sediment dispersal and quantitative stratigraphic architecture across an ancient shelf two large 200 to 300 km near continuous outcrop transects and extensive well log data ca 2800 wells allow analysis of sedimentological characteristics and stratigraphic architecture across a large area ca 60 000 km2 of the latest santonian to middle campanian shelf along the western margin of the western interior seaway in eastern utah and western colorado usa genetically linked depositional systems are mapped at high chronostratigraphic resolution ca 0 1 to 0 5 ma within their sequence stratigraphic context in the lower part of the studied interval sediment was dispersed via wave dominated deltaic systems with a compound clinoform geomorphology in which an inner wave dominated shoreface clinoform was separated by a muddy subaqueous topset from an outer clinoform containing sand poor gravity flow deposits these strata are characterized by relatively steep net regressive shoreline trajectories 0 1 with concave landward geometries narrow nearshore belts of storm reworked sandstones 2 to 22 km wide offshore mudstone belts 250 km and relatively high sediment accumulation rates ca 0 27 mm year 1 the middle and upper parts of the studied interval also contain wave dominated shorefaces but coeval offshore mudstones enclose abundant isolated tide influenced sandstones that were transported sub parallel to the regional palaeoshoreline by basinal hydrodynamic tidal circulation these strata are characterized by relatively shallow net regressive shoreline trajectories 190 km and relatively low sediment accumulation rates ca 0 11 mm year 1 the change in shelfal sediment dispersal and stratigraphic architecture from i compound clinoform deltas characterized by across shelf sediment transport to ii wave dominated shorelines with isolated tide influenced sandbodies characterized by along shelf sediment transport is interpreted as reflecting increased interaction with the hydrodynamic regime in the seaway as successive shelfal depositional systems advanced out of a sheltered embayment utah bight this advance was driven by a decreasing tectonic subsidence rate which also suppressed autogenic controls on stratigraphic architecture

correlation and provenance of upper cretaceous campanian fluvial strata utah u s a from zircon u pb geochronology and petrography abstract detrital zircon and petrographic provenance analysis of upper cretaceous campanian strata corroborate correlation of the fluvial kaiparowits formation in southern utah with post castlegate strata of the mesaverde group in eastcentral utah sandstone samples of the kaiparowits formation in the kaiparowits plateau and mesaverde group neslen bluecastle tongue of castlegate farrer and tuscher formations in gray canyon north of green river utah contain six u pb detrital zircon age populations ranging in age from archean to late cretaceous thrust belt derived sublitharenite and quartzarenite of the lower part of the mesaverde group neslen and bluecastle lack or have only rare mesozoic grains but contain abundant archean proterozoic and paleozoic grains that record recycling of proterozoic paleozoic and jurassic sandstones exposed in uplifted thrust sheets to the west south and southwest derived feldspathic litharenite of the kaiparowits and farrer formations contains proterozoic grains and a diverse population of mesozoic grain ages archean grains are rare to absent maximum depositional ages interpreted from young zircon grains in two kaiparowits samples statistically overlap 40ar 39ar ages 76 74 ma from interbedded bentonitic tuffs and weighted mean ages of young grains from the farrer formation kolmogorov smirnoff statistics in conjunction with young grain ages and detrital age spectra corroborate petrographic evidence which indicates that the kaiparowits rivers were connected northward with a river system that deposited the farrer formation the young grain ages although imprecise indicate that the uppermost mesaverde group strata of the tuscher formation are younger than the kaiparowits formation and record partitioning of the former foreland basin by laramide uplifts

observations of a deep mixing event in crater lake oregon we present observations of the evolution of a deep mixing event in a deep temperate lake the observations were obtained from thermistors mounted on a long term mooring in the lake the event seems to have originated near 150 m depth and resulted in a plume or layer of cold water from the upper half of the lake that descended to the lake bottom 590 m over a 3 d period net mixing associated with this event resulted in an overall vertical heat exchange of nearly loi j and a volume exchange of 0 7 3 2 km 4 18 of the lake volume between the upper and lower portions of the lake the deep water displaced during the event is estimated to have carried 0 32 5 x lo6 mol of nitrate to the upper lake which accounts for a significant portion of the average annual nitrate flux 2 4 x 10 mol yr thought to be upwelled in this highly oligotrophic system

decoding downstream trends in stratigraphic grain size as a function of tectonic subsidence and sediment supply downstream grain size fining in stratigraphy is driven primarily by selective deposition of sediment and the long term efficiency of this process is determined by 1 the magnitude and characteristics of the input sediment supply 2 the spatial distribution of subsidence rate which creates accommodation for sediment preservation and 3 the dynamics of sediment transport and deposition a key challenge is to determine how these first two factors control the caliber and spatial distribution of deposits over time scales of 10 4 10 6 yr without incorporating sediment transport details that are largely unknowable for time averaged stratigraphy in the geological past we address this using grain size data collected from fluvial conglomerates in the eocene pobla basin spanish pyrenees a synorogenic basin where the timing of sediment deposition is well constrained the sediment budget is closed and good exposure enables time lines within stratigraphy to be picked out unambiguously for successive stratigraphic horizons downstream trends in grain size and composition are derived for basin filling sediment routing systems with length scales of 6 and 40 km respectively our data show that the rate of grain size fining varies over time and with system length and can be linked to changes in source area these results are contrasted with grain size data from the antist group a 60 km long oligocene system that mantles the southern pyrenees where very slow rates of grain size fining on the wedge top of this fold and thrust belt are observed we apply a self similarity based selective deposition model to quantify the competing controls of tectonic subsidence and sediment supply on derived grain size trends and model results are compared with independent constraints on the eocene oligocene evolution of the pyrenees our results suggest that it is now possible to invert time averaged grain size trends in stratigraphy to gain quantitative information on the geological boundary conditions governing the evolution of sedimentary basins

making geological sense of big data in sedimentary provenance analysis abstract sedimentary provenance studies increasingly apply multiple chemical mineralogical and isotopic proxies to many samples the resulting datasets are often so large containing thousands of numerical values and complex comprising multiple dimensions that it is warranted to use the internet era term big data to describe them this paper introduces multidimensional scaling mds generalised procrustes analysis gpa and individual differences scaling indscal a type of 3 way mds algorithm as simple yet powerful tools to extract geological insights from big data in a provenance context using a dataset from the namib sand sea as a test case we show how mds can be used to visualise the similarities and differences between 16 fluvial and aeolian sand samples for five different provenance proxies resulting in five different configurations these configurations can be fed into a gpa algorithm which translates rotates scales and reflects them to extract a consensus view for all the data considered together alternatively the five proxies can be jointly analysed by indscal which fits the data with not one but two sets of coordinates the group configuration which strongly resembles the graphical output produced by gpa and the source weights which can be used to attach geological meaning to the group configuration for the namib study the three methods paint a detailed and self consistent picture of a sediment routing system in which sand composition is determined by the combination of provenance and hydraulic sorting effects

marine and nonmarine gas bearing rocks in upper cretaceous blackhawk and neslen formations eastern uinta basin utah sedimentology diagenesis and source rock potential the upper cretaceous blackhawk and neslen formations in the eastern uinta basin contain large amounts of thermogenic gas that was generated from interbedded humic rich source rocks the geometry and distribution of hydrocarbon source and reservoir rocks are controlled by depositional environment the blackhawk composed of laterally extensive sandstone and locally interbedded carbonaceous siltstone and minor coal reflects deposition in nearshore marine and backshore environments the neslen contains organic rich siltstone and mudstone with lesser amounts of carbonaceous shale coal and lenticular sandstone that formed in coastal and lower alluvial plain depositional settings potential reservoir sandstones are composed dominantly of monocrystalline quartz grains and sedimentary lithic fragments mechanical compaction during early burial was followed by the precipitation of quartz carbonate and barite later in the burial history variations in porosity and permeability 2 10 1 md reflects the presence of authigenic clay mineral cements and dissolved lithic grains natural fractures cemented with carbonate barite and kaolinite occur locally active hydrocarbon generation occurred in the neslen and blackhawk during the oligocene and miocene when these units were near their maximum burial depth and temperature the rate of hydrocarbon generation decreased from the late miocene to the present owing to widespread cooling that occurred in response to regional uplift and erosion associated with the development of the colorado plateau temporally equivalent rocks in other areas of the basin may have experienced similar diagenetic and hydrocarbon generation histories

thin section grain size analysis revisited existing proposals for converting thin section data to their sieve equivalents are all flawed in various ways while questions concerning the significance of the grain size of spherical grains measured on a volume frequency basis in thin section using units and of non spherical ellipsoidal grains using both millimetres and units have not been satisfactorily resolved in the literature it can be shown mathematically that the mean thin section diameters of spherical grains or axis lengths of a series of parallel sections through ellipsoidal grains will underestimate the dimensions of the corresponding central section i e one passing through the grain centre by 0 2023 when measured on a volume frequency basis in order to approximate the effect of measuring particle size on random cuts through ellipsoidal grains the dimensions of a series of sections cut in 49 unique directions symmetrically arranged and evenly spread with respect to the ellipsoidal axes were calculated this calculation was carried out for five different ellipsoids which between them covered the mean sphericity and thin section axial ratio values normally encountered among naturally occurring quartz grain populations the data indicated that the mean true nominal diameters d of ellipsoidal quartz grains can be obtained in thin sections from the mean nominal sectional diameters d and major axes of the central sections derived from the observed values by multiplying the millimetre means by 1 1318 and subtracting 0 2023 from the means using the following equations a rough estimate to within c 5 of both the mean nominal diameters and the mean long axes of ellipsoidal quartz grains can be arrived at by applying a simple correction factor to the mean long axis lengths as measured in thin section using either millimetres or units

basin scale diagenetic alteration of shoreface sandstones in the upper cretaceous spring canyon and aberdeen members blackhawk formation book cliffs utah abstract leached zones whitecaps and dolomite cement bodies are volumetrically and areally significant features in shoreface sandstones of the upper cretaceous spring canyon and aberdeen members blackhawk formation book cliffs utah quantitative spatial and stratigraphic data of their distribution together with petrography and geochemistry allow development of a model for their formation within a sequence stratigraphic framework leached zones up to 5 m thick and 15 km in lateral extent are present beneath coals capping parasequences concretionary dolomite cement is present in shoreface sandstones downdip of parasequence capping coals and associated whitecaps these concretions are up to 2 m thick and 6 m in length and are present for up to 7 km downdip of these coals petrographic and field data indicate an early diagenetic timing for whitecap and dolomite cement formation 13c data suggest carbonate derivation from detrital dolomite whereas 18o data suggest that cement precipitated from porewater with a significant meteoric component although later diagenetic re equilibration and recyrstallization cannot be rejected we propose that organic acid generation during early diagenesis of coals led to the leaching of detrital dolomite from underlying sandstones and the formation of whitecaps meteoric water flowed basinward in response to base level lowering and sequence boundary development in the upper part of the aberdeen member remobilizing dolomite into shoreface sandstones dolomite precipitation resulted from the mixing of these meteoric fluids with downdip marine pore fluids and the presence of detrital dolomite in the shoreface sandstones that acted as nucleation sites for dolomite precipitation the geometry and extent of dolomite cement in the spring canyon and aberdeen members is in marked contrast to the much greater spatial extent of such cement in low accommodation space settings such as the stratigraphically younger desert member blackhawk formation the relatively simple aggradational to progradational evolution of the spring canyon and aberdeen member parasequences with only minor sequence boundary development in its upper part resulted in spatially limited meteoric fluid input into shoreface sandstones this resulted in dolomite cementation of shoreface sandstones up to a maximum of 7 km downdip of leached zones in the desert member extensive meteoric fluid migration as a result of major sequence boundary development resulted in dolomite cementation of shoreface sandstones for over 25 km downdip of leached zones this highlights that the degree and extent of early fluid diagenesis can be significantly controlled by the nature of sequence development having clear implications for developing predictive models for porosity permeability evolution in sandstone reservoirs

the effects of source lithology transport deposition and sampling scale on the composition of southern california sand the transverse ranges of southern california represent an uplifted and variably dissected mesozoic magmatic arc and mesozoic to holocene sedimentary and volcanic strata deposited in convergent and transform tectonic settings modern sand within part of the western transverse ranges represents first order sampling scale of the santa monica and the san gabriel mountains second order sampling scale of the santa clara river draining both mountain ranges and third order sampling scale of the beach system between the mouth of the santa clara river and the eastern santa monica mountains and turbidite sand of the hueneme mugu submarine fan source lithology includes plutonic and metamorphic rocks of the san gabriel mountains and sedimentary and volcanic rocks of the santa monica mountains first order sands have large compositional variability sand from local coastal drainage of the santa monica mountains ranges from basaltic feldspatholithic to quartzofeldspathic sand of the san gabriel mountains local drainages has three distinct petrofacies ranging from metamorphiclastic feldspatholithic to mixed metamorphi plutoniclastic and plutoniclastic quartzofeldspathic second order sand is represented by the main channel of the santa clara river the sand has an abrupt downstream compositional change from feldspathic to quartzofeldspathic third order sand beaches and deep sea turbidite samples of the santa monica basin is quartzofeldspathic beach sand is more quartz rich than is santa clara river sand whereas turbidite sand is more feldspar rich than is beach sand deep sea sand has intermediate composition with respect to second order samples of the santa clara river and third order samples of the beach system suggesting that 1 the santa clara river is the main source of sediments to the marine environment and 2 local entry points from canyons located near local drainages may generate turbidity currents during exceptional flood conditions petrologic data of modern sand of the study area are highly variable at first and second order scale whereas third order sand is homogenized the homogenized composition of deep marine sand is similar to the composition of most ancient sandstone derived primarily from the mesozoic dissected magmatic arc of southern california this study of the western transverse ranges illustrates the effects of source lithology transport depositional environment and sampling scale on sand composition of a complex system which provides insights regarding actualistic petrofacies models

facies control on sandstone composition and influence of statistical methods on interpretations in the john henry member straight cliffs formation southern utah usa abstract the upper cretaceous john henry member of the straight cliffs formation preserves regressive shoreface and channel facies and transgressive lagoonal tidal inlet facies that suggest distinct modal sandstone compositions detrital modes from six sandstone facies upper shoreface lower shoreface deflected mouth bars fluvial channels tidal inlets and washover fans and their spatial and temporal variations provide additional data regarding the depositional environments and setting of the john henry member three statistical methods were utilized univariate standard deviation and confidence interval and multivariate logratio transformations to assess the compositional difference between facies using estimation of means both univariate statistical methods have some inherent problems standard deviation does not account for sample size while the confidence interval method incorporates a t test to account for only some of the uncertainty of small sample size the results of the univariate methods differ slightly and both indicate statistically distinct sandstone compositions based on facies multivariate statistics are much more robust and suggest similar trends yet display different compositional means and have inconclusive confidence fields as they incorporate all of the uncertainty associated with small sampling sizes in general sandstone compositions become more quartz rich and compositionally mature as sediment is transported from proximal fluvial environments to distal upper shoreface environments this trend reflects the degree of preferential reworking or winnowing of unstable grains prior to lithification more complicated relationships are observed as facies distributions shift through space and time sandstone compositions support a deflected wave dominated deltaic interpretation for the john henry member in this area sandstone compositions become more lithic rich from north to south corresponding to the facies distribution of upper shoreface and deflected mouth bars respectively mouth bars occur at the intersection of the fluvial channel and the coastline where sand is deflected via longshore drift to the southern portion of the field area upper shoreface facies located further away from mouth bar facies are heavily reworked by wave processes and contain more mature quartz rich modal compositions additionally high feldspathic and lithic concentrations in tidal inlet facies suggest that this facies was sourced closer to mouth bars rather than updrift upper shoreface sediments a shift in sandstone composition occurs at the end of the second transgressive regressive cycle of the john henry member throughout the rogers canyon area this compositional change is concurrent with a relatively large basinward shift in facies which suggests that it reflects the transition from regressive to transgressive facies associated with the relative sea level fall rather than a change in the main sediment source area

drivers of deep water renewal events observed over 13 years in the south basin of lake baikal lake baikal with a depth of 1637 m is characterized by deep water intrusions that bridge the near surface layer to the hypolimnion these episodic events transfer heat and oxygen over large vertical scales and maintain the permanent temperature stratified deep water status of the lake here we evaluate a series of intrusion events that reached the bottom of the lake in terms of the stratification and the wind conditions under which they occurred and provide a new insight into the triggering mechanisms we make use of long term temperature and current meter data 2000 2013 recorded in the south basin of the lake combined with wind data produced with a regional downscaling of the global ncep ra1 reanalysis product a total of 13 events were observed during which near surface cold water reached the bottom of the south basin at 1350 m depth we found that the triggering mechanism of the events is related to the time of the year that they take place we categorized the events in three groups 1 winter events observed shortly before the complete ice cover of the lake that are triggered by ekman coastal downwelling 2 under ice events and 3 spring events that show no correlation to the wind conditions and are possibly connected to the increased spring outflow of the selenga river

processes of deep water renewal in lake baikal deep water renewal in lake baikal siberia the world s deepest lake and largest lake by volume is relatively fast water age calculated from tritium and helium as well as from chlorofluorocarbons does not exceed 19 yr relative saturation of dissolved oxygen typically exceeds 80 the equation of state of baikal water was determined including the effect of dissolved ions and silicic acid based on nearly 600 ctd profiles taken between 1993 and 1995 two mechanisms of deep water mixing were identified 1 in spring cold and relatively saline water from the selenga the major inflow to the lake forms a density plume that reaches the bottom of the central basin during april and early may due to entrainment of lake water the plume transports about 125 km of water per year to the deepest part of the basin later in spring the river water forms the thermal bar observed along the eastern shore there are indications that parts of the selenga are also plunging to the deep part of the southern basin 2 at academician ridge separating the cold and saline water of the central basin from the warmer and slightly less saline water of the northern basin horizontal mixing results in a water mass that can sink on either side of the sill whereas in the central basin the water mass stays at intcrmediatc depth in the northern basin it sinks to the decpcst part more detailed data are needed to quantify this density flux no indication of a wind induced thermobaric instability was found

detrital zircon provenance of the late triassic songpan ganzi complex sedimentary record of collision of the north and south china blocks the majority of the songpan ganzi triassic flysch sequence is believed to have derived from denudation of the dabie and sulu ultrahigh pressure uhp metamorphic belt in eastern china e g nie et al 1994 1 zhou and graham 1996 2 however intense debate still exists on the sources of

sediment supply dominated stratal architectures in a regressively stacked succession of shoreline sand bodies campanian desert member to lower castlegate sandstone interval book cliffs utah colorado usa

fragmentation model of the grain size mix of sediment supplied to basins abstracta key factor in the downstream dispersal and fractionation of sediment is the grain size distribution of sediment supplied by upstream catchments modeling of the grain size distribution of modern bedload in the main trunk channels of tectonically uplifting catchments including the sediment at their outlets and the weathering products of a range of bedrock lithologies in southern italy and sicily reveals fractal dimensions of 2 3 2 7 similar to the fractal dimension of many natural materials undergoing fragmentation we examine the impact of changing statistical properties of the grain size distribution of the sediment supply in simulating grain size trends in sedimentary basins model simulations show a marked movement of the gravel front and patterns of progradation and retrogradation in basin stratigraphy these grain size trends and sedimentary architectures are generated simply by variations in the grain size mix of the sediment supply without variations in base level or sediment discharg

deep water renewal in lake issyk kul driven by differential cooling during two field campaigns on lake issyk kul in march and august 2001 179 high resolution conductivitytemperature depth profiles were measured along with profiles of dissolved oxygen and light transmission on the basis of this extensive data set we investigated the large scale vertical advective processes responsible for deepwater renewal in lake issyk kul at some locations sampled in march variable peak structures in the tracer profiles were observed that indicate horizontally localized intrusions these intrusions have their origin in density plumes that propagate along the bottom of the channels in the eastern shelf region the cold dense water at the bottom of the channels is most likely generated by differential cooling of the water in the shallow shelf regions during winter during summer vertical advective processes appear to be limited to the upper 200 m where upwelling in the open water leads to a doming structure the august data support the results of earlier investigations that suggested that dynamic forcing by a basinwide gyre is responsible for the upwelling in the open water

sandstone detrital modes central utah foreland region stratigraphic record of cretaceous paleogene tectonic evolution abstract within a sedimentary basin the analysis of sandstone petrofacies defined by detrital modes of framework grains is a powerful means to detect areal or temporal changes in provenance related to evolving paleotectonics and paleogeography in the central utah foreland the regional tectonic transition from thin skinned sevier thrusting during the late cretaceous to deep seated laramide deformation during the paleogene is recorded by four contrasting petrofacies in uppermost cretaceous and paleogene sandstones of fluvial and deltaic facies coeval subaqueous environments were marine during the cretaceous and lacustrine during the paleogene the cretaceous quartzose petrofacies qm93 f1 lt6 of mainly campanian age was derived from sedime tary sources in the active sevier thrust belt and transported into a broad adjacent foreland basin by transverse paleocurrents the heterogeneous cretaceous quartzolithic petrofacies qm40 70 f5 20 lt25 40 of uppermost campanian age was derived from the sevier orogenic belt during the waning phases of sevier tectonism and was distributed by longitudinal paleocurrents within a foreland basin whose floor had begun to be deformed by incipient laramide tectonism the paleogene feldspathic petrofacies qm50 f35 lt15 in paleocene and eocene strata is composed of arkosic detritus that was derived principally from basement rocks then exposed in the extensive san luis uplift of laramide age in south central colorado the feldspathic sand was transported to the laramide uinta basin and vicinity in utah by a trunk river which flowed generally northwestward between monoclinal laramide uplifts of the colorado plateau the paleogene quartzolithic petrofacies qm75 f2 lt23 of dominantly eocene age was derived mainly from sedimentary sources in the laramide uinta uplift to the north but also in part from similar sources in the dormant sevier thrust belt to the west in the rocky mountain and intermountain regions more widespread and systematic use of petrofacies analysis in combination with standard paleocurrent and lithofacies analyses could lead to better definition of the timing of laramide uplift and improved understandi g of the evolution of complex laramide paleogeography

a three dimensional numerical model of deep ventilation in temperate lakes because of the variation in the temperature of maximum density with depth it is known that the upper above 250 m and lower water columns circulate separately in deep temperate lakes while near surface water overturns twice per year the deep waters often mix only partially during a complete annual cycle it is believed that deep convection is triggered by storm surge forcing of some of the relatively cold upper water column downward through its compensation depth so that it becomes unstable and sinks the scale and intensity of the resulting deep water forming plumes are studied numerically a high resolution model based on the nonhydrostatic boussinesq equations is used deep water formation is initiated by applying a statically unstable initial temperature profile over various regions of the domain at depths below 300 m the grid spacing is small enough to resolve individual plumes which carry surface water to the lake bottom the domain of study is also large enough that the geostrophic eady 1949 wave breakup of newly formed deep water can be observed it is found that when the initial instability is applied in midbasin remote from the solid sidewalls relatively little fresh deep water is formed and the fluid quickly reaches a geostrophic and hydrostatic balance vigorous vertical mixing ceases after 4 days and the resulting baroclinic fluid has a well defined and predictable scale in contrast when the initial instability is applied immediately adjacent to a solid boundary vigorous plume motion continues for the duration of the numerical simulations 12 days producing a much greater volume of fresh deep water a parametric study investigates the scale and intensity of this boundary mixing it is found that reduced surface water temperature coriolis acceleration or higher horizontal diffusion coefficients increase the rate of deep water renewal

downstream changes in sand composition roundness and gravel size in a short headed high gradient stream northwestern italy abstract we assessed changes in grain composition and roundness of the 1 2 and 2 3 size fractions of sand along a 16 km length of the graveglia river liguria italy to its mouth at the tyrrhenian sea and then for 1 km along the beach rocks exposed in the drainage area include ophiolites ribbon chert limestone shale sandstone and quaternary sands the erosion of shale and limestone bedrock yields large amounts of sand but sand grains of these rock types decrease rapidly in abundance downstream chiefly through dilution rather than abrasion carbonate rock fragments that reach the beach survive wave abrasion but most shale grains do not predictably monocrystalline and polycry talline quartz and chert are the most durable grain types but serpentine basalt and unidentified rock fragments also show significant resistance to both stream and wave abrasion polycrystalline quartz feldspar basalt serpentine sandstone and shale grains are more abundant in the coarser sand size fraction monocrystalline quartz carbonate rock fragments and unidentified rock fragments are more abundant in the finer sand size fraction and chert and plutonic rock fragments have no size preference a comparison of the outcrop areas of the different rock types with the corresponding percentages of different grain types present in each of three drainage areas indicates that shale which breaks down readily to silt and clay size particles and chert which does not readily break down into sand size fragments are underrepresented in the sands limestone and serpentine however are overrepresented in comparison to outcrop area in certain drainage areas the overrepresentation of limestone reflects in part a sampling bias sand was sampled adjacent to limestone outcrops but the overrepresentation of serpentine reflects its resistance to weathering compared to other aluminosilicates and its durability shale limestone and serpentine increase in roundness downstream and along the beach to a maximum limiting value of 5 rho units medium grained shale clasts attain high rounding in only a few kilometers of transport downstream decrease in gravel size follows an exponential formula that can be expressed in linear form using phi size size 0 1167 distance km 10 29

high resolution linkage of channel coastal plain and shallow marine facies belts desert member to lower castlegate sandstone stratigraphic interval book cliffs utah colorado usa

sequence stratigraphic significance of sharp based lowstand shoreface deposits kenilworth member book cliffs utah the kenilworth member of the blackhawk formation upper cretaceous campanian is nearly continuously exposed from price to hatch mesa in the book cliffs utah five main depositional environments are recognized coastal plain foreshore and upper shoreface lower shoreface inner shelf and incised valley fill deposits the shelf to shoreface deposits combine to form nine coarsening upward wave to storm dominated parasequences that are 7 32 m thick and that split basinward into smaller coarsening upward successions or bedsets that are 2 18 m thick a maximum of four bedsets occurs within an individual parasequence bedset bounding surfaces are occasionally marked by thoroughly bioturbated iron rich carbonate cemented sandstones within the parasequences in the subsu face similar bedset bounding surfaces may act as permeability barriers or baffles leading to reservoir compartmentalization parasequences 1 6 form an aggradational to progradational parasequence set of the highstand systems tract parasequences 7 and 8 occur as sharp based lowstand shoreface deposits at price river and battleship butte forming the attached lowstand systems tract and parasequence 9 forms the transgressive systems tract the base of each lowstand shoreface is marked by an organic rich lag deposit that consists of granules coarse grained sandstone wood fragments coal intraclasts and shell debris the sharp base basal lag deposit and basinward shift in facies delineate a sequence boundary at the base of each lowstand shoreface deposit the presence of two sharp based lowstand shorefaces suggests that the kenilworth lowstand was punctuated by a stillstand the sharp based lowstand shoref ce sandstones form the bulk of the attached lowstand systems tract and represent one end member in a continuum of lowstand deposits the other end member is the detached lowstand systems tract revising existing sequence stratigraphic models to include both types of lowstand systems tracts is a first step toward improving the accuracy of these models which are often used as prospecting tools in lowstand deltaic environments

dynamic versus flexural controls of late cretaceous western interior basin usa the united states cretaceous western interior basin has long been considered a foreland basin driven by the sevier thrust and associated basin sediment loads however flexural studies demonstrate that this effect exists only within a narrow band in front of the thrust belt most of the basin appears to be due to mantle flow induced dynamic subsidence associated with farallon plate subduction here we show how the components of evolving long wavelength dynamic subsidence and flexural subsidence created the accommodation space and controlled the stratigraphy across the western united states based on a correlated stratigraphic section across central utah and colorado these backstripped subsidence data reveal the dynamic topography driven nature of the western interior basin the results seem to support that the depocenters track the trough of dynamic subsidence with ca 18 myr cycles through time and space and the stratigraphic patterns of large scale progradation eastward migration of depocenter and regional clinoform like downlap are related with the dynamic subsidence interpretation of these data also provides more insights into the repeated ca 2 to 6 myr cycles of thrust induced subsidence in front of the thrust belt which control the local eastward progradation of the sand bodies from the thrust belt the dynamic flexural subsidence and eustatic sea level changes interacted and controlled the timing and distribution of unconformities our work shows how the stratigraphy precisely records the timing patterns and position of dynamic versus flexural subsidences and that combination of such data leads to important geophysical discoveries and supplies strict constraints for geodynamic modeling

isotope geochemistry of the tieluping silver lead deposit henan china a case study of orogenic silver dominated deposits and related tectonic setting the tieluping silver deposit which is sited along ne trending faults within the high grade metamorphic basement of the xiong er terrane in the qinling orogenic belt is part of an important recently discovered mesozoic orogenic type ag pb belt ore formation includes three stages an early barren quartz pyrite stage e an intermediate polymetallic sulfide ore stage m and a late barren carbonate stage l carbon sulfur and lead isotope systematics indicate that the e stage fluids are deeply sourced the l stage fluids are shallow sourced meteoric water whereas the m stage fluids are a mix of deep sourced and shallow sourced fluids sulfur and lead isotope data show that the ore forming fluids must have originated from a source with elevated radiogenic lead and low 34s values that differs significantly from exposed geologic units in the xiong er terrane the lower crust and the mantle this supports the view that the carbonate shale chert sequences of the guandaokou and luanchuan groups south of the machaoying fault might be the favorable sources although little is known about their isotopic compositions a tectonic model that combines collisional orogeny metallogeny and hydrothermal fluid flow is proposed to explain the formation of the tieluping silver deposit during the mesozoic collision between the north china craton and south china block early mid triassic indosinian orogeny crustal slabs containing the carbonate shale chert sequences of the guandaokou and luanchuan groups locally rich in organic matter carbonaceous shale were thrust northwards beneath the xiong er terrane along the machaoying fault metamorphic devolatilisation of this underthrust slab probably provided the ore forming fluids to develop the ag pb ore belt which includes the tieluping silver deposit fluids and magmas were emplaced during extensional stages related to the jurassic cretaceous yanshanian orogeny

tectonic control on coarse grained foreland basin sequences an example from the cordilleran foreland basin utah newly released reflection seismic and borehole data combined with sedimentological provenance and biostratigraphic data from upper cretaceous paleocene strata in the proximal part of the cordilleran foreland basin system in utah establish the nature of tectonic controls on stratigraphic sequences in the proximal to distal foreland basin during campanian time coarse grained sand and gravel were derived from the internally shortening charleston nebo salient of the sevier thrust belt a rapid regional campanian progradational event in the distal foreland basin 200 km from the thrust belt in 8 m y can be tied directly to active thrust generated growth structures and an influx of quartzose detritus derived from the charleston nebo salient eustatic sea level variation exerted a minimal role in sequence progradation

epithermal deposits in north xinjiang nw china the north xinjiang region nw china is an important part of the central asia orogenic belt situated at the junction of siberia tarim and kazakhstan plates it is an area characterized by multiple stages of phanerozoic continental growth during which several porphyry and epithermal systems were formed the relationship of these mineral systems to the geodynamic evolution of the region has not yet been well understood in this paper we list the main geological characteristics of 21 significant epithermal precious and base metal deposits in north xinjiang and classify them into high sulfidation and low sulfidation styles with the latter being predominant we have selected seven epithermal deposits representing different styles formed under different tectonic regimes and discuss their geology and geochemistry in some detail the deposit scale geology and geochemistry of epithermal systems in north xinjiang are essentially similar to those in other parts of the world all epithermal deposits in north xinjiang are hosted in volcanic rocks with ages ranging from devonian to triassic with the early carboniferous volcanic sequences being the most important followed by the permian and triassic the devonian early carboniferous host rocks belong to the calc alkaline series that developed in pre collisional arc back arc basin systems whereas the permian triassic host volcanic rocks of shoshonite series formed in post subduction regimes available isotopic ages of these epithermal systems cluster in two periods early carboniferous 320 ma and late carboniferous triassic 320 220 ma reflecting two metallogenic episodes that occurred during subduction related accretion and post subduction collision regimes respectively accordingly three groups of epithermal deposits in north xinjiang can be recognized as 1 pre collisional deposits without or with negligible collisional related modification 2 deposits formed in collision regime and 3 ore systems strongly overprinted by fluid flow in post subduction collision regime

tectonic implications from re os dating of mesozoic molybdenum deposits in the east qinling dabie orogenic belt abstract the east qinling dabie molybdenum belt is part of a larger east west trending metallogenic belt in eastern china most of the molybdenum deposits occur as porphyry or porphyry skarn type but there are also some vein type deposits following systematic re os dating of molybdenite from 13 deposits and comparisons with two previously dated deposits we have recognized that the molybdenum mineralization in the east qinling dabie belt was developed during hydrothermal activity linked to magmatism and the emplacement of granitoid stocks three pulses of granitoid magmatism and mo mineralization are recognized corresponding to significant tectonic events in the east qinling dabie belt vein type deposits dated at 233 221 ma were formed in detachment fractures indicating localized extension within the collisional setting of the north china and yangtze cratons i type and transitional i and s type granites and related mineralization dated at 148 138 ma may have formed part of a continental magmatic arc with widespread magmatism and back arc extension caused by subduction of the izanagi or paleopacific plate beneath the eurasian continent in a wnw ese direction in the late jurassic early cretaceous both s type and transitional s and i type granite associated porphyry molybdenum deposits dated at 131 112 ma are part of an extensive mineralization event throughout east china that can be ascribed to regional large scale lithospheric thinning delamination and thermal erosion

sediment routing controls on sandstone bulk petrographic composition and texture across an ancient shelf example from cretaceous western interior basin utah and colorado u s a

wind and buoyancy driven horizontal exchange in shallow embayments of a tropical reservoir lake argyle western australia many factors including depth vegetation density wind and gyres may act to influence the littoral exchange in a water body but very few studies have investigated the interaction between more than two of these factors at any time to investigate these controls on horizontal exchange in a large tropical reservoir we conducted a 9 d intensive field experiment in lake argyle western australia the experiment began with a 7 d cooling period that generated water in the shallows of the reservoir embayments that was persistently cooler than the interior this led to an underflow of dense water that moved from the lake boundary toward the center of the reservoir a three dimensional hydrodynamic model elcom was able to adequately reproduce this thermal structure and was used to demonstrate its sensitivity to wind sheltering effects and submerged macrophyte presence further analysis of the predictions indicated that when the ratio of the shear and buoyancy force averaged over 6 h b6h and 6 h averaged wind speed in the direction of the embayment u6h was 1 greater than 0 5 ms 1 and 4 5 ms 1 respectively the exchange was dominated by a topographic gyre formation 2 when 0 1 b6h 0 5 and 2 4 ms 1 u6h 4 5 ms 1 the resulting circulation was a combination of differential cooling flows and a topographic gyre circulation and 3 when u6h fell below 2 4 ms 1 purely buoyancy driven flow occurred but only if the buoyancy forces across the embayments were an order of magnitude greater than wind induced velocity shear

provenance environmental and paleogeographic controls on sandstone composition in an incised valley system the eocene la meseta formation seymour island antarctica abstract the eocene la meseta formation is the youngest exposed unit of the back arc james ross basin antarctic peninsula cropping out in seymour marambio island the formation comprises 720 m of clastic sedimentary rocks of deltaic estuarine and shallow marine origin it was subdivided into six unconformity based units valle de las focas acantilados campamento cucullaea i cucullaea ii and submeseta allomembers grouped into three main facies associations facies association i represents valley confined deposition in a progradational aggradational tide dominated and wave influenced delta front delta plain environment facies association ii includes tidal channels mixed tidal flats tidal inlets and deltas washover and beach environments facies association iii represents nonconfined tide and storm influenced nearshore environments la meseta formation sandstones are quartzofeldspathic with some hybrid arenites glauconite and carbonate bioclasts rich sandstone detrital modes are subdivided into two distinctive petrofacies the low quartz petrofacies petrofacies i q 12 interpreted to retain the original provenance signal and the high quartz petrofacies petrofacies ii q 55 and l 1 4 is clearly dominated by volcanic derived clasts it developed at times of high sea level and or during later stages of the valley fill when an energy fence at the shoreline prevented delivery of sediment from the antarctic peninsula thus enhancing the relative participation of local volcanic sources

fluid evolution of the yuchiling porphyry mo deposit east qinling china the yuchiling mo deposit east qinling china belongs to a typical porphyry mo system associated with high k calc alkaline intrusions the pure co2 pc co2 bearing c aqueous h2o naci w and

extensive carbonate cementation of fluvial sandstones an integrated outcrop and petrographic analysis from the upper cretaceous book cliffs utah abstract extensive large scale pervasive cementation in the form of cement bodies within fluvial strata has rarely been documented although fluvial strata commonly act as important hydrocarbon reservoirs as well as groundwater aquifers here we present outcrop petrographic and geochemical data for pervasive ferroan dolomite cement bodies up to 250 m in size from upper cretaceous desert member and castlegate sandstone fluvial strata exposed in the book cliffs in utah these cement bodies are present with coastal plain fluvial strata within both the desert and castlegate lowstand sandstones and are most abundant in the thin distal fluvial strata cement bodies are almost entirely absent in updip thicker fluvial strata petrographic observations suggest a predominantly early diagenetic timing to the mildly ferroan dolomite with a component of later burial origin 13 c values for the cement 4 8 to 5 7 v pdb suggest a marine derived source for the earliest phase with a burial organic matter source for later cement 18 o data 6 3 to 11 8 v pdb suggest precipitation from freshwater dominated fluids it is proposed here that dolomite was derived from leaching of detrital dolomite under lowstand coals and cementation took place in coastal aquifers experiencing mixed meteoric marine fluids as a result of base level fluctuations this data presented here shows that large cement bodies can be an important component within fluvial sandstones with a potentially significant impact upon both reservoir quality and fluid flow within reservoirs especially at the marine non marine interface

high resolution sequence stratigraphic correlation between shallow marine and terrestrial strata examples from the sunnyside member of the cretaceous blackhawk formation book cliffs eastern utah the sunnyside member of the upper cretaceous blackhawk formation in the book cliffs of eastern utah provides an ideal opportunity to investigate high resolution sequence stratigraphic correlation between shallow marine and terrestrial strata in an area of outstanding outcrop exposure the thick laterally extensive coal seam that caps the sunnyside member is critical for correlating between its shallow marine and terrestrial components petrographic analysis of 281 samples obtained from 7 vertical sections spanning more than 30 km 18 mi of depositional dip enabled us to recognize a series of transgressive regressive coal facies trends in the seam on this basis we were able to identify a high resolution record of accommodation change throughout the deposition of the coal as well as a series of key sequence stratigraphic surfaces the stratigraphic relationships between the coal and the siliciclastic components of the sunnyside member enable us to correlate this record with that identified in the time equivalent shallow marine strata and to demonstrate that the coal spans the formation of two marine parasequences and two high frequency fourth order sequence boundaries this study has important implications for improving the understanding of sequence stratigraphic expression in terrestrial strata and for correlating between marine and terrestrial records of base level change it may also have implications for improving the predictability of vertical and lateral variations in coal composition for mining and coalbed methane projects

the geometry and internal architecture of stream mouth bars in the panther tongue and the ferron sandstone members utah u s a abstract clinothems are seaward dipping beds which are deposited during the progradation of delta front mouth bars measurements taken from clinothems in the field and from geospatially constrained photo realistic virtual outcrops were used to record clinothem dip maximum bed thickness and bed thickness every 10 m along a series of depositional dip oriented profiles from two ancient river dominated delta successions which crop out in central utah usa these data show systematic changes in bed dip and bed thinning which highlight discrete packaging of the beds into bedsets interpreted to represent the progradation of stream mouth bars in the delta front individual bedsets are characterized by a progressive steepening of beds coupled with a more rapid thinning systematic collection of 2800 locations along 73 separate clinothems from the panther tongue sandstone member and parasequence 1f from the ferron sandstone were used to study the relationship between bed thickness dip and decay gradient parameter which describes the down dip bed thinning clinothems in the panther tongue are much longer and more gently dipping than the clinothems in the ferron sandstone in both systems beds can be clustered into groups bedsets which show a systematic decrease in values and an increase in dip angle boundaries between the groups are defined by a sudden increase in values and a concurrent decrease in dip angle these bedsets are interpreted to represent individual stream mouth bars which amalgamate to form mouth bar complexes within the delta front sand bodies the use of virtual outcrops was essential for the collection of the large volumes of thickness data and the recognition of very subtle 1 changes in dip angle which have made these interpretations possible

the castlegate sandstone of the book cliffs utah sequence stratigraphy paleogeography and tectonic controls abstract earlier stratigraphic work had predicted that at the type section of the castlegate formation the castle gate near price utah the unit consists of two sequences separated by a sequence boundary representing approximately one million years of unrecorded time although the type section is well exposed it consists of a monotonous succession of braided fluvial sandstones and no obvious boundary can be identified using facies criteria this is a good example of a cryptic sequence boundary petrographic data indicate however a significant change in detrital composition 20 m above the base of the section at a through going erosion surface that is therefore interpreted as the sequence boundary revised sequence correlations together with other petrographic data and regional paleocurrent patterns provide the basis for a model of the paleogeographic evolution of the area rocks assigned to the castlegate sandstone comprise two or possibly three sequences formed at times of slow regional subsidence erosional sequence boundaries and tilts in paleoslope between each sequence record thrust loading and unloading of the basin and the growing influence of intrabasinal upwarps movement of which was beginning to be affected by laramide movements toward the end of castlegate sedimentation

provenance of volcaniclastic beach sand in a magmatic arc setting an example from lipari island aeolian archipelago tyrrhenian sea lipari an active volcanic island in the aeolian magmatic arc is an excellent area to determine the effects of multiple source lithology climate weathering transport and depositional environment on epiclastic sand composition volcaniclastic sand samples from 12 modern beaches were petrographically characterized using the gazzi dickinson method and the proportions of source rocks in combination with topography in associated coastal drainage basins were quantified using gis several types of bedrock in the 12 drainage basins that are the likely prominent sources for sand at each sampled beach were recognized and divided into two categories of provenance lithotypes lavas and pyroclastic rocks ranging in composition from basaltic andesitic to andesitic to rhyolitic volcanic lithic fragments from lipari beach sand consist of colourless and black glassy volcanic fragments with lathwork felsitic vitric and microlitic textures moreover high amounts of detrital less durable minerals such as pyroxene olivine and fe oxides illustrate how the analysed sands preserve the source rock s provenance signals applying the concept of sand generation index we see that these lithotypes have different propensities to create detritus in terms of both grain size and composition clastic contribution from pyroclastic rock outcrops such as pumice is not found in the size ranges studied suggesting that these pumiceous source rocks probably only produce gravel or very fine sand and silt this finding has implications for the stratigraphic record because pumice clasts ranging from medium to fine grain size could be underrepresented in older volcaniclastic deposits and overrepresented in other size fractions

geomorphological and sequence stratigraphic variability in wave dominated shoreface shelf parasequences physical stratigraphy within shoreface shelf parasequences contains a detailed but virtually unstudied record of shallow marine processes over a range of historical and geological timescales using high quality outcrop data sets it is possible to reconstruct ancient shoreface shelf morphology from clinoform surfaces and to track the evolving morphology of the ancient shoreface shelf our results suggest that shoreface shelf morphology varied considerably in response to processes that operate over a range of timescales 1 individual clinoform surfaces form as a result of enhanced wave scour and or sediment starvation which may be driven by minor fluctuations in relative sea level sediment supply and or wave climate over short timescales 10 1 10 3 years these external controls cannot be distinguished in vertical facies successions but may potentially be differentiated by the resulting clinoform geometries 2 clinoform geometry and distribution changes systematically within a single parasequence reflecting the cycle in sea level and or sediment supply that produced the parasequence 10 2 10 5 years these changes record steepening of the shoreface shelf profile during early progradation and maintenance of a relatively uniform profile during late progradation modern shorefaces are not representative of this stratigraphic variability 3 clinoform geometries vary greatly between different parasequences as a result of variations in parasequence stacking pattern and relict shelf morphology during shore face progradation 10 5 10 8 years these controls determine the external dimensions of the parasequence

fluid inclusion study of the nannihu giant porphyry mo w deposit henan province china implications for the nature of porphyry ore fluid systems formed in a continental collision setting abstract the nannihu mo w deposit located in the henan province of china is a giant porphyry deposit formed in the qinling orogen during the jurassic continental collision between the north china and yangtze cratons mo w mineralization is associated with the nannihu porphyritic monzogranite occurring as numerous stockwork veinlets in the altered wallrocks and the causative porphyry both the porphyry stock and wallrocks underwent intense hydrothermal alteration ranging outwardly from potassic to phyllic alteration and to carbonation zones with increasing distance from the intrusion the hydrothermal ore forming process can be divided into four stages characterized by veinlets from early to late 1 quartz potassic feldspar molybdenite pyrite 2 quartz molybdenite veins containing minor pyrite and chalcopyrite 3 quartz polymetal sulfide and 4 quartz carbonate fluorite most of the ores are formed during stages 2 and 3 four types of fluid inclusions fis are distinguished in this study based on petrographic and microthermometric criteria i e pure co 2 nacl h 2 o co 2 h 2 o and daughter mineral bearing fluid inclusions all of the four types of fis can be observed in the hydrothermal quartz formed in stages 1 2 and 3 while the stage 4 minerals contain only nacl h 2 o fluid inclusions fluid inclusions of stage 1 are mainly homogenized between 350 and 460 c with salinities ranging from 5 7 to 17 9 wt nacl equiv the stage 2 fis yield homogeneous temperatures of 300 380 c and salinities of 3 5 16 9 wt nacl equiv fis of stage 3 are homogenized between 250 and 370 c with salinities of 1 8 14 3 and 28 6 39 1 wt nacl equiv fis of stage 4 are homogenized at temperatures of 115 to 265 c yielding salinities of 0 5 to 1 2 wt nacl equiv daughter minerals such as halite chalcopyrite and some unknown minerals are frequently present in stage 3 fis which probably represent a reducing and oversaturated fluid system resulting from fluid boiling the daughter mineral bearing fis coexist with vapor and liquid rich nacl h 2 o fis that have contrasting salinities these fis are homogenized in divergent ways at similar temperatures suggesting that fluid boiling took place in stages 2 and 3 the estimated pressures range from 70 to 270 mpa in stage 1 through 30 150 mpa in stage 2 to 30 85 mpa in stage 3 corresponding to a depth of no less than 3 km in other words the ore forming fluids are characterized by high temperature high salinity high f o 2 and high co 2 content and fluid boiling resulted in co 2 release f o 2 decrease and ore mineral precipitation we suggest that the co 2 rich fluid is a distinctive feature of porphyry systems developed in continental collision setting in transitional compressional to extensional regime contrasting to the co 2 poor nacl h 2 o fluids observed in volcanic arcs

investigation of the spring thermal regime in lake ladoga using field and satellite data we use a combination of field and satellite data to investigate the thermal regime in lake ladoga in spring 1992 the analysis concentrates mainly on the temperature structure in the convectively mixed region and the dynamics of a special thermo hydrodynamic phenomenon called thermal bar a zone of descending water with the temperature of maximum density equal to 4 c a theoretical model of the temperature distribution in the convectively mixed region temperatures 4 c and the thermal bar progression is also applied and compared with satellite data the study shows that the temperature offshore the 4 c isotherm in the convectively mixed region of the lake is almost depth constant because of strong convective mixing and that the horizontal heat flux seems to be of minor importance in this region the comparison between predictions from the simple theoretical model describing the temperature evolution and movement of the thermal bar with observations showed a fairly good agreement however calculations of the change of heat content in water columns along sections indicate heat transport from the nearshore stably stratified region toward the 4 c isotherm which will affect the movement of the thermal bar this effect has been incorporated in an improved model of the thermal bar progression a better agreement between predictions and observations was also obtained with this model

zircon u pb ages and geochemistry of the wenquan mo bearing granitioids in west qinling china constraints on the geodynamic setting for the newly discovered wenquan mo deposit abstract east qinling is the largest porphyry molybdenum province in the world these mo deposits have been well documented in west qinling however few mo deposits have been discovered although granitic rocks are widespread recently the wenquan porphyry mo deposit has been discovered in gansu province which provides an insight into mo mineralization in west qinling in this paper we report pb isotope compositions for k feldspar and sulfides s isotope ratios for sulfides the results obtained from petrochemical study and from in situ la icp ms zircon u pb dating and hf isotopes the granitoids are enriched in lile and lree with ree and trace element patterns similar to continental crust suggesting a crustal origin the mg 40 05 to 56 34 and cr and ni contents are high indicating a source of refractory mafic lower crust the e hf t values of zircon grains from porphyritic monzogranite range from 2 9 to 0 6 and from granitic porphyry vary from 3 3 to 1 9 the zircons have t dm2 of 1014 to 1196 ma for the porphyritic monzogranite and 954 to 1224 ma for the granitic porphyry implying that these granitoids were likely derived from partial melting of a late mesoproterozoic juvenile lower crust the pb isotope compositions of the granitoids are similar to granites in south china showing that the magma was sourced from the middle lower crust in the southern qinling tectonic unit the pb isotopic contrast between the mo bearing granitoids and ores shows that the pb in the ore forming solution was derived from fractionation of a triassic magmatic system 34 s values of sulfides are between 5 02 and 5 66 similar to those associated with magmatic hydrothermal systems la icp ms zircon u pb dating yields crystallization ages of 216 2 1 7 and 217 2 2 0 ma for the granitoids consistent with a previously reported molybdenite re os isochron age of 214 4 7 1 ma this suggests that the mo mineralization is related to the late triassic magmatism in the west qinling orogenic belt in view of these geochemical results and known regional geology we propose that both granitoid emplacement and mo mineralization in the wenquan deposit resulted from the triassic collision between the south qinling and the south china block along the mianlue suture since triassic granitoid plutons commonly occur along the qinling orogenic belt the triassic wenquan mo bearing granitoids highlight the importance of the triassic tectono magmatic belt for mo exploration in order to apply this metallogenic model to the whole qinling orogen further study is needed to compare the wenquan deposit with other deposits

a source to sink compositional model of a present highstand an example in the low rank tiber depositional sequence latium tyrrhenian margin italy abstract our source to sink compositional model of sediment distribution in the present highstand of the tiber depositional sequence has important implications for sediment source lithology generation transport and deposition in the tiber river system sand compositional trends reflect provenance mixing anthropic intervention and the effects of local autogenic factors in continental to marine depositional environments fluvial feldspatho quartzo lithic sand results from the contribution of the major tributaries of the tiber drainage basin which can be divided into two sub basins separated by the corbara dam built in the 1950s upstream drainage basin sand has a siliciclastic sedimentary lithic signature whereas carbonate and volcanic lithic fragments dominate downstream drainage basin sand downstream sand is further modified in the coastal environment by hydraulic sorting and mixed with detritus derived from the recycling of coastal dune sand and altered volcaniclastic paleosols the latter are associated with lower course floodplain and channel deposits which produce a quartzo feldspatho lithic sand sediment grain size zonation in the marine environment is influenced by coastal hydrodynamics which in turn produce two detrital populations with distinct compositional signatures and hydraulic behavior coarser minerals essentially pyroxene phenocrysts and finer feldspar grains are progressively concentrated in higher energy and lower energy environments respectively biogenic continental shelf and slope deposits off the tiber river mouth show very little riverine influence this study of the last highstand system tract in the tiber depositional sequence clarifies the effects of hydraulic sorting grain size dependence and sediment reworking in controlling the final composition of modern sand this knowledge can be used to better understand detrital modes of ancient sedimentary successions

a sedimentological and sequence stratigraphic reinterpretation of the upper cretaceous prairie canyon member mancos b and associated strata book cliffs area utah usa the mancos shale book cliffs eastern utah usa represents the open marine mudstones of the cretaceous western interior seaway and encloses the prairie canyon member which is located over 50 km seaward of interpreted contemporaneous highstand shoreline deposits in the blackhawk formation examination of the member reveals that it does not wholly represent offshore deposition as previously interpreted but instead contains three nearshore facies associations 1 tidally influenced fluvial channel fills 2 fluvial dominated delta fronts and 3 weakly storm influenced shorefaces tidally influenced fluvial channel fills are commonly stacked into multistory bodies that can be traced for tens of kilometers at discrete stratigraphic levels defining incised valley fill networks four such incised valley networks are identified at outcrop fluvial dominated deltas and weakly storm influenced shorefaces are eroded into by and lie at the down dip terminations of incised valley fills and are interpreted as forced regressive and lowstand shoreface deposits one incised valley fill appears to be onlapped by additional fluvial dominated deltas which represent pulses of shoreface progradation during an overall transgression forced regressive lowstand and transgressive shorefaces in the prairie canyon member differ significantly from highstand shorefaces in the blackhawk formation the former are sand poor and weakly wave storm influenced whereas the latter are sand rich and wave dominated this change in shoreface style reflects increased mud supply and an enhanced embayment paleogeography during periods of relative lowering of sea level

ventilation and dissolved oxygen cycle in lake superior insights from a numerical model ventilation and dissolved oxygen in lake superior are key factors that determine the fate of various natural and anthropogenic inputs to the lake we employ an idealized age tracer and biogeochemical tracers in a realistically configured numerical model of lake superior to characterize its ventilation and dissolved o2 cycle our results indicate that lake superior is preferentially ventilated over rough bathymetry and that spring overturning following a very cold winter does not completely ventilate the lake interior while this is unexpected for a dimictic lake no part of the lake remains isolated from the atmosphere for more than 300 days our results also show that lake superior s oxygen cycle is dominated by solubility changes as a result the expected relationship between biological consumption of dissolved o2 and ventilation age does not manifest

ore geology fluid inclusions and four stage hydrothermal mineralization of the shangfanggou giant mo fe deposit in eastern qinling central china article i nfo the eastern qinling central china containing more than 20 mesozoic porphyry skarn systems is the most important mo province in the world the shangfanggou giant mo deposit luanchuan county henan province is a porphyry skarn system hosted in a lithologic association comprising carbonaceous sandstone shale carbon ate and chert within the neoproterozoic luanchuan group mo ores are mainly altered porphyry skarn and hornfels with minor altered gabbro the mineralization process includes four stages potassic alteration of the porphyry and skarnization of dolomite marble in stage 1 stockworks of quartz molybdenite sulfide stage 2 pyrite quartz sulfides stage 3 and carbonate quartz fluorite stage 4 respectively mo mineralization was generally associated with strong silicification and or phyllic alteration the fluid inclusions in minerals include three compositional types i e co2 bearing c type aqueous w type and daughter mineral bearing s type minerals formed in stages 1 to 3 contain all the three types of fis but the stage 4 minerals only contain the w type fis oxides and cu phosphate are recognized as daughter minerals in s type inclusions in minerals of stage 1 whereas the daughter sulfide and reducing gases such as co ch4 h 2 sa nd c2h6 can be observed in quartz of stages 2 and 3 suggesting that the ore forming fluids were initially oxidizing and then evolved to reducing boiling fluid inclusion assemblages can be observed in minerals formed in stage 2 or earlier but not in stage 3 or later fluid boiling caused co2 escape oxygen fugacity decrease and rapid precip itation of ore minerals and was a key factor causing mo mineralization at shangfanggou data and interpreta tions presented in this contribution show that the fluids forming the shangfanggou mo deposit evolved from co2 rich high salinity hypothermal to co2 poor low salinity epithermal low t the mo mineralization at theshangfanggoudepositmainlyoccurredatdepthof6 6 7 0 km deeperthanthemajorityofporphyrysystems in volcanic arcs which resulted from a co2 rich magma fluid system originating from partial melting of thick ened lower crust the shangfanggou mineral system developed during 158 134 ma when the yangtze north china continental collision began to evolve from compression to extension magmatic hydrothermal deposits developed in a continental collision regime are generally formed by co2 rich high salinity fluids

isotope systematics and fluid inclusion studies of the qiyugou breccia pipe hosted gold deposit qinling orogen henan province china implications for ore genesis abstract the qiyugou gold deposits henan province are hosted in breccia pipes within the xiong er terrane qinling orogen on the southern margin of the north china craton in these deposits three paragenetic assemblages have been recognized an early k feldspar epidote quartz pyrite a middle quartz polymetallic sulfide and a late quartz carbonate adularia in this paper we review and interpret fluid inclusion and stable and radiogenic isotopic data of host rocks and ores fluid inclusions in quartz and calcite include water rich co 2 rich and daughter crystal bearing the co 2 rich and daughter mineral bearing fluid inclusions are common in the early stage quartz and absent in the late stage quartz and calcite which only contain water rich fluid inclusions accordingly the early stage ore fluids are magmatic in origin and characterized by high temperature 350 c high salinity 30 wt nacl equiv and are co 2 rich fluid boiling in the middle ore stage resulted in co 2 release decreasing oxygen fugacity and rapid precipitation of ore materials the late stage fluids have low temperature low salinity are co 2 poor and lack daughter minerals these fluids are probably sourced from meteoric water h o c isotope systematics confirm that the ore fluid system evolved from magmatic to meteoric the carbon and lead isotope ratios indicate that the meso neoproterozoic sequence south of the xiong er terrane was the likely source of the ore forming materials the qiyugou breccia pipes and their associated gold ores were emplaced during an extensional regime following a transition from collision to rifting tectonics linked to collision and subduction of the yangtze plate beneath the north china craton geochronological studies show that mesozoic magmatism in the region occurred between the triassic and cretaceous the triassic to jurassic magmas were mostly derived from partial melting of ancient crust whereas the cretaceous magmas show juvenile signatures indicating mantle derived components processes of fragmentation of lithospheric roots crustal and lithospheric thinning extension and rifting were probably associated with the subducting pacific izanagi plate these crust mantle geodynamic processes were responsible for the development of anorogenic granitic melts that interacted with the meso neoproterozoic volatile rich sedimentary successions producing a flow of gas rich hydrothermal fluids that resulted in the emplacement of the qiyugou auriferous breccia pipes we conclude that the qiyugou gold deposits are intrusion related explosive breccia pipe type that evolved from hypothermal through mesothermal to epithermal

physical controls on sand composition and relative durability of detrital minerals during ultra long distance littoral and aeolian transport namibia and southern angola 2014 international association of sedimentologists sediment in coastal namibia to southern angola is supplied dominantly from the orange river with minor additional fluvial input and negligible modifications by chemical processes which makes this a great test case for investigating physical controls on sand texture and composition this study monitored textural mineralogical and geochemical variability in beach and aeolian dune sands along a ca 1750 km stretch of the atlantic coast of southern africa by using an integrated set of techniques including image analysis laser granulometry optical microscopy raman spectroscopy and bulk sediment geochemistry these results contrast with previous reports that feldspars and volcanic detritus break down during transport that sand grains are rounded rapidly in shallow marine environments and that quartzose sands may be produced by physical processes mechanical wear is unable to modify the relative abundance of detrital components including pyroxene and mafic volcanic rock fragments traditionally believed to be destroyed rapidly the sole exceptions are poorly lithified or cleaved sedimentary metasedimentary rock fragments readily lost at the transition to the marine environment and slow settling flaky micas winnowed and deposited offshore coastal sediments tend to be depleted in relatively mobile amphibole preferentially entrained offshore or re deposited in sheltered beaches while less mobile garnet is retained onshore no detrital mineral displays a significant increase in grain roundness after 300 to 350 km of longshore transport in high energy littoral environments from the orange mouth to south of the namib erg but all minerals get rapidly rounded after passing into the dunefield pyroxene and opaques get rounded faster than harder quartz and garnet but sand mineralogy remains unchanged excepting strong transient selective entrainment effects physical processes are unable to modify sand composition significantly selective mechanical breakdown can be largely neglected in quantitative provenance analysis of sand and sandstone even in the case of ultra long distance transport in high energy environments dominated by strong persistent winds and waves

deep ventilation of lake baikal waters due to spring thermal bars increase of density due to mixing cabbeling instability in a spring thermal bar in lake baikal results in the sinking of cold surface water t 3 2 3 4 c w 0 3 cm s 1 below the profile of tmd this density increase generates forced convection and subsequent movement of cold water along the underwater slope to maximum depths cooling of deep and near bottom waters caused by forced convection is compensated during other seasons of the year by eddy heat flux directed toward the bottom on a long term basis vertical temperature profiles in deep waters remain constant

direct evolution of brine from a crystallizing silicic melt at the questa new mexico molybdenum deposit molybdenum mineralization in the southwest orebody at the questa deposit is associated with crystallization of aplite porphyry explosive brecciation and exsolution of magmatic hydrothermal fluids quartz k feldspar fluorophlogopite and molybdenite precipitated from exsolving aqueous fluids and cemented aplite porphyry and andesite wall rock clasts forming a magmatic hydrothermal breccia ore fluid inclusions in quartz in the breccia matrix trapped aqueous fluids that transported and precipitated molybdenum two fluid inclusion populations associated with molybdenite mineralization were identified the largest population commonly contains liquid vapor halite sylvite and one or more opaque daughter crystals these inclusions homogenize between 200 degrees and 500 degrees c and have a prominent mode at 360 degrees to 400 degrees c salinities vary from 31 to 57 wt percent nacl equiv low first ice melting temperatures suggest that additional fluid components possibly calcium or magnesium chlorides may be present approximately 80 percent of these inclusions homogenize by halite dissolution phase equilibria constraints require that these inclusions trapped fluids in the vapor absent field the remaining saline inclusions homogenize to liquid at temperatures above halite dissolution temperatures significantly the saline fluid did not coexist with a low density aqueous fluid a second population of inclusions contains fluids with salinities of 2 7 to 25 0 wt percent nacl equiv and homogenizes by vapor bubble disappearance vapor bubble expansion or critical behavior textural relationships and phase behavior during microthermometry indicate that these inclusions constitute a single population which formed as pressure and temperature fluctuated at near critical conditions pressure changes related to brecciation followed by crystallization and system resealing produced the observed fluids saline fluids were trapped as the system sealed following a major brecciation event these high salinity fluids were produced as the melt under pressure that increased from hydrostatic to lithostatic partitioned increasing amounts of chlorine into the exsolving aqueous fluid renewed fracturing and abrupt pressure decrease to hydrostatic conditions reduced the mass of chlorine partitioning to the exsolving fluid lower salinity fluids exsolved at near critical conditions and were trapped by inclusions that homogenize to liquid to vapor or by critical behavior the lack of cogenetic liquid and vapor rich fluid inclusions and phase equilibria constraints indicate that high salinity fluids or 57 wt nacl equiv were generated directly by the crystallizing magma and were not a product of aqueous fluid immiscibility

geodynamic settings and tectonic model of skarn gold deposits in china an overview seventy skarn type gold deposits including 1 super large 19 large and 24 medium sized are known from different geotectonic units of china they contain a total resource of approximately 1000 t of gold 625 t in south china and account for 20 of china s gold reserves these skarn deposits are sited in collisional orogenic belts fault controlled magmatic belts and reactivated cratonic margins all of the chinese skarn gold provinces were affected by phanerozoic collisional orogenesis the timing of the metallogenic events and the spatial temporal distribution of the chinese skarn gold deposits indicates that they were formed during ore forming processes linked to the transition from shortening to extension in the geodynamic evolution of a collision orogen and not to subduction systems as is commonly advocated for porphyry copper systems around the pacific rim

mesozoic molybdenum deposits in the east qinling dabie orogenic belt characteristics and tectonic settings abstract the east qinling dabie orogenic belt accommodates the largest mo ore district in the world it contains 8 43 mt of proven mo metal reserves which accounts for 66 of the total proven chinese mo reserves the mo ore district includes 24 deposits and 12 occurrences with four major types of mo mineral systems i e porphyry porphyry skarn skarn and hydrothermal veins the latter can be further subdivided into quartz vein and carbonatite vein types although mo mineralization in the belt began in the paleoproterozoic 1680 24 to 2044 14 ma all economically significant deposits were formed during the mesozoic re os dating of molybdenite has shown that there are three episodes of mo mineralization i e late triassic 233 221 ma late jurassic to early cretaceous 148 138 ma and early to middle cretaceous 131 112 ma late triassic mo deposits developed as molybdenite quartz veins and carbonatite vein types stable isotope systematics c o s and high contents of re and sr indicate that the carbonatite mo veins are mantle derived porphyry and porphyry skarn mo mineral deposits were formed in the late jurassic to early cretaceous and early to middle cretaceous the late jurassic to early cretaceous granite porphyries that are associated with the mo deposits usually occupy less than 1 5 km2 at the surface and are situated in the east qinling area far west of china s continental margin on the other hand the early to middle cretaceous batholiths and granite porphyries with associated mo deposits are located in the dabieshan area and eastern part of the east qinling area the late jurassic to early creataceous granitoids and related mo deposits possibly formed in a back arc extensional setting of the eurasian continental margin which was probably triggered by the oblique subduction of the izanagi plate the early to middle cretaceous batholiths and granite porphyries are linked to the tectonic regime of lithospheric thinning asthenospheric upwelling and partial melting of the crust induced by a change in izanagi plate motion parallel to the continent margin in the east qinling dabie belt there are vein type pb zn ag deposits surrounding porphyry and or porphyry skarn mo w deposits forming well defined ore clusters the same spatial arrangement i e porphyry mo stockworks and outlying pb zn ag ore veins is also observed at the deposit scale thus mo porphyry stockworks and distal polymetallic veins belong to the same ore system and may reflect an outward temperature decrease from the highly fractionated granite plutons both porphyry stockworks and polymetallic veins can be used as vectors for further prospecting

impact of lake level change on deep water renewal and oxic conditions in deep saline lake van turkey 1 changes in the hydrological regime of the saline closed basin lake van a large deep lake in eastern turkey resulted in a lake level increase by about 2 m between 1988 and 1995 followed by a 1 5 m decrease until 2003 and a relatively constant lake level thereafter based on measurements of transient tracers sulfur hexafluoride cfc 12 3h 3he 4he ne dissolved oxygen light transmission conductivity temperature depth profiles and thermistor data we investigate the implications associated with lake level fluctuations for deep water renewal and oxygenation our data suggest that deep water renewal was significantly reduced in lake van between 1990 and 2005 this change in mixing conditions resulted in the formation of a more than 100 m thick anoxic deep water body below 325 m depth apparently the freshwater inflows responsible for the lake level rise between 1988 and 1995 decreased the salinity of the surface water sufficiently that the generation of density plumes during winter cooling was substantially reduced compared to that in the years before the lake level rise significant renewal and oxygenation of the deep water did not occur until at least 2005 although by 2003 the lake level was back to almost the same level as in 1988 this study suggests that short term changes in the hydrological regime resulting in lake level changes of a couple of meters can lead to significant and long lasting changes in deep water renewal and oxic conditions in deep saline lakes

the age of the potassic alkaline igneous rocks along the ailao shan red river shear zone implications for the onset age of left lateral shearing abstract the potassic alkaline igneous rocks along the ailao shan red river asrr shear zone range in composition from ultramafic to felsic and are characterized by similar trace element patterns and radiogenic isotope ratios their distribution and in some cases their structure and outcrop outline suggest a genetic relationship to the asrr shear zone zircons separated from 12 potassic alkaline bodies along the asrr zone have been dated by an in situ u pb method to temporally constrain the left lateral movements along the shear zone the ages of the alkaline bodies range from 34 0 to 36 3 ma these new zircon ages together with previous data suggest that the onset age of the left lateral movements along the asrr shear zone began at or slightly before 36 ma and that the movements lasted from 36 to 17 ma when uncertainties are taken into account the duration of motion on the asrr shear zone coincides with the opening of the south china sea implying a genetic relationship between these two events

physical and chemical properties of the waters of saline lakes and their importance for deep water renewal lake issyk kul kyrgyzstan the relationships between electrical conductivity temperature salinity and density are studied for brackish lake issyk kul these studies are based on a newly determined major ion composition which for the open lake shows a mean absolute salinity of 6 06 g kg 1 the conductivity temperature relationship of the lake water was determined experimentally showing that the lake water is about 1 25 times less conductive than seawater diluted to the same absolute salinity as that of the lake water based on these results an algorithm is presented to calculate salinity from in situ conductivity measurements applied to the field data this shows small but important vertical salinity variations in the lake with a salinity maximum at 200 m and a freshening of the surface water with increasing proximity to the shores the algorithm we adopt to calculate density agrees well with earlier measurements and shows that at 20 c and 1 atm lake issyk kul water is about 530 g m 3 denser than seawater at the same salinity the temperature of maximum density at 1 atm is about 0 15 c lower than that for seawater diluted to the same salinity despite its small variations salinity plays an important role together with temperature changes in the static stability and in the production of deep water in this lake changes in salinity may have had important consequences on the mixing regime and the fate of inflowing river water over geological time uncharged silicic acid is negligible for the stability of the water column except near an 15 m thick nepheloid layer observed at the bottom of the deep basin copyright 2002 elsevier science ltd

sequence stratigraphy and marine to nonmarine facies architecture of foreland basin strata book cliffs utah u s a the desert member of the blackhawk formation and the castlegate sandstone in the book cliffs of utah and colorado were analyzed to develop a model of sequence stratigraphy and facies architecture in foreland basins stratal architecture of these rocks is controlled by two regionally extensive surfaces of incision and subaerial exposure interpreted as major sequence boundaries and at least six surfaces of incision and subaerial exposure with more limited lateral extent interpreted as minor sequence boundaries each sequence boundary is a regionally correlatable single surface major sequence boundaries can be traced from marine into proximal alluvial plain environments sequence boundaries have different physical expressions depending upon where in the basin they are observed strata beneath sequence boundaries are unrelated to strata above and time lines cannot be carried across these boundaries flooding surfaces called parasequence or parasequence set boundaries also exert an important control on facies architecture based on parasequence stacking patterns position of sequence boundaries and facies associations the desert member and castlegate sandstone have been divided into sequences with durations of 200 000 to 300 000 yr there are an order of magnitude more sequences in this interval than are predicted by the global sea level chart of haq et al 1988 the major sequences have been divided into the following systems tracts or sequence sets 1 grassy highstand sequence set below the desert sequence boundary named for the grassy member of the blackhawk formation 2 desert lowstand transgressive and highstand systems tracts between the desert and castlegate sequence boundaries 3 castlegate lowstand sequence set resting on the castlegate sequence boundary and 4 castlegate transgressive systems tract parasequence stacking patterns suggest that the grassy highstand sequence set and the desert highstand systems tract were deposited during a relative rise in baselevel the grassy highstand sequence set is punctuated by minor relative falls in baselevel both of these stratal units contain thick

evidence of across shelf transport of fine grained sediments turbidite filled shelf channels in the campanian aberdeen member book cliffs utah usa the shore normal transport of fine grained sediments by shelf turbidity currents has been the focus of intense debate over the last 20 years many have argued that turbidity currents are unlikely to be a major depositional agent on the shelf however sedimentological architectural stratigraphic and palaeogeographic data from the campanian aberdeen member book cliffs eastern utah suggests otherwise and clearly demonstrates that storm generated and river flood generated underflows can transport a significant volume of fine grained sediments across the shelf these across shelf flowing turbidity currents cut large subaqueous channel complexes up to 7 m deep tens of kilometres basinward of their time equivalent shoreface the shelf channels were filled with organic rich siltstones mudstones and very fine to fine grained bouma like sandstone beds including wave modified turbidites hyperpycnites and classical turbidites deposition was above storm wave base palaeocurrent data reveal an overwhelmingly dominant across shelf east south east offshore directed transport trend tectonic activity and or concomitant palaeogeographic reorganization of the basin may favour the generation of these turbidite rich shelf deposits by altering the relative balance of wave versus fluvial energy increased erosion and sediment supply rates because of tectonic uplift of the hinterland may have increased the probability of fluvial dominance along the coastline and hence the possibility of submarine channelization in front of the river mouths additionally the coastline may have become more sheltered from direct wave energy thus allowing the fluvial processes to dominate seasonal increases in rainfall and storm activity may also favour the generation of across shelf underflows on wave dominated shorelines isolated shelf channels and lobes are most likely to be found down dip of fluvial feeder systems in relatively high sediment supply settings these features are also most likely to occur in systems tracts that straddle a sequence boundary especially those which are tectonically generated as these would enhance the potential for altering basin morphology and hence the balance of fluvial and wave energy isolated shelf channels are recognized in older and younger strata in the book cliffs region implying that wave supported gravity flows were a recurrent phenomena in the campanian of utah it is probable that isolated shelf bodies are preserved in other stratigraphic intervals in the cretaceous western interior of north america and other basins worldwide and are currently being overlooked or misidentified shoreface to shelf facies models should be revised to incorporate turbidite rich shelf deposits in some shelf settings

a model for migrating shelf bar sandstones in upper mancos shale campanian northwestern colorado the duffy mountain sandstone was deposited by migrating submarine shelf bars that are now completely encased in marine mudstones of the mancos shale upper cretaceous the shelf bars were deposited at least 10 mi 16 km offshore and stood approximately 100 to 150 ft 30 to 46 m above a shallow shelf the bars were never emergent but were shallow enough for fair weather waves to form ripples along their crests these elongate sand bodies trend northeast southwest approximately parallel to the shoreline the sediment was probably derived from reworking of transgressed littoral deposits in southwestern wyoming four subenvironments are recognized 1 landward flank of the shelf bar the back bar 2 the axial crest of central bar 3 a seaward facing ramp subfacies and 4 the shelf upon which the shelf bars migrated two major processes were active during deposition 1 fair weather longshore southwesterly currents and 2 storm erosion and westerly across the shelf bar sediment transport during fair weather sand waves transported sediment along the central bar while the back bar and shelf were being bioturbated storms eroded the seaward face of the bar and portions of the central bar creating hummocky erosion surfaces eroded sediment transported across the bar was deposited in coarsening upward spillover lobes in the back bar after the storm waned sediments deposited in t e back bar were bioturbated and sand waves were deposited on the eroded central bar migration of sand waves onto the eroded face of the bar formed the ramp facies as the shelf bar migrated the central bar facies climbed stratigraphically over the back bar facies the direction of shelf bar migration was probably controlled by the interaction of fair weather and storm sediment transport