danian selandian boundary stratigraphy paleoenvironment and ostracoda from sidi nasseur tunisia abstract two detailed records nsf and 05nsc sidi nasseur tunisia across the danian selandian d s boundary were investigated for their micropaleontological content calcareous nannofossils and planktic foraminifera provided a biostratigraphic framework the interval spans part of planktic foraminiferal zone p2 subzone p3a and part of subzone p3b this corresponds to calcareous nannoplankton zone np4 using a more detailed nannofossil zonation the studied section spans part of zone ntp6 zone ntp7a and part of ntp7b quantitative ostracod and qualitative benthic foraminiferal data were used to characterize environmental changes across the d s boundary the two subsections have yielded a total of 50 ostracod taxa the ostracod assemblage of the entire section belongs to the southern tethyan type showing subtle but distinct changes up section based on statistical analysis of the quantitative ostracod data faunal changes at a glauconitic maker bed p3a p3b boundary were demonstrated the local reticulina proteros assemblage with the typical species r proteros oertliella vesiculosa and cytheroptheron lekefense is gradually replaced by the protobuntonia nakkadii assemblage with the typical species cristaeleberis arabii xestoleberis tunisiensis cytheropteron sp and p nakkadii across the glauconitic bed the benthic foraminifera also demonstrated distinct changes at this marker bed the changes in ostracods and foraminifera are related to changes in paleoproductivity and an overall relative sea level fall the lithological and faunal changes at the p3a p3b zone boundary within the sidi nasseur sections seem to correspond to the d s boundary in the type region in danmark and are characterized by a significant hiatus yielding this section not suitable as a gssp candidate for this boundary

paleocene sea level and productivity changes at the southern tethyan margin el kef tunisia integrated analysis of quantitative distribution patterns of organic walled dinoflagellate cysts dinocysts and benthic foraminifera from the paleocene el kef section nw tunisia allows the reconstruction of sea level and productivity fluctuations our records indicate that the environment evolved from an initially oligotrophic open marine outer neritic to upper bathyal setting towards a more eutrophic inner neritic setting influenced by coastal upwelling by the end of the paleocene an overall second order change in paleodepth is reflected by both microfossil groups from the base of planktic foraminifera zone p4 onwards the main phase of shallowing is evidenced by an increase of inner neritic dinocysts of the areoligera group disappearance of deeper water benthic foraminifera and increasing dominance of shallow marine taxa several buliminids haplophragmoides spp trochammina spp the total magnitude of this shallowing is obscured by interaction with a signal of eutrophication but estimated to be around 150 m from 200 to 50 m superimposed on the overall trend third order sea level fluctuations have been identified and correlated to sequences in other regions paleoproductivity indicators notably protoperidinioid dinocysts and buliminids show a trend from an oligotrophic to a eutrophic setting d 2005 elsevier b v all rights reserved

dinoflagellate cysts sea level changes and planktonic foraminifers across the cretaceous tertiary boundary at el haria northwest tunisia abstract dinoflagellate cysts and planktonic foraminifers have been studied from the cretaceous tertiary k t boundary interval at el haria northwest tunisia a high resolution integrated biostratigraphy is presented the k t boundary is drawn at the level of extinction of cretaceous planktonic foraminifers and is coincident with the first occurrence of the dinoflagellate cyst species danea californica the final extinction of planktonic foraminifers is foreshadowed by a reduction in their total abundance some 5 kyr earlier at the base of the boundary clay this reduction is coeval with reported anomalies in siderophyle elements and 13 c values in the same area dinoflagellate cysts do not show accelerated rates of extinction at k t time associations of dinoflagellate cysts however change drastically and parallel changes in relative numbers of sporomorphs spores and pollen and in the quantity of land derived organic matter jointly these changes reflect a rapidly falling sea level during the final 17 kyr of the mesozoic which culminates at the level of the k t boundary this steep sea level fall at k t time represents a peak regressive pulse at the end of the well documented latest cretaceous regressive trend this short term sea level fall might show to be a wide spread phenomenon which could have caused an excess shrinking of the already reduced areal extent of marginal seas since deep waters in cretaceous oceans were primarily produced in shallow marginal seas the rate of formation of deep water might have been minimized at k t time minimum rates of formation of deep water might have curtailed the slow upward mixing of relatively cool and nutrient rich deeper water through which the thermocline weakened and surficial waters became depleted in nutrients consequently phytoplankton productivity rapidly diminished which in combination with a weakened thermal gradient pushed the highly depth stratified cretaceous planktonic foraminiferal fauna to extinction over a period of time of some 5 kyr guembelitria cretacea was the sole planktonic foraminifer which could accommodate to the low productivity conditions the oscillating rise in sea level at the beginning of the cenozoic reinforced the upward mixing of relatively cool and nutrient rich deeper water steepened the thermocline and replenished the photic layer with nutrients concomitant niche differentiation in the photic layer progressively stimulated morphological innovation amongst early cenozoic planktonic foraminifers the final return of normally sized planktonic foraminifers and of stable and well balanced dinoflagellate cyst associations at about 125 kyr after the k t boundary seems to indicate that primary productivity and niche differentiation in the photic layer begin to revert to optimum levels the earliest cenozoic planktonic foraminiferal species globoconusa minutula and parvularugoglobigerina fringa are thought to have developed from a benthic foraminiferal species rather than having a planktonic ancestry

increasing restriction of the egyptian shelf during the early eocene new insights from a southern tethyan carbonate platform the evolution of the isolated galala carbonate platform has been studied intensively with respect to the paleocene eocene thermal maximum petm and the strong climatic variability from the late paleocene to the early eocene in this study we compare the results of different approaches which deal with the early palaeogene evolution of the egyptian shelf including new data from the galala platform microfacies analyses along a platform to basin transect reveal a sedimentological response to a massive tectonic uplift along the syrian arc fold belt in the early eocene this uplift triggered the restriction of the egyptian shelf by modulating and weakening tethyan onshore currents from the north the increasing deposition of quartz and proliferating gastropods green algae and radiolaria which indicate elevated nutrient levels reflect an intensified eutrophication of shallow marine platforms and deeper marine shelf environments strongly depleted carbon isotope ratios in the sediments of the galala succession strongly suggest the presence of restricted conditions throughout the early eocene we assume that a strong climatic divergence with arid conditions on the shelf and humid conditions at the african hinterland triggered intensified chemical weathering at the nubian arabian craton the enhanced riverine transport of terrestrial organic material to the north african shelf caused the increased availability of trophic resources and a strong negative shift of carbon isotope ratios between np10 and np14a the recovery to open ocean conditions is linked to the termination of tectonic uplift along the syrian arc fold belt in the latest early eocene and to stronger ocean currents caused by increasing latitudinal temperature gradients additionally the post petm carbon isotope evolution at the galala platform indicates at least two further negative carbon isotope excursions which reflect hyperthermal events on a global scale the associated reorganization of shallow marine assemblages as described for example for the larger foraminifera turnover at the petm boundary event is however missing we assume that the absence of a foraminiferal reorganization in this region can be linked to an increasing robustness of the major early eocene platform organisms larger benthic foraminifera and their adaption to unfavorable conditions and repeated environmental shifts 2011 elsevier b v

correlation of cenozoic late cretaceous geomagnetic polarity time scales an internet archive since the development of the first comprehensive cenozoic geomagnetic polarity time scale in 1968 at least 11 additional time scales have been produced potentially leading to confusion when comparing geologic studies using different time scales this compilation correlates 12 different time scales published from 1968 to 1995 graphically and in tabular form in order to enable geoscientists to compare studies dated on the basis of different time scales the table and supporting documents are stored electronically on line at the world data center a for paleoclimatology national oceanographic and atmospheric administration national geophysical data center

impact of sedimentology and diagenesis on the petrophysical properties of a tight oolitic carbonate reservoir the case of the oolithe blanche formation bathonian paris basin france the oolithe blanche formation was studied in three quarries located at the south eastern edge of the paris basin france heterogeneities in reservoir properties were assessed through a sedimentological diagenetic and petrophysical study the relationships between depositional settings diagenesis and petrophysical properties were analysed using detailed petrographic studies image analysis nano ctscans and petrophysical measurements the carbonate reservoir pore network is mainly controlled by intraparticle microporosity which ensures the connectivity with interparticle meso and macroporosity early cementation vs early compaction processes mainly grain interpenetration may have considerable influence on fluid flow properties and parameters such as permeability acoustic velocities and tortuosity better reservoir properties are found when compaction processes begin before cementation from statistical analyses e g principal component analysis and linear discriminant analysis a sedimentological diagenetic and petrophysical model is proposed that is in a good agreement with the geological model developed from field work

controls on sonic velocity in carbonates compressional and shear wave velocities v p and v s of 210 minicores of carbonates from different areas and ages were measured under variable confining and pore fluid pressures the lithologies of the samples range from unconsolidated carbonate mud to completely lithified limestones the velocity measurements enable us to relate velocity variations in carbonates to factors such as mineralogy porosity pore types and density and to quantify the velocity effects of compaction and other diagenetic alterations

abrupt deep sea warming palaeoceanographic changes and benthic extinctions at the end of the palaeocene a remarkable oxygen and carbon isotope excursion occurred in antarctic waters near the end of the palaeocene 57 33 myr ago indicating rapid global warming and oceanographic changes that caused one of the largest deep sea benthic extinctions of the past 90 million years in contrast the oceanic plankton were largely unaffected implying a decoupling of the deep and shallow ecosystems the data suggest that for a few thousand years ocean circulation underwent fundamental changes producing a transient state that although brief had long term effects on environmental and biotic evolution

petroacoustics of carbonate reservoir rocks although more than half of hydrocarbon reserves are in carbonate reservoir rocks little has been published concerning their petroacoustics acoustics of rocks one reason is that conventional measurement techniques ultrasonic propagating waves first break picking for velocity spectral ratio for attenuation do not always perform adequately in carbonate rocks because of their heterogeneity frequently encountered problems include

paleooceanography of the mesogean sea based on ostracods of the northern tunisian continental shelf between the late cretaceous and early paleogene a new method analysis used in the study of the el kef section north western tunisia led to the paleooceanographic reconstruction of the mesogean between late cretaceous and early paleogene several changes observed are in fact worthy of particular mention paleobathymetrically the area changed from an upper bathyal environment of about 400 m deep to an outer shelf domain of 100 50 m furthermore the oxygen minimum zone o m z became highly intense at a the cretaceous tertiary transition catastrophic event b the p1 p2 boundary intense thermic stratification and c between p4 and p6 very active paleoproductivity in this last episode the continental shelf environment was subjected to intense upwelling responsible for the formation of a prephosphatic environment at water sediment interface the paleooceanographic history of phosphates in the gafsa metlaoui basin is in fact in perfect stratigraphic and paleoenvironmental agreement with the paleobathymetric evolution of the kef region finally paleooceanographic communication between the mesogean and the north atlantic was at this period highly free because of lack of hydrologic relations between the north atlantic and the norwegian sea

burial dissolution of micrite in middle east carbonate reservoirs jurassic cretaceous keys for recognition and timing abstract this paper discusses burial diagenesis and especially a burial dissolution phase and its effects on micrite microtexture in reservoirs in the middle east three microporous reservoirs were selected the cenomanian mishrif formation in iraq the kimmeridgian tithonian arab d and the barremian kharaib formations both in abu dhabi staining cathodoluminescence and scanning electron microscopy were used for petrographic observations in the selected reservoirs three typical micrite microtextures are distinguished micro rhombic compact anhedral and rounded the chronology of diagenesis based on petrographic observations shows that mineralogical stabilisation through high magnesian calcite replacement by low magnesian calcite led to the formation of micro rhombic micrites non reservoir facies such as seals present compact anhedral micrites correlation between these micrites and high aluminium content suggests alumino silicate minerals clays as a catalyst for pressure dissolution and thus for reservoir degradation through cementation micrites from the upper part of oil reservoirs are dissolved during burial diagenesis dissolution is responsible for rounded shape and for reduction of crystal size it also implies pore diameter and pore throat size enlargement comparison of porosity and permeability with scanning electron microscope data confirms that rounded micrites are better reservoirs than micro rhombic micrites

a benthic foraminiferal record of paleocene sea level and trophic redox conditions at gebel aweina egypt we quantitatively analyzed benthic foraminiferal assemblages in order to reveal biotic and paleoenvironmental trends in the paleocene section of gebel aweina egypt on the southern tethyan shelf the first correspondence axis ranks taxa along an empirically derived bathymetric gradient with neritic taxa e g discorbis duwi and haplophragmoides walteri opposed to bathyal taxa e g nuttallides truempyi and gavelinella beccari ormis the estimated paleodepth as reflected by the various assemblages was mostly 200 m but varied between 50 m p3a np4 and 300 m p4 n p8 the resultant four relative sea level cycles appear to be at least of regional extent and may in part be eustatically controlled the second correspondence axis reflects trends in trophic and redox development low food high oxygen conditions prevailed during biochrons plc p3b np4 np5 and late p4 np8 when assemblages were mostly dominated by cibicidoides spp most oligotrophic conditions coincided with maximum paleodepth intermediate trophic levels were established during middle p4 np6 and early p5 np9 from the level of the latest paleocene benthic extinction event bee middle p5 and np9 onwards until biochron p6a np10 assemblages dominated by buliminids marked increased trophic levels and reduced ventilation probably resulting from enhanced surface productivity enhanced surface productivity along the southern tethyan margin started during biochron p4 and at least on some shelves intensified after the bee increasing productivity during the latest paleocene contrasts with global trends this may be expected during climatic warming and an expanding trophic resource continuum leading to regionally intensified eutrophy and oligotrophy high productivity through upwelling along the southern tethyan provides support for gcm predictions of intense wind stress in this region during the warm late to latest paleocene 1998 elsevier science b v

stable isotope toc and caco3 record across the cretaceous tertiary boundary at el kef tunisia we report the results of stable oxygen and carbon isotope analysis of carbonate fine fraction and benthic and planktic foraminifers caco3 and toc determinations of sediments across the cretaceous tertiary k t boundary at el kef tunisia we used grain size analysis of the fine fraction carbonate to determine possible compositional effects and smearslide and scanning electron microscope examinations to evaluate possible diagenetic alteration and microfossil preservation the data suggests the following sequence of events upper maastrichtian oxygen and carbon isotope signals indicate relatively warm temperatures a decreasing thermal gradient possibly related to a shallowing sea and relatively high surface water productivity a sharp cooling appears to begin just below the k t boundary the k t boundary is characterized by a sudden 2 negative shift in fine fraction 13c a slight 0 6 enrichment in benthic 13c and a reduction of about 40 in caco3 sedimentation these data imply strongly reduced surface water productivity as also observed in numerous deep sea sequences worldwide the lower danian planktic foraminiferal zones p0 p1a is marked by generally low productivity and unstable environmental conditions as indicated by generally low but fluctuating fine fraction 13c values and low 5 15 carbonate deposition at the base of subzone p1b caco3 benthic and fine fraction 13c values increase gradually and reach near pre k t boundary levels in subzone p1c indicating initial recovery after the k t boundary event about 300 000 400 000 years after the k t boundary the prolonged low productivity episode after the k t crisis and the pre k t boundary cooling associated with a major reduction in planktic foraminiferal diversity are difficult to explain by a single k t boundary bolide impact

recent planktonic foraminifers and their relationships to surface ocean hydrography of the south china sea the relative abundances of recent planktonic foraminifers from surface sediments on the sea floor reveal relationships to hydrographic variables of the ocean surface to investigate whether the evect of the vertical structure of oceanic upper layer environments is important to the changes in the abundance of planktonic foraminifers a set of 173 coretop faunal data from modern south china sea scs surface sediments was compiled for comparison with direct observations of sea surface temperature sst and the depth of thermocline dot the coretops used in this study are distributed within the area of 25 n and 105 125 e with water depths ranging from 68 to 3990 m the relationships between the abundances of planktonic foraminifer species and hydrographic variables were examined using simple correlation analyses in the analyses four groups of planktonic foraminifers with diverent ecological preferences were identified group i faunas primarily reliant on dot with positive correlations n dutertrei group ii faunas reliant on both sst and dot showing negative correlations with sst and positive correlations with dot g glutinata p obliquiloculata and g bulloides group iii faunas reliant on both sst and dot showing positive correlations with sst and negative correlations with dot including g sacculifer g menardii and g aequilateralis and group iv faunas reliant on both sst and dot with positive correlations g ruber though each of these species displays selectivity of ecological controls these results indicate that in the scs correlations between faunal abundances of planktonic foraminifers and sst or dot are about equally significant this study also indicates a need for re evaluating the relationships between planktonic foraminifer abundances and many other important hydrographic variables in the upper layer of oceans on a more regional scale 1998 elsevier science b v all rights reserved

latest paleocene lithologic and biotic events in neritic deposits of southwestern new jersey in the southwestern new jersey coastal plain four drill holes contain continuous neritic sedimentation across the paleocene eocene boundary calcareous nannofossil zone np 9 np 10 boundary significant lithologic and biotic changes occur in these strata near the top of the paleocene global warming increased precipitation and other oceanographic and climatic events that have been recognized in high latitude deep oceanic deposits of the latest paleocene also influenced mid latitude shallow marine and terrestrial environments of the western north atlantic the diverse well preserved calcareous nannofossil flora that is present throughout the entire new jersey boundary section accurately places these events within the uppermost part of the upper paleocene zone np 9 several rapid but gradational changes occur within a 1 1 m interval near the top of zone np 9 the changes include 1 a change in lithology from glauconitic quartz sand to clay 2 a change in clay mineral suites from illite smectite dominated to kaolinite dominated 3 a change in benthic foraminiferal assemblages to a lower diversity fauna suggestive of low oxygen environments 4 a significant increase in planktonic foraminiferal abundance and 5 an increased species turnover rate in marine calcareous nannofossils pollen was sparse in the new jersey drill holes but terrestrial sporomorph species in virginia exhibit increased turnover rates at a correlative level foraminiferal assemblages and lithology indicate that relative sea level rose in new jersey at the same time as these late paleocene events occurred in late biochron np 9 the higher sea levels influenced sediment type and absolute abundance of planktonic foraminifers in the deposits above the initial increase of kaolinite in the upper part of zone np 9 the kaolinite percentage continues to increase and the maximum kaolinite value occurs in the uppermost part of zone np 9 there are few changes in either the sediments or the biota precisely at the zone np 9 np 10 boundary in new jersey the clay rich deposits with a high kaolinite clay mineral suite the lowered diversity benthic foraminiferal assemblages the abundant planktonic foraminiferal specimens and the calcareous nannofossil assemblages continued essentially unchanged into the earliest eocene zone np 10 within the lower part of zone np 10 the kaolinite percentage decreased to very low values

paleoenvironmental change at the danian selandian transition in tunisia foraminifera organic walled dinoflagellate cyst and calcareous nannofossil records abstract in the present study we document paleoenvironmental change across the danian selandian transition planktic foraminiferal interval p2 p3b calcareous nannofossil zone np4 subzones ntp6 ntp8a 61 59 ma in nw tunisia diversifications of paleogene planktic foraminifera with the evolution of the muricate and photosymbiotic lineages morozovella acarinina and igorina and of the biostratigraphically important nannofossils genus fasciculithus are recorded within this interval the present study aims to understand early paleogene environmental changes in the southern tethys by analyzing the evolution of surface water and to a lesser extent seafloor conditions three localities were investigated ain settara elles and el kef all representing outer neritic deposition in the same basin the tunisian trough paleoenvironmental changes are explored by combining planktic foraminiferal organic dinocyst and calcareous nannofossils assemblages and several proxy parameters planktic benthic ratio numbers of planktic foraminifera per gram peridinioid gonyaulacoid ratio terrestrial marine palynomorph ratio in addition also some geochemical parameters calcite content and stable isotopes are examined our records indicate that the environment evolved from an initially oligotrophic open marine deep outer neritic setting in p2 p3a towards a shallower and nutrient rich setting from the base of subzone p3b this change is seen in the foraminiferal assemblages with the substitution of praemurica by morozovella among the planktic foraminifera and an upward decrease in deeper benthic taxa also the organic dinocyst assemblages show a peak of peridinioid cysts cerodinium and lejeunecysta associated to these dinocyst assemblages the lowest occurrence of apectodinium is recorded which seem to have evolved in this region possibly in response to enhanced nutrient levels on the shelf additionally a distinct change in calcareous nannofossil assemblages is also described marked by the lowest appearance of chiasmolithus edentulus the lowest consistent occurrence of fasciculithus and a slight increase in near shore taxa essentially pontosphaera this project provides an accurate understanding of paleoenvironmental change across the danian selandian transition in tunisia especially integrating different proxies demonstrates a paleobathymetric shallowing from the danian to the selandian associated to increase surface paleoproductivity furthermore the results are compared with those from other localities along the southern tethyan margin egypt and jordan and a more regional paleoclimatic paleoceanographic perturbation in the southern tethys is suggested

benthic foraminifera and environmental turnover across the cretaceous paleogene boundary at blake nose odp hole 1049c northwestern atlantic sediments recovered at lower bathyal odp site 1049 on blake nose northwestern atlantic offer an opportunity to study environmental changes at the cretaceous paleogene k p boundary relatively close to the chicxulub impact structure on the yucatan peninsula mexico in hole 1049c the boundary is located at the base of a 9 cm thick layer with abundant spherules considered to be impact ejecta uppermost maastrichtian oozes below and lowermost danian pelagic oozes above the spherulebed contain well preserved bathyal benthic foraminifera the spherule bed itself in contrast contains a mixture of shallow neritic and deeper bathyal species and specimens vary strongly in preservation this assemblage was probably formed by reworking and down slope transport triggered by the k p impact across the spherule bed i e the k p boundary only f7 of benthic foraminiferal species became extinct similar to the low extinction rates of benthic foraminifera worldwide quantitative analysis of benthic foraminiferal assemblages and morphogroups in the 63 am size fraction indicates a relatively eutrophic stable environment during the latest maastrichtian interrupted by a sudden decrease in the food supply to the benthos at the k p boundary and a decrease in diversity of the faunas followed by a stepped recovery during the earliest danian the recovery was probably linked to the gradual recovery of surface dwelling primary producers d 2004 elsevier b v all rights reserved

palaeoenvironmental changes across the danian selandian boundary in the north sea basin abstract the danian selandian boundary 60 ma marks the cessation of 40 million years of carbonate deposition in the north sea basin and a shift to siliciclastic deposition on the basis of variations in lithology benthic and planktonic foraminifera and calcareous nannofossils in three cores from storebaelt in the eastern part of the north sea basin we have reconstructed the palaeoenvironmental changes across the boundary the benthic foraminiferal faunas belong to the midway type fauna they are extremely rich and more than 260 taxa have been recognized q mode cluster analysis groups the benthic assemblages into four biofacies which correspond fairly closely to lithological units correlation of the storebaelt records with marine palaeorecords from the danish basin and the north sea basin indicate that the transformation of the north sea from a carbonate to a siliciclastic basin occurred in four steps separated by relatively long stable periods the most important external factors involved in the change are firstly a drop in the relative sea level during the late danian leading to the disappearance of bryozoans from the north sea basin and to non deposition and erosion in many areas secondly coinciding with the danian selandian boundary an uplift of the scotland shetland area resulting in a massive input of siliciclastic deposits to the north sea basin thirdly during the early selandian inversion of the sorgenfrei tornquist zone and mesozoic basins in the southern and eastern part of the north sea basin resulted in a huge influx of reworked cretaceous chalk and an almost complete stop of carbonate production finally later in the early selandian in connection to a general sea level rise and a reduction in the gateway between the north sea basin and the tethys sea the sea bottom conditions became colder and more acidic this resulted in partial dissolution of the carbonates and the deposition shifted from marl to clay comparison with records from the western pyrenees the nile basin and the eastern north america suggests that sea level changes across the danian selandian boundary are primarily of eustatic nature

modeling elastic properties in carbonate rocks carbonate limestone and dolomite reservoirs account for approximately 50 of oil and gas production worldwide however seismic responses in carbonate rocks are poorly understood in addition dhi ranking and avo classification systems developed for clastic rocks are unlikely to be applicable to carbonate rocks an accurate and physically sound carbonate rock physics model is needed to address these technical issues

perturbation of a tethyan coastal environment during the paleocene eocene thermal maximum in tunisia sidi nasseur and wadi mezaz abstract despite the large number of studies on the paleocene eocene thermal maximum petm the knowledge of environmental and biotic responses in shallow marine environments remains quite poor benthic foraminiferal assemblages of the sidi nasseur and wadi mezaz sections in tunisia were studied quantitatively and the paleoecologic interpretations provide new insights into the complex relationship between petm global warming and perturbations of shallow marine settings these sections expose upper paleocene to lower eocene shales and marls of the el haria formation up to the phosphate layers of the chouabine formation underlying the el garia limestones the sidi nasseur section contains a more complete and expanded paleocene eocene boundary interval compared to wadi mezaz although being truncated at the top the wadi mezaz section contains a more complete post petm interval the studied interval can be subdivided into a sequence of 4 biofacies representing respectively a latest paleocene biofacies two petm biofacies and one post petm eocene biofacies the latest paleocene biofacies 1 consists of numerous calcareous benthic foraminifera e g anomalinoides midwayensis frondicularia aff phosphatica and various bulimina and lenticulina species abundant non calcareous taxa haplophragmoides and rare planktic foraminifera indicating a slightly hypersaline eutrophic inner neritic to coastal environment regularly interrupted by oxygen deficiency moderate dysoxia during the latest paleocene this highly productive environment shallowed as indicated by the increasing abundances of a midwayensis the variable dominance of non calcareous agglutinated taxa in biofacies 1 indicates post mortem dissolution effects the toc 13 c org record reveals a sharp negative excursion marking the base of the eocene in general the absence of lithologic changes an increasing sedimentation rate and absence of reworking indicate that the initial part of the petm is complete and expanded in the sidi nasseur section a sharp faunal turnover coincides with this negative 13 c org excursion and is characterized by the disappearance or diminution of common paleocene taxa in this area during the petm benthic foraminifera are less abundant and consist of opportunistic non calcareous taxa together with deeper dwelling middle neritic lagenids and buliminids biofacies 2 and 3 planktic foraminifera dominated by flat spired acarinina mainly a multicamerata become more abundant as observed in many open marine sequences worldwide all these faunal parameters suggest more stressed probably severe dysoxic sea floor conditions within a transgressive phase during the onset of the petm an estimation of the total duration of the sidi nasseur petm interval is difficult to establish yet the lack of recovery carbon isotope values suggests that the preserved petm interval reflects only a part of the cie core the top of the petm interval is truncated due to local erosion during the early eocene the eocene recovery fauna is mainly composed of lenticulina and stainforthia species biofacies 4 indicating restricted coastal to hyposaline lagoonal eutrophic conditions distinctly different from earlier environmental conditions

frequency and fluid effects on elastic properties of basalt experimental investigations 1 in order to investigate the effects of fluid and frequency on the elastic properties we performed hydrostatic experiments on an icelandic basalt specimen under both dry and saturated conditions this basalt is characterized by a bimodal porosity i e cracks and equant pores the elastic properties bulk moduli in our case were investigated under high pressure through two experimental methods 1 a classical one using ultrasonic p and s waves velocities frequency 106 hz 2 and a new one using oscillation tests frequency 10 2 hz in dry condition experimental data show no significant difference between high hf and low lf frequency bulk moduli however in saturated conditions two effects are highlighted a physico chemical effect emphasized by a difference between drained and dry moduli and a squirt flow effect evidenced by a difference between hf and lf undrained moduli

changes in coiling direction of cibicidoides pseudoacutus nakkady across the cretaceous tertiary boundary of tunisia palaeoecological and biostratigraphic implications abstract the analysis of coiling direction preference in the benthic foraminifera cibicidoides pseudoacutus nakkady has been carried out across the cretaceous tertiary boundary k t boundary from four tunisian sections representing a palaeobathymetric transect from a middle outer neritic to lower upper bathyal depositional setting our study reveals that c pseudoacutus developed a preference for sinistral coiling in a short time period during the lowermost danian the comparison of the coiling ratio number of sinistral vs dextral individuals record with isotope data and dinoflagellate cyst assemblage distribution suggests that the development of sinistrally coiled populations of cibicidoides pseudoacutus might be related to a short term cooling of both surface and bottom waters which occurred at the k t boundary and lasted for some 7 kyr the continuous occurrence and the high abundance of cibicidoides pseudoacutus through the k t boundary in neritic to upper bathyal depositional environments around southern tethys make identification of the shift in its coiling ratio relatively easy the development of a sinistrally coiled population in this benthic foraminiferal species is regarded as a potential marker for the base of planktonic foraminiferal zone p0 in tethyan shallow water settings

trace elements stable isotopes and clay mineralogy of the elles ii k t boundary section in tunisia indications for sea level fluctuations and primary productivity abstract trace elements and stable isotopes in bulk rocks and foraminifera bulk rock and clay mineral compositions are used as palaeoproxies to evaluate sea level fluctuations climatic changes and variations in primary productivity across the k t transition at elles ii in tunisia from 1 m 33 kyr below to 1 m 70 kyr above the k t boundary results on clay minerals major and trace elements stable isotopes in bulk rock samples e g ca cu zn rb sr zr ba 13c and 18o and in foraminifera sr ca 13c 18o indicate that the latest maastrichtian last 33 kyr in tunisia was marked by a relatively warm but humid climate and a rising sea level the transgressive surface is marked by deposition of a foraminiferal packstone just below the k t boundary followed by maximum flooding across the k t boundary red layer and black clay layer humid warm conditions accompanied the maximum flooding along with increased total organic carbon values and rapidly decreasing primary productivity at the k t boundary an impact event ir anomaly ni rich spinels spherules exacerbated already stressed environmental conditions leading to the mass extinction of tropical planktic foraminifera increasingly more humid conditions prevailed within the lowermost danian zone p0 50 kyr culminating in a sea level lowstand near the top of p0 a slow recovery of the ecosystem in zone p1a coincided with a rising sea level and gradually less humid climatic conditions

experimental simulation of chemomechanical processes during deep burial diagenesis of carbonate rocks chemomechanical processes involved in the deep burial diagenesis of carbonate petroleum reservoirs are still poorly understood to better understand these processes and explain how porosity and permeability can be preserved at the great depth of dbrs deeply buried reservoirs we developed an experimental device allowing both the simulation of high pressure stresses temperature conditions 80 c 60 mpa of confining pressure and differential stress up to 40 mpa of dbr and the circulation of different fluids in rock samples we tested triaxial multistep creep tests four core samples of a cemented limestone and analyzed creep deformations fluids chemistry and petrographical and petrophysical properties of samples different flow conditions no flow and flow through and chemical compositions natural meteoric water with and without phosphate ions were considered our study showed that the precipitation of calcite on free pore walls of micrites blocks the microporosity between micrite crystals thus rendering the microporosity inaccessible to fluids hence the connected porosity decreased strongly after experimentation this is due to the psc pressure solution creep which is the main process implied in the porosity reduction of a carbonate rock during deep burial the preservation of macropores during psc allows the preservation of permeability in addition calcite solubility is positively dependent on mechanical parameters axial compaction and axial stress thus suggesting that calcite can precipitate during decompression of deep basinal fluids resulting in changes in porosity a comparison of experimental results with theoretical calculations showed that the integration of the psc process into calculation databases would greatly improve the modeling of dbr

in search of the latest danian event in a paleobathymetric transect off kasserine island north central tunisia danian lower paleocene sequences in north central tunisia are dominantly composed of marls and shales but a conspicuous indurated glauconite bearing marker bed is associated with the p3a p3b transition this glauconite bed is considered to correlate with the latest danian event lde described from the nile basin in egypt with the top chron c27n event atlantic and pacific oceans and with the cie ds1 zumaia spain the lde is thought to reflect a short period of global warming similar to the paleocene eocene thermal maximum but of lesser magnitude the presence of a glauconitic bed at the p3a p3b transition in tunisia suggests that the sequence is condensed which is confirmed by planktic foraminifer and nannofossil biostratigraphy and by the absence of the typical lde beds found in most egyptian sections benthic foraminiferal assemblages were quantitatively analyzed in three sections in north central tunisia sidi nasseur garn halfaya elles in order to characterize the paleoenvironmental evolution during the late danian and compare this with sections in egypt the benthic foraminiferal assemblages indicate that the tunisian sections were located along a depth and a paleoenvironmental gradient on the shelf north of kasserine island the reconstructed depth range is comparable with sections in egypt and encompasses middle neritic sidi nasseur section to shallow upper bathyal depths elles section with up to 16 gavelinella beccariiformis below the p3a p3b like in egypt assemblage shifts across the p3a p3b subzonal transition indicate shallowing and a transition to a more eutrophic paleoenvironment characterized by relatively high abundances of buliminids and stainforthia sp the 13c and 18o records generated on well preserved specimens of the ostracode species bairdia failed to demonstrate the presence of the carbon isotope excursion cie associated with the lde at the base of subzone p3b a condensed section or a hiatus associated with the glauconite bed would explain why the cie is not recorded in the tunisian sections

an integrated study of the petrophysical properties of carbonate rocks from the oolithe blanche formation in the paris basin abstract petrophysical properties were measured on oolitic limestone from the oolithe blanche formation middle jurassic in the paris basin eighteen oriented blocks were collected from three outcrops regarding of the three main facies oolitic shoal facies tide dominated facies and prograding oolitic facies we investigated the relationship between both compressional wave and electrical conductivity with different petrophysical properties such as porosity water porosity and mercury porosity permeability and capillarity imbibition these have led us to relate the variations of petrophysical properties to several microstructural parameters among them the microporous structure is the most important concerning p wave velocities the general trend observed is as expected a decrease of velocities as the porosity increases but with a significant fluctuation of velocities for a given value of porosity we have used two distinct effective medium approximations to describe the velocity variations the self consistent sc approximation and the cemented contact theory cct but no unique model can simply explain our velocity behaviours the main parameter that controls the p wave velocities is the distribution of microporosity inside oolites for samples with velocities higher than 4 km s the microporosity is mainly located in the rim of the ooids while for samples with velocity lower than 4 km s the microporosity is homogeneous across the ooids acoustical fabrics which are controlled by the facies indicate that sedimentary textural components such as the amount of cement and arrangement of elements within the oolitic limestones bioclasts pellets and ooids and their degree of connectivity may have some influences on the acoustic velocities in contrast with acoustic properties the electrical conductivity data are not so clustered by facies indicating that transport properties are more influenced by microstructural heterogeneities one single archie s law can well account for all the data sets but these sets also show a large range of tortuosity factor related to the microporosity arrangement inside oolites some good predictive permeability modeling were found using mercury injection spectra our investigations reveal that the best way for fluids to flow is to pass through the microporosity in the oolites and that permeability depends mainly of the connectivity of the ooids which is certainly related to the facies

factors controlling elastic properties in carbonate sediments and rocks carbonate sediments are prone to rapid and pervasive diagenetic alterations that change the mineralogy and pore structure within carbonate rocks in particular cementation and dissolution processes continuously modify the pore structure to create or destroy porosity in extreme cases these modifications can completely change the mineralogy from aragonite calcite to dolomite or reverse the pore distribution whereby original grains are dissolved to produce pores as the original pore space is filled with cement to form the rock figure 1 all these modifications alter the elastic properties of the rock and therefore the sonic velocity the result is a dynamic relationship among diagenesis porosity pore type and sonic velocity the result is a wide range of sonic velocity in carbonates in which compressional wave velocity vp ranges from 1700 to 6600 m s and shear wave velocity vs from 600 to 3500 m s

benthic foraminiferal assemblages between two major extinction events the paleocene el kef section tunisia abstract the development of benthic foraminiferal assemblages from the paleocene outcrops of the el haria formation near el kef tunisia is discussed qualitatively and quantitatively the aim of the study is to reconstruct the paleoenvironmental evolution between the k pg boundary interval and the late paleocene event and to compare this evolution with results from other sites along the southern tethyan margin eighty four samples covering virtually the entire paleocene provide a dataset that allows detailed qualitative and multivariate analysis the benthic foraminiferal faunas indicate a complex pattern of environmental changes during the paleocene marked by the succession of different benthic associations following the k pg boundary event community restoration was characterized by the gradual build up of faunal diversity decreasing dominance and the entry of taxa common to normal marine outer neritic to upper bathyal environments indicate the completion of the ecosystem restoration in zone plb a highly diverse benthic foraminiferal assemblage persisted throughout the remainder of the early paleocene into the earliest late paleocene at the p3a p3b zonal transition relative sea level lowering is evidenced by the sudden disappearance or decreasing abundance of deeper water taxa e g anomalinoides affinis a susanaensis gavelinella beccariiformis neritic deposition continued into zone p4 when trophic levels at the seafloor increased as indicated by the entry and increasing dominance of species such as anomalinoides cf aegyptiacus bulimina midwayensis and b strobila which we consider to be sensitive to eutrophication the combined effect of shallowing and the subsequent eutrophication led to the establishment of assemblages similar to late paleocene benthic foraminiferal assemblages from egyptian sections some of which record the latest paleocene extinction event these assemblages were interpreted to be indicative of a middle neritic highly eutrophic environment enhanced vertical fluxes of organic matter along the southern tethyan margin may have resulted from intensified upwelling this eventually led to oxygen deficiency at the seafloor it appears that oxygen deficient high productivity shelves were a common feature of the southern tethyan margin during the latest paleocene

paleoproductivity from benthic foraminifera abundance glacial to postglacial change in the west equatorial pacific surface productivity is correlated with the rate of accumulation of benthic foraminifera on the deep sea floor as a rule of thumb for each 1 mg of organic carbon arriving at the sea floor one benthic foram shell 150 m is deposited the correlation can be used to reconstruct organic flux to the sea floor in the past and hence the productivity of past oceans applying the appropriate equations to box core data from the ontong java plateau in the western equatorial pacific we found that productivity during the last glacial maximum exceeded present productivity by a factor of between 1 5 and 2 0 with intermediate values for the mid transition period accumulation of benthic foraminifera was depressed on top of the plateau during the glacial and transitional period presumably because increased winnowing removed part of the food supply

the impact of paleocene eocene boundary events on middle neritic benthic foraminiferal assemblages from egypt abstract a 25 m upper paleocene to lower eocene marly sequence exposed at gebel duwi quseir red sea coast of egypt provides a good opportunity for studying paleocene eocene p e boundary stratigraphy and events various bio eco and isotope stratigraphic correlations accurately delineate the position of the p e boundary i e the level of stable isotopic excursions and deep sea benthic extinctions in the middle part of this section within zones p5 and np9 in this paper the impact of p e boundary environmental perturbations on benthic foraminiferal communities of the shallow tethyan shelf is examined benthic foraminiferal assemblages from gebel duwi characterized by large frondicularia phosphatica and f nakkadyi in addition to a number of other neritic taxa but without any typical outer neritic bathyal taxa suggest middle neritic 75 100 m deposition throughout the studied interval and only minor relative sea level variations perhaps some 10 20 m across the boundary sea level appears to have been stable yet a distinct faunal turnover marks the p e boundary of this shallow site which in contrast to deep sea records is less abrupt being preceded by a gradual diversity decrease starting some four meters below the boundary moreover most exits are either local or just temporary and thus not true extinctions many lazarus taxa reappear at some point above the boundary while all but one of the disappearing taxa are known from other lower eocene neritic deposits in egypt in general benthic foraminiferal assemblages display low diversities and high dominance values notably anomalinoides aegyptiacus up to 74 suggesting high levels of environmental stress at the sea floor in combination with occasionally very high p b ratio s up to 98 p and generally laminated sediments the character of the benthic assemblage points to a strong influence of recurrent dysoxia and or anoxia we suggest that these resulted from surface eutrophication by intermittent coastal upwelling and reduced ventilation of the bottom environment although these conditions prevailed during most of the time interval studied they were most severe during the latest paleocene and early eocene when eutrophication intensified and the organic carbon flux to the sea floor increased enhanced atmospheric contrasts between the tethys seaway and the african continent resulting in intensified longshore tradewinds may have controlled these changes at the p e boundary the bottom environment became minimally ventilated perhaps due to reduced oxygen advection from deeper waters three meters above the boundary a succession of increasingly diverse assemblages indicate a gradual decrease of environmental stress and a return to more normal conditions although the organic carbon flux to the sea floor remained high

paleoproductivity the benthic planktonic ratio in foraminifera as a productivity index abstract when the effects of differential dissolution are excluded the benthic to planktonic ratio in deep sea foraminifera can be read as a productivity index for pelagic conditions we use the bz index which is the product of the benthic planktonic ratio in percent and the depth of deposition which controls supply of organic matter for hemipelagic conditions we use bz d which is the product of the bz value and a factor for proximity to the shore square root of distance from land which controls coastal productivity anomalous values readily stand out from the normal populations which cluster around typical values of bz or bz d off northwest africa wherever calcite dissolution can be excluded as a factor because of presence of aragonite these anomalies are due to lateral supply of redeposited organic matter

interrelations of the petrophysical sedimentological and microstructural properties of the oolithe blanche formation bathonian saline aquifer of the paris basin abstract the paris basin seems a suitable location for co2 capture and storage given both the amount of co2 produced and the availability of depleted fields and deep saline aquifers this study investigates the petrophysical properties in relation to the sedimentary and diagenetic environment of the oolithe blanche formation middle jurassic a deep saline aquifer considered a potential candidate for co2 storage because of the scarcity of core data in the paris basin our investigation was based on the study of field analogues in the south east part of the paris basin the oolithe blanche formation bathonian is 70 80 m thick eighteen oriented blocks were collected from three outcrops selected for the different sedimentological facies identified in the formation their petrophysical properties were measured porosity pore size distribution derived from mercury injection tests permeability and capillary imbibition parameters the sedimentary and diagenetic facies were defined by using optical microscopy coupled with image analysis on thin sections and sem the oolithe blanche formation is composed of oolitic and bioclastic limestones deposited in a shallow marine setting three main sedimentological facies were defined the oolitic shoal facies the tide dominated facies and the prograding oolitic facies they exhibit subtle variations in composition and in the distribution of carbonate textures porosity measured using the water saturation triple weight method ranges from 6 to 34 permeability values are low between 0 1 md and 9 md the data from mercury intrusion porosimetry show that the distribution of the pore throat diameter is either unimodal microporosity only or bimodal macro and microporosity microporosity is intraparticle intraooid and macroporosity is interparticle and is related to dolo dedolomitization variations of petrophysical parameters can be explained by the microstructure now these latter results calibrated by studying field analogues must be extended to borehole data and core data to optimize our knowledge of the deep saline aquifer of the oolithe blanche formation without such investigations it will be impossible to estimate the suitability of this deep saline aquifer for co2 storage

the depth dependency of planktonic benthic foraminiferal ratios constraints and applications abstract study of the ratio between planktonic and benthic foraminifera in a great number of areas shows that variation of this ratio with depth can be described using organic matter flux equations essentially the share of benthic foraminifera in the total association is inversely proportional to depth as is the amount of organic matter resulting from primary productivity reaching the sea bottom variation in the p b ratio from area to area appears to be strongly dependent on the amount of inbenthic living foraminifera if the ratios are corrected for this the regressions between the proportion of planktonic foraminifera p and depth appear to be near identical in the gulf of mexico the gulf of california the west coast of the usa and the adriatic sea this regression can be described by depth e 3 58718 0 03534 p a study of the behaviour of this function in nine cores from the adriatic upper quaternary reveals that the palaeodepth reconstructions are not influenced by fluctuations in productivity and temperature but that they are significantly influenced by redeposition of fine grained deposits

the campanian paleoenvironment inferences based on benthic foraminifera from northeastern iran abstract the benthic foraminifera from the campanian rocks globotruncanita elevata to globotruncana aegyptiaca zones exposed in the kopeh dagh basin northeast iran are studied quantitatively to reconstruct the campanian paleoenvironment based on unconstrained heriarchial clustering nonmetric multidimensional scaling nmds and analysis of similarity anosim three statistically significant benthic foraminiferal assemblages are noted paralabamina lunata lower and upper haplophragmoides spp and gyroidinoides nitida based on benthic foraminiferal marker species the following paleodepths are assigned lower p lunata upper bathyal upper p lunata upper middle bathyal boundary haplophragmoides spp and g nitida outer neritic the p lunata assemblage can be further subdivided into a lower coryphostoma incrassata dominated interval whereas the upper interval is p lunata dominated and reflects a change in the quality of food the upper experienced higher input of fresh phytodetritus the overall p lunata assemblage reflects a stable bottom water environment the haplophragmoides spp assemblage is characterized by reduced paleoproductivity and environmental instability whereas the g nitida assemblage is marked by increasing oligotrophy within a well oxygenated bottom water and ventilated basinal conditions the partial least squares regression yielded significant correlations with planktic positive proxy for sea level and agglutinated species negative proxy for shallow depths and low organic flux the reduced major axis regression models also yielded significant negative correlations with agglutinated and infaunal species nutrient availability suggesting that these factors were responsible for the inferred benthic foraminiferal distribution patterns two globally comparable shallowing trends are also noted one in the middle of the r calcarata zone haplophragmoides spp assemblage and the other in the g aegyptiaca zone gyroidinoides nitida assemblage that coincide with kca6 and kca7 sequence boundaries and lowstands respectively for the kca6 event the occurrence of spiroplectammina haplophragmoides spp assemblage represents a shallow water outer neritic fauna invasion event within a deeper upper bathyal setting paralabamina lunata assemblage and for the kca7 event a similar shallowing from upper middle bathyal boundary to outer neritic depths is noted g nitida assemblage and attributed to eustasy and basinal paleohighs and lows

biotic turnover in benthic foraminifera across the cretaceous tertiary boundary at el kef tunisia abstract the cretaceous tertiary boundary section exposed near el kef tunisia is the most complete boundary sequence known to date it contains nearly 1 m of black and gray boundary clay containing planktic foraminiferal zone poa b 2 m of clayey shales of p1a globigerina eugubina zone and 4 m of shales and marls of p1b g taurica zone quantitative analysis of the benthic foraminiferal fauna suggests that deposition during the latest cretaceous occurred in an upper slope to outer shelf environment which shallowed at the k t boundary to an outer to middle shelf depth and shallowed further by p1b time to mid shelf depth a major reduction in benthic diversity occurred near the k t boundary with about 50 of the fauna disappearing diversity remained an average of 37 lower during deposition of the first 3 m of sediment above the boundary poa b p1a and productivity was very low surviving and thriving foraminifers during this interval were primarily low oxygen tolerant epifaunal and infaunal species a sharp decrease in the low oxygen tolerant fauna and appearance of a shallow mid shelf fauna at about 4 m above the boundary p1b zone signals a second regression return to higher oxygen levels and higher productivity although the environmental effects of the k t boundary event can be inferred from benthic faunas the ultimate cause remains elusive faunal changes prior to and the long recovery period after the k t boundary are difficult to explain by a single impact hypothesis