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

palaeoenvironmental reconstruction of a middle miocene alluvial fan to cyclic shallow lacustrine depositional system in the calatayud basin ne spain the middle miocene sedimentary fill of the calatayud basin in north eastern spain consists of proximal to distal alluvial fan floodplain and shallow lacustrine deposits four main facies groups characteristic of differentsedimentary environments are recognized 1 proximal and medial alluvial fan facies that comprise clast supported gravel and subordinate sandstone and mudstone the latter exhibiting incipient pedogenic features 2 distal alluvial fan facies formed mainly of massive mudstone carbonate rich palaeosols and local carbonate pond deposits 3 lake margin facies which show two distinct lithofacies associations depending on their distribution relative to the alluvial fan system i e front lithofacies a comprising massive siliciclastic mudstone and tabular carbonates or lateral lithofacies b showing laminated and or massive siliciclastic mudstone alternating with tabular and or laminated carbonate beds and 4 mudflat shallow lake facies showing a remarkable cyclical alternation of green grey and or red siliciclastic mudstone units and white dolomitic carbonate beds the cyclic mudflat shallow lake succession as exposed in the orera composite section ocs is dominantly composed of small scale mudstone carbonate dolomite cycles the mudstone intervals of the sedimentary cycles are interpreted as a result of sedimentation from suspension by distal sheet floods the deposits evolving either under subaerial exposure or water saturated conditions depending on their location on the lacustrine mudflat and on climate the dolomite intervals accumulated during lake level highstands with mg rich waters becoming increasingly concentrated lowstand to highstand lake level changes indicated by the mudstone dolomite units of the small scale cycles reflect a climate control from dry to wet conditions on the sedimentation in the area the spatial distribution of the different lithofacies implies that deposition of the small scale cycles took place in a low gradient shallow lake basin located in an interfan zone the development of the basin was constrained by gradual alluvial fan aggradation additional support for the palaeoenvironmental interpretation is derived from the isotopic compositions of carbonates from the various lithofacies that show a wide range of 1 8 o and 1 3 c values varying from 7 9 to 3 0 pdb and from 9 2 to 1 7 pdb respectively more negative 1 8 d and 1 3 c values are from carbonate rich palaeosols and lake margin carbonates which extended in front of the alluvial fan systems whereas more positive values correspond to dolomite beds deposited in the shallow lacustrine environment the results show a clear trend of 1 8 o enrichment in the carbonates from lake margin to the centre of the shallow lake basin thereby also demonstrating that the lake evolved under hydrologically closed conditions

late visean thermal event in the northern part of the french massif central new 40ar 39ar and rb sr isotopic constraints on the hercynian syn orogenic extension he french massif central belongs to the central metamorphic domain of the european hercynian belt 40ar 39ar mica and amphibole dates have been obtained on magmatic and metamorphic rocks from the northern part of the french massif central sioule and brevenne violay series the 336 to 337 ma dates recorded by a granodiorite the st gervais pluton and its mylonitic border along the ste christine fault and the 337 5 ma muscovite ages from the brevenne series are consistent with the age of wrenching related to the late stage of the hercynian compression the remaining age spectra from the sioule area provide ages ranging from 331 to 335 ma that are interpreted as cooling ages related to rock exhumation after the main stages of metamorphism and deformation in the studied area late visean dates widespread in north massif central correspond to a huge magmatic event characterized by the emplacement of red granites granophyres and sub aerial acidic volcanics known as the tufs anthraciferes formation rb sr isotopic data from volcanic and hypovolcanic rocks from the sioule and montagne bourbonnaise areas place constraints on the source of the magmas simple metapelite crustal melting or a major contribution from depleted mantle sources are ruled out and instead mantle derived magmas were probably involved at least as a heat source during the late visean magmatism exhumation and cooling of metamorphic rocks below 300 c occurred contemporaneously with this late visean magmatism in the geodynamic evolution of the hercynian belt the late visean ca 335 330 ma magmatism corresponds to a major break marking the onset of post collisional extension in the inner zone which had been thickened by collision in latest devonian earliest carboniferous this late visean extension in the inner zone which is synchronous to compression in the northern and southern forelands of the belt appears as a syn orogenic process

the beginning of the buntsandstein cycle early middle triassic in the catalan ranges ne spain sedimentary and palaeogeographic implications abstract the early middle triassic siliciclastic deposits of the catalan ranges ne spain are dominated by aeolian sediments indicating a predominance of arid climate during this time span in sharp contrast with the coeval fluvial sediments found in the castilian branch of the iberian ranges 300 km to the sw the ne sw oriented catalan basin evolved during the middle late permian as the result of widespread extension in the iberian plate this rift basin was bounded by the pyrenees ebro and montalban oropesa highs the permian early triassic age sediments of the catalan basin were deposited in three isolated subbasins montseny garraf prades separated by intrabasinal highs but linked by transversal nw se oriented faults the three subbasins show evidence of diachronic evolution with different subsidence rates and differences in their sedimentary records the buntsandstein sedimentary cycle started in the late early triassic smithian spathian in the central and southern domains garraf and prades with conglomerates of alluvial fan origin followed by fluvial and aeolian sandstones source area of the fluvial sediments was nearby paleozoic highs to the north and west in contrast with the far away source areas of the fluvial sediments in the iberian ranges to the sw these fluvial systems were interacting with migrating aeolian dune fields located towards the s which developed in the shadow areas behind the barriers formed by the paleozoic highs these highs were separating the subbasins under arid and semi arid climate conditions the dominating winds came from the east where the westernmost coast of the tethys sea was located and periods of water run off and fields of aeolian dunes development alternated some of the fluvial systems were probably evaporating as they were mixed into the interdune areas never reaching the sea from the end of the smithian to the spathian the catalan basin and neighbour peri tethys basins of the present day southern france sardinia and minorca islands constituted a geographical arch where arid and semi arid conditions represented an extension of the prevailed arid and hyper arid conditions in surrounding areas of the variscan belt harsh climatic conditions in this area prevented the life recovery in the aftermath of the permian triassic extinction event until the early anisian when more humid climate allowed for the colonisation of the area by plants amphibians and reptiles the boundary between desert areas and semi arid and or seasonal climate domains during the smithian spathian in sw europe can be precisely established in ne iberia between the catalan ebro region and the castilian branch of the iberian ranges to the sw

sedimentologic and dynamic differences between hot and cold laharic debris flows of mayon volcano philippines numerous hot lahars produced during and immediately after the 1984 eruption of mayon volcano along with frequent cold lahars of the succeeding wet monsoon seasons have left widespread debris flow deposits fresh deposits of hot debris flows have thin crusts that are remarkably resistant to erosion and to vegetal growth these crusts contain clasts with uniform thermoremanent magnetization directions rare soft sediment deformation structures and gas escape tubes deposits of unchannelized hot and cold debris flows both have sheetlike or lobate geometry non erosional bases poor sorting relatively minor silt and only traces of clay sized ash either matrix or clast support and common out sized clasts at their tops it is difficult to distinguish between the deposits after burial but they have subtle significant sedimentologic differences the inversely graded bases of hot debris flow deposits are thick suggesting a lack of cohesion and considerable dispersive pressure they have long clast axes aligned parallel to bedding due to strongly sheared laminar flow and generally they are succeeded by gradual normal grading from waning flow conditions in cold debris flow beds only the basal few centimeters may be inversely graded the bulk being commonly ungraded indicating the active role of cohesive forces in the hot flows vaporization of water by heat from large clasts may have facilitated mobility by decreasing internal friction indirect velocity calculations indicate that they moved faster and traveled farther than did cold flows proximal hot debris flows were all supercritical with froude numbers decreasing enroute the most distal hot debris flows and all of the cold ones were subcritical cold debris flows show no correlation between froude number and distance of transport

chronostratigraphy and paleoclimatology of the lodeve basin france evidence for a pan tropical aridification event across the carboniferous permian boundary abstract paleosols preserved within the carboniferous permian succession of the lodeve basin massif central france change stratigraphically from histosols to calcic vertisols and calcisols to gypsic vertisols and ultimately back to calcic vertisols and calcisols new high precision u pb zircon ages ca idtims for tuff beds within the lodeve and adjacent graissessac basins significantly revise the chronostratigraphy of these and correlated permian terrestrial basins of eastern euramerica under the newly revised chronostratigraphy presented here these stratigraphic changes in morphology indicate a substantial drying of paleoenvironments across the carboniferous permian boundary with a trend toward progressively more arid and seasonal climates through most of the early permian this newly realized chronology provides a paleoenvironmental and paleoclimatic timeline for eastern tropical pangea that is contemporaneous with similar records in western pangea and suggests pan tropical progressive climate change toward aridity and seasonality occurred from the late carboniferous through early permian

crustal thinning recorded by the shape of the namurian westphalian leucogranite in the variscan belt of the northwest massif central france in the western part of the variscan belt of the french massif central the gueret massif is an extensional allochthon emplaced to the southeast during namurian westphalian time the internal structure of the coeval leucogranites surrounding the western edge of the gueret massif consists of the plateau d9aigurande brame st sylvestre and st goussaud massifs these plutons are asymmetric diapirs rooted in the marche bussiere madeleine and arrenes faults respectively the plutons indicate diverging extravasation from the gueret massif whatever their shapes the plutons have a northwest trending stretching lineation that is also marked in the granite host rocks by retrograde metamorphic minerals the same extension direction is also inferred from namurian westphalian leucogranites and dikes intruding the gueret massif extension related granitoids present typical structural patterns such as asymmetric shapes extravasation from the collapsing area and persistence of a stretching lineation parallel to the regional extension direction these features may be used to diagnose crustal thinning

inversion of small basins effects on structural variations at the leading edge of the axial zone antiformal stack southern pyrenees spain the southern axial zone of the pyrenees consists of a foreland dipping system of thrusts and backthrusts forming the leading edge of a basement involved antiformal stack several small stephanian permian extensional basins were strongly inverted during the pyrenean cainozoic orogeny and controlled thrust geometry and kinematics causing lateral structural variation palinspastic restoration reveals three main grabens erill castell estac and gramos basins capped by undeformed triassic strata in the lower orri and erta thrust sheets the overlying nogueres thrust sheet partitioned into several slices contains smaller basins northern basins the erill castell half graben with a steeply dipping sedimentary infill was inverted along its border fault and extruded by bedding parallel backthrusts the narrow thick estac basin which was less deformed internally was a heterogeneity causing major lateral variation in the system the gramos basin originally wide and covered by a gentle unconformity angle was also inverted along its border fault but caused less lateral variation in the thrust system the northern basins appear only in the western part of the present day nogueres thrust sheet where minor units are strongly stacked and rotated in the east thrust slices are large and shallow dipping the study case is a good example of complex 3d thrust development influenced by the initial geometry of a heterogeneous basin system

imaging links between lithospheric architecture and surface geology in the proterozoic curnamona province australia 1 potential field magnetic and gravity analysis is an effective method to investigate crustal scale architecture and provides a means of linking continental scale geophysical data sets e g seismic tomography with detailed geological and geophysical studies here we image deep crustal structure of the proterozoic curnamona province australia in aeromagnetic and gravity data sets and establish spatial and temporal links between deep structures and near surface geological features by superimposing first vertical derivative responses on upward continued images upward continued gravity and aeromagnetic data show nw se ne sw e w and n s oriented long wavelength discontinuities and boundaries to anomalies which we interpret as deep seated structures these structures predate the oldest known tectonic events recorded in outcropping rocks and appear to have been long lived thereby influencing the tectonic history of the province for example outcropping cambrian shear zones evident in vertical derivative data appear to have nucleated off displaced segments of a once continuous deep seated structure of proterozoic origin that has been imaged in upward continued data long wavelength gradients defining e w and nw se structures in upward continued aeromagnetic data intersect beneath the dominantly felsic benagerie igneous province in the central province and are coincident with a large negative gravity anomaly interpreted as felsic igneous rocks that are coeval to the volcanic pile tectonic implications of this study include 1 deep seated structures in the curnamona province have protracted histories 2 these structures appear to have controlled the location and distribution of younger shear zones igneous activity and possibly basin subsidence in the upper crust 3 geophysical lineaments are likely to have evolved and propagated during multiple tectonic cycles and hence record the protracted evolution of a geological province

origin of the permian triassic iberian basin central eastern spain abstract the iberian basin was an intracratonic rift basin in central eastern spain developed since early permian times the basin boundary faults were normal listric faults controlling an asymmetric extension propagating northeast with time hercynian or older lineaments controlled the orientation of the iberian basin and extension was accommodated basically in the hanging wall block by the formation of secondary grabens and a central high the basin was related with the coeval ebro catalan and cuenca mancha basins and their connections are discussed subsidence curves show that the early permian early jurassic period of extension can be subdivided into three rifting episodes and a flexural one extension factor increases from 1 17 in the northwest to 1 29 near the mediterranean coast the increasing extension rate was accommodated by transfer faults trending nne ssw more important in the levante area the rift evolution is intermittent and seems to reflect distinct stress fields the collapse of the late hercynian orogen and related increased heat flux extension and rifting is the most probable origin of the iberian basin and related basins the origin of the catalan and the valencia prebetic basins is related to the southwards migration of the hesse burgundy rift along the eastern margin of the iberian microplate

precambrian protoliths and early paleozoic magmatism in the french massif central u pb data and the north gondwana connection in the west european variscan belt abstract u pb geochronological data were collected on zircon by la mc icp ms on orthogneiss and paragneiss from the limousin area in the french massif central fmc in order to investigate the connection between the west european variscan belt and the northern margin of gondwana fifteen samples were collected in the four main tectonostratigraphic units of the fmc namely the para autochthonous unit the lower gneiss unit lgu the upper gneiss unit ugu and the thiviers payzac unit orthogneiss yield intrusion age between 521 7 and 446 6 ma considering all the results from both magmatic and metasedimentary samples two peaks at 531 and 473 ma are recognized rifting processes taking place along the north gondwana margin during the lower paleozoic went on until the end of the ordovician as suggested by the magmatic event recorded around 450 ma several maximum depositional ages were ascertained in the metasedimentary formations of the fmc as determined by the youngest detected detrital zircon crystal ranging from 604 16 ma for metasediments of the para autochthonous unit 573 12 ma for the lgu 564 9 ma for the thiviers payzac unit and 523 4 ma in the ugu minimum depositional ages are given by magmatic emplacement ages obtained in the crosscutting orthogneiss there is some evidence for a decrease of this maximum age upwards in the tectonostratigraphy detrital zircon in metasedimentary formations and inherited zircon in orthogneiss display a wide spectrum of ages with significant peaks at around 590 ma and 560 ma archean paleoproterozoic and neoproterozoic detrital zircons suggest a west african craton source of the sedimentation the large amount of neoproterozoic and lower paleozoic ages obtained in this study suggests that these periods played a significant role in the continental crustal growth history of western europe

cenozoic vertical motions of the catalan coastal ranges ne spain the role of tectonics isostasy and surface transport 1 we analyze the cenozoic topographic evolution of the catalan coastal ranges ne spain and the role of fault activity erosion sedimentation and isostasy in controlling uplift and subsidence a forward numerical model constrained by an extensive geological and geophysical data set is used to examine the temporal and spatial record of cenozoic vertical motions we show that the effect of isostasy erosion and sedimentation is as important as the contribution of fault deformation to the topography of the catalan coastal ranges the model predicts that paleogene topography generation by thrusting was compensated by erosion up to 1 3 km and isostatic subsidence up to 1 2 km resulting in a 1 2 1 9 km high mountain range by the end of compression 29 ma during the neogene strong tectonic subsidence related to normal faulting and the consequent flexural uplift of 0 7 1 2 km surface erosion as much as 1 6 2 3 km and sedimentation up to 4 5 km led to the present landscape configuration extension rates along the barcelona fault controlled flexural uplift and in combination with erosion and sedimentation processes led to the migration of the topographic maximum of the prelitoral range toward the easternmost ebro basin

40ar 39ar white mica ages reveal neoproterozoic paleozoic provenance and an alleghanian overprint in coeval upper ordovician lower devonian rocks of meguma and avalonia abstract 40ar 39ar analyses ir single grain total fusion of white micas from upper ordovician lower devonian sedimentary strata in the meguma annapolis section and avalon arisaig section terranes of the canadian appalachians complement recent detrital zircon studies by providing constraints on local source areas and identifying the age of low temperature a remarkable outcome of the study is that many muscovite ages are significantly younger than the depositional age of the strata they do not record the middle late devonian age of acadian folding or adjacent intrusions but instead preserve a precise age of 322 6 2 1 ma 16 analyses although the sections sampled display no discernable evidence for carboniferous tectonism these ages are coeval with documented alleghanian deformation in both avalonian and meguma terrane rocks and we interpret them to reflect distributed fluid flow coeval with dextral shear along the avalon meguma terrane boundary

permo carboniferous climate early pennsylvanian to late permian climate development of central europe in a regional and global context a well justified stratigraphical correlation of continental successions and new palaeogeographic reconstruction of pangaea reveal new insights into the northern pangaean climate development influenced by palaeogeography palaeotopography glacio eustatic sealevel changes and ocean currents the overall permo carboniferous aridization trend was interrupted by five wet phases these are linked to the gondwana icecap the aridization and weakening of wet phases over time were not only caused by the drift of northern pangaea to the arid climatic belt but also by the successive closure of the rheic ocean which caused the expansion of arid semi arid environments in the lower middle permian the end of the gondwana glaciation rearranged ocean circulation leading to a cold coast parallel ocean current west of northern pangaea blocking moisture coming with westerly winds the maximum of aridity was reached during the roadian wordian the trans pangaean mountain belt was non existent its single diachronous parts never exceeded an average elevation of 2000 m the maximum elevation shifted during time from east to west the hercynian orogen never acted as an orographic east west barrier and the inter tropical convergence zone was widely displaced causing four seasons dry summer winter wet spring autumn at the equator and a strong monsoon system the climate history of the european realm during the late carboniferous pennsylvanian and permian is stored in many solitary basins fig 1 within the hercynian orogen and the foreland basin the story of westphalian climate is well known because of the numerous investigations of the coal bearing variscan foredeep the younger westphalian is characterized by a slight aridization abbink van kronijnenburgvan cittert 2003 oplustil 2004 which was accompanied by an increase of seasonality nevertheless the environment was strongly influenced by the ocean and epi continental seas with multiple transgression events the last extensive marine ingression was the aegir mansfield band westphalian b c the post westphalian climate development is more differentiated and

diachronous post orogenic magmatism within a developing orocline in iberia european variscides 1 u pb zircon crystallization ages of 52 late variscan granitoid intrusions from nw iberia 19 from new data 33 from previous studies constrain the lithospheric evolution of this realm of the variscan belt of western europe and allow assessment of the relationship between oroclinal development and magmatism in late carboniferous early permian times the u pb ages in conjunction with a range of geological observations are consistent with the following sequence of events i oroclinal bending starts at 310 305 ma producing lithospheric thinning and asthenospheric upwelling in the outer arc of the orocline accompanied by production of mantle and lower crustal melts ii between 305 and 300 ma melting continues under the outer arc of the orocline central iberian zone of the iberian variscan belt and mid crustal melting is initiated coevally the lithospheric root beneath the inner arc of the orocline thickened due to progressive arc closure iii between 300 and 292 ma foundering of the lithospheric root followed by melting in the lithospheric mantle and the lower crust beneath the inner arc due to upwelling of asthenospheric mantle iv cooling of the lithosphere between 292 and 286 ma resulting in a drastic attenuation of lower crustal high temperature melting by 285 ma the thermal engine generated by orocline driven lithospheric thinning delamination had cooled down beyond its capability to produce significant amounts of mantle or crustal melts the model proposed explains the genesis of voluminous amounts of granitoid magmas in post orogenic conditions and suggests that oroclines and similar post orogenic granitoids common constituents of numerous orogenic belts may be similarly related elsewhere

fining upward cycles in the sandy braided river deposits of the westwater canyon member upper jurassic morrison formation new mexico abstract vertical and lateral profiles demonstrate that fining upward cycles are present in the sandy braided fluvial units of the westwater canyon member an upper jurassic morrison formation sheet sandstone in northwestern new mexico the technique of bounding surface classification successfully delineates these cycles on three scales of sedimentary influence namely the macroform scale cycle the channel scale cycle and the sheet scale cycle autocyclic macroform scale cycles are generally 1 6 m in thickness and bounded above and below by 3rd or higher order surfaces one of which must be of 3rd or 4th order channel scale cycles deposits infilling large scale scours and possibly individual channels are 1 10 m in thickness bounded above and below by laterally inextensive 5th or 6th order surfaces sheet scale cycles in contrast are 4 16 m in thickness the products of autocyclic channel avulsion processes bounded both above and below by laterally extensive planar 5th or 6th order surfaces a proposal by previous workers that lithofacies cyclicity also exists in the westwater canyon member is examined and rejected following field work and markov chain analysis further theoretical discussion of markov chain analysis points out several problems with the identification of cycles including the need for proper definition of the bounding surfaces that mark lithofacies transitions

sedimentary products of avulsions in the holocene rhine meuse delta the netherlands abstract the main objective of this study was to describe the characteristics of deposits related to avulsion to determine if avulsion locations can be recognized by characteristic sediment architecture in the rhine meuse delta the majority of avulsion sites is accompanied by crevasse splay deposits with a relatively large areal extent these crevasse splay complexes occur near the base of the overbank deposits of the newly formed channel belt and are similar to avulsion belt deposits described by smith et al sedimentology 36 1989 1 can j earth sci 35 1998 453 the lithology of all investigated crevasse splay deposits ranges from coarse sand to silty clay sand is concentrated in crevasse splay channels and silty and sandy clay occurs as distal deposits and as levee deposits between the channels the total volume of sand is small relative to clay and silt of a total of 91 avulsion sites three sites were studied in detail one each representing the sedimentary architecture of a full nodal avulsion a failed avulsion and a crevasse splay complex that did not lead to avulsion it is concluded that dating evidence of the abandoned and newly formed paleo channel is always required to verify if avulsion really occurred although the presence of large scale sandy crevasse splay deposits in combination with two main meandering channels often indicates avulsion based on a 2 d outcrop or just one cross section it is impossible to determine whether a splay complex was associated with an avulsion or not because the architecture and lithology in both cases can be identical not all avulsion locations are characterized by crevasse splay deposits there are two possible explanations for this 1 splay deposits were eroded by the newly formed channel or 2 splay deposits were never formed this may be a result of reoccupation of an old channel in this case avulsive flow is immediately appropriated by the pre existing channel and no large scale splay formation occurs alternatively splay deposits were not formed because avulsion resulted from headward erosion

chronological link between deep seated processes in magma chambers and eruptions permo carboniferous magmatism in the core of pangaea southern pyrenees abstract in the southern pyrenees there are upper carboniferous lower permian sedimentary basins with a significant volume of volcanic material derived from explosive eruptions rhyolitic ignimbrites and andesitic flows these basins are spatially associated with granodiorites and dacitic dykes emplaced in variscan basement rocks u pb shrimp dating of zircons extracted from three granodiorites an andesitic flow a dacitic dyke and six ignimbrites revealed that magmatism occurred over an extended period of thirty eight million years from ca 304 ma to ca 266 ma upper carboniferous middle permian a scattering of zircon ages in each sample shows that the history of melt crystallization was complex with more than one zircon forming event in each magma chamber the prolonged crystallization history was transferred to the product of the eruptions a chronological link between the deep seated magma chambers and processes in eruptions was identified on the basis of four overlapping intervals at ca 309 307 ma upper carboniferous ca 304 296 ma upper carboniferous lower permian ca 294 282 ma lower permian and ca 276 ma lower permian the variation of zircon u th ratios exposes a tendency for an increase in mafic sources as crystallization advances in the permian zircons probably crystallized from melt phases related to both a felsic intermediate metaluminous source from ca 310 293 ma mostly 0 1

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

global time scale and regional stratigraphic reference scales of central and west europe east europe tethys south china and north america as used in the devonian carboniferous permian correlation chart 2003 dcp 2003 the boundaries of the devonian carboniferous and permian stages of the global stratigraphic reference scale abbreviated to global stratigraphic scale gss are described in relation to the biostratigraphic and or lithostratigraphic units of the regional stratigraphic reference scales abbreviated to regional stratigraphic scales rss of central and west europe east europe tethys south china eastern tethys and north america in their type regions the boundaries of gss units rarely coincide with those of homonymous rss units moreover the definitions of some rss units have changed several times over the last decades and subsequent misunderstanding of the stratigraphical significance of these changes has often introduced errors into proposed global correlation charts the stratigraphic framework proposed in our global devonian carboniferous permian correlation chart 2003 dcp 2003 devonian carboniferous permian correlation chart 2003 menning m schneider j w alekseev a s amon e o becker g von bitter p h boardman d r bogoslovskaya m braun a brocke r chernykh v chuvashov b i clayton g dusar m davydov v i dybova jachowicz s forke h c gibling m gilmour e h goretzki j grunt t a hance l heckel p h izokh n g jansen u jin y g jones p kading k ch kerp h kiersnowski h klets a klug ch korn d kossovaya o kotlyar g v kozur h w laveine j p martens th nemyrovska t l nigmadganov a l paech h j peryt t m rohn r roscher m rubidge b schiappa t a schindler e skompski s ueno k utting j vdovenko m v villa e voigt s wahlman g p wardlaw b r warrington g weddige k werneburg r weyer d wilde v winkler prins c f work d m 2004 abschlusskolloquium dfg schwerpunktprogramm 1054 evolution des systems erde wahrend des jungeren palaozoikums im spiegel der sedimentgeochemie abstracts univ erlangen germany 2004 p 43 herein abbreviated to dcp 2003 and cited as dcp 2003 in references is an attempt to reduce these errors the dcp 2003 is the stratigraphic base for project 1054 of the deutsche forschungsgemeinschaft dfg the evolution of the late palaeozoic in the light of sedimentary geochemistry this composite time scale has been carefully balanced as far as data allows to remove unnecessary artificial compression and expansion of time intervals biozonations and depositional events the ages selected in dcp 2003 are markedly different to those in the geologic time scale 1989 gts 1989 harland w b armstrong r l cox a v craig l e smith a g smith d g 1990 a geologic time scale 1989 cambridge univ press cambridge harland w b armstrong r l cox a v craig l e smith a g smith d g 1990 a geologic time scale 1989 cambridge univ press cambridge pp 1 263 and in gradstein and ogg gradstein f m ogg j 1996 a phanerozoic time scale episodes 19 1 2 3 4 insert whereas they are closer to those of the geologic time scale 2004 gts 2004 gradstein f m ogg j g smith a g 2004 a geologic time scale 2004 cambridge univ press cambridge pp 1 589 mostly the ages are rounded to the nearest 0 5 ma in order to avoid estimates of questionable accuracy whereas ages of 0 1 ma in the gts 2004 and their error bars of 0 4 ma to 2 8 ma for the devonian to permian stage boundaries suggest an improved accuracy in contrast in the dcp 2003 questionable ages and positions of stratigraphic boundaries are marked by arrows c 2006 elsevier b v all rights reserved

architectural elements and bounding surfaces in fluvial deposits anatomy of the kayenta formation lower jurassic southwest colorado abstract three well exposed outcrops in the kayenta formation lower jurassic near dove creek in southwestern colorado were studied using lateral profiles in order to test recent regarding architectural element analysis and the classification and interpretation of internal bounding surfaces examination of bounding surfaces within and between elements in the kayenta outcrops raises problems in applying the three fold classification of allen 1983 enlarging this classification to a six fold hierarchy permits the discrimination of surfaces intermediate between allen s second and third order types corresponding to the upper bounding surfaces of macroforms and internal erosional reactivation surfaces within the macroforms examples of the first five types of surface occur in the kayenta outcrops at dove creek the new classifications is offered as a general solution to the problem of description of complex three dimensional fluvial sandstone bodies the kayenta formation at dove creek consists of a multistorey sandstone body including the deposits of lateral and downstream accreted macroforms the storeys show no internal cyclicity neither within individual elements nor through the overall vertical thickness of the formation low paleocurrent variance indicates low sinuosity flow whereas macroform geometry and orientation suggest low to moderate sinuosity the many internal minor erosion surfaces draped with mud and followed by intraclast breccias imply frequent rapid stage fluctuation consistent with variable seasonal monsonal ephemmeral flow the results suggest a fluvial architecture similar to that of the south saskatchewan river through with a three dimensional geometry unlike that interpreted from surface studies of that river

u pb zircon ages for post variscan volcanism in the ligurian alps northern italy abstract ages of permian volcanic rocks from the ligurian brianconnais domain western italian alps have been determined by laser ablation inductively coupled plasma mass spectrometry u pb dating of zircon three major volcanic units yielded zircons that were dated calc alkaline rhyolites 285 6 2 6 ma andesites with inherited cores yielded ages c 476 ma and older and voluminous rhyodacites rhyolites 272 7 2 2 ma following an amagmatic sediment starved time gap of c 14 ma alkaline volcanic activity is recorded at the top of the sequence by k alkaline rhyolites dated at 258 5 2 8 ma the ligurian segment of the southern variscan belt records transtensional and then extensional tectonics associated with the volcanic activity the switch from calc alkaline to alkaline activity corresponds to the transition from a post orogenic to an anorogenic setting in the southern variscides it may represent progressive and increasing delamination of the continental lithosphere accompanied by partial melting of the lithospheric mantle supplementary material technical and data acquisition parameters u th pb isotope analyses and calculated ages of zircons from samples and standard and trace element compositions of selected zircons are available at http www geolsoc org uk sup18322

sedimentary evolution of the continental early middle triassic canizar formation central spain implications for life recovery after the permian triassic crisis the permian triassic transition p t was marked by important geochemical perturbations and the largest known life crisis consequences of this event as oxygen depleted conditions and the unusual behavior of the carbon cycle were prolonged during the early triassic interval delaying the recovery of life in both terrestrial and marine ecosystems studies on lower triassic sediments of continental origin as in the case of western europe are especially problematic due to the scarcity of fossils and absence of precise dating the canizar fm is an early middle triassic unit of continental origin of the se iberian ranges e spain a detailed sedimentary study of this unit allows a shedding of light on some unresolved problems of the continental deposits of this age the top of this unit is dated as early anisian by means of a pollen association while the age of its base is here estimated as late smithian or smithian spathian transition different facies associations and architectural elements have been defined in this unit in the western and central parts of the basin this unit shows sedimentary characteristics of fluvial deposits with locally intercalated aeolian sediments while in the eastern part there is an alternation of both aeolian and fluvial deposits sedimentary structures also indicate changes in the climate conditions mainly from arid to semiarid two marked arid periods when well preserved aeolian sediments developed during early middle spathian and spathian anisian transition they alternated with two semiarid but more humid periods during the late spathian and early anisian these conditions basically correspond with the general arid and very arid conditions described for central western european plate during the same period of time the ateca montalban high in the northern border of the study basin must have represented an important topographic barrier in the western tethys separating aeolian dominated areas to the n and ne from fluvial dominated areas to the south the canizar fm has been subdivided into six members a f separated by seven 1 7 major bounding surfaces mbs these surfaces are well recognized laterally over hundred of km and they represent 104 105 my mbs 5 is considered to be of late spathian age and it is a clear indication of tectonic activity represented by a mild unconformity this event represents a change in the sedimentary characteristics reactivation of the unit and from here to the top of the unit are found the first signals of biotic recovery represented by tetrapod footprints plants roots and bioturbation all of these characteristics and the estimated age represented by the mbs 5 event permit this surface to be related to the coeval hardegsen unconformity of central western europe these first signals of biotic recovery can thus be related to an increased oxygen supply due to the new created paleogeographical corridors in the context of this tectonic activity these biotic signals occurred 5 my after the permian triassic limit crisis a similar delay as occurred in other coeval and neighboring basins