palaeo mixing zone karst features from palaeocene carbonates of north spain criteria for recognizing a potentially widespread but rarely documented diagenetic system abstract marine meteoric mixing zone dissolution effects are a major feature of present day karst systems in carbonate platforms yet are rarely reported in the geological record an example is described from the upper danian platform limestones of the alava province in the western pyrenees north spain this consists of several narrow zones with sponge like porosity analogous to the swiss cheese features found in present day mixing zones these zones are stained by fe oxides and overlie limestones which are irregularly dolomitized and contain disseminated pyrite these high porosity zones are interpreted as having developed in marine mixing zones where mixing corrosion and microbially mediated processes increased dissolution if collapsed ancient mixing zones could be misinterpreted as terra rossa palaeosols the main criteria to identify them as mixing zone products are their occurrence below a palaeo meteoric phreatic zone their association with stratified oxic and anoxic redox zones and petrographic evidence for highly variable calcite saturation states

multikilometer sized reefs built by foraminifera solenomeris from the early eocene of the pyrenean domain s france n spain palaeoecologic relations with coral reefs abstract solenomeris foraminifera reefs of the early ypresian pyrenean gulf were previously mistaken for red algal or incertae sedis algal reefs solenomeris has recently been referred to the acervulinid foraminifera these foraminifera buildups are described in detail and their palaeoecology is discussed the distribution of these reefs within the languedoc basin demonstrates their preference for bathymetric highs of external platforms in common with coral reefs to which they locally succeed during the early ypresian transgression all solenomeris reefs examined are located either at the outer periphery of a lagoon with small operculina or on the external margin of a carbonate platform characterized by various miliolida they extend into deeper waters than the associated coral reefs even in turbid environments unfavourable for encrusting coralline algae the reconstruction of the palaeoecology of solenomeris shows many similarities with corals however corals probably require higher light and oxygen levels especially when present near their northern limit the global distribution of solenomeris reefs can not be established until their correct identifications have been made instead of algal reefs

taphonomic field experiments and the role of the shelf and slope experimental taphonomy initiative abstract fossilization of organism remains is the result of biological physical and chemical processes at work in the environment of deposition the pathways taken by the remains of organisms through death decay burial and diagenesis known as taphonomic pathways affect the fossil record of life in important ways from complete removal and recycling of remains to preservation of hard parts and sometimes to exceptional preservation of soft tissues our understanding of taphonomic processes informs our interpretations of the fossil record and helps in the reconstruction of ancient environments research into taphonomic pathways in modern environments provides important insight into the fossilization process in 1993 a group of paleontologists formed the shelf and slope experimental taphonomy initiative sseti and began a long term comparative study of taphofacies and differential decay of taxonomic groups by placing experimental arrays containing bivalves gastropods decapod crustaceans sea urchins and wood species at multiple marine shelf and slope sites in the bahamas and gulf of mexico the goal of sseti is to observe taphonomic processes over a period of decades to better understand taphonomic pathways for these various groups of taxa in a wide variety of depositional environments beyond the shallow near shore region this special volume brings together eight studies that are the result of the sseti program the focus of this contribution is to first review the body of published work concerned with the fossilization process through the experimental manipulation of the remains of organisms in modern marine environments we also present the methods of the sseti project and its contributions to our understanding of taphonomic processes in relation to carbonate and wood recycling and preservation

similarities between planktonic and larger foraminiferal evolutionary trends through paleogene paleoceanographic changes abstract the paleogene evolutionary records of planktonic foraminifera and larger benthic foraminifera show parallel patterns in development that may in part reflect changes in nutrient flux to surface waters following the terminal cretaceous extinctions faunas were dominated by a few cosmopolitan opportunistic species more specialized k strategists in both groups diversified during the paleocene dominating into the early eocene consistent with he globally mild climatic regime and probable limited rates of nutrient flux to surface waters high latitude cooling intensified in the middle eocene promoting diversification of less specialized taxa characteristic of cooler and deeper waters higher latitudes meridional upwelling zones and boundary currents geographic ranges of warm water taxa diminished and fragmented yet many species survived thus global diversities during the middle eocene were the highest in the cenozoic as cooling and increased rates of nutrient flux further intensified in the late eocene extinction rates of warm water planktonic and larger benthic species exceeded origination rates of cooler water and less specialized forms so diversity dropped to intermediate levels where it remained through the late eocene and oligocene previous observations that planktonic foraminiferal faunas dominated by warm water taxa are often replaced by cool water faunas even though oxygen isotopes only recorded relatively minor cooling can be reconciled by the explanation that the biotic communities responded to changes in trophic resources and euphotic habitats that accompany the temperature reduction as well as to temperature change itself

paleocene coralgal reefs of the western pyrenean basin northern spain new evidence supporting an earliest paleogene recovery of reefal ecosystems abstract the rate of recovery of photic reefal ecosystems after the cretaceous tertiary crisis is controversial most reports from earlier authors concluded that paleogene reef systems did not completely recover from that crisis at least until oligocene miocene times several other authors however have pointed out that such conclusion was biased by poor preservation and or inaccessibility of many early paleogene successions and that the recovery of reefs might have been a faster process the latter possibility is here strongly supported with data from the pyrenean basin where paleocene shallow water carbonate deposits are thickly developed and outcrop widely five growth phases of reef development have been recognized and age dated with calcareous nannofossils which together define a complete sequence of expansion reduction of reef ecosystems during the paleocene epoch reef growth phase 1 early danian lower middle np3 calcareous nannofossil zone the initial step of that sequence demonstrates that coral dominated reef systems came back into existence less than 2 ma after the k t boundary a comparatively short time considering the magnitude of the end cretaceous biological crisis the climax of the sequence is recorded by growth phase 3 late danian np4 zone when a thick barrier reef complex was developed which was at least 200 km in length but probably much larger and made up by a well diversified coralgal assemblage reef growth phases 4 and 5 early and middle thanetian np6 to np8 zones were characterized by low relief reef banks dominated by encrusting calcareous algae and had less well diversified coral assemblages features that point to a deterioration of environmental conditions tentatively interpreted in terms of a climatic cooling reef bioconstruction almost disappeared in the pyrenean basin during late thanetian times although in all likelihood this is a regional effect of no evolutionary relevance the new data suggest that the cenozoic recovery of reefs was rapid but punctuated with a phase of important reef expansion already in the late danian

ocean quahogs arctica islandica and atlantic surfclams spisula solidissima on the mid atlantic bight continental shelf and georges bank the death assemblage as a recorder of climate change and the reorganization of the continental shelf benthos abstract the degree to which evidence of range shifts in shelf biomass dominants atlantic surfclams and ocean quahogs as a function of climate change is examined by comparing the dissimilarity in distribution of the living community and the record of habitation ensconced in the death assemblage comparison of the distribution of live animals and dead shells reveals for both species that live animals are rarely found where dead shells were not collected but dead shells were collected at a substantively larger number of sites than where live animals were found the geographic footprint resolved by the dead shells was much broader than that of live animals extensive spatially coherent regions exist inshore and offshore of the present day habitat of occupation where evidence of previous occupation exists sites where ocean quahog shells were found without live ocean quahogs included a portion of the continental shelf inshore of the present day habitable range an area only habitable under colder climatic conditions than observed today surfclam shells were found offshore of the present day habitable region in deeper water additional warming of bottom waters offshore would be necessary for surfclams to occupy the region now occupied solely by dead shells the death assemblage shows that these biomass dominants have repositioned themselves across the continental shelf during the past and this repositioning certainly is driven by changes in bottom water temperature moreover the distribution of surfclam shells indicates that the death assemblage may provide a possible window into the future as movement of the present day population is towards these deeper water previously occupied regions overall the death assemblage may provide an important source of information on range shifts sparing the need to carry out extensive and frequent benthic surveys and may permit reconstruction of ongoing shifts in community composition as a product of climate change when adequate survey data are not available

onset of the late paleozoic glacioeustatic signal a stratigraphic record from the paleotropical oil shale bearing big snowy trough of central montana u s a

neutral winds in the lower thermosphere from dynamics explorer 2 doppler line profile measurements of the oi 557 7 nm green line emission made by the fabry perot interferometer on dynamics explorer 2 have provided altitude profiles of the meridional component of the lower thermospheric neutral wind the wind inversion technique of nardi 1991 has been used to extract the neutral wind profiles from the line of sight measurements individual 557 7 nm doppler line profiles and inverted volume emission rate and neutral wind profiles are presented neutral wind measurements from the 120 km altitude level obtained on multiple orbital passes over the summer hemisphere polar region have been merged to produce a synthesized averaged vector wind field in geomagnetic coordinates the wind pattern exhibits a region of anticyclonic vorticity in the daytime sector of the magnetic polar cap averaged winds of 300 m sec in the equatorial direction are observed in the early morning sector the satellite winds are in reasonable agreement with the predictions of the ncar and ucl thermosphere general circulation models with significant regional discrepancies evident in both magnitude and direction

studies on settling traction and entrainment of larger benthic foraminiferal tests implications for accumulation in shallow marine sediments settling and traction velocities were measured on optimally preserved tests of larger foraminifera using a settling tube and flume tank within larger foraminifera with porcelaneous tests the peneroplids peneroplis antillarum p planatus p pertusus and dendritina cf d zhengae are distinguished by low test densities ca 1 2 that do not change with growth buoyancy is high because of low reynolds numbers and increases in large individuals because of the allometric change of test shape the fusiform alveolinella quoyi with test densities ca 1 6 is characterized by high reynolds numbers inducing the weakest buoyancy within porcelaneous larger foraminifera the highest buoyancy was recorded for the three soritids parasorites orbitolitoides sorites orbiculus and amphisorus hemprichii because of their low test densities ca 1 25 and the extremely flat biconcave plate like shape flat tests however reduce traction and entrainment from smooth surfaces within hyaline larger foraminiferat the amphisteginids show thick lenticular amphistegina lobifera a radiata to thin lenticular tests a bicirculata a papillosa influencing buoyancy here high test densities ca 1 8 decrease with growth in a lobifera a lessonii and a bicirculata and remain constant in a radiata and a papillosa minimum velocities required for entrainment are lower for thick lenticular tests and higher for thin lenticular tests test densities remain constant with growth in the calcarinid baculogypsina sphaerulata 1 78 and decrease slightly in calcarina gaudichaudii and neorotalia calcar starting at 1 85 all living under extreme hydrodynamic conditions density decreases the most in baculogypsinoides spinosus starting at 1 8 resulting in higher buoyancy through low reynolds numbers traction is promoted in spherical tests of baculogypsina and baculogypsinoides within nummulitids the thick lenticular palaeonummulites venosus test density decreasing with size starting at 1 78 is less buoyant expressed in high reynolds numbers but easily entrained thick lenticular juveniles and extremely flat adults distinguish operculinella cumingii heterostegina depressa and the giant cycloclypeus carpenteri test densities increase during growth starting from ca 1 6 and attaining a maximum of 1 8 buoyancy is low in small tests and high in large tests while entrainment velocities are reduced as the tests flatten high buoyancy is also a characteristic of the entirely flat tests in operculina ammonoides from deeper regions and planostegina operculinoides which is expressed in the lowest reynolds numbers within larger foraminifera

architecture growth patterns and early diagenetic modifications of a greenhouse ramp to rimmed shelf system danian of the urbasa andia plateau western pyrenees north spain the danian carbonates exposed in the urbasa andia plateau western pyrenees north spain provide the opportunity to examine at different scales the facies types and architecture of a greenhouse ramp to rimmed shelf from the slope to coralgal reefal margin through to the highly restricted evaporitic inner shelf areas integrated with a range of porosity forming early diagenetic phases associated with third order highstands and lowstands the detailed nature of the stratal architecture of this greenhouse system provides an understanding of potential reservoir layering lateral facies and facies cycle changes and widespread early dolomitization but significantly allows a whole paleokarst macroporosity system related to a third order lowstand to be accessed illustrating how eogenetic karstic porosity can vary drastically from margins to shelf interiors the outcrops serve as potential analogs for fields in paleocene carbonates in north africa and the middle east and also offer valuable depositional and digenetic models for greenhouse platforms of other ages

on the role of wall pressure fluctuations in deterministic motions in the turbulent boundary layer the wall pressure fluctuations beneath a turbulent boundary layer have been conditionally sampled on a basis of the high frequency activity of the pressure fluctuations themselves the high frequency activity of the streamwise velocity fluctuations in the vicinity of the wall and the excursions in velocity in the vicinity of the wall this has led to the identification of a characteristic wall pressure fluctuation pattern which is associated with the burst sweep cycle of events in the wall region the pattern has the form of an overpressure over a streamwise extent of about 1 5 2 0 with a region of underpressure and a pressure minimum to either side of it the distance between pressure minima being about 3 0 3 5 this pattern is convected at a velocity 0 67 times the freestream velocity its phase relationship with velocity fluctuations close to the wall and the wall shear stress fluctuations during the burst sweep cycle have been established it appears to be produced by the inclined shear layer which forms the upstream surface of the large organized structures in the layer and calculated pressure patterns support this conclusion the phase relationships indicate that fluid involved in the bursting process is subjected to a favourable streamwise pressure gradient by the characteristic wall pressure pattern at the time that the lift up of low speed streaks in the wall region begins in addition order of magnitude estimates suggest that the adverse pressure gradients associated with the characteristic pressure pattern even if their phasing with streak lift up were appropriate would be insufficient to initiate the lift up it is therefore concluded that the streamwise pressure gradients associated with the pressure patterns do not play an active role in the dynamics of the wall flow and are not the direct cause of the bursting process

settling velocities and entrainment thresholds of biogenic sands shell fragments under unidirectional flow settling velocities and entrainment thresholds of biogenic sedimentary particles under unidirectional flow conditions are derived on the basis of settling tower and laboratory flume experiments material consisting predominantly of equant blocks shell fragments of cerastoderma edule density s 2800 kg m 3 or of mica like flakes and elongate rods mytilus edulis fragments s 2720 kg m 3 are used in separate series of experiments differences in the measured settling and threshold properties are related primarily to particle shape the selection of a characteristic length scale for non spherical grains is investigated by comparing two approaches used to define the grain size d of the sediment samples grain settling and sieve analysis that are used to derive data for the threshold criteria in terms of the shields and movability diagrams the empirical curves effectively predict the threshold conditions for any grain shape provided that grain size is defined in terms of grain settling velocity however a functional distinction is made between the characteristic hydraulic grain size defined by grain settling for grain transport applications and the actual physical grain size defined by sieve analysis

hydrodynamic behaviour of coarse bioclastic sand from shelly cheniers cheniers from mont saint michel bay france are coarse shelly sand ridges migrating on the mudflat up to the salt marshes where they accumulate and merge in a littoral barrier in this macrotidal setting and low wave forcing the cheniers are rarely submerged however they are found to move up to several metres during coincidence of spring tide and wave activity their processes of migration morphology and internal structure composition of the beddings grain size sorting and grain arrangement are thought to be closely related to the hydrodynamic behaviour of the coarse and shelly sediment this paper focuses on the hydrodynamic behaviour of bioclastic sand sampled from the cheniers settling velocities of the shell fragments were measured using a 2 m long sedimentation tube thresholds of motion under unidirectional current velocity and turbulence vertical profiles were characterized in a small recirculating flume using laser doppler anemometry lda the flat shaped bioclastic particles feature low settling velocities and reveal a good resistance to the re suspension effect of the flow when imbricated in a sediment bed the shear stress in the bottom boundary layer has been measured in the viscous and log sub layers nikuradse roughness heights ks for shell debris beds of different sizes have been quantified it is found that ks 2 56d50 this value is close to the ones used for classic rounded sand grains despite their major differences of shape the dual behaviour of the shell fragments low settling velocity good resistance to unidirectional flow should be considered as a key to understanding how this coarse material is transported across the tidal flat and finally accumulated as cheniers further flume experiments including wave activity and tidal fluctuations are necessary to better quantify these complex processes copyright 2010 john wiley sons ltd

the first microbialite coral mounds in the cenozoic uppermost paleocene from the northern tethys slovenia environmentally triggered phase shifts preceding the petm abstract upper thanetian microbialite coral mounds from the adriatic carbonate platform sw slovenia are described herein for the first time representing an important case study of extensively microbially cemented boundstones in the early paleogene the mounds are constructed primarily by microbialites associated to small sized coral colonies forming metric bioconstructions in a mid ramp setting detailed macroscopic and microscopic studies show that microbes are the major framework builders playing a prominent role in the stabilization and growth of the mounds with corals being the second most important component microbial carbonates represent up to 70 of the mounds forming centimetric thick crusts alternating with coral colonies the microbial nature of the crusts is demonstrated by their growth form and internal microfabrics showing accretionary binding and encrusting growth fabrics often with gravity defying geometries thin sections and polished slabs reveal a broad range of mesofabrics with dense structureless micrite leiolite laminated crusts stromatolites and clotted micritic masses thrombolites a first layer of micro encrusters including leiolites and thrombolites occurs in cryptic habitats whereas discontinuous stromatolites encrust the upper surface of corals a second encrustation the major mound construction phase follows and is dominated by thrombolites encrusting corals and other micro encrusters this sequence represents the basic constructional unit horizontally and vertically interlocked in an irregular pattern to form the mounds the processes which favored the deposition of these microbial carbonates were mainly related to in situ precipitation with minor evidences for grain agglutination and trapping processes scleractinian corals comprise moderately diversified community of small centimetric colonial massive platy encrusting and branching forms coral colonies are distributed uniformly throughout the mounds without developing any ecological zonation these features indicate that coral development remained at the pioneer stage throughout the mound growth the spatial relationships between corals and microbialites as well as the characteristics of microbial crusts and coral colonies indicate a strong ecological competition between corals and microbes a model for the evolution of the trophic structures during the mound growth is proposed with changes in the paleoecology of the main bioconstructors triggered by frequent environmental perturbations turbidity and nutrient pressure interpreted here as related to frequent recurrences of wet phases during the warm humid climate of the uppermost thanetian might have promoted temporary dominance of microbes over corals causing rapid environmentally driven phase shifts in the dominant biota

reef geometries erosion surfaces and high frequency sea level changes upper miocene reef complex mallorca spain the upper miocene reef complex of mallorca is a 20 km prograding unit which crops out in sea cliffs along the southern side of the island these vertical and exceptionally clean outcrops permit i identification of different facies lagoon reef front reef slope and open platform and their geometries and boundaries at different scales ranging from metre to kilometre and ii construction of a 6 km long high resolution cross section in the direction of reef progradation this cross section shows vertical shifts of the reefal facies and erosion surfaces linked to a general progradational pattern that defines the accretional units four hierarchical orders of magnitude 1 m to 4 m of accretional units are identified by consideration of the vertical facies shifts and by which erosion surfaces are truncated by other erosion surfaces all these orders show similar patterns horizontal beds of lagoonal facies in the upper part landward reefal and slope facies with sigmoidal bedding in the central part and open platform facies with subhorizontal bedding in the lower part basinwards the boundaries are erosion surfaces horizontal over the lagoon facies dipping basinwards over the reef front facies and connecting basinwards with their correlative conformities over the reef slope and open platform facies the four orders of accretional units are interpreted in terms of four 1 m to 4 m hierarchies of sea level cycles because i there is a close relation between the coral growth and the sea surface ii there are vertical shifts in the reefal facies and their relation to the erosion surfaces and iii there was very little tectonic subsidence in the study area during the late miocene additionally all these units can be described in terms of their position relative to the sea level cycle i the reefs prograde on the open platform sediments during low stands of sea level ii aggradation of the lagoon reef and open platform facies dominates during sea level rises and the lagoonal beds onlap landwards upon the previous erosion surface iii reefal progradation occurs during high stands of sea level and iv the 2 m sea level fall produces an off lapping reef and there is progradation with downward shifts of the reefal facies and erosion landward on the emerged older reefal units a erosion surfaces the 3 m and 4 m sea level falls produce only erosion b and c erosion surfaces although precise age data do not exist at present some speculations upon the frequency of these miocene relative sea level cycles can be made by comparisons with pleistocene cyclicity there is a good correlation between the miocene 2 m cycles and the 100 ka pleistocene cycles consequently the 1 m cycles can be assigned to a fourth order in relation to previously proposed global cycles and the 2 m to fifth order cycles all these accretional units could be defined as sequences according to the definition as commonly used in sequence stratigraphy however they represent higher than third order sea level cycles but are not parasequences the term subsequence therefore is suggested to define a part of a sequence bounded by erosion surfaces mostly subaerial and their correlative conformities basinwards a hierarchy of subsequences can be established

palaeohydrogeological control of palaeokarst macro porosity genesis during a major sea level lowstand danian of the urbasa andia plateau navarra north spain abstract an extensive palaeokarst porosity system developed during a pronounced mid paleocene third order lowstand of sea level is hosted in danian limestones of the urbasa andia plateau in north spain these limestones were deposited on a 40 50 km wide rimmed shelf with a margin characterised by coralgal buildups and coarse grained bioclastic accumulations the sea level fall that caused karstification was of approximately 80 90 m magnitude and 2 5 ma in duration during the exposure a 450 m wide belt of sub vertical margin parallel fractures developed a few hundred metres inboard of the shelf edge most fractures are 90 100 m deep average 1 m in width and are associated with large erosional features created by collapse of the reefal margin inland from the fracture belt three superimposed laterally extensive cave systems were formed over a distance of 3 5 km perpendicular to shelf edge at depths ranging from 8 31 m below the exposure surface the palaeocaves range from 0 3 to 2 m in height average 1 5 m high they show no evidence of meteoric processes and are filled with thanetian grainstones rich in reworked microcodium a lithology that also occurs infilling the fractures the caves are interpreted as due to active corrosion at the saline water fresh water mixing zone caves are missing from the shelf edge zone probably because the fractures beheaded the meteoroic lens preventing mixing zone cave development beyond the fracture zone towards the platform interior each cave system passes into a prominent horizon averaging 1 m in thickness of spongy porosity with crystal silt infills and red fe oxide coatings the spongy horizons can be traced for 5 5 km inboard from the cave zone and occur at 10 5 m 25 m and 32 m below the exposure surface in the inland zone two additional horizons with the same spongy dissolution have been recognised at depths of 50 m and 95 m all are analogous to swiss cheese mixing zone corrosion in modern carbonate aquifers and probably owe their origins to microbially mediated dissolution effects associated with a zone of reduced circulation in marine phreatic water in the most landward sections a number of collapse breccia zones are identified but their origin is unclear the palaeokarst system as a whole formed during the pulsed rise that followed the initial sea level drop with the three main cave spongy zones representing three successive sea level stillstands recorded by stacked parasequences infilling large erosional scallops along the shelf margin the geometry of the palaeo mixing zones indicates a low discharge system and together with the lack of meteoric karstic features favours a semi arid to arid climatic regime which is further supported by extensive calcrete bearing palaeosols occurring in coeval continental deposits

the vigny limestones a record of palaeocene danian tectonic sedimentary events in the paris basin danian marine sedimentation in the paris basin occurred between two major erosional phases the earlier was responsible for the stripping of presumably deposited maastrichtian sediments and of a variable thickness of campanian chalk the later occurred during the late palaeocene and resulted in the erosion of almost all danian deposits which are now limited to small and scattered outcrops one of these outcrops corresponds to reefal and peri reefal limestones of middle to late danian age exposed in the quarries of vigny nw of paris danian deposits here show intricate relations with the surrounding campanian chalk danian sedimentation was contemporaneous with faulting which generated signifiant sea floor relief and resulted in contrasting depositional areas topographic highs with coralgal reefs and depressions where calcirudite channel fill accumulated normal faulting occurred along wnw ese master faults the generation of submarine fault scarps gave rise to various types of gravity driven phenomena including the sliding and slumping of large blocks of reefal limestone and the deposition of carbonate debris flows along with the redeposition of the danian carbonates flows of fluidized and reworked campanian chalk resulted from the peculiar physical properties of the undercompacted chalks erosion and faulting occurred predominantly during the palaeocene and represent a major episode in the physiographic evolution of the paris basin

reefs are not so different they follow the evolutionary pattern of level bottom communities there is a pervasive attitude that reels were isolated from the mainstream of evolution and that their history had quite a different pattern from the level bottom marine biota however three striking similarities exist between the evolution of reefs and other marine communities 1 reef composition and ecologic structure were governed by the composition of the three phanerozoic evolutionary faunas 2 reefs were decimated by the major extinction events of the geologic record 3 reefs conform to the pattern of level bottom community evolution intervals when reefs were absent were due either to the absence of appropriate frame building organisms in the biota for example in the middle and late cambrian or to the absence of reefs following extinction events before frame building organisms re evolved a reef building mode of life

tectonic history of the western tethys since the late triassic the tectonic history of the western tethys since the late triassic is illustrated through a set of computer generated plate reconstructions which are based on a rigorous plate motions model of this region the model is constrained by the atlantic plate kinematics and on land geologic evidence and defines 13 tectonic phases spanning the time interval from the late ladinian 230 ma to the present the kinematics associated with the late triassic western tethyan rifts produced the detachment of a large composite fragment from the northern margin of gondwana it can be considered as the eastern propagation of the central pangea breakup during the early jurassic these rift zones became inactive while new zones of extension formed along the southern margin of eurasia the eastern margin of iberia and within the rifted northern gondwana fragment itself plate motions associated with the first two extensional centers can still be considered as an eastern branch of the central atlantic plate kinematics conversely the kinematic parameters of the latter rift result from the composition of the euler rotation describing the central pangea breakup and the euler pole of closure of the paleo tethys ocean the late triassic early jurassic rifting phases determined the formation of a number of independent microplates at the interface between africa and eurasia starting from the early cretaceous convergence between africa and eurasia triggered further deformation within the dispersed continental fragments and the formation of backarc basins at the active margins ultimately leading to an increase in the number of tectonic elements that were moving independently in the western tethyan region during the late cretaceous and the cenozoic the proposed tectonic evolution of the western tethys area is compatible with both global scale plate kinematics and geological constraints from on land data observed across the present day mosaic of displaced terranes surrounding the mediterranean region

the role of nutrient availability in bioerosion consequences to carbonate buildups abstract zooxanthellate organisms which are among the major carbonate producers on coral reefs are highly adapted to nutrient deficient conditions and tend to be outcompeted by filamentous or fleshy algae if nutrients are abundant reef dwelling bioeroding organisms on the other hand seem to increase in abundance with increasing availability of nutrient and food resources maximum rates of calcium carbonate production in a reef system are comparable in magnitude to maximum rates of bioerosion the dynamic interplay between accretion destruction of coral reefs is therefore likely to be strongly influenced by nutrient availability nutrient availability may also influence development of carbonate facies in reef systems that develop in oligotrophic waters skeletal sands and framework should dominate carbonate buildups in systems that develop in mesotrophic waters enhanced bioerosion should reduce much of the skeletal material to carbonate muds increasing the prevalence of mud rich facies eutrophic conditions should result in bioeroded hardgrounds and carbonate depositional hiatuses when carbonate accumulation rates fail to equal or exceed rates of local relative sea level rise reefs drown bored and lithified pavements with crusts of ferromanganese oxides phosphates or glauconite often separate shallow reef from overlying deeper water deposits nondeposition bioerosion and evidence for low redox potentials at the sediment water interface all implicate excess nutrient availability as a factor in reef drowning some carbonate depositional hiatuses and bioerosional surfaces are local phenomena evidence of responses to local increases in nutrient availability resulting from submergence of soils runoff or topographic upwelling others appear to reflect regional or worldwide events because many carbonate producing organisms have life history strategies specialized to nutrient deficient conditions they are unable to compete when nutrients become plentiful events that triggered ocean turnover or sharp increases in the rate of deep ocean circulation would have increased sea surface nutrient availability worldwide such eutrophication could have caused widespread extinctions in reef communities because eutrophication promotes bioerosion details of the fossil records of those events are probably lost in bioerosional hiatuses

depth controlled changes in grain size and carbonate content on a shelf edge sand bank abstract analysis of sediment samples from a shelf edge sand bank in the celtic sea has shown that the overall mean grain size of the sediments may be closely related to the proportion of carbonate material this has been found to vary from 80 on top of the bank to 20 on its flanks while the mean grain size of the quartz sand fraction of these sediments has been found to be independent of depth it has also been found that the coarsest carbonate fragments occur on top of the bank it is suggested that the observed changes in carbonate content and size can be explained by depth controlled variations in tidal current amplitude and enhanced winnowing of fine quartz sand and the finer shell fragments from the carbonate deposits on the top of the bank the importance of this mechanism is illustrated by reference to tidal current measurements and from considerations of the effects of wave induced currents at the seabed

stratigraphy of the paleocene continental sedimentary succession of the northern pyrenean basin corbieres southern france using δ13corg isotopes continental dominated successions are often poorly constrained stratigraphically due to a lack of robust biostratigraphic markers this study provides the first dataset of 13corg together with magnetostratigraphic and biostratigraphic data from a thick continental dominated succession at lairiere northern pyrenees france this section encompasses the latest cretaceous up to the paleocene eocene thermal maximum interval and is characterized by fluvial deposits occasionally intercalated with continental carbonates lacustrine deltaic deposits and shallow marine sediments this work identifies 13corg events and assigns them to global 13c geochemical events defined in pyrenean and tethyan marine successions in which the stage boundaries are well calibrated as the isotopic measurements are performed on dispersed organic matter in sedimentary rocks with a low organic content we propose that analyses of the signal should take into consideration the depositional environment because variations in the organic matter content might affect the signal we establish a high resolution chronostratigraphy in terrestrial paleocene deposits in the ne pyrenean zone recognize a late selandian interval and define the paleocene eocene thermal maximum event supplementary material palaeomagnetic results geochemistry details and palynological analysis are available at https doi org 10 6084 m9 figshare c 4871214

a currents of removal approach for interpreting carbonate sedimentary processes abstract this study develops a currents of removal methodology to examine and quantify the nature of physical transport processes affecting the formation of bioclastic deposits in the cocos keeling islands an indian ocean atoll this approach is based on the hydraulic settling and threshold of entrainment characteristics of bioclastic deposits and measured current energy potential mobility pm analysis of 157 samples quantifies the proportion of deposits able to be transported in each geomorphic zone results show that under mean energy conditions wave induced currents entrain and transport sediment within the atoll and show that transport of sediment is not solely reliant on storm energy conditions gradients of pm values are used to reconstruct sediment transport pathways from the reef flat 85 100 pm through shallow passages 75 100 pm to sand aprons 50 75 pm and shallow 0 20 pm and deep lagoon 0 pm comparison of settling velocity distributions of bed material and sediment retained in sediment trap experiments show that actual mobility levels correspond with pm estimates potential mobility analysis also identifies the immobile portions of deposits which increase lagoonward constituent analysis of immobile fractions and analysis of settling frequency distributions are used to differentiate the importance of physical and biological processes in the formation of deposits throughout cocos and identify the role of each geomorphic zone in the transport system the pattern of sediment is controlled by physical processes between the reef flat the primary sediment production zone with sediment transported through the shallow passage conduits to the sand aprons the formation of shallow and deep lagoon deposits is controlled by autochthonous sediment production and storm deposition potential mobility analysis is a powerful tool enabling physical transport processes within bioclastic sedimentary environments to be quantified the ability to examine an individual deposit s hydraulic behaviour and development also enables depositional processes to be examined at a much finer resolution than previously attempted using conventional textural approaches

reef building and carbonate production modes in the west central tethys during the cenozoic abstract changing components rock textures lithofacies platform types and architecture throughout time are unique characteristics of carbonate rocks characterizing these attributes has been approached by 1 building reference models for specific phanerozoic intervals 2 recognizing the climatic impact in modulating carbonate production and 3 analyzing the influence of changing bio geochemical conditions the reference model approach is mostly based on biological evolution the climatic impact approach emphasizes temperature and the bio geochemical approach considers the changes in mg ca ratios and ca concentrations in the oceans to date however an analysis integrating all of these factors is still missing the analysis presented here includes all these factors but also co 2 which is fundamental for both photosynthesis and caco 3 precipitation here we analyze the waxing and waning of cenozoic reef limestones from the central tethys region through several steps 1 on the basis of rock volume rock textures associated sediments and light dependent skeletal components as records of light penetration and wave energy depth 2 on global environmental conditions 13 c 18 o p co 2 temperature and 3 on the basis of functionality nutritional requirements and available resources through the cenozoic water motion whether induced by surface or internal waves or by currents increased as the thermal gradients strengthened both with depth and with latitude active water motion is essential for plankton catchers such as corals but less so for many larger benthic foraminifers lbf pycnoclines in the meso oligophotic zone would then favor the benthic plankton catchers such as corals but would be detrimental for many lbf warm temperatures favored lbf the eocene lbf families predominated during lowering of atmospheric p co 2 by using respiratory co 2 to enhance the symbiont production of photosynthates under oligotrophic conditions and limited turbulence whereas the miocene families had to adapt to a progressive increase in turbulence the eurythermal coralline red algae however became preponderant producers in the mesophotic zone during times when the 13 c was relatively high this explains two apparent paradoxes 1 corals thrive best when the earth s high latitudes cool and 2 the dominance of corals and lbf is inversely correlated despite they both require tropical conditions and have similar trophic strategies mixotrophy

middle cretaceous reef collapse linked to ocean heat transport biologically defined fluctuations in cretaceous tropical reef boundaries of the caribbean region record a dynamic rather than stable environmental history these fluctuations may be related to major thermal changes resulting from ocean heat transport with simultaneous poleward movement of surface and subsurface waters on sea level highstands the superheated middle cretaceous tropics cooled the reef line contracted diversity decreased and reef ecosystems collapsed leading to mass extinction geologic data qualitatively test and support the hypothesis of enhanced cretaceous ocean heat transport formulated from general circulation models in these models four times the present day atmospheric concentration of co 2 and twice the present day model value of ocean heat transport cooled the superheated tropics and provided the best match to the distribution of inferred middle cretaceous temperature data these dynamic changes suggest an important role for large scale disturbance in the evolution of tropical ecosystems

late cretaceous to late eocene palaeogeographic evolution of southwest europe abstract a synthesis of personal research concerning the peri pyrenean region and previously published data is presented as a series of palaeogeographic reconstructions subsequent to the progressive regression at the end of the cretaceous the sea invaded three times parts of the earlier senonian marine domain on both sides of the eastern palaeo pyrenees pre cuisian climatic rewarming combined with cuisian continental epeirogenic deformations resulted in major biogeographic modifications during the cuisian local tectonics forced the sea from the northern pyrenean basin whereas in the southern pyrenean basin the sea retreated much later as a consequence of the pyrenean tectonic phase however the pyrenean tectogenesis seems to have affected a much larger region including the alps shoreline migrations are compared and related to the geodynamic behaviour of the meridional and septentrional european provinces in order to distinguish between tectonic and eustatic causes

analytical modelling of wave refraction and convergence on coral reef platforms implications for island formation and stability abstract an analytical model was constructed to simulate the refraction of waves on coral reef platforms comprising an idealised bathymetry of uniform depth and vertical reef faces model simulations were conducted to investigate the influence of key parameters such as reef shape and depth as well as wave period on the propagation behaviour of incident waves results of the refraction analysis demonstrate that different reef shapes produce characteristic patterns of wave convergence on reef surfaces the location and stability of focal zones and hence wave convergence is largely controlled by the shape of platforms platform configuration further controls the distribution of wave energy across platform surfaces and determines the influence of incident wave forcing on different reef sections results have significant implications for sedimentation processes and hence the formation and stability of islands on reef platforms wave propagation patterns define sediment transport vectors and subsequently control the transport and deposition of different sized material platforms which promote marked wave convergence behaviour such as elliptical and circular reefs are more likely to retain sediment on reef surfaces whereas narrow linear structures have a higher potential for the off reef evacuation of sediment over leeward reef margins and the subsequent infill of deeper lagoonal areas the study provides a physical basis for future investigations of reef hydrodynamics and platform sedimentation processes

experiments on the settling overturning and entrainment of bivalve shells and related models an experimental and theoretical examination has been made of the settling entrainment and overturning of 176 valves representing 16 common northwest european marine bivalve species together with a comparative study of 15 plastic models in the form of segments from cylindrical tubes settling behaviour in both stagnant and moving water depends on particle mass symmetry and concavo convexity separated empty bivalve shells spin and spiral while settling and if sufficiently elongated also pitch at the observed reynolds numbers the shells and models fall concave up the terminal fall velocity increasing as the square root of the unit immersed mass or weight the drag coefficient is independent of reynolds number but increases with surface roughness and particularly particle elongation turbulence slightly lowers the critical elongation for pitching a separation vortex lies captive on the upper side of each descending particle consequently an empty bivalve shell traversing a suspension of sand traps grains on its upper side at a rate proportional to their volume concentration and terminal fall velocity this process increasing the effective shell mass is limited only by the capacity of the shell and grain spillage due to the possible onset of pitching the ratio non dimensional of a quantity proportional to the applied fluid force and the particle unit immersed weight consistently describes the entrainment of concave up and convex up particles and also the immediate overturning of a valve on settling concave up to the bed these thresholds vary in relative magnitude with bed particle friction and particle concavo convexity in general convex up particles are the most stable the concave up entrainment and overturning thresholds are of a substantially lower but similar magnitude the high frequency of concave up bivalve attitudes in turbidites is understandable largely in terms of the ability of a settling valve to increase in effective mass by grain entrapment convex up attitudes in the lower parts of turbidites may record currents stronger than the overturning threshold

sedimentology of coastal deposits in the seychelles islands evidence of the indian ocean tsunami 2004 the seychelles an archipelago in the indian ocean at a distance of 4 500 5 000 km from the west coast of sumatra were severely affected by the december 26 2004 tsunami with wave heights up to 4 m since the tsunami history of small islands often remains unclear due to a young historical record it is important to study the geological traces of high energy events preserved along their coasts we conducted a survey of the impact of the 2004 indian ocean tsunami on the inner seychelles islands in detail we studied onshore tsunami deposits in the mangrove forest at old turtle pond in the curieuse marine national park on the east coast of curieuse island it is thus protected from anthropogenic interference towards the sea it was shielded until the tsunami in 2004 by a 500 m long and 1 5 m high causeway which was set up in 1909 as a sediment trap and assuring a low energetic hydrodynamic environment for the protection of the mangroves the causeway was destroyed by the 2004 indian ocean tsunami the tsunami caused a change of habitat by the sedimentation of sand lobes in the mangrove forest the dark organic rich mangrove soil 1 9 was covered by bimodal fine to medium carbonate sand 1 7 2 2 containing coarser carbonate shell fragments and debris intertidal sediments and the mangrove soil acted as sources of the lobe deposits the sand sheet deposited by the tsunami is organized into different lobes they extend landwards to different inundation distances as a function of the morphology of the onshore area the maximum extent of 180 m from the shoreline indicates the minimum inundation distance to the tsunami the top parts of the sand lobes cover the pneumatophores of the mangroves there is no landward fining trend along the sand lobes and normal grading of the deposits is rare occurring only in 1 of 7 sites the sand lobe deposits also lack sedimentary structures on the surface of the sand lobes numerous mostly fragmented shells of bivalves and molluscs were distributed up to 150 m from the coastline intact bivalve shells were mostly found positioned with the convex side upwards on small ledges of a granitic body at 130 150 m from the shore mostly fragmented and gravel sized shells were deposited at different elevations up to 4 m above sea level this implies a run up height of at least 4 m above sea level up to 150 m from the present shoreline

crustose coralline algae from the flower garden banks northwestern gulf of mexico controls on distribution and growth morphology abstract the east and west flower garden banks in the northwestern gulf of mexico represent the northernmost tropical coral reefs and caribbean coralline algal flora on the north american continental shelf coralline algae are the dominant framework builders and sediment contributors below 50 m on the banks on the basis of growth form and taxonomic composition coralline algae on the flower garden banks can be divided into four overlapping depth zones upper coral reefs 20 30 m madracis algal ridges 30 40 m algal nodule zone 45 80 m and deep algal reefs 50 90 m corallines on the upper coral reefs are dominated by hydrolithon lithophyllum and porolithon their growth form as thick laterally restricted crusts and knobs results from intensive grazing by parrotfish and urchins grazing is diminished on the madracis algal ridges below the upper reefs and corallines grow here as laterally extensive plates binding coral rubble dominant corallines on the ridges are lithophyllum paragoniolithon and tenarea algal nodules rhodoliths o the deeper bank slopes are the most widespread algal growth form on the flower garden banks on the basis of shape internal structure and composition rhodoliths are divided into an upper zone where they have a spherical shape with concentric laminae and a lower zone discoidal shape with irregular laminae diminishing current velocity with increasing depth controls nodule morphology the red alga peyssonnelia and the foraminifer gypsina are two non coralline components that contribute substantially to nodule growth reduced current velocity in the lower nodule zone enables corallines and peyssonnelia to develop laterally extensive pavements and 1 2 m high algal reefs taxonomic composition high framework porosity and irregular internal growth morphology f the deep algal reefs distinguish these structures from shallow algal ridges described elsewhere the 90 m isobath at the flower garden banks approximates the upward limit of a turbid nepheloid layer composed of continually resuspended sediment reefal structures within this water layer are dead and are now covered by fine sediment

bedload abrasion and the in situ fragmentation of bivalve shells the aim of this study was to determine how unio bivalve shells fragment within the channel of the sakmara river southern urals russia the sakmara river has an abundant bivalve population and a highly variable flow regime which at low flow allowed much of the channel bed to be examined a large data set of 1013 shells unio sp was examined and these were shown to have consistent patterns of orientation aspect shell abrasion perforation and fracture the close spatial relationship between areas of shell abrasion shell perforation and shell fracture showed that they form part of a continuum whereby areas of abrasion evolve into perforations and perforations coalesce and enlarge into fractures the mechanism of shell damage proposed is one of abrasion in place whereby the shell remains stationary on the surface of the point bar and is impacted by bedload underpinning this process are the hydrodynamic properties of the bivalve shell with consistency in the orientation and aspect of the valve in a flowing current producing consistency in the distribution of damage on the shell surface valves preferentially lie in a convex up position and orientate in the flow such that the umbo faces upstream the elevated upstream facing umbo region is exposed to particle impact and is the first to be abraded and perforated the vulnerability of the umbo to perforation is greatly increased by the thinness of the shell at the umbo cavity the in situ abrasion process is enhanced by the development of an armoured gravel bed which restricts valve mobility and maintains shells within the abrasion zone at the sediment water interface the in situ abrasion process shows that broken shells are not a reliable indicator of long distance transport the study also raises the issue that tumbling barrel experiments which are generally used to simulate shell abrasion will not replicate the type of directionally focused sand blasting which appears to be the principal cause of shell fragmentation in the sakmara river

meco and alpine orogenesis constraints for facies evolution of the bartonian nummulitic and solenomeris limestone in the argentina valley ligurian alps

application of the rayleigh lidar to observations of noctilucent clouds the feasibility of lidar detection of noctilucent cloud nlc returns with the rayleigh lidar technique was determined by calculations of lidar photocount profiles for the nd yag lidar wavelength of 532 nm rayleigh temperature lidar these results affirm the feasibility of the application of this instrument to study the high latitude summer phenomenon of nlcs rayleigh 532 nm lidar observations were carried out in greenland for late july and august 1990 extended cloudiness hampered these measurements and a display of nlcs was seen only on august 14 15 1990 out of a total of 11 nights examination of photographs of the nlcs for this night indicates that the spatial distribution of the clouds was patchy and fragmentary no visual detection of nlcs in the region of the zenith when the solar depression angle was 8 6 was noted at this time the sky was sufficiently dark and if there had been any nlcs overhead visual nlc sightings should have been possible the lidar observations provided measurements of the middle atmosphere temperature from 25 km to about 70 km for times near local midnight the shapes of these profiles agreed with that of the u s 76 standard model profile but with an increase of about 5 at the stratopause examination of the results for an indication of lidar mie returns from nlcs was negative which was consistent with the lack of visual detection

lidar observations of ice crystals associated with noctilucent clouds at middle latitudes lidar observations at aberystwyth 52 4 n 4 1 w have shown layers of enhanced backscatter at heights just below the mesopause during four nights in late june and early july 1993 the characteristics of these layers and their association with noctilucent clouds indicate that they are comprised of ice crystals an examination is made of the temperature prior to the formation of a layer the rates of descent of layers and their integrated backscatter coefficients the results are discussed in terms of the size of the crystals giving rise to backscatter the ambient water mixing ratio and the equivalent water vapour represented by these crystals

lidar observations of polar mesospheric clouds at south pole diurnal variations polar mesospheric clouds pmcs were observed by a ground based fe boltzmann temperature lidar for 65 h on 17 19 and 24 26 january 2000 above the geographic south pole the mean pmc backscatter ratio volume backscatter coefficient total backscatter coefficient layer centroid altitude and layer rms width are 53 5 2 9 l0 9 m 1sr 1 4 3 10 6 sr 1 85 37 km and 0 78 km respectively strong semidiurnal and diurnal oscillations were observed in the pmc backscatter ratio volume backscatter coefficient total backscatter coefficient and centroid altitude the oscillations are all maximum around 0630 and 1900 ut the variations appear to be linked to vertical advection of the pmc scattering layers by a persistent oscillation in the vertical wind velocity scattering is strongest when the pmcs are highest which suggests that the colder temperatures at higher altitudes near the mesopause facilitate the formation of larger pmc particles

carbonate platform depositional sequences upper cretaceous south central pyrenees spain abstract the upper cretaceous cenomanian maastrichtian of the south central pyrenees shows five carbonate platform sequences where the major parameters are tectonism relative sea level fluctuations and inherited depositional profile depositional geometries and basin analysis permit an understanding of the depositional history five depositional sequences have been recognized 1 the santa fe sequence middle upper cenomanian a ramp to a skeletal rimmed shelf with an escarpment bypass margin the lower boundary is an angular unconformity and the upper one records a sea level drop the platform location of the margin was determined by a listric normal fault 2 an abrupt sea level rise drowned the former platform the congost sequence turonian lower coniacian a distally steepened ramp with erosional distal deep slope the depositional model was largely controlled by pre existing basin morphology cessation of platform development was due to a relative sea level drop 3 the sant corneli sequence upper coniacian lower santonian a mixed terrigenous skeletal homoclinal ramp with upright margin deep slope and dysaerobic basin the slope results from the backstepping by 24 km of the previous margin and gentle basin tilting the platform margin remained more or less at the same position and relief between platform and slope increased indicating continuous relative sea level rise the upper boundary is an angular unconformity at the platform margin produced by an abrupt sea level rise and platform drowning and by listric normal faulting 4 the vallcarga sequence upper santonian campanian a distal steepened skeletal homoclinal ramp erosional escarpment and turbidite basin which corresponds to the mesozoic maximum marine expansion a listric normal fault created two depositional areas a more or less flat footwall block with a north northwest prograding carbonate ramp

the campo section pyrenees spain revisited implications for changing benthic carbonate assemblages across the paleocene eocene boundary abstract the campo section is a parastratotype section for the shallow water ilerdian and cuisian stages although a lot of work has been concentrated during the last years on biostratigraphy sequence stratigraphy magnetostratigraphy and geochemistry surprisingly little work has been published on the facies development here we evaluate the facies evolution with particular emphasis on the biogenic assemblages of the latest paleocene shallow benthic zonation 4 to the earliest eocene shallow benthic zonations 5 and 6 of the campo and the nearby serraduy section overall the facies show a deepening in the paleocene and the eocene interrupted by a terrestrial interval across the newly defined paleocene eocene boundary in the late paleocene altogether seven microfacies types were distinguished these are dominated by various algal taxa and subordinate corals and larger foraminifera the lower eocene carbonate platform is characterised by twelve microfacies types which are dominated by larger foraminifera such as alveolinids orbitolitids and nummulitids and subordinate corals this facies dichotomy recognized in the campo and serraduy sections can be extrapolated to the whole pyrenean region in the early paleogene and is even found in egypt the comparison of the two regions shows that the facies dichotomy is less pronounced in the pyrenean region this is interpreted to reflect a latitudinal trend where corals are absent in the low latitudes while in the middle latitudes they occur subordinately this gradient within the facies distribution can be explained by latitudinal temperature changes and by the long time warming in the early paleogene and the short time warming of the paleocene eocene thermal maximum hot temperatures in the low latitudes hamper the growth of temperature sensitive corals while in the middle latitudes the temperatures were still in a favourable temperature range