thunderstorm genesis zones in the colorado rocky mountains as determined by traceback of geosynchronous satellite images abstract mountain thunderstorms often originate in preferred regions of the topography as shown qualitatively by pilot reports and more quantitatively by meteorological radar satellite and lightning detector studies to further investigate the phenomenon of mountain thunderstorm initiation we used time sequences of goes imagery to locate storms and to trace them back to their points of origin using three summers of data from days which started out clear we backtracked over 600 storms in the mountains of colorado and northern new mexico we plotted the origin points on a terrain map and drew contours of initiation frequency to identify regions with a high likelihood of producing thunderstorms we found that initiation sites tended to cluster into identifiable geographical locations or genesis zones consistent with findings based on the other data sources when cloud propagation effects were taken into account the locations of these genesis zones were also consistent with the locations of clusteri

defining the timing and duration of the kacak interval within the eifelian givetian boundary gssp mech irdane morocco using geochemical and magnetic susceptibility patterns abstract here we present new geochemical and magnetic susceptibility ms data from the global boundary stratotype section and point gssp for the middle devonian eifelian givetian e g boundary at mech irdane in the anti atlas mountains of eastern morocco these data come from 395 samples collected over a stratigraphic interval of 20 m beginning 4 5 m below the boundary and extending to the upper pumilio marker bed 14 5 m above the boundary ms data show long term transgressive regressive t r eustatic cyclicity upon which is superimposed shorter term climate cyclicity fourier analysis of these data yield high power at four frequencies that are consistent with milankovitch band orbital forcing eccentricity e1 and e2 at 400 and 100 kyr obliquity o1 at 32 kyr and precession p2 at 20 kyr the latter two corrected for secular changes in earth s orbit since the middle devonian a floating point time scale fpts for the boundary interval has been developed using a p2 cyclicity that allows temporal resolution to 10 kyr within the section based on the stratigraphic ranges of geochemical and ms anomalies as well as previously reported biostratigraphic extinctions from the boundary interval we estimate the kacak interval to extend from 1 0 m below the e g boundary to 1 0 m above it with a duration of 200 10 kyr geochemical proxies demonstrate that the kacak interval was characterized by more reducing conditions greater organic carbon burial and an increase in the flux of detrital materials especially clays reflecting an increase in subaerial weathering rates the pumilio beds located 12 15 m above the e g boundary were deposited during successive maximum highstands under conditions of elevated primary productivity and reduced detrital influx

msec data sets record glacially driven cyclicity examples from the arrow canyon mississippian pennsylvanian gssp and associated sections abstract here we report magnetic susceptibility ms analyses from three mainly marine sections the mississippian pennsylvanian mid carboniferous global boundary stratotype section and point gssp in arrow canyon se nevada and two secondary sections nearby one in arrow canyon 200 m distant and the second in battleship wash 2 km south of the gssp all three sections are easily correlated using the magnetosusceptibility event and cyclostratigraphy method msec cyclicity is clearly apparent in all three sections and time series analysis independently verifies the ms zonation developed from the smoothed data set the periods determined in the three sections support the argument that deposition of these mid carboniferous rocks resulted from climate controlled glacio eustatic fluctuations that were driven by gondwana glaciation given the published average thicknesses of t r cycles 50 m and the estimates for timing of glacial interglacial cyclicity during the mid carboniferous we assign the strong ft peak observed for the three ms data sets a value of 400 000 years corresponding to the milankovitch e1 eccentricity band we then calculate a floating point time scale fpts for the sampled sequence the fpts results indicate that 1 sediment accumulation rates bracketing the mid carboniferous boundary averaged 0 7 cm 1000 years and 2 were relatively constant for these reference sections

stream driven high density gravelly traction carpets possible deposits in the trabeg conglomerate formation sw ireland and some theoretical considerations of their origin within high density flood flows a prominent mechanism of gravel transport and deposition is by stream driven high density traction carpet with a rheology similar to grain flow these gravel carpets are envisaged to form the basal portion of a bipartite high density flood flow decoupled from an overlying sand and silt laden turbulent flow several examples already documented in the literature are reviewed and an additional case from the lower old red sandstone of southwest ireland is presented two mechanisms of traction carpet initiation are discussed by rapid entrainment of gravel into suspension on rising stage followed by settling into the gravel traction carpet at peak and falling stage and by overconcentration of a normal low density bedload gravel entrainment suspension and traction carpet development are significantly easier if the flood water already carries a high concentration of sand and silt in suspension theoretical consideration further shows that gravelly traction carpets can be maintained in channels of relatively low gradient by the shear stress exerted by the high density sand bearing turbulent flood flow above this tangential shear stress is converted to dispersive pressure which aids buoyancy and quasi static grain to grain contacts in the support of the clasts within the gravel carpet the carpet is thought to have a quasi plastic rheology but behave much like a viscous fluid at high shear rates stream driven gravelly traction carpets are expected to produce sheet like units of clast to matrix supported conglomerate characterized by a parallel or an a p a i clast fabric these units may be ungraded normally or inversely graded depending on the rate of shear the viscosity of the flow and the celerity of deposition

influence of sedimentary setting on the use of magnetic susceptibility examples from the devonian of belgium bulk magnetic susceptibility measurements on sedimentological samples from all geological periods have been used widely in the last two decades for correlations and as a proxy for sea level variations this paper explores the link between magnetic susceptibility depositional setting and environmental parameters these environmental parameters include distal proximal transects microfacies successions and fourth order trends on different carbonate platform types platform ramp carbonate mound or atoll during different devonian stages eifelian givetian and frasnian average magnetic susceptibility values over a distal proximal trending facies succession vary markedly with depositional setting on carbonate platforms average magnetic susceptibility generally increases towards the top of shallowing upward sequences on a distal proximal transect average magnetic susceptibility is intermediate for the deepest facies decreases for the reef belts and increases to a maximum in the back reef zone in ramps and atolls magnetic susceptibility trends clearly differ average magnetic susceptibility generally decreases towards the top of shallowing upward sequences and is highest in the deepest facies the strong relationship between magnetic susceptibility facies and sequences implies a strong environmental influence however the different responses in the different platform types suggest that sea level changes leading to variation in detrital input is not the only parameter controlling average magnetic susceptibility values other primary or secondary processes also probably influenced magnetic mineral distribution primary processes such as carbonate production and water agitation during deposition are probably key factors when carbonate production is high the proportion of magnetic minerals is diluted and the magnetic susceptibility signal decreases high water agitation during deposition will also selectively remove magnetic minerals and will lead to low average magnetic susceptibility values these parameters explain the lowest values observed on the reef platform inner ramp and atoll crown which are all in areas characterized by higher carbonate production and greater water agitation during deposition the lowest values observed in the lagoon inside the atoll crown can be related to detrital isolation by the atoll crown however other parameters such as biogenic magnetite production or diagenesis can also influence the magnetic signal diagenesis can change magnetism by creating or destroying magnetic minerals however the influence of diagenesis probably is linked strongly to the primary facies permeability amount of clay or organic matter and probably enhanced the primary signal the complexity of the signal gives rise to correlation problems between different depositional settings thus while magnetic susceptibility has the potential to be an important correlation tool the results of this investigation indicate that it cannot be used without consideration of sedimentary processes and depositional environments and without strong biostratigraphical control

mixing of siliciclastic and carbonate sediments in shallow shelf environments the inhibiting effect that siliciclastic material has on carbonate secreting organisms has lead to the generalization that sediments composed of mixtures of carbonate and siliciclastic material should rarely form however many modern and ancient shelf deposits contain a spectrum of sediments that are of mixed composition the processes responsible for this mixing can be grouped into four categories 1 punctuated mixing where sporadic storms and other extreme periodic events transfer sediments from one depositional environment to another 2 facies mixing where sediments are mixed along the diffuse boundaries between contrasting facies 3 in situ mixing where the carbonate fraction consists of the autochthonous or parautochthonous death assemblages of calcareous organisms that accumulated on or within siliciclastic substrates and 4 source mixing where admixtures are formed by the uplift and erosion of nearby carbonate source terranes the allochemical constituents of mixed sediments are both coralgal and foram mollusc in composition the foram mollusc assemblage is the most common because of the effects of increased turbidity unstable substrates and the clogging of filter feeding mechanisms associated with a siliciclastic influx

ancient lacustrine hyperpycnites a depositional model from a case study in the rayoso formation cretaceous of west central argentina abstract hyperpycnal flows originate when sediment laden fluvial discharges enter standing lower density water because of their excess density the flows plunge near the river mouth and continue to travel basinward as a quasi steady and fully turbulent underflow the related deposits are hyperpycnites and constitute a particular type of turbidite with poorly known facies and facies tracts although hyperpycnal flows seem to be quite common in present times their occurrence in fossil strata is poorly documented this paper addresses the characteristics and depositional processes of shallow lacustrine sandy hyperpycnites on the basis of the field analysis of well exposed lower cretaceous strata rayoso formation in the neuquen basin of west central argentina the rayoso formation is composed of clastic and minor evaporitic red beds up to 1200 m thick deposited in a shallow perennial lake of variable salinity affected by long lived hyperpycnal flows main clastic facies are composed of fine grained sandstones with climbing ripples and plane beds other common sandstone facies include massive beds and low angle cross stratification most sandstone facies are related to traction plus fallout processes and often show a vertical fluctuation between sedimentary facies originated under different traction plus fallout conditions within single beds these fluctuations are interpreted to be evidence of deposition from flow fluctuations in sustained hyperpycnal flows most beds internally show the existence of three depositional phases acceleration ap erosion plus bypass ep and deceleration dp which record the complete evolution of a single long lived hyperpycnal flow at a fixed point additionally the depositional evolution of a single long lived hyperpycnal flow with distance records initially the progressive basinward migration of the ap and ep phases and finally an overall deposition under the dp phase both in proximal and distal areas this evolution provides an adequate explanation for the basinward extension of channelized features and for the occurrence of fine grained sandstones with climbing ripples both in proximal and distal positions within the same hyperpycnal system consequently facies analysis derived from application of the bouma sequence is not valid for deposits of quasi steady hyperpycnal flows

jurassic deep water fans in the neo tethys ocean the kashafrud formation of the kopet dagh basin iran abstract the middle jurassic kashafrud formation of northeast iran was deposited in the kopet dagh basin linked to the neo tethys ocean the 2 km thick succession commences with fluvio marine boulder conglomerates that occupy bedrock valleys but the bulk of the formation comprises a deep water succession of interbedded sandstone and mudstone packages with trace fossils and sparse ammonites neogene collisional events deformed the strata to create the kopet dagh mountains the deep water succession represents channel lobe systems and associated levees and overbank areas on slope to basin floor fans northward paleoflow suggests that rivers drained uplands along the paleo tethys suture zone forming fan deltas on a narrow shelf with associated sediment transport to deeper water coarse sands extrabasinal pebbles and plant fragments are present throughout the formation and a thick boulder conglomerate unit lies within the turbidite succession these observations suggest proximity to terrestrial sources throughout deposition sandstone packages are mainly less than 10 m thick maximum 84 m and numerous lensoid packages of thick bedded sandstone tens of meters thick and up to 200 m wide represent submarine channel fills thick bedded lenses and sheets show a relatively narrow range of paleoflow direction and represent major submarine conduits whereas the more varied paleoflow direction of thin bedded packages suggests that many were deposited on levees the presence in the kashafrud formation of potential source rocks in the form of organic rich mudstones and abundant plant fragments suggests that the formation may have contributed to hydrocarbon fields within overlying formations sandstone sheets and channel fills could form local reservoirs

magnetosusceptibility event and cyclostratigraphy method applied to marine rocks detrital input versus carbonate productivity magnetic susceptibility data from marine rocks can be used for global correlation due to synchronous variations in global erosion we show here that the magnetic susceptibility signature found in two forms resides mainly in paramagnetic and other detrital constituents in most marine rocks the first form is a short term low magnitude high frequency cyclic climate signature that is often useful for regional correlation the second form is a longer term higher magnitude low frequency signature resulting from transgressive and regressive events that can be used for global correlation fluctuations in detrital input due to eustatic based erosion are the primary cause of events these fluctuations are driven by large scale processes such as global orogenic cycles however variations in carbonate productivity cannot be ruled out when explaining the low magnitude climate driven cyclicity also observed in magnetic susceptibility data sets

the frasnian famennian boundary interval in the south polish moravian shelf basins integrated event stratigraphical approach abstract the late devonian mass extinction event near the frasnian famennian f f boundary has been analysed using conodont biostratigraphy and biofacies sedimentology magnetic susceptibility and geochemistry in reference sections of the south polish moravian shelf holy cross mountains cracow and brno areas high resolution biostratigraphic study revealed difficulties in the precise recognition of this natural stage boundary but confirmed the occurrence of a major third order sequence boundary in the f f transition in an active synsedimentary tectonic setting marked by erosional discontinuities hardgrounds and brecciation or omission surfaces conclusive evidence of an extraterrestrial impact has not been found among earth bound factors the main devastating role in the shelf habitats is ascribed to fluctuating anoxia and or nutrient dynamics in a disturbed greenhouse climatic setting the long term facies changes were determined by a conspicuous break in carbonate production accompanied by replacement of mature stromatoporoid coral reefs by pioneer shelly crinoid banks microbial mounds and localised oolitic bars the key f f passage interval was marked by intermittent but generally accelerated periplatform ooze debris input and severe storm events as well as by probably highly fluctuating oxygenation and biological overproduction best manifested in radiolarian silicisponge and cephalopod acmes eutrophication phenomena at least partly stimulated by various hydrothermal and volcanic processes were one of the major biogeochemical processes during this climax of the late devonian biotic crisis however significant oceanographic perturbations were also linked with the onset of the transgressive hypoxic upper kellwasser event still within the latest frasnian linguiformis zone i e well before the f f conodont collapse implied variations in the redox state of seawater through the kellwasser timespan probably in regionally highly variable temporal scales are in agreement with recent palaeoecological and biogeochemical inferences in particular suggesting recovering oxygenation just prior to the f f boundary in the other laurussian intrashelf basins all the data support a long time multicausal earth bound crisis instead a worldwide cosmic catastrophe

ten turbidite myths abstract during the past 50 years the turbidite paradigm has promoted many myths related to deep water turbidite deposition john e sanders 1926 1999 a pioneering process sedimentologist first uncovered many of these turbidite myths this paper provides a reality check by undoing 10 of these turbidite myths myth no 1 turbidity currents are non turbulent flows with multiple sediment support mechanisms reality turbidity currents are turbulent flows in which turbulence is the principal sediment support mechanism myth no 2 turbidites are deposits of debris flows grain flows fluidized flows and turbidity currents reality turbidites are the exclusive deposits of turbidity currents myth no 3 turbidity currents are high velocity flows and therefore they elude documentation reality turbidity currents operate under a wide range of velocity conditions myth no 4 high density turbidity currents are true turbidity currents reality ph h kuenen 1950 introduced the concept of turbidity currents of high density based on experimental debris flows not turbidity currents high density turbidity currents are sandy debris flows myth no 5 slurry flows are high density turbidity currents reality slurry flows are debris flows myth no 6 flute structures are indicative of turbidite deposition reality flute structures are indicative only of flow erosion not deposition myth no 7 normal grading is a product of multiple depositional events reality normal grading is the product of a single depositional event myth no 8 cross bedding is a product of turbidity currents reality cross bedding is a product of traction deposition from bottom currents myth no 9 turbidite facies models are useful tools for interpreting deposits of turbidity currents reality a reexamination of the annot sandstone in se france which served as the basis for developing the first turbidite facies model suggests a complex depositional origin by plastic flows and bottom currents myth no 10 turbidite facies can be interpreted using seismic facies and geometries reality individual turbidity current depositional events commonly centimeters to decimeters in thickness cannot be resolved in seismic data all turbidite myths promote falsehood and should be abandoned

the mid cimmerian tectonic event bajocian in the alborz mountains northern iran evidence of the break up unconformity of the south caspian basin

composition porosity and reservoir potential of the middle jurassic kashafrud formation northeast iran abstract in the kopet dagh basin of iran deep sea sandstones and shales of the middle jurassic kashafrud formation are disconformably overlain by hydrocarbon bearing carbonates of upper jurassic and cretaceous age to explore the reservoir potential of the sandstones we studied their burial history using more than 500 thin sections supplemented by heavy mineral analysis microprobe analysis porosity and permeability determination and vitrinite reflectance the sandstones are arkosic and lithic arenites rich in sedimentary and volcanic rock fragments quartz overgrowths and pore filling carbonate cements calcite dolomite siderite and ankerite occluded most of the porosity during early to deep burial assisted by early compaction that improved packing and fractured quartz grains iron oxides are prominent as alteration products of framework grains probably reflecting source area weathering prior to deposition and locally as pore fills minor cements include pore filling clays pyrite authigenic albite and k feldspar and barite existing porosity is secondary resulting largely from dissolution of feldspars micas and rock fragments with some fracture porosity porosity and permeability of six samples averages 3 2 and 0 0023 md respectively and 150 thin section point counts averaged 2 7 porosity reflectance of vitrinite in eight sandstone samples yielded values of 0 64 0 83 in the early mature to mature stage of hydrocarbon generation within the oil window kashafrud formation petrographic trends were compared with trends from first cycle basins elsewhere in the world inferred burial conditions accord with the maturation data suggesting only a moderate thermal regime during burial some fractures iron oxide cements and dissolution may reflect cenozoic tectonism and uplift that created the kopet dagh mountains the low porosity and permeability levels of kashafrud formation sandstones suggest only a modest reservoir potential for such tight sandstones fractures may enhance the reservoir potential

the cretaceous pyonghae sequence southeast korea terminal fan facies abstract the cretaceous pyonghae sequence southeast korea comprises a nonmarine clastic sequence of dominant purplish siltstone with subordinate gravelstone and sandstone the sequence consists of eight sedimentary facies which can be organized into three facies associations facies association i occurs along the basin margins and is represented by disorganized gravelstone facies g1b and g2 and stratified gravelly sandstone facies gs the gravelstone and sandstone facies are interpreted as debris flow deposits and braided stream deposits respectively formed in alluvial fans n facies association ii mainly occurs in the central part of the basin and comprises sheet like sandstone bodies facies gs s1 and s2 intercalated with purplish siltstone beds facies m1 the sheet like sandstone beds show a fining upward trend with sharp base and lateral margins and are often horizontally stratified these features most likely result from frequent diversion of ephemeral shallow stream channels on floodplain and subsequent infilling with coarse grained sediments facies association iii is characterized by thick siltstone beds facies m1 with lenticular sandstone and gravelstone beds the siltstone beds contain calcareous nodules the facies association iii is well developed in the southern part of the basin where it represents floodplain environments alluvial fans facies association i and adjacent floodplain facies association iii which are connected by ephemeral stream channel networks facies association ii can be referred to as terminal fan system autocyclic processes such as spasmodic floods under semi arid climatic conditions are important for the development of terminal fan systems

facies and petrophysical signature of the tournaisian visean lower carboniferous sea level cycle in carbonate ramp to basinal settings of the wales brabant massif british isles we studied the relationships between stratigraphic distribution of outcrop spectral gamma ray magnetic susceptibility and carbonate facies stacking patterns across the regionally significant transgressive regressive cycle at the tournaisian visean boundary tn v early carboniferous in southern great britain and ireland south wales north staffordshire and dublin basin the tn v boundary coincides with a prominent climatic pulse connected with the late paleozoic glaciation of gondwana the aim was to correlate the gamma ray and magnetic susceptibility log patterns in carbonate ramp and basin settings and discuss the global regional nature and magnitude of this transgressive regressive cycle a robust ramp to basin correlation was produced based on the log patterns facies stacking patterns and foraminifer biostratigraphy the concentrations of k and th the clay gamma ray values and partly magnetic susceptibility are dependent on facies and show systematic changes along the inferred bathymetric profile from inner ramp to outer ramp and basin a model of carbonate productivity driven dilution of fine grained siliciclastics in caco3 as the major control on the petrophysical patterns is discussed the cleaning up and cleaning down petrophysical trends are related to down dip and up dip shifts of the carbonate factory with changing relative sea level in middle to outer ramp and basin settings this generates petrophysical trends just opposite to paleozoic carbonate shelves where peaks in magnetic susceptibility are known to be associated with peak regressions a distinct late tournaisian to early visean regressive to transgressive cycle with a prominent sequence boundary located close to the tn v stage boundary can be seen in the sections glacioeustatic origin of the sequence boundary is inferred from its correlation with tn v boundary sections from europe carbon isotope data from south china and the glacial deposits in the southern hemisphere mentioned by previous authors

plate tectonic evolution of the southern margin of eurasia in the mesozoic and cenozoic abstract thirteen time interval maps were constructed which depict the triassic to neogene plate tectonic configuration paleogeography and general lithofacies of the southern margin of eurasia the aim of this paper is to provide an outline of the geodynamic evolution and position of the major tectonic elements of the area within a global framework the hercynian orogeny was completed by the collision of gondwana and laurussia whereas the tethys ocean formed the embayment between the eurasian and gondwanian branches of pangea during late triassic early jurassic times several microplates were sutured to the eurasian margin closing the paleotethys ocean a jurassic cretaceous north dipping subduction boundary was developed along this new continental margin south of the pontides transcaucasus and iranian plates the subduction zone trench pulling effect caused rifting creating the back arc basin of the greater caucasus proto south caspian sea which achieved its maximum width during the late cretaceous in the western tethys separation of eurasia from gondwana resulted in the formation of the ligurian penninic pieniny magura ocean alpine tethys as an extension of middle atlantic system and a part of the pangean breakup tectonic system during late jurassic early cretaceous times the outer carpathian rift developed the opening of the western black sea occurred by rifting and drifting of the western central pontides away from the moesian and scythian platforms of eurasia during the early cretaceous cenomanian the latest cretaceous paleogene was the time of the closure of the ligurian pieniny ocean adria alcapa terranes continued their northward movement during eocene early miocene times their oblique collision with the north european plate led to the development of the accretionary wedge of the outer carpathians and its foreland basin the formation of the west carpathian thrusts was completed by the miocene the thrust front was still propagating eastwards in the eastern carpathians during the late cretaceous the lesser caucasus sanandaj sirjan and makran plates were sutured to the iranian afghanistan plates in the caucasus caspian sea area a north dipping subduction zone jumped during paleogene to the scythian turan platform the shatski terrane moved northward closing the greater caucasus basin and opening the eastern black sea the south caspian underwent reorganization during oligocene neogene times the southwestern part of the south caspian basin was reopened while the northwestern part was gradually reduced in size the collision of india and the lut plate with eurasia caused the deformation of central asia and created a system of nw se wrench faults the remnants of jurassic cretaceous back arc systems oceanic and attenuated crust as well as tertiary oceanic and attenuated crust were locked between adjacent continental plates and orogenic systems

tectonically controlled sedimentation impact on sediment supply and basin evolution of the kashafrud formation middle jurassic kopeh dagh basin northeast iran the kashafrud formation was deposited in the extensional kopeh dagh basin during the late bajocian to bathonian middle jurassic and is potentially the most important siliciclastic unit from ne iran for petroleum geology this extensional setting allowed the accumulation of about 1 700 m of siliciclastic sediments during a limited period of time upper bajocian bathonian here we present a detailed facies analysis combined with magnetic susceptibility ms results focusing on the exceptional record of the pol e gazi section in the southeastern part of the basin ms is classically interpreted as related to the amount of detrital input the amount of these detrital inputs and then the ms being classically influenced by sea level changes climate changes and tectonic activity facies analysis reveals that the studied rocks were deposited in shallow marine slope to pro delta settings a major transgressive regressive cycle is recorded in this formation including fluvial dominated delta to turbiditic pro delta settings transgressive phase followed by siliciclastic to mixed siliciclastic and carbonate shoreface rocks regressive phase during the transgressive phase hyperpycnal currents were feeding the basin these hyperpycnal currents are interpreted as related to important tectonic variations in relation to significant uplift of the hinterland during opening of the basin this tectonic activity was responsible for stronger erosion providing a higher amount of siliciclastic input into the basin leading to a high ms signal during the regressive phase the tectonic activity strongly decreased furthermore the depositional setting changed to a wave to tide dominated mixed carbonate siliciclastic setting because of the absence of strong tectonic variations bulk ms was controlled by other factors such as sea level and climatic changes fluctuations in carbonate production possibly related to sea level variations influenced the ms of the siliciclastic carbonate cycles carbonate intervals are characterized by a strong decrease of ms values indicates a gradual reduction of detrital influx therefore the intensity of tectonic movement is thought to be the dominant factor in controlling sediment supply changes in accommodation space and modes of deposition throughout the middle jurassic sedimentary succession in the pol e gazi section and possibly in the kopeh dagh basin in general

arenite petrography in sequence stratigraphy stratigraphic boundary surfaces and internal anatomy of unconformity bounded units may be deciphered by using properly conceived petrography that identifies compositional spatial and temporal characteristics of sand grains discussion of two case studies of synorogenic deep marine successions indicates the potential of this method when intrabasinal source areas are present relative sea level changes can exert direct influence on the intrabasinal extrabasinal grain budget in this case genetically significant unconformity bounded units are not only characterized by their internal facies architecture but also by internal organization in petrosomes as it is for biozones in biostratigraphy when intrabasinal source areas are narrow or absent relative sea level changes only control the timing of the record in deep sea sands of tectonic modifications in hinterland sources in this case unconformity bounded sequences may be fingerprinted with distinctive detrital compositions these results emphasiz

magnetostratigraphy susceptibility of the frasnian famennian boundary magnetosusceptibility event and cyclostratigraphy msec is used to establish a non polarity based magnetostratigraphy susceptibility mss between the stratotype region for the frasnian famennian f f boundary sequence in the montagne noire of southern france the eastern rheinisches schiefergebirge of germany belgium the eastern anti atlas of morocco and the arbuckle mountains of southern oklahoma usa despite differences of depositional environment the mss is remarkably consistent and can be described in the context of a hierarchy of magnetozones that allow the extension of correlation away from the montagne noire reference section the nature of the controls on the influx of iron into the marine system produces a natural hierarchy of at least seven orders or magnetozones designated msz1 msz2 msz3 msz4 msz5 msz6 and msz7 these are characterized in terms of the magnitude of their duration the mss reference section of choice for the f f boundary is the well known trench c at la serre lsc in the northeastern montagne noire of southern france the f f boundary is located at the lower boundary of magnetozone la serre i 3b at la serre as well as in all other sections studied msz4 and msz5 magnetozones are used to establish intra and inter regional correlation between the reference sequence and the other regions the base of the upper kellwasser event is as variable within the mss zonation as it is within the biostratigraphic zonation as is the position of the lower kellwasser event

unroofing history of late paleozoic magmatic arcs within the turan plate tuarkyr turkmenistan abstract stratigraphic sedimentologic and petrographic data collected on the kizilkaya sedimentary succession western turkmenistan demonstrate that the turan plate consists in fact of an amalgamation of late paleozoic to triassic continental microblocks separated by ocean sutures in the kizilkaya area an ophiolitic sequence including pyroxenite gabbro pillow basalt and chert interpreted as the oceanic crust of a back arc or intra arc basin is tectonically juxtaposed against volcaniclastic redbeds documenting penecontemporaneous felsic arc magmatism amanbulak group a collisional event took place around mid carboniferous times when oceanic rocks underwent greenschist facies metamorphism and a thick volcaniclastic wedge with pyroclastic rocks interbedded in the lower part accumulated kizilkaya formation the climax of orogenic activity is testified by arid fanglomerates shed from the rapid unroofing of a continental arc sequence including middle upper devonian back reef carbonates and cherts and the underlying metamorphic and granitoid basement rocks yashmu formation after a short period of relative quiescence renewed tectonic activity is indicated by a conglomeratic sequence documenting erosion of a sedimentary and metasedimentary succession including chert sandstone slate and a few carbonates a final stage of rhyolitic magmatism took place during rapid unroofing of granitoid basement rocks kizildag formation such a complex sequence of events recorded by the kizilkaya episutural basin succession documents the stepwise assemblage of magmatic arcs and continental fragments to form the turan microblock collage during the late paleozoic evolution of detrital modes is compatible with that predicted for juvenile to accreted and unroofed crustal blocks the deposition of braidplain lithic arkoses in earliest triassic time indicates that strong subsidence continued after the end of the volcanic activity possibly in retroarc foreland basin settings the occurrence of transgressive coquinas yielding endemic ammonoids dorikranites characteristic of the whole caspian area suggests proximity to the southern margin of the newly formed eurasian continent in the late early triassic the late triassic eo cimmerian orogeny caused only mild tilting and rejuvenation of the underlying succession in the study area only at this time were the turan blocks a series of indonesian type terranes comprised between the mashad paleo tethys suture in the south and the mangyshlak belt in the north finally incorporated into the eurasian landmass

debris flow and hyperconcentrated flood flow deposits in an alluvial fan northwestern part of the cretaceous yongdong basin central korea abstract the alluvial fan deposits in the cretaceous yongdong basin korea consist of conglomerates with a muddy or sandy matrix and sandstones with thick or thin laminations the conglomerates and sandstones occur commonly in couplets constituting apparently single sedimentation units facies transitions in the deposits can be summed up in a tripartite facies sequence 1 a clast supported conglomerate with a muddy or sandy matrix and parallel clast alignment facies a and b 2 a matrix supported coarse tail normally graded conglomerate with random clast orientation facies c and thickly stratified pebbly sandstone facies d and 3 laminated sandstone facies e the clast supported conglomerate is interpreted as deposits of debris flows dominated by frictional grain interactions development of pervasive parallel clast alignment lacking large floating clasts and inverse grading suggests deposition via incremental aggradation rather than en masse freezing the matrix supported conglomerate an

precise timing of the upper taghanic biocrisis geneseo bioevent in the middle upper givetian middle devonian boundary in northern spain using biostratigraphic and magnetic susceptibility data sets abstract the ability to correlate with high precision among geological successions is critical in evaluating the global coincidence and therefore magnitude and duration of geological events this is a difficult problem given resolution uncertainties and ambiguities in biostratigraphic data sets the magnetostratigraphy susceptibility mss method based on low field bulk magnetic susceptibility ms measurements of closely spaced samples provides a well established abiotic high resolution correlation tool in stratigraphy that when combined with bio chemostratigraphic and other geophysical techniques offers ways to resolve correlation problems in addition such data sets lend themselves to time series analysis where developing high resolution timing of events becomes possible this paper examines the final episode equivalent to the geneseo bioevent in the appalachian basin of the important taghanic biocrisis known from globally distributed middle devonian geological sections the geneseo bioevent is important because the extinction of some major fossil groups occurred during this time while other groups declined significantly including many benthonic groups however the maxima of extinctions does not appear to have occurred everywhere simultaneously to help resolve timing of this bioevent results are reported for two middle devonian successions from northern spain the s huergas de gordon and punta boletos sections both showing the final taghanic biocrisis geneseo interval and correlate these successions to the same interval within an independent global database time series analyses of the mss data sets from the spanish sections was performed using multi taper mtm and fourier transform ft methods and have extracted well defined milankovitch bands from the primary ms data from each section using ft and mtm values for eccentricity at 400 kyr and 100 kyr a floating point time scale was developed for the two spanish sections that provides age resolution to 50 kyr for these successions the results show that the geneseo bioevent in northern spain occurred within a narrow time window estimated to have lasted for 70 kyr this time window fall s within the polygnathus ansatus uppermost part ozarkodina semialternans conodont zones just at the middle upper givetian boundary of the middle devonian in what appears to be the upper regressive phase of t r cycle iia

upper devonian carbonate platform correlations and sea level variations recorded in magnetic susceptibility abstract this paper concerns the analysis of four outcrops in the frasnian upper devonian of belgium we compare the results of a precise sedimentological analysis with magnetic susceptibility ms data this comparison allows us to improve stratigraphic correlations and to test the relationship between magnetic susceptibility and sea level changes considering the sedimentological study different microfacies have been identified from the external belt dominated by relatively argillaceous open marine facies with crinoids to the biostromal and the lagoonal belt dominated by algae rich muddy facies fourth and third order sequences have also been identified and are probably related to sea level variations magnetic susceptibility data provides us very good fourth order correlations and the link between magnetic susceptibility and different sedimentological parameters is obvious more precisely ms appears to be related to fourth and third order sequences and to microfacies

behaviour of particle laden flows into the ocean experimental simulation and geological implications the behaviour of subaerial particle laden gravity currents e g pyroclastic flows lahars debris flows sediment bearing floods and jokulhlaups flowing into the sea has been simulated with analogue experiments flows of either saline solution simple suspensions of silicon carbide sic in water or complex suspensions of sic and plastic particles in methanol were released down a slope into a tank of water the excess momentum between subaerial and subaqueous flow is dissipated by a surface wave at relatively low density contrasts between the tank water and the saline or simple suspensions the flow mixture enters the water and forms a turbulent cloud involving extensive entrainment of water the cloud then collapses gravitationally to form an underwater gravity current which progresses along the tank floor at higher density contrasts the subaerial flow develops directly into a subaqueous flow the flow slows and thickens in response to the reduced density contrast which is driving motion and then continues in the typical gravity current manner complex suspensions become dense flows along the tank floor or buoyant flows along the water surface if the mixtures are sufficiently denser or lighter than water respectively flows of initially intermediate density are strongly influenced by the internal stratification of the subaerial flow material from the particulate depleted upper sections of the subaerial flow becomes a buoyant gravity current along the water surface whereas material from the particulate enriched lower sections forms a dense flow along the tank floor sedimentation from the dense flow results in a reduction in bulk density until the mixture attains buoyancy lifts off and becomes a secondary buoyant flow along the water surface jokulhlaups lahars and debris flows are typically much denser than seawater and thus will usually form dense flows along the seabed after sufficient sedimentation the freshwater particulate mixture can lift off to form a buoyant flow at the sea surface leading to a decoupling of the fine and coarse particles flood waters with low particulate concentrations 2 may form buoyant flows immediately upon entering the ocean subaerial pyroclastic flows develop a pronounced internal stratification during subaerial run out and thus a flow splitting behaviour is probable which agrees with evidence for sea surface and underwater flows from historic eruptions of krakatau and mont pelee a pyroclastic flow with a bulk density closer to that of sea water may form a turbulent cloud resulting in the deposition of much of the pyroclasts close to the shore dense subaqueous pyroclastic flows will eventually lift off and form secondary buoyant flows either before or after the transformation to a water supported nature

structural evolution of the kopeh dagh fold and thrust belt ne iran and interactions with the south caspian sea basin and amu darya basin abstract we present a detailed stratigraphic and structural study of the kopeh dagh fold and thrust belt in ne iran which is an investigation of the complex polyphased tectonic history of this belt and its links with the adjacent south caspian sea and amu darya basins based on numerous field surveys a large amount of 2d and 3d seismic data borehole data and more than 150 new biostratigaphic datings a new detailed biostratigraphic chart and 4 main regional cross sections illustrate the importance of lateral facies variations and structural inheritance in the present day structure of the belt after the cimmerian orogeny corresponding to the closure of the paleotethys ocean in late triassic early jurassic times a middle jurassic post collisional rifting event was associated with the deposition of one of the main source rocks of the kopeh dagh and the amu darya basin kashafrud formation following this rifting event over 7 km of sediments were accumulated until the tertiary above a regional post triassic unconformity the occurrence of local uplifts during the late cretaceous early paleocene is interpreted as a consequence of regional scale modification of plate slab coupling in the neotethys subduction zone the main inversion of the kopeh dagh occurred at late eocene times when the far field deformation developed in eurasia as a consequence of the locking of the neo tethys subduction this folding phase is sealed in the western part of the belt by a major eocene oligocene unconformity at the base of the thick sedimentary series belonging to the south caspian sea basin the bulk of sedimentary infill in the south caspian sea basin is oligocene and younger and it is probably related to syn compressional downward flexure of the resistant basement basin at the onset of the alpine phase in the eastern part of the kopeh dagh this deformation is characterized by middle jurassic graben inversion with evidence of forced folding short cuts and as well by larger scale basement uplifts in contrast the northwestern part of the belt shows thrust faults involving basement and fault propagation folds within the sedimentary sequence the kopeh dagh presents tectonic structures that are parallel to the paleotethys suture zone which emphasizes the importance of the structural inheritance and inversion processes during the structural evolution of the belt finally a change from a mostly dip slip to a mostly strike slip tectonics occurred during the pliocene within the kopeh dagh as a consequence of a major tectonic reorganization in north east iran

oblique to orthogonal convergence across the turan block in the post miocene the 2 17 km thick post triassic sediments of the turan continental block accumulated in a south dipping basin characterized by fault controlled facies and thickness variations since the late miocene the thickest part of the basin fill on the southern margin of the turan block has been folded and uplifted as the kopet dag range in response to the iran turan convergence the apsheron sill which separates the northern continental from the southern oceanic caspian sea basins links the kopet dag greater balkan ranges turkmenistan to the caucasus azerbaijan the large scale east west to west northwest east southeast oriented arrays of periclinal folds of the kopet dag range which indicate a north south oriented compression were generated by a fault propagation mechanism the migration and accumulation of hydrocarbons has been controlled by the deformation pattern the 75 km of north south shortening in the western kopet dag greater balkan area can be resolved into 70 km of pure compression orthogonal to the n120 oriented ashgabat fault and 35 km of dextral slip along this fault the north south iran asia relative motion has produced the oblique convergent northwest southeast structures along the dextral ashgabat fault and the pure convergent east west structures in the western kopet dag greater balkan region the orientation of the structures has been controlled by the angular relationship between the relative motion of two blocks and the orientation of their boundaries the ashgabat fault as a major crustal anisotropy has concentrated the deformation into a narrow fold and thrust belt whereas in the west the deformation is distributed over a wider area the pattern of deformation has been controlled by the iran turan boundary conditions

stratigraphy of the middle devonian boundary formal definition of the susceptibility magnetostratotype in germany with comparisons to sections in the czech republic morocco and spain abstract one major difficulty in geology is high resolution correlation among widely separated sections especially in the paleozoic where magnetostratigraphy polarity is not well established because rocks are often remagnetized where critical biostratigraphic zonation may be poor or lacking or where structural complexities make correlations very difficult to address this problem we have been using magnetostratigraphy susceptibility measurements here we report our work from the middle devonian in europe and north africa the middle devonian emsian eifelian global boundary stratotype section and point gssp located in the eifel hills western germany was ratified by the international subcommission on stratigraphy in 1985 after careful evaluation of the biostratigraphy for this and many other sections the boundary interval has been characterized using biostratigraphy and the beginning of the eifelian stage has been specifically defined by the first occurrence of the conodont polygnathus costatus partitus we have collected the eifel hills section for magnetic susceptibility ms measurement and here we establish it as the magnetostratotype for the emsian eifelian stage boundary by formally defining the magnetostratigraphy susceptibility for the section we then collected measured and compared the magnetostratotype to four other sections for which conodont biostratigraphy has been studied and where p costatus partitus is present two emsian eifelian sections in morocco and two sections in the czech republic including the emsian eifelian parastratotype finally we have measured the ms for the el puerto creek section in the cantabrian mountains of spain and identified the location of the emsian eifelian boundary within the section based on ms comparison to the gssp in conjunction with excellent biostratigraphic indicators primarily brachiopods while the conodont zonation in the el puerto creek section is poorly defined we believe that the correspondence between the ms and biostratigraphy in the section allows the identification of the emsian eifelian boundary these results indicate that this method can be successfully applied to marine sequences where ambiguities in correlation exist

land ocean correlations during the last interglacial glacial transition baffin bay northwestern north atlantic a review abstract evidence from terrestrial sections ice cores and marine cores are reviewed and used to develop a scenario for environmental change in the area of the extreme northwest north atlantic during marine isotope stages 5 and 4 the critical physical link between the landbased glacial chronology and marine events in baffin bay is the presence of carbonate rich drift along the baffin bay coast of bylot island and a detrital carbonate facies facies b in baffin bay sediments cores from baffin bay labrador sea can be dated by means of oxygen isotope variations and by peaks in the abundance of volcanic glass shards one occurrence of facies b is dated between late stage 5 and stage 4 and we correlate this event with the eclipse glaciation of bylot island and the ayr lake stade of the foxe glaciation of baffin island kogalu aminozone in contrast on west greenland amino acid racemization evidence suggests that the greenland ice sheet developed throughout stage 4 and reached a maximum in stage 3 svartenhuk advance 40 ka the oxygen isotope record in the devon island ice cap northwest baffin bay indicates that baffin bay was largely open during marine isotope stage 5 analyses of shallow water molluscan and foraminiferal assemblages deep water foraminifera pollen from iand sections and deep sea cores and dinoflagellates from marine cores indicate that interglacial conditions prevailed during much of the stage 5 4 glaciation

geohistory analysis and petroleum reservoir characteristics of lower cretaceous neocomian sandstones eastern kopet dagh basin northeastern iran the eastern part of the kopet dagh basin of northeastern iran contains over 4000 m of upper jurassic through tertiary strata deposited in a variety of shallow marine and terrestrial environments geohistory diagrams from well and outcrop data provide a useful mechanism with which to relate the stratigraphic framework of this part of the basin to the tectonic history of the region during some episodes of regional tectonic uplift e g episodes occurring 99 95 ma 74 70 ma and 63 54 ma sediment accommodation space continued to be created in the basin due to sediment loading and compaction of increased amounts of fine grained sediments in some cases concomitant with eustatic sea level rises much of the post jurassic subsidence in this part of the kopet dagh basin was aused by sediment loading rather than tectonism the effects of basin geohistory on petroleum reservoir properties were studied using the lower cretaceous neocomian shurijeh formation as an example detailed petrologic sedimentologic and geohistory analyses done on this formation show that the petroleum reservoir properties of shurijeh sandstones were affected by their depositional settings and the subsequent subsidence of these units through meteoric and compactional hydrogeologic regimes in this part of the kopet dagh basin these rocks consist mostly of sublitharenitic red beds deposited during a regressive phase of sedimentation dominated by rapid siliciclastic sediment supply the lower and middle parts of the interval studied were deposited in low sinuosity braided fluvial systems and the upper part was deposited in high inuosity meandering systems by relating the paragenetic sequence of the shurijeh sandstones to the geohistory of this formation we determined the timing of both porosity destroying and porosity enhancing diagenetic processes and related these processes to the timing of petroleum generation

the cimmerian orogeny in northern iran tectono stratigraphic evidence from the foreland from the permian onwards the gondwana derived iran plate drifted northward to collide with eurasia in the late triassic thereby closing the palaeotethys this eo cimmerian orogeny formed the cimmeride fold and thrust belt the upper triassic middle jurassic shemshak group of northern iran is commonly regarded as the cimmerian foreland molasse however our tectono stratigraphic analysis of the shemshak group resulted in a revised and precisely dated model for the triassic jurassic geodynamic evolution of the iran plate initial cimmerian collision started in the carnian with subsequent late triassic synorogenic peripheral foreland deposition flysch lower shemshak group subduction shifted south in the norian onset of neotethys subduction below iran and slab break off around the triassic jurassic boundary caused rapid uplift of the cimmerides followed by liassic post orogenic molasse middle shemshak group during the toarcian aalenian upper shemshak group neotethys back arc rifting formed a deep marine basin which developed into the oceanic south caspian basin during the late bajocian late jurassic

platform carbonates of the upper jurassic mozduran formation in the kopet dagh basin ne iran facies palaeoenvironments and sequences abstract the mozduran formation a thick carbonate succession over 1200 m of the upper jurassic callovian kimmeridgian in northeast iran has been studied to determine its palaeoenvironments and sequences detailed petrographic investigations have led to the recognition of several microfacies and microfacies groups which constitute four palaeoenvironmental associations tidal flat beach lagoonal platform margin and open marine most of the mozduran formation sediments were deposited on a rimmed carbonate platform adjacent to a deeper marine environment the mozduran carbonate succession consists of five thick shallowing upward sequences 3rd order cycles no major hiatus has been recognized between these cycles therefore the contacts are considered subtidal conformities drowning unconformities these 3rd order cycles can be correlated with those recognized in upper jurassic strata in other parts of the world thus they are considered largely eustatic mainly tectono eustatic in origin numerous small scale shallowing upward cycles parasequences are contained within the major shallowing upward cycles both subtidal and peritidal parasequences showing an abrupt deepening of microfacies have been recognized a combination of episodic subsidence and autocyclic processes could have been responsible for the formation of these small scale cycles rapid carbonate accumulation reflected in rare first generation marine cements including meteoric cements resulted in grain to grain pressure solution and sutured contacts during burial with late cements filling the remaining pores many of the platform margin grainstones packstones have been replaced by coarsely crystalline dolomite possibly through seawater pumping and kohout convection during the transgressive and highstand phases of sea level