specific surface area and pore size distribution in clays and shales one of the biggest challenges in estimating the elastic transport and storage properties of shales has been a lack of understanding of their complete pore structure the shale matrix is predominantly composed of micropores pores less than 2 nm diameter and mesopores pores with 2 50 nm diameter these small pores in the shale matrix are mainly associated with clay minerals and organic matter and comprehending the controls of these clays and organic matter on the pore size distribution is critical to understand the shale pore network historically mercury intrusion techniques are used for pore size analysis of conventional reservoirs however for unconventional shale reservoirs very high pressures 414 mpa 60 000 psi would be required for mercury to access the full pore structure which has potential pitfalls current instrumental limitations do not allow reliable measurement of significant portions of the total pore volume in shales nitrogen gas adsorption techniques can be used to characterize materials dominated by micro and mesopores 2 50 nm a limitation of this technique is that it fails to measure large pores diameter 200 nm we use a nitrogen gas adsorption technique to study the micro and mesopores in shales and clays and compare the results from conventional mercury porosimetry techniques our results on pure clay minerals and natural shales show that i they have a multiscale pore structure at different dimensions ii fine mesopores with a characteristic 3 nm pore size obtained with n2 gas adsorption are associated with an illite smectite group of clays but not with kaolinite iii compaction results in a decrease of pore volume and a reduction of pore size in the inter aggregate macropores of the illitesmectite clays while the fine intra tachoid mesopores are shielded from compaction iv for natural shales mineralogy controls the pore size distributions for shales and the presence of micropores and fine mesopores in natural shales can be correlated with the dominance of the illite smectite type of clays in the rock our assessment of incompressible 3 nm sized pores associated with illite smectite clays provides an important building block for their mineral modulus

late quaternary terraced marine deposits as tools for wide scale correlation of unconformity bounded units in the volcanic aeolian archipelago southern italy abstract late quaternary raised terraced marine deposits are commonly interlayered with volcanic deposits along the coasts of the aeolian archipelago they mostly reflect the interplay between long term crustal vertical movements and glacio eustatic sea level changes during marine isotope stages mis 5 and 9 key discontinuity surfaces are represented by those bounding terraced marine deposits formed in correspondence of recurrent individual interglacial sea level peaks they are the basal ravinement surface formed during gradual sea level rise at the onset of a sea level peak and the upper surface of subaerial erosion developed during ensuing sea level fall and lowstand the discontinuity surfaces are classified according to their sequence stratigraphic significance field documentation and areal extent mis 5 marine deposits are bounded by the first order ui and uii unconformities the ui unconformity is the ravinement surface formed during mis 5e sea level rise age between 130 and 124 ka the uii unconformity is the surface of subaerial erosion and non deposition developed during sea level lowering after mis 5a age 70 ka unconformities ui and uii are correlated throughout the entire aeolian archipelago thus assuming a regional stratigraphic significance by linking to the global sea level curve they are assigned a relative age and assume a substantial chronostratigraphic significance and potential for dating of volcanic rocks further correlation on most of the aeolian archipelago is provided by the l3 unconformity that is the ravinement surface formed during sea level rise of mis 5c 100 ka moreover the f1 unconformity bounds at the base marine deposits older than the last interglacial i e mis 9 and is ascribed of an inter island stratigraphic outcome these allogenic unconformities driven by sea level fluctuations allow definition of a regional unconformity bounded framework for the aeolian archipelago into which local volcanic successions subdivided by autogenic unconformities of volcanic origin may be arranged

morphostructural evolution and related kinematics of rockfalls in campania southern italy a case study abstract on the southern slope of the sorrentine peninsula there are many subtriangular depressions in which the main townsof the area are located the depressions are linked to block rotation during strike slip fault activity and are oftenmarked by high subvertical cliffs and related rockfall phenomena with consequent damage to the underlying towns on the basis of back analyses carried out using hoek s method an in depthstudy of some of the rockfalls enabled us todefine for one of these towns the most suitable shock restitution coefficients of the detritical pyroclastic deposits present on the terraces situated at the foot of the cliffs on the basis of the main kinematic parameters of actual rockfalls and approximately 6600 simulated rockfalls a planning of the high level rockfall risk valley bottoms was drawn up the size of the high level rockfall risk sites depends above all on the presence number and size of the terracings wherecitrus fruit trees are cultivated the calculation method suggested by paronuzzi was also adopted in order to make a detailed evaluation of the role the terraces play in modifying the trajectory height the translation velocity and the endpoint of the boulders although there are methodological and statistical differences between the two methods results from both studies showed sufficient correlation in particular concerning the trajectories endpoints

the architectural variability of small scale cycles in shelf and ramp clastic systems the controlling factors many sedimentary successions are composed of metre to decametre scale cycles exhibiting various stratal architectures that depend on the complex interplay among several syndepositional controlling factors these controlling factors may produce extremely different stratal and facies architectures along relatively brief distances in the same basin but in contrast they also may form similar architectures in basins that experience a radically different tectonic setting the recognition of factors that controlled the architecture of small scale cycles therefore is very important to reconstruct the depositional history of sedimentary successions these factors include 1 the interplay between the rate of accommodation development and the rate of sediment supply a s 2 the amplitude and shape of the relative sea level curve 3 the position in the shoreface shelf system 4 the basin physiography 5 the shoreline trajectory 6 the climate driven environmental energy 7 the siliciclastic input vs carbonate production shoreface to shelf small scale cycles can be grouped into three main categories r cycles showing a dominant regressive interval t r cycles with transgressive and regressive intervals of similar thickness t cycles showing a dominant transgressive interval although some depositional settings may favour the deposition of a particular type of cycle these cycle motifs appear to be mainly controlled by the interaction of local and wider scale controlling factors for example t cycles may be present in both subsiding and uplifting settings depending on the interplay between the a s and the other factors cited above as a result r t r and t cycles may be recognized within the same depositional system these evidences suggest that care must be taken to apply general models that predict the stratal architecture of cycles mainly in function of the long term a s the correct prediction of the cycle architecture is important also for hydrocarbon researches as the thickness of potential reservoir deposits is the result of the interplay among factors discussed here

truncated higher order sequences as responses to compressive intraplate tectonic events superimposed on eustatic sea level rise abstract high resolution sequence stratigraphic analysis of the lignite bearing miocene siliciclastic sequence of the salotarjan lignite formation slf has been performed by lithostratigraphic dissection of more than 1350 boreholes and by detailed analysis of well logs from more than 150 boreholes biostratigraphic data indicate that the slf represents a single 3rd order eustatic sequence namely the bur 4 of vakarcs et al vakarcs g hardenbol j abreu v s vail p r varnai p tari g 1998 oligocene middle miocene depositional sequences of the central paratethys and their correlation with regional stages sepm special publication vol 60 209 231 as for facies conditions facies models for sandy shorefaces and or wave dominated deltas can be applied twenty six parasequences have been identified and mapped in the adjacent sub basins from well log correlations the sharp based sand bodies of ps 10 and 17 were interpreted as the falling stage systems tract fsst of higher order sequences the subsequent transgressive systems tracts tst are represented by retrograding sets of 2 3 parasequences ps 11 13 18 19 based on the regional unconformity at the base and the regionally extended sharp based sand bodies three sequence boundaries sb were determined that dissect the 3rd order sequence into three higher order sequences one of the special features of the sequence is that the fssts interrupt the rapid relative sea level rises ps 9 and 16 and lie directly on the silty material of nearshore environments leading to the lack of the higher order highstand system tracts hst truncated transgressive semi cycles another characteristic is the striking basinward fore stepping of the sedimentary depocentres and that of the facies belts of the lignite seams the rapid relative sea level falls implied by the two fssts are unexpected in the context of an overall eustatic rise thus the possibility of tectonic origin of shallowing was investigated this verification was based primarily on the observations that 1 the basin was united when parasequences 1 to 13 were developed whereas 2 by the end of the sequence development the palaeozoic basement protruded to the surface dividing the basin reflecting intense tectonic events simultaneous with sequence development the fssts with the sbs above and the formation of higher order sequences can thus be regarded as sedimentary responses to syn sedimentary tectonic elevation and tilting of the basement this elevation was induced by tectonic compression and associated imbrication along a regional reverse fault that was known as the darno line the imbrication could have controlled not only the repeated relative sea level falls but also the striking fore stepping of the sedimentary depocentres and facies belts of the associated lignite seams tectonic tilting influenced not only the fssts but the subsequent early tsts as well thus lignite seams associated with the tectonically counteracted tsts are characterized by multiple seams with several accessory seams va iiia b and ia while those associated with tectonically quiescent periods are aerially extensive and solitary comparison with other coal bearing formations enhanced the importance of the fsst in the interpretation of stratigraphic truncations coal seam geometry conditions facies shiftings and stratal geometry enabling a more accurate description of syn sedimentary tectonic events

forced regression across the marine to continental transition in jammu sub basin implication to the oligo miocene unconformity in the himalayan foreland abstract similar to the other sub basins marine to continental transition in jammu foreland also shows the presence of a characteristic greenish gray quartz arenite unit locally termed as white sandstone unit process based sedimentological and sequence stratigraphic work carried out across this white sandstone unit suggest that this unit was deposited in a shoreface settings during a forced regression the sharp base of the white sandstone unit represents a surf diastem a kind of regressive surface of marine erosion and does not signify a 10 myr unconformity the gradational top of the unit showing various degree of exposure and soil development has been interpreted as type 1 sequence boundary the white sandstone unit present along the entire stretch of the western sub himalaya also shows forced regressive nature in the subathu sub basin situated 350 km se of jammu so the forced regression across the marine to continental transition in the entire western himalayan foreland is a regional phenomena and not a local one contrary to the earlier works which proposed the presence of an unconformity spanning 10 myr encompassing the oligo miocene period the present study showed that the unconformity if present is of small duration possibly spanning

high resolution sequence stratigraphy of clastic shelves vii 3d variability of stacking patterns abstract in the geological record high frequency sequences at the scale of fourth order and lower rank stratigraphic frameworks are usually stacked to compose higher rank lower frequency systems tracts i e sequence sets along dip oriented transects higher rank transgressive normal regressive highstand and or lowstand and falling stage systems tracts are defined by retrogradational upstepping progradational and downstepping progradational stacking patterns of component high frequency sequences respectively however these stacking patterns may vary markedly along depositional strike due to lateral changes in the rates of accommodation and sedimentation resulting in the coeval deposition of different types of higher rank systems tracts in this case surfaces bounding such systems tracts are diachronous along depositional strike moreover if the high frequency sequences that compose the lower frequency systems tracts are laterally continuous the higher rank bounding surfaces are discontinuous along depositional strike consisting of a series of stepped surfaces that can be observed in high resolution studies these aspects have important implications for petroleum exploration and need to be considered in high resolution sequence stratigraphic analysis

sequence stratigraphy in active extensional basins implications for the interpretation of ancient basin fills abstract systematic variations in sequences their component units and their stacking patterns exist within rift basins these variations can be related to displacement gradients associated with the large scale 12 50 km segmentation of normal fault zones which control accommodation sediment supply and basin physiography sediment supply is also strongly influenced by the nature of pre rift drainage networks and variations in bedrock lithology high rates of hangingwall subsidence close to the centre of normal fault segments may cancel out the effects of glacio eustatic sea level fall so that accommodation development is normally characterized by the continual addition of new space the resulting sequences lack type 1 sequence boundaries and lowstand systems tracts and stack into aggradational sequence sets the adjacent footwall is subject to uplift which may lead to subaerial exposure and incision generating a composite type 1 sequence boundary away from the fault zone and near segment boundaries slip rates are much lower and hence relative sea level change is dominated by eustasy here falls in relative sea level are important resulting in type 1 sequences sequence stacking patterns reflect not only eustasy and local fault controlled subsidence but also the interaction of these with adjacent uplifting footwalls and or regional uplift tectonic influence on sequence development will be more pronounced during greenhouse times than icehouse times

progressive evolution of a fault related fold pair from growth strata geometries sant llorenc de morunys se pyrenees abstract new structural stratigraphical mapping constrains the three dimensional kinematics and mechanisms of eocene oligocene growth folding at sant llorenc de morunys ne ebro basin spain a 1 km wide sub vertical panel of syntectonic alluvial gravels passes southwards via a highly asymmetrical growth fold pair to shallowlydipping strata the axial surface of the anticline comprises either continuous or en echelon segments while that of the syncline is concave and usually continuous while converging upwards the axial surfaces do not define growth triangles principal and subsidiary growth unconformities and thickness changes occur across both axial surfaces and the common limb dips within the common limb decrease up stratigraphy and up dip mesostructures indicate that internal deformation was ongoing during folding at all stratigraphical levels and concentration of cleavage in the syncline indicates that this hinge was essentially fixed sequential restoration of three profiles shows that folds amplified principally by limb rotation but incorporated minor passive hinge migration particle movement vectors generated by section restoration are arcuate about a hinterland pinpoint a new trishear model of fault propagation folding involving non rigid limb rotation reproduces the rounded hinge forms thickening geometries and limb dip variations observed simple kink band migration models fixed axis and constant thickness theories do not replicate these features

ichnofabric analysis of the shallow marine nukhul formation miocene suez rift egypt implications for depositional processes and sequence stratigraphic evolution abstract the shallow marine early syn rift miocene nukhul formation suez rift egypt is highly bioturbated and allows relationships between changes in trace fossils and ichnofabrics within a shallow marine depositional system to be documented and placed in a high resolution sequence stratigraphic framework seven ichnofabrics are present in a succession of interfingering calcareous mudstones and calcarenites forming coarsening up units of up to 30 m thick bounded by marine flooding surfaces the units grade upwards from a basal mudstone package with bed parallel concretions and a planolites chondrites ichnofabric offshore through a coarsening up succession of alternating calcarenites and mudstones with thalassinoides mottled sediment offshore transition ophiomorpha irregulaire lower shoreface ophiomorpha nodosa thalassinoides lower middle shoreface thalassinoides taenidium middle shoreface and o nodosa upper shoreface ichnofabrics gastrochaenolites hardground ichnofabric is separate as it is not genetically related to the other ichnofabrics ichnofabric development is primarily controlled by depositional environment e g bottom water oxygenation sediment type food abundance and energy level which control substrate colonisation sedimentation rate marine flooding surfaces are generally well cemented and marked by distinctive epifaunal and infaunal colonisation and can be traced out from proximal to distal settings over distances of 5 km the epifaunal colonisation in proximal settings consists of abundant oysters and corals with the substrate below marine flooding surfaces containing abundant thalassinoides and ophiomorpha isp abundance and diversity of epifauna and trace fossils and burrow size decreases distally into the basin in the most distal settings epifaunal colonisation is absent and only planolites and chondrites colonise the basinal mudstone marine flooding surfaces in the most distal settings are poorly cemented but are marked by carbonate concretions 10 15 cm below the surface

tectonically enhanced forced regressions examples from growth folds in extensional and compressional settings the miocene of the suez rift and the eocene of the pyrenees

marine to continental transition in himalayan foreland mapping sedimentological studies and sequence stratigraphic analysis in parts of the himalayan peripheral foreland basin of northwest india suggest that deposition of basinal turbidites derived from both the orogenic and ramp sides took place due to progressive uplift of the basin margin causing forced regression the forced regressive wedge of shoreface white sandstone thus deposited throughout the foreland basin across the regressive surface of marine erosion cannot be included in the alluvial sediments of dagshai formation contrary to earlier inferences the unconformity between the subathu and dagshai formations is found to occur at the top of the white sandstone marked by caliche development or erosion by dagshai channel sand interpreted as a type 1 sequence boundary the reworked fossils in calciturbidite units suggest that the upper limit of the subathu formation must be significantly younger than ca 44 ma and the proposition of a synchronous orogen scale unconformity of 10 m y duration and early exhumation of himalayan rocks should be reassessed the duration of unconformity between subathu and dagshai formations is interpreted to be 3 m y the sea level fall and shoaling of subathu sea that was already set in by forced regression received tectonic enhancement only at the beginning of the dagshai formation which resulted a total turnaround from a marine to a continental alluvial system

fault propagation folding in extensional settings examples of structural style and synrift sedimentary response from the suez rift sinai egypt field data from the oligocene miocene gulf of suez rift demonstrate that coeval growth faults folds and transfer zones exerted a major control on synrift stratigraphic sequence development growth folds in the suez rift are related to steeply dipping normal faults that propagated upward resulting in broad upward widening monoclines in overlying strata folding during fault propagation was accommodated by layer parallel slip and detachment along mudstone horizons as well as by normal and rare reverse secondary faults that propagated away from the master fault the eventual propagation of the master fault through to the surface left the steep limb of the monocline and most of the secondary faults in the hanging wall this evolving structural style exerted a marked control on the geometry and stacking patterns of coeval synrift sediments synrift sediments display onlap and intraformational unconformities toward the growth monoclines and buried faults whereas they diverge into broadly synclinal expanded sections away from the growth monocline continued movement across buried faults resulted in the progressive rotation of the monoclinal limb and associated synrift sediments each successively younger sequence dipping basinward at a shallower angle than the previous one the resulting synrift geometries differ significantly from stratal geometries normally anticipated adjacent to normal faults along strike variations in facies stacking patterns are also commonly associated with decreasing displacement across faults and associated folds toward low relief transfer zones data from other rift basins indicate that fault propagation folds are not unique to the gulf of suez

evolution of ganges brahmaputra western delta plain clues from sedimentology and carbon isotopes abstract sedimentology carbon isotope and sequence stratigraphic analysis of subsurface sediments from western part of ganges brahmaputra gb delta plain shows that a late quaternary marine clay and fluvial channel overbank sediments of mis 5 and 3 highstands are traceable below the holocene strata during the last glacial maximum lgm sea level lowering of 100 m produced a regional unconformity type 1 represented by palaeosols and incised valley c4 vegetation expanded on exposed lowstand surface in an ambient dry glacial climate at 9 ka transgression inundated the lowstand surface pushing the coastline and mangrove front 100 km inland simultaneous intensification of monsoon and very high sediment discharge 4 8 times than modern caused a rapid aggradation of both floodplain and estuarine valley fill deposits between 8 and 7 ka the hoogli river remaining along its present drainage possibly acted as the main conduit for transgression and sediment discharge that was subsequently abandoned c3 vegetation dominated the delta plain during this time from 7 ka onward progradation of delta plain started and continued till recent this period experienced a mixed c3 c4 vegetation with localized mangroves in the mid holocene to dominant return of c4 vegetation in the late holocene period the study indicates that while the initiation of western part of gb delta occurred at least 1 ka earlier than the global mean delta formation age the progradation started at 7 ka at least 2 ka earlier than thought before the terrestrial vegetation change was modulated by changes in depositional environment specific ecological niches and climate rather than pco 2

using t z plots as a graphical method to infer lithological variations from growth strata the t z plot method consists of plotting the throw of sedimentary horizons across a growth fault versus their depth in the hanging wall this method has been initially developed for the analysis of growth fault kinematics from seismic data a brief analytical examination of such plots shows that they can also provide valuable information about the evolution of fault topography when growth is a continuous process stages of topography creation fault scarp and filling of the space available in the hanging wall are related to non dynamic draping mud prone pelagic settling and dynamic sand prone dynamically deposited sedimentation respectively in this case the t z plot analysis becomes a powerful tool to predict major lithological variations on seismic profiles in faulted settings q 2004 elsevier ltd all rights reserved

the role of trace fossil ichnofabric analysis in the development of depositional models for the upper jurassic fulmar formation of the kittiwake field quadrant 21 ukcs

alluvial and coastal hazards caused by long range effects of plinian eruptions the case of the lattari mts after the ad 79 eruption of vesuvius abstract the lattari mountains a limestone ridge about 20 km south of vesuvius received 1 2 5 m of fallout from the famous plinian eruption of ad 79 as demonstrated by many residual outcrops of thick volcanoclastic debris flow and alluvial deposits referred to here as the durece unit the pyroclastic fall was soon followed by rapid erosion and landsliding that produced 1 decametre scale aggradation of some narrow valley floors 2 reactivation of alluvial fans and 3 growth of new fan deltas extending as far as 500 m at the coast this response was primarily due to the steep topography of the area and the high erodability of the pyroclastic materials light and cohesionless pumice fragments several geo archaeological data indicate that the accelerated sedimentation had a duration of the order of decades and was followed by rapid dissection of the durece unit deposits and fast dismantling by wave action of the newly created fan deltas this case highlights the need to consider the possibly catastrophic reaction of fluvial and coastal systems to large explosive eruptions even in non volcanic terrains at some distance from the volcano

architecture of the tectonically influenced sobrarbe deltaic complex in the ainsa basin northern spain abstract the syn tectonic sobrarbe deltaic complex eocene of the ainsa basin spanish pyrenees is confined by lateral thrust ramps and influenced by intra basinal growth anticlines six facies associations have been distinguished within the deltaic complex i slope marls and turbidite sandstones ii distal delta front silty and bioturbated sandstones iii proximal delta front and delta plain deposits tidal inlet tidal flat mouth bar bay distributary channel and floodplain environments iv biogenic deposits at flooding surfaces v collapse zone sediments and vi nummulite dominated shallow marine carbonates the deltaic complex comprises four composite sequences which each contain a number of minor sequences of the genetic maximum flooding surface bounded type regressive unconformities and their correlative surfaces separate the composite sequences cs and each cs can be divided into lowstand transgressive and highstand components at the base the comaron cs is a wnw prograding deltaic complex containing six minor sequences characterized by basinward stepping sandstone wedges separated by transgressive mudstones double regressive unconformities are often associated with these sandstone wedges proximally in the basin growth of the intra basinal arcusa anticline caused gentle folding of the comaron cs and syn growth strata at the base of the overlying las gorgas cs contain a prominent forced regressive sandstone wedge the las gorgas sandbody and display thinning of bedsets onto the crest of the anticline moreover it can be demonstrated that relative sea level rise took place in the growth synclines at the same time as a fall in relative sea level occurred on the growth anticlines the tectonic deformation caused a shift in the direction of deltaic progradation towards the north northwest as demonstrated by the well developed clinoforms in the highstand sequence set of the las gorgas cs a second phase of tectonic activity this time triggering large scale collapse of the delta front occurred at the transition between the las gorgas and barranco el solano cs tilting of the basin floor led to the development of coeval transgressive and regressive strata separated by a fulcrum line of zero net vertical movement of the shoreline in the post tilt phase reduced sediment supply and accelerated subsidence led to widespread transgression and a change from clastic to carbonate dominated sedimentation this phase was terminated by a gradual increase in sediment supply causing progradation of a mixed clastic carbonate system dominated by large nummulite banks and bioturbated shoreface marls and sandstones finally a pronounced fall in relative sea level associated with the transition to the buil cs triggered slope instabilities and eventually established fluvial conditions all over the study area with the exception of the anticline crests the relatively high rate of tectonic subsidence in the study area suppressed relative sea level falls resulting in development of discontinuous lowstand strata and bounding surfaces the segmented nature of many regressive unconformities may be related to incremental growth of thrust related structures and each segment is separated from neighbouring segments by gaps of limited vertical and lateral displacement precursors of progressive unconformities are seen in the upper proximal part of the comaron cs by downdip fanning and updip convergence of minor sequences these differentially tilted stratal units provide reliable indicators of syn sedimentary tectonism

style contrast between forced regressive and lowstand transgressive wedges in the campanian of south central wyoming hatfield member of the haystack mountains formation

linked sequence stratigraphic and structural evolution of propagating normal faults two distinct phases in the structural evolution of normal faults can be identified in the miocene gulf of suez rift 1 an initial growth fold stage when the fault is a buried structure and 2 a subsequent surface faulting stage during the growth fold stage strata thin and become truncated toward the fault zone and are rotated and diverge away from the buried fault into growth synclines in contrast once the fault breaks surface strata form a divergent wedge which is rotated and thickens into the fault the two tectono stratigraphic styles also occur contemporaneously along the length of a single fault segment growth folding characterizes deformation around the ends of fault segments where the fault is blind whereas the center of fault segments are characterized by surface faulting these observations suggest that marked along strike variation in stratal surfaces and facies stacking patterns will occur in depositional sequences in areas of normal faulting

a pattern in the incidence of major coastal mudslides the communication considers eroding coastal cliffs which consist predominantly of stiff fissured clay overlying a more resistant stratum the contact having a gentle component of coastwise dip from the southern coasts of england five such cliffs are described in each of these a zone of dominant mudsliding exists which stands out from the background of lesser mudslides and other forms of failure the common feature is that in each case the zone of major mudsliding coincides closely with the length of cliff over which the base of the clay stratum lies within the tidal range and generally within the upper part of this it is suggested that this pattern results from optimum conditions for continuing stimulation of mudslide activity by toe erosion being reached in the above zone

a revised sedimentary and biostratigraphical architecture for the type llandovery area central wales the global standard for the llandovery series early silurian in central wales is re assessed in the light of detailed geological surveying biostratigraphical sampling and a rigorous examination of published datasets a new sedimentary and biostratigraphical architecture is presented key graptolite brachiopod acritarch and for the first time chitinozoan assemblages are critically assessed upper hirnantian to aeronian strata record events that followed the late ordovician glacial maximum and comprise a series of progradational sequences bounded by flooding surfaces but inferred still to be glacioeustatic in origin significant faunal renewals associated with many of the flooding levels underpin their potential for international recognition compound non sequences are a feature of proximal parts of the system where erosion associated with fault footwall uplift was an important process extensive slump sheets contribute to further stratal loss and displacement in distal facies a re assessment of the aeronian stage gssp reveals shortcomings with the biostratigraphical criteria used in its selection telychian portions of the succession display the disrupting effects of intra wenlock synsedimentary sliding hence the relevance of key published fossil assemblages and the criteria used to erect the stage gssp are undermined however the llandovery area remains one of the best studied early silurian successions in the world this together with regional considerations supports the retention of the series standard in mid wales where the contiguous deep water basinal succession affords internationally cited exposure of richly graptolitic facies for the whole series and significantly for the post sedgwickii biozone interval

the role of structural inheritance in the development of high displacement crustal faults in the necking domain of rifted margins the klakk fault complex froya high offshore mid norway abstract the role of inherited structures during the development of normal faults in continental rifts and proximal domains of passive margins have been extensively studied few studies however have a focus on deciphering the role of inheritance in the development of high displacement 10 km low angle 25 km is present during rifting

tectonic controls on sequence stacking pattern and along strike architecture in the pleistocene mejillones formation northern chile implications for sequence stratigraphic models abstract in the mejillones formation a shallow marine pleistocene succession of northern chile the cyclic stratigraphic record is the result of the complex interaction of regional uplift glacio eustasy local tectonics sediment supply and sedimentary processes stratal geometries characteristics of sedimentary facies and nature of sequence bounding unconformities have been investigated to evaluate the influence of i intrabasinal short term normal faulting on both along strike variations in sequence architecture and genetic complexity of key stratal surfaces and ii long term regional uplift on sequence stacking pattern the stratigraphic succession dissected by small displacement few meters normal faults striking obliquely with respect to the palaeo shoreline trends displays systematic variations in sequence architecture and the nature of bounding surfaces across them indeed depending on position with respect to the fault plane two basic types of internal organisation can be recognised in the examined shallow marine almost clastic starved sequence within grabens it consists of a siliciclastic rich transgressive systems tract tst which is bounded beneath by a transgressively modified glossifungites demarcated sequence boundary sb rs overlain by a mollusc bearing falling stage systems tract fsst the erosional downlap surface that separates the tst from the fsst is the regressive surface of marine erosion rsme on the footwall crests the combination of marine regressive erosion during falls in relative sea level and uplift has resulted in complete removal of the sediments of the tst from these sites leading to the formation of a tectonically enhanced basal unconformity composed of the rsme superimposed onto the previous sb rs sb rs rsme the prominent lateral change in component units systems tracts and nature of bounding surfaces within the studied sequence is directly related to the presence of normal faults and indicates that fault activity had a major impact on the sequence stratigraphic evolution of the mejillones formation enhancing subsidence within the grabens and promoting unconformities in the horsts overall the mejillones formation records a long term sea level fall driven by the contemporaneous regional uplift punctuated by repeated high frequency eustatic sea level changes the effect of this superimposition was that glacio eustatic sequences were displaced progressively downward and basinward and stacked in a distinct downstepping tectonically enhanced falling stage sequence set which reflects basin wide loss in accommodation space the sequence set is underlain by a composite rsme that becomes progressively younger basinward and is made up by the lateral and down dip connection of a series of lower rank sequence boundaries including hanging wall sb rss and footwall sb rs rsmes of successive sequences

numerical modelling of depositional sequences in half graben rift basins a three dimensional numerical model of sediment transport and deposition in coarse grained deltas is used to investigate the controls on depositional sequence variability in marine half graben extensional basins subject to eustatic sea level change using rates of sea level change sediment supply and fault slip reported from active rift basins the evolution of deltas located in three contrasting structural settings is documented 1 footwall sourced deltas in high subsidence locations near the centre of a lault segment 2 deltas fed by large drainage catchments at fault tips and 3 deltas sourced from drainage catchments on the hangingwall dip slope different es in the three dimensional form and internal stratigraphy of the deltas result from variations in tilting of the hangingwall and the impact of border fault slip rates on accommodation development because subsidence rates near the centre of fault segments are greater than all but the fastest eustatic falls footwall sourced deltas lack sequence boundaries and are characterized by stacked highstand systems tracts high subsidence and steep bathymetry adjacent to the fault result in limited progradation in contrast the lower subsidence rate settings of the fault tip and hangingwall dip slope deltas mean that they are subject to relative sea level fall and associated fluvial incision and forced regression low gradients and tectonic tilting of the hangingwall influence the geometry of these deltas with fault tip deltas preferentially prograding axially along the fault creating elongate delta lobes in contrast broad sheet like delta lobes characterize the hangingwall dip slope deltas the model results suggest that different systems tracts may be coeval over length scales of several kilometres and that key stratal surfaces defining and subdividing depositional sequences may only be of local extent i urthermore the results highlight pitfalls in sequence stratigraphic interpretation and problems in interpreting controlling processes from the preserved stiatigraphic product

progressive unconformities within an evolving foreland fold thrust belt zagros mountains a major angular unconformity between the bakhtyari conglomerates and the underlying agha jari formation has long been interpreted as indicating that orogeny in the zagros simply folded zone took place in plio pleistocene times this study uses field evidence of unconformities between older units in conjunction with geological maps and cross sections to argue that the front of the zagros simply folded zone has propagated in time and space these unconformities indicate that deformation started as early as end eocene in the northeast of the simply folded zone and propagated progressively to the southwest where unconformable contacts are only seen between younger units as shortening continued the southwest migration of the deformation front drove the foreland basin in front of it to its present position along the persian gulf and mesopotamia the climax of orogeny took place at end pliocene time when the most extensive unconformity in the zagros simply folded zone developed between the upper bakhtyari formation and older units active seismicity and documented present uplift imply that the simply folded zone is still propagating southwestward

the influence of the evolution of the pyrenees on adjacent basins abstract important thicknesses of syn and post orogenic sediments are observed in the southern part of the aquitaine basin and in the north of the ebro basin their deposition cannot be explained only as a result of the extensional history of the early cretaceous thus the influence of the compression associated with the pyrenees formation upon the subsidence of these basins is studied europe and iberia are considered to behave as two semi infinite elastic plates the evolution through time of the sedimentary thicknesses is explained by the deflections of these two plates induced not only by the topographic load of the pyrenees but also by additional forces 10 12 n m that may have their origin in the formation of a cold lithospheric root during the shortening a series of calculations is presented for an approximately north south profile across the aquitaine basin the pyrenees and the ebro basin a good fit for the shape of the basins and the gravity anomalies was obtained with flexural rigidities of 1 5 10 23 nm for the northern plate and the outer part of the southern plate and 1 4 10 21 nm for the inner part of the southern plate

stratigraphic control on laterally persistent cementation book cliffs utah field data from the upper cretaceous blackhawk formation in the book clitfs utah colorado demonstrate the presence of laterally extensive carbonate cements beneath major marine flooding surfaces the occurrence of firmgrounds compaction around concretions and high minus cement porosities indicate that cementation occurred during early diagenesis it is proposed that the early cementation associated with these marine flooding surfaces occurred as a result of reduced sediment accumulation rates or non depositional hiatuses linked to abrupt deepening during marine flooding these reduced sediment accumulation rates extended sediment residence time within early diagenetic zones leading to enhanced early cementation in shallow marine sandstones and mudstones