ordovician emplacement of the mount dingley diatreme western ranges of the rocky mountains southeastern british columbia external and internal morphologies are well shown by a newly discovered diatreme that is exceptionally well exposed in a cirque within the north face of mount dingley the diatreme contains abundan

arenigian early ordovician sea level history and the response of conodont communities western newfoundland four cluster analyses were performed which recognized 17 conodont communities in the arenigian lower ordovician of western newfoundland the analyses include 69 598 identifiable conodont specimens recovered from 153 conodont bearing samples from four stratigraphical sections representing the environmental settings of the platform upper proximal slope lower proximal slope and distal slope the distribution of conodont communities along the platform to slope environmental gradient shows that sea level changes simultaneously affected the development and replacement of the conodont communities in the different facies the pattern of change in conodont communities allows an interpretation of sea level change that is correlated precisely into the detailed graptolite biozonation a gradual transgression lasted most of tetragraptus approximatus zone time which was followed by a brief regression a transgression regression cycle occurred in the t akzharensis zone time a major transgression caused a highst

late oligocene miocene syn late orogenic successions in western and central mediterranean chains from the betic cordillera to the southern apennines the identification of syn and late orogenic flysch deposits extending from the betic cordillera to the southern apennines assists in the reconstruction of the tectonic sedimentary evolution of the perimediterranean chains a microplate was located between the european and african plates during the late jurassic early cretaceous bordered northwards by the piemontese ocean and southwards by another north africa flysch basin or maghrebian ocean the piemontese ocean and the northern margin of the microplate were structured from the late cretaceous to the eocene to create an eo alpine chain the southern margin of the microplate was deformed in the aquitanian when the internal areas of the maghrebian ocean were characterized by syn orogenic flysch deposits this episode culminated with metamorphism 25 22 ma and nappe emplacement which destroyed the former palaeogeography and created an orogenic belt alkapeca afterwards a lower burdigalian late orogenic cycle started in the deformed area which as a result of the opening of the algero provencal basin caused the fragmentation of the alkapeca its thrusting on the flysch basin and the collision with the north africa and south iberia margins these latter were folded and thrusted the flysch units pushed over the external domain and also back thrusted langhian late orogenic deposits suture the new tectonic features finally the whole orogen was thrust onto the foredeep during the middle late miocene

conodont color and textural alteration an index to regional metamorphism contact metamorphism and hydrothermal alteration experimental and field data are used to extend the utility of conodonts as semi quantitative thermal indices into the regimes of regional and contact metamorphism as well as hydrothermal alteration an arrhenius plot of data from induced conodont color alteration by pyrolysis in air at 1 atm was used to generate the geologic temperatures for conodont color alteration indices cai above 300 c that is for cai values of 5 through 8 such cai values occur in very low to medium grade regionally metamorphosed contact metamorphosed and hydrothermally altered rocks the uniformity or variability of cai values within a sample together with conodont texture can help to distinguish grades and environments of metamorphism particularly in metacarbonate sequences induced cai by pyrolysis in a water methane mixture at kbar results in retardation of cai and in a disparate mixture of both low and high cai values within each experimental sample in this system color alteration processes above a cai of 2 to 3 seem to change from predominantly carbonization to predominantly loss of organic matter presumably by oxidation and volatilization of oxides these experiments approximate the type of cai mixture characteristically found in conodonts recovered from hydrothermally altered rocks these data indicate that cai values of 6 to 8 cannot be used to assess precise temperatures of hydrothermally altered rocks but may serve as useful indicators of potential mineralization

conodonts as biostratigraphic tools for redefinition and correlation of the cambrian ordovician boundary the cambrian ordovician boundary is recognized at different horizons on various continents by utilizing several fossil groups conodonts are abundant diverse and less provincial and facies controlled than other fossils in this interval many species are widespread and some are cosmopolitan strata representing the cambrian ordovician boundary interval from asia australia and north america can be correlated easily when those strata are from cratonal or shelf environments strata from slope facies have fewer conodonts fewer taxa and taxa may have different ranges compared with cratonal and shelf facies it may be easier to correlate intercontinentally within cratonal shelf facies than to correlate intracontinentally from cratonal shelf facies to slope facies a new hierarchical arrangement of conodont interval zones and subzones is proposed for western north america these include the proconodontus tenuiserratus zone the p posterocostatus zone new the p muelleri zone new the eoconodontus zone new with eoconodontus notchpeakensis and cambrooistodus minutus subzones the cordylodus proavus zone emended with hirsutodontus hirsutus fryxellodontus inornatus and clavohamulus elongatus subzones the cordylodus intermedius zone new with hirsutodontus simplex and clavohamulus hintzei subzones the cordylodus lindstromi zone new and cordylodus angulatus zone new the boundary point for the base of the ordovician system will be chosen so as to coincide with a correlatable conodont zonal boundary other fossil groups will support correlation of this boundary point three alternative horizons are being considered the base of the cordylodus proavus zone is the most distinctive but is regarded by some as older than is appropriate for the base of the ordovician the base of the cordylodus intermedius zone is recognizable by faunal changes in several evolutionary lineages at a level that is slightly younger than the presently recognized boundary in australia north america and parts of asia but slightly older than the base of the tremadoc series of europe the base of the c lindstromi zone can be recognized in most areas by the lowest occurrence of the nominate species which is of questioned taxonomic validity and uncertain biostratigraphic utility this horizon is closest to the base of the tremadoc series of europe choice of a stratotype section has been narrowed to the cow head group in newfoundland eastern canada and to the fengshan and yehli formations in jilin province northeastern china the cow head group was deposited on and near the base of the continental slope erosion by debrisslide breccias resulted in a significant hiatus near the boundary interval in the broom point sections a condition contrary to guidelines for choice of boundary sections this may be less of a problem in other sections such as green point the dayangcha section in china was deposited on the outer part of a continental shelf and has acritarchs conodonts graptolites and trilobites additional study of the china section is needed to document fully the ranges of critical conodont taxa

the numidian sequence between guelma and constantine eastern tell algeria the numidian sequence represents one of the main tectono stratigraphic units involved in the geological evolution of the maghrebian orogen during the upper oligocene lower miocene geo structural aqalysis led to the reconstruction of tectonc stratigraphic units and recognition of two main tectonic phases eocene and lower miocene sedimentological analysis of the studied sections has resulted in the distinction of arenaceous and conglomeratic facies generated by debris flows or high density turbidity currents on a submarine slope present within the pelitic arenaceous and arenaceous pelitic sequences which also contain slumped units in places previous and new micropalaeontological data indicate late oligocene early burdigalian ages for the numidian sequences of the constantine mountains on the basis of petrographic study the numidian rocks can be classified as poorly sorted quartzarenites containing siliciclastic matrix the overall petrographic data indicate that the continental intercalaire hoggar tassili and fezzan and series pharusienne hoggar and eglab are possible supply areas for the numidian quartz

segmented african lithosphere beneath the anatolian region inferred from teleseismic p wave tomography summary lithospheric deformation throughout anatolia a part of the alpine himalayan orogenic belt is controlled mainly by collision related tectonic escape of the anatolian plate and subduction roll back along the aegean subduction zone we study the deeper lithosphere and mantle structure of anatolia using teleseismic finite frequency p wave traveltime tomography we use data from several temporary and permanent seismic networks deployed in the region approximately 34 000 p wave relative traveltime residuals measured in multiple frequency bands are inverted using approximate finite frequency sensitivity kernels our tomograms reveal segmented fast seismic anomalies beneath anatolia that corresponds to the subducted portion of the african lithosphere along the cyprean and the aegean trenches we identify these anomalies as the subducted aegean and the cyprus slabs that are separated from each other by a gap as wide as 300 km beneath western anatolia this gap is occupied by slow velocity perturbations that we interpret as hot upwelling asthenosphere the eastern termination of the subducting african lithosphere is located near the transition from central anatolia to the eastern anatolian plateau or arabian eurasian collision front that is underlain by large volumes of hot underplating asthenosphere marked by slow velocity perturbations our tomograms also show fast velocity perturbations at shallow depths beneath northwestern anatolia that sharply terminates towards the south at the north anatolian fault zone nafz the associated velocity contrast across the nafz persists down to a depth of 100 150 km hence our study is the first to investigate and interpret the vertical extent of deformation along this nascent transform plate boundary overall the resolved upper mantle structure of anatolia is directly related with the geology and tectonic features observed at the surface of the anatolian plate and suggest that the segmented nature of the subducted african lithosphere plays an important role in the evolution of anatolia and distribution of its tectonic provinces

geodynamic implications derived from numidian like distal turbidites deposited along the internal external domain boundary of the betic cordillera s spain this research was supported by urbino university carlo bo grant responsible f guerrera spanish cicyt research projects cgl2009 09249 cgl2011 30153 co2 02 and cgl2012 32169 portuguese fct research project ptdc cli 72585 2006 research groups and projects of the generalitat valenciana from alicante university ctma iga and research group 146 of the junta de andalucia the first author is also grateful to the portuguese fct ciencia 2008 programme contract c2008 ist cvrm 1

reply to comment on european provenance of the numidian flysch in northern tunisia dorrik stow christine fildes sami riahi mohamed soussi urval patel j andy milton and stuart marsh institute of petroleum engineering heriot watt university edinburgh eh14 4as uk school of environment university of auckland private bag 92012 auckland new zealand geology department faculty of science university of tunis tunis tunisia core laboratories redhill surrey rh1 2lw uk national oceanography centre southampton so14 3zh uk anadarko algeria company llc 1 harefield road uxbridge ub8 1yh uk

evolution of the early paleozoic cordilleran margin of laurentia tectonic and eustatic events interpreted from sequence stratigraphy and conodont community patterns several field seasons in the canadian cordillera have allowed the measurement description and sampling of over 20 000 m of lower paleozoic strata from 26 stratigraphic sections across four platform to basin transects with the recovery of over 100 000 conodonts from more than 1200 4 5 kg samples this work was part of the lithoprobe slave northern cordillera lithospheric evolution snorcle project but is also being extended through a pan lithoprobe project to understand the tectonic and eustatic response of much of the laurentian plate through the early paleozoic based on the abundant field data the complex stratigraphic framework is interpreted in terms of sequence stratigraphy and a derived relative sea level curve using detailed conodont taxonomic and biostratigraphic results cluster analysis of conodont distributional data identified an evolving series of conodont communities through space and time these communities were partitioned across the platform to basin gradient and provide an additional sensitive indicator of relative sea level change these two independent approaches generated comparable eustatic curves for this cordilleran laurentian margin during much of the early paleozoic and identified some global eustatic events noted by earlier workers this part of laurentia was not a simple passive margin during the early paleozoic but rather was affected by four main tectonic events complicated by six principal eustatic changes some success was achieved in filtering the global and regional tectonic eustatic effects and in proposing causes for some of the events

tectono sedimentary evolution of the numidian formation and lateral facies southern branch of the western tethys constraints for central western mediterranean geodynamics this research was supported by urbino university grant awarded to f guerrera cgl2009 09249 and cgl2011 30153 co2 02 research projects spanish ministry of education and science research groups and projects of the generalitat valenciana from alicante university ctma iga and rnm 208 rnm 3715 of the junta de andalucia

new kinematic and geochronologic evidence for the quaternary evolution of the central anatolian fault zone cafz as the kinematics of active faults that bound the anatolian plate are well studied it is now essential to improve our understanding of the style and rates of intraplate deformation to constrain regional strain partitioning and improve seismic risk assessments one of these internal structures the central anatolian fault zone cafz was originally defined as a regionally significant left lateral tectonic escape structure stretching for 700 km in a ne direction across the anatolian plate we provide new structural geomorphic and geochronologic data for several key segments within the central part of the cafz that suggest that the sinistral motion has been overstated the ecemis fault the southernmost part of the cafz has a late quaternary minimum slip rate of 1 1 0 4 mm a 1 slower than originally proposed farther north the erciyes fault has fed a linear array of monogenetic vents of the erciyes stratovolcano and 40ar 39ar dating shows a syneruptive stress field of ese wnw extension from 580 130 ka to 210 180 ka in the erciyes basin and central part of the cafz we mapped and recharacterized the erkilet and gesi faults as predominantly extensional these long term geological rates support recent gps observations that reveal ese wnw extension which we propose as the driver of faulting since 2 73 0 08 ma the slip rates and kinematics derived in this study are not typical of an escape tectonic structure the cafz is a transtensional fault system that reactivates paleotectonic structures and accommodates e w extension associated with the westward movement of anatolia

geotechnical and landslide aspects in weathered granitoid rock masses serre massif southern calabria italy abstract the weathering processes produce important chemical and physical transformations in rock masses producing a decay of their strength and then stability in this study different methodologies were employed to define the physical mechanical properties and the minero petrographical changes at each grade of weathering useful to determine a geological model of the weathered granitoids involved in mass movements the paper focuses on a multidisciplinary research on the weathering profiles of the paleozoic granitoid rocks surrounding the village of fabrizia located in the serre massif southern calabria italy fabrizia lies on an old erosion surface composed of basement rocks made up of weathered granitoids belonging to the serre massif granitoid complex and overlain by thin eluvial colluvial deposits the tectonic uplift of the area combined with mediterranean climatic conditions both active at least since the quaternary are the main causes of the deep weathering of the plutonic rocks the weathered profiles of the granitoid complex have been studied through field observations borehole explorations with geotechnical tests and seismic surveys coupled to minero petrographical analysis and laboratory tests weathered profiles are mainly composed by rock masses varying from completely weathered and residual soil classes v vi to moderately weathered rocks class iii characterized by a progressive increase of geotechnical properties e g seismic wave velocity rock quality designation internal friction angle uniaxial compressive strength with a decrease of weathering the weathered rocks display a wide variety of mass movement landslide types are rockfalls for the fresher rocks class iii translational slides occur between different weathering degrees classes iv and v and rotational slides dominate at the top of the slopes and generally involve the weathering grades from class iv to classes v vi the shallow horizons are composed of thin eluvial colluvial deposits and more weathered granitoids classes v vi that may generate dangerous debris flows or debris avalanches during intense and prolonged rainfall the landslide surface is usually at a depth lower than 2 m in the debris flow type while deeper landslides depth 2 m are rotational and translational types with sliding surfaces occurring mainly in the transition between the classes iv and v the field survey coupled to geotechnical geophysical and minero petrographical data allowed the recognition of the different weathered horizons and relative geotechnical properties useful to the reconstruction of the reliable geological model the model represents an important support for the study of the landslide processes and for a sustainable management of the territory the used approach provided results to set a general reference framework for establishing more precise correlations between mass movement phenomena and weathering processes

tempo of earliest ordovician graptolite faunal succession conodont based correlations from the tremadocian of quebec successive tremadocian planktic dendroid graptolite assemblages from continental slope sequences in quebec can be correlated with north american platform biozonations on the basis of conodonts anisograptid bearing assemblage 2 middle tremadocian matane faunas are associated with early ordovician rossodus manitouensis zone new designation conodonts younger middle tremadocian faunas with adelograptids assemblage 3 are no younger than the rossodus manitouensis zone key dendroid evolutionary immigration events take place within the lower conodont fauna b interval rooted dendroids near cap des rosiers quebec and in eastern new york state occur with lower fauna b conodonts and the trilobites pareuloma and borthaspidella however the earliest tremadocian and earliest ordovician dendroid immigration event represented by the local lowest occurrence of faunas with dictyonema flabelliforme s l at localities in western newfoundland eastern new york state norway and eastern china also lies with

latest miocene and pleistocene ages of faulting determined by 40ar 39ar single crystal dating of airfall tuff and silicic extrusives of the erciyes basin central turkey evidence for intraplate deformation related to the tectonic escape of anatolia the ericiyes basin is a trans tensional basin situated 20 km north of the regional ecemis fault zone recently it has been hypothesized that faulting within the erciyes basin links with the ecemis fault zone further south as part of a regional central anatolian fault zone new 40ar 39ar dating of volcanic and volcaniclastic rocks adjacent to faults both along the margins and in the centre of the erciyes basin constrains the timing of basin inception and later faulting extensional faulting occurred along the eastern and western margins of the basin during the early messinian latest miocene sinistral and minor normal faulting were active along the axis of the basin during the early pleistocene these fault timings are similar to those inferred for the ecemis fault zone further south and support the hypothesis that faulting within the erciyes basin and the ecemis fault zone are indeed linked

provenance of mesozoic to cenozoic circum mediterranean sandstones in relation to tectonic setting abstract the composition and stratigraphic relations of clastic strata in diverse sedimentary basins of the circum mediterranean region reflect a complete record of provenance relations since break up of pangea neo tethyan taphrogenesis and subsequent plate convergence between the two major plates of europe and africa and other related microplates of iberia adria mesomediterranean and toward to the eastern mediterranean the anatolian microplate since plate reorganization after the breakup of pangea at the end of paleozoic earliest mesozoic clastic wedges filled sedimentary basins within geodynamic settings evolving from intracontinental rifts rifted continental margins protoceanic basins arc trench basin systems remnant ocean basins foreland basin systems and intramontane and back arc basins within the circum mediterranean region the changing nature of clastic particles in these clastic wedges reflect the provenance relations from different source rocks within the spatial and temporal evolving geo puzzle terranes including relations between ophiolite bearing uplifted continental crust both shallow to deep crust terranes volcanic and sedimentary particularly carbonate strata source rocks mixed siliciclastic and carbonate shallow to deep marine clastic wedges are diffuse in many filled basin systems along the mediterranean as such as occurrence of volcaniclastic layers interbedded with siliciclastic wedges the variable mosaic of source terranes within the mediterranean region offered the possibility to investigate provenance relations with a new plane of precision and sophistication discriminating grain particles in clastic wedges using spatial extrabasinal versus intrabasinal and temporal coeval versus noncoeval distinction of detrital signals the spatial temporal approach in deciphering particles in clastic rocks has been widely used to detail the basinal dispersal pathways in different geotectonic settings wherever mixed silicate and carbonate terranes act as the major source rocks from rifted continental margins to collisional orogens

unravelling hinterland and offshore palaeogeography from pre to syn orogenic clastic sequences of the betic cordillera sierra espuna spain abstract the malaguide complex betic cordillera occurs in the sierra espuna area se spain providing a favorable setting to study a sedimentary successions from continental and shallow marine to deep marine environments using structural and stratigraphic relations and petrological and geochemical signatures the aim of this work is to outline the sedimentary evolution of the malaguide complex and the el nino fm this succession is arranged into pre orogenic paleocene early oligocene and syn orogenic late oligocene early miocene stages the detrital modes of sandstones of the overall succession are heterogeneous and indicate a multi source area marked by exhumation till an unknown malaguide basement and probably lower units of the internal betic zone e g alpujarride complex in the case of the el nino fm pre orogenic deposits are mainly carbonate with abundant skeletons of intrabasinal to extra basinal larger foraminifera calcareous lithic fragments and quartz grains and metamorphic lithic fragments minor metamorphic lithic fragments occur in the eocene deposits i e espuna fm calcareous lithic fragments and extra basinal fossils lithoclastic bioclasts are mostly present in the early oligocene pre orogenic formations i e as fm and were derived from the paleocene eocene sedimentary successions of the malaguide complex syn orogenic sandstones are quartzolithic with abundant metamorphic and sedimentary lithic fragments slate phyllite fine grained schist ooidal grainstone mudrock and quartz rich siltstone fragments sedimentary lithic fragments were derived from the mesozoic successions of the malaguide complex while metamorphic detritus is related to the malaguide basement probably also alpujarride from burdigalian on that was exhumed starting from the late oligocene mudrocks of the syn orogenic clastics record an increase of phyllosilicate quartz and feldspars and an abrupt decrease in calcite and dolomite the abundance of calcite and dolomite and traces of hematite occur dominantly in the pre orogenic mudrocks the geochemical signatures suggest a provenance mostly derived from felsic source rocks with a minor supply from mafic metavolcanic rocks in some samples of the syn orogenic stage the syn orogenic formations i e rio pliego fm and el nino fm are characterized by higher cr v values than the pre orogenic formations suggesting a mafic supply for the syn orogenic samples in particular the contents of cr average 85 ppm and ni average 48 ppm for the samples of the rio pliego and el nino formations are higher than those samples cr average 20 ppm ni average 14 ppm of the pre orogenic formations palaeoweathering indices suggest low to moderate weathering conditions for the source area s the cenozoic studied succession played a key role in the geodynamic evolution of the betic cordillera representing the key tectonic element of the western mesomediterranean domains

comparative lower middle ordovician conodont oxygen isotope palaeothermometry of the argentine precordillera and laurentian margins abstract stratigraphic palaeontologic and palaeomagnetic data support a hypothesis that argues for the argentine precordillera rifting from the southwestern margin of laurentia in low latitudes during the cambrian migrating across the iapetus ocean colliding with the gondwanan margin in the late middle ordovician and receiving glaciogenic sediments in the late ordovician an alternative model proposes that the precordillera originated as a low latitude segment of gondwana migrated southward through major transform faulting toward high latitudes in the late middle ordovician to reach its present position in the devonian new conodont oxygen isotope compositions 18ophos have been determined by ion microprobe shrimp ii using samples from both the precordillera and laurentia marathon area of texas wilcox pass in alberta and western newfoundland significantly the 18o values of conodonts from all four widely separated areas show a consistent pattern of a cyclic but overall increasing trend in 18o ca 16 to 18 hence ocean cooling through the early and middle ordovician an apparent change occurs at the basal late ordovician where 18o values obtained from conodonts in the uppermost sample from the precordillera are significantly higher 1 5 than those from laurentia albeit from a single sample this higher value implies significantly cooler conditions as would be anticipated with a southerly poleward migration of the precordillera irrespective of either hypothesis the virtual absence of conodont bearing carbonates in most of the precordilleran upper ordovician precluded analysis of younger samples when combined with existing macrofaunal and palaeomagnetic data the oxygen isotope data would tend to favour the model of a drift of the precordillera from tropical to higher latitudes during the ordovician however further studies are needed to determine unequivocally whether the precordillera originated from southern laurentia ouachita embayment these new oxygen isotope values provide the best and regionally most consistent data through the early middle ordovician

detrital zircon u pb ages in the rif belt northern morocco paleogeographic implications abstract detrital zircon u pb age distributions in mesozoic and cenozoic rocks from the external rif and maghrebian flysch complex including the so called mauretanian internal flysch units are very similar strongly suggesting that the external rif and the entire maghrebian flysch complex were part of the same nw african paleomargin these patterns include scarce paleozoic zircon grains that show influence from the sehoul block neoproterozoic and paleoproterozoic grains are abundant with a dominant ediacaran zircon population at ca 590 ma which could have been sourced from the variscan moroccan mesetas the northern components of the west african craton or from triassic sediments from the central high atlas and argana basins mesoproterozoic zircon ages between 1 1 and 1 6 ga were also observed 15 in the combined age spectra the nearest sources for these being in the central part of the west african craton transport of the mesoproterozoic grains to the nw african paleomargin requires northward directed fluvial systems parallel to the central atlantic continental margin of africa in contrast samples from the internal rif or alboran domain are different to those from the external rif and maghrebian flysch complex especially in the scarcity of mesoproterozoic zircons suggesting that the alboran domain was not a source area for zircons found in the nw african paleomargin

the early miocene bisciaro volcaniclastic event northern apennines italy a key study for the geodynamic evolution of the central western mediterranean the early miocene bisciaro fm a marly limestone succession cropping out widely in the umbria romagna marche apennines is characterized by a high amount of volcaniclastic content characterizing this unit as a peculiar event of the adria plate margin because of this volcaniclastic event also recognizable in different sectors of the central western mediterranean chains this formation is proposed as a marker for the geodynamic evolution of the area in the bisciaro fm the volcaniclastic supply starts with the raffaello bed earliest aquitanian that marks the base of the formation and ends in the lower portion of the schlier fm late burdigalian langhian p p forty one studied successions allowed the recognition of three main petrofacies 1 pyroclastic deposits volcanic materials more than 90 including the sub petrofacies 1a vitroclastic crystallo vitroclastic tuffs 1b bentonitic deposits and 1c ocraceous and blackish layers 2 resedimented syn eruptive volcanogenic deposits volcanic material 30 90 including the sub petrofacies 2a high density volcanogenic turbidites 2b low density volcanogenic turbidites 2c crystal rich volcanogenic deposits and 2d glauconitic rich volcaniclastites 3 mixing of volcaniclastic sediments with marine deposits volcanic material 5 30 mixed with marine sediments marls calcareous marls and marly limestones coeval volcaniclastic deposits recognizable in different tectonic units of the apennines maghrebian and betic chains show petrofacies and chemical geochemical features related to a similar calc alkaline magmatism the characterization of this event led to the hypothesis of a co genetic relationship between volcanic activity centres primary volcanic systems and depositional basins depositional processes in the early miocene palaeogeographic and palaeotectonic evolution of the central western mediterranean region the results support the proposal of a geodynamic model of this area that considers previously proposed interpretations

first u pb detrital zircon ages from numidian sandstones in southern apennines italy evidences of african provenance abstract two samples of quartz rich sandstones collected in the numidian flysch of southern apennines italy have been studied to highlight the provenance of detritus using radiometric dating by la icp ms of detrital zircons and to compare the obtained ages with those of the betic and maghrebian chains the provenance of quartzose detritus from european or african plates is still debated in these chains accordingly the ages of the detrital zircons can contribute significantly to discriminate the origin of the quartzose supply the u pb zircon ages n 47 vary from 3047 13 ma mesoarchean to 516 19 ma cambrian the predominance of paleo proteozoic ages 2500 1600 ma and the lack of hercynian and alpine ones suggest a provenance of the numidian supply from north african cratonic areas during the early middle langhian when the numidian successions of southern apennines were deposited in addition a cluster of ages at 773 24 ma and 668 12 ma in one sample and at 664 17 ma in the other sample calculated on zircon domains with magmatic zoning testify to an important contribution from neo proterozoic granitic rocks widely outcropping in the north african craton the age data on detrital zircons from numidian sandstones in southern apennines overlap those found in the numidian sandstones widespread in the betic cordillera and in the maghrebian chain from south spain to sicily this suggests that the entire depositional zone in which numidian flysch deposited was fed from a southerly source represented by the african craton where archean proterozoic and cambrian rocks widely crop out from the atlantic coast to the hoggar and tibesti massifs finally it must be outlined that a meso archean zircon age 3047 ma has been found in the numidian flysch of the southern apennines whereas in the numidian flysch of the maghrebian chain zircons older than paleo proterozoic 1840 ma have not yet been found

the rif chain northern morocco in the late tortonian early messinian tectonics of the western mediterranean orogenic belt evidence from the tanger al manzla wedge top basin

late quaternary alluvial fans of emli valley in the ecemis fault zone south central turkey insights from cosmogenic nuclides abstract alluvial fans within the paraglacial ecemis river drainages on the aladaglar mountains in south central turkey were studied using geomorphological sedimentological and chlorine 36 terrestrial cosmogenic nuclide tcn surface exposure dating methods to examine the timing of alluvial fan abandonment incision and to understand the role of climatic and tectonic processes in the region these alluvial fan complexes are among the best preserved succession of alluvial fans in turkey and they were offset by the major strike slip ecemis fault of the central anatolian fault zone the alluvial fans are mostly composed of well lithified limestone cobbles 5 to 25 cm in size and comprise crudely stratified thick beds with a total thickness reaching up to about 80 m tcn surface exposure dating indicates that the oldest alluvial fan surface yalak fan was likely formed and subsequently abandoned latest by 136 0 23 4 ka ago largely on the transition of the penultimate glaciation marine isotope stage 6 mis 6 to the last interglacial mis 5 i e termination ii the second set of alluvial fan emli fan was possibly developed during the last interglacial mis 5 and incised twice by between roughly 97 0 13 8 and 81 2 13 2 ka ago a younger alluvial fan deposit placed on relatively older erosional terraces of the emli fan suggests that it may have been produced during the last glacial cycle mis 2 these events are similar to findings from other fluvial and lacustrine deposits throughout central anatolia the incision times of the ecemis alluvial fan surfaces largely coincide with major climatic shifts from the cooler glacial periods to warmer interglacial interstadial conditions this indicates that alluvial fans were produced by outwash sediments of paleoglaciers during cooler conditions and later when glaciers started to retreat due to a major warming event the excess water released from the glaciers incised the pre existing fan surfaces an alluvial fan in the study area was also cut by the ecemis fault highlighting the influence of tectonics on fan development it was offset vertically 35 3 m since at least 97 0 13 8 ka which suggests a 0 36 0 06 mm a 1 vertical slip rate of the fault

evidence for late rifting of the cordilleran margin outlined by stratigraphic division of the lower cambrian gog group rocky mountain main ranges british columbia and alberta the lower cambrian mcnaughton formation of the gog group occupies a stratigraphic position transitional between the rift related rocks of the underlying upper proterozoic miette group and the overlying paleozoic passive margin succession a major regional unconformity overlain by a distinctive orthoquartzite marker has been traced within the mcnaughton formation this unconformity has been shown to truncate normal faults active during the deposition of the lower mcnaughton formation the lower mcnaughton formation consists of mature coarse grained fluvial sediments accumulated in hanging wall half grabens of active normal faults these faults represent the final stage of rifting on the continental margin the unconformity on the footwall blocks of these faults can be traced into the hanging wall and is overlain by the shoreface sediments of the transgressive upper mcnaughton formation formal subdivision of the mcnaughton formation into four lithostratigraphic members is proposed in order to describ

conodont biostratigraphy of the latest cambrian early ordovician upper mckay group southeastern british columbia the age of the upper mckay group based on conodont biostratigraphy is latest cambrian cordylodus proavus zone to late early ordovician middle floian oepikodus communis zone a collection of 12 940 conodont elements was recovered from 306 samples of upper mckay group strata exposed in the western main ranges of the southern canadian rocky mountains southeastern british columbia the conodont fauna is assigned to 53 species representing 30 genera twelve zones are recognized two of which are cosmopolitan cordylodus proavus zone and iapetognathus zone seven midcontinent realm zones in ascending order include polycostatus falsioneotensis rossodus tenuis rossodus manitouensis low diversity interval scolopodus subrex and acodus kechikaensis zones and tropodus sweeti subzone of the oepikodus communis zone three atlantic realm zones in ascending order include cordylodus angulatus acodus deltatus and paroistodus proteus zones the zonation for the upper mckay group establishes correlation w

geologic evolution of the betic cordilleras in the western mediterranean miocene to the present abstract the betic cordilleras were formed during the eo meso and neo alpine evolution of the western mediterranean area during the neo alpine stage the northward subduction of the african plate took place and the algerian provencal basin opened with the creation of oceanic floor associated space problems produced the expulsion and extensive stretching of the internal zones to the west which in turn disrupted and deformed the external zones of the betic and rif cordilleras these occurrences essentially took place in the burdigalian and continued with diminished intensity into the middle miocene following the suturing of the transcurrent contact between the internal and external zones important n60 90 e and nw se faults occurred the betic cordilleras are characterized as having been deformed by regional horizontal shortening compression oriented wnw ese or nw se which gradually rotated to the nnw sse in the late miocene when its most important intramontane neogene basins were formed the alboran basin with a thinned continental crust was formed as a western prolongation of the opening of the algerian provencal basin with its basic features already apparent in the burdigalian the volcanism present in the southeast of the betic cordilleras and in northeast morocco crossing the alboran basin is mainly late miocene in age it is linked to fracturing and exhibits chemistry related to the different thickness of the crust

the initiation of the early paleozoic cordilleran miogeocline evidence from the uppermost proterozoic lower cambrian hamill group of southeastern british columbia the uppermost proterozoic lower cambrian hamill group of southeastern british columbia contains geologic evidence for a phase of extensional tectonism that led directly to the onset of thermally controlled subsidence in the cordilleran miogeocline moreover the hamill group contains the sedimentological record of the passage of the ancient passive margin from unstable tectonic conditions associated with rifting and or the earliest phases of thermal subsidence to post rift conditions characterized by stabilization of the margin and dissipation of the thermal anomaly generated during the rift phase the rift to post rift transition widespread uplift that occurred prior to and during the deposition of the lower hamill group is indicated by an unconformable relation with the underlying windermere supergroup and by stratigraphic relations between middle and upper proterozoic strata and unconformably overlying upper lower cambrian quartz arenites upper hamill group in the southern borderlands of the hami

an early cambrian rift to post rift transition in the cordillera of western north america the upper proterozoic and lower palaeozoic wedge of miogeoclinal strata in the north american cordillera is widely regarded as evidence for a proto pacific passive margin1 3 the rifting history of this margin appears to have been protracted possibly spanning 200 myr in a tectonic setting that is not well understood3 quantitative subsidence analyses of lower palaeozoic strata between british columbia and utah however provide indirect evidence that the transition from rifting to post rift cooling occurred within a relatively short interval of time although probably not synchronously between 600 and 555 myr refs 4 6 this age is significantly younger than that implied in previous studies1 2 we describe here new field data which together with published geological data provide direct evidence of a latest proterozoic or early cambrian age for the rift to post rift transition the data support recent arguments for widespread initiation of passive margins around the edge of the north american craton close to the cambrian precambrian boundary7

tectono sedimentary evolution of the southern branch of the western tethys maghrebian flysch basin and lucanian ocean consequences for western mediterranean geodynamics the evolution of the oceanic maghrebian flysch basin and its continuation in the southern apennines was studied by reconstructing mainly representative stratigraphic successions in all sectors a common evolution has been identified rifting and drifting phases are indicated by remnants of oceanic crust jurassic limestones cretaceous palaeogene turbiditic and pelagic deposits the pre orogenic sedimentation was mainly controlled by extensional tectonics and sea level changes the occurrence of a generalized foredeep stage since the early miocene is testified by thick siliciclastic and volcaniclastic syn orogenic flysch successions the deformation of the oceanic areas began in the burdigalian and the resulting nappes were stacked in the growing chains during the middle miocene piggy back basins developed and the building of the chains was accomplished in the late tortonian areal distribution and ages of flysch deposits represent an important tool for the study of the diachronous growth of the accretionary wedges