high temperature alteration and porosity generation in upper ordovician microbial reefs hudson bay intracratonic basin arctic canada abstract upper ordovician biohermal mounds of the red head rapids river formation in the hudson bay basin consist of microbial and sponge boundstone and cementstone the cementstone is made up of isopachous layers and botryoids of former aragonite now calcite secondary dissolution porosity and small fractures are cutting through the bioherm secondary pore fillings consist of drusy calcite cement and subsequent bitumen the 18ovpdb and 13cvpdb values of late cements are invariably more negative than those of the marine cements fluid inclusion microthermometry documents the presence of two distinct populations of homogenization temperatures one in secondary pore filling burial calcite cement th average 93 10 c and a second one in recrystallized marine calcite cements th average 118 25 c the combined 18ovpdb and th data suggest that burial cements precipitated from a fluid having 18osmow values between 0 5 and 2 whereas the marine cement data indicate resetting of the fluid inclusions in the presence of a high temperature 18osmow heavy brine 2 5 to 12 the lower temperature fluid inclusions of the late pore filling cement agree with recent apatite fission track data suggesting early oil window temperature at maximum burial the higher th values recorded in the marine cement represent resetting of initial or entrapment of new fluid inclusions from fracture controlled circulation of basement derived fluids the petrographic and geochemical data suggest that fracture controlled high temperature brine circulation occurred after the inception of burial and recrystallization of original marine aragonite to calcite which resulted in the generation of significant secondary porosity that was later filled by lower temperature burial cements and hydrocarbons

the stratigraphic position and the age of the ordovician organic rich intervals in the northern hudson bay hudson strait and foxe basins evidence from graptolites graptolites recovered from the organic rich intervals previously named the boas river formation in the upper ordovician succession on southampton akpatok and southern baffin islands provide a reliable age assessment for the upper ordovician petroleum source rocks in the northern hudson bay hudson strait and foxe basins they are characterised by anticostia lata and anticostia hudsoni in the lower red head rapids formation on southampton island anticostia decipiens and rectograptus socialis in the lower foster bay formation on akpatok island and diplacanthograptus spiniferus and amplexograptus praetypicalis in the lower amadjuak formation on southern baffin island these data suggest that the organic rich intervals in the northern hudson bay and hudson strait basins can be correlated to the dicellograptus anceps and paraorthograptus pacificus zones of the upper katian and the horizon in the foxe basin to the diplacanthograptus spiniferus zone of the lower katian the boas river formation is not dee

inbank and overbank velocity conditions in an arid zone anastomosing river relative to those at sub bankfull flow hydraulic conditions at overbank flow whether in the channel or on the floodplain are poorly understood here velocity conditions are analysed over an unusually wide range of flows in the arid zone river of cooper creek with its complex system of anastomosing channels and large fluctuations in floodplain width at a station hydraulic geometry relationships reveal sharp discontinuities in velocity at the inbank overbank transition the nature of the discontinuity varying with the degree of flow confinement and the level of channel floodplain interaction however despite inter sectional differences velocities remain modest throughout the flow range in this low gradient river and the large increases in at a station discharge are principally accommodated by changes in cross sectional area velocity distribution plots suggest that within channel conditions during overbank flow are characterized by a central band of high velocity which penetrates far toward the bed helping to maintain already deep cross sections floodplain resistance along cooper creek is concentrated at channel bank tops where vegetation density is highest and the subsequent flow retardation is transmitted across the surface of the channels over distances as large as 50 70 m the rough floodplain surface affects flood wave transmission producing significant decreases in wave speeds downstream the character of the wave speed discharge relationship also changes longitudinally from log linear in the upper reaches to nonlinear where the floodplain broadens appreciably the nonlinear form is similar in several respects to relationships proposed for more humid rivers with flood wave speed reaching an intermediate maximum at about four fifths bankfull discharge before decreasing to a minimum at approximately q2 33 it does not regain the value at the intermediate maximum until the 10 year flood by which time floodplain depths have become relatively large and broad floodways more active copyright 2002 john wiley sons ltd

seasonal variation and instability nature of the north pacific subtropical countercurrent and the hawaiian lee countercurrent 1 the relation between baroclinic instability of the north pacific subtropical countercurrent stcc and the hawaiian lee countercurrent hlcc and seasonal evolution of mesoscale sea surface height ssh variability was investigated by using historical hydrographic data and altimeter derived ssh anomaly data during 1992 2000 the annual and monthly mean dynamic height climatologies show two robust eastward flowing countercurrents the stcc extends typically along 24 n from 130 e to 160 w and slightly shifts to the north as it flows toward the east and the hlcc is located typically along 20 n and extends from about 150 e to just west of the hawaiian islands seasonal variations of the stcc in the western north pacific and the hlcc west of the hawaiian island where the eddy variability is relatively larger than the background were quite different the stcc hlcc is strong in winter summer to summer winter and weak in fall spring in contrast seasonal evolution of mesoscale ssh variability has almost the same cycle in the two countercurrent regions the eddy kinetic energy eke is a maximum in spring and a minimum in fall the dominant zonal scales are shortest in late winter and become longer with time a linear quasigeostrophic stability analysis using a three layer model indicates that instability properties are very similar between the two countercurrent regions the stcc and the hlcc become baroclinically more unstable during winter and late fall to winter respectively due to strong vertical velocity shear and weak stratification between the stcc hlcc and underlying westward flow and the most unstable wave during this season has an e folding timescale of about 2 3 months and a zonal wavelength of about 300 400 km the same behavior of the seasonal evolution of the mesoscale variability in the two countercurrent regions is a manifestation of these similarities in terms of increasing nonlinearity of the unstable waves and an inverse cascade of the eddy energy we discussed generation processes of the mesoscale ssh disturbances

the vertical partition of oceanic horizontal kinetic energy to produce an interpretation of the surface kinetic energy as measured by altimeters a survey is made of the vertical structure of kinetic energy profiles in a large number of globally distributed long current meter records although the data are geographically confined primarily to a latitude band in the north pacific to the north atlantic and to a few moorings in the south atlantic the results show generally speaking that most regions are dominated by the barotropic and first baroclinic modes because of the near surface intensification of baroclinic modes altimeters primarily reflect the first baroclinic mode and thus the motion of the main thermocline there is good quantitative agreement with a few exceptions with estimates of the surface kinetic energy obtained from the topex poseidon altimeter and from vertical extrapolations to the surface of the mooring profiles these results are consistent with previous suggestions that barotropic models have little skill in depicting variability as seen in the altimeter data an eof analysis is shown to produce fictitious mode coupling unless the dynamical modes have very different energy levels

tribes hill rochdale formations in east laurentia proxies for early ordovician tremadocian eustasy on a tropical passive margin new york and west vermont slow subsidence and tectonic quiescence along the new york promontory margin of laurentia mean that the carbonate dominated tribes hill and overlying rochdale formations serve as proxies for the magnitude and timing of tremadocian eustatic changes both formations are unconformity bound deepening shoaling depositional sequences that double in thickness from the craton into the parautochthonous western appalachian mountains a consistent layer cake succession of member level units of the formations persists through this region the tribes hill formation late early tremadocian late skullrockian late fauna b rossodus manitouensis chron unconformably overlies the terminal cambrian little falls formation as the lowest ordovician unit on the new york promontory it was deposited during the strong early tremadocian or stonehenge transgression that inundated laurentia brought dysoxic anoxic d a slope water onto the shelf and led to deposition of the schaghticoke d a interval black mudstone and ribbon limestone on the laurentian continental slope the uniform lithofacies succession of the tribes hill includes a lower sand rich member a middle dark grey to black mudstone that records d a in eastern exposures and an upper shoaling up carbonate highstand facies a widespread 12000 km 2 thrombolitic interval in the highstand carbonate suggests the new york promontory was rimmed by thrombolites during deposition of the tribes hill offlap and erosion of the tribes hill was followed by the relatively feeble sea level rise of the rochdale transgression new in laurentia and deposition of the rochdale formation the rochdale transgression correlated with the kierograptus drowning interval in baltica marks a eustatic rise the rochdale formation represents a short early ordovician interval early late tremadocian middle late stairsian macerodus dianae chron it correlates with a depositional sequence that forms the middle boat harbour formation in west newfoundland and with the rte 299 d a interval on the east laurentian slope the rochdale has a lower carbonate with abundant quartz silt comstock member new and an upper thrombolitic hawk member new high stand facies tribes hill and rochdale faunas are mollusc rich generally trilobite poor and have low diversity laurentian faunal province conodonts ulrichodina rutnika landing n sp is rare in rochdale conodont assemblages trilobites are also low in diversity but locally form coquinas in the middle tribes hill the poorly preserved rochdale trilobites include the bathyurid randaynia at least two hystricurid species and leiostegium

mass and volume transport variability in an eddy filled ocean eddy activity in the north atlantic ocean produces fluctuations in ocean wide volume transport on the order of 20 106 cubic metres per second on multi year timescales such background noise makes it impossible to detect possible trends in the ocean circulation due to a changing climate without multi decadal observations in three spatial dimensions the possibility that the oceanic general circulation is undergoing changes as part or the cause of major climate shifts is being intensely discussed1 with some published results relying on data from moorings spanning the north atlantic ocean2 3 the circulation is however extremely noisy here i use existing estimates of the frequency and wavenumber content of geostrophic eddies in the ocean4 to show that variations in ocean wide integrated transport must appear even in the absence of a true long term trend expected fluctuations exceed 20 109 kg s 1 or 20 106 m3 s 1 and exhibit multi year timescales existing knowledge of the eddy field allows predictions of observed variability and produces lower bounds on the multi decadal timescale required to detect true trends of a large magnitude detecting and understanding the effect of climate change on the ocean circulation requires observations in three dimensions over long periods of time

conodont paleontology and biostratigraphy of ordovician carbonates and petroliferous carbonates on southampton baffin and akpatok islands in the eastern canadian arctic carbonate and petroliferous carbonate units oil shales on southampton baffin and akpatok islands have yielded a total of 2277 conodonts the more biostratigraphically useful of which indicate not all units are correlative the boas river shale the lower of the two petroliferous units on southampton island overlies the bad cache rapids group and contains a diverse fauna including elements of amorphognathus ordovicicus branson and mehl previous reports have indicated the presence of culumbodina penna sweet a species whose range only barely overlaps that of a ordovicicus in the middle maysvillian carbonate beds and bedding plane surfaces of the higher red head rapids formation at sixteen mile brook yielded a ordovicicus faunas containing aphelognathus cf a divergens sweet these beds are likely richmondian since a divergens is known elsewhere only from richmondian strata a metasicula of glyptograptus hudsoni jackson several natural conodont assemblages and fused enigmatic coniform el

spatiotemporal variability of the global ocean internal processes inferred from satellite observations abstractusing a new analysis tool namely multiscale window transform mwt and the mwt based theory of canonical transfer this study investigates the spatiotemporal variations of the nonlinear

geographical variability of the first baroclinic rossby radius of deformation global 1 83 18 climatologies of the first baroclinic gravity wave phase speed c1 and the rossby radius of deformation l1 are computed from climatological average temperature and salinity profiles these new atlases are compared with previously published 5 83 58 coarse resolution maps of l1 for the northern hemisphere and the south atlantic and with a 1 83 18 fine resolution map of c1 for the tropical pacific it is concluded that the methods used in these earlier estimates yield values that are biased systematically low by 5 15 owing to seemingly minor computational errors geographical variations in the new high resolution maps of c1 and l1 are discussed in terms of a wkb approximation that elucidates the effects of earth rotation stratification and water depth on these quantities it is shown that the effects of temporal variations of the stratification can be neglected in the estimation of c1 and l1 at any particular location in the world ocean this is rationalized from consideration of the wkb approximation

tempo of earliest ordovician graptolite faunal succession conodont based correlations from the tremadocian of quebec successive tremadocian planktic dendroid graptolite assemblages from continental slope sequences in quebec can be correlated with north american platform biozonations on the basis of conodonts anisograptid bearing assemblage 2 middle tremadocian matane faunas are associated with early ordovician rossodus manitouensis zone new designation conodonts younger middle tremadocian faunas with adelograptids assemblage 3 are no younger than the rossodus manitouensis zone key dendroid evolutionary immigration events take place within the lower conodont fauna b interval rooted dendroids near cap des rosiers quebec and in eastern new york state occur with lower fauna b conodonts and the trilobites pareuloma and borthaspidella however the earliest tremadocian and earliest ordovician dendroid immigration event represented by the local lowest occurrence of faunas with dictyonema flabelliforme s l at localities in western newfoundland eastern new york state norway and eastern china also lies with

late ordovician conodont biostratigraphy and redefinition of the age of oil shale intervals on southampton islandearth science sector contribution 20100054 southampton island was located on the north margin of the hudson bay basin one of the largest paleozoic sedimentary basins in north america the upper ordovician sequence on the island includes the bad cache rapids and churchill river groups and the red head rapids formation the latter contains three oil shale intervals in its lower part which may have significant potential as hydrocarbon source rocks but their precise biostratigraphic position remains unclear numerous conodont elements from 14 localities allow establishment of four interval zones throughout the upper ordovician on southampton island the belodina confluens and pseudobelodina v vulgaris zones in the bad cache rapids group which are correlative to the upper edenian lowest richmondian stage the amorphognathus ordovicicus zone from the uppermost bad cache rapids group to the top of churchill river group to the lower richmondian stage and the rhipidognathus symmetricus zone in the red head rapids formation to the upper richmondian

the scales and equilibration of midocean eddies freely evolving flow quasigeostrophic turbulence theory and numerical simulation are used to study the mechanisms determining the scale structure and equilibration of mesoscale ocean eddies the present work concentrates on using freely decaying geostrophic turbulence to understand and explain the vertical and horizontal flow of energy through a stratified horizontally homogeneous geostrophic fluid it is found that the stratification profile in particular the presence of a pycnocline has significant qualitative effects on the efficiency and spectral pathways of energy flow specifically with uniform stratification energy in high baroclinic modes transfers directly quickly within a few eddy turnaround times and almost completely to the barotropic mode by contrast in the presence of oceanlike stratification kinetic energy in high baroclinic modes transfers intermediately to the first baroclinic mode whence it transfers inefficiently and incompletely to the barotropic mode the efficiency of transfer to the barotropic mode is reduced as the pycnocline is made increasingly thin the b effect on the other hand improves the efficiency of barotropization but for oceanically realistic parameters this effect is relatively unimportant compared to the effects of nonuniform stratification finally the nature of turbulent cascade dynamics is such as to lead to a concentration of first baroclinic mode kinetic energy near the first radius of deformation which in the case of a nonuniform and oceanically realistic stratification has a significant projection at the surface this may in part explain recent observations of surface eddy scales by topex poseidon satellite altimetry which indicate a correlation of surface height variance with the scale of the first deformation radius

streamflow routing in the indian arid zone a lumped model for streamflow routing in arid ephemeral channels has been developed the governing equations for movement of flood waves subjected to transmission losses are simplified through a time averaging process to develop an ordinary differential equation describing transmission losses as a function of distance inflow channel width time parameters of flow and effective hydraulic conductivity the resulting equation has an analytical solution and simulates runoff volume and peak discharge rates for individual storm events the outflow hydrograph is fairly well approximated with a triangular approximation the model is simplified and constructed to require a minimum of observed data for calibration it can also be used for ungauged basins in arid regions through parameterization

conodonts recovered from the carbonate xenoliths in the kimberlites confirm the paleozoic cover on the hall peninsula nunavut hall peninsula located on southeastern baffin island nunavut hosts the newly discovered chidliak kimberlite province presently this area lacks phanerozoic sedimentary cover except for the unconsolidated glacial deposits however late ordovician and early silurian microfossil conodonts have been recovered from carbonate xenoliths preserved in the late jurassic early cretaceous kimberlites over 1300 conodont specimens were recovered among which 32 species representing 23 genera are recognized with four elements indeterminate the well preserved conodont faunas provide reliable evidence on the hall peninsula for i reconstructing the lower paleozoic stratigraphic units including the upper ordovician frobisher bay amadjuak akpatok and foster bay formations and the lower silurian severn river formation ii estimating a total of 270 305 m in thickness of lower paleozoic sedimentary cover prior to the emplacement of the kimberlites iii tracing the erosion history after the emplacement of t

upper ordovician conodont biostratigraphy and revised lithostratigraphy and geological map akpatok island ungava bay nunavut stratigraphic units exposed on akpatok island ungava bay nunavut were previously recognized as boas river and akpatok formations their biostratigraphic ages and correlations in particular the stratigraphic position and age of the organic rich boas river formation were largely based on limited data new detailed field observations have recognized three stratigraphic units namely the amadjuak akpatok and foster bay formations in which extensive microfossil sampling recovered over 22 000 conodont elements from 66 productive samples from both outcrops and rubble at over 20 localities in four areas four upper ordovician conodont zones and one unzoned interval are established for the three redefined formations belodina confluens and oulodus velicuspis interval zones are confined to the exposed amadjuak formation and correlated to edenian and maysvillian amorphognathus ordovicicus plegagnathus dartoni concurrent range zone occurs with the akpatok formation and correlated to lower richmondian rh

a leaky reservoir model for ephemeral flow recession the flood wave in ephemeral streams can often be portrayed accurately by assuming instantaneous rise to peak flood stage depth and specifying a recession curve here recession is modeled as a conceptual analog of discharge from a single leaky reservoir physically the reservoir may be considered to approximate that portion of the ephemeral stream channel that is flowing at the onset of recession the discharging reservoir is described by a continuity equation and by discharge stage stream rating and storage stage reservoir configuration relations no input is routed through the reservoir at the onset of recession the reservoir has water in storage a good fit to observed curves is obtained by calibrating two parameters reservoir leakage rate and initial storage reservoir shape the agreement is most sensitive to changes in initial storage the best fit parameter values are physically plausible

kimberlite emplacement temperatures from conodont geothermometry abstract kimberlites are mantle derived ultramafic rocks preserved in volcanic and sub volcanic edifices and are the main primary source of diamonds the temperatures of formation transport eruption and deposition remain poorly constrained despite their importance for understanding the petrological and thermodynamic properties of kimberlite magmas and styles of volcanic eruption here we present measured values of colour alteration indices cai for conodonts recovered from 76 paleozoic carbonate xenoliths found within 11 pipes from the chidliak kimberlite field on baffin island nunavut canada the dataset comprises the largest range of cai values 1 5 to 8 and the highest cai values reported to date for kimberlite hosted xenoliths thermal models for cooling of the chidliak kimberlite pipes and synchronous heating of conodont bearing xenoliths indicate time windows of 10 20 000 h and for these short time windows the measured cai values indicate heating of the xenoliths to temperatures of 225 to 925 c we equate these temperatures with the minimum temperatures of the conduit filling kimberlite deposit i e emplacement temperature t e the majority of the xenoliths record cai values of between 5 and 6 5 suggesting heating of xenoliths to temperatures of 460 c 735 c the highest cai values are consistent with being heated to 700 c 925 c and establish the minimum conditions for welding or formation of clastogenic kimberlite deposits lastly we use t e variations within and between individual pipes in conjunction with the geology of the conduit filling deposits to constrain the styles of explosive volcanic eruption

terminal cambrian and lowest ordovician succession of mexican west gondwana biotas and sequence stratigraphy of the tinu formation the tinu formation of oaxaca state is the only fossiliferous lower palaeozoic unit between the laurentian platform in northwest mexico and gondwanan successions in andean south america the tinu traditionally has been referred to the lower ordovician tremadoc and regarded as having a provincially mixed fauna with laurentian avalonian and gondwanan elements bio and lithostratigraphic re evaluation demonstrates that the tinu is a gondwanan passive margin succession it includes a lower thin to 16 m condensed uppermost cambrian yudachica member new the yudachica nonconformably overlies middle proterozoic basement as a result of very high late late cambrian eustatic levels the yudachica changes from storm dominated but slightly dysoxic shelf facies fossil hash limestone and shale in the south to an upper slope facies with debris flows 50 km to the north three biostratigraphically distinct depositional sequences comprise the yudachica the yudachica has gondwanan aspect trilobites with low diversity conodonts characteristic of unrestricted marine temperate facies the upper tinu or rio salinas member new is a lower ordovician tremadoc depositional sequence that records strong early but not earliest tremadoc eustatic rise marked by graptolite and olenid bearing dysoxic mudstones higher strata shoal upward into shell hash limestones and proximal tempestite sandstones with upper lower tremadocian unrestricted marine temperate conodonts new taxa include orminskia rexroadae landing gen et sp nov from the cordylodus andresi zone this euconodont is related to hyaline coniform genera best known from ordovician tropical platform successions cornuodus clarkei landing sp nov resembles the coeval upper lower tremadoc tropical species scalpellodus longipinnatus ji barnes

length scales of eddy generation and nonlinear evolution of the seasonally modulated south pacific subtropical countercurrent the dynamical processes behind the seasonal modulation of the two dimensional eddy kinetic energy eke wavenumber spectrum in the subtropical countercurrent region of the south pacific are investigated with 14 yr of satellite altimeter data and climatological hydrographic data the authors find a seasonally modulated generation of eke via baroclinic instability in modes with larger meridional length scales subsequent nonlinear eddy eddy interactions redistribute the eke to larger total horizontal length scales and larger zonal scales in particular this is confirmed by diagnosing the spectral transfer of eke in the surface geostrophic flow which is found to drive an anisotropic inverse cascade being redirected in the sense consistent with the effect as predicted by geostrophic turbulence theory on the plane because of the seasonal renewal of meridionally elongated anomalies by baroclinic instability and possibly because of the barotropization process however the net outcome for the formation of surface zonal flows is observed to be limited

spectral energy fluxes in geostrophic turbulence implications for ocean energetics abstract the energy pathways in geostrophic turbulence are explored using a two layer flat bottom f plane quasigeostrophic model forced by an imposed horizontally homogenous baroclinically unstable mean flow and damped by bottom ekman friction a systematic presentation of the spectral energy fluxes the mean flow forcing and dissipation terms allows for a comprehensive understanding of the sources and sinks for baroclinic and barotropic energy as a function of length scale the key new result is a robust inverse cascade of kinetic energy for both the baroclinic mode and the upper layer this is consistent with recent observations of satellite altimeter data over the south pacific ocean the well known forward cascade of baroclinic potential and total energy was found to be very robust decomposing the spectral fluxes into contributions from different terms provided further insight the inverse baroclinic kinetic energy cascade is driven mostly by an efficient interaction between the baroclinic velo

interpretation of the propagation of surface altimetric observations in terms of planetary waves and geostrophic turbulence 1 the interpretation of surface altimetric signals in terms of rossby waves is revisited rather than make the long wave approximation the horizontal scale of the waves is adjusted to optimally fit the phase speed predicted by linear theory to that observed by altimetry assuming a first baroclinic mode vertical structure it is found that in the tropical band the observations can be fit if the wavelength of the waves is assumed to be large of order 600 km or so however poleward of 30 it is more difficult to fit linear theory to the observations and the fit is less good than at lower latitudes the required scale of the waves must be reduced to about 100 km somewhat larger than the local deformation wavelength it is argued that these results can be interpreted in terms of rossby wave baroclinic instability and turbulence theory at low latitudes there is an overlap between geostrophic turbulence and rossby wave timescales and so an upscale energy transfer from baroclinic instability at the deformation scale produces waves at high latitudes there is no such overlap and waves are not produced by upscale energy transfer these ideas are tested by using surface drifter data to infer turbulent velocities and timescales that are compared to those of linear rossby waves a transition from a field dominated by waves to one dominated by turbulence occurs at about 30 broadly consistent with the transition that is required to fit linear theory to altimetric observations

transmission losses in rills on dryland hillslopes transmission losses through the beds of hillslope rills were studied at two sites in the semi arid south western united states at one site the rills were sand bedded and at the other they were gravel bedded transmission losses in the sand bedded rills are about 66 higher than those in the gravel bedded rills the former show evidence of increasing transmission loss with increasing depth of flow whereas the latter do not in both cases transmission losses in the rills are about an order of magnitude greater than infiltration losses in adjacent interrill areas copyright 1999 john wiley sons ltd

hydrologic routing of flow in arid ephemeral channels hydrographs of ephemeral streams in an arid region usually decrease significantly in magnitude downstream unless they are augmented by tributary flows estimation of outflow hydrographs from a channel reach is essential for the development of water resources systems a hydrologic flow routing technique for arid ephemeral channels is developed the hydrologic routing equations for the movement of flood waves are modified by the inclusion of a nonlinear volumetric transmission loss rate term which is empirically estimated from the observed inflow outflow data for a channel reach the predicted outflow hydrographs match better with the observed than the outflow hydrographs generated through the lumped regression model for ephemeral channels the hydrologic flow routing technique may also be used for ungaged channel reaches through parameterization

upper cambrian and lower ordovician conodont biostratigraphy and revised lithostratigraphy boothia peninsula nunavut the strata exposed along lord lindsay river on southern boothia peninsula were previously named the netsilik formation and then recognized as the turner cliffs formation the interpretation of the

on eddy viscosity energy cascades and the horizontal resolution of gridded satellite altimeter products motivated by the recent interest in ocean energetics the widespread use of horizontal eddy viscosity in models and the promise of high horizontal resolution data from the planned wide swath satellite altimeter this paper explores the impacts of horizontal eddy viscosity and horizontal grid resolution on geostrophic turbulence with a particular focus on spectral kinetic energy fluxes p k computed in the isotropic wavenumber k domain the paper utilizes idealized two layer quasigeostrophic qg models realistic highresolution ocean general circulation models and present generation gridded satellite altimeter data adding horizontal eddy viscosity to the qg model results in a forward cascade at smaller scales in apparent agreement with results from present generation altimetry eddy viscosity is taken to roughly represent coupling of mesoscale eddies to internal waves or to submesoscale eddies filtering the output of either the qg or realistic models before computing p k also greatly increases the forward cascade such filtering mimics the smoothing inherent in the construction of present generation gridded altimeter data it is therefore difficult to say whether the forward cascades seen in present generation altimeter data are due to real physics represented here by eddy viscosity or to insufficient horizontal resolution the inverse cascade at larger scales remains in the models even after filtering suggesting that its existence in the models and in altimeterdata is robust however themagnitudeofthe inverse cascadeis affectedbyfiltering suggestingthat the wide swath altimeter will allow a more accurate determination of the inverse cascade at larger scales as well as providing important constraints on smaller scale dynamics

upper ordovician conodont biostratigraphy and the age of the collingwood member southern ontario canada11earth science sector ess contribution 20100302 the upper ordovician stratigraphy in southern ontario represents the clastic foredeep associated with the appalachian taconic orogeny transitioning northwest into coeval carbonate platform facies ten measured and sampled sections in both the collingwood area and on manitoulin island lake huron provide two relatively complete composite sections 277 and 95 m respectively through the marine part of the sequence a total of 100 2 kg samples collected for a conodont biostratigraphic study yielded 77 215 well preserved specimens taxonomic study of the fauna illustrated herein identified 34 species representing 22 genera and three taxa in open nomenclature taxonomic revisions are made to five species of pseudobelodina and one of rhipidognathus a new species pseudobelodina microdentata is established the fauna primarily represents the midcontinent province with incursions from the north atlantic province primarily in the collingwood area four conodont zones are recognized that help refine the ages

ordovician conodont biostratigraphy and redefinition of the age of lithostratigraphic units on northeastern melville peninsula nunavut northeastern melville peninsula nunavut canada preserves the stratigraphic record of the northwestern margin of the foxe basin the ordovician sequence on the peninsula includes the lower ordovician ship point formation and upper ordovician frobisher bay amadjuak akpatok and foster bay formations their biostratigraphic ages and correlations are poorly understood in particular it is unclear whether the organic rich boas river formation exists on the peninsula following extensive sampling of these stratigraphic units studies of numerous conodont elements from both outcrops and rubble at about 60 localities have established five conodont assemblages through the five lithostratigraphic units on the peninsula oepikodus communis jumudontus gananda assemblage in the ship point formation is correlated to the reutterodus andinus zone in the uppermost ibexian lower ordovician the other four assemblages from the upper ordovician are as follows appalachignathus delicatulus polyplacognathus ramosus

bottom enhanced diapycnal mixing driven by mesoscale eddies sensitivity to wind energy supply abstractit has been estimated that much of the wind energy input to the ocean general circulation is removed by mesoscale eddies via baroclinic instability while the fate of this energy remains a subject of research arguments have been presented suggesting that a fraction of it may get transferred to lee waves that upon breaking result in bottom enhanced diapycnal mixing here the authors propose several parameterizations of this process and explore their impact in a low resolution ocean climate model focusing on their impact on the abyssal meridional overturning circulation moc of antarctic bottom water this study shows that when the eddy energy is allowed to maintain diapycnal mixing the abyssal moc generally intensifies with increasing wind energy input to the ocean in such a case the whole system is driven by the wind wind steepens isopycnals and generates eddies and the parameterized eddies generate small scale mixing driving the moc it is also demonstrated that if the model diapycn

geochronology of the cambrian a precise middle cambrian u pb zircon date from the german margin of west gondwana a volcanic tuff 1 0 m above the base of the triebenreuth formation in the franconian forest provides the first precise and biostratigraphically bracketed date within the traditional middle cambrian the first illustration of fossils from the triebenreuth formation in this report and their discussion allow a more highly refined correlation within the middle cambrian a weighted mean 206 pb 238 u date of 503 14 0 13 0 25 0 59 ma on zircons from this subaerial pyroclastic tuff was determined by u pb chemical abrasion isotope dilution mass spectrometry ca tims techniques at c 6 0 7 0 ma younger than the base of the traditional middle cambrian in avalonia the new west gondwanan date from east central germany suggests that estimates of 500 ma for the base of the traditional upper cambrian and 497 ma on the base of the furongian series may prove to be too old biostratigraphically well bracketed dates through most of the middle cambrian series 3 and below the upper upper cambrian upper furongian series do not exist an earlier determined 494 4 3 8 ma date from the southwell group of tasmania may actually prove to be a reasonable estimate for the age of the base of the traditional upper cambrian until high precision dates are determined on the base of the traditional upper cambrian and base of the furongian series the rates of biotic replacements and geological developments and the durations of biotic zones in the middle series 3 and upper cambrian furongian series remain as best guesses

tracing the source of ancient reworked organic matter delivered to the north atlantic ocean during heinrich events a major effort of the geochemical and paleoclimate community has been to identify the specific sources of the ice rafted debris ird in heinrich layers hls although the general consensus is that the majority of the ird originated from the hudson area of northern canada the specific sources are not well constrained here we compare the diagnostic organic geochemical signature of hls to that of a number of paleozoic outcrops across the former margin of the laurentide ice sheet we show that the biomarker signature of upper ordovician strata from southampton and baffin island is compatible with that found in hls in the labrador sea and north atlantic while the biomarker signature of other paleozoic formations from the former margin of the laurentide ice sheet is not in addition to the biomarker signature key inorganic characteristics 18o end and 87sr 86sr ratios of these formations from southampton and baffin island are consistent with those reported from hls the location of these formations in and around the hudson strait is compatible with palaeo ice flow regimes through the hudson strait allowing for easy entrainment and rapid transport to the ocean based on these results we propose that these specific upper ordovician formations form a main source of ird in hls and hence infer an active role of the hudson strait paleo ice flow in these events