the record of the messinian salinity crisis in the tertiary piedmont basin nw italy the alba section revisited abstract the alba succession tertiary piedmont basin nw italy preserves the northernmost record of the messinian salinity crisis msc and was deposited on the southern margin of a wide wedge top basin related to the involvement of the piedmont basin in the apennine compressional tectonics pre msc sediments consist of a cyclic succession of marine euxinic shales and calcareous marls deposited under the influence of precession modulated climate changes and document the progressive restriction of the basin prior to the onset of the msc they are followed by the primary lower gypsum unit plg deposited during the first msc stage from 5 96 to 5 60 ma these sediments show a clear precession related cyclic stacking pattern and record the lateral transition from a shallow water marginal setting in the sw to a deeper one in the ne in marginal settings six plg cycles are recognised truncated by an erosional unconformity placed at the base of the post evaporitic sediments the lowermost five cycles are composed of massive and banded selenite beds separated by thin shale intervals a sharp change evidenced by the appearance of the branching selenite facies is recorded by the 6th gypsum bed that represents a distinctive marker bed here called sturani key bed that can be mapped throughout the study area basinward the lower plg cycles are transitional to decimetre thick carbonate rich layers interbedded to euxinic shales that are overlain by the sturani key bed above the marker bed other seven plg cycles are present the gypsum beds form thinner bodies compared to the sturani key bed and are characterised by a greater amount of fine grained terrigenous fraction suggesting an increase of continental runoff related in turn to humid climate conditions at the end of the first msc stage plg cycles are followed by slumped mudstones and clastic gypsum beds that correspond to the resedimented and chaotic facies resedimented lower gypsum deposited in the mediterranean basins during the second msc stage from 5 60 to 5 55 ma they are in turn overlain by continental and brackish water facies with lago mare fossil assemblages recording the final stage of the msc the messinian succession of alba provides the opportunity to reconstruct the lateral facies transition between marginal and distal settings and to shed new light on the deep water msc sedimentary record moreover the appearance of the branching selenite facies from the 6th plg cycle upward provides a tool for properly placing the piedmont record in the msc chronostratigraphic framework allowing us to investigate the influence of climate gradients on the sedimentary response to the mediterranean salinity crisis

doppler radar observations of horizontal shearing instability in quasi linear convective systems abstractdual doppler radar observations of two cold season wave propagating quasi linear convective systems qlcs which evolved in high shear low cape hslc environments are analyzed to deter

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

a concentrated outbreak of tornadoes downbursts and microbursts and implications regarding vortex classification abstract a remarkable case of severe weather occurred near springfield illinois on 6 august 1977 aerial and ground surveys revealed that 17 cyclonic vortices an anticyclonic vortex 10 downbursts and 19 microbursts occurred in a limited 20 km 40 km area associated with a bow shaped radar echo about half of the vortices appeared to have occurred along a gust front some of the other appear to have occurred within the circulation of a mesocyclone accompanying the bow echo but these vortices seem to have developed specifically in response to localized boundary layer vorticity generation associated with horizontal and vertical wind shears on the periphery of microbursts some of these vortices and other destructive vortices in the literature do not qualify as tornadoes as defined in the glossary of meteorology a moon pragmatic definition of a tornado is suggested

mesovortices within the 8 may 2009 bow echo over the central united states analyses of the characteristics and evolution based on doppler radar observations and a high resolution model simulation abstracta derecho producing bow echo event over the central united states on 8 may 2009 is analyzed based on radar observations and a successful real data wrf simulation at 0 8 km grid spacing emphasis is placed on documenting the existence evolution and characteristics of low level mesovortices mvs that form along the leading edge of the bowing system the genesis of near surface high winds within the system is also investigated significant mvs are detected from the radar radial velocity using a linear least squares derivatives llsd method and from the model simulation based on calculated vorticity both the observed and simulated bow echo mvs predominantly form north of the bow apex mvs that develop on the southern bow tend to be weaker and shorter lived than their northern counterparts vortex mergers occur between mvs during their forward movement which causes redevelopment of some mvs in the decaying stage of the bow echo mvs located at or near the bow apex are found to persist for a not

solid pole tide in global gps and superconducting gravimeter observations signal retrieval and inference for mantle anelasticity abstract the mantle anelasticity plays an important role in earth s interior dynamics here we seek to determine the lower mantle anelasticity through the solution of the complex love numbers at the chandler wobble period the love numbers h 21 l 21 21 and k 21 are obtained in the frequency domain by dividing off the observed polar motion or more specifically the pole tide potential from the observed gps 3 d displacement field and sg gravity variation the latter signals are obtained through the array processing method of ose optimal sequence estimation that results in greatly enhanced signals to be extracted from global array data the resultant love number estimates h 21 0 6248 5 e 4 0 013 5 e 3 i l 21 0 0904 8 e 4 0 0008 2 e 3 i 21 1 156 2 e 3 0 003 1 e 3 i and k 21 0 3125 2 e 3 0 0069 3 e 3 i are thus well constrained in comparison to past estimates that vary considerably they further lead to estimates of the corresponding mantle anelastic parameters f r and f i which in turn determines under the single absorption band assumption the dispersion exponent of 0 21 0 02 with respect to the reference frequency of 5 mhz we believe our estimate is robust and hence can better constrain the mantle anelasticity and attenuation models of the earth interior

tide gauge data analysis of the pole tide in the north sea summary it is generally accepted that the pole tide the oceanic response to the chandler wobble is in the north sea characterized by anomalously large amplitudes in this paper we test that postulate by extracting amplitudes and phases at the chandler frequency from sea level signals recorded over the past century and a half around the north sea we have also determined the equilibrium pole tide and tidal admittances over the same time span using long term polar motion our analysis has focused on three sub intervals of time 1872 1900 1900 1964 and 1955 1984 we find that the eastward intensification is not a persistent feature of the north sea pole tide over all three intervals furthermore the typical pole tide amplitude during these three time spans varies but not in the same way as the chandler potential this supports naito s 1977 and daillet s 1981 conclusion that the variation of the pole tide amplitude with respect to time is at least partially independent of the chandler forcing finally we have analysed the north sea annual tide at the same sites and found that it also exhibits an eastward intensification however in contrast to the pole tide the annual tide s eastward intensification persists clearly over all three time intervals these data analyses combined with our earlier theoretical study of the north sea pole tide xie dickman 1995 suggest that the observed pole tide signal in the north sea may be attributed largely to a combination of chandler wobble and meteorological forcing but that other causes must exist as well

bow echo mesovortices part ii their genesis abstract this two part study examines the damaging potential and genesis of low level meso scale mesovortices formed within bow echoes this was accomplished by analyzing quasi idealized simulations of the 10 june 2003 saint louis bow echo event observed during the bow echo and mesoscale convective vortex experiment bamex in part ii of this study mesovortex genesis was investigated for vortices formed at different stages of convective system evolution during the early cellular stage cyclonic mesovortices were observed the cyclonic mesovortices formed from the tilting of baroclinic horizontal vorticity acquired by downdraft parcels entering the mesovortex as the convective system evolved into a bow echo cyclonic anticyclonic mesovortex pairs were also observed the vortex couplet was produced by a local updraft maximum that tilted baroclinically generated vortex lines upward into arches the local updraft maximum was created by a convective scale downdraft that produced an outward bulge in th

bow echo mesovortices part i processes that influence their damaging potential abstract this two part study examines the damaging potential and genesis of low level meso scale mesovortices formed within bow echoes this was accomplished by analyzing quasi idealized simulations of the 10 june 2003 saint louis bow echo event observed during the bow echo and mesoscale convective vortex experiment bamex this bow echo produced both damaging and nondamaging mesovortices a series of sensitivity simulations were performed to assess the impact of low and midlevel shear cold pool strength and coriolis forcing on mesovortex strength by analyzing the amount of circulation maximum vertical vorticity and number of mesovortices produced at the lowest grid level it was observed that more numerous and stronger mesovortices were formed when the low level environmental shear nearly balanced the horizontal shear produced by the cold pool as the magnitude of deeper layer shear increased the number and strength of mesovortices increased larger coriolis forcing and stronger cold pools als

tidal parameters for an inelastic earth abstract the gravimetric factors for an elliptical uniformly rotating earth are computed according to a new definition with respect to wahr s results and considering the mantle inelasticity the love numbers h and k are defined in the elliptical earth case to correspond to the love spherical definition they become latitude dependent the tidal parameters discussed in this paper are computed for an inelastic earth s mantle the numerical results show an increase of 0 4 of the gravimetric factors with respect to the wahr s values the love numbers h and k increase by 1 4 to 3 with respect to the elastic case

the numerical simulation of non supercell tornadogenesis part i initiation and evolution of pretornadic misocyclone circulations along a dry outflow boundary abstract high resolution three dimensional simulations are used to study misocyclone initiation and development along the leading edge of an outflow boundary model conditions were designed such that this development could be simulated independent of moist processes the outflow boundary is allowed to propagate into a region of southerly low level flow which results in a vertical vortex sheet along the outflow s leading edge lobe and cleft instabilities follow and provide perturbations for the subsequent development of horizontal shearing instabilities these growing instabilities are the inaugural circulations of leading edge misocyclones with wavelengths ranging from 1 6 to 3 2 km the structure of these modeled misocyclones compares favorably to observed pretornadic misocyclones along outflow boundaries in northeast colorado vortex sheet dynamics are observed to exert substantial control over the structure of the evolving outflow leading edge the vertical vortex sheet passes through discrete evoluti

a theory for strong long lived squall lines abstract we study herein the mechanics of long lived line oriented precipitating cumulus convection squall lines using two and three dimensional numerical models of moist convection these models used in juxtaposition enable us to address the important theoretical issue of whether a squall line is a system of special long lived cells or whether it is a long lived system of ordinary short lived cells our review of the observational literature indicates that the latter is the most consistent paradigm for the vast majority of cases but on occasion a squall line may be composed of essentially steady supercell thunderstorms the numerical experiments presented herein show that either type of squall line may develop from an initial line like disturbance depending on the magnitude and orientation of the environmental shear with respect to the line with shallow shear oriented perpendicular to the line a long lived line evolves containing individually short lived cells our analysis of this type o

putative greigite magnetofossils from the pliocene epoch greigite crystals of bacterial origin are widespread in modern sedimentary environments but their occurrence in the fossil record remains controversial grains from romanian pliocene aged sediments have now been identified as bacterial in origin tentatively placing them among the oldest known greigite magnetofossils

a comparison of the vorticity dynamics governing the oceanic bomb cyclone of 4 5 january 1989 and the super derecho of 8 may 2009

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

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

modelling the pole tide and its effect on the earth s rotation summary the pole tide is the response of the ocean to incremental centrifugal forces associated with the chandler wobble the tide has a potentially important effect on the period and damping of the wobble but it is at present not well constrained by observations here we construct both analytical and numerical models for the pole tide the analytical models consider the tide first in a global ocean and then in an enclosed basin on a beta plane the results are found to approach equilibrium linearly with decreasing frequency and inversely with increasing basin depth the numerical models solve laplace s tidal equations over the world s oceans using realistic continental boundaries and bottom topography the results indicate that the effects of the non equilibrium portion of the deep ocean tide on the chandler wobble period and damping are negligible

north sea pole tide dynamics s u m m a r y laplace tide equations ltes augmented to include linear bottom friction and chandler wobble forcing have been solved numerically for the pole tide in the north sea employing realistic bottom topography and geometrical boundaries the motivation for our study is the need to explain observations of enhanced pole tide amplitudes and eastward intensification along the southern boundary of the sea following wunsch 1974 the tidal dynamics are considered to depend on non equilibrium pole tide behaviour at the open northern boundary of the sea with reasonably small bottom friction and open boundary forcing the amplitude of the pole tide in the north sea is found to be close to equilibrium i e the coastal amplitudes do not match the observations however the phase lag obtained is close to those inferred from tide gauge analyses under these conditions the north sea has the potential to dissipate a considerable fraction 25 per cent of chandler wobble energy if much larger bottom friction is considered the resulting pole tide amplitudes are more highly variable within the sea and if the open boundary forcing is also much larger the tidal amplitudes match many of the observations in this case however the tidal currents dissipate an unacceptably huge amount of wobble energy an earlier version of this problem proposed by wunsch 1974 and reconsidered by dickman preisig 1986 in which time independent ltes are postulated in a north sea modelled with analytical bottom topography and a rectangular domainis also fully solved via the method of weighted residuals the solutions include one in which the non equilibrium portion of the tide height is nearly constant all over the domain the corresponding tidal currents are negligibly slow our work points to the importance of realistic bottom topography and coastline geometry in affecting the tidal dynamics such factors to date have not been considered in theoretical analyses of the north sea pole tide the realistic bathymetry and geometry produce a large variability in bottom friction which is inversely proportional to the water depth and thereby generate substantial dynamic behaviour despite the long period of the pole tide we find that these factors significantly enhance the tidal currents and promote an eastward intensification of the non equilibrium tide height near the southern coast

deformation induced by polar motion variations in the geocentric position of the earth s rotation axis polar motion cause deformation within the earth we estimate the effects of this deformation on radial and horizontal positions of points on the earth s surface on baseline lengths between those points and on surface gravity the effects of the oceans and of the earth s anelasticity on this deformation are found to be negligible peak to peak variations in radial motion are typically 10 20 mm over a year horizontal displacements are less than 7 8 mm variations in baseline length can be as large as 30 40 mm variations of up to 13 gal in surface gravity are possible these numbers are all small enough that they can probably not be used to learn about the earth however they are large enough to affect noticeably present high quality geodetic observations

low level mesovortices within squall lines and bow echoes part i overview and dependence on environmental shear this two part study proposes fundamental explanations of the genesis structure and implications of lowlevel meso g scale vortices within quasi linear convective systems qlcss such as squall lines and bow echoes such mesovortices are observed frequently at times in association with tornadoes idealized simulations are used herein to study the structure and evolution of meso g scale surface vortices within qlcss and their dependence on the environmental vertical wind shear within such simulations significant cyclonic surface vortices are readily produced when the unidirectional shear magnitude is 20 m s 21 or greater over a 0 2 5 or 0 5 km agl layer as similarly found in observations of qlcss these surface vortices form primarily north of the apex of the individual embedded bowing segments as well as north of the apex of the larger scale bow shaped system they generally develop first near the surface but can build upward to 6 8 km agl vortex longevity can be several hours far longer than individual convective cells within the qlcs during this time vortex merger and upscale growth is common it is also noted that such mesoscale vortices may be responsible for the production of extensive areas of extreme straight line wind damage as has also been observed with some qlcss surface vortices are also produced for weaker shears but remain shallow weak and short lived although similar in size and strength to mesocyclones associated with supercell storms and also sometimes producing similar hooklike structures in the rain field it is also shown that the present vortices are quite distinct structurally and dynamically most critically such vortices are not associated with long lived rotating updrafts at midlevels and the associated strong dynamically forced vertical accelerations as occur within supercell mesocyclones

no major deglaciation across the miocene pliocene boundary integrated stratigraphy and astronomical tuning of the loulja sections bou regreg area nw morocco 1 an integrated high resolution stratigraphy and orbital tuning is presented for the loulja sections located in the bou regreg area on the atlantic side of morocco the sections constitute the upward continuation of the upper messinian ain el beida section and contain a well exposed continuous record of the interval straddling the miocene pliocene m p boundary the older loulja a section which covers the interval from 5 59 to 5 12 ma reveals a dominantly precession controlled color cyclicity that allows for a straightforward orbital tuning of the boundary interval and for detailed cyclostratigraphic correlations to the mediterranean the high resolution and high quality benthic isotope record allows us to trace the dominantly obliquity controlled glacial history our results reveal that the m p boundary coincides with a minor partly precession related shift to lighter interglacial values in d18o this shift and hence the m p boundary may not correlate with isotope stage tg5 as previously thought but with an extra weak obliquity controlled cycle between tg7 and tg5 consequently the m p boundary and basal pliocene flooding of the mediterranean following the messinian salinity crisis are not associated with a major deglaciation and glacio eustatic sea level rise indicating that other factors such as tectonics must have played a fundamental role on the other hand the onset of the upper evaporites in the mediterranean marked by hyposaline conditions coincides with the major deglaciation step between marine isotope stage tg12 and tg11 suggesting that the associated sea level rise is at least partly responsible for the apparent onset of intermittently restricted marine conditions following the main desiccation phase finally the loulja a section would represent an excellent auxiliary boundary stratotype for the m p boundary as formally defined at the base of the trubi marls in the eraclea minoa section on sicily

the deep water counterpart of the messinian lower evaporites in the apennine foredeep the fanantello section northern apennines italy abstract a possible deep water non evaporitic unit equivalent of the messinian lower evaporites has been recognised in the northern apennine foredeep this unit whose existence is implicitly admitted in the two step model of the mediterranean messinian salinity crisis is documented here for the first time it occurs throughout the apennine foredeep basin below a thick horizon of resedimented gypsum deposits usually ascribed to the lower evaporites actually the lower evaporites of the apennine foredeep basin include both shallow water in situ precipitated facies and deep water resedimented facies deposited in distinct depocenters the usually envisaged coeval nature of the two deposits has been recently challenged in several works based on a physical stratigraphic considerations about the downbasin correlation of the messinian erosional surface cutting on top the in situ evaporites with the sharp base of the resedimented evaporites unit and b the common occurrence of a barren unit below the resedimented evaporites which has no obvious equivalents in pre evaporitic successions underlying the in situ precipitated evaporites in this work a multidisciplinary study has been carried out on a 140 m thick composite section fanantello section to definitely assess the age and palaeoenvironmental characteristics of the unit underlying the resedimented gypsum deposits the topmost part of the section comprises a 60 m thick succession of barren euxinic shales falling entirely within a reversed polarity chron and characterised by a the complete disappearance of foraminifera b the occurrence of high salinity tolerant thecosomatous pteropods creseis sp c the abundance peaks of the calcareous nannofossil sphenolithus abies interpreted as related to highly stressed likely hyperhaline conditions d the appearance of hyperhaline and or stratified water molecular indicators gammacerane based on a multidisciplinary integrated stratigraphic approach this barren interval is here proposed to be a deeper water time equivalent of the in situ primary lower evaporites thus allowing to assess the events connected to the onset and the first phase of the messinian salinity crisis from a basinal perspective these data lend support to the hypothesis that the resedimented evaporite deposits of the apennine foredeep basin postdate the in situ evaporites thus implying that the term lower evaporites actually comprises rock bodies with different origins and separated in time and space by the messinian erosional surface and its correlative conformity this could be true also for other mediterranean basins where the stratigraphy of deep water successions should be carefully re examined

mesoscale convection and bimodal cyclogenesis over the bay of bengal abstractmesoscale convective systems mcss are an essential component of cyclogenesis and their structure and characteristics determine the intensity and severity of associated cyclones case studies were performed by simulating tropical cyclones that formed during the pre and postmonsoon periods in 2007 and 2010 over the bay of bengal bob the pre post monsoon environment was characterized by the coupling of northwesterly southwesterly wind to the early advance southwesterly northeasterly monsoonal wind in the bob the surges of low level warm southwesterlies with clockwise rotating vertical shear in the premonsoon period and moderately cool northeasterlies with anticlockwise rotating vertical shear in the postmonsoon period transported moisture and triggered mcss within preexisting disturbances near the monsoon trough over the bob mature mcss associated with bimodal cyclone formations were quasi linear and they featured leading edge deep convection and a trailing stratiform precipitation r

doppler radar observations of non occluding cyclic vortex genesis within a long lived tornadic storm over southern england on 3 november 2009 a long lived tornadic storm developed close to the apex of a small frontal wave moving eastwards over southern england ten tornadoes and several instances of non tornadic wind damage occurred along a narrow path extending for over 120 km the storm passed within 5 km of two of the radars in the met office s network providing an opportunity for detailed observation initial development was in the form of an intense segment of line convection at the northern flank of the frontal wave and associated deepening surface mesolow diameter 60 70 km the line evolved rapidly the southern portion bowed out to form a transient s shaped echo before dissipating the northern section persisted leaving a hook shaped storm which became quasi steady in overall echo shape radars revealed the cyclic development of five discrete low level mesovortices diameter 1 4 km between 1130 and 1330 utc along a zone of intense cyclonic vertical vorticity at the southeastern edge of the storm these vortices intensified rapidly typically from initial detection to maximum observed differential velocity in 10 min some attaining low level differential velocities exceeding 40 m s 1 however significant differential velocities 20 m s 1 were not observed above 2 5 km above ground level and no persistent mid level mesocyclone was present the cyclic behaviour was unusual in that vortices were non occluding moving southeastwards relative to the storm to the right of the storm motion vector away from the core this is in contrast to the more commonly observed evolution of vortex occlusion by storm downdraughts and subsequent leftward and rearward storm relative movement during decay copyright 2011 british crown copyright the met office published by johnwiley sons ltd

tornadogenesis in a simulated mesovortex within a mesoscale convective system abstractthe advanced regional prediction system arps is used to simulate a tornadic mesovortex with the aim of understanding the associated tornadogenesis processes the mesovortex was one of two tornadic mesovortices spawned by a mesoscale convective system mcs that traversed southwestern and central oklahoma on 8 9 may 2007 the simulation used 100 m horizontal grid spacing and is nested within two outer grids with 400 m and 2 km grid spacing respectively both outer grids assimilate radar upper air and surface observations via 5 min three dimensional variational data assimilation 3dvar cycles the 100 m grid is initialized from a 40 min forecast on the 400 m grid results from the 100 m simulation provide a detailed picture of the development of a mesovortex that produces a submesovortex scale tornado like vortex tlv closer examination of the genesis of the tlv suggests that a strong low level updraft is critical in converging and amplifying vertical vorticity associated with the mesovortex

the primary lower gypsum in the mediterranean a new facies interpretation for the first stage of the messinian salinity crisis abstract the detailed facies and physical stratigraphic analysis of the primary lower gypsum in the mediterranean indicates a surprising bed by bed correlation at basin scale spain italy hellenic arc and cyprus arc that is tuned to the orbital calibration for the first stage of the messinian salinity crisis from 5 96 to 5 61 ma ago a total of 16 precessionally controlled gypsum cycles were deposited rapidly in less than 350 ka forming sequences up to 300 m thick the lack of subaerial exposure features and the common facies associations and stacking pattern for sections located thousands of kilometers apart in different geological settings indicates a modest depositional depth not extremely shallow selenite deposition occurred only at the bottom of restricted marginal basins less than 200 m deep while no gypsum could precipitate in the deeper euxinic mediterranean portions where only thin and barren shale dolostone couplets formed the lowermost selenite beds pass laterally to dolomite rich limestones interbedded with barren euxinic shales in poorly oxygenated settings indicating that the gypsum sedimentation was diachronous and did not necessarily mark the onset on the messinian salinity crisis evaporite facies sequences ef1 to 8 within individual gypsum beds show small scale subaqueous sedimentary cycles that mimic regressive transgressive cycles a initial evaporite precipitation at relatively low supersaturation produced the massive selenite facies ef3 in a relatively deep setting b continuous evaporation and drawdown by oscillating brine level formed the banded selenite ef4 at the aridity acme of the precessionally controlled cycle c general progressive brine level rise with strong brine flow led to the formation of large selenite supercones branching laterally supercones in spain and branching selenite ef5 in the rest of the mediterranean and d flooding by undersaturated continental water terminated gypsum precipitation with the deposition of argillaceous sediments ef1 northern apennines and or limestone ef2 sicily and spain during the humid phase in the precession climate cycle the stacking pattern and selenite facies associations suggest an overall shallowing upward trend with a basin wide hydrologic change starting from the 6th cycle 5 84 ma which is marked by the appearance of the branching selenite facies supercones in spain and indicates that the brines became current dominated the sr isotope stratigraphy suggests that in the northern apennines the brines were strongly modified by continental waters 87 sr 86 sr 0 708893 to 0 708998 and received direct pulses of atlantic seawater 87 sr 86 sr 0 70900 to 0 709024 only in the upper part of the section in areas away from the mainland such as sicily the continental input was by far less important

the mediterranean messinian salinity crisis an apennine foredeep perspective abstract owing to its expanded stratigraphic sections the apennine thrust belt offers the opportunity to better understand the evaporitic and post evaporitic messinian events a physical stratigraphic framework of messinian deposits based on facies analysis and basin wide correlation of key surfaces and sedimentary cycles is presented it is shown that the messinian apennine foredeep had marginal basins with shallow water primary evaporites and deeper basins where resedimented evaporites accumulated under relatively deep water conditions like many other mediterranean examples primary shallow water evaporites of apenninic marginal basins show evidence for subaerial exposure and erosion however the development of such an erosional surface does not correspond to the deposition of primary evaporites in the deepest part of the basin s here the unconformity can be traced towards the base of resedimented evaporites or to a level within them implying that the deeper basins of the apennine foredeep never underwent desiccation during the messinian salinity crisis but rather received the eroded marginal evaporites this fact usually overlooked raises important questions about the deep desiccation model of the mediterranean

messinian salinity crisis a novel unifying shallow gypsum deep dolomite formation mechanism abstract the messinian salinity crisis is a dramatic event that took place between 5 96 and 5 33 ma and resulted not only in the desiccation and reflooding of the mediterranean but also in the deposition of 0 3 3 km thick evaporites at its seafloor there has been considerable controversy on the modes of their formation the first stage gypsum deposits are considered to have only formed at silled marginal basins whereas anoxic marls and dolostones are found at deeper settings we agree with these observations but reject the coincidental presence of similar sills as being too fortuitous to explain gypsum formation in silled basins alone alternatively we present a unifying mechanism in which gypsum precipitation takes place basin wide at all shallow water depths but its preservation is limited to silled marginal basins taking a realistic early messinian scenario including a moderate primary production rate the sulphate consumption rate in the deep water appears to exceed the sulphate supply rate as deduced from reported shallow water gypsum deposition rates the consequent lower dissolved sulphate content limits gypsum preservation but permits dolomite formation to take place in the deep water the often observed concurring anoxic environment and absence of gypsum formation is thus related to diminished dissolved sulphate content via organic matter degradation and not to oxygen free conditions as such

integrated stratigraphy and astrochronology of the messinian gssp at oued akrech atlantic morocco a much improved high resolution integrated stratigraphy calcareous plankton biostratigraphy magnetostratigraphy cyclostratigraphy is presented for the classic section of oued akrech atlantic morocco straddling the tortonian messinian boundary magnetobiostratigraphic correlations with time equivalent and astronomically dated sections in the mediterranean indicate that cyclic alternations of indurated light beige coloured marls and softer more clayey and reddish coloured marls are dominantly precession controlled characteristic sedimentary cycle patterns in particular those reflecting precession obliquity interference allow for one possible tuning thus providing accurate astronomical ages for cycles calcareous plankton events and magnetic reversals the tuning further indicates that the reddish layers are the equivalent of sapropels in the mediterranean the messinian global boundary stratotype section and point gssp has recently been formally defined at the base of the reddish layer of cycle no 15 in section oued akrech this level coincides closely with the first regular occurrence of the globorotalia miotumida group and is astronomically dated at 7 251 ma the global correlation potential is guaranteed by the straightforward calibration of the oued akrech magnetostratigraphy to the geomagnetic polarity time scale locating the gssp within c3br 1r in the marine realm the calcareous nannofossil genus amaurolithus provides a series of extremely useful events to delimit the boundary on a global scale the astronomical tuning guarantees a direct first order calibration of the messinian gssp to the standard geological time scale once as anticipated the late miocene part of the astronomical time scale has been incorporated fl 2000 elsevier science b v all rights reserved

environment and early evolution of the 8 may 2009 derecho producing convective system abstractthis study documents the complex environment and early evolution of the remarkable derecho that traversed portions of the central united states on 8 may 2009 central to this study is the comparison of the 8 may 2009 derecho environment to that of other mesoscale convective systems mcss that occurred in the central united states during a similar time of year synoptic scale forcing was weak and thermodynamic instability was limited during the development of the initial convection but several mesoscale features of the environment appeared to contribute to initiation and upscale growth including a mountain wave a midlevel jet streak a weak midlevel vorticity maximum a denver cyclone and a region of upper tropospheric inertial instability the subsequent mcs developed in an environment with an unusually strong and deep low level jet llj which transported exceptionally high amounts of low level moisture northward very rapidly destabilized the lower troposphere and enhanced frontogenetica

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

a high plains squall line associated with severe surface winds abstract the characteristics of a severe squall line are examined using data acquired from the 1981 cooperative convective precipitation experiment ccope the case is unusual in that the squall line was decoupled from an immediate surface based inflow source due to a meso scale 20 200 km outflow pool produced by a separate mesoscale convective system both systems participated in the development of a mesoscale convective complex which subsequently produced sustained severe surface winds throughout its entire life cycle despite the absolutely stable presquall atmospheric boundary layer the squall line produced radar reflectivity values of 70 dbz and storm induced outflow of 30 m s 1 aircraft soundings in the presquall environment suggest the storm was sustained by an elevated layer of high valued c air overriding the cold dome produced by the developing mcc the strongest surface winds were located upshear from the convective line and consisted of a northerly alongline component because the

damaging surface wind mechanisms within the 10 june 2003 saint louis bow echo during bamex abstract detailed radar and damage survey analyses of a severe bow echo event that occurred on 10 june 2003 during the bow echo and mesoscale convective vortex mcv experiment are presented a bow echo formed just east of saint louis missouri and produced a continuous straight line wind damage swath approximately 8 km in width and 50 km in length along with five f0 f1 tornadoes careful superposition of the damage survey analysis and weather surveillance radar 1988 doppler wsr 88d data from saint charles missouri klsx showed that the primary straight line wind damage swath was not collocated with the bow echo apex as has been suggested in previous studies rather the primary damage swath was found north of the bow apex collocated with a low level vortex that formed on the leading edge of the bow echo much of the primary damage swath appeared to have been created by the low level vortex moreover most of the surface straight line wind damage was generated during the early stages of bow echo mo

site displacement due to variation in earth rotation we study site displacement caused by changes in the rate of rotation of the earth and in the orientation of the earth s pole we include small effects which have been previously neglected most notably those caused by polar motion induced ocean loading using very long baseline interferometry vlbi data we estimate the real and imaginary love numbers associated with vertical and horizontal deformations caused by polar motion the estimates of the real part of the love numbers are consistent with theoretical predictions although the imaginary parts are too large including the loading effect improves the agreement of the real part

measurement of horizontal motions in alaska using very long baseline interferometry we have analyzed 6 years of very long baseline interferometry vlbi data beginning in 1984 from a network of sites in alaska the yukon and the conterminous united states the analysis of these 53 data sets includes constrained continuous piecewise linear estimation of the site atmospheres and clocks application of values and correlations from a self consistent earth orientation series derived from other vlbi data and simultaneous estimation of site positions and velocities from a solution that includes 21 007 observations with a fit of 40 ps in delay and 64 fs s in delay rate we have determined the horizontal velocities of seven sites with precisions of 0 5 2 mm yr 1 standard deviation the three vlbi sites within the alaska aleutian subduction boundary zone yakataga kodiak and sand point have higher instantaneous velocities relative to eastern north america than the interior sites of alaska fairbanks and sourdough the estimated velocity of yakataga relative to fairbanks is 37 8 1 3 mm yr at n27 w 2 modeling of the yakataga data suggests that the observed motion is the result of elastic straining of the overriding plate due to a locked main thrust zone with a component of oblique slip the estimated velocity of kodiak relative to fairbanks is 13 6 0 8 mm yr at n41 w 3 this result is lower than the rate predicted on the basis of simple elastic dislocation models the estimated velocity of sand point relative to fairbanks is 6 4 0 9 mm yr at n65 w 8 the component of this velocity in the plate direction 3 5 1 1 mm yr is not consistent with either an aseismic slip model i e no strain accumulation in the overriding plate or a model in which the site is undergoing compressional strain 10 9 mm yr at n28 w due to simple subduction at the predicted orientation of pacific plate convergence in a north america fixed reference frame the estimated velocities of fairbanks 1 5 0 5 mm yr at s12 e 20 and sourdough 3 9 1 0 mm yr at s13 w 13 are both southward these results may imply motion of this region relative to stable north america but more observations are required to reduce the uncertainties in the azimuths the time evolution of the estimated site positions from vlbi in alaska are in general consistent with constant velocity however in 1988 the yakataga site showed a significant departure from the position predicted from a constant velocity model obtained from the previously estimated position this departure may be static displacement associated with two major strike slip earthquakes that occurred in the gulf of alaska between the 1987 and 1988 measurement sessions

the self consistent dynamic pole tide in non global oceans summary fluid dynamic theories of the pole tide are in conflict with pole tide observations the former predict that the oceanic response to the chandler wobble should be nearly static while the latter reveal the tide to possess significant non equilibrium characteristics resolution of the conflict would determine whether mantle anelasticity or non equilibrium oceans is responsible for a measurable contribution to the chandler period it is possible that resolution might be achieved through a more exact mathematical investigation of pole tide fluid dynamics than theories have carried out to date the theories have also neglected to consider a unique property of the pole tide its ability to lengthen the period of its own forcing function this property implies that the pole tide characteristics and effects on wobble cannot be correctly determined unless the tide and wobble equations are jointly solved this work constitutes a first attempt to determine accurately and self consistently the nature of the pole tide and its effects on the chandler wobble the laplace tidal equations modified by the addition of bottom friction but with no simplifying approximations are employed together with the liouville equations to elucidate pole tide characteristics this work is a first attempt because the earth model chosen is a crude one consisting of global oceans of uniform depth overlying a rigid mantle with a fluid core results for this model suggest that departures of the pole tide from equilibrium may indeed be minimal the relevance of these results to the actual pole tide however must await the application of our self consistent and more exact dynamical theory to the situation of realistic oceans

age refinement of the messinian salinity crisis onset in the mediterranean we propose a revised age calibration of the messinian salinity crisis onset in the mediterranean at 5 971 ma based on the recognition of an extra gypsum cycle in the transitional interval of the perales section sorbas basin spain and the revision of the magnetostratigraphy of the monticino section vena del gesso basin italy this age re calibration allows to state more accurately that i the interval encompassing the msc onset is continuous thus ruling out any erosional feature or stratigraphic hiatus related to a major sea level fall affecting the mediterranean ii the first gypsum was deposited during the summer insolation peak at 5 969 ma associated with an eccentricity minimum and roughly coincident with glacial stage tg32 iii the msc onset was preconditioned by the tectonically driven reduction of the hydrological exchanges with the atlantic ocean and finally triggered by glacial conditions in the northern hemisphere and by arid conditions in northern africa

radar and damage analysis of severe bow echoes observed during bamex abstract this study examines damaging wind production by bow shaped convective systems commonly referred to as bow echoes recent idealized numerical simulations suggest that in addition to descending rear inflow at the bow echo apex low level mesovortices within bow echoes can induce damaging straight line surface winds in light of these findings detailed aerial and ground surveys of wind damage were conducted immediately following five bow echo events observed during the bow echo and mesoscale convective vortex mcv experiment bamex field phase these damage locations were overlaid directly onto weather surveillance radar 1988 doppler wsr 88d images to i elucidate where damaging surface winds occurred within the bow shaped convective system in proximity to the apex north of the apex etc and then ii explain the existence of these winds in the context of the possible damaging wind mechanisms the results of this study provide clear observational evidence that low level mesovortices wit

vortex structure and evolution within bow echoes part i single doppler and damage analysis of the 29 june 1998 derecho abstract single doppler radar along with damage observations are examined to investigate the structural evolution of vortices observed within the 29 june 1998 derecho event that propagated through southeastern iowa into central and eastern illinois a total of 13 meso scale vortices observed primarily at low levels 0 3 km agl along the leading edge of the convective system were detected by the weather surveillance radar 1988 doppler wsr 88d radars at davenport iowa and lincoln illinois all but one of the vortices formed after the system evolved into a bow echo ten of the vortices formed north of the apex while three formed south of the apex seven of the vortices produced tornadoes that created f0 f1 surface damage none of the vortices exhibited appreciable upscale growth careful analysis of the radar data suggests that it may be possible to discern between the tornadic and nontornadic vortices the tornadic vortices tended to be stronger longer lived and deeper than their nontornadic count

evolution of a quasi linear convective system sampled by phased array radar abstracton 2 april 2010 a quasi linear convective system qlcs moved eastward through oklahoma during the early morning hours wind damage in rush springs oklahoma approached enhanced fujita ef1 scale intensity and was likely associated with a mesovortex along the leading edge of the qlcs the evolution of the qlcs as it produced its first bow echo was captured by the national weather radar testbed phased array radar nwrt par in norman oklahoma the nwrt par is an s band radar with an electronically steered beam allowing for rapid volumetric updates 1 min and user defined scanning strategies the rapid temporal updates and dense vertical sampling of the par created a detailed depiction of the damaging wind mechanisms associated with the qlcs key features sampled by the par include microbursts an intensifying midlevel jet and rotation associated with the mesovortex in this work par data are analyzed and compared to data from nearby operational radars highlighting the advantages of using

tornadoes and downbursts in the context of generalized planetary scales abstract in order to cover a wide range of horizontal dimensions of airflow the author proposes a series of five scales maso meso miso to be read as my so moso and muso arranged in the order of the vowels a e 1 o u the dimensions decrease by two orders of magnitude per scale beginning with the planet s equator length chosen to be the maximum dimension of masoscale for each planet mesoscale highs and lows were described on the basis of mesoanalyses while sub mesoscale disturbances were depicted by cataloging over 20 000 photographs of wind effects taken from low flying aircraft during the past 15 years various motion thus classified into these scales led to a conclusion that extreme winds induced by thunderstorms are associated with misoscale and mososcale airflow spawned by the parent mesoscale disturbances

a new facies model for the upper gypsum of sicily italy chronological and palaeoenvironmental constraints for the messinian salinity crisis in the mediterranean the upper gypsum unit of the caltanissetta basin sicily records the last phase of the messinian salinity crisis comprising the so called lago mare event a new facies analysis study recognizes nine to ten depositional cycles consisting of seven rhythmically interbedded primary gypsum bodies and two to three sandstone bodies separated by marly terrigenous horizons showing laterally persistent vertical organization a basal thin gypsum bed is overlain by a cluster of five thicker gypsum bodies a marly interval containing two distinct sandstone horizons separates this cluster from the overlying uppermost seventh gypsum body the terrigenous arenazzolo formation in turn followed by the lower pliocene trubi formation is considered here to form the uppermost part of the upper gypsum unit the rhythmic alternation in the sandy marls and gypsum sandstone bodies records the response of sediments from shelfal to deltaic systems to precession driven arid wet climate fluctuations causing cyclical changes of both base level and water concentration during wet climate phases at insolation maxima marl and sandstone were deposited in a hypohaline environment as suggested by i the typical lago mare faunal assemblage and ii the negative 18o values during arid phases at insolation minima the reduced meteoric supply recorded by higher 18o values in the carbonate caused the development of a negative hydrological budget leading to evaporite precipitation at a basinal scale the upper gypsum unit unconformably overlies a mainly clastic evaporite unit containing carbonate breccia the so called calcare di base and or clastic gypsum towards the basin centres where the basal contact becomes conformable a primary gypsum cumulate horizon is present this layer is interpreted as a possible lateral equivalent of the halite unit present only in the deepest depocentres based on astronomical calibration of the depositional cycles the upper gypsum unit including the arenazzolo formation spans the interval between 5 33 and 5 53 ma this new age calibration allows the deposition of the halite unit to be dated between 5 6 ma top of the lower evaporites and 5 55 ma base of the upper evaporites corresponding to isotopic stages tg12 and or tg14

the genesis of mesovortices within a real data simulation of a bow echo system abstractthe genesis of two mesovortices mvs within a real data convection resolving simulation of the 8 may 2009 central u s bow echo system is studied both mvs form near the bow apex but differ distinctively in intensity lifetime and damage potential the stronger and longer lived mesovortex mva stays near the bow apex where the system scale rear inflow jet rij is present the descending rij produces strong downdrafts and surface convergence which in turn induce strong vertical stretching and intensification of mva into an intense mesovortex in contrast the weaker and shorter lived mesovortex mvb gradually moves away from the bow apex accompanied by localized convective scale downdrafts lagrangian circulation and vorticity budget analyses reveal that the vertical vorticity of mvs in general originate from the tilting of near surface horizontal vorticity which is mainly created via surface friction the circulation of the material circuit that ends up to be a horizontal circuit at the fo

high winds generated by bow echoes part ii the relationship between the mesovortices and damaging straight line winds airborne radar analysis of a mesovortex that developed near the apex of a bow echo is presented the mesovortex was shown to play a critical role in determining the location of intense straight line wind damage at the surface the perturbation pressure gradient force in natural coordinates along the parcel path accelerated the horizontal winds however intense mesovortices modified the low level outflow and largely determined the locations where the strongest winds occurred regions of maximum winds are accounted for as a superposition of the vortex and the flow in which it is embedded the strongest winds occur on the side of the vortex where translation and rotation effects are in the same direction this model explains the observed tongue of high wind speeds that were confined to the periphery of the mesovortex the origin of the mesovortex is also examined similarities and differences of this bow echo event with recent modeling studies are presented

the development of severe vortices within simulated high shear low cape convection abstractenvironments characterized by large values of vertical wind shear and modest convective available potential energy cape are colloquially referred to as high shear low cape hslc environ

numerical simulations of bow echo formation following a squall line supercell merger abstractoutput from idealized numerical simulations is used to investigate the storm scale processes responsible for squall line evolution following a merger with an isolated supercell a simulation including a squall line supercell merger is compared to one using the same initial squall line and background environment without the merger these simulations reveal that while bow echo formation is favored by the strongly sheared background environment the merger produces a more compact bowing structure owing to a locally enhanced rear inflow jet the merger also represents a favored location for severe weather production relative to other portions of the squall line with surface winds vertical vorticity and rainfall all being maximized in the vicinity of the merger an analysis of storm scale processes reveals that the premerger squall line weakens as it encounters outflow from the preline supercell and the supercell becomes the leading edge of the merged system subsequent localized strengthening of th

low level mesovortices within squall lines and bow echoes part ii their genesis and implications this two part study proposes a fundamental explanation of the genesis structure and implications of lowlevel meso g scale vortices within quasi linear convective systems qlcss such as squall lines and bow echoes such mesovortices are observed frequently at times in association with tornadoes idealized experiments with a numerical cloud model show that significant low level mesovortices develop in simulated qlcss especially when the environmental vertical wind shear is above a minimum threshold and when the coriolis forcing is nonzero as illustrated by a qlcs simulated in an environment of moderate vertical wind shear mesovortexgenesis is initiated at low levels by the tilting in downdrafts of initially crosswise horizontal baroclinic vorticity over a 30 min period the resultant vortex couplet gives way to a dominant cyclonic vortex as the relative and more notably planetary vorticity is stretched vertically hence the coriolis force plays a direct role in the low level mesovortexgenesis a downward directed vertical pressure gradient force is subsequently induced within the mesovortices effectively segmenting the previously nearly continuous convective line in moderate to strong environmental shear the simulated qlcss evolve into bow echoes with straight line surface winds found at the bow echo apex and additionally in association with and in fact induced by the lowlevel mesovortices indeed the mesovortex winds tend to be stronger more damaging and expand in area with time owing to a mesovortex amalgamation or upscale vortex growth in weaker environmental shear in which significant low level mesovortices tend not to form damaging surface winds are driven by a rear inflow jet that descends and spreads laterally at the ground well behind the gust front

the role of momentum transport in the motion of a quasi idealized mesoscale convective system abstract momentum transport is examined in a simulated midlatitude mesoscale convective system mcs to investigate its contribution to mcs motion momentum budgets are computed using model output to quantify the role of specific processes in determining the low level wind field in the system s surface based cold pool results show that toward the leading convective line of the mcs and near the leading edge of the cold pool the momentum field is most strongly determined by the vertical advection of the storm induced perturbation wind across the middle rear of the system the wind field is largely a product of the pressure gradient acceleration and to a lesser extent the vertical advection of the background environmental i e base state wind the relative magnitudes of the vertical advection terms in an eulerian momentum budget suggest that for gust front driven systems downward momentum transport by the mcs is a significant driver of mcs motion and potentially severe surface winds results furthe

pole tide modulation of slow slip events at circum pacific subduction zones episodic slow slip ess events have been detected at several circum pacific subduction zones such as cascadia japan and mexico notably at least eight ess events along the northern cascadia subduction zone recurred with a period of 13 16 months we study the relationship between pole tide associated with chan dler wobble with a period of 14 months induced stress and the occurrence of the ess events our quantitative analysis shows that 14 of the 20 documented ess events occurred during the ascension phase prior to the maximum of a pole tide induced coulomb failure stress change and three events occurred at the stress change peak the pole tides modulate the stress field at the downdip edge of the transition zone along the plate interface and may trigger ess events when conditions are favorable the phase advance of the triggered events with respect to the induced coulomb failure stress change may reflect that the fault slip is dictated by a rate and state dependent friction law inferred from laboratory experiments

deep water clastic evaporites deposition in the messinian adriatic foredeep northern apennines italy did the mediterranean ever dry out a new genetic facies model for deep water clastic evaporites is presented based on work carried out on the messinian gessoso solfifera formation of the northern apennines during the last 15 years this model is derived from the most recent siliciclastic turbidite models and describes the downcurrent transformations of a parent flow mainly composed of gypsum clasts the model allows clearer comprehension of processes controlling the production and deposition of clastic evaporites representing the most common evaporite facies of the northern apennines and the definition of the genetic and stratigraphic relationship with primary shallow water evaporites formed and preserved in marginal settings due to the severe recrystallization processes usually affecting these deposits petrographic and geochemical analyses are needed for a more accurate interpretation of the large spectrum of recognized gravity driven deposits ranging from debrisflow to low density turbidites almost all the laminar balatino gypsum previously considered a deep water primary deposit is here reinterpreted as the fine grained product of high to low density gravity flows facies associations permit the framing of the distribution of clastic evaporites into the complex tectonically controlled depositional settings of the apennine foredeep basin the messinian salinity crisis occurred during an intense phase of geodynamic reorganization of the mediterranean area that also produced the fragmentation of the former miocene apennine foredeep basin in this area primary shallow water evaporites equivalent to the mediterranean lower evaporites apparently only formed in semi closed thrust top basins like the vena del gesso basin the subsequent uplift and subaerial exposure of such basins ended the evaporite precipitation and promoted a widespread phase of collapse leading to the resedimentation of the evaporites into deeper basins vertical facies sequences of clastic evaporites can be interpreted in terms of the complex interplay between the messinian tectonic evolution of the apennine thrust belt and related exhumation erosional processes the facies model here proposed could be helpful also for better comprehension of other different depositional and geodynamic contexts the importance of clastic evaporites deposits has been overlooked in the study of other mediterranean areas based on the apennine basins experience it is suggested here that evaporites diffused into the deeper portions of the mediterranean basin may consist mainly of deep water resedimented deposits rather than shallow water to supratidal primary evaporites indicative of a complete basin desiccation

postglacial rebound from vlbi geodesy on establishing vertical reference difficulty in establishing a reference frame fixed to the earth s interior complicates the measurement of the vertical radial motions of the surface i propose that a useful reference frame for vertical motions is that found by minimizing differences between vertical motions observed with vlbi ma and ryan 1995 and predictions from postglacial rebound predictions peltier 1995 the optimal translation of the geocenter is 1 7 mm yr toward 36 n 11l e when determined from the motions of 10 vlbi sites this translation gives a better fit of observations to predictions than does the vlbi reference frame used by ma and ryan 1995 but the improvement is statistically insignificant the root mean square of differences decreases 20 to 0 73 mm yr and the correlation coefficient increases from 0 76 to 0 87 postglacial rebound is evident in the uplift of points in sweden and ontario that were beneath the ancient ice sheets of fennoscandia and canada and in the subsidence of points in the northeastern u s germany and alaska that were around the periphery of the ancient ice sheets