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

site amplification investigation in dhaka bangladesh using h v ratio of microtremor the degree of damage during earthquakes strongly depends on dynamic characteristics of buildings as well as amplification of seismic waves in soils among the other approaches microtremor is perhaps the easiest and cheapest way to understand the dynamic characteristics of soil non reference microtremor measurements have been carried out in 45 locations in and around the capital dhaka city of bangladesh subsoil investigations standard penetration test and shear wave velocity have also been executed in those locations soil model has been developed for those locations for site response analysis by means of the program shake among those 45 locations predominant frequency of microtremor observation varies from 0 48 to 3 65 hz out of those 45 for 35 locations transfer function obtained from the program shake have higher frequency compared to microtremor h v ratio and for one location it has lower predominant frequency for six locations frequencies obtained from two methods are identical for three other locations there are no similarities between predominant frequency obtained from microtremor and transfer function the seismic vulnerability index kg for 45 sites varies between 0 45 and 31 85 ten sites have been identified as having moderate vulnerability of soil layers to deform

paleoaquifer and deep burial related cements defined by regional cathodoluminescent patterns middle ordovician carbonates virginia middle ordovician ramp carbonates virginia were deposited in a subsiding foreland basin bordered on the southeast by tectonic highlands ramp carbonates were lithified in part by turbid marine cements but major cementation was by nonferroan clear rim and equant cements zoned defined by cathodoluminescence clear cements consist of nonluminescent oldest bright and dull youngest cements the zonation relates to increasingly reducing conditions of pore waters zoned cements in peritidal beds best developed in southeastern belts have complex zonations pendant to pore rimming fabrics and are associated with crystal silt which abuts all cement zones solutional cavities and erosional surfaces which locally truncate dull cement these cements are meteori vadose to shallow phreatic cements in northwestern exposures of peritidal beds are dominated by non zoned dull cement which lacks abundant evidence of early near surface precipitation major cementation of subtidal facies occurred under burial conditions burial cements best developed in southeastern belts have a simple zonation reflecting progressive burial up to 7 5 km 4 5 mi of the carbonate ramp shallow burial nonluminescent cement formed from oxidizing meteoric waters which expelled anoxic connate marine waters these meteoric waters were carried by aquifers from tectonic upland recharge areas on the southeastern basin margin bright cement formed under more reducing conditions following stagnation of the paleoaquifer with burial and possibly was precipitated at depths of 2 to 3 km 1 to 2 mi burial cements in northwestern exposures of subtidal beds are dominated by dull cement initial generations of which precipitated from downdip portions of aquif rs deeper burial dull calcite and ferroan dolomite cements largely formed at burial depths of 2 to 3 km 1 to 2 mi and temperatures of 75 to 135 c 165 to 275 f or more associated with hydrocarbon formation emplacement during the late devonian to mississippian latest clear dull cement fills tectonic fractures and was emplaced during late paleozoic alleghenian deformation probably at temperatures of 200 to 300 c 390 to 575 f and depths of 5 to 7 km 3 to 4 5 mi deeper burial diagenesis appears to be genetically linked to late paleozoic mississippi valley type mineralization in the southern appalachians zoned peritidal and burial cements are confined mainly to southeastern portions of the ramp where cementation was influenced by meteoric waters shed from tectonic uplands on the southeast and carried northwest by paleoaquifers northwestern portions of the ramp were influenced very little by upland sourced meteoric waters and nonzoned dull cements precipitated from relatively reducing waters the distribution of nonluminescent cement in middle ordovician subtidal facies defines the regional distribution of oxidizing portions of the paleoaquifer system such incursion of upland sourced oxidizing meteoric waters into ramp carbonates should be a common feature of foreland basin carbonates deposited adjacent to tectonic uplands furthermore foreland basin carbonates that undergo progressive burial should show a simple nonluminescent to bright to dull sequence of cement zones the close association of zoned cements and regional uplands in the middle ordovician sequence indicates the importance of assessing regional geologic relationships environmental parameters geologic history and tectonics in understanding regional cementation patterns and cementation processes of anci nt carbonate platforms

dissociation of oceanic methane hydrate as a cause of the carbon isotope excursion at the end of the paleocene isotopic records across the latest paleocene thermal maximum lptm indicate that bottom water temperature increased by more than 4 c during a brief time interval 104 years of the latest paleocene 55 6 ma there also was a coeval 2 to 3 excursion in the 13c of the ocean atmosphere inorganic carbon reservoir given the large mass of this reservoir a rapid 13c shift of this magnitude is difficult to explain within the context of conventional hypotheses for changing the mean carbon isotope composition of the ocean and atmosphere however a direct consequence of warming bottom water temperature from 11 to 15 c over 104 years would be a significant change in sediment thermal gradients and dissociation of oceanic ch4 hydrate at locations with intermediate water depths in terms of the present day oceanic ch4 hydrate reservoir thermal dissociation of oceanic ch4 hydrate during the lptm could have released greater than 1 1 to 2 1 1018 g of carbon with a 13c of approximately 60 the release and subsequent oxidation of this amount of carbon is sufficient to explain a 2 to 3 excursion in 13c across the lptm fate of ch4 in oceanic hydrates must be considered in developing models of the climatic and paleoceanographic regimes that operated during the lptm

shear wave velocity characteristics of geological units throughout tehran city iran abstract one simple way of accounting for site conditions in calculating seismic hazards is to use the shear wave velocity vs in the shallow subsurface to classify materials we used the average shear wave velocity to a depth of 30 m v s 30 to develop site categories for tehran this parameter can further be used for modifying a calculated ground motion to account for site conditions the national earthquake hazard reduction program nehrp classification was used to group sites into different classes our classification was based on v s 30 values measured in 188 seismic profiles and on the assumption of similar values for similar geological materials for each geological unit characteristics of shear wave velocity distribution including histograms of shear wave velocity and variation of vs versus depth were calculated and shown this study reveals that the v s 30 of the mountainous zones fall into categories a and b of nehrp site classification but in the tehran plain the northern alluvium tends to have v s 30 values which fall into range of category c of the nehrp site classification whereas those in the southern alluvium would be categorized as nehrp d

faulting associated with historical and recent earthquakes in the eastern mediterranean region summary this paper summarizes evidence for surface faulting in historical and recent earthquakes in the eastern mediterranean region and in the middle east such information is particularly important for studies of active tectonics and for palaeoseismology we have found 78 cases of faulting pre 1900 and 72 post 1900 some of which show that faults that have apparently been inactive this century had already ruptured before 1900 for some cases faulting could not have been predicted from 20th century activity and in others it could have been expected but has not been observed during the instrumental period the data are suycient to allow the derivation of relationships between magnitude and rupture length

diagenetic evolution of tortonian temperate carbonates close to evaporites in the granada basin se spain abstract the granada basin se spain is a small basin located in the central part of the betic cordillera structured as such in the late tortonian and initially connected to the atlantic ocean and to the mediterranean sea during the late tortonian normal marine conditions prevailed leading to the deposition of skeletal carbonate sediments on platforms around structural highs the marine connections were later interrupted first to the atlantic ocean and then to the mediterranean sea and a thick evaporite sequence marking the transition from marine to continental conditions was deposited during the latest tortonian in this work the diagenetic evolution of the tortonian temperate carbonates ttc underlying and close to the evaporite bodies is revealed and discussed the diagenetic study includes petrographic analyses conventional petrography cathodoluminescence and fluorescence geochemical analyses major minor and trace elements and 13c and 18o stable isotopes and microthermometry of fluid inclusions in the ttc marine diagenetic processes such as micritization and fibrous calcite cement precipitation and mechanical compaction took place during or just after deposition eogenesis an initial burial event mesogenesis 1 is characterized by 1 stabilization of the temperate water carbonates by freshwater and 2 porosity occlusion via precipitation of low mg bladed and syntaxial mosaic calcite cements the ttc were then subaerially exposed or got close to the surface during evaporite deposition and underwent pedogenesis mg smectite infiltration and pyrite formation telogenesis 1 subsequent brine related diagenetic alterations such as dolomitization and silica halite and sylvite replacements of carbonate grains occurred during a second burial episode mesogenesis 2 concomitant with the messinian lacustrine deposition this being followed by chemical compaction stylolite formation finally the area was uplifted and the ttc exhumed microstalactitic dripstone and fibre whisker calcite cement precipitation and extensive dissolution relate to this pliocene quaternary late event telogenesis 2 in the study case diagenetic history is closely linked to basin evolution as diagenetic pathways of carbonate rocks were related to major geodynamic events including basin restriction leading to evaporite deposition and several episodes of subsidence and uplift up to now only very few diagenetic studies have attempted to demonstrate this correlation between diagenetic history and basin evolution

multi risk interpretation of natural hazards for settlements of the hatay province in the east mediterranean region turkey using srtm dem many scientists have recently alarmed natural hazards due to global climate change such natural disasters are coastal inundation in response to sea level rise and or river flooding caused by heavy rain falls additionally earthquakes and etc in terms of natural hazards one of the most sensitive and culturally significant areas in turkey is the hatay province in the east mediterranean region the hatay province is located on such a region which is not only vulnerable to coastal inundation and river flooding but also is a tectonically and seismically sensitive area in this study for taking conservation measures against the natural hazards beforehand and decision making on any future land planning a digital terrain model and a 3d fly through model of the hatay province were generated then quantitatively and or qualitatively interpreted by employing the shuttle radar topographic mission digital elevation model besides stream drainage patterns lineaments and structural geological features were extracted for natural hazard risk interpretation of settlements and their relationships among the landscape characteristics were exhibited by combining tectonic information previously confirmed regarding the sea level rise the coastal inundation risk map indicates that the most vulnerable areas are coastlines of iskenderun arsuz payas and samandag respectively by after analyzing the digital terrain of the study region and stream drainage patterns the karasu valley zone where the amik plain settlements of antakya iskenderun arsuz payas and samandag with their flood plains have the most flooding risk in decreasing order respectively when a heavy raining occurs finally analysis of tectonics has revealed that antakya iskenderun hassa kirikhan samandag payas arsuz altinozu kumlu and hacipasa regions have the most sensitivity to earthquake disaster in the study region

graphic correlation in frontier petroleum provinces application to upper paleozoic sections in the tarim basin western china when they were graphically correlated against a composite standard database paleontologic data sets from the carboniferous and lower permian of the western tarim basin revealed a punctuated stratigraphic succession in which most of geologic time is contained within regional hiatuses up to 15 m y duration these hiatuses occur beneath rock packages of late bashkirian middle moscovian late moscovian early kasimovian late gzhelian early asselian and early sakmarian artinskian ages this interpretation differs from other views that hold that permian carboniferous deposition in the tarim basin was continuous or nearly continuous with only minor breaks the results suggest that late paleozoic sedimentation in the tarim basin was controlled primarily by local processes not by third order global sea level cycles 1 3 m y duration the graphic correlation technique is capable of superior biostratigraphic resolution because it uses the ranges of all fossils within a data set not just guide fossils or those associated with zonal definitions moreover a composite standard that is linearly calibrated to geologic time makes possible inferences regarding rates of rock accumulation within stratigraphic sequences and the durations of sequence bounding hiatuses the resulting chronostratigraphic framework enables and constrains sequence stratigraphic and seismic stratigraphic interpretations

derivation of the original isotopic composition of permian marine cements abstract diagenesis of former aragonite and magnesian calcite marine cements of the permian reef complex has resulted in a fine scale intermixture of two distinct secondary phases a luminescent and a nonluminescent calcite multiple carbon and oxygen isotopic analyses of these marine cements from any single sample result in a linear covariant trend reflecting random proportions of the two calcite phases contained in individual analyses the convergence of four trends derived from samples of former aragonite marine cement collected at four sites along a single upper capitan paleoslope fixes the isotopic composition of the nonluminescent calcite at a value of 2 518o 5 313c likewise covariant trends from former aragonite cements in the lower capitan and the youngest upper capitan yield nonluminescent calcite compositions of 2 818o 5 213c and 0 718o 5 813c respective y the single covariant trend generated from former magnesian calcite cements does not converge with equivalent former aragonite covariant trends indicating that the precursor mineralogy influences the isotopic composition of the nonluminescent calcite considered as a whole the invariance of the nonluminescent calcite signature the timing of luminescent calcite emplacement and the fine scale of the fabric retention suggest that the precipitation of the nonluminescent calcite occurred while isolated from effective isotopic exchange with external diagenetic fluids a direct consequence of this low water rock ratio closed system is that the isotopic signature of the nonluminescent calcite also represents the original isotopic composition of the marine cement this is further support d by the preservation of primary differences between the original isotopic compositions of aragonite and magnesian calcite cements the constancy of the marine isotopic signature throughout the reef massive and foreslope facies requires that the delaware basin water mass was relatively well mixed comparison of marine compositions throughout the range of the capitan samples indicates that although the oxygen composition of the marine cements was apparently constant through much of the guadalupian a substantial enrichment in 18o occurred at the very end of the guadalupian this relatively abrupt change recording a concomitant change in the oxygen composition of the delaware basin water mass was probably the result of increased restriction of the delaware basin and marked the first step in the sequence of events which led to the deposition of the deep basin evaporites of the castile formation

the east anatolian fault an oblique collisional belt abstract the tectonic setting for the area around the arabia africa anatolia triple junction is described from combined landsat spot satellite image analysis and field observations since the late miocene the motion along the east anatolian fault generated major structures corresponding to shortening with a sinistral slip component the 150 km wide area of the triple junction is highly deformed by folding and thrusting distributed mainly on the border of the anatolian block in addition kinematic reconstructions confirm that the arabia anatolia relative motion is both sinistral and convergent the sinistral strike slip faults of the east anatolian fault zone are of second order and local consequences of the n s arabia anatolia collision

the cooling history of connemara western ireland from k ar and rb sr age studies k ar age determinations are reported on 26 hornblendes 17 coexisting muscovites and biotites nine muscovites and nine biotites from the dalradian connemara schists metagabbros and gneisses these are supplemented by 19 rb sr whole rock mica ages and four 40 ar 39 ar incremental heating ages on micas a long at least 75 ma and complex cooling history without a simple pattern of ages has been obtained the ages are not correlated with the grain sizes or the chemical compositions of the analysed minerals or the topographic elevation from which the samples came but there is an irregular increase of hornblende k ar ages to 480 10 ma with increase of metamorphic grade southwards towards the metagabbros and gneiss the preservation of the complex cooling pattern is ascribed to the action of syn and post metamorphic slides or faults which moved slices of the massif upwards by varying amounts closely spaced samples give results which rule out simple tilting of the massif rapid cooling c 30 ma 1 at 480 10 ma arenig llanvirn during the f3 fold phase was followed by slower cooling until 455 10 ma caradoc when renewed rapid uplift occurred possibly correlated with the southward thrusting of connemara and with synchronous renewed uplift in the scottish dalradian rocks widespread biotite k ar and rb sr ages of 440 5 ma end ordovician throughout connemara and the dalradian rocks of scotland are ascribed to the major taconic tectonic event which docked the dalradian rocks against the flanking folded ordovician successions of the midland valley and the south mayo trough biotites giving k ar ages of about 415 ma may have been reset during the late silurian folding of the cover rocks the importance of very close sampling integrated with structural studies is emphasized

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

assessment of potential seismic hazard and site effect in antakya hatay province se turkey antakya city is at risk because of strong earthquakes occurring in the area and different soil conditions that can produce variation of the ground motion amplification microzonation of cities provides a basis for site specific hazard analysis in urban settlements in particular seismic microzonation can be provided by means of detailed seismic assessment of the area including earthquake recordings and geological studies in this paper we propose a preliminary microzonation map for the city of antakya based on the variation of the dominant periods and shear velocities of the sediments covering the area the periods are retrieved from microtremor measurements conducted at 69 sites using the horizontal to vertical spectral ratio technique the results of microtremor analysis were compared with data obtained from refraction microtremor remi measurements at four profiles crossing the studied area according to the classification of dominant periods antakya city can be divided into five zones probably prone to different levels of seismic hazard the shorter natural periods are in inner antakya and both the sides of asi river i e northern and southern parts the eastern and western parts of antakya have maximum dominant periods the vs30 values were calculated by using the remi method along the profiles antakya city has vs30 values in the range of category c of the national earthquake hazard reduction programme site classification

petrographic and geochemical constraints on the formation and diagenesis of anhydrite cements smackover sandstones gulf of mexico abstract anhydrite cement is common in sedimentary rocks yet its origin is poorly understood the high concentration of sulfate in sea water and the lack of appreciable sulfate in most other natural waters suggests that anhydrite cement may have a marine origin but the relatively late timing of most anhydride cement tends to preclude sea water as the source of sulfate anhydrite cement is present in upper jurassic sandstones in the gulf of mexico as poikilotopic masses in which detrital grains are replaced and as smaller patches that have replaced single detrital grains anhydrite is a relatively late cement and postdates all other volumetrically significant authigenic phases including k feldspar dolomite quartz and most calcite cements the expected isotopic composition and trace element concentration of marine derived late jurassic anhydrite cement is predicted based on analyses of bedded anhydrite and on analyses found in the literature the expected chemical signature is 34s cdt 16 18o smow 14 87sr 86sr 0 7069 sr 1500 2500 ppm ba 200 ppm when geochemical analyses of smackover anhydrite cements are compared to the predicted composition it is apparent that most of the cement is not of marine origin two generations of anhydrite cement have been identified in the east texas basin on the basis of their strontium isotopic compositions and their strontium concentrations an early cement may have been derived from slightly modified late jurassic sea water whereas a second group of cements may have precipitated later in the burial history or may represent recrystallization of the first cement the chemistry of louisiana and mississippi basin anhydrite cements indicates that the sulfate was derived from dissolved bedded anhydrite and was reprecipitated in the sandstones from fluids that had undergone extensive water rock interaction after considerable burial this study suggests that late anhydrite cements in sedimentary rocks are most likely derived from remobilized calcium sulfate de osits

cement geochemistry of photozoan carbonate strata upper carboniferous lower permian finnmark carbonate platform barents sea the following figure was originally printed without the vertical axis labels the paper appeared in the

vs30 mapping and soil classification for seismic site effect evaluation in dinar region sw turkey summary the dinar earthquake m s 6 1 of 1995 october 1 killed 90 people and destroyed more than 4000 buildings despite the moderate size of the earthquake the level of damage was extremely high which led to many studies that were carried out in the region the majority of these studies concluded that the main reasons for the damage were the construction errors and the poor soil conditions however at that time no appropriate soil condition map based on extended high density measurements was available shear wave velocity is an important parameter for evaluating the dynamic behaviour of soil in the shallow subsurface thus site characterization in calculating seismic hazards is usually based on the near surface shear wave velocity values the average shear wave velocity for the top 30 m of soil is referred to as v s 30 for earthquake engineering design purposes both the uniform building code ubc and eurocode 8 ec8 codes use v s 30 to classify sites according to the soil type the v s 30 values calculated by using multichannel analysis of surface waves masw were used to create a new soil classification map of the dinar region surface seismic measurements were carried out at 50 locations mostly in dinar city and its surroundings the dispersion data of the recorded rayleigh waves were inverted using a genetic algorithm ga method to obtain shear wave velocity profiles of the investigated sites thus the derived v s 30 map of the dinar region was transformed to the ubc and ec8 standards soil classification results show that most parts of the region located in alluvial basin have low shear wave velocity values these values are within the range of 160 240 m s 1 and thus fall into the s d and s e categories according to the ubc and the c and d categories according to ec8 within the region some parts located on the hill zone and the transition zone have better soil conditions corresponding to s c ubc and b ec8 categories and have comparatively high shear wave velocities in the range of 500 740 m s 1 and 350 450 m s 1 respectively v s 30 and soil classification maps were compared with the damage distribution associated with the earthquake in possession of a detailed shear wave velocity map of dinar city in general the results show that there is a correlation between the v s 30 values and the damage distribution of the region in addition to the low v s 30 values the likely causes of the damage were investigated and it is observed that one of the major factors for high levels of damage is 3 d variations of geological structures

enhanced carbonate petrography using fluorescence microscopy abstract fluorescence microscopy can recognize depositional facies and delineate diagenetic fabrics and porosity relationships in certain highly dolomitized or recrystallized limestones previously uninterpretable using standard petrographic techniques this tool has other valuable applications in the study of carbonate rocks these other applications include differentiating carbonate cements from neomorphic spar enhancing depositional and diagenetic fabrics rapidly evaluating mineralogical stabilization and recrystallization in holocene and pleistocene deposits and improving delineation of porosity and pore geometries in sedimentary rocks fluorescence microscopy is a rapid easily used and nondestructive technique that can be applied to unpolished thin sections or rock slabs by itself or in conjunction with other petrographic and geochemical tools it has the potential to expand our understanding of carbonate diagenetic processes and products in particular dolomitization and neomorphism and carbonate porosity evolution we strongly encourage routine usage of fluorescence microscopy in future carbonate petrographic studies

site characterization through combined analysis of seismic and electrical resistivity data at a site of dhanbad jharkhand india we present the seismic site characterization study using joint modelling of horizontal to vertical spectral ratio hvsr and rayleigh wave phase velocity dispersion curves obtained from multi channel simulation with one receiver msor in a part of dhanbad jharkhand india the joint analysis of these two different but complementary datasets puts stronger constraints on the model parameter search space than one dataset and may help us in finding more unique shear wave velocity model the microtremor data from 12 observation points were utilized to iteratively search 1d shear wave velocity profiles in a predefined model search space these 1d shear wave velocity models were interpolated to generate a 2d shear wave velocity profile of the site using the cubic spline method our results show that the high peak amplitude value of hvsr is associated with low peak period values of hvsr at a distance of 60 m from the southern end of the profile which may indicate the presence of the basin edge effect we identified four layers based on significant changes in the shear wave velocities to a depth of 60 m the major impedance contrasts are located at average depths of 13 m 40 m and 55 m respectively these layers from the surface may indicate the presence of soil highly weathered rock mass moderately weathered rock and bedrock respectively the depth of engineering solid bedrock vs 600 m s is found at the depth of 55 m in the south which gradually decreases to a depth of 40 m in the northern end of the profile the shear wave velocity vs 30 for this area varies between 293 and 357 m s which can be classified as d type site for validation and comparison of our results the electrical resistivity tomography ert data were also recorded along the same traverse using wenner and schlumberger configurations our results show a significant amount of correlation between the 2d shear wave velocity and resistivity profiles obtained from joint analysis of tremor and ert data

present day kinematics of the middle east and eastern mediterranean the middle east and eastern mediterranean regions contain three major strike slip fault zones the dead sea fault zone dsfz and the north and east anatolian fault zones nafz and eafz these accommodate northward motion of the african and arabian plates relative to eurasia and westward motion of the small turkish plate this study deduces an internally consistent solution for the present day kinematics of these plates which is accurate to better than 20 and applicable throughout time since 5 ma by constraining the slip senses and rates on these strike slip fault zones the 7 0 5 mm yr 1 left lateral slip rate on the dsfz is associated with counterclockwise rotation of arabia relative to africa at 0 33 m y 1 around an eulcr pole near 33 n 23 e the nafz takes up counterclockwise rotation of the turkish plate relative to eurasia at 0 83 m y 1 13 around a pole at 31 n 35 5 e with right lateral slip rate 15 mm yr 1 the resulting prediction for the eafz involves 14 mm yr 1 left lateral motion and 2 mm yr 1 of shortening between arabia and turkey the triple junction of africa arabia and turkey is near the city of kahramanmaras this locality contains a narrow promontory bounded by ssw trending left lateral faults at the edges of the arabian and turkish plates which is loosely attached to the african plate moving westward relative to its interior at 4 mm yr 1

diagenesis of fossil ostracods implications for stable isotope based palaeoenvironmental reconstruction a protocol for assessing the diagenetic alteration of ostracod carapaces for use in palaeoenvironmental reconstruction is proposed based on comparison between fossil carboniferous and recent specimens recent ostracods have a carapace ultrastructure of fine 0 5 m diameter crystals of primary low magnesium calcite the degree of recrystallisation in fossil ostracods is assessed based on the carapace ultrastructure and geochemistry six diagenetic stages are identified 1 replacement of the original finely crystalline calcite carapace with neomorphic calcite 2 framboidal and euhedral pyrite growth 3 ferroan calcite carapace replacement and cavity void filling cement 4 ferroan dolomite carapace replacement and void fills 5 siderite growth and 6 sphalerite and barite mineralisation stage 1 occurs during early shallow burial stages 2 3 soon after and stages 4 6 during much later burial possibly hydrothermal alteration ostracods and macrofossils exhibiting diagenetic stages 1 5 were analysed for oxygen and carbon isotope ratios the oxygen isotope compositions clearly reflect the diagenetic stages the most negative oxygen isotopes 18o 12 9 represent the precipitation of ferroan dolomite stage 4 and the most positive values of the neomorphic calcite 18o 0 9 represent stage 1 and are within the predicted range of carboniferous seawater 18o 4 to 0 the diagenetic protocol established here is specific to palaeozoic fossil ostracods from carbonate and clastic sediments that were subject to shallow burial diagenesis and later hydrothermal alteration nevertheless the approach could be used to assess the utility of fossil ostracods for palaeoenvironmental interpretation from a wide range of geological settings

the 1759 earthquake in the bekaa valley implications for earthquake hazard assessment in the eastern mediterranean region analysis of macroseismic data based on primary sources for large though infrequent historical earthquakes ms 6 5 that occurred along an approximately 350 km long segment of the northern part of the dead sea fault system primarily in lebanon and syria for the period 1100 1988 reveals the following 1 ten events occurred in three relatively short periods tens of years with repeat times of 200 350 years 2 the events most probably broke this north segment of the dead sea fault system possibly including the westernmost segment of the east anatolian fault system near the border between syria and turkey 3 the lack of such large events during the past 100 years should not be interpreted to minimize potential earthquake hazard in this region and 4 the ms 7 plus earthquake on november 25 1759 almost certainly produced surface faulting probably along the yammouneh fault in the bekaa valley and caused heavy destruction with great loss of life in numerous villages and towns including safad damascus beirut and baalbek this main event was preceded by a ms 6 plus foreshock on october 30 1759 in the southern part of the epicentral area of the main shock near the towns of safad and qunaitra which were almost totally destroyed with considerable loss of life

microcodium an extensive review and a proposed non rhizogenic biologically induced origin for its formation abstract microcodium has been previously described as a mainly cenozoic calcification pattern ascribed to various organisms a review of the available literature and our data reveal two peaks in microcodium abundance the moscovian early permian and the latest cretaceous paleogene a detailed analysis of late paleozoic and cenozoic examples leads to the following new conclusions typical microcodium forming unilayered corn cob aggregates of elongated grains and thick multilayered palisade replacing structures cannot be linked to smaller grained intracellular root calcifications as became widely accepted after the work of klappa klappa c f 1979 calcified filaments in quaternary calcretes organo mineral interactions in the subaerial vadose environment j sediment petrol 49 955 968 typical microcodium is recognized from the early carboniferous with doubtful devonian reports to quaternary as a biologically induced mineralization formed via dissolution precipitation processes in various aerobic ca rich soil and subsoil terrestrial environments morphology and 13c signatures of microcodium suggest that neither plants algae or roots and root associated mycorrhiza regulate the formation of these fossil structures non recrystallized microcodium grains basically consist of slender 1 5 4 m curved radiating monocrystalline prisms with occasionally preserved hyphae like morphology thin 0 5 3 m hypha like canals can also be observed these supposed hyphae may belong to actinobacteria however thin fungal mycelia cannot be excluded we propose a model of microcodium formation involving a mycelial saprotrophic organism responsible for substrate corrosion and associated bacteria capable of consuming acidic metabolites and caco3 reprecipitation into the microcodium structures

late cenozoic stress evolution along the karasu valley se turkey abstract this study defines the mio pliocene to present day stress regime acting at the northeastern corner of the eastern mediterranean region along the karasu valley i e the amanos range taking in the antakya osmaniye and kahramanmaras provinces the inversion slip vectors measured on fault planes and chronologies between striations indicate that the stress regime varied from transpressional initially to transtensional having consistent nw and ne trending hmax 1 and hmin 3 axes respectively there are significantly different mean stress ratio rm values however the older mean stress state is characterized by n151 11 e trending 1 and n59 12 e trending 3 axes and by a mean arithmetic rm value of 0 76 indicating that the regional stress regime is transpressional the younger stress regime is characterized by n154 8 e trending 1 and n243 8 e trending 3 axes and by a mean arithmetic rm value of 0 17 indicating a transtensional character for this regional stress regime the low r values of the stress deviators related to the recent stress state reflect normal component slips the earthquake focal mechanism inversions confirm that the younger stress regime continues into the recent the inversion identifies a transtensional stress regime representing strike slip and an extensional stress state with a consistent ne trending hmin 3 axis these stress states are characterized by n66 e and n249 e trending 3 axes respectively both significant regional stress regimes induce left lateral displacement along the southern part of the east anatolian fault eaf or amanos fault the temporal change probably in quaternary time within the regional stress regime from transpression to transtension resulted from the coeval influences of subduction processes in the west southwest i e along the cyprus arc continental collision in the east and westward escape of the anatolian block

dolomitization and dolomite neomorphism trenton and black river limestones middle ordovician northern indiana u s a abstract the trenton and black river limestones are dolomitized extensively along the axis of the kankakee arch in indiana with the proportion of dolomite decreasing to the south and southeast of the arch planar and nonplanar dolomite replacement textures and rhombic type 1 and saddle type 2 void filling dolomite cements are present three stages of dolomitization involving different fluids are inferred on the basis of petrographic and geochemical characteristics of the dolomites nonferroan planar dolomite has relatively high 18o values 1 8 to 6 1o oo pdb and has 87sr 86sr ratios 0 70833 to 0 70856 that overlap those of middle ordovician seawater petrography geochemistry and the geometry of the dolomitized body suggest that the planar dolomite was formed in middle and late ordovician seawater during the deposition of the overlying maquoketa shale ferroan planar and nonplanar dolomite occurs in the upper few meters of the trenton limestone confined to areas underlain by planar dolomite this dolomite contains patches of nonferroan dolomite with cathodoluminescence cl characteristics similar to underlying planar dolomite ferroan dolomite has relatively low 18o values 5 1 to 7 3o oo pdb and has slightly radiogenic 87sr 86sr ratios 0 70915 to 0 70969 similar to those obtained for the overlying maquoketa shale these data indicate that ferroan dolomite formed by neomorphism of nonferroan planar dolomite as fluids were expelled from the overlying maquoketa shale during burial the absence of ferroan dolomite at the trenton maquoketa contact in areas where the earlier formed nonferroan planar dolomite also is absent indicates that the fluid expelled from the overlying shale did not contain enough mg2 to dolomitize limestone type 1 dolomite cement has isotopic compositions similar to those of the ferroan dolomite suggesting that it also formed from shale derived burial fluids cl growth zoning patterns in these cements suggest that diagenetic fluids moved stratigraphically downward and toward the southeast along the axis of the kankakee arch type 2 saddle dolomite cements precipitated late their low 18o values 6 0 to 7 0o oo pdb are similar to those of the type 1 dolomite cement however fluid inclusion data indicate that the saddle dolomite was precipitated from more saline basinal fluids and at higher temperatures 94 to 143 c than the type 1 cements 80 to 104 c a trend of decreasing fluid inclusion homogenization temperatures and salinities from the michigan basin to the axis of kankakee arch suggests that these fluids emerged from the michigan basin after precipitation of type 1 cement

geochemical imprint of meteoric diagenesis in holocene ooid sands schooner cays bahamas correlation of calcite cement geochemistry with extant groundwaters abstract the geochemistry of meteoric calcite cements and their parent waters on three small holocene ooid sand islands in the schooner cays bahamas is explicated in terms of observed hydrologic and hydrochemical processes dissolved mg is derived soley from admixed seawater or aerosols the mg contents of the cements 0 4 to 3 0 mole are thus a salinity indicator and suggest cementation in waters composed of 16 mmoles liter per yr variations in mg and sr contents across cement mosaics reflect long term temporal fluctuations in the amou t of aragonite to calcite alteration and incursions of brackish waters the pore water oxygen reservoir is water buffered and derived from meteoric rainfall and seawater mixing but is seasonally enriched in 18o by evaporation the 18o values of the cements 3 4 to 5 0 pdb reflect the relative proportions of cements formed during and immediately after the rainy season versus those formed during the dry season the pore water carbon is derived from organic respiration atmospheric carbon and dissolved aragonite organic respiration dominates the 18c of the vadose cements 7 8 to 1 1 pdb and the 13c of phreatic groundwaters 2 2 to 14 0 pdb in contrast 13c enriched phreatic cements 1 2 to 3 7 pdb reflect carbon from dissolved aragonite and are not in carbon isotopic equilibrium with the present groundwaters this case example reveals the complex geochemical signal that can result from even a very simple diagenetic history such as a single phase of meteoric diagenesis acting on a purely aragonitic sediment

the control of cathodoluminescence in dolomite by iron and manganese variations in the cathodoluminescent properties of carbonates are usually attributed to differing proportions of manganese mn2 as the most important activator and iron fe2 as the main inhibitor of luminescence interactions between manganese and iron concentrations and the luminescent properties of dolomite are demonstrated by petrographic and chemical analyses of 86 samples of dolomite representing a range of depositional environments and ages cambrian to cretaceous and a wide geographical distribution north america and europe iron and manganese are positively correlated in the dolomites with the former showing a greater range of variation very small amounts of manganese are sufficient to activate the luminescence and as little as 100 ppm mn2 is present in highly luminescing samples the intensity of luminescence is not proportional to the manganese concentration iron begins to quench luminescence as its concentration reaches 10 000 ppm above that level luminescence is rapidly lost and total extinction occurs among samples containing more than 15 000 ppm fe2 regardless of the manganese concentration

quaternary stress regime change in the hatay region se turkey in this study we determine the plio quaternary to present day stress regime acting in the hatay region located at the northeastern corner of the east mediterranean region the modern state of stress is obtained from inversion of focal mechanism solutions of shallow earthquakes this inversion identifies a dominantly extensional stress regime with a ne trending h m i n 3 axis at the present day the stress regime determined from inversion of slip vectors measured on fault planes confirms that this regime is extensional in the studied area both the kinematics and chronologies of fault slip vectors show that the stress state changed from an earlier strike slip regime to a younger extensional stress regime with a consistent ne trending h m i n 3 axis the change from strike slip to extensional stress regimes probably occurred during the quaternary regionally both stress regimes induce sinistral displacement on the east anatolian fault and dead sea fault systems the north anatolian fault naf is a dextral strike slip fault which runs about 1400 km from east to west and has been active since collision between the eurasian and arabian plates together with the sinistral east anatolian fault the naf intracontinental deformation zone contributes to the westward extrusion of anatolia as a consequence of northward drift of arabia consequently the late cenozoic stress regimes acting in the hatay region result from the coeval influence of forces due to 1 the subduction processes in the west and southwest 2 the continental collision in the east and 3 the westward escape of the anatolian block however the timing of the temporal stress transition suggests that the quaternary stress regime change resulted from subduction processes with the extensional stress regime in the hatay region being mainly attributable to roll back of the mediterranean subducted slab along the cyprus arc

the use of ambient seismic noise measurements for the estimation of surface soil effects the motril city case southern spain this paper presents a study of the ambient seismic noise features in motril city the predominant resonant period at each site was determined using the horizontal to vertical noise ratio hvnr of the microtremors records it was applied to 91 points which cover the city and we present the distribution of the periods over a map which shows important characteristics requiring consideration in a study focussing on the mitigation of the seismic risk using these results two zones can be distinguished north of the gg profile with predominant periods smaller than 0 25 sec which corresponds with a hard soil and south of gg with periods ranging from 0 25 to 0 6 indicating a medium soft soil microtremors are a preliminary useful tool that compensates for the lack of seismic recorded data and that can complement other valuable information borehole logs geology etc to evaluate the seismic risk on places as motril city where some of this information is unavailable through the predominant period the hvnr indicates the kind of soil we are dealing with

disequilibrium trace element partitioning in jurassic sparry calcite cements implications for crystal growth mechanisms during diagenesis sparry calcite cements from middle jurassic limestones in central england contain complex non concentric zoning patterns produced by a combination of sector zonation and a sector specific lamellar or polygonal zonation electron microprobe analyses of individual zones within crystals document 1 a sympathetic covariation of fe mg and sr between two non equivalent sectors and 2 episodic further increase of sr contents coupled with exclusion of fe mg and mn within the more enriched sectors comparison of results from three different localities demonstrates the regional consistency of this pattern although the magnitude of the differential trace element partitioning varies from combined petrographic and geochemical data the trace element variation in the crystals can be shown to bear no simple relationship with either 1 the chemical evolution of the 9bulk9 precipitating porefluid or 2 the relative overall growth rates of the different crystal faces previous sector zoning models based on crystal surface configurations and internal structure are unable to account directly for the geochemical patterns observed in this study differences between growth mechanisms on the crystal faces of the studied spars are likely to have exerted a significant influence on trace element partitioning in particular they offer a plausible explanation for the geometric and compositional characteristics of the sector specific episodic zoning on the most enriched crystal faces in general crystal morphology and composition will be intimately linked by the growth mechanisms operating on different faces and by their response to changes in the diagenetic environment the validity of diagenetic interpretations from bulk geochemical analysis of sparry calcite cements thus rests upon a detailed analysis of any zonation that they contain

trace element and isotope geochemistry of zoned calcite cements lake valley formation mississippian new mexico insights from water rock interaction modelling abstract regionally extensive pre pennsylvanian meteoric zoned calcite cements from the mississippian age lake valley formation new mexico comprise three major zones zones 1 2 and 3 each with a distinct isotope and trace element geochemistry zone 1 has the highest mg 18o and 13c contents zone 2 intermediate values and greatest mn and fe and zone 3 has the lowest trace element 18o and 13c values covariation of c and o isotopes for the three zones define an inverted l shaped trend and covariations of mg mn and mg fe define l shaped trends all suggestive of rock evolution curves resulting from water rock interaction these covariant trends were the impetus for quantitative mass balance modelling of water rock interaction iterative mass balance modelling of covariations of stable isotopes c and o and trace elements mg mn fe of these zoned cements implies that water rock interaction progressively decreased water rock ratios increased during precipitation cementing waters for the oldest cement zone zone 1 resulted from water rock ratios in the range of tens to a few hundred whereas the youngest cement zone 3 resulted from water rock ratios in the 100 s to 1000 s the modelling also implies that differences in geochemistry of the cement zones cannot be explained solely by changes in water rock ratios but require greater 18o and greater ca and mg concentrations in input waters that evolved to zone 1 precipitational waters than those for zones 2 and 3 zones 2 and 3 can reasonably be modelled using input waters with the same isotopic compositions the same ca concentration and for some zone 2 cement the same mg concentrations the minimum mg ca ratios in input waters is constrained by the lower mg plateau in mg mn space and is about the same for all three zones about 1 25 the maximum mg ca ratios about 1 20 occurred in zone 2 input waters mn fe covariations also show an l shaped trend a trend whch fits neither a simple water rock interaction model nor a simple eh model a model is proposed in which eh and limited mn sources determine the amount of fe and mn available in solution to partake in water rock interaction water rock interaction modelling provides one useful approach to quantitatively interpreting isotopic and trace element data from diagenetic carbonates to gain a clearer understanding of evolution of diagenetic fluids

microtremor array measurements for shallow s wave profiles at strong motion stations in hatay and kahramanmaras provinces southern turkey abstract we conducted microtremor array exploration of shallow s wave velocity profiles at 28 sites in hatay and kahramanmaras in the southern part of turkey to provide fundamental data to assess seismic hazards in the two areas a total of 16 and 12 sites were located in hatay and kahramanmaras provinces respectively we temporarily installed two small arrays to obtain simultaneous records of vertical microtremors the spatial autocorrelation method was applied to retrieve rayleigh wave phase velocity in a 1 30 hz frequency range the phase velocities at most of the sites in kahramanmaras province were high in the entire frequency range whereas those in hatay province were widely distributed suggesting significant variation in soil conditions low phase velocities were identified at sites near the coast in hatay subsequently the phase velocity observed at each site was inverted to a 1d s wave velocity profile to a depth of 100 m using a hybrid heuristic inversion most of the profiles in kahramanmaras had very thin near surface layers with s wave velocities of less than 300 m s and thicknesses of less than 10 m the top layers at the sites in hatay showed significant variation with different s wave velocities from 110 to 760 m s and thicknesses from 2 to 40 m these layers were thicker at the sites near the coastal area we finally discuss amplification factors of s waves using the inverted profiles the fundamental predominant periods of the amplification factors distributed across a wide frequency range from 0 8 to 10 hz in hatay the peak frequencies concentrated in a high frequency range of more than 5 hz in kahramanmaras the profiles observed were used to map average s wave velocities in the top 30 m at strong motion stations

holocene dolomitization of calcium carbonate sediments from the coastal sabkhas of abu dhabi u a e a stable isotope study secondary dolomitization of holocene calcium carbonate sediments occurs beneath the coastal sabkhas of abu dhabi u a e a stable isotope study of the sabhka sediments and brines indicates that the

geotechnical comparison of weathering degree and shear wave velocity in the decomposed granite layer in hongseong south korea as part of a fundamental characterization of a subsurface layer in south korea the weathering degree and shear wave velocity v s were evaluated in a decomposed granite in hongseong using x ray fluorescence analyses and site investigations including borehole drilling with standard penetration test spt and in situ seismic tests the subsurface layer was composed of a weathered layer 10 40 m thick at most sites weathering degree analyses indicated that three chemical weathering indices the modified weathering potential index mwpi vogt ratio vr and weathering index of parker wip generally increased with decreasing depth in situ seismic tests revealed that v s ranged between 200 and 500 m s in the weathered layer using the v s and n values from the spt at borehole seismic testing sites correlations between v s and n values were established for the weathered layer furthermore examination of the relationships of the v s and n values with the mwpi wip and 100 vr indices showed that the index values increased linearly with increasing v s and exponentially with increasing n values

neodymium isotopic profiling of carbonate platform strata correlation between siliciclastic provenance signature and sequence stratigraphy abstract the nd isotopic composition of core samples from the mid carboniferous to upper permian finnmark carbonate platform is interpreted as representing their siliciclastic content the nd content of the carbonate fraction being relatively insignificant trends of upward increase in 143nd 144nd in these strata correlate with the two largest scale second order depositional sequences defined by previous sedimentologic study these trends are interpreted as the result of mixing between two hypothetical siliciclastic provenance terranes the relatively old low 143nd 144nd material dominating the base of each cycle is suggested to be derived from local caledonian basement the relatively young high 143nd 144nd material comprising the upper part of each cycle is suggested to be an open marine siliciclastic composition representing mixing of more widespread sources dominance of the basement provenance signature at the base of each second order sequence could reflect tectonic movements that exposed local basement areas to erosion the subsequent gradual shift to younger open marine provenance signature could result from progressive peneplanation or burial of the basement uplifts higher frequency depositional sequences have little to no effect on nd composition suggesting that these fluctuations in facies distribution were largely unrelated to patterns of siliciclastic supply this model implies that the mid asselian second order lowstand was a time of major siliciclastic bypass suggesting the possible existence in the nordkapp basin of extensive sandstones of this age the observed pattern of cyclic asymmetric 143nd 144nd variation should be a universal characteristic of finnmark platform stratigraphy and may therefore be useful for stratigraphic correlation between widely separated well locations the broader interest of these results is the demonstration that 1 the nd isotopic composition of even relatively pure carbonate rocks can reflect mainly the provenance signature of the siliciclastic component and 2 nd isotopic profiling of carbonate strata can indicate patterns of tectonic influence on depositional cyclicity

faster better shear wave velocity to 100 meters depth from refraction microtremor arrays current techniques of estimating shallow shear velocities for assessment of earthquake site response are too costly for use at most construction sites they require large sources to be effective in noisy urban settings or specialized independent recorders laid out in an extensive array this work shows that microtremor noise recordings made on 200 m long lines of seismic refraction equipment can estimate shear velocity with 20 accuracy often to 100 m depths the combination of commonly available equipment simple recording with no source a wavefield transformation data processing technique and an interactive rayleigh wave dispersion modeling tool exploits the most effective aspects of the microtremor spectral analysis of surface wave sasw and multichannel analysis of surface wave masw techniques the slowness frequency wavefield transformation is particularly effective in allowing accurate picking of rayleigh wave phase velocity dispersion curves despite the presence of waves propagating across the linear array at high apparent velocities higher mode rayleigh waves body waves air waves and incoherent noise two locations illustrate the application of this technique in detail coincident with a large accelerometer microtremor array in reno nevada and atop a borehole logged for shear velocity in newhall california refraction equipment could duplicate microtremor results above 3 hz but could not estimate velocities deeper than 100 m refraction microtremor cannot duplicate the detail in the velocity profile yielded by a suspension logger but can match the average velocity of 10 to 20 m depth intervals and suggest structure below the 100 m logged depth of the hole eight additional examples from southern california and new zealand demonstrate that the refraction microtremor technique quickly produces good results from a wide range of hard and soft sites

3d seismic analysis of karstified interbedded carbonates and evaporites lower permian gipsdalen group loppa high southwestern barents sea abstract this paper presents a detailed seismic analysis of a hitherto undescribed permian succession interpreted to consist of interbedded anhydrite and carbonate from the northern flank of the loppa high western barents sea the fafner succession forms a locally restricted transgressive unit down dip on the rotated loppa high it is subdivided into four seismic sequences each interpreted to be composed of a basal transgressive anhydrite overlain by highstand carbonates fafner seismic sequences 2 and 3 include well developed buildup complexes which in map view form polygonal patterns analysis of attribute maps indicates that the fafner succession is overprinted by two dissolution systems related to two prominent events of subaerial exposure creating numerous paleo sinkholes breccia pipes and collapsed composite cavern systems the stratigraphical position of the fafner succession below the mid sakmarian artinskian bjarmeland group and above the top orn unconformity resembles that of the lower permian gipshuken formation on spitsbergen and the fafner succession is thus regarded as its offshore equivalent

stable isotope signatures associated with palaeosols pennsylvanian holder formation new mexico the holder formation pennsylvanian virgilian of southern new mexico usa consists of limestones interbedded with siliciclastics it was deposited during times of glacio eustatic sea level change and was exposed subaerially during multiple sea level lowstands microcomponents and whole rock samples of limestones were analysed for 13c and 18o values to examine the method of whole rock isotopic analysis for detecting subaerial exposure events and to determine the diagenetic processes acting during subaerial exposure whole rock isotopic shifts are not consistently present across petrographically identified subaerial exposure surfaces apparently whole rock isotopic shifts do not result from wholesale replacement of the host sediment during soil formation however the isotopic shifts are present in calcareous soil precipitated microcomponents such as rhizoliths laminated crusts and soil precipitated cements the components are heterogeneous in isotopic composition but converge on a meteoric calcite line at about 18o 5 5 these microcomponents are heterogeneous in distribution and may either dominate or be a minor constituent of the whole rock at a single stratigraphic horizon without petrographic selection of palaeosol components the detection of whole rock isotopic shifts may depend on the selection or chance sampling of a rock containing abundant microcomponents precipitated in a soil environment only minor whole rock isotopic shifts come from those rocks bearing no evidence of exposure and bearing lithological characteristics suggesting subaerial exposure was unlikely

diagenesis of the palaeo oil water transition zone in a lower pennsylvanian carbonate reservoir constraints from cathodoluminescence microscopy microthermometry and isotope geochemistry abstract oil water transition zones in carbonate reservoirs represent important but rarely studied diagenetic environments that are now increasingly re evaluated because of their potentially large effects on reservoir economics here data from cathodoluminescence and fluorescence microscopy isotope geochemistry microthermometry and x ray tomography are combined to decipher the diagenetic history of a 5 m long core interval comprising the oil water transition zone in a lower pennsylvanian carbonate reservoir the aim is to document the cementation dynamics prior during and after oil emplacement in its context of changing fluid parameters intergrain porosity mean values of 7 are present in the upper two sub zones of the oil water transitions zone but values sharply increase to a mean of 14 in the lower sub zone grading into the water saturated portions of the reservoir and a very similar pattern is observed for permeability values in the top of the water filled zone cavernous porosity with mean values of about 24 is found carbonate cements formed from the earliest marine to the late burial stage five calcite ca 1 through 5 and one dolomite dol phase are recognized with phase ca 4b recording the onset of hydrocarbon migration carbon and oxygen cross plots clearly delineate different paragenetic phases with ca 4 representing the most depleted 13c ratios with mean values of about 21 during the main phase of oil emplacement arguably triggered by far field alpine tectonics carbonate cementation was slowed down and eventually ceased in the presence of hydrocarbons and corrosive fluids with temperatures of 110 140 c and a micro hiatal surface formed in the paragenetic sequence these observations support the oil inhibits diagenesis model the presence an earlier corrosion surface between phase ca 3 and 4 is best assigned to initial pulses of ascending corrosive fluids in advance of hydrocarbons the short lived nature of the oil migration event found here is rather uncommon when compared to other carbonate reservoirs the study is relevant as it clearly documents the strengths of a combined petrographic and geochemical study in order to document the timing of oil migration in carbonate reservoirs and its related cementation dynamics

dolomite from clay in argillaceous or shale associated marine carbonates abstract postcompactional late stage ferroan dolomite commonly occurs as 1 finely disseminated rhombic microspar in argillaceous lime mudstone 2 sparry cement within voids in argillaceous carbonates and 3 sparry cement within carbonates adjacent to marine shales the distribution and abundance of these dolomites correspond with that of clay deposited in the marine environment and cannot easily be explained by alternative models of dolomite formation conversion of smectite to illite during burial is a common diagenetic process which is capable of releasing large amounts of fe mg ca na and si sandstone petrologists have emphasized the significance of this process in generating quartz cements in sandstone shale sequences however the potential of this conversion for producing postcompactional dolomite cement in limestone shale sequences or in argillaceous limestones has been neglected smectite illite conversion is here invoked as the source of ions that formed late stage postcompactional dolomites in examples of the pennsylvanian of oklahoma kansas missouri and iowa the devonian of iowa and the ordovician of oklahoma the smectite illite conversion model for generating dolomite may be widely applicable to many other ex mples of late stage dolomitization it should prove useful in predicting the distribution of late stage dolomite cement that reduces reservoir quality and may prove useful for estimating the timing of hydrocarbon migration relative to carbonate cementation

evolution and distribution of porosity associated with subaerial exposure in upper paleozoic platform limestones west texas middle pennsylvanian lower permian limestones in the subsurface of west texas were studied to determine how subaerial exposure and freshwater diagenesis karstification affected porosity distribution in meter scale cycles approximately 87 depositional cycles are present in the gross reservoir interval depths of 2600 3000 m and each cycle is interpreted to represent a glacio eustatic sea level fluctuation using recent radiometric age dating average cycle duration is estimated at 160 000 yr per cycle reservoir grade porosity 4 occurs in 5 25 of the gross reservoir section porosity is stratified occurring in 1 6 m thick intervals in the upper part of cycles that were subaerially exposed however many cycles that were subaerially exposed now lack porosity diagenesis and porosity development have distinct patterns related to duration of subaerial exposure four stages of porosity development are identified 1 very brief or no subaerial exposure estimated at less than 5000 yr caused little or no diagenetic change 2 brief to moderate subaerial exposure estimated at 5000 50 000 yr resulted in most primary pores being filled with calcite cement and dissolution creating fine matrix pores molds and intercrystalline pores 3 moderately long subaerial exposure estimated at 50 000 130 000 yr resulted in cements filling primary pores and some fine secondary pores and dissolution creating small conduit pores vugs fractures fissures 4 prolonged subaerial exposure estimated at greater than 130 000 yr resulted in most primary and secondary matrix pores being filled with calcite cement but dissolution enlarged conduit pores vugs fractures fissures present subsurface porosity in this field preferentially occurs in thick grainstones phylloid algal boundstones and a few wackestone packstones in cycles subjected to brief subaerial exposure stages 2 and 3 matrix porosity molds intercrystalline pores is dominant because most conduit pores formed during prolonged subaerial exposure were filled with either shale during subsequent transgressions or burial cements derived from pressure solution associated with the shales the distribution of porosity in the southwest andrews area indicates that duration of subaerial exposure and supply of clastics are major factors determining ultimate porosity in limestones subjected to subaerial exposure and karstification

porosity permeability relationships in miocene carbonate platforms and slopes seaward of the great barrier reef australia odp leg 194 marion plateau this paper reports a series of 700 porosity permeability analyses and supporting petrographic and sedimentologic descriptions from early to late miocene carbonate strata cored on the marion plateau offshore from north eastern australia during ocean drilling program odp leg 194 the samples analysed are not only mainly coarse bioclastic limestones and dolomitized equivalents from platform top facies but also include 79 plugs from deeper water slope to hemipelagic drift facies outstanding characteristics of this data set are the wide ranges of porosity and permeability in both limestones and dolostones the large degree of short range heterogeneity typical of these strata and the better porosity permeability correlation of dolostones than limestones the platforms have experienced widely varying calcite cementation dolomitization and dissolution but show little clear evidence of meteoric diagenesis suggesting that subaerial exposure may have played little role in porosity permeability evolution permeability for given porosity is controlled by grain size and calcite cement content in grainstones and by occurrence of larger shelter pores and vugs in mud rich samples dolomitization tends to reduce the variation of permeability for given porosity by recrystallizing mud matrix to form intercrystalline macroporosity that connects vugs and moulds to become integrated with the effective pore system as a result there are no differences in permeability porosity trends for different dolostone textures whether dominated by intercrystalline vuggy or preserved intergranular pore types two platform top sites separated by only 5 km display a major lateral variation in dolostone porosity permeability characteristics within the youngest dolostone units this difference is interpreted as reflecting a relatively windward current facing setting of the site with the overall higher permeability for given porosity site 1199 that led to less muddy depositional facies greater cementation and lesser grain dissolution pore geometry parameters measured by petrographic image analysis confirm that the windward dolostones have pores that are both larger and less intricate than dolostones comprising the more current protected location

illite smectite diagenesis in the nanxiang yitong and north china permian carboniferous basins application to petroleum exploration in china the nanxiang basin in henan province and the yitong basin in jilin province located in the eastern part of china are composed mainly of tertiary nonmarine clastic sequences that thicken to more than 4000 5000 m the north china permian carboniferous basin consists of permian carboniferous systems composed of marine and nonmarine coal bearing sequences clay diagenesis in these basins was studied by systematic x ray diffraction analysis the clay mineralogy consists of illite smectite mixed layered illite smectite i s kaolinite and chlorite the major clay reaction is the illitization of smectite with depth and temperature the reactions generally involve discrete smectite stage to smectite plus the randomly interstratified i s r 0 in the reichweite nomenclatur followed by the first rapid change i to the ordered i s of short range stacking r 1 and the second rapid change ii to the metastable stage with the ordered i s of long range stacking r 3 the first rapid change leads to the appearance of i s ordered i s and disappearance of discrete smectite the proportion of smectite layers ps in the i s in the metastable stage remained unchanged 15 20 over a thick burial interval the discrete illite stage finally occurs in highly mature areas potassium feldspar k feldspar in rocks and k ions in present formation waters are available for the i s reactions i s reactions in these areas responded mainly to temperature the i s transition from the randomly interstratified i s r 0 to the ordered i s occurred at 80 95 c and coincided with the onset of the oil window in source rocks and with secondary porosity enhancement of sandstones the transition from the r 1 to r 3 happened around 130 165 c corresponding to the wet gas stage the illite stage corresponds to the dry gas stage of organic materials the duration of burial did not contribute significantly to the reaction integrating the i s reactions with thermal histories hydrological regimes structure sedimentation and sandstone diagenesis of eac basin allows formulation of clay diagenetic models for each specific basin

temporary seismic quiescence se turkey summary the border zone that is the contact of the arabian plate with the three plates of turkey eurasia and iran to the north has been remarkably aseismic during this century by extending the period of observation backwards in time by a few centuries it is shown that this seismicity is atypical of the long term behaviour of the zone and due to a quiescent period in the activity of the area during the 20th century in turn this implies that short term data alone do not provide a reliable assessment of earthquake hazard

hydrocarbon inclusions in late calcite cements migration indicators in the great oolite group weald basin s england abstract the fluorescence responses of hydrocarbon inclusions in calcite and dolomite cements are used to indicate the timing and longevity of oil migration in great oolite reservoirs of the weald basin of southern england oil migration and late stage calcite cementation were penecontemporaneous processes the gravity of the included hydrocarbons increases towards the basin depocentre through the range of 20 to 40 api reflecting the maturity of the source rocks reservoirs with a spread in the gravity of oil within inclusions were charged throughout source rock maturation those reservoirs with oil inclusions of a single gravity were charged in a discrete event

uranium depletion across the permian triassic boundary in middle east carbonates signature of oceanic anoxia we present a geochemical profile through a 445 m 1459 9 ft section of shallow water carbonate platform strata in the upper part of the khuff formation the permian triassic boundary ptb is recognized in this section based on the immediately preceding negative shift in bulk rock carbonate carbon isotope composition equivalent to the end permian extinction horizon combined with biostratigraphic control from nearby wells these strata show an abrupt and long lasting decrease in bulk rock uranium u content coincident with the carbon isotope shift because of low siliciclastic content and the consequently low potassium and thorium of these carbonates the decrease in u is clearly reflected in the total gamma ray gr profile recorded by wire line logging published log curves show similar distinctive gr profiles throughout a large area of the middle east indicating that u depletion across the ptb is a regional characteristic this feature cannot be explained as diagenetic and is not related to the organic matter content of the host sediments but it is suggested to reflect the global depletion of u in earliest triassic seawater caused by the abrupt onset of deep ocean anoxia and the resulting increase in u precipitation in oxygen poor sediments this explanation carries the implication that similar u depletion should be characteristic of lowermost triassic carbonates from shallow water oxygenated settings worldwide analogous signatures of u depletion should also have developed in shallow water carbonates deposited contemporaneously with episodes of deep ocean anoxia during other periods of geological time these predictions can be tested by high accuracy u profiling of other well characterized carbonate successions potentially yielding a new approach for tracking the degree of oceanic circulation throughout earth s history

isotope signatures associated with early meteoric diagenesis the environments in which carbonate diagenesis proceeds have been documented in previous studies of holocene and late pleistocene sediments and limestones on barbados west indies variations in the carbon and oxygen isotopic composition of limestones produced during early freshwater diagenesis have been observed in this study to occur in specific patterns six potentially useful patterns emerge when one views stable isotope data within a stratigraphic framework 1 the subaerial exposure surface is characterized by strongly 12c enriched limestones 13c compositions of underlying limestones grow progressively heavier with increasing depth 2 the subaerial exposure surface may also be marked by slight 18o enrichment 3 an abrupt shift in 18o values may differentiate sediments above the exposure surface from those below 4 sediments altered in the marine meteoric mixing zone may be characterized by positive covariance between their 18o and 13c compositions 5 the vadose phreatic boundary may be marked by a sharp increase in 13c values in the seaward portions of a fresh groundwater system and 6 samples contemporaneously altered in a single fresh groundwater system within an areally restricted region should display a narrow range of 18o and a wide range of 13c compositions analysis of samples from five palaeozoic and mesozoic formations which contained petrographic evidence of early freshwater diagenesis showed that isotope patterns similar to those observed in barbados limestones have been preserved in rocks as old as mississippian these isotope patterns could prove to be useful for identifying diagenetically induced porosity trends in carbonate rocks they might be used to identify limestones diagenetically altered in meteoric environments to identify mixing zone cements and dolomites and to trace the regional and vertical distributions of early meteoric groundwater systems in ancient carbonate formations

factors controlling porosity in upper carboniferous lower permian carbonate strata of the barents sea a 300 m 1000 ft thick succession of shallow and warm water carbonates has been studied in well cores from the southernmost barents sea offshore north norway these upper paleozoic strata contain numerous zones of moderate to high porosity including a wide range of depositional facies despite moderately high burial temperatures and the absence of petroleum charge most porosity appears to be either primary or created during early eogenetic diagenesis negative correlation between porosity and both bulk rock alumina content and stylolite frequency reflects the influence of phyllosilicate minerals in localizing stylolitic dissolution this provides part of the explanation for the overall correlation between porosity and the platform s stratigraphic evolution the early stage of mixed siliciclastic carbonate deposition has low porosity because of extensive chemical compaction in aluminous beds the following siliciclastic poor stage shows upward increasing porosity associated with aggradation of muddy buildups and wackestones followed by the progradation of a more proximal facies belt of thinly bedded dolomitic mudstones maximum porosity development occurs in the overlying little dolomitized grain shoal facies belt which shows upward decrease in porosity because of a transgressive trend that developed progressively lower energy depositional conditions favoring the occurrence of stylolite prone shaly laminations a general porosity favorable factor is the presence of a stratified column of high salinity brine enforcing a closed diagenetic system during burial limestones and dolostones comprising this platform have very different proportions of low and high porosity values limestones have positively skewed frequency distribution many samples 5 porosity whereas dolostones have higher average porosity with symmetric distribution few samples 5 porosity the low limestone porosities result from cementation by coarse calcite spar in grain dominated samples and matrix compaction and cementation in muddy facies features that are less common in dolostones possibly because of lesser propensity for stylolite development and the resistance of early dolomitized matrix to compaction steve received a ph d from the university of california at los angeles in 1978 he works on sandstone and carbonate petrology sedimentology and stratigraphy

porosity permeability relationships in interlayered limestone dolostone reservoirs porosity and permeability data from five carbonate platform successions of different settings ages and burial depths are examined to identify overall similarities and differences in the reservoir quality of interlayered limestones and dolostones each succession consists mainly of limestone and dolostone with subordinate proportions of intermediate partly dolomitized compositions in the three deeply buried platforms the key features are that limestones have much lower average porosity than associated dolostones and that limestones and dolostones show little difference in average permeability for given porosity in contrast the shallowly buried platforms show little difference in average porosity between limestones and dolostones and also display higher average permeability for given porosity in dolostones than limestones these data suggest the following general guidelines for depositional and diagenetic controls on reservoir architecture in carbonates consisting of interlayered limestone and dolostone 1 reservoir compartmentalization by the formation of tight limestone barriers is largely a burial diagenetic process involving calcite cementation locally produced by chemical compaction 2 both the pattern of early dolomitization and the distribution of clay minerals because they influence the localization of chemical compaction are key factors that determine the distribution of tight limestone barriers separating flow units thus the pattern of eventual burial compartmentalization follows a template that is hardwired into the stratigraphic architecture by depositional mineralogy and early diagenesis 3 after burial 2 3 km 1 2 1 8 mi dolostones should not be expected to have higher permeability for given porosity than associated limestones these rules assume dolomitization to occur early relative to chemical compaction which will commonly be the case because of combined hydrologic and mass balance constraints dolomitization and concentration of clay appear linked to cycle and sequence architecture in the present examples and thus may have a useful degree of predictability at least in terms of statistical parameters such as net gross and probability of flow unit thickness distribution

are microtremors useful in site response evaluation we have reviewed the applicability of microtremor measurements to evaluate site response of soft soils to this end we evaluated three different techniques commonly used to estimate site effects from microtremor measurements interpretation of fourier amplitude spectra computation of spectral ratios relative to a firm reference station and finally computation of spectral ratios of horizontal components relative to the vertical component of ground motion nakamura s technique these techniques are applied to microtremor records obtained in three cities in mexico mexico city oaxaca and acapulco these cities differ in their local geological conditions and in their seismotectonic environment in order to evaluate the results obtained from microtremor measurements we compare them with standard spectral ratios of the intense s wave part of weak or strong motion records obtained at the same sites our results showed that microtremor measurements can be used to estimate the dominant period of a site with very acceptable reliability in the range 0 3 to 5 hz the best results were obtained with nakamura s technique which also gives a rough estimate of amplification of seismic waves when the local geology is relatively simple simple numerical simulations indicate that the underlying assumptions of nakamura s technique are consistent with the propagation of rayleigh waves these simple numerical simulations also explain why different researchers have been able to successfully characterize 1d site effects using microtremor records regardless of whether they consider microtremors to consist of surface or body waves our results strongly suggest that the technique by nakamura effectively compensates for source effects in microtremor measurements which eliminates a major limitation to their application in earthquake engineering

palaeomagnetism of east siberian traps and kimberlites two new poles and palaeogeographic reconstructions at about 360 and 250 ma summary we studied basalt sills and dykes and kimberlite pipes from the eastern part of the siberian platform these are spread out over a few hundred kilometres and are divided into two age groups late permian early triassic mir aikhal and olenyek regions and late devonian early carboniferous viluy and markha basins aikhal region the palaeomagnetic poles determined for each sill or dyke are statistically different from each other but averaging all corresponding directions from these sills and dykes with those from kimberlites of different generations yields results with acceptable statistics this is probably due to the averaging out of secular variation and or changes in magnetic polarity the resulting palaeomagnetic poles allow one to reconstruct the palaeopositions of siberia during the two large flood basalt events at about 360 and 250 ma a significant rotation of the siberian platform during the devonian and carboniferous is suggested the new data are in general agreement with some earlier palaeomagnetic poles for the late permian early triassic traps of the tungusska basin and significantly reduce uncertainties for previous late devonian early carboniferous siberian poles which were very scattered together with geological and absolute age data the palaeomagnetic data support the hypothesis that kimberlite magmatism and trap intrusions were both rapid and relatively close in time the 360 ma event is emerging as a magmatic event with considerable extent over the russian and siberian platforms related to incipient continental break up and triple junction formation possibly at or near the time of the frasnian famennian mass extinction

geochemistry of meteoric calcite cements in some pleistocene limestones in this study the stable isotope and trace element geochemistries of meteoric cements in pleistocene limestones from enewetak atoll western pacific ocean cat island bahamas and yucatan were characterized to help interpret similar cements in ancient rocks meteoric calcite cements have a narrow range of 18o values and a broad range of 13c values in each geographical province these pleistocene cements were precipitated from water with stable oxygen isotopic compositions similar to modern rainwater in each location enewetak calcite cements have a mean 18o composition of 6 5 0 pdb and 13c values ranging from 9 6 to 0 4 0 pdb sparry calcite cements from cat island have a mean 18o composition of 4 1 0 and 13c values ranging from 6 3 to 1 1 0 sparry cements from yucatan have a mean 18o composition of 5 7 0 and 13c values of 8 0 to 2 7 0 the mean 18o values of these pleistocene meteoric calcite cements vary by 2 4 0 due to climatic variations not related directly to latitude the 13c compositions of meteoric cements are distinctly lower than those of the depositional sediments variations in 13c are not simply a function of distance below an exposure surface meteoric phreatic cements often have 13c compositions of less than 4 0 0 which suggests that soil derived co2 and organic material were washed into the water table penecontemporaneous with precipitation of phreatic cements concentrations of strontium and magnesium are quite variable within and between the three geographical provinces mean strontium concentrations for sparry calcite cements are for enewetak atoll 620 ppm 510 ppm for cat island 1200 ppm 980 ppm and for yucatan 700 ppm 390 ppm equant cements intraskeletal cements and bahamian cements have higher mean strontium concentrations than other cements equant and intraskeletal cements probably precipitated in more closed or stagnant aqueous environments bahamian depositional sediments had higher strontium concentrations which probably caused high strontium concentrations in their cements magnesium concentrations in pleistocene meteoric cements are similar in samples from enewetak atoll mean 1 00 mol mgco3 0 60 mol mgco3 and cat island mean 0 84 mol mgco3 0 52mol mgco3 but yucatan samples have higher magnesium concentrations mean 2 20 mol mgco3 0 84mol mgco3 higher magnesium concentrations in some yucatan cements probably reflect precipitation in environments where sea water mixed with fresh water

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

cathodoluminescence in calcite cements new insights on pb and zn sensitizing mn activation and fe quenching at low trace element concentrations abstract the role of pb and zn as sensitizers of cathodolumines cl in sedimentary carbonates is still speculative as is the relationship between mn fe and cl intensity at low concentrations of mn and fe we address these questions using calcite cements from the lower oligocene suwannee formation of florida which have mean mn pb zn and fe concentrations less than 45 ppm only a small fraction of these cements exhibit visible cl but when present the luminescence is orange to reddish orange trace element contents were measured using a synchrotron x ray fluorescence microprobe and cl intensity was approximated by spot metered photomicrograph exposure times based on mn and fe contents four cement populations can be defined group i is luminescent calcite with mn 25 ppm and molar mn fe 1 8 group ii contains both luminescent and nonluminescent cements all with mn 25 ppm molar mn fe 25 ppm molar mn fe 100 ppm group iv is nonluminescent calcite with mn 25 ppm and variable fe these groupings and statistical analyses of the data mann whitney tests and factor analyses confirm that 25 ppm mn is necessary to initiate visible cl and that mn is the sole control on cl intensity when mn and fe contents are very low 100 ppm the data also establish 100 ppm fe as a new minimum for the quenching of cl when mn is below 200 ppm there is no evidence in our data that pb or zn concentrations in tens of parts per million either activate or sensitize cl the mann whitney test shows that there is no statistical evidence at the 95 confidence level to indicate that luminescent and nonluminescent cements reflect different populations of pb and zn except for group ii cements that have more pb in nonluminescent cements than in otherwise chemically equivalent luminescent cements factor analysis shows that cl intensity in all luminescent cements is unrelated to pb or zn concentrations given that pb or zn sensitizing is lacking in low mn calcites like the suwannee cements it is hard to imagine how these elements could play a significant role in calcites containing even more mn as is typical of most sedimentary carbonates

use of spectral gamma ray signature to interpret stratigraphic surfaces in carbonate strata an example from the finnmark carbonate platform carboniferous permian barents sea spectral gamma ray gr profiles were examined in well 7128 6 1 the stratigraphic reference section of the entirely subsurface finnmark carbonate platform detailed bulk chemical profiling of selected gr peaks shows that potassium k and thorium th are mutually correlated and are a direct index of siliciclastic aluminosilicate content whereas uranium u is uncorrelated with k th and all other chemical components measured uranium tends to be enriched in thin shale and argillaceous carbonate layers within otherwise carbonate dominated intervals uranium is thus associated with aluminosilicate minerals and is not particularly concentrated in dolomite two types of gr peaks are observed potassium thorium dominated peaks are suggested to indicate relatively major transgressions during which aluminosilicate detritus was derived from sources interior to the fennoscandian shield uranium dominated peaks correspond with relatively minor transgressions within intervals of cyclic shallow water carbonate deposits uranium enriched aluminosilicate detritus is suggested to be the product of extended subaerial exposure of the platform during which u was concentrated by groundwater movement these results can be useful as a basis for applying spectral gr signature as a tool for stratigraphic interpretation in uncored or incipiently understood carbonate sections