experimental study of the stress dependence of the absolute and relative permeabilities of some tight gas sandstones connected porosity and dry gas permeability at 5 mpa hydrostatic stress have been measured for thirteen tight gas sandstone samples originating from a rotliegend sandstone reservoir in germany the samples have then been preserved into hermetic chambers at fixed relative humidity rh values until mass and water saturation level stabilisation this allows a first characterisation of pore size distribution showing that most of the pore network is constituted with pores with entrance radii greater than 50 nm the relative gas permeability was then measured for different water saturation and hydrostatic stress up to 60 mpa the analysis of the results has allowed us to identify the limiting conditions water saturation and hydrostatic stress for the apparition of a hydraulic cut off also called the permeability jail dry gas permeability at low confining pressure 5 mpa has appeared to be a good indicator of the sensitivity of a sample to both hydraulic stress and liquid saturation this gives an efficient tool to predict the global behaviour of the gas reservoir despite its heterogeneity with a single gas permeability measure

a common feeding system of the ne and s rifts as revealed by the bilateral 2002 2003 eruptive event at mt etna sicily italy mount etna volcano is often characterized by bilateral eruptive events involving both the south s and the north east ne rifts the last event occurred in 2002 2003 from october 27 to january 28 a detailed stratigraphically time controlled sampling of lavas and tephra of the southern eruptive fissure was performed in order to 1 track the petrological features of products during the eruption and 2 integrate the results with those previously obtained on the ne rift whole rock composition and textural observations were implemented by major and minor element analyses of plagioclases in lavas and tephra from both sides of the volcano fractionation models constrained by mass balance major and trace elements and rayleigh calculations suggest that magmas are linked by the same liquid line of descent by fractionating 9 11 of a mineral assemblage of cpx 52 69 plg 21 41 and ol 7 46 these new data allowed us to identify at least two feeding episodes through the southern fissure and infer that high k2o porphyritic magmas emitted on both the s and ne rifts derives by fractionation from the same parent magma however lavas and tephra from the southern flank were slightly more primitive textural and petrological study of plagioclase moreover indicates that chemical physical conditions in the deep feeding system were similar for magmas erupting from both rifts as suggested by the presence of dissolved rounded cores in both lavas magmas evolved differently on the s and the ne rifts only at shallow levels comparison with published seismotectonic data supports the idea that the main magma feeding the eruption on october 27 ascended along the same pathway at depth and was intercepted by the fracture system of the s and ne rifts at shallow depth between 6 and 3 km b s l

the 1986 kalamata south peloponnesus earthquake detailed study of a normal fault evidences for east west extension in the hellenic arc tectonic and seismological data collected in the field following the september 13 1986 kalamata earthquake south peloponnesus are presented and analyzed to discuss the earthquake rupture process and the regional tectonics the event occurred on the kalamata normal fault whose trace was mapped with spot images and topographic and field observations this fault is part of an approximately nnw sse en echelon system cutting through the hellenic nappes the fault striking n15 e on the average with a dip of about 50 has a minimum cumulated quaternary throw of the order of 1 km the measured coseismic slip is 6 18 cm over a length of 6 km the main shock focal mechanism obtained from long period waveform modeling strike 201 10 20 dip 45 5 rake 283 10 25 represents almost pure east west extension and is in good agreement with tectonic observations the centroid depth is constrained to 5 3 km and the seismic moment to 7 0 2 5 1017 n m over 700 aftershocks located by a 16 station network installed after the earthquake for a period of 2 weeks define two clusters separated by a gap of aftershock activity from the surface to a depth of about 10 km the main cluster to the south defines a 45 west dipping plane which lies on the downward extension of the fault mapped at the surface focal mechanisms of aftershocks on this fault plane are homogeneous and represent e w extension as the main shock in contrast the majority of focal mechanisms in the uppermost part of the foot wall show more or less e w compression probably corresponding to postseismic stress release the northern cluster of aftershocks is very dense and located away from the surface rupture within a relay zone between the kalamata and the next en echelon faults to the nw the thouria faults there focal mechanisms represent extension from about n115 to n70 and n20 corresponding mostly to fault reactivation in an area where nonrigid deformations prevail the main shock probably initiated in this relay zone 3 4 s before the rupture front reached the main fault plane and released most of the energy there the rupture presumably propagating southward the focal mechanism of the kalamata earthquake and that of the april 27 1965 earthquake located to the northwest of crete as well as the regional active normal fault pattern imply that e w extension oblique to the hellenic arc is presently the dominant tectonic regime e w stretching occurs partly on reactivated nw se faults parallel to the hellenic structures but mostly on newly formed n s normal faults across those structures the latter faults are responsible for the apparent segmentation of the hellenic belt from southern peloponnesus to crete the existence of active e w extension in this region implies a recent change in the tectonic regime and consequently a change in boundary conditions at the subduction zone probably in response to the incoming margin of africa

magmatic evolution of a volcano studied by 230th 238u disequilibrium and trace elements systematics the etna case age determinations of several lava flows from etna through 230th 238u disequilibrium internal isochrons yield a precise chronology of the volcano s history for the last 200 000 years and emphasize the main episodes in the formation of this huge complex strato volcano study of 230th232th 0 initial ratios of lavas together with their trace element compositions yields a consistent model of magmatic evolution implying the existence for 200 000 years of a deep reservoir of alkalic magma periodically mixed with magmas of tholeiitic affinity these short periods of mixing appear to be related to the formation of the large calderas of etna in addition to these processes affecting the deep reservoir fractional crystallization also occurred in more superficial levels of the volcanic edifice thereby yielding several series of differentiation of relatively short duration as for its geochemistry etna s volcanism is of oceanic type but with its own characteristics and in a peculiar geodynamic context at the edge of the african plate

the history of the major rivers of southern britain during the tertiary the evolution of the drainage system of lowland britain is discussed on the basis of available geological evidence including that from terrestrial sites and that which has more recently become available from offshore exploration of the north sea the english and bristol channels and the irish sea tertiary stratigraphy throws considerable light on landform and river development paleocene destruction of a chalk cover which seems to have been incomplete in western britain was accompanied by basin sedimentation under a tropical climate the major elements the thames solent hampshire proto avon river irish sea river and possibly an early trent river existed almost throughout the cenozoic the influence of atlantic rifting and thermal doming in nw britain appears to have been stronger and more temporally focused than the persistent flexuring that determined and maintained tertiary drainage lines in the se here also the folded mesozoic terrains on the surface contrast with the more dominant block faulted relief of the palaeozoic oldlands the rivers of the se can be shown to have extended or reduced their lengths in response to relative sea level change and gentle warping drainage antecedence the destruction of the solent system and the breaching of the english channel are also evident by contrast the major river systems of the west are now entirely submerged long term stability of the drainage pattern reflects a persistent tectonic regime in the south with a subdued low relief landscape having a weathered regolith and dense vegetation cover meandering river channels and alluvial styles predominated although channel forms varied according to sediment load slope and discharge variability coarse gravel dominated accumulations are rare and localized chemically stable lithologies dominate the clastic component throughout it is apparent that the deeply incised river valleys seen today are related to high predominantly coarse sediment yields encouraged by substantial rapid climate changes in the pleistocene this emphasizes the significance of mechanical compared with chemical weathering for the rate and nature of landscape dissection and the modifications that have arisen as a result of glaciation frost climate weathering rapidly changing climates and sea levels the stratigraphical evidence here reviewed is at variance with older largely geomorphologically based landform evolution models denudational chronology but gives considerable support to the recent proposals emphasizing the significance of paleocene erosion and enduring low relief landscapes and drainage systems evolving alongside fold development during the paleogene given the depobasin evidence now available postulated fluvially active episodes can and must be linked to contemporaneous deposition some at least of the many controversies involving the identity of erosion surfaces the dating of them using only residual deposits and weathering mantles and the selection of particular tertiary episodes as ones of landscape development can now be resolved

recent dyke induced large scale block movement at mount etna and potential slope failure here we report the results of a geodetic survey undertaken on mount etna between 1981 and 1988 observed horizontal ground movements in the vicinity of the valle del bove caldera demonstrate that dyke emplacement during 1983 and 1985 resulted in the 2 8 m eastward displacement of a block of western caldera rim a history of past instability and collapse along the rim is indicated by the presence of large back rotated blocks of prehistoric volcanics1 furthermore the unusually linear form of the present western rim indicates past slope failure along north south aligned surfaces and therefore that dyke induced collapse may have been an important agent in caldera enlargement we suggest a self sustaining mechanism whereby the stress regime generated as a consequence of the caldera s existence results in the repeated injection of north south orientated dykes adjacent to the western rim2 3 dilation associated with magma intrusion leads in turn to periodic phases of slope instability and failure of the cliff wall causing a progressive westward migration of the western rim

geochemistry of late palaeocene and early eocene tephras from the north sea basin the late palaeocene to early eocene balder and sele formations of the north sea basin contain over 200 air fall water lain tephras these occur over the entire north sea area extending onshore into denmark nw germany the netherlands and se england they have also been recorded in the bay of biscay and goban spur areas of the ne atlantic and offshore mid norway results from cores drilled in two widely separated areas of the north sea have been integrated with earlier work on the northern north sea and danish sequences to demonstrate that the stratigraphic and geochemical development of the tephra sequence is regionally consistent this indicates that a single source or group of sources was responsible rather than a number of geographically separated intrabasinal volcanoes for which little geophysical evidence can be found the sequence comprises a lower group of sporadic thin tephras of variable composition including tholeiitic alkalic trachytic trachyandesitic and peralkaline varieties and an upper group of thicker more abundant tephras almost exclusively of fe ti tholeiitic composition general thickness trends and geochemical evidence indicates that the source volcanoes lay on the proto greenland scotland ridge with the tephras showing several features that ally them to the early palaeogene faeroe greenland igneous province the reasons behind the highly explosive nature of the basaltic magmatism remain enigmatic

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

very shallow earthquakes and brittle deformation in active volcanic areas the eatnean region as an example abstract some aspects of the stress field acting in active volcanic areas were investigated by studying the relationship between surficial seismicity h 1 2 km and the brittle deformation pattern of the etna volcano the magmatic composition and structural character of mt etna are described together with its geodynamic regional context after a discussion of the problem of the state of stress in active volcanoes and a definition of very shallow seismicity the high level of surficial seismicity the morphology of the sedimentary basement and the kinematic behaviour of the faults suggest that the eastern flank of mt etna is a shallow seismotectonic domain structurally decoupled from the rest of the volcanic body this flank shows a tendency to slide in an eastern direction and is bound to the north by a left lateral oblique slip normal fault trending e w and in the south by an arcuate fault system with right lateral features right lateral oblique slip normal faults

late quaternary slip rates on the acireale piedimonte normal faults and tectonic origin of mt etna sicily abstract mt etna is located along the east coast of sicily near the boundary between the continental crust of the hyblean plateau and the mesozoic oceanic crust of the ionian basin the main active faults near mt etna cut the base of its eastern flank forming a 30 km long system of nne and nnw trending ene chelon fault segments the acireale piedimonte system showing dip slip and oblique right lateral motion most segments are associated with shallow depth seismicity and all have late pleistocene to holocene vertical slip rates ranging between 1 and 2 mm yr typical of major active normal faults worldwide eruptive fissures arranged in nne to ne trending zones cut the highest slopes of the volcano on the footwall of the normal fault system structural analysis suggests that current motions along both the active faults and eruptive fissures are kinematically compatible and simply linked with ongoing wnw ese directed regional extension such extension characterizes at a greater scale the active tectonics of southern italy where all large shallow historical earthquakes have remained confined within a narrow normal fault belt or rift zone stretching from the northern calabrian arc to southeastern sicily the southernmost west dipping faults of that rift zone in calabria aspromonte cut across the calabro peloritan thrust belt to join the mostly east dipping acireale piedimonte faults along the western boundary of ionian oceanic lithosphere which continues southwards as the malta escarpment we thus relate magmatism at etna to dilational strain on the footwall of an east facing crustal scale normal fault at the bend where the siculo calabrian rift zone veers 60 eastwards as it begins to cross the calabrian arc leaving the east facing margin of the ionian sea to catch up with the west facing margin of the tyrrhenian sea farther north

stress induced permeability changes in indiana limestone abstract this paper examines the influence of triaxial stress states with confining stresses between 5 and 30 mpa including post failure on the alteration of intrinsic permeability of indiana limestone the permeating fluid used in the experiments was distilled de aired water experimental results are used to develop an empirical state space model of permeability evolution due to the action of maximum and minimum principal stresses imposed on the sample the developed empirical model is implemented in a computational code to examine the influence of stress induced permeability alterations on the flow into an unlined cylindrical cavity located in a rock mass subjected to geostatic stresses

recognition of chron c25n in the upper paleocene upnor formation of the london basin uk lithostratigraphic studies of four borehole cores drilled through the late paleocene lambeth group upnor woolwich and reading formations and basal london clay formation of central london have been supplemented with palaeomagnetic calcareous nannoplankton and palynological data the woolwich and reading formations and the lower london clay formation are reversely magnetized and were deposited during the early part of chron c24r the first record of both np9 and chron c25n hitherto missing from the paleogene record in southern england has been identified in the upnor formation formerly the woolwich bottom bed it provides a key reference marker for linking events associated with the paleocene eocene boundary positioned within chron c24r to the type area of the internationally recognized thanetian and ypresian stages work carried out to establish the chronostratigraphy of the paleogene in southern england fig 1 has been concerned principally with the late paleocene thanet sand formation and the early eocene london clay formation e g aubry et al 1986 ali et al 1993 knox et al 1994 the thanet sand formation lies within calcareous nannoplankton zones np6 np8 and magnetochrons c26r to c25r magnetochron nomenclature from cande kent 1992 the base of division b of the london clay formation sensu king 1981 coincides with the start of chron c24n 3n the intervening lambeth group upnor woolwich and reading formations harwich formation ellison et al 1994 and lower part of the london clay formation are allocated to chron c24r aubry et al 1986 indicated that an hiatus in excess of 0 6 million years marked by the absence of chron c25n separates the thanet sand formation from the lambeth group in recent years the drilling of fully cored boreholes fig 2 through the lambeth group in central london has provided a unique opportunity for multidisciplinary study one borehole in particular jubilee 404t bgs registration number tq 37 nw 2118 national grid reference tq 3363 7960 has become a key reference section for the lambeth group in central london ellison et al 1994 the main reasons for its importance are firstly the wide variety of lambeth group facies including marine sands brackish lagoonal muds and pedogenic horizons and secondly the presence 55

the occurrence of the dinoflagellate cyst apectodinium costa downie 1976 lentin williams 1977 in the moray and montrose groups danian to thanetian of the uk central north sea

volcanism and mantle crust evolution the etna case abstract mount etna is located in a particular region of convergence of african and eurasian plates where intense post collisional tectonics caused considerable uplift however we present arguments supporting the hypothesis that volcanism and associated seismic activity would result from a local mantle uprise leading to a horst probably linked to a deep rooted hot spot it ensued deformation and fracturing of the overlying crust with emission of aphyric tholeiitic basalts directly from their mantle source and subsequent development of a deep reservoir or complex of intrusions at the top of a mantle diapir near 30 km depth this is advocated by the appearance of porphyritic alkaline lavas whose mineral equilibria and differentiation processes are consistent with an 8 10 kbar pressure and by the development of central volcanoes the horst itself appears to have begun in the sw sector of the present volcanic area its uplift was greater westward as seen from the trend of the terraces along the simeto river and became later obvious toward the se these differential movements produced fractures and faults which are to day evident in the southern area of mt etna the growth of the horst then proceeded in a ne direction following the regional tectonic lines and with a greater intensity along the side facing se crossed by the regional nnw sse line aeolian maltese escarpment the seismicity and ground deformation registered over the last twenty years support the proposed model earthquakes are unfrequent in the lower southern and western areas of the volcano whereas they are numerous and stronger to the north east in the summit area above 1600 m a s l and in the eastern sector along the nw se faults and fractures finally a digital elevation model recently published reveals the existence of two tectonic domains the first one is associated with the horst and contains prevalently ne sw oriented faults whereas the second is mainly linked to regional tectonics with nnw sse and nw se faults and fractures

basaltic explosive volcanism but no comet impact at the paleocene eocene boundary high resolution chemical and isotopic records from egypt spain and denmark in the search for a triggering mechanism for the paleocene eocene p e boundary event 55 ma centimeter resolution chemical e g ir os pt and isotope e g os o 187 os 188 he 3 he 4 sr 87 sr 86 records across this boundary have been established for six uplifted marine sections in egypt spain and denmark the sections studied represent some of the stratigraphically most complete records across the onset of the carbon isotopic excursion cie and associated benthic foraminifera extinctions that mark the paleocene eocene boundary high sensitivity analyses failed to uncover evidence of extraterrestrial element or isotope enrichments in the six sections refuting the hypothesis of a major comet impact at the boundary preliminary searches for other impact indicative features such as spherules or shocked quartz also gave negative results in the danish section studied three basaltic ir rich ash layers occur at the paleocene eocene boundary but no similar ashes were found in egypt or spain the three ashes represent the earliest known manifestation of an unusual i to 2 million year long phase of explosive basaltic volcanism in the faero greenland region this volcanism is synchronous with major flood basalt effusions in east greenland and is associated with prominent paleogeographic changes in the high latitude north atlantic region discharge of mantle derived os to seawater during this volcanism may explain a small decrease in os o 187 os o 188 ratio at the paleocene eocene boundary in the zumaya section in spain the environmental perturbations at the paleocene eocene boundary appear to have been triggered by basaltic volcanism but any model for the detailed causal relation remains speculative c 2004 elsevier b v all rights reserved less

generalized poroelasticity framework for micro inhomogeneous rocks poroelastic modelling of micro inhomogeneous rocks is of interest for applications in rock physics and geomechanics laboratory measurements from both communities indicate that the biot poroelasticity framework is not adequate for the case of a macroscopically homogeneous and isotropic rock we present the most general poroelasticity framework within the scope of equilibrium thermodynamics that is able to capture the effects of micro inhomogeneities in a natural way within this generalized poroelasticity framework the concept of micro inhomogeneity is generically related to partial localization of the deformational potential energy either in the solid phase including the interfacial region or in the fluid phase the former case can occur in the presence of surface roughness or multi mineralic frame and the latter case can be related to suspended particles residing in the fluid phase a measure for micro inhomogeneity is the coefficient that governs the effective pressure dependence of porosity changes as described by the porosity perturbation equation of this framework it can be therefore equivalently interpreted as porosity effective pressure coefficient or as micro inhomogeneity parameter we show how this parameter and the other poroelastic constants embedded in this framework can be expressed in terms of experimentally accessible poroelastic constants

variations in the strontium isotope composition of seawater during the paleocene and early eocene from odp leg 208 walvis ridge we refined the strontium isotope seawater curve for the paleocene and early eocene by analysis of samples recovered from the walvis ridge during ocean drilling project odp leg 208 the highest sr 87 sr 86 values occurred in the earliest paleocene at similar to 65 ma and generally decreased throughout the paleocene reaching minimum values between 53 and 51 ma in the early eocene before beginning to increase again at similar to 50 ma a plausible explanation for the sr 87 sr 86 decrease between 65 and 51 ma is increased rates of hydrothermal activity and or the eruption and weathering of large igneous provinces e g deccan traps and north atlantic strontium isotope variations closely parallel sea level and benthic delta o 18 changes during the late paleocene and early eocene supporting previous studies linking tectonic reorganization and increased volcanism to high sea level high co2 and warm global temperatures

a pulse in the planet regional control of high frequency changes in relative sea level by mantle convection abstract an explanation for high frequency cycles of sea level in non glacial times has remained elusive despite more than two centuries of research since lavoisier9s seminal observations were published in 1789 in the development of seismic stratigraphy in the 1970s putatively global high frequency changes in relative sea level vail third order cycles were attributed to an unknown eustatic mechanism prompting a search for mesozoic ice ages over the last decade a regional mechanism of sea level control has been developed from studies of the sedimentary record in high quality oil industry data these geological studies have supported the geophysical prediction that significant regional control of sea level is exercised by mantle induced vertical motions of the earth9s surface these vertical motions can occur over time intervals from several tens of million years to less than a million years with amplitudes of tens of metres or more even at the shorter intervals the vertical motions are not confined to regions with major hotspots there are two related controls of surface vertical motion evolution of mantle convection cells and pulsing flow within each cell the effects are evident in the sedimentary record of north atlantic basins mantle convection provides an alternative regional mechanism to eustatic control for explaining medium frequency to high frequency sea level cycles

cenozoic uplift and subsidence in the north atlantic region geological evidence revisited abstract the topographic evolution of the passive margins of the north atlantic during the last 65 myr is the subject of extensive debate due to inherent limitations of the geological geomorphological and geophysical methods used for studies of uplift and subsidence we have compiled a database of sign time and amplitude where possible of topographic changes in the north atlantic region during the cenozoic 65 0 ma our compilation is based on published results from reflection seismic studies aft apatite fission track studies vr vitrinite reflectance trends maximum burial sediment supply studies mass balance calculations and extrapolation of seismic profiles to onshore geomorphological features the integration of about 200 published results reveal a clear pattern of topographic changes in the north atlantic region during the cenozoic 1 the first major phase of cenozoic regional uplift occurred in the late palaeocene early eocene ca 60 50 ma probably related to the break up of the north atlantic between europe and greenland as indicated by the northward propagation of uplift it was preceded by middle palaeocene uplift and over deepening of some basins of the north sea and the surrounding areas 2 a regional increase in subsidence in the offshore marginal areas of norway the northern north sea the northern british isles and west greenland took place in the eocene ca 57 35 ma 3 the oligocene and miocene 35 5 ma were characterized by regional tectonic quiescence with only localised uplift probably related to changes in plate dynamics 4 the second major phase of regional uplift that affected all marginal areas of the north atlantic occurred in the plio pleistocene 5 0 ma its amplitude was enhanced by erosion driven glacio isostatic compensation despite inconclusive evidence this phase is likely to be ongoing at present

origin damping and pattern of development of faults in granite observations of brittle fractures in the granite of the massif de la borne as well as in other rocks allow us to discuss the different hypotheses regarding the origin of faults it seems that all faults originate by shear along a preexisting plane which can be an important fracture joint former fault or a microflaw pore grain boundary the shear on the plane gives rise to an array of en echelon cracks that makes the rock less resistant and permits the lengthening of the fault we also found an arrangement of horsetail fractures damping the movements on the faults we then propose a pattern for the development of the faults they originate on preexisting plane and propagate by initiating en echelon cracks the movements are damped by horsetails which permit by faults connection in relays the creation of larger faults

fossil plants record an atmospheric 12co2 and temperature spike across the palaeocene eocene transition in nw europe the large negative excursion of carbon isotope composition 13 c recorded from foraminifera and bulk carbonates indicates a major anomaly in the operation of the global carbon cycle across the palaeocene eocene boundary therefore we sought terrestrial evidence for the transfer of isotopically light carbon 12 co 2 from the ocean to the atmosphere by making systematic 13 c measurements or well dated sequences of fossil pollen from nw europe the results indicate an atmospheric 12 co 2 spike of c 2 between 58 and 55 ma coincident with the ocean isotopic anomalies pollen spectra from these sequences suggest a marked shift in dominance from mixed mesophytic to paratropical forests synchronous with the terrestrial isotope excursion

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

lower paleogene denudation of upper cretaceous cover of the morvan massif and southeastern paris basin france revealed by aft thermochronology and constrained by stratigraphy and paleosurfaces abstract low temperature thermochronology data have been acquired from outcrop samples from the southeastern edge of the paris basin morvan they provide indications about the former sedimentary cover its denudation and about inversion tectonics in the paris basin apatite fission track data acquired on variscan granites and triassic sandstones reveal that the basement was subjected to temperatures of about 70 10 c during the late cretaceous we suggest that the peak temperature was generated by an upper cretaceous sedimentary cover of low thermal conductivity chalk additional stratigraphic sedimentological paleogeographic paleoweathering and continental paleosurface data support the reconstruction of this chalk paleocover and of its erosion this former blanketing sequence was removed during the early paleogene regional inversion episode which affected the southern edge of the basin intensively and was related to far field compression between europe and africa this study shows that i for the se border of the intracontinental paris basin kilometer scale vertical deformation occurred ii the sedimentary sequences of the paris basin covered considerably larger areas than the present contours of the sediment fill iii paleoweathering and erosion processes later removed the sedimentary cover rather quickly

forward and reverse stratigraphic modelling of cretaceous tertiary post rift subsidence and paleogene uplift in the outer moray firth basin central north sea

construction of a palaeogene tide dominated shelf influence of top chalk topography and sediment supply wessex basin uk palaeogene siliciclastic sediments reading and london clay formations in the wessex basin record an upward change through four tidally influenced deposition systems the lowest reading formation was deposited in estuarine and coastal plain environments the overlying london clay records discrete upward changes from deltaic to mixed tidal flat to tidal sandsheet bagshot sands erosional topography on the top chalk surface had an important control on deposition 1 topographic lows controlled the initial sites of marine flooding and sedimentation 2 lows would have acted as conduits for sediment delivery 3 lows created additional accommodation by the compaction of thick mud fills 4 lows may have formed preferential sites for delta growth as topography was reduced by sediment infill depositional units tended toward more sheet like geometries heavy minerals reveal that an upward progradational aggradational trend and the development of more sand rich facies are related to a change in provenance toward sand rich cornubian sources

how does micropetrography help us to understand the permeability and poromechanical behaviour of a rock many poromechanical studies of rocks give little regard to the micropetrographic observation of their constituents the aim of this study is to show how such a detailed study can help understand and provide more precision on the poromechanical behaviour of the material the rock studied here is an oolitic limestone micropetrography reveals the nature of the constituents calcite mostly in the form of fine grained micrite their abundance their organization micrite organized in ooids linked by a calcitic cement small sized highly connected isotropic porosity scarce unconnected porosity and the structure of the rock global isotropy small heterogeneities due to sedimentological phenomena no microcracks micropetrography completes the information obtained by poromechanics in that it allows the observation of elements deduced from macroscopical tests the aim of this paper is to show the effect of microporosity on permeability and flow in a rock where microporous grains are in contact with each other

palaeocene oligocene tectonics of nw europe s u m m a r y during the palaeogene in nw europe a gallic subplate was very nearly created this plate was almost entirely bordered by plate boundaries although not of equivalent ages to the n the n atlantic began to open about 56 ma ago the alpine convergent boundary extended southwestwards to the pyrenean subduction zone on the ne side a n british pataeocene early eocene fracture dyke boundary appears to pass southeastwards across the north sea into a lutetian to burdigalian rift system there is an age disparity between the fracturing and nw dyke intrusion in britain and the fracturing and formation of the rhine graben the last dykes in britain ypresian were intruded not long before the important subsidence of the rhine graben earliest lutetian but their causes were different the british dyke fractures propagated southeastwards via the cleveland dyke towards the north sea whereas the rhine graben propagated northwards towards the zuider zee depression however the structures from both sides converged in the sole pit basin in the north sea with the result that a continuous though not coevally originated fracture system developed from nw scotland to the alps during the early tertiary there was a wide range of tectonic activity throughout nw europe fig 1 in nw britain lavas were extruded and plutonic complexes and extensive dyke swarms were intruded in the north sea tufts were deposited as a result of volcanism along the rockall faeroe rift reactivation of faults con trolled magmatism localization of gas fields devolatilization of coal and inversion of basins caused uplift deformation and erosion along the rhine graben doming subsidence and rift propagation took place in association with alka line volcanism and plutonism coevally with the meso alpine compressive deformations that oc curred in the alps faulting controlled sedimen tation patterns during inversion of basins in southern england the english channel northern france and holland old rift faults were reacti vated in the western approaches basin thrust faults formed in the southern bay of biscay contemporaneously with thrusting in the pyre nees and variscan massifs were tilted and uplifted along steep reverse faults the main tectonic activity lasted from about 60 ma to about 30 ma but it was diachronous generally earlier in the nw and later in the se the igneous activity in northern britain was related to the opening of the n atlantic in the late palaeocene but the formation of the rhine graben and the inversion of sedimentary basins in the north sea and near the english channel were caused by major orogenic events in the alpine region in the late eocene to mid oligocene frisch 1981 tectonic phenomena in the north sea provide the link between those in northern britain and those in the rhine graben the aim of this paper is to demonstrate that these movements from the atlantic and alpine sides almost fragmented the lithospheric plates of nw europe during the creation of a gallic sub block an earlier northern boundary from nw scotland to northern germany being transected by a later eastern boundary along the rhine graben

phosphate lu hf geochronology abstract igneous metamorphic and biogenic apatite contains lu and hf in proportions that make this mineral suitable for dating by the 176lu 176hf method we present a new method for separation of lu and hf from apatite that involves a single extraction column step for hf and a second exchange column step for lu this procedure allows rapid sample processing prior to analysis by mc icp ms results from the igneous gardiner skaergaard and khibina intrusions indicate that the closure temperature for the lu hf isotopic system in apatite is relatively high the lu hf isochron age of 60 ma for the skaergaard intrusion east greenland is older than the generally accepted emplacement age but does not appear to be a product of mixing a centimeter sized apatite from the otter lake area grenvillian province yields high and variable 176lu 177hf ratios showing that metamorphic apatite may in some cases allow for mono mineral dating the most important application of the method is undoubtedly its potential use for dating sedimentary formations although we find biogenic apatite in porous matrix highly susceptible to post depositional resetting of the lu hf isotopic system the preservation of a near depositional age for a shark tooth from the impermeable london clay and recent work on crystalline authigenic phosphorites earth planet sci lett 201 2002 203 show the lu hf system to be a promising tool for direct dating of sedimentary formations

a biostratigraphy for the london clay in london biostratigraphy enables specific layers of strata to be given a unique stratigraphic address that can be used to identify the horizons in which in situ tests are conducted and from which samples for testing are collected this is particularly valuable when working in fine grained deposits where stratigraphic position is not easily recognised by lithology alone and permits any data bank of geotechnical values and performance to be used without fear of confusing one stratigraphic layer with another construction in the london clay formation and its supporting research has necessitated an accurate and speedy method for identifying with a precision of centimetres the stratigraphic layer from which geotechnical data have been obtained the principles that enable biostratigraphy to be used for this purpose are explained and illustrated with reference to the london clay formation in london this approach can be used in most sedimentary strata an example of biostratigraphic data used in london is presented

present day kinematics of the plate boundary zone between africa and europe from the azores to the aegean anticlockwise rotation of africa relative to europe around an euler pole in the eastern atlantic causes plate convergence in the central mediterranean towards n20 w at rate considered a priori to be 5 10 mm yr 1 however previous summaries of the present day deformation sense in the central mediterranean are inconsistent with observations in southern italy recent investigations of italy and adjacent parts of north africa enable local deformation sense observed to be reconciled with sense predicted from relative plate motions suggested angular velocity of the african plate relative to europe is 0 07 myr 1 around a pole near 21 n 21 w this predicts 2 6 mm yr 1 maximum extension rate towards n64 e near the azores consistent with the minimum local accretion of new oceanic crust in the past few millions of years and 4 3 mm yr 1 plate convergence towards n20 w in the central mediterranean at 13 e further east the northern margin of the african plate can be regarded as the gargano seismic zone in the central adriatic sea the northern adriatic sea is a microplate rotating anticlockwise relative to europe at 0 3 myr 1 around a pole in northwestern italy causing northeastward shortening in yugoslavia and up to 4 mm yr 1 extension in central and northern italy the african plate is deforming internally in tunisia and northern libya extending obliquely in direction e10 s at rate up to 5 5 mm yr 1 the resultant velocity relative to europe in the ionian and southern adriatic seas 5 mm yr 1 towards n50 e explains the observed relative velocity across southern italy kinematic consistency requires present day shortening rate east of calabria associated with subduction on the tyrrhenian sea benioff zone and tyrrhenian sea extension rate to be both zero or equal to within 1 mm yr 1

importance of gravitational spreading in the tectonic and volcanic evolution of mount etna the interaction between gravity and thermal effects largely determines the structural and magmatic evolution of volcanic constructs at scales spanning several orders of magnitude from small cones to the oceanic crust1 3 although gravitational spreading is a direct consequence of this interaction and a fundamental process in volcano growth it is rarely recognized as such here we describe a striking example of this process at etna volcano in italy the volcano and its clay rich substratum are slowly spreading towards the east and south driven by gravity spreading produces extensional structures in the summit region and contpressional structures at the base of the volcano eastward movement of the volcanic edifice over a stationary magma supply may be the cause of an apparent westward migration of volcanic activity as gravitational spreading seems to control the location and magnitude of shallow seismicity and flank eruptions an appreciation of its effects could become an essential element of future volcanic hazard evaluation our model proposed here for etna may also be relevant to a reinterpretation of the geological history of a number of other volcanoes

3d_fault_offsets a matlab code to automatically measure lateral and vertical fault offsets in topographic data application to san andreas owens valley and hope faults measuring fault offsets preserved at the ground surface is of primary importance to recover earthquake and long term slip distributions and understand fault mechanics the recent explosion of high resolution topographic data such as lidar and photogrammetric digital elevation models offers an unprecedented opportunity to measure dense collections of fault offsets we have developed a new matlab code 3d fault offsets to automate these measurements in topographic data 3d fault offsets mathematically identifies and represents nine of the most prominent geometric characteristics of common sublinear markers along faults especially strike slip in 3 d such as the streambed minimum elevation top free face and base of channel banks or scarps minimum laplacian maximum gradient and maximum laplacian and ridges maximum elevation by calculating best fit lines through the nine point clouds on either side of the fault the code computes the lateral and vertical offsets between the piercing points of these lines onto the fault plane providing nine lateral and nine vertical offset measures per marker through a monte carlo approach the code calculates the total uncertainty on each offset it then provides tools to statistically analyze the dense collection of measures and to reconstruct the prefaulted marker geometry in the horizontal and vertical planes we applied 3d fault offsets to remeasure previously published offsets across 88 markers on the san andreas owens valley and hope faults we obtained 5 454 lateral and vertical offset measures these automatic measures compare well to prior ones field and remote while their rich record provides new insights on the preservation of fault displacements in the morphology

the relationship between late quaternary deformation and volcanism of mt etna eastern sicily new evidence from the sedimentary substratum in the catania region abstract stratigraphical and structural analyses have been carried out on the late quaternary foredeep succession forming the etnean substratum in the catania region eastern sicily in order to investigate in detail the chronology of deformation events that have accompanied a significant period of the eruptive activity of mt etna i e from 240 ka to the present this episode was characterised at about 200 ka by a main change of the petrochemical features of the emitted products from sub alkaline to alkaline this can be related to an evolving mantle diapir located beneath the volcano the new stratigraphical and structural field data presented in this paper constrain the development from 240 to 125 ka of nw se trending dextral faults associated with minor e w to ne sw oriented accommodation thrusts and nnw sse trending normal faults that originated in a dominant transpressive regime strike slip tectonics were active during the earlier emissions of sub alkaline lavas 320 200 ka old and part of the ancient alkaline products 180 100 ka old from scattered eruptive systems which developed in local transtensive zones distributed throughout the whole etnean region a major change in the mode of deformation since 125 ka bp was related to the propagation of a normal fault belt along the ionian coast of the catania region and the eastern sectors of the etnean edifice this process was associated with the growth of open folds that deformed the entire foredeep sequence exposed along the southern boundary of the etnean edifice during this period eruptive activity concentrated along the main extensional features where steady and very efficient feeding systems originated this resulted in a rapid increase in the volume of emitted alkaline products that gave rise to the construction of the modern stratovolcano during the last 80 ka the collected data emphasise some main aspects of the relationship between tectonic deformation at a regional scale and volcanism in the etna area firstly the mode of deformation at the onset of etnean volcanism seems to be inadequate to explain the emplacement at depth of a mantle diapir related to the occurrence of a hotspot almost independent from the local crustal dynamics on the other hand the late quaternary structural assemblages recognised on the surface can be interpreted as direct effects of the europe africa convergence rather than as the products of deformation induced by the emplacement of the mantle diapir in the different stages of etnean evolution a direct relationship exists between the mode of deformation and the distribution as well as the capacity of the feeding systems in particular the amounts of emitted products in the different stages depend on the intensity of crustal stretching associated with deformation rather than the volume of available molten material at depth these conclusions represent a new perspective for the interpretion of the early stages and subsequent evolution of the volcanic activity of mt etna the proposed model also represents an useful tool in deciphering the relationship between the deformation path seismicity and volcanic activity of mt etna

stress dependence of the permeability and porosity of sandstone and shale from tcdp hole a abstract we utilize an integrated permeability and porosity measurement system to measure the stress dependent permeability and porosity of pliocene to pleistocene sedimentary rocks from a 2000 m borehole experiments were conducted by first gradually increasing the confining pressure from 3 to 120 mpa and then subsequently reducing it back to 3 mpa the permeability of the sandstone remained within a narrow range 10 14 10 13 m2 the permeability of the shale was more sensitive to the effective confining pressure varying by two to three orders of magnitude than the sandstone possibly due to the existence of microcracks in the shale meanwhile the sandstone and shale showed a similar sensitivity of porosity to effective pressure whereby porosity was reduced by about 10 20 when the confining pressure was increased from 3 to 120 mpa the experimental results indicate that the fit of the models to the data points can be improved by using a power law instead of an exponential relationship to extrapolate the permeability or porosity under larger confining pressure e g 300 mpa using a straight line in a log log plot might induce unreasonable error but might be adequate to predict the stress dependent permeability or porosity within the experimental stress range part of the permeability and porosity decrease observed during loading is irreversible during unloading

a hydrogeological model for the early diagenesis of late triassic alluvial sediments the late triassic mercia mudstone group of southwest britain a problematic complex arid playa floodplain aeolian deposit contains a variety of mg clays and carbonates recent interpretations have invoked marine waters as a source of mg in clays however both the mg rich clays and other early diagenetic features seen in the late triassic in europe are directly analogous to those found in the inland drainage basins of australia a simple hydrogeological model is offered based on these basins where shallow groundwater evolution takes place within the basin producing a range of early diagenetic products including groundwater dolocretes and mg clays such a model as developed in australia is probably widely applicable to ancient arid alluvial systems the mercia mudstone group is a problematic sequence of predominantly red siltstones and mudstones with minor sand dolomite and limestone intercalations ruffell 1991 it has been extensively studied in outcrops in southwest and southern britain particularly in the bristol channel area the siltstones and mudstones of late triassic age are the distal equivalents to alluvial fan deposits and are associated at least locally with lake margin and spring travertine deposits leslie et al 1992 some workers have favoured a marine influenced setting for the deposition of the mudrocks or playa lakes see review in taylor 1983 most recently they have been interpreted as the deposits of complex floodplain playa systems with a signficant aeolian input talbot et al 1994 extensive evaporites occur locally in the unit including thick halite deposits and have been interpreted as evidence of marine

regional uplift gas hydrate dissociation and the origins of the paleocene eocene thermal maximum much of the north atlantic region experienced hundreds of metres of transient uplift during the latest paleocene regional uplift should cause dissociation of gas hydrates stored in marine sedimentary strata and the subsequent release of carbon to the atmosphere should enhance warming through the greenhouse effect we have developed models of the spatial distribution of uplift to match observational constraints from sedimentary basins fringing the north atlantic in order to provide quantitative estimates of the carbon released upon uplift these models are coupled to a simple parameterisation of carbon storage in sub seafloor gas hydrates results of modelling indicate that large quantities of carbon can be released by uplift with some models generating over 2000 gt of carbon release the possibility that latest paleocene regional uplift occurred over the same time interval as onset of the paleocene eocene thermal maximum petm around 30 kyr cannot be ruled out using current stratigraphical observations or mantle convection models in this case the uplift mechanism alone can account for the magnitude and timing of the carbon isotope excursion associated with the petm alternatively if the duration of latest paleocene uplift was closer to the upper bound of around 1 myr or if other paleocene uplift events were equally significant then gas hydrate dissociation upon uplift could have contributed to longer term changes in ocean temperature and carbon isotope composition through the late paleocene these temperature changes in combination with development of the north atlantic land bridge during the latest paleocene culmination of uplift may be able to force rapid changes in ocean circulation and cause phenomena such as the petm

the role of regional tectonics magma pressure and gravitational spreading in earthquakes of the eastern sector of mt etna volcano italy data concerning m 3 3 earthquakes that occurred in the eastern sector of mt etna volcano sicily italy in the period 1984 1989 are here presented and discussed only events with reliable focal mechanisms and detailed macroseismic investigations have been considered instrumental information come from local seismic networks both permanent and temporary run by the university of catania uct the seismological observatory of acireale soacr the cnrs grenoble france and the institut de physique du globe de paris ipg france observations regarding the macroseismic effects have been collected by means of field recognitions mainly carried out by the authors all available data are analyzed in light of the more recent interpretations on the kinematic behaviour of the shallowest structures of etna with particular reference to its eastern flank which according to borgia et al 1992 is likely affected by a seaward gravitational migration driven by the sliding of this sector of the volcanic apparatus over its clay rich substratum the results obtained support the hypothesis that the shallow seismicity of the eastern flank of mt etna is related to a complex stress field due to the combined effects of a the tectonics associated with the interaction between the african and eurasian plates b the rise of magma into the crust and c the gravitative seaward sliding of the eastern sector of the volcano in particular we hypothesize that 1 tectonic forces caused the end of the 1984 eruption by means of a locking mechanism 2 the increment of magma pressure at depth is periodically responsible for local re orientation of the stress field acting on the volcano which also produces earthquakes of high intensity 3 shallow earthquakes z 5 km showing eastward compression mechanism could be related to the gravitational sliding of unbuttressed sectors of the volcanic body accompanying the emplacement of intrusive dykes

micromechanical modeling of the effective elastic properties of oolitic limestone a new micromechanical approach to analytical modeling of oolitic limestone is proposed limestone is modeled as a multiphase composite consisting of sparry calcite matrix spherical oolitic inhomogeneities oblate spheroidal pores of aspect ratio 0 2 and concave pores in the shape of superspheres the concavity factor is the key parameter affecting overall properties maxwell s homogenization scheme is used to calculate effective bulk and shear moduli of this multiphase composite as functions of total porosities the results are in good agreement with experimental data available in the literature

determination of the main hydraulic and poro elastic properties of a limestone from bourgogne france this study is a part of a large experimental program intended to characterise the effects of increasing temperature upon the hydraulic and poro mechanical behaviour of a limestone from anstrude france methods of measurement as well as experimental devices designed by our laboratory are presented and commented on permeability values measured on six different samples either with gas or ethanol clearly show that the results obtained with the two fluids are virtually identical as soon as the gas measurements are corrected for the klinkenberg effect as the permeability is not very sensitive to confining pressure variation it can be assumed that the intact rock is slightly cracked this is confirmed with microscopic observations as well as poro elastic property measurements concerning the latter various ways of obtaining their values are presented and compared they include drained and undrained bulk modulus biot and skempton coefficients and biot modulus the consistency between these parameters is finally highlighted and demonstrates that the classical theory of poro elasticity hold very well for such a rock which is almost monomineralic with quite a high porosity

surface water freshening and high latitude river discharge in the eocene north sea abstract a shark tooth apatite 18 o record of the early palaeogene north sea reflects changes in regional hydrography by showing variable temperatures and salinities a 2 4 ma period in the early eocene was particularly influenced by substantial surface water freshening indicated by a 3 4 reduction of 18 o values the magnitude of the 18 o decrease indicates a depletion in 18 o of surface waters by 2 3 relative to eocene mean ocean water this value is lower than that of coeval lakes reconstructed from freshwater gastropod 18 o values from the paris basin suggesting that large rivers with high latitude catchment areas drained into the north sea the period of surface water freshening began close to the palaeocene eocene thermal maximum when relative sea level fall tectonic uplift and basaltic volcanism caused a temporary isolation of the north sea north atlantic and north sea surface waters became reconnected during a series of early eocene transgressions

contemporary holocene and quaternary deformation of the asal rift djibouti implications for the mechanics of slow spreading ridges because the frequency and character of rifting events along mid ocean ridges are largely unknown how the repetition of such events gives rise to rift structures is unexplored the asal rift in the afar depression of djibouti africa provides the world s best subaerial analogue for young slow spreading mid ocean ridges seismic geodetic and field observations of a seismovolcanic event in 1978 at asal yield estimates of the fault and dike locations geometry displacement and volume of basalt extruded in a rifting event a 6 9 kyr old lake shore highstand at asal has been warped downward by 70 m providing a holocene measure of the vertical deformation across the rift the rift topography furnishes an older datum which we infer to be 34 6 kyr old using the holocene deformation rate we find that faults throughout the rift valley are active holocene slip rates diminish beyond 4 km from the rift axis late quaternary rates decrease beyond 6 7 km the holocene slip rates are used to estimate repeat times by taking the displacement on the faults which slipped in 1978 as characteristic we find tectonic events on individual faults recur every 200 300 years half the rift faults slipped together in the 1978 event if this is typical then groups of faults are activated every 100 150 years we suggest that half the events take place in the rift axis accompanied by volcanic extrusion the remainder occur peripheral to the neovolcanic zone and involve fault slip only both events having a repeat time of 200 300 years given the 10 km width of the rift and its 16 mm yr 1 spreading rate the mean age of the material in the rift should be 350 kyr an order of magnitude older than the inferred age of the formation of the rift topography the subsidence rate of the rift axis during the past 35 kyr is 8 9 mm yr 1 with the rate of infilling by volcanic extrusion 1 mm yr 1 the resulting net subsidence rate about equal to the half spreading rate of the rift could not be sustained for 300 kyr without significant infilling by lavas thus both observations suggest that the long term vertical deformation in the rift has not been steady state instead we suggest that there is a rifting filling cycle at asal with the most recent filling episode ending 35 kyr

quaternary normal faulting in southeastern sicily italy a seismic source for the 1693 large earthquake summary we present geological and morphological data combined with an analysis of seismic reflection lines across the ionian ovshore zone and information on historical earthquakes in order to yield new constraints on active faulting in southeastern sicily this region one of the most seismically active of the mediterranean is avected by wnw ese regional extension producing normal faulting of the southern edge of the siculo calabrian rift zone our data describe two systems of quaternary normal faults characterized by diverent ages and related to distinct tectonic processes the older nw se trending normal fault segments developed up to 400 kyr ago and striking perpendicular to the main front of the maghrebian thrust belt bound the small basins occurring along the eastern coast of the hyblean plateau the younger fault system is represented by prominent nnw sse trending normal fault segments and extends along the ionian ovshore zone following the ne sw trending avola and rosolini ispica normal faults these faults are characterized by vertical slip rates of 0 7 3 3 mm yr 1 and might be associated with the large seismic events of january 1693 we suggest that the main shock of the january 1693 earthquakes m 7 could be related to a 45 km long normal fault with a right lateral component of motion a long term net slip rate of about 3 7 mm yr 1 is calculated and a recurrence interval of about 550 50 yr is proposed for large events similar to that of january 1693

problems in chronostratigraphy stages series unit and boundary stratotypes global stratotype section and point and tarnished golden spikes abstract stratigraphy is a magnificent subject magnificent in its breadth and scope magnificent in its importance to so many lines of human endeavor it is essentially that branch of geology which deals with the arrangement the distribution and the chronological succession of rock strata and other associated rock bodies with respect to any or all of the various characters properties and attributes which rocks may possess hedberg 1958 p 1881 chronostratigraphy the temporal ordering of geologic strata is at the heart of earth history in reviewing chronostratigraphic theory from d orbigny to hedberg we see that concepts and practices have evolved under pressure of constant improvements in time control and data quality such stimuli are naturally felt more strongly in the youngest part of the stratigraphic record where dating is most precise and the biostratigraphic data are most abundant and well preserved it is not surprising therefore to find that chronostratigraphy is conceptually more advanced in the cenozoic erathem than in the mesozoic and paleozoic erathems where biostratigraphy and chronostratigraphy are widely confused evidently out of necessity taking the five inter series boundaries in the cenozoic erathem as case histories we review their current status in relation to the lower boundary of the lowest standard stage above the boundary in light of the hierarchical principle recommended in the international stratigraphic guide hedberg 1976 salvador 1994 in each instance what should be a simple nested relationship turns out to be complex and difficult and in the cases of the proposed global stratotype section and point gssps for the eocene oligocene series boundary and the paleocene eocene series boundary there are discrepancies so large with regard to the base of the rupelian and ypresian standard stages respectively that some essential relaxation of the hierarchic rule seems to be required if the historic value of these long known stages is not to be violated since stage boundaries should not be defined a posteriori to fit series boundaries we propose here to reconsider the role of the standard stage as the obligate elemental subdivision in a rigidly hierarchical chronostratigraphic scale and suggest that series and subseries should be formalized and their boundaries defined by gssps we do not suggest that stages be abandoned on the contrary we propose to integrate them in a two step hierarchical chronostratigraphic framework so as to use them in complementary fashion with series and subseries however the boundary concept is more appropriate for stage than the gssp we recognize the need for precise and globally valid chronostratigraphic correlations based on gssps in attempts to understand the earth system while at the same time we emphasize the need for conceptual continuity with regard to the central place that the stage has played in chronostratigraphy over several decades

seismic moment summation for historical earthquakes in italy tectonic implications tectonic deformation rates in and around the apennine mountains of italy are studied using seismic moments estimated from macroseismic effects of historical earthquakes northeastward extension in the northern apennines north of 42 5 n accompanies shortening along their northeast flank since the seventeenth century the sparse seismicity in these two zones has included no earthquake with magnitude 6 5 or seismic moment above 6 1018 n m their spatially averaged deformation rates are only 0 3 mm yr 1 but are equal such that the extension and shortening balance with no relative motion between their external surroundings in contrast the numerous historical earthquakes in the central and southern apennines with magnitude 7 and seismic moment 20 1018 n m require northeastward relative velocity across the deforming zone up to 5 mm yr 1 matching the expected relative motion of their surroundings this relative velocity is taken up in part by extension and in part by strike slip depending on the trend of the deforming zone and is not accompanied by en echelon shortening elsewhere in italy the northern apennines thus show different senses and rates of deformation from localities farther south and are thus technically distinct at present in contrast with previous interpretations

new dating of rapid vertical deformation of santa tecla fault scarps mt etna volcano sicily by lichenometry method abstract the eastern slope of mt etna is characterised by shallow seismicity originating from normal oblique faulting timpe fault system related to wnw ese regional extension recent research has demonstrated that in the fault population of mt etna s eastern flank the minimum earthquake magnitude that will have a ground rupture effect is ca 2 5 this system is characterised by high frequency seismic activity due to thinned seismogenic crustal layer this characteristic together with the high density of the fault segments does not always for identification of the segments responsible for the earthquake the earthquakes affecting the medium lower eastern flank have been historically reconstructed by macroseismic analysis and reported in a macroseismic database and in recent decades by instrumental seismic registration which provide the seismological parameters capable of evaluating focal mechanism hypocentre and relative algorithms related to geometric parameters which control the growth of fault segments in this paper we present a methodology to evaluate the age of the rapid exhumation of the free face fault plane of the nnw sse oriented normal fault segment named s tecla timpe fault system it consists of the measurement of the thalli species lichenometry method in order to evaluate the parameters which characterise their growth the seismic history of the s tecla fault indicates eight certain events from 1865 to 2005 with 3 4 4 7 magnitude de guidi et al 2012 and reference therein we found evidence of two different recent rapid vertical deformation events at the base of the s tecla fault escarpment the oldest 20 m long and 0 25 m in height and the youngest with a 0 02 m high nude surface exposed we have observed that there are thalli of xanthoparmelia conspersa ehrh ex ach hale colonizing part of the nude surface on the escarpment the results highlight that the oldest thalli was dated at 43 7 years old showing that rapid vertical deformation generated the surface where the thalli after 4 years took root the displacement of this surface could be related to the seismic events occurring on 3rd august 1973 3 8 m in s m ammalati area probably accompanied by intense post seismic deformation the second and last event could be attributable to a 3 1 m seismic event occurring on 25th september 2014 iside 2016

the development and seismic expression of synsedimentary features within the chalk of southern england seismic reflection data acquired onshore to the north of bournemouth southern england image clearly a series of prominent concave up troughs or depressions and concave down mounded structures within the white chalk subgroup the chalk lithostratigraphy in the area of study is established from borehole geophysical log correlations these correlations then provide calibration of the seismic reflection data indicating that the structures are concentrated at levels between the lewes nodular chalk formation and tarrant chalk member and towards the base of the portsdown chalk formation onlap downlap and truncation of reflectors are observed with the most dramatic features forming a stacked series directly overlying faulting of jurassic strata similar stratal geometries have been described from comparable levels in the chalk of the north sea and in outcrop in britain and france to many they represent channels formed by submarine erosion and redeposition of the chalk during relative sea level falls linked to tectonics we also interpret a number of apparently incisive structures and slumped infill sequences described here as being of primary syndepositional origin the slumping and the close association of these features with underlying faults and proximity to nearby major crustal faults may be indicative of submarine erosion of the chalk caused by sea level changes linked to syndepositional fault movements however evidence of toplap downlap pairs is also suggestive of more aggradational mounding or laterally migrating surfaces or facies belts the presence of any such structures implies rapid lateral variations in the chalk that would have implications not only for aquifer management and future storage schemes but also during the processing of seismic reflection data and general studies and correlations of the chalk across southern britain

warming and environmental changes in the eastern north sea basin during the palaeocene eocene thermal maximum as revealed by biomarker lipids analysis of sediments deposited at different latitudes around the world during the palaeocene eocene thermal maximum petm 56 ma have revealed a globally profound warming phase regionally varying from 5 8 c such records from europe have not yet been obtained we studied the variations in sea surface and continental mean annual air temperatures sst and mat respectively and the distribution patterns and stable carbon isotopes of higher plant derived n alkanes in two proximal petm sections fur and store baelt denmark from the epicontinental north sea basin a negative carbon isotope excursion cie of 4 7 was recorded in land plant derived n alkanes similar to what has been observed for other petm sections however differences observed between the two proximal sites suggest that local factors such as regional vegetation and precipitation patterns also influenced the cie the presence of s bound isorenieratene derivatives at the onset of the petm and increased organic carbon contents points to a rapid shift in depositional environment from well oxygenated to anoxic and sulfidic these euxinic conditions are comparable with those during the petm in the arctic ocean ssts inferred from tex86 show relatively low temperatures followed by an increase of 7 c across the petm at the fur section a remarkably similar temperature record was obtained for mat using the mbt cbt proxy however the mat record of the store baelt section did not reveal this warming

permeability and permeability anisotropy in crab orchard sandstone experimental insights into spatio temporal effects abstract permeability in tight crustal rocks is primarily controlled by the connected porosity shape and orientation of microcracks the preferred orientation of cross bedding and sedimentary features such as layering this leads to a significant permeability anisotropy less well studied however are the effects of time and stress recovery on the evolution of the permeability hysteresis which is becoming increasingly important in areas ranging from fluid migration in ore forming processes to enhanced resource extraction here we report new data simulating spatio temporal permeability changes induced using effective pressure simulating burial depth on a tight sandstone crab orchard we find an initially measured at 5 mpa anisotropy of 2 5 in p wave velocity and 180 in permeability anisotropy is significantly affected by the direction of the effective pressure change and cyclicity anisotropy values decrease to 1 and 10 respectively after 3 cycles to 90 mpa and back furthermore we measure a steadily increasing recovery time 10 20 min for flow parallel to cross bedding and a far slower recovery time 20 50 min for flow normal to cross bedding these data are interpreted via strain anisotropy and accommodation models similar to the seasoning process often used in dynamic reservoir extraction

crustal motion along the eurasia nubia plate boundary in the calabrian arc and sicily and active extension in the messina straits from gps measurements 1 we investigate crustal deformation along the eurasia nubia plate boundary in calabria and sicily revealed by the gps velocity field obtained by the combination of continuous site velocities with previous results from episodic campaigns we recognize two distinct crustal domains characterized by different motions and styles of deformation convergence in sicily is taken up by crustal shortening along the former tyrrhenian back arc passive margin in agreement with seismological data and geological evidence of recent cessation of deformation along the plio pleistocene subduction front the analysis of the gps data and the consistency between earthquake slip vectors and convergence direction suggest that eu nu convergence in sicily does not require intermediate crustal blocks significant eurasia 3 mm yr to nne and nubia fixed 5 mm yr to ese residual velocities in calabria suggest instead the presence of an intermediate crustal block which can be interpreted as a forearc sliver or as an independent ionian block according to the first hypothesis subduction is still active in the ionian wedge although we find no evidence for active back arc spreading in the tyrrhenian sea the n115 e oriented sicily calabria gps relative motion is consistent with the extension observed during the 1908 mw 7 1 messina earthquake we suggest that up to 3 mm yr 80 of this estimated relative motion between sicily and the calabrian arc may be taken up in the messina straits

middle paleocene uplift of the brabant massif from central belgium up to the southeast coast of england during the middle paleocene laramide phase several basins in europe experienced subsidence while others experienced uplift previous studies have shown that during the laramide phase some basins surrounding the brabant massif experienced subsidence into shallow depocentres this study discusses how the brabant massif simultaneously experienced uplift along its wnw ese caledonian structural axis from central belgium in the east up to the southeast coast of england ipswich in the west uplift resulted in erosion of the formerly deposited chalk group on top of the axis of the brabant massif the erosion products of the chalk group were reworked in the latest danian to earliest thanetian deposits that filled the surrounding depocentres early to middle thanetian pulsed marine transgressions caused flooding and deposition across the entire region including the previously uplifted axis of the brabant massif the depositional thicknesses however indicate that the axis of the brabant massif remained a relative high up to the middle thanetian both the geometry and timing of the middle paleocene vertical surface movements of the brabant massif and surrounding areas are very similar to those described for other structural entities in central and northern europe despite their often strongly differing mesozoic tectonic evolutions we discuss several mechanisms that might have triggered these vertical surface movements of which lithospheric folding seems the most likely

a hot spot model for early tertiary volcanism in the n atlantic s u m m a r y the initial stages of rifting of the n atlantic were accompanied by massive extrusion of volcanic rocks and the accretion to the lower crust of even greater volumes of igneous rock emplacement of the bulk of the igneous rocks along the 2000 km long continental rift occurred in as little as 2 3 my the pattern and timing of magmatic activity can be explained by partial melting of anomalously hot asthenosphere as it welled up to fill the space left by the stretched and thinned continental lithosphere asthenosphere temperatures were elevated regionally by 100 150 over a 2000 km diameter region by the mushroom shaped head of hot material fed by a mantle plume which at present is centred beneath iceland

laboratory measurements of a complete set of poroelastic moduli for berea sandstone and indiana limestone measurements have been completed for eight different poroelastic moduli of water saturated berea sandstone and indiana limestone as a function of confining pressure and pore pressure the poroelastic moduli for indiana limestone are generally consistent to 10 which was verified by a formal inversion procedure for independent moduli from the eight measurements for indiana limestone best fit values were drained bulk modulus 21 2 gpa the undrained bulk modulus 31 7 gpa drained poisson s ratio 0 26 undrained poisson s ratio 0 33 and pore pressure buildup coefficient 0 47 at 20 35 mpa effective stress the poroelastic moduli for berea sandstone are generally consistent to 20 the greater inconsistency is most likely caused by the nonlinear variation of the moduli at different strains for berea sandstone best fit values were drained bulk modulus 6 6 gpa undrained bulk modulus 15 8 gpa drained poisson s ratio 0 17 undrained poisson s ratio 0 34 and pore pressure buildup coefficient 0 75 at 10 mpa effective stress

control of rock rheology on deformation style and slip rate along the active pernicana fault mt etna italy abstract the already known part of the active left lateral strike slip pernicana fault on the eastern flank of mt etna volcano has a holocene high slip rate of 1 5 2 7 cm yr but its surface trace abruptly disappears eastward approaching the lower slope of the volcano using geological geomorphological and structural surveys we found that the pernicana deformation zone extends 8 km further to the east beyond this point through a different mechanism as the thickness of the volcanic pile decreases the single e w to ese striking main fault plane gives way to a set of faults arranged in a splay structure which partitions the fault motion here slip rates are 0 4 to 1 4 cm yr on each fault further east where the lava succession is very thin and unfaulted we suggest that lavas are decoupled from plastic deforming sub etnean clay deposits which absorb the strain or that lavas have a too low mass to slide on the very lowest slope of the volcano i e further east lavas are once again thicker and the pernicana deformation zone behaves at the surface once again in a brittle manner locally known as the fiumefreddo fault with a low slip rate of

the morphostructural setting of mount etna sedimentary basement italy implications for the geometry and volume of the volcano and its flank instability abstract the reinterpretation of more than 2500 subsurface data consisting of geoelectric and borehole prospecting undertaken at mount etna allows reconstructing the contour map of the sedimentary basement this reconstruction highlights a complex asymmetric topography due to the inhomogeneous long term updoming of the region and the interrelationship between the development of the drainage network and flank instability these different processes have produced a major morphological difference between the eastern sector characterised by a 17 km wide horseshoe shaped depression and the other flanks formed by palaeovalleys the origin of the wide horseshoe shaped depression can be attributed to the large scale flank instability processes involving the entire continental margin in the etna offshore this depression of the etna basement was generated by a series of coalescent landslides before the beginning of the eruptive activity of the timpe phase more than 220 ka ago this wide depression is the main cause of the flank instability that produced the gravitational slope failures of the valle del bove about 10 ka ago regarding mt etna s geometry we have estimated a total volume of about 532 km 3 that was emplaced during the past 330 ka resulting in an average rate of volcanic output of 0 0016 km 3 a the reconstruction of the temporal variation of the average eruptive rate highlights a drastic increase of volcanism during the last 100 ka in response to the gradual stabilization of the plumbing system in the etna region that led to the build up of the composite stratovolcano structure the data presented in this paper represent the state of knowledge of the sedimentary basement of etna which can be used for future studies aimed at developing a detailed understanding of the deep structure of the volcano s unstable flanks

recent and active tectonics in the calabrian arc southern italy normal faulting which has developed since the middle pleistocene with an overall ese wnw extension is the dominant mode of deformation which has characterized the calabrian arc up to the present quaternary normal faults extend for a total length of about 180 km along the inner side of the arc the different normal fault segments which during the pleistocene controlled the evolution of the main marine sedimentary basins are varying in length from 10 to 20 km and have fault escarpments showing a very young morphology which define the fronts of the major mountain ranges of the arc the morphological features of the fault escarpments suggest slip rates of 0 8 1 1 mm yr for the last 700 k y and values of 0 6 0 9 mm yr for the last 120 k y indicating a uniform rate of faulting since the middle pleistocene crustal seismicity and the mesoseismic areas of historical large events 6 5 m 7 1 which occurred in the calabrian arc are located within a narrow belt along the hanging walls of the quaternary normal fault segments this suggests that the normal faults which dissect the inner side of the calabrian arc may be seismically active

influences of provenance and diagenesis on detrital garnet suites in the paleocene forties sandstone central north sea abstract the geochemistry of detrital garnets in the upper paleocene forties formation has been studied by electron microprobe techniques in this sand body variations in garnet geochemistry can be related to provenance and diagenetic factors two separate sand fans can be mapped using the technique the dominant forties montrose fan being supplied from the metamorphic terrain of the northern highlands of scotland and the subsidiary gannet fan supplied from the mainly granitic terrain of the grampian highlands intrastratal solution caused by high temperature pore fluids circulating at depth has removed some of the garnets from the assemblages garnets with the highest calcium contents are the least stable and are dissolved at comparatively shallow depths the dependence of garnet stability on calcium content in deep burial must be taken into account when assessing provenance by this technique but nevertheless garnet is far less sensitive to diagenetic and hydraulic controls than is the total heavy mineral suite

oblique rifting in salina lipari and vulcano islands aeolian islands southern italy a structural analysis carried out on the volcanic products of the islands of salina lipari and vulcano aeolian archipelago points out that the large scale tectonic setting is dominated by nw se trending right lateral extensional strike slip faults and by n s to ne sw trending normal faults and fractures this fault pattern generates pull apart type structures developing between different right hand overlapping fault segments and a characteristic extensional imbricate fan geometry at the tip of the major strike slip faults all the structures representing the surface expression of an active crustal discontinuity which controls the evolutionary history of the magmatism of the three islands are kinematically compatible with a n100 e extension related to a rifting process affecting southern italy

the feeding of the eruptive activity of etna volcano the regional stress field as a constraint to magma uprising and eruption an analysis of the structural lineaments as observed on the middle and upper slopes of etna volcano was made with the aim of checking stress distribution within the volcanic structure

magnetic and calcareous nannofossil stratigraphy of the lower palaeogene formations of the hampshire and london basins a magnetostratigraphic study of the lower palaeogene formations exposed in the hampshire and london basins southern uk has led to the identification of eight stratigraphically distinct normal polarity magnetozones within an otherwise reverse polarity sedimentary sequence which spans the late palaeocene to middle eocene a complementary study of the calcareous nannofossil biostratigraphy of these sections and related sections elsewhere in nw europe allows a correlation of this succession of normal polarity magnetozones with the biostratigraphically calibrated geomagnetic polarity timescale based on marine magnetic anomalies it is concluded that the normal polarity chrons corresponding to anomalies 20 21 and 23 are recorded within the huntingbridge earnley and wittering divisions of the bracklesham group respectively that anomalies 24a and 24b are represented within divisions d to b2 of the london clay and anomaly 26 is represented in the lower part of the thanet beds an additional normal polarity magnetozone within the oldhaven beds is believed to represent a short normal polarity event between anomalies 24b and 25 anomalies 22 and 25 appear not to be represented in the uk lower palaeogene succession because of major unconformities at the early middle eocene boundary within the wittering division of the bracklesham group and within the late palaeocene respectively the former appears to correlate with a widespread erosional event in the oceans identified from seismic records vail et al 1979 and interpreted as reflecting a major eustatic sea level fall

geomorphology and seismotectonic elements in the giarre area sicily a morphostructural analysis has been performed on the eastern flank of mt etna located between the towns of st alfio and linera and the ionian sea the research has been carried out through analysis of aerial photographs and has allowed recognition of morphoneotectonic elements such as some scarps with rectilinear trend laterally becoming morphological flexures according to the lithology anomalies in the hydrographic network such as rectilinear tracts of drainage valleys with simple or double bends hanging valleys and truncated valleys narrow deeply engraved valleys with meanders and fluvial captures all these elements are caused by a fault system oriented nnw sse with a mainly vertical component seismic events with very shallow foci have been recorded in the study area these earthquakes triggered several small landslides on the fault scarps and large series of coseismic and coaxial fractures it is possible to show that the morphostructures examined have been reactivated during many of the seismic events that have occurred in the area the combination of these elements verifies that the morphostructures have a real neotectonic cause which is associated with uplifts which have occurred in the area at different times

age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr