sandy contourite drift in the late miocene rifian corridor morocco reconstruction of depositional environments in a foreland basin seaway abstract the rifian corridor was a seaway between the atlantic ocean and the mediterranean sea during the late miocene the seaway progressively closed leading to the messinian salinity crisis in the mediterranean sea despite the key palaeogeographic importance of the rifian corridor patterns of sediment transport within the seaway have not been thoroughly studied in this study we investigated the upper miocene sedimentation and bottom current pathways in the south rifian corridor the planktic and benthic foraminifera of the upper tortonian and lower messinian successions allow us to constrain the age and palaeo environment of deposition encased in silty marls deposited at 150 300 m depth there are i 5 to 50 m thick mainly clastic sandstone bodies with unidirectional cross bedding and ii 50 cm thick mainly clastic tabular sandstone beds with bioturbation mottled silt lack of clear base or top and bi gradational sequences furthermore seismic facies representing elongated mounded drifts and associated moat are present at the western mouth of the seaway we interpret these facies as contourites the products of a westward sedimentary drift in the south rifian corridor the contourites are found only on the northern margin of the seaway thus suggesting a geostrophic current flowing westward along slope and then northward this geostrophic current may have been modulated by tides by comparing these fossil examples with the modern gulf of cadiz we interpret these current dominated deposits as evidence of late miocene mediterranean overflow into the atlantic ocean through the rifian corridor this overflow may have affected late miocene ocean circulation and climate and the overflow deposits may represent one of the first examples of mainly clastic contourites exposed on land

locally and remotely triggered aseismic slip on the central san jacinto fault near anza ca from joint inversion of seismicity and strainmeter data we study deep aseismic slip along the central section of the san jacinto fault near the anza seismic gap in southern california elevated strain rates following the remote m w7 2 4 april 2010 el mayor cucapah and the local m w5 4 7 july 2010 collins valley earthquakes were recorded by plate boundary observatory borehole strainmeters near anza and were accompanied by vigorous aftershock sequences we introduce a method to infer the distribution of triggered aseismic slip from combined seismicity and geodetic data based on a rate and state friction model that maps observed changes in seismicity rates into stress changes we invert for the cumulative slip in the 10 day period following each main shock synthetic tests show that the effect of aftershock interactions on the inferred slip distribution is negligible the joint data set is more consistent with a model in which aseismic slip on a principal fault triggers seismicity on adjacent faults than with one in which aseismic slip and seismicity are coplanar our results indicate that aseismic slip primarily occurs along the rim of two seismicity clusters adjacent to anza gap as well as beneath the anza gap itself at depths larger than 10 km the triggered aseismic slip generated by the two main shocks has little overlap a pattern also found in sequences of large earthquakes occurring on a same fault stresses inferred from seismic activity leading to the collins valley main shock suggest that this earthquake was triggered by stresses imposed by the el mayor cucapah remote triggered aseismic slip which persisted for more than 2 months

macaronichnus and contourite depositional settings bottom currents and nutrients as coupling factors abstract the trace fossil macaronichnus segregatis degiberti 7 15 mm in diameter is recorded for the first time in deep marine contourites which were deposited in a late miocene outer shelf to upper slope of the rifian corridor morocco macaronichnus is typical of shallow marine mainly foreshore environments it is produced by deposit feeding opheliid polychaetes in high to intermediate latitudes this record supports the significance of bottom current processes on environmental conditions as a major limiting factor affecting the macrobenthic trace maker community mediterranean overflow water during the late miocene enabled a high nutrient supply to the seafloor favouring colonization by macaronichnus producers thus m s degiberti should be used as an indicator for nutrient availability instead of mainly a palaeodepth indicator this finding provides significant information for oceanographic and environmental reconstructions related to contouritic processes as well as to contourite characterization

the mesozoic margin of the maghrebian tethys in the rif belt morocco evidence for polyphase rifting and related magmatic activity

major hydrological shifts in the black sea lake in response to ice sheet collapses during mis 6 130 184 ka bp abstract the saalian was one of the largest glaciations during the quaternary with an ice sheet extending considerably wider into the eurasian continent than during other glacials orbital variations caused the ice sheet to switch between growing and shrinking the partial retreat of the ice sheet and meltwater discharge resulted in global sea level rise and increased lake levels of inland seas with broader environmental implications during marine isotope stage 6 mis 6 meltwater entered the formerly enclosed black sea at least twice as documented in a 18o record from anatolian speleothems here we present a sedimentary record from the black sea lake covering mis 6 and provide evidence for three meltwater periods coinciding with insolation maxima bswp 6 1 180 167 ka bp bswp 6 2 160 145 ka bp bswp ii 133 130 ka bp while 18oostracods and sr caostracods point to pronounced meltwater supply and decreasing salinity 87sr 86srostracods shed light on meltwater sources and pathways during all three periods meltwater drained most likely via the dnieper and volga into the black and caspian seas and connected both basins relatively low 87sr 86srostracods values during the oldest meltwater period suggest melting solely of the eastern eurasian ice sheet in contrast during the younger meltwater periods exceptional high 87sr 86srostracods values point towards additional meltwater from the western eurasian ice sheet a surplus from melting glaciers in the tian shan and pamir mountains that finally entered the caspian sea via the amu darya and sry darya probably amplified the input of high radiogenic sr isotope water we also show that higher temperatures and productivity suggest dansgaard oeschger like climate variability during the first half of mis 6

compositional heterogeneity in tephra deposits resulting from the eruption of multiple magma bodies implications for tephrochronology abstract tephra deposits of unknown age and or occurring in distal sequences that lack stratigraphic markers are commonly identified by their glass compositions and mineralogical assemblages recent studies of widespread rhyolitic tephra deposits from okataina volcanic centre ovc new zealand reveal a hitherto unrecognised geochemical and mineralogical diversity within individual deposits and sometimes between and within individual lapilli in these deposits these variations subtle in some units can occur both vertically and laterally through a tephra deposit and result from the sequential or simultaneous eruption of separate batches of rhyolitic magma this process often includes mingling of magmas in the eruption conduits as demonstrated by disequilibrium mineral assemblages in pumice clasts some eruption episodes e g 36 cal ka hauparu 17 6 cal ka rerewhakaaitu have tapped two or more magmas simultaneously while others 0 7 cal ka kaharoa 15 4 cal ka rotorua have tapped multiple magmas sequentially some tephra deposits display the sequential and or simultaneous emissions of different magmas from multiple vents through temporal phases of the episode 5 5 cal ka whakatane the resulting deposits can also show variations between different azimuths around the vent due to changes of wind direction during the episode the internal heterogeneity in ovc tephra deposits was only recognised after comprehensive sampling through their thick proximal pyroclastic sequences and associated lavas the internal heterogeneity highlights the inadequacy of fingerprinting tephra deposits from a small number of samples of restricted dispersal magma mingling at a single clast scale also has implications for geochronological techniques that use accessory phases u series and or require uniform melt geochemistry fission track on glass

a reinterpretation of seismicity associated with the january 1983 dike intrusion at kilauea volcano hawaii in january 1983 a dike intrusion fissure eruption generated a swarm of 375 magnitude 1 to 3 earthquakes along a 16 km segment of kilauea s middle east rift zone we searched the hawaiian volcano observatory catalog for multiplets of similar events from this region from 1980 through 1985 and obtained precise relative locations by waveform cross correlation over 150 of the intrusion earthquakes could be grouped into 14 multiplets of five or more events with sufficient similarity for accurate relocation some multiplets were active for only a few minutes during the downrift migration phase of the seismic swarm consistent with generation near the propagating dike tip while others were active for several days the two multiplets nearest the origin of the seismic swarm include events from the preceding days and months most multiplets span only 50 to 100 m following relocation are located at about 3 to 4 km depth and appear to deepen downrift the catalog depths of those earthquakes in multiplets and those not in multiplets are similar suggesting that most of the recorded seismicity may have come from a very limited depth interval despite the fact that the dike breached the surface by analogy with a mechanical model used to explain a similar clustering of background seismicity in the upper east rift in 1991 we infer that the earthquakes are generated in regions of high stress concentration immediately above kilauea s deforming deep rift body this conclusion is consistent with the depth of the top of the deep rift body inferred from geodetic data and with numerical calculations suggesting that a significant ambient differential stress is required for dikes to produce earthquakes larger than magnitude 1

near real time double difference event location using long term seismic archives with application to northern california we present a real time procedure that uses cross correlation and double difference methods to rapidly relocate new seismic events with high precision relative to past events with accurately known locations waveforms of new events are auto matically cross correlated with those archived for nearby past events to measure accu rate differential phase arrival times these data together with delay times computed from arrival time picks are subsequently inverted for the vector connecting the new event to its neighboring events using the double difference algorithm the new seis mic monitoring technique is applied to earthquakes recorded in northern california using near real time data feeds from the northern california seismic network ncsn and the northern california earthquake data center and a locally stored copy of the ncsn seismic archive new events are automatically relocated in near real time tens of seconds relative to a high resolution double difference earthquake catalog for northern california back testing using past events across northern california indi cates that the real time solutions are on average within 0 08 km laterally and 0 24 km vertically of the double difference catalog locations we show that the precision with which new events are located using this technique will improve with time helped by the continued increase in density of recorded earthquakes and growth of the digital seismic archives real time double difference location allows for monitoring spatio temporal changes in seismogenic properties of active faults with unprecedented res olution and therefore has considerable social and economic impact in the immediate evaluation and mitigation of seismic hazards

vent distribution and its relation to regional tectonics cappadocian volcanics turkey abstract the distribution of polygenetic and monogenetic volcanoes of the neogene quaternary cappadocian volcanic province cvp is analyzed to investigate the relationship between vent location and regional tectonic lineaments two fault systems exist in the province one system miocene quaternary tuzgolu ecemis system is oblique whereas the other system late miocene pliocene cvp system is parallel to the long axis of the cvp the polygenetic volcanoes are aligned parallel to the second system but concentrate around the major faults of the first system regional offsets are proposed along the first fault system based on the distribution of the polygenetic volcanoes the monogenetic volcanoes group into five geographically distinct clusters in the western part of the cvp the monogenetic cones are aligned parallel to the cvp system whereas in the central part the cones are fed by dikes injected along the recent fractures of the tuzgolu ecemis system in the eastern part the monogenetic cones form along the radial fractures of the erciyes composite volcano

tephrological implications of beam size sample size effects in electron microprobe analysis of glass shards this paper concerns the potential consequences of varying procedures for the determination of tephra geochemistry by electron microprobe application of electron probe microanalysis to tephrostratigraphical methods has increasingly facilitated the resolution and refinement of quaternary chronology associated with records of proxy environmental or proxy climatic change the geographical range over which tephras are recovered has expanded significantly with the identification and analysis of crypto or hidden tephras in areas far removed from tephra sources these tephras are dominated by glass shards which in many distal environments may be either small in size m or may be highly pumiceous with low glass void ratios and thin 10 m shard walls we demonstrate that reducing the size of the electron beam used to analyse shard geochemistry cannot be used reliably to permit analysis of thin glass walls this approach distorts the geochemical data creating analytical differences that may generate inappropriate tephrogeochemical fingerprints additional distortion of the geochemical fingerprint in the form of hybrid analyses may be encountered in glass fragments containing micron sized crystalline phases such as feldspar copyright 2001 john wiley sons ltd

slip parallel seismic lineations on the northern hayward fault california a high resolution relative earthquake location procedure is used to image the fine scale seismicity structure of the northern hayward fault california the seismicity defines a narrow near vertical fault zone containing horizontal alignments of hypocenters extending along the fault zone the lineations persist over the 15 year observation interval implying the localization of conditions on the fault where brittle failure conditions are met the horizontal orientation of the lineations parallels the slip direction of the fault suggesting that they are the result of the smearing of frictionally weak material along the fault plane over thousands of years

discriminant function analysis of late quaternary tephras from five volcanoes in new zealand using glass shard major element chemistry abstract the microprobe determined glass shard major element chemistry of tephras derived from five north island new zealand volcanoes mayor island okataina taupo tongariro and mount egmont and younger than ca 20 000 yr b p was subjected to discriminant function analysis four separate approaches were adopted to test the match of the tephras with their known sources 1 an analysis of raw microprobe data 2 an analysis of normalized data 3 an analysis of the data transformed by calculating the log 10 of oxide scores divided arbitrarily by the chlorine content and 4 a repeat of 3 with multivariate outlier scores as determined by principal components analysis deleted all yielded excellent classification functions efficiencies of 91 100 with the eruptives associated with each of the five volcanoes being chemically distinct from one another in each approach the first two canonical discriminant functions accounted for 90 of the variation between groups the removal of multivariate outliers from the data set had only minor effects on the performance of the discriminant function procedures separate discriminant function analysis of the relatively alike taupo and okataina eruptives gave a greater degree of multivariate separation the numerical classifications generated should enable unidentified tephras erupted since ca 20 000 yr b p from the five volcanoes to be provisionally matched with their sources

age refinement and basin evolution of the north rifian corridor morocco no evidence for a marine connection during the messinian salinity crisis abstract the connection between the mediterranean and the open ocean during the messinian and the messinian salinity crisis msc remains largely unsolved however such a connection is required to supply the salts required for the formation of the thick evaporite successions deposited during the msc a potential candidate for a mediterranean atlantic connection is the northern branch of the rifian corridor through morocco but existing biostratigraphic constraints of unspecified late tortonian messinian age are insufficient to test the hypothesis we present new calcareous plankton biostratigraphic data using among others an improved planktonic foraminiferal zonal scheme that is based on an assemblage rather than on a typology based taxonomic concept the results of this study invariably reveal a late tortonian age for the youngest open marine sediments in the individual intramontane basins in the central part of the north rifian corridor nrc and no marine sediments of messinian age have been found the high sedimentation rates and the observed shallowing in the top part of several nrc successions suggest that although the marine connection through the nrc may have continued in the earliest messinian it was likely closed before 7 0 7 2 ma i e well before the onset of the msc this closure is likely related to a phase of enhanced and localised uplift in the rif foreland and excludes the north rifian corridor as the long lasting marine connection between the mediterranean and open ocean during most of the msc

first evidence of a distal early holocene ash layer in eastern mediterranean deep sea sediments derived from the anatolian volcanic province article i nfo a hitherto unknown distal volcanic ash layer has been detected in a sediment core recovered from the southeastern levantine sea eastern mediterranean sea radiometric stratigraphic and sedimentological data show that the tephra here termed as s1 tephra was deposited between 8970 and 8690 cal yr bp the high silica rhyolitic composition excludes an origin from any known eruptions of the italian aegean or arabian volcanic provinces but suggests a prevailing central anatolian provenance we compare the s1 tephra with proximal to medial distal tephra deposits from well known mediterranean ash layers and ash fall deposits from the central anatolian volcanic field using electron probe microanalyses on volcanic glass shards and morphological analyses on ash particles we postulate a correlation with the early holocene dikkartin dome eruption of erciyes dag volcano cappadocia turkey so far no tephra of the central anatolian volcanic province has been detected in marine sediment archives in the eastern mediterranean region the occurrence of the s1 tephra in the south eastern part of the levantine sea indicates a wide dispersal of pyroclastic material from erciyes dag more than 600 km to the south and is therefore an important tephrostratigraphical marker in sediments of the easternmost mediterranean sea and the adjacent hinterland

some numerical considerations in the geochemical analysis of distal microtephra abstract the use of late quaternary tephra horizons as isochronous markers for high resolution correlation between records is of growing importance in a number of scientific fields particular advancements have been made through the identification of microtephra deposits very distal deposits of volcanic ash invisible to the naked eye the successful correlation of ash layers and volcanic eruptions depends on the acquisition of the major element chemistries of a tephra layer derived from microprobe analyses of individual glass shards this is particularly important for microtephras where aeolian fractionation has removed much of the mineral phase of the ash deposit which often aids tephra discrimination there are however difficulties in distinguishing precisely between different eruptions of the same volcano using major element composition and this may not always be resolved by the use of trace elements given the potential of tephrochronology as a correlative tool in many disciplines it is important to resolve this difficulty one way forward is to perform more robust statistical analyses on the geochemical data as in general analyses are confined to a series of bi plots of major elements here the authors explore some of the problems associated with dealing with microprobe data generated for individual tephras and pay particular attention to the unit sum problem using a subset of data generated as part of a eurodelta project on tephra distribution in the adriatic the authors demonstrate that this problem is detectable in major element data from tephras and have consequently applied the logratio method before further analyses of the data it is demonstrated that the use of logratios combined with discriminant functions analysis provides a more robust assessment of likely chemical correlations between tephras and are superior to the use of bi plots alone and obviate the need for any data normalization a particular point of contention between tephrochronologists

deep fault plane geometry inferred from multiplet relative relocation beneath the south flank of kilauea dense microearthquake swarms occur in the upper south flank of kilauea providing multiplets composed of hundreds of events the similarity of their waveforms and the quality of the data have been sufficient to provide accurate relative relocations of their hypocenters a simple and efficient method has been developed which allowed the relative relocation of more than 250 events with an average precision of about 50 m horizontally and 75 m vertically relocation of these events greatly improves the definition of the seismic image of the fault that generates them indeed relative relocations define a plane dipping about 6 northward although corresponding absolute locations are widely dispersed in the swarm a composite focal mechanism built from events providing a correct spatial sampling of the multiplet also gives a well constrained northward dip of about 5 to the near horizontal plane this technique thus collapses the clouds of hypocenters of single event locations to a plane coinciding with the slip plane revealed by previous focal mechanism studies we cannot conclude that all south flank earthquakes collapse to a single plane there may locally be several planes perhaps with different dips and depths throughout the south flank volume the 6 northward dipping plane we found is too steep to represent the overall flexure of the oceanic crust under the load of the island of hawaii this plane is probably an important feature that characterizes the basal slip layer below the upper south flank of kilauea volcano differences in seismicity rate and surface deformations between the upper and lower south flank could be related to the geometry of this deep fault plane the present work illustrates how high precision relative relocations of similar events in dense swarms combined with the analysis of geodetic measurements can help to describe deep fault plane geometry systematic selection and extensive relative relocation of similar earthquakes could be attempted in other well instrumented highly seismic areas to provide reliable basic information especially useful for understanding of earthquake generation processes

characteristics of repeated detached miocene pliocene tectonic inversion events in a large delta province on an active margin brunei darussalam borneo abstract the baram delta province evolved during the middle miocene to present day from a foreland basin to a shelf margin episodic folding events affected the region causing uplift of the hinterland delta progradation and inversion of gravity related faults existing models place the n s and ne sw trending folds in a strike slip transpressional setting new geological mapping and re interpretation of existing data suggest the region is better understood as the development of a west verging thrust belt in a middle miocene foreland basin filled by sandstones and shales of the belait and setap formations with key major folds jerudong and belait anticlines belait syncline forming during the middle miocene as fault bend and fault propagation folds the deformation style is complicated by the predominantly shaley middle miocene pliocene setap formation becoming thicker and more overpressured from south to north onshore where the setap formation is thin or absent the belait formation is attached to the underlying lower miocene and older sequences offshore and in a narrow onshore strip the overpressured setap formation causes deformation in the beltait formation to be detached from the underlying cretaceous tertiary accretionary prism basement the detached style exhibits considerable structural complexity including lift off folds growth faults shale diapirs and pipes onshore thrust and inversion features are dominantly n s trending and began activity in the middle miocene deformation is probably associated with an e w maximum horizontal stress direction in the late miocene around 7 5 ma watters et al 1999 ne sw striking inversion folds developed located mostly over early counter regional faults and associated reactive diapirs folds verge towards the nw when underlain by counter regional faults and towards the s or se when underlain by regional faults folds and diapirs along n s trends were also reactivated continuation of this deformation into the pliocene is largely confined to the offshore area onshore the n s structures no detachment were not reactivated during the pliocene

geochemical features of collision related volcanic rocks in central and eastern anatolia turkey in central and eastern anatolia volcanism related to continental collision occurred in neogene to quaternary times major and trace element compositions 87sr86 sr and k ar ages were determined for volcanic rocks from selected volcanoes in this region 87sr86 sr for basalts from erciyes volcano in the eastern part of central anatolia as well as ararat nemrut and karacadag volcanoes in eastern anatolia are in the range 0 7035 0 7040 these ratios are higher than those of n type morb but overlap arc volcanic rock values this suggests that the mantle source which was possibly contaminated by fluids and melts with higher87sr86 sr during the pre collisional events has similar sr isotopic compositions in wide areas of the eastern part of central anatolia and eastern anatolia even across the collision plate boundary in addition chemical compositions of the mantle source are not homogeneous with respect to hfs element contents indicating that the slab derived components resulting from past subductions are not homogeneously distributed the mantle source beneath the western part of central anatolia which corresponds to the transitional region from collision tectonics in the east to subduction tectonics in the west has different chemical and sr isotopic signatures from other parts of anatolia in the western part of central anatolia the87sr86 sr of basaltic rocks from three regions characterized by monogenetic volcanoes are in the range 0 70427 to 0 70581 and differ from region to region in spite of indistinguishable chemical compositions this indicates either source heterogeneity on a small scale or different contributions of local crustal contaminants calc alkaline lavas from ararat and kars in eastern anatolia have chemical compositions with subduction signatures inherited from pre collision subduction events in contrast the chemical and sr isotopic features of volcanic rocks from erciyes volcano in central anatolia indicate that the combined process of fractional crystallization of basaltic magma and crustal assimilation without injection of slab derived components is the dominant process generating calc alkaline andesite under the collision tectonics regime operating in this region

mid pleistocene acheulean like stone technology of the bose basin south china stone artifacts from the bose basin south china are associated with tektites dated to 803 000 3000 years ago and represent the oldest known large cutting tools lcts in east asia bose toolmaking is compatible with mode 2 acheulean technologies in africa in its targeted manufacture and biased spatial distribution of lcts large scale flaking and high flake scar counts acheulean like tools in the mid pleistocene of south china imply that mode 2 technical advances were manifested in east asia contemporaneously with handaxe technology in africa and western eurasia bose lithic technology is associated with a tektite airfall and forest burning

monitoring velocity variations in the crust using earthquake doublets an application to the calaveras fault california we present a technique that greatly improves the precision in measuring temporal variations of crustal velocities using an earthquake doublet or pair of microearthquakes that have nearly identical waveforms and the same hypocenter and magnitude but occur on different dates we compute differences in arrival times between seismograms recorded at the same station in the freqency domain by cross correlation of short windows of signal a moving window analysis of the entire seismograms including the coda gives t the difference in arrival times versus running time along the seismogram the time resolution of the method is an order of magnitude better than the digitization interval the t technique is illustrated with a pair of microearthquakes m 1 7 and 2 0 that occurred before and after the coyote lake california earthquake m 5 9 of august 6 1979 and on the same segment of the calaveras fault that ruptured during the earthquake the coda wave arrivals for some stations are progressively delayed for the second earthquake in the doublet so that its seismogram appears as a stretched version of the earlier event we interpret this systematic variation in t along the coda as a change in the average s velocity in the upper crust in the time interval between the two doublets s wave velocities appear to have decreased by 0 2 in an oblong region 5 10 km in radius at the south end of the aftershock zone

sequence of tuffs between the kbs tuff and the chari tuff in the turkana basin kenya and ethiopia this paper describes a sequence of tuffs between the kbs and the chari tuff of omo group formations in kenya and ethiopia these tuffs have recently been shown to be 1 87 0 02 ma and 1 38 0 03 ma in age respectively the sequence of tuffs that is derived is consistent with 40 ar 39 ar ages reported separately and provides the stratigraphic framework for interpreting those ages further new correlations are established to the konso formation in southern ethiopia as drainage from the ethiopian rift to the omo turkana basin developed after deposition of the konso formation pumice clasts in tuffs of the omo turkana basin probably were transported there by the omo river the tuffs are divided into five groups on the basis of their stratigraphic position in relation to extensive ash layers the sequence of tuffs has import for the placement and age of archaeological sites in the koobi fora formation and for ages of mammalian faunas including hominids many tuffs were deposited during a 90 ka interval during which mediterranean sapropels are lacking suggesting that nile flow was reduced and that the level of a lake that occupied the omo turkana basin at the time was low thus the record of climatic influence on deposition in the omo turkana basin previously shown for the kibish formation 200 ka extends at least to early pleistocene time

stratigraphic record of the early mesozoic breakup of pangea in the laurasia gondwana rift system rift basins of the central atlantic margins cam of north america and morocco preserve largely continental sequences of sedimentary strata and less important minor basalt flows spanning much of the early mesozoic the best known is the newark basin of new jersey new york and pennsylvania where an astronomically calibrated magnetic polarity time scale is developed lacustrine cycles of milankovitch origin are commonly present in cam basins with the period changing from 10 ky paleoequator with coals to 20 ky 4 10n to perhaps 40 ky northward with evaporites cycles of100 ky 413 ky and2 my are also important four mostly unconformity bounded tectonostratigraphic sequences are present the anisian ts i is fluvial and eolian ts ii ts iv late triassic to early jurassic consist of tripartite lacustrine sequences caused by extension pulses the newark basin accumulation rate history allows comparison with quantitative rift basin models the north american plate s slow northward drift resulted in a relative shift of climate although the rapid humidification during the latest triassic and early jurassic is associated with a sea level rise the triassic jurassic mass extinction is of independent origin plausibly impact related

acigol rhyolite field central anatolia part ii geochemical and isotopic sr nd pb δ18o constraints on volcanism involving two high silica rhyolite suites the acigol rhyolite field erupted the most recent high silica rhyolites within the cappadocian volcanic province of central anatolia turkey it comprises two sequences of domes and pyroclastic rocks with eruption ages of 150 200 ka eastern group and 20 25 ka western group compositionally the eastern rhyolite group lavas are less evolved sio2 74 76 wt whereas the western group has higher silica abundance sio2 77 wt with extremely depleted feldspar compatible trace elements within each group compositional variability is small and 143nd 144nd 0 51257 0 51265 and pb isotope compositions 206pb 204pb 18 87 18 88 207pb 204pb 15 65 15 67 and 208pb 204pb 38 94 38 98 are homogeneous the western group rhyolites have 18o zircon overlapping mantle values 5 7 0 2 whereas eastern group rhyolites are enriched in 18o by 0 5 consistent with a tendency to lower end values by contrast western group rhyolites have markedly more radiogenic 87sr 86sr ratios 0 7065 0 7091 compared to those of the eastern group 0 7059 0 7065 the presence of angular granitic xenoliths and a correlation between hydration based on loss on ignition data and 87sr 86sr in the western lavas however indicates that sr was added during the eruption or post eruption alteration isotope constraints preclude the possibility that the rhyolite magmas formed by partial melting of any known regional crystalline basement rocks basalts and andesites erupted in the periphery of the acigol field are characterised by 87sr 86sr ratios between 0 7040 and 0 7053 143nd 144nd 0 51259 0 51300 206pb 204pb 18 85 18 87 207pb 204pb 15 646 15 655 208pb 204pb 38 90 38 97 the isotopic and trace element data favour an origin of the rhyolites by mixing of basaltic andesitic magmas with minor amounts of crustal melts and followed by extensive fractional crystallization

the reset project constructing a european tephra lattice for refined synchronisation of environmental and archaeological events during the last c 100 ka this paper introduces the aims and scope of the reset project response of humans to abrupt environmental transitions a programme of research funded by the natural environment research council uk between 2008 and 2013 it also provides the context and rationale for papers included in a special volume of quaternary science reviews that report some of the project s findings reset examined the chronological and correlation methods employed to establish causal links between the timing of abrupt environmental transitions aets on the one hand and of human dispersal and development on the other with a focus on the middle and upper palaeolithic periods the period of interest is the last glacial cycle and the early holocene c 100 8 ka during which time a number of pronounced aets occurred a long running topic of debate is the degree to which human history in europe and the mediterranean region during the palaeolithic was shaped by these aets but this has proved difficult to assess because of poor dating control in an attempt to move the science forward reset examined the potential that tephra isochrons and in particular non visible ash layers cryptotephras might offer for synchronising palaeo records with a greater degree of finesse new tephrostratigraphical data generated by the project augment previously established tephra frameworks for the region and underpin a more evolved tephra lattice that links palaeo records between greenland the european mainland sub marine sequences in the mediterranean and north africa the paper also outlines the significance of other contributions to this special volume collectively these illustrate how the lattice was constructed how it links with cognate tephra research in europe and elsewhere and how the evidence of tephra isochrons is beginning to challenge long held views about the impacts of environmental change on humans during the palaeolithic

scale in tephrostratigraphic correlation an example from turkish pleistocene archaeological sites issues of scale are persistent but rarely made explicit in tephrostratigraphy eruption magnitude the nature of available outcrop and the resolution and type of data available define the scale of any proposed correlation different scales require different approaches to demonstrate or more accurately to estimate the likelihood of correlation among two or more deposits this is emphasized through a probabilistic approach to the correlation of proximal and distal tephra deposits associated with lower and middle paleolithic archaeological sites from central turkey through the use of discriminant analyses and multiple analyses of variance

early holocene volcanic ash fallout in the yammouneh lacustrine basin lebanon tephrochronological implications for the near east article i nfo a volcanic ash layer tyam 1 was identified in holocene sediments from the yammouneh paleo lake lebanon the ash layer consisted of colourless shards the major elemental chemistry of the glass as determined by electron microprobe analyses indicates a rhyolitic composition radiocarbon dating of detrital wood fragments located in the ash layer suggests an age of approximately 8 6 ka cal bp the timing of the layer and a chemical comparison with other published data suggest that tyam 1 likely originated from anatolia and likely corresponds to early holocene z3 z4 z5 tephras the preliminary results provided in this manuscript suggest a new stratigraphical and chronological marker for the continental records of lebanon and neighbouring regions

palaeogeographic evolution of the late miocene rifian corridor morocco reconstructions from surface and subsurface data abstract the rifian corridor was one of the mediterranean atlantic seaways that progressively restricted and caused the messinian salinity crisis msc many key questions concerning the controls on the onset progression and termination of the msc remain unanswered mainly because the evolution of these seaways is poorly constrained uncertainties about the age of restriction and closure of the rifian corridor hamper full understanding of the hydrological exchange through the msc gateways required connections to sustain transport of salt into the mediterranean for the primary lower gypsum and halite stages here we present integrated surface subsurface palaeogeographic reconstructions of the rifian corridor with improved age control information about age and timing of the closure have been derived from high resolution biostratigraphy palaeoenvironmental indicators sediment transport directions and the analysis of published onshore subsurface core and seismic datasets we applied modern taxonomic concepts to revise the biostratigraphy of the rifian corridor and propose astronomically tuned minimum maximum ages for its successions finally we summarise the palaeogeographic evolution in four time slices corresponding to the middle tortonian 10 57 8 37 late tortonian 8 37 7 25 ma early messinian 7 25 6 35 ma and late messinian 6 35 5 33 ma several successions record the closure of the corridor via a continuous marine to continental lacustrine transition the youngest dated marine sediments represent a good approximation of the age of seaway closure the closure of the south rifian corridor is constrained to 7 1 6 9 ma that of the north rifian corridor is more uncertain and ranges from 7 35 to ca 7 ma we conclude that the rifian corridor was already closed in the early messinian and did not contribute to the restriction events that resulted in the msc because the betic corridor is also closed by the early messinian the modern gibraltar straits remain the sole option in the western mediterranean as last messinian seaway that was open during the msc our results imply that the gibraltar straits could have been established as the exclusive mediterranean atlantic portal already in the late miocene and therefore we suggest that future field and drilling campaigns should target the alboran sea and the gibraltar region to investigate water exchange before and during the messinian salinity crisis and its impact on atlantic circulation and global climate

ar ar ages from transitionally magnetized lavas on la palma canary islands and the geomagnetic instability timescale 1 a detailed study of 43 lava flows comprising two stratigraphic sequences exposed along the north and south walls of barranco de los tilos on the island of la palma canary islands reveals a complex temporally segmented record of geodynamo behavior that contains no less than three distinct geomagnetic events the matuyama brunhes m b reversal is recorded in five transitionally magnetized lava flows from the north tn section the isochrons obtained from three of the lower four m b lavas are defined by 14 incremental heating experiments that together with a previous age determination yielded a weighted mean of 798 4 6 2 ka all uncertainties 2s in addition a 780 3 10 3 ka isochron was determined for the overlying transitionally magnetized flow indicating that it was erupted during a distinctly younger portion of the transition near the base of the south ts section one finds a sequence of weakly magnetized flows associated with virtual geomagnetic pole vgp positions in the southwest indian ocean between latitudes 56 s and 65 s suggesting instability of the geomagnetic field beyond that of typical secular variation 40 ar 39 ar isochrons from three of these flows defined by 11 separate incremental heating experiments gave a weighted mean of 822 2 8 7 ka this anomalous field behavior recorded 24 11 kyr prior to the m b reversal may coincide with an event featured in several marine sediment records directly above two normal polarity flows 40 ar 39 ar isochrons of 751 9 18 1 ka and 675 0 15 7 ka are nine transitionally magnetized lavas having magnetization directions associated with low to midlatitude vgps spanning 23 60 n these flows are then capped by a single flow possessing normal polarity based on 12 incremental heating experiments 40 ar 39 ar isochrons of five of these nine lavas along with the uppermost flow gave a weighted mean age of 580 2 7 8 ka for this period of transitional to normal field behavior from these same transitional lavas quidelleur et al 1999 reported three unspiked k ar ages with a weighted mean of 602 24 ka and proposed a new event called the la palma excursion however the 40 ar 39 ar age presented here is three times more precise than the k ar age and is indistinguishable at the 95 confidence level from the 40 ar 39 ar age of a lava from the snake river plain idaho that originally defined the big lost event transitional field behavior of similar age observed in astronomically dated marine cores further establishes that the big lost event recorded at la palma was indeed global in extent rigorous temporal and geomagnetic constraints for several additional periods of geomagnetic field instability during the last several million years will comprise a geomagnetic instability timescale that can be factored confidently into models of the dynamo process index terms 1560 geomagnetism and paleomagnetism time variations secular and long term 1520 geomagnetism and paleomagnetism magnetostratigraphy 1035 geochemistry geochronology 1513 geomagnetism and paleomagnetism geomagnetic excursions keywords argonargon dating lavas excursion paleomagnetism reversal

structural style of the offscraped ligurian oceanic sequences of the northern apennines new hypothesis concerning the development of melange block in matrix fabric shaly dismembered formations crop out extensively on the eastern side of the northern apennines as overthrusted cretaceous oceanic units the lack of metamorphism and the unconformably overlain epi ligurian sequence which represents the trench slope basin sedimentary sequence suggest that these units are accreted sequences accomplished by offscraping and imbrication these units are characterized by stratal disruption lack of internal coherence and complete destruction of the original stratigraphic sequence block in matrix fabric results in symmetric boudins and systematic presence of isolated or intrafolial hinges of isoclinal folds two orthogonal sets of tight to isoclinal folds are always recognizable involving the break up and the boudinage of the competent layers now transposed parallel to the axial planes of the disrupted isoclinal folds the superposition of two generations of orthogonal tight to isoclinal folds may be locally observed either in single bed fragments or in some preserved coherent units disruption and block in matrix fabric is a consequence of polyphase folding and intense shortening this geometry and kinematic interpretation well constrain the tectonic environment where these rocks were deformed to the proximity of the prism toe and within the prism itself thus the apennine broken formations result from the disruption of a sedimentary pile lying on the subducting plate of the cretaceous to eocene trench fore arc system which generated the ligurian accretionary wedge

the pre mousterian industrial complex in europe between 400 and 300 ka interpreting its origin and spatiotemporal variability abstract the author discuss data indicating that the non handaxe non acheulean tradition of small tools and core choppers was present in parts of west eurasia during the early middle pleistocene the period marked by a wide spread of acheulean in west asia and west europe and survived until 400 300 ka and perhaps later in some areas beyond the area of the maximum acheulean distribution in the danube basin and the balkans and to a limited extent north of the danube basin in central europe and in the south of russian plain and northern caucasus in eastern europe the author defines these middle pleistocene assemblages which are totally lacking true acheulean handaxes and debitage resulted from large flake or levallois knapping technologies as the pre mousterian industrial complex the assemblages of pre mousterian complex are variable due to their functional differentiation and other reasons but generally comprise the next three components 1 simple mostly primary and orthogonal and also rare unipolar and centripetal cores with short reduction sequences consisting of flaking of 1 3 flakes from one platform followed by the core rotation or discard 2 flake tools which are made mostly but not exclusively on small sized flakes with beveled platforms and include varieties of simple side scrapers denticulates notches thick end scrapers awls and convergent pieces as well as small numbers of tools with flat ventral retouch or bifacial retouched edges and 3 large sized tools are always present and include mostly unifacial choppers and more rare chopping tools and proto bifaces or pointed choppers with partial bifacial processing the author discuss that the hominids that produced lithic industries of pre mousterian complex acquired a high behavioural plasticity to settle in most uncomfortable within western eurasia forested and forest steppe environments with cold winters in central and eastern europe the hominids developed tool inventories well suited for bone and woodworking made real wooden throwing spears and composite tools with wooden hafts that are found in schoningen in contrast to the acheulean complex in west europe and west asia assemblages of pre mousterian complex do not show a transition temporally being placed now during mis 8 mis 7 between c 300 200 ka in both the regions toward the middle palaeolithic or mousterian technology in contrast to the acheulean to middle palaeolithic transition which is associated with final neanderthalization of h heidelbergensis and the origin of h neanderthalensis the assemblages of pre mousterian complex disappear with the spread of early middle paleolithic neanderthals

basin inversion and magma migration and emplacement insights from basins of northern chile abstract during the structural modelling of inverted basins influenced by magmatism is very important understand the geometric and kinematic relationships between inverted structures and intrusive bodies the northern chile is a natural laboratory to analyze this situation since its cenozoic tectonic evolution was marked by the tectonic inversion of mesozoic extensional basins which occurred simultaneously with the emplacement of km scale intrusions in order to provide insights on the interplay between basin inversion and magma emplacement we completed a comparative analysis based of field data from four inverted mesozoic basins of northern chile and a series of previous and new analogue models reproducing the tectonic inversion of half grabens and magma emplacement the experiments showed that the magma migration and emplacement is controlled by the initial distribution of normal faults and occur preferentially along the inverted normal faults high magma injection rate can cause a major reactivation of the normal faults favoring a comparatively increase in bulk shortening the most favorable condition for which the magma reaches the surface is under simultaneous high magma injection and shortening rates the latter allow the magma to be emplaced along the core of inversion related anticlines such as it is recognized in northern chile

recognition of the minoan tephra in the acigol basin western turkey implications for inter archive correlations and fine ash dispersal here we report the recognition of the minoan tephra layer in the acigol basin western turkey which represents the most eastward occurrence of this tephra on land and the first in continental deposits out of lacustrine sediments in mainland turkey the correlation is supported by glass and mineral geochemistry which includes solution and laser ablation icp ms data for trace and rare earth elements thickness and grain size data allow the extension of already described occurrences to an area of about 359 000 km 2 from the eastern mediterranean to black sea throughout central western turkey coupling dispersal area and grain size data suggests the joint influence of high and low atmosphere dynamics in dispersal of fine ash during volcanic eruptions the thickness and lateral continuity of the minoan tephra in the acigol basin testifies to the widespread impact on the late bronze age environment of mainland turkey of this important ash deposit copyright 2013 john wiley sons ltd

paleostress evolution in the moroccan african margin from triassic to present abstract paleostresses were calculated from more than 1000 fault slip data on sites located in the rif moutains the middle and high atlas chains the occidental moroccan meseta and northeastern morocco we sorted the state of stress according to the main tectonic events in order to present new synthetic maps of paleostresses of morocco in the late triassic early cretaceous time nw se to ne sw extensions occurred they are consistent with the opening of the atlasic and atlantic rifts in the late cretaceous paleocene an e w to wnw ese compression took place conjugated strike slip faults developed in northeastern morocco and in the atlas chain this event was followed by a n s eocene compression where most of the reverse faults and the folds of the atlasic area developed together with strike slip faulting compression extended from oligocene to middle miocene with a ne sw direction in the rif chain the middle and high atlas and the coastal atlantic basins continuous deformation during the neogene in the atlasic area was responsible for shortening of the basement and detachment of the sedimentary cover thrust faults at the front of the atlas were either visible or blind in the lower tortonian nne ssw and ene wsw to e w compressions occurred respectively east and west of the nekor fault this tectonic regime led to the formation of post nappes basins separated by emerged lands in the tortonian early messinian the direction of compression varies from n s to nne ssw or ne sw east and west of the nekor fault respectively in the early messinian a large transgression occurred throughout the meseta domain and the middle atlas area in the late messinian a marine regression was synchronous with the mediterranean salinity crisis in the late miocene the atlas chain emerged and was progressively uplifted together with folding and thrusting of its foreland nappes involving paleozoic basement formed along the axis of the chain in the plio quaternary the compression varies from n s to n140 e and contributes to continuous uplift of the atlas chain

rheological and tectonic modeling of salt provinces abstract technological improvements and a more rigorous research approach have led the petroleum industry to renew and expand its interest in physical modeling of faulting associated with halokinesis salt tectonics and the formation of structural hydrocarbon traps can be reproduced in models using viscous polymers for the substratum and frictional plastic granular materials for the overburden the fault patterns simulated in these dynamically scaled models are remarkably similar to those in depth converted seismic sections scale models are therefore useful for generating new concepts and for reconstructing the structural evolution of hydrocarbon traps although even unsealed models may help generating ideas the full transfer of quantitative data requires that models be dynamically scaled to their natural prototypes previously published scaling theory for salt tectonics has erroneously assumed fluid behaviour of the overburden this paper provides a sound scaling approach for geological deformations involving brittle overburdens on ductile substrata rheological data from overburden rocks and salt are compiled and compared to model rheologies using dimensions of laboratory analogs and other intrinsic material properties scaling approaches are compared and rules are formulated for achieving dynamic similarity in models of salt tectonics including those with synkinematic sedimentation

a pleistocene pyroclastic poor maar from central anatolia turkey influence of a local fault on a phreatomagmatic eruption in central anatolia the late pleistocene narkoy maar formed on a fault zone a 5 m thick pyroclastic succession erupted from a crater 900 m in diameter the presence of gas fumeroles hot springs and hydrothermal alteration zones indicates that the area is geothermally active the products of the maar are large blocks and lapilli to coarse ash planar bedding and cross stratification are well developed within coarse ash beds the maar deposits were generated by a single period of phreatomagmatic explosion with two episodes the first episode produced wet eruption clouds while the second one was relatively dry in nature the estimate of the volume of pyroclastic ejecta compared with the dimensions of the maar demonstrates a material deficiency which is attributed to a large volume of gas emanated during the phreatomagmatic explosion along a fault presently cross cutting the maar in addition a relatively small volume of magma intruded along the fault and mixed with meteoric water in the fault zone to produce the phreatomagmatic eruption the existence of a hydrothermal system in the fault zone is important in affecting the eruption style and evolution of narkoy maar

precise 40ar 39ar geochronology for the upper koobi fora formation turkana basin northern kenya the plio pleistocene koobi fora formation about 560 m thick crops out east of lake turkana and is part of the much larger depositional system of the omo turkana basin the upper half of the koobi fora formation from just below the kbs tuff to above the chari tuff is particularly notable for its wealth of hominid fossils and archaeological sites silicic tuffaceous horizons have provided the basis for stratigraphic subdivision and correlation pumice clasts within the tuffs contain anorthoclase phenocrysts ideal for 40ar 39ar single crystal dating feldspars from pumice clasts in about 15 tephra within the stratigraphic interval from the kbs tuff to the silbo tuff have yielded precise ages that allow much finer definition of the numerical time framework for the sedimentary sequence between the kbs tuff 1 869 0 021 ma and the chari tuff 1 383 0 028 ma and to yet higher in the sequence to the silbotuff 0 751 0 022 ma these results provide a precise and accurate time scale for the upper part of the sequence in the whole of the omo turkana basin a number of these tuffs are recognized elsewhere in east africa thus ages determined at koobi fora also apply to the wider region

positive fault inversion triggering intrusive diapirism an analogue modelling perspective understanding the formation and the development of salt structures is very important especially because they are of significant economical interest for hydrocarbon trapping and for long term storage of radioactive waste and energy reserves generally the activity of normal faults developed in extensional regimes is considered the most efficient mechanism for salt diapirs the results of analogue models reported in this paper suggest a new triggering mechanism for the rise of salt structures during basin inversion this mechanism relates the localization of ductile diapirs to early normal faults only after their inversion during later shortening in this case diapiric growth is related to the strong dip slip reactivation component along the fault extruding the silicone simulating salt upward some natural cases in which the timing and the mechanism of diapiric growth is not clear can be re interpreted in the light of these analogue model results

high precision relative locations of two microearthquake clusters in southeastern sicily italy in november 1999 and january 2000 two microearthquake swarms occurred in southeastern sicily italy they were analytically located in the depth range 17 25 km some kilometers northward from the buried front of a regional foredeep below the active thrust zone of the sicily mountain chain their hypocentral distribution showed two distinct clusters and comparison of the waveforms revealed clearly that the two swarms formed two distinct families of multiplet events this led us to 1 carry out a precise relocation relative to two chosen master events of the families and 2 better define the geometrical structure of the two clusters the cross spectral method was applied to obtain precise readings of the wave onsets sh wave onsets were used instead of p waves as they showed clearer onsets and a good signal to noise ratio residuals of the relative locations showed small values no more than several meters on average the vertical extent of the two relocated clusters was 500 and 250 m respectively while the horizontal extent was 250 m hypocenters of the first cluster clearly delineate a north northwest trending plane with almost vertical dip matching one nodal plane of the focal mechanism obtained as a composite solution of all events of the cluster given the considerable gap angles because of unfavorable network geometry with respect to the events the stability of our results was tested carrying out a monte carlo experiment varying the onset times randomly in the range of 5 msec a dispersion of the locations less than 10 m in longitude and less than 50 m both in latitude and depth was found similar results were obtained when comparing relocations carried out with different master events thus the overall geometrical characteristics of the clusters were not affected seriously by random errors considering the geostructural framework of the region together with the location and time evolution of the two clusters fluids of plutonic origin are suggested as the trigger mechanism manuscript received 26 june 2002

thick skinned tectonics closing the rifian corridor abstract tectonic processes in the gibraltar region are associated with africa iberia convergence and the formation of the betic rif orogenic system the late miocene shortening recorded in the rif orogen resulted in gradual shallowing and eventual closure of the rifian corridor a narrow marine gateway connecting the atlantic ocean with the mediterranean sea this closure is associated with paleoenvironmental changes that ultimately led to the mediterranean messinian salinity crisis here we present a structural analysis based on a combination of field kinematic data and interpretation of reflection seismic lines acquired for petroleum exploration to understand the deformational phases associated with the closure of the rifian corridor we show the succession of three late miocene to present day events an initial thin skinned nappe thrusting followed by regional subsidence and continued by thick skinned contraction the transition from in sequence thin skinned tectonics during subduction to thick skinned contraction during continental collision resulted in significant acceleration of tectonic uplift and associated exhumation this is related to a change in the regional deformation linked to plate convergence but possibly also coupled with deep lithospheric or dynamic topography processes such a mechanism is also common for other mediterranean orogens during late stages of slab retreat where accelerated tectonics resulted in rapid sedimentation and associated basins evolution we conclude that the thick skinned contraction in the rif orogeny initiated in the late tortonian has created a cumulative uplift in the order of 1 km and provided high enough uplift rates to close the rifian corridor

geochemical characterization of quaternary tephras from the campanian province italy the campanian province has a rich history of human interaction with volcanic eruptions in a region currently inhabited by 3 million people it is crucial to have precise and accurate geochemical characterization of volcanic units within the region so as to identify the spatial distribution of past events furthermore tephrochronology is becoming an important tool in the region for correlating past environmental records unfortunately many of the key units have been geochemically analysed using relatively imprecise methods making correlation problematic although robust correlations have been established in the campanian province using a range of methods including stratigraphy and geochronology more distal correlation requires precise geochemical characterisation of individual glass shards here we report major oxide data geochemically characterising 17 key tephra units within the campanian province using wavelength dispersive spectrometry wds the new data confirm the trachytic nature of most of the eruptions to effect more precise correlations between units especially in distal locations proximal units must be individually analysed for major oxides using wds on the vitreous phase and statistically analysed for robust correlations in cases where similar geochemistry exists analysis of trace and rare earth elements may be necessary

tephra geochemistry a discussion of some persistent analytical problems distal tephrochronological studies are reliant upon precise and accurate geochemical quantitation this quantitation can involve difficulties not often encountered in more conventional petrology solving these problems is of particular importance in the holocene and late quaternary of northwest europe where numerous tephra layers of icelandic origin have been detected in peat bogs and lake and marine sediments electron probe microanalysis epma has proved the most applicable analytical technique when insufficient quantities of tephra are available for bulk analysis standard epma techniques require fine tuning to the tephra problem as the geochemical instability of glass is a common feature in many previous studies geochemical data of avoidably low quality have been produced and little attention appears to have been directed to modification of epma methods it is suggested that the black box approach to geochemical analysis should be avoided by the consideration of several factors these include

geochemical approach to magmatic evolution of mt erciyes stratovolcano central anatolia turkey erciyes stratovolcano culminating at 3917 m is located in the cappadocian region of central anatolia during its evolution this quaternary volcano produced pyroclastic deposits and lava flows the great majority of these products are calc alkaline in character and they constitute kocdag and erciyes sequences by repeated activities alkaline activity is mainly observed in the first stages of kocdag and approximately first middle stages of erciyes sequences generally kocdag and erciyes stages terminate by pyroclastic activities the composition of lavas ranges from basalt to rhyolite 48 4 70 5 wt sio calc alkaline rocks are represented mostly by andesites and dacites some compositional 2 differences between alkaline basaltic basaltic and andesitic rocks were found while the composition of dacites remain unchanged all these volcanics are generally enriched in lil and hfs elements relative to the orogenic values except rb ba nb depleted alkaline basalt 87 srr 86 sr and 143 ndr 144 nd isotopic composition of the volcanics range between 0 703344 0 703964 0 512920 0 512780 for alkaline basalts and change between 0 704322 0 705088 0 512731 0 512630 for alkaline basaltic rocks whereas calc alkaline rocks have relatively high sr and nd isotopic ratios 0 703434 0 705468 0 512942 0 512600 low rb ba nb content with high zrrnb low barnb laryb ratio and low sr isotopic composition suggest an depleted source component while high ba rb nb content with high laryb barnb low zrrnb and low 87 srr 86 sr ratios indicate an oib like mantle source for the generation of erciyes alkaline magma these elemental and ratio variations also indicate that the different mantle sources have undergone different degree of partial melting episodes the depletion in ba rb nb content may be explained by the removal of these elements from the source by slab derived fluids which were released from pre collisional subduction modified the asthenospheric mantle the chemically different mantle sources interacted with crustal materials to produce calc alkaline magma the barnb increase of calc alkaline samples indicates the increasing input of crustal components to erciyes volcanics sr and nd isotopic compositions and elevated lil and hfs element content imply that calc alkaline magma may be derived from mixing of an oib like mantle melts with a subduction modified asthenospheric mantle and involvement of crustal materials in intraplate environments q 1998 elsevier science b v all rights reserved

the geodynamics of the aegean and anatolia introduction the complexity of the plate interactions and associated crustal deformation in the eastern mediterranean region is reflected in many destructive earthquakes that have occurred throughout its recorded history many of which are well documented and intensively studied the eastern mediterranean region including the surrounding areas of western turkey and greece is indeed one of the most seismically active and rapidly deforming regions within the continents fig 1 thus the region provides a unique opportunity to improve our understanding of the complexities of continental tectonics in an actively collisional orogen the major scientific observations from this natural laboratory have clearly been helping us to better understand the tectonic processes in active collision zones the mode and nature of continental growth and the causes and distribution of seismic volcanic and geomorphological events e g tsunamis and their impact on societal life and civilization the tectonic evolution of the eastern mediterranean region is dominated by the effects of subduction along the hellenic aegean arc and of continental collision in eastern turkey anatolia and the caucasus northward subduction of the african plate beneath western turkey and the aegean region is causing extension of the continental crust and volcanism in the overlying aegean extensional province eastern turkey has been experiencing crustal shortening and thickening as a result of northward motion of the arabian plate relative to eurasia and the attendant postcollisional magmatism taymaz et al 1990 1991a b mcclusky et al 2000 2003 dilek pavlides 2006 and references therein fig 2 the resulting combination of forces the pull from the subduction zone to the west and push from the convergent zone to the east is causing the turkish plate to move southwestward bounded by strike slip fault zones the north anatolian fault zone nafz to the north and the east anatolian fault zone eafz to the south interplay between dynamic effects of the relative motions of adjoining plates thus controls large scale crustal deformation and the associated seismicity and volcanism in anatolia and the aegean region taymaz et al 2004

apatite fission track analyses on basement granites from south western meseta morocco paleogeographic implications and interpretation of aft age discrepancies abstract this work is based on apatite fission track analysis of samples mostly granites from the basement of the cretaceous tertiary phosphate and ganntour plateaus exposed in the jebilet and rehamna massifs western meseta morocco this basement belongs to the carboniferous early permian variscan belt and the earlier marine onlap is late triassic in age however the aft ages are post triassic and different in the jebilet 186 203 ma and rehamna 148 153 ma track length modelling support the occurrence of moderate heating events during the jurassic and the eocene respectively with cooling during the permian and cretaceous intervals these results are partly accounted for by considering a moderate subsidence during the late triassic liassic which is a noticeable change in the regional paleogeographic concept of west moroccan arch however the discrepancies between the aft results from the studied massifs make necessary to explore further explanation we interpret the observed discrepancies by the difference in age and depth of crystallization of the sampled granites in the variscan orogen i e 330 ma 5 6 km in the jebilet versus 300 ma 8 10 km in the rehamna the importance of the late jurassic early cretaceous uplift and erosion of the entire meseta and that of its late eocene burial are emphasized

correlation of pliocene and pleistocene tephra layers between the turkana basin of east africa and the gulf of aden abstract electron microprobe analyses of glass shards from volcanic ash in pliocene and pleistocene deep sea sediments in the gulf of aden and the somali basin demonstrate that most of the tephra layers correlate with tephra layers known on land in the turkana basin of northern kenya and southern ethiopia previous correlations are reviewed and new correlations proposed together these data provide correlations between the deep sea cores and to the land based sections at eight levels ranging in age from about 4 to 0 7 ma specifically we correlate the moiti tuff 4 1 ma with a tephra layer at 188 6 m depth in dsdp hole 231 and with a tephra layer at 150 m depth in dsdp hole 241 the wargolo tuff with a tephra layer at 179 7 m in dsdp hole 231 and with a tephra layer at 155 3 m depth in dsdp hole 232 the lomogol tuff defined here with a tephra layer at 165 m in dsdp hole 232a the lokochot tuff with a tephra layer at 140 1 m depth in dsdp hole 232 the tulu bor tuff with a tephra layer at 160 8 m depth in dsdp hole 231 the kokiselei tuff with a tephra layer at 120 m depth in dsdp hole 231 and with a tephra layer at 90 3 m depth in dsdp hole 232 the silbo tuff 0 74 ma with a tephra layer at 35 5 m depth in dsdp hole 231 and possibly with a tephra layer at 10 9 m depth in dsdp hole 241 we also present analyses of other tephra from the deep sea cores for which correlative units on land are not yet known the correlated tephra layers provide eight chronostratigraphic horizons that make it possible to temporally correlate paleoecological and paleoclimatic data between the terrestrial and deep sea sites such correlations may make it possible to interpret faunal evolution in the lake turkana basin and other sites in east africa within a broader regional or global paleoclimatic context

high precision relative locations of earthquakes at mount st helens washington several earthquake sequences have occurred at mount st helens as clusters of shallow events with nearly identical waveforms multiplets we present a technique that allows the relative relocation of events within a multiplet to at least an order of magnitude higher precision than is typically possible with traditional techniques a multiplet is studied in pairs of events called doublets each doublet is made up of a reference event and one other event from the multiplet the cross spectrum of a short window beginning just before the p arrival is used to compute differences in arrival times between seismograms from the same station for each doublet these time differences computed with a precision of 1 2 ms are then used to locate each earthquake relative to the reference event engineering explosions with well known locations are used to test the relocation technique explosions can be relocated with accuracy better than 20 m for events within 250 m of the reference explosion the relocation technique is applied to earthquakes preceding the september 10 1984 and the may june 1985 dome building eruptions of mount st helens forty events that occurred during a 12 hour period in september 1984 are located in a volume approximately 30 m in diameter beneath the lava dome the earthquakes following the extrusion do not occur in multiplets and appear to be distributed over a much larger volume in the may june 1985 eruption we recognize three multiplet sets that took place successively in time the multiplets are interpreted as repeated failure or slip within a relatively small volume due to high strain rates around the magma supply conduit

a methodology for converting traditional vertical electrical soundings into 2d resistivity models application to the saiss basin morocco we demonstrated a simple methodology for the reinterpretation of sets of electrical vertical soundings and the production of 2d resistivity models the method is applied to the northern central part of the subsiding saiss basin morocco where a series of vertical electrical soundings ves were acquired in 1982 and 1984 using the schlumberger array with current electrodes semispacings between 3 and 3000 m we describe a methodology used to estimate and sample apparent resistivities collected from traditional single soundings acquired by using a schlumberger configuration we then construct a resistivity pseudosection in a format compatible with a wenner schlumberger array to perform 2d electrical tomography the methodology takes into account the lateral and vertical spatial correlations shown by the apparent resistivities the tomographic inversions are performed using a commercial inversion software commonly used in industry geostatistical tools are used to quantify the spatial correlation between ap

discovery of cryptotephra at middle upper paleolithic sites arma veirana and riparo bombrini italy a new link for broader geographic correlations

tracing marine cryptotephras in the north atlantic during the last glacial period improving the north atlantic marine tephrostratigraphic framework tephrochronology is increasingly being recognised as a key tool for the correlation of disparate palaeoclimatic archives underpinning chronological models and facilitating climatically independent comparisons of climate proxies tephra frameworks integrating both distal and proximal tephra occurrences are essential to these investigations providing key details on their spatial distributions geochemical signatures eruptive sources as well as any available chronological and or stratigraphic information frameworks also help to avoid mis correlation of horizons and provide important information on volcanic history here we present a comprehensive chronostratigraphic framework of 14 tephra horizons from north atlantic marine sequences spanning 60 25 cal ka bp horizons previously discovered as visible or coarse grained deposits have been combined with 11 newly recognised volcanic deposits identified through the application of cryptotephra identification and characterisation methods to a wide network of marine sequences their isochronous integrity has been assessed using their physical characteristics all horizons originated from iceland with the vast majority having a basaltic composition sourced from the grimsvotn kverkfjoll hekla vatnafjoll and katla volcanic systems new occurrences improved stratigraphic placements and a refinement of the geochemical signature of the naaz ii are reported and the range of the fmaz iv has been extended in addition several significant geochemical populations that further investigations could show to be isochronous are reported this tephra framework provides the foundation for the correlation and synchronisation of these marine records to the greenland ice cores and european terrestrial records to investigate the phasing rate timing and mechanisms controlling rapid climate changes that characterised the last glacial period

recent tectonic deformations and stresses in the frontal part of the rif cordillera and the saiss basin fes and rabat regions morocco prerif ridges are located at the frontal part of the rif cordillera which develops at the eurasian african plate boundary the ridges are formed by recent tectonic structures that also deform foreland basins saiss and gharb basins and the foreland moroccan meseta the position of the ridges is the consequence of inversion tectonics undergone in the area the ene wsw trend of the northern edge of the neogene saiss basin is determined by the location of mesozoic basins although prerif ridges probably started to develop since the early miocene the most active deformation phase affecting pliocene rocks consisted of n s to nw se oriented compression striated pebbles show that this compression has prolate stress ellipsoids the deformation produces southwards vergent folds and nnw sse striae on reverse faults at the base of the ridges the flexure of the paleozoic basement by the emplacement of the ridges produced extensional deformation and the development of the saiss foreland basin the extension in this basin is oblate and features a well determined nne ssw trend near the ridges whereas it becomes prolate and pluridirectional near the foreland edge represented by the rabat region this part of the moroccan meseta commonly considered to be stable is deformed by sets of orthogonal joints and faults with short slip that affect up to quaternary sediments southwestward the meseta rocks are also deformed by transcurrent faults which indicate nw se and n s trends of compression the nw se approximation of eurasia and africa determines a regional stress field with the same trend of compression regional stresses are notably disturbed by the development of the active structures in the rif which exhibit alternating trends of compression and extension the clearest evidence of the relationship between the local deformation and the general plate motion is found at the deformation front of the cordillera that is the prerif ridges

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

fission track dating obsidians in central and northern anatolia twenty obsidian samples from central and north anatolia were dated by the fission track method split samples analyzed in two different laboratories give consistent results data presented refer to three volcanic fields and are summarized as follows orta sakaeli northern anatolia obsidians with ages from 21 23 ma gollu dagi dome complex near ciftlik central anatolia has given ages between 1 33 0 98 ma acigol caldera central anatolia shows three age groups 1 eruptions of precaldera bogazkoy obsidians with ages 0 18 0 15 ma 2 formation of the large intracaldera dome kocadag taskesiktepe at about 0 08 ma uncorrected apparent age of 0 075 ma and 3 acigol peripheral obsidian domes with plateau ages of 0 020 and 0 019 ma and an additional uncorrected age of 0 018 ma form a distinct age group this fission track parameters discriminate between the various obsidian sources of prehistoric obsidian artifacts

tephrostratigraphy chronology and climatic events of the mediterranean basin during the holocene an overview the identification and characterisation of high frequency climatic changes during the holocene requires natural archives with precise and accurate chronological control which is usually difficult to achieve using only 14c chronologies the presence of time spaced tephra beds in quaternary mediterranean successions represents an additional independent tool for dating and correlating different sedimentary archives these tephra layers are potentially useful for resolving long standing issues in paleoclimatology and can help towards correlating terrestrial and marine paleoclimate archives known major tephras of regional extent derive from central and southern italy the hellenic arc and from anatolia a striking feature of major holocene tephra deposition events in the mediterranean is that they are clustered rather than randomly distributed in time several tephra layers occurred at the time of the s1 sapropel formation between c 8 4 and 9 0 ka bp mercato gabellotto fiumebianco e1 cappadocia and ot

correlation and characterisation of individual glass shards from tephra deposits using trace element laser ablation icp ms analyses current status and future potential pearce nicholas denton j s perkins w t westgate j a 2007 correlation and characterisation of individual glass shards from tephra deposits using trace element laser ablation icp ms analyses current status and future potential journal of quaternary science 22 7 pp 721 736 rae2008

building a tephrostratigraphic framework for the paleolithic of central anatolia turkey the central anatolian volcanic province cavp in turkey preserves widespread deposits of quaternary tephra presently associated with a small but growing number of paleolithic archaeological sites we use multivariate analyses of the abundances of a suite of nine major and minor element oxides determined by electron probe microanalysis from these data we construct a classificatory model for correlating distal tephra to one of five volcanic edifices or eruptive phases within the cavp application of this model to distal deposits of primary tephra fall and reworked tuffaceous sediments from the archaeological sites of korkuyu and kaletepe deresi 3 indicates late to possibly early pleistocene ages for the artifact assemblages there and provides a fundamental tephrostratigraphic framework to examine spatial and temporal variation in hominin behavior comparable to that of other regions such as eastern africa

rupture geometry from high precision relative hypocentre locations of microearthquake clusters summary in 1987 two microearthquake sequences with a duration of about a week each and consisting of 37 and 46 events respectively occurred in the upper crust below the jura mountains of northern switzerland the seismograms within each sequence exhibit a high degree of similarity indicating tight clustering of hypocentres and similar focal mechanisms using a cross correlation technique applied to the seismograms in the time domain together with a new least squares adjustment procedure it was possible to determine relative hypocentre locations of the earthquakes in each cluster with a precision of a few tens of metres the results show that hypocentres of events with the same focal mechanism lie on a plane which coincides exactly with one of the nodal planes of the fault plane solution and that consequently swarm like sequences of similar earthquakes are due to repeated slip on the same fault in one case slip occurred as right lateral motion on a steeply dipping plane striking in wnw ese direction whereas the other case corresponds to left lateral slip on two almost vertical planes striking roughly n s in 1988 an additional earthquake triplet occurred on a wnw ese oriented normal fault nearby all three mechanisms are consistent with a general nnw sse oriented direction of maximum crustal shortening and a corresponding wsw ene oriented extension repeated slip on the same fault is indicative of a large degree of heterogeneity and of short term temporal variability of both frictional resistance and stress distribution on the fault an explanation for the occurrence of such swarm like seismic activity in terms of barriers or asperities would require that shear stress on the unbroken patches increase from one event to the next since however the overall shear stress would be expected to decrease as a consequence of the stress released in each event a more plausible mechanism involves pore pressure fluctuations caused by fluids under suprahydrostatic pressures migrating upward through pre existing zones of weakness in the crust

high precision relocation of microearthquakes at mt etna 1991 1993 eruption onset a tool for better understanding the volcano seismicity abstract the beginning of the 1991 1993 large eruption at mt etna was marked by a seismic swarm and a sudden increase of volcanic tremor amplitude several earthquakes were recognized as clusters of shallow events with nearly identical waveforms multiplets we have analyzed these signals with a cross spectral technique that allows us to locate the relative position of the events within a multiplet obtaining a precision higher than with traditional routines the relocated shocks occurred some kilometers away from the propagating eruptive fracture east of both the summit craters and the modeled eruptive dykes they clustered in a relatively small volume elongated in the nnw sse direction the depth of which ranged from about 1100 to 2000 m below sea level these earthquakes are interpreted as the passive brittle response of the volcanic basement to the intrusion of the eruptive dyke rather than being directly linked to the magma transport

towards a european tephrochronological framework for termination 1 and the early holocene the record of deposition of tephras in europe and the north atlantic during the period 18 5 8 0 14 c ka bp the last termination and early holocene is reviewed altogether 34 tephras originating from four main volcanic provinces iceland the eifel district the massif central and italy have been identi ed so far in geological sequences spanning this time interval most of the records have been based until very recently on observations of visible layers of tephras here we report on the potential for extending the areas over which some of the tephras can be traced by the search for layers of micro tephra which are not visible to the naked eye and on the use of geochemical methods to correlate them with known tephra horizons this approach has greatly extended the area in northern europe over which the vedde ash can be traced the same potential exists in southern europe which is demonstrated for the rst time by the discovery of a distinct layer of micro tephra of the neapolitan yellow tu in a site in the northern apennines in italy far to the north of the occurrences of visible records of this tephra the paper closes by considering the potential for developing a robust european tephrostratigraphy to underpin the chronology of records of the last termination and early holocene thereby promoting a better understanding of the nature timing and environmental e ects of the abrupt climatic changes that characterized this period

the detailed tephrostratigraphy of a core from the south east black sea spanning the last 60 ka one visible volcanic ash layer and 21 non visible cryptotephra horizons have been identified in the m72 5 25 gc1 core from the south east black sea that spans the last 60 ka glass chemistry suggests that the tephras derive from italian hellenic and turkish sources the visible tephra layer is trachytic in composition and has been correlated to the 39 ka campanian ignimbrite super eruption from campi flegrei caldera italy two cryptotephra layers are associated with eruptions from acigol volcano turkey around the last glacial maximum another is linked to activity at erciyes dagi in the early holocene perikartini or karagullu and a cryptotephra layer near the top of the core correlates to the 3 6k cal a bp minoan marine z2 tephra from santorini thera greece this extends the known dispersal area for all these volcanic ash units many other calc alkaline rhyolite layers preserved in the core are likely to be from central anatolian sources but the lack of detailed proximal data for many of the volcanoes in the region prohibits further correlations the tephrostratigraphy and glass compositional data presented here allow the tephra layers to be used to correlate sedimentary archives across the region and help to extend the mediterranean tephrochronology framework towards the east

a real time procedure for progressive multiplet relative relocation at the hawaiian volcano observatory a real time procedure has been set up to select and relocate relatively similar events recorded by the u s geological survey hawaiian volcano observatory hvo hawaii seismic network at the observatory it allows the relocation of such similar events with an uncertainty whose order of magnitude is 50 m horizontally and 100 m vertically as a first step a systematic exploration of the volcano to find similar events within the seismicity recorded between years 1988 and 2000 has been undertaken and allows events to be gathered into large multiplets a generalized relative relocation of these similar events has been performed and a database has been built from the result of this relocation incoming earthquakes are routinely compared to this database and relocated and the database is updated preliminary results are presented and discussed manuscript received 21 may 2001

an inter laboratory comparison of the electron probe microanalysis of glass geochemistry abstract tephrochronology commonly relies upon grain discrete analysis of glass shards to reveal the subtle geochemical differences between tephras from past explosive volcanic eruptions the use of electron probe microanalysis for this purpose is widely accepted by tephrochronologists it is widely recognised that both precision and accuracy must be maximised and that rigorous standardisation procedures must be followed in this paper the performances of seven northern european electron microprobe centres are compared using a geochemically homogeneous obsidian secondary standard the results reveal that a number of tephra oriented probe centres could benefit from exercises similar to the programme outlined within in particular it is evident that a number of these centres undertaking tephrochronological investigations have generated geochemical data that may be inadequate in terms of distinguishing between tephras inaccuracy in the determination of sodium is seen to be the main difficulty in recent years the application of distal tephrochronology to stratigraphical problems in the northern european quaternary record has become increasingly common geochemical standardisation is essential at an early stage in the development of a regional tephrochronological framework and we hope exercises such as presented here will encourage the production of reliable tephra geochemical data

basin inversion and contractional reactivation of inherited normal faults a review based on previous and new experimental models abstract compressional inversion of former extensional sedimentary basins is a particularly common phenomenon given that passive margins share the same destiny of being subsequently incorporated into fold and thrust belts during basin inversion pre existing faults may concentrate stress and localise future thrust ramps or may be reactivated recording reversal of movement from extension to reverse this process has attracted attention largely because of its economic implications related to petroleum and ore deposit prospects and seismic hazard assessment since more than two decades analogue modelling has been used to indentify and or test a number of parameters relevant for the inversion process this paper aims therefore to offer a reasoned review of the analogue modelling work done on the subject coupling such previous results with those of a new experimental series inspired to the northern apennines stratigraphy and evolution past models have explored the role of main factors governing fault reactivation susceptibility such as fluid pressure fault weakness fault steepness angle of shortening and sediment loading the new models have addressed the role played by geometry and strength of a basal ductile layer during inversion two sets of sand silicone models were first extended orthogonally at different velocities to produce dissimilar pre inversion internal geometries and then shortened coaxially at different velocities to vary the brittle ductile coupling the experimental results confirm the selectiveness of fault inversion and reveal strong similarities with structural styles of tectonic inversion reported from the northern apennines and various areas worldwide the preferred geological model inferred from this modelling involves contribution of 1 syn inversion rotation of pre existing faults to shallower dip and 2 rotation of principal stress axes which could explain the invariable reactivation of only one of the two oppositely dipping graben bounding faults these factors would thus interact with the other well established parameters controlling the fault reactivation process

identification and dating of tephra layers from quaternary sedimentary sequences of inner anatolia turkey abstract results presented here are part of a research programme to investigate the environmental evolution in central anatolia during the pleistocene in this study tephra are used as chronostratigraphical markers between lacustrine sequences studied in cores or in sections surrounding eruptive centres of the central anatolian province at different locations in the konya plain and cappadocia tephra have been identified characterized and linked to eruptions of the nearby volcanoes seven different tephra have been clearly identified in lacustrine sequences of the konya plain 14 c dates on shells or organic matter as well as 230 th 234 u ages on gypsum give a chronological framework to the tephra layers in addition the study of the sediment fill of the eski acigol maar near nevsehir has allowed the recognition of several eruptions during late glacial and holocene in the vicinity of acigol the results show the first tephra to be identified in lacustrine sequences of anatolia they also show the cappadocian volcanism to be very young 35 ka this young volcanism is often of a basaltic type and does not include thick differenciated pyroclastic deposits

use of single grain geochemistry of cryptic tuffs and volcaniclastic sandstones improves the tephrostratigraphic framework of olduvai gorge tanzania single grain geochemical composition of volcaniclastic sandstones can be a potential tool to improve correlations of mixed pyroclastic epiclastic deposits to test this trachytic tuffs of the paleoanthropologically important flk flk n and flk nn sites of pleistocene olduvai gorge bed i tanzania are used as an established tephrostratigraphic framework against which to test volcaniclastic sandstone correlations fluvio lacustrine sandstones and tuff samples were collected from eight archeological trenches between tuffs ib and id across a 500 m transect including leakey s famous zinjanthropus flk and oh 7 oh 8 flk nn sites a previously unknown thin fine mineralogically unique black trachyandesitic fallout ash was discovered below tuff ic compositions of individual augite feldspar and titanomagnetite grains from sandstones between tuffs ib and ic reveal some ib equivalent material and a new compositional assemblage distinct from the sandwiching marker tuffs mineral compositions of the tripartite volcaniclastic sandstone between tuffs ic and id are similar to id volcaniclastic sandstone grain fingerprints further refine correlations between fluvio lacustrine sections within the area providing support for proposed high resolution stratigraphic reconstruction of the zinjanthropus and oh 7 oh 8 land surfaces this method might be applied to other sections where pyroclastic particles are admixed but distinct tuffs are not preserved

basin inversion and fault reactivation in laboratory experiments abstract a series of analogue models have been performed to get insights into the relationships between the reactivation of pre existing normal faults and the orientation of a successive compressive stress field the models were deformed in two phases 1 a first extension phase h 3 generating a graben and 2 a successive compressive phase with the orientation of the shortening direction h 1 trending between 0 and 90 obliquity angle to the faults bounding the graben the deepening of this graben was accompanied by syn tectonic sedimentation that included a basal ductile layer simulating salt in nature overlain by a brittle sand pack the experimental results suggest that the development of compressive structures is strongly controlled by the pre existing normal faults and by the obliquity angle the experiments have invariably shown that the extensional faults were reactivated during shortening whatever the value of the angle whereas strike slip reactivation of major normal faults is favoured by low obliquity angles mostly dip slip reactivation of pre existing structures is instead promoted for high obliquity angles the analysis of model results highlights the important role played by a ductile layer at the base of the basin fill and the obliquity angle in controlling both strain partitioning and brittle ductile decoupling

structural development of the taza guercif basin as a constraint for the middle atlas shear zone tectonic evolution abstract the neogene taza guercif basin in north eastern morocco is located in correspondence of the eastern termination of the rifian arc and is aligned along with the middle atlas shear zone since tortonian the tectonic evolution of the taza guercif basin was tied to repeated advancements of the rifian front and to the transpressive tectonics of the middle atlas shear zone the major structures in this basin consist of thrust related anticlines aligned along with the middle atlas structures and second order normal faults elongated according to the rifian trend the latter are well developed mainly in the north western sector of the basin bab stout area apart from the bab stout area the basin is dominated by compressive and transpressive structures guercif transpressive area the shortening directions responsible for the development of the major and minor compressive structures in the basin vary from nnw to nne but no superposition relationships have been found this change of the paleo stress field orientations is here ascribed to a progressive deformation under the constant push between africa and europe an evolutionary model for the development of these two structural areas in relation to the tectonics of the rif and of the middle atlas is here proposed in this model the sinistral transpressive middle atlas shear zone is regarded as the boundary between the moroccan meseta microplate to the west and the african indenter to the east which is moving faster to the north

late oligocene recent stress evolution in rift basins of northern and central thailand implications for escape tectonics abstract the tertiary rift basins of thailand are known through sub surface seismic and borehole data collected for hydrocarbon and coal exploration outcrops in open cast coal mines and a few natural outcrops these data provide mixed perspectives on how the basins evolved some providing data on ages and structural geometries others palaeostress data in general the region evolved under approximately e w extension although the extension direction probably changed periodically within basins extension was episodically interrupted by inversion events associated with sub horizontal nw se to ne sw 1 direction there is no evidence to suggest that the string of rift basins running from n thailand and laos into the gulf of thailand evolved in a similar way on the contrary the evolution of each basin seems different although certain regional trends along the rift system are apparent as follows 1 oligocene lower miocene extension is widespread in the region 2 in central and northern thailand middle miocene extension is also important and extension persisted into the upper miocene pliocene 3 in the extreme south of the area w natuna basin penyu basin malay basin extension ceased in the earliest miocene 4 in the northern gulf of thailand extension ceased in the middle miocene 5 thermal subsidence is greatest up to 4 km in the south malay pattani w natuna and penyu basins and least in northern thailand a few tens to hundreds of metres 6 inversion in the southern gulf of thailand was intense and occurred during the lower and middle miocene in the northern gulf of thailand inversion is very mild and occurred during the lower and middle miocene onshore inversion is patchy during the miocene but is strongest in the northwestern rift basins particularly the li basin the most widespread inversion event that affects the north occurred during the plio pleistocene it might be associated with the change from left to right lateral motion on the red river fault the relationship between strike slip faults and rift basins in terms of timing of extensional and inversion events and palaeostress orientation and evolution is more complex than can be explained by simple escape tectonic models

structural evolution of the rides prerifaines morocco structural and seismic interpretation and analogue modelling experiments the rides prerifaines rp of morocco constitute the leading edge of the rif chain they involve a triassic palaeocene succession deposited on a peneplained palaeozoic fold belt and accumulated in basins delimited by ne sw trending normal fault systems a significant hiatus separates an overlying middle miocene upper miocene foredeep sequence the reconstruction of the complex structural evolution of the rp during the later compressive phases that affected the rif chain since middle miocene time has been the aim of this paper we integrated field structural analyses seismic line interpretation and analogue modelling in order to evaluate the control exerted by the late triassic jurassic normal fault systems onto the later compressive tectonics the maximum compression direction associated with the first compressive phase is roughly ne sw to ene wsw oriented during this phase the mesozoic basin fill was scooped out from the graben and the main decollement level were the triassic evaporites since pliocene times the maximum compression direction was oriented roughly n s during this phase the rp assumed their present structural setting the earlier normal faults delimiting the mesozoic graben were reactivated in a strike slip mode also involving the palaeozoic basement the analogue modelling experiments demonstrated that the basement reactivation promoted salt tectonics and favoured fluid circulation

the geology of mount hasan stratovolcano central anatolia turkey mount hasan is a double peaked stratovolcano located in central anatolia turkey the magmas erupted from this multi caldera complex range from basalt to rhyolite but are dominated by andesite and dacite two terminal cones big mt hasan and small mt hasan culminate at 3253 m and 3069 m respectively there are four evolutionary stages in the history of the volcanic complex stage 1 kecikalesi volcano 13 ma stage 2 palaeovolcano 7 ma stage 3 mesovolcano and stage 4 neovolcano the eruptive products consist of lava flows lava domes and pyroclastic rocks the later include ignimbrites phreatomagmatic intrusive breccias and nuees ardentes sometimes reworked as lahars the total volume is estimated to be 354 km 3 the area extent 760 km 2 textural and mineralogical data suggest that both magma mixing and fractional crystallization were involved in the generation of the andesites and dacites the magmas erupted from the central volcanoes show a transition with time from tholeite to calc alkaline three generations of basaltic strombolian cones and lava flows were emplaced contemporaneously with the central volcanoes the corresponding lavas are alkaline with a sodic tendency

correlating tephras and cryptotephras using glass compositional analyses and numerical and statistical methods review and evaluation abstract we define tephras and cryptotephras and their components mainly ash sized particles of glass crystals in distal deposits and summarize the basis of tephrochronology as a chronostratigraphic correlational and dating tool for palaeoenvironmental geological and archaeological research we then document and appraise recent advances in analytical methods used to determine the major minor and trace elements of individual glass shards from tephra or cryptotephra deposits to aid their correlation and application protocols developed recently for the electron probe microanalysis of major elements in individual glass shards help to improve data quality and standardize reporting procedures a narrow electron beam diameter 3 5 m can now be used to analyze smaller glass shards than previously attainable reliable analyses of microshards defined here as glass shards in part 2 of the review we describe critically assess and recommend ways in which tephras or cryptotephras can be correlated in conjunction with other information using numerical or statistical analyses of compositional data statistical methods provide a less subjective means of dealing with analytical data pertaining to tephra components usually glass or crystals phenocrysts than heuristic alternatives they enable a better understanding of relationships among the data from multiple viewpoints to be developed and help quantify the degree of uncertainty in establishing correlations in common with other scientific hypothesis testing it is easier to infer using such analysis that two or more tephras are different rather than the same adding stratigraphic chronological spatial or palaeoenvironmental data i e multiple criteria is usually necessary and allows for more robust correlations to be made a two stage approach is useful the first focussed on differences in the mean composition of samples or their range which can be visualised graphically via scatterplot matrices or bivariate plots coupled with the use of statistical tools such as distance measures similarity coefficients hierarchical cluster analysis informed by distance measures or similarity or cophenetic coefficients and principal components analysis pca some statistical methods cluster analysis discriminant analysis are referred to as machine learning in the computing literature the second stage examines sample variance and the degree of compositional similarity so that sample equivalence or otherwise can be established on a statistical basis this stage may involve discriminant function analysis dfa support vector machines svms canonical variates analysis cva and anova or manova or its two sample special case the hotelling two sample t2 test randomization tests can be used where distributional assumptions such as multivariate normality underlying parametric tests are doubtful compositional data may be transformed and scaled before being subjected to multivariate statistical procedures including calculation of distance matrices hierarchical cluster analysis and pca such transformations may make the assumption of multivariate normality more appropriate a sequential procedure using mahalanobis distance and the hotelling two sample t2 test is illustrated using glass major element data from trachytic to phonolitic kenyan tephras all these methods require a broad range of high quality compositional data which can be used to compare unknowns with reference training sets that are sufficiently complete to account for all possible correlatives including tephras with heterogeneous glasses that contain multiple compositional groups currently incomplete databases are tending to limit correlation efficacy the development of an open online global database to facilitate progress towards integrated high quality tephrostratigraphic frameworks for different regions is encouraged

machine learning classifiers for attributing tephra to source volcanoes an evaluation of methods for alaska tephras glass composition based correlations of volcanic ash tephra traditionally rely on extensive manual plotting many previous statistical methods for testing correlations are limited by using geochemical means masking diagnostic variability we suggest that machine learning classifiers can expedite correlation quickly narrowing the list of likely candidates using well trained models eruptives from alaska s aleutian arc alaska peninsula and wrangell volcanic field were used as a test environment for 11 supervised classification algorithms trained on nearly 2000 electron probe microanalysis measurements of glass major oxides representing 10 volcanic sources artificial neural networks and random forests were consistently among the top performing learners accuracy and kappa 0 96 their combination as an average ensemble effectively improves their performance using this combined model on tephras from eklutna lake south central alaska showed that predictions match traditional methods and can speed correlation although classifiers are useful tools they should aid expert analysis not replace it the eklutna lake tephras are mostly from redoubt volcano besides tephras from known holocene active sources holocene tephra geochemically consistent with pleistocene emmons lake volcanic center dawson tephra but from a yet unknown source is evident these tephras are mostly anchored by a highly resolved varved chronology and represent new important regional stratigraphic markers

mechanisms of subduction accretion as implied from the broken formations in the apennines italy mesoscale structural analysis of the ligurian broken formations of the northern apennines and the regional occurrence of subduction related structures indicate polyphase folding as the mechanism responsible for progressive disruption the evidence for direct correlation between regionally extensive noncylindrical folds and tectonic disruption has a strong bearing on determining how the ligurian accretionary prism evolved for example the block in matrix structure of the ligurian tectonic melanges is produced through extension developed along fold limbs in a compressive stress field as expected from offscraping and intraprism deformation the model implied by the mesoscale and macroscale analyses of the ligurian tectonic melanges provides one mechanism of accretion reconciling two deformation styles i e stratal disruption and folding commonly seen in ancient accretionary prisms furthermore this model could be relevant in active accretionary prisms especially in the intraprism part where the seismic and drilling data are sparse

insights from analogue modelling into the deformation mechanism of the vaiont landslide abstract the vaiont landslide southern alps italy represents one of the most catastrophic landslides in the world recorded in the modern history the landslide occurred on 9th october 1963 involved about 3 10 8 m 3 of rock that collapsed in an artificial lake more than 1900 people died as a consequence of the tsunami produced by the sudden fall of the mass in the water despite the importance of this event many aspects of the vaiont rockslide still remain unexplained particularly its fast emplacement in order to obtain a better understanding of the vaiont disaster this paper focuses on the results of analogue models designed to get insights into the internal and surficial deformation patterns that characterized the sliding rock mass plan view reconstructions of surface model displacement reveal that the rock mass is subdivided into compartments with different relative movements and differential rotations believed to have played a significant role in causing the fast collapse the deformation of the analogue models compared with geological cross sections and in situ data suggests that sliding of the rock mass was accomplished by the development of some new or the reactivation of pre existing fractures into the rock mass

southern california hypocenter relocation with waveform cross correlation part 2 results using source specific station terms and cluster analysis we obtain precise relative relocations for more than 340 000 southern california earthquakes between 1984 and 2002 by applying the source specific station term ssst method to existing p and s phase picks and a differential lo cation method to about 208 000 events within similar event clusters identified with waveform cross correlation the entire catalog is first relocated by using existing phase picks a reference 1d velocity model and the ssst method of richards dinger and shearer 2000 we also perform separate relocations of imperial valley events by using a velocity model more suited to this region next we apply cluster analysis to the waveform cross correlation output to identify similar event clusters we re locate earthquakes within each similar event cluster by using the differential times alone keeping the cluster centroid fixed to its initial ssst location we estimate standard errors for the relative locations from the internal consistency of differential locations between individual event pairs these errors are often as small as tens of meters in many cases the relocated events within each similar event cluster align in planar features suggestive of faults we observe a surprising number of such faults at small scales that strike nearly perpendicular to the main seismicity trends in general the fine scale details of the seismicity reveal a great deal of structural com plexity in southern california fault systems

a classification of thrust fronts variations in structural style at thrust fronts are examined to determine whether they represent different stages of typical thrust sheet development or unique events as orogenic stresses declined thrust fronts are classified as buried or emergent in which either the sole thrust died out in the subsurface or emerged to the synorogenic surface buried thrust fronts are subdivided into two types type 1 fronts end in broad zones of low strain type 2 fronts end in zones of high strain emergent thrust fronts may display significant horizontal displacement strongly emergent or limited displacements of about 1 km weakly emergent tip stick thrust fronts exhibit high strains and out of sequence thrusting different types of thrust fronts are linked by transitional tip li e anticlines and strike slip zones most thrust front types represent different stages of typical thrust sheet development but those in type 1 display atypical development unique to thrust fronts

continental arc volcanism and tectonic setting in central anatolia turkey abstract the neogene and quaternary volcanism of central anatolia represents the central sector of the anatolian volcanic arc related to continental collision between the afro arabian and eurasian plates it is closely associated with a complex system of tectonic depressions related to brittle deformations of transtentional type and which commenced in the late miocene the volcanism here considered can be divided into three main periods of activity separated by important deformative and erosive events the first period is represented by a mostly andesitic effusive activity the second period is characterized by the emplacement of a thick ignimbritic sequence and shows an areal distribution up to 11 000 km 2 seven ignimbrite units have been recognized the three main units were found at a distance of more than 100 km from the presumed source area geological and sedimentological data lead us to recognize the melendiz dag volcanic complex and the ciftlik caldera as the probable ignimbrites source vent during the third period great andesitic basaltic stratovolcanoes and a number of prevalently acid monogenic centres developed the relationship between the volcanic activity is clearly conditioned by the main transcurrent fault systems present in central anatolia the neogene quaternary volcanic activity prevalently developed along the ene wsw karaman sivas lineament most of the great central volcanoes developed at the intersection between the ene wsw trends and the ecemis and tuz golu transcurrent faults the structural interpretation of the quaternary monogenic centres is more difficult probably they are related to the very recent n s fault swarms which cross the anatolides and the taurus range