quantitative seismostratigraphic inversion of a prograding delta from seismic data quantitative stratigraphy predicts the geometry of geologic strata and their petrophysical properties based on mathematical models of geological processes and parameters which affect the formation and evolution of geologic strata such processes include erosion sediment transport and deposition quantitative stratigraphic inversion estimates the process parameters from a priori data by systematic modeling until the predictions are compatible with the observations in the case of quantitative seismostratigraphic inversion the a priori data are predominantly of the seismic kind to evaluate feasibility we designed a preliminary algorithm which we applied in a prograding delta environment we found that by fixing the sediment influx rate subaerial transport rate and the initial topography we were able to reproduce the basic features of the delta with only three to five parameters which included subaqueous transport rate and its depth dependent decay rate base level and sediment source location and spatial extent

early cretaceous bimodal volcanism in the duolong cu mining district western tibet record of slab breakoff that triggered ca 108 113 ma magmatism in the western qiangtang terrane abstract we report new zircon u pb ages and hf isotope compositions and whole rock major and trace element and sr nd isotope data for the meiriqiecuo formation mf bimodal volcanic rocks collected from the duolong cu mining district dcmd in the western qiangtang terrane qt western tibet these data provide important constraints on the petrogenetic evolution and geodynamic setting of early cretaceous magmatism in the dcmd the mf bimodal volcanic rocks are mainly basaltic andesite and andesite with subordinate rhyolite four mafic samples yielded zircon u pb ages of ca 108 2 113 0 ma and one silicic sample has an age of 109 3 2 2 ma indicating that the mafic and silicic eruptions were contemporaneous the mf bimodal volcanic rocks belong to the medium k calc alkaline to shoshonite series the rocks show arc type affinities characterized by significant enrichment in light rare earth lan ybn 7 74 12 60 and large ion lithophile elements rb cs k and pb but depletions in the high field strength elements nb ta and ti which geochemically resemble andean arc basalts therefore the mf bimodal volcanic rocks were likely emplaced at an andean type active continental margin and represent an early cretaceous magmatic arc that was located at the western qt margin moreover the mafic volcanic rocks have high initial sr isotopic ratios 0 705269 0 705413 and negative end t values of 1 5 to 0 6 compared with the silicic volcanic rocks 87sr 86sr i 0 704770 0 704903 end t 1 2 to 1 3 zircons from silicic samples have significantly higher ehf t values 11 6 to 15 5 and predominantly lower paleoproterozoic hf crustal model ages tdmc 180 428 ma than the mafic samples which have variable ehf t values of 3 4 to 13 0 and tdmc ages of 346 952 ma these results indicate that the mafic and silicic end members of the mf bimodal suite were generated from mantle and crustal sources respectively the basaltic andesite and andesite may have been derived from mantle enriched by the metasomatism of subducted fluids whereas the rhyolite could have been derived by partial melting of mafic juvenile crust that originated from an older and more depleted mantle in light of the geochemical characteristics and field relationships we propose that breakoff of the bangong nujiang oceanic lithosphere was responsible for the generation and emplacement of the mf bimodal volcanic rocks the fact that the mf bimodal volcanic arc magmatism was active at ca 108 113 ma indicates that it was associated with closure of the bangong nujiang ocean via an arc arc soft collision during the early cretaceous

palaeontology and u pb detrital zircon geochronology of upper triassic strata on the northern margin of the bangong co nujiang suture zone tibet constraints on the age of opening of the meso tethys abstract we present the results of field mapping paleontology and detrital zircon geochronology of newly found clastic rocks with intercalations of limestone in the gaerqin area of tibet gaerqin formation the gaerqin formation consists of sandstone siltstone and shale with intercalations of bioclastic limestone abundant late triassic norian fossils are found in the limestone beds the fossils include distichophyllia norica retiophyllia litangensis and mesozoic chaetetida in addition 273 detrital zircons were selected for u pb dating yielding the following age groups 210 300 500 600 800 1100 1600 1800 and 2400 2600 ma more than 80 of the detrital zircons are older than 550 ma and the most reliable youngest detrital zircon age for the gaerqin formation is 219 ma the results indicate that the gaerqin formation formed in a shallow marine to bathyal continental slope environment and represents the first reported upper triassic norian strata in the gaerqin area of tibet the findings also suggest that the bangong co nujiang tethys ocean was a bathyal basin by the late triassic

stratigraphy and spatial and temporal paleoclimatic trends in southeastern eastern european loess paleosol sequences abstract the loess paleosol sections batajnica stari slankamen serbia mircea voda romania and stary kaydaky ukraine are presently located in areas of different types of steppe and are highly sensitive for recording climatic changes a stratigraphy for these three southeastern eastern european sections is presented based on pedostratigraphy and correlation of recently obtained susceptibility records with susceptibility data of other sections of the area koriten mostistea vyazivok of the chinese loess plateau and with the benthic 18o record of odp 677 six pedocomplexes were studied at the serbian and romanian sections and five at the ukrainian section the oldest are related to marine isotope stage mis 17 batajnica stari slankamen and mircea voda and mis 13 15 stary kaydaky some points concerning the existing loess chronostratigraphies of bulgaria ukraine and china are discussed comparative study of the profiles allows the tracing of paleoclimatic and paleoenvironmental changes in southeastern eastern europe in time and space reconstruction of paleoprecipitation based on susceptibility rainfall relationships and calculations of sedimentation rates are evaluated

petrogenesis of ore bearing porphyries from the duolong porphyry cu au deposit central tibet evidence from u pb geochronology petrochemistry and sr nd hf o isotope characteristics abstract the duolong porphyry cu au deposit 5 4 mt at 0 72 cu 41 t at 0 23 g t au which is related to the granodiorite porphyry and the quartz diorite porphyry from the bangongco copper belt in central tibet formed in a continental arc setting here we present the zircon u pb ages geochemical whole rock sr nd whole rock and zircon in situ hf o isotopic data for the duolong porphyries secondary ion mass spectrometry sims zircon u pb analyses for six samples yielded consistent ages of 118 ma indicating a cretaceous formation age the duolong porphyries sio2 of 58 81 68 81 wt k2o of 2 90 5 17 wt belong to the high k calc alkaline series they show light rare earth element lree enriched distribution patterns with la yb n 6 1 11 7 enrichment in large ion lithophile elements e g cs rb and ba and depletion of high field strength elements e g nb with negative ti anomalies all zircons from the duolong porphyries share relatively similar hf o isotopic compositions 18o 5 88 7 27 ehf t 3 6 7 3 indicating that they crystallized from a series of cogenetic melts with various degrees of fractional crystallization this along with the general absence of older inherited zircons rules out significant crustal contamination during zircon growth the zircons are mostly enriched in 18o relative to mantle values indicating the involvement of an 18o enriched crustal source in the generation of the duolong porphyries together with the presence of syn mineralization basaltic andesite the mixing between silicic melts derived from the lower crust and evolved h2o rich mafic melts derived from the metasomatized mantle wedge followed by subsequent fractional crystallization fc and minor crustal contamination in the shallow crust could well explain the petrogenesis of the duolong porphyries significantly the hybrid melts possibly inherited the arc magma characteristics of abundant f cl cu and au elements and high oxidation state which contributed to the formation of the duolong porphyry cu au deposit

loess stratigraphy in central china abstract loess sequences in central china provide a detailed record of climate changes during the last 2 5 million years at least 44 major shifts from glacial to interglacial conditions occurred during this time in china prolonged loess deposition lasting more than 40 millennia occurred eleven times with only four of these intervals in brunhes chron the climate oscillations took place with increased frequency between 2 4 and 0 5 ma compared to the last half million years major shifts toward cooler and drier climates occurred at about 2 4 ma 1 2 ma and 0 5 ma while less pronounced shifts are dated to 1 65 ma 0 8 ma and 0 2 ma three of the last four reversals of the earth s magnetic field whose lithostratigraphic position has been detail are recorded in a glacial deposit the low field magnetic susceptibility of loess and soils which reflects the concentration of ultrafine magnetite is related to the degree of pedogenesis and serves as a proxy measure of climate the accumulation rate of the magnetite was fairly constant throughout the last 1 2 million years and can serve as a measure of time susceptibility records from localities near xifeng and luochuan located 160 km apart are compared and used to define informal lithostratigraphic units in the loess plateau of china

digital reconstruction and stratigraphic evolution of a microbial dominated isolated carbonate platform terminal proterozoic nama group namibia abstract a terminal proterozoic ca 550 ma isolated carbonate platform developed downdip on a carbonate ramp of the nama group of southern namibia the stratigraphic evolution of the platform was reconstructed from an extensive dataset that was compiled by using digital surveying technologies and traditional outcrop observations digital field geology techniques enabled rapid and accurate mapping over the 10 km outcrop belt with spatial and geological information captured at scales ranging from centimeters to kilometers furthermore these digital geology techniques made the reconstruction and interpretation of the development of the carbonate platform considerably more efficient and quantitative the carbonate platform deposits encompass three accommodation cycles in which each subsequent cycle experienced progressively greater influence of a long term accommodation increase aggradation and progradation during the first cycle produced a flat topped sheet like platform deposits of the first cycle show a coarsening upward motif grading from dominantly columnar stromatolitic thrombolites and interbedded mudstone grainstone at the base to dominantly massive and cross bedded dolostones toward the top the second cycle features aggradation and is typified by the formation of a distinct margin and development of a bucket shaped geometry the margin contained thrombolite mounds and domes whereas columnar stromatolitic thrombolites dominated the platform interior the third and last cycle records a gradual deepening trend with initial aggradation and formation of well bedded thin deposits in the interior and microbial mounds at the margins while the interior drowned the platform margins kept up with rising sea level and complex pinnacle reefs formed which contained fused and coalesced thrombolite mounds flanked by bioclastic grainstones and collapse breccias the top of the unit consists of a set of isolated large thrombolite mounds flanked by shale and is interpreted to indicate the final stage of the carbonate platform before drowning the overall geometric evolution and spatial scale of this platform from flat topped to bucket shaped with elevated margins is recorded in many proterozoic and phanerozoic isolated carbonate platforms this study clearly illustrates that accommodation changes are a fundamental control on the development of carbonate platforms regardless of whether they are formed from microbial or metazoan components or are of precambrian or phanerozoic age significantly the architectural elements and spatial dimensions are comparable throughout earth history

numerical modelling of drainage basin evolution and three dimensional alluvial fan stratigraphy abstract a forward numerical model is presented to study the effects of bedrock erodability thrust displacement rate pulsating tectonic activity and sea level fluctuations on drainage basin morphology and stratigraphy of large alluvial fan systems a low value of the bedrock erodability coefficient k b 0 5 10 4 year 2 3 vs thrust rate 2 0 m ky is associated with a time lag between cessation of tectonic activity and maximum sedimentation rates observed on the alluvial fans applying higher k b values ranging between 1 0 and 8 0 10 4 year 2 3 results in higher sediment yields due to more rapid headward catchment erosion and elaborate sideways branching of drainage networks pulsating tectonic activity is reflected in a stratigraphic alternation of prograding and retrograding alluvial fan gravels during tectonic activity fan gravel fronts and coastlines retreat because catchment yields are insufficient to fill the accommodation space created by the flexural response due to thrust loading phases of tectonic quiescence and cessation of flexural subsidence are indicated by progradation of the gravel front depending on the position in the basin the lag time for arrival of the gravel associated with tectonic cessation is several tens to hundred thousands of years a combination of pulsed tectonic activity with sinuous sea level fluctuation leads to a more complex stratigraphic pattern in that case stratigraphic response to tectonic pulses is masked by a similar but higher order frequency stacking pattern especially in the more distal parts

three dimensional numerical modeling of deltaic depositional sequences 2 influence of local controls abstract we investigate the influence of three local controls sediment supply subsidence and physiography on delta development and sequence variability using the three dimensional numerical model of deltaic deposition presented in a companion paper ritchie et al 2004 independently varying a single local control within geologically constrained limits produces marked differences in three dimensional morphology cross sectional stratal geometry and delta evolution during a cycle of sea level change sediment supply strongly influences not only the timing of transgressive and maximum flooding surface development during sea level rise and hence the diachroneity of lowstand transgressive and highstand systems tracts but also the timing of onset of fluvial incision and the characteristics of incised valleys and forced regressive wedges low sediment supply leads to early drowning of forced regressive and lowstand prograding wedges high magnitude transgressions and the late development of maximum flooding surfaces during relative sea level fall low sediment supply results in early initiation of fluvial incision and development of few but major incised valleys that route sediment to elongate forced regressive lobes at their mouths in contrast high sediment supply leads to early onset of normal regression and late transgression during relative sea level rise and numerous poorly developed incised channels and a broad laterally continuous forced regressive apron during relative sea level fall on basin margins with a shelf slope morphology base of slope deepwater deposits may occur at times of sea level highstand due to sediment bypass across the slope during relative sea level fall fluvial incision is enhanced by the relatively steep gradient of the slope leading to the early onset of incision and rapid headward propagation as a result major deep incised valleys develop that capture sediment and feed it directly to thick shelf edge forced regressive and lowstand prograding wedges the greater water depth ahead of the shelf edge and the steep slope gradients result in limited forced and normal regression compared to a ramp setting in contrast to other controls tectonic subsidence or uplift leads to modification of accommodation so that relative sea level change may vary significantly along a basin margin in high subsidence settings relative sea level may continue to rise even at times of high rates of background sea level fall in such settings deltas lack incised valleys forced regressive delta lobes and prominent sequence boundaries furthermore normal regression and even transgression in high subsidence locations can be contemporaneous with forced regression and incised valley development in adjacent lower subsidence locations the results of this sensitivity analysis suggest that systems tracts and their bounding surfaces are likely diachronous along many basin margins and may locally be absent more than one control can produce a similar stratigraphic response making interpretation of controlling processes from the stratigraphic product equivocal the models provide a framework for understanding the stratigraphy of natural basin fills but further research on the interplay between the controls is required in order to understand the climatic tectonic and sea level signals concealed in the stratigraphic record

the post glacial downcutting history in the waihuka tributary of waipaoa river gisborne district implications for tectonics and landscape evolution in the hikurangi subduction margin new zealand abstract determining the spatial and temporal deliveries of sediment from the waipaoa river catchment in the post glacial period is a major goal of integrated source to sink landscape evolution studies in the region in a 2 2 km long section of the waihuka tributary 217 km 2 of the waipaoa river 2150 km 2 in eastern north island new zealand a sequence of at least ten fluvial terraces and abandoned meanders up to 45 m above the present river records rates and times of post glacial downcutting dateable organic and tephra horizons in the terrace and meander infill stratigraphy indicate that downcutting at this location on the waihuka tributary was dominated by a short lived event in the early holocene from 10 8 ka bp when as much as half of the downcutting was accomplished in only 10 15 of post glacial time the large downcutting event is interpreted to record the passing of a succession of major knickpoints or a knickzone through this tributary the initiation of knickpoint retreat in the catchment was primarily a consequence of reduction in sediment supply at the end of mis 2 based on the timing of rapid downcutting in the waipaoa river mainstem we estimate that the rate of knickpoint retreat along the waihuka tributary was about 2 km kyr in the period before and after rapid downcutting in the waihuka tributary modest incision rates averaging 1 2 mm yr probably represent the regional tectonic uplift rate

origin and tectonic setting of the giant duolong cu au deposit south qiangtang terrane tibet evidence from geochronology and geochemistry of early cretaceous intrusive rocks abstract we constrain the origin and tectonic setting of the giant duolong porphyry epithermal cu au deposit in the south qiangtang terrane of northern tibet based on new zircon u pb ages and hf isotopic data as well as whole rock major and trace element data from poorly studied ore associated intrusions in the duolong area the la icp ms zircon u pb dating indicates that the ore associated rocks formed between 121 and 126 ma these ore associated rocks are geochemically similar to low k tholeiitic m type granitoids and to mid to high k calc alkaline i type granitoids they have variable and predominantly positive zircon e hf t values 1 4 to 15 6 and variable crustal model ages t c dm hf 176 1122 ma taking into account previous data and the regional geology of the study area we propose that the ore associated rocks originated from fractional crystallization of mantle derived mafic melts and magma mixing of mantle derived mafic and hybrid lower crust derived felsic melts and the hybrid lower crust included a mix of juvenile and older continental material the duolong porphyry epithermal cu au deposit formed within an ensialic forearc of an active continental margin as a result of the northwards subduction of the bangong nujiang ocean crust beneath the south qiangtang terrane

basin scale stratigraphic architecture and potential paleocene distributive fluvial systems of the cordilleran foreland basin alberta canada abstract the paleocene paskapoo formation in western canada is composed of several hundred meters of fluvial strata that were deposited in an actively subsiding retro arc foreland basin adjacent to the southern canadian cordillera here we utilize newly available subsurface data from down hole gamma ray well logs to reconstruct the large scale fluvial stratigraphy and depositional history of the paskapoo formation in the central portion of the cordilleran foreland basin in alberta paleocene fluvial strata in this region contain several notable characteristics including variable degrees of channel sandstone amalgamation regionally variable stratigraphic architecture and a large fan shaped sandstone unit that emanated from the adjacent fold thrust belt fluvial channel sandstone bodies are abundant and amalgamated near the base of the formation in the southern portion of the basin but become less apparent in the northernmost 100 km of the basin the middle interval of the paskapoo formation characterized by abundant mudstone with isolated channel sandstone bodies is prevalent across the entire study area the upper portion of paskapoo formation is dominated by a large 5000 km2 north northwest trending laterally continuous sandstone in the northern portion of the basin that abuts against the fold thrust belt and fans outward into the basin this feature is interpreted as either a distributive fluvial system or a fixed outlet river system that experienced repeated avulsions this area of the fold thrust belt may be the site of a long lived fluvial outlet the variable degree of sandstone amalgamation in the paskapoo formation suggests two different modes in the relative ratio of accommodation to sediment supply periods of rapid subsidence likely associated with thrust emplacement in the adjacent fold thrust belt resulted in mudstone dominated successions with isolated sandstone bodies whereas tectonically inactive periods associated with less subsidence resulted in amalgamated sandstone units the principal stratigraphic features reconstructed from the data in this area can be used to better understand and predict fluvial stratigraphy within other foreland basins

time scales of tectonic landscapes and their sediment routing systems abstract in regions undergoing active tectonics the coupling between the tectonic displacement field the overlying landscape and the redistribution of mass at the earth9s surface in the form of sediment routing systems is particularly marked and variable coupling between deformation and surface processes takes place at a range of scales from the whole orogen to individual extensional fault blocks or contractional anticlines at the large scale the attainment of a steady state between the overlying topography and the prevailing tectonic conditions in active contractional orogens requires an efficient erosional system with a time scale dependent on the vigour of the erosional system generally in the range 10 6 10 7 years the catchment fan systems associated with extensional fault blocks and basins of the western usa are valuable natural examples to study the coupling between tectonic deformation landscape and sediment routing systems even relatively simple coupled systems such as an extensional fault block and its associated basin margin fans have a range of time scales in response to a tectonic perturbation these response times originate from the development of uniform steady state relief during the accumulation of displacement on a normal fault c 10 6 years the upstream propagation of a bedrock knickpoint in transverse catchments following a change in tectonic uplift rate c 10 6 years or the relaxation times of the integrated catchment fan system in response to changes in climatic and tectonic boundary conditions 10 5 10 6 years the presence of extensive bedrock or alluvial piedmonts increases response times significantly the sediment efflux of a mountain catchment is a boundary condition for far field fluvial transport but the fluvial system is much more than a simple transmitter of the sediment supply signal to a neighbouring depocentre fluvial systems appear to act as buffers to incoming sediment supply signals with a diffusive time scale c 10 5 10 6 years dependent on the length of the system and the extent of its floodplains stream channels and proximal gravel fans the vocabulary for explaining landscapes would benefit from a greater recognition of the importance of the repeat time and magnitude of perturbations in relation to the response and relaxation times of the landscape and its sediment routing systems landscapes are best differentiated as buffered or reactive depending on the ratio of the response time to the repeat time of the perturbation furthermore landscapes may be regarded as steady or transient depending on the ratio of the response time to the time elapsed since the most recent change in boundary conditions the response of tectonically and climatically perturbed landscapes has profound implications for the interpretation of stratigraphic architecture

scale dependent compensational stacking an estimate of autogenic time scales in channelized sedimentary deposits recent studies show that paleoenvironmental allogenic signals preserved in the stratigraphic record may be contaminated or overprinted by internally generated autogenic sedimentation this is problematic but it is unclear over what temporal and spatial scales autogenic patterns are most prevalent we propose that scale breaks in basin fi lling trends can be used to identify the transition between allogenic and autogenic stratigraphy using data from numerical and physical experiments and an ancient outcrop we explore how compensation the tendency for sediment transport systems to preferentially fi ll topographic lows varies with stratigraphic scale object based models demonstrate the temporal scales at which stratigraphy changes from being partially infl uenced by autogenic processes to being completely determined by allo genic forcings and suggest that this transition occurs at a time scale set by the maximum scale of surface roughness in a transport system divided by the long term aggradation rate this hypothesis is validated in a physical experiment where delta topography was monitored along fl ow perpendicular transects at a high temporal resolution relative to channel kine matics the strength of compensation in the experiment changes at the predicted time scale where the maxi mum surface roughness is equal to the depth of the experimental channels above this compensation time scale deposits stack purely compensationally but below this time scale deposits stack somewhere between randomly and deterministically similar scale dependent stacking is also observed in the ferris formation cretaceous paleogene hanna basin wyoming united states this study demonstrates that scale dependent compensational stack ing may be useful for isolating allogenic and autogenic stratigraphy in sedimentary basins

magmatism and metallogenic mechanism of the ga erqiong and galale cu au deposits in the west central lhasa subterrane tibet constraints from geochronology geochemistry and sr nd pb hf isotopes abstract the ga erqiong galale ore district in the bangong nujiang metallogenic belt hosts two large skarn cu au deposits associated with voluminous late cretaceous volcanism and plutonism in this study we present new zircon u pb age and hf isotopic data whole rock geochemical and sr nd pb isotopic data to constrain the geodynamic mechanisms of late cretaceous magmatism and metallogenesis within the ga erqiong galale ore district the intrusive rocks in the district include diorite quartz diorite granodiorite granite and dioritic porphyrite zircon u pb analyses suggest those rocks mainly emplaced at early late cretaceous 84 95 ma which coincide with the ore forming age of ga erqiong and galale deposits 87 and 88 ma respectively geochemically the granodiorite and dioritic porphyrite are metaluminous with depletion of nb ta and ti and characterized by high mgo 2 68 4 16 wt mg 55 87 sr 414 616 ppm sr y 30 56 cr 22 5 105 0 ppm and ni 26 6 59 7 ppm low y 10 6 14 0 ppm and heavy rare earth elements hree showing geochemical signatures of high mg adakitic rocks four dioritic porphyrite and three granodiorite samples exhibit homologous sr nd pb isotope compositions and have positive whole rock end t values of 1 1 to 3 0 87sr 86sr i values of 0 7045 0 7048 206pb 204pb t ratios of 18 42 18 73 207pb 204pb t ratios of 15 58 15 63 and 208pb 204pb t ratios of 38 54 38 88 besides 116 analyses from the ga erqiong galale adakitic rocks give positive zircon ehf t values 4 3 to 12 1 the geochemical and isotopic data indicate that the early late cretaceous high mg adakitic rocks in the ga erqiong galale ore district originated from the delaminated juvenile lower mafic crust that has been modified by the previously subduction partial melting of previously subduction modified delaminated juvenile lower crust not only formed the hydrous adakitic melts in highly oxidation state but also provided the ore metals e g cu au mo for the subsequent mineralization such melts reacted with surrounding mantle peridotite to elevate the contents of metallic elements again then the melts experienced varying degrees of fractional crystallization process in the shallow magma chamber to form the dioritic and granodioritic magmas those magmas emplaced into the limestone of duo ai and jiega formation to form the ga erqiong and galale skarn cu au deposits respectively field observation together with geochronological and geochemical data indicate that the early late cretaceous mineralization events in the northern and central lhasa subterranes took place in a transition tectonic setting from collisional orogeny to extension and the input of subduction modified juvenile crust play an important role in the late cretaceous ore forming events

glacial interglacial climate changes recorded by debris flow fan deposits owens valley california abstract it is hotly debated whether and how climate changes are recorded by terrestrial stratigraphy basin sediments produced by catchment alluvial fan systems may record past climate over a variety of timescales and could offer unique information about how climate controls sedimentation unfortunately there are fundamental uncertainties about how climatic variables such as rainfall and temperature translate into sedimentological signals here we examine 35 debris flow fan surfaces in owens valley california that record deposition throughout the past 125 000 years during which climate has varied significantly we show that the last full glacial interglacial cycle is recorded with high fidelity by the grain size distributions of the debris flow deposits these flows transported finer sediment during the cooler glacial climate and became systematically coarser grained as the climate warmed and dried we explore the physical mechanisms that might explain this signal and rule out changes in sediment supply through time instead we propose that grain size records past changes in storm intensity which is responsible for debris flow initiation in this area and is decoupled from average rainfall rates this is supported by an exponential clausius clapeyron style scaling between grain size and temperature and also reconciles with climate dynamics and the initiation of debris flows the fact that these alluvial fans exhibit a strong sustained sensitivity to orbital climate changes sheds new light on how eroding landscapes and their sedimentary products respond to climatic forcing finally our findings highlight the importance of threshold controlled events such as storms and debris flows in driving erosion and sedimentation at the earth s surface in response to climate change

jurassic cretaceous granitoids and related tectono metallogenesis in the zapug duobuza arc western tibet abstract the zapug duobuza magmatic arc zdma located along the southern edge of the south qiangtang terrane in western tibet extends east west for 400 km small scattered granite and porphyry intrusions crop out in the zdma but a large amount of granite may be buried by late cretaceous to paleogene thrusting two stages of magmatism have been identified at 170 150 ma and 130 110 ma the widely distributed middle late jurassic granite intrusions in the zdma exhibit sr nd isotopic characteristics similar to those of ore bearing porphyries in the duolong giant cu au deposit and their ehf t values mostly overlap those of other porphyry cu mo deposits in the zdma and the gangdese zone the sr nd hf isotopic geochemistry suggests variable contributions of mantle and qiangtang crustal sources and indicates the presence of two new ore districts with potentials for cu au fe and pb zn ores located in the jiacuo liqunshan and larelaxin caima areas except for the duolong ore forming porphyries which show significant contributions of mantle components intruded into an accretionary melange setting the early cretaceous granites in other areas of the belt are of mostly crustal origin from sources in qiangtang felsic basement and permo carboniferous strata indicating the weak ore forming potential of skarn type fe and pb zn deposits the ephemeral but deep bangong co nujiang ocean in the early jurassic evolved into a shallow compressional marine basin in the middle late jurassic possibly transitioning to northward flat subduction of oceanic crust at this time the subducted slab broke off in the early cretaceous initiating a peak in arc magmatism and metallogenesis at 125 110 ma

petrogenesis and metallogenic setting of porphyries of the duobuza porphyry cu au deposit central tibet china abstract given that the duobuza deposit was the first porphyry cu au deposit discovered in central tibet the mineralization and mineralized porphyry in this area have been the focus of intensive research yet the overall porphyry sequence associated with the deposit remains poorly understood new geological mapping logging and sampling of an early granodiorite porphyry an inter mineralization porphyry and a late mineralization diorite porphyry were complemented by la icp ms zircon dating whole rock geochemical and sr nd isotopic analyses and in situ hf isotopic analyses for both inter and late mineralization porphyry intrusions all of the porphyry intrusions are high k and calc alkaline and were emplaced at ca 120 ma the geochemistry of these intrusions is indicative of arc magmatism as all three porphyry phases are enriched in light rare earth elements and large ion lithophile elements and depleted in heavy rare earth elements and high field strength elements these similar characteristics of the intrusions when combined with the relatively high 87 sr 86 sr i negative e nd t and positive e hf t values suggest that the magmas that formed the porphyries were derived from a common source region and shared a single magma chamber the magmas were generated by the mixing of upwelling metasomatized mantle wedge derived mafic magmas and magmas generated by partial melting of amphibolite within the lower crust the inter mineralization porphyry has the lowest e nd t and highest 87 sr 86 sr i values suggesting that a large amount of lower crust derived material was incorporated into the melt and that metals such as cu and au from the enriched lower crust were scavenged by the parental magma the relative mafic late mineralization diorite porphyry phase was formed by the residual magma in the magma chamber mixing with upwelling mafic melt derived from metasomatized mantle the magmatic hydrothermal evolution of the magma in the chamber released ore forming fluid that was transported mainly by the inter mineralization porphyry phase during the mineralization stage which ultimately formed the duobuza porphyry cu au deposit these porphyritic intrusions of the duobuza deposit have high mg and low la yb n values and show some high lile hfse ratios indicating the magma source was enriched by interaction with slab derived fluids combined with age constraints on the regional tectonic evolution these dating and geochemical results suggest that the duobuza porphyry cu au deposit formed in a subduction setting during the final stages of the northward subduction of the neo tethyan ocean

reconstructing in space and time the closure of the middle and western segments of the bangong nujiang tethyan ocean in the tibetan plateau when and how the bangong nujiang tethyan ocean closed is a highly controversial subject in this paper we present a detailed study and review of the cretaceous ophiolites ocean islands and flysch deposits in the middle and western segments of the bangong nujiang suture zone bnsz and the cretaceous volcanic rocks late mesozoic sediments and unconformities within the bnsz and surrounding areas our aim was to reconstruct the spatial temporal patterns of the closing of the middle and western segments of the bangong nujiang tethyan ocean our conclusion is that the closure of the ocean started during the late jurassic and was mainly complete by the end of the early cretaceous the closure of the ocean involved both longitudinal diachronous closure from north to south and transverse diachronous closure from east to west the spatial temporal patterns of the closure process can be summarized as follows the development of the bangong nujiang tethyan oceanic lithosphere and its subduction started before the late jurassic after the late jurassic the ocean began to close because of the compressional regime surrounding the bnsz along the northern margin of the bangong nujiang tethyan ocean collisions involving the arcs back arc basins and marginal basins of a multi arc basin system first took place during the late jurassic early early cretaceous resulting in regional uplift and the regional unconformity along the northern margin of the ocean and in the southern qiangtang terrane on the northern side of the ocean however the closure of the bangong nujiang tethyan ocean cannot be attributed to these arc arc and arc continent collisions because subduction and the development of the bangong nujiang tethyan oceanic lithosphere continued until the late early cretaceous the gradual closure of the middle and western segments of bangong nujiang tethyan ocean was diachronous from east to west starting in the east in the middle early cretaceous and being mainly complete by the end of the early cretaceous the bnsz and its surrounding areas underwent orogenic uplift during the late cretaceous

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

quantitative models of sedimentary basin filling summary quantitative modelling of the filling of sedimentary basins was begun in earnest in the 1960s dozens of themes and variations have been proposed since then and have yielded an abundance of idealized stratigraphic patterns as functions of both imposed changes and basin properties post plate tectonic modelling began with rigid lid models which show the stratigraphic signature of subsidence variation this work introduced the connection between stratigraphy and the rheology of the lithosphere rigid lid models are the simplest type of geometric model in which the sediment surface is assigned prescribed geometries usually corresponding to different depositional environments these can reproduce many aspects of overall stratal geometry but are formally restricted to relatively long timescales for which quasi steady surface topography can be assumed so called dynamic models attempt to represent the morphodynamics of the sediment surface by abstracting and averaging short term transport processes most of the dynamic models proposed to date can be seen as special cases of a single general morpho dynamic equation the most important result of the first wave of quantitative basin filling models is that even relatively simple models can produce reasonable stratal patterns we now have a wide array of tools for exploring scenarios searching for general behaviours and effects and making initial quantitative predictions we have also learned that basin response to external forcing as recorded in stratigraphy can be as sensitive to the characteristics of the basin as to the forcing the main brake on the development of basin modelling is not computing power but lack of methods and data for testing the models we have already developed physical experiments which are only just beginning are one means of doing this experimental stratigraphy is a bridge to quantitative field tests which will require collaboration among academic researchers from a wide range of areas and between academia and industry on projects of greater scale and degree of integration than we have seen so far the advancement of quantitative sedimentary geology will also require significant changes in the way the subject is taught at all levels

geochemistry and pb sr nd isotopic features of ore bearing porphyries in bangong lake porphyry copper belt western tibet detailed geochemical and pb sr nd isotopic researches on the duobuza copper deposit and the garqiong copper deposit were conducted in the bangong lake copper belt the result shows that compared with the porphyries of the gandese copper belt the ore bearing porphyries of the bangong lake copper belt are weaker in the enrichment of large ion lithophile elements lile and are also weaker in the depletion of high field strength elements and high rare elements thus having weak positive eu anomaly viewed from pb sr nd isotopic features the ore bearing porphyries are characterized by the enrichment of radiogenic pb the obviously low ratios of 143nd 144nd and the source nearer to the indian ocean sedimentary area indicating that the magma source of the ore bearing porphyries is much shallower with the mixture of more crustal materials the forming tectonic environment of the ore bearing porphyries in the bangong lake copper belt belonged to the active continental ridge whereas that in the gangdese copper belt was far away from the active continental ridge the bangong lake porphyry copper belt was formed in a post collisional crustal up lift stage whereas the gangdise porphyry copper belt in a stage of post collisional crustal extensional collapse when the crust rose to the maximum height

automatic calibration of stratigraphic forward models for predicting reservoir presence in exploration understanding and predicting reservoir presence and characteristics at regional to basin scales is important for evaluating risk and uncertainty in hydrocarbon exploration simulating reservoir distribution within a basin by a stratigraphic forward model enables the integration of available prior information with fundamental geologic processes embedded in the numerical model stratigraphic forward model predictions can be significantly improved by calibrating the models to independent constraints such as thicknesses from seismic or well data a three dimensional basin scale stratigraphic forward modeling tool is coupled with an inversion algorithm the inversion algorithm is a modification of the neighborhood algorithm a type of genetic algorithm which is designed to sample complex multimodal objective functions and is parallelized on computer clusters to accelerate convergence the process generates a set of representative geological models that are consistent with prior ranges for uncertain parameters calibration constraints and associated tolerance thresholds the workflow is first demonstrated on two data sets a synthetic example based on a clastic passive margin and a real hydrocarbon exploration example for slope and basin floor stratigraphic traps in the neocomian lower cretaceous of the west siberian basin the analysis of calibrated models provides constraints on stratigraphic controls and allows prediction of locations with higher potential to develop stratigraphic traps these locations are related to complex interactions between paleobathymetry subsidence eustatic fluctuations characteristics of sediment input sources and sediment transport parameters results show the potential of stratigraphic forward modeling combined with inverse methods as an additional tool to support conventional play based exploration and reservoir presence prediction

three dimensional interplay of advective and diffusive processes in the generation of sequence boundaries quantitative stratigraphic models have been generated using either geometric constructs or diffusion algorithms to simulate the development and timing of sequence boundaries and how they vary in response to tectonics eustasy climate and sediment supply while diffusion models provide a physical basis for the generation of clinoforms the resulting model predictions appear to do little more than track the transgressive and regressive movements of the shoreline on the other hand geometric models do a relatively good job in simulating the observed stratigraphy but offer little in actually ascertaining the physics controlling the processes of deposition and erosion all these stratigraphic models fail to predict the most fundamental response of depositional systems namely the development of a downward shift in coastal onlap during a fall in relative sea level this basinward shift and the development of an onlap surface are the critical observations that define chronostratigraphic sequences and are not simply a consequence of shoreline transgressions and regressions a major assumption in these two dimensional models is that the observed stacking patterns are solely the consequence of deposition processes and sediment transport within the modelling section in marked contrast to the observation that the major sediment transport direction along margins is sub parallel to the margin we present a variation on the diffusion theme in which across margin transport and deposition are dominated by advection type processes and along margin erosion and deposition processes are dominated by diffusion with this combination of advection and diffusion it is possible to generate a lowstand system tract and sequence boundaries i e onlap surfaces in particular the generation of the lowstand system tract is in large part the result of depositional processes operative along the margin i e out of the section

loess stratigraphy in central china abstract the loess deposits in central china record world wide climate changes of the last 2 5 ma numerous climatic oscillations are marked by alternating loess and soil units with continuous coverage of the matuyama and brunhes epochs magnetic susceptibility of the deposits correlates closely with the oxygen isotope record of the deep sea sediments and provides an independent measure of climate and time the key marker bed of the chinese loess sequence is the paleosol s5 the time equivalent of the mid brunhes oxygen isotope stages 13 14 and 15 it marks a prolonged interval of warm humid climate lasting from approximately 615 to 470 thousand years ago several episodes of river downcutting coincide with deposition of the exceptionally thick loess units l1 oceanic oxygen isotope stages 2 to 4 l2 stage 6 l5 stage 12 l6 stage 16 l9 stage 22 l15 stage 38 about 1 15 ma and ws4 about 2 3 ma these erosional events are interpreted as a result of episodic uplift of the loess plateau the deposition of the earliest loess layers between 2 5 and 2 3 ma ago marks a first order shift from warm and humid environments toward harsh continental steppes comparable to those of the middle and late pleistocene little if any lithologic or paleontologic changes were noted within or above the olduvai magnetozone so that the proposed plio pleistocene boundary at approximately 1 65 ma has no lithostratigraphic and biostratigraphic representation in the chinese loess series comparison with the deep sea drilling program core 552a in the north atlantic and with the santerno river section near bologna shows that the occurrence of the earliest loess in china coincides with the timing of the first significant ice rafting in the north atlantic and with the appearance of cold water foraminifers in the marine deposits of northern italy an extension of the stage system of the oxygen isotope signal extended back to the gauss matuyama boundary is proposed

the simulation of the sedimentary fill of basins an interactive computer simulation which erects models of sedimentary geometries by filling in a two dimensional basin from both sides with a combination of clastic sediment and or in situ and transported carbonate sediments is described the simulation program is implemented in c using graphical plotting functions data entry including the initial basin configuration the local tectonic behavior the sea level curves the amount and source direction of clastic sediment and the growth rates of carbonates as a function of water depth is performed interactively geometries of clastic and carbonate sediments evolve through time and respond to tectonic movement eustasy and sedimentation clastic modeling includes sedimentary bypass and erosion and sedimentation in alluvial and coastal plains marine shelf basin slope and basin floor settings carbonate modeling includes progradation the development of hard grounds downslope aprons keep up catch up back step and drowned reef settings as well as lagoonal and epeiric settings also included in the model are extensional vertical faulting of the basin sediment compaction and isostatic response to sediment loading sediment geometries are plotted on a graphics terminal as they are computed so the user can immediately view the results based on these observations parameters can be changed and the program rerun until the user is satisfied with the resultant geometry this paper includes output showing the simulation s sensitivity to eustatic sea level variations and variations in sedimentation and subsidence rates also shown are outputs demonstrating the modeling of some examples from the geologic section in the permian basin of west texas and the upper permian of the sichuan basin

palaeoenvironment and geoconservation of mammoths from the nosak loess palaeosol sequence drmno northeastern serbia initial results and perspectives a quaternary site at drmno comprising of middle and late pleistocene loess palaeosol sequences near kostolac northeast serbia attracted attention from the general public and scientists when several steppe mammoth and other mammal skeletons from middle pleistocene fluvial deposits were discovered in 2009 and 2012 this paper presents the combination of malacological and enviromagnetic analyses preliminary luminescence dating litho pedostratigraphic and palaeo relief investigations that were applied to the nosak loess palaeosol sequence for the 2012 findings the results confirm and emphasize the antiquity of the sediments preserved in the nosak section and demonstrate the significance of the detailed and relatively complete palaeoenvironmental record they contain these discoveries can significantly contribute to setting the background towards an improved understanding of the evolution of mammoths on the european continent

the latest steppe mammoths mammuthus trogontherii pohlig and associated fauna on the late middle pleistocene steppe at nosak kostolac basin northeastern serbia abstract in 2012 bones and tusks of mammoths and remains of other large mammals scattered in a line 130 m long have been discovered in the loess deposits at the nosak mound in the kostolac basin northeastern serbia preliminary analyses indicate that remains come from mammuthus trogontherii equus ferus mosbachensis and cervidae indet steppe mammoth remains originate from at least four individuals three adults and one juvenile they include the largest steppe mammoth tusks ever reported the mammalian remains were mostly found disarticulated except for few articulated skeleton elements individual bones and teeth were encased within thick carbonate concretions from their composition morphology and manner of formation these carbonate concretions resemble the characteristic loess dolls that form in loess bones were exposed to subaerial weathering for some time before burial some damage on the bones indicates biogenic agents of their fragmentation and dispersal animals were probably attracted to the spot by a water source in the vicinity such as a spring or intermittent stream the bones and teeth accumulated at a single level within the loess likely deposited in mis 6 just above the upper of two paleosols formed during mis 7 a sample from a mammoth molar plate has been esr dated at 192 5 ka correlating with the very early mis 6 near the mis 6 7 boundary this makes the nosak mammoth the most recent occurrence of steppe mammoths in europe and the sole find dated to mis 6

differentiating the effect of episodic tectonism and eustatic sea level fluctuations in foreland basins filled by alluvial fans and axial deltaic systems insights from a three dimensional stratigraphic forward model many studies of foreland basins have recognized a hierarchical organization in the stacking of sequences deposited by axial deltaic and alluvial fan systems the hierarchy is often explained in terms of the competing control of eustasy and pulsed tectonic subsidence and the different frequencies at which these processes operate unravelling the relative contributions of tectonic and eustatic controls on the sequence stacking pattern is a fundamental question in foreland basin analysis yet this is difficult because of the lack of independent stratigraphic evidence in this study a three dimensional numerical model is presented which aids in the interpretation of alluvial successions in foreland basins filled by transverse and axial depositional systems under conditions of variable tectonism and eustatic sea level change the tectono sedimentary model is capable of simulating the hierarchical stratigraphic response to both eustatic and tectonic forcing and is of higher resolution than previous models of foreland basin filling numerical results indicate that the onset of tectonic activity is reflected by rapid retrogradation of both depositional systems and by widespread flooding and onlap of carbonate sediments syntectonic fluvial patterns on the axial deltaic plain are dominated by bifurcating channels swiftly relocating in response to the general rise in relative sea level induced by flexural subsidence the resulting surface morphology of the axial delta is convex upwards syntectonic eustatic sea level fluctuations result in parasequence scale packages of retrograding and prograding fan and delta sediments bounded by minor flooding surfaces and type 2 sequence boundaries incised channels are rare within the syntectonic parasequences and are formed only during phases of tectonic quiescence when eustatic falls are no longer compensated by the subsidence component in the rise in relative sea level suites of amalgamating axial channels corresponding to multiple eustatic falls delineate the resulting type 1 unconformities coarse grained incised channel fills are found in the zone between the alluvial fan fringes and the convex upward body of the axial delta as the axial streams tend to migrate towards this zone of maximum accommodation

early cretaceous ca 100 ma magmatism in the southern qiangtang subterrane central tibet product of slab break off the lack of early cretaceous magmatic records with high quality geochemical data in the southern qiangtang subterrane has inhibited a complete understanding of the magmatic processes and geological evolution of central tibet in this study we present zircon u pb ages whole rock geochemistry and sr nd pb and zircon hf isotopic data for the newly discovered moku pluton in the southern qiangtang subterrane zircon u pb dating reveals that the moku granites were emplaced in the early cretaceous ca 100 ma and are coeval with the hosted dioritic enclaves the granites are slightly peraluminous and high k calc alkaline i type granites and characterized by initial 87sr 86sr i ratios of 0 70605 0 70658 negative e nd t values 4 44 to 3 35 and nd isotopic model ages of 1 19 1 29 ga the granites have a wide range of zircon e hf t values 24 4 to 2 6 and concordant ratios of 206pb 204pb t 18 645 18 711 207pb 204pb t 15 656 15 666 and 208pb 204pb t 38 751 38 836 the coeval dioritic enclaves are medium to high k calc alkaline rocks with zircon e hf t values of 13 3 to 3 6 the geochemical signatures of the host granites and coeval dioritic enclaves indicate that the moku pluton was most likely generated by partial melting of the ancient lower crust with contributions from mantle derived melts our new data together with other recently published data indicate that the ca 100 ma magmatic rocks were derived from anatexis of the qiangtang lower crust that mixed with upwelling asthenosphere materials in response to the slab break off of the northward subduction of the bangong nujiang oceanic lithosphere

mathematical modelling of sedimentary basin processes abstract mathematical models of various sedimentary basin processes including hanging wall deformation evaporite deposition carbonate platform sedimentation and sequence development on active domino style fault blocks are presented many of these processes may be formulated using the equation of continuity of an open system as a starting point sedimentary and tectonic processes may be combined into a single mathematical formulation provided that an eulerian coordinate system is used and this ensures that tectonics and sedimentation are modelled as simultaneous rather than sequential processes the resulting algorithms are fast robust and applicable to many geologically very different situations but may be limited to relatively simple examples the conditions under which the models are numerically stable are also easily found the abstract nature of the mathematical models requires that simply determined properties such as palaeo water depth and palaeo slope must be used as proxy facies markers the main limitation of the method is that it is restricted to modelling processes which change slowly with time and space and the method can therefore not cope properly with episodic or chaotic processes

relative geologic time age volumes relating every seismic sample to a geologically reasonable horizon the age volume described in this paper can significantly increase the amount of useful geologic information extracted from a seismic data volume this paper has three goals the first is to introduce and describe the relative geologic time volume referred to herein as either an rgt volume or an age volume every seismic sample in an age volume contains an estimate of the relative geologic time for that sample which automatically relates every sample to a geologic horizon the second goal is to discuss some of the applications and advantages of using a rgt volume to store and access seismic interpretation for example it can be used to sculpt a seismic volume along a desired horizon or view depositional changes as a function of geologic time the third goal is to describe two methods for generating such a volume the first employing standard interpretation techniques and the second relying on unwrapping instantaneous phase unwrapping the instantaneous phase is a new holistic approach to interpreting seismic data that can produce a very detailed seismic interpretation the goal of building and using an rgt volume is to extract significantly more geologic information from the seismic data than is available from conventional methods the rgt volume is both a way of storing and retrieving seismic horizons to generate such a volume each seismic sample needs to be assigned an estimate of relative geologic time which in essence connects it to a geologically reasonable horizon in normal sections these relative geologic time values will increase with depth or traveltime high gradients in the rgt volume could be indicative of faults unconformities fluid contacts or interpretation errors while a constant value surface in a rgt volume is a seismic horizon figure 1 contains a portion of the seismic data used to illustrate the

towards process based geological reservoir modelling obtaining basin scale constraints from seismic and well data abstract forward stratigraphic modelling aims at representing the spatial distribution of lithology as a function of physical processes and environmental conditions at the time of deposition so as to integrate geological knowledge into the reservoir modelling workflow thus increasing predictive capabilities of reservoir models and efficient exploitation of hydrocarbons application of process based models in inverse mode is not yet well established due to our limited insight into the information content of common subsurface data and the computational overhead involved in this paper we examine inverse modelling of stratigraphy by using a typical dataset acquired in the hydrocarbon industry which consists of seismic data and standard logs from a limited number of wells the approach is based on the use of a forward model called simclast developed at delft university of technology to generate facies distribution and architecture at the regional scale three different goodness of fit functions were proposed for model inversion following an inference approach a synthetic reservoir unit was used to investigate the impact of the uncertainty affecting the input parameters and the information content of seismic and well data the case study showed that the model was more sensitive to the initial topography and to the location of the sediment entry point than to sea level the depth of the seismic reflector corresponding to the top reservoir surface was the most informative data source the initial and boundary conditions of the simulation were constrained by evaluating the depth of this reflector across the whole basin area in the reservoir area where the seismic to well tie was established the depth of the reservoir top does not give enough information for constraining the model parameters our results thus indicate that evaluation of basin scale data permits reduction of uncertainty in geostatistical reservoir models relative to the current workflow in which only local data are used effective use of well data to generate reservoir models conditioned to basin scale scenarios requires post processing methods to downscale the output of the forward model used in the experiments

u series analyses of the lower travertine at ehringsdorf ddr abstract u series analyses have been made of travertine samples from the archaeological site at ehringsdorf weimar the lower travertine in which hominid remains were found yields apparent ages from 350 000 to 200 000 yr correlation between isotope ratios yields an age of about 230 000 yr one sample of the upper travertine gives and age of 111 000 47 000 yr both upper and lower travertines contain fauna and flora indicative of interglacial conditions the lower travertine was deposited during isotope stage 7 while the upper travertine may have been formed during isotope stage 5 this contradicts most earlier biostratigraphic studies which assigned both lower and upper travertines to stages of the eem interglaciation correlative with isotope stage 5 the fauna and flora of the lower travertine are significantly different from those of the upper travertine however and in some respects are transitional to those of the travertines of bilzingsleben which appear to be older yet

a skeleton of steppe mammoth mammuthus trogontherii pohlig from drmno near kostolac serbia abstract the kostolac mammoth was discovered in 2009 in pleistocene deposits adjacent to the drmno open cast lignite mine in the serbian danube basin on the basis of cranial and dental features the individual is identified as the so called steppe mammoth mammuthus trogontherii the remains are those of an old male of estimated age around 62 years and comprise one of the most complete and best preserved known skeletons of this species and the first from the region skeletal height is estimated as around four metres and body mass 9 5 t the excellent preservation of the skeleton provides new information about the osteology of m trogontherii an evolutionary intermediate between the better known ancestral mammoth mammuthus meridionalis and woolly mammoth mammuthus primigenius the find is also remarkable for the articulated condition of the skeleton the animal occupying a crouching posture which is probably little altered from its original death position this and the depositional environment of the skeleton a broad fast flowing river suggest that the animal died in relatively shallow water and was very rapidly buried in river sediments based on the known european record of typical large sized m trogontherii of this kind the age of the kostolac skeleton and its enclosing sediments is between 1 0 and 0 4 ma

seismic simulations of experimental strata experimental strata formed in the new experimental earthscape xes basin at the st anthony falls laboratory of the university of minnesota offer a realistic model for simulating the seismic response of natural strata and thus for advancing understanding of the geologic information that can be extracted from seismic data a new method is presented here for using digital photos of the experimental strata to generate synthetic seismic data at the length scales and frequencies relevant to oil and gas exploration in the method the digital photos are transformed into models of acoustic velocity and bulk density which are then input into algorithms that generate synthetic seismic data three such algorithms are used to demonstrate the approach a convolutional algorithm which produces the equivalent of ideal poststack time migrated seismic data an exploding reflector algorithm which produces unmigrated poststack seismic data and a full wave equation algorithm which we use to produce a synthetic version of prestack unmigrated multichannel seismic data data generated by the latter two algorithms are processed to compare their information content against both the experimental strata and the ideal seismic data derived from the convolutional algorithm the qualitative comparison nicely illustrates the filtering of geologic information in seismic data and its further degradation by wave propagation phenomena such as diffractions multiples and interbed reverberations

three dimensional numerical modeling of deltaic depositional sequences 1 influence of the rate and magnitude of sea level change abstract a three dimensional numerical model of deltaic deposition is used to investigate the influence of sea level changes on delta development and sequence variability results illustrate the three dimensional morphology of key stratal surfaces and architecture of stratal units systems tracts and highlight the importance of the rate and magnitude of sea level change in controlling the evolution of deltaic depositional sequences high rates of sea level fall lead to the development of a limited number of major incised channels that focus sediment supply to a few elongate finger like forced regressive lobes separated by large areas of nondeposition in contrast low rates of sea level fall cause only minor channel incision which occurs late during sea level fall as a result sediment is supplied more uniformly to the delta front leading to an attached laterally continuous forced regressive apron during lowstand and subsequent sea level rise the delta morphology and internal geometry are strongly controlled by the rate of rise high rates lead to i poorly developed lowstand wedges that are drowned early ii high magnitude transgressions and iii the late development of maximum flooding surfaces the stratigraphy developed during sea level rise is also strongly influenced by the incised valley system created during the preceding sea level fall if deep major valleys developed that captured most of the sediment supply the resultant stratigraphy has well developed lowstand wedges that are flooded relatively late during sea level rise even within a single delta systems tracts and key stratal surfaces show three dimensional variability and two dimensional sections often lack significant elements of the stratigraphy as a result analysis of two dimensional sections can often lead to miscorrelation and erroneous interpretations of the controlling processes

high oxidation magmatic evolution in the naruo porphyry cu deposit tibet china abstract the naruo porphyry cu deposit is the third largest deposit discovered in the duolong metallogenic district previous research has focused mainly on the geochemistry of the ore bearing granodiorite porphyry the metallogenesis remains poorly understood in the present work on the basis of outcrops and drilling core geological mapping phases of early mineralization diorite two inter mineralization granodiorite porphyries and late mineralization granodiorite porphyry have been distinguished furthermore the alteration zones were outlined and the vein sequence was identified the diorite and three porphyry phases were subjected to laser ablation inductively coupled plasma mass spectrometry la icp ms zircon u pb dating and in situ hf isotope analyses as well as bulk major element trace element and sr nd isotopic analyses molybdenite re os dating was also conducted the zircon u pb dating results show that the diorite and porphyry intrusions were emplaced at about 120 ma and the molybdenite re os isochron age is 118 8 1 9 ma this indicates that the naruo porphyry cu deposit was formed during a continuous magmatic hydrothermal process all of the diorite and granodiorite porphyry samples showed arc magmatic characteristics moreover the moderate 87 sr 86 sr i ratios and low e nd t and e hf t values of the diorite and porphyry intrusions suggest the source region of the juvenile lower crust the lower 87 sr 86 sr i and 143 nd 144 nd i ratios and higher e nd t values and incompatible element concentrations than those in the granodiorite porphyry samples indicate a two stage magmatic generation process for the intrusions the early mineralization diorite has a high cu concentration implying that the source is enriched in cu however the slightly lower cu content of the late mineralization granodiorite porphyry samples might imply cu release from magmas and deposition within the metallogenic stage the multiple stages of intrusions and subsequent volcanism within the duolong metallogenic district together with high sr y features indicate persistent magmatism during the metallogenic epoch which is necessary for maintaining the activity of magmatic hydrothermal and mineralization processes thus the high cu content in the source region mantle derived melt upwelling and multiple stages of persistent magmatism were favorable for the formation of the naruo porphyry cu deposit the high fe 2 o 3 feo ratios of the diorite and granodiorite porphyry intrusions show very high oxidation features which is coincident with estimated magmatic oxidation state calculated by the zircon trace element compositions the high oxidation facilitates sulfur and chalcophile metals to be scavenged into the magmatic hydrothermal systems which is crucial for the metallogenesis of the naruo porphyry cu deposit

cretaceous structures in the duolong region of central tibet evidence for an accretionary wedge and closure of the bangong nujiang neo tethys ocean abstract this article focuses on the cretaceous structures in the duolong region northern tibet our aim was to constrain the metallogenic setting of the duolong giant porphyry cu au deposit and to discuss the implications for the closure of the bangong nujiang neo tethys ocean there are two tectonic stages in the duolong region during the early to late cretaceous the first stage is characterised by numerous large scale folds and faults with ne sw compression the 40ar 39ar plateau age of sericite from mylonite is 127 8 1 1 ma which represents the timing of tectonic emplacement of the jurassic mugagangri formation jm and ophiolite this stage corresponds to the northward subduction of the bangong nujiang neo tethys ocean the second stage is characterised by the duolong thrust nappe with a series of sinter deposits slip surfaces fault fracture zones klippes and tectonic windows basalt from the hanging wall yields a zircon u pb age of 110 4 1 7 ma which is older than the upper cretaceous abushan formation ka of the footwall a red layer obtained from drillcores is younger than the overlying jurassic strata on the basis of the youngest detrital zircon u pb age of 116 2 ma this stage is correlated with the closure of the bangong nujiang neo tethys ocean we suggest the upper triassic riganpeicuo formation jm and ophiolite successively accreted to the southern margin of the south qiangtang terrane during the late jurassic to early cretaceous these constitute the main body of the epicontinental accretionary wedge this accretionary wedge includes many early cretaceous epicontinental arc volcanic rocks and granites and the duolong cu au deposits were formed in an andean type active continental margin setting we also conclude that the bangong nujiang neo tethys ocean closed during the late early cretaceous to early late cretaceous and that continental collision continued until the end of the late cretaceous

land sea correlations in the pleistocene based on isoleucine epimerization in non marine molluscs the correlation between the oxygen isotope stratigraphy of the oceans and continental stratigraphic records is one of the main challenges for quaternary research most continental classifications however are based on techniques and hypotheses that predate recent advances nevertheless the deep sea oxygen isotope global stratigraphic framework has been extended to the continents by means of some long sequences1 but these are exceptional and regional geology is unsatisfactorily classified for correlation with the oxygen isotope signal because successive geological events produced similar evidence homotaxis geochronometric dating is essential for correlation but available methods are highly site regional or sample specific fortunately non marine molluscs are ubiquitous in time and space and here we use the time dependent epimerization of l isoleucine in these fossils to subdivide the pleistocene of the british isles and to identify more events than recognized by the existing classification2 by calibrating the relative aminostratigraphic scale with independent dating methods we have set up a geochronology which is the basis for land sea correlations back to oxygen isotope stage 15

age of mammuthus trogontherii from kostolac serbia and the entry of megaherbivores into europe during the late matuyama climate revolution abstract at the drmno open pit coal mine near kostolac in serbia a nearly complete skeleton of mammuthus trogontherii nicknamed vika was discovered in a fluvial deposit overlain by a loess paleosol sequence where a second paleontological level named nosak with remains of m trogontherii was found we studied the magnetostratigraphy of the kostolac sedimentary sequence and found that the vika layer dates to 0 8 ma shortly before the brunhes matuyama boundary in addition according to our age model and previously reported optically stimulated luminescence and electron spin resonance dates the nosak fossils have an estimated age of 0 19 ma and lived during the earliest part of marine isotope stage 6 it appears therefore that at kostolac m trogontherii is preserved both at its earliest occurrence at 0 8 ma and close to its latest occurrence at 0 19 ma and may well have been present in between albeit not yet found we speculate that megaherbivores such as m trogontherii entered europe along a conjunct danube po river migration conduit connecting western asia levant with central southern europe where vast and exploitable ecosystems particularly suited for steppe or savanna adapted megaherbivores from asia and africa developed during the late early pleistocene climate revolution at around 0 8 ma