biofacies and foraminiferal content most planktic foraminifers exhibit a high frequency cyclicity in their distribution pattern and show little relationship to the sequence stratigraphic subdivision a few characteristic species of benthic foraminifers tritaxia pyramidata ataxophragmium compactum dorothia levis and gavelinella cenomana are related in their frequency distribution to certain systems tracts other benthic foraminiferal species are more evenly distributed through the systems tracts cluster analysis and factor analysis allow the separation of three benthic foraminiferal biofacies domains which exhibit a characteristic frequency distribution pattern with respect to sequence stratigraphy biofacies 1 is dominant in the highstand systems tract hst and biofacies 3 is characteristic for the transgressive systems tract tst biofacies 2 is most abundant around the maximum flooding downlap surface mfs and less abundant around the sequence boundary factor analysis shows that most of the variance in the data set is explained by variables related to plankton productivity variables related to changes in water depth and changes in sea level have minor influence on the variance of the whole data set but have some influence on the variance of the benthic foraminiferal data set the different reaction of benthic and planktic foraminifers to relative sea level changes is also recorded in the total number of foraminifers per gram sediment foraminiferal number and in the ratio between planktic and benthic foraminifers p b ratio the foraminiferal number is highest at the mfs and lowest at the sequence boundaries of the investigated depositional sequences the p b ratio has no correlation with the sequence stratigraphic subdivision but shows a high frequency cyclicity the abundance pattern of planktic foraminifers is controlled by changes in the productivity of calcareous plankton the regular variation in calcareous plankton productivity leads to marl low productivity chalk high productivity cycles that form conspicuous couplets in the section the productivity cycles are also recorded in gamma ray logs in the environmental setting of the escalles section in contrast the abundance patterns of benthic foraminifers are more influenced by relative sea level changes changes in water depth and variations in substrate composition the stacking of probably precession controlled development of couplets lead to a distinct 100 000 year cyclicity that does not match very well with published sequence stratigraphic subdivisions

sea level changes and geochemical anomalies across the cenomanian turonian boundary pecinov quarry bohemia relationships between geochemical anomalies sea level change and other events were studied in the cenomanian turonian boundary interval in the pecinov quarry in southwestern part of the bohemian cretaceous basin czech republic a major 3rd order sea level rise at the base of the late cenomanian m geslinianum zone was followed by deposition of organic enriched mudstones in a succession of parasequences deposited in response to high frequency 4th order sea level fluctuations and recording a stepwise decrease in bottom oxygenation towards intensely dysaerobic conditions a complex 13c excursion occurs in total organic matter of the late cenomanian deposits a sequence boundary of latest cenomanian age in the pecinov section is correlated to a global sea level fall during the n juddii zone a renewed sea level rise occurred during the early turonian w coloradoense zone and reached maximum flooding during the m nodosoides zone during the early turonian bottom waters were generally aerobic and the positive 13c excursion waned early in the w coloradoense zone the magnitude of the 13c excursion more than 4 is approximately the same as in north america and northern africa confirming that it was controlled by a global paleoceanographic mechanism the absence of anoxia and a 13c anomaly during the peak flooding of early turonian age suggests that widespread deposition of organic enriched deposits as well as the positive shift in 13c generally did not depend on the absolute elevation of sea level but rather on the area of newly flooded land during transgression abrupt small scale shifts in 13c towards higher values coincide with the flooding surfaces of parasequences and may reflect either regional changes in the proportion of marine and terrestrial organic matter or rapid global changes in isotopic composition of marine organic matter related to high frequency sea level changes abundances of ir sc cr v and other elements previously reported as forming anomalous concentrations in the boundary interval showed no enrichment in the bohemian section this is most probably due to the large distance of the depositional site from the presumed volcanic source of element enriched deep waters in the proto caribbean region anomalous concentration of mn at the base of the turonian deposits was caused by diagenetic incorporation of mn into siderite

chondrites a trace fossil indicator of anoxia in sediments the trace fossil chondrites a highly branched burrow system of unknown endobenthic deposit feeders occurs in all types of sediment including those deposited under anaerobic conditions in some cases such as the jurassic posidonienschiefer formation of germany chondrites occurs in black laminated carbonaceous sediment that was deposited in chemically reducing conditions in other cases such as numerous oxic clastic and carbonate units throughout the geologic column chondrites typically represents the last trace fossil in a biotutbation sequence this indicates that the burrow system was produced deep within the sediment in the anaerobic zone below the surficial oxidized zone that was characterized by freely circulating and oxidizing pore waters

the stromboli volcano landslides of december 2002 a seismological description 1 we analyse seismograms of the slump episodes at stromboli on december 30 2002 using a simple single force model we estimate the volume involved in the individual subevents and attempt a chronological reconstruction of the whole process our results indicate the occurrence of two main events that could be interpreted as a submarine slump which caused the observed tsunami and a subaerial slump which did not produce destructive sea waves a total volume of about 20 106 m3 results for the submarine event which developed over about 2 minutes with several distinct detachments the first and largest displacing a volume of 10 8 106 m3 the second subaerial slump involved at least 2 5 106 m3 in about 90 s a large long period pulse is also recognizable in the seismograms of the stromboli station we tentatively interpret this feature as tilt caused by the water load associated with the inundation in the ficogrande area on the northeastern side of the island

origin of channel systems in the upper cretaceous chalk group of the paris basin abstract the upper cretaceous chalk group of the anglo paris basin is known to show wedging beds and channel like features which disrupt the quietly deposited pelagic chalk that covered most of nw europe in the late cretaceous two d reflection seismic data from the brie region se of paris show the presence of at least two distinct intra chalk discordant reflections a top santonian and a mid campanian reflection these reflections are in places associated with up to 120 m deep channel like structures trending preferentially n s and nw se the mid campanian reflection is also sporadically associated with a massive secondary dolomite layer the thicknesses of which may reach 110 m diagenesis does not seem to account for the formation of the discordant reflections as there is neither a one to one relationship between the dolomite and discordant reflections nor are there signs of systematic collapse of the cenozoic succession over the channel like features as a result of intra chalk dissolution both reflections correlate with indurated chalk layers and hardgrounds and represent real unconformities the mid campanian reflection is furthermore associated with a stratigraphic hiatus a submarine origin is suggested due to the uninterrupted deep marine chalk facies below and above both unconformities and the unrealistically large sea level drop of more than 200 m which would be necessary for subaerial exposure of the central paris basin during the campanian the channels are oriented parallel to the margins of the basin and important bathymetric elements which could induce erosion by slope failure are not observed the channels are thus interpreted as having formed by strong mainly slope parallel bottom currents major channeling events are common in the chalk group throughout nw europe and represent palaeoceanographic re organization of bottom currents probably driven by changes in sea level and water temperature

the calcareous nannofossil biostratigraphic framework of the late maastrichtian danian north sea chalk abstract the calcareous nannofossil biostratigraphy of cored maastrichtian tor formation and danian ekofisk fm chalk sections from 10 selected wells of the greater ekofisk area central north sea was studied wells come from the edda tor se tor ekofisk and eldfisk fields among others more than 1000 m of cores were examined and about 500 samples were selected and analysed most of them quantitatively the main emphasis was placed on the danian sequence and on the k t boundary biostratigraphy provided detailed subdivision for the danian sediments intra danian hiatuses were detected and consistently recorded at the regional scale extensive mass movement was observed highlighting the complex depositional history during this time interval intervals of cretaceous chalk were found embedded in the danian sequence well 2 5 7 redeposited by slides as discrete chalk packages similarly lower danian intervals were recognised as transported into younger danian sediments well 2 4 b19a an attempt to reconstruct a regional stratigraphic picture for the area north of edda field including ekofisk se tor and tor fields has been made this suggests the following salient features the k t boundary of three wells of the northern sector of the studied area tor field is preceded by a prediscosphaera stoveri acme suggesting the presence of a rather complete maastrichtian sequence below the boundary above the k t boundary a few tens of centimetres of generally clay enriched pelagic chalk of the basal danian d1 biantholithus sparsus zone are present in most of the studied wells above this a condensed section often marked by hard ground levels or clay rich intervals was detected in almost all the wells the sedimentary expression of upper d1 above cruciplacolithus primus fad d2 and d3 time interval is lacking or extremely reduced in some cases sediments whose age is near the early late paleocene boundary were found unconformably overlying pelagic chalk referred to d5 d6 biozones

the coupling of a submarine slide and the surface waves which it generates underwater landslides are a common source of small scale tsunamis in coastal areas they have been the object of only a few theoretical and experimental studies a numerical model is developed to study the coupling of a submarine landslide and the surface waves which it generates a formulation of the dynamics of the problem is presented where the landslide is treated as the laminar flow of an incompressible viscous fluid and the water motion is assumed irrotational long wave approximation is adopted for both water waves and the mudslide the resulting differential equations are solved by a finite difference method we present the numerical results which contrast the behavior of the mud flow under a fixed surface in the presence of one way coupling bottom deformations affect the free surface and with full coupling surface pressure gradients react on the mud flow it is found that three main waves are generated by a landslide starting from rest on a gentle uniform slope the first wave is a crest which propagates away from the mudslide site into deeper water this crest is followed by a trough in the form of a forced wave which propagates with the speed of the mudslide front the third wave is a relatively small trough which propagates shoreward two major parameters dominate the interaction between the slide and the waves it produces the density of sliding material and the depth of water at the mudslide site the two way interactions are significant for the cases of a smaller mud density and shallower waters for the cases of larger mud density and shallower waters the two way interactions are small but the waves generated are very large for larger initiation depth of the mudslide the interactions are weak and the waves generated are small we also examined the possibility of a resonance between the slide and the waves our numerical results indicate that a resonance is not expected in many practical cases

synoptic scale disturbances with circular symmetry abstract ate balanced flow structure of various classic synopitc scale disturbances is reviewed using the invertibility principle for isentropic potential vorticity ipv distributions complete solutions are shown for cold and warm core structures of various types the basic model imagines the tropopause to be the interface between the lower potential vorticity of the troposphere and the approximately six fold larger value typical of the lower stratosphere the sensitivity of the structure of the potential temperature variation along the tropopause and at the surface is described results are presented in diagrammatic form to allow easy diagnosis of the vortex structure from synoptic data available at perhaps only a few levels the point is made that upper air ipv and surface potential temperature distributions are often the most crucial in accounting for the balanced flow structure

energy of water waves induced by submarine landslides water waves generated by submarine landslides may constitute a serious hazard for coastal population and environment these masses may be giant as documented by several examples in recent history and by numerous geological traces of paleo events a theoretical investigation on wave generation and wave energy is performed here by using a model that is based on some simplifying assumptions the landslide is treated as a rigid body moving underwater according to a prescribed velocity function water waves are governed by the shallow water wave equations where water velocity is constant through the water layer and vertical velocity is negligibly small geometrically simple basins are considered with either constant depth or constant slope since attention is focused on the fundamental characteristics of the generation process analytical 1 d solutions as well as 1 d and 2 d numerical results obtained by means of a finite element model are used to gain understanding of the energy transfer from a moving body to the water from the 1 d examples it is found that if slide duration is sufficiently long water usually gains energy in the form of waves until a saturation point is reached when body motion is no longer capable of producing a net transfer of energy from the rigid body to water finite duration motions of a body moving at constant speed along a flat ocean floor can be used as canonical examples since bottom slopes cannot significantly change the generated wave pattern typically two trough crest systems are developed that travel in opposite directions with the leading crest in the direction of the slide and the leading trough toward the other direction the amplitude of the former is generally higher with amplitude controlled by the froude number ratio of body velocity to long waves phase celerity and wavelength dictated by landslide length generation and propagation of 2 d cases show a more complicated pattern since lateral radiation plays an important role some of the features present in the 1 d models are observed in 2 d wavefields however substantial differences arise the most significant difference is that no energy saturation takes place in 2 d since the body transfers energy to the water as long as it moves

the development and seismic expression of synsedimentary features within the chalk of southern england seismic reflection data acquired onshore to the north of bournemouth southern england image clearly a series of prominent concave up troughs or depressions and concave down mounded structures within the white chalk subgroup the chalk lithostratigraphy in the area of study is established from borehole geophysical log correlations these correlations then provide calibration of the seismic reflection data indicating that the structures are concentrated at levels between the lewes nodular chalk formation and tarrant chalk member and towards the base of the portsdown chalk formation onlap downlap and truncation of reflectors are observed with the most dramatic features forming a stacked series directly overlying faulting of jurassic strata similar stratal geometries have been described from comparable levels in the chalk of the north sea and in outcrop in britain and france to many they represent channels formed by submarine erosion and redeposition of the chalk during relative sea level falls linked to tectonics we also interpret a number of apparently incisive structures and slumped infill sequences described here as being of primary syndepositional origin the slumping and the close association of these features with underlying faults and proximity to nearby major crustal faults may be indicative of submarine erosion of the chalk caused by sea level changes linked to syndepositional fault movements however evidence of toplap downlap pairs is also suggestive of more aggradational mounding or laterally migrating surfaces or facies belts the presence of any such structures implies rapid lateral variations in the chalk that would have implications not only for aquifer management and future storage schemes but also during the processing of seismic reflection data and general studies and correlations of the chalk across southern britain

trace fossil model for reconstruction of paleo oxygenation in bottom waters recognition of fluctuations in the degree of paleo oxygenation of bottom waters recorded in fine grained pelagic strata is important for interpretation of paleoceanographic and paleoclimatologic conditions general sedimentary fabric composition of trace fossil assemblages and burrow size and crosscutting relationships have been incorporated into a trace fossil tiering model that permits detailed reconstruction of changes in paleo oxygenation of bottom waters applications of this model to the miocene monterey formation california and the cretaceous niobrara formation colorado indicate that the ichnologic approach is more sensitive to both magnitude and rates of change in oxygenation levels compared to macrobenthic body fossil information

integrated depositional model for the cenomanian turonian organic rich strata in north africa abstract during the late cenomanian early turonian c t oceanic anoxic event oae2 organic rich strata was deposited in rift shelf basins and slopes across north africa and in deep sea basins of the adjacent oceans based on a review of published and unpublished information this paper documents the distribution and organic richness of c t strata across the whole region within a palaeogeographic framework and systematically analyses the conditions and processes which controlled their deposition previously the c t in north africa has been most intensively studied in southern morocco tarfaya and tunisia only little data is availabe for other parts of north africa namely algeria libya and egypt because distribution of c t corg strata there becomes more patchy a general decrease in peak organic richness and black shale thickness occurs from west to east partly as a result of upwelling along the moroccan atlantic coast and the absence of upwelling in the eastern mediterranean area furthermore in the confined central atlantic the oxygen minimum zone omz in many places reached down to the deep sea floor 3 4 km while the lower limit of the omz along the north african tethys was much shallower and underlain by oxic water masses as documented by high resolution biostratigraphic and chemostratigraphic data c t black shale deposition in most areas outside the upwelling zone are restricted to a strong eustatic latest cenomanian transgressive phase triggered by this sea level rise the omz impinged onto the north african continental shelf and the margins of intrashelf basins which mostly formed during the early cretaceous as halfgrabens important units containing c t organic rich strata in the region are the atlantic tarfaya black shales morocco western sahara black shales and phtanites in the moroccan and algerian atlas the bahloul fm in the se constantine basin and in northern and central tunisia the etel fm in the sirte basin the al hilal fm in cyrenaica libya the abu roash fm in the abu gharadig and fayium basins western desert egypt the daliyya fm along the ne sinai palestine isreal coast and the shueib fm in west central jordan

cenomanian sequence stratigraphy and sea level fluctuations in the tarfaya basin sw morocco we investigated the sequence architecture of two expanded cenomanian successions along a depth transect in the tarfaya basin sw morocco and correlated these successions to published records from northwest europe and india changes in terrigenous material carbonate and organic carbon content carbonate microfacies and foraminiferal biofacies as well as nondepositional and erosional surfaces were used to define depositional sequences and systems tracts we identified two main transgressive cycles in the lower and middle upper cenomanian separated by a major regression at the early middle cenomanian transition sequence boundary ce 3 this regressive interval is characterized by lagoonal low stand deposits indicating an overall sealevel fall of more than 30 m superimposed on the two main transgressive cycles there are 11 third order depositional sequences that correlate to globally recognized sealevel fluctuations and appear to be paced by long eccentricity variations 400 ka period positive carbon isotope excursions in the middle cenomanian 96 0 ma and latest cenomanian 94 0 ma following sealevel lowstands together with planktonic foraminiferal and ammonite datums provide a robust framework for stratigraphic correlation we suggest that the onset of these excursions was triggered by eccentricity minima during periods of low variability in obliquity nodes which probably coincided with glacioeustatic lowstands

convective inhibition beneath an upper level pv anomaly upper level potential vorticity pv anomalies reduce the convective stability of the troposphere through their impact on the vertical potential temperature profile thus reducing convective inhibition cin and increasing convective available potential energy here by contrast we show the impact of a layer of stable air that was intrinsically linked with an upper level pv anomaly and that increased cin this layer descended and tracked beneath the small upper level pv anomaly which in this case was a shallow upper level trough this low humidity relatively high pv layer originated from the tropopause fold generated by a breaking rossby wave which also produced the upper level pv anomaly two days later despite conditions favourable for deep convection as demonstrated by the development of a single storm the cin produced by this dry layer or lid was largely responsible for capping convection over much of southern england at around 2 5 km during the case presented here which comes from the convective storm initiation project copyright c 2008 royal meteorological society

tropopause undulations and the development of extratropical cyclones part ii diagnostic analysis and conceptual model abstract a case study of a developing cyclone is used to show that the three dimensional distribution of height change during development can be strongly sensitive to temperature changes which occur in the lower stratosphere in association with an evolving tropopause undulation quantitative analysis of the storm with a geopotential height tendency equation indicates that a synergistic process developed between the stratosphere and troposphere whereby the vertical motion pattern maintained and intensified the upper level temperature anomalies while the subsequent upper level temperature advection led to an enhanced vertical circulation using the results of this diagnostic study a conceptual model is constructed the conceptual model is based on the hydrostatic and wind field adjustments that occur as tropopause undulations propagate over favored regions of tropospheric warm advection and less stable air

the landslides and tsunamis of the 30th of december 2002 in stromboli analysed through numerical simulations on the 30th of december 2002 two tsunamis were generated only 7 min apart in stromboli southern tyrrhenian sea italy they represented the peak of a volcanic crisis that started 2 days before with a large emission of lava flows from a lateral vent that opened some hundreds of meters below the summit craters both tsunamis were produced by landslides that detached from the sciara del fuoco this is a morphological scar and is the result of the last collapse of the northwestern flank of the volcanic edifice that occurred less than 5 ka b p the first tsunami was due to a submarine mass movement that started very close to the coastline and that involved about 20 106 m3 of material the second tsunami was engendered by a subaerial landslide that detached at about 500 m above sea level and that involved a volume estimated at 4 9 106 m3 the latter landslide can be seen as the retrogressive continuation of the first failure the tsunamis were not perceived as distinct events by most people they attacked all the coasts of stromboli within a few minutes and arrived at the neighbouring island of panarea 20 km ssw of stromboli in less than 5 min the tsunamis caused severe damage at stromboli

optimal initial conditions for simulation of seismotectonic tsunamis numerical simulation of seismotectonic tsunamis usually starts with specification of the initial elevation of the water surface in the tsunami source the initial elevation is traditionally set equal to the vertical residual bottom deformation resulting from earthquakes we discuss the imperfectness of the traditional approach and suggest an improved practical method of calculating the initial elevation from the solution of the 3d problem in the framework of potential theory the method takes into account horizontal and vertical components of bottom deformation and bathymetry in the source area within the assumption of instant tsunami generation the suggested method represents the optimal way to specify the initial condition in the tsunami propagation problem the tsunamis in the central kuril islands on 15 november 2006 and 13 january 2007 are taken as examples to demonstrate the efficiency of the new method

composite ichnofabrics and tiering of burrows infaunal communities in marine environments typically are tiered that is different taxa live at different depths within the sediment tiered suites of biogenic structures yield complex biogenic sedimentary fabrics ichnofabrics with the traces of deep burrowing organisms overprinted on those of shallow burrowing organisms careful analysis of crosscutting relationships of burrows in such composite ichnofabrics allows reconstruction of the tiered nature of fossil endobenthic communities it is important to recognize that the best preserved and most prominently displayed trace fossils in most assemblages usually represent the deepest tier thus they were farther removed from the sea floor and therefore less indicative of actual sea floor conditions than the more poorly preserved traces of the shallower tiers on which the deeper traces are juxtaposed

simulation of small amplitude frequency dispersive transient waves by means of the mild slope equation a numerical model based on the mild slope equation is applied to reproduce the propagation of small amplitude transient waves the model makes use of the fourier transform to convert the time dependent hyperbolic equation into a set of elliptic equations in the frequency domain the results of two available experimental studies on tsunamis generated by landslides are used to validate the model which appears to be able of carefully reproducing the effects of the frequency dispersion an example application of tsunamis propagating around the stromboli island is also presented to show the applicability of the present approach to real life scenarios it is finally discussed how this model could be applied as support to a tsunami early warning system

a modal decomposition method for the analysis of long waves amplification at coastal areas abstract this paper presents a model for the evaluation of long waves amplification at coastal areas based on a modal decomposition method it is able of modelling the growth and the decay of the natural modes of the area under investigation and their contribution to the total wave field the model is an improvement of that developed by bellotti et al 2012b that was able of calculating the frequencies and the shapes of the natural modes but not their amplification under the action of forcing waves three test cases are used for the validation and to show the capabilities of the model the first considers the long waves resonance into a long and narrow harbour bay over a constant water depth it is a case for which a high degree of wave trapping into the semi enclosed coastal area is induced by the specific shape of the coastline the second test deals with the propagation of a group of edge waves along a straight coast with a constant sloping bottom generated in proximity of the shoreline by a special wave maker the model in this case properly evaluates what are the edge waves modes that contribute to the total wave field the third case involves the interaction of a solitary wave with a conical island for which laboratory data are available in this test a low degree of trapping exists but it is interesting for the present aims as the propagation of the waves around the island is expected to occur under the form of wave modes partially trapped by the bathymetry i e edge waves excited by the transient wave arriving from offshore on the basis of the tests results it is shown what is the role of the more relevant natural modes in the formation of the total surface elevation