spectrally based remote sensing of river bathymetry this paper evaluates the potential for remote mapping of river bathymetry by 1 examining the theoretical basis of a simple ratio based technique for retrieving depth information from passive optical image data 2 performing radiative transfer simulations to quantify the effects of suspended sediment concentration bottom reflectance and water surface state 3 assessing the accuracy of spectrally based depth retrieval under field conditions via ground based reflectance measurements and 4 producing bathymetric maps for a pair of gravel bed rivers from hyperspectral image data consideration of the relative magnitudes of various radiance components allowed us to define the range of conditions under which spectrally based depth retrieval is appropriate the remotely sensed signal must be dominated by bottom reflected radiance we developed a simple algorithm called optimal band ratio analysis obra for identifying pairs of wavelengths for which this critical assumption is valid and which yield strong linear relationships between an image derived quantity x and flow depth d obra of simulated spectra indicated that water column optical properties were accounted for by a shorter wavelength numerator band sensitive to scattering by suspended sediment while depth information was provided by a longer wavelength denominator band subject to strong absorption by pure water field spectra suggested that bottom reflectance was fairly homogeneous isolating the effect of depth and that radiance measured above the water surface was primarily reflected from the bottom not the water column obra of these data 28 of which were collected during a period of high turbidity yielded strong x versus d relations r2 from 0 792 to 0 976 demonstrating that accurate depth retrieval is feasible under field conditions moreover application of obra to hyperspectral image data resulted in spatially coherent hydraulically reasonable bathymetric maps though negative depth estimates occurred along channel margins where pixels were mixed this study indicates that passive optical remote sensing could become a viable tool for measuring river bathymetry copyright 2009 john wiley sons ltd

carbonate platform evolution from a bioconstructed platform margin to a sand shoal system devonian guilin south china the depositional organization and architecture of the middle late devonian yangdi rimmed carbonate platform margin in the guilin area of south china were related to oblique extensional faulting in a strike slip setting the platform margin shows two main stages of construction in the late givetian to frasnian with a bioconstructed margin evolving into a sand shoal system in the late givetian the platform margin was rimmed with microbial buildups composed mainly of cyanobacterial colonies mostly renalcis and epiphyton these grew upwards and produced an aggradational locally slightly retrogradational architecture with steep foreslope clinoforms three depositional sequences s3 s5 are recognized in the upper givetian strata which are dominated by extensive microbialites metre scale depositional cyclicity occurs in most facies associations except in the platform margin buildups and upper foreslope facies in the latest givetian at the top of sequence s5 relative platform uplift subaerial exposure and associated rapid basin subsidence probably a block tilting effect caused large scale platform collapse and slope erosion to give local scalloped embayments along the platform margin and the synchronous demise of microbial buildups subsequently sand shoals and banks composed of ooids and peloids and a little later stromatoporoid buildups on the palaeohighs developed along the platform margin from which abundant loose sediment was transported downslope to form gravity flow deposits another strong tectonic episode caused further platform collapse in the early frasnian at the top of sequence s6 leading to large scale breccia release and the death of the stromatoporoid buildups siliceous facies banded cherts and siliceous shales were then deposited extensively in the basin centre as a result of the influx of hydrothermal fluids the platform margin sand shoal bank system possibly with gullies on the slope persisted into the latest frasnian until the restoration of microbial buildups four sequences s6 s9 characterized by abundant sand shoal deposits on the margin and gravity flow and hemipelagic deposits on the slope are distinguished in the frasnian strata smaller scale depositional cyclicity is evident in all facies associations across the platform slope basin transect the distinctive depositional architecture and evolution of this yangdi platform are interpreted as having been controlled mainly by regional tectonics with contributions from eustasy environmental factors oceanographic setting biotic and sedimentary fabrics

late paleozoic glacial episodes in gondwanaland reflected in transgressive regressive depositional sequences in euramerica the late paleozoic glaciation of gondwanaland comprised two short episodes in the famennian i and visean ii confined to brazil and adjacent northwest africa and a long episode that started in the namurian iiia of eastern australia and bolivia argentina expanded to cover much of gondwanaland in the stephanian asselian iiib and collapsed in the early sakmarian iiic dropstones in eastern australia indicate that small ice centers lingered to the kazanian across the belt of low latitudes north of gondwanaland short ranging fossils in widespread shallow marine and paralic deposits indicate synchronous deposition of transgressive regressive sequences in different parts of euramerica these sequences correlate with glacial events in gondwanaland at three levels a four major regressions in euramerica in the famennian 1 visean 2 namurian 3 stephanian 4 and the tastubian transgression that preceded the sterlitamakian regression 5 also recorded in gondwanaland correlate with glacial episodes i ii and iiia iiib and iiic b the time interval of cyclothemic deposition in euramerica brigantian or latest visean to sterlitamakian correlates with that of glacial episode iii and c the dominant period of the euramerican cyclothems as estimated from the middle and late pennsylvanian deposits of the mid continent of north america and of the thickest known gondwanaland glacigenic sediment the earliest permian lyons group of western australia is 0 4 ma equivalent in turn to the long orbital eccentricity period of the quaternary ice age and the dominant period of fluctuation of the late miocene antarctic ice cap the three levels of correlations confirm wanless and shepard9s 1936 hypothesis that the late paleozoic cyclothems are controlled largely by sea level fluctuations related to the gondwanaland glaciation

the foreslope and toe of slope facies of the middle triassic latemar buildup dolomites northern italy abstract the latemar buildup was a circular carbonate buildup 4 km wide with a central platform core flat bedded interior platform and massive reef margin flanked on all sides by slope facies steeply dipping 30 35 foreslope breccias are present adjacent to the margin and flat lying graded grainstones at the toe of slope slope facies relate directly to depositional profile and slope angle the steeply dipping foreslopes consist of lobate breccia beds that are 25 m thick and a few tens of meters across and extend tens to hundreds of meters downslope some beds are conformably overlain by thinner 1 m thick beds of finer grained carbonate sediment the basal surfaces of the breccias are erosional and are anastamosing in both strike and dip views the breccia rains was derived principally from margin boundstones and deposited by rockfalls and avalanches planar clinoforms extend the entire height of the foreslope hundreds of meters and bracket depositional units clinothems tens of meters thick clinoforms appear to be shear surfaces formed during large slope failures avalanches graded grainstone beds less than 1 m thick are present at the nearly flat lying toe of slope these consist of redeposited shallow water platform interior and reef margin carbonate sands some with nodular limestone caps that are interpreted as proximal carbonate turbidites toe of slope breccias are the downdip extensions of foreslope breccias and pinch out abruptly basinward some slope depositional processes are related to high frequency fourth order and fifth order sea level changes toe of slope graded grainstones correspond to times of platform submergence in contrast foreslope breccia was deposited during both platform submergence and exposure the slope deposits do not record the high frequency cyclic rhythms identified in shallow water platform sections this is attributed to the nature of slope deposition downslope talus transport was episodic and localized graded grainstone beds reflect storm redeposition

construction versus accumulation in phylloid algal mounds an example of a small constructed mound in the pennsylvanian of kansas usa abstract most phylloid algal mounds are currently interpreted as no more than accumulations of leaf like thalli supported by mud we report here phylloid algae from the upper pennsylvanian late carboniferous frisbie limestone member in kansas usa which built small mounds with recognizable primary topographic relief cup shaped algal thalli growing closely packed and juxtaposed near and above one another produced a framework in the shapes of topographically conspicuous mounds from smaller centimeter scale to meter scale features meter scale mounds are composites of smaller juxtaposed centimeter scale mounds and intramound areas contain crinoid debris sponges bryozoans brachiopods and skeletal grains the intercup voids enclosed in the framework fabrics of individual thalli are filled with a variety of matrix and cements 1 peloidal grains both in clotted wackestone and grainstone 2 early marine cement 3 microbial encrustations often oriented against gravity and 4 mudstone bedded limestones equivalent to and overlying the mounds are bioclastic wackestone and differ fundamentally from the mound limestone in facies biotic components absence of both frameworks and of peloidal clotted grains topographic relief above the sea floor the growth fabrics with a framework including primary intramound and intercup voids and their complex infillings and the lithic and biotic differences between mound and off mound intervals fulfil the stratigraphic and biological criteria characterizing reefs the model proposed here interprets these mounds as the result of active constructional algal growth in contrast to published hypotheses that most phylloid algal mounds were passive accumulations of algal thalli within a mud matrix and or early diagenetic marine cements

controls and predictability of carbonate facies architecture in a lower jurassic three dimensional barrier shoal complex djebel bou dahar high atlas morocco spatial information on lithofacies from outcrops is paramount for understanding the internal dynamics external controls and degree of predictability of the facies architecture of shallow water carbonate platform tops to quantify the spatial distribution and vertical stacking of lithofacies within an outer platform shoal barrier complex integrated facies analysis and digital field technologies have been applied to a high relief carbonate platform exposed in the djebel bou dahar lower jurassic high atlas morocco the outer platform is characterized by subtidal cross bedded coarse grainstone to rudstone grading into supratidal pisoidal packstone rudstone with tepees that together formed a 350 to 420 m wide shoal barrier belt parallel to the margin this belt acted as a topographic high separating a restricted lagoon from the subtidal open marine region low energy tidal flats developed on the protected flank of the barrier facing the lagoon lithofacies patterns were captured quantitatively from outcrop and integrated into a digital outcrop model the outcrop model enabled rapid visualization of field data and efficient extraction of quantitative data such as widths of facies belts in addition the spatial heterogeneity was captured in multiple time slices i e during different phases of cyclic base level fluctuations in general the lateral continuity of lithofacies is highest when relative water depth increased during flooding of the platform top establishing low energy subtidal conditions across the whole platform and when the accommodation space was filled with tidal flat facies heterogeneity increased during deposition of the relief building bar facies that promoted spatial diversification of depositional environments during the initial phases of accommodation space creation cycles commonly are composed of a thin transgressive tidal flat unit followed by coated grain rudstone bar facies lateral to the bar facies pisoidal grainstone beach deposits accumulated these bar and beach deposits were overlain by subtidal lagoonal facies or would grow through the maximum flooding and highstand there the bars either graded into supratidal pisoidal facies with tepees when accommodation space was filled or were capped by subaerial exposure due to a sea level fall modified embedded markov analysis was used to test the presence of common ordering in vertical lithofacies stacking in a stationary interval constant depositional mode analysis of individual sections did not reveal any ordering which may be related to the limited thickness of these sections composite sections however rejected the null hypothesis of randomness the addition of stratigraphically significant information to the markov analysis such as exposure surfaces and lateral dimensions of facies bodies strengthens the verdict of unambiguous preferential ordering through careful quantitative reconstruction of stratal geometry and facies relationships in fully integrated digital outcrop models accurate depositional models could be established that enhanced the predictability of carbonate sediment accumulation 2009 the authors journal compilation 2009 international association of sedimentologists

stratal architecture and platform evolution of an early frasnian syn tectonic carbonate platform canning basin australia facies architecture and platform evolution of an early frasnian reef complex in the northern canning basin of north western australia were strongly controlled by syn depositional faulting during a phase of basin extension the margin attached hull platform developed on a fault block of precambrian basement with accommodation largely generated by movement along the mount elma fault zone recognition of major subaerial exposure and flooding surfaces in the hull platform from outcrop and drillcore has enabled comparison of facies associations within a temporal framework and led to identification of three stages of platform evolution stage 1 records initial ramp development on the hangingwall dip slope with predominantly deep subtidal conditions that prevented any cyclic facies arrangements this stage is characterised by basal siliciclastic deposits and a major deepening upward facies pattern that is capped by a sequence boundary towards the footwall north west and a major flooding surface towards the hangingwall stage 2 reflects the bulk of platform aggradation significant platform growth towards the hangingwall and the development of reef margins and cyclic facies arrangements thickening of this stage towards the hangingwall indicates that accommodation was generated by rotation of the fault block and overlying platform stage 3 records a major flooding and backstep of the platform margin the hull platform illustrates important elements of margin attached carbonate platforms in a half graben setting including i prominent but limited coarse siliciclastic input that does not have a major detrimental effect on carbonate production near the rift margin in arid to semi arid settings ii wedge shaped accommodation created by syn depositional rotation of fault blocks and tilting of the hangingwall dip slope resulting in shallow water facies and subaerial exposure up dip of the rotational axis and deeper water facies down dip and iii evolution of a ramp to rimmed shelf coincident with a sequence boundary flooding surface that is accelerated by tilting of the hangingwall dip slope during fault block rotation

microbialite and microstratigraphy the origin of encrustations in the middle and upper capitan formation guadalupe mountains texas and new mexico usa abstract the permian capitan reef of the guadalupe mountains was bound lithified and preserved by microbially precipitated micrite a microbial origin or association is based on the distribution texture fossil content and order of microstratigraphic succession in samples from the middle capitan formation micrite layers about 1 cm thick encrusted the top sides and undersides of in situ organisms and also piled above organisms in thick 0 5 to 3 cm accumulations with high angles of repose up to 90 primary encrustations commonly consist of thin homogeneous subparallel layers of archaeolithoporella interpreted to be a red alga that probably lived in dimly lit cavities secondary encrustations 0 5 30 mm thick contain 10 50 m diameter peloids and fossil cyanophytes and are usually bound by thin layers of micrite secondary encrustations of gravity defying peloidal micrites are interpreted as having precipitated within mucilaginous microbial aggregations probably in dark cavities the secondary microbial micrites were followed by cavity filling aragonitic botryoids thin 1 mm layers of clotted micrite were deposited on the first botryoids probably by microbial biofilms in contrast to samples from the middle capitan formation samples from the upper capitan formation taken near the transition from reef to outer shelf are composed of smaller 1 2 mm framework organisms and are bound by layers of thinner 1 mm primary encrustations in the upper capitan formation samples dense clotted micrite forms secondary encrustations 1 mm thick commonly underneath primary framework secondary encrustations are succeeded by more abundant tertiary encrustations 1 4 mm thick of sparse clotted micrite with vague dendritic structures the secondary and tertiary encrustations are interpreted as microbial the samples from the upper capitan formation were deposited in the shallowest part of the reef 1 to 10 m deep and most of the samples from the middle capitan were deposited in deep water 10 140 m the difference in the encrustations and in the overall scale of the two fig 1 map of the study area observations were made on samples from each of the canyons shown but samples from mckittrick and walnut canyons are the focus of this study end page 956 fabrics is probably related to differences in environmental energy during deposition

on the origin of a phosphate enriched interval in the chattanooga shale upper devonian of tennessee a combined sedimentologic petrographic and geochemical study abstract the devonian chattanooga shale contains an uppermost black shale interval with dispersed phosphate nodules this interval extends from tennessee to correlative strata in kentucky indiana and ohio and represents a significant period of marine phosphate fixation during the late devonian of north america it overlies black shales that lack phosphate nodules but otherwise look very similar in outcrop the purpose of this study is to examine what sets these two shales apart and what this difference tells us about the sedimentary history of the uppermost chattanooga shale in thin section the lower black shales pbs show pyrite enriched laminae and compositional banding the overlying phosphatic black shales phbs are characterized by phosbioclasts have a general banded to homogenized texture with reworked layers and show well defined horizons of phosphate nodules that are reworked and transported in the phbs up to 8000 particles of p debris per cm2 occur in reworked beds whereas the background black shale shows between 37 88 particles per cm2 in the pbs the shale matrix contains between 8 16 phosphatic particles per cm2 the shale matrix in the phbs contains 5 6 inertinite whereas just 1 inertinite occurs in the pbs the shale matrix in both units is characterized by flat ree patterns shale normalized whereas phosbioclast rich layers in the phbs show high concentrations of rees and enrichment of mrees negative ce anomalies are common to all samples but are best developed in association with phosbioclasts redox sensitive elements co u mo are more strongly enriched in the pbs when compared to the phbs trace elements associated with organic matter cu zn cd ni show an inverse trend of enrichment deposited atop a sequence boundary that separates the two shale units the phbs unit represents a transgressive systems tract and probably was deposited in shallower water than the underlying pbs interval the higher phosphate content in the phbs is interpreted as the result of a combination of lower sedimentation rates with reworking winnowing episodes three types of phosphatic beds that reflect different degrees of reworking intensity are observed strong negative ce anomalies and abundant secondary marcasite formation in the phbs suggests improved aeration of the water column and improved downward diffusion of oxygen into the sediment the associated oxidation of previously formed pyrite resulted in a lowering of pore water ph and forced dissolution of biogenic phosphate phosphate dissolution was followed by formation of secondary marcasite and phosphate repeated episodic reworking caused repetitive cycles of phosphatic dissolution and reprecipitation enriching mrees in reprecipitated apatite a generally deeper seated redox boundary favored p remineralization within the sediment matrix and multiple repeats of this process in combination with wave and current reworking at the seabed led to the formation of larger phosphatic aggregates and concentration of phosphate nodules in discrete horizons

theoretical regime equations for mobile gravel bed rivers with stable banks a system of rational regime equations is developed for gravel bed rivers with stable banks using the optimality theory ot the optimality theory is based on the premise that equilibrium river geometry is characterised by an optimum configuration defined here as maximum sediment transport efficiency theoretical dimensionless equations are derived for width depth slope width depth ratio and meandering braiding transition independent dimensionless variables comprise discharge sediment concentration and relative bank strength which is defined as the ratio of the critical shear stresses for the bank and bed sediments discharge exponents and general form of the equations agree well with previously developed empirical relations relative bank strength is used to parameterise the influence of riparian vegetation on bank strength and is evaluated by calibrating against observed width depth ratio once calibrated the hydraulic geometry of natural gravel rivers is well described by the theoretical equations including discrimination between meandering and braiding channels the results provide strong support for the assumption that equilibrium or regime river behavior is equivalent to an optimal state and underline the importance of bank strength and sediment load as controls on hydraulic geometry

discussion on high precision 40ar 39ar spectrum dating on sanidine from the donets basin ukraine evidence for correlation problems in the upper carboniferous journal vol 156 1999 527 533 scientific editing by ray burgess manfred menning dieter weyer immo wendt nicholas j riley vladimir i davydov write hess et al 1999 p 528 investigated about one dozen rock samples from coal tonsteins from the donets basin for ar ar sanidine dating unfortunately only one proved could be dated isotopically all other samples contain no chronometer minerals that which were 1 of primary volcanic origin and 2 unaffected by secondary alterations the datable sample has an age of 305 5 1 5 ma 1 without the age errors of the monitors using sanidines for high precision ar ar spectrum dating however the expected age is about 6 ma older according to sanidine tuff ages from central europe lippolt et al 1984 hess et al p 532 concluded that the most plausible explanation for this deviation is an inaccurate or even erroneous biostratigraphic correlation of the donets basin carboniferous with the western european and non european carboniferous occurrences they suggest a reconsideration of the validity of the current biostratigraphic correlation between the carboniferous of western and east europe p 527 we reconsider the biostratigraphic correlation because an age difference of about 6 ma corresponds to the duration of about two substages stages of the upper carboniferous e g westphalian b c duckmantian bolsovian such fundamental biostratigraphic miscorrelation between best known mining areas is extremly improbable we explain the presumed age difference by a significant correction of the erroneous biostratigraphic correlation used by hess et al fig 2 which reduces the discussed about 6 ma to a markedly smaller difference of about 4 ma these 4 ma are not significant if necessarilly 2 analytical age uncertainties are taken into account biostratigraphy according to the lithostratigraphic standard scheme of the donets basin the tonstein in coal seam l31 studied by hess et al occurs in the middle part of the c26 suite

diagenetic evolution of the upper devonian phosphorites alborz mountain range northern iran abstract the upper devonian mixed siliciclastic carbonate stratigraphic succession of the geirud formation in the alborz mountain range north of iran hosts numerous phosphorites and phosphatic rocks these phosphorites which represent one of the most globally important deposits in the devonian have gained little attention regarding their genesis and diagenetic evolution this study focuses mainly on the post depositional changes that occurred during shallow to deep burial diagenetic evolution and subaerial weathering of the geirud phosphorites the phosphorites consist of phosphatic massive mudclasts detritus rich lithoclasts bioclasts and bones formed by several stages of phosphogenesis and erosion reworking winnowing and condensation associated with famennian sea level changes the phosphatic clasts consist of early diagenetic poorly crystalline carbonate fluorapatite cfa and pyrite cementing detrital quartz illite muscovite rutile and zircon phosphatic clasts are intensely compacted with sutured grain contacts along which dissolution and reprecipitation of chemically refined well crystalline cfa with a bright blue cathodoluminescence and illite occurred during deep burial diagenesis similarly quartz shows deformation planar features overgrowth cement was developed as a result of pressure dissolution in phosphatic sandstones followed by precipitation of ferroan dolomite ankerite and chlorite in secondary porosity subaerial weathering led to oxidation of pyrite and generation of acidic ph condition under which ca and p from phosphates fe and s from pyrite fe ca mg and mn from ferroan carbonates and al and si from aluminosilicates were released to form goethite psilomelane calcite gypsum and crandallite the paas normalized rare earth elements rees show bell shaped patterns with middle rees enrichment positive eu anomaly and a weak negative ce anomaly this implies recrystallization of cfa in phosphorites and phosphatic rocks during deep burial diagenesis deviating from the modern seawater like ree patterns in this regard deep burial diagenesis affecting the upper devonian geirud phosphorites is possibly a common process in the proterozoic paleozoic phosphorites in northern iran and elsewhere in the world

depositional facies and stratal geometry of an upper carboniferous prograding and aggrading high relief carbonate platform cantabrian mountains n spain seismic scale continuous exposures of an upper carboniferous bashkirian moscovian carbonate platform n spain provide detailed information about the lithofacies and stratal geometries quantified with differential global positioning system measurements of microbial boundstone dominated steep prograding and aggrading platform margins progradational and aggradational platform to slope transects are characterized by distinct lithological features and stratal patterns that can be applied to the understanding of geometrically comparable high relief depositional systems the bashkirian is characterized by rapid progradation at rates of 415 970 m my 1 characteristic outerplatform facies are high energy grainstones with coated intraclasts ooids and pisoids moderate energy algal skeletal grainstones to packstones and lower energy algal packstone and boundstone units the moscovian aggradational phase is characterized by aggradation rates of 108 m my 1 coated grain shoals are less common whereas crinoidal bars nucleated in well circulated settings below wave base boundstones form a belt 30 300 m wide at the platform break and interfinger inwards with massive algal skeletal wackestones mud rich banks the progradational phase has divergent outer platform strata with basinward dips of 12 to 2 steep clinoforms with dips of 20 28 are 650 750 m in relief and possibly sigmoidal to concave in the lower part the basinward dipping outer platform strata might be depositional for less than 6 consistent with lithofacies deepening seaward the basinward dip is attributed to the downward shift of upperslope boundstone forced by late highstand and relative sea level fall and to compaction induced differential subsidence during progradation the aggradational phase is characterized by horizontally layered platform strata clinoforms steepen to 30 45 reaching heights of 850 m and are planar to concave the evolution from progradation to aggradation at the bashkirian moscovian boundary is attributed to increased foreland basin subsidence and decreased boundstone accumulation rates progradation was primarily controlled by boundstone growth rather than by highstand shedding from the platform top within the major phases aggradational progradational increments are produced by third to fourth order relative sea level

quantitative radiometric and biostratigraphic calibration of the pennsylvanian early permian cisuralian time scale and pan euramerican chronostratigraphic correlation a quantitative biostratigraphic and radiometric calibration is presented for the pennsylvanian through early permian global time scale based upon high precision isotope dilution thermal ionization mass spectrometer id tims u pb zircon ages for interstratified ash beds in the parastratotype sections of the southern urals of russia twenty four ash bed ages in three outer ramp and basinal sections of the pre uralian foredeep bracket the biotic definitions of global stages and regional substages from the base of the upper pennsylvanian kasimovian stage to the base of the lower permian artinskian stage four additional ash bed ages in two sections of the eastern slope of the urals constrain the global bashkirian and serpukhovian stages quantitative stratigraphic methods conop9 are applied to a compilation of over 2000 bioevents in 22 stratigraphic sections supplemented by our dated volcanic horizons to refine the pennsylvanian early permian global time scale significant shifts in the duration of several stages are demonstrated ranging from one to six million years compared with prior estimates the unprecedented density of radiometric calibration points for the pennsylvanian permian transition provides a high resolution 0 1 ma global chronostratigraphic standard for testing and improving biostratigraphic correlations across euramerica we integrate radiometric ages biostratigraphic correlation and cyclostratigraphic tuning of major cyclothems to the long period 404 ka eccentricity cycle to elucidate the tempo magnitude and forcing of eustatic changes and cyclothemic deposition associated with the waxing and waning of gondwanan ice sheets and establish a pan euramerican chronostratigraphic framework for most of pennsylvanian and early permian time

mass transport deposits in a variscan wedge top foreland basin pisuerga area cantabrian zone nw spain abstract large scale mass transport deposits mtds from two wedge top depocentres in a variscan foreland basin system cantabrian zone iberian massif northern spain have been studied to gain a better understanding of the processes involved in comparable deposits found in modern submarine environments the well exposed outcrops allow documenting the composition internal organization and lateral changes of the mtd units and additionally to know their frequency and significance in a tectonically active depositional setting the synorogenic 5000 m thick succession that contains these resedimented units comprises seven major tectonically controlled sequences whose bounding unconformities were recognised by seismic scale stratal patterns such as fault propagation and growth fold geometries wedging truncation and onlap these major sequences range between 4 and 0 4 myr in duration and between 1300 and 200 m in thickness and display an overall shallowing upward trend from a basal mtd and deep water sediments prodeltaic mudstone wedges turbidites to shallow marine carbonates and deltaic deposits each major sequence consists of one or more transgressive regressive high frequency sequences up to several hundred metres in thickness showing rapid lateral changes of facies associations across the wedge top depocentres the mtd units are composed of megaclasts up to 2 km long and 360 m thick embedded in mudstones matrix and clast supported breccias and conglomerates with variable internal organization and subordinate turbidite sandstones deposited from slides and gravity flows from cohesive debris flows to high density turbidites these en masse deposits originated from the failure of shelf to slope reaches and some of them constitute multiepisodic units resulting from several large scale collapse events these collapses could have been triggered by several factors mainly related to the growth of fault propagation anticlines during thrust emplacement the ensuing tectonic overload would lead to strong flexural subsidence and to the modification of the basin profile both the major sequences and the mtd units are a useful tool for correlating the highly deformed and faulted successions across the three fault bounded synclines and establishing a coherent stratigraphic framework

steep microbial boundstone dominated plaform margins abstract seaward progradation of several kilometers has been documented mostly for leeward margin low angle carbonate slope systems with a dominant platform top sediment source however steep and high relief margins fronting deep basins can also prograde and as such are somewhat perplexing characteristics of two prograding carboniferous examples provide a model which may apply elsewhere 1 outcrops in asturias northern spain serve as important analogs for 2 hydrocarbon reservoirs in steep sided isolated platforms of the north caspian basin kazakhstan such as tengiz seismic and well data from tengiz corroborate outcrop patterns for slope development showing progradation of up to 5 and more than 10 km respectively despite the high relief up to 600 m and steep 20 35 nature of these margins the two examples share a highly productive microbial boundstone factory extending from the platform break down the slope to nearly 300 m or more depth and a lower slope dominated by mega breccias and grain flow deposits derived from the margin and slope itself the broad depth range of microbial boundstone increases the potential for production during both lowstands and high stands of sea level and thereby facilitates progradation independent from platform top derived sediment rapid in situ lithification of the boundstone provides stability to the steep slopes but also leads to readjustment through shearing and avalanching what controls the microbial cement boundstone formation remains a debate but its presence is a key factor controlling the progradational geometry of these and possibly other margins this new model of slope shedding has implications for slope readjustment processes and resulting architecture sequence stratigraphic interpretation reservoir characterization and reservoir modeling especially the isotropic character of microbial boundstone will reduce the potential for coherent seismic reflections to develop and possibly invoke under certain stress regimes shattering and fracturing thereby generating significant non matrix permeability key considerations are the contrasts with the bahamian high stand shedding depositional model slope progradation rates that range from 450 to 1500 m my and net growth rates of in situ boundstone of 1000 m my comparable to or higher than accretion rates for metazoan skeletal reef growth

isotopic fingerprints of milankovitch cycles in pennsylvanian carbonate platform top deposits the valdorria record northern spain sedimentary cyclic sequences deposited during the late palaeozoic ice age are widespread glacio eustatic control of the cyclic patterns is commonly accepted and the durations of the cyclothems generally match the short and long eccentricity milankovitch orbital parameters nevertheless geochemical fingerprints of orbital parameters are poorly documented in deep time sedimentary records here we report on well exposed bashkirian cyclothems of c 123 ka and c 400 ka durations from the valdorria platform the shorter term cyclothems can be grouped into longer term composite sequences that are consistent with generally accepted durations of c 125 ka and c 400 ka for milankovitch eccentricity cycles the stratigraphic pattern is mirrored by the isotope geochemical signals which show distinct recurring trends these trends are confirmed by statistical tests whereas intrinsic factors and or subaerial exposure related to sea level lowstands might have truncated cycle patterns in tectonically stable basins rapid subsidence of the valdorria platform s foreland basin appears to have contributed to a faithful recording of cyclothems of different orders the patterns and biostratigraphic constraint revealed in this study demonstrate the power of orbital forcing in imprinting sedimentary and geochemical signals in the rock record

speculations on the controls on cyclic peritidal carbonates ice house versus greenhouse eustatic controls abstract metre scale peritidal cyclothems which are distinctive components of lower palaeozoic and many mesozoic platform carbonates are not common in carboniferous sequences in their place the platform sequences are characterized by 5 10 m thick largely subtidal limestones with prominent exposure surfaces the former type of platform cyclothems developed during greenhouse phases when in the absence of major continental ice sheets sea level oscillations were caused by small scale obliquity and precession milankovitch rhythms under such conditions platforms rapidly aggraded with the deposition of peritidal cyclothems the carboniferous was an ice house phase when the waxing and waning of gondwanan ice sheets caused by eccentricity rhythm generated climatic changes created high amplitude rapid falls and rises in sea level the resulting carbonates reflect such changes with catch up subtidal dominated sequences and pronounced subaerial exposure surfaces capping the cyclothems

coral reefs and growth dynamics of a low angle carboniferous platform records from tianlin southern china abstract metazoan reef building receded globally during the carboniferous after the late devonian extinction events shallow water bioconstructions were generally small and scarce and corals played a minor role in their construction however in southern china one large 50 m high and three small 6 16 m high coral reefs dating from the late visean serpukhovian have recently been discovered in two localities in guangxi to understand the occurrence of these coral reefs and to constrain the factors that controlled their growth three sections around langping guangxi were measured and selected samples were analysed using petrography biostratigraphy and chemostratigraphy the depositional environment of these exceptional mississippian reefs was interpreted as a low angle platform 1 2 5 recording oligotrophic conditions and normal salinity the three small reefs have grown around the fair weather wave base whereas the large coral reef has grown in a deeper environment between the fair weather and storm wave base during carboniferous the global temporal reef distribution can be partly ascribed to paleoclimate changes however in southern china the growth of extended mississippian coral reefs is restricted to a short time window the late visean serpukhovian which coincides with high amplitude and high frequency sea level fluctuations most likely related to glacial pulses recent studies revealed that several rugose coral species survived the mid carboniferous glaciation event thanks to the persistence of warm water ocean currents maintaining tropical conditions on the platform due to the scarcity of extended coral reefs elsewhere it cannot be excluded that tianlin provided an ecological refuge for corals related to oceanic currents another potential favorable factor could be the mid ramp depositional setting the deep water platform areas could potentially provide more stable conditions less affected by global stress events however the deep reef refugia hypothesis remains debatable as only very few studies have explored its validity at the community level even if the causes of the occurrence of an extended coral reef in southern china cannot be fully constrained the existence of this large coral framework in the late visean serpukhovian provides additional evidence that coral communities did build reefs after the late devonian extinction events

sedimentologic role of microproblematica donezella in a lower pennsylvania donezella siliceous sponge dominated carbonate buildup frontal ouachita thrust belt oklahoma u s a abstract the problematic organism donezella emerged worldwide as one of the main carbonate mound builders in the middle carboniferous donezella is composed of thin 70 160 m in diameter bifurcating 45 to 90 degrees tubes microfacies analysis of a donezella buildup from the wapanucka formation frontal ouachita thrust belt oklahoma u s a was undertaken to examine the role of donezella in a carbonate buildup donezella is the predominant biotic component of the wapanucka buildup and the buildup is composed of irregular pockets of boundstone dominated by donezella worm tubes peloids and micritic crusts siliceous sponge spicules less common siliceous sponge boundstone and peloidal wackestone with other bioclasts in the lower part of the buildup donezella colonies are robust convex upward and up to several centimeters in diameter these colonies are composed of delicately branching donezella with an enclosed constructional pore system these robust upward growing donezella structures formed a substrate for other binders therefore it appears that on a microscale donezella together with siliceous sponges and worm tubes played the role of a constructor donezella occurs as a long semicontinuous row of thalli when encrusting other framework grains and encrusts siliceous sponges donezella colonies corals and worm tubes thus it also acted as a member of the binder guild deciphering these various roles of donezella is a crucial first step toward documenting a possible spectrum of donezella dominated lithologies that constitute key elements in carbonate buildups in the early to middle pennsylvanian

spatial patterns of sediment accumulation on a holocene carbonate tidal flat northwest andros island bahamas abstract to characterize spatial patterns of sedimentation and analyze the morphology of part of the modern tidal flats of northwest andros island in the bahamas this study integrated remote sensing geographic information systems gis and carbonate sedimentology the fundamental data are a landsat tm image that has been classified to create a thematic map of eight subfacies interpreted to represent a distinct tidal flat subenvironment such as adjacent marine exposed levee beach ridge pond and algal marsh spatial statistics of the thematic map characterize the patterns of sediment accumulation quantitative analysis highlights several interesting results concerning subfacies character and distribution 1 of the eight mapped subfacies low algal marsh is most widespread representing 27 5 of the total area whereas exposed levee beach ridge is the least widespread accounting for 10 of the area 2 the patches of different subfacies have different shape complexities with low algal marsh high algal marsh and mangrove ponds being the least complex and exposed levee beach ridge being the most complex 3 markov chain analysis suggests that lateral transitions between different subfacies are highly ordered and 4 frequency distribution of subfacies patch area and lacunarity gap size distribution data exhibit power law relationships over several orders of magnitude consistent with fractal characteristics the fractal nature of patch size and gaps between facies illustrate that on this tidal flat neither the size nor the spatial distribution of subfacies has a characteristic scale this statistical behavior is consistent with the presence of self organization or emergence of pattern in the absence of a template or external forcing the statistical self organization on the tidal flat is the cumulative expression of local processes but it becomes apparent only through analysis of the whole system these results are inconsistent with models suggesting that tidal flats include a migrating complex of randomly distributed randomly sized subenvironments ancient successions that include random patterns may reflect the more pronounced influence of forces external to the sedimentary system instead of an absence of those forces

depositional setting and diagenetic processes and their impact on the reservoir quality in the late visean bashkirian kashagan carbonate platform pre caspian basin kazakhstan the kashagan isolated carbonate platform developed from the visean to the bashkirian in the pre caspian basin sedimentation is organized in shallowing upward cycles marked at the top by subaerial exposure surfaces this study is based on analyses of 12 cored wells integrated sedimentology petrography fluid inclusion stable isotopes and trace element data we reconstructed the pore system evolution in the platform interior and margin near surface diagenesis includes marine cement fringes followed by meteoric dissolution and cementation meteoric diagenesis was stronger in the bashkirian sequence and progressively decreased down section in the visean the main karst surfaces are evidenced by root traces sharp 13c depletion and meteoric water fluid inclusions in calcites porosity in the platform interior follows a cyclic pattern due to the interaction of the freshwater dissolution and cementation and compaction that destroyed the porosity at the tops and bases of the cycles burial diagenesis represented by some calcite cementation did not significantly alter the cyclic porosity distribution in the platform interior in the platform margin porosity distribution is more heterogeneous due to more poorly defined sedimentary cyclicity and stronger burial diagenetic overprint linked to exotic fluid circulation basin sourced fluids caused dissolution cementation and local dolomitization these cements show bright luminescence a high manganese content depleted 18o a high homogenization temperature and low salinity fluid inclusions the complex diagenetic evolution diagenesis produced better matrix porosity in the platform interior and heterogeneous porosity with larger pores and fractures but with poor matrix porosity in the platform margin

a pulse of ooid formation in maui nui hawaiian islands during termination i abstract we describe the first recorded occurrence of oolite in the main hawaiian islands well cemented oolite was recovered at several locations at 140 to 150 m depth south of lana i the ooids contain foraminiferal skeletal and peloidal nuclei coated by thin to moderately thick 20 50 of ooid radius tangential cortices and are cemented by fibrous aragonite needles the extent of amino acid racemization aar analysed on 127 ooid grains and 55 pristine foraminifera in the same deposits confirm that the particles formed during a brief interval estimated at 1900 yr duration a single large benthic foraminiferan amphisorus sp intermixed with the ooid grains yielded a calibrated 14 c age of 12 2 0 3 ka in contrast a series of progressive leaches on two splits of ooid grains yielded a sequence of 14 c ages ranging from 27 ka for the nuclei to 14 c leach ages and further research is needed however assuming that the age of the ooids lies between the 14 c ages of the youngest cortex 14 9 ka and the amphisorus 12 2 ka then eustatic sea level history records suggest two intervals of slowing sea level history rise that could accommodate ooid formation these occurred immediately preceding mwp1a 15 ka and mwp1b 12 5 ka in the area of the oolite deposit there is no terrace or hardground morphology that coincides with a 100 m sea stand preceding mwp1a thus we suggest that conditions required for ooid formation converged when a flat carbonate hardground in the broad au au channel was initially flooded with energetic shallow water as sea level rose to and slowed at 60 to 55 m during the onset of the younger dryas yd interval around 12 7 ka ooid formation ensued for a short period 1900 yr and then abruptly ceased most reasonably as a result of a 7 5 m deepening of the sea during mwp1b around 11 5 ka the oolitic sediments were subsequently transported longshore and offshore to southern lana i

analyzing spatial patterns in modern carbonate sand bodies from great bahama bank abstract three carbonate sand bodies on great bahama bank which show a range of depositional facies patterns typifying modern deposits as well as their ancient counterparts are quantitatively interrogated to broaden our perspective of the types of information that can be derived from studies of modern environments rimming the southern end of tongue of the ocean toto is the broadest expanse of high energy sands found in the bahamas characterized by narrow sandbars separated by wide deep channels and a lack of islands a variation of the tidal bar motif with broader and more irregular sandbars relatively narrow channels and few small islands occurs at the northern end of exuma sound schooners sands associated with tidal channels and the numerous islands of the exumas chain along the western edge of exuma sound occur primarily as flood tidal deltas the geometry of sandbars that inhabit the three sand bodies is quantified using landsat remote sensing and assembled along with optically derived bathymetric surfaces into a gis this database is quantitatively examined using a suite of morphometric tools to compare and contrast geometric character of sandbars within and between the three sand bodies considered are properties such as the size shape complexity distribution orientation and topography of the individual sandbars profiles and spatial analysis tools enable sandbar and channel spacing position relative to the platform margin connectedness separation distances and density to be characterized as has been previously reported for reef dominated environments certain aspects of the geometry of the three systems are found to behave in a systematic and hence predictable manner though important mathematical differences are revealed between the scaling of reefal landscapes and the grainy geobodies considered by this study because the three sand bodies are disparate in their overall extent and depositional settings e g orientation prevalence of islands this predictable behavior has the potential to impart considerable insight to the characterization of grainstone systems

facies geometry and growth phases of the valdorria carbonate platform pennsylvanian northern spain the 14 km wide valdorria outcrop pennsylvanian northern spain is one of the few examples of entirely exposed flat topped and high relief carbonate platforms reported in the fossil rock record laterally and vertically traceable stratal patterns expose three phases of growth phase i is a 430 m thick platform to slope succession that prograded over 6 km and is dated as early bashkirian akavasian askynbashian phase ii aggraded and prograded exhibiting 180 m thickness of cyclical platform top deposits dated as late bashkirian asatauian phase iii is a mound shape structure that developed over the platform top of phase ii as a new phase of platform nucleation it is 535 m thick and 2 km wide and dated as late bashkirian asatauian transition interval the observed changes of growth styles during platform evolution from a prograding to an aggrading prograding system and a rapid aggradational phase are inferred to be controlled by flexural subsidence in the active cantabrian foreland basin at the variscan orogenic front the metre scale shallowing upward cycles of the platform top are most probably due to glacioeustasy as evidenced by well recorded subaerial exposure surfaces superimposed on subtidal deposits and by a stratal pattern recurrent in a short interval of about 160 kyr observations of outcropping bashkirian cyclothems in an isolated carbonate system devoid of siliciclastic input are relevant for a better understanding of the impact of high frequency sea level fluctuations on the carbonate factory moreover progradation of the platform margin during phase i reaches a rate of 2500 m myr and 1810 m myr during phase ii rates that are high when compared to other pennsylvanian examples the aggradation rate of 447 m myr calculated for late bashkirian transition interval phases i and ii uncorrected for compaction missing beats and erosion is uncommonly high in comparison to coeval pennsylvanian examples the platform exhibits a self nourishing prograding microbial boundstone dominated slope thus the slope shedding model applies well to valdorria however phase ii recorded eustatic variations able to inhibit the slope microbial boundstone factory during low sea level stands this is marked by common slope red stained breccias synchronous to platform top subaerial exposure phases contrarily periods of relative high sea level and rapid subsidence in phase iii registered a greater development of cemented microbial boundstone these observed partly opposing relationships of sea level stands shedding modes and slope architecture provide an improvement of the currently used slope shedding model the overall architecture of the valdorria outcrop compares well with that of other contemporaneous platforms such as sierra del cuera and bolshoi karatau valdorria shares the high relief and flat topped steep slopes cyclothemic patterns and occurrence of karst features with the pricaspian basin platforms tengiz karachaganak and kashagan with minor variations in facies distribution of the internal platform furthermore the continuous seismic scale outcrop of valdorria together with its isolated setting and asymmetrical growth makes it an additional good candidate for potential subsurface analogues of hydrocarbon bearing systems

scaling of sedimentation rates and drowning of reefs and carbonate platforms the rule that sedimentation rates decrease as the time interval increases has been examined by a procedure that avoids the mathematical problem of plotting a variable time against its inverse the test confirms that the scaling trend has real physical meaning in the time range of 10 1 108 yr sedimentation rates change roughly proportionally to the inverse of the square root of time this report proposes and evaluates the hypothesis that the growth potential of reefs and carbonate platforms follows the same scaling trend the trend implies that a growth of 104 m yr sustained over 103 yr an upper limit of reef growth in the holocene translates into 102 m yr sustained over 107 yr decrease of the growth potential with increasing time solves the paradox of drowned platforms if the decrease results largely from environmental factors and not simply from increase of the time fraction of subaerial exposure

a phosphatocopid crustacean with appendages from the lower cambrian here we describe a phosphatocopid arthropod with preserved soft anatomy from lower cambrian rocks of shropshire england which provides evidence for the occurrence of crustacea including eucrustacea in the early cambrian the find identifies an important stratigraphically early source of well preserved fossils konservat lagerstatte

sequence stratigraphy and onlap history of the donets basin ukraine insight into carboniferous icehouse dynamics abstract the degree to which permo carboniferous cyclothemic successions archive evidence for long term variations in ice volume during the late paleozoic ice age is insufficiently resolved here we develop the sequence stratigraphy and onlap offlap history for a 33 my interval of the carboniferous using the u pb calibrated succession of the donets basin ukraine in order to assess the relationship between sea level high latitude changes in glacial extent and climate integrated subsurface and outcrop data permit meter scale correlation of 242 biostratigraphically constrained limestones and coals and in turn individual cyclothems across 250 km of the donets basin rapid uniform subsidence and basinwide continuity of marker beds indicate pennsylvanian deposition under relatively stable tectonic conditions three scales of sequences avg durations of 140 ky 480 ky and 1 6 my are recognized on the basis of stratigraphic stacking patterns and basinwide architecture of marine to terrestrial facies assemblages the hierarchy of sequences and the geographic and stratigraphic positions of shifts in base level sensitive facies across the donets ramp permit the construction of an onlap offlap history at a sub 400 ky scale major sea level lowstands occur across the mid carboniferous boundary and during the early moscovian these lowstands coincide with glacial maxima inferred from high latitude glacigenic deposits the middle to late pennsylvanian is characterized by a stepwise onlap culminating in an earliest gzhelian highstand suggesting contraction of carboniferous ice sheets prior to the initiation of early permian glaciation the stratigraphic position of climate sensitive facies within individual donets cyclothems indicates a turnover from seasonal sub humid or semi arid climate to everwet conditions during the late lowstand and maximum ice sheet accumulation comparison of the stratigraphic and aerial distribution of coals and evaporites in the donets basin with the onlap offlap history further indicates everwet conditions during lowstands and inferred glacial maxima and drier climate during onlap and inferred ice sheet contraction at the intermediate 0 8 to 1 6 my and long 106 yr time scales taken together the relationship between inferred climate and glacioeustasy suggests a likely teleconnection between high latitude ice sheet behavior and low latitude atmospheric dynamics

woody vegetation and channel morphogenesis in low gradient gravel bed streams in the ozark plateaus missouri and arkansas woody vegetation affects channel morphogenesis in ozark streams of missouri and arkansas by increasing local roughness increasing bank strength providing sedimentation sites and creating obstructions to flow variations in physiographic controls on channel morphology result in systematic changes in vegetation patterns and geomorphic functions with increasing drainage basin area in upstream reaches streams have abundant bedrock control and bank heights that typically are less than or equal to the rooting depth of trees in downstream reaches where valleys are wider and alluvial banks are higher vegetation has different geomorphic functions at drainage areas of greater than 100 200 km2 ozarks streams are characterized by longitudinally juxtaposed reaches of high and low lateral channel migration rates referred to as disturbance reaches and stable reaches respectively whereas stable reaches can develop stable forested floodplains if they are not farmed disturbance reaches are characterized by dynamic vegetation communities that interact with erosion and deposition processes disturbance reaches can be subdivided into low gradient and high gradient longitudinal zones low energy zones are characterized by incremental unidirectional lateral channel migration and deposition of gravel and sand bars the bars are characterized by prominent bands of woody vegetation and ridge and swale topography channel monitoring data indicate that densely vegetated bands of woody vegetation formed depositional sites during bedload transporting events the same floods caused up to 20 m of erosion of adjacent cutbanks scoured non vegetated areas between vegetation bands and increased thalweg depth and definition in high energy or riffle zones channel movement is dominantly by avulsion in these zones vegetation creates areas of erosional resistance that become temporary islands as the channel avulses around or through them woody vegetation on islands creates steep root defended banks that contribute to narrow channels with high velocities calculation of hydraulic roughness from density and average diameter of woody vegetation groups of different ages indicates that flow resistance provided by vegetation decreases systematically with group age mainly through decreasing stem density if all other factors remain constant the stabilizing effect of a group of woody vegetation on a gravel bar decreases with vegetation age

sea level curve for pennsylvanian eustatic marine transgressive regressive depositional cycles along midcontinent outcrop belt north america at least 55 cycles of marine inundation and withdrawal are recognized in the mid desmoinesian to mid virgilian midcontinent outcrop sequence in north america they range from widespread major cycles classic cyclothems with deep water facies extending across the northern shelf through intermediate cycles persisting as marine horizons across the shelf to minor cycles developed on the lower shelf or as parts of major cycles biostratigraphic differentiation of the cycles should establish interbasinal correlation on a scale fine enough to allow evaluation of differential tectonics and sedimentation sequential groupings of cycles are more irregular than proposed megacyclothems or mesothems but they may be obscured by the distinctness of the major cyclothems estimates of cycle periods range from about 40 to 120 x 10 sup 3 yr for the minor cycles up to about 235 to 400 x 10 sup 3 yr for the major cyclothems the range for all cycles corresponds well to the range of periods of earth s orbital parameters that constitute the milankovitch insolation theory for the pleistocene ice ages and it further supports gondwanan glacial control for the pennsylvanian cycles even though the dominant period of the major pennsylvanian cyclothems is up to four times longer than the dominant 100 000 yr period inmore the pleistocene the shapes of both curves display rapid marine transgression rapid melting of ice caps and slow interrupted regression slow buildup of ice caps which suggest similar linkages between the climatic effects of the orbital parameters and ice cap formation and melting at the two different scales widely separated in time 28 references 3 figures less

accumulation rates of carbonate platforms the growth potential of carbonate platforms i e the maximum rate at which they can aggrade vertically is difficult to assess to estimate the growth potential from the conservative side and search for variations with time we have compiled published accumulation rates from the phanerozoic accumulation rates vary in a pattern with maximum rates up to 200 m ma or more not corrected for compaction in the late devonian permian late triassic late jurassic and mid cretaceous separated by intervals of reduced rates e g carboniferous early jurassic and late cretaceous the most dramatic drop occurs at the permo triassic boundary after which there is no documented platform growth this pattern resembles the evolutionary rhythm of bloom and demise of reefs and reef builders the observed maximum accumulation rate of 200 m ma over 10 6 10 7 yr is probably imposed by the maximum rate of long term relative sea level rise on passive margins the most favorable site for carbonate platform deve

lower cambrian anabaritids from south china anabaritids are a distinctive group of early skeletal fossils with tri radially symmetrical tubes they occur in the earliest cambrian deposits and seem to be especially characteristic of the tommotian strata and putative pre tommotian units e g manykay horizon a detailed redescription of anabarites rotundus qian from near kuanchuanpu shaanxi province emphasizes the degree of morphological variation new data on shell composition suggest a bilayered structure the outer unit composed of fibres parallel to growth lines overlying a distinctive inner lamella with a chevron ultrastructure tentative evidence for anabaritids possibly being operculate is presented the putative operculum being a simple convex disc more poorly preserved anabaritids from the yangtze gorges hubei province and meishucun yunnan province are referred to a trisulcatus all these chinese occurrences of anabaritids are consistent with a lower tommotian age of the associated faunas but reliable and precise correlations with other precambrian cambrian boundary sections remain inconclusive

modelling bedload yield in braided gravel bed rivers abstract this paper outlines an approach for estimating the annual bedload yield of a braided channel this procedure is based on the extension of theory of flow and sediment transport in braided rivers recently presented by paola 1996 the revised approach accounts explicitly for the relationship between increasing discharge and varying channel hydraulics and is suitable for use in obtaining bedload transport rate estimates over a range of discharges integration of such estimates using flow duration data allows annual bedload yield to be determined model parameterisation is achieved using topographic survey data for the waimakariri river new zealand comparison of modelled bedload yield with values estimated from repeated topographic surveys indicates that the model is able to accurately predict both the medium term c 30 years mean annual bedload yield of the waimakariri at crossbank the section 17 8 km upstream of the river mouth and also short term fluctuations in bedload yield associated with varying annual flow statistics streamwise patterns of volumetric erosion and deposition determined for a 45 km length of the waimakariri using the model are also in broad agreement with trends identified in topographic survey data for the period 1961 1997 however significant deviations between modelled and surveyed volumes of cut and fill are evident at some locations comparison of model performance with conventional applications of bedload transport equations which tend to underestimate transport rates for braided channels suggests that the approach presented here may represent a significant improvement this is the case because the model quantifies the relationship between braid intensity and spatial variability in flow hydraulics at a cross section output from the model suggests that braided rivers may transport a significant proportion of their annual bedload at lower discharges than those indicated by earlier theoretical approaches results also provide quantitative support for the argument that increased intensity of braiding may promote higher rates of bedload transport in gravel bed rivers

a pennsylvanian microbial boundstone dominated carbonate shelf in a distal foreland margin picos de europa province nw spain abstract a pennsylvanian bashkirian moscovian high rising microbial boundstone dominated carbonate platform 12 000 km2 developed in the external margin of a variscan foreland basin intensely studied in the northern domain cuera area the stratigraphy and sedimentology of the southern domain the picos de europa province is here revisited distribution of the bashkirian facies valdeteja formation defines a ramp low angle platform with an internal zone central and eastern sectors of the picos de europa province consisting of huge amounts of massive cement rich microbial boundstones surrounded by an external zone comprising lower slope boundstone derived breccias and basinal lime mudstones from the bashkirian moscovian transition to the early kasimovian picos de europa formation the carbonate platform moderately aggraded acquiring a high rising and flat topped geometry and then prograded rapidly into the external zone where platform derived carbonate sediment and clay sourced from the orogen were deposited seismic scale exposures of the western margin of the shelf show angular bedding relationship between basin toe of slope slope and platform top stratal domains with slope inclination up to 32 and a topographic relief of 550 m the platform evolution above described for the picos de europa province significantly differs with respect to the cuera area where platform mostly prograded during the bashkirian and subsequently aggraded during early moscovian the evolutionary differences between these two carbonate domains which are geographically close are interpreted as changes in tectonic subsidence distribution acting as the major factor controlling the large scale platform geometries in the active foreland basin context finally the tectonic overload due to the emplacement of the cuera thrust sheets during the moscovian kasimovian transition changed the platform growth style from progradational to aggradational and consequently the stacking pattern of the platform top cycles in the picos de europa province

lithofacies character and architecture across a pennsylvanian inner platform transect sierra de cuera asturias spain abstract seismic scale outcrops of lower pennsylvanian steep margined carbonate platforms in northern spain sierra de cuera cantabrian mountains provide the opportunity to link depositional facies to platform interior architecture lithofacies character vertical stacking patterns and spatial distribution of depositional facies and shallowing upward cycles were investigated to provide a semiquantitative depositional model for inner platform strata a 70 m thick succession of eight shallowing upward cycles 2 5 15 m thick was studied across a 2 km wide transect cycles consist of algal bioherms and skeletal packstone lithofacies association b deposited in an open marine and sub wave base environment which are locally lateral to crinoid dominated packstone lithofacies association d lithofacies association b developed on a transgressive one meter thick high energy coated grain grainstone lithofacies association a and is overlain by open marine to restricted lagoonal deposits lithofacies association c indicative of decreased paleo water depth cycle boundaries are marine flooding surfaces occurring at the base of lithofacies a and the top of lithofacies c petrographic and outcrop evidence of subaerial exposure is conspicuously lacking cycle and lithofacies thickness varies laterally and all the lithofacies can be either continuous for the 2 km width of investigation or discontinuous terminating within tens to hundreds of meters in most of the cycles the lithofacies succession changes laterally because of lateral facies transitions between lithofacies b and d and pinching out of lithofacies a and c meter scale variations in depositional topography are related to the stacked lens shaped bioherms assigned to lithofacies b and appear to control the thickness and lateral continuity of the overlying facies sierra de cuera strata do not resemble other pennsylvanian cycles driven by high frequency high amplitude glacio eustasy which are commonly characterized by subaerial exposure surfaces developed on subtidal deposits except for the absence of peritidal facies and the presence of low relief algal bioherms on the platform top the necessary accommodation to enhance the growth of bioherms on the platform top was probably due to high frequency 100 240 ky moderate amplitude nearly 40 m sea level fluctuations combined with subsidence rates of 70 140 m my tectonic subsidence might have been responsible for the lack of evidence of subaerial exposure surfaces in the examined moscovian strata the studied inner platform lithofacies character and architecture were controlled by the interplay of high frequency changes in accommodation and the presence of meter scale depositional topography attributed to lateral variations of carbonate accumulation

cnidarian like embryos associated with the first shelly fossils in siberia phosphatized spheroids similar to 0 5 mm in diameter in the lower cambrian manykay formation at the bol shaya kuonamka river in northern sakha yakutia are interpreted as cnidarian embryos of late developmental stages one of the poles has a double cro

paleoshoreline patterns in the transgressive regressive sequences of pennsylvanian rocks in the northern appalachian basin u s a abstract sheets of sponge spicule flint of pennsylvanian age bashkirian moscovian kasimovian that are present in the northern appalachian basin of ohio and adjacent parts of kentucky pennsylvania and west virginia are important indicators of paleoshorelines this flint typically occurs with or occupies the position normally held by shallow water limestone and contains a normal marine fauna the flint was deposited above coal or underclay representing the detritus starved marine portion of a transgressive regressive sequence and marking the eastern limit of transgression across a westward spreading alluvial plain flint occurs at several stratigraphic positions in the upper pottsville lower conemaugh interval the most important are boggs upper mercer and kanawha flints of the upper pottsville group kilgore flint ridge zaleski and vanport flints of the lower allegheny group and brush creek flint of the lower conemaugh group lithofacies maps of these beds were constructed to show the distribution of the flint limestone hosted flint occurs in long discontinuous chains of sheetlike bodies whereas shale hosted flint occurs in single sheets with restricted geographic distribution chains of limestone hosted flint attain maximum dimensions of a few meters in thickness a few kilometers in width and several hundreds of kilometers in length the upper mercer vanport and brush creek flints are particularly extensive forming arcuate shoreline patterns that parallel the fronts of large delta systems beds of clay ironstone and or coal above flint indicate that the lagoonal environment in which flint was deposited was followed closely by a change to stagnant waters cementation of flint with silica likely occurred under the lower ph conditions existing at that time and when depths of burial were shallow

destabilization of streambanks by removal of invasive species in canyon de chelly national monument arizona as part of a study to investigate the causes of channel narrowing and incision in canyon de chelly national monument the effects of tamarisk and russian olive on streambank stability were investigated in this study root tensile strengths and distributions in streambanks were measured and used in combination with a root reinforcement model riproot to estimate the additional cohesion provided to layers of each streambank the additional cohesion provided by the roots in each 0 1 m layer ranged from 0 to 6 9 kpa for tamarisk and from 0 to 14 2 kpa for russian olive average root reinforcement values over the entire bank profile were 2 5 and 3 2 kpa for tamarisk and russian olive respectively the implications of vegetation removal on bank stability and failure frequency were evaluated in two incised reaches by modeling bank toe erosion and bank stability with and without vegetation the effects of a series of 1 0 and 1 5 m deep flows on bank toe erosion pore pressure distributions and bank stability were evaluated first in addition bank stability model runs were conducted using iterative modeling of toe erosion and bank stability using a discretized flow and groundwater record for one year results showed that the effects of root reinforcement provided by tamarisk and russian olive have a significant impact on bank stability and bank failure frequency because the bank materials are dominated by sands cohesion provided by roots is significant to bank stability providing an average 2 8 kpa of cohesion to otherwise cohesionless bank materials bank retreat rates at one site following vegetation removal have approximately doubled when compared to the control reach from an approximate rate of 0 7 0 8 m y between 2003 and 2006 to 1 85 m y during the year modeled vegetation removal along the entire riparian corridor in canyon de chelly may lead to the introduction of significantly more sediment to the system through bank widening processes although it is not known whether this change alone would be sufficient to cause a shift in channel morphology to the wide braided channels that were once characteristic of this canyon

carbonate platform flanks slope angle and sediment fabric more than 20 examples of fossil carbonate platform systems were compared for slope angle and sediment fabric plots of slope angle versus sediment fabric show that grainy non cohesive mud free sediments build steeper slopes than muddy cohesive sediments examples near the end members of grainy and muddy carbonate platform flanks are found in the triassic of the dolomites in northern italy and in the bahamas respectively they document the flank geometry and the processes readjusting the slope profile once the limiting slope angle is exceeded the grainy flank sediments in the dolomites modified by shearing and avalanching produce straight slope profiles with declivities up to 35 whereas the muddy bahamian flank sediments modified by large scale creep and rotational to translational sliding and slumping produce a concave upwards slope profile inclined at less than 4 the comparison between slope angle and sediment fabric indicates that the physical behaviour of sediments in the gravity field angle of shearing and mode of readjustment processes is linked to the composition of the slope sediment among the variables such as sea level subsidence climate plate motion and oceanographic setting windward leeward sediment fabric is suggested to be a major if not the major control on slope angle and slope curvature of carbonate platform flanks besides the recently documented tendency of carbonate sediments to build steeper slopes than siliciclastics this proposed relation sheds new light on the analysis and quantification of the variables influencing the geometry and depositional evolution of carbonate systems furthermore it provides an opportunity to deduce sediment composition from seismic lines and predict lithology prior to drilling

fossil preservation through phosphatization and silicification in the ediacaran doushantuo formation south china a comparative synthesis phosphatized and silicified microfossils preserved through replication of organic templates by authigenic calcium phosphate and silica respectively form through mechanistically similar mineralization processes but under notably different conditions in order to characterize the environments and taphonomic processes associated with these preservational pathways we compare phosphatized and silicified fossil assemblages in the ediacaran doushantuo formation south china in terms of stratigraphic and paleogeographic distribution preservation and biodiversity several differences are recognized 1 phosphatization and silicification both occurred in sub tidal doushantuo sediments but phosphatized fossils generally occur in shallower sub tidal facies than silicified fossils 2 although both phosphatized and silicified fossils are preserved three dimensionally the latter are typically more compressed and 3 whereas phosphatized assemblages are numerically dominated by multicellular acritarchs putative metazoan eggs and embryos silicified assemblages are dominated by prokaryotes these differences can be explained by environmental and taphonomic distinctions phosphatized fossils occur in intraclastic phosphorites and phosphatic carbonates and were likely fossilized near the suboxic anoxic boundary in sediments under oxic bottom waters with redox and biogeochemical gradients conducive to p remineralization phosphate burial via iron pumping and calcium phosphate precipitation reworking and winnowing of phosphatized fossils preferentially concentrated certain taxa prior to final burial in contrast silicified fossils typically occur in chert nodules which formed deeper in the sediment column in ferruginous pore waters and perhaps under ferruginous bottom waters where bacterial sulfate reduction and pyrite formation created low ph conditions conducive to calcite dissolution and silica precipitation once formed chert nodules mostly remained in situ but some were reworked with turbidites and olistostromes developed in slope facies despite these distinctions phosphatized and silicified fossil assemblages in the doushantuo formation generally overlap in time and space and representatives of all major groups and many common genera of doushantuo organisms are present in both phosphorites and cherts consequently although both preservational pathways have paleoenvironmental and taphonomic biases their relative biases on taxonomic presence absence data are minimal given sufficient sampling efforts and paleobiologic and biostratigraphic information based on presence absence but not abundance data from the doushantuo formation appears to be robust

high precision u pb zircon age calibration of the global carboniferous time scale and milankovitch band cyclicity in the donets basin eastern ukraine 1 high precision id tims u pb zircon ages for 12 interstratified tuffs and tonsteins are used to radiometrically calibrate the detailed lithostratigraphic cyclostratigraphic and biostratigraphic framework of the carboniferous donets basin of eastern europe chemical abrasion of zircons use of the internationally calibrated earthtime mixed u pb isotope dilution tracer and improved mass spectrometry guided by detailed error analysis have resulted in an age resolution of 0 05 or 100 ka for these carboniferous volcanics this precision allows the resolution of time in the milankovitch band and confirms the long standing hypothesis that individual high frequency pennsylvanian cyclothems and bundles of cyclothems into fourth order sequences are the eustatic response to orbital eccentricity 100 and 400 ka forcing tuning of the fourth order sequences in the donets basin to the long period eccentricity cycle results in a continuous age model for the middle to late pennsylvanian moscovian kasimovian ghzelian strata of the basin and their record of biological and climatic changes through the latter portion of the late paleozoic ice age detailed fusulinid and conodont zonations allow the export of this age model to sections throughout euramerica additional ages for mississippian strata provide among the first robust radiometric calibration points within this subperiod and result in variable lowering of the base ages of its constituent stages compared to recent global time scale compilations

fluvial processes and vegetation glimpses of the past the present and perhaps the future abstract most research before 1960 into interactions among fluvial processes resulting landforms and vegetation was descriptive since then however research has become more detailed and quantitative permitting numerical modeling and applications including agricultural erosion abatement and rehabilitation of altered bottomlands although progress was largely observational the empiricism increasingly yielded to objective recognition of how vegetation interacts with and influences geomorphic process a review of advances relating fluvial processes and vegetation during the last 50 years centers on hydrologic reconstructions from tree rings plant indicators of flow and flood frequency parameters hydrologic controls on plant species regulation of sediment movement by vegetation vegetative controls on mass movement and relations between plant cover and sediment movement extension of present studies of vegetation as a regulator of bottomland hydrologic and geomorphic processes may become markedly more sophisticated and widespread than at present research emphases that are likely to continue include vegetative considerations for erosion modeling response of riparian zone forests to disturbance such as dams and water diversion the effect of vegetation on channel and bottomland dynamics and rehabilitation of stream corridors research topics that presently are receiving attention are the effect of woody vegetation on the roughness of stream corridors and hence processes of flood conveyance and flood plain sedimentation the development of a theoretical basis for rehabilitation projects as opposed to fully empirical approaches the effect of invasive plant species on the dynamics of bottomland vegetation the quantification of below surface biomass and related soil stability factors for use in erosion prediction models and the effect of impoundments on downstream narrowing of channels and accompanying encroachment of vegetation bottomland vegetation partially controls and is controlled by fluvial geomorphic processes the purposes of this paper are to identify and review investigations that have related vegetation to bottomland features and processes to distinguish the present status of these investigations and to anticipate future research into how hydrologic and fluvial geomorphic processes of bottomlands interact with vegetation

late devonian carbon isotope stratigraphy and sea level fluctuations canning basin western australia the upper devonian reef complexes of the canning basin contain some of the world s best exposed continuous stratigraphic sections through the frasnian famennian boundary the facies distribution and composition of these reef complexes record interactions among sea level changes sediment supply ocean chemistry and paleoecology changes in relative sea level produced spatial shifts in reef platform development and regional changes in sediment supply that can be correlated across facies boundaries using a combination of sequence stratigraphy biostratigraphy and carbon isotope stratigraphy during the lowstand interval below the frasnian famennian boundary the reef margin advanced down the reef slope in shallow water environments and siliciclastics locally dominated in the marginal slope environment compilation of a broad late frasnian to early famennian sequence stratigraphic framework for the canning basin demonstrates that transgressive intervals correlate to positive carbon isotopic excursions within the basin these isotopic shifts also can be correlated to time equivalent positive carbon isotopic excursions reported from transgressive intervals in europe thus the late frasnian transgressions in the canning basin were primarily eustatic rather than tectonic in origin and positive carbon isotopic signatures of the kellwasser horizons are globally correlative c 2002 elsevier science b v all rights reserved

architecture of coastal and alluvial deposits in an extensional basin the carboniferous joggins formation of eastern canada abstract the joggins formation was deposited in the cumberland basin which experienced rapid mid carboniferous subsidence on bounding faults a 600 m measured section of coastal and alluvial plain strata comprises cycles tens to hundreds of metres thick the cycles commence with coal and fossiliferous limestone siltstone intervals interpreted as widespread flooding events these intervals are overlain by coarsening upward successions capped by planar based sandstone mounds up to 100 m in width that represent the progradation of small river generated delta lobes into a standing body of open water developed during transgression the overlying strata contain sand rich heterolithic packages 1 8 m thick that are associated with channel bodies 2 3 m thick and 10 50 m wide drifted plant debris calamites groves and erect lycopsid trees are preserved within these predominantly green grey heterolithic sediments which were deposited on a coastal wetland or deltaic plain traversed by channel systems the cycles conclude with red siltstones containing calcareous nodules that are interbedded with thin sandstones and associated with both single storey channel bodies 1 1 5 m thick and 2 3 m wide and larger multistorey channels 3 6 m thick with incised margins numerous channel bodies at the same level suggest that multiple channel anastomosed river systems were developed on a well drained floodplain many minor flooding surfaces divide the strata into parasequences with dominantly progradational and aggradational stacking patterns multistorey channel bodies are relatively thin fine grained and modestly incised and palaeosols are immature and cumulative the abundance and prominence of flooding surfaces suggests that base level rise was enhanced whereas the lack of evidence for abrupt basinward stepping of facies belts coupled with the absence of strong fluvial incision and mature palaeosols suggests that base level fall was suppressed these architectural features are considered to reflect a tectonic architectural signature in accordance with the high subsidence basinal setting evidence for restricted marine influence and variation in floral assemblages suggests modulation by eustatic and climatic effects although their relative importance is uncertain

spatial and temporal distribution of microbial carbonates skeletal and non skeletal grains in a pennsylvanian carbonate platform valdorria northern spain abstract the valdorria carbonate platform in northern spain features a well preserved and continuous outcrop of a bashkirian platform to basin transect during the asatauian late bashkirian the platform growth changed gradually from a progradational to an aggradational mode recording 10 most likely short eccentricity controlled cyclothems the facies of the platform top and slope have been mapped and the architecture of each cyclothem schematically reconstructed the distribution of microbial carbonates microbially mediated precipitates skeletal grazers burrowers corals filter feeders algae foraminifera osagia like oncoids and thartarella terebella worm tubes and non skeletal grains faecal pellets has been quantified for the transgressive regressive periods of deposition transgressive maximum flooding early and late regressive intervals of each cyclothem this study shows that the distribution of microbial carbonates skeletal and non skeletal grains along a carbonate platform transect is variable through time and mainly governed by a set of measurable interconnected factors regulating the local palaeoenvironments the water depth and the wave energy facies along the platform profile inner outer break slope during periods of sea level fluctuations transgressive to regressive intervals of deposition auloporid corals siliceous sponges phylloid algae and osagia like oncoids are characteristic of a low energy environment situated from estimated palaeo water depths of 25 to 80 metres below sea level mbsl onward that formed in the outer platform during the maximum flooding intervals anthracoporella archaeolithoporella boundstone is characteristic of the moderate energy environments created in the horizontal inner platform during the transgressive intervals microbially mediated precipitates are reliable indicators of the slope and masloviporidium indicator of low energy environments of the upper slope on the platform top ungdarella and donezella are more abundant during the early regressive intervals than during any other interval stacheoids are mainly present in the water depth range of 10 to 60 mbsl tournayellids from 15 to 35 mbsl and archaediscids from 15 to 75 mbsl all in low to moderate energy conditions rugose corals are common in the water depth range of 5 to 35 mbsl either during the transition from the early to the late regressive intervals as solitary forms or forming boundstone or during periods of higher sea level stand as solitary forms in floatstone fenestellids fistuliporids and trilobites occur mainly in the slope but are also common in the platform top during the maximum flooding and or the early regressive intervals archaeolithoporella is a reliable indicator of the platform top deposits but its abundance is closely linked to the presence of adequate substrates a high abundance in the assemblage of gastropods endothyrids palaeotextulariids bradyinids and fusulinids characterizes the platform top shallow water coated grain grainstones formed under high energy currents during the late regressive intervals tetrataxids act as encrusters on microbial precipitates of the slope or on phylloid algae and archaeolithoporella of the platform top but are also observed as nuclei of coated grains brachiopods are more abundant in low to moderate energy and 35 to 55 mbsl environments that prevailed during the transgressive intervals faecal pellets were commonly observed in low energy environments from 50 to 325 mbsl at the platform break and in the slope and the same applies for thartarella terebella worm tubes that are virtually absent in high energy deposits finally crinoids lasiodiscids and tuberitinids are randomly distributed and are not indicative of any specific environment the here well constrained distribution patterns of microbial carbonates skeletal and non skeletal grains in valdorria outcrop hold the potential to serve as a reference for interpretation of depositional environments of other platforms using biota associations and depositional texture particularly in regions where the platform geometry is not preserved or is not fully exposed

accommodation and sedimentary architecture of isolated icehouse carbonate platforms insights from forward modeling with carb3d abstract a fundamental control on the evolution of carbonate platforms is accommodation the space available for sediment deposition here we adopt a sensitivity analysis approach using the process based forward model carb3d to quantitatively investigate the sedimentary response of isolated carbonate platforms to individual accommodation drivers of eustasy subsidence and surface dissolution sediment production the mechanism invoked to fill accommodation is also investigated fourth order milankovich driven sea level cycles dominate icehouse carbonate sedimentology with 400 ky cycles modulating the effect of 100 ky cycles of comparable magnitude when both cycles are present both overwhelm higher frequency lower amplitude fifth order cycles which are rarely preserved on the platform top subsidence is a fundamental control on sedimentary stacking patterns sequence boundary frequency sbf and platform geometry with rapid subsidence increasing the preservation of platform top sequences most icehouse platforms are subject to extended periods of platform top exposure missed beats when the platform top remains emergent at a sea level maximum are common and create non milankovich sbfs furthermore during platform emergence surface lowering via surface dissolution also creates accommodation for the subsequent platform flooding event with surface dissolution rates in humid climates comparable to moderate rates of subsidence however accommodation generation by surface dissolution is self limiting in as much as accommodation generated by dissolution is rapidly refilled on flooding sediment production is a key control on unfilled accommodation which our simulations suggest is considerable on icehouse platforms increased shallow water 3 m depth sediment production enhances intra platform bathymetric relief between the margin and interior this is driven in large part by a higher sedimentation rate at the margin than in the interior platforms can be flooded to depths up to 45 m during marine transgressions and accommodation often remains unfilled there are two distinct phases of platform top sedimentation during the transgression and early highstand platform margins accumulate at a greater rate than interior sediments generating differential intra platform bathymetry subsequently accommodation in the interior fills by forced regression and progradation from the margins into the platform interior numerical forward models can augment our understanding of icehouse carbonate platform evolution by identifying the nature of the sedimentary response to individual controls they can thus contribute to improving characterization of carbonate reservoirs in icehouse platforms such as the large hydrocarbon fields in the north caspian and s e asia

gravity driven structures and deposits resulting from slope collapse in the margin of a carbonate platform pennsylvanian cantabrian zone nw iberia abstract lower slope to basin floor deposits associated to isolated microbial carbonate platforms of the valdeteja formation carboniferous foreland basin cantabrian zone nw spain containing large slid blocks and debrites exhibit a combination of contractional and extensional structures which include thrusts backthrusts folds extensional faults and joints and boudinaged beds several lines of evidence indicate that deformation took place in poorly lithified conditions such as thickened hinges hydroplastic fractures fold axes scatter or folding of microbial limestones once restored all structures indicate a transport direction towards the nne ene this azimuth coincides with the direction towards which the thrust nappes of the southern branch of the cantabrian zone were emplaced during the variscan orogeny however the interpretation of the deposits and structures as gravity related associated to the collapse of the carbonate platform slope is supported by features such as the rootless character of thrusts the parallelism between transport direction and paleocurrent orientation the concomitant development of contractional and extensional structures the development of normal listric faults affecting the valdeteja platform the sedimentary environment lower slope to basin floor and the geological context of the valdeteja carbonate platforms which predate the variscan deformation in the study area

the importance of microbial binding in neogene quaternary steep slopes abstract the geometry and inclination of carbonate platform slopes are typically described as the result of the sediment texture components and grain size occurring in the slope three carbonate slopes from the holocene of the tongue of the ocean bahamas and three slopes from an upper miocene carbonate platform in se spain are investigated to identify the factors controlling dip angles although platforms differ in size and elevation with regard to the surrounding basin both locations present slopes with linear profiles and steep angles over 35 the slope facies in both locations are very similar with the matrix and some bioclasts presenting microfabrics that evidence microbial activity during deposition these include 1 clotted micrite patches locally connecting bioclasts or infilling primary pores 2 porostromate structures in the micrite 3 dense micritic masses 4 binding structures 5 micritic crusts and 6 peloidal textures the holocene and miocene depositional geometries and facies distribution are the response to various sedimentary processes including rockfalls gravity flows and in situ carbonate production extensive microbial binding is identified as the controlling factor for early stabilization of the slope which in combination with subsequent rapid cementation produces and maintains the steep slope angles consequently microbial induced stabilization of modern and neogene slopes is as significant as in paleozoic and triassic examples

growth and demise of late carboniferous carbonate platforms in the eastern cantabrian zone asturias northwestern spain abstract geometric relationships of seismic scale stratal patterns observed on aerial photographs of late carboniferous carbonate platforms in the cuera region in asturias northwestern spain allow the identification of two discrete stages of platform development with different styles of deposition the first phase represented by the bashkirian valdeteja formation is characterized by progradation of more than 10 km with steep clinoforms of up to 35 and slope heights up to 650 m during the second phase corresponding to the moscovian picos de europa formation the platform aggraded mainly vertically nearly 850 m both phases of platform growth were terminated by major relative sea level lowstands in conjunction with local filling of the adjacent basins by shales and mudstones that onlap the platform flanks calibration with outcrops suggests a subdivision into the following lithofacies directly related to the depositional profile 1 platform interior parallel well to thick bedded skeletal pack to grainstones 2 margin algal and sponge dominated bioherms with little internal structure 3 slope clinothems of medium to thick bedded margin derived breccia beds 4 toe of slope alternating grain and packstones with spiculites and 5 basin marly shales shales sandstones and calcareous mudstones relative sea level changes caused by regional tectonic movements are suggested to be responsible for the generation of the two platform phases sea level highstands triggered the nucleation and growth of the platforms whereas major sea level lowstands in combination with terrigenous infill of the basins terminated the platform growth in addition it is proposed that the termination of late carboniferous carbonate platforms is caused by the combined effect of a sea level fall subaerial exposure and erosion and finally a rapid transgression that drowned and polluted the platform with shales and mudstones local variations in the infilling of the basins controlled the variations in the style of progradation the subsidence rates for the vertically aggrading phase picos de europa formation were approximately twice that for the progradational phase valdeteja formation and may explain the aggradational versus progradational character

quantification of braided river channel change using archival digital image analysis historical archives of grey scale river channel imagery are extensive here we present and test a methodology to extract detailed quantitative topographic date from such imagery of sand bed rivers extracting elevation information from rivers is difficult as they are characterized by a low relative relief less than 4 m the area of interest may be spatially extensive e g active channel widths 500 m in large braided rivers the rate of change of surface elevation is generally low except in the vicinity of individual channel banks where the rate of change is very high there is the complication that comes from innundation and there may be an added complication caused by blockage of the field of view by vegetation here we couple archival photogrammetric techniques with image processing methods and test these for quantification of sand bed braided river dynamics illustrated for a 500 m wide 3 km long reach of the spouth sasketchewan river canada digitial photogrammetry was used to quantify dry areas and water edge elevations a methodology was then used to calibrate the special signature of inundated areas by combining established two media digital photogrammetric methods and image matching this allowed determination of detailed depth maps for inundated area and when combined with dry area data creation of depths detectable from sequential digital elevation models the result was a series of elevation models that demonstrate the potential for acquiring detailed and precise elevation data from any historical aerial imagery of rivers without needing associated calibration data provided that imagery is of the necessary scale to capture the features of interest we use these data to highlight several aspects of channel change on the south saskatchewan river including bar movement bank erosion and channel infilling

the influence of terrestrial run off on marine biotic communities an example from a thrust top carbonate ramp upper pennsylvanian foreland basin picos de europa nw spain article i nfo high diversity marine biotic communities characterize the lower kasimovian upper pennsylvanian carbonates of the las llacerias formation in the andara massif picos de europa province cantabrian mountains spain the carbonates accumulated on a small thrust top ramp system within the shallow low energy and euphotic realms biotic communities were characterized by abundant photozoans calcareous algae and cyanobacteria and heterozoans including filter and suspension feeders calcareous and siliceous sponges bryozoans brachiopods crinoids diverse other metazoans rugose solitary and colonial corals tabulate corals bivalves gastropods and echinoids benthic foraminifers including very abundant small incrusting tubiforms and conspicuous swarms of cement filled spheres calcispheres or penella small sized buildups of chaetetid sponges syringoporids branching rugose corals anthracoporella and phylloid algae commonly developed in these shallow water environments meanwhile mud mounds formed at greater water depths mostly below the lower limit of the phothic zone the occurrence of such diverse biotic communities and the grain composition of the shallow water deposits not recorded in the platform top successions of the antecedent bashkirian moscovian carbonate shelf valdeteja and picos de europa formations are interpreted as linked to increased nutrient levels mesotrophic to mildly eutrophic conditions in the actual sea surface water the nutrients are inferred to have resulted from land derived fluxes from the rivers draining the adjacent growing variscan orogenic chain nutrients were subsequently transported into the narrowed marine shallowing foreland basin located in the eastern side of pangea within the palaeoequatorial humid belt comparison to the pennsylvanian auernig group in the carnic alps allows the discrimination between the influence of land derived versus upwelling derived nutrients providing a useful tool in the interpretation of biotic assemblages in the fossil rock record

lithofacies and depositional processes on a high steep margined carboniferous bashkirian moscovian carbonate platform slope sierra del cuera nw spain the depositional slope of the sierra del cuera a carboniferous bashkirian moscovian high steep margined carbonate platform provides excellent cross sections of lithofacies zonations and associated stratal geometries the steep 30 40 and nearly planar upper slope is dominated by massive sheet like layers of microbial cement rich boundstone which alternate with intercalations of red stained bryozoan cementstone with crinoids and brachiopods the slightly gentler 20 26 and concave upward lower slope is characterized by clast supported resedimented deposits the upper slope extended from platform break to ca 300 m water depth whereas lower slope sediments were deposited in water depths up to 600 700 m at which level the slope beds flatten to a few degrees toe of slope and interfinger with spiculitic and argillaceous basinal sediments between 250 and 450 m water depth boundstones and breccias alternated in a transitional zone the lower slope sediments include clast supported breccias with radiaxial fibrous cement in interparticle space mud to clast supported breccias with red stained carbonate mud matrix and packstone to grainstone and rudstone beds most of the clasts comprise boundstone reworked from an upper slope setting and smaller grains are platform and slope derived a pervasive submarine cementation occurs along the upper two thirds of the flank and this stabilized the slope slope deposition is interpreted as follows during active boundstone accretion microbial boundstone layers slid off and formed breccia tongues extending from the lower upper slope down to the toe of slope rock falls and avalanches were generated whenever the shear strength of the substrate of loose or partly lithified sediment was exceeded upper slope boundstone accretion and shedding independent of the depth of light penetration controlled most of the depositional processes on the slope cement dominated intervals are considered to be related to early highstand and or flooding phases relative sea level fluctuations and or associated changes in the water conditions are believed to be responsible for intervals of low boundstone production or cement precipitation whether the in situ boundstone and breccia are preferentially related to lowstand or highstand periods is as yet unclear

accumulation of bank top sediment on the western slope of great bahama bank rapid progradation of a carbonate megabank high resolution seismic profiles and submersible observations along the leeward slope of western great bahama bank show large scale export of bank top sediment and rapid progradation of the slope during the holocene a wedge shaped sequence up to 90 m thick is present along most of the slope and consists of predominantly aragonite mud derived from the bank since flooding of the platform 6 8 ka total sediment volume of the slope sequence is 40 80 that of holocene sediment currently retained on the bank maximum rates of vertical accumulation and lateral progradation are 11 15 m ka and 80 110 m ka respectively 10 to 100 times greater than previously known for periplatform muds slope deposition of exported mud during sea level highs appears to have been a major mechanism for the westward progradation of great bahama bank throughout the quaternary this may provide a critical modern analogue for ancient progradational margins

assessment of morphological changes induced by flow and flood pulses in a gravel bed braided river the tagliamento river italy large gravel bed braided rivers show a highly dynamic evolution where even moderate flow pulses can produce significant morphological adjustment an estimation of network variations is needed by river authorities as well as by ecologists for better managing river ecosystems however few field investigations have been performed to measure the effect of unsteady discharges in braided rivers in this paper we report on the morphological changes induced by six different floods in a 1 km long reach of the tagliamento river italy topographic surveys were performed after each significant flood and an automatic digital camera continuously monitored the planimetric configuration repeated measurements of cross section profiles allowed the quantification of the transported sediments volume and in particular provided a basis to estimate the percentage of the floodplain subject to morphological evolution data analysis showed a good relationship between peak flow level active width and mean bed level changes similarly lateral channel shifting is likely to increase for larger floods monitoring of a range of discharges up to bankfull conditions revealed a fundamental difference between flow pulses events on the average occurring one or more times per year and flood pulses with a return period larger than two years the morphological evolution in the former case is mainly limited to a few active branches and is locally driven by bank erosion at the bend apex on the other hand larger floods induce a complete reworking of the network configuration where bifurcations and confluences play a crucial role single morphological units like branches nodes bars are no longer recognizable after this type of event braided rivers are therefore characterized by the occurrence of two different spatial and temporal scales that force the ecosystem dynamics

the topographic signature of vegetation development along a braided river results of a combined analysis of airborne lidar color air photographs and ground measurements 1 this paper combines archived remotely sensed data airborne lidar and digital color air photographs with nonsynchronous ground observations including observations of topographic form and vegetation cover and growth to test the hypothesis that colonization of exposed river sediments by riparian trees has an impact on channel form and to quantify any impact that is identified this is achieved along a 21 km reach of the braided gravel bed tagliamento river in northeast italy where the width of the braided corridor typically exceeds 800 m lidar data are analyzed to extract a 2 m resolution digital evolution model dem and determine riparian vegetation extent height and structure within the active corridor aerial photographs are used to map the topography of the submerged parts of the corridor these data are divided into 1 km length subreaches which possess strong contrasts in vegetation height and extent joint analysis of vegetation and morphological properties of these subreaches reveals significant associations between vegetation properties and reach morphology residuals from a gamma function fitted to the topographic data for each subreach show a good fit with poorly vegetated reaches but a weakening fit with increasing vegetation cover largely as a result of the appearance of secondary peaks in the elevation frequency distribution associated with the heavily vegetated areas furthermore the overall skewness and kurtosis of the elevation frequency distribution within each of the subreaches are both significantly correlated with vegetation extent height median elevation and growth rate indicating a clear topographic signature of vegetation development along this braided river that reflects sediment accumulation within and around the vegetated patches

marine red staining of a pennsylvanian carbonate slope environmental and oceanographic significance abstract red stained platform facies are a common feature of many carbonate settings throughout the geological record although the mechanisms involved in red staining of subaerially exposed or argillaceous peri platform limestones are reasonably well understood the environmental and oceanographic significance of red carbonates often remains uncertain here sedimentological sequence stratigraphic geochemical paleontological and quantitative bathymetric data from pennsylvanian red intervals across a well exposed carbonate platform top and slope are documented and interpreted in a process oriented context on the upper slope 80 350 meters below the shelf break red intervals alternate with gray mainly microbial algal boundstones on the lower slope 350 600 meters below the shelf break redeposited red stained mud builds matrix supported breccia tongues interbedded with predominantly redeposited clast supported carbonate debris the presence of large volumes of fibrous calcite biocementstones as well as firmgrounds point to low sedimentation rates or omission in terms of sequence stratigraphy red intervals occur within maximum flooding intervals and reflect near platform drowning elevated 18o values 2 3 and an essentially cool water heterotrophic biotic association in red intervals on platform top and slope suggest deposition during sea level highs associated with colder water masses and high nutrient levels the most likely drivers are an elevated thermocline and upwelling the red staining is the result of iron oxidation which occurred during early diagenesis likely by iron bacteria these red intervals provide an important bathymetric benchmark against which other mainly paleozoic red facies can be tested and calibrated

a steep fronted carboniferous carbonate platform clinoformal geometry and lithofacies picos de europa nw spain a steep margined carbonate platform is developed in the carboniferous synorogenic foreland basin of northern spain dips of 60 90 produced during late carboniferous thrusting enable cross sections of a 4 km wide portion of the marginal area of this platform las llacerias outcrop to be studied in aerial photographs at a seismic scale three stratal domains are observed 1 a horizontal bedded platform 2 a clinoformal bedded margin with a relief of up to 500 m and 3 a low angle toe of slope where slope beds interfinger with basin sediments the slope shows well bedded sigmoidal clinoforms with depositional dips ranging from 15 to 32 based on lithology and stratal patterns four facies groups have been recognized 1 a flat topped platform in which thick algal boundstone skeletal packstone grainstone and peloidal micrite wackestone with a poorly rhythmic character prevail 2 the platform margin and upper slope characterized by microbial boundstone spanning a bathymetric range of 150 m measured from the break of slope 3 a slope predominantly composed of margin derived rudstones and breccias and 4 a toe of slope to basin zone where a cyclic alternation of spiculitic siltstones packstone to grainstone calciturbidites and rudstone breccia is visible five successive stages of platform development are deduced 1 bashkirian flooding of the pre existing serpukhovian platform giving rise to the nucleation of a low angle ramp to the south east of the study area with microbial mud mound accumulations and breccias and calciturbidites on the margins 2 early moscovian an influx of siliciclastic sediment buried part of the platform and reduced the area of carbonate sedimentation 3 moscovian aggradation and progradation of the carbonate system produced an extensive steep margined and flat topped shallow water platform shelf system 4 latest moscovian earliest kasimovian drowning of the platform and 5 kasimovian covering of the platform by marly calcareous ramp sediments

effects of vegetation on braided stream pattern and dynamics 1 investigations using a 16 m by 2 m recirculating experimental flume model of an ephemeral braided river indicate that the presence of large and erosion resistant plants within the channel e g trees or shrubs can have a significant impact on channel pattern and planform dynamics simulations show that these plants have two effects first they act as obstructions in some cases forcing the flow to divide this flow separation can allow the deposition of a small island immediately in the lee of the plant splitting the channel the net result is a substantial increase in the number of channels and correspondingly the braid index this is in direct contrast to previous studies where increased levels of vegetation in perennial streams have decreased the braid index second the plants stabilize braid bars and can form relatively stable islands in their lee significantly reducing the longitudinal migration of islands typically associated with braided rivers

syndepositional deformation of the permian capitan reef carbonate platform guadalupe mountains new mexico usa abstract permian shelf strata equivalent to the capitan reef are cut by at least 13 closely spaced syndepositional dip slip faults in slaughter canyon guadalupe mountains new mexico usa the control of five of these faults on platform development architecture stratigraphy and diagenesis is revealed by an integrated stratigraphic sedimentological and structural framework within a 500 m wide and 200 m high outcrop window here faulting and fault related deformation acted as a primary control on changes in thickness facies and stratal geometry and resulted in the local steepening shallowing and even the reversal of dip in shelf strata the role of primary depositional relief in controlling changes in thickness and stratal geometry was of secondary importance the relationship between geopetal fabrics average dip 12 towards 141 and bedding shows that during deposition of the yates formation fault growth was concurrent with down to the basin tilting and rotation of at least 6 8 this tilting appears to have been the main control on the down dip expansion of shelf strata towards the basin a further 4 6 of basinward tilt occurred after fault growth during deposition of the tansill formation and later the syndepositional faults reported here have a maximum displacement of 24 m most tip out below asymmetric growth folds and have high displacement distance gradients typical of growth faults and faults cutting unlithified strata the average rate of fault displacement 0 021 m ka and the maximum rates of fault propagation 0 088 0 123 m ka were normally less than the platform accumulation rates 0 053 0 336 m ka thus the faults were normally blind and rarely broke the platform top so that slumps and fault scarp degradation breccias are rare the fault zones were substantially modified by diagenesis during platform development they are up to 9 m wide taper both up and downward have irregular margins and complex fills mainly of sedimentary origin their margins and fill were subject to extensive modification by karstic mixing zone dissolution gravitational collapse and dolomitising fluids consequently tectonic fabrics and kinematic indicators are rare preserved tectonic fabrics consistently indicate a normal and reverse dip slip sense of movement previously these faults were mistaken for neptunian dykes and fissures so that the seven rivers and yates 1 2 hfs shelf stratigraphy has been miscorrelated across them it is apparent that the stratal relationships exposed in the guadalupe mountains do not simply preserve the original depositional morphology of the capitan equivalent shelf the subsidence history stratigraphy and development of the platform succession is more complex than previously thought the study has important implications for many aspects of the capitan system including i shelf reef correlations ii the controls on platform architecture and development iii capitan reef palaeobathymetry iv diagenesis and v the amplitude of sea level changes affecting the platform s stratigraphic development

famennian mud mounds in the proximal fore reef slope canning basin western australia abstract famennian late devonian carbonate buildups and in particular mud mounds are poorly known in general and few have been documented in detail relatively small famennian mud mounds occur in proximal fore reef slope settings in the canning basin western australia the famennian platform margin facies passes from typical shoaling carbonate facies in the back reef through massive calcimicrobial cement rich reef margin facies to relatively steeply dipping 20 30 well bedded fore reef slope facies containing shelf derived winnowed grainy sediments and extremely coarse reef block debris isolated or coalescing mounds occur in the proximal slope immediately adjacent to and in some cases possibly grading into the margin facies mounds are elongate perpendicular to the margin and some had synoptic relief greater than 2 m mounds are lithologically variable and consist of varying proportions of micrite multiple generations of marine cement abundant rothpletzella renalcis poorly preserved sparry microbial crusts and sporadically distributed laminar stromatoporoids surrounding grainy slope facies abut and slope off of mound flanks mound facies are very similar to nearby reef margin facies with the exceptions that stromatoporoids have not been observed in margin facies and solenoporoid algae which occur in the margin have not been observed in the mounds stromatolites are conspicuously absent from both facies mound facies appear to be more closely related to frasnian and famennian calcimicrobe cement dominated reef margin facies than to famennian deep water stromatolite sponge mound facies such as those that occur elsewhere in the canning basin the observed canning famennian reef and mound frameworks were constructed by communities that appear to be very similar to earlier frasnian communities despite the frasnian famennian extinction event and provide good examples of microbial reef framework construction in a high energy setting

precursor and ambient rock paleothermometry to assess the thermicity of burial dolomitization in the southern cantabrian zone northern spain paleozoic rocks in the cantabrian zone and the variscan foreland fold and thrust belt on the iberian peninsula have been affected by a sequence of diagenetic to epizonal thermal events late to post variscan hot fluid circulation caused a large scale burial dolomitization and ore mineralization mostly in cambrian and a lower to middle carboniferous carbonate sucessions the goal of this study is to analyze and compare the temperatures experienced by the carbonate precursor rocks as well as the under and over lying siliciclastic ambient rocks to gain a better understanding of the thermicity of dolomitization these temperatures are evaluated based on published paleothermal datasets combined with new data obtained from rock eval pyrolysis and vitrinite reflectance analysis of carboniferous rocks rich in organic matter the overall results indicate that reworking of detrital sediments in synorogenic ambient siliciclastics results in an anomalously high thermal maturity recorded by bulk rock techniques such as illite crystallinity and rock eval pyrolysis in situ vr derived paleotemperatures recorded by ambient siliciclastic rocks appear to be higher compared to cai derived temperatures for carbonate precursor rocks this variation in thermal maturity is likely related to the analytical techniques used to obtain cai and vr data and the empirical equations applied to calculate corresponding paleotemperatures conodont fragments were not as sensitive compared to vitrinite and the color alteration process could have suffered from hydrothermal alteration a secondary cause might be a different response to mechanical deformation between siliciclastic and carbonate units during the variscan and post variscan geodynamic evolution of the study area rigid precursor carbonate units experienced fluid circulation mainly along distinct and spaced fracture zones creating fracture related dolomite geobodies and ore mineralization soft ambient siliciclastic rocks experienced more diffuse fluid circulation and heat dissipation the different paleothermometry datasets compiled for the study area indicate that the fluids circulating during late to post variscan times with associated fracture related dolomitization and ore mineralization in carbonate precursors are hydrothermal the highest paleotemperatures were recorded in ambient and precursor rocks in the highly tectonized northern part of the study area where several thrusts and faults allowed intense fluid circulation positive temperature anomalies within the precursor carbonates correlate well with the occurrence of dolomite geobodies and ore mineral deposits such anomalies could thus be used as an exploration tool for hydrothermal dolomite bodies in analog sub surface settings

internal structure and depositional environment of late carboniferous mounds from the san emiliano formation carmenes syncline cantabrian mountains northern spain well exposed mounds are common in limestone of the late carboniferous san emiliano formation cantabrian mountains northern spain they occur as obvious primary topographic features careful study of the mound intervals and surrounding strata revealed the internal structures of mounds and the factors controlling their growth the substrate 2 3 m of the mounds consists of greyish to reddish bedded oolitic and oncolithic packstone and grainstone crinoids fragments of the alga epimastopora and rarely bryozoans are present ooids and oncoids indicate a wave dominated high energy environment presence of quartz indicates the influence of terrigenous siliciclastic input mound intervals 6 12 m thick are characterized by skeletal microbial boundstone donezellid algae agglutinated worm tubes and calcisponges are the dominant fossils smaller foraminifers gastropods and brachiopods are also present a peloidal clotted matrix is characteristic and accounts for more than 30 of the mound volume intraframe pores are mainly filled by peloidal sediment and early marine cement intermound strata are approximately one third as thick as time equivalent mounds mound fossils algae agglutinated worm tubes and sponges are uncommon however intermound strata are generally more diverse than the mounds containing fusulinids smaller foraminifers bryozoans gastropods crinoids and bioclasts some of these fossils have micritic envelopes bedded packstone and grainstone 3 6 m thick with siliciclastic debris rugose corals and chaetetid sponges characterize the capping facies coated grains and small ooids are uncommon this facies indicates shallowing to a higher energy environment and or a higher input of siliciclastics inhibiting mound growth mounds are interpreted to have accreted in a quiet environment below wave base this position is comparable to the depositional environment inferred for many late paleozoic mounds described elsewhere e g from texas and new mexico canadian archipelago and carnic alps in austria mound relief is explained by 1 accumulation of peloidal clotted sediments limited to boundstone and probably related to microbial activities 2 widespread marine cementation within this area and 3 low export of mound fossils to intermound areas the position of the mounds within the sequence and their initiation size and termination seem to be mainly controlled by sea level fluctuations and siliciclastic input d 2001 elsevier science b v all rights reserved

glacioeustatic cyclicity of a pennsylvanian carbonate platform in a foreland basin setting an example from the bachende formation of the cantabrian zone nw spain abstract by analysis of outcrop data sequence stratigraphy was used to interpret the stratal architecture and evolution of a moscovian pennsylvanian carbonate platform bachende formation located in the variscan foreland basin of the cantabrian zone nw spain the bachende formation represents a delta top carbonate platform developed in highly subsiding average subsidence rate of 254 m my distal shelf areas of the basin it reached a thickness of 650 m and covered an area of 170 km 2 after conservative palinspastic restorations the platform interior succession is mostly composed of low relief mound shaped micritic boundstones alternating with bioclastic mudstones wackestones peloidal foraminiferal packstones grainstones calcareous algal bafflestones and skeletal and ooidal grainstones landwards to the w carbonate platform beds alternate and interfinger with deltaic sandstones and shallow marine shales the platform interior consists of three sequences s1 s2 and s3 ranging from 180 to 230 m in thickness and from 1 3 to 0 5 my in age these sequences are in turn subdivided into several meter scale 10 6 m average thickness high frequency 110 to 15 ky subtidal transgressive regressive cycles these cycles are bounded by subaerial exposure or marine flooding surfaces and are inferred to be laterally continuous across the platform top they vary from mixed carbonate siliciclastic to carbonate dominated cycles cyclicity on the bachende platform was strongly influenced by glacioeustatic sea level variations and changes in subsidence and sedimentation rates subaerial exposure surfaces capping high frequency cycles are better developed in the sequence 1 late kashirian early podolskian when subsidence was relatively low and glacioeustatic sea level fluctuations could have exposed subtidal deposits during base level falls on the basis of the conservative estimated duration of each cycle and spectral analysis of cycle thickness the precessional 20 ky and obliquity 40 ky cycles were detected in all the sequences the short eccentricity cycle 100 ky in the sequence 1 and the long eccentricity cycle 400 ky in the sequences 2 and 3 podolskian nevertheless precessional and obliquity frequencies seem to dominate during sequences 2 and 3 which were deposited under significant higher subsidence and sedimentation rates additionally spectral peaks at 60 80 ky are randomly present across the whole succession and they cannot be explained as a linear response of the climate system to the milankovitch forcing

genesis of limestone megabreccias and their significance in carbonate sequence stratigraphic models a review a re appraisal of the factors controlling the deposition of carbonate megabreccias and their sequence stratigraphic significance is presented based on an examination of the mechanisms for instigating carbonate seafloor slope instability and a review of the depositional settings of these distinctive rock deposits limestone megabreccias have classically been interpreted as formed by the catastrophic collapse of high angle metastable oversteepened carbonate platform margins however a review of megabreccia occurrence shows that these deposits formed on a broad range of carbonate slope angles and that metastable oversteepened slopes are not necessary for their genesis a re evaluation constructed from first principles of mechanisms promoting submarine gravitational instability indicates that pore water overpressure of confined aquifer horizons beneath the seafloor rather than slope oversteepening is the critical control on megabreccia deposition catastrophic release of overpressure may initiate gravitational instability of previously kinematically stable slopes the relative importance of endogenic processes intrinsically linked to the depositional system and exogenic processes operating independently in generating megabreccias is assessed two particularly important mechanisms in generating megabreccias are endogenic processes causing overpressure at discrete hydrologically confined horizons beneath the seafloor during relative sea level falls and increases in stress as pore fluid drains from the sediment when the platform top becomes subaerially exposed during relative lowstands of sea level the increased likelihood of megabreccia genesis during relative sea level falls is supported by an empirical trend identified from a review of the stratigraphic distribution of documented megabreccias exogenic causes of gravitational instability with inherently random periodicity especially seismicity may account for the small number of documented megabreccias that do not conform to this underlying trend the proposed endogenic pattern favouring megabreccia deposition during relative sea level falls is important in a sequence stratigraphic context megabreccia deposits may build volumetrically significant toe of slope wedges and aprons during relative lowstands of sea level partially compensating for the decrease loss in the supply of fresh granular sediment as the platform top carbonate factory contracts lowstand wedges and aprons in carbonate systems therefore generally differ in composition from equivalent highstand deposits in being composed not of calciturbidite deposits but of megabreccias cannibalized from the upper slope

stratigraphic imprint of the late palaeozoic ice age in eastern australia a record of alternating glacial and nonglacial climate regime stratigraphic and sedimentological data from new south wales and queensland eastern australia indicate that the late palaeozoic ice age comprised at least eight discrete glacial intervals each 1 8 ma in duration here termed glaciations separated by nonglacial intervals of comparable duration these events spanned an interval from mid carboniferous c 327 ma to the early late permian c 260 ma and illustrate a pattern of increasing climatic austerity and increasingly widespread glacial ice from initial onset until an acme in the late early permian followed by an opposite trend towards the final demise of glaciation in the late permian the alternating glacial nonglacial motif suggests that the late palaeozoic ice age was considerably more dynamic than previously thought these patterns are remarkably consistent with recent interpretations of palaeofloral change eustatic sea level fluctuations and co 2 climate glaciation relationships for this interval of time the detailed record of alternating glacial and nonglacial climate mode disclosed herein may facilitate more closely resolved evaluations of stratigraphic records elsewhere notably in far field ice distal northern hemisphere successions

floodplain roughness parameterization using airborne laser scanning and spectral remote sensing abstract floodplain roughness parameterization is one of the key elements of hydrodynamic modeling of river flow which is directly linked to exceedance levels of the embankments of lowland fluvial areas the present way of roughness mapping is based on manually delineated floodplain vegetation types schematized as cylindrical elements of which the height m and the vertical density the projected plant area in the direction of the flow per unit volume m 1 have to be assigned using a lookup table this paper presents a novel method of automated roughness parameterization it delivers a spatially distributed roughness parameterization in an entire floodplain by fusion of casi multispectral data with airborne laser scanning als data the method consists of three stages 1 pre processing of the raw data 2 image segmentation of the fused data set and classification into the dominant land cover classes khat 0 78 3 determination of hydrodynamic roughness characteristics for each land cover class separately in stage three a lookup table provides numerical values that enable roughness calculation for the classes water sand paved area meadows and built up area for forest and herbaceous vegetation als data enable spatially detailed analysis of vegetation height and density the hydrodynamic vegetation density of forest is mapped using a calibrated regression model herbaceous vegetation cover is further subdivided in single trees and non woody vegetation single trees were delineated using a novel iterative cluster merging method and their height is predicted r 2 0 41 rse 0 84 m the vegetation density of single trees was determined in an identical way as for forest vegetation height and density of non woody herbaceous vegetation were also determined using calibrated regression models a 2d hydrodynamic model was applied with the results of this novel method and compared with a traditional roughness parameterization approach the modeling results showed that the new method is well able to provide accurate output data the new method provides a faster repeatable and more accurate way of obtaining floodplain roughness which enables regular updating of river flow models

dynamic single thread channels maintained by the interaction of flow and vegetation most rivers on earth today flow as a single channel in some cases with occasional islands and follow a more or less sinuous course however single thread channels have proven difficult to reproduce and study experimentally experimental self formed channels tend to widen and subdivide leading to a braided pattern cohesive sediment has been the main mechanism studied for stabilizing banks and producing a single thread channel we show how laboratory experiments using vegetation to stabilize banks can organize the flow and convert the planform morphology from braided to single thread our experimental strategy a repeated cycle of short periods of high water discharge alternating with longer periods of low discharge accompanied by plant seeding and growth leads to the evolution of a dynamic self maintaining single thread channel with well defined banks and floodplain by eliminating weak flow paths the vegetation corrals the water into a single dominant channel until the reduction in total wetted width leads to a new self organized state in which the flow removes vegetated area as fast as it is produced the new channel is deeper and has a broader distribution of depths than the braided one with channel size adjusted to carry almost all the flood flow the resulting system maintains a dynamic steady state via similar mechanisms to those that operate in meandering channels in the field specifically erosion at the outside of bends bend growth and bar development our methodology provides a basis for experimental development of self sustaining high amplitude meanders and has applications for river management and basic research purposes

lithofacies and sequence development on an upper devonian mixed carbonate siliciclastic fore reef slope canning basin western australia detailed sedimentological and stratigraphical analysis coupled with conodont biostratigraphy of a fore reef slope succession in the napier range napier formation is used to develop a depositional model and relative sea level history for late frasnian to late famennian reef evolution in the canning basin of north western australia changes in sedimentary style on the slope reflecting differing rates of carbonate production on the platform are linked to third and higher order relative sea level fluctuations overlapping slope aprons accumulated along the base of a steep walled platform margin coarse carbonate debris was deposited adjacent to the margin as talus breccias via rockfall and debris flow breccias depositional slopes up to 45 and locally steeper are demonstrated using rotated geopetal cavity fills the predominance of channel filling lithofacies throughout the slope succession indicates the highly channelized nature of the aprons the middle slope is dominated by sandy oolitic peloidal turbiditic grainstones interpreted as sediment exported from an active platform the turbidites and associated debris flow breccias contrast with condensed carbonate intervals and deep water non fenestral stromatolites that record times of very low platform production lower slope turbidites and associated intraclastic breccias indicate widespread redeposition of sediment eroded from lithified and semi lithified limestones higher up the slope several third order sequences are recognized in the fore reef succession and these are composed primarily of transgressive and highstand deposits carbonate production was severely restricted in the early famennian coinciding with development of onlapping siliciclastic aprons during a relative sea level lowstand evidence for a subaerial exposure event is also preserved within the siliciclastic strata controls on sequence development are difficult to constrain although two sequence boundaries can be correlated with falls on the global sea level curve the reef complexes evolved in an active extensional regime and it is highly likely that tectonism in conjunction with eustasy controlled accommodation on the platform and therefore carbonate productivity