description of a partial dromiceiomimus dinosauria theropoda skeleton with comments on the validity of the genus dromiceiomimus brevitertius is a north american ornithomimid diagnosed primarily by the ratio of tibia length to femur length it has recently and perhaps incorrectly been considered synonymous w

the alberta foreland basin relationship between stratigraphy and cordilleran terrane accretion events a foreland basin sequence resulting from accretion of a terrane to a continental passive margin ideally should be unconformity bounded with a shallowing upward pattern like the classic flysch to molasse sequence of alpine foreland basins the basal unconformity is cut as the peripheral bulge associated with lithospheric flexure migrates cratonward ahead of the basin and the advancing overthrusts the shallowing occurs because sediment supply at first is low early stages of accretion near the continental slope generate little or no topography above sea level later stages result in significant tectonic uplift and much sediment is shed into the foreland filling the basin the upper unconformity is cut as lithospheric bending stresses are relaxed following overthrusting and reduction of the flexural load on the lithosphere through erosion and or tectonic denudation of the overthrusts causes regional uplift or basin rebound actual sequences show differences from this idealized version in that i

introduction to albertosaurus special issue this special issue is being published to mark the passage of a century since barnum brown made a remarkable discovery in the badlands of alberta brown was from the american museum of natural history amnh in new york and he had come to alberta the previous year 1909 to check a report of dinosaur bones near the present day town of drumheller he had been impressed enough to mount an expedition that set off in a flat bottomed scow down the red deer river on august 3 1910 as they floated downstream they frequently stopped and looked for fossils in the badlands on august 11th they found what they thought was much of an albertosaurus skeleton in hard rock they realized by the next day however that they were in fact excavating the well preserved bones of several individuals in his fieldnotes brown s assistant peter kaisen noted that the whole top of a hill is nothing but a mass of bone there are four hind feet in sight vertebrae and a lot of limb bones on september 4th they loaded eight boxes of bones the product of 29 man days spent in the bonebed on the scow and floated the expedition farther downstream the specimens were shipped to new york where they were prepared put on display for a short time and then mostly forgotten although brown occasionally mentioned the 1910 discovery in papers brown 1914 matthew and brown 1923 and

hadrosaurid edmontosaurus bonebeds from the horseshoe canyon formation horsethief member at drumheller alberta canada geology preliminary taphonomy and significance three monodominant hadrosaurid bonebeds in the horsethief member of the horseshoe canyon formation uppermost campanian in southern alberta canada are documented each bonebed is hosted by a dec

a new ceratopsid dinosaur ornithischia from the uppermost horseshoe canyon formation upper maastrichtian alberta canada a skeleton of a new ceratopsid dinosaur eotriceratops xerinsularis gen et sp nov is described in this paper it is the first associated vertebrate skeleton found within the upper 20 m of the horseshoe canyon formation eotriceratops xerinsularis is a large chasmosaurine that differs from other chasmosaurines in a unique set of features in the premaxilla nasal horn core squamosal frill and epijugal the most striking of those features includes an extremely tall non recessed narial process of the premaxilla the presence of greatly elongate spindle shaped epoccipitals on the squamosal frill a deep well demarcated fossa on the anteroventral surface of the squamosal frill a sharply conical epijugal with a pronounced proximoposterior process and separate fossa like facets for the jugal and quadratojugal and the presence of an obliquely extending vascular trace meeting a transverse vascular trace ventrally on the anterior surface of the nasal horn core our phylogenetic analysis suggests that e x

relationship between cyclone tracks anticyclone tracks and baroclinic waveguides abstract this study presents observational results concerning the structure and evolution of high frequency fluctuations with periods shorter than 6 days in the geopotential height field the results are based on a statistical analysis of 1000 500 and 250 mb height fields derived from twice daily nmc final analyses over the northern hemisphere for the 20 winters 1964 65 through 1983 84 the disturbances assume the form of waves elongated in the meridional direction with a mean wavelength of 4000 km a westward tilt with height and a mean eastward phase propagation of 12 1 5 m s 1 these results support an interpretation in terms of finite amplitude baroclinic waves whose structure and evolution varies with geographical location over the continents and especially along the eastern slopes of the rockies and the tibetan plateau the waves show marked departures in structure and evolution from those over the oceans in particular we find evidence of a systematic influence of the terrain in steering the

interannual and decadal modulations recently observed in the pacific storm track activity and east asian winter monsoon abstract interannual variability of the north pacific storm track observed over 17 recent winters is documented the local storm track activity is measured by a meridional flux of sensible heat associated with the lower tropospheric subweekly fluctuations the interannual variability in the heat flux over the northwestern nw pacific is found to be strongest in midwinter the first empirical orthogonal function of the interannual variability in midwinter captures the decadal tendency toward the enhanced storm track activity in midwinter over the nw pacific in association with the decadal weakening of the east asian winter monsoon siberian high and the aleutian low that occurred in the late 1980s the most marked signature of this enhancement is that the midwinter minimum in the storm track activity which had been apparent in the early to mid 1980s almost disappeared afterward as opposed to linear theory of baroclinic instability the enhanced activity occurred despite the weakening of the pacific j

faunal assemblages from the upper horseshoe canyon formation an early maastrichtian cool climate assemblage from alberta with special reference to the albertosaurus sarcophagus bonebed the faunal assemblage from the early maastrichtian portion of the horseshoe canyon formation is described on the basis of four new vertebrate microfossil localities and remains from the albertosaurus bonebed all of the localities sampled were deposited during a cool dry climate at a palaeolatitude of 58 n thus these assemblages provide insight into a northern cool climate assemblage in the early maastrichtian of western north america this fauna is characterized by the presence of taxa with more northern affinities such as holostean a champsosaurs troodon and toothed birds warm climate taxa such as crocodylians large and diverse turtles and albanerpetontids are notable in their absence the albertosaurus bonebed locality at the top of unit 4 of the horseshoe canyon formation was deposited during the initial stages of a trend to a warmer and wetter climate that is represented in unit 5 the bonebed shares many taxa with the underlying vertebrate microfossil localities however a notable diffe

a taphonomic analysis of a multitaxic bonebed from the st mary river formation uppermost campanian to lowermost maastrichtian of alberta dominated by cf edmontosaurus regalis ornithischia hadrosauridae with significant remains of pachyrhinosaurus canadensis ornithischia ceratopsidae scabby butte is an isolated exposure of upper cretaceous uppermost campanian to lowermost maastrichtian strata of the st mary river formation these rocks have produced a diverse assemblage of b

the chicxulub asteroid impact and mass extinction at the cretaceous paleogene boundary the cretaceous paleogene boundary similar to 65 5 million years ago marks one of the three largest mass extinctions in the past 500 million years the extinction event coincided with a large asteroid impact at chicxulub mexico and occurred within the time of deccan flood basalt volcanism in india here we synthesize records of the global stratigraphy across this boundary to assess the proposed causes of the mass extinction notably a single ejecta rich deposit compositionally linked to the chicxulub impact is globally distributed at the cretaceous paleogene boundary the temporal match between the ejecta layer and the onset of the extinctions and the agreement of ecological patterns in the fossil record with modeled environmental perturbations for example darkness and cooling lead us to conclude that the chicxulub impact triggered the mass extinction

occurrence of faecal pellet filled simple and composite burrows in cold seep carbonates a glimpse of a complex benthic ecosystem abstract ichnofossils preserved in marine sedimentary records provide unique information on various activities feeding dwelling excretion etc of benthic organisms here we report faecal pellet filled tubular simple and composite burrow casts from cold seep carbonate layers 16 18 mbsf deposited at least 46 58 kyr ago in the krishna godavari basin bay of bengal india deposition of these chemosynthetic clam bearing authigenic carbonate sediments with highly depleted carbon stable isotope ratios indicates methane expulsion that resulted in the development of a cold seep ecosystem although cold seep communities are extensively reported from the rock record and modern seep sites hardly any information is available on burrowing activity of the seep biota our findings open up a window for future investigation of the ecological significance of such burrows

new information on the rare horned dinosaur arrhinoceratops brachyops ornithischia ceratopsidae from the upper cretaceous of alberta canada arrhinoceratops brachyops is a poorly understood chasmosaurine ceratopsid from the upper cretaceous horseshoe canyon formation of alberta previously described on the basis of only a single skull here we report on a second specimen attributable to this species including a relatively complete skull syncervical and partial left forelimb this second specimen clarifies aspects of morphology not visible in the holotype and also elucidates variation in a brachyops the species is distinguished by a square shaped triangular process of the premaxilla a steeply inclined triturating surface of the predentary and a triangular nasal horncore in horizontal section the dentary is also distinctive in bearing a bony lateral ridge similar to that of anchiceratops ornatus but more strongly developed phylogenetic analysis cannot resolve the relationships of arrhinoceratops beyond the level of chasmosaurinae owing to both missing data and conflicting characters however we do find some support for a deep split

assessing the age of the late cretaceous danek bonebed with u pb geochronology an ash rich volcaniclastic sandstone immediately underlying dinosaur rich material from the danek bonebed in the horseshoe canyon formation hcf edmonton alberta canada contains accessory zircon which have been dated employing u pb geochronology both laser ablation inductively coupled plasma mass spectrometry la icp ms and chemical abrasion isotope dilution thermal ionization mass spectrometry id tims u pb analyses have been conducted the zircon age distributions are complex with u pb dates ranging from precambrian to cretaceous we consider the youngest id tims 206pb 238u date of 71 923 0 068 ma as the maximum deposition age of the ash rich sandstone placing the overlying danek bonebed in the early maastrichtian this age is compatible with the paleontological assemblage from the danek bonebed and the regional stratigraphy the zircon age distribution also implies that the hcf had a complex provenance of the detritus with some archean and proterozoic zircons a group of mesozoic and a large compliment of cretaceous grains the results highlight the importance of high precision geochronology in constraining the age of important fossil deposits such as the danek bonebed

on the dynamics of a storm track abstract an idealized primitive equation model is used to determine the factors controlling the dynamics and maintenance of eddy activity in a storm track the results show that localized regions of enhanced baroclinicity do not necessarily lead to localization of eddy activity by studying the energetics of the storm track it is shown that while baroclinic conversion does indeed correlate with the region of maximum baroclinicity it is the downstream radiation of energy through the ageostrophic geopotential fluxes which acts as a trigger for the development and maintenance of eddy activity over less baroclinic regions extending the region of eddy activity much further downstream from the region of high baroclinicity examples of eddy life cycles are given that show that convergence and divergence of ageostrophic fluxes can dominate baroclinic and barotropic conversion especially in regions with weak baroclinicity factors that may limit the zonal extent of a storm track are discussed evidence of down

albertosaurus dinosauria theropoda material from an edmontosaurus bonebed horseshoe canyon formation near edmonton clarification of palaeogeographic distribution tyrannosaurid cranial bones including a maxilla dentary and pterygoid were collected from a monodominant edmontosaurus bonebed in the horseshoe canyon formation exposed near the city of edmon

basal ornithopod dinosauria ornithischia teeth from the prince creek formation early maastrichtian of alaska a diverse and prolific record of polar dinosaurs comes from the upper cretaceous campanian maastrichtian sediments of the prince creek formation exposed on alaska s north slope previous assignment of basal ornithopod material from this formation has been based solely on teeth which have either been referred to hypsilophodontid indet or thescelosaurus sp here we re examine this material and describe several new specimens including five isolated premaxillary teeth and three cheek teeth the premaxillary teeth are most similar to those of thescelosaurus whereas the cheek teeth are more similar to its sister taxon parksosaurus for which premaxillary teeth are unknown referral of this new material to thescelosaurus would represent the oldest occurrence of this taxon and considerably extend its stratigraphic range a more likely possibility is that the premaxillary teeth are referable to parksosaurus an interpretation that is more parsimonious from a stratigraphic perspective intriguingly one ch

redescription of ankylosaurus magniventris brown 1908 ankylosauridae from the upper cretaceous of the western interior of north america the armor plated dinosaur ankylosaurus magniventris is redescribed based on specimens from the hell creek formation of northeastern montana usa lance formation of wyoming usa and from the scollard formation of south central alberta canada except for brief descriptions most of these specimens have not been described in detail ankylosaurus is one of the largest known ankylosaurids having an estimated length of up to 6 25 m 20 5 ft it is characterized by a long low skull having very prominent cranial horns that project laterally or dorsolaterally the body armor includes a large half ring that sat across the base of the neck and shoulders and a large low tail club

geological and anthropogenic controls on the sampling of the terrestrial fossil record a case study from the dinosauria dinosaurs provide excellent opportunities to examine the impact of sampling biases on the palaeodiversity of terrestrial organisms the stratigraphical and geographical ranges of 847 dinosaurian species are analysed for palaeodiversity patterns and compared to several sampling metrics the observed diversity of dinosaurs theropoda sauropodomorpha and ornithischia are positively correlated with sampling at global and regional scales sampling metrics for the same region correlate with each other suggesting that different metrics often capture the same signal regional sampling metrics perform well as explanations for regional diversity patterns but correlations with global diversity are weaker residual diversity estimates indicate that sauropodomorphs diversified during the late triassic but major increases in the diversity of theropods and ornithischians did not occur until the early jurassic diversity increased during the jurassic but many groups underwent extinction during the late jurassic or at the jurassic cretaceous boundary although a recovery occurred during the cretaceous only sauropodomorphs display a long term upward trend the campanian maastrichtian diversity peak is largely a sampling artefact there is little evidence for a gradualistic decrease in diversity prior to the end cretaceous mass extinction except for ornithischians and when such decreases do occur they are small relative to those experienced earlier in dinosaur evolution the geological society of london 2011

cretaceous extinctions multiple causes figure 1 deccan plateau basalts lava from deccan volcanism formed distinct layering credit gsfc nasa in the review the chicxulub asteroid impact and mass extinction at the cretaceous paleogene boundary p schulte et al 5 march p 1214 2 the terminal cretaceous

quantitative diagenetic analyses of edmontosaurus regalis dinosauria hadrosauridae postcranial elements from the danek bonebed upper cretaceous horseshoe canyon formation edmonton alberta canada implications for allometric studies of fossil organisms for fossil assemblages quantitative size and shape studies are often complicated by diagenetic distortion different vertebrate elements although subjected to similar burial stresses exhibit def

biogeography of terrestrial and freshwater vertebrates from the late cretaceous campanian western interior of north america abstract previous biogeographic studies of late cretaceous late campanian vertebrate faunas in the western interior basin wib of north america have suggested the presence of faunal and floral provincialism characterized by distinct northern and southern biomes however the provincialism hypothesis has been questioned based largely on the contention that the investigated faunas were recovered from a series of diachronous time transgressive deposits and are therefore non correlative extensive work in several fossiliferous units of late campanian age including the dinosaur park judith river two medicine kaiparowits fruitland kirtland and aguja formations has greatly increased understanding of wib vertebrate faunas and their chronostratigraphic relationships here updated and greatly expanded faunal and chronostratigraphic datasets are utilized to undertake an extensive biogeographic analysis of these six terrestrial fossiliferous formations within the wib of north america quantitative biogeographic comparisons of the formations and their constituent faunas are conducted using four statistical methods analysis of similarity q mode cluster analysis parsimony analysis of endemicity and correspondence analysis the results of this study provide strong support for highly divergent faunas in northern and southern regions of the wib with a latitudinal faunal gradient as an interface yet the nature of the interface between these faunas remains unclear with possibilities including 1 two or more discrete provinces separated by a zone or zones of faunal mixing and 2 a continuous latitudinal gradient or cline with no discrete zones of endemism lacking evidence of any physiographic barrier to north south dispersal climatic variation within the wib is regarded as the most likely explanation for the overarching biogeographic patterns observed for late campanian vertebrate taxa

the late surviving duck billed dinosaur augustynolophus from the upper maastrichtian of western north america and crest evolution in saurolophini we amend the taxonomy and provide new anatomical information on the hadrosaurid dinosaur saurolophus morrisi upper maastrichtian moreno formation central california usa derived from full preparation of the referred skull roof the cranial morphology of this species is distinct enough to justify the new combination augustynolophus morrisi gen nov the morphology of the nasals and surrounding cranial bones indicates that a morrisi sported a solid nasal crest ending in an elongate triangular plate that extended above the skull roof autapomorphies include a crescentic base of the frontal caudodorsal process and extension of the process caudal to the frontal dome distal end of nasal crest with knob like process inflected rostrally circumnarial depression lightly incised and weakly emarginated adjacent to caudolateral margin of nasal and occupying two thirds the width of lateral surface of distal region of crest and caudal surface of distal nasal crest subrectangular we formally establish the new tribe saurolophini consisting of prosaurolophus augustynolophus and saurolophus saurolophin synapomorphies include a premaxilla with broad arcuate contour of rostrolateral region of thin everted oral margin and flat and steeply inclined occlusal surface of dentary dental battery among other characters saurolophin crests evolved towards increasing caudodorsal length along with caudal extension of the circumnarial fossa and involvement into the crest of adjacent facial elements augustynolophus is the second described genus of north american late maastrichtian hadrosaurids its recognition implies a greater diversity among late maastrichtian dinosaur faunas than previously recognized and is congruent with hypotheses of endemism and or provinciality during late cretaceous time

palaeoenvironmental and palaeoclimatic reconstruction of the upper cretaceous late campanian early maastrichtian horseshoe canyon formation alberta canada abstract pedogenic features and geochemical signatures of paleosol profiles exposed in the horseshoe canyon formation hcfm were studied to reconstruct the ancient environments and climates that prevailed at high latitude 60 n in the north american western interior during the late campanian to early maastrichtian eight pedotypes representing hydromorphic moderately drained and well drained paleosols were recognized when considered within their stratigraphic context these paleosols show that palaeoenvironmental and palaeoclimatic changes occurred either gradually between major lithological subdivisions of the hcfm or relatively rapidly within subdivisions hydromorphic paleosols predominant in the coal bearing stratigraphic interval at the base of the hcfm were gradually replaced by well drained paleosols in the overlying coal poor interval while climate remained warm and humid during this change in soil drainage conditions mean annual temperature and precipitation dropped rapidly higher in section shortly prior to the campanian maastrichtian boundary without concomitant lithological or pedological changes a brief return of poorly drained paleosols in the middle of the hcfm coincides with a regional marine transgression drumheller marine tongue well drained palaeoenvironments associated with a warm and dry climate persisted through the upper part of the hcfm until a gradual return to poorly drained conditions and to a warm humid climate occurred at the top of the formation an important decline in turtle diversity through the hcfm previously attributed to climate is shown to coincide instead with changes in soil drainage conditions where aridity landscape instability and migratory barriers possibly acted as secondary limiting factors to faunal recovery

sediments and sedimentary processes in mutsu bay japan pelletization as the most important mode in depositing argillaceous sediments abstract mutsu bay is a large transgressive inland basin that originated in a set of structural depressions brought about by tectonic processes in early quaternary time the offshore beds of the bay consist of muds rich in organic material while sands and gravels occur as a coastal sediment facies active sediment palletization of muds owing to feeding by polychaetes is recognized throughout the bay and the bed surface is mostly covered with fecal pellets laboratory experiments in a seawater flume suggest that isolated fecal pellets are removed more easily than ambient muds continued pelletization dramatically reduces the critical entrainment velocity of the bed surface sedimentary processes in mutsu bay have been influenced not only by sea level fluctuations but also by the oceanographic conditions of the sea of japan offshore mud deposition in the bay can be attributed to warm water circulation which came into existence about 10 000 years ago a wet and mild climate in consequence of temperatere seawater of post glacial warming increased biochemical weathering of the land surface leading to a voluminous discharge of fine grained materials into the bay sediment pelletization by polychaetes facilitated easy transport of argillaceous grains in response to bottom currents resulting in the development of offshore mud layers

comment on occurrence of faecal pellet filled simple and composite burrows in cold seep carbonates a glimpse of a complex benthic ecosystem by a mazumdar r k joshi and m kocherla marine geology 289 2011 117 121 abstract the pellet filled burrows described in mazumdar et al 2011 were originally not unequivocally ascribed to a specific ichnotaxon in fact these burrows match the diagnosis of the ichnogenus phymatoderma most likely phymatoderma cf melvillensis there is the general similarity in overall shape such as branching pattern as well as in detailed characteristics such as locally present meniscate fill structure furthermore morphometrical parameters and general depositional setting are basically similar between the pellet filled burrows and p melvillensis based on the refined ichnotaxonomy ethological interpretation by mazumdar et al 2011 especially about how the pellets were stuffed within the burrows is refined

a new species of troodontid theropod dinosauria maniraptora from the horseshoe canyon formation maastrichtian of alberta canada troodontid material from the maastrichtian of north america is extremely rare beyond isolated teeth from microvertebrate sites here we describe troodontid frontals from the early maastrichtian horseshoe canyon formation horsethief member the most complete specimen tmp 1993 105 0001 is notably foreshortened and robust when compared with numerous specimens referred to troodon from the dinosaur park formation and exhibits several characteristics that distinguish it from other late cretaceous troodontids morphometric analyses reinforce shape differences between tmp 1993 105 0001 and other north american troodontids and show that proportional differences are independent of size we therefore erect a new taxon albertavenator curriei gen et sp nov which is diagnosed by the following autapomorphies 1 primary supraciliary foramen is truncated anteriorly by the lacrimal contact 2 superficial ectocranial surface of the frontal proportionally shorter than all known troodontids with a length to

midwinter suppression of baroclinic wave activity in the pacific abstract seasonal variations in baroclinic wave activity and jet stream structure in the northern hemisphere are investigated based upon over 20 years of daily data baroclinic wave activity at each grid point is represented for each day by an envelope function the lowpass filtered time series of the squared highpass filtered geopotential height baroclinic wave activity over the atlantic exhibits a single maximum in january whereas in the pacific it exhibits peaks in late autumn and in early spring and a significant weakening in midwinter which is more evident at the tropopause level than near the surface this suppression occurs despite the fact that the low level baroclinity and the intensity of the jet stream are strongest in midwinter based on the analysis of 31 day running mean fields for individual winters it is shown that over both the oceans baroclinic wave activity is positively correlated with the strength of the upper tropospheric jet for wind speeds up to 45 m s 1 when the strength of t

a stroll in the forest of the fucoids status of melatercichnus burkei the doctrine of ichnotaxonomic conservatism and the behavioral ecology of trace fossil variation abstract the ichnogenus melatercichnus was described in 1991 from cretaceous deep ocean turbidte beds at trinidad bay northern california the type and only ichnospecies melatercichnus burkei features all the primary characters ichnotaxobases of phymatoderma and is here reassigned to this ichnogenus in so doing phymatoderma now consists of two palmate forms p penicillum and p alcicorne two digitate forms p melvillensis and p granulata and the reassigned ichnospecies p burkei representing a kind of intermediate form reassignment follows the doctrine of ichnotaxonomic conservatism by employing a limited number of primary characters and abandoning a superfluous ichnotaxon all of the ichnospecies now included within phymatoderma as seems to be true of many of the so called fucoids and certain other groups of trace fossils are extremely variable in terms of morphology although basic structure in this case bunches of outward branching unlined tunnels stuffed with fecal pellets is consistent this aspect of trace fossils needs more attention both from an ichnotaxonomic and a biologic point of view at the trinidad bay collecting site the perfect examples of p burkei featuring all the characters of the ichnospecies grade into specimens that would be identified with p granulata or possibly alcyonidiopsis isp if preserved in isolation or if the perfect specimens had never been observed these variants are difficult to accommodate in traditional ichnotaxonomy pointing to a need for special categories in open nomenclature e g identification of some of the imperfect specimens as phymatoderma forma variabilis or possibly phymatoderma f v p burkei p granulata to reflect the kind and degree of variation in terms of behavioral ecology p burkei appears to be a fancy cesspit the producer either fed at a different level and simultaneously deposited fecal pellets at depth polychaete echiuran or fed at or near the seafloor then dove into the turbidite sand blanket to discharge the pellets sipunculan variations in the structure could have resulted from the producer encountering different conditions in the substrate at different times and places e g owing to dewatering interruptions in the typical pattern caused by encounters with other organisms limited time available to construct the usual pellet filled structure avoidance of other conspecific burrowers or simply the inability of some individuals to execute precisely the construction plan

tectonic stratigraphic and sedimentologic significance of a regional discontinuity in the upper judith river group belly river wedge of southern alberta saskatchewan and northern montana the lithostratigraphic interval between the taber and lethbridge coal zones in the upper portion of the nonmarine judith river group of southeastern alberta is divisible into two lithostratigraphic units separated by a regionally extensive and diachronous discontinuity the lower unit referred to here as the oldman formation is characterized by very fine grained to fine grained sandstones that contain fewer than 2 volcanic rock fragments sandstone bodies with numerous sets of horizontally stratified sandstone showing little or no evidence of lateral accretion siliceous paleosols ganisters and a relatively high gamma ray signal in the upper half of the formation the oldman formation comprises deposits of a low sinuosity perhaps ephemeral fluvial system that originated in the southern cordillera of canada and northern montana and flowed northeastward perpendicular to the axis of the alberta basin the upper unit is assigned to a new formation the dinosaur park formation and is characterized by

marine transgressions and the evolution of cretaceous dinosaurs fluctuations transgressions and regressions of intercon tinental sea ways during the mesozoic era affected the habitat area of coastal plains by alternately restricting the space during transgressive phases and expanding the space during regressive phases in western north america a coastal plain stretched along the eastern front of the young rocky mountains during most of the late cretaceous here we report results of a six year field study of the sediments and dinosaur remains from this coastal plain in montana that provide evidence that anagenesis characterized dinosaur evolution at this time and that the evolutionary pulse coincided with a marine transgression

the dorothy bentonite an extraordinary case of secondary thickening in a late campanian volcanic ash fall in central alberta the late campanian 73 ma dorothy bentonite outcrops in the marine bearpaw shale for 20 km along the red deer river valley east of drumheller alberta and is up to 13 5 m thick an isopach map based upon 230 sub surface and surface thickness measurements illustrates an elongated southwest northeast lobe with maximum dimensions of about 300 km by 50 km the volume is 57 km3 distributed within an area of 11 000 km2 this bentonite is the altered product of what is believed to be a short lived plincan type eruption from part of the howell creek instrusives in southeastern british columbia fortuitous preservation of the original ash in an up to 2 5 m thick calcite cemented tuffaceous zone near the middle of the bentonite shows the original ash to have been 99 glass shards and pumice the remainder of the ash is a crystal component consisting mostly of plagioclase and biotite the silica content of the isotropic glass shards of about 77 and a refractive index of 1 503 0 001 suggest a magma of rhyo

taphonomy of the danek bonebed a monodominant edmontosaurus hadrosauridae bonebed from the horseshoe canyon formation alberta the danek bonebed horsethief member horseshoe canyon formation late campanian is dominated by the remains of at least 12 edmontosaurus regalis skeletal remains of a tyrannosaurid and ceratopsid are also known the predominantly disarticulated remains were interred on a periodically inundated floodplain and although the cause of death is unknown a sudden catastrophic death explains the demographic spread faunal diversity rare greenstick fractures and homogeneous weathering abrasion categories of the assemblage the danek bonebed shares a similar taphonomic signature to the liscomb bonebed prince creek formation alaska but it is unique among all other described hadrosaurid bonebeds in the unusually high proportion of bite marked bones 30 suggesting scavenging played a major role in the reworking of the assemblage the highest frequency of bite marks is found on small often unidentifiable and commonly ignored bone fragments underscoring the role that such fragments can play in taphono

dinosaur biostratigraphy of the edmonton group upper cretaceous alberta canada evidence for climate influence a high resolution biostratigraphic analysis of 287 dinosaurian macrofossils and 138 bonebeds in the edmonton group upper cretaceous of southern alberta provides evidence for at least three dinosa

40ar 39ar age and correlation of the nonmarine two medicine formation upper cretaceous northwestern montana u s a the age of the nonmarine two medicine formation of northwestern montana is currently based upon correlations with k ar dated western interior ammonite zones 40ar 39ar dating of biotite and plagioclase separated from four bentonites and one crystal rich tuff permits for the first time direct determination of the age of two medicine strata biotite and plagioclase from a bentonite 10 m below the top of the two medicine formation yield concordant 40ar 39ar ages of 74 ma while biotite and plagioclase from two bentonites and a crystal rich tuff from approximately 100 m above the base of the formation cluster in age around 80 ma the total duration of two medicine deposition is estimated using these new radio isotopic ages via extrapolation of an average rock accumulation rate the new 40ar 39ar ages facilitate regional correlation of the dinosaur dominated paleofauna recovered from the two medicine formation and help constrain the timing of the claggett and bearpaw transgressions the ages support correlatio

stratigraphy of the danek bonebed upper cretaceous horseshoe canyon formation central alberta and correlations with strata in the drumheller and grande prairie regions although considerable work has been conducted on the stratigraphy and dinosaur assemblages of the horseshoe canyon formation of southern alberta equivalent strata and assemblages in central alberta remain poorly understood data from the danek bonebed edmonton alberta are beginning to fill this gap the bonebed occurs 4 m above the 9 big island coal seam this stratigraphic position lies just below the middle of the horseshoe canyon formation in the edmonton region and also lies below a thick stratigraphically significant non coaly interval that is expressed throughout central and southern alberta the stratigraphic position of the danek bonebed equates best with the uppermost horsethief member of the horseshoe canyon formation in the drumheller region and the upper part of unit 4 of the wapiti formation in the grande prairie region in both drumheller and grande prairie the correlated position of the bonebed underlies a zone of marine transgression drumheller marine tongue which in turn incl

the danek edmontosaurus bonebed new insights on the systematics biogeography and palaeoecology of late cretaceous dinosaur communities1 vertebrate bonebeds are rich sources of palaeontological information throughout the world rogers et al 2007 and they have long been sources of information on dinosaur anatomy behaviour ecology growth and variability although dinosaur dominated bonebeds have been known in alberta for a long time brown 1919 sternberg 1970 they received relatively little attention during the first seven decades that dinosaurs were collected in the province this was primarily because collectors came to alberta for the relatively common well preserved articulated dinosaur skeletons that produced both new species and spectacular museum displays currie 1981 1987 since the beginning of the 1980s the dinosaur bonebeds of dinosaur provincial park have received considerable attention currie and dodson 1984 visser 1986 ryan 1992 andersen 2000 ryan et al 2001 ryan 2003 ryan and russell 2005 eberth and getty 2005 however younger bonebeds from farther north in the province have enjoyed less attention ryan et al 1995 1998 2011 eberth et al 2013 two notable exceptions are the albertosaurus bonebed near dry island buffalo jump provincial park currie and koppelhus 2010 and the pachyrhinosaurus lakustai bonebed along pipestone creek near grande prairie currie et al 2008 in and around edmonton in particular dinosaur remains have been largely ignored in the published literature bell and campione 2014 despite easy access to outcrops along the north saskatchewan river and its associated streams and creeks this special issue of the canadian journal of earth sciences increases our knowledge of edmonton s urban dinosaurs especially the iconic and serendipitously named hadrosaurid

simulating the seasonal cycle of the northern hemisphere storm tracks using idealized nonlinear storm track models abstract in this study an idealized nonlinear model is used to investigate whether dry dynamical factors alone are sufficient for explaining the observed seasonal modulation of the northern hemisphere storm tracks during the cool season by construction the model does an excellent job simulating the seasonal evolution of the climatological stationary waves yet even under this realistic mean flow the seasonal modulation in storm track amplitude predicted by the model is deficient over both ocean basins the model exhibits a stronger sensitivity to the mean flow baroclinicity than observed producing too large midwinter eddy amplitudes compared to fall and spring this is the case not only over the pacific where the observed midwinter minimum is barely apparent in the model simulations but also over the atlantic where the october april eddy amplitudes are also too weak when the january amplitude is tuned to be about right the nonlinear model generally produces stronger eddy amplitude with stronger b

what is the source of the stratospheric gravity wave belt in austral winter abstractduring austral winter and away from orographic maxima or hot spots stratospheric gravity waves in both satellite observations and interim european centre for medium range weather forecasts ecmwf re analysis era interim data reveal enhanced amplitudes in a broad midlatitude belt extending across the southern ocean from east of the andes to south of new zealand the peak latitude of this feature slowly migrates poleward from 50 to 60 s wave amplitudes are much weaker across the midlatitude pacific ocean these features of the wave field are in striking agreement with diagnostics of baroclinic growth rates in the troposphere associated with midlatitude winter storm tracks and the climatology of the midlatitude jet this correlation suggests that these features of the stratospheric gravity wave field are controlled by geographical variations of tropospheric nonorographic gravity wave sources in winter storm tracks spontaneous adjustment emission from the midlatitude winter jet frontogenesi

an idealized model study relevant to the dynamics of the midwinter minimum of the pacific storm track the synoptic variability of a two level quasigeostrophic flow in response to plausible changes in the forcing of a localized baroclinic jet is investigated in the context of the midwinter minimum of the pacific storm track mwm the changes in the model forcing are introduced in terms of a reference potential vorticity field that is associated with plausible changes in the global baroclinicity zonal variation of the baroclinicity and horizontal deformation over the pacific from early winter to midwinter conditions it is found that the modal instability growth rate of perturbation in such a localized jet is significantly reduced in spite of an increase in the local baroclinicity the dynamical nature of such an effect can be interpreted as a generalized barotropic governor effect on localized baroclinic instability the existence of three instability regimes is established on the basis of energetics characteristics the intensity of the nonlinear model storm track is reduced by about 30 in response to a change in the forcing condition from early to midwinter the characteristics of the linear model storm track and nonlinear model storm track are compared the overall results support a hypothesis that mwm could stem from a sufficiently large increase in the stabilizing influence of the local barotropic process in spite of a simultaneous increase in its local baroclinicity in the pacific jet from early to midwinter

impact of enso on the atmospheric variability over the north atlantic in late winter role of transient eddies abstractthe dynamical mechanism for the late winter teleconnection between el nino southern oscillation enso and the north atlantic oscillation nao is examined using the output from a 2000 yr integration of a coupled general circulation model gcm the coupled model captures many salient features of the observed behavior of both enso and nao as well as their impact on the surface climate in late winter both the observational and model data indicate more occurrences of negative phase of nao in late winter during el nino events and positive nao in la nina episodes the potential role of high frequency transient eddies in the above teleconnection is diagnosed during el nino winters the intensified transient disturbances along the equatorward shifted north pacific storm track extend their influences farther downstream the eddy induced negative height tendencies are found to be more coherent and stronger over north atlantic than that over north pacific these negative height tendencies over the north

origins of dinosaur bonebeds in the cretaceous of alberta canada upper cretaceous dinosaur bonebeds are common in alberta canada and have attracted continuous scientific attention since the 1960s since its inception the royal tyrrell museum of palaeontology has documented the presence of hundreds of these sites and has been involved directly in the scientific study of many tens because many of these bonebeds have been used to address questions about the paleobiology and paleoecology of dinosaurs questions have arisen about bonebed origins and preservation in the cretaceous of alberta this study of 260 bonebeds delineates broad paleoenvironmental settings and associations and taphonomic signatures of assemblages as a first step in assessing patterns of dinosaur bonebed origins in the upper cretaceous of alberta bonebeds are known predominantly from the belly river group and the horseshoe canyon lower st mary river wapiti and scollard formations in these units bonebeds are mostly associated with river channel and alluvial wetland settings that were influen

formation process of the trace fossil phymatoderma granulata in the lower jurassic black shale posidonia shale southern germany and its paleoecological implications abstract the ichnogenus phymatoderma is a subhorizontal branching burrow system consisting of radiating tunnels filled with fecal pellets this ichnogenus has been interpreted as a product of a deposit feeding animal but the question of whether the phymatoderma producer was a subsurface deposit feeder or a surface deposit feeder is still a topic of controversy herein i present evidence based on carbon isotope analyses for the formation of the trace fossil phymatoderma granulata occurring in the lower toarcian black shale in southern germany carbon isotope ratios of organic carbon 13corg in the pelletal infill of p granulata the surrounding black shale and the overlying gray mudstone are 26 64 0 42 2 28 49 0 44 2 and 26 27 0 13 2 respectively the difference between the pelletal infill and overlying mudstone in terms of 13corg is much smaller than that between the fillings and black shale therefore these data clearly indicate that the phymatoderma producer ingested the surface sediments and subsequently excreted fecal pellets into the subsurface sediments such a surface deposit feeding style would be an especially effective means of absorbing nutrients because surface sediments contain much fresh organic material whereas organic matter in subsurface deposits consists mostly of refractory material that is poorly utilized by most marine benthos

trapping of synoptic scale disturbances into the north pacific subtropical jet core in midwinter 1 over the northwestern nw pacific a subtropical jet stream develops at 30 n in midwinter as the east asian winter monsoon intensifies eddies with subweekly periods propagating through the midlatitude tropopause into the nw pacific storm track tend to be trapped into the jet core 1000 km away from a surface baroclinic zone at 40 n while lifted up by 3 km the trapping appears to weaken the interaction of the upper level eddies with the baroclinic zone thus acting against eddy amplification and thereby contributing to the midwinter minimum in the eddy activity as observed before the late 1980s since then under the reduced trapping effect by the weakened jet upper level eddies tended to propagate right above the surface baroclinic zone while strongly interacting it even in midwinter as in fall and spring this midwinter tendency acted to enhance the eddy amplification that led to the recent disappearance of the activity minimum

late maastrichtian paleoenvironments and dinosaur biogeography in the western interior of north america during late maastrichtian time three major sedimentary depositional provinces existed in continental environments of the western interior region of north america the sediments accumulated within these provinces are herein termed the piedmont alluvial plain and coastal lowland lithosomes these sedimentary lithosomes correspond to broad paleoenvironmental and paleophysiographic provinces that resulted from the westward shift of the pacific coast the bisection and retreat of the interior epeiric sea and the development of an intermontane basin system during maastrichtian time these dramatic physiographic changes created environments markedly different from those that had prevailed during most of the late cretaceous when western north america consisted of a narrow peninsula flanked on the east by a remarkably stable and monotonous coastal plain in conjunction with these physiographic and environmental changes three diverse dinosaur dominated continental vertebrate faunas arose herein termed the leptoceratops triceratops and alamosaurus faunas each was peculiar to a sedimentary environmental province and among them there was little interchange the separation of these faunas indicates that the dinosaur dominated communities had adapted to changing or deteriorating environmental conditions at the close of cretaceous time the alamosaurus fauna characterized markedly seasonal semi arid environments of the intermontane basins south of about 35 n latitude the triceratops fauna inhabited humid coastal floodplains and swamps bordering the retreating northern embayment of the epeiric sea north of latitude 35 n the leptoceratops fauna inhabited cool piedmont environments flanking the mountainous cordilleran overthrust belt north of 35 n latitude recognition of this biogeographic zonation indicates that the triceratops biozone is only of local utility and that the biostratigraphy of upper cretaceous continental deposits in north america must reflect the provincialism now recognized moreover the evident adaptability of dinosaur faunas to varied and changing environmental conditions suggests that climatic change alone may not have been responsible for their demise

magnetostratigraphic and biostratigraphic correlation of late campanian and maastrichtian marine and continental strata from the red deer valley to the cypress hills alberta canada two stratigraphic sequences red deer valley and cypress hills sections in alberta spanning the late campanian to paleocene are magnetostratigraphically and biostratigraphically characterized the red deer valley section had previously been studied but additional material has allowed the extension of the magnetozonation downwards into the bearpaw formation higher sample resolution has allowed the identification of a number of magnetosubzones in 32n 32r and 33n four reversed magnetosubzones have been identified in magnetozone 32n in addition to the one presently recognized in geomagnetic polarity time scales one normal subzone in 32r and one reversed subzone in 33n have also been recorded the 32r 33n boundary is shown to occur in the baculites cuneatus zone the campanian maastrichtian boundary is indicated to be at or near the baculites eliasi baculites baculus boundary at the top of 32n comparisons of the biostratigraphy between the two areas indicate that palynomorph ranges differ from data p

first high precision u pb ca id tims age for the battle formation upper cretaceous red deer river valley alberta canada implications for ages correlations and dinosaur biostratigraphy of the scollard frenchman and hell creek formations the battle formation bfm is a widespread upper cretaceous marker horizon in western canada that records a time of low sediment input and marks the boundary between the edmontonian and lancian lan

introduction to the special issue commemorating the 30th anniversary of the royal tyrrell museum of palaeontology with a summary of the museum s early history and its research contributions located just west of drumheller in southern alberta canada the royal tyrrell museum of palaeontology rtmp is nestled among outcrops of the upper cretaceous horseshoe canyon formation exposed along the red deer river valley fig 1 since it officially opened on 25 september 19851 the museum has become one of alberta s must see tourist attractions a significant contributor to the local economy and earned an international reputation for the quality of its palaeontological collections and the research conducted by its scientists the rtmp is unique within canada in being the only government supported museum dedicated to palaeontology and it is one of the few such institutions in the world fig 1 the royal tyrrell museum of palaeontology a front of museum and main entrance circa 2010 looking westwards and with horizontal beds of the upper cretaceous horseshoe canyon formation exposed in the walls of the red deer river valley in the distance b aerial photograph oblique angle and looking to the north northeast the museum sits on top of the number 7 coal seam sensu gibson 1977 and at the base of the horsethief member of the horseshoe canyon formation d a eberth pers comm 2015 that stratigraphic position correlates with an age of about 71 5 ma i e late campanian and lies within the upper part of the edmontosaurus regalis pachyrhinosaurus canadensis dinosaur assemblage zone see eberth et al 2013 fig 6 c the iconic running theropod logo that until recently graced the exterior of the museum below a life sized tyrannosaurid sculpture by brian cooley one of many such sculptures by cooley that have been featured at the museum since its opening in 1985 and with the education wing opened in 2003 as the atco tyrrell learning centre in the background d the cretaceous alberta life sized diorama opened in 2007 an example of a rtmp exhibit that relies heavily on discoveries and interpretations by museum researchers in this case work done in the albertosaurus bonebed and at other localities throughout the horseshoe canyon formation all photographs courtesy of the royal tyrrell museum of palaeontology this special issue of the canadian journal of earth sciences presents a collection of papers commemorating the rtmp s 30th or pearl anniversary our rationale for doing a 30th anniversary volume was two fold first it is an opportunity to showcase the breadth of research conducted by current and former museum scientists as well as by some colleagues having a history of collaboration with the rtmp the 13 invited papers included in this volume are a mix of review and original research papers all thematically focused on the geology and palaeontology of alberta to varying degrees each contribution is the result of work supported by the rtmp and relies on specimens housed in the museum s collections second the 30th anniversary is an opportunity to reflect on the rtmp s history and its research program as is typical for most institutions the rtmp has done little to formally document its own history this year likely will be the last major milestone for which the original generation of museum staff are still working and available to share their recollections about the museum fieldwork and research already deaths and departures have winnowed away part of the original

dynamics of the stationary anomalies associated with the interannual variability of the midwinter pacific storm track the roles of tropical heating and remote eddy forcing abstract the leading mode of interannual variability of the midwinter pacific storm track is such that the storm track is weaker during the winters when the pacific jet is strong and stronger when the jet is weak in this paper experiments are conducted using a stationary wave model as well as an idealized global circulation model to explore the roles of anomalous tropical heating and eddy fluxes in forcing the observed pacific jet anomalies it is found that enhanced tropical heating over the region 60 e to the date line 25 s to 25 n acts to force a stronger and narrower pacific jet on average tropical heating may account for about one third of the strong jet anomaly but there is significant year to year variability moreover tropical heating does not appear to contribute to the weak jet anomaly much of the pacific jet anomalies are forced by anomalous eddy fluxes by examining the regional contributions from the pacific the atlantic and asia it is found that local eddy feedback over the paci

dinosaur eggshells from the lower maastrichtian st mary river formation of southern alberta canada north america is known for its rich uppermost cretaceous record of dinosaur egg remains although a notable fossil gap exists during the lower maastrichtian here we describe a diverse dinosaur eggshell assemblage from the st mary river formation of southern alberta that in conjunction with recently described eggs from the same formation in montana helps fill this gap and sheds light on the dinosaur diversity in this poorly fossiliferous formation three theropod eggshell types continuoolithus cf c canadensis montanoolithus cf m strongorum and prismatoolithus cf p levis and one ornithopod spheroolithus cf s albertensis are reported from albertan exposures of the st mary river formation increasing the ootaxonomic diversity of the formation from two to five ootaxa the taxonomic composition of the eggshell assemblage is consistent with the dinosaurian fauna known from the st mary river formation based on skeletal remains spheroolithus eggshells constitute the majority of identifiable e

interdecadal variations in northern hemisphere winter storm track intensity abstract in this paper the interannual variations in the northern hemisphere winter storm tracks have been examined based on 51 winters december january february of ncep ncar reanalysis data the leading empirical orthogonal function eof corresponds to the simultaneous strengthening weakening of both the pacific and atlantic storm tracks interannual and month to month variations in the pacific and atlantic storm tracks are found to be significantly correlated the principal component associated with the leading hemispheric eof exhibits pronounced interdecadal variability there appears to be a transition during the early 1970s from a weak storm track state prior to 1972 73 to a strong storm track state subsequently decadal mean storm track intensity during the 1990s is about 30 stronger than that during the late 1960s and early 1970s the relationship between variations in storm track intensity and low frequency seasonal mean flow anomalies has also been examined it is shown that storm track va

maastrichtian paleocene foreland basin stratigraphies western canada a reciprocal sequence architecture palynological and magnetostratigraphic chronostratigraphic correlations of lower maastrichtian to paleocene strata along an east west western canada basin transect allow for the recognition of a reciprocal sequence architecture in nonmarine strata reference sections include three canadian continental drilling program cretaceous tertiary boundary project core holes and outcrops in alberta southern saskatchewan and north central montana the spatial and temporal position of the third order sequences provides evidence for the correlation of proximal sector regional disconformities and sedimentary wedges with distal sector sedimentary wedges and regional disconformities respectively the boundary between the two sectors is represented by a hingeline which separates the foreland basin syncline from the peripheral bulge the stratigraphies defined by reciprocal third order sequences are complicated by fourth order boundaries developed within proximal sedimentary wedges and with no correlative distal strata these results support tectonic control on foreland basin sedimentation a model for interpreting the various types of sequences in terms of foreland basin evolution vertical tectonics and orogenic cycles is provided it is argued that nonmarine sequence boundaries times of maximum uplift in the foreland region may be expressed as disconformities incised valleys top of mature paleosol levels or base of fluvial channels whereas nonmarine equivalents of marine maximum flooding surfaces times of maximum basinal subsidence may be indicated by extensive coal seams and or lacustrine sediments resume les correlations palynologiques magnetostratigraphiques et chronostratigraphiques des strates echelonnees du maastrichtien inferieur au paleocene le long du transect est ouest du bassin de la cordillere occidentale au canada permettent la reconnaissance d une ordonnance architecturale de sequences reciproques dans les strates continentales les coupes de reference incluent trois trous de forage carottes du canadian continental drilling program cretaceous tertiary boundary project et des affleurements localises en alberta dans le sud de la saskatchewan et dans le centre nord du montana la position spatiale et temporelle des sequences de troisieme ordre plaide pour la mise en correlation des discordances regionales et des depots sedimentaires en coin dans le secteur proximal avec les depots sedimentaires en coin et les discordances regionales dans le secteur distal respectivement une ligne de jonction represente la limite entre les deux secteurs qui separe le bassin d avant pays en forme de cuvette du bombement peripherique les stratigraphies definies par les sequences de troisieme ordre reciproques sont embrouillees par les limites de quatrieme ordre developpees au sein des depots sedimentaires en coin proximaux sans la presence de strates distales correlatives ces resultats appuient la these d un controle tectonique sur le bassin sedimentaire d avant pays on presente ici un modele interpretant les divers types de sequences en termes d evolution d un bassin d avant pays de tectonique verticale et de cycles orogeniques nous tentons de demontrer que les discordances les vallees entaillees les horizons sommitaux de paleosols matures ou la base des chenaux fluviaux peuvent aider a definir les limites des sequences continentales periodes de soulevement maximum dans la region de l avant pays tandis que les couches de charbon etendues et ou les sediments lacustres representent plutot les equivalents continentaux des aires d inondation maximale periodes de subsidence maximum du bassin traduit par la redaction catuneanu and sweet 703

the generation of global rotational flow by steady idealized tropical divergence abstract tropical convective heating is balanced on the large scale by the adiabatic cooling of ascent the horizontal divergence of the wind above this heating may be viewed as driving the upper tropospheric rotational wind field a vorticity equation model is used to diagnose this relationship it is shown that because of the advection of vorticity by the divergent component of the flow the rossby wave source can be very different from the simple fd source often used in particular an equatorial region of divergence situated in easterly winds can lead to a rossby wave source in the subtropical westerlies where it is extremely effective this part of the source can be relatively insensitive to the longitudinal position of the equatorial divergence a divergence field which is asymmetric about the equator can lead to a quite symmetric rossby wave source for a steady frictionless flow the rossby wave source averaged over regions within closed streamfunction or absolute vorticity contours is under cert

on the existence of storm tracks abstract given that middle latitude weather systems transport heat in a manner such as to weaken the baroclinicity that is thought to be crucial to their growth it is perhaps surprising that concentrated regions of such eddy activity i e storm tracks are found in the northern hemisphere winter the existence and possible self maintenance of storm tracks is investigated using a linear stationary wave model with storm track region forcings taken from data averaged over a number of winters it is found that the direct thermal effect of the eddies does indeed act against the existence of the storm track their vorticity fluxes lead to some reduction of this effect it is argued that the mean diabatic heating in the storm track region is an indirect eddy effect this heating is found to maintain the mean maximum in baroclinicity in the region further the mean low level flow induced by the eddy effects is such as to enhance the warm western oceanic boundary currents that are crucial to the existence of t

seasonal variations of the synoptic scale transient eddy activity and polar front jet over east asia abstract seasonal variations of the synoptic scale transient eddy activity stea and the jet streams over east asia are examined through analysis of the 40 yr european centre for medium range weather forecasts ecmwf re analysis era 40 data extracted from the 6 hourly upper level wind fields the distribution of the jet core numbers exhibits a distinct geographical border for the east asian subtropical jet easj and the east asian polar front jet eapj at the latitudes of the northern tibetan plateau tp in the cool seasons two branches of the stea and low level baroclinicity exist over the east asian landmass accompanied by the two jet state of the easj and eapj in the warm seasons a single jet pattern of the easj along the north flank of the tp is accompanied by the weakened stea over the mid to high latitudes of east asia further analysis shows two distinct features of the seasonal variations of the stea over east asia compared with that over the north pacific first during the transit

taphonomy age and paleoecological implication of a new pachyrhinosaurus dinosauria ceratopsidae bonebed from the upper cretaceous campanian wapiti formation of alberta canada the grande prairie region alberta canada includes some of the richest cretaceous fossil sites in north america including the recently described bonebed of pachyrhinosaurus lakustai at the pipes

high precision u pb ca id tims dating and chronostratigraphy of the dinosaur rich horseshoe canyon formation upper cretaceous campanian maastrichtian red deer river valley alberta canada the non marine horseshoe canyon formation hcfm southern alberta yields taxonomically diverse late campanian to middle maastrichtian dinosaur assemblages that play a central role in documenting

the role of the central asian mountains on the midwinter suppression of north pacific storminess abstractthe role of the central asian mountains on north pacific storminess is examined using an atmospheric general circulation model by varying the height and the areas of the mountains a series of model integrations show that the presence of the central asian mountains suppresses the north pacific storminess by 20 30 during boreal winter their impact on storminess is found to be small during other seasons the mountains amplify stationary waves and effectively weaken the high frequency transient eddy kinetic energy in boreal winter two main causes of the reduced storminess are diagnosed first the decrease in storminess appears to be associated with a weakening of downstream eddy development the mountains disorganize the zonal coherency of wave packets and refract them more equatorward as the zonal traveling distance of wave packets gets substantially shorter downstream eddy development gets weaker second the central asian mountains suppress the global baroclinic energy conversion the decre

evidence for taphonomic size bias in the dinosaur park formation campanian alberta a model mesozoic terrestrial alluvial paralic system a study of the distribution of dinosaurian body masses in the dinosaur park formation dpf campanian southern alberta reveals a prominent negative skew a pattern distinct from those of modern terrestrial faunas we find a direct and robust correlation between taxon size estimated live body mass and known completeness there is a clear dichotomy between large and small bodied taxa at around 60 kg in which taxa less than 60 kg are significantly less complete mean completeness 7 6 than those with an estimated mass of 60 kg or greater mean 78 2 along with completeness there is also a strong association of body size and taphonomic mode with small taxa known largely from isolated and occasionally associated remains and large taxa known from articulated skeletons in addition there is a significant correlation between taxon body mass and both date of discovery and of description with taxa 60 kg the rates of both cumulative discovery and description for large taxa are best described by a logarithmic curve nearing an asymptote whereas small taxa show either a linear or power increase through time this suggests that our current knowledge of the large bodied dinosaur assemblage is reasonably representative of the true biological fauna with few discoveries likely to be made in the future however small taxa are greatly underestimated in both their diversity and abundance with many more potential discoveries to be made given that 1 the sedimentary deposits and fossil assemblages in the dpf together represent one of the best studied examples of a mesozoic alluvial paralic terrestrial palaeoecosystem and 2 similar patterns have been suggested but not documented for other mesozoic terrestrial ecosystems in the western interior of north america we suggest that this pattern of size bias may typify vertebrate fossil assemblages in terrestrial mesozoic systems if so such biases must be considered before patterns of diversity in dinosaur communities through time can be considered accurate or used to compare and interpret mesozoic palaeoecosystems