fluid flow and late diagenesis of fault infill carbonates in the aptian dolostones at jabel semmama kasserine area western central tunisia abstract in western central tunisia kasserine area dolomitization of jabel semmama aptian limestones of the serj formation fm led to the dolostones of the orbata fm these dolostones are cross cut by several generations of faulting and fracturing the current study focused on e w trending faults and fractures system incorporating carbonate infills and freshwater flows which have stimulated continental diagenetic processes the faulting fracturing and rock fluid interactions yielded nine fault infill diagenetic and tectonic sedimentary phases the purpose of studying the tectonic stresses and the nine phases was to elucidate their late impact on the aptian dolostone reservoir quality this enquiry was based on lithological tectonic microfacies and oxygen carbon o c isotopes investigations analyses of stable o c isotopes are performed on crushed and dedolomitized dolostones as well as on calcite cement laminae and spherulites c1 c2 the crushed and dedolomitized dolostones 18o and 13c data averages 4 0 v pdb 1 75 v pdb remain close to the moderately depleted results of the aptian replacive dolostone host rocks averages 3 6 v pdb 2 0 v pdb inversely calcite cement laminae and spherulites c1 c2 yielded strikingly depleted oxygen values 18o averages 7 77 v pdb 8 0 v pdb pointing out to freshwater controlled diagenesis the discrepancy between the two records 0 23 v pdb is ascribed to cooling during the precipitation of calcitic cement spherulites the divergence between the two depleted 13c values of the two cements c1 c2 averages 6 19 v pdb and 4 0 v pdb is attributed to climatic control wet dry alternations that controlled the micritization phenomenon the latter orchestered the release of ca12co3 being more mobile than ca13co3 this process is in agreement with the strong variation of fluid flow supplies vadose phreatic transcribed in the lithology as cement phases lamellar spherulites gelatinous vadose and granular the study series record two major climatic changes a wet period encompassing phases p1 p4 and a dry period extending on phases p5 p9 two short cool and wet episodes accompany this period the nine tectonic sedimentary and diagenetic phases occurred into two periods through the telogenetic stage uplift they started at the miocene pliocene during the atlasic foldings along e w faults and fractures phases p1 p6 and continued throughout the quaternary period villafranchian along a reactivation of the same direction phases p7 p9 we believe that the nine phases arose after the oae s organic matter maturity and thus had nearly no impact on any early oil migration while the earlier diagenesis phases remain the most useful for the reservoir quality

paleogeographic and sedimentary evolution of the south pyrenean foreland basin abstract during the paleogene and neogene the ne iberian plate underwent significant paleogeographic changes driven by the iberian and european plate collision and the resulting formation of the pyrenean orogen and its corresponding foreland basin shortening resulted in the advance of the orogenic wedge emplacement of allochthonous units and progressive basin partitioning sediment transfer systems reacted to the evolving paleogeographic scenario shifting from forebulge to foredeep and wedge top settings critical reorganizations included successive shifts from open to close drainage conditions which had an strong impact on accommodation and the stratigraphic architecture of the basin infill overfill and later erosion the aim of this work is to synthesize the paleogeographic and sedimentary evolution of the south pyrenean foreland with emphasis on the reconstruction of sediment routing the evaluation of sedimentation rate trends the timing of sedimentary shifts and the analysis of their causes stratigraphic data are compiled in a comprehensive magnetostratigraphy based chronostratigraphic framework besides sedimentary and structural data are put together to produce a series of palinspastically restored paleogeographic maps which reflect five key stages in the evolution of the region these stages include 1 the late cretaceous tectonic inversion of the extended iberian margin 2 the early eocene formation of the southern pyrenean foredeep 3 the middle eocene widening and overfilling 4 the late eocene shift into an internal drainage and 5 the late miocene drainage opening and erosion in the light of these results the variable role of tectonics climate and eustacy at different time scales are discussed

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

dolomitization of the latemar platform fluid flow and dolomite evolution abstract the anisian ladinian latemar platform northern italy presents a spectacularly exposed outcrop analogue for dolomitized carbonate reservoirs in relation to fracture controlled igneous intrusions although the latemar is one of the best studied carbonate platforms worldwide timing and evolution of dolomitization and the link to fractures and dikes have not been explored in detail previous dolomite observations are based on a stratigraphically limited portion of the platform this study extends observations to the complete exposed interval in which dolomite bodies occur including those within the less accessible valsorda valley numerous parallel mafic dikes crosscut the latemar platform and border several of its large dolomite bodies 50 m wide 100 m high within dikes and along dike carbonate contacts there are abundant dolomite veins that are geochemically related to surrounding dolomite bodies dolomitization is the result of limestone interaction with hydrothermal fluids delivered along these dikes at dike boundaries impermeable marble aureoles exist derived from contact metamorphism the marble aureoles have locally shielded surrounding limestone from dolomitizing fluid dolomite occurs only where the protective marble is missing or crosscut by fractures based on geometric relationships we conclude that dikes and their damage zones formed the pathways for the dolomitizing fluids and functioned as boundaries for dolomite bodies from field observations and petrography we established a detailed paragenesis dolomitization started shortly after dike emplacement there is an evolution in the fe content of matrix dolomite and dolomite veins from highly ferroan dolomite to non ferroan saddle dolomite alternating with episodes of silica cementation non ferroan calcite precipitation followed dolomitization possibly indicating concurrent depletion in mg this stage likely resulted in further limestone recrystallization rather than dolomitization stable and radiogenic isotopes suggest that the dolomitizing fluid comprised carnian seawater with elevated fe and mg from interaction with other lithologies possibly the nearby predazzo intrusion

climate and bioproductivity control on carbonate turbidite sedimentation paleocene to earliest eocene gulf of biscay zumaia spain abstract the paleocene to lowermost eocene zumaia series situated along the basque coast northern spain consists of pelagic limestones and marlstones with interbedded mixed calcarenite turbidites we have compared the composition and frequency of turbidite beds in time as well as the clay mineral and bulk rock carbon isotope composition of the pelagic beds to discern the factors controlling turbidite deposition the pelagic beds are coccolithic mudstones with mainly planktic foraminifera the sources of detrital material to turbidites were the carbonate producing shelves bearing foramol associations around the evolving bay of biscay and to a minor extent the incipient pyrenean chain for siliciclastic components we have found close relationships between variations of turbidite facies and depositional rates with clay mineral assemblages and carbon isotopes in the pelagic beds the latter are in line with global trends it appears that in the early bay of biscay climate and nutrient availability controlled turbidite sedimentation the bulk rock late paleocene np 5 np 9 positive carbon isotope excursion coincides with a period of relatively cool and dry climate characterized by the highest frequency of turbidity flow we propose that during this period globally enhanced latitudinal temperature gradients and strong thermohaline ocean circulation increased bioproductivity in surface waters by upwelling and or by wind driven ekman pumping in contrast warm perennially wet periods such as the early paleocene np 1 np 4 and the paleocene eocene transition upper np 9 np 10 are characterized by low frequency of turbidity flow in the basin this may have been caused by sluggish thermohaline circulation and low carbonate productivity during this time period

influence of climate and dolomite composition on dedolomitization insights from a multi proxy study in the central oman mountains abstract dedolomitization is an important diagenetic process that can yield information on the history of paleo fluids in a given aquifer or outcrop and by extension it offers a window into past hydrologic conditions dedolomitization is also relevant economically as it can alter the porosity and permeability of carbonates thus affecting reservoir quality despite considerable research the process of dedolomitization is still not entirely understood here new findings from the central oman mountains highlight the importance of dolomite chemistry and fluctuating climate on dedolomitization petrographic mineralogical and geochemical data from both altered and pristine dolomite hosted in jurassic carbonate rocks from the sahtan group and outcropping at wadi mistal in the jebel akhdar tectonic window reveal two dolomite bodies with different characteristics stratabound and fault related dolostone the ferroan dolomite crystals are larger in the fault related dolostone whereas the non ferroan dolomite crystals are smaller in the stratabound dolostone petrography reveals a complex suite of alteration textures including pristine dolomite recrystallized dolomite and calcitized dolomite dedolomite iron oxides are present pervasively in the altered rocks and different alteration textures co occur in the same sample relative to unaltered dolomite in this outcrop the recrystallized dolomite is characterized by similar positive carbon isotope values but less negative oxygen isotope values and the calcitized dolomite is characterized by even less negative oxygen isotope values and more negative carbon isotope values based on field data and petrography two phases of alteration are evident an earlier dedolomitization event affecting the stratabound dolomite only and a more pervasive pleistocene holocene alteration phase associated with surface weathering that affected both the fault related dolomite and to a lesser extent the stratabound dolomite stable isotope results further suggest that the more recent subaerial weathering phase happened under two alternating climate regimes dedolomitization was triggered by meteoric fluids that interacted with soil related carbon during humid climatic period s whereas recrystallization of ferroan fault related dolomite happened during more arid climatic period s with less developed soils and lower fluid rock interaction these results suggest that weathering of ferroan fault related dolomite can lead to formation of goethite and recrystallized non stoichiometric dolomite with a reset stable oxygen isotope signature and sometimes to dedolomitization

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

paleomagnetic and petrographic investigation of the taum sauk limestone southeast missouri paleomagnetic results from 17 sites in one quarry of the cambrian dresbachian stage taum sauk limestone member bonneterre formation reveal two components of magnetization on the basis of thermal demagnetization coercivity spectrum analysis and petrographic evidence both components reside in hematite sites can be divided into three groups based on behavior during thermal demagnetization and petrographic criteria the first group consists of massive pink limestones and contains a component with declination 270 inclination 11 corresponding to a cambrian pole at 175 6 e 3 6 s the second group of sampling sites consists of specimens with numerous burrows filled with hematite intergrown with calcite the sites are dominated by the second component of magnetization which has declination 147 and inclination 10 and corresponds to a reversed pole position at 133 1 e 37 3 n a significant fraction of this component which is interpreted to be carboniferous in age resides in hematite intergrown with calcite in the burrows petrographic relationships indicate that the calcite and hematite were acquired before dolomite which places a maximum age on dolomitization the third group consists of massive pink limestones with variable amounts of burrowing and contains both directions of magnetization in roughly equal proportions with closely overlapping blocking temperature spectra the presence of two stable directions of magnetization from one location with neither being dominant or even present throughout the quarry indicates the significant effect that diagenetic and sedimentologic processes may have on the magnetization of sedimentary units

petrography geochemistry and origin of burial diagenetic facies siluro devonian helderberg group carbonate rocks central appalachians petrographic and geochemical studies of pore filling cements and replacement products in the helderberg group upper silurian lower devonian central appalachians document the diagenetic history of these rocks shallow ramp skeletal limestones and buildups were partially lithified by marine cements however most pore filling cement formed under shallow 300 m to deep burial 300 4 000 m conditions regional cathodoluminescent zonation patterns in early calcite cements indicate meteoric ground waters were involved in shallow burial cementation early zoned calcite cements consist of updip nonluminescent cements with thin luminescent laminae in limestone or sandstone that pass downdip into subzoned dull cements interlayered bright and dull laminae and then into nonzoned dull cement in basinward limestone the regional distribution stable isotopic compositions and timing of early zoned cements relative to other diagenetic events suggest that all of the early cements formed synchronously from meteoric ground waters that became progressively more reducing as they flowed downdip at least 150 km helderberg sandstone tongues probably were preferential conduits for meteoric gro nd waters because early calcite cements formed only on scattered skeletal grains in sandstones late void filling dull cement formed from deep burial pore fluids at burial depths of 300 to 4 000 m deep burial pore fluids were dilute to saline na ca cl brines from primary fluid inclusion data with stable isotopic compositions that probably were similar to isotopic compositions of formation waters from modern oil fields void filling dull calcite cements occluded nearly all remaining porosity before late paleozoic fracturing and deformation latest diagenetic phases include dolomite fluorite silica and fracture filling dull calcite this study shows that integrated petrographic and geochemical approaches to diagenetic studies are useful for relating various diagenetic phases and fabrics to burial history and paleoaquifer distribution

late miocene sedimentary architecture of the ebro continental margin western mediterranean implications to the messinian salinity crisis the messinian salinity crisis msc resulted from a significant multi phase drop and subsequent reflooding of the mediterranean sea from 5 96 to 5 33 ma well developed drainage networks characterized by step like profiles and abrasion platforms are associated to this event the ebro continental margin western mediterranean presents an additional complexity since the capture of the drainage of the adjacent subaerial ebro basin took place sometime prior to the messinian stage using 3d seismic reflection data this work provides new insights into the origin of the step like profile of the messinian erosional surface mes and timing of the capture of the subaerial ebro basin the results obtained indicate a sedimentary active continental slope and delta progradation during middle late miocene in a normal regressive context associated to a pre messinian proto ebro river the mature development attained by the messinian ebro river network during the msc corroborates that the capture of the ebro basin occurred prior to the msc the configuration of the clinoforms below the mes suggests that deltaic sediments of the messinian paleo ebro river deposited during the tortonian and initial messinian sea level drawdown the mes formed at the top of the tortonian highstand where a fluvial network was deeply carved and in the topset region of the messinian falling stage systems tract where minor erosion occurred fluvial deposits are outstandingly preserved on the main valleys of the mes therefore the step like profile of the mes was not created during zanclean inundation but during the latest stages of the main messinian sea level fall and lowstand

did the european dinosaurs disappear before the k t event magnetostratigraphic evidence abstract debate on the non catastrophic or catastrophic extinction of the dinosaurs by an asteroid impact k t event remains a controversy and is mainly based on the interpretation of the sedimentary continental sequences in the north american western interior the global aspect of this event needs to be tested in sedimentary record from all continents where continuous terrestrial deposits through the cretaceous paleogene are well preserved in the western mediterranean realm recognition of the cretaceous paleogene boundary is limited by the lack of biostratigraphic data in the upper cretaceous lower tertiary continental sedimentary sequences new magnetostratigraphic results were obtained from the analysis of two sections in southern france and compared to previous results in northern spain the last occurrence of in situ dinosaurs eggshells the only dinosaur remains found is located in chron 30n southeast france or 31n southwest france and northern spain this last occurrence could demonstrate that the extinction of the european dinosaurs occurred prior to the cretaceous paleogene boundary and would therefore support the idea of a gradual or stepwise extinction unlinked to the k t event

retro wedge foreland basin evolution along the ecors line eastern pyrenees france the eastern aquitaine basin and north pyrenean zone show many characteristics of retro wedge models however they differ significantly in that slow subsidence and low deformation continued throughout orogenesis so that growth and steady state phases cannot be distinguished we show that the eastern pyrenees record two clear phases of convergence and probably never attained steady state analysis of the aquitaine retro foreland basin along the ariege ecors deep seismic line eastern french pyrenees integrates a new litho and chronostratigraphy subsidence analysis low temperature thermochronology data new interpretations of seismic lines and a balanced cross section within an overall regression two shallowing up cycles latest santonian danian thanetian oligocene record slow tectonic subsidence of the eastern aquitaine basin separated by a quiet period continuing thick skinned shortening was low to moderate the early marine basin generated by loading of the weak extended margin was supplied axially from an unknown eastern edifice while the young pyrenean orogeny to the south remained submerged during the quiet period of ultra slow subsidence no basin migration and negligible sediment supply continental conditions characterized the eastern orogen the second marine transgression was quickly followed by continental conditions the basin was supplied by the now emerging pyrenean orogen and continued to subside until miocene time

dolomite carbonate replacement textures in veins cutting carboniferous rocks in east fife abstract carbonate veins cutting carboniferous sediments in fife scotland contain three apparently paragenetically equivalent types of ferroan dolomite all of which show somewhat unusual fabrics the most spectacular of these are fence textured crystals comprising an open rhombic network of inclusion rich dolomite which is partially filled by later syntaxial inclusion free ankerite the more common paragenetic equivalents to the fence textured dolomite are dolomite filled rhombic moulds and two dolomite intergrowth fabrics all three fabrics appear to indicate dolomite replacement of a rhombohedral carbonate precursor and seem to reflect different degrees of development in a common sequence of events 1 precipitation of a metastable phase 2 precipitation of dolomite 3 precipitation of dolomite coupled with dissolution of the metastable phase neomorphism 4 dissolution of the metastable phase this progression is compatible with gradual cooling within a series of hydrothermal systems centred on adjacent namurian volcanics and the range of fabrics developed by the dolomite may reflect differential cooling in different parts of these hydrothermal systems the ankerite which partially fills the fence texture and the rhombic moulds also occurs in veins cutting stephanian rocks indicating a much later origin

pore pressure distribution along plate interface that causes a shallow asperity of the 2011 great tohoku oki earthquake 1 kato and yoshida 2011 conducted a numerical simulation for understanding the mechanics of the 2011 tohoku oki earthquake in this model a strong asperity with higher effective normal stress was assumed at a shallower part of the plate interface this shallow strong asperity controls the occurrence cycle of great earthquakes the present paper discusses pore pressure distribution along the interface at the pacific plate subducting beneath northern honshu tohoku japan assuming that the permeability is exponentially dependent on effective stress and that the proportional constant drops to a lower value at a critical effective stress due to pore collapse we obtained nearly hydrostatic pore pressure at a shallow part and nearly lithostatic pressure at a deep part of the plate interface assuming a different permeability model in which increase of confining pressure has a larger effect than decrease of pore pressure we obtained similar results such pore pressure distributions provide a possible generation mechanism for a shallow strong asperity

dolomite calcitization and cement zonation related to uplift of the raisby formation zechstein carbonate northeast england abstract the raisby formation is the basal zechstein carbonate of northeast england it has undergone a complex diagenetic history during burial including multiphase dolomitization and replacement by sulphates upon uplift meteoric derived fluids have dissolved this replacive sulphate and precipitated calcite cements in the resultant porosity study of these cements by cathodoluminescence and trace element geochemistry shows that they are zoned and different cathodoluminescence zones correlate well with iron and manganese geochemical changes demonstrating a gradual increase in oxygenation of the precipitating fluids through time major diagenetic processes during cement growth include precipitation of anhydrite fluorite and barite calcitization of dolomite and internal sedimentation relating these processes to cement zonation allows this complex diagenesis to be explained in terms of uplift under the influence of meteoric derived groundwaters of constantly changing geochemical and electrochemical characteristics

a siliciclastic braid delta within a lower paleogene carbonate platform ordesa monte perdido national park southern pyrenees spain record of the paleocene eocene thermal maximum perturbation abstract the la pardina formation is a siliciclastic dominated unit up to 26 m thick intercalated within a 300 m thick danian lower ilerdian succession of shallow marine carbonates in the southern pyrenees the unit is composed of four interdigitated facies three of them of a coarse grained siliciclastic character sf1 sf2 sf3 and the fourth one composed of bioclastic packstones with argillaceous matrix calcareous facies cf the siliciclastic facies make up the bulk of the la pardina formation in the ordesa monte perdido national park while the cf is subordinate in the park but widespread throughout the southern pyrenees biostratigraphic and isotopic data suggest that the cf pertains to the paleocene eocene thermal maximum petm no isotopic or biostratigraphic information could be obtained from the siliciclastic facies but they are also assigned to the petm because of their interfingering with the cf the siliciclastic facies were accumulated in a braid delta system fed by either a major river or by several minor rivers draining the ebro massif the sf3 sf2 and sf1 respectively represent the top set foreset and bottomset parts of the braid delta whereas the cf correspond to the prodelta in proximal parts of the braid delta the sf3 overlies a subaerial surface carved into upper thanetian marine carbonates a proof of a pre petm sea level fall in the remainder of the braid delta the la pardina formation exhibits an overall thickening coarsening up trend that attests to rapid progradation the development of the braid delta implies a dramatic increase in the influx of both coarse and fine grained siliciclastics which temporarily halted a long lasting period of carbonate dominated sedimentation this abrupt change demonstrates that the environmental impact caused by the intensification of the hydrological cycle during the petm was particularly severe at middle latitudes

dedolomitization in the taum sauk limestone upper cambrian southeast missouri abstract coarse dolomite crystals in the taum sauk limestone upper cambrian southeast missouri contain both calcite and iron oxides in rhombohedral zones and along fractures and cleavage traces the dolomite crystals are demonstrably nonstoichiometric averaging 57 mole percent caco3 and are compositionally zoned ranging from 1 40 to 4 56 mole percent feco3 cathodoluminescene study and microprobe analyses of the dolomite coupled with scanning electron microscope sem examination of etched fracture surfaces reveal that 1 scattered dolomite within the calcite iron oxide zones is the most iron rich 2 calcite within dolomite rhombs is brightly luminescent nonferroan and is intergrown with iron oxides 3 the iron oxides display two crystal habits thin red hematite circular plates typically 0 7 to 1 0 microns across grouped in rosettes and prismatic bundles and prismatic radiating aggregates of brown crystals goethite typically 1 to 3 microns in length 4 narrow veinlets of dolomite associated with calcite and iron oxides along cleavage traces form a three dimensional network this feature which aided in interpreting the iagenetic history of the dolomite was not observed during petrographic examination but was readily observed with the sem the occurrence of nonferroan calcite and ferric oxides in rhombohedral zones in taum sauk dolomite suggests that dedolomitization occurred by the oxidation and alteration of ferroan dolomite zones and probably reflects alteration related to recent weathering

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

evidence for slowly changing 87sr86sr in runoff from freshwater limestones of southern france abstract 87 sr 86 sr ratios have been determined in modern rivers and freshwater limestones dating from 65 ma to the present over an area extending from the pyrenees to the massif central southern france about 40 ma ago the alpine mountain range of the pyrenees was strongly uplifted by the alpine orogenic activity and its pre hercynian basement dominated by schists gneisses and granites was rapidly exposed from beneath its blanket of mesozoic marine limestones meanwhile the 87 sr 86 sr ratio of the rivers has remained remarkably constant in both space with the exception of the very few northernmost samples and time in this area extreme variations through the orogenic period are small with 87 sr 86 sr lying between 0 7073 and 0 7084 at 55 65 ma and 0 7077 0 7096 for the last 30 ma river sr is controlled by a nearly binary mixing of silicate 3 4 and 1 4 end members with negligible influence of evaporites it is inferred that the silicate sediment contribution ratio of the world average rivers to seawater sr changes at a very slow rate even taking major basaltic events into account does not alter this conclusion as their contribution to the river sr is very subordinated to other components it is inferred that the seawater 87 sr 86 sr secular main trend over the phanerozoic is controlled by hydrothermal alteration of oceanic basalts and slow variation of the limestone silicate contribution ratio to the riverine sr oceanic events changes in organic productivity and carbonate compensation depth ccd may produce intense short term variations but recovery of steady state seawater 87 sr 86 sr is delayed by 40 80 ma through diagenetic sr remobilization in carbonate sediments

dedolomitization and calcite cementation in the middle devonian winnipegosis formation in central saskatchewan canada limestone consisting of finely to medium crystalline calcite mosaics is present in the upper part of the winnipegosis formation on the east central margin of the elk point basin where the overlying prairie evaporite deposits have been removed this type of crystalline limestone is interpreted as dedolomite based on petrographic observations the 18o and 13c values of the winnipegosis dedolomite vary from 12 8 to 11 9 vpdb vienna pee dee belemnite and from 0 5 to 1 7 vpdb respectively both values are significantly lower than those for the corresponding dolomite the 87sr 86sr ratios of the dedolomite are significantly higher between 0 7082 and 0 7087 the spatial distribution and geochemical data of the winnipegosis dedolomite suggest that dedolomitization was related to an influx of fresh groundwater and dissolution of the prairie evaporite anhydrite during the latest mississippian to the early cretaceous when the basin was subjected to uplift and erosion the winnipegosis dedolomite displays a series of replacement fabrics showing progressive calcitization of dolomite including the occurrence of dedolomite restricted along fractures and adjacent areas dolomite patches floating in the dedolomite masses and massive dedolomite with sparsely scattered dolomite relicts however the characteristic fabrics resulting from dedolomitization documented in the literature have not been observed in the winnipegosis dedolomite coarsely to very coarsely crystalline subhedral to euhedral calcite cement is restricted in the dedolomite the petrographic features isotopic compositions and homogenization temperatures coupled with the burial history of the winnipegosis formation constrain the precipitation of the calcite cement from a mixing of basinal brines and fresh groundwater during late cretaceous to neogene time the more negative c isotopic signatures of the calcite cement 5 3 to 2 3 vpdb probably reflect a hydrocarbon derived carbon

dedolomitization review and case study of uncommon mesogenetic formation conditions abstract dedolomitization converts a dolomite into a calcite and conventionally is interpreted to form in an eogenetic or telogenetic diagenetic environment where meteoric water dissolves evaporites to supply excess calcium hydrologic connectivity between a dolostone and the surface water may then lead to a dedolomitized interval often times being a diagnostic indicator for an erosional unconformity subaerial exposure and or karst in contrast to the classic models we present a case study for pervasive burial dedolomitization unrelated to meteoric fluids dedolomitization of the zechstein 2 carbonate ca2 gas reservoir in nw germany is strongly altering reservoir quality on a regional scale the ca2 shows a textbook correlation between reservoir quality and mineralogy petrographic analyses show that approximately 80 of all observed calcite reveal a dedolomite microtexture causing a reduction of average matrix porosity by 5 to 10 compared to the dolomite dedolomite follows initial layering and abundantly forms massive concretions which are surrounded by compaction related curvature of the depositional layering in the dolomite host rock such an early burial timing is supported by a slight burial related shift of 3 18o and 1 13c towards lighter values in the dedolomites compared to dolomite an exceptionally large amount of calcium rich fluids must have been mobilized to account for 50 of the ca2 rock volume to be dedolomitized however core fabrics related to meteoric diagenesis such as karst fabrics or typical fresh water stable isotope signatures have been observed neither in the ca2 nor in over and underlying anhydrite beds instead excess calcium likely comes from gypsum to anhydrite conversion and pressure solution within over and underlying anhydrites an influx of strontium rich waters from the anhydrite beds is indicated by up to 5 times higher strontium contents measured in dedolomite fabrics compared to their dolomite host rock homogenization temperatures between 51 and 56 c measured in some early fluid inclusions in dedolomite textures further exclude a pristine meteoric water input and suggest fluid entrapment in a burial depth range of 900 to 1400 m comparing these results with literature data furthermore indicates that mesogenetic dedolomite is either volumetrically underestimated in other carbonate evaporite settings or formed under unique diagenetic conditions across the southern permian basin during zechstein times

syntectonic burial and post tectonic exhumation of the southern pyrenees foreland fold thrust belt in the oligocene to earliest miocene the entire southern pyrenean foreland fold and thrust belt was backfilled and buried in up to 3 km of syntectonic continental conglomerates from the range9s own erosional debris then starting in the mid to late miocene the pyrenees were exhumed by erosional excavation to their present relief a model is proposed for this unusual development whereby late eocene oligocene tectonic uplift of the margins of the ebro basin raised local base level and blocked normal dispersal of erosional debris to adjacent oceans thus causing the basin to fill then backfill northwards across the entire southern flank of the pyrenees subsequent miocene rifting of the catalan mediterranean margin and the messinian salinity crisis lowered base level allowing the ebro river to cut headward capture the ebro basin and re excavate the pyrenees

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

micro sized dolomite inclusions in ferroan calcite cements developed during burial diagenesis of kimmeridgian reefs northern iberian basin spain burial diagenesis of the upper jurassic torrecilla reef complex is recorded by a complex paragenetic sequence initiated with emplacement of ferroan calcite cements and followed by the precipitation of ferroan saddle dolomite ferroan calcite cements contain micro sized dolomite inclusions mdis elemental and isotopic compositions of mdis are virtually indistinguishable from those of ferroan saddle dolomite cements in contrast to other scenarios for the formation of microdolomite inclusions that invoke either a magnesian calcite precursor or incomplete dedolomitization the paragenetic relations of mdis to their host ferroan calcite and their geochemical composition implies formation by fine scale burial replacement of ferroan calcite by fluids associated with the emplacement of ferroan saddle dolomite petrographic observations and mass balance considerations suggest that it is unlikely that fe and mg incorporated into ferroan dolomite could have been derived from the cannibalization of the reefal host rock rather dolomitizing fluids were likely associated with the hydrothermal low grade metamorphic event that affected the cameros basin during the middle to late cretaceous interaction of these fluids with preexisting burial cements produced mdis in the ferroan calcites

multistage dolomitization in the society cliffs formation northern baffin island northwest territories canada dolostones of the upper proterozoic society cliffs formation on northern baffin island are host to the nanisivik lead zinc sulfide deposits two distinct stages of dolomitization have occurred distinguished by their petrographic cathodoluminescence and isotopic characteristics 1 massive dolomitization of precursor carbonates and 2 late stage cementation sabkha facies of the lower member of the formation and laminated algal stromatolitic to massive dolostones of the upper member are isotopically similar 18o ranges from 1 5 to 6 5 13c from 1 7 to 3 1 pdb and 87sr 86sr averages 0 70761 petrographic and geochemical evidence indicates that these dolostones formed chiefly by seawater thermal convection beneath shale of the overlying victor bay formation although mixing of meteoric and marine water also could have occurred later fracture filling dolomitic cements have consistently lower 18o but 13c is similar to that in the host dolostones microtraverses of single fractures filled wit

petrographic fluid inclusion and isotopic study of the dikulushi cu ag deposit katanga d r c implications for exploration the dikulushi cu ag vein type deposit is located on the kundelungu plateau in the southeastern part of the democratic republic of congo d r c the kundelungu plateau is situated to the north of the lufilian arc that hosts the world class stratiform cu co deposits of the central african copperbelt a combined petrographic fluid inclusion and stable isotope study revealed that the mineralisation at dikulushi developed during two spatially and temporally distinct mineralising episodes an early cu pb zn fe mineralisation took place during the lufilian orogeny in a zone of crosscutting ew and ne oriented faults and consists of a sequence of sulphides that precipitated from moderate temperature saline h2o nacl cacl2 rich fluids these fluids interacted extensively with the country rocks sulphur was probably derived from thermochemical reduction of neoproterozoic seawater sulphate undeformed post orogenic cu ag mineralisation remobilised the upper part of the cu pb zn fe mineralisation in an oxidising environment along reactivated and newly formed ne oriented faults in the eastern part of the deposit this mineralisation is dominated by massive ag rich chalcocite that precipitated from low temperature h2o nacl kcl fluids generated by mixing of moderate and low saline fluids the same evolution in mineralisation assemblages and types of mineralising fluids is observed in three other cu deposits on the kundelungu plateau therefore the recognition of two distinct types of vein type mineralisation in the study area has a profound impact on the exploration in the kundelungu plateau region the identification of a cu ag type mineralisation at the surface could imply the presence of a cu pb zn fe mineralisation at depth

biostratigraphic and magnetostratigraphic intercalibration of latest cretaceous and paleocene depositional sequences from the deep water basque basin western pyrenees spain abstract latest cretaceous late maastrichtian and paleocene depositional sequences from the deep water basque basin have been calibrated with published 1 2 and newly acquired magnetostratigraphic data sequences mostly consist of hemipelagic marls and limestones and their relative ages are well constrained with planktic foraminifera they accumulated during a phase of tectonic tranquillity and reduced clastic input into the basin and therefore they can be attributed to eustatic sea level changes with reasonable confidence on the basis of the planktic foraminifera zonation a good match has been observed previously between the depositional sequences of the basque basin and specific sea level cycles of the 1988 version of the exxon global cycle chart gcc 3 here a new attempt at correlation using their respective magnetostratigraphic data has failed to confirm such a match the disagreements observed may indicate that for the studied interval 1 the current planktic foraminifera biostratigraphy lacks the necessary level of resolution to ensure synchrony between sequences of different basins and or 2 the magnetostratigraphy of the gcc needs to be revised whatever the case the new findings lend support for some criticism on the use of the gcc for interregional correlations

large scale facies change in the middle eocene south pyrenean foreland basin the role of tectonics and prelude to cenozoic ice ages abstract the present study reports a sedimentological analysis of the guara limestone formation deposited during the lutetian in the sierras exteriores in the south pyrenean foreland basin we provide a detailed facies analysis of the carbonates to precise the paleoenvironmental context during their deposition we show that those limestones are mainly composed of shallow water foraminifers and were deposited in relative shallow water environments

manganese deposits in a carboniferous paleokarst profile um bogma region west central sinai egypt the carboniferous carbonates of the um bogma formation of the west central sinai include two rock successions the lower succesion consists of karstic carbonates intrakarstic products weathering varieties manganese deposits and soil cover the lower karstic rocks and the associated soil cover are preserved under a rhythmic alternation of dolostone and shale forming the upper rock succession of the um bogma formation the all over congruent relations between the manganese deposits and the fossilized karst profile karst products and the associated pedogenesis demonstrate the role of weathering in the accumulation of these deposits during carboniferous karstification it is clear that the manganese oxides were deposited during the mature stage of carboniferous karstification i e during the soil formation preceeding initial diagenetic change of the karstic rocks and final deposition of the related late diagenetic caliche cement the geochemical behavior of mn during the karstification and the microbiological processes involved in pedogenesis played an essential role in the concentration of the manganese ore in the subsoil horizon of the paleokarst profile the um bogma formation has been subjected to another episode of karstification during the quaternary and resulted in lowering of the landforms of the carboniferous carbonates and destruction of the carboniferous karst and the associated manganese deposits in some localities

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