earthquake induced resedimentation in the badenian middle miocene gypsum of southern poland in the badenian middle miocene basin of the carpathian foreland of southern poland gypsum breccias occur associated with laminated gypsum deposits these breccias consist of large clasts of gypsum carbonates marls and clay chips of variable size embedded in a gypsarenitic matrix constituent gypsum grains and clasts commonly appear to be mechanically abraded and chemically corroded crystals or fragments of selenitic laminated and alabastrine gypsum gypsorudites are commonly accompanied by laminated gypsarenites and gypsolutites which show graded bedding a vertical sequence of graded gypsum beds showing bouma sequences may be recognized in borehole sections microfolding is common within the folded laminated gypsum and is closely associated with expressions of extensional strain both are accompanied by pervasive microfaulting suggesting a semi coherent downslope mass movement the stratiform geometry of the breccias together with the intensity of slumping relatively independent of the palaeoslope suggest earthquake shocks as the initial main cause gypsum deposits form a constant laterally extensive sequence of different lithofacies the occurrence of the same lithologies and shallowing up cycles over a wide area reflects thrusting of the carpathians over the carpathian foredeep local tectonism has also played a significant role the tectonic framework favoured activation of dip slip faults promoting shallow focus earthquakes these in turn resulted in the resedimentation of gypsum by slumps debris flows and turbidites a similar basinward resedimentation of clastic material by gravity flows initiated by fault induced earthquakes could be of great importance in the foreland geological setting and may explain some phenomena observed in other evaporite formations from different geological settings especially of rift type

symbiotic interactions in the ordovician of baltica abstract eleven symbiotic associations between taxa occur in the ordovician of baltica most involving colonial animals bryozoans formed the most numerous associations including possible polychaete bioclaustrations possible polychaete borings conulariids and crinoids and had the highest number of symbiosis cases in baltica the late ordovician symbiotic associations differ from those in the middle ordovician by a remarkable increase in the numbers of recorded cases this is most likely explained by the great ordovician biodiversification event gobe the higher faunal diversity may have created more opportunities for symbiotic relationships these changes in the symbiotic interactions in the ordovician of baltica were probably not related to climate change but had an evolutionary cause

coordinated biotic and abiotic change during the great ordovician biodiversification event darriwilian assembly of early paleozoic building blocks abstract the ordovician period records an extraordinary biodiversity increase known as the great ordovician biodiversification event gobe which coincided with a series of environmental changes to the earth system notably a cooling global ocean increased oxygenation and increased nutrient supply from volcanism and continental weathering the co evolution of earth and its biota during this interval has been studied in various contexts on multiple paleocontinents emerging patterns depend on the lens of investigation here we summarize the current state of understanding by reviewing and synthesizing the fossil and sedimentary records recent paleontological studies mainly focused on rhynchonelliform articulated brachiopods bryozoa cephalopods trilobites graptolites echinoderms and reef organisms have documented details of diversification body size increase development of ecosystem complexity and intensification of inter continental dispersal from the late cambrian through late ordovician biomass increased markedly between the early and middle ordovician furthermore diversification rates increase statistically during the mid darriwilian age both globally and regionally coincident with these biotic changes geochemical proxies record significant changes to earth s physical system oceanic temperatures decreased and atmospheric oxygen levels increased to near modern levels in concert with the middle ordovician diversification of shelly fauna anoxic pulses ceased and evidence for deep ocean ventilation prevails in middle ordovician strata furthermore a major middle late ordovician change in oceanic strontium isotopic composition indicates increased weathering of juvenile volcanic rocks and delivery of nutrients to marine settings this multi proxy dataset records near simultaneous changes in fossil rich shallow marine environments during exactly the interval of greatest diversification by integrating biotic and geochemical datasets a clear picture of the co evolution of earth and its biota emerges indicating that the darriwilian was the critical interval facilitating increased capacity of ecosystems we therefore recommend restricting the term gobe to indicate this short interval of rapid diversification and ecosystem change and using ordovician radiation when referencing the sum of diversifications that occurred throughout the ordovician period

symbiosis of conulariids with trepostome bryozoans in the upper ordovician of estonia baltica abstract the trepostome bryozoans diplotrypa abnormis d bicornis d petropolitana esthoniopora communis e subsphaerica mesotrypa excentrica m expressa m raritabulata and monotrypa jewensis have symbiotic associations with the conulariid climacoconus bottnicus in the upper ordovician of estonia all bryoimmured conulariids are very small and oriented perpendicular or nearly so to the growth surface of the host trepostome colony muddy seafloors may have promoted this symbiosis between conulariids and bryozoans because the former required a hard substrate for attachment it is possible that the numerous smaller specimens among endobiotic conulariids usually died as juveniles together with their bryozoan host or alternatively the smaller endobiotic conulariids may have been lilliput forms of free living conulariids that died at a mature age conulariid trepostome associations were likely not a result of accidental intergrowth of two organisms additional protection against predators provided by the calcitic bryozoan skeleton may have been among the benefits for the conulariid symbionts usually trepostomes with conulariid symbionts do not contain other invertebrates but in the katian in some cases they also hosted anoigmaichnus bioclaustrations the exact type of symbiosis between trepostomes and conulariids remains unresolved but most likely the associations were slightly parasitic or commensal the available data suggest that bryozoans preferred cnidarians over the other invertebrates as symbionts

timing of post depositional events in the burano formation of the secchia valley upper triassic northern apennines clues from gypsum anhydrite transitions and carbonate metasomatism the burano evaporite formation from the secchia river valley is an up to 2200 m thick sequence composed of meter to decameter scale interbeds of gypsum anhydrite and dolostones with minor halite the deposit has been affected by a complex array of post depositional modifications thermal events and large scale evaporite dissolution preventing a satisfactory reconstruction of the environment of deposition the modifications are intense because these rocks were the main decollement horizon during the formation of the northern apennines chain the carbonate rocks are massive and or laminated dolomitic mudstone wackestone oolitic packstones and oolitic peloidal bioclastic grainstones which commonly appear as mega boudins within a sulfate groundmass the dolostones to 3 7 to 3 0 pdb have been affected by mg metasomatic replacement by magnesite to 2 6 to 1 4 pdb induced by hydrothermal circulation total homogenization temperatures of fluid inclusions in hydrothermal magnesite range from 275 to 310 c the anhydrite rocks are characterized by flow structures such as centimeter scale pseudo lamination composed of aligned prismatic crystals with transposed isoclinal folds outlined by dolostones fragments homogenization temperatures of fluid inclusions in authigenic quartz incorporated into sulfate rocks range from 260 to 305 c emilia and from 230 to 315 c tuscany the gypsum rocks are composed of xenotopic irregular cloudy crystals and more rarely by centimeter scale idiotopic crystals showing the same structures as the anhydrite rocks the origin of the gypsum rocks is due to late alteration of anhydrite by migration of sharp hydration fronts the hydration is a two step process and is revealed by the presence in the gypsum rocks of corroded anhydrite micro relics and authigenic quartz crystals which include anhydrite the role of the burano evaporites during the apennines tectogenesis can be depicted as follows a prevalent deposition of gypsum in the upper triassic b gypsum dehydration at burial conditions to form anhydrite cretaceous c syn tectonic flow of anhydrite rocks brecciation of dolostones syn tectonic growth stage of quartz euhedra at deep burial conditions possibly related to the development of the oligocene miocene greenschist facies apuane metamorphic complex d hydrothermal deposition of sparry magnesite and partial mg metasomatic replacement of dolostones by magnesite e sub surface dissolution of halite to form thick matrix supported residual caprock like anhydrite mega breccias f complete gypsification of anhydrite at sub surface conditions and g evaporite dissolution at surface exposure producing dolostone breccias with partial calcitization and removal of most clasts calcare cavernoso

the role of salt in fold and thrust belts davis d m and engelder t 1985 the role of salt in fold and thrust belts in n l carter and s uycda editors collision tectonics deformation of continental lithosphere tectonophysics 119 67 88 the style of deformation in thin skinned fold and thrust belts is critically dependent upon the resistance to sliding along the detachment between the mass of deforming sediments and the underlying rocks evaporites can provide an extremely weak horizon within which a basal detachment can form and along which only a relatively small shear traction can be supported fold and thrust belts that form atop a salt layer such as the appalachian plateau the franklin mountains in northwestern canada and the jura of the alps among others share several readily observable characteristics as predicted by a simple mechanical model for fold and thrust belts a detachment in salt permits a thrust belt to have an extremely narrow cross sectional taper in addition predicted orientations of the principal stress axes over a salt dtcollement are consistent with the commonly observed lack of a consistently dominant vergence direction of structures within the thrust belt other common attributes of salt basal thin skinned deformation include the presence of several widely but regularly spaced folds and abrupt changes in deformational style at the edge of the salt basin

sulfur redox reactions and formation of native sulfur veins during low grade metamorphism of gypsum evaporites cameros basin ne spain vein deposits containing native sulfur gypsum quartz and rare sphalerite are described from cervera del rio alhama in the very low grade metasediments of the mesozoic cameros basin of ne spain the veins are hosted by lacustrine evaporites which comprise alternations of dolomite and gypsum anhydrite during metamorphism layers fluid inclusion homogenization temperatures and quartz sulfate oxygen isotope geothermometry indicate formation of the veins at 225 c fluid inclusions contain s along with a gas phase comprising h2s n2 co2 and minor ch4 these are all likely reactants and products of s generation by thermochemical sulfate reduction tsr by organic matter followed by partial re oxidation of some h2s by so42 to produce s tsr type reactions during low grade metamorphism are thus concluded to be the origin of the s veins the tsr reactions we described differ from those observed in most petroleum related sour gas settings firstly there is no evidence for secondary carbonate precipitation secondly significant s isotopic fractionations exist between sulfate around 20 and reduced products s is around 11 this is attributed to relatively increased rates of isotopic equilibration compared to tsr that may be related to low availability of organic matter during the formation

criteria for recognition of localization and timing of multiple events of hydrothermal alteration in sandstones illustrated by petrographic fluid inclusion and isotopic analysis of the tera group northern spain stratigraphic relations detailed petrography microthermometry of fluid inclusions and fine scale isotopic analysis of diagenetic phases indicate a complex thermal history in tithonian fluvial sandstones and lacustrine limestones of the tera group north spain two different thermal events have been recognized and characterized which are likely associated with hydrothermal events that affected the cameros basin during the mid cretaceous and the eocene multiple stages of quartz cementation were identified using scanning electron microscope cathodoluminescence on sandstones and fracture fills primary fluid inclusions reveal homogenization temperatures th from 195 to 350 c in the quartz cements of extensional fracture fillings the high variability of th data in each particular fluid inclusion assemblage is related to natural reequilibration of the fluid inclusions probably due to cretaceous hydrothermal metamorphism some secondary fluid inclusion assemblages show very consistent data th 281 305 c and are considered not to have reequilibrated they are likely related to an eocene hydrothermal event or to a retrograde stage of the cretaceous hydrothermalism this approach shows how multiple thermal events can be discriminated a very steep thermal gradient of 97 214 c km can be deduced from 18o values of ferroan calcites 18o 14 2 11 8 v pdb that postdate quartz cements in fracture fillings furthermore illite crystallinity data anchizone epizone boundary are out of equilibrium with high fluid inclusion th these observations are consistent with heat flux related to short lived events of hydrothermal alteration focused by permeability contrasts rather than to regional heat flux associated with dynamo thermal metamorphism these results illustrate how thermal data from fracture systems can yield thermal histories markedly different from host rock values a finding indicative of hydrothermal fluid flow

solution collapse breccias of the minkinfjellet and wordiekammen formations central spitsbergen svalbard a large gypsum palaeokarst system large volumes of carbonate breccia occur in the late syn rift and early post rift deposits of the billefjorden trough central spitsbergen breccias are developed throughout the moscovian minkinfjellet formation and in basal parts of the kazimovian wordiekammen formation breccias can be divided into two categories i thick cross cutting breccia bodies up to 200 m thick that are associated with breccia pipes and large v structures and ii horizontal stratabound breccia beds interbedded with undeformed carbonate and siliciclastic rocks the thick breccias occur in the central part of the basin whereas the stratabound breccia beds have a much wider areal extent towards the basin margins the breccias were formed by gravitational collapse into cavities formed by dissolution of gypsum and anhydrite beds in the minkinfjellet formation several dissolution fronts have been discovered demonstrating the genetic relationship between dissolution of gypsum and brecciation textures and structures typical of collapse breccias such as inverse grading a sharp flat base breccia pipes collapse dolines and v structures cave roof collapse are also observed the breccias are cemented by calcite cements of pre compaction shallow burial origin primary fluid inclusions in the calcite are dominantly single phase containing fresh water final melting points are ca 0 c suggesting that breccia diagenesis occurred in meteoric waters cathodoluminescence cl zoning of the cements shows a consistent pattern of three cement stages but the abundance of each stage varies stratigraphically and laterally d 18 o values of breccia cements are more negative relative to marine limestones and meteoric cements developed in unbrecciated minkinfjellet limestones there is a clear relationship between d 18 o values and the abundance of the different cement generations detected by cl paragenetically later cements have lower d 18 o values recording increased temperatures during their precipitation carbon isotope values of the cements are primarily rock buffered although a weak trend towards more negative values with increasing burial depth is observed the timing of gypsum dissolution and brecciation was most likely related to major intervals of exposure of the carbonate platform during gzhelian and or asselian sakmarian times these intervals of exposure occurred shortly after deposition of the brecciated units and before deep burial of the sediments

seismically induced slumps in lower maastrichtian peritidal carbonates of the apulian platform southern italy abstract in the southeastern murge apulian foreland southern italy a lower maastrichtian carbonate section showing soft sediment deformation structures is composed of peritidal lithofacies associations developed in a wide low energy inner platform system shear induced soft sediment deformation structures correspond to multilayer deformed horizons 1 5 to 2 m in thickness sandwiched between undeformed layers overturned and recumbent folds lying on decollement surfaces and asymmetrical fault inception folds allow us to interpret the observed deformed horizons as slump sheets the detailed description of the main morphological features of the deformed beds and the recognition of unconformable surfaces and undeformed beds between slumped beds allow us to distinguish three different events of deformation preferential orientation of slump folds has been measured and every slumped bed shows a different direction of shortening randomly oriented direction of shortening suggests that each deformation event was driven by the presence of local very gentle gradients developed in peritidal settings by excluding other potential trigger mechanisms of deformation the observed slumps are interpreted as seismically induced slides even if no data about the distance of the seismic source may be obtained near field earthquake tectonics affected the apulian platform during late cretaceous times

passive acoustic detection and localization of whales effects of shipping noise in saguenay st lawrence marine park the performance of large aperture hydrophone arrays to detect and localize blue and fin whales 15 85hz signature vocalizations under ocean noise conditions was assessed through simulations from a normal mode propagation model combined to noise statistics from 15960h of recordings in saguenay st lawrence marine park the probability density functions of 2482 summer noise level estimates in the call bands were used to attach a probability of detection masking to the simulated call levels as a function of whale depth and range for typical environmental conditions results indicate that call detection was modulated by the calling depth relative to the sound channel axis and by modal constructive and destructive interferences with range masking of loud infrasounds could reach 40 at 30km for a receiver at the optimal depth the 30db weaker blue whale d call were subject to severe masking mapping the percentages of detection and localization allowed assessing the performance of a six hydrophone array under

baltica a synopsis of vendian permian palaeomagnetic data and their palaeotectonic implications torsvlk t h smethurst m a van der voo r trench a abrahamsen n and halvorsen e 1992 baltlca a synopsis of vendlan permmn palaeomagnetic data and their palaeotectonlc implications earth sci rev 33 133 152 in light of recent additions to the palaeozoic palaeo magnetlc data base particularly for the ordovlclan era a revised apparent polar wander apw path for baltica has been constructed following a rigorous synthesis of all late precambrlan perm lan data the apw path is characterized by two prominent loops firstly a late precambrlan camb rlan loop probably relating to a rifting event and secondly a younger loop relating to a mid silurian scandlan colhsion event these features imply major change in plate tectonic reconfiguratlon baltlca probably represented an individual continental unit m early palaeozoic times and was positioned m high southerly latitudes in an inverted geographic orientation in such a reconstruction baltlca was separated from the northern margin of gondwana by the tornqulst sea and from laurentla by the iapetus ocean the tornqulst zone is thus interpreted as a passive or dextral transform margin during the early palaeozoic while undergoing counter clockwise rotations up to 1 6 ma baltica drifted northward through most ol the palaeozoic except for a short period of southerly movement in late silurian early devonian times after colhslon with laurentla rapid movements in latitude up to 9 cm yr are noted m late precambrlan earl y palaeozoic times and slgmficant decrease in velocities throughout palaeozoic time probably reflect the progressive amalgamation of a larger continent by early devonian euramerlca and permian pangea times the tornqulst sea had a principal component of palaeo east west orientation hence it is difficult to be precise in the timing of when micro continents such as eastern avalonla and the european masslfs ultimately collided along the southwestern margin of baltica these micro continents are considered to have been peripheral to gondwana m high southerly latitudes during the early ordovlclan eastern avalonla clearly had rifted off gondwana by llanvlrn llanded o times and may have collided with baltlca during late ordovlclan times although the present available sdunan palaeomagnetlc data from eastern avalonia may suggest colhslon in late silurian times across the lapetus facing margin of baltica laurentla was s tuated in equatorml to southerly latitudes during most of the lower palaeozoic these continents collided in mid silurian times l e a first collision between southwestern norway and greenland scotla nd which gave rise to the early scandlan orogeny 425 ma in southwestern norway possible followed by a later but less dramatic scandlan event in northern norway at around 410 ma since baltlca was geographically reverted m early palaeozoic times the colhsional margin could not have been a margin that once rifted off laurentm as assumed in a number of plate tectonic models

origin and significance of lamination in lower cretaceous stromatolites and proposal for a quantitative approach stromatolite lamination is typically defined as alternation of dark and light laminae study of lower cretaceous stromatolites fromthe leza fm n spain supports this statement but recognises additional complexities in lamination that have implications for interpreting accretion processes these stromatolites are partial analogues of present day coarse grained carbonate stromatolites in the bahamas and shark bay australia that mainly form by trapping and binding carbonate sand the leza examples contain both grain rich and micrite rich laminae with scarce particles suggesting that they accreted both by trapping and not trapping grains lamination in modern and ancient coarse grained stromatolites is commonly defined by thinmicritic crusts that formed during interruptions in accretion and separate contiguous grainy laminae repetitive lamination leza examples also contain these thin hiatal crusts and locally showrepetitive lamination but their conspicuous macroscopic lamination is defined by thicker alternating grain rich and micrite rich laminae alternating lamination this indicates that although hiatuses in accretion occurred change in accretion process was the main cause of macroscopic lamination these differences in accretion processes and lamination styles between leza examples and modern coarse grained stromatolites may reflect differences in their environmental settings modern examples occur in shallow marine tidal environments whereas leza fm coarse grained stromatolites developed in ideinfluencedwater bodies in coastal wetlands that experienced fluctuations inwater salinity and hydrochemistry analysis of lamina thickness in these cretaceous stromatolites and similar published examples provides a quantitative approach to the processes that underlie stromatolite lamination

the south pyrenean eocene carbonate megabreccias revisited new interpretation based on evidence from the pamplona basin abstract the south pyrenean foreland basin contains numerous units of eocene carbonate megabreccias intercalated with siliciclastic turbidites and derived by resedimentation of shallow marine carbonate platforms previous studies were limited mainly to the foreland eastern part known as the jaca basin the present study from the pamplona basin a western part of the foreland trough sheds new light on the origin and regional significance of these south pyrenean eocene carbonate megabreccias specms the number of the specm units in the foreland basin is higher than previously recognized and their age is somewhat older than originally assumed the specm units appear to occur as time stratigraphic clusters which can be correlated with the relative sea level lowstands and linked with phases of tectonic activity the megabreccias were derived from a carbonate platform system hosted by the foreland basin s southern passive margin the episodic instability and mass wasting were triggered by phases of structural steepening forebulge uplift accompanied by high magnitude earthquakes with the former causing platform emergence increased load stresses and excess pore water pressure in the carbonate ramp the specm deposits were emplaced by cohesive debris flows evolving into high density turbidite currents an ideal specm unit consists of 1 an immature homogeneous debrite in the proximal part 2 a differentiated bipartite debrite and turbidite in the medial part and 3 an incomplete base missing debrite overlain by turbidite or a turbidite alone in the distal part the debrite component volumetrically predominates in the specm units and the original terms megaturbidite and seismoturbidite thus seem to be inappropriate for these deposits

a rugose coral bryozoan association from the lower devonian of nw spain abstract a new rugose coral cystoporate bryozoan association is here described from the devonian of nw spain this is the first evidence of intergrowths between devonian rugose corals and bryozoans in this case bryozoans provided a suitable substrate for the settlement of corals which were subsequently encrusted by the bryozoans the hypothesis of intergrowth between living organisms is supported by the absence of encrustation of the rugose coral calices by the cystoporates we suggest that the association was specific and developed through chemical mediation this symbiosis was facultative for the bryozoans but likely not for the corals the association provided the bryozoan host with additional substrate for encrustation as well as protection from various predators and it allowed the rugose corals to grow in a muddy environment and benefit from the feeding currents of the bryozoans

tectono stratigraphic evolution of an inverted extensional basin the cameros basin north of spain the cameros basin is a part of the mesozoic iberian rift it is an extensional basin formed during the late jurassic and early cretaceous in the mesozoic iberian rift context and it was inverted in the cenozoic as a result of the alpine contraction this work aims to reconstruct the tectono stratigraphic evolution of the basin during the mesozoic using new and revised field geophysical and subsurface data the construction of a basin wide balanced section with partial restorations herein offers new insights into the geometry of the syn rift deposits field data seismic lines and oil well data were used to identify the main structures of the basin and the basin forming mechanisms mapping and cross sectional data indicate the marked thickness variation of the depositional sequences across the basin suggesting that the extension of the depositional area varied during the syn rift stage and that the depocentres migrated towards the north from field observation and seismic line interpretation an onlap of the depositional sequences to the north over the marine jurassic substratum can be deduced in the last few decades the structure and geometry of the basin have been strongly debated the structure and geometry of the basin infill reconstructed herein strongly support the interpretation of the cameros basin as an extensional ramp synclinal basin formed on a blind south dipping extensional ramp the gradual hanging wall displacement to the south shifted the depocentres to the north over time thus increasing the basin in size northwards with onlap geometry on the pre rift substratum the basin was inverted by means of a main thrust located in a detachment located in the upper triassic beds keuper which branched in depth with the mesozoic extensional fault flat the reconstruction of the tectono stratigraphic evolution of the cameros basin proposed herein represents a synthesis and an integration of previous studies of the structure and geometry of the basin this study can be used as the basis for future basin scale research and for modelling the ancient petroleum system of the basin

petrography and geochemistry of the belle roche breccia lower visean belgium evidence for brecciation by evaporite dissolution the lower visean belle roche breccia east belgium displays a number of features that indicate brecciation by evaporite dissolution collapse the sharp lower contact of the breccia the gradual transition into the overlying strata the presence of semi continuous beds within the breccia giving it a crude stratification and the existence of several types of calcite dolomite and silica evaporite pseudomorphs furthermore the majority of the breccia fragments indicates hypersaline to lagoonal sedimentation conditions most of these fragments display an interlocking fabric the interpretation is also supported by the existence of continuous evaporite beds replaced by carbonates calcite and dolomite both under and overlying the breccia the brecciation history is characterized by gradual subsidence multiple brecciation episodes are recognized and are best seen in the lower breccia which underwent at least two major brecciation episodes here brecciated and veined breccia fragments occur within a microsparite neomorphosed mud matrix brecciation of these strata was due to the dissolution of interlayered evaporites the second brecciation event relates to infiltration of meteoric water and to the dissolution of the remaining evaporites this infiltration was probably triggered by the orogenic event at the end of the visean sudetic orogenic phase the whole breccia was finally cemented by a blocky calcite the different lithologies and cements were characterized by their trace element mg sr na fe mn k insoluble residue and organic matter content carbon oxygen isotope data of the cements and replaced evaporite layers helped to place the multiple collapse episodes within a general diagenetic model solution reprecipitation processes within the original aragonite dominated mud fragments as well as in the early diagenetic dolomite fragments have been recognized the geochemical data show that these transformation processes occurred in equilibrium with the same fluid these processes may have occurred within a freshwater lens very early in the diagenetic evolution or under shallow burial conditions cementation of blocky calcite occurred in a meteoric realm under burial conditions

book review the techniques of modern structural geology volume 2 folds and fractures john g ramsay and martin i huber academic press london 1987 xi 309 398 pp price stg17 50 us 34 50 paperback

life in a living substrate modular endosymbionts of bryozoan hosts from the devonian of spain abstract a new bioclaustration structure is described from the emsian lower devonian aguion formation of asturias nw spain it is the result of intergrowth of two bryozoan species leioclema elegans and loxophragma cf leptum hosting an unknown soft bodied modular symbiont these structures point to the development of host specific symbiotic associations in which both partners grew simultaneously the association is tentatively assessed as commensalism no evidence suggesting parasitism or mutualism has been found a revision of the existing literature on devonian bryozoans reveals that tubular structures similar to those described herein have been observed in different regions of the world only a few trepostome genera developed this kind of association during the devonian and leioclema seems to have been a suitable partner in intergrowths with a range of soft bodied and skeletonized organisms it is suggested that the association described herein was relatively common during the devonian and that molecular factors such as chemical mediation may have played a role in conducting the development of these specific intergrowths

stress field and thrust kinematics a model for the tectonic inversion of the cameros massif spain abstract alpine tectonics of the cameros thrust has been studied from several points of view geometry surface and sub surface structure three dimensional outline of the thrust kinematics transport direction and dynamics characterization of the regional compressional stress field all three aspects are related by means of a model based on bott s equation under a n to nne horizontal compression with an average stress ratio r z x y x 0 2 the eastern ramp of the cameros thrust oriented 155 30 w underwent a strike slip right lateral movement with a small reverse component this gave rise to rigid displacement of the cameros block towards the nnw and produced a guided movement on the western frontal ramp oriented 060 13 s

diverse early endobiotic coral symbiont assemblage from the katian late ordovician of baltica abstract a diverse early endobiotic coral symbiont assemblage has been detected within heliolitid tabulate corals of katian age from northwestern estonia this assemblage indicates that the earliest endobiotic coral symbiont communities were not restricted to north america the symbiotic endobiont assemblage comprises abundant cornulites aff celatus and rare conchicolites hosholmensis and chaetosalpinx sp the cornulitids are the earliest known symbiotic endobionts of this group the symbiotic endobionts presumably occurred in certain hosts only and preferred protoheliolites dubius over propora speciosa this record indicates that early endobiotic cornulitids were more diverse than previously thought and appeared in large numbers in the katian it is possible that the appearance of abundant skeletal symbiotic coral endobionts may coincide with the global ordovician biodiversification event supporting the hypothesis of escape from increased predation

pathways and distances of fluid flow during low grade metamorphism evidence from pyrite deposits of the cameros basin spain new geochemical and sulphur isotopic data are presented for a number of pyrite deposits from the late jurassic early cretaceous cameros basin spain the deposits were formed at or close to the peak of metamorphism and are always related to sandstone units in the mainly metapelite sequence iron remained immobile and conservative pyrite iron being derived by sulphidation of chlorite in the host metapelites reduced sulphur however was supplied from two external sources thermochemical reduction of sulphate and release of s during metamorphism of sedimentary sulphides these sources provided isotopically heavy and light s respectively with variation in pyrite isotopic composition between different deposits resulting from differences in their relative importance at each site during metamorphism the sandstone units acted as aquifers carrying the sulphidic pore waters to locations where permeability provided by syn depositional fractures on a scale of 0 5 5 m allowed its interaction with the metapelites transport distances for sulphide during metamorphism were of the order of hundreds of metres

from carbonate sulphate interbeds to carbonate breccias the role of tectonic deformation and diagenetic processes cameros basin lower cretaceous n spain interpreting the origin of carbonate breccias requires a detailed analysis because they may be the result of a wide variety of processes that produce similar features this is the case of the lower cretaceous carbonate breccias of the cameros basin previously interpreted as slump or collapse breccias whose origin is interpreted after performing a detailed sedimentary petrographic and tectonic study the studied carbonate breccias consist of angular carbonate mudstone fragments floating in a matrix of calcite and quartz crystals the breccias are interbedded with and laterally associated to alternating layers of carbonate mudstone and calcite and quartz pseudomorphs after gypsum which show strong similirities to the breccia fragments and matrix respectively suggesting that the brecciated beds were originally composed of identical alternating carbonate mudstone and gypsum layers as the unbrecciated layers the breccias are associated with frequently polyharmonic deformation structures which are similarly oriented as the regional tectonic structures indicating that they are related with the alpine contractional deformation of this area of the cameros basin all these features suggest that the carbonate breccias were formed by tectonic deformation of alternating layers of carbonate mudstone and calcium sulphate which have very different rheological behaviours as a result during tectonic deformation sulphate flowed and carbonate layers were broken and displaced producing a breccia of carbonate fragments within a sulphate groundmass afterwards the sulphate groundmass was replaced by quartz and calcite and the breccia acquired its final composition

crustal extension in the northern apennines the transition from compression to extension in the alpi apuane core complex an interpretation of northern apennine geology is presented which relates the temporal and spatial occurrence of both compressional and extensional deformation features in terms of the changing dynamic evolution within an accretionary wedge after a model proposed by platt 1986 followed by the initiation and development of continental rifting during cretaceous to eocene time an accretionary wedge formed as remnant tethyan oceanic crust subducted beneath the rotating corsica sardinia microplate microplate collision during the oligocene was characterized by the rapid imbrication of buoyant continental crust of the italian continental margin the record of which is preserved within the duplex structure geometry of the alpi apuane region the overthickened wedge geometry returned to a more stable configuration by developing extensional features during the miocene both listric normal faults at upper crustal levels and shear zones indicating evidence of distributed ductile extensional strain at mid crustal levels are recorded it is proposed that large scale regional extension with associated volcanism beginning in the messinian was represented by the intrusion of asthenospheric material from the subducted plate into the already attenuated accretionary complex further rifting perhaps aided by subduction and back arc processes in the southern apennines led to the formation of the tyrrhenian sea as an oceanic basin both the apennines and north american core complexes record evidence of crustal thickening followed by crustal thinning and finally of continental rifting this suggests that the similar histories of these regions with vastly different plate tectonic settings may both be explained by processes linked to the changing internal dynamics of accretionary wedges

late quaternary lacustrine groundwater aeolian and pedogenic gypsum in the prungle lakes southeastern australia abstract detailed petrographic studies of recent or sub recent evaporites where many critical environmental parameters are defined can help in the analysis of ancient deposits and in the establishment of chemical and environmental models for evaporite formation the prungle lakes are part of the now dry willandra lakes system in semi arid southwestern new south wales the willandra lakes have been a site of cyclic quaternary sedimentation in response to the well documented global climatic fluctuations associated with the glacial interglacial cycle at times of hydrologic stress low lake levels are associated with high salt volumes inherited from evaporative concentration in large shallow lakes upstream and the inflow of saline groundwaters thus at prungle a complex array of concentric shorelines lake floor terraces and lunettes has developed as basin within basin landforms which formed in response to filling and drying cycles sediments associated with these geomorphic units include 1 1 freshwater littoral nearshore and deep water deposited laminated sands and muds with biogenic carbonates chiefly of ostracodal and algal origin 2 2 evaporites comprising interbedded clay and laminated gypsum clay couplets which consist of discrete thin laminae of sugary white euhedral prismatic gypsum separated by detrital clay layers with a high degree of optical orientation primary accessory celestite srso4 occurs as discrete patches within the gypsum laminae 3 3 groundwater pyramidal discoidal or lenticular gypsum crystals grown from supersaturation produced by evaporation at the capillary fringe of the water table these have formed displacively within the sediments and caused considerable disruption of the sediment matrix 4 4 aeolian deposition in irregular transverse ridges of sand sized reworked groundwater gypsum and disrupted lacustrine clays the gypsum crystals are predominantly discoidal pyramidal forms which are conspicuously oriented parallel to bedding well sorted and extensively corroded the clay pellets are well sorted and moderately well rounded higher in the profile bedding is indistinct due to pedogenic processes which include modification of detrital grains and secondary crystallization of gypsum and carbonate a thin gypcrete horizon occurs at the surface the last cycle of sedimentation in the prungle lakes is believed from correlation with lakes higher in the willandra system to have occurred during the period 50 000 16 000 yr b p since then groundwaters have dropped below the zone of interaction with the lake floor and surface water no longer reaches the lakes sedimentation has ceased and soil formation with secondary carbonate and gypsum has continued to the present a range of sedimentary environments is identified which depend on strong seasonal oscillations these environments are virtually absent from the australian continent today and their occurrence during the pleistocene supports the contention of enhanced climatic seasonality at that time the array of sediment types and mineralogies is almost identical to that characteristic of coastal sabkha sequences highlighting the difficulty of relying on unusual evaporative mineralogy to differentiate marine and non marine environments detailed petrographic analyses of the prungle sequence have been made in association with a review of theoretical experimental and observational studies of the environmental controls of calcium sulfate mineralogy and crystal habit this has enabled the correlation at prungle of depositional environment with gypsum petrofacies and associated compositional fabric or structural features these observations are more generally applicable to other evaporite deposits many gypsum evaporites reported in the literature have been compared with this scheme developed at prungle

synsedimentary versus metamorphic control of s o and sr isotopic compositions in gypsum evaporites from the cameros basin spain abstract sulfate 34s and 18o and sr isotope compositions are presented for berriasian upper jurassic gypsum evaporites from the cameros basin a continental basin in the iberian ranges of northern spain solute sources to the ephemeral lakes in which the evaporites formed are dominated by weathering of sediments containing older keuper marine evaporites and granitic metamorphic variscan basement strontium isotopic ratios of the continental evaporites 87sr 86sr 0 707882 to 0 707933 are elevated compared to the keuper source 87sr 86sr 0 707605 to 0 707799 most likely reflecting a radiogenic component from basement lithologies sulfate 34s in the continental evaporites at around 18 2 v cdt is higher than any possible mixture of solutes to the basin the degree of 34s enrichment is small 3 7 and is most likely the result of partial bacterial reduction of lake water sulfate the same process would also enrich sulfate in 18o but by only 1 evaporite sulfate 18o at around 21 7 v smow is in fact enriched by 10 relative to sulfate sources to the basin this large effect is most likely the result of re equilibration of oxygen isotopes during low grade metamorphism of the basinal sequence sulfur and strontium isotopes in the evaporites remained internally buffered and thus unchanged during metamorphism while oxygen isotopes were open to exchange with aqueous fluid and or interbedded carbonates that constituted a large exchangeable oxygen reservoir the potential of sulfate oxygen to undergo isotopic exchange at elevated temperatures must be taken into account when interpreting the significance of evaporite sulfate oxygen data from units that have undergone deep burial or low grade metamorphism

soft sediment deformation induced by sinkhole activity in shallow marine environments a fossil example in the apulian foreland southern italy abstract soft sediment deformation structures are exposed in sea cliffs in the lower part of the calcarenite di gravina formation late pliocene early pleistocene in the cala corvino area n of monopoli adriatic sector of the apulian foreland southern italy deformation affects a thickness of about 5 m involving a lower calcareous terrigenous sand and gravel unit and an upper heavily bioturbated grainstone and packstone unit deformation is absent from the overlying part of the succession large scale soft sediment deformation structures are collapse features comprising irregularly elongated conical zones of sinking in vertical section narrow drop zones occur in the lower sandy gravelly facies and large gentle folds in the upper grainstone packstone beds the degree of deformation decreases upwards small scale soft sediment deformation structures adjacent to the large scale conical collapse structures are narrow vertically elongated load structures about 2 m high and 30 50 cm wide that involve only the basal terrigenous facies the distribution of small and large scale soft sediment deformation structures corresponds closely to zones of fracturing in the underlying cretaceous limestones and the elongation directions of soft sediment deformation structures correspond to the orientation of major fractures in the limestones the soft sediment deformation occurred due to collapse associated with karstic sinkhole formation along fractures in the bedrock geometrical relationships between deformed and undeformed sedimentary units show that deformation occurred in a shallow marine environment the structures at cala corvino provide a rare outcrop scale record of sinkhole induced soft sediment deformation occurring in a shallow marine environment