kinematics of the western africa eurasia plate boundary from focal mechanisms and gps data summary the western mediterranean displays a complex pattern of crustal deformation distributed along tectonically active belts developed in the framework of slow oblique plate convergence we used earthquake and global positioning system gps data to study the present day kinematics and tectonics of the africa eurasia plate boundary in this region crustal seismicity and focal mechanisms analysed in terms of seismic moment release and seismic deformation outline the geometry of major seismic belts and characterize their tectonics and kinematics continuous gps data have been analysed to determine euler vectors for the nubian and eurasian plates and to provide the global frame for a new mediterranean gps velocity field obtained by merging continuous and campaign observations collected in the 1991 2005 time span gps velocities and displacements predicted by the nubia eurasia rotation pole provide estimates of the deformation accommodated across the tectonically active belts the rather simple deformation occurring in the atlantic region characterized by extension about perpendicular to the middle atlantic and terceira ridges and right lateral motion along the gloria transform fault turns into a complex pattern of deformation occurring along broader seismic belts where continental lithosphere is involved our analysis reveals a more complex fragmentation of the plate boundary than previously proposed the roughly e w trending mainly compressive segments i e southwestern iberia northern algeria and southern tyrrhenian where plate convergence is largely accomodated across rather localized deformation zones and partially transferred northward to the adjacent domains i e the algero balearic and tyrrhenian basins are interrupted by regions of more distributed deformation i e the rif alboran betics tunisia libya and eastern sicily or limited seismicity i e the strait of sicily which are characterized by less homogeneous tectonics regimes mainly transcurrent to extensional in correspondence of the observed breaks tectonic structures with different orientation interfere and we find belts with only limited deformation i e the high and middle atlas the tunisian atlas and the offshore tunisia libya belt that extends from the plate boundary into the nubian plate along pre existing tectonic lineaments our analysis suggest that the sicilian pelagian domain is moving independently from nubia according to the presence of a right lateral and extensional decoupling zone corresponding to the tunisia libya and strait of sicily deformation zone despite the space variability of active tectonic regimes plate convergence still governs most of the seismotectonic and kinematic setting up to the central aeolian region in general local complexities derive from pre existing structural features inherited from the tectonic evolution of the mediterranean region on the contrary along calabria and the apennines the contribution of the subducted ionian oceanic lithosphere and the occurrence of microplates i e adria appear to substantially modify both tectonics and kinematics finally gps data across the gibraltar arc and the tyrrhenian calabria domain support the hypothesis that slab rollback in these regions is mostly slowed down or stopped

formal ratification of the quaternary system period and the pleistocene series epoch with a base at 2 58 ma in june 2009 the executive committee of the international union of geological sciences iugs formally ratified a proposal by the international commission on stratigraphy to lower the base of the quaternary system period to the global stratotype section and point gssp of the gelasian stage age at monte san nicola sicily italy the gelasian until then had been the uppermost stage of the pliocene series epoch the base of the gelasian corresponds to marine isotope stage 103 and has an astronomically tuned age of 2 58 ma a proposal that the base of the pleistocene series epoch be lowered to coincide with that of the quaternary the gelasian gssp was also accepted by the iugs executive committee the gssp at vrica calabria italy which had hitherto defined the basal boundary of both the quaternary and the pleistocene remains available as the base of the calabrian stage age now the second stage of the revised pleistocene in ratifying these proposals the iugs has acknowledged the distinctive qualities of the quaternary by reaffirming it as a full system period correctly complied with the hierarchical requirements of the geological timescale by lowering the base of the pleistocene to that of the quaternary and fully respected the historical and widespread current usage of both the terms quaternary and pleistocene copyright 2009 john wiley sons ltd

fluids in coesite bearing rocks of the tso morari complex nw himalaya evidence for entrapment during peak metamorphism and subsequent uplift fluid inclusions trapped in coesite bearing rocks provide important information on the fluid phases present during ultrahigh pressure metamorphism the subduction related coesite bearing eclogites of the tso morari complex himalaya contain five major types of fluids identified by microthermometry and raman spectroscopy these are 1 high salinity brine 2 n 2 3 ch 4 4 co 2 and 5 low salinity aqueous fluids these fluids were trapped during both deep subduction and exhumation processes the coesite bearing rocks are inferred to have been buried to a depth of 120 km where they experienced ultrahigh pressure metamorphism the fluid rock interaction provides direct evidence for fluid derivation during a deep subduction process as demonstrated by silica carbonate assemblages in eclogite high salinity brine n 2 and ch 4 inclusions are remnants of prograde and peak metamorphic fluids whereas co 2 and low salinity aqueous fluids appear to have been trapped late during uplift the high salinity brine was possibly derived from subducted ancient metasedimentary rocks whereas the n 2 and ch 4 fluids were likely generated through chemical breakdown of nh 3 bearing k minerals and graphite alternatively ch 4 might have been formed by a mixed fluid that was released from calcareous sediments during subduction or supplied through subducted oceanic metabasic rocks high density co 2 is associated with matrix minerals formed during granulite facies overprinting of the ultrahigh pressure eclogite during retrogression to amphibolite facies conditions low salinity fluids were introduced from external sources probably the enclosing gneisses this source enhances salinity differences as compared to primary saline inclusions the subducting indian lithosphere produced brines prior to achieving maximal depths of 120 km where fluids were instead dominated by gaseous phases subsequently the indian lithosphere released co 2 rich fluids during fast exhumation and was then infiltrated by the low salinity aqueous fluids near the surface through external sources elemental modelling may improve quantitative understanding of the complexity of fluids and their reactions

numerical simulations of an observed gravity current and gravity waves in an environment characterized by complex stratification and shear abstract numerical simulations of a gravity current in an environment characterized by complex stratification and vertical wind shear have been performed using a nonhydrostatic two dimensional dry primitive equation model data from one of the most complete documentations to date of gravity waves associated with a gravity current presented in an earlier study are used both to prescribe the gravity current s environment and for validation of the simulated gravity current and its associated gravity waves these comparisons indicate that the gravity current observed by a doppler wind profiler and sodars was well simulated in terms of depth density contrast and propagation speed and that the model produced a variety of gravity waves similar in many ways to these observed because uncertainties remained concerning the gravity wave generation mechanisms derived from the observations e g wavelengths were not observed the validated simulations are used to test these tentative hypotheses the simulatio

mineralogy fluid inclusions and carbon isotopes of the kaman iron deposits central anatolia turkey implication for ore genesis and hydrothermal evolution abstract the kaman iron deposits are located in central anatolia and are hosted by the triassic bolcadag marble and upper cretaceous celebi granitoid magnetite mineralization manifests as rhythmic banded and irregular lenses which can be massive or disseminated within calcic marble and skarn zones six main paragenetic stages of skarn formation and ore deposition have been identified 1 na ca alterations composed of plagioclase an4 31 and actinolite 2 a prograde stage representing oxidized mineralogy dominated by diopside di62 98joh0 4 grossular andradite grs15 84alm4 8sps1 4 and magnetite 3 a retrograde stage consisting of epidote ep51 62cli38 49 magnetite calcite quartz and less abundant sulfides and chlorite 4 a quartz calcite pyrite stage containing pyrite quartz calcite and chlorite and 5 6 quartz carbonate and supergene stages characterized by quartz calcite hematite and chalcedony goethite fluid inclusion and carbon isotope studies have shown that the prograde stage formed from moderate high salinity 7 1 to 70 wt nacl eq and high temperature 339 to 600 c fluids liquid and vapor rich inclusions in an early garnet were homogenized in the liquid and vapor phases in a similar temperature range 513 and 529 c the 18o and 13c of calcites that accompany rhythmic banded magnetite ranged from 22 82 to 23 50 and 4 68 to 5 31 respectively the retrograde stage was formed from low high salinity 2 9 to 45 4 wt nacl eq and low high temperature 167 to 459 c fluids the 18o and 13c of skarn calcites ranged from 4 34 to 15 86 and 3 57 to 0 23 respectively the quartz calcite pyrite stage was formed from low salinity 3 1 7 5 wt nacl eq and temperature 171 392 c fluids the 18o and 13c values were 2 38 and 2 43 respectively the quartz carbonate stage formed from low salinity 3 6 to 5 7 wt nacl eq and temperature 129 to 169 c in all phases the eutectic and clathrate melting temperatures ranged from 59 5 to 52 2 c and 4 4 to 12 0 c respectively this indicates that the solutions contain h2o nacl cacl2 mgcl2 co2 these fluid inclusion data suggest that fluid boiling occurred under pressures between 60 and 70 mpa based on hydrostatic consideration during the prograde stage the main magnetite deposition occurred following boiling with rising salinity and temperature magmatic hydrothermal fluids and in the pressure range of 15 to 50 mpa depletion in 13c was attributed to high temperature fluid infiltration and indicates an open system volatilization process it is suggested that the retrograde stage had developed in two episodes with the carbofracturing effect triggered by co2 the carbon isotope data of calcites indicate the mixing of low temperature metasomatic and meteoric water in later stages the mineralogy microthermometry and carbon isotope results reveal that kaman iron deposits were developed by a combination of processes such as contact infiltration metasomatism fluid rock interaction cooling and fluid mixing as a result of decreasing pressure

scale independence of basin hypsometry and steady state topography abstract basin hypsometry has long been used as an indicator of stages in landscape evolution it has also served as a tool for detecting tectonically active regions whether hypsometric curve and its integral are independent of differences in basin size and relief has been discussed in many recent studies the taiwan mountain range the result of an oblique collision between the phillipine sea plate and the eurasian plate provides an excellent opportunity to study landscape evolution in relation to steady state conditions taking advantage of the space for time substitution concerning the building process of taiwanese mountains this study sampled major drainage basins for hypsometric analysis from the southern tip of the island to the northern end this study found that the area previously known as steady state topography is characterized by 1 the hypsometric integral hi close to 0 5 2 s shaped hypsometric curves and 3 normally distributed elevations the response time required for a drainage basin of various strahler orders to evolve from exposure of sub aerial erosion to steady state topography ranges from 0 5 to 2 0 my and is longer for basins of a higher strahler order the hi value of 0 5 for a drainage basin seems critical in terms of landscape evolution the scale dependence of basin hypsometry is manifested mainly by the fact that hi of basins increases as basin order and or basin size decreases this study also found that basin hypsometry is scale independent where topography is in a steady state scale dependence occurs only when drainage basins are in a non steady state the basin hypsometry may therefore be useful to probe into the nature of steady state topography

goringe alboran tell tectonic zone a transpression system along the africa eurasia plate boundary neotectonic structures distributed from the goringe bank to the tell atlas mountains show that the africa eurasia plate boundary in the western mediterranean corresponds to an east west trending deforming zone goringe alboran tell main pliocene and quaternary tectonic structures of the northern atlas mountains are northeast southwest striking fault related folds similar to that of el asnam and are related to north south to northwest southeast compressional movements active tectonics in agreement with the main seismicity distribution and focal mechanisms also support an oblique plate convergence and the existence of a 50 100 km wide transpression zone from goringe across alboran to the tell atlas mountains a kinematic model shows the interaction between dextral transcurrent faults and left lateral faults with block rotations and no lateral extension pinned model shortening and lateral movement rates during the quaternary are estimated to be 1 0 2 3 mm yr and block rotation rate is estimated as 2 5 3 9 m y the plate boundary may correspond to a transpression zone active thrust faults being controlled by deep seated dextral transcurrent faults

upb and rbsr geochronological evidence for late hercynian tectonic and alpine overthrusting in kabylian metamorphic basement massifs northeastern algeria abstract a geochronological study was carried out on rocks from the petite kabylie massif in northeastern algeria to determine the timing of magmatic and metamorphic events affecting a metamorphic complex involved in a major phase of alpine overthrusting this type of metamorphic complex is known throughout the northwestern african orogenic domain the maghrebide chain northern algeria the betic cordilliera southeastern spain and calabria southern italy the study which is mainly focused on the petite kabylie area is supplemented with the dating of rocks from a key occurrence of synkinematic granite in the grande kabylie massif in petite kabylie an early phase of magmatism at 455 19 ma and a second phase in the range 270 280 ma 278 3 ma and 273 6 ma are dated using the u pb zircon method a hercynian metamorphic event is recorded in detrital zircons dated at 370 6 ma rb sr micas ages are scattered between 280 ma and 7 ma suggesting a mixing system or a history of complex cooling between the late hercynian and the alpine events the basement here is also characterized by two superimposed metamorphic events the first one of lp and the second of hp type the earlier event could be around 280 ma or older 370 ma while the second event is thought to be either late hercynian eoalpine or even alpine in age the petrological and geochronological data can best be explained by a continuous evolution of the 280 ma old granite and its associated hp metamorphism taking place over a short time span and ending with extensive deformation around 270 ma ago as suggested by the fast cooling of the crust this interpretation is in agreement with the u pb zircon age of the synkinematic granite from grande kabylie dated between 284 2 ma and 273 6 ma which corresponds to a late hercynian transtensional regime the eoalpine tectono metarmorphic events are not constrained from geochronological data a low grade alpine event is recorded during the eocene oligocene 40 25 ma from rb sr biotite ages which agrees with the age of basement overthrusting late stage of low temperature activity continued up to 7 10 ma as indicated by some biotite ages

effect of drainage area on hypsometry from an analysis of small scale drainage basins in the siwalik hills central nepal hypsometry of drainage basins area elevation analysis has generally been used to infer the stage of geomorphic development and to study the influence of varying forcing factors i e tectonics climate lithology on topography however the scale dependence of hypsometry has generally been neglected in order to assess the scale dependence of hypsometry this study focuses on the sensitivity of hypsometry to different digital elevation model dem resolutions and on the influence of drainage area hypsometry inferred from different dems is shown to be robust against variations of their resolution however hypsometry appears to be dependent on drainage area we propose that this scale dependence may reflect the varying importance of river and hillslope processes with basin area copyright 1999 john wiley sons ltd

ice volume and sea level during the last interglacial during the last interglacial period 125 000 years ago sea level was at least several meters higher than at present with substantial variability observed for peak sea level at geographically diverse sites speculation that the west antarctic ice sheet collapsed during the last interglacial period has drawn particular interest to understanding climate and ice sheet dynamics during this time interval we provide an internally consistent database of coral u th ages to assess last interglacial sea level observations in the context of isostatic modeling and stratigraphic evidence these data indicate that global eustatic sea level peaked 5 5 to 9 meters above present sea level requiring smaller ice sheets in both greenland and antarctica relative to today and indicating strong sea level sensitivity to small changes in radiative forcing

evaluation of morphometric proxies for uplift on sequences of coral reef terraces a case study from sumba island indonesia sequences of coral reef terraces characterized by staircase morphologies and a homogeneous lithology make them appropriate to isolate the influence of uplift on drainage morphology along the northern coast of sumba island indonesia we investigated the correlations between landscape morphology and uplift rates which range from 0 02 to 0 6 mm yr 1 we studied eight morphometric indices at two scales whole island 11 000 km2 and within sequences of reefal terraces 3000 km2 at the latter scale we extracted morphometric indices for 15 individual catchments draining mostly the reefal terraces and for 30 areas undergoing specific ranges of uplift rates draining only the reefal terraces indices extracted from digital elevation models include residual relief incision stream gradient indices sl and ksn the hypsometric integral drainage area mean relief and the shape factor we find that sl the hypsometric integral mean relief and the shape factor of catchments positively correlate with uplift rates whereas incision residual relief and ksn do not more precisely we find that only the areas that are uplifting at a rate faster than 0 3 mm yr 1 can yield the extreme values for these indices implying that these extreme values are indicative of fast uplifting areas however the relationship is not bivalent because any uplift rate can be associated with low values of the same indices for all indices the transient conditions of the drainage influence the correlation with pleistocene mean uplift rates illustrating the necessity to extract morphometric indices with an appropriate choice of catchment scale this type of analysis helps to identify the morphometric indices that are most useful for tectonic analysis in areas of unknown uplift allowing for easy identification of short spatial variations of uplift rate and detection of areas with relatively fast uplift rates in unstudied coastal zones

equilibrium dihedral angles in the system h2o co2 nacl calcite and implications for fluid flow during metamorphism fluid calcite calcite dihedral angles have been measured for fluids in the system h2o co2 nacl between 1 and 2 kbar and 550 750 c it is found that the calcite calcite h2o dihedral angle decreases steadily with addition of nacl from a value of about 80 pure water to 44 60 wt nacl the co2 h2o system displays a well defined minimum at x co 2 0 5 with a dihedral angle of 50 in contrast to those of pure co2 and h2o which are 90 and 80 respectively experiments containing fluids which are immiscible at run conditions showed a bimodal distribution of dihedral angles in the co2 h2o nacl system which can be approximately correlated with the compositions of the two fluid phases such bimodality was only observed for immiscible fluids in the h2o nacl system if the quench rate exceeded about 200 c per min this is probably due to the extremely rapid establishment of the single phase dihedral angle on quenching the fluid phase topology in devolatilising marbles will only be a connected network for very saline brines and fluids with x co 2 close to 0 5 fluids trapped in fluid inclusions in calcite grains in marbles may be predominantly h2o rich or co2 rich and of low salinity all other fluid compositions in the h2o co2 nacl calcite system will occupy isolated pores the largest of which will grow at the expense of the smallest escape of fluid produced during devolatilisation reactions under such conditions will occur by fluid overpressuring and hydrofracture in contrast previous experimental studies of quartz fluid dihedral angles between 950 and 1100 c watson and brenan 1987 predict that quartz dominated lithologies will permit pervasive flow of h2o nacl fluids but not of h2o co2 fluids documented geological examples of differences in permeability and fluid flow mechanism between metamorphic argillites psammites and limestones which support the results of the experimental studies are discussed

mineral virginia earthquake illustrates seismicity of a passive aggressive margin 1 the august 2011 m 5 8 mineral virginia earthquake that shook much of the northeastern u s dramatically demonstrated that passive continental margins sometimes have large earthquakes we illustrate some general aspects of such earthquakes and outline some of the many unresolved questions about them they occur both offshore and onshore reaching magnitude 7 and are thought to reflect reactivation of favorably oriented generally margin parallel faults created during one or more wilson cycles by the modern stress field they pose both tsunami and shaking hazards however their specific geologic setting and causes are unclear because large magnitude events occur infrequently microseismicity is not well recorded and there is little if any surface expression of repeated ruptures thus presently active seismic zones may be areas associated with higher seismicity over the long term the present loci of activity that migrates or aftershock zones of large prehistoric earthquakes the stresses causing the earthquakes may result from platewide driving forces glacial isostatic adjustment localized margin stresses and or dynamic topography the resulting uncertainties make developing cost effective mitigation strategies a major challenge progress on these issues requires integrating seismic geodetic and geological techniques

alternate interpretation of the messinian salinity crisis controversy resolved a high resolution chronology of the mediterranean messinian salinity crisis is proposed two types of evaporite deposition may be distinguished those in marginal areas vs those in basinal ones their diachroneity is deduced from the stratigraphic relationships linking these evaporites to a major messinian erosional surface a two step model is proposed for the evolution of the salinity crisis through time during the first phase from 5 75 to 5 60 ma the deposition of marginal evaporites took place in response to a modest sea level fall in the second interval from 5 60 to 5 32 ma the mediterranean basin became isolated during this later period the deposition of basinal evaporites and the cutting of the mediterranean canyons took place

a nonclassical cold front observed during cops 91 frontal structure and the process of severe storm initiation abstract this case study addresses the issue of gravity current and bore development at surface cold fronts and the role of these phenomena in the generation of severe frontal convection the event investigated occurred on 27 april 1991 during the cooperative oklahoma profiler studies 1991 field project the development of a bore from a gravity current like structure along a cold front the subsequent propagation of the bore ahead of the front on a low level inversion and the process of severe thunderstorm development along the front are revealed by a dense network of remote sensing and other special observations evidence for the gravity current and bore is strengthened by comparisons made between the synthesized observations and theory the bore developed after a nocturnal inversion which acted as a waveguide had become established the bore and gravity current were both evident as fine lines in the radar reflectivity displays a microscale envelope of enhanced water vapor with an embedded roll cl

evidence for a post 3 16 ma change in nubia eurasia north america plate motions we combine updated gps velocities from the nubian nu eurasian eu and north american na plates with 500 new 3 16 myr average seafloor spreading rates and nine transform fault azimuths from the northern atlantic and arctic basin seafloor spreading centers to estimate and test for changes in the relative motion between these plates the numerous new seafloor spreading rates and gps velocities improve our ability to detect recent changes in the relative motions of these plates the angular velocity vector that best fits the eu na gps velocities lies significantly north of the 3 ma average pole in accord with previously published geologic evidence that the eu na pole has migrated northward since v3 ma although we also find evidence for a significant post 3 ma change in nu na motion it is less compelling because the nubian plate gps velocity field is sparse and nu na seafloor spreading rates appear to have remained steady within the 1 mm yr 31 uncertainties if we systematically decrease the seafloor spreading rates to correct for outward displacement of seafloor spreading magnetic lineations the nu eu pole derived from gps site velocities lies more than 30 angular degrees south of the tightly constrained 3 ma average estimate and predicts significantly slower and more oblique present day nu eu convergence in the mediterranean both models for nu eu motion pass a key test for their accuracy namely they correctly predict strike slip motion along the well mapped gloria fault east of the azores the change to more oblique nu eu motion may reflect increasing difficulty in maintaining margin normal convergence within this continent continent collision zone 8 2003 published by elsevier b v

active folding in the algerian earthquake of 10 october 1980 a fold controlling the form of the local topography near el asnam algeria increased in amplitude at the time of the earthquake of 10 october 1980 the deformation occurred rapidly in an elastic brittle manner and not in the gradual ductile fashion in which folds are normally thought to develop

blind reverse faulting system associated with the mont chenoua tipaza earthquake of 29 october 1989 north central algeria a shallow and damaging earthquake struck the region of tipaza located on the coast 70 km to the west of algiers north central algeria the main shock was felt as far as 200 km from the epicentral area and particularly in the urbanized zone of algiers the main shock epicentre determined by craag is on mt chenoua close to the coastline coseismic surface breaks with 4 0 km of fault length and 7 0 cm of vertical displacement appeared on the southern side of mt chenoua they consist of cracks and fissures on vertical bedding planes that belong to a neogene flexure the aftershock activity was recorded for several weeks and comprised more than 100 seismic events per day with 1 m 5 aftershocks are distributed in a ene wsw to ne sw zone extending offshore a nw se cross section indicates that seismic events affect the crust to a maximum depth of 20 km showing a complex fault plane geometry dipping to the nw for the main shock the focal mechanism solution obtained from the readings of first motion polarities of seismograms yields an ene wsw reverse fault dipping to the nnw which is in good agreement with both field observations and the aftershock distribution at depth the occurrence of the mt chenoua tipaza moderate sized event in a previously identified active zone improves the seismotectonic characterization of this part of the tellan atlas mountains this thrust and fold geological domain also shows active folds capable of producing larger earthquakes since only a small portion of the sahel anticline ridge has been reactivated a serious seismic hazard must be urgently recognized in the algiers region

fluid immiscibility in metamorphic rocks evidence of fluid immiscibility in metamorphic rocks comes in the best of all worlds from fluid inclusion observations in fact fluid immiscibility should be anticipated over the full range of metamorphic conditions provided that appropriate bulk fluid compositions are present in a review paper entitled metamorphic fluids the evidence from fluid inclusions crawford and hollister 1986 summarized the role of fluid immiscibility in metamorphism was only recognized after serious study of fluid inclusions in metamorphic rocks was underway in the late 1970s and has yet to attract the attention of more than a handful of petrologists studying metamorphic rocks since then tremendous progress has been made a huge amount of fluid inclusion studies have convincingly shown that immiscible fluids can be present in rocks of all bulk compositions and at all p t conditions thermodynamic databases of minerals solid solutions and fluid mixtures along with the development of gibbs free energy minimization programs now allow for detailed prediction of the evolution of phase assemblages and mineral compositions in p t space significant progress has also been made in understanding reaction kinetics diffusional and convective mass transport and the interpretation of fluid rock interaction during metamorphism given the vast fluid inclusion evidence of immiscibility it would appear however that phase petrology and mass transport in any specific rock where fluids are involved are not correctly interpreted if possible or proven immiscibility is not considered relatively few studies directly link mineral reactions with immiscible fluids therefore this review aims at working out the effects of fluid immiscibility on the progress of metamorphic reactions and fluid transport over a wide range of conditions questions arise directly from the fluid inclusion record in metamorphic rocks this chapter however is organized the other way round at first it summarizes phase relations of fluid systems pertinent to

on the long lasting sequences of coral reef terraces from se sulawesi indonesia distribution formation and global significance many islands of the eastern indonesian archipelago exhibit late cenozoic sequences of coral reef terraces in se sulawesi on the tukang besi and buton archipelagos we identified 23 islands bearing such sequences remote sensing imagery and field mapping combined to u th and 14c dating enable to establish a chronologic framework of the reef terrace sequences from wangi wangi buton as well as on the neighbouring smaller islands of ular siumpu and kadatua we identified the terraces from the last interglacial maximum mis 5e at elevations lower than 20 m except on w kadatua where it is raised at 34 5 m such elevations yield low to moderate upper pleistocene uplift rates 0 3 mm yr 1 on se buton island a sequence culminates at 650 m and includes at least 40 undated strandlines next to this exceptional sequence on the sampolawa peninsula 18 strandlines culminate at 430 m dated samples at the base of this sequence 40 m yield mean middle pleistocene uplift rates of 0 14 0 09 mm yr 1 extrapolation of these uplift rates compared to the geological setting suggests that the sequences of the sampolawa peninsula provide a record of sea level high stands for the last 3 8 0 6 ma the sequences on se buton island therefore constitute the best preserved long lasting geomorphic record of plio quaternary sea level stands worldwide

active thrust faulting offshore boumerdes algeria and its relations to the 2003 mw 6 9 earthquake 1 we investigate the active seismogenic fault system in the area of the 2003 mw 6 9 boumerdes earthquake algeria from a high resolution swath bathymetry and seismic survey a series of 5 main fault propagation folds 20 35 km long leave prominent cumulative escarpments on the steep slope and in the deep basin fault activity creates plio quaternary growth strata within uplifted areas such as a rollover basin on the slope and piggyback basins in the deep ocean most thrusts turn to fault propagation folds at the sub surface and depict ramp flat trajectories we find that the two main slip patches of the 2003 mw 6 9 boumerdes earthquake are spatially correlated to two segmented cumulative scarps recognized on the slope and at the foot of the margin the overall geometry indicates the predominance of back thrusts implying underthrusting of the neogene oceanic crust

plio quaternary reactivation of the neogene margin off nw algiers algeria the khayr al din bank the algiers region northern algeria is known to be seismically active with recurrent large m 6 earthquakes because of the lack of high resolution bathymetry the offshore structures remained for a long time poorly known thanks to a new marine data base maradja 2003 cruise the offshore part of the margin is accurately mapped and new active and recent structures are described west of the bay of algiers the margin enlarges forming the khayr al din bank interpreted as a tilted block of the passive margin born during the opening of the algero provencal basin at the slope break a 80 km long fault tip quaternary fold namely the khayr al din fault extends at the foot of the margin off nw algiers and represents the largest active structure of the coastal area together with the sahel anticline we also map for the first time a set of overlapping en echelon active folds in the upper part of the khayr al din bank located off previously known active structures on land most of these faults represent actually a threat for the algiers region in terms of seismic hazard but also geological hazards such as tsunamis as most of them depicts significant dimensions and slip rates the highest long term horizontal shortening rate is found on the khayr al din fault and is estimated at 0 5 0 1 mm yr with a maximal magnitude of 7 3 which provides one of the highest seismogenic potential in the region a new tectonic framework for the algiers region is proposed in which the main south dipping offshore structure of opposite vergence relative to most thrusts on land appears to be nowadays the main driving fault system as also found further east in the boumerdes m 6 8 2003 rupture zone the overall apparent pop up structure of the recent and active faults may result from a progressive migration of the plate limit from the late miocene north dipping suture zone on land to the quaternary south dipping main khayr al din fault at sea suggesting a process of subduction inception

e w opening of the algerian basin western mediterranean we present geophysical and geological evidence of fast 2 cm yr 1 in the east and 5 cm yr 1 in the west e w spreading between 16 and 8 ma in the region behind the gibraltar arc in the algerian basin

modelled atmospheric temperatures and global sea levels over the past million years the climate has passed through a series of glacials and interglacials over the past million years but the nature of this cyclicity in terms of temperature ice volume and sea level and the underlying causes are not well known bintanja et al use a new method to deduce a one million year time series of these variables the reconstructed records are much longer than other methods have provided for any of these variables individually the most intense glacial stages were 17 c colder than today and most of the continental ice was present in north america strong cooling in the beginning of glacials was found to precede ice sheet build up these findings may shed light on the causes of ice age cycles marine records of sediment oxygen isotope compositions show that the earth s climate has gone through a succession of glacial and interglacial periods during the past million years but the interpretation of the oxygen isotope records is complicated because both isotope storage in ice sheets and deep water temperature affect the recorded isotopic composition1 2 3 4 5 separating these two effects would require long records of either sea level or deep ocean temperature which are currently not available here we use a coupled model of the northern hemisphere ice sheets6 and ocean temperatures forced to match an oxygen isotope record for the past million years compiled from 57 globally distributed sediment cores to quantify both contributions simultaneously we find that the ice sheet contribution to the variability in oxygen isotope composition varied from ten per cent in the beginning of glacial periods to sixty per cent at glacial maxima suggesting that strong ocean cooling preceded slow ice sheet build up the model yields mutually consistent time series of continental mean surface temperatures between 40 and 80 n ice volume and global sea level we find that during extreme glacial stages air temperatures were 17 1 8 c lower than present with a 120 10 m sea level equivalent of continental ice present

turbulent mixing processes in atmospheric bores and solitary waves deduced from profiling systems and numerical simulation abstract families of solitary waves solitons associated with two atmospheric bores on the same day were observed by an unprecedented number of ground based and airborne profiling systems during the international h2o project ihop in addition a very high resolution numerical weather prediction model initialized with real data was used with success to simulate one of the bores and the evolving soliton the predicted wave amplitude phase speed wavelength and structure compared well to these extraordinarily detailed observations the observations suggest that during the active phase when turbulent mixing was active which was prior to bore collapse the bores and waves vigorously mixed dry air from above a nocturnal boundary layer down to the surface refractivity computed from near surface radar observations showed pronounced decreases due to sudden drying during the passage of the bores in this phase but refractivity increases appeared during the period of bore collapse during both phases the

the role of slab detachment processes in the opening of the western central mediterranean basins some geological and geophysical evidence abstract a review of the geological and geophysical data from the central and western mediterranean region and the present day upper mantle structure derived from tomographic studies are utilized in order to define the oligocene recent geodynamic evolution for the area in line with previous work we suggest that the miocene quaternary opening of the western and central mediterranean basins is the result of back arc extension due to the roll back toward the southeast of a northwestward subducting african slab in a geodynamic setting pinned between the alpine and betic collisional zones we find however that this general pattern is complicated by four different detachment events which occurred beneath the alps early oligocene the betic chain aquitanian northern africa langhian and the apennines late miocene pliocene we show that each of these events determines a major tectonic reorganization within the european plate

geomorphic response of coastal streams to low intermediate and high rates of uplift medocino triple junction region northern california analysis of three dimensional morphological properties of 24 coastal drainage basins that have evolved in areas of low 3 m 1 000 yr rates of uplift near the mendocino triple junction mtj coastal northern california identified channel gradients as the best indicator of tectonism in the landscape lower order tributaries best reflect tectonically controlled differences the largest streams examined of third order are able to adjust to most base level change and maintain their profile form whereas lower order streams farther upstream tend to accumulate the effects of net base level fall and have steepest profiles in the areas of highest uplift rates variations in steepness of first order channel gradients indicate that 1 high uplift rates in the wake of the mtj have existed for at least 73 000 yr and 2 differential tilt of the region to the north and south of the current locus of highest uplift rate is occurring in association with regional uplift although first order streams are excellent indicators of areas of both high uplift rates and regional differential tilting they are less useful in distinguishing between areas of low and intermediate uplift rate analysis of the longitudinal profile of the main trunk stream of ten of the 24 drainage basins using the stream gradient index was more useful to categorize broadly the uplift rates and to distinguish between streams in low and intermediate uplift rate areas although the hypotheses tested herein do not identify the exact mechanism off uplift in the mtj region they do indicate that the nature of deformation is most likely regional tilt rather than crustal shortening with localized compressional folding and thrust faulting they also indicate that geomorphic responses trail in the wake of the uplift rate response caused by development of a slab window beneath the north american plate 1 maximum uplift rates occur 9 km south of the northern boundary of the slab window 2 maximum mean first order channel gradient occurs 16 km south of the northern edge of the slab window and 3 maximum drainage basin relief occurs 20 km south of the northern edge of the slab window associated lag times between passage of the southern edge of the subducted gorda plate slab and geomorphic responses are 160 000 yr for maximum uplift rates 290 000 yr for maximum channel gradients and 370 000 yr for maximum relief

landscape response to tectonic forcing digital elevation model analysis of stream profiles in the mendocino triple junction region northern california the topographic evolution of orogens is fundamentally dictated by rates and patterns of bedrock channel incision quantitative field assessments of process based laws are needed to accurately describe landscape uplift and denudation in response to tectonics and climate we evaluate and calibrate the shear stress or similar unit stream power bedrock incision model by studying stream profiles in a tectonically active mountain range previous work on emergent marine terraces in the mendocino triple junction region of northern california provides spatial and temporal control on rock uplift rates digital elevation models and field data are used to quantify differences in landscape morphology associated with along strike northwest to southeast changes in tectonic and climatic conditions analysis of longitudinal profiles supports the hypothesis that the study area channels are in equilibrium with current uplift and climatic conditions consistent with theoretical calculations of system response time based on the shear stress model within uncertainty the profile concavity of the trunk streams is constant throughout the study area 0 43 as predicted by the model channel steepness correlates with uplift rate these data help constrain the two key unknown model parameters the coefficient of erosion k and the exponent associated with channel gradient n this analysis shows that k cannot be treated as a constant throughout the study area despite generally homogeneous substrate properties for a reasonable range of slope exponent values n best fit values of k are positively correlated with uplift rate this correlation has important implications for landscape evolution models and likely reflects dynamic adjustment of k to tectonic changes due to variations in orographic precipitation and perhaps channel width sediment load and frequency of debris flows the apparent variation in k makes a unique value of n impossible to constrain with present data

coastal staircase sequences reflecting sea level oscillations and tectonic uplift during the quaternary and neogene many coasts feature sequences of quaternary and neogene shorelines that are shaped by a combination of sea level oscillations and tectonics we compiled a global synthesis of sea level changes for the following highstands mis 1 mis 3 mis 5e and mis 11 also we date the apparent onset of sequences of paleoshorelines either from published data or tentatively extrapolating an age for the uppermost purported oldest shoreline in each sequence including the most documented mis 5e benchmark we identify 926 sequences out of which 185 also feature holocene shorelines six areas are identified where elevations of the mis 3 shorelines are known and 31 feature elevation data for mis 11 shorelines genetic relationships to regional geodynamics are further explored based on the elevations of the mis 5e benchmark mean apparent uplift rates range from 0 01 0 01 mm yr hotspots to 1 47 0 08 mm yr continental collision passive margins appear as ubiquitously uplifting while tectonic segmentation is more important on active margins from the literature and our extrapolations we infer ages for the onset of formation for 180 coastal sequences sea level fingerprinting on coastal sequences started at least during mid miocene and locally as early as eocene whether due to the changes in the bulk volume of seawater or to the temporal variations in the shape of ocean basins estimates of eustasy fail to explain the magnitude of the apparent sea level drop thus vertical ground motion is invoked and we interpret the long lasting development of those paleoshore sequences as the imprint of glacial cycles on globally uplifted margins in response to continental compression the geomorphological expression of the sequences matches the amplitude and frequency of glacial cyclicity from middle pleistocene to present day moderately fast 100 000 yrs oscillating sea levels favor the development of well identified strandlines that are distinct from one another pliocene and lower pleistocene strandlines associated with faster cyclicity 40 000 yrs are more compact and easily merge into rasas whereas older cenozoic low frequency eustatic changes generally led to widespread flat lying coastal plains

coastal uplift west of algiers algeria pre and post messinian sequences of marine terraces and rasas and their associated drainage pattern the north africa passive margin is affected by the ongoing convergence between the african and eurasian plates this convergence is responsible for coastal uplift folding and reverse faulting on new and reactivated faults on the margin the active deformation is diffuse and thus rather difficult to locate precisely we aim to determine how a coastal landscape evolve in this geodynamic setting and gain insights into active tectonics more particularly we evidence and quantify coastal uplift pattern of the chenoua sahel and algiers reliefs algeria using sequences of marine terraces and rasas and computing several morphometric indices from the drainage pattern upper and middle pleistocene uplift rates are obtained by fossil shoreline mapping and preliminary u th dating of associated coastal deposits extrapolation of these rates combined to analyses of sea level referential data and spatial relationships between marine terraces rasas and other geological markers lead us to tentatively propose an age for the highest coastal indicators purported the oldest values of morphometric indices showing correlations with uplift rate allow us to analyze uplift variation on area devoid of coastal sequence geological and geomorphological data suggest that coastal uplift probably occurred since the middle miocene it resulted in the emergence of the algiers massif followed by the sahel ridge massif the sahel ridge has asymmetrically grown by folding from west to east and was affected by temporal variation of uplift compared to previous study the location of the sahel fold axis has been shifted offshore near the coast the chenoua fault vertical motion does not offset significantly the coastal sequence mean apparent uplift rates and corrected uplift rates since 120 ka are globally steady all along the coast with a mean value of 0 055 0 015 mm year apparent and of 0 005 0 045 mm year corrected for eustasy mean apparent coastal uplift rates between 120 and 400 ka increase eastward from 0 045 0 025 to 0 19 0 12 mm year without correction for eustasy or from 0 06 0 06 to 0 2 0 15 mm year with correction for eustasy in addition the combination of structural and geomorphic data suggests a low uplift rate for the southern part of the algiers massif

simulated density currents beneath embedded stratified layers abstractthe goal of this research is to investigate the impacts of a stably stratified layer embedded within a neutrally stratified environment on the behavior of density currents in an effort to extend the environmental regimes examined by liu and moncrieff such environments frequently support severe weather events to accomplish this goal nonhydrostatic numerical model experiments are performed in which the strength and height of the embedded stably stratified layer within a neutrally stratified environment are varied the 1 km deep stable layer base is varied between 1 2 and 3 km agl additionally the strength of the stable layer is systematically varied between brunt vaisala frequencies of 0 006 0 012 and 0 018 s 1 following the methodology of liu and moncrieff the model and grid setup are also similar to that of liu and moncrieff utilizing the arakawa c grid leapfrog advection a robert asselin filter and grid spacing of 100 and 50 m in the horizontal and vertical directions respectively

aridity and humidity two aspects of the late miocene climate of north africa and the mediterranean abstract the physiography of north africa is not greatly changed from that of the messinian with the drawdown of the mediterranean in the late messinian the then existing river systems were incised into the landscape and emptied into lake cyrenaica which occupied the substantially drained eastern mediterranean basin the record of incision provides a record of the magnitude of the messinian river systems an analysis of these river systems demonstrates that messinian rainfall a consequence of the zeit wet phase was greatest in east and south central north africa in keeping with the derivation of the water mainly from the indian ocean in central north africa the eosahabi river flowed from messinian lake chad eroding the east tibesti valley and cutting a channel which is especially well preserved near the coast of the gulf of sirt the penetrated sediments of lake cyrenaica and the marginal basins of the messinian transgression are known as the upper evaporites and are generally fine clastics gypsarenites and gypsum anhydrite they were rapidly deposited underlying them is the halite of the lower evaporites this sequence of upper and lower evaporites is much like the lower halite of the tortonian south gharib formation and the overlying clastics and anhydrite of the messinian zeit formation in the gulf of suez red sea area this type of sequence is termed an evaporitic couplet and as has been demonstrated for the gulf of suez red sea is a consequence of a transition from a dry to a more humid climate in a restricted or semirestricted basin this transition occurred at about 7 5 ma in the gulf of suez red sea and at about 5 8 ma in the mediterranean the zeit wet phase manifest in the above events developed in association with the initiation and development of the asian monsoon and the drying of the mediterranean it can be understood in terms of the development of an evolving monsoon desert system the asian monsoon was initiated 8 7 ma in association with the uplift of tibet at this time the north african desert zone was displaced northwards to be over the mediterranean and central and eastern north africa became seasonally humid a concept is advanced in which the early stage of the development of the asian monsoon is seen as having two phases alternating at the precessional ca 21 ka cycle one phase transferred moisture from the indian ocean mainly to southern asia the other phase transferred moisture mainly to north africa with the drawdown of the mediterranean at about 5 8 ma the zeit wet phase intensified a further northward movement of the humid and desert zones occurred at the time of drawdown with the messinian and early pliocene transgressions the wet phase ameliorated but a substantial river system still crossed central north africa at about 4 6 ma north africa became drier probably in response to the developing dominance of the features of the monsoon that transferred moisture mainly to southern asia features of the monsoon that are well recognised today

preliminary results of a paleoseismological analysis along the sahel fault algeria new evidence for historical seismic events abstract the 60 km long sahel ridge west of algiers tell atlas north algeria is considered as an ene wsw fault propagation fold running along the mediterranean coast and associated with a north west dipping thrust its proximity with algiers makes this structure a potential source of destructive earthquakes that could hit the capital city as occurred in 1365 ad and 1716 ad the first paleoseismologic investigation on the sahel ridge was conducted in order to detect paleo ruptures related to active faulting and to date them from the first investigations in the area a first trench was excavated across bending moment normal faults induced by flexural slip folding in the hanging wall of the sahel anticline thrust ramp paleoseismological analyses recognize eight rupture events affecting colluvial deposits 14c dating indicates that these events are very young six of them being younger than 778 ad the first sedimentary record indicates two ruptures before 1211 ad i e older than the first historical earthquake documented in the region three events have age ranges compatible with the 1365 1673 and 1716 algiers earthquakes whereas three other ones depict very recent ages i e younger than 1700 ad potential of these secondary extrados faults for determining paleoseismic events and thrust behaviour is discussed

structural styles and neogene petroleum system around the yusuf habibas ridge alboran basin mediterranean sea the algerian offshore is part of the southern margin of the western mediterranean sea the western part of this offshore area represents the transitional margin between the south algero balearic basin and the alboran basin the study area includes the southern and eastern parts of the alboran basin and the northwestern part of the algerian margin and is in the western part of the plate boundary between eurasia and africa figure 1 the yusuf habibas ridge is a major ew striking structure of this complex plate boundary separating the eastern and southern parts of the alboran basin from the south algero balearic basin martinez garcia et al 2011 and references therein the ridge played an important role during the neogene alboran westward block migration between the africa and iberia plates while the kabylies blocks migrated southward and accreted to africa furthermore the ongoing nw se convergence between africa and iberia has induced a new stress field since 7 ma ago replacing an earlier stress

high density co2 n2 inclusions in eclogite facies metasediments of the munchberg gneiss complex se germany the eclogite facies metasedimentary rocks in the munchberg gneiss complex t 630 30 c p 17 24 kbar locally contain co2 n2 rich fluid inclusions of extremely low molar volumes 32 cm3 mol in quartz these fluid compositions are mainly found in rocks intercalated with calcsilicate bands densities were determined from low temperature phase transitions like stable or metastable homogenization l v l partial homogenization s l v s l and the transition s l l l liquid v vapour s solid the high fluid densities are in agreement with eclogite facies pressure and temperature and subsequent amphibolite facies co2 n2 inclusions were not observed in adjacent eclogites nor in non calcareous metasediments these rock types contain predominantly h2o rich inclusions correlating with amphibolite facies conditions the variation of fluid composition with lithological differences indicates local fluid gradients and speaks against a pervasive fluid flow during eclogite facies metamorphism

relative sea level fall since the last interglacial stage are coasts uplifting worldwide the growing interest in quantification of vertical ground motion stems from the need to understand in detail how the earth s crust behaves for both scientific and social reasons however only recently has the refinement of dating techniques made possible the use of paleoshorelines as reliable tools for tectonic studies although there are many local studies of quaternary vertical motions of coastlines we know of no comprehensive worldwide synthesis here we provide a compilation of 890 records of paleoshoreline sequences with particular emphasis on the last interglacial stage marine isotopic stage mis 5e 122 ka the quality of dating mis 5e makes it a reliable marker to evaluate vertical ground motion rates during the late quaternary on a global scale the results show that most coastal segments have risen relative to sea level with a mean uplift rate higher than 0 2 mm yr i e more than four times faster than the estimated eustatic drop in sea level the results also reveal that the uplift rate is faster on average for active margins than for passive margins neither dynamic topography nor glacio hydro isostasy may explain sustained uplift of all continental margins as revealed by the wide distribution of uplifted sequences of paleoshorelines instead we suggest that only plate tectonic processes reconcile all observations of quaternary coastal uplift we propose that long term continental accretion has led to compression of continental plates and uplift of their margins therefore this study concludes that plate tectonics processes impact all margins and emphasizes the fact that the notion of a stable platform is unrealistic these results therefore seriously challenge the evaluation of past sea levels from the fossil shoreline record

revisiting tectonic corrections applied to pleistocene sea level highstands tectonic displacement contaminates estimates of peak eustatic sea level and equivalently minimum continental ice volumes determined from the elevation of quaternary interglacial highstand markers for sites at which a stratigraphic or geomorphic marker of peak marine isotope stage mis 5e sea level exists the standard approach for estimating local tectonic uplift or subsidence rates takes the difference between the elevation of the local highstand marker and a reference mis 5e eustatic value commonly chosen as 6 m and divides by the age of the marker the resulting rate is then applied to correct the elevation of all other local observed sea level markers for tectonic displacement including peak highstands of different ages e g mis 5a mis 5c and mis 11 under the assumption that the tectonic rate remained constant over those periods this approach introduces two potentially significant errors first the peak eustatic value adopted for mis 5e in most previous studies i e 6 m is likely incorrect second local peak sea level during mis 5e is characterized by significant departures from eustasy due to glacial isostatic adjustment in response to both successive glacial interglacial cycles and excess polar ice sheet melt relative to present day values we use numerical models of glacial isostatic adjustment that incorporate both of these effects to quantify the plausible range of the combined error and show that even at sites far from melting ice sheets local peak sea level during mis 5e may depart from eustasy by 2 4 m or more we also demonstrate that the associated error in the estimated tectonic rates can significantly alter previous estimates of peak eustatic sea level during quaternary highstands notably those associated with earlier interglacials e g mis 11

comment on active coastal thrusting and folding and uplift rate of the sahel anticline and zemmouri earthquake area tell atlas algeria by s maouche m meghraoui c morhange s belabbes y bouhadad h haddoum tectonophysics 2011 509 69 80 abstract based on geomorphologic analyses and leveling survey of quaternary coastal indicators i e marine terraces and notches along of a 50 km long coastal stretch of the algerian coast west of algiers maouche et al 2011 interpret the coastal segment to have undergone high uplift rates i e 0 84 1 19 mm yr since last interglacial maximum mis 5e 122 6 ka in table 1 140 ka in maouche et al 2011 and 2 5 mm yr for the last 31 ka this uplift was said to be due to repeated seismic events that would have occurred during the last 140 ka and more particularly during the late pleistocene we raise major issues about the interpretation proposed by maouche et al 2011 these issues deal with 1 the use of previous chronological data and the chronostratigraphy proposed 2 processes involved in the creation of coastal staircase morphology on the coast west of algiers 3 anomalously high uplift rates compared to other available data on the same geomorphic features marine terraces in the same setting of reactivated passive margins and 4 the fold geometry used for modeling of fold growth and its implications for coseismic surface deformation and uplift estimates in other words we contest the statements that coseismic deformation is the cause of staircase morphology on the mediterranean coast west of algiers and that very large m 7 earthquakes have occurred there in the past

neogene quaternary slow coastal uplift of western europe through the perspective of sequences of strandlines from the cotentin peninsula normandy france abstract the cotentin peninsula normandy france displays sequences of marine terraces and rasas the latter being wide late cenozoic coastal erosion surfaces that are typical of western european coasts in portugal spain france and southern england remote sensing imagery and field mapping enabled reappraisal of the cotentin coastal sequences from bottom to top the n cotentin sequence includes four previously recognized pleistocene marine terraces t1 to t4 at elevations

finescale vertical structure and dynamics of some dryline boundaries observed in ihop abstract several radar fine lines all with a humidity contrast were sampled in the central great plains during the 2002 international h2o project ihop this study primarily uses aircraft and airborne millimeter wave radar observations to dynamically interpret the presence and vertical structure of these fine lines as they formed within the well developed convective boundary layer in all cases the fine line represents a boundary layer convergence zone this convergence sustains a sharp contrast in humidity and usually in potential temperature across the fine line the key question addressed herein is whether at the scale examined here 10 km the airmass contrast itself in particular the horizontal density virtual potential temperature difference and resulting solenoidal circulation is responsible for the sustained convergence and the radar fine line for the 10 cases examined herein the answer is affirmative

tectonic and lithologic controls on bedrock channel profiles and processes in coastal california 1 recent theoretical models suggest that topographic characteristics of bedrock channels are products of interactions among tectonics substrate resistance and the climatically modulated erosive ability of the river the degree to which these factors influence the form of channel profiles is poorly quantified at present here we investigate bedrock channels developed across the southern flank of the santa ynez mountains california uniform climate and systematic variations in lithology and rock uplift rate along the range allow comparison of channel morphology between 1 channels eroding rocks of uniform and nonuniform strength and 2 channels experiencing differences in tectonic forcing we combine field observations surveys and analysis of digital data to determine topographic and hydraulic characteristics of bedrock channels at a constant rock uplift rate streams flowing from resistant to less resistant bedrock exhibit highly concave profiles and increased gradients along lower reaches relative to channels developed in uniform bedrock these effects are interpreted as responses to 1 an increase in substrate resistance to channel incision in the upper reaches and 2 transport limited gradients along lower reaches comparisons of channels developed across uniform lithology but experiencing an approximately sevenfold difference in rock uplift rate reveal an approximately twofold increase in gradient and an approximately threefold decrease in width in this landscape the combined channel adjustments of gradient and width are consistent with a fluvial incision model in which channel incision rate is linearly proportional to mean bed shear stress

grain boundary migration of water and carbon dioxide during uplift of garnet zone alpine schist new zealand deformed quartz veins in garnet zone schist adjacent to the active alpine fault new zealand have fluid inclusions trapped along quartz grain boundaries textures suggest that the inclusions formed in their present shapes during annealing of the deformed veins many of the inclusions are empty but some contain carbon dioxide with densities that range from 0 16 to 0 80 g cm 3 no water nitrogen or methane was detected the inclusions are considerably more co2 rich than either the primary metamorphic fluid 5 co2 or fluids trapped in fracture related situations in the same or related rocks 50 co2 enrichment of co2 is inferred to have resulted from selective migration wicking of saline water from the inclusions along water wet grain boundaries after cooling induced immiscibility of a water co2 mixture inclusion volumes changed after loss of water non wetting co2 remained trapped in the inclusions until further percolation progressively removed co2 in solution this mechanism of fluid migration dominated in ductile quartz rich rocks near but below the brittle ductile transition at deeper levels hydraulic fracturing is also an important mechanism for fluid migration whereas at shallower levels advection through open fractures dominates the fluid flow regime

synthetic h2oco2 fluid inclusions in spontaneously nucleated forsterite enstatite and diopside hosts the method and applications abstract synthetic h2o co2 fluid inclusions have been produced in forsterite diopside and enstatite hosts during the spontaneous nucleation and growth of these phases at t 800 980 c and p 6100 7800 bars via the reactions 2 trem 18h 2 o 4 diopside 3 forsterite 5si oh 4 2h 2 o 1 trem 3h 2 o 2 diopside 3 enstatite si oh 4 2h 2 o 2 the inclusions are large 10 40 m abundant and commonly of regular shape making them ideal as standards for microthermometric and spectroscopic analyses the technique provides the opportunity to study fluid inclusion trapping mechanisms and their potential effect on inclusion chemistry the fluid inclusions exhibit a small degree of compositional scatter about the ambient composition deviations between the ambient and inclusion composition increase for experiments performed in the presence of low 3 8 c thermal gradients along the capsule length this observation suggests that compositional heterogeneities may develop in the absence of fluid convection in the capsule the effect on the inclusion composition however does not exceed 3 mol in xco2 for all inclusions studied the advantages of this technique are 1 it provides a means of producing fluid inclusions of known compositions in hosts other than quartz and 2 inclusion formation is relatively slow allowing ample time for the p t x fluid conditions of the run to equilibrate the disadvantages are that the small grains produced can be difficult to work with and the host producing reactions are viable over a relatively narrow range of p t x fluid conditions

production of carbonic fluids during metamorphism of graphitic pelites in a collisional orogen an assessment from fluid inclusions abstract fluid inclusions in quartz veins within proterozoic metamorphic rocks in the black hills south dakota were examined by microthermometry and raman spectroscopy to assess the evolution of fluid compositions during regional metamorphism of organic rich shales and late orogenic magmatism both of which were related to the collision of the wyoming and superior crustal blocks fluid inclusions occur in veins that began to be generated before or during regional compression and metamorphism that reached at least garnet grade conditions and in veins within the aureole of the harney peak granite hpg where temperatures reached second sillimanite grade conditions early veins in the schists have undergone recrystallization during heating and deformation that modified the composition of early ch4 or co2 and n2 dominated inclusions these fluids were apparently trapped under conditions of immiscibility with a saline aqueous fluid phase they are interpreted to represent components generated during maturation of organic matter and dehydration of phyllosilicates during incipient metamorphism at reducing fo2 conditions most inclusions in the quartz veins are however secondary co2 bearing they imply a transition to higher fo2 conditions with increasing temperature of regional metamorphism the fo2 conditions may have been controlled by the mineral assemblage in the host metapelites the prevalence of bimodal distributions of trapped co2 n2 and aqueous endmembers in the biotite and garnet zones also suggests that two immiscible fluid phases existed during the regional metamorphism in the aureole of the hpg graphite was evidently consumed by influx of magmatic fluids co2 h2o fluid inclusions dominate but they have significantly less n2 than inclusions at lower metamorphic grades all inclusions define secondary trails in mostly unstrained quartz the bimodality of inclusion compositions is not as well defined as at lower grades with many inclusions containing intermediate co2 h2o compositions this suggests that a single fluid phase existed at the high temperatures in the granite aureole but then unmixed during cooling a set of late quartz veins with graphitized and tourmalinized selvages in the granite aureole contains ch4 bearing inclusions with little n2 the existence of ch4 in these inclusions is attributed to complexing of magmatic b with hydroxyl anions taken from the co2 h2o fluid phase effectively causing reduction in fo2 and promoting precipitation of graphite

geodetic measurements of crustal deformation in the western mediterranean and europe geodetic measurements of crustal deformation over large areas deforming at slow rates 5 mm yr over more than 1000 km such as the western mediterranean and western europe are still a challenge because 1 these rates are close to the current resolution of the geodetic techniques 2 inaccuracies in the reference frame implementation may be on the same order as the tectonic velocities we present a new velocity field for western europe and the western mediterranean derived from a rigorous combination of 1 a selection of sites from the itrf2000 solution 2 a subset of sites from the european permanent gps network solution 3 a solution of the french national geodetic permanent gps network rgp and 4 a solution of a permanent gps network in the western alps regal the resulting velocity field describes horizontal crustal motion at 64 sites in western europe with an accuracy on the order of 1 mm yr or better its analysis shows that central europe behaves rigidly at a 0 4 mm yr level and can therefore be used to define a stable europe reference frame in that reference frame we find that most of europe including areas west of the rhine graben the iberian peninsula the ligurian basin and the corsica sardinian block behaves rigidly at a 0 5 mm yr level in a second step we map recently published geodetic results in the reference frame previously defined geodetic data confirm a counterclockwise rotation of the adriatic microplate with respect to stable europe that appears to control the strain pattern along its boundaries active deformation in the alps apennines and dinarides is probably driven by the independent motion of the adriatic plate rather than by the africa eurasia convergence the analysis of a global gps solution and recently published new estimates for the african plate kinematics indicate that the africa eurasia plate motion may be significantly different from the nuvel1a values in particular geodetic solutions show that the convergence rate between africa and stable europe may be 30 60 slower than the nuvelia prediction and rotated 10 30 counterclockwise in the mediterranean

trench investigations through the trace of the 1980 el asnam thrust fault evidence for paleoseismicity during the ei asnam earthquake of 10 october 1980 ms 7 3 a clear active thrust fault with left lateral offset was observed three trenches have been excavated across this fault in order to determine slip rate and recurrence intervals between large earthquakes and thus reconstruct its past activity exposure i was excavated in the flood area created in 1980 by a pressure ridge across the cheliff and fodda rivers six flood deposits silty sandy and muddy horizons alternating with paleosoils appear in this exposure they are affected by normal faults associated with the main thrust fault assuming that every flood deposit results from a tectonic event of magnitude greater than 7 we can correlate previous flood deposits with these events exposures ii and iii display thrust faults displacing different paleosoils we propose a sequence of reconstructions based on the thickness of the various deposits and the dip slip of each tectonic event the late holocene slip rate is 0 65 mm yr for the dip slip and 0 46 mm yr for each of the horizontal and the vertical movements radiocarbon dates of coseismic movements indicate a rather irregular seismic activity during the past 7000 yr two sequences of large earthquakes around 4000 yr b p and around the modern age are separated with a period of quiescence the average late holocene recurrence interval of large earthquakes is 1061 yr however during the active faulting episodes the recurrence time varies from approximately 300 to 500 yr

deep tropospheric gravity waves created by leeside cold fronts abstract the water vapor channel of the geostationary operational environmental satellite goes 8 reveals narrow 30 km wide elongated 500 1000 km bands that propagate southward on the eastern side of the rocky mountains from colorado to texas two events in which surface and wind profiler observations show that these bands are associated with leeside cold fronts are documented in detail and several other cases are summarized the wind profilers observe vertical motions exceeding 1 m s 1 in narrow plumes at the leading edge of the fronts in broader zones in the upper troposphere and in the lower stratosphere these cause vertical displacements of up to 1 km and are responsible for the signature in water vapor images the bands occur when the rocky mountains block either arctic leeside cold fronts coming from the north or northeast or pacific cold fronts coming from the northwest the blocking changes the frontal orientation and disrupts geostrophic thermal wind balance near the terrain modified fron

the messinian diatomite deposition in the mediterranean region and its relationships to the global silica cycle abstract diatomites constitute a widely represented lithology in the messinian sections of the circum mediterranean neogene marginal basins although traditionally interpreted as genuine evidence of the gradually restricted conditions that characterized the mediterranean just before the messinian salinity crisis their coeval occurrence with a global intensification of the opaline production in the world oceans late miocene early pliocene biogenic bloom suggests that an integrative analysis of the origins of these sediments is necessary a comprehensive analysis of the geological and paleontological records suggests that the synergistic intervention of abiotic tectonic and climate reconfigurations and biotic expansion of grass dominated opal rich biomes controlling factors may have promoted a remarkable enhancement of silica flux from continents to oceans which in turn can explain the opaline burst that occurred during the late miocene at both the global and mediterranean scale the finely laminated pattern and the rich fossil content of diatomaceous deposits that are usually considered to be byproducts of anoxic conditions are briefly discussed some studies seem to indicate that instead of anoxia the aggregation and sedimentation of diatom tests may play a critical role in these processes the lower messinian diatomites of the mediterranean region are generally interbedded with organic rich sediments sapropels clearly attesting prolonged precessionally controlled periods of basin stratification and bottom water anoxia or hypoxia a causal relationship between sapropel and diatomite deposition in the mediterranean is proposed considering the possible interplay between stratification adapted diatoms and anaerobic bacteria and their respective role in influencing the marine silica cycle

seismicity and tectonic structures in the site of algiers and its surroundings a step towards microzonation we intend to reappraise the seismogenic potential of the geologic structures in the site of algiers and its surroundings a compilation of a working earthquake catalogue is first made using all events reported in all previous documentation available however for the sake of homogeneity and a certain degree of reliability of the data only revised seismic events with epicenter coordinates magnitude and or intensity are included a tectonic setting of the zone under investigation and available fault plane solutions are presented the results obtained in previous seismological studies of the most recent earthquakes of the area are also discussed the findings highlight the great interest to be taken in the detailed and timely assessment of the seismic hazard of algiers and its surroundings which is made possible by the realistic modelling of the scenario seismic input

towards subduction inception along the inverted north african margin of algeria insights from thermo mechanical models abstract while ocean subduction at continental margins is a prominent process of plate tectonics understanding how and where it begins is still being debated especially because examples of emerging ocean continent subduction in the world are rare northern algeria is currently undergoing a slow compression deformation due to the ongoing african eurasian convergence active compressional seismic activity recorded both on land and at sea indicates that the margin might be transitioning from a passive stage to an active one in order to test this hypothesis we perform thermo mechanical models of margin inversion varying thermal and rheological parameters as well as the geometry of the margin boundary we find that tectonic inversion of a young passive margin localizes at the margin toe only if the latter is strongly heated i e with an abrupt thermal gradient between oceanic and continental lithospheres otherwise deformation propagates into the weak hot oceanic lithosphere the presence of a thinned continental crust at the ocean continent transition favors either subduction of the oceanic lithosphere when the transition zone plunges towards the continent or an indentation of the lower continental crust by the oceanic lithosphere when the transition zone is vertical if the oceanic lithosphere is directly in contact with the continental margin subduction like deformation occurs during the early stages of the model but rapidly gives place to intra oceanic buckling and faulting comparing the results of the simulation to the active tectonic structures of the algerian margin we conclude that both processes emerging subduction or indentation are possible and that the presence of a thermal anomaly beneath the thinned continental margin is probable in relation with slab rupture at depth or with other thermal weakening processes

tectonic inheritance and pliocene pleistocene inversion of the algerian margin around algiers insights from multibeam and seismic reflection data 1 the algerian margin has originated from the opening of the algerian basin about 25 30 ma ago the central margin provides evidence for large scale normal faults of oligo miocene age whereas transcurrent tectonics characterizes the western margin a set of nw se oriented dextral transform faults was active during basin opening and divided the 600 km long central margin into segments of 120 150 km the upper miocene plio quaternary and present day tectonic setting is however compressional and supports the occurrence of a margin inversion a process still poorly documented worldwide we show that the central algerian margin represents a rare example of inverted margin where the process of subduction inception is particularly well expressed and helps understand how extensional and transtensive structures are involved in margin shortening using multibeam bathymetry and multichannel seismic reflection sections from the maradja 2003 and 2005 cruises we evidence pliocene pleistocene shortening with contrasting styles along the margin between west khayr al din bank and east boumerdes dellys margin of algiers pre miocene structures such as basement highs and transform faults appear to control changes of the deformation pattern along this part of the margin resulting in different widths geometries and relative positions of folds and faults plio quaternary and active blind thrust faults do not reuse oligo miocene normal and transform faults during inversion but instead grow within the continental margin as testified for instance by the 21 may 2003 mw 6 8 boumerdes zemmouri earthquake at the foot of the continental slope and at the northern sides of basement highs interpreted as stretched continental blocks of the rifted margin the inherited structures of the margin appear therefore to determine this deformation pattern and ultimately the earthquake and tsunami sizes offshore the complex geometry of the fault system along the algerian margin suggests a process of initiation of subduction in its central and eastern parts

how do sea level curves influence modeled marine terrace sequences abstract sequences of uplifted marine terraces are widespread and reflect the interaction between climatic and tectonic processes at multiple scales yet their analysis is typically biased by the chosen sea level sl curve here we explore the influence of quaternary sl curves on the geometry of marine terrace sequences using landscape evolution models lems first we modeled the young rapidly uplifting sequence at xylokastro corinth rift

evidence of mis 5 sea level highstands in gebel mousa coast strait of gibraltar north of africa abstract the last interglacial is considered the most suitable episode from which to infer patterns of rapid sea level change since its climatic conditions were similar to those of the present interglacial however specifying the true position of its sea level with high accuracy is very troublesome in the absence of sedimentological erosional or even palaeontological markers this study investigates the morphosedimentary evidence beach deposits cliff notch and shore platform of two highstands registered and dated during mis 5 stage by u series dating in the north of morocco strait of gibraltar bioerosive notches and mixed siliciclastic and carbonate deposits high energy beaches with algal bioherms were formed in coastal environments during mis 5a a sea level height of 10 m asl can be inferred for this substage the record of mis 5e substage is less defined in the geomorphological record consisting of backshore foreshore deposits located at 13 to 15 m asl a tectonic uplift rate of 0 1 mm yr has been estimated for the last 130 kyr these data are consistent with models of coastal uplifting calculated for the strait of gibraltar

the origin of intraplate deformation in the atlas system of western and central algeria from jurassic rifting to cenozoic quaternary inversion abstract analysis of petroleum exploration data supplemented by paleostress data enabled discussion of the origin of the deformation in the western and central saharan atlas algeria this intraplate area has recorded the breakup of pangea late triassic the opening of the maghrebian tethys since the dogger and subsequently its closure oligocene to present however the two periods of strong coupling between europe and africa late lutetian and pleistocene which correspond to rapid uplifts of the atlas system and important deformations are not collision related they can be correlated to the beginning and the end of the development of the western mediterranean sea

investigation of short period gravity waves with the lindenberg 482 mhz tropospheric wind profiler during four consecutive days in may 2001 convectively forced short period 6 45 min gravity waves were observed with a 482 mhz wind profiler which is continuously operated by the deutscher wetterdienst german weather service at the lindenberg observatory 60 km south east of berlin the objective of this campaign was to investigate onset and development of convectively forced gravity waves in the lower and middle troposphere the wave character could be unambiguously identified by simultaneous vertical wind and temperature measurements and their respective phase shift of 2 in accordance with previous findings convection waves were found to be generated at the top of the convective boundary layer they propagate predominantly horizontally with a slow but clearly recognizable vertical increase of wave activity the layer with significant wave activity reached the upper detection range at 7 0 km within a couple of hours on each of the observational days gravity wave activity started to decay after 16 utc with a slower rate than the simultaneously decaying forcing convection some wave activity remained during the night but at low amplitude levels the vertical wind energy component of the free atmosphere was found to be about 30 of the corresponding convective boundary layer cbl energy which is much more than previously reported values from numerical simulations the wavelet analysis of highly resolved wind profiler vertical velocity data t 16 s z 250 m in the boundary layer and free troposphere gives new insights into the temporal and vertical development of very short period convection waves through the troposphere at the cbl top a broad spectrum of wave scales with intrinsic periods between 6 and 45 min is generated with increasing height shorter scales t 13 min disappear and only longer ones remain wave trapping which is confirmed by vertically orientated phase lines is an important mechanism here copyright 2004 royal meteorological society

active coastal thrusting and folding and uplift rate of the sahel anticline and zemmouri earthquake area tell atlas algeria abstract major uplifts of late quaternary marine terraces are visible along the coastline of the tell atlas of algeria located along the africa eurasia convergent plate boundary the active tectonics of this region is associated with large shallow earthquakes m 6 5 numerous thrust mechanisms and surface fault related fold we conducted a detailed levelling survey of late pleistocene and holocene marine notches in the algiers region that experienced 0 50 m coastal uplift during the 2003 zemmouri earthquake mw 6 8 east of algiers holocene marine indicators show three pre 2003 main notch levels formed in the last 21 9 ka west of algiers on the sahel anticline the levelling of uplifted marine terraces shows a distinct staircase morphology with successive notches that document the incremental folding uplift during the late pleistocene and holocene the timing of successive uplifts related to past coseismic movements along this coastal region indicates episodic activity during the late holocene modelling of surface deformation in the zemmouri earthquake area implies a 50 km long 20 km wide ne sw trending se dipping fault rupture and an average 1 3 m coseismic slip at depth further west the 70 km long sahel fold is subdivided in 3 sub segments and shows 0 84 1 2 mm yr uplift rate in the last 120 140 ka the homogeneous holocene uplift of marine terraces and the anticline dimensions imply the possible occurrence of large earthquakes with mw 7 in the past the surface deformation and related successive uplifts are modelled to infer the size and characteristics of probable future earthquakes and their seismic hazard implications for the algiers region

kinematics of the iberia maghreb plate contact from seismic moment tensors and gps observations the iberian peninsula and the maghreb experience moderate earthquake activity and oblique nw se convergence between africa and eurasia at a rate of 5 mm yr coeval extension in the alboran basin and a n35 e trending band of active left lateral shear deformation in the alboran betic region are not straightforward to understand in the context of regional shortening and evidence complexity of deformation at the plate contact we estimate 86 seismic moment tensors mw 3 3 to 6 9 from time domain inversion of near regional waveforms in an intermediate period band those and previous moment tensors are used to describe regional faulting style and calculate average stress tensors the solutions associated to the trans alboran shear zone show predominantly strike slip faulting and indicate a clockwise rotation of the largest principal stress orientation compared to the regional convergence direction 1 at n350 e at the n algerian and sw iberian margins reverse faulting solutions dominate corresponding to n350 e and n310 e compression respectively over most of the betic range and intraplate iberia we observe predominately normal faulting and wsw ene extension 3 at n240 e from gps observations we estimate that more than 3 mm yr of african nubian eurasian plate convergence are currently accommodated at the n algerian margin 2 mm yr in the moroccan atlas and 2 mm yr at the sw iberian margin 2 mm yr is a reasonable estimate for convergence within the alboran region while alboran extension can be quantified as 2 5 mm yr along the stretching direction n240 e superposition of both motions explains the observed left lateral transtensional regime in the trans alboran shear zone two potential driving mechanisms of differential motion of the alboran betic gibraltar domain may coexist in the region a secondary stress source other than plate convergence related to regional scale dynamic processes in the upper mantle of the alboran region as well as drag from the continental scale motion of the nubian plate along the southern limit of the region in the atlantic ocean the 3 5 mm yr westward motion of the gibraltar arc relative to intraplate iberia can be accommodated at the transpressive sw iberian margin while available gps observations do not support an active subduction process in this area

a comparative fluid inclusion study of the waterville and sangerville vassalboro formations south central maine petrologic and oxygen isotope data indicate that water rich fluids infiltrated metasedimentary rocks of the waterville and sangerville formally vassalboro formations south central maine during peak metamorphism and depleted sangerville rocks in alkalis but not equivalent waterville rocks fluid inclusion data from two outcrops 1 km apart one of the waterville and the other of the sangerville formations suggest a cause for the geochemical difference between the two units postulated peak metamorphic inclusions the texturally earliest of aqueous inclusions in the metasediments approximate the water rich compositions of peak fluids predicted by mineral fluid equilibria and have average salinity in the sangerville formation three times that of equivalent waterville inclusions the higher salinity in the sangerville fluids could explain the greater alkali depletion in these rocks probable pre peak or prograde inclusions are preserved in metasediments as the texturally earliest carbonic inclusions which contain co2 ch4 n2 h2o as determined by microthermometry and raman spectrometry they may have formed by breakdown of organic matter probable retrograde inclusions occur as texturally late aqucous inclusions in healed fractures with salinity ranges indistinguishable between the two formations synmetamorphic granitic dikes present in the two outcrops were ruled out as a source for fluids in metasediments because composition and density ranges of inclusions in dikes and metasediments are fundamentally different and because there is no correlation between the abundance or composition of inclusions in a sample and proximity to dikes isochores for many of the inclusions in both metasediments and dikes are not consistent with the inferred p t conditions of their trapping but intersect at 300 to 400 c and 1 to 2 kbar the intersections probably resulted because inclusion densities continued to equilibrate during uplift and cooling until quartz became rigid the present densities are those at the last equilibration not the time of trapping in contrast the clear distinctions in inclusion compositions between dikes and between dike and country rock show that the original compositional differences generally have been preserved

global sea level fluctuations during the last interglaciation mis 5e the geomorphology and morphostratigraphy of numerous worldwide sites reveal the relative movements of sea level during the peak of the last interglaciation marine isotope stage mis 5e assumed average duration between 13072 and 11972 ka because sea level was higher than present deposits are emergent exposed and widespread on many stable coastlines correlation with mis 5e is facilitated by similar morphostratigraphic relationships a low degree of diagenesis uranium thorium u th ages and a global set of amino acid racemization aar data this study integrates information from a large number of sites from tectonically stable areas including bermuda bahamas and western australia and some that have experienced minor uplift 2 5 m 100 ka including selected sites from the mediterranean and hawaii significant fluctuations during the highstand are evident at many mis 5e sites revealed from morphological stratigraphic and sedimentological evidence rounded and flat topped curves derived only from reef tracts are incomplete and not representative of the entire interglacial story despite predictions of much different sea level histories in bermuda the bahamas and western australia due to glacio and hydro isostatic effects the rocks from these sites reveal a nearly identical record during the last interglaciation the last interglacial highstand is characterized by several defined sea level intervals slis that include sli 1 post glacial mis 6 5e termination ii rise to above present before 130 ka sli 2 stability at 2 to 3 m for the initial several thousand years 130 to 125 ka during which fringing reefs were established and terrace morphology was imprinted along the coastlines sli 3 a brief fall to near or below present around 125 ka sli 4 a secondary rise to and through 3 4 m 124 to 122 ka followed by sli 5 a brief period of instability 120 ka characterized by a rapid rise to between 6 to 9 m during which multiple notches and benches were developed and sli 6 an apparently rapid descent of sea level into mis 5d after 119 ka u th ages are used to confirm the last interglacial age of the deposits but unfortunately in only two cases was it possible to corroborate the highstand subdivisions using radiometric ages sea levels above or at present were relatively stable during much of early mis 5e and the last 6 7 ka of mis 1 encouraging a comparison between them the geological evidence suggests that significant oceanographic and climatic changes occurred thereafter midway through and continuing through the end of mis 5e fluctuating sea levels and a catastrophic termination of mis 5e are linked to the instability of grounded and marine based ice sheets with the greenland gis and west antarctic wais ice sheets being the most likely contributors late mis 5e ice volume changes were accompanied by oceanographic reorganization and global ecological shifts and provide one ominous scenario for a greenhouse world r 2007 elsevier ltd all rights reserved

late miocene environmental change in nepal and the northern indian subcontinent stable isotopic evidence from paleosols neogene sediments belonging to the siwalik group crop out in the himalayan foothills along the length of southern nepal carbon and oxygen isotopic analyses of siwalik paleosols from four long siwalik sections record major ecological changes over the past 11 m y the carbon isotopic composition of both soil carbonate and organic matter shifts dramatically starting ca 7 0 ma marking the displacement of largely c3 vegetation probably semi deciduous forest by c4 grasslands by the beginning of the pliocene all the flood plains of major rivers in this region were dominated by monsoonal grasslands the floral shift away from woody plants is also reflected by the decline and final disappearance of fossil leaves and the decrease in coal logs in the latest miocene a similar carbon isotopic shift has been documented in the paleosol and fossil tooth record of pakistan and in terrigenous organic matter from the bengal fan showing that the floral shift was probably continentwide the latest miocene also witnessed an average change of 4 in the oxygen isotopic composition of soil carbonate as observed previously in pakistan the reasons for this are unclear if not diagenetic a major environmental change is indicated perhaps related to that driving the carbon isotopic shift recently described pollen and leaf fossils from the surai khola section show that evergreen forest was gradually displaced by semi deciduous and dry deciduous forest between 11 and 6 ma the gradual nature of this floral shift which culminated in the rapid expansion of c4 grasses starting 7 0 m y ago is difficult to explain by a decrease in atmospheric pco2 alone cerling et al 1993 but fits well with a gradual onset of monsoonal conditions in the late miocene in the northern indian subcontinent himalayan uplift driving both monsoonal intensification and consumption of co2 through weathering may be the common cause behind major late miocene environmental change globally however the decline of effective moisture associated with monsoon development has probably slowed not increased the rate of consumption of co2 by chemical weathering of himalayan sediments

intensification of northern hemisphere glaciations in the circum atlantic region 3 5 2 4 ma ice rafted detritus evidence abstract records of ice rafted detritus ird from ocean drilling program sites 644 and 907 in the nordic seas and deep sea drilling program sites 610 and 607 in the north atlantic ocean are used to determine the growth and history of northern hemisphere glaciations spanning the interval from 3 6 to 2 4 ma the records document that the initiation of large scale glaciation in the circum atlantic region occurred stepwise between 3 5 and 2 4 ma with greenland leading the other areas the first major pulse of ird occurs at 3 3 ma suggesting a distinct expansion of the greenland ice sheet progressive increases in ird occur from 3 0 ma with a synchronous ice sheet development between the greenland scandinavian and north american regions starting around 2 72 2 75 ma the regional records of ird correspond to major trends in the oxygen isotope record suggesting a tight connection between the record of global ice volume and evidence for expanding glaciers in the northern hemisphere it appears as if widespread ird distribution occurs when the global ice volume surpasses certain thresholds similar to the late quaternary situation

structural analysis and interpretation of the surface deformations of the el asnam earthquake of october 10 1980 the el asnam earthquake of october 10 1980 represents the major seismotectonic event of these last decades in the west mediterranean area it has induced a large amount of surface breaks this earthquake reveals the importance of compressional phenomena that characterize nowadays the tectonics of north africa the tectonic analysis of surface rupture shows the complexity of the deformation mechanism the principal mechanism consists of the activation of a nw se trending thrust fault accompanied with a left lateral motion and with an intense deformation of the northwestern overthrusting block an accurate description of these deformations shows that for a large part the breaks geometry depends closely on the substratum structure finally the analysis of the dislocations on irrigation ducts just above the fault traces allowed a quantitative study of the deformation

evolution of the mo rich scheelite skarn mineralization at kozbudaklar western anatolia turkey evidence from mineral chemistry and fluid inclusions abstract the kozbudaklar scheelite skarn deposit in the tavsanli zone located approximately 22 km southeast of bursa is hosted by the triassic calcic inonu marble and eocene topuk pluton at least four stages have been recognized through skarn evolution scheelite skarn distributed close to the topuk pluton occurred during the early stage 1 and late stage 2 prograde substages the early prograde endo and exoskarn are composed of hedenbergite hd 96 joh 4 plagioclase an 55 64 and hedenbergite hd 61 94 joh 4 7 accompanied by calcic garnet grs 38 94 sps 1 5 alm 0 and scheelite pow 1 6 the second stage represents a relatively oxidized mineralogy dominated by diopside hd 16 48 joh 0 9 subcalcic garnet grs 24 92 sps 0 11 alm 0 31 and scheelite pow 7 32 the stage 3 and 4 mineral assemblages are characterized by few hydrous minerals in the retrograde stage and intense fracturing fluid inclusions from skarn rocks are indicative of multiple fluid events 1 low moderate salinity 5 16 wt nacl equiv inclusions homogenized dominantly by a high temperature 308 c to 600 c liquid phase in stage 1 fluid inclusions in an early garnet homogenized over a similar temperature range 440 c and 459 c into both liquid and vapor phases eutectic temperatures ranging from 61 7 c to 35 0 c that indicate the presence of h 2 o nacl mgcl 2 cacl 2 co 2 solutions 2 coexisting daughter mineral bearing high salinity 29 5 70 wt nacl equiv and vapor rich moderate salinity 11 5 16 7 wt nacl equiv inclusions that homogenized in the liquid phase by the disappearance of the vapor phase at a similar temperature range 308 c to 600 c in stage 2 eutectic temperatures range from 67 9 c to 51 8 c that shows the presence of h 2 o nacl co 2 ch 4 n 2 solutions 3 low moderate salinity 12 5 7 6 wt nacl equiv and temperature 320 c to 215 c inclusions homogenized by the liquid phase in stage 3 eutectic temperatures range from 59 5 c to 44 2 c indicating the presence of h 2 o nacl mgcl 2 cacl 2 co 2 solutions 4 inclusions of low salinity 9 9 0 9 wt nacl equiv and homogenization temperature 183 c to 101 c in stage 4 these data show that the kozbudaklar skarn deposit was formed in a magmatic hydrothermal system in this model carbonaceous fluids may have been exsolved from the plutonic rock during its emplacement and crystallization fluid inclusion data indicate that fluid boiling and immiscibility occurred at temperatures between 440 c and 459 c and pressures ranging from 50 mpa to 60 mpa based on hydrostatic considerations early scheelite was precipitated with relatively reduced mineral compositions as a result of depressurization mo rich scheelite with oxidized minerals formed via high salinity and vapor rich inclusions the second scheelite mineralization occurred in a normal hydrothermal system by an infiltration mechanism at pressures between approximately 40 and 1 5 mpa at shallow depths

on the initiation of subduction zones analysis of the relation between intraplate stress fields and lithospheric rheology leads to greater insight into the role that initiation of subduction plays in the tectonic evolution of the lithosphere numerical model studies show that if after a short evolution of a passive margin time span a few tens of million years subduction has not yet started continued aging of the passive margin alone does not result in conditions more favorable for transformation into an active margin

sea level and climate changes during ois 5e in the western mediterranean palaeontological geomorphological and sedimentological data supported by isotopic dating on oxygen isotopic stage ois 5e deposits from the spanish mediterranean coast are interpreted with the aim of reconstructing climatic instability in the northern hemisphere data point to marked climatic instability during the last interglacial ois 5e with a change in meteorological conditions and consequently in the sedimentary environment the oolitic facies generated during the first part of ois 5e ca 135 kyr shift into reddish conglomeratic facies during the second part ca 117 kyr sea surface temperature sst and salinity are interpreted mainly on the basis of warm senegalese fauna which show chronological and spatial differential distribution throughout the western mediterranean present hydrological and meteorological conditions are used also as modern analogues to reconstruct climatic variability throughout the last interglacial and this variability is interpreted within the wider framework of the north atlantic record all the available data indicate an increase in storminess induced by an increase in the influence of northwesterlies a slight drop of sst in the northern western mediterranean and an important change in meteorological conditions at the end of ois 5e 117 kyr these changes correlate well with the decrease in summer insolation and with the climatic instability recorded in north atlantic high latitudes

a one million year long sequence of marine terraces on sumba island indonesia abstract an exceptional sequence of raised coral reef terraces is visible at cape laundi on the north coast of the island of sumba in the savu sea in which at least eleven terraces wider than 100 m six of them even being over half a kilometer wide are geomorphologically distinguishable between an ancient patch reef now at 475 m and the present sea level esr date estimations of almost unrecrystallized corals most of them in situ make possible a tentative identification of the terraces corresponding to isotope stages 15 ca 600 ka ago and 9 ca 330 ka ago when the uplift trend deduced from the present altitude of dated terraces 0 49 0 01 mm yr is extrapolated to the whole raised section most geomorphological features appear to correspond to interglacial stages of the astronomically calibrated oxygen isotope record up to stage 27 ca 0 99 ma beyond the matuyama jaramillo geomagnetic boundary the upper terraces would in this case be twice as old as previously estimated ca 0 5 ma main terraces seem to correspond to high sea levels at certain interglacial stages and substages but in some cases the action of low sea levels at glacial stages cannot be ruled out for terraces between 30 and 70 m in altitude th u and esr dates reveal that aragonitic corals at similar elevations may differ in age as much as 100 ka this can be explained by taking into account a polycyclic origin for several terraces reconstructions available of changes in the eustatic sea level during the last 250 kyr and the fact that coral reef development may have been scattered at some periods only without totally covering subjacent older formations the sumba sequence of marine terraces at cape laundi is among the longest and most complete for the past million years reported in the literature its relatively good state of preservation will probably give impetus to a number of new studies on the chemical physical isotopic morphological palaeoclimatic pedological ecological and diagenetic changes which have occurred during the past one million years

geochemical and geochronological constraints on the formation of shear zone hosted cu au bi te mineralization in the stanos area chalkidiki northern greece abstract copper gold bismuth tellurium mineralization in the stanos area chalkidiki peninsula greece occurs in the proterozoic to silurian aged serbomacedonian massif which tectonically borders the mesozoic circum rhodope metamorphic belt to the west and crystalline rocks of the rhodope massif to the east this area contains the paliomylos chalkoma and karambogia prospects which are spatially related to regional nw se trending shear zones and hosted by marble amphibolite gneiss metagabbro and various muscovite biotite chlorite actinolite feldspar quartz schists of the silurian vertiskos unit metallic minerals occur as disseminated to massive aggregates along foliation planes and in boudinaged quartz veins iron bearing sulfides pyrite arsenopyrite and pyrrhotite formed prior to a copper bearing stage that contains chalcopyrite along with galena sphalerite molybdenite and various minerals in the system bi cu pb au ag te fluid inclusion homogenization temperatures of primary aqueous liquid vapor inclusions in stage i quartz veins range from 170 1 c to 349 6 c peak at 230 c with salinities of 4 5 to 13 1 wt nacl equiv calculated isochores intersect p t conditions associated with the upper greenschist facies caused by local overpressures during late stage tectonic movement along the shear zone in the eocene which produced stretching and unroofing of rocks in the region values of 34 s for sulfides in the stanos shear zone range from 2 42 to 10 19 and suggest a magmatic sulfur source with a partially reduced seawater contribution for fluids in equilibrium with quartz 18 o at 480 c varies from 5 76 to 9 21 but does not allow for a distinction between a metamorphic and a magmatic fluid a 187 re 187 os isochron of 19 2 2 1 ma for pyrite in the paliomylos prospect overlaps ages obtained previously from intrusive rocks spatially related to the skouries porphyry cu au the asimotrypes au and the intrusion related palea kavala bi te pb sb au deposits in northern greece as well as alteration minerals in the carbonate replacement madem lakkos pb zn deposit ore forming components of deposits in the stanos area were likely derived from magmatic rocks at shallow depth that intruded an extensional shear environment at 19 ma

multiple stage tungsten mineralization in the silurian jiepai w skarn deposit south china insights from cathodoluminescence images trace elements and fluid inclusions of scheelite abstract the jiepai deposit located in the northeastern part of the miao ershan yuechengling batholith south china is characterized by predominant skarn mineralization that formed near the contact between the silurian biotite granites and the upper cambrian carbonate rocks jiepai scheelites are recognized as two main generations based on their occurrences cathodoluminescence cl signatures and ree systematics prograde skarn hosted scheelite i has uniformly dark cl characteristics and lree enriched patterns retrograde skarn hosted scheelite iia is homogeneously dark under cl and has a slightly mree enriched pattern whereas quartz vein hosted scheelite iib is delineated by fine oscillatory cl zones and a relatively flat ree pattern additionally the cl images reveal that both scheelite i and ii were modified by later stage hydrothermal overprints which occur as ubiquitous overgrowth rims and cutting veins with bright cl signatures low ree but similar ree patterns to their precursors the compositional variations and fluid inclusions in jiepai scheelites identify episodic pulses of hydrothermal fluids with different properties the ore forming fluids with high nb ta but low nb ta and rey in the early retrograde stage are featured by moderate to high temperature and low to moderate salinity under relatively oxidizing conditions they interacted with the host rock and underwent boiling to precipitate scheelite i by contrast the fluids with higher nb ta and rey but lower nb ta in the late retrograde stage have slightly lower temperature and higher salinity we therefore speculate that scheelite ii may deposit from later magmatic fluids that have experienced continued boiling in more reducing environment

the mid pliocene sea level conundrum glacial isostasy eustasy and dynamic topography abstract determining eustatic sea level during the mid pliocene warm period 3 3 to 2 9 ma has been a central but elusive goal in the study of past warm climates estimates of eustatic sea level based on geologic data span a broad range variation that we now recognize is due in part to geographically varying post depositional displacement caused by glacial isostatic adjustment and dynamic topography in this study we combine field observations and glacial isostatic adjustment modeling to estimate the dynamic topography signal in three areas that are important to paleo sea level studies of the mid pliocene warm period south africa west australia and southeastern united states we show that dynamic topography played a significant role in the post depositional displacement of pliocene and even younger pleistocene shorelines in this regard we provide a robust paleo sea level elevation data set corrected for glacial isostatic adjustment that can be used to evaluate predictions from mantle flow models of dynamic topography

enrichment of co2 in fluid inclusions in quartz by removal of h2o during crystal plastic deformation abstract ductile strain induced leakage of h 2 o from mixed co 2 h 2 o fluid inclusions in quartz is proposed as a mechanism for producing occurrences of pure co 2 fluid inclusions in metamorphic rocks the h 2 o needed for hydrolytic weakening of quartz under stress may be provided by the h 2 o in fluid inclusions with dislocation creep as dislocations nucleate on the walls of fluid inclusions or intersect them h 2 o can be transported with the dislocations from the inclusion to the grain boundaries the process should continue so long as there is stress on the host quartz and the inclusion contains h 2 o the h 2 o taken to the grain boundaries would due to its wetting properties be wicked out along the grain boundaries if the h 2 o is totally removed from an inclusion by a flux of dislocations through the quartz during the crystal plastic flow then a residual inclusion bearing components other than water should remain a mixed co 2 h 2 o inclusion would as a consequence of the process become a pure co 2 fluid inclusion during dynamic recrystallization the co 2 would collect at grain boundary triple junctions and following grain boundary migration would become incorporated into the recrystallized quartz as fluid inclusions this mechanism of generating pure co 2 inclusions could result in co 2 fluid inclusions having densities appropriate for the pressure temperature conditions during deformation using estimates of temperature of deformation the total confining pressure during deformation could be determined from the density of the co 2 fluid in these inclusions

cenozoic expansion of grasslands and climatic cooling abstract mountains ocean currents forests and swamps have played an important role in regulating global climate for hundreds of millions of years but the truly novel event of the cenozoic was the evolution and expansion of grasslands with their uniquely coevolved grasses and grazers neogene expansion of the climatic and geographic range of grasslands at the expense of woodlands is now revealed by recent studies of paleosols fossils and their stable isotopic compositions grasslands and their soils can be considered sinks for atmospheric co2 ch4 and water vapor and their cenozoic evolution a contribution to long term global climatic cooling grassland soils are richer in organic matter than are woodland and desert soils of comparable climates and when eroded their crumb clods form sediment unusually rich in organic matter grasslands also promote export of bicarbonate and nutrient cations to lakes and to the oceans where they stimulate productivity and c burial this increased productivity and

channel response to tectonic forcing field analysis of stream morphology and hydrology in the mendocino triple junction region northern california abstract an empirical calibration of the shear stress model for bedrock incision is presented using field and hydrologic data from a series of small coastal drainage basins near the mendocino triple junction in northern california previous work comparing basins from the high uplift zone huz uplift rates around 4 mm year to ones in the low uplift zone luz 0 5 mm year indicates that the huz channels are about twice as steep for a given drainage area this observation suggests that incision processes are more effective in the huz it motivates a detailed field study of channel morphology in the differing tectonic settings to test whether various factors that are hypothesized to influence incision rates discharge channel width lithology sediment load change in response to uplift or otherwise differ between the huz and luz analysis of regional stream gaging data for mean annual discharge and individual floods yields a linear relationship between discharge and drainage area increased orographic precipitation in the huz accounts for about a twofold increase in discharge in this area corresponding to an assumed increase in the erosional efficiency of the streams field measurements of channel width indicate a power law relationship between width and drainage area with an exponent of 0 4 and no significant change in width between the uplift rate zones although interpretation is hampered by a difference in land use between the zones the huz channel width dataset reveals a scaling break interpreted to be the transition between colluvial and fluvial dominated incision processes assessments of lithologic resistance using a schmidt hammer and joint surveys show that the rocks of the study area should be fairly similar in their susceptibility to erosion the huz channels generally have more exposed bedrock than those in the luz which is consistent with protection by sediment cover inhibiting incision in the luz however this difference is likely the result of a recent pulse of sediment due to land use in the luz therefore the role of sediment flux in setting incision rates cannot be constrained with any certainty to summarize of the four response mechanisms analyzed the only factor that demonstrably varies between uplift rate zones is discharge although this change is likely insufficient to explain the relationship between channel slope and uplift rate the calibrated model allows us to make a prediction of channel concavity that is consistent with a previous estimate from slope drainage area data we show that the inclusion of nonzero values of critical shear stress in the model has important implications for the theoretical relationship between steady state slope and uplift rate and might provide an explanation for the observations this analysis underscores the importance of further work to constrain quantitatively threshold shear stress for bedrock incision

coastal uplift and thrust faulting associated with the mw 6 8 zemmouri algeria earthquake of 21 may 2003 1 a shoreline uplift marked by a continuous white band visible at rocky headlands occurred during the 21 may 2003 earthquake mw 6 8 in northern algeria we measured the amount of coastal uplift on a white band emerged algae and harbors quays between boumerdes and dellys most of measured points were collected using tape and differential gps on rocky headlands with 0 15 m error bar tidal prism leveling lines running parallel and orthogonal to the coast also provide the precise amount of uplift in the epicentral area the uplift distribution shows an average 0 55 m along the shoreline with a maximum 0 75 m east of boumerdes and a minimum close to 0 near cap djinet the active deformation related to a thrust fault is modeled along the 55 km coastline the dislocation model predicts surface slip on a n 54 e trending reverse fault dipping 50 se in agreement with cmt solution and coastal uplift the faulting characteristics imply a fault geometry with possible sea bottom ruptures between 5 to 10 km offshore

magmatic evolution of the alboran region the role of subduction in forming the western mediterranean and causing the messinian salinity crisis the magmatic evolution of the alboran region westernmost mediterranean contains important clues for improving our understanding of the origin of mediterranean style back arc basins and the desiccation of the mediterranean sea in the messinian we use new laser 40ar 39ar age and geochemical major and trace element and o sr nd pb isotope data from igneous rocks from southern spain the alboran sea and northern morocco to reconstruct the magmatic evolution of the westernmost mediterranean since the eocene lower oligocene dikes near malaga 33 6 0 6 ma and middle to upper miocene volcanic rocks from the alboran sea area 6 57 0 04 to 11 8 0 4 ma can be subdivided into two groups 1 lree depleted relative to n morb primarily tholeiitic series and 2 lree enriched primarily calc alkaline series volcanic rocks both groups are generally enriched in fluid mobile elements e g rb th u k and pb relative to fluid immobile elements e g nb ta lree the lree depleted group has 143nd 144nd 0 5128 0 5130 isotope ratios similar to atlantic morb but higher 87sr 86sr 0 7046 0 7100 in contrast the lree enriched group has less radiogenic nd 0 5121 0 5126 and tend to more radiogenic sr 0 7066 0 7205 isotopic composition pb isotope ratios are surprisingly uniform and have compositions similar to marine sediments analyses of mineral separates show that mafic melts with relatively low 18o 5 6 7 2 had high 87sr 86sr 0 7048 0 7088 7 4 10 6 14 1 and 8 4 40 0 49 3 modeling of the trace elements and sr nd pb o isotopic compositions provides compelling evidence for the contamination of the mantle source with hydrous fluids melts which can be explained through subduction of oceanic lithosphere beneath the alboran basin but not through detachment delamination of lithospheric mantle we present a geodynamic model that reconstructs the late eocene to quaternary evolution of the western mediterranean through westward roll back of subducted tethys oceanic lithosphere slab roll back resulted in a large scale reorganization of the western mediterranean paleogeography causing the closure of marine gateways linking the atlantic ocean to the mediterranean sea isolation of the mediterranean sea led to its desiccation causing the messinian salinity crisis

neogene and quaternary rollback evolution of the tyrrhenian sea the apennines and the sicilian maghrebides reconstruction of the evolution of the tyrrhenian sea shows that the major stage of rifting associated with the opening of this basin began at similar to10 ma it involved two episodes of back arc extension which were induced by the rollback of a west dipping subducting slab the first period of extension 10 6 ma was prominent in the northern tyrrhenian sea and in the western part of the southern tyrrhenian sea the second period of extension mainly affected the southern tyrrhenian sea began in the latest messinian 6 5 ma and has been accompanied by subduction rollback at rates of 60 100 km myr 1 slab reconstruction combined with paleomagnetic and paleogeographic constraints indicates that in the central apennines the latest messinian 6 5 ma arrival of a carbonate platform at the subduction zone impeded subduction and initiated a slab tear and major strike slip faults these processes resulted in the formation of a narrow subducting slab beneath the ionian sea that has undergone faster subduction rollback and induced extreme rates of back arc extension

comment on zemmouri earthquake rupture zone mw 6 8 algeria aftershocks sequence relocation and 3d velocity model by a ayadi et al although often difficult to characterize the relationship between a seismic rupture its aftershock sequence and cumulative subsurface or surface faulting or folding is an important challenge to modern seismology and seismotectonics among other benefits it helps document fault length slip and magnitude relationships reconstruct the evolution of the rupture process through historical and prehistorical times and identify the complexity of the deformation in its path toward the surface this approach is a prerequisite to any seismic hazard assessment but is particularly difficult for faults whose surface trace projects offshore a specific effort to identify and quantify the source parameters of large earthquakes in coastal areas is therefore needed not only in subduction zones but also in areas of slow rate and or diffuse deformation

observations of nonclassical frontal propagation and frontally forced gravity waves adjacent to steep topography through the integrated analysis of remote sensing and in situ data taken along the front range of colorado this study describes the interactions that occurred between a leeside arctic front and topographically modulated flows these interactions resulted in nonclassical frontal behavior and structure across northeastern colorado the shallow arctic front initially advanced southwestward toward the front range foothills before retreating eastward then a secondary surge of arctic air migrated westward into the foothills during its initial southwestward advance the front exhibited obstacle like density current characteristics its initial advance was interrupted by strong downslope northwesterly flow associated with a high amplitude mountain wave downstream of the continental divide and by a temporal decrease in the density contrast across the front due to diurnal heating in the cold air and weak cold advection in the warm air the direction and depth of flow within the arctic air also influenced the frontal propagation the shallow obstacle like front actively generated both vertically propagating and vertically trapped gravity waves as it advanced into the downslope northwesterly flow resulting in midtropospheric lenticular wave clouds aloft that tracked with the front because the front entered a region where strong downslope winds and mountain waves extended downstream over the high plains the wave field in northeastern colorado included both frontally forced and true mountain forced gravity waves a sequence of scorer parameter profiles calculated from hourly observations reveals a sharp contrast between the prefrontal and postfrontal wave environments consequently analytic resonant wave mode calculations based on the scorer parameter profiles reveal that the waves supported in the postfrontal regime differed markedly from those supported in the prefrontal environment this result is consistent with wind profiler observations that showed the amplitude of vertical motions decreasing substantially through 16 km above mean sea level msl after the shallow frontal passage

multiphased tectonic evolution of the central algerian margin from combined wide angle and reflection seismic data off tipaza algeria 1 the origin of the algerian margin remains one of the key questions still discussed in the western mediterranean sea due to the imprecise nature and kinematics of the associated basin during the neogene for the first time the deep structure of the maghrebian margin was explored during the spiral seismic survey in this work we present a n s transect off tipaza west of algiers a place where the margin broadens due to a topographic high khayr al din bank new deep penetration seismic profiles allow us to image the sedimentary sequence in the algerian basin and the crustal structure at the continent ocean boundary modeling of the wide angle data shows thinning of the basement from more than 15km in the continental upper margin to only 5 6km of oceanic type basement in the algerian basin and reveals a very narrow or absent transitional zone analysis of the deep structure of the margin indicates features inherited from its complex evolution 1 an oceanic type crust in the deep basin 2 similarities with margins formed in a transform type setting 3 a progressive deepening of the whole sedimentary cover and the thickening of the plio quaternary sediments at the margin foot coeval with 4 a downward flexure of the basement in the basin these features argue for a multiphased evolution of the margin including 1 an early stage of rifting and or spreading 2 a late transcurrent episode related to the westward migration of the alboran domain and 3 a diffuse plio quaternary compressional reactivation of the margin

fluids in the crust during regional metamorphism forty years in the waterville limestone figure 1 research over the last four decades on carbonate rocks of the waterville limestone maine u s a has contributed to the development of both concepts and methodologies for understanding fluid rock interaction during regional metamorphism including 1 buffering of fluid composition by mineral reactions 2 infiltration of carbonate rocks by aqueous fluids 3 petrologic fluid rock ratios 4 infiltration driven metamorphism 5 one and two dimensional continuum models for coupled fluid flow and mineral reaction 6 time integrated fluid fluxes and 7 channelized horizontal fluid flow in the direction of increasing temperature within chemically isolated layers disagreement between the last concept and both hydrodynamic models for metamorphic fluid flow and empirical evidence for homogenization of fluid composition at a scale much larger than layer thickness motivated development of the latest models for coupled fluid flow and mineral reaction in the waterville limestone the new models consider a flow medium composed of layers that differ in the initial amounts and compositions of minerals both horizontal flow in the direction of increasing temperature and vertical flow in the direction of decreasing pressure and temperature significant but imperfect homogenization of fluid composition across layering by co2 h2o interdiffusion and infiltration by fluids that are spatially variable in composition on the kilometer scale with co2 content increasing with increasing grade of metamorphism the new models reproduce measured progress of the biotite forming reaction in the waterville limestone over a range of spatial scales spanning six orders of magnitude from differences in reaction progress of up to a factor of 100 between adjacent centimeter thick layers to the coexistence of mineral reactants and products over a distance of 13 km parallel to the metamorphic field gradient results imply that the present spatial distributions of reaction progress represent a steady state achieved when rocks closely approached equilibrium with the infiltrating fluid during metamorphism the new models resolve what for many years appeared to be fundamental discrepancies among petrologic data for regionally metamorphosed carbonate rocks hydrodynamic models of regional metamorphism and the length scales of mass transport of volatiles across layering by diffusion 1 pending yes