the interrelation of glaciotectonic and glaciodepositional processes within the glacial environment abstract in recent years it has been recognised that ice sediment coupling occurred beneath the quaternary ice sheets that advanced over the soft sediments of lowland areas this paper looks in detail at the effects of this coupling on the sediments which results in glaciotectonic deformation and also discusses the interaction of deformation and deposition within the subglacial environment two types of glaciotectonic deformation are discussed that are produced by the active movement of ice 1 proglacial tectonics at the margin which include compressive fold styles such as listric thrusts and faults and open folding 2 subglacial tectonics formed beneath the glacier which include fold styles resulting from simple shear and represent a soft rock purely dynamic shear zone styles of deformation associated with stagnant ice are also investigated we argue that glaciotectonic deformation is a common phenomenon and an integral part of geological record from continental ice sheets it is suggested that zones of deformation within the sediment are related to similar zones of strain in the ice sheet and complex deformation sequences are produced by the superimposition of these differing styles upon one another as the ice sheet advances and retreats it is also argued that subglacial deposition and deformation are related and that on soft beds underformed till is rare whilst deformed till is very common

the pleistocene glaciolacustrine sediments in the belchatow mine central poland endogenic and exogenic controls abstract the quaternary overburden of belchatow outcrop contains five glaciolacustrine units the three most widespread are presented they originated during the advance of the sanian elsterian odranian drenthian and wartanian warthian ice sheets the following lake environments are distinguished lake bottom plain tectonically active subaqueous slope subaqueous fan terminoglacial subaqueous fan and prodelta fan the lakes formed under changing conditions the most significant tectonic activity of the graben took place during the odranian and the lake deposits from this glaciation represent terminoglacial conditions the wartanian lake deposits are the only ones that show a shallow water facies that has not been eroded because it has not been overridden by an ice sheet sedimentation conditions changed during the succeeding glaciations endogenic factors affecting sedimentation i e tectonic activity of the graben complemented some exogenic controls such as the distance from the ice sheet the thermal conditions of the lake and the type of sediment supply tectonics changed the style of deposition so much that the lakes although situated in a lowland area displayed characteristics of deep valleys

magnetic susceptibility anisotropy strain and progressive deformation in permian sediments from the maritime alps france abstract the relationships among magnetic susceptibility anisotropy finite strain and progressive deformation have been studied in permian red shales and slates of the maritime alps southeastern france these rocks contain deformed reduction spots which serve as finite strain indicators the magnetic fabric of undeformed regions is modified during deformation to yield characteristic magnetic susceptibility anisotropy patterns and a magnetic equivalent of the deformation path derived from strain measurements the magnetic fabric changes progressively from oblate to prolate and back to oblate as deformation increases the quantitative relationships between natural strain and magnetic anisotropy in these rocks have been determined they differ between the less and more deformed areas perhaps due to a change in deformation mechanism accompanying an increase in metamorphism the relationships provide a rapid means of strain determination using magnetic measurements but their variation emphasizes the need for local structural control

shallow subduction beneath italy three dimensional images of the adriatic european tyrrhenian lithosphere system based on high quality p wave arrival times 1 this paper presents a velocity model of the italian central mediterranean lithosphere in unprecedented detail the model is derived by inverting a set of 166 000 pg and pn seismic wave arrival times restricted to the highest quality data available the tomographic images reveal the geometry of the subduction collision system between the european adriatic and tyrrhenian plates over a larger volume and with finer resolution than previous studies we find two arcs of low vp anomalies running along the alps and the apennines describing the collision zones of underthrusting continental lithospheres our results suggest that in the apennines a significant portion of the crust has been subducted below the mountain belt from the velocity model we can also infer thermal softening of the crustal wedge above the subducting adriatic plate in the tyrrhenian back arc region strong and extensive low vp anomalies depict upwelling asthenospheric material the tomographic images also allow us to trace the boundary between the adriatic and the tyrrhenian plates at moho depth revealing some tears in the adriatic ionian subducting lithosphere the complex lithospheric structure described by this study is the result of a long evolution the heterogeneities of continental margins lithospheric underthrusting and plate indentation have led to subduction variations slab tears and asthenospheric upwelling at the present day the high resolution model provided here greatly improves our understanding of the central mediterranean s structural puzzle the results of this study can also shed light on the evolution of other regions experiencing both oceanic and continental subduction

calibrating fluvial erosion laws and quantifying river response to faulting in sardinia italy abstract it is now widely accepted that rivers modify their erosion rates in response to variable rock uplift rates resulting in changes in channel slope that propagate upstream through time therefore present day river morphology may contain a record of tectonic history the simple stream power incision model can in principle be used to quantify past uplift rates over a variety of spatial and temporal scales nonetheless the erosional model s exponents of area and slope m and n respectively and bedrock erodibility k remain poorly constrained in this paper we will use a geologically and geomorphically well constrained plio pleistocene volcanic landscape in central sardinia italy to calibrate the stream power erosion equation and to investigate the slip rate of faults that have been seismically quiescent in the historic past by analysing digital elevation models geological maps and landsat imagery we have identified the geomorphic expression of several volcanic features eruption centres and basaltic lava flows and three normal faults with 6 to 8 km fault traces within the outcrop downstream river longitudinal profiles show a similar transient response to relative base level fall probably as a result of relief inversion at the edge of the volcanic outcrop from measurements of incision local slope and upstream catchment area across eight different rivers we calculate n 1 m 0 50 0 02 and using a landscape age from literature of 2 7 ma bedrock erodibility k 0 10 0 04 m 1 2m myr 1 there are also knickpoints on rivers upstream of two normal faults and we used numerical inverse modelling of the longitudinal profiles to predict the slip rate of these faults since 2 7 ma the results from the inverse model show that the erosional parameter values derived in this study can produce theoretical longitudinal profiles that closely resemble observed river profiles upstream of the faults the lowest misfit theoretical longitudinal profiles were generated by a model of temporally discontinuous footwall uplift with consistently low throw rates

sedimentary response to intra arc extension controls on oligo miocene deposition sarcidano sub basin sardinia the oligo miocene sardinian rift is a rare example of a well exposed intra arc basin comprising several independent depocentres synthesis of field observations from one such depocentre the sarcidano sub basin in central sardinia not only allows a new and integrated sedimentological and tectonostratigraphic history for the area but also provides insights into controls on syn and post rift sedimentation in intra arc settings initial rifting during the late rupelian early chattian oligocene occurred on nw se trending normal faults and produced a half graben topography which controlled the dispersal of locally supplied coarse continental clastic sediments latest chattian aquitanian miocene ne sw trending normal faulting defined a more complex block topography that remained underfilled in all areas except those which received voluminous ignimbritic volcanic material subsequent marginal and shallow marine sedimentation progressively infilled the fault topography as sea level rose deposition of coarse clastic sediments eroded from fault scarps was focused in the hanging wall depocentres of the intersecting fault trends whilst platform carbonates became established in topographically higher areas protected from clastic sedimentary supply finally as the relative rise in sea level drowned sediment source areas in the burdigalian deeper marine marlstones dominated sedimentation the results demonstrate that the sarcidano sub basin was dominated by a mixed volcanic siliciclastic carbonate basin fill with abrupt facies changes developed in response to complex fault defined topography relative rise in sea level and an episodic volcanic supply whilst the rift structure largely controlled the provenance supply and accumulation of sediments relative sea level primarily controlled the types of facies that developed

relations among subduction parameters clues to the dynamics of the subduction process are found in the many measurable parameters of modern subduction zones based on a critical appraisal of the geophysical and geological literature 26 parameters are estimated for each of 39 modern subduction zones to isolate causal relationships among these parameters multivariate analysis is applied to this data set this analysis yields empirical quantitative relations that predict strain regime and strike slip faulting in the overriding plate maximum earthquake magnitude benioff zone length slab dip arc trench gap and maximum trench depth excellent correlation is found between length of the benioff zone and the product of convergence rate and age of the downgoing slab this relationship is consistent with the conductive heating model of molnar et al 1979 if the model is modified in one respect the rate of heating of the slab is not constant it is substantially slower during passage of the slab beneath the accretionary prism and overriding plate the structural style in the overriding plate is determined by its stress state though the stress state of overriding plates cannot be quantified one can classify each individual subduction zone into one of seven semiquantitative strain classes that form a continuum from strongly extensional class 1 back arc spreading to strongly compressional class 7 active folding and thrusting this analysis indicates that strain class is probably determined by a linear combination of convergence rate slab age and shallow slab dip interplate coupling controlled by convergence rate and slab age is an important control on strain regime and the primary control on earthquake magnitude arc parallel strike slip faulting is a common feature of convergent margins forming a forearc sliver between the strike slip fault and trench optimum conditions for the development of forearc slivers are oblique convergence a compressional environment and a continental overriding plate the primary factor controlling presence of strike slip faulting is coupling strongly oblique convergence is not required the rate of strike slip faulting is affected by both convergence obliquity and convergence rate maximum trench depth is a response to flexure of the underthrusting plate the amount of flexural deflection at the trench depends on the vertical component of slab pull force which is very sensitive to slab age and shallow slab dip shallow slab dip conforms to the cross sectional shape of the overriding plate which is controlled by width of the accretionary prism and duration of subduction deep slab dip is affected by the mantle trajectory established at shallow depth but may be modified by mantle flow much of the structural complexity of convergent margins is probably attributable to terrane juxtaposition associated with temporal changes in both forearc strike slip faulting and strain regime empirical equations relating subduction parameters can provide both a focus for future theoretical studies and a conceptual and kinematic link between plate tectonics and the geology of subduction zones

geodynamic history and mantle evolution recorded in cenozoic lavas of sardinia two cenozoic magmatic cycles occurred in sardinia separated by a 5 myr gap oligo miocene subduction related calc alkaline magmatism associated with sardinia migrating from the european continental margin to its current location and plio pleistocene intraplate alkaline magmatism associated with the opening of the southern tyrrhenian basin based on an integration of new and published geochemical data on the cenozoic volcanic rocks of sardinia and regional tectonics we propose that a northward propagating slab tear formed south of sardinia at the end of the oligo miocene cycle this was responsible for the transition from subduction controlled calc alkaline to extension controlled mildly alkaline to peralkaline magmatism in the sulcis area sw sardinia and for the end of the oligo miocene magmatism the inflow of hotter material from the european asthenospheric reservoir ear through the slab window could have produced the minor ear type alkaline lavas that erupted at the end of the oligo miocene cycle and at the beginning of the plio pleistocene cycle the dominant younger plio pleistocene lavas with emi type compositions probably formed from decompression melting of a shallower lithospheric mantle with little influence from the ear forming event supplementary material a summary of sulcis rocks petrography representative whole rock analysis of sulcis rocks sr nd and pb isotope analytical methods and results a list of sources of whole rock geochemical data from the literature and complementary diagrams are available at https doi org 10 6084 m9 figshare c 4447802

magnetic fabric and structural setting of plio pleistocene clayey units in an extensional regime the tyrrhenian margin of central italy abstract results are presented of structural analysis and anisotropy of magnetic susceptibility ams analysis of plio pleistocene clayey units from the extensional tyrrhenian margin of central italy data have been collected in different tectonic settings mainly strike slip and transverse extensional structures at the sites with major evidence of plio pleistocene tectonics there appears a close relationship between magnetic lineations and stretching directions stretching processes that were able to modify the original magnetic fabric pre dated significant normal fault related tilting and therefore were active at the very first stage of extensional deformation the relationships between ams and structural trends in an extensional regime seem distinctively different from those reported in compressional regimes this kind of analysis may be useful in the geodynamic interpretation of ambiguous structures

oligo miocene rift of sardinia and the early history of the western mediterranean basin the geodynamic evolution of the western mediterranean basin in spite of many studies is still uncertain there is some consensus for interpreting this basin as a kind of small oceanic marginal basin its opening has generally been related to a subduction process which was active during the oligocene miocene somewhere east of sardinia corsica1 7 as the margins of the basin are deeply buried below miocene to present sediments direct lithological and stratigraphical data which could explain the events responsible for its formation are rare8 10 or missing altogether to obtain such data detailed field studies have been undertaken in sardinia fig 1 and the first results are presented here this approach is justified by the fact that in that island oligocene and miocene sediments were deposited in a rift fossa tettonica sarda of verdabasso11 which is the easternmost arm of the complex rift system that affected the european plate during oligocene and miocene times one of these arms evolved towards a small oceanic basin the western mediterranean or algero provencal basin while others such as the gulf of valencia and the sardinia rift aborted and remained at the rift stage its exceptional exposures make it possible to examine the sardinia rift to clarify the sequence of events which created it and to establish a sedimentological model which we believe is directly applicable to the western mediterranean basin

alpine tectonics in the calabrian peloritan belt southern italy new 40ar 39ar data in the aspromonte massif area this study provides new ar 40 ar 39 geochronological constraints on the age of the alpine tectonics in the aspromonte massif southern part of the calabrian peloritan belt this massif exposes the upper units of the calabride complex which originated from the european continental margin the calabride complex was incorporated in the alpine orogenic wedge and then integrated into the apennines and maghrebides fold and thrust belts throughout the calabride complex there is evidence for a two stage tectonic history which remains however rather poorly dated alpine nappe stacking is followed by extensional reworking along the former thrust contacts or along new detachment surfaces our new ages suggest that exhumation of the uppermost units which accompanied nappe stacking probably started at 45 ma and that the deepest units were almost completely exhumed at 33 ma this kinematics probably corresponds to syn orogenic extension while the end of exhumation is clearly related to the extensional tectonics dated at 28 6 ma along detachment structures our geochronological data reveal a very short lag time between accretional and extensional processes in this part of the mediterranean alpine orogenic belt the direction of extension when the units are restored to their initial position i e before the opening of the western mediterranean basins and the bending of the arc is nne ssw such a direction does not fit with the eastward slab retreat model generally put forward to explain extension in the western mediterranean in contrast we provide evidence for roughly n s middle oligocene extension in the accretionary prism not previously described in this part of the mediterranean domain

post rift sequence architecture and stratigraphy in the oligo miocene sardinia rift western mediterranean sea abstract rift basins provide important sedimentary archives to reconstruct past tectonic and climatic conditions understanding their sedimentary history is however largely hampered by the competing influence of tectonic versus climatic forcing the aim of this study is to comprehend the effects of local to regional tectonic and global climatic eustatic changes on shallow marine depositional systems in the sardinia rift western mediterranean sea for this purpose the stratigraphic and depositional relations of a mixed siliciclastic carbonate ramp at the porto torres basin margin were studied along extensive proximal to distal transects three depositional sequences ds1 to ds3 of late burdigalian to early serravallian age have been identified which are separated by erosional unconformities each contains a lower transgressive part and an upper regressive part the former includes shoreface sandstone ds2 or coral reef ds3 deposits on the proximal ramp and channelized sheet sandstone ds1 or basinal mudstone ds2 ds3 deposits on the distal ramp typically recording an upsection trend of sediment starvation the latter is represented by basinward prograding coralline red algal carbonate wedges due to enhanced shallow water carbonate production rates in the long term the depositional evolution from ds1 to ds3 reveals basin margin progradation associated with decreasing siliciclastic supply integrated calcareous nannoplankton foraminiferal pectinid biostratigraphy links the depositional sequences to third order sea level cycles and allows to correlate the erosional unconformities at the top of ds1 and ds2 with the bur 5 lan 1 and lan 2 ser 1 sequence boundaries the improved sequence stratigraphic framework enables better regional and global correlations this shows that rhodalgal carbonate slopes started prograding in the western branch of the sardinia rift during the late burdigalian because 1 of a worldwide bloom of rhodalgal facies and 2 decreasing tectonic activity at the transition from the syn rift to the post rift stage caused a continuous reduction of the siliciclastic sediment input

fluid geochemistry of the sardinian rift campidano graben sardinia italy fault segmentation seismic quiescence of geochemically active faults and new constraints for selection of co2 storage sites abstract sardinia is typically seismically quiescent displaying an almost complete lack of historical earthquakes and instrumentally recorded seismicity this evidence may be in agreement with the presence of a ductile layer in the northern sector of the island as suggested by the he isotopic signature in fluids rising to the surface through quiescent fault systems the fault systems have been found to be segmented and therefore isolated in fluid circulation the study of fluid behaviour along fault systems becomes strategically important when applied to solve some geological risk assessments such as rn indoor or to define geological structures like potential co 2 storage sites both of these have been recently requested by the exploitation in italy of the euratom directive and the evolution of the kyotoprotocol policy four water dominated hydrothermal areas of sardinia located along regional fault systems were considered campidano graben tirso valley logudoro and casteldoria a fluid geochemical survey was carried out taking into account physical chemical and environmental parameters major elements within gaseous and liquid phases a few minor and trace elements selected isotope ratios 2 h 18 o 13 c 3 he 4 he 222 rn concentration and some dissolved gases two different fluids have been recognised as regards both water chemistry and dissolved gases i co 2 rich gases poor in he and rn with a relatively high 3 he 4 he ratio up to r r a 2 32 associated with na hco 3 cl thermal and cold groundwater ii gases rich in he and n 2 poor in co 2 and rn with a low 3 he 4 he ratio associated with alkaline thermal and cold waters the distribution of these two groups of fluids characterises the sardinian tectonic systems in fact gas fluxes are not homogeneous being mainly related to the different fault segments and to the areas where quaternary basalts crop out the underground geochemical evolution of the sardinian fluids as a function of the geological and tectonic systems provides some suggestions for solving one of the most important problems co 2 geological sequestration in order to reduce the co 2 excess produced by human activity the best geological disposal sites are reservoirs with low hydraulic conductivity sealed to fluid movement or aquifers characterised by maximum ph buffering capacity of their mineralogical matrix the knowledge of the role of faults as permeability barriers or as deep fluid uprising pathways is prerequisite

magnetic fabric of pleistocene continental clays from the hanging wall of an active low angle normal fault altotiberina fault italy anisotropy of magnetic susceptibility ams represents a valuable proxy able to detect subtle strain effects in very weakly deformed sediments in compressive tectonic settings the magnetic lineation is commonly parallel to fold axes thrust faults and local bedding strike while in extensional regimes it is perpendicular to normal faults and parallel to bedding dip directions the altotiberina fault atf in the northern apennines italy is a plio quaternary nnw sse low angle normal fault the sedimentary basin tiber basin at its hanging wall is infilled with a syn tectonic sandy clayey continental succession we measured the ams of apparently undeformed sandy clays sampled at 12 sites within the tiber basin the anisotropy parameters suggest that a primary sedimentary fabric has been overprinted by an incipient tectonic fabric the magnetic lineation is well developed at all sites and at the sites from the western sector of the basin it is oriented sub perpendicular to the trend of the atf suggesting that it may be related to extensional strain conversely the magnetic lineation of the sites from the eastern sector has a prevailing n s direction the occurrence of triaxial to prolate ams ellipsoids and sub horizontal magnetic lineations suggests that a maximum horizontal shortening along an e w direction occurred at these sites the presence of compressive ams features at the hanging wall of the atf can be explained by the presence of gently n s trending local folds hardly visible in the field formed by either passive accommodation above an undulated fault plane or rollover mechanism along antithetic faults the long lasting debate on the extensional versus compressive plio quaternary tectonics of the apennines orogenic belt should now be revised taking into account the importance of compressive structures related to local effects

characterization of the magnetic fabric of rocks abstract an inextensive system of magnetic susceptibility anisotropy factors is suggested which is sufficient in the majority of practical applications for characterizing the magnetic fabric of rocks the system involves three newly devised factors the corrected anisotropy degree the shape factor and the difference shape factor the first of these characterizes the quantity of anisotropy somewhat better than the commonly used anisotropy degree the shape factor characterizes the quality of anisotropy i e the shape of the susceptibility ellipsoid in a convenient way its definition is based on a certain analogy between the anisotropy ellipsoid and the strain ellipsoid the difference shape factor can replace the shape factor when only the differences between the principal susceptibilities are given while the mean susceptibility is unknown

recent spatial and temporal changes in the stress regime along the southern tunisian atlas front and the gulf of gabes new insights from fault kinematics analysis and seismic profiles tectonic deformations in the southern atlassic front of tunisia saft and the gulf of gabes result from the nubia eurasia convergence this study based on the inversion of geologically determined fault slip vectors presents evidences for spatial and temporal changes in the stress state fault kinematics analyses reveal a temporal change in states of stress during the late cenozoic a paleostress miocene pliocene state is characterized by a regional compressional tectonic regime with a mean n134 09 e trending horizontal maximum stress axis 1 a modern quaternary to present day state of stress also corresponds to compressional tectonic regime with a regionally mean n05 10 e trending horizontal 1 the saft corresponds to two distinct domains a far foreland atlassic front related to contractional deformation associated with southward propagate thrusting and eastward the gulf of gabes characterized by normal component nw to wnw trending faults at the crustal margin scale probably related with a transtensional tectonic regime we propose that the spatial and temporal changes in the stress during the miocene pliocene and quaternary may result from the geodynamic evolution of the tunisian atlas in relation to the rotation of corsica sardinia blocks and the separation of the sicilian continental lithosphere from the ionian oceanic lithosphere these temporal and spatial stress changes along the saft and the gulf of gabes are probably the engine behind the moderate seismicity leading at the same time to a reactivation of the inherited major structures created during the evolution of the southern tethyan margin

magnetic fabric of clay sediments from the external northern apennines italy abstract we report on the anisotropy of magnetic susceptibility ams analyses of fine grained sediments deposited during the messinian in foredeep basins at the front of the northern apenninic chain the data refer to 32 sampling sites mostly distributed in the fine grained intervals of the laga and colombacci formations extending along the belt for a total length of about 300 km rock magnetism analyses indicate that the magnetic susceptibility and its anisotropy are in most cases dominated by the paramagnetic minerals of the clay matrix in order to delineate the contribution of the ferrimagnetic fraction to the overall susceptibility fabric the anisotropy of the anhysteretic remanent magnetisation was investigated at some representative sites the magnetic fabric of the studied sediments mostly reflects the effects of compaction showing a predominant magnetic foliation parallel to the bedding plane at all the sites a well distinct magnetic lineation was also found which is parallel to the fold axes and thrust fronts both at local and regional scales this feature is maintained in sequences that differ for sedimentological character and age implying that the magnetic lineation was produced by a mild tectonic overprint of the primary sedimentary compactional fabric the relationship between the magnetic lineation trends and the vertical axis rotations detected by speranza et al speranza f sagnotti l mattei m 1997 j geophys res 102 3153 3166 indicates that the magnetic lineation formed during the compressive phases of the messinian early pliocene when the apenninic front was almost rectilinear and oriented n320

paleomagnetism of jurassic carbonate rocks from sardinia no indication of post jurassic internal block rotations 1 several paleomagnetic studies on carboniferous and permian sedimentary and volcanic rocks from sardinia and corsica have recently demonstrated 1 the tectonic coherence between southern corsica and northern sardinia and 2 significant rotations between individual crustal blocks within sardinia itself the geodynamic significance of these rotations however is not clearly understood mainly because of uncertainties in defining their timing and causes in order to contribute to these issues a pioneering paleomagnetic study on jurassic carbonates from the baronie supramonte region of eastern central sardinia has been extended regionally and stratigraphically a total of 280 oriented drill cores were taken from 44 sites of middle and late jurassic age in the nurra baronie supramonte barbagia sarcidano and sulcis regions despite generally weak remanent magnetization intensities on the order of less than 1 ma m thermal and alternating field demagnetizations were successfully applied to define a characteristic remanent magnetization component in about 60 of the samples site mean directions show rather good agreement after correction for bedding tilt and yield middle and late jurassic overall mean directions of d 269 7 and i 45 0 95 8 0 k 14 and n 25 sites and d 275 5 and i 50 7 95 7 2 k 45 3 and n 10 sites positive regional and local fold and reversal tests demonstrate the primary character of the natural magnetic remanence which is carried by magnetite these results indicate only insignificant amounts 10 of post jurassic rotations within the island of sardinia the resulting middle and late jurassic paleopoles latitude lat 16 5 longitude long 299 1 dp 6 4 and dm 10 1 and lat 23 4 long 301 2 dp 6 5 and dm 9 7 corrected for the opening of 1 the liguro provencal basin and 2 the bay of biscay using rotation parameters from the literature fall near the coeval segment of the european apparent polar wander path these results constrain the timing of large differential block rotations found in late carboniferous permian rocks to a pre middle jurassic age and lead us to exclude tectonics related to the alpine orogeny for such rotations

magnetic fabric of pleistocene clays from the tyrrhenian arc a magnetic lineation induced in the final stage of the middle pleistocene compressive event we present the results of an analysis of the anisotropy of magnetic susceptibility ams in early pleistocene clay sediments from the southern apennines and its foreland apulia measurements were performed on samples from different tectonic units the apulian unit the bradano unit and the apenninic belt the ams is characterized by a dominant magnetic foliation parallel to the bedding plane in all cases pointing to a primary sedimentary magnetic fabric no lineation is found in the clays from the apulian unit whereas the inner part of the bradano unit and the apenninic belt show a clear nw se trending magnetic lineation which is perpendicular to the main compressive stresses known for this area there is a very consistent wnw ese trending magnetic lineation for the clays from the southern apennines and the calabrian block to the south correction of this lineation with the established tectonic rotations shows that the lineation is clearly of postrotational origin and reflects the latest stages of deformation the lineation is linked to middle and late pleistocene tectonics its alignment occurred in the final stages of the compressive event affecting the tyrrhenian arc system for the sant arcangelo basin in the southern apennines anomalous trends of magnetic lineation compressive stress were established

displaced re worked rhodolith deposits infilling parts of a complex miocene multistorey submarine channel a case history from the sassari area sardinia italy abstract in the sassari area north western sardinia italy the miocene porto torres sub basin sequences represent the complex multistorey mixed carbonate siliciclastic submarine feature called the sassari channel during the late burdigalian early serravallian repeated terrigenous supplies from uplifted paleozoic crystalline substrata fed the sassari channel system by means of turbidity and locally hyper concentrated turbidity flows shelfal areas were the source of terrigenous clasts but open shelf rhodalgal foramol carbonate areas were very productive and largely also contributed to the channel infilling re worked sands and skeletal debris were discontinuously re sedimented offshore as pure terrigenous mixed and or carbonate deposits major sediment supply was introduced between the latest burdigalian and the start of the middle langhian during which a large amount of carbonate mixed and siliciclastic sediments reached the porto torres basin sassari channel i contributions from shallow proximal source areas typify the lower intervals unit a in marginal sectors of the channel upward these evolve into autochthonous rhodolith deposits winnowed by strong currents in relatively shallow well lit settings within a complex network of narrow tidally controlled channels unit d locally bearing coral assemblages conversely re sedimented rhodoliths from the units b and c accumulated under conditions of higher turbidity in deeper parts of the channel taxonomically diversified rhodoliths point to the mixing of re deposited skeletal components from different relatively deep bathmetric settings in the latest early langhian major re sedimentation episodes resulting in large prograding bodies unit d triggered by repeated regression pulses in a frame of persistent still stand during these episodes photophile assemblages dwelled in the elevated margin sectors of the channel a significant latest early langhian drop in relative sea level resulted in impressive mass flows involving early cemented channel margin and levee blocks and culminated in the formation of major erosional surface er e such events seemingly correlate with the long term global cooling trend of the mid miocene climatic transition episodes of middle langhian re sedimentation concluded with the channel abandon phase after which new erosive episodes followed overall this led to a shift in the sassari channel ii with phases presumably started during the earlymost serravallian subsequent to the major sea level drop at the langhian serravallian boundary

landforms and structures of the waterlain west end of st thomas moraine sw ontario canada abstract the western part of st thomas moraine was deposited by the erie lobe terminating in lake maumee ii during the bruce stadial of the late wisconsinan the marginal 5 km wide zone of the erie lobe became stagnant in the relatively shallow 15 20 m part of the lake crevasse fillings in the form of hundreds of slightly curved ridges were deposited as mesoforms upon the 5 km wide and 10 m high morainic macroform that consisted of port stanley basal till most crevasse fillings trend n s and consist of stratified pebbly sand deposited upon silty clay till squeezed up by the load of the ice blocks from the macroform underneath a couple of the till ridges were overthrusted eastward this overthrusting was accomplished probably by wind driven ice blocks at the time when lake level rose by about 7 m from lake maumee ii to lake maumee iii the stagnant ice blocks did not melt out until after lake whittlesey time south of the southwestern end of the st thomas moraine at wallacetown the area is flat without any morainic landforms gently sloping for about 7 km as far as the lake erie bluffs about 7 km south of wallacetown natural exposures along creeks and lake bluffs reveal the northern edge of an erosional depression cut at least 20 m deep into the port stanley drift and covered by glaciolacustrine sediments two small morainic ridges each of them about 10 m high and about 1 km wide are exposed in lake bluffs at the extension of the st thomas moraine on land the lower one consists of port stanley basal till the upper one of waterlain till and glaciotectonically deformed glaciolacustrine sediments the erosional depression was cut probably by an ice stream that was more active than the rest of the erie lobe and the buried morainic ridges are probably contemporaneous with the st thomas moraine

a two stage rifting in the basins of the corsica sardinian straits abstract a set of seismic and field data from the corsica sardinian straits allowed us to define three well separated oligocene deep basins the castelsardo and porto torres basins forming the northern end of the sardinian graben and the bonifacio basin on the continental shelf of the bonifacio straits a seismostratigraphic investigation of these three basins revealed two major tectonic events a first oligocene to middle aquitanian rifting phase followed by oceanic spreading in the western mediterranean and then a second rifting event between corsica and sardinia in lower burdigalian time the first rifting is noticed in the three basins but the second one only in the porto torres and castelsardo basins

flow thermal structure and subglacial conditions of a surge type glacier temperature measurements in a subpolar surge type glacier reveal a distinctive thermal structure associated with the boundary between the ice reservoir and receiving areas in the receiving area the glacier is cold based but bottom temperature has increased as much as 0 5 c between 1981 and 1982 and the basal heat flux is roughly 10 times the expected geothermal flux water percolation through permeable subglacial material is the probable energy source deformation of the substrate could destroy this drainage system and trigger a surge

thermochronological evidence for mesozoic tertiary tectonic evolution in the eastern sardinia apatite fission track analyses on samples from eastern sardinia document a complex tectonic history whose reconstruction is problematic because of the reactivation of faults and structures at different times from jurassic to miocene the oldest ages 150 154 ma have been detected on the southern margin of the gulf of orosei and are related to the extensional tectonics that characterize the european passive margin during early and middle jurassic times thermal modelling of these data allows reconstruction of the burial history of the mesozoic basin and estimation of a sedimentary thickness of 2000 m part of these sediments was eroded during the following uplift documented by mid cretaceous fission track ages a further exhumation episode of eocene age has been revealed by fission track data on granite samples and has been inferred to be related to the alpine orogenic phase this tectonic episode caused the exhumation of crustal blocks bound by faults that were finally reactivated during the late oligocene early miocene

extensional tectonics on sardinia italy insights into the arc back arc transitional regime although the tectonic features and stress regime typical for accretionary complexes and back arc domains have been widely documented so far few are known on the transitional zone separating these two systems here we report on structural analysis and anisotropy of magnetic susceptibility ams results from eocene pliocene sediments exposed in western sardinia from late oligocene to middle miocene the studied area was located between the alpine apennine wedge to the east which was undergoing shortening and accretion and the liguro provencal basin undergoing extension and spreading we find that prior to the formation of the liguro provencal basin the middle eocene lower oligocene sediments cropping out at the southwesternmost edge of sardinia were subjected to ne sw shortening in present day coordinates in agreement with recently reported geological information conversely the upper oligocene pliocene sedimentary sequences record a different evolutionary stage of extensional processes upper oligocene middle upper burdigalian sediments clearly show a n s oriented magnetic lineation that can be related to extensional direction along the prevalent e w oriented normal faults on the other hand no magnetic lineation has been detected in upper burdigalian serravallian sediments which mark the end of the first rifting process in sardinia which likely coincides with the rift to drift transition at the core of the liguro provencal basin finally a ne sw extension is observed in two tortonian pliocene sites at the northwestern margin of the nnw sse oriented campidano graben our study confirms that ams may represent a valuable strain trajectory proxy and significantly help to unravel the characters of temporally superimposed tectonic events

extensional tectonics in the amantea basin calabria italy a comparison between structural and magnetic anisotropy data abstract we report on structural and anisotropy of magnetic susceptibility ams results from the upper miocene sediments of the amantea basin located on the tyrrhenian coast of the calabrian arc southern italy the stratigraphic succession of the basin is organized in three depositional sequences separated by two major angular unconformities detailed geological mapping and structural analysis demonstrate that the stratigraphic evolution of the amantea basin is strongly controlled by a synsedimentary extensional tectonic regime several nne ssw trending normal fault arrays with large scatter in inclination values have been interpreted as due to a domino faulting mechanism consistent with a wnw ese stretching direction ams data have been obtained for 13 sites both in the not constrained in age first depositional sequence 3 sites and in the upper tortonian lower messinian clays from the second depositional sequence 10 sites all the sites show a strong magnetic foliation parallel to the bedding planes and a well defined magnetic lineation subparallel to the local bedding dip directions the magnetic lineations cluster around a wnw ese trend and are parallel to the stretching directions inferred by fault slip analysis and basin architecture these new data then confirm the possibility to use the magnetic lineation to map the strain trajectory in weakly deformed extensional sedimentary basins paleomagnetic data from previous studies show that the whole calabrian block underwent a 15 20 clockwise rotation probably in the pleistocene postdating the extensional tectonic events which controlled the amantea basin geometry therefore we suggest for the amantea basin an original e w oriented stretching direction which may be considered as the older extensional direction characterizing the late miocene evolution of the southern tyrrhenian sea domain

geomorphology and sedimentology of surging glaciers a land systems approach the identification of surging glaciers and ice streams in glaciated landscapes is of major importance to the understanding of ice sheet dynamics and for reconstructing ice sheets and climate no single landform or diagnostic criterion has yet been found with which to identify surging glaciers a surging glacier land system model is constructed using observations and measurements from contemporary surging glacier snouts in iceland svalbard u s a and canada for differentiating ancient surging margins from other non surging palaeoglaciers this integrates the suite of landforms sediments and stratigraphy produced at surging glacier margins landforms produced during surging include thrust moraines concertina eskers and subglacial crevasse squeeze ridges sedimentary sequences are usually characterized by multiple stacked diamictons and stratified interbeds which display severe glaciotectonic contortion and faulting hummocky moraine comprising interbedded stratified sediments and mass flow diamictons has also been associated with surge margins where large quantities of supraglacial and englacial debris entrained during the surge event have melted out in situ an example of the application of the land system model is presented for east central alberta canada a surging palaeo ice stream is identified within this part of the southwestern laurentide ice sheet where thrust block moraines crevasse squeeze ridges flutings hummocky moraine and glaciotectonized sediments are juxtaposed

probing the sources of ambient seismic noise near the coasts of southern italy 1 in this study we probe the source of ambient noise in the southern apennines and the calabrian arc by crosscorrelating two months of ambient seismic noise records collected during the calabria apennine tyrrhenian subduction collision acretion network cat scan project significant rayleigh wave energy is observed on the vertical component of the noise correlation stacks and reveals multiple sources of ambient noise in southern italy the most dominant noise sources are found along 1 the tyrrhenian coast of northern calabria southern campania and 2 the adriatic sea near the gargano promontory enhanced ocean currents evident from buoy records during the study period could be responsible for the observed microseisms we validate the source locations using earthquake records and the consistency between noise and earthquake correlation functions supports the observed dominant directions of ambient seismic noise citation gu y j c dublanko a lerner lam k brzak and m steckler 2007 probing the sources of ambient seismic noise near the coasts of southern italy geophys res lett 34 l22315 doi 10 1029 2007gl031967

the cenozoic fold and thrust belt of eastern sardinia evidences from the integration of field data with numerically balanced geological cross section newly collected structural data in eastern sardinia italy integrated with numerical techniques led to the reconstruction of a 2 d admissible and balanced model revealing the presence of a widespread cenozoic fold and thrust belt the model was achieved with the forc software obtaining a 3 d 2 d time numerical reconstruction of the continuous evolution of the structure through time the mesozoic carbonate units of eastern sardinia and their basement present a fold and thrust tectonic setting with a westward direction of tectonic transport referred to the present day coordinates the tectonic style of the upper levels is thin skinned with flat sectors prevailing over ramps and younger on older thrusts three regional tectonic units are present bounded by two regional thrusts strike slip faults overprint the fold and thrust belt and developed during the sardinia corsica block rotation along the strike of the preexisting fault ramps not affecting the numerical section balancing this fold and thrust belt represents the southward prosecution of the alpine corsica collisional chain and the missing link between the alpine chain and the calabria peloritani block relative ages relate its evolution to the meso alpine event eocene oligocene times prior to the opening of the tyrrhenian sea tortonian results fill a gap of information about the geodynamic evolution of the european margin in central mediterranean between corsica and the calabria peloritani block and imply the presence of remnants of this double verging belt missing in the southern tyrrhenian basin within the southern apennine chain the used methodology proved effective for constraining balanced cross sections also for areas lacking exposures of the large scale structures as the case of eastern sardinia

till and moraine emplacement in a deforming bed surge an example from a marine environment the glacier sefstrombreen in spitsbergen surged across an arm of the sea between qsr 1882 and 1886 and rode up onto the island coraholmen marine and terrestrial geological observations and archive records show that the glacier advanced on a deforming carpet of marine mud which was eroded from its original location transported and smeared over the sea bed and coraholmen as a deformation till the glacier emplaced about 210sm 0 2 km 3 of drift in the terminal 2 km of its advance in a maximum of 14 years leaving a thickness of up to 20 m on coraholmen which was doubled in size as a result during the surge subglacial muds were characterised by high water pressures low effective pressures and low frictional resistance to glacier movement original sedimentary inhomogenities permit fold structures to be identified but repeated refolding and progressive remoulding produce mixing and homogenisation of deformation tills the surge was probably shortlived and as the heavily crevassed glacier stagnated underlying water saturated muds were intruded into crevasses and then extruded on the glacier surface reticulate crevasse intrusion ridges on coraholmen and the sea floor reflect the orientation of surge generated crevasses water and sediment was also extruded beyond the glacier at its maximum extent to form extensive flows producing till tongues both on coraholmen and the sea floor extending over 1 3 km from the glacier it is argued that subglacial deformation of pre existing sediment will almost invariably be associated with glaciation of marine areas and that this process will not only produce deformation tills through remoulding of pre existing sediments but will also play a fundamental role in glacier dynamics criteria which perrait glacial tills produced by such events from marine and glaciomarine muds are discussed copyright 1996 elsevier science ltd

sedimentary successions in ice marginal fans of the late saalian glaciation southwestern poland abstract the late saalian end moraines of southwestern poland contain several features that may be attributed to the formation that is predominantly controlled by the deposition of sorted waterlaid sediments these hills are essentially small alluvial fans with ice contact facies they have a semi conical form plano convex geometry their distal slopes are up to 5 and proximal slopes are between 5 and 20 the sedimentary sequences contain two units the lower unit comprises coarse grained material of gravel bed sheetflow facies and gravel bed channel facies with subordinate high energy channel flow facies and boulders up to 1 8 m in diameter the upper unit contains sand bed sheetflow facies and sand bed channel facies the sediment bedding is usually conformable with and parallel to the inclined fan surface these sequences represent typical proximal distal fan facies associations with a high energy and pulsatory water discharge in the proximal zone the fans in spite of their formation in the proglacial zone have geomorphological features and sedimentary sequences that are very similar to present day fans and are equivalent to sheetflow dominated or humid alluvial fans in non glacial environments

arc related high k magmatism in the ceuta peninsula internal rif spain discovery and consequences we document the occurrence of micro diorite magmatic sills with magmatic enclaves in the ceuta peninsula within metapelites from the lower sebtides units internal rif all magmatic rocks show a primary magmatic mineralogy and geochemical signature diagnostic for high k calc alkaline to shoshonitic island arc magmatism moreover these rocks are significantly affected by secondary metamorphic transformations under greenschist to amphibolite facies conditions regionally dated at c 21 ma geometric relationships between the sills and the main regional foliation developed under intermediate pressure granulite facies conditions at c 28 ma demonstrate that the sills emplaced during the late stage of this main tectonic event new u pb in situ analyses of monazite performed on the micro diorite sills provide an age of 20 64 0 19 ma coherent with this chronological framework and interpreted as the age of greenschist facies re equilibration the discovery of pre miocene high k calc alkaline to shoshonitic arc related magmatism is clearly consistent with the subduction context proposed for the alboran basin evolution according to geophysical investigations in this framework the lower sebtides units could be considered as part of the upper plate of the subduction system while the upper sebtides must be regarded as the lower subducted plate

hummocky moraine sedimentary record of stagnant laurentide ice sheet lobes resting on soft beds abstract over large areas of the western interior plains of north america hummocky moraine hm formed at the margins of laurentide ice sheet lis lobes that flowed upslope against topographic highs current depositional models argue that hm was deposited supraglacially from stagnant debris rich ice disintegration moraine across southern alberta canada map and outcrop data show that hm is composed of fine grained till as much as 25 m thick containing rafts of soft glaciotectonized bedrock and sediment chaotic non oriented hm commonly passes downslope into weakly oriented hummocks washboard moraine that are transitional to drumlins in topographic lows the same subsurface stratigraphy and till facies is present throughout these landforms and others such as doughnut like rim ridges flat topped moraine plateaux and linear disintegration ridges are identified as belonging to subglacially deposited soft bed terrain this terrain is the record of ice lobes moving over deformation till derived from weakly lithified bentonite rich shale drumlins record continued active ice flow in topographic lows during deglaciation whereas hm was produced below the outer stagnant margins of ice lobes by gravitational loading pressing of remnant dead ice blocks into wet plastic till intervening zones of washboard moraine mark the former boundary of active and stagnant ice and show hybrid drumlins whose streamlined form has been altered by subglacial pressing humdrums below dead ice the presence of hummocky moraine over a very large area of interior north america provides additional support for glaciological models of a soft bedded laurentide ice sheet

integrated chronostratigraphy of an intra arc basin 40ar 39ar datings micropalaeontology and magnetostratigraphy of the early miocene castelsardo basin northern sardinia italy the chronostratigraphy of the lower miocene deposits of northwestern sardinia is refined in the castelsardo basin the combination of new 40ar 39ar isotopic datings 19 micropalaeontological datings calcareous nannofossils planktonic and large benthic foraminifers and 16 palaeomagnetic polarity measurements led to a new chronostratigraphic framework the continental deposits of the first megasequence valledoria and casteldoria members are possibly aquitanian the overlying marine sediments are early burdigalian vaginella depressa molasse the marine transgression can be dated to around 19 7 ma marine conditions ceased 18 83 0 13 ma the age of the index aerial 2 ignimbrite the continental part of the second megasequence lacustre unit is early middle burdigalian between 18 8 and 18 ma the overlying marine part campulandu and sedini members is middle late burdigalian the second marine transgression began in the earliest late burdigalian during the chron c5dr reversal at the time of the eustatic bur 4 event the castelsardo basin went through two main extensional tectonic episodes the first one occurred as the valledoria member was deposited and possibly dates back to the aquitanian the second one occurred as the uppermost part of the vaginella depressa molasse was deposited during the early burdigalian the second extensional episode is related to a rapid rotation of sardinia palaeomagnetic results confirm that corsica and sardinia acted as a single block which suffered a 28 17 ccw rotation after 19 2 ma the castelsardo basin is held to be an aquitanian early burdigalian intra arc rift basin that later evolved in a thermally controlled subsident margin of the ligurian provencal basin during the middle late burdigalian

genesis of transverse kame trains in eastern poland abstract transverse kames forming trains perpendicular to the direction of ice sheet advance are rare morphological elements in previously glaciated areas the genesis of an example from the ice contact zone of the wartanian glaciation in eastern poland is discussed the transverse kames there form two main distinctly separated sub parallel trains their sedimentary successions fill erosional troughs incised in the pre wartanian deposits on northern slopes they consist of thick glaciofluvial sand and glaciofluvial glaciolacustrine sandy silty units that are covered with a thin usually discontinuous glacial till succession the genesis of this kame type has been modelled it is concluded that transverse kames developed in two phases 1 erosion of the substratum in subglacial channels during initial deglaciation and 2 glaciofluvial deposition in crevasses during advanced deglaciation in the form of low energy fans periodically submerged under stagnant water followed locally by a cover of flowtills both the ablation of the ice and the accumulation of the kame deposits were controlled by the co occurrence of ice zones either enriched or impoverished with sediment zonal enrichment of ice with debris was determined by the development of shear zones over substratum elevations that were inclined up ice the formation and subsequent infilling of crevasses both took place in zones of relatively clean ice so that the resulting kames form a train perpendicular to the direction of ice movement

3 d shear wave velocity model of the lithosphere below the sardinia corsica continental block based on rayleigh wave phase velocities rayleigh wave dispersion curves from both ambient noise and teleseismic events allow us to provide the first high resolution 3 d shear wave velocity vs model of the crust and upper mantle below the sardinia corsica microplate an important continental block for understanding the evolution of the central western mediterranean for a wide range of periods from 3 to 30 s the phase velocities of the study area are systematically higher than those measured within the italian peninsula in agreement with a colder geotherm relative and absolute variations in the vs allow us to detect a very heterogeneous upper crust down to 8 km as opposed to a relatively homogeneous middle and lower crust the isosurface at 4 1 km s 1 is consistent with a rather flat moho at a depth of 28 0 1 8 km 2 the lithospheric mantle is relatively cold and we constrain the thermal lithosphere asthenosphere boundary at 100 km we find our estimate consistent with a continental geotherm based on a surface heat flow of 60 mw m 2 our results suggest that most of the lithosphere endured the complex history of deformation experienced by the study area and imply in general that deep tectonic processes do not easily destabilize the deeper portion of the continental lithosphere despite leaving a clear surface signature

anisotropy of magnetic susceptibility in the scaglia rossa pelagic limestone abstract during folding of the scaglia rossa limestone in umbria italy deformation was mainly accommodated by pressure solution cleavage fossils between the cleavage planes appear visibly undeformed yet the limestone possesses a weak magnetic fabric the maximum and intermediate principal axes of the magnetic anisotropy ellipsoid define a distinct magnetic foliation plane within which a weak concentration of the maximum axes forms a magnetic lineation neither of these features is of sedimentary origin results from a slumped outcrop where bedding and a cleavage induced by overburden compaction have different attitudes show that the magnetic foliation is caused by the compaction comparisons with field derived structural data suggest that the magnetic lineation was produced tectonically during deformation of the apennine fold belt

neogene to quaternary rifting and inversion in corsica retreat and collision in the western mediterranean 1 stratigraphic structural and fission track data have been integrated in order to unravel the neogene to quaternary tectonic evolution of northeastern corsica results indicate that during early to middle miocene the study area was affected by a rapid cooling at low temperatures accompanied by exhumation and rifting basin inversion occurred during the tortonian again followed by extension in the messinian to early pliocene compressional deformations are finally recorded by early pliocene to quaternary deposits alternating rifting and inversion events are recorded not only in northeastern corsica but also in many peri tyrrhenian regions this alternation can be explained in terms of intraplate propagation of the compressional stress related to the africa europe convergence and to a discontinuous slab retreat along the apennine subduction system a pause in the slab retreat implies a break of the back arc extension in the upper plate and it allows a temporary propagation of africa europe compression

transverse supraglacially derived crevasse infillings in a pleistocene ice sheet margin zone eastern poland genesis and sedimentary record abstract the so called crevasse infillings in the marginal zone of the saalian ice sheet in eastern poland are atypical relief forms for lowlands glaciated in the pleistocene they are located on a high of the cretaceous palaeogene substratum and form isolated ridges arranged in trains parallel to the former ice sheet margin i e transverse to the movement of the ice sheet the sedimentary succession of the crevasse infillings consists mainly of undeformed glaciodeltaic deposits we propose a model of the crevasse infilling development in three phases against the background of ice mass dynamics 1 ice sheet advance over a high of the substratum compressive ice flow that bumped against the high s slope and enrichment of the ice with debris 2 an overriding of the substratum high by ice masses a tensional ice flow regime resulted in significant crevassing and 3 ice mass stagnation low energy supraglacial deltaic sedimentation in isolated ponds between disintegrated ice blocks under frozen bed conditions considering this genesis we suggest classifying these forms as kames instead of crevasse infillings

hummocky moraine landscape on jaeren sw norway implications for glacier dynamics during the last deglaciation abstract the jaeren area sw norway can topographically be divided in two regions lagjaeren and hogjaeren hogjaeren is a plateau 120 m a s l covered by quaternary sediments the stratigraphically youngest deposit is a sandy diamicton which accumulated in ridges and hummocks during the last deglaciation this hummocky moraine landscape has previously been interpreted as the record of a stagnant glacier detailed morphological mapping and sedimentological investigations have revealed that various glacigenic elements exist and dominate different areas of the hogjaeren plateau glacigenic elements formed by an active wet based glacier characterize the southern central hummocky area and include marginal moraine ridges and drumlins while circular moraine ridges and glaciofluvial features formed in a stagnant glacial regime dominate the northern central hummocky area the distribution of glacigenic elements within the hummocky moraine landscape shows that active and stagnant ice coexisted on hogjaeren during the last deglaciation and that actively flowing ice was focused through eastward extending valleys it is not possible to determine whether ice flow was kept active in the southern area throughout the deglaciation or if the glacier was reactivated a possible readvance is suggested to have happened simultaneous to a readvance previously suggested based on the morphology on lagjaeren

when did sardinia stop rotating new palaeomagnetic results previous palaeomagnetic results from tertiary volcanic rocks of sardinia suggest that the island underwent a quick counterclockwise rotation between 20 5 and 19 ma in order to test this hypothesis a new palaeomagnetic study was carried out on sediments and volcanic rocks with well controlled biostratigraphic or radiometric ages younger than the suggested age for the end of the rotation unrotated palaeomagnetic directions obtained from the upper ignimbrites radiometric age 18 5 19 7 myr and the aquitanian tuffs collected in the anglona region n sardinia would suggest that the rotation ended earlier than 20 5 myr the directions found in the volcanics are perhaps the result of secular variation rather than differential rotation of the anglona region with respect to surrounding regions two sites belonging to the upper ignimbritic unit si2 in the monte traessu monte rispisu area logudoro region exhibited a large amount of rotation d 320 4 i 60 which may be age related radiometric age 19 9 myr four dikes radiometric age 18 3 16 7 myr in the arcuentu volcanic complex arburese region yield results d 348 4 i 33 8 that indicate a further amount of rotation after their emplacement stable end point directions were successfully isolated from three upper burdigalian langhian sedimentary sites biostratigraphic age 18 15ma from the marmilla and logudoro regions consistent paleomagnetic directions obtained from these sites d 352 i 49 indicate that a small amount of rotation was still to be completed in the langhian time this result is consistent with the history of sardinian volcanism which did not end until 13 ma

sequential extension as a record of corsica rotation during apennines slab roll back the mediterranean geodynamic system is an exceptional natural laboratory to study the complexities of back arc extension during subduction rollback corsica is a key locality that recorded the alpine subduction collision history followed by 30 ma of the apennines slab rollback responsible for the successive opening from west to east of the liguro provencal basin and the tyrrhenian sea the overall strain pattern of the alpine metamorphic units of alpine corsica is studied through a synthesis of i available geological maps ii geochronological data and iii newly acquired structural data relative to successive events of ductile and brittle extension three main stages of extension are recorded 1 syn metamorphic oligocene extension accommodated by n140 trending ductile shear zones that correspond to the reactivation of a major alpine thrust 2 burdigalian ramp flat extension with n60 70 trending fault zones that controlled the deposition of onshore piggy back basins e g st florent basin and 3 serravalian n s trending fault zones from a geodynamical point of view these successive extensional deformations in alpine corsica can be correlated to the history of the apennines slab rollback the two first stages are related to a southeastward rollback of the appennines slab that successively triggered 1 continental rifting in oligocene leading to the opening of the liguro provencal basin and 2 burdigalian extension with n60 70 trending fault zone oblique to the alpine thrust that after a counterclockwise rotation of the corso sardinian block became unable to accommodate extension finally the third stage that gave ns trending fault zones developed in serravalian at the onset of tyrrhenian rifting related to an eastward rollback of the apennines slab as a response of slab tearing in sicily

sicily s fold thrust belt and slab roll back the si ri pro seismic crustal transect sicily is a thick orogenic wedge formed by 1 the foreland african and its sicilian orogen and 2 the thick skinned calabrian peloritani wedge the crust under central sicily from the tyrrhenian margin to the coastline of the sicily channel has been investigated by the multidisciplinary si ri pro research project the project dealt with the nature and thickness of the crust and depth and geometry of the moho which is essential in formulating subduction models and improving the knowledge of african and tyrrhenian european lithospheres the results resolve features such as 1 the main orogenic wedge 2 the very steep nw se trending regional monocline suggesting inflection of the foreland crust 3 the deep caltanissetta synform imaged for the first time to about 25 km and 4 the top of the crystalline basement and the inferred crust mantle boundary the si ri pro transect confirmed that the nnw dipping autochthonous iblean platform of se sicily and its basement extends all the way into central sicily further nw towards the nnw end of the transect a large uplift involves the iblean platform and its underlying basement the associated gravity anomaly is interpreted as the southern wedge edge of the tyrrhenian mantle that splits the subducting iblean pelagian african continental slab from an overlying synformal stack of allochthonous thrust sheets supplementary materials additional data are available at www geolsoc org uk sup18594

siliciclastic carbonate sequences of miocene grabens of northern sardinia western mediterranean sea abstract the small crustal block of sardinia island western mediterranean underwent major rifting events during oligocene early miocene aquitanian early burdigalian and plio pleistocene times sedimentation in the resulting extensional and transtensional basins was affected by both local tectonic and worldwide sea level changes the mixed siliciclastic carbonate sequences which developed are readily comparable with those predicted by sequence stratigraphy this paper focuses on the post volcanic uppermost burdigalian to lower messinian sedimentation at the confluence between a main n s trending basin and a secondary sw ne trending graben in northern sardinia silty marlstones of late burdigalian early langhian age characterize the central part of the main basin whereas variable siliciclastic and carbonate sequences affected by up to three major transgression and regression cycles developed at its margins and at the confluence with the smaller graben differential movements along the main boundary fault led to rotation of blocks which localized narrow elongated offshore algal carbonate platforms low sea level stand led to deep erosion type 2 sequence boundary of these carbonates and to the formation of siliciclastic sandy lowstand wedges high sea level stand led to re establishment of algal platforms at the shelf margin which were bounded farther inland by siliciclastic carbonate mixed parasequences although it is not possible to date directly every stratigraphic unit local sequences are well structured and can be tentatively correlated with reported worldwide transgressive regressive events

an aem tem study of nanometer scale mineral associations in an aquifer sand implications for colloid mobilization abstract analytical and transmission electron microscopy aem tem techniques were used to identify mineral juxtapositions at the nanometer scale in the interstitial matrix of a shallow southeastern coastal plain aquifer sand georgetown south carolina usa in doing so we sought to infer particle particle interaction mechanisms holding the matrix intact the aquifer is a fine to medium quartz sand with approximately 12 by weight

the messinian salinity crisis new seismic evidence in the west sardinian margin and eastern sardo provencal basin west mediterranean sea abstract we processed and interpreted a newly acquired geophysical dataset ws10 project integrated with vintage seismic profiles to study the evolution of the sardinian passive margin of the sardo provencal basin the most prominent features of the area of study are a consequence of the messinian salinity crisis msc which produced a thick salt layer in the deep basin complex halokinetic tectonics deformed the overlying messinian upper unit uu and the pliocene quaternary pq sediments sometimes also bending the sea bottom a thinner autochthonous salt in the uu suggests at least one further low stand during the late msc the messinian erosional surface mes separates the erosional truncation of the pre messinian sedimentary sequence from the overlaying plio pleistocene sequence with a clear angular discordance which almost completely masks possible earlier erosional events the mes is present across the middle and upper slopes of the sardinian margin and can be easily recognized down to the lower slope where it interfingers with the messinian evaporites which gradually thicken basinward we propose a correlation between the main erosional surface of the lower slope and the salt layer recognized in the uu as a consequence of a falling stage during the last part of the msc the seismic profiles now available along the west sardinian margin provide novel and crucial information to correlate the messinian depositional units in the deep basin with those present in the lower continental slope and with the erosional surface of the middle and upper slopes our data and interpretation highlight the main units of the messinian trilogy and further internal sequences that are probable related to cyclic fluctuations during their deposition

40ar 39ar dating and paleomagnetism of the miocene volcanic succession of monte furru western sardinia implications for the rotation history of the corsica sardinia microplate although it is widely acknowledged that the corsica sardinia microplate rotated counterclockwise with respect to europe during oligocene miocene time the precise timing of this event has yet to be determined we have measured the age and degree of rotation of a single tie point in the rotation history of the microplate biotite and sanidine 40ar 39ar age determinations of the 200m thick monte furru volcanic succession indicates that most of the volcanic pile accumulated within less than 200 ky the paleomagnetic pole obtained for the 12 volcanic flow units comprising this succession indicates that by 18 2 ma sardinia remained 13 shy of its final rotation angle these results demonstrate that the movement of the corsica sardinia block and the opening of the liguro provencal basin terminated later than previously estimated based on paleomagnetic and geochronologic studies of sardinian volcanic rocks in agreement with paleomagnetic data from sardinian sediments

mesozoic extension in the basque cantabrian basin n spain contributions from ams and brittle mesostructures abstract in this work we analyse and check the results of anisotropy of magnetic susceptibility ams by means of a comparison with palaeostress orientations obtained from the analysis of brittle mesostructures in the cabuerniga cretaceous basin located in the western end of the basque cantabrian basin north spain the ams data refer to 23 sites including triassic red beds jurassic and lower cretaceous limestones sandstones and shales these deposits are weakly deformed and represent the syn rift sequence linked to basins formed during the mesozoic and later inverted during the pyrenean compression the observed magnetic fabrics are typical of early stages of deformation and show oblate triaxial and prolate magnetic ellipsoids the magnetic fabric seems to be related to a tectonic overprint of an original compaction sedimentary fabric most sites display a ne sw magnetic lineation that is interpreted to represent the stretching direction of the early cretaceous extensional stage of the basin without recording of the tertiary compressional events except for sites with compression related cleavage brittle mesostructures include normal faults calcite and quartz tension gashes and joints related to the extensional stage the results obtained from joints and tension gashes show a dominant n s to ne sw and secondary nw se extension direction paleostresses obtained from fault analysis right dihedra and stress inversion methods indicate nw se to e w and n s extension direction the results obtained from brittle mesostructures show a complex pattern resulting from the superposition of several tectonic processes during the mesozoic linked to the tectonic activity related to the opening of the bay of biscay during the early cretaceous this work shows the potential in using ams analysis in inverted basins to unravel its previous extensional history when the magnetic fabric is not expected to be modified by subsequent deformational events brittle mesostructure analysis seems to be more sensitive to far field stress conditions and record longer time spans whereas ams records deformation on the near distance during shorter intervals of time

alpine structural and metamorphic signature of the sila piccola massif nappe stack calabria italy insights for the tectonic evolution of the calabrian arc combined structural and petrographical investigations coupled with 40ar 39ar geochronology were carried out in the sila piccola massif of the calabrian arc in order to define the structural geometry and map out the major structural and metamorphic breaks within the exposed nappe sequence on the basis of the contrasting alpine pressure temperature p t and structural signatures the nappe stack can be divided in two major tectonic complexes bounded by a flat lying ductile to brittle extensional shear zone the upper complex consists of a nappe like structure where a major top to the east compressional shear is recorded the lower tectonic complex consists of an ophiolite bearing sequence showing typical high p low t parageneses mg carpholite and na amphibole the 40ar 39ar geochronology on phengites in equilibrium with blueschist minerals provided a minimum age estimate for the blueschist event in the lower complex rocks at the oligocene eocene boundary around 35 ma ductile to brittle top to the west extensional shear accompanied the nearly isothermal retrogression and exhumation of the lower complex rocks reworking the previous nappe contacts with shear localization along the upper lower tectonic complex discontinuity the 40ar 39ar dating indicates that this postnappe stacking tectonic evolution took place from 30 ma onward it is proposed that exhumation of the deep seated rocks occurred below a top to the west extensional detachment active during convergence and orogenic complex formation synorogenic extension the age of this detachment is bracketed between 30 ma and the post orogenic neogene basin sedimentation middle upper miocene the revised structural and metamorphic scenario is here integrated into a new tectonic evolutionary reconstruction which involves an early high p low t top to the east crustal thickening episode during the construction of the apennine orogenic wedge eocene oligocene followed and overprinted by a top to the west extensional shear probably active from the late oligocene

timing and magnitude of rotations in the frontal thrust systems of southwestern sicily we report new paleomagnetic and anisotropy of magnetic susceptibility ams results from upper tortonian to middle pleistocene sediments which were deposited upon and adjacent to active thrust structures in southwestern sicily the data show that the plio pleistocene sediments from the belice and menfi basins covering the saccense shelf limestones underwent any internal shortening after the early pleistocene santernian as well as any net rotation sediments around this area which overlie basinal meso cenozoic successions record systematic rotations one upper tortonian site to the west is 30 counterclockwise rotated while to the east lower pliocene to middle lower pleistocene sites within the gela nappe domain show 25 to 56 clockwise cw rotations these data show that the ductile basinal sediments were bent and rotated around the rigid saccense carbonates during the thin skinned southward propagation of the orogenic front we document here that the coastal sediments from the southwestern gela nappe underwent both a post middle early pleistocene 30 cw rotation and a post middle pleistocene e w to ese wnw flattening revealed by ams our data then constrain to the late pleistocene holocene the age of the last shortening episode occurring in the southwestern gela nappe front pleistocene rotations of similar amount also characterize the sicanian domain implying that it was incorporated in the gela nappe wedge during the recentmost episodes of deformation this evidence allows us to better understand the very large up to 114 post mesozoic rotations reported by channell et al 1980 1990 for the sicanian limestones as related to both miocene or older deformational episodes and the plio pleistocene evolution of the gela nappe

seismicity and p wave velocity image of the southern tyrrhenian subduction zone summary this paper focuses on the deep earth structure and earthquake distribution within the southern tyrrhenian subduction zone we discuss seismological observations which provide insight into the mechanics of subduction processes for an unusual compressional margin the motivation for this work derives from the recognition that little is known about one of the most intriguing geodynamic features of the italian peninsula and the fact that a large amount of information can be extracted from data collected by the istituto nazionale di geofisica national seismic network we show that the hypocentres of intermediate and deep earthquakes that have occurred since 1988 image a nw dipping plane continuous from the ionian sea to the tyrrhenian down to 450 km depth we also present a 3 d model of the deep structure beneath southern italy derived using deep earthquake seismic tomography tomographic images reveal a high velocity body dipping from the apulian and iblean forelands towards the tyrrhenian basin in the crust and upper mantle at least down to 320 km depth this high velocity body may be related to the cold subducted ionian lithosphere earthquake hypocentres are confined within the high velocity body delineating the subduction beneath the calabrian arc

crustal extension in the northern apennines the transition from compression to extension in the alpi apuane core complex an interpretation of northern apennine geology is presented which relates the temporal and spatial occurrence of both compressional and extensional deformation features in terms of the changing dynamic evolution within an accretionary wedge after a model proposed by platt 1986 followed by the initiation and development of continental rifting during cretaceous to eocene time an accretionary wedge formed as remnant tethyan oceanic crust subducted beneath the rotating corsica sardinia microplate microplate collision during the oligocene was characterized by the rapid imbrication of buoyant continental crust of the italian continental margin the record of which is preserved within the duplex structure geometry of the alpi apuane region the overthickened wedge geometry returned to a more stable configuration by developing extensional features during the miocene both listric normal faults at upper crustal levels and shear zones indicating evidence of distributed ductile extensional strain at mid crustal levels are recorded it is proposed that large scale regional extension with associated volcanism beginning in the messinian was represented by the intrusion of asthenospheric material from the subducted plate into the already attenuated accretionary complex further rifting perhaps aided by subduction and back arc processes in the southern apennines led to the formation of the tyrrhenian sea as an oceanic basin both the apennines and north american core complexes record evidence of crustal thickening followed by crustal thinning and finally of continental rifting this suggests that the similar histories of these regions with vastly different plate tectonic settings may both be explained by processes linked to the changing internal dynamics of accretionary wedges

from mantle to crust stretching the mediterranean abstract the origin of forces driving the deformation of the continental crust near subduction zones and especially in backarc regions is debated this work is based on a compilation of sks fast splitting directions that give an image of flow lines in the mantle around the mediterranean subduction zones and a comparison with stretching and shear directions in metamorphic core complexes that show the pattern of deformation at the scale of the middle and lower crusts we find that 1 the two sets of directions are parallel in the three main backarc regions namely the alboran sea the tyrrhenian sea and the aegean sea showing that the lithosphere deforms with the same direction of stretching in the crust and the mantle suggesting that 2 crustal deformation is mainly driven from below by slab retreat and 3 the lithospheric fabric is reset within a few millions of years in backarc environments

reply to comments on the cenozoic fold and thrust belt of eastern sardinia evidences from the integration of field data with numerically balanced geological cross section by arragoni et al 2016 the comment by berra et al 2017 on the evidence of alpine tectonics in eastern sardinia proposed by arragoni et al 2016 is based on the sedimentological interpretations of few local outcrops in a marginal portion of the study area the cenozoic alpine fold and thrust setting which characterizes this region presents flat over flat shear planes acting along originally stratigraphic contacts where stratigraphic continuity is obviously maintained the ramp sectors present steeply dipping bedding attitudes and there is no need to invoke and to force prograding clinoforms with unrealistic angles to justify them the balanced geological cross section proposed by arragoni et al 2016 is fully supported by robust newly collected structural data and is compatible with the overall tectonic setting while the interpretation proposed by berra et al 2017 lacks a detailed structural investigation we believe that the partial application of the techniques available to modern geology may lead to incorrect interpretations thus representing an obstacle for the progress of knowledge in the earth sciences

neotectonics of coastal jeffara southern tunisia state of the art abstract helped by the studies and results of previous researchers we herein study the neotectonic of the coastal jeffara with the input of numerous 2d reflection seismic profiles onshore combined with digital elevation model analyses issued from srtm and field works acquired and available data were then integrated within a gis geodatabase where jerba zarzis and jorf appear to be part of a n s pull apart basin within a nw se transtensive right lateral major fault zone our structural geologic and geomorphologic analyses confirm and prove the presence of nnw sse right lateral en echelon tension gashes nw se aligned salt diapirs numerous active folds offsets en echelon folds and so on they are associated with this major right lateral nw se transtensive major coastal jeffara fault zone that affect the holocene and the villafranchian deposits we therefore confirm herein a new structural geodynamic jeffara model due to the post lower cretaceous northward migration of northern african to the eurasian plates this nw se transtensive fault zone is interpreted as a part of the southern branch of the eastward sahel block extrusion toward the free mediterranean sea boundary therefore this geodynamic movement may explain the presence offshore of small elongated nw se n s and ne sw transtensive basins and grabens with petroleum interest to conclude at the regional scale the structural geomorphologic approach combined with both field work and 2d reflection seismic profile analyses appear to be an excellent tool to prove and confirm the nw se right lateral transtensive extrusion fault zone of the coastal jeffara

three dimensional moho topography in italy new constraints from receiver functions and controlled source seismology in complex tectonics regions seismological geophysical and geodynamic modeling require accurate definition of the moho geometry various active and passive seismic experiments performed in the central mediterranean region revealed local information on the moho depth in some cases used to produce interpolated maps in this paper we present a new and original map of the 3 d moho geometry obtained by integrating selected high quality controlled source seismic and teleseismic receiver function data the very small cell size makes the retrieved model suitable for detailed regional studies crustal corrections in teleseismic tomography advanced 3 d ray tracing in regional earthquake location and local earthquake tomography our results show the geometry of three different moho interfaces the european adriatic ionian and tyrrhenian the three distinct moho are fashioned following the alpine and apennines subduction collision and back arc spreading and show medium to high frequency topographic undulations reflecting the complexity of the geodynamic evolution

the syn and post collisional evolution of the romanian carpathian foredeep new constraints from anisotropy of magnetic susceptibility and paleostress analyses abstract the first results of anisotropy of the magnetic susceptibility ams data from the romanian carpathian foredeep reveal compression directions generally perpendicular to the highly bended carpathian orogenic arc the distribution of the present day stress field in the pannonian carpathian region reflects pre imposed plate boundaries that were established during late miocene collision analysis of the ams along the eastern and southern carpathian foredeep at the contacts of the orogenic nappe pile the lower plate and the overlying sedimentary rocks indicates that two factors are critical for the distribution of the stress field during and after collision i e 1 the inherited highly bended plate geometry and 2 the quaternary deformation that lead to differential vertical and horizontal movements in the se carpathians the ams analysis was successfully used in the weakly deformed mio pliocene sedimentary rocks from the carpathian foredeep revealing information about the deformation history of the soft non competent rocks where the poor preservation of traditional kinematic indicators e g faults and folds is difficult

sequence analysis of early saalian glacial lake deposits nw germany evidence of local ice margin retreat and associated calving processes abstract this paper presents a detailed analysis of high resolution facies architecture of glaciolacustrine ice margin deposits which formed at the southern margin of the scandinavian ice shield the ice margin depositional systems are characterised by coarse grained deltas and subaqueous fans which are formed by stacked transgressive regressive sequences recording an overall lake transgression interrupted by minor short term lake level falls the delta complexes at the northern margin of glacial lake rinteln are thought to reflect a relatively stable position of the ice margin in front of the weser chains mountain ridges the onset of delta progradation probably represents a halt in ice advance and a related high sediment supply period the sedimentary facies and depositional architecture resemble those of nonglacial gilbert type deltas except for the deposition of glacial debris the main delta progradation is recorded from the highstand systems tract when high meltwater and sediment discharge occurred during the melt season a forced regression during opening of outlets led to the formation of subaerially exposed sequence boundaries and the erosion of the highstand systems tract deeply incised channels incised valleys were filled during the subsequent transgression at the eastern lake margin subaqueous fan deposits reflect an unstable ice front that was rapidly retreating and subject to periodic calving which resulted in the generation of floating icebergs dumping ice rafted debris and ploughing into subaqueous fan deposits the rapid retreat of this eastern ice margin is interpreted to result from the overall lake level rise the fan stacking pattern and bulk geometry were determined by the ice front fluctuations the shifting of meltwater outlets and the short term lake level fluctuations depositional processes reflect the character of sediment supply and distance from the ice margin ice proximal upper fan deposits are characterised by coarse grained gravel deposited by debris flows that document continuous discharge slump and slide deposits are related to steep depositional slopes the mid fan contains basinward fining and thinning deposits of quasi steady and surge type high and low density turbidity currents indicating more ice distal and periodic deposition the outer fan deposits mainly consist of surge type low density turbidites and glacial debris dumped by icebergs the forcing parameters governing the development of depositional sequences in both delta and fan settings were lake level fluctuations sediment yield rates and physiography the depositional sequences were deposited on a time scale of seventh and eighth order high frequency cycles 101 102 years in this short time span lake level fluctuations were on the order of 120 m therefore accommodation space was largely controlled by lake level and subsidence can be ignored

ice walled lake plains implications for the origin of hummocky glacial topography in middle north america abstract ice walled lake plains are prominent in many areas of hummocky till topography left behind as the laurentide ice sheet melted from middle north america the formation of the hummocky till topography has been explained by 1 erosion by subglacial floods 2 squeezing of subglacial till up into holes in stagnant glacial ice or 3 slumping of supraglacial till the geomorphology and stratigraphy of ice walled lake plains provide evidence that neither the lake plains nor the adjacent hummocks are of subglacial origin these flat lake plains up to a few kilometers in diameter are perched as much as a few tens of meters above surrounding depressions they typically are underlain by laminated fine grained suspended load lake sediment many ice walled lake plains are surrounded by a low rim ridge of coarser grained shore sediment or by a steeper rim ridge of debris that slumped off the surrounding ice slopes the ice walled lakes persisted for hundreds to thousands of years following glacial stagnation shells of aquatic molluscs from several deposits of ice walled lake sediment in south central north dakota have been dated from about 13 500 to 10 500 b p calibrated radiocarbon ages indicating a climate only slightly cooler than present this is confirmed by recent palaeoecological studies in nearby non glacial sites to survive so long the stagnant glacial ice had to be well insulated by a thick cover of supraglacial sediment and the associated till hummocks must be composed primarily of collapsed supraglacial till

inverse to normal magnetic fabric transition in an upper miocene marly sequence from tuscany italy the magnetic susceptibility fabric of an upper miocene marly sequence exposed along the morra creek tuscany italy changes from inverse maximum susceptibility axis sub perpendicular to bedding to normal from the bottom to the top of the section the change is gradual with the presence of anomalous magnetic susceptibility fabrics at some levels the anhysteretic remanence anisotropy is always normal throughout the sequence the changes in the magnetic fabric seem to be controlled by sedimentological variations with the inverse susceptibility fabric related to the abundance of iron bearing carbonates in the lower part of the section in the upper part of the section subtle changes in the detrital inputs in the basin and particularly a larger contribution of clayey and ferrimagnetic particles turned the susceptibility fabric to a normal type

the pleistocene end moraine fans controls on their sedimentation and location abstract this paper presents a model of end moraine sedimentation based on data from pleistocene ice sheet margins according to this model end moraines quite often constitute alluvial fans or coalesced fans formed at the ice margin by redeposition of supraglacial material three types of end moraine fan have been recognized those composed mainly of mass flow deposits type a equivalent to dry alluvial fan in nonglacial settings those containing both mass flow and waterlain sediments type b and those that contain mainly sorted waterlain material type c equivalent to wet alluvial fan in nonglacial settings for each type of fan several sedimentary subenvironments differentiated by distance from the ice front are identified the diagnostic processes on the end moraine fans are cohesive and cohesionless debris flows or grain flows types a and b or hyperconcentrated flows and sheetflows types b and c the type b fan seems to represent the most typical sequence in the end moraine zones but the type c fan is also quite common at the pleistocene ice sheet margins our studies also suggest that the terminal supraglacial drainage controls the type of end moraine fan sedimentary subenvironment moraine types a b c whereas subglacial hydrology and ice stream regime which determine the mobility of the ice front and larger scale conditions of sediment supply to the ice margin control the location and size of the end moraine fan

sedimentology and origin of deposits from a small ice dammed lake leirbreen norway this paper describes recent proglacial lacustrine sediments exposed by the drainage of a small probably never more than 0 03 km2 ice dammed lake basin at leirbreen central jotunheimen norway the dominant facies include ripple laminated massive and horizontally stratified sands massive and horizontally laminated silts and irregularly laminated fine sands and silts the major control on lake circulation and the nature and distribution of these facies was an underflow driven by a subglacial meltwater stream which formed the major lake input although much of the sedimentary sequence indicates a pulsatory input the proximal character of this small lake prevented the development of classic varved silts compressional deformation of shoreline sediments was due to winter lake ice push other deformational processes included the grounding of icebergs water escape and syn sedimentary downslope collapse observations from an adjacent small ice marginal lake at leirbreen provide support for several of the inferences drawn from the sediments of the former ice dammed lake

palaeo shorelines of the historic period sant antioco island south western sardinia italy abstract this article illustrates the results of the recent multidisciplinary studies carried out in the southern part of sardinia western mediterranean sea on the last 2 5 ka palaeo sea level the survey has specifically investigated some geo archaeological sea level markers related to two submerged structures the first represents a near port building of punic roman age 2300 100 bp and is located in the sant antioco lagoon the second structure is a road of roman age 1030 20 bp in the near coastal area of palmas gulf a bone and ceramics fragment rich pericoastal beach rock chronologically referable to the imperial roman age between tiberius and claudius 1940 20 bp has been studied the results of this study fit the new predicted glacio hydro isostatic model of lambeck et al and agree with similar data from other sardinian sites that show almost no vertical tectonic mobility during the late holocene the study of a new stratigraphic section along the western coast of sant antioco island has identified the inner margin of a wave cut platform with fossils referred to mis 5 5 at 7 5 m highlighting a relative tectonic stability since the upper pleistocene for this area the geomorphological context of palmas gulf continental shelf shows a buried palaeo riverbed referred to mis 2 and a coastal palaeo system related to the holocene sea level change between 15 and 25 m these features are typical of the conservative style of low tectonic mobility areas

palaeoecology and taphonomy of spatangoid dominated echinoid assemblages a case study from the early middle miocene of sardinia italy abstract the early middle miocene marine sedimentary succession of the borutta formation cropping out at porto torres northern sardinia represents one of the most diverse and well preserved spatangoid dominated sedimentary successions in the miocene of the mediterranean area the echinoid bearing succession is studied with the twofold purpose of firstly reconstructing the palaeoenvironmental setting in which these echinoids occurred and secondly investigating factors influencing the preservation potential of spatangoid echinoids in the fossil record these goals are accomplished by 1 detailed logging of sedimentary facies 2 applying functional morphological interpretations of echinoid skeletons in order to reconstruct their behaviour and life habits 3 quantifying the relative abundance of taxa and taphonomic features of test preservation and 4 analyzing associated trace fossils within the beds the sedimentary succession is composed mainly of fine grained sandstones which are intensely bioturbated by thalassinoides like burrows spatangoid abundance is high throughout the profile declining only in intercalated dm thick rhodolith beds a 20 cm thick bed with a bedding surface of approximately 250 m2 was investigated in detail with respect to relative abundance of spatangoid taxa and taphonomic signatures the echinoids consist almost exclusively of deposit feeding irregular forms with a dominance of the spatangoids ova and brissopsis and the minute clypeasteroid echinocyamus the spatangoids opissaster holanthus metalia and hemipatagus as well as the clypeasteroid clypeaster marginatus are also present a low energy moderately deep outer sublittoral environment with high rates of bioturbation and episodes of sediment deposition by storms is inferred interspecific competition among deposit feeding echinoids appears to be limited by their different burrowing depths feeding strategies and resource partitioning the gregarious behaviour of spatangoid echinoids their habitat in quiet deeper environments and episodes of rapid deposition seem to represent the main factors leading to this spatangoid bearing deposit since both shallow and deep burrowing spatangoid echinoids are well represented as complete specimens mode of life does not appear to play a major role in their preservation potentials

paleomagnetic evidence for a pre early eocene 50 ma bending of the patagonian orocline tierra del fuego argentina paleogeographic and tectonic implications abstract the southernmost segment of the andes of southern patagonia and tierra del fuego forms a 700 km long orogenic re entrant with an interlimb angle of 90 known as patagonian orocline no reliable paleomagnetic evidence has been gathered so far to assess whether this great orogenic bend is a primary arc formed over an articulated paleomargin or is due to bending of a previously less curved or rectilinear chain here we report on an extensive paleomagnetic and anisotropy of magnetic susceptibility ams study carried out on 22 sites 298 oriented cores predominantly sampled in eocene marine clays from the external magallanes belt of tierra del fuego five sites out of six giving reliable paleomagnetic results containing magnetite and subordinate iron sulphides yield a positive fold test at the 99 significance level and document no significant rotation since 50 ma thus the patagonian orocline is either a primary bend or an orocline formed after cretaceous earliest tertiary rotations our data imply that the opening of the drake passage between south america and antarctica probably causing the onset of antarctica glaciation and global climate cooling was definitely not related to the formation of the patagonian orocline but was likely the sole consequence of the 32 2 ma scotia plate spreading well defined magnetic lineations gathered at 18 sites from the magallanes belt are sub parallel to mostly e w local fold axes while they trend randomly at two sites from the magallanes foreland our and previous ams data consistently show that the fuegian andes were characterized by a n s compression and northward displacing fold thrust sheets during eocene early miocene times 50 20 ma an unexpected kinematics considering coeval south america antarctica relative motion both paleomagnetic and ams data suggest no significant influence from the e w left lateral magallanes fagnano strike slip fault system mffs running a few kilometres south of our sampling sites we thus speculate that strike slip fault offset in the fuegian andes may range in the lower bound values 20 km among those proposed so far in any case our data exclude any influence of strike slip tectonics on the genesis of the great orogenic bend called patagonian orocline