late quaternary paleohydrology of the madre de dios river southwestern amazon basin peru abstract late quaternary climatic and hydrologic variability triggered changes in fluvial deposition and erosion along the course of the madre de dios river peru the largest tributary basin of the madeira basin itself the largest tributary basin of the amazon three laterally extensive quaternary age terrace tracts are present within the madre de dios basin analysis of sedimentary facies present in the modern cut banks and terraced sequences along with radiocarbon dates on fossil wood and leaf material preserved in the terraced strata allow reconstruction of the late quaternary depositional history of the sedimentary sequences including determination of the approximate timing of aggradation and downcutting episodes and its relationship to the timing of past climate change in this portion of the amazon basin and beyond the quaternary sediments underlying the terraces most often recorded deposition in a coarse grained meandering fluvial system the t3 terrace the highest terrace is underlain by the miocene ipururi formation which is unconformably overlain by the late miocene pleistocene 48 000 cal yrs bp madre de dios formation a multistory coarse sandy to gravelly channel and point bar complex the latter was downcut before 29 850 100 cal yrs bp this downcut landscape was infilled by meandering fluvial strata characterized by gravelly channel deposits in a sequence dominated by floodplain and lateral accretion deposits these strata were in turn downcut to form the t2 terrace before 11 970 100 cal yrs bp a third episode of aggradation resulted in the deposition of a sand dominated meandering channel complex that infilled the t2 valley and was subsequently downcut after 3780 50 cal yrs bp this most recent terrace is infilled by the modern fluvial sediment which has been actively aggrading since at least 870 50 cal yrs bp importantly the madre de dios fluvial system actively aggraded between 30 000 and 25 000 cal yrs bp and likely much younger as dated samples were thus far only found near the base of the t2 sequence this observation implies that some combination of 1 increased precipitation and decreased temperature 2 decreased evapotranspiration and increased runoff 3 increased andean glacial erosion and increased sediment supply and 4 decreased atmospheric co 2 hence decreased rain forest primary productivity and altered rain forest physiology ecology entering the last glacial maximum period brought about increased floodplain deposition in the southwestern amazon elsewhere in the amazon basin few if any fluvial sediments of this age range have been observed the start of the next major phase of aggradation coincided with the younger dryas and suggested that floodplain sedimentation in the lowlands was again related to cold and wet conditions in the adjacent highlands and perhaps in the lowlands as well and that madre de dios history was also tied to large scale global climate this aggradation may have continued throughout the early and mid holocene until at least 3 780 cal yr bp if so and this is uncertain this episode of sedimentation took place during a dry period

quaternary deposits of the buyuk menderes graben in western anatolia turkey implications for river capture and the longest holocene estuary in the aegean sea abstract the buyuk menderes graben is a seismically active depositional basin in the n s extensional tectonic region of western anatolia turkey it extends in an e w direction and is bounded by the aegean sea to the west the infill of this tectonic basin comprises ca 850 m and 245 m thick clastic sequences of neogene and quaternary respectively and the quaternary part of the basin fill is presented here by the help of seismic sections and boreholes results show that the studied succession was made of unconsolidated mostly fine grained clastic sediments of marine and continental sequences interfingered with each other the marine counterpart forms three relatively short approx 30 km and one long approx 100 km from modern coastline sediment wedges representing sea transgressions onto the graben the last one was a rapid incursion that occurred in the middle holocene forming the longest estuary of the aegean sea in western anatolia the filling of this estuary caused the decline of some historical harbours and settlements in the region while marine based events occurred in the west of the graben alluvial and fluvial processes produced marginal and axial deposits in the east of graben respectively in general the continental succession of quaternary is thinner than its marine equivalent probably due to sea level fluctuations in addition the sedimentation rate increased suddenly during deposition of the last marine sequence estuarine deposits in the holocene it is likely that this was the result of enlargement of the drainage area of the river buyuk menderes due to a river capture that occurred in the latest stages of pleistocene

genesis and internal architecture of the middle to upper devonian gwirat al hyssan reef mound western sahara abstract on the southern flanks of the tindouf basin western sahara reefal complexes of various sizes were developed mostly of givetian age but possibly reaching into the early frasnian surrounding sedimentary rocks were dominantly sandstones siltstones and marls the larger reef complexes in the northeastern part of western sahara show three reef cycles within the givetian and lowermost frasnian interrupted by marly sedimentation farther to the west more isolated reef structures in open shelf settings occur often showing smaller dimensions the present study focuses on one of these western reefal build ups besides large scale reefs dominated by stromatoporoids ne several smaller bioherms have been investigated such as the gwirat al hyssan reef mound near smara initial reef growth was of late givetian age as indicated by corals e g heliolites the main reef builders were the corals alveolites thamnopora aulopora frechastraea phillipsastrea and to a lesser degree heliolites scoliopora and roemerolites stromatoporoids also contributed but were less frequent chaetetids e g rhaphidopora acted as pioneer stabilizers on bare sediment surfaces preservation in life position was frequently observed in both groups of organisms crinoids are not rare but only present as debris in distinct areas of the reef depressions concentrations of brachiopods and small solitary corals occur the reef mound has a present elevation of 17 m and measures about 370 m in diameter vertical as well as horizontal zonation could be recognized in detail the initial reef growth started on a submarine shoal of siliciclastic sediments containing various trace fossils and sedimentary structures such as cross bedding and wave ripples interference ripples suggest generation in very shallow water the initial reef building organisms were encrusting chaetetids followed by platy frechastraea colonies thamnoporids were also present the overlying reef limestones consist of different corals and to a minor degree stromatoporoids the latter are sparsely distributed vertically as well as horizontally depending on their position within the reef growth forms are more robust bulbous towards higher hydrodynamic conditions at the southern reef front reef growth is interrupted by debris limestones of thamnoporid and crinoid bioclasts intercalated with detrital platy stromatoporoids generally the debris was not transported over long distances as demonstrated by the presence of relatively large fragments this debris phase early frasnian is overlain by the last documented stage in reef development represented by medium to thin bedded coral rich limestones the onset of the carbonate production of the gwirat al hyssan reef mound is maybe related to the global transgressive givetian frasnian boundary event

quaternary ichnofacies model for paleoenvironmental and paleosealevel interpretations a study from the banas river basin western india abstract integration of data from ichnological and other interdisciplinary sources from the quaternary banas river basin india has permitted the reconstruction of a composite ichnofacies model for the interpretation of paleoenvironments and paleosealevels a glacioeustatic transgressive regressive system tract of the ancient arabian sea has been recognized from the superposition of ichnofacies the pleistocene shallow marine psilonichnus ichnofacies ichnogenus psilonichnus skolithos arenicolites and thalassinoides of infaunal polychaete crab and bivalve origin developed in the vadpag vend segment of the lower banas sequence corresponds to interglacial high sea stands the overlying late pleistocene holocene continental coprinisphaera scoyenia mixed ichnofacies paleosol association of delicate surficial traces of terrestrial insects and river floodplain association of aquatic traces of worms and crustaceans formed in the radhanpur varahi segment of the upper banas sequence represents the last glacial regressive mode of sealevel levee bound oriented crustacean burrows may be used as new ichnological tools to locate buried paleochannels and aquifers the juxtaposition of levees with alternate worm burrow and barren zones and floodplains with gastropod and barren zones indicates monsoonal lows and highs in the holocene the overprinting of the coprinisphaera elements on the scoyenia forms has resulted from the recent sub recent environmental degradations rising temperature spread of desert shrinking saltmarshes and weakened fluvial forces probably related to global warming and other greenhouse processes the readable ichnological signatures of the quaternary glacioeustatic sealevel fluctuations and consequent climatic changes qualify the banas model for wider application

tidal energy dissipation at the sill of sechelt inlet british columbia abstract the energy budget of a tidally active shallow silled fjord is discussed constriction of the flow over the shallow sill causes a reduction in tidal amplitude and a phase lag across the sill a generalized expression for the total power extracted from the barotropic tide by dissipation at the sill is derived as a function of the tidal amplitude difference and phase lag of the tidal elevation using tide gauge data from both sides of the sill at the entrance to sechelt inlet british columbia this generalized expression yields estimates for the energy flux of the barotropic tide which approach 100 mw during spring tides from direct measurements of the currents the estimated frictional dissipation is equal to the flux out of the barotropic tide within experimental error a small amount of the energy flux 5 is estimated to go into the generation of a tidal jet which dissipates within a few kilometers of the sill and contributes to the formation of a mid water layer

stratigraphic and geochemical evidence for the depositional environment of the early archaean isua supracrustal belt southern west greenland the highly deformed c 3800 ma isua supracrustal belt is a fragment of a more extensive early archaean sedimentary and volcanic succession intruded by and tectonically intercalated with tonalitic and granitic amftsoq gneisses in the period 3800 3600 ma the supracrustal rocks recrystallised under amphibolite facies conditions between 3800 and 3600 ma in the late archaean and locally at c 1800 ma layered sequences of rock of sedimentary and probable volcanic origin form over 50 of the belt bodies of high mg al basic rocks and ultramafic rocks were intruded into the layered sequences prior to isoclinal folding and intrusion of amitsoq gneisses the layered rocks which are 1 km thick are divided into two sequences that are in faulted contact with each other the way up of these sequences has been determined from facing directions of locally preserved graded layering in felsic metasediments at several localities the overall upwards change in sedimentary succession is interpreted as showing change from dominantly basic to dominantly felsic volcanism which provided the major clastic component of the sediments clastic sedimentation took place against a background of chemical sedimentation shown by interlayers of banded iron formation metachert and calc silicate rocks throughout the sequences the felsic rocks locally preserve graded bedding and possible conglomerate structures indicating deposition from turbidite flows and possibly as debris flows nodules in the felsic rocks contain structures interpreted as fiamme there is an irregular enrichment in k2o na2o in many of the felsic rocks at constant sio2 and al2o3 content interpreted as owing to alteration of original andesitic to dacitic volcanic rocks banded iron formations locally contain conglomeratic structures suggesting sedimentary reworking possibly under shallow water conditions lithological and geochemical characters of the clastic components of the supracrustal sequences are consistent with derivation from felsic and basic volcanic rocks and do not require a continental source

the comparison of a numerical model to observations of velocity and scalar data in burrard inlet and indian arm british columbia a laterally integrated time dependent numerical model of burrard inlet and indian arm is compared to time series of cyclesonde velocity and scalar data that have 10 m vertical resolution as long as deep water renewal is not occurring the model can reproduce the observed m2 and k1 tidal response in the basin of indian arm also although the rate of freshwater inflow into indian arm and burrard inlet is not large the simulated tidal response is noticeably improved if freshwater inflow is taken into account when deepwater renewal is observed to occur the model also simulates renewal but it does so poorly and the ability of the model to accurately simulate the m2 and k1 tide degrades significantly

chronology of bathymetric variations of the pueyrredon posadas salitroso lacustrine system during the late pleistocene to early holocene abstract the pueyrredon posadas salitroso lacustrine system pps ls is located in the andean patagonia region of argentina 47 22 28 s 71 55 34 w and represents a series of lakes formed as glaciers retreated during the late pleistocene and early holocene these lakes began as proglacial lakes and later evolved into periglacial lakes this research presents the chronological evolution of the pps ls bathymetric variations based on the analysis of stratigraphic profiles surveyed at different locations and the dates obtained from lake sediments four paleogeographic sketches representing the chronological evolution of the pps ls between 23 580 bp and 5208 bp have been developed based on the integration of these data

stratigraphy and depositional environments of the kanawha formation middle pennsylvanian southern west virginia u s a abstract the kanawha formation of southern west virginia consists of up to 620 m of lithic sandstone and mudrocks with subordinate coal and impure limestone that accumulated in a subsiding foreland basin the formation contains 26 of the state s 62 minable coal seams it accounts for about 43 of the coal currently produced in west virginia component sedimentary facies from 46 outcrop localities reflect alluvial paludal lacustrine paralic and shallow marine environments internal and architectural facies attributes indicate more evidence for coastal and tidal estuarine deposition than traditional deltaic models evidence for tidal processes includes bipolar paleocurrents rhythmic textures and structures and associated biogenic structures a new two part model is presented that relates facies to changing coastal morphology during transgressive regressive cycles eustatic sea level changes played a major role in basin wide development of major coal zones and marine units lowstandss of sea level caused incisement of fluvial channels whereas rising sea level led to expansion of tidal plains and estuaries shoreface retreat produced ravinement surfaces and transgressive lags that now separate coastal plain and marginal marine facies from shallow subtidal facies coastal progradation began during highstands after estuarine sediment sinks had filled and may have been intensified during falling sea level

global warming and south indian monsoon rainfall lessons from the mid miocene precipitation over india is driven by the indian monsoon although changes in this atmospheric circulation are caused by the differential seasonal diabatic heating of asia and the indo pacific ocean it is so far unknown how global warming influences the monsoon rainfalls regionally herein we present a miocene pollen flora as the first direct proxy for monsoon over southern india during the middle miocene climate optimum to identify climatic key parameters such as mean annual temperature warmest month temperature coldest month temperature mean annual precipitation mean precipitation during the driest month mean precipitation during the wettest month and mean precipitation during the warmest month the coexistence approach is applied irrespective of a 3 4 c higher global temperature during the middle miocene climate optimum the results indicate a modern like monsoonal precipitation pattern contrasting marine proxies which point to a strong decline of indian monsoon in the himalaya at this time therefore the strength of monsoon rainfall in tropical india appears neither to be related to global warming nor to be linked with the atmospheric conditions over the tibetan plateau for the future it implies that increased global warming does not necessarily entail changes in the south indian monsoon rainfall

a numerical model of stratified circulation in indian arm british columbia a laterally integrated numerical model has been developed for the study of stratified circulation in inlets the model is time dependent and includes advective terms horizontal and vertical turbulent diffusion of momentum and salt and variations in width and depth initial and boundary conditions based on winter measurements in burrard inlet and indian arm were used to study the inlet s response to tidal forcing the friction term was tuned to match calculated and observed dissipation rates evidence for a standing wave pattern in the response of the m2 and k1 tidal constituents is discussed a comparison of model results with cyclesonde current meter time series at two locations in indian arm is consistent with resonance a modal decomposition of the calculated response shows that most of the energy is contained in the barotropic and first baroclinic modes with the former dominating near the sill and the latter dominating in the deep basin second mode energy was significant for the k1 at some locations

upper jurassic stratigraphy and sedimentary facies in the central outer moray firth basin north sea abstract the upper jurassic of the outer moray firth basin can be divided into two main stratigraphic units the piper and kimmeridge clay formations in each of these formations five major sedimentary facies can be recognized the piper formation of late oxfordian to early kimmeridgian age comprises very fine to coarse grained sandstones and minor mudstone of clastic shelf to shoreline origin large scale upward coarsening sequences are well developed in some areas particularly in the reservoir sands of the tartan oilfield and are interpreted as regressive possibly deltaic deposits the unconformably overlying kimmeridge clay formation ranges in age from late oxfordian through volgian to ryazanian the formation is predominantly argillaceous but also contains locally thick accumulations of sandstone deposited by gravity flow processes the claymore sandstone member is proposed as a new name for these sandstones in the region of the claymore oilfield where they form the major reservoir sands of the piper formation were derived mainly from the south west although some input from the north may also have occurred deposition may have extended further eastwards than the present erosional limit of the sands thick sand sequences in the kimmeridge clay formation are probably restricted to the margins of the witch ground graben where contemporaneous faulting occurred

out of our depth on the impossibility of fathoming eustasy from the stratigraphic record the evolution of a sedimentary basin s gross morphology depends upon 1 basement movement 2 sediment accumulation and compaction and 3 variations of eustasy with time thus if an accurate history of eustasy could be derived it would aid in our understanding of basin stratigraphy and help in the prediction of sediment geometry from described areas techniques which attempt to determine the magnitude of eustatic sea level excursions include the measurement of 1 the amount of sedimentary onlap onto the continental margins with and without the use of hypsometric curves 2 the thickness of marine sedimentary cycles and the elevation and distance between indicators of old strandlines 3 the perturbations on individual thermo tectonic subsidence curves and stacked crustal subsidence curves 4 the variations in deep ocean oxygen isotopes found in sediments and 5 the size of variables used in graphical and numerical simulations of basin fill in terms of tectonic behavior rates of sediment accumulation and eustasy which invert the problem to date a combination of the use of relative sea level charts derived from sediment onlap of the continental margin with dimensioning by oxygen isotopes responding to glacial events offers the best potential for relative tectono eustatic sea level curves but even this method can not produce a unique solution for absolute eustatic variations mathematical modelling shows that at best it is possible to obtain only the sum of tectonic basement subsidence and sea level variations from the above methods and at worst not even that simple a combination thus every proposed scheme to measure eustatic sea level excursions assumes some behavior for two of the three underlying processes tectonic movement of the basement sedimentary accumulation and eustatic sea level each scheme then determines the third process relative to the assumed model behavior of the other two it would seem that like king canute we cannot command the sea though we can still use undifferentiated relative tectono eustatic sea level curves to generate a family of solutions which are the product of a variety of absolute sea level curves and tectonic models each solution has then to be assessed in terms of geologic setting and the hypotheses it generates

the internal tide and resonance in indian arm british columbia the nature of the internal tide in indian arm is discussed in the winter of 1983 1984 this internal tide was observed to change from a predominantly m2 internal response to a predominantly k1 one this change in the response is explained as a partial resonance response of the system during the 1983 1984 winter the resonance period steadily increased from 14 hours at the start to 22 hours at the end it is suggested that the enhanced internal response at the k1 frequency late in the winter is due to resonance the fitting of normal modes was done to look at the energy flux in indian arm about 20 30 of the energy flux is found to return from the head of the inlet a finding supporting the resonance hypothesis which requires energy to be reflected from the head

simulation of density driven frictional downslope flow in z coordinate ocean models abstract an important component of the ocean s thermohaline circulation is the sinking of dense water from continental shelves to abyssal depths such downslope flow is thought to be a consequence of bottom stress retarding the alongslope flow of density driven plumes in this paper the authors explore the potential for explicitly simulating this simple mechanism in z coordinate models a series of experiments are performed using a twin density coordinate model simulation as a standard of comparison the adiabatic nature of the experiments and the importance of bottom slope make it more likely that the density coordinate model will faithfully reproduce the solution the difficulty of maintaining the density signal as the plume descends the slope is found to be the main impediment to accurate simulation in the z coordinate model the results of process experiments suggest that the model solutions will converge when the z coordinate model has sufficient vertical resolution to resolve the bottom viscous laye

sedimentology of rocky shorelines 1 a review of the problem with analytical methods and insights gained from the hulopoe gravel and the modern rocky shoreline of lanai hawaii abstract hypotheses advanced concerning the origin of the pleistocene hulopoe gravel on lanai include mega tsunami abandoned beach multiple event rocky shoreline and for parts of the deposit native hawaiian constructions and degraded lava flow fronts uplift of lanai shorelines has been suggested for deposits occurring up to at least 190 m these conflicting hypotheses highlight problems with the interpretation of coarse gravel deposits containing marine biotic remains the geological records of the processes implied by these hypotheses should look very different discrimination among these or any other hypotheses for the origins of the hulopoe gravel will require careful study of vertical and lateral variations in litho and biofacies facies architecture contact relationships and stratal geometries of this deposit observations of modern rocky shorelines particularly on lanai adjacent to hulopoe gravel outcrops have shown that distinctive coarse gravel facies are present several of which occur in specific geomorphic settings tectonic isostatic and eustatic changes which cause rapid shoreline translations on steep slopes favour preservation of former rocky shorelines and associated sedimentary deposits both above and below sea level the sedimentary record of those shorelines is likely to be complex the modern rocky shoreline sedimentary environment is a hostile one largely neglected by sedimentologists a range of high energy processes characterize these shorelines long period swell tsunami and storm waves can erode hard bedrock and generate coarse gravel they also erode older deposits depositing fresh ones containing mixtures of materials of different ages additional gravelly material may be contributed by rivers draining steep hinterlands to fully evaluate rocky shoreline deposition in the broadest sense for both the hulopoe gravel and other deposits sedimentary facies models are needed for rocky shorelines occurring in a range of settings recognition and description of rocky shoreline deposits are crucial for correctly interpreting the geological history of oceanic and volcanic arc islands for distinguishing between ancient tsunami and storm deposits and for interpreting coarse grained deposits preserved on high energy coasts of continents problems include not only the absence of appropriate sedimentary facies models linking rocky shoreline deposits and environments but also until recently lack of a systematic descriptive scheme applicable to coarse gravel deposits generally two complementary methods serve to integrate the wide range of bed and clast attributes and parameters which characterize complex coarse gravel deposits the composition and fabric caf method has a materials focus providing detailed description of attributes of the constituent clasts petrology the proportions of gravel sand and mud and the ways in which these materials are organized the sedimentary facies model building fmb method emphasizes the organization of a deposit on a bed by bed basis to identify facies and infer depositional processes the systematic use of a comprehensive gravel fabric and petrography log gfpl in conjunction with detailed vertical profiles provides visual representations of a range of deposit characteristics criteria useful for distinguishing sedimentary facies in the hulopoe gravel are grain size modes amount of matrix bed geometry sedimentary structures bed fabric and clast roundness

statistical analysis of turbidite bed thickness patterns from the alpine fold and thrust belt of western and southeastern greece abstract a statistical evaluation of turbidite bed thickness was performed for 11 turbidite successions which constitute part of foreland basins formed along the alpine fold and thrust belt of western and southeastern greece the purpose was to compare the results from this study with previously published investigations and discuss if and how statistical approaches could contribute to the environmental analysis of turbidite deposits in tectonically complex areas bed thickness datasets exhibit a clear non normal signal in their distribution behavior statistical analysis was focused on i fitting of widely used non normal theoretical distribution models using robust non parametric goodness of fit statistical tests and ii detecting the possible presence of asymmetric bed thickness cycles and or non random bed thickness clustering results indicate that the studied bed thickness datasets are well characterized by a bimodal lognormal distribution model probably reflecting deposition from both high and low density turbidity currents several datasets exhibit distributions characterized by power law tails exponential distribution types were not observed all datasets exhibit non random thinning upward bed thickness trends probably due to tectonically induced gravity flows proposed methods for identifying depositional sub environments using turbidite bed thickness statistics were found to have limited applicability observations of the present study may prove useful for the environmental analysis of turbidite deposits in fold and thrust belt areas characterized by limited outcrop exposures

on deep water renewals in indian arm british columbia sensitivity to the production of turbulent kinetic energy caused by horizontal variations in the flow field abstract a two dimensional i e laterally averaged numerical model of the circulation in burrard inlet and indian arm near british columbia canada is used to examine the sensitivity of deep water renewal events in indian arm to the turbulent mixing in the lee of the narrow sills in burrard inlet horizontal variations in the flow field can have an important influence on the production of turbulent kinetic energy near the sills and therefore also on the renewal events in indian arm an ad hoc modification to the expression for the production of turbulent kinetic energy required to obtain an acceptable simulation downstream of second narrows in burrard inlet also results in a reasonable simulation of the observed circulation in indian arm the modified laterally averaged model can reproduce the main features of the circulation away from the narrow sills however it seems that a three dimensional model will be required if the circulation is to be simulated with greater accuracy and without the ad hoc

paleoecological constraints on reef coral morphologies in the tortonian early messinian of the lorca basin se spain abstract coral reefs represent one of the main carbonate factories that contributed to the control of the stratigraphic architecture of carbonate platforms which had a widespread development during the late miocene in the paleo mediterranean area the late miocene reef complexes of the lorca basin in southeastern spain are composed of five mixed siliciclastic carbonate units middle tortonian to early messinian in age the development of coral reefs probably ceased when the first evaporitic event occurred in the basin centre in the early messinian this study mainly focuses on the response of reef communities and the modifications of reef organisation to global and regional parameters at the platform scale the carbonates are intermixed with terrigenous deposits related to two main types of clastic systems torrential fans and fluvial to deltaic systems the amount of clastic input greatly affected reef growth and coral morphologies three different types of stratal geometries were delineated in the reef complex sigmoids bioherms and patches and carpets the reef frameworks are mainly constructed by a poorly diversified assemblage of corals composed of poritids faviids and mussids porites is the principal reef builder of the sigmoids and carpets where it is widely distributed tarbellastraea is common in bioherms and acanthrastraea appears generally associated with porites in patches five basic growth forms of porites are observed thin branching or finger shaped thick branching to columnar domed to hemispheric encrusting and platy to dish differences in coral morphology are used to define a relative water depth zonation in monogeneric reefs the distribution of these growth forms was principally controlled by water depth the reef flat is dominated by small thin branching or finger shaped corals that are replaced towards the reef front by domed to hemispheric corals commonly encrusted by coralline algae downslope columnar morphologies grade into thin branching shapes the reef morphologies are variable throughout the five mixed siliciclastic carbonate units at the platform scale the first and oldest unit is dominated by bioclasts whereas units 2 3 and 5 are porites dominated sigmoid complexes unit 4 is a well developed biohermal complex mainly composed of tarbellastraea these units started to develop as early as middle tortonian and stopped as late as early messinian and show a progradational trend where the two latest units are well developed thus carbonate production changed from grain producing biota in the basal unit to framework producing biota in the overlying units consistent with evolution from a distally steepened ramp to a reef rimmed shelf at the scale of individual reef units the relative water depth zonation of the corals is controlled by ecological changes substrate nutrients synecologic relations and diversification of coral species in the transects across the carbonate platform related to the different units the coral zonation records changes in spatial distribution of corals in response to ecological stresses and changes in regional and global environments tectonic relative sea level changes and runoff

connectivity of fluvial point bar deposits an example from the miocene huesca fluvial fan ebro basin spain the huesca fluvial fan miocene ebro basin spain contains a low gradient mixed load fluvial system a detailed outcrop study of its meandering river deposits shows that the preservation of elongate channel floor sandstone ribbons is common and that these deposits create a continuous along stream sand to sand connectivity between successive crescent shaped sandy point bar accumulations on both sides of the channel the combined appearance of the sandstone resembles a string of beads consisting of a thin sinuous ribbon with thick and wide protuberances on either side the studied meandering river sandstone bodies are laterally amalgamated and vertically stacked with a net to gross n g ratio of about 40 they occur in 1 1 5 km 0 62 1 mi wide northeast southwest oriented elongate meander belts occupying paleochannels beyond these belts the sandstone is limited to isolated bodies with a very low n g ratio a generic model of the string of beads geometry based on the outcrop data analysis showed a significant increase of bulk rock volume for the connected string of beads compared with the model of isolated point bars the outcrop results demonstrate the potential for channel floor sandstone bodies to be preserved in a low gradient mixed load fluvial system and their importance in connecting point bar units in an along stream direction we recommend that fluvial reservoir architecture modeling programs include a function that allows the connectivity between channel floor and point bar architectural elements this may greatly impact the estimated reservoir volumes and recovery factors in primary and secondary production as well as influence the sweep efficiency of enhanced recovery technologies marinus e donselaar received his m sc degree in geology from the university of utrecht and his doctor of science degree in reservoir geology from delft university of technology both in the netherlands he worked at the comparative sedimentology division at the university of utrecht since 1987 he has been a lecturer in sedimentology at delft university of technology his research interests are in the modeling of fluvial and barrier island reservoir architecture irina overeem has a ph d from the faculty of civil engineering and geosciences delft university of technology netherlands where she was an assistant professor in geological modeling from 2005 to 2007 her research focuses on the numerical modeling of fluviodeltaic processes over the last six years she has held a position at institute of arctic and alpine research instaar and she is presently working at the community surface dynamics modeling facility at the university of colorado

an analysis of the low frequency current fluctuations in the strait of georgia from june 1984 until january 1985 abstract a description of the low frequency ap 10 to 30 days period current fluctuations in the strait of georgia is presented velocity time series from four cyclesonde moorings and five current meter mooring spanning the time interval from june 1984 until january 1985 are analyzed emphasis is placed on identifying the forcing mechanisms and determining the spatial structure of low frequency flow the nonlinear interaction of semidiurnal tidal constituents with bottom topography caused a near bottom low frequency oscillation that was coherent over the span of the experimental array ap 11 km the tides were important elsewhere in the water column too and altogether directly accounted for 37 of the low frequency energy in the strait there is evidence of significant wind forcing an empirical orthogonal function analysis of the vertical structure of the current fluctuations yields strong evidence for the existence of wind forced ekman spirals typically the orthogonal modes that dominate the var

deep water renewal in the upper basin of loch sunart a scottish fjord abstract recording current meters were deployed near the surface and bottom in the upper basin of loch sunart during the summers of 1987 1989 and 1990 the measurements revealed frequent though irregular deep water renewal events when the basin water was replaced by density driven intrusions the data suggested that these events were induced by wind enhanced estuarine circulation during periods of low fresh water runoff a semi implicit laterally integrated estuarine model was modified to allow variable vertical grid spacing and to permit the sea surface to move vertically through the grid both modifications being necessary in order to apply the model to the sea loch environment a turbulence closure scheme was also incorporated the model can simulate the evolution of the salinity field over periods of several weeks and was used to examine the mechanisms that induce deep water renewal model results suggested that very weak stratification in the basin is required for renewal to occur and indicated

the simulation of deep water exchange in a fjord indian arm british columbia canada abstract a numerical model is used to simulate deep water renewals that were observed to occur in burrard inlet indian arm over a time period of about 100 days during winter 1984 85 the renewals bottom water flowing from burrard inlet into indian arm occurred or intensified during neap tide and caused a steady increase in the density near the bottom in indian arm the model successfully reproduces the renewal events for a simulation time of at least 85 days it uses a mellor yamada level two turbulence closure scheme for which the local turbulent energy production is balanced by local dissipation and for which the turbulent length scale is prescribed the length scale varies linearly with depth near the surface and bottom and is constrained to never be larger than 1 20 of the water depth and 2 the ozmidov length scale a lower bound is imposed on the vertical diffusion coefficients that depends on the brunt vaisala frequency n its magnitude for a given n is different in burrard inlet and in

dependence of currents and density on the spring neap cycle and the diurnal inequality in burrard inlet british columbia simulations and observations abstract observations of the circulation in a hole near a constriction in burrard inlet are simulated using a two dimensional i e laterally integrated numerical model the model uses a level 2 version of the mellor yamada turbulence closure scheme during spring tides when mixing is at its most intense the density in the hole decreases increases during the large small floods and there is an up inlet current pulse into the hole during each flood regardless of the flood s strength during the large floods in particular the simulation is significantly improved if the explicit influence of horizontal spatial variations on the production of turbulent kinetic energy is taken into account during neap tides the simulated density is much less variable and the currents in the hole are much weaker in agreement with the observations the model differs from the observations in that the simulated current pulses are significantly weaker than the observed pulses possibly because the cross channel averages

a numerical model of the circulation in knight inlet british columbia canada abstract during spring 1988 a period of low freshwater runoff and summer 1989 a period of high freshwater runoff month long observations of velocity temperature and salinity were made throughout the water column in knight inlet both up inlet and down inlet of the sill measurements were made at depths of 2 4 6 9 and 12 m using s4 current meters at depths down to about 200 m using profiling current meters and at depths deeper than 200 m using aanderaa current meters anemometers were deployed at two locations along the inlet a laterally integrated two dimensional numerical model of the inlet that uses the mellor and yamada level 2 5 turbulence closure scheme and that accounts for the combined influence of the winds tides and freshwater runoff has been used to produce 30 day simulations of the velocity and density field in the inlet the vertical coordinate is transformed in the model so that very fine vertical resolution can be attained near the surface even though the tidal range is larg

the deepwater exchange cycle in indian arm british columbia abstract a silled fjord on the british columbia coast indian arm was used to study the exchange processes controlling deepwater exchange in fjords bottom water renewal took place during the winter of 1984 85 hydraulic control of the exchange is exerted over the long sill which restricts access to the fjord the maximum density at the sill occurs during neap tides no distinct peaks in the velocity at the sill are observed during periods of inflow reduced vertical mixing over the long sill during periods of neap tides sets the timing of the bottom water exchange during each inflow over the 1984 85 winter about 20 of the water in the fjord was replaced these exchanges occurred over periods of 5 10 days between the exchange years diffusion of the water in the basin is important in conditioning the water for the next exchange event the vertical diffusion coefficient k t was determined from an analysis of the salinity data and was found to be related to the buoyancy frequency n by the relationship k v n 1 6

facies architecture of the stuttgart formation schilfsandstein upper triassic central germany and its comparison with modern ganga system india abstract the stuttgart formation schilfsandstein is approximately 50 m thick in thuringia representing deposition during the mid carnian wet intermezzo stratigraphically it occurs between the grabfeld and weser formations which formed under arid conditions it comprises nne ssw trending elongate anastomosing channelized sand rich bodies with erosional bases channel belts that are several kilometres wide and pass laterally into predominantly mudstones deposited in interfluve areas the source area of these clastics was the uplifted norwegian caledonides muddy interfluve facies is dominant in exposures in thuringia central germany the lower stuttgart formation has an unconformable base that is locally overlain by metre thick basal beds these consist of grey mudstones and thin sandstones deposited under humid conditions in predominantly shallow brackish water environments after a marine ingression via the eastern carpathian upper silesian gate the following 30 40 m grey fine grained sandstones siltstones and mudstones were deposited in fluvial environments in channel belts and interfluve areas under humid conditions these are followed by predominantly reddish mudstones and sandstones of mainly fluvial origin deposited under somewhat drier conditions with seasonal droughts the upper stuttgart formation may be more than 16 m thick it comprises reddish and grey sandstones and mudstones that were mostly deposited in lake delta settings by recurring flash floods during the deposition of this unit climate was weakly humid with less prominent seasonal draughts the modern ganga plain of india is an analogue for the depositional setting of the stuttgart formation climatic conditions in ganga plain are humid monsoonal with seasonal droughts and roughly comparable with those interpreted for mid carnian times in germany the sandy deposits of incised channel belts and channels and muddy deposits of interfluve areas in the ganga plain are comparable with the sandstone dominated channelized facies and mudstone dominated interfluve facies of the stuttgart formation respectively

the influence of the spring neap tidal cycle on currents and density in burrard inlet british columbia canada abstract tidal mixing through two constrictions at the entrance to a fjord type estuary in british colombia canada is studied from a mooring programme in the spring of 1995 and from ship born adcp measurements in the spring of 1997 time series from the moorings show that during spring tides currents at depth are as high as 1 5 m s 1 small floods bring outside water through the narrows relatively unmixed which sinks down to depth in contrast large floods result in intrusions of highly mixed water up to 1 kg m 3 lower in density during neap tides currents at depth are generally small density decreases slowly and turbulent vertical diffusion is believed to be the dominant process at depth analysis of vertical diffusion near the bottom at one station during neap tides produces estimates of the vertical eddy diffusivity which are somewhat higher than those from similar studies in other b c fjords results from the adcp study reveal the presence of strong vertical velocities downstream of the narrows during large floods possibly associated with hydraulic jumps the flow through the narrows at such times is indeed supercritical with respect to the first baroclinic mode

alluvial pedogenesis in pleistocene and holocene mississippi river deposits effects of relative sea level change comparison of pleistocene and holocene soils developed in mississippi river meander belt deposits in louisiana illustrates the influence of relative sea level change on pedogenesis holocene and pleistocene meander belts have similar landscape morphologies lithofacies and soil characteristics and probably formed under similar hydrologic regimes the pleistocene avoyelles prairie meander belt is now terraced but it was originally graded to a lower relative sea level position than the holocene flood plain holocene alluvial soils are generally weakly expressed cumulative profiles with abundant redoximorphic features and formed on an aggrading flood plain with a shallow fluctuating water table the soil morphology varies with respect to landscape position and overbank lithofacies pleistocene alluvial paleosols show evidence for two stages of pedogenesis during the first stage of pedogenesis water table fluctuations and flood plain aggradation produced profiles with color mottles iron and carbonate nodules and weak b and c horizons similar to holocene flood plain soils the second stage of pedogenesis occurred after the avoyelles prairie was terraced and the regional water table fell a minimum of 30 m improved soil drainage created oxidizing and acidic conditions removed free carbonates dehydrated iron oxides and transformed clay minerals this stage produced pleistocene profiles with brighter matrix and mottle hues lower ph values larger and harder iron nodules and greater kaolinite contents than comparable holocene flood plain soils the primary influence on regional water table lowering in the southern lower mississippi valley was relative sea level fall mississippi river flood plain lowering adjacent to the avoyelles prairie most likely occurred between the end of oxygen isotope stage 3 and the maximum period of valley entrenchment during oxygen isotope stage 2 water table fall affected pedogenic processes a minimum of 400 km upvalley of the continental shelf margin pleistocene mississippi river paleosols represent excellent analogs for interpreting ancient alluvial paleosols formed during episodes of base level fall and valley incision as fluvial entrenchment terraced the meandering avoyelles prairie a pedogenic threshold was crossed that altered the pathway of chemical weathering the complexity of a multiple step pedogenic history also highlights the fact that interpretation of relative profile development as a function of time can be problematic

radiocarbon reservoir effect and the timing of the late glacial early holocene humid phase in the atacama desert northern chile we revise substantially the regional chronology of lake level fluctuations from the late glacial early holocene humid phase along a high altitude transect 3500 to 4500 m between 18 s and 28 s in the southwestern altiplano of northern chile radiocarbon dates and 210pb profiles for limnic and terrestrial materials allow us to estimate and justify reservoir correction values for conventional 14c dates our chronology suggests that the latest pleistocene early holocene humid phase started between 13 000 and 12 000 14c yr b p and that maximum lake levels were reached between 10 800 and 9200 14c yr b p this is significantly younger than what has been established so far for the titicaca uyuni basin in bolivia the paleolakes disappeared sometime between 8400 and 8000 14c yr b p our revised chronology agrees with the regional history of human occupation and is broadly synchronous with vegetation changes in subtropical continental south america and with the onset of wetland expansion in the northern hemisphere tropics

a modal decomposition of the internal tide in a deep strongly stratified inlet knight inlet british columbia this paper seeks to answer the question how much of the internal tide propagating up knight inlet british columbia is reflected by a right angled bend the internal tide in knight inlet is generated by the interaction of the barotropic tide with a shallow sill seaward of the bend it then propagates in both directions as a traveling kelvin wave the up inlet propagating wave then encounters the bend where some of it may be reflected the study is based upon 2 months of cyclesonde current meter data from four stations taken during the summers of 1981 and 1983 the vertical profiles of amplitude and phase of the m2 constituent of longitudinal velocity and density fluctuations are decomposed into a truncated series of normal modes for waves propagating both up inlet and down inlet at the two stations up inlet of the sill acceptable fits can be obtained using only two up inlet propagating waves indicating that the data are compatible with the low reflection found by webb and pond 1986 at the two stations seaward of the sill the up inlet energy flux is of the same order of magnitude as the down inlet flux indicating a second source of internal tide seaward of those two stations the results indicate that only 30 50 of the power removed from the barotropic tide is being fed into the internal tide in the summer

tidally forced internal wave mixing in a k e model framework applied to fjord basins abstract a simple method for including tidally forced internal wave mixing in a two equation turbulence closure framework the k e model is presented the purpose is to model the vertical mixing in the basin waters of stagnant sill fjords an internal wave energy iwe term of the form an where n is the buoyancy frequency and a is a weighted average of the locally available iwe is added to the equation for the turbulent kinetic energy tke the total available iwe f is given by the energy flux from the barotropic tide to baroclinic internal waves and a is determined assuming that all the available iwe is transferred to tke namely f an dv where the integral is taken over the entire volume of the fjord comparisons with observations from two scandinavian fjords show that the model successfully describes the vertical mixing in the basin water further the buoyancy term in the equation for dissipation of tke e is found to be irrelevant during stable stratification that is the empirical param

a numerical study of the tidal circulation and buoyancy effects in a scottish fjord loch torridon 1 the tidal and buoyancy driven circulation in loch torridon a scottish fjord is investigated using a three dimensional hydrostatic primitive equation model the predictions from the model have been quantitatively compared to available data gathered between 1998 and 2001 the model performed well in reproducing the tidal characteristics and density evolution of the fjord over the 3 month simulation period results show that tidal currents are dominated by the constraint imposed on the flow by the shallow sill separating the upper and middle basins the flow is strongly accelerated during flood and ebb tides and significant residual currents are generated that may influence exchange and residence times of the middle basin a strong baroclinic response to the flow over the sill is predicted throughout the fjord with a propagating linear m2 tide displacing isopycnals vertically by up to 32 m at the sill the formation of stationary lee waves on both flood and ebb tides is predicted with the wave generated during flood tide being notably larger as the growth of the ebb wave is inhibited by deep dense water this allows more energy to transfer into the seaward propagating internal tide as the tidal flow weakens the lee waves propagate over the sill and upstream estimates of the total vertical turbulent buoyancy flux in the fjord are made and the distribution of mixing over a tidal cycle is shown vertical mixing is seen to be highly spatially and temporally variable and strongly linked to the presence and dissipation of lee waves near the sill

a model study of density intrusions into and circulation within a deep silled estuary puget sound a laterally averaged hydrodynamical model is used to investigate episodic intrusions of denser more oceanic water across the shallow double silled entrance of puget sound and the resulting circulation within the interior deep basin tidal freshwater discharge and wind effects are also encompassed in model results model simulations were made of the 4 month period from december 1983 through march 1984 during that period hourly measurements of currents and salinity were made at the estuary entrance and on four moorings in the interior basin the first 60 days of salinity data were used with the model to choose rates of vertical turbulent mixing and the lag times between fresh water appearance at river gauges and its arrival in the main basin of the sound comparison of model results with the full 120 days of salinity and velocity data shows that the model incorporates the important circulation features of this estuary the model was then used to study intrusions and mixing in the sill region the model identifies these factors as controls on the occurrence and strength of intrusions the trans sill salinity gradient the intensity of tidal stirring and mixing over the sills the supply of fresher surface water resulting from river runoff and the winds time series of salinities in the interior basin show local maxima following local maxima in the trans sill salinity difference vertical transport in the sill region at both tidal and subtidal time scales is dominated by advection rather than diffusion though much of the vertical exchange occurs over the shallower sill a depth depression between the two entrance sills appears to be the site of significant overturning downwelling of surface water occurs on the landward side of both sills substantial freshening of the interior basin occurs during the winter months because river discharges are large and are stirred downward in the sill region to be entrained into landward bottom flows extraordinarily large river discharges can suppress the effect of large trans sill salinity differences with the effect of weakening potential intrusions winds can indirectly influence intrusions by longitudinally positioning fresher river influenced surface water in the sill region winds can directly influence intrusions via bottom compensation flows in admiralty inlet with northward winds encouraging intrusions and by changing salinities at the entrance to the sound and thus the trans sill salinity gradient