stromatolitic framework of carbonate mud mounds abstract mud mounds are an important phanerozoic reef type generally formed in deeper water on carbonate shelf to basin slopes they commonly contain radiaxial calcite spar filled depositional cavities stromatactis but lack abundant metazoan framebuilders mud mounds are often flanked by steeply dipping bioclastic grainstones and sometimes attained widths and depositional reliefs of over a hundred meters they occasionally occur as basal cores on which developed shallow water metazoan constructed reefs stromatactoid mud mounds are composed of a framework of submarine cemented crudely reticulate masses or a succession of laminar crusts surrounded by cement filled cavities these cavities developed when unconsolidated sediment around the framework was removed by winnowing mud mound frameworks of all ages show strong geometric and petrographic similarities to shallow water cryptalgal structures especially thrombolites unlaminated stromatolites which occur in many phanerozoic shallow water reefs both thrombolites and mud mound frameworks are largely composed of lime mudstone cemented on the sea floor and contain fenestral fabric and diagnostic cryptalgal microstructure their depositional surfaces were irregular not bored or burrowed and rarely encrusted stromatolitic lamina ion although commonly not well developed in the subtidal zone anyway occasionally occurs in mud mounds it is proposed that mud mounds accumulated from organic probably blue green algal binding of locally derived lime mud and bioclasts deposited relatively slowly from suspension patchy distribution of algal mats resulted in areas of both bound and unbound sediment sporadic floodlike episodes of rapid sedimentation however temporarily smothered the living algal mat and also left layers of unbound sediment periods of winnowing washed out unconsolidated unbound sediment and promoted synsedimentary cementation of resulting stromatactoid cavities and algal bound framework

early devonian kess kess carbonate mud mounds of the eastern anti atlas morocco and their relation to submarine hydrothermal venting abstract spectacular conical early devonian carbonate buildups up to 55 m high that crop out in the eastern anti atlas of southern morocco are microbially mediated carbonate mud mounds that were surfaced by soft bottom communities dominated by small tabulate corals they formed on the hamar laghdad elevation which was created by a submarine volcanic eruption and were associated with a network of synsedimentary radial and tangential faults that originated by uplift of the intrusive laccolithic body underlying the kess kess formation these faults served as conduits for the migration of hydrothermal fluids to the sea floor most mounds developed over cross points of radial and tangential faults vents were episodically active until the famennian but extensive vent carbonate production occurred only during the emsian preliminary geochemical results document that mud mound carbonates and calcite cements in neptunian dikes precipitated from brines comprising a mixture of hydrothermal fluids and seawater in addition carbon isotope compositions 13c as low as 18o oo pdb suggest a contribution from thermogenic methane derived presumably from underlying basaltic intrusives aerobic bacterial oxidation of methane is favored as the main process driving carbonate precipitation in and rapid lithification of the mounds

evinosponges in the triassic esino limestone southern alps documentation of early lithification and late diagenetic overprint a carbonate buildup of middle triassic age the esino limestone outcrops in the southern calcareous alps of lombardy n italy along its margin and within the open subtidal facies the esino limestone contains calcite cement filled cavities of cm to m size these features known as evinosponges may form pervasive networks within the host rock the filling consists of concentric isopachous layers of fibrous low mg calcite crystals characterized by strong undulose extinction and bent cleavages the cement crusts are non luminescent under cathodoluminescence but both cements and host rock are cross cut by microfractures filled with bright luminescent calcite related to late void filling sparite mixing of different carbonates is reflected in stable isotope data on the hand specimen scale the oxygen and carbon isotope compositions of cements and host rock show little variation when compared on a regional scale the values cover a broad range from 6l80 pdb 5 to 12 and from 613c pdb o to 3 the linear covariant trends defined by the oxygen and carbon isotope data for different sampling regions reflect the admixture of late isotopically depleted calcite with an isotopically enriched non luminescent calcite of early diagenetic origin the esino limestone fibrous cements which were probably precipitated in the marine or marinemeteoric phreatic environment were affected by late diagenetic processes that caused mineral deformation and isotopic depletion through recrystallization and the admixture of a later calcite these later calcites precipitated from penetrative fluids possibly related to late triassic volcanic activity and or to the late cretaceous early palaeogene alpine orogeny

paleozoic stromatactis and zebra carbonate mud mounds global abundance and paleogeographic distribution carbonate mud mounds with zebra and stromatactis structures are present in every paleozoic system and series but are more common in devonian and carboniferous deposits reaching their acme in mississippian system lower carboniferous rocks global distributions illustrate that mud mounds spanned the planet ranging from tropical to polar circles such a wide latitudinal span signifies that they not only grew in and occupied warm depositional environments but also in settings where oceanic waters were cold and seasonally light limited moreover their proliferation during the devonian and carboniferous was at a time when planet wide climatic ice house conditions are thought to have prevailed mud mounds therefore may also be products of cool and cold water carbonate sedimentation

growth dynamics and ecology of upper jurassic mounds with comparisons to mid palaeozoic mounds the mid palaeozoic including the late jurassic was a time of both widespread coral reef growth and pronounced mound formation a comparison of mound features and their general setting highlights despite all differences general similarities in overall growth dynamics mound formation was frequently driven by discontinuous patterns particularly by background sedimentation in many examples episodes of mound stabilisation by early lithification growth of microbolite crusts and winnowing of fines was followed by growth episodes of benthic fauna under reduced to negligible background sedimentation this pattern of variable sedimentation and organic buildups may have occurred in different orders and magnitudes inducing a fractal pattern in some mound complexes a composite approach in estimating growth rates of mounds demonstrates that highfrequency oscillations necessary for growth of most mounds might have ranged from a few thousand years to 4th and 5th order milankovich cycles that were superimposed by autocyclic factors d 2001 elsevier science b v all rights reserved

middle jurassic stromatactis mud mounds in the pieniny klippen belt carpathians a possible clue to the origin of stromatactis abstract four occurrences of jurassic stromatactis mud mounds were found in the czorsztyn unit of the pieniny klippen belt western carpathians in western slovakia slavnicke podhorie babina and in the transcarpathian ukraine priborzhavskoe and veliky kamenets their stratigraphic range is from bajocian to callovian the mounds consist of micropeloidal mudstones wackestones to packstones with a fauna including pelecypods brachiopods ammonites and crinoids spicules and skeletons of siliceous sponges are abundant in every section all of the mounds contain networks of stromatactis cavities that are partially filled with radiaxial fibrous calcite rfc and locally by internal sediments at slavnicke podhorie the sparry masses that fill stromatactis cavities are weathered out and show casts of sponges parallel study of the weathered casts and their cross sections in slabs showed that they bear all the signs of stromatactis relatively flat bottoms and digitate upper parts rfc initial fillings and eventual blocky calcite later filling almost no original sponge structures were preserved this strongly supports the possible sponge related origin for stromatactis cavities

significant decadal channel change 58 67 years post dam accounting for uncertainty in topographic change detection between contour maps and point cloud models abstract construction of digital elevation models dems and the subtraction of dems between different points in time as a method to determine temporal patterns of scour and fill is a highly valuable procedure emerging in geomorphology these dems of differences dods must be assessed for error in order to distinguish actual topographic change from uncertainty and surface error current methods include 1 uniformly excluding all values that fall below a minimum threshold 2 using a spatially variable approach such as the construction of minimum level of detection lod grids or 3 the creation of a fuzzy inference system although spatially variable methods for determining error have been more accurate in excluding noise without discarding large amounts of meaningful data a challenge remains in performing dods against preexisting contour based maps for which no original point data are available the goals of this study were to 1 develop a method that overcomes the unknown point density of contour and other historical data sets and allows for some assessment of dod uncertainty on the basis of information on topographic variability 2 perform comprehensive uncertainty analysis testing to understand the opportunities and constraints associated with this new method and 3 report and interpret the overall pattern and volume of decadal topographic change for a regulated river 67 years post dam in light of alternate conjectured mechanisms of post dam longitudinal profile adjustment the key feature of the new approach is the introduction of a high density artificial point grid that samples the topographic variability evident in the available historical data set the testbed used to develop and assess this new dod method was the 37 5 km lower yuba river california historical data consisted of 0 6 m contours from a 1999 survey while a more detailed point cloud was available for the most recent survey in 2006 2008 to evaluate uncertainty in the method this study applied seven different uncertainty metrics of varying strictness t 1 t 1 96 uniform 0 3 m exclusion t 1 plus uniform 0 3 m exclusion t 1 with lod minimum at 0 3 t 1 96 plus uniform 0 3 m exclusion and t 1 96 with lod minimum at 0 3 and two different dod adjustment methods exclusion and subtraction a stringent approach involving joint use of the contour half interval and the spatially distributed lod grid at a 95 confidence limit excluded 44 3 of the study area from spatial assessment of channel change and volumetric change computation this preferred approach yielded an estimated 2 518 million m 3 of total scour and 2 455 million m 3 of total fill in 7 9 years after considering different mapping epochs the net annual average export was 17 000 m 3 32 500 tons to the feather river and a river valley sediment yield of 2205 tons km 2 year this amount is 36 of the post dam annual yield of gravel and cobble to the upstream reservoir that blocks sediment conveyance into the study domain suggesting that the lowland system is still highly dynamic 67 years after the dam was built the scientific significance of this is that the response of rivers to dams can be far more long lasting and complex depending on the suite of cumulative societal impacts to rivers the ability to account for spatially explicit dod uncertainty i e data retention when uncertainty is low and data removal when uncertainty is high when comparing historic contour based and modern point cloud based dems will allow for more detailed and reliable dods and sediment budgets in these cases

sponge constructed stromatactis mud mounds silurian of gaspe quebec abstract stromatactis calcilutite mounds from upper silurian rocks of gaspe peninsula quebec canada are important constituents of a reef complex in the southern part of the peninsula they reach thicknesses up to 115 m and had paleoslopes of about 40 stromatactis constitutes up to 30 percent of the rock volume the microfacies of the calcilutite consists of agglomerates of pelletlike bodies forming a pelletoidal network surrounded by uniform mudstone sponge spicules are ubiquitous by analogy with textural features of a well documented sponge malumispongium hartnageli clark 1924 which occurs slightly above the mounds it is suggested that the pelletoidal network of the mound calcilutite represents a former sponge network that underwent very early dingenetic change and cemen ation stromatactis would have originated as early marine cementation of growth cavities in the sponge network and of cavities created by decay of local uncemented sponge tissues

investigation of structural heterogeneity at the spe site using combined p wave travel times and rg phase velocities we present analyses of the 2d seismic structure beneath source physics experiments spe geophone lines that extended radially at 100 m spacing from 100 to 2000 m from the source borehole with seismic sources at only one end of the geophone lines standard refraction profiling methods cannot resolve seismic velocity structures unambiguously in previous work we demonstrated overall agreement between body wave refraction modeling and rg dispersion curves for the least complex of the five lines a more detailed inspection supports a 2d reinterpretation of the structure we obtained rg phase velocity measurements in both the time and frequency domains then used iterative adjustment of the initial 1d body wave model to predict rg dispersion curves to fit the observed values our method applied to the most topographically severe of the geophone lines is supplemented with a 2d ray tracing approach whose application to p wave arrivals supports the rg analysis in addition midline sources will allow us to refine our characterization in future work

the modern calcifying sponge spheciospongia vesparium lamarck 1815 great bahama bank implications for ancient sponge mud mounds abstract modern calcified siliceous sponges from the great bahama bank living at water depth ranges of 2 to 5 m have been proposed as likely analogues for calcified sponges in upper jurassic sponge reefs e g southern germany or lower jurassic bioherms that consist of reddish spiculiferous limestones e g broccatello formation of the southern alps indeed sponge related calcification or siliceous sponge diagenesis in general is widely considered a key feature for the mechanisms of accretion and textural maturation in phanerozoic sponge mounds or spiculiferous carbonate mud mounds based on a revisit of the original sites on the great bahama bank nw of andros island the biostratonomy of the calcifying sponge spheciospongia vesparium lamarck 1815 was explored using the patterns of fluorescent dissolved organic matter fdom as revealed by the application of three dimensional excitation emission matrix eem fluorescence spectroscopy geochemical sampling distinguished between fdom that was extracted from sponge tissue and fdom that was intimately associated with caco 3 from particles due to sediment agglutination and authigenic caco 3 both obtained from the living sponge at the sediment surface and from the calcified sponge at the shallow subsurface from 5 to 10 cm of depth as expected the sponge tissue shows highest intensities for protein like fluorescence however from the surface to the subsurface there is a loss of such relatively pristine fluorescent material in the range of 70 humic like fluorescence that occurs associated with sponge tissue is relatively mature or aged thus it most probably represents seawater fdom taken up through active filter feeding relative to the sponge tissue material the fdom patterns associated with ca carbonates show much lower total fluorescence intensities by up to two orders of magnitude the agglutinated sedimentary carbonate particles from the surface pellets ooids grapestones exclusively show a relatively mature humic like fluorescence the deeper calcified parts of spheciospongia which represent a mixture of particles and authigenic caco 3 provided a fdom pattern that obviously combines the mature fdom pattern of particles with diagenetically fresh protein like and fulvic acid like fluorescence we conclude that shallow subsurface calcification of s vesparium correlates with the initial stage of sponge biomass humification such a mechanism of biomass transformation i e from biopolymers to geopolymers via degradation and condensation has also been suggested for the large scale development of carbonate sponge mud mounds therefore we consider the modern calcifying siliceous sponge s vesparium lamarck 1815 a potential pardigm to decipher in more detail the geologically important process of biomass induced calcification or organomineralisation with its subsequent effect of pore water fdom preservation and sediment lithification

palaeogeographic evolution of the pieniny klippen basin using stratigraphic and palaeomagnetic data from the veliky kamenets section carpathians ukraine abstract a 40 m thick carbonate succession of the bajocian to berriasian age from the veliky kamenets quarry novoselica area pieniny klippen belt ukraine resembles both the czorsztyn and niedzica successions of the pieniny klippen belt traditionally considered ridge slope related deposits a total of 176 individually oriented cores collected from the bottom to the top of the sequence with sampling density dependent on inferred sedimentation rates show multicomponent remanent magnetization with magnetite as a main magnetic carrier thermal demagnetization revealed two main components of natural remanent magnetization nrm a low blocking temperature component s of normal polarity is considered of posttectonic probably thermoviscous origin due to overheating by neogene volcanics a stable high blocking temperature nrm component p shows dual polarity distribution and is considered primary it was possible to recognize 23 polarity zones that have been correlated with a biostratigraphic scale since two significant sedimentary gaps occur at 422 and 860 cm the main hiatus ms from the base the latter comprising the middle callovian early oxfordian time span 6 8 ma an obtained pattern of magnetic reversals presented in this study cannot be considered complete a palaeolatitude of 41 5 is calculated for the mid jurassic part below ms similar to that expected for the european craton at the kamenets locality the mid oxfordian limestone directly overlying the ms has palaeolatitudes around 28 6 this implies a relatively fast opening of the oceanic domain to the north from the kamenets block this conclusion combined with similarity of the kamenets sequence to ridge related sediments of the pieniny klippen belt makes it possible to speculate on the existence of the kamenets ridge a new term a structure of uncertain although possible structural links to the czorsztyn ridge palaeomagnetic declinations suggest 100 counterclockwise rotation of the whole section before the neogene

the anatomy of a deep water mud mound complex to the southwest of the dinantian platform in derbyshire uk an elongate waulsortian mud mound complex developed at dovedale on a ramp to the southwest of a developing carbonate platform in derbyshire during chadian early visean times the complex occupied an area of approximately 6 km2 and grew to a maximum relief of 80 m with longitudinal and transverse valleys developed near the southern margin five mound associated facies have been identified mound core mound flank fine mound flank coarse intermound fine and intermound coarse the mound core facies is a massive skeletal wackestone with comminuted sponge debris foraminifera ostracodes and crinoid debris set in a matrix of clotted micrite the mound flank sediments display moderately inclined bedding surfaces while the mound flank fine contains sponge debris the mound flank coarse is dominated by articulated crinoid columnals and includes algal encrusted micritized intraclasts and coarse peloids the well bedded intermound fine facies is bituminous and micritic while the intermound coarse facies is composed of skeletal peloidal intraclast grainstones which locally contain calcified algae although the fauna is diverse the density of colonization by metazoans was low and the supply of macrofossil debris modest the clotted micrite texture is interpreted as the product of micro organisms which precipitated and trapped fine grained sediment the mud mound complex is dominated by the bathymetric assemblages b and c proposed by lees hallet hibo which on their model of the belgian waulsortian indicate depths of between 220 and 280 m intercalation of assemblages b c and c d on the northern margin of the complex is interpreted as the result of local storm disturbance a deep water drift is postulated to explain the nw se alignment of the complex which probably fitted the export model of bosence rowlands quine beneath the sediment surface phreatic flow eroded unlithified sediments and developed interconnected cavities which were filled by cement and sediment relatively eariy mound instability triggered the opening of fissures which filled with crinoid debris peloids indurated lithoclasts and micrite

genesis of stromatactis cavities between submarine crusts in palaeozoic carbonate mud buildups it is concluded that the sedimentary structure stromatactis is a calcite cement fill of a swarm of labyrinthine cavities developed in marine carbonate muds of palaeozoic bioherms commonly with geopetal sediment field and petrographic evidence is examined from the ordovician of dalarna sweden the devonian of the canning basin australia and of belgium and the carboniferous of lancashire u k in all four occurrences the host microspar encloses masses of radiaxial fibrous calcite with sub horizontal floors following other workers radiaxial fibrous calcite is regarded as an altered marine cement a conclusion supported by the presence of overlying geopetal sediments with marine fossils widespread evidence of early submarine cementation in palaeozoic mud mounds isotopic analyses and the presence of microdolomites the stromatactis masses are separated from each other by laminae of host biomicrospar which show discontinuities resembling fractures which are healed with the early marine cement or filled with marine internal sediments the fractures are therefore of submarine origin the evidence points to episodic submarine lithification of the carbonate muds yielding successive crusts between which cavities were eroded and then filled the crusts were broken and rotated during bioturbation differential compaction or shearing during burial

the role of internal erosion and sedimentation in the formation of stromatactis mudstones and associated lithologies abstract a distinctive suite of lithologies occurs in the lower devonian rocky camp mound of eastern victoria lime mudstones contain abundant stromatactis cavities and wackestones contain shelter cavities beneath skeletal constituents together with unsheltered stromatactis cavities irregularly distributed muddy masses occur in grain supported lithologies together with abundant shelter cavities and perched internal sediment these lithologies are completely intergradational and clast content is the principal variant controlling the fabric developed it is proposed that the fabrics in this lithological suite resulted from a process of internal erosion and sedimentation internal reworking which occurred directly below the sediment water interface each stromatactis cavity was subject to erosion of carbonate mud from the roof and redeposition of this material on the floor either directly below the point of erosion or downstream from it in this way cavities migrated upwards leaving a trail of internal sediment beneath in wackestones the migrating cavities were trapped beneath skeletal constituents forming diagenetic shelter cavities the fabrics of grain supported lithologies can be similarly explained a precursor cavity system of organic or inorganic origin is required to initiate the process of internal erosion there is no evidence relating to the origin of this cavity system in the rocky camp mound

why is stromatactis so rare in mesozoic carbonate mud mounds the sedimentary diagenetic structure stromatactis is widespread in palaeozoic spiculitic carbonate mud mounds but occurs only sporadically in mesozoic sponge carbonate mud mounds comparative analysis of palaeozoic and mesozoic stromatactis limestones suggests that this variation results from the degree of siliceous sponge skeletal rigidity and the amount of internal sediment accumulation in the original cavity network partial to entire filling by internal sediment resulted in a continuum from a small amount of internal sediment and large amount of cement stromatactis common in the palaeozoic to only internal sediments aborted stromatactis common in the mesozoic these observations match independent lines of evidence concerning the siliceous sponge evolution and sediment recycling e g bioerosion across the palaeozoic to mesozoic biotic revolution

climatic and oceanographic isotopic signals from the carbonate rock record and their preservation stable isotopic data from marine limestones and their constituent fossils and marine cements can provide quantitative evidence for changes in global climate and ocean circulation oxygen isotopic data can indicate changes in temperature and ocean composition whereas stratigraphic variation in carbon isotope ratios may reflect changes in the carbon cycle that can be linked to changes in oceanic productivity and atmospheric greenhouse gases terrestrial carbonates meteoric cements calcretes and speleothems similarly offer significant potential for understanding the evolution of terrestrial climates by providing evidence for the composition of rainwater and the nature of vegetative cover primary environmental isotopic signals may be obscured by the effects of post depositional diagenetic alteration cementation and replacement reactions can take place in a wide range of diagenetic environments the diagenetic history of an individual limestone is determined by a combination of its mineralogical diagenetic potential and depositional setting together with subsequent changes in relative sea level and burial history carbon isotopic values are less prone to alteration during diagenesis than oxygen values but shifts can be significant where organogenic carbon is incorporated linear covariation of carbon and oxygen values is not a reliable indicator of diagenetic alteration water rock interaction and fluid mixing may produce non linear distributions attempts to determine long term changes in climatic and oceanographie conditions through isotope stratigraphy of shallow water limestones must include an assessment of the diagenetic history of the materials analysed petrographic examination using conventional microscopy backed up where appropriate by cathodoluminescence and scanning electron microscopy together with elemental and strontium isotopic analysis can help to identify the effects of diagenetic alteration where material with a range of different degrees of alteration is preserved in the same sediment it may be possible to compare patterns of isotopic and elemental variation and to attempt to unravel the effects of diagenesis in order to determine primary environmental isotopic signals recent research has shown that these techniques can be successfully employed in both phanerozoic and precambrian sediments

genesis and geometry of the meiklejohn peak lime mud mound bare mountain quadrangle nevada usa ordovician limestone with submarine frost heave structures a possible response to gas clathrate hydrate evolution abstract during the early middle ordovician early whiterockian the meiklejohn peak lime mud mound a large whaleback or dolphin back dome grew on a carbonate ramp tens to hundreds of kilometres offshore this ramp extended from the northwest margin of laurentia into the open waters of the ancestral pacific ocean to the north the mound developed in an outer ramp environment in relatively deep and cold water a steep northern margin with a slope that exceeds 55 characterizes the mound this margin is split by a 14 m long vertical fracture that separates a zone of slumped drag folded and brecciated rocks from the main mass of the mound failure along this fracture occurred subcutaneously as highlighted by covering beds that are folded next to the mound brecciated blocks and clasts contain zebra and stromatactis structures indicating that these rocks and structures were lithified early in the history of the mound the southern end of the mound is less steep and is characterized by large echinodermal grainstone cross beds these deposits are part of a large subaqueous dune that grew northwards and preceded the main development of the mound southward dipping and downlapping layers of mud mound mudstone and wackestone overlie the dune these muddy limestone layers are cut in several places by injection dykes and are pierced near the contact with the underlying dune by a 25 m long pipe filled with rotated nodular and brecciated mud mound clasts this long pipe extends to the edge of the mound and appears to have been a conduit where fluidized materials that came from the mound s interior were vented the interior of the mound is typified by light grey limestone with zebra bands and stromatactis structures both structures represent former cavity systems that are filled with fibrous and bladed calcite and pelleted and laminated geopetal mudstone spar bands of zebra limestone often extend for several metres and appear to have been unsupported over these distances zebra banded rocks are also accompanied by snout and socket structures and in some instances are folded and sheared by curving kink bands zebra and stromatactis limestone structures found throughout the mud mound resemble frost heave and cryoturbation structures identified in both holocene and pleistocene cryosols and in laboratory experiments with advancing freezing fronts in clay size sediment significantly modern occurrences of methane clathrate hydrate methane charged ice display parallel and digitate layering similar in depositional appearance to that of zebra and stromatactis limestone from meiklejohn peak early carbonate cements are also commonly associated with these modern clathrate hydrate deposits consequently gas clathrate hydrates may have been the propping agent for zebra and stromatactis structures observed in the mud mound in this scenario carbonate cements would have precipitated and stabilized these structures both with the consolidation and dissociation of gas clathrate hydrates and with the oxidation and reduction of associated gases stable 13 c and 18 o isotope ratios collected from mudstone and spar of zebra and stromatactis structures indicate that they were lithified in equilibrium with ordovician seawater the 13 c isotope ratios recorded at meiklejohn peak are similar to 13 c isotopic ratios obtained from co 2 evolving from modern seafloor these isotopic ratios may indicate that frost heave structures in the meiklejohn peak mud mound are the result of consolidation and dissociation of carbon dioxide clathrate hydrates even though the bulk of gas clathrate hydrates identified to date in modern ocean floors are composed of methane carbon dioxide clathrate hydrates are known from the modern seafloor of the okinawa trough they may also be common in areas of abundant carbonate sediment accumulation as suggested by recent observations from the great australian bight

degradative calcification of a modern siliceous sponge from the great bahama bank the bahamas a guide for interpretation of ancient sponge bearing limestones abstract organic colloids are involved in the early calcification of the modern siliceous sponge spheciospongia vesparium lamarck 1815 from the great bahama bank electron microscopy and in situ fluorescence microspectometry studies indicate that colloids attached within or onto a collagen network promote the precipitation of aragonite crystals in these sponges calcification occurs within those portions of the sponge that are buried in the sediment preferentially in regions of agglutinated sediment particles with sponge connective tissue being subjected to necrosis and significant degradation of the extracellular collagen matrix the dismantling of collagen bundles leads to collagen scaffolds which act as a sorbent and have significant adhesive effects for ions and or organic colloids bacteria and other microorganisms support tissue degradation but neither act as a substrate for aragonite precipitation or are present in significant numbers at calcification sites this process of early calcification may explain the origin of fossil calcified siliceous sponges sponge mummies and tuberoids as well as the occurrence of patchy calcified sponge materials thereby calling into question the commonly accepted idea that pelletoidal texture associated with these fossil sponges indicates that bacteria are directly responsible for the calcification

diagenesis of middle devonian carbonate mounds of the mader basin eastern anti atlas morocco abstract in the mader basin of the eastern anti atlas middle devonian carbonate mounds were established on a gently sloping ramp at moderate water depths primary stromatactis cavities in these mounds exhibit early marine shallow burial and deeper burial cementation the mound matrix was affected by neomorphic alteration stylolitization and dolomitization earliest cementation occurred in the marine environment nonluminescent to blotchy luminescent cloudy radiaxial calcites of originally high mg calcite composition coat the walls of stromatactis cavities and take up more than 50 of the primary pore space the isotopic signature d18o 2 6 0 2 pdb d13c 2 7 0 5 pdb is close to that of nonluminescent fabric retentive brachiopod shells in the same mounds and taken as the nearly pristine stable isotopic signature of mader basin seawater the high d18o values compared with middle devonian data of north america are interpreted to result from the mid latitudinal ca 35 s temperate water settings of the mader basin carbonate mounds the transition to the shallow burial realm is indicated by a typical non bright dull luminescence sequence nonluminescent scalenohedral cements pass into bright luminescent and banded luminescent scalenohedral cements which are overgrown in turn by dull to moderate luminescent blocky spar meteoric influence on that cement sequence can be excluded deeper burial diagenesis is represented by stylolitization ferroan calcite cementation and neomorphic alteration of the fine grained mound carbonates pressure solution and or outgassing of co2 are possible ion sources for ferroan calcite precipitation in the remaining pore space 18o depletion d18o 6 8 to 8 9 pdb of these cements can be calculated to elevated precipitation temperatures of 21 33 5 c and burial depths of 420 670 m microspar making up the bulk of the mounds was formed by a one step transformation of a precursor calcitic micrite low d18o values 6 9 p 2 1 pdb mottled luminescence and high fe concentrations indicate that this transformation also took place in the deeper burial realm

mesozoic lower jurassic red stromatactis limestones from the southern alps arzo switzerland calcite mineral authigenesis and syneresis type deformation the broccatello lithological unit lower jurassic hettangian to lower parts of upper sinemurian near the village of arzo southern alps southern switzerland is a mound shaped carbonate deposit that contains patches of red stromatactis limestone within the largely bioclastic broccatello unit the stromatactis limestone is distinguished by its early diagenetic cavity system a relatively fine grained texture and an in situ assemblage of calcified siliceous sponges various demosponges and hexactinellids a complex shallow subsurface diagenetic pathway can be reconstructed from sediment petrography in combination with comparative geochemical analysis carbon and oxygen isotopes trace and rare earth elements ree y this pathway includes organic matter transformation aragonite and skeletal opal dissolution patchy calcification and lithification sediment shrinkage sagging and collapse partial ree remobilization and multiple sediment infiltration these processes occurred under normal marine essentially oxic conditions and were independent from local recurring syn sedimentary faulting it is concluded that the stromatactis results from a combination of calcite mineral authigenesis and syneresis type deformation the natural stromatactis phenomenon may thus be best explained by maturation processes of particulate polymer gels expected to form in fine grained carbonate sediments in the shallow subsurface conditions favorable for the evolution of stromatactis appear to be particularly frequent during drowning of tropical or subtropical carbonate platforms