a late cretaceous turonian ichthyofauna from lac des bois northwest territories canada with paleobiogeographic comparisons with turonian ichthyofaunas of the western interior seaway a fish fauna from a turonian sequence of the great bear basin at lac des bois is described the fauna includes examples of ichthyodectes cf osmeroides a euteleost and several aulopiforrn fishes such as enchodus cimolichthys and a juvenile that cannot be further identified the fauna of lac des bois most closely resembles other arctic fish assemblages of the western interior seaway based on a upgma unweighted pair group method with arithmetic averages cluster analysis of various north american turonian localities there are also slight differences between eastern and western localities along the seaway the north south differences of the ichthyofauna can be explained by current patterns distributing the fishes in the seaway or transgressive events during the turonian the east west differences may be due to changes in water depth from east to west

the mid cretaceous earth paleogeography ocean circulation and temperature atmospheric circulation a reconstruction of the global paleogeography of the mid cretaceous 100 m y ago including adjustment of continental outlines to account for microplate movements cmstal shortening and accretion in mid cretaceous and later orogenic regions is described and a map presented on the modified continents coastlines and significant mountain ranges are added this paleogeography is used as a framework for a reconstruction of ocean surface circulation and temperature distribution then the main features of the atmospheric circulation are deduced using the paleogeography and ocean temperatures as boundary conditions relative to the present these features are a much weaker westerly wind belt and greater seasonality of wind patterns leading to more extreme surface climates over the continents slightly equatorward positions of the subtropical anticyclones and monsoonal regimes over the continental margins bordering tethys and the central atlantic a comparison of the results with climatic evidence from t

the magnetic stratification of layered mafic intrusions natural examples and numerical models abstract mafic ultramafic intrusions commonly display a prominent petrographic and geochemical layering attributed to differentiation in a magma chamber this layering occurs at scales from several hundreds of meters in some large intrusions down to scales of a few millimeters layering forming processes are numerous and include both internal processes such as crystal settling double diffusive convection flow segregation and compaction and external processes such as magma recharge extraction or mixing mafic magma chambers may operate as a closed system or as an open system several recent investigations have been conducted on borehole cores through the insizwa sill south africa the great dyke zimbabwe and the bushveld complex south africa we present an overview of magnetic results on these intrusions the magnetic properties of mafic rocks are dominated by the presence of magnetite in most layers pyrrhotite the only ferrimagnetic sulfide is generally restricted to sulfide rich reefs merensky j m bohmke or to massive sulfide deposits at the base of the intrusion all intrusions display distinct variations of their magnetic properties anisotropy of magnetic susceptibility magnetic remanence magnetic saturation high field magnetic susceptibility across the layering the significance of these magnetic zones varies depending on the nature of variations from zone to zone for example a drop in magnetic susceptibility does not necessarily correspond to a new magma batch unless it is also associated with a change in magnetic anisotropy parameters in the studied cases all open systems the magnetic susceptibility and the total iron content estimated from high field measurements increase towards the top of these intrusions suggesting a general pattern of iron enrichment a numerical petrologic model for a tholeiitic magma predicts magnetic susceptibility variations across a statically differentiated closed system intrusion no convection the effects of sequential magma recharge and discrete magma extraction are investigated from the magnetic properties point of view conversely these models can be used to interpret the magnetic stratification pattern in natural examples and test for its possible causes

an offshore geophysical survey of the freetown igneous complex sierra leone abstract gravity magnetic and bathymetric surveys have been carried out to determine the offshore extent of the basic igneous intrusion exposed on the freetown peninsula sierra leone although the westward continuation of the complex is not expressed bathymetrically positive free air anomalies show that it is an elongated feature some 150 km in length with a nw se trend gravity modelling indicates that the intrusion has a maximum width of about 50 km and reaches depths exceeding 17 km southwest of freetown where free air values exceeding 150 mgal have been observed the thickness of the body decreases towards the north as the top dips under the sediments of the outer continental shelf to the west of the complex a wnw ese gravity low on the outer shelf reflects a basement depression which is filled with almost 6 km of sediments large magnetic anomalies with a total range of more than 1000 nt are recorded over the freetown intrusion the dominant feature of the magnetic field is an area of negative anomalies within the complex flanked by positive anomalies west of freetown two dimensional magnetic models show that the main part of the complex is normally magnetised but large positive magnetic anomalies also indicate the presence of reversely magnetised zones within the intrusion the linearity and trend of the complex are consistent with an igneous origin which is closely related to atlantic rifting and early movements along the guinee fracture zone

a geomorphological investigation of the formation and evolution of the kaiafas sand dune field kyparissiakos gulf ionian sea eastern mediterranean in the late holocene the present investigation concerns the formation and evolution of the dune field of the central part of the kyparissiakos gulf western coast of peloponnesos greece this dune field is associated with the kaiafas lagoon and consists of four dune lines that lie at distances of 600 200 100 and 70 m from the coastline the dune field has developed on top of a barrier beach that formed subsequently to the completion of the last phase of rapid sea level rise i e after 6 000 bp consisting mostly of medium sand with good sorting due to its aeolian formation assuming a steady wind regime and adequate sediment availability during the late holocene a period of approximately 1 350 years has been estimated to be the minimum time required for the formation of the dune field this formation period may also include intervals when the development processes were more or less intensive on the basis of radio carbon dating secondary fluctuations of air temperature and published information it is proposed that the 4th oldest dune line started forming between the years 400 ad and 1 000 ad whilst the 1st youngest dune line started forming after 1 520 ad the dune field especially its youngest line seems to be in equilibrium with its adjacent beach zone and the nearshore hydrodynamics being beyond the reach of wave run up on the other hand the dune field over the past decades has been subjected to intense human intervention agriculture construction forest fires etc that has locally destroyed and or destabilised part of the dunes finally the expected sea level rise due to global warming is undoubtedly a threat to the existence of the dune field

shear heating in continental strike slip shear zones model and field examples summary a two layer crust and upper mantle finite diverence steady state thermomechanical model of a long lived several million years lithospheric strike slip fault is presented and its predictions compared with field observations from various major fault zones in order to estimate the maximum amount of shear heating all mechanical energy is assumed to be dissipated in heat in ductile as well as in brittle layers deformation follows a friction law in the brittle layer s and a power flow law in the ductile one s variations of several independent parameters and their influence on the thermomechanical state of the fault zone and on shear heating are systematically explored shear heating is found to be more important in fault zones avecting an initially cold lithosphere and increases with slip rate friction coeycient and stivness of materials in extreme cases slip rate of 10 cm yr 1 stiv lithosphere shear heating could lead to temperature increases close to 590 c at the moho and 475 c at 20 km depth for more common cases shear heating leads to smaller temperature increases but can still explain high grade metamorphic conditions encountered in strike slip shear zones however modelled temperature conditions often fall short of those observed this could be due to heat transport by mechanisms more eycient than conduction common syntectonic emplacement of granitic melts in ductile strike slip shear zones can be explained by lower crust partial melting induced by shear heating in the upper mantle besides slip rate the possibility of such melting depends mostly on the upper mantle rheology and on the fertility of the lower crust for hard upper mantle and highly fertile lower crust partial melting could occur at rates of 1 cm yr 1 while in most cases it would result from the breakdown of micas for slip rates over 3 cm yr 1 as a result of shear heating partial melting of the upper mantle could occur in the presence of small amounts of fluids rise of magmas and or hot fluids in the shear zone will further enhance the temperature increase in shallower parts of the fault zone in nature shear heating would inevitably cause strain localization in the deeper parts of strike slip faults as is often observed in the field for crustal shear zones

intracontinental movements in western gondwanaland a palaeomagnetic test abstract early cretaceous intracontinental movements within africa and or south america to account for misfit problem in the pre drift reconstruction of western gondwana have been tested using palaeomagnetic poles from both continents each continent has been considered as comprising separate subplates according to the boundaries proposed by pindell and dewey 1982 and curie 1983 i e northern africa naf southern africa saf northern south america nsa and southern south america ssa visual and statistical distribution of late permian to jurassic poles from the african subplates indicate two distinct groups before rotating saf relative to naf while after the rotation they become indistinguishable the distribution and sparsity of data from south america limit the study in this continent as the data are statistically indistinguishable before and after rotation of ssa with respect to nsa when the test is extended to the reconstruction of western gondwana the tightest grouping of the poles occurs when an intracontinental movement is assumed within africa this suggests that the misfit between the two continents is probably due to intracontinental deformation within africa and not in south america if confirmed this may have profound implications in the kinematics of the processes related to the opening of the south and central atlantic oceans and also the origin of the west african rift system

numerical simulations of tidal and wind driven circulation in the cretaceous interior seaway of north america twenty two numerical experiments using a multi layer numerical model of turbulent flow in shallow seas better define fluid circulation and sediment transport paths in the cretaceous interior seaway of north america each experiment consists of a different combination of paleogeography paleobathymetry coriolis acceleration boundary tidal amplitudes wind stresses and bed friction the paleogeographies and paleobathymetries represent three seaway configurations a seaway of intermediate size and depth 200 m during a transgressive peak t5 in late albian time a seaway of maximum size and depth 400 m during peak transgression t6 in early turonian time and a seaway of minimum size and depth 100 m during a peak regression r8 in the campanian values for the other key model parameters are m 2 co oscillating boundary tides of 0 1 to 0 2 m range at the arctic ocean boundary and 0 5 to 1 m range at the proto gulf of mexico boundary coriolis accelerations corresponding to 30 n 45 n and 60 n latitude chezy friction factors ranging from 31 to 70 m s 1 and average winter winds and two winter storms computed by the community climate model at the national center for atmospheric research for paleogeographic conditions during the late albian results of the numerical experiments and comparison of these results with geologic observations allow the following conclusions 1 circulation in the seaway was generally storm dominated 2 typical winter storms crossing the seaway from west to east generated 0 3 m s 1 shore parallel geostrophic currents on the shelves north of arizona at first flowing weakly to the north but later during the storm flowing strongly to the south 3 extreme storms could have produced 0 8 m s 1 currents over the shelves and 0 3 m s 1 currents in 200 m of water 4 co oscillating tides propagated into the seaway as progressive kelvin waves and therefore tidal ranges in the seaway were mesotidal to macrofdal along the southeastern margin but microtidal everywhere else 5 significant deep water wave heights and periods of the fully developed wave field are predicted to have been 5 to 6 m high and 10 s respectively the northwestern shore of the seaway would have experienced these storm waves approaching from the north and thus net sediment drift should have been to the south limited available field data support these conclusions

the drift history of adria and africa from 280 ma to present jurassic true polar wander and zonal climate control on tethyan sedimentary facies article i nfo the orogenic belts surrounding the undeformed adriatic sea represent the margins of an area known as adria the african promontory we have undertaken a critical appraisal of paleomagnetic data from regions of adria considered parautochthonous relative to africa obtained either from biostratigraphically dated sed imentary rocks corrected for inclination shallowing or from igneous rocks that are regarded as free from any inclination shallowing bias paleomagnetic directions were used to calculate paleomagnetic poles for compar ison with coeval and inclination flattening free paleomagnetic poles from stable africa visual coherence of paleopoles for several time slices from the early permian to the eocene supports the construction of a com posite apparent polar wander path apwp valid for parautochthonous adria and stable africa this compos ite apwp is compared to previous apwps finding good agreement with the global apwp of kent and irving 2010 both apwps show a remarkable and rapid polar shift of 40 in the jurassic that other apwps tend to underestimate we interpret this shift to represent a major episode of true polar wander tpw from 183 ma in the early jurassic to 151 ma in the late jurassic using a simple zonal climate model the drift motion of adria attached to africa appears to be consistent with the distribution of permian cretaceous sed imentary facies on adria

the sedimentary and geomorphological imprint of the ad 365 tsunami on the coasts of southwestern crete greece examples from sougia and palaiochora abstract the southwestern coast of crete one of the most seismically active regions in europe experienced co seismic crust uplift by 9 m during the ms 8 3 mega earthquake that struck the eastern mediterranean world on 21 july ad 365 an associated tsunami event caused thousands of fatalities and destroyed many coastal settlements and infrastructure between the levante in the east and the adriatic sea in the northwest so far coastal sedimentary archives in southwestern crete including distinct palaeotsunami fingerprints are rarely investigated therefore a multi proxy study including sedimentological geochemical geochronological and microfaunal methods was conducted in order to detect onshore coastal sedimentary archives that functioned as fine sediment traps and document palaeotsunami imprint we found adequate archives at the sougia and palaiochora coastal plains that were used to reconstruct the palaeogeographical evolution and the palaeoseismological history of sw crete during the late holocene our studies revealed distinct geomorphological sedimentological geochemical and microfaunal traces of high energy impact from the marine side related to seismic events at the sougia coastal plain a sheet of fine sand with a neat microfossil and geochemical fingerprint was found sandwiched between underlying pre tsunami muds and overlying post tsunami colluvial silt in the palaiochora coastal plain tsunami overflow of a flat neogene bedrock platform led to the accumulation of sand dominated deposits that were subsequently covered by colluvial material from the adjacent hillslopes based on radiocarbon and luminescence dating approaches it is shown that the ad 365 tsunami event is the best fit candidate for the tsunami related sediments deposited at both sougia and palaiochora this study for the first time presents multi proxy evidence of the ad 365 tsunami imprint on fine sedimentary archives along the western and southwestern coast of crete

ichthyornis aves from the early turonian late cretaceous of alberta an isolated left humerus from the cretaceous toothed bird ichthyornis is described the fossil comes from the vimy member of the kaskapau formation at watino alberta and is early turonian in age the watino specimen is the oldest well authenticated record of ichthyornis and the oldest cretaceous skeletal fossil of a bird from the western hemisphere the wide geographic distribution of ichthyornis within the western interior of north america is in keeping with nomadic habits as inferred from strongly flying modern marine birds

open system magma chamber process in the freetown complex of sierra leone evidence from zone 3 the 7 km thick freetown layered complex of sierra leone consists of four zones each composed of a cyclically layered sequence of troctolite gabbro olivine gabbro gabbronorite and anorthosite the complex is thought by previous workers to have solidified in situ from a single parental magma without stratigraphic changes in mineral compositions evidence for cryptic variation is presented based on electron microprobe analyses of mega unit zone 3 two reversals in olivine forsterite content plagioclase anorthite content and 100 mg mg fe 2 in clinopyroxene match the variations of ni in olivine and cr in clinopyroxene these changes are consistent with a magma chamber that was open to periodic influxes of new magmas and the mixing of new and fractionated resident magmas expansion of the magma chamber is thought to have occurred at 2000 m corresponding to the level of a major influx

tidal notches in mediterranean sea a comprehensive analysis abstract recent works evelpidou et al 2012 suggest that the modern tidal notch is disappearing worldwide due sea level rise over the last century in order to assess this hypothesis we measured modern tidal notches in several of sites along the mediterranean coasts we report observations on tidal notches cut along carbonate coasts from 73 sites from italy france croatia montenegro greece malta and spain plus additional observations carried outside the mediterranean at each site we measured notch width and depth and we described the characteristics of the biological rim at the base of the notch we correlated these parameters with wave energy tide gauge datasets and rock lithology our results suggest that considering the development of tidal notches the consequence of midlittoral bioerosion as done in evelpidou et al 2012 is a simplification that can lead to misleading results such as stating that notches are disappearing important roles in notch formation can be also played by wave action rate of karst dissolution salt weathering and wetting and drying cycles of course notch formation can be augmented and favoured also by bioerosion which can in particular cases be the main process of notch formation and development our dataset shows that notches are carved by an ensemble rather than by a single process both today and in the past and that it is difficult if not impossible to disentangle them and establish which one is prevailing we therefore show that tidal notches are still forming challenging the hypothesis that sea level rise has drowned them

a new late triassic liasic palaeomagnetic pole from superimposed and juxtaposed magnetizations in the saharan craton summary palaeomagnetic measurements in the late triassic liasic zarzaytine formations of the la recul6e area showed the existence of superimposed and juxtaposed magnetizations the separation of the juxtaposed magnetizations yielded late triassic liasic magnetization directions of normal and reversed polarities the new corresponding palaeomagnetic pole agrees well with a pangea a configuration it confirms from autunian to lias a latitudinal displacement of stable africa towards the north with important anti clockwise rotation contrary to laurussia which did not undergo significant rotation this transition of pangea from a2 to a ended before the late triassic it corresponds to dextral movements in the hercynoappalachian collision area and perhaps to part of the northwards drift of microcontinents of gondwanian origin located north of the arabian promontory

weathering of pge sulfides and pt fe alloys in the freetown layered complex sierra leone fresh and weathered rocks and saprolite from horizon b of the freetown layered complex contain platinum group minerals pgm the pgm in the fresh rocks are 1 7 m across including cooperite pts isoferroplatinum pt3fe minor tetraferroplatinum ptfe tulameenite pt2fecu os bearing laurite rus2 and other base metal sulfide bms bearing pgm the weathered rocks contain fewer of those pgm but a high proportion of disordered cu pd bearing pt fe alloys the saprolite hosts scarce smaller 1 3 m ordered ptfe and disordered ptfe3 the pt fe alloys became increasingly fe rich as weathering proceeded pt fe oxides appeared during weathering copper sulfides associated with the primary pgm and cooperite with 3 pd were destroyed to provide the minor cu and pd found in some of the disordered pt fe alloys platinum and pd bearing saprolites have retained the original rock fabric and to a depth of about 2 m surround residual rocks that show progressive weathering corestones ground water passing through the saprolite has transported pt and pd and probably au in solution down slope into saprolite over unmineralized rocks transport is marked by changes in the pt pd ratio indicating that the metals have moved independently palladium is present in marginally higher concentrations in the deeper saprolite than in the corestones suggesting some retention of pd in the deeper saprolite platinum and pd are less concentrated in the upper saprolite than the deeper saprolite indicating surface leaching alteration occurred over a long period in an organic and microbial rich environment that may have contributed to the leaching and transport of pge

mesozoic alpine facies deposition as a result of past latitudinal plate motion the fragmentation of pangaea as a consequence of the opening of the atlantic ocean is documented in the alpine mediterranean region by the onset of widespread pelagic sedimentation1 shallow water sediments were replaced by mainly pelagic limestones in the early jurassic period radiolarian cherts in the middle late jurassic period and again pelagic limestones in the late jurassic cretaceous period1 during initial extension basin subsidence below the carbonate compensation depth ccd is thought to have triggered the transition from early jurassic limestones to middle late jurassic radiolarites1 it has been proposed that the transition from radiolarites to limestones in the late jurassic period was due to an increase in calcareous nannoplankton abundance when the ccd was depressed below the ocean floor1 but in modern oceans sediments below the ccd are not necessarily radiolaritic here we present palaeomagnetic samples from the jurassic cretaceous pelagic succession exposed in the lombardian basin italy on the basis of an analysis of our palaeolatitudinal data in a broader palaeogeographic context we propose an alternative explanation for the above facies tripartition we suggest that the lombardian basin drifted initially towards and subsequently away from a near equatorial upwelling zone of high biosiliceous productivity our tectonic model for the genesis of radiolarites adds an essential horizontal plate motion component to explanations involving only vertical variations of ccd relative to the ocean floor it may explain the deposition of radiolarites throughout the mediterranean and middle eastern region during the jurassic period

linear and planar structure in ordered multivariate data as applied to progressive demagnetization of palaeomagnetic remanence summary consider a sequence of say 10 to 20 vector observations in threedimensional space it is suspected that a few subsets of consecutive observations are made up of collinear points the purpose of this paper is to construct a statistically based algorithm to find such linear segments and to assess their accuracy a similar assessment is made for coplanar sets of points this algorithm is applied here to palaeomagnetic data and is claimed to be superior to previous methods of palaeomagnetic analysis in terms of completeness and balance of analysis treatment of measurement errors and other sources of scatter criteria for identification of linear and planar sets of points and statistical rigour stability spectra with statistically based confidence limits are obtained as a by product 1 palaeomagnetic analysis background to the geometrical problem the natural remanent magnetization nrm in rocks is known in general to have originated in one or more relatively short time intervals during their formation and subsequent history i e during rock forming or metamorphic events during which nrm is frozen in stabilized by falling temperature grain growth etc the nrm acquired during each such event is a single vector magnetization parallel to the then prevailing geomagnetic field and is called a component of nrm rocks which have suffered more than one event of this kind are therefore liable to carry multi component nrm in the laboratory these components can be identified by demagnetizing the rock step by step usually by thermal alternating field or chemical demagnetization which involves the analysis of the distribution of blocking rzmperature coercivity and chemical leaching respectively resistance to these treatments is called stability of remanence and the range of treatment over which a particular component is removed is called the stability range of the component the various discrete

exsolved magnetite inclusions in silicates features determining their remanence behavior submicroscopic needle shaped titanomagnetite inclusions exsolved in silicate minerals commonly occur in mafic intrusive rocks and are protected from alteration by their silicate hosts making them excellent candidates for paleomagnetic studies a suite of samples containing clinopyroxene and plagioclase hosted magnetite inclusions from five geologically diverse sites was examined using magnetic force microscopy to image the inclusions magnetic domain state alternating field demagnetization experiments indicate that some inclusions are more stable recorders than others the two factors controlling the remanence behavior of the inclusions are internal microstructures and inclusion dimensions magnetite ulvospinel unmixing within an inclusion subdivides the original titanomagnetite solid solution into a boxwork structure composed of 103 105 magnetite prisms separated by thin ulvospinel lamellae the conversion of multidomain sized needles into assemblages of interacting single domains increases the coercivity and hence relaxation time of the inclusions and results in a thermochemical magnetic remanence in samples without this exsolution microstructure the inclusions diameters determine coercivity and their magnetization is thermoremanent both styles of high coercivity inclusions successfully record paleomagnetic directions in mesozoic rocks and their ubiquity within silicate minerals clinopyroxene and plagioclase of mafic intrusive rocks indicates their value as chemically and magnetically stable tools for elucidating the ancient magnetic field marine magnetic anomalies and crustal kinematics

sensitivity of wave model predictions to wind fields in the western mediterranean sea abstract the paper compares the wave hindcast in the western mediterranean sea using the reanalysis wind fields from hipocas and era 40 from ecmwf for november 2001 the study has concentrated on the mediterranean coast of spain where there are known difficulties with the wind and wave modelling two winter storms have been compared the main differences between the significant wave heights using the era 40 reanalysis ecmwf and hipocas reanalysis winds were observed to increase when moving southwards in the geographical domain at the offshore locations systematic negative biases of hs were obtained with the era 40 data at all the coastal locations analyzed whereas positive biases are typical for the hipocas reanalysis for offshore and coastal locations when using the era 40 data the hs biases increased moving to south while this pattern was not so clear for the hipocas data the inconsistencies in the comparisons of modelled waves against measurements seem to be associated with the quality of the wind fields

the role of true polar wander on the jurassic palaeoclimate from the late carboniferous until the middle jurassic continents were assembled in a quasi rigid supercontinent called pangea the first palaeomagnetic data of south america indicated that the continent remained stationary in similar present day latitudes during most of the mesozoic and even the palaeozoic however new palaeomagnetic data suggest that such a scenario is not likely at least for the jurassic in order to test the stationary versus the dynamic continent model we studied the jurassic apparent polar wander paths of the major continents that is eurasia africa and north america that all in all show the same shape and chronology of the tracks with respect to those from south america we thus present a master path that could be useful for the jurassic pangea one of the most remarkable features observed in the path is the change in pole positions at 197 ma early jurassic which denotes the cessation of the counter clockwise rotation of pangea and commencement of a clockwise rotation that brought about changes in palaeolatitude and orientation until the end of the early jurassic 185 ma here we analyse a number of phenomena that could have triggered the polar shift between 197 and 185 ma and conclude that true polar wander is the most likely in order to do this we used morgan s tectonophysics 94 123 139 1983 grid of hotspots and performed absolute palaeogeographical reconstructions of pangea for the late triassic and jurassic the palaeolatitudes changes that we observe from our palaeomagnetic data are very well sustained by diverse palaeoclimatic proxies derived from geological and palaeoecological data at this time of both the southern and northern hemispheres

an improved methodology for thellier type paleointensity determination in igneous rocks and its usefulness for verifying primary thermoremanence we propose a new methodology for thellier type paleointensity experiments in standard paleointensity experiments the blocking temperatures of most stable remanences are often not reached before thermal alteration of magnetic mineralogy begins and subsequent data have to be discarded we emphasize that when alteration begins at low temperature and continues throughout the experiment which then fails in standard analyses the resulting unblocking temperature tub spectrum of the alteration product does not necessarily overlap with the whole tub spectrum of natural remanent magnetization nrm because tub depends on physical characteristics of the new grains not the temperatures at which they were formed nrm may survive in an uncontaminated higher tub window if alteration remanence only has low tub then partial thermoremanent magnetization ptrm checks at temperature step tj 1 can be used to correct for alteration that has occurred at tj and furthermore thermal demagnetization of a full trm acquired in the laboratory at the end of the progressive thellier thellier experiment should reveal the true uncontaminated tub spectrum of the nrm in higher temperature intervals we propose a new experimental sequence which allows monitoring and correction of alteration and provides two semi independent estimates of palaeointensity in the circumstances described above we illustrate the issues involved through new experimental work on igneous rocks from a paleozoic charnockitic syenite where we unravel trm from multidomain isothermal remanence despite massive alteration during laboratory heating finally we point out the value of these experiments for verifying primary trm in igneous rocks indicating properties that distinguish trm from other remanence

magnetostratigraphy nannofossil stratigraphy and apparent polar wander for adria africa in the jurassic cretaceous boundary interval article i nfo existing correlations of early cretaceous nannofossil events to polarity zones in italian pelagic limestones are the basis for correlation of polarity chrons to geologic stages and hence calibration of the early cretaceous geomagnetic polarity timescale here we present correlations of nannofossil events to polarity chrons for the late jurassic and jurassic cretaceous boundary interval from the southern alps making the case for revisions of current geologic timescales in this interval the jurassic cretaceous and kimmeridgian tithonian boundaries can be usefully defined at the onsets of polarity chrons cm18r and cm22r respectively the oxfordian kimmeridgian boundary can be assigned to cm25 an apparent polar wander path apwp for the southern alps derived from and time calibrated by bio magnetostratigraphic data is similar to and provides a proxy for the african apwp in the absence of adequate african data of this age the southern alpine apwp is characterized by a cusp hairpin at 30 n 270 e at a time close to the oxfordian kimmeridgian boundary polarity chron cm25 154 ma rapid apwp from high latitude n60 n in the preceding middle jurassic bajocian oxfordian interval coincident with the onset of central atlantic ligurian oceanic rifting and a return to high latitudes during the cretaceous early jurassic poles at high latitudes n60 n are evident for sinemurian to toarcian aalenian time 175 195 ma an apwp for this time interval with this level of temporal calibration cannot be constructed using data from africa itself or from other atlantic bordering continents by rotation to african coordinates

late cretaceous antarctic fish diversity new material from the santa marta formation late coniacian early maastrichtian of james ross island contributes significantly to the current knowledge of late cretaceous antarctic fish diversity the taxon list for the santa marta formation is extended and new records of neoselachians and teleosts are reported the stratigraphic ranges of some previously known taxa are enlarged and the palaeobiogeography and palaeoecology of late cretaceous antarctic fishes are discussed top predators that occupied the higher levels in the food chain along with marine tetrapods dominate the marine faunas from the santa marta and lopez de bertodano formations the only fish adapted to crushing hard shelled invertebrates were the chimeroids rays an important component of marine fish associations as well as fish from lower trophic levels remain unknown from the late cretaceous of antarctica

a new 200 ma paleomagnetic pole for africa and paleo secular variation scatter from central atlantic magmatic province camp intrusives in morocco ighrem and foum zguid dykes available apparent polar wander apw paths for the 200 ma configuration of pangea just prior to the opening of the central atlantic ocean differ as much as 10o in arc length here we add new data from northwest africa for this time obtained from the northeasttrending foum zguid and ighrem dykes ca 200 ma these dykes form part of the northern domain of the central atlantic magmatic province camp and crosscut the anti atlas ranges in morocco and compositionally correspond to quartz normative tholeiites intruded in continental lithosphere shortly before the opening of the central atlantic ocean the foum zguid dyke has been intensively studied whereas the ighrem dyke has received less scientific focus we sampled both dykes for paleomagnetic investigation along 100 km of each dyke 12 sites for foum zguid and 11 for ighrem 188 samples included in the final analyses rock magnetic experiments indicate a mixture of multidomain and single domain magnetite and or low ti titanomagnetite particles as the principal remanence carriers in both dykes the primary nature of the characteristic remanent magnetization is supported by positive contact tests related to fe metasomatism or baked overprints of the corresponding sedimentary country rocks the directions of the characteristic magnetization exhibit exclusively normal polarity site mean virtual geomagnetic poles are differently grouped in each dyke suggesting distinct geomagnetic secular variation records the foum zguid paleomagnetic pole n 12 plat 67 9 n plon 247 9 e 125 a95 3 9 plots close to that of ighrem n 11 plat 78 4 n plon 238 2 e 47 a95 6 7 confirming those mineralogical and geochemical evidences supporting that they represent dissimilar magmatic stages virtual geomagnetic poles dispersion from both dykes s 10 5 13 0 8 1 is in line with those obtained from recent studies of a camp related dyke in iberia and results from camp lavas in the argana basin these three new estimates of paleosecular variation at low latitudes around the triassic jurassic boundary are concordant with a recently proposed dispersion curve for the jurassic but suggest a slightly lower geomagnetic scatter than considered so far after combining results from both dykes the resulting paleomagnetic pole plat 73 0 n plon 244 7 e n 23 55 a95 4 1 is statistically compared with existing and coeval african paleopoles and with global synthetic 200 ma running mean poles in northwest africa coordinates

distribution anisotropy the cause of ams in igneous rocks understanding of ams in pristine basic igneous rocks in terms of flow orientation of ellipsoidal magnetite grains is thwarted by the fact that these grains 1 typically are irregularly equant or skeletal rather than distinctly ellipsoidal and 2 usually crystallize interstitially and late after magma flow has ceased however the distribution of such grains will be relatively anisotropic if they grew in residual liquid volumes within a preferredly oriented by flow silicate template this constraint may impose a slight preferred shape orientation to the irregular magnetite grains during their growth but in addition we suggest it is the anisotropic magnetic interaction between the grains which is the basic cause of ams experiments involving the casting of magnetite epoxy mixtures in various foliated or lineated glass templates have yielded samples with the expected ams symmetry i e k3 perpendicular to glass plates or k1 parallel to glass rods slicing of near isotropic synthetic blank and natural rock cores and interleaving with glass slides showed a progressive increase in anisotropy of the blank from 0 4 to 2 and the natural rock from 0 9 to 2 9 in both the k3 axis migrates to be perpendicular to the glass slides

paleobiogeography of the cretaceous western interior seaway of north america the vertebrate evidence abstract distribution patterns of marine vertebrates of the cretaceous western interior seaway of north america are analysed in a biogeographical context the analysis is based on fossil vertebrate assemblages from the following lower campanian localities 1 anderson river fauna n w t 2 pembina fauna southern manitoba 3 sharon springs fauna south dakota wyoming 4 niobrara fauna kansas 5 mooreville fauna alabama due to the cosmopolitan nature of many marine vertebrates relative abundance is used in preference to presence absence data in identifying faunal distribution patterns the analysis demonstrates the presence of two faunal subprovinces in the seaway the northern interior subprovince is characterized by a low diversity in all groups and is dominated by plesiosaurs hesperornithiforms and the mosasaur platecarpus the southern interior subprovince is characterized by a high diversity in all groups and is dominated by sharks turtles and the mosasaur clidastes these biogeographical subdivisions support the hypothesis of warm temperature and cool temperate zones in the seaway that have been proposed on the basis of invertebrate faunas

shallow water application of the third generation wam wave model we present the results of detailed tests of the third generation wam wave model the tests are carried out under well known conditions and they are chosen so as to check different aspects of the model the test area is the adriatic sea east of italy which is very shallow in its northern part as expected from the basic physical approach of wam to the problem the results show the model s capability of responding equally well to different meteorological situations some discrepancies present at short nondimensional fetch and in shallow water are addressed with different formulations for breaking and bottom friction

a middle cenomanian euselachian assemblage from the dunvegan formation of northwestern alberta a euselachian assemblage was recovered from the middle cenomanian dunvegan formation situated in northwestern alberta this assemblage is the most northern described within the western interior seaway and provides an important insight into the euselachian faunal diversity of this little known region of the seaway despite its high paleolatitude the assemblage contains a number of elasmobranch taxa including hybodus squalicorax archaeolamna cretodus dallasiella and cretoxyrhina the dunvegan assemblage also contains the first known reports from canada of the odontaspid shark johnlongia parvidens the cretoxyrhinid shark protolamna carteri and the ray pseudohypolophus mcnultyi this assemblage extends the northern geographical range of all taxa preliminary comparisons with other middle cenomanian western interior seaway assemblages show that the core composition of the dunvegan assemblage is remarkably similar to that of other time equivalent assemblages however conspicuously absent are species t

late cretaceous campanian actinopterygian fishes from the kristianstad basin of southern sweden although a diverse range of aquatic vertebrates are documented from the upper cretaceous mid campanian marine strata of the kristianstad basin in southern sweden only chondrichthyans and marine amniotes have been described in detail to date in contrast coeval actinopterygians are virtually unreported yet their remains are extremely abundant at most sampled localities a comprehensive assessment of these fossils has identified the first late cretaceous actinopterygian fauna from the fennoscandian shield incorporating indeterminate lepisosteids the durophagous pycnodontid anomoeodus subclavatus the predatory pachycormid protosphyraena sp a large ichthyodectid pachyrhizodontids resembling pachyrhizodus the enchodontid enchodus cf gladiolus and indeterminate small teleosts these taxa are diagnosed mainly from isolated teeth and scales implying substantial taphonomic loss prior to burial moreover the prolific recovery of actinopterygian skeletal remnants in recent excavations suggests that historical collecting biases rather than ecological paucity have contributed to their under representation in the swedish cretaceous record palaeobiogeographically the kristianstad basin actinopterygians show compositional resemblance to assemblages from the northern european platform and the western interior seaway of north america advocating distributional communication across the boreal proto atlantic ocean

palaeomagnetism and magnetic fabric in the freetown complex sierra leone summary about six separately orientated cores were collected at each of 14 sites distributed throughout the arcuate west dipping 6 km thick freetown layered igneous complex alternating field and thermal demagnetization both isolate a stable component of remanent magnetism which corresponds to a palaeomagnetic south pole from 13 sites nine reverse four normal polarity at 82 9 s 32 7 e a 95 5 6 this is indistinguishable from that reported in 1971 based on alternating field demagnetization of cores from 10 orientated hand samples the diverence between the freetown pole age 193 3 ma and other mid jurassic poles from west africa could be due to its greater age the diverence between the whole west african jurassic pole group and the karoo pole from southern africa however suggests moderate 10 d i verential rotation of west africa relative to the kaapvaal craton a prevalent magnetic foliation fabric coincides generally with the petrological layering as might be expected but a ubiquitous magnetic lineation is predominantly down dip this is compatible with a down dip pyroxene lineation reported to be present in some field outcrops and interpreted in terms of late stage deformation during the slow crystallization and cooling of the large igneous body however a fold test shows that the igneous layering had already achieved its present attitude before the complex cooled to 570 c the maximum blocking temperature of the characteristic remanence

effects of internal mineral structures on the magnetic remanence of silicate hosted titanomagnetite inclusions an electron holography study 1 titanomagnetite inclusions in pyroxene and plagioclase are carriers of stable magnetic remanence in some slowly cooled rocks such as gabbros anorthosites granulites and diorites needle shaped inclusions with average dimensions of 1 1 25 m form epitaxially by exsolution from their host silicate close examination of clinopyroxene hosted inclusions reveals an internal microstructure which consists of magnetite fe3o4 prisms and ulvospinel fe2tio4 lamellae that formed as a result of phase unmixing during initial cooling this internal structure exerts a profound influence on the magnetic remanence properties of each inclusion primarily by transforming it from a multidomain grain into an assemblage of magnetostatically interacting single domain prisms here we use off axis electron holography to image the magnetization states of individual prisms and the magnetostatic interactions between them we show that the inclusions exhibit both single domain and collective magnetic states that depend primarily on the shape anisotropies of individual magnetite prisms magnetostatic interactions between closely spaced prism stacks and the shape anisotropy of the needle itself prisms that are separated by thick ulvospinel lamellae show uniformly magnetized and or vortex states in contrast closely spaced magnetite prisms behave as multipart vortices or as long composite columns whose strong net magnetization may not be related directly to the orientation and shape of either the needle or the constituent prisms the overall remanence direction recorded by clinopyroxene crystals containing finely exsolved inclusions is a reflection of both the inclusions elongation directions and the prism arrangements within them

a new late cretaceous turonian basal euteleostean fish from lac des bois of the northwest territories of canada a new genus and species of late cretaceous euteleost avitosmerus canadensis is described from an assemblage of fossil fishes found in a late cretaceous turonian unnamed member unit e of the great bear basin from lac des bois northwest territories canada it is a small fusiform fish characterized by a long slender supraorbital the presence of a small suprapreopercle branches of the preopercular sensory canal that reach the edge of the preopercle and an anterior supraneural that is twice as large as those posterior to it additionally elements of its caudal fin show a high degree of fusion avitosmerus is one of ten described cretaceous basal euteleosts that are found worldwide avitosmerus barcarenichthys erichalcis gaudryella gharbouria humbertia kermichthys manchurichthys paravinciguerria and stompooria avitosmerus and erichalcis are the only two basal euteleosts that have been described from the cretaceous of north america placement of avitosmerus into the euteleostei is based on

paleomagnetism of the lesotho basalt southern africa paleomagnetic study of four sections from middle jurassic karoo lava located in lesotho and south africa yielded a new paleomagnetic pole for africa with coordinates 71 6 n 273 5 e a95 3 7 k 33 n 47 paleosecular variation estimated as the angular standard deviation of vgps distribution is 14 1 2 4 1 8 which is considerably lower than expected for this time interval and latitudinal band preliminary paleointensity results indicate a low field intensity during the acquisition of the magnetization this new result tends to support a possible correlation between secular variation and dipole intensity when the lower to middle jurassic paleomagnetic data set for africa is considered a difference of 13 9 8 7 of arc is found to exist between the mean northwest and south african poles furthermore while the northwest african pole is in very good agreement with the lower to middle jurassic north american pole whichever set of rotation parameters is used to close the north atlantic ocean the south african pole falls some 12 15 of arc apart as intraplate deformation models developed to achieve tighter fit of west gondwana prior to the opening of the south atlantic fail to account fully for the difference between northwest and south african poles the pre cretaceous apparent polar wander path for africa has to be considered with caution

fossil marine actinopterygian fishes from the kaskapau formation upper cretaceous turonian near watino alberta turonian fossil marine fishes occur at several localities near watino alberta in sandstones and in shale concretions of the vimy member kaskapau formation the actinopterygian fossils in the san

geochemistry and mineralogy of the freetown layered basic igneous complex of sierra leone abstract the northern part of the freetown tholeiitic layered complex is mapped this lowermost exposed part of the intrusion is divided into units characterized by an olivine rich and or an ilmenite magnetite rich basal layer grading upward through hypersthene and or augite rich zone to a plagioclase rich top whole rock analyses were made for major oxides and for sr cu ni ba zn zr rb and pb from 29 samples collected from base to top of seven units one sample of an ilmenite magnetite layer was also analyzed the analyses showed a consistent depletion in ni and zn and enrichment in sr upward in each layered unit the abundances of trace elements which are concentrated in the cumulate minerals as shown by close correlation of ni and mgo sr and al 2 o 3 reflect modal variations related to stratigraphic height mineralogical investigations failed to indicate a consistent cryptic variation the compositional variations olivine fo 71 63 hypersthene en 70 65 augite ca 36 37 mo 47 45 1bfe 17 18 and plagioclase an 63 54 are narrow and irregular in height in the sequence an explanation for the apparent lack of fe enrichment in the mafic minerals may be sought in the mode of occurrence of fe 1bti oxide minerals it is believed that magnetite and ilmenite crystallized from an early stage as a result of high oxygen fugacity and water content of the magma withdrawal of fe 1bti minerals from the residual liquid by sinking led to lack of enrichment in fe in successive liquid fractions the investigation reveals that the layered units are replicas produced by pulses from one parent magma replenishment from the reservoir of magma would lead to a narrow and irregular trend in the composition of various mineral series that accumulated in the intrusion

hindcast gis and susceptibility modelling to assist oil spill clean up and mitigation on the southern coast of cyprus eastern mediterranean this study uses new oil spill models bathymetric meteorological oceanographic geomorphological and geological data to assess the impact of distinct oil spill scenarios on the southern coast of cyprus eastern mediterranean this approach results from the urgent need to predict oil spill dispersion after new oil terminals and depots were built at vasilikos southern coast of cyprus the terminals have been able to receive tankers with 500 000 deadweight tonnes from november 2014 the new geomorphological and geological data in this work show the shoreline of cyprus to be of high susceptibility due to a the presence of a narrow continental shelf capable of trapping large quantities of hydrocarbons b the existence of uplifted wave cut platforms coastal lagoons and pools forming natural traps for oil and c the presence of important tourist and natura 2000 sites under particular weather and oceanographic conditions oil spills offshore larnaca bay will quickly spread and reach the shoreline 46 h after the initial accident significantly the models in this paper show a reduction from 84 to 19 in the volume of oil trapped on the coast if dispersants are applied with the latter 19 being potentially kept at bay using booms and mechanical removal techniques based on these results we suggest the early use of dispersants booms and mechanical removal procedures to prevent the spreading of oil spilt in the broad area of larnaca bay

global cretaceous paleogeography international geologic correlation program project 191 abstract five global cretaceous paleogeographic maps within a plate tectonic framework are illustrated based on the ten contributions in this special volume

wind wave cast in the mediterranean sea an advanced third generation wave model has been repeatedly applied to the mediterranean sea we have studied the accuracy of the results and the factors that control it the grid resolution when less than 0 5 is shown to have in general negligible effect in the open sea the related accuracy of description of the coastal border can have a relevant effect on the wave field on the side and on the wake of the coastal details for a distance of a few grid points the difficulty of correctly evaluating the wind in the mediterranean basin is dramatically shown by comparing the results obtained using wind fields with different resolution the crucial role of the orography in shaping the wind fields and the need for higher resolution models is established it is found that owing to the strong dependence of wave height on wind speed for resolution coarser than 70 km the loss of accuracy of the wind fields even if meteorologically acceptable makes them useless for an efficient evaluation of the wave conditions the exception explained by the local absence of relevant mountain ridges is the case of a southerly wind in the eastern mediterranean the accuracy of wave forecasting is obtained by comparing analysis and forecast fields for a very severe storm in connection with the preferential west to east flow of most of the mediterranean storms and with the scarcity of information on the atlantic ocean the equality of the meteorological forecast rapidly deteriorates beyond 1 or 2 days of forecast this leads to an even faster deterioration of the wave forecast whose practical limits in the western mediterranean can at present be established at 1 day

plagioclase hosted fe ti oxide micro inclusions in an oceanic gabbro plagiogranite association from the mid atlantic ridge at 13 34 n

insights into the geotectonic evolution of the southern rhodope as inferred from a combined ams microtextural and paleomagnetic study of the tertiary symvolon and vrondou plutons abstract the present study focuses on the tertiary granitoids of the rhodope massif northern greece namely the early miocene symvolon pluton and the composite miocene oligocene vrondou pluton in this paper we provide new anisotropy of magnetic susceptibility ams data from symvolon pluton discussed along with previously published ones from vrondou as well as new paleomagnetic data from samples widely distributed over both studied regions combined with macroscopic observations and microtextural examinations the magnetic fabric study pointed out anisotropic bodies with strong preferred orientations of the magnetic grains however the paleomagnetic vectors corrected for anisotropy effect remain unchanged two groups of magnetic lineations were identified a prevailing ne sw trending linear fabric visible mainly in the early miocene plutons and a second nw se trending fabric clearly imprinted in the mid oligocene eastern part of the vrondou pluton macro and microtextural study revealed the presence of magmatic textures mainly in eastern vrondou and sub solidus plastic deformation textures in symvolon and western vrondou paleomagnetic results displayed a complex pattern with prevailing clockwise rotations reinforcing the existing pattern for n greece and supporting the capacity of granitic bodies to reliably record the earth s magnetic field independently of their anisotropy