the permian triassic transition and the onset of mesozoic sedimentation at the northwestern peri tethyan domain scale palaeogeographic maps and geodynamic implications the main aim of this paper is to review middle permian through middle triassic continental successions in european secondly areas of middle late permian sedimentation the permian triassic boundary ptb and the onset of triassic sedimentation at the scale of the westernmost peri tethyan domain are defined in order to construct palaeogeographic maps of the area and to discuss the impact of tectonics climate and sediment supply on the preservation of continental sediment at the scale of the western european peri tethyan basins the upper permian is characterised by a general progradational pattern from playa lake or floodplain to fluvial environments in the northern variscan belt domain areas of sedimentation were either isolated or connected to the large basin which was occupied by the zechstein sea in the southern variscan belt during the late permian either isolated endoreic basins occurred with palaeocurrent directions indicating local sources or basins underwent erosion and or there was no deposition these basins were not connected with the tethys ocean which could be explained by a high border formed by corsica sardinia palaeorelief and even parts of the kabilia microplate the palaeoflora and sedimentary environments suggest warm and semi arid climatic conditions at the scale of the whole study area an unconformity more or less angular is observed almost everywhere between deposits of the upper permian and triassic except in the central part of the germanic basin the sedimentation gap is more developed in the southern area where in some basins upper permian sediment does not occur the large sedimentary supply erosion and or lack of deposition during the late permian as well as the variable palaeocurrent direction pattern between themiddle late permian and the early triassic indicate a period of relief rejuvenation during the late permian during the induan all the intra belt basins were under erosion and sediment was only preserved in the extra belt domains the northern and extreme southern domains in the northern domain the central part of the germanic basin sediment was preserved under the same climatic conditions as during the latest permian whereas in the extreme southern domain it was probably preserved in the tethys ocean implying a large amount of detrital components entering themarinewaters mesozoic sedimentation began in the early olenekian the ephemeral fluvial systems indicate arid climatic conditions during this period three distinct areas of sedimentation occur a northern and southern domain separated by an intra belt domain the latter accumulated sediments during the early middle permian and experienced erosion and or no deposition conditions between the middle late permian and the beginning of mesozoic sedimentation dated as anisian to hettangian at the top of the lower triassic another tectonically induced more or less angular unconformity is observed the hardegsen unconformity which is dated as intra spathian and is especially found in the north european basins this tectonic activity created new source areas and a new fluvial style with marine influences at the distal part of the systems during the anisian and ladinian continental sedimentation was characterised by a retrogradational trend in other words the fluvial system evolved into fluvio marine environments attesting to a direct influence of the tethys ocean in the southern and northern domains both at the end of the olenekian spathian and during the anisian the presence of palaeosols micro andmacrofloras indicate less arid conditions throughout this domain

chronology of internal drainage development and uplift southern puna plateau argentine central andes fundamental to understanding the late cenozoic evolution of the central andes is knowledge of the age that the puna altiplano plateau became a unique tectonomorphic entity within the orogen the two attributes that define the puna altiplano are 1 its average elevation of 3 km and 2 regions of high elevation that correspond spatially to regions with internal drainage the chronology of plateau uplift to elevations similar to modern ones is equivocal owing to an inability to define the absolute elevation of the plateau surface through time however because regions of the puna altiplano have nonmarine evaporites nad because such evaporites must accumulate within regions of internal drainage the chronology of these strata elucidates when the plateau became internally drained we show that for the southern puna between lat 24 and 26 s internal drainage was established between 14 1 and 24 2 ma and probably by 15 ma these results corroborate and refine other workers inferences that the puna altiplano plateau became uplifted and paleogeographically isolated from the adjacent fore arc and foreland during middle to late miocene time

late early permian continental ichnofauna from lake kemp north central texas usa abstract continental trace fossils of early permian age are well known in the western united states from wolfcampian asselian to artinskian strata but few examples are known from leonardian kungurian deposits a substantial ichnofauna from strata of the lower part of the clear fork formation at lake kemp baylor county texas augments the meager north american record of leonardian continental trace fossil assemblages ichnofossils at lake kemp occur in the informally named craddock dolomite member of the clear fork formation which is 12 15 m above the local base of the clear fork the trace bearing stratum is an up to 0 3 m thick laminated to flaser bedded dolomitic siltstone that also contains mud cracks raindrop impressions microbially induced mat structures and some land plant impressions we interpret the craddock dolomite member as the feather edge of a marine transgressive carbonate deposit of an irregular coastline marked by shallow bays or estuaries on the eastern shelf of the midland basin and the trace fossil bearing stratum at lake kemp is an unchannelized flow deposit on a muddy coastal plain the fossil site at lake kemp yields a low to moderately diverse fauna of invertebrate and vertebrate traces a sparse invertebrate ichnofauna consists of arthropod feeding and locomotion traces assigned to walpia cf w hermitensis white 1929 and diplichnites gouldi gevers in gevers et al 1971 tetrapod footprints are most common and assigned to batrachichnus salamandroides geinitz 1861 cf amphisauropus kablikae geinitz and deichmuller 1882 and dromopus lacertoides geinitz 1861 which represent small temnospondyl seymouriamorph and basal sauropsid trackmakers both the traces and sedimentary features of the fossil horizon indicate a freshwater setting at the time of track formation and the trace assemblage represents the scoyenia ichnofacies and the batrachichnus ichnofacies in an overbank environment with sheet flooding and shallow ephemeral pools on an extensive coastal plain the lake kemp tetrapod track assemblage is characteristic of the global early permian tetrapod ichnofauna found in red beds which is dominated by a handful of ichnogenera that include batrachichnus limnopus amphisauropus dromopus varanopus hyloidichnus ichniotherium and dimetropus which are the tracks of temnospondyls seymouriamorphs diadectomorphs pelycosaurs captorhinomorphs and araeoscelids the lake kemp tracks also further document the continuity of the ichnogenera batrachichnus amphisauropus and dromopus from wolfcampian into leonardian time and thus support the concept that wolfcampian and leonardian red bed tetrapod footprints represent a single biostratigraphic assemblage

an anatomy consistent study of the lopingian eolian tracks of germany and scotland reveals the first evidence of the end guadalupian mass extinction at low paleolatitudes of pangea abstract the poor preservation and apparent monospecifity of permian tetrapod footprints from eolian paleoenvironments have thus far hampered their reliable interpretation this study clarifies how this is due to distinct and repeated ichnotaphonomic effects on trackway pattern and footprint morphology on originally inclined planes once these effects are excluded the anatomy consistent ichnotaxobases useful for ichnotaxonomy can be recognized several nomina dubia are identified among these the ichnogenus chelichnus here considered a taphotaxon the eolian ichnoassociations from the lopingian of scotland and germany include six different ichnotaxa cf capitosauroides isp eutheriodont therapsid dicynodontipus geinitzi cynodont therapsid dolomitipes isp dicynodont therapsid pachypes loxodactylus n comb pareiasaurian parareptile procolophonichnium isp small parareptile and rhynchosauroides isp non archosauriform neodiapsid this is completely different from the interpretations of the last 20 years which postulated that these paleoenvironments comprised monospecific associations of synapsid tracks these ichnoassociations are instead moderately diverse similar to low latitude marginal marine to floodplain ichnoassociations and belong to the lopingian paradoxichnium footprint biochron the cornberg formation of germany being constrained between the illawarra reversal and the mid wuchiapingian kupferschiefer at the rotliegend zechstein transition constitutes the earliest evidence of lopingian tetrapod faunas at low paleolatitudes and the first evidence of low paleolatitude faunal turnover related to the end guadalupian mass extinction from both the skeleton and the track record this suggests a global extension of the dinocephalian extinction event which occurred at high mid south africa and russia and low western europe paleolatitudes of pangea about 259 260 ma and was probably triggered by the eruption of the emeishan large igneous province of sw china which considerably changed global environmental conditions in both marine and continental settings

permian continental basins in the southern alps italy and peri mediterranean correlations the late carboniferous to permian continental successions of the southern alps can be subdivided into two main tectono sedimentary cycles separated by a marked unconformity sealing a middle permian time gap generally estimated at over 10 ma the lower cycle 1 between the variscan crystalline basement and the early permian is mainly characterised by fluvio lacustrine and volcanic deposits of calc alkaline acidic to intermediate composition which range up to a maximum thickness of more than 2 000 m the upper cycle 2 which is devoid of volcanics is mostly dominated through the mid late permian by alluvial sedimentation which covered the previous basins and the surrounding highs giving rise to the subaerial verrucano lombardo val gardena groden red beds up to about 800 m thick the palaeontological record from the terrigenous deposits of both the above cycles consists mainly of macro and microfloras and tetrapod footprints the age of the continental deposits is widely discussed because of the poor chronological significance of a large number of fossils which do not allow reliable datings however some sections are also controlled by radiometric calibrations the comparison with some selected continental successions in southern europe allows to determine their evolution and set up correlations a marked stratigraphic gap shows everywhere between the above mentioned cycles 1 and 2 as in the southern alps the gap reaches the greatest extent during the mid permian near the illawarra reversal geomagnetic event 265 ma in western europe however such as in provence and sardinia the discussed gap persists upwardly to late permian and early triassic or slightly younger times i e to the onset of the alpine sedimentary cycle even though in northeastern spain iberian ranges balearic islands this gap results clearly interrupted by late guadalupian lopingian deposits the above two major tectonosedimentary cycles reflect in our view two main geodynamic events that affected the southern europe after the variscan orogenesis the late carboniferous early permian transformation of the gondwana eurasia collisional margin into a diffuse dextral transform margin and the middle late permian opening of the neotethys ocean with the onset of a generalised extensional tectonic regime and the progressive westward marine ingression

new timing and geochemical constraints on the capitanian middle permian extinction and environmental changes in deep water settings evidence from the lower yangtze region of south china the capitanian guadalupian witnessed one of the major crises of the phanerozoic and like many other extinctions it coincided with the eruption of a large igneous province in this case the emeishan traps of sw china however the timing and causal relationships of this event are in dispute this study concentrates on the deep water chert mudstone strata of the gufeng formation and its transition to the yinping formation at chaohu zircons from tuffs in the uppermost gufeng formation yield a u pb age of 261 6 1 6 ma and comparison with sections around emeishan suggests that the tuffs appeared in the jinogondolella altudaensis conodont zone and persisted to the jinogondolella xuanhanensis zone this coincides with the emeishan eruptions and suggests that the tuffs probably derived from this province mineralogical and geochemical characteristics also show the tuffs are of acid volcanogenic origin and have a geochemical fingerprint of the emeishan large igneous province our dating shows that a crisis amongst radiolarian and a subsequent productivity decline occurred during the middle capitanian prior to the guadalupian lopingian boundary the emeishan eruptions began immediately before this indicating a likely causal relationship between these events major regression and marine anoxia euxinia are two other important extinction relevant environmental changes that occurred during this critical interval

tectonic development southeastern border of the puna plateau northwestern argentine andes the puna altiplano a 500 000 km2 area at an average elevation of 3 7 km in the central andes occurs in a non collisional plate setting over a 30 east dipping segment of the benioff zone and is bounded to the north and south by nearly flat segments of the subducted nazca plate a 120 km long portion of the southeastern boundary of the puna in northwestern argentina was studied to gain insight into the structures associated with uplift of the plateau and into the nature of structures over the transition from flat to steeper subduction the structural geometry and kinematic evolution of the region was determined from geologic mapping and kinematic analysis of minor fault arrays the present southeastern margin of the puna was uplifted between 5 10 and 2 ma northwest southeast horizontal shortening and vertical extension during uplift were produced by northeast striking en echelon thrust faults dipping 17 55 northwest four to seven en echelon structural blocks each 20 30 km long constitute the border of the puna their structural geometry precludes large scale overthrusting as an important mechanism of plateau uplift along the studied segment in the past 2 m y there has been a 45 change in the direction of shortening and locally a 90 change in the extension direction indicating that the structures accompanying uplift are no longer active this change could be due to a change either in the geometry of the subducted plate or in convergence directions although neither of these hypotheses is testable given presently available data

large scale cenozoic wind erosion in the puna plateau the salina del fraile depression wind erosion is integral to the evolution of arid landscapes on earth and mars but the nature of long term wind erosion of bedrock is poorly understood here we describe the salina del fraile sdf

accurate source depths and focal mechanisms of shallow earthquakes in western south america and in the new hebrides island arc synthetic seismograms are matched to long period p waveforms in order to obtain accurate depths of shallow earthquakes with known focal mechanisms accurate depths are obtained for a large sample of moderate sized 6 ms 7 events which produced relatively simple p waveforms and do not require intensive analysis the estimated error in the determination of depth is about 5 km or less for most of the events considered the procedure is applied to two suites of events one in south america 83 events and one in the new hebrides 61 events in these two areas of contrasting styles of subduction the accurate depths provide new information on the bending of descending plates near trenches the seismicity and tectonics of the upper plate and the geometry and structure of the zone of contact between the upper and descending plates depths of suboceanic earthquakes which occurred near the trench and which have either tensional and compressional horizontal stress axes agree well with chapple and forsyth s 1979 preferred model of a bending elastic perfectly plastic plate however an unusually deep event occurred beneath the fiji plateau in an area of young ocean floor supposed to have been formed by sea floor spreading processes only since late miocene time the calculated depth of the event 48 km places it below the lithosphere asthenosphere boundary derived from thermal models vertical cross sections through the shallow parts of the subduction zones show that most of the earthquakes with thrust faulting focal mechanisms can be interpreted to be interplate events located in a thin 10 km thick curved zone of contact dipping arcward or landward from the trench axis however a few events with focal mechanisms similar to the interplate events do not fit on the inferred thin zone of contact these events would be accommodated by an interplate zone 15 km thick in both subduction zones interplate events occur at depths between about 15 and 50 km however the downdip width of the south american interplate zone is 2 to 3 times larger than that in the new hebrides most of the intraplate events near the interplate boundary are located in the descending plate in the upper plate seismicity is more pronounced in the back arc regions of the two subduction zones thus our results support the generality of a relatively aseismic zone in the upper plate located trenchward of the magmatic arc depths of shallow earthquakes in the eastern andes and sub andean regions of south america range between about 9 and 36 km indicating that both the upper and middle crust are seismically active about 75 of the events occurred in the upper 25 km furthermore the focal mechanisms indicate that from ecuador to argentina the crust of the eastern side of the andean cordilleran is in a state of east west compression oriented nearly parallel to the direction of convergence between the nazca and south american plates the depths the orientations of the earthquake nodal planes and the close relationships to quaternary tectonics imply basement involved crustal shortening in much of the eastern andes and sub andean zones of peru and argentina

permian triassic vertebrate footprints from south africa ichnotaxonomy producers and biostratigraphy through two major faunal crises abstract the fossil record of mid to late permian terrestrial vertebrates in the south african karoo basin is regarded as the most abundant and diverse in the world despite the extensive research on body fossils to date the vertebrate footprint sites have not been subjected to an anatomy consistent ichnotaxonomic investigation here we present a comprehensive ichnotaxonomic revision of permian early triassic tracksites in the main karoo basin of south africa furthermore a track trackmaker correlation for all permian synapsid groups is provided for the first time based on the analysis of the functional morphology of potential producers the following ichnotaxa and their proposed trackmakers are recognized brontopus giganteus dinocephalians cf capitosauroides isp therocephalians cf dicynodontipus isp cynodonts dolomitipes accordii small dicynodonts dolomitipes icelsi n comb large dicynodonts karoopes gansfonteinensis n igen n isp gorgonopsids procolophonichnium nopcsai procolophonids and rhynchosauroides isp non archosauriform diapsids three different footprint assemblages fa i iii are proposed for footprint biostratigraphy fa i lower tapinocephalus az a guadalupian assemblage dominated by dinocephalian tracks fa ii topmost tapinocephalus cistecephalus az a latest guadalupian wuchiapingian assemblage dominated by gorgonopsid and dicynodont tracks in association with subordinate therocephalian tracks and fa iii lower lystrosaurus az an induan assemblage with dicynodont cynodont procolophonid and diapsid tracks the lower fa ii includes the earliest ichnofauna with lopingian affinity all over the world topmost tapinocephalus pristerognathus az 260 259 ma and could indicate an early recovery phase after the end guadalupian mass extinction because of the high abundance of large gorgonopsid tracks and absence of dinocephalian tracks this footprint record may also predate the body fossil record suggesting an earlier gorgonopsid radiation fa iii represents the earliest and most complete post end permian extinction ichnofauna which includes an early phase of abundant small dicynodont tracks potentially indicating a stressed post event community nevertheless this ichnofauna looks very similar to pre extinction ichnofaunas from europe in agreement with the skeletal record at the daptocephalus lystrosaurus az transition

relative motion of the nazca farallon and south american plates since late cretaceous time by combining reconstructions of the south american and african plates the african and antarctic plates the antarctic and pacific plates and the pacific and nazca plates we calculated the relative positions and history of convergence of the nazca and south american plates despite variations in convergence rates along the andes periods of rapid convergence averaging more than 100 mm a between the times of anomalies 21 49 5 ma and 18 42 ma and since anomaly 7 26 ma coincide with two phases of relatively intense tectonic activity in the peruvian andes known as the late eocene incaic and mio pliocene quechua phases the periods of relatively slow convergence 50 to 55 30 mm a at the latitude of peru and less farther south between the times of anomalies 30 31 68 5 ma and 21 and between those of anomalies 13 36 ma and 7 correlate with periods during which tectonic activity was relatively quiescent thus these reconstructions provide quantitative evidence for a correlation of the intensity of tectonic activity in the overriding plate at subduction zones with variations in the convergence rate

three dimensional modeling of pull apart basins implications for the tectonics of the dead sea basin we model the three dimensional 3 d crustal deformation in a deep pull apart basin as a result of relative plate motion along a transform system and compare the results to the tectonics of the dead sea basin the brittle upper crust is modeled by a boundary element technique as an elastic block broken by two en echelon semi infinite vertical faults the deformation is caused by a horizontal displacement that is imposed everywhere at the bottom of the block except in a stress free shear zone in the vicinity of the fault zone the bottom displacement represents the regional relative plate motion results show that the basin deformation depends critically on the width of the shear zone and on the amount of overlap between basin bounding faults as the width of the shear zone increases the depth of the basin decreases the rotation around a vertical axis near the fault tips decreases and the basin shape the distribution of subsidence normalized by the maximum subsidence becomes broader in contrast two dimensional plane stress modeling predicts a basin shape that is independent of the width of the shear zone our models also predict full graben profiles within the overlapped region between bounding faults and half graben shapes elsewhere increasing overlap also decreases uplift near the fault tips and rotation of blocks within the basin we suggest that the observed structure of the dead sea basin can be described by a 3 d model having a large overlap more than 30 km that probably increased as the basin evolved as a result of a stable shear motion that was distributed laterally over 20 to 40 km

the late miocene quaternary antofalla volcanic complex southern puna nw argentina protracted history diverse petrology and economic potential abstract the antofalla volcanic complex avc is located on the southern puna plateau of nw argentina 100 km east of the main axis of the cordillera occidental volcanic arc it lies on the nw se archibarca lineament one of several transverse structures that cut across the andes from chile and divert arc magmatism in se trending fingers across the puna 40ar 39ar dating of volcanic products from the avc reveals a protracted magmatic history from 10 9 to 1 6 ma initial volcanism was characterized by eruption of voluminous rhyolitic ignimbrites deposited directly onto exposed crystalline basement and supracrustal sedimentary rocks these rhyolites record significant geochemical evidence for crustal contamination or derivation by crustal melting which decreases upwards through the pyroclastic sequence they were followed by extrusion of potassic lavas of the shoshonite latite trachydacite suite from 10 1 to 9 5 ma subsequent magmatism 9 1 1 6 ma was of basaltic andesite andesite dacite composition with localized smaller volume dacitic and rhyolitic ignimbrites monogenetic basaltic andesite cinder cones and lava flows were erupted in the quaternary in response to a change to transtensional tectonics in the puna the volcanic sequence is interpreted to record the early development of a lower crustal mash zone at 11 ma where mantle derived arc magmas interacted extensively with felsic lower crustal rocks to produce evolved shoshonitic compositions and crustal melts that erupted to form rhyolitic ignimbrites common at this time throughout the puna after establishment of a steady state mash zone by 9 ma subsequent basaltic andesite andesite magmas show less evidence of felsic crustal contamination and may have developed largely by interaction with previous ultramafic mafic fractionates of early magmas in the lower crust more felsic dacitic magmas appear to have evolved largely by fractional crystallization from basaltic andesites and andesites with widespread evidence of mixing and mingling between magmas of different degrees of differentiation some contamination by upper crustal components is also evident in these dacites but is shown more clearly by small volume rhyolites some of which may again represent predominantly crustal melts epithermal deposits of au and pb zn ag occur within the avc apparently associated with the formation of rhyolite domes the mineralization style is typical of other andean volcanic centres and may be underlain by deeper seated porphyry styles of mineralization extensive blanketing by younger lavas and limited erosion restricts exposure of these altered and mineralized sequences however although the potential for further discoveries beneath cover or at depth in this system appears high

extinction of pull apart basins numerous pull apart basins are present along the haiyuan fault zone in northwestern china detailed geological mapping of these basins reveals an evolution of faulting and subsidence that leads toward extinction of some pull apart basins the most common cause of pull apart basin extinction appears to be the development of new strike slip faults along one of the basin margin normal faults or diagonally across the basin the strike slip faults may develop together with normal faults to form a complex zone within the basin the migration of boundary strike slip faults toward the basin center can also cause the extinction of pull apart basins the extinction of these pull apart basins suggests that there is probably a tendency for a strike slip fault zone to straighten itself and the examples show how this takes place

reconstruction of a late cisuralian early permian floodplain lake environment palaeontology and sedimentology of the tregiovo basin trentino alto adige northern italy abstract the late cisuralian is known as a time of increasing aridity compared to the late pennsylvanian early cisuralian although several studies highlighted this trend at low latitudes of western pangaea little is known from central pangaea environments the discovery of new fossiliferous horizons in the late cisuralian tregiovo formation northern italy allowed a new palaeoenvironmental study based on facies analysis ichnology palaeobotany plant insect interaction and palynology three facies associations were identified a c and correspond to floodplain lake ephemeral lacustrine and distal alluvial fan environments respectively the tetrapod ichnoassociation is more diverse than previously known including abundant diapsid and non diapsid reptile tracks and rarer temnospondyl amphibian tracks plant fossils are characterized by a predominance of hinterland taxa conifers hygrophytic plants are present as well the sporomorph association is dominated by miospores of cordaitales voltziales and peltaspermales while trilete lycopsid and fern miospores are rare which corresponds well with the macroflora invertebrate trace fossils and feeding traces on plant fossils are described for the first time from the tregiovo basin suggesting transitional low energy environments and a relatively low level of herbivory respectively this study evidences the development in the tregiovo basin of a wet and dry probably seasonal climate which became drier between facies associations a b this environment constitutes an important reference since few data are known to infer the late cisuralian climatic conditions of central pangaea

ichniotherium tracks from the permian of france and their implications for understanding the locomotion and palaeobiogeography of large diadectomorphs abstract the lower permian continental succession of the lodeve basin southern france contains a rich tetrapod ichnofossil record in this paper we re describe 20 large footprints from the autunian asselian lunas locality using new data and photogrammetric techniques analysis of the best preserved footprints permits the recognition of two trackways of ichniotherium cottae and we compare this material with all known carboniferous permian occurrences of the ichnogenus the large size slow gait footprint arrangement and depth pattern inferred from the trackways are consistent with a primitive diadectomorph and suggest a progressive adaptation to more terrestrial locomotion a synapomorphy based track trackmaker correlation indicates limnoscelis or analogous forms as possible trackmakers these footprints increase our knowledge of the ichnofaunal diversity of central pangaea

early permian tetrapod ichnofauna from the intra sudetic basin sw poland abstract tetrapod footprints from late palaeozoic deposits of poland have been known for 150 years but are poorly studied here we present the first comprehensive analysis of an extensive assemblage of fossil tracks from two artificial outcrops near tlumaczow in the polish part of the intra sudetic basin accompanied by conifer macrofloral remains and a few invertebrate traces all footprints occur in reddish to greyish brown fluvio lacustrine siltstones and sandstones of the early permian slupiec formation based on the study of nearly 120 slabs with tracks and trackways we discern four distinct types of tetrapod footprints these are assigned to the ichnotaxa amphisauropus kablikae geinitz and deichmuller 1882 ichniotherium cottae pohlig 1885 dimetropus leisnerianus geinitz 1863 and dromopus lacertoides geinitz 1861 that can be referred to seymouriamorph diadectomorph pelycosaurian grade synapsid and early sauropsid track makers the tlumaczow vertebrate track assemblage represents a typical early early permian asselian sakmarian ichnofauna remarkable features are the dominance of footprints of terrestrially adapted tetrapods and the relative abundance of diadectomorph tracks supporting interpretation of the fossil bearing strata as part of an intermontane hinterland basin outside the range of semiaquatic anamniotes

the precordilleran fault system of chuquicamata northern chile evidence for reversals along arc parallel strike slip faults abstract the chilean precordillera situated between the longitudinal valley and the western cordillera of northern chile was the site of the andean magmatic arc from the late cretaceous to the eocene oligocene boundary magmatism came to an end during the incaic tectonic phase 38 ma which caused arc normal shortening and the development of longitudinal dextral strike slip faults precordilleran fault system this magmatic arc tectonism is also related to the formation of the chuqicamata porphyry copper ore deposit as well as of other important deposits of this type in the precordillera structural investigations in and around the chuqicamata open pit mine have shown that wrench tectonics determined the kinematics of the area the n s striking west fissure which separates a 35 ma old non mineralised pluton to the west from a central late paleozoic basement ridge containing the mineralization became a sinistral fault along with other parallel faults in the area the central part is separated from similar paleozoic rocks to the east by the messabi este fault and a narrow faulted and sheared syncline of mesozoic cenozoic sediments this fault bears structures indicating dextral movements which probably are of an age that is similar to the mylonites 34 8 ma in the western pluton the dextral movements preceded the sinistral shear thus the fault system of chuqicamata displays a reversal of arc parallel shear movements according to the orientation of quartz veins in the mineralized body it is presumed that the sense of displacement of these strike slip motions reversed when mineralization started at about 32 ma during this time the stress field must have changed fundamentally the incaic phase dextral transpression is supposed to have been induced by the oblique vector of plate motion the following sinistral transtension corresponds to a time of reduced convergence rate and possibly reduced plate coupling as however the vector of plate motion remained unchanged during that time oblique subduction cannot be used as an argument for arc parallel sinistral shear movements

geodynamic and magmatic stages on a traverse through the andes between 20 and 24 s n chile s bolivia nw argentina metamorphic precambrian basement is exposed in the chilean pre cordillera in the form of a narrow horst and also in the argentinian puna miogeosynclinal pelites and psammites of devonian age dominate in the western part of the andes while early palaeozoic clastics occur in the e insignificant triassic sediments were followed by wide spread shallow marine jurassic deposition cretaceous and tertiary strata are predominantly terrestrial deposits whereas the precambrian and palaeozoic series were intensely deformed by folding block faulting dominates in the volcano sedimentary cover magmatic activity has been significant since the precambrian while s type intrusives and extrusives occurred mainly in the palaeozoic i type magmatic rocks predominated in the mesozoic the cenozoic volcanism in the cordillera occidental originated in the lower and upper crust magnetotelluric and seismic investigations on the traverse show extremely low electric resistivity values coinciding with a strong absorption of seismic waves below the chilean pre cordillera and the cordillera occidental this phenomenon can best be explained by the existence of partial melts at depths of more than 10 km the bouguer values decrease by about 430 mgal from the coast to the cordillera occidental in the precambrian and palaeozoic the continent apparently extended farther to the w the change from a passive to an active continental margin took place at the palaeozoic mesozoic boundary with the break up of pangea in order to grasp better the tectonic and magmatic evolution as well as the recent structure of the crust in the central andes a combined geological geophysical investigation has been made along a traverse through the andes between 20 and 24 s fig 1 the following pages present a review of the geological development together with the first results of work from the chilean section of the traverse

analogue models of pull apart basins sandbox analogue models of pull apart basins that developed in sedimentary strata above releasing steps in underlying basement faults are characterized by rhombic basins that are flat bottomed box grabens with a subhorizontal synkinematic basin infill steep to nearly vertical sigmoidal oblique slip and segmented oblique extensional faults are the dominant bounding structures of the pull apart basins cross basin short cut faults link the offset principal displacement zones that are characterized by flower structure development the structural architectures of the physical models compare directly in form and dimensions to natural examples of strike slip pull apart basins

sedimentary architecture structural setting and late cenozoic depocentre migration of an asymmetric transtensional basin lake izabal eastern guatemala abstract lake izabal located in eastern guatemala lies in an ew trending basin located along the transform margin between the north american and caribbean plates this plate boundary consists of two main left lateral strike slip faults known as the polochic and motagua fault system pmfs the basin is a 100 20 km lens shaped depression in which the lake occupies its eastern half to the north the basin is confined by a principal deformation zone pdz which is recognized in this area as the most important upper crustal branch of the polochic fault the eastern part of the basin has been uplifted and dissected exposing the basin infill along the slopes of the montana del mico analysis of a set of multichannel seismic reflection profiles most of them acquired within the lake combined with well and outcrop information allowed to outline the structure and evolution of the basin and its stratigraphic architecture the basin is strongly asymmetrical both in cross and along strike directions and is filled up by neogene to quaternary sediments with the deepest side of the basin being to the north close and parallel to the pdz the base of the infill is a mid tertiary unconformity whose differential subsidence through time brought the basin to its present structural setting five main evolutionary stages are recognized based on seismo stratigraphic and structural features which are related to the development and activity of the bordering faults development of the basin began in its easternmost sector a small half graben tilted to the south developed in response to the activity of an oligocene or early middle miocene growth fault in the second stage late miocene the basin tilts to the north causing the sedimentary sequences to thicken towards the northern pdz this stage is dominated by oblique extension and by progressive migration of the basin depocenter towards the west the third stage early pliocene records a strong acceleration of the strike slip activity which causes a rapid westward migration of the depocenter the fourth stage late pliocene although still dominated by regional transtension is related to the development of a transpressional event along the eastern side of the basin as evidenced by the occurrence of folds and reverse faults parallel to the northern bend of the polochic fault during the fifth stage quaternary the eastern part of the basin remains relatively quiescent while the western part undergoes subsidence with localized transtension still related to the activity in this sector of the polochic fault left lateral movement along the polochic fault caused the depocenter to migrate 75 80 km at different velocities with slip rates ranging between 2 1 and 16 3 mm yr this study suggests that the polochic fault developed in the early middle miocene in connection to the deposition of the early sediments of the izabal basin even though an older age oligocene could also be possible to our knowledge this is one of the best examples of sedimentary architecture documenting depocentre migration due to fault movement along a transform system

constraining the permian triassic transition in continental environments stratigraphic and paleontological record from the catalan pyrenees ne iberian peninsula abstract the continental permian triassic transition in southern europe presents little paleontological evidence of the permian mass extinction and the subsequent faunal recovery during the early stages of the triassic new stratigraphic sedimentological and paleontological analyses from middle upper permian to lower middle triassic deposits of the catalan pyrenees ne iberian peninsula allow to better constrain the permian triassic succession in the western tethys basins and provide new bio chronologic data for the first time a large vertebra attributed to a caseid synapsid from the middle permian is reported from the iberian peninsula one of the few reported from western europe osteological and ichnological records from the triassic buntsandstein facies reveal a great tetrapod ichnodiversity dominated by small to medium archosauromorphs and lepidosauromorphs rhynchosauroides cf schochardti r isp 1 and 2 prorotodactylus rotodactylus an undetermined morphotype a and to a lesser degree large archosaurians chirotheriids overall suggesting a late early triassic early middle triassic age this is in agreement with recent palynological analyses in the buntsandstein basal beds that identify different lycopod spores and other bisaccate and taeniate pollen types of late olenekian age early triassic the permian caseid vertebra was found in a playa lake setting with a low influence of fluvial water channels and related to the distal parts of alluvial fans in contrast the triassic buntsandstein facies correspond to complex alluvial fan systems dominated by high energy channels and crevasse splay deposits hence a faunal and environmental turnover is observed the pyrenean biostratigraphical data show similarities with those of the nearby western tethys basins and can be tentatively correlated with north african and european basins the triassic pyrenean fossil remains might rank among the oldest continental records of the western tethys providing new keys to decipher the triassic faunal biogeography and recovery

the agost basin betic cordillera alicante province spain a pull apart basin involving salt tectonics the agost basin is characterized by a miocene quaternary shallow marine and continental infilling controlled by the evolution of several curvilinear faults involving salt tectonics derived from triassic rocks from the serravallian on the area experienced a horizontal maximum compression with a rotation of the maximum stress axis from e w to n s the resulting deformation gave rise to a strike slip fault whose evolution is characterized progressively by three stages 1 stepover releasing bend with a dextral motion of blocks 2 very close to pure horizontal compression and 3 restraining bend with a sinistral movement of blocks in particular after an incipient fracturing stage faults generated a pull apart basin with terraced sidewall fault and graben subzones developed in the context of a dextral stepover during the lower part of late miocene p p the occurrence of triassic shales and evaporites played a fundamental role in the tectonic evolution of the study area the salty material flowed along faults during this stage generating salt walls in root zones and salt push up structures at the surface during the purely compressive stage middle part of late miocene p p the salt walls were squeezed to form extrusive mushroom like structures the large amount of clayish and salty material that surfaced was rapidly eroded and deposited into the basin generating prograding fan clinoforms the occurrence of shales and evaporites both in the margins of the basin and in the proper infilling favored folding of basin deposits faulting and the formation of rising blocks later in the last stage upper part of late miocene p p the area was affected by sinistral restraining conditions and faults must have bent to their current shape the progressive folding of the basin and deformation of margins changed the supply points and finally caused the end of deposition and the beginning of the current erosive systems on the basis of the interdisciplinary results the agost basin can be considered a key case of the interference between salt tectonics and the evolution of strike slip fault zones the reconstructed model has been compared with several scaled sandbox analogical models and with some natural pull apart basins

discovery geology and origin of the fruta del norte epithermal gold silver deposit southeastern ecuador fruta del norte is a completely concealed and extraordinarily well preserved epithermal gold silver deposit located in the remote cordillera del condor mountain ranges of southeastern ecuador currently defined resources in a single steep relatively small body displaying exceptional grade continuity contain 9 81 million ounces moz of gold and 15 0 moz of silver with an indicated resource grade of 9 59 g t au and 12 9 g t ag the deposit was discovered in early 2006 during a greenfields program conducted by aurelian resources a canadian junior explorer discovery resulted from systematic drill testing of a conceptual geologic model which predicted that auriferous veins would be present in andesitic volcanic rocks inferred to underlie a steep silicified rib cutting a fluvial conglomerate sequence the rib is highly anomalous in arsenic antimony and mercury but contains low order gold values the second drill test the discovery hole intersected 230 m of ore grade gold silver mineralization beneath 200 m of the barren conglomerate cover the host andesitic volcanic rocks crosscutting feldspar porphyry and associated phreatic breccias are assigned to the piuntza unit of the santiago formation which along with the zamora batholith and a series of porphyry copper stocks was generated in a continental margin magmatic arc during the middle to late jurassic the deposit is located near the northeastern extremity of the 10 km long suarez pull apart basin where it is linked to the steep west and central faults part of the regionally extensive las penas strike slip fault zone the pull apart basin was progressively filled by fluviatile conglomerate dacitic ignimbrite flows finer grained siliciclastic sedimentary rocks and finally andesite flows all assigned to the chapiza formation the fruta del norte deposit consists of a 1 3 km long and up to 300 m wide vein stockwork associated with quartz illite pyrite alteration the deposit comprises two principal vein types one in the south dominated by quartz manganoan carbonates and abundant base metal sulfides and the other in the north dominated by manganese and base metal poor quartz and calcite adularia is a minor main stage gangue mineral in each both types are abruptly transitional upward and westward to a third ore type marked by intense silicification and chalcedony veining with disseminated and veinlet marcasite pyrite the uppermost part of this silicic zone is sulfide deficient probably the result of a short lived supergene oxidation event prior to initial conglomerate deposition the deposit is notable for the widespread occurrence of fine to coarse visible gold which gives rise to bonanza grades and is closely associated with quartz chalcedony carbonate and sulfide gangue the sulfide free silicic zone is overlain by an extensive silica sinter horizon which may either directly overlie the piuntza volcanic rocks and or occur as interbeds in the basal 20 m of the conglomerate which are invariably silicified and marcasite bearing otherwise the conglomerate above the orebody lacks silicification with one critical exception the steeply inclined zone that is exposed as the silicified rib that led to discovery the sinter horizon containing localized mud pool deposits and hydrothermal eruption breccias is in unusual proximity to the underlying gold silver orebody the northern and southern parts of the fruta del norte deposit possess characteristics that are usually considered typical of low and intermediate sulfidation epithermal deposits respectively they may have required two discrete mineralizing fluids both of which are suspected to have ascended via the west and central faults the upward change to the silicified zone is attributed to cooling of the ascendant fluid on approach to the paleosurface sinter progressive burial of the deposit beneath the suarez basin fill may have contributed to the suppression and eventual extinction of the epithermal system with gold mineralization of the conglomerate being inhibited by rheologic and chemical factors formation of the fruta del norte deposit and complete filling of the suarez basin took place in 3 to 6 m y during the late jurassic 157 154 ma

structure of the hanmer strike slip basin hope fault new zealand hanmer basin 10 x 20 km located in northern south island new zealand is evolving where two major segments of the dextral strike slip hope fault are projected to converge across a 6 to 7 km wide releasing step over the structural geometry and development of hanmer basin does not conform to traditional pull apart basin models the respective fault segments do not overlap but are indirectly linked along the southwest margin of the basin by an oblique normal fault the hope river segment terminates in an array of oblique normal faults along the northwestern basin range front and east west striking normal faults on the west hanmer plain faulted holocene alluvial fan surfaces indicate west hanmer basin is actively subsiding evolving under north south extension the conway segment along the southeastern margin of the basin terminates in a complex series of active fault traces small pop up ridges and graben depressions early basin fill sediments of pleistocene age are being folded elevated and dissected as the eastern part of hanmer basin is progressively inverted and destroyed by north south contraction the north margin of the basin is defined by a series of topographic steps caused by normal faulting outside of the area of the releasing step over these normal faults we interpret to reflect large scale upper crustal collapse of the hanging wall side of the hope fault new seismic reflection data and geologic mapping reveal a persistent longitudinal and lateral asymmetry to basin development four seismic stratigraphic sequences identified in the eastern sector of the basin thicken and are tilted southward with insequence lateral onlaps occurring to the north and east and also onto basement near the fault controlled basin margins the basin depocenter currently contains 1000 m of sediment adjacent to the south margin and is disrupted by faulting only at depth in the western part of the basin the sediment fill is thinner today the rate of basin deepening under transtension at the western end is matched by its progressive inversion and destruction under transpression in the eastern sector with the oldest basin fill now being recycled we propose a hybrid model for hanmer strike slip basin one in which geometric elements of a fault wedge basin downward and upward tipped spindle shaped ends are combined with those of a pull apart basin step over region between the major fault segments we also conclude that changes in fault geometry releasing and restraining bends and step overs at a variety of scales and over short distances control the development of the extensile and contractile parts of the basin and three dimensional basin asymmetry strain partitioning is complex and cannot be related simply to local reorientation of the regional stress field

active tectonics of the andes nearly 90 mm a 1 of relative plate convergence is absorbed in the andean plate boundary zone the pattern of active tectonics shows remarkable variations in the way in which the plate slip vector is partitioned into displacement and strain and the ways in which compatibility between different segments is solved along any traverse across the plate boundary zone the sum of relative velocities between points must equal the relative plate motion we have developed a kinematic synthesis of displacement and strain partitioning in the andes from 47 s to 5 n relevant for the last 5 ma based upon 1 relative plate motion deduced from oceanic circuits giving a roughly constant azimuth between 075 and 080 2 moment tensor solutions for over 120 crustal earthquakes since 1960 3 structural studies of deformed plio pleistocene rocks 4 topographic geomorphic studies 5 palaeomagnetic data and 6 geodetic data we recognize four neotectonic zones with subzones and boundary transfer zones that are partitioned in different ways these zones are not coincident with the classic zones defined by the presence or absence of a volcanic chain or differences in finite displacements and strains and tectonic form the long term segmentation and finite evolution of the andes may not occur in constantly defined segments in space and time in segment 1 47 39 s the slip vector is partitioned into roughly orthogonal benioff zone slip with large magnitude large slip surface earthquakes and both distributed dextral shear giving clockwise rotations of up to 50 and dextral slip in the curved liquine ofqui fault system giving 5 10 of anticlockwise fore arc rotation in segment 2 39 20 s the slip vector is partitioned into benioff zone slip roughly parallel with the slip vector andean crustal shortening and a very small component of dextral slip including that on the atacama fault system between 39 and 34 s a cross strike dextral transfer which deflects the chile trench and the volcanic arc absorbs the shortening contrast between segments 1 and 2 in segment 3 20 6 s the slip vector is partitioned into roughly orthogonal benioff zone slip crustal shortening sinistral trench parallel faulting and northeast southwest extension compatibility between segments 2 and 3 is maintained by the sinistral east southeast trending cochabamba shear zone and north trending dextral faults in segment 4 6 s to 5 n the slip vector is partitioned into roughly orthogonal benioff zone slip and dextral strike slip faulting in the fore arc and volcanic chain

aridification across the carboniferous permian transition in central equatorial pangea the catalan pyrenean succession ne iberian peninsula abstract the carboniferous permian terrestrial successions record a global climatic shift from icehouse to hothouse conditions our multidisciplinary study documents an aridification trend throughout the 1000 m thick composite terrestrial succession of the western catalan pyrenees ne iberian peninsula representing this time period the detailed stratigraphic framework integrates sedimentology paleopedology biochronology plant fossils and tetrapod footprints and geochronology paleomagnetism additional absolute age correlation is also carried out the new and reviewed data show that the late carboniferous wet environments with short drought periods progressively changed to a strong seasonal semi arid and arid climate with short humid periods through the early permian this paleoclimatic trend supports the previously suggested aridification of the pangean pan tropical belt and supports the hypothesis of the influence of the recurrent climatic fluctuations in central pangea being tentatively correlated to the southern gondwanan glaciation deglaciation periods therefore the carboniferous permian terrestrial succession from the catalan pyrenees emerges as a continuous record that can help to constrain late paleozoic paleoenvironmental events

revision of a classic site for permian tetrapod ichnology collio formation trompia and caffaro valleys n italy new evidences for the radiation of captorhinomorph footprints abstract the recent studies on permian captorhinomorph non diapsid eureptile footprints from north america north africa and europe raised the interest on their taxonomic and biostratigraphic significance they seem to radiate in the late early permian but the scarcity of absolute dating in the classic sections bearing these trace fossils is not helpful in order to unravel their distribution the continental collio formation cropping out extensively in the central southern alps of italy can cover this gap of knowledge since it preserves a rich testimony of these trace fossils erpetopus hyloidichnus varanopus and it is well constrained from radiometric datings and fossil content for this and because of the huge amount of stored but unanalyzed material a revision was necessary through careful taxonomic assignations these taxa are here confirmed and or identified as being amphisauropus kablikae cf batrachichnus isp dromopus lacertoides erpetopus cassinisi hyloidichnus bifurcatus limnopus heterodactylus and varanopus isp the occurrence of erpetopus at the base of the collio formation kungurian base suggests its minimum age of first appearance in a global context this is a very important presence in order to build a reliable tetrapod footprint biostratigraphy during the permian the quantity of material yielded in the different facies of the collio and dosso dei galli formations also permit new insights on the paleoenvironments and climatic settings

palaeoenvironmental reconstruction and early permian ichnoassemblage from the ne iberian peninsula pyrenean basin this work was supported by the synthesys project e m de taf 2560 at mfn and fr taf 3621 and fr taf 4808 at mnhn http www synthesys info and secretaria d universitats i de recerca del departament d economia i coneixement de la generalitat de catalunya e m expedient number 2013 ctp 00013 at ise m for visits to collections e m received financial support from the pif grant of the geology department at uab field works have been developed on the project vertebrats del permia i el triasic de catalunya i el seu context geologic and evolucio dels ecosistemes amb faunes de vertebrats del permia i el triasic de catalunya ref 2014 100606 based at institut catala de paleontologia and we acknowledge the financial support of the departament de cultura generalitat de catalunya

tectonic and magmatic evolution of the andes of northern argentina and chile abstract two orogenic cycles both with different evolution are developed in the western margin of the south american continent in northern argentina and chile the paleozoic hercynic cycle and the meso cenozoic andean cycle the hercynic cycle a wide marine basin extending westward of the cordillera oriental which developed in cambrian ordovician times marks the beginning of this cycle in contrast to peru and bolivia where this basin developed between two precambrian blocks the western margin of this basin in northern argentina and chile is still unknown the ordovician sedimentation and accompanied volcanism ends with the ocloyic deformation phase and its synkinematic granitic plutonism two basins were developed in the silurian devonian separated by the puna arc uplifted during this ocloyic phase the shallow water marine terrigeneous sediments which were deposited in them were deformed by a new tectono magmatic associated phase chanic phase carboniferous to lower permian marine carbonates were deposited west of the puna arc and red beds east of it later on during the permian to triassic a magmatic belt was developed along the cordillera occidental the rhyolites ignimbrites and the granitic to granodioritic related intrusives are well represented in chile although the overall geologic history of this period is known many problems concerning its origin and relations to plate tectonics are still unsolved the andean cycle during this cycle a series of magmatic arc systems related to the subduction of the pacific crust was built up along the western margin of south america huge volumes of calc alkaline lavas and related plutons were emplaced since the jurassic along belts parallel to the present coastline showing a general eastward migration trend up to the lower cretaceous an ensialic back arc basin was formed east of this magmatic arc thousands of meters of marine and continental sediments were deposited in it this basin disappeared during the middle cretaceous probably as a result of the final opening of the atlantic and the active westward movement of the south american plate since middle cretaceous times the magmatic arc has been the fundamental paleogeographic element the arc progressively migrated stepwise eastward each step marked by a tectonic phase subduction related crustal erosion could explain the lack of fore arc petrotectonic assemblages the eastward magmatic polarity which characterizes this section of the andes could also be explained by such a mechanism

the late palaeozoic early mesozoic from the catalan pyrenees spain 60 myr of environmental evolution in the frame of the western peri tethyan palaeogeography the eastern catalan pyrenees form the southernmost segment of the pyrenean axial zone they experienced complex multistage process as the result of both the variscan and the pyrenean orogenic cycles after the late palaeozoic several small extensional sub basins were filled by continental successions as a response to the changing tectonic setting within the frame of the southwestern europe this stratigraphic record perfectly exposed in the studied eastern pyrenean areas preserves the signatures of the late palaeozoic pangea break up during the progressive dismantling of the variscan chain up to the triassic diffused extension despite structural network being severely affected by cenozoic reworking the stratigraphic framework can be unravelled by the detailed sedimentological and stratigraphical analysis of the well exposed sequences in short this paper addresses facies patterns and architectural elements of late carboniferous permian triassic continental sections studied in the catalan pyrenees and aims to use these signatures for correlation not only at a regional scale but also within the broader picture of the southwestern europe our stratigraphical reconstruction clearly demonstrates that the thick studied succession consists of fluvial lacustrine basal units affected by intense volcanic activity and overlaying predominantly fluvial fining upwards units for each unit several lithofacies architectural elements and bounding surfaces of different order have been identified and their lateral and vertical staking characterized deposition and erosion processes are controlled by alternating periods of tectonic activity producing different stages of high and low subsidence the uplift of the sub basin margins and subsequent extended erosive events marked by angular unconformities on the strength of the major rank bounding surfaces analysis the studied sedimentary packages have been grouped into different tectono stratigraphic units and then correlated they have been contextualized within the latest palaeogeographic reconstructions of the studied sector contributing to detail the role of the study area within the frame of the s european palaeogeography

giant evaporite belts of the neogene central andes large volumes of continental evaporites accumulated within the central andes during neogene uplift of the altiplano puna plateau and development of the andean volcanic arc halite and gypsum are dominant minerals along with local and economically important borates playa conditions have existed since ca 15 ma halite and borate deposition has occurred for the past 7 to 8 m y evaporites formed in salar environments e g playa lakes and are characterized by complex mineral assemblages occurrence zonation and geochemistry evaporite deposition was controlled by volcanism geothermal activity closed drainage and climate these andean deposits and their controls differ from evaporites in other continental and marine environments

a mid pleistocene deformation transition in the hula basin northern israel implications for the tectonic evolution of the dead sea fault the dead sea fault dsf plate boundary has accommodated relative sinistral motion between the sinai and arabian plates since the neogene geologically based models point to a long term 5 0 ma n trending relative motion roughly parallel to the central sector of the dsf gps based calculations of present day relative motion between the sinai and arabian plates indicate a northward increasing convergent component across the dsf suggesting a kinematic change over the plio pleistocene period we study the evolving deformation of the hula rhomb shaped graben situated along the central sector of the dsf in order to examine the possible kinematic change the hula graben is widely accepted as a pull apart basin part of a series of basins extending southward we use a 3 d approach combining mapped surface structures with subsurface seismic reflection profiles 173 km and borehole data 38 boreholes gathered here into a single geographic information systems database results indicate that during the mid pleistocene a major tectonic transition modified the structure of the basin fill a subvertical nnw trending left lateral throughgoing strike slip fault developed diagonally across the basin consequently the basin entered a new geodynamic phase where subsidence was controlled by both the basin bordering faults and the diagonal fault while the vertical displacement across the transverse faults is minor synchronous structural changes recorded in additional localities along the dsf attests to a mid pleistocene 1 ma regional tectonic transition that was associated with a northward increasing convergent component across the central and northern sectors of the dsf

strike slip deformation in the confidence hills southern death valley fault zone eastern california usa the confidence hills form a well exposed composite positive flower structure developed in pliocene to recent lacustrine and alluvial fan sediments the structure has developed along the current trace of the southern death valley dextral strike slip fault zone california usa nw se striking fault zones bound the confidence hills in 3d these fault segments are inferred to link at depth to a common basal fault system the flower structure is formed by doubly plunging anticlines that roughly parallel the bounding fault segments fold development was aided by a the presence of a basal salt deposit and numerous detachment horizons within the sedimentary pile and b buttressing and uplift along and against the bounding oblique slip reverse faults structural and palaeomagnetic evidence indicates that the anticlines developed with axial surfaces parallel and sub parallel to the trace of both fault zones folding appears to have initially developed adjacent to and above the southeastern fault segment and then propagated outwards and to the northwest the latest displacements along the current southern death valley fault zone are probably only in the orders of hundreds of metres and as young as 0 9 ma to recent this young fault zone is highly segmented along the length of the floor of southern death valley the high proportion of oblique slip faulting consistent with the strike slip zone being immature the confidence hills structure displays close geometric similarities with other natural examples of positive flower structures and to the features found in scaled analogue sandbox experiments of strike slip faulting

a paleomagnetic study of permian and triassic rocks from the toulon cuers basin se france evidence for intra pangea block rotations in the permian 1 the identification of a massive shear zone separating gondwana from laurasia during late palaeozoic times is one of the prerequisites for the controversial pangea b to a transition here we present new paleomagnetic data from permian and triassic sediments and volcanic rocks from the toulon cuers basin se france likely to be situated within this intra pangea shear zone a total of 150 samples from 14 sites were collected in the field 108 samples yielded reliable paleomagnetic component directions based on stepwise thermal demagnetization up to maximum temperatures of 690 c after removal of an initial viscous magnetic component from room temperature up to 200 c a second component of reverse polarity oriented to the south and up was identified in almost all samples of permian age the triassic samples behave similarly with the notable difference that here two polarities of magnetization are present positive field tests suggest the primary character of this characteristic magnetization the latitudes of the resulting early to mid permian paleopoles agree well with the corresponding segment of the apparent polar wander path apwp for europe whereas the longitudes are strung out along a small circle segment indicating relative rotations between the sampled regions and stable europe the triassic poles instead plot close to the triassic segment of the european apwp and provide an upper time limit for the observed rotations these results suggest a wrench faulting event associated with intra pangea crustal instability and transformation during the permian

tetrapod footprint ichno associations from french permian basins comparisons with other euramerican ichnofaunas in order to take into account the studies of the european and american usa collections carried out by one of the authors and of the recent nomenclatural revisions from new footprint discoveries which have occurred during the last decade the authors present a critical review of the french permian palichnofauna the distribution of the ichnospecies in the stratigraphy of the lodeve basin taken as a reference is outlined the ichno associations are then compared with those of other french provence european italy germany and usa basins based on the ages of different ichnofossiliferous formations three successive ichnofaunal units can be distinguished in the permian of europe the first developed in the cisuralian asselian to kungurian the second is found in the south of france in kazanian to lower tatarian strata equivalent to the roadian wordian the third and youngest dated as lopingian is only found in italy in the bolzano basin because of sedimentary gaps limited observations sometimes erroneous determinations and ichnospecies with great vertical distribution it currently appears that footprints have a low utility for biochronological resolution nevertheless they allow us to discriminate three time intervals in the permian as is also the case for skeletal remains