structure of a frontal cyclone a diagnostic study of a mid latitude cyclone has been carried out using routinely available numerical weather prediction model products and imagery the cyclone was intense but not exceptionally so and the results are believed to have some generality the detailed description of the cyclone structure just before it began to deepen rapidly integrates concepts from a number of researchers into a common framework a dominant feature of the cyclone close to its centre was the cloud head a region of cloud with a sharp convex outer edge which formed poleward of the main polar front cloud band the cloud head was caused by two flows that entered it from the east ascending and fanning out within it one flow the cold conveyor belt brought low wet bulb potential temperature w air back into the cloud head from low levels ahead of the warm front the other flow was due to high w air that peeled off from the base of the main warm sector airflow i e part of the warm conveyor belt and travelled in the boundary layer back towards the cyclone centre first undercutting dry air that had earlier descended from the upper troposphere called a dry intrusion and then ascending at the upper boundary of the cloud head above the cold conveyor belt the transverse circulation that gave the ascent within the cloud head also led to the cold front fracturing along its length into two separate sharp surface cold fronts with a more diffuse frontal region in between frontal fracture the two sharp surface cold fronts were associated with narrow cold frontal rainbands line convection one of the line convection segments forming the southern edge of the cloud head the overrunning of the dry intrusion in the region of the frontal fracture led to a structure known as a split front in which an upper level humidity front began to run ahead of the position of the surface cold front a feature of the cyclone at this intermediate stage in its evolution was that a large proportion of the precipitation was being generated by ascent of relatively cold air the cold conveyor belt in the cloud head as part of the thermally indirect circulation at the left exit of a developing secondary upper level jet

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

yvonaspis nouveau genre d osteostraci vertebrata agnatha du devonien emsien eifelien des gres de gaspe quebec canada all osteostracan species of the gaspe sandstones devonian of canada formerly attributed to the genus cephalaspis are referred here to the new genus yvonaspis the latter is characterized by the very elongated shape of the naso hypophysal opening this monophyletic genus may be the sister group of parameteoraspis among cephalaspidians

distribution and dispersal history of eurypterida chelicerata abstract the distribution and dispersal histories of eurypterida are examined in a phylogenetic and palaeogeographic context it is suggested that all the eurypterid clades originated and had most of their evolutionary history on the palaeocontinents of laurentia baltica avalonia the rheno hercynian terrane and some presence in siberia the siluro devonian stylonurina and the eurypterine superfamilies eurypteroidea and waeringopteroidea are confined in their entirety to these continents the late palaeozoic records of adelophthalmoidea and hibbertopteroidea in china south america and africa can be explained by rafting on the continental plates that amalgamated into the supercontinent pangaea however two clades have distributions that suggest abilities to cross open stretches of ocean the silurian and devonian pterygotoids and some devonian adelophthalmoids however one silurian mixopteroid and the basal swimming form onychopterella outside the core area suggest the dispersal patterns are more complicated the pterygotoids might be the only clade whose members frequently undertook oceanic excursions since almost all eurypterid evolution took place in laurentia baltica and avalonia and some in the early devonian of the rheno hercynian terrane prior to the carboniferous it is unlikely that many taxonomically rich pre carboniferous eurypterid faunas will be encountered outside of these palaeocontinents

the red island road formation early devonian terrestrial fill in the anticosti foreland basin western newfoundland more than 100 m of nearly flat lying fluvially derived thick bedded and lensoid clast supported conglomerate and sandstone are found on red island off the coast of the port au port peninsula western newfoundland formally described herein and named red island road formation the strata represent a unique lithologic formation not exposed or known anywhere else in the region characteristic features include abundant rounded highly weathered and varnished cobbles and boulders derived from an unknown mixed volcanic and very low to low grade metamorphic terrane although the unit is largely unfossiliferous a thin sandstone bed near the top of the type section contains primitive dichotomously branched plant remains and biostratigraphically significant palynomorphs among more than 25 species of spores it is the diversity of emphanisporites dictyotriletes and dibolisporites and in particular dibolisporites echinaceus dictyotriletes canadensis emphanisporites annulatus e erraticus and e schultzi

tropical cooling at the last glacial maximum and extratropical ocean ventilation1 1 the ncar csm is used to simulate the climate at last glacial maximum the csm simulates a tropical sst cooling of 2 1 c it is shown that about half of this tropical cooling is associated with the upper ocean circulation especially the ventilation of thermocline and intermediate waters from the mid high latitude south pacific

biogeochemical assessment of sources of organic matter and paleoproductivity during the early aptian oceanic anoxic event at shatsky rise odp leg 198 this study investigates organic rich sedimentary sequences deposited during the early aptian oceanic anoxic event oae1a at sites 1207 and 1213 on shatsky rise odp leg 198 in the west central pacific biomarker analyses provide evidence of the algal and bacterial origin of organic matter om in these sediments where the abundance of steroidal components particularly sterenes and sterones suggests that the om includes major contributions from eukaryotic sources in an environment characterized by high phytoplankton productivity the presence of alkenones at site 1213b is diagnostic of om derived from representatives of haptophyte algae among the calcareous nannoplankton and their 13c values average 31 6 are consistent with those expected during elevated pco2 the occurrence and prominence of 2 methylhopanes and 2 methylhopanones indicates significant contributions to the om from cyanobacteria which are also likely contributors of hopanoids based on their 13c compositions these biomarker data suggest that oceanic conditions perhaps nitrate or iron limited were conducive to cyanobacteria production during oae1a which appears to distinguish this event from other cretaceous oae

paleogeography and tectono sedimentary history at the margin of laurentia during silurian to earliest devonian time the gaspe belt quebec the silurian lower devonian sequence of the gaspe belt at the laurentia margin south of the quebec reentrant and st lawrence promontory was deposited during the period between the two main orogenies that created the northern appalachians the late ordovician taconian and the middle devonian acadian orogenies although this sequence is traditionally considered to have been deposited during a period of quiescence between both orogenies significant tectonic activity attributed to the salinic disturbance began during late llandoverian telychian time and persisted until the acadian orogeny this tectonic activity has profoundly influenced the composition and distribution of the silurian earliest devonian sedimentary facies the shelf and shelf edge history at the laurentia margin along the quebec reentrant st lawrence promontory is summarized according to four broad phases phase 1 is a llandoverian wenlockian regressive phase r1 related to post taconian successor basin filling that culminated with extensive carbonate platform development phase 2 is a late wenlockian ludlovian transgressive phase t1 phase 3 corresponds to a later ludlovian pridolian second regressive phase r2 phases 2 and 3 were accompanied by extensional tectonics that produced shelf faulting and block tilting on top of which block reefs and reef complexes settled and built a reef tract all the way along the gaspe temiscouata shelf phase 4 is an early devonian phase of accelerated subsidence transgression t2 affecting the northwestern part of the segment quebec reentrant area while the southeastern part st lawrence promontory area was already uplifted due to the ongoing collision between laurentia and the western margin of gondwana related terranes to the south composition and distribution of sedimentary facies were controlled by the interaction of tectonics sediment influx and sea level fluctuations construction of a post taconian pre acadian palinspastic map to plot facies has proven to be basic to obtaining a realistic picture of the paleogeography of the shelf and shelf edge of the gaspe temiscouata segment at the margin of the laurentia craton during the silurian earliest devonian time interval

the basal unconformity of the nanaimo group southwestern british columbia a late cretaceous storm swept rocky shoreline the turonian to santonian comox formation forms the basal unit of the nanaimo group in the southern gulf islands of british columbia the comox formation nonconformably overlies devonian metavolcanic and jurassic intrusive rocks and is interpreted to reflect a rocky foreshore reworked by waves and ultimately drowned during transgression the nonconformity displays a relief of metres to tens of metres basal deposits vary in thickness as does the facies character along the several kilometres of paleoshoreline studied in the study area three distinct but related environments are expressed typical of a complex rocky shoreline with headlands and protected coves crudely stratified conglomerates represent gravel dominated fans characterized by debris flow processes building out from local coastal cliffs and gullies directly onto the rocky shoreline fine grained basal units represent shoreline environments protected from higher energy shoreline processes presumably in small embayments sandstone facies associations reflect storm dominated shoreface environments the unusual thickness and coarseness of these shoreface intervals suggest a combination of increasing accommodation space proximal and high sediment supply and high frequency and energy of storm activity this in turn suggests that the majority of the shoreline was exposed to the full effects of large open ocean storms this interpretation differs from most previous models for the lower nanaimo group which suggest that deposition occurred in more sheltered strait or bay environments

biomarker geochemistry of black shales from cretaceous oceans an overview abstract cretaceous black shales have an extensive distribution in the atlantic and other areas of the world oceans they are sediments rich in organic matter which were deposited in anoxic environments under various paleoenvironmental conditions of sedimentation the literature is reviewed briefly and some type areas are examined using biomarker geochemistry to assess the sources and maturity of the organic matter and the paleoenvironmental conditions of sedimentation these areas are the eastern angola basin the cape verde basin and eastern north atlantic the western north and south atlantic and the pacific oceans molecular marker indicators were identified in bitumens and in kerogen pyrolysates in addition bitumens were characterized by other geochemical techniques thus delineating the terrigenous versus autochthonous sources and the paleoenvironmental preservation of this organic fraction the kerogens were characterized by their elemental composition stable carbon isotope composition and by pyrolysis gc or pyrolysis gc ms including rock eval data these parameters confirmed that the organic matter in sediments of the cretaceous oceans was derived from several different sources is relatively immature and was preserved under various paleoenvironmental conditions

early devonian putative gyracanthid acanthodians from eastern canadainternational geoscience programme igcp contribution 491 middle palaeozoic vertebrate biogeography palaeogeography and climate in 1890 traquair assigned isolated fin spines from the early devonian of eastern canada to a new gyracanthid acanthodian gyracanthus incurvus based on the similarity of the distinctive oblique ri

early devonian trace fossils in marine to non marine redbeds in podolia ukraine palaeoenvironmental implications abstract lochkovian redbeds in the dnester formation in podolia ukraine record an upward transition from marginal marine to fluvial conditions a 60 m thick section through transitional strata reveals a regressive stack of three facies associations laid down in offshore lagoon inshore lagoon or bay and a fluvial estuarine plain the offshore lagoonal association shows green to variegated alternation of fossiliferous bioturbated limestones quartz arenites and shales numerous coquinas contain schizohaline ostracods vermiform gastropods lingula charophyte gyrogonites all mixed with fragments of marine forms such as articulate brachiopods tabulates goniatites and leiospheres trace fossil assemblages contain abundant skolithos spirophyton teichichnus and simple tubular forms the inshore lagoon or bay association is a largely non fossiliferous locally bioturbated red succession of interbedded mudstones and sandstones which are arranged in coarsening up units capped by thin channelized sandstones the presence of lockeia monomorphichnus rusophycus and skolithos suggests that the coarsening up units could have originated as small bayhead deltas and washover fan channel complexes a new ichnospecies monomorphichnus podolicus described here occurs also in these deposits in the overlying fluvial estuarine association the only trace fossil recorded is skolithos which occurs in dense clusters along upper levels of cross bedded ribbon shaped channel fills until now piperock has been considered as an ichnofabric of the skolithos ichnofacies that is typical of sandy beaches bars and spits whereas the findings presented here expand landwards the environmental range of skolithos piperocks into more intracoastal marine influenced settings

palaeoenvironments of early devonian fish and other aquatic fauna of the campbellton formation new brunswick canada abstract the palaeoecology and palaeoenvironments of the classic fish bearing strata of the campbellton formation are here described a well documented fossil assemblage includes acanthodian placoderm chondrichthyan and cephalaspid fishes tracheophyte remains eurypterids ostracods and molluscs as part of the old red sandstone continent the emsian campbellton formation occupied a small basin within the mountainous terrain of the acadian orogen and may have connected through a narrow seaway to a closing foreland basin the highest diversity of vertebrate fossils was found above a basal unconformity with val d amour formation volcanics marked by fissure fills and unstratified breccia representing a craggy irregular palaeosurface that provided shelter for some fauna and sediment for rapid burial of skeletal remains overlying prodeltaic calcareous siltstones are also highly fossiliferous and represent a low energy habitat occurrences of pterygotid eurypterids cephalaspids and chondrichthyans in deltaic sandstones place these taxa in a habitat that may have been variably fresh or brackish the surrounding landscape was vegetated with primitive tracheophytes and abundant plant debris is preserved throughout the basin the diverse assemblage of fish arthropods gastropods plants and microbial growths suggests that a trophically complex ecosystem was in existence

diagnosis of frontal instabilities over the southern ocean the development of three fronts over the southern ocean is described using seawinds on quikscat scatterometer surface winds and an attribution technique to partition the wind field in three components nondivergent and irrotational components at the scale of the front and the remaining harmonic component or environmental flow induced by the synoptic scale flow the front and the environment in which the front is embedded are analyzed separately a frontal wave is shown to develop out of the first front when the large scale alongfront stretching decreases the environmental flow becomes frontolytic and a connection with the upper levels is established in the second case the stretching remains relatively strong and no frontal wave develops the third front exhibits a developing wave but is not in a favorable configuration with the upper levels the frontal wave does not deepen significantly

palaeozoic landscapes shaped by plant evolution fluvial landscapes diversified markedly over the 250 million years between the cambrian and pennsylvanian periods the diversification occurred in tandem with the evolution of vascular plants and expanding vegetation cover in the absence of widespread vegetation landscapes during the cambrian and ordovican periods were dominated by rivers with wide sand beds and aeolian tracts during the late silurian and devonian periods the appearance of vascular plants with root systems was associated with the development of channelled sand bed rivers meandering rivers and muddy floodplains the widespread expansion of trees by the early pennsylvanian marks the appearance of narrow fixed channels some representing anabranching systems and braided rivers with vegetated islands we conclude that the development of roots stabilized the banks of rivers and streams the subsequent appearance of woody debris led to log jams that promoted the rapid formation of new river channels our contention is supported by studies of modern fluvial systems and laboratory experiments in turn fluvial styles influenced plant evolution as new ecological settings developed along the fluvial systems we suggest that terrestrial plant and landscape evolution allowed colonization by an increasingly diverse array of organisms

large sea ice volume anomalies simulated in a coupled climate model the processes leading to the formation of a large anomaly of sea ice volume integrated over the northern hemisphere have been investigated in a coarse resolution three dimensional atmosphere ocean sea ice model this anomaly lasts for about 20 years and reaches 8 6 103 km3 i e 6 standard deviations it is associated with a maximum surface cooling of more than 5 c in the annual mean close to spitzbergen the trigger of the large event in the model is a sequence of years presenting an atmospheric circulation characterised by negative geopotential height anomalies over greenland and positive ones in the barents and norwegian seas this atmospheric anomaly induces an increase in the ice volume as well as of the ice extent sea ice survives in the area located close to spitzbergen where deep convection occurs during normal years this is associated with a shut down of convection in that area and thus by a strong reduction of the upward heat flux from the ocean to the atmosphere that strongly amplifies the initial cooling the long sequence of following years presenting the same type of anomaly in the atmosphere is not just a rare realisation of the intrinsic atmospheric variability a positive feedback between the modification of surface conditions and the atmospheric circulation reinforces the initial atmospheric anomaly finally the large event stops when convection increases again as a result of an increase in ocean surface density close to spitzbergen this density increase is due to both the advection of a positive salinity anomaly created in the arctic because of brine rejection and to local ice formation southward of spitzbergen during the cold event sensitivity experiments performed with the model have shown that the frequency of the events is very sensitive to the mean climate simulated by the model the frequency being higher in a colder climate

lower devonian coaly shales of northern new brunswick canada plant accumulations in the early stages of terrestrial colonization abstract we describe two early devonian occurrences of coaly shale composed mainly of the compacted remains of early plants such that they resemble coal among the earliest thick phytodebris accumulations known the occurrences lie within pragian strata of the val d amour formation and emsian strata of the campbellton formation of northern new brunswick and were deposited in low energy wetlands where they were rapidly buried although the coaly shales did not yield recognizable plant taxa numerous taxa are present in adjacent beds petrographic analysis revealed an average of 80 7 vitrinite predominantly telovitrinite and 18 7 liptinite predominantly sporinite on a mineral matter free basis with a higher vitrinite content than most devonian coals low sulfur content and atomic c n ratios that vary from 44 3 to 82 1 in organic rich samples indicate terrestrial derivation vitrinite reflectance in organic rich samples 21 4 35 6 wt total organic carbon ranges from 0 48 to 1 00 indicating a low degree of thermal alteration that is supported by cross polarization spectra from studies of 13c nuclear magnetic resonance two carbon poor samples were thermally altered to anthracitic rank adjacent to an intrusive body although plants at this time were still comparatively primitive the presence at both sites of specimens with recognizable lignified cellular structures in vitrinite and particularly thick and resistant cuticle may represent an important step in peat development in these early devonian formations diverse assemblages of small vascular plants are present in a range of environments and the plants were sufficiently abundant to form coal like accumulations under suitable burial conditions serving as a proxy for plant biomass and vegetation cover in the early stages of terrestrial colonization

a scheme for improving scatterometer surface wind fields a method is presented for improving quikscat surface wind fields the university of washington planetary boundary layer model is used to retrieve a surface pressure field from any swath of quikscat surface wind vectors an alternate set of surface wind vectors is computed from the newly calculated pressure field the latter can be smoothed and the process can be iterated new surface wind vectors can be calculated where ambiguity removal fails and where measurements are missing the present methodology preserves boundary layer dynamics and is an improvement over a statistical filter

multiphase magmatic and tectonic evolution of a large igneous province evidence from the crustal structure of the manihiki plateau western pacific the manihiki plateau a large igneous province lip in the western pacific has been proposed to be emplaced as part of the greater ontong java event during the early cretaceous shortly after its formation the manihiki plateau fragmented into multiple sub provinces plate tectonic reconstructions ignore this fragmentation treating the manihiki plateau as a single crustal block by analyzing two seismic refraction wide angle reflection profiles crossing the two largest sub provinces of the manihiki plateau we provide new insight into their deep crustal structure and magmatic evolution our data indicate that the high plateau and the western plateaus were emplaced as a single unit during an initial phase of massive magmatic activity but later magmatic stages altered the individual sub provinces considerably the high plateau has a crustal thickness of 20 km and its p wave velocity distribution is comparable to previously surveyed oceanic lips strong secondary magmatic phases are visible by eruptive centers and former magmatic pathways in the middle and lower crust the western plateaus which have a crustal thickness decreasing gradually from 17 3 km east to 9 2 km west experienced smaller amounts of magmatism mainly along fault zones and on local seamounts therefore we propose a distinct development of the two main sub provinces of the manihiki plateau after their initial joint emplacement the high plateau experienced voluminous multi phase magmatic accretion and extrusion whereas the thinner western plateaus exhibit only relatively minor magmatic growth such a large difference in the evolution process has not been reported from any other oceanic lip so far

ocean surface pressure fields from satellite sensed winds abstract the university of washington s planetary boundary layer model is inverted to use remotely sensed satellite scatterometer derived surface winds as input to calculate maritime surface pressure fields the analysis of three different synoptic storm situations is performed using the model and is then compared to conventional national weather service analyses agreement is good isolation of the pbl secondary flow stratification and thermal wind effects in the model revealed that each may be significant under certain conditions however the model shows sensitivity to the thermodynamic features only in a general sense and even a neutral stratification solution gives a good approximation the high density of the scatterometer data produces mesoscale hundreds of kilometers dynamic details which cannot be confirmed by conventional data at this stage

evolution of the freshwater ecosystem the fossil record abstract the freshwater ecosystem may be as old as most life although freshwater life is taxonomically impoverished in comparison with marine and terrestrial biotas and ultimately derived from them it cannot be assumed that freshwater communities have necessarily been less complex in the geologic past than they are today although it is clear they have undergone a number of major changes freshwaters contain not only their own ancient and peculiar groups some with ancestries as far back as the middle paleozoic but they have been a theater for adaptive radiation of more recent immigrants from the land or sea and a way station for still other groups that passed through both from sea to land and the reverse this review summarizes first fossil records in freshwaters for many of these organisms and examines the question of the changing complexity of the freshwater ecosystem through time by looking at the fossil record of continental aquatic habitats

organic matter provenance and paleoenvironment in the cretaceous on the manihiki plateau south pacific abstract three holes at site 317 on the high manihiki plateau were drilled in 1973 as part of the deep sea drilling project dsdp this plateau is of special interest because of its organic rich shale formation during its early history potentially linking paleo depositional conditions and water depth or land exposure a multi tracer approach was used to analyze target organic rich layers of hole 317a core 16 sections 2 and 3 from the early cretaceous this included bulk elemental and stable carbon isotope compositions of specific chemical classes lipids humic acids kerogen as well as individual biomarkers separated by thin layer chromatography and analyzed by gas chromatography mass spectrometry the major natural product contributions found in the core sediments were derived from three primary sources algal low molecular weight c22 aliphatic lipids phytosterols diterpenoids algal and bacterial derived compounds were observed at the shallowest layers of the core sample 680 30 m below sea floor and decreased with increasing core depth terrestrial inputs increased down core and peaked between 680 33 and 680 70 m below sea floor this trend coincides with a thick sapropel layer and agrees with the oceanic anoxic event oae in the early cretaceous indicating deposition in a shallow water environment in proximity to land e g atoll

stratigraphy and tectono sedimentary evolution of the late ordovician to middle devonian gaspe belt in northern new brunswick evidence from the restigouche area the gaspe belt in the restigouche area comprises three successions separated by a late silurian salinic disconformity and an early devonian angular unconformity the lower upper ordovician to lower silurian sequence consists of siliciclastic turbidites of the boland brook and whites brook formations grog brook group overlain by calcareous turbidites of the pabos and white head formations matapedia group and slope and shelf deposits of the upsalquitch and limestone point formations lower chaleurs group above the salinic disconformity the upper chaleurs group and the dalhousie group record a transgressive regressive cycle the former comprises pridolian carbonate rocks of the west point formation and overlying pridolian to lochkovian sedimentary rocks of the indian point formation the chaleurs group is conformably overlain by lochkovian to early emsian subaerial volcanic rocks of the dalhousie group val d amour formation which is unconformably overlain by alluvial lacustrine deposits of the late emsian campbellton formation acadian orogenesis began during the emsian and is characterized by open to closed folding heterogenous cleavage development and reverse and strike slip faults the salinic orogeny is manifested in extensional block faulting within plate volcanism and uplift and deep erosion of early silurian strata early devonian high level intrusion of the matapedia group white head clasts in indian point conglomerate and thermal maturation data all indicate an extended period of late silurian early devonian uplift in parts of the restigouche area thermal maturities of west point and indian point strata are within the oil and condensate windows and suggest potential for hydrocarbons in the study area

facies architecture and late pliocene pleistocene evolution of a felsic volcanic island milos greece the volcanic island of milos greece comprises an upper pliocene pleistocene thick up to 700 m compositionally and texturally diverse succession of calc alkaline volcanic and sedimentary rocks that record a transition from a relatively shallow but dominantly below wave base submarine setting to a subaerial one the volcanic activity began at 2 66 0 07 ma and has been more or less continuous since then subaerial emergence probably occurred at 1 44 0 08 ma in response to a combination of volcanic constructional processes and fault controlled volcano tectonic uplift the architecture of the dominantly felsic intermediate volcanic succession reflects contrasts in eruption style proximity to source depositional environment and emplacement processes the juxtaposition of submarine and subaerial facies indicates that for part of the volcanic history below wave base to above wave base and shoaling to subaerial depositional environments coexisted in most areas the volcanic facies architecture comprises interfingering proximal near vent medial and distal facies associations related to five main volcano types 1 submarine felsic cryptodome pumice cone volcanoes 2 submarine dacitic and andesitic lava domes 3 submarine to subaerial scoria cones 4 submarine to subaerial dacitic and andesitic lava domes and 5 subaerial lava pumice cone volcanoes the volcanic facies are interbedded with a sedimentary facies association comprising sandstone and or fossiliferous mudstone mainly derived from erosion of pre existing volcanic deposits the main facies associations are interpreted to have conformable disconformable and interfingering contacts and there are no mappable angular unconformities or disconformities within the volcanic succession

plio pleistocene cliff bound wedge shaped warm temperate carbonate deposits from rhodes greece sedimentology and facies abstract the pliocene to pleistocene temperate carbonates of rhodes were deposited in a tectonically active region strongly influenced by a complicated and rapidly changing topography provided by the highly tectonised late cretaceous lindos limestone as basement rock deposition on this basement took place in accommodation loci restricted to micrograbens and their downslope extension to the foot of steep submarine cliffs to basement neptunian dykes and depressions in the basement rock consequently the sediments comprise a high degree of facies variability and are typically thin and laterally discontinuous the integration of several outcrops is necessary for the reconstruction of the stratigraphy and the relative sea level changes the sediments were deposited during a large scale tectonically driven transgressive regressive cycle in water depths changing from zero to several hundreds of metres at the studied lindos pefkos road cutting the kolymbia limestone bound to the foot of lindos limestone cliffs marks the onset of the marine deposition in the late pliocene its fabric is a rudstone consisting of unsorted angular lindos limestone clasts up to boulder size with a matrix dominated by molluscs and coralline algae the overlying plio pleistocene st paul s bay limestone consists of deep water float and rudstones containing the white coral community dominated by the coral lophelia pertusa its matrix shows a complex fabric of up to five sediment zones separated by differing states of lithification in this maximum flooding phase mineralised hardgrounds indicate depositional hiati the subsequent shallowing phase is represented by the cape arkhangelos calcarenite a series of distinctive facies of very patchy distribution they are characterised by the bryozoan brachiopod facies overlain by a facies heavily dominated by the bivalve mytilaster sp mytilaster facies conspicuous for the mytilaster facies is the inverse concave up stacking pattern of shelly material this facies is followed by a serpulid framestone and associated serpulid rudstone neptunian dykes cut through the first two facies and are filled with an intraformational breccia grading into a breccia with abundant mytilaster facies clasts neptunian dyke facies the sedimentology and interpretation of each facies include a description of the ichnology in particular the bioerosion peculiar to each facies the separation of different gravity transport processes in steep submarine environments is rarely described and most of the literature concentrates on siliciclastic dominated coarse grained sandy or gravely sand delta environments for a classification of the transport processes of the examined deposits the following criteria were evaluated sediment body symmetry inclination of the palaeorelief sediment constituents fabric complexity sedimentary structures and availability of fine matrix sedimentary structures and grading can be camouflaged in carbonates due to density differences of bioclasts however bioclast orientations such as bivalve stacking patterns can give information about the sedimentary process we suggest the inverse concave up stacking pattern of bivalve shells to be a texture potentially indicative for debris falls because of the above mentioned criteria we classified the kolymbia limestone as rock fall deposits and the st paul s bay limestone as well as the mytilaster facies of the cape arkhangelos calcarenite as debris fall deposits the bryozoan brachiopod facies could not be classified with certainty because of the lack of sedimentary structures and bioclast orientation however a grain flow or most likely a debris fall transport process seems probable

peperite a review of magma sediment mingling the study of peperite is important for understanding magma water interaction and explosive hydrovolcanic hazards this paper reviews the processes and products of peperite genesis peperite is common in arc related and other volcano sedimentary sequences where it can be voluminous and dispersed widely from the parent intrusions it also occurs in phreatomagmatic vent filling deposits and along contacts between sediment and intrusions lavas and hot volcaniclastic deposits in many environments peperite can often be described on the basis of juvenile clast morphology as blocky or fluidal but other shapes occur and mixtures of different clast shapes are also found magma is dominantly fragmented by quenching hydromagmatic explosions magma sediment density contrasts and mechanical stress as a consequence of inflation or movement of magma or lava magma fragmentation by fluid fluid shearing and surface tension effects is probably also important in fluidal peperite fluidisation of host sediment hydromagmatic explosions forceful intrusion of magma and sediment liquefaction and shear liquification are probably the most important mechanisms by which juvenile clasts and host sediment are mingled and dispersed factors which could influence fragmentation and mingling processes include magma host sediment and peperite rheologies magma injection velocity volatile content of magma total volumes of magma and sediment involved total volume of pore water heated presence or absence of shock waves confining pressure and the nature of local and regional stress fields sediment rheology may be affected by dewatering compaction cementation vesiculation fracturing fragmentation fluidisation liquefaction shear liquification and melting during magma intrusion and peperite formation the presence of peperite intraclasts within peperite and single juvenile clasts with both sub planar and fluidal margins imply that peperite formation can be a multi stage process that varies both spatially and temporally mingling of juvenile clast populations formed under different thermal and mechanical conditions complicates the interpretation of magma fragmentation and mingling mechanisms

basinwide stratigraphic synthesis and sequence stratigraphy upper pragian emsian and eifelian stages lower to middle devonian appalachian basin

lacustrine deltas in a mesozoic alluvial sequence from camp hill antarctica sedimentary rocks of late mesozoic age exposed at camp hill northern antarctic peninsula are associated with calc alkaline volcanic rocks they represent deposition on a fault controlled floodplain with marginal alluvial fans on a volcanic arc finely laminated mudstone and occasional graded laminae were deposited from suspension and by density underflow currents respectively in small shallow lakes thickening and coarsening upward sandstone bodies overlying the lake deposits are interpreted as lacustrine deltas of which two types are preserved 1 gilbert type with steep foresets and 2 mouth bar type which lack steep foresets sections through the latter type reveal the presence of sub environments characteristic of fluvial dominated marine deltas i e prodelta distributary mouth bar and distributary channel abandoned mouth bars resulting from avulsion are recognized it is suggested that the processes which operated during formation of the mouth bar deltas resulted from hyperpycnal flow by contrast the gilbert type delta is thought to be the consequence of a reduced inflow of suspended sediment causing homopycnal flow and thorough mixing of the river and lake waters

a coupled climate model simulation of the last glacial maximum part 2 approach to equilibrium the climate of the last glacial maximum lgm is simulated with a coupled climate model the simulated climate undergoes a rapid adjustment during the first several decades after imposition of lgm boundary conditions as described in part 1 and then evolves toward equilibrium over 900 model years the climate simulated by the coupled model at this period is compared with observationally based lgm reconstructions and with lgm results obtained with an atmosphere mixed layer slab ocean version of the model in order to investigate the role of ocean dynamics in the lgm climate global mean surface air temperature and sea surface temperature sst decrease by about 10 c and 5 6 c in the coupled model which includes ocean dynamics compared to decreases of 6 3 and 3 8 c in slab ocean case the coupled model simulates a cooling of about 6 5 c over the tropics which is larger than that of the climap reconstruction 1 7 c and larger than that of the slab ocean simulation 3 3 c but which is in reasonable agreement with some recent proxy estimates the ocean dynamics of the coupled model captures features found in the climap reconstructions such as a relative maximum of ocean cooling over the tropical pacific associated with a mean la nina like response and lead to a more realistic sst pattern than in the slab model case the reduction in global mean precipitation simulated in the coupled model is larger 15 than that simulated with the slab ocean model 10 in conjunction with the enhanced cooling some regions such as the usa and the mediterranean region experience increased precipitation in accord with proxy paleoclimate evidence the overall much drier climate over the ocean leads to higher sea surface salinity sss in most ocean basins except for the north atlantic where sss is considerably lower due to an increase in the supply of fresh water from the mississippi and amazon rivers and presumably a decrease in salt transport by the weakened north atlantic overturning circulation the north atlantic overturning stream function weakens to less than half of the control run value the overturning is limited to a shallower depth less than 1000 m and its outflow is confined to the northern hemisphere in the southern ocean convection is much stronger than in the control run leading to a stronger overturning stream function associated with enhanced antarctic bottom water formation as a result southern ocean water masses fill the entire deep ocean the antarctic circumpolar current acc transport through the drake passage increases by about 25 the acc transport despite weaker zonal winds is enhanced due to changes in bottom pressure torque the weakening of the overturning circulation in the north atlantic and the accompanying 30 decrease in the poleward ocean heat transport contrasts with the strengthening of the overturning circulation in the southern ocean and a 40 increase in heat transport as a result sea ice coverage and thickness are affected in opposite senses in the two hemispheres the lgm climate simulated by the coupled model is in reasonable agreement with paleoclimate proxy evidence the dynamical response of the ocean in the coupled model plays an important role in determining the simulated and undoubtedly the actual lgm climate

spines of the stem chondrichthyan doliodus latispinosus whiteaves comb nov from the lower devonian of eastern canada the higher taxonomic affinities of fin spines from the lower devonian emsian atholville beds campbellton formation near campbellton new brunswick canada originally identified as ctenacanthus latispinosus have been uncertain since they were first described by whiteaves in the late 19th century woodward subsequently referred the species to climatius because the isolated canadian fin spines were similar to those preserved in articulated specimens of climatius reticulatus from the lower old red sandstone lochkovian of scotland spines of the same form as the atholville beds specimens are also found in emsian mudstones on the gaspe peninsula quebec one of the fin spine forms appears identical to the pectoral fin spines on an articulated specimen from the campbellton formation that has been assigned to the stem chondrichthyan doliodus problematicus a taxon erected for isolated diplodont teeth by comparison with median and paired fin spine morphology on the climatiiform climatius reticulatus from

the campbellton formation new brunswick canada paleoenvironments in an important early devonian terrestrial locality strata of the campbellton formation nearly 1 km thick and known for its diverse fossil assemblage of early plants arthropods and fish can be divided into six facies associations 1 restricted lacustrine 2 marginal lacustrine 3 near shore lacustrine 4 coastal deltaic 5 sandy to gravelly alluvial plain and 6 gravelly proximal alluvial environments lacustrine deposits with restricted circulation due to depth or stagnation are fine grained with preserved organic material the marginal lacustrine association consists of massive siltstone and very fine sandstone interbedded with conglomerate the latter are interpreted to have shed from older volcanic units forming the basin walls the near shore lacustrine association is characterized by rippled sandstone with microbialites alluvial strata include interbedded imbricate to nonimbricate conglomerate trough cross stratified sandstone and barren to plant bearing siltstone rare exposures of thickly bedded imbricate to weakly imbricated

onset of the mid cretaceous greenhouse in the barremian aptian igneous events and the biological sedimentary and geochemical responses basalts and biostratigraphy dated at 125 120 ma from the ontong java and manihiki plateaus in the western pacific evidence the largest volcanic event in earth history in at least the past 160 m y the intervening nova canton trough rifted at about 121 118 ma and a number of guyots and seamounts formed concurrently or slightly later geological events that probably were responses to these volcanic tectonic events occurred in the following chronostratigraphic order biotic fluctuations began at about 122 5 ma at about 122 0 ma 87sr 86sr began to decline slowly metal concentrations of co mn pb yb and cu in sediments peaked at about 121 5 121 2 ma changes in planktonic communities and sedimentation culminated in a nannoconid crisis just prior to 120 5 ma and in the selli black shale oae la at about 120 5 119 5 ma a sharp drop in 13c occurred at the beginning of the selli event and rebounded into a longer positive excursion that reached a peak after the selli event at about 119 5 118 5 ma at 120 5 ma 87sr 86sr declined rapidly and reached a minimum at about 116 113 ma we speculate that the intensity of these latter responses suggests a corresponding peak in volcanic tectonic activity at about 121 119 ma

modeling evidence for enhanced el nino southern oscillation amplitude during the last glacial maximum we present a numerical eigenmode analysis of an intermediate el nin o southern oscillation enso model which is driven by present day observed background conditions as well as by simulated background conditions for the last glacial maximum lgm about 21 000 years ago the background conditions are obtained from two lgm simulations which were performed with the national center for atmospheric research climate system model csm1 4 and an earth system model of intermediate complexity ecbilt clio our analysis clearly shows that the leading present day unstable recharge discharge mode changes its stability as well as its frequency during lgm conditions simulated lgm background conditions were favorable to support large amplitude self sustained interannual enso variations in the tropical pacific our analysis indicates that off equatorial climate conditions as well as a shoaling of the thermocline play a crucial role in amplifying the lgm enso mode

environment of the early paleozoic vertebrates abstract a comprehensive review of the known pre devonian vertebrate localities suggests that the non marine environment was not invaded until about wenlock early mid silurian time known well dated late cambrian ordovician and early silurian vertebrate localities are all in the marine environment considerations of paleogeography for the pre wenlock indicate that most of the vertebrate localities are too distant from shorelines to provide any basis for transport from the non marine environment to a marine depositional site as a favored explanation the articulated nature of the vertebrates from some of these pre wenlock occurrences also supports this interpretation reconsideration of both the physiological and embryological evidence relative to living vertebrates and some related chordates is also consistent with the view that the vertebrates originated in the marine environment

thermal alteration of cretaceous black shale by diabase intrusions in the eastern atlantic ii effects on bitumen and kerogen abstract the thermal effects of three one major and two minor miocene diabase intrusions on cretaceous black shales from dsdp site 41 368 have been analyzed a concentration gradient was observed especially for the hydrocarbons decreasing towards the major intrusion and between the three sills the thermally altered samples in the proximity of and between the sills contained elemental sulfur and an excess of thermally derived pristane over phytane whereas the unaltered sediments contained no elemental sulfur and more phytane than pristane a maximum yield of the extractable hydrocarbons was observed at a depth of 7 m below the major sill two classes of molecular markers were present in this bitumen suite the first was sesqui di and triterpenoids and steranes which could be correlated with both terrigenous and autochthonous sources they were geologically mature and showed no significant changes due to the thermal stress the second class was found in the altered samples which contained only polynuclear aromatic hydrocarbons with low alkyl substitution and sulfur and oxygen heterocyclic aromatic compounds these compounds were derived from pyrolytic reactions during the thermal event kerogen was isolated from all of these samples but only traces of humic substances were present the h c n c 13 c 34 s and d all exhibit the expected effects of thermal stress the kerogen becomes more aromatized and richer in 13c 34s and d in the proximity of and between the sills maturation trends were also measured by the vitrinite reflectance and electron spin resonance where the thermal stress could be correlated with an elevated country rock temperature and an increased degree of aromaticity the effects of in situ thermal stress on the organic rich shales resulted in the generation and expulsion of petroliferous material from the vicinity of the sills

coarse grained nonmarine volcaniclastic sediment terminology and depositional process modern and ancient volcaniclastic sedimentary sequences contain depositional units whose features cannot be attributed to fully turbulent dilute stream flow or viscous debris flow the characteristics of these poorly sorted sediments suggest rapid deposition from high concentration dispersions but not en masse sedimentation thus appears related to high discharge flows intermediate in sediment water ratio between stream flow and debris flow the term hyperconcentrated flood flow is proposed for describing this intermediate condition hyperconcentrated flood flow deposits are distinguished from debris flow deposits by lack of matrix support or reverse grading and instead exhibit distribution normal grading and horizontal stratification these deposits are distinguished from normal dilute stream flow deposits by lack of cross stratification in sand facies and by very poor sorting poor imbrication and numerous clasts with long axes oriented parallel to flow direction in gravel facies the horizontal bedding that dominates sandy hyperconcentrated flood flow deposits consists of sediment too coarse grained and strata too thick to have been produced in the boundary layer of the upper flow regime and should not be confused with the more familiar thin graded laminae of fine to medium grained sand often associated with parting lineation hyperconcentrated flood flow deposits are not unique to volcanic settings they also occur in arid alluvial fan sequences debris flow and hyperconcentrated flood flow deposits however are much thicker and more extensive in volcanic regions than on alluvial fans because explosive volcanism leads to rapid mobilization of large volumes of sediment and water on a scale unparalleled in nonvolcanic settings in volcanic regions therefore these deposits have greater preservation potential show greater lateral variability and are more voluminous transformation of channelized debris flow to hyperconcentrated flood flow by dilution with stream water recently observed at mount st helens is recorded in ancient volcaniclastic sequences and may serve as the primary mechanism for generating hyperconcentrated flood flow

emsian synorogenic paleogeography of the maine appalachians abstract the acadian deformation front in the northern appalachians of maine and new hampshire can now be closely located during the early emsian early devonian 408 406 ma tight correlations between paleontologically and isotopically dated rocks are possible only because of a new 408 ma time scale tie point for the early emsian the deformation front lay between a belt of lower devonian flysch and molasse that were deposited in an acadian foreland basin and had not yet been folded and a belt of early emsian plutons that intruded folded lower devonian rocks this plutonic belt includes the newly dated ore mountain gabbro u pb 406 ma which hosts magmatic sulfide mineralization along the deformation front a 407 ma pluton that locally truncates acadian folds katahdin was the feeder to volcanic rocks traveler rhyolite 406 407 ma that are part of the foreland basin succession involved in these same folds the emsian igneous rocks thus define a syncollisional magmatic province that straddled the d

nannofossil carbonate fluxes during the early cretaceous phytoplankton response to nutrification episodes atmospheric co2 and anoxia 1 greenhouse episodes during the valanginian and aptian correlate with major perturbations in the c cycle and in marine ecosystems carbonate crises and widespread deposition of corg rich black shales quantitative analyses of nannofossil micrite were conducted on continuous pelagic sections from the southern alps northern italy where high resolution integrated stratigraphy allows precise dating of early cretaceous geological events rock forming calcareous nannofloras were quantified in smear slides and thin sections to obtain relative and absolute abundances and paleofluxes that are interpreted as the response of calcareous phytoplankton to global changes in the ocean atmosphere system increased rates of volcanism during the formation of ontong java and manihiki plateaus and the parana etendeka large igneous province lip are proposed to have caused the geological responses associated with early aptian oceanic anoxic event oae 1a and the valanginian event respectively calcareous nannofloras reacted to the new conditions of higher pco2 and fertility by drastically reducing calcification the valanginian event is marked by a 65 reduction in nannofossil paleofluxes that would correspond to a 2 3 times increase in pco2 during formation of the parana endenteka lip a 90 reduction in nannofossil paleofluxes which occurred in a 1 5 myr long interval leading into oae1a is interpreted as the result of a 3 6 times increase in pco2 produced by emplacement of the giant ontong java and manihiki plateaus high pco2 was balanced back by an accelerated biological pump during the valanginian episode but not during oae1a suggesting persisting high levels of pco2 in the late aptian and or the inability of calcareous phytoplankton to absorb excess pco2 above threshold values

stratigraphy and subsidence of the mururoa atoll french polynesia three deep holes drilled in 1964 1965 at mururoa atoll french polynesia penetrated the entire carbonate cap and reached the underlying volcanic rocks study of the carbonate reef gave three main results 1 1 diagenetic processes have been responsible for the development of a vertical mineralogical zonation in the reef column a clear dolomite front near 125 m depth separates upper non dolomitic from bottom dolomitic series 2 2 hydrologic isotopic and organic geochemical studies converge to suggest that dolomitization could develop at the interface between upper fresh water and lower marine water 3 3 age determinations in the carbonate series were made using 14c and 234u io isotopes and l isoleucine d alloisoleucine racemization these studies show that discontinuities in coral ages occur and that these correspond to glacial falls of sea level no coral growth between 500 000 and 300 000 between 120 000 and 5500 and since 3600 yrs b p at the base of the reef carbonate beds of volcanic hyaloclastites and limestone debris alternate the limestone debris is dated by foraminifera as miocene the subsidence of the now submerged volcano is estiamted from basaltic samples dated 7 2 m y and cored at 240 m below present sea level the mean rate of subsidence since 7 2 m y b p is about 8 m 100 000 yrs 1

paleocene pacific plate reorganization mirrored in formation of the suvarov trough manihiki plateau the suvarov trough is a graben structure that deviates from the danger islands troughs within the manihiki plateau a large igneous province lip located in the central pacific new high resolution seismic reflection data provide evidence that the graben formed in two phases during the paleocene 65 45 ma in a first phase extension occurred in south westward direction pulling apart the northern part of the suvarov trough and a parallel trending unnamed trough in a second phase a change of extensional force direction occurred from southwest to west northwest forming the southern part of the suvarov trough that extends onto the high plateau the formation of the suvarov trough is accompanied by a series of normal fault systems that apparently formed simultaneously comparing the seismic results to existing pacific paleo strain reconstructions the timing of increased strain and local deformation direction fits well to our findings we thus suggest that the multiple strike directions of the suvarov trough represent an extensional structure that was caused by the major stepwise pacific plate reorganization during the paleocene

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

satellite based midlatitude cyclone statistics over the southern ocean 1 scatterometer derived pressure fields and storm tracking 1 a wavelet based method is described for incorporating swaths of surface pressure derived from scatterometer measurements into surface pressure analyses obtained from the european centre for medium range weather forecasts ecmwf the resulting modified pressure fields are used to identify low pressure centers over the southern ocean and to build statistics of midlatitude cyclones during 7 years of the seawinds on quikscat operational period july 1999 to june 2006 the impact of the scatterometer derived pressure swaths is assessed with a statistical analysis of cyclone characteristics central pressure radius depth performed in parallel on the ecmwf and on the modified pressure fields more low pressure centers 5 10 depending on the season are identified with the modified pressure fields in particular incipient lows captured earlier than ecmwf and more short lived mesoscale cyclones with a life span less than 4 days the cyclones identified with the modified pressure fields are characterized by lower central pressure and tighter isobars on average a parallel spectral analysis reveals 1 additional energy at scales less than 2000 km in the modified pressure fields

outer rocky shores of the mowanbini archipelago devonian reef complex canning basin western australia abstract the oscar range in western australia s canning basin features inliers of folded paleoproterozoic quartzite quartzitic conglomerate and phyllite that formed islands during the late devonian undisturbed strata of the pillara limestone upper devonian frasnian stage surround individual paleoislands that rise above the former seabed with a maximum topographic relief of 90 m on average the mowanbini archipelago aboriginal name for the oscar range lies 15 km off the granitic and metamorphic mainland represented by the kimberley block to the north devonian facies on outer rocky shores were studied at three localities near the southeast end of the oscar range at the west end of the study area a devonian reef margin sits unconformably on paleoproterozoic phyllite but to the east the reef is separated from rocky shores by a wide lagoon massive clast supported conglomerate and sandstone beds interfinger with backreef carbonates where the reef is closest to land across the lagoon 2 5 km eastw

ocean model validation of the nasa scatterometer winds the suitability of basin scale satellite based scatterometer winds for forcing of numerical ocean models is examined using a reduced gravity primitive equation model of the tropical pacific ocean three surface forcing fields are validated in a comparison of upper layer thickness ult from the ocean model with observed sea level data the forcing fields are the florida state university observed winds winds derived from the nasa scatterometer nscat and stresses derived directly from nscat the sea level data sets are the world ocean circulation experiment fast sea level data set from island measurements and sea level anomalies from topex poseidon results of this comparison demonstrate that while the three model results are qualitatively similar the results are quantitatively better when forcing with the nscat derived stresses this is particularly true in the eastern tropical pacific and in convergent zones where forcing with the nscat stresses can lead to large differences in ult 40 m compared with results from the other two wind products

terpenoid composition of fossil resins from western india new insights into the occurrence of resin producing trees in early paleogene equatorial rainforest of asia abstract the terpenoid composition of well preserved fresh and oxidized fossil resins ambers from early paleogene lignite bearing sequences of india have been examined using gas chromatography mass spectrometry for determining their botanical origin the samples were collected from two sedimentary basins viz barmer akli formation and bikaner nagaur palana formation western india the total extracts of the studied ambers are represented by hydronaphthalenes sesquiterpenoids and significant occurrence of diterpenoids such terpenoid distribution is typical for gymnosperm especially conifer derived sources the diterpenoids are comprised of majorly abietane phyllocladane kaurane pimarane isopimarane and podocarpane class compounds tertracyclic diterpenoids such as 18 norkauranes ent 16 h kaurane and 16 h phyllocladane and a rearranged tricyclic diterpenoid rosane are detected in the fossil resins from barmer basin the occurrence of tetracyclic diterpenoids and rosane together with 8 13 dimethyl 16 norpodocarpa 6 ene suggests that podocarpaceae family is the possible source of the ambers however chemotaxonomic assignment at family level for the fossil resin from bikaner nagaur basin is difficult due to the absence of source specific diterpenoids previous reports had documented the occurrence of angiosperm derived dammar resins from early paleogene sediments of india dutta et al 2009 rust et al 2010 the present study suggests that the early paleogene resins of the equatorial rainforests were not always represented by the dammar resins derived from dipterocarpaceae a family of angiosperm some of them were also contributed by the conifers

cyclone surface pressure fields and frontogenesis from nasa scatterometer nscat winds two extratropical marine cyclones and their associated frontal features are examined by computing surface pressure fields from nasa scatterometer nscat winds a variational method solves for a new surface pressure field by blending high resolution 25 km relative vorticity computed along the satellite track with an initial geostrophic vorticity field employing this method with each successive pass of the satellite over the study area allows this surface pressure field to evolve as dictated by the relative vorticity patterns computed from nscat winds the result is a high resolution surface pressure field that captures features such as fronts and low pressure centers in more detail than national centers for environmental prediction ncep reanalyses while using the actual relative vorticity to adjust the geostrophic vorticity ignores the ageostrophy of surface winds which can be significant in the vicinity of fronts and jet streaks it is a necessary approximation given that the technique uses only surface data the nscat surface pressure fields prove to be nearly as accurate as ncep reanalyses when compared to ship and buoy observations which is an encouraging result given that ncep reanalyses incorporate a myriad of data sources and the nscat fields rely primarily on one source in addition the high resolution relative vorticity fields computed from nscat winds reveal the location of surface fronts in great detail these fronts are verified using ncep analyses in situ data and satellite imagery

pre vegetation alluvial fan facies and processes an example from the cambro ordovician rozel conglomerate formation jersey channel islands prior to the silurian a lack of land vegetation is expected to have influenced the processes of sedimentation on alluvial fans principally by causing increased rates of run off and erosion in the fan catchments in the cambro ordovician rozel conglomerate formation this effect was central to the generation of alluvial fan deposits that are unusually deficient in sand and clay despite being sourced from a catchment dominated by sandstone and mudstone seven facies are identified interpreted as representing the deposits of i shallow stream and sheetfloods ii channelized non cohesive debrisflows iii sub aerial mud rich debrisflows iv sub aqueous mud rich debrisflows v low energy streams that reworked abandoned fan sectors vi a sandflat playa lake system and vii talus slopes the first two facies are both clast supported conglomerate comprise 98 of the deposit and represent deposition on active depositional lobes and in the fan head trench the remaining facies are the products of infrequent sedimentary processes fan abandonment processes and marginal sub environments the facies assemblage in many ways mimics that of a modern day water lain arid region fan however the palaeolatitude of these fans was high and the climate is inferred to have been cool and wet the near absence of sandstone and mudstone beds with few mudflows is ascribed to rapid hinterland uplift and high rates of erosion resulting in minimal chemical breakdown of source rocks in the catchments such high rates of erosion are in turn ascribed to a combination of frequent rainstorms and an absence of vegetation cover