assimilation of scatterometer winds into surface pressure fields using a variational method a variational formulation was used to assimilate seasat a scatterometer sass surface wind measurements near and during a severe storm in the north atlantic into conventional national meteorological center sea level pressure fields an estimate of the relative vorticity at every point on a grid was calculated using each of these two data sets a solution to a modified geostrophic stream function is found subject to the constraints that 1 the relative vorticities calculated from the data agree as closely as possible with the relative vorticities from the variational solution and that 2 the average kinetic energy is a minimum results are obtained which support the idea that averaged satellite data can be treated as synoptic data direct substitution rather than a time weighted insertion made from sass winds generally resulted in more accurate pressure analyses in addition this relatively simple model provides surface pressure fields which agree extremely well with surface truth and the results of other investigators who required additional sources of input data into more complex models it will be possible to obtain improved wind field maps from future scatterometer pressure fields in mid latitudes

bentonites in the chalk of central eastern england and their relation to the opening of the northeast atlantic abstract within the post cenomanian chalk sequence of central eastern england about 20 thin persistent marl horizons occur these marls contain from 30 to 65 non carbonate material the bulk of which is composed of a well crystallised mg rich smectite with a notable paucity of illite and quartz the chalk matrix above and below the marls contains up to 2 0 of non carbonate matter which again is dominated by the presence of an mg rich smectite but which contains a larger proportion of illite and quartz than occurs in the marls for both sets of non carbonate materials the excellent crystallinity and mg rich nature of the smectite strongly suggest that it was formed by the in situ alteration of an aeolian transported volcanic ash i e it is a true bentonite quartz and illite in the chalk matrix are probably detrital components relative to a standard shale non carbonate materials from the chalk marl horizons exhibit a highly anomalous trace element pattern with accentuated levels of zr nb and th but depleted levels of ba rb and k this trace element chemistry corroborates a volcanogenic origin for the smectite insofar as it is not explicable in terms of any realistic sedimentary process the chemistry is best interpreted in terms of the magnetic processes responsible for the formation of the original ash precursor of the marls it appears that this precursor had a pantelleritic composition and therefore originated from a source overlying an area where incipient continental rifting was taking place micromorphological examinations prove that residues from the chalk marls contain small amounts of pyroclastic debris including pumice and fragments of sideromelane glass the morphology of the fragments suggests that the volcanic eruptions responsible for the ejection of the original ash into the air were of the shallow water phreatomagmatic surtseyan type the distribution of marls in the chalk of eastern england suggests that the ashfalls responsible for their origin were of the tropospheric type and were drawn by westerly winds from a centre to the west or northwest of mainland britain of the numerous volcanic centres that lie in offshore areas to the west the anton dohrn seamount in the rockall trough appears to a likely centre of origin for the ashfalls however ashfalls responsible for the formation of the traces of smectite in the chalk matrix were probably of the general background stratospheric type and may have been drawn from more distant centres volcanism at the anton dohrn seamount was related to tensional effects in the continental crust that immediately preceded the formation of the rockall trough and the separation of greenland from northwestern europe during tertiary times activity at the centre and cretaceous bentonites derived therefrom therefore represent the earliest stages in the development of the thulean igneous province

dynamical aspects of the october storm 1987 a study of a successful fine mesh simulation a diagnostic study of a successful numerical simulation of the october storm 1987 is described this good non operational forecast was obtained using the meteorological office s fine mesh model run from a revised analysis at 00 gmt on 15 october 1987 the meteorological office s mesoscale model was also run using initial conditions at 12 gmt 15 october obtained by interpolating the above fine mesh forecast fields to examine the benefits of very high horizontal resolution 15km grid length diagnostic maps and cross sections derived are used to address two scientific issues i the role of weak moist slantwise stability or alternatively positive slantwise convective potential energy ii the dynamical significance of the striking cloud structure the cloud head seen in the satellite imagery early in the storm s life it appears that the baroclinic zone in which the storm develops is highly receptive to forcing by an upper trough and the warm boundary layer air just ahead of the main surface front is characterized by substantial slantwise convective available energy the cloud head is identified with a region of intense slantwise ascent in the warm air just above the main frontal zone its great meridional extent is associated with the upper tropospheric outflow and horizontal spreading of air which has recently undergone rapid slantwise ascent the low level temperature field exhibits throughout the development period a remarkable shape preserving thermal ridge of considerable intensity the sensitivity of the forecast to the removal of surface energy fluxes and latent heat of condensation are investigated separately it is found that on the timescale of the simulation surface energy fluxes have negligible impact on the explosive development on the other hand the contribution of latent heat release to the development appears to dominate the dry baroclinic instability process

regional gravity anomalies depth of the foreland basin and isostatic compensation of the new guinea highlands the new guinea highlands form an active thrust belt advancing southward over the australian continental margin surface geology indicates thin skinned deformation of sediments and continental basement building mountains 2 4 km in average elevation the depth of the adjacent foreland basin is no more than 1500 m in papua new guinea and in many places only 100 200 m indicating little deflection of the australian lithosphere beneath the load of the mountains calculations of elastic loading in which the topographic load of the entire mountain range is supported by australian lithosphere of uniform flexural rigidity d predict a basin 2 10 times deeper than observed in eastern new guinea for a wide range of flexural rigidities 1021 1025 nm bouguer gravity anomalies in the eastern highlands between 143 e and 144 e are consistent with local airy compensation of the mountains and preclude a continuous plate with d 1022 nm underlying any significant portion of the mountains in contrast the observed broad foredeep flexure in central new guinea near 141 142 e requires a strong lithosphere d 1024 1025 nm and limited gravity and sediment thickness observations farther west indicate similar flexural rigidities bouguer gravity measurements and observed foreland basin depths throughout new guinea can be explained by a strong and continuous lithosphere beneath the foreland basin extending no more than 20 60 km north of the range front implying that the plate has weakened beneath the thrust belt collateral evidence for plate weakening beneath the highlands may be found in earthquakes at 10 25 km depth with high angle thrust mechanisms and in widespread quaternary volcanism throughout the eastern thrust belt a 50 mgal positive residual anomaly over the northern 100 km of the eastern highlands cannot be explained by local compensation or mechanical support from the south indicating either a large excess mass at depth or some additional form of support for the northeastern highlands the gravity observations in eastern new guinea require 10 15 km of crustal thickening but observed sediment thicknesses can only account for 0 5 km necessitating 5 15 km of thickening in the basement

observations of mesoscale circulations within extratropical cyclones over the north atlantic ocean during erica abstract pseudo dual doppler analyses of two mesoscale circulations 20 40 km in horizontal dimensions that formed along a warm front within a rapidly deepening extratropical cyclone over the ocean are presented the circulations were analyzed using airborne doppler radar during erica experiment on rapidly intensifying cyclones over the atlantic iop intensive observing period 4 and are believed to be a type of frontal instability that has not been addressed in past theoretical studies of frontal waves and cyclones these features may be the shallow circulations that have been documented to play a role in cyclogenesis when they become coupled with an upper level baroclinic wave the present case is compared and contrasted with the only other well analyzed event during erica iop 5 a retrieval of the perturbation pressure and buoyancy fields using the kinematic wind fields is performed in order to facilitate the interpretation of the dynamic structure of these vortices in addition a set of equations

an unusual and characteristic sedimentary mineral suite associated with the evolution of passive margins abstract comparison of the blanche point formation south australia with sedimentary sequences of passive margins world wide reveals a common mineralogy typified by the presence of smectite clinoptilolite and opal ct explosive volcanic activity associated with passive margin evolution appears to have produced this mineralogy

surface flux regulation of the coupling between cumulus convection and baroclinic waves abstract the authors examine the role of convection in the dynamics of eddy life cycles through numerical experiments using initial states that are baroclinically and conditionally unstable in midlatitudes the location of wave induced convection and its influence on the growing wave depends on how strongly the wave is coupled to the lower boundary through surface fluxes for all three convective schemes used here emanuel modified grell modified kuo convective destabilization is favored in the wave s warm sector when there are no surface fluxes included in the simulation and in the cold sector when there are convection is also shallower when it occurs in the cold sector though still precipitating for simulations using emanuel convection the relatively shallow convection plays a central role in a water cycle wherein 1 evaporation gives moisture to the cold sector s boundary layer 2 convection pumps some of the moisture into the lower troposphere above the boundary layer 3 the large scale circ

tectonic evolution of the meatiq infrastructure central eastern desert egypt the pan african basement exposed in the meatiq area central eastern desert egypt was found to possess tectonic styles belonging to infrastructure transition and super structure levels tectonic style of the infrastructure was developed during an old orogeny in the lower pan african and overprinted by those of the transition and superstructure levels of a younger orogeny in the middle and upper pan african respectively in the lower pan african old sequences of sediments and volcanics together with ophiolitic rocks were intensely deformed and regionally highly metamorphosed into gneisses and amphibolites in the infrastructure level such rocks were migmatized plastically deformed and intruded by synkinematic granitoid diorite to alkali granite lenses sheets and plutons which were probably crystallized as amphibolite facies gneisses later on these infrastructural rocks were cut by mafic to intermediate dykes and sills isostically uplifted and cratonized parts were exposed to erosion in the middle pan african the cratonized rocks sank into a transition tectonic level where they underwent large scale thrusting varying degrees of cataclasis and mylonitization and low to medium grade regional metamorphism an episode of plutonism guided by thrusts followed mainly in the form of synkinematic intrusion of tonalite granodiorite and quartz monzodiorite in the upper pan african isostatic uplift occurred and the mylonitic rocks attained the superstructure level there they were subjected to two main phases of folding resulting in the major meatiq domal structure subsequently the folded rocks were intruded by a postkinematic quartz monzonite pluton

statistical differences of quasigeostrophic variables stability and moisture profiles in north american storm tracks abstract three common synoptic storm tracks observed throughout the united states are the alberta clipper the colorado cyclone and the east coast storm numerous studies have been performed on individual storm tracks analyzing quasigeostrophic dynamics stability and moisture profiles in each this study evaluated storms in each track to help diagnose patterns and magnitudes of the aforementioned quantities documenting how they compare from track to track six diagnostic variables were computed to facilitate the comparison of the storm tracks differential geostrophic absolute vorticity advection temperature advection q vector divergence mean layer specific humidity low level stability and midlevel stability a dataset was compiled consisting of 101 alberta clippers 165 colorado cyclones and 159 east coast cyclones and mean fields were generated for this comparison maxima and minima of the 25th and 75th percentiles were generated to diagnose magnitudes and patterns of strong versus weak cyclo

on the evolution of the qe ii storm i synoptic aspects abstract the hurricane force winds and heavy seas which battered the liner queen elizabeth ii on 10 and 11 september 1978 were associated with an extreme example of a meteorological bomb as defined by sanders and gyakum despite the existence of surface buoys and the relatively high density of mobile ships in the north atlantic real time weather analyses subjective forecasts and numerical prognoses all erred in the intensity and track of this storm in this study deficiencies in the real time surface analysis were compensated for by the addition of seasat a surface wind fields and previously discarded conventional ship reports this paper examines the synoptic aspects of this case with emphasis on physical mechanisms most likely responsible for the development the cyclone originated as a shallow barocline disturbance west of atlantic city new jersey and explosive deepening 60 mb 24 h commenced once the storm moved offshore and in association with cumulus convection adjacent to the storm cent

structure of the papuan fold belt papua new guinea 1 the structure of the papuan fold belt differs substantially from the classical thin skinned structures of the canadian rockies mainly due to the weak and broken papuan lithosphere and incompetent clastic section compared to the strong cratonic lithosphere in canada overlain by limestones and quartzites the papuan margin was dissected by mesozoic extensional faults in part reactivated during neogene compression which created basement involved anticlines or elevated plateaus in the papuan fold belt the sedimentary section in the fold belt is deformed into large ramp anticlines in the southwest smaller miocene and mesozoic duplexes in the center and fault propagation folds in the northeast hydrocarbon discoveries to date have occurred in the southwestern anticlines which are interpreted as reactivated extensional structures the precursor rollover anticlines trapped oil generated in the late cretaceous such that present accumulations probably result from preservation of that oil during neogene thrusting mesozoic duplex structures are likely to be prospective but difficult to define and fault propagation folds rely upon unproven upper cretaceous sandstones as a reservoir

evolution and mesoscale structure of a polar low outbreak an observational study of an unusual polar low outbreak is described in which four lows formed in succession near south east iceland because all the lows tracked south east close to scotland an unusually dense network of surface observations was available for analysis including radar this complemented the geostationary and polar orbiting satellite data that are more commonly used in polar low studies each of the four polar lows displayed a different structure and evolution the first was a circular convective low the second a relatively weak surface signature of an upper level feature while the final two cyclones appeared as a wave train with one cyclone decaying and the other developing into an intense disturbance because of the high resolution of the surface data it was possible to identify unambiguously mesoscale frontal features within the polar lows these are described in detail a close examination was made of the final intense low which showed that its evolution and frontal structure closely matched those found in standard conceptual models of rapidly developing maritime cyclones this polar low also showed evidence of a warm core and symmetric instability within an extensive cloud head

the energy cycle and structural evolution of cyclones over southeastern south america in three case studies 1 in this paper the lorenz energy cycle over a limited area was applied for three cyclones with different origins and evolutions where each of them was formed in an important cyclogenetic region near southeastern south america the synoptic conditions and energetics were analyzed during each system s life cycle and showed important relationships between their energy cycle and the evolution of their vertical structure in the case of the weak baroclinic cyclone which formed on brazil s south southeastern coast the analysis showed that it originated through a midlevel cutoff low with contribution from barotropic instability its evolution would indicate potential transition to a hybrid system if the convective activity were stronger the system that occurred in the la plata river mouth had features of an oceanic bomb type cyclogenesis and showed an important contribution from the available potential energy generation term through the latent heat release by the convection meanwhile the system of the southern argentina coast presented a classical baroclinic development of extratropical cyclogenesis in the energy cycle from the wave amplification up to the final occlusion of the associated frontal system these analyses revealed that the development of some cyclones that occur in eastern south america can present different mechanisms that are not related to the classical extratropical cyclogenesis

the muller anticline papua new guinea basement cored inverted extensional fault structures with opposite vergence abstract throughout the nw se trending papuan foldbelt two dominant structural styles are present in the northeast the 1 km thick thrust imbricate slices of miocene limestone attest to the classical thin skinned nature of the deformation in the southwest adjacent to the undeformed foreland fold structures are 1 or 2 orders of magnitude greater in size are strongly asymmetrical and commonly have relatively thicker stratigraphie sections on the crests such structures are the result of mio pliocene compression that caused thrusting along faults that are hypothesized to have been extensional in the mesozoic and palaeogene geological traverses from the undeformed foreland heading northeast across the 150 km by 50 km muller range in western papua new guinea provided detailed surface structural data when combined with analysis of existing geological maps exploration wells regional gravity surveys and extensive seismic in the foreland moderately constrained balanced and restorable cross sections through the muller anticline could be constructed interpretations of gravity data are consistent with the muller anticline being cored by basement and seismic data extrapolated beneath the mountains show the outcrop of basement in the centre of the muller range to be elevated 8 km above regional the eastern muller anticline ema has a shallow northeast limb and steeper southwest limb suggesting a ne dipping fault below such that basement was thrust to the southwest the cecilia wai asi juha and lavani anticlines to the southwest of the ema are interpreted to be formed by shortening of the whole sedimentary section to balance the shortening in basement there are no such structures to the southwest of the western muller anticline wma where the southwest limb is gently dipping and the northeast limb is steep hence the wma is interpreted as having formed above a sw dipping fault along which basement was thrust to the northeast the marked difference in shortening of the southwest limbs requires a tear fault between the ema and wma the tear fault is here interpreted to coincide with the northwestern end of the cecilia and lavani anticlines and the marked change in strike of the muller anticline by analogy with other very large asymmetrical basement involved structures in the papuan foldbelt it is suggested that the faults underlying the muller anticline were active as extensional faults in the mesozoic soling at a mid crustal detachment the extensional faults beneath ema and wma had opposite vergence and were separated by a transfer zone subsequent compressional reactivation of the extensional faults in the pliocene gave rise to the present muller anticline

late cretaceous to oligocene burial and collision in western papua new guinea indications from low temperature thermochronology and thermal modelling abstract recent field and analytical work have considerably improved our understanding of the structure of the muller range along the frontal trend of the papuan fold and thrust belt pftb in western papua new guinea png however numerous questions remain unresolved concerning the geological evolution of the region in particular the late cretaceous to oligocene history of the region is largely unknown due to the absence of a continuous stratigraphic record here we use both new and existing low temperature thermochronology data to investigate the geological history of the muller range thermal history models based on these data suggest two major cenozoic cooling episodes the youngest and best constrained is clearly recorded in the stratigraphic record and relates to neogene collision at the northern margin of the australian continent an older episode of comparable or greater magnitude occurred in the eocene to oligocene and may relate to the removal of 1500 3000 m of late cretaceous to eocene section across the muller range prior to the widespread deposition of the shelfal darai limestone we suggest that extension along major faults beneath the muller range accommodated sedimentation from the late cretaceous to the eocene consistent with long lived extensional structures observed in neighbouring regions in contrast to the muller range area an almost continuous late cretaceous to eocene stratigraphic sequence is preserved in the hinterland

northern new guinea wrench fault system a manifestation of late cenozoic interactions between australian and pacific plates abstract cenozoic plate interactions between the australian and pacific plates have yielded a variety of convergent tectonic styles two major products of this convergence are the sorong fault zone of irian jaya and the ramu markham fault zone of papua the sorong fault system has been documented to extend westward more than 500 mi 800 km from teluk sarera to kep banggai as a left lateral strike slip fault the ramu markham fault system is of disputed displacement and has been previously interpreted to extend from over 310 mi 500 km just east of the sepik river into the huon gulf a consideration of australian pacific cenozoic plate kinematics holocene vectors earthquake focal mechanisms photogeologic lineation analyses and the assimilation of other pertinent geologic data suggests that the ramu markham fault zone is an extension of the sorong fault system and that together they represent significant left lateral strike slip motion in rigid crustal basement this motion has produced large scale en echelon surface expressed faults and folds in detached overlying neogene sediments furthermore this wrench fault system has led to the transcompressional development and deformation of the meervlakt piore sepik and ramu basins of northern new guinea an understanding of the tectonic evolution of these basins is tantamount to an assessment of their evolving hy rocarbon potential end of article last page 980

the integral role of a diabatic rossby vortex in a heavy snowfall event abstract on 24 25 february 2005 a significant east coast cyclone deposited from 4 to nearly 12 in 10 30 cm of snow on parts of the northeastern united states the heaviest snowfall and most rapid deepening of the cyclone coincided with the favorable positioning of an upper level short wave trough immediately upstream of a preexisting surface cyclone the surface cyclone in question formed approximately 15 h before the heaviest snowfall along a coastal front in a region of frontogenesis and heavy precipitation the incipient surface cyclone subsequently intensified as it moved to the northeast consistently generating the strongest convection to the east northeast of the low level circulation center the use of potential vorticity pv inversion techniques and a suite of mesoscale model simulations illustrates that the early intensification of the incipient surface cyclone was primarily driven by diabatic effects and was not critically dependent on the upper level wave these facts taken in conjunct

reexamining the dynamics of short scale diabatic rossby waves and their role in midlatitude moist cyclogenesis abstract as a step toward a more comprehensive study of the physical processes that underlie explosive cyclogenesis a two dimensional semigeostrophic model with a now standard parameterization of latent heat release is used to diagnose the structure energetics and propagation characteristics of short scale diabatic normal modes in a moist baroclinic atmosphere with the eady basic state upon revisiting the inviscid problem it is found that when a thermodynamically consistent vertical profile of latent heat release is used the short wave cutoff vanishes and growth rates become independent of zonal wavelength for zonal wavelengths shorter than approximately 1900 km the destabilized short scale modes identified previously as diabatic rossby waves owe their existence to the continuous generation of potential vorticity by moist processes associated with warm air advection rising motion and latent heat release to determine if these short scale diabatic rossby wave modes continue to grow at small

pan african structures ophiolites and melange in the eastem desert of egypt a traverse at 26 n a detailed structural traverse across the basement rocks of the eastern desert of egypt shows that they consist apart from intrusions of four broadly recumbent tectonic units the lowest of arkosic metasediments of continental shelf facies is exposed in a dome this unit is overlain by an allochthonous ophiolitic melange containing complete and dismembered ophiolitic masses in a matrix of deep oceanic graphitic pelites and turbidites a near horizontal schistose to mylonitic fabric most intense near and below the base of the melange indicates extensive lateral tectonic transport of the ophiolitic melange over the shelf metasediments but the melange originated as an olistostrome before being tectonically transported the melange extends over an area of at least 10 000 km 2 it is locally overlain by calc alkaline volcanics in which deformation is less intense but increases and schistosity flattens downwards indicating some translation over the melange unconformable on the melange and calc alkaline volcanics is a molasse facies series itself also locally strongly deformed late tectonic granites preceded and locally post date the molasse facies sediments still later diapiric peralkaline riebeckite granites locally up domed the recumbent structures the tectonic evolution is related to a late proterozoic subduction zone to the se of the region

foraminiferal biofacies in a silica rich neritic sediment late eocene south australia abstract the highly siliceous blanche point formation accumulated during the late eocene zones p15 p16 in the st vincent basin when the climate was warm it differs from shelly neritic carbonates above it and below it by higher but fluctuating numbers of benthonic foraminifera of the family uvigerinidae and by high dominance in different horizons of infaunal crustacean traces and of infaunal gastropods within the blanche point formation changes from a banded siliceous opal ct sediment to a homogeneous spongolite are paralleled by biofacies changes high numbers of uvigerinidae and in part of the formation high numbers of robertinacea bolivinidae sphaeroidina cassidulina are more consistent with generally lowered levels of oxygen at the sediment surface than with other forms of environmental stress the study is consistent with a recent conclusion based on mineralogy that the abundant silica came from volcanic ash it suggests too that restricted circulation permitted biogenic and other mechanisms of fix the silica in the st vincent basin whilst silica was being flushed away from more open environments facing the nascent southern ocean

life cycle study of a diabatic rossby wave as a precursor to rapid cyclogenesis in the north atlantic dynamics and forecast performance abstractthe life cycle of a north atlantic cyclone in december 2005 that included a rapid propagation phase as a diabatic rossby wave drw is investigated by means of operational analyses and deterministic forecasts from the ecmwf a quasigeostrophic omega diagnostic has been applied to assess the impact of upper level forcing during the genesis propagation and intensification phase respectively the system was generated in the gulf of mexico as a mesoscale convective vortex mcv influenced by vertical motion forcing from a nearby upper level trough the drw propagation phase was characterized by a shallow low level diabatically produced potential vorticity pv anomaly that rapidly propagated along the southern border of an intense baroclinic zone no significant upper level forcing could be identified during this phase of the development eventually explosive intensification occurred as the region of vertical motion forced by an approaching upper level trough reached the position of the drw the

displacement distance methods in the analysis of fold thrust structures and linked fault systems a new method for analysing the internal strain in thrust sheets is described the displacement distance diagram can be used to quantify the relative shortening or relative stretch between the hangingwall and footwall beds of a thrust and is a useful way of analysing commonly occurring fold thrust structures the stretch is a function of the relative rates of thrust propagation and thrust slip the cumulative displacement distance diagram described here can be used to calculate the absolute shortening or extension when this is accommodated above a single decollement in a linked fault system this method offers a useful way of analysing duplex structures and large scale foreland thrust zones as well as extensional fault systems and can be used as an alternative to or in conjunction with balanced cross sections both methods can be used to quantify the variation in shortening above a single detachment zone this variation may be mechanically significant reflecting lithological control on thrust or normal fault growth

wind and pressure fields near tropical cyclone oliver derived from scatterometer observations the results of this study demonstrate that the surface wind velocity and pressure fields derived from spaceborne scatterometers are useful in monitoring the location and intensity of tropical cyclones satellite borne microwave scatterometers can penetrate the cloudy core regions of tropical cyclones to resolve the circulation in detail over data sparse regions the location of the cyclone observed by the ers 1 scatterometer is very close to that revealed in geostationary meteorological satellite images the surface winds provided by the ers 1 scatterometer are used here with a modified two layer planetary boundary layer model which includes effects of curvature stability and secondary flow to derive surface pressures near tropical cyclone oliver the curvature effect is found to be more significant than stability and secondary flow which are crucial in deriving accurate surface pressure fields in midlatitudes

eocene cool water carbonate and biosiliceous sedimentation dynamics st vincent basin south australia middle and upper eocene biogenic sediments in the willunga embayment along the eastern margin of the st vincent basin are a series of warm temperate limestones marls and spiculites the middle eocene tortachilla limestone is a thin coarse grained quartzose biofragmental bryozoan mollusc calcarenite of stacked metre scale depositional cycles with hardground caps lithification aragonite dissolution and the filling of moulds by sediment and cement characterize early marine meteoric diagenesis further meteoric diagenesis at the end of tortachilla deposition resulted in dissolution fe oxide precipitation and calcite cementation the upper eocene blanche point formation is composed of coccolith and spiculite marl and spiculite all locally rich in glauconite turritellid gastropods and sponges decimetre scale units locally capped by firmgrounds have fossiliferous lower parts and relatively barren upper parts carbonate diagenesis is minor with much aragonite still present but early silicification is extensive except in the spiculite which is still opal a all depositional environments are interpreted as relatively shallow water high energy during the middle eocene and low energy during the upper eocene reflecting the variable importance of a basin entrance archipelago of carbonate highs marls and spiculites are interpreted to have formed under an overall estuarine circulation system in a humid climate basinal waters although well mixed were turbid and rich in land derived nutrients yet subphotic near the sea floor these low energy inner shelf biosiliceous sediments occur in coeval environments across other parts of australia and elsewhere in the rock record suggesting that they are a recurring element of the cool water carbonate shelf depositional system thus spiculites and spiculitic carbonates in the rock record need be neither deep basinal nor polar in origin the paradox of a shallow water carbonate spiculite association may be more common in geological history than generally realized and may reflect a characteristic mid latitude humid climate temperate water palaeoenvironmental association

extensive volcanism associated with the separation of australia and antarctica alternating hard and soft layers characterize the gull rock and tuit members of the late eocene blanche point formation south australia originally the formation was mainly a mixture of volcanic ash sponge spicules and calcareous fossil remains with hard layers produced later by selective silicification it resembles cretaceous sediments from western europe and the eastern coast of the united states and in each case it appears that alteration of volcanic ash produced smectite and clinoptilolite with release of silica that subsequently crystallized as opal ct the occurrence of similar deposits from new zealand to as far west as albany western australia indicates extensive volcanic activity south of australia in the late eocene resulting from rifting and separation from antarctica

the march 1993 superstorm cyclogenesis incipient phase synoptic and convective scale flow interaction and model performance abstract the incipient stages of the 12 14 march 1993 superstorm ss93 cyclogenesis over the gulf of mexico are examined noteworthy aspects of ss93 include 1 it is the deepest extratropical cyclone ever observed over the gulf of mexico during the 1957 96 period and 2 existing operational prediction models performed poorly in simulating the incipient cyclogenesis over the northwestern gulf of mexico a dynamic tropopause dt analysis shows that ss93 is triggered by a potent potential vorticity pv anomaly as it crosses extreme northern mexico and approaches the gulf of mexico the low level environment over the western gulf of mexico is warmed moistened and destabilized by a persistent southerly flow ahead of the approaching pv anomaly ascent and a lowering of the dt associated with a lowering of the potential temperature ahead of the pv anomaly contributes to further destabilization that is realized in the form of a massive convective outbreak an examination of the national centers for envi

rifting of the northern margin of the australian continent and the origin of some microcontinents in eastern indonesia abstract continental australia is bounded on the east south and west sides by passive margins and the geological histories of these are well documented falvey and mutter 1981 the northern margin of the australian continent is now an active collision margin its previous history as a passive margin has rarely been examined this paper shows how the late palaeozoic to mesozoic sequence which forms the northern margin of the australian continent in the island of new guinea is readily related to the tectonic stages of a rift drift sequence rifting start of breakup began at about 230 m y ago at the permian triassic boundary the onset of seafloor spreading is marked by a post breakup unconformity and ranges in age along the northern margin of the continent from 185 m y in papua new guinea to 170 m y in irian jaya from there the age of the post breakup unconformity continues to young in a southwesterly direction along the western margin of the australian continent reflecting the opening of the indian ocean off western australia the timing of the onset of spreading in central papua new guinea is consistent with the timing of the initiation of spreading in the proto pacific ocean proposed by nur and ben avraham 1977 by the end of the jurassic the northern margin of the australian continent faced a seaway which linked the proto indian and proto pacific oceans this newly formed ocean was separated from the pre existing oceans of the neo tethys and panthalassa by a screen of continents or microcontinents the identity of this screen is discussed and it is suggested that part of it is preserved in the microcontinents of eastern indonesia

structure of the alice anticline papua new guinea serial balanced cross sections and their restoration abstract the structure of the western part of the papuan fold belt is characterised by both thin skinned thrusting and basement involved structures basement involvement is attributed to inversion of earlier formed extensional faults the alice anticline is a frontal structure of the papuan fold belt and formed due to inversion of a tertiary extensional fault system complex forelimb geometry of the alice anticline changes markedly along strike and suggests varying amounts of shortening in this part of the structure balanced cross sections quantify differential shortening along the anticline whereas palinspastic restoration shows that the differential shortening is compatible between cross sections three dimensional restoration of the alice anticline makes use of a series of balanced cross sections and is based on a line length method paradoxically the restoration reveals non plane strain in the balanced cross sections upon which it relies however the restoration also reveals and quantifies a component of rotation about vertical axes which would not be detected by application of conventional methods of structural analysis rotations about vertical axes are attributed to pinning of progressive foreland propagating deformation the distribution of rotations about vertical axes suggest that zones of pinning are coincident with relay zones in the early extensional fault geometry two relay zones associated with the original geometry acted as obstructions to deformation and have effectively pinned contractional structures during their formation causing the rotations about vertical axes such rotations are not manifested in changing fold axis orientations and have only been derived from a consideration of material balance during deformation

the structure of mountain fronts commonly the part of a mountain front which is visible at the surface consists of foreland dipping thrust belt rocks elevated above their regional structural position and overlain more or less conformably by molasse several explanations for their geometry are possible 1 major detachments exist within or beneath the molasse resulting in transport of the foreland basin examples of this geometry come from the swiss molasse plain the southern pyrenees and the mackenzie mountains of canada 2 displacement is lost on major backthrusts beneath the frontal monocline examples cited here are the rockies of alberta the sulaiman ranges of pakistan the mackenzies and the andes in peru 3 thrust sheets travelled over an old land surface and syntectonic molasse contemporaneously offlaps the topographic high of the thrust front this phenomenon occurs along the alpine thrust front in haute provence 4 the frontal fold represents deformation above a large scale thrust tip no unequivocal example of tip line strain at this scale has been recorded although this type of deformation may occur in the brooks range of alaska in many areas mountain fronts show a combination of these idealized geometries

smectite zeolite biotite and apatite in the corallian oxfordian sediments of the baulking area in berkshire england

structure of the irian jaya mobile belt irian jaya indonesia image interpretation and field investigation over the central ranges of irian jaya has provided a structural overview of the inaccessible and largely unmapped irian jaya mobile belt ijmb in the region bounded by longitudes 136 30 e and 141 00 e throughout much of the southern para autochthonous part of the belt structural facing directions are visible on imagery through selective illumination of hogbacks and cuestas formed on thick bedded mesozoic siliciclastics and extensive late cretaceous neogene platform carbonate sequences north of the regional derewo fault zone the derewo metamorphics are regarded in part as correlatives of the metamorphosed om beds in western papua new guinea and display a regional structural grain parallel to the orogen the limited extent of spectrally anomalous features associated with ultramafic rocks indicate that ophiolites are confined to the southern part of the irian jaya ophiolite belt which may be largely composed of metamorphic rocks interpreted macroscopic and megascopic structures suggest the presence of seven discrete structural domains in the ijmb from north to south these are 1 north coast basin region consisting of paleogene neogene volcanics and sediments overlain by a pliocene pleistocene successor basin sequence 2 an allochthonous terrane composed of ophiolites and high grade metamorphic rocks 3 the derewo metamorphic assemblage displaying polyphase deformation 4 a complex marginal zone within mesozoic paleogene miogeoclinal sediments which includes steep duplex structures and remnant klippen 5 a 40 to 50 km wide partly inverted synclinorium composed of miogeoclinal sediments 6 a regional south vergent overturned anticlinorium formed by incompetent paleozoic sediments and 7 a foreland thrust domain involving both mesozoic cenozoic miogeoclinal cover and a deformed neogene foreland molasse basin sequence the regional disposition of interpreted structures in the irian jaya mobile belt and reference to published mapping in western irian jaya and western papua new guinea strongly indicates polyphase deformation late oligocene miocene docking of metamorphics island arc assemblages and ophiolites produced tectonically stacked e w trending structures thrust on to the north margin of the australian continent with its miogeoclinal cover late miocene pliocene collision with the melanesian arc brought the accreted australian margin into contact with the westward moving pacific plate and instituted a regime of oblique transpressional convergence resulting structures include e w sinistral wrenching and nw thrusts along lateral e w ramps

a cyclone phase space derived from thermal wind and thermal asymmetry abstract an objectively defined three dimensional cyclone phase space is proposed and explored cyclone phase is described using the parameters of storm motion relative thickness asymmetry symmetric nonfrontal versus asymmetric frontal and vertical derivative of horizontal height gradient cold versus warm core structure via the thermal wind relationship a cyclone s life cycle can be analyzed within this phase space providing substantial insight into the cyclone structural evolution an objective classification of cyclone phase is possible unifying the basic structural description of tropical extratropical and hybrid cyclones into a continuum stereotypical symmetric warm core tropical cyclone and asymmetric cold core extratropical cyclone life cycles are illustrated using 1 navy operational global atmospheric prediction system nogaps operational analyses and 2 5 ncep ncar reanalyses the transitions between cyclone phases are clearly illustrated within the phase space including extratro

the impact of seasat a scatterometer data on the numerical prediction of the queen elizabeth ii storm the development of the queen elizabeth ii storm from 1200 ut on september 9 1978 to 0000 ut on september 11 1978 is forecast with a limited area fine resolution 100 km numerical weather prediction model forecasts from initial conditions that include and exclude seasat scatterometer surface winds are performed when the seasat winds are allowed to influence the upper levels of the atmosphere a large positive impact is found

geology and origin of meatiq dome egypt a precambrian metamorphic core complex meatiq dome a metamorphic complex in the precambrian basement of the eastern desert of egypt exhibits many of the essential features of cordilleran metamorphic core complexes it is an antiformal structure with low dipping foliation and unidirectional mineral slickenside lineation the core consists of granite gneiss and is conformably overlain by a heterogeneous isoclinally folded mylonitic carapace the carapace grades upward into a nonmylonitic cover of low grade ophiolitic rocks the mylonitic rocks are interpreted to have formed in a low angle ductile shear zone during a compressional tectonic event accompanied by syntectonic intrusion of tonalite doming postdated mylonitization the absence of a brittle detachment surface at meatiq dome is its primary distinction from the otherwise similar cordilleran complexes

classification and synoptic analysis of subtropical cyclones within the northeastern atlantic ocean abstractsince more research is needed on subtropical cyclones stcs formed within the north atlantic eastern basin this survey analyzes them from a synoptic point of view on a climatological basis with the main aims of studying their common features complementing other studies of these storms in the north atlantic and aiding the forecasting community fifteen cases of stcs were identified during the period 1979 2011 by applying a set of criteria from two databases composite analysis reveals that an extratropical depression acts as a precursor when it is isolated from the westerlies and then suffers a deepening when becoming subtropical instead of decaying through occlusion this process is accompanied by an atmospheric circulation within the north atlantic whose main feature is characterized by notable departures from the climatological pattern with a statistically significant anomalous high pressure to the north of the stcs three conceptual models of synoptic pattern of subtropical cyclogenesis

passive roof duplex geometry in the frontal structures of the kirthar and sulaiman mountain belts pakistan abstract exploration for hydrocarbons over the past few years has greatly improved our understanding of the geometry of frontal mountain belt structures in this study we introduce and discuss the concept of the passive roof duplex using as the main example the kirthar and sulaiman ranges in the baluchistan province of pakistan structures similar to those described here have been recognized previously in other mountain belts and they appear to exist as a common feature in many more frontal regions of mountain belts our example of a passive roof duplex which we describe from pakistan is compared briefly with similar structures reported by others the passive roof duplex is here defined as a duplex whose roof thrust has backthrust sense passive roof thrust and whose roof sequence those rocks lying above the roof thrust remains relatively stationary during foreland directed piggy back style propagation of horses within the duplex