reflection and refraction seismics in areas of complex geology an example in the northern apennines an experimental survey employing refraction wide angle reflection seismic techniques dss deep seismic soundings was carried out in the northern apennines north italy the main objective of the experiment was the application of dss to better define the structure of the upper crust down to about 15 km depth in the crucial alps apennines boundary zone a second objective was to understand the potential of dss as a complementary tool in areas of complex geology where the results of near vertical reflection nvr are generally poor the results of the experiment show that dss if properly planned can continuously follow deep markers and therefore impart a greater significance to faint and discontinuous nvr as well as data on the p wave velocity of the seismic units

reconstructing daily temperatures from growth rates of the intertidal bivalve mollusk chione cortezi northern gulf of california mexico abstract we establish a model for the reconstruction of average daily sea surface temperatures from calcification rates of an intertidal bivalve mollusk the rate of shell production in chione cortezi carpenter 1864 ex sloat ms is mainly controlled by water temperature ontogenetic age and the effect of tidal cycles statistical methods developed by dendrochronologists can successfully extract the water temperature signal from daily growth increment chronologies after removal of noise the growth rates are expressed as scaled daily growth indices average daily water temperatures during the first half of the year are highly correlated with the scaled daily growth index values of recent and subrecent specimens using the multi valued function presented here increment width analysis can reconstruct daily average water temperatures with a mean error of less than 3 this technique provides an independent method for reconstructing temperatures in fossil specimens of species with living representatives and can supplement high resolution temperature reconstructions based on geochemical analysis

cathodoluminescence of late triassic terebratulid brachiopods implications for growth patterns abstract upper triassic terebratulid brachiopod rhaetina shows differential preservation of shell structure under cathodoluminescent cl and scanning electron microscope sem indicating intra and interspecific differences in brachiopod growth patterns in longitudinal sections the cl lines appear firstly in inner ontogenetically older parts of the shell and their outlines are parallel with the internal valve surface in posterior parts of the shell in anterior parts of the shell cl lines run diagonally towards the external valve surface and terminate in external growth lines the shell structure of external growth lines indicates that major growth lines associated with gradual reorientation of calcitic crystals due to reflection of the mantle edge and disturbance lines associated with abrupt mantle regression are present at the terminations of cl lines these data indicate that cl lines correspond to zones recording slowing cessation of the growth rate under sem shell layers that are luminescent can be locally recognized as amalgamated or altered relicts of the secondary fibres the origin of luminescence in these areas can be related to 1 the increased mn bearing diagenetic fluid flow favoured by higher porosity of altered secondary fibres or can be caused by 2 temporal changes in the redox state controlling the solubility of mn2 and fe2 during the mantle anaerobiosis similarly amalgamated altered shell structure could either point to 1 the primary modification of shell secretory regime during the slowing cessation in growth rate or could be 2 the product of diagenetic processes responsible for post depositional alteration of a shell structure due to the primary shell heterogeneity porosity in areas of growth discontinuities although presented data do not convincingly solve this uncertainty the important point is that cl lines of studied brachiopods reflect changes in the growth rate and can be used in the investigation of growth dynamics in brachiopods complementary to external growth lines and isotope or trace element analysis in order to verify the modification of shell structure and understand the origin of associated luminescence during the change in growth rate unbiased by diagenetic overprint it is necessary to examine modern brachiopods the distribution pattern of cl lines that correlates with growth rate fluctuations potentially reflects a short term environmental instability on the time scale of an individual life span the data show correlation between cl line pattern and different bathymetric settings regular repetition of cl lines is preserved in rhaetina gregaria rhaetina hybensis and rhaetina pyriformis that occur in relatively uniform depositional settings below a normal storm wave base in contrast irregular pattern of cl lines is typical of r gregaria from highly variable deposit associations derived from very shallow subtidal settings above a normal storm wave base in the case of r gregaria this difference reflects intraspecific variations in growth dynamics among bathymetric settings indicating environmental control on their growth rates rhaetina gregaria is mostly the only one brachiopod species present in benthic assemblages from very shallow marginal marine environments in the western tethys the implication is that r gregaria in contrast to most other brachiopods could live in physically stressed habitats characterized by higher environmental instability unpredictability

spatial variability of hurst statistics in the castagnola formation tertiary piedmont basin nw italy discrimination of sub environments in a confined turbidite system

structure and composition of organic reefs and carbonate mud mounds concepts and categories defined here as essentially in place calcareous deposits created by sessile organisms organic reefs are diverse and complex structures with a long geological history their classification has been the subject of fierce debate often characterized by reliance on subjective features such as wave resistance and qualitative attempts to discriminate between first and second class reefs in contrast emphasis is here placed on the objective characteristic of the type of sedimentary support which largely determines the sedimentary composition of the deposit constructional and depositional processes result in three principal sedimentary components matrix m essentially in place skeletons s and cavity cement c whose proportions can be represented on msc triangular plots separately or together these components also provide the structural support for the reef on these compositional and structural bases three main categories of organic reef are recognized 1 matrix supported reefs agglutinated microbial reefs cluster reefs segment reefs 2 skeleton supported reefs frame reefs 3 cement supported reefs cement reefs agglutinated microbial reefs possess laminated clotted or aphanitic fabrics created by microbial trapping of particulate sediment in place skeletons and large primary cavities are rare early cementation may provide added support topographic relief is limited by the need for currents to provide sediment to accreting surfaces cluster reefs skeletal reefs in which essentially in place skeletons are adjacent but not in contact resulting in matrix support characterized by relatively high matrix skeleton ratios and low volumes of extra skeletal early cement sediment trapping is an important corollary of skeletal growth and cluster reef organisms are tolerant of loose sediment absence of framework limits the topographic relief that cluster reefs can attain relative to spatial extent and may permit bedding to develop within the reef close cluster reefs have skeletons up to 1 unit distance apart spaced cluster reefs have skeletons more than 1 and up to 2 unit distances apart with increasing separation of skeletons they grade to level bottom communities segment reefs matrix supported reefs in which skeletons are adjacent and may be in contact but are mostly disarticulated and mainly parauthochtonous matrix abundance is high and early cement relatively low moderate relief can develop in response to intense on reef sediment production frame reefs skeletal reefs in which essentially in place skeletons including calcified microbes are in contact characterized by relatively high skeleton matrix ratio skeletal support enables them to raise themselves above the substrate independently of cementation and particulate sedimentation simultaneously by creating partly open shelter cavities skeletal support may facilitate early cementation both relief and early lithification promote marginal talus formation skeletal shape and orientation distinguish conical stick like dendritic domical and laminar frames each of these may be open or filled open frame reefs

further development of a high frequency seismic source for use in boreholes a borehole sparker seismic source enclosed in a semi flexible tube has been developed to produce a short compressional seismic pulse with a frequency content in the range 250 hz to 3 5 khz with a peak power at 570 hz the pulse shape and frequency content are shown to be a function of the input power the diameter of the spark chamber the salinity of the electrolyte the material of the spark chamber and the electrode configuration when in a borehole the source produces a vertically polarized shear wave but being similar to a small explosive charge does not allow phase reversal as a means of identifying the shear wave in the received pulse train the source is shown to be ideal for tomographic imaging surveys because of its repetitive nature high frequency content and reliability very high resolution seismic reflection surveys are also shown to be possible under favourable circumstances

prediction of coal seam details and mining safety using multicomponent seismic data a case history from china abstractwith the increasing mining depth of coal mines geologic hazards have become the main source of accidents for this reason coal seam prediction requires more assessment parameters such as the degree of anisotropy vp vs value and elastic modulus these parameters are difficult to determine using only the pp wave we have inverted and interpreted multicomponent seismic data acquired from a 2 56 km2 area in the guqiao mine located on the southern margin of the north china plate under the constraints of drill log and rock physics test data the production coal seam 11 2 of the mine located in the permian formation was our focus of this study and our objective was to determine the structure fracture development thickness surrounding rock lithology roof stability and mining safety of the seam to achieve this we first performed an analysis of s wave splitting and joint pp and ps wave inversions the inversion results were then combined to derive additional parameters such as the vp vs

diagenetic history and reservoir properties of the cenomanian turonian carbonates in southwestern iran and the persian gulf abstract shallow marine carbonates of the mid cretaceous sarvak formation are important reservoir rocks in southern iran and the persian gulf region these carbonates were deposited on the margin of the arabian plate and rest on the kazhdumi formation which is one of the major hydrocarbon source rocks in the region the top of the sarvak formation coincides with the regional turonian unconformity most of the observed diagenetic features are genetically related to meteoric waters entering the sarvak formation during cenomanian turonian and mid turonian uplift and the subsequent paleoexposure integration of field and petrographic studies and isotope geochemistry reveals the history of a variety of diagenetic processes which include dissolution and development of secondary porosity which enhance reservoir properties of the upper sarvak carbonates various types of calcite cements were identified as the main cause for porosity loss in these carbonates their diagenetic environment is discussed using the geochemical data acquired as part of the present study the 18 o and 13 c values 12 3 to 0 6 and 5 8 3 6 vpdb respectively of the cements indicate precipitation from marine meteoric and or mixed meteoric marine fluids some drusy calcite cements exhibit 18 o and 13 c values 5 1 and 0 8 vpdb respectively and higher 87 sr 86 sr ratios comparing to mid cretaceous carbonates i e 0 70747 which may indicate precipitation from meteoric waters lower 18 o and 13 c values e g 5 1 0 8 vpdb combined with higher 87 sr 86 sr ratios e g 0 70747 of some drusy calcite could confirm their precipitation from meteoric waters lower 18 o values of some blocky calcite cements e g 12 3 vpdb and matrix replacive compression related dolomites i e 7 3 to 3 4 vpdb suggest their precipitation at rising temperatures during burial the range of 13 c values 5 8 3 6 vpdb suggests that the main source of carbon in the calcite cements was primarily marine mixed with isotopically more negative carbon from atmospheric soil derived co 2

inverse and forward modelling of groundwater circulation in a seismically active area monferrato piedmont nw italy insights into stress induced variations in water chemistry municipality of nizza monferrato asti italy and the regional administration of regione piemonte italy

the origin and timing of multiphase cementation in carbonates impact of regional scale geodynamic events on the middle jurassic limestones diagenesis paris basin france the middle jurassic carbonates of the eastern part of the paris basin display surprisingly low values of porosity and permeability 15 and k 0 5 md the main objective of this study is to determine the causes and timing of the cementation that altered the petrophysical properties of these carbonates thereby destroying their potential as oil reservoirs a fate that did not befall their equivalents in deeper central parts of the paris basin using petrographic and geochemical analyses stable o and c isotopes sr isotopes major elements we identify six calcitic spar stages two dolomite stages and several episodes of fracturing and stylolitization ordered in paragenetic sequence cement quantification shows the predominance of two blocky calcite cement stages 75 of total cementation o and sr isotopes from these calcite cements suggest that the parent fluids resulted either from a mixing of trapped jurassic seawater and meteoric water or from buffered meteoric waters in the geological history of the paris basin major meteoric water inputs were possible during the early cretaceous when the middle jurassic carbonates cropped out at its northern and eastern borders lateral meteoric recharge may have occurred as a result of two separate uplift events late cimmerian unconformity and late aptian unconformity and the related exposures of carbonates to the north of the study area this palaeohydrological circulation brought about a significant reduction of porosity from 40 to 10 through calcite cement precipitation the early cretaceous events are of great importance in the diagenetic evolution of the sedimentary basins bordering the london brabant massif across all of northwestern europe a subsequent dolomite and calcite cementation stage accounts for about 5 of the total cement volumes this late cementation may have been caused by hydrothermal fluids ascending along permeable fractures during the late oligocene extension episode

considerations on the seismotectonics of the northern apennines abstract the northern apennines have been subdivided into homogeneous zones on the basis of recent structural evolution and crustal structure in which the earthquake distribution can find a coherent framework these zones whose physiography is in strict connection with their structure are the internal peri tyrrhenian belt the external or main belt the buried belt and the pede alpine homocline earthquake activity has a tendency to cluster along well defined bands particularly in the easternmost border of the peri tyrrhenian belt as well as along the zone between the external belt and the buried belt i e along the padanian margin of the northern apennines a minimum of seismic activity seems to be correlated with some zones of the external belt as well as with the late tertiary and quaternary magmatic province of tyrrhenian southern tuscany the fault plane solutions are coherent with the structural picture a tentative seismotectonic model of the northern apennines is discussed

ligamental increments of the mid holocene pacific oyster crassostrea gigas are reliable independent proxies for seasonality in the western bohai sea china abstract modern living and mid holocene shells of crassostrea gigas from the western bohai sea in china were subjected to sclerochronological analysis with the aim of determining whether their concave bottoms and growth breaks on resilifer surfaces as well as corresponding translucent growth bands visible in cross section have seasonal significance an additional aim was to obtain ontogenetic information from mid holocene fossil shells we compared 18 o and 13 c profiles compiled with high and low sampling resolution for the same shell in order to test the consistency of the results and identify a suitable sampling strategy for future sclerochronological studies the results show that concave bottoms on the resilifer surface and corresponding translucent growth bands in cross section formed during the cold season these features are appropriate indicators of annual growth increments in fossil c gigas shells moreover growth breaks located near convex tops indicate annual growth increments for that part of the shell which grew when the organism was sexually mature therefore spawning related growth breaks and alternating winter freeze shocks concave bottoms are excellent morphological features in determining annual growth increments consequently the life span growth rate and timing of spawning and death can be determined from the increments of ligament growth of these fossil oyster shells for future sclerochronological studies an adaptive micro sampling strategy could be used for different increments of ligament growth that represent different seasons such a strategy would be more efficient in providing reliable insights into growth history of shells with variable growth rates of annual increments

the detection of monumental tombs buried in tumuli by seismic refraction a tumulus is a construction erected to cover a tomb some tumuli are impressively massive and may conceal architectural masterpieces seismic refraction is employed to locate the tomb and to allow selective excavation without destroying the tumulus the detectors are spread along a circular profile on the periphery of the tumulus and acoustic waves are generated on its top time delays observed in the arrivals of the headwaves reveal the position of the monument the delays are not caused by the monument itself but are an effect caused by the presence of a ramp that was dug in the undisturbed soil to help in the construction of the tomb three case histories in northern greece establish the efficiency of the technique in the first example an experiment was conducted at a previously excavated tumulus and time delays attributed to the revealed ramp are observed the second case study led to the discovery of an impressive monument 3 d modeling by finite difference verifies the interpretation a third s

matrix micrite δ13c and δ18o reveals synsedimentary marine lithification in upper jurassic ammonitico rosso limestones betic cordillera se spain abstract matrix micrites are a commonly used carbonate archive for the reconstruction of past environmental parameters but one that is submitted to known limitations main reasons for the often ambiguous value of many micrite based isotope data sets are the unknown origin of the micrite components and their poorly resolved diagenetic history here we present carbon and oxygen isotope data retrieved from oxfordian to tithonian ammonitico rosso nodular micrites sampled from three sections in the betic cordillera southern spain all three sections were correlated and sampled using a rigorous biostratigraphic framework a noteworthy feature is that analyzed matrix micrites are more conservative in terms of their isotopic composition than other carbonate materials commonly considered to resist diagenetic alteration under favourable circumstances remarkably this refers not only to 13 c ratios which reflect the typical late jurassic global trend but also to 18 o ratios that range around 0 3 the 18 o enriched oxygen isotope ratios are considered to represent diagenetic stabilization of carbonate ooze under the influence of marine porewaters within the sediment water interphase i e the immature sedimentary section usually submitted to biogenic activity this interpretation agrees with the very early lithification of micrite nodules with cements precipitated from marine porewaters enriched by the dissolution of aragonite skeletals i e ammonite shells according to the model proposed low sedimentation rates as well as rapid early marine differential cementation under the influence of currents and seawater pumping affected the sediment water interphase of epioceanic swells where deposition resulted in early lithified ammonitico rosso facies the data obtained show that special care must be taken to prevent oversimplified interpretations of carbonate archives particularly in the context of epioceanic settings

burrow mediated carbonate dissolution in rudist biostromes aurisina italy implications for taphonomy in tropical shallow subtidal carbonate environments abstract in upper cretaceous rudist biostromes at aurisina italy marked taphonomic loss of radiolitids by burrow mediated dissolution and mechanical disintegration illustrates the relation between synecology and early diagenesis in the fossilization of tropical shallow water bioconstructions the studied platform succession accumulated in a prevalently open lagoon with bioturbated carbonate sand rudist thickets bioclastic dunes and areas with shelly lime ooze rudist biostromes consist of radiolitids and hippuritids or of radiolitids only and have an open parautochthonous rudist fabric with a matrix of bioclastic bioturbated wackestone swirly disorientation of bioclasts records early softground bioturbation later firmground burrows comprise an irregular network of tunnels and chambers filled with bioclastic packstone to grainstone the size geometry and sediment fill of the firmground burrows suggest that they were produced by crustaceans radiolitid preservation ranges from complete to relictic radiolitid relicts formed by a spalling and or dissolution of the cellular boxwork ostracum of the attached valve leaving calcite tubes built by a distinct thin ostracal shell layer or b dissolution of the entire shell leaving the sedimentary fills of the intertabular spaces of the attached valve as a diagnostic vestige or c shell dissolution within the firm sediment with subsequent filling of the biomould by bioclastic wackestone to packstone to grainstone loss of radiolitids produced a taphonomic bias towards rudists with non cellular ostracum locally taphonomic loss produced ghost biostromes composed nearly entirely of faint radiolitid relicts shell dissolution resulted from chemical gradients in the sediment within and near the burrows and from enhanced microboring and microbial infestation dissolution of radiolitids was favoured by the combined effects of chemical instability of hypostracal aragonite and by the structure of the calcitic boxwork ostracum of thin walled cells some biostromes are intercalated with or are capped or overlain within a short vertical distance by a hardly recognizable emersion surface as a consequence of the shallow depth of biostrome accumulation taphonomic loss by dissolution is widespread in open parautochthonous rudist fabrics and confirms actuogeological results of other authors that bioturbation mediates carbonate dissolution also under shallow tropical waters supersaturated for calcium carbonate the amount of carbonate dissolved upon burrowing of the biostrome matrix is hardly quantifiable but by analogy to recent carbonate environments may have been large within bioconstructions deep tiered burrowing occurred at least since the carboniferous taphonomic loss by dissolution thus may have been active in the fossilization of tropical shallow water mounds and biostromes over much of phanerozoic times

a critical assessment of mollusk 18 o 16 o mg ca and 44 ca 40 ca ratios as proxies for cretaceous seawater temperature seasonality seasonal temperature fluctuations of tethyan coastal water are recorded in a pristine 80 my old rudist shell from turkey in order to critically assess factors other than seawater temperature that might have influenced the shell geochemical record three different paleo temperature proxies 18o mg ca and 44ca were applied in a qualitative manner all three proxies reflect the same cyclical trends and thus yield robust evidence for seasonal fluctuations in late cretaceous surficial seawater temperature this suggests the successful application of the new 44ca temperature proxy to fossil mollusk calcite the direct comparison of the three data sets however demonstrates that all proxies are fraught with problems similar to other studies 18o 16o ratios point to warmer summer temperature maxima than those in comparable costal settings today nevertheless the 18o 16o proxy is subject to environmental factors that might lead to an overestimation of peak temperatures moreover mg ca molar ratios are less sensitive to environmental factors but were strongly affected by the ion regulating capability of the rudist bivalve that responded to the low mg ca ratio of cretaceous seawater similarly uncertainties of the 44ca composition of cretaceous seawater and the complex bio calcification of mollusks presently limit the interpretation of 44ca values in terms of absolute seawater temperature the multiproxy approach applied here however documents that these limitations do not obscure the dominant patterns of seasonal sea surface temperature variations recorded in the biogeochemical rudist archive

the collisional knot in liguria a series of 8 new seismic refraction profiles were computed as extensions of the borehole controlled reflection profiles of the po plain into the northern apennines and the ligurian alps they help to more clearly define the subsurface structure of this intricate ligurian knot in particular it has been possible to identify a number of high velocity bodies and they may be correlated with such geological entities as the adriatic mesozoic ophiolites of the apenninic liguride nappes and ophiolites or mesozoic carbonates underlying the antola flysch in the alpine part of the knot when combining the refraction and reflection lines these bodies appear to be bounded by important dislocation surfaces such as the padanide sole thrust plio pleistocene the villalvernia varzi line oligo miocene the ottone levanto line oligo miocene and the volpedo valle salimbene fault oligo miocene reactivated as a transfer fault in the plio pleistocene the 3d geometry may be interpreted in terms of regional kinematics and is compatible with a model that envisages an oligo early miocene nw translation of the adriatic indenter coupled with collapse in the provencal ligurian sea and rotation of the sardinia liguria complex into the roll back of the adriatic subduction zone the refraction interpretations extending to a depth of 15 km are supplemented by data on the moho configuration obtained for the european geotraverse the moho appears to be dissected into a series of patches which may be interpreted in terms of the shallow crustal configuration and its history in particular the deepest patch appears to be terminated by the volpedo valle salimbene fault which consequently would displace the entire crust

carbonate production by rudist bivalves the record of late barremian requieniid communities from provence se france abstract rudist bearing sediments from platform carbonates of late barremian age early cretaceous cropping out in the marseille region provence se france were investigated on a 46 km wide transect after seven stratigraphic sections to quantify the role of rudists in the corresponding stratigraphic system by using various proxies the regional stratigraphic contribution of total thickness of rudist beds is relatively high 43 1 each rudist community type possesses a specific skeletal contribution of skeletal content in the range of 19 2 to 31 5 at a stratigraphic scale including rudist rich and rudist free beds the skeletal contribution drops to 13 8 this value is derived from the standard skeletal contribution obtained for each community type combined with the stratigraphic contribution of rudist beds in vertical successions and horizontal stratigraphic units a closely related value 12 8 is obtained from calculations using specific lateral dimensions of rudist bodies and their spacing i e modules depending on community types each community has a particular potential quantitative contribution to the overall regional stratigraphic system rudist production is deduced from the cyclostratigraphic approach of accumulation rates for each community type estimates of caco 3 net production are in the range of 19 to 50 kg m 2 ka 1 these values are very low when compared with those obtained at a biological scale for modern bivalves late cretaceous rudists and recent coral reefs the geological scale used for our estimates may partly account for this difference whereas low accommodation rates linked to cretaceous greenhouse conditions appear a potential important factor in this respect the low net production of requieniid dominated communities sediment dwellers not framework builders also reflects their limited sedimentogenetic power

cool episode and platform demise in the early aptian new insights on the links between climate and carbonate production the early aptian encountered several crises in neritic and pelagic carbonate production major perturbations in the carbon cycle and an oceanic anoxic event oae1a yet the causal links between these perturbations and climate changes remain poorly understood partly because temperature records spanning the early aptian interval are still scant we present new 18o data from well preserved bivalves from a carbonate platform of the galve subbasin spain that document a major cooling event postdating most of oae1a our data show that cooling postdates the global platform demise and cannot have triggered this event that occurred during the warmest interval the warmest temperatures coincide with the time equivalent of oae1a and with platform biotic assemblages dominated by microbialites at aliaga as well as on other tethyan platforms coral dominated assemblages then replace microbialites during the subsequent cooling nannoconids are absent during most of the time equivalent of the oae1a probably related to the well known crisis affecting this group yet they present a transient recovery in the upper part of this interval with an increase in both size and abundance during the cool interval portion that postdates oae1a an evolution toward cooler and drier climatic conditions may have induced the regional change from microbial to coral assemblages as well as nannoconids size and abundance increase by limiting continent derived input of nutrients

the giant marine gastropod campanile giganteum lamarck 1804 as a high resolution archive of seasonality in the eocene greenhouse world

biotic interaction and synecology in a late cretaceous coral rudist biostrome of southeastern spain abstract a coral rudist biostrome exposed in campanian limestones near the village of tabernas de valldigna in south east spain was analysed with respect to its palaeontology sedimentology and palaeoecology special attention was given to possible evidence for synecological interactions between corals and rudists changes in the rudist shell accretion process are evident in some polished slabs and thin sections and resulted from in vivo contact with coral colonies these unusual balcony like shell protuberances exist where the rudist s commissure was in contact with corals they likely represent defence reactions of rudists against the coral cnidia nevertheless the fossil record of these biotic interactions is rare this may be due to different growth rates of rudists and corals differing shape and size of interacting areas or different life spans in consequence the discrete window of intergroup biotic interaction was small sedimentation and resuspension rates were high in the biostrome and corals only established pioneer associations under these unfavourable conditions a higher diversity of corals is reached however when rudists are present this increase in diversity resulted from the availability of additional ecological niches such as rudist shell hard substrates and elevation above mobile sediment surface rudists on the other hand received support from stabilisation of their shells through coral encrustation and framework building in consequence both groups benefited from their co existence

late paleocene arctic coastal climate inferred from molluscan stable and radiogenic isotope ratios abstract characterizing polar climates during past warm intervals is important for understanding greenhouse climate dynamics because high latitude surface temperatures and precipitation patterns are extremely sensitive to global climatic conditions model data comparisons of high latitude climates during past warm intervals cretaceous eocene pliocene are currently at odds specifically simulations of past warm climates produce polar regions characterized by sub freezing temperatures and significant seasonality whereas limited fossil proxy data indicate higher mean annual temperatures and low seasonality i e an equable climate we have constructed a data set to infer northern hemisphere polar marine temperatures during the late paleocene seasonal and mean annual temperature and the oxygen isotopic composition of precipitation are reconstructed for an arctic coastal setting during the thanetian 57 58 ma using fossil shell stable isotope profiles we estimate that coastal water temperatures varied between 10 and 15 c during the seasons of growth presumably spring summer and fall these findings support paleontological evidence implying northern hemisphere polar climates were seasonally warm during the late paleocene in addition estuarine fossil oxygen isotope profiles show periodic excursions to low values as low as 19 vpdb which indicate seasonal pulses of isotopically depleted freshwater

recent and historical discharge of a large european river system oxygen isotopic composition of river water and skeletal aragonite of unionidae in the rhine abstract seasonal variations in the oxygen isotopic composition of rhine river water were analyzed in detail and compared with the oxygen isotopic record from recent and historical specimens of freshwater bivalves unionidae the purpose of this study was to investigate the potential use of these aragonitic bivalves as proxy recorders for varying amounts and sources of discharge and thereby infer climate change seasonal variations in the river water 18 o are on the order of 1 2 during summer alpine melt water contributes significantly to the total discharge resulting in average values of 10 to 10 5 whereas the non alpine contribution is higher during winter as indicated by mean 18 o values of 8 5 to 9 the basic pattern of the modern seasonal variation of 18 o of river water can be described by a numerical mass balance approximation of the various contributions from the alpine and non alpine catchments with their average 18 o composition the 18 o of growth increments in the prismatic shell layer of anodonta corresponds perfectly to what is predicted by known fractionation of 18 o between water and aragonite shell growth is restricted to water temperatures above 8 10 c so variations in 18 o and the river water temperature are faithfully recorded by relatively large growth increments during summer the distinctive isotopic signatures of individual flood events during summer and autumn are also recorded in the shells

microfacies and geochemistry of the middle cretaceous sarvak formation in zagros basin izeh zone sw iran abstract the sarvak formation albian to cenomanian forming part of the bangestan group comprises a thick succession of carbonate rocks in the zagros basin of southern iran the sarvak formation forms one of the main hydrocarbon reservoirs of this region three sections in the northern 252 m thickness and southern flanks 348 m thickness of the mish and anneh anticlines 245 m thickness in the izeh zone of sw iran were selected for this study petrographic analysis led us to define 10 microfacies units deposited in four facies belts i tidal flat ii lagoonal iii shoal and iv open marine all of these form part of a platform ramp environment geochemical investigations limited to outcrops of the mish anticline aided in understanding geochemical and diagenetic characteristics of carbonate rocks from the sarvak formation variations of oxygen and carbon isotope data from limestones of the sarvak formation indicate near primary marine phreatic and partially meteoric digenesis for both flanks of the mish anticline respectively lower abundances of mn and fe suggest that the carbonates at both sites appear to have stabilized under mainly oxic conditions the sarvak carbonates from the north flank of the mish anticline indicate higher rock water interaction and a closed diagenetic system in comparison to the south flank of the mish anticline vertical and lateral variations in stratigraphic thicknesses in selected outcrops can be related to the presence of syn sedimentary faults in the zagros basin that resulted in regional instability or due to rates of sedimentation with lower rates of deposition in the basin during middle cretaceous times

studies of the influence of non linear stress strain characteristics in soil structure interaction recent field and laboratory studies have shown that even at very small strains many soils exhibit non linear stress strain behaviour nevertheless because of its convenience linear elasticity will continue to play an important role in the analysis of such problems as settlement deformation and soil structure interaction in this paper the measured non liqear stress strain properties of a low plasticity clay are used in the finite element analysis of footings piles excavations and pressuremeter tests to assess the influence of small strain non linearity in comparison with linear elastic behaviour in all cases non linear behaviour results in the concentration of strain and deformation towards the loading boundaries this is shown to have important consequences for soil structure interaction problems such as settlement profiles pile group interaction and contact stress distributions small strain non linearity also has a significant influence on the interpretation in terms of equivalent elastic modu

late turonian climate variability in the bohemian cretaceous basin a sclerochronological study of inoceramus hercules shells from the upohlavy quarry czech republic abstract the 18o record of well preserved shells of the inoceramid inoceramus hercules from the upohlavy working quarry czech republic provides an insight into the climate variability in the late turonian benthic environment of the bohemian cretaceous basin similar to modern bivalves this inoceramid species built its shell near equilibrium with the oxygen isotope value of the ambient water due to the nearly year round shell growth sequentially sampled 18o values allowed to estimate the narrowest sub annual temperatures fluctuations that prevailed during lifetime of the organisms in accordance with previous studies reconstructed temperatures suggest colder water conditions 19 0 0 9 c during the earliest late turonian coinciding with the hyphantoceras event also known as hitch wood event than during the later part of the substage 20 9 1 1 c climate warming however did not affect the sub annual temperature fluctuations evenly but predominantly affected the warmest part of the year at least 4 0 c on the contrary the coldest recorded temperatures remained more or less invariant varying not much more than 1 0 c across the studied time interval the observed changes in the benthic temperature estimates likely reflect shifts in seasonal sea surface temperature amplitudes in response to climate forcing given the widespread distribution of i hercules in the upper turonian lower coniacian hemipelagic strata of europe the present study sets the basis for future continent wide sub annually resolved climate reconstructions

isotopic and chemical intra shell variations in low mg calcite of rudist bivalves mollusca hippuritacea disequilibrium fractionations and late cretaceous seasonality isotopic 13c 18o and elemental mg sr mn fe compositions were analysed in sclerochronological profiles of several shells of late cretaceous rudist bivalves from greece turkey somalia and the arabian peninsula the preservation of original compositions of low mg calcite of outer shell layers is indicated by constant and high sr generally low fe and mn and the preservation of fibrous prismatic ultrastructures cyclic variations in 18o and mg are interpreted to reflect seasonal temperature salinity cycles and thus annual growth increments in shells of torreites amplitudes of correlated 13c and 18o cycles cannot be related to reasonable palaeotemperatures or salinity this isotopic pattern reflects vital fractionations of an extent which is unknown from modern bivalves in contrast almost identical ranges and amplitudes of 18o cycles are observed in 13 shells of five species from santonian campanian localities in central greece and northern turkey suggesting that seasonal variations in environmental conditions were recorded without significant vital fractionations the effect of seasonal salinity changes on 18o of the shells is evaluated and mean palaeotemperatures are constrained within the range of 30 32 5 c the annual range of temperature was estimated to be 7 c assuming a constant salinity this agrees with other isotopic proxies of late cretaceous palaeotemperatures and with global circulation models which predict higher low latitude sea surface temperatures than the present ones

stable isotope sclerochronology of rudist bivalves growth rates and late cretaceous seasonality the almost complete translation of shell accretion to vertical growth was a successful morphogenetic adaptation of rudist bivalves which replaced coral algal hydrozoan communities in most tethyan shallow marine environments during the cretaceous growth rates of rudist shells are therefore important in reconstructions of cretaceous shallow marine benthic communities carbon and oxygen isotopic compositions were analyzed in sclerochronological profiles through the shells of two late cretaceous rudist bivalves from greece and turkey values of 13 c vary between 0 8 and 2 2 in the hippuritid vaccinites ultimus and between 0 8 and 2 6 in the radiolitid gorjanovicia cf costata ranges in 18 o are 5 3 to 2 9 and 4 6 to 2 1 respectively a distinct cyclicity of 13 c and 18 o in both shells reflects late cretaceous seasonality and indicates annual vertical growth increments of 45 mm in v ultimus and 54 mm in gorjanovicia the concentrations of minor elements are similar to those of extant bivalves with low mg calcite shells

the structure of the upper crust in the alps apennines boundary region deduced from refraction seismic data abstract analysis of data gathered during the 1983 european geotraverse southern segment egt s 83 experiments in the region extending from the emilia liguria apennines to the western alpine arc together with data from seismic profiles in the northwestern apennines accumulated within the framework of the alps apennines orogene study group indicate new details on the structure of the upper crust east and west of the alps apennines boundary the main results of this analysis centre on two areas in the piedmont tertiary basin we could determine the depocenter configurations of the 6 7 km thick terrigenous sequence and differentiate the tectonic units in the piedmont alpine and the ligurian apennine domains within the basement in the other area the insubric domain underneath the ligurian nappes of the northern apennines we found indications of tectonic doubling within the terrigenous carbonate sequence in which thrusting attenuates towards the underlying basement detected at a depth of 12 15 km in addition we found that on a line from the emilia apennines to the monferrato hills displacement of the ligurian nappes over the insubric domain diminishes to nearly one third its original extent

a gravity model of the crust beneath the tertiary piemonte basin northwestern italy abstract a gravity model of a crustal section crossing the tertiary piemonte basin from north to south is presented it was constructed by combining geological data and the results of the application of several geophysical methods with particular reference to the seismic findings a model is proposed for the morphology of the deep crust crust mantle transition identified by the wide angle reflection seismic data from the european geotraverse egt project and its geological consequences are discussed the existence of substantial displacements at the crust mantle boundary is stressed they do not appear to be directly related to superficial structures but underscore the wedging of the ligurian mantle on the insubrian crust compared with the observed bouguer gravity field gravity modelling of the section has supplied a calculated anomaly with a persistent short wavelength negative residual anomaly curve in the area of the asti basin it is suggested that this anomaly is due to a wedge of sedimentary rocks within the crust the wedge consists of both apennine and padane units and is located along a major structural boundary where metamorphic crust and tertiary sediments belonging to the alpine domain overthrust apennine and padane units during the tertiary

improving shallow water carbonate chemostratigraphy by means of rudist bivalve sclerochemistry deep time shallow marine carbonate platforms record distinct biotic responses to climatic and environmental stressors unfortunately precise temporal assignment of these biotic responses is often problematical due to poor biostratigraphic control and or a significant diagenetic overprint of the neritic bulk carbonate chemostratigraphic inventory an accurate stratigraphic framework is essential to better understand the causal relation between biotic events recorded by carbonate platforms and environmental changes that for instance culminated in mass extinction events or prolonged episodes of oceanic anoxia here we provide an integrated carbon and strontium isotope stratigraphy of the early cretaceous subtropical provence carbonate platform in se france that is based solely on pristine low mg calcite from rudist bivalves carbon isotope data of geochemically screened rudist fragments enabled reconstruction of a characteristic barremian pattern including the mid barremian event mbe that allowed for a precise correlation with stratigraphically well constrained tethyan shallow water and hemipelagic reference sections in order to evaluate ontogenetic carbon isotope changes and the overall variability of the shell derived carbon isotope data numerous sclerochronological carbon isotope profiles of individual large rudist shells are presented strontium isotope stratigraphy supports the carbon isotope based age of the studied sections but also provides unequivocal evidence for a major hiatus in the depositional record covering large parts of the late barremian in contrast to biostratigraphic and bulk carbonate chemostratigraphic archives the here established chronostratigraphy of carbonate platform evolution in the southern provence region demonstrates a twofold resurgence of rudist rich carbonate platform production during the early aptian and arguably the latest early aptian

impact of diagenetic alteration on brachiopod shell magnesium isotope δ26mg signatures experimental versus field data due to their thermodynamically stable low mg calcite mineralogy the shells of brachiopods are often counted among the most reliable archives of the physicochemical conditions that occurred during the phanerozoic in marine waters consequently traditional and non traditional isotope and elemental proxy data from brachiopod valves have been analyzed in numerous studies and results obtained have been placed in context with ancient seawater properties this paper tests the sensitivity of brachiopod shell magnesium isotope 26mg data to diagenetic alteration we apply a dual approach by i performing hydrothermal alteration experiments using meteoric marine and burial reactive fluids and ii comparing these data to naturally altered ancient brachiopod shells the degree of alteration of individual shells is assessed by a combination of fluorescence and cathodoluminescence microscopy the absence of luminescence might indicate both well preserved shell material but also the secondary enrichment of quenching elements such as iron along diagenetic pathways complementary oxygen isotope data provide insight into the question of open versus closed system behavior of brachiopod shells brachiopod shell magnesium isotope values respond to differential fluid temperature chemistry and experiment durations the patterns observed are complicated by the interplay of kinetic and thermodynamic patterns and the presence of variable amounts of water soluble and water insoluble organic matter within these biominerals generally the range in bulk 26mg from experimentally altered 1 52 and that of bulk samples from ancient diagenetically altered brachiopod valves 1 53 exceed the geochemical variability of 26mgbrachiopod bulk values of most recent specimens 1 26 in the lower and upper range more 26mg enriched 0 8 and more 26mg depleted 0 7 values respectively are found in altered shells in comparison to unaltered ones the data shown here are considered significant for those aiming to reconstruct palaeoenvironmental parameters based on brachiopod archives consequently we propose tentative guidelines for magnesium isotope research applied to ancient carbonates

tropical seasonality in the late campanian late cretaceous comparison between multiproxy records from three bivalve taxa from oman abstract geochemical proxy records from calcite shells of bivalves constitute an important archive for the reconstruction of palaeoenvironmental conditions on sub annual timescales however the incorporation of these trace element and stable isotope proxies into the shell is influenced by a multitude of physiological and environmental factors that need to be disentangled to enable reliable reconstruction of palaeoclimate and palaeoenvironment in this study records of multiple proxies in three bivalve taxa from the same late campanian locality in oman are used to study the expression of various geochemical proxies in relation to each other and to the palaeoenvironment micro x ray fluorescence mapping allows the localization discussion and evasion of diagenetically altered parts of the fossil shells x ray fluorescence line scanning calibrated with laser ablation inductively coupled plasma mass spectrometry is used to measure trace element profiles through well preserved calcitic parts of the shells records of stable carbon and oxygen isotope ratios of shell calcite are combined with these high resolution trace element concentration profiles to study sub annual variations in shell chemistry and reconstruct changes in the palaeoenvironment of the bivalves on a seasonal scale spectral analysis routines are used to detect cyclicity in stable isotope 18o and 13c and trace element mg ca sr ca s ca and zn ca records differences in seasonal expression between these chemical proxies and between individual shells are discussed in terms of the relative influence of palaeoenvironment and potential species specific physiological effects stable oxygen isotope ratios between shells suggest a local palaeotemperature seasonality of 8 c around an annual mean of 28 c with the shell of the rudistid torreites sanchezi milovanovici yielding slightly higher average temperatures the discussion of the application of various mg ca palaeotemperature calibrations on mg ca records in these bivalve species emphasizes the complexity of using trace element proxies in extinct bivalve species it shows that long term changes in mg ca ratios in ocean water need to be taken into account and that mg ca ratios in bivalves might be influenced by vital effects sr ca and s ca ratios in these fossil taxa are likely controlled by growth and metabolic rates of the shell although an influence of local salinity on strontium to calcium ratios cannot be excluded sub annual variations in zinc concentrations in shell calcite may reflect seasonal variations in palaeoproductivity and redox conditions in the water column

evolution of the mg ca ratio of cretaceous seawater implications from the composition of biological low mg calcite abstract for the evaluation of variations in the cretaceous seawater mg ca ratio 12 shells of rudist bivalves ranging in age from the late barremian 112 2 ma to the early campanian 81 4 ma have been analysed for intra shell variations in chemical mg sr fe mn and isotopic 18 o 13 c compositions of low mg calcite preservation of fibrous prismatic ultrastructure low fe and mn concentrations as well as sr concentrations within the range of marine biological calcite indicate only very minor diagenetic alteration in all studied shells mg concentrations and 18 o values show a more or less well defined inverse covariance this pattern is similar to the conditions observed in modern skeletal calcite and interpreted to result from a combination of a temperature effect and an unidentified metabolic control on the incorporation of mg into calcite average mg concentrations in rudist calcite are significantly lower than those of modern bivalves and increase from the barremian albian to the campanian while slopes of 18 o mg regressions are similar to those of modern bivalves assuming that the mg incorporation is linearly dependent on the mg ca ratio of seawater and that mg incorporation into calcite of modern bivalve mollusks follows the same metabolic pathway than in their extinct cretaceous relatives the mg ca molar ratio of cretaceous seawater increased from 1 in the late barremian to 3 in the early campanian this trend matches previous model predictions of seawater composition and experimental results from fluid inclusions in halite a very low mg ca ratio of seawater is confirmed here to have occurred before the onset of the significant mid cretaceous increase of seafloor production rates in the late barremian uncertainties in the secular variations of seafloor spreading are discussed as hydrothermal alteration of young oceanic crust is an important driver of changes in the seawater mg ca ratio

exploring aberrant bivalve shell ultrastructure and geochemistry as proxies for past sea water acidification throughout much of earth s history marine carbonates have represented one of the most important geological archives of environmental change several pivotal events during the phanerozoic such as mass extinctions or hyperthermal events have recently been associated with ocean acidification nevertheless well defined geological proxies for past ocean acidification events are at best scarce here experimental work explores the response of bivalve shell ultrastructure and isotope geochemistry c 13 o 18 and mg 26 to stressful environments in particular to sea water acidification in this study the common blue mussel mytilus edulis was cultured from early juvenile stages to one year of age at four ph regimes ph nbs 72 to ph 80 shell growth rate and ultrastructure of mainly the calcitic portion of the shells were compared between experimental treatments specimens exposed to low ph environments show patches of disordered calcitic fibre orientation in otherwise well structured shells furthermore the electron backscattered diffraction analyses reveal that under acidified conditions the c axis of the calcite prisms exhibits a bimodal or multi modal distribution pattern similar shell disorder patterns have been reported from mytilids kept under naturally acidified sea water conditions in contrast this study found no evidence that different ph regimes affect shell carbon oxygen or magnesium isotope ratios based on these observations it is proposed that i stressful environments in this case low sea water ph predictably affect bivalve biomineralization patterns and ii these findings bear potential as a novel petrographic proxy for ancient sea water acidification an assessment of the applicability of these data to well preserved fossil shell material from selected time intervals requires additional work

plate tectonic control on the evolution of cretaceous platform carbonate production carbonate producing biota on cretaceous carbonate platforms changed from early cretaceous aragonitic coral algal and coral rudist associations to turonian maastrichtian calcite dominated rudist associations abundance patterns of rudist bivalves examined from a large database show a shift from barremian cenomanian aragonite dominated to post cenomanian calcite dominated shells these skeletal mineral changes agree with a decrease in the mg ca ratio of seawater owing to high rates of production of oceanic crust during the barremian early turonian and its effect on seawater saturation with respect to aragonite and calcite increasing sr concentrations in biotic calcite from the barremian to the maastrichtian reflect the shift from aragonite dominated to calcite dominated platform sedimentation because aragonite precipitation is a major sink for seawater sr it is speculated that a particularly low mg ca ratio and the corresponding low supersaturation of seawater with respect to aragonite during the middle cretaceous was a major cue for the radiation of calcite dominated rudist bivalves which became important carbonate producers on turonian maastrichtian carbonate platforms changing mg ca ratios of seawater are not considered to have caused middle cretaceous crises in the evolution of carbonate platforms but seawater composition could have selected for calcite dominated biota when carbonate production resumed

application of cross hole seismic measurements in site investigation surveys application of the cross hole seismic method to site investigation surveys for civil engineering developments is illustrated by case histories from the united kingdom using the borehole sparker probe developed in mccann et al 1975 as the seismic source at newborough anglesey it is shown that this source generates both a compressional wave and a vertically polarized shear wave in the borehole the measured velocity values are used to determine the dynamic elastic moduli of the saturated sand deposit at this site at cocking sussex and east fleet dorset the presence of an air filled void between two boreholes is shown to have a significant effect on the velocity of propagation and amplitude of the transmitted seismic signals this work is extended at maidstone kent where the technique is used to confirm the presence of a cavity below the foundation of a house in the hot dry rock geothermal project at rosemanowes cornwall increased fracturing of the granitic rock mass following explosive stimul

strontium isotope stratigraphy of cretaceous hippuritid rudist bivalves rates of morphological change and heterochronic evolution abstract strontium isotope stratigraphy of 17 localities of rudist formations in the region of the former mediterranean tethys has provided a reliable and precise stratigraphical frame for the evaluation of morphological change in hippuritid rudist bivalves during the coniacian campanian the phyletic lineage vaccinites cornuvaccinum bronn vaccinites chaperi douville evolved from the early coniacian until the early campanian and is characterized by phyletic size increase and allometric growth as shown by morphometrical measurements of 102 shells these chronospecies intergrade in the late coniacian so that v cornuvaccinum is considered to be a reliable marker species for the coniacian the taxonomy of vaccinites alpinus douville is discussed and the species is recognized as a senior synonym of vaccinites ultimus milovanovic it appears first in the late santonian and the last appearance is probably in late campanian both lineages are characterized by phyletic size increase and peramorphic evolution involving hypermorphosis a doubling of the length of the mantle margin occurred within 5 m y in both lineages the results demonstrate that the combination of morphometric analyses and stratigraphical precision provides an important tool for the delineation of tempo and mode of evolution in rudist bivalves strontium isotope stratigraphy resulted in a considerable revision of the ranges of the species investigated as the stratigraphy of many tethyan carbonate platforms relies on the distribution of rudist bivalves and the species investigated are abundant in many rudist formations the history of many late cretaceous carbonate platforms must be re evaluated

geophysical interpretation of a high resolution seismic refraction profile in the northern apennines a combined seismic and gravimetric interpretation in the northern apennines area italy is presented to the knowledge of the authors this is one of the few attempts to apply tomographic methodology to a seismic refraction profile this procedure together with the classical interpretation for defining lower reflectors led to the formulation of quite an accurate model of the upper crust a gravity analysis was performed concurrently taking into account the seismic results at different depths which correspond to different frequency domains in the gravity signal while the medium and high frequency patterns have been solved by trial and error the regional trend has been modelled applying the collocation procedure to the gravity data

petrology of lower cretaceous carbonate mud mounds albian n spain insights into organomineralic deposits of the geological record the process of organomineralization is increasingly well understood with respect to modern carbonate sediments accumulating adjacent to tropical reef atolls and reef caves mineralization related to non living organic substrates results in autochthonous micrite production automicrites automicrites are the main constructive element of lower cretaceous albian carbonate mud mounds in northern spain these slope mud mounds occur within transgressive and early highstand system tracts encompassing several macrobenthic ecological zones they are clearly separated from the biocalcifying carbonate factory urgonian carbonate platforms in both space and time within these build ups most automicrites were initially indurated and accreted to form a medium relief growth framework automicrites have a uniform presumably high mg calcite precursor mineralogy they show an inorganic stable isotope signature 13c around 3 3 within the range of early marine cements and skeletal compounds lacking major vital effects epifluorescence microscopy shows that they have facies specific fluorescence which is similar to skeletal compounds of acanthochaetetes but clearly different from allomicritic sediment and cements which are mostly non fluorescent the edta soluble intracrystalline organic fraction siof of albian automicrites shows an amino acid spectrum that is similar to shallow subsurface samples from their modern counterparts gel electrophoresis of the siof demonstrates an exclusively acidic character and a mean molecular size range between 20 and 30 kda experiments in vitro inhibition tests indicate that the siof has a significant ca2 binding capacity fluorescence and chemical characteristics of siof point to a main substance class such as humic and fulvic acids compounds that form from pristine organic matter during early diagenesis biomarker analyses provide evidence for the crucial role of biodegradation by heterotrophic microorganisms but no biomarker for cyanobacteria has been found primary sources of organic material should have been manifold including major contributions by metazoans such as sponges it is concluded that many carbonate mud mounds are essentially organomineralic in origin and that the resulting fabric of polygenetic muds polymuds may represent ancestral metazoan reef ecosystems which possibly originated during the neoproterozoic

retrogressive fabric development during exhumation of the voltri massif ligurian alps italy arguments for an extensional origin and implications for the alps apennines linkage geological mapping coupled with structural investigations carried out in the voltri massif eastern ligurian alps italy provide new data for the interpretation of the tectonic context controlling main fabric development during exhumation of its high pressure core the voltri massif is here interpreted as a c 30 km long eclogite bearing asymmetric dome formed by the progressive verticalisation of the regional second phase mylonitic foliation developed during retrogressive greenschist metamorphic conditions in this light the exhumation history is driven by a ductile to brittle extensional process operating through low angle top to the w multiple detachment systems a late eocene early oligocene age for this extensional episode is proposed on the basis of structural correlations stratigraphic and radiometric constraints in this scenario the voltri massif is interpreted as an extensional domain developed to accommodate the late eocene early oligocene arching of the western alps northern apennines orogenic system

improving the detection of shell alteration implications for sclerochronology abstract sclerochronology makes use of fossil shell archives to establish records allowing for investigation of high resolution environmental dynamics nevertheless this potential can often not be fully exploited due to the interplay between paleoenvironmental variability vital effects and the potential diagenetic modification of skeletal materials which often results in highly complex records a novel dynamic approach aiming to separate pristine from altered shell material for paleoclimate and paleoenvironmental reconstructions is proposed seventeen fossil bivalve shells requieniid rudists pectinids and chondrodonts from two neighbouring lower cretaceous albian shallow water sections lusitanian basin western portugal were analysed for their major and trace elemental compositions using high resolution quantitative xrf line scans their complex records were subject to a novel statistical analysis protocol which tested mono and multi species datasets as well as comparing shells from both locations characteristic elemental associations reveal the differential impact of early and late diagenetic alteration processes the incorporation of elements associated with detrital contribution fe si al is attributed to syn depositional bioerosion shell boring in clear contrast shell portions showing a strong correlation between fe and mn are indicative of later diagenetic alteration the influence of each process is different at each site revealing local differential alteration pathways mono specific comparisons provides identical geochemical responses suggesting that intra specific differences do not control the observed elemental patterns in contrast inter species tests rendered a clear separation in the way elements are incorporated in the shells of pectinids and requieniids e g as evidenced by differences in mg or sr content such differences can be linked to differential biomineralization pathways easily detected by the applied method we present a new dynamic method for distinguishing pristine from altered shell material not relying on arbitrary diagenetic thresholds for trace element content by clearly identifying shell alteration pathways syn to post depositional processes are recognized a progressive cleaning of the elemental dataset allows paleoenvironmental studies to be based on the most pristine data contributing to unravelling the complex interplay between climate environmental dynamics and their impact on biomineralization processes and sclerochronological archives

foundation evaluation of underground metro rail station using geophysical and geotechnical investigations abstract excavations for underground space developments in a thickly populated urban area are sometimes hindered by unexpected formidable consequences like formation of sinkholes or uneven settlement of foundations such troublesome incidences occasionally damage structures in the vicinity of excavations although adequate design guidelines and codes of practices are adopted the disturbance of subsurface regime due to excavation or construction activities often leads to undesired stability issues with resultant appearance of weak zones the reinforcement of weak zones by grouting is one of the common remedies without demarcating the weak or the affected zones becomes counter productive excavation at a location in chennai mega city for metro rail was severely affected by soil piping with development of sinkholes and weakening of the surrounding strata subsequently development of cracks in the adjacent buildings and caused tilting of the nearby taller structures the mandated the geophysical and geotechnical investigations were carried out to demarcate the affected area to avoid further deterioration of the site cross hole seismic p and s wave velocities were estimated between10 pairs of boreholes up to 20 m depth on both the sides of the excavation two electrical resistivity tomography ert profiles each of 141 m in length were carried out in the same location cross hole s wave velocity profiles and resistivity tomograms clearly indicate the presence of weak zones and possible sinkhole locations site specific empirical relationship was established between s wave velocity and standard penetration test spt n value this relationship was further used for determination of spt n values from the measured vs values to compare the subsurface conditions identified under pre and post excavations the results confirmed the presence of weak zones which are responsible for the weakening of the surrounding strata in the foundation geophysical and geotechnical investigations similar to present investigation can be useful for designing metro rail projects in a subsurface environment comprising alluvium sand clay mixed with silt pebbles and boulders lying near a region of ground water pocket in a thickly populated urban area

species richness and abundance patterns of tethyan cretaceous rudist bivalves mollusca hippuritacea in the central eastern mediterranean and middle east analysed from a palaeontological database abstract data about the stratigraphical and regional distribution of cretaceous rudist bivalves in the central eastern mediterranean and middle east from the barremian to the maastrichtian have been compiled in a taxonomic databank system the investigated region comprises northern central and southern regions of the cretaceous tethys the regionally different quality of taxonomic data is critically discussed both species richness and abundance number of species records peak in the early aptian late cenomanian and early campanian temporal patterns in species richness are examined in relation to evolutionary innovations of the group crises in species richness and abundance during the early and mid cretaceous were coeval with oceanic anoxia associated with platform drowning also regional emergence affected large parts of the apulian plate and other central tethyan carbonate platforms during the mid cretaceous period of globally high sea level so that these crises can be attributed to regional environmental perturbations induced by either oceanic anoxia or tectonic movements the cenomanian turonian transition marks an important faunal turnover as indicated by the demise of taxonomic groups which are characterised by recumbent ecological morphotypes and predominantly aragonitic shells during the turonian they were replaced by associations dominated by largely calcitic radiolitidae and hippuritidae among which elevator morphotypes dominated the stratigraphy of many post turonian deposits in the studied region is too imprecise for a detailed analysis of late cretaceous distributional patterns and the demise of rudists during the maastrichtian in particular the regional pattern of species richness and abundance is similar throughout most of the investigated region a notable exception is the broad north eastern african shelf from libya to lebanon where rudists were almost completely absent after the coniacian this coincided with shallow water phosphorite and black shale formation on the extended shelf of this region indicating the upwelling of nutrient rich waters and stagnant conditions during this time campanian maastrichtian species rich associations thrived along the north eastern afro arabian margin now exposed in south eastern turkey iran the united arab emirates uae and oman this region forms the single distinct faunal province during the cretaceous in the studied region as indicated by an endemism of 40 at the genus level the low species richness and abundance of hippuritidae on turonian maastrichtian central tethyan carbonate platforms when compared with regions having mixed calcareous siliciclastic sedimentation is interpreted to argue against a widespread photosymbiosis in the group several aspects of this study highlight the importance of regional tectonic and oceanographic controls of distributional and perhaps also evolutionary patterns of rudist bivalves their delineation still suffers from the regionally different quality of stratigraphical and taxonomic data