three dimensional quantitative modeling of clinoform development abstract clinoform geometry pervades stratigraphic sequences across a variety of scales it is a composite surface which records the complex interplay between accommodation sediment supply physiography and hydrodynamics much of the sequence stratigraphic technique employs clinoform geometry to discriminate between the various systems tracts that constitute depositional sequences however many sequence stratigraphic models treat the generation of accommodation and the input of sediment supply as a two dimensional problem by assuming a line source of sediment entering a system impacted by relative sea level fluctuations one common attribute of clinoforms regardless of size and or shape is that their formation is inherently three dimensional therefore the clinoform geometry varies spatially and temporally throughout a region depending on the proximity to the sediment source and the character of the hydrodynamic regime we present a three dimensional stratigraphic model that combines both diffusion and advection to simulate across and along margin sediment transport and deposition this model allows us to examine how the morphology and internal clinoform geometry of deltas vary away from the sediment source in this application we simulate the development of a delta in a low energy environment to understand the importance of along shelf diffusion on clinoform geometry and the morphology of the delta we predict the three dimensional geometry and how it varies throughout a relative sea level cycle our model indicates that when the clinoform rollover is spatially coincident with the shoreline position the clinoform geometry changes dramatically along strike away from the sediment source region throughout a relative sea level cycle for example oblique clinoforms develop near the source region and evolve into an onlapping sequence along strike on the basis of stratal geometry and the technique of sequence stratigraphy this deposit would be interpreted as two different sequences with very different connotations for their formation we surmise that when the clinoform rollover and the shoreline position are separated e g a subaqueous delta the along strike variability of the clinoform geometry diminishes because of the hydrodynamic forces operative across the shelf consequently it is important to determine how clinoforms develop in three dimensions and to ensure that our window of observation is sufficient to discern between local and regional variability

quantitative seismostratigraphic inversion of a prograding delta from seismic data quantitative stratigraphy predicts the geometry of geologic strata and their petrophysical properties based on mathematical models of geological processes and parameters which affect the formation and evolution of geologic strata such processes include erosion sediment transport and deposition quantitative stratigraphic inversion estimates the process parameters from a priori data by systematic modeling until the predictions are compatible with the observations in the case of quantitative seismostratigraphic inversion the a priori data are predominantly of the seismic kind to evaluate feasibility we designed a preliminary algorithm which we applied in a prograding delta environment we found that by fixing the sediment influx rate subaerial transport rate and the initial topography we were able to reproduce the basic features of the delta with only three to five parameters which included subaqueous transport rate and its depth dependent decay rate base level and sediment source location and spatial extent

geomorphic thresholds and complex response of fluvial systems some implications for sequence stratigraphy first generation sequence stratigraphic models have dealt in a very rudimentary fashion with the response of fluvial systems to eustasy a major element of presently accepted models is that rivers incise when sea level falls and aggrade during the ensuing rise well established geomorphic principles state that fluvial systems are complex process response systems that can adjust to internal and external changes in other ways besides incision and aggradation by modifying their stream patterns and channel geometries application of geomorphic principles to sequence stratigraphic models results in the following observations during eustatic lowstands rivers may adjust to lowered base levels and changes in slope by modifying channel patterns therefore not all lowstands produce type 1 sequence boundaries type 1 sequence boundaries characterized by fluvial valley incision are more likely to develop when sea level drops below the shelf slope break resulting in topological relief near the strandline in which headwardly eroding knickpoints form rates of eustatic change although rapid in a geological context are sufficiently low that geomorphic systems can easily maintain their equilibrium during eustatic changes and migrate back and forth across the shelf without major modifications finally und r conditions of relatively static sea level sequences and parasequences of the same scale in time and space as those which form during eustatic change can be deposited as the result of purely intrinsic causes and responses of a fluvial system in general eustasy controls the location of deposition and erosion but the resultant stratal geometry is controlled by sediment supply and processes acting on the sediments as the shoreline moves across the shelf in response to eustasy

high resolution sequence stratigraphy of lower paleozoic sheet sandstones in central north america the role of special conditions of cratonic interiors in development of stratal architecture well known difficulties in applying sequence stratigraphic concepts to deposits that accumulated across slowly subsiding cratonic interior regions have limited our ability to interpret the history of continental scale tectonism oceanographic dynamics of epeiric seas and eustasy we used a multi disciplinary approach to construct a high resolution stratigraphic framework for lower paleozoic strata in the cratonic interior of north america within this framework these strata proved readily amenable to modern sequence stratigraphic techniques that were formulated based on successions along passive margins and in foreland basins settings markedly different from the cratonic interior parasequences parasequence stacking patterns systems tracts maximum flooding intervals and sequence bounding unconformities can be confidently recognized in the cratonic interior using mostly standard criteria for identification the similarity of cratonic interior and foreland basin successions in size geometry constituent facies and local stacking patterns of nearshore parasequences is especially striking this similarity indicates that the fundamental processes that establish shoreface morphology and determine the stratal expression of retreat and progradation were likewise generally the same despite marked differences in tectonism physiography and bathymetry between the two settings our results do not support the widespread perception that paleozoic cratonic interior successions are so anomalous in stratal geometries and constitute such a poor record of time that they are poorly suited for modern sequence stratigraphic analyses the particular arrangement of stratal elements in the cratonic interior succession we studied is no more anomalous or enigmatic than the variability in architecture that sets all sedimentary successions apart from one another thus paleozoic strata of the cratonic interior are most appropriately considered as a package that belongs in a continuum of variable stratigraphic packages reflecting variable controls such as subsidence and shelf physiography special conditions of exceptionally slow subsidence rate shallow bathymetry and nearly flat regional shelf gradient are manifest mostly by the presence of individual systems tracts of relatively long duration that extend for much greater distances across depositional strike than those that characterize successions deposited in more dynamic tectonic and physiographic settings these results suggest that if other cratonic interior successions are as anomalous as reported a low sediment supply may have played a primary role in development of their apparently condensed stratal architecture the results also lead us to suggest that a nonvegetated lower paleozoic landscape played a relatively insignificant role in the development of what are commonly perceived to be enigmatic stratigraphic features of sheet sandstones particularly their widespread yet thin geometry and a scarcity of shale and siltstone

clinoforms and clinoform systems review and dynamic classification scheme for shorelines subaqueous deltas shelf edges and continental margins abstract clinoforms are inclined and normally basinward dipping horizons developed over a range of spatial and temporal scales in both siliciclastic and carbonatic systems the study of clinoform successions underpins sequence stratigraphy and all efforts to reconstruct the relative partitioning of reservoir seal and source rocks along shoreline to basin floor profiles here we review clinoform research and propose a more systematic description and classification of clinoforms this is a crucial step to improve predictions of facies and lithology distribution within shoreline to continental shelf and abyssal plain successions together with the genesis drivers and dynamics of their constituent sedimentary units four basic clinoform types are here distinguished in delta shorelines lacustrine and marine environments on the basis of their overall spatial and temporal scale morphology outbuilding dynamic and geodynamic and depositional setting 1 2 delta scale clinoforms which in turns are sub divided into shoreline and delta scale subaqueous clinoforms 3 shelf edge clinoforms and 4 continental margin clinoforms delta scale clinoform sets are tens of metres high and typically represent 1 103 kyr with progradation rates ranging from 1 000 100 000 m kyr for shorelines and subaerial deltas to 100 20 000 m kyr for subaqueous deltas shelf edge clinoform sets are hundreds of metres high and are nucleated and accreted in 0 1 20 myr usual progradation rates of 1 100 m kyr by successive cross shelf transits of delta scale clinoforms continental margin clinoform sets are thousands of metres high hallmark key geodynamic crustal boundaries e g continent ocean transition and slowly prograde basinwards in ca 5 100 myr with typical rates of 0 1 10 m kyr as a consequence of the very different progradation rates and of the difficulty of large scale clinothems to backstep during transgressions shorelines are the most dynamic clinoforms with regards to position continental margins the least and shelf edges are intermediate shortly after a transgression therefore the four clinoform types may prograde synchronously along shoreline to abyssal plain transects forming compound clinoform systems during the subsequent regressive cycle however due to the dissimilarity in progradation rates different clinoform types will normally merge progressively with each other giving rise to hybrid clinoforms e g shelf edge deltas and fewer depositional breaks in slope are distinguished along a single shoreline to abyssal plain transect overall all clinoform systems are the result of the dynamic evolution of compound and hybrid clinoforms along a temporal and spatial continuum regulated by the cyclical backstepping of the smaller scale system within natural progradational retrogradational cycles of larger scale clinothem outbuilding all clinothem types may show either an accretionary active or draping passive style depending on the proximity to the sediment source draping clinothems are nearly always composed of condensed fine grained sediments while actively accreting clinothems can be composed of predominantly coarse grained i e reservoir forming or predominantly fine grained i e non reservoir lithotypes a novel hierarchical classification scheme for both recent and ancient clinoforms is here proposed consisting of 12 classes the four basic clinoform types delta scale shoreline delta scale subaqueous shelf edge and continental margin are sub divided into eight accretionary active and draping passive sub types 8 division each accretionary sub type is then sub divided into a sandstone prone and mudstone prone variant 12 division which can be at least tentatively predicted on the basis of the clinoform morphology even in the absence of direct stratigraphic logs

change in the probability for earthquakes in southern california due to the landers magnitude 7 3 earthquake the landers earthquake in june 1992 redistributed stress in southern california shutting off the production of small earthquakes in some regions while increasing the seismicity in neighboring regions up to the present this earthquake also changed the ratio of small to large events in favor of more small earthquakes within about 100 kilometers of the epicenter this implies that the probabilistic estimate for future earthquakes in southern california changed because of the landers earthquake the location of the strongest increase in probability for large earthquakes in southern california was the volume that subsequently produced the largest slip in the magnitude 7 1 hector mine earthquake of october 1999

seismostratigraphic inversion appraisal ambiguity and uncertainty geologic process models predict the geometry of geologic strata and their petrophysical properties based on mathematical models of geological processes that affect the formation and evolution of geologic strata such processes include erosion sediment transport and deposition the resulting forward model is typically nonlinear given observations and a misfit measure one may attempt inversion of these models to estimate process parameters that yield compatible predictions for seismostratigraphic inversion seismic data are used as observations we tested such an algorithm in a prograding delta environment to examine the effect of using different seismic attributes as observations and thus different choices of misfit measures the first measure based on the degree of parallelism between seismic reflectors and modeled geologic strata demonstrated a trade off between geologic time and the sediment influx rate used to parameterize the model a second misfit measure used unwrapped seismic instantaneous phase as a crude proxy to relative geologic time which regularized the model parameters then last we combined the two measures to take advantage of their individual characteristics for most of these inversion experiments we obtained results that capture the geometry of the geologic strata as observed on the seismic data with the exception of the depositional time rate trade off where the same strata can be obtained in a shorter geologic interval when rates are increased we found the inversion to be surprisingly stable with a unique cluster of acceptable parameters despite the nonlinearity of the geologic forward model

an integrated geophysical investigation of recent seismicity in the al hoceima region of north morocco abstract data produced by the moroccan national seismological network and marine seismic reflection profiles are used to investigate the most seismically active region in morocco located on the mediterranean coast at the intersection of the rif mountain belt and the submarine alboran ridge this region in the vicinity of the city of al hoceima marks an east west transition in the marine and land deformation styles of the distributed plate boundary between africa and iberia and was the site of an m w 6 0 earthquake on 26 may 1994 the epicenter of the al hoceima earthquake is relocated onshore refining the initial submarine location close to the alboran ridge the spatial distribution of foreshocks and aftershocks shows a ne sw trend that continues partly offshore and is subparallel to the earlier yet still prominent miocene geologic structural trend the predominantly strike slip focal mechanism for the al hoceima event is characteristic of earthquakes in the region marine seismic reflection profiles that intersect the offshore region of seismicity image active high angle faults with possible strike slip components the seismicity trend is not directly related to the submarine alboran ridge or the geomorphologically prominent nekor fault deformation appears to be occurring on a number of subsidiary strike slip faults that together compose a ne sw zone of distributed shear the distributed strike slip and documented normal faulting taking place in the eastern rif mountains although characteristic of the rif region are in contrast to the thrusting style of deformation that occurs farther to the east in the algerian tell atlas this may be related to the reported lateral variations and evolution of the convergent plate boundary in these regions during the neogene and quaternary times

seismicity and active tectonics in the alboran sea western mediterranean constraints from an offshore onshore seismological network and swath bathymetry data seismicity and tectonic structure of the alboran sea were derived from a large amphibious seismological network deployed in the offshore basins and onshore in spain and morocco an area where the convergence between the african and eurasian plates causes distributed deformation crustal structure derived from local earthquake data suggests that the alboran sea is underlain by thinned continental crust with a mean thickness of about 20 km during the 5 months of offshore network operation a total of 229 local earthquakes were located within the alboran sea and neighboring areas earthquakes were generally crustal events and in the offshore domain most of them occurred at crustal levels of 2 to 15 km depth earthquakes in the alboran sea are poorly related to large scale tectonic features and form a 20 to 40 km wide nne ssw trending belt of seismicity between adra spain and al hoceima morocco supporting the case for a major left lateral shear zone across the alboran sea such a shear zone is in accord with high resolution bathymetric data and seismic reflection imaging indicating a number of small active fault zones some of which offset the seafloor rather than supporting a well defined discrete plate boundary fault moreover a number of large faults known to be active as evidenced from bathymetry seismic reflection and paleoseismic data such as the yusuf and carboneras faults were seismically inactive earthquakes below the western alboran basin occurred at 70 to 110 km depth and hence reflected intermediate depth seismicity related to subducted lithosphere

shock temperatures of sio2 and their geophysical implications the temperature of sio 2 in high pressure shock states has been measured for samples of single crystal quartz and fused quartz pressures between 60 and 140 gpa have been studied using projectile impact and optical pyrometry techniques at lawrence livermore national laboratory both data sets indicate the occurrence of a shock induced phase transformation at 70 and 50 gpa along the and fused quartz hugoniots respectively the suggested identification of this transformation is the melting of shock synthesized stishovite with the onset of melting delayed by metastable superheating of the crystalline phase some evidence for this transition in conventional shock wave equation of state data is given and when these data are combined with the shock temperature data it is possible to construct the stishovite liquid phase boundaries the melting temperature of stishovite near 70 gpa pressure is found to be 4500 k and melting in this vicinity is accompanied by a relative volume change and latent heat of fusion of 2 7 and 2 4 mj kg respectively the solid stishovite hugoniot centered on quartz is well described by the linear shock velocity particle velocity relation u s 1 822 up 1 370 km s while at pressures above the melting transition the hugoniot centered on quartz has been fit with u s 1 619 u p 2 049 km s up to a pressure of 200 gpa the melting temperature of stishovite near 100 gpa suggests an approximate limit of 3500 k for the melting temperature of sio 2 bearing solid mantle mineral assemblages all of which are believed to contain si 4 in octahedral coordination with o 2 thus 3500 k is proposed as an approximate upper limit to the melting point and the actual temperature in the earth s mantle moreover the increase of the melting point of stishovite with pressure at 70 gpa is inferred to be 11 k gpa using various adiabatic temperature gradients in the earth s mantle and assuming creep is diffusion controlled in the lower mantle the current results could preclude an increase of viscosity by more than a factor of 10 3 with depth across the mantle

cybertectonic earth and gaia s weak hand sedimentary geology sediment cycling and the earth system tectonics climate and sea level are dominant controls on the nature and distribution of sedimentary environments by inverse logic recognition of influences on sedimentation from the stratigraphic record as a result of perturbations in these variables leads to clarification of past environmental and structural change the succession of sedimentary environments in time and place is determined by a wider combination of variables namely sediment flux biological evolution atmosphere and water body productivity and chemistry the feedbacks and interrelationships between all variables cause the complexity seen in sedimentation processes over geological time the processes of global tectonics that cause widespread mountain belt and continental plateau uplift have produced numerous severe events during earth history these often random workings out of the plate tectonic cycle define the state of cybertectonic earth from cyber after the greek kubernan to steer or govern this has worked within a usually zonally arranged series of climatic belts and within the framework provided by biological evolution at certain times in the geological past a combination of factors arose as a response to continental uplift and have acted to cause certain earth surface conditions and variables notably mean global surface temperature atmospheric p co 2 p o 2 to have varied by very large amounts 2 10 compared with present values these large fluctuations such as those responsible for the neoproterozoic late palaeozoic and late tertiary glaciations lead one to doubt the reality of homeostatic control of surface conditions as proposed in lovelock9s gaia hypothesis the gaian kuberne0te0s steersman had a weak hand on the helm frequently unable to prevent vast areas of the globe experiencing rapid fluctuations in environmental conditions and inimical conditions to life for very long periods during neoproterozoic and phanerozoic times at the same time biogenic and abiogenic processes have proved capable of returning earth to states of mean stability although biogeochemical cycling models seem alarmingly ad hoc and largely untestable as scientific hypotheses in any true geological sense

mineral assemblages of basalt in the lower mantle high pressure x ray diffraction and analytical transmission electron microscopy of laser heated diamond cell samples show temperature dependent phase assemblages in mid ocean ridge basalt morb at lower mantle pressures the assemblage observed below 2250 k consists of only stishovite plus an orthorhombic perovskite phase space group pbnm or cmcm having a composition close to that of morb but slightly depleted in sio2 with increasing temperature the assemblage transforms to orthorhombic and cubic perovskites plus stishovite and then at 3250 k to orthorhombic and cubic perovskites plus stishovite and the cafe2o4 phase all of these assemblages could be present in slabs that have penetrated deep into the mantle and can therefore contribute to the seismological heterogeneity of the lower mantle

moment tensor inversion for iberia maghreb earthquakes 2005 2008 abstract we present and discuss a set of 77 moment tensor solutions for earthquakes in the iberia maghreb region from mid 2005 to the end of 2008 with moment magnitudes ranging from 3 2 to 6 0 inversion is based upon full three component intermediate period waveforms recorded at regional seismic broadband stations following the recent densification of permanent broadband networks and large scale temporary deployments at present more than 150 stations are recording in spain portugal and morocco this unprecedented station density allows analysis of small events from available short distance recordings and in general leads to more reliable source estimates due to data redundancies that permit elimination of waveforms affected by noise or complicated propagation effects the solutions for 2005 2008 constitute an important upgrade of the iberia maghreb moment tensor inventory to 225 solutions to date enhancing the image of seismotectonics at the compressive n algerian margin in the betic alboran shear zone and at the transpressive sw iberian margin as well as providing valuable constraints on seismic deformation in the western betics and the iberian foreland where little information has been previously available new solutions for the foreland and three recent seismic series in the western betics show strike slip and reverse faulting style contrasting with the dominance of normal faulting in the adjacent areas towards east in these areas as well as at the sw iberian margin faulting orientations are heterogeneous including solutions with opposite kinematics this indicates control by local stress conditions and points to fault interaction along the n algerian margin a counterclockwise rotation of slip vectors of thrust events from east to west becomes apparent several solutions for the area offshore cape st vincent are located at sub moho depths between 40 and 60 km supporting a large brittle layer thickness in the oceanic lithosphere

mineral chemistry and density of subducted basaltic crust at lower mantle pressures subducted slabs are less dense than the surrounding mantle near the base of the transition zone 660 km depth because of the survival of garnet in former basaltic crust by this depth mantle peridotite has transformed to denser perovskitite1 2 the buoyancy of the former basaltic crust may contribute to the observed accu mulation or horizontal displacement of many slabs at the base of the transition zone3 here we report experimental confirmation of the widely held belief that the basaltic crust of slabs eventually transforms to a dense perovskititic lithology stable in the lower mantle synthetic mid ocean ridge basalt more glass subjected to pressures of 45 80 and 100 gpa in a laser heated diamond anvil cell transforms to an assemblage of aluminous mg fe silicate perovskite non quenchable casio3 perovskite stishovite and a sodic aluminous phase with the ca ferrite structure fig 1 per ovskititic more is about 0 06 g cm 3 more dense than a model lower mantle prem derived from seismological data thus even thermally equilibrated perovskititic slabs should encounter no sig nificant hindrance to subduction and convection in the lower mantle

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

effects of variations in fault slip rate on sequence stratigraphy in fan deltas insights from numerical modeling results from a newly developed numerical model incorporating tectonic subsidence eustasy and sedimentation are presented for rift basin settings in particular we simulate contemporaneous fan delta deposition subsidence and eustatic sea level variations to investigate the three dimensional nature of depositional sequences in the hanging wall of a normal fault a random walk algorithm is used for sediment delivery from source to shoreline together with a nonlinear three dimensional diffusion equation for sediment movement on steep delta foresets three sediment sources are modeled they are located along strike in areas of low medium and high subsidence rates of hanging wall subsidence eustatic sea level variation and sediment supply are derived from studies of active extensional basins the resulting stratigraphy contains three fan deltas with distinct morphologies and internal stacking patterns sequence boundaries and offlap forced regression are restricted to areas of low subsidence toward the fault tip aggradationally stacked deltaic wedges are along strike where subsidence rates are high near the fault center the simulated geometries compare well to natural examples and highlight along strike sequence variability and the importance of local controls in such settings

sediment supply as a control on the variability of sequences an example from the late namurian of northern england currently variations in accommodation space are seen as the major control on facies stacking patterns and stratal geometries this paper emphasizes the importance of the sediment supply variable through the use of a regional stratal surface based interpretation of the late namurian stratigraphy of northern england late highstand palaeogeographies and stacking pattern variations highlight spatial and temporal variations in sediment supply which promote the contemporaneous development of prograda tional aggradational and retrogradational stacking patterns this questions the derivation of relative sea level curves from specific stacking patterns and highlights the potential for miscorrelation in areas with major sediment supply variations

three dimensional numerical modeling of deltaic depositional sequences 2 influence of local controls abstract we investigate the influence of three local controls sediment supply subsidence and physiography on delta development and sequence variability using the three dimensional numerical model of deltaic deposition presented in a companion paper ritchie et al 2004 independently varying a single local control within geologically constrained limits produces marked differences in three dimensional morphology cross sectional stratal geometry and delta evolution during a cycle of sea level change sediment supply strongly influences not only the timing of transgressive and maximum flooding surface development during sea level rise and hence the diachroneity of lowstand transgressive and highstand systems tracts but also the timing of onset of fluvial incision and the characteristics of incised valleys and forced regressive wedges low sediment supply leads to early drowning of forced regressive and lowstand prograding wedges high magnitude transgressions and the late development of maximum flooding surfaces during relative sea level fall low sediment supply results in early initiation of fluvial incision and development of few but major incised valleys that route sediment to elongate forced regressive lobes at their mouths in contrast high sediment supply leads to early onset of normal regression and late transgression during relative sea level rise and numerous poorly developed incised channels and a broad laterally continuous forced regressive apron during relative sea level fall on basin margins with a shelf slope morphology base of slope deepwater deposits may occur at times of sea level highstand due to sediment bypass across the slope during relative sea level fall fluvial incision is enhanced by the relatively steep gradient of the slope leading to the early onset of incision and rapid headward propagation as a result major deep incised valleys develop that capture sediment and feed it directly to thick shelf edge forced regressive and lowstand prograding wedges the greater water depth ahead of the shelf edge and the steep slope gradients result in limited forced and normal regression compared to a ramp setting in contrast to other controls tectonic subsidence or uplift leads to modification of accommodation so that relative sea level change may vary significantly along a basin margin in high subsidence settings relative sea level may continue to rise even at times of high rates of background sea level fall in such settings deltas lack incised valleys forced regressive delta lobes and prominent sequence boundaries furthermore normal regression and even transgression in high subsidence locations can be contemporaneous with forced regression and incised valley development in adjacent lower subsidence locations the results of this sensitivity analysis suggest that systems tracts and their bounding surfaces are likely diachronous along many basin margins and may locally be absent more than one control can produce a similar stratigraphic response making interpretation of controlling processes from the stratigraphic product equivocal the models provide a framework for understanding the stratigraphy of natural basin fills but further research on the interplay between the controls is required in order to understand the climatic tectonic and sea level signals concealed in the stratigraphic record

precursory seismic quiescence seventeen cases of precursory seismic quiescence to mainshocks with magnitudes fromml 4 7 toms 8 0 are summarized the amount of rate decrease ranges from 45 to 90 the significance of these changes varies between 90 and 99 99 the assumption that the background rate is approximately constant is fulfilled in most crustal volumes studied all quiescence anomalies seem to have abrupt beginnings and the rate during the anomalous period is fairly constant the duration of the precursors ranges from 15 to 75 months and it is not clear what factors determine that time at least three successful predictions have been based on seismic quiescence these cases have shown that mainshocks can be predicted based on quiescence but they have also shown that the interpretation of the data in real time is difficult and nonunique if a false alarm is defined as a period of quiescence with a significance level larger than a precursory quiescence in the same tectonic area then we estimate based on searches in four areas that the false alarm rate may be on the order of 50 failure to predict may be expected in perhaps 50 of mainshocks even in carefully monitored areas quiescence cannot be used as a precursor in tectonic environments with low seismic activity most characteristics of the phenomenon are still poorly defined but data exist which probably permit at least a doubling of the presently available data on case histories

characterization of controls on high resolution stratigraphic architecture in wave dominated shoreface shelf parasequences using inverse numerical modeling abstract a new inverse numerical modeling method is used to constrain the environmental parameters e g relative sea level sediment supply and wave climate histories that control stratigraphic architecture in wave dominated shallow marine deposits the method links a process response forward stratigraphic model that simulates wave and storm processes barsim to a combination of inverse methods formulated in a bayesian framework that allows full characterization of uncertainties this method is applied for the first time to a real geologic dataset collected at outcrop from two shoreface shelf parasequences in the aberdeen member blackhawk formation of the book cliffs east central utah usa the environmental parameters that controlled the observed stratigraphic architecture are quantified and key aspects of stratigraphic architecture are successfully predicted from limited data stratigraphic architecture at parasequence stacking and intra parasequence scales was driven principally by relative sea level varying by up to about 55 m and sediment supply varying by up to 70 m2 yr whose interplay determines the shoreline trajectory within zones of distinctive shoreline trajectory variations in wave climate of up to about 3 m in fairweather wave height controlled superimposed variations in sandstone and shale content e g the development of upward coarsening and upward fining bedsets the modeling results closely match the observed stratigraphic architecture but their quality is limited by 1 the formulation and assumptions of the forward modeling algorithms and 2 the observed data distribution and quality which provide poor age constraint

phase transformations in subducted oceanic crust and buoyancy relationships at depths of 600 800 km in the mantle abstract phase transformations in a representative oceanic crust composition morb have been studied at pressures up to 28 gpa at 1200 c and 1500 c using a multi anvil apparatus the assemblage of majorite casio 3 rich perovskite stishovite which is displayed by the morb composition at pressures above 20 gpa was found to transform further into an assemblage containing a new aluminous phase at pressures above 25 gpa this al phase has a complex composition and is also relatively sodium rich its x ray diffraction pattern is similar to that observed for mgal 2 o 4 calcium ferrite type and is tentatively indexed on the basis of an orthorhombic cell yielding a zero pressure density of 3 87 2 g cm 3 majorite garnet was found to remain as the most abundant phase at the highest pressure studied 28 gpa and does not appear likely to transform to perovskite until pressures exceed 29 30 gpa these results imply that the basaltic crust component of subducted oceanic lithosphere would be 0 1 0 2 g cm 3 less dense than surrounding mantle pyrolite between the depths of 660 800 km thereby confirming an earlier hypothesis of anderson moreover the underlying layer of harzburgite would be 0 05 g cm 3 less dense than pyrolite throughout most of this depth interval these buoyancy relationships contribute to a barrier which impedes and may sometimes prevent the entry of slabs into the lower mantle

an experimental study of the effects of base level change on fluvial coastal plain and shelf systems abstract several of the concepts of sequence stratigraphic models were tested by experiments in a large flume using different gradients for successive runs a physical model of a fluvial drainage basin coastal plain continental shelf and continental slope was constructed in all experiments initial gradients of the coastal plain and shelf were identical systematic raising and lowering of the water surface simulated the changes in relative sea level i e base level that are similar to most sequence stratigraphic models base level changes significantly affected the shelf area but they had little effect on the fluvial drainage basin during base level falls fluvio deltaic progradation occurred fluvial aggradation occurred only during periods of base level stillstand or rise because of the slow rate of head ward erosion of incised valleys a significant time gap existed from the time base level first fell below the shelfbreak and the development of a cross shelf bypass valley during this lag time deposition occurred on the exposed shelf to form a fluvial braid plain concurrently channels developed at the shelfbreak and grew by headward erosion at various rates continuous incision and widening of these channels formed valleys these valleys were not linked directly to the main drainage basin unt l ultimately one captured the flow from that drainage at that point other valleys were abandoned and ceased to grow during the subsequent base level rise the single large cross shelf valley filled with coarser sediments while the other valleys partially filled with finer suspended load sediments the main cross shelf valley also supplied coarser sediments to the slope

hydrogen incorporation in stishovite at high pressure and symmetric hydrogen bonding in δ alooh first principles calculations of stishovite sio2 alooh and stishovite alooh solid solutions reveal that coupled substitutions of al3 and h for si4 provide a means for dissolving significant amounts of hydrogen in stishovite under lower mantle conditions the enthalpy of solution is positive decreasing in magnitude with increasing pressure combining our results with a model of the configurational entropy we find that the solubility of water in stishovite exceeds 0 3 wt h2o at 25 gpa and 1500 k realistic temperatures for subducting slabs and that the solubility increases with increasing pressure and temperature we predict asymmetric hydrogen bonding in the stishovite alooh solid solution that becomes increasingly symmetric with increasing pressure our results support the recently predicted symmetric hydrogen bonding in alooh and indicate that symmetric hydrogen bonding may be stable at ambient conditions in this material

geomorphology and sequence stratigraphy due to slow and rapid base level changes in an experimental subsiding basin xes 96 1 subsidence is a major factor in the accumulation and architecture of natural basin fills a recently built experimental facility experimental earthscape facility xes at st anthony falls laboratory of the university of minnesota incorporates for the first time a flexible subsiding floor in its design thus the experimental basin can model erosion and deposition associated with independent variations in sediment supply absolute base level change and rates and geometries of subsidence the results of the first experiment in a prototype basin 1 1 6 0 8 m are described here wherein the stratigraphic development associated with first slow and then rapid base level cycles in a basin that has a sag geometry has been analyzed a videotape of the experiment and subsequent serial slicing of the dried strata in the basin allow interpretation of the sequence development under conditions of precisely known changes of absolute base level subsidence and sedimentation relative base level changes which strongly varied in the basin owing to the sag geometry of subsidence seem to exert primary control on sedimentary patterns although autocyclic changes were also important style of sequence boundaries differed between slow and fast base level falls during the slow base level fall an incised valley developed once the shoreline prograded out of the zone of maximum subsidence suggesting that incision at the shoreline may be very sensitive to changes in relative base level once started however the valley quickly widened by knickpoint retreat into a broad low relief erosion surface that stretched across the entire basin as erosion took place at the knickpoint deposition occurred immediately downflow so both the knickpoint and the upstream limit of deposition migrated landward together producing a strong time transgressive erosion and onlap sequence the stratigraphic begin page 818 record of this sequence boundary is a single yet very subtle widespread unconformity that becomes conformable downstream which is difficult to trace in stratigraphic cross section in contrast the incised valley that formed during the rapid base level fall was relatively narrow deep and lengthened over time as deposits at the mouth of the valley were gradually exposed and incised through wholesale backfilling of the incised valley did not begin until the rapid base level rise started as a result the rapid base level change produced a more easily recognized incised valley in the stratigraphic record than did the slow base level change potential reservoir development within the strata is evaluated by means of a gray scale proxy for porosity four distinctive zones of enhanced reservoir quality occurred in the basin the most proximal part of the basin the upper part of growth fault bounded sedimentary wedges deep water forced regressive systems tract composed of grainflow deposits and transgressive systems tract formed during the rapid base level rise this distribution of relatively porous units suggests that for a variety of reasons rapid sea level cycles may produce the best reservoir units

principles of regression and transgression the nature of the interplay between accommodation and sediment supply the rate of change of accommodation at the shoreline a and the rate of sediment supply s are the primary factors controlling regression and transgression in the geological record or retreat and advance of a coastal depositional system the generally accepted notion here referred to as the a s ratio concept stating that the migration of a shoreline is controlled principally by the magnitude of the ratio of a to s is insufficient and somewhat misleading partly owing to the problem of dimensional confusion the interplay of a and s inevitably results in autoretreat of the shoreline whereby the seaward advance of any shoreline is halted and is subsequently turned to landward retreat provided there is a continuous rise of relative sea level how effective the autoretreat process is depends for a given period of relative sea level rising upon the length of potential time period for the seaward advance of shoreline and is proportional to a 2 s and a super 1 5 s super 0 5 in two and three dimensional sediment dispersal modes respectively autoretreat becomes more effective as a increases and or s decreases a functions more critically to the effectiveness than s does the a s ratio concept is only approximately applicable when autoretreat is less effective i e with very low a and or very high s in this sense the autoretreat theory and the a s ratio concept are complementary to each other the autoretreat mechanism is expected to be substantially useful not only in fluvial deltas but also in many other depositional systems e g barrier islands whose evolution has been considered in terms of the a s ratio concept

the al hoceima morocco earthquake of 24 february 2004 analysis and interpretation of data from envisat asar and spot5 validated by ground based observations abstract the magnitude mw 6 3 earthquake in al hoceima morocco of 24 february 2004 occurred in the active plate boundary accommodating the oblique convergence between africa and eurasia three different sets of estimates of its source parameters have already been published we try to resolve the discrepancies between them by using additional data including two remote sensing satellite systems envisat and spot5 using a model with a dislocation in an elastic half space we constrain the source parameters the hypothesis of two subevents on distinct faults as inferred from seismological inversions is confirmed here by adopting a cross fault mechanism the rupture began on a left lateral strike slip fault striking at n10 azimuth with 90 cm of horizontal slip and then transferred to a right lateral strike slip fault striking at n312 azimuth with 85 cm of horizontal slip the first fault is at 500 m depth from the free surface and the second fault is at 3 km depth this model is consistent with ground based observations including gps seismology and mapped surface fissures the pair of faults activated in 2004 appears to constitute part of a complex seismogenic structure striking nne ssw that separates the rif tectonic blocks

strike variability of clastic depositional systems does it matter for sequence stratigraphic analysis current sequence stratigraphic models are two dimensional in nature and predict variability in depositional dip sections strike and dip variability of sediment supply to clastic depositional systems causes significant changes to sequence architecture so that contrasting yet coeval stacking patterns result these changes ultimately affect prediction potential based on fixed systems tract stacking patterns and relation to relative sea level curves identification of key surfaces in sequences rather than stacking patterns is the most reliable indicator of relative sea level history

three dimensional stratigraphic evolution of the miocene baltimore canyon region implications for eustatic interpretations and the systems tract model a seismic stratigraphic analysis of miocene deposits in the baltimore canyon region offshore new jersey reveals tremendous threedimensional complexity and challenges traditional approaches to sequence stratigraphic interpretation individual sequences vary dramatically in along strike thickness revealing the locations of the sediment sources within sequences the lowstand wedge thins dramatically along strike tens to hundreds of meters and is interpreted to record variable paleobathymetry along strike as indicated by sequence thickness distributions shelf break positions lithologic composition and stratigraphic relationships sequences record sediment migration and progradation across the basin through time as a result of these depositional complexities relative sea level curves interpreted from parallel dip lines vary in magnitude and amplitude across the basin development of neogene stratal patterns within the baltimore canyon region has been closely linked to glacioeustatic change our reconstructions of delta switching and progradation emphasize that miocene stratal patterns were greatly influenced by autocyclic depositional processes

controls on clastic sequence geometries in a shallow marine transtensional basin the bohemian cretaceous basin czech republic the bohemian cretaceous basin combines features of a shallow water mostly 100 m epicontinental seaway formed during a global transgression with those of a tectonically active transtensional setting the basin formed under a greenhouse climate and was affected by strong axial currents dense well log coverage combined with locally high quality exposures and biostratigraphic control make it possible to examine in three dimensions the geometries of genetic sequences and interpret their controlling variables sand dominated deltas formed sequences at several spatial scales that reflect nested transgressive regressive cycles with durations ranging from tens of thousands of years to millions of years progradation directions and distances thicknesses and internal geometry of the individual sequences were controlled primarily by intrabasinal faulting basin scale changes in subsidence rate eustatic fluctuations and localized bathymetric changes due to successive filling of the basin along strike change in sediment input from different parts of the source area and a short lived uplift of a secondary clastic source provided additional controls on the sequence geometry efficient hypopycnal transport combined with redeposition of fine clastics in shallow water promoted development of steep slopes of sand dominated deltas while preventing downlap of muddy clinoforms most of the suspended load became deposited downcurrent in subhorizontal or gently dipping bottomsets long term accommodation rates were low during the early to middle turonian with minor intrabasinal faulting but became accelerated in the late turonian and early coniacian this acceleration was caused at least partly by increased subsidence rate accompanied by structural partitioning of the depocentre and partly compensated by increased sediment input indicating increased uplift rates in the western sudetic island source area this event probably reflected an increase in the regional strain rate in central europe the succession of two major flooding events in the early turonian and late early coniacian separated by a low accommodation interval in the middle turonian shows a close similarity to published estimates of long term eustatic curves however the eustatic component of accommodation rate in the bohemian late turonian and coniacian is difficult to separate from accelerated subsidence in several cases evidence for short term 100 kyr scale forced regressions independent of basinal structural activity suggests small scale eustatic falls at rates which as presently understood cannot be explained other than by a glacio eustatic mechanism

the 1994 2004 al hoceima morocco earthquake sequence conjugate fault ruptures deduced from insar abstract we study the may 26 1994 mw 6 0 and february 24 2004 mw 6 4 earthquakes that affected the al hoceima region of northern morocco these events are the two strongest earthquakes recorded in this region yet the exact location kinematics and relationships between these earthquakes are poorly known since neither of them produced surface ruptures using synthetic aperture radar interferometry insar we mapped the surface displacement field of the two earthquakes to characterize their seismic source parameters analysis of the interferograms constructed from ascending and descending orbits for both earthquakes and subsequent elastic modeling using slip inversions on triangular fault patches suggest that the two mainshocks occurred on blind conjugate strike slip faults the 1994 earthquake being associated with n23 e trending left lateral fault and the 2004 earthquake with n45 w trending right lateral fault this result contradicts previous inferences on the kinematics location and rupture geometry of the earthquakes deduced from conventional analyses of seismic waveforms and aftershocks distribution the insar analysis reveals the fragmentation of the rif mountain throughout a complex network of conjugate blind faults consistent with the transpression tectonics along the plate boundary in north africa although the two earthquakes took place in the rif thrust and fold belt the late quaternary deformation indicates e w extension in agreement with the nw se and ne sw trending conjugate strike slip faulting

the al hoceima earthquake sequence of 1994 2004 and 2016 stress transfer and poroelasticity in the rif and alboran sea region

accommodation and supply a dual control on stratigraphic sequences abstract it is widely accepted that both eustatic and tectonically controlled regional changes of sea level have contributed to the record of stratigraphic sequences i suggest that environmental change be added as a third autonomous control sedimentologic principles clearly indicate that sequences and their systems tracts are controlled by the interplay of two rates the rate of change in accommodation space available for sedimentation and the rate of sediment supply sea level has direct control on accommodation but its influence on sediment supply is remote and easily overshadowed by environmental factors for instance the record of the most recent sea level rise is a transgressive systems tract where supply is low it is a prograding highstand systems tract in deltas where the supply is high examples of sequence boundaries generated by changes in sediment supply include tectonically driven shifts in sediment input into basins changes in ocean currents pulsating supply from failure of submarine slopes and drowning of carbonate platforms by environmental stress furthermore the stratigraphic sequences in fluviatile continental basins are physically removed from sea level induced changes in accommodation and must have formed by changes in the rate and pattern of supply subaerial exposure of marine sediments at the sequence boundary is a most important criterion for recognizing sea level cycles as opposed to supply cycles other criteria include downstepping of shelf breaks and characteristic patterns in the spacing of time lines within sequences some third order cycles ca 0 5 3 ma duration meet these criteria others do not cycle stacking patterns and the shifting facies belts on cratons indicate that many second and third order cycles lack pronounced exposure unconformities and represent gradual changes superimposed on more rapid shorter oscillations seismic data yield poor images of these gradational changes because they lack resolution seismic models of outcrops show that near the limits of resolution the seismic tool tends to portray rapid changes in facies and bed thickness i e lateral variations in supply as unconformities seismic unconformities do not necessarily correspond to unconformities in outcrop the succession of stratigraphic sequences is best considered a composite record of sea level and environmental change separating the various controls requires carefully planned experiments work on the oxygen isotope curve another proxy for sea level has set an example in this respect

strain and stress fields along the gibraltar orogenic arc constraints on active geodynamics abstract the gibraltar orogenic arc in the western mediterranean represents a complex region of active deformation related to the oblique nubia eurasia convergence process to increase the knowledge on the ongoing active processes in this region we have used the most up to date and comprehensive geodetic crustal motion and stress fields to this end we analyzed both continuous and campaign mode gps data collected between 1999 00 and 2011 00 across the area and compiled a multidisciplinary dataset of well constrained stress indicators to be compared with the geodetic results the main results highlight the oblique nature of the nubia eurasia convergence which provides the largest component of the observed stress pattern and is responsible for a significant strain rate field along the gibraltar orogenic arc we discuss our findings with respect to available geological seismological and geophysical data in order to verify their coherency compared to more relevant geodynamical models proposed in literature according to previous studies we confirmed how much of the secondary stress pattern can be related to the gravitational potential energy field which may also be responsible for some 2d stress strain rate angular discrepancies observed in large areas of the betics in addition taking into account the sub orthogonal azimuthal relationship between the shmax and ehmin directions and the fast polarization directions we conjectured a deep dynamic process controlling both the crustal stress field and the surface deformation on large areas of the orogenic arc finally although the models proposed to explain the geodynamic pattern of the gibraltar orogenic arc are supported by a discrete number of geological and geophysical observations it is only the back arc extension and westward rollback model that is able to adequately account for the vast majority of the observations based on our findings and other evidences we retain that this process could still be active beneath the gibraltar orogenic arc

forced regressions in a sequence stratigraphic framework concepts examples and exploration significance sequence stratigraphic concepts suggest that stratal geometries develop and are largely controlled by changes in relative sea level on the shelf lowstand deposits which form during falls and subsequent stillstands of relative sea level can be recognized by the presence of an unconformity at the base the isolated and basinward position relative to the previous shoreline and the abrupt seaward translation of shallow water and shoreline facies into the basin across an unconformity surface this seaward translation of facies and shoreline regression in response to relative sea level lowering is termed a forced regression a forced regression is independent of variations of sediment flux and is in contrast with normal regressions that occur in response to excess sediment flux relative to space available on the shelf i e accommodation forced regressions commonly are associated with a zone of sedimentary bypass subaerial exposure and possible fluvial erosion between the newly formed and preceding shorelines certain shelf sands previously interpreted as offshore or mid shelf sand bodies thus can be reinterpreted as stranded lowstand shorelines associated with forced regressions this alternative interpretation has economic significance insofar as it suggests different subsurface correlations and reservoir geometries with the potential for development of new play types and enhanced recovery in o der fields examples of forced regression can be observed at a variety of scales and ages several such examples include the modern east coulee fan delta and the lower cretaceous viking formation in alberta canada the quaternary rhone delta and the quaternary hudson valley system

equation of state of stishovite and interpretation of sio2 shock compression data 1 we present an isothermal equation of state for the high pressure stishovite phase of sio2 based on synchrotron x ray diffraction at 300 k to 60 gpa the inferred equation of state is the same for stishovite synthesized from pure sio2 glass as from a natural basalt glass that forms stishovite in association with other mineral phases yielding a zero pressure bulk modulus k0t 312 9 3 4 gpa and pressure derivative k 0 4 8 0 2 our measurements of stishovite at static high pressures predict a shock compressed hugoniot state that is 2 4 1 6 denser than observed for sio2 suggesting that an amorphous phase rather than stishovite is produced under impact loading

goringe alboran tell tectonic zone a transpression system along the africa eurasia plate boundary neotectonic structures distributed from the goringe bank to the tell atlas mountains show that the africa eurasia plate boundary in the western mediterranean corresponds to an east west trending deforming zone goringe alboran tell main pliocene and quaternary tectonic structures of the northern atlas mountains are northeast southwest striking fault related folds similar to that of el asnam and are related to north south to northwest southeast compressional movements active tectonics in agreement with the main seismicity distribution and focal mechanisms also support an oblique plate convergence and the existence of a 50 100 km wide transpression zone from goringe across alboran to the tell atlas mountains a kinematic model shows the interaction between dextral transcurrent faults and left lateral faults with block rotations and no lateral extension pinned model shortening and lateral movement rates during the quaternary are estimated to be 1 0 2 3 mm yr and block rotation rate is estimated as 2 5 3 9 m y the plate boundary may correspond to a transpression zone active thrust faults being controlled by deep seated dextral transcurrent faults

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

strike slip fault terminations at seismogenic depths the structure and kinematics of the glacier lakes fault sierra nevada united states 1 structural complexity is common at the terminations of earthquake surface ruptures similar deformation may therefore be expected at the end zones of earthquake ruptures at depth the 8 2 km long glacier lakes fault glf in the sierra nevada is a left lateral strike slip fault with a maximum observed displacement of 125 m within the fault pseudotachylytes crosscut cataclasites showing that displacement on the glf was accommodated at least partly by seismic slip the western termination of the glf is defined by a gradual decrease in the displacement on the main fault accompanied by a 1 4 km wide zone of secondary faulting in the dilational quadrant of the glf the secondary faults splay counterclockwise from the main fault trace forming average angles of 39 with the main fault slip vectors defined by slickenlines plunge more steeply west for these splay faults than for the glf static stress transfer modeling shows that the orientations of the splays and the plunge of displacement on those splays are consistent with displacement on the main fault the glf termination structure shows that structural complexity is present at the terminations of faults at seismogenic depths and therefore ruptures that propagate beyond fault terminations or through step overs between two faults will likely interact with complex secondary fault structures models of dynamic rupture propagation must account for the effect of preexisting structures on the elastic properties of the host rock additionally aftershock distributions and focal mechanisms may be controlled by the geometry and kinematics of structures present at fault terminations

anatomy of a subaqueous ice contact fan and delta complex middle pleistocene north west germany this paper presents a detailed analysis of the high resolution facies architecture of the middle pleistocene porta subaqueous ice contact fan and delta complex deposited on the northern margin of glacial lake weser northwest germany a total of 10 sand and gravel pits and more than 100 wells were examined to document the complex facies architecture the field study was supplemented with a ground penetrating radar survey and a shear wave seismic survey all collected sedimentological and geophysical data were integrated into a high resolution three dimensional geological model for reconstructing the spatial distribution of facies associations the porta subaqueous fan and delta complex consist of three fan bodies deposited on a flat lake bottom surface at the margin of a retreating ice lobe the northernmost fan complex is up to 55 m thick 6ae2 km wide and 6ae5 km long the incipient fan deposition is characterized by high energy flows of a plane wall jet very coarse grained highly scoured jet efflux deposits with an elongate plan shape indicate a high froude number probably 5 these jet efflux sediments are deposited in front of a large 3ae2 km long up to 1ae2 km wide and up to 25 m deep flute like scour indicating the most proximal erosion and bypass area of the jet that widens and deepens with distance downstream to the region of maximum turbulence approximately five times the conduit diameter evidence for subsequent flow splitting is given by the presence of two marginal gravel fan lobes deposited in front of 1ae 3t o 2ae5 km long flute like scours that are 0ae8 to 1 km wide and 7 to 20 m deep in response to continued aggradation small jets developed at the periphery of these bar like deposits and filled in the low areas adjacent to the original superelevated regions locally raising the depositional surface and characterized by large scale trough cross stratified sand and pebbly sand the incision of an up to 1ae2 km wide and up to 35 m deep channel into the evolving fan is attributed to a catastrophic drainage event probably related to a lake outburst and lake level fall in the range of 40 to 60 m at the mouth of this channel highly scoured jet efflux deposits formed under hydraulic jump conditions during flow expansion subsequently gilbert type deltas formed on the truncated fan margin recording a second lake level drop in the range of 30 to 40 m these catastrophic lake level falls were probably caused by rapid ice lobe retreat controlled by the convex up bottom topography of the ice valley

quaternary crustal movements examined from facies distribution in the atsumi and hamana areas central japan abstract quaternary sediments are distributed from the east coast of lake hamana to the atsumi peninsula on the pacific side of central japan the sediments in the eastern hamana area include fluvial estuary and deltaic facies whereas sediments in the western atsumi area include fluvial estuary shoreface beach and coastal marsh facies the sediments in the hamana area comprise four sedimentary units those in the atsumi area comprise seven sedimentary units each unit in the hamana area was formed by the alternation of a transgressive estuary system and a regressive fan delta system in contrast each unit in the atsumi area was formed by the alternation of a transgressive estuary system and a regressive fan delta system in contrast each unit in the atsumi area was formed by the alternation of a transgressive estuary system and a regressive strand plain system stratal correlation with the ocean oxygen isotope variation indicates that the four younger units in both areas can be correlated and that the five younger units were formed at the sea level maxima during interglacial stages the oxygen isotope stages being 1 5 7 9 and 11 the top of each sequence is marked by the beach or fluvial facies deposited during highstand the present altitude of which was used as a marker for the palaeo highstand sea level a record of palaeo highstand sea level change was obtained from five locations in the atsumi area and one location in the hamana area comparison of the palaeo highstand sea level changes with the glacio eustatic highstand sea level change determined from raised coral reef terraces shows that the atsumi area subsided at the mean rate of 27 cm 1000 yr until 331 000 yr b p and the whole area was then uplifted between 331 000 and 122 000 yr b p with a maximum uplift rate of 29 cm 1000 yr the differential crustal movements were more active in the latter period the wavelength of the crustal bending is estimated at 50 100 km and the amplitude of the bending was less than 10 m before 331 000 yr b p and was 50 m thereafter the change in vertical crustal movement is synchronous in japan new zealand and new guinea such a synchronous change in the vertical crustal movement may be explained by a change in the regional horizontal stress field due to rotation of the pacific plate

p v t equation of state of stishovite up to mid lower mantle conditions 1 in situ p v t measurements of stishovite have been performed throughout its stability field from 17 to 54 gpa and from 300 to 1700 k by using a sintered diamond multianvil apparatus and synchrotron radiations the p v t equation of state of stishovite was precisely determined on the basis of the mie gruneisen debye model using both morse rydberg vinet and third order burch murnaghan equations for reference isotherms the new equation of state of stishovite gives the thermoelastic properties such as density adiabatic bulk modulus thermal expansivity and isobaric heat capacity without extrapolation to mid lower mantle conditions and these properties at zero pressures are consistent with those of previous measurements the present equation of state yields a lower density and larger adiabatic modulus at lower mantle conditions compared to those obtained by extrapolate on using a previous equation of state determined at upper mantle conditions our new equation of state and thermoelastic properties for stishovite at lower mantle conditions is important for quantitatively modeling the fate of subducted silica rich rocks such as morb and pelagic sediments and for interpreting seismological observations

surface deformation associated with the mw 6 4 24 february 2004 al hoceima morocco earthquake deduced from insar implications for the active tectonics along north africa we study the surface deformation associated with the 24 february 2004 al hoceima earthquake mw 6 4 that recently affected the rif mountains of mo rocco the coseismic displacement field is mapped using synthetic aperture radar interferometry insar with the envisat esa satellite data acquired in the ascend ing and descending modes our analysis and modeling of insar data suggest that the earthquake is associated with a northwest southeast trending right lateral ap parently blind strike slip fault with a seismic moment reaching 6 8 10 18 n m this result is in contrast with the north northeast south southwest left lateral fault mech anism inferred from the modeling of seismic waves thrust and fold structures of the rif mountains developed during the tertiary period but the recent significant seismic events and late quaternary deformation indicate east west extension accom modated by north south trending normal and northwest southeast and northeast southwest trending conjugate strike slip faults the active deformation illustrates the fragmentation of the rif mountain range due to the africa iberia collision and west southwestward escape tectonics

glacial isostatic adjustment as a control on coastal processes an example from the siberian arctic the geomorphology of the western siberian arctic coast represents a significant departure from the global trend of holocene delta formation by major rivers the ob and yenisei rivers in western siberia drain into the arctic ocean via estuaries 900 and 500 km long respectively eastern siberian rivers such as the lena indigirka and kolyma terminate at significant marine deltas we show that this spatial variation in coastal geomorphology can be explained by the glacial isostatic adjustment of the region the development and collapse of a peripheral bulge in western siberia associated with the glaciation and subsequent deglaciation of the eurasian ice sheets led to a distinct spatial variation in sea level change that continues to this day in particular since the marked decrease in global scale ice melting ca 7 ka our model predicts a sea level rise at the mouth of the ob river of 14 m compared to a rise of 6 m at the mouth of the lena river which ceased at 3 ka we propose that the enhanced sea level rise in the western siberian arctic associated with peripheral bulge subsidence has prevented the establishment of marine deltas at the mouths of the ob and yenisei rivers we conclude that regional variations in relative sea level change driven by glacial isostatic adjustment should be considered when interpreting large scale coastal morphology and deltaic stratigraphy which is normally assumed to correlate with eustatic fluctuations

high pressure phase relations in the composition of albite naalsi3o8 constrained by an ab initio and quasi harmonic debye model and their implications abstract phase relations in the composition of albite naalsi3o8 at pressures up to 40 gpa were constrained by a theoretical method that combines the ab initio calculation and quasi harmonic debye model first the p t dependence of the thermodynamic potentials of the individual phase stishovite sio2 st the calcium ferrite type naalsio4 cf jadeite naalsi2o6 jd or the hypothetical hollandite structured naalsi3o8 na holl was derived our results are generally in consistent agreement with available experimental data and previous theoretical predictions second the gibbs free energy of the hypothetical na holl phase was compared with that of the phase assemblage jd st js or cf 2st cs our results show that the na holl phase is not a thermodynamically stable phase over the studied p t conditions of 0 40 gpa and 100 600 k which rules it out as a possible intermediate phase along the transition path from the js phase assemblage to cs phase assemblage our calculations have predicted that the js phase assemblage transforms into the cs phase assemblage at about 33 6 gpa at 0 k and the clayperon slope of this phase transition is about 0 014 gpa k this study implies that lingunite na holl found in some meteorites is not possibly a thermodynamically stable high p phase and the cf phase probably plays an important role in maintaining the sodium budget and hosting the large ion lithophile elements in the deep interior of the earth

high resolution sequence stratigraphy the east coulee delta alberta abstract the fundamental concept on which sequence stratigraphy is based is that stratal architectures develop in response to the interaction between base level change and sediment flux a small lacustrine fan delta at east coulee alberta illustrates these principles and demonstrates that sequence stratigraphic concepts are scale and time independent this fan delta formed in a matter of days in a roadside drainage ditch as water level rose and then fell changes in the subaqueous space available for sediment to fill i e accommodation resulted in the development of a succession of systems tracts analogous to those formed within sedimentary basins over much longer time frames deposition began during lake level rise with progradation of a fan deltaic wedge accelerating lake level rise resulted in a backstepping of the shoreline and deposition of a transgress systems tract subsequent lake level fall resulted in subaerial exposure of the relatively steep delta front and caused incised valley formation and deposition of a lowstand delta this stratigraphic response to base level fall is typical of lowstand systems tract development on basin margins characterized by high relief slopes e g passive margins further lake level fall resulted in minor additional valley incision and development of a second lowstand delta on a surface characterized by lower relief as lowering water level exposed a flatter physiography this development of lowstand deltas and coa tlines during base level fall constitutes a forced regression of posamentier et al 1990 and is typical of lowstand systems tracts on basin margins characterized by gentle slopes in spite of its small size this example clearly illustrates that sequence stratigraphic principles apply to lacustrine as well as marine settings and at all spatial and temporal scales

experimental delta formation in crater lakes and implications for interpretation of martian deltas 1 the morphology of delta deposits in crater lakes on mars is indicative of upstream e g flow discharge and sediment properties and downstream e g basin characteristics parameters from which the hydrological conditions at the time of formation can be inferred to investigate the influences of these parameters on delta morphology we experimentally created deltas in crater shaped basins by feeding a range of constant flow discharges over a feeder channel of various sand textures we reproduced three categorically different types of deltas including most of the types that have been identified on mars our most striking observation is that water level behavior itself a unique function of flow discharge basin size and hypsometry and basin floor permeability can explain most delta morphologies observed on mars stepped retrograding deltas formed during water level rise prograding deltas formed during water level still stand and during water level fall deltas were partially destroyed by erosion on mars numerous retrograding and prograding deltas were preserved most of them without indications of channel incisions or other fluvial modification we conclude that the main difference between a single foreset prograding delta and a multiple foreset retrograding delta is the behavior of the water level in the basin these simple delta morphologies cannot be reconciled with long duration hydrological activity because that would imply crater lake fluctuations due to inherent complex water level histories along with complex sediment delivery histories our experiments and numerical verifications demonstrate that such deltas preferentially form during one aqueous event which parsimoniously argues for short duration hydrological activity

sequence stratigraphy in alluvial settings a flume based model with applications to outcrop and seismic data a simple theoretical model for generating proximal alluvial depositional sequences was developed from flume experiments and illustrated by seismic reflection geometries during periods of low discharge the transport system is inefficient and the sediment is mainly deposited in proximal areas at extreme conditions of hydrological deficit maximum backfilling occurs the rise of discharge begins to retransport sediment stored in proximal areas during low efficiency periods at maximum discharge the maximum degree of incision is reached concomitant with a progradation of coarse material toward the basin center in this model a transit cycle of the knickpoint occurs caused only by transport efficiency changes and not by base level change a dominantly fining upward sequence ending with a short coarsening upward interval is thus deposited bounded by truncation surfaces well developed at the basin margins flume experiments were designed to explore this model two runs were analyzed that differed in the rate of volume growth of the water sediment system of the flume with the first run at no volume growth and the second run at 0 38 l min these runs simulated different rates of generation of accommodation space a single grain size 1 mm was used to simplify the analysis and to avoid high relief bed forms during each cycle four main behaviors occur 1 the rise of discharge produces an immediate proximal erosion and progradation of the sedimentary wedge 2 within the interval of high discharge a maximum erosion forms the truncation surface and soon after that slow deposition at high regime occurs in proximal areas minor onlap 3 a fall of discharge produces a rapid onlap on the simulated basin margin the sedimentary wedge moves upstream and a surface of nondeposition or an interval of very low rate of accumulation is formed distally 4 during the low discharge interval onlap proceeds together with the progradation over the nondeposition surface a downlap surface of the sediment wedge formed at the basin margin these behaviors were observed in both runs but the timing degree of progradation and retrogradation and the relief of stratal geometries differ slightly however the higher rate of volume growth more accommodation space led to less proximal erosion and to better downlap development application of the model is demonstrated with a natural example in a neogene basin showing well defined truncations in seismic lines at the unfaulted margin and major proximal incisions in the active part of the basin downlap stratal geometry occurs as predicted by the model nondepositional surfaces or intervals deposited at low rates were located close to where the analog model predicted a method for correlating these sequences is proposed using the global water cycle as a link times of maximum alluvial incision due to the cycle of peak discharge can be correlated to the time of fastest eustatic rise and marine onlaps however when water is stored on the continents and not delivered to the oceans hydrological deficits might produce alluvial onlaps

mgsio3 fesio3 al2o3 in the earth s lower mantle perovskite and garnet at 1200 km depth natural pyroxene and garnet starting materials are used to study the effects of joint fe and al substitution into mgsio3 perovskite at 50 gpa garnet is found to coexist with perovskite in samples containing both fe and al to pressures occurring deep into the lower mantle 1200 km depth the volume of the perovskite unit cell is vo a3 162 59 5 95xfesio3 10 80xal2o3 with aluminum causing a significant increase in the distortion from the ideal cubic cell on the basis of a proposed extension of the mgsio3 al2o3 high pressure phase diagram toward fesio3 fe is shown to partition preferentially into the garnet phase the stability of garnet deep into the lower mantle may hinder the penetration of subducted slabs below the transition zone

molecular dynamics modeling of stishovite a morse stretch potential charge equilibrium force field for silica system has been employed to simulate the thermodynamics of stishovite with the molecular dynamics md method the equation of state thermal expansivity and melting curve of stishovite have been obtained this simple force field yielded results in accordance with the static and dynamic experiments the stishovite melting simulation appears to validate the interpretation of superheating of the solid along the hugoniot in the shock melting experiments md simulations show that the thermal expansivity of stishovite at lowermost mantle conditions is a weak function of temperature the phase diagram of silica up to the mega bar regime is proposed based on the experimental and theoretical studies the related physical and geophysical implications are addressed 5 2002 elsevier science b v all rights reserved

common dependence on stress for the two fundamental laws of statistical seismology the gutenberg richter relation and the omori utsu law both power laws are two of the long standing relationships of statistical seismology here aftershock sequences are described according to the faulting style of their main shocks showing that the time delay before the onset of the power law aftershock decay rate is on average shorter for thrust main shocks than for normal fault earthquakes these similar dependences on the faulting style indicate that both the fundamental power laws are governed by the state of stress

transport of water into the lower mantle role of stishovite when subjected to lower mantle pressures and temperatures natural anhydrous basalt containing 0 2 wt h sub 2 o forms a phase assemblage in which sio sub 2 stishovite is a significant carrier of hydrogen up to 500 ppm h sub 2 o by weight as hydroxide whereas the coexisting mg fe al ca sio sub 3 perovskite appears to be not upper bound of 50 ppm wt h sub 2 o contrary to the devolatilization characteristically observed at lower pressures we find that the abundance of h sub 2 o in residual stishovite increases from approx 100 to approx 400 ppm by weight upon partially melting the high pressure mineral assemblage at 28 60 gpa we infer that the trace concentration of al within residual stishovite increases upon partial melting thereby increasing the coupled abundance of h in this crystalline phase the anhydrous component of subducted oceanic crust can thus recycle a significant amount of water into the lower mantle over the age of the earth with subducted stishovite potentially returning approx 10 sup 2 times the amount of water present in today s atmosphere

new gps constraints on active deformation along the africa iberia plate boundary abstract we use velocities from 65 continuous stations and 31 survey mode gps sites as well as kinematic modeling to investigate present day deformation along the africa iberia plate boundary zone in the western mediterranean region the gps velocity field shows southwestward motion of the central part of the rif mountains in northern morocco with respect to africa varying between 3 5 and 4 0 mm yr consistent with prior published results stations in the southwestern part of the betic mountains of southern spain move west southwest with respect to eurasia 2 3 mm yr the western component of betics motion is consistent with partial transfer of nubia eurasia plate motion into the southern betics the southward component of betics motion with respect to iberia is kinematically consistent with south to southwest motion of the rif mountains with respect to africa we use block modeling constrained by mapped surface faults and seismicity to estimate the geometry and rates of strain accumulation on plate boundary structures our preferred plate boundary geometry includes one block between iberia and africa including the sw betics alboran sea and central rif this geometry provides a good fit to the observed motions suggesting a wide transpressive boundary in the westernmost mediterranean with deformation mainly accommodated by the gloria azores fault system to the west and the rif tell lineament to the east block boundaries encompass aspects of earlier interpretations suggesting three main deformation styles i extension along the ne sw trending trans alboran shear zone ii dextral strike slip in the betics corresponding to a well defined e w seismic lineament and iii right lateral strike slip motion extending west to the azores and right lateral motion with compression extending east along the algerian tell we interpret differential motion in the rif alboran betic system to be driven both by surface processes related the africa eurasia oblique convergence and sub crustal dynamic processes associated with the long history of subduction of the neotethys ocean lithosphere the dextral slip identified in the betic mountains in southern spain may be related to the offshore fault that produced the great 1755 lisbon earthquake and as such may represent a significant seismic hazard for the west mediterranean region

a physical basis for time clustering of large earthquakes we develop a theory that links stress interaction between earthquakes and the occurrence of temporal clustering coseismic static stress change in the vicinity 50 km of large earthquakes suggests that perturbations of 0 1 to 1 bars may affect the occurrence of other earthquakes at larger distances interactions also seem to exist four m 8 earthquakes have occurred in mongolia on distant faults 400 km during the last century also paleoseismic observations documenting much longer time periods display a time clustering of major events we demonstrate with simple mechanical concepts that postseismic stress relaxation magnifies the coseismic stress change and has a major effect on fault interaction during the seismic cycle in the simple case where two distant faults are coupled the probabilistic occurrence of triggered earthquakes may increase dramatically due to long range postseismic coupling

correlation migration using gaussian beams of scattered teleseismic body waves correlation migration for structural imaging using gaussian beams is described for the inversion of passively recorded teleseismic waves gaussian beam migration is based on an overcomplete frame based representation of the seismic wave field and uses localized slant stack windows of the data paraxial gaussian beams are then utilized for the backpropagation of the seismic waves into the me dium the method can provide stable imaging of seismic data in smoothly varying background media where caustics and triplicated arrivals exist we develop gaussian beam migration for structural imaging which allows for incident teleseismic waves from beneath the structure using directly scattered or surface reflected phases the method is applied to synthetic data computed for a collisional zone model and the inversions show that the gaussian beam migration can image structure using passive teleseismic data the method is next applied to synthetic data that have been con volved with an observed pulse from the 1993 cascadia experiment the autocorre lation is computed and the autocorrelated data are migrated by using gausian beams for direct p to s scattered waves and surface reflected waves although the migra tions of the autocorrelation data with the source pulse included have more noise than the migrations of the impulsive source data the subduction zone structure can still be clearly identified in the migrated results without removal of the source pulses

three dimensional numerical modeling of deltaic depositional sequences 1 influence of the rate and magnitude of sea level change abstract a three dimensional numerical model of deltaic deposition is used to investigate the influence of sea level changes on delta development and sequence variability results illustrate the three dimensional morphology of key stratal surfaces and architecture of stratal units systems tracts and highlight the importance of the rate and magnitude of sea level change in controlling the evolution of deltaic depositional sequences high rates of sea level fall lead to the development of a limited number of major incised channels that focus sediment supply to a few elongate finger like forced regressive lobes separated by large areas of nondeposition in contrast low rates of sea level fall cause only minor channel incision which occurs late during sea level fall as a result sediment is supplied more uniformly to the delta front leading to an attached laterally continuous forced regressive apron during lowstand and subsequent sea level rise the delta morphology and internal geometry are strongly controlled by the rate of rise high rates lead to i poorly developed lowstand wedges that are drowned early ii high magnitude transgressions and iii the late development of maximum flooding surfaces the stratigraphy developed during sea level rise is also strongly influenced by the incised valley system created during the preceding sea level fall if deep major valleys developed that captured most of the sediment supply the resultant stratigraphy has well developed lowstand wedges that are flooded relatively late during sea level rise even within a single delta systems tracts and key stratal surfaces show three dimensional variability and two dimensional sections often lack significant elements of the stratigraphy as a result analysis of two dimensional sections can often lead to miscorrelation and erroneous interpretations of the controlling processes

stress triggering and earthquake probability estimates 1 stress triggering and fault interaction concepts are beginning to be incorporated into quantitative earthquake probability estimates however the current methods are limited in their range of compatible earthquake nucleation models i introduce a new general method for translating stress changes into earthquake probability changes which can potentially be used with any physical fault model given the large uncertainties in earthquake probability calculations it is unclear whether the small probability changes resulting from stress transfer are significant and meaningful for the purposes of seismic hazard assessment i present a case study of the effect of the 1992 m7 3 landers california earthquake on the probability of a major earthquake on the san andreas fault in southern california this is a large event in a well studied region which should maximize the probability change signal and minimize the uncertainty even for this scenario the earthquake probability change for a 30 year period is not significant with respect to the initial uncertainty in the earthquake probability this example comparisons with other studies and exploration of parameter space imply that the probability changes due to stress triggering are significant only for time intervals which are short compared to the repeat time of the target fault therefore stress change calculations will be useful in long term seismic hazard assessment only for low slip rate faults otherwise stress triggering calculations are best utilized in the short term immediately following a major earthquake

oceanographic currents differential subsidence and physiography control three dimensional clinothem growth in the gulf of papua papua new guinea abstract a regional high resolution chirp seismic survey in the gulf of papua gop extends the geographic scope of previous studies by 125 km and reveals that the holocene clinothem along margin geometries surfaces of lap and steepness of foreset slopes appear less dependent on eustatic sea level changes and sediment supply than previously suggested clinothems imaged by chirp profiles and sampled by sediment cores include two older relict clinothems and a younger holocene clinothem divided into three units by two surfaces of lap new radiocarbon ages from this study establish that depositional timing is more recent than previously proposed for the transgressive deposits the holocene clinothem units and surfaces of lap while previous ages suggested that observed stratal relationships could coincide with meltwater pulses or sea level stillstands the younger ages from this study question these results and suggest the dominant control on holocene clinothem architecture may be inherited physiography sw ne differential subsidence along margin currents and seasonal variations in wave energy inherited physiography underlying the holocene clinothem consists of valleys incised during relative lowstands of marine isotope stages mis 4 and 2 valleys in the relict clinothem potentially served as across margin conduits for an older holocene clinothem unit after the older holocene unit filled valleys and accommodation younger holocene units preferentially grew along rather than across margin as bottom shear stresses increased relict clinothems have undergone differential subsidence since deposition due to foreland basin loading which has engendered more accommodation in the northeast gop that systematically decreases toward the southwest areas with less accommodation are more likely to experience toplap as they are exposed to increased shear stresses therefore the surfaces of lap are caused by interactions between accommodation and oceanographic currents examining stratal relationships along the holocene clinothem has broad implications for sequence stratigraphy as many clinothems exhibit a three dimensional stacking pattern measurements of seafloor slopes yield complicated results illustrating that seafloor steepness within lobes is influenced by a complex interplay of accommodation sediment supply underlying physiography and oceanographic currents this suggests that clinothem architecture in the gop cannot simply be interpreted as a rate related problem between rates of sediment supply and relative sea level

towards a sequence stratigraphic solution set for autogenic processes and allogenic controls upper cretaceous strata book cliffs utah usa upper cretaceous strata exposed in the book cliffs of east central utah are widely used as an archetype for the sequence stratigraphy of marginal marine and shallow marine deposits their stratal architectures are classically interpreted in terms of accommodation controls that were external to the sediment routing system allogenic and that forced the formation of flooding surfaces sequence boundaries and parasequence and parasequence set stacking patterns processes internal to the sediment routing system autogenic and allogenic sediment supply controls provide alternatives that can plausibly explain aspects of the stratal architecture including the following 1 switching of wave dominated delta lobes expressed by the internal architecture of parasequences 2 river avulsion expressed by the internal architecture of multistorey fluvial sandbodies and related deposits 3 avulsion generated clustering of fluvial sandbodies in delta plain strata 4 autoretreat owing to increasing sediment storage on the delta plain as it lengthened during progradation expressed by progradational to aggradational stacking of parasequences 5 sediment supply control on the stacking of and sediment grain size fractionation within parasequence sets the various potential allogenic controls and autogenic processes are combined to form a sequence stratigraphic solution set this approach avoids anchoring of sequence stratigraphic interpretations on a specific control and acknowledges the non unique origin of stratal architectures

forced regressive deposits of a deglaciation sequence example from the late quaternary succession in the lake saint jean basin quebec canada differentiating between forced regressive deposits from deglacial periods in high latitude domains and forced regressive deposits from the onset of glacial periods in low latitude domains is fundamental for the accurate interpretation of glacial cycles within the geological record and then for the reconstruction of palaeogeography and palaeo climate a forced regressive deglacial sequence is documented from the lake saint jean basin quebec canada in this area the late pleistocene to holocene sediments have recorded the laurentide ice sheet retreat accompanied by the invasion of marine waters laflamme gulf from ca 129 cal kyr bp subsequently fluviodeltaic and coastal prograding wedges were deposited they followed the base level fall due to glacio isostatic rebound this succession representing a transition from glacial to post glacial periods within a previously glaciated area was investigated through recent mapping preserved landforms facies analysis and new optical stimulated luminescence and radiocarbon dates three basin scale geological sections share a common lower part made of isolated ice contact fan deposits overlying bedrock throughout the entire basin ice contact fans are capped by glacimarine muds above fluvial and coastal prograding systems were deposited and evolved through four steps i deltaic systems progressively increased in width ii coastal influence on sedimentation increased iii hydrographic drainage systems became more organised and iv deltas graded from steep gilbert delta to low angle foresets mouth bar delta deposited during the base level fall from glacioisostatic rebound the complete succession has been designated as a single falling stage system tract referred to as a deglacial falling stage system tract it is representative of a deglaciation sequence in areas previously covered by ice during glacial periods i e medium to high latitude domains diagnostic criteria are provided to identify such a deglacial falling stage system tract in the geological record which may aid identification of previously unknown glacial cycles

tectonic sedimentology sediment systems deciphering global to local tectonics tectonic sedimentology has broad appeal because it can be applied at many time and length scales such as sedimentary consequences of changing rates of plate creation at mid ocean ridges continent continent collisions plateaux uplift active plate margins extensional rift tectonics and the birth growth and death of individual folds and faults tectonic sedimentology deals with the direct influence of neotectonics on sedimentation and basin development and with the inverse problem of reconstructing the order and development of palaeotectonic structures this review attempts to show how the scope and importance of the subject has developed over the last decade and is divided into five themes i at the largest tectonic scale constraints on mid ocean ridge activity and continent continent collisions come from a precise chemical analyses of fluid inclusions in marine halite deposits dating back to ca 550 ma b sr isotopic ratios of marine phanerozoic calcitic fossils and c chemical composition of archaean and proterozoic banded iron formations ii at regional scales constraints on the timing and extent of continental plateau uplift incision and cratonic tilting are given by a palaeoaltimetry estimates from oxygen isotope depletion in carbonate palaeosols b radiometric dating of palaeowater table speleothems and c preferential river migration iii at basin scales catchment processes are emphasized as key controls on sediment flux from tectonic uplands to sedimentary basins the inadequacy of sediment transport algorithms based on tractive stress and flow power to describe erosion incision and sediment transport during the most formative catchment hydrological events is emphasized iv rates of basin scale fault and fold growth displacement death and basement uplift are provided by application of facies analysis and sequence stratigraphy to accurately dated sediments in sedimentary basins v the effects of changing climate and varying basin base level in modifying tectonic influences on erosion and sedimentation are examined in such cases experimental and numerical modelling using multi variate parameters of subsidence rate sediment supply and sea level change can shed light on the problem future developments will undoubtedly improve such models hopefully establishing full linkage and feedback between sediment water supply and changing climate within an overall tectonic framework that may itself be changing

theory of time dependent rupture in the earth at a velocity x which is a well defined function of k this propagation is stable and quasi static and is referred to as subcritical crack growth we shall use the terms stable quasistatic and subcritical to mean propagation at velocities much less than the sonic velocities of the medium this behavior results from stress induced corrosion at the crack tip the principal corrodent for the present application being h20 this behavior has been firmly established in the laboratory for mode i tensile cracks in a wide variety of materials ineluding silicates and silicate glasses see cholz 1968a 1972a martin 1972 wiederhorn and bolz 1970 atkinson 1979 lawn and wilshaw 1975 knott 1973 the form of the relationship between k and x does not vary significantly with the material only the parameters in the law vary as an example we show in figure 1 data on subcritical crack growth in quartz after atkinson 1979 the empirical relationship is found to take the form

three dimensional numerical modeling of coarse grained clastic deposition in sedimentary basins a three dimensional numerical model of clastic deposition in sedimentary basins is used to investigate the development of coarse grained deltas in response to relative sea level changes the model incorporates fully three dimensional sediment delivery and deposition together with incised channel formation and slope failure a combined random walk steepest descent algorithm is used to simulate sediment delivery from a drainage basin outlet to the depositional shoreline together with a nonlinear three dimensional diffusion equation for modeling slope dependent sediment erosion transport and deposition when sediment channels transport pathways are out of a specified grade advective erosion occurs thereby increasing the total sediment supply delivered to the basin multiple sediment sources into a basin can be simulated together with tectonic subsidence and eustatic sea level changes the model results presented display many of the key features observed in both modern and ancient coarse grained deltas during periods of slowly changing and high relative sea level highstands a broad delta front progrades approximately radially away from the sediment source conversely incised channels are developed during rapid falls of relative sea level leading to localized deposition of deltaic lobes at the mouths of these channels the incised channels initiate at the exposed delta front and propagate backward toward the sediment source the rate of growth of incised channels is shown to be an important control on delta morphology sediment distribution and lowstand lobe size and location lobes are particularly well developed during periods of slowly changing low relative sea level lowstands periods of rapid rise of relative sea level lead to flooding and infilling of incised channel systems and a rapid landward shift in deposition transgressions incised channels and delta lobes are best developed in a model where tectonic subsidence is similar to that expected for hanging wall sourced deltas in extensional half graben settings in contrast both channels and lobes are less well developed in a model where tectonic subsidence is similar to that expected for footwall sourced deltas in such settings many of the features developed in the models are by their nature three dimensional and two dimensional analysis of the model results can lead to erroneous interpretations of the causes of along strike variability these aspects of sequence variability have important implications for the application of the sequence stratigraphic methodology to many sedimentary basins