continental extension from core complexes to rigid block faulting extension of overthickened continental crust is commonly characterized by an early core complex stage of extension followed by a later stage of crustal scale rigid block faulting these two stages are clearly recognized during the extensional destruction of the alpine orogen in northeast corsica where rigid block faulting overprinting core complex formation eventually led to crustal separation and the formation of a new oceanic backarc basin the ligurian sea here we investigate the geodynamic evolution of continental extension by using a novel fully coupled thermomechanical numerical model of the continental crust we consider that the dynamic evolution is governed by fault weakening which is generated by the evolution of the natural state variables i e pressure deviatoric stress temperature and strain rate and their associated energy fluxes our results show the appearance of a detachment layer that controls the initial separation of the brittle crust on characteristic listric faults and a core complex formation that is exhuming strongly deformed rocks of the detachment zone and relatively undeformed crustal cores this process is followed by a transitional period characterized by an apparent tectonic quiescence in which deformation is not localized and energy stored in the upper crust is transferred downward and causes self organized mobilization of the lower crust eventually the entire crust ruptures on major crosscutting faults shifting the tectonic regime from core complex formation to wholesale rigid block faulting

marine geologic evidence for a levantine sinai plate a new piece of the mediterranean puzzle marine geophysical data recorded offshore egypt illustrate the presence of an active fault belt trending n145 e that obliquely transects the eastern nile deep sea fan this belt more than 150 km long consists of a series of linear transtensive faults with an apparent right lateral horizontal component these fault zones bound thick sediment filled grabens where linear salt ridges and diapirs represent likely messinian salt reactive response to regional transcurrent geodynamics we infer that this tectonic belt might correspond to an offshore extension of the gulf of suez rift system if our hypothesis is correct this fault belt might represent the western boundary of a levantine sinai microplate locked between the major arabia and africa plates and the anatolian aegean microplate

the tectonic development of the western margin of the gulf of elat aqaba rift abstract along the western coast of the gulf of elat a 30 km wide shear belt of subparallel faults trending n s to ne sw is developed this shear belt is observed mainly within the precambrian basement terrain sinistral movements on these faults have been recognized based on offsets of magmatic bodies and lithological contacts in rocks of precambrian age the cumulative displacement measured independently at several localities across the belt attains a total of 24 km early neogene volcanism in the form of long dikes trending nw se is known from the eastern desert of egypt of the gulf of suez and along the red sea coast of saudi arabia volcanic bodies of a similar pattern have been identified in eastern sinai these bodies mainly dolerites and basalts intruding mesozoic sediments are parallel to each other and to the gulf of suez they are tens to hundreds of kilometers long and spaced several tens of kilometers apart dating k ar of bodies in sinai saudi arabia and in the eastern desert of egypt suggest an age of 20 22 m y for this extensive volcanism all the dikes are sinistrally displaced by the individual faults of the eastern sinai shear belt the amount of movement recorded using the precambrian markers is identical to movement recorded by offsets of the early neogene dikes this proves that the total 24 km shear of this fault system postdates the 20 22 m y volcanic phase it is assumed that the recorded movements are part of the 105 110 km shear persumed to exist along the gulf of elat which is also younger than 20 22 m y preliminary results suggest that a similar amount of movement is observable along a shear zone developed on the eastern coast of the gulf of elat thus only some 60 km movement are taken up by faults in the gulf itself the evolving model suggests that 1 a the intrusion of very long basaltic dikes in a nw se direction on both sides of the red sea accompanied the initial stage of development of the red sea gulf of suez rift valley 2 b a basic change in the geotectonic regime occurs after the intrusion of this volcanic suite large scale horizontal movements are initiated being recorded as a 105 110 km sinistral movement along the arava jordan rift this movement implies a synchronous opening of the red sea

a complex trace fossil from the spitskop member terminal ediacaran lower cambrian of southern namibia streptichnus narbonnei igen et isp nov a new trace fossil from the upper part of the spitskop member of the urusis formation southern namibia consists of clusters of unidirectionally curved radial elements in which individual elements typically are composed of imbricated sickle shaped segments somewhat comparable to those of treptichnus pedum such complex trace fossils generally are found only in cambrian or younger strata this opens to question the position of the ediacaran cambrian boundary in the nama group suggesting that it may locally be within the uppermost part of the urusis formation rather than at the base of the nomtsas formation

neogene patterns of relative plate motion for africa europe some implications for recent central mediterranean tectonics a detailed relative motion picture for the neogene africa europe plate kinematics is presented the kinematic reconstruction was carried out using the finite difference solution between the rotation parameters determined for anomalies 7 to 2 in the africa north america europe plate motion circuit the analysis shows a motion of africa with respect to europe which is nne directed during late oligocene to burdigalian times becoming nnw trending from the langhian to the early tortonian from upper tortonian times onward the motion changes to a clear north west directed convergence major late neogene tectonic features of the central mediterranean region can to a large extent be explained within the context of the reconstructed major plate motions late tortonian to recent africa europe slip vectors are compatible with a variety of geological phenomenoa such as north west directed subduction beneath calabria south east translation of calabria and extension in the tyrrhenian sea north west trending slip vectors from thrust earthquakes between gibraltar and sicily and dextral strike slip across the north african margin

uplift and extension at the gulf of suez indications of induced mantle convection reconstruction of tectonic movements since the initiation of the gulf of suez rift indicates that there has been 25 27 km of extension the uplift bordering rift indicates that lithosphere heating greatly exceeds that producible by uniform lithosphere extension i propose that small scale convection induced by the rifting augments the heating introduced by extensional rifting and produces the broad uplifts flanking the rift

the dead sea rift from continental rift to incipient ocean abstract the dead sea rift is a 600 km long approximately 20 km wide geomorphological depression showing a topographic relief of 1 000 to 3 000 m from the axial depression to the mountainous margins in many places the rift is the northern extension of the red sea young oceanic spreading centre and it is built of a series of internal basins the rift is the product of vertical displacements that downfaulted its floor and uplifted its margins but some sinistral strike slip offset affected the rift as well the tectonic evolution of the rift started probably in the pliocene subsequent to the termination of the intensive tectonic activity in the suez rift the transition of the tectonic activity from suez rift to the dead sea rift is due to a probable clockwise jump of the northern extension of the red sea spreading centre the dead sea rift with its internal basins and faulted precipitous escarpments presents an exceptional example for the earliest stages of the evolution of continental break up and of nascent passive continental margins tectonic interpretations of the voluminous geological and geophysical data from the rift and its margins are complicated because the information is equivocal part of the data suggests that the rift is an extensional structure whereas another part indicates that the rift is a product of regional sinistral strike slip faulting however it is suggested that the equivocal data are not necessarily conflicting because the evolution of the rift is probably associated with oblique resultant displacement of combined normal and strike slip faulting the quantitative ratio between the extensional and the lateral offset processes in the dead sea rift is controversial there is ground to presume that large downfaulting of the rift floor and intensive erosion of its uplifted margins removed and obscured critical data that could have provided reliable correlation between the eastern and western flanks nevertheless reconstruction of mesozoic depositional fades zones across the rift apparently indicates that the lateral displacements are approximately 10 km and seismic reflection profiles suggest vertical offsets reaching 7 km the series of secondary internal basins in the rift that seem equivalent to the linear system of axial basins in the northern red sea support the concept that the dead sea is under a tectonic regime that is comparable to the one that affected the red sea in the miocene these findings and the 25 to 50 reduction of crustal thicknesses underneath the rift indicate an incipient oblique oceanic spreading centre

the oldest evidence of bioturbation on earth comment here we question the conclusions of rogov et al 2012 who claim to describe the oldest evidence of bioturbation on earth in the form of meniscate back lled burrows and escape traces from late ediacaran car bonates of the siberian khatyspyt formation because trace fossils can constrain early metazoan origins and are used to de ne the base of the cambrian period brasier et al 1994 such a signi cant claim requires jus ti cation by careful interpretation of the material and critical analysis both of which appear wanting here although we agree that multiple biological and ecological revolutions took place during the late ediacaran period we question whether those events can be tied to these problematic fossils

mantle circulation models with sequential data assimilation inferring present day mantle structure from plate motion histories data assimilation is an approach to studying geodynamic models consistent simultaneously with observables and the governing equations of mantle flow such an approach is essential in mantle circulation models where we seek to constrain an unknown initial condition some time in the past and thus cannot hope to use first principles convection calculations to infer the flow history of the mantle one of the most important observables for mantle flow history comes from models of mesozoic and cenozoic plate motion that provide constraints not only on the surface velocity of the mantle but also on the evolution of internal mantle buoyancy forces due to subducted oceanic slabs here we present five mantle circulation models with an assimilated plate motion history spanning the past 120 myr a time period for which reliable plate motion reconstructions are available all models agree well with upper and mid mantle heterogeneity imaged by seismic tomography a simple standard model of whole mantle convection including a factor 40 viscosity increase from the upper to the lower mantle and predominantly internal heat generation reveals downwellings related to farallon and tethys subduction adding 35 bottom heating from the core has the predictable effect of producing prominent high temperature anomalies and a strong thermal boundary layer at the base of the mantle significantly delaying mantle flow through the transition zone either by modelling the dynamic effects of an endothermic phase reaction or by including a steep factor 100 viscosity rise from the upper to the lower mantle results in substantial transition zone heterogeneity enhanced by the effects of trench migration implicit in the assimilated plate motion history an expected result is the failure to account for heterogeneity structure in the deepest mantle below 1500 km which is influenced by jurassic plate motions and thus cannot be modelled from sequential assimilation of plate motion histories limited in age to the cretaceous this result implies that sequential assimilation of past plate motion models is ineffective in studying the temporal evolution of core mantle boundary heterogeneity and that a method for extrapolating present day information backwards in time is required for short time periods of the order of perhaps a few tens of myr such a method exists in the form of crude backward convection calculations for longer time periods of the order of a mantle overturn a rigorous approach to extrapolating information back in time exists in the form of iterative nonlinear optimization methods that carry assimilated information into the past through the use of an adjoint mantle convection model

platform subsidence behind an active subduction zone numerical models of viscous mantle flow indicate that a broad subsidence should occur above subduction zones1 4 this platform subsidence is predicted to cause an asymmetrical depression 500 1 000 km wide with a maximum depth of 2 km if filled with water direct evidence linking platform subsidence to mantle flow has remained elusive however here we offer evidence from western new zealand for a complete link in both space and time between subduction initiation and platform subsidence because of the broad wavelength 200 km of the observed 1 500 m subsidence it is unlikely that the subsidence is due to a flexural foredeep the observed subsidence does however match in both wavelength and amplitude that predicted by a model of subduction induced mantle flow the occurrence of platform subsidence has implications not only for understanding mantle convection but also for explaining geoid anomalies over active margins5 and patterns of continental submergence6 and sedimentation7 that could otherwise be interpreted as a eustatic sea level change8

identification of future earthquake sources in the carpatho balkan orogenic belt using morphostructural criteria the carpatho balkan mountain belt the most seismic zone of the circum pannonian region is studied with a goal to identify sites where shallow earthquakes with m 6 5 may occur the study is based on the assumption that strong earthquakes associate with disjunctive nodes that are formed around the junctions of lineaments in the study region lineaments and disjunctive nodes were defined by a morphostructural zonation method the morphostructural map compiled at the scale of 1 1 000 000 shows a hierarchical system of homogeneous blocks the network of morphostructural lineaments and the loci of disjunctive nodes shallow earthquakes with m s 5 0 recorded in the region were found to be nucleated at the mapped nodes in the carpatho balkan mountain belt the nodes where earthquakes with m 6 5 may occur have been identified using morphostructural criteria of high seismicity previously derived from pattern recognition of potential seismic nodes in the pamirs tien shan region in total 64 of the 165 nodes mapped in the studied region have been defined to be prone to earthquakes of m 6 5 these 64 nodes include the seven where earthquakes of m s 6 0 already took place

fission track evidence on the initial rifting of the red sea two pulses no propagation fission track analyses indicate that the red sea initially opened simultaneously along its entire length two distinct pulses of uplift and erosion characterized the early stages of rifting in the red sea throughout egypt and in southwestern saudi arabia the first pulse began at 34 million years ago ma the second pulse began in the early miocene 21 to 25 ma and marked the start of the main phase of extension these data support a rigid plate model for continental extension these results also indicate that the initiation of rift flank uplift and therefore rifting and volcanism occurred nearly simultaneously this conflicts with classical models of active and passive extension that predict sequential development of these features

redox dependent distribution of early macro organisms evidence from the terminal ediacaran khatyspyt formation in arctic siberia abstract the ediacaran period witnessed the first appearance of macroscopic animal life in earth s history however the biogeochemical context for the stratigraphic occurrence of early metazoans is largely uncertain in part due to the dearth of integrated paleobiological and chemostratigraphic datasets in this study a comprehensive geochemical analysis was conducted on the fossiliferous khatyspyt formation in arctic siberia in order to gain insights into the ediacaran paleoenvironments this study was designed to specifically address the relationship between paleoredox conditions and ediacaran fossil occurrences in the khatyspyt formation our data reveal a dramatic shift in pyrite sulfur isotope compositions 34 s pyrite from ca 20 to ca 55 and this shift is intriguingly associated with the first occurrence of ediacara type macrofossils at the studied section suggesting a possible link between seawater redox conditions and distribution of early macroscopic organisms based on multiple lines of sedimentological and geochemical evidence we propose that the development of oceanic euxinia which may be widespread in the continental margins due to enhanced oxidative weathering in the terminal ediacaran period may have locally prohibited the colonization of ediacara type organisms and resulted in low 34 s pyrite values in the lower khatyspyt formation in the middle and upper khatyspyt formation progressive secular transition from euxinic to non euxinic and more habitable conditions may have allowed for the colonization of ediacara type and other macro organisms

the oldest evidence of bioturbation on earth detailed study of the khatyspyt formation in arctic siberia has shown that contrary to common expectations the earliest ichnofabric is of late ediacaran age records a food seeking behavior and is found in a distal carbonate ramp setting where it co occurs with fossils of avalon type ediacaran soft bodied organisms preserved depth of bioturbation reaches 5 cm the ichnofabric solely comprises nenoxites the oldest known meniscate trace fossil which is interpreted as burrows with terminal backfill structure formed as a result of active displacement of sediment to form a tunnel within the substrate followed by emplacement of the material behind the animal as it progressed through the sediment in addition to being the most reliable paleontological evidence for the existence of bilaterians at ca 555 ma the late ediacaran bioturbation is regarded as a key step in the escalatory engineering of phanerozoic ecospace leading to sudden diversification of macroscopic organisms and macrocommunities

dem based morphometry of range front escarpments in attica central greece and its relation to fault slip rates in this paper we apply current geological knowledge on faulting processes to digital processing of digital elevation models dem in order to pinpoint locations of active faults the analysis is based on semiautomatic interpretation of 20 and 60 m dem and their products slope shaded relief in northern eastern attica five normal fault segments were recognized on the 20 m dem all faults strike wnw ese the faults are from west to east thriassion thfs fili fifs afidnai affs avlon avfs and pendeli pefs and range in length from 10 to 20 km all of them show geomorphic evidence for recent activity such as prominent range front escarpments v shaped valleys triangular facets and tilted footwall areas however escarpment morphometry and footwall geometry reveal systematic differences between the bexternalq segments pefs thfs and avfs and the binternalq segments affs and fifs which may be due to mechanical interaction among segments and or preexisting topography in addition transects across all five escarpments show mean scarp slope angles of 22 18f0 78 for both carbonate and metamorphic bedrock the slope angle equation for the external segments shows asymptotic behaviour with increasing height we make an empirical suggestion that slope angle is a function of the long term fault slip rate which ranges between 0 13 and 0 3 mm yr the identified faults may rupture up to magnitude 6 4 6 6 earthquakes the analysis of the 60 m dem shows a difference in fault patterns between western and northern attica which is related to crustal rheology variations d 2004 elsevier b v all rights reserved

extensional hard linkages eastern gulf of suez egypt the araba abu durba area on the eastern margin of the gulf of suez exhibits two superb outcrop examples of extensional hard linkages in a rift basin here three large domino style basement cored northeast dipping fault blocks are formed by a series of major northwest trending normal faults these are offset by two north northeast trending sinistral oblique slip transfer faults that terminate in horsetail normal fault splays the transfer faults do not extend across the entire rift basin detailed mapping and structural analysis show that they developed by breakage of initial low strain relay ramps along reactivated north northeast trending basement fabrics between overlapping northwest trending normal fault segments paleostrain analysis of fault slip indicators shows that both the normal and the sinistral oblique slip transfer faults were formed synchronously in response to northeast southwest extension perpendicular to the main northwest rift trend

red sedimentary units as indicators of early pleistocene tectonic activity in the southern negev desert israel abstract alluvial units termed red units accumulated along the western margin of the dead sea rift dsr valley southern negev desert israel in the early pleistocene these sedimentary units consist of coarse to fine grained alluvium of local origin which contain calcic paleosols the sediments of the red units accumulated in stream valleys and newly forming semi closed local tectonic basins during a tectonic phase that deformed the western margin of the dsr as a result of this deformation the pliocene northward flowing regional drainage system of the southern negev disintegrated to the present northeast flowing ephemeral drainage systems of nahal zihor nahal hiyyon and nahal paran all of them draining to the arava valley in the dsr this change was induced by two deformation episodes 1 reactivation of the zihor and the milhan faults two major northeast trending tectonic lines and 2 east and northeast tilting of the entire region during upwarp arching of the central negev the paleosols of the red units are characterized by pedogenic features such as rhizoconcretions and bk horizons the paleosols developed in the alluvial sediments that were deposited and preserved in local small structural basins along the main fault lines and in reversed or abandoned westward flowing pliocene stream valleys formation of paleosols was initiated in the stream valleys when they attained a near horizontal gradient due to gradual eastward directed regional tilting followed by low rates of deposition the sections of the red units in the pliocene valleys were incised due to continuing tilting which completely reversed the primary westward gradient of the valleys and they were incised by new east and northeast flowing streams the red units have paleoclimatic implications since the middle pleistocene the southern negev has been characterized by gypsic and salic soils typical of an extremely arid climate while the calcic soils detected in the red units point to a semi arid climate this indicates a gradual transition from more humid conditions in the early pleistocene to the present extreme aridity therefore the red units reflect a distinct tectonic and climatic regime and can serve as regional morphostratigraphic marker of early pleistocene age in this paper we used this marker to reconstruct the tectonic deformation that established the present configuration of the southern negev terrain

revised neoproterozoic and terreneuvian stratigraphy of the lena anabar basin and north western slope of the olenek uplift siberian platform abstract the early to mid neoproterozoic pre glacial sedimentary succession of the lena anabar basin northeast siberian platform records protracted faulting and subsidence possibly as part of the widespread continental rifting and the break up of rodinia there is a significant stratigraphic unconformity separating the pre glacial neoproterozoic strata and the overlying upper ediacaran succession in the lena anabar basin with the terreneuvian strata most likely to be deposited in a foreland of the central taimyr accretionary belt the cryogenian sensu strictum i e younger than 720 ma and lower ediacaran deposits are missing in the area in this study we assess the palaeontological content of the precambrian and terreneuvian strata of the lena anabar basin and the adjacent north western slope of the olenek uplift and revise the chronostratigraphy of the region with special emphasis to biostratigraphic index taxa for the pre glacial neoproterozoic section we establish the new tukulan kulady taimylyr formations and redefine the khastakh formation we also refine the ediacaran and terreneuvian stratigraphy by formalising the maastakh khatyspyt and turkut formations of the khorbusuonka group whereas the kessyusa formation is raised to group rank and subdivided into the syhargalakh oppokun mattaia and chuskuna formations the proposed stratigraphic correlation scheme is based upon depositional unity and is consistent both lithologically and biostratigraphically providing a robust framework for future stratigraphic sedimentological and palaeobiological studies

neoproterozoic substrate condition vis a vis microbial mat structure and its implications sonia sandstone rajasthan india dst fast track project young scientist scheme no sr ftp es 03 2011 cas phase v upe ii programme of jadavpur university national research foundation and university of pretoria south africa

the oldest evidence of bioturbation on earth reply brasier et al 2012 1 raise concerns over our interpretation of the meniscate structure in the late ediacaran carbonates of the khatyspyt formation of siberia rogov et al 2012 2 although serial sectioning or ct scanning would no doubt reveal the three dimensional morphology of the

geomorphic limits to climate induced increases in topographic relief recognition of the potential for strong dynamic coupling between atmospheric and tectonic processes has sparked intense cross disciplinary investigation and debate on the question of whether tectonics have driven long term climate change or vice versa it has been proposed that climate change might have driven the uplift of mountain summits through an isostatic response to valley incision because isostasy acts to compensate mean elevations the debate hinges on the question of whether climate change can significantly increase topographic relief or more precisely increase the volume of missing mass between summits and ridges here we show that in tectonically active mountain ranges geomorphic constraints allow only a relatively small increase in topographic relief in response to climate change thus although climate change may cause significant increases in denudation rates potentially establishing an important feedback between surficial and crustal processes neither fluvial nor glacial erosion is likely to induce significant isostatic peak uplift

late cenozoic tectonics and denudation in the central kenya rift quantification of long term denudation rates abstract long term average denudation rates were calculated for the last 3 4 million years ma using digital topographic data related to the present surface of the intrarift bahati kinangop plateau in the central kenya rift well established relations between stratigraphy and faulting chronology and a detailed digital topographic database allow reconstruction of the idealized uneroded plateau surface for an area of 710 km2 the reconstruction refers to the time when the plateau came into existence 3 4 2 6 ma due to widespread deposition of ashflow tuffs and subsequent faulting the reconstruction of this palaeosurface is based on erosional surface remnants occurring within the present plateau surface relict surfaces elements were determined by analyzing the present digital surface representation and geological information within a geographical information system gis after generating digital elevation models of the present and palaeosurfaces long term denudation rates were calculated using the elevation difference method about 80 of the study area are characterized by denudation rates between 0 relict parts and 20 m per one million years m ma for deeply eroded plateau regions denudation reaches 80 100 m ma these rates are comparable to denudation rates which are known from other studies in similar settings the gis based approach provides spatially high resolution denudation rates allowing for further regional analysis of factors controlling spatial variations in sediment supply to the rift basin

senonian basin inversion and rejuvenation of rifting in africa and arabia synthesis and implications to plate scale tectonics abstract the late paleozoic to tertiary stratigraphic record of much of the african plate reflects the effects of continental rifting and passive margin development several short lived but widespread and tectonically important compressional or wrench dominated events occurred however during the permian to recent evolution of africa we focus here on the best documented of these events which occurred during the late santonian at that time older sedimentary basins mostly ene wsw trending were folded and inverted including some basins along the tethyan margin from morocco to the syrian arc and the intraplate benue southern chad basins and the lugh mandera basin in oman ophiolites were obducted following the santonian tectonism an extensive phase of rifting occurred in central and north africa and northern arabia spanning from campanian to maastrichtian or paleocene times rejuvenation or acceleration of subsidence occurred in several basins located along the tethyan margin along the atlantic and indian ocean margins as well as within the intraplate domain rifting was sometimes accompanied by magmatic activity especially in offshore northern libya and along the indian ocean margin compressional deformations rejuvenated or developed by latest maastrichtian times along the tethyan margin and locally within the intraplate domain one of the most remarkable attributes of the santonian tectonic event which we consider representative of the major trans african stress field changes is the rapidity with which the change was reflected stratigraphically across north and central africa and its short duration the cause of the santonian compressional event is directly linked to the change in poles of rotation for the opening of the atlantic at 83 85 ma the end of the cretaceous normal magnetic quiet zone this was also synchronous with the obduction of ophiolites along the northeast margin of arabia oman the onset of separation between india and madagascar with formation of the mascarene oceanic basin and the development of the european alpine chain we interpret these phenomena as causally related aspects of a global tectonic event the santonian compressional event as well as the campanian maastrichtian rifting event and the end cretaceous compressional event illustrate the critical connection between intraplate tectonic histories and processes occurring at sometimes very distant plate boundaries

evidence for surface uplift of the atlas mountains and the surrounding peripheral plateaux combining apatite fission track results and geomorphic indicators in the western moroccan meseta coastal variscan paleozoic basement this work represents an initial attempt to link the evolution of the topography in relation to the general tectonic framework of western morocco for this purpose in a section of the western moroccan meseta different tools are combined in order to attain the general objective apatite fission track aft data of granitic rocks of the rabat khenifra area give ages around 200 ma with track length distributions which are compatible with the thermal models already established for the area an inverse correlation between aft ages and elevation is observed which is compatible with previous models indicating northward tilting of the whole western moroccan meseta which is younger than 20 25 ma in order to test this possibility a detailed analysis of the topography at different scales in the estern moroccan meseta has been performed results indicate that two open folds with different amplitudes are recognized and that the one with wider wavelength could correspond to a lithospheric fold as previously stated by other authors on the basis of independent geological arguments the northward tilting proposed based on the aft data agrees with the results obtained in the analysis of the topography which reinforces the presence of a very open fold with a wavelength of 200 300 km in the north western limb of the western moroccan meseta

bathymetric prediction from dense satellite altimetry and sparse shipboard bathymetry the southern oceans south of 30 s are densely covered with satellite derived gravity data track spacing 2 4 km and sparsely covered with shipboard depth soundings hundreds of kilometers between tracks in some areas flexural isostatic compensation theory suggests that bathymetry and downward continued gravity data may show linear correlation in a band of wave lengths 15 160 km if sediment cover is thin and seafloor relief is moderate at shorter wave lengths the gravity field is insensitive to seafloor topography because of upward continuation from the seafloor to the sea surface at longer wavelengths isostatic compensation cancels out most of the gravity field due to the seafloor topography we combine this theory with wiener optimization theory and empirical evidence for gravity noise to signal ratios to design low pass and band pass filters to use in predicting bathymetry from gravity the prediction combines long wavelengths 160 km from low pass filtered soundings with an intermediate wavelength solution obtained from multiplying downward continued band pass filtered 15 160 km gravity data by a scaling factor s s is empirically determined from the correlation between gravity data and existing soundings in the 15 160 km band by robust regression and varies at long wave lengths we find that areas with less than 200 m of sediment cover show correlation between gravity and bathymetry significant at the 99 level and s may be related to the density of seafloor materials in these areas the prediction has a horizontal resolution limit of 5 10 km in position and is within 100 m of actual soundings at 50 of grid points and within 240 m at 80 of these in areas of very rugged topography the prediction underestimates the peak amplitudes of seafloor features images of the prediction reveal many tectonic features not seen on any existing bathymetrie charts because the prediction relies on the gravity field at wavelengths 160 km it is insensitive to errors in the navigation of sounding lines but also cannot completely reproduce them therefore it may be used to locate tectonic features but should not be used to assess hazards to navigation the prediction is available from the national geophysical data center in both digital and printed form

active faulting in the dead sea rift abstract manifestations of late quaternary and holocene faulting were studied in a 500 km long segment of the dead sea transform rift most prominent are left slip faults whose characteristic physiographic features are recognizable along most of the studied segment where these faults bend or are stepped to the left rhomb shaped grabens or pull aparts are produced forming depressions in the reverse situation compressional features such as pressure ridges domes and folds form positive topographic features such structures are combined on a variety of scales ranging from a few hundred meters long to tens of kilometers normal faults sub parallel to the left slip faults produce a trough like valley along much of the dead sea transform but are most prominent along the margins of the large rhomb grabens e g the dead sea trough they apparently record a small component of transverse extension generally their motion is slow young slip did not occur along some segments during the last few 10 4 y elsewhere throws of 10 20 m at least occurred in this period the dead sea transform is seismically active the instrumental and historic records indicate a seismic slip rate of 0 15 0 35 cm y during the last 1000 1500 y while estimates of the average pliocene pleistocene rate are 0 7 1 0 cm y either much creep takes place or the slip rate varies over periods of a few 10 3 y

the oldest skeletal macroscopic organism palaeopascichnus linearis abstract the existing problems regarding the phylogenetic resolution of ediacaran macroscopic organisms stem from a failure to factor in the information captured through different taphonomic windows here we integrate the information from sandstone and limestone hosted occurrences of the fossil palaeopascichnus linearis that together show a conspicuously greater range of taxonomic and taphonomic variation the limestone hosted material comes from a new locality discovered on the northwestern slope of the olenek uplift in arctic siberia that characterises the uppermost ediacaran strata of the khatyspyt formation khorbusuonka group detailed taphonomic and morphodynamic studies of the fossil material revealed evidence of possible chamber wall agglutination and growth through addition of new chambers with little sideway growth palaeopascichnus linearis outlived the intra ediacaran 550 myr ago drop in species richness the advent of bilaterians and the increase in complexity of burrowing behaviour in metazoans it remains to be seen whether or not the remarkable ecological success achieved by palaeopascichnus linearis during the times of rich evolutionary experimentation has anything to do with the invention of an agglutinated test palaeopascichnus poses major scientific challenges and it is now clear that such preservation as occurs in siberia may hold the answer to what they were how they lived and what they were related to

late precambrian rifting and crustal evolution in the northeastern desert of egypt basement exposures along the northwestern flanks of the gulf of suez record the rapid formation of continental crust during the interval 670 550 ma a variety of field petrographic petrologic and isotopic considerations indicate that this episode of crust formation took place in an extensional tectonic setting analogous to that of the late paleozoic oslo rift of norway crustal evolution in this region thus contrasts with other regions of the afro arabian shield where the crust appears to have been formed by convergent margin accretionary processes and collisional tectonics this imposes new constraints on our understanding of late precambrian crustal evolution

paleomagnetic and geological investigation into southern sinai volcanic rocks and the rifting of the gulf of suez two volcanic occurrences from southern sinai were sampled for paleomagnetic petrographic and geochemical investigations 29 oriented samples were taken from six sites of the middle jurassic basaltic intrusion at wadi budra southwest sinai 28 55aen 33 20aee after alternating field af demagnetization and tilt correction all samples exhibit normal magnetization with a mean paleomagnetic direction d 63 3 i 8 0 and a 95 10 2 this yields a paleopole position at lat 25 n long 133 e and a 95 8 6 also six oriented blocks 34 core samples were taken from the sant catherine doleritic dike at wadi sahl el raha south sinai 28 33aen 33 55aee after af demagnetization all sites showed normal polarity with a mean direction of magnetization d 3 i 39 and a 95 15 3 and a paleopole position at lat 83 e long 179 e and a 95 16 5 the paleomagnetic pole of w budra is found to be incompatible with poles of similar age from africa the cause of this cannot be uniquely determined but most probably could be referred to local tectonic rotations and or geomagnetic secular variations avecting the paleomagnetic directions of these samples in contrast the tertiary pole of wadi sahl el raha is consistent with the part of the apparent polar wander path apwp of africa for the time period 20 ma oligo miocene age petrographical and geochemical investigations revealed that the volcanic rocks of both localities are continental within plate rift related alkali olivine basalt w budra and olivine dolerite sahl el raha the primary magnetite is the main opaque mineral present in the samples which represents the main carrier of magnetization in these rocks 2000 elsevier science b v all rights reserved

discussion on the jurassic evolution of the arabian carbonate platform edge in the central oman mountainsjournal vol 162 2005 pp 349 362 b r c granier r g peebles and n j sander write the model proposed by rousseau et al 2005 for the jurassic evolution of the arabian carbonate platform edge is in part based on field observations made in jabal akhdar central oman fig 1 and on material collected there some of their conclusions based on these data are sound but they are not original for instance the diachroneity of the main pre kahmah group unconformity and the extent of the associated hiatus were documented in the seminal memoir published by glennie et al 1974 and illustrated by murris 1980 fig 24 and by hughes clarkes 1988 fig 27 among many others although these three references were cited by rousseau et al the authors omit aspects of this published previous work that does not support their own interpretations similarly published micropalaeontological data calpionellids that constrain these time relationships in onshore abu dhabi de matos 1994 are not incorporated into their interpretations published work that documents sedimentary breccias fig 2 just above the main unconformity at the base of the rayda formation hudson chatton 1959 toland et al 1993 is also not cited this omission is unfortunate because the occurrence of these sedimentary breccias does not fit well with their model the lack of any discussion of pre existing models and the omission or inappropriate use of published regional data undermines rousseau et al 2005 s efforts to provide a satisfactory new model of late jurassic events in the jabal akhdar area in the context of the arabian carbonate platform margin in consequence their conclusions based on supra regional correlations or comparisons with saudi arabia iran tunisia algeria morocco yugoslavia and france are also not sustainable we present alternative interpretations below that incorporate all

the oldest evidence of bioturbation on earth comment recently rogov et al 2012 1 discovered dense bioturbation fabrics the preserved depth of which reached 5 cm from the ediacaran khatyspyt formation of the northern siberian platform the age of the bioturbated beds is estimated at ca 555 ma the ichnotaxon itself is attributed to the

morphotectonics inferred from the analysis of topographic lineaments auto detected from dems application and validation for the sinai peninsula egypt abstract morphotectonic lineaments observed on the sinai peninsula in egypt were auto detected from shuttle radar topography mission 90 m digital elevation model dem and gravity grid data and then analyzed to characterize the tectonic trends that dominated the geologic evolution of this area the approach employed consists of dem shading segment tracing grouping statistical analysis of the distribution and orientation of the lineaments fault plane characterization and smooth representation techniques statistical quantification of counts mean lengths densities and orientations was used to infer the relative severity of the tectonic regimes to unravel the prominent structural trends and to demarcate the contribution of various faulting styles that prevailed through time restored to the present day geographic position prominent n50 60 w n20 40 w n50 60 e and n20 30 e and less prominent n s e w and ene trends were common the prominence of these trends varied through time the nw and ne trends showed relatively equal abundances in the precambrian and the cambrian whereas the prominence of the nw trends prevailed from the carboniferous to the holocene lineaments in all formations were near vertical and on average about 65 showed as strike slip 22 as reverse and 13 as normal faulting styles statistics from the detected linear features and the reference geological data reveal the relative severity of five dominant tectonic regimes precambrian compression followed by extension at its end cretaceous compression eocene compression miocene extension and finally holocene compression auto detected lineaments and the severity of the characterized tectonic periods correspond well with reference data on the geologic structure geodynamic framework and the gravity anomaly furthermore the recent significance of the broad structural zones was confirmed by the foci of the earthquake epicenters along and at the intra plate intersections of the broad lineament zones and at the plate boundaries the spatial distribution of trends with varying styles of faulting distinguished four main tectonic provinces of marked geodynamics variances

the northern red sea and the dead sea rift abstract the results of geophysical measurements at sea when combined with mesostructural measurements on land demonstrate systematic extensional features in the region of the northern red sea and the dead sea rift rifts and diapirs were encountered in the northern red sea showing an arcuate trend whereas the faulted continental margins at that region are oriented nw se the rifts and the diapirs changed their trend northwards from nnw sse to n s systems of rifts and diapirs are considered to be extensional features therefore the tectonic extensional axis probably changed its orientation accordingly a series of rifts and diapirs was found also in the gulf of elat trending approximately parallel to the coastlines and is interpreted to be the northern extension of the red sea rift and diapir system mesostructural measurements that were carried out in the western flank of the dead sea rift indicated further evidence for structural extension trending e w to ene wsw in addition to measurements of left lateral offset of approximately 10 km all these data when combined with the geophysical measurements of the characteristics of the earth crust underneath the dead sea rift suggest a tectonic regime of oblique extension in the region of the red sea and the dead sea rift this tectonic regime indicates that the red sea spreading center extends northwards along the dead sea rift and the clockwise change of the axial trend imposed a sinistral offset to the tectonic extension thus it is suggested that the dead sea rift is an incipient oblique spreading center

late quaternary reorientation of stress field and extension direction in the southern gulf of suez egypt evidence from uplifted coral terraces mesoscopic fault arrays and borehole breakouts uplifted pleistocene coral terraces and modern earthquakes show that several large normal faults are presently active in the southern gulf of suez rift basin the footwall of one of these faults is exposed at gebel el zeit where terraces at elevations of 10 18 and 42 m have been radiometrically dated as 125 ka and 426 ka respectively after correcting for eustatic sea level changes this results in net tectonic uplift rates of about 0 1 m kyr published interpretations and our own observations indicate that the average extension direction during the miocene to pliocene synrift history was 055 analysis of borehole breakouts and published earthquake fault plane solutions however suggests that the present day stress field in the southern gulf has a 010 020 shmin orientation detailed structural observations show that a change in extension direction occurred in the late pleistocene with rotation of the stress field beginning prior to formation of the 125 ka terraces but after formation of older pleistocene terraces whose ages are less tightly constrained using a horizontal slip direction of 015 and our observed net footwall uplift rate we calculate a separation velocity between sinai and africa of 0 8 1 2 m kyr the proposed pleistocene change in extension direction in the gulf of suez corresponds closely with the post 500 ka change in extension direction documented in the kenyan rift system and a similar change in extension direction recorded in the central red sea these regional similarities in tectonic history suggest that the underlying causes of these events may be a plate scale phenomenon affecting the entire afro arabian rift system rather than local changes in the quaternary stress field

burrowing below the basal cambrian gssp fortune head newfoundland the range of treptichnus pedum the index trace fossil for the treptichnus pedum zone extends some 4 m below the global standard stratotype section and point for the base of the cambrian period at fortune head on the burin peninsula in southeastern newfoundland the identification of zigzag traces of treptichnus isp even further below the gssp than t pedum in the fortune head section and in other terminal proterozoic successions around the globe supports the concept of a gradational onset of three dimensional burrowing across the proterozoic cambrian boundary although t pedum remains a reasonable indicator for the base of the cambrian period greater precision in the stratotype section can be achieved by a detailed re evaluation of the stratigraphic ranges and the morphological variation of ichnotaxa included in the t pedum zone

21ne versus 10be and 26al exposure ages of fluvial terraces the influence of crustal ne in quartz abstract the accuracy of 21 ne surface exposure ages depends critically on the correction for a trapped ne component commonly the amount of cosmogenic ne used to calculate 21 ne exposure ages is considered to be the ne excess relative to a trapped component of atmospheric composition 21 ne 20 ne 0 00296 here we document a trapped ne component in quartz samples from a series of river terraces at the northern margin of tibet hetzel et al nature 417 2002 428 432 which has a non atmospheric 21 ne 20 ne ratio varying from 0 00299 to 0 00398 vacuum crushing of amalgamated samples each derived from 30 80 quartz clasts revealed that the non atmospheric trapped component is present in fluid inclusions it has probably been incorporated into the quartz crystals during their growth in veins at low grade metamorphic conditions only if the amount of cosmogenic 21 ne is determined relative to this trapped component are the calculated 21 ne exposure ages consistent with the relative ages of the tectonically induced terraces and in agreement with independent 10 be and 26 al exposure ages of the fluvial terraces a significant in situ production of nucleogenic 21 ne by the reaction 18 o n 21 ne in the paleozoic quartz minerals is ruled out by extremely low u contents of the order of 1 5 ppb all ages have been corrected for an inherited cosmogenic component that results from cosmic ray exposure during erosion of the host rock and transport of the clasts to the terraces the origin of the trapped component from crustal fluids is supported by high 40 ar 36 ar ratios of 2000 6000 and slightly elevated 136 xe 132 xe ratios relative to air which can be explained by radioactive decay of 40 k and spontaneous fission of u in the crust

geochemical and sr nd pb isotopic data bearing on the origin of pan africangranitoids in the kid area southeast sinai egypt the kid plutonic suite in southeast sinai egypt is composed of 1 a gabbro diorite complex 2 quartz monzodiorite 3 granodiorite monzogranite association 4 syenogranite major and traceelement analyses and radiogenic isotope data rb sr sm nd and pb pb are presented for these rocks rb sr isochrons indicate ages of 581 11 ma 576 11 ma and 570 4 ma for the quartz monzodiorite granodiorite monzogranite association and syenogranite respectively the gabbro diorite complex is a layered intrusion varying in sio2 from 42 to 59 wt it shows a calc alkaline trend and the trace element characteristics of arc lavas subsequently this magma fractionated to give quartz monzodiorite andsyenogranite magmas the quartz monzodiorite has low initial 87 sr 86 sr ratios 0 703 and high nd values 4 4 0 3 with trace element characteristics of volcanic arc granites the granodiorite monzograniteassociation has higher initial sr ratio 0 7044 lower nd 1 5 2 7 and relatively high 207 pb 204 pb and 208 pb 204 pb significantly different from those of the older rocks isotopic data and ree modelling suggestthat it formed by partial melting of an early pan african amphibolitic lower crust the syenogranite isa typical highly fractionated post orogenic granite with a deep negative eu anomaly hfse and reeenrichment a 87 sr 86 sr initial ratio of 0 7033 nd of 4 5 0 5 and distinct variations in the 206 pb 204 pbratio the isotopic compositions of sr nd and pb indicate that the syenogranite and the quartzmonzodiorite are comagmatic increasing fluorine concentration from the quartz monzodiorite to thesyenogranite suggests that fluid fractionation involving fluorine complexing played an important role inthe genesis of the syenogranite this process led to the enrichment of hfse and hree to extensivefractional crystallization to changes in the u pb ratios and a distinct variation in 206 pb 204 pb

application of high resolution interferometric dems to geomorphic studies of fault scarps fish lake valley nevada california usa abstract recent developments in interferometric radar remote sensing provide a method for deriving detailed topographic and slope information for fault scarp detection in october 1996 the airborne topsar instrument ieee trans geosci remote sens 30 1992 933 was flown over southwest nevada and east central california topography calculated from topsar data are in the form of a high resolution 5 m spatial grid digital elevation model dem in this study we focus upon the large steep fault scarps that cut alluvium and alluvial fans in fish lake valley east of the white mountains of nevada california a series of topographic profiles extracted from the dem reveal that the larger fault scarps are greater than 40 m in height and that the average midsection slope angle for all measured scarps is approximately 23 these large scarps are the product of multiple offsets rather than a single event other relevant geomorphic features present in the digital topography include splays and benches along the main fault levees cutbanks gullies incising fault scarp slopes shutterridges offset drainage and small normal faults with scarp heights of only 4 6 m field work corroborated general geomorphologic landforms confirmed fault scarp morphometry and aided the evaluation of the accuracy of the dem we are also able to assess fault segmentation models that divide the fish lake valley fault zone flvfz into discrete segments based upon surface rupture characteristics

ediacaran biota in the aftermath of the kotlinian crisis asha group of the south urals abstract the asha group of the south urals is dominated by laminated shales and thin siltstone sandstone alternations interpreted as a prograding low energy inner shelf depositional system the succession includes several thick sharp based sandstone bodies comprising interstratified fine to medium grained fine laminated planar laminated hummocky convolute and wave bedded planar and trough cross bedded sandstones occasionally pebble to boulder conglomerates regarded as tidal deltaic and shoreface depositional systems the sandstone shoreface bodies are interpreted as forced regressive deposits stranded in offshore positions during subsequent transgressions although palaeoecological and taphonomic context of the asha group is favourable for the ediacara type biofacies the associated fossil assemblages nevertheless are depauperate and consist of frondomorph holdfast structures palaeopascichnids microbial colonies arumberiamorph structures as well as lithified microbial substrates shagreen texture biolaminites in terms of fidelity and fossil completeness preservation of ediacaran fossils in the asha group is by no means inferior to that seen in other ediacaran macrofossil localities the low biodiversity of ediacaran macrofossils can be attributed to a relatively young ediacaran age of the asha group which is constrained by a u pb zircon date of 547 6 3 8 ma from an ash bed in the lower part of the sedimentary succession the uppermost part of the asha group has yielded bilobed burrows with a backfill structure suggesting an affinity with the ichnogenus didymaulichnus from the ediacaran cambrian boundary strata the asha group therefore offers an important glimpse into the history of the edacaran biota in the aftermath of the kotlinian crisis that caused extinction of dickinsoniomorphs tribrachiomorphs and bilateralomorphs in wave and current agitated shoreface depositional systems 550 million years ago but did not significantly affect frondomorphs and palaeopascichnids

palynological evidence for the age and rate of sedimentation along the dead sea rift and structural implications abstract pollen diagrams obtained for eight deep boreholes penetrating the thick sequences of the dead sea rift fill correlated with dated marine sequences of the coastal plain in israel enable stratigraphie assignment of the continental deposits to be made the sedimentary units of the rift valley are of two main provenances those deposited in troughs within the rift limits of predominantly lacustrine environment attaining thicknesses in the order of 1 2 km for which the trough is the final erosion base level and those not limited to the rift boundaries but known from wide areas in israel mostly laid down in river systems that crossed the rift region on their way to the sea these fluviatile formations are in the order of hundreds of meters thick in the rift valley region which acted as an intermediate basin the first group of rock units of late miocene through early middle pliocene to glacial pleistocene ages indicate phases of considerable subsidence the earlier termed the erythrean and the later the levantine phase these are predated in the late oligocene through middle miocene by gentle subsidence and separated during the late pliocene preglacial pleistocene by another period of relative quietness in tectonic activity