architecture of an unconformity based tidal sandstone unit in the ametlla formation spanish pyrenees abstract this study is concerned with the sedimentary architecture of a shallow marine sandstone unit in the lower eocene ametlla formation ager basin spanish pyrenees the sandstone unit was formed in a tide dominated setting and is continuously exposed in a 10 5 km long mainly strike parallel cutcrop its base is a prominent unconformity sequence boundary and it consists of two sub units separated by a tidal ravinement surface sub unit 1 lower sub unit formed in an estuarine setting that was created by flooding of an incised valley system outside the incised valleys an oyster bed is present as a lateral equivalent to the estuarine deposits the sequence bounding unconformity was generated during relative sea level lowstand whereas the overlying estuarine and bioclastic deposits of sub unit 1 formed in the early stages of the transgressive systems tract in sub unit 2 above the tidal ravinement surface estuary mouth bar and tide dominated delta deposits are the main facies associations interfingering with offshore to inner shelf sediments westwards these deposits formed in later stages of the transgressive systems tract the large scale model of the sandstone unit served as a framework within which the internal arrangement of architectural elements ae was recorded twelve ae were recognized they mostly have a lensoid geometry and their lateral transitions are abrupt or occur by interfingering over distances of 50 250 m the ae distribution shows that the tide influenced setting was characterized by a high degree of spatial and temporal variability with regard to sedimentary processes this together with the prominent thickness variation of the unit studied makes correlation between vertical profiles difficult even over distances of only a few hundred metres stratal surfaces such as the sequence bounding unconformity the tidal ravinement surface and the flooding surfaces represent the only reliable correlation markers in this kind of environment

events of sediment deformation and mass failure in upper cretaceous estuarine deposits cameta basin northern brazil as evidence for seismic activity abstract event beds recording late cretaceous synsedimentary seismicity occur in the cameta subbasin northern brazil the deposits consist of nearly 40 m of kaolinized fluvio estuarine deposits the lower fluvial tidal influenced complex which carries a high quality commercial kaolin includes genetically related channel fill floodplain crevasse splay and mud plug deposits the upper estuarine deposits contain trace fossils indicating marine influenced settings thalassinoides ophiomorpha teichichnus diplocraterion skolithos cylindrichnus rhizocorallium and planolites and include heterolithic sandy and bioturbated units interpreted as tidal flat storm overwash and low energy estuarine bay deposits respectively in the upper portion of the estuarine lithosomes four successive events events 1 4 of synsedimentary brittle and ductile deformation and large scale sediment failure anomalous in estuarine settings were recognized and attributed to earthquakes event 1 is recorded by heterolithic and bioturbated deposits with vertical to subvertical fractures that disappear into underlying undeformed deposits event 2 is recorded by thin sharply bounded sections composed of heterolithic mudstone and very fine grained sandstone that shows convolute folds and pillow like structures event 3 is documented by intraformational conglomerate and breccia and minor mudstones and sandstones with abundant trace fossils skolithos and thalassinoides event 4 is characterized by vertical to subvertical fractures and faults with homogenized sandstone intrusions along their planes mostly developed in the upper parts of the deposits corresponding to event 3 a detailed analysis of facies relationships combined with consistent orientations of brittle deformation structures and the regional tectonics of the cameta subbasin suggests earthquakes as the triggering mechanism for sediment deformation and large scale mass failure

depositional environment and hydrocarbon potential of marginal marine sediments of eocene from western india a palynofacies perspective abstract palynofacies and palynological data from eocene sediments documents a comprehensive picture of the nature degraded structured non structured amorphous etc of organic matter their distribution and depositional setting for matasukh lignite mines of nagaur basin in western india four sporomorph eco groups seg are defined based on the palynological data viz upland seg lowland seg coastal seg and tidally influenced seg principal component analysis was used to categorize the organic matter into two palynofacies palynofacies a is dominated by brown phytoclasts in particular cuticles and palynofacies b is dominated by amorphous organic matter mainly derived from terrestrially degraded material in palynofacies b there is a reduced frequency of cuticles and high frequency of non biostructured amorphous phytoclasts in comparison to palynofacies a further the integration of tidal limit index and phytoclast preservation index suggest that the sediments were deposited in a proximal setting and were regularly influenced by brackish marine water the sand bed with current bedding in which the troughs are draped with lignitic clay indicate the tidal wave action tyson s ternary diagram indicates the deposition of these sediments in a sub oxic to dysoxic condition rich in kerogen type ii iii thermal alteration index tai shows that the sediments of matasukh lignite mine have attained maturation the characteristic value reached by hydrocarbon generating sediments to generate dry gas as majority of the organic matter is of type iii kerogen with few samples yielding type ii these sediments were deposited in deltaic plain in particular fluvial dominated marginal marine environment

geologist controlled trends versus computer controlled trends introducing a high resolution approach to subsurface structural mapping using well log data trend surface analysis and geospatial analysisa companion paper to mei s 2009 new insights on faults in the peace river arch region northwest alberta based on existing well log data and refined trend surface analysis canadian journal of earth sciences 46 1 41 65 this paper introduces a refined trend surface analysis tsa for detecting faults with small metre scale offsets 5 20 m conventional tsa uses a global polynomial method to model the trend the power of the polynomial e g first second or third order is the only parameter for input the refined approach is different in that it uses local fit techniques to generate the trend the refined approach provides greater flexibility for inputting geological knowledge in the trend surface modelling process this results in a trend surface with the maximum amount of unwanted information which is removed from the residual surface after removal of the trend from the data leaving features of interest optimally highlighted in the residuals such a trend is referred to as a geologist controlled trend to differentiate it from the trend surface modelled by conventional tsa which is primarily a computer controlled global polynomial surface the refined approach goes one step beyond conventional tsa by incorporati

fish taphonomy and environmental inference in paleolimnology abstract the contribution of fish studies to palaeoecology generally takes the form of 1 inference from analogies in modern fish faunas and 2 fish taphonomy the pattern of death and dispersal of bones 1 modern fish faunas and associated organisms provide taxonomic ecological or functional analogues for interpretation of ancient limiting factors and behaviors these inferences presume taxonomic conservatism they also presume functional relationships between morphological form and feeding mode or habitat they become weak with increased geologic age or phyletic distance between ancient subject and modern anaogue 2 fish taphonomy may contribute information about limnology community composition life history mortality depositional environment and preservation taphonomic reconstruction of ecology and preservation depends on the applicability of analogous processes in modern ecology and l limnology in aquatic taphonomy temperature is the most important factor in determining the fate of a carcass above about 16 c depending on depth and pressure most carcasses are made buoyant by bacterial decay gases and are transported to the surface where they may decay further and fall piecemeal into deepwater environments or drift to beach environments where wave energy disarticulates abrades and scatters the bones below about 16 c most carcasses remain on the bottom until buried they may be disturbed by scavengers depending on oxygen concentration in the hypolimnion

temporal changes of a delta example from the holocene yahagi delta central japan abstract the depositional history of a delta was investigated by using radiocarbon dated borehole cores from the yahagi delta nishimikawa plain central japan in particular historical changes in the gradient thickness and grain size distribution of the delta front and sediment discharge of the yahagi river are discussed the latest pleistocene to holocene sequence in the yahagi delta is interpreted as an incised valley fill system formed after the last glacial and subdivided into five sedimentary facies facies a fluvial facies b estuary facies c prodelta facies d delta front and facies e gravelly tidal flat in the main axis of the incised valley facies a facies b facies c facies d and facies a are deposited in ascending order in the western area of the valley facies e adjoins facies d the delta front was formed by river floods without reworking by wave or tide the succession was interpreted as a transgressive systems tract and highstand systems tract formed under sea level rise until ca 7 cal kyr bp and the subsequent highstand after the formation of the delta in ca 7 cal kyr bp characteristic features of the delta front changed twice as the delta prograded first during 4 5 cal kyr bp the delta front became thicker and steeper this change was induced by differences in water depth between the middle incised valley and the outer incised valley which resulted from a buried clinoform second in ca 3 cal kyr bp the grain size distribution of the delta front became coarser and the sorting became poorer the sediment discharge of the yahagi river also increased abruptly this change was induced by the increase of erosional capacity in the hinterland increasing human activities such as deforestation and poor soil conservation might have induced this change

estuarine deposits of the albian paddy member peace river formation and lowermost shaftesbury formation alberta canada abstract outcrop exposures of the peace river formation in northwestern alberta contain evidence of significant relative sea level fluctuations that occurred during the middle to late albian these include paddy member channels that incised into the cadotte member shoreline deposits and the subsequent estuarine frill the upper cadotte member contact is irregular and siderite cemented it has been scoured into and infilled by sandstone of the paddy member the lower sandstone of the paddy member is crossbedded with abundant comminuted carbonaceous debris channels cut into the cadotte member are up to 5 m deep and are locally overlain by in situ coal and roots the channels are infilled with alternating couplets of moderately to intensely bioturbated sand and mud which form inclined h terolithic stratification mud plugs are also present internally these sands are ripple and parallel cross laminated this part of the paddy member is interpreted as estuarine fill that resulted from a relative sea level rise the channel fill is overlain by intensely bioturbated locally rooted finely interbedded sandstone siltstone and shale with minor reworked bentonites interpreted as tidal flat deposits tidal flat sediments are overlain by 2 to 3 m of scoured parallel laminated sandstone and capped by 1 5 m of planar tabular crossbedded sandstone interpreted as shoreface and transgressive estuary mouth deposits respectively evidence for tides throughout the paddy member includes inclined heterolithic stratification mud couplets reactivation surfaces reversing paleoflows and compound crossbeds the incised channels and related fill are correlative with a sequence of paleosols 300 km southwest in the boulder creek formation a brackish influence is indicated by the presence of a few species of peridinioid dinoflagellates occurring in abundance at certain levels and the trace fossil assemblage the paddy member is overlain by marine mudstone of the shaftesbury formation a 20 to 30 cm thick wave rippled layer of fish teeth fish bones and pebbles near the base of the shaftesbury formation can be traced along the peace river for at least 75 km the layer of fish remains is interpreted as transgressive lag

proterozoic fluvial styles response to changes in accommodation space rivieradal sandstones eastern north greenland abstract fluvial styles recorded by the uppermost part of the neoproterozoic rivieradal sandstones succession of eastern north greenland reflect variations in rate of generated accommodation space and possibly climatic changes three facies associations arranged in two genetic sequences are recognised within the succession the lower sequence initially records little available accommodation space a high degree of reworking results in sheet like high energy bed load dominated braided river deposits lacking recurrent facies patterns as accommodation space increases upwards through the sequence reduction in reworking is recorded by the development of fining and thickening upward muddy fluvial cycles evidence of desiccation or prolonged periods of drought are absent within the deposits and climate was probably relatively humid channel deposits in the lower sequence reflect mixed load braided fluvial systems with stable channel banks and floodplains and the gradient appears to have been low to moderate these features are generally considered favourable for the establishment of meandering river systems but channels nevertheless retained an overall braided character and their deposits show no evidence of meandering despite indications of a climatic setting without significant periods of drought sediments indicate that large fluctuations in discharge occurred within the mixed load streams and this is suggested to be the main cause for the absence of meandering the swift and rather dramatic response of the fluvial systems to changes in precipitation probably resulted from rapid runoff rates caused by the absence of vegetation the upper sequence shows an initial return to shallow sandy braided river deposition recording little available accommodation space a subsequent increase in the rate of generated accommodation space is indicated by the presence of alternating sheet sandstones and sand streaked mudstones with abundant desiccation cracks the sheet sandstones show evidence of high energy unconfined ephemeral fluvial flash flood deposition while the mudstones are interpreted to represent muddy floodplain deposits the change in fluvial style combined with the widespread evidence of desiccation suggest an evolution towards a more semi arid climate in the upper sequence this climatic change could account for the reduced clastic input seen in the overlying marine succession which culminated in carbonate platform deposition the present study suggests that even under conditions considered favourable for the formation of meandering streams these will rarely occur in proterozoic deposits due to the lacking influence of vegetation although meandering deposits cannot be ruled out as having formed in pre vegetational times the conditions for their formation appear to have been even more restricted than previously realised

reconstructed summer degree days in central alaska and northwestern canada since 1524 abstract three time series based on precisely dated annual tree ring widths have been used to reconstruct june plus july degree days for the central alaska and northwestern canada region the time series are the longest recently developed chronologies for the area and represent 57 core samples from 27 trees the degree day reconstruction extending back to a d 1524 exhibits much year to year variation and extended warming and cooling trends including a general warming trend from about 1840 to 1960 the reconstruction is in agreement with some subaretic glacial information and with data of percentage melting from arctic ice cores this and similar reconstructions can provide quantitative information to compare with general circulation and energy budget models for longer time periods than are available in recorded meteorological data

variations of the last glacial warm pool sea surface temperature contrasts between the open western pacific and south china sea 1 high resolution paleoceanographic records from the southern south china sea scs and the tropical open western pacific reveal multicentennial to millennial scale variations of the western pacific warm pool wpwp over the last 40 kyr during the last glacial maximum lgm in marine isotope stage mis 2 planktonic globigerinoides sacculifer do 18 in core ns93 5 from the southern scs and in core wp92 5 from the central wpwp registered a similar average value of about 1 5p however the average do 18 value was about 0 5p more negative in the scs than in the central wpwp as was their difference before and after the lgm in the later part of mis 3 and early portion of mis 1 these results indicate weaker monsoonal and fluvial effects on the southern scs during the last glacial than during pleniglacial and postglacial periods owing to different oceanic circulation modes and regional topography the calculated seasonal temperature differences of summer and winter sea surface temperatures ssts between the open wpwp and the southern scs were up to 3 4 5 d c during the lgm but only slightly over 3 d c in the southern scs and less than 2 d c in the open wpwp during other periods from about 29 to 25 ka the mis 2 3 transition was marked by a sudden sst increase in the southern scs but a decrease in the open wpwp over this 4 kyr period the average annual sst appeared to be only 28 d c in the central wpwp but more than 28 d c in the southern scs indicating a shift of the central wpwp toward the far west during that time furthermore our results imply a period of nearly 6 kyr from 22 5 to 16 5 ka without an apparent warm pool of 28 d c in the western pacific

palaeodrainage on marajo island northern brazil in relation to holocene relative sea level dynamics a large area in northeastern marajo island northern brazil has been characterized geomorphologically applying information acquired from landsat imagery this study was combined with detailed sedimentologic analysis of continuous cores which provided a record of depositional settings developed in this area through the holocene the results revealed well preserved meandering to anastomosed drainage networks of wide palaeochannels that were superimposed by a narrower palaeochannel system in both cases the sedimentary record consists of sands heterolithic deposits and muds locally rich in plant debris the strata are organized into fining upward successions that reach approximately 18 m thick in the wide channels and 4 m thick in the narrow channels sedimentary features suggestive of a coastal location for the wider palaeochannels and reworking of sediments by tidal currents include the prevalence of well to moderately sorted rounded to sub rounded fine to medium grained sands displaying foreset

early cretaceous early late albian echinoderms from northeastern british columbia canada an echinoderm association is reported from the early late albian paddy member of the peace river formation of british columbia canada the association includes frasericrinus mauricensis gen et sp nov two additional distinctive crinoid column types a poorly preserved asteroid and an umbilical fragment of the cephalopod stelckiceras this is the first report of a cretaceous isocrinid from north america the echinoderm fossils are from the top of a succession of storm deposited sandstones and mudstones boulder creek formation that can be correlated southward into nearshore and terrestrial facies of the paddy member of the peace river formation the echinoderm fossils were buried and probably lived about 12 14 km from the contemporaneous shoreline in an estimated water depth of 10 20 m integration of biostratigraphic and allostratigraphic schemes suggests that the echinoderms are of earliest late albian age the association of the echinoderm fauna with ammonites of boreal affinity indicates depos

light volatile liquid and gas shale reservoir potential of the cretaceous shaftesbury formation in northeastern british columbia canada the geologic controls on reservoir properties and potential hydrocarbon volatile low molecular weight liquid and gas resources of the cretaceous shaftesbury formation in northeastern british columbia have been investigated maturity varies from the oil to dry gas window tmax 429 486c with increasing maturity and depth of burial toward the south the tmax in degrees celsius is the oven temperature at the peak generation of s2 during pyrolysis total organic carbon toc content ranges between 0 64 and 8 0 wt with an average of 2 2 wt the toc content distribution mirrors the trends in maturity with lower toc content in areas of high maturity kerogen is characterized as either type ii iii or type iii the quartz content ranges between 33 and 66 with higher quartz content in areas with lower toc content and greater maturities porosity ranges between 4 5 and 14 6 with higher porosities observed within shallower wells low quartz content or maturities or a combination of all three the porosity is reduced in high maturity samples by mechanical compaction and silica cementation total gas capacities range between 4 5 and 24 8 cm3 g and gas in place gip estimates are between 0 98 and 3 39 bcf section meter the calculated hydrocarbon generation is less than 3 6 bcf section meter with light liquid generation between 3 7 and 516 2 mmbo present day depths and organic maturity have strong influences on the hydrocarbon capacity more so than toc content deeper higher maturity samples in the south have the largest total gas capacity and gip estimates 0 98 3 39 bcf section meter maturity is within the dry gas window in the southern one third of the study area highest volumes of light liquid hydrocarbons are found within the less mature northern part of the study area

nearshore articulate crinoid from the albian of alberta canada early cretaceous echinodermata during the middle albian a southward incursion of the boreal ocean flooded northern alberta and adjacent british columbia forming a large embayment known as the hulcross sea marine mudstones of the hulcross formation and harmon member of the peace river formation record transgression whereas sandstones of the cadotte member of the peace river formation record shoreline regression to the north abundant hummocky and swaley lamination in the cadotte sandstone attest to the influence of storms on a shallow shelf the cadotte sandstone undergoes a lateral facies change from mud free shoreface sandstone in the south to heterolithic offshore facies in the north an articulated crinoid was found within a hummocky sandstone bed about 15 km seaward north of the shoreface shelf facies transition the articulated state of the crinoid indicates that it was buried very rapidly and never exhumed the arms through 20 mm of the column are preserved but because the details of the aboral cup are not well preserved

reconstructing a mid cretaceous landscape from paleosols in western canada abstract the albian stage of the mid cretaceous was a time of equable climate conditions with high sea levels and broad shallow epeiric seas that may have had a moderating affect on continental climates a late albian landscape surface that developed during a regression and subsequent sea level rise in the western canada foreland basin is reconstructed on the basis of correlation of paleosols penetrated by cores through the paddy member of the peace river formation reconstruction of this landscape refines chronostratigraphic relationships and will benefit future paleoclimatological studies utilizing continental sphaerosiderite proxy records the paleosols developed in estuarine sandstones and mudstones and they exhibit evidence of a polygenetic history upon initial exposure and pedogenesis the paddy member developed deeply weathered well drained cumulative soil profiles later stages of pedogenesis were characterized by hydromorphic soil conditions the stages of soil development interpreted for the paddy member correlate with inferred stages of pedogenic development in time equivalent formations located both basinward and downslope upper viking formation and landward and upslope boulder creek formation on the basis of the genetic similarity among paleosols in these three correlative formations the paleosols are interpreted as having formed along a single continuous landscape surface results of this study indicate that the catena concept of pedogenesis along sloping landscapes is applicable to ancient successions sphaerosiderites in the paddy member paleosols are used to provide proxy values for meteoric 18o values at 52 n paleolatitude in the cretaceous western interior basin the meteoric 18o values are used to refine existing interpretations about the mid cretaceous paleolatitudinal gradient in meteoric 18o values and the mid cretaceous hydrologic cycle

paleo oxygenation in tertiary epeiric seas evidence from dinoflagellate cysts the dinoflagellate cyst record from an epeiric setting in the oligocene of southwest germany exhibits major changes associated with variations in paleo oxygenation inferred from benthic foraminifera dinoflagellate cyst diversity and equitability strongly decline in the case of extreme oxygen depletion the relative abundance of the dinoflagellate cyst thalassiphora pelagica inversely correlates with the availability of benthic oxygen the t pelagica spectrum consists of different morphotypes which are considered to represent different stages within the cystal part of the t pelagica life cycle following the concept of benedek and gocht the distribution of these morphotypes is also linked to oxygen availability horizons with highest t pelagica abundances are characterized by the occurrence of t pelagica specimens representing an early stage in cyst formation a model is proposed that uses t pelagica as a proxy to assess oxygenation both at the sediment surface and in the water column the occurrence of t pelagica specimens representing an early stage in cyst formation is interpreted to reflect the extension of oxygen depletion upwards into the water column because t pelagica is an easily recognized globally distributed element of paleogene and early neogene dinoflagellate cyst assemblages the application of this model may be of importance in the reconstruction of paleo oxygenation in epeiric settings from these times its sensitivity to changes in benthic oxygenation can be as high as if not higher than that of the approach based on foraminifera moreover it is applicable to decalcified sediments

recurrent depletion of benthic oxygen with 4th order transgressive maxima in the cretaceous western interior seaway abstract a study was designed to investigate the relationship between depletion of benthic oxygen and 4th order sea level change within the cretaceous western interior seaway of north america three 4th order sea level change cycles were studied in strata belonging to the tropic shale and the tununk shale member of the mancos shale in utah these sedimentary deposits accumulated within prodeltaic environments in utah strata belonging to all three 4th order cycles exhibit evidence for depletion of benthic oxygen at times of peak 4th order transgression and development of condensed sections the evidence includes decreased intensities of bioturbation increased cr al ni al and zn al ratios and decreased mn fe ratios the data also suggest that depletion of benthic oxygen in the distal section preceeded that in the more proximal one and thus may reflect episodic expansion of an oxygen depleted water mass es from the pelagic to the prodeltaic environment of the seaway evidence for subsequent increases in benthic oxygen level with the onset of 4th order regressions is interpreted to reflect either aggradation of the seafloor above the oxygen poor water due to sediment accumulation or contraction of the oxygen depleted water mass from the prodeltaic part of the seaway or a combination of the two s organic c ratios of strata interpreted to have been deposited under conditions of depleted benthic oxygen are distinctly below 0 4 and thus were not useful for recognition of paleo oxygen levels in the prodeltaic environment this study highlights the importance of depletion of benthic oxygen as a mechanism for enhancing preservation of organic carbon in condensed sections on a hundred thousand year time scale our results underline the potential for source rock formation in similar prodeltaic deposits of other epicontinental seaways during periods of relatively high sea level and global depletion of benthic oxygen

middle cenomanian late cretaceous molluscs of the shaftesbury formation birch mountains northeastern alberta canada historical resources impact assessment and mitigation studies have documented a new middle cenomanian invertebrate fauna from the shaftesbury formation in the birch mountains northwest of fort mcmurray in northeastern alberta canada although older portions albian of the shaftesbury formation in alberta and british columbia have yielded invertebrate fossils this is the first fauna of middle cenomanian age known for the unit the fauna includes the ammonites acanthoceras wyomingense and borissjakoceras orbiculatum the inoceramid bivalves inoceramus dunveganensis and inoceramus prefragilis stephensoni and the gastropod pirsila tensa the occurrence of the late middle cenomanian zonal fossil a wyomingense allows correlation between the middle fish scales formation of the shaftesbury formation and the lower part of the labiche formation of alberta and with five units farther to the south in the united states namely the greenhorn limestone lincoln formation and graneros shale of kansas the fron

foraminiferal zonation of the viking interval in the hasler shale albian northeastern british columbia a dominantly arenaceous foraminiferal fauna of over 33 genera and 65 species was recovered from silty shales in the mid portion of the hasler formation in the upper albian part of the fort st john group the assemblages lie stratigraphically below occurrences of neogastroplites and below the miliammina manitobensis zone the foraminifera come from above the occurrence of haplophragmoides gigas gigas although assignment of the beds is to the upper part of the h gigas zone the upper part of the haplophragmoides gigas zone may be divided into several subzones above the h gigas gigas sub zone in ascending order viz h gigas ssp a subzone reophax tundraensis subzone trochammina depressa subzone trochammina umiatensis subzone and reophax troyeri subzone the assemblages have close affinities with the faunas of both the overlying and underlying shales and are an expression of a late shallowing deepening cycle within the skull creek joli fou seaway they were penecontemporaneous with viking sandstone

sequence stratigraphy of a tidally dominated carbonate siliciclastic ramp the tithonian early berriasian of the southern neuquen basin argentina the tithonian berriasian vaca muerta carrin cura and picun leufu formations in the southern neuquen basin were deposited on a tidally dominated mixed carbonate siliciclastic ramp basinal outer middle shallow and back ramp facies associations are recognized and a sequence stratigraphic analysis reveals that the ramp record consists of three shallowing upwards sequences ti1 ti2 and ti3 set within a lower order progradational cycle a higher order of cyclicity is superimposed on to the middle ti2 sequence the majority of the ramp facies belong to the transgressive and highstand systems tracts however at the base of ti2 a lowstand systems tract is identified characterized by a basal unconformity and an abrupt basinward shift of the shallow marine lithofacies transgressive systems tracts were characterized by slow sedimentation rates and rapid sea level rises that affected carbonate productivity highstand systems tracts show the greatest carbonate productivity and an increased progradation rate on account of a reduction in accommodation space generation palaeogeography played a major role in the development of the depositional systems partial isolation from the pacific ocean reflecting the growth of the andean magmatic arc and geographic restriction due to tectonic inversion in the central part of the basin resulted in a meso macrotidal regime that produced a tidally dominated sedimentary record in the shallow and back ramp environments coeval anoxic conditions in the central part of the neuquen basin favoured distal ramp and basinal black shale deposition during episodes of relative sea level rise

influence of low amplitude high frequency relative sea level changes in a wave dominated estuary miocene sao luis basin northern brazil abstract miocene deposits exceptionally well exposed along several coastal cliffs between the towns of alc ntara and guimaraes maranhao state northern brazil record the history of low amplitude high frequency sea level changes in a wave dominated incised valley estuarine setting these deposits are interpreted as estuarine in origin based on i depauparated ichnological assemblage and occurrence of gyrolithes both typical of highly stressed brackish water conditions ii dominance of sedimentary structures diagnostic of tidal processes e g alternating thicker thinner sand bundles marked by reactivation surfaces and or mud drapes and iii presence of widespread channel deposits this estuarine fill consists of three stratigraphic units units 1 3 1 unit 1 shoaling shoreline sh and tidal channel ch 2 unit 2 shoaling shoreline sh tidal channel ch facies associations lagoon lg and flood tidal delta washover ftd w facies associations and 3 unit 3 tidal channel ch estuarine bay eb and fluvial influenced channel fch facies associations the individual units internally show a dominantly prograding character a pattern also reflected throughout the succession by the overall upward stacking of units showing successively more restricted conditions these characteristics combined with the position in the uppermost portion of the valley fill succession led to suggest that the deposits exposed in the study area likely formed during the transition from rising to highstand stages of relative sea level mapping of regionally significant discontinuity surfaces led to the recognition of a sequence boundary i e discontinuity surface ds1 marked by erosion and subaerial exposure at the valley floor this surface separates the miocene succession from underlying cretaceous rocks and it is attributed to a major period of incision that led to the genesis of the incised valley during relative sea level fall unit 1 onlaps against ds1 and is bounded above by discontinuity surface ds2 which probably formed by tidal ravinement during a period of transgressive erosion this ravinement surface is the boundary between two shoaling up successions i e units 1 and 2 interpreted as parasequences from a same depositional sequence discontinuity surface ds3 between units 2 and 3 is attributed to a sequence boundary marked by significant erosion and subaerial exposure and is interpreted as a reflex of a renewed period of incision within the estuary due to a strong drop in relative sea level the top of unit 3 is defined by another discontinuity surface i e ds4 with pronounced erosion and subaerial exposure which is attributed to a sequence boundary that ended the estuarine deposition in the study area thus unit 3 defined at the base and top by unconformities is a complete depositional sequence resulting from a low amplitude high frequency relative sea level cycle superposed upon the overall highstand stages of the estuary evolution

a calcareous foraminiferal faunule from the upper albian viking formation of the giroux lake and kaybob north fields northwestern alberta implications for regional biostratigraphic correlation arenaceous foraminifera from the upper albian viking formation and associated strata are recorded and charted from five wells in the northwestern portion of the west alberta basin viz gulf giroux lake 04 11 66 21w5 candel arco giroux lake 00 10 05 65 20w5 pan am b 1 giroux 02 10 05 65 20w5 calstan b a kaybob w 02 28 63 20w5 and chevron fox creek 10 15 62 19w5 an anomalous calcareous foraminiferal component in three gulf giroux lake samples is illustrated ichnological sedimentological and stratigraphic studies of the viking formation strata based on 26 cored intervals indicate largely transgressive shallow marine deposition in the area the microfaunal and ichnological assemblages indicate a general increase in salinity toward normal marine conditions facies analysis demonstrates the stacking of two shoreface parasequences truncated by wave ravinement surfaces the calcareous foraminifera in the viking formation are associated with abundant and diverse arenaceous foraminifera with arctic affinities that we have used for determining the microfaunal zone positions biostratigraphic correlation has been made with a calcareous faunule in the lower part of the hasler formation within the expanded fort st john group found in the southern portion of the keg river subbasin hudson hope region northeastern british columbia this helps to resolve the problem of correlating the stratigraphically equivalent paddy member at the type section near the town of peace river alberta

sequence stratigraphy of a condensed low accommodation succession lower upper cretaceous dakota sandstone henry mountains southeastern utah cretaceous low accommodation deposits have been extensively studied in the subsurface of the western interior of north america because of their prolific hydrocarbon production and remaining potential understanding the stratigraphic complexities of these deposits in the subsurface relies strongly on detailed outcrop analogs in this study the dakota sandstone was examined along 100 km 62 mi of semicontinuous outcrop between the towns of hanksville and ticaboo in the henry mountains of southeastern utah this region represented a low accommodation setting located over the forebulge of the cretaceous western interior basin during accumulation of the unit the dakota sandstone is 0 to 38 m 125 ft thick of cenomanian age and records multiple cycles of sediment accumulation the dakota sandstone is subdivided into two condensed top truncated stratigraphic sequences the upper of which contains two parasequences the basal parts of both sequences are composed of braided fluvial conglomerates and sandstone overlain by tidally influenced fluvial sandstone inclined heterolithically stratified estuarine mudstone carbonaceous shale and coal the overlying parasequences consist of coarsening upward lower to upper shoreface mudstone sandstone tidal inlet deposits and oyster shell concentrations these facies define tripartite subdivisions of depositional environments typical of wave dominated estuaries the fluvial deposits may represent lowstand deposits but overall sediments accumulated during transgressive systems tracts tst the parasequences recorded in the henry mountains are similar to the dakota sandstone of northwestern new mexico and to high frequency sequences identified in the kaiparowits plateau approximately 80 km 50 mi to the southwest which suggests eustatic driving mechanisms the best potential for hydrocarbon reservoirs occurs in fluvial sandstones and conglomerates

tree rings δ13c and climate in picea glauca growing near churchill subarctic manitoba canada abstract white spruce picea glauca moench voss trees were sampled to investigate the relationship between ring width and 13c as well as between these descriptors and climate cross sections from eight white spruce trees growing in the hudson bay lowlands subartic manitoba with an establishment date prior to 1775 were selected from our archive for each cross section two radii were measured to produce ring width chronologies for stable carbon isotope measurements every fifth ring 2000 1995 1750 was analyzed separately from each tree whereas approximately equal masses from the eight trees were pooled into composite samples for each of the intermediate years mixing masses from each tree equal to that from the tree with the least amount alpha cellulose was extracted and 13c was determined using continuous flow mass spectrometry the ring width residual chronology derived from eight trees was highly correlated to that previously developed for the area a small but significant correlation was also found between the ring width and the 13c residual chronologies the climate signal contained in both ring width and the 13c residual chronologies suggests that warm early summers were conducive to larger rings whereas the 13c best reflects the overall growing season temperature precipitation relative humidity and or drought index have little to no association with either chronology significant correlations were observed between 13c and the historical ice records from the hudson bay co archive data suggesting that during long warm growing season the 13c content of alpha cellulose increases our results indicate that both ring width and 13c provide complementary information future work will involve looking at long term trends in carbon isotope ratios and the potential use of 13c for dendroclimatic reconstruction

impact of recent north atlantic anomalies on surrounding land areas based on dendroclimatic evidence tree rings are useful indicators of interannual to decadal scale climate variability in this paper we show that tree ring data from the northwestern atlantic sector may reflect the great negative salinity gsa and related positive sea ice anomalies of the 1960 s 70 s along with cold surface air temperatures at coastal land stations there were declines in ring widths in the 1970 s in temperature sensitive birch trees in southern greenland white spruce in labrador and white spruce and white pine from newfoundland tree ring and other data from both sides of the north atlantic also indicate a decadal scale warm event with subsequent cooling around the 1820 s 1830 s

climate and ice sheet mass balance at the last glacial maximum from the genesis version 2 global climate model abstract at the last glacial maximum lgm about 21 000 calendar years ago 21 ka bp the overall mass balance of the laurentide and eurasian ice sheets should have been close to zero since their rate of change of total ice volume was approximately zero at that time the surface mass balance should have been zero or positive to balance any iceberg iceshelf discharge and basal melting but could not have been strongly negative in principle this can be tested by global climate model cgm simulations with prescribed ice sheet extents and topography we describe results from a suite of 21 ka bp simulations using a new global climate model genesis version 2 0 a with ssts prescribed from climap 1981 and predicted by a mixed layer ocean model and with ice sheets prescribed from clih the ice 4g peltier 1994 and climap 1981 reconstructions in common with previous gcm simulations using mixed layer oceans substantial cooling over and around antarctica occurs due to normal gcm dynamics and polar sea ice feedback without recourse to changes in thermohaline circulation we find slightly enhanced cooling and cloudiness over low latitude land masses compared to over ocean especially over the andes which decreases the disagreement with land based data and suggests that tropical climap ssts may only be 1 2 c too warm the gcm used here is well suited for ice sheet mass balance studies because i the surface can be represented at a finer resolution than the atmospheric gcm ii an elevation correction accounts for spectral distortions of the atmospheric gcm topography iii a simple post processing correction for refreezing of meltwater is applied and iv the model s precipitation and mass balances for present day greenland and antarctica are realistic however for all reasonable combinations of ssts and ice sheet configurations the predicted annual surface mass balances of the lgm laurentide and eurasian ice sheets are implausibly negative possible reasons for this discrepancy are discussed including increased ice age aerosols higher climap like ice sheet profiles in the few thousand years preceding lgm and a surge of the southern laurentide just before lgm to fleetingly produce the ice 4g profile at 21 ka bp

oceanic freshwater transport during the last glacial maximum annual mean freshwater transports during the last ice age are calculated using data from a global atmospheric general circulation model the atmospheric model is used to simulate the climate of 18 000 years ago using climate long range investigation mapping and prediction data for the model s seasonally varying sea surface temperatures ice coverage and surface topography the water transports are calculated for each ocean basin using the model s evaporation precipitation and runoff for the present climate the model s glacial ice sheets and the global water budget are near equilibrium for the ice age the model does not maintain the glacial ice sheets at steady state but causes them to melt therefore we reduced the runoff from melting ice to bring the global water budget into equilibrium recent studies have shown that salinity anomalies in the north atlantic caused by changes in the freshwater transport could change the thermohaline circulation for the present climate the evaporation exceeds the sum of precipitation and runoff in the atlantic ocean which leads to a higher mean salinity in the atlantic than in the pacific ocean the results suggest that this water budget reversed in the atlantic during the last ice age this conclusion however cannot be stated firmly because the model s global water budget was not in equilibrium for the ice age the model s freshwater transports for the last ice age are compared with those for the present climate and implications on changes in thermohaline circulation are discussed

sea level changes and organic walled phytoplankton response in a late albian epicontinental setting lower saxony basin nw germany abstract samples from a 245 m long core from the upper albian of nw germany have been analysed palynologically in accordance with the concept of sequence palynology of prauss 1993 two completed cycles of 3rd order sea level change are inferred superimposed by a 2nd order cycle during the 3rd order cycles the response of both the ratio of terrigenous sporomorphs to marine palynomorphs t m index and dinoflagellate diversity shows a gradual decrease within the transgressive systems tracts the quantitative response of certain dinoflagellate taxa however is different within each 3rd order cycle the abundance of skolochorate cysts increases strongly only during the earlier cycle this difference is suggested to be a function of the 2nd order cycle which is transgressive during most of the earlier 3rd order cycle but regressive throughout the later one the layer at about 135 m is interpreted to represent the maximum flooding surface of the 2nd order cycle the succession in peak abundance of the dinoflagellate genera oligosphaeridium surculosphaeridium pterodinium may characterise a transgressive systems tract to early highstand systems tract interval during a 3rd order cycle however the proportions of surculosphaeridium respond much more distinctly to the 2nd order sea level changes being highest during the corresponding maximum flooding surface higher proportions of palaeoperidinium cretaceum may indicate enhanced primary productivity and or estuarine circulation during transgressive and advanced late highstand conditions with respect to water mass characteristics within the photic zone no clear dominance of tethyan or arctic waters is distinguishable based on dinoflagellate taxa a rather mixed water mass dominated by cosmopolitan and boreal taxa seems to be present throughout most of the section the influence of warmer water masses largely indicated by the proportion of skolochorate cysts is enhanced during each transgressive interval of the 3rd order cycles but it is less well developed within the transgressive systems tract at the top of the section it is suggested that a strong tethyan influence in terms of water mass introduction into the nw german basin was predominant only during the transgressive pulse of the 2nd order cycle above 135 m the tethyan or warm water influence is considered largely as a function of oceanic circulation rather than sea level rise but is episodically enhanced during the relatively weak pulses of 3rd order transgressions certain dinoflagellate taxa known from the upper albian arctic region vesperopsis mayii luxadinium primulum l propatulum luxadinium cf l primulum are absent

the salinity contrast between the atlantic and pacific oceans during glacial time in today s ocean the salinity of low latitude surface waters in the pacific is on the average 1 per mil lower than in the atlantic oxygen isotope records for planktonic foraminifera suggest that an even larger salinity deficit may have existed for pacific surface water during glacial time if so the transport of water vapor from the atlantic to the pacific must have been as strong as or even stronger to balance the tendency toward salt buildup the atlantic would have had to export during glacial time waters saltier than it received from the other oceans

recognition of facies bounding surfaces and stratigraphic patterns in foreland ramp successions an example from the upper devonian appalachian basin u s a abstract a detailed stratigraphic study of the upper devonian lock haven formation in the appalachian basin provides new interpretations applicable to understanding sedimentation and stratigraphic architecture in the foreland ramp setting the common occurrence of graded beds hummocky cross stratification and shell lags indicates that storm processes played an important role in deposition gradational based coarsening upward shoreface sequences of interbedded sandstone and mudstone formed during gradual fall in relative sea level in contrast sharp based regressive sequences consist of laminated sandstone facies overlying a submarine erosion surface that developed in response to more rapid fall in relative sea level transgressive sequences become finer grained upward from conglomerate lag which was deposited on a basal transgressive surface to heterolithic facies and mudstone facies a combination of eustasy and tectonic subsidence of the foreland ramp produced changes of relative sea level these fluctuations provided a means for transporting sand onto the ramp and for producing repetition of stratigraphic patterns in the lock haven formation the upper devonian clastic succession which includes both the lock haven formation and the catskill formation represents northwestward progradation of shoreline to nonmarine environments as sediment supply to the foreland ramp exceeded the rate of formation of accommodation compared to passive margin shelves thick fine grained successions such as the lock haven formation are more likely to form in foreland basins where tectonic subsidence provides a mechanism for creating accommodation sediment influx from uplifted areas and absence of a slope break on the foreland ramp results in a higher rate of fine grained clastic sedimentation than occurs on shelves of passive margins

late albian dinoflagellate cyst paleobiogeography as indicator of asymmetric sea surface temperature gradient on both hemispheres with southern high latitudes warmer than northern ones abstract late albian temperature sensitive dinoflagellate cysts are characterized in order to better understand mid cretaceous sea surface temperature gradients distribution maps of thirty seven species recovered from one hundred fifty outcrops and deep sea drilling holes odp dsdp sites located from low and high paleolatitudes over the two hemispheres 75 n 70 s are encountered fifty years of published data available in eighty seven articles have been considered and synthesized using a database coupled with a geographical information system gis the continuous and disjoint biogeographic patterns of dinocyst species along latitudes define seven climatic belts four in the northern hemisphere high mid high mid low low latitude belts and three in the southern hemisphere low mid low mid high latitude belts dinocysts restricted along latitudes are temperature sensitive species limit ranges of temperature sensitive dinocysts of mid low and mid high latitude belts reveal mixing belts located at 40 45 n and 50 70 s they represent major palaeofrontal systems as paleosubtropical fronts with strongly mixed water column the northern frontal system 40 45 n was located as in the modern ocean the large southern frontal system 50 s 70 s was 10 20 poleward to antarctica semi quantitative temperature range limits for mid cretaceous dinoflagellates and sst gradients in the two hemispheres are suggested by setting dinocyst climatic belts against estimated 18o temperature curve from fish teeth a paleoecological classification is suggested latitudinal distribution of extant temperature sensitive dinoflagellate cysts follows the asymmetric modern temperature gradient asymmetric latitudinal ranges of late albian dinocyst species of mid low latitude belts restricted between 45 n and 70 s demonstrate asymmetric temperature gradients with southern high latitudes being warmer than northern high latitudes

reconstruction of past ice conditions in a hudson bay estuary using tree rings descriptions of ice conditions ranging from lake and sea ice to glacial advances and retreats form an important portion of the climatic record ice formation deterioration and changing areal extent are of increasing interest in climatology sea transportation petroleum exploration and the fishing industry with few exceptions quantitative information on ice conditions is generally brief with many records in the us and canada beginning only in the 1950s1 tree ring data from long lived trees can be used as quantitative proxy data for past climatically related parameters the record of first complete freezing of the churchill river estuary on hudson bay is reconstructed here for 298 yr 1680 1977 by means of tree ring analysis

marine flooding surfaces recorded in permian black shales and coal deposits of the main karoo basin south africa implications for basin dynamics and cross basin correlation abstract the marine origin of black shales in the context of the permian postglacial development of the karoo basin south africa is subject of an ongoing controversial discussion here we present and discuss palynological and sedimentological data providing evidence of a transgressive event during the early guadalupian palynofacies assemblages of the black shales of the southern basin include marine phytoplankton that exhibit peak abundance within the whitehill shales and which also occur within siltstones and glauconitic sandstones on top of the no 5 coal seam of the north eastern basin palynostratigraphic control makes this marine signal a powerful tool for cross basin correlation moreover palynofacies analysis demonstrates a facies transition from terrestrial lacustrine and fluvio deltaic in the northeast to deep marine in the south western parts of the basin

sedimentation and basin fill history of the neogene clastic succession exposed in the southeastern fold belt of the bengal basin bangladesh a high resolution sequence stratigraphic approach abstract the tertiary basin fill history of the bengal basin suffers from oversimplification the interpretation of the sedimentary history of the basin should be consistent with the evolution of its three geo tectonic provinces namely western northeastern and eastern each province has its own basin generation and sediment fill history related mainly to the indo burmese and subordinately to the indo tibetan plate convergence this paper is mainly concerned with facies and facies sequence analysis of the neogene clastic succession within the subduction related active margin setting oblique convergence in the southeastern fold belt of the bengal basin detailed fieldwork was carried out in the sitapahar anticline of the rangamati area and the mirinja anticline of the lama area the study shows that the exposed neogene succession represents an overall basinward progradation from deep marine through shallow marine to continental fluvial environments based on regionally correlatable erosion surfaces the entire succession 3000 m thick has been grouped into three composite sequences c b and a from oldest to youngest composite sequence c begins with deep water base of slope clastics overlain by thick slope mud that passes upward into shallow marine and nearshore clastics composite sequence b characteristically depicts tide dominated open marine to coastal depositional systems with evidence of cyclic marine regression and transgression repetitive occurrence of incised channel tidal inlet tidal ridge shoal tidal flat and other tidal deposits is separated by shelfal mudstone most of the sandbodies contain a full spectrum of tide generated structures e g herringbone cross bedding bundle structure mud couplet bipolar cross lamination with reactivation surfaces tidal bedding storm activities appear to have played a subordinate role in the mid and inner shelf region rizocorallium rosselia planolites and zoophycos are the dominant ichnofacies within the shelfal mudstone this paralic sedimentation of neogene succession in the study area can serve as a good point of reference for tide dominated regressive shelf depositional systems the top of the composite sequence b is marked by a pronounced erosion surface indicating the final phase of marine regression followed by the gradual establishment of continental fluvial depositional systems represented by composite sequence a in this composite sequence stacked channel bars of low sinuosity braided rivers gradually pass upsequence into high sinuosity meandering river deposits a sequence stratigraphic approach has been adopted to interpret the basin fill history with respect to relative sea level changes and to subdivide the rock record into several sequences and units systems tracts and parasequences based on identified bounding discontinuities such as transgressive erosion surface tes regressive erosion surface res marine flooding surface mfs and incised valley floor ivf this approach provides new insight for both exploration and exploitation strategy for hydrocarbon plays that may prove vital to the oil companies engaged in exploration activities in the bengal basin it is strongly recommended here that the traditional lithostratigraphic classification of this part of the basin which is based on the assam stratigraphy be abandoned or at least revised a tentative allostratigraphic scheme is presented and it is suggested that to formalize the scheme further study both surface and subsurface is needed

architectural elements from lower proterozoic braid delta and high energy tidal flat deposits in the magaliesberg formation transvaal supergroup south africa abstract three architectural elements are identified in the lower proterozoic magaliesberg formation pretoria group transvaal supergroup of the kaapvaal craton south africa 1 medium to coarse grained sandstone sheets 2 fine to medium grained sandstone sheets and 3 mudrock elements both sandstone sheet elements are characterised by horizontal lamination and planar cross bedding with lesser trough cross bedding channel fills and wave ripples as well as minor desiccated mudrock partings double crested and flat topped ripples due to the local unimodal palaeocurrent patterns in the medium to coarse grained sandstone sheets they are interpreted as ephemeral braid delta deposits which were subjected to minor marine reworking the predominantly bimodal to polymodal palaeocurrent trends in the fine to medium grained sandstone sheets are inferred to reflect high energy macrotidal processes and more complete reworking of braid delta sands the suspension deposits of mudrocks point to either braid delta channel abandonment or uppermost tidal flat sedimentation the depositional model comprises ephemeral braid delta systems which debouched into a high energy peritidal environment around the margins of a shallow epeiric sea on the kaapvaal craton braid delta and tidal channel dynamics are inferred to have been similar fine material in the magaliesberg formation peritidal complexes indicates that extensive aeolian removal of clay does not seem applicable to this example of the early proterozoic

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

source rock potential and thermal maturity of lower cretaceous strata monkman pass area british columbia shale and coals from 1 2 km of core through most of the preserved lower cretaceous in western canada were analyzed for source rock potential and maturation level although much of the core lies within the oil window none of the formations are notably oil prone oxidizing bottom conditions and the large predominance of terrestrial organic matter om in the relatively nearshore depositional setting of the marine sediments have led to the dominance of terrestrial om throughout this sequence of rocks including the marine shales as such mostly gas will be or has been generated the nonmarine minnes group and gething and gates formations average 2 7 6 3 and 5 2 total organic carbon toc respectively with fair to very good gas source potential the nonmarine boulder creek formation contains 1 1 toc and has poor source rock potential due to the presence of several thick paleosols the marine moosebar hulcross and basal shaftesbury formations contain 1 5 1 7 and 1 5 average toc contents respectively and have poor to fair source rock potential these marine sediments which may have generated limited amounts of oil show a progressive decrease of hydrogen index hi with depth due to thermal degradation with increased burial hi for nonmarine sediments remains constant with depth the marine sediments contain mostly type iii kerogen with lesser amounts of thermally degraded type ii kerogen vitrinite reflectance increases systematically with depth from 0 94 to 1 5 romax tmax values correspond well with vitr nite reflectance although tmax values for marine sediments increase more slowly with increasing maturation than nonmarine sediments

the impact of cold north atlantic sea surface temperatures on climate implications for the younger dryas cooling 11 10 k the sensitivity of global climate to colder north atlantic sea surface temperatures is in vestigated with the use of the giss general circulation model north atlantic ocean temperatures 18 000 b p resembling those prevalent during the younger dryas were incorporated into the model of the present climate and also into an experiment using orbital parameters and land ice characteristic of 11 000 b p the results show that with both 11 000 b p and present conditions the colder ocean temperatures produce cooling over western and central europe in good agreement with younger dryas paleoclimatic evidence cooling also occurs over extreme eastern north america although the precise magnitude and location depends upon the specification of ocean temperature change in the western atlantic despite the presence of increased land ice and colder ocean temperatures the younger dryas summer air temperatures at northern hemisphere midlatitudes in the model are warmer than those of today due to changes in the orbital parameters chiefly precession and atmospheric subsidence at the perimeter of the ice sheets

fossil marine actinopterygian fishes from the kaskapau formation upper cretaceous turonian near watino alberta turonian fossil marine fishes occur at several localities near watino alberta in sandstones and in shale concretions of the vimy member kaskapau formation the actinopterygian fossils in the san

organic rich radioactive marine shale a case study of a shallow water condensed section cretaceous shaftesbury formation alberta canada abstract organic rich radioactive shales are a common regional feature resting on cretaceous transgressive surfaces in western canada the basal shale in the shaftesbury formation late albian from the peace river area of northern alberta is characterized by high gamma ray high resistivity and low neutron wireline log signatures three facies in ascending order are present within the basal shaftesbury formation 1 a brackish water estuarine shale 2 a restricted marginal marine shale which is radioactive and 3 an open marine normal salinity shale the radioactive shale contains an abundance of large lenticular algal cysts cf lancettopsis lanceolata madler 1963 which are rare in overlying and underlying shale the algal cysts and high organic content may be the locus of th radioactivity the total organic carbon content 6 and sulphur content 3 4 of the radioactive shale also are higher than the shale above and below with a different mineralogy as well the radioactive portion of the basal shaftesbury shale has the characteristics of a condensed section it is directly above a ravinement surface and transgressive lag deposit which in turn locally overlie estuarine sediments deposited within an incised valley other characteristics include evidence of low oxygen values low concentrations of benthonic foraminifera and evidence of a slow sedimentation rate palynological micropaleontological and geochemical results indicate that the radioactive s ale was deposited in restricted marginal marine conditions and that overlying shale shows a progressive deepening to nearshore open marine conditions this radioactive shale does not represent the deepest water sediments of the transgression but is a condensed section deposited in relatively shallow water

quaternary tectonics in a passive margin marajo island northern brazil marajoisland is located in a passive continental margin that evolved from rifting associated with the opening of the equatorial south atlantic ocean in the late jurassic early cretaceous period this study based on remote sensing integrated with sedimentology as well as subsurface and seismographic data available from the literature allows discussion of the significance of tectonics during the quaternary history of marginal basins results show that eastern marajoisland contains channels with evidence of tectonic control mapping of straight channels defined four main groups of lineaments i e nne ssw ne sw nw se and e w that parallel main normal and strike slip fault zones recorded for the amazon region additionally sedimentological studies of late quaternary and holocene deposits indicate numerous ductile and brittle structures within strati graphic horizons bounded by undeformed strata related to seismogenic deformation during or shortly after sediment deposition this conclusion is consistent with subsurface bouguer mapping suggestive of eastern marajoisland being still part of the marajograben system where important fault reactivation is recorded up to the quaternary together with the recognition of several phases of fault reactivation these data suggest that faults developed in association with rift basins might remain active in passive margins imposing important control on development of depositional systems copyright 2007 john wiley sons ltd

high latitude salinity effects and interhemispheric thermohaline circulations a general circulation model for the ocean is used to investigate the interaction between the global scale thermohaline circulation and the salinity distribution it is shown that an equatorially asymmetric circulation can be maintained even under equatorially symmetric basin geometry and surface forcing multiple equilibrium solutions are obtained for the same forcing by perturbing the high latitude salinity field in an otherwise equatorially symmetric initial condition the timescale of the transition from the symmetric circulation to an asymmetric circulation depends critically on the sign of the initial salinity perturbation

an anoxic event at the albian cenomanian boundary the fish scale marker bed northern alberta canada abstract the fish scale marker bed fsmb of the shaftesbury formation which marks the albian cenomanian boundary is a regional stratigraphic marker in the western interior of canada at the outcrop studied on the smoky river in northwestern alberta three major shale units can be distinguished in the fsmb and contiguous strata the lowermost shale unit 1 is bioturbated and contains high diversity dinoflagellate and moderate diversity foraminiferal assemblages it has dominantly type iii terrestrial organic matter om and low total organic carbon content toc the unit was deposited in an open marine neritic environment of normal salinity the fsmb unit 2 represents a zone of condensed bioclastic accumulation composed of abundant fish remains the dinoflagellate species diversity is drastically reduced in this unit and it lacks benthonic foraminifera and bioturbation unit 2 is characterized by mainly type ii marine om and high toc values unit 2a contains rippled sandstone related to either a shallowing or to deeper water currents a fish hash conglomerate making up unit 2b can alternatively be interpreted as a bioclastic condensed and winnowed deposit or as a transgressive lag unit 2c consists of black platy shale with abundant fish remains and represents a minor marine trangression during the deposition of fsmb when the bottom waters were dominantly anoxic collectively the features of unit 2 suggest deposition under a stratified water column with moderate productivity of planktonic and nektonic organisms in the upper oxygenated layers but with anoxic bottom waters unit 3 overlying the fsmb consists of blocky shale with reduced concentration of fish remains due to increased rate sedimentation during its deposition the organic rich sediment of unit 3 was progressively diluted by clastic material and there was an increase in the dissolved oxygen content of the bottom waters the anoxic event at the fsmb is related to a relative rise in sea level and possibly to the mixing of waters different salinities and temperatures from the arctic ocean and the gulf of mexico in the western interior seaway

multiple cycles of wave dominated estuarine deposits in low accommodation settings cretaceous j sandstone northwestern nebraska the j sandstone comprises less than 46 m 151 ft of sandstone dominated strata within the mudrock dominated lower upper cretaceous succession of northwestern nebraska the unit is a prolific hydrocarbon producer in this region denver julesburg basin but its lithostratigraphic and sequence stratigraphic framework critical for reservoir characterization and mapping is poorly known we have achieved an improved understanding of depositional history and sequence stratigraphy by describing and correlating cores and wireline logs from wells within sioux dawes and box butte counties nebraska and niobrara and goshen counties wyoming coals paleosols fluvial or inner estuarine sandstones estuarine mudstones fluvial conglomerate shoreface sandstone and reworked volcanic fallout bentonite lithofacies were identified trace fossil assemblages representing stressed expressions of the skolithos and cruziana ichnofacies are common these lithofacies are arranged vertically into three erosionally based cycles each less than 28 m 92 ft thick and each grade upward from fluvial or inner estuarine sandstones into estuarine mudstones and in turn into shoreface sandstones the lateral and vertical stacking patterns of the lithofacies are complex however and the upper cycles appear to fill space eroded into the underlying ones northeast southwest elongate isochore trends appear in all three cycles lithofacies transition downdip from inner estuarine sandstones in the northeast to estuarine basin mudstones and shoreface sandstones toward the southwest detrital mineralogy indicates an easterly cratonic provenance for the entire unit our data suggest that the j sandstone in northwestern nebraska accumulated in wave dominated estuarine settings as part of a long lived transgressive systems tract the unit as a whole occupies a complexly incised landscape cut during a third order lowstand ca 98 ma coeval cycles of similar magnitude throughout the western interior suggest that the three cycles represent eustatic fluctuations the highest quality reservoirs occur at the base of the unit in inner estuarine lithofacies in the central and southwestern parts of the study area

stratigraphic significance of ooidal ironstones from the cretaceous western interior seaway the peace river formation alberta canada and the castlegate sandstone utah u s a ooidal ironstones form prominent units and an appreciation of their sedimentological and stratigraphic significance is important for the interpretation of sedimentary successions ooidal ironstones from the albian paddy member of the peace river formation alberta canada and the campanian castlegate sandstone of the mesaverde group in colorado have been analyzed the ooidal ironstones are associated with a major sequence boundary and subsequent transgressive surface both are interpreted to have been deposited under conditions of low net sediment accumulation in well oxygenated bottom water conditions with episodic storm events reworking the sediments the paddy member ironstone is interpreted to have been deposited in an estuarine environment and the castlegate ironstone is interpreted to have been deposited in a shallow marine environment both ironstones are dominated by berthierine ooids and grain rimming and pore filling siderite with later ferroan dolomite and calcite in the castlegate ooidal ironstone petrographic geochemical and isotopic evidence coupled with thermodynamic considerations indicates that the ooidal ironstone mineralogy formed during suboxic diagenesis the conditions required for suboxic diagenesis were extensive sediment reworking and slow net sediment accumulation rates we propose that these conditions arose as a result of marine transgression during the initial relative sea level rise following the development of a sequence boundary ooidal ironstone formation ceased once sedimentation rates increased and transgression deepened water depths considerably these results illustrate the association between ooidal ironstones and major stratal surfaces in sedimentary successions and highlights the complexity that early diagenesis at such surfaces can take

foraminiferal response to albian relative sea level changes in northwestern and central alberta canada albian foraminiferal assemblages from three wells in northwestern imperial spirit river no 1 12 20 78 6w6 central anglohome c e fort augustus no 1 7 29 55 21w4 and southern alberta amoco

cretaceous albian turonian foraminiferal biostratigraphy and paleontology of northern montana and southern alberta abstract in albian turonian time the interior of north america was flooded by a seaway extending from the present gulf of mexico to the arctic ocean transgressive phase greenhorn cyclothem detailed studies of this interval north and south of the international border have usually not been integrated the present foraminiferal biostratigraphic study includes a 38 000 km2 area straddling the alberta montana border from the lewis thrust in the west to the sweetgrass hills in the east including the sweetgrass arch stratigraphic cross sections and isopach maps of 6 albian early turonian stratigraphic units prepared from 57 surface and subsurface sections demonstrate that sedimentation was controlled primarily by 1 spasmodic volcanism to the west 2 tectonic activity coincident with the present location of the sweetgrass arch the occurrence of the late cenomanian planktonic foraminifer rotalipora cushmani in association with three other keeled species suggests an east west marine connection between the eastern pacific and the western interior at the maximum greenhorn transgression this is consistent with the facies model described by kauffman 1967 1969 1977 the paleogeographic model developed in the present study reported gastropod paleo biogeographic data and reevaluation of pelecypod and ammonite paleo zoogeographic interpretations