local atmospheric forcing during the coastal ocean dynamics experiment 1 a description of the marine boundary layer and atmospheric conditions over a northern california upwelling region as part of the coastal ocean dynamics experiment code meteorological instruments were deployed on buoys and at coastal stations and instrumented aircraft flights and coastal soundings were made to study the three dimensional structure of the marine boundary layer over the continental shelf off northern california during the 1981 and 1982 upwelling seasons these measurements show that after the atmospheric spring transition the airflow in the marine layer is dominated by the north pacific high and the surface wind field over the shelf is characterized by periods of strong 7 15 m s upwelling favorable alongshelf winds lasting for up to 30 days interrupted by shorter periods of much weaker winds directed either equatorward or poleward these periods of weak or reversed winds typically last several days and are called wind relaxations even though they are primarily associated with coastally trapped perturbations of the marine layer along the central and northern california coast and not with a large scale weakening of the north pacific high the atmospheric boundary layer measurements made in code suggest a simple conceptual model which can explain much of the physiology or structure of the marine layer and associated surface wind field during periods of persistent upwelling favorable winds during these periods which represent the quasi steady state regime during the upwelling season the inversion base of the marine layer drops eastward toward the coast until it intersects the coastal mountain range at a height of several hundred meters and the associated thermal wind produces an alongshelf wind jet which has a maximum speed just below the inversion base turbulent mixing tends to homogenize any stratification in the marine layer beneath the jet and couple the jet to the ocean surface producing strong upwelling favorable winds over the shelf day night heating cooling over the narrow coastal strip beneath the marine layer generates a weak cross coast secondary circulation which causes the core of the alongshelf jet to drop in elevation and shift onshore this diurnal change in the marine layer structure explains both the daytime acceleration of the surface winds observed over and near the coast and its offshore decay and the associated offshore increase in the subdiurnal alongshelf wind thus the quasi steady component of the wind stress has a significant curl over the inner shelf during periods of active upwelling this mean summer atmospheric boundary layer regime is occasionally interrupted by synoptic and or mesoscale events or anomalous conditions analysis of the code observations suggests five types of events two primarily synoptic scale conditions which lead to stronger than normal upwelling favorable winds over the shelf and three primarily mesoscale events which lead to wind relaxation about half of the wind relaxation events observed in 1981 and 1982 are believed to be associated with either coastal trapped gravity currents or internal kelvin waves which propagate north ward in the marine layer along the central and northern california coastal mountain range

numerical simulation of a low level jet over complex terrain in southern iran the lut desert of iran is an elongated valley oriented north northwest to south southeast the valley descends southward to the jaz murian dry lake through a pass the navy s coupled ocean atmosphere mesoscale prediction system is used to study a northerly low level jet in the valley and across the dry lake the dynamics of the jet are investigated with force balance and froude numbers to determine the contribution of various mechanisms to the jet formation and maintenance the jet is initiated as a channeled gap flow in the convergent topography of the lut valley by the valley parallel pressure gradients generated by the large scale processes and by the presence of cold air over the valley s sloping terrain the pressure gradient is mainly counteracted by the frictional force the imbalance between them controls the intensity and persistence of the jet in the valley farther south the jet evolves into a downslope flow resembling a hydraulic jump on the steep slope of the dry lake a transition of subcritical situation to supercritical faster flow is found at the mountain crest between the lut valley and dry lake the depth of stably stratified cold layer the static stability of upstream inversion and magnitude of upstream winds all determine the jet configuration over the dry lake the lee troughing over the gulf of oman and the persian gulf as the large scale inland flow crosses the coastal mountains supports this low level jet through the increased along jet pressure gradient the jet is also influenced by diurnal forcing being strong at night and weak during daytime

the structure of the marine inversion layer off the central california coast mesoscale conditions abstract data collected on board an instrumented aircraft during the marine atmospheric boundary layer experiments west coast mables wc field study are examined the data were collected at several levels in the marine and inversion layers approximately 200 km west of the central california coast during august 1978 composite sounding and cross sections of wind and temperature variables are presented to provide an overview of the mesoscale structure of the offshore marine and inversion layers at the time of mables wc under typical summertime synoptic conditions which prevailed early in the study period three flights examined a strong inversion is found base heights and temperature increases across the inversion base are comparable to values observed in the san francisco bay area the topography of the inversion base shows a slope downward toward the east during all three of these flights and also suggests the presence of convective activity gravity wave activity or both during two of the three

ice water pits upon the yellow river delta plain abstract the erosion circular pit is a common sedimentary structure but its genesis is complex many erosion pits occur on the yellow river delta plain with some formed by ice water erosion the ice water pits are generally circular or semi circular in cross section and are typically 2 40 cm across and 2 20 cm in depth we identify four types of pits on the basis of their origin i pits that formed by liquefaction and tight arrangement ii pits that formed by spattering iii pits that formed by lateral leakage and iv pits that formed by bottom leakage the formation of the ice water pits is likely a function of many complex variables including frequent runoff channel structure ice run and fine sediment size the example of ice water pits from the yellow river delta plain offers a useful frame of reference for the interpretation of formation conditions and environment significances of some circular pits pot or pothole in ancient rocks

mesoscale forcing of a boundary layer jet along the california coast mesoscale numerical model simulations were examined to investigate the thermal and topographic forcing of a boundary layer jet along the northern california coast from 0000 utc may 2 to 1200 utc may 3 1990 routine surface and upper air observations satellite and higher resolution coastal observations r v point sur and doppler wind profiler data documented the diurnal evolution of a coastal marine atmospheric boundary layer mabl coastal cloud structure and mesoscale features such as the coastal jet and land sea breeze circulations that were reasonably well forecast by the numerical model sensitivity model simulations to coastal baroclinicity showed that the diurnal development and intensification of the coastal mabl jet located north of the san francisco bay area was a result of thermal forcing due to differential land sea heating simulations in which the coastal baroclinicity was held fixed in time at a minimal strength showed no diurnal development of the mabl jet the strength of the jet was approximated well by the thermal wind relationship with the jet core located in the sloping marine inversion layer within one rossby radius of deformation from the coastline the steepness of the marine inversion at the coastline was enhanced by regions of strong mabl divergence just offshore and strong convergence onshore resulting from the sea breeze circulation modifications to coastal terrain in two separate sensitivity model simulations illustrated that the primary effect of coastal topography was to act as a barrier to the onshore intrusion of higher momentum offshore air this blocking was due to a topographically forced vertical circulation with a strong descending branch located at the coast this downslope flow and adiabatic warming steepened the mabl inversion at the coast and enhanced the coastal baroclinicity and the coastal jet simulations without coastal terrain showed a jet structure that was spatially diffuse across the coastline and displaced more shoreward simulations in which coastal valleys were removed and replaced by a larger coastal mountain range resulted in little modification to the coastal jet intensity or offshore displacement

preservation of mollusca in copano bay texas the long term record abstract the stratigraphic taphonomic and biologic records from two cores in copano bay texas were analyzed to determine 1 whether variations in shell content with depth were caused by variations in carbonate preservation carbonate production or sedimentation rate and 2 the extent to which characteristics of fossil assemblages such as species composition numerical abundance biomass and trophic and habitat structure identified similar or different trends below the top few cm of the sedimentary column variations in carbonate content with depth could be attributed to variations in carbonate production most biological attributes varied similarly with depth and hence time on both long 100 yr and short 10 yr temporal scales these variations could not be explained by any taphonomic process sediment reworking and burial or sedimentation rate despite a vigorous taphonomic milieu to obtain the shell content of copano bay sediments requires the preservation of nearly all carbonate produced preservation of a large fraction of the shell carbonate added requires the preservation of most of the relatively large shelled biota large species and adults which retain important evidence of changes in the community s history in this area the results reemphasize the importance of large individuals and biomass in paleontologic reconstruction and suggest that changes in community productivity which in paleontologic usage must be carbonate productivity are preserved in the fossil record

late mississippian bryozoan microbial build ups on a drowned karst terrain port au port peninsula western newfoundland bryozoan and microbial carbonate build ups occur within the late mississippian mid visean codroy group on the port au port peninsula western newfoundland build ups formed only adjacent to a rocky cliffed shoreline filling narrow submerged palaeovalleys of a well developed late devonian early mississippian karst terrain the nearshore setting was a stressed environment as indicated by 1 the absence of normal marine biota such as corals echinoderms and calcareous algae 2 high numbers and low species diversity of dominant taxa bryozoans brachiopods and microbial communities and 3 abundant plant bearing siliciclastics deposited by the episodic influx of fresh water from adjacent uplands build up development was terminated by meramec time due to falling sea level and seaward progradation of terrestrial sediments preserved structural and constructional fabrics within the build ups include 1 thickets of bryozoans and microbial microthrombolites structurally enhanced by probable marine mg calcite and aragonite cements 2 multigeneration internal sediment and 3 small colonies of serpulid worms and terebratulid brachiopods submarine cementation within the build ups appears to have been abundant during arrested sedimentation whereas intermound sediments carbonates and siliciclastics were lithified only during burial diagenesis shallow burial fracturing stylolitization sulphide and sulphate mineralization and precipitation of phreatic iron poor calcite cement occurred during burial diagenesis codroy build ups are distinct from the more common mississippian mud mounds their internal characteristics and the geologic setting are more like other late palaeozoic and holocene bryozoan rich build ups

brunswick subduction complex in the canadian appalachians record of the late ordovician to late silurian collision between laurentia and the gander margin of avalon the brunswick subduction complex in the new brunswick part of the canadian appalachians records the late ordovician to late silurian collision between laurentia and the gander margin of avalon the brunswick complex is anomalously well preserved compared with equivalent rocks and structures elsewhere owing to its unique position in the deepest part of the quebec reentrant of the laurentian margin this part of the margin experienced less underthrusting and exhumation and overprinting by orogen parallel faulting than the adjacent promontories where collision started earlier the early southeast to east vergent thrust related structures represent a progressive d1 deformation that formed in response to northwestward subduction of the previously extended gander margin and subsequent tectonic unroofing of the subduction complex the original shallow northwestward dipping envelope to s1 was deformed in the late silurian by d2 upright folds and associated shear zones into a steep belt during terminal collision the d2 structures probably formed in response to sinistral transpression together d1 and d2 indicate that convergence was oblique and sinistral most rocks incorporated in the subduction complex formed in the tetagouche back arc basin that evolved from rifting of an arenig magmatic arc built on the gander margin into a wide marginal basin subduction was initiated in the late ordovician 455 ma in the back arc basin following collision of the middle ordovician popelogan arc with laurentia in the caradoc shortly after its opening in the late arenig 473 ma the closure history of the iapetus ocean involved more than one subduction zone and arc continent collision and rivals the southwestern pacific ocean in its complexities

evidence of episodic fluid gas and sediment venting on the northern gulf of mexico continental slope surficial sediments and sea floor features of the northern gulf of mexico continental slope record dramatic episodic venting and slower seepage of formation fluids brines crude oil gases and fine grained sediments faults activated by massive sediment input during periods of plio pleistocene falling to low sea levels accompanied by compensating salt movement provide avenues of vertical transport to the continental slope surface many of these faults cut thick sedimentary sequences that frequently contain geopressured zones which provide the driving force for fluid and gas expulsion flux rate and fluid characteristics are interpreted as important determinants of modern sea floor geology and biology qualitatively under conditions of rapid flux of sediment rich fluids mud volcanoes up to 1 km wide and 50 m high and extensive sheets of extruded mud result these sediments contain old and displaced microfaunas muds are frequently extruded with large volumes of crude oil and gas both biogenic and thermogenic in water depths greater than approximately 500 m rapid to moderate vertical flux of hydrocarbon gases and fluids results in the construction of relief features composed of gas hydrates ejected mud and authigenic carbonates areas with near surface hydrates frequently support complex chemosynthetic communities with associated hardgrounds containing calcareous remains of mussels clams and associated gastropods slow flux seeps promotes the formation of 13 c depleted carbonate hardgrounds stacked carbonate slabs and moundlike carbonate buildups frequently 20 m relief barite along with carbonate has been found in areas where rapid flux of sediment carrying fluids has waned in the recent past and mineral rich brines are now being ejected crests chimneys and cones of these minerals are found in such settings both recent numerical simulations of fluid release from geopressured zones and direct observations at the sea floor support a pattern of episodic venting short term episodes of venting are probably regulated by fault movement perhaps controlled by local salt adjustment destabilization of gas hydrates by oceanographic processes also causes short term episodic gas expulsion these events occur with interannual to intra annual frequencies longer gas hydrate stabilization destabilization cycles in continental margin settings are forced by hydrostatic loading and unloading at the frequency of sea level change radiometric dating suggests that other long term episodes of venting and major venting expulsion events are also probably modulated by sea level change time scales of thousands of years in response to low stand sedimentary loading results of this summary of vent seep related phenomena suggest that sediment input from the shelf margin associated with cyclic plio pleistocene falling to low sea level periods followed by major listic fault and salt adjustments to a new sediment load have activated venting seepage throughout this period and perhaps longer

deep biological communities in the subduction zone of japan from bottom photographs taken during nautile dives in the kaiko project abstract twenty seven dives of the submersible nautile in the subduction zone around japan conducted in the french japanese project kaiko proved that fairly luxuriant benthic communities dominated by deep sea giant clams of the genus calyptogena family vesicomyidae were consistently present on the accretionary prism at abyssal depths benthic communities characterized by three hitherto undescribed bivalves of the genus calyptogena were found between depths of about 3800 and 4020 m at the mouth of tenryu canyon and at the top of basement swell of the zenisu ridge both situated in the eastern nankai subduction zone sporadic but discrete patches of organisms characterized by one more undescribed bivalve belonging to the genus calyptogena were observed and collected between depths of 5130 and 5960 m on the landward wall of the japan and kouriles trenches photographic inventories were prepared semiquantitatively using each series of bottom photographs taken in these areas with bow cameras of the submersible nautile observations on the sporadic but dense distribution of the clams and other characteristic associated organisms match well with the scheme that communities sustained by chemosynthetic energy sources can be present at connate water seepages in subduction zones these are to date the deepest record of benthic communities supposedly associated with chemosynthetic processes

why did ancient chemosynthetic seep and vent assemblages occur in shallower water than they do today cold seep communities have relatively low diversity are dominated by one or two taxa present in high density and high biomass in comparison with the surrounding fauna and are restricted to aphotic habitats their associated heterotrophic fauna are usually distinctive from the fauna of their surroundings in contrast a more commonplace chemoautotrophically based community occurs in shallow photic habitats the associated heterotrophic fauna includes many of the species typical of the surrounding communities and typically dominates abundance whereas the species with chemoautotrophic symbionts dominate biomass all modern seep assemblages are deeper than 550 m many fossil seep assemblages occurred in water as shallow as the mid shelf 200 m in contrast communities where species with chemoautotrophic symbionts are biomass dominants but not numerical dominants are common in shallow waters at present but rarely reported in the geological record we suggest that the absence of cold seep communities on the continental shelf presently is due to a combination of predation and competitive exclusion by primary consumers limiting the presence of species dependent on chemoautotrophic symbionts we suggest that cold seep assemblages are more common at shelf depths in the fossil record for two reasons a the biases of preservation have accentuated their distribution by transforming communities where species with chemoautotrophic symbionts dominate by biomass but not numerically into cold seep appearing assemblages b the importance of predation pressure and oligotrophy has varied with decreased predation pressure accompanying increased oligotrophy favoring cold seep communities we suggest that the paucity of shallow water assemblages with species harboring chemoautotrophic symbionts as biomass dominants in the fossil record is based on the reliance of paleoecological analysis on numerical abundance data when energy flow analyses are required to identify these assemblages the distinctiveness of the fossil seep assemblage is intensified by taphonomic processes that bias the assemblage against small individuals and epifaunal species so that diversity declines the small heterotrophic component of the assemblage is significantly reduced and the epifaunal component is minimized the final assemblage is usually dominated by the better preserved large infaunal clams which perchance are also the species with chemoautotrophic symbionts in contrast preservation does not enhance the distinctiveness of these chemoautotroph harboring species in shallow water

coastal jets in the lower atmosphere abstract low level winds over land ocean boundaries are generally alongshore two types of forcing that generate alongshore jets in the lower atmosphere are considered here using as simple a model as possible the first type of forcing is the blocking of the low level zonal winds by topographies winter alongshore wind off the west coast of north america is topography forced our simple model produces wind fields that have horizontal structure similar to the observed based on the distribution of zonal wind stress with latitudes the model suggests that the alongshore wind over the west coast of the united states reveres its direction near 40 n in fair agreement with observations however the linear model underestimates the alongshore wind off the california coast by a factor of about 1 7 2 consequently linear prediction of nearshore wind stress is about 3 4 times smaller than the observed the discrepancy is attributed to nonlinear effects a nonlinear analysis is presented to show how nonlinearity

a three dimensional numerical investigation of a carolina coastal low level jet during gale iop 2 abstract the pennsylvania state university ncar mesoscale model is used to examine the structure and dynamics of three low level jets lljs observed during the second intensive observation period of the genesis of atlantic lows experiment 1 a piedmont llj along the east slope of the appalachians 2 a coastal llj the focus of this study along the carolina coastline and 3 an llj to the rein of a cold frontal system positioned over the gulf stream geostrophic forcing was important for the formation of the lljs shallow local baroclinity near the top of the cold dome associated with the cold air dammed to the east of the appalachian mountains forced the piedmont llj an analysis of the model momentum tendencies reveals that the coastal llj developed and was maintained by strong geostrophic forcing associated with the coastal baroclinic zone and its strength was modulated by strong inertial accelerations significant horizontal structure in the coastal llj developed during the daytime as a result of

ecologie des pseudobiohermes des terres noires jurassiques lies a paleo sources sous marines le site oxfordien de beauvoisin drome bassin du sud est france abstract pseudobioherms are fossiliferous calcareous bodies well exposed within jurassic calcareous shales of se france their genesis is unknown oxfordian psedobioherms of the outcrop of beauvoisin are studied here several kinds of results show that they are probably built at vent of submarine springs in a bathyal environment among their related fauna bivalves are thriving they show some remarkable analogies morphology growth distribution with some typical bivalves of recent springs hydrothermal vents or cold seeps like calyptogena isotopic composition of their shell exhibits a highly positive 13c and emphasizes this resemblance this suggests a chemosynthetic food supply through a bacterial symbiosis the whole fauna microfauna and macrofauna was inventoried within pseudobioherms and their close and far environment a comparative paleoecological study has been carried out to evaluate the faunal anomaly shown by a selected pseudobioherm two contemporaneous sections one close to this pseudobioherm and one other in a distant area without pseudobioherms have been studied in detail all taphonomic disturbances which are able to alter data have been carefully studied the paleobiocoenose suggests a slightly higher environmental stability because of an additional food supply within an environment usually less favorable it also suggests some permanency of spring activity the impact of the supposed springs on the benthic fauna is localized and slightly preserved through fossil fauna it mainly expresses itself in bivalves and organisms able to eat them crustacean cephalopods considering these various observations and after a critical comparison with characteristics and geological setting of recent submarine springs a model is suggested to understand the highly original paleo ecosystem of pseudobioherms

deep sea communities dominated by the giant clam calyptogena soyoae along the slope foot of hatsushima island sagami bay central japan abstract calyptogena vestimentiferan tube worm communities were observed over a distance of roughly 7 km along the foot of the hatsushima escarpment sagami bay central japan between depths of 900 and 1200 m by means of towed tv still camera system and a submersible the composition of the communities the occurrence of a positive temperature anomaly of about 0 5 c within the community beds and an extremely high amounts of methane in the bottom water indicated the presence of cold seepage the biomass of living calyptogena was estimated to surpass 10 kg m 2 which was three orders of magnitude higher than that of the usual nearshore deep sea benthic communities at an equivalent depth the present results combined with the electron microscopic evidence for symbiotic bacteria and the high sulfur content and negative 34 s value in the gills of the calyptogena soyoae collected from the communities and the stable and radioactive carbon isotopic compositions of the clam suggested that the seepage system of the hatsushima site is similar to those found at other plate convergent areas such as off oregon and off peru and in the japan trench with symbiotic bacteria probably sulfur and or methane bacteria playing important nutritional roles to support the seepage communities

marine stratocumulus layers part 1 mean conditions abstract the mean radiational dynamical and thermodynamical structure of the marine stratocumulus topped mixed layers of the california coast is described for two days in june 1976 using data from the ncar electra aircraft we suggest that the synoptic conditions found may be typical of about half of the shallow stratocumulus topped boundary layers that occur in this region during summer the inversion was low near the coast and increased in height to the west consistent with the average westward increase in sea surface temperature north south inversion height change was largely due to entrainment and mean mesoscale vertical motions below the inversion strong winds 12 20 m s 1 from the north and horizontal inhomogeneities resulted in large advection terms in mean field equations the sloping inversion often produced large vertical shears of the actual and geostrophic wind velocities across the inversion because of low liquid water contents 0 1 g kg 1 temperature and water vapor could be measure

a numerical study of the coastal cyclogenesis in gale iop 2 sensitivity to pbl parameterizations the effects of different parameterizations of the boundary layer on atmospheric mesoscale structure are tested in a three dimensional limited area weather forecast model model simulations are perfored for three model designs 1 a 10 layer model with a 1 layer bulk planetary boundary layer pbl 2 a 16 layer model with a 1 layer bulk parameterization of the surface layer but a mixing length pbl parameterization and 3 a 16 layer model with a surface energy budget monin obukhov similarity surface layer and a pbl parameterization based on turbulent kinetic energy tke closure model simulations are compared to genesis of atlantic lows experiment gale data including aircraft observations for the period 25 26 january 1986 during intensive observing period iop 2 in which coastal frontogenesis and cyclogenesis were prominent

structural evolution of sulphide tectonites and their host rocks stratmat mine new brunswick the sulphide orebodies at the stratmat mine in new brunswick are treated as tectonites because their primary characteristics have been so modified by deformation recrystallization and vein injection that most of their original features have been obscured pb zn cu sulphide orebodies at the stratmat mine consist of sulphide and sulphide silicate tectonites gneisses schists phyllites and slates produced by the mixing of two sulphide precursors and silicate host rocks by polyphase deformation much of which relates to progressive non coaxial deformation quartz vein injection during and after this period of deformation and the intermixing of nonsulphide lithotypes led to dilution of the initial ore composition both the deformation of the orebodies and fluid migration manifested by vein injection reflect processes that were operative in a major shear zone no indisputable primary characteristics of the orebodies are preserved although a number of tectonic and or tectonically modified features m

australian southerly busters part i analysis of a numerically simulated case study abstract a diagnostic study of the australian southerly buster is performed using a numerical weather prediction model it is demonstrated that the model run at 50 km resolution is capable of capturing the transition of a cold front into a southerly buster as it traverses the cut coast of the australian continent the main features of the modified front am identified through comparison of the simulation with an adiabatic simulation from which precipitation and surface processes including orography have been removed from this comparison the southerly buster effect is defined in terms of the deformation of the front from its adiabatic ostentation and in terms of enhancement of temperature gradients and southerly winds along the coastal strip sensitivity experiments are then analyzed with a view to objectively determining the relative roles of mountains precipitation and land sea contrasts of heating and friction in bringing about these perturbations the major conclusions are that i the primary e

the marine atmospheric boundary layer jet in the coastal ocean dynamics experiment the vertical and horizontal structure of the atmospheric boundary layer near the northern california coast was investigated during spring upwelling conditions as part of the 1981 coastal ocean dynamics experiment two daytime aircraft flights were devised to measure mean and turbulent quantities for 25 km tracks along and across the continental shelf from 30 to 1200 m altitude the pacific high offshore and an inland thermal low characterized the synoptic situations and equatorward winds resulted which produced intense ocean upwelling the wind profile was found to be jet shaped maximum wind speeds were 25 m s 1 and 16 m s 1 at 400 and 100 m respectively in the two flights above and below the heights of the jet speed maxima the wind speed decreased rapidly sharp density inversions existed at the levels of the peak wind speeds in one flight the inversion also sloped down toward the coast turbulence was effectively confined below the inversions strong zonal temperature gradients above the inversion between the hot land and cool marine air caused a thermal wind for which the wind speed decreased with height below the inversion turbulent stress divergence was large and effective in transferring the horizontal momentum of the wind to the sea slowing the wind there was also a small thermal wind below the inversion but opposite to the one above owing to the well mixed air temperature following the sea surface temperature which was cold at the coast and relatively warmer offshore owing to the upwelling these effects explain the jet shaped wind profile the mean momentum equations show that an acceleration toward the coast can balance the pressure gradient coriolis and turbulent stress divergence forces and there were some observations to support this complete balance was not obtained for the turbulent kinetic energy budget inferred dissipation rates were too large

a theoretical study of mountain barrier jets over sloping valleys abstract a shallow water model is developed to examine the dynamics of mountain barrier jets over a mesoscale sloping valley between two mountain ridges in this model the cold air trapped in the valley is represented by a shallow water layer that is coupled with the upper layer flow through a free slip interface the pressure gradient exerted from the upper layer plus the pressure gradient generated by the sloping cold layer itself drive the cold air down the valley forming a jet against the surface friction in the cross valley direction the jet induced coriolis force is balanced by the pressure gradient force for a given cross valley terrain profile the solution is controlled by eight dimensional environmental parameters in the nondimensional space the solution is controlled only by three parameters the froude number modified by the ratio between the valley width and the rossby radius of deformation the surface drag coefficient normalized by the ratio between the valley depth and the inertial r

the influence of mesoscale orography on a coastal jet and rainband abstract the role of mesoscale orography along the central california coast in the development and evolution of a coastal jet and rainband is investigated using a high resolution triply nested nonhydrostatic numerical model comparison of the model simulations which use horizontal grid increments of 5 and 2 km on the inner computational meshes with a coastal mesoscale observation network indicates that the finescale structure of the jet and rainband dynamics are adequately simulated although phase and orientation errors occur the observed and simulated near surface winds have maximum speeds that exceed 22 m s 1 and a direction nearly parallel to the coastline and topography force balance analysis indicates that blocking in the lowest 500 m and flow over the coastal range above this layer contribute to mesoscale pressure perturbations including pressure ridging upstream of the coastal mountains which forces the ageostrophic dynamics of the coastal jet pressure perturbations associated with the to

time averaging taphonomy and their impact on paleocommunity reconstruction death assemblages in texas bays the death assemblages in upper copano bay and upper laguna madre texas were compared with the living communities as sampled over a two year period in order to determine how taphonomy and time averaging affect paleocommunity reconstruction the living and death assemblages were compared using taxonomic composition numerical abundance diversity biomass and trophic and habitat proportions taxonomic composition particularly adult taxonomic composition and the biomass of the death assemblage more accurately reflect the characteristics of the living community than do numerical abundance and other community attributes based upon numerical abundance such as diversity taxonomic composition and biomass are less modified by taphonomy and time averaging because they are temporally more persistent characteristics of the community community and paleocommunity attributes are not equivalent because the paleocommunity is described using time averaged data ecological theory must be supplanted by paleoecological theory that takes into account this temporal component

large scale structure of the june july 1996 marine boundary layer along california and oregon abstract data from surface stations profilers long range aircraft surveys and satellites were used to characterize the large scale structure of the marine boundary layer off of california and oregon during june and july 1996 to supplement these observations june july 1996 averages of meteorological fields from the u s navy s operational coupled ocean atmospheric mesoscale prediction system coamps model were generated for the region model calculations show a broad band of fast northerly surface winds exceeding 7 m s 1 extending along the california oregon coast buoy measured peaks of 7 1 m s 1 off bodega bay 7 2 m s 1 off point piedras blancas and 8 8 m s 1 near point conception were reported mean winds at the buoys located 15 25 km offshore are generally faster than those at coastal stations and all station winds are faster in the afternoon the aircraft and station observations confirm that an air temperature inversion typically marks the top of the marine boundary layer which deepens offs

a case study of the interaction of the summertime coastal jet with the california topography coast parallel low level jets are commonplace in the marine boundary layer off the west coast of the united states during summer a field study was conducted in early summer of 1997 to document the forcing of boundary layer winds in the near coastal environment off california on 8 june 1997 the wyoming king air collected data along a 350 km stretch of coastal margin from cape mendocino to san francisco in order to examine the interaction between the coastal topography and the low level jet during the course of the flight 32 soundings were conducted the maximum speed of the coastal jet was found near the top of the marine boundary layer at altitudes from 200 to 600 m analysis of the data revealed a westward increase in the height of the marine boundary layer and maximum jet wind speeds strongest jet winds were observed southwest of cape mendocino with a maximum speed of 28 m s21 the coastal jet was characterized by a broad horizontal extent wind maxima were found at distances approximately 30 km to more than 100 km offshore hydraulic features such as jumps and expansion fans have previously been observed downwind of coastal capes and points along the california coast the flow upwind of cape mendocino and point arena was found to be supercritical but the king air data showed that accelerations associated with possible expansion fan phenomena were minimal it is proposed that the sloping inversion at the top of the marine boundary layer and attendant coastal jet are fundamentally the result of a geostrophic adjustment process arising because of the horizontal temperature contrast between the cool ocean and warm continent this view emphasizes that the coastal jet is a ubiquitous large scale feature of the summertime coastal environment terrain induced wind speed variations associated with expansion fans and hydraulic jumps only modulate the primary jet structure

australian southerly busters part ii the dynamical structure of the orographically abstract a methodology is presented for comparing nonlinear 3d model output to the physical principles embodied in idealized and analytical models through the use of the transformation of wind components v vg va to accelerations k f fk v p dv dt this methodology is applied to numerical simulations of the interaction of a cold front with coastal topography leading to the formation of a southerly busier current along australia s east coast it is found that while the front is moving along the south coast mountain chain the dynamics of the perturbation are similar in character to an orographically trapped density current type perturbation on the background front along the east coast however the southerly busier current bears no dynamical relationship to either an orographically trapped density current or a kelvin wave the balance of forces here being dominated by inertial terms

supercritical flow interaction within the cape blanco cape mendocino orographic complex abstract supercritical flow interaction occurring in the marine boundary layer between closely spaced coastal capes is investigated with a mesoscale numerical prediction model as an extension of previous work the u s navy s coupled ocean atmosphere mesoscale prediction system coamps is used to perform idealized model simulations with marine layers of varying upstream froude number to elucidate the different flow responses for a single convex bend the impact upon the supercritical flow of introducing a series of closely spaced coastal bends is then investigated the expansion fan is significantly reduced in magnitude and size by the formation of a compression wave at a blocking concave bend approximately 150 km downstream building upon the idealized marine layer response real data forecasts are then examined for several time periods of supercritical flow interaction between cape blanco oregon and cape mendocino california observations from the coastal waves 1996 cw96 field program were colle

the exaerobic zone a new oxygen deficient marine biofacies classical biofacies models1 2 for reconstructing palaeoenvironments of strata deposited in oxygen deficient marine settings define three principal facies aerobic 1 0 ml 1 1 o2 dysaerobic 1 0 to 0 1 ml 1 1 o2 and anaerobic 0 1 ml 1 1 o2 zones these models have postulated a decrease in organism size and degree of calcification as well as a drastic reduction in the relative percentage of fauna possessing calcified skeletons as the dysaerobic anaerobic boundary is approached through use of evidence independent of that provided by body fossils we demonstrate here that in portions of the monterey formation miocene california the bivalve anadara montereyana occurs in situ almost exclusively in strata deposited at the dysaerobic anaerobic boundary the occurrence of fossils of large well calcified benthic macroinvertebrates at this redox boundary contradicts classical biofacies models1 2 and there fore provides the basis for definition of a new oxygen related biofacies the exaerobic zone the exaerobic zone concept when adjusted for differences in basin configuration and palaeoceano graphic conditions provides a potentially useful model for explain ing occurrences of shelly benthic fossils within laminated organic rich strata of other phanerozoic marine sequences

early carboniferous low temperature hydrothermal vent communities from newfoundland living vent communities dependent on microbial chemosynthesis rather than photosynthesis were discovered only in the 1970s1 since then six fossil vent communities have been identified they range in age from early carboniferous to early tertiary2 7 here we describe fossil tubes an abundant low diversity fauna and sulphide mineralization in 340 myr old carboniferous carbonate mounds in newfoundland fig 1a these features together with evidence for microbial activity point to the existence of a seventh chemosynthetic community clustered around low temperature hydrothermal vents the remarkable preservation of this newfoundland community allows a direct comparison to be made with the composition and structure of modern vent communities

kelvin waves and internal bores in the marine boundary layer inversion and their relationship to coastally trapped wind reversals abstract detailed observations of a coastally trapped disturbance or wind reversal on 10 11 june 1994 along the california coast provide comprehensive documentation of its structure based on aircraft wind profiler radio acoustic sounding system and buoy measurements unlike the expectations from earlier studies based on limited data which concluded that the deepening of the marine boundary layer mbl was a key factor the 1994 data show that the perturbation was better characterized as an upward thickening of the inversion capping the mbl as the event propagated over a site the reversal in the alongshore wind direction occurred first within the inversion and then 3 4 h later at the surface a node in the vertical structure defined here as the altitude of zero vertical displacement is found just above the inversion base with up to 200 m upward displacements of isentropic surfaces above the node and 70 m downward displacements below although this is a single event it is shown that the vertic

the marine layer off northern california an example of supercritical channel flow abstract during the spring and summer northerly winds driven by the north pacific high pressure system are prevalent over the northern california continental shelf only interrupted for periods of a few days when weak or southerly winds occur in the course of the coastal ocean dynamics experiment code fixed station and observations were made to describe the temporal and spatial structure of the lower atmosphere and their relation to the strong upwelling of coastal waters in a region extending up to 40 km offshore and 100 km along the coast these observations suggest that atmospheric conditions during the spring and summer usually fall into one of three categories the surface wind can be everywhere weak pattern 1 it can blow at large speeds in a uniform pattern pattern 2 or finally the structure of the northerly surface wind can be complex with large changes in the wind speed and corresponding changes in the surface pressure over short spatial scales pattern 3 the latter pattern which o

modern analogues to middle ordovician sedimentary mounds and washout depressions abstract mounds and depressions containing dense fossil accumulations occur in a bed of middle ordovician age in the upper ottawa valley canada the appearance of these relict seabed features is similar to modern features containing dense accumulations of live species in the north sea it is suggested that the middle ordovician fossil accumulations relied on a similar local upward flux of minerals and nourishment as north sea communities which live in areas where sediments contain light hydrocarbon gases if further petrological and sedimentological studies on the middle ordovician deposits could confirm such a relationship then it would be the first time relict or fossil pockmarks were found in the sedimentary column

temperatures from triple junction angles in sulfides experiments carried out between 280 and 980 c demonstrate that dihedral angles for galena g n in sphalerite galena sphalerite triple junctions decrease with increasing temperature and that the rate of change increases in the same direction similar behavior is evident for sphalerite s p in galena sphalerite galena triple junctions and also for pyrrhotite p o in sphalerite pyrrhotite sphalerite triple junctions triple junction thermometry tjt is therefore most sensitive at high to very high temperatures where isotope thermometers are least sensitive the method relies on the temperature dependence of competitive surface tensions between shared surfaces of intergrown minerals because chemical interaction is not a prerequisite the tjt method is potentially applicable to a variety of mineral pairs found in regional metamorphic situations the method requires a slightly modified microscope equipped with a precision x y stage the application of s p temperature and s p calibrations to regionally metamorphosed sulfide ores yields temperatures that compare reasonably with temperatures obtained from sulfur isotopes and other geothermometers maximum regional metamorphic temperatures of 470 480 590 and 700 c were obtained for the bathurst new brunswick greenschist facies ruttan manitoba amphibolite facies and broken hill n s w granulite facies deposits respectively the g n and p o thermometers also reveal recrystallization effects in microfabrics

australian southerly busters part iii the physical mechanism and synoptic conditions contributing to development abstract the physical mechanism responsible for the formation of the southerly busier is investigated using simulations from a version of the australian bureau of meteorology s numerical weather prediction model froude number calculations are performed on a numerically simulated event to determine the blocking capacity of the mountains while the separate roles of the southern and eastern topography are explored through a series of idealized topography simulations it is found that the topography along the southern coastline plays a crucial role in the formation of the southerly buster through blocking of the cold air and subsequent channeling around to the east coast where the southerly surge occurs the interaction of four other summertime cold fronts with the southeastern australian topography is studied only two of these events in reality produced southerly busters on the east coast the model demonstrates ability to simulate the additional fronts accurately and hence distinguish between the southerl

numerical study of the diurnal cycle along the central oregon coast during summertime northerly flow abstract a triply nested mesoscale atmospheric numerical model is used to study the dynamics of the diurnal cycle of the summertime lower atmosphere along the central oregon coast simulations of four consecutive days in september 1998 during which the winds were strong and northerly are analyzed comparisons with profiler observations suggest that the model performed well enough to provide a useful estimate of the diurnal circulation during the four days of interest the low level wind pattern has a broad maximum between cape blanco and cape mendocino with a large north south gradient along the oregon coast the low level jet undergoes diurnal horizontal and vertical displacements which partially resemble previous observational and modeling results along the california coast in both the model and the profiler data there is a minimum in northerly wind between 1500 and 1800 utc 0700 and 1000 local time and a double maximum in offshore flow above the marine boundary layer with peaks near 0700 and

uplift of africa as a potential cause for neogene intensification of the benguela upwelling system the benguela current cooled over the past 12 million years numerical modelling suggests that uplift of parts of africa during this time enhanced coastal low level winds and promoted greater upwelling of cool subsurface waters

eocene deep sea communities in localized limestones formed by subduction related methane seeps southwestern washington densely populated communities of soft bottom dwelling taxa similar to those found today along subduction zones off the coasts of japan and oregon have been discovered in very localized deep water limestones of late middle to late eocene age along the southwestern margin of washington subduction was prevalent in this area during this time and compressive forces squeezed subsurface methanerich waters onto the ocean floor where opportunistic bivalves especially modiolus calyptogena and thyasira vestimentiferan tube worms serpufid tube worms siliceous sponges very small limpets trochid and turbinid archaeogastropods and other macrobenthos colonized these assemblages are the earliest recorded biologic communities formed in response to methane seeps in subduction zones

formation of low temperature mylonites and phyllonites by alkali metasomatic weakening of felsic volcanic rocks during progressive subduction related deformation abstract dacitic to rhyolitic volcanic rocks of the spruce lake nappe experienced two phases of alkali metasomatism as a result of fluids channelling along shear zones the shear zones formed during a progressive thrust related deformation associated with underplating and incorporation of the volcanic rocks into the brunswick subduction complex of northern new brunswick the fluids mainly represent chemically and isotopically modified seawater released by dewatering of the associated underthrusted shaly sedimentary rocks both phases of metasomatism weakened the felsic rocks leading to strain localisation albitisation of felsic volcanic rocks as a result of na metasomatism during underthrusting facilitated formation of mylonites near peak high pressure metamorphism 330 370 c 600 800 mpa the mylonites are preferentially preserved in the roof thrust shear zone of the spruce lake nappe core mantle structures bulging and crystallographically preferred orientations indicate that albite behaved more ductilely than k feldspar the ductility of albite at these low temperatures is interpreted as a function of abundant intragranular fluids phengite rich phyllonites formed after peak high pressure metamorphism during uplift by out of sequence thrusting these phyllonites are generally characterised by a slight gain in k and loss of na and are best developed in the basal shear zones of the spruce lake nappe

characteristics of nocturnal low level jets observed in the north florida area the seasonal and interannual variability of the nocturnal low level jets over the north florida region are investigated using sodar measurements spanning 540 nights on average jets are present in 62 of the nocturnal periods examined the observed jet speeds range between 3 and 21 m s 21 and heights are between 80 and 700 m observations show that the low level jet occurs more frequently 70 of the nocturnal periods during the colder months november february in contrast with the warmer months june august 47 the presence of southerly jets dominates the summer months whereas northerly jets are more frequent during winter colder months frequently exhibit jets with speeds exceeding 14 m s 21 often associated with the passage of frontal systems the interannual variability observed using the north american regional reanalysis narr wind profile data during a 4 yr period shows only minimal differences in jet characteristics a comparison of jet heights with narr planetary boundary layer heights suggests that jets at the north florida location frequently occur within the planetary boundary layer the occurrence and speed of observed low level jets are linked to both the land ocean temperature contrast and to the strength and orientation of surface pressure gradients over the region a high occurrence of large amplitude oscillations with approximately a 24 h period near the jet height is shown using the hilbert huang transform analysis suggesting that inertial oscillations are one possible cause of jet formation in north florida

sedimentary mounds and washout depressions from the middle ordovician limestone ottawa valley canada abstract small elliptical mounds and depressions about 1 m long occur on and within a bed of fine grained middle ordovician limestone in the ottawa valley canada both the mounds and the bottoms of the depressions contain abundant fossils in contrast to the surrounding bed which is essentially barren the mounds and depressions formed in the outer and deepest part of a quiet tropical marine lagoon behind a carbonate bank where bottom conditions were normally anoxic an unusually diverse and abundant fauna lived on the bottom just prior to deposition of the bed containing the mounds and depressions indicating an abnormally high oxygen concentration at the sediment water interface at the time as bottom conditions deteriorated many of the species survived only on the mounds which had fo med by the trapping and holding of sediment by large branching bryozoans the suspension feeding fauna that flourished on the mounds slightly above the barren sea floor implies a location at the interface between the oxygenated normal sea water and a bottom lens of anoxic water of somewhat higher salinity the depressions are washout features that formed when sediment was eroded from the mounds

cretaceous cold seep communities and methane derived carbonates in the canadian arctic lower cretaceous cold seep fossil assemblages have been found in the canadian arctic archipelago serpulid worm tubes and bivalves are most abundant in these communities in contrast fossils are scarce in the surrounding strata the fossils are contained in an isotopically light delta 13 c 25 to 50 per mil carbonate rock groundmass that is interpreted to have formed from bacterial oxidation of methane the rocks were deposited at intermediate depth 400 meters in a cold marine environment nearby normal faults may have provided a conduit for seeping methane and hydrogen sulfide needed to fuel chemosynthetic bacteria and in turn the higher life forms

structure and evolution of the heath steele base metal sulfide orebodies bathurst camp new brunswick canada a structural analysis of the base metal sulfide deposits at the heath steele mines northern new brunswick is presented the structural similarity of the deposits is defined and their relationships to one another discussed the deposits are spatially associated with ordovician sedimentary rocks which are situated in an igneous rock complex comprising felsic and basic volcanics volcaniclastics and intrusives the complex has been subjected to low grade metamorphism and five generations of deformation d 1 d 5 the first two generations of deformation d 1 and d 2 are represented by transposition foliations s 1 and s 2 the present attitude of the s 2 foliation is a result of recumbent folding d 3 and two generations of open folds with vertical axial planar cleavages striking northwest s 4 foliation and northeast s 5 foliation the s 1 foliation is axial planar to conical f 1 folds regionally such folds have been associated with thrusting d 1 along the earliest recognized layering s 0 foliation vein swarms illustrate the local importance of solute mass transfer during this event at the heath steele mines culminating in fracture controlled alteration along a brittle ductile deformation d 1 shear zone near the sulfide deposits and development of metasomatic breccia in the sulfide deposits overall the deposits occur along the s 0 foliation the contact between augen schists and the metasedimentary rocks but massive sulfides are concentrated in f 1 fold closures forming pods and slabs parallel to the s 1 foliation this concentration reflects either mobilization of preexisting sulfides during d 1 or deposit formation by mineralization during d 1 if the contact in s 0 is nontectonic a stratigraphic control on the location of the deposits is indicated and their association with iron formation argues for a syngenetic origin conclusive evidence for these models has been obliterated by the intense deformation and solution transfer

pliocene pleistocene genesis for the murray brook and heath steele au ag gossan ore deposits new brunswick from paleomagnetism several au ag gossans occur over massive sulphide deposits in the ordovician tetagouche group near bathurst new brunswick the murray brook and heath steele b zone goethite gossans were about 45 and 15 m thick respectively prior to mining they contain no minerals suitable for radiometric age dating geologically they must be younger than the devonian acadian orogeny and older than the last glaciation paleomagnetic methods were used to analyse specimens from 29 sites mostly from ore on the pit walls host rocks and sulphide mineralization retain characteristic remanent magnetization directions in magnetite and pyrrhotite with a variety of directions that include possible devonian overprints fertile and barren gossan specimens at 21 sites retain antiparallel normal and reversed a characteristic remanence components in goethite and or hematite the a direction is d 357 7 i 61 7 95 4 5 k 31 its pole of 134 2 e 85 2 n dp 5 4 dm 7 0 falls on the north american apparent polar

air discharge pits on the yellow river delta plain abstract a large number of air discharge pits varying in size and shape are developed on the yellow river delta their planar cross sections are circular sub circular elongated and frequently irregular and their spatial configurations may be in form of a shallow dish to root like or other extremely irregular shapes they range in diameter from less than 1 cm to over 60 cm and their depth varies from less than 1 mm to more than 20 cm they most commonly occur individually or in groups on the point bar our investigation indicates that the occurrence of the air discharge pits is closely associated with the unique hydrological channel and hydrodynamic conditions caused by the intermittent flow interruptions of the yellow river and the fine sediments typical of the river course during a yellow river flow interruption an underground air saturation zone in the dry layer of the riverbed may be formed due to the lowering of the ground water level when flooding originates from the up stream section of the yellow river the water quickly inundates the channel and rapidly submerges the extremely dry river bed and point bar as a result due to the blocking effect caused by the silty sand and mud preferential percolation occurs along the outer edge of the point bar and levee trapping air in the process the resulting air pocket and pressure capsule are enclosed in the air saturation zone providing the source material required for the subsequent formation of air discharge pits the trapped air may also form a high pressure capsule caused by the slow downward percolation of the river water the differential relatively lower pressure on the point bar permits the trapped air to escape provided the air is discharged in a shallow body of water

structural geology of the vangorda pbznag orebody yukon canada abstract the vangorda pb zn ag orebody is a 7 1 m tonne polydeformed polymetamorphosed stratiform massive sulphide orebody in the anvil mining district yukon canada the orebody consists of fine to medium grained semi massive and massive sulphides with a dominant sulphide mineralogy of pyrite pyrrhotite sphalerite galena and minor chalcopyrite five sulphide lithofacies have been identified within the orebody ribbon banded carbonaceous pyritic quartzite pyritic quartzite massive pyritic sulphides baritic massive pyritic sulphides and pyrrhotite sphalerite massive sulphides the orebody is elongate in a northwest southeast orientation and plunges shallowly towards the northwest the host rocks and the various sulphide lithofacies have been complexly deformed during two penetrative phases of deformation d 1 and d 2 respectively and associated metamorphism m 1 and m 2 m 2 metamorphism resulted in extensive recrystallisation and subsequent grain growth of sulphide minerals m 2 metamorphic grade recorded by arsenopyrite and chlorite thermometry and sphalerite hexagonal pyrrhotite barometry is of mid greenschist facies with temperatures of 336 to 363 c respectively and a pressure of 4 kb the earliest structure that can be recognised in the orebody is a penetrative s 1 spaced cleavage that is well developed in the host phyllites and a differentiated layering in the semi massive and massive sulphides however f 1 folds have not been identified in the orebody although they do occur within the anvil district the s 1 cleavage has been deformed into downward facing southwest verging recumbent f 2 folds that plunge shallowly northwest southeast a penetrative axial planar s 2 crenulation cleavage is developed in the phyllites and ribbon banded carbonaceous pyritic quartzite but is found only locally in the massive sulphide lithofacies in the baritic lithofacies f 2 folds have thickened hinges suggesting remobilisation of the ore along the overturned limbs of the f 2 folds and at lithofacies contacts centimetric to metric scale zones enriched in pyrrhotite sphalerite and galena are developed these areas commonly have a significantly reduced grain size a well developed sulphide foliation and numerous shear indicators such as winged and rotated clasts f 2 folds and the s 2 form surfaces are cut by syn to post d 2 nw se dipping extensional faults minor strike slip faults cut d 1 and d 2 structures

a fossil hydrothermal worm assemblage from the tynagh lead zinc deposit in ireland fossil hydrothermal chimneys were first discovered at silvermines1 ireland subsequent discoveries of fossils associated with mounds and chimneys in sulphide deposits within the ophiolite complexes of cyprus2 and oman3 prove that life forms similar to those colonising active vents on the east pacific rise4 7 were extant 100 myr ago around ridge crest hot springs here i report the discovery of 350 myr old worm like fossils recovered from pyrite chimneys associated with sedimentary exhalative mineralization at tynagh ireland this find suggests that even older examples of life existing at seafloor hot springs may be awaiting discovery